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Biomedical subjects

J M Anderson

Publications and source records attributed to J M Anderson.

At least 217 records · Page 12Linked to original sources
PubMed1993

Staphylococcus epidermidis adhesion to hydrophobic biomedical polymer is mediated by platelets.

A quantitative investigation on the effects of plasma proteins and platelets on the adhesion of Staphylococcus epidermidis RP62A to a hydrophobic biomedical polymer (National Heart, Lung, and Blood Institute reference polyethylene) was carried out under well-defined shear conditions approximating human blood circulation by using a rotating disk system. The results showed that contact-activated platelets mediated S. epidermidis adhesion to the polymer surface. In the range of physiologic shear conditions, the adhesive coefficient (ratio of bacteria per unit area to the product of bacterial flux and the duration of the experiment) to platelets was significantly greater than to the protein-adsorbed polyethylene surface by at least one order of magnitude (P < or = .01). The presence of absorbed plasma proteins on polyethylene reduced the adhesion of S. epidermidis compared with that seen with the bare polymer surface. These studies show that S. epidermidis adhesion to polyethylene is mediated by contact-activated platelets, not absorbed plasma proteins.

Adsorption↗
PubMed1993

Transoesophageal versus transchest DC cardioversion.

Attempted cardioversion via the oesophagus (transoesophageal cardioversion) was compared with the transchest approach (transchest cardioversion) in a randomized trial of 100 consecutive patients with atrial fibrillation. For the transoesophageal group, 30, 50 and 100 J were delivered via an oesophageal electrode with subsequent 200 and 360 J transchest if required. For the transchest group, 50, 100, 200 and 360 J were delivered if required. In the transoesophageal group, 36/50 (72%) of patients cardioverted using the transoesophageal route alone, and in the transchest group, 41/50 (82%) of patients cardioverted (p = NS). First shock success was similar for the transoesophageal and transchest groups: 13/50 (26%) vs. 8/50 (16%) respectively. The mean number of shocks required to achieve successful cardioversion was identical for the transoesophageal and transchest groups (2.6). However, transoesophageal cardioversion was more successful than transchest cardioversion at energies < or = 100 J (36/50 [72%], and 17/50 [34%], p < 0.05). Median total energy for successful cardioversion was lower for patients in the transoesophageal group (180 J) than the transchest group (350 J) and mean peak current at successful cardioversion was also lower for patients in the transoesophageal group (21.7 A) than the transchest group (27.3 A) (p < 0.05). No oesophageal complications occurred. Thus, using an oesophageal electrode, cardioversion can be achieved as successfully as using the transchest route. The transoesophageal approach offers a low impedance, and consequently a low-energy pathway for cardioversion.

Atrial Fibrillation↗
PubMed1993

Oral streptococcal colonization of infants.

The objective of this study was to determine the prevalence and proportions of different streptococcal species among the streptococcal flora during infancy. A total of 60 oral samples were collected by oral swabbing of the buccal mucosa and alveolar ridges of 18 infants before tooth eruption and from buccal and lingual surfaces of teeth after tooth eruption. A total of 549 isolates on mitis salivarius agar were speciated, principally by recently revised biochemical criteria of Kilian et al. Streptococcus mitis biovar 1 predominated, both in prevalence (89%) and proportion of oral streptococci recovered in each sample (median = 87% of streptococcal flora). Streptococcus salivarius was also prevalent (94%) but generally represented a small percentage of the total streptococcal flora (median = 3%). Streptococcus oralis and Streptococcus anginosus strains were detected in approximately one third of predentate and dentate infants in the first year of life. Streptococcus sanguis strains were not detected before tooth eruption, but could be detected in 7/14 of the infants with teeth. Thus, S. mitis constitutes the major component of the initially colonizing streptococcal microbiota of the young infant.

Alveolar Process↗
PubMed1993

Two classes of tight junctions are revealed by ZO-1 isoforms.

