Physical separation and reduction of contact duration with sexually hyperactive bucks decrease testosterone concentrations and sexual behaviour in bucks in sexual rest.

Sexually hyperactive bucks are more efficient than sexually hypoactive bucks in stimulating testosterone secretion and sexual behaviour in other bucks in seasonal sexual rest by the phenomenon that we called the "buck-to-buck effect". Here, we determined whether physical separation and reduction of the duration of contact with the sexually hyperactive bucks would modify those parameters in sexually hypoactive bucks exposed to the "buck-to-buck effect". Bucks were subjected to natural day length throughout the study; this was the sexually hypoactive group. Other bucks were subjected to artificial long days (16 h of light per day) from 15 November to 15 January followed by exposure to natural day length to stimulate their sexual activity during the rest season; this was the sexually hyperactive group. In Experiment 1, we determined testosterone concentrations and sexual behaviour of six sexually hypoactive bucks separated 1.5 m from six sexually hyperactive bucks for 60 days by a metal open work fence, while a control group of six sexually hypoactive bucks was in permanent contact with six sexually hyperactive bucks. In Experiment 2, the duration of contact with sexually hyperactive males was reduced from 31 days (contact group, six bucks) to 10 days (withdraw group, seven bucks). In experiments 1 and 2, there was an effect of time (P < 0.01) and an interaction between time and groups (P < 0.05). In Experiment 1, testosterone plasma concentrations were greater in bucks in contact with sexually hyperactive bucks than in those separated from bucks at 20 and 30 days after the introduction of sexually hyperactive bucks (P < 0.01). The bucks from the contact group also displayed more nudging than bucks from the separated group from 0 to 30 days (P < 0.001). In Experiment 2, testosterone concentrations were greater in the contact group than in those from the withdraw group from 19 to 31 days after the introduction of sexually hyperactive bucks (P < 0.05). Bucks from the withdraw group displayed more nudging than the contact group 7 days after the introduction of the sexually hyperactive bucks (P < 0.05). Afterwards, bucks from the contact group displayed more nudging than the withdraw group 14, 21 and 28 days after the introduction of the sexually hyperactive bucks. We concluded that physical separation and reduction of the duration of contact with the sexually hyperactive bucks decrease testosterone concentrations and sexual behaviour of bucks in sexual rest exposed to the "buck-to-buck effect".

Undernutrition reduces the body weight and testicular size of bucks exposed to long days but not their ability to stimulate reproduction of seasonally anestrous goats.

In semiarid conditions, feed is often scarce and variable with underfeeding being common; these factors can potentially induce fertility reductions in both sexes. Sexually active bucks are able to very efficiently fertilize out-of-season goats, but we do not know whether underfeeding would reduce the ability of bucks to fertilize goats during these periods. Two experiments were conducted to determine (i) testicular size and change of odor intensity of undernourished bucks exposed to long days and (ii) the ability of these bucks to stimulate reproductive activity in seasonally anestrous goats. In experiment 1, bucks (n = 7) were fed 1.5 times the normal maintenance requirements from September to May and formed the well-fed group. Another group of bucks (n = 7) were fed 0.5 times the maintenance requirements and formed the undernourished group. All bucks were subjected to artificially long days from 1 November to 15 January; this period was followed by a natural photoperiod until 30 May. Body weight, scrotal circumference and male odor intensity changes were determined every 2 weeks. In experiment 2, two groups of female goats (n = 26 each) were exposed to well-fed (n = 2) or undernourished bucks (n = 2) on 31 March. Ovulations and pregnancy rates were determined by transrectal ultrasonography. In experiment 1, a treatment by time interaction was detected for BW, scrotal circumference and odor intensity changes (P < 0.001). The BWs of well-fed bucks were greater than those of the undernourished bucks from October to May (P < 0.01), as were the scrotal circumferences from December to March (P < 0.05) and odor intensities from February to May (P < 0.05). In experiment 2, the proportions of females that ovulated at least once (100% v. 96%) or those that were diagnosed as pregnant (85% v. 77%; P > 0.05) did not differ significantly between the goats exposed to well-fed or undernourished bucks. The interval between the introduction of bucks and the onset of estrous behavior was shorter in goats exposed to well-fed bucks compared to the interval for those goats exposed to undernourished bucks (2.5 ± 0.2 v. 9.5 ± 0.6 days; P < 0.05). We conclude that undernourishment reduces the testicular size and odor intensity responses in bucks exposed to long days, but that undernourished bucks are still able to stimulate reproductive activity in seasonally anestrous goats, as is also the case for well-fed bucks.

