Changes of fatty acid composition of phospholipids and lipid structural order in rat liver mitochondrial membrane subsequent to galactosamine intoxication. Effect of clofibrate

Since it has been earlier reported that D-galactosamine induces an inhibition of palmitoylcarnitine transferase I and a depletion of mitochondrial phospholipids which were both prevented by clofibrate, an evaluation of the effects of these drugs on mitochondrial fatty acid composition was made. Galactosamine does not alter the fatty acid pattern of these fatty acids whereas clofibrate induces a 2-fold increase in monounsaturated/saturated fatty acids ratio and a 10-fold decrease of the 20:4 (n - 6)/20:3 (n - 6) ratio in phosphatidylcholine. These alterations suggest an increase of delta 9-desaturation and a decrease of delta 5-desaturation. To determine whether the drug-induced changes in mitochondrial phospholipids has an effect on the physical properties of the membrane, the lipid structural order of mitochondrial preparations was studied using the lipophilic probes DPH and TMA-DPH. Mitochondrial isolated either from galactosamine- or clofibrate-treated rats showed a decrease in fluorescence polarization, indicating an overall decrease in lipid structural order. This alteration is more drastic when both drugs are administered. This phenomenon suggests drastic changes in the bulk phase of inner mitochondrial membrane lipids after treatments and could explain the altered kinetic properties of palmitoylcarnitine transferase I.     

Measurement of Endogenous Noradrenaline Release in the Rat Cerebral Cortex In Vivo by Transcortical Dialysis: Effects of Drugs Affecting Noradrenergic Transmission

The release of endogenous noradrenaline was measured in the cerebral cortex of the halothane-anesthetized rat by using the technique of brain dialysis coupled to a radioenzymatic assay. A thin dialysis tube was inserted transversally in the cerebral cortex (transcortical dialysis) and perfused with Ringer medium (2 microliter min-1). Under basal conditions, the cortical output of noradrenaline was stable over a period of at least 6 h and amounted to 8.7 pg/20 min (not corrected for recovery). Histological control of the perfused area revealed very little damage and normal morphology in the vicinity of the dialysis tube. Omission of calcium from the perfusion medium caused a marked drop in cortical noradrenaline output. Bilateral electrical stimulation (for 10 min) of the ascending noradrenergic pathways in the medial forebrain bundle caused a frequency-dependent increase in cortical noradrenaline output over the range 5-20 Hz. Stimulation at a higher frequency (50 Hz) resulted in a levelling off of the increase in cortical noradrenaline release. Systemic administration of the dopamine-beta-hydroxylase inhibitor bis-(4-methyl-1-homopiperazinylthiocarbonyl) disulfide (FLA 63) (25 mg/kg i.p.) markedly reduced, whereas injection of the monoamine oxidase inhibitor pargyline (75 mg/kg i.p.) resulted in a progressive increase in, cortical noradrenaline output. d-Amphetamine (2 mg/kg i.p.) provoked a sharp increase in cortical noradrenaline release (+450% over basal values within 40 min). Desmethylimipramine (10 mg/kg i.p.) produced a twofold increase of cortical noradrenaline release. Finally, idazoxan (20 mg/kg i.p.) and clonidine (0.3 mg/kg i.p.), respectively, increased and decreased the release of noradrenaline from the cerebral cortex.(ABSTRACT TRUNCATED AT 250 WORDS)     

Suppression of the Escherichia coli dnaA46 mutation by amplification of the groES and groEL genes

Summary A hybrid phage (Sda1), containing an 8.1 kb EcoRI DNA fragment from the Escherichia coli chromosome, was selected on the basis of its ability to suppress bacterial thermosensitivity caused by the dnaA46 mutation. We have shown that this suppression is due to a recA ⁺-dependent amplification of the 8.1 kb fragment; consistent with this observation, cloning of the 8.1 kb fragment into a high copy number plasmid (pBR325) leads also to suppression of dnaA46. In the suppressed strains growing at high temperature, bidirectional replication starts in or near the oriC region and requires the presence of the DnaA polypeptide. These findings suggest that the overproduction of a gene product(s), encoded by the cloned 8.1 kb fragment, can restore dnaA-dependent initiation of replication at high temperature in the oriC region. Genetic mapping shows that the groES (mopB) and groEL (mopA) genes are located on the 8.1 kb suppressor fragment. Further analysis, including in vitro mutagenesis and subcloning, demonstrates that the amplification of the groES and groEL genes is both necessary and sufficient to suppress the temperature sensitive phenotype of the dnaA46 mutation.     