The tight junction forms the intercellular barrier separating tissue compartments. The characteristics of this barrier are remarkably diverse among different epithelia and endothelia and are not explained by our limited knowledge of its molecular composition. Two isoforms of the 220-kDa tight junction protein ZO-1 result from alternative RNA splicing and differ by an internal 80-amino acid domain, termed alpha (E. Willott, M. S. Balda, M. Heintzman, B. Jameson, and J. M. Anderson. Am. J. Physiol. 262 (Cell Physiol. 31): C1119-C1124, 1992). Using antibodies specific for each isoform and double-labeled immunofluorescence microscopy, we observed that the ZO-1 alpha- isoform is restricted to junctions of endothelial cells and highly specialized epithelial cells of both seminiferous tubules (Sertoli cells) and renal glomeruli (podocytes); in contrast, the ZO-1 alpha+ isoform is expressed in cells of all other epithelia examined. Both immunoblotting and ribonuclease protection analysis confirmed this pattern of expression. This distribution does not correlate with differences in junctional resistance or ultrastructural complexity. Instead, we observe a correlation with junctional plasticity; ZO-1 alpha- is expressed in structurally dynamic junctions, whereas ZO-1 alpha+ is expressed in those which are less dynamic. This is the first molecular distinction among tight junctions and reveals a fundamental dichotomy with implications for how the paracellular barriers of endothelia and epithelia are regulated.

Amino Acid Sequence↗
PubMed1993

ZO-1 maintains its spatial distribution but dissociates from junctional fibrils during tight junction regulation.

Tight junctions restrict diffusion of hydrophilic solutes through the paracellular pathways of columnar epithelia. It is now apparent that the barrier function of tight junctions is physiologically regulated. Current models of the tight junction envisage junctional subunits consisting of extracellular "kisses" between plasma membranes of adjacent cells, intramembrane components represented by freeze-fracture fibrils, and cytoplasmic elements of the cytoskeleton. Insights into functional relationships between these various components of tight junctions should be provided by mapping component interrelationships in states of altered junctional permeability. Here we define the spatial distribution of ZO-1 during a state of physiological regulation of intestinal absorptive cell tight junctions. Enhanced permeation of absorptive cell junctions in response to activation of apical membrane Na(+)-solute cotransporters does not lead to redistribution of the ZO-1 pool, as judged from quantitative ultrastructural immunolocalization studies employing two different ZO-1 antibodies. Surprisingly, ZO-1, which normally localizes under junctional kisses/fibrils, focally persists at sites where junctional kisses/fibrils are cleared. These findings suggest that 1) spatial redistribution of ZO-1 does not contribute to physiological regulation of junctions elicited by activation of Na(+)-solute cotransport and 2) ZO-1 and junctional fibrils may spatially dissociate during such regulated states.

Animals↗
PubMed1993

Altered expression and localization of the tight junction protein ZO-1 after common bile duct ligation.

Hepatocyte tight junctions form the intercellular barrier between bile and blood. Cholestasis due to common bile duct ligation (CBDL) results in structural changes in the tight junction (TJ) and an overt paracellular leak, although the molecular basis for these alterations is undefined. Using the epithelial isoform of the TJ protein ZO-1 (ZO-1 alpha +) as a marker for molecular changes in hepatocyte TJs, we investigated the effects of CBDL on ZO-1 alpha + immunofluorescence (IF) localization and on ZO-1 alpha + mRNA and protein expression over 2 wk of CBDL. ZO-1 alpha + IF staining was altered after 2 days of CBDL and appeared to accumulate in pericanalicular regions after 7 and 9 days. Quantitative immunoblotting and ribonuclease protection revealed a marked increase in hepatic ZO-1 alpha + protein expression and ZO-1 alpha + mRNA levels, respectively. In contrast to changes in ZO-1 alpha + IF, which occurred throughout the lobule, and changes in mRNA and protein expression, which were maximal after 9 days of ligation, the maximal hepatocyte proliferation occurred within 2 days after CBDL and was confined to periportal regions. CBDL results in altered hepatic localization and increased expression of the TJ protein ZO-1 alpha + and appears to represent a specific response by hepatocytes to pathological junction injury independent of cell proliferation.

