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Biomedical subjects

C Barrett

Publications and source records attributed to C Barrett.

At least 55 records · Page 3Linked to original sources
PubMed1990

Cryptic Na+,K(+)-ATPase activity in rat liver canalicular plasma membranes: evidence for its basolateral origin.

Controversy exists concerning the localization of the enzyme Na+,K(+)-ATPase to canalicular membranes in hepatocytes. Most studies find enzyme activity only at the basolateral plasma membrane domain of the hepatocyte. However, Na+,K(+)-ATPase activity has been detected recently in a canalicular membrane fraction prepared by Mg++ precipitation, suggesting that differences in membrane domain fluidity account for these discrepancies. To reinvestigate this question, we used free-flow electrophoresis to further purify canalicular liver plasma membranes originally separated by sucrose density centrifugation. With this technique, canalicular membranes devoid of Na+,K(+)-ATPase activity by routine assay were separated into six subfractions. More than 80% of the activities of canalicular marker enzymes was recovered in two subfractions closest to the anode, which were totally devoid of Na+,K(+)-ATPase activity. However, Na+,K(+)-ATPase activity could now be detected in the four other fractions that contained only small amounts of canalicular marker enzymes. The basolateral marker enzyme, glucagon-stimulated adenyl cyclase, comigrated with this cryptic Na+,K(+)-ATPase activity. Furthermore, addition of 6 mumol/L [12-(2-methoxyethoxy)-ethyl-8-(cis-2-n-octylcyclopropyl)-octanoate ], a membrane-fluidizing agent, to the original canalicular membrane preparation and to all subfractions did not stimulate or unmask latent Na+,K(+)-ATPase activity. Finally, when canalicular membranes isolated by Mg++ precipitation were subjected to free-flow electrophoresis, they could not be separated from the more positively charged Na+,K(+)-ATPase-containing fractions, probably because of alterations in surface charge. Together these findings suggest that Na+,K(+)-ATPase is a basolateral enzyme, that represents a small contaminant when present in canalicular liver plasma membranes and that methodological differences may account for previous discrepancies.

Animals↗
PubMed1989

A statistical assessment of the dependability of transcutaneous tissue oxygen tension measurements.

Transcutaneous oxygen tension measurements (PtcO2) were obtained for subjects in two groups: peripheral vascular patients (N = 15) and disease-free controls (N = 9). Readings were taken in each of three locations, arm, knee and foot, in supine and erect positions, at fixed and random times, on each of 3 consecutive days. The dependability (the proportion of true variance in total variance) of PtcO2 measurements was evaluated using a generalizability model. The preliminary generalizability study analysis indicated that day-to-day variation of PtcO2 level was larger than within-day variation. Therefore, in order to decrease the measurement error variance one would preferably increase the number of days for measurements (nd) rather than increase the number of measurements within each day (nt). A decision study analysis was also performed which resulted in estimates of error variance and two interdependent dependability measures: dependability coefficients (DCs) and signal to noise ratios (S/Ns). PtcO2 dependability values were generally different for the two groups. Cases had high DCs and S/Ns (DC greater than or equal to 0.9, S/N greater than or equal to 9) in all location-position combinations except for arm measurements. On the other hand, controls had low and unacceptable DCs and S/Ns (DC less than 0.8, S/N less than 4) in all location-position combinations. Cases and controls had generally lower dependability values when PtcO2 ratios were analyzed. The only two ratio-position categories for which dependability values were in the acceptable range (DC greater than or equal to 0.8, S/N greater than or equal to 4) were foot/arm erect and foot/arm supine for the cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Biliary catabolism of glutathione and differential reabsorption of its amino acid constituents.

