冰醋酸致小鼠实验性腹膜炎模型的研究

目的研究建立小鼠实验性腹膜炎模型,探讨建立一种简便、易行、效果稳定、便于获取实验数据的实验方法。方法小鼠腹腔分别注射2%冰醋酸生理盐水溶液0.1 ml(高浓度组)、1%冰醋酸生理盐水溶液0.2 ml(低浓度组),观察小鼠一般情况及腹腔解剖情况,进行血细菌培养;肝、回肠组织病理学观察;比色法测定肝、回肠LDH活性和MDA含量。结果注射不同浓度和剂量的冰醋酸,均表现出腹膜炎临床征象,高浓度组的小鼠模型病程快、死亡率高,血细菌培养有大量G-杆菌;低浓度组的小鼠模型,经21 d可自愈,无死亡。组织病理学观察,肝和回肠有病理改变。结论高浓度组的小鼠腹膜炎模型可作为急性腹膜炎的实验研究模型,低浓度组的小鼠腹膜炎模型,可作为研究实验性腹膜炎自愈过程机体抗损伤机制的实验模型。     

Induction of parturition with prostaglandin f2 alpha as a possible model to study impaired reproductive performance in the dairy cow

Parturitions were induced in five cows, 2 weeks before term using prostaglandin (PG) F(2alpha). Two i.m. injections were performed with an interval of 24 h. All cows calved within 5 days (average 2.7 days) after the first injection of PGF(2alpha). Out of five cows, four had retained fetal membranes (RFM). Each animal was sampled for bacteriological examination using uterine biopsies twice a week during 42 days postpartum (PP). Jugular vein blood samples were withdrawn for PGF(2alpha)-metabolite and progesterone analyses five times per day during the first week PP and eight times per 24 h during the 2nd and 3rd weeks PP. From the 4th week, the sampling interval was reduced back to five times per day. From the 5th week PP, the sampling was reduced to two times per day and sampling was terminated after day 46 PP. Only morning samples were used for progesterone analyses. From day 10 PP, ultrasonography (US) was performed every 3rd day until day 39 PP for detection of ovarian activity and follicular dynamics. The highest incidence of bacteriological species was found during the first 3 weeks PP. After the 5th week of collection, all animals were free from bacteria. The species of bacteria found were Arcanobacterium (Actinomyces) pyogenes, Escherichia coli, alpha-hemolytic streptococcae and Pasteurella multocida. Immediately after parturition, very high levels of the PG-metabolite were seen in all animals, with a sharp decrease to line of significance around days 9-12 PP. Small increases above the line of significance were detected up to day 27 PP in cows with RFM, and after that time the levels were considered to be at baseline. Low levels of progesterone were seen in four animals during the whole experimental time. In one animal, an increase was seen on day 43 PP, which was maintained until the end of the experimental period on day 46 PP. Based on US, follicular waves were detected in all animals during the experimental period. In three animals, three non-ovulatory follicular waves were detected and in two animals, four non-ovulatory follicular waves were detected during 39 days of ultrasound sessions. Based on progesterone levels, only one animal was considered to have ovulated around day 40 PP. Results from the present study indicate that reproductive performance of cows after PG-induced parturitions differs from those of spontaneous cases of RFM. Differences regarding the resumption of ovarian activity were also observed between previous studies of dexamethasone-induced parturitions and the present study.     

