Bruce Goldman - Academia.edu (original) (raw)

Papers by Bruce Goldman

Melatonin, 2020

Page 237. Chapter 9 MELATONIN AND SEASONALITY IN MAMMALS Bruce D. Goldman and Randy J. Nelson TAB... more Page 237. Chapter 9 MELATONIN AND SEASONALITY IN MAMMALS Bruce D. Goldman and Randy J. Nelson TABLE OF CONTENTS I. Introduction 226 A. Circannual Rhythms 226 B. Environmental Zeitgebers 227 II. Physiology ...

Advances in Experimental Medicine and Biology, 2021

Naked mole-rats (Heterocephalus glaber) are small rodents native to east Africa, living in subter... more Naked mole-rats (Heterocephalus glaber) are small rodents native to east Africa, living in subterranean colonies of up to 300 individuals. Within each colony, reproduction is restricted to a single breeding female and 1-3 breeding males; all other colony members are reproductively suppressed and socially subordinate unless removed from the suppressive cues of the colony. Due to their striking reproductive skew, naked mole-rats are often considered eusocial mammals. Consistent with this idea, there are behavioral specializations and at least some evidence for morphological distinctions within and between the breeding and non-breeding members of the colony. Importantly, naked mole-rats show plasticity in their behavioral phenotype whereby changes in the social environment influence expression of both type and amount of social behavior. Thus, naked mole-rats provide the opportunity to examine the proximate mechanisms controlling individual differences in social behavior, shedding light on how mammals live in complex social groups.

Biology of Reproduction, 1994

In Siberian hamsters, long and short durations of nightly melatonin secretion are associated with... more In Siberian hamsters, long and short durations of nightly melatonin secretion are associated with testicular regression and development, respectively; surprisingly, the absence of a nightly melatonin signal induced by pinealectomy is less effective than a short (4-6 h) melatonin duration for promoting gonadal development. We compared the patterns of serum FSH and prolactin concentrations underlying pinealectomy-induced and photostimulated testicular growth in juvenile hamsters. Pinealectomy in photoinhibited hamsters on Day 18 produced significant gonadal development compared to that in short-day controls by Day 23. By Day 28, however, testes weights of pinealectomized hamsters were significantly lower than those of intact hamsters transferred to a long photoperiod. Pinealectomy was associated with significant elevations in serum FSH and prolactin concentrations over baseline by Day 21, but peak values were attenuated compared with those induced by exposure to long days. FSH titers of pinealectomized animals were significantly lower than those of photostimulated animals between Days 21 and 30 but were significantly greater on Days 35 and 40; prolactin values were comparable in pinealectomized and photostimulated hamsters between Days 21 and 25 but were significantly lower in the former group thereafter. Blunted elevation of FSH and prolactin secretion may underlie the slower rates of gonadal maturation observed in pinealectomized, juvenile hamsters. The neuroendocrine systems of pinealectomized hamsters appear to be in a state intermediate between those characteristic of hamsters kept in long and in short day lengths.

Animal Behaviour, 2019

Eusociality is exhibited by colonial-living organisms where only a few individuals within a colon... more Eusociality is exhibited by colonial-living organisms where only a few individuals within a colony reproduce; the remaining members are nonbreeders and support reproduction of the breeders. Damaraland mole-rats, Fukomys damarensis, are one of two mammal species considered eusocial. Colonies include a breeding pair and their offspring. Unusual aspects of reproductive behaviour include the observation that both sexes display all components of mating even after long-term absence of gonadal hormones. Mating does not occur between siblings or offspring and parents, but nonbreeders from one colony will mate with individuals from other colonies. However, following 5 weeks of separation from each other, siblings will exhibit mutual sexual behaviour. Thus, familiarity through frequent proximity, rather than genetic identity, mediates inbreeding avoidance. One caveat is that breeding pairs maintain a mating relationship for years, although they obviously become familiar with each other. Among Damaraland mole-rats that are familiar with each other, two types of relationships can form, a mating relationship or a ‘sibling-like’ relationship marked by inbreeding avoidance. The factors determining the relationship between pairs of Damaraland mole-rats remain undefined. This experiment tested the hypothesis that the behaviour during the initial meeting of a pair of Damaraland mole-rats determines which relationship forms, i.e. mating versus ‘sibling-like’. The initial pairing occurred either with unrestrained physical contact (allowing for mating behaviours) or with the two animals separated from each other by a mesh barrier (no mating could occur). This initial pairing was followed by daily 20 min pairings with the barrier in place for 2 weeks and then a final pairing without any restraint. Results indicate that the nature of the interaction within the first 20 min of meeting determines the long-term sexual relationship between pairs of Damaraland mole-rats. The results suggest a mechanistic basis for establishment and maintenance of the reproductive hierarchy in this eusocial species.

