Effect of photoperiod variation on testes and accessory sex organs in the male blind mole rat Spalax ehrenbergi.

The blind mole rat is a seasonally breeding fossorial rodent that is perceptionally blind. This study examines the effect of photoperiod on the morphology and histology of the male mole rat reproductive system, three groups of male mole rats were maintained in the laboratory under short day (SD) conditions (9L: 15D); long day (LD) conditions (15L:9D); and constant darkness (CD), and compared to animals trapped in the field (FL). It was found that the field animals revealed higher testes and prostate gland weights, higher prostate tubuli volume (v*) and lower testes tubuli volume (v*) compared to the other three groups. Distribution of the tubuli in the testes (Vv) was low in the FL group compared to the SD and LD groups but still higher than in the CD group. Distribution of lumen in the testes (Vv) was higher in the CD group in comparison to the other three groups. Distribution of interstitial tissue in the testes (Vv) was higher in the FL group than in the other three groups. Electrolytes and elements secreted from the prostate gland did not differ among the four groups. In the FL group distribution of the tubuli (Vv) in the prostate gland was low and lumen ratio (Vv) was high compared to the other three groups. Distribution of connective tissue in the prostate gland did not differ among all four groups. Testosterone levels and total sperm count was highest in the FL group. Sperm production was noted in all groups; however spermatid and spermatozoa cell production was higher in the FL group. This study shows that photoperiod could be important in initiating timing in the breeding season but that certain other conditions which are absent in the laboratory appear to be responsible for successful breeding in the field.

Possible dopaminergic system involvement in LH and PRL responses to naltrexone treatment.

Naltrexone (Nalt) causes a rapid increase in luteinizing hormone (LH) level. This short term increase of LH concentration declines to baseline levels in less than 1 hour. Addition of pimozide (0.1 mg) caused a blunted response to Nalt challenge, with significantly reduced LH peak values compared with Nalt treatment alone. Pimozide alone caused a delayed decrease compared with baseline LH values. By following plasma prolactin (PRL) levels it was shown that pimozide administration increased PRL levels rapidly for more than 2 hours. Addition of Nalt to pimozide-treated rats significantly decreased plasma PRL values compared with pimozide alone. Nalt injected by itself attenuated PRL baseline levels. Thus, the mechanism by which pimozide caused PRL elevated level is via the dopaminergic as well as the opioid system. It is suggested that the opioid system controls plasma PRL and LH levels through other hypothalamic neurotransmitters in addition to dopamine.

Opiate system involvement in the control of LH secretion in diabetic and normoglycemic male rats.

The effect of Naltrexone (Nalt), a specific opiate receptor blocker, on LH secretion was studied at frequent intervals during the first hour following treatment. Nalt was injected i.v. by one bolus (1 mg/rat) to diabetic and normoglycemic rats. Blood samples (0.8 ml) were withdrawn at short intervals after injection, through an indwelling cannula. The diabetic rats responded by secretion of LH, which was lower, but not significantly, than that of normal rats, (peak levels 0.74 +/- 0.17 and 0.97 +/- 0.21 ng/ml respectively). After 45 min., LH levels were in the same range as baseline level in the diabetic group; but were still significantly elevated in the control rats. Thus, it can be concluded that in normal rats, as well as in diabetics, LH secretion as a response to Nalt was episodic in spite of Nalt's long half life time. In order to explain the rapid fall in LH levels after Nalt administration, normal rats were injected with a second bolus of Nalt, 2 hours after the first. The second bolus caused only a blunted response of LH secretion. In another experiment, administration of morphine (1 mg/rat) 2 hours after pretreatment with Nalt did not stimulate the prolactin secretion which normally follows morphine treatment. These results indicate that the rapid decrease of LH levels after Nalt treatment in normal rats is not due to absence of the drug in the system. It is suggested that other neural mechanisms, such as the dopaminergic system, are activated during Nalt influence.

Blood luteinizing hormone and prolactin concentrations in response to naltrexone challenge: studies on rats with diabetes induced by different doses of streptozotocin.

