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Biomedical subjects

W M Brown

Publications and source records attributed to W M Brown.

At least 73 records · Page 4Linked to original sources
PubMed1995

Myocardial protection for coronary artery bypass in patients with acute myocardial infarction: resuscitation of ischemic myocardium.

An increasing body of evidence suggests that the majority of myocardial injury that occurs during ischemia and reperfusion is effected during the reperfusion phase. There is also convincing evidence that controlling the conditions of reperfusion and composition of the reperfusate can markedly minimize the ultimate injury following an ischemic insult. Medical reperfusion (PTCA, thrombolytics) has the disadvantage of reperfusing with unmodified whole blood under uncontrolled conditions, whereas surgical reperfusion allows very stringent control of both. A brief review of the pathophysiology of ischemia and reperfusion is presented to gain insight into the mechanisms of injury that can be counteracted by controlling the conditions of reperfusion and composition of the reperfusate. Surgical protocols that have been developed independently at two separate institutions are outlined, along with the experimental data supporting each method, and the advantages and disadvantages of each method. This information should allow implementation of a rational plan of myocardial protection for resuscitation of the ischemic myocardium when performing coronary artery bypass grafting in the setting of acute myocardial ischemia and infarction.

Clinical Protocols↗
PubMed1994

The second kappa B element, kappa B2, of the HLA-A class I regulatory complex is an essential part of the promoter.

The MHC class I regulatory complex (CRC) contains the well characterized palindromic kappa B element, kappa B1, to which a number of nuclear factors are known to bind. This cis element plays an important role in controlling the transcription of MHC class I genes. In addition, the CRC contains a second kappa B element, kappa B2, which is located in tandem with the kappa B1 site, 5 bp upstream. In this study, from reporter gene transfection experiments, we present evidence that this kappa B2 site is as important as kappa B1 in regulating HLA-A locus transcription. Mutations introduced into either kappa B site reduced promoter activity to approximately the level obtained when the entire CRC was deleted. Electrophoretic mobility shift and supershift assays showed that the kappa B2-binding complex (BIII) contained a p65-like subunit, but apparently not the p50 subunit of NF-kappa B. Complex BIII also bound to the kappa B1 site, but the kappa B2 sequence was poorly recognized by the kappa B1-binding complex, BI, probably KBF1, the p50 homodimer. These results demonstrate that both kappa B sites are essential components of the promoter and suggest that they may function together to control MHC class I gene transcription.

Base Sequence↗
PubMed1994

The nucleotide sequence of the murine Hox-D3 (Hox-4.1) gene reveals extensive identity with the human protein.

We report the sequence of the murine Hox-D3 gene, formerly referred to as Hox-4, Hox-4.1 and Hox-4A. This gene is located on murine chromosome 2 in the Hox-D complex. The predicted Hox-D3 protein comprises 417 amino acids and displays 95% identity to the human protein. We have demonstrated that Hox-D3 is expressed in the skin, kidney and thymus, but not in lung, liver, spleen or stomach.

Amino Acid Sequence↗
PubMed1994

The 5'-sequence of the murine Hox-b3 (Hox-2.7) gene and its intron contain multiple transcription-regulatory elements.

We sought to clone and characterize the murine Hox-b3 gene. In Xenopus embryos, the homologous gene has been shown to be responsive to retinoic acid, an agent which has profound effects on tissue growth and development. By plaque hybridization, using a partial, murine Hox-b3 cDNA as a probe, we screened a genomic library and isolated a series of overlapping clones. Restriction fragments from positive clones were sequenced by the dideoxy method on an automated DNA sequencer. We report the genomic sequence of the murine Hox-b3 gene. The sequence has been submitted to the GenBank database (accession number U02278). Our sequence extends from the P1 promoter through the coding sequence of the gene to the 3'-untranslated region. In common with other homeobox genes, there is an intron between the conserved hexapeptide and the homeobox. It is 866 bp long and has 3'- and 5'-splice sites very similar to the consensus, a long polypyrimidine tract and a potential branch point near the 3'-splice site. We have analyzed the sequence 5' to the initiation codon and the intron for putative control elements, and have identified a series of putative transcription factor binding sites in the P1 promoter and intron, including two for the retinoid X receptor-beta. Their possible significance is discussed. The sequences we have identified may be responsible for the observed pattern of expression of the gene. This sequence and the clones from which it is derived will enable a molecular dissection of the P1 promoter region.

Amino Acid Sequence↗
PubMed1994

Sequences with the potential to form stem-and-loop structures are associated with coding-region duplications in animal mitochondrial DNA.

