Showing papers in "Acta Physiologica Scandinavica in 1972"

General Characteristics of Sympathetic Activity in Human Skin Nerves

Abstract: Synchronized bursts of efferent sympathetic impulses, appearing either spontaneously or triggered by various peripheral stimuli, were recorded with microelectrodes inserted percutaneously into skin nerve fascicles in alert, adult subjects. The signals were abolished by sympathetic ganglion blocking agents and by Lidocaine nerve blocks proximal to the recording site. Many of the sympathetic discharges were succeeded by skin resistance changes and plethysmographic vasoconstrictor responses within the innervation zone of the fascicle impaled. The sympathetic activity was not pulse synchronous as in muscle nerves and the spontaneous sympathetic volleys occurred largely independently of spontaneous blood pressure variations, indicating a relative lack of baroreflex control of the vasoconstrictor outflow to the skin. A loose coupling was observed, however, between the resting respiratory rhythm and the spontaneous sympathetic bursts in the skin nerves.

Manoeuvres affecting sympathetic outflow in human skin nerves.

Abstract: Sympathetic activity was recorded from human skin nerves during the execution of a variety of different manoeuvres. The neural activity (composed of vasoconstrictor and sudomotor impulses) was regularly affected by emotional, thermal and respiratory stimuli. Mental stress, body cooling and increased respiratory movements all increased the sympathetic outflow, whereas the activity decreased during moderate body warming and when the. subject was calm and relaxed. Manoeuvres known to cause changes in baroreceptor activity usually did not affect the sympathetic outflow to the skin. When comparing neural and effector organ responses during the different manoeuvres the changes in sympathetic activity correlated well with changes in skin vascular resistance (either measured simultaneously or as reported in the literature). A comparison of the sympathetic responses recorded from human skin- and muscle nerves was also made. It was concluded that most manoeuvres had different effects in the two nerve types, thereby confirming earlier indirect evidence for selective regional control of the sympathetic outflow.

The Oxygen Supply to the Retina, II. Effects of High Intraocular Pressure and of Increased Arterial Carbon Dioxide Tension on Uveal and Retinal Blood Flow in Cats

Abstract: Alm, A. and A. Bill. The oxygen supply to the retina, II. Effects of high intraocular pressure and of increased arterial carbon dioxide tension on uveal and retinal blood flow in cats. A study with radioactively labelled microspheres including flow determinations in brain and some other tissues. Acta physiol. scand. 1972. 84. 306–319. 15 μ and 35 μ microspheres labelled with 8SSr and 169Yb were used to determine the rate of blood flow through various intraocular tissues, optic nerve, brain, kidney cortex and small intestine in cats at normal and increased Paco2- One eye had its spontaneous intraocular pressure, the other eye had its pressure stabilized at a higher level. At normal Paco2 a reduction in perfusion pressure resulted in decreased vascular resistance in the iris, the ciliary body and the retina, but not in the choroid. In the retina the eye with reduced perfusion pressure had a significantly higher blood flow than the control eye. Increased PaCO2 resulted in increased blood flow in all ocular tissues and all extraocular tissues studied except the kidney cortex. Reductions in perfusion pressure at high Paco2 resulted in further decreases in vascular resistance in two eyes of seven only. The results suggest that about 21 % of the O2 consumed by the retina is delivered by the retinal blood vessels, the rest by the choroid. Both myogenic and metabolic mechanisms seem to contribute to the adjustment of retinal vascular resistance after a change in perfusion pressure.

The Role of Muscle Stiffness in Meeting the Changing Postural and Locomotor Requirements for Force Development by the Ankle Extensors

Abstract: The relationship between the length and stiffness (force/length change) of active muscle and the rates at which motor units are activated by distributed stimulation of divided ventral rootlets supplying the muscle has been explored in cat soleus and lateral gastrocnemius. At stimulus rates equivalent to those used in locomotion (15—55 p/s) peak muscle stiffness is at muscle lengths also used in locomotion. At lower rates of stimulation equivalent to those developed in the tonic stretch reflex of the decerebrate cat, peak muscle stiffness occurs at larger muscle lengths but these lengths are within the range of those used for investigation of the reflex. These experimental results were then compared to the sets of theoretically derived results concerning: a) the amount of force needed from the ankle extensors to counteract a load applied to the hindlimb along a vertical axis when ankle and metatarsophalangeal angles are changed relative to the mechanical axis; and b) the amount of force developed by ankle extensors during slow walking. In all cases (theoretical and experimental) the results reveal a close correlation between required force, muscle length and muscle stiffness. The time lag between a change in motor unit discharge and tension development was also calculated to reveal that in many situations (notably gallop) only muscle stiffness can provide a load compensation, whereas the delays are too long to allow a reflexly induced load compensation.

