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Image 7 of Progress report (Kentucky Agricultural Experiment Station) n.196

Part of Kentucky Agricultural Experiment Station

-5- GENETICS AND PHYSIOLOGY SECTION HISTOLOGICAL CHANGES IN THE CIRCULATORY SYSTEM WITHIN THE PAMPINIFORM PLEXUS AND TESTIS OF HEATSTRESSED RAMS R. S. Sand and R. H. Dutt Blood flow in ram testes has been shown by use of a 133Xenon washout technique to double initially and then to decline to approximately onehalf control values by the fifth and seventh days of heat stress. Blood flow changes were similar with both whole body heat stress and with local application of heat to the scrotum, which suggests that a mechanism responsible for regulating testis blood flow rate is located in or near the testes. The role of the pampiniform plexus in regulating blood flow was studied. Histological sections of the circulatory system were prepared from the pampiniform plexus, testis and a portion of the spermatic artery anterior to the pampiniform plexus from control rams and from rams . ( after 7 days of heat stress (320C, 62 to 72% relative humidity). No significant changes were detected in the venous vessels at any location sampled. Exposing the rams to heat for 1 week significantly increased thickness of arterial walls (Table 1). The arterial wall was significantly (P < . 05) thicker anterior to the pampiniform plexus (21%) and at the top of the pampini- form plexus (22%). The increase (62%) in arterial wall thickness in the middle of the pampiniform plexus was highly (P < . 01) significant. The treatment had no significant effect on arterial wall thickness at the base of the pampiniform plexus nor at the testis locations. Table 1. Mean Arterial Wall Thickness (microns) by Location for Treated and A Control Rams ; Locationa Anterior Group Spermatic Pam iniform Plexus Testis Arter To Middle Base Middle Distal Control 178b 171 125 098 095 076 Treated 216C 209C 202d 121 109 089 Percent change due to treatment +21 +22 +6 2 +23 +1 5 +1 7 %/Difference among locations highly significant (P< . 01). E/Mean of 8 observations (2 sections from each testis from 2 rams). H/Sinificantly (P< . 05) thicker than controls. Significantly (P< .01) thicker than controls. Diameter of the spermatic artery in the middle of the pampiniform plexus was significantly (P . 05) decreased by 28%. The decrease in arterial diameter suggests that this location may be the site of blood flow regulation to the testis. It should be pointed out that the arterial diameter was decreased from 4 to 28% at locations in the pampiniform plexus and increased from 14 to 16% in the testis from the treated rams (Table 2). Thus, there is no evidence to suggest that changes in the blood vessels within the testis were responsible for the decreased blood flow. In the treated rams the mean crosssection area of the artery in the middle of the pampiniform plexus was 0. 14 mm2 compared with 0. 27 mm2. Exposure to heat stress reduced the area of the lumen of the artery in this region to 52% of that for control rams. Changes induced in arterial wall thickness and lumen diameter in the midregion of the pampini- form plexus by heat stressing indicate that the pampiniform plexus acts as a biological thermostat to control blood flow to the testes. Furthermore, results of this study suggest that the reduced blood flow may be responsible for spermatogenic impairment in heatstressed rams.

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