Tandem duplications of gene-encoding regions occur in the mitochondrial DNA (mt DNA) of some individuals belonging to several species of whiptail lizards (genus Cnemidophorus). All or part of the duplicated regions of the mtDNAs from five different species were sequenced. In all, the duplication endpoints were within or immediately adjacent to sequences in tRNA, rRNA or protein genes that are capable of forming energetically stable stem-and-loop structures. In two of these mtDNAs, the duplication endpoints were also associated with a direct sequence repeat of 13 bp. The consistent association of stem-and-loop structures with duplication endpoints suggests that these structures may play a role in the duplication process. These data, combined with the absence of direct or palindromic repeats at three of the pairs of duplication endpoints, also suggest the existence of a mechanism for generating de novo duplications that is qualitatively different from those previously modeled.

Animals↗
PubMed1994

Complete DNA sequence of the mitochondrial genome of the black chiton, Katharina tunicata.

The DNA sequence of the 15,532-base pair (bp) mitochondrial DNA (mtDNA) of the chiton Katharina tunicata has been determined. The 37 genes typical of metazoan mtDNA are present: 13 for protein subunits involved in oxidative phosphorylation, 2 for rRNAs and 22 for tRNAs. The gene arrangement resembles those of arthropods much more than that of another mollusc, the bivalve Mytilus edulis. Most genes abut directly or overlap, and abbreviated stop codons are inferred for four genes. Four junctions between adjacent pairs of protein genes lack intervening tRNA genes; however, at each of these junctions there is a sequence immediately adjacent to the start codon of the downstream gene that is capable of forming a stem-and-loop structure. Analysis of the tRNA gene sequences suggests that the D arm is unpaired in tRNA(ser)(AGN), which is typical of metazoan mtDNAs, and also in tRNA(ser)(UCN), a condition found previously only in nematode mtDNAs. There are two additional sequences in Katharina mtDNA that can be folded into structures resembling tRNAs; whether these are functional genes is unknown. All possible codons except the stop codons TAA and TAG are used in the protein-encoding genes, and Katharina mtDNA appears to use the same variation of the mitochondrial genetic code that is used in Drosophila and Mytilus. Translation initiates at the codons ATG, ATA and GTG. A + T richness appears to have affected codon usage patterns and, perhaps, the amino acid composition of the encoded proteins. A 142-bp non-coding region between tRNA(glu) and CO3 contains a 72-bp tract of alternating A and T.

Amino Acid Sequence↗
PubMed1993

Synthesis of the foetal protein fetuin by early developing neurons in the immature neocortex.

The presence of the foetal protein fetuin has previously been demonstrated by immunocytochemistry to be specifically confined to the primordial plexiform layer, the early cortical plate and subplate zone cells in the developing neocortex of a number of species. In order to investigate its origin there, we have applied in situ hybridization in paraffin sections of Bouin's fixed foetal sheep brain, using a short anti-sense oligonucleotide probe. The distribution of fetuin mRNA has been compared with that of the protein by using anti-fetuin antibodies and immunocytochemistry. This allowed us to confirm that fetuin is synthesised initially in cells of the primordial plexiform layer and subsequently cortical plate and subplate cells. On the other hand, cells in the ventricular zone that are fetuin (protein) positive do not contain detectable fetuin mRNA. The time course of fetuin mRNA expression in the developing neocortex follows closely the previously described pattern of fetuin (protein) distribution in the sheep brain, apart from its absence from the ventricular zone where its origin is probably by uptake from cerebrospinal fluid.

Animals↗
PubMed1993

Warm blood cardioplegia: superior protection after acute myocardial ischemia.

Three myocardial protection techniques were studied in a canine model of acute myocardial ischemia with subsequent revascularization. Eighteen animals were randomly assigned to one of three treatment regimens: cold oxygenated crystalloid cardioplegia (CC), cold blood cardioplegia with modified reperfusate (CB), and continuous aerobic warm blood cardioplegia (WB) (n = 6 per group). Systemic hypothermic cardiopulmonary bypass (28 degrees C), antegrade arrest, and intermittent retrograde and antegrade delivery were used for the CC and CB groups. Systemic normothermic cardiopulmonary bypass, antegrade arrest, and continuous retrograde delivery were used for the WB group. Fifteen minutes of warm global ischemia was followed by occlusion of the left anterior descending coronary artery (15-minute duration) and simultaneous initiation of cardioplegic arrest (60-minute duration) to simulate clinical revascularization. After reperfusion, the animals were separated from cardiopulmonary bypass. Myocardial function, electrocardiogram, myocardial energetics, water content, histopathology, and defibrillation requirements were compared between groups. There was no significant difference in maximum elastance, myocardial oxygen consumption, myocardial edema, or histopathologic evidence of injury between groups. However, overall ventricular function, assessed by the slope of the preload recruitable stroke work relationship, was significantly better for the WB group (p = 0.04) (WB, 73 +/- 9; CB, 56 +/- 7; CC, 47 +/- 5). Diastolic function as assessed by the slope of the stress-strain relationship was significantly worse overall for the cold groups (p = 0.001) (WB, 20 +/- 2.2; CB, 39 +/- 1.3; CC, 37 +/- 3.1). Myocardial injury as assessed by ST segment elevation (millimeters) was less for the WB group (p = 0.03) (WB, 0.4 +/- 0.3; CB, 1.7 +/- 0.2; CC, 1.6 +/- 0.7). Countershocks necessary to restore sinus rhythm after cross-clamp removal were fewer in the WB group (p = 0.03) (WB, 0.8 +/- 0.3; CB, 4.0 +/- 1.2; CC, 5.5 +/- 1.5). In this model of acute global myocardial ischemia, continuous aerobic warm blood cardioplegia has important advantages over two widely used clinical hypothermic protection techniques.