Physical properties of bovine cervical mucus during normal and induced (progesterone and/or PGF2alpha) estrus

Ninety two Friesian cows were used to determine physical properties of cervical mucus collected during normal estrus and estrus induced. Estrus was induced using either progesterone (P4) releasing intravaginal devices (PRID) and/or prostaglandin F2alpha (PGF2alpha). The animals were assigned to 4 groups (no treatment, a PRID for 12 days plus an injection of 1000 IU PMSG at the removal of the PRID, a double injection of 3 mL PGF2alpha 11 days apart, and a PRID for 7 days plus an injection of PGF2alpha 24 h before the removal of PRID). A number of cows with normal estrus exhibited three consecutive estrus cycles after calving. Cows that had not shown estrus for three months after calving had their reproductive system palpated twice at 10-day intervals, to determine their ovarian activity. Then PRID and/or PGF2alpha was administered to cows that were found to have a palpable corpus luteum in one of two palpations (cycling cows). The cows of the three induced estrous groups were artificially inseminated (AI) twice, while those with normal estrus received only a single AI. Cervical mucus samples were collected from all cows 5 to 30 min before the first AI. Additionally, samples of cervical mucus were collected from 20 cows at their first estrus after the induced estrus. The results are summarized as follows: 1) The physical properties of cervical mucus were similar in the first three normal consecutive estrus cycles after calving. 2) The physical properties of cervical mucus in normal estrus after calving were similar to those in the first estrus after an induced estrus. 3) The pH values for normal estrus were similar to those for induced estrus. 4) Viscosity of cervical mucus in the normal estrous group was significantly lower than that in the induced estrus. Furthermore, significant differences were noticed among the three induced estrous groups. 5) Spinnbarkeit, crystallization and receptivity of cervical mucus (penetration test) were significantly higher in the normal estrous group than in the induced estrous groups, while no difference was detected among induced estrus groups. 6) Pregnancy rates in the normal estrus group were the same as in the induced estrus groups. 7) The percentages of cows in the induced estrous groups that produced cervical mucus with similar viscosity, spinnbarkeit and receptivity (penetration test) characteristics as the normal estrus group, was very low.     

Continuous fetal heart rate monitoring during late gestation in cattle by means of Doppler ultrasonography: reference values obtained by computer-assisted analysis

Continuous fetal heart rate (FHR) monitoring using transabdominal Doppler ultrasonography can be assumed to provide information about the viability of the bovine fetus during late gestation, as has been found in humans. To be able to recognize unfavourable fetal conditions, first the normal ranges of FHR parameters in cattle should be established. Therefore, in this study we aimed to determine the normal ranges of computerized FHR parameters, like basal fetal heart rate (BHR), number of accelerations and decelerations per hour and short and long term variation (STV and LTV) during the last 3 weeks before calving (n = 21 cows). Each cow had one recording in each of three episodes of 7 days before parturition. As recording time in the cow is limited, we also studied whether these FHR parameters differ between recordings of 30 and 60 min duration (n = 31 pairs of recordings). The outcomes of FHR recordings with a duration of 30 or 60 min did not differ significantly, except for a higher percentage of signal loss in the 60 min recordings. Therefore, determination of normal ranges was performed in 30 min recordings. BHR decreased from 3 to 2 weeks (114 to 109 bpm; P < 0.0001) before parturition and then remained constant until 2 days before calving. The mean number of accelerations per hour ranged between 4.4 and 5.0 h(-1) and did not change significantly with time. Compared to 3 weeks before parturition, STV was significantly higher at 2 weeks (P < 0.05), but not at 1 week before parturition (8.1, 10.0, and 9.2 ms, respectively). Changes in LTV showed a time course comparable to that of STV, but significance was not reached (51.4, 58.6, and 58.4 ms for respectively 3, 2 and 1 weeks before parturition). No decelerations were found during the period understudy. In conclusion, this study has provided normal ranges of bovine computerized FHR parameters during the last 3 weeks of gestation, allowing a comparison with data from cows with compromised gestations in future.     

