PubMed Health⌕ Search

Biomedical subjects

M J Daly

Publications and source records attributed to M J Daly.

At least 91 records · Page 5Linked to original sources
PubMed1995

Interchromosomal recombination in the extremely radioresistant bacterium Deinococcus radiodurans.

Deinococcus radiodurans and other members of the genus Deinococcus are remarkable for their extreme resistance to ionizing radiation and many other agents that damage DNA. We have recently shown that recombinational processes participate in interplasmidic repair following in vivo irradiation. We now present direct studies on interchromosomal recombination among chromosomes irradiated in vivo during stationary phase (four chromosomes per cell). Following an exposure to 1.75 Mrad (the dose required to achieve a survival of 37%, which degrades the cells' four chromosomes into about 500 fragments), we determined that there may be as many as 175 crossovers per chromosome (700 crossovers per nucleoid) undergoing repair. In addition, these studies suggest that many of the crossovers occurring during repair are nonreciprocal.

Alleles↗
PubMed1995

A molecular marker based linkage map of Vitis.

Genetic linkage maps of Vitis (2n = 38) have been constructed from a single interspecific hybrid grape population (60 seedlings) of 'Cayuga White' X 'Aurore'. The maps were primarily based on 422 RAPD markers but also included 16 RFLP and isozyme markers. These maps had an average distance of 6.1 cM between markers and were developed using a double-pseudotestcross strategy. The 'Cayuga White' map had 214 markers covering 1196 cM and that of 'Aurore' spanned over 1477 cM with 225 markers. The 'Cayuga White' map consisted of 20 linkage groups, whereas 22 linkage groups comprised the 'Aurore' map. The number of groups reduced to 19, as in some instances two or more groups from one parent showed homology with a single group from the other parent on the basis of markers heterozygous in both parents. Each linkage group ranged in size from 14 to 135 cM in 'Aurore' and from 14 to 124 cM in 'Cayuga White'. These maps provide enough coverage of the genome to allow quantitative trait locus analysis and map-based gene cloning.

Base Sequence↗
PubMed1995

Rapid multipoint linkage analysis of recessive traits in nuclear families, including homozygosity mapping.

Homozygosity mapping is a powerful strategy for mapping rare recessive traits in children of consanguineous marriages. Practical applications of this strategy are currently limited by the inability of conventional linkage analysis software to compute, in reasonable time, multipoint LOD scores for pedigrees with inbreeding loops. We have developed a new algorithm for rapid multipoint likelihood calculations in small pedigrees, including those with inbreeding loops. The running time of the algorithm grows, at most, linearly with the number of loci considered simultaneously. The running time is not sensitive to the presence of inbreeding loops, missing genotype information, and highly polymorphic loci. We have incorporated this algorithm into a software package, MAPMAKER/HOMOZ, that allows very rapid multipoint mapping of disease genes in nuclear families, including homozygosity mapping. Multipoint analysis with dozens of markers can be carried out in minutes on a personal workstation.

Algorithms↗
PubMed1994

In vivo damage and recA-dependent repair of plasmid and chromosomal DNA in the radiation-resistant bacterium Deinococcus radiodurans.

Deinococcus radiodurans R1 and other members of this genus share extraordinary resistance to the lethal and mutagenic effects of ionizing radiation. We have recently identified a RecA homolog in strain R1 and have shown that mutation of the corresponding gene causes marked radiosensitivity. We show here that following high-level exposure to gamma irradiation (1.75 megarads, the dose required to yield 37% of CFU for plateau-phase wild-type R1), the wild-type strain repairs > 150 double-strand breaks per chromosome, whereas a recA-defective mutant (rec30) repairs very few or none. A heterologous Escherichia coli-D. radiodurans shuttle plasmid (pMD68) was constructed and found to be retained in surviving D. radiodurans R1 and rec30 following any radiation exposure up to the highest dose tested, 3 megarads. Plasmid repair was monitored in vivo following irradiation with 1.75 megarads in both R1/pMD68 and rec30/pMD68. Immediately after irradiation, plasmids from both strains contained numerous breaks and failed to transform E. coli. While irradiation with 1.75 megarads was lethal to rec30 cultures, a small amount of supercoiled plasmid was regenerated, but it lacked the ability to transform E. coli. In contrast, wild-type cultures showed a cell division arrest of about 10 h, followed by exponential growth. Supercoiled plasmid was regenerated at normal levels, and it readily transformed E. coli. These studies show that D. radiodurans retains a heterologous plasmid following irradiation and repairs it with the same high efficiency as its chromosomal DNA, while the repair defect in rec30 prevents repair of the plasmid. Taken together, the results of this study suggest that plasmid DNA damaged in vivo in D. radiodurans is repaired by recA-dependent mechanisms similar to those employed in the repair of chromosomal DNA.