Increased Activity in Left Ventricular Receptors during Hemorrhage or Occlusion of Caval Veins in the Cat. ‐ A Possible Cause of the Vaso‐vagal Reaction

Abstract: Impulse activity in vagal afferent fibres and changes in heart rate were simultaneously recorded during rapid hemorrhage or blood pooling in cats in order to elucidate whether the sudden reflex bradycardia, sometimes evoked with the mentioned interventions, was correlated to an increased activity in any type of heart receptors. The results show that the slowing of the heart, resulting from an emptying of the central blood reservoirs was correlated to, and preceded by, an increased activity in receptors located in the left ventricle and signalling in non-medullated afferents. The receptors were found to be activated also by obstructions of the ascending aorta and mechanical stimulation of the heart, and therefore seem to operate as mechanorecepton, stimulated by a “distortion” of the myocardium. - It is conceivable that with rapid bleeding or pooling of blood, the receptors are excited by an improper squeezing of the myocardium when the ventricles contract vigorously around an almost empty chamber, and then induce a reflex bradycardia. This reflex mechanism, resembling the so-called vaso-vagal syncope reaction in man, may therefore serve as a protective system causing a break on the heart and allowing for an improved diastolic filling in situations when venous return is critically reduced.

Production and Removal of Lactate during Exercise in Man

Abstract: Blood lactate concentration (LA) was measured in 4 female and 3 male well-trained subjects before and during 30 min of continuous treadmill running at 4 different speeds, demanding about 30, 60, 70 and 80% of the individuals' maximal oxygen uptake (Vo2 max). The same subjects also performed in another series of experiments where maximal intermittent exercise preceded 30 min of running at the same 4 speeds, or resting in a chair. During continuous running, starting from resting conditions, the blood LA increased only slightly up to a critical Ievel (i.e. 60—80%) of Vo2-max. From then on, a pronounced lactate production may occur. During the maximal intermittent exercise, blood LA increased to 130—220 mg/100 ml. In the recovery period, i.e. continuous running at the same 4 speeds, or resting in a chair, blood LA decreased towards resting values. The lactate removal rate was calculated from the rectilinear part of the curves describing the changes in LA with time, and expressed as mg/100 ml X min. The lactate removal rate was higher during exercise than during rest, and increased with increasing work load up to the same critical level (i.e. 60—80% of Vo2 max), beyond which a reduction was observed. The highest removal rate was 8 mg lactate/100 ml x min at 63% of Vo2 max (average values). These results indicate that human skeletal muscle possesses a pronounced capacity to oxidize lactate. Therefore, a production of lactate is possible even with no increase in the blood LA. These results also indicate that the skeletal muscle, rather than the liver, may be regarded as the main site for lactate removal during exercise.

The effect of bilateral carotid artery ligation upon the blood flow and the energy state of the rat brain.

Abstract: The cerebral effects of bilateral carotid artery ligation were studied in ligthly anesthetized rats, either alone or combined with moderate reductions in the mean arterial blood pressure. The relative decreases in cerebral blood flow were estimated from the a-v differences for O2 and CO2 on the assumption of an unchanged cerebral metabolic rate. Ligation of the carotid arteries alone was found to decrease cerebral blood flow to about 50 % of normal, but to give no significant changes in the energy state of the tissue, as judged from the tissue contents of the ATP, ADP and AMP. When the cerebral blood flow was reduced further by means of an induced decrease in blood pressure, the energy state of the tissue was severely affected. At this point the cerebral venous Po2 was reduced from about 50 to about 30 mm Hg. Since pure hypoxemia with a reduction of venous Po2 to about 10 mm Hg can be tolerated without changes in the energy state of the tissue, it is concluded that ischemia may lead to a grossly inhomogenous reduction in the tissue perfusion.

Microvascular dimensions and blood flow in skeletal muscle.

