Search

We prove, as an analogy of a conjecture of Artin, that if $ Y \rightarrow X $ is a finite flat morphism between two singular reduced absolutely irreducible projective algebraic curves defined over a finite field, then the numerator of the zeta function of X divides that of Y in $ \mathbb{Z}[T] $ . Then, we give some interpretations of this result in terms of semi-abelian varieties.

ABSTRACTThe presence of hepatitis C virus (HCV) RNA-containing particles in the low-density fractions of plasma has been associated with high infectivity. However, the nature of circulating HCV particles and their association with immunoglobulins or lipoproteins as well as the characterization of cell entry have all been subject to conflicting reports. For a better analysis of HCV RNA-containing particles, we quantified HCV RNA in the low-density fractions of plasma corresponding to the very-low-density lipoprotein (VLDL), intermediate-density lipoprotein, and low-density lipoprotein (LDL) fractions from untreated chronically HCV-infected patients. HCV RNA was always found in at least one of these fractions and represented 8 to 95% of the total plasma HCV RNA. Surprisingly, immunoglobulins G and M were also found in the low-density fractions and could be used to purify the HCV RNA-containing particles (lipo-viro-particles [LVP]). Purified LVP were rich in triglycerides; contained at least apolipoprotein B, HCV RNA, and core protein; and appeared as large spherical particles with a diameter of more than 100 nm and with internal structures. Delipidation of these particles resulted in capsid-like structures recognized by anti-HCV core protein antibody. Purified LVP efficiently bind and enter hepatocyte cell lines, while serum or whole-density fractions do not. Binding of these particles was competed out by VLDL and LDL from noninfected donors and was blocked by anti-apolipoprotein B and E antibodies, whereas upregulation of the LDL receptor increased their internalization. These results suggest that the infectivity of LVP is mediated by endogenous proteins rather than by viral components providing a mechanism of escape from the humoral immune response.

Germ cell production and organization of the testicular epithelium in a prosimian species, the grey mouse lemur, Microcebus murinus, was investigated to extend knowledge of comparative primate spermatogenesis. In addition, semen samples collected from adult male lemurs (body weight 53-92 g; n = 16) by rectal probe electroejaculation were evaluated using computer-assisted morphometric and kinematic analysis of spermatozoa. Epididymidal spermatozoa were collected from six animals after hemicastration; the testes were weighed and prepared for stereological analysis and flow cytometry. The relative testis mass (as a percentage of body weight) ranged between 1.17 and 5.6%. Twelve stages of testicular seminiferous epithelium as described for macaques were applied and only a single stage was observed in most of the seminiferous tubule cross-sections. On average (mean SD), a single testis contained 1870 +/- 829 x 10(6) germ cells and 35 +/- 12 x 10(6) Sertoli cells. Germ cell ratios (preleptotene:type B spermatogonia = 2, round spermatid:pachytene = 3; elongated spermatid:round spermatids = 1) indicated high spermatogenic efficacy. Sperm head dimensions and tail lengths of the ejaculated and epididymidal spermatozoa were similar. Percentages of defects (neck/mid-piece and tail) were low ( 10%) and similar for ejaculated and epididymidal spermatozoa. Spermatozoa were highly motile, characterized by extensive lateral head displacement, but relatively low progressive motility. In conclusion, the grey mouse lemur has unusually large testes with a highly efficient spermatogenic process and large sperm output. These features, together with the high proportion of morphologically normal and highly motile spermatozoa in the ejaculates, indicate that Microcebus murinus is a species in which sperm competition after ejaculation is likely to occur. The predominantly single spermatogenic stage system seems to be an ancestral feature among primates.

