The formation and thermal stability of in vitro assembled fibrils from acid-soluble and pepsin-treated collagens.

The role of the non-helical regions of the collagen molecule in fibrillogenesis has been investigated by comparing the kinetics of fibril formation of pepsin-treated acid-soluble collagen, acid-soluble collagen and mixtures of the two and by comparison of the thermal stabilities of the fibrils formed. The acid-soluble collagen was found to aggregate more rapidly than the pepsin-treated collagen under physiological conditions of pH and ionic strength. Variations in ionic strength, at physiological pH, were found to have differing effects on the aggregation of these two forms of soluble collagen. Fibrils formed from the pepsinized-collagen had a lower thermal stability tha n those formed from the intact collagen. The behavior observed with mixtures of acid-soluble and pepsin-treated collagens was found to be quantitatively consistent with the pepsinized collagen being able to utilize the nuclei formed by the acid-soluble collagen for subsequent growth. However, the use of the acid-soluble nuclei by the pepsinized collagen for growth did not enhance its rate of precipitation during the growth phase, nor did it enhance the thermal stability of the fibrils formed from the pepsinized collagen.     

Apolipoprotein C3 SstI polymorphism and triglyceride levels in Asian Indians

Background  

A close association between Sst I polymorphism in the 3' untranslated region of the apolipoproteinC3 (APOC3 ) gene and levels of plasma triglycerides (TG) had been reported by different investigators. Hypertriglyceridemia(HTG) is a known risk factor for coronary artery disease (CAD) in the context of Asian Indians. We conducted a study on the relationship between APOC3 SstI polymorphism (S1S1, S1S2 and S2S2 genotypes) and plasma TG levels in a group of 139 male healthy volunteers from Northern India.     

Apolipoprotein (apo) E genotypes by polymerase chain reaction and allele-specific oligonucleotide probes: no detectable linkage disequilibrium between apo E and apo CII

Summary Allelic sequence variation in the apolipoprotein (apo) E gene has been analysed by means of synthetic oligonucleotide probes that detect single base pair substitutions in the codons for amino acid positions 112 and 158, substitutions that are responsible for the common isoforms. Use of the polymerase chain reaction procedure to amplify a sequence of 330 base pairs of the human apo E gene has permitted the development of a robust method for apo E genotyping. This technique has been used to determine the apo E genotype in 95 individuals in whom the genotype for an apo CII TaqI restriction fragment length polymorphism has also been determined. No strong linkage disequilibrium between the two gene loci was detected. This suggests that the metabolic effects of variation, in the apo E and apo CII genes, as detected by the polymorphisms used here, would operate in a statistically independent manner.     

A flow-cytometric method for the separation and quantitation of normal and apoptotic thymocytes.

Using flow cytometry, we describe a method for separating and quantifying normal and apoptotic thymocytes. Apoptosis was induced in isolated thymocytes from immature rats by treatment with the glucocorticoid dexamethasone or the antitumor agent etoposide. Subsequent incubation with the vital bisbenzimidazole dye Hoechst 33342 and the DNA intercalating agent propidium iodide enabled three distinct populations of cells to be identified and sorted by flow cytometry. Dead cells fluoresced red due to propidium iodide whereas normal and apoptotic cells fluoresced blue due to Hoechst 33342. Apoptotic cells were distinguished from normal thymocytes both by their higher intensity of blue fluorescence and by their smaller size as determined by a reduction in forward light scatter. The larger cells, with low blue fluorescence, showed normal thymocyte morphology by electron microscopy and the absence of any DNA fragmentation as measured by agarose gel electrophoresis. In contrast, the smaller cells showed both the morphological characteristics of apoptosis and extensive internucleosomal fragmentation of DNA to multiples of approximately 180 bp. Using this method, a time-dependent induction of apoptosis by dexamethasone, which was inhibited by cycloheximide, actinomycin D, and aurin tricarboxylate, was observed. The method should facilitate mechanistic studies on the induction of apoptosis in thymocytes.     

The molecular and genetic regulation of shoot branching

The architecture of flowering plants exhibits both phenotypic diversity and plasticity, determined, in part, by the number and activity of axillary meristems and, in part, by the growth characteristics of the branches that develop from the axillary buds. The plasticity of shoot branching results from a combination of various intrinsic and genetic elements, such as number and position of nodes and type of growth phase, as well as environmental signals such as nutrient availability, light characteristics, and temperature (Napoli et al., 1998; Bennett and Leyser, 2006; Janssen et al., 2014; Teichmann and Muhr, 2015; Ueda and Yanagisawa, 2019). Axillary meristem initiation and axillary bud outgrowth are controlled by a complex and interconnected regulatory network. Although many of the genes and hormones that modulate branching patterns have been discovered and characterized through genetic and biochemical studies, there are still many gaps in our understanding of the control mechanisms at play. In this review, we will summarize our current knowledge of the control of axillary meristem initiation and outgrowth into a branch.

The key regulatory genes and the role of multiple plant hormones coordinate the process of axillary meristem initiation and subsequent growth into a branch.     

Squalestatin 1, a potent inhibitor of squalene synthase, which lowers serum cholesterol in vivo.

Squalestatin 1 is a member of a novel family of fermentation products isolated from a previously unknown Phoma species (Coelomycetes). Squalestatin 1 is a potent, selective inhibitor of squalene synthase, a key enzyme in cholesterol biosynthesis; in vitro, 50% inhibition of enzyme activity is observed at a concentration of 12 +/- 5 nM (range of 4-22 nM). Squalestatin 1 inhibits cholesterol biosynthesis from [14C]acetate by isolated rat hepatocytes (50% inhibition at 39 nM) and by rat liver in vivo. In marmosets, a species with a lipoprotein profile similar to that of man, squalestatin 1 lowers serum cholesterol by up to 75%. This compound will allow further investigation of the control of the sterol biosynthesis pathway and could also lead to the development of new therapies for elevated serum cholesterol.     

Encephalitozoon hellem in Two Eclectus Parrots (Eclectus roratus): Identification from Archival Tissues

ABSTRACT Members of the phylum Microspora are obligate, intracellular, single-celled parasites identified in a wide range of vertebrate and invertebrate hosts. Only a few cases of microsporidial infections have been documented in psittacine birds including peach-faced, masked, and Fischer's lovebirds ( Agapornis roseicollis, A. personata , and A. fischeri. respectively), budgerigars ( Melopsittacus undulatus ), and a double yellow-headed Amazon parrot ( Amazona ochrocephala ). Parasite identification has typically been limited to phylum or genus, and no avian species of microsporidia has clearly been described. In this report, microsporidia were identified in the kidney and intestine of a new host, the eclectus parrot ( Eclectus roratus ). Parasites were identified as Encephalitozoon hellem using morphologic, ultrastructural, and small subunit ribosomal RNA gene sequence data obtained from archived tissues. This parasite species was first identified in immunocompromised humans and may be a potential zoonotic pathogen. The epidemiology and prevalence of this parasite in humans and birds should be further explored.     

Animal models of human microsporidial infections

Two new models have been described for Enterocytozoon bieneusi, non-human primates and immuno-suppressed gnotobiotic pigs, but there still is no successful cell culture system. The intestinal xenograft system holds promise as an animal model for Encephalitozoon intestinalis. Encephalitozoon hellem is easily propagated in mice, and also may be an important cause of spontaneous disease of psittacine birds. Encephalitozoon cuniculi occurs spontaneously in a wide variety of animals and can be induced experimentally in athymic mice. This is a useful experimental system and animal model, but the infection is relatively rare in man. Mammalian microsporidioses first were recognized as spontaneous diseases of animals that later confounded studies intended to elucidate the nature of diseases of humans. Much was learned about both experimental and spontaneous animal microsporidial infections that subsequently has been applied to the human diseases. In addition, new diseases have appeared, in both animals and humans, for which models are being developed. Since there are now animal models for almost all the known human microsporidioses, information on pathogenesis, host defenses, and effective treatments may become available soon. The microsporidioses provide a good example of the value of comparative pathology. Dr. Payne: Joe Payne. How much accidental infection has occurred with adjacent laboratory animals? Dr. Shadduck: A hard question. The organisms are thought to spread horizontally, and there is some pretty good evidence for that in rabbits. One assumes that this also is the explanation for the occurrence in infected kennels. Horizontal transmission probably occurs via contaminated urine, at least in the case of rabbits and dogs. Experimentally, horizontal transmission has been difficult to demonstrate in mice. Relative to the danger in people, I don't know how to answer that. I have always treated this as one of those things where you should be careful, but you shouldn't get paranoid. So, we have handled infected cell cultures and animals as if they were potentially infectious for man, but not as if they were something as hot as the human AIDS virus, for example. With the increasing number of reports in humans, I think it is clear that one would never want anybody who was at risk of being immunocompromised to work with these organisms. Dr. Fenkel: Are there other questions? Dr. Mysore: How do the parasites spread within the infected hosts? Dr. Shadduck: The usual answer is hematogenously via infected macrophages, but data that actually support that statement are rare. One does see infected macrophages in tissues, so it is not unreasonable to think that some of them escape and lodge in other tissues. But that has never actually been formally demonstrated. Dr. Nakeeb: Is E. bieneusi a human pathogen? Dr. Shadduck: The answer depends on which paper you read and what approach the authors took. There are papers in which the authors argue that the organism is not a cause of clinical disease in AIDS patients, but the general belief today is that the parasite does cause diarrhea and enteritis. I think the evidence for pathogenicity is quite strong for the various species of the Encephalitozoon, based on the severity and distribution of the lesions.