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PubMed1997

Median arcuate ligament syndrome: a possible cause of idiopathic gastroparesis.

The median arcuate ligament syndrome (MALS) is characterized by abdominal pain, nausea, and vomiting attributed to compression of the celiac axis by a fibrous band (the median arcuate ligament) connecting the diaphragmatic crura. The pathophysiologic origin of these symptoms is not clearly understood. Theories invoking either a neurogenic or vascular origin for the clinical features associated with MALS have been proposed, but objective evidence to support these theories is lacking. We describe the clinical course and gastric myoelectrical features of a patient with postprandial epigastric pain, weight loss, gastroparesis, and gastric dysrhythmias in whom a diagnosis of MALS was established. Surgical decompression of the celiac axis in our patient resulted in resolution of abdominal pain, return to a full diet within 4 weeks without nausea or vomiting, improvement in radionuclide gastric emptying, and restoration of the gastric electrical rhythm to a normal 3 cycle/min conduction rate. This is the first demonstration of altered gastric myoelectrical activity in a patient with MALS. The regularization of the gastric electrical rhythm in our patient after surgical decompression of the celiac axis would support a neurogenic basis for the symptoms associated with MALS. MALS should be excluded in patients with idiopathic gastroparesis and unexplained epigastric pain.

Abdominal Pain↗
PubMed2001

Regulation of bovine E-selectin expression by recombinant tumor necrosis factor alpha and lipopolysaccharide.

Induction of adhesion molecules by cytokines and LPS is an important mechanism of regulating leukocyte migration into tissue. Expression and regulation of E-selectin may be differentially influenced by the stimuli involved with effects on mRNA or surface protein kinetics. Surface protein and mRNA expression kinetics of bovine E-selectin were measured and compared in primary cultures of bovine aortic endothelial cells (BAEC) stimulated for various periods of time with recombinant bovine tumor necrosis factor alpha (rbTNF-alpha) or Escherichia coli lipopolysaccharide (LPS). E-selectin mRNA expression was measured via quantitative reverse transcription polymerase chain reaction (Q-RT-PCR) using a construct that contained multiple synthetic oligonucleotides for several bovine adhesion molecules and cytokines. Surface expression of E-selectin was measured by flow cytometry. Unstimulated BAECs expressed minimum or no E-selectin on the surface. A low number of endothelial cells expressed surface E-selectin as early as 1h post-stimulation and surface expression was sustained after both stimuli for 24-72h. Mean fluorescence intensity (MFI) indicated peak surface concentration of E-selectin at 6 h post-stimulation after LPS followed by a gradual decrease to 72h without returning to baseline values. Mean fluorescence intensity following stimulation with TNF-alpha increased slightly between 0 and 72h. The pattern of mRNA expression differed between stimuli. LPS-stimulated BAECs expressed peak amounts of E-selectin mRNA at 6 h, followed by a decline to baseline by 24 h. Conversely, BAECs stimulated with rbTNF-alpha expressed significantly (p pound 0.05) higher amounts of mRNA at 1h than compared to unstimulated controls (0 h), but this decreased to below baseline levels by 6h; followed by a gradual increase and eventually a sharp increase between 18 and 72 h. To account for the lack of correlation between mRNA and protein expression, it was hypothesized that shedding of surface E-selectin accounted at least in part, for the large increase in mRNA expression seen at 18-72h. Culture supernatants from rbTNF-alpha-treated BAECs were harvested, and tested for the presence of shed E-selectin using ELISA. Unstimulated culture supernatants contained little or no E-selectin. Between 6 and 48 h, the concentration of E-selectin in culture supernatants from rbTNF-alpha-stimulated BAECs increased approximately two-fold, suggesting that the sharp increase in E-selectin mRNA expression around 18 h may be related to significant loss of surface E-selectin during this period.

Animals↗
PubMed2001

Dentate hilar mossy cells and somatostatin-containing neurons are immunoreactive for the alpha8 integrin subunit: characterization in normal and kainic acid-treated rats.

