Abnormal low density lipoprotein metabolism in apolipoprotein E deficiency

Apolipoprotein(apo) E deficiency is an inherited disease characterized by type III hyperlipoproteinemia and less than 1% normal plasma apoE concentration. The role of apoE in LDL metabolism was investigated by quantitating the metabolism of radiolabeled normal and apoE-deficient LDL in both normal and apoE-deficient subjects. ApoE deficiency resulted in an accumulation of plasma IDL, and a decreased synthesis of LDL consistent with a block in the conversion of IDL to LDL. The LDL isolated from the apoE-deficient patient was similar to normal LDL in hydrated density, size, and composition. However, the apoE-deficient LDL was kinetically abnormal with delayed catabolism in both normal subjects and the apoE-deficient patient. In addition, the catabolism of normal LDL in the apoE-deficient subject was increased. These results were interpreted as indicating that apoE is necessary for the conversion of IDL to LDL and the formation of kinetically normal LDL. The rapid catabolism of normal LDL in the apoE-deficient patient suggests an up-regulation of the hepatic LDL receptor pathway. Based on these results, apoE is proposed to play an important role in the conversion of IDL to LDL, the formation of kinetically normal LDL, and the regulation of LDL receptor function.     

Antiepileptic effects of amphetamine may require GABA (benzodiazepine) activity

Secondary components of visual evoked potentials (slow negative wave-SNW, and photically-evoked sensory afterdischarge-SAD) are known to be precursors of experimentally activated wave-spike discharges, similar to wave-spikes of petit mal epilepsy. Both SNW and SAD may be potently suppressed wither by amphetamine or GABAergic compounds such as diazepam and sodium valproate. A hypothesis was tested in the present study, that amphetamine-induced suppression of wave-spike discharges may require GABA-benzodiazepine activity for its expression.Electrocortical activity was recorded and averaged in unrestrained albino rats with chronically implanted epicortical electrodes. SNW and SAD obtained in habituated rats in the predrug state were potently suppressed by amphetamine (1 mg/kg, i.p.). Fifteen minutes after amphetamine injection, a challenging drug (metrazol, picrotoxin, convulsant benzodiazepine, Ro 5-3663, or imidazodiazepine, Ro 15-1788) was administered intraperitoneally. Subconvulsive doses of metrazol (10 mg/kg) reversed amphetamine suppression; imidazodiazepine (20 mg/kg) and picrotoxin (1.5 mg/kg) reliably opposed the SNW suppression; convulsant benzodiazepine, Ro 5-3663 (2 mg/kg), showed modest and nonsignificant effect in the same direction. It is proposed that the antiepileptic potency of amphetamine may be associated with its ability, apparently via modulatory effect of norepinephrine, to facilitate the activation of benzodiazepine-GABA receptors.     

Lipid,lipoprotein, and apolipoprotein models: past,present, and future

Mones Berman's untimely death on 12 August 1982 put an end to his work in the development of theoretical biology. Arguments are examined, and it is concluded that a formal theory of lipoprotein metabolism flourished and expanded under the guidance of Dr. Berman. Not many scientists in the field of biology spend a major portion of their energies on theoretical work xxx was outstanding because of his early decision to follow the theoretical path.     

THE STRUCTURE OF CELLS DURING TOBACCO MOSAIC VIRUS REPRODUCTION : Mesophyll Cells Containing Virus Crystals

The submicroscopic organization of mesophyll cells from tobacco leaves systemically infected with tobacco mosaic virus (TMV) is described. After fixation with glutaraldehyde and osmium tetroxide the arrangement of the TMV particles within the crystalline inclusions is well preserved. Only the ribonucleic acid-containing core of the virus particles is visible in the micrographs. Besides the hexagonal virus crystals, several characteristic types of "inclusion bodies" are definable in the cytoplasm: The so-called fluid crystals seem to correspond to single layers of oriented TMV particles between a network of the endoplasmic reticulum and ribosomes. Unordered groups or well oriented masses of tubes with the diameter of the TMV capsid are found in certain areas of the cytoplasm. A complicated inclusion body is characterized by an extensively branched and folded part of the endoplasmic reticulum, containing in its folds long aggregates of flexible rods. Certain parts of the cytoplasm are filled with large, strongly electron-scattering globules, probably of lipid composition. These various cytoplasmic differentiations and the different forms of presumed virus material are discussed in relation to late stages of TMV reproduction and virus crystal formation.     

Temperature-related divergence in experimental populations of Drosophila melanogaster. II. Correlation between fitness and body dimensions

From a laboratory stock of Drosophila melanogaster (Oregon), reared for more than 20 years at 18° C, a new population was derived and maintained at 28° C for 8 years. The chromosomal and cytoplasmic contribution to genetic divergence between the two populations was estimated. Six body traits and reproductive fitness were taken into account. The third chromosome is responsible for the adaptive difference for temperature between the two lines. Temperature-selected genes which control body size are located on the second and third chromosomes, although the contribution of each chromosome depends on the environment in which the flies develop. The correlation between the chromosomal and cytoplasmic contributions to different traits and fitness, changes with temperature. At 28° C the correlation between fitness and each body trait is proportional to the response to selection exhibited by each of them, but this is not true at 18° C. Body size has, therefore, an adaptive significance in relation to temperature, which is expressed only in the environment where selection occurs. Cytoplasmic genes affect almost all characters to an extent similar to that of chromosomal genes. Inter-chromosomal and nucleo-cytoplasmic interactions are present and also change with temperature. In general, genes selected in a given environment produce greater phenotypic changes in that environment than in another. The population that experienced both temperatures is fitter in both environments, suggesting that the capacity to adapt to warm temperatures depends on genes other than those which are involved in the adaptation to cold.     

Modulation of secretion of human chorionic gonadotropin by biologic response modifiers on term placenta and choriocarcinoma cells

The effects of biologic response modifiers such as interferon-gamma, tumor necrosis factor alpha (TNF), and retinoic acid on the human chorionic gonadotropin (hCG) secretion of cultured choriocarcinoma cells (JAR) and term placenta have been studied. Although the proliferation of JAR cells was not inhibited by these agents, retinoic acid and TNF markedly increased both the intracellular levels as well as the secreted amounts of hCG. In the case of the term placenta, only retinoic acid increased the hCG secretion into the culture medium, whereas interferon-gamma and TNF both markedly reduced secretion. The cytostatic agent etoposide (VP-16) was able to augment the hCG secretion on the choriocarcinoma cells but did not alter its production on term placenta. The The data presented indicate different mechanisms of regulation of hCG secretion in the normal and malignant trophoblast.     

Apolipoprotein A-I metabolism in subjects with a PstI restriction fragment length polymorphism of the apoA-I gene and familial hypoalphalipoproteinemia

Familial hypoalphalipoproteinemia (hypoalpha), characterized by a decreased high density lipoprotein level, is associated with an increased incidence of premature cardiovascular disease. Restriction fragment length polymorphism analysis of genomic DNA has detected a polymorphism for the PstI restriction endonuclease near the apoA-I gene, with either a 2.2 or a 3.3 kb fragment. The latter has been previously found to occur with significantly higher frequency in probands of families with familial hypoalpha. ApoA-I was isolated from three unrelated subjects with familial hypoalpha and the 3.3 kb PstI polymorphism of the apoA-I gene, and from normal control subjects. The apoA-I from the hypoalpha subjects was structurally normal as determined by amino acid analysis and by two-dimensional gel electrophoresis. When normal apoA-I and hypoalpha apoA-I were simultaneously injected into either normal controls or hypoalpha subjects, both forms of apoA-I were catabolized at the same rate in the same subject, indicating that the hypoalpha apoA-I is also metabolically normal. Analysis of the kinetics of metabolism of apoA-I in the hypoalpha subjects, compared to the normal controls, revealed that the reduced plasma levels of apoA-I were due to an increased apoA-I fractional catabolic rate, and that the synthetic rate was normal. Based on these results, we conclude that the apoA-I gene in these hypoalpha subjects is normal, and the PstI polymorphism near the apoA-I gene, which is associated with familial hypoalpha, is likely to be a marker for a mutant gene closely linked to, but not in, the apoA-I gene.     

Studies on the metabolism of apolipoprotein B in hypertriglyceridemic subjects using simultaneous administration of tritiated leucine and radioiodinated very low density lipoprotein

To study the metabolic pathways of apolipoprotein B (apoB), a series of studies were carried out in which both radioiodinated very low density lipoproteins (VLDL) and tritiated leucine were simultaneously injected into three hypertriglyceridemic subjects. The appearance and disappearance of tritium activity in VLDL apoB, intermediate density lipoprotein (IDL) apoB, and low density lipoprotein (LDL) apoB were followed as was the disappearance of iodine activity from VLDL and the appearance and disappearance of iodine activity in IDL apoB and LDL apoB. It was found that a delipidation chain could describe the kinetics of both endogenously and exogenously labeled VLDL. A slow component of VLDL was necessary to fit the VLDL 131I-labeled apoB data and was consistent with the observed VLDL [3H]apoB kinetics. In addition, the estimated rate of conversion of VLDL apoB to LDL exceeded that which appeared to pass through the measured IDL pools, suggesting that a fraction of the IDL was not directly observed. It was also found that a higher percentage of VLDL 131I-labeled apoB was converted to LDL apoB than was VLDL [3H]apoB. To evaluate possible causes of this apparent anomaly, simultaneous examination of all kinetic data was performed. This exercise resulted in the resolution of removal pathways from multiple compartments in the VLDL delipidation chain and the conversion of slowly metabolized VLDL to IDL and LDL. The wide spectrum of this loss pathway indicates that previous estimates of VLDL apoB production rate using the radioiodinated methodology probably represent lower bounds for the true physiologic variable. It is important to note that these direct losses were apparent only when the combination of endogenous and exogenous labeling was used.     

Effect of exogenous amino acids on the intracellular content of proline and other amino acids in Daucus carota cells

The effect of tryptophan on the biosynthesis of proline has been investigated. Cells of Daucus carota grown in B5 medium supplemented with 5×10^–4M tryptophan acquired the ability to grow in the presence of inhibitory concentrations of azetidine-2-carboxylic acid, an analog of proline. When trp was added to carrot cell cultures at sub-growth inhibiting concentrations, overproduction of intracellular free proline was observed. An increase was also observed for lys, his, ala, leu and phe. Likewise, the addition of asparagine, glutamic acid and phenylalanine to the medium stimulated the intracellular increase of free proline and other amino acids.Abbreviations A2CA azetidine-2-carboxylic acid - 2,4-D 2,4-dichlorophenoxyacetic acid - 5MT 5-methyltryptophan - P5C pyrroline-5-carboxylic acid - f.wt. fresh weight - d.wt. dry weight     

The incidence of Listeria spp. in soft cheeses, butter and raw milk in the province of Bologna

Samples of soft cheese, butter and raw milk were examined for Listeria species. Listeria monocytogenes (serotype 1, haemolytic and virulent for mice) and L. innocua (the only other Listeria sp. isolated) were each found in 2/21 (1.6%) of soft cheese samples. Five per cent of butter samples were contaminated with L. innocua . No Listeria spp. were detected in 40 raw milk samples. The results were compared with similar studies in Italy and abroad. and accepted 14 June 1989