Lessons learned from the DIASTAT vascular access graft

In male Syrian hamsters, short days induce regression of the reproductive system, but eventually spontaneous recrudescence occurs ensuing from refractoriness to the inhibitory photoperiod. Although the photoperiod of 12 L:12 D (12 h light:12 h dark) may act like a short day by inducing the testicular cycle outlined above, it may fail to evoke the increase of circulating concentrations of prolactin that accompanies testicular recrudescence. This photoperiod may fail to induce photorefractoriness, as indicated by the prolonged low concentrations of prolactin in the blood. Herein, hamsters were exposed to either 8 L:16 D or 12 L:12 D from weaning and by 28 weeks exposure to either photoperiod, the hamsters had large testes following recrudescence from a photoperiod induced-regression). Transfer to 8 L:16 D from 12 L:12 D at 28 weeks resulted in a second testicular regression and recrudescence. In a second experiment, the testes of hamsters moved to 8 L:16 D from 12 L:12 D after 29 weeks exposure to the latter photoperiod similarly regressed and then regrew. Serum concentrations of prolactin decreased in these males after transfer to the shorter daylength but also decreased in hamsters kept under 12 L:12 D both groups were usually below those of hamsters moved to 14 L:10 D. These results show that exposure for 28 or 29 weeks to 12 L:12 D was insufficient to induce photorefractoriness, despite the recrudescence of the testes following involution.     

Lesions in the anterior bed nucleus of the stria terminalis in Syrian hamsters block short-photoperiod-induced testicular regression

To elucidate the neural circuitry involved in the photoperiodic control of seasonal reproduction, adult male Syrian hamsters, previously housed under long photoperiods (LD; 14 h of light per day), received sham or bilateral radiofrequency-current lesions directed towards one of three anterior-to-posterior levels of the bed nucleus of the stria terminalis (BNST; far anterior, anterior, posterior). They were then transferred to a short photoperiod (SD; 6 h of light per day) for 12 wk, and their testicular weights and plasma FSH, LH, and testosterone concentrations were determined. All of these parameters became markedly inhibited in the sham-lesioned SD controls and also in the far anterior and posterior BNST lesioned groups. In contrast, this inhibitory response to SD was completely abolished in 8 of 14 animals that had received anterior BNST lesions; only in these 8 animals did the lesion encompass the lateral aspect of the anterior BNST. In a second experiment, hamsters that had previously been exposed to SD for 12 wk in order to induce testicular regression were lesioned in the anterior BNST and for the next 4 weeks were either exposed to LD or further maintained in SD. However, in neither case did the anterior BNST lesions perturb the normal photoperiodic response. Paired testes weights and plasma FSH, LH, and testosterone concentrations at 4 wk did not differ significantly (p > 0.05) between the lesioned animals and their respective sham-lesioned LD and SD controls, which, respectively, showed recrudescence of the reproductive axis or remained in a regressed condition. Taken together, the results suggest that lateral aspects of the anterior BNST contain a cell group that is critical for perception of the SD neuro-inhibitory signal; obliteration of this cell group interrupts the transmission of the inhibitory signal to the reproductive axis but does not directly stimulate it.     