Integrins are heterodimeric cell surface receptors composed of different alpha and beta subunits that mediate cell-cell and cell-extracellular matrix interactions. They have been implicated in the regulation of neuronal migration, differentiation, process outgrowth, and plasticity. The alpha8 integrin subunit associates exclusively with the beta1 subunit to form a receptor (alpha8beta1) for fibronectin, vitronectin, tenascin, and osteopontin. In a previous study, we demonstrated that hippocampal dentate hilar neurons are immunoreactive for alpha8. The present study identifies the major types of alpha8-immunoreactive hilar neurons and characterizes the effects of kainic acid-induced seizures on alpha8-immunoreactivity in these cells. Examination of the hilus in normal rats revealed alpha8-immunoreactivity in the somatodendritic compartments of large hilar neurons identified as mossy cells, including a subset of dendritic thorny excrescences that were contacted by large mossy fiber terminals. alpha8-immunoreactivity also was found in approximately 71% of somatostatin-containing hilar cells. Kainic acid-induced seizures dramatically and rapidly altered the levels and distribution of alpha8-immunoreactivity in hilar neurons. After 1.5 h of seizures, alpha8-immunoreactivity in their dendrites was reduced greatly. One day after kainic acid treatment, labeling was diminished throughout the somatodendritic compartments of most hilar cells. This decrease appeared to be transient, since alpha8 labeling returned to normal levels in surviving hilar neurons within 2 weeks of treatment. In addition, many alpha8-immunoreactive hilar neurons, particularly in caudal dentate regions, were lost 3-5 weeks after kainic acid treatment. Our findings suggest that alpha8beta1 may mediate adhesive interactions of the dendritic processes of mossy cells and somatostatin-containing hilar neurons with other cellular elements or with extracellular matrix components. They also suggest that alpha8 may be susceptible to activity-dependent proteolysis that could modulate its function in the somatodendritic compartment of these cells.

Animals↗
PubMed2002

Gene expression of adhesion molecules in pulmonary and hepatic microvascular endothelial cells during sepsis.

OBJECTIVE: To study the gene expression of adhesion molecules in pulmonary and hepatic microvascular endothelial cells during sepsis in mice. METHODS: Male mice were subjected to cecal ligation and puncture (CLP) and microvascular endothelial cells in pulmonary and hepatic tissues were harvested at 3 hours (early sepsis) and 12 hours (late sepsis) after CLP, respectively. Gene expression of the adhesion molecules was assessed by reverse transcription polymerase chain reaction (RT-PCR). Simultaneously, the alterations of myeloperoxidase (MPO) activity in pulmonary and hepatic tissues were also examined. RESULTS: E-selectin mRNA levels markedly increased at 3 hours after CLP in both pulmonary and hepatic microvascular endothelial cells, then they returned to the normal level at 12 hours after CLP. Increases in intercellular adhesion molecule-1 (ICAM-1) mRNA levels were found at 3 hours after CLP in both pulmonary and hepatic microvascular endothelial cells, and these levels became higher at 12 hours after CLP. Adhesion molecule-1 (VCAM-1) mRNA expression of vascular cells also increased significantly at 3 hours and 12 hours after CLP in both pulmonary and hepatic microvascular endothelial cells. The level of VCAM-1 mRNA in hepatic microvascular endothelial cells was higher at 3 hours than that at 12 hours after CLP, while the level of VCAM-1 mRNA in pulmonary microvascular endothelial cells was higher at 12 hours than that at 3 hours after CLP. The MPO activity in pulmonary and hepatic tissues increased at 3 hours after CLP, compared with that of the sham group. They both declined significantly at 12 hours after CLP, but they were still higher than that of the sham group. CONCLUSIONS: The up-regulation of the gene expression of adhesion molecules in pulmonary and hepatic microvascular endothelial cells is an important step for the migration and accumulation of leukocytes at the site of inflammation, which plays a critical role in organ damage during sepsis. And the contribution of the heterogeneity of endothelial cells in organs' vulnerability during sepsis is worth a further investigation.

Animals↗
PubMed1994

Comparing earnings profiles in urban areas of an LDC: rural-to-urban migrants vs. native workers.

"We use Tanzanian data to test a recently proposed hypothesis that rural-to-urban migrants have an incentive to supply greater work effort than native urban workers, because of the migrants' positive probability of returning to the low-wage rural areas. We treat the choice between public- and private-sector employment as endogenous and, for theoretical and empirical reasons, distinguish migrants with access to rural land from those without access. Our results show that migrants in both sectors face lower initial wage offers than native urban workers. But, the wage gap is eliminated within a decade or less, and thereafter, migrants surpass the wage offers of native workers."

Africa↗
PubMed2005

An EST-based approach for identifying genes expressed in the intestine and gills of pre-smolt Atlantic salmon (Salmo salar).

