Studies on glutamic-oxalacetic (GOT) and glutamic-pyruvic (GPT) transaminases of swine kidney worm Stephanurus dentatus (Diesing, 1839). I. Assay and general properties.

Biochemical studies on the two transaminases GOT and GPT of swine kidney worm Stephanurus dentatus have been made. GOT has been found much more active than GPT. Enzyme activities are based on the formation of oxaloacetate (GOT) or pyruvate (GPT) from aspartic acid and alanine respectively with oxoglutarate. A linear relationship is observed between the enzyme concentration and activity. GOT shows a maximum activity at pH 8.0 and Michaelis constant 9 X 10(-3) M for male and 2.9 X 10(-3) M for female. GPT has an optimum pH of 7.5 and a Michaelis constant 19 X 10(-3) M for male and 8 X 10(-3) M for female. The optimum temperature for both GOT and GPT was 60 degrees C.     

Characterization of shrinkage cracks in medium black clay soil of madhya pradesh

Summary In a field experiment, the pattern and size of shrinkage cracks were studied under three vegetative covers of wheat crop, grass and cultivated fallow. Both the pattern and size of cracking varied widely. Under wheat crop, the major cracks developed parallel to the rows particularly midway between the two rows of plants. The cracks were few in number and simple in nature. And so was the case under grass where the major cracks developed either in between or around the grass tussocks. However, under cultivated fallow development of too many cracks forming an intricate network showed no definite pattern of cracking. In a soil other than the cultivated fallow, the pattern of cracking appeared to be a function of positioning of the plants rather than of the soil itself.As far as the size of cracks is concerned, the widest and deepest cracks developed under wheat crop and narrowest and shallowest under cultivated fallow. Under grass, the width and depth of the cracks was observed to be intermediate between the two extremes of wheat and cultivated fallow. The size of cracks seemed to depend on the magnitude of water loss from the soil. re]19760713     

Biochemical characteristics,metabolism, and antitumor activity of several acetylated hexosamines

We have synthesized several potential inhibitors and/or modifiers of the carbohydrate portion of plasma membrane glycoconjugates. These include fluorinated and actylated analogs of D-glucosamine, D-galactosamine, and D-mannosamine. These compounds have been tested to determine their effects on both [¹⁴C] glucosamine and [³H] leucine incorporation into glycoconjugate and on cell growth and viability using P-288 murine lymphoma cells maintained in tissue culture. The most cytotoxic agent tested was 2-acetamido-2-deoxy-1,3,4,6-tetra-O-acetyl-β-D-glucopyranose or simply β-pentaacetylglucosamine which prevented cell growth at 10^?4–10^?3 M. β-Pentaacetylglucosamine cytotoxicity was correlated with its high lipid solubility, having an octanol/water partition coefficient of 0.424 as compared with 0.278 for the β-anomer and 0.017 for N-acetylglucosamine. In vitro metabolism studies with [¹⁴C]-and/or [³H]-labeled pentaacetylglucosamine have indicated intracellular de-O-acetylation leading to the biosynthesis of UDP-N-acetylglucosamine, followed by the incorporation of this sugar into cellular glycoprotein. Concomitant with the formation of increased amounts of this nucleotide sugar, intracellular UTP and CTP pools fell to one third normal within 3 h after the administration of 1 mM pentaacetylglucosamine. At present it is unclear whether the cytotoxicity of β-pentaacetylglucosamine or other similar agents is due to alterations in nucleotide and nucleotide-sugar pools causing a decrease in energy charge and polynucleotide biosynthesis or is due to a direct effect on membrane glycoconjugate biosynthesis.     

alpha-adrenergic receptor in rat heart. Effects of thyroidectomy.

