Gender differences in influence of prenatal photoperiods on postnatal pineal melatonin rhythms and serum prolactin and follicle-stimulating hormone in the Siberian hamster (Phodopus sungorus)

In Siberian hamsters, the rate of testicular maturation during juvenile life can be influenced by both the prenatal photoperiod and the day length experienced postnatally. In this report, potential postnatal photoperiodic mechanisms modified by prenatal photoperiod were investigated in this species. The study examined the effect of prenatal photoperiodic history on the postnatal pineal melatonin (MEL) rhythm and on postnatal secretion of FSH and PRL. In the first study, the pineal MEL content of hamsters, gestated in either 16 h of light and 8 h of darkness/day (16L) or 10L and raised postnatally in 14L, was monitored at various times of the day and night at 18 days of age. We found that prenatal photoperiod did influence the postnatal pineal MEL rhythm in 18-day-old males, but a similar effect was not evident in females. For males, the durations of the nocturnal elevation of pineal MEL were 8.5 and 7 h in 16L and 10L gestated hamsters, respectively. However, MEL rhythms were similar to each other in the corresponding groups of females (8.5- and 9-h durations of elevated pineal MEL in 16L and 10L prenatal photoperiod groups, respectively). In a subsequent study using the same photoperiod paradigm, FSH and PRL concentrations were examined in both genders at 3- to 10-day intervals between 18-62 days of age. The serum PRL (day 22) and FSH (days 18 and 22) concentrations in males were significantly affected by prenatal photoperiod. Specifically, circulating serum PRL (on day 22) and FSH (on days 18 and 22) concentrations were increased substantially in 10L gestated, compared to 16L gestated, males raised in 14L after birth. In contrast, serum FSH concentrations in female hamsters were not different between 16L and 10L gestated groups at these times. In another study using the same experimental design, the pattern of testicular development was explored in males. Hamsters that had experienced a 10L photoperiod prenatally and were raised in 14L exhibited rapid testicular growth from 27-52 days of age compared to hamsters that had experienced a 16L prenatal photoperiod and were reared in 14L. These results support the hypothesis that in juvenile male hamsters exposed to 14L postnatally, endogenous MEL production and serum FSH concentrations are influenced by photoperiodic information received during fetal life. In addition, these findings help to explain why males gestated in 10L and raised in 14L exhibit accelerated testicular development in the first 2 months of life compared to males gestated in 16L and transferred to 14L after birth.(ABSTRACT TRUNCATED AT 400 WORDS)

Influence of prenatal photoperiods on postnatal reproductive responses to daily infusions of melatonin in the Siberian hamster (Phodopus sungorus)

Prepubertal reproductive development in juvenile male Siberian hamsters can be strongly influenced by photoperiod information received during gestation. Information transmitted from the mother hamster to her fetuses appears to modify the photoperiodic mechanism of the developing hamsters so that they may respond differently to certain intermediate day lengths [i.e. 14 h of light and 10 h of darkness/day (14L)] experienced after birth depending on whether gestation occurred in longer or shorter day lengths. In adult and juvenile hamsters, the duration of the nocturnal elevation of pineal and serum melatonin (MEL) is an important component of the photoperiodic system coding for day length. In the present study, we investigated whether the photoperiod in effect during gestation could influence the responsiveness of developing male hamsters to daily MEL infusions of fixed durations administered after weaning. The results indicated that hamsters gestated under 16L or 10L did not differ from each other with respect to testicular growth in response to any of the fixed duration MEL infusions. Thus, target tissue responsiveness to fixed duration MEL infusions (over a range of 6-10 h) was the same regardless of the gestation photoperiod to which the animals had been exposed.