Endocrine profiles of dairy cows following experimentally induced clinical mastitis during early lactation

Concentrations of LH, cortisol, estradiol-17beta (E(2)), prolactin and 13,14-dihydro-15-keto-prostaglandin F(2alpha) (PGFM) were determined in cows with experimentally induced clinical mastitis during early lactation. Cows free of intramammary infection (IMI) and in the luteal phase of the estrous cycle were balanced by lactation number and days in milk and assigned to either control (n=5) or treatment (n=5) groups. Treated cows were infected experimentally (day 0), in two mammary quarters, with Streptococcus uberis and developed clinical mastitis within 60 h after inoculation as evidenced by increased mastitis scores, elevated rectal temperatures, mammary swelling and isolation of S. uberis pathogen. Four days following bacterial challenge, blood samples were collected every 20 min for 8 h for determination of PGFM and LH following administration of oxytocin and GnRH, respectively. Blood samples were also collected on days 0, 4 and 7 of the experiment to determine concentrations of E(2), prolactin and cortisol. Four days after bacterial challenge, concentrations of cortisol were higher (P=0.04) in experimentally infected cows than controls. Experimentally challenged cows had increased (P=0.02) concentrations of cortisol on days 4 and 7 compared with day 0. Control cows had no significant increase in blood cortisol during the experimental period. Baseline concentrations of PGFM did not differ between groups; however, peak concentrations of PGFM following oxytocin challenge were elevated (P=0.006) in cows with clinical mastitis compared with control animals. Prolactin, E(2) and LH did not differ between cows with clinical mastitis or controls. Experimentally induced mastitis during early lactation elevated concentrations of cortisol during the luteal phase of the estrous cycle. Furthermore, mastitic cows demonstrated an increased PGFM response following oxytocin administration. Altered reproductive efficiency in cows with clinical mastitis caused by Gram-positive pathogens may be the result of increased uterine sensitivity to prostaglandin F(2alpha) (PGF(2alpha)).     

Alterations of the composition and metabolism of pulmonary surfactant phospholipids induced by experimental peritonitis in rats

Pulmonary complications often accompany the development of acute peritonitis. In this study, we analyzed the alterations of alveolar surfactant phospholipids in rats with experimentally induced peritonitis. The results showed a reduction of almost all phospholipid fractions in pulmonary surfactant of experimental animals. The most abundant alveolar phospholipids-phosphatidylcholine and phosphatidylglycerol were reduced significantly in surfactant of rats with experimental peritonitis. In addition, analysis of the fatty acid composition of these two phospholipids revealed marked differences between experimental and control animals. The activity of phospholipase A2, which is localized in the hydrophyllic phase of alveolar surfactant, was higher in rats with experimental peritonitis compared to sham-operated ones. Also, a weak acyl-CoA:lysophospholipid acyltransferase activity was detected in alveolar surfactant of rats with experimental peritonitis, whereas in control animals this activity was not detectable. The lipid-transfer activity was quite similar in pulmonary surfactant of control and experimental rats. The total number of cells and the percentage of neutrophils were strongly increased in broncho-alveolar lavage fluid from rats with peritonitis. Thus, our results showed that the development of peritonitis was accompanied by pulmonary pathophysiological processes that involved alterations of the phospholipid and fatty acid composition of alveolar surfactant. We suggest that the increased populations of inflammatory cells, which basically participate in internalization and secretion of surfactant components, contributed to the observed alterations of alveolar phospholipids. These studies would be useful for clarification of the pathogenic mechanisms underlying the occurrence of pulmonary disorders that accompany acute inflammatory conditions, such as peritonitis and sepsis.     

Induction of ovulatory estrus and fertility in non-cycling buffaloes with norgestomet during low breeding season

