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Biomedical subjects

M Cook

Publications and source records attributed to M Cook.

At least 73 records · Page 4Linked to original sources
PubMed1985

Ultrasound in the diagnosis of jaundice--a review.

A retrospective study of 92 jaundiced patients undergoing ultrasound examination was undertaken to assess the clinical utility of this test. The patients were graded according to the likelihood of biliary obstruction. In those in whom biliary obstruction was proven to be present, the sensitivity of ultrasound to detect the obstruction was 91% and the test specificity was 100%. In patients who had undergone cholecystectomy no increase in the diameter of the common duct was observed. Liver function tests proved to be unreliable in discriminating between extrahepatic obstructive jaundice and other forms of jaundice. Ultrasound scanning is a useful screening test in the diagnosis of the jaundiced patient. However, follow-up is suggested for those with a negative result of this test but in whom biliary obstruction is suspected. An approach to the investigation of the jaundiced patient should include early ultrasound examination in those with possible biliary obstruction.

Adolescent↗
PubMed1985

The binding of leukotriene C4 and leukotriene D4 to membranes of a smooth muscle cell line (BC3H1) and evidence that leukotriene induced contraction in these cells is mediated by thromboxane, protein and RNA syntheses.

Leukotriene C4 (LTC4) and leukotriene D4 (LTD4) are important mediators of anaphylaxis and induced thromboxane (TxA2) synthesis in vivo and in vitro. The mechanism by which this occurs is not known and the cellular source of leukotriene (LT) induced TxA2 has not been identified. To obtain insights into this problem we have established an in vitro system using the BC3H1 murine smooth muscle cell line. A membrane fraction obtained from these cells contained binding sites for [3H]LTC4 having high specificity and affinity. Binding of [3H]LTC4 was saturable, specific and reversible with a dissociation constant (KD) of 33 +/- 16 nM and a maximum number of binding sites (Bmax) of 25 +/- 6 pmol/mg membrane protein. However, the amount of [3H]LTD4 specifically bound was considerably less than that of [3H]LTC4. LTC4 and LTD4 induced these cells to contract, a process which was blocked by inhibitors of cyclooxygenase and thromboxane synthetase. Using a radioimmunoassay, we have shown that the level of TxB2 (a stable metabolite of TxA2) was increased in response to LTC4 and LTD4 treatment in a dose-dependent manner. Cycloheximide, a protein synthesis inhibitor, and actinomycin D, an inhibitor of RNA synthesis, were found to inhibit both LTC4- and LTD4-induced TxB2 synthesis and cellular contraction. Arachidonic acid, in the absence of LT, increased the levels of TxB2 synthesis and contraction even in the presence of cycloheximide and actinomycin D. These data are consistent with the hypothesis that the rate-limiting step in LT-induced TxB2 synthesis is the formation of free arachidonic acid, a process which requires RNA and protein synthesis.

Animals↗
PubMed1984

Leukotriene C4 ([3H]-LTC4) binding to membranes isolated from a hamster smooth muscle cell line (DDT1MF2).

Leukotriene C4 (LTC4) has been demonstrated to induce contraction of the smooth muscle cell line DDT1MF2. A partially purified membrane fraction obtained from these cells exhibited a high affinity binding site for LTC4. Binding of [3H]-LTC4 was saturable, specific and reversible with a dissociation constant (Kd) of 21 +/- 4 nM. The maximum number of binding sites (Bmax) was 55 +/- 5 pmol/mg of protein. Specificity was demonstrated in competition studies in which the Ki of LTC4 against specifically bound [3H]-LTC4 was 12 nM whereas Leukotriene D4 (LTD4) and Leukotriene E4 (LTE4) had a Ki of 38 +/- 4 and 4.7 +/- 0.5 nM respectively. A previously described antagonist of leukotriene-induced smooth muscle contraction PFL 55712 had a Ki of 23 +/- 2 nM as determined by competition binding experiments.

Animals↗
PubMed1984

The identification of a DNA polymorphism of the alpha fibrinogen gene, and the regional assignment of the human fibrinogen genes to 4q26-qter.

We have identified a common restriction fragment length polymorphism of the alpha fibrinogen gene with the enzyme TaqI. This polymorphism is probably due to a single base change that creates or destroys a TaqI recognition site about 1000 basepairs from the 3' end of the alpha fibrinogen géne. The frequency of the rare allele in 83 unrelated healthy individuals is 0.33. We have used in situ hybridisation of the alpha fibrinogen cDNA to localise the gene on chromosome 4q29-31. We have confirmed this regional localisation by restriction fragment detection in a human X Chinese hamster somatic cell hybrid which contains a translocated human chromosome 4 with a breakpoint at 4q26. The alpha, beta, and gamma fibrinogen genes are all present on human chromosome 4q26-qter.

Base Sequence↗
PubMed1984

Relation between simultaneous spatial-discrimination thresholds and luminance in man.

Simultaneous spatial-discrimination thresholds of 6 human subjects were measured at luminances between 0.2 and 2000 cd/m2. Subjects were tested on a forced-choice discrimination task which required them to distinguish between test and control stimuli of high contrast square-wave gratings with similar space-average luminances. The form of the function depicting the relationship between acuity and luminance is similar to that obtained by other researchers. The estimated maximum acuity of 72 cycles/degree (c/deg) is higher than the commonly cited value of 60 c/deg and this is probably due to the combination of the high stimulus luminance and the psychophysical technique employed in this study.

