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Biomedical subjects

R W Henderson

Publications and source records attributed to R W Henderson.

At least 19 recordsLinked to original sources
PubMed1995

Origin of West Indian populations of the geographically widespread boa Corallus enydris inferred from mitochondrial DNA sequences.

Corallus enydris (Serpentes: Boidae: Boinae) is an arboreal snake with an extremely wide mainland distribution from southern Costa Rica to southeastern Brazil and is one of two boine species that has invaded the Lesser Antilles (Grenada Bank and St. Vincent). Mitochondrial DNA sequences of samples from seven geographically disparate localities provided evidence of phylogenetic relationships. The monophyly of C. enydris is corroborated and a major dichotomy between northern samples (Panama and Trinidad) and southern samples (Guyana, Perú, southeastern Brazil) was found and corresponds to the two currently recognized subspecies. Unexpectedly, the two samples from the West Indies (southern Lesser Antilles) cluster with the southern rather than the geographically closer northern samples (e.g., Trinidad). The results imply a fairly recent Guianan-Amazonian origin of West Indian populations.

Animals↗
PubMed1993

Modulation of uptake of heme by rat small intestinal mucosa in iron deficiency.

Although body iron status modulates whole body retention of heme derived iron, it is not known with certainty whether modulation occurs by regulation of mucosal uptake of heme. In vivo uptake from perfused intestine of heme labeled with 14C in the porphyrin ring was studied in groups of rats of differing iron status ranging from fully replete to markedly iron deficient. Heme extraction from infusate and mucosal heme uptake were significantly different between test groups (P < 0.005 and 0.001, respectively). Marked iron deficiency induced a 4.8-fold rise in heme extraction relative to iron-replete animals; rats with latent iron deficiency showed a smaller but still significant rise. Heme extraction correlated negatively with indicators of iron status: hemoglobin (r = -0.76, P < 0.001) and serum iron (r = -0.56, P < 0.05). The specific binding of [14C]heme to purified brush borders from iron-replete and iron-deficient rats was 1.4-fold higher in deficient rats when expressed per milligram of protein (P = 0.046) and 3.3-fold higher when expressed relative to alkaline phosphatase activity (P = 0.014). Thus mucosal uptake of heme in iron deficiency is increased because of an increase in its binding to the brush border.

Animals↗
PubMed1991

Use of Rambach Propylene Glycol Containing Agar for identification of Salmonella spp.

When grown on Rambach Propylene Glycol Containing Agar (Rambach agar), 216 of 230 (93.9%) Salmonella organisms isolated from patients and 54 of 62 (87.1%) Salmonella stock cultures produced a crimson-colored growth. Of the 14 clinical Salmonella isolates which displayed colors other than crimson, 8 were Salmonella typhi, 2 were Salmonella paratyphi A, and 4 belonged to other commonly isolated serotypes. All eight Salmonella stock cultures which failed to produce a crimson color belonged to rarely isolated serotypes. In contrast, of 83 non-Salmonella stock cultures distributed among 29 bacterial species, none produced a crimson color. These results suggest that while Rambach agar cannot preidentify S. typhi and S. paratyphi A, the medium can be used for the presumptive identification and can assist in the definitive identification of the overwhelming majority of Salmonella isolates.

Agar↗
PubMed1990

External exposure estimates for individuals near the Nevada Test Site.

Individuals living near the Nevada Test Site were exposed to both beta and gamma radiations from fission products and activation products resulting from the atmospheric testing of nuclear devices. These exposures, and the resultant doses, were functions of the amount of material deposited, the time of arrival of the debris, and the amount of shielding afforded by structures. Results are presented for each of nine generic life-styles. These are representative of the living patterns of people residing in the area. For each event at each location for which data exist, a representative of each life-style was closely followed for 30 d. The results of these detailed calculations were then extrapolated to the present, employing a stochastic model. Results displayed are the geometric means and standard deviations derived from 25 independent determinations of the various quantities shown. For each determination, required parameters were randomly selected from appropriate distributions. Calculations yielded estimates for: 1) whole-body and skin dose due to gamma rays from material on the ground; 2) skin dose due to beta particles from material deposited directly on the skin; and 3) skin dose due to beta particles from material deposited on the ground. Organ dose estimates were established from the whole-body dose using appropriate conversion factors. For the homemaker life-style, the uterus dose was also calculated as a function of time for 9 mo. This assisted in estimating fetal dose as a function of gestation.

Beta Particles↗
PubMed1989

Singlet oxygen formation in monomeric and aggregated porphyrin c.

The absorption and fluorescence spectra of monomeric and aggregated species present in aqueous solutions of porphyrin c have been resolved by steady-state and time-resolved spectroscopy. The dependence of the singlet oxygen formation yield (phi delta) on excitation wavelength has also been determined. In the Q-band spectral region, the aggregate absorption and emission spectra are shifted to longer wavelengths with respect to the monomer spectrum with phi delta (monomer) = 0.59 and phi delta (aggregate) = 0.33. The relevance of these findings to the optimization of irradiation conditions in tumour phototherapy using porphyrin c are discussed.

