Search PubMed⌕ Search

Biomedical subjects

R S Baker

Publications and source records attributed to R S Baker.

At least 127 records · Page 7Linked to original sources
PubMed1982

An investigation of the mutagenic potential of pulsed ultrasound.

The possible mutagenic effect of microsecond pulses of ultrasound was investigated using 3 MHz ultrasound at diagnostic dosages, and also under conditions of increased pulse repetition frequency and acoustic power output. The first part of the study involved 5 strains of Salmonella typhimurium bacteria in which mutagenicity and viability were assessed using the Ames test, while functional competence was evaluated from microscopic observations of motility. No changes were observed in survival, in the incidence of mutants, or in microbial motility following irradiation with ultrasound intensities of 4.5 W/cm2 at temperatures ranging from 37 degrees to 43 degrees C. In the second part of this study, the frequency of sister chromatid exchange (SCE) in Chinese hamster ovary (CHO) cells, treated with similar ultrasound dosages, remained unaltered when cells were irradiated at temperatures up to 41 degrees C. At 43 degrees C and above, cell division was arrested by hyperthermia, an effect unrelated to ultrasound.

Animals↗
PubMed1981

Mutagenicity of arylmethane dyes in Salmonella.

22 arylmethane dyes which have been used as food colours, commercial dyes, laboratory stains and pH indicators were tested in the Salmonella/mammalian microsome mutagenicity assay. 8 mutagenic dyes were identified, including 5 food colours and 3 common laboratory strains; none of the 11 indicator dyes tested was mutagenic. The commercial and laboratory dyes Methyl Violet 2B C.I. 42535 and Crystal Violet C.I. 42555 were mutagenic in base-pair substitution mutation detector strain TA1535 in the absence of metabolic activation. By contrast, the food colours Benzyl Violet 4B C.I. 42640, Guinea Green B.C.I. 42085, Light Green SF C.I. 42095, Lissamine Green B C.I. 44090 and Violet BNP C.I. 42581 and the bacteriological stain, Basic Fuchsin C.I. 42500-42510, were all mutagenic in frameshift mutation detector strains TA98 and/or TA1538 and required metabolic activation. Most of these compounds gave weak mutagenic responses with Salmonella and were positive only within narrow dose ranges. Since conflicting results were obtained using dyes from different sources, minor dye components may have been responsible for their mutagenicity. This suggests the need to improve knowledge about impurities in arylmethane colours still used in food and to review the toxicological role of such impurities.

Animals↗
PubMed1981

Carotid-retinal embolism with coexistent mitral valve prolapse.

A 63-year-old hypertensive woman with a prolapsing mitral valve developed sudden blindness of the left eye secondary to a central retinal artery embolus. The decision to perform carotid arteriography led to discovery of an ulcerated plaque in the left internal carotid artery, which was found at the time of endarterectomy to bear a large friable platelet thrombus. The frequent occurrence of mitral valve prolapse in normal populations suggests that this anomaly may be incidental rather than etiologic in patients with cerebral embolic phenomena. The finding of mitral valve prolapse should not routinely exclude evaluation for other sources of embolic stroke.

Aged↗
PubMed1980

Comparison of rat and guinea pig as sources of the S9 fraction in the Salmonella/mammalian microsome mutagenicity test.

A highly significant enhancement of mutagenicity occurs with 11 polycyclic aromatic hydrocarbons when 3-methylcholanthrene-induced guinea pig liver S9 is substituted for Aroclor-induced rat liver S9 in the Ames test. The use of MC-induced guinea pig liver S9 is particularly valuable for detecting the weak mutagenicity of benz[c]acridine, which is barely positive in a standard Ames assay. However, anthracene and phenanthrene, which are generally considered not to be carcinogens, remain non-mutagenic for strain TA100. This enhancement of mutagenicity does not correlate with arylhydrocarbon hydroxylase activities of the various liver preparations and does not apply to certain other non-PAH mutagens, including beta-naphthylamine, aflatoxin B1 and 4-dimethylaminoazobenzene.

Acridines↗
PubMed1979

Variation of phenotype in Charcot-Marie-Tooth disease.