To cope with the 6-month dry winter occurring in its natural habitat, the gray mouse lemur (Microcebus murinus), a Malagasy prosimian primate, exhibits a pre-wintering fattening phase that has been previously demonstrated to be dependent on the photoperiod. To assess early changes in energy balance following a photoperiodic shift, food intake (FI), resting metabolic rate (RMR), plasma triglycerides, plasma thyroxine and urinary excretion of cortisol were measured in 12 males and 12 females for 8 weeks following a shift from short (SP: 10 h light/day) to long (LP: 14 h light/day) photoperiod or from LP to SP. Shift from LP to SP led to a high, linear body mass (BM) increase in both sexes, concomitant to an increase in plasma triglycerides and a decrease in plasma thyroxine, while no change in RMR occurred. FI significantly increased from 30 to 40 kcal/day as early as the first week following SP exposure but spontaneously decreased after 4 weeks, reaching minimal values (10 kcal/day) after 14 weeks of SP exposure. Shift from SP to LP led to a decrease in BM and an increase in FI, but both were slow and different between males and females. No change in RMR was observed except a significant increase in males during the first week of LP exposure. However, plasma thyroxine levels and cortisol excretion similarly increased in both sexes following LP exposure. These results suggest that autumnal fattening mainly proceed from changes in FI and in thyroxine secretion triggered by exposure to SP. In contrast, BM loss following LP exposure would be related to seasonal sexual activation rather than to a direct control by photoperiod.

Summary: The vomeronasal system (VNS) seems to be functional in some primates and involved in the detection of urinary signals. Anterograde tracing (WGA-HRP) and evoked metabolic activity (2-DG method) were used in order to clarify the conditions under which the VNS is activated in the prosimian mouse lemur. After WGA-HRP deposition at one of the oral entries of the nasopalatine duct, reaction product was observed within the accessory bulb (AOB). 2-DG experiments show that urine in the volatile phase stimulates the main but not the accessory bulb (AOB). Liquid urine produced bilateral or unilateral activation of AOB depending on whether the stimulation was exclusively unilateral or not; under the same conditions distilled water could not produce 2-DG labelling. It is concluded that VNS is activated by urine in the liquid but not the volatile phase. The biological implications of these results are discussed.

The sexual activity of the lesser mouse lemur, unlike that of most living primates, is clearly dependent on photoperiod. Males responded to long daylengths (> 12 h light/day) by rapid testicular development and an increase in testosterone levels reaching 65.8 ± 1.5 ng/ml (n = 12) after 3 wk of inductive photoperiod. Levels were maintained unchanged until 14 wk of exposure to long photoperiod, when spontaneous gonadal regression was observed. Under short daylengths, intact males exhibited regressed gonadal function with low plasma concentrations of testosterone: 5.4 ± 1 ng/ml. To investigate the effect of olfactory bulb deprivation on gonadal responses to photoperiod, 12 males were bulbectomized (BX) during exposure to either long (n = 8, BX1) or short (n = 4, BX2) daylengths. In both groups of BX males, responses to long or short daylengths were maintained. However, the timing and the amplitude of gonadal responses to photoperiod were modified; BX males underwent a significant delay in testis development and also had reduced testosterone levels (53.3 ± 2.3 ng/ml and 37.3 ± 0.9 ng/ml for BX1 and BX2 groups, respectively). Moreover, BX males did not exhibit spontaneous gonadal regression after 14 wk of exposure to long daylengths, indicating that the photorefractory state did not appear, at least under our experimental conditions. In this primate, olfactory bulbs exert an important effect on the neuroendocrinological control of reproductive responsiveness to photoperiod.

Not Available

We have described the occurrence in freely moving gerbils of slow potential changes (SPC) in two different models of experimental epilepsy: 1) maximal electroshock and 2) bilateral epileptic foci induced by penicillin.SPC is considered a by-product of epileptiform activity in both models and correlates to the SPC which occurs during spreading depression. In the first model there develops a cortical SPC simultaneous with a depression of EEC activity, although there is no propagation of the wave. We suggest that a non-propagated multifocal depression (MD) occurs in the MES model. In the model of focal epilepsy, all requirements are fulfilled, and the SPC is characterized as the one which occurs during spreading depression propagating with an average velocity of 8 mm/min.

