Biomedical subjects

J Alexander

Publications and source records attributed to J Alexander.

At least 253 records · Page 14Linked to original sources

PubMed1996

Determination of aluminium in samples from bone and liver of elderly Norwegians.

Recent reports associating aluminium with several skeletal and neurological disorders in humans suggest that exposure to aluminium may pose a health hazard. In connection with an epidemiological study on aluminium and Alzheimer's disease, information on the body burden of aluminium was needed. Aluminium is stored in the body mainly in bone and soft tissues such as the liver. Therefore, an analytical procedure was developed for the determination of aluminium in the head of femur and the liver using graphite furnace atomic absorption spectrometry. Problems in such analyses are associated with low levels of aluminium, risk of contamination during sample preparation, inhomogeneity of the sample tissues, and complexity of the matrices. Bone samples gave poorer repeatability compared to liver samples and up to four replicate analyses were performed. In the analyses of the digested bone samples, severe chemical interference occurred when these either contained much dissolved bone mineral or had a high A1 concentration. It is possible that this interference is brought about by formation of aluminium phosphate in the graphite tube. The analytical results for bones are given relative to ash weight because the samples sometimes contained a lot of fat. The ash weight of the bone tissue varied between 8 and 69 per cent. The material consisted of 84 samples of head of femur and 95 liver samples from deceased elderly Norwegians. Two cases had high A1 levels in bone (16.8 and 18.0 mg/kg ash weight) and liver (10 and 22.7 mg/kg dry weight) tissues. The remaining cases showed about ten to fifteen-fold variation of the A1 level in both liver (0.4 - 5.7 mg/kg) and bone (0.5 - 5.8 mg/kg). There was no correlation between the level in liver and bone when the two cases with the highest levels were excluded.

Aged↗

PubMed1996

Effect of acetylator genotype on 3,2'-dimethyl-4-aminobiphenyl induced aberrant crypt foci in the colon of hamsters.

Aberrant crypt foci (ACF) are assumed to be preneoplastic lesions in both rodent and human carcinogenesis. The colon carcinogen 3,2'-dimethyl-4-aminobiphenyl (DMAB), like other arylamines, undergoes N-acetylation and O-acetylation by polymorphic acetyltransferase (NAT2). In the present study we characterized ACF in hamster colon for the first time and compared the ability of DMAB to induce ACF in homozygous rapid and slow acetylator congenic Syrian hamsters (Bio 1.5/H-NAT2r and Bio 1.5/H-NAT2s, respectively), differing only at the NAT2 gene locus and other closely linked loci. The animals received DMAB (75 mg/kg body weight s.c.) or vehicle (PBS/DMSO 1:1) as a control, twice weekly for 2 weeks, then once a week for 4 weeks. Ten weeks after the first injection ACF were observed in the DMAB treated hamsters, but not in the controls. However, the number of ACF was three times higher (P=0.016) in the colons of the NAT2r hamsters compared with the colons of the NAT2s hamsters. In the two congenic hamster lines we also studied the induction of ACF with 1,2-dimethylhydrazine (DMH) treatment, a colon carcinogen not metabolized by NAT2. Hamsters given DMH (25 mg/kg body weight s.c.), once a week for 3 weeks, showed ACF induction in the colon after 10 weeks, but there was no difference between the NAT2r and NAT2s hamsters. Further scanning electron microscopic and histological examination of ACF observed with the light microscope, revealed the same gross morphology and therefore confirmed the basis for the scoring of ACF. The ACF in hamster colons were principle similar to the lesions observed in other species.

Acetylation↗

PubMed1996

Biotransformation of the cyclopenta-fused polycyclic aromatic hydrocarbon benz[j]aceanthrylene in isolated rat liver cell: identification of nine new metabolites.

The biotransformation of benz[j]aceanthrylene (B[j]A) was studied in suspensions of hepatocytes isolated from Aroclor 1254-treated or untreated rats. Using radiolabeled cofactors and metabolic inhibitors combined with UV, mass and 1H-NMR spectroscopy, we have detected five known metabolites and characterized nine new metabolites: metabolite 1 was tentatively assigned as B[j]A-1,2-dihydrodiol-8-sulfate; metabolite 2, B[j]A-1,2,9,10-tetrahydrotetrol; metabolite 3, B[j]A-1,2-dihydrodiol-10-O-glucuronide; metabolite 4, B[j]A-1-one-8-sulfate; metabolite 5, B[j]A-1,2-dihydrodiol-10-sulfate; metabolite 6, the sulfate conjugate of B[j]A-dihydrodiol-phenol; peak 7 in the chromatogram is a mixture of one glutathione conjugate and two sulfate conjugates of a B[j]A-metabolite; metabolite 8, B[j]A-10-O-glucuronide; metabolite 8', B[j]A-1,2-dihydrodiol; metabolite 9, B[j]A-10-sulfate; metabolite 9', B[j]A-9,10-dihydrodiol and metabolite 10, B[j]A-9,10-dihydro-9-hydroxy-10-sulfate. The metabolites identified support the notion that epoxidation at the cyclopenta region is an important activation step of B[j]A. Furthermore, sulfation appears to play a very important role in the conversion of hydroxylated B[j]A metabolites into more polar excretable products.

