Testosterone and estrogen act via different pathways to inhibit puberty in the male Siberian hamster (Phodopus sungorus).

The peripubertal transition in male mammals is accompanied by a gradual decrease in sensitivity to the inhibitory effects exerted by gonadal hormones, such as T and E2. Here, we investigated the effects of chronic T and its metabolites, 5alpha-dihydrotestosterone and E2 on the hypothalamo-pituitary-gonadal axis at puberty. We also examined if T effects are distinct or mediated through its conversion to 5alpha-dihydrotestosterone or E2. Twenty-day-old male Siberian hamsters were sc implanted with a SILASTIC brand capsule containing varying doses of T, 5alpha-dihydrotestosterone, or E2. Several functional parameters of the hypothalamo-pituitary-gonadal axis were evaluated including hypothalamic GnRH concentration, pituitary and plasma FSH levels, pituitary FSH and LH mRNA, and testicular status. Our results showed that gonadal steroids inhibited puberty in a dose-dependent manner as evaluated by testes mass (undiluted steroid: T, 27 +/- 3 mg; 5alpha-dihydrotestosterone, 18 +/- 1 mg; and E2, 62 +/- 4 mg relative to cholesterol-implanted controls, 510 +/- 42 mg). Also, T decreased plasma FSH below detectable levels, but pituitary FSH concentration was unaffected (1.37 +/- 0.16 ng/microg protein) while E2-treated hamsters had normal plasma FSH levels (3.5 +/- 0.98 ng/ml) yet significantly lower pituitary FSH concentration (0.09 +/- 0.04 ng/microg protein). These results showed that the pathways of T and E2 action on the hypothalamo-pituitary-gonadal axis are distinct.

Timing of testicular recrudescence in siberian hamsters is unaffected by pinealectomy or long-day photoperiod after 9 weeks in short days.

In this study, the authors asked whether pinealectomy or temporary exposure to a stimulatory photoperiod affects the timing of spontaneous testicular recrudescence in adult Siberian hamsters chronically exposed to short days (9:15 light:dark). In Experiment 1, hamsters were pinealectomized after 6, 9, or 12 weeks in short days. Pinealectomy after 9 or 12 weeks did not affect the timing of spontaneous gonadal growth (27.7 +/- 1.9 and 25.4 +/- 1.3 weeks, respectively) compared to sham-operated controls (28.6 +/- 0.9 weeks). Enlarged testes occurred earlier in animals that were pinealectomized after 6 weeks in short days (21.8 +/- 2.1 weeks). In Experiment 2, adult hamsters were exposed to short days for 9 weeks, transferred to long days (16:8 light:dark) for 4 weeks, and then returned to short days for 23 additional weeks. Although long-day interruption caused gonadal growth in 15 out of 19 hamsters, the temporary long-day exposure did not affect the timing of spontaneous gonadal growth following return to short days (28.2 +/- 0.9 weeks) in 10 of the 15, relative to the timing observed in control hamsters continuously maintained in short days (28.2 +/- 1.1 weeks). Four out of 19 hamsters did not show gonadal growth following long-day exposure. Spontaneous gonadal growth in these hamsters (28.0 +/- 1.4 weeks) also occurred at the same time as controls. The remaining 5 hamsters exhibited enlarged testes following long-day exposure (12.0 +/- 0.0 weeks) but were refractory to the second short-day exposure. All hamsters exhibited entrainment of wheel-running activity following the change in photoperiod. A final group of 13 animals were pinealectomized before long-day transfer. They exhibited gonadal growth (at 17.2 +/- 0.8 weeks) but failed to regress a second time when returned to short days. The timing of gonadal growth in these animals was delayed relative to the sham-operated hamsters temporarily transferred to long days (Experiment 2) but accelerated relative to the hamsters pinealectomized at 9 weeks, which remained continuously in short days (Experiment 1). The results of both experiments suggest that a pineal-independent process mediates the timing of spontaneous gonadal growth in Siberian hamsters chronically exposed to a short-day photoperiod.

Postradiation squamous cell cancer of the breast.