Siberian hamsters are seasonal breeders that use changes in day length to synchronize their repro... more Siberian hamsters are seasonal breeders that use changes in day length to synchronize their reproductive effort with those times of the year most favorable for successful reproduction. The ability of Siberian hamsters to measure and respond to changes in day length depends upon accurate photoentrainment of the circadian clock in the suprachiasmatic nucleus (SCN) of the hypothalamus. Two pathways have been characterized through which entraining stimuli reach the SCN: the retinohypothalamic tract (RHT), which transmits light information from the retinae, and the geniculohypothalamic tract (GHT) from the intergeniculate leaflet of the thalamus (IGL), which is involved in transmitting both photic and nonphotic cues. Ablating the IGL/GHT results in only modest alterations in entrainment to static day lengths and fails to interfere with seasonal responses induced by transfer from static long day to static short day lengths. Because several studies suggest that the IGL may be involved in t...

Journal of Biological Rhythms, 2001

Photoperiodism is a process whereby organisms are able to use both absolute measures of day lengt... more Photoperiodism is a process whereby organisms are able to use both absolute measures of day length and the direction of day length change as a basis for regulating seasonal changes in physiology and behavior. The use of day length cues allows organisms to essentially track time-of-year and to “anticipate” relatively predictable annual variations in important environmental parameters. Thus, adaptive types of seasonal biological changes can be molded through evolution to fit annual environmental cycles. Studies of the formal properties of photoperiodic mechanisms have revealed that most organisms use circadian oscillators to measure day length. Two types of paradigms, designated as the external and internal coincidence models, have been proposed to account for photoperiodic time measurement by a circadian mechanism. Both models postulate that the timing of light exposure, rather than the total amount of light, is critical to the organism’s perception of day length. In mammals, a circa...

Journal of Comparative and Physiological Psychology, 1980

Two experiments were carried out to explore the relation between postpartum aggressive behavior i... more Two experiments were carried out to explore the relation between postpartum aggressive behavior in rats and other aspects of maternal behavior. In Experiment 1, nulliparous females experimentally induced to behave maternally; i.e., sensitized, failed to show elevations in aggressive responding above levels seen in untreated nulliparous controls; lactating females displayed characteristically high levels of aggression. In Experiment 2, animals in these groups were tested, along with parturient females allowed varying amounts (0 hr, 2 days, or 9 days) of postpartum exposure to young, spanning a period that is sensitive for the induction of maternal behavior. The three parturient groups responded with levels of aggression that were similar to one another and significantly higher than those seen in controls. Sensitized animals in Experiment 2 exhibited high levels of fighting; differences between these animals and those in Experiment 1 may be due to differences in both length of sensitization and ovarian cyclicity. These data indicate that the experiences of pregnancy and/or parturition prime the postparturient female to respond aggressively to an intruder later in lactation and that, unlike the initiation of pup-oriented maternal behaviors, establishment of postpartum aggression is not dependent upon pup exposure during the immediate postpartum period.