Animals↗

PubMed1996

Content of brain aluminum is not elevated in Alzheimer disease.

Several studies have reported that the bulk aluminum (Al) concentration is increased in the brain in Alzheimer disease (AD), while other studies have failed to demonstrate an increase. Most of these investigations have had one or more methodological deficiencies, including lack of adequate neuropathological assessment; failure to age-match the control samples; small sample sizes, lacking statistical power; and geographical heterogeneity in the AD and control populations. The present population-based study of 92 clinically and histopathologically diagnosed AD patients and normal elderly nursing home residents was designed to avoid these potential biases. When a subsample of AD cases with the most severe brain pathology was compared with controls having no or minimal pathology, no statistically significant differences were found in the bulk aluminum concentration measured by graphite furnace atomic absorption spectrometry in frontal cortex (1.8 +/- 0.7 vs. 1.7 +/- 0.7 micrograms/g dry wt), temporal cortex (1.4 +/- 0.3 vs. 1.5 +/- 0.5 micrograms/g dry wt), liver (2.0 +/- 1.3 vs. 2.0 +/- 1.2 micrograms/g dry wt), or head of femur (2.4 +/- 1.6 vs. 2.2 +/- 1.0 micrograms/g ash wt). Within the whole series of 92 cases, there was no difference in the bulk aluminum concentration of the frontal cortex between individuals diagnosed as definite, probable, and possible cases of AD using the CERAD (Consortium to Establish a Registry for Alzheimer's Disease) criteria. The density of senile plaques and neurofibrillary tangles in frontal and temporal cortex showed no correlation with the bulk aluminum concentration. Logistic regression analyses, which controlled for age and sex, did not influence outcome for any of the comparisons. The data show conclusively that in AD, bulk aluminum concentration is not increased in two cortical brain regions that are selectively vulnerable to the neuropathological changes associated with this disorder.

Aged↗

PubMed1996

Different roles for interleukin-4 during the course of Toxoplasma gondii infection.

The course of Toxoplasma gondii infection from initiation of disease perorally until day 28 postinfection was compared between interleukin-4 (IL-4) gene knockout (IL-4-/-) mice and their wild-type (IL-4+/+) counterparts on a disease-susceptible genetic background. The rate of mortality was significantly greater in mice deficient in Il-4 than in the immunocompetent controls. Although levels of T. gondii-specific spleen cell proliferation measured in vitro were similar between groups at all time points examined throughout infection, the quantities of cytokines released into the culture supernatant differed. Culture supernatants from spleen cells derived from IL-4-deficient mice contained significantly more gamma interferon than those derived from IL-4+/+ mice at day 7 postinfection. Conversely, IL-10 production was significantly greater from the spleen cells derived from wild-type mice at day 28 postinfection. Splenocytes from both groups of mice had a marked inhibition of proliferation in response to soluble tachyzoite antigen as well as reduced proliferation in response to concanavalin A between days 7 and 14 postinfection and marked proliferation on days 21 and 28 postinfection. At day 28 postinfection, histological examination of the brains indicated that IL-4+/+ mice had more severe pathological changes and more cysts than IL-4-/- mice. In addition, although many nonencysted single organisms were present in IL-4+/+ mice within both necrotic lesions and microglial nodules, few nonencysted parasites were found, and no necrotic lesions were present in IL-4-deficient animals. These results suggest that the observed reduction in mortality during the early acute phases of infection may be due to the down-regulatory effects of Il-4 or associated Th2-derived products on proinflammatory cytokines such as gamma interferon. However, the long-term effects of IL-4 are detrimental, possibly because of the ability of this cytokine to inhibit proinflammatory antiparasitic products. This may explain the increased parasite multiplication with cysts observed in the brains of IL-4+/+ mice.

Animals↗

PubMed1996

Langerhan's cell histiocytosis complicating small bowel Crohn's disease.

Langerhan's cell histiocytosis is a rare infiltrative disorder of unknown aetiology. A variety of tissues may be affected, but clinically evident intestinal involvement is unusual. An adult patient is described with Crohn's disease of the terminal ileum who subsequently developed Langerhan's cell histiocytosis with extensive infiltration of the small bowel.