BACKGROUND: The Atlantic salmon is an important aquaculture species and a very interesting species biologically, since it spawns in fresh water and develops through several stages before becoming a smolt, the stage at which it migrates to the sea to feed. The dramatic change of habitat requires physiological, morphological and behavioural changes to prepare the salmon for its new environment. These changes are called the parr-smolt transformation or smoltification, and pre-adapt the salmon for survival and growth in the marine environment. The development of hypo-osmotic regulatory ability plays an important part in facilitating the transition from rivers to the sea. The physiological mechanisms behind the developmental changes are largely unknown. An understanding of the transformation process will be vital to the future of the aquaculture industry. A knowledge of which genes are expressed prior to the smoltification process is an important basis for further studies. RESULTS: In all, 2974 unique sequences, consisting of 779 contigs and 2195 singlets, were generated for Atlantic salmon from two cDNA libraries constructed from the gills and the intestine, accession numbers [Genbank: CK877169-CK879929, CK884015-CK886537 and CN181112-CN181464]. Nearly 50% of the sequences were assigned putative functions because they showed similarity to known genes, mostly from other species, in one or more of the databases used. The Swiss-Prot database returned significant hits for 1005 sequences. These could be assigned predicted gene products, and 967 were annotated using Gene Ontology (GO) terms for molecular function, biological process and/or cellular component, employing an annotation transfer procedure. CONCLUSION: This paper describes the construction of two cDNA libraries from pre-smolt Atlantic salmon (Salmo salar) and the subsequent EST sequencing, clustering and assigning of putative function to 1005 genes expressed in the gills and/or intestine.

Animals↗
PubMed1999

Correlation of VEGF expression by leukocytes with the growth and regression of blood vessels in the rat cornea.

PURPOSE: To determine the temporal and spatial relationships between neovascularization and basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) mRNA and protein expression in the rat cornea after cautery with silver nitrate. METHODS: In female Sprague-Dawley rats, a silver nitrate applicator was placed on the central cornea to elicit circumferential angiogenesis, and blood vessel growth was quantified by digital image analysis of corneal flat-mounts. Total RNA or protein was extracted from whole corneas until 1 week after cautery, and bFGF and VEGF mRNA and protein levels were determined by reverse transcription-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). To localize VEGF mRNA and protein, paraformaldehyde-fixed and paraffin-embedded histologic cross sections of corneas were examined by in situ hybridization and immunohistochemistry. Macrophages were identified by ED2 immunohistochemistry. To examine the regulation of VEGF, rats were treated with dexamethasone (0.5 mg/kg per day) and hyperoxia (70% O2). RESULTS: The neovascular response progresses in three phases: (1) a nonproliferative phase preceding vessel growth (< or = 48 hours after cautery); (2) a proliferative phase with maximal growth rate between 3 and 4 days; and (3) a regressive phase (day 7) with a decrease in vessel density accompanying the completion of vessel elongation. In corneas after cautery, bFGF mRNA expression was unchanged, and bFGF protein concentration decreaseed by 97% after 24 hours and returned to control levels by day 7. In contrast, VEGF164 and VEGF188 mRNA splice variants and protein peaked 48 hours after cautery, remained elevated 4 days after cautery, and decreased to near baseline by day 7. The peak concentration of VEGF in the cornea at 48 hours was calculated to be 720 pM, which is sufficient to evoke a functional response. In situ hybridization and immunohistochemistry showed VEGF expressed initially in neutrophils (24 - 48 hours) and subsequently in macrophages (4 days) adjacent to the cautery site. Treatment with either dexamethasone or systemic hyperoxia inhibited both neovascularization and the increase in VEGF expression. Dexamethasone inhibited 27% of cautery-induced VEGF upregulation at 24 hours and 23% at 48 hours, hyperoxia inhibited 32% at 24 hours and 43% at 48 hours, and combined treatment with both dexamethasone and hyperoxia had an additive effect (56% inhibition at 24 hours). CONCLUSIONS: VEGF production by leukocytes correlates temporally and spatially with cautery-induced angiogenesis in the rat cornea. Both inflammatory products and hypoxia appear to sufficiently increase VEGF expression near the cautery lesion to increase vascular permeability of limbal vessels and induce endothelial cell migration and proliferation.

Animals↗
PubMed1989

Chemoattractant-elicited translocation of myosin in motile Dictyostelium.

