Volume 2, Issue 4
December 1980, pages 267-388
pp 267-274 December 1980
Arginase from rat fibrosarcoma was purified about 1900-fold and its properties were compared with those of the enzyme from liver and kidney. Arginase from fibrosarcoma was a neutral protein of molecular weight 120,000 with a Km value of 11 mM for arginine. The activation energy was 7.2 kcal/mol and the pH optimum was 10. The fibrosarcoma enzyme was immunologically different from that of the liver. The arginase from fibrosarcoma closely resembled the arginase from the kidney in its electrophoretic, kinetic and immunological properties.
pp 275-282 December 1980
The presence of arginase in rat fibrosarcoma not synthesizing urea, suggested that this enzyme may have additional functions. Ornithine carbamoyl transferase, a key enzyme of the urea cycle was absent in this tissue, when compared to normal tissues, lower amount of ornithine was found in the fibrosarcoma, but this tumour contained a higher level of proline. The radioactivity present in L-[U-14C] arginine was incorporated into putrescine, spermidine, spermine, proline glutamate and glutamine suggesting that arginine was a possible precursor and that arginase may have a role in the synthesis of these metabolites.
pp 283-290 December 1980
Among several metal ions tested, Cu2+ was unique in slowing down methylene blue sensitized photodynamic breakdown of some nucleic acid bases and nucleosides. The t1/2 values were increased in the case of xanthine and uric acid by Cu2+, but without any alteration in the nature or amounts of photoproducts formed. Xanthine was degraded quantitatively to allantoin and urea.
The breakdown of the sugar moiety of nucleosides was more drastically retarded than that of the purine ring. The decomposition rate and its magnitude was dependent on the concentration of Cu2+ as well as the nucleoside. The most profound increase in t1/2 values was found with xanthosine—7 min for the purine ring and 65 min for the ribose moiety, at 0.6 mM Cu2+ Hg2+ in the case of xanthine, and some paramagnetic metal ions in the case of the nucleosides, slowed down the photobreakdown to a small extent; however, differential effects were not observed unlike with Cu2+. None of the other metal ions tested significantly influenced the process.
pp 291-297 December 1980
Green chillies(Capsicum annum L.) and tamarind (Tamarindus indica) contain appreciable amount of L-asparaginase. The enzyme was purified 400-fold from green chillies, by successive precipitations with ammonium sulphate and sodium sulphate, Sephadex-gel filtration and affinity chromatography and the purified enzyme was homogenous on gel electrophoresis. The enzyme exists in two forms, only one having antitumour activity.
The purified enzyme has a molecular weight of 120,000 ±500. The N-terminal and the C-terminal amino acids are alanine and phenylalanine, respectively. The enzyme has a sharp optimum pH of 8.5 and a temperature optimum of 37‡C. It is stable upto 40‡C. The energy of activation is 3 kilo calories. The Km value for the enzyme is 3.3. mm. The enzyme has little action on D-asparagine, which is a strong inhibitor. The enzyme has inseparable glutaminase ctivity and is thus an asparaginase—glutaminase. In addition, it possesses urease activity.
pp 299-304 December 1980
A comparative study of the collagen of the foot ofLamellidens Sp. and that of the unmodified part of the foot inMytilus edulis shows marked differences in physical properties, amino acid composition and in the degree of stabilization. But both conform to type I collagen of vertebrates. In these respects, the latter shows agreement with the features characteristic of byssus collagen, which is highly crosslinked, involving dimers and trimers of tyrosine. It is suggested that such differences may reflect the different functions of the organs concerned, the foot ofLamellidens being a locomotary organ of the animal, while the foot ofMytilus edulis is modified for anchorage of the animal. The vertigial part though not morphologically modified shows the essential compositional characteristics of the byssus being a mere remanant of it.