Secondarily infected wounds and dermatoses: a diagnosis and treatment guide

In golden hamsters, seasonal changes in day length act via a pineal-dependent mechanism to regulate feedback and behavioral effects of androgen. Endogenous opiates participate in photoperiodically regulated neuroendocrine functions, but the effects of androgen on expression of the gene encoding POMC, the precursor of beta-endorphin, have been controversial. We used quantitative in situ hybridization to examine regulation of POMC messenger RNA (mRNA) by testosterone and to test the hypothesis that short day lengths act through the pineal gland to amplify POMC mRNA expression. We studied intact hamsters and castrates with or without androgen treatment held in long (14 h of light, 10 h of darkness) or short (5 h of light, 19 h of darkness) days for 10 weeks. POMC gene expression differed with rostral-caudal plane, photoperiod, and surgical treatment (castration and testosterone administration). Testosterone increased the number of silver grains in labeled cells throughout the arcuate nucleus, and short day castrates given androgen consistently had more silver grains per labeled cell than did their long day counterparts. Testosterone exerted an inhibitory effect, however, on the number of POMC mRNA-positive cells, and more POMC mRNA-labeled cells were found in the arcuate nucleus of long than short day castrates treated with testosterone. Photoperiod had no significant influence in castrates not receiving androgen. Testosterone treatment had generally similar effects whether it was begun at the time of castration or 5 weeks later. Pinealectomy blocked the influence of photoperiod on both the mean number of silver grains per labeled cell and the number of labeled cells. The results indicate that day length regulates POMC gene expression when androgen levels are held constant, but that androgen is necessary for photoperiod effects to be expressed.     

Seasonal neuroendocrine rhythms in the male Siberian hamster persist after monosodium glutamate-induced lesions of the arcuate nucleus in the neonatal period

The aim of these experiments was to examine the role of the arcuate nucleus in the control of seasonal cycles of body weight, feed intake, moulting and reproduction in the Siberian hamster. The arcuate nucleus has previously been implicated as a central site where systemic feedback signals (e.g. leptin) might act to regulate feed intake and body weight, so it was predicted that hamsters with lesions of this structure would be unable to display the inhibitory effects of short days on these parameters. In the first series of studies, lesions that destroyed approximately 80% of the cells in the arcuate nucleus were produced by treating hamsters neonatally with monosodium glutamate (MSG; 4 mg/g body weight sc), and vehicle- and MSG-treated males were raised from birth in long days (LD) or short days (SD). In hamsters raised in LD, the initial gain in body weight and testicular growth were significantly reduced by MSG treatment, however, growth rate and testis weight were still significantly greater than in vehicle- or MSG-treated hamsters raised in SD. In the second study, hamsters treated neonatally with vehicle or MSG were raised in LD for 8 weeks and, subsequently, approximately half in each group were transferred to SD for 18 weeks. As expected, vehicle-treated hamsters showed a characteristic decline in body weight when exposed to SD, while those remaining in LD continued to increase body weight. Feed intake decreased in parallel with the decline in body weight in SD, a complete moult to the white winter pelage occurred by 16 weeks in SD, and testicular regression occurred. Responses to SD also occurred in the MSG-treated hamsters: body weight decreased in SD but increased in their lesioned litter mates remaining in LD, and feed intake paralleled body weight changes in these groups. The moult to winter pelage was significantly retarded in MSG-treated hamsters transferred to SD. The testes were completely regressed in sham- and MSG-treated hamsters exposed to SD, whereas testes weights in MSG-treated hamsters maintained in LD were intermediate between those in vehicle-treated hamsters in SD and LD. Thus, despite initial effects on growth, the MSG-treated hamsters bearing substantial lesions of the arcuate nucleus were able to show appropriate responses to photoperiod, although not always of the same magnitude as the unlesioned controls. We conclude that feedback mechanisms operating via the arcuate nucleus are not the major regulators of seasonal cycles of body weight, feed intake, pelage and reproduction.     

Influence of olfactory bulb removal on ingestive behaviors, activity levels and self-stimulation in hamsters.

Examined the influence of olfactory bulb removal on running activity, body weight, food and water consumption, and lateral hypothalamic self-stimulation rates in 24 male and 4 female golden hamsters. 2 experiments were conducted in an attempt to characterize more completely the behavioral and physiological deficits which might be related to the total abolition of male sexual behavior produced by ablation of the olfactory bulbs. This operation depressed food consumption and body weight during the 1st 5-10 postoperative days only and had no effect on water intake. During the same postoperative period, running activity declined by 50% before returning to normal. Self-stimulation rates were reduced below normal during the 1st 2 postoperative days but returned to preoperative levels by 7 days. These transient effects of bulbectomy on the measured variables were contrasted with the permanent deficit in male sexual behavior which results from olfactory bulb removal. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The AEP T-complex to synthesised musical tones: left-right asymmetry in relation to handedness and hemisphere dominance

