Strain differences in the branching of the sciatic nerve in rats

The sciatic nerve in the rat is the site most often used for peripheral nerve regeneration studies. The length of sciatic nerve available for research, however, depends on the point at which the sciatic nerve divides into the peroneal and tibial nerves. In the present study, the hind limbs of 150 adult male rats of five different strains (Sprague-Dawley, Fischer 344, Wistar-Han, Lewis and Nude) were analysed with regard to femur length, the point at which the sciatic nerve divides into the tibial and peroneal nerves, and where these are surrounded by the same epineurium, and the point at which they are encased in individual epineurial sheaths. The results indicate that the lengths of sciatic nerve are fairly constant in all strains of rats. In absolute terms, they amount to about one-third of the length of the femur for stretches of undivided sciatic nerve, and up to nearly half of the femur length for stretches where the tibial and peroneal nerves are already present, but are still enclosed by the same epineurium. In 61.7% of the hind limbs examined in Fischer rats, however, no sciatic nerve could be seen as such, but only in the form of its successors surrounded by the separate epineuria. This makes it highly advisable not to use male adult Fischer rats in peripheral nerve regeneration studies with the sciatic nerve as the point of focus.     

Endocrine mechanisms responsible for different follicular development during the estrous cycle in Hatano high- and low-avoidance rats

Hatano high- and low-avoidance rats (HAA and LAA strains, respectively) were selected and bred according to the avoidance rate in a shuttle-box task. Although they have clear strain differences in ovarian function, their endocrine mechanisms still remain to be clarified. Differences in female reproductive endocrinology between the strains were investigated by means of measuring the plasma concentration of reproductive hormones during the estrous cycle. LAA rats showed approximately threefold lower basal and surge levels of LH, a more than fourfold lower level of FSH surges and higher levels of inhibin A and inhibin B during the estrous cycle compared with the levels seen in HAA rats. The concentration of estradiol-17β in the proestrous stage was significantly lower in LAA rats than in HAA rats. Additionally, LH and FSH secretions from primary cultured anterior pituitary cells with or without in vitro GnRH stimulation were lower in the cells derived from LAA rats and, in terms of FSH secretion, were unresponsive to GnRH in contrast to cells derived from HAA rats. Although an increased number of preantral follicles in diestrus were observed in LAA rats, number of hCG-induced ovulation was lower in LAA rats. LAA rats may have much more follicle growth during the early stage of folliculogenesis, but most follicles might not grow into mature follicles. These results strongly suggest that the strain difference in ovarian function of these two Hatano rats is due to the difference in the regulation of hypothalamo-hypophyseal system for gonadotropins secretion.     

Strain differences in morphometrical characteristics of rat kidneys

To clarify the strain differences in the morphology of the rat kidneys, we investigated the morphometrical characteristics of the kidneys of Slc:Wistar, Slc:SD, and F344/NSlc rats. The diameter of the renal corpuscles in female F344/N rats is smaller than that in female Wistar rats. Although sex differences (males>females) were shown in SD and F344/N rats, no effects of castration were detected in any of the groups. Strain-dependent differences in the percentage of renal corpuscles with a cuboidal parietal layer were found in both male and female groups. The highest percentage of them was noted in male Wistar rats. Effects of castration were observed in female Wistar and male F344/N rats, and the values after castration were significantly higher than those in the intact animals. As for the number of proximal convoluted tubular nuclei, no strain differences were detected in either the male or female groups. Although a sex difference was found in SD rats (female>male), no effects of castration were detected in any of the groups. In female F344/N rats, numerous numbers of PAS-positive granules, which were observed in the proximal convoluted and straight tubular epithelia, were noted. Orchiectomy induced an increase of these granules in male SD and F344/N rats, but ovariectomy showed no effects on them in any strains. This is the first study to clarify the strain differences in the morphological characteristics of the kidneys in ordinary rat strains.     