The distribution of myosin was studied in amebae of the Ax-3 and NC-4 strains of Dictyostelium migrating at room temperature, using indirect immunofluorescence of aggregation-competent amebae and the agar-overlay technique. Amebae were fixed in methanol-formaldehyde or absolute acetone at -15 degrees C before or after stimulation with micromolar cyclic AMP at room temperature (20-25 degrees C). Myosin was detected by monoclonal antibodies to Dictyostelium myosin heavy chain followed by a fluorescent secondary antibody that had been preabsorbed to remove nonspecific staining. In both strains there was a striking increase in intensity of anti-myosin immunofluorescence in the cortex where it appeared as a continuous ring 30 seconds after addition of cyclic AMP. This correlated with a rounding up of the cell body. Sixty seconds after stimulation there was a clear reduction of cytoplasmic myosin rods in conjunction with the increased cortical localization. At this time extensions of largely hyaline cytoplasm were observed that extended beyond the cortical shell of myosin. Two minutes after the stimulus the immunofluorescence remained as a distinct line at the cortex, but the cells began to resume in elongated shape. By 3 minutes (NC-4 strain) or 5 minutes (Ax-3 strain) the amebae had largely returned to the control shape, and myosin had returned to its control distribution. Counts of the treated cells at different time points substantiated the observations of individual cells. The time course of translocation of myosin in the Ax-3 strain parallels the time course of myosin phosphorylation reported in previous studies. The results are interpreted in terms of a working hypothesis for the mechanism of translocation.

Antibodies, Monoclonal↗
PubMed1976

Radioimmunoassay of serum concentrations of melatonin in sheep exposed to different lighting regimens.

A specific and sensitive double-antibody radioimmunoassay for melatonin (N-acetyl-5-methoxytryptamine) has been developed utilizing rabbit antisera to a bovine serum albumin conjugate of N-succinyl-5-methoxytryptamine and utilizing N-3-(4-hydroxyphenl)-propionyl-5-methoxytryptamine for radioiodination. The least detectable concentration of melatonin standard was 10 pmolar (2.3 pg/tube) with 50% inhibition resultinhibition curves obtained with increasing quantities of melatonin or increasing quantities of chloroform extracts of ovine sera were parallel. The immunoreactivity found in ovine sera c-migrated with [3H]melatonin on silica gel G when developed with chloroform:methanol (9:1). N-Acetylserotonin, 5-methoxytryptamine, serotonin, tryptophan, 6-hydroxymelatonin, 6-methoxytetrahydroharmalan, and several other indole and beta-carboline compounds do not influence the estimation of melatonin in the radioimmunoassay. Concentrations of melatonin could be accurately determined when 31 to 1000 pg were added to 1 ml ovine serum. Serum samples with melatonin concentrations of 1000 pg/ml, 500 pg/ml and 75 pg/ml had intra-assay coefficients of variation of 9.1%, 8.6%, and 17.4%, respectively. The respective inter-assay coefficients of variation were 22.7%, 18.1%, and 37.1%. Ewes exposed to a 12 h light: 12 h dark lighting regimen demonstrated a circadian rhythm in serum concentrations of melatonin. Concentrations ranged from 10-30 pg/ml during periods of light to 100-300 pg/ml during periods of dark. During exposure to continuous light, the circadian rhythm was abolished and concentrations of melatonin were maintained at 10-50 pg/ml. When exposed to conditions of continuous dark the circadian rhythm persisted. A precipitous drop in serum concentrations of melatonin resulted when ewes experiencing peak melatonin concentrations were exposed to light. Concentrations returned to peak levels when the lights were turned off 3.5 h later.

Animals↗
PubMed1994

Crypt cell production rate, enterocyte turnover time and appearance of transport along the jejunal villus of the rat.