Elevated serum silicon levels in women with silicone gel breast implants

The metabolic fate of silicone gel leaked from an intact or ruptured prosthesis is unknown. In this study, serum was blindly assayed by inductively coupled plasma atomic emission spectroscopy (ICP-AES) for elemental silicon in 72 women with silicone gel breast implants and 55 control women (mean age 48 yr, both groups). Blood was drawn and processed using silicon-free materials. The mean silicon level in controls was 0.13 +/- 0.07 mg/L (range 0.06-0.35 mg/L), whereas in implant patients, the mean was significantly higher at 0.28 +/- 0.22 mg/L (range 0.06-0.87 mg/L) (P < 0.01, Student's t-test with correction for unequal variances). Using the mean of the control group + 2 SD as a cutoff for normal range (0.27 mg/L), 25/72 (34.7%) implant patients exceeded this value, compared with 2/55 (3.6%) controls. There was no significant correlation between past rupture of one or both implants, current rupture at the time of the blood draw, or the number of years with implants and silicon levels. The results suggest that serum silicon levels are elevated in many women with silicone gel breast implants. The chemical species involved and kinetics of this elevation remain to be determined.

Influence of prenatal and postnatal photoperiods on postnatal testis development in the Siberian hamster (Phodopus sungorus)

In Siberian hamsters, juvenile testicular development is regulated to a large extent by photoperiod. Mother hamsters are able to pass photoperiodic information to their male fetuses, and this information can influence their postnatal gonadal development. In this study, we investigated the effects of gestation in long (16L:8D) and short (10L:14D) day lengths on the rates of juvenile testicular growth in several different postnatal photoperiods. On the day of parturition, parents and young from each gestation photoperiod were raised in 14L:10D through Day 13 of life and then were exposed to one of six photoperiods--16L:8D, 15L:9D, 14L:10D, 13L:11D, 12L:12D, or 10L:14D--until Day 32 of age. The data indicated that 15L and 14L are the minimal day lengths required to prevent complete inhibition of testis growth in long (16L) and short day (10L)-gestated hamsters, respectively. These results support earlier findings suggesting that gestation photoperiod can influence the rate of reproductive development in a certain range of "intermediate" postnatal day lengths (14L to 15L), but that gestation photoperiod does not alter the pattern of testis development in hamsters exposed to other (i.e., longer or shorter) postnatal photoperiods. Thus, both the absolute length and the direction of change of photoperiods experienced in early life can influence prepubertal testis growth.

Gonadal growth and hormone concentrations in photoregressed Siberian hamsters: pinealectomy versus photostimulation

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.

Reproductive and nonreproductive responsiveness to photoperiod in laboratory rats

Laboratory rats (Rattus norvegicus) have been traditionally considered nonphotoperiodic because reproductive function is unaffected by day length. However, at least three experimental manipulations of rats--perinatal androgen injection, peripubertal androgen implants, and peripubertal olfactory bulbectomy--have been reported to unmask reproductive responsiveness to photoperiod. The physiological means by which early testosterone treatment or olfactory bulbectomy affect the expression of photoperiodism were hypothesized to operate through similar underlying mechanism(s) that involved gonadotropin and prolactin blood levels. Short day lengths reduce blood levels of gonadotropins in so-called photoperiodic rodent species. Reduced prolactin levels result in virtually all reproductively photoperiodic species housed in short day lengths. In Experiment 1, male weanling rats either were olfactory-bulbectomized or received a sham-procedure and housed for 10 weeks in long (LD 16:8) or short (LD 8:16) days. Short-day rats reduced body mass, testicular sperm counts, and the size of their reproductive systems; olfactory bulbectomy amplified this inhibitory effect for some parameters including testicular and epididymal sperm counts. However, neither short days nor olfactory bulbectomy affected blood titers of follicle stimulating hormone (FSH) or prolactin. Pelage density was also unaffected by photoperiod, but rats retained their juvenile fur color; i.e., short-day rats remained white, but long-day rats became yellowish. In Experiment 2, male rats were injected with testosterone at 3 days of age, then housed in long or short days until 10 weeks of age. Day length alone did not affect any experimental parameter measured in Experiment 2 except fur color; again, short-day rats retained their juvenile fur color.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolactin secretion in female Siberian hamsters following hypothalamic deafferentation: role of photoperiod and dopamine