Animals↗
PubMed1993

Rates and patterns of base change in the small subunit ribosomal RNA gene.

The small subunit ribosomal RNA gene (srDNA) has been used extensively for phylogenetic analyses. One common assumption in these analyses is that substitution rates are biased toward transitions. We have developed a simple method for estimating relative rates of base change that does not assume rate constancy and takes into account base composition biases in different structures and taxa. We have applied this method to srDNA sequences from taxa with a noncontroversial phylogeny to measure relative rates of evolution in various structural regions of srRNA and relative rates of the different transitions and transversions. We find that: (1) the long single-stranded regions of the RNA molecule evolve slowest, (2) biases in base composition associated with structure and phylogenetic position exist, and (3) the srDNAs studied lack a consistent transition/transversion bias. We have made suggestions based on these findings for refinement of phylogenetic analyses using srDNA data.

Animals↗
PubMed1993

Homeobox genes and the patterning of skin diseases.

Fundamental to our understanding of skin diseases and their presentation is an understanding of the pattern of their development. When we have established the molecular basis of their development we will be in a much better position to control and treat such diseases. The homeobox genes are a family of regulatory proteins that influence pattern formation at many levels. Their presence in skin implicates them in this important role. It seems highly likely that they will be shown to be fundamental to the development of the patterns used in diagnosing skin diseases.

Genes, Homeobox↗
PubMed1992

Structure and novel exons of the human tau gene.

The microtubule-binding protein tau is important in establishing and maintaining neuronal morphology and is a major component of the neurofibrillary tangles (NFTs) characteristic of Alzheimer's brain. The neuron-specific tau transcript undergoes complex alternative splicing. The human tau gene has been cloned and mapped. The restriction analysis and partial sequencing of the gene shows that it contains (1) four alternatively spliced exons previously described in rodent and bovine but not in human tau cDNAs and (2) two CpG islands, one associated with the promoter region, the other with exon 9. Examination of human tau mRNA indicates that the human cerebrocortical splicing pattern differs from that previously reported for the murine and bovine tau mRNAs, despite conserved exon organization in all three genes.

Alternative Splicing↗
PubMed1992

The nucleotide and deduced amino acid structures of sheep and pig fetuin. Common structural features of the mammalian fetuin family.

This study was initiated to gain further insight into the structural features of the mammalian fetuin family. The cDNA structures of sheep and pig fetuin were determined. The cDNA insert encoding sheep (pig) fetuin comprised 1550 (1470) nucleotides, including 54 (46) nucleotides encoding a signal peptide of 18 (15) residues and 1038 (1041) nucleotides encoding the 346 (347) amino acids of the mature plasma protein. The predicted amino-terminal sequence of the mature pig fetuin was confirmed by the amino-terminal sequence of the purified protein. However, two alternative sheep amino-terminal sequences were found in fetuin purified from the plasma of a single sheep fetus; the minor product was the one predicted by comparison with other fetuin sequences while the major product was two amino acids longer. Comparison of the deduced amino acid sequences of sheep and pig fetuin showed an extensive sequence identity between them (75%) and with other proteins of the mammalian fetuin family, i.e. human alpha 2-HS glycoprotein, and bovine and rat fetuins. Twelve cysteine residues were found at invariant positions in all fetuin sequences, suggesting strongly that the arrangement of disulphide bridges identified in human alpha 2-HS glycoprotein is common to the members of the family. Further sequence comparisons revealed that the structures of mammalian fetuins are organised in three domains: two cystatin-like domains (D1 and D2) and a complex carboxyl-terminal domain (D3). The proposed three-domain structure of the protein is reflected in the organisation of the rat fetuin structural gene which has recently been published.

