Expression of Occludin in Testis and Epididymis of Wild Rabbits, Lepus sinensis coreanus

Tight junctions (TJs) in inter-Sertoli junctional areas and epididymal epithelia build up the blood–testis barrier (BTB) and the blood–epididymal barrier (BEB), respectively. In this study, the expression of occludin, an integral member of the TJs, was examined in testis and different regions of epididymis of Lepus sinensis coreanus , an Korean wild rabbit species. In testis, intense occludin immunoreactivity was found in the basally located inter-Sertoli junctional area together with diffused immunoreactivity of occludin in the cytoplasm of Sertoli cells. It can be suggested that occludin is one of the robust elements of BTB in seminiferous tubules of rabbit testis. In proximal and distal caput epididymis, occludin immunoreactivity was found in the lateral as well as apical contacts of epithelial cells. In corpus epididymis, intense occludin immunoreactivity was found in the basolateral as well as apical contacts of epithelial cells together with cytoplasmic signal. In cauda epididymis, occludin immunoreactivity in luminal epithelia was relatively strong but largely found in the cytoplasm. This suggests that intriguing regulatory mechanisms differentially recruit occludin to the TJ in the different regions of epididymal epithelia. The differences in the subcellular localization as well as expression levels of occludin among the epididymal segments may reflect differential paracellular permeability of epithelia along the epididymal tubules and be correlated with sperm maturation in rabbit. In Western blot, a major form of occludin was MW 62 kDa together with small fragments of MW 34–39 kDa in testis and epididymis, suggesting the peptide cleavage of occludin. This is the first report on the molecular nature of TJs in a wild rabbit testis and epididymis.     

Are the concepts of andragogy and pedagogy relevant to veterinary undergraduate teaching?

Knowles and colleagues have described teaching methods as being either teacher centered, with dependent learning (pedagogy), or learner centered, with independent learning underpinned by the learners' experience and intrinsic motivation (andragogy). This paper argues that both models can be recognized within veterinary undergraduate programs. Veterinary students enter the program with a high level of intrinsic motivation and are prepared to invest considerably in comprehending the material that is presented to them. While this should result in learners whose behavior fits the assumptions underlying andragogy, information overload, poor communication of the relevance of material, teaching by transmission, and examination by memorization often confine learning to the dependent learning characteristic of pedagogical approaches. Students' experience and practical ability should develop as they progress through the program. Drawing upon experience provides opportunities for both fleshing out and putting in context the declarative knowledge from the didactic components of the curriculum. Where this is achieved (either in the clinical or preclinical curriculum), students' motivation and interest is stimulated, resulting in andragogical responses of enhanced motivation and engagement with the subject. Pedagogy and andragogy can, however, be complementary, rather than antithetical. Students enter a new subject with minimal experience and little knowledge about it, so a pedagogical methodology may be the most efficient way of initiating understanding. However, as understanding develops, an andragogical method becomes more appropriate, progressively developing students' independence of learning. The cycle may repeat itself during the program, with the balance changing along with changes in knowledge, goals, experience, and context.     

Element and polychlorinated biphenyl deposition and effects in sheep fed cabbage grown on municipal sewage sludge.

Sheep were fed a diet containing 30 per cent (dry weight) cabbage which had been grown on municipal sewage sludge from Syracuse, NY for 77 days. Slight increases were found in the concnetration of nickel in kidney, copper in liver and cadmium in certain animal organs as compared to those in sheep fed a control ration containing cabbage grown on soil. Polychlorinated biphenyls were also found at higher levels in the sludge-grown cabbage and in the livers of the respectively fed sheep as compared to controls. An increase in liver weight, proliferation of hepatic smooth endoplasmic reticulum and various degenerative changes were noted in the livers of the sheep fed the sludge-grown cabbage ration as compared to the controls.     

Using time domain reflectometry to characterize cattle and pig slurry infiltration into soil

Abstract. The rate and extent to which cattle or pig slurry infiltrates into soil after application is one of the important factors determining the rate and extent of subsequent ammonia (NH₃) volatilization. Better characterization of the infiltration process is required to improve predictive models of NH₃ losses after land spreading. This paper describes a laboratory system using time domain reflectometry to measure slurry infiltration into soil columns. This system enabled semi-continuous, non-destructive infiltration measurements to be made, assessing the influence of slurry type, dry matter (DM) content, soil type and soil water tension. Differences were noted in the infiltration behaviour of cattle and pig slurries. For cattle slurry, DM content (range 1.7–7.1%) was the main influencing factor. Infiltration rate rapidly decreased with increasing DM content and there was no influence of soil type or water tension. For pig slurry, all of the slurry infiltrated into a sandy clay loam soil within the first hour, regardless of DM content (range 1.5–4.7%), whereas only 60% infiltrated into a clay loam soil over the same time period (slurry DM content 2.1%).     

