PubMed Health⌕ Search

Biomedical subjects

B C Black

Publications and source records attributed to B C Black.

10 recordsLinked to original sources
PubMed1991

Temporal and spatial expression of the yellow gene in correlation with cuticle formation and dopa decarboxylase activity in Drosophila development.

The yellow (y) gene of Drosophila is required for the formation of black melanin and its deposition in the cuticle. We have studied by immunohistochemical methods the temporal and spatial distribution of the protein product of the y gene during embryonic and pupal development and have correlated its expression with events of cuticle synthesis by the epidermal cells and with cuticle sclerotization. Except for expression in early embryos, the y protein is only found in the epidermal cells and may be secreted into the cuticle as it is being deposited. The amount of y protein in various regions of the embryo and pupa correlates directly with the intensity of melanization over any section of the epidermis. Expression of the y gene begins in the epidermal cells at 48 hr after pupariation and is well correlated with the beginning deposition of the adult cuticle. At this stage the adult cuticle is unsclerotized and unpigmented and dopa decarboxylase levels, a key enzyme in catecholamine metabolism which provides the crosslinking agents as well as the precursors for melanin, is low. As a separate event 26 hr after the onset of y gene expression, the first melanin deposition occurs in the head bristles and pigmentation continues in an anterior to posterior progression until eclosion. This melanization wave is correlated with elevated dopa decarboxylase activity. Crosslinking of the adult cuticle also occurs in a similar anterior to posterior progression at about the same time. We have shown by imaginal disc transplantation that timing of cuticle sclerotization depends on the position of the tissue along the anterior-posterior axis and that it is not an inherent feature of the discs themselves. We suggest that actual melanization and sclerotization of the cuticle by crosslinking are initiated at this time in pupal development by the availability of the catecholamine substrates which diffuse into the cuticle. Intensity of melanization and position of melanin pigment is determined by the presence or absence of the y protein in the cuticle, thus converting the y protein prepattern into the melanization pattern.

Animals↗
PubMed1990

Mutations affecting phenol oxidase activity in Drosophila: quicksilver and tyrosinase-1.

The complex enzyme phenol oxidase plays a major role in sclerotization and melanization of cuticle in insects. Production of active enzyme from the inactive proenzyme involves at least six protein components in Drosophila. We examine here the biochemical phenotype of two loci that affect phenol oxidase activity--quicksilver (qs; 1-39.5) and tyrosinase-1 (tyr-1; 2-54.5). Three mutations isolated by different procedures in three different laboratories are alleles at the quicksilver locus. The effects of these mutations have been monitored by means of enzyme assays in vitro and in polyacrylamide gels and by measurement of catecholamine pool sizes. The activity of all three active enzyme components (A1, A2, and A3) is reduced in qs mutants. The activated enzyme of one qs allele is thermolabile, while its activator is normal. Deletion and genetic mapping place tyr-1 near purple (pr; 2-54.5). Enzyme activity is reduced to 10% of normal but is not thermolabile and the activator is normal. The activity of all three A components is reduced. The diphenol oxidase activity in double mutant combinations shows that these mutations and Dox-A2 (Pentz et al., 1986) affect this enzyme in different ways.

Alleles↗
PubMed1987

The alpha methyl dopa hypersensitive gene, 1(2)amd, and two adjacent genes in Drosophila melanogaster: physical location and direct effects of amd on catecholamine metabolism.

The dopa decarboxylase gene (Ddc) is located in a very dense cluster of genes many of whose functions appear to be related to the physiological role of dopa decarboxylase (DDC) in catecholamine metabolism. In Drosophila melanogaster catecholamine metabolism is involved in the production of neurotransmitters and in the synthesis of cross-linking agents for cuticular sclerotization. In this report we consider three loci near Ddc that affect cuticle formation. The alpha methyl dopa hypersensitive gene, 1(2)amd, is definitively assigned to a transcriptional unit 2 kb distal to Ddc. The assignment of 1(2) 37 Bd and 1(2)37 Cc to coding regions in the immediate vicinity of amd and Ddc is examined. amd+ gene activity performs a vital function essential for the formation of insect cuticle and also determines the level of sensitivity to the DDC analogue inhibitor, alpha methyl dopa. We present data that provide direct evidence that the amd+ gene product is required for a step in the metabolism of dopa to one or more novel catecholamines involved in the colorless sclerotization of cuticle.

Animals↗
PubMed1986

A kinetic analysis of Drosophila melanogaster dopa decarboxylase.

The kinetic mechanism of dopa decarboxylase (3,4-dihydroxy-L-phenylalanine carboxy-lyase, EC 4.1.1.28) was investigated in Drosophila melanogaster. Based on initial velocity and product inhibition studies, an ordered reaction is proposed for dopa decarboxylase. This kinetic mechanism is interpreted in the context of measured enzyme activities and the catecholamine pools in Drosophila. The 1(2)amd gene is immediately adjacent to the gene coding for dopa decarboxylase (Ddc) and determines hypersensitivity to alpha-methyldopa in Drosophila. Dopa decarboxylase does not decarboxylate alpha-methyldopa and hence does not generate a toxic product capable of inhibiting 1(2)amd gene function. We propose that the 1(2)amd gene is involved with an unknown catecholamine pathway involving dopa but not dopamine.

