Reproductive inhibition in the Cape porcupine, Hystrix africaeaustralis

Sexually mature female Cape porcupines kept under natural conditions of illumination and temperature did not conceive while housed within their natal groups. Before removal from their natal groups the sexually mature offspring copulated and experienced cyclic ovarian activity, but conception occurred only 70-120 days after dispersal. Mean oestrous cycle length of these females (36.9 +/- 11.5 days; n = 34) was similar to that of breeding females (33.0 +/- 11.64 days; n = 16), but mean peak plasma progesterone concentration (6.45 +/- 6.03 ng/ml; n = 34) was significantly (P less than 0.01) lower than that of cyclic breeding females (13.58 +/- 6.98 ng/ml; n = 16). Mean progesterone concentration at oestrus in non-breeding females (0.72 +/- 0.45 ng/ml; n = 34) was also significantly (P less than 0.01) lower than that of non-pregnant breeding females (4.21 +/- 2.44 ng/ml; n = 16). Reproductive inhibition within natal groups, in which only one female reproduces, therefore cannot be ascribed to a failure to copulate, but may be due to some factor inhibiting full expression of luteal activity or affecting ovulation.     

Reproductive biology of the male Cape porcupine, Hystrix africaeaustralis

The reproductive tract of the male Cape porcupine is morphologically and histologically similar to that of New World hystricomorph rodents. Males are reproductively active throughout the year and attained sexual maturity (complete spermatogenesis) at an age of 8-18 months. Testes weight, epididymides weight and seminiferous tubule diameter attained asymptotic values at the age of 23-30 months. A tendency towards seasonality in the activity of accessory glands, preceded and accompanied by an increase in circulating plasma testosterone values, may be considered as a factor enforcing seasonal breeding in females. Testosterone concentrations in pubertal males were significantly higher than those recorded in sexually mature males.     

Demography of a Cape porcupine, Hystrix africaeaustralis, population

The Cape porcupine is a large (12.0 kg), nocturnal hystricomorph rodent and widely distributed throughout southern Africa. The present paper examines age-specific survival, mortality and fecundity rates in a population, evaluates the roles of possible density-dependent changes of population parameters in the regulation of porcupine numbers, and describes the life history strategy of the species. The study is based on data sets obtained from animals collected during 1977/78 and during 1981/82. Changes in demographic characteristics are ascribed to an artificial reduction in density, resulting in the relaxation of social factors inhibiting reproduction in young adults.     

Metabolic rates,food consumption and thermoregulation in seasonal acclimatization of the Cape porcupine Hystrix africaeaustralis

Summary Metabolic rates by means of oxygen consumption (VO₂) at various ambient temperatures (T _a) and food consumption as well as water intake and thermoregulation were compared between individuals of the Cape porcupine Hystrix africaeaustralis acclimated to T _a=32°C with a photoperiod of 16L:8D summer-acclimated and T _a=10°C; 8L:16D winter-acclimated. The lower critical temperature as well as overall minimal thermal conductance were lower for the winter-acclimated porcupines when compared to summer-acclimated ones, while VO₂ at the thermoneutral-zone was significantly (P<0.001) higher in the winter-acclimated porcupines. Dry matter intake, apparent digestible dry matter intake, gross digestible energy intake, as well as water intake, were significantly higher in the winter-acclimated porcupines. Yet, while dry matter intake increased 4 times in the winter-acclimated porcupines, apparent digestible dry matter increased only at a rate of 2.9 times. This difference is better reflected in terms of digestibility efficiency which in the winter-acclimated porcupines is only at a rate of 67.5% while in the summer-acclimated porcupines it is at a rate of 90%. From the results of this study, it is possible to assume that heat production in the winter-acclimated porcupines is partly increased by food intake. Increased heat production on the one hand, and a decrease in overall minimal thermal conductance on the other, seem to be important mechanisms in winter acclimatization of the Cape porcupine.     

Circulating progesterone, progesterone-binding proteins and oestradiol-17 beta concentrations in the pregnant Cape porcupine, Hystrix africaeaustralis

Circulating concentrations of progesterone, progesterone-binding plasma proteins (PBPP) and oestradiol-17 beta in pregnant porcupines remained relatively low until Days 25-30 post coitum. Progesterone values peaked (102-180 ng/ml; N = 3) 42-60 days post coitum and the rapid increase in oestradiol-17 beta concentrations approximated that of progesterone with peak values (170-210 pg/ml) being attained 60-85 days post coitum. The pattern of PBPP synthesis, as suggested by circulating concentrations, was closely related to that of plasma progesterone, with values remaining low (less than 20 pmol/ml) until Day 31 post coitum, reaching peak levels at Days 50-56 and Days 73-77 post coitum. The production of PBPP during pregnancy is, as in related New World hystricomorph species, considered to be a mechanism which facilitates a reduction in the rate of progesterone metabolism during pregnancy.     

