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Biomedical subjects

A Locatelli

Publications and source records attributed to A Locatelli.

At least 163 records · Page 9Linked to original sources
PubMed1987

Effect of adrenalectomy on LH release in sheep during the anoestrous season.

An experiment was conducted to measure LH pulse frequencies in bilaterally adrenalectomized Ile-de-France ewes during the mid-anoestrous season. Seven ewes were adrenalectomized under general anaesthesia and maintained on daily injections of 3 mg deoxycorticosterone acetate (DOCA). Adrenalectomy did not affect the patterns of LH release and the mean intervals between pulses in the adrenalectomized and sham-operated control ewes were 48 and 52 min respectively. Small implants of oestradiol significantly reduced the frequency of LH pulses in both groups and, in the presence of oestradiol, there were no differences in LH release between adrenalectomized and sham-operated ewes, with the mean interpulse intervals being 91 and 89 min respectively. In a second experiment, designed to assess the effects of DOCA on LH release, the mean interpulse intervals in unoperated control ewes (46 min) and unoperated ewes given daily injections of 3 mg DOCA (47 min) were similar to those observed in adrenalectomized and sham-operated ewes. In the presence of small implants of oestradiol, the combination of DOCA and oestradiol decreased the pulse frequency significantly more than oestradiol alone (mean interpulse intervals of 85 and 65 min respectively) suggesting that DOCA may act as a progestagen in sheep. Thus alternative treatments to DOCA for the maintenance of adrenalectomized sheep must be found for future studies on the role of adrenal steroids in the reproductive system. It appears that adrenal steroids do not play a major role in the seasonal changes in LH release in the ewe.

Adrenal Glands↗
PubMed1987

[Augmentation, by naloxone, of the frequency and amplitude of LH-RH pulses in hypothalamo-hypophyseal portal blood in the castrated ram].

The effect of naloxone administration on the LH-RH secretion in hypophyseal portal blood and LH secretion in peripheral blood was studied in four short term castrated rams (between 2 to 4 days after castration). For two animals (A and B) given a single naloxone injection, an increase of LH-RH pulse amplitude was observed (A, 22.3 to 80.5 pg/ml and B, 22.5 to 34.5 pg/ml) with only a small (nonsignificant) increase in LH-RH pulse frequency. For animals C and D given four injections of naloxone, both LH-RH pulse amplitudes and LH-RH pulse frequency were increased. Means of LH-RH pulse amplitude increase from 29.3 to 65.1 pg/ml and from 34.6 to 50.8 pg/ml for animals C and D respectively and the number of LH-RH pulses detected during the 3 hrs. before and after the first injection of naloxone were respectively 3 vs. 5 and 3 vs. 7. Whereas all LH pulses were preceded with a LH-RH pulse in animals A and B, after the multiple naloxone injections in animals C and D, a rapid LH-RH pulse frequency was associated with a sustained increment of LH secretion in peripheral blood in such a way that individual LH pulses were not clearly defined. The present report is the first documentation on naloxone increasing the release of LH-RH secretion in hypophyseal portal blood of conscious, unrestrained, short-term castrated rams. The results indicate: (1) that the opiate antagonist naloxone is able to increase both the amplitude and the frequency of LH-RH discharge by the hypothalamus and (2), when the LH-RH pulse frequency exceeds one pulse every 30 min., discrete LH secretory episodes are not observed in peripheral blood.

Animals↗
PubMed1986

Non-pheromonal stimulation by the male of LH release in the anoestrous ewe.

In the anoestrous ewes, the introduction of rams leads to an increase in the secretion of LH and ovulation. Several studies have led to the hypothesis that a ewe's response to the male is mediated by pheromones, implicating a prevalent role of olfaction. In order to analyse if sensory cues other than smell could influence the ewe's physiological response to the male, an olfactory bulbectomy which destroys both main and accessory systems was performed in seven Ile-de-France ewes with a surgical laser. When presented to intact males, the ewes still reacted to the rams by displaying a LH release similar to the controls (n = 11) whereas no response was obtained after ram's fleece stimulation. This suggests that other sensory cues may replace the pheromone to trigger LH release.

Anestrus↗
PubMed1986

Production, freezing and transfer of embryos from a bluetongue-infected goat herd without bluetongue transmission.