Intestinal nutrient absorption is subject to adaptation with, for example, diabetes, diet lipid variations (isocaloric semisynthetic diets enriched with saturated (S) or polyunsaturated (P) fatty acids), ileal resection and abdominal irradiation. These models were used in rats to assess dynamic morphology and distribution of amino acid transporter along the villus. The enterocyte migration rate (EMR) was measured using [3H]thymidine; the vincristine metaphase arrest technique was used to determine the crypt cell production rate (CCPR); quantitative autoradiography was used to assess the time and age of enterocytes when the uptake of 1 and 20 mM [3H]leucine and [3H]lysine was initiated along the villus. The enhanced jejunal uptake of nutrients which occurs after a 50% distal enterectomy was associated with a fall in EMR and CCPR, yet the enhanced nutrient uptake which occurs in diabetes is not associated with any alteration in EMR, CCPR, enterocyte transport pool (ETP), i.e., the length of the enterocyte column along with the villus containing amino acid transporter) or expression of transporter along the villus. The reduced uptake of nutrients in rats fed P as compared with S was associated with increased rather than decreased ETP and age of the enterocytes at the tip of the villus. The reduced nutrient uptake which occurs 3 days after abdominal irradiation was associated with increased EMR and CCPR, and reduced ETP and age of enterocytes of the tip of the villus. However, 14 days after irradiation when nutrient transport remains reduced, these parameters have returned to normal. Thus, alterations in nutrient transport may be associated with changes in the dynamic morphology of the intestine, but the two processes are not necessarily interdependent. We speculate that the changes in the dynamic morphology of the intestine, and the changes of amino acid transport which occurs in these models of intestinal adaptation, are independently controlled.

Amino Acid Transport Systems↗
PubMed2004

Wavelength dependency of light-induced effects on photoperiodic clock in the migratory blackheaded bunting (Emberiza melanocephala).

The effects of light wavelength on photoperiodic clock were determined in the migratory male blackheaded bunting (Emberiza melanocephala). We constructed an action spectrum for photoperiodic induction (body fattening, gain in body mass, and gonadal recrudescence) by exposing birds for 4.5 weeks to 13 h light per day (L:D = 13:11 h) of white (control), blue (450 nm), or red (640 nm) color at irradiances ranging from 0.028 to 1.4Wm(-2). The threshold light irradiance for photoinduction was about 10-fold higher for blue, compared to red and white light. Phase-dependent effects of light wavelength on the photoperiodic clock were further examined in the next two sets of skeleton photoperiods (SKPs). In the first set of SKPs, birds were exposed for four weeks to asymmetrical light periods (L:D:L:D= 6:6:1:11 h) at 0.25+/-0.01 W m(-2); two light periods applied were of the same (450nm: blue:blue, B:B; 640nm, red:red, R:R) or different (blue:red, B:R or red:blue, R:B) wavelengths, or of white:white (W:W, controls). Photoperiodic induction occurred under R:R and B:R, but not under B:B and R:B light conditions; the W:W condition induced an intermediate response. The second set of SKPs used symmetrical light periods (L:D:L:D = 1:11:1:11 h), and measured effects also on the activity rhythm. Birds were first exposed to one of the four SKPs (R:R, B:B, R:B, or B:R) for three weeks, subsequently were released into dim constant light (LLdim; approximately 0.01 Wm(-2), the night light used in an L:D cycle) for two weeks, and then were returned to respective SKPs for another three weeks. Activity was greater in the R:R compared to B:B, and in B:R compared to R:B light condition. Zugunruhe (intense nighttime activity, indicating migratory restlessness in a caged situation) developed under the R:R and B:R, but not the B:B and R:B, light condition. Under LLdim, all birds free-ran with a period >24h, the Zugunruhe had a circadian period longer than the daytime activity, and the re-entrainment to SKPs was influenced by the position of light periods relative to circadian phase of the activity rhythm. Photoperiodic induction at the end of 8 weeks was found in the R:R and B:R, but not in B:B, light conditions; in the R:B condition only one bird had initiated testes. Taken together, these results suggest that in the blackheaded bunting, the circadian photoperiodic clock is differentially responsive to light wavelengths; this responsiveness is phase-dependent, and the development of Zugunruhe reflects a true circadian function. Wavelength-dependent response of the photoperiodic clock could be part of an adaptive strategy in evolution of the seasonality in reproduction and migration among photoperiodic species under wild conditions.

Animals↗
PubMed2006

Percutaneous endoscopic interlaminar discectomy for intracanalicular disc herniations at L5-S1 using a rigid working channel endoscope.

