PubMed Health⌕ Search

Biomedical subjects

N Konda

Publications and source records attributed to N Konda.

29 records · Page 2Linked to original sources
PubMed1984

Hyperbaric diuresis at a thermoneutral 31 ATA He-O2 environment.

The basic pattern of body water exchange was studied in four Japanese male divers during exposure to a thermoneutral 31 ATA (He-O2) environment for 3 d (Seadragon V). The hyperbaric chamber temperature was raised from 25 degrees C +/- 0.5 degrees C at 1 ATA (air) predive to 31.5 degrees C +/- 0.3 degrees C at 31 ATA. Both rectal and mean skin temperatures were measured every hour (including during sleep) and were maintained at the same level at both pressures. The exposure to 31 ATA induced an increase in the daily urine flow and a corresponding reduction in the insensible (and evaporative) water loss without changing the total daily water output. However, the daily fluid intake decreased by 600 ml at 31 ATA, and hence the divers developed a state of negative fluid balance, as reflected by a reduction in body weight and an increase in hematocrit. All changes in the pattern of body water exchange observed at 31 ATA were gradually reversed during subsequent decompression. As observed in a previous dive to 31 ATA (Seadragon IV) in which there was a subtle cold stress (as indicated by the 1 degree C reduction in mean skin temperature at 31 ATA), the increase in daily urine flow at pressure was almost entirely due to the increase in overnight urine flow. However, the hyperbaric nocturia observed in the present dive was a water diuresis in nature whereas that in the previous dive was an osmotic diuresis. These results indicate that the hyperbaric diuresis at 31 ATA is due to an increase in overnight urine flow and that the hyperbaric nocturia is not in any way related to the subtle cold stress attendant in many hyperbaric environments.

Adult↗
PubMed1983

Fragility of red blood cells under 31 atmosphere absolute for 14 days.

The present investigation was undertaken during the course of a 14-day dry saturation dive at 31 ATA to study hematologic changes and osmotic fragility of red blood cells in relation to lipid contents of the plasma and red cells. Increase in the hematocrit and blood cell count was observed in the early phase at 31 ATA, which was attributed to the hemoconcentration caused by the hyperbaric diuresis. Osmotic fragility of red blood cells fluctuated during the course of the experiment, but the change was not related to the atmospheric pressure. Cholesterol and phospholipid contents in red blood cells and the plasma also fluctuated but the change was not caused by the pressure. However, an overall correlation between the osmotic fragility and the phosphatidyl choline of red cells and the correlation between the osmotic fragility and the total cholesterol level in the plasma were observed at both 1 and 31 ATA. These correlations revealed an intimate relation between the red cell fragility and lipid composition of the cell membrane and the plasma within intra- and interindividual variations during the course of the dive. The present result did not indicate any significant alteration of red blood cell function due to prolonged exposure to 31 ATA He-O2 environment.

Adult↗
PubMed1983

[The use of a heat flux transducer for measuring non-evaporative heat exchange in man].

Ten healthy males, 20-45 years of age, were subjected to measure the non-evaporative heat exchange by using thermal flux transducers at different ambient temperatures, atmospheric pressures, air velosities and body postures. Fifteen thermal flux transducers were mounted on each subject at the same points as Winslow's method (1936) proposed for calculating mean skin temperature. Non-evaporative heat exchange (Q) was computed from 15 heat flux measurements using the same weighting formula of Winslow. Evaporative heat loss (E) was estimated from body weight changes measured on a Potter bed scale. Metabolic heat production (M) was estimated indirectly from the oxygen consumption and carbon dioxide production. Mean body temperature was estimated from mean skin temperature calculated from 15 points and the esophageal temperature. In a wide variation of environmental conditions the summation of body heat storage during the experiment equaled that of the heat that reduced E and Q from M. However, the transducer seemed to overestimate the non-evaporative heat exchange of the body at high ambient temperatures where sweat rate was very high. The above results suggest that thermal flux transducer is a reliable tool in estimating non-evaporative heat exchange under a wide variation of environmental and physical conditions when used with great caution.

