The Gliding Force and Work of Flexion in the Early Days after Primary Repair of Lacerated Flexor Tendons: an Experimental Study

We measured the resistance to tendon mobilisation within the first 5 days after primary repair of digital flexor tendons of chickens. Forty-six long toes of 23 chickens were assigned to six surgical groups and one unoperated control group. The tendons were partially lacerated and surgically repaired. The resistance to simulated active digital flexion was assessed in six operated groups at 0, 1, 2, 3, 4 and 5 days postoperatively. The force of tendon motion and work of flexion increased gradually from day 0 to day 5. The force and work at days 4 and 5 were significantly higher than those at days 0 and 1. No statistical difference was found in the resistance at days 0, 1, 2 and 3. Our results indicate that the gliding resistance gradually increases over the first 5 days after surgery and suggest that tendon motion may be started after the first 3 days, to avoid moving during this period of increased resistance with increased risk of tendon rupture.

Effect of carotid body denervation on breathing in neonatal goats

The objective of the present study was to determine in goats whether carotid body denervation (CBD) at 1–3 days of age causes permanent changes in breathing greater than those that occur after CBD in adult goats. Goats underwent CBD ( n = 6) or sham CBD ( n = 3) surgery at 1–3 days of age. In addition, one unoperated control animal was studied. Bolus intravenous injections of NaCN 2 days postsurgery verified successful CBD surgery. However, at 3, 11, and 18 mo of age, the CBD goats had regained a NaCN response that did not differ ( P > 0.10) from that of intact goats. Intracarotid NaCN injections elicited a hyperpnea in the sham CBD but not the CBD goats. Only one animal exhibited highly irregular breathing [characterized by prolonged (>9-s) apneas] after CBD, and the irregularity disappeared by 3 mo of age. One CBD goat died at 35 days of age, and autopsy revealed that death was associated with pneumonia. After 3 mo of age, there were no statistically significant differences ( P > 0.10) between sham and CBD goats in eupneic breathing, hypoxia and CO2 sensitivity, and the exercise hyperpnea. It is, therefore, concluded that CBD at 1–3 days of age in goats does not appear to affect selected aspects of respiratory control after 3 mo of age, conceivably because of the emergence of other functional chemoreceptors that compensate for the loss of the carotid chemoreceptor.

The effect of malnutrition on the metabolic response to surgery

The effect of previous malnutrition on the metabolic response to surgical hysterectomy was investigated in adult female rats. Malnutrition was achieved by feeding a 20 g protein/kg diet and restricting food intake to 50 % of normal. This dietary regimen was maintained for 3 weeks before surgery and for 4 d after surgery. Unoperated control rats were pair-fed with the hysterectomized rats after surgery. Energy balance was measured by the comparative carcass technique and, in a second experiment, urinary N excretion was measured. Surgery caused energy expenditure to increase by 37 % in ad libitum-fed rats but in malnourished rats it increased by only 22 %. Urinary N excretion rose immediately after surgery. In the ad libitum-fed rats it was on average 85 % greater in hysterectomized rats than controls for the first 3 d after surgery, whereas in the restricted rats it was 74 % greater on the first day and not significantly elevated thereafter. Thus, malnutrition attenuated the metabolic response to surgery but did not abolish it completely.

Evaluation of a Method for Biopsy of the Distal Radial Physeal Growth Plate in Neonatal Foals

SummaryA technique was devised for taking biopsies from the distal radial physeal growth plate in neonatal foals to study cartilage morphology. The biopsy taken from the right forelimb of 21 Thoroughbred foals, four to 10 days of age, was performed under inhalation anaesthesia, using a 9 mm diameter trephine on a multi speed drill. Due to their exercise not being adequately restricted postoperatively, five foals (24%) developed excessive incisional granulation tissue at the biopsy site. Nine foals (43%) developed some flexion of the carpus (over at the knee) and 15 (71%) developed outward rotation of the left limb. There was significantly greater carpal valgus in the left limb when compared with the right limb (p <0.005), a situation which was not present in six agematched, unoperated, control foals. Abnormalities in the congruency of the antebrachiocarpal joint were not detected grossly at postmortem at five months of age. However, there were localised gross and histological abnormalities of the distal radial physeal growth plate. Postoperative morbidity, significant changes to conformation, and the unknown long term consequences of the disruption to the biopsied physeal growth plate are likely to make this procedure inappropriate for clinical usage. However, the biopsy procedure was easy to perform, and provided a suitable sample for both histological and histomorphometric examination of the physeal growth plate cartilage. Therefore this technique provides a useful research method for study of growth plate morphology in neonates.A technique was developed for biopsy of the distal radial physeal growth plate in neonatal foals. Additionally, the effects on conformation, and on gross and histological abnormalities at five months of age, were reported. There were significant, mild conformational abnormalities, which self-corrected without intervention, and there were abnormalities detected at postmortem examination, but these abnormalities did not appear to affect the joint. The expected effects of this procedure are stated, and provided that these are accounted for, the technique is useful for harvesting and studying the physeal growth plate of neonates.

