Biomedical subjects

W J Brammar

Publications and source records attributed to W J Brammar.

At least 55 records · Page 3Linked to original sources

PubMed1989

Kidney renin mRNA levels in the early and chronic phases of two-kidney, one clip hypertension in the rat.

The effect of clipping the left renal artery on left and right kidney renin mRNA levels during the early and chronic phases of two-kidney, one clip Goldblatt hypertension in the rat was studied. Renin mRNA levels were determined using northern and dot blotting. Four weeks after clipping, renin mRNA levels were sixfold higher in the left kidney and eightfold lower in the right kidney of the Goldblatt rats compared with the left kidney of the sham-operated rats. Similar analysis at 20 weeks after clipping showed a fourfold increase in the left kidney and a 16-fold suppression in the right kidney compared with age-matched sham-operated control rats. The study demonstrates the profound changes that occur in renin gene expression in the clipped and contralateral kidneys in this model of hypertension and shows that these changes persist into the chronic phase of the hypertension.

Animals↗

PubMed1989

A major structural abnormality in the renin gene of the spontaneously hypertensive rat.

The renin genes of the spontaneously hypertensive rat (SHR) and Wistar-Kyoto (WKY) rat were compared by Southern blotting using cDNA and oligonucleotide probes. A 'deletion' of approximately 650 base pairs was found in the first intron (intron A) of the SHR gene compared with the WKY gene. Our studies strongly suggest that this is due to a decrease in the number of copies of the tandemly repeated sequence present within intron A of the rat renin gene. In both SHR and WKY, this region of the gene was found to be different from that of the parent Wistar rat and those of other Wistar-based inbred strains. The functional significance of the abnormality and any role it may have in hypertension in the SHR remain to be determined.

Animals↗

PubMed1988

The Escherichia coli LexA repressor-operator system works in mammalian cells.

We have demonstrated the use of the Escherichia coli LexA repressor-operator system to down-regulate gene expression in mouse cells. The LexA gene was placed downstream of the RSVLTR promoter with polyadenylation and splice signals from SV40. This expression unit was introduced into mouse Ltk- cells by calcium phosphate transfection and stable transfectants selected which express LexA protein. We have used the bacterial chloramphenicol acetyltransferase gene (CAT) as our reporter gene. Transcription of this gene was driven by the HSV tk promoter, into which we have introduced one or two synthetic LexA operator sequences in various positions throughout the promoter. Necessary 3' signals were from the HSV tk gene. Repression by LexA was assessed by comparing the transient expression of tkCAT target constructs, containing LexA operator sequences in the promoter, in cells expressing LexA protein with that in control cells not expressing the repressor. We have observed up to 10-fold repression of CAT expression in LexA+ cells from promoters containing LexA operator sequences.

Animals↗

PubMed1988

Expression of the renin gene in extra-renal tissues of the rat.

Expression of the renin gene in several rat organs is demonstrated by the detection of renin mRNA using a ribonuclease-protection technique. In two of these sites, the brain and the liver, renin mRNA levels are unaffected by changes in dietary salt which markedly affect renal renin mRNA levels. The findings provide the basis for an important ubiquitous local regulatory role for the renin-angiotensin system extending beyond the circulation.

Animals↗

PubMed1988

Histochemical localization of IGF-I and IGF-II mRNA in the rat between birth and adulthood.

We describe the postnatal ontogeny and localization of insulin-like growth factors I and II (IGF-I and -II) in the rat. We have used oligodeoxyribonucleotide probes for in situ hybridization (hybridization histochemistry) and for Northern blotting. IGF-II mRNA is strongly expressed in liver, skeletal muscle, perichondrium, leptomeninges and choroid plexus of the newborn. Demonstrable levels fall dramatically in the liver at 18-20 days postnatally but persist for longer periods in muscle and remain undiminished throughout life in the pia/choroid plexus, indicating that different control mechanisms operate in these tissues. IGF-I mRNA is predominantly found in the liver. Its level in this organ rises well before levels of IGF-II fall. This suggests that distinct factors govern the expression of IGF-I and -II genes.

Animals↗

PubMed1988

Control of IGF-II mRNA levels by glucocorticoids in the neonatal rat.

Insulin-like growth factor-II (IGF-II) is thought to be a major growth factor during fetal and neonatal development. Levels of IGF-II mRNA fall dramatically in the liver - the major site of endocrine production - between 18 and 20 days post-natally. No information concerning the control of gene expression post-natally has hitherto been available. Using Northern blotting and in-situ hybridization, we show here that cortisone acetate rapidly extinguishes IGF-II mRNA expression in the neonatal rat liver. The effect at putative autocrine/paracrine locations such as skeletal muscle and choroid plexus is much less marked or absent. The repression by cortisone acetate is discussed in the light of the available IGF-II gene sequence.

