Cent O2 Research Articles

Modification of the radiation sensitivity of bacteriophage T7 by O 2 and N 2 O.

SummaryThe radiation sensitivity of T7 suspensions is strongly dependent on chemical additives. We have compared the response to x-irradiation in the presence of 100 per cent N2, 100 per cent O2 (eaq− and H· scavenger) and 100 per cent N2O an eaq−(scavenger that increases ·OH concentration), in the presence of a 10−2 dilution of medium and a 10−5 dilution (equivalent to medium free).Survival curves are frequently multicomponent, with sharp break points, and radiation sensitivity must be measured at varying dosage levels. In the 10−3 dilution, the order of radiation sensitivity at low doses is, kL = N2 > N2O > O2, and at high doses, kH = O2 ≅ N2O > N2. In the 10−5 dilution, or medium free, the order at low doses is kL = N2O > N2 ≅ O2 with kH difficult to define.It is concluded: (1) the OH radical is an important damaging species for T7, and (2) ‘O2 protection’ is an experimental artifact associated with impurities in the suspension.

The effect of hypoxia on progesterone synthesis by placental villi in organ culture

To study the effect of hypoxia on progesterone synthesis, explants of human term or immature placental villi were maintained in an environment of moderate (6 per cent O2) or severe (1 per cent O2) hypoxia for 6 to 24 hours. Measurements of lactic and pyruvic acid production as well as pH indicated the presence of hypoxia and metabolic acidosis in culture. The explants were then homogenized and incubated in room air with pregnenolone-7α-3H. Term placental villi were affected only by extreme oxygen deprivation, whereas placental explants from 11 to 19 week pregnancies were impaired by both moderate and severe hypoxia. The resistance of term placental endocrine function to periods of limited oxygen supply can be related to its potential for anaerobic metabolism. The cellular distribution of the enzymes required for the conversion of pregnenolone to progesterone may restrict their ability to withstand a hypoxic insult.

Effects of low oxygen gas inhalation on the circulation and electrolyte metabolism in patients with liver diseases. 1. Renal circulation and electrolyte metabolism during room air inhalation

The studies of renal circulation and electrolyte metabolism in liver disease are mostly based on the patients in resting state except those investigating the reaction of renal function against water, Na load and other medical agent. Consequently the detail of the functional disorder is not made clear. In the present study the patients with liver disease are given low oxygen gas inhalation as a stress, with a view to investigating the influence on the renal circulation and electrolyte metabolism under such condition. And, by comparing its result with the same with normal adults and various patients reported by with clinical symptoms of the patients with liver disease, it will be made clear whether latent renal disorder exists or not. By doing so, the kinds and extents of functional disorder in the kidney of patients with liver disease will be investigated as the purpose of this study. Method The standard renal clearance methods were employed simultaneously while 10 per cent O2 inhalation was carried out. Before and after the low oxygen gas inhalation, determinations of renal circulation and electrolyte metabolism. Material 45 patients with liver disease (12 cases of acute hepatitis, 19 of chronic hepatitis and 14 of cirrhosis) aged ranging from 20 to 64 (34 men and 11 women). Classification (1) Classified by disease Acute hepatitis : (without anamnesis history of hepatitis and diagnosed on general clinical examination). Chronic hepatitis : (in which recovery of acute hepatitis is delayed by more than 4 months, and diagnosed on general clinical examination). Cirrhosis : (diagnosed on general clinical examination). In respect to chronic hepatitis and cirrhosis, liver biopsy was carried out, to confirm the diagnosis. (2) Classified by age A group : (younger than 39 age). B group : (older than 40 age). (3) Classified by RBF in a resting state α group : (more than 760 ml/min). β group : (less than 759 ml/min).