Chromosomes, Bacterial↗
PubMed1994

Interplasmidic recombination following irradiation of the radioresistant bacterium Deinococcus radiodurans.

Deinococcus radiodurans R1 and other members of the eubacterial family Deinococcaceae are extremely resistant to ionizing radiation and many other agents that damage DNA. For example, after irradiation, D. radiodurans can repair > 100 DNA double-strand breaks per chromosome without lethality or mutagenesis, while most other organisms can survive no more than 2 or 3 double-strand breaks. The unusual resistance of D. radiodurans is recA dependent, but the repair pathway(s) is not understood. Recently, we described how a plasmid present in D. radiodurans (plasmid copy number, approximately 6 per cell; chromosome copy number, approximately 4 per cell) during high-dose irradiation undergoes extreme damage like the chromosome and is retained by the cell without selection and fully repaired with the same efficiency as the chromosome. In the current work, we have investigated the repair of two similar plasmids within the same cell. These two plasmids were designed to provide both restriction fragment polymorphisms and a drug selection indicator of recombination. This study presents a novel system of analysis of in vivo damage and recombinational repair, exploiting the unique ability of D. radiodurans to survive extraordinarily high levels of DNA damage. We report that homologous recombination among plasmids following irradiation is extensive. For example, 2% of Tcs plasmids become Tcr as a result of productive recombination within a 929-bp region of the plasmids after repair. Our results suggest that each plasmid may participate in as many as 6.7 recombinational events during repair, a value that extrapolates to > 700 events per chromosome undergoing repair simultaneously. These results indicate that the study of plasmid recombination within D. radiodurans may serve as an accurate model system for simultaneously occurring repair in the chromosome.

DNA Repair↗
PubMed1993

Identification of two divergently transcribed genes centromere-proximal to the ARG4 locus on chromosome VIII of Saccharomyces cerevisiae.

We have sequenced a 3296 bp segment of the chromosome VIII adjacent to the 3' end of the ARG4 gene. This segment contains two divergently oriented open reading frames (YSC83 and YSC84). Northern blot analysis showed the presence of transcripts corresponding to these two open reading frames in vegetative cells. Levels of these transcripts increase five to ten-fold during sporulation. These two genes are not essential for vegetative growth or sporulation. Analysis of the putative protein products on the SwissProt database revealed that the C-terminal region of the Ysc84 protein contains a putative SH3 domain.

Amino Acid Sequence↗
PubMed1992

The effects of Ca(2+)-free perfusion and the calcium paradox on [125I] endothelin-1 binding to rat cardiac membranes.

The binding characteristics of [125I]endothelin-1 (ET-1) to cardiac membranes isolated from rat hearts subjected to Ca(2+)-free perfusion or the Ca2+ paradox were examined. The effect of treatment with 2, 3 butanedione monoxime (BDM), which inhibits the tissue damage associated with the calcium paradox, was also investigated. Membranes from rat hearts perfused under control conditions bound [125I]ET-1 to a single population of sites with a Bmax of 107.7 +/- 3.7 fmol/mg protein and an affinity (KD) of 153 +/- 12 pM. Ten minutes of Ca(2+)-free perfusion resulted in a significant (P < 0.01) increase in Bmax to 167.5 +/- 8.3 fmol/mg protein without change in KD. Ca2+ repletion following Ca(2+)-free perfusion tended to increase further the Bmax (180.6 +/- 10.4 fmol/mg protein) without change in KD. Treatment with BDM attenuated but did not prevent the rise in Bmax following Ca(2+)-free perfusion. Following Ca2+ repletion, however, Bmax returned to control levels in the BDM treated group. These changes were not associated with changes in the ability of ET-1 and ET-3 to inhibit [125I]ET-1 binding. The results demonstrate that Ca(2+)-free perfusion is associated with an increase in the binding site density of [125I]ET-1 which is maintained or further increased upon Ca2+ repletion. If, however, the tissue damage associated with the Ca2+ paradox is prevented with BDM, Ca2+ repletion is associated with a reversal of the increase due to Ca(2+)-free perfusion.

Animals↗
PubMed1992

Effect of age on endothelin-1 binding sites in rat cardiac ventricular membranes.

To establish whether the density, affinity, or selectivity of endothelin-1 (ET-1) binding sites in cardiac ventricular membranes varies with age, membranes were harvested from 5- to 7-day-, 20-day-, and 8- to 9-week-old Sprague Dawley rats and labeled with [125I]ET-1. Selectivity was established by using cold ET-1, ET-2, ET-3, big ET-1, and (+)PN200-110 to inhibit specific binding of [125I]ET-1. Over the age span studied, selectivity and affinity of the [125I]ET-1 binding sites was unchanged, but density (Bmax) decreased from 209.7 +/- 18.4 at 5-7 days to 154.0 +/- 8.9 (p less than 0.02) at 20 days, and to 89.7 +/- 5.2 (p less than 0.01) fmol/mg protein at 8-9 weeks. These age-dependent differences in Bmax were not accompanied by a change in membrane yield and occurred at a time when the specific binding of (+)[3H]PN200-110 increased.