Field trials were designed to evaluate use of norgestomet treatment to induce ovulatory estrus in non-cycling buffalo cows and heifers during low breeding season. Twenty-five buffalo cows and 50 heifers under village management were given a 9-day treatment with a polymer implant containing 6 mg norgestomet with IM injections of 5 mg estradiol valerate + 3 mg norgestomet at the time of implantation and 600 IU PMSG when the implant was removed. Fifty animals served as controls without any treatment. Seventy-four treated animals showed estrus during the period between 36 to 80 hours after removal of the implant. Twenty-five buffalo cows and 40 heifers that could be further followed up were inseminated twice at 8-hour intervals, 12 hrs after induction of estrus with chilled semen by recto-vaginal method. Of these, 15 (23.1%) conceived, 9 (36%) among buffalo cows and 6 (15%) among heifers. Fourteen buffalo cows and 30 heifers that did not conceive manifested cyclic estrus at an interval of 22.4 and 20.6 days. The conception rate in the cyclic estrus was 57% and 23.3%, respectively, for buffalo cows and heifers. The overall conception rate over two inseminations was 46.2%, 68% in buffalo cows and 32.5% in heifers. In the control group, five (10%) showed spontaneous estrus and two (40%) conceived during the period of the experiment.     

实验性腹膜炎时内毒素血症及肺脏的变化

目的探讨实验性腹膜炎时,内毒素与肺损伤的变化.方法用酵母多糖A腹腔注射制备大鼠急性实验性腹膜炎模型,随机分为模型组和对照组;观察实验性腹膜炎时,肺损伤变化.结果模型组内毒素、肺匀浆脂质过氧化物,以及白细胞计数均明显增高;而还原谷胱甘肽(GSH)明显降低,与对照组比差异有显著性(P＜0.05).结论实验性腹膜炎时,内毒素的形成、细菌因子的释放及脂质过化与肺损害有一定的联系.     

Effect of one spontaneous estrus cycle (after synchronization with PGF2alpha) on reproductive performance in dairy cows

The objective of the study was to analyze the effect of a spontaneous estrus cycle after synchronization of estrus with prostaglandin F2alpha (PGF2alpha) in dairy cows on the degree of synchronization and reproductive performance. We assigned 557 Holstein cows to two treatment groups. In Group 1 estrus was synchronized by two treatments with 25 mg of Dinoprost-Trometamol in 14-day intervals. Cows were treated 27 to 33 days postpartum (dpp) and 41 to 47 dpp, respectively. Cows in Group 2 were treated with 25 mg of Dinoprost-Trometamol three times in 14-day intervals, starting at 34 to 40 dpp. The second and third injections were administered at 48 to 54 dpp and 62 to 68 dpp, respectively. All cows were inseminated on observed estrus after a voluntary waiting period of 65 days post partum. Thus cows in Group 1 were inseminated on spontaneous estrus and cows in Group 2 on induced estrus. Cows not inseminated at 80 days post partum were palpated per rectum and treated according to a predefined protocol. Herd reproductive performance measures did not differ significantly between groups. The proportion of cows with low serum progesterone levels was significantly higher 3 days after synchronization than 24 days after synchronization (97% vs 39%). The first-service conception rate was 34.8% in Group 1 and 30.7% in Group 2 (P > 0.05). Days open were 113.5 in Group 1 and 110.9 in Group 2 (P > 0.05). It is concluded that postponing artificial insemination for one spontaneous estrus cycle after synchronization decreased the degree of synchronization. This procedure, however, had no effect on herd reproductive performance compared to insemination on first observed estrus after synchronization.     

Delayed termination of third-trimester gestations in dairy cows after treatment with the PGF(2alpha)analog Tiaprost

Six dairy cows of the German Black Pied breed were treated between days 190 and 266 of gestation with 0.75 mg of the PGF(2alpha) analog Tiaprost (Iliren(R)-Hoechst). Luteolysis occurred within 24 hours, with progesterone blood levels dropping to baseline values of about 3.18 nmol/l (l ng/ml), but pregnancies were terminated by spontaneous abortions or premature parturitions only after an average of 24.2 days (range 5 to 50 days) after treatments. Four of six deliveries were premature and all deliveries were preceded by a rise in blood estrogen levels which commenced 1 to 12 days prepartum and peaked intrapartum. Unsuccessful attempts were made to induce this estrogen rise earlier by using treatments with Tiaprost, PGF(2alpha)-THAM or estradiol benzoate; treatments with a progesterone-releasing intravaginal device did not prevent the estrogen rise. Abortions and parturitions were spontaneous or by slight pulling. The placenta was retained in all six animals. Two immature fetuses were stillborn, and one immature born calf died three hours after birth.     