Studies on the Effect of Low Oxygen Gas Inhalation on the Renal Circulation and Electrolyte Metabolism in Patients with Liver Disease

The studies of renal circulation and electrolyte metabolism in liver disease are mostly based on the patients in resting state except those investigating the reaction of renal function against water, Na load and other medical agent. Consequently the detail of the functional disorder is not made clear. In the present study the patients with liver disease are given low oxygen gas inhalation as a stress, with a view to investigating the influence on the renal circulation and electrolyte metabolism under such condition. And, by comparing its result with the same with normal adults and various patients reported by with clinical symptoms of the patients with liver disease, it will be made clear whether latent renal disorder exists or not. By doing so, the kinds and extents of functional disorder in the kidney of patients with liver disease will be investigated as the purpose of this study. Method The standard renal clearance methods were employed simultaneously while 10 per cent O2 inhalation was carried out. Before and after the low oxygen gas inhalation, determinations of renal circulation and electrolyte metabolism. Material 45 patients with liver disease (12 cases of acute hepatitis, 19 of chronic hepatitis and 14 of cirrhosis) aged ranging from 20 to 64 (34 men and 11 women). Classification (1) Classified by disease Acute hepatitis : (without anamnesis history of hepatitis and diagnosed on general clinical examination). Chronic hepatitis : (in which recovery of acute hepatitis is delayed by more than 4 months, and diagnosed on general clinical examination). Cirrhosis : (diagnosed on general clinical examination). In respect to chronic hepatitis and cirrhosis, liver biopsy was carried out, to confirm the diagnosis. (2) Classified by age A group : (younger than 39 age). B group : (older than 40 age). (3) Classified by RBF in a resting state α group : (more than 760 ml/min). β group : (less than 759 ml/min).

Effects of Controlled Atmosphere (CA) Storage on Amino Acids, Organic Acids, Sugars, and Rate of Respiration of ‘Lambert’ Sweet Cherry Fruit1

Abstract Sweet cherries (cultivar—‘Lambert’) were kept in a controlled atmosphere (CA) consisting of 10.5 per cent CO2 and 2.5 per cent O2 at 1°C. The sample fruits were taken periodically during the treatment and also after termination of the CA treatment. The concentration of amino acids, tyrosine and α-amino butyric acid; organic acid, malic acid; and total sugars were determined on an ethanolic extract of the fruit pulp. The respiratory CO2 was measured for separate lots of 1.2 to 1.5 kg of fruit. Fruit stored at higher CO2 concentration had a lower amount of tyrosine, higher amounts of α-amino butyric and malic acids than in fruits stored in the conventional refrigerator at 1°C. The respiratory rate was inhibited, and there was no significant effect on total sugar content.

Postoperative Hypoxemia

When venous admixture and oxygen consumption remain constant, a decrease in cardiac output will necessarily decrease arterial oxygenation. To test this as a cause of postoperative hypoxemia, hemodynamic and respiratory gas exchange measurements were made in 14 patients before and after open repair of acquired cardiac valvular disease. Cardiac output was measured by dye-dilution. True shunt (JOURNAL/anet/04.02/00000542-197002000-00011/ENTITY_OV0422/v/2017-07-22T055310Z/r/image-pngS/JOURNAL/anet/04.02/00000542-197002000-00011/ENTITY_OV0422/v/2017-07-22T055310Z/r/image-pngT) breathing 100 per cent O2 and venous admixture (JOURNAL/anet/04.02/00000542-197002000-00011/ENTITY_OV0422/v/2017-07-22T055310Z/r/image-pngVA/JOURNAL/anet/04.02/00000542-197002000-00011/ENTITY_OV0422/v/2017-07-22T055310Z/r/image-pngT) breathing air were measured. A relationship between cardiac index (C.I.) and arterial oxygen saturation (SaO2) was established for groups with JOURNAL/anet/04.02/00000542-197002000-00011/ENTITY_OV0422/v/2017-07-22T055310Z/r/image-pngVA/JOURNAL/anet/04.02/00000542-197002000-00011/ENTITY_OV0422/v/2017-07-22T055310Z/r/image-pngT 0–10 per cent and 10–20 per cent. A decrease in C.I. produced a decrease in arterial oxygenation with JOURNAL/anet/04.02/00000542-197002000-00011/ENTITY_OV0422/v/2017-07-22T055310Z/r/image-pngVA/JOURNAL/anet/04.02/00000542-197002000-00011/ENTITY_OV0422/v/2017-07-22T055310Z/r/image-pngT constant.