Primary squamous cell carcinoma of the breast is a rare clinical entity. We diagnosed a patient who presented with a pure squamous cell cancer of the breast 12 years after local radiation for a primary adenocarcinoma of breast. Previously reported cancers related to radiation of the breast have been squamous cell of skin and esophagus and sarcomas, especially angiosarcomas, and on literature review this is the first reported case of primary squamous carcinoma of the breast related to previous radiation. Although our observation suggests a possible link, no established cause and effect relationship is known at this point.

Evidence of an annual rhythm in a small proportion of Siberian hamsters exposed to chronic short days.

Siberian hamsters are photoperiodic seasonally breeding rodents. To date, there has been no evidence that Siberian hamsters exhibit an annual rhythm in reproductive, thermoregulatory, molt, or body mass changes. However, given that the termination of their winter cycle is under endogenous control, the authors thought it possible that under particular conditions, other aspects of their seasonal cycle may be endogenously mediated. Consequently, the authors monitored the reproductive condition, body mass, and molt of hamsters chronically exposed to short days (LD 9:15) for up to 2 years. All animals were taken from previous experiments and had exhibited gonadal regression, followed by refractoriness to shorts days and spontaneous gonadal growth, as well as a complete cycle of body mass and molt changes. Although some hamsters died during the study, the authors continued to monitor some animals for up to 106 weeks of short-day exposure. Of the 57 animals monitored, 4 (7.02%) exhibited a second cycle of reproductive regression and recrudescence. Furthermore, the timing of the second regression was similar in the 4 animals, occurring about 1 year after the initial short-day exposure (50.5 +/- 1.71 weeks). However, the timing of the second bout of recrudescence was more variable, occurring at about week 80 (79.5 +/- 8.01 weeks). Hamsters exhibited regressed gonads for about 7 months (29.0 +/- 8.02 weeks). Although the body mass of the 4 hamsters declined at the time of the second cycle of gonadal regression, it never recovered. No hamster exhibited a second molt cycle. These observations indicate that a small percentage of Siberian hamsters chronically exposed to short days can exhibit an annual cycle of reproduction.

Pancreatic head mass from metastatic meningeal hemangiopericytoma.

Purpose. To illustrate the propensity of meningeal hemangiopericytoma to spread extraneurally, as a distinction to the ordinary meningioma.Patients or subjects. A patient with long history of meningeal hemangiopericytoma was reported.Methods. A case report on meningeal hemangiopericytoma with a literature review was presented.Results. The patient has multiple local recurrence as well as distant metastases.This is the first case report of metastatic meningeal hemangiopericytoma causing compression of the pancreatic head.The patient also has biopsy-proven pulmonary metastases.The patient received both local and systemic therapy.Discussion. It is important to recognize the distinctive features differentiating meningeal hemangiopericytoma from meningioma. The positive impact of clinico-pathological correlation on patient management is emphasized.

AIDS-related Kaposi's sarcoma involving bone and bone marrow.

AIDS-related Kaposi's sarcoma rarely involves bone or bone marrow. Computed tomography of the abdomen and pelvis of an AIDS patient with lower back pain and bilateral limb edema revealed multiple lesions involving liver, spleen, and axial skeleton. Bone marrow examination of the involved iliac crest revealed Kaposi's sarcoma. Pathologic diagnosis is important so that appropriate treatment can be prescribed.

Psychological impact of receiving negative BRCA1 mutation test results in Ashkenazim.

PURPOSE: Most DNA test results for breast/ovarian cancer susceptibility are negative. Because negative test results might be interpreted incorrectly and may have serious psychological and behavioral implications, determining the psychological impact of such results is important. METHODS: A community-based sample of 289 Ashkenazim was tested for 185delAG. The 199 mutation-negatives provided data at baseline and follow-up. Increased risk participants included those who received negative test results but remained at increased risk because positive family and/or personal histories of breast or ovarian cancer made the results uninformative. Average risk meant those who tested negative and had negative family and personal histories of breast or ovarian cancer. Using a logistic regression analysis, both groups' psychological distress levels were compared at baseline and at 1 and 6 months after notification of DNA test results. RESULTS: A logistic regression analysis showed significant but small differences in cancer-specific distress after 6 months between increased and average risk participants (P < 0.006). Increased risk participants reported more distress than average risk. General distress declined among all participants after 1 month. Although baseline and follow-up differences in cancer-specific distress obtained by the increased and average risk participants were statistically significant, none of the absolute levels observed reflected especially high degrees of stress. CONCLUSIONS: Receipt of negative DNA test results does not have a deleterious psychological impact, whether results are informative or uninformative.