Depuration of geosmin- and 2-methylisoborneol-induced off-flavors in recirculating aquaculture system (RAS) farmed European whitefish Coregonus lavaretus.

European whitefish Coregonus lavaretus has increasingly become an important species for aquatic food production, especially in the Nordic countries. Whitefish is produced in traditional cage and pond operations, and in recirculating aquaculture system (RAS) in which, unfortunately, off-flavors and odors, mostly caused by geosmin (GSM) and 2-methylisoborneol (MIB), can accumulate in fish flesh from the circulating water. GSM and MIB have very low human sensory detection limits and, therefore, often disliked by consumers even at low concentrations. In this study, concentrations of GSM and MIB in RAS farmed European whitefish were studied by an analytical method based on headspace solid phase microextraction and gas chromatography-mass spectrometry. Concentrations were determined in different parts of fish: fillet, neck, belly, and tail during a depuration period and in depuration water. The highest initial concentrations were on average 32 ng g-1 (GSM) and 24 ng g-1 (MIB) in European whitefish fillet and 128 ng L-1 (GSM) and 94 ng L-1 (MIB) in water, respectively. After a depuration period of 16 days, concentrations decreased to below the detection limits, indicating the importance of the depuration period.

Melatonin administration during the dry period stimulates subsequent milk yield and weight gain of offspring in subtropical does kidding in summer.

In the present experiment, we tested the hypothesis that in does kidding in summer, melatonin administration during dry period is galactopoietic for the subsequent lactation and results in improved growth of their suckling kids. Twenty-five multiparous pregnant creole does were enrolled into a randomized complete block design during their dry period in the 49 d prepartum, and under natural long photoperiods around the summer solstice, pregnant does either received 2 subcutaneous ear implants (18 mg) of melatonin (MEL, n = 10) or served as nonimplanted controls (CONT, n = 15). During the first 14 wk of subsequent lactation (suckling and milking periods), MEL does yielded more milk than CONT does. Throughout subsequent lactation, milk composition was not affected by treatment. In MEL does, peripheral triiodothyronine levels peaked at 2 wk of lactation, remaining higher than in CONT does. The mean daily weight gain was higher in MEL compared with CONT kids and was also higher in males than females, and for males, was positively correlated with milk yield. The current data support our hypothesis that melatonin during the prepartum period is galactopoietic in suckling does.

Continuous presence of females in estrus does not prevent seasonal inhibition of LH and androgen concentrations in bucks.

In male goats, being in permanent visual contact with females in estrus does not prevent seasonal variation in certain endocrine hormone levels and sexual activities. In this study, we tested whether continuous and full contact with females in estrus prevented seasonal endocrinological variation in bucks. In 1 experiment (Exp. 1), we verified that the sudden introduction of goats in estrus increased the plasma concentrations of androgen in bucks during the nonbreeding season under our experimental conditions. In another experiment (Exp. 2), we tested the ability of estrous goats to prevent seasonal inhibition of LH and androgen secretions in bucks kept in permanent and full contact with them. In Exp. 1, 3 groups of bucks (n = 5 in each group) were isolated from females from the months of July to January. On January 27, one group continued being isolated from females; a second group was exposed to ovariectomized, untreated goats; and a third group was exposed to ovariectomized goats with induced estrus. Plasma androgen concentrations were determined every 2 h from 8 h before to 8 h after the introduction of females. The introduction of estrus-induced goats significantly increased androgen concentrations, which were higher than in the isolated bucks, as well as in those exposed to untreated goats (P < 0.05). In Exp. 2 (n = 5 per group), one group of bucks was isolated from females from October to July, whereas two other groups remained in contact with ovariectomized goats, either untreated or regularly induced to estrus. In the three groups of bucks, plasma concentrations of LH were determined once during the months of October, February, March, and June, whereas androgen concentrations were determined weekly from October to July. The mean plasma LH and androgen concentrations were low and did not differ among the groups of bucks during the normal seasonal period of sexual inactivity (P > 0.05). We conclude that full contact and sexual interactions with estrus-induced goats failed to stop the seasonality of LH and androgen plasma concentrations of bucks, although bucks could respond to the introduction of females by acute increases in plasma LH and androgen.