Maturational effects of cortisol on the exocrine abomasum and pancreas in fetal sheep

The role of cortisol in the prenatal development of digestive enzymes in the abomasum (prochymosin and pepsinogen) and pancreas (amylase, trypsin, chymotrypsin) has been investigated in the fetal lamb during late gestation. The abomasum and pancreas were collected from 22 unoperated control fetuses (99-145 days gestation; term, 145 +/- 2 days), from seven pairs of twins infused with either saline or cortisol for five days preceding delivery at 127-133 days, and from four 139-143-day-old fetuses adrenalectomized at 120-123 days. Developmental increases (2-8-fold) occurred in protease concentrations in the fetal abomasum and in amylase and chymotrypsin contents in the fetal pancreas. These increases paralleled the normal prepartum rise in fetal plasma cortisol. In addition, the enzyme values were significantly higher in cortisol-infused than in saline-infused fetuses (with the exception of pancreatic amylase) and were significantly lower in adrenalectomized fetuses than in control fetuses at term. The pH of abomasal fluid remained neutral (pH 6.8-8.0) during late gestation and was not affected by cortisol treatment or adrenalectomy. The results suggest that cortisol stimulates the development of the exocrine abomasum and pancreas in fetal sheep and may, thereby, increase the digestive capacity in neonatal lambs. Compared with the pig, another long-gestation species, the sheep has an early development of gastric pepsinogen but a late development of gastric acidity and pancreatic protease activities.

Control of compensatory lung growth by adrenal hormones

The effects of adrenalectomy and/or in vivo treatment with hydrocortisone acetate (HCA;5 mg X kg-1 X day-1) on lung growth were investigated in control and pneumonectomized rats of 250 g body wt. Left pneumonectomy (day 0) initiated rapid hyperplastic growth of the right lung, which was unaffected by HCA. Similarly, HCA had no effect on lung growth in unoperated control animals. Two weeks after pneumonectomy, right lung dry mass, protein, RNA, and DNA were equal to that in both lungs of unoperated rats. Adrenalectomy 5 days before (day -5) left pneumonectomy increased the rate and extent of right lung growth, but did not change its hyperplastic character. Continuous HCA treatment (days -5 to 14) prevented the adrenalectomy-mediated increase in postpneumonectomy lung growth. "Early" HCA dosing (days -5 to 6) of adrenalectomized-pneumonectomized animals suppressed lung growth to the pneumonectomy level, but from days 7 to 14 growth accelerated to the adrenalectomized-pneumonectomized rate. Conversely, "late" HCA, initiated when adrenalectomized-pneumonectomized animals had restored normal total lung mass (days 6 to 14), quickly reduced right lung growth to rates typical of unoperated controls. The latter effects were not observed unless continuous steroid treatment was provided throughout this interval. The data support a role for glucocorticosteroids in modulation of the accelerated compensatory lung growth initiated by partial resection of the tissue.

Effect of adrenalectomy on LH release in sheep during the anoestrous season

ABSTRACT An experiment was conducted to measure LH pulse frequencies in bilaterally adrenalectomized Ile-de-France ewes during the mid-anoestrous season. Seven ewes were adrenalectomized under general anaesthesia and maintained on daily injections of 3 mg deoxycorticosterone acetate (DOCA). Adrenalectomy did not affect the patterns of LH release and the mean intervals between pulses in the adrenalectomized and sham-operated control ewes were 48 and 52 min respectively. Small implants of oestradiol significantly reduced the frequency of LH pulses in both groups and, in the presence of oestradiol, there were no differences in LH release between adrenalectomized and sham-operated ewes, with the mean interpulse intervals being 91 and 89 min respectively. In a second experiment, designed to assess the effects of DOCA on LH release, the mean interpulse intervals in unoperated control ewes (46 min) and unoperated ewes given daily injections of 3 mg DOCA (47 min) were similar to those observed in adrenalectomized and sham-operated ewes. In the presence of small implants of oestradiol, the combination of DOCA and oestradiol decreased the pulse frequency significantly more than oestradiol alone (mean interpulse intervals of 85 and 65 min respectively) suggesting that DOCA may act as a progestagen in sheep. Thus alternative treatments to DOCA for the maintenance of adrenalectomized sheep must be found for future studies on the role of adrenal steroids in the reproductive system. It appears that adrenal steroids do not play a major role in the seasonal changes in LH release in the ewe. J. Endocr. (1987) 114,437–442

