Effect of experimental diabetes and vagotomy on gastric emptying in rats.

The present study was performed to evaluate the rate of whole stomach emptying (WSE) in streptozotocin (STZ) induced rat model of diabetes mellitus by assessing the effect of bilateral gastric vagotomy in control as well as in experimental animals. Our results revealed that delayed emptying of solid foods by the stomach is demonstrated within 5 days of induction of diabetes in rats. After bilateral vagotomy, the later stages of WSE slowed down because of the diabetic state, most probably due to the direct effect of diabetes on the gastric antrum.

Differences in active avoidance behaviour of hypoactive and hyperactive rats subjected to immobilisation stress.

Open field activity was studied in Wistar rats. Animals with low scores of ambulatory and rearing behaviours were grouped as hypoactive and those with high scores as hyperactive. Acquisition of active avoidance learning in a shuttle box was studied in the two groups. Hyperactive rats in contrast to hypoactive rats showed a better acquisition of avoidance learning. Learning was suppressed in both groups by domperidone, but was facilitated by immobilisation stress in the hypoactive group only. The two groups did not differ in the basal and stress evoked heart rates. These observations suggest that immobilisation stress favours enhancement of the dopaminergic related behaviour like avoidance learning in hypoactive rats.

Nucleus accumbens lesion does not affect schedule induced polydipsia.

Rats with lesion of nucleus accumbens were hypodipsic under free-feeding conditions. In schedule-induced polydipsia (SIP) tests conducted by reducing the rats to 70% of free-feeding body weight and delivering 60 mg bengal gram pellets on a fixed time 1-min schedule, nucleus accumbens lesions did not delay the acquisition or show a decrease in the maintenance of S.I.P.

Effect of different feeding schedules on food intake in caudate lesioned rats.

Inbred albino rats were exposed to different feeding schedules before and after caudate nucleus lesions. The animals show adaptation to the new patterns of food deprivation even after caudate nucleus lesions. However, the lesioned animals are not able to elevate their food intake or body weight to the prelesion levels. These findings suggest that feeding, satiety and body weight mechanisms are disturbed in the absence of intact caudate nucleus, possibly due to removal of nigro-striatal dopamine influence.

Primary taste discrimination in alloxan diabetic rats with restricted access to testant and water.

This study was conducted to assess the primary taste discrimination in 18 h water deprived control and alloxan diabetic rats for a period of 60 min duration by using two bottle choice paradigm. Different concentrations of sodium chloride, sucrose, urea and hydrochloric acid were used for salty, sweet, bitter and sour taste sensations respectively. Alloxan diabetic rats showed loss of discrimination for sucrose and urea solutions, increased sensitivity for low concentration of hydrochloric acid and no change in sodium chloride taste sensitivity.

Modulation of feeding and drinking by dopamine in caudate and accumbens nuclei in rats.

Injection of dopamine (DA) into accumbens and caudate nuclei facilitates a dose-dependent increase in food and water intake, whereas administration of spiperone (SP), a central D2-receptor antagonist suppresses DA-facilitated food and water intake. Bilateral lesions of nucleus accumbens and caudatus result in a sustained and significant decrease in food and water intake. The results suggest that DA is a neurotransmitter involved in feeding and drinking behavior in accumbens and caudate nuclei and this effect is mediated by central D2 receptors.

The effect of bilateral gastric vagotomy and histamine stimulation on parietal cell activity in streptozotocin induced diabetic rat model.

Disturbances in gastric secretions are commonly associated with diabetes mellitus and are usually attributed to autonomic neuropathy. Systematic documentation of the effects of experimental diabetes on parietal cell functions are not available. This study has been designed to evaluate the acid secretory status of the parietal cells in streptozotocin (STZ) induced rat model of diabetes mellitus by assessing the effect of bilateral gastric vagotomy and histamine administration on them. Results show that bilateral gastric vagotomy in the control rats as well as in experimental diabetes lowers the acid secreting capacity of the parietal cells. In the diabetic rats, however, vagotomy does not further decrease the gastric acid secretion. Histamine stimulation augments the acid secretory response in the controls but this rise is substantially prevented in the diabetic state. Histamine challenge following vagotomy in normal controls elicits a sharp rise in gastric acid secretion though not to the same extent as seen in rats with intact vagi. In the diabetic rats however, histamine fails to augment acid secretion after vagotomy. Diabetes is thus seen to severely impair the acid secretory response of the parietal cells and their responsiveness to histamine.

Effect of yoga training on reaction time, respiratory endurance and muscle strength.

