Quarterly journal of experimental physiology and cognate medical sciences最新文献

Conscious Merino ewes were given an intravenous hypertonic sodium chloride load of 4 mmol.min-1 for 100 min. This resulted in increases in urine flow, sodium and potassium excretion and plasma sodium concentration and osmolality. Urinary vasopressin output and solute-free water reabsorption increased and plasma renin activity declined. Renal plasma flow and glomerular filtration rate (GFR) rose, as did the solute clearance. The change in urinary osmolality was related to the initial urine osmolality such that when the initial urine osmolality was high the urine became more dilute, and vice versa. Tubular sodium reabsorption increased but the fractional reabsorption rate fell. It is suggested that the increase in GFR was at least partly due to the increase in AVP and that the electrolyte loss can be accounted for by the increase in GFR without necessarily involving AVP or other hormonal effects at the tubular level.

The pattern of breathing following the breaking-point of sixty breath-holds has been studied in five healthy adults and compared with the pattern during recovery from CO2-rebreathing. The volume and direction of the first respiratory movement, and the VT, V relation for the first four complete breaths was measured. Only when breath-holds were terminated with an inspiration was the accumulated drive to breathe reflected in an increased volume of the first respiratory movement: terminating expirations simply returned the chest to the resting respiratory level. The volume of the first inspiration was not influenced by the intervention of a terminating expiration, suggesting that expiratory movements do not dissipate the non-chemical component of the drive to breathe. In three of the five subjects the tidal volumes for given levels of ventilation were greater following breath-holding than following rebreathing. This altered pattern of breathing has been interpreted in terms of an insiratory-augmenting reflex.

Several haematological parameters such as haemoglobin concentration, haematocrit, erythrocyte number, reticulocyte concentration, plasma iron and total iron binding capacity were determined in 118 urban pigeons of both sexes. No statistically significant sex differences among these parameters were found. In 36 specimens (23 males and 13 females), the plasma iron turnover was determined using 59Fe. The results obtained in this species, expressed per 100 ml-1 blood. day-1 and Kg-1 body weight. day-1, were compared with those of turkeys, ducks and chickens calculated from earlier papers. The highest values versus body weight were observed in pigeons. Organ (liver, spleen, tibia, heart, leg muscle, ribs, sternal keel, gonads and blood) distribution of 59Fe intravenous injection was analyzed during a period from 5 min up to 120 days (19 different times) in groups of 4 pigeons. At the 6 h period, the organs retained the highest dose (20% of total Fe injected), but by the 2nd day period, the radioiron in the blood represented about 98% of the total injected. A fast iron uptake by the circulatory blood was checked and compared with that of other species (domestic fowl, ducks and turkeys). The reticulocyte count in pigeons normally ranged from 4 to 12%, which was consistent with these results. A linear decreasing radioactivity in blood, with an inflexion point on the 40th day was observed. An inverse correspondence between blood and liver was found. Content in other organs decreased uniformly with time, except the heart where the iron content was practically constant during the whole time. Ribs and sternal keel are erythropoietic organs in young pigeons.

The effect of intraduodenal administration of fats was studied in the rat to define the mechanisms responsible for the substantial increase in intestinal lymph flow and protein transport which follows fat ingestion. Triglyceride in the intestinal lumen, protected from hydrolysis, does not appear to enhance intestinal lymph production. Giving both long- and medium-chain fatty acids, however, causes intestinal lymph flow and protein transport to increase in a manner similar to that found after giving triglyceride which is allowed to undergo hydrolysis. Bile by itself does not seem to be responsible for the phenomenon.

A detailed description is given of a method to section the pituitary stalk of the fetal lamb after 105 days gestational age. The approach to the stalk is made through a window in the frontal bone. In order to prevent regeneration of the hypothalamo-pituitary connections a silicone plate is introduced through the probe used to fracture the stalk. The surgical outcome and viability of 11 pituitary stalk sectioned fetuses is described over periods of up to 23 days. The presence of pituitary infarction following stalk section was related to damage of the anterior hypophysial vesssels if the probe was deviated from the mid-line at any time in its course. The effect of this procedure on fetal plasma T4 and PRL concentrations and the initiation of premature labour by the continuous infusion of cortisol into the fetus is described.

Intra-luminal pressures were measured in in vitro preparations of the guinea-pig gall bladder. Intrinsic tone and spontaneous activity were recorded together with the response of the gall-bladder to Pancreozymin. The effect of the presence of a variety of conjugated and unconjugated bile salts in the luminal fluid [pH 7.4] was studied. Sodium deoxycholate and sodium chenodeoxycholate had in inhibitory effect on motor activity at concentrations as low as 6.0 times 10(-6) mol. 1(-1) Sodium taurocholate at a concentration of 3 times 10(-3) mol. 1(-1) promoted regular spontaneous activity. The results are discussed in relation to their possible physiological, pathological and pharmacological implications.

Binucleate cells are a normal component of the ovine chorionic epithelium, but are usually separated from the fetal-maternal interface by a thin layer of cytoplasm derived from the principal or uni-nucleate cells of the trophoblast. They are distinguished not only by two distinct and separate nuclei, but also by conspicuous membrane-bound cytoplasmic inclusions in the form of haloed droplets. After fetal pituitary stalk section binucleate cells move up to and participate in the formation of the fetal-maternal interface; furthermore they extend clear blunt-ended pseudopodia into the maternal epithelial syncytium. These activities do not appear to be supppressed by fetal infusion of cortisol or ACTH. The apparent motility of binucleate cells, together with the presence of haloed droplets within the maternal epithelial syncytium, suggests that after fetal pituitary stalk section binucleate cells invade the uterine syncytium, lose their limiting membranes and discharge their contents into the syncytial cytoplasm. Large molecules such as ovine placental lactogen may be transported from fetal to maternal tissues by this mechanism.

Cardiac performance in moderate bicycle exercise has been measured in five groups of New Guineans (N = 161). Men and women in both coastal and highland (2000 m) locations were studied, as well as a group of highland men after migration to the coast. The results have all been standardized to an oxygen consumption of 1 1.min(-1). Cardiac output values are similar to those previously quoted for Europeans; a significant positive correlation with body size is found, and resident highlanders appear to have slightly larger cardiac outputs (+4%) and larger stroke volumes (+10%) after adjustment for body size, but this is not because they have larger hearts. The highland migrants at sea-level share none of the 'altitude' characteristics of the highland residents and, after size-adjustment, correspond with the lowlanders. The cardiac frequencies of the lowland women are higher than the other groups (+15 beats.min(-1)) after adjustment for differences in body size. Their values are close to those found previously for moderately active Europeans, while all the other New Guinean subjects have lower cardiac frequencies probably because of their greater habitual activity.

The emptying of a liquid test meal from the stomach was studied during, and in the absence of, electrical stimulation of cut ends of a thoracic branch of the vagus in anaesthetized cats. The test meal (154 mmol.1-1 NaCl and 30 mg.1-1 phenol red) was measured by collecting effluent from a duodenal fistula over a 30 min period. The stomach emptied about 60% of the meal under control conditions compared with over 90% during efferent stimulation of the vagus. The increased volumes emptied during efferent stimulation were not accounted for by secretion of gastric acid. Coincident with the vagally evoked antral contractions there was a gush of liquid from the duodenal cannula. Afferent vagal stimulation resulted in an initial marked delay of emptying followed by an acceleration so that the volume emptied after 30 min was similar to that in control experiments. Antral contractions, evoked by efferent vagal stimulation, accelerated the emptying of a liquid test meal from the stomach.