The role of the hypothalamic paraventricular nucleus (PVN) region in the control of seasonal prolactin (PRL) responses was investigated in female Siberian hamsters via disruption of PVN afferent connections from the region of the suprachiasmatic nucleus (SCN). Adult female hamsters received sham surgery or horizontal knife cuts placed ventral to the PVN so as to sever dorsally projecting fibers from the SCN and were either immediately transferred to a short-day photoperiod [10 h light:14 h dark (10L:14D); experiment (exp.) 1A] or returned to the long-day photoperiod (16L:8D; exp. 1B and 2). Serial blood samples were analyzed for determination of circulating PRL and follicle-stimulating hormone (FSH; exp. 1A) levels at various time points after surgery. In exp. 1A, sham-operated animals showed a steady decline in circulating levels of both PRL and FSH during exposure to 10L. Animals with knife cuts that passed through the extent of the SCN were prevented from showing declines in PRL and FSH during exposure to 10L. Animals with knife cuts located ventral to or through the PVN but dorsal to the SCN maintained high FSH levels during short-day exposure but showed a decline in PRL. Similarly, animals with knife cuts in exp. 1B and 2 showed a decline in circulating PRL despite continued exposure to a stimulatory photoperiod. In exp. 2, the efficacy of a dopaminergic agonist (CB154) and an antagonist (pimozide) in altering circulating PRL under the 16L photoperiod was evaluated. CB154 induced declines in PRL in knife-cut but not sham-operated animals, whereas administration of pimozide elevated circulating PRL in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

The timed infusion paradigm for melatonin delivery: what has it taught us about the melatonin signal, its reception, and the photoperiodic control of seasonal responses?

This review summarizes the evidence showing that the duration of the nocturnal secretory profile of pineal melatonin (MEL) is critical for eliciting seasonally appropriate reproductive physiological and behavioral responses in mammals. We review experiments using the timed infusion paradigm (TIP) to deliver MEL either systemically or centrally to pinealectomized hamsters and sheep. In this paradigm, MEL is infused, usually once daily, for a specific number of hours and at a predetermined time of day. This experimental strategy tests most directly those features of the MEL signal that are necessary to trigger photoperiodic responses. The data suggest that the duration of the MEL stimulation is the critical feature of the MEL signal for both inhibitory and stimulatory effects of the hormone on the photoperiodic control of reproductive development in juvenile Siberian hamsters, and for the photoperiodic control of reproductive and metabolic responses in adult Siberian and Syrian hamsters and sheep. The use of the TIP reveals the importance of the frequency of the signal presentation of MEL and suggests the importance of a period of low-to-absent circulating concentrations of the hormone. The TIP also reveals that the characteristics of the MEL signal that regulate male sexual behavior are similar to those that are critical for reproductive and metabolic responses in Syrian hamsters. We summarize the locations of possible functional MEL target sites identified by combining the TIP with traditional brain lesion techniques. Evidence from such studies suggests that the integrity of the suprachiasmatic nucleus (SCN) region in Siberian hamsters and the anterior hypothalamus in Syrian hamsters is necessary for the response to short-day MEL signals. The TIP has been used to deliver MEL to putative target sites for the hormone in the brain of juvenile and adult Siberian hamsters. The results of these preliminary experiments suggest that the regions of specific MEL binding in this species, especially the SCN, are effective sites where MEL may stimulate short-day-type responses. In contrast, results from intracranial application of MEL in sheep suggest the medial basal hypothalamus as a critical site of action. Finally, we also discuss potential applications of the TIP for identification of brain MEL target sites, understanding of other photoperiodic phenomena and responses, and resolution of the cellular/molecular basis underlying the reception and interpretation of MEL signals.(ABSTRACT TRUNCATED AT 400 WORDS)

Serum soluble interleukin 2 receptor levels in erythrodermic cutaneous T-cell lymphoma correlate with response to photopheresis-based treatment

