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Biomedical subjects

K C Smith

Publications and source records attributed to K C Smith.

252 records · Page 14Linked to original sources
PubMed1968

Dark recovery processes in Escherichia coli irradiated with ultraviolet light. I. Effect of rec mutations on liquid holding recovery.

We have examined various derivatives of Escherichia coli K-12 for liquid holding recovery, a type of recovery originally observed in E. coli B irradiated with ultraviolet light. Although most of the K-12 derivatives tested showed relatively little or no recovery under our conditions, four of the six independent rec(-) mutants examined, those carrying recA1, rec-12, recA13, and rec-56, respectively, displayed marked recovery. These mutants are distinguished from rec(+) strains by their increased sensitivity to ultraviolet radiation and decreased ability to undergo genetic recombination. Two of them have also been reported to release large amounts of their deoxyribonucleic acid as acid-soluble material, especially after irradiation. None of the three uvr(-) mutants examined, containing uvrA6, uvrB5, or uvrC34, showed comparable liquid holding recovery. The one rec(-) uvr(-) derivative tested, carrying recA13 and uvrA6, did not appear to undergo liquid holding recovery, although recA13 uvr(+) strains did. Genetic analysis of one strain, a recA13 mutant, indicated that all the rec(+) derivatives obtained from it by conjugation, transduction and reversion, had lost the property of showing liquid holding recovery. From these results, we conclude that in E. coli K-12 the expression of liquid holding recovery depends upon certain rec(-) mutations.

Conjugation, Genetic↗
PubMed1967

Photoinduced DNA-protein cross-links and bacterial killing: a correlation at low temperatures.

The increased sensitivity of Escherichia coli to killing by ultraviolet irradiation when frozen and the variation in this sensitivity as a function of the temperature during irradiation have been correlated with changes in the amount of DNA that was cross-linked to protein by ultraviolet light. These variations in sensitivity to killing do not correlate with the production of thymine dimers.

Carbon Isotopes↗
PubMedDate not supplied

Congenital abnormalities of the ovine paramesonephric ducts.

A 15 month survey of ovine reproductive tracts was undertaken in slaughterhouses in southwest England. A total of 33506 tracts were examined; 23536 from lambs and 9970 from adults. In total, 3.4% of tracts were pregnant and 3.3% exhibited abnormalities. Twenty cases of uterus unicornis, six of uterus didelphys and 11 of segmental aplasia were encountered, such that partial aplasia of the paramesonephric ducts accounted for 3.3% of all abnormalities. Although developmental abnormalities of the ovine female genital system are relatively uncommon, a substantial proportion of these can be accounted for by development defects of the paramesonephric ducts.

Animals↗
PubMedDate not supplied

Calvarial hyperostosis syndrome in two bullmastiffs.

Two bullmastiffs with calvarial hyperostosis syndrome are described and are the first documented examples in females. The clinical and radiologic features were similar to those previously reported in males. Magnetic resonance (MR) imaging findings have not previously been reported. One dog underwent MR imaging and abnormalities included thickening of the frontal bones with loss of normal fat signal and changes in the overlying soft tissues. In one of the dogs, long bone changes were seen in the femora and resembled those seen with craniomandibular osteopathy.

Animals↗
PubMedDate not supplied

Abattoir survey of congenital reproductive abnormalities in ewes.

A survey of abnormalities of the reproductive tract of female sheep was undertaken at two abattoirs in the south west of England over a period of 12 months. During the survey, 9970 reproductive tracts from cull ewes and 23,536 tracts from nulliparous sheep (prime lambs and hoggets) were examined. A total of 655 (6.57 per cent) ewes and 459 (1.95 per cent) nulliparous sheep had abnormalities of the reproductive tract. Of these, congenital abnormalities of the paramesonephric ducts accounted for 2.4 per cent of the ewes and 7.4 per cent of the nulliparous sheep, congenital abnormalities of the ovaries accounted for 2.6 per cent of the ewes and 7.4 per cent of the nulliparous sheep and cystic structures that were considered to have been of congenital origin accounted for 27.2 per cent of the ewes and 52.7 per cent of the nulliparous sheep. The most common lesion was paraovarian cysts (26.6 per cent of ewes and 39.0 per cent of nulliparous sheep), but few of these appeared to have affected the sheep's reproductive function. Several specific conditions were recorded, including some described for the first time in sheep. Uterus unicornis occurred in 20 sheep and other forms of segmental aplasia of parts of the paramesonephric ducts occurred in a further 13 animals. Uterus didelphys occurred in six sheep, and 11 animals were intersex. Intersex sheep had vestigial structures that were derived from the paramesonephric ducts, hypoplastic or masculinised gonads and some had masculinised external genitalia. Ovarian hypoplasia occurred in 34 sheep, and in a further 12 mainly nulliparous animals, the ovaries were fused. Sixty nulliparous animals and two ewes had hydatids of Morgagni.

Abattoirs↗