Complete intron/exon organization of DNA encoding the alpha' chain of human C3

The third component of human complement (C3), a central molecule in both the classical and alternative pathways of complement, is comprised of two polypeptides, termed the alpha and beta chains. Activation of C3 cleaves the alpha chain into two fragments, C3a, an inflammatory peptide, and the alpha' chain which remains covalently linked to the beta chain. Proteolytic fragments derived from the alpha' chain during activation and regulation of complement play a significant role in host defense and regulation of the immune response. Two cosmid clones covering the alpha' chain region were used to characterize the structure of this portion of the C3 gene. The alpha' chain is encoded by 24 exons, which range in size from 52 to 213 base pairs (bp) with an average size of 115 bp. The splice donor sequence at the beginning of intron 12 has a rare sequence variant of GC instead of the usual GT sequence. Ten introns have been completely sequenced and were surprisingly short, ranging in size from 85 to 242 bp with an average of 140 bp. Other introns range in size from 250 bp to over 4 kilobases in length. The gene size for this portion of C3 is estimated to be 23-24 kilobases. Comparison of exon structure with protein domains and with peptide mapping studies demonstrates that several binding sites on C3 are encoded by single exons. These data support the hypothesis that individual exons can code for functional protein domains.     

Selective inhibition of prostaglandin biosynthesis by gold salts and phenylbutazone

Gold salts and phenylbutazone selectively inhibit the synthesis of PGF_2α and PGE₂ respectively. Lowered production of one prostaglandin species is accompanied by an increased production of the other. Selective inhibition by these drugs was observed in the presence of adrenaline, reduced glutathione and copper sulphate under conditions when most anti-inflammatory compounds inhibited PGE₂ and PGF_2α syntheses equally. It is postulated that selective inhibitors may have a different mode of action in vivo and beneficial effects may be related to the endogenous ratio of PGE to PGF required for normal function.     

Coyote laparotomy: in vivo determination of reproductive success

Reproductive tracts of 24 female coyotes hand-reared for behavioral research were examined by laparotomy following the 1977-78 breeding season. Litter counts revealed 51 whelps with 10 of the 24 females while examination by laparotomy indicated 83 uterine swellings in 18 of the same 24 females. The laparotomy proved to be an effective, relatively precise procedure and gave a 39% increase in data acquisition.     

Formation of temporary flagellar structures during insect organogenesis

Cilia and flagella are rare in nongerminal tissues of anthropods, and are generally thought to be restricted to sperm and sensory cells in insects (2). Whitten (5) has reported the presence of kinetosomes at the base of mitotrichia in the dipteran fly Sarcophaga bullata, but reports no evidence of the organization of fibrous elements characteristic of cilia and or flagella. During an ultrastructural analysis of morphogenesis of the colleterial gland of the silk moth Hyalophora cecropia, we found the first example of paired flagella associated with an insect secretory cell. These structures are also unusual in that they serve a temporary role in morphogenesis and subsequently disappear at the terminal stages of differentiation.     

Rates of nuclear and cytoplasmic mitochondrial DNA sequence divergence in mammals

Differential rates of nucleotide substitution among different gene segments and between distinct evolutionary lineages is well documented among mitochondrial genes and is likely a consequence of locus-specific selective constraints that delimit mutational divergence over evolutionary time. We compared sequence variation of 18 homologous loci (15 coding genes and 3 parts of the control region) among 10 mammalian mitochondrial DNA genomes which allowed us to describe different mitochondrial evolutionary patterns and to produce an estimation of the relative order of gene divergence. The relative rates of divergence of mitochondrial DNA genes in the family Felidae were estimated by comparing their divergence from homologous counterpart genes included in nuclear mitochondrial DNA (Numt, pronounced "new might"), a genomic fossil that represents an ancient transfer of 7.9 kb of mitochondrial DNA to the nuclear genome of an ancestral species of the domestic cat (Felis catus). Phylogenetic analyses of mitochondrial (mtDNA) sequences with multiple outgroup species were conducted to date the ancestral node common to the Numt and the cytoplasmic (Cymt) mtDNA genes and to calibrate the rate of sequence divergence of mitochondrial genes relative to nuclear homologous counterparts. By setting the fastest substitution rate as strictly mutational, an empirical "selective retardation index" is computed to quantify the sum of all constraints, selective and otherwise, that limit sequence divergence of mitochondrial gene sequences over time.      

Nitrogen fixation activity of a filamentous,nonheterocystous cyanobacterium in the presence and absence of exogenous,organic substrates

Gallionella ferruginea is able to utilize Fe(II) and the reduced sulfur compounds sulfide and thiosulfate as electron donor and energy source. Tetrathionate and elemental sulfur, on the other hand, are not metabolized. In sulfide-O₂ microgradient cultures G. ferruginea grows at the interface between the oxidizing and the reducing zones. Optimal growth depends on low oxygen and sulfide concentrations. Establishing within the gradient protects the bacterium from too high sulfide concentrations. G. ferruginea excretes extracellular polymeric substances (EPS). While in FeS-gradient cultures 2×10⁶ cells/ml were obtained the bacterial mass could be increased to 1–3×10⁸ cells/ml in shaken batch cultures using thiosulfate as substrate. A further increase of bacterial mass by adding an organic carbon source was not possible confirming that G. ferruginea is an obligate autotrophic organism. When growing on sulfide or thiosulfate the otherwise characteristic twisted stalk consisting of ferric hydroxide is lacking. It is thus shown to be a metabolic end product of Fe(II) oxidation rather than metabolically active cellular material.     