Chemical properties of bovine cervical mucus during normal estrus and estrus induced by progesterone and/or PGF2alpha

Ninety-two Friesian cows were used to determine the chemical properties of cervical mucus during normal estrus and estrus induced by progesterone (P4)-releasing intravaginal devices (PRID) and/or prostaglandin F2alpha. The animals were assigned to 4 groups (no treatment, a PRID for 12 days plus injection of 1000 IU PMSG at the removal of PRID, a double i.m. injection of PGF2alpha 11 days apart, or PRID for 7 days plus an im injection of PGF2alpha 24 h before the removal of PRID). A number of cows with normal estrus exhibited three consecutive estrous cycles after delivery. Cows that had not shown estrus for 3 months after delivery had their ovaries palpated twice at 10-day intervals, to determine their ovarian activity. Then PRID and/or PGF2alpha was administered in cows that had a palpable corpus luteum in one of the two palpations (cyclic cows). A double artificial insemination (AI) was performed to the cows of the three induced-estrus groups, while the cows with normal estrus received only one AI. Cervical mucus samples were collected from all cows 5 to 30 min before the first AI. Additionally, samples of cervical mucus were collected from 20 cows during their first estrus after the induced one. The results are summarized as follows: 1) The biochemical properties of cervical mucus in the first three estrus periods after delivery were similar. 2) These properties were similar both in normal estrus after delivery and in the first estrus after an induced one. 3) Glucose and fructose concentrations for normal estrus were similar to those for induced estrus groups. 4) Total protein and cholesterol concentrations were significantly lower (P < 0.001) in normal than in induced estrus, while no difference was found among the induced estrus groups. 5) Pregnancy rates of the cows did not differ significantly among the normal and the induced-estrus groups. 6) The percentages of cows in the induced-estrus groups that produced cervical mucus with total protein and cholesterol concentrations similar to those for the normal estrus groups was very low.     

Rapid-eye movement sleep and muscarinic receptor binding in rats are augmented during withdrawal from chronic scopolamine treatment

The purpose of this study was to determine whether a seven day, once-daily morning administration of scopolamine produces upregulation of muscarinic receptors and augments REMS during withdrawal. After obtaining two, six-hour baseline sleep recordings, beginning at 0900, independent groups of rats were administered either scopolamine or saline every morning for seven days. Six hour sleep recordings were obtained following the first and seventh day of injection and during the two subsequent withdrawal days. After obtaining the last sleep recording the rats were sacrificed and the following brain areas removed: cerebral cortex, hippocampii, caudate nuclei, brainstem, and cerebellum. 3H-QNB was used as the ligand to assess for changes in muscarinic receptor binding. Compared to baseline, scopolamine produced a significant decrease in REMS during the period of drug administration. During the withdrawal days, however, REMS increased during the morning period. Compared to the saline group, the scopolamine treated animals had increased muscarinic receptor binding in the caudate and hippocampus; no significant change in receptor density was observed in the cortex, brainstem or cerebellum.     

Does exogenous progesterone and oestradiol treatment from the mid-luteal phase induce follicular cysts in goats?

