Biomedical subjects
Publications and source records attributed to S Malcolm.
Human globin cDNA-derived recombinants with plasmid pCR1 have been prepared for use as specific hybridisation probes and for the partial sequencing of alpha-, beta- and gamma-globin genes.
The adolescent smoker (aged 14 to 17 years) shows little difference from the non-smoker in terms of scores on the Cattell 16 personality factor inventory. In particular, there is no evidence of tension, extroversion, or reversal of sexually-biased personality characteristics. The sexual promiscuity of the adolescent smoker is probably related more to liberal attitudes and a propensity for risk-taking behavior than to uncertainty regarding sexuality. In this age group the decision to start smoking regularly may depend more on the influence of parents and friends than on an inherent personality structure.
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Unfixed nucleoproteins may be banded isopycnically in metrizamide (2(3-acetamido-5-N-methylacetamido-2,4,6-triiodobenzamido)-2-deoxy-D-glucose) according to the protein/nucleic acid ratio. Unsheared or lightly sheared chromatin bands sharply (p=1.2 g/ml); it has a protein/DNA ratio of 1.4. Chromatin sheared by sonication to approximately 350 base pairs of DNA contains two components with protein/nucleic acid ratios of approximately 1.3 (p=1,185 g/ml) and 2 (p=1.245 g/ml). When chromatin is digested exhaustively with staphylococcal nuclease, two density components are found, one with a protein/DNA ratio of 1.5 (p=1.21 g/ml), the other with a protein/DNA ratio of 2 (p=1.24 g/ml). In both instances the denser particle (p=1.24 g/ml) contains nearly all the nonhistone proteins, while both dense and light fractions contain histones in similar amounts. The base sequence complexity of DNA from the fractions is not distinguishable from that of total DNA and there is no evidence of any concentration of sequences complementary to polysomal polyadenylated RNA molecules.
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Two experiments with Sprague Dawley rats tested their ability to hydrolyse myristoyl-methionine (M-M) into myristic acid and L-methionine (M). In the first experiment, lasting for 3 days. male rats were orally administered [9,10-3H]myristoyl-L-[35S]methionine. The recovery of radioactivity was approximately 90% for both isotopes; 19% of the administered 3H was recovered in the urine and 16% in the faeces, while the recovered 35S activity was 13 and 12%, respectively. The balance of the radioactivity was found among the tissues, organs and blood. In the second experiment, male and female rats received soybean-based diets which were supplemented with either 0.305% M-M or 0.2% M (both diets contained equal amounts of M) for periods up to 4 weeks. The growth rate of the rats receiving the 0.305% M-M diets was slightly slower than that for the rats on the 0.2% M diet, but the difference was not statistically significant (P > 0.05). The M-M rats had a transitory decrease in feed consumption, suggesting that palatability may have contributed to the growth difference and that a somewhat greater amount of M-M was necessary for the rat to attain the same growth rate as that produced by 0.2% M. When the amount of dietary M-M was increased to 3.05% M-M, a greater reduction in feed consumption and body weight gain was observed. This latter diet was an initial attempt to study the potential toxicity of M-M. None of the haematological, clinical chemistry or organ weight data suggested that M-M was overtly toxic per se, but longer-term feeding studies are needed to evaluate the potential toxicity of M-M more fully.
In a study designed to minimize interspecies extrapolation of toxicological data, nine rhesus (Macaca mulatta) and 15 cynomolgus (M. fascicularis) day-old infant monkeys were separated from their dams following parturition and hand-reared using a liquid non-human primate formulation. The infants were randomly divided into a control and a treated group which received a mixture of polychlorinated biphenyl (PCB) congeners analogous to those found in breast milk from Canadian women. The concentration of congeners in the dosing media resulted in each infant receiving a total of 7.5 microg PCB congeners/kg body weight/day. The congeners were added either to the liquid formulation or to corn oil and administered to the back of the monkey's mouth for 20 weeks. Monthly blood and adipose specimens were obtained during the dosing period and then periodically until the monkey was necropsied or taken off test (minimum of 66 weeks on test) for congener analysis. Parameters such as body weight, formula consumption, tooth eruption, somatic measurements, haematology and serum biochemistry were monitored throughout the study. In addition, a qualitative evaluation of the absorption and depletion of the various congeners was undertaken as was an immunological evaluation. For the monitored parameters, very few differences were found to be statistically significant. For the immunological parameters, the only statistically differences found were a reduction over time for immunoglobulins M and G antibodies to sheep red blood cells (cyno, P = 0.025; rhesus, P = 0.002) and a treatment-related reduction in the levels of the HLA-DR cell surface marker (mean percent, P = 0.016; absolute levels, P = 0.027). There were some qualitative differences regarding absorption and depletion rates for the various congeners, but it could not be definitely ascertained whether these differences were due to species differences or dosing mode. However, statistically significant differences were found for treatment (P = 0.0293) as well as for species and vehicle regarding the concentration of PCB in blood (species;--P = 0.0399; treatment--P = 0.0001) and adipose tissue (species--P = 0.0489; treatment--P = 0.0001).
In Burkitt lymphoma cells reciprocal chromosomal translocations are observed between the long arm of chromosome 8 (8q24) and either the long arm of chromosome 14 (14q32), the short arm of chromosome 2 (2p12) or the long arm of chromosome 22 (22q11). Gene mapping studies have shown that c-myc, the cellular homologue of the viral myc oncogene, is localized at 8q24 (ref 3-5) and that the three immunoglobulin gene loci map at the breakpoints involved in the translocation: immunoglobulin heavy-chain genes are located at 14q32 (refs 6, 7), kappa light chains at 2p12 (ref. 8) and delta light chains at, or close to, 22q11 (ref 9, 10). This correlation suggests an association of immunoglobulin gene rearrangements with the occurrence of these specific translocations. By using in situ hybridization we have examined the translocation point with respect to c-myc in two cell lines containing 2;8 translocation, and report here that the c-myc gene remains on the chromosome 8 involved in the reciprocal exchange with chromosome 2. We have also confirmed that the c-myc gene moves from the translocated chromosome 8 in a cell line having a 8;14 translocation. These results show that chromosomal breakage can occur on either side of the c-myc gene in Burkitt lymphoma cells.
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Recent reports of fatal transfusion-associated Yersinia enterocolitica sepsis prompted a study of the feasibility of adding a question to the routine donor health history as a method of reducing this risk. In three American Red Cross blood centers, 11,323 donors were asked one of two questions about gastrointestinal symptoms during their health history screenings. Affirmative responses were obtained from 0.6 or 4.0 percent of the donors, depending on how the question was asked. In one center, more than 6 percent of donors gave affirmative answers. The efficacy of asking a relatively simple question about gastrointestinal symptoms as a way of preventing Y. enterocolitica should be evaluated further, because relatively large numbers of donors may respond affirmatively. Other methods of reducing the risk of transfusion-associated Y. enterocolitica infection should be pursued.
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Being an X-linked condition, the sisters of men with X-linked agammaglobulinaemia have a 50% risk of being carriers of the disease gene (provided the disease has not developed as a results of a new mutation). We demonstrate how this risk can be modified very significantly by DNA analysis using linked DNA probes. The value of such tests for genetic purposes is discussed.