There is evidence that the practice of yoga improves physical and mental performance. The present investigation was undertaken to study the effect of yoga training on visual and auditory reaction times (RTs), maximum expiratory pressure (MEP), maximum inspiratory pressure (MIP), 40 mmHg test, breath holding time after expiration (BHTexp), breath holding time after inspiration (BHTinsp), and hand grip strength (HGS). Twenty seven student volunteers were given yoga training for 12 weeks. There was a significant (P < 0.001) decrease in visual RT (from 270.0 +/- 6.20 (SE) to 224.81 +/- 5.76 ms) as well as auditory RT (from 194.18 +/- 6.00 to 157.33 +/- 4.85 ms). MEP increased from 92.61 +/- 9.04 to 126.46 +/- 10.75 mmHg, while MIP increased from 72.23 +/- 6.45 to 90.92 +/- 6.03 mmHg, both these changes being statistically significant (P < 0.05). 40 mmHg test and HGS increased significantly (P < 0.001) from 36.57 +/- 2.04 to 53.36 +/- 3.95 s and 13.78 +/- 0.58 to 16.67 +/- 0.49 kg respectively. BHTexp increased from 32.15 +/- 1.41 to 44.53 +/- 3.78s (P < 0.01) and BHTinsp increased from 63.69 +/- 5.38 to 89.07 +/- 9.61 s (P < 0.05). Our results show that yoga practice for 12 weeks results in significant reduction in visual and auditory RTs and significant increase in respiratory pressures, breath holding times and HGS.

Effects of undernutrition and sex difference on skeletal muscle function in young rats.

The effects of undernutrition and sex difference on skeletal muscle contractile characteristics were studied in young albino rats. The skeletal muscle (gastrocnemius) of 8 week old pups with only one-third normal food intake (undernourished group = UN group; n = 18), as compared to free fed pups (control group = cont. group; n = 16), showed prolongation of contraction time (23.6 +/- 1.0 Vs 20.9 +/- 0.8 msec, Mean +/- SE, P < 0.05) and relaxation time (31.5 +/- 1.8 Vs 22.9 +/- 1.1 msec, P < 0.001) and retention of contraction force and endurance time. In 18 week old rats the effects of sex difference in females (n = 10), as compared to males (n = 10) were prolongation of contraction time in gastrocnemius (32.2 +/- 1.5 Vs 27.8 +/- 1.5 msec, P < 0.05), less force production in gastrocnemius (668.9 +/- 48.0 Vs 895.4 +/- 93.3 g, P < 0.05) and extensor digitorum longus (20.1 +/- 3.3 Vs 29.9 +/- 2.5 g, P < 0.05) and shorter endurance time (160.8 +/- 10.2 Vs 187.2 +/- 7.1 sec, P < 0.05) in soleus. Thus, it is concluded that early undernutrition has prolonged the contraction and relaxation times of the skeletal muscles and the effect of sex difference in the early adulthood was different in different skeletal muscles.

Septal polydipsia in rats is a primary polydipsia not mediated by dopamine.

Bilateral lesions of nucleus septal lateralis resulted in a sustained and significant increase in water intake, without any change in food intake. Intracerebral injection of dopamine (DA) or of spiperone (a central D2-receptor antagonist) did not elicit any change in water or food intake. The polydipsia resulting from septal lesions is thus a primary polydipsia, which is independent of food intake, and is not mediated by neurotransmitter dopamine.

Effect of head-up tilting on systolic time intervals in normal young volunteers.

Systolic time intervals (STI) are sensitive indices of myocardial function. Passive tilting is a rapidly reversible and non-invasive method for inducing cardiovascular stress. The present work was conducted to study the effect of graded head-up tilt (HUT) on STI. 20 male medical students were subjected to 30 degrees, 60 degrees and 80 degrees HUT on a tilting table. ECG, phonocardiogram and carotid pulse were recorded simultaneously on Grass polygraph. Electromechanical systole (QS2), left ventricular ejection time (LVET), pre-ejection period (PEP), PEP/LEVT ratio, heart rate (HR) and corrected STI were determined immediately after and at 1, 2, 3, 4 and 5 min after each angle tilt. HUT produced a decrease in QS2 which was more pronounced at higher angle tilt. LVET decreased after 60 degrees and 80 degrees HUT. PEP and PEP/LVET ratio decreased after each angle tilt. These changes in STI can be explained on the basis of sympathetic stimulation-induced increase in the inotropic state of the heart.

A membrane-free plethysmograph for recording volume changes including microlitres.

A method of plethysmography which does not require an air/water tight chamber is described. The method is sensitive enough to record microlitre volumes/volume changes. Its application in two situations, viz. in experimental (artificial) edema and blood flow measurement in the human hand has been demonstrated.

Electrophysiological studies on human phrenic nerve & diaphragm.

