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Biomedical subjects

D Howes

Publications and source records attributed to D Howes.

At least 37 records · Page 2Linked to original sources
PubMed1978

Metabolism of the surfactants sodium undecyltriethoxy sulphate and sodium dodecyltriethoxy sulphate in the rat.

The metabolic fates of the synthetic surfactants, sodium [1-(14)C]undecyltriethoxy sulphate and sodium [1-(14)C]dodecyltriethoxy sulphate were studied in the rat. Both compounds were extensively metabolized regardless of the route of administration, oral, intraperitoneal or intravenous. Short-chain radioactive products were eliminated in the urine: the major metabolite of the dodecyl homologue in the urine was identified as (-)O(2)C(14)CH(2)- (OC(2)H(4))(3)OSO(3) (-) by n.m.r. and g.l.c.-mass spectrometry, whereas the major metabolite of the undecyl homologue in the urine was tentatively identified as (-)O(2)CCH(2) (14)CH(2)- (OC(2)H(4))(3)OSO(3) (-). In contrast with experiments with the dodecyl derivative, when [1-(14)C]undecyltriethoxy sulphate was administered to rats, appreciable amounts of radioactivity were recovered as (14)CO(2) in expired air. Whole-body radioautography implicated the liver as the major site of metabolism of both surfactants. The nature of the metabolic products establishes that both compounds are degraded by omega,beta-oxidation. Cleavage of the ether linkage proximal to the sulphate moiety may account for the small amounts of (14)CO(2) recovered in expired air after the administration of [1-(14)C]dodecyltriethoxy sulphate. It is suggested the substantial amounts of (14)CO(2) recovered after [1-(14)C]-undecyltriethoxy sulphate administration originate from (-)O(2) (14)C(OC(2)H(4))(3) OSO(3) (-), an unstable product of omega,beta-oxidation. An n.m.r. spectrum of the metabolite identified as 2-(triethoxy sulphate)acetic acid and a mass spectrum of the trimethylsilyl derivative of the parent alcohol of that metabolite have been deposited as Supplementary Publication SUP50086 (5 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies can be obtained on the terms indicated in Biochem. J. (1978) 169, 5.

Administration, Oral↗
PubMed1977

Timing of intraventricular haemorrhage.

The detection of the onset of intraventricular haemorrhage (IVH) during life is a necessary preliminary to understanding the cause of this condition. In 10 infants of very low birthweight treated with serial transfusions of adult blood the proportions of transfused cells circulating after each transfusion were compared with the proportion of transfused cells found in the intraventricular clot at necropsy. This allowed the timing of IVH to be restricted retrospectively to the period between consecutive blood transfusions. In addition, the proportional changes of transfused cells produced by infusion of a known red cell mass allow changes in the babies' original red cell mass to be followed during life. A fall in this value occurred in 8 infants dying with IVH and was taken to indicate haemorrhage. Comparison of the two methods in 9 infants suggested that, while in some cases intraventricular bleeding occurs rapidly, in others it takes place over a period of time. The interval between birth and the onset of haemorrhage was directly proportional to the gestational age of the infant.

Blood Transfusion↗
PubMed1976

Percutaneous absorption of triclocarban in rat and man.

The route and rate of excretion by rats of the germicide (1 4 C) Triclocarban formerly called trichlorocarbanilide, given by parenteral injection has been investigated. Blood levels based on radioactivity and by chemical determination after parenteral injection have been compared with those obtained after topical application of (1 4 C) Triclocarban in soaps and in dimethylformamide (DMF) through occluded rat skin has been studied. Other soaps and a hand cleanser containing (1 4 C) Triclocarban have been applied to rat skin without occlusion and the effects of duration of contact, concentration and the use of a solubilizer have been investigated. In humans, absorption of Triclocarban through skin after bathing daily for 28 days has been investigated by chemical analysis of blood and urine. The data show that elimination by the rat is rapid and complete principally via the faeces. Blood levels after parenteral injection are low and comparison of the radioactivity and chemical determinations suggest rapid metabolism of the Triclocarban. After application to the skin, blood levels based on 1 4 C are very low. Absorption of (1 4 C) Triclocarban through occluded rat skin was greater from DMF than from soaps. With non-occluded rat skin, absorption from soaps was less and was dependent on concentration but independent of duration of contact. The use of a solubilizer did not increase absorption through skin. No measurable Triclocarban (less than 25 ppb) was present in blood and urine samples of volunteers during or shortly after a 28-day intensive bathing regimen.