Adult↗
PubMed1984

Representational drawings of solid objects by young children.

Two groups of children aged 6 and 8 years were given three tasks requiring graphical representations of solid geometric forms. These tasks were drawing from life models, copying from photographs, and copying from line drawings of these objects. Performance was assessed on the basis of level of approximation to correct perspective. Older children used more perspective features than younger children in their drawings. At all ages, the drawings from life were most difficult. Results on the two copying tasks were not consistent. Drawings made by copying photographs were either as advanced as or poorer than copies of line drawings. The results are explained in terms of the difficulties exhibited by young children in translating the three-dimensional scene to a two-dimensional picture plane and strategies adopted by them to cope with these problems.

Art↗
PubMed1983

The subcellular location of isozymes of NADP-isocitrate dehydrogenase in tissues from pig, ox and rat.

Antibodies against purified NADP-isocitrate dehydrogenase from pig liver cytosol and pig heart were raised in rabbits. The purified enzymes from these sources are different proteins, as demonstrated by differences in electrophoretic mobility and absence of crossreactivity by immunotitration and immunodiffusion. The NADP-isocitrate dehydrogenase in the soluble supernatant homogenate fraction from pig liver, kidney cortex, brain and erythrocyte hemolyzate was identical with the purified enzyme from pig liver cytosol, as determined by electrophoretic mobility and immunological techniques. The enzyme in extracts of mitochondria from pig heart, kidney, liver and brain was identical with the purified pig heart enzyme by the same criteria. However, the 'mitochondrial' isozyme was the major component also in the soluble supernatant fraction of pig heart homogenate. The 'cytosolic' isozyme accounted for only 1-2% of total NADP-isocitrate dehydrogenase in pig heart, as determined by separation of the isozymes with agarose gel electrophoresis and immunotitration. The mitochondrial isozyme was also the predominant NADP-isocitrate dehydrogenase in porcine skeletal muscle. The ratio of cytosolic/mitochondrial isozyme for porcine whole tissue extract, determined by immunotitration, was about 2 for liver and 1 for kidney cortex and brain. The distribution of isozymes in cell homogenate fractions from ox and rat tissues corresponded to that observed in organs of porcine origin. The mitochondrial and cytosolic isozymes from ox and rat tissues exhibited crossreactivity with the antibodies against the pig heart and pig liver cytosol enzyme, respectively, and the electrophoretic migration patterns were similar qualitatively to those found for the isozymes in porcine tissues. Nevertheless, there were species specific differences in the characteristics of each of the corresponding isozymes. NAD-isocitrate dehydrogenase was not inhibited by the antibodies, confirming that the protein is distinct from that of either isozyme of NADP-isocitrate dehydrogenase.

Animals↗
PubMed1982

The ability to see solid form in early infancy.

The perception of three-dimensional attributes of solid objects by twelve-week-old infants was studied. In the first experiment the rates of habituation of fixation to a cube in a fixed orientation, to one which changed in orientation between presentations, and to a sequence of photographs of cubes in different orientations were determined. Habituation rate was also determined for a photograph of a cube in a fixed orientation. No difference was found between the initial fixation times for solids and photographs, or between the habituation curves for the solids in fixed and varying orientation. For the photographs habituation was much greater for the fixed orientation than the varying orientation condition. These data were interpreted as providing strong evidence that the infants were responding to the stimuli on the basis of their three-dimensional attributes. In the second experiment the same discriminations were examined by a recovery-from-habituation technique. One group was habituated to a cube in a fixed orientation and tested for recovery of fixation to a new orientation. A second group was habituated to a photograph of a cube in a single orientation and tested for recovery to a photograph of a new orientation. Both groups showed recovery and the recovery was the same for both conditions. These data demonstrated that the subjects were, after all, capable of discriminating between different orientations of a solid cube, and they provided no further evidence that the infants were perceiving three-dimensional attributes of the stimuli.

Depth Perception↗
PubMed1982

Radiographic studies on bone in beagles subjected to low levels of dietary lead since birth.

This experiment studies the effects of low-level oral lead administration on bone in standardized colony-raised research male Beagles. Lead was administered to lactating mothers from parturition through weaning and directly to the pups thereafter. Results of bone radiographic morphometric and bone radiographic densitometric findings in five experimental and four control animals are reported. Total femoral length, and femoral diaphysal width, combined with cortical thickness, thickness/width ratio, and radiographic photodensitometry did not vary significantly between both groups, although bone lead and blood lead levels were significantly higher in the experimental group.

Absorptiometry, Photon↗
PubMed1982

Radiographic morphometry and radiographic photodensitometry of the femur in the Beagle at 13 and 21 months.

A study was made of x-ray morphometry and x-ray photodensitometry of bones of 2 small groups of healthy standardized colony-raised male research Beagles, ages 13 and 21 months. The morphometry and photodensitometry results were correlated to other variables of interest. The total width of the femur and its optical density to x-rays increased significantly with age and body weight, but not so the length of the femur nor the combined cortical thickness (CCT). This last measurement (CCT) did not increase in parallel with the whole length of the bone either. The CCT/width ratio decreased as body weight increased. The clear-cut increase in the optical density of the whole bone is therefore explained by the age-related variations in bone envelope activity.

Absorptiometry, Photon↗