Biomedical subjects
Publications and source records attributed to R Clayton.
The largest collection yet assembled of year-to-year data on the seroprevalence of antibody to HIV in practicing dentists confirms that dentists--along with other health care workers--remain at low risk for occupationally acquired HIV infection.
In a study designed to examine the role of the genotype on sensitivity to drug-induced behavioural changes, pregnant C57BL/6J and CBA mice were administered 60 mg/kg phenobarbital (PHB) intraperitoneally during days 10-16 of gestation. Following a balanced intrastrain fostering procedure, the behaviour of lactating dams was observed in their home cage at 2, 3, 5, 7 and 14 days postpartum. As the pups became older, maternal behaviour declined in control groups, whereas PHB dams of the CBA strain persisted in nursing their pups. C57 dams were generally affected in an opposite way by PHB exposure. For example, treated dams spent significantly less time in licking behaviour. Nest quality score was especially elevated in PHB dams of the CBA strain, while in C57 dams, nest-building was inhibited and nest quality unaffected by the previous PHB exposure. These results indicate that specific items of maternal behaviour can be differently affected by PHB exposure, and that the responses are affected by the genotype. To summarise, pups raised by treated dams may receive either exaggerated or insufficient maternal attention, as a result of changes in neurotransmitter systems and behavioural regulation following phenobarbital exposure. These results point to the need for a better understanding of mother/pup interactions in studies aimed at characterizing drug and toxicant effects on postnatal development.
Survey data from the United States indicate that tobacco use is associated with the initiation of use of other addicting substances, and that increasing levels of tobacco use are associated with increasing levels of use of other psychoactive substances. Furthermore, factors affecting initiation, abstinence, and relapse to the use of tobacco, alcohol, and opioids are similar in nature. In addition, there are similarities in the addictive process underlying the use of these substances. Taken together, these data suggest that tobacco use is involved, possibly more than by simple association, in the use of other substances containing psychoactive chemicals. In the present paper we discuss the involvement of tobacco in the use of alcohol, opioids, cocaine, and other substances, as well as some of the implications of these observations for researchers and clinicians. One such implication is that it may be possible to use tobacco and nicotine as models for phenomena of interest to other substance use researchers. For example, drug abuse treatment and prevention strategies could be explored using tobacco use as a target behavior, and biological phenomena such as the development of tolerance and physical dependence may be more readily studied with nicotine than with many other drugs. Certain pharmacologic differences across substances are also discussed in light of their implications for development of treatment and drug control policies.
In the lens, epithelial cells from the equatorial zone differentiate into postmitotic elongated fibers. One aspect of this differentiation is nuclear shape transformation and DNA degradation. This process is controlled by DNase activity which in fiber nuclei increases with development. DNase activity is also present in the epithelial cell nuclei which appears to be non-functional but could be activated in vitro by exogenous addition of Ca2+. We have analyzed the possible selective action of endogenous DNase on 3 genes involved in lens terminal differentiation, namely delta-crystallin, beta-tubulin and vimentin, and on 1 gene not thought to participate in this process, ovalbumin. We have compared restriction DNA patterns of these genes in nuclei isolated from 11-day-old chick embryos and incubated in Ca2+-free medium or in fresh epithelial and fiber lens tissue at 11 and 18 days of development. During incubation in vitro of 11-day fiber nuclei, there is a net increase in the sensitivity of the delta-crystallin, beta-tubulin, ovalbumin and vimentin chromatin to the endogenous DNase. The vimentin gene appears to be more stable than the beta-tubulin and delta-crystallin genes indicating a degree of specificity of the endogenous DNase activity. In the epithelial nuclei, the lens-specific genes appear to be more stable but paradoxically there is a net degradation of the ovalbumin gene. In freshly isolated tissues the 4 genes were detected in epithelial and fiber cells at 11 and 18 days. Furthermore, in the mature fibers in which the nuclei were degenerating, the latter genes were still not completely digested.
The airborne dust generated when cutting splinting bandages represents a potential respiratory hazard, particularly to those who regularly remove casts with a power saw. Plaster of Paris (POP) dust is already classified by the Health and Safety Executive as a nuisance dust. This paper reports on a study to determine the nature, size and concentration of dust produced when cutting polyurethane (PU) impregnated bandages using a power saw. It has been shown that, under severe conditions PU bandages produce lower airborne dust concentrations than POP bandage but that all of the bandages tested produced particles small enough to reach the final divisions of the lung. It is therefore recommended that a dust extraction unit be used when cutting all types of bandage.
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Immunoperoxidase staining and radioimmunoassay were used to identify gonadotropin-releasing hormone (GnRH) and chorionic gonadotropin (hCG) in 4 mammary carcinoma cell lines. GnRH-like immunoreactivity was found in all cell lines; 2 lines also contained hCG. Binding of a GnRH agonist was demonstrated by radioreceptor assay in cultured mammary carcinoma cells. In cell column perfusion of the same cells, exogenous GnRH did not stimulate release of hCG.
Dairy products, including milk, cheese, and casein, can reduce the caries-causing potential of cariogenic substrates as measured in various animal, plaque acidity, and in vitro systems. Although the mechanisms responsible for protection are not completely identified, substances containing Ca and P may contribute to the protective potential by reducing demineralization and/or promoting remineralization of enamel. Casein may reduce demineralization by forming a protective coat on the enamel surface. By means of a rat model, this study evaluated the ability of three casein-free milk mineral concentrates with various levels of whey protein, calcium, and phosphate to modify the cariogenicity of a powdered diet containing 20% sucrose. Analysis of these data indicates that there were no significant differences among groups for weight gain, total food consumption, or feeding frequency, as monitored by a computer-based infrared activity monitor. All three mineral concentrates significantly reduced buccal caries, and two of the three reduced sulcal caries by from 10 to 30%. The analysis further shows that casein-free milk mineral fractions can modify the cariogenicity of sucrose-containing foods in a rat model.