The Siberian hamster, Phodopus sungorus, breeds seasonally. In the laboratory, the seasonal breeding can be controlled by photoperiod, which affects the durations of nightly melatonin secretions. Winterlike short day lengths induce gonadal regression in adult animals, and pups born and maintained in short days undergo gonadal development much later than animals born into long days. The spinal nucleus of the bulbocavernosus (SNB) and its target muscles, the bulbocavernosus (BC) and levator ani (LA), comprise a sexually dimorphic, androgensensitive neuromuscular system involved in male reproduction. The SNB neuromuscular system was studied in male Siberian hamsters maintained from conception in short-day (8:16 h light/dark cycle) versus long-day (16:8 h light/dark cycle) conditions. At 40-47 days of age, development of three components of the SNB neuromuscular system were all significantly delayed in hamsters raised in the short photoperiod: BC/LA muscle weight, the size of SNB motoneuronal somata, and the area of the neuromuscular junctions at the BC/LA muscles of short-day hamsters were each significantly reduced relative to those of longday counterparts. Thus, development of the SNB reproductive system is delayed under short day lengths in this species.     

Effects of photoperiod on reproduction and the gonadotropin-releasing hormone-immunoreactive neuron system in the postpubertal male Djungarian hamster

The present study tested the hypothesis that photoperiodic control of reproductive function in the postpubertal Djungarian hamster is associated with changes in the number, morphology, or distribution of GnRH-immunoreactive cell bodies in the brain. To initiate or arrest sexual maturation, males were reared in long (LD, 16L:8D) or short (SD, 10L:14D) days from birth. In two other groups that were chronologically past the normal onset of puberty, males were transferred at 30 days of age from LD to SD or from SD to LD to arrest or initiate reproductive function, respectively. At 40, 60, or 90 days of age, 4-6 hamsters in each of the four photoperiod treatment groups were killed by intracardiac perfusion. Testes weights were significantly increased in males exposed to long days (LD and SD-to-LD groups) compared to those treated with short days (SD and LD-to-SD groups). Serum FSH concentrations at 40 days of age were also increased in the two groups of males in long days compared to those in both groups in short days (p < 0.05, ANOVA); LH concentrations were unaffected by photoperiod treatments. Brain sections (60 microns) from the corpus callosum decussation to the suprachiasmatic nucleus in the anterior hypothalamus were processed for GnRH immunocytochemistry. In brain regions that contained the majority of GnRH neurons, i.e., the medial preoptic area and diagonal band of Broca, the numbers of GnRH-immunoreactive cell bodies were the same among the four treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

The red wine provocation test: intolerance to histamine as a model for food intolerance

The effect of flutamide (FLU) administered during 6 weeks at doses of 50 or 100 mg kg-1 body weight, on various reproductive characteristics of sexually active male golden hamsters was studied. The weight of seminal vesicles and epididymides showed a dose dependent inhibition with FLU, while testicular weight exhibited a biphasic response, its value being increased by 20% at lower FLU doses and reduced by 15% at higher FLU doses. An elevation of testicular and epididymal androgen-binding protein (ABP) content and also of testicular testosterone content was observed with both doses of FLU. Serum levels of LH and testosterone exhibited a four-fold increase, at both doses of FLU, while FSH serum level was elevated depending on the dose of FLU used. Results suggest that in the golden hamster the maintenance of the weight of testes and accessory organs depends mainly on androgenic stimulation, while production and transport of ABP is probably regulated by gonadotropins.     

Maturational loss of thermotaxis prevented by olfactory lesions in golden hamster pups (Mesocricetus auratus).