Trisomy 8p: unusual origin detected by fluorescence in situ hybridization

Summary Chromosomal analysis of a neonate with brain and heart abnormalities revealed trisomy for 8p. The mother's karyotype showed 47 chromosomes with one chromosome 8 being represented as two separate chromosomes, an acrocentric 8p and a telocentric 8q. Gbanding and silver staining revealed a satellite and nucleolus organizing region (NOR) on the 8p. Centromericspecific probes to the centromeres of chromosomes 8, 15, 13/21, 22 and the acrocentric chromosomes revealed that only the 8q centromere was of chromosome-8 origin, while the 8p centromere was of chromosome-14 origin.     

A Cerulenin Insensitive Short Chain 3-Ketoacyl-Acyl Carrier Protein Synthase in Spinacia oleracea Leaves

A cerulenin insensitive 3-ketoacyl-acyl carrier protein synthase has been assayed in extracts of spinach (Spinacia oleracea) leaf. The enzyme was active in the 40 to 80% ammonium sulfate precipitate of whole leaf homogenates and catalyzed the synthesis of acetoacetyl-acyl carrier protein. This condensation reaction was five-fold faster than acetyl-CoA:acyl carrier protein transacylase, and the initial rates of acyl-acyl carrier protein synthesis were independent of the presence of cerulenin. In the presence of fatty acid synthase cofactors and 100 micromolar cerulenin, the principal fatty acid product of de novo synthesis was butyric and hexanoic acids. Using conformationally sensitive native polyacrylamide gel electrophoresis for separation, malonyl-, acetyl-, butyryl-, hexanoyl, and long chain acyl-acyl carrier proteins could be detected by immunoblotting and autoradiography. In the presence of 100 micromolar cerulenin, the accumulation of butyryl- and hexanoyl-acyl carrier protein was observed, with no detectable long chain acyl-acyl carrier proteins or fatty acids being produced. In the absence of cerulenin, the long chain acyl-acyl carrier proteins also accumulated.     

Optimization of polyphosphate degradation and phosphate secretion using hybrid metabolic pathways and engineered host strains

Polyphosphate degradation and phosphate secretion were optimized in Escherichia coli strains overexpressing the E. coli polyphosphate kinase gene (ppk) and either the E. coli polyphosphatase gene (ppx) or the Saccharomyces cerevisiae polyphosphatase gene (scPPX1) from different inducible promoters on medium- and high-copy plasmids. The use of a host strain without functional ppk or ppx genes on the chromosome yielded the highest levels of polyphosphate, as well as the fastest degradation of polyphosphate when the gene for polyphosphatase was induced. The introduction of a hybrid metabolic pathway consisting of the E. coli ppk gene and the S. cerevisiae polyphosphatase gene resulted in lower polyphosphate concentrations than when using both the ppk and ppx genes from E. coli, and did not significantly improve the degradation rate. It was also found that the rate of polyphosphate degradation was highest when ppx was induced late in growth, most likely due to the high intracellular polyphosphate concentration. The phosphate released from polyphosphate allowed the growth of phosphate-starved cells; excess phosphate was secreted into the medium, leading to a down-regulation of the phosphate-starvation (Pho) response. The production of alkaline phosphatase, an indicator of the Pho response, can be precisely controlled by manipulating the degree of ppx induction. Copyright 1998 John Wiley & Sons, Inc.     

The self-incompatibility phenotype in brassica is altered by the transformation of a mutant S locus receptor kinase

The self-incompatible (SI) Brassica napus line W1, which carries the 910 S allele, was transformed with an inactive copy of the 910 S locus receptor kinase (SRK) gene. Two transformed lines were analyzed based on their heritable ability to set self-seed. The first line was virtually completely self-compatible (SC), and reciprocal pollinations with the original W1 line demonstrated that only the stigma side of the SI phenotype was altered. An analysis of the expression of endogenous SRK-910 demonstrated that the mechanism of transgene action is via gene suppression. Furthermore, the expression of the S locus glycoprotein gene present in the 910 allele (SLG-910), SLG-A10, which is derived from a nonfunctional S allele, and an S locus-related gene were also suppressed. When the transgene was crossed into another SI line carrying the A14 S allele, it was also capable of suppressing the expression of the endogenous genes and of making this line SC. The second transgenic line studied was only partly SC. In this case as well, only the stigma phenotype was affected, although no gene suppression was detected for endogenous SRK-910 or SLG-910. In this line, the expression of the transgene most likely was causing the change in phenotype, and no effect was observed when this transgene was crossed into the other SI line. Therefore, this work reinforces the hypothesis that the SRK gene is required, but only for the stigma side of the SI phenotype, and that a single transgene can alter the SI phenotype of more than one S allele.