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Biomedical subjects

J M Kelly

Publications and source records attributed to J M Kelly.

At least 127 records · Page 7Linked to original sources
PubMed1990

An inversion truncating the creA gene of Aspergillus nidulans results in carbon catabolite derepression.

The creAd-30 mutation leading to carbon catabolite derepression in Aspergillus nidulans is a pericentric inversion, having one breakpoint within the creA gene on the left arm of chromosome I and the other breakpoint between binG and yA on the right arm. The left-arm breakpoint alters the creA transcript. The likelihood that the inversion truncates creA centrally strengthens a previous proposal that derepression is the phenotype of loss-of-function mutations in creA.

Aspergillus nidulans↗
PubMed1990

Localization of vasopressin binding sites in rat tissues using specific V1 and V2 selective ligands.

Arginine vasopressin (AVP) acts on at least two receptor types, classified on the basis of their second messengers. The V1 receptor acts via mobilization of intracellular calcium through phosphatidylinositol hydrolysis and influences blood pressure and hepatic glycogenolysis. The V2 receptor acts via cAMP through activation of adenylate cyclase and causes antidiuresis. Previous studies of the different AVP receptors have been hampered by the use of nonselective radioligands, such as [3H]AVP (which binds to all types of V1 and V2 receptors, certain oxytocin receptors, and neurophysins) as well as the difficulty of measurement of second messengers. This paper describes the use of selective V1 and V2 radioligands with in vitro autoradiography to study V1 and V2 binding sites in rat tissues. [125I][1-(beta-mercapto-beta,beta-cyclopentamethylene propionic acid), 7-sarcosine] arginine vasopressin ([125I][d(CH2)5,Sarcosine7]AVP), a selective V1 antagonist radioligand, bound to regions of the brain, testis, superior cervical ganglion, liver, blood vessels, and renal medulla. Pharmacological characterization of [125I][d(CH2)5,Sarcosine7]AVP binding was consistent with that expected for binding to V1 receptors. There was no specific binding demonstrable to pituitary, renal glomeruli, gut, heart, spinal cord, ovary, adrenal medulla, or adrenal cortex. [3H]1-deamino [8-D-arginine] vasopressin [( 3H]DDAVP), a potent V2 receptor agonist radioligand, was used to study V2 receptors. Specific binding was only identified in the kidney consistent with the known distribution of antidiuretic V2 receptors on renal collecting tubules. No binding was demonstrated on endothelium or liver where DDAVP might influence clotting factor release, nor in the brain, spinal cord, sympathetic ganglia, heart or vascular smooth muscle, regions where DDAVP might cause vasodilatation. These studies demonstrate the use of these radioligands to study V1 and V2 receptors in a variety of tissues. Also, since these ligands are selective they are of particular use to study the different receptor subtypes in tissues where V1 and V2 receptors coexist, such as in the kidney.

Animals↗
PubMed1990

Energy cost of absorption and metabolism in the ruminant gastrointestinal tract and liver: a review.

Contributions of various biochemical processes to overall energy expenditure in the gastrointestinal tract (GIT) and liver have been assessed in this review. The GIT and liver are responsible for a disproportionately high fraction of whole-body energy utilization. The energetic cost of Na+, K(+)-ATPase, protein synthesis and degradation, substrate cycling and urea synthesis contribute substantially to energy expenditure in the ruminant. In the splanchnic bed, these biochemical processes account for approximately 22.8% of whole-body O2 and, consequently, ATP utilization; they are influenced by several factors, including dietary composition, level of intake, age, endocrine status and physiological state. In the GIT and liver, the energetic cost of Na+, K(+)-ATPase is by far the most energetically demanding process; it is related to the active transport of substrates and the maintenance of ionic homeostasis. The high rate of protein synthesis in the GIT is associated with cellular turnover and sloughing, secretion and enzymatic action. In the liver, protein synthesis is important in the mediation of hormonal induction, which influences regulation of body systems, synthesis of plasma proteins, enzymatic and cellular turnover and detoxification of blood. Regulation of these processes and the signals involved in the differential contribution of each biochemical event are not well understood. The large contribution of these biochemical events in the GIT and liver to whole-animal energy utilization suggests that their manipulation may alter the energetic efficiency of meat, milk or wool production.

Absorption↗
PubMed1990

Interaction of tetra-azaphenanthrene ruthenium complexes with DNA and oligonucleotides. A photophysical and photochemical investigation.