The purpose of the present study was to investigate the effects of exogenous ovarian steroid treatment, which is known to induce follicular cyst experimentally in cows, on ovarian activity in goats. Eleven female Shiba goats with the length of the normal oestrous cycle (approximately 21 days) received subcutaneously either 1 ml of ethanol (control group, n=4) or 4 mg of progesterone and 2mg of oestradiol (treatment group, n=7) daily for 7 days beginning on day 14 of the oestrous cycle (day 0=ovulation). Ultrasonographic images of the ovary and blood samples were collected daily to monitor the ovarian activity. Ovulation was observed before 1 day after the end of treatment in the control group. In the treatment group, no detectable structures of follicles or corpus luteum (static ovarian condition) were found for 6.0+/-1.4 days (mean+/-S.D.) after the end of treatment. Then, detectable follicles appeared and ovulation was observed in all animals of the treatment group. There was no significant difference in the maximum diameter of the ovulatory follicle between the control and treatment group (4.7+/-0.4mm versus 5.1+/-0.7 mm). The large non-ovulatory follicles, which grew more than 10mm in diameter were observed after the static ovarian condition in one goat of the treatment group, whereas no turnover of the cystic follicular structures was found. The length of the inter-ovulatory intervals in the treatment group was significantly longer than that in the control group (38.4+/-7.4 days versus 20.3+/-0.5 days, P<0.05). The present results demonstrated that the exogenous treatment of progesterone and oestradiol, which was adapted from the follicular cyst model in cows, did not induce follicular cysts in goats, suggesting that there is/are different mechanism(s) mediating the occurrence of follicular cysts between cows and goats.     

Acute Phase Response in Dairy Cows with Experimentally Induced Escherichia coli Mastitis

Six Finnish Ayrshire cows were challenged intramammarily with 1500 CFU of Escherichia coli (E. coli) into single udder quarters, and the challenge was repeated into contralateral quarters 3 weeks later. All cows received flunixine meglumine once, and 3 of them were also treated with enrofloxacin. At the 2nd challenge, treatments were changed vice versa. The development of mastitis was followed by monitoring of systemic and local clinical signs, and with serial milk and serum samples. Intramarnmary challenge with E. coli produced clinical mastitis in all cows, the severity of the disease varying greatly between the animals. No significant changes between the 2 treatment regimens or sequent challenges were found for any of the clinical parameters. The response of each cow followed the same pattern after both challenges; three of the cows became mildly and the other 3 either moderately or severely affected. Two severely affected cows had to be euthanized because of severe mastitis. Serum haptoglobin and amyloid-A concentrations peaked 2–3 days after bacterial challenge. Serum haptoglobin did not correlate with the severity of the disease. Serum amyloid-A rose gradually in the severely affected cows, and significant differences were found between severely versus moderately or mildly affected cows at day 4. Serum tumor necrosis factor alpha concentrations increased only in the severely affected cows. Serum Cortisol response was prolonged in the severely diseased animals, and was significantly lower after the second challenge. Serum nitrite/nitrate concentration increased in the severely affected cows. This indicated excess nitric oxide production during acute E. coli mastitis. Strongly decreased milk production, and high bacterial growth in the infected quarters were best predictors for the outcome from acute E coli mastitis.     

Effects of the presence of a dominant follicle and exogenous oestradiol on the duration of the luteal phase of the bovine oestrous cycle.

The presence of a developing dominant follicle may be a factor in the control of the luteolytic cascade mechanism and the number of follicular waves during the bovine oestrous cycle. In this study, ovaries of all animals were examined once a day by transrectal ultrasonography. It was expected that heifers (n = 18) would have two follicular waves if the second wave occurred later than day 10 after oestrus (Expt 1) and that cows (n = 14) would have three waves if the second wave occurred on or before day 10 (Expt 2). The objective of Expt 1 was to determine if absence of a large follicle late in the luteal phase delays luteal regression in heifers that are expected to have two follicular waves. Nine heifers were injected i.v. with 10 ml charcoal-treated bovine follicular fluid three times a day for 4 days, starting on the day after initiation of the second follicular wave, to delay growth of the second wave dominant follicle. Nine heifers were injected with 0.9% NaCl as controls. The duration of the luteal phase (calculated as the number of days that serum progesterone was > 0.5 ng ml-1) was greater (P < 0.01) in the follicular fluid-treated group compared with the controls (18.7 versus 14.1 days). FSH and follicular growth were suppressed during the period of injection of follicular fluid (P < 0.01 and 0.03, respectively). The objective of Expt 2 was to determine the effect of increased oestradiol on the duration of the luteal phase in cows that were expected to have three follicular waves. Seven cows were injected i.m. three times a day for 4 days with 1 ml oestradiol (100 micrograms ml-1 in corn oil) and seven cows were similarly injected three times a day with 1 ml 0.9% NaCl (control) starting the day after cessation of growth of the second wave dominant follicle. Luteal phase duration was shorter in oestradiol-treated animals than in the controls (14.0 versus 19.0 days; P < 0.04). Serum oestradiol concentrations were higher in the oestradiol-treated group during the period of injection (P < 0.01). In summary, luteolysis was delayed when follicular growth was suppressed with follicular fluid (Expt 1). Exogenous oestradiol administration during the development of uterine oestradiol responsiveness initiated luteolysis earlier compared with control animals (Expt 2).     