Sexually active bucks counterbalance the seasonal negative feedback of estradiol on LH in ovariectomized goats.

We showed previously that the permanent presence of bucks rendered sexually active by photoperiodic treatments, thereafter called photostimulated bucks, prevents the occurrence of seasonal anovulation; also, the introduction of these sexually active bucks induces ovulations during seasonal anestrus. Here, we studied the response of ovariectomized goats bearing 12-mm subcutaneous implants filled or not with estradiol to sexually active males to determine (1) whether the permanent presence of such bucks prevents the decrease of LH despite the presence of a negative feedback by estradiol mimicking that of seasonal anestrus (experiment 1) and (2) whether the introduction of photostimulated bucks increases the plasma LH concentrations in spite of this negative feedback (experiment 2). In experiment 1, one group of goats remained in contact with sexually active bucks, whereas the other group remained in contact with control bucks. Plasma LH concentrations were high and did not differ with time or between groups of females from November to February (P > 0.05), when both types of bucks were sexually active. Afterward, in goats in contact with control and sexually inactive bucks, LH concentrations decreased from March (P ≤ 0.01) and remained low until May, whereas LH levels remained high from March to May in goats in contact with the photostimulated bucks (P > 0.05). In experiment 2, 2 groups of females bearing empty subcutaneous implants, and 2 groups of goats bearing subcutaneous implants filled with estradiol, were exposed to control or photostimulated bucks. Plasma LH concentrations did not increase in goats bearing empty implants, when exposed to control or photostimulated bucks (from 2.01 ± 0.26 to 1.98 ± 0.31 ng/mL, and from 2.45 ± 0.29 to 2.42 ± 0.21 ng/mL respectively; P > 0.05). In contrast, plasma LH concentrations increased from 0.97 ± 0.41 to 2.80 ± 0.62 ng/mL in goats exposed to the photostimulated bucks and bearing estradiol implants (P < 0.05). Thus, the permanent presence of sexually active bucks prevented the decrease of plasma LH concentration in OVX + E2 goats during the seasonal anestrus, and the introduction of the photostimulated bucks increased the plasma LH concentrations in OVX + E2 goats during the seasonal anestrus. Therefore, we conclude that in both cases, the photostimulated bucks are able to reduce or counterbalance the seasonal negative feedback of estradiol on LH secretion.

Fifteen minutes of daily contact with sexually active male induces ovulation but delays its timing in seasonally anestrous goats.

The present experiment was conducted to determine (1) whether the sexually active bucks are able to stimulate the ovulatory activity of seasonal anestrous goats when the daily contact is reduced to 15 min/day during 15 days and (2) the exact ovulatory activity in anestrous goats exposed to bucks for 2 hours or less per day during 15 days. One group of goats (n = 15) was isolated from bucks. The other six groups (n = 15 each) were exposed to sexually active bucks (n = 1 each) for 15 minutes, 30 minutes, 1 hour, 2 hours, 4 hours, or 24 hours during 15 days. Goats with plasma concentrations of progesterone greater than 0.5 ng/mL were considered to have ovulated. More than 93% of females exposed to bucks ovulated throughout the experiment regardless of the duration of contact with males, whereas none of them ovulated in the isolated group (P < 0.0001). The proportions of females that ovulated at least once did not differ among groups as well as the proportions of goats that displayed normal or short ovulatory cycles. The interval between the introduction of males and the first ovulation did not differ among groups of goats in contact with bucks for 15 minutes, 30 minutes, 1 hour, or 2 hours. However, in these groups, this ovulation occurred about 2 days later than in females in contact with males during 4 or 24 hours (6.3 vs. 4.4 days; P < 0.05). We conclude that 15 minutes of daily contact with sexually active buck is sufficient to stimulate the ovulatory activity in seasonally anestrous goats, but the first ovulation is delayed in goats exposed to males for 2 h/day or less during 15 days in comparison with those in contact with males for 4 or 24 h/day.

Sexually active males prevent the display of seasonal anestrus in female goats.