Biliary excretion of glutathione, free amino acids, and total amino acids (after acid hydrolysis) was measured in hepatic bile collected from guinea pigs, rabbits, and dogs anesthetized with pentobarbital sodium. In controls, the concentration of glutathione in bile was less than 20 microM in all three species. However, when hepatic gamma-glutamyltransferase activity was decreased by retrograde intrabiliary infusion of the irreversible inhibitor acivicin (AT-125; 20 mumol/kg), there was a marked increase in biliary glutathione excretion (in mumol glutathione equivalents.kg body wt-1.h-1) from 0.10 +/- 0.04 to 2.2 +/- 0.6 in guinea pigs, from 0.014 +/- 0.013 to 2.5 +/- 1.9 in rabbits, and from an undetectable level (less than 0.001) to 0.11 +/- 0.05 in dogs. Amino acid analysis of bile revealed that the concentration of glutathione's constituent amino acids (free glutamate, cystine, and glycine) in control bile samples from these three species were quite low and were not affected by AT-125. However, acid hydrolyzates of these same bile samples revealed an unusually high degree of amino acid conjugation. Glutamate (0.06-0.5 mM), cystine (0.2-1.1 mM), and glycine (1.7-2.8 mM) constituted the overwhelming majority of total amino acids in hydrolyzed bile from controls. After AT-125, concentrations of total glutamate and cystine were elevated in hydrolyzed bile, while concentrations of all other amino acids remained the same. Thus glutathione is avidly secreted into bile in the guinea pig, rabbit, and dog but is almost quantitatively broken down within the biliary tree. Subsequently, the glutamate and cysteine moieties derived from catabolism of glutathione must be partially reabsorbed either as peptides, conjugates, or free amino acids.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1986

Sonography of adrenal glands in neonates and children: changes in appearance with age.

The sonographic appearance of the normal adrenal gland in children varies with age. In newborns, the cortex is large and hypoechoic, whereas the medulla is relatively small and hyperechoic. With increasing age, the cortex becomes smaller and the medulla relatively larger. The cortex remains hypoechoic and the medulla hyperechoic until age 5-6 months, by which time the gland has become hyperechoic and smaller, with poor or absent sonographic differentiation between cortex and medulla. After 1 year of age, the appearance of the gland is similar to that of the adult gland, with straight or concave borders and a hypoechoic character.

Adolescent↗
PubMed1986

Adaptation of a commercially available indirect fluorescent antibody slide test for measuring measles-specific immunoglobulins.

A commercially available indirect fluorescent antibody (IFA) test was evaluated for the determination of measles-specific immunoglobulins G and M (MIgG, MIgM). The IFA test detected fourfold rises of MIgG in 34 of 35 (97%) cases of measles confirmed by complement fixation or hemagglutination inhibition. In determining immune status, MIgG-IFA correlated with hemagglutination inhibition in 22 of 23 (96%) cases. The IFA test detected MIgM in only 11 of 34 acute-phase sera collected within 5 days of the reported onset of rash and in the convalescent specimens of another 13 of the 35 specimens. The IFA test is an effective method for the conventional diagnosis of measles and for determining immune status. This IFA test has a limited role as a rapid diagnostic test for measles when used to detect measles-specific MIgM in acute-phase sera obtained from patients with suspected measles.

Agglutination Tests↗
PubMed1986

Neurologic complications in oral polio vaccine recipients.

Between April 1982 and June 1983 four children 3 to 24 months of age were referred for evaluation of neurologic abnormalities found to be compatible with vaccine-related poliovirus infection, which had not been suspected by referring physicians. Patients were epidemiologically unrelated residents of Indiana, and none had prior symptoms suggestive of immunodeficiency. All had received poliovirus vaccine orally (first dose in three, fourth dose in one) and a diphtheria-tetanus-pertussis injection in the left anterior thigh within 30 days of symptoms. A vaccine-like strain of poliovirus was isolated from each patient, and each had symptoms (left leg paralysis in three; developmental regression, spasticity, and progressive fatal cerebral atrophy in one) persisting for at least 6 months. Immune function was normal in two with poliovirus type 3 infection, and abnormal (hypogammaglobulinemia, combined immunodeficiency) in two with type 1 and type 2 infection, respectively. The incidence of observed vaccine-related poliovirus infection in Indiana recipients of orally administered poliovirus vaccine was 0.058 per 100,000 per year, significantly greater (P less than 0.001) than predicted.

