Biomedical subjects

G Meyer

Publications and source records attributed to G Meyer.

At least 145 records · Page 8Linked to original sources

PubMed1999

B1 integrin activation inhibits in vitro tube formation: effects on cell migration, vacuole coalescence and lumen formation.

Human endothelial cells (EC), when plated onto gels of extracellular matrix proteins such as Matrigel or collagen form capillary tubes in a process thought to mimic angiogenesis. We have shown previously that the extent of tube formation and the phenotype of the lumen are regulated by integrins (Gamble et al 1993) and lumen formation occurs through a process of vacuolization, coalescence and ultimate directional fusion of these vacuoles with the plasma membrane (Meyer 1997 et al). We now show here that activation of beta1 integrins on endothelial cells inhibits tube formation. On collagen gels, endothelial cells treated with 31 activating antibody 8A2 failed to migrate into the gel and tube formation was inhibited. Although several integrins mediate EC attachment to collagen alpha2beta1 is the chief determinant of EC behaviour since a blocking antibody to (alpha2beta1 reversed the effect of 8A2. On Matrigel tube formation was also inhibited by 8A2 treatment although cell alignment and sprout formation was still evident. Electron microscopy revealed the organisation of normal numbers of cells into solid sprouts and the formation of small intracellular vacuoles suggesting that initial stages of tube formation including cell migration were unaffected. However, beta1 integrin activation inhibited the coalescence of these small vacuoles into larger vacuoles, the recruitment of more cells into the sprout and the subsequent formation of mature lumen. The inhibition of capillary tube formation by beta1 activation was time dependent and long lasting. The critical time for activation of the beta1 integrin was the initial 1-2h after plating in order to inhibit tube formation although once activated, the beta1 mediated inhibition on Matrigel was still evident 4 days later. Our results suggest that beta1 integrins are critical in capillary tube formation in at least two phases. beta1 integrins are essential for migration of EC through collagen gels. Independently, beta1 integrins, although not involved in initial vacuole formation, are involved in the process of vacuole coalescence and subsequent lumen formation since beta1 integrin activation inhibits these processes.

Antibodies, Monoclonal↗

PubMed1999

Patients, diagnoses, and procedures in a military internal medicine clinic: comparison with civilian practices.

BACKGROUND: Our goal was to compare the demographic features, diagnoses, and procedures in civilian and military ambulatory internal medicine clinics. METHODS: One year (September 1996 to August 1997) of data from the Ambulatory Data System of the Adult Primary Care Clinic at Madigan Army Medical Center was extracted and compared with the most recent (1995) National Ambulatory Medical Care Survey. RESULTS: A total of 41,374 Madigan patient encounters were compared with civilian data from the National Ambulatory Medical Care Survey. The age distribution was similar, with military patients averaging 53.5 years of age and civilian patients averaging 54.5 years. Military patients were more likely to be female (71 vs. 60%) and were more ethnically diverse (military: 68% white, 17% African American, 7% Hispanic, 7% Asian American, and 1% Native American; civilian: 78% white, 10% African American, 6% Hispanic, 5.9% Asian American, and 0.3% Native American). There were similar rank orderings of the top 189 diagnostic groups seen in each setting (Spearman's rho = 0.87). There were also no differences in the type or rank order of procedures performed between military and civilian internists (p = 0.53). CONCLUSION: The practice content of military and civilian practices appears to be more similar than different.

Age Distribution↗

PubMed1999

[Transabdominal preperitoneal hernia repair (TAPP). Results of 1,000 completed operations].