Studies on the effect of low oxygen gas inhalation on the renal circulation and electrolyte metabolism in patients with diabetes mellitus. 1. Renal circulation and electrolyte metabolism in room air inhalation

Among the causes of death by diabetes mellitus in recent years, vascular disturbrance has been increased and especially, diabetic nephropathy has drawn our attention. Studies on this diabetic nephropathy have been done on various aspects. However, most of them were based on the examinations at resting state. Therefore, the author examined the reactivity of renal circulation and electrolyte metabolism against stress produced by inhalation of low oxygen gas on patients with diabetes mellitus. Method and Meterials Method The standard renal clearance methods were employed simultaneously while 10 per cent O2 inhalation was carried out. Before and after the low oxygen gas inhalation, determinations of renal circulation and electrolyte metabolism. Materials 41 patients with diabetes mellitus, age from 18 to 78, 24 men and 17 women. The subjects were classified as follow: (i) Existence of urine protein. (ii) Existence of urine sugar. (iii) Blood sugar: (a) under 139 mg/dl, (b) over 140 mg/dl: (vi). Blood pressure: (a) Normal type, systolic pressure under 149 mmHg and diastolic pressure under 89 mmHg, (b) Old age type, systolic pressure under 149 mmHg and diastolic pressure over 90 mmHg systolic pressure, over 150 mmHg and diastolic pressure under 89 mmHg, (c) Essential type, systolic pressure over l 50 mmHg and diastolic pressure over 90 mmHg; (v) Eye ground: (a) normal group, under KW I, (b) Abnormal group, over KW II; (vi) Duration (a) under 5 years, (b) over 5 years; (vii) Age: (a) under 39 years old, (b) 40 to 59 years old, (c) over 60 years old; (viii) Renal blood flow in the resting state: (a) over 760 cc/min, (b) 759 cc/min-480 cc/min, (c) under 479 cc/min. Result and Comments A. In room air inhalation. (1) Renal circulation. RBF of patients with diabetes mellitus, as compared with normal adults, has shown slightly low in general. In the study of this decrease of renal circulation by classification of clinical symptoms, it was proved with the abnormal eye ground group and the group of patients with diabetes mellitus over 5 years.

The air space and embryonic respiration

Synopsis Blocking the respiratory exchange through the shell over the air space by coating the shell with paraffin was attended by a sharp decrease in the oxygen content and a moderate increase in the carbon dioxide content of the air space. Before the parafoetal period the paraffin‐coated air space contained 6.4–8.5 per cent O2 and 7.2 per cent CO2. In normal eggs the composition of the gas mixture was 14.2 per cent O2 and 5.6 per cent CO2. During the parafoetal period the air space of paraffin‐coated eggs contained 4.6–6.5 per cent O2 and 7.3–7.7 per cent CO2 as compared with 9.0 per cent O2 and 6.6 per cent CO2 in the controls. Shortly before pipping the O2 content was 5.2 per cent and the CO2 content 9.1 per cent in the paraffin‐coated eggs and 8.6 per cent O2 and 8.1 per cent CO2 in the controls. It has been shown that the time of pipping is accelerated by a decreased O2 content as well as by an increased CO2 content in the air space. The stimulating effect of CO2, however, was about twice that of O2...

Antiarrhythmic properties of stereoisomers of a beta-adrenergic blocking agent (H56-28).

Cardiac arrhythmias were produced in the cat by inhalation of 1 per cent halopropane, 10 per cent CO2 and 89 per cent O2 and also by injection of epinephrine during inhalation of 1 per cent halopropane and 99 per cent O2. Dextro-H56/28, which has local anesthetic properties but only 1/40th the beta receptor blocking activity of the levo form of H56/28, had a weak, brief antiarhythmic effect on the halopropane-CO2 arrhythmia and did not significantly increase the threshold dose of epinephrine required to produce an arrhythmia during halopropane administration. However, levo-H56/28, when tested against the halopropane- CO2 and halopropane-epinephrine arrhythmias, had a marked, prolonged antiarrhythmic effect which was attributed to its beta-adrenergic blocking action.