OBJECTIVE: Percutaneous endoscopic transforaminal discectomy is often used as a minimally invasive procedure for lumbar disc herniation. However, a transforaminal approach posts limitations at the L5-S1 level owing to anatomic constraints, such as a high iliac crest or small intervertebral foramen and especially for migrated large intracanalicular disc herniations. We discuss the procedure and clinical results of percutaneous endoscopic interlaminar discectomy using a rigid working channel endoscope at the L5-S1 level and the relevant surgical anatomy. METHODS: We performed percutaneous endoscopic discectomy through the interlaminar approach in 67 patients who satisfied our inclusion criteria during the period from March 2002 to November 2002. All procedures were performed under local anesthesia. Under fluoroscopic guidance, we performed discography using indigocarmine mixed with radio-opaque dye. The 6-mm working channel endoscope was then introduced into the epidural space. Herniated disc material was removed using forceps and laser under clear endoscopic visualization. We retrospectively evaluated the 65 cases with more than 1.5 years of follow-up. The patients were evaluated using the visual analogue scale (VAS) and the Oswestry Disability Index (ODI). RESULTS: VAS for leg pain (preoperative mean, 7.89; postoperative mean, 1.58) and ODI (preoperative mean, 57.43; postoperative mean, 11.52) showed statistically significant (P = 0.00) improvement in their values at the last follow-up examination compared with preoperative scores. Of the study group, 90.8% individuals showed favorable result. The mean hospital stay was 12 hours. The average time to return to work was 6.79 weeks. Complications included two cases of dural injury with cerebrospinal fluid leakage, nine cases of dysesthesia that were transient, and one case of recurrence. Two patients required conversion to open procedure at the initial operation. There was no evidence of infection in any patients. CONCLUSION: Percutaneous endoscopic interlaminar discectomy is a safe, effective, and minimally invasive procedure for the treatment of intracanalicular disc herniations at the L5-S1 level in properly selected cases, especially when the transforaminal approach is not possible because of anatomic constraints.

Adult↗
PubMed2004

Gene deletion of dopamine beta-hydroxylase and alpha1-adrenoceptors demonstrates involvement of catecholamines in vascular remodeling.

In vitro studies have shown that stimulation of alpha1-adrenoceptors (ARs) directly induces proliferation, hypertrophy, and migration of arterial smooth muscle cells and adventitial fibroblasts. In vivo studies confirmed these findings and showed that catecholamine trophic activity becomes excessive after experimental balloon injury and contributes to neointimal growth, adventitial thickening, and lumen loss. However, past studies have been limited by selectivity of pharmacological agents. The aim of this study, in which mice devoid of norepinephrine and epinephrine synthesis [dopamine beta-hydroxylase (DBH-/-)] or deficient in alpha1-AR subtypes expressed in murine carotid (alpha1B-AR-/- and alpha1D-AR-/-) were used, was to test the hypothesis that catecholamines contribute to wall hypertrophy after injury. At 3 wk after injury of wild-type mice, lumen area and carotid circumference increased significantly, and hypertrophy of media and adventitia was in excess of that needed to restore circumferential wall stress to normal. In DBH-/- and alpha1B-AR-/- mice, increases in lumen area, circumference, and hypertrophy of the media and adventitia were reduced by 50-91%, resulting in restoration of wall tension to nearly normal (DBH-/-) or normal (alpha1B-AR-/-). In contrast, in alpha1D-AR-/- mice, increases in lumen area, circumference, and wall hypertrophy were unaffected and wall thickening remained in excess of that required to return tension to normal. When examined 5 days after injury, proliferation and leukocyte infiltration were inhibited in DBH-/- mice. These studies suggest that the trophic effects of catecholamines are mediated primarily by alpha1B-ARs in mouse carotid and contribute to hypertrophic growth after vascular injury.

Animals↗
PubMed1989

Microvasculature of normal and involuted mouse thymus. Light- and electron-microscopic study.

The spatial arrangement of blood vessels in the thymus of normal and hydrocortisone-injected mice was studied by light and electron microscopy. The thymus is supplied by one thymic artery which branches into arterioles as it enters the parenchyma. These, in turn, feed capillary networks in the cortex and in the medulla. Cortical networks at the periphery of the lobule form loops which return blood to postcapillary venules at the corticomedullary junction and in the medulla. There is no subcapsular venous drainage. The overall distribution of blood vessels in the involuted thymus is essentially the same as in the normal thymus but the pattern becomes irregular and the vessels are tortuous. The endothelium of the postcapillary venules is flat and surrounded by a wide perivascular space containing many lymphocytes. This space is delimited by basal laminae, on the one side by that of the abluminal surface of the venular endothelium, on the other side by that of a thin, sheet-like epithelial layer formed by cytoplasmic processes of reticular cells. The perivascular space is in continuity with the surrounding interstitial space via gaps in its epithelial sheet. It does not form continuous longitudinal channels along the venules, but is interrupted by epithelial trabeculae. There is no obvious difference in structure between the postcapillary venules and their perivascular space of normal and those of involuted thymuses. Lymphocytes are intercalated in the venular endothelium particularly in involuted glands. They are present in the perivascular space and in gaps of the outer epithelial sheet. These findings suggest that the postcapillary venules and the perivascular spaces may function as pathways for the migration of thymic lymphocytes into or out of the blood circulation.