BACKGROUND

Cutaneous T-cell lymphoma (CTCL) comprises a spectrum of presentations, including erythroderma, pruritus, lymphadenopathy, and circulating atypical lymphocytes. Photopheresis is an extracorporeal treatment in which white blood cell concentrates are subjected to UV irradiation when the serum methoxypsoralen level is above 50 ng/mL. Of patients with CTCL, those with erythroderma have been most responsive to this therapy. In some conditions, including certain malignant hematologic neoplasms, serum soluble interleukin 2 receptor levels (SIL2R) correlate with disease activity. We sought to determine whether serum SIL2R levels correlated with disease activity in six erythrodermic patients with CTCL treated primarily with photopheresis. We measured SIL2R levels in five patients with stage III or greater erythrodermic CTCL and one with stage IIa CTCL. We compared SIL2R values with clinical course, skin scores, CD4/CD8 ratios, peripheral white blood cell counts, and Sézary cell counts, using Pearson correlation coefficients.

OBSERVATIONS

The SIL2R levels correlated with clinical course and skin scores, even when controlled for other factors noted above.

CONCLUSION

Data preliminarily suggest that serum SIL2R levels may be useful indicators of disease activity in erythrodermic CTCL patients treated with photopheresis.

Central sites mediating reproductive responses to melatonin in juvenile male Siberian hamsters

Juvenile male Siberian hamsters received infusions of varying doses of melatonin (MEL), or saline vehicle, via microdialysis probes implanted in brain regions which have previously been shown to contain MEL receptors. Daily infusions were 10 h in length and occurred during exposure to constant light on days 22-34 of age. All animals were sacrificed on day 35 and paired testis weights recorded prior to preparation of the brain tissue for histological evaluation of the infusion site. Some animals were also blood-sampled prior to sacrifice for determination of circulating levels of prolactin (PRL). Saline infusions did not have a significant effect upon gonadal maturation, regardless of the infusion site, when compared with unoperated control animals reared under similar photoperiod conditions. In contrast, animals which received infusions of 75 pg MEL into the suprachiasmatic nucleus (SCN), paraventricular nucleus of the thalamus, or nucleus reuniens regions, showed a marked inhibition of gonadal growth. Infusions of this dose of MEL into various other neural regions (e.g. lateral hypothalamus, ventromedial nucleus of the hypothalamus, paraventricular nucleus of the hypothalamus) did not result in decreased testis weights at the time of sacrifice. Daily administration of 20 pg MEL inhibited gonadal maturation and resulted in decreased circulating PRL levels only when infused into the SCN region. For animals receiving the 7.5 pg dose, infusions into the midline thalamic nuclei were not successful in inhibiting testis growth, and infusions in the SCN region had only a marginal effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Object play and exploration in children with and without disabilities: a longitudinal study

The development of object play was examined in 40 children (20 with and 20 without disabilities). The children with disabilities were assessed at ages 11, 15, 19, and 27 months; the children without disabilities, at 6, 11, 15, and 27 months. At each assessment, the children were videotaped during 20 minutes of play with their mothers in a controlled environment. Child's play level was positively related to developmental age for the disabled group at each assessment and for the nondisabled group at 6, 11, and 15 months of age. The types of object play observed in children with no disabilities were observed in the children with disabilities at comparable developmental ages. In a subsample matched for developmental age, the duration and frequency of active involvement with objects were greater for the children without disabilities than for the children with disabilities.

Seasonal regulation of neuroendocrine activity in male Turkish hamsters (Mesocricetus brandti): role of the hypothalamic paraventricular nucleus