Atrophy↗
PubMed1986

Oestrogen-induced systemic lupus erythematosus.

The subject of this case report, a 64-year-old white female, was treated for osteoporosis with oestrogens. She developed unequivocal systemic lupus erythematosus, from which she had suffered as a young woman and which had remitted with her menopause at 38. The close relationship of the relapses and remissions of her disease with her hormonal status underlines the importance of endocrine factors in the clinical expression of systemic lupus erythematosus.

Estrogens↗
PubMed1985

Delayed pulmonary maturation in the fetus of the streptozotocin-diabetic rat.

Pulmonary maturation was studied in fetuses in streptozotocin-diabetic rats on the final four days of gestation. Diabetes was induced prior to conception by the intravenous injection of streptozotocin. Fetuses were hyperglycemic but did not manifest hyperinsulinemia. Whole lung total phospholipid, phosphatidylcholine, and disaturated phosphatidylcholine were significantly decreased in the diabetic group on day 21 (term = 22 days), but not prior to or after that point in gestation. Morphologic analysis also revealed a decreased number of type II cells and lamellar bodies per alveolar lining cell in the diabetic group only on day 21, coincident with the changes in phospholipid analysis. Activities of enzymes involved in fetal pulmonary phospholipid synthesis were measured to see if differences could account for the observed developmental delay. No significant differences between diabetic and control lungs were noted in any of the enzymes studied from days 20-22, with the exception of an increase in cholinephosphate cytidylyltransferase activity in the diabetic fetuses on day 22. Immaturity in both biochemical and morphologic indices of lung development was present at a specific time late in the diabetic rat gestation. This maturational delay could not be accounted for by changes in the activities of enzymes involved in phospholipid synthesis. The fetus of the streptozotocin-diabetic rat provides a useful model to study the effects of hyperglycemia on fetal lung development.

Animals↗
PubMed1985

Characteristics of primary isolates of alveolar type II cells from neonatal rats.

Alveolar type II cells from 6-day-old rat pups were obtained at approximately 90% purity, as judged by light and electron microscopy. Within 48-72 h in culture, the cells formed a monolayer with tight junctions typical of epithelial cells. Type II cells aggregated into raised domelike areas, which when sectioned showed alveolarlike structures comprised of type II cells. After 3 days in culture these structures showed abundant lamellar body secretion. Phospholipid profiles were characteristic of type II cells, with disaturated phosphatidylcholine (DSPC) the predominant secreted phospholipid. The cells also released DSPC in response to beta-adrenergic stimulation. This release was inhibited by the specific beta-antagonist propranolol. The results show that morphologic differentiation and biochemical properties of neonatal type II cells can be studied using an isolated cell system in tissue culture.

Animals↗
PubMed1984

Mechanisms of taurocholate transport in canalicular and basolateral rat liver plasma membrane vesicles. Evidence for an electrogenic canalicular organic anion carrier.

The driving forces for taurocholate transport were determined in highly purified canalicular (cLPM) and basolateral rat liver plasma membrane (LPM) vesicles. Alanine transport was also examined for comparison. Inwardly directed Na+ but not K+ gradients transiently stimulated [3H]taurocholate (1 microM) and [3H]alanine (0.2 mM) uptake into basolateral LPM 3-4- fold above their respective equilibrium values (overshoots). Na+ also stimulated [3H]taurocholate countertransport and tracer exchange in basolateral LPM whereas valinomycin-induced inside negative K+ diffusion potentials stimulated alanine uptake but had no effect on taurocholate uptake. In contrast, in the "right-side out" oriented cLPM vesicles, [3H]taurocholate countertransport and tracer exchange were not dependent on Na+. Efflux of [3H]taurocholate from cLPM was also independent of Na+ and could be trans-stimulated by extra-vesicular taurocholate. Furthermore, an inside negative valinomycin-mediated K+ diffusion potential inhibited taurocholate uptake into and stimulated taurocholate efflux from the cLPM vesicles. These studies provide direct evidence for a "carrier mediated" and potential-sensitive conductive pathway for the canalicular excretion of taurocholate. In addition, they confirm the presence of a possibly electroneutral Na+-taurocholate cotransport system in basolateral membranes of the hepatocyte.