In order to import non-seasonal Creole goats from the Carribean to Europe for an experimental purpose, thirty Creole goats were treated with 10 mg of FSH; embryos were collected at slaughter, washed and deep frozen. After rapid thawing, they were reimplanted surgically into European dairy goats. Twenty-four females ovulated but only 17 of the ovulating females had functional corpora lutea (CL) at collection. Ovulation rate (CL goat ) and recovery rate (embryo CL ) were 13.8 and 78% for females with functional CL. Of 191 embryonic structures collected, 79% were considered suitable for deep freezing: 23% were young blastocysts, 47% were expanded blastocysts, and 30% were zona-pellucida (zp)-free and zp-damaged embryos. Seventy-eight embryos were thawed and 63 were reimplanted. Sixty-eight percent of the recipient females delivered 19 kids. The percentage of kids born relative to good-quality re-implanted embryos was higher for zp-free embryos (64%) than for young and expanded blastocyts (36%). Forty-seven percent of the donor females had strong positive serological reactions for bluetongue virus antibodies against serotypes 6 and 14. However, no recipient goats or newborn kids were positive. Virus isolation attempts on the collection media and last embryo washes were negative.

Journal Article↗
PubMed1986

Influence of transport stress on trichostrongylid infection in feedlot beef cattle.

The influence of stresses due to transport of beef cattle and their allotment to feedlots on trichostrongylid infection was studied. The greatest increases in worm egg counts and serum pepsinogen levels were seen at 5 h and 30 days after allotment. These apparently resulted from reactivation of arrested larvae which the animals ingested while grazing during late autumn at the breeding farm.

Animals↗
PubMed1985

[Autonomic neuropathy in reduced glucose tolerance].

33 subjects belonging to I.G.T. class according to N.D.D.G. criteria and controlled in our ambulatory, have been studied for the response to the tests usually employed for the investigation of parasympathetic and sympathetic cardiovascular innervation. We have found pathological values for the SL1 test and borderline values for SL2 and LS tests; on the contrary all the other tests presented normal values. The Authors conclude that signs of deterioration of cardiac and vascular innervation, especially regarding the parasympathetic nervous system, can be present also in the subjects showing a small glucose metabolism alteration. This subclinical alterations do not depend on factors which can interfere with the responses to the tests (as age, boyd weight, sex and presence or absence of diabetic familiarity) but on glucose metabolism alteration. Hence also the subjects with I.G.T. have to be considered as a at risk population, like the neuropathic diabetics.

Adult↗
PubMed1985

Functional evaluation of a CPAP circuit with a high compliance reservoir bag.

Continuous positive airway pressure is widely used in the treatment of ARF and an evaluation of the systems is important. The authors used an artificial model to test a continuous flow system with a high compliance reservoir bag. The results confirm that the system is effective in maintaining positive pressure stability within a wide range of inspiratory peak flow rates, even when a low fresh gas flow rate is employed. Nevertheless, rebreathing of expired gases is possible and may be noticeable at high expiratory flow rates, caused by the high compliance of the reservoir bag.

Acute Disease↗
PubMed1985

Biochemical modifications involved in the maturation of the ovine fetal adrenal gland in late gestation: their modalities and regulation.

During the last month of intra-uterine life, the steroidogenic response of the ovine fetal adrenal glands to ACTH increases and becomes maximal at the time of birth. This development involves modifications at different steps of the adrenocorticotropic hormone (ACTH) action mechanism. It has been shown that the enhanced capacity of the cells to produce cAMP is related to at least three factors: an increased number of ACTH receptors, increased activity of the Ns subunit of adenylate cyclase, and enhancement of guanosine 5'-triphosphate (GTP) availability. The ability to produce pregnenolone and the activity of both 3 beta-hydroxy steroid dehydrogenase/isomerase and 17 alpha-hydroxylase are mainly enhanced in the steroidogenic pathway. The infusion of ACTH for 5 days into 115 to 120-day old fetuses results in the development of most of these biochemical process. Similarly, ACTH can induce maturation of cultured fetal adrenal cells and some other proopiomelamocortin (POMC)-derived peptides can potentiate its acute steroidogenic activity in vitro. However, even in the absence of ACTH, the adenylate cyclase system and the steroidogenic potency of cultured cells increase but to a lesser extent than when ACTH is present in the culture medium. It is suggested that ACTH is the main trophic hormone of the ovine fetal adrenal during the last month of gestation, even if other stimulatory factors may also be important. The in vivo maturation of ovine fetal adrenal is blocked by the presence of some unknown inhibitory factors in the fetal circulation which are of likely extrapituitary origin.

