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Biomedical subjects

B J Potter

Publications and source records attributed to B J Potter.

At least 73 records · Page 4Linked to original sources
PubMed1986

Depression of iron uptake from transferrin by isolated hepatocytes in the presence of ethanol is a pH-dependent consequence of ethanol metabolism.

Incubation of freshly isolated rat hepatocytes with highly purified radiolabeled rat transferrin in weakly buffered medium in the presence of 10 mM ethanol resulted in a marked diminution of iron uptake by these cells, associated with a greater pH depression than in ethanol-free control studies. This effect on iron uptake persisted, even when the cells were preincubated for 90 min with ethanol before the addition of transferrin. Increasing the buffering capacity of the system or the addition of a metabolic inhibitor of alcohol dehydrogenase (4-methylpyrazole) returned iron uptake to control values. Acetaldehyde, acetate, lactate (products of ethanol metabolism), and 3-butanol (an alcohol not metabolized by alcohol dehydrogenase) had no influence on iron uptake. Further investigation of iron uptake over the pH range 6-8.5 revealed a marked dependency of iron uptake on the extracellular pH. Leucine incorporation into cell protein was also found to be pH dependent. It is suggested that, in the light of current understanding of transferrin recycling by other cell types, the disturbances of iron homeostasis observed in alcoholics can be partially accounted for by alterations in their acid-base metabolism.

Acetaldehyde↗
PubMed1986

The effect of maternal thyroidectomy prior to conception on foetal brain development in sheep.

Merino ewes were surgically thyroidectomized, and mated 6 weeks later when their plasma thyroxine (T4) levels were negligible. Their foetuses were delivered by hysterotomy at 52, 71, 84, 98, 125, 140 days gestation or at term (150 days). Despite the very low levels of T4 in maternal plasma, the concentrations of T4 in foetal plasma were not significantly different after 71 days gestation from those of foetuses of sham-operated (control) ewes. Foetal brain and body weights, however, were reduced from 71 days compared to those of foetuses of sham-operated ewes. The foetal brain weights but not the body weights were restored to normal from 125 days to term. In addition to the weights, cell number (DNA) and cell size (protein:DNA ratio) appeared to be normal in the neonatal brain at parturition and this was confirmed by histological examination of the brains. Thus lack of maternal thyroid hormones in early pregnancy may cause a reduction in brain and body growth in the foetus which, in the case of the brain, appears to be restored to normal after the onset of foetal thyroid function.

Animals↗
PubMed1985

Low-iodine diet for the production of severe I deficiency in marmosets (Callithrix jacchus jacchus).

A low-iodine diet consisting of maize, peas (Pisum sativum), torula yeast, meat meal, maize oil and added vitamins, minerals and amino acids was given to eight pairs of adult, common cotton-eared marmosets (Callithrix jacchus jacchus). Eight control pairs were given the same diet to which potassium iodate was added. Both groups also received low-I apple and deionized water. The diet provided adequate nutrition, as confirmed by the maintenance of body-weight and good health. In the I-deficient marmosets the concentration of plasma thyroxine was decreased from 140.1 nmol/l to 22.4 nmol/l and thyroid-stimulating hormone increased significantly from 1.8 ng/ml to 9.0 ng/ml compared with control marmosets, thereby indicating severe I deficiency. Compared with newborn offspring from control marmosets, the thyroid glands from the I-deficient offspring showed an increase in weight, a decrease in I content and, on histological examination, hyperplasia, hypertrophy and a total absence of colloid material in the follicles.

Animals↗
PubMed1984

Iron uptake from transferrin by isolated hepatocytes: effect of ethanol.

Freshly isolated rat hepatocytes incubated with highly purified 59Fe-labelled diferric 125I-rat transferrin for 90 minutes in the presence of 10 mM ethanol took up significantly less 59Fe than did cells incubated without ethanol, while producing a significantly greater reduction of the pH of the incubation medium. Total transferrin binding was equivalent in both groups, but the molecular ratio of iron:transferrin on cell membranes isolated after 90 minutes was markedly reduced in the presence of ethanol, suggesting increased retention of apotransferrin. These data are compatible with the hypothesis that iron uptake from transferrin by hepatocytes is mediated by a pH dependent transferrin receptor mechanism similar to that in reticulocytes.