Aging↗
PubMed1991

The role of calcium in the toxic effects of tert-butyl hydroperoxide on adult rat cardiac myocytes.

Oxidant stress has been implicated in reoxygenation damage following hypoxia and can lead to loss of membrane integrity and cell death. In this study the effects of oxidant stress, induced by tert-butyl hydroperoxide (tBHP), on cell conformation and intracellular free calcium ([Ca2+]i) of cardiac myocytes isolated from rat ventricles were examined. Incubation in the presence of 1 mM tBHP lead to a rise in [Ca2+]i, hypercontracture and loss of membrane integrity (as judged by trypan blue staining and loss of fluorescence of fura-2 loaded cells). Incubation in calcium-free medium or medium containing 2,3 butanedione-monoxime (BDM), which decreases myofibrillar calcium sensitivity, delayed but did not prevent the cell shape changes and loss of membrane integrity. In the presence of BDM, hypercontracture occurred at a higher [Ca2+]i than in control cells, indicating a possible role for [Ca2+]i in the generation of hypercontracture in this model. Treatment with calcium antagonists (10(-6) or 10(-7) M nisoldipine or 10(-6) M amlodipine) did not afford any protection against tBHP. ATP depletion did not accelerate loss of membrane integrity. Pretreatment of cells with the iron chelator, desferrioxamine mesylate greatly attenuated the effect of tBPH, delaying the rise in [Ca2+]i, cell shape changes and loss of membrane integrity. It appears, therefore, that tBHP-induced changes are mediated by the iron dependent generation of butyl alkoxyl radicals. The evidence suggests that tBHP-induced contracture is [Ca2+]i dependent rather than ATP dependent. Calcium modifies, but is not essential for the action of tBHP on isolated myocytes. During reoxygenation of hypoxic hearts calcium overload and free radical generation may act synergistically resulting in the characteristic changes associated with this condition, including loss of sarcolemmal integrity.

Adenosine Triphosphate↗
PubMed1991

Gynaecomastia and heart failure--adverse drug reaction or disease process?

The presence of gynaecomastia was assessed in 444 male patients in order to determine the overall incidence of this condition. In addition, patients were assessed for liver function, age, weight, height and drug therapy, in an attempt to identify causative factors for the presence of gynaecomastia. The results indicate that there is a positive correlation between gynaecomastia and right and/or left cardiac failure. In addition, drug therapy with frusemide, amiloride and captopril was significantly correlated with an increased incidence of gynaecomastia in the study population; however this correlation was not present for either age or body weight index. These drugs are commonly used in the therapy of heart failure. This study highlights the difficulty of differentiating between whether or not pathology or drug therapy is the main contributing factor to a proposed adverse drug reaction.

Adolescent↗
PubMed1991

Treatment of refractory peptic ulcer with omeprazole or continued H2 receptor antagonists: a controlled clinical trial.

We tested the hypothesis that the gastric H+/K+ adenosine triphosphatase inhibitor, omeprazole, because of its different mode of action and pronounced inhibitory effect on gastric acid secretion, may be more effective in peptic ulcer that is refractory to histamine H2 receptor antagonist treatment than continuing the same therapy. Altogether 107 patients (duodenal ulcer, n = 88; prepyloric ulcer, n = 14; gastric ulcer, n = 3; mixed sites, n = 2) with refractory peptic ulcer - that is ulcer unhealed after at least two months' treatment with cimetidine 0.8 g or 1 g daily or with ranitidine 0.3 g daily - were randomly allocated to receive either omeprazole 40 mg daily (n = 54) or to continue treatment with the same H2 receptor antagonist and at the same dose (n = 53) for up to eight weeks. The patients in the two treatment groups were well matched demographically. Healing by 'intent to treat' analysis was as follows: at four weeks, omeprazole 46 of 54 (85%), H2 receptor antagonist 18 of 53 (34%) (p less than 0.0001); and at eight weeks, 52 of 54 (96%) and 30 of 53 (57%) respectively (p less than 0.0001). One patient was lost to follow up but of the 22 patients whose ulcers were shown to be unhealed at endoscopy after receiving continued H2 receptor antagonist treatment, 21 healed in four to eight weeks when changed to omeprazole. Daytime epigastric pain cleared at four weeks in 43 of 47 (91%) patients on omeprazole and in 32 of 46 (70%) on H2 receptor antagonists (p=0.01) and relief of all dyspeptic symptoms occurred in 39 of 47 (83%) and 23 of 45 (51%) (p=0.0009) patients respectively. Adverse events occurred in 11 of 54 (20%) patients on omeprazole and in 12 of 35 (34%) on cimetidine but in none on ranitidine. The events were mild and none required treatment withdrawal. The commonest event in patients on omeprazole was loose stools or diarrhoea (n=5). Omeprazole was significantly better than continued H2 receptor antagonist treatment for the short term management of refractory peptic ulcer as judged by healing rate and pain relief, and it was safe.