5 day-old golden hamster pups preoperatively were tested on a thermal gradient, subjected to bilateral or unilateral olfactory bulbectomy or control dorsal cortical removal, and then tested on Days 6–25. Locomotion and rectal or belly temperature were monitored throughout the 2-min test. Controls became quiescent in the hot end of the gradient on Days 5–7 but after Day 8 chose cooler regions and increased their activity. Both unilaterally and bilaterally bulbectomized Ss spent more time in the heat throughout testing, were less active, and allowed their temperature to rise more rapidly than controls. Percentage of time in the heat was elevated in all bulbectomized Ss although some retained the ability to make an olfactory discrimination. Enhanced thermal behavior is apparently not due to anosmia per se. Altered thermal perception or responsitivity may result from loss of "nonspecific" olfactory projections that normally would mature at the beginning of the 2nd week. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The photoperiodic control circuit in euthyroid American tree sparrows (Spizella arborea) is already programmed for photorefractoriness by week 4 under long days

The aim of this investigation was to determine whether spontaneous testicular regression in male American tree sparrows (Spizella arborea) that were thyroidectomized at week 4 of photostimulation manifests photorefractoriness, as it does in chronically photostimulated euthyroid controls. On the basis of our demonstration that exogenous thyroxine stimulates the gonads only when recipient birds are photosensitive, male tree sparrows were thyroidectomized at week 4 of photostimulation (20 h light:4 h dark) and given thyroxine periodically to assay for photosensitivity. When initiated at weeks 4, 7, 10, 13 and 16 of photostimulation, thyroxine replacement therapy had no effect on testis size until week 16, when most recipient birds showed robust testicular growth. The inductive effect of exogenous thyroxine at week 16 confirms that chronic thyroidectomy dissipates photorefractoriness and simulates the effect of short days. The failure of replacement thyroxine to halt spontaneous testicular regression between week 7 and week 13 establishes that spontaneous testicular regression after thyroidectomy manifests photorefractoriness. Moreover, the failure of replacement thyroxine to induce testicular growth between week 4 and week 7 indicates that by week 4 of photostimulation, at least 3 weeks before photoinduced testicular growth ends, male tree sparrows are programmed for photorefractoriness. This conclusion is strengthened by the finding that thyroidectomy at week 4 of photostimulation does not uncouple photorefractoriness and postnuptial moult, which in euthyroid tree sparrows are tightly linked. In another experiment, photosensitive thyroid-intact tree sparrows were moved from 8 h light:16 h dark to 20 h light:4 h dark and given exogenous thyroxine or vehicle through week 6 of photostimulation. Exogenous thyroxine augmented testicular growth.     

The effects of pineal indoles given late in the light period on reproductive organs and pituitary prolactin levels in male golden hamsters

Intact and pinealectomized adult male hamsters kept in light:dark cycles of 14:10 (in hours) were given daily injections of either 25 microgram melatonin, 5-methoxytryptophol, N-acetylserotonin, or 6-hydroxymelatonin at 19.00 hours (13h after lights on). The injections were continued for 50 consecutive days. The daily melatonin injections significantly elevated body weights and depressed the growth of the testes and accessory sex organs and pituitary prolactin levels in intact hamsters. By comparison, in pinealectomized animals daily afternoon melatonin injections failed to alter body or testicular weights or pituitary prolactin levels. These findings indicate that for single injections of melatonin to be antigonadotrophic in the male hamster, the pineal must be intact. In intact animals, 5-methoxytryptophol and N-acetylserotonin slightly depressed the growth of the reproductive organs and pituitary prolactin levels, respectively. Again, these effects were negated by removal of the pineal gland. 6-Hydroxymelatonin was without influence on any of the parameters of reproduction that were measured.     

