Factors influencing the fecal egg and oocyst counts of parasites of wild European rabbits Oryctolagus cuniculus (L.) in Southern Western Australia.

Abundance of intestinal parasites was monitored by fecal egg and oocyst counts for samples of wild rabbits Oryctolagus cuniculus with different levels of imposed female sterility from 12 populations in southwestern Australia. Differences in egg counts of Trichostrongylus retortaeformis between seasons and age groups were dependent on the sex of the host. Pregnancy may have been responsible for these differences because egg counts were consistently higher in intact females than in females surgically sterilized by tubal ligation. Egg counts for Passalurus ambiguus were influenced by season and host age but there were no differences between sexes or between intact and sterilized female rabbits. No differences were detected in the oocyst counts of the 8 species of Eimeria between male and female rabbits or between intact and sterilized females. Seasonal differences were detected in oocyst counts of Eimeria flavescens and Eimeria stiedai. The overwhelming determinant of coccidian oocyst counts was host age, with 6 species being much more abundant in rabbits up to 4 mo of age. There was a suggestion that egg counts of T. retortaeformis and oocyst counts of several species of Eimeria were reduced in populations where rabbit numbers had been depressed for at least 2 yr, but there was no evidence that short-term variations in rabbit numbers had a measurable effect on parasite abundance.

Evaluation of the association of parasitism with mortality of wild European rabbits Oryctolagus cuniculus (L.) in southwestern Australia.

Abundances of the parasitic nematodes Trichostrongylus retortaeformis and Passalurus ambiguus, and 8 Eimeria species were estimated by fecal egg and oocyst output in 12 discrete free-ranging populations of wild rabbits (Oryctolagus cuniculus) in southwestern Australia. Comparisons of parasite egg and oocyst counts were made between those rabbits known to have survived at least 2 mo after fecal samples were collected and those rabbits that did not survive. There were significant negative relationships between parasite egg and oocyst counts and survival when all age groups and collection periods were pooled for several species of coccidia and for T. retortaeformis. However, when the same comparisons were made within rabbit age groups and within collection periods, there were very few significant differences even where sample sizes were quite large. The differences indicated by the pooled analysis for coccidia were most likely due to an uneven host age distribution with respect to survival, combined with an uneven distribution of the oocyst counts with rabbit age. The result for T. retortaeformis was similarly affected but by a seasonal pattern. Parasitism by nematodes and coccidia did not appear to be an important mortality factor in these rabbit populations, at least at the range of host densities we examined. This suggests that other factors must have been responsible for the observed pattern of density-dependent regulation in these rabbits.

Function of hormonally-induced corpora lutea in the domestic cat.

Hysterectomy (3 animals) or diversion of the uterine venous blood from the ovarian vasculature (3 animals) has no effect on the duration of hormonally-induced luteal activity in the pseudopregnant luteal-phase cat (control: 4 animals), suggesting that the uterus exerts no local or systemic influence on the duration of luteal function.

Peripheral progesterone concentrations in the luteal-phase ewe: effects of a beta-adrenergic receptor antagonist and two beta 2-adrenergic agonists.

Peripheral blood samples were collected at 10-min intervals from three conscious sheep in which ovulation had been induced 6-10 days previously using exogenous hormones. Saline was infused into a jugular vein for about 1 h, followed by the experimental drug for 1-2 h and followed by saline again for a further 2 h. The experiments were repeated following induced luteolysis and ovulation. The infusion of a beta-adrenergic antagonist (propranolol) into three conscious luteal-phase ewes decreased (P less than 0.05) the peripheral progesterone concentration in each animal. Infusions of beta 2-adrenergic agonists (ritodrine and salbutamol) increased (P less than 0.05) the progesterone concentration in four out of eight experiments. The beta-adrenergic antagonist decreased the heart rate and the beta 2-adrenergic agonist increased it; the arterial blood pressure and respiratory rate were unaffected. The decrease in the progesterone concentration in response to the beta-adrenergic antagonist suggests that the normal ovarian secretion of progesterone is partly the result of sympathetic stimulation, and that the sympathetic innervation of the ovary may have a physiological role in modulating progesterone secretion.