The effects of thyroid status on alpha-adrenergic receptors in the rat myocardium were investigated. The potent antagonist [3H]dihydroergokryptine was used to identify alpha-adrenergic receptors in rat heart particulate and sarcolemmal fractions. Administration of triiodothyronine to thyroidectomized rats decreased specific binding to alpha-adrenergic receptors in heart particulate and sarcolemmal fractions by 41% and 45%, respectively. Scatchard analysis revealed that the cardiac sarcolemmal fraction from thyroidectomized rats contained 29.3 fmol/mg of protein, as compared with 17.0 fmol/mg of protein found in the heart preparation of thyroidectomized rats treated with triiodothyronine. The equilibrium dissociation constants for the interaction of receptors with dihydroergokryptine were similar (about 1.5 nM) in the heart sarcolemmal fractions derived from these two groups of rats. The results of this study demonstrate that thyroid hormone can regulate the number of cardiac alpha-adrenergic receptors. In addition, there appears to be a reciprocal relationship between alpha-adrenergic and beta-adrenergic receptors in the rat myocardium.     

Cellular reaction to group A beta-haemolytic streptococcal membrane antigen and its relation to complement levels in patients with rheumatic heart disease.

Cell-mediated immunity and blood complement activities were studied in 35 patients with chronic rheumatic heart disease (RHD) and 17 normal subjects. The T-cell population in patients with RHD was reduced, as were the CH50 and C3 complement levels. The response to phytohaemagglutinin stimulation was deficient, but the lymphocytes of patients with RHD showed increased avidity for 3H-thymidine when stimulated with specific streptococcal membrane antigen. No differences were found between patients with acute rheumatic activity and those without such activity. The susceptibility of individual patients may be related to the specific sensitisation of lymphocytes, while the fact that this persisted even when T-cell numbers had returned to normal may account for the well-known recrudescenses after streptococcal infections in these patients.     

Adrenocortical cyclic GMP-dependent protein kinase: purification, characterization, and modification of its activity by calmodulin, and its relationship with steroidogenesis

Cyclic GMP-dependent protein kinase has been purified to apparent homogeneity from bovine adrenal cortex and its presence in the rat adrenal cortex has been demonstrated. Sucrose density sedimentation studies indicated that the M_r of the enzyme was 145,000. This protein was composed to two identical subunits each with M_r of 75,000. The enzyme molecule was asymmetric with a frictional coefficient of 1.54, Stokes radius of 53.5 Å and a sedimentation coefficient of 6.5. The enzyme self-phosphorylated and the stoichiometry of cyclic GMP binding was two molecules per holoenzyme. Calmodulin or troponin C markedly stimulated the apparent maximal velocity of cyclic GMP-dependent protein kinase without affecting its basal activity. This effect of protein modulators was independent of calcium. Sucrose density gradient studies indicated that the stimulatory effect of calmodulin was due to its interaction with histones. An interaction of calmodulin with the enzyme was not observed. The steroidogenic potential of cyclic GMP and its analogs correlated closely with their ability to stimulate cyclic GMP-dependent protein kinase; the order of potency for both activities was 8-bromocylic GMP > cyclic GMP > N²-monobutyryl cyclic GMP > N², O²-dibutyryl cyclic GMP. In each case, calmodulin enhanced the cyclic GMP-dependent protein kinase activity for histone phosphorylation. These results indicate that although cyclic GMP is the primary regulator of cyclic GMP-dependent protein kinase, other modulator proteins such as calmodulin could act as additional regulators of the phosphorylation of substrate proteins. In addition, the demonstration of cyclic GMP-dependent protein kinase in rat adrenal glands, and the results with cyclic GMP and its analogs relating to their activation of protein kinase and steroidogenesis are consistant with the concept that cyclic GMP is one of the mediators of adrenal steroidogenesis.     

The distribution of the group specific component (Gc) in four endogamous groups of Punjab, North India

The paper reports the distribution of group specific component (Gc) types among four endogamous groups of Punjab: Jat Sikh, Khatri, Ramgarhia, and Ramdasia. A total of 418 individuals were tested for this polymorphism. The frequency of Gc1 alleles ranges between 0.7056 and 0.7636. These frequencies are compared with those obtained in other Indian populations.     

