Radioligand binding of antagonists of platelet-activating factor to intact human platelets

Two new antagonists of platelet-activating factor (PAF), the pyrrolothiazole derivative 52770 RP and the triazolodiazepine WEB 2086, have been studied as radioligands in intact human platelets. [3H]52770 RP and [3H]WEB 2086 bound specifically to high-affinity sites with dissociation constants (Kd) of 14.8 and 6.1 nM, respectively. The maximal number of sites for [3H]52770 RP binding was approx. 15-fold higher than for [3H]PAF and [3H]WEB 2086. In addition, C16-PAF, lyso-PAF, WEB 2086 and 52770 RP had Ki values which were nearly identical for both [3H]PAF and [3H]WEB 2086, whereas only 52770 RP competed for [3H]52770 RP-binding sites. These results demonstrate that in human platelets the sites of [3H]WEB 2086 binding are identical to [3H]PAF-binding sites, whereas those of [3H]52770 RP are not. [3H]WEB 2086 appears, therefore, to be a suitable antagonist radioligand for labelling PAF receptors.     

Photoperiodic response of serotonin- and galanin-immunoreactive neurons of the paraventricular organ and infundibular nucleus in Japanese quail, Coturnix coturnix japonica

We investigated the photoperiodic response of serotonin- and galanin (GA)- immunoreactive (ir) cells in the paraventricular organ (PVO) and infundibular nucleus (IF) of the Japanese quail and the interaction of these cells with gonadotropin-releasing hormone (GnRH)-ir neurons in the hypothalamus. Serotonin-ir cells were located in series from the PVO to the IF, and were connected with each other. The number of serotonin-ir cells differed significantly between light and dark phases on the short days (SD), but did not differ between light and dark phases on long days (LD). GA-ir cells were also found in the PVO and IF. The number of GA-ir cells under SD conditions was significantly greater than under LD conditions but did not change diurnally. Both serotonin-ir and GA-ir fibers ran along the GnRH-ir cells in the nucleus commissurae pallii. Serotonin-ir and GA-ir fibers were connected with the GnRH-ir fibers in the external layer of the median eminence (ME). We confirmed that GA-ir fibers were closely associated with serotonin-ir neurons in the PVO and IF. GA-ir neurons have at least 2 routes of regulating GnRH neurons directly, and indirectly via the serotonin-ir cells in the PVO and IF.     

Biosynthesis and action of neurosteroids in the cerebellar Purkinje neuron

The brain is considered to be a target site of peripheral steroid hormones. In contrast to this classical concept, new findings over the past decade have established that the brain itself also synthesizes steroids de novo from cholesterol through mechanisms at least partly independent of peripheral steroidogenic glands. Such steroids synthesized de novo in the brain, as well as other areas of the nervous system, are called neurosteroids. To understand neurosteroid actions in the brain, we need data on the specific synthesis in particular sites of the brain at particular times. Therefore, our studies for this exciting area of brain research have focused on the biosynthesis and action of neurosteroids in the identified neurosteroidogenic cells underlying important brain functions. We have demonstrated that the Purkinje cell, a typical cerebellar neuron, is a major site for neurosteroid formation in the brain. This is the first observation of neuronal neurosteroidogenesis in the brain. Subsequently, genomic and nongenomic actions of neurosteroids have become clear by a series of our studies using an excellent Purkinje cellular model. On the basis of these findings, we summarize the advances made in our understanding of biosynthesis and action of neurosteroids in the cerebellar Purkinje cell.     

Hypothalamic LPXRF-amide peptides in vertebrates: identification, localization and hypophysiotropic activity

Probing undiscovered neuropeptides that play important roles in the regulation of pituitary function in vertebrates is essential for the progress of neuroendocrinology. Recently, we identified a novel hypothalamic neuropeptide with a C-terminal LPLRF-amide sequence in the quail brain. This avian neuropeptide was shown to be located in the hypothalamo-hypophysial system and to decrease gonadotropin release from cultured anterior pituitary. We, therefore, designated this novel neuropeptide as gonadotropin-inhibitory hormone (GnIH). We further identified novel hypothalamic neuropeptides closely related to GnIH in the brains of other vertebrates, such as mammals, amphibians, and fish. The identified neuropeptides possessed a LPXRF-amide (X = L or Q) motif at their C-termini. These LPXRF-amide peptides also were localized in the hypothalamus and other brainstem areas and regulated pituitary hormone release. Subsequently, cDNAs that encode LPXRF-amide peptides were characterized in vertebrate brains. In this review, we summarize the identification, localization, and hypophysiotropic activity of these newly identified hypothalamic LPXRF-amide peptides in vertebrates.     

Carbon and Nitrogen Mineralization of Lead Treated Soils in the Eastern Mediterranean Region,Turkey

The aim of this study was to determine the first effect of lead on microbial activity in soil. The study was carried out in the soil samples from four different radish (Raphanus sativus L. var. radicula, Brassicaceae) fields along the highway in a district (Kadirli, Osmaniye) of the Eastern Mediterranean Region, Turkey. After the calculation of Pb contents, the Pb amounts of the soil samples were brought up to 50 and 100 mg Pb kg^?1 by treatment with Pb(NO ₃ ) ₂ , and the samples for the carbon and the nitrogen mineralization were incubated under controlled conditions (28°C, constant moist). The carbon mineralization was determined by a CO ₂ respiration method for 30 days. The nitrogen mineralization was observed in vitro for 6 weeks. The untreated group was statistically different from the 50 and 100 mg Pb kg^?1 treatments in the aspect of the C(CO ₂ ) outlet during mineralization (P ≤ 0.05), but difference between the 50 and 100 mg Pb kg^?1 treatments was not significant. NH ₄ -N and NO ₃ -N contents of each soil were shown differences between across treatments. Based on these results, it is possible to conclude that the addition of 50 and 100 mg Pb kg^?1 provided a toxic effect threshold for the microbial activity into 30 days.