Isolation and identification of a metabolite of cidofovir from rat kidney.

Cidofovir is an acyclic nucleotide analog with potent and broad-spectrum antiviral activity against adenoviruses and herpesviruses including cytomegalovirus (CMV). Cidofovir undergoes intracellular phosphorylation by host enzymes to cidofovir phosphate and cidofovir diphosphate (the active form). An unidentified metabolite has been observed previously in rat tissues and in urine of rabbits, rats and monkeys dosed with cidofovir. In the present study, this metabolite was isolated from rat kidney following an intravenous dose of 100 mg kg-1 cidofovir. The metabolite (metabolite I) was separated from cidofovir and impurities using extraction on anion-exchange resin followed by preparative normal and reversed-phase high-performance liquid chromatography (HPLC). The isolated metabolite I was subjected to proton, 13C and phosphorus nuclear magnetic resonance (NMR) and matrix-assisted laser desorption/ionization mass spectroscopy, and confirmed to be cidofovir-phosphocholine. The uptake of cidofovir by rat kidney was saturated at an intravenous dose of 100 mg kg-1, probably as a result of saturation of the renal tubular secretion pathway. However, the relative abundance of cidofovir phosphocholine was not affected by dose.

Pharmacokinetics and bioavailability of the anti-human immunodeficiency virus nucleotide analog 9-[(R)-2-(phosphonomethoxy)propyl]adenine (PMPA) in dogs.

The pharmacokinetics, bioavailability, and metabolism of the anti-human immunodeficiency virus nucleotide analog 9[(R)-2-(phosphonomethoxy)propyl]adenine (PMPA) were determined in beagle dogs following intravenous, intraperitoneal, and oral administration. Fasted male beagle dogs (n = 5) were pretreated with pentagastrin and received PMPA (10 mg/kg of body weight) by the intravenous and oral routes with a washout period of 1 week between doses. A further group of male dogs received PMPA as a single dose via the intravenous (1 mg/kg; n = 5) and the intraperitoneal (10 mg/kg; n = 3) routes, with 1-week washout period between doses. The concentrations of PMPA in plasma and urine were determined over 48 h postdosing by fluorescence derivatization and high-performance liquid chromatography (HPLC). The potential for metabolism or biliary excretion of PMPA was evaluated in a dog with a chronic indwelling bile cannula. Urine, feces, and bile were collected at intervals over 48 h following the intravenous administration of [14C]PMPA (10 mg/kg; 55 microCi/kg). The concentrations of PMPA in plasma after intravenous injection were best described by an open two-compartment model with a terminal half-life of approximately 10 h. PMPA was excreted unchanged in urine (70%); recovery in feces (0.42%) or bile (0.26%) was negligible. The plasma clearance of PMPA (0.28+/-0.05 liter/h/kg) was substantially greater than the glomerular filtration rate in this species, suggesting active tubular secretion of PMPA. No metabolites of [14C]PMPA were observed in urine, feces, or bile on the basis of HPLC with radioactive flow detection. The remainder of the dose was probably excreted unchanged in urine beyond 48 h postdosing. The mean+/-standard deviation observed bioavailabilities of PMPA following oral and intraperitoneal administration at 10 mg/kg were 17.1%+/-1.88% and 73.5%+/-10.5%, respectively.

Effects of pinealectomy on SCN electrical firing rhythm in Djungarian hamsters.