Opiate system involvement in diabetes induced by three different doses of streptozotocin (STZ; 40, 50, and 60 mg/kg body weight [BW]) was studied by monitoring luteinizing hormone (LH) and prolactin (PRL) levels as a response to naltrexone (Nalt) administration. After four weeks of diabetes a marked decrease in BW, as well as severe hyperglycemia and increased blood urea nitrogen (BUN) levels were found. The rats, whose diabetes was induced by 50 mg/kg of STZ, exhibited the highest amount of blood glucose (P < 0.05, compared with the 40 mg/kg induced group) and BUN levels (P < 0.004 compared with the other two groups) and BW loss. The normal response to Nalt, which is expressed by elevation of plasma LH and decreased plasma PRL levels was observed only in the low-dose STZ (40 mg/kg BW) diabetes-induced group, while in the other two diabetic groups (50 and 60 mg/kg BW) there was no significant change in plasma LH and PRL as a result of the Nalt challenge. Presensitization of the endogenous opioid receptors by morphine in normoglycemic (control) and "low-dose diabetic" rats (40 mg/kg BW of STZ), presented a clear difference between the two. Morphine pretreatment inhibited LH response to Nalt in the low-dose, STZ-induced diabetic rats, while no effect of morphine pretreatment on LH response to Nalt could be recorded in the normoglycemic group. Thus it can be concluded that in STZ-induced diabetes, plasma glucose and BUN levels do not reflect the neuroendocrine injury observed when monitored by LH and PRL secretion in response to Nalt challenge. Supersensitization of the opioid receptors before the Nalt challenge may increase the ability to reveal neuroendocrine system impairment.

Social stress in neighboring and encountering blind mole-rats (Spalax ehrenbergi).

Blind mole-rats (Spalax ehrenbergi) are solitary aggressive subterranean rodents. They inhabit individual territories, comprised of branched tunnels. Each such tunnel system is completely separate from that of any neighboring mole-rat. Although intraspecific encounters between neighbors are infrequent, when they do occur, they may result in the injury or death of one or both animals. Avoidance of encounters may be due to the awareness of a neighbor's whereabouts through scent-marking and/or seismic (vibratory) communication. The present study was intended to examine whether encounters between individual mole-rats result in physiological stress. Two experimental conditions were designed to simulate natural situations: a brief encounter between two neighboring mole-rats, taking place either once or several times and long-term residency of neighbors whose only contact was either vibratory or vibratory plus odor communication. Blood samples were taken before, during, and after encounters in the first experiment and at set intervals in the second. The blood variables measured were blood glucose levels (BGL) and neutrophil/lymphocyte ratio (N/L). Blood glucose levels and neutrophil/lymphocyte ratio ratios increased in both members of encountering pairs. Long-term residency with a neighbor resulted in the establishment of a dominant-subordinate relationship through vibratory communication only, with increased neutrophil/lymphocyte ratio ratio in the subordinate males. However, long-term residency of males exposed to both vibrations and odors of neighboring males resulted in the death of both individuals. It seems that brief direct encounters and long-term neighboring conditions without physical contact are sufficient to cause severe stress to mole-rats. It is possible that in the wild, in some situations in which neighboring mole-rats cannot avoid constant exposure to each other's vibratory and odor signals, the consequent extensive stress may result in death.

Urinary testosterone levels in the male blind mole rat (Spalax ehrenbergi) affect female preference.

This study investigated the sexual attraction of female blind mole rats to four groups of male mole rats: (a) intact males raised in captivity; (b) intact males trapped in the field; (c) captive males injected with testosterone; (d) captive castrated males. In the first part we measured blood testosterone, androstenedione, and dihydrotestosterone (DHT) levels, by radioimmunoassay; and urine testosterone levels, measured by GC-MS. The second part examined the relationship between urine testosterone levels in males and their attractiveness to females. Higher blood and urine testosterone levels were found in the field animals and in those injected with testosterone compared to captive intact or castrated animals: urine testosterone levels in the two other groups were not detectable. Blood androstenedione levels were also higher in the field animals and in those injected with testosterone compared to captive intact or castrated mole rats. Blood dihydrotestosterone levels were not detectable in all four experimental groups. Female mole rats chose to spend a longer period of time next to males with high blood and urine testosterone levels and high blood androstenedione levels than next to those with lower levels of these hormones. Because courtship and sexual behavior are influenced both by high levels of blood and urine testosterone and high levels of blood androstenedione, we suggest that the low levels of courtship and other sexual behavior in captive mole rats may be related to the lack of female attraction to these males, which display low levels of all three parameters.