Aged↗

PubMed1996

Bidirectional augmentation of heart rate regulation by autonomic nervous system in rabbits.

Although the characteristics of the static interaction between the sympathetic and parasympathetic nervous systems in regulating heart rate (HR) have been well established, how the dynamic interaction modulates the HR response remains unknown. We therefore investigated dynamic interaction by estimating the transfer function from nerve stimulation to HR using a band-limited Gaussian white-noise technique. The transfer function relating dynamic sympathetic stimulation to HR had characteristics of a second-order low-pass filter. Simultaneous tonic vagal stimulation at 5 and 10 Hz increased gain of the transfer function by 55.0 +/- 40.1 and 80.7 +/- 50.5%, respectively (P < 0.05). The transfer function from dynamic vagal stimulation to HR had characteristics of a first-order low-pass filter. Simultaneous tonic sympathetic stimulation at 5 and 10 Hz increased the gain by 18.2 +/- 17.9 and 24.1 +/- 18.0%, respectively (P < 0.05). Thus interaction augmented dynamic gain bidirectionally, even though it affected mean HR antagonistically. By virtue of this interaction, the autonomic nervous system appears to extend its dynamic range of operation.

Animals↗

PubMed1996

Neural arc of baroreflex optimizes dynamic pressure regulation in achieving both stability and quickness.

The baroreflex loop consists of a fast neural arc and a slow mechanical arc. We hypothesized that the neural baroreflex arc compensates the slow mechanical response and thus improves the quality of blood pressure regulation. We estimated the open-loop transfer characteristics of the neural baroreflex arc (HP), i.e., from carotid sinus pressure to sympathetic nerve activity (SNA), and that of the effective peripheral baroreflex arc (Hp), i.e., from SNA to arterial pressure, in anesthetized rabbits. The gain of Hn was constant below 0.12 +/- 0.057 Hz and increased with a slope of 6.1 +/- 0.06 dB/octave above its frequency up to 1 Hz. In contrast, the gain of Hp was constant below 0.071 +/- 0.03 Hz and decreased with a slope of -11.0 +/- 1.48 dB/octave above the frequency. These data indicate that Hn accelerates slow peripheral responses in the frequency range of 0.1-1 Hz. Although too much acceleration in the high-frequency range could result in instability of the system, numerical analysis of the closed-loop baroreflex response indicated that the neural arc optimized arterial pressure regulation in achieving both stability and quickness.

Animals↗

PubMed1996

PCDDs, PCDFs, and PCBs in human blood in relation to consumption of crabs from a contaminated Fjord area in Norway.

Consumption of fish and shellfish from contaminated areas may be an important source of human exposure to persistent organohalogen compounds such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs). We determined concentrations of 2,3,7,8-substituted PCDDs and PCDFs and 19 PCB congeners in whole blood samples from three groups of men, 40-54 years of age, with different consumption levels of crabs from a fjord area in southern Norway polluted with organochlorine compounds from a magnesium production plant. A significant increase of many PCDD/PCDF congeners was found in the blood when comparing the referents, moderate-, and high-intake groups. The greatest difference was observed for several of the PCDFs that are characteristic for the contamination of the marine biota of the fjord. PCBs, in general, play a minor role in the contamination of the fjord by the magnesium production process, except for the highly chlorinated congeners such as PCB-209. Nevertheless, almost all PCBs increased from the referents to the high-intake group. However, the relative concentrations of several highly chlorinated PCBs (particularly PCB-209) in blood are unexpectedly low compared to their abundance in crabs, indicating low uptake of these congeners. The exposure to PCDDs/PCDFs from crab consumption calculated from individual body burdens of these compounds were in good agreement with the intake estimated from previously measured concentrations in crabs, reported fishing sites, and consumption. Almost all subjects in the high-intake group exceeded the tolerable weekly intake of 35 pg TEQ/kg body weight/week proposed by a Nordic Expert Group.

Adult↗

PubMed1996

Managed care and physician/hospital integration.

This paper examines the extent to which hospitals and physicians use new organizational structures designed to facilitate contracting with managed care firms and the extent to which this use is associated with managed care revenue. The data come from a nationally representative sample of 1,495 U.S. community hospitals responding to a 1993 survey about different organizational structures. The results indicate that only 23.3 percent of hospitals participate in at least one form. Hospitals with more than 15 percent of revenues from managed care are twice as likely to participate and favor forms that provide tighter linkages with physicians.

Delivery of Health Care, Integrated↗

PubMed1996

The influence of cytokines on the adhesion of renal cancer cells to endothelium.

