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Biomedical subjects

D W Roberts

Publications and source records attributed to D W Roberts.

At least 163 records · Page 9Linked to original sources
PubMed1984

Hemangioma calcificans. Case report.

A 44-year-old woman presented with intraventricular hemorrhage and a calcified avascular mass lesion in the anterior third ventricle. This lesion proved to be a densely calcified variant of cavernous hemangioma, namely, hemangioma calcificans. Twelve previous cases of this lesion have been reported in the neurosurgical literature. Association with spontaneous intraventricular hemorrhage has not been previously reported. The clinical presentation, radiological appearance, surgical findings, and histopathology of this lesion are discussed and a brief review of the literature is presented.

Adult↗
PubMed1983

Entomogenous Fusarium species.

Fusarium species are known for their abundance in nature and their diverse associations with both living and dead plants and animals. Among animals Fusarium is found primarily in relationship with insects. This literature review of the past 50 years includes both non-pathogenic and pathogenic relationships between Fusarium and insects. Special attention is given to the host range, particularly between plant- and insect-hosts, and to the possible microbial potential of the fungus to control insect pests. Correct classification of this fungus has been difficult because of its diverse and non-uniform morphological features. However, by now a usable and reliable taxonomic system has been developed. The fungus can be easily cultured and mass produced. Among the non-pathogenic associations mutualism and allotrophy are found between Fusarium and wood-inhabiting and flour beetles, respectively, enhancing development and production of beetle larvae. Some insects contribute to the dispersal of the fungus in the environment by means of spore passage through their guts. Plant-pathogenic Fusarium species gain access to host tissue by plant-feeding insects. A large number of Fusarium spp. are entomopathogenic; some are weak, facultative pathogens, especially of the lepidopteran and coleopteran orders, and they will colonize their dead hosts as saprophytes. In a few cases pathogenicity to both plant and insect by one isolate was found. Strong pathogens were reported primarily from homopterans and dipterans from field observations of natural mortalities as well as from pathogenicity tests. Potential Fusarium isolates which cause high insect mortalities also show high host specificity and no damage to crop plants. The question of host invasion has been addressed by few investigators. Entrance of the fungus via the oral route, oviposition tubes, wounds, or ectoparasitic activity, were stated, but no claim for penetration of the insect cuticle. Mycotoxins, such as trichothecenes (T-2) and other secondary metabolites, contributed to mortalities of termites, mealworms, flour beetles, maize borers and blow flies, while zearalenone (F-2) exhibited a beneficial effect on egg production in flour beetles and a detrimental effect on fecundity in mammals. Studies on adverse effects of the fungus on beneficial organisms (including mammals and plants) revealed that both harmful as well as safe Fusarium isolates exist in nature. Highly host-specific and strongly entomopathogenic Fusarium isolates should be more extensively studied and tested for their possible use in biological control.

Animals↗
PubMed1983

Flow cytometric analysis of the effect of phenytoin and its major metabolite on mitogen stimulated mouse spleen cells.

The in vitro immunopharmacological effects of phenytoin (PHT) and its major metabolite 5-(4-hydroxyphenyl)-5-phenylhydantoin (HPPH) were investigated by flow cytometric analysis of the DNA content of mitogen stimulated mouse spleen cells. The qualitative effects of PHT and HPPH were similar in concanavalin A stimulated mouse spleen cells with both compounds causing an increase in the percentage of S phase cells. The data suggests that this effect is due to an augmentation of cell cycling as demonstrated by the significant increase in 4N cells in PHT treated cultures relative to control cultures following colcemid treatment. A PHT time course study revealed an increase in S phase cells and a subsequent increase in 4N cells. PHT had no significant effect on congenitally athymic nude mouse spleen cells stimulated with lipopolysaccharide (LPS) except at the highest concentration tested (80 micrograms/ml) where a depression of cell cycling was observed. HPPH caused a colcemid-like accumulation of 4N cells in the LPS stimulated nude mouse spleen cell cultures. PHT and HPPH were found to be effective in enhancing cell cycling in cultures containing a significant population of T-cells stimulated with a T-cell mitogen whereas an inhibitory effect was observed in cultures without T-cells stimulated with a B-cell mitogen. The capacity of PHT to enhance the mitogenic action of concanavalin A may relate to its capacity to induce immunologic abnormalities and lymphadenopathy in humans.

