الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 158 |  |  |
| | | from | 158 | | |
Abstract
The present study is an endeavor for profound exploration about the role of some inhibitory (GABA and taurine) and excitatory (L-argnine and glutamic acid) neurotransmitters on gonadotropins release from pituitary cell cultures collected from normal camel bulls and those suffering from trypanosomiasis during the breeding season before and after addition of GnRH. Attention was also directed to find out the influence of calcium agonists and antagonists on these cultures.
For this purpose, 266 blood samples with their corresponding pituitaries were collected from bull camels during the breeding season. The blood samples were divided into two halves; the first was used for parasitological examination while the other half for testesterone assay. The corresponding pituitaries were used for tissue culturing.
Detection of Trypanosoma evansi infection was done by examination of Giemsa-stained blood smears as well as mouse inoculation test. Moreover, the prepared tissue cultures were subjected to inhibitory neurotransmitters (GABA at dose rates of 0.1, 0.5 and 1.0 mM as well as taurine at dose rates of 0.1, 0.5 and 1.0 mM) and excitatory neurotransmitters (L-argnine at dose rates of 10.89, 21.77 and 43.55mM as well as L-glutamic acid at 0.5, 1.0 and 2.0 mM). The cultures were also subjected to calcium agonist (calcium chloride at dose rates of 1.0, 10.0 and 100.0 µg / ml) and antagonist (verapamil hydrochloride at dose rates of 50.0, 100.0 and 200 µl /ml). FSH and LH as well as testosterone levels were estimated using ELISA techniques.
Geimsa staining blood smear technique indicated that 11 animals (4.14 %) were infected with T. evansi while mouse inoculation test indicated that 50 animals (18.79 %) were infected with T. evansi during breeding season. Regarding the effect of different neurotransmitters in healthy cultures, GnRH supplementation alone resulted in significant release of both FSH and LH. GABA neurotransmitter at dose rate of 10.3 and 51.5 µg / ml before GnRH led to significant inhibition of FSH and LH release from camel pituitaries. Addition of GABA (10.3 and 51.5 µg / ml) together with GnRH did not affect either the stimulatory effect of GnRH or the neurotransmitter inhibitory effect on gonadotropins release. Increasing GABA concentration to 103 µg / ml either alone or in combination with GnRH did not display any significant variation in gonadotropins level than their corresponding pre-treatment values. Addition of taurine at different concentrations did not affect the release of both gonadotropins from the pituitary cell cultures either before or after GnRH supplementation. On the other side, the effect of L-arginine on the release of FSH and LH in healthy male camel pituitary cell cultures was dose-dependent. At dose rate of 10.89 mM, the neurotransmitter stimulated gonadotropin release as well as augmented GnRH effect. The two other higher dose rates of L-arginine resulted in depression of gonadotropins release and antagonized GnRH effect. Addition of L-glutamine to the media resulted in stimulation of both gonadotropins release, particularly LH, and augmented GnRH induced action. This effect was dose-dependent at dose rates of 0.5 and 1.0 mM. However, increasing the dose rate to 2.0 mM did not accompany with increased release of both hormones than that recorded at 1.0 mM.
On the contrary, pituitary cell cultures of trypanosoma-infected camel bulls, reveal that all pituitaries collected from infected animals did not show any response to either inhibitory or excitatory neurotransmitters and/or GnRH. In addition, there was an apparent significant DROP in gonadotropins level of infected animals as compared with their corresponding values of healthy ones.
Regarding the effect of calcium, in healthy cases, GnRH induced a stimulatory effect on the release of gonadotropins; a result which was augmented by the addition of calcium chloride at a dose rate of 1.0 µg / ml. Other dose rates of calcium chloride did not show any increase in gonadotropins release as compared with their corresponding pre-treatment values. Application of verapamil HCl (calcium antagonist) at a dose rate of 50 µl / ml to pituitary cultures of healthy camels led to remarkable DROP in gonadotropins level as well as it antagonized the stimulatory effect of GnRH on both hormones. These results were also recorded at dose rates of 100 and 200 µl / ml but the hormonal levels did not show significant variation than those recorded upon application of 50 µl / ml.
The present results revealed that infection by the parasite resulted in remarkable DROP in testosterone level (from 12.25 2.65 ng / ml in healthy bulls to 6.77 2.04 ng / ml in infected ones).
Therefore, it was concluded that T. evansi infection in camel bulls resulted in deleterious effects upon the release of pituitary gonadotropins and consequently reproduction. Also, infection led to remarkable DROP in circulating testosterone level. These deviations could not be corrected by neurotransmitters, GnRH or calcium agonists and antagonists.