Djungarian hamsters (Phodopus sungorus) from a long day photoperiod (16:8 h light-dark cycle) were either pinealectomized (PINX; n = 7) or sham-pinealectomized (SHAM; n = 6). One week after surgery coronal brain slices (500 microm), containing the suprachiasmatic nucleus (SCN), were prepared. The firing-rate rhythm of SCN neurons was recorded over at least a 22 h period. The amplitude of the firing rhythm for SHAM slices (3.42 +/- 0.26 Hz) was not significantly different from PINX slices (3.45 +/- 0.29 Hz). Maxima and minima of the firing rhythms also could not be distinguished statistically between PINX and SHAM groups. However, two-way ANOVA of 2 h firing-rate averages indicated a statistically significant effect of pinealectomy on the firing rhythm (P < 0.01). The results show that pinealectomy one week prior to brain slice preparation only had a minor effect on the in vitro neuronal firing rhythm in the SCN. In this study, SCN firing-rate rhythm in the Djungarian hamster is largely independent of endogenous melatonin secretion.

Reentrainment of motor activity and spontaneous neuronal activity in the suprachiasmatic nucleus of Djungarian hamsters.

Neurons in the suprachiasmatic nucleus (SCN) of the hypothalamus exhibit a daily rhythm in spontaneous electrical activity. Essentially two methods have been employed to record this circadian rhythm: (1) an in vitro brain slice technique and (2) in vivo multiunit recordings. Reentrainment of a circadian output to a shifted light:dark cycle commonly takes several cycles (depending on the amount of shift) until completed. Such a resetting kinetic has also been shown to be valid for SCN electrical activity if recorded in vivo. In an in vitro slice preparation, however, pharmacologically induced resetting is much faster and lacks transients; that is, a shift is completed within one cycle. This study was designed to probe for the presence of transients in the neuronal activity of the SCN in a brain slice preparation. The authors exposed Djungarian hamsters to an 8-h advanced or delayed light:dark cycle and monitored wheel-running activity during reentrainment. Additional groups of identically treated hamsters were used to record the pattern of spontaneous neuronal activity within the SCN using the brain slice preparation. Neuronal activity exhibited the usual rhythm with high firing rates during the projected day and low firing rates during the projected night. However, following 1 day of exposure to the 8-h advanced light:dark cycle, this rhythm disappeared in 6 of 7 slices. Rhythmicity was still absent following 3 days of exposure to the advanced light:dark cycle (n = 4). By contrast, 3 of 7 slices prepared from hamsters exposed to a delayed light:dark cycle for 3 days exhibited a daily rhythm in electrical activity. Although pharmacological agents reset the in vitro SCN neuronal activity almost instantaneously and in in vivo studies a stable phase relationship to a shifted light:dark cycle occurs gradually over several cycles, the authors did not detect either of these patterns. Such differences in resetting kinetics (e.g., rapid resetting, gradual reentrainment, temporary lack of measurable rhythmicity) may be due to (a) application of a resetting stimulus in vivo versus in vitro, (b) duration of the resetting stimulus, (c) the nature of the resetting stimulus, or (d) the recording technique employed.

Monitoring of cisplatin ototoxicity by distortion-product otoacoustic emissions.

Cisplatin is one of the most commonly used chemotherapeutic agents. However, ototoxicity, in particular, damage to the outer hair cells of the cochlea, is one of its major side effects. Otoacoustic emissions are acoustical signals that originate from the contractile activity of the outer hair cells. They are transmitted from the cochlea to the external ear canal via the middle ear apparatus. Testing is quick, painless, objective, and non-invasive. Distortion-product otoacoustic emissions (DPOAEs) are one of the evoked types of otoacoustic emissions. They are quite sensitive to any insult to the outer hair cells, even before damage is manifested in pure tone audiometry (PTA). A patient, who was on cisplatin chemotherapy due to prostate cancer, was monitored periodically for ototoxicity using DPOAEs and PTA. DPOAEs were found to detect ototoxicity one course of chemotherapy earlier than PTA during cisplatin chemotherapy. The clinical application and sensitivity of DPOAEs in monitoring ototoxicity were discussed.

Photoperiodic time measurement in Djungarian hamsters evaluated from T-cycle studies.