Adult↗
PubMed1983

Properties of red blood cell after multiday exposure to 31 ATA.

Hematologic changes, osmotic fragility of red cells, and lipid contents of plasma and red blood cells were determined during the course of a 14-day dry saturation dive at 31 ATA (SEADRAGON IV). Increases in hematocrit and red blood cell count were observed during the early period at 31 ATA, which was attributed to hemoconcentration resulting from a diuresis. The osmotic fragility of red blood cells decreased slightly during the course of the experiment, but the changes were not related to the atmospheric pressure. Cholesterol and phospholipid content of the red blood cell and the plasma showed slight, insignificant daily variations independent of pressure. However, the same overall correlation was observed between the osmotic fragility and the phosphatidylcholine content of red blood cells and between the osmotic fragility and the total cholesterol level in the plasma, at both 1 ATA and 31 ATA. These correlations revealed an intimate relationship between the cell fragility and lipid composition of the cell membrane and the plasma within intra- and interindividual variations during the course of the experiment, but did not indicate any significant alteration of red blood cell function by the prolonged exposure to 31 ATA helium-oxygen environment. These results indicate that the exposure of human divers to 31 ATA for 14 days does not seem to induce any irreversible chemical changes in the red blood cell.

Adult↗
PubMed1982

Body heat balance and urine excretion during a 4-day saturation dive at 4 ATA.

Five male volunteers were exposed for 4 days to a 4-ATA helium-oxygen saturation dive. Partitional calorimetry was performed during 2-h test periods at various ambient temperatures (Ta). Heat production during the period at 4 ATA in helium-oxygen was identical to that at 1 ATA in air. The nonevaporative heat loss (convective and radiant heat losses) was increased with a concomitant decrease in evaporative heat loss. The mean skin and mean body temperatures fell significantly at 4 ATA, and a slight reduction was observed in the rectal temperature. The conductive heat transfer coefficient from the core to skin (hk) was reduced, probably due to vasoconstriction at 4 ATA. Subjective thermal neutrality at rest at 4 ATA was obtained around Ta = 32 degrees C. A diuresis was observed at 4 ATA, but it disappeared with an increase in chamber temperature. An inverse relationship of urine flow to mean skin temperature was observed. An increase in urine flow at 4 ATA might be attributed to cold stress due to lower skin temperature that was caused by the increased nonevaporative heat loss.

Adult↗
PubMed1981

Electrophysiology of olfacto-limbic-hypothalamic connections in the pig.

To analyse fibre connections between the olfactory bulb (OB) and limbic-hypothalamic structures, the lateral olfactory tract (LOT) was stimulated electrically and extracellular action potentials were recorded from single units in the OB, the cortico-medial portion of the amygdala (AMY) and the mediobasal hypothalamus (MBH). More than 29% of the antidromically identified mitral cells in the OB showed a spontaneous episodic firing pattern consisting of alternating periods of activity and inactivity. Nearly 14% of the orthodromically excited non-mitral cells showed the same phasic firing pattern. 2.9% of AMY neurons were antidromically activated by LOT stimulation, whereas more than 52% showed orthodromic responses. In contrast to the AMY no neuron in the MBH could be antidromically invaded by electrical stimulation. The incidence of orthodromic responses was much less in the MBH when compared to the AMY (13.5%). It is concluded that the firing pattern of OB cells in the pig is complex, often phasic and unrelated to respiration or sniffing. The main OB is more closely related to the AMY than to the MBH. It is suggested that olfactory information is probably transmitted to the MBH via the AMY. The AMY may play a role in the regulation of OB activity.

Amygdala↗
PubMed1979

A method for recording single unit activity from the brains of foetal pigs in utero.

A technique is described for recording single unit activity from foetal miniature pigs in utero. The method involved anaesthetizing the sows with halothane and exteriorizing a sufficient length of the uterus to contain a single foetus. Both foetus and uterus were placed in a stereotaxic frame which was held independent of the mothers' support. Preliminary analysis of recordings obtained from spontaneously firing single nerve cells in the post-central cerebral cortex indicate that the patterns of spike activity in prenatal pigs are very similar to those observed in prepubertal animals.