Ovarian function in Holstein cows immunized against pregnant mare serum gonadotrophin

Six Holstein-Friesian cows were immunized against pregnant mare serum gonadotrophin (PMSG) using Freunds' adjuvant during the mid-luteal phase of the estrous cycle. Antibody response was maintained by five booster immunizations at 2- to 3-wk intervals. Four cows were treated with a single intramuscular injection of PMSG (2350 I U) 107 d after primary immunization. Cloprostenol (500 ug) was administered at 56 h and 72 h after the treatment with PMSG; the cows were inseminated three times at 12-h intervals starting 56 h after cloprostenol treatment. Five days after insemination, the animals were slaughtered and their reproductive organs were recovered to quantify the population of corpora lutea and unovulated follicles (>10 mm dia). Antibody titres and progesterone concentrations were determined from blood samples collected either on alternate days or twice a week. Initially, progesterone concentrations were measured in milk samples. All cows produced antibodies, and titres were elevated within 6 to 9 d following each booster immunization. After each boost, however, the antibody titres declined rapidly. Progesterone concentrations declined to below 1 ng/ml after two weeks of initial immunization and remained low throughout the study, except in one cow that ovulated on Day 75. All animals were observed to have large follicular cysts during this period. Treatment with PMSG induced a single ovulation in one cow. Ovulations were neither induced by PMSG nor observed in any of the other animals. In PMSG-treated animals, the mean number of large follicles (5.0) was greater than in those which were not treated (2.0). The results of this study suggest that low titres of antibodies against PMSG are sufficient to disturb ovarian activity, result in follicular cysts and block multiple ovulations in response to exogenous PMSG.     

Evaluation of drug effects on spinal cord injury--an experimental study in monkeys.

Contusion injury is produced experimentally in anaesthetised monkeys by weight drop method. A group of animals having laminectomy alone served as sham controls. Drugs were administered 30 min after injury initially. Naloxone and nifedipine were administered as single dose administration immediately after injury. Dipyridamole and DMSO were administered daily for a period of 1 week. Acetylcholinesterase (AchE) was estimated in 2 spinal tissue segments, S1-at the site of injury and S2-the segment above the site of injury, at the end of 1 week after sacrificing the animals. Contusion injury produced significant decrease in specific activity of AchE in the traumatised segment of the experimental animals. The non-traumatised adjacent segment did not show any significant change. Nifedipine, naloxone and DMSO produced a decrease in AchE activity in S1 and S2 segments. Monkeys developed paraplegia after contusion injury. A score 2+ was observed after 1 week as compared to the score of 4+ of sham controls. Single dose administration of naloxone seemed to reverse the motor deficit by getting a score of 3+; other drugs did not produce any beneficial effect on motor deficit.     