The interaction of complexes Ru(bpy)n(TAP)3-n2+ (1a-1d for n = 0-3) with DNA has been investigated using photophysical methods (emission spectroscopy and laser flash photolysis), by studying the induction of single-strand breaks in plasmid DNA and the formation of adducts using 32P-labelled 27-mer oligonucleotides. Two classes of behaviour are found. Complexes 1a and 1b show quenched emission in the presence of calf thymus DNA and yield photoadducts with the 27-mer, whereas 1c and 1d show enhanced emission and do not form photoadducts. 1a and 1b are more efficient sensitizers for single-strand breaks than are 1c and 1d. It is proposed that the excited states of 1a and 1b, which are stronger oxidizing agents than those of 1c and 1d, are capable of oxidizing guanine. Direct evidence for electron transfer has been obtained from laser flash photolysis of Ru(TAP)3(2+) and dGMP, CT-DNA and polynucleotides.

Animals↗
PubMed1990

The Angelchik antireflux device: a 5-year experience.

A total of 44 patients had an Angelchik antireflux prosthesis inserted over a 5-year period. Of these, 41 were available for review and were assessed by interview using a modified Visick grading. Of the 23 patients followed up for a minimum of 3 years 74% had an excellent or satisfactory outcome; 92% of patients with symptoms of reflux obtained relief, but less than 50% of those patients presenting with dysphagia had a satisfactory outcome. The incidence of mild postoperative dysphagia increased the longer the period of follow-up. The main cause of a Visick 3 or 4 result was prosthesis migration. We have modified our technique of insertion to reduce these complications, and in a more recent series have achieved a Visick Grade 1 or 2 in up to 92% of patients. We conclude that dysphagia is a relative contraindication to the insertion of the Angelchik prosthesis. Our recent results encourage the use of the prosthesis provided steps are taken to reduce the incidence of migration and pericapsular fibrous tissue formation.

Adult↗
PubMed1990

Heat illness.

A 17-year-old girl collapsed during a field hockey practice on a hot August afternoon, apparently suffering from heat illness, which is responsible for about 5,000 deaths annually. A panel of experts explores this girl's case, discusses heat illness in general, and makes recommendations about diagnosis, prevention, and treatment.

Adolescent↗
PubMed1989

Physical characterization of the aldehyde-dehydrogenase-encoding gene of Aspergillus niger.

To facilitate a better understanding of the regulation of aldA, the gene encoding aldehyde dehydrogenase (AldDH) in the ascomycete fungus, Aspergillus niger, the gene has been physically characterized. The complete nucleotide (nt) sequence of the gene and its flanking regions has been determined. Analysis of the gene has revealed the presence of three introns. The homologous gene in the related fungus, Aspergillus nidulans, contains only two introns. The coding regions of these genes, excluding the intron sequences, show 80% homology at the nt level and 82% homology at the amino acid (aa) level. The aa sequence of the A. niger enzyme is significantly homologous to mammalian sequences, particularly around one Cys residue, which is hypothesized to be adjacent to another Cys known to be at the active site of mammalian AldDHs. The 5' region of the gene shows one major and two minor transcription start points and a general structure common to highly expressed fungal genes. The 3' region shows four sites of polyadenylation. Sequence comparisons of the 5' region of the A. niger aldA gene to other Aspergillus genes has shown a common sequence in the 5' regions of several A. nidulans genes, all but one of which are subject to carbon catabolite repression. This sequence may be important for the regulatory mechanism.

Aldehyde Dehydrogenase↗
PubMed1989

Milk production, weight changes and blood biochemical measurements in dairy cattle receiving recombinant bovine somatotropin.

Fortnightly injections with 500 mg (1.4 ml) of recombinant bovine somatotrophin in 20 dairy cows and heifers at 80 +/- 7 days after calving resulted in increasing milk yields, compared with paired control cows, for three to four days. The advantage was maintained for a further seven to eight days with a decline occurring during the last two to three days before the next injection. The milk yield did not return to the level of the control cows, and the gap between the lactation curves widened as treatment continued, until two to three weeks after the last injection. The cows' response to treatment was greater than the response to heifers. Blood beta-hydroxybutyrate concentrations reflected the higher energy requirements of the treated animals and the weight loss of the treated heifers. Urea-nitrogen concentrations were significantly lower in the treated animals, suggesting that they utilised protein more efficiently. Treated animals had higher inorganic phosphate concentrations, although they remained within the normal ranges. Differences in calcium, magnesium, albumin and globulin concentrations were either statistically or practically not significant.

3-Hydroxybutyric Acid↗
PubMed1989

Cloning of the creA gene from Aspergillus nidulans: a gene involved in carbon catabolite repression.

