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Biomedical subjects

M Freeman

Publications and source records attributed to M Freeman.

At least 127 records · Page 7Linked to original sources
PubMed1975

Causes and consequences of Robertsonian exchange.

At least two types of Robertsonian exchange are now known in the acrocentric chromosomes of man. Both types involve breakage in the arms adjacent to the centromere. Evidence is presented for a third type of exchange, one involving breakage within the centromere itself, in the grasshopper Percassa rugifrons. In this species, which is regularly homozygous for a single fusion metacentric, the eighteen rod autosomes have small but pronounced granules at the centric end of the chromosome. When C-banded these granules show differential Giemsa staining and appear to represent centromeric chromomeres; these chromomeres are lacking in the metacentric fusion product. Equivalent fusions may have occurred in some mammal species too and possible examples of this are discussed in sheep and mice. The Percassa fusion has led to a modification in both the frequency and the distribution of chiasmata as judged by a comparison of these properties in the metacentric relative to the two next smallest rod equivalents. Comparable modifications are known to occur in other naturally occurring fusions but these changes are certainly not automatic consequences of fusion since they are not shown in at least some newly produced fusion mutants.

Animals↗
PubMedDate not supplied

Lack of uniformity in evaluation of endoscopic prognostic features of bleeding ulcers.

Management strategies in patients with bleeding ulcers are based on ulcer appearance. We assessed the level of agreement among endoscopists regarding the labeling of endoscopic features of bleeding ulcers and also evaluated the effect of a short teaching session on the level of agreement. Two hundred two endoscopists at the 1992 American College of Gastroenterology Postgraduate Course answered multiple-choice questions using interactive keypads. They were shown 6 slides of typical ulcer stigmata of recent hemorrhage, attended a brief teaching session, and then saw 6 different slides of comparable stigmata plus 2 additional slides. Color of stigmata was assessed in 9 slides. Information on years of endoscopic experience and numbers and types of procedures performed was also obtained. The proportion of correct answers before the teaching session increased significantly with years of experience, reaching a plateau in endoscopists who were 6 years or more beyond training. The proportion of correct answers for physicians performing no more than 5 upper gastrointestinal endoscopies per month was significantly lower than for those performing more than 5 per month: 33/56 (59%) compared with 647/891 (73%), a difference of 14% (95% CI, 0.4% to 27%; p = 0.03), but performance of a greater number of endoscopies was not associated with a further increase in the rate of correct answers. The total number of correct answers increased from 845/1181 (72%) before the teaching session to 1268/1554 (82%) afterwards, a difference of 10% (95% CI, 7% to 13%; p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Education, Medical, Continuing↗
PubMedDate not supplied

Experimental studies on the virus of "Q" fever.

The virus isolated by Derrick from cases of fever produces characteristic pathogenic effects on monkeys and mice. A well-defined febrile reaction, during which the blood is infective for guinea-pigs, follows subcutaneous inoculation of virus in the monkey. Mice inoculated intraperitoneally show enlargement of spleen and liver with characteristic histological changes. In sections and smears of infected mouse liver and spleen large numbers of rickettsial organisms are visible. These occur in relatively large intracytoplasmic microcolonies. Inoculation of mouse virus into guinea-pigs and monkeys gives a febrile reaction with a very short incubation period. Cross immunity tests indicate that mouse virus is identical with guinea-pig virus. The virus produces an inapparent infection in albino rats. The virus survives, but does not produce characteristic lesions on the chorio-allantois of the developing egg. The virus is filterable with difficulty through relatively permeable (0.7 mu) gradocol membranes. Agglutination of semi-purified rickettsial suspensions by immune human monkey and guinea-pig sera has been observed; this reaction appears to be specific.

Animals↗