Animals↗

PubMed1987

The nucleotide sequence of the amiE gene of Pseudomonas aeruginosa.

The nucleotide sequence of the amiE gene, encoding the aliphatic amidase of Pseudomonas aeruginosa, has been determined. The sequence of 1038 nucleotides shows a strong bias in favour of codons with G or C in the third position, and only 44 different codons are utilised.

Amidohydrolases↗

PubMed1987

Detection of renin messenger RNA in rat tissues: increased sensitivity using an RNAse protection technique.

Total cellular RNA and poly A+ RNA isolated from various tissues of Wistar-Kyoto (WKY) rats were screened for renin-specific messenger RNA by Northern blotting and RNAse protection. Northern blot analysis, carried out with a copy DNA (cDNA) probe of mouse submandibular gland renin, demonstrated a single RNA species of 1.8 kb in the kidneys of WKY rats. Other tissues screened by this technique were negative. With the more sensitive RNAse protection technique, our initial results indicate more widespread expression of renin, messenger RNA (mRNA) being detected in aorta, adrenal, heart, lung and spleen.

Adrenal Glands↗

PubMed1987

An unusual alteration in c-myc in tissue from a primary breast carcinoma.

We have identified a rearranged c-myc gene in DNA from tumour tissue from a patient with an aggressive carcinoma of the breast. Analysis of this rearranged gene isolated from a size-fractionated genomic library revealed that a deletion had occurred within exon 3. This deletion, of approximately 5 kb, interrupts the coding region of exon 3, and would result in a truncated myc protein with an altered C-terminus. Sequence analysis of the rearranged c-myc gene and the sequence downstream of c-myc which is involved in the deletion has shown precisely where the breakpoint has occurred in both sequences and reveals a short region of homology which could perhaps permit illegitimate recombination between the two sequences.

Base Sequence↗

PubMed1987

Alterations to either c-erbB-2(neu) or c-myc proto-oncogenes in breast carcinomas correlate with poor short-term prognosis.

We have examined the genomic organisation of c-myc, N-myc, L-myc, neu and N-ras in tissue from 41 breast carcinomas, lymph node metastases from 10 of these carcinomas, one fibrosarcoma, 10 cases of benign fibrocystic breast and six fibroadenomas. We have not observed an alteration in either N-myc or N-ras in any of the samples studied. We have seen a 2-fold amplification of L=myc in DNA from one infiltrating ductal (ID) carcinoma, but otherwise we have seen no alterations to this gene. Amplification of c-myc was seen in 22% of ID breast carcinoma sample. Levels of amplification ranged from 2- to 10-fold. We have found a significant (p less than 0.02) correlation between an altered c-myc gene and a very poor short-term prognosis. Amplification of neu was seen in 19% of ID breast carcinomas, but the levels of amplification were higher than those seen for c-myc. Alterations to neu also correlated well with poor short-term prognosis (p less than 0.0002). Finally, we have observed a low level of amplification of c-myc in DNA from a benign fibrocystic breast lesion. This lesion exhibited some features characteristic of those thought to be associated with an increased risk of developing breast cancer.

Breast Neoplasms↗

PubMed1986

Isolation and computer-aided characterization of MmeI, a type II restriction endonuclease from Methylophilus methylotrophus.

A Type II restriction endonuclease, MmeI, has been purified from the obligate methylotroph, Methylophilus methylotrophus. The enzyme was shown to have the non-palindromic recognition sequence 5'-T C C Pu A C (N)20-3', 3'-A G G Py T G (N)18-5' and to cleave (as indicated) on the 3' side, generating a two nucleotide 3' projection. Determination of the recognition sequence was achieved using two new computer programs; RECOG, which predicts recognition sequences from the pattern of restriction fragments obtained from DNAs of known sequence, and GELSIM, which generates graphical simulations of DNA band patterns obtained by gel electrophoresis of restriction digests of sequenced DNA molecules.

Chromosome Mapping↗

PubMed1986

The isolation and nucleotide sequence of the complex AROM locus of Aspergillus nidulans.

The AROM locus of A. nidulans, which governs five consecutive steps in pre-chorismate aromatic amino acid biosynthesis, has been cloned in a bacteriophage vector. The nucleotide sequence of the locus reveals a single, open reading-frame of 4,812 base-pairs, apparently without introns. An internal segment of the A. nidulans AROM sequence has extensive homology with the E. coli aroA gene that encodes the 5-enolpyruvylshikimate 3-phosphate synthase.