Relaxin acts centrally to inhibit oxytocin release during parturition: an effect that is reversed by naloxone

ABSTRACT Experiments were carried out to establish whether infusion of relaxin prolongs gestation and labour in the rat by suppressing release of oxytocin, and whether the effects of relaxin on birth could be reversed by the opioid antagonist naloxone. Female rats were implanted with subcutaneous osmotic minipumps for the infusion of purified porcine relaxin into the jugular vein for 84 h from either day 19 or day 20 of gestation. Infusion of relaxin delayed the onset of labour and in those animals which delivered during relaxin infusion, delivery was longer by approximately 45 min. Plasma oxytocin levels 40 min after delivery of the first fetus were 45·25 ± 3·6 pmol/l (mean ± s.d.) in unoperated controls and significantly (P < 0·01) depressed (23·89 ± 3·9) in rats that delivered during infusion of relaxin. Rats that delivered after the infusion of relaxin had finished, gave birth significantly (P < 0·05) faster than controls and plasma oxytocin levels were significantly (P < 0·01) raised (77·87 ±15·9 pmol/l). Naloxone treatment (1 mg/kg; i.m.) given immediately after the delivery of the first fetus reversed the inhibitory effect of relaxin and the interval between successive deliveries was slightly faster than that of controls. Plasma oxytocin levels in relaxin-infused naloxone-treated rats were significantly (P < 0·01) higher than values in unoperated control rats. The results confirm that relaxin suppresses oxytocin release possibly through an opioid system and this may be important in the control of the timing of birth. J. Endocr. (1986) 111, 99–102

Hyperstriatal Lesions and Short-Term Retention of Non-Visual Information in Pigeons

Short-term retention of non-visual information was investigated using three series of hyperstriatal-lesioned and unoperated control pigeons. Neither retention (Experiment 1) nor acquisition (Experiment 3) of go/no-go alternation was disrupted by the lesions. Similarly, Experiments 2 and 5 failed to detect significant disruption of either retention or acquisition of spatial alternation. Increases in the retention intervals used in these tasks reduced accuracy in both groups but did not differently affect hyperstriatal as opposed to control performance. A lasting deficit was, however, obtained in a delayed-response task (Experiment 4), but this deficit, which was independent of retention interval, appeared to be the result, not of a disruption of memory, but of an exaggerated perseverative tendency. Experiment 6 confirmed that all three series of hyperstriatal birds showed disruption of reversals of a spatial discrimination. It is concluded that hyperstriatal lesions do not disrupt memory processes, and the hypothesis that hyperstriatal damage induces perseveration of central sets is discussed.

Paleostriatal Lesions and Instrumental Learning in the Pigeon

In three experiments, pigeons with lesions of the paleostriatum (experimental subjects) and unoperated control birds were trained on tasks designed to assess their instrumental learning abilities. In Experiment 1, using an orthodox Skinner box, training was given on a variable interval (VI) followed by a fixed interval (FI) schedule of reinforcement and only non-significant differences between the groups emerged. Experiment 2 examined the performance of the same subjects on a VI schedule in which a response-contingent signal accompanied reinforcement. For control subjects the presence of the signal resulted in a low rate of response compared with that found in equivalent conditions with the signal omitted. Experimental subjects showed the same response rate when the signal was present as when it was absent. Experiment 3 employed naive subjects, and a Skinner box modified to facilitate key-pecking in total darkness. In this apparatus, experimental subjects showed a lowered response rate on a VI schedule. These tasks were analyzed in terms of the classical (stimulus-reinforcer) and instrumental (response-reinforcer) learning they involve. The results suggest that pigeons with paleostriatal lesions show a deficit in forming response-reinforcer associations, perhaps because the lesions reduce the salience of response-produced cues.