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Biomedical subjects

A Walker

Publications and source records attributed to A Walker.

At least 271 records · Page 15Linked to original sources
PubMed1986

The screening of Duchenne muscular dystrophy patients for submicroscopic deletions.

We have probed the DNA of 156 Duchenne muscular dystrophy (DMD) patients, representing 140 kindreds, with cloned DNA sequences derived from Xp21 and known to show deletions in some DMD patients. Sixteen cases showed a deletion, as defined by lack of hybridisation to one or more of the four probes used. However, two of these cases were brothers, so 15 independent deletions (10.7%) are represented. The deletion map is compatible with the suggested order for the sites of the probes used in the study, that is, telomere----pERT87.15----pERT87.8----pERT87.1----pX J1.1----754----centromere. Further mapping of these deletions and characterisation of the deletion breakpoints should facilitate more accurate molecular localisation of the gene or genes which, when mutated, are responsible for causing DMD.

Chromosome Deletion↗
PubMed1986

Linkage studies in Duchenne and Becker muscular dystrophies.

We have studied the inheritance of four cloned DNA sequences which recognise restriction fragment length polymorphisms on the short arm of the X chromosome in families with Becker and Duchenne muscular dystrophy. We have confirmed linkage of two probe loci to the disease loci and have combined our results with those previously published to give a maximum lod score of 11.642 at a recombination fraction of 0.15 for DXS41 (probe 99.6), and a maximum lod of 15.84 at a recombination fraction of 0.15 for DXS84 (probe 754). Linkage of these diseases to the loci defined by the pERT87 probes and probe pXJ1.1 has also been studied, giving maximum lod scores of 8.634 and 5.118 at recombination fractions of 0.02 and 0.00 respectively. The information obtained using these polymorphic DNA markers, combined with pedigree and CK data, can be used to give more accurate genetic counselling to women at risk in Becker and Duchenne families.

DNA↗
PubMed1986

New wrist bones of Proconsul africanus and P. nyanzae from Rusinga Island, Kenya.

The anatomy of the wrist of two species of the early Miocene hominoid Proconsul is described based on new material collected on Rusinga Island, Kenya. These fossils generally confirm previous findings that the wrist of Proconsul is monkey-like in much of its morphology. However, the structure of the ulnar side of the wrist, particularly the ulnocarpal joint, is significantly different from that of extant monkeys and suggests some functional affinities with extant hominoids. Thus the wrist of Proconsul is neither monkey-like nor ape-like in its total morphology. Instead, it shows a unique combination of features which once again point to the oversimplicity of forcing fossil forms into categories based only on extant taxa.

Animals↗
PubMed1985

Molecular distinctions between heparan sulphate and heparin. Analysis of sulphation patterns indicates that heparan sulphate and heparin are separate families of N-sulphated polysaccharides.

Heparan sulphate and heparin are chemically related alpha beta-linked glycosaminoglycans composed of alternating sequences of glucosamine and uronic acid. The amino sugars may be N-acetylated or N-sulphated, and the latter substituent is unique to these two polysaccharides. Although there is general agreement that heparan sulphate is usually less sulphated than heparin, reproducible differences in their molecular structure have been difficult to identify. We suggest that this is because most of the analytical data have been obtained with degraded materials that are not necessarily representative of complete polysaccharide chains. In the present study intact heparan sulphates, labelled biosynthetically with [3H]glucosamine and Na2(35)SO4, were isolated from the surface membranes of several types of cells in culture. The polysaccharide structure was analysed by complete HNO2 hydrolysis followed by fractionation of the products by gel filtration and high-voltage electrophoresis. Results showed that in all heparan sulphates there were approximately equal numbers of N-sulpho and N-acetyl substituents, arranged in a similar, predominantly segregated, manner along the polysaccharide chain. O-Sulphate groups were in close proximity to the N-sulphate groups but, unlike the latter, the number of O-sulphate groups could vary considerably in heparan sulphates of different cellular origins ranging from 20 to 75 O-sulphate groups per 100 disaccharide units. Inspection of the published data on heparin showed that the N-sulphate frequency was very high (greater than 80% of the glucosamine residues are N-sulphated) and the concentration of O-sulphate groups exceeded that of the N-sulphate groups. We conclude from these and other observations that heparan sulphate and heparin are separate families of N-sulphated glycosaminoglycans.