Prevalence and incidence of serum magnesium abnormalities in hospitalized cats

Total serum magnesium concentration ([Mg2+]s) was prospectively determined for 57 cats admitted to the intensive care unit (ICU) of the Cornell University Hospital for Animals. Data were collected and analyzed to determine the following: prevalence and incidence of [Mg2+] abnormalities, medical disorders associated with altered [Mg2+]s, association of altered [Mg2+]s with other electrolyte abnormalities, length of hospitalization for cats with abnormalities of [Mg2+]s versus those with normal [Mg2+]s, and survival of cats with abnormal [Mg2+)s versus those with normal [Mg2+]s. The point prevalence of magnesium abnormalities was 26%, the period prevalence was 46%, and the cumulative incidence was 23%. Hypermagnesemia was associated with abnormalities of serum potassium (P = .04) and phosphate (P = .01) concentrations. Abnormalities of [Mg2+]s were not associated with abnormal serum concentrations of Na+, Ca2+, or Cl-. On admission. hypomagnesemia was detected in cats with gastrointestinal, endocrine, and other disorders; hypermagnesemia was detected only in cats with renal disease, obstructive uropathy, or neoplastic disease. The median hospital stay for cats that developed abnormal [Mg2+]s after admission was longer than for cats that remained normomagnesemic (5 versus 4 days, respectively; P = .03). Despite the longer hospital stay, the survival of these cats was lower than that of normomagnesemic cats (54 versus 77%; P = .05). When all cats were considered, the survival of cats with abnormal [Mg2+]s also was decreased compared with normomagnesemic cats (62 versus 81%; P = .05). We conclude that abnormalities of [Mg2+]s may affect morbidity and mortality of affected cats.     

Strain differences in whole-body protein turnover in the chicken embryo.

1. Whether or not there is a strain difference in embryonic whole-body protein turnover rates was tested using the chicken embryos of Rhode Island Red carrying a sex-linked dwarf gene (dwarf), White Leghorn (layer), and White Cornish X White Plymouth Rock (broiler) strains on day 12 of incubation. 2. Whole-body protein synthesis was estimated by injecting L-[15N]-phenylalanine either intraperitoneally or intravenously on day 12 of incubation in order to investigate the effect of the route of isotope administration. The results showed that the values for fractional and absolute synthesis rates were approximately 13% higher by intravenous injection than by intraperitoneal injection. 3. Whole-body protein turnover, both in terms of fractional and absolute rates, was significantly faster in dwarf than in broiler embryos, with intermediate values in layer embryos, although no growth differences were observed on day 12. 4. Difference in egg weight, measured before incubation, did not affect protein turnover. 5. It was concluded that the strain difference manifested in whole-body protein turnover of the chicken embryo would probably be a reflection of differences in genetic background.     

Strain differences in the number and size of glomeruli in domestic fowl

1. An investigation was made into strain differences and the effect of the type of drinker on the number and size of glomeruli of Single Comb White Leghorn pullets. 2. The Dekalb XL strain had more glomeruli per kidney and per g of kidney than the Hyline W-36. The glomeruli of the Dekalb XL were smaller in circumference. There were no significant differences in the absolute or relative weights of the kidney. 3. The type of drinker, bell or trigger-cups, had no effect on the body weight or those kidney variables studied.     

Clinical and morphological studies on spontaneous rupture of the gastrocnemius tendon in broiler breeders

1. Clinical and morphological studies were performed in 8 broiler breeder flocks (one hybrid) originating from two different farms in Bulgaria, with an incidence of lameness in female birds between 3 and 4% on one farm and 7 and 8% on the other. Clinical and morphological studies were performed. 2. Ruptured gastrocnemius tendons were observed in 78 broiler breeders, 24 to 31 weeks old with signs of lameness, selected for pathoanatomical study from different flocks. Unilateral ruptures predominated, over 80%. 3. A histological study of 20 samples from one farm and 8 samples from the other revealed that lesions varied between birds. In about 50% of them, haemorrhages, dystrophic and necrobiotic changes in tendons were present. In the other 50% of cases, the resolving haematoma and ruptured tendon were surrounded by fibrous tissue growth. No inflammatory changes were detected.     

