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S K Manchanda

Publications and source records attributed to S K Manchanda.

66 records · Page 4Linked to original sources
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Central nervous control of venous tone. III. Responses of capacitance and resistance vessels of skin to bulbar and hypothalamic stimulation.

Electrical stimulation of 350 points in the bulbar formation of 35 dogs under chloralose anaesthesia demonstrated the presence of sites producing increase or decrease of systemic arterial pressure (SAP) in the same general morphological limits of bulbar pressor and depressor regions as described by earlier authors. Simultaneous recording of pressure changes in the cutaneous vessels however demonstrated that pressure changes in these vessels did not correspond to the pressor or depressor effects of the SAP. Instead, responses were obtained in which pressures in cutaneous capacitance and resistance vessels followed a trend which was opposite in direction and magnitude to that of SAP. Thus there were 30 depressor sites which produce increase in cutaneous vessel pressure and 23 pressor sites which produced a fall in cutaneous vessel pressure. For a marked rise in the SAP, only 62 sites elicited equally marked increase in both capacitance and resistance vessel pressure, while another 52 elicited only a small increase of equivalent magnitude in the capacitance and resistance vessels. Stimulation of 84 points produced dissimilar effects on capacitance and resistance vessels out of which 38 elicited moderate increase in resistance vessel tone with minimal changes in the capacitance vessel tone, while 46 points elicited moderate increase in capacitance vessel tone with only a small increase in the resistance vessel tone. These points were diffusely admixed in the bulbar reticular formation. Effects which were exclusive to the capacitance and resistance vessels of skin, singly or in combination, without affecting the SAP were elicited from 12 points while another 28 points produced marked rise or fall of systemic arterial pressure without affecting the cutaneous vessels. These observations suggest that the neuronal organisation regulating cardiovascular activities at the bulbar level is quite complex having the capacity to generate varying activities in different components of the vascular circuits by differentially altering the discharge of the efferent sympathetic fibres on the one hand, and marked selectivity of action on any particular vascular bed or circulatory component on the other hand. Stimulation of 93 points in the hypothalamus produced similar patterns of response as obtained from medulla oblongata. In addition, stimulation of 6 points in the anterior hypothalamus produced a distinctive response accompanied by dilatation of cutaneous resistance and capacitance vessels with marked increase in respiratory rate and minimal changes in the SAP. This type of response which resembled the physiological response employed for heat loss was not obtained from any stimulation site in the medulla oblongata.

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Haemodynamic effects of hypothalamic stimulation on skin and muscle venous beds.

Twenty three points mainly located in the posterior hypothalamus were stimulated to study its effect on the pressures, flows and calculated segmental resistances of the skin and muscle venous beds of hind limbs in the dog. Stimulation of these points produced a uniform pattern of rise in pressures of the muscle veins consisting consisting of a steep rise during stimulation followed by a rapid decline to basal level on its cessation. Skin veins, on the other hand registered a gradual increase in pressure during stimulation followed by a secondary rise during post stimulatory period. Large veins of both muscle and skin exhibited comparatively smaller pressure increases than small vein. These pressure changes were accompanied by a similar marked rise in systemic arterial pressure. Out of 23 points, 21 points produced similar increases in the calculated resistances of skin and muscle veins. Two points produced greater increase of the skin vein resistance. Total venous resistance of the limb was therefore, raised by all the points stimulated. None of these points elicited any fall in the pressures or calculated resistances of either the muscle or skin venous bed. Muscle venous outflow always registered an increase while the skin venous outflow recorded either a small increase or decrease or at times no change during the hypothalamic stimulation. These findings demonstrate that hypothalamic stimulation can profoundly alter the haemodynamics of the hind limb venous beds and actively mobilize the post capillary venous sections of both skin and muscle venous beds.

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Effect of luteinizing hormone-releasing hormone (LH-RH) on the multiunit activity of the arcuate nucleus in the proestrous rats.

Multiple Unit Activity (MUA) of the hypothalamic arcuate nucleus as indicated by discriminated spikes with window setting between 18-30 uV, the integrated MUA and the cortical EEG of the urethane anaesthetized rats on the proestrous day was recorded with the help of a polygraph. Infusion of LH-RH in the 3rd ventricle markedly increased the arcuate nucleus MUA. The effect started within minutes of infusion, peak came after 20-30 minutes and the activity remained increased for 3-4 hours. Saline infusion in the 3rd ventricle was ineffective. Feedback action of CSF-LH-RH to the arcuate nucleus for the regulation of LH-RH is suggested.

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Development and initial evaluation of a vas deferens valve.

In 17 cases of vasectomy, the external diameter of vas deferens was found to be 2.07 +/- .27 mm (Mean +/- S.D.) with a range from 1.7 to 2.8 mm. The internal diameters were 0.93 +/- 0.13 at 5 g and 1.24 +/- 0.16 mm at 100 g insertion force applied to the measuring cone, with lumen ranges from 0.7 to 1.2 and 1.0 to 1.7 mm, respectively. The left-right variations in the same inidividual were of a similar order as between different individuals. Measurements in 6-10 kg rhesus monkeys revealed an internal vas diameter around 0.6 mm with the measuring cone only eased in. At considerably high pressure the vas could be distended to show an internal diameter around 1 mm. The external diameters ranged from 1.5 to 2 mm. Local application to the vas in vivo or in vitro of alpha or beta adrenergic blocking agents, and sodium nitrate had no appreciable effects on the diameters. Three types of valves were developed and tested. The tap-like and the rotary valves were not satisfactorily leak-proof. But the valve with stop-cock mechanism was found to be satisfactory. It was further tested by examining the ejaculate obtained by the method of electro-ejaculation after implanting the valve in the monkey vas. The stop-cock valve is being proposed as a working model for producing reversible vas-occlusion.

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