We investigated the photoperiodic response to T-cycles (0.5 h of light at intervals ranging from 23.0 h to 25.3 h) of two phenotypes of Djungarian hamsters that either exhibit or lack physiological short-day adjustments under a photoperiod of 9 h light:15 h darkness. Illumination of the same circadian time caused a similar photoperiodic response in both phenotypes. Thus hamsters found to be insensitive under a full short-day photoperiod can exhibit short-day adjustments after exposure to certain T-cycles. Given these results we conclude that the absence of photoperiodic adjustments normally found in short-day-insensitive hamsters results from their atypical entrainment under a full short-day photoperiod. We further suggest that the photoperiodic phenomena seen in Djungarian hamsters cannot be adequately explained by an external coincidence model of photoperiodic time measurement. As a more suitable model, we propose one form of internal coincidence where duration of daily motor activity reflects the phasing of multiple, endogenous oscillators. This conclusion is supported by the close relationship between duration of activity and the photoperiodic response as well as by the observation that a light pulse modulates duration of activity in a phase-dependent manner.

An in vitro circadian rhythm of melatonin sensitivity in the suprachiasmatic nucleus of the djungarian hamster, Phodopus sungorus.

Past studies in the rat and Syrian hamster show that metabolic and electrical activity of the suprachiasmatic nuclei (SCN) is inhibited by melatonin (MEL) at about circadian time (ct) 8-11 h. The present experiment examined the effect of MEL on the firing frequency of SCN cells in brain slices prepared from long day (LD 16:8) Djungarian hamsters to determine the timing of MEL sensitivity and if sensitivity persists in vitro. Pressure ejection of MEL (2 mM in 165 mM NaCl) suppressed the firing rate of 26% of SCN neurons recorded, excited 13%, and had no effect on 61% of the 161 cells tested. MEL elicited the highest percent response (64%) during the 4-h time bin immediately preceding the dark phase of the projected light:dark cycle on day 1 (ct 8-12 h). A similar temporal pattern of MEL sensitivity was found during the second day of recording. In contrast, application of vehicle to 52 SCN cells had little effect on firing rate. These results demonstrate that a sensitivity rhythm to MEL is present in the SCN of the Djungarian hamster and persists with a period of about 24 h in vitro.

Melatonin-induced desensitization in amphibian melanophores.

Video-microscopic examination of pigment granule translocation in cultured amphibian melanophores provides continuous, real-time observation of cellular responses to hormonal and pharmacologic agents and is particularly useful for studying the mechanisms underlying melatonin-induced pigment aggregation. We have used such video-microscopic technology to show that pigment cells become refractory to prolonged melatonin treatment and that the speed at which the desensitized condition becomes evident is dependent upon the countervailing concentration of antagonistic hormone, alpha-melanocyte stimulating hormone (MSH). When melanophores were treated with 10 nM melatonin, desensitization occurred within 30 minutes in the presence of 5 ng/ml MSH, whereas five hours of melatonin treatment was required before the desensitized state was observed in the presence of 1 ng/ml MSH. The persistence of desensitization after melatonin removal depends upon the duration of initial melatonin exposure. When melanophores were treated with melatonin (10 nM) in the presence of 10 ng/ml MSH for two hours, the desensitized condition lasted less than 30 minutes; if the initial melatonin treatment was increased to four hours, however, the melanophores remained in the desensitized state for more than two hours after the melatonin was removed from the medium. During the course of these treatments, there was no substantial degradation of melatonin activity; i.e., a second population of melanophores responded normally to the melatonin-containing media overlying desensitized melanophores.

Melatonin injections affect circadian behavior and SCN neurophysiology in Djungarian hamsters.