Male Turkish hamsters received horizontal knife cuts within the hypothalamus to investigate the role of afferent and efferent projections of the paraventricular nucleus (PVN) in seasonal regulation of endocrine function. Following surgery, the animals were exposed to either a long (16 h light/8 h dark) or a short (8 h light/16 h dark) photoperiod. Similar to pinealectomy, knife cuts placed ventral to the PVN, so as to disrupt transfer of photic information to the pineal gland, resulted in a rapid decline in circulating prolactin (PRL) and follicle-stimulating hormone (FSH) levels, as well as a reduction in testicular size, under both long- and short-photoperiod conditions. In contrast, knife cuts placed just dorsal to the PVN, 50 as to leave connections to the pineal gland intact, did not prevent the effects of short-day exposure on PRL secretion; however, short-day induced declines in FSH levels and testicular size were largely prevented by these lesions. The present results are consistent with past findings that the integrity of the neural pathway to the pineal gland is necessary for the maintenance of appropriate reproductive responses to photoperiod in seasonal mammals. They further indicate a dissociation between the role of hypothalamic connections in the photoperiod-dependent secretion of two anterior pituitary hormones, i.e., PRL and FSH, and suggest that release of these hormones may depend upon different neural pathways for their expression.

Prolactin-dependent seasonal changes in pelage: role of the pineal gland and dopamine

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.

Cutaneous multilobated T-cell lymphoma with aggressive course

Cutaneous multilobated T-cell lymphoma is an uncommon variant of skin-based peripheral T-cell lymphoma typically characterized by cutaneous nodules in elderly patients and a chronic clinical course. We report a case of the disease that led to the patient's death within 2 years after onset. This disease may be associated with a more aggressive clinical course than generally recognized.

Parameters of the circadian rhythm of pineal melatonin secretion affecting reproductive responses in Siberian hamsters

The major function of the mammalian pineal gland appears to be its central role in photoperiodism. The pineal hormone, melatonin, is synthesized and secreted primarily at night, under the control of a circadian oscillator that is entrained to the light-dark cycle. Both the circadian phase and the duration of the nocturnal peak of melatonin secretion are established primarily by interactions between the endogenous circadian oscillator and the daily photic cycle. The duration of the melatonin peak varies inversely with day length, and this relationship between day length and the duration of each circadian melatonin peak appears to be an integral part of the photoperiodic mechanism. When pinealectomized animals are given daily melatonin infusions of long duration, they exhibit physiologic responses that normally are observed during exposure to short day photoperiods; when administered short-duration melatonin infusions, the animals display long photoperiod-type responses. In addition to the importance of the duration of each melatonin peak, certain other parameters appear to be significant. If a long-duration infusion of melatonin is interrupted by a period of 2 hours or more without melatonin (i.e., to produce two short duration infusions), the responses are those typical for long day-exposed animals. Thus, to elicit short day-type responses, each long-duration melatonin peak must be relatively continuous; responses are not determined simply by the total time of exposure to melatonin in each circadian cycle. Also, long-duration melatonin peaks may not be effective to elicit photoperiod-type responses unless they are present at frequencies of nearly once every 24 hours or more.

Making the transition to restraint-free care

When implementing a change to restraint-free care, education and communication at all levels of the organization are powerful strategies to overcome resistance. Within each facility, there are at least six identifiable groups, with attitudes based on their educational background, life experiences and perceptions that are targets for change. An anonymous attitudinal survey and sensitivity session serve as effective "unfreezing" tools for all levels of staff to express concerns regarding physical restraints and to recognize the need for change. Change requires a slow, methodical system where specific alternatives are gradually introduced. Success with the easier cases encourages staff to continue efforts with more challenging cases.

Suprachiasmatic and paraventricular control of photoperiodism in Siberian hamsters

The effects of lesions of the suprachiasmatic (SCN) and paraventricular nuclei (PVN) of the hypothalamus on photoperiodic responses were examined in adult Siberian hamsters. SCN lesions reduced nocturnal water intake in long days, whereas PVN lesions increased body weight and food intake in both short and long days. SCN or PVN lesions blocked short-day-induced decreases in body, fat pad, and testes weights and in food intake. Serum prolactin (PRL), but not follicle-stimulating hormone, levels were increased. The distribution of immunostained neurons and fibers for gonadotropin-releasing hormone (GnRH), beta-endorphin, arginine vasopressin (AVP), and vasoactive intestinal polypeptide (VIP) resembled that of other rodent species. Short-day exposure reduced AVP staining in lateral septum, medial amygdala, and bed nucleus of the stria terminalis but not in the PVN of the thalamus or the SCN. Short-day-exposed hamsters had fewer beta-endorphin-positive arcuate nucleus cells and tended to have fewer GnRH-positive preoptic cells than long-day controls. VIP staining was unaffected by photoperiod. Most day length effects on immunostaining were eliminated by either lesion. These results establish the importance of the SCN and PVN in the photoperiodic control of several seasonal responses in Siberian hamsters.