Photoperiodic control of gonadotrophin secretion in the ram: a detailed study of the temporal changes in plasma levels of follicle-stimulating hormone, luteinizing hormone and testosterone following an abrupt switch from long to short days

Six adult Soay rams were housed under artificial lighting conditions of long days (16 h light:8 h darkness) for 4 months and this caused the animals to lapse into a state of reproductive quiescence with low levels of gonadotrophins in the circulation and regressed testes secreting very low amounts of testosterone. The photoperiod was changed abruptly to short days (8 h light:16 h darkness) to induce a resurgence of sexual activity, and a detailed study was made of the pituitary and testicular responses over the first 100 days. Plasma levels of LH and FSH first began to increase between days 6 and 12 of short days, and rose progressively until days 33-54 before declining again. Testicular growth of the rams began on days 19-26 and continued for most of the remaining period of study. Plasma testosterone levels rose in parallel with the growth of the testes, and were greatly increased by day 100 when gonadotrophin levels were reduced. At most stages there were short-term fluctuations in the plasma levels of FSH, LH and testosterone indicative of episodic secretion. Peaks in plasma levels of LH were especially conspicuous and from the changes in frequency and amplitude of these peaks it was possible to predict the way in which photoperiod influenced gonadotrophin secretion by its effect on hypothalamic LH-RH secretion. A slight 24 h rhythm in the plasma levels of all three hormones was observed, and the significance of this in relation to the photoperiodic response is discussed.     

Oxygen tension in the oviduct and uterus of rhesus monkeys, hamsters and rabbits

Oxygen tension was measured using flexible polarographic microelectrodes within the oviductal and uterine lumen in rhesus monkeys (n = 9), golden hamsters (n = 21) and rabbits (n = 6), during the reproductive cycle (monkey), during oestrus and pseudopregnancy (hamsters, rabbits) and during pregnancy (hamsters). In general, oxygen tensions in each species were much less than half of atmospheric O2, ranging from high values of about 60 mm Hg (8.7% O2) in the rabbit oviduct, rabbit and hamster uterus, to as low as 11 mm Hg (1.5% O2) in the monkey uterus. Oxygen tensions did not vary significantly between left and right sides of the reproductive tracts (all species), nor between pregnant and pseudopregnant states nor between oviduct and uterus (hamsters). Differences owing to reproductive stage were found in the monkey oviduct, hamster oviduct and uterus, and rabbit uterus. Oxygen tensions were consistently very low (11-14 mm Hg) in the monkey uterus throughout the menstrual cycle. In hamsters and rabbits, intrauterine O2 decreased significantly at about the normal time of blastocyst formation and implantation, to 37 mm Hg (5.3% O2) and 24 mm Hg (3.5% O2), respectively. This study indicates that embryos develop in vivo under low oxygen concentrations, especially during the peri-implantation period. The data have implications for investigations of embryo metabolism and for improving embryo development in vitro.     

Study of the function of nerve growth factor in the olfactory tract of the mouse

The aim of this study was to examine the function of nerve growth factor (BGF) in the olfactory tract of mice. Using the mice which had received unilateral olfactory bulbectomy and in which antibodies to NGF had been continuously infused with into the contralateral olfactory blub, three kinds of analysis were performed: histological analysis of the olfactory epithelium by HE staining, immunohistochemical analysis of the olfactory epithelium using polyclonal antibodies to trk which forms the NGF receptor, and olfactory-mediated behavioral analysis with cycloheximide. These animals had been sacrificed at day 1, 3, 7, 14, 21 or 28. Several findings were obtained as a result of the above analysis. Degeneration of the olfactory epithelium and trk expression by the olfactory cells were observed on day 7, and the olfactory epithelium was incompletely regenerated on day 28. However, trk expression by the olfactory cell was still recognized and the olfactory function was not restored by day 28. These examinations suggest that NGF produced in the olfactory bulb was transported retrogradely to olfactory cells through the olfactory nerves, and was associated with sustaining the existence of those cells and with regenerating the olfactory tract after injury.     