We investigated the effects of daily melatonin (MEL) injection on phase angle of entrainment, duration of wheel-running activity (alpha), and frequency of suprachiasmatic nuclei (SCN) neuronal discharge in the photo-nonresponsive phenotype of the Djungarian hamster, Phodopus sungorus. Photo-nonresponsiveness is characterized by an absence of physiological adjustments to short days (SD). With respect to wheel-running activity, photo-nonresponsive hamsters have a large negative phase angle of entrainment and a compressed alpha under SD. These hamsters also have a delayed nocturnal MEL pulse. These circadian differences are correlated with the daily profile of SCN neuronal activity. In the present experiments, daily MEL injections to photo-nonresponsive hamsters resulted in molt, gonadal regression, and expansion in alpha until entrainment to lights off. Vehicle-injected controls did not exhibit any of these responses. SCN neuronal activity patterns recorded from MEL-injected photo-nonresponders, but not vehicle-injected controls, resembled electrical activity profiles of photoresponsive hamsters. These results demonstrate that MEL induces "photoresponsiveness" in previously photo-nonresponsive hamsters, that MEL modifies circadian behavior to resemble that of photoresponders, and that MEL injections affect the circadian rhythm of SCN neuronal firing.

Absence of a daily neuronal rhythm in the suprachiasmatic nuclei of acircadian Djungarian hamsters.

The suprachiasmatic nuclei (SCN) in mammals generate and maintain a variety of daily rhythms. In nocturnally active rodents, SCN electrical activity is high during the subjective day (that time of locomotor inactivity) and low during the subjective night. The present experiment examines the relationship between SCN neuronal activity and the expression of overt circadian behavior in the Djungarian hamster (Phodopus sungorus). Wheel-running locomotor activity was measured in 2 groups of hamsters housed in constant dark (DD). Twelve hamsters, selected from ongoing experiments in our laboratory, showed no overt circadian rhythm in locomotor activity. A second group of 9 control animals exhibited rhythmic wheel-running activity in DD. In contrast to control animals, in vitro SCN electrical activity in brain slices prepared from acircadian hamsters showed no circadian variation. These data indicate that in acircadian animals SCN electrical activity properly reflects behavioral patterns.

Relationship between phase resetting and the free-running period in Djungarian hamsters.

A data set of 293 phase shifts was analyzed in order to determine the relationship between phase resetting and the free-running period (tau) in Djungarian hamsters. Phase shifts in response to a 15-min light pulse were assigned to one of two groups (tau short, less than 24 hr; tau long, greater than 24 hr), and two phase response curves (PRCs) were constructed. The two PRCs differed predominantly in the advance region, which extended so far into the subjective day of PRClong that a dead zone was lacking. The functional significance of PRC differences was assessed by computer simulations of entrainment to varying skeleton photoperiods and entrainment to a 12-hr skeleton photoperiod with varying tau's. Results from these simulations confirmed the theoretical predictions by Pittendrigh and Daan: Stability of entrainment under varying photoperiods depended on the ratio of the PRC slopes at the phases illuminated by light (SE/SM). This ratio was always larger than 1 for PRClong. It approached 0 for PRCshort as soon as the evening light illuminated the dead zone; this occurred for entrainment to very short photoperiods. Stability of entrainment to lights-off was in general better for PRClong than for PRCshort, especially if PRClong was used in combination with tau long. This suggests that it can be advantageous for stability of entrainment to lights-off to express a tau greater than 24 hr in combination with a PRC lacking a dead zone. Stability of entrainment under varying tau's was not much different for PRClong or PRCshort. However, stability of entrainment deteriorated for PRClong in combination with short tau's, whereas it deteriorated for PRCshort in combination with long tau's.

Evidence for genetic variation in the occurrence of the photoresponse of the Djungarian hamster, Phodopus sungorus.

The Djungarian hamster generally responds to a short-day photoperiod with a complex syndrome of physiological and behavioral changes; however, not all hamsters are photoresponsive. The phenotypic difference is, in part, genetically determined. Parent-offspring regression on a number of continuous and discontinuous measures indicated significant heritability for photoresponsiveness. Four generations of replicated bidirectional selection on a photoresponse index (PI) resulted in significant shifts in the percentage of responsive hamsters, although the average PI of responsive individuals was not significantly changed. Eight estimates of heritability ranged from 0.20 to 0.52. We hypothesize that the circadian system is responsible for the occurrence of the photoresponse, but that the extent of photoresponse is controlled by a separate functional system.