Hormones and Behavior, Jun 30, 2006

Naked mole-rats (Heterocephalus glaber) are fossorial, eusocial rodents that live in colonies whi... more Naked mole-rats (Heterocephalus glaber) are fossorial, eusocial rodents that live in colonies which typically include 60-80 individuals. Generally, only one of the females and 1-3 of the males in a colony are reproductives. The reproductives engage in mutual genital nuzzling behavior that is rarely exhibited by subordinates (non-reproductives). Thus, genital nuzzling may represent a mechanism of bonding and/or specific recognition between reproductive individuals. We investigated whether gonadal hormones are involved in the maintenance of genital nuzzling behavior and mating behaviors in isolated pairs of mole-rats and also in established breeding pairs of mole-rats within colonies. We also explored whether sex hormone deprivation would alter the strict partner preference for performance of nuzzling within colonies. Our results indicate (a) considerable variation between pairs in the frequency of nuzzling, (b) a reduction in the frequency of nuzzling following castration of the male and restoration of the 'baseline' frequency after replacement of testosterone in castrated males, (c) the failure of either castration or combined castration and ovariectomy to eliminate genital nuzzling in established pairs, and (d) the exhibition of nuzzling behavior by some of the subordinates in all three experimental colonies beginning several weeks after gonadectomy of both of the reproductives. No cases of lordosis behavior were seen during the approximately 109 h of behavioral observations. This is not surprising, since female mole-rats have an approximately 30-day ovulatory cycle, and lordosis only occurs during a peri-ovulatory period of a few hours. A total of 44 cases of mounting behavior were recorded; all these involved breeding males in colonies or males from isolated pairs, and all occurred when males were either gonad-intact or castrated with testosterone replacement. Thus, in contrast to nuzzling behavior, male sex behavior appeared to be eliminated during androgen deprivation.

J Biol Rhythm, 1986

Gonadal state, pineal melatonin rhythms, and locomotor activity rhythms were examined in juvenile... more Gonadal state, pineal melatonin rhythms, and locomotor activity rhythms were examined in juvenile male Djungarian hamsters exposed to non-24-hr light cycles ("T-cycles") or to full photoperiods. At the end of 1 month, hamsters exposed to a 1-hr pulse of light every 24.33 hr (T 24.33) exhibited small testes, whereas those receiving the same amount of light every 24.78 hr (T 24.78) displayed stimulated gonads, ten-fold larger in size. Accompanying the nonstimulatory effect of the T 24.33 cycle were nocturnal peaks in both pineal melatonin content and serum melatonin concentration which were longer by approximately 4 hr than those observed on the photostimulatory T 24.78 cycle. Exposure to an intermediate-length T-cycle (T 24.53) resulted in a mixed gonadal response and in pineal and serum melatonin peaks of intermediate duration. Wheel-running activity was entrained to the T-cycles such that light was present only near the beginning of the subjective night, its phase (relative to activity onset) differing only slightly among T-cycle groups. Hence the durational differences observed in the melatonin peaks were apparently not due to the acute suppressive or phase-advancing effects of morning light on melatonin biosynthesis, but were rather the result of differences in the endogenous control of pineal activity by the circadian pacemaker system. While no strong correlation was detected between gonadal state and the phase of locomotor activity onset relative to the light pulse, a significant correlation was observed between gonadal state and the duration of daily locomotor activity (alpha). These data were compared to similar measures obtained from hamsters exposed to long-versus short-day full photoperiods (LD 16:8 vs. LD 10:14). In summary, the results of this study indicate involvement of the circadian pacemaker system of Djungarian hamsters in the control of pineal melatonin synthesis and secretion, and in photoperiodic time measurement. Furthermore, these data strengthen the hypothesis that it is the duration of nocturnal pineal melatonin secretion that is the critical feature of this neuroendocrine gland's photoperiodic signal.