SCN lesions block responses to systemic melatonin infusions in Siberian hamsters

The role of the suprachiasmatic nuclei (SCN) in the response to short-day melatonin (MEL) signals was examined in long-day-housed pinealectomized (PINX) Siberian hamsters. Five- or ten-hour MEL infusions that mimicked the peak nocturnal durations of serum MEL levels in long or short days, respectively, or control saline infusions were given for 5 wk. Half the hamsters in each infusion group also received bilateral electrolytic SCN lesions. The 10-h MEL infusions reduced testes weight, body and fat pad weights, and serum prolactin (PRL) and follicle-stimulating hormone (FSH) concentrations in unoperated controls. These short-day-type effects were blocked by SCN lesions, which often produced hyperprolactinemia. Circadian rhythms of locomotor activity were disrupted or sparse in hamsters with lesions in or near the SCN. In a second experiment, 5 wk of long-day-like, short-duration (5-h) MEL infusions were administered to hamsters that had been PINX after 8 wk of short-day exposure. Control hamsters given 5-h MEL infusions, but not 10-h MEL or saline infusions, exhibited testicular growth and increased serum PRL levels. Hamsters with SCN lesions showed similar responses, regardless of the duration or type of infusion. Although the blockade of 10-h MEL infusion-induced testicular regression by SCN lesions in experiment 1 may have been due to stimulation of the testes by PRL, it is unlikely that the hyperprolactinemia accounted for the ability of SCN lesions to block effects of 10-h MEL infusions on fat pad and body weights. Therefore, the SCN and/or neighboring structures may participate in the response to short-day MEL signals in Siberian hamsters.

Regional differences in fat pad responses to short days in Siberian hamsters

Siberian hamsters exhibit decreased body weight and fat after initial exposure to short photoperiods and increased body weight and fat after extended short photoperiod exposure. The purpose of the present experiments was to determine if uniform changes in white adipose tissue (WAT) pad weights and lipid metabolism correspond to these short photoperiod-induced changes in body fat. Carcass lipid content and testes and fat pad weights [retroperitoneal WAT (RWAT), epididymal WAT (EWAT), and inguinal and dorsal subcutaneous WAT, respectively] were decreased in male hamsters relative to their long day counterparts after 6 and 12 wk of short-day exposure. Moreover, EWAT and RWAT weight, EWAT specific lipoprotein lipase activity, and specific and total lipogenesis were disproportionately decreased relative to the subcutaneous fat pads. The changes in fat pad weight and metabolism were generally reversed coincident with the return to a long-day-like reproductive status after prolonged short-day exposure (24 and 30 wk). In a less detailed experiment, female Siberian hamsters had decreased body, fat pad, and uterine weights after 6 wk of short-day exposure; however, no fat pad-specific changes in weight were observed. The results of these experiments demonstrate that short-day-exposed male Siberian hamsters may be a useful model for examining mechanisms underlying fat pad-specific responses. In addition, gender appears to influence the pattern of short-day-induced lipid depletion in this species.