Animals↗
PubMed1993

Infrared spectral analysis of extractables from poly(etherurethane urea) (PEUU) elastomers.

Poly(etherurethane urea) (PEUU) elastomers when employed as biomedical devices may be susceptible to extraction upon implantation. Four PEUU elastomers containing a single PEUU formulation, but varying in terms of their additives, were subjected to an in vitro extraction procedure. The additives in the PEUUs were Methacrol 2138 F at 5 wt% and Santowhite powder at 1 wt% levels. Only 1-2 wt% of the PEUUs was extractable with methanol. Fourier transform infrared spectroscopy (FT-IR) furnished qualitative and quantitative information on the extractables. The extractables consisted of a PEUU component that on the average was richer in soft segment than the bulk PEUU, and the two additives, Methacrol 2138 F and Santowhite powder.

Biocompatible Materials↗
PubMed1993

On chronic illness: immigrant women in Canada's work force--a feminist perspective.

Data from a comparative ethnographic study were examined to define factors that influence the management of illness among Euro-Canadian and first-generation Chinese women in the Canadian labour force. Compared with Euro-Canadians, Chinese women had a lower level of education, and more of them held blue collar jobs. Many of them had reservations about disclosing their chronic health problem (diabetes) to coworkers and employers, some fearing job loss if this information was revealed. Life circumstances prevented some of these individuals from properly managing their illness. In many cases they had difficulty gaining access to health facilities, learned little from health professionals, and had few resources to help them understand their condition. These complex issues that add to the burden of living with a chronic illness are not always recognized by health professionals, whose interactions with immigrant women are not structured to reveal the social context of the patient's illness.

Adaptation, Psychological↗
PubMed1993

Primary hyperaldosteronism--evaluation of procedures for diagnosis and localization.

We have reviewed the clinical, investigative and pathological findings in 16 patients with primary hyperaldosteronism, 6 with idiopathic adrenal hyperplasia and 10 with an aldosterone-producing adenoma. The ratio of serum aldosterone to plasma renin activity was > 1400 pmol/micrograms/l/h in all patients when measured supine on a normal salt diet, negating the need for salt loading to confirm primary hyperaldosteronism. Postural changes in serum aldosterone confirmed the presence of an aldosterone-producing adenoma in all but one patient when results on normal and high salt intakes were reviewed together. Nevertheless, the need for salt loading for discrimination is questioned, as the combination of postural changes in serum aldosterone on normal salt intake combined with CT confirmed and localized all aldosterone-producing adenomas. Urinary aldosterone measurements were of little value. Localizing procedures consisting of CT and isotopic scanning using 75Se-seleno-methyl-cholesterol proved most useful; adrenal venous sampling yielded less useful information. The latter may be due to the high predominance of patients (8) showing a background of micronodular hyperplasia with a dominant aldosterone-producing tumour. Only three of these patients have remained normotensive and normokalaemic on no medication. The presence of micronodular background suggests the need for life-long monitoring of such patients.

Adenoma↗
PubMed1992

A defective replicase gene induces resistance to cucumber mosaic virus in transgenic tobacco plants.

Nicotiana tabacum cv. Turkish Samsun NN plants were transformed with a modified and truncated replicase gene encoded by RNA-2 of cucumber mosaic virus strain Fny. The replicase gene had been modified by deleting a 94-base-pair region spanning nucleotides 1857-1950; the deletion also caused a shift in the open reading frame, resulting in a truncated translation product approximately 75% as large as the full-length protein. Upon transformation via Agrobacterium tumefaciens, transgenic plants were obtained that were resistant to virus disease when challenged with either cucumber mosaic virus virions or RNA at concentrations up to 500 micrograms/ml or 50 micrograms/ml, respectively, the highest concentrations tested. This resistance was absolute, as neither symptoms nor virus could be detected in uninoculated leaves, even after prolonged incubation (120 days after inoculation). These data suggest, therefore, that such a "replicase-mediated" resistance strategy may be applicable to other plant and animal viruses.