PURPOSE: The development of tumor metastasis requires direct adhesive interactions between tumor cells and vascular endothelium. We examined the adherence of renal cell carcinoma (RCC) lines to endothelium after stimulation with different cytokines that induce expression of the vascular adhesion molecules endothelial leukocyte adhesion molecule (ELAM)-1, vascular cell adhesion molecule (VCAM)-1 and intercellular adhesion molecule (ICAM)-1, MATERIALS AND METHODS: Human umbilical vein endothelial cells (HUVEC) were used to determine the adhesion of the RCC lines CCF-RC1, 2 and 7 to endothelium. Expression of cell adhesion molecules (CAM) on HUVEC and RCC lines was measured with immunoflowcytometry. RESULTS: Stimulation of HUVEC with rIl-1 beta, rTNF-alpha, or PMA resulted in a time-dependent 1.4- to 2.9-fold increase of RCC adhesion to HUVEC. Significant increased tumor cell binding was observed after 4 hours and paralleled the time-dependent induction of ELAM-1 and VCAM-1. Immunocytometry demonstrated the presence of the ligands sialyl Lewis X and VLA-4 on RCC, and blocking studies with monoclonal antibodies directed against tumor cell-endothelial interactions mediated by VCAM-1/VLA-4 and ELAM-1/sialyl Lewis X demonstrated marked inhibition of tumor cell adherence to cytokine-stimulated HUVEC. CONCLUSIONS: This study demonstrates that cytokine-induced increases in RCC adherence to HUVEC are mediated in part by VCAM-1/VLA-4 and ELAM-1/sialyl Lewis X interactions and suggest that these molecules may play an important role in the ability of RCC to metastasize.

Carcinoma, Renal Cell↗

PubMed1996

Tissue expansion vaginoplasty for treatment of congenital vaginal agenesis.

BACKGROUND: A patient with congenital vaginal agenesis was unsuccessful in the use of dilation to create a vaginal orifice and rejected the option of a buttock graft. CASE: Two tissue expanders were introduced beneath the labia majora bilaterally and slowly expanded over 4 weeks. Redundant labial tissue was advanced as a bipedicle flap to line the neovagina created intraoperatively. Postoperative stent placement and dilation resulted in a vaginal canal lined by full-thickness mucosa exceeding 8 cm in depth. CONCLUSION: A modified method of tissue expansion vaginoplasty using a bipedicle flap is an option for the surgical creation of a vaginal orifice.

Adult↗

PubMed1996

Managing care, incentives, and information: an exploratory look inside the "black box" of hospital efficiency.

OBJECTIVE: We sought to estimate the impact of individual dimensions of hospitals' managed care strategies on the cost per hospital discharge. STUDY SETTING/DATA SOURCES: Thirty-seven member hospitals of seven health systems in the Pacific, Rocky Mountain, and Southwest regions of the United States were studied. STUDY DESIGN: Separate cross-sectional regression analyses of 21,135 inpatient discharges were performed in 1991 and 23,262 discharges in 1992. The multivariate model was estimated with hospital cost per discharge as the dependent variable. Model robustness was checked by comparing regression results at the individual discharge level with those at the level of the hospital/clinical condition pair. DATA COLLECTION/EXTRACTION METHODS: Information on hospitals' managed care strategies was provided by mail and phone survey of key informants in 1991 and 1992. Other hospital characteristics were collected from AHA Annual Survey data, and discharge data from hospital abstracting systems. PRINCIPAL FINDINGS: The pooled discharge analysis indicated three dimensions of hospital managed care strategy that consistently related to lower costs per hospital discharge: the proportion of hospital revenues derived from per case or capitation payment, the hospital's mechanisms for sharing information on resource consumption with clinicians, and the use of formalized, systematic care coordination mechanisms. CONCLUSIONS: Three strategies appear to hold promise for enhancing the efficiency of inpatient resource use: (1) "fixed price" hospital payment incentives, (2) hospital approaches to sharing resource use information with clinicians, and (3) the application of formal care management mechanisms for specific clinical conditions.

Aged↗

PubMed1996

Radiation injury.

Despite advance radiotherapy techniques, long-term complications of radiation injury are still commonly seen. Acute effects are largely time dependent and can be controlled by alteration of therapy schedule. Chronic effects are dose dependent, and are associated with increased fibrosis and decreased vascularity which can lead to tissue necrosis, infection, and ulceration. The damaging effects of radiation therapy may not be clinically apparent for months or even years after treatment is given. The most commonly accepted theory explaining the effects of radiation injury on tissue healing has focused on decreased vascularity and hypoxia in affected tissues. More recently, impaired leukocyte function has been implicated as an additional factor in the pathophysiology of radiation injury. Reconstructive surgical plans may require alteration when operating in a radiated field, especially in the head and neck. Radiation wounds are best treated by standard, accepted techniques of thorough debridement and coverage with well-vascularized tissue. Hyperbaric oxygen may have a role in the management of early radiation injury or in prophylaxis against postoperative wound complications.

