An investigation into thee mechanism of citrate---FE-dependent lipid peroxidation

Chelation by citrate was found to promote the autoxidation of Fe²⁺, measured as the disapperance of 1,10-phenanthroline-chelatable Fe²⁺. The autoxidation of citrate---²⁺ could in turn promote the peroxidation of microsomal phospholipid liposomes, as judged by malondialdehyde formation. At low citrate---Fe²⁺ ratios the autoxidation of Fe²⁺ was slow and the formation of malondialdehyde was preceded by a lag phase. The lag phase evidence of this, linear initial rates of lipid peroxidation were obtained via the combination of citrate---Fe²⁺ and citrate---Fe³⁺, optimum activity occurring at a Fe³⁺---Fe²⁺ ratio of 1:1. Evidence is also presented to suggest that the superoxide and the hydrogen peroxide that are formed during the autoxidation of citrate---Fe²⁺ can either stimulate or inhibit lipid peroxidation by affecting the yield of citrate---Fe³⁺ from citrate---Fe²⁺. No evidence was obtained for the participation of the hydroxyl radical in the initiation of lipid peroxidation by citrate---Fe²⁺.     

Quantitative assessment of vaginal microflora during use of tampons of various compositions.

Although the effect of vaginal tampons on the microbial flora during menstruation has recently been studied by several investigators, quantitative effects attributable to particular tampon fibers have received less attention. The purposes of the present study were (i) to determine and then to compare the effects of polyacrylate rayon tampons and viscose rayon tampons on the normal vaginal flora, (ii) to compare quantitative bacterial counts obtained from these tampons with those obtained from concomitant vaginal swabs, and (iii) to determine whether either of these tampon types alters the vaginal microflora when compared with the microflora in the same women using all-cotton tampons or external catamenial pads. Tampon and swab samples were obtained at predetermined times from 18 women for an average of seven menstrual cycles. Samples consisting of swabs from women wearing menstrual pads were compared with swab and tampon samples taken at predetermined times during the menstrual cycle from women using cotton, polyacrylate rayon, or viscose rayon tampons. Samples were analyzed for total aerobic, facultative, and anaerobic bacterial counts. Statistical evaluation of the results indicated that, on the whole, total bacterial counts decreased during menstruation and that the numbers of bacteria in tampons tended to be lower than those in swab samples taken at the same time. The tampon type had little effect on the vaginal microflora.     

Seminiferous tubule involution in elderly men

The observation of different types of seminiferous tubules (from tubules with normal spermatogenesis to sclerosed tubules) in aging human testes points to the progressive stages of tubular involution in elderly men. The tubules with hypospermatogonesis (reduced number of elongated spermatids) show numerous morphological anomalies in the germ cells, including multinucleated cells. Abnormal germ cells degenerate, causing Steroli cell vacuolation. These vacuoles correspond to dilations of the extracellular spaces resulting from the premature exfoliation of germ cells. Degenerating cells that are phagocytized by Sertoli cells lead to an accumulation of lipid droplets in the Sertoli cell cytoplasm. The loss of germ cells begins with spermatids, but progressively affects the preceding germ cell types, and tubules with maturation arrested at the level of spermatocytes or spermatogonia are observed. Simultaneously, an enlargement of the tunica propria occurs. This leads to the formation of sclerosed tubules, some of which display a low seminiferous epithelium consisting of a few cells--including lipid-loaded Sertoli cells and both Ap and Ad spermatogonia--and others, showing complete sclerosis, are devoid of seminiferous epithelium. The development of tubular involution is similar to that reported after experimental ischemia, which also seems to cause nonspecific effects on the testis such as multinucleate cells, vacuoles, and increased lipids in Sertoli cells.     

Amino-acid sequence of human alpha 2-antiplasmin

The amino-acid sequence of human alpha 2-antiplasmin was determined by Edman degradation of peptides purified from CNBr, tryptic and chymotryptic digests. Of the total sequence of 452 amino acids of mature alpha 2-antiplasmin, as deduced from the cDNA sequence [Holmes et al. (1987) J. Biol. Chem. 262, 1659-1664], 444 residues were identified by amino-acid sequencing. Two differences were found between the peptide and cDNA analyses (Gly instead of Leu at position 10 and Gly instead of Ser at position 369). alpha 2-Antiplasmin contains two disulfide bridges (Cys64-Cys104 and Cys31-Cys113) and four glucosamine-based carbohydrate chains attached to Asn87, Asn256, Asn270 and Asn277. alpha 2-Antiplasmin is homologous with 12 other proteins belonging to the serine protease inhibitor (serpin) superfamily.     