Reception of photoperiodic information by fetal Siberian hamsters: role of the mother's pineal gland

The rate of reproductive development in juvenile male Siberian hamsters is strongly influenced by daylength (photoperiod). Recent studies indicate that reception of photoperiodic cues begins during fetal life. The present experiments yielded a further demonstration that developing male Siberian hamsters receive information about the photoperiod to which their mother is exposed during pregnancy. The possibility that photoperiodic information is transmitted from mother to young after birth was investigated by cross-fostering young gestated on 12L and 16L to mothers from the other photoperiod. Litters were cross-fostered on the day of birth and then were transferred, along with their foster mothers, to 14L. We found no influence of the mother after birth, indicating that transmission of photoperiodic information from mother to young must occur during gestation. To determine if the pineal gland of the mother is required for this response, adult females were pinealectomized or sham-operated and paired with intact males in 12L, 14L, or 16L. After parturition parents and offspring were exposed to 14L. The influence of prenatal photoperiod on postnatal testicular development in 14L was blocked by pinealectomy of the mother. Postnatal testicular development was retarded in offspring that experienced a photoperiod transfer from either 15L to 14L or 8L to 12L at birth. In contrast, the inhibitory effect of a transfer from 16L to 14L at birth was abolished when juvenile males were exposed to a single long photoperiod (16.3 h light) at age 17-21 days and then were returned to 14L.

Effect of melatonin infusion duration and frequency on gonad, lipid, and body mass in pinealectomized male Siberian hamsters

The goal of this study was to discriminate between two hypotheses regarding how the circadian rhythm of pineal melatonin (MEL) production transmits photoperiodic information: (1) A circadian rhythm of sensitivity to MEL regulates the hormone's effect; (2) the duration of the MEL signal, rather than its circadian timing, is the critical parameter of the MEL rhythm. The experiment examined the response of pinealectomized (PINX) male Siberian hamsters to 10-hr (short-day-type) versus 6-hr (long-day-type) duration MEL infusions (10 ng/infusion) in cycles with period lengths (T) of 18, 24, 36, and 48 hr. After cannula implantation, animals were moved from LD 16:8 to LD 10:14 (lights-on from 0500 to 1500 hr, EST), where the timed infusions began. Additional T 24 cycles included as controls employed 18-hr MEL, 18-hr saline (SAL), and 10-hr SAL infusions: Body weight and food intake were measured weekly. After 6 weeks, animals were killed; blood samples were taken for radioimmunoassay (RIA) of serum follicle-stimulating hormone (FSH) and prolactin (PRL); and terminal body, epididymal white adipose tissue (EPIWAT), and paired testis weights were recorded. Six-hour MEL infusions failed to induce short-day-type effects, regardless of the period (T) of the infusion cycle. In contrast, compared to SAL and 6-hr MEL infusions, 10-hr MEL resulted in decreases in body, EPIWAT, and testis weights in T 24, but not in T 36 or T 48. In T 18, testis, body, and EPIWAT mass were decreased, but not to the same extent as in T 24. Similarly, daily 18-hr MEL infusions (T24) were less effective as a short-day stimulus than were 10-hr MEL infusions. The effectiveness of 10-hr, but not 6-hr, MEL infusions in T 18 and T 24 is consistent with the duration hypothesis and argues against the circadian hypothesis. Neither hypothesis could have predicted that all infusion cycles of T greater than or equal to 36 hr, regardless of the infusion durations, would fail to elicit short-day-type responses. This outcome suggests a need for relatively frequent (T less than 36 hr) MEL stimulation in addition to the requirement for adequate duration of each MEL infusion.

Feelings of depression and parenting competence of mothers of handicapped and nonhandicapped infants: a longitudinal study

Relations of maternal depression and feelings of parenting competence with measures of child characteristics and mother's social support system were examined across time. Full assessments were made of mothers of handicapped infants at infant ages 11, 15, 19, and 27 months and mothers of nonhandicapped infants at infant ages 6, 11, 15, 19, and 27 months. Although the two groups of infants differed significantly in level of functioning and difficulty of caregiving, the two groups of mothers did not differ on the measures of maternal depression and feelings of parenting competence. In the handicapped group, caregiving difficulty predicted maternal depression, and the quality of family relations predicted the mothers' feelings of parenting competence. In the nonhandicapped group, both feelings of depression and of parenting competence were predicted by child irritability and the quality of family relations.