Differential effects of short photoperiod on 2-[125I]iodomelatonin binding in the testis and brain of quail

The affinities and densities of 2-[125I]iodomelatonin binding sites in the brains and gonads of male Japanese quail following short photoperiod treatment were studied. At 6 weeks old, control quail were placed under a 14 hour light/10 hour dark photo-stimulatory cycle and experimental quail were housed under a 7 hour light/17 hour dark photo-inhibitory lighting regime. Eighteen weeks after photic manipulation, the birds were killed at mid-light. The photo-inhibited quail had very small testes. Brains and testes of control and experimental quail were collected for receptor binding studies. The maximum number of binding sites (Bmax) of 2-[125I]iodomelatonin determined by saturation studies and the number of 2-[125I]iodomelatonin binding sites determined by a one-point binding assay in the testes of short-day quail were significantly lower (p < 0.05) than those of the testes in reproductively active birds kept under long photoperiod. There was no significant difference (p > 0.05) between the testicular Kd (equilibrium dissociation constant) values of these two groups. As for the Kd and Bmax of 2-[125I]iodomelatonin binding sites in the whole brain, there were no significant differences (p > 0.05) between the two groups. The higher level of testicular 2-[125I]iodomelatonin binding sites in photostimulated birds may be related to an up-regulation of melatonin receptors by the suppressed pineal melatonin secretion under long photoperiod. The lower testicular 2-[125I]iodomelatonin binding sites under short photoperiod may be the result of down-regulation of melatonin receptors by the stimulated melatonin pattern in the photo-inhibited birds.(ABSTRACT TRUNCATED AT 250 WORDS)     

Modulation of serotonin binding sites in the brain of the Djungarian hamster, Phodopus sungorus, during adaptation to a short photoperiod

During the physiological adaptation of the Djungarian hamster, Phodopus sungorus, to a short photoperiod in autumn the modulation of specific serotonin (5-HT) binding sites of synaptic membranes was investigated in two brain regions, i.e. cerebral cortex and basal brain (CNS without cerebral cortex, cerebellum, pineal gland, and spinal cord). The radioligands [3H]5-HT and [3H]ketanserin were used to characterize total 5-HT1 and 5-HT2 binding sites, respectively. An increase of 5-HT1 and 5-HT2 binding sites was observed in both brain regions within 14 days after reduction of the photoperiod from a 14:10 h light/dark (l/d) cycle to an 8:16 h l/d cycle. The increase was still present after 56 days of the short photoperiod. Binding kinetics assayed after 4 days of the short photoperiod show that maximal specific binding of [3H]5-HT and [3H]ketanserin was increased, while dissociation constants (KD) were not changed. The membrane anisotropy of synaptic membranes, measured by fluorescence polarization, was reduced transiently during the early part of the adaptation. Neither the phospholipids nor the mole ratio of cholesterol to phospholipids were significantly affected by adaptation to short photoperiod. The results suggest an important role of the central nervous 5-HT system in the physiological adaptation of the Djungarian hamster to a short photoperiod.     

Seasonal and circadian changes in the episodic release of follicle-stimulating hormone, luteinizing hormone and testosterone in rams exposed to artificial photoperiods

Six rams of an ancient breed of domesticated sheep (SOAY) were subjected to an artificial light régime of alternating periods of long days (16 h light: 8 h darkness) and short days (8 h light: 16 h darkness) which induced seasonal development and regression of the testes during a period of 36 weeks. Over 2000 blood samples were taken, and the changes in plasma levels of FSH, LH and testosterone were related to the cycle of testicular activity. During long days plasma levels of gonadotrophins became very low and the testes regressed to about 20% of their maximum size; there was a corresponding reduction in plasma testosterone levels. When the rams were returned to short days reproductive development was again stimulated after 2-3 weeks with a progressive increase in plasma FSH and LH levels and consequent hypertrophy of the testes. It took about 16 weeks of short days for testicular activity to become maximal. Blood samples collected at hourly intervals for 24 h on ten occasions during the study revealed transitory peaks in plasma FSH and LH levels indicative of episodic release. Changes in gonadotrophin secretion were modulated primarily by alterations in the frequency of episodic releas; less than 1 spike per 24 h during long days increased to a maximum of 10 spikes/24 h under short daylengths. The peaks of FSH release were of smaller amplitude than those of LH, although during periods of frequent episodic release basal levels of fsh were increased to a greater extent than those of LH. A circadian rhythm was observed in the plasma levels of FSH, LH and testosterone, which was related to increased gonadotrophin release during the dark phase of the 24 h cycle; changes in blood haematocrit were also observed. The circadian changes appeared to be correlated with the activity cycle of the animals which in turn was dictated by daylight. A possible interrelationship between the circadian cycle and the seasonal cycle is discussed.     

