The effect of thermal injury on the regulation of phosphofructokinase in the mucosa of rat small intestine

The effects of thermal injury (72 h post-injury), 72 h-partial (20% less food) or full starvation on the regulation of phosphofructokinase in the mucosa of rat small intestine were studied. Thermal injury and 72 h-partial or full starvation decreased the activity ratio v0.5/V, but the ratios obtained for thermally injured or fully starved rats were significantly lower than those of controls or partially starved rats. The susceptibility of phosphofructokinase to ATP inhibition was increased after thermal injury and 72 h-partial or full starvation compared to that of normal controls. However, these changes that occurred in the enzyme activities of the rat small intestine were mainly specific to injury per se but do not exclude the contribution of partial starvation during the same period of time.     

The stable evolutionary fixation of a bifunctional tyrosine-pathway protein in enteric bacteria

Abstract The bifunctional T-protein (chorismate mutase-T: cyclohexadienyl dehydrogenase) of l -tyrosine biosynthesis was found to be present in all genera making up the enteric bacteria. The dehydrogenase component of the T-protein was active with both prephenate and l -arogenate, showing it to be a cyclohexadienyl dehydrogenase. The dehydrogenase component, but not the mutase component, of the T-protein was feedback-inhibited by l -tyrosine. Unlike some other bifunctional proteins, the T-protein has evolved recently and is not ubiquitous. However, once the biochemical specialization of bifunctionality becomes established, the results indicate that such character states are strongly conserved through evolutionary time. Thus, bifunctional proteins can provide particularly reliable markers for small (recent origin), intermediate, and large (ancient origin) phylogenetic clusters.     

New prospects for deducing the evolutionary history of metabolic pathways in prokaryotes: Aromatic biosynthesis as a case-in-point

Metabolic pathways of prokaryotes are more biochemically diverse than is generally recognized. Distinctive biochemical features are shared by phylogenetic clusters. The hierarchical levels of characterstate clustering depends upon evolutionary events which fortuitously became fixed in the genome of a common ancestor. Prokaryotes can now be ordered on a phylogenetic tree. This allows the evolutionary steps that underlie the construction and regulation of appropriately complex biochemical pathways to be traced in an evolutionary progression of prokaryote types that house these pathways. Essentially the approach is to deduce ancestral character states at ever deeper phylogenetic levels, utilizing logical principles of maximum parsimony. The current perspective on the evolution of the biochemical pathway for biosynthesis of aromatic amino acids is developed as a case-in-point model for analyses that should be feasible with many major metabolic systems. Phenylalanine biosynthesis probably arose prior to the addition of branches leading to tyrosine and tryptophan. An evolutionary scenario is developed that begins with non-enzymatic reactions which may have operated in primitive systems, followed by the evolution of an enzymatic system that pre-dated the divergence of major lineages of modern eubacteria (Gram-positive bacteria, Gram-negative purple bacteria, and cyanobacteria).Florida Agricultural Experiment Station, Journal Series No. 8251.     

Three-dimensional structure prediction of the NAD binding site of proton-pumping transhydrogenase from Escherichia coli

A three-dimensional structure of the NAD site of Escerichia coli transhydrogenase has been predicted. The model is based on analysis of conserved residues among the transhydrogenases from five different sources, homologies with enzymes using NAD as cofactors or substrates, hydrophilicity profiles, and secondary structure predictions. The present model supports the hypothesis that there is one binding site, located relatively close to the N-terminus of the α-subunit. The proposed structure spans residues α145 to α287, and it includes five β-strands and five α-helices oriented in a typical open twisted α/β conformation. The amino acid sequence following the GXGXXG dinucleotide binding consensus sequence (residues α172 to α177) correlates exactly to a typical fingerprint region for ADP binding βαβ folds in dinucleotide binding enzymes. In the model, aspartic acid α195 forms hydrogen bonds to one or both hydroxyl groups on the adenosine ribose sugar moiety. Threonine α196 and alanine α256, located at the end of βB and βD, respectively, create a hydrophobic sandwich with the adenine part of NAD buried inside. The nicotinamide part is located in a hydrophobic cleft between αA and βE. Mutagenesis work has been carried out in order to test the predicted model and to determine whether residues within this domain are important for proton pumping directly. All data support the predicted structure, and no residue crucial for proton pumping Was detected. Since no three-dimensional structure of transhydrogenase has been solved, a well based tertiary structure prediction is of great value for further experimental design in trying to elucidate the mechanism of the energy-linked proton pump. © 1995 Wiley-Liss, Inc.     

