Young coconut juice significantly reduces histopathological changes in the brain that are induced by hormonal imbalance: a possible implication to postmenopausal women.

BACKGROUND AND AIM: Some degenerative diseases of the nervous system have been linked to hormonal imbalance in postmenopausal women. It is argued that young coconut juice (YCJ) could have some estrogen-like characteristics, but this is still debatable. Our aim was to investigate this argument, and to examine whether YCJ has any neuroprotective effects. MATERIALS AND METHODS: Four groups of female rats (10 in each group) were included in this study. These included sham-operated, overiectomized (ovx), ovx and receiving estradiol benzoate (EB) injections intraperitoneally, and ovx and receiving YCJ orally. At the end of the five-week study, the rats were sacrificed, and their serum estradiol (E2) level was measured by chemiluminescent immunoassay. Moreover, the rat brains were excised, and the cortical pyramidal neurons were examined using markers of neuronal cell death, namely anti-neurofilament (NF200) and anti-parvalbumin (PV) antibodies. RESULTS: Our results showed that the rat group which received YCJ had its serum E2 level significantly (P<0.05) higher than the ovx group which did not receive any treatment, and the sham-operated group. A similar trend was observed with the group which received EB injections, but no significant difference was present when the latter was compared with the sham-operated group. In addition, a significant reduction in neuronal cell death was observed in the YCJ-treated group, as compared to the ovx group which did not receive any treatment. This was indicated by the significantly (P<0.05) higher number of neurons which were immunopositive for NF200 and PV. Interestingly, the number of these neurons was also significantly (P<0.05) higher in the YCJ group, as compared to the EB group. CONCLUSION: This study confirms the argument that YCJ has estrogen-like characteristics, and it also adds more evidence to the observation that hormonal imbalance could induce some brain pathologies in females.

The in vitro anti-giardial activity of extracts from plants that are used for self-medication by AIDS patients in southern Thailand.

This study evaluated the anti-giardial activity of chloroform, methanol and water extracts of 12 medicinal plants (39 extracts), commonly used as self medication by AIDS patients in southern Thailand. The plant extracts and a standard drug, metronidazole, were incubated with 2x10(5) trophozoites of Giardia intestinalis per millilitre of growth medium in 96-well tissue culture plates under anaerobic conditions for 24 h. The cultures were examined with an inverted microscope and the minimum inhibitory concentration and the IC50 value for each extract was determined. The chloroform extracts from Alpinia galanga, Boesenbergia pandurata, Eclipta prostrata, Piper betle, Piper chaba, Zingiber zerumbet, and the methanol extracts from B. pandurata and E. prostrata were classified as "active", i.e. with an IC50 of <100 microg/ml, whereas the chloroform extract from Murraya paniculata was classified as being "moderately active". This study shows that extracts from some medicinal plants have potential for use as therapeutic agents against G. intestinalis infections.

Effects of pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) on hormone secretion from sheep pituitary cells in vitro.