Animals↗
PubMed1984

Restoration of brain growth in fetal sheep after iodized oil administration to pregnant iodine-deficient ewes.

Iodized oil was administered as a single intramuscular injection to pregnant iodine-deficient ewes at 100 days gestation and the subsequent growth of their fetuses compared with that of fetuses of severely iodine-deficient ewes and of iodine-replete ewes, all of which were fed the same low-iodine diet. The administered iodine produced a remarkable improvement in thyroid function and physical appearance of the fetuses, accompanied by an increase in brain growth and to a lesser extent in body growth, which at 140 days was only slightly (but significantly) less than that of the controls. There was restoration of the number of cells (DNA) and myelination (cholesterol/DNA) in the cerebellum and cerebral hemispheres which suggests a catch-up of neuroblast development during pregnancy. Histological examination, however, revealed that counts of synapses (density) in the cerebral cortex after iodized oil were still less than those of the control fetal brains. The relevance of these findings to the effects of iodine deficiency on human brain development is discussed.

Animals↗
PubMed1983

A new recycling technique for human placental cotyledon perfusion: application to studies of the fetomaternal transfer of glucose, inulin, and antipyrine.

A previously described technique has been modified to permit the continuously recirculating perfusion of the separate maternal and fetal circulations of an isolated cotyledon of human placenta. Viability of the perfused cotyledons was established by measurements of oxygen consumption (average, 0.18 ml/gm/hr), glucose utilization (average, 1.0 mg/gm/hr), and lactate production (less than 0.01 mumol/gm/hr), and integrity of the placental barrier by the failure of India ink, 125I-albumin, or 35S-sulfobromophthalein to cross from fetal to maternal circulation. Clearance of 3H-inulin from the fetal circuit, 0.0059 +/- 0.0005 (SE) ml/min/gm, corresponded to 2.5% of its clearance by the adult human kidney. Clearance of 14C-antipyrine was 0.013 +/- 0.003 ml/min/gm. After introduction into the fetal circuit, the observed appearance of both inulin and antipyrine in the maternal circuit closely paralleled curves predicted by a simple mathematical model. The use of a continuously recirculating perfusion system is technically feasible, and has advantages over the single-pass technique for studying transplacental transfer of metabolites with a low efficiency of extraction.

Animals↗
PubMed1983

Studies of albumin binding to rat liver plasma membranes. Implications for the albumin receptor hypothesis.

To characterize a previously proposed hepatocyte albumin receptor, we examined the binding of native and defatted 125I-labeled rat albumin to rat liver plasma membranes. After incubation for 30 min, binding was determined from the distribution of radioactivity between membrane pellet and supernatant following initial centrifugation (15000 X g for 15 min), and after repeated cycles of washing with buffer and re-centrifugation. 125I-labeled albumin recovered in the initial membrane pellet averaged only 4% of that incubated. Moreover, this albumin was only loosely associated with the membrane, as indicated by recovery in the pellet of under 0.5% of the counts after three washes. Binding of 125I-labeled albumin to the plasma membranes was no greater than to erythrocyte ghosts, was not inhibited by excess unlabeled albumin, and was not decreased by heat denaturation of the membranes, all suggestive of a lack of specific binding. Failure to observe albumin binding to the membranes was not due to a rapid dissociation rate or 'off-time', as incubations in the presence of sufficient ultraviolet light to promote covalent binding of ligands to receptors did not increase 125I counts bound to the membrane. Finally, affinity chromatography over albumin/agarose gel of solubilized membrane proteins provided no evidence of a membrane protein with a high affinity for albumin. These studies, therefore, do not support the hypothesis that liver cell plasma membranes contain a specific albumin receptor.

Animals↗
PubMed1982

Serum inhibitors of leukocyte chemotaxis in Crohn's disease and ulcerative colitis.