A dodecamer of globin chains is the principal functional subunit of the extracellular hemoglobin of Lumbricus terrestris

Repeated dissociation of the approximately 3600-kDa hexagonal bilayer extracellular hemoglobin of Lumbricus terrestris in 4 M urea followed by gel filtration at neutral pH produces a subunit that retains the oxygen affinity of the native molecule (approximately 12 torr), but only two-thirds of the cooperativity (nmax = 2.1 +/- 0.2 versus 3.3 +/- 0.3). The mass of this subunit was estimated to be 202 +/- 15 kDa by gel filtration and 202 +/- 26 kDa from mass measurements of unstained freeze-dried specimens by scanning transmission electron microscopy. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of this subunit showed that it consists predominantly of the heme-containing subunits M (chain I, 17 kDa) and T (disulfide-bonded chains II-IV, 50 kDa). Mixing of subunits M and T isolated concurrently with the 200-kDa subunit resulted in partial association into particles that had a mass of 191 +/- 13 kDa determined by gel filtration and 200 +/- 38 kDa determined by scanning transmission electron microscopy and whose oxygen affinity and cooperativity were the same as those of the 200-kDa subunit. The results imply that the 200-kDa subunit is a dodecamer of globin chains, consisting of three copies each of subunits M and T (3 x chains (I + II + III + IV], in good agreement with the mass of 209 kDa calculated from the amino acid sequences of the four chains, and represents the largest functional subunit of Lumbricus hemoglobin. Twelve copies of this subunit would account for two-thirds of the total mass of the molecule, as suggested earlier (Vinogradov, S. N., Lugo, S. L., Mainwaring, M. G., Kapp, O. H., and Crewe, A. V. (1986) Proc. Natl. Acad. Sci. U. S. A. 83, 8034-8038). The retention of only partial cooperativity by the 200-kDa subunit implies that full cooperativity is dependent on the presence of a complete hexagonal bilayer structure, wherein 12 200-kDa subunits are linked together by approximately 30-kDa heme-deficient chains.     

Manganese in cell metabolism of higher plants

Manganese, a group VII element of the periodic table, plays an important role in biological systems and exists in a variety of oxidation states. The normal level of Mn in air surrounding major industrial sites is 0.03 μg/m³, in drinking water 0.05 mg/liter and in soil between 560 and 850 ppm. Manganese is an essential trace element for higher plant systems. It is absorbed mainly as divalent Mn²⁺, which competes effectively with Mg²⁺ and strongly depresses its rate of uptake. The accumulation of Mn particularly takes place in peripheral cells of the leaf petiole, petiolule and palisade and spongy parenchyma cells. Mn is involved in photosynthesis and activation of different enzyme systems. Mn deficiency may be expressed as inhibition of cell elongation and yield decrease. Mn toxicity is one of the important growth limiting factors in acid soils. Plant tops are affected to a greater extent than root systems. The toxicity symptoms are, in general, similar to the deficiency symptoms. Toxic effects of Mn on plant growth have been attributed to several physiological and biochemical pathways, although the detailed mechanism is still not very clear. Higher O₂ uptake and loss of control in Mn activated enzyme systems have been associated with Mn toxicity. Mn interferes with the uptake, transport and use of several essential elements including Ca, Fe, Cu, Al, Si, Mg, K, P and N. Excess of Mn reduces the uptake of certain elements and increases that of others. pH plays an important role in Mn uptake. Acidic pH causes a lack of substantial amount of nitrate as an alternative electron acceptor and leads to a high amount of Mn in leaves. High microbial activity, water logging and poorly structured soils cause severe Mn toxicity even in neutral soils. The molecular mechanism of Mn-tolerance is not yet clear. The level of tolerance is different in different species and seems to be controlled by more than one gene. Further information is required on the factors affecting the distribution, accumulation and membrane permeability of the metal in different plant parts and different species. Understanding of the genetic basis of Mn-tolerance is necessary to improve adaptation of crops against acid soils, water logging and other adverse soil conditions.