Chronic Disease↗

PubMed1995

Major histocompatibility complex binding affinity of an antigenic determinant is crucial for the differential secretion of interleukin 4/5 or interferon gamma by T cells.

Differential activation of CD4+ T-cell precursors in vivo leads to the development of effectors with unique patterns of lymphokine secretion. To investigate whether the differential pattern of lymphokine secretion is influenced by factors associated with either the display and/or recognition of the ligand, we have used a set of ligands with various class II binding affinities but unchanged T-cell specificity. The ligand that exhibited approximately 10,000-fold higher binding to I-Au considerably increased the frequency of interferon gamma-producing but not interleukin (IL) 4- or IL-5-secreting cells in vivo. Using an established ligand-specific, CD4+ T-cell clone secreting only IL-4, we also demonstrated that stimulation with the highest affinity ligand resulted in interferon gamma production in vitro. In contrast, ligands that demonstrated relatively lower class II binding induced only IL-4 secretion. These data suggest that the major histocompatibility complex binding affinity of antigenic determinants, leading to differential interactions at the T cell-antigen-presenting cell interface, can be crucial for the differential development of cytokine patterns in T cells.

Amino Acid Sequence↗

PubMed1995

T helper 2 cells are subject to high dose oral tolerance and are not essential for its induction.

Oral administration of aqueous protein Ag results in profound immunologic tolerance, and it has been suggested previously that this reflects selective activation of Th subsets. Here we show that the induction of oral tolerance by feeding a single high dose of OVA to mice significantly reduces the production of both Th1- and Th2-dependent cytokines and is accompanied by a marked reduction of specific Abs of both the IgG2a and IgG1 isotypes in vivo. Oral tolerance was also induced normally in IL-4-deficient mice. These results indicate that both subsets of the Th cell are equally susceptible to the induction of tolerance with a single high dose of Ag delivered via the oral route and that this phenomenon does not require Th2 cells.

Administration, Oral↗

PubMed1995

[Target dose markers. Exposure indicators for environmental epidemiological studies].

It is of major importance to have good characterization of individual exposures in environmental epidemiological studies. Quantification of the dose at the site of action (target dose, biologically effective dose) gives the best correlation with health outcome. Target dose markers are indicators which have recently been applied in environmental epidemiological studies. Especially, measurements of adducts to macromolecules (DNA, protein) have been much used. The authors give an overview over available exposure markers, focusing on studies were target dose markers have been employed. It is important to be aware of the limitations associated with the use of such markers.

Biomarkers↗

PubMed1995

Experimental autoimmune encephalomyelitis-resistant mice have highly encephalitogenic myelin basic protein (MBP)-specific T cell clones that recognize a MBP peptide with high affinity for MHC class II.

BALB/c mice are resistant to disease induction when experimental protocols that induce experimental autoimmune encephalomyelitis (EAE) in susceptible strains of animals are used. We have previously described a panel of myelin basic protein (MBP)-specific CD4+ T cell clones from BALB/c mice, two of which induce moderate EAE when transferred to syngeneic recipients. These clones are I-E(d) restricted and recognize residues 151-160 of mouse MBP. Here, we describe a series of 17 MBP-reactive T cell clones, which were derived from two BALB/c mice. All are I-A(d) restricted and recognize nested epitopes in peptide 59-76 of mouse MBP. Four different TCR V beta chains are used by this panel of clones; these include V beta 8.2 (10/17), V beta 8.1 (2/17), V beta 7 (3/17), and V beta 14 (2/17). Twelve of fourteen clones tested adoptively transferred severe demyelinating EAE to syngeneic recipients. Studies of relative binding affinities of MBP peptides to class II molecules I-A(d) and I-E(d) show that peptide 59-76 binds with extremely high affinity to I-A(d), whereas three peptides that contains residues 151-160 bind poorly to I-E(d). These results are consistent with a growing number of reports that show that high affinity binding to class II is required for autoantigenic stimulation. Despite encephalitogenicity of 59-76-reactive T cells, active immunization of BALB/c mice with peptide 59-76 in adjuvant failed to induce either clinical or histologic signs of EAE. The implications of these findings for mechanisms of genetically determined EAE resistance are discussed.

Amino Acid Sequence↗