Animals↗
PubMed1985

The skeleton of early Eocene Cantius, oldest lemuriform primate.

A recently discovered partial skeleton of the adapid Cantius trigonodus from the early Eocene Willwood Formation of the Bighorn Basin, Wyoming, documents substantial new information about the anatomy of the oldest lemuriform primates. It is very similar in all features to its descendant, middle Eocene Notharctus, and both exhibit numerous resemblances to certain extant Malagasy lemurs, particularly Lepilemur, Propithecus, Lemur, and Hapalemur griseus. Like these forms, Cantius had relatively long hind limbs and short forelimbs. Forelimb traits (prominent brachialis flange of the humerus, well-developed olecranon process of the ulna, and strong shafts of the ulna and radius) suggest active use of the forelimbs in progression. Specializations in the hind limb (e.g., expanded articular surface of the femoral head, narrow and elevated patellar trochlea and prominent lateral trochlear ridge, posteriorly oriented femoral and tibial condyles, narrow and elongate talus, and hallucal metatarsal with prominent peroneal tubercle) indicate capabilities for leaping and for powerful grasping with an opposable hallux. Cantius was presumably primitive in having a relatively long ischium and much more distal inferior tibial tuberosity than most extant lemurs--traits suggesting that powerful extension of the thigh and flexion at the knee were important in its locomotion and posture. We interpret Cantius as an active arboreal quadruped with a propensity for leaping. The existence of this skeletal structure in one of the oldest primates of modern aspect suggests that it represents the primitive lemuriform morphology.

Animals↗
PubMed1985

Calcium and phosphorus absorption in lambs exposed to Trichostrongylus colubriformis.

Ten lambs (29 +/- 1.2 kg) reared parasite-free and prepared with rumen, duodenal and ileal cannulae were paired and one of each pair was given a daily oral dose of 2500 Trichostrongylus colubriformis larvae for 14 weeks. Untreated animals received the amount of ration consumed by their infected pair-mates the previous day. During weeks 6 and 12 of infection, all lambs underwent a 7 day calcium (Ca) and phosphorus (P) balance. During weeks 7 and 13, duodenal and ileal samples were collected to determine the amounts of Ca and P entering and leaving the small intestine. The infection caused varying degrees of feed refusal in all infected animals. As a result, the data on Ca and P in excreta and the amounts of Ca and P entering and leaving the small intestine were regressed against dry matter (DM) intake for each group at each period. There were no between-period differences in these relationships. Calcium absorption and retention were unaffected by the stress of infection. Infection affected several aspects of P metabolism. Blood P concentrations were markedly reduced. Absorption of P from the small intestine was greater (P less than 0.01) in control lambs (at 1 kg DM intake 6.6 g per day) than in infected animals (2.2 g P per day), but there was a greater (P less than 0.05) duodenal flow rate of P in control lambs which suggested much higher rates of salivary secretion of P than in infected animals. Phosphorus flow rates at the ileum were greater (P less than 0.01) in infected lambs, despite the lower duodenal flow rates, which indicated a major abnormality (P less than 0.01) in small intestine absorption of P in infected animals; this may have contributed to the growth check experienced by these lambs.

Animals↗
PubMed1985

Protein variation in clones of Plasmodium falciparum detected by two dimensional electrophoresis.

Two dimensional electrophoresis has been used to examine protein variation in clones of two Plasmodium falciparum isolates. Variant forms of 12 proteins were detected. Five genetically distinct parasite types were identified in one isolate, and two in the second isolate. Examination of uncloned parasites using this technique showed that the frequency of each genotype altered during six months of culture.

Animals↗
PubMed1985

The efficiency of utilization of metabolizable energy and apparent absorption of amino acids in sheep given spring- and autumn-harvested dried grass.