It was the aim of this report to evaluate the laparoscopic transabdominal preperitoneal hernia repair (TAPP) which has been standardized at our department. Along with the demographic characterisation of 795 patients with 1000 inguinal hernia repairs we report about complications and early recurrences. The patient data were collected prospectively. The rate of follow-up amounted to 79.9% with an average follow-up of 1 year. The complications were divided into intraoperative, minor, major, as well as severe ones. In 30 repairs minor complications (3%) were detected. Major (n = 28) and severe (n = 9) complications were detected in 3.7% of the cases. There were two deaths, 3 patients with an intestinal obstruction due to adhesions (2 segmental small bowel resections), two patients with testicular atrophy, two mesh infections, two trocar hernias, 6 surgical revisions for removal of hematomas, one exploration of a testicle, 4 diagnostic laparoscopies for suspected recurrences with a negative result, and 15 patients with a nerve irritation syndrome. The early rate of recurrence was 0.7%. In 6 cases primary hernias had been repaired and in one case a recurrent hernia. The recurrent hernias became apparent in an average of 2 years (minimum 2.5 months, maximum 36 months) after surgery. The results of the clinical study demonstrate an acceptable rate of complications and a low rate of early recurrences. Based on these data we recommend the laparoscopic transabdominal preperitoneal technique and see an ideal indication in the case of bilateral, recurrent and femoral hernias.

Adolescent↗

PubMed1999

Comparison of discharge diagnoses and inpatient procedures between military and civilian health care systems.

BACKGROUND: Our goal was to compare the demographics and discharge diagnoses between civilian and military health care systems. METHODS: One year (1997) of data from the Retrospective Case Mix Adjustment System from the Military Health Services System were compared with the most recent (1994) civilian National Hospital Discharge Survey data. RESULTS: Military and civilian inpatient age (52.5 and 52.9 years), gender (54% and 59% female), and ethnic distributions (military: 71% white, 16% African American, 3% Asian American, 10% other; civilian: 65% white, 12% African American, 2.6% Asian American, 1.2% Native American, 18% unclassified) were similar. There were similar rank orderings of diagnosis-related groupings (Spearman's rank correlation = 0.72) and procedures performed during hospitalization (Spearman's rho = 0.74), although the military inpatients yielded a higher proportion associated with pregnancy and strenuous activity (traumatic joint disorders and hernias) than their civilian counterparts. CONCLUSION: The practice content of military and civilian inpatients appear to be more similar than different.

Diagnosis-Related Groups↗

PubMed1999

ICln, an ion channel-forming protein associated with cell volume regulation.

It is not resolved whether the anionic channel involved in volume regulation after cell swelling comprises one or more subunits. Moreover, it remains to be determined which of the different proteins cloned so far, for which an involvement in cell volume regulation has been postulated, is the ideal candidate. In this review, we consider the role of the ICln protein, cloned from MDCK cells, in cell volume regulation.

Animals↗

PubMed1998

[Role of spiral CT in the emergency diagnosis of pulmonary embolism].

The pulmonary arteries can be visualized with spiral CT after injection of iodinated contrast material. Its contribution to emergency diagnosis of pulmonary embolism has been recently evaluated. Sensitivity for the detection of segmentary or more proximal thrombi is nearly 100% with a specificity estimated at 96%. These figure are much lower for subsegmentary emboli, varying from 63% to 83% for sensitivity and from 85% to 100% for specificity. The requirement for treatment in these minor forms remains however a topic of debate. Due to its noninvasive character and the diagnostic performance, spiral CT is well adapted for cases of suspected massive embolism. Inversely, for minimal embolism, spiral CT cannot eliminate the diagnosis before the results of other explorations are known.

Angiography↗

PubMed1998

Identification of genes involved in replication and movement of peanut clump virus.

The genome of peanut clump pecluvirus (PCV) consists of two messenger RNA components which contain, respectively, three and five open reading frames (ORFs). Inoculation of transcripts from full-length cDNA clones derived from the PCV RNAs showed that RNA-1 is able to replicate in the absence of RNA-2 in protoplasts, but both RNAs are necessary for plant infection. To investigate the role of different gene products in viral RNA replication and movement, transcripts from mutant cDNA clones were inoculated to protoplasts and to Chenopodium quinoa or Nicotiana benthamiana plants, and progeny RNA was detected by Northern blot analysis. The protein P15, encoded by the third ORF of RNA-1, is essential for efficient replication of the viral genome. The three proteins, P51, P14, and P17, of the triple gene block contained in RNA-2 are involved in localized movement of the viral genome, whereas the coat protein (P23) is also required for vascular movement. Insertion of the beta-glucuronidase reporter gene (GUS) in place of the P23 or P39 genes (the first and the second genes of RNA-2) allows visualization of the virus infection in inoculated leaves. Although the presence of the GUS gene resulted in a lower accumulation of progeny RNA and, despite instability of the construct in planta, histochemical detection of PCV multiplication was more sensitive than Northern blot detection.