Influence of Temperature on Isometric Contractions of Rat Skeletal Muscles

THE influence of temperature on isometric contractions of rat skeletal muscles in vitro has been determined for fast extensor digitorum longus muscles (EDL) and slow soleus muscles (SOL) from 4 week old female Wistar rats. Isometric contractions were recorded with the long axis of the muscle vertical, with one tendon tied to the frame below and the other tendon tied to a short steel wire connexion which linked it with the tension transducer above. The compliance of the transducer (Statham, Gl-80-350) and the steel wire connexion to the muscle was 4.5 × 10−5 cm/g and the natural frequency of vibration was 2 kHz. The muscle was immersed in about 100 ml. of fluid (137 mM Nacl; 5 mM KCl; 2 mM CaCl2; 1 mM MgCl2; 1 mM NaH2PO4; 2 g/l. of NaHCO3 and 2 g/l. of glucose) which was bubbled continuously with 95 per cent O2 and 5 per cent CO2. Neuromuscular transmission was blocked by adding 2.0 × 10−5 g of tubocurarine chloride/ml. of bath fluid. The muscles were stimulated directly by a transverse electrical field of 15 V/cm for 0.2 or 0.3 ms applied to the bath fluid by “massive” bright platinum electrodes set about 1 cm apart1. All recordings were made with the muscle set at the optimal length determined for twitch contractions at 20° C.

Storage of barley in an underground pit sealed with a polyethylene liner

Fifty tons of locally grown barley were stored in an underground pit hermetically sealed inside a polyethylene liner at Kibbutz Lahav. Gas measurements and observations showed that a satisfactory hermetic seal was obtained within the liner after seven weeks of storage (1·0–3·2 per cent O2). However, the efficiency of the seal was reduced by the gnawing activity of rodents which damaged the liner, and this appears to be a limiting factor for this type of storage. Changes in moisture content and in germination power were minimal during the storage period. Marked seasonal temperature changes were only recorded at the periphery of the grain bulk, while at the centre the temperature remained stable. The barley which was removed after 15 months of storage, during nine of which the liner was sealed, was clean, of natural brightness and colour, of low moisture content, and uninfested.

Some effects of maternal hyperoxia and hypoxia on the blood gas tensions and vascular pressures in the foetal sheep.

Blood gas tensions, pH and intravascular pressures have been measured at various sites in 22 foetal sheep of gestational age 110–147 days. Umbilical venous oxygen tension did not change significantly with age. The mean pulmonary artery pressure always exceeded that in the aorta and this pressure gradient did not change with age. By contrast the umbilical arterio‐venous pressure gradient increased with age. When the ewe breathed room air, the oxygen difference between uterine artery and umbilical vein was 43–62 mm. Hg. When the ewe breathed 100 per cent 02 umbilical venous P02 rose by 4–15 mm. Hg and umbilical venous pH fell by 0·04–0·07 pH units. There were no consistent changes in foetal heart rate or blood pressures.When the ewe breathed 10 per cent O2 in N2, umbilical venous P02. fell by 7–14 mm. Hg, mean pressures in pulmonary artery and aorta and the pulmonary artery/aortic pressure gradient increased as did the size of the right to left shunt across the ductus arteriosus. Heart rate invariably increased. The oxygen saturation difference between ascending and descending aorta was maintained or increased.These results suggest (1) that factors other than a diffusion barrier to oxygen are responsible for the maternal/foetal oxygen gradient and (2) that, with maternal hypoxia, there is a redistribution of blood flow in the foetus so that as high a tissue P02 as possible is maintained in coronary and cerebral circulations.

Effect of daily exposure to high pressure oxygen on tumor growth.

EFFECT OF DAILY EXPOSURE TO HIGH PRESSURE OXYGEN ON TUMOR GROWTHHERMAN D. SUIT, M.D., JANE SMITH and CHIROTCHANA SUCHATO, M.D.Audio Available | Share

Neuroendocrine and metabolic effects of general Anaesthesia during spontaneous breathing, controlled breathing, mild Hypoxia, and mild Hypercarbia

