bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetics and mechanism of oxygen debt contraction in man
Authors: Margaria R. , Cerretelli P. , diPrampero P. E. , Massari C. , Torelli G. 
Published: December 2017

Oxygen consumption, along with lactic and pyruvic acid in blood, have been measured throughout the performance of heavy muscular exercise of different intensities, all leading to exhaustion in 1–10 min. Oxygen consumption increases exponentially with time; the maximum level attained seems to be independent of the intensity of exercise except in exercises of very high intensity and short duration, when it seems to be slightly increased. The rate of increase of oxygen consumption increases with the intensity of exercise. Pyruvic acid in blood increases exponentially also, and a steady state is reached at a level which tends to be higher, the heavier the exercise. Lactic acid increases as a linear function of time, the line eventually flattening down only toward the end of the exercise when the maximal values of lactic acid are reached. The lactic acid increase, grams per minute, is a linear function of the intensity of exercise; no lactic acid is produced if the exercise is below 220 cal/kg min, or a higher value for athletes. The caloric equivalent of lactic acid production from glycogen can be calculated at about 222 cal/g. This value in man is discussed in relation to previous values given. The kinetic of the lactic acid increase during exercise is in agreement with the hypothesis of an additional (alactacid) mechanism of oxygen debt contraction. Submitted on July 31, 1962
Alveolar gas exchange during breath holding with air
Authors: Lanphier E. H. , Rahn H. 
Published: December 2017

Four normal subjects used a partial rebreathing procedure to deliver frequent alveolar gas samples during breath holding with air. In breath holding during mild exertion, O2 uptake declined steadily while CO2 transfer dropped abruptly and later ceased entirely as alveolar Pco2 reached a virtual plateau. Application of estimated instantaneous values of R provided an indication of mixed venous blood values and permitted interpretation in terms of the changing venous-alveolar-arterial relationships. Arterial Pco2 very early equaled mixed venous Pco2 and then exceeded it increasingly. The plateau of alveolar Pco2 was due in part to the fall in alveolar Po2 since decreasing O2 uptake lessened the CO2-concentrating effect of lung-volume reduction while the Pco2-elevating effect of blood oxygenation was also diminishing. However, an important slowing of the rise in mixed venous CO2 content and Pco2 was also noted and remains unexplained. Submitted on October 17, 1962
Relation between anatomic respiratory dead space and body size and lung volume
Authors: Hart M. C. , Orzalesi M. M. , Cook C. D. 
Published: December 2017

The respiratory anatomic dead space has been measured by the single breath nitrogen washout method of Fowler in 73 normal subjects ranging from 4 to 42 years of age. The volume of the anatomic dead space correlated closely with height (Vd (ml) = 7.585 x Ht (cm)2.363 x 10-4·ɣ = .917), but also with body weight, surface area, and functional residual capacity. When compared on the basis of any of these parameters there was no significant difference between the anatomic dead space values for males and females. Comparisons with available data for newborn infants suggest that the value of the anatomic dead space has a relatively constant relation to height from birth to adulthood. Dead space appears to increase more rapidly than weight, surface area, and functional residual capacity during, at least, the early period of somatic growth. Note: (With the Technical Assistance of J. H. Shaw) Submitted on October 25, 1962
Respiratory responses mediated through superficial chemosensitive areas on the medulla
Authors: Mitchell R. A. , Loeschcke H. H. , Massion W. H. , Severinghaus J. W. 
Published: December 2017

We have demonstrated respiratory chemosensitivity to changes in (H+) and Pco2 of the cerebrospinal fluid (CSF) in the subarachnoid space on the ventrolateral surface of the medulla. Respiratory stimulation was elicited from this region by increased Pco2 and (H+), nicotine, and acetylcholine; and respiratory depression by procaine, NaCN, lobeline, cold CSF, decreased Pco2 and (H+). CSF made acid by high (Cl-) at constant Pco2 moved the entire CO2 response curve to the left and was a more effective stimulus than normal CSF made acid by equilibration at high Pco2, presumably because of rapid diffusion loss of CO2 from the perfusing CSF into the underlying tissue and blood. Steady rapid perfusion of this area with a mock CSF of normal (H+) and Pco2 had no effect on respiration but depressed the respiratory response to inhaled CO2 by 40%. When placed in the fourth ventricle, procaine and high (H+) and Pco2 did not affect respiration, but nicotine and acetylcholine depressed it. This suggests that part of the medullary respiratory response to inhaled CO2 originates in an (H+)-sensitive surface exposed to CSF on the ventrolateral medulla. Submitted on August 8, 1962
Circulatory responses to high altitude in the cat and rabbit
Authors: Reeves John T. , Grover Estelle B. , Grover Robert F. 
Published: December 2017

