Volume 14, Issue 2
June 1989, pages 69-202
pp 69-78 June 1989
Castration had no effect on prostatic inhibin-like activity as compared to normal controls. Consequent upon castration there is a significant reduction in the inhibin content of the ventral prostate on a per gland basis. However, when expressed as a function of protein content, there is no change. The data suggest that the very same epithelial cells which under the influence of androgen carry out the characteristic exocrine secretory activity are responsible for the synthesis and secretion of inhibin-like material.
pp 79-90 June 1989
Studies on the characterization of inhibin and inhibin-like factors have depended for the most part on the classicalin vitro pituitary cell culture assay. A major drawback with this assay is the turn-around time which is in the order of two weeks and consequently slows down purification efforts. The 24 h bioassay for inhibin has been found to be sufficiently sensitive and also statistically valid. Unfortunately, based as it is on a secondary response, ambiguities arise in interpreting the results. By including a parallel assay in which the mice are primed with human menopausal gonadotropin rather than human chorionic gonadotropin, it was possible to device the coupled bioassay. This enables distinguishing inhibin-like factors acting to suppress pituitary follicle stimulating hormone output from those acting at the level of gonads. In this study the coupled assay for inhibin has been compared with the classical pituitary cell culture assay in order to assess its biological and statistical validity. The data validates the bioassay on both the above counts and when considered in conjunction with the short turn-around time suggests that this assay can be highly useful in studies on isolation of inhibin from various sources.
pp 91-100 June 1989
The relative ability of ovine follicle stimulating hormone and itsβ-subunit, two potential candidates for male contraceptive vaccine, to generate antibodies in monkeys capable of bioneutralizing follicle stimulating hormone was assessed usingin vitro model systems. Antiserum against native ovine follicle stimulating hormone was found to be highly specific to the intact form with no cross-reactivity with either of the two subunits while the antiserum againstβ-subunit of follicle stimulating hormone could bind to theβ-subunit in its free form as well as when it is combined withα-subunit to form the intact hormone. Both antisera could block the binding of the hormone to the receptor if the hormone was preincubated with the antibody. However, the follicle stimulating hormoneβ-antisera could only inhibit the binding of the hormone partially (33% inhibition) if the antibody and receptor were mixed prior to the addition of the hormone, while antisera to the native follicle stimulating hormone could block the binding completely (100% inhibition) in the same experiment. Similarly antisera to the native follicle stimulating hormone was significantly effective in blocking (100%) response to follicle stimulating hormone but not theβ-subunit antisera (0%) as checked using anin vitro granulosa cell system. Thus the probability of obtaining antibodies of greater bioneutralization potential is much higher if intact hormone is used as an antigen rather than itsβ-subunit as a vaccine.
pp 101-109 June 1989
The role of gonadotropins and estrogen on the regulation of ovarian ornithine decarboxylase was studied during follicular differentiation/maturation. In intact immature rats follicular differentiation/maturation was initiated with sequential administration of estrogen and follicle stimulating hormone. Ornithine decarboxylase activity in response to human chorionic gonadotropin was markedly enhanced (2-fold) in rats with preovulatory antral follicles when compared to rats with non-ovulatory follicles. This increase could be attributed to the alteration in the turnover of the enzyme. Following follicle maturation the half life of the human chorionic gonadotropin stimulated ornithine decarboxylase was increased from 18 to 62 min. This increase in half life was associated with differentition of follicles. In the estrogen treated group (which does not induce follicular differentiation), the half life of the enzyme remained unaltered. The regulation of ornithine decarboxylase through the formation of protein inhibitor antizyme induced by diamino hexane, was unaltered during follicular differentiation.