Amino Acid Sequence↗

PubMed1985

Nucleotide sequence encoding the biosynthetic dehydroquinase function of the penta-functional arom locus of Aspergillus nidulans.

The nucleotide sequence of a 1.9 Kb HindIII fragment of DNA derived from the arom locus of A.nidulans and encoding the biosynthetic dehydroquinase activity has been determined. The sequences encoding the biosynthetic and catabolic dehydroquinase enzymes of A.nidulans show no detectable homology, strongly suggesting convergent evolutionary pathways. The messenger RNA specified by the arom locus was detected as a 5.3 Kb RNA species.

Aspergillus nidulans↗

PubMed1985

A mouse gene family associated with a major submaxillary-gland glycoprotein.

A gene family encoding msp36 (mouse submaxillary protein 36), a major product of the mouse submaxillary gland, was shown by Southern analysis and genomic cloning to contain approx. 10 related genes. Heteroduplex mapping has elucidated the structure of one of the genes. Close physical linkage of four of the genes in this family has been demonstrated by the use of specific oligonucleotide probes.

Animals↗

PubMed1985

Rec-dependent and Rec-independent recombination of plasmid-borne duplications in Escherichia coli K12.

Plasmidic recombination in E. coli K12 has been previously demonstrated to be dependent on the host rec genotype. The construction of plasmids that carry a duplication within an antibiotic-resistance gene is described. Recombination between the direct repeats recreates an active antibiotic-resistance gene, allowing quantitative analysis of recombination frequencies in a closely related set of E. coli K12 strains carrying various rec mutations. Using this system, intraplasmidic recombination of a duplication within the pBR322 tetracycline-resistance gene is shown to be rec-dependent while recombination of a similar duplication within the kanamycin-resistance gene of Tn903 is shown to be independent of recA, recB, recC, recE, recF and sbcB.

Bacterial Proteins↗

PubMed1984

A retroviral provirus closely associated with the Ren-2 gene of DBA/2 mice.

We have determined the entire nucleotide sequence of an intra-cisternal A particle (IAP) genome, associated with the Ren-2 gene of DBA/2 mice. This genome (MIARN) displays features common to other IAP retroviral-like genomes. Long terminal repeats (LTRs) are approximately 430 base pairs (bp) in length and show typical retroviral U3-R-U5 organisation, though the R-region, at 120 bp, is much larger than the average IAP. This difference probably arose by the amplification of a pyrimidine-rich sequence, by a slippage-mispairing mechanism. Flanking the 5' LTR is a sequence complementary to a phenylalanine tRNA, strongly conserved in all rodent IAP genomes and probably required to prime the initiation of (-) strand synthesis. Flanking the 3' LTR, is a purine-rich sequence probably required for (+) strand synthesis. The tRNA binding site (TBS) is flanked by six tandem copies of a sequence homologous to the TBS. The relationship of the MIARN element to other IAP genomes and the significance of its association with the highly expressed Ren-2 is discussed.

Animals↗

PubMed1984

Molecular cloning of cDNAs from androgen-independent mRNA species of DBA/2 mouse sub-maxillary glands.

cDNA libraries have been constructed from mRNAs isolated from mature male DBA/2 mouse submaxillary glands. Several recombinant plasmids have been assigned to particular mRNA species and their in vitro translation products by HART and hybrid selection. Clones containing copies of two abundant mRNA species that showed no sexual dimorphism were selected for detailed characterisation. Nucleotide sequences determined from one series of clones define an 850 nucleotide mRNA encoding a polypeptide of 16.5 kd having an N-terminal signal sequence, an acidic core and four glycosylation sites. A second family of clones correspond to an mRNA of 800 nucleotides, the sequence of which can be interpreted as coding for an intracellular protein of 14.7 kd. Computer searches of protein and nucleic acid sequences have not revealed the identity of either of these submaxillary gland products.

Amino Acid Sequence↗

PubMed1984

A genetic analysis of defective plasmid formation by N-deficient phage lambda chromosomes.

Plasmid formation by N- derivatives of lambdoid phages has been reinvestigated with transducing phages carrying the trp, lac and gal genes of Escherichia coli. Transduction by lambda N- cI- derivatives was inefficient and short-lived in each case, under both selective and nonselective conditions. Mutant-operators were introduced to relieve possible auto-repression by the cro gene product. Such N-defective phage genomes were able to propagate continually as plasmids, although without selection they were gradually lost from the carrier cells. Plasmid formation remained inefficient, however. The entire chromosome of N- phages can be expressed by transcription that leaks through the serially arranged Rho-dependent terminators. Some functions so expressed are deleterious to the plasmid state and cause the instability of lambda N- plasmids.

Bacteriophage lambda↗