The distribution of phosphofructokinase isoenzymes in the liver of camel, rat and rabbit

1. The distribution of phosphofructokinase isoenzymes have been compared among camel, rat and rabbit livers. 2. Only a single phosphofructokinase isoenzyme is present in the camel liver which has shown different physical and regulatory properties from the isoenzymes of rat and rabbit liver. 3. The ammonium sulphate precipitation curves of the camel and rabbit enzymes were monophasic, whereas the rat enzyme was biphasic. 4. Rabbit liver phosphofructokinase was slightly more anodic than the rat enzyme, whereas the camel enzyme was the least anodic as shown by the techniques of DEAE-cellulose chromatography and cellulose acetate electrophoresis. 5. Partially purified camel liver phosphofructokinase showed different regulatory properties from the rabbit and rat isoenzymes as the apparent Km values were 0.58, 0.45 and 0.82 mM respectively.     

Employers’ perspective of workplace breastfeeding support in Karachi,Pakistan: a cross-sectional study

Background

Breastfeeding is considered to be an important measure to achieve optimum health outcomes for children, women’s return to work has frequently been found to be a main contributor to the early discontinuation of breastfeeding. The aim of the study is to assess workplace breastfeeding support provided to working mothers in Pakistan.

Method

A workplace based cross-sectional survey was conducted from April through December 2014. Employers from a representative sample of 297 workplaces were interviewed on pre-tested and structured questionnaire. The response rate was 93.7 %. Prevalence of workplace breastfeeding facilities were assessed in the light of World Alliance for Breastfeeding Action (WABA) guidelines.

Results

Among non-physical facilities, all workplaces offered 3 months paid maternity leave, 45 % of the sites were offering task adjustment to mothers during lactation period. Only 15 % of the sites were offering breastfeeding breaks to working mothers. Physical facilities that include a breastfeeding corner, refrigerator for storing breast milk, breast milk pump and nursery for childcare were provided in less than 7 % of the sites. Multinational organizations provided better support compared to national organizations.

Conclusion

Support for continuation of breastfeeding by working women at workplaces is inadequate; hence, women discontinue breastfeeding earlier than planned. Policies need to be developed and enforced, employers and employees need to be educated and supportive environment needs to be created to encourage and facilitate breastfeeding friendly worksite environment.

     

Diagnostic criteria for diabetes revisited: making use of combined criteria

Background  

Existing cut-offs for fasting plasma glucose (FPG) and post-load glucose (2hPG) criteria are not equivalent in the diagnosis of diabetes and glucose intolerance. Adjusting cut-offs of single measurements have not helped so we undertook this project to see if they could be complementary.     

Protective role of vitamin E on mefenamic acid-induced alterations in erythrocytes

Erythrocyte osmotic fragility (O.F.), acetylcholinesterase (AChE) activity,and the level of malonyl dialdehyde (MDA) of control, mefenamic acid treated, and mefenamic acid with vitamin E treated rats were investigated. Administration of mefenamic acid to albino rats brought about a significant increase in the osmotic fragility of red cells and a significant (p<0.01) decrease in the activity of AChE. We have also observed increased red cell level of MDA and decreased cholesterol (Chl), hemoglobin (Hb), and reduced glutathione (GSH) content. Supplementation of vitamin E to the mefenamic acid treated rats restored the O.F., AChE activity, level of MDA, and Chl, Hb, and GSH content almost to normal. These observations suggest that mefenamic acid causes functional impairment of red cell membrane, while vitamin E shows its protective role in maintaining normal red cell functions.