Serial crossover tests were carried out on 10 to 15 large, trained, male dogs that were moderately deeply anaesthetized for 90 minutes, at two-week intervals, with thiopental, Innovar, diethyl ether cyclopropane, chloroform, trichlorethylene, fluroxene, halothane, halothane-ether azeotrope, and methoxyflurane. These tests were done under four conditions: spontaneous breathing with 50 per cent N2O + 50 per cent O2 unless apnoea became imminent (chloroform-usual, cyclopropane-occasional, Innovar-briefly); controlled breathing with 50 per cent N2O + 50 per cent O2; controlled breathing with 85 per cent N2O + 15 per cent O2; and controlled breathing with 50 per cent N2O + 47.5 per cent O2 + 2.5 per cent CO2. Anaesthesia was induced in all experiments with 20 mg./kg. thiopental. Cyclopropane was administered with 70 per cent oxygen in a closed-circle system with an absorber under the first two conditions only. The remaining inhalation agents were administered in a non-rebreathing system. Thiopental and Innovar were administered intravenously by drip infusion for one hour. Blood assays of histamine, serotonin, epinephrine, and norepinephrine were carried out at the beginning and end of each test along with measurements of the pH,\(P_{aCO_2 } ,P_{aO_2 } \), haematocrit, SGOT, SGPT, lactate, pyruvate, blood water, sugar, potassium, and inorganic phosphorus. Volume of blood withdrawn for the tests was replaced with 0.9 per cent saline. During each test, mean arterial blood pressure was measured directly from the femoral artery; breathing rate and volume were monitored with a respirometer during spontaneous breathing or regulated at 350 to 400 ml./kg./min. during controlled breathing; heart rate and rhythm were monitored and recorded from E.C.G. (lead 2), and urine excretion was monitored and recorded by gravity drainage with a catheter attached to a calibrated trap bottle. All data were analyzed statistically. The following effects were noted: 1. Thiopental usually caused a rise in the catecholamines, but no hypotension or oliguria; 2. Innovar usually caused a rise in blood sugar, hypotension and oliguria; elevation of catecholamines was inconsistent; 3. Diethyl ether caused metabolic acidosis, haemoconcentration, water loss, hyperglycaemia, excess lactate, elevation of catecholamines and oliguria, but no hypotension; 4. Cyclopropane caused hypercapnoea (during spontaneous respiration) and oliguria, but no hypotension; catecholamines rose slightly; 5. Chloroform caused slight hyperglycaemia and oliguria; 6. Trichlorethylene caused ollguria and a rise in serotonin when CO2 was administered; 7. Fluroxene caused hyperglycaemia and elevated lactate and pyruvate during spontaneous breathing, a rise in the catecholamines during mild hypoxia, and oliguria; 8. Halothane, halothane-ether azeotrope, and methoxyflurane caused hypotension and oliguria, but no consistent metabolic changes. It was evident that diethyl ether caused the most obvious metabolic disturbances, and these were usually accompanied by a rise in the catecholamines. There were virtually no consistent or appreciable changes in the histamine or serotonin assays. Theoretically, it is possible that alterations in the latter two biogenic amines might have occurred to a greater extent than the reported values indicate, since it is possible that they were released and then were taken up rapidly by the tissues or receptors of the effector organs or broken down metabolically. For that matter, catecholamines released into the blood during anaesthesia with some agents (the halogenated agents and cyclopropane) may have had the same fate, whereas with diethyl ether they remained in the bloodstream. However, it is unlikely that this occurred, for if it had, there might have been less likelihood of hypotension, at least with the more potent halogenated anaesthetics. It is important to keep in mind also that when considering the percentage changes in these biogenic amines one takes a distorted view, particularly with respect to the catecholamine values, because the assay method involves technical errors of such a magnitude that when the amount measured is near zero, or near the lower limit of detectability (as was observed with many of the control values of epinephrine), it is difficult to accept as significant those changes that appear large during an experiment.

Mammalian pancreatic islet tissue in organ culture: II. Insulin contents of tissues and culture medium

Summary Pancreatic explants obtained from 17-day fetal rats were cultured in a 95 per cent O2−5 per cent CO2 atmosphere on a semi-defined liquid culture medium, as previously described. Insulin immunoassays of whole culture medium and tissue extracts were performed. Tissunes explanted from 17-day fetal rats and cultured for 2, 4 or 6 days contained more insulin (p≤0.02) than did uncultured control pancreata of comparable ages (i.e., 19, 21 and 23 fetal days). Assays of tissue and medium indicated continuous synthesis and release of insulin during 10 days of culture. Total insulin recovered from tissue plus medium (medium changed each 48 hr) was over 50 times that recoverable from uncultured 17-day fetal pancreas. These data support our hypothesis of selective differentiation and maintenance of metabolically active pancreatic beta cells in explants of fetal rat pancreas cultured under the specified conditions.

