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Biomedical subjects

E R Smith

Publications and source records attributed to E R Smith.

At least 253 records · Page 14Linked to original sources
PubMed1980

Facilitation of mounting behavior in male rats by intracranial injections of luteinizing hormone-releasing hormone.

Luteinizing hormone-releasing hormone (LH-RH) administration has been reported to facilitate male sex behavior. This laboratory has previously reported development of the 'mounting test', a paradigm which reflects sexual arousal mechanisms. We have used this test to study the interaction of LH-RH with the central components of male copulatory behavior in the rat. Sixty 90-day-old Long-Evans male rats were screened for sex behavior and divided into 5 treatment groups. For all mounting tests, a local anesthetic was applied to the penis and mounts were scored during a 15-min exposure to a stimulus female. The animals were given 3 successive weekly tests. By the final test, a significant decrement in mounting behavior was noted, and those males given 50 ng LH-RH i.c.v. displayed more mounting in this test than animals given either no treatment or saline (P less than 0.01). A slight but significant (P less than 0.05) enhancement of performance was also noted in peptide-treated rats in test I. There was no significant difference in any of the tests between animals given lateral cerebroventricular (i.c.v.) injections of 2 microliter acidified saline and those given no treatment. When blood samples were taken from similarly treated animals and assayed by radioimmunoassay for luteinizing hormone and testosterone, plasma levels of these hormones were not different at either 30 min or 2 h after injection of saline or LH-RH. Thus, in animals with diminished genital sensory input, LH-RH administration increases mounting behavior without inducing measurable reproductive endocrine changes. It is proposed that this effect results from an interaction of this peptide with the neural substrates of the arousal mechanism.

Animals↗
PubMed1980

Effects of centrifugation stress on pituitary-gonadal function in male rats.

The effects of centrifugation for various lengths of time were investigated on circulating levels of luteinizing hormone (LH) and testosterone in male rats. In a chronic 52-day experiment, centrifugation at 4.1 G significantly reduced LH and testosterone levels for the entire period. Centrifugation at 2.3 G had less effect inasmuch as LH levels were not significantly decreased and testosterone levels were significantly reduced only during the first few days of centrifugation. In more acute experiments, centrifugation at 4.1 G for 4 h resulted in reduced testosterone levels, whereas centrifugation for 15 min did not significantly alter the hormone levels. These results indicate that centrifugation can decrease circulating LH and testosterone levels if the gravitational force is of sufficient magnitude and is maintained for a period of hours. Chronic centrifugation may also inhibit the acute excitatory response of LH to handling and ether stress.

Animals↗
PubMed1980

Gonadotropin regulation in middle-aged male rats.

Gonadotropin regulation was compared in middle-aged (13 months old) and young adult (3 months old) male rats. Two experiments were conducted on castrated animals given testosterone in Silastic capsules; the dimensions were adjusted to insure equivalent circulating testosterone levels in the two age groups, as validated by RIA. Plasma LH and FSH were also measured by RIA. In Exp 1, each animal was implanted immediately after castration with multiple capsules sufficient to maintain tonic suppression of LH. One capsule was removed each week, thereby reducing testosterone levels in 0.4 ng/ml steps, in order to determine the testosterone level (threshold) at which LH is released from tonic suppression. Middle-aged animals had a threshold 50% lower than young animals, requiring much less testosterone to maintain tonic LH levels. They also showed an attenuated rise in LH and FSH after release from tonic suppression. In Exp 2, long term castrates were given capsules which produced plasma testosterone levels of approximately 1.5 ng/ml in order to evaluate the negative feedback effects of testosterone on elevated LH levels. The testosterone was more effective in suppressing LH in middle-aged rats than in young animals. These results indicate that: 1) middle-aged male rats develop an increased sensitivity to the feedback effects of testosterone, and this increased sensitivity is operative within the normal physiological range of LH and testosterone; and 2) middle-aged animals have a reduced capacity to increase LH and FSH levels after release from tonic suppression. These changes in gonadotropin regulation can account, to a large extent, for the pituitary-testicular decline which develops during middle age in male rats.

Aging↗
PubMed1980

Plasma and pituitary concentrations of LH, FSH and prolactin in aged female C57BL/6 mice.

Plasma and pituitary concentrations of LH, FSH and prolactin were determined by radioimmunoassay in 2-month-old (young) and 16-20-month-old (old) C56BL/6 mice. There were no statistical differences in hormonal levels between aged females in oestrus (those exhibiting a copulatory plug) and those in constant dioestrus. In the old females plasma levels of LH (P < 0.002) and FSH (P < 0.001) were significantly elevated, while levels of prolactin (P < 0.001) were significantly depressed when compared with those from young animals. Pituitary homogenates from old females also contained more gonadotrophins (P < 0.001) and less prolactin (P < 0.001) than those of the young females. A radioreceptor assay utilizing a plasma membrane of luteinized rat or mouse ovaries indicated that LH from 2-month-old animals bound better to ovarian receptors (P < 0.05) than did LH from old mice, although radioimmunoassay of the same samples gave higher (P < 0.01) plasma LH levels for the old mice. Since the radioreceptor assay is considered to be a more sensitive test for biologically active LH, the results from these two types of assays suggest that there may be an alteration in the mouse LH molecule with age.