Postpartum gonadotropin secretion in Holstein-Friesian dairy cows differing genetically in liveweight

AIM: To determine whether there are differences in postpartum gonadotrophic activity between strains of Holstein-Friesian dairy cows genetically selected on mature liveweight that might explain differences between the strains in fertility, and the interval between calving and the resumption of ovarian follicular activity. METHODS: Mixed-age Holstein-Friesian cows fed generous allowances of ryegrass/white clover pasture, and genetically selected for heavy (H) or light (L) mature liveweight, were given 10 microg buserelin on Days 21, 28, 35 and 42 (Experiment 1a; n=8/group), or Days 7, 14, 21 and 28 (Experiment 1b; n=8/group) postpartum. The same dose of buserelin was also given to first-calved heifers from each strain (Experiment 1c; n=6/group) on Days 7, 14, 21, and 28 postpartum. Luteinising hormone (LH)concentrations were measured in serial blood samples that were taken for up to 240 min after administration of buserelin. In Experiment 2, serial blood samples were taken at 15-min intervals from H and L cows (n=7/group) over 8 h on Days 14, 21, 28 and 35 postpartum, to examine the endogenous secretion patterns of LH and follicle stimulating hormone (FSH).The time-course of the restoration of positive feedback between oestradiol and LH was examined by giving 1 mg oestradiol benzoate(ODB) 48 h after administration of 500 microg cloprostenol to mixed-age cows from each strain on Days 7 and 21 (n=8/group), or 14 and 28 (n=8/group) after calving (Experiment 3). Relationships between nutrition and the restoration of positive feedback were studied by giving 0.75 mg ODB/500 kg liveweight on Day 17 or 18 after calving to pure-bred Holstein (OSH) and New Zealand Friesian (NZF) cows that were fed either pasture (n=12 OSH, 12 NZF) or a total mixed ration (TMR; n=13 OSH,12 NZF) (Experiment 4). Plasma LH and FSH concentrations were measured in samples collected for 42 h (Experiment 3) or 48 h (Experiment 4) after treatment with ODB. Milk progesterone concentrations were measured 3x weekly to define the reproductive status of animals in each experiment. Conception rates were recorded for animals in all of the experiments. RESULTS: First-service conception rates were lower (p<0.05) in H than L cows (46% vs 59%). In Experiments 1b and 1c, LH response to buserelin increased between Days 7 and 28 postpartum (both p<0.001), but did not differ between strains (p=0.77 and p=0.19, respectively). In Experiment 1a, LH responses to buserelin did not change between Days 21 and 42 postpartum, but overall mean peak concentrations were significantly(p<0.001) greater in L than H cows. In Experiment 2, anoestrous H cows had higher mean (p=0.004) and episodic (p=0.001) concentrations of LH than did L cows, but in cows that had active corpora lutea there were no such differences. There were no differences in FSH concentrations between strains. LH secretion in response to exogenous oestradiol (Experiment 3) increased between Days 7 and 28 postpartum (p<0.001), but there were no differences between strains. Responses were also similar in OSH and NZF cows on Day 17 or 18 postpartum, although there was a significant effect of ration upon the proportion of cows that exhibited an LH surge (20/24 cows on grass vs 12/25 on a TMR; p=0.005). CONCLUSION: These results confirm that H cows have poorer first-service conception rates than L cows, but do not support an hypothesis that there are major differences between these strains of Holstein-Friesian dairy cows in the rate of restoration in the hypothalamo-pituitary axis. However, in anoestrous cows, differences between strains in the endogenous release of LH maybe related to an earlier onset of oestrous cycles in H animals.     

Anatomical, cytogenetic and behavioural studies of freemartin ewes

The external phenotype and reproductive behaviour of 21 freemartin sheep and two male pseudohermaphrodite sheep were recorded with the aim of identifying any characteristics which might be used to predict a failure to breed. The size and shape of the vulva and clitoris, the length of the vagina, the size of the teats, the presence or absence of inguinal gonads, and the ultrasonographic characteristics of the inguinal gonads were recorded. A subjective assessment of the masculinity of each animal's body form was also made, and its behavioural responses to a virile ram and to an oestrus ewe were recorded. A number of physical and behavioural abnormalities were detected but the only consistent finding in all 23 animals was a short vagina which varied in length from 3.1 to 7.0 cm, compared with 10 to 14 cm in normal animals.     

Comparative efficacy of three dry-cow antibiotic formulations in spring-calving New Zealand dairy cows

AIM: To evaluate the efficacy of a dry-cow antibiotic preparation containing cloxacillin plus ampicillin in a formulation that gives a 10-week duration of action, in comparison to products containing cephalonium (10-week action) or cloxacillin alone (7-week action). METHODS: A total of 493 cows were selected from 6 spring-calving dairy herds in the Manawatu region of New Zealand, according to the criteria of the SAMM plan, to receive intramammary antibiotic therapy at the end of lactation (drying off). Cows were randomly allocated to receive 1 of the 3 dry-cow antibiotic products under investigation. Cows were examined twice during the dry period and twice daily during the first 10 days of their subsequent lactation for the presence of mastitis. Milk samples were collected from individual quarters at the time of drying off and at 7 and 28-35 days after calving, for determination of milk somatic cell counts (SCC). Bacteriology was carried out on milk samples taken from cows that developed mastitis during the first 10 days after calving. RESULTS: No cows developed mastitis during the dry period. Sixteen cows developed clinical mastitis within 10 days of calving; there was no difference in incidence between treatments. Streptococcus uberis was the most commonly isolated organism. Mean SCC on Day 7 were lower (p = 0.019) in cephalonium-treated quarters (189.9+/-28.4 x 10(3) cells/ml) than in cloxacillin-treated quarters (388.7+/-71.2 x 10(3) cells/ml); values in quarters receiving cloxacillin plus ampicillin were intermediate (252.0+/-47.0 x 10(3) cells/ml). SCC were similar between treatment groups on Day 28-35. CONCLUSIONS: The use of a combination of cloxacillin plus ampicillin was effective for the prevention of mastitis during the dry and peri-calving-periods in pastured dairy cattle.