Cimetidine↗
PubMed1990

Omeprazole in the treatment of erosive oesophagitis refractory to high dose cimetidine and ranitidine.

Forty five patients with refractory oesophagitis, defined as persisting erosive changes or ulceration despite a minimum of three months' treatment with cimetidine 3.2 g daily or ranitidine 0.9 g daily, were treated in an open trial with omeprazole 40 mg daily for up to eight weeks. Endoscopically defined healing was observed in 73% of patients after four weeks' treatment and in 91% after eight weeks' treatment. Symptoms were completely relieved in 60% of patients, improved in 34%, unchanged in 4%, and worsened in 2%. After healing patients returned to maintenance treatment with cimetidine 1.6-3.2 g daily, depending on the severity of their illness before treatment with omeprazole. By six months and 12 months only 55% and 33% of patients respectively were still in remission. This study suggests that when erosive oesophagitis is refractory to treatment with high dose cimetidine or ranitidine, treatment with omeprazole 40 mg daily for up to eight weeks is effective in inducing healing and relieving symptoms.

Adult↗
PubMed1990

Effect of acidosis and alkalosis on postischemic Ca gain in isolated rat heart.

The effect of pH of the reperfusion buffer on postischemic changes in tissue Ca and Na was examined in isolated Langendorff-perfused Sprague-Dawley rat hearts. Reperfusion began after 15-, 25-, or 60-min ischemia at 37 degrees C. After 60-min ischemia, reperfusion at pH 6.4 or 6.6 attenuated the reperfusion-induced Ca gain so long as the acidotic conditions were maintained (3.08 +/- 0.22, 1.37 +/- 0.41, and 16.96 +/- 1.18 mumol Ca gain/g dry wt for pH 6.4, 6.6, and 7.4, respectively after 15-min reperfusion). Conversely, reperfusion under alkalotic conditions (pH 7.9) after 60-min ischemia exacerbated the gain (27.45 +/- 4.75 and 8.92 +/- 1.53 mumol Ca gain/g dry wt during 5-min reperfusion at pH 7.9 and 7.4, respectively). Similar, but less pronounced Ca gains occurred during reperfusion after 15- or 25-min ischemia. Sodium content during reperfusion, but not during aerobic perfusion, was also found to be pH sensitive with acidosis causing a reduction and alkalosis an increase. These results could not be explained in terms of an effect of pH on recovery of high-energy phosphates, percentage "reflow" during reperfusion, or reperfusion-induced increases in tissue water or resting tension. The results are in agreement with the hypothesis that the "inhibitory" effect of acidosis on postischemic Ca overload could involve an effect of pH on the Na(+)-H+ exchanger and intracellular Ca storage.

Acidosis↗
PubMed1989

Enterochromaffin-like cell populations in human fundic mucosa: quantitative studies of their variations with age, sex, and plasma gastrin levels.

The human gastric fundal mucosa contains a variety of endocrine cells, the most numerous of which are the so-called enterochromaffin-like (ECL) cells. We have studied the variations with age and sex of the ECL cell populations, utilizing an assessment based on multiple endoscopic biopsies from four groups of subjects. Plasma gastrin levels were also determined in these subjects. In males, endocrine cell densities declined with age but the ECL cell numbers in females opposed this trend. ECL cell counts showed no appreciable differences between young and old females. In older females, there was a high rate of gastritis and increased levels of circulating gastrin. Concentrations in older females (29.6 +/- 8.7 pmol/l) were higher than in both younger (less than 45 years) males (5.3 +/- 1.1 pmol/l) and older (greater than 55 years) males (6.3 +/- 0.6 pmol/l) (P less than 0.05). The plasma gastrin level was also higher in older females than in young females (13.1 +/- 4.5 pmol/l), although this difference failed to reach statistical significance. In conclusion, clinically silent gastritis, raised gastrin levels, and maintenance or rise of ECL cells numbers, in opposition to a general decrease in endocrine cells with age, appear to be features of women of more than 55 years of age. The variations in ECL cell populations reported here should be taken into account when evaluating possible pathological alterations of the stomach.

Adult↗