Seasonal differences in the incidence of infection with Fasciola gigantica in cambodian cattle

Farmer's cattle were treated with triclabendazole and used as tracer animals to detect new infections with Fasciola gigantica in three villages located on the bank of the Bassac River (a major tributary of the Mekong River) and in a fourth village located on farmland away from the river, from April 1999 until January 2001. The month of infection was estimated by subtracting 4 months from the date when eggs of F. gigantica were detected in faeces. Farmers were interviewed each month to record the nature of the agricultural and animal husbandry activities that occurred during the previous month, especially events that might have exposed cattle to infection with F. gigantica. Results support the conclusions that infection of cattle in riverbank villages acquired from about August or September until November originated from herbage and water in irrigation canals and dams on the riverbank, and that the progressively increasing monthly incidence from December until April (up to 87% per month in April 2000) was derived from herbage and water in recently harvested rice fields and lakes adjacent to the riverbank. The abrupt cessation of new infection in riverbank villages in May coincided with flooding of low-lying land, the movement of cattle to land above flood height on the riverbank, and a change of diet to dry-land crop residues, stored dry rice stalks, and herbage and water that were unlikely to contain metacercariae. It was concluded that snails in dams and canals on the riverbank became infected with F. gigantica after cattle were moved to the riverbank in May, and cercariae shed from these snails provided the new infections that occurred in cattle in August and September. In the village located away from the river, infection of cattle between September and March coincided with the rice harvest, supporting the conclusion that feeding of fresh rice stalks and stubble after the rice was harvested was the main source of infection. The low monthly incidence observed (up to 6.4% per month) was consistent with the hypothesis that snails did not survive in the dry rice fields between crops and that few snails would have been available from the small number of aquatic refuges that persisted through the dry season to recolonize rice fields during the wet season. Between April and August there was no opportunity for new infection because cattle were fed forage from around houses and headlands, and on dry-land crop residues and stored dry rice stalks. Control of fasciolosis was proposed using a single treatment of cattle with triclabendazole in riverbank villages in May when cattle were moved to the riverbank, and after harvest of the last rice field in villages located away from the river.     

Effects of age and season on the type and occurrence of sperm abnormalities in Nubian bucks

Effects of age and season on type and occurrence of sperm abnormalities were examined in semen samples collected from 3 groups of Nubian bucks at ages of 4 to 9 months, 10 to 21 months, and 39 to 50 months. The average total percentage of sperm abnormalities at the onset of puberty (141 +/- 4 days) was 64.6 +/- 14.8% (head, 19.5 +/- 13.6%; middle piece, 17.2 +/- 9.3%; and proximal protoplasmic droplets, 14.6 +/- 10.5%), but this improved rapidly and was reduced to 12.5 +/- 7.5% by 8 months of age (head, 1.9 +/- 4.5%; middle piece, 4.6 +/- 2.8%). Further increase in age, at least up to 4 years, did not reveal a significant effect (P less than 0.05) on the type or percentage of total abnormalities. Similar to age, a comparison of data among seasons did not reveal a significant effect on the type or occurrence of sperm abnormalities in 10- to 21-month-old or 39- to 50-month-old bucks. Seemingly, Nubian bucks started producing good quality semen at 8 months of age, and season did not influence sperm abnormalities.     

Strain differences in the erythrocyte and spermatozoan head dimensions of White Leghorn cocks

Differences amongst the length, breadth and area of erythrocyte nuclei, and the length, breadth, shape and area of the heads of spermatozoa were observed in six strains of White Leghorn cocks. Erythrocyte nuclear and spermatozoan head dimensions were negatively correlated. The negative correlations were explained on the basis of cellular oxidation rate.     

