Biomedical subjects

S Bhatti

Publications and source records attributed to S Bhatti.

22 records · Page 2Linked to original sources

PubMed1994

Immunization with the larger isoform of mouse glutamic acid decarboxylase (GAD67) prevents autoimmune diabetes in NOD mice.

The 65-kDa isoform of glutamic acid decarboxylase (GAD65) has been implicated in autoimmune diabetes in NOD mice, but the role of the 67-kDa GAD isoform (GAD67) is less clear. We found that immunization of 4-week-old NOD mice with purified recombinant mouse GAD67 prevented or significantly delayed the onset of diabetes. To further explore this phenomenon, we characterized anti-GAD67 immune responses in naive and GAD-immunized NOD mice. Anti-GAD67 antibodies titers were relatively low in naive mice at all ages, but a single immunization with GAD67 at 4 weeks induced high titers of anti-GAD antibodies by 6 weeks of age. In both 4-week-old and diabetic NOD mice, there were significant endogenous T-cell proliferative responses against purified recombinant mouse GAD67. These T-cell proliferative responses were blocked by anti-I-ANOD and anti-CD4 antibodies. To characterize the anti-GAD T-cell responses in the NOD mice, we established T-cell lines and T-cell clones which recognized GAD67, and we used recombinant subfragments of GAD to localize the predominant T-cell epitopes in GAD67. T-cells from naive NOD mice proliferated in response to all GAD subfragments, whereas T-cells from diabetic mice responded primarily to the COOH-terminal 83 amino acids of GAD67. These results suggest that GAD67 is an autoantigen in IDDM and immunization of prediabetic NOD mice with GAD67 can prevent the onset of diabetes.

Animals↗

PubMed1993

Cholic acid and ursodeoxycholic acid therapy in primary biliary cirrhosis. Changes in bile acid patterns and their correlation with liver function.

We treated 6 patients with Stage II primary biliary cirrhosis with cholic acid (CA) 10 mg.kg-1 per day for 3 months and then with the same dose of ursodeoxycholic acid (UDCA). A matching group of 6 patients was observed for 3 months without any therapy. Liver function tests and serum and stool bile acids were investigated before, during and at the end of CA and UDCA therapy. The results of liver function tests deteriorated after 6-8 weeks of CA therapy and the changes were correlated (r = 0.92) with an increase in alpha-dihydroxy-bile acids (chenodeoxycholic acid and deoxycholic acid) in the serum. The 24 h excretion of DCA in 24 h faeces was markedly increased. Ursodeoxycholic acid treatment improved liver function tests; after 4 weeks glutamate dehydrogenase (GLDH) had decreased. After 8-12 weeks of therapy ursodeoxycholic acid had increased to 50-60% of the total serum bile acids whereas the more apolar bile acids were significantly decreased. No changes in liver function tests or bile acid metabolism were found in the untreated group. Since CA and UDCA are non-toxic in man, this trial indicates that the apolar bile acids chenodeoxycholic acid and deoxycholic acid may be responsible for the deterioration of liver function in primary biliary cirrhosis. However, the therapeutic effect of UDCA cannot be explained merely by the decrease in alpha-dihydroxy-bile acids in the serum, since the laboratory results had improved prior to the decrease in the serum apolar bile acids.

Bile Acids and Salts↗

PubMed1993

Molecular aspects of membrane stabilization by ursodeoxycholate [see comment].

BACKGROUND: Ursodeoxycholate, used for therapy in biliary liver diseases, prevents bile salt damage in animal experiments. Using isolated red blood cell and both canalicular and basolateral hepatocyte membranes, the present study examined this protective effect. METHODS: Membranes were incubated with chenodeoxycholate, with chenodeoxycholate and ursodeoxycholate simultaneously, and first with ursodeoxycholate followed by chenodeoxycholate. Changes in membrane structure were investigated by electron paramagnetic resonance spectroscopy, using different spin labels. Data were confirmed by analysis of membrane lipids and studies with 14C-labeled bile acids. RESULTS: The increase of polarity in the apolar domain of the membrane caused by chenodeoxycholate corresponded to the amount of solubilized lipids. After preincubation with ursodeoxycholate or its conjugates, membrane damage by subsequent chenodeoxycholate incubation was prevented. This effect was caused by binding of ursodeoxycholate in the apolar domain, of its conjugates in the interface of the membrane. CONCLUSIONS: Chenodeoxycholate solubilizes membrane lipids and permits water to permeate into plasma membranes. The steroid nucleus of ursodeoxycholate is bound to the apolar domain and that of the conjugates to the interface of the membrane, thus stabilizing membrane structure.

Animals↗

PubMed1989

Enzyme release from chick myocytes during hypoxia and reoxygenation: dependence on pH.

On reoxygenation of ischemic or hypoxic hearts a sudden release of cytosolic enzymes coupled with hypercontraction and cell injury occurs, which has been termed the "oxygen paradox". We have attempted to imitate this phenomenon in cultured chick myocytes to try to find the cause of this sudden enzyme release. During 4 hours of normoxic perfusion (pH 7.4) monolayer cultures of chick embryonic myocytes retain their normal morphology, beat rhythmically, and show no release of creatine kinase (CK) into the perfusate. Hypoxic perfusion (O2 less than or equal to 0.25 microliter/ml) stops cell contraction (15-20 min) and causes "blebbing" of the sarcolemma (20-30 min). Membrane blebs increase in size and number with continuing hypoxia and eventually the cells become irreversibly damaged. Perfusion at pH 7.4 leads to a release of CK shortly after membrane damage occurs (30-40 min), with peak enzyme levels at 60-90 min. Reoxygenation after 120 min hypoxia does not exacerbate release. Hypoxic perfusion at pH 7.0 suppresses the release of CK from the cells despite extensive membrane blebbing. Normoxic perfusion at pH 7.4 after 100 min hypoxia (pH 7.0) causes an efflux of enzyme from the irreversibly injured cells. This can be prevented by reoxygenating the cells at pH 7.0 and stimulated by raising the pH of the hypoxic perfusate to 7.4. Shorter hypoxic periods (30 mins) at pH 7.0 followed by normoxic perfusion at pH 7.4 lead to a sudden large efflux of CK, arrhythmic contractions and hypercontraction of myofilaments, i.e. the typical symptoms of the "oxygen paradox". Thus changes in external pH can influence the release of intracellular enzymes during hypoxia and reoxygenation.

Animals↗