Animals↗
PubMed1986

Morphology of staphylococcus bacteriophage P 1.

The group D staphylococcal phage P 1 was examined in the electron microscope after preparation by a variety of procedures. The virion was found to have an icosahedral capsid attached to a long contractile tail structure, the viral tail could be seen in partially contracted configurations. Morphological variants in the length of the sheath and needle were frequently found.

Capsid↗
PubMed1986

A diphenol oxidase gene is part of a cluster of genes involved in catecholamine metabolism and sclerotization in drosophila. I. Identification of the biochemical defect in Dox-A2 [l(2)37Bf] mutants.

Phenol oxidase, a complex enzyme, plays a major role in the processes of sclerotization and melanization of cuticle in insects. Several loci have been reported to affect levels of phenol oxidase activity, but to date only one structural locus has been identified [Dox-3F (2-53.1+)]. Recently isolated Dox-A2 mutations (2-53.9) are recessive, early larval lethals, which as heterozygotes reduce phenol oxidase activity. A homozygous mutant escaper had weak, completely unpigmented cuticle and unpigmented bristles. Enzyme assays show that Dox-A2 heterozygotes have diphenol oxidase activity reduced to 47-79% of wild type, whereas monophenol oxidase activity, at 94-106% of wild type, is normal. Elevated pool sizes of the diphenol oxidase substrates DOPA, dopamine, and N-acetyldopamine are observed in the mutant, confirming the enzyme assay results. Separation of the three phenol oxidase A component activities on polyacrylamide gels shows that Dox-A2 mutations reduce the activity of only the A2 component. Dox-A2 may identify a structural locus for the A2 component of the diphenol oxidase enzyme system. The Dox-A2 locus is one of 18 loci in the dopa decarboxylase, Df (2L)TW130 region of the second chromosome, at least 14 of which affect the formation, melanization or sclerotization of cuticle in some way. These loci form an apparent cluster of functionally related genes.

Alleles↗
PubMed1981

The genetics of dopa decarboxylase in Drosophila melanogaster. IV. The genetics and cytology of the 37B10-37D1 region.

Of 204 mutations located in the 8-12 band Df(2L)130 region, 37B9-C1,2;37D1-2, 199 have been assigned to twelve lethal genes and one visible gene (hook). The 13 genes are not evenly distributed. Twelve, (possibly all thirteen) are in the seven band region 37B10-C4 giving a gene-to-band ratio of almost two. Only one gene, 1(2)37Cf, may be in the four band region 37C5-7, and none are localized in band 37D1. In situ hybridization places the dopa decarboxylase structural gene, Ddc, in or very close to band 37C1,2 (Hirsh and Davidson, 1981). The chi methyl dopa hypersensitive gene, 1(2) and, is 0.002 map units distal to Ddc. Df(2L)VA17, 37C1,2; 37F5-38A1 may actually break in the 37C1,2 singlet. It places six genes, hook, 1(2) and, and four lethal genes, in a maximum of five bands, 37B10, 11, 12, 13 and perhaps part of the 37C1,2 singlet and localizes six genes, Ddc plus five lethal genes, in a maximum of three bands; probably part of the 37C1,2 singlet plus bands, C3, and C4. Wild type activity of five of twelve lethal genes is necessary for female fertility. --Band 37C5 puffs at the time of pupariation; Puff Stages 8-10. Twelve of eighteen alleles of 1(2)37Cf have been examined as heterozygotes over CyO and none affect the appearance of a homozygous 37C5 puff. --Of the 204 mutations considered here only one Ddcpl, affects the function of more than one gene. It eliminates Ddc+ and 1(2)37Ca+ function and at 30 degrees C reduces 1(2)37Ce+ function. It is not a deficiency but could be a polar mutant.

Animals↗
PubMed1979

DNA-binding properties of the major core protein of adenovirus 2.

The major adenovirus core protein (P.VII) binds to various species of duplex and single-stranded DNA molecules as a linear function of P.VII concentration. P.VII progressively condenses 32S Ad2 DNA into rapidly sedimenting forms having an S value of around 2,280. P.VII does not coat DNA like cytochrome C, instead DNA-protein beads are visualized in the electron microscope at low protein concentration. These beads appear to interact forming larger structures and at high P.VII concentrations the DNA molecule becomes highly compacted. Analysis of DNA fragments formed after digestion of P.VII-DNA complexes and isolated cores with micrococcal nuclease suggest that the organization of the DNA in the two structures is essentially identical. The initial P.VII and DNA interaction is sensitive to both ionic and hydrophobic environments, whereas the in vitro DNA-P.VII complexes are extremely stable and are not disrupted in the presence of 3 M NaCl, 1% sarcosyl or 5% deoxycholate. Properties of these in vitro DNA-protein VII complexes share striking similarities to isolated viral core particles.

Adenoviruses, Human↗