Abstract: In cats anesthetized with chloralose the lengths and diameters of the different vascular segments in the tenuissimus muscle were measured in the vital microscope. The flow characteristics, including red cell velocity, were registered. Fixed and stained muscle specimens were analyzed histologically as well as Indian ink-perfused muscles treated according to the method of Spalteholz. The average muscle fibre diameter was 44 μm. 62% of the muscle fibres were red (48% B-fibres, diameter 41 μm and 14% C-fibres, diameter 26 μm) and the remaining 38% were white (A-fibres, diameter 55 μm). The average muscle fibre was surrounded by 3.6 capillaries. The capillaries were 1015 ± 16.3 (S.E.) μm long and 5.3 ± 0.0(3) (S.E.) μm in internal diameter. The calculated capillary surface area was 0.9 m2/100 cm3 of muscle tissue. Average red cell velocity in the capillaries was found to be 0.5 mm/s, but there was a wide variation with time and between different capillaries. Neither “spontaneous” changes in internal diameters of the microvessels nor a distinct precapillary sphincter activity could be observed. Arterio-venous anastomoses within the muscle tissue were rare exceptions.

Coding of Amplitude and Frequency Modulated Sounds in the Cochlear Nucleus of the Rat

Abstract: The responses of single units in the cochlear nucleus of the rat to sinusoidally amplitude- and frequency-modulated tones and amplitude-modulated broadband noise were studied. The distribution of discharges within a cycle of modulation was determined from cycle histograms locked to the modulation wave. In response to amplitude-modulated tones and broadband noise, all units investigated showed a peak in the degree of modulation of the spike frequency within the modulation frequency range from 50 to 200 Hz. In many units the relationship between the degree of modulation of the stimulus sound and of the modulation of the resulting spike train was almost unchanged over a wide range of sound intensities. In other units, enhancement of modulation within a certain range of modulation frequency became more pronounced when the sound intensity was increased. This was mainly due to a suppression of modulation at lower modulation frequencies. The shape of the histograms was nearly sinusoidal even at modulation depths which resulted in nearly 100% modulation of the neural discharge frequency. The amount of modulation of the discharge frequency in response to frequency-modulated tones was dependent on the frequency of the tone in relation to the CF of the unit.

The oxygen supply to the retina. I. Effects of changes in intraocular and arterial blood pressures, and in arterial P O2 and P CO2 on the oxygen tension in the vitreous body of the cat.

Abstract: The Po2 in the vitreous body close to the retina, PvrO2, was determined continuously with an O2 electrode. In cats with a mean arterial blood pressure of 176±7 cm H2O, a PaO2 of 98±2 mm Hg, a PaC02 of 27.0±1–2 mm Hg and a pH of 7.43±0.16 units the mean PVr02 was 18.9±1.5 mm Hg. Stepwise increments in the eye pressure had no effect on PVrO2 at perfusion pressures above 50–100 cm H2O. At lower perfusion pressures PvrO2 decreased. Changes in perfusion pressure caused by hemorrhage and retransfusion gave similar results. At low Paco2 levels PvrO2 decreased; at high PaCo2 levels values of 40–60 mm Hg were observed. Reductions in Pao2 decreased Pvro2, increments gave either no change or a rise in Pvr02- Hypercapnia combined with high Pao2 in several cases resulted in PVr02 values between 100 and 150 mm Hg. The results indicate that the blood flow through the retina is very efficiently autoregulated, that oxygen tends to induce vasoconstriction in the retinal blood vessels, that hypocapnia gives vasoconstriction and hypercapnia marked vasodilatation.

Fluid transfer between blood and tissues during exercise.

Abstract: During 6 min exercise on a bicycle ergometer the volume of the leg in normal males increased so as to indicate, after correction for increased regional blood volume, an average trans-capillary fluid loss into the leg muscles of 19, 31, and 45 ml/kg tissue at light (300 kpm/min), moderate (900 kpm/min), and heavy (1200–1500 kpm/min) work load. The total fluid loss into the active muscle mass was calculated to comprise about 1100 ml during heavy work. Since the concomitant decrease of plasma volume was 600 ml, it follows that some 500 ml of fluid must have entered the circulatory system during the work. The study indicated that this compensatory fluid gain was accomplished by absorption of extravascular fluid from inactive tissues and partly caused by osmosis resulting from work induced arterial hyperosmolality (average increase 22 mOsm/kg H2O). Fluid absorption from inactive tissues was studied in experimental animals during exercise and in resting humans during arterial hyperosmolality produced by intravenous hypertonic infusions. The investigations suggested that at least half of the fluid gain to the circulatory system in heavy exercise could be ascribed to the increased arterial osmolality and the remainder to a reflex decrease of capillary pressure.