Although vasoactive intestinal polypeptide (VIP) is thought to be a prolactin releasing factor, in vivo studies on sheep suggest that it is inactive in this species. Recent studies, based primarily on the rat, suggest that the related pituitary adenylate cyclase-activating polypeptide (PACAP) is also a hypophysiotrophic factor but again in sheep, this peptide has no in vivo effects on hormone secretion despite being a potent activator of adenylate cyclase in vitro. This lack of response to either peptide in vivo in sheep could be due to the low concentration of peptide that reaches the pituitary gland following peripheral injection. In the present study we therefore adopted an alternative approach of evaluating in vitro effects of these peptides on GH, FSH, LH or prolactin secretion from dispersed sheep pituitary cells. In a time-course study, PACAP (1 mumol/l) increased GH concentrations in the culture medium between 1 and 4 h and again at 12 h but had no effect in the 6 and 24 h incubations. Prolactin, LH and FSH were not affected by PACAP. The response to various concentrations of PACAP (1 nmol/l-1 mumol/l) were then evaluated using a 3 h incubation. Again prolactin and LH were not affected by PACAP and there was a small increase in GH concentrations but only at high concentrations of PACAP (0.1 and 1 mumol/l; P < 0.05). PACAP also stimulated FSH secretion in cells from some animals although this effect was small. The GH response to PACAP was inhibited by PACAP(6-38), a putative PACAP antagonist, but not by (N-Ac-Tyr1, D-Arg2)-GHRH(1-29)-NH2, a GH-releasing hormone (GHRH) antagonist. The cAMP antagonist Rp-cAMPS was unable to block the GH response to PACAP suggesting that cAMP does not mediate the secretory response to this peptide. At incubation times from 1-24 h, VIP (1 mumol/l) had no effects on prolactin, LH or GH secretion and, in a further experiment based on a 3 h incubation, concentrations of VIP from 1 nmol/l-1 mumol/l were again without effect on prolactin concentrations. Interactions between PACAP and gonadotrophin releasing hormone (GnRH), GHRH and dopamine were also investigated. PACAP (1 nmol/l-1 mumol/l) did not affect the gonadotrophin or prolactin responses to GnRH or dopamine respectively. However, at a high concentration (1 mumol/l), PACAP inhibited the GH response to GHRH. In summary, these results show that PACAP causes a modest increase in FSH and GH secretion from sheep pituitary cells but only at concentrations of PACAP that are unlikely to be in the physiological range. The present study confirms that VIP is not a prolactin releasing factor in sheep.

A method for drug infusion into the lateral median eminence and arcuate nucleus of sheep.

The role of catecholamines in the control of the GnRH pulse generator is unclear as studies have relied on the use of peripheral or intracerebroventricular injections, which lack specificity in relation to the anatomical site of action. Direct brain site infusions have been used, however, these are limited by the ability to accurately target small brain regions. One such area of interest in the control of GnRH is the median eminence and arcuate nucleus within the medial basal hypothalamus. Here we describe a method of stereotaxically targeting this area in a large animal (sheep) and an infusion system to deliver drugs into unrestrained conscious animals. To test our technique we infused the dopamine agonist, quinpirole or vehicle into the medial basal hypothalamus of ovariectomised ewes. Quinpirole significantly suppressed LH pulsatility only in animals with injectors located close to the lateral median eminence. This in vivo result supports the hypothesis that dopamine inhibits GnRH secretion by presynaptic inhibition in the lateral median eminence. Also infusion of quinpirole into the medial basal hypothalamus suppressed prolactin secretion providing in vivo evidence that is consistent with the hypothesis that there are stimulatory autoreceptors on tubero-infundibular dopamine neurons.

Pituitary adenylate cyclase-activating polypeptide acts within the medial basal hypothalamus to inhibit prolactin and luteinizing hormone secretion.

In this study, we investigated the hypothalamic regulatory role of pituitary adenylate cyclase-activating polypeptide (PACAP) in the control of LH and PRL secretion. Overiectomized ewes were surgically prepared with bilateral guide tubes directed at the preoptic area (POA) or medial basal hypothalamus (MBH). After recovery from surgery, PACAP38 (0.1 nmol in 2.5 microliters over 1 h) or vehicle was bilaterally infused into each site in separate trials. Infusion of PACAP38 into the POA had no effect on either LH or PRL secretion. However, infusion of the peptide into the MBH suppressed PRL secretion during the 3-h postinfusion period; the responding animals (n = 9) had injectors located in the arcuate nucleus. In the three nonresponding animals, both injectors were outside the arcuate nucleus. Mean LH concentration, LH pulse frequency, and pulse amplitude were also significantly suppressed, with LH pulsatility declining in seven of eight animals during infusion of the peptide in the MBH. These results suggest that PACAP acts in the arcuate nucleus region of the MBH, and not the rostral POA, to inhibit both LH and PRL secretion.

