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Biomedical subjects

W M Brown

Publications and source records attributed to W M Brown.

At least 91 records · Page 5Linked to original sources
PubMed1990

The complete cDNA and amino acid sequence of bovine fetuin. Its homology with alpha 2HS glycoprotein and relation to other members of the cystatin superfamily.

The cDNA sequence encoding the bovine fetal protein fetuin is reported. The deduced amino acid sequence is identical with that obtained from amino acid sequencing. The protein is a single chain preceded by a signal sequence. The three N-linked glycosylation sites have been determined. The sequence of fetuin shows over 70% similarity to human alpha 2HS glycoprotein. All of the cysteine residues are conserved in both proteins, suggesting that fetuin has the same arrangement of disulfide loops as alpha 2HS glycoprotein and may also be a member of the cystatin family. Southern blot analysis indicates that a single gene codes for fetuin. No evidence for a separate gene for a bovine alpha 2HS glycoprotein was obtained; thus, fetuin in cattle and alpha 2HS glycoprotein in the human are equivalent proteins.

Amino Acid Sequence↗
PubMed1990

Carcinoid tumor of the bile duct. A case report and literature review.

A 35-year-old woman presented with painless jaundice that on evaluation was attributed to a tumor at the confluence of the hepatic ducts. There was no evidence of tumor spread on preoperative workup. The tumor was resected and histologically was typical for carcinoid. There have been only ten previously described cases of bile duct carcinoid tumors excluding gallbladder and ampullary lesions. This study presents a discussion of the management of these tumors and a review of the literature.

Adult↗
PubMed1989

Neotropical Africanized honey bees have African mitochondrial DNA.

Non-indigenous African honey bees have invaded most of South and Central America in just over 30 years. The genetic composition of this population and the means by which it rapidly colonizes new territory remain controversial. In particular, it has been unclear whether this 'Africanized' population has resulted from interbreeding between African and domestic European bees, or is an essentially pure African population. Also, it has not been known whether this population expanded primarily by female or by male migration. Restriction site mapping of 62 mitochondrial DNAs of African bees from Brazil, Venezuela and Mexico reveals that 97% were of African (Apis mellifera scutellata) type. Although neotropical European apiary populations are rapidly Africanized by mating with neotropical African males, there is little reciprocal gene flow to the neotropical African population through European females. These are the first genetic data to indicate that the neotropical African population could be expanding its range by female migration.

Animals↗
PubMed1988

Comparisons of ape and human sequences that regulate mitochondrial DNA transcription and D-loop DNA synthesis.

The mitochondrial DNA (mtDNA) control regions for common chimpanzee, pygmy chimpanzee and gorilla were sequenced and the lengths and termini of their D-loop DNA's characterized. In these and all other species for which there are data, 5' termini map to sequences that contain the trinucleotide YAY. 3' termini are 25-51 nucleotides downstream from a sequence that is moderately conserved among vertebrates. Substitutions were greater than 1.5 times more frequent in the control region than in regions encoding structural genes. Additions and deletions were also frequent, especially in gorilla. Sequences of promoters and of two of four transcription factor binding sites were highly conserved. Comparisons of sequence similarity and transition/transversion ratios suggest that human and chimpanzees may be more closely related to each other than either is to gorilla, if substitution rates are approximately equal among these species.

Animals↗
PubMed1988

Polymorphisms in mitochondrial DNA of European and Africanized honeybees (Apis mellifera).

This study demonstrates polymorphisms in both the length and in the restriction enzyme cleavage sites of honeybee mitochondrial DNA (mtDNA). The levels of variation are typical of those found in other metazoan species. These polymorphisms are potentially useful for the identification of Africanized bees in the western hemisphere and for study of honeybee phylogenetics.

Animals↗
PubMed1987

Tandem duplications in animal mitochondrial DNAs: variation in incidence and gene content among lizards.

Size, location, gene content, and incidence were determined for 10 lizard mitochondrial DNA duplications. These range from 0.8 to 8.0 kilobases (kb) and account for essentially all of the observed size variation (17-25 kb). Cleavage-site mapping and transfer-hybridization experiments indicate that each duplication is tandem and direct, includes at least one protein or rRNA gene, and is adjacent to or includes the D loop-containing control region. Duplication boundaries are nonrandomly distributed, and most appear to align with tRNA genes, suggesting that these may play a role in the duplication process. Duplications are infrequent and usually restricted to particular individuals or populations. They appear to be ephemeral; in no case is the same duplication shared by mitochondrial DNAs from closely related species. Mitochondrial DNA duplications occur significantly more often in triploid than diploid lizards and at similar frequencies in hybrids and nonhybrids.

Animals↗
PubMed1987

A new type of collapsible insect-surveillance light trap for sampling Diptera.