ATP-Binding Cassette Transporters↗
PubMed1984

An acellular human amnionic membrane model for in vitro culture of type II pneumocytes: the role of the basement membrane in cell morphology and function.

To determine whether a preformed basement membrane contributes to the maintenance of morphology and function of type II pneumocytes, we cultured isolated adult rat type II pneumocytes on the basement membrane and stromal surfaces of an acellular human amnionic membrane and on plastic. The presence of lamellar bodies on transmission electron microscopy and epithelial morphology in culture and a characteristic phospholipid profile after incubation with 3H-acetate identified the cells as type II. When type II cells were cultured on a preexisting basement membrane, they formed a well-organized monolayer with polarity, centrally located surface microvilli, and more basally located nuclei. Individual cells maintained a cuboidal morphology for 8-10 days. Intracellularly, there were numerous mitochondria, endoplasmic reticulum (ER), and lamellar bodies. The cells secreted a new basal lamina of their own. When cultured on the stromal side of the amnion, the cells became flattened within 48-60 hours, formed small lamellar bodies, and had scanty surface microvilli; they formed clumps and appeared less ordered. These cells did not secrete a visible basement membrane, and the majority detached from the stromal surface after 7-8 days in culture. In addition, culture on the basement membrane aspect of the amnion prevented the rapid decline in the percentage of 3H-acetate label incorporated in phosphatidylcholine after 72 hours of culture. We conclude that a preformed basement membrane influences the function and morphology of type II pneumocytes, organizes them into a monolayer in culture, and influences deposition of a visible basal lamina. Thus, the acellular human amnion provides an excellent model for the systematic study of basement membrane influence on the biology and pathology of these cells.

Amnion↗
PubMed1984

High-resolution spinal sonography in infants.

High-resolution, real-time sonography of the spine revealed significant anatomic details in 29 infants, including nine with congenital malformations. Transverse sections were most useful for detecting osteochondral anomalies and for evaluating the symmetry of the spinal column and its soft-tissue contents. Longitudinal sections augmented the transverse sections and provided the most detailed anatomy of the cord and spinal arteries. A normal screening sonographic examination obviates ionizing radiation and invasive procedures, while an abnormal study implies the need for further, complementary diagnostic investigations.

Humans↗
PubMed1983

Placental growth and glycogen metabolism in streptozotocin diabetic rats.

Placental glycogen metabolism was investigated in rat pregnancies complicated by streptozotocin-induced diabetes mellitus. Both diabetic and control placentas had increasing glycogen concentration from day 14 to day 16, after which glycogen concentration declined rapidly. The diabetic placentas had significantly elevated glycogen concentration when compared to controls from day 16 through term (day 22). Near term, when control glycogen content fell close to zero, the diabetic placentas still had appreciable glycogen levels. Total phosphorylase activity in the diabetic placentas was significantly higher than control values from day 16-22. Phosphorylase A activity, however, was lower in the diabetic placentas late in gestation, corresponding to the increased glycogen concentration seen at that time. Diabetic placentas had increased total synthase activity on the final 3 days of gestation, although synthase A activity was lower than corresponding control values. The placentas in this model are markedly increased in size late in gestation. No difference in protein concentration or protein/DNA ratio was noted. Total DNA content per placenta was significantly increased in the diabetic placentas after day 16 when compared to controls. Placental DNA in the diabetics continued to increase until day 18-19 of gestation, whereas DNA content in control placentas remained constant after day 16. Thus, the diabetic placentas apparently continue the process of DNA replication after DNA synthesis is complete in the controls.

Animals↗