Influence of adrenergic receptors on ovarian progesterone secretion in the pseudopregnant cat and oestradiol secretion in the oestrous cat.

The infusion of isoprenaline or propranolol into the abdominal aorta of the pseudopregnant cat caused an increase or decrease respectively in the ovarian progesterone secretion rate. These observations suggest that the sympathetic innervation of the ovary has a physiological influence on normal progesterone secretion, and this mechanism may explain stress-related increases in progesterone concentrations. The infusion of isoprenaline or propranolol after the stimulation of follicular growth had no consistent or convincing effect on oestradiol secretion.

Effect of cold and hot ambient temperatures on plasma progesterone concentrations in ewes with intact and denervated ovaries containing experimentally maintained corpora lutea.

Twenty ewes in which maintained corpora lutea had been established were subject to 1 of 3 treatments: denervation of the ovaries by freezing, denervation of the ovaries using the chemical 6-hydroxydopamine, or control. The animals were exposed sequentially to normal (24.5 degrees C), cold (10.7 degrees C), normal (23.8 degrees C), hot (39.4 degrees C) and normal (24.6 degrees C) temperatures, each for 1 week. On the final 3 days of exposure rectal temperatures and heart rates were measured, and on the final day the body weights, respiratory rates, and blood glucose concentrations were measured and a series of 5 blood samples was collected from each ewe for determination of the progesterone concentrations. The progesterone concentration was greatest during the hot period in 8 of the 12 animals, particularly in the ewes with denervated ovaries (6 of the 7 animals). This suggests that high ambient temperatures increase progesterone concentrations non-specifically, and that denervated ovaries are more sensitive to the circulating catecholamines that presumably mediate this effect. The progesterone concentrations were lower (P less than 0.001) in the groups with freezing or chemically denervated ovaries (2.86 and 2.73 ng/ml respectively) than in the control group (3.38 ng/ml), suggesting that the ovarian innervation plays a physiological role in regulating progesterone secretion.

A review of toxicology studies on cyanurate and its chlorinated derivatives.

Chlorinated cyanurates are added to swimming pools as disinfectants. In the presence of water, these materials hydrolyze to yield cyanurate and hypochlorous acid. To evaluate the safety of exposure to these materials, a comprehensive testing program was undertaken. This review summarizes the results of acute and subchronic tests on chlorinated isocyanurates. Findings from acute, subchronic, reproduction, metabolism, mutagenicity, and chronic/carcinogenicity tests on cyanurate are also summarized. Results from these tests indicate that chlorinated isocyanurates are safe for use in swimming pools.

Three-generation reproduction study of rats ingesting up to 10% sorbitol in the diet--and a brief review of the toxicological status of sorbitol.

Groups of 12 male and 24 female 5-wk-old Charles River CD (SD) BR rats (F0) were fed a sucrose-containing ground cereal-based diet in which 0, 2.5, 5.0 and 10.0% (w/w) sorbitol was included at the expense of sucrose. The rats were first mated after 14 wk on the diet. F1a litters were born 19 wk after the start of the study and F1b litters at wk 30. Groups of 12 male and 24 female F1b rats were first mated when 18 wk old. They gave rise to F2a litters after 3 wk and to F2b litters 10 wk later. Likewise, groups of 12 male and 24 female F2b rats were first mated when 18 wk old, producing F3a and F3b litters 3 wk and 10 wk later, respectively. F0 rats were killed 33 wk after the start of the study, F1a in wk 22, F1b in wk 68, F2a in wk 57, F2b in wk 92 and F3a in wk 96. Apart from slight reductions in food consumption in sorbitol-fed F1b males and in body-weight gain in sorbitol-fed F0, F1b and F2b rats of both sexes, treatment was associated with no clinically observed effects. There were no deaths attributable to treatment and no adverse effects on mating performance or pregnancy rates in the parent animals of any generation. Treatment was associated with no consistent adverse effect on any measure of reproductive performance or behaviour during gestation or lactation. No abnormal pups were observed in any generation. Not unexpectedly, caecal enlargement was consistently observed at necropsy of sorbitol-treated rats of all generations and significant rises in serum calcium were observed in F0 males and females exposed to 10% sorbitol and in F1b males exposed to either 5 or 10% sorbitol. Differences between treated and control F3a rats in respect of T3 and TSH levels were probably spurious as they followed no consistent pattern. Similarly, between-group variations in gonadal weight were considered to have no toxicological significance because they lacked consistency and were not accompanied by any histologically-evident changes. Microscopic examination of lesions from F1a and F2a animals, of gonads from F1b and F2b and of selected tissues from the F3a generation revealed no changes of toxicological significance.(ABSTRACT TRUNCATED AT 400 WORDS)