Subcellular localization of the prostaglandin system in the rabbit renal papilla.

Abstract: The occurrence of prostaglandins (PG), prostaglandin precursor acids, prostaglandin synthetase and 15-hydroxy prostaglandin dehydrogenase was studied in subcellular fractions isolated from homogenates of rabbit renal papilla by sucrose density gradient centrifugation. The investigated fractions were lipid droplets, supernatant, microsomes and mitochondria as verified by electron microscopy. Most of the prostaglandins was found to be prostaglandin E2 and was present in the supernatant whereas the prostaglandin synthetase occurred most abundantly in the microsomal fraction.-Nearly all of the recovered prostaglandins were formed during the preparation of the subcellular fractions. Arachidonic acid was the major esterified C20 acid and had the highest relative concentrations in the supernatant, microsomes, and mitochondria, whereas the lipid droplets had lower concentrations. No detectable 15-hydroxy prostaglandin dehydrogenase was present in the supernatant fraction of the papilla. The results indicate that in the rabbit renal papilla prostaglandin E2 is formed mainly from locally available arachidonate in membranes which sediment in the microsomal fraction and which may be derived from either cell membranes or membranes of the endoplasmic reticulum. After their formation the prostaglandins are probably released into the cytoplasm of the cells rather than being concentrated within specific subcellular particles and may leave the papilla without undergoing metabolic inactivation.

Correlation between Hyperinsulinemia and Hyperphagia in Rats with Ventromedial Hypothalamic Lesions

Abstract: Plasma levels of immunoreactive insulin (IRI) and glucose were determined in unrestrained rats equipped with chronically implanted venous catheters. Electrolytic lesions were then placed bilaterally in the ventromedial hypothalamic area. Food intake was restricted in order to prevent hyperphagia. A 60–280 % increase in the IRI level with a concomitant small increase in blood glucose was demonstrated on the second day post-operatively. The animals were then given free access to food. The gain in body weight during the following 3 days of ad lib feeding and the post-operative increase in the IRI level of each animal was positively correlated.

Studies on left ventricular receptors, signalling in non-medullated vagal afferents.

Abstract: Left ventricular receptors, signalling in non-medullated vagal fibres and displaying a low, irregular spontaneous activity, have been analysed by recordings of impulse activity in cardiac afferent nerves. The receptors were distributed diffusely all over the ventricle and in both superficial and deep layers of the myocardium. They were activated by occlusions of the ascending aorta, by substantial elevations of arterial blood pressure and by rapid infusions of saline or dextran, whenever these procedures produced a clearcut increase of intraventricular diastolic pressure and end-diastolic volume. The endings were also excited by veratrum alkaloids, nicotine and digitalis alkaloids. When activated, the receptors usually displayed a cardiac rhytm, but with intense stimulation the activity usually became continuous. The receptors evidently function as mechano- or deformation receptors, responding primarily to a distension of the ventricle. Activation of the receptors causes a reflex bradycardia and, in all probability, vasodilatation and blood pressure fall. They may contribute to the homeostatic control of blood pressure and blood volume, but their main function seems to be to protect the heart from e.g. imminent overloading. The endings are probably of main importance for the emergence of the Bezold-Jarisch reflex.

Convergence on interneurones in the reciprocal Ia inhibitory pathway to motoneurones.