Studies were undertaken to determine the incidence and nature of serum chemotaxis inhibitors in patients with Crohn's disease and ulcerative colitis. Sera from patients with active Crohn's disease were shown to contain chemotactic factor-directed inhibitory activity. The molecular size of the inhibitor estimated by gel filtration is similar to the 7S gamma-globulins and it is precipitable by 40% ammonium sulfate. Less marked inhibitory activity is present in the same fractions of sera from patients with ulcerative colitis and from healthy controls, suggesting that it represents increased activity of one or more normal serum globulins. Leukocyte-directed serum inhibitors have also been demonstrated in patients with Crohn's disease and ulcerative colitis, particularly in patients with active disease. In Crohn's disease the presence of serum chemotactic factor inhibitors may explain the diminished chemotaxis of neutrophils into skin window chambers reported previously. The inhibitors are nonspecific and are probably secondary to the disease state but may have some bearing on the nature of the mucosal inflammation.

Chemotactic Factors↗
PubMed1980

Experimental production of growth retardation in the sheep fetus after exposure to alcohol.

The effect of excessive alcohol consumption during pregnancy on fetal development has been studied in sheep. Fetuses of ewes which had consumed 10% ethanol in water before, and during, pregnancy were delivered by hysterotomy 10 days before parturition and found to be shorter (P < 0.01), lighter (P < 0.01), and to have significantly lighter brains (P < 0.05) than normal fetuses of comparable gestational age. Heart, liver, spleen, kidneys and adrenal glands all weighed less than those of fetuses from ewes which drank water instead of alcohol. The findings provide experimental evidence for growth retardation after exposure of the sheep fetus to alcohol, and are consistent with clinical reports on the human fetal alcohol syndrome.

Animals↗
PubMed1980

Low-iodine diet for producing iodine deficiency in rats.

A low-iodine diet has been prepared for rats, using locally available low-iodine ingredients. On analysis it has been shown to consistently contain 15-20 ng iodine/g. When fed to growing female rats, this diet produced severe iodine deficiency while not significantly affecting growth or reproduction. The deficiency was manifested by a fall in daily urinary iodine excretion (to less than 1 microgram/day) and a seven-fold increase in thyroid uptake (131I) observable within 3 months. Levels of plasma thyroxine (T4) and thyroid stimulating hormone (TSH) continued to change for 4-5 months, T4 falling from 69.9 to 7.5 nmol/l and TSH increasing seven-fold from a control value of 364 to 2406 ng/ml. Goitre was present in all iodine-deficient rats and iodine content in the thyroid was 10% of the control value.

Animal Feed↗
PubMed1980

Complement inhibitors and immunoconglutinins in ulcerative colitis and Crohn's disease.

The serum concentrations of the complement inactivators C1INH, C3bINA and beta 1H have been determined in patients with ulcerative colitis and Crohn's disease and their correlation with C3 and properdin factor B examined. The incidence of immunoconglutinins (1K) in these patients was investigated. Raised serum concentrations of C1INH and C3bINA have been found in patients with active disease, but no significant alteration was found in serum concentration of beta 1H. An increasing incidence of positive 1K titres was found with increased length of disease history. These results suggest continuing complement activation in these diseases.

Colitis, Ulcerative↗
PubMed1980

Metabolism of 125I-labelled trypsin in man: evidence of recirculation.

125I-labelled human trypsin metabolism has been investigated in man. Three subjects received 125I-trypsin and 131I-albumin intravenously. Against a background secretin infusion (1 U/kg/h), trypsin decayed biexponentially from the serum with half-lives of 17.5, 21, and 24 minutes for the rapid disappearance phase and 520, 540, and 560 minutes for the slow phase. Between 13% and 38% of the 125I injected was recovered from duodenal juice aspirated continously over 300 minutes. In contrast, less than 1% of the 131I-albumin injected was recovered. When bile and pure pancreatic juice were collected at endoscopic retrograde cholangiopancreatography after intravenous 125I-trypsin in a fourth subject 125I radioactivity was found to be secreted via both these routes. After 125I-trypsin infusion into the duodenum 11% of the total dose was found to be present in the circulation after 75 minutes. These results support the concept that recirculation of trypsin exists in man.

