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Biomedical subjects

R Kirby

Publications and source records attributed to R Kirby.

At least 109 records · Page 6Linked to original sources
PubMed1987

Measurement of ventricular volumes in the dog by nuclear magnetic resonance imaging.

Nuclear magnetic resonance (NMR) imaging is a new, noninvasive approach for imaging the cardiovascular system. Being a three-dimensional technique, NMR imaging has the capability of measuring volumes without the need for assumptions regarding ventricular geometry. In this study, the technique was validated in 19 excised dog hearts, filled with silicone-rubber, imaged using a multislice spin-echo sequence. The volume of the cavity in each slice was calculated from the number of pixels outlined for each slice multiplied by the pixel volume. Ventricular volumes measured by NMR imaging were highly correlated with cast volumes measured by water displacement: right ventricle (RV):RVNMR = 1.05 RVcast - 1.62; r = 0.99, SEE = 0.96 ml; left ventricle (LV):LVNMR = 0.98 LVcast + 0.35, r = 0.98, SEE = 1.48 ml. After validation in casts, NMR imaging volumes were measured in eight living dogs using a multiphasic gated technique to obtain images at 5, 105, 205, 305 and 405 ms after the QRS complex. Cardiac output (CO) and stroke volume (SV) measured by NMR imaging were significantly correlated with thermodilution (TD) measurements (CONMR = 0.63 COTD + 0.51 liters/min; r = 0.78, SEE = 0.57 liters/min; SVNMR = 0.67 SVTD + 1.95 ml; SEE = 5.58 ml). Right and left stroke volumes were closely related (LVSVNMR = 0.9 RVSVNMR + 1.75; r = 0.94, SEE = 4.32 ml), with the slope and intercept of the regression line showing no difference from 1 and 0, respectively. However, volumes determined by NMR imaging underestimated the thermodilution measurements, presumably reflecting the inability to obtain a true systolic image with the present sampling rate.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Nucleotide sequence of the gene encoding the nitrogenase iron protein of Thiobacillus ferrooxidans.

The DNA sequence was determined for the cloned Thiobacillus ferrooxidans nifH and part of the nifD genes. A putative T. ferrooxidans nifH promoter was identified whose sequences showed perfect consensus with those of the Klebsiella pneumoniae nif promoter. Two putative consensus upstream activator sequences were also identified. The amino acid sequence was deduced from the DNA sequence. In a comparison of nifH DNA sequences from T. ferrooxidans and eight other nitrogen-fixing microbes, a Rhizobium sp. isolated from Parasponia andersonii showed the greatest homology (74%) and Clostridium pasteurianum (nifH 1) showed the least homology (54%). In a comparison of the amino acid sequences of the Fe proteins, the Rhizobium sp. and Rhizobium japonicum showed the greatest homology (both 86%) and C. pasteurianum (nifH 1 gene product) demonstrated the least homology (56%) to the T. ferrooxidans Fe protein.

Amino Acid Sequence↗
PubMed1986

High dose AZQ in renal cancer. A Southwest Oncology Group phase II study.

Fifty-seven patients with renal cancer were treated with AZQ, utilizing one of three IV push schedules. Only one partial response was seen in 55 evaluable patients, and considerable myelosuppression was encountered. Gastrointestinal toxicity was more severe in those patients who had received prior treatment. At these higher doses AZQ is deemed an inactive agent in patients with renal cell carcinoma, at least when the drug is administered as a push schedule.

Antineoplastic Agents↗
PubMed1986

Enzyme-linked immunosorbent assay (ELISA) as a means of taxonomic analysis of Streptomyces and related organisms.

Fourteen Streptomyces strains from various numerical taxonomic classes and representatives of three other genera of actinomycetes were studied using an indirect enzyme-linked immunosorbent assay (IND-ELISA) to determine their serological relationships. The IND-ELISA results agreed with those from previous numerical taxonomic analyses and Ouchterlony double-diffusion studies. The IND-ELISA method is quicker, more quantitative and less subjective than Ouchterlony assays and thus should be useful in Streptomyces taxonomy. The results indicated that Frankia sp. CpI1 was related to Streptomyces.

Enzyme-Linked Immunosorbent Assay↗
PubMed1986

Urethro-vesical dysfunction in progressive autonomic failure with multiple system atrophy.

