Distribution of mRNAs Encoding the Peroxisome Proliferator-Activated Receptor α, β, and γ and the Retinoid X Receptor α, β, and γ in Rat Central Nervous System

Abstract: We report the isolation, by RT-PCR, of partial cDNAs encoding the rat peroxisome proliferator-activated receptor (PPAR) isoforms PPARα, PPARβ, and PPARγ and the rat retinoid X receptor (RXR) isoforms RXRα, RXRβ, and RXRγ. These cDNAs were used to generate antisense RNA probes to permit analysis, by the highly sensitive and discriminatory RNase protection assay, of the corresponding mRNAs in rat brain regions during development. PPARα, PPARβ, RXRα, and RXRβ mRNAs are ubiquitously present in different brain regions during development, PPARγ mRNA is essentially undetectable, and RXRγ mRNA is principally localised to cortex. We demonstrate, for the first time, the presence of PPAR and RXR mRNAs in primary cultures of neonatal meningeal fibroblasts, cerebellar granule neurons (CGNs), and cortical and cerebellar astrocytes and in primary cultures of adult cortical astrocytes. PPARα, PPARβ, RXRα, and RXRβ mRNAs are present in all cell types, albeit that PPARα and RXRα mRNAs are at levels near the limit of detection in CGNs. PPARγ mRNA is expressed at low levels in most cell types but is present at levels similar to those of PPARα mRNA in adult astrocytes. RXRγ mRNA is present either at low levels, or below the level of detection of the assay, for all cell types studied.     

Mucus trail following by the snail Biomphalaria glabrata (Say)

An experimental procedure involving time-lapse cinematography was used to investigate the responses of the freshwater pulmonate, Biomphalaria glabrata (Say), to their mucus trails. It has been shown that individuals of this species are capable of following their own trails and also those laid by other individuals of the same species. The capacity of mucus trails to influence snail behaviour is lost after a brief period of between 10 and 30 min. The snails tend to move in the direction the trail was laid with expectation greater than by chance. They do not follow mucus trails laid by another species, Limnaea stagnalis. The possible adaptive significance of trail following is discussed.     

The isocitrate dehydrogenases of Acinetobacter lwoffi. Separation and properties of two nicotinamide–adenine dinucleotide phosphate-linked isoenzymes

Two isoenzymes of NADP-linked isocitrate dehydrogenase have been identified in Acinetobacter lwoffi and have been termed isoenzyme-I and isoenzyme-II. The isoenzymes may be separated by ion-exchange chromatography on DEAE-cellulose, by gel filtration on Sephadex G-200, or by zonal ultracentrifugation in a sucrose gradient. Low concentrations of glyoxylate or pyruvate effect considerable stimulation of the activity of isoenzyme-II. The isoenzymes also differ in pH-dependence of activity, kinetic parameters, stability to heat or urea and molecular size. Whereas isoenzyme-I resembles the NADP-linked isocitrate dehydrogenases from other organisms in having a molecular weight under 100000, isoenzyme-II is a much larger enzyme (molecular weight around 300000) resembling the NAD-linked isocitrate dehydrogenases of higher organisms.     

Effects of chronic exercise on the kidneys at different ages

In order to determine the effects of chronic exercise on the kidneys at different ages, young, adult, and old rats swam 1 hour either daily or twice a week for 10 weeks and then were killed along with unexercised controls. The kidneys were removed and sections were prepared for histometric analysis including planimetric measurements on camera lucida drawings of renal components and line sampling. With both degrees of exercise young rats showed lower kidney weight, fewer glomeruli and less medullary tissue than unexercised controls. In the adult group no significant differences were noted between exercised and unexercised rats. In old rats both degrees of exercise resulted in a loss of kidney weight and medullary and cortical mass, and a decrease in size of glomeruli while total number of glomeruli remained unchanged. Thus the effects of chronic exercise on the kidneys varied with age. Retarded kidney development occurred in young animals; a loss of renal tissue in old animals; and no change in adult animals.     

Synthesis of deoxyribonucleic acid in BHK-21/C13 cells

Newly synthesized (3)H-labelled DNA was extracted from baby hamster kidney cells (BHK-21/C13 cells) and was shown to possess single-stranded properties when examined by column chromatography on benzoylated naphthoylated DEAE-cellulose, hydroxyapatite and methylated albumin on kieselguhr, and by its affinity for nitrocellulose filters. Some of the newly synthesized DNA was shown to be of lower molecular weight than the bulk of the DNA when examined by alkaline sucrose-density-gradient centrifugation. The properties observed were not affected by treatment of the DNA with ribonuclease, Pronase or amylase. The effect of the size of the DNA on its observed properties was examined and is discussed. It is concluded that DNA synthesis in BHK-21/C13 cells proceeds according to the discontinuous-mechanism model in at least one of the strands.     

The isocitrate dehydrogenases of Acinetobacter lwoffi. Studies on the regulation of nicotinamide–adenine dinucleotide phosphate-linked isoenzyme

Of the two NADP-linked isocitrate dehydrogenases in Acinetobacter lwoffi the higher-molecular-weight form, isoenzyme-II, is reversibly stimulated sixfold by low concentrations of glyoxylate or pyruvate. Kinetic results indicate that this stimulation of activity involves both an increase in V(max.) and a decrease in the apparent K(m) values for substrates, most markedly that for NADP(+). Other changes brought about by glyoxylate or pyruvate include a shift in the pH optimum for activity and an increased stability to inactivation by heat or urea. Mixtures of glyoxylate plus oxaloacetate, known to inhibit isocitrate dehydrogenases from other organisms, produce inhibition of both A. lowffi isoenzymes, and do not reflect the stimulatory specificity of glyoxylate for isoenzyme-II. Isoenzyme-II is also stimulated by AMP and ADP, but the activation by glyoxylate or pyruvate is shown to be quite independent of the adenylate activation. Differential desensitization of the enzyme by urea to the two types of activator further supports the view that the enzyme possesses two distinct allosteric regulatory sites. The metabolic significance of the activations is discussed.