Not Available

Summary.Plasma testosterone and progesterone concentrations were measured in captive woolly opossums, a didelphid marsupial originating from neotropical forests in French Guyana. Although not exposed to cyclic environmental conditions as in the field, both sexes exhibited spontaneous circannual changes in sexual hormones. Males showed synchronous variations in plasma testosterone characterized by significant elevated concentrations during April and September 8·6 ± 1 ng/ml, N = 5) and lower levels from May to July (3·6 ± 0·4 ng/ml). In females, synchronous periods of 2–3 successive oestrous cycles occurred. Between these periods, females remained acyclic. The oestrous cycle, determined by urogenital smears, lasted 28–45 days (n= 14) and included a 20-day spontaneous luteal phase in which progesterone concentrations reached 30–40 ng/ml plasma. Even though testosterone concentrations in paired males increased significantly in response to oestrous periods of the paired females, spontaneous circannual rhythms of sexual activity were not well synchronized between the sexes in captivity. When compared to field data, sexual activity of captive animals followed a pattern similar to that in wild animals, without any changes in males but with a delay of 3 months in females.Keywords:reproduction; circannual cycles; progesterone; testosterone; woolly opossum

The body weight and sexual activity of the male lesser mouse lemur, a prosimian primate, undergo cyclic changes that are photoperiod-dependent. Exposure to long daylength (LD; 14 h light/day) led to sustained sexual activity, fully developed testes and high plasma testosterone concentrations (228 ±25 nmol/l, n= 10). After 14 weeks under LD, a marked decrease in testosterone levels occurred. Gonadal regression was completed within 20 weeks under LD without concomitant changes in body weight. Exposure to short daylength (SD; 8 h light/day) reinforced the sexual quiescence and was associated with a high ponderal gain (from 60 to 110 g). However, independent of the date of gonadal arrest, the sexual activity of males spontaneously resumed at a fixed time after exposure to SD. The testes developed, testosterone concentrations increased to 155 nmol/l and the body weight decreased (from 110 to 80 g) within 20 weeks under SD exposure. The timing for refractoriness appeared very similar under inhibitory and stimulatory photoperiods. This is consistent with the hypothesis that the perception of a critical daylength is used to regulate the timing of the following sexual phase through a mechanism involving photorefractoriness.Contrary to cricetid rodents, a direct response to photoperiodic signals for both body weight and sexual activity were not prevented by olfactory bulb removal in male mouse lemurs. In bulbectomized males (n= 12), sexual activity was stimulated by LD and inhibited by SD. Their plasma testosterone levels, however, significantly differed from those of controls in both photoperiods. Likewise, ponderal cycles remained intact but the fattening phase was delayed and reduced. Finally, whereas the sexual recrudescence of bulbectomized males occurred under SD with a delay of only 2–4 weeks, spontaneous testicular regression under exposure to LD did not appear in our experimental photoperiodic conditions.Journal of Endocrinology(1993) 137,511–518

The effect of dominant urine odour on plasma levels of testosterone and cortisol was studied in the prosimian primate Microcebus murinus. This species shows a photoperiod-dependent cycle of sexual activity. In particular, mean testosterone levels vary from 15 nmol/l during the annual rest period to 245 nmol/l during the breeding season. When males of this solitary and territorial species are artificially grouped in captivity, they develop a social hierarchy which in turn results in physiological disorders, especially of reproductive function, in non-dominant individuals. Since olfactory behaviours appear to be important in the establishment and maintenance of the social structure, we have tested the effects of dominant odorant signals upon the sexual inhibition observed in male conspecifics. A preliminary experiment showed that a decrease in plasma testosterone concentrations could be induced by dominant scent marks. Furthermore, dominant urine odour alone was found to be sufficient to induce this modification. Plasma cortisol levels also increased in these animals. Conversely, when sexually inhibited males were olfactorily isolated from dominant urine odour, testosterone and cortisol concentrations returned to a normal seasonal level. These effects were observed even in males which had had no previous contact with the dominant urine donor. It is inferred from these results that a pheromone-like process could lead to sexual inhibition in male Microcebus murinusexposed to an odorant urinary signal produced by a dominant individual. Nevertheless, the endocrine response seems to vary according to the seasonal period of the sexual activity cycle which suggests that the social effect described is modulated by other external (e.g. photoperiodic) or internal (e.g. reproductive physiology) factors.J. Endocr.(1984) 102, 143–151