The creA gene from A. nidulans has been cloned by complementation of a non-revertable mutant allele using a genomic library and marker rescue techniques. The rescued sequence was subcloned and a 2.3 kb fragment identified which complements several creA mutant alleles. Northern analyses showed that creA encodes a transcript of approximately 1.8 kb in length and that the levels of this transcript varied by up to two fold depending on the carbon source. Transformants containing more than two extra copies of creA grew as wildtype on a range of carbon sources, but there was evidence for tighter carbon catabolite repression.

Aspergillus nidulans↗
PubMed1989

Orally active aldose reductase inhibitors derived from bioisosteric substitutions on tolrestat.

A series of aldose reductase inhibitors was prepared in which structural modifications were made to three positions of the potent, orally active inhibitor tolrestat (1), namely, the 6-methoxy substituent, thioamide sulfur, and the N-methyl moiety. These compounds were evaluated in two in vitro systems: an isolated enzyme preparation from bovine lens to assess their intrinsic inhibitory activity and an isolated rat sciatic nerve assay to determine their ability to penetrate membranes of nerve tissue. These compounds were also evaluated in vivo as inhibitors of galactitol accumulation in the lens, sciatic nerve, and diaphragm of galactose-fed rats. Bioisosteric replacement of the 6-methoxy group of 1 with a methylthio substituent gave 5, and replacement of the thioamide substituent of 1 with a cyanoamidine gave 7. Both 5 and 7 retained high in vitro potency but were less potent in vivo than 1. Replacement of the tolrestat N-methyl group by a carbomethoxy moiety gave 10 and led to a substantial reduction in activity in each of the three assays employed. However, this same structural modification on oxo-tolrestat (2) led to 11 and resulted in an enhancement of the intrinsic activity and a comparable in vivo potency. The isolated nerve data suggest that some compounds in these series do not readily penetrate into peripheral nerves, and this presumably is a factor in their lack of oral activity.

Aldehyde Reductase↗
PubMed1989

Laser flash spectroscopy of methylene blue with nucleic acids. Effects of ionic strength and pH.

Laser flash spectroscopic measurements were made on methylene blue complexed to the synthetic polynucleotides poly[d(G-C)] and poly[d(A-T)] in solutions of varying ionic strength and pH. Triplet decay rates and rates of triplet quenching by oxygen have been measured for the polymer/dye solutions. The triplet decay and oxygen quenching rates of methylene blue in complex with poly[d(A-T)] are much less sensitive than those with poly[d(G-C)] with respect to variations in ionic strength. It is also shown that protonation of the triplet state of MB+ with poly[d(A-T)] is slower than that of free dye. These results indicate strong binding of the dye to poly[d(A-T)]. Excitation of the MB+/poly[d(A-T)] complex at 665 nm yielded single exponential decay kinetics, in contrast with excitation at 600 nm where double exponential kinetics were measured. This is tentatively assigned to excitation of dye dimer bound to this polymer.

Hydrogen-Ion Concentration↗
PubMed1989

A study of some polypyridylruthenium(II) complexes as DNA binders and photocleavage reagents.

The nature of the binding of several ruthenium polypyridyl complexes containing 2,2'-bipyridine (bipy), 4,4'-dimethyl-2,2'-bipyridine (DMB), 1,10-phenanthroline (phen), 4,7-diphenyl-1,10-phenanthroline (DPP), 2,2',2"-terpyridine (terpy), 2,2'-biquinoline (biq), 1,4,5,8-tetraazaphenanthrene (TAP) and 1,4,5,8,9,12-hexaazatriphenylene (HAT), with calf thymus DNA, poly[d(A-T)] and poly[d(G-C)] were studied by absorption and emission spectroscopy, DNA melting techniques, and emission lifetime measurements. In low ionic strength phosphate buffer, spectroscopic changes and DNA stabilization depended on the polypyridyl ligands present, and indicated binding that varied from substantially electrostatic to intercalative. Ru(bipy)2(HAT)2+ and Ru(phen)3(2+), which bind by partial intercalation, also show a strong preference for poly[d(A-T)]. The emission quantum yields for most complexes were increased in the presence of DNA. An exception was Ru(TAP)3(2+) which has a markedly reduced emission quantum yield and lifetime in the presence of poly[d(G-C)] or CT-DNA, due to photoredox interaction with quanines. Emission decays of the complexes generally showed multiexponential behaviour. The ability of the ruthenium complexes to sensitise DNA cleavage was determined using pBR322 plasmid DNA. Ru(TAP)3(2+) is the most efficient sensitiser while uncharged complexes and complexes with very short-lived excited states do not cleave DNA.

DNA↗
PubMed1989

[125I]-[d(CH2)5, Sar7]AVP: a selective radioligand for V1 vasopressin receptors.

