[Preimplantation genetic diagnosis: current status and perspective]. / Preimplantatsionna genetichna diagnostika: s'vremenno s'stoianie i perspektivi.

Scientific and clinical aspects of preimplantation genetic are represented.

Albumin microsphere as a drug delivery system for dexamethasone: pharmacokinetics in sheep, residue amount in cows and distribution in rats.

The aim of this study was to evaluate the potential use of albumin microspheres as a drug delivery system to provide sustained release of dexamethasone in vivo. Pharmacokinetic studies were carried out in sheep and tissue distribution in rats given dexamethasone in two injectable forms--water suspension of dexamethasone associated with albumin microspheres and water-ethanol solution of dexamethasone. When dexamethasone was associated with albumin microspheres the amount of free dexamethasone, available for absorption did not reach the high values typical of the pattern of release of dexamethasone from water-ethanol solution. The time of withdrawal in lactating cows after i.m. administration of DXM-AM was found to be 5 days. The release of dexamethasone from the albumin microspheres was accomplished gradually thus allowing sustained levels of the corticosteroid to be maintained for several days in blood plasma, milk, liver, kidney and muscles.

Chronic melatonin treatment counteracts glucocorticoid-induced dysregulation of the hypothalamic-pituitary-adrenal axis in the rat.

Transient exposure of rats to high doses of dexamethasone (DEX; 500 microg/day for 5 days) produced a host of symptoms that are indicative of hypothalamic-pituitary-adrenal (HPA) axis dysregulation, such as increased adrenocortical secretion over 24 h, blunted and prolonged secretory response to emotional stress, refractoriness of adrenocorticotropin in vitro release to stimulation with the secretagogues corticotropin-releasing hormone (CRH) and vasopressin, decreased levels of mRNA encoding type II corticosteroid receptors in the hippocampus and increased numbers of transcripts encoding CRH in the paraventricular nucleus. Daily administration of melatonin (MEL; 80 microg/kg) concomitantly with, and for 5 days after discontinuation of, glucocorticoid treatment 'normalized' most of the symptoms of impaired HPA regulation caused by the exposure to DEX. While none of the treatments used caused major shifts in circadian patterns of corticosterone secretion, MEL administration was associated with diminished overall corticosterone secretion and increased sensitivity to glucocorticoid feedback. Taken together, these findings indicate that chronic MEL treatment may protect several regulatory components of the HPA axis from glucocorticoid-induced deterioration.

Chronic melatonin treatment and the hypothalamo-pituitary-adrenal axis in the rat: attenuation of the secretory response to stress and effects on hypothalamic neuropeptide content and release.

The pituitary-adrenal secretory response to acute and chronic stress, suppressibility of adrenocortical secretions by exogenous glucocorticoids, and hypothalamic content and in vitro release of the two major peptidergic activators of the hypothalamo-pituitary-adrenal (HPA) axis, corticotropin-releasing hormone (CRH) and arginine-vasopressin (AVP), were examined in rats receiving daily melatonin (MEL) injections coincident with the circadian increment of endogenous pineal and adrenocortical secretory activity. After 7 days of MEL administration, the rats displayed a significant attenuation of the adrenocortical secretory response to acute and chronic stress. Chronic MEL treatment also prevented the decline in adrenocorticotropic hormone (ACTH) release resulting from chronic stress exposure. Hypothalamic CRH content was significantly lower in rats receiving MEL treatment, while AVP remained largely unaltered; however, MEL administration counteracted the chronic stress-induced decrease in hypothalamic AVP content and in vitro release. When exposed to dexamethasone in vitro, hypothalamic explants from MEL-treated rats responded with a stronger suppression of CRH and AVP release than those originating from vehicle-injected animals. These observations indicate that MEL attenuates the adrenocortical response to stress and influences the biosynthesis, release and glucocorticoid responsiveness of hypothalamic ACTH secretagogues.

Selective effect of methoxyindoles on the lymphocyte proliferation and melatonin binding to activated human lymphoid cells.

Three pineal methoxyindoles (melatonin (Mel), 5-methoxytryptamine (5-MTA) and 5-methoxytryptophol (5-MTO)) were studied for their ability to influence the proliferative response of human peripheral blood lymphocytes (PBL) and tonsillar lymphocytes (TL) following activation with concanavalin A (ConA) in vitro. The ConA-stimulated DNA synthesis was affected in a different dose-dependent mode by the methoxyindoles tested. Melatonin and 5-MTO inhibited and 5-MTA increased the ConA-induced [3H]thymidine incorporation in PBL and TL. The initial screening for 2-[125I]iodomelatonin binding using a single point assay revealed significantly increased specific binding to PBL and TL after 72-h stimulation with ConA as compared to the non-activated cell cultures. Coincubation of separate lymphocyte cultures with ConA and Mel or 5-MTO resulted in inhibition of the specific 2-[125I]iodomelatonin binding (85% and 74%, respectively). The specific binding determined in the presence of 5-MTA did not differ from control values. Series of saturation and competition experiments were performed to examine the binding characteristics of ConA-stimulated lymphocytes for 2-[125I]iodomelatonin. The radioligand labelled binding sites of high affinity (Kd = 0.14 +/- 0.03 nM) and low capacity (Bmax = 6.8 +/- 1.5 fM/mg protein). Competitive studies with a variety of indoles determined the following order of relative potency for inhibition of 2-[125I]iodomelatonin binding in TL: 2-iodomelatonin > melatonin > > 5-methoxytryptophol. 5-Methoxytryptamine did not show displacement potency for the labelled ligand. Collectively, our data suggest that pineal hormones might be directly involved in the regulation of the T-lymphoproliferative response of human lymphoid cells. We show the availability of melatonin receptors, which seem to be an intrinsic characteristic of activated human lymphocyte populations. While the effects of Mel and 5-MTO can be linked to the binding sites described, it is unlikely that serotonin agonists like 5-MTA may act through the same sites to influence the mitogen-stimulated lymphocyte proliferation.

Substance P modulating effect on the binding capacity of hamster Leydig cell LH receptors.

The influence of Substance P was studied on the binding characteristics of LH receptors in purified Leydig cells collected from golden hamsters kept under natural long or short days. Substance P exerted a differential effect on the binding capacity of LH receptors. A significant increase in Bmax was estimated in Leydig cells obtained from young hamsters living under long days. In contrast, Substance P reduced the number of the LH binding sites in Leydig cell cultures prepared from adult hamsters housed under short-day conditions.

Melatonin effects on glucocorticoid receptors in rat brain and pituitary: significance in adrenocortical regulation.

1. The effects of chronic melatonin treatment on glucocorticoid binding sites in hippocampus, hypothalamus and pituitary were investigated in rats, subjected to long-term manipulation of circulating corticosterone concentrations. 2. Melatonin treatment decreased the affinity of glucocorticoid receptors. 3. The effect of melatonin was apparent in the presence of normal or enhanced systemic corticosterone levels, but not in long-term adrenalectomized animals.