Differential Regulation of Malate Dehydrogenase Isoenzymes by Hydrocortisone in the Liver and Brain of Aging Rats

The activities and induction patterns of the isoenzymes of malate dehydrogenase (MDH) of the liver and brain of male rats of various ages were studied. The activities of both the isoenzymes of MDH of the liver and brain show a gradual increase with increasing age of the rats. Adrenalectomy decreases and hydrocortisone treatment increases the activity of cytoplasmic MDH of the liver and brain of rats of all the ages except that of the brain isoenzyme of old rats. This hormone-mediated induction of the isoenzyme is actinomycin D-sensitive. Furthermore, adrenalectomy decreases and hydrocortisone treatment increases the activity of mitochondrial MDH of the liver of young and adult rats but not in old rats. However, these treatments do not show any significant effect on the activity of mitochondrial MDH of the brain of rats of all the ages.     

Cloning and expression profiles of tumor suppressor QM homologue in response to granulovirus in Pieris rapae

The tumor suppressor, QM, has been cloned and characterized from various model organisms such as human, plant and invertebrates. Yet, it has not been seriously investigated for its role in conjunction with antiviral mechanisms involving innate insect immunity. From the expressed sequence tag (ESTs) project, conducted with larval cDNA library of cabbage butterfly, Pieris rapae, a partial fragment (718 bp) of QM homologue, termed PrQM containing 660 bp long open reading frame (ORF) encoding protein of 219 amino acids was identified. In silico analysis of PrQM ORF revealed the presence of ribosomal protein L10a/L10e type domain. Phylogenetic analysis of the P. rapae QM‐like protein showed high amino acid sequence similarity with other PrQM polypeptides identified from Heliothis virescenes (95%), Plutella rapae (92%), Bombyx mori (92%), Drosophila melanogaster (89%), and Polyrhachis vicina (85%). The butterfly QM has the closest phylogenetic relationship to a moth (Hv) QM homologue. Further investigations revealed the expression of PrQM at all developmental stages, with pronounced presence at the egg stage. In addition, spatial pattern analysis indicated its high expression in the head, salivary gland, integument and fat body with visible presence in Malpighian tubule and gut. Time course expression studies conducted after immune‐challenge with lipoteichoic acid (LTA) showed the induction of PrQM mRNA at 12 h and 24 h after challenge and also in response to granulovirus (GV). Results of this investigation therefore suggest possible role of QM‐like proteins from Pieris rapae to be involved in innate antiviral immune responses. Further elucidation on the precise function of PrQM during antiviral immune responses by using RNA interference remains a viable research front.     

Effects of Ammonium and Potassium Ions on Some Physiological and Biochemical Processes of Excised Cucumber Cotyledons

Incubation of excised cucumber cotyledons (Cucumis sativus L.) with NH₄Cl solutions exceeding 0.001 M inhibited their greening, fresh weight increases, and incorporation of ¹⁴C-leucine into insoluble N compounds. The absorption of ¹⁴C-leucine during incubation and retention of moisture by the excised cotyledons after incubation were greatly diminished by the NH₄Cl treatments. Treatment with KCl solutions of the same concentrations as the NH₄Cl stimulated the greening, fresh weight increases, and the absorption and incorporation of ¹⁴C-leucine. Desiccation of cotyledons stored at 5°C for 10 days was inhibited by dilute KCl solutions. The toxicity of NH₄Cl was alleviated by KCl solutions at low concentrations.