Not Available

Abstract: The lesser mouse lemur, a small Malagasy primate, is exposed to strong seasonal variations in ambient temperature and food availability in its natural habitat. To face these environmental constraints, this nocturnal primate exhibits biological seasonal rhythms that are photoperiodically driven. To determine the role of daylength on thermoregulatory responses to changes in ambient temperature, evaporative water loss (EWL), body temperature (T b) and oxygen consumption, measured as resting metabolic rate (RMR), were measured in response to ambient temperatures ranging from 5 C to 35 C, in eight males exposed to either short (10L:14D) or long (14L:10D) daylengths in controlled captive conditions. In both photoperiods, EWL, T b and RMR were significantly modified by ambient temperatures. Exposure to ambient temperatures below 25 C was associated with a decrease in T b and an increase in RMR, whereas EWL remained constant. Heat exposure caused an increase in T b and heat loss through evaporative pathways. Thermoregulatory responses to changes in ambient temperature significantly differed according to daylength. Daily variations in T b and EWL were characterized by high values during the night. During the diurnal rest, lower values were found and a phase of heterothermia occurred in the early morning followed by a spontaneous rewarming. The amplitude of T b decrease with or without the occurrence of torpor (T b < 33 C) was dependent on both ambient temperature and photoperiod. This would support the hypothesis of advanced thermoregulatory processes in mouse lemurs in response to selective environmental pressure, the major external cue being photoperiodic variations.

Plasma testosterone-binding globulin (TeBG)-binding capacity was determined by equilibrium dialysis in the lesser mouse lemur (Microcebus murinus), a prosimian which exhibits a clear photoperiod-dependent sexual cycle. Plasma TeBG-binding capacity showed significant seasonal changes which were inversely correlated to those of plasma testosterone concentrations. The capacity of TeBG was at its maximum (1·72 ± 0·4 μmol/l) during the sexual rest period and decreased to 0·98 ±0·24 μmol/l during the breeding season when testosterone concentrations were about 200–280 nmol/l. In addition, when males developed a social hierarchy in groups, the decreased sexual function in non-dominant animals was associated with a higher TeBG-binding capacity. However, although TeBG-binding capacity increased when testosterone concentrations decreased either during sexual rest or under social dominance, a positive correlation was found between TeBG-binding capacity and testosterone levels during the breeding season in males with a normal reproductive cycle, i.e. in both isolated and dominant males. This suggests that factors other than sex steroids are involved in the changes in TeBG-binding capacity occurring under seasonal and social influences.J. Endocr.(1986) 110,169–175

Summary.Plasma progesterone concentrations and the occurrence of oestrous cycles were studied in isolated woolly opossums subsequently subjected to male influences during a 40-day period. Pairing (N = 48) or exposure to male urine (N = 15) resulted in all females exhibiting oestrous during the stimulation phase, providing evidence that the activation of ovarian activity in the woolly opossum involves pheromonal cues from males. The latency of occurrence of oestrous in stimulated females depended upon their sexual state before male stimulation. In anoestrous females, the mean latency was 20·7 ± 0·9 days (N = 35), a value which agrees with the duration of the follicular phase. In females which first entered oestrous before male stimulation, the latency of induced oestrous was inversely correlated to the date of occurrence of the previous oestrous. The inter-oestrous interval was normal (38·1 ± 1 days, N = 5) when females were in oestrous at the beginning of male stimulation. In contrast, the inter-oestrous interval was significantly shortened (28·7 ± 2 days, N = 7) or lengthened (51·1 ± 1·7 days, N = 16) depending on whether females were in the luteal or follicular phases at the beginning of male stimulation. During pairing several females became pregnant and gave birth 24 ± 0·9 days (N = 13) after copulation.In the woolly opossum, the response to male influences involves mechanisms similar to those observed in eutherians and results in enhancement and synchronization of oestrous cycles in females. Pheromonal interactions could play an important role in synchronizing oestrous cycles in wild females during the dry season, a period when animals regroup to feed on spatially localized food resources.Keywords:male effect; pheromone; oestrous cycles; progesterone; marsupial