Adult↗
PubMed1980

Studies on monocytes in inflammatory bowel disease: factors influencing monocyte lysosomal enzyme activity.

The effect of endotoxin and immune complexes on monocyte lysosomal enzyme activity has been studied in patients with Crohn's disease and ulcerative colitis. Immune complexes made at equivalence or in antigen excess caused a rapid fall in intracellular activity of the enzyme N'acetyl-beta-D-glucosaminidase which was significantly greater than that seen when cells were incubated with medium alone. Endotoxin had no effect on intracellular enzyme activity but there was a significant elevation of activity in the supernatants. Cells from patients with inflammatory bowel disease were no different to cells from healthy control subjects in their response to either endotoxin or immune complexes.

Acetylglucosaminidase↗
PubMed1980

Complement metabolism in chronic liver disease: catabolism of C1q in chronic active liver disease and primary biliary cirrhosis.

The fractional catabolic rate of C1q was increased markedly in primary biliary cirrhosis, and in HBsAg-positive chronic liver disease. In 3 out of 4 patients with HBSAg-negative chronic active liver disease C1q catabolism was normal. The rate of synthesis of the protein was increased in primary biliary cirrhosis, but it was normal in patients with chronic active liver disease. The fractional catabolic rate and synthetic rate of albumin were normal in these subjects. These data provide further evidence for the activation of the classical pathway of complement in primary biliary cirrhosis and HBsAg-positive chronic active liver disease. In HBsAg-negative chronic active liver disease, the presence of C1q binding macromolecules was not associated with increased C1q catabolism.

Adult↗
PubMed1980

Production of severe iodine deficiency in sheep using a prepared low-iodine diet.

Extensive tests on dietary materials suitable for ingestion by sheep have led to the preparation of an appropriate diet which, when fed to the sheep, caused severe iodine deficiency. The deficiency was manifested by daily urinary excretion values which fell to levels of less than 20 micrograms iodine and by thyroxine (T4) and triiodothyronine (T3) concentrations in blood plasma which were reduced from more than 90 and 1.80 nmol/l to the low levels of less than 2.58 and 0.31 nmol/l respectively. The values were attained 5 months after feeding the low-iodine diet. Goitre was present in most of the animals and the reductions in T4 and T3 values were accompanied by increased concentrations of plasma thyroid stimulating hormone (TSH) from less than 8.6 to more than 68 ng/ml. Samples of wool removed from selected areas of the sheep showed that the iodine-deficient diet also caused a reduction in the growth of wool.

Animals↗
PubMed1979

Reduction of immune complexes and immunoglobulins induced by D-penicillamine in primary biliary cirrhosis.

Penicillamine has an effect on immune complexes and immunoglobulins both in vivo and in vitro. We therefore studied the effect of penicillamine on immune complexes and immunoglobulins in primary biliary cirrhosis. Twenty-eight patients were randomly allocated into a treatment group receiving 600 to 900 mg of penicillamine, or a control group, and followed for a maximum of 24 months. After 12 and 24 months, serum immune complexes had fallen significantly in treated patients as compared to controls (P less than 0.05, P less than 0.01). Treatment reduced IgA, IgG and IgM concentrations, with IgM being significantly different from controls at six, 12 and 24 months (P less than 0.01). Over 24 months, serum aspartate transaminase levels fell in treated patients but rose in controls (P less than 0.01). Bilirubin concentrations increased at a slower rate in treated patients. Penicillamine may favorably influence the course of primary biliary cirrhosis by its immunologic action in addition to its copper-chelating action.

Antigen-Antibody Complex↗
PubMed1979

Clq metabolism in ulcerative colitis and Crohn's disease.

The metabolism of pure radioiodine labelled Clq has been observed in five patients with ulcerative colitis, five patients with Crohn's disease, and in five control subjects. Both the fractional catabolic rate and the synthesis rate of Clq were increased in the five patients with Crohn's disease and in four of the five patients with ulcerative colitis. The fifth patient was in remission and had a normal synthesis rate. These results support the hypothesis that complement activation plays a role in the pathogenesis of these disease states and that the increased complement activation is primarily via the classical pathway.

Adult↗