Amino Acid Sequence↗
PubMed1992

Diversity among tight junctions in rat kidney: glomerular slit diaphragms and endothelial junctions express only one isoform of the tight junction protein ZO-1.

ZO-1 is a 225-kDa peripheral membrane protein present in all tight junctions. It was recently shown to consist of two isoforms that differ in the presence of an internal 80-amino acid domain termed motif-alpha. To obtain information on their distribution and potential functional significance we have localized the two isoforms in rat kidney by using antibodies that recognize either both ZO-1 isoforms or the larger, motif-alpha-containing isoform. By immunofluorescence, staining with both antibodies was demonstrated at all tight junctions of tubular epithelial cells and the epithelial cells of Bowman's capsule. In contrast, the motif-alpha-containing isoform was absent from the slit diaphragms of the glomerular epithelium and the tight junctions of glomerular and peritubular capillary endothelial cells. This restricted isoform expression was confirmed by immunoblot analysis comparing proteins from purified glomeruli with those from kidney cortex or medulla. Thus, while both isoforms are expressed in typical epithelial tight junctions, only a single isoform, lacking motif-alpha, is expressed in the highly specialized slit diaphragms, where the intercellular spaces are normally open, and in endothelial junctions, which are readily opened by physiologic signals. The differential expression of ZO-1 isoforms in structurally and functionally distinct junctions in the kidney suggests that they may contribute to defining the variable functional properties, in particular the lability of these intercellular junctions.

Aging↗
PubMed1992

Protein adsorption of biomedical polymers influences activated monocytes to produce fibroblast stimulating factors.

The studies presented in this manuscript were based upon the hypothesis that monocytes/macrophages selectively produce cytokines and growth factors due to their interactions with polymers and proteins which are adsorbed to their surfaces. These factors in turn selectively influence the ability of fibroblasts to proliferate. The factors which influence fibroblast proliferation were released from monocytes incubated with polymers: Biomer, polydimethylsiloxane (PDMS), polyethylene (PE), expanded polytetrafluoroethylene (ePTFE), Dacron, and control polystyrene with and without preadsorption with physiological concentrations of IgG, fibrinogen, fibronectin, hemoglobin, or albumin. No simple correlation was found between adsorbed protein, biomedical polymer, and the ability of monocytes to produce growth factors and cytokines which influence fibroblast proliferation. This is evidence for selective protein-polymer interactions which in turn selectively activate monocytes to produce variable cell cycle competence and progression factors controlling fibroblast growth.

Adsorption↗
PubMed1992

Cytokine and growth factor production by monocytes/macrophages on protein preadsorbed polymers.

These studies evaluate the effect of biomedical polymers: Biomer, polydimethyl-siloxane (PDMS), polyethylene, expanded polytetrafluoroethylene (ePTFE), Dacron, and the control polystyrene with or without adsorbed proteins IgG, fibrinogen, and fibronectin on the ability of activated human monocytes/macrophages to produce Interleukin 1 Beta (IL-1-B), Interleukin 6 (IL-6), and Tumor Necrosis Factor Alpha (TNF-A). Monocytes/macrophages incubated on biomedical polymers with or without protein preadsorption produce variable levels of IL-1-B, IL-6, and TNF-A dependent on the polymer and adsorbed protein. IL-6 was produced in the greatest quantity and was the most influenced by protein adsorption. ePTFE and PDMS polymers were least stimulating while polystyrene was the most stimulating of monocyte activity. Adsorbed IgG consistently altered the ability of the polymers to activate monocytes/macrophages to produce cytokines. These studies provide important insight into conditions which modulate monocyte/macrophage activity in response to protein preadsorbed biomedical polymers.

