Time course of the effects of different cannabimimetics on prolactin and gonadotrophin secretion: evidence for the presence of CB1 receptors in hypothalamic structures and their involvement in the effects of cannabimimetics

Several reports have demonstrated that (-)-delta9-tetrahydrocannabinol (delta9-THC) and arachidonylethanolamide [anandamide (AEA)] were able to inhibit prolactin (PRL) secretion from the anterior pituitary gland in male rodents, whereas ovarian phase-dependent effects were seen in females. However, in most of these studies, the analysis of PRL levels was performed at times longer than 30 min after cannabinoid administration. In the present study, we examined the time course of the effects of three different cannabimimetics, delta9-THC, AEA, and AM356 (R-methanandamide), a more stable analog of AEA, on PRL and gonadotrophin secretion in male Wistar rats. In addition, we characterized the presence of cannabinoid receptors in hypothalamic structures related to neuroendocrine control and studied their potential involvement in the effects of cannabimimetics. We found that the three compounds decreased plasma luteinizing hormone (LH) levels, although only the effects of delta9-THC were statistically significant. The inhibitory effect was already apparent at 40 min after administration, but only in the case of delta9-THC did it persist up to 180 min after administration. No significant changes were seen in plasma follicle-stimulating hormone (FSH) levels after the administration of any of the three different cannabimimetics at any of the four times analyzed. Both AEA and AM356 produced a significant decrease in plasma PRL levels, which appeared at 20 min after administration and persisted up to 60 min, waning after this time. Interestingly, the time course of the effect of delta9-THC resembled that of AEA and AM356 only during the later part of the response, because delta9-THC produced a marked increase in plasma PRL levels at 20 min, no changes at 40 min and a decrease from 60 min up to 180 min. In additional experiments, we tried to elucidate which of these two phases observed after delta9-THC administration was mediated by the activation of cannabinoid receptors. These receptors are present in hypothalamic structures related to neuroendocrine control, with the highest densities in the arcuate nucleus (dorsal area) and the medial preoptic area, and the lowest in the lateral hypothalamic area, although none of these regions exhibited high densities for this receptor as compared with classical regions containing cannabinoid receptors, such as the basal ganglia. The activation of these receptors by delta9-THC seems to be involved in the inhibitory phase of the effect of this cannabinoid on PRL release, but not in the early stimulation; when these receptors were blocked with a specific antagonist, SR141716, the stimulation by delta9-THC was still observed, but the late inhibition was abolished. In summary, AEA and AM356 markedly decreased PRL release and slightly decreased LH secretion, with no changes on FSH release. delta9-THC also produced a marked inhibition of LH secretion, but its effects on PRL were biphasic with an early stimulation not mediated by the activation of cannabinoid receptors, followed by a late and cannabinoid receptor-mediated inhibition. Their site of action may well be the hypothalamic structures related to neuroendocrine control, which contain a small, but probably very active, population of cannabinoid receptors.     

Herpetic syringitis associated with eccrine squamous syringometaplasia in HIV-positive patients

In Canada, ostriches are now slaughtered for their meat and hides. The mortality rate in ostrich farming is highest in chick units. An increased chick survival rate impacts positively on production and profit. This paper will focus on common health disorders that affect chick production costs. These are discussed under the following categories: digestive, orthopedic, respiratory, and integumentary disorders. Methods for elimination or reduction of these mortality factors are also discussed.     

Eliminating small stopping sets in irregular low-density parity-check codes

We present a novel scheme to eliminate small stopping sets in irregular low-density parity-check (LDPC) codes. By adding several new check nodes and having their edges connected to small stopping sets in the original code, the improved code decreases the number of small stopping sets efficiently. Simulation results show that the proposed scheme decreases the frame error rate (FER) significantly in the error floor region, whereas having almost the same rate as the original code.     

Rapid and accurate determination of VFAs and ethanol in the effluent of an anaerobic H2-producing bioreactor using near-infrared spectroscopy

A rapid quantification method, based on Fourier transform near-infrared (FT-NIR) spectroscopy, was developed and validated to nondestructively quantify the concentrations of volatile fatty acids and ethanol in the effluent of an anaerobic H₂-producing bioreactor. The first-derivative spectra calculated by a simple numerical difference, combined with the orthogonal signal correction method, were used as spectral preprocessing options. A calibration model was established and validated using gas chromatography measurement results. The number of internal latent variables was optimized based on the lowest root-mean-square error of calibration. The calibration model established shows the satisfactory results for the lowest root-mean-square errors of prediction compared to other preprocess methods. The method developed in this work is demonstrated to be more flexible compared with other approaches to determine the concentrations of volatile fatty acids and ethanol in the anaerobic reactor effluents.