pp 111-125 June 1989
X-ray studies on crystalline complexes involving amino acids and peptides: Part XVIII. Crystal structure of a new form of L-arginine D-glutamate and a comparative study of amino acid crystal structures containing molecules of the same and mixed chirality
The new form of L-arginine D-glutamate is monoclinic, P21, witha = 9.941(1),b = 4.668(2),c = 17.307(1) Å,β = 95.27(1)°, and Z = 2. In terms of composition, the new form differs from the old form in that the former is a monohydrate whereas the latter is a trihydrate. The structure has been solved by the direct methods and refined to R = 0.085 for 1012 observed reflections. The conformation of the arginine molecule is the same in both the forms whereas that of the glutamate ion is different. The change in the conformation of the glutamate ion is such that it facilitates extensive pseudosymmetry in the crystals. The molecules arrange themselves in double-layers stabilised by head-to-tail sequences involving main chains, in both the forms. However, considerable differences exist between the two forms in the interface, consisting of side chains and water molecules, between double-layers. A comparative study of the relationship between the crystal structures of L and DL amino acids on the one hand and that between the structures of LL and LD amino acid-amino acid complexes on the other, provides interesting insights into amino acid aggregation and the effect of chirality on it. The crystal structures of most hydrophobic amino acids are made up of double-layers and those of most hydrophilic amino acids contain single layers, irrespective of the chiralities of the amino acids involved. In most cases, the molecules tend to appropriately rearrange themselves to preserve the broad features of aggregation patterns when the chirality of half the molecules is reversed as in the structures of DL amino acids. The basic elements of aggregation in the LL and the LD complexes, are similar to those found in the crystals of L and DL amino acids. However, the differences between the LL and the LD complexes in the distribution of these elements are more pronounced than those between the distributions in the structures of L and DL amino acids.
pp 127-132 June 1989
Synthesis of a radioactive photoactivable heterobifunctional reagent, N-oxysuccinimide ester of 2-[14C]glycyl carboxy-9-diazofluorene is described. This reagent on photolysis gives rise to a reactive carbene which rapidly inserts into solvents like methanol. The probe can be easily linked to aldolase which on photolysis gives rise to aldolase dimer, trimer and tetramer depending on the density of linked probe. This probe has also been linked to concanavalin A. The radioactive concanavalin A so obtained was incubated with erythrocyte ghosts and photolysed. The membrane protein analysis by gel electrophoresis indicated that concanavalin A has been covalently crosslinked to band 3.
pp 133-142 June 1989
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 hemoglobinβ-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.
pp 143-152 June 1989
Transcriptional and translational changes following temperature shock at 37, 39 or 41°C to ovarian cells ofAnopheles stephensi were studied. Temperature shock at 39°C induced 6 puffs on polytene chromosomes in the nurse cells as revealed by [3H] uridine incorporation studies. Only the 2R-19B puff was induced at 37°C and was found to be a major temperature shock locus remaining most active at all the 3 temperatures tested. Other temperature shock loci were activated only at 39°C. There was progressive inhibi tion of general chromosomal transcription with the rise of temperature. Transcription was drastically inhibited at 41°C but all the temperature shock loci still remained relatively active. Examination of [35S]methionine labelled newly synthesized ovarian proteins using sodium dodecyl sulphate-polyacrylamide slab gels revealed that all the heat shock polypeptides except the HSP 70 were synthesized in ovarian cells even at control temperature (29°C). Temperature shock induced the synthesis of HSP 70 and elevated the levels of other heat shock polypeptides (82, 30, 29, 23 and 17 KD). Present results suggest that the threshold level for induction of a complete heat shock response in mosquitos is higher (39°C) than the other dipteran insects studied and that a 41°C treatment is not lethal as in the case ofDrosophila, Chironomus etc. These features reflect the adaptations of mosquitos to tropical climate and their dietary habit of warm blood meal.
pp 153-162 June 1989
Total tRNA was isolated, purified and quantitated from earthworm, cockroach, fresh water mussel and rat liver. The total tRNA content of invertebrates was found to be much lower than that of rat liver. When checked for aminoacylation capacity with homologous and heterologous enzymes and algal protein hydrolysate, the tRNA preparation from rat liver and fresh water mussel, a mollusc, were found to be active. On the other hand, the tRNAs from earthworm, an annelid, and cockroach, an arthropod, were completely inactive with the homologous enzymes but showed partial activity with heterologous enzymes. Similar results were obtained with individual amino acids also. The low activity or inactivity of earthworm and cockroach tRNAs appears to be due to certain endogenous aminoacylation inhibitors.