A well-defined season of sexual rest controlled by photoperiod is observed in female sheep and goats during spring and summer, delineating their "anestrous season"; bucks also decrease sexual activity at about the same time. Nutrition and/or socio-sexual stimuli play only secondary roles. However, the presence of sexually active males can reduce the length of seasonal anestrus. Whether it can also completely suppress anestrus has not been investigated. Here we tested this in goats in 3 experiments, using bucks rendered sexually active out of season by exposure to long days. The continuous presence of these males prevented goats to display seasonal anestrus: 12/14 females cycled the year round, vs. 0/13 and 0/11 for females with un-treated bucks or without bucks (experiment 1). When active bucks were removed, females immediately entered anestrus (7/7 stopped ovulating vs. 1/7 if maintained with active bucks; experiment 2). Finally, 7/7 anestrous does with bucks in sexual rest since 1.5months commenced cycling rapidly during mid-anestrous, when these bucks became sexually active following a treatment with artificial long days, vs. 0/7 with un-treated bucks or no bucks (experiment 3). The presence/withdrawal of active bucks had a highly significant effect in the three experiments (P≤0.002). Therefore, the presence of a mating opportunity can completely override the photoperiodic inhibition of reproduction of females throughout the anestrous season. Results suggest that we must re-evaluate the relative contributions of photoperiod vs. other external cues in controlling seasonal reproduction, thus offering new non-pharmaceutical ways for controlling out-of-season reproduction in small ruminants.

Importance of intense male sexual behavior for inducing the preovulatory LH surge and ovulation in seasonally anovulatory female goats.

The present study was carried out to determine whether the presence of photostimulated sedated male goats could stimulate the LH preovulatory surge and ovulation in seasonal anestrous goats. Sexually experienced male goats were treated with artificial long days (16 hours light per day) from 1 November to 15 January to stimulate their sexual activity in March and April, corresponding to the natural sexual rest. A female group of goats (n=20) was exposed to non-sedated males who displayed an intense sexual behavior and provided strong odor (non-sedated group). Another female group of goats (n=20) was exposed to the photo-stimulated male goats, but these males were sedated with Xylazine 2% to prevent the expression of sexual behavior (sedated group). The sedated males also provided a strong odor. Females of both groups had full physical and visual contact with non-sedated or sedated males. In both groups, the males remained with females during 4 days. The LH preovulatory surge of 10 female goats per group was measured by determination of LH plasma concentrations in samples taken every 3 hours. In addition, in all goats, (n=20 by group), ovulation was determined by measuring plasma concentrations of progesterone. The proportion of female goats showing a preovulatory LH surge was higher in goats exposed to non-sedated (10/10) than in those exposed to sedated bucks (0/10; P<0.0001). Similarly, most of does in contact with non-sedated males ovulated (19/20), but none of those in contact with sedated males did so (0/20; P<0.0001). We conclude that the expression of an intense sexual behavior by male goats is necessary to induce LH preovulatory surge and ovulation in seasonally anovulatory goats.

Two or 24 h of daily contact with sexually active males results in different profiles of LH secretion that both lead to ovulation in anestrous goats.

Two experiments were conducted to (a) determine whether sexually active males are able to stimulate the sexual activity of anestrous female goats when duration of contact is reduced to an intermittent contact shorter than 4 daily hours and (b) compare the pattern of secretion of LH when anestrous goats are exposed either permanently or intermittently to males. In the first experiment, 4 groups of anovulatory goats were exposed to sexually active males for 24, 4, 2, or 1 h/d during 15 consecutive days, whereas control females remained isolated. More than 89% of females in the groups exposed to the sexually active bucks ovulated, whereas only 5% did so in the control group (P < 0.001). However, the proportion of females ovulating before day 4 was greater in the 2-, 4-, or 24-h contact groups than in the control, whereas it did not differ between the control group and the 1-h contact group (P = 0.02, <0.001, <0.001 and 0.23, respectively). In the second experiment, 3 groups of anovulatory goats were exposed permanently (24 h/d) or intermittently (2 h/d) to bucks during 5 d or remained isolated. We found that pulsatility of luteinizing hormone (LH) increased in the intermittent and permanent contact groups after males were introduced to females (P = 0.05); this pulsatility of LH remained elevated in the permanent-contact group, whereas it decreased in the intermittent-contact group, once the male was removed (P = 0.32 and 0.05, respectively). We conclude that 1 or 2 daily hours of contact with sexually active males is sufficient to stimulate ovulatory activity in anovulatory goats; however, ovulation is obtained through a different pattern of secretion of LH.