Cats were taken from Denver (5,200 ft.) to Mt. Evans (14,150 ft.) anticipating that this degree of hypoxia would induce pulmonary hypertension. Rabbits were included for comparison with the cat. All cats died without developing pulmonary hypertension or right heart failure, and in spite of arterial and mixed venous O2 tensions maintained well above those of the rabbit. Presumably the cat's failure to survive was not a failure of oxygen transport to the arterial blood, or to the systemic capillaries. Paradoxically, five of eight rabbits survived despite poor arterial blood oxygenation. The rabbits developed marked polycythemia associated with modest right ventricular hypertension and dilatation. Submitted on June 6, 1962
Metabolic and thermal response of Eskimos during muscular exertion in the cold
Authors: Andersen K. Lange , Hart J. S. , Hammel H. T. , Sabean H. B. 
Published: December 2017

Performing muscular work in cold surroundings results in a greater energy requirement than that in a neutral environment at low levels of work, but is the same as that in a neutral environment at higher levels of work when rectal temperature is increased by the work. No higher heat production could be demonstrated in Eskimos than in Caucasians. It was found that rectal temperature increases during muscular work up to a certain level, this being almost constant over a wide range of environmental temperatures if the rate of work is constant. But when work rate becomes sufficiently low, the heat production is too small to compensate for the increased heat loss in the cold, so that the rectal temperature falls. A quicker onset of the rewarming of the previously cooled skin of the hands was found in Eskimos than in Caucasians as a result of exercise in the cold. This suggests a different vasomotor control of the blood supply to the skin. Submitted on August 6, 1962
Tissue gas tensions in experimental anemia
Authors: Bartlett D. , Tenney S. M. 
Published: December 2017

“Tissue-venous” O2 and CO2 tensions were determined by the subcutaneous gas pocket technique in rats with induced anemia of varying severity. Correlative ventilatory and metabolic measurements were made under light anesthesia. Gas pocket CO2 tension remained unchanged in all animals, but O2 tension decreased in anemic animals. Making use of the gas pocket tensions, rat blood nomogram, and certain assumptions, largely supported by the other measurements, a number of physiological values were calculated. From these it was concluded that in the anemic animal alveolar ventilation remained unchanged but, in the region of the gas pocket, blood flow increased with every decrement of hemoglobin concentration below the normal value. There was no “threshold” concentration of hemoglobin below normal at which point the blood flow response was initiated—the response was a continuous one. An in vivo slope value of the CO2 blood dissociation curve was derived and this was shown to vary directly with the hemoglobin concentration. Finally, the rate of disappearance of gas from the subcutaneous pocket suggested that there was a diffusion factor, in addition to blood flow, which played a role in the rate process. Submitted on November 13, 1962
Effect of CO2 on respiration using a new method of administering CO2
Authors: Fenn Wallace O. , Craig Albert B. 
Published: December 2017

When a subject inhales air containing a given concentration of CO2, the total load of CO2 is not fixed, but is increased linearly with the ventilation. The alveolar CO2 tension can never be reduced below the inspired CO2 tension, and the greater the response, the greater the CO2 load. By contrast, when CO2 is added to the inspired air stream at a constant rate, the load of CO2 and the challenge to the respiratory control is fixed and independent of the response, as it is in muscular exercise. The ventilatory response necessary to maintain a normal alveolar CO2 tension is much less with fixed amounts per minute than with fixed concentrations of inspired C02. These different methods of administering CO2 were tested in two subjects, both of whom increased their alveolar ventilation equally for the same increase in alveolar CO2 tension whether the CO2 was presented as a fixed concentration or a fixed load. Furthermore, other experiments designed to change the magnitude of the fluctuations of CO2 tension which must occur in the arterial blood during the respiratory cycle also failed to alter the subjects' ventilatory responses. respiration control; ventilation; exercise Submitted on January 21, 1963
Right ventricular hypertrophy in animals at high altitude
Authors: Hultgren Herbert N. , Marticorena Emilio , Miller Harry 
Published: December 2017