pp 163-172 June 1989
The incorporation of [35S]-SO4 into glycosaminoglycans of liverin vivo and in in liver slices and into the glycosaminoglycans associated with the hepatic plasma membrane of rats at different periods after a heavy dose of CC14 have been studied. The incorporation of [35S]-SO4 into total glycosaminoglycans decreased to as low as 40% of the control at 24 h after the administration of CC14 and later on increased reaching a maximum on the 4th day. The amount of [35S]-SO4 incorporation into heparan sulphate was also reduced to about 40% of control at 12–24 h after the onset of injury and increased thereafter reaching a maximum on the 4th day. There was only a partial reduction in the synthesis of chondroitin sulphate in the early stage of injury and then it steadily increased reaching about 3 times the control level on 4–6 days. The [35S]-SO4-incorporation into dermatan sulphate, after a slight initial decrease remained at the control levels. On the 8th day after the CCl4-induced liver injury, the rate of [35S]-SO4-incorporation was almost equal to that in normal controls. The incorporation of [35S]-SO4 into hepatic plasma membrane glycosaminoglycans showed a similar change decreasing to about 35% of control at 24h followed by an increase, reaching normal levels on the 4th day after the administration of CC14. About 90% of the plasma membrane glycosaminoglycans was found to be heparan sulphate. The yield of plasma membrane from normal and CCl4-induced regenerating liver was found to be similar and therefore the results obtained were not due to difference in the yield of the membrane preparation. The data also indicate that there was no difference in the degree of sulphation. The significance of these changes in the metabolism of sulphated glycosaminoglycans particularly plasma membrane heparan sulphate in tissue regeneration has been discussed.
pp 173-182 June 1989
Minimal inhibitory concentration values of HgCl2 and 5 organomercurials were determined against 24 mercury-resistant N2-fixing soil bacteria previously isolated from soil and identified in our laboratory. These bacterial strains also displayed multiple antibiotic resistant properties. Typical growth pattern of a highly mercury-resistantBeijerinckia sp (KDr2) was studied in liquid broth supplemented with toxic levels of mercury compounds. Four bacterial strains were selected for determining their ability to volatilize mercury and their Hg-volatilizing capacity was different. Cell-free extracts prepared from overnight mercury-induced cells catalyzed Hg2+-induced NADPH oxidation. Specific activities of Hg2+-reductase which is capable of catalyzing conversion of Hg2+ →Hg(o) of 10 Hg-resistant bacterial strains are also reported.
pp 183-187 June 1989
Channa punctatus, an air-breathing freshwater teleost, mobilizes more protein for its energy requirement during summer and spawning months, as revealed by the data on endogenous nitrogen excretion in the form of ammonia-N, urea-N, free amino acids, creatinine and creatine.
pp 189-202 June 1989
Protein factors play a crucial role in establishing gene-specific and cell-specific regulation of the process of transcription. These include general transcription factors which recognize TATA and CCAAT boxes and which form components of the RNA polymerase II system. Specific transcription factors interact with characteristic promoter elements of individual genes. Some of the examples are SP1, glucocorticoid receptor, GCN4, GAL4 and many others. Transcription factors have a DNA binding domain demarcated from the transcription activation domain. Some factors may have an additional ligand (small molecule) binding domain. Typical structural features such as helix-turn-helix motif, zinc finger and leucine zipper have been recognized in the DNA binding domain of the transcription factors. The acidic domain of the protein factors is involved in the transcription activation process. It appears that activation is the result of the combined action of several regulatory proteins binding at different regions of the promoter. Interaction between proteins bound to DNA but seperated by long stretches of nucleotides is facilitated by DNA bending. Functional specificity as well as diversity are feasible with a limited number of transcription factors through alterations in the architecture of interaction between a group of proteins bound to promoter elements.
Volume 44 | Issue 5
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