Phosphorylase a-b ratio in the lamprey heart.

CYCLOSTOME branchial hearts are known to contain large amounts of endogenous catecholamines1 and to be markedly insensitive to added adrenaline2,3. There is considerable evidence to suggest that the process whereby the sympathomimetic amines normally enhance the force of cardiac contraction involves the transformation of the enzyme phosphorylase from the b to the a form4,5. The lack of sensitivity of cyclostome hearts to added adrenaline or noradrenaline might therefore be due to the endogenous amines having already activated the conversion of the phosphorylase enzyme from the b to the a form so that even in the absence of any added adrenaline or noradrenaline the enzyme phosphorylase would exist mainly in the a form. This possibility was investigated using hearts isolated from freshly decapitated lampreys (Mordacia). After five minutes immersion in aerated (95 per cent O2 + 5 per cent CO2) modified Ringer solution6 at 22° C, under which conditions isolated hearts will beat spontaneously for many hours, the hearts were rapidly frozen and the phosphorylase activity determined as described previously7, using tissue dilutions of 1/150 (w/v) and rabbit liver glycogen (Nutritional Biochem. Lab.) which had been purified as described by Krebs et al.8. The reaction mixture was incubated at 25° C.

A METHOD FOR INDEPENDENT AND REVERSIBLE EXCLUSION OF CHANGES IN ACTIVITY OF THE CAROTID CHEMORECEPTORS AND BARORECEPTORS: STUDIES ON SYSTEMIC HYPOXIA

A method is described whereby, in the anæsthetized dog, changes in the activity of the carotid body chemoreceptors and carotid sinus baroreceptors can be independently and reversibly excluded. The carotid sinuses and bodies are isolated from the circulation and perfused at constant volume flow with arterial blood from the same animal. The perfusion pressure is controlled by means of a Starling type of resistance, the air‐space of which is connected to an artery so that the carotid sinus pressure is automatically maintained at the same level as the systemic blood pressure. Changes in carotid body chemoreceptor activity are excluded by perfusing the carotid bifurcation regions with arterial blood from a donor dog, the baroreceptors remaining functionally normal. Changes in activity of the carotid baroreceptors are excluded by maintaining constant the pressure in the air‐space of the Starling resistance, and therefore in the carotid sinuses; the carotid bodies are perfused with recipient dog's blood and remain functionally normal. Evidence is presented that in the vagotomized dog, reflexes from both the carotid chemoreceptors and baroreceptors contribute to the maintenance of the arterial blood pressure in acute systemic hypoxia produced by inhalation of 7–12 per cent O2 in N2. It is concluded that caution is necessary when interpreting the results of experiments based on observations made before and after interruption of the passage of nerve impulses in the carotid sinus or aortic nerves which contain afferent fibres to both types of receptor.

CLINICAL PATHOPHYSIOLOGICAL STUDY ON EFFECTS OF PULMONARY ARTERIAL PRESSURE DECREASE UPON EJECTION TIME AND MECHANICAL EFFECTS OF THE RIGHT VENTRICLE. I. RIGHT VENTRICULAR EJECTION TIME