A two year old from a family with typical Charcot-Marie-Tooth disease has extensive ocular and central abnormalities, severe generalized neuropathy, and amyotrophy. Many abnormalities previously described in association with Charcot-Marie-Tooth disease are combined in this patient, including chorioretinal degeneration, optic atrophy, facial weakness, oligophrenia, and generalized amyotrophy. Documentation of the diagnosis in the child's ancestors and the precedent for each of his abnormalities suggest that these features represent a virulent expression of the inherited defect.

Amyotrophic Lateral Sclerosis↗
PubMed1979

Internuclear ophthalmoplegia following head injury. Case report.

The most common causes of internuclear ophthalmoplegia (INO) are multiple sclerosis and vascular disease of the brain stem. Rarer causes are tumor, Arnold-Chiari malformation, and syphilis. Myasthenia gravis has, on occasion, presented with ocular abnormalities indistinguishable from INO. A case is described of bilateral INO of brief duration following head trauma. There were no other brain-stem abnormalities. This brings to 11 the number of reported patients in whom head trauma precipitated this abnormality.

Adult↗
PubMed1977

Treatment of recurrent syndrome of inappropriate secretion of antidiuretic hormone with lithium.

The usual treatment for recurrent syndrome of inappropriate secretion of antidiuretic hormone has been fluid restriction. Recently White and Fetner described an adult with SIADH successfully managed with lithium carbonate. Described here is a child with recurrent SIADH who was diagnosed as having an acute hyponatremic episode and who then relapsed twice in a two-month period while chronic fluid restriction was attempted. He has now been maintained on 300 mg/day of lithium carbonate and is asymptomatic with normal serum sodium concentration and urine osmolalities. Lithium appears to be effective in the management of recurrent SIADH and may allow control in a patient who cannot comply with long-term fluid restriction.

Child↗
PubMed1976

The influence of MuLV and SV40 viruses on senescence in mouse fibroblasts in vitro.

Mouse cells productively infected with Moloney leukaemia virus (MuLV) underwent senescence in a manner similar to control cells, although they recovered more readily as an established line. Rapidly growing cell lines were also obtained following simian virus 40 (SV40) infection of senescent cells. However, superinfection of senescent MuLV-producing cells by SV40 led to slower growing cells with a reduced output of infectious MuLV.

Aging↗
PubMed1975

Capsular polymer of Haemophilus influenzae, type b. I. Structural characterization of the capsular polymer of strain Eagan.

The capsular type-specific antigen of Haemophilus influenzae, type b, has been reported to have a unit structure composed of D-ribose and phosphate. Recently, the presence of ribitol was found in preparations of type b capsular antigen. Our analytical results show equimolar proportions of ribose, ribitol, and phosphate. Periodate oxidation studies, paper chromatography of acidic and alkaline hydrolysates, and NMR spectral data indicate the structure of the capular antigen of H. influenzae b, strain Eagan to be a polyribosylribitol phosphate polymer.

Antigens, Bacterial↗
PubMed1975

Growth enhancement of myogenic tumor cells by conditioned medium from embryo fibroblasts.

Growth medium was conditioned by incubation on mouse embryo cells in vitro. Supplementation of agar suspension cultures with conditioned medium from primary cells, but not from established lines, readily enhanced colony development by mouse tumor cells. Only cells with the properties of myoblasts responded to conditioned medium. Other fibroblastoid cells and virus-transformed cell lines were not affected. Myogenic cells in agar cultures grew in the presence of conditioned medium but did not differentiate. Soluble collagen at 400 mug/ml possessed little colony-stimulating activity by comparison with fresh conditioned medium.

Cell Division↗
PubMed1975

Antibody responses to a combination vaccine against Haemophilus influenzae type b, diphtheria, pertussis, and tetanus.

Forty-one children were studied in order to provide information on antibody responses to H. influenzae type b polyribophosphate (PRP), given in combination with diphtheria-pertussis-tetanus vaccine (DPT). When PRP was administered alone, 9 of 15 children demonstrated fourfold or greater increases in titres of anti-PRP antibody. In contrast, in the group receiving a combination vaccine consisting of DPT and PRP only 1 of 13 children showed a similar rise in anti-PRP antibody. It was concluded that, in the population studied, the combination vaccine was less effective than PRP alone. The reasons for this difference and its potential significance are discussed.

Antibody Formation↗