Animals↗
PubMed1998

Emigration of New Zealand and Australian physicians to the United States and the international flow of medical personnel.

One in five physicians practising in the US received their initial medical qualifications in another country. Contrary to expectations, a large cadre come from developed nations such as New Zealand and Australia. In particular, these two countries provide a unique prism with which to view the international flow of medical talent. While they differ from developing nations that primarily export physicians without attracting others in return, they are distinguished from importing nations such as the US which rarely export. Our analysis is based on a unique dataset collected from three cross-sectional sources. We found that, compared to post-resident physicians remaining at home, New Zealand medical graduates (NZMGs) and Australian medical graduates (AMGs) in the US are typically older, more likely to be male, more likely to have received their initial medical qualifications from certain schools, less likely to be employed in a public hospital setting, more likely to work in a medical school and more likely to practice in a specialty than primary care. Additional findings show that NZMGs and AMGs in the US are more likely than other US physicians to have established themselves in areas with 50,000 or more people and are therefore more likely to serve a population with sociodemographic characteristics typical of the nation's urban centers. It appears then, that NZMGs and AMGs may be emigrating to the US for educational and professional opportunities that may be unavailable at home. In short, the emigration of NZMGs and AMGs may be an instance of what has come to be called the 'international equity problem' or 'brain drain'. However, losses resulting from the disproportionate migration of New Zealand and Australian physicians to the US may be compensated for by the importation of foreign trained physicians from other nations. Future analysis must be extended to take this facet of the international flow phenomena into account.

Age Factors↗
PubMed1993

[Effects of de-endothelialization and angiotensin II on the vascular remodeling in a model of rabbit aorta organ culture].

The effects of de-endothelialization and angiotensin II (A II) on smooth muscle cell (SMC) growth are still controversial. Cell culture experiments suggest an hypertrophic effect of AII, whereas in vivo experiments in de-endothelialized arteries using angiotensin converting enzyme inhibitors suggest a possible role of AII on proliferation and/or migration of SMC. Phenotype of SMC in culture does not necessarily reflect that in the whole organ. Yet, in vivo models are too complex to permit conclusions as to the proper effect of AII or endothelium. Therefore, we examined the effect of de-endothelialization and AII on SMC growth in an organ culture of vessel wall. Rabbit thoracic descending aortas (n = 42) held at their in vivo length, perfused at 40 ml/min and pressurized to 70 mmHg (P70) were maintained in DME medium supplemented with 20% fetal calf serum for periods of time varying between 0 and 15 days. In another group (n = 26), aortas were relaxed and not pressurized (P0). In each group, some arteries were de-endothelialized; 21 arteries were exposed to AII (10(-6) M) and indomethacin (10(-5) M) during the incubation. SMC proliferation was evaluated by 3H-thymidine uptake by the vessel wall. Statistics were performed using covariance analysis. In P0 group, de-endothelialization or AII had no effect on the vessel wall. In P70 group, de-endothelialization or led to a significant increase in media area which was reported to extracellular matrix synthesis and in 3H-thymidine uptake (p < 0.005) which peaked at 3-5 days and returned to basis levels at 6-8 days. All had no effect on 3H-thymidine uptake (p = 0.516) in P70 group. Our results obtained in rabbit aortic organ culture suggest that de-endothelialization induces SMC growth depending on pressure and/or wall stretching. AII, per se, had no additional effect on SMC growth in this model.

Angiotensin II↗
PubMed2001

Gastric myoelectrical activity and its relationship to the development of nausea and vomiting after intensive chemotherapy and autologous stem cell transplantation.