Fourteen patients with progressive autonomic failure and multiple system atrophy have been investigated by urodynamic, electromyographic and neurohistochemical means and the results compared with a series of age-matched controls. Three fundamental abnormalities of lower urinary tract function have been identified: (1) Involuntary detrusor contractions in response to bladder filling. It is suggested that these may be the result of a loss of inhibitory influences from the corpus striatum and substantia nigra. (2) Loss of the ability to initiate a voluntary micturition reflex. This may reflect the degeneration of neurons in pontine and medullary nuclei and in the sacral intermediolateral columns. In addition, these studies have demonstrated a significant reduction in the density of acetylcholinesterase-containing nerves in bladder muscle. (3) Profound urethral dysfunction. This appears to be partly due to a loss of proximal urethral sphincter tone, which causes bladder neck incompetence. In addition, the function of the striated component of the urethral sphincter is impaired. Individual motor units recorded from this muscle were clearly abnormal when compared with controls and suggested that reinnervation had occurred. We suggest that this is the result of degeneration of a specific group of sacral anterior horn cells known as Onuf's nucleus. The evidence that these particular motor units are affected, while others are spared, poses fundamental questions about the nature of selective vulnerability in degenerative diseases of the nervous system.

Acetylcholinesterase↗
PubMed1986

VC11: an actinophage virulent to Streptomyces cattleya and Streptomyces olivaceus.

Five soil samples were screened for the presence of a virulent actinophage. Phage VC11 was found to be virulent on Streptomyces olivaceus, S. cattleya, S. chartreusis, S. griseus (all important beta-lactam antibiotic producers), S. ambofaciens, S. parvulus, S. alboflavus, S. aureofaciens, and S. lividans TC10. Although restriction-modification systems have been observed in S. olivaceus and S. cattleya, the phage EOP on these hosts remained relatively constant, indicating that these systems do not affect VC11.

Bacteriophages↗
PubMed1986

Discordance between male and female deaths due to the respiratory distress syndrome.

General neonatal mortality statistics and those for the respiratory distress syndrome (RDS) were examined for the State of Wisconsin from 1979 through 1982. The objectives were to ascertain whether there are differences in total neonatal mortality related to sex and birth weight, to determine the veracity of reported gender differences in deaths due to RDS, and to assess the contribution of other risk factors for neonatal mortality to overall and sex-specific deaths occurring secondary to RDS. Additionally, a prospective analysis was performed at one perinatal center during a 5-year period in attempts to determine whether gender remained a significant factor in deaths due to RDS after adjusting for incidence. Overall, the most frequent diagnoses in those who died were RDS (15.6%), deaths due to complications of pregnancy (8%), immaturity (4.2%), and asphyxia (3.4%). The majority of fatalities for both sexes occur in neonates weighing less than 1 kg and the percentage of deaths attributable to RDS is greatest between 1 and 1.5 kg. The difference between sexes is also maximal in the latter weight group. Deaths secondary to RDS are greater for males regardless of Apgar score at one and five minutes, mode of delivery, maternal age, or ancillary diagnosis. These data suggest that deaths secondary to RDS are consistently greater in male neonates and that delivery within a limited "window" of time during gestation increases male susceptibility to fatal RDS.

Apgar Score↗
PubMed1985

The loss of a large DNA fragment is associated with an aerial mycelium negative (Amy-) phenotype of Streptomyces cattleya.

Hybridization of various Streptomyces cattleya aerial mycelium negative (Amy-) mutants with a probe containing the gene for argininosuccinate synthetase (pTG17) has revealed the presence of two different types of mutants (stable and unstable). Stable mutants appear to have lost all or part of the region covered by the probe, while the unstable mutants demonstrate no detectable changes in this region. In one group of stable mutants (those demonstrating a partial loss of sequences hybridizing to the probe), a 4.17 kb extrachromosomal element was detected, which hybridized with the pTG17 probe. The significance of this finding is discussed with reference to the genetic instability of the genus Streptomyces.

Autoradiography↗
PubMed1984

Evidence for the wide distribution of repetitive DNA sequences in the genus Streptomyces.