Animals↗
PubMed1978

Data on the sites of stimulatory feedback action of gonadal steroids indispensable for luteinizing hormone release in the rat.

The sites of the stimulatory feedback action of gonadal steroids on LH release were investigated in estrogen-primed ovariectomized rats. Either estradiol benzoate (E2) or estrone (E1) injections 72 h after E2 priming induced a significant increase in serum LH 30 h later, whereas injections of progesterone (P) did so 6 h later. Horizontal sections placed above the medial preoptic area prevented the increase after E2 injections but not after E1 and P injections. Retrochiasmatic sections or bilateral lesions placed in the medial-basal part of the suprachiasmatic area prevented any increases in serum LH induced by steroid injections. Intracerebral implantations of E2 and P in E2-primed ovariectomized rats induced a similar significant increase in serum LH when E2 was implanted into the bed nucleus of stria terminalis (BST), the lateral septum (l-SEPT) and the preoptic suprachiasmatic area (POSC), and when P was implanted in to the medial amygdala, the diagonal band of Broca (DBB), the POSC, the l-SEPT and the anterior hypothalamic area (AHA). These results suggest that the stimulatory feedback effect of E2 is exerted on the limbic structures, especially the BST and the l-SEPT, while the main sites of the stimulatory feedback action of P are located in the DBB, the POSC, and the AHA.

Animals↗
PubMed1975

[Electrophysiological studies of the forebrain-limbic inhibitory systems in relation to gonadotropin regulation (author's transl)].

By the earlier studies it has been shown that electrical stimulation of some brain areas such as the medial amygdala and the medial septum increased multiple unit activity (MUA) in the medial preoptic area (MPO) and the arcuate nucleus (ARC) and resulted in gonadotropin release and/or ovulation. On the basis of this evidence, the present study was made to elucidate the effects of stimulation of the forebrain-limbic inhibitory systems on MUA in the MPO and the ARC in relation to the control of gonadotropin release using Wistar female rats. 1) In proestrous rats, electrical stimulation of the basolateral complex of amygdala (1-AMYG), the anterior amygdala (AAA), the hippocampus (HPC), the anterior hippocampus (HIA) and the ventral and lateral part of the central gray matter at the caudal midbrain level (CG) depressed the MUA levels in both the MPO and the ARC in almost of all cases. In the same experiments using ovariectomized and no-primed rats, it was observed that electrical stimulation of the above-mentioned areas was also successful to depress the MUA levels in the MPO and the ARC. But the incidence of inhibition was somewhat lower than that of in proestrous rats. 2) Simultaneous stimulation of the HPC and the 1-AMYG decreased in their inhibitory effects on the MUA in the MPO and the ARC which were apparently observed through the separate stimulation. This was true in combined stimulation of the CG and the 1-AMYG or of the CG and the HPC. It seemed that inhibitory effect on gonadotropin release which was induced by the separate stimulation was cancelled by the combined stimulation. 3) The 1-AMYG and the HPC seemed to form an inhibitory feedback circuit, excitation of a site inhibiting the other. 4) In ovariectomized rats, electrical stimulation of the 1-AMYG or the HPC decreased the MUA levels in the MPO and the ARC after the estrogen injection even in the case that facilitatory effects were observed before estrogen administration. It seemed that inhibitory effects of these inhibitory areas on the hypothalamic activity were enhanced under the dominant influence of estrogen. 5) After an injection of atropine, electrical stimulation of the HPC increased the MUA levels in the MPO and the ARC, while the stimulation of the same sites decreased when no treatment. On the other hand, atropine did not alter the effects of 1-AMYG stimulation on the MUA in the MPO and the ARC. It seems that the forebrain-line inhibitory systems have more important roles in the control of gonadotropin release than it has been assumed, through inhibiting the electrical activity in the MPO and the ARC.

Amygdala↗