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Biomedical subjects

J Herbert

Publications and source records attributed to J Herbert.

At least 235 records · Page 13Linked to original sources
PubMed1976

Studies on the duration of the breeding season and photorefractoriness in female ferrets pinealectomized or treated with melatonin.

Oestrous ferrets became anoestrous on exposure to short photoperiods (8 h light: 16 h darkness, 8L:16D) at the summer solstice, and this effect was prevented by pinealectomy. Removal of the pineal alone did not alter the duration of oestrus in animals kept in natural daylight. Melatonin (1 mg, thrice weekly) given to oestrous ferrets kept in daylight also terminated oestrus prematurely. Animals made photorefractory by prolonged exposure to long photoperiods (14L:10D) became photosensitive again if either given melatonin or transferred to short photoperiods (8L:16D) for 7 weeks. These findings show that the pineal gland of the oestrous ferret is involved in the termination of oestrus when the animal is exposed to experimental short photoperiods. This is in addition to its role in inducing oestrus when anoestrous animals are exposed to long days, an effect shown previously. Thus, neither phase of the annual breeding cycle is altered by experimental lighting regimes in pinealectomized animals. Furthermore, some of the effects of short days (but not of long days), including that on photosensitivity, can be replicated by melatonin in the ferret.

Anestrus↗
PubMed1975

5-hydroxytryptamine in the central nervous system and sexual receptivity of female rhesus monkeys.

The role of 5-hydroxytryptamine (5-HT) in the control of sexual receptivity in female rhesus monkeys has been studied in 24 adult females paired with 6 adult males. p-Chlorophenylalanine (PCPA, 75 mg/kg or 100 mg/kg, every fourth day), a selective inhibitor of 5-HT, was found to reverse unreceptivity induced by adrenalectomy in ovariectomised, oestrogen-treated females. PCPA-treated females presented more frequently and initiated more sexual behaviour, or else they refused fewer of the male's attempts to mount. These effects were in turn reversed by 5-hydroxytryptophan (5-HTP, 20 mg/kg every second day), when this was given to PCPA-treated animals. In addition, 5-HTP given alone to ovariectomised oestrogen-treated females reduced their receptivity. Parallel biochemical experiments showed that PCPA in the doses used lowered the levels of 5-HT in the brain as measured by the levels of 5-hydroxyindole-3-acetic acid (5-HIAA) in the CSF, and that these were restored by 5-HTP. Both oestradiol benzoate (15 mug/day for 10 days) and testosterone propionate (250 mug/day or 400 mug/day for 10 days) lowered the turn-over rates of 5-HT in the brain (as measured by the probenecid test) in ovariectomised female monkeys. These effects of oestradiol on turnover were antagonised by progesterone (15 mg/day for 10 days, given with oestradiol). A substance other than an adrenal androgen has thus been found to reverse the effects of adrenalectomy on sexual receptivity in female monkeys. It is therefore possible that androgens regulate receptivity in female monkeys by modifying the activity of 5-HT-containing neural systems.

Adrenalectomy↗
PubMed1975

The effects of implanting testosterone propionate into the central nervous system on the sexual behaviour of adrenalectomised female rhesus monkeys.

Bilateral adrenalectomy rendered ovariectomised, oestrogen-treated female rhesus monkeys sexually unreceptive. Small unilateral implants of testosterone propionate (mean weight 140 mug) into the anterior hypothalamus/preoptic area restored receptivity in 7 out of 8 of these monkeys. Cholesterol implanted into the same area, or similar amounts of testosterone propionate implanted into the posterior hypothalamus/pretectal area (4 females) or cerebral cortex/dorsal thalamus (5 monkeys) had no consistent effect on behaviour. It therefore seems likely that androgens regulate sexual receptivity in female monkeys by acting on some part of the anterior hypothalamus. Thus, though the hormonal control of receptivity in female primates differs from non-primates, the site on which hormones act to regulate this behaviour may be similar in both.

Adrenal Glands↗
PubMed1975

Decreased bactericidal activity of leukocytes of stressed newborn infants.

Previous studies have established that leukocyte phagocytosis and intracellular killing are normal in term and low-birthweight newborns who are well. To determine the effect of stress or illness on newborn leukocyte function, the phagocytic and bactericidal activity of leukocytes from 40 sick newborns was compared with that of leukocytes from 12 newborns and 23 normal adults. To eliminate abnormal phagocytosis resulting from serum opsonic defects in newborn sera, pooled adult sera were used in all assays. Twenty-five of the 40 stressed newborns (63%) had decreased in vitro activity against either Staphylococcus aureus 502A or Escherichia coli, or both, compared with decreased activity in two of 12 well infants (17%) and in four of 23 adult controls (17%). The mean bactericidal activity (percentage of organisms killed after two hours) of leukocytes from stressed newborns against S. aureus (83% +/- 2 [SEM]) and E. coli. (87% +/- 4 [SEM]) was significantly less than in the combined well infant and adult control group (94% +/- 1 for S. aureus and 97% +/- .5 for E. coli). Although the more severely ill infants had an increased incidence of impaired antibacterial activity, the degree of impairment was not related to the severity of illness. No consistent relationship of decreased activity to birthweight, gestational age, age when studied, or specific diagnosis was seen. The leukocyte abnormality in stressed infants against S. aureus was principally a killing defect, while against E. coli both phagocytosis and killing were abnormal. This study indicates that a wide variety of neonatal disorders may affect one or more of the steps required for normal bacterial killing. The lability of leukocytic antibacterial function under stress is an additional mechanism for the newborn's increased susceptibility to infection.

Blood Bactericidal Activity↗