Effect of season and supplementation on percentage live sperm and sperm abnormalities in Horro (Zebu) bulls in sub-humid environment in Ethiopia

A total of 32 Horro (Bos indicus) bulls, with an average initial body weight and age of approximately 211 kg and 6 years were evaluated. The bulls were divided into two treatment groups. One group was given a supplementary concentrate at a rate of 1.5 kg/day and the second group served as the control and received no supplementation. The observation period lasted for 50 weeks. Semen was collected every two weeks by mean of electrical stimulation with the aid of an electro-ejaculator. The percentage of abnormal sperm (total abnormalities, head, midpiece and tail) remained lower in the supplemented group than in the non-supplemented group. The percentage of live sperm tended to be higher in the supplemented group throughout the 50-week trial period. Until week 17 of the trial there were no significant differences; however, starting at week 18 there were significant differences between the two treatment groups except for week 26. Thereafter, significant differences were recorded until week 38; from week 40 no significant differences were observed between the two groups in respect of percentage of live sperm (except for week 48). Season (week) during which the semen samples were collected had no significant effect on the percentage of abnormal sperm in both treatment groups (supplemented and non-supplemented). At the start of the trial the nutritionally supplemented group had a higher occurrence of sperm abnormalities (11.4% ± 1.1%) compared to 8.3% ± 1.3% in the control group. Thereafter, sperm abnormalities declined rapidly in the supplemented group (except for week 50). The sperm abnormalities for the non-supplemented group showed a tendency to increase during the entire observation period.     

Fertility of a stallion with low sperm motility and a high incidence of an unusual sperm tail defect

At the beginning of the breeding season an eight-year-old standardbred stallion had semen with virtually zero sperm motility and an approximately 90 per cent incidence of midpiece and tail defects. The motility of the sperm improved to 7 per cent when semen was collected daily but its morphology did not improve. Electron microscopy revealed that the defects consisted mainly of a loss of microtubules in the axoneme and of disorganised midpieces. A pregnancy rate of 24 per cent per cycle and 44 per cent for the season was achieved in 32 mares after the insemination of whole ejaculates collected from the stallion frequently. The fertility was much higher than would have been expected from the characteristics of the semen. It is concluded that this sperm defect, reminiscent of the 'Dag defect' in bulls and the defect in T-locus mice, does not render the animal infertile.     

The sequential appearance of sperm abnormalities after scrotal insulation or dexamethasone treatment in bulls.

Scrotal insulation and dexamethasone treatment were used as a model to compare the effect of testicular heating and stress on spermatogenesis. Insulation was applied to the scrotum of eight bulls (insulated) for a period of four days, eight bulls were treated daily for seven days with 20 mg dexamethasone injected intramuscularly, and four bulls were untreated controls. Semen from four bulls in each group was collected and evaluated over a six-week period after treatment. Blood samples for testosterone analysis were taken hourly for eight hours at the beginning and the end of the six-week period from the control bulls and before and after treatment from the four insulated and four dexamethasone-treated bulls that were not used for semen collection. At the end of the last blood sampling period, the four bulls in each group were castrated for the collection of testicular tissue for the determination of testosterone concentrations. Basal, peak episodic, and mean serum testosterone concentrations among control bulls, pre and postinsulated bulls, and pretreatment samples of dexamethasone-treated bulls were not different (p > 0.05); however, bulls that had received dexamethasone treatments had significantly lower basal, peak episodic, and mean testosterone concentrations (p < 0.05). Tissue concentrations of testosterone in control, insulated, and dexamethasone-treated bulls were not significantly different but tended to be lower in dexamethasone-treated bulls (p > 0.13). The spermiograms of the control bulls varied insignificantly over the six-week sampling period; however, there was a marked increase in sperm defects in insulated and dexamethasone-treated bulls. The types of sperm defects and the temporal relationships of rises and declines of sperm defects were quite similar for both treatments. All bulls recovered to approximately pretreatment levels of sperm defects by six weeks after the initiation of treatment. Results indicate that two of the most common types of insults to spermatogenesis in bulls, heat and stress, result in similar spermiograms.