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Biomedical subjects

D D Smith

Publications and source records attributed to D D Smith.

At least 127 records · Page 7Linked to original sources
PubMed1978

Cockroaches as vectors of Sarcocystis muris and of other coccidia in the laboratory.

To assess the roles of the German cockroach (Blatella germanica) and the American cockroach (Periplaneta americana) in the transmission of Sarcocystis muris and of 3 other coccidia of cats-Toxoplasma gondii, Isospora felis, and Isospora rivolta, cockroaches exposed to feces containing these coccidia were periodically fed to mice, as was a portion of the fecal matter. Sarcocystis muris sporocysts, which in feces remained infectious for at least 20 days, were also transmitted to mice by P. americana for at least 20 days and by B. germanica for 5 days after exposure to infectious feces. Toxoplasma gondii oocysts were transmitted by P. americana intermittently up to 10 days, but by B. germanica only immediately after exposure to feces. Oocysts of 2 species of Isospora, when associated with fecal matter, remained infectious for 20 days. Those of I. rivolta were transmitted by both cockroach species for 10 days, but I. felis was transmitted only by by B. germanica, and for only 2 days.

Animals↗
PubMed1977

Group B streptococcal infection in neonates.

A study of 866 vaginal swabs from non-pregnant women showed that 167 (19.3%) contained Group B beta-haemolytic streptococci, with a predominance of Types 3 (31.4%) and Ib (25.2%). The incidence of severe neonatal infections due to Group B streptococci during a 3 1/2 year period at The Prince of Wales Hospital was examined, and a study was made of the distribution of serotypes and associated clinical features (including prematurity and abnormal deliveries) in 16 neonates with septicaemia and/or meningitis admitted to the Royal Alexandra Hospital for Children, and the Paediatric Department of The Prince of Wales Hospital. From this study it was concluded that prophylactic antibiotic therapy should be administered to neonates with evidence of Group B streptococcal colonization of the throat, umbilicus, or gut, when there is also evidence of prematurity, prolonged interval between membrane rupture and delivery, or other associated obstetric complications.

Adolescent↗
PubMed1977

Chloroplast membrane sidedness. Location of plastocyanin determined by chemical modifiers.

Intact grana and stroma membranes (outer membrane absent) and detergent or sonication disrupted thylakoid membranes were treated with the hydrophilic covalent chemical modifiers [35S]diazonium benzene sulfonic acid ([35S]DABS) and [14C]glycine ethylester plus 1-cyclohexyl-3-(2-morpholinoethyl)-carbodiimide metho-p-toluenesulfonate (CDIS). Plastocyanin was purified using column chromatography followed by polyacrylamide gel electrophoresis and the incorporation of [35S]DABS and [14C]glycine ethylester into plastocyanin was determined by slicing the gels and counting the radioactivity in the plastocyanin band. Plastocyanin isolated from thylakoids disrupted prior to chemical modification binds two to four times as much of either modifier than the plastocyanin isolated from intact chloroplasts. This ratio is five to ten times lower than the ratio expected for a component buried behind the permeability barrier of a membrane. The data suggest that plastocyanin is partially exposed at the external surface of the thylakoid membrane rather than being completely buried in, or behind, the lipo-protein membrane.

Biological Assay↗
PubMed1977

Besnoitia darlingi (Protozoa: Toxoplasmatinae): cyclic transmission by cats.

Two of five opossums examined from the Kansas City area were found to be infected with Besnoitia darlingi. Inoculation of cysts resulted in acute lethal infections in mice and hamsters. Chronic infections with development of tissue cysts were obtained in mice by prophylaxis with sulfadiazine. Cysts were fed to cats and a dog which resulted in the shedding of isosporoid oocysts by cats. The prepatent period was 11 to 14 days. Unsporulated oocysts averaged 11.9 by 12.3 micrometer and sporulated in 48 to 72 hr. Mouse-to-mouse tramsmission was achieved by injecting triturated tissue containing cysts. This is the third species of Besonitia to be cyclically transmitted by cats.

Animals↗
PubMed1976

Quantitative throat-swab culture in the diagnosis of streptococcal pharyngitis in children.

A striking difference in the detection of a heavy growth of Streptococcus pyogenes in throat swabs taken from 1054 children with pharyngitis compared with those from 462 normal children was demonstrated when a standardised technique of quantitative culture was used. In patients with pharyngitis 71% of the isolates were heavy whereas a heavy culture was obtained in only 1-7% of healthy children. Also, a significant correlation between the clinical observations suggestive of streptococcal pharyngitis and the results of culture was confined to those patients whose throat swabs yielded a heavy growth of streptococci. It is concluded that bacteriological examination is of value as a diagnostic test only when the results of culture are quantitatively assessed.

