Antistress activity of P-GABA in experimental animals.

A new gamma-aminobutyric acid derivative N-phthloyl GABA (P-GABA) was found to possess anticonvulsant, antiepileptic, antiulcer and antinociceptive activities. Effect of cold restrain stress (CRS) and its modulation by P-GABA were evaluated on some biochemical and biophysical parameters in rats. CRS induced elevations in blood sugar level were unaffected by P-GABA treatment. CRS also caused an increase of Na+K+ ATPase activities, and decrease of lipid peroxidation in RBC membrane. CRS also induced (a) membrane protein clusterization, (b) increased membrane fluidity and (c) reduced thickness. CRS induced RBC membrane dynamics were reversed by P-GABA in a differential manner. However, these parameters in synaptosomal membrane were unaffected by P-GABA.

Fibrolamellar carcinoma of the liver--an unusual presentation.

Non-bacterial thrombotic endocarditis was found at autopsy in a 17 year old male patient of fibrolamellar type of hepatocellular carcinoma with pericardial metastases. This had resulted in multiple embolic cerebral infarcts with long standing hemiplegia and later death due to acute left ventricular failure.

Involvement of active site in self-association of proteins: a case of alpha-chymotrypsin.

The self-association of proteolytic enzymes can be looked upon as an interesting possibility of the manifestation of enzyme-substrate complex. Hence the involvement of active site in such processes is a centre of investigation for many years. In the case of alpha-chymotrypsin, considerable controversy exists with regard to the involvement of active site of the enzyme in its self-association. A historical perspective of the problem and an overview of the available evidence, for and against, is presented and critically analysed. Despite contradicting observations, accumulated evidence indicates that His-57 and Ser-195 at the active site are involved, at least partially, in the self-association; a few other groups such as Tyr-146 and Met-192 are also involved in such processes.

Efficacy of serum lactate dehydrogenase and its isozymes in monitoring the therapy in patients with acute leukemia.

The pretreatment levels of serum Lactate Dehydrogenase (LDH) and its isozymes are measured in 12 cases of Acute Lymphoid Leukemia (ALL) and 8 cases of Acute Myeloid Leukemia (AML) and compared with 14 matched healthy controls. Patients showed only first three bands of LDH while normal sera exhibited five bands. A significant increase in total LDH activity was observed in patients of both the groups as compared to controls at the time of admission. The patients were treated with chemotherapy and were followed at 72 hrs. and after 4 weeks. The patients who successfully responded to the therapy showed increased levels of total LDH and LDH2 and LDH3 isoenzymes as early as 72 hrs. after commencement of the therapy. The nonresponders, on the other hand, circulated, decreased or unaltered values of isozymes during this interval. Following them up for a month, ALL responders showed decreased values of total LDH activity, LDH2 and LDH3 activities when compared with their 72 hour values except LDH1. Non responders of this group had practically unaltered values of these isozymes. AML responders circulated decreased values of all the isozymes while AML non responders "showed significant increases in total LDH, and all its isozymes as compared with their 72 hour values. The determination of total enzyme and its isozyme levels at pre, mid and end of treatment seems to be a promising biochemical parameter to predict the early response to chemotherapy administered.

Hydrophilicity and antigenicity of proteins—A case study of myoglobin and hemoglobin.

Hydrophilicity index is used to locate antigenic determinants on two related groups of proteins—myoglobin and hemoglobin. The data on 41 species (including 34 mammals) of myoglobin show that average hydrophilicity for the complete myoglobin molecules as well as the average hydrophilicity for all hydrophilic regions put together seem to remain constant; the variation in the size and location of the antigenic determinants in these species is very small indicating that the antigenic sites are not shifted during evolution. In the case of both the proteins there is a good agreement between the antigenic sites picked up by using hydrophilicity index and the experimentally determined antigenic sites. The data on 56 species of hemoglobin α-chains and 44 species of hemoglobin β-chains showed that although there are few sites on hemoglobin which have remained invariant during evolution, there is a significant variation in other sites in terms of either a splitting of a site, or a drastic change in the hydrophilicity values and/or a length of the site. Comparison of the hydrophilicity data on these two groups of proteins suggests that hemoglobins which perform a variety of functions as compared to myoglobins are evolving faster than myoglobins supporting the contention of earlier workers.

Self-association of α-chymotrypsin: Effect of amino acids.

The concentration-dependent self-association of α-chymotrypsin is known to be influenced by various factors including the presence of small molecules and autolysis products. In this connection the effect of various amino acids on the self-association of α- chymotrypsin has been studied, as a point of interest, by measuring the sedimentation coefficient of α-chymotrypsin. The influence of an amino acid is seen to be governed by the nature of its side chain. Some amino acids do not affect the self-association of α- chymotrypsin at all while some affect it moderately and some others considerably. Functional groups such as the – OH group of Ser or the phenolic ring of Tyr do not seem to influence self-association behaviour. Based on these effects, amino acids could be categorized into 3 groups. Activity studies in the presence of amino acids indicate that the site of self-association and the active-site are probably mutually exclusive.

Prediction of secondary structures of 16S and 23S rRNA from Escherichia coli.

Small and large subunits of Escherichia coli ribosome have three different rRNAs, the sequences of which are known. However, attempts by three groups to predict secondary structures of 16S and 23S rRNAs have certain common limitations namely, these structures are predicted assuming no interactions among various domains of the molecule and only 40% residues are involved in base pairing as against the experimental observation of 60 % residues in base paired state. Recent experimental studies have shown that there is a specific interaction between naked 16S and 23S rRNA molecules. This is significant because we have observed that the regions (oligonucleotides of length 9–10 residues), in 16S rRNA which are complementary to those in 23S rRNA do not have internal complementary sequences. Therefore, we have developed a simple graph theoretical approach to predict secondary structures of 16S and 23S rRNAs. Our method for model building not only uses complete sequence of 16S or 23S rRNA molecule along with other experimental observations but also takes into account the observation that specific recognition is possible through the complementary sequences between 16S and 23S rRNA molecules and, therefore, these parts of the molecules are not used for internal base pairing. The method used to predict secondary structures is discussed. A typical secondary structure of the complex between 16S and 23S rRNA molecules, obtained using our method, is presented and compared briefly with earlier model building studies.