A novel galactosyl-binding lectin from the plasma of the blood clam,Anadara granosa (L) and a study of its combining site

Control Analysis has been carried out in the first steps of a rat liver glycolytic system. Attention has been focused on the effect of several glucose concentrations on the control, particularly regarding the role of glucokinase. From kinetic studies of the whole metabolic system we have obtained information on the flux variation under different glucose concentrations. This information together with the kinetics of glucokinase has allowed us to calculate Flux Control and Elasticity Coefficients for glucokinase and the Response Coefficient of the system with respect to glucose. The changes in of the value of Flux Control Coefficients demonstrates that in conditions of low glucose concentration, glucokinase is the main enzyme in controlling the flux through the pathway, but at high glucose concentration the control moves to phosphofructokinase. Next, we have compared our results with those obtained with the shortening and titration method, previously described (Torres, N.V., Mateo, F., Mélendez-Hevia, E. and Kacser, H., (1986) Biochem. J. 234, 169–174; Torres, N.V. and Meléndez-Hevia, E. 1991. Molec. Cell. Biochem. 101, 1–10). Furthermore, from knowledge of the enzyme kinetics of the system we have been able to build a model of the pathway that allows us computer similation of its behavior and calculation of the Flux Control Coefficient profile at different glucose concentrations. By the three methods the results correlate, supporting the use of the pathway substrate as external modulator of the metabolic system as a tool for practical application of Control Analysis.     

On the Estimation of Mean Infecundable Period Following Childbirth (Using Information on Lactation Period)—A Competing Risk Theory Approach

The methodological paper envisages to provide two measures of infecundable period following childbirth; one based on the lactation period when expiry period of amenorrhoea (P.P.A.) follows the same immediately. The other one is based on P.P.A. when expiry of P.P.A. precedes the lactation period. The weighted average of the two measures (duly weighted by the probabilities of both the events) has been given as the estimate of the mean infecundable period. A competing risk oriented approach is adopted to evolve the methodology.     

Anemia in experimental visceral leishmaniasis in hamsters.

Experimental infection of hamsters with Leishmania donovani caused visceral leishmaniasis in which hematological changes occurred. The infected hamsters were anemic and reticulocyte counts were high. No significant change in the serum erythropoietin level was noted. Red cell membrane Na(+)-K(+)-ATPase and acetylcholinesterase activities increased. Osmotic fragility of the erythrocytes from infected animals increased. The level of 2,3-diphosphoglycerate of the red cells increased with the degree of anemia.     

The stimulation of collagenase production in rabbit articular chondrocytes by interleukin-1 is increased by collagens

Osteoarthritis is characterized by a loss of articular cartilage due at least in part to the action of degradative enzymes secreted by chondrocytes. We have investigated the effect of type II collagen from cartilage and interleukin 1 on collagenase production in cultures of rabbit articular chondrocytes. Interleukin 1 alone stimulated the chondrocytes to secrete collagenase but this response was increased as much as fivefold by the addition of rabbit type II collagen. Bovine type II and chick type I collagens were also stimulatory. The native form of the collagens was not required since denatured collagens and purified chick type II alpha chains were effective. The observed effects of collagens and interleukin 1 may contribute to the progressive nature of osteoarthritis.     

Regulation of dnaB function in DNA replication in Escherichia coli by dnaC and lambda P gene products

The dnaB protein of Escherichia coli, a multifunctional DNA-dependent ribonucleotide triphosphatase and dATPase, cross-links to ATP on ultraviolet irradiation under conditions that support rNTPase and dATPase activities of dnaB protein. The covalent cross-linking to ATP is specifically inhibited by ribonucleotides and dATP. Tryptic peptide mapping demonstrates that ATP cross-links to only the 33-kDa tryptic fragment (Fragment II) of dnaB protein. The presence of single-stranded DNA alters the covalent labeling of dnaB protein by ATP, suggesting a possible role of DNA on the mode of nucleotide binding by dnaB protein. Present studies demonstrate that the dnaC gene product binds ribonucleotides independent of dnaB protein. On dnaB-dnaC protein complex formation, covalent incorporation of ATP to dnaB protein decreases approximately 70% with a concomitant increase of ATP incorporation to dnaC protein by approximately 3-fold. The mechanism of this phenomenon has been analyzed in detail by titrating dnaB protein with increasing amounts of dnaC protein. The binding of dnaC protein to dnaB protein appears to be a noncooperative process. The lambda P protein, which interacts with dnaB protein in the bacteriophage lambda DNA replication, does not bind ATP in the presence or absence of dnaB protein. However, lambda P protein enhances the covalent incorporation of ATP to dnaB protein approximately 4-fold, suggesting a direct physical interaction between lambda P and dnaB proteins with a probable change in the modes of nucleotide binding to dnaB protein. The lambda P protein likely forms a lambda P-dnaB-ATP dead-end ternary complex. The implications of these results in the E. coli and bacteriophage lambda chromosomal DNA replication are discussed.     

Effect of erythropoietin on the glucose transport of rat erythrocytes and bone marrow cells

The effect of Ep on radioactive glucose and methyl-alpha-D-glucoside transport by rat erythrocytes and bone marrow cells were studied. There is initial linearity followed by saturation kinetics of [14C]glucose transport by the erythrocytes of starved and starved plus Ep-treated rats at different concentrations of glucose. Starvation caused slight inhibition of glucose transport which increased markedly on Ep administration to starved rats. Normal animals failed to show any significant change in glucose transport after Ep treatment. Methyl-alpha-D-glucoside inhibited the Ep-stimulated glucose transport significantly. Ep also stimulated the transport of radioactive methyl-alpha-D-glucoside which was competitively inhibited in presence of D-glucose. Glucose transport in erythrocytes was found to be sensitive to metabolic inhibitors like azide and DNP. A sulfhydryl reagent and ouabain also inhibited the transport process. Ep stimulated glucose and methyl-alpha-D-glucoside transport in the bone marrow cells of starved rats. The sugar analog competitively inhibited the glucose transport in bone marrow cells and vice versa.     

A multistate Markov chain model for evaluating a sterilization policy

"A multistate Markov chain model corresponding to varying fertility and mortality rates at different levels of surviving children of a couple was developed. Asymptotic probabilities of having a fixed number of children have been worked out." The implied geographical focus is on India.     

In vitro studies of iron bioavailability

The bioavailability of iron from foods is ultimately determined by interactions between iron and other components in the digestive milieu. Perhaps the most important factor is the concentration of Fe2+ during transit through the duodenum. During in vitro simulations of human digestion it is possible to probe the concentration of Fe2+, the rate of Fe2+ formation, and total iron concentration using ferrous chromogens. It is crucial, of course, that the chromogen not interfere with the redox reactions occurring during digestion. Accordingly, ferrozine was examined with regard to its ability to reduce complexes Fe3+, alter rates of Fe3+ production, detect Fe2+ present in the digestive mixture and differentiate the effects of chelating and reducing agents in the mobilization of iron from pinto beans. The chromogen was found to be free from apparent artefacts and to be a sensitive and reproducible probe of the state of iron in digestive mixtures.