pp 305-310 December 1980
There was a definite relationship between growth and ascorbic acid content inAchras sapota. Increase in ethrel concentration from 250 ppm to 500 ppm hastened early ripening and increased the amount of reducing sugars but depleted the ascorbic acid content. Other aspects of ascorbic acid turnover viz. ascorbigen, bound form of ascorbic acid, ascorbic acid utilization, net ascorbic acid bound and ascorbic acid oxidase were also studied.
pp 311-319 December 1980
High concentration of L-cystine (0.25%) when present in a glucose-mineral salt medium inhibited sporulation-specific events like protease production, calcium uptake and dipicolinic acid synthesis inBacillus thuringiensis var.thuringiensis. In addition, the enzymes of the Krebs cycle from aconitase onwards were completely inhibited by a high concentration of cystine. At a low concentration of cystine (0.05%), none of the above mentioned macromolecular changes were affected. Lipid synthesis monitored by [1,214 C]-acetate incorporation into lipid as well as into whole cells was completely inhibited.
pp 321-328 December 1980
The effect of the addition of different concentratons of cystine and cysteine on sporulation and parasporal crystal formation inBacillus thuringiensis var.thuringiensis was studied. The effect was well pronounced when the cystine/cysteine additions were made after the stationary phase. Heat stable spores and crystals were formed when the culture was provided with a low concentration of cystine/cysteine (0.05 per cent w/v). At a moderate concentration of cystine or cysteine (0.15%), only heat labile spores were formed without the production of the crystal. When the cystine/cysteine concentration was high (0.25%), spore and crystal formation were completely inhibited. Partial reversal of inhibition of sporulation was brought about by sodium sulphate or Zinc sulphate and lead, copper, cadmium or cobalt acetate at 0.2 mM or at 0.2% of sodium or potassium pyruvate, citrate, cisaconitate, oxalosuccinate, ∞ -keto-glutarate, succinate, fumarate, malate, or oxalacetate. Glutamate (0.2%) overcame the inhibitory effect of cystine/cysteine completely. The structural changes observed using phase contrast microscopy were dependent upon the concentration of cystine/cysteine.
pp 329-335 December 1980
A study was conducted on the structure of extracellular, water-soluble polysaccharides from 5 different strains ofRhizobium viz. R. trifolii J60 andR. meliloti strains J7017, 202, 204 and 207. All these polysaccharides were found to contain glucose and galactose in the approximate molar ratio of 7:1. Methylation analysis revealed these polysaccharides to contain (1 → 3), (1 → 6), (1 → 4), (1 → 4, 1 → 6)-linked D-glucose residues, (1 → 3)-linked D-galactose and nonreducing terminal D-glucose attached to pyruvate. These polysaccharides were also found to be acylated by both acetyl and succinyl residue. This structure was found to be similar to that of succinoglycan, a succinic acid-containing water-soluble, extra-cellular polysaccharide elaborated byAlcaligenes faecalis var.myxogenes 10C3. This similarity in structure of polysaccharides from two different species ofRhizobium and also the polysaccharide produced byAlcaligenes has been discussed.
pp 337-348 December 1980
The growth patterns ofMycobacterium smegmatis SN2 in a minimal medium and in nutrient broth have been compared. The growth was monitored by absorbancy (Klett readings), colony forming units, wet weight and content of DNA, RNA and protein. During the early part of the growth cycle, the bacteria had higher wet weight and macromolecular content in nutrient broth than in minimal media. During the latter half of the growth cycle however, biosynthesis stopped much earlier in nutrient broth and the bacteria had a much lower content of macromolecules than in the minimal medium. In both the media, a general pattern of completing biosynthesis rapidly in the initial phase and a certain amount of cell division at a later time involving the distribution of preformed macromolecules was seen. The possible adaptive significance of this observation has been discussed.