Three experiments were conducted with sheep given spring-harvested dried grass (SHG) and autumn-harvested dried grass (AHG). The first was a calorimetric trial to determine the metabolizable energy (ME) content of each grass and the efficiency with which sheep utilize their extra ME intakes above the maintenance level of intake. The second examined the relative amounts of extra non-ammonia-nitrogen (NAN) and individual amino acids absorbed from the small intestine per unit extra ME intake as the level of feeding was raised from energy equilibrium (M) to approximately 1.5 M. The third was a further calorimetric trial to investigate the effect of an abomasal infusion of 30 g casein/d on the efficiency of utilization of AHG. The ME content of the SHG (11.8 MJ/kg dry matter (DM] was higher than that of AHG (10.0 MJ/kg DM). The efficiency of utilization of ME for productive purposes (i.e. above the M level of intake; kf) was higher when given SHG (kf 0.54 between M and 2 M) than when given AHG (kf 0.43 between M and 2 M). As the level of intake of each grass was raised from M to 1.5 M there was a greater increment in the amounts of NAN (P less than 0.001) and the total amino acid (P less than 0.05) absorbed from the small intestines when sheep were given the SHG (NAN absorption, SHG 5.4 g/d, AHG 1.5 g/d, SED 0.54; total amino acid absorption SHG 31.5 g/d, AHG 14.3 g/d, SED 5.24). Infusion of 30 g casein/d per abomasum of sheep given AHG at M and 1.5 M levels of intake increased (P less than 0.05) the efficiency of utilization of the herbage from kf 0.45 to kf 0.57. Consideration is given to the possibility that the higher efficiency of utilization of ME in sheep given SHG may be related to the amounts of extra glucogenic amino acids absorbed from the small intestine which provide extra reducing equivalents (NADPH) and glycerol phosphate necessary for the conversion of acetate into fatty acids.

Absorption↗
PubMed1985

Enhancement of human growth hormone-stimulated mitogenesis of Nb2 node lymphoma cells by 12-O-tetradecanoyl-phorbol-13-acetate.

The tumor promoter 12-O-tetradecanoyl-phorbol-13-acetate (TPA) enhanced human (h) GH- and ovine PRL-stimulated mitogenesis of the Nb2-11C clone of rat lymphoma cells. Maximal enhancement of 25% in the proliferation rate was achieved with 20 nM TPA. The enhancing effect was found at all levels of hGH (0.031-2.0 ng/ml), but was more pronounced at lower hormone concentrations. TPA alone had no effect on cell proliferation, and its activity was absolutely dependent on the simultaneous presence of the lactogenic hormones. We have analyzed the changes that occurred in the distribution of cells in different phases of the cell cycle during the first 22 h after exposure to hGH and measured the proliferation rate through 3 days. We have found that the mitogenic effect of hGH resulted from 1) an increase in the rate of G0/G1----S transition, 2) a decrease in the lag period required for entry into the S phase, and 3) an increase in the number of cells entering this transition. TPA enhanced all three effects. Binding of [125I]hGH was not affected by prior exposure to TPA, suggesting that the effect of TPA is at a postreceptor level. Proliferation of an autonomous clone of Nb2 cells that does not require lactogenic hormones for growth was not stimulated by TPA, although these cells bound [3H]TPA to the same extent as the PRL-dependent Nb2-11C clone.

Animals↗
PubMed1985

Cancer in Hispanics in Los Angeles County.

Using ethnicity of surname, nativity, residential social class, and inferred age at migration to characterize and subdivide Hispanics in Los Angeles, we compared risk ratios and proportional incidence ratios to examine the patterns of occurrence of selected neoplasms within the Hispanic community. Common neoplasms for which Hispanics have high, low, and intermediary risk were examined in detail. Although the patterns expected on the basis of current concepts of etiology were generally found and served to reinforce presumptions about the biologic significance of the risk factors, a number of observations cannot be explained easily with current knowledge. The risks for stomach and bowel cancers do not conform to the mirror-image patterns to be expected on the basis of inverse patterns of dietary acculturation. Incidence of cancer of the breast, in contrast to that of cervix, does not appear to reflect early cultural practice. Consistent details in the patterns of cancers of the bladder, rectum, ovary, prostate, and possibly pancreas imply unrecognized determinants of disease. Gallbladder cancer in Hispanic women is the disease most closely tied to Hispanic origin or culture, or both, but the ethnic pattern in women differs greatly from that in men.

California↗
PubMed1984

Quantitative differences in dental microwear between primate species with different diets and a comment on the presumed diet of Sivapithecus.