The newly designed Army Collapsible Insect Surveillance trap for nocturnal collection of flying Diptera that are attracted by light is described. A polyvinyl chloride construction increases durability, while the capability to collapse from a height of 92.1 cm to 24.1 cm facilitates transportation and storage.

Animals↗
PubMed1986

Nuclear and mitochondrial DNA comparisons reveal extreme rate variation in the molecular clock.

The discovery that the rate of evolution of vertebrate mitochondrial DNA is rapid, compared to the rate for vertebrate nuclear DNA, has resulted in its widespread use in evolutionary studies. Comparison of mitochondrial and nuclear DNA divergences among echinoid and vertebrate taxa of similar ages indicates that the rapid rate of vertebrate mitochondrial DNA evolution is, in part, an artifact of a widely divergent rate of nuclear DNA evolution. This disparity in relative rates of mitochondrial and nuclear DNA divergence suggests that the controls and constraints under which the mitochondrial and nuclear genomes operate are evolving independently, and provides evidence that is independent of fossil dating for a robust rejection of a generalized molecular clock hypothesis of DNA evolution.

Animals↗
PubMed1986

Tandem duplication of D-loop and ribosomal RNA sequences in lizard mitochondrial DNA.

Some Cnemidophorus exsanguis have mitochondrial DNA's (mtDNA's) that are 22.2 kilobases (kb) in size, whereas most have mtDNA's of 17.4 kb. Restriction site mapping, DNA transfer hybridization experiments, and electron microscopy show that the size increment stems from the tandem duplication of a 4.8-kb region that includes regulatory sequences and transfer and ribosomal RNA genes. This observation is notable in that sequences outside of the control region are involved in major length variation. Besides revealing a novel form of mtDNA evolution in animals, these duplications provide a useful system for investigating the molecular and evolutionary biology of animal mtDNA.

Animals↗
PubMed1986

A comparison of the small ribosomal RNA genes from the mitochondrial DNA of the great apes and humans: sequence, structure, evolution, and phylogenetic implications.

Restriction endonuclease fragments produced by EcoRI/AvaI or KpnI digestion and containing the small (12S) ribosomal RNA (rRNA) genes from the mitochondrial DNAs (mtDNAs) of the common chimpanzee, pygmy chimpanzee, gorilla, and orangutan were inserted into the plasmids pBR322 or pADD1. After species verification the inserted fragments were digested with SauIIIA, subcloned into M13mp7 vectors, and sequenced. The small rRNA gene sequences were compared with each other and with the published human sequence (Anderson et al. 1981). Substitutions were detected at 118 of the 955 nucleotide positions compared. Pairwise, the sequence differences ranged from 1% (between the chimpanzee species) to 9% (comparisons involving the orangutan); the proportion that were transitions ranged from 87% to 100%. Deletions and/or additions were noted at seven locations. With respect to evolutionary sequence lability, kinetic analysis indicated the presence of at least two classes of nucleotide positions; the more labile class occurs in sequences thought to form self-complementary duplexes (stems) in the mature rRNA. The high frequency of compensating substitutions, which maintain base-pairing within these sequences, corroborates their inferred structure. Phylogenetic inferences drawn from the sequence comparisons support the notion of an approximately equidistant relationship among chimpanzees, gorilla, and man, with the orangutan much less closely related. However, inference from a shared deletion suggests that the gorilla and the chimpanzees may be more closely related to one another than they are to man.

Animals↗
PubMed1985

Length variation and heteroplasmy are frequent in mitochondrial DNA from parthenogenetic and bisexual lizards (genus Cnemidophorus).

Samples of mtDNA isolated from each of 92 lizards representing all color pattern classes of Cnemidophorus tesselatus and two populations of C. tigris marmoratus were digested with the restriction endonucleases MboI, TaqI, RsaI and MspI. The mtDNA fragment sizes were compared after radioactive labeling and gel electrophoresis. Three features were notable in the comparisons: there was little variation due to gain or loss of cleavage sites, two fragments varied noticeably in length among the samples, one by a variable amount up to a maximum difference of approximately 370 base pairs (bp) and the other by a discrete amount of 35 bp, these two fragments occasionally varied within, as well as between, samples. Two regions that corresponded in size to these variants were identified by restriction endonuclease cleavage mapping. One of these is adjacent to the D-loop. Heteroplasmy, heretofore rarely observed, occurred frequently in these same two regions. Variability in the copy number of a tandemly repeated 64-bp sequence appears to be one component of the variation, but others (e.g., base substitutions or small additions/deletions) must also be involved. The frequent occurrence of these length variations suggests either that they can be generated rapidly or that they were inherited from a highly polymorphic ancestor. The former interpretation is favored.

Animals↗