The use of an electric freezer in human semen banking.

The use of an electric freezer for cryostorage of human semen is described. A simple method for semen freezing in liquid nitrogen after dilution with 7.5% glycerol was used. Thawing for quality analysis revealed only a small decrease (10%) in post-thaw sperm motility (59 +/- 1.4 vs. 53 +/- 1.8%; mean +/- SE, n = 12, P less than 10(-5)) and 14% in post-thaw sperm vitality (85.0 +/- 1.3 vs. 72.9 +/- 1.8%). After the freezing process, the samples, three of each donor, were cryopreserved in a regular electric freezer which maintained temperatures in the range of -85 degrees C (+/- 2 degrees C). The samples were stored for 1 week, 2 and 6 months, thawed and then assayed for motility and vitality. No effect of storage was found for a period up to 2 months. An additional decrease of 17.2% in sperm motility and 18% in sperm vitality were noted only after 6 months of preservation. The final motility and vitality rates of these sperm samples were 44 +/- 2.4 and 60 +/- 3.0%, respectively. According to these results, in cases of sperm storage for limited periods, it is recommended to cryopreserve human semen by the use of a combination of freezing in liquid nitrogen and storage of the samples in an electric freezer at -85 degrees C.

Quantitative microscopic changes in the mole rat's accessory sex organs during an annual cycle.

BACKGROUND: The mole rat, Spalax ehrenbergi, is a solitary, aggressive subterranean rodent. The present study summarizes a year-round investigation of morphological changes in the mole rat's accessory sex organs. METHODS: Mole rats maintained in the laboratory were killed after 3 months of acclimation; additional animals trapped in the wild were killed immediately. The accessory sex organs were processed for routine histological examination. Tissues were fixed in Bouin's solution, embedded in paraffin blocks, and stained by hematoxylin-eosin. A systemic sampling approach was used to photomicrograph the tissues for histomorphometric assessment. RESULTS: The volume fraction (Vv, mean +/- SEM) of prostate connective tissue from animals kept in captivity increased significantly in January (0.49 +/- 0.05 mm3/mm3) and April (0.43 +/- 0.04 mm3/mm3) but only 0.26 +/- 0.03 mm3/mm3 in November. In the field group, the Vv of prostate connective tissue was significantly higher in January (0.58 +/- 0.08 mm3/mm3) and April (0.62 +/- 0.08 mm3/mm3) and lower in November (0.44 +/- 0.03 mm3/mm3) and February (0.43 +/- 0.03 mm3/mm3), with a concomitant decrease in prostate tubuli and lumen. The prostate tubuli star volume (v*) in laboratory animals increased in November (0.009 +/- 0.002 mm3) and May (0.09 +/- 0.02 mm3). The same pattern was shown in the field group, with a significant increase in December (0.012 +/- 0.002 mm3) and March (0.007 +/- 0.001 mm3). The Cowper tubuli Vv in the captive animals increased during February (0.24 +/- 0.02 mm3/mm3), with a concomitant reduction in the connective tissue (0.05 +/- 0.02 mm3/mm3). The Cowper tubuli v* in same animals increased in December, April, and July (1.37 +/- 0.18 x 10(-4) mm3, 0.94 +/- 0.10 x 10(-4) mm3, 1.52 +/- 0.20 x 10(-4) mm3, respectively). In field group, a slight decrease in star volume took place from November to May (1.25 +/- 0.16 mm3 to 0.39 +/- 0.05 mm3, respectively). Testosterone levels appeared to be higher in the field group than in the laboratory group. In December the values were 1.62 +/- 0.15 ng/ml in the field group and 0.55 +/- 0.12 ng/ml in the laboratory group, and in May the laboratory group values were 1.66 +/- 0.12 ng/ml. CONCLUSIONS: In captivity and in the field, male mole rats probably undergo an annual cycle of accessory gland tissue structural changes that are correlated with testosterone secretion.