Adsorption↗
PubMed1992

Biocompatibility studies on plasma polymerized interface materials encompassing both hydrophobic and hydrophilic surfaces.

The biocompatibility of radiofrequency plasma polymerized films (less than 100 nm thick) deposited on biomedical polymer supports has been characterized by in vitro and in vivo methods. The polymer interface materials covered a wide range of elemental composition and surface properties, and were prepared from N-vinyl-2-pyrrolidone, gamma-butyrolactone, n-hexane, and hexamethyldisilazane (PPHMDSZ). The biocompatibility studies showed that the interface materials were noncytotoxic to mouse and human fibroblasts, as shown by morphologic evaluation, and by determination of extracellular LDH; and they did not stimulate interleukin-1-like production from human monocytes, as indicated by a thymocyte proliferation assay. The human fibroblast proliferation assay showed that three of the polymers supported cell growth at levels comparable to, or greater than, polymer controls, while the hydrophobic PPHMDSZ inhibited both cell attachment and proliferation. The response to subcutaneous implantation for all test materials was indicative of biocompatibility, with rapid resolution of the acute phase response and normal wound healing. The wide range of composition and surface properties for the plasma polymerized films evaluated in this study suggest that this general class of materials is likely to exhibit excellent biocompatibility.

Animals↗
PubMed1992

Theoretical analysis on cell size distribution and kinetics of foreign-body giant cell formation in vivo on polyurethane elastomers.

The nature of in vivo leukocyte adhesion and foreign-body giant cell (FBGC) formation on polyurethanes was studied through theoretical and statistical analyses in terms of cell size distribution, density changes, and kinetics of FBGC formation. The results showed that the size distribution of FBGCs followed a "most probable" distribution. During FBGC formation, the densities of FBGCs changed with time. At an early stage, the number of FBGCs increased with time to a maximum at the expense of macrophages. As more FBGCs were formed and less macrophages were present, the fusion of FBGCs among themselves became significant. This, in turn, caused a gradual decrease of FBGC density with time. The rate of FBGC formation was characterized by a rate constant that represented certain characteristics of cell fusion and FBGC formation and the density of initial FBGC-forming macrophages that were a small fraction of leukocytes adhering to the surface. The direct correlations of surface cracking and pitting and adherent FBGCs demonstrated the influence of phagocytic actions of FBGCs on the biostability of implanted polyurethanes. While the cracking was thought to be caused by oxidative degradation facilitated by oxygen ion/radical release of FBGCs, the pitting appeared to result from the Methacrol 2138F aggregates diffusing out of the polymer in an acidic microenvironment under FBGCs, which in turn could be enhanced by the surface degradation and cell phagocytosis. The added Santowhite powder in polyurethane had a significant influence on FBGC formation: It reduced FBGC density and rate of FBGC formation by reducing leukocyte adhesion and the number of macrophages participating in FBGC formation.

Amines↗
PubMed1992

Cellular automation model of ventricular conduction.

A computer simulation of ventricular conduction is presented with a discrete element ventricular conduction model. The model is shown to be capable of demonstrating normal ventricular rhythm, including QRS and T-waves, plus a variety of rhythm disturbances including missed beats, electrical alternans and self-sustaining instability with arrhythmias. The morphology of the range of alternans produced bears a strong resemblance to certain clinically recognised arrhythmias.

Arrhythmias, Cardiac↗
PubMed1992

Electrical stimulation of cultured myocardial cells.

This paper reports on the use of a cardiac tissue monolayer model in the investigation of some of the fundamental electrical properties of cardiac muscle. The response of cardiac tissue to increasing levels of electrical stimulus is investigated and the strength-duration curve for rectangular waveform stimulation is measured. An experimental protocol is established which provides for uniform field stimulation of the cells, and allows the cellular response (contraction) to be recorded.

Animals↗