Animals↗
PubMed1983

Correlations between skin sensitization potential and chemical reactivity for p-nitrobenzyl compounds.

Quantitative relationships between skin sensitization potential and certain physico-chemical properties of alkylating agents have been reported. This study demonstrates the correlation of the relative alkylation index (RAI), derived from the alkylation rate and lipophilicity of an alkylating agent, with a set of experimental sensitization data obtained for a series of p-nitrobenzyl compounds.

Alkylation↗
PubMed1983

Depth electrode recording in patients undergoing corpus callosotomy for intractable epilepsy.

6 patients undergoing anterior corpus callosotomy for intractable epilepsy have been studied with depth electroencephalography (EEG). Recording before, during and after surgery has confirmed the ability of depth EEG to demonstrate and identify lateralized, focal and often multifocal disturbances. Callosal section has an immediate and lasting effect on clinical seizures and is accompanied by EEG changes with loss of generalization and synchrony following commissurotomy. Depth electrodes within the corpus callosal radiations variably reflect preoperative epileptiform activity recorded from the temporal and frontal regions and postoperatively confirm loss of a potential route of propagation through the commissure.

Adolescent↗
PubMed1982

Evaluation of the immune response to type III pneumococcal polysaccharide as a means to evaluate T-independent immune function in the rat.

Since the rat is frequently the experimental animal of choice for toxicology testing, studies were undertaken to adapt assays routinely used to evaluate immune function in mice so that immune function could likewise be evaluated in collaborative projects employing toxicant-treated rats. Contrary to previous reports in the literature, Type III pneumococcal polysaccharide (S3) was immunogenic in rats. Specific antibody responses to S3 were demonstrated in two strains of rats following immunization by either the subcutaneous (sc) or intraperitoneal (ip) route with purified S3, with S3 contained in polyvalent pneumococcal polysaccharide vaccine (pneumovax), or with heat-killed Type III Streptococcus pneumoniae. Dose-response studies demonstrated that the optimal immunizing dose in Sprague-Dawley or Fischer rats was 25 micrograms S3. Reimmunization with S3 on d 21 did not produce an anamnestic response, and the kinetic data were consistent with S3 being a thymus-independent (T-independent) antigen in the rat. In contrast to our previous studies in the mouse, concurrent sc or ip injections of pertussis vaccine did not modify the response to S3 in rats. Sprague-Dawley rats acquired the capacity to respond immunologically to S3 between 24 and 31 d of age. In mature animals, sex had no effect on the ability to respond to S3. The utility of this model as a means of characterize toxicant-induced immune dysfunction was demonstrated using the prototype immunotoxicant cyclo-phosphamide.

Aging↗
PubMed1981

Dandy-Walker malformation in identical twins.

The mother of a stillborn anencephalic child subsequently had twins with macrocephaly due to a cystic malformation of posterior brain structures, compatible with the Dandy-Walker syndrome.

Dandy-Walker Syndrome↗
PubMed1980

Growth of breast fed and bottle fed infants.

One hundred and sixty-seven infants were measured at birth, then monthly until four or five months of age. Growth in weight, length, occipito-frontal circumference and three skinfold measurements, and the velocities of these parameters, were compared between breast fed and bottle fed infants. Although bottle fed female infants tended to gain more weight and have greater skinfold measurements than female breast fed infants the difference was not significant. This trend was not evident in males. The proportion of the total population breast fed declined from 78 percent at birth to 43 percent at five months. Solid food was introduced significantly earlier to bottle fed infants. Breast fed babies were significantly more likely to come from a higher socio-economic group, to have a married mother, and to have a mother in the 20-29 year age group.

Adult↗
PubMed1980

The metabolism of oxamniquine in the gut wall.

1. The extent of metabolism of oxamniquine, 6-hydroxymethyl-7-nitro-2-isopropylaminomethyl-1,2,3,4-tetrahydroquinoline, in the gut of the dog has been studied using an intestinal preparation which allows collection of the outflow from the portal vein. 2. Oxamniquine undergoes substantial conversion to 2-isopropylaminomethyl-7-nitro-1,2,3,4,-tetrahydroquinoline-6-carboxylic acid before or during absorption. 3. This oxidation is not significantly inhibited by pretreatment with pyrazole, erythromycin or gentamicin. 4. Results indicate that appreciable oxidation of oxamniquine is mediated via enzymes in the gut wall.

Animals↗