Biomedical subjects

K R Clarke

Publications and source records attributed to K R Clarke.

10 recordsLinked to original sources

PubMed2000

Comparison of postmortem techniques for the detection of Mycobacterium bovis in white-tailed deer (Odocoileus virginianus).

A retrospective study of various diagnostic postmortem techniques used in a 4-year surveillance program for detection of Mycobacterium bovis infection in wild white-tailed deer (Odocoileus virginianus) was conducted. The tests evaluated were routine histopathology, acid-fast staining, detection of acid-fast bacilli in culture, and an M. tuberculosis group-specific genetic probe applied to pure cultures. Each of these techniques were compared with a reference or "gold standard" of mycobacterial culture and identification. Histopathology, the most rapid form of testing for M. bovis infection in white-tailed deer samples, had a sensitivity of 98% and a specificity of 87%, resulting in a positive predictive value of 94%. The detection of acid-fast bacilli by staining was less sensitive than histopathology (90%), but its higher specificity (97%) resulted in a positive predictive value of 99%. The detection of acid-fast bacilli on culture was both highly specific (93%) and sensitive (100%). The group-specific genetic probe had the highest sensitivity and specificity and produced results in complete agreement with those of mycobacterial culture, suggesting that this technique could be used as the new "gold standard" for this particular wildlife tuberculosis surveillance program.

Animals↗

PubMed1984

An investigation of adhesion and detachment in slime mould amoebae using columns of hydrophobic beads.

Vegetative amoebae of Dictyostelium discoideum (strain AX2) adhere to columns of hydrophobic beads (Bio-Beads SM-2) which have been coated with axenic growth medium. This binding is blocked by sodium azide and other inhibitors of aerobic respiration. Bound cells are not detached by lowering the temperature but they can be eluted from the column by including azide in the medium. However, this effect is critically influenced by temperature. The elution profiles become progressively shallower as the temperature is lowered. The profiles represent a set of probability distributions whose means and variances increase with decreasing temperature. Below 20 degrees C, the mean time to cell detachment is a linear function of temperature. A statistical model of this azide-stimulated detachment has been developed which closely predicts the real data. It assumes that each amoeba has k binding sites whose stochastically independent behaviour is governed by a parameter theta; the mean time to detachment of each site is 1/theta. Both parameters have been estimated. The value of k is close to 3 and does not vary with temperature below 20 degrees C. In contrast, theta varies in such a way that the value of 1/theta increases linearly with decreasing temperature, so paralleling the behaviour of the mean cell detachment time.

Adhesiveness↗

PubMed1982

Use of microstereology and quantitative cytochemistry to determine the effects of crude oil-derived aromatic hydrocarbons on lysosomal structure and function in a marine bivalve mollusc, Mytilus edulis.

The marine bivalve mollusc, Mytilus edulis (blue mussel), is a noted accumulator of many environmental pollutants and is increasingly used for the chemical and biological assessment of environmental impact. The toxic effects of crude oil-derived aromatic hydrocarbons (30 micrograms/l total hydrocarbons) of the lysosomal-vacuolar system of the digestive cells have been investigated in cryostat sections of hexane-frozen digestive glands. Exposure to aromatic hydrocarbons reduced the cytochemically determined latency of lysosomal beta-N-acetylhexosaminidase; lysosomal volume density and surface density increased while the numerical density decreased. Experimental exposure resulted in the formation of very large lysosomes which are believed to be largely autophagic in function and these results indicate a significant structural and functional disturbance of digestive cell lysosomes in response to hydrocarbons.

Animals↗

PubMed1974