Maharaj K. Sahib

Inhibition of Diabetes-Associated Complications by Nucleophilic Compounds

Mono- and diaminoguanidine inhibited ambient glucose-induced glycosylated end product formation of albumin and collagen 125I-labeled albumin covalent binding in vitro. Diaminoguanidine was a stronger inhibitor than monoaminoguanidine. These compounds also inhibited rat eye lens aldose reductase activity in vitro noncompetitively with respect to NADPH with Ki = 30.6 mM for monoaminoguanidine and Ki = 12.5 mM for diaminoguanidine. When administered daily for 98 days at a dose of 25 mg/kg body wt i.p., both compounds lowered eye lens sorbitol and aldose reductase activity in normoglycemic and alloxan-induced diabetic rats. Again, diaminoguanidine was a better inhibitor. Daily long-term administration of mono- and diaminoguanidine (25 mg/kg body wt i.p.) inhibited and prevented experimental diabetes–induced lens opacity in rats, respectively. It appears that diaminoguanidine has a better therapeutic potential in controlling diabetic complications.

Synthesis and secretion of alpha-fetoprotein and albumin by newborn rat brain cells in culture

Brain cells of newborn rat were found to synthesize and secrete alpha-fetoprotein (AFP) and albumin in short-term culture. Synthesis of AFP and albumin was demonstrated by time-related linear incorporation of [14C]leucine into immunoprecipitable AFP and albumin by brain cells from newborn rat during 6 h incubation of the cultures. Newly synthesized labeled AFP and albumin were also accumulated (secreted) linearly as a function of incubation period. Cycloheximide could inhibit this incorporation of [14C]leucine into immunoprecipitable AFP and albumin. Synthesis of AFP and albumin accounted for 11-13% and 5-6% respectively, while their secretion into the culture medium was about 27-30% and 11-13% respectively of the total proteins synthesized and secreted by brain cells of newborn rat. Rate of AFP synthesis was about 2-fold greater than that of albumin. AFP and albumin secreted by brain cells displayed a complete immunological identity with, and electrophoretic mobilities similar to, the serum AFP and albumin. Molecular weights of AFP and albumin secreted by brain cells were also similar to their corresponding serum proteins. AFP was identified as the only active estradiol binding protein secreted by newborn rat brain cells in culture. Our studies suggest that albumin and estrophilic AFP originate in the developing rat brain in situ by intracellular synthesis.

In vitro insulin action on different ATPases of erythrocyte membranes in normal and diabetic rats

SummaryThein vitro effect of porcine insulin on Na++K+-, Ca2+- and Mg2+-ATPases of the rat erythrocyte membrane of normal and alloxan-induced diabetic rats was investigated. Na++K+- and Ca2+-stimulated enzyme activities were significantly decreased in diabetic rats in comparison to normal animals. The specific activities of both these ATPases in the latter group were markedly reduced on pre-incubating the ghosts with insulin. Similar treatment of the erythrocyte membranes of diabetic animals, however, resulted in a significant increase of these activities. These qualitatively different effects of the hormone in the two groups increased progressively with hormone concentration and duration of pre-incubation. Mg2+-stimulated ATPase activity was not significantly affected in diabetes or by insulin.

In vitro insulin effect on acetylcholine esterase of erythrocyte membranes of normal and diabetic rats

SummaryAlloxan induced diabetes in rats was associated with a significant reduction in the acetylcholine esterase activity of the erythrocyte membrane. Preincubation of these membranes with insulin caused a rapid but transient stimulation of this enzyme activity in both normal and diabetic rats, the effect being more marked in the latter group.

Precocious induction of hepatic aniline hydroxylase and aminopyrine N-demethylase with hydrocortisone in neonatal rat

Abstract The pre- and postnatal development of hepatic aniline hydroxylase and aminopyrine N -demethylase activities was studied in rats in order to identify the natural trophic factors, if any, responsible for early neonatal formation of the enzymes. The postnatal development of these two enzymes up to 3 weeks of age was comparable with that of cytoplasmic tyrosine aminotransferase. They could be precociously induced in 7-day-old rats by hydrocortisone. Cycloheximide inhibited their induction.

Isolation, Characterization, and Synthesis of AlphaFetoprotein from Neonatal Rat Brain

Abstract: Monospecific anti‐rat serum alpha‐fetoprotein (AFP) IgG was coupled to cyanogen bromide‐activated Sepharose‐4B (4.5 mg/ml packed volume of gel) to yield an immunoaffinity matrix. The immunoaffinity column was used to isolate AFP from feto‐neonatal rat brain. The purified AFP was immunologically and electrophoreti‐cally similar to serum AFP. It yielded a single band with a molecular weight of 70,000 on sodium dodecyl sulphate polyacrylamide gel electrophoresis. Polyacrylamide gel electrophoresis of the protein under nondenaturing conditions yielded two charge variants of AFP, reminiscent of AFP from feto‐neonatal rat serum. The AFP was observed to bind estradiol with Ka= 5.8 × 108M−1 and 1.3 × 108M−1 by dextran‐coated charcoal adsorption and Sephadex gel filtration techniques, respectively. Newborn rat brain cells linearly incorporated [14C]leucine into immunoprecipitable AFP during 6 h in culture. It is, therefore, concluded that feto‐neonatal rat brain contains AFP similar to that present in fetal serum and that it may arise in brain as a result of its in situ synthesis.

Changes in alpha-fetoprotein and albumin synthesis rates and their levels during fetal and neonatal development of rat brain☆

An attempt was made to find a correlation between AFP and albumin levels in brain and their rates of synthesis in the brain cells during maturation of rat brain. Levels of alpha-fetoprotein (AFP) and albumin in the developing brain were studied by rocket immunoassay. Rate of synthesis of AFP and albumin in brain cell cultures, established from rat brain at various stages of development, were determined by incorporation of [14C]leucine into immuno-precipitable intracellular AFP and albumin. AFP and albumin levels in brain as well as rates of their synthesis by brain cells in culture registered a continuous decline during development. Synthesis of AFP and albumin in the brain is switched off after first week of postnatal life with a concomitant disappearance of these proteins from the brain. Levels of AFP and albumin in brain correlated well with rates of their synthesis by brain cells in vitro at any specific stage of brain maturation implying that levels of AFP and albumin in brain are regulated by controlling rates of their synthesis in the maturing brain cells.

Retrospective glycemic status of diabetic patients: Glycosylation of blood proteins in diabetes and chronic renal failure

SummaryIn vivo andin vitro studies were carried out to evaluate the clinical application of glycosylated hemoglobin and plasma proteins in the diagnosis and management of diabetes mellitus. Glycosylated hemoglobin registered an almost 80% fall in diabetic patients following controlled glycemia for two months while glycosylated, plasma protein level registered an 80% fall in the patients after fifteen days of blood glucose homeostasis. Human serum proteins were glycosylatedin vitro and glycosylation was linearly proportional to the glucose concentration and incubation time. Polyacrylamide gel electrophoresis of glycosylated serum proteins revealed that albumin and transferrin are the major, proteins that are significantly glycosylated. Glycosylated hemoglobin and plasma protein levels were also increased in chronic renal failure patients without any history of diabetes.