Clinical and experimental studies are described on the effects of a gonadotropin-releasing hormone (GnRH) agonist (A) and antagonist (Ant.) on testicular endocrine function. Testicular effects of long-term gonadotropin suppression by GnRH-A were assessed during treatment of prostatic cancer patients. The testis tissue removed after 6 months of A treatment had less than 5% of the testosterone(T)-producing capacity in comparison to testis tissue removed from untreated control patients. However, the LH receptors (R) and responsiveness of T output to LH stimulation in vitro were unchanged. FSH-R decreased by 70%. Hence, despite suppression of gonadotropins and testicular androgen production during long-term GnRH-A treatment the responsiveness to exogenous gonadotropins is maintained. The testicular effects of a gonadotropin suppression induced with GnRH-Ant. and testicular GnRH-R blockade were studied in rats. Besides decreases of gonadotropins and testicular T, systemic Ant. treatment decreased testicular Prl-R, but had no effect on LH-R or FSH-R. Bromocriptine-induced hypoprolactinemia, in contrast, decreased LH-R but had no effect on Prl-R. The results indicate reciprocal regulation of LH-R and Prl-R, and that testicular steroidogenesis and LH-R are under differential regulation, the former by LH, the latter by Prl. In another study, testicular GnRH-R, and consequently the action of a putative testicular GnRH-like factor, were blocked by unilateral intratesticular infusion of Ant. (1 week, Alzet osmotic pumps). The treatment resulted in 90% occupancy of testicular GnRH-R in the Ant.-infused testes, and this was associated with decreased levels of R for LH, FSH and Prl, and of T. The results indicated that the testicular GnRH-R have a physiological function in subtle stimulation of Leydig cell functions.
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Testicular descent was prevented unilaterally in newborn rats by cutting the gubernaculum testis. At 100 days of age, the number of Leydig and Sertoli cells per testis, the concentration of receptors for LH, FSH, prolactin and GnRH, and endogenous concentrations of progesterone and testosterone were determined. The weight of the abdominal testes was reduced by 80%, but in spite of this they contained as many Sertoli (32.8 +/- 1.3 X 10(6), mean +/- s.e.m., n = 6) and Leydig (28.2 +/- 1.7 X 10(6) cells as did scrotal testes (32.1 +/- 2.5 X 10(6) and 24.3 +/- 1.2 X 10(6) respectively). The numbers of receptors for LH (3.2 +/- 0.2 and 1.0 +/- 0.2 pmol/testis, mean +/- s.e.m., n = 11), FSH (358 +/- 11.0 and 96.3 +/- 12.6 fmol/testis) and prolactin (535 +/- 32.7 and 92.4 +/- 13.2 fmol/testis) were reduced (P less than 0.001) in abdominal testes, but the number of GnRH receptors was unaffected (8.9 +/- 1.4 and 12.1 +/- 1.8 fmol/testis, n = 6). Testicular testosterone concentration (30.9 +/- 4.4 vs 15.4 +/- 3.2 ng/g, n = 11, P less than 0.001), but not that of progesterone (0.87 +/- 0.10 vs 1.01 +/- 0.21 ng/g), was decreased in abdominal testes. The decreased receptor and androgen values reflect functional disturbances in the abdominal testes. The changed local milieu within abdominal testes may reduce hormone receptor concentrations which are then involved in the observed Leydig cell dysfunction.
Patients treated with azelaic acid (15%) cream for chloasma reported simultaneous improvement of acne lesions within the treated areas. This prompted an open study of its effect in cases of acne without chloasma. One hundred patients with acne vulgaris were treated for 3-9 months by twice-daily application of the cream with significant improvement in every case.
The specific activities of glutathione reductase (GR), EC 1.6.4.2, and aldolase, (ALD) EC 4.1.2.13, were determined in the homogenates of 60 cataractous lenses. Concentrations of certain plasma constituents and the morphological types of cataract of the patients were known. Investigations were aimed at establishing a possible correlation between enzyme activities and plasma constituents as well as between the specific activities of GR and ALD and type of cataract. A correlation between the specific activity of GR and the urea content of the blood could be identified. Results also indicated a relationship between the decrease in GR activity and the formation of cortical cataracts.
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Seven black or dark skinned patients with pityriasis lichenoides chronica (PLC) are described, who presented with widespread hypopigmentation. The evidence on which a diagnosis of PLC was made is presented and the differential diagnosis discussed. The hypopigmentation was noted in some patients to be especially marked on the proximal parts of the limbs and axillary folds. A diagnosis of PLC should be considered in all dark skinned patients with a widespread hypopigmented rash.
In a study of 27 patients with pityriasis lichenoides IgM and C3 have been observed on direct immunofluorescence of fresh lesions. Other immunoglobulins and complement components were not observed. Immunofluorescence was seen in 31 (72%) of 43 fresh lesions. It occurred in the walls of superficial dermal vessels and along the dermal-epidermal junction. This pattern of immunofluorescence appears to be characteristic of the disease. Uninvolved skin showed the immunofluorescence less frequently and old scaly lesions none. The concept that pityriasis lichenoides is an immune complex disorder is discussed.