OBJECTIVES: Gastric motor dysfunction may be responsible, in some patients, for the nausea and emesis that occur after high-dose chemotherapy (HDT) and autologous stem cell transplantation (SCT). Because gastric myoelectrical abnormalities may result in nausea and vomiting in other contexts, we sought to define the prevalence of these abnormalities and their relationship to the development of nausea and vomiting in patients undergoing autologous HDT and SCT, and to determine whether electrogastrography (EGG) could serve to detect gastric motor dysfunction in this population. METHODS: We prospectively studied patients with a variety of malignancies who received standard transplantation doses of chemotherapeutic agents and antiemetics. Gastric emptying scintigraphy was performed before HDT. Gastric myoelectrical activity was assessed before HDT and on days 0, 7, 14, 21, and 28 from SCT using cutaneous EGG electrodes and a portable EGG recorder, and was analyzed by means of a dedicated software program after removal of motion artifact. Symptom assessment was obtained daily from initiation of HDT to 28 days after SCT. RESULTS: A total of 25 patients were studied: 13 women and 12 men, with a median age of 50 yr (range = 32-65 yr). Before HDT, gastric emptying scintigraphy was normal in all patients (median T(1/2) of 50 min [range = 22-75 min]) and only one patient had mild nausea and anorexia. Nausea, emesis, and anorexia occurred in all patients, peaked in severity at day +7 from SCT and, with the exception of anorexia, had returned toward baseline levels by day +28. Fasting dysrhythmias were present in 63% of the studies at baseline. Serial EGG recordings revealed significant slowing of the dominant frequency with a consequent decrease in tachygastria and increase in normogastria and bradygastria as the symptoms peaked in severity with a subsequent return to baseline values at the study's end. The only clinical variable that was predictive of symptom severity was gender. Women had a higher risk of developing anorexia (score > or = 2) at day +14 compared to men (odds ratio = 11.2; 95% CI = 1.7-76.9; p = 0.01). CONCLUSIONS: Baseline abnormalities in gastric myoelectrical activity occur frequently in patients who undergo HDT and autologous SCT despite normal gastric emptying scintigraphy and an absence of symptoms. Although slowing of the dominant frequency was seen as symptoms worsened, we failed to identify any EGG parameter at baseline that could predict the severity of nausea, vomiting or anorexia after transplantation.

Adult↗
PubMed2006

Midwives' perception of the intrapartum risk of healthy nulliparae in spontaneous labour, in The Flanders, Belgium.

OBJECTIVE: to explore midwives' perception of intrapartum risk for healthy nulliparous women in spontaneous labour at term of a healthy singleton pregnancy, in the Belgian Flanders, and to compare these results with those of a previous study undertaken in England. DESIGN: survey of the care midwives would advocate and their perception of intrapartum risk using a standardised scenario. This study replicates part of a survey undertaken with British midwives (Mead & Kornbrot 2004b). With an added section to capture the particulars of the Belgian situation and explore the likelihood of midwives being fully responsible for the whole intrapartum care of healthy women, including their delivery. The questionnaire was translated into Dutch by MR and distributed by the Flemish Midwives' Association (Vlaamse Organisatie van Vroedvrouwen-VLOV). PARTICIPANTS: all 845 midwives and 143 student midwives who were members of VLOV were sent a questionnaire with their invitation to take part in their annual conference. Two hundred and seventy-five midwives and 107 students attended the conference, and 128 questionnaires were returned at the conference: 99 midwives (36% of the attendees), 26 students (24% of attendees), with three unidentified respondents. This convenience sample represented 12% of all midwives and 18% of all students. ANALYSIS: SPSS for Windows was used for the statistical analysis. Descriptive statistics were used and differences between categorical variables were analysed using chi(2) and Fisher's Exact tests, and differences between continuous variables were analysed by analysis of variance. FINDINGS: midwives generally described a more medicalised approach to intrapartum care on admission and during the first stage of labour than their British counterparts, but were much more optimistic about the chances of healthy women in spontaneous labour achieving a normal delivery within 12 hours. However, Belgian midwives had only a limited ability to undertake normal deliveries because of the high proportion of obstetricians who fulfil this responsibility. This contravenes the European Union (EU) directive on the activities of the midwife. KEY CONCLUSIONS: despite much greater involvement of obstetricians in the care, of women suitable for full midwifery care, and a more medicalised approach to intrapartum care, the Belgian Flanders have a significantly lower caesarean section rate than the UK. The inability of Belgian midwives to fulfil the activities of the midwives as identified by the EU directives raises questions about the migration of midwives trained in Belgium to other EU member states.

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