Angioma capilar espinal intradural: reporte de un caso y revisión de la literatura / Spinal cord capillary hemangioma: a case report and literature review

INTRODUCTION: Capillary angiomas are extremely rare in the spinal intradural space (being even less frequent in the intramedullary location)10-24. We analyze the characteristics of these lesions. METHODS: We present a case report of a patient with a symptomatic spinal-intradural capillary hemangioma at the thoracic level, followed by a review of the literature. RESULTS: We found a total of 41 patients reported with single angiomas, and three more patients with multiple lesions. Most patients were male (33/44 patients), and the mean age was 53,5 years. The localization of these lesions was mainly in the dorsal spine (24), cauda equina (15) and conus medullaris (6), with one case reported in the cervical spine 11. Most patients presented with back pain, mielopathy or radiculopathy. Contrary to the case of cavernous angiomas, we did not find cases of capillary angiomas presenting with subarachnoid or intramedullary hemorrhage. The imaging characteristics (isointense at T1WI, hyperintense at T2WI and with intense contrast enhancement) were constant in almost all the reports. CONCLUSIONS: Spinal intradural capillary angiomas are rare vascular lesions, frequently mistaken for intradural tumors. It affects mostly males in the fifth or sixth decade of life, and is preferentially located in the thoracolumbar spine. It can be occasionally associated with marked spinal cord edema, specially when there is a intramedullary component. These lesions have a good prognosis after surgical treatment, and must be taken into account in the differential diagnosis of intradural tumors of thoracolumbar spine and cauda equina.

Sexually active bucks are able to stimulate three successive groups of females per day with a 4-hour period of contact.

Bucks rendered sexually active by a photoperiod treatment of long days can induce fertile ovulation in a group of goats with only 4 h of contact daily with a male:female ratio of 1:10. Here we tested whether such bucks could induce fertile ovulations when stimulating successively three different groups of anovulatory goats when interacting 4 h per day during 15 consecutive days. Control males (n=3) were introduced in the control group (n=25) of does at 8:00 h and were removed at 12:00 h. Experimental males (n=3) were in contact with the experimental groups of does: from 8:00 h to 12:00 h with a first group (n=27), from 12:00 h to 16:00 h with a second group (n=26) and with a third one (n=27) from 16:00 h to 20:00 h. Bucks were then placed until next day in another pen. Both in the control and the experimental groups, more than 85% of females ovulated, and the proportions did not differ between the control and experimental groups (P≥0.67) or between the three experimental groups (P≥0.67). Moreover, the ovulation rate did not differ significantly between the control and the experimental females nor between the three experimental groups. Bucks were able to fertilize more than 72% of does independently of the number of females they were exposed to (P≥0.17). Finally, more than 58% of females kidded and fertility did not differ between the control and experimental groups (P=1) nor among experimental groups (P≥0.77). We conclude that sexually active bucks are able to induce fertile ovulation in three successive groups of anovulatory goats even when the period of contact between sexes is reduced to 4 h per day.

The effect of dietary phosphorus deficiency on the immune responses of European whitefish (Coregonus lavaretus L.).

Low phosphorous (P) feeds in aquaculture are recommended to reduce eutrophication of water systems. However, the feed should be adequate for normal growth and intact immune defence. Influence of low dietary P supply on non-specific and specific immune defence of European whitefish (Coregonus lavaretus) was studied in two trials. For Trial 1, a semi-purified, low-P diet was formulated and supplied with 0, 2.5, 5.0, 7.5, or 10.0 g P kg(-1)to obtain a P gradient of 4.4-14.9 g kg(-1)diet. Diets were fed to four replicate groups of fingerling whitefish for 42 days in a flow-through, freshwater system maintained at 15 degrees C. Fish fed with the P-unsupplemented diet had significantly lower plasma immunoglobulin M (IgM) levels than fish fed with the P-fortified diets (means 2.53 vs. 3.19 mg ml(-1); P=0.047). Plasma lysozyme activity did not differ between fish fed with the P-unsupplemented diet and fish fed with the P-fortified diets (means 21.8 vs. 25.5 U ml(-1); P=0.107). For Trial 2, fish were acclimated for 49 days by feeding the lowest or highest dietary P contents, and thereafter immunised with a single intraperitoneal injection of a novel antigen, bovine gamma globulin (BGG). A clear antibody response against BGG was elicited but the antibody levels did not differ between fish fed low-P or high-P contents. Similar to Trial 1, plasma IgM was lower in fish fed low-P diets, and low-P diet did not influence plasma lysozyme activity. In both trials the growth of fish, having received low-P diet, was significantly lowered. It is concluded that P deficiency has only minor effects on the immune parameters in whitefish, and the practical aquafeed with P contents sufficient for normal growth does not compromise immune functions of this species.