The integration of the transfer of frozen embryos with artificial insemination in a commercial beef herd

This trial was designed to examine the integration of the transfer of frozen embryos and artificial insemination (A.I.) in a commercial herd of beef cows. Embryos were collected nonsurgically from 15 superovulated cows and all embryos judged viable (n = 69) were frozen in 0.25 ml plastic A.I. straws. Glycerol was used as a cryoprotectant and the embryos were frozen with omission of the traditional "seeding" step. On three consecutive days immediately preceding the onset of a 60-day breeding season, 54 embryos were transferred to multiparous cows with calves at foot. The remaining 82 cows in the same herd were used as controls. Cows receiving embryos were maintained under observation, but not inseminated for 21 days, after which cows exhibiting signs of estrus were inseminated up to Day 60. Cows in the control group were inseminated at observed estrus throughout the 60-day period. The overall pregnancy rate for the experimental and control groups did not differ (77.8 % and 73.2 % respectively). Of the experimental cows, 24.1 % conceived to the embryo transfer, and 53.7 % to A.I. The mean calving to conception interval for the experimental cows was 96.3 days (median 101 days) and for the control cows it was 92.3 days (median 88 days). The calving pattern in the experimental cows was biphasic, calvings resulting from embryo transfer of A.I. accounting for the two peaks. Reconception rates in the following breeding season were not different between the embryo transfer or A.I. groups or between experimental and control herds. Weaning masses of calves born of embryo transfer were significantly higher than the other groups, but calves resulting from A.I. in the experimental herd were not different from calves in the control herd. It was concluded that the transfer of frozen embryos could be successfully integrated into an A.I. program with a limited breeding season without detrimentally affecting the overall reproductive performance of the recipient herd.     

Ultrasonic cervimetry to study the dilatation of the caudal cervix of the cow at parturition

The objective of this study was to investigate the temporal changes in dilatation of the caudal cervix during induced calvings (n = 5). We used ultrasound cervimetry, allowing the continuous recording of the distance between a transmitting and receiving ultrasound crystal, which were implanted opposite to each other on the caudal rim of the cervix. We started recording between 19 and 21 h after injecting a prostaglandin analogue (PG) on day 272 of gestation. A fluid-filled catheter had been introduced transcervically between the fetal membranes and the uterine wall for measurements of intra-uterine pressure (IUP). While the characteristics of calving varied widely between the five animals, it appeared possible to divide the process of dilatation into four phases. During the latent phase, which lasted until 25-43 h after PG, no net gain in dilatation occurred. We found an acceleration phase (4.3-6.8 h), in which the dilatation rate speeds up (0.49-0.84 cm/h) in three of the cows. During the phase of maximum slope (lasting 0.5-4.8 h), we measured an even higher rate (1.47-8.48 cm/h), decreasing again during the deceleration phase (rate 0.24-2.28 cm/h) in four cows. The quality of the IUP measurements precluded us from continuously investigating the relationship between cervical dilatation and uterine contractions. However, short term simultaneous recordings revealed that the cervical opening changed momentarily in the absence of IUP during the latent phase, while during the phase of maximum slope, temporary changes of dilatation coincided with uterine contractions. We concluded that the method of ultrasound cervimetry used in this study provides a valuable way to study the process of cervical dilatation in parturient cows in vivo.     

Active stabilization of electrodes for intracellular recording in awake behaving animals

Intracellular recording is a powerful electrophysiology technique that has revealed much of what is known about the biophysical properties of neurons. However, neuronal properties are strongly affected by activity dependent and modulatory influences, making it essential, ultimately, to study these properties in behaving animals. Unfortunately, intracellular recording has only been widely applied in vitro, since cardiac and respiratory pulsations make intracellular recording difficult in vivo. In awake behaving animals, spontaneous movements make intracellular recording nearly impossible. Here I present a novel technique to dynamically stabilize the position of a recording electrode relative to the brain. Physiological signals that are predictive of brain motion at the recording site, such as the electrocardiogram (EKG), respiratory pressure, or cranial motion, are used to control a piezoelectric manipulator, making possible stable intracellular recordings in awake active animals.