Absence of mutagenic activity for monosodium cyanurate.

The mutagenic potential of monosodium cyanurate was evaluated using in vitro and in vivo tests. All in vitro tests were carried out in the presence and absence of metabolic activation. In each assay, the highest concentration tested generally exceeded the solubility of monosodium cyanurate in the incubation medium. In the Salmonella microbial assay, monosodium cyanurate was not mutagenic towards test strains TA 98, 100, 1535, and 1537 up to a concentration of 10,000 micrograms/plate. Monosodium cyanurate did not induce forward mutations at the TK locus of L5178Y mouse lymphoma cells up to a concentration of 2000 micrograms/ml. No significant increases in sister chromatid exchanges were observed when monosodium cyanurate was incubated with Chinese hamster ovary cells at concentrations up to 1500 micrograms/ml. In an in vivo test, rats were administered monosodium cyanurate by gavage at single dosages up to 5000 mg/kg and killed 24 and 48 hr after dosing. Bone marrow cells were collected and examined for chromosomal aberrations. At the time points examined, there was no evidence of monosodium cyanurate-induced chromosomal aberrations in rat bone marrow cells.

Seasonal, genetic and age variation in non-esterified fatty acid concentrations in the ewe.

Plasma samples were collected at intervals of about 2 weeks from about ten 2 1/2 year old, or older, and five 1 1/2 year old ewes of each of the Scottish Blackface, Finnish Landrace and Tasmanian Merino ewes and were assayed for their non-esterified fatty acid (NEFA) concentrations. The NEFA concentrations showed an increase with time for every animal. The NEFA concentrations and their linear increase was least in the Finnish Landrace animals. The increase with time was greatest in the Merinos. There was no difference between the age groups. There was no evidence of any annual, cyclical trend.

Variation in peripheral progesterone concentrations with environmental temperature in ewes on Days 7 and 11 of the oestrous cycle.

Progesterone concentrations in peripheral plasma samples on Days 7 and 11 of oestrous cycles throughout the breeding season showed a negative relationship to the mean minimum environmental temperature for the Days 0-7 and 0-11 respectively of that cycle during which the samples were collected.

Peripheral plasma progesterone and oestradiol concentrations associated with successful and unsuccessful recovery of uterine embryos in rhesus monkeys with and without intra-uterine devices.

Concentrations of progesterone and oestradiol were measured in peripheral plasma samples collected at the time when the uteri of rhesus monkeys with an intra-uterine device (IUD) and those without an IUD were flushed in attempts to recover uterine embryos. The proportion of successful attempts in IUD-bearing monkeys was much lower than in the non-IUD-bearing animals. Steroid measurements indicated that this reduced success rate was not due to an effect of the IUD on the timing of ovulation within the menstrual cycle or to a steroid-mediated disturbance in the rate of embryo transport to the uterine lumen. Successful embryo recoveries were associated with a higher progesterone concentration, suggesting that one reason for failure was that the attempt had been made too close to ovulation. There was no evidence of any asymmetry between the left or right ovaries in their ovulatory or steroidogenic activity.

Uterine histology and prostaglandin concentrations and utero-ovarian venous steroid and prostaglandin concentrations during the luteal phase of the menstrual cycle in baboons (Papio spp.) with or without an IUD.