Induction of sexual activity in lactating anovulatory female goats using male goats treated only with artificially long days.

Two experiments were conducted to determine the response of Creole male goats treated with long days and melatonin implants, and the response of the anovulatory does to male effect using males treated only with artificially long days. All animals were allocated to open sheds. In Exp. 1, one group of males was under natural photoperiod (CG; n = 7); the second group was submitted to 2.5 mo of long days followed by the insertion of two s.c. melatonin implants (LD+MEL; n = 7); the third group was subjected only to 2.5 mo of long days (LD; n = 7). Testicular weight was measured every 2 wk. Plasma testosterone concentrations were determined weekly. A treatment x time interaction was detected (P < 0.001) for testicular weight and plasma testosterone concentration. In the LD+MEL and LD groups, testicular size and plasma testosterone levels varied in a similar way, but differed from those observed in CG (P < 0.001). In this latter group, testicular weight displayed seasonal variations and peaked in June, whereas in treated groups this peak occurred in March. In CG, testosterone varied in a seasonal manner and plasma concentrations increased in June and remained elevated throughout the study. In experimental groups, testosterone increased in February and peaked in March. In Exp. 2, one group of males was left under natural photoperiod (CG, n = 5) and the other one was submitted to 2.5 mo of artificially long days (LD, n = 4). On March 16, two control and two treated males were put in contact with 20 and 19 females, respectively. Sexual behavior of the bucks was observed during the 5 d following male introduction. Progesterone assays and estrous behavior were used to determine ovarian and behavioral responses of the females to teasing. The anogenital sniffing, nudging, and mount instances registered in LD-treated males were greater than those observed in CG (P < 0.05). Of the does exposed to CG, none ovulated and only two of 20 females displayed estrous behavior. All does in contact with LD-treated males ovulated and showed at least one estrous behavior during the 15 d following joining (P < 0.001). These results indicate that the sexual activity of male goats from subtropical latitudes can be induced using only artificially long days. In addition, males treated in this way are capable of stimulating sexual activity in anovulatory females by the male effect.

Male effect in seasonally anovulatory lactating goats depends on the presence of sexually active bucks, but not estrous females.

A study was conducted in subtropical northern Mexico (26 degrees N) to determine whether the presence of estrous females can improve the response of seasonally anovulatory goats to the introduction of bucks in the group. The induction of estrous activity was studied in three groups of anovulatory lactating goats during seasonal anestrus. These females were of the Mexican Creole breed. In the control group (sexually inactive (SI), n = 20), two control (SI) bucks exposed to normal seasonal daylength variations were used. In the second group (SI + E, n = 20 + 3), two control males were also used, but in addition, three females of the group were in estrus at the time of male introduction. In the third group (sexually active, SA + E, n = 19 + 4), anovulatory females were exposed to two bucks made sexually active by exposure to 2.5 months of long days (16L:8D) followed by two subcutaneous 18 mg melatonin implants, and four estrous females were also present when introducing the bucks. In all groups, males were introduced on 15 March and estrous detection was conducted twice daily for 15 days. The sexual activity of the bucks was observed from 08:00 to 10:00 h during the first five days of exposure to females. More females displayed estrous behavior in the first 15 days following the introduction of the males in the SA + E group (18/19) as compared with the SI or SI + E groups (2/20 and 0/20, respectively; P < 0.001). No difference was observed between the two latter groups. Thirteen females of SA + E group showed a second estrus between days 6 and 11 (short estrous cycle duration: 5.4 +/- 0.4 days). By contrast, in the SI group none showed a second estrus. The sexual behavior of the males in the SA + E group was greater as compared with that of the males in SI and SI + E groups (over 80% of the total sexual activity recorded in the three groups; P < 0.001). By contrast, no differences were found between SI and SI + E males. These results indicate that the presence of estrous females alone at the time of buck introduction is not sufficient to induce an adequate stimulation of seasonally inactive males. The use of sexually active bucks is necessary to induce reproductive activity in anovulatory females, whereas preparation of the bucks with long days followed by melatonin implants allows them to gain such a capacity.