Sexual size monomorphism in the crested porcupine (Hystrix cristata)

Amongst mammals, female-biased sexual size dimorphism (SSD) is rare and it occurs mostly in species where reduced male intrasexual competition is present. Reverse SSD has been reported for Old World porcupines Hystrix spp. We compared weight and six metric body measurements of 40 male and 42 female crested porcupines from Southern Tuscany, Italy. No significant difference was observed between sexes. The monogamous mating system of porcupines, sharing parental care, together with no evidence of territoriality, militate against previous claims of SSD presence, probably due to small sample size and inappropriate statistical analyses.     

Observations on the structure and innervation of the carotid sinus complex in the African porcupine (Hystrix cristata)

The carotid arterial system of the porcupine Hysitrix cristota has been studied using light and electron microscopy. Emphasis has been placed on describing the structure and innervation of the carotid sinus area located at the origin of the internal carotid artery. The sinus wall has a largely elastic structure and a reduced smooth muscle content. A functional relationship is proposed between the elastic structure of the sinus wall and baroreceptor mechanisms.     

Functional anatomy of the ovaries of pregnant and lactating Cape porcupines, Hystrix africaeaustralis

The constituent cell types of the ovary of the porcupine were similar to those of New World hystricomorph rodents and accessory corpora lutea and luteal bodies were formed through the luteinization of the membrana granulosa or theca interna of antral follicles. All luteal bodies were histologically similar. The total volume of luteal tissue per female was not affected by fetal age and was unrelated to circulating concentrations of maternal plasma progesterone. Maternal plasma progesterone concentrations were correlated with fetal age. Follicular activity occurred throughout pregnancy but was not affected by fetal age or related to circulating values of oestradiol-17 beta. The formation of accessory corpora lutea during pregnancy is regarded as important in supplementing progesterone during pregnancy.     

Pre- and postnatal aminopeptidase activities in the rat brain

Research concerning the functional role of brain peptides is performed, in part, by studying peptidase enzymes which might be involved in brain peptide processing or inactivation. Aminopeptidase (AP) activity has been proposed as a candidate regulator of the degradation of these peptides. In this paper, changes in Lys- and Leu-aminopeptidase activities in rat brain hemispheres, cerebellum and medulla were examined in 20 day fetuses and one day postnatal subjects. Aminopeptidase activities were studied by measuring the rate of hydrolysis of the artificial substrates Lys- and Leu-2-naphthylamides (fluorimetrically detected in triplicate). Both enzyme activities increase from the last fetal stage up to the first day of birth in all the brain areas examined except for the case of Leu-AP activity in the medulla. It is suggested that these activities play a part in the neurochemical changes that take place during rat brain maturation, possibly by regulating the activity of several neuroactive peptides.     

Circulating progesterone and oestradiol-17 beta concentrations in cyclic Cape porcupines, Hystrix africaeaustralis

The general pattern of steroid secretion during the 30-day oestrous cycle of the Cape porcupine is that of a surge (25-176 pg/ml) in oestradiol-17 beta secretion at the time of perforation of the vaginal closure membrane, followed by an increase in progesterone concentrations, the latter attaining peak values (mean 5.9 +/- 2.1 ng/ml) 8-19 days (13.8 +/- 2.8 days) after vaginal opening. Copulation occurred after the oestradiol-17 beta surge and the length of the luteal phase of the cycle varied from 21 to 35 days (29.3 +/- 4.7 days), this representing 93% of the length of the cycle. Perforation of the vaginal closure membrane was not always accompanied by an increase in oestradiol-17 beta levels and some instances (19%) of vaginal opening were not followed by an increase in progesterone secretion. The hormonal characteristics of the oestrous cycle of females housed with vasectomized males were similar to those of females housed with intact males.     

Properties of proteins binding plasma progesterone in pregnant Cape porcupines (Hystrix africaeaustralis).