Chemical Phenomena↗
PubMed1989

Magnetic resonance imaging of cardiac sarcomas.

Two patients with cardiac sarcomas were evaluated with magnetic resonance imaging (MRI). In both cases, MRI provided more information regarding the extent of the tumor than computed tomography, two-dimensional echocardiography, or angiography.

Adult↗
PubMed1989

Effect of ingestion of hemoproteins on fecal excretion of hemes and porphyrins.

Stools from asymptomatic volunteers on diets containing red meat, whole blood, or high fiber were analyzed for their content of hemes and dicarboxylic (heme-derived) porphyrins by the "HemoQuant" assay, the "Hemoccult" test, and "high-performance" liquid chromatography (HPLC). In 49 subjects, ingestion of red meat increased HemoQuant-determined combined fecal heme plus dicarboxylic porphyrins by an average 375%; the contribution of heme-derived porphyrins to total fecal porphyrins increased from 37% to 78%. Of subjects on a red-meat diet, 27% passed stools with a porphyrin content suggestive of a porphyria, compared with only 4% on a red-meat-free diet. These increases were due largely to protoporphyrin and its derivatives pemptoporphyrin and deuteroporphyrin, all of which were present in feces as iron-free porphyrins and iron-ligated (heme) forms. Ingestion of blood had an effect similar to that of red meat, but ingestion of fiber had no effect. These effects of dietary and endogenous hemoproteins must be considered when such methods are used to test feces for occult blood or to test for excess fecal porphyrins as an indicator of a porphyria.

Adolescent↗
PubMed1986

MR imaging of pulmonary emboli: an experimental study in dogs.

Experimental pulmonary emboli, consisting of tantalum-labeled autologous blood clots and barium-labeled 3-mm plastic spheres that did not produce an MR signal, were introduced through the femoral vein into each of five dogs. The sensitivity of MR to detect autologous clots of known size was assessed, and the size of the clot on MR was compared with its actual size. Emboli were localized by using chest radiographs made in multiple projections. Cardiac-synchronized MR imaging was performed on a 0.35-T superconducting magnet and was followed by a 99mTc macroaggregated lung scan. All 12 blood clots larger than 3 mm, and three of 20 clots less than 3 mm in transverse diameter were correctly visualized with MR. Five of the 15 clots seen on MR were larger than 150% of the actual size. There were nine false-positive emboli on MR. Two of six plastic spheres resulted in an abnormal signal on MR. MR signal from pulmonary emboli results from the thrombus itself and probably also from slow blood flow proximal to the obstruction. MR may be of value in detecting pulmonary emboli; clinical trials to evaluate its usefulness should be carried out.

Animals↗
PubMed1984

Phialophora parasitica, an emerging pathogen.

Monoconidial cultures derived from 12 clinical and environmental isolates of Phialophora parasitica were compared with respect to morphologic and physiologic characteristics and response to antifungal agents. No yeast cells were seen in 1- and 3-week-old slide culture preparations. Also, not all of the distinguishing characteristics of this species were displayed by all isolates on all media examined. Although the isolates grew on Sabouraud agar with chloramphenicol and cycloheximide, some inhibition was observed. All cultures were strongly urease-positive and hydrolyzed casein and starch; most decomposed tyrosine but not gelatin. All but one environmental isolate grew well at both 23 and 37 degrees C, but none grew at 40 degrees C. In the sensitivity testing the isolates did not vary much in their response to each drug, although some anomalies were observed. Amphotericin B and miconazole had minimum inhibitory concentrations in the low sensitivity range (2.0-8.0 and 2.5-10 micrograms m-1 respectively), for most isolates, and most isolates were resistant to both 5-fluorocytosine and ketoconazole. Limited observations were made on three other Phialophora species which might be confused with P. parasitica.

Amphotericin B↗
PubMed1982

Effects of ethnicity and child's age on maternal judgements of children's transgressions against persons and property.

Mothers (N = 256) of four different cultural groups judged the culpability of children whose actions were described in Piaget-type stories depicting commission of harm under various conditions. Child's age, harm to persons vs material objects, intentions, and amount of harm were systematically varied. All main effects (culture, intent of transgressor, age, and magnitude of harm) were significant, but several effects were qualified interactions. A cognitive social learning explanation is proposed to account for group differences in judgement, with special attention to cultural differences in values attached to harm to persons vs damage to property.

Age Factors↗
PubMed1980

Haematoporphyrin diacetate: a probe to distinguish malignant from normal tissue by selective fluorescence.

Haematoporphyrin diacetate has been synthesized and purified. Following introduction into mice bearing squamous-cell carcinomas it was found to produce a fluorescence of the tumour tissue which was much stronger than that of the surrounding normal tissue. Haematoporphyrin diacetate was also shown to be the major active component of the impure compound known as haematoporphyrin derivative which has been widely used in tumour fluorescence studies.

9,10-Dimethyl-1,2-benzanthracene↗