Arginine8-vasopressin (AVP) acts on vascular and hepatic V1 receptors to influence blood pressure and glycogenolysis respectively. We have radioiodinated the AVP V1 receptor antagonist, [1-(beta-mercapto-beta, beta-cyclopentamethylenepropionic-acid), 7-sarcosine, 8-arginine] vasopressin ([d(CH2)5, Sar7]AVP) and determined its receptor-binding properties in rat liver and kidney plasma membranes. The binding was of high affinity to single classes of receptors (liver: Kd = 3.0 nM and Bmax = 530 +/- 10 fmol/mg protein, kidney: Kd = 0.5 +/- 0.9 nM and Bmax = 11 +/- 8 fmol/mg protein). Competition of [125I]-[d(CH2)5, Sar7]AVP binding by unlabelled AVP analogues gave the following order of potency in both tissues, consistent with that expected for binding to a V1 receptor: [d(CH2)5, Tyr(Me)2]AVP greater than AVP greater than [d(CH2)5, D-Ile2, Ile4] AVP greater than DDAVP. No degradation of [125I]-[d(CH2)5, Sar7]AVP during incubation or storage was detected by HPLC analysis. We have used [125I]-[d(CH2)5, Sar7]AVP and in vitro autoradiography to demonstrate its use in localizing brain AVP receptors. These studies suggest that [125I]-[d(CH2)5, Sar7]AVP is a suitable selective radioligand for labelling V1 receptors and will provide a valuable tool for the study of the localization and regulation of AVP V1 receptors in tissues and in receptor isolation.

Animals↗
PubMed1988

Health, welfare and fertility implications of the use of bovine somatotropin in dairy cattle.

Twenty-two Friesian and Friesian cross Ayrshire cows and 16 first lactation heifers were paired. Twenty were injected subcutaneously with 500 mg recombinant bovine somatotropin (sometribove) and 18 with a placebo at fortnightly intervals, starting 80 (+/- 7) days after calving, through the winter of 1986-87. The cows' weights and changes in condition, milk yields, milk solids, health and fertility were recorded regularly. Compound cake was fed at a fixed stepped rate according to the number of days since the cow calved. Silage was available on an easy-feed basis. Ten cows had their daily silage intake measured. Sometribove treated cows produced on average 27.7 kg of milk per day, 4.5 kg more than the controls. Treated heifers produced 23.5 kg per day, 2.5 kg more than the controls. Milk quality was unchanged. Treated cows gained weight during the trial, but not by as much as the controls. Control heifers also gained weight but the treated heifers lost, on average, 3 kg. Local reactions at the injection site were not felt to be of welfare concern, nor was the general effect of the extra milk production. A small number of treated animals experienced mastitis and had poorer fertility but the differences were mostly not statistically significant. If bovine somatotropin should become licensed for use in Britain it is recommended that clear guidelines should be issued on the management practices necessary for economic success and for the welfare of the treated animals.

Animal Welfare↗
PubMed1988

Differences in the regulation of aldehyde dehydrogenase genes in Aspergillus niger and Aspergillus nidulans.

In order to study mechanisms of gene regulation in A. niger, and to compare these to similar systems in A. nidulans, a gene encoding an aldehyde dehydrogenase enzyme has been cloned. In wild-type strains of A. niger the gene shows expression which is regulated by induction and repression. Levels of induction by various compounds and the extent of repression under various growth conditions differs from that seen for the A. nidulans aldA gene. Unlike the A. nidulans aldA gene, the A. niger gene has both carbon catabolite repressible and nonrepressible induction mechanisms. Studies of heterologous expression of the A. niger gene in A. nidulans have shown that its expression is regulated by the alcR gene product of A. nidulans.

Aldehyde Dehydrogenase↗
PubMed1988

Specific serodiagnosis of visceral leishmaniasis using a Leishmania donovani antigen identified by expression cloning.

A lambda gt11 expression library was constructed using mRNA from the promastigote form of Leishmania donovani (African isolate MHOM/ET/67/HU3). The library was screened with serum obtained from a patient who contracted visceral leishmaniasis in the Sudan. Several cDNA clones which expressed beta-galactosidase/L. donovani antigen fusion proteins were isolated. One of these clones corresponded to a 60 kDa membrane-associated antigen. By a Western blot assay antibodies against the fusion protein were detected universally in the sera of visceral leishmaniasis patients. They were not detected in sera from patients with cutaneous leishmaniasis or other parasitic protozoan infections. The gene coding for this antigen was specific to the genus Leishmania as judged by DNA hybridisation, and its chromosomal location was conserved. A 20 kb mRNA was detected on Northern blots of promastigote RNA.

Animals↗