The weight of the ventricles and septum in formalin-fixed hearts were determined in six animal species living continuously at altitudes between 10,000 and 15,400 ft in the central Peruvian Andes. Control studies were made of a similar number of hearts obtained from sea-level animals. Guinea pigs, rabbits, dogs, lambs, pigs, and steers all exhibited a moderate hypertrophy of the right ventricle roughly equivalent to a 25% increase in weight. A lesser degree of septal hypertrophy occurred in all animals except steers. The data suggest that a moderate degree of pulmonary hypertension is the probable cause of the right ventricular hypertrophy. In steers this would be roughly the equivalent of a mean pressure of 35 mm Hg at 11,800 ft compared with sea-level pressures of 24 mm Hg. ventricular hypertrophy; altitude; pulmonary hypertension; lambs; pigs; steers Submitted on December 3, 1962
Left ventricular ejection time index in man
Authors: Weissler Arnold M. , Harris Leonard C. , White George D. 
Published: December 2017

The present studies were undertaken in an attempt to formulate an accurate expression of the relationship between the duration of left ventricular ejection and heart rate in man. On the basis of regression equations relating the duration of left ventricular ejection and heart rate in normal individuals, the index LVET + .0016 HR was derived and tested in normal adults and prepubertal children. The left ventricular ejection time index (ETI) remained constant and reproducible over the range of heart rate from 50 to 150 and yielded more consistent values in this range of heart rate than did previously derived equations. A slight but significantly higher value of the ETI was present in the adult females when compared to the adult males, while no significant difference according to sex was apparent in the children. A decrease in ETI was found when cardiac output was diminished in normal individuals during 60° head-up tilt and in patients with congestive heart failure. Of note was the finding of a significant correlation between the level of the ETI and the cardiac output in these situations. Submitted on December 13, 1962
Hemodynamics of collapsible vessels with tone: the vascular waterfall
Authors: Permutt S. , Riley R. L. 
Published: December 2017

A theoretical analysis is presented of pressure-flow relationships in arterioles based on the assumption that the presence of active tension produced by smooth muscle contraction causes a critical closing pressure which is itself a function of the magnitude of the active tension. This analysis differs from those previously carried out in that it uses the pressure-flow relationships of a waterfall rather than those described by Poiseuille's law to characterize the flow between arterioles and capillaries in the presence of active tension. It is suggested that, under some conditions, the driving pressure for the flow through arterioles is not the difference between the inflow pressure and outflow pressure of the arterioles, but rather the difference between the inflow pressure and the critical closing pressure. This seemingly slight modification causes marked differences in the interpretation of pressure-flow relationships and vascular resistance in the presence of active tone. Submitted on December 10, 1962
Seasonal variation of magnesium and calcium in serum of the hypothermic rat
Authors: Nowell N. W. , White D. C. 
Published: December 2017

Records of changes in blood Mg and Ca during body cooling are conflicting. Although a rise in serum magnesium is established in hibernators and with less certainty in artificially cooled animals, some workers have associated these changes with CO2 accumulation. In the present experiments rats were cooled to a rectal temperature of 15 C with artificial respiration to prevent CO2 accumulation. Cardiac arrest did not occur. A mean 24% rise in serum magnesium was found in the winter months. A fall occurred in the summer but the mean figure for these months was not significant. No change in the calcium levels was observed. The possible significance of the findings is discussed. Submitted on June 1, 1962
Effect of repeated exercise on the lesser circulation
Authors: Widimsky Jiri , Berglund Erik , Malmberg Rolf 
Published: December 2017