Aging↗
PubMed1979

Neoplasms in rats and mice fed butylurea and sodium nitrite separately and in combination.

In projected 485-day studies, Fischer 344 rats and C57BL/6 mice were fed 0.58% butylurea and 0.50% sodium nitrite mixed in the diet separately or in combination. The number and type of neoplasms were not significantly increased in either species receiving butylurea or sodium nitrite only. Feeding the two chemicals simultaneously induced neoplasms of the lung, Zymbal's gland, forestomach, intestine and hemopoietic tissues in rats, and malignant lymphomas in mice. The increased incidence of neoplasms in rats and mice fed butylurea and sodium nitrite in combination may result from in vivo formation of the carcinogen, N-butyl-N-nitrosourea.

Animals↗
PubMed1979

New antiarrhythmic agents. 1. Primary alpha-amino anilides.

Thirty-two alpha-amino anilides with various substituents in the aromatic ring and in the alpha position are described. Their abilities to protect mice against chloroform-induced fibrillation and to elicit toxicity were determined. Substitution of an alkyl or aryl group in the alpha position enhanced the antifibrillatory activity. In most cases, increased potency was accompanied by increased toxicity. Eleven compounds were tested in dogs with surgically induced myocardial infarction; most showed antiarrhythmic activity. 2-Aminopropiono-2',6'-xylidide, tocainide, was chosen for clinical investigation.

Anilides↗
PubMed1979

Effects of androgen on sexual behavior in hypogonadal men.

Despite the widespread use of androgen in the treatment of hypogonadal men, its efficacy in restoring sexual behavior to hypogonadal patients has not been established in appropriately controlled behavioral studies. Accordingly, testosterone enanthate or vehicle was injected once every 4 weeks im in a double blind experiment. The subjects were six adult males, aged 32-65 yr, two with gonadal failure and four with secondary hypogonadism. Two doses of testosterone (100 and 400 mg) were administered for approximately 5 months, with the treatments varied at random within and among subjects. Details of sexual activity and experience were followed by the use of daily logs. Frequencies of erections, including nocturnal erections and coitus, showed significant dose-related responses to androgen treatment which closely followed the fluctuations in the circulating testosterone level. As indicated by the Profile of Mood States test, behavioral responses did not appear to be mediated by changes in mood. We concluded that the stimulatory effects of testosterone on sexual activity are rapid, reliable, and not due to a placebo effect. To maintain plasma testosterone and adequate sexual function within normal levels, even high doses of testosterone enanthate should be given no less frequency than once every 3 weeks.

Adult↗
PubMed1978

The virus of hepatitis B a new dimension in the diagnosis of sexually transmitted disease.

Ten patients presenting with venereal or dermatological disorders have been found to have evidence of infection with the virus of hepatitis B; only five had distinguishable liver dysfunction, yet all had either detectable antigen or antibody. Antigen subtype ayw has been identified in four of these people. Once rare in the local population, hepatitis B virus infection appears to be increasing in incidence with cases attributable to inoculation and to direct contact, as well as presenting as a covert partner to gonorrhoea, urethritis and candidiasis. Testing for hepatitis B antigen and antibody is recommended for patients attending the venereal diseases clinic, for patients presenting for removal of tattoos, for those with suspected drug taking and for Polynesians, in whom the carrier rate may be expected to be high (Austin and others, 1974). In our current clinical practice the sterilisation of instruments, the handling of patients, and the transmission of specimens to the laboratory have been reviewed in the light of the US Public Health Service supplement 1976, Perspectives on the Control of Viral Hepatitis, Type B.

Adolescent↗
PubMed1978

Goodpasture's syndrome complicated by nocardia asteroides infection.

A case of Goodpasture's syndrome--an immunological disorder characterised by a proliferative glomerunlonephritis with haemorrhagic pulmonary alveolitis--is described. There has been complete functional recovery of the presenting renal failure, but the immunosuppressive therapy was complicated by a severe episode of metastasising nocardiosis.

Adult↗
PubMed1978

Angiokeratoma corporis diffusum (Anderson-Fabry disease) in a single large family in Nova Scotia.

Eighteen males, 17 of whom were members of a single family, affected with angiokeratoma corporis diffusum were examined in detail to determine the extent of clinical variation of the expression of what was almost certainly the same X-linked mutation in each. The commonest symptom was episodic bouts of severe, painful dysaesthesia in hands and feet. This was a major complaint of 12, a minor complaint of 5, and absent in 1. In over half the subjects, the skin rash that is considered a characteristic sign of the disease was absent or inconspicuous. All exhibited mild clubbing of fingers and toes, and 15 showed variable limitation of active and passive extension of the 5th fingers bilaterally. Only 2 (age 36 and 47) had evidence of significant renal disease. Electrocardiograms showed abnormally short PR intervals in 4, and right ventricular conduction disturbances in 5. Echocardiograms on 9 showed no evidence of myocardial dysfunction. The marked variation of the expression of some features of the disease indicates that the clinical expression of the mutation is likely to be subject to considerable genetic or environmental modification in each individual.

Adolescent↗