Proceedings in Life Sciences, 1988

Journal of biological rhythms, 2016

Journal of Andrology, 1982

Ciba Foundation symposium, 1985

In adult mammals, the daily light-dark cycle acts via the retinohypothalamic pathway to entrain t... more In adult mammals, the daily light-dark cycle acts via the retinohypothalamic pathway to entrain the circadian clock in the suprachiasmatic nuclei (SCN) and to communicate information about daylength to photoperiodic species. Studies in rats show that during late fetal and early neonatal life, before the retinohypothalamic pathway has innervated the SCN, the maternal circadian system entrains the timing of the developing clock to prevailing lighting conditions. Although the nature of the maternal output signal(s) used to entrain the developing clock has not been elucidated, the maternal SCN are a necessary component of maternal entrainment during both prenatal and postnatal life. Maternal entrainment of the fetal and neonatal clock thus ensures that the developing circadian system is synchronized to the outside world until maturation of the retinohypothalamic pathway permits direct photic entrainment. The maternal circadian system is not only necessary for entrainment of the developi...

Annales de Biologie Animale Biochimie Biophysique, 1976

The Syrian hamster is a spontaneous ovulator and, in the wild, a seasonal breeder. Daylength (i.e... more The Syrian hamster is a spontaneous ovulator and, in the wild, a seasonal breeder. Daylength (i.e. photoperiod) appears to be an important factor in the regulation of seasonal periodicity in this species. Female hamsters became acyclic after 6-8 weeks exposure to a short days &dquo; (t'.e. a io-hour photoperiod). During the period of acyclicity these animals displayed a pronounced diurnal rhythmicity in LH secretion with peak serum LH concentrations during the mid-afternoon. Serum FSH and progesterone concentrations, showed a similar rhythmicity to that observed for LH, but the fluctuations were of lesser magnitude. Ovariectomy reduced serum progesterone levels and abolished the afternoon rise in serum progesterone. Serum LH was unaffected by ovariectomy while serum FSH levels were somewhat increased. Following removal of the ovaries, both gonadotropins continued to display peak concentrations in the serum during the afternoon. Daily injections of melatonin, a pineal product, inhibited ovulatory cyclicity in hamsters maintained on « long days » (i.e. a y-hour photop 3 riod) when the compound was administered q hours prior to lights off (r 5 .oo h). This effect was not present when the melatonin was given at 0 8. 00 h nor was it present in pinealectomized hamsters. Similar inhibitory effects of melatonin on the male hamster reproductive system have been observed, and these effects are also dependent upon the time of day at which the compound is administered.

The American journal of physiology, 1985

The Djungarian hamster exhibits a dark agouti pelage during the summer. Under the influence of de... more The Djungarian hamster exhibits a dark agouti pelage during the summer. Under the influence of decreased daylength, this species molts and develops a predominantly white winter coat. After a patch of white fur was plucked from hamsters housed in short photoperiod, chronic infusion of 10 or 20 micrograms ovine prolactin (o-PRL)/day led to the growth of a patch of pigmented fur, thus reversing the effect of the decreased daylength. Circulating o-PRL levels produced by the 10-micrograms/day infusions ranged from 17.9 +/- 4.0 to 35.1 +/- 13.8 (SE) ng/ml and thus approximated the endogenous circulating prolactin levels found in hamsters with the dark summer pelage (6, 9). Infusion of o-PRL stimulated pigmentation of the pelage of castrated as well as intact hamsters, suggesting that the testes do not mediate this effect. Infusion of ovine growth hormone (20 micrograms/day) did not stimulate pigmentation, and infusion of alpha-melanocyte-stimulating hormone (10 micrograms/day) gave inconc...

The American journal of physiology, 1989

Two experiments were designed to assess whether the short-day-induced patterns of shallow daily t... more Two experiments were designed to assess whether the short-day-induced patterns of shallow daily torpor, body weight, and other seasonal responses (food intake and pelage pigmentation) exhibited by Siberian hamsters (Phodopus sungorus sungorus) are under the control of a "seasonal timekeeping mechanism" that is independent of reproductive status [testosterone, (T)]. We examined whether the patterning and expression of these seasonal responses were altered by decreases in serum T that accompany gonadal regression during the first 8 wk of short-day exposure (i.e., the "preparatory phase" of the torpor season) or by experimental increases in serum T after this phase. Short-day-housed, castrated hamsters bearing T implants had long-day levels of the hormone and did not exhibit torpor. Appropriate seasonal patterns and levels of torpor, body weight, pelage color stage, and food intake were exhibited after T implant removal although serum T was clamped to long-day level...