Studies of dental microwear have been used to relate tooth form to function in a variety of recent and extinct mammals. Probably the most important aspect of microwear analysis is the possibility of using it to deduce the diet of extinct animals. Such deductions must be based on comparative studies of modern species with known diets, but to date, only qualitative studies have been attempted and all have been based on small samples. Here we report quantitative differences in dental microwear between primate species that are known to have different diets. Occlusal facets with different functions have previously been shown to exhibit different microwear patterns. However, the differences between facets of one species are shown to be far less than those between homologous facets of different species. Study of seven species of extant primates shows that enamel microwear can be used to distinguish between those with a mainly frugivorous diet and those with a mainly folivorous one. Microwear can also distinguish hard-object feeders from soft-fruit eaters. The microwear of Miocene Sivapithecus indicus cannot be distinguished statistically from that of the chimpanzee, but it is different from that of the other species. On this evidence S. indicus was not a hard-object feeder and the adaptive significance of its thick molar enamel is at present unknown.

Animals↗
PubMed1984

Mechanisms of honing in the male baboon canine.

Male baboons use their sharp upper canines in aggressive interactions. These teeth are sharpened against specialized lower third premolars. The honing premolar is protected against wear by having very thick enamel and the upper canine having very thin enamel, not by structural or mineral differences between the two enamels. Evidence is presented which shows the interactions of enamel ultrastructure and both dentin and enamel wear in canine sharpening.

Adaptation, Physiological↗
PubMed1984

Clonal diversity in a single isolate of the malaria parasite Plasmodium falciparum.

Clones of an isolate of Plasmodium falciparum from Mae Sod (Thailand) were prepared by a dilution procedure. Some of the parasite cultures thus obtained have been typed for the following characters: (i) electrophoretic variants of three enzymes; (ii) susceptibility to chloroquine and pyrimethamine; (iii) antigen diversities recognized by ten strain-specific monoclonal antibodies; (iv) presence or absence of knobs on infected erythrocytes and (v) two-dimensional PAGE variants of seven proteins. Amongst the clones there was variation involving each of these five characters. At least seven different types of clones were found in ten cultures produced by dilution. The amount of phenotypic variation within a single isolate has thus been shown to be surprisingly great. Variations in drug susceptibility and antigens are considered to be particularly important in view of their relevance to anti-malarial treatments.

Animals↗
PubMed1984

The epidemiology of ovarian cancer in Greece: a case-control study.

One hundred and fifty women with common malignant epithelial tumors of the ovary (cases) and 250 comparison women hospitalized for various orthopedic conditions were interviewed regarding demographic, reproductive, socio-economic and biomedical characteristics, including their use of coffee, tobacco, alcohol, drugs and exogenous estrogens. The data were analyzed with standard X2 procedures and by modelling relative risk (r) through multiple logistic regression. The main results are as follows: women with ovarian cancer had fewer liveborn children (one-tailed, P congruent to 0.13, for women with 4+ children, r = 0.6) and later menarche (P congruent to 0.02, for women with age at menarche 15+, r = 1.9) and menopause (P congruent to 0.07, for women with age at menopause 50+, r = 1.5); they were slightly taller and heavier (P congruent to 0.15 and 0.30 respectively); they belonged to smaller sibships (P congruent to 0.05); they reported more frequently than controls familial occurrence of ovarian, endometrial and breast cancer (P less than 0.05 in each instance); they were regular consumers of alcoholic beverages more frequently than controls, and the excess was both statistically significant (P congruent to 0.02) and dose-related; they were regular users of coffee slightly more frequently than controls (r = 1.2) but the excess was small and it was neither statistically significant nor dose-related (P congruent to 0.27); and they reported less frequently than controls the use of oral contraceptives (relative risk for users, 0.4; 95% confidence interval, 0.1-1.1).

Adult↗
PubMed1984

Intussusception: a case review.

This study is a review of all cases of intussusception from December 1971 to December 1981 at the Erlanger Medical Center in Chattanooga. Only 24 cases were found. A disproportionate number of patients were white (92%). The male to female ratio was 2 to 1. There was no regular seasonal variation. Several patients were below the third percentile in weight for their ages. The most common signs and symptoms were vomiting, pain, and bleeding per rectum. The occurrence of anatomic lead points was high, and the success rate for hydrostatic reductions was low. The use of glucagon before barium enema increased the success rate of hydrostatic reduction by 75%, from four successful reductions to seven of 20 attempts.

Adult↗