Beneficial effects of induced hypertension on experimental stroke in awake monkeys.

The authors performed a controlled study of induced hypertension therapy for treatment of experimental stroke in unanesthetized monkeys. Ten control and 10 treated animals were subjected to a 4-hour occlusion of the middle cerebral artery (MCA) by an implanted tourniquet. Neurological status and local cerebral blood flow (CBF) were monitored serially. Local CBF was determined by hydrogen clearance in and around the elevated 20% to 40% by intravenous infusion of phenylephrine hydrochloride. Neuropathological evaluation was performed after about 2 weeks. A 4-hour occlusion of the MCA in control animals caused moderate stable neurological deficits, moderate stable decreases in local CBF, and medium-sized infarcts. With induced hypertension, five of 10 treated animals showed neurological improvement, and eight exhibited increased CBF in the ischemic zone. Average infarct size tended to be smaller in the treated group, although the difference did not reach statistical significance. Hemorrhagic infarcts were not observed. In four animals, phenylephrine caused cardiac dysrhythmias and hypotension which were reversed by appropriate measures. In this unanesthetized primate model of moderate experimental stroke, induced hypertension had beneficial effects on neurological status, local CBF, and infarct size without causing hemorrhagic infarction. Induced hypertension may be beneficial for some clinical cases of focal cerebral ischemia.

Proton NMR imaging in experimental ischemic infarction.

Proton nuclear magnetic resonance (NMR) images depict the distribution and concentration of mobile protons modified by the relaxation times T1 and T2. Using the steady-state-free-precession (SSFP) technique, serial coronal images were obtained sequentially over time in laboratory animals with experimental ischemic infarction. Image changes were evident as early as 2 hours after carotid artery ligation, and corresponded to areas of ischemic infarction noted pathologically. Resulting SSFP images in experimental stroke are contrasted to inversion-recovery NMR images in an illustrative patient with established cerebral infarction. Bulk T1 and T2 measurements were made in vitro in three groups of gerbils: normal, those with clinical evidence of infarction, and those clinically normal after carotid ligature. Infarcted hemispheres had significantly prolonged T1 and T2 (1.47 +/- .12 sec, 76.0 +/- 9.0 msec, respectively) when compared to the contralateral hemisphere (T1 = 1.28 +/- .05 sec, T2 = 58.7 +/- 3.9 msec) or to the other two groups. These data suggest that changes in NMR parameters occur and can be detected by NMR imaging as early as two hours after carotid artery ligation.

Delayed cerebral vasospasm is not reversible by aminophylline, nifedipine, or papaverine in a "two-hemorrhage" canine model.

Angiographic spasm of cerebral arteries was produced in dogs by successive injections of cisternal blood 48 hours apart. Angiograms were taken before and after each cisternal injection. There was progressively greater angiographic vasospasm of the basilar artery. Intravenous aminophylline, 10 mg/kg/hr, reversed vessel constriction on the 1st and 3rd day after one injection of cisternal blood. On the 5th day after two blood injections (on Day 1 and Day 3), intravenous aminophylline, nifedipine (1 mg/kg), and intra-arterial bolus injection of 2 mg/kg papaverine failed to reverse the constriction. The intractable constriction produced in this model resembles that found in patients. The calcium antagonist, nifedipine, is as ineffective as the more traditional vasodilators in reversing vasospasm in this model.

Cranial anatomy and detection of ischemic stroke in the cat by nuclear magnetic resonance imaging.

Proton nuclear magnetic resonance (NMR) images of cat heads were obtained using a small, experimental imaging system. As a prelude to the study of experimental ischemic brain infarction, the normal cat head was imaged for identification of anatomical features. Images of one cat which had undergone ligation of the middle cerebral artery three weeks previously showed brain changes associated with chronic ischemic stroke and compared favorably with findings on computed tomography (CT). The NMR images have millimetric spatial resolution. NMR parameters inherent in the tissues provide intensity variations and are sufficiently sensitive to yield contrast resolution surpassing that of CT.