In four healthy subjects and four patients with lung disease, hemodynamic studies were done during two periods of identical exercise, 1 hr apart. Pulmonary artery pressure was lower in the second exercise period in all subjects studied. Pulmonary arterial wedge pressure was measured in four cases and was unchanged or even slightly increased. The “total pulmonary” and pulmonary vascular resistances were markedly lower in the second exercise period. The decrease in pulmonary artery pressure was found also in the second postexercise period when compared with the starting resting level. It is believed that this fall in pulmonary artery pressure and resistance was due to opening or widening of previously closed or constricted lung vessels. Repeated exercise must be used with caution when studying the effect of pharmacological or physiological agents on the lesser circulation. Submitted on November 30, 1962
Increase in fibrinolytic activity by venous occlusion
Authors: Holemans Rudolf 
Published: December 2017

Venous occlusion for 10 min, by a sphygmomanometer cuff applied above the elbow and maintained at a pressure midway between systolic and diastolic pressure, increases the fibrinolytic activity of the blood within the occluded part of the arm. In six normal human subjects the magnitude of this increase was compared with changes in blood cellular elements, plasma protein concentration, plasma antifibrinolytic activity, and plasma levels of glutamic-oxalacetic transaminase (GOT) and glutamic-pyruvic transaminase (GPT). The increase in fibrinolytic activity of the euglobulin fraction of the plasma was 3–20 times larger than the increase in plasma protein concentration and 8–24 times larger than the increase in hematocrit. Venous occlusion produced a rise in antiplasmin and antiurokinase activity of the plasma. The level of GOT in the plasma rose significantly more than the plasma protein concentration. These observations tend to indicate that the activation of fibrinolysis during venous occlusion is brought about by the release of intracellular enzyme(s). fibrinolytic activity of blood; euglobulins; antiplasmin; antiurokinase Submitted on May 31, 1963
Temperature regulation by hypothalamic proportional control with an adjustable set point
Authors: Hammel H. T. , Jackson D. C. , Stolwijk J. A. J. , Hardy J. D. , Stromme S. B. 
Published: December 2017

The role of the hypothalamic and skin temperatures in controlling the thermal response of a resting animal was studied by measurements of 1) hypothalamic, rectal, ear skin, and trunk skin temperatures on the resting dog and rhesus monkey in hot, neutral, and cold environments; and 2) the thermal and metabolic responses of a dog in neutral and cold environments during and immediately after holding the hypothalamus at approximately 39.0 C by means of six thermodes surrounding the hypothalamus and perfused with water. The results indicate that 1) a resting animal shivers in a cold environment with the same or higher hypothalamic temperature as the same animal in a neutral environment; 2) a resting animal pants in a hot environment with the same or lower hypothalamic temperature as the same animal in a neutral environment; 3) the hypothalamus is nonetheless strongly responsive to an increase or decrease of 1 C; 4) the rate of heat loss increases at the onset of sleep while the hypothalamic temperature is falling; 5) the hypothalamic temperature is 1–2 C lower during sleep even though thermoregulatory responses are the same as when awake; 6) the rate of heat loss decreases upon awakening while the hypothalamic temperature is rising. The discussion of these results includes a suggestion that the set point for temperature regulation is 1) decreased by a rising or elevated skin and extrahypothalamic core temperature, 2) increased by a falling or lowered skin and extrahypothalamic core temperature, 3) decreased upon entering and during sleep and is increased upon awakening. hypothalamic temperature; temperature set point; hypothalamic stimulation; dog temperature regulation; monkey temperature regulation Submitted on October 15, 1962
Viscosity of normal human blood under normothermic and hypothermic conditions
Authors: Rand Peter W. , Lacombe Eleanor , Hunt Hamilton E. , Austin William H. 
Published: December 2017

Although blood viscosity varies in relation to shear rate, hematocrit, and temperature, equipment is now available with which it may be measured in respect to each of these variables. A simple, clinically practical technique for such measurement is presented. Blood from 60 normal subjects was adjusted to hematocrits 0, 20, 40, 60, and 80, and the viscosity-shear rate relationships measured at 37.0, 32.0, 27.0, and 22.0 C. The data obtained are presented as a reference for future studies using this method. Technical details are discussed and some deserving areas of application are considered. shear rate; cone-plate viscometer; hematocrit-viscosity relationships; blood, plasma; hematocrit; temperature; blood flow impedance; perfusion; shock; oliguria; dyspnea; coma; heart surgery; blood rheology; metabolism Submitted on May 31, 1963
Effect of a brief contraction of forearm muscles on forearm blood flow
Authors: Corcondilas Adrian , Koroxenidis Gabriel T. , Shepherd John T. 
Published: December 2017