pp 349-354 December 1980
Progesterone receptors, both nuclear and cytosolic, were determined in the embryonic and inter-embryonic segments of the rabbit uterus at 6, 7 and 8 daypost-coitum. At day6 postcoitum a higher concentration of nuclear receptor in the embryonic segment was observed compared with that in the inter-embryonic segment. A reverse situation was observed in the case of cytoplasmic receptors. On the 7th daypost-coitum, no significant alteration in the concentration of either kind of the receptors was observed. However, on day 8, a higher concentration of both nuclear and cytosolic receptors at the embryonic site was observed compared to that in inter-embryonic segment. Since receptors are influenced only in the immediate vicinity of the blastocyst, it can be suggested that the blastocyst plays a role in the induction of its own implantation. Further, at day 8 increase in receptor concentration at the embryonic site may be related to the presence of decidual tissue at this site.
pp 355-360 December 1980
Progesterone receptors were determined in the cytosol from the ampulla, ampullaryisthmic junction and isthmus of rabbit fallopian tube and uterus of estrus and pregnant rabbits. The receptor levels when compared among its various anatomical segments, were the same in ampulla, isthums and uterus but maximum in ampullary-isthmic junction. Significant differences were observed in mated animals at 14, 24, 34, 48, 70 and 144 h after coitus. The receptor concentrations in portions of the fallopian tube showed no significant change between 14 and 24 h after coitus, except for a decrease in ampullary-isthmic junction at 24 h. At 34 h the concentration of receptor further decreased in all parts of the tube. At 48 and 70 h after coitus, receptor concentrations decreased gradually in ampulla and ampullary-isthmic junction, while isthmus showed a gradual increase. At 144 h, the receptor concentration showed no further change in ampulla and ampullary-isthmic junction; however, isthmus showed a decline. The uterine receptor concentration declined steadily from estrus till 70 h after coitus, however, it was increased at 144 h. The dissociation constant (Kd) of cytosol receptor in all the tissues at estrus and during early pregnancy was found similar. The implications of these changes in relation to the normal ovum transport have been correlated in this paper.
pp 361-367 December 1980
The degenerative changes in the spermatids as measured by changes in fine structure abnormalities increased with time following injection of Cd2+ into rat testis. The spermatids in the twelve hours group appear as peculiarly club shaped and elongated structures with one or two small but perceptible vacuoles. The subacrosomal area and the space between the nucleus and the middle piece are seen abnormally dilated. In the 30 day group, the central filaments are the most susceptible unit of 9+2 axoneme complex. The plasma membrane, the cytoplasmic matrix, the mitochondria of the middle piece and the fibrous sheath appear shrunken, discontinuous and degenerative.
pp 369-378 December 1980
The evolutionary origin of murine line based on a phylogenetic tree made on sequence data of ∞-and β-hemoglobin chains, followed by the diversity spectrum of hemoglobin genes in two wild species of murine rodents:Rattus rattus rufescens (house rat) andBandicota indica (bandicoot rat) has been reported. Each house rat contains six hemoglobin types involving two ∞-and three β-chains, which suggests a probable gene duplication at the oc chain locus and a gene triplication at the β-chain locus. Each bandicoot rat contains one ∞-and two β-chains suggesting a probable gene duplication at the β-chain locus. Peptide pattern analysis of the polypeptide chains of these murine hemoglobins further indicates that intraspecies differences among duplicated chains of the same kind are less than interspecies differences among corresponding ∞-and β-chains.
pp 379-386 December 1980
On sucrose gradient centrifugation, the ribosomal preparation from chloramphenicol-treated32P labelledEscherichia coli AB301/105 (RNase III-) showed the presence of a radioactive peak moving slower than the 70S ribosome; this peak disappeared on treatment with RNase III. The presence of precursor 30S RNA was shown in such preparations by affinity chromatography on a lysine-sepharose 4B column as well as polyacrylamide gel electrophoresis. Dialysis against low Mg2± concentration followed by sucrose density gradient electrophoresis. Dialysis against dissociation of 70S ribosome into its subunits, did not lead to the dissociation of the precursor ribosome. However, the dissociation took place upon treatment with RNase III. A tentative model of coupled rRNA transcription and ribosome assembly has been presented.
pp 387-388 December 1980