Adenylyl Cyclases↗
PubMed1985

Effects of fetal hypophysectomy and the in vitro treatment by pituitary extracts on the maturation of cultured ovine fetal adrenal cells.

In the first series of experiments, the ability of cultured adrenal cells from 113-day-old ovine fetuses to produce both cAMP and corticosteroids in response to ACTH-(1-24) or to fetal (FPE) or newborn acidic pituitary extracts (NPE) was investigated daily. Basal cAMP output did not change during the culture period. When cells from 124-day-old ovine fetuses, or from 5-day-old lambs, were repeatedly stimulated (2 h/day for 4 days) by ACTH-(1-24) or by pituitary extracts, the cAMP responses increased with the same pattern. Outputs on day 4 were 7-fold higher than those on day 1 for ACTH-(1-24)-matured cells or for cells matured by FPE or NPE. The steroid output induced by ACTH-(1-24) or by FPE or NPE developed identically during the experiment to become, on day 4, more than 40-fold higher than on day 1. The response to ACTH-(1-24) on day 5 was also identical both in cAMP and corticosteroids whether the cells had been previously treated with ACTH-(1-24) or with FPE or NPE, In the second set of experiments, adrenal cells from 124-day-old-ovine fetuses either intact of hypophysectomized (Hx) at 118 days of gestation were cultured for 6 days in the absence or presence of ACTH-(1-24). ACTH-(1-24) treatment resulted in a development of cAMP and corticosteroid responses to the hormone which was slower for cells from Hx than cells from control fetuses during the first 3 days of culture. Likewise both cAMP and corticosteroids responses to ACTH-(1-24) of adrenal cells from Hx fetuses cultured for 1 to 3 days in the absence of ACTH were lower than those of cells from control fetuses cultured under the same conditions. These results demonstrate that the pituitary from 124-day-old ovine fetuses contains trophic (and steroidogenic) substances in a sufficient amount to allow in vitro adrenal maturation. Moreover, it appears that high mol wt forms of ACTH, which are most probably extracted by the method we used, did not prevent the in vitro development of the response to ACTH-(1-24). Finally, they show that removal of pituitary hormones in vivo resulted in a decreased potency of fetal adrenal cells to respond in vitro to ACTH-(1-24).

Adrenal Cortex↗
PubMed1983

Fasciola hepatica: increase of glycogen phosphorylase activity due to prostaglandins.

Both prostaglandin E1 (PGE1) and prostaglandin F2 alpha (PGF2 alpha) stimulate the glycogen phosphorylase (EC 2.4.1.1.) activity of Fasciola hepatica. Whole or sliced parasites were incubated with PGE1 (2.8 X 10(-7) and 2.8 X 10(-5) M) and PGF2 alpha (2.1 X 10(-7) and 2.1 X 10(-5) M) and enzyme activity was measured in homogenates prepared immediately following the incubation. No substantially different effect was noted between the two assayed doses of prostaglandins. Prostaglandins appeared to be less effective in sliced parasites.

Alprostadil↗
PubMed1983

A study of ovarian activity in the ewe using chronic catheterization of the utero-ovarian vein.

Eighty-six adult, cyclic, anestrous and postpartum Ile-de-France ewes were placed under general anaesthesia. A catheter was inserted in the utero-ovarian vein (u.o.v.) of one or both ovaries in each ewe. The animals were kept unrestrained in pens and allowed to experience normal maternal behaviour, including suckling. Oestrus was detected with rams. Out of 167 catheters inserted, 70.7% allowed repetitive blood collection, 24.0% were obstructed for short periods and 5.4% remained completly blocked. Oestradiol- 17beta was assayed without extraction from the u.o.v. plasma samples. From these results, we conclude that this technique is suitable for investigating the mechanisms involved in the recovery of cyclical ovarian activity after parturition, particularly because the follicular response to endogenous gonadotropins can be assessed. This is not possible when plasma samples are obtained from a jugular vein.

Journal Article↗
PubMed1982

Influence of the duration of daylight on prolactin secretion in the pig: hourly rhythm in ovariectomized females, monthly variation in domestic (male and female) and wild strains during the year.

In wild boars and sows, plasma prolactin varied among seasons with highest levels in July and lowest during the winter months. In domesticated breeds of pigs, plasma prolactin of intact boars did not vary among seasons but plasma prolactin of gilts tended to be higher in the summer than in winter. However, this difference was more conclusive in ovariectomized as compared to intact gilts. There was not a significant circadian rhythm in hourly samples from ovariectomized gilts.

Animals↗