The properties of progesterone-binding proteins in plasma of pregnant Cape porcupines were investigated using radiolabelled progesterone and either progesterone or cortisol as competing ligands as well as native plasma and heated (60 degrees C for 30 min) plasma. The results demonstrated that plasma from pregnant porcupines contains corticosteroid-binding globulin, but that it constitutes a significant portion of plasma progesterone-binding proteins only during the early stages of pregnancy. Corticosteroid-binding globulin of porcupines appears to be as heat labile as that of guinea-pigs. Concentrations of progesterone-binding proteins in plasma increased during pregnancy to reach concentrations at the eleventh week that were 25 times higher than those of progesterone; concentrations increased significantly (r2 = 0.88) with the increase in progesterone concentration. The results indicate that plasma progesterone-binding proteins in Cape porcupines (Old World hystricomorph) are similar in composition to those in guinea-pigs (New World hystricomorph).     

Pre- and early postnatal nongenetic determinants of type 2 diabetes

Epidemiological studies have revealed strong and internationally reproducible links between early growth restriction and subsequent risk of developing type 2 diabetes and the metabolic syndrome (glucose intolerance, hypertension and hypertriglyceridaemia). This effect can exist independently of genetic factors. There is also direct evidence that poor maternal nutrition and maternal smoking cause both a reduction in birthweight and subsequent loss of glucose tolerance. High rates of growth in childhood may add to these effects. The 'thrifty phenotype' hypothesis attempts to explain these associations in terms of an altered programming of growth and metabolism that aids survival both pre- and postnatally. Type 2 diabetes is envisaged as a consequence of a clash of this programming with adult obesity. Tests of this hypothesis in animal models have shown that both the metabolic syndrome and type 2 diabetes can result from early growth restriction in rats consequent upon rat dams being fed a reduced protein, isocaloric diet (in which the protein is replaced by an equal quantity of nonprotein energy). A variety of other models of early growth restriction in rats lead to a similar phenotype. Several structural and gene expression changes have been shown in many tissues, including pancreas, liver, kidney, muscle and adipose tissue. Changes in gene expression include those concerned with hormone receptors, signalling and glycolytic enzymes. Many important questions remain for future research.     

Unveiling an ancient biological invasion: molecular analysis of an old European alien, the crested porcupine (Hystrix cristata)

Background  

Biological invasions can be considered one of the main threats to biodiversity, and the recognition of common ecological and evolutionary features among invaders can help developing a predictive framework to control further invasions. In particular, the analysis of successful invasive species and of their autochthonous source populations by means of genetic, phylogeographic and demographic tools can provide novel insights into the study of biological invasion patterns. Today, long-term dynamics of biological invasions are still poorly understood and need further investigations. Moreover, distribution and molecular data on native populations could contribute to the recognition of common evolutionary features of successful aliens.     

Pre- and postnatal toxicity induced in guinea pigs by N-nitrosomethylurea.

Oral administration of N-nitrosomethylurea at maximally tolerated doses to guinea pigs on alternate days from days 34-58 of pregnancy induced prenatal toxicity, as evidenced by a high frequency of stillbirths and intrauterine growth retardation, and postnatal toxicity, as evidenced by stunting and progressive mortality. Similar administration of N-nitrosomethylurethane at maximally tolerated doses did not induce such toxic effects.     

Pre- and postnatal development of differentiated functions in rat intestinal epithelial cells

A panel of monoclonal antibodies to intestinal cell surface components has been used to compare the expression of differentiation-specific antigens in the epithelial cells of fetal, suckling, and adult rat small intestine. Indirect immunofluorescence staining, and immunopurification of detergent-solubilized membrane proteins, followed by single- and two-dimensional slab gel electrophoretic analysis, have demonstrated that fetal intestinal cells (at day 21 of gestation) express most differentiation-specific markers typical of adult absorptive villus cells. A marked heterogeneity in antigen expression was observed among different villus cell populations in suckling rat intestine, and three cell surface components were identified which are exclusively present during this period of intestinal development. Striking changes in the patterns of antigen expression in crypt and villus cells, and variations in the apparent isoelectric points for most luminal membrane components, were associated with the maturation of the intestinal mucosa at weaning. These changes could not be prematurely induced by cortisone injection in newborn rats, suggesting that factors other than glucocorticoids are responsible for the postnatal development of the intestinal epithelium. These results suggest that basic differences in biological properties and regulatory mechanisms exist among intestinal epithelial cells at different stages of pre- and postnatal maturation.