Amino Acid Sequence↗
PubMed1992

Fetuin--an old friend revisited.

Bovine fetuin, the first fetal protein to be described, has recently been shown to be a species homologue of a well known human plasma protein--alpha 2HS glycoprotein (alpha 2HS). The fetuins are now known to be members of the cystatin superfamily. The structural properties of the six fetuins that have been fully sequenced are compared. Despite the structural homology of these proteins, their described properties in the literature make them appear to be quite different. The diverse in vitro properties claimed for fetuin/alpha 2HS are reviewed. In vivo, fetuins are involved in the acute phase response. In development, in all species studied so far, fetuins are present in a specific cell population that forms the developing neocortex. The possible functional significance of this distribution is discussed.

Acute-Phase Reaction↗
PubMed1992

Fetuin: an acute phase protein in cattle.

Fetuin is a plasma protein present in high concentrations during fetal development in animals of the order Artiodactyla. Its role is not known. The human homologue of fetuin--alpha 2HS glycoprotein--has been shown to be a negative acute phase protein in adult plasma. In the present study, the concentration of fetuin was measured in the serum of healthy cattle (Bovis bovis) and in animals with various injuries and inflammatory disorders. The levels were decreased by 30% in pregnancy but increased up to 10-fold in some trauma cases. A significant negative correlation between the concentrations of fetuin and albumin has also been found. Thus, fetuin appears to be a positive acute phase protein in cattle.

Acute-Phase Proteins↗
PubMed1992

A novel mitochondrial genome organization for the blue mussel, Mytilus edulis.

The sequence of 13.9 kilobases (kb) of the 17.1-kb mitochondrial genome of Mytilus edulis has been determined, and the arrangement of all genes has been deduced. Mytilus mitochondrial DNA (mtDNA) contains 37 genes, all of which are transcribed from the same DNA strand. The gene content of Mytilus is typically metazoan in that it includes genes for large and small ribosomal RNAs, for a complete set of transfer RNAs and for 12 proteins. The protein genes encode the cytochrome b apoenzyme, cytochrome c oxidase (CO) subunits I-III, NADH dehydrogenase (ND) subunits 1-6 and 4L, and ATP synthetase (ATPase) subunit 6. No gene for ATPase subunit 8 could be found. The reading frames for the ND1, COI, and COIII genes contain long extensions relative to those genes in other metazoan mtDNAs. There are 23 tRNA genes, one more than previously found in any metazoan mtDNA. The additional tRNA appears to specify methionine, making Mytilus mtDNA unique in having two tRNA(Met) genes. Five lengthy unassigned intergenic sequences are present, four of which vary in length from 79 to 119 nucleotides and the largest of which is 1.2 kb. The base compositions of these are unremarkable and do not differ significantly from that of the remainder of the mtDNA. The arrangement of genes in Mytilus mtDNA is remarkably unlike that found in any other known metazoan mtDNA.

Adenosine Triphosphatases↗
PubMed1991

Heteroplasmy suggests limited biparental inheritance of Mytilus mitochondrial DNA.

Strict maternal inheritance of mitochondrial DNA is commonly observed in animals. There is usually only one mitochondrial DNA population (homoplasmy) within an individual. Mussels of the Mytilus edulis species group appear to be exceptions in both respects. Of 150 Mytilus individuals examined, 85 were heteroplasmic. Mitochondrial DNA types within heteroplasmic individuals differed greatly; in one comparison, the inferred sequence difference was 20 +/- 5 percent. Homoplasmic individuals with mitochondrial DNA similar to the heteroplasmic mitochondrial DNA types were found. These observations are best explained by the hypothesis that biparental inheritance of mitochondrial DNA can occur in Mytilus.

Animals↗
PubMed1991

Resolution of the African hominoid trichotomy by use of a mitochondrial gene sequence.

Mitochondrial DNA sequences encoding the cytochrome oxidase subunit II gene have been determined for five primate species, siamang (Hylobates syndactylus), lowland gorilla (Gorilla gorilla), pygmy chimpanzee (Pan paniscus), crab-eating macaque (Macaca fascicularis), and green monkey (Cercopithecus aethiops), and compared with published sequences of other primate and nonprimate species. Comparisons of cytochrome oxidase subunit II gene sequences provide clear-cut evidence from the mitochondrial genome for the separation of the African ape trichotomy into two evolutionary lineages, one leading to gorillas and the other to humans and chimpanzees. Several different tree-building methods support this same phylogenetic tree topology. The comparisons also yield trees in which a substantial length separates the divergence point of gorillas from that of humans and chimpanzees, suggesting that the lineage most immediately ancestral to humans and chimpanzees may have been in existence for a relatively long time.

Animals↗