The Journal of experimental zoology, 1992

The Siberian hamster displays seasonal changes in pelage that are dependent upon fluctuations in ... more The Siberian hamster displays seasonal changes in pelage that are dependent upon fluctuations in circulating prolactin levels. Pinealectomy prevented the decrease in serum prolactin and molt to the winter pelage displayed by castrated males housed under a short-day photoperiod. A dopaminergic antagonist, pimozide, enhanced prolactin levels in both pinealectomized and sham-operated animals under both long and short photoperiods. In the short-day animals, this effect of pimozide was associated with a prevention of the development of winter pelage. These results indicate that seasonal prolactin levels and related pelage changes are dependent upon the integrity of the pineal gland. However, basal prolactin levels under different photoperiod conditions appear to be only partly regulated by the actions of the dopaminergic system.

Fertility and sterility, 1975

Male mice were castrated on the day of birth or were treated with anti-gonadotropin serum (AGS) s... more Male mice were castrated on the day of birth or were treated with anti-gonadotropin serum (AGS) successively on days 1, 3, and 5 of age. When the adult AGS-treated males were compared with normal rabbit serum (NRS)-treated males with respect to fertility, male sexual behavior, gonadotropin release, body size, and penis size it was found that: (1) fertility of AGS-treated males did not differ from that of NRS-treated males; (2) AGS-treated males showed a significant reduction in penis size, compared with NRS-treated males; (3) both groups showed high levels of male sexual behavior; (4) neither group showed the capacity to support ovulation in ovarian grafts from immature mice. It was also observed that the fertility of female mice treated with AGS on days 1, 3, and 5 of age did not differ from that of control females treated with comparable doses of NRS. Male mice castrated at birth showed a significant reduction in male sexual behavior and penis size compared with males first sham-o...

Journal of steroid biochemistry, 1979

ABSTRACT When hamsters are exposed to a short photoperiod (10L:14D) suppression of gonadal functi... more ABSTRACT When hamsters are exposed to a short photoperiod (10L:14D) suppression of gonadal function is observed in both sexes, and this is accompanied by alterations in the pattern of pituitary gonadotropin (GTH) secretion. Short photoperiod exposure leads to decreased serum concentrations of both LH and FSH in males. In females daily surges of LH and FSH were observed during the midafternoon in short photoperiod. The daily cycle in GTH release continued after ovariectomy in short photoperiod females. Daily surges of GTH were not observed in short photoperiod males. Females treated with androgen shortly after birth failed to show estrous cyclicity in adulthood and also failed to display daily GTH surges when exposed to short photoperiod. These data suggest (1) that the capacity to release GTH cyclically in both long and short photoperiods is a sexually differentiated trait in the hamster, (2) that the development of this trait depends on the presence or absence of sex steroids during perinatal life, and (3) that the daily surges of GTH in short photoperiod females are probably regulated by the same neural mechanism which is responsible for triggering the preovulatory surge of GTH in the ovulating female.

Advances in experimental medicine and biology, 1999

The Siberian hamster has been a useful model for studies of mammalian photoperiodism for a number... more The Siberian hamster has been a useful model for studies of mammalian photoperiodism for a number of reasons: 1) Siberian hamsters are hardy animals that are easily maintained and bred in the laboratory. 2) The species exhibits a large number of seasonal, photoperiod-driven, pineal-dependent responses. Thus, the Siberian hamster is an excellent species in which to examine whether several different types of photoperiod responses share similar mechanistic features with respect to their control by MEL. Are all the responses cued to the duration of the nocturnal MEL peak? Does MEL act at a single site to influence all the types of responses, or are there separate MEL target sites for different responses? 3) Juvenile Siberian hamsters exhibit an unusually rapid (for mammals) response to photoperiod change or to MEL treatments, making them ideal subjects for certain types of photoperiod-related studies. 4) Populations of Siberian hamsters show individual variations in photoperiod responsi...