To determine normal values for phrenic nerve stimulation, the phrenic nerve was stimulated transcutaneously in 22 healthy adolescent male volunteers. The phrenic latency, amplitude and duration of the evoked diaphragm action potential (EDAP) were noted. Maximum mouth inspiratory pressure (MMIP) and maximum ventilation volume (MVV) were also measured to evaluate the maximal strength of the diaphragm. No significant correlations were observed between EDAP and the parameters of diaphragm strength. The correlation coefficient between the amplitude-duration product of EDAP (integral EDAP) and MMIP was +0.15 and it was +0.29 between the integral EDAP and MVV.

Effect of altered ventilations on human spinal and supra spinal reflexes.

The present study was aimed at evaluating the alterations in the human reflexes brought about by briefly altered ventilations. In 20 healthy young male volunteers, the H reflex and blink reflex were studied during normal ventilation, voluntary hypoventilation and voluntary hyperventilation. The latencies of these reflexes were compared. It was observed that the amount of altered ventilations used in the present study could not produce any significant change in these reflexes except in the case of the early response of the blink reflex.

Avoidance learning under hypo and hyperglycemia in rats.

Learning behaviour under different glycaemic conditions were studied in albino rats using an avoidance box. When insulin and glucose levels were low after fasting, animals showed delay in avoidance learning. But there was no change in acquisition of learning after hypoglacaemia induced by insulin. This difference in behaviour under hypoglycaemia of almost similar severity is possibly due to difference in its rate of induction and activation of counter regulatory neuro-endocrine mechanisms. Diabetic (alloxan) rats failed to improve learning. Besides, hyperglycemia, other factors like metabolic disturbances, cytotoxic effects of alloxan may have inhibited learning in this group. Hypo or hyperglycemia disturb the function of neuronal substrates responsible for learning and memory.

Effects of central administration of insulin in normal and VMH (ventromedial hypothalamus) lesioned rats on food intake.

Central effects of insulin on 20 min. food intake were studied in rats. Insulin administration in the lateral ventricular cerebrospinal fluid (CSF) did not alter food intake in the intact or lesioned ventromedial hypothalamus (VMH) rats. Whereas, after insulin injection in VMH there was a decrease in food intake. In VMH lesioned rats, subcutaneous injection of insulin increased food intake.

Effect of inadequate frequency response of direct writing electrocardiograph on rat electrocardiogram.

Fairly good electrocardiograms of rats can be recorded by using a band width of 0.5 to 75 Hz. Change in low frequency did not alter the wave pattern or duration. Change in high frequency altered the durations and wave pattern grossly. 50 Hz filter is useful in avoiding AC interference but creates artificial notches in all the waves.

Effect of posture on heart rate and cardiac axis of mice.

Effect of change in body posture on cardiac electrical axis has not been well documented. Hence the present work was undertaken to study the effect of passive head-up and head-down postures on ventricular QRS axis and heart rate of anesthetised mice. During head-up posture, there was a statistically significant (P less than 0.02) increase in heart rate whereas during head-down posture, the heart rate decreased insignificantly. These changes in heart rate can be explained on the basis of synus and aortic nerve mediated baroreceptor reflexes. Ventricular QRS axis showed a significant increase (P less than 0.02) during head-up posture and an insignificant decrease during head-down posture. A change in the posture is likely to produce a change in anatomical orientation of heart within the thorax resulting in alteration of electrical axis of the heart.

Acute effect of streptozotocin induced diabetes on bar pressing for food reward in albino rats.

The operant behaviour in streptozotocin (45 mg or 65 mg/kg) treated rats was studied using albino rats of either sex. Animals were trained daily for 15 days in an operant chamber (Takei & Co.) to press the bar for getting the reward in the form of 45 mg food pellet following 18 hr of food deprivation. After initial training under continuous reinforcement schedule (CRF), animals were trained under FR2 and FR4 schedules, in which after every second (FR2) or every fourth bar press (FR4) rat received the pellet. The results indicate that the bar pressing for food reward is not altered after induction of experimental diabetes with streptozotocin. It is suggested that insulin lack or hyperglycaemia in this condition fails to influence higher centres associated with regulation of motivated behaviour.

Effect of yoga type breathing on heart rate and cardiac axis of normal subjects.

Effect of inspiratory and expiratory phases of normal quiet breathing, deep breathing and savitri pranayam type breathing on heart rate and mean ventricular QRS axis was investigated in young, healthy untrained subjects. Pranayam type breathing produced significant cardioacceleration and increase in QRS axis during the inspiratory phase as compared to eupnea. On the other hand, expiratory effort during pranayam type breathing did not produce any significant change in heart rate or QRS axis. The changes in heart rate and QRS axis during the inspiratory and expiratory phases of pranayam type breathing were similar to the changes observed during the corresponding phases of deep breathing.