With an increasing interest in cor pulmonale, several factors influencing pulmonary hemodynamics have been investigated by many authors. Most of these authors have estimated the ventricular mechanical effect from minute mean value of both systolic and diastolic phases of the cardiac cycle. however, considering the fact that the maximum ventricular mechanical effect is performed at the ejection period during the systole and more particularly during the period when the semilunar valvular open, the measurement of the accurate ventricular mechanical effect should be obtained during the ejection period rather than during both systolic and diastolic phases as in previous works. In the present study, the author used three different vasopresser agents and analyzed various phases of pulmonary circulation. From these results, ejection time of the right ventricle, mean pulmonary pressure per ejection phase and the mechanical effects of the ejection were obtained and were compared with the results of previously described methods. Material and Method A total of 24 cases was used in this study including 3 cases of normal individuals, 16 cases of cardiacs, 4 with pulmonary diseases and one with hepatic disorder. A routine right heart catheterization was carried out with a double lumen catheter. The pressures of the right ventricle and pulmonar artery were measured with simultaneous recordings of both electrocardiogram and phonocardiogram. The subjects were divided into 2 groups according to their resting mean pulmonary arterial pressure. The group I of 11 cases showed their mean pressure not exceeding 11 mmHg, the group II, consists of 13 cases with mean pressure exceeding 18 mmHg. The blood gas analysis was carried out by the method of VAN SLYKE-NEIL and expired air was analyzed with SCHOLANDER'S gas analyzer. Cardiac output was measured by FICK'S method. The control pressure as first measured during room air breathing without drugs and the second measurement was carried out 15 to 20 minutes namely, 7-chlor-ethyl-theophylline (Cl. E. T.) intravenously (200 mg), 1.4 : 3.6-dianhy-drosorbitol-2.5-dinitrate (I. S. D. N.) sublingual (10 mg) and inhalation of 50 per cent O2, and following measurements were made.

Mechanism of action of nitrous oxide, ether, and chloroform on the uterus

The effect of nitrous oxide, chloroform, and ether was studied on uterine contractions in dogs which had been lightly anesthetized with sodium barbital. Some of the dogs were pregnant, and a few were in heat. The remainder of the animals were estrogenized (1 mg. diethylstilbestrol daily for 5 days) previous to the experiment. Nitrous oxide, even in high concentrations (95 per cent N2O and 5 per cent O2) had no effect on uterine contractions. Both ether and chloroform in effective concentrations inhibited uterine contractions. It was shown that this inhibition was not caused by release of epinephrine, since infusion of the latter agent, even in high dosages, did not affect uterine contractions. It was concluded that ether and chloroform caused inhibition by acting directly on the uterine musculature.

OPTIMUM O2/CO2 RATIO IN RADIOTHERAPY.

Numerous experiments have established that the presence of oxygen in the cell at the time of irradiation is an important factor in the determination of response to the dose. Some radiotherapists have accepted this to the extent of making a clinical trial of treating patients in a chamber containing oxygen at high pressure. Putting the oxygen under pressure increases the amount dissolved in the plasma, which then carries more oxygen to the tumor. In an earlier paper, comparison of cure rates in spontaneous tumors in mice showed that more oxygen could also be delivered to the tumor cell by allowing the mice to breathe 95 per cent O2 + 5 per cent CO2 at atmospheric pressure. The vasodilatation and respiratory stimulation of CO2 is probably the explanation. Cure rates were about the same as for oxygen under three atmospheres pressure, but systemic effects, as shown by the number of deaths during the treatment series, were much less with the O2/CO2 mixture. The hazards of high pressure are well known but the toxic effect of oxygen has not received the same attention. Using pure oxygen even at atmospheric pressure increased early deaths although it did not increase cure rates over air. The use of atmospheric pressure O2/CO2 eliminates the complications of both pure oxygen and high pressure and increases cure rates as well. The next question to be answered was that of the optimum fraction of CO2 which should be put in the oxygen for maximum cure rate and minimum systemic effects. To determine this, 279 C3H/HeJ mice with spontaneous mammary adenocarcinomas between 8 and 17 mm. in diameter were treated with x-rays in a chamber containing the gas mixture at atmospheric pressure, with the fraction of CO2 2, 5, 10, or 20 per cent. The mice were assigned at random to one of these. All were given 1,000 r twice a week to 6,000 r in eighteen days. They were all about the same age and weight and tumor size distribution was the same in all groups. The mice were immobilized for treatment by wrapping them in wire mesh, cut away over the tumor. They were shielded from radiation by a heavy sheet of lead, except for the tumor and a margin of 5 mm. around it. They were placed in the chamber, the gas mixture was allowed to flow through it to flush out the air, and treatment was started. The gas continued to flow during treatment so that the fraction of CO2 remained constant. Control of tumor was determined by palpation. The gas mixture used during treatment was not known at the time of examination. The mice were examined weekly so that classification was made within a week of death. Thirteen mice were classed as indeterminate because of obvious geographical miss of the tumor or because it was impossible to come to a clear decision on classification.