Abstract: Summary 1. The present studies have aimed at analyzing the excitatory and inhibitory convergence from various neuronal systems onto the inter-neurones mediating the reciprocal inhibition of motoneurones from large muscle spindle (Ia) afferents. The conclusions regarding the convergence on the Ia inhibitory interneurones rest on studies of how transmission in the Ia inhibitory pathway is influenced from other neuronal systems; an excitatory convergence being indicated by facilitation and an inhibitory by depression of the Ia IPSPs. The depression of Ia IPSPs by volleys in motor axon collaterals has also been an important tool in the analysis. 2. It is known that Ia afferents from several muscles often can evoke inhibition in a given species of motoneurones. It has now been demonstrated that this convergence, at least partly, takes place already at the interneuronal level. 3. In spinal cats under chloralose anesthesia Ia IPSPs in flexor as well as extensor motoneurones were regularly facilitated by volleys in cutaneous afferents and high threshold muscle and joint afferents. In decerebrate cats with a low pontine lesion (in which volleys in these afferents evoke inhibition in both extensor and flexor motoneurones) Ia inhibitory transmission was not facilitated but depressed from high threshold muscle and joint afferents. Volleys in low threshold cutaneous afferents, on the other hand, facilitated Ia IPSPs also in this preparation. It is postulated that the Ia inhibitory interneurones receive excitatory actions from the ipsi-lateral flexor reflex afferents (transmission depressed in the decerebrate state) and through a separate pathway from low threshold cutaneous afferents. 4. A bulk of evidence has been gathered demonstrating that excitatory as well as inhibitory actions from various segmental and descending pathways, which control Ia inhibitory transmission, in fact do converge onto the same Ia inhibitory interneurones. Thus the interneuronal pool mediating Ia inhibition to a given motor nucleus can so far be regarded as functionally homogeneous. 5. Whenever conditioning volleys in the ventral root depressed transmission of inhibition to motoneurones from segmental or descending pathways, volleys in these pathways were found to facilitate Ia inhibitory transmission. It was postulated that the recurrent depression of IPSPs in motoneurones indicaces to which extent these IPSPs are mediated by the Ia inhibitory interneurones. 6. The investigation of the relative contribution from different efferent nerves to recurrent depression of Ia inhibitory interneurones revealed that the strongest depression is always evoked from motor fibres to muscles whose Ia afferents produce the IPSPs. For example, the Ia IPSP from the knee extensor recorded in motoneurones to a knee flexor is most effectively depressed by antidromic stimulation of motor fibres to the knee extensor. The prevailing pattern of recurrent effects indicates that activity in one motor nucleus will cause recurrent inhibition of aL- and γ-moto-neurones within that motor nucleus and other nuclei innervating synergists and also of Ia inhibitory interneurones impinging on motoneurones to antagonists. 7. The convergence onto the Ia inhibitory interneurones was discussed in the light of the recently introduced concept of an “α-γ-linkage in the reciprocal inhibition”.

Storage of 5‐Hydroxytryptamine in Rat Mast Cells. Evidence for an Ionic Binding to Carboxyl Groups in a Granule Heparin‐Protein Complex

Abstract: Bergendorff, A. and B. Uvnas. Storage of 5-hydroxytryptamine in rat mast cells. Evidence for an ionic binding to carboxyl groups in a granule heparin-protein complex. Acta physiol. scand. 1972. 84. 320–331. Basophil granules were isolated from rat peritoneal and thoracic mast cells. The granules were depleted of their endogenous Hi and 5-HT and the amine storing properties of these depleted granules were studied. The influence of pH, the uptake capacity, the releasing action of sodium ions and the competitive uptake of Hi and 5-HT by the granule stores all support the hypothesis that the granule stores have the properties of a weak cation exchange resin. It appears that 5-HT release, as we previously showed for Hi-release, is due to a cation exchange occurring on mast cell degranulation, when the amine-containing granules become exposed to cations of the extracellular milieu.

Effect of 6-hydroxydopamine on the ganglion cells and the small intensely fluorescent cells in the superior cervical ganglion of the rat.

Abstract: Hydrocortisone acetate was administered intraperitoneally to newborn rats daily for 5 days, 40 mg/kg b.w. They were killed on the 6th day. Adult rats were given the same dose daily for 14 days and killed on the 16th day. Catecholamines were demonstrated by formaldehyde vapour induced fluorescence. In the 6-day-old rats treated with hydrocortisone there was a distinct increase in the size of the extra-adrenal chromaffin bodies, in the number of fluorescent cells in them and in the intensity of the fluorescence of these cells, as compared with the controls. Hydrocortisone treatment also caused about a tenfold increase in the number of the small intensely fluorescent (SIF) cells in the superior cervical ganglion, the coeliac ganglion and the lumbar prevertebral ganglia of the young rats. The newly formed SIF cells were scattered single or in clusters of a few cells throughout the ganglia, including sites in which no SIF cells were normally present before hydrocortisone treatment. In the adult rats, hydrocortisone did not cause any dramatic changes in the sympathetic ganglia. The SIF cells were present in clusters in the same way as in the control ganglia but there was a tendency towards an increase in the number of SIF cells in the clusters. It is concluded that hydrocortisone causes in young rats a greatly increased formation of the SIF cells from poorly differentiated, weakly fluorescent stem cells, while proliferation of already existent SIF cells is less pronounced.

Reactions within Consecutive Vascular Sections of the Small Intestine of the Cat during Prolonged Hypotension

Abstract: A plethysmography technique was utilized to