Repeated DNA sequences were detected as rapidly reannealing sequences in the chromosomal DNA of 13 out of 14 Streptomyces species using either hypochromicity measurements or hydroxyapatite chromatography. These sequences made up between approximately 4% and 11% of the total DNA of these species; only in Streptomyces rimosus were repeated DNA sequences not detected. The repeated sequences fall into a number of distinct percentage G + C (%G + C) classes, many being of rather low %G + C. Analytical density ultracentrifugation of the DNA of these species indicated satellite bands of low %G + C, and high-resolution thermal denaturation profiles indicated the presence of blocks of DNA of low G + C content too. No such satellite band could be found in Streptomyces coelicolor and no low-%G + C DNA could be detected in its thermal denaturation profile. The possible relationship of this repeated DNA, an unusual occurrence in a procaryote, to genetic instability and genetic control mechanisms in Streptomyces is discussed.

Base Composition↗
PubMed1984

The effect of inhibitors of DNA repair on the genetic instability of Streptomyces cattleya.

Various streptomycetes show well defined instabilities that do not appear to be attributable to plasmid loss. The unstable phenotype, in many cases, arises at frequencies too high to be explained by point mutations. The frequency of instability can be enhanced by UV irradiation. Two major repair systems have been found in Escherichia coli: the 'error-free' system which is inhibited by caffeine and the 'error-prone' system which is inhibited by arsenite. Using spores of Streptomyces cattleya NRRL 8057 and the virulent actinophage VC11 we have shown that a caffeine inhibitable, host mediated UV repair system is active in spores during early development. Some evidence was also found for the presence of an arsenite inhibitable UV repair system. The caffeine inhibitable UV repair system was found to be involved in the induction of genetic instability in S. cattleya. The arsenite system may be implicated in the repair of such events. Genetic instability was also induced by single strand breaks in DNA caused by 32P.

Arsenic↗
PubMed1977

Genetic determination of methylenomycin synthesis by the SCP1 plasmid of Streptomyces coelicolor A3(2).

Evidence is presented that genes determining the pathway of methylenomycin A synthesis are carried on the SCP1 plasmid. All 16 mutations (mmy) leading to lack of antibiotic synthesis were SCP1-linked. Phenotypic classification, by co-synthesis and other criteria, suggested that they fell into at least five classes. When the wild-type SCP1 plasmid was transferred to Streptomyces lividans or Streptomyces parvulus, material that was chromatographically and biologically indistinguishable from methylenomycin A was produced. Recombination between some pairs of mmy mutations was detected. In crosses of mmy mutants of NF (integrated SCP1 donor) strains with SCP1-, a very high frequency of chromosomal recombination occurred; thus methylenomycin production appears not to be an important cause of the ultra-fertility normally associated with NF X SCP1- crosses.

Anti-Bacterial Agents↗
PubMed1975

Emergency and elective surgical treatment of portal hypertension. A review of 23 years' experience.

A retrospective review of surgical treatment for portal hypertension during a 23-year period in a regional unit is reported and the immediate and subsequent management of patients with bleeding oesophageal varices is discussed. Fifty-four patients with recurrent varix haemorrhage uncontrolled by conservative methods have been treated by oesophageal transection with a mortality of 22.2% (26.6% for cirrhotic patients). Thirty-two per cent of the cirrhotics were alive after 2 years. Only a minority (12%) of the survivors were considered suitable for a subsequent shunt procedure. Therapeutic portacaval anastomosis has been performed on 65 patients with a 51.2% 5-year survival (43-5% for cirrhotic patients). Further haemorrhage due to shunt thrombosis occurred in 5-3% of cases. The frequent occurrence of portal-systemic encephalopathy, increasing with duration of time following a shunt, is emphasized. The high morbidity and mortality in the poor-risk cirrhotic indicated that this type of patient is unsuitable for a portal-systemic shunt and is better treated by medical means.

Adult↗
PubMed1975

Postnatal growth of the dog heart.

We have found that, in the dog at birth, the right ventricle weighed significantly more than the left. At 3 days the left ventricle weighed the same as the right ventricle. No evidence for postnatal atrophy of the right ventricle was found--the right ventricle simply gained weight at a much slower rate than the left. The left ventricle weighed significantly more than the right at 7,9,11,13,15 and 17 days.

Age Factors↗