Scale-down and optimization studies of the gluconic acid fermentation by Gluconobacter oxydans

To simulate production-scale conditions of gluconic acid fermentation by Gluconobacter oxydans, different experimental setups are presented in this study. From the determination of the time constants of a production-scale reactor, it can be concluded that mixing and oxygen transfer are the rate-limiting mechanisms. This results in oxygen concentration gradients which were simulated in a one-compartment reactor in which the oxygen concentration was fluctuated by a fluctuated gassing with air and nitrogen. It could be concluded that only very long periods of absence of oxygen (ca. 180 s) results in lower specific oxygen uptake rates by Gluconobacter oxydans. From scale-down studies carried out in a two-compartment system to simulate a production-scale reactor more accurately, it could be concluded that not only the residence time in the aerated part of the system is important, but the liquid flow in between the different parts of the reactor is also an essential parameter. It could also be concluded that the microorganisms are not influenced negatively by the fluctuated oxygen concentrations with respect to their maximal oxidation capacity. The two-compartment system can also be used for optimization experiments in which the "aerated" compartment was gassed with pure oxygen. From these experiments it was concluded that also a short residence of the cells at high oxygen concentrations diminished the growth and product formation rates. These experiments show the necessity of the scale-down experiments if optimization is carried out. The two-compartment system presented in this study is a very attractive tool for reliable scale-down experiments.     

Sugar cane bagasse as a possible source of fermentable carbohydrates. I. Characterization of bagasse with regard to monosaccharide, hemicellulose, and amino acid composition

Individual monosaccharides present in bagasse hemicellulose were determined using HPLC and other chromatographic procedures. The presence of higher oligomers of the monosaccharides could also be determined. No single procedure can separate and identify all the naturally occurring monosaccharides. The pentosan fraction of bagasse wa successfully hydrolyzed and extracted with 5% (m/v)HCl, and the rate of release of individual monosaccharides was determined. Xylose was the main component in the hydrolyzates, while glucose, arabinose, and galactose present in the side chains of the pentosans were initially released at a fast rate. This treatment resulted in obtaining 229 mg/g xylose (85% of theoretical maximum) and 44 mg/g glucose from bagasse. Only arabinose (2.8 mg/g) and galactose (0.75 mg/g) was also present in detectable quantities. A total of 309 mg monosaccharides were obtained from 1 g of bagasse by this treatment. The results indicated that hydrolysis conditions for specific plant materials depend on the composition of the specific material being utilized. A part of the pentosan fraction (77.1%) was hydrolyzed at a high rate, while 22.9% was more stable and hydrolyzed more slowly. Although 39.8% dry bagasse could be obtained in solution by treatment with dilute alkali, only about 72% of the available hemicelluloses could be extracted in this way if the bagasse was not delignified beforehand. Amino acids and peptides or proteins were also extracted to very much the same with the alkali.     

Is the Golgi apparatus the obligatory final step for lipoprotein secretion by intestinal cells?

It is currently admitted that the synthesis and excretion of triglyceride-rich lipoproteins (chylomicrons and 'small chylomicrons') by intestinal epithelial cells involves the Golgi apparatus as an obligatory final step before exocytosis. The cells of the proximal intestine of the trout are an excellent model for investigating functional compartmentalization in the course of lipid absorption. Using this model, our data invalidate morphological data which were the basis for considering the Golgi apparatus as the mandatory final stage for their secretion. In particular, we show that triglyceride-rich particles can be transported directly from the endoplasmic reticulum to the intercellular space. Two pathways of intestinal lipoprotein excretion appear to coexist. One follows the classical export route, the second functions in a manner that bypasses the Golgi apparatus. The arguments used to affirm the requirement for the Golgi apparatus as a final step (glycosylation of apoprotein B, membrane vehicle for exocytosis) are discussed.     

Immunoglobulin allotypes of Kenyan olive baboons: Troop frequencies,linkage disequilibria,and comparisons with other studies

Sera from a total of 564 olive baboons collected at six different localities in west central Kenya were examined for the presence of cross-reactive immunoglobulin allotypes with reagents used for human sera. Serum samples were tested for Km (1 and 3), Glm (1–3 and 17), andG3m (5, 6, 10, 11, 13–16, 21, 24, and 26). Polymorphism was found for Glm (1 and 17) and G3m (10, 13, and 15). These findings on antigen presence, absence, and polymorphism show broad similarities to, along with some differences from, previous studies of baboons. Our data support the view that there are variations in allotype frequencies between troops at single localities, as well as differences among geographically separated areas. Linkage disequilibria for Gm allotypes differ in strength and direction among the various local Kenya olive baboon populations.     

A reinvestigation of the Gn-RH (gonadotrophin-releasing hormone) systems in the goldfish brain using antibodies to salmon Gn-RH

Summary The organization of Gn-RH systems in the brain of teleosts has been investigated previously by immunohistochemistry using antibodies against the mammalian decapeptide which differs from the teleostean factor. Here, we report the distribution of immunoreactive Gn-RH in the brain of goldfish using antibodies against synthetic teleost peptide.Immunoreactive structures are found along a column extending from the rostral olfactory bulbs to the pituitary stalk. Cell bodies are observed within the olfactory nerves and bulbs, along the ventromedial telencephalon, the ventrolateral preoptic area and the latero-basal hypothalamus. Large perikarya are detected in the dorsal midbrain tegmentum, immediately caudal to the posterior commissure. A prominent pathway was traced from the cells located in the olfactory nerves through the medial olfactory tract and along all the perikarya described above to the pituitary stalk. In the pituitary, projections are restricted to the proximal pars distalis. A second immunoreactive pathway ascends more dorsally in the telencephalon and arches to the periventricular regions of the diencephalon. Part of this pathway forms a periventricular network in the dorsal and posterior hypothalamus, whereas other projections continue caudally to the medulla oblongata and the spinal cord. Lesions of the ventral preoptic area demonstrate that most of the fibers detected in the pituitary originate from the preoptic region.     

The dopaminergic innervation of the goldfish pituitary

Summary The dopaminergic innervation of the goldfish pituitary gland was studied by immunocytochemistry at the electron-microscope level using highly specific antibodies against dopamine coupled to bovine serum albumin with glutaraldehyde. A satisfactory preservation of the tissue was achieved after immersion in 5% glutaraldehyde in phosphate buffer containing sodium metabisulfite to prevent oxidation of the endogenous dopamine. The immunocyto-chemical procedure was performed on Vibratome sections using the preembedding method. Immunoreactivity was restricted to part of the neurosecretory type-B fibers (diameter of the secretory vesicles lower than 100 nm) in which it was found to occupy the whole cytoplasm. Labeled fibers were observed within the neurohypophysis in the different parts of the gland and in the adenohypophyseal tissue where immunoreactive profiles were detected in close apposition to the different cell types. These data are in agreement with previous results obtained by means of radioautography and further support a role for dopamine in the neuroendocrine regulation of pituitary functions in teleosts.     

Gradualismus und Punktualismus Komplementäre Modelle evolutiven Wandels

The models of punctuated and gradual evolution are put in a historical perspective and contrasted with each other. Mechanisms of saltational change are discussed. A synthesis of the two models might be achieved on the basis ofC. H. Waddington’s theory of developmental canalization as recently discussed byA. Hoffman.