Summary.Plasma progesterone concentrations were recorded during one breeding season in 19 lesser mouse lemur females living in different social conditions. The oestrous cycle length and the progesterone profile mainly depended on the social environment of the female. For totally isolated females, the oestrous cycle lasted 38 ± 5·7 days and included a 25–30-days spontaneous luteal phase with a progesterone peak about 100 ng/ml between the 20th and 25th days after oestrus, and a prolonged preovulatory period of 10–15 days which could be considered equivalent to the follicular phase of a menstrual cycle. When females were able to communicate through olfactory, visual and auditory signals, the oestrous cycle was significantly lengthened (53·7 ± 5·9 days). When females had tactile contacts, the oestrous cycle was further lengthened (62·7 ± 0·8 days). This lengthening of the oestrous cycle was related to an extension of the luteal phase associated with a decrease in progesterone concentrations during this period. In females maintained with one male (paired) or with males and females (heterosexually grouped), large individual variations were shown in cycle lengths or in progesterone concentrations. In these females, cycle lengths and progesterone concentrations were inversely correlated to plasma cortisol concentrations.

Summary.In 6 isolated adult male lesser mouse lemurs, concentrations of testosterone in plasma were determinated at 6-h intervals over a 24-h period. Blood samples were collected at monthly intervals and for a period of 12 months under natural photoperiod. In this nocturnal prosimian, there were no apparent diurnal changes in testosterone concentrations during the non-breeding season (autumn). During seasonal sexual activity (January—August), diurnal changes in testosterone concentrations were characterized by a significant rise during the light phase. The daily testosterone peak occurred about 8·5 h after sunrise from February to July, but at the beginning (January) or at the end (August) of the breeding season, the daily testosterone peak was displaced to the morning. A circannual testosterone rhythm occurred with the highest testosterone values in May/June and the lowest values 6 months later. The dramatic fall in testosterone concentrations after the summer solstice may be associated with a change in the peripheral metabolism of testosterone.

Sexual activity of the male lesser mouse lemur can be induced by a long photoperiod, and plasma testosterone concentrations increase from 20 to 220 nmol/l within 3 weeks of photoperiodic stimulation. When isolated males were exposed to the volatile compounds from the urine of an active dominant male for 4 weeks at the beginning of the long daylight period, they demonstrated a significant decrease in testosterone concentrations (134± 11 nmol/l) compared with controls (210 ± 26 nmol/l) within 2 weeks. Lowering concentrations of prolactin by daily injections of bromocriptine prevented the decrease in testosterone in males simultaneously exposed to the odorant stimulation. Increasing concentrations of prolactin by daily injections of sulpiride mimicked the effect of the odorant stimulation in males receiving only fresh non-odorized air. The decrease in testosterone was strengthened when sulpiride was administered concurrently with exposure to urine. These results support the conclusion that variations in the concentration of prolactin are involved in the neuroendocrinological process mediating the pheromone-like sexual inhibition in the male lesser mouse lemur. However, daily injections of bromocriptine in males which were photoperiodically stimulated but not exposed to dominant male urine odour, also induced a significant decrease in testosterone concentrations. This finding suggests that two different systems involving prolactin and leading to opposite effects might be implicated in the regulation by environmental factors of sexual activity in the male lesser mouse lemur.J. Endocr. (1987) 114,279–287

Brachytherapy is now a widely accepted palliative method for desob-structing the bronchial lumen. However, its place as a curative treatment is still debated. We have tried to distinguish between patients who can be cured with endobrachytherapy and palliative treatments. We report here the results of such a distinction.