Arachis↗

PubMed1998

Different origins and developmental histories of transient neurons in the marginal zone of the fetal and neonatal rat cortex.

Two major classes of early-born neurons are distinguished during early corticogenesis in the rat. The first class is formed by the cortical pioneer neurons, which are born in the ventricular neuroepithelium all over the cortical primordium. They appear at embryonic day (E) 11.5 in the lateral aspect of the telencephalic vesicle and cover its whole surface on E12. These cells, which show intense immunoreactivity for calbindin and calretinin, are characterized by their large size and axonal projection. They remain in the marginal zone after the formation of the cortical plate; they project first into the ventricular zone, and then into the subplate and the internal capsule. Therefore, these cells are the origin of the earliest efferent pathway of the developing cortex. Pioneer neurons are only present in prenatal brains. The second class is formed by subpial granule neurons, which form the subpial granular layer (SGL), previously considered to be found exclusively in the human cortex. SGL neurons are smaller than pioneer neurons. They are generated in a transient compartment of the retrobulbar ventricle between E12 and E14, and we propose the hypothesis that they invade the marginal zone, through tangential subpial migration, at different moments of fetal life. SGL neurons contain calbindin, calretinin, and gamma-aminobutyric acid (GABA), but the GABA-immunoreactive group becomes inconspicuous before birth. The extracellular matrix-like glycoprotein reelin, a molecule crucial for cortical lamination, is prenatally expressed by SGL neurons; postnatally, it is present in both Cajal-Retzius cells and subpial pyriform cells, both derivatives of SGL cells. In the rat, Cajal-Retzius cells are horizontal neurons that remain only until the end of the first postnatal week. They are located in layer I at a critical distance of approximately 20 microm from the pial surface and express reelin and, only occasionally, calretinin. Subpial pyriform cells coexpress reelin and calretinin and remain in layer I longer than Cajal-Retzius cells. Both pioneer neurons and subpial granule neurons are specific to the cortex. They mark the limit between the rudimentary cerebral cortex and olfactory bulb in the rat during early corticogenesis.

Aging↗

PubMed1998

Prenatal development of reelin-immunoreactive neurons in the human neocortex.

Reelin, the protein defective in reeler mutant mice, is a secreted glycoprotein involved in the architectonic development of the central nervous system, more particularly in the development of neocortical lamination. In mice, reelin mRNA and protein expression are most robust in horizontal neurons of the embryonic marginal zone (MZ). By using monoclonal anti-reelin antibodies (de Bergeyck et al. [1998] J. Neurosci. Methods), the morphology and evolution of reelin-expressing neurons were studied in the MZ of the prenatal human neocortex. At 11 gestational weeks (GW), the MZ contained a single layer of reelin-positive mono- or bipolar horizontal Cajal-Retzius (CR) cells. From 14 GW onward, the subpial granular layer (SGL) invaded the MZ, forming a transient layer of undifferentiated, initially reelin-negative granule cells. In parallel to the emergence of the SGL and the morphological differentiation of the CR cells, a second population of reelin-positive cells appeared within the SGL. These cells, termed CR-like cells, were intermediate in size and shape between the CR cells and SGL granule cells. Between 16 GW and 24 GW, the packing density of the reelin-producing cells remained remarkably stable, despite the continuous growth of the cortical surface. During this period, CR cells settled progressively deeper within the MZ, although they remained in contact with the pial surface through radially ascending processes. Most CR cells disappeared at around 27 GW, in parallel with the dissolution of the SGL. During the last weeks of gestation, reelin was expressed by a few medium-sized, often horizontal neurons. These observations show that different neuronal populations in the human MZ express reelin and suggest that a possible function of the SGL is to supply reelin-producing cells through a gradual transformation of reelin-negative precursor cells into reelin-immunoreactive CR-like cells, thus coping with the protracted neurogenesis and dramatic surface expansion of the human neocortex.