Animals↗
PubMed1975

Absorption, metabolism and excretion by goldfish of the anionic detergent sodium lauryl sulphate.

The route of absorption, tissue distribution, metabolism route of excretion, and excretion rate of the anionic detergent sodium lauryl sulphate (SLS) in goldfish was investigated using [35-S] or [1-14-C] SLS. It has been shown that goldfish absorb SLS from solution principally through the gills, and that SLS is rapidly distributed throughout the body tissues, the highest concentration being found in the gall bladder. SLS was metabolised by the fish to butyric acid-4-sulphate, and was excreted by the kidney. Over a 24-h period 68% and 38% of a prescribed dose was excreted from freely fed and unfed fish, respectively.

Animals↗
PubMed1975

Skin deposition and penetration of trichlorocarbanilide.

Studies are reported on the localization and quantitative distribution of 3,4,4'-trichloro[14C]carbanilide([14C]TCC) in guinea-pig and human skin, and on the percutaneous absorption of TCC following topical application to guinea pigs. [14C]TCC was applied to guinea-pig skin in various vehicles (conventional, superfatted, 10 percent non-soap detergent (NSD) and 30 percent NSD soap suspensions or in N,N-dimethylformamide [DMF]) and under various conditions (e.g. freshly prepared or equilibrated suspensions; single or multiple washes). Most of the amount of TCC remaining in the skin after rinsing was deposited on the skin surface and only relatively minute amounts actually penetrated through the epidermis into the dermis. Whereas conventional soap facilitated a greater deposition of TCC on the skin surface than NSD, the latter caused greater amounts of TCC to be deposited in the pilosebaceous system and lower dermis than conventional soap. The absence of TCC in the blood and tissues of guinea pigs given topical applications of TCC lends further support to the very low order of percutaneous absorption of TCC. The localisation of TCC followed a similar pattern in human skin as in guinea-pig skin, but the amount deposited was less and the rate of disappearance was more for human than for guinea-pig skin.

Animals↗
PubMed1975

Comparative percutaneous absorption of pyrithiones.

The percutaneous absorption of 3H or 35S labelled pyridine-2-thione-N-oxide (PT) through the skin of rat, rabbit and guinea pigs in vivo is reported. The sodium (Na) zinc (Zn) and zirconium (Zr) derivatives of PT were studied and the effects of duration of contact and concentration of the NaPT and ZnPT in test solutions were examined. Shampoo test solutions containing the isotopically labelled PT were applied to the skin of the animals. The skins were then rinsed, the treated areas of skin protected and excreta were monitored for the isotope for 2 days after treatment. Penetration was calculated from the amounts of isotope in the excreta. Further groups of animals were treated with test solutions applied under occlusive patches for 6 h before rinsing the skin. The turnover of Na and ZnPT in the three species after intraperitoneal and subcutaneous injection was measured. All three species rapidly excreted the injected isotope principally via the urine. The comparative penetration of the three PT samples was Na greater than Zr greater than Zn from all treatments. The comparative permeability of the animals' skins to these PTs was rabbit greater than rat greater than guinea pig. NaPT penetration was found to be dependent upon duration of contact and concentration in the test solution whereas the penetration of ZnPT was found to be proportional to concentration but independent of duration of contact of the test solution. Extrapolation of these findings to the use of shampoos containing up to 1% (w/v) ZnPT by man indicated an adequate margin of safety for use of this type of product.

Animals↗
PubMed1975

Simple reaction time: evidence for focal impairment from lesions of the right hemisphere.

Simple reaction time is significantly increased in patients with unilateral lesions of either cerebral hemisphere responding with the hand ipsilateral to the lesion, but the effect is much greater when the lesion is in the non-dominant hemisphere. This difference cannot be attributed to asymmetries in the size or type of lesion. It applies over the complete distribution of reaction times as well as to the means, and is not diminished by practice. Neither the classical conduction model of reaction time nor the mass-action hypothesis proposed by De Renzi and Faglioni (1965) can account for the findings. Although the increase of about 100 ms observed with lesions of the dominant hemisphere probably represents a non-specific effect of brain disease, the much larger increases resulting from lesions of the non-dominant hemisphere appear to be of focal origin. The critical areas cannot yet be specified with certainty, but maps of the brain scans for patients with the highest reaction times suggest that structures in or near the basal ganglia and the posterior parietal region of the non-dominant hemisphere are involved, and other studies show that the focal effect is not found when patients with contralateral motor involvement are excluded.

Acoustic Stimulation↗