With the use of a strain-gauge plethysmograph, the effect of a brief (0.3 sec) contraction of the forearm muscles on forearm blood flow has been studied in eight healthy adults. An increase in flow due to dilatation of the muscle vessels could be detected within a second after the completion of the contraction. This increase was proportional to the strength of the contraction. The blood flow was maximal immediately and decreased rapidly. A second contraction of the same magnitude made during the period of increased flow caused an additional increase in flow. The maximal increase in flow caused by a strong brief contraction was only about 25% of that recorded after strong repeated rhythmic contractions or a sustained contraction. Cervical sympathectomy did not change these findings, indicating the local nature of the response. Since breathing oxygen failed to reduce the dilatation for a given strength of contraction, it is unlikely that oxygen lack was the stimulus for vasodilatation. The oxygen saturation of blood that drained the muscles could not be determined accurately immediately after contraction because at this time, muscle venous blood was contaminated by venous blood from the skin. exercise-induced vasodilatation; local mechanism of vasodilatation; venous O2 saturation during muscle contraction; brachial arterial pressure during vasodilatation; speed of muscle vasodilatation Submitted on May 8, 1963
Oxygen consumption during three yoga-type breathing patterns
Authors: Miles Walter R. 
Published: December 2017

Short periods of conscious control of the rate and depth of breathing as a health-promoting exercise has claimed wide human interest. In India, yoga cults based in part on persevering efforts to achieve physiological control of bodily functions have included systems for the control of respiration. Such breathing patterns have a long history, but have received little scientific attention. This paper reports a large series of repeated yoga respiration tests, graphically recorded under laboratory conditions by an Indian man who served as subject. The study was made by means of basal metabolism technique, employing the Krogh recording spirometer. All three of the yoga breathing patterns examined, when individually continued for 20 min or more and compared with previous relaxed quiet breathing, were found to demand an increased oxygen consumption of a mere 12–35% above basal need. The relaxed breathing that immediately followed a yoga pattern gave little or no indication that the subject had been exerting himself. There is some indication that such respiratory training may have elements in common with adaptation to high altitude and may serve to fortify an individual against the early onset of hypoxia in emergencies concerned with oxygen supply. respiration training exercises; BMR during trained respiratory behavior; respiratory measurements during yogic breathing; thoracic and abdominal breathing; breathing patterns versus breathing rates; yogic breathing patterns; voluntary pause after inspiration; domestication of respiration; discipline for the diaphragm; higher education for the respiratory center Submitted on February 21, 1963
Improved technique for estimating pleural pressure from esophageal balloons
Authors: Milic-Emili J. , Mead J. , Turner J. M. , Glauser E. M. 
Published: December 2017

Esophageal pressure has been measured in eight healthy men during breath holding (glottis open) at various fixed lung volumes with a rubber balloon (length: 10 cm; perimeter: 3.5 cm; wall thickness: ca. 0.06 mm) containing various volumes of air. The tip of the balloon was placed at a constant distance of 45 cm from the nares. Esophageal pressure was found to increase with balloon volume at all lung volumes but not uniformly, the effect of balloon volume being greatest at both extremes of the vital capacity. As a result, lung volume-pressure curves obtained from balloons containing volumes of gas such as are commonly used are distorted. One can avoid these distortions by repeating measurements at different balloon volumes and extrapolating esophageal pressure to zero balloon volume, or by making measurements at very small balloon volumes. A close approximation of the extrapolated pressures was obtained with the present balloon containing 0.2 ml air. The esophageal pressures at or near zero balloon volume probably reflect closely local absolute pleural pressures over the full vital capacity range in some subjects and above 20% of the vital capacity in most subjects. lung volume-pressure curves Submitted on August 13, 1963