Determination of urinary luteinizing hormone for prediction of ovulation.

Detection of the approximate time of ovulation is important in the in vitro fertilization-embryo transfer programs in order to avoid a possible early surge of luteinizing hormone (LH) before human chorionic gonadotropin administration in the induction of ovulation and for timing of artificial insemination. In the present study correlation between the detection of LH in urine and serum levels (mean +/- SEM) of estradiol greater than 557 +/- 118 pg/ml, progesterone less than 1.9 +/- 0.37 ng/ml and leading follicle diameter greater than 26.2 +/- 1.3 mm (mean +/- SEM) was found. Thus, the prediction of ovulation via detection of urinary LH in urine by a dipstick procedure is a good semiquantitative method, accurate enough, reliable, cheap and acceptable by the women.

Luteinizing hormone secretion as a response to a second naltrexone administration.

Previous studies with naltrexone (Nalt), a "long-lasting" opioid antagonist, demonstrated a rapid increase in luteinizing hormone (LH) secretion which gradually declined, reaching baseline values after 1 hr. A second Nalt challenge, 120 min later, caused only a blunted response. This poor reaction has been shown in this study not to be due to lack of pituitary responsiveness, because LH-releasing hormone treatment revealed a normal response. A time-response study was carried out in order to establish the refractory period length, by administering a second Nalt injection at 0 hr (immediately after the first injection) and at 2, 4, 8, 16, and 24 hr after the first bolus. Partial responsiveness could be achieved 2 and 4 hr after the first challenge. However, only after 8 hr was a full response recorded. The diurnal changes in serum LH (nadir at 18.00 hr) did not affect the response to Nalt challenge. It is suggested that in the presence of a Nalt blockade, nonopioid systems are able to "normalize" LH blood levels. However, when Nalt blood levels have fallen sufficiently to allow the endogenous opioid system to take primary control again, then a second Nalt injection will provoke a renewed response.

Serum prolactin response to ether stress in diabetic rats: opiate system contribution.

Diabetes in streptozotocin-treated rats is associated with alterations in various neuroendocrine systems, including endogenous opioids. These changes are suggested to be responsible for the significant reduction in serum prolactin (PRL) response to a brief restraint stress in diabetic male rats, as compared with normoglycemic controls. The present study examines serum PRL response to ether exposure in diabetic male rats. The animals' response to ether stress, which is known to be related to the opioid system, was examined twice in each rat: shortly after cannula insertion (Day 1), and seven days later. In order to evaluate the opiate system involvement, the experiment was repeated on Day 1 and 7 after surgery in a group of rats which were pretreated with naltrexone (Nalt), an opioid receptor antagonist. Opioid receptor sensitization was also performed by prior acute morphine administration on Day 7 after cannulation surgery. Following adaptation to the cannulation, no difference in serum PRL response to ether stress was found between diabetic and normoglycemic rats. However, on Day 1 after surgery, a significant difference was found between the diabetic and control groups: the normoglycemic (control) group exposed to ether responded to the surgical stress by augmented serum PRL levels. This response was not recorded in the diabetic rats. Opioid receptor blockade by Nalt administration 30 min before ether exposure eliminated this difference. Opioid receptor sensitization by morphine pretreatment facilitated PRL secretion in normoglycemic rats exposed to either, while no effect could be distinguished in the diabetic group. It is therefore concluded that the streptozotocin-induced diabetic rats do not differ from normoglycemic ones in their ability to respond to acute ether stress by itself. However, enhanced PRL secretion induced by ether exposure under additional surgical stress, or by presensitization of the opioid receptors by morphine, is prevented in diabetic rats, probably due to diminished opioid receptor response.