PubMed · 4245943
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J D Maloney, J P Smith. 1970. Temporary cutaneous loop ureterostomy.. https://doi.org/10.1016/s0022-5347(17)62050-0
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The role of the gubernaculum during the inguino-scrotal phase of testicular descent remains controversial. Some authors propose involution and eversion while others suggest active migration, although the site of growth is unknown. We aimed to determine whether the gubernacular bulb is actively proliferating or regressing during inguino-scrotal testicular descent in the rat. Gubernacula were removed from Sprague-Dawley rats and congenitally-cryptorchid TS mutant rats. Animals (0, 3, 7, 10, and 11 days of age) were treated with bromodeoxyuridine (BUdR) 2 hr before they were killed. BUdR incorporation into newly synthesized DNA served as a marker of cell division. The gubernacula were histologically processed for hematoxylin-eosin (H&E) and immunoperoxidase staining. Four different areas within the gubernaculum were examined for BUdR-positive cells: area 1: plica gubernaculi (cord); area 2: pars infravaginalis gubernaculi (bulb); area 3: distal part of the cremaster muscle; and area 4: proximal part of the cremaster muscle. The rate of cell division for each of these areas was determined by counting the number of BUdR-positive cells per 100 cells. The highest rate of BUdR labeling in both types of rats was in area 2, which is the tip of the gubernacular bulb, and this was significantly greater (P < 0.0001) than in the gubernacular cord or developing cremaster muscle. The mitotic activity was also noted to be significantly greater (P < 0.0001) at the distal end of the cremaster muscle than at the proximal end. The amount of mitosis decreased significantly (P < 0.01) in areas 2 and 4 of the gubernaculum in Sprague-Dawley rats across the period studied. This trend was not observed in TS rats. Our results suggest that the bulb actively proliferates after birth, with possible differentiation into new cremaster muscle cells. We propose that the bulb is the growing end of the elongating gubernaculum, analogous to the growth of a limb bud.
We tested the hypothesis that abdominal muscles are active during the expiratory phase of the respiratory cycle during exercise. Electromyographic (EMG) activities of external oblique and rectus abdominis muscles were recorded during incremental exercise to exhaustion and during 30 min of constant work rate exercise at an intensity of 85 % of the peak oxygen consumption rate (V(O(2))). High amplitude intramuscular EMG activities of both abdominal muscles could be evoked with postural manoeuvres in all subjects. During cycling, respiratory-related activity of the external obliques was evoked in four of seven subjects, whereas rectus abdominis activity was observed in six of the seven subjects. We measured only the activity that was confined exclusively to the expiratory phase of the respiratory cycle. Expiratory activity of both muscles increased with exercise intensity, although peak values averaged only 10-20 or 20-40 % of the peak activity (obtained during maximal, voluntary expiratory efforts) for the external oblique and rectus abdominis muscles, respectively. To estimate how much of the recorded abdominal muscle activity was supporting leg movements during exercise, we compared the activity at the very end of incremental exercise to that recorded during the first five respiratory cycles after the abrupt cessation of exercise, when ventilation was still very high. Although external oblique activity was reduced after exercise stopped, clear expiratory activity remained. Rectus abdominis activity remained high after exercise cessation, showing a gradual decline that approximated the decline in ventilation. During constant work rate exercise, EMG activities increased to 40-50 and 5-10 % of peak in rectus and external oblique muscles, respectively, and then plateaued for the remainder of the bout in spite of a continual upward drift in (V(O(2))) and pulmonary ventilation. Linear regression analysis showed that the rise in respiratory-related expiratory muscle activity during progressive intensity exercise was significantly correlated with ventilation, although weakly. In constant work rate exercise, expiratory EMG activities increased, but the changes were highly variable and did not change as a function of exercise time, even though ventilation drifted significantly with time. These experiments suggest that abdominal muscles play a role in regulating the ventilatory response to progressive intensity bicycle exercise, although some of the observed activity may support postural adjustments or limb movements. The contribution of abdominal muscles to ventilation during constant work rate exercise is variable, and expiratory activity does not 'drift' significantly with time.
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