Immobilization stress increases hepatic IL-6 expression in mice

Male Djungarian hamsters (Phodopus sungorus; 45 animals per group) were either sham-exposed or exposed to a sinusoidal magnetic field for 56 days (Experiment 1: 50 Hz, 450 microTesla peak; max. dB/dt = 140 mTesla s(-1); 24 hrs day(-1)). Except for day 7, no effects were observed with respect to body weights during exposure. However, testicular cell numbers were significantly increased by exposure (tetraploid (4C): p=0.022; diploid (2C): p=0.039). Rectangular magnetic fields (Experiment 2: 360 microTesla; max. dB/dt = 2.5 Tesla s(-1)) caused a significant (p<0.001) but transient suppressing effect on body weights. Significant increases were also observed in testicular cell numbers (4C: p=0.034; haploid (1C): p=0.014) and in serum melatonin (p=0.001). It is concluded that weak magnetic fields may affect reproductive and physiological functions in the mammalian species tested and that the degree of these effects depends upon the fields' gradients.     

Effects of perinatal gonadal secretions on parameters of receptivity and weight gain in hamsters.

Examined the influence of ovarian and testicular secretions on lordosis in 64 female golden hamsters (Mesocricetus auratus) ovariectomized when 1 or 43 days old and in 80 males castrated when 1, 3, 5, or 43 days old. The 1st of 8 weekly 10-min mating tests was initiated at 57 or 113 days. Receptivity was not different among female groups except for higher initial scores for those with ovaries through puberty. Initial and maximum receptivity in males was inversely proportional to castration age. Rate of decrease from maximum appeared higher in males castrated at Days 3 and 5 than at Day 1. Age of initial test was significant for males; older Ss had lower initial and maximum receptivity scores. Gonadal secretions decreased weights in both sexes. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Macular hole in a case of choroidal melanoma

This study reports intraspecific variations of native isolates of Leishmania (Viannia) braziliensis from patients with leishmaniasis from Salta, Argentina. These isolates induced skin lesions in golden hamsters, initially showing rapid development, reaching their largest size between 28 and 35 days postinfection (PI). Thereafter, the infections were self-limiting and total regression was observed at 80-150 days PI. The majority of the native isolates were characterized by low infectivity in the experimental animals, and a classic pattern of dissemination to systemic organs was established. However, unusual features for L. braziliensis were displayed by two isolates; one showed evidence of high infectivity in hamsters characterized by a short prepatent period and larger, severe and persistent lesions at the inoculation site. The other isolate, of low infectivity, showed cutaneous metastasis and recurrent systemic dissemination in the same animals, suggesting dissociation between infectivity and pathogenicity. Metastasis has been frequently described in hamsters infected with L. (V) guyanensis and L. (V) panamensis, but not in infections induced by L. (V) braziliensis, as was observed in this study. Active and/or regressive histopathologic lesions were observed, depending on the stage of the infection. An exudative and mixed inflammatory pattern with microabscesses and necrotic areas was observed during early infection, while well-defined granulomas and collagen formation were the predominant features detected at a later time. Amastigotes were easily detected in the tissues, although in low numbers. Schaumann bodies were always detected. The characterization of the unique features of these native isolates, and the verification of their reproducibility in vitro and in vivo will be useful tools in tests related to immunoprophylaxis and chemotherapy.