Age Factors↗
PubMed1976

Adenosine 3',5'-cyclic monophosphate levels in x-ray-induced small-bowel adenocarcinoma in the rat.

X-ray-induced adenocarcinomas in the small bowels of outbred Lewis Brown Norway and Holtzman rats contained significantly lower concentrations of adenosine 3',5'-cyclic monophosphate than did normal rat intestinal tissue. No significant differences were observed between the intracellular concentrations of the nucleotide in the normal rat small bowel and those occurring in normal-appearing intestinal tissue exposed to tumor induction conditions.

Adenocarcinoma↗
PubMed1976

The detection of toxin production by Corynebacterium diphtheriae in diagnostic laboratories.

In vitro tests for assessing the toxigenicity of strains of C. diphtheriae using the original agar plate precipitin method of Elek are unreliable. At high concentrations of antitoxin (500-1000 U/ml) multiple non-specific precipitin lines occur making interpretation difficult. Increased specificity was obtained by diluting the antitoxin but this in turn caused a delay in the appearance of toxin-antitoxin lines. Also, the failure of lines to appear on media enriched with unsuitable serum may lead to false-negative results. Final assessment of the toxigenicity of strains of C. diphtheriae can probably only be made reliably by guinea-pig tests.

Animals↗
PubMed1975

Relevance of "significant bacteriuria" to aetiology and diagnosis of urinary-tract infection.

28 of 74 female domiciliary patients who presented with urinary-tract symptoms did not fulfil the usually accepted laboratory criterion required for confirmation of urinary-tract infection (i.e., a urinary bacterial viable count in excess of 100 000/ml). The progress of the disease was similar in non-bacteriuric and bacteriuric patients. In addition, a significant proportion of the bacteriuric group did not show the response to therapy expected from the results of in-vitro tests of antibiotic sensitivity and urinary antibacterial activity. To explain these findings, it is postulated that bacteria may not be primary pathogens in uncomplicated urinary-tract infection even where "significant bacteriuria" is demonstrated.

Adolescent↗
PubMed1975

Photosynthetic activity and membrane polypeptide composition of supergranal chloroplasts from plant tissue cultures containing a viruslike particle.

Tissue culture cells of Streptanthus tortuosus (Kell.) var. orbiculatus (Greene) Hall (Cruciferae), having a viruslike particle in their nucleoli, the STV cell line, contain "supergranal" chloroplasts. Freeze-fracture studies of chloroplasts of a control cell line, which lacks the viruslike particles, reveal two complementary faces similar to those observed in spinach chloroplasts. Replicas of freeze-fractured STV supergranal chloroplasts, however, show that one membrane face (B) contains widely spaced 80 A particles and the other face (C) is essentially smooth. Isolated STV supergranal chloroplasts lack photosystem II activity as indicated by their inability to reduce dichlorophenolindophenol and are unable to reduce NADP with electrons from photosystem II or from ascorbate-reduced dichlorophenolindophenol. However, partial photosystem I activity is indicated by the reduction of methyl viologen with electrons from dichlorophenolindophenol-ascorbate. This supports the concept that there is not a direct correspondence between grana formation and photosystem II activity. Electrophoresis shows that all of the major polypeptide bands present in the STV supergranal chloroplasts are also present in the control chloroplast membranes. One band, molecular weight 33,000, is present in a greatly increased amount in the STV supergranal chloroplast membranes and may be associated with grana stacking.

Journal Article↗
PubMed1975

New satellitism test for isolation and identification of Haemophilus influenzae and Haemophilus parainfluenzae in sputum.

A new satellitism test designed to facilitate the isolation and identification of Haemophilus influenzae and Haemophilus parainfluenzae is described. In the basal medium, nicotinamide adenine dinucleotide is incorporated at a concentration of 0.2 mug per ml, an amount adequate for H. influenzae but not for H. parainfluenzae. Two disks are placed on the surface of the medium, one disk being impregnated with 60 mug of hemin and the other with 15 mug of nicotinamide adenine dinucleotide. Under these conditions, H. influenzae strains grow around the hemin disk only and the majority of H. parainfluenzae grow around the nicotinamide adenine dinucleotide disk. This procedure gives results which are more clear cut than other established methods, especially in sputum culture.

Bacteriological Techniques↗