Arachis oil was infused via the oviducts into the uterus of baboons 6-9 days after ovulation; uterine tissue was collected towards the end of the luteal phase (3-7 days after the oil infusion) for histological assessment of the occurrence of any deciduomal reaction. To exclude the possibility that a variation in the endogenous steroid concentrations was responsible for any observed variation in the incidence of the deciduomal reaction, blood samples were collected and assayed for progesterone and oestradiol-17 beta. The effect of the IUD on endometrial prostaglandin release was examined by measuring PGE and PGF concentrations in uterine tissue and utero-ovarian venous plasma. The IUD stimulated a deciduomal response in every animal, whereas the traumatization with arachis oil had no such effect; the variation in the peripheral and utero-ovarian steroid levels could not explain the variation in the incidence of the deciduomal reaction. Greater concentrations of PGF but not PGE were present in the endometria of those animals bearing an IUD and in which a deciduomal reaction had been stimulated. The corpus luteum was the major source of progesterone and of oestradiol-17 beta, although non-luteal ovarian tissue also secreted oestradiol-17 beta.

A study of uterine embryos recovered from rhesus monkeys fitted with intrauterine devices.

Fifteen mature female rhesus monkeys were mated and operated upon to recover preimplantation uterine embryos. This resulted in the recovery of 25 embryos or unfertilized ava in 43 attempts. The same animals were fitted with plastic intrauterine devices (IUDs) and the recovery procedure was repeated. In this series 61 recovery attempts yielded only 10 embryos, 7 of which were sectioned and analyzed by transmission electron microscopy. This approach revealed the ultrastructural details of embryo degeneration and leukocyte association seen in embryos recovered from IUD-bearing animals. Samples of peripheral venous blood were analyzed for levels of ovarian steroids at the time of embryo recovery. The results are discussed in relation to the mechanism of action of IUDs.

An ultrastructural study of preimplantation uterine embryos of the rhesus monkey.

Two cleavage stage embryos, two blastocyts surrounded by zona pellucida, and two azonal ('hatched') blastocysts were recovered from uteri of rhesus monkeys and examined with the electron microscope. Cleavage-stage embryos showed no striking differences between inside and outside blastomeres, all of them displaying primitive junctional complexes, heteromorphic mitochondria, large ovoid nuclei and a few polyribosomes. The zonal blastocysts had distinctive trophectoderm and inner cell mass areas in which tight junctional complexes and occasional desmosomes were observed at cell membrane junctions. Such embryos also contained numerous polyribosome complexes and cisternae of rough endoplasmic reticulum, while some inner cell mass cells displayed large autophagic vacuoles. Hatched blastocysts showed an increased number and length of microvilli on the free surface of the embryo, and the trophectoderm cells contained microfibrillar bundles not seen in equivalent regions of zonal blastocysts. Most of the listed ultrastructural features of the rhesus preimplantation embryo are also present in similar embryos of other mammalian species.

Comparisons of the ovulatory and steroidogenic activities of the left and right ovaries of the ewe.

The ovary in which a CL was observed by laparoscopy in Finnish Landrace, Tasmanian Merino and Scottish Blackface ewes had no apparent effect on the location of the CL during the succeeding oestrous cycles, on the duration of the associated oestrous cycles, or on the peripheral progesterone concentrations on Days 7 and 11. Although 53% of CL were present in the right ovaries, the difference between the two sides was not significant.

Seasonal variation in oestrus, the secretion of oestrogen and progesterone and LH levels before ovulation in the ewe.

Ewes with cervical ovarian autotransplants were studied after PGF-2alpha-induced luteal regression in November and February (mid- and late-breeding season) and June (anoestrum). Progesteron and oestradiol-17beta secretion rates and LH concentrations were determined in serial ovarian venous blood samples and the ewes were frequently tested for oestrus. All 4 ewes in November and 3 of the 4 ewes in February exhibited oestrus and endocrine changes indicative of ovulation. The remaining ewe in February and the three ewes in June failed to show elevated oestradiol-17beta secretion rates after luteal regression, indicating the absence of follicles in the final stages of maturation. The preovulatory rise in the oestradiol-17beta secretion rate, the LH surge and the display of oestrus all occurred earlier, with respect to the PGF-2alpha infusion, in November than in February, suggesting a greater stimulation of folliculogenesis, and therefore a greater availability of maturing follicles, in November than in February.