Effects of pituitary adenylate cyclase-activating polypeptide and vasoactive intestinal polypeptide on cyclic AMP accumulation in sheep pituitary cells in vitro.

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) are known to stimulate adenylate cyclase activity in rat pituitary cells but no direct effects have been reported on sheep pituitary cells. In this study we determined whether either peptide could stimulate intracellular cAMP accumulation in dispersed sheep pituitary cells in primary culture. Time course studies with PACAP showed that tachyphylaxis developed rapidly and so a short incubation time (5 min) was used to define the dose-response relationship. PACAP dose-dependently stimulated intracellular cAMP levels with a half-maximum response at 2.9 +/- 0.2 nmol/l (n = 4). In contrast, VIP only caused a small increase in intracellular cAMP levels at the highest dose tested (1 mumol/l). The VIP antagonist [4Cl-D-Phe6,Leu17]VIP had no effect on the cAMP response to either PACAP or VIP while the peptide PACAP(6-38), a putative PACAP antagonist, blocked the cAMP response to PACAP. The desensitisation to PACAP was further investigated by pretreating cells with PACAP for 30 min. After a further 15 min in culture medium alone, these cells showed no cAMP response to subsequent treatment with PACAP but could respond to forskolin. When a longer incubation period of 240 min was used between the first and second treatment with PACAP, a partial return in responsiveness to PACAP was observed. In summary, these results show that PACAP activates adenylate cyclase in sheep pituitary cells but that there is rapid development of tachyphylaxis. Experiments with the antagonists suggest that the response to PACAP is via the PACAP type I receptor. In contrast, physiological doses of VIP do not stimulate cAMP accumulation in sheep pituitary cells.

Effects of pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) on prolactin, luteinizing hormone and growth hormone secretion in the ewe.

This study was undertaken to investigate the roles of PACAP and VIP in the control of pituitary hormone secretion in the ewe. The first experiment was designed to identify any direct effects at the level of the pituitary and was conducted during the luteal phase of a prostaglandin-synchronized oestrous cycle. PACAP (0.008, 0.04, 0.2 and 1.0 nmol/min) or VIP (0.06, 0.2, 0.6 and 1.8 nmol/min) was infused into the carotid artery over a 10 min period. Blood samples were taken before and after the infusions so that plasma PRL, LH and GH concentrations could be measured. Blood pressure was also monitored to determine if the doses used were biologically active. In no case was an effect on hormone secretion observed. In contrast, the highest dose of each peptide induced an increase in heart rate to almost three-fold the resting value. Although both peptides are active in vivo, this result suggests that neither peptide has a direct effect on hormone release from the pituitary of prostaglandin-synchronized ewes. In a second experiment, we investigated whether the peptides had central effects on hormone secretion. Intracerebroventricular (ICV) injection of PACAP or VIP at the dose 10 nmol was tested in ovariectomized ewes. After injection, PACAP suppressed PRL and GH secretion so that plasma hormone concentrations from 1-3 h after injection were significantly different from the control (P < 0.05 for PRL, P < 0.01 for GH). In addition, PACAP significantly reduced mean LH concentration (P < 0.05) and LH pulse frequency (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of pituitary adenylate cyclase activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) on the cardiovascular system in sheep.

The cardiovascular effects of PACAP and VIP were studied in intact conscious sheep; PACAP (0.008, 0.04, 0.2, and 1.0 nmol/min) and VIP (0.07, 0.2, 0.6, and 1.8 nmol/min) were infused in conscious sheep for periods of 10 min. For each peptide there was a dose-dependent increase in heart rate. At the highest doses tested, pulse pressure and mean arterial pressure tended to increase and decrease, respectively. However, only the decrease in mean arterial pressure following the highest dose of VIP reached significance. At the highest doses tested, heart rate increased nearly threefold during the infusion while mean arterial pressure declined by 18.5%. In individual animals the decrease in blood pressure and increase in heart rate occurred simultaneously, so that we were unable to conclude whether the increase in heart rate was due to a baroreceptor reflex.