Calbindin 2↗

PubMed1998

Changes in the secretory activity of the subcommissural organ of spontaneously hypertensive rats.

The subcommissural organ (SCO) is a glandular circumventricular organ secreting glycoproteins into the cerebrospinal fluid. The SCO of 15-week-old spontaneously hypertensive rats (SHR) and of matched normotensive Wistar-Kyoto rats (WKY) was studied immunocytochemically by using an antibody against the glycoproteins secreted by the SCO. The blood pressure, water intake and volume of brain ventricles of SHR and WKY rats were also recorded. The SHR were hypertensive, drank more water and did not display dilatation of the brain ventricles. The SCO of the SHR rats showed a drastic decrease of the immunoreactive material stored in the rough endoplasmic reticulum whereas the amount of immunoreactive apical secretory granules did not vary with respect to the SCO of WKY rats. These changes are compatible with an increased secretory activity of the SCO of the SHR rats. It is suggested that the changes in the SCO of SHR rats, and their hypertensive state, are interrelated phenomena.

Animals↗

PubMed1998

The acquisition of skilled motor performance: fast and slow experience-driven changes in primary motor cortex.

Behavioral and neurophysiological studies suggest that skill learning can be mediated by discrete, experience-driven changes within specific neural representations subserving the performance of the trained task. We have shown that a few minutes of daily practice on a sequential finger opposition task induced large, incremental performance gains over a few weeks of training. These gains did not generalize to the contralateral hand nor to a matched sequence of identical component movements, suggesting that a lateralized representation of the learned sequence of movements evolved through practice. This interpretation was supported by functional MRI data showing that a more extensive representation of the trained sequence emerged in primary motor cortex after 3 weeks of training. The imaging data, however, also indicated important changes occurring in primary motor cortex during the initial scanning sessions, which we proposed may reflect the setting up of a task-specific motor processing routine. Here we provide behavioral and functional MRI data on experience-dependent changes induced by a limited amount of repetitions within the first imaging session. We show that this limited training experience can be sufficient to trigger performance gains that require time to become evident. We propose that skilled motor performance is acquired in several stages: "fast" learning, an initial, within-session improvement phase, followed by a period of consolidation of several hours duration, and then "slow" learning, consisting of delayed, incremental gains in performance emerging after continued practice. This time course may reflect basic mechanisms of neuronal plasticity in the adult brain that subserve the acquisition and retention of many different skills.

Adult↗

PubMed1998

Recruitment of a nicotinic acetylcholine receptor mutant lacking cytoplasmic tyrosine residues in its beta subunit into agrin-induced aggregates.

During synaptogenesis at the vertebrate skeletal neuromuscular junction, acetylcholine receptors (AChRs) form high-density aggregates opposite the presynaptic terminal in response to nerve-derived agrin. Agrin has been shown to stimulate tyrosine phosphorylation of a muscle-specific receptor tyrosine kinase MuSK and of the AChR beta subunit, and tyrosine kinase inhibitors and a tyrosine kinase-deficient mutant of MuSK prevent AChR aggregation. To evaluate the role of tyrosine phosphorylation of the AChR beta subunit in receptor aggregation, we replaced all three putative cytoplasmic tyrosine residues of the AChR beta subunit with phenylalanine residues and expressed the mutant receptors in cultured myotubes. Upon agrin treatment, transfected myotubes formed AChR aggregates that contained receptors with mutant beta subunits. Thus, AChRs can be recruited into agrin-induced specializations by protein-protein interactions that do not depend on tyrosine phosphorylation of the AChR beta subunit.

Agrin↗

PubMed1998

Technetium-99m mercaptoacetyltriglycine clearance values in children with minimal renal disease: can a normal range be determined?

Use of technetium-99m labelled mercaptoacetyltriglycine (99mTc-MAG3) simplifies and improves the quantification of renal clearance in children by virtue of its permanent availability, good imaging properties and low radiation exposure. Due to the lack of reference values for 99mTc-MAG3 clearance in children, the Paediatric Task Group of the EANM initiated a multicentre study to evaluate 99mTc-MAG3 clearance values in children with minimal renal disease. One hundred and twenty-five children aged between 12 months and 17 years, classified as renally healthy using defined diagnostic criteria, were included in the study. 99mTc-MAG3 clearance was calculated using an algorithm on the basis of a single blood sample taken at any time between 30 and 40 min after tracer injection. In addition, the absolute 99m-Tc-MAG3 clearance values were normalized to body surface area. For further evaluation the children were classified into several groups according to age. There was a continuous increase in non-corrected 99mTc-MAG3 clearance values from the age of 1 year up to the age of 17 years (mean value <2 years: 98+/-57 ml/min; mean value >8 years: 208+/-66 ml/min). Normal clearance values for adults were achieved by the age of 8 years. Analysis of the relationship between non-corrected clearance and age yielded a correlation coefficient of r=0.7. When these absolute clearance values were normalized to body surface area, we found nearly constant clearance values for all age groups, with a mean clearance value of 315+/-114 ml/minx1.73 m2. The correlation coefficient for the relationship between normalized clearance and age was r=0.28. In conclusion, the clearance of 99mTc-MAG3 increases continuously throughout childhood into adolescence due to the maturation and growth of the kidney. After normalization of the absolute clearance to body surface area, no correlation between clearance and age could be proven.

Child↗

PubMed1998

Longitudinal monthly body measurements from 1 to 12 months of age: a study by practitioners for practitioners. Zurich Association of Practicing Paediatricians.

UNLABELLED: A longitudinal growth study with monthly measurements during the 1st year of life was conducted by nine paediatricians working in private practice in Zurich. Of 92 children, none was lost to the study and only 32 of 1104 planned visits were missed; the quality of the measurements was comparable to that of a specialised university clinic. Compared to the Zurich Longitudinal Growth Studies, children of this study were considerably heavier and taller. In 92% of the subjects, growth velocity was at least once outside the reference range (3rd 97th percentile). For weight increments, the corresponding proportion was 87%. CONCLUSIONS: The data indicate that current standards for the 1st year of life for the Zurich area might no longer be appropriate and need to be updated. The currently used velocity percentiles based on 3-monthly measurements are not suitable to assess individual height and weight increments calculated from monthly measurements.

Anthropometry↗

PubMed1998

Laparoscopic splenectomy for idiopathic thrombocytopenic purpura. A 1-year follow-up study.

BACKGROUND: Laparoscopic splenectomy is a novel approach for the treatment of idiopathic thrombocytopenic purpura (ITP) in patients requiring surgical intervention. This technique was used for treatment in 16 consecutive patients. Follow-up was initiated at a median of 13.5 months after surgery to determine whether or not laparoscopic splenectomy is a safe and successful procedure that should be used in all patients requiring splenectomy for ITP. METHODS: Sixteen patients underwent laparoscopic splenectomy for ITP between May 1994 and September 1996. They were evaluated prospectively prior to surgery, immediately following surgery, at discharge, and at 13.5 months following surgery (n = 14) to determine the short- and long-term results of the procedure. RESULTS: Mean operation time was 123.4 +/- 12.1 min, and there were no significant intra- or postoperative complications. Mean intraoperative blood loss was 437.5 +/- 73.5 ml. Autologous blood transfusion was necessary in one patient (6.3%). Mean organ weight was 202.2 +/- 47.3 g. Mean postoperative hospital stay was 4.6 +/- 0. 4 days. Before discharge, mean platelet count rose by 100.7%. At follow-up (13.5 months postoperatively), it was 77.7% above preoperative values. No additional surgery was necessary in any of the patients undergoing laparoscopic splenectomy, and hematologic success was achieved in 12 patients (85.7%). CONCLUSIONS: Our results clearly indicate that laparoscopic splenectomy is a safe and successful procedure in patients suffering from ITP. It offers the well-known advantages of minimal invasive surgery as well as the surgical effectiveness of the open approach. This surgical technique should therefore be considered in all patients requiring splenectomy for the treatment of ITP.

Adolescent↗

PubMed1998

Incidence and predictors of major hemorrhagic complications from thrombolytic therapy in patients with massive pulmonary embolism.

PURPOSE: The risk factors for bleeding in patients receiving recombinant tissue-type plasminogen activator for massive pulmonary embolism are not known. PATIENTS AND METHODS: The hospital records of 132 consecutive patients who received recombinant tissue-type plasminogen activator for massive pulmonary embolism were retrospectively reviewed. Bleeding was estimated by using the bleeding severity index, a method previously validated in patients receiving anticoagulants. Multivariate stepwise logistic regression was used to identify independent risk factors for bleeding. Four other definitions of bleeding in large pulmonary embolism thrombolytic trials were also used, and the agreement among these criteria was assessed. RESULTS: According to the bleeding severity index, 33 patients (25%) had one or more major bleeding complications. Hemorrhage at the venous puncture site for angiography was the most frequent complication (15 patients, 11%). Major bleeding at the catheterization site was more common at the femoral site (14 of 63 patients = 22%) than at the brachial site (1 of 63 patients = 2%; P = 0.0004). The use of the five different bleeding definitions resulted in a variation in the major bleeding rate from 3% to 43%. The kappa coefficient varied from 0.07 to 0.84, indicating poor agreement between most of the classifications. CONCLUSION: The use of the femoral vein for pulmonary angiography was the only variable significantly associated with major bleeding. Most of the differences observed in the pulmonary embolism thrombolytic trials are likely related to the differences in the definition of bleeding rather than to the thrombolytic regimen.

Aged↗

PubMed1998

Diagnostic value of two rapid and individual D-dimer assays in patients with clinically suspected pulmonary embolism: comparison with microplate enzyme-linked immunosorbent assay.

A semiquantitative enzyme-linked immunosorbent assay (ELISA) test (Instant IA D-dimer) and a new quantitative rapid and individual test (STA-Liatest DDi) were compared with the reference microplate ELISA (Asserachrom D-Di) for D-dimer testing in 142 patients clinically suspected of pulmonary embolism, on the basis of clinical symptoms and signs, electrocardiogram, blood gases and chest X-Ray abnormalities. The cut-off value for the quantitative tests was 500 ng/ml and Instant IA was interpreted by three readers. Pulmonary embolism was confirmed by lung scan or angiography in 60 patients (42%). The sensitivities of ELISA and STA-Liatest DDi were 92% [95% confidence interval (CI) 82-97%] and 93% (95% CI 84-98%), respectively. The three readings of Instant IA D-dimer disagreed in 27 (19%) of the patients and sensitivity varied from 83 to 93% according to the readers. In the 115 patients with concordant readings, sensitivity was 92% (95% CI 82-98%). These results suggest that STA Liatest DDi may be used instead of microplate ELISA for the exclusion of pulmonary embolism, whereas the use of Instant IA D-dimer for this purpose is limited by the number of discordant results.

Adult↗

PubMed1998

Bovine herpesvirus type 1 glycoprotein H is essential for penetration and propagation in cell culture.

Bovine herpesvirus type 1 (BHV-1) glycoprotein H (gH) is a structural component of the virion which forms a complex with glycoprotein gL. To study the role of BHV-1 gH in the virus infectious cycle, a gH null mutant was constructed in which the gH coding sequences were deleted and replaced by the Escherichia coli lacZ cassette. The BHV-1 gH null mutant was propagated in trans-complementing MDBK cells, stably transfected with plasmid pMEP4 containing the BHV-1 gH gene under the control of the inducible mouse metallothionein promoter. Experiments with the BHV-1 gH null mutant showed that gH is essential in the infectious cycle of the virus and is specifically involved in virus entry and cell-to-cell spread. The lack of infectivity of virions devoid of gH is not due to a defect in attachment. Moreover, PEG-induced fusion of virions to target cells provides evidence that BHV-1 gH is required for virion penetration.

Animals↗