Complete Nucleotide Sequence of the Mouse Lactate Dehydrogenase-a Functional Gene: Comparison of the Exon-Intron Organization of Dehydrogenase Genes

The complete sequence of 12,851 nucleotides of the mouse lactate dehydrogenase-A (LDH-A) gene has been determined. It includes eight exons, seven introns, promoter and regulatory regions. The B1 repetitive elements present in intron III and VI are oriented in opposite orientation, and they share 72% sequence homology. The exon-intron organization of mouse LDH-A gene is compared with the organizations of other dehydrogenase genes, and the molecular evolution of the nicotinamide adenine dinucleotide binding domains is discussed.     

Molecular Evolution and Nucleotide Sequences of the Maize Plastid Genes for the α Subunit of Cf1 (atpA) and the Proteolipid Subunit of Cf0 (atpH)

The nucleotide sequences of the maize plastid genes for the alpha subunit of CF1 (atpA) and the proteolipid subunit of CF0 (atpH) are presented. The evolution of these genes among higher plants is characterized by a transition mutation bias of about 2:1 and by rates of synonymous and nonsynonymous substitution which are much lower than similar rates for genes from other sources. This is consistent with the notion that the plastid genome is evolving conservatively in primary sequence. Yet, the mode and tempo of sequence evolution of these and other plastid-encoded coupling factor genes are not the same. In particular, higher rates of nonsynonymous substitution in atpE (the gene for the epsilon subunit of CF1) and higher rates of synonymous substitution in atpH in the dicot vs. monocot lineages of higher plants indicate that these sequences are likely subject to different evolutionary constraints in these two lineages. The 5'- and 3'-transcribed flanking regions of atpA and atpH from maize, wheat and tobacco are conserved in size, but contain few putative regulatory elements which are conserved either in their spatial arrangement or sequence complexity. However, these regions likely contain variable numbers of "species-specific" regulatory elements. The present studies thus suggest that the plastid genome is not a passive participant in an evolutionary process governed by a more rapidly changing, readily adaptive, nuclear compartment, but that novel strategies for the coordinate expression of genes in the plastid genome may arise through rapid evolution of the flanking sequences of these genes.     

Isolation and culture of cells derived from human cerebral microvessels

Summary Microvessels were isolated from non-neoplastic human cerebral cortical fragments resected for treatment of intractable seizure disorder. The microvessels were incubated in modified Lewis medium with 20 or 30% fetal bovine serum. Within 1–2 weeks, two cell populations emerged from the isolates. One type of cells had polygonal morphology, showed density-dependent contact inhibition at confluence in vitro, showed lectin-binding characteristics of endothelium (but only moderate positivity for factor VIII antigen), demonstrated induction of -glutamyl trans-peptidase when exposed to astrocyte-conditioned media, and responded to insulin by a pronounced increase in DNA synthesis. The other variety of cells grew in vitro more slowly in irregular strands separated by clear zones, showed ultrastructural features of smooth muscle, and isoelectric focusing of cell proteins revealed the presence of smooth-musclespecific -isoactin. Both types of cells could be serially subcultured. The ability to isolate and grow the two cell types, tentatively identified as human cerebral microvascular endothelium and smooth muscle, may facilitate studies of human blood-brain barrier function as well as the pathogenesis of cerebral microangiopathies unique to the human brain.Funded by Canadian Heart Foundation, Heart and Stroke Foundation of Ontario and UCLA Biomedical Research Support Grant     

p82H identifies sequences at every human centromere

Summary A cloned alphoid sequence, p82H, hybridizes in situ to the centromere of every human chromosome. After washing under stringent conditions, no more than 8% of the grains are located on any specific chromosome. p82H thus differs from other centromeric sequences which are reported to be chromosome specific, because it detects sequences that are conserved among the chromosomes. Two experimental approaches show that the p82H sequences are closely associated with the centromere. First, p82H remains with the relocated centromeres in an inv(19) and an inv(6) chromosome. Second, p82H hybridizes at the centromere but not to the centromeric heterochromatin of chromosomes 1, 9 and 16 that have elongated 1qh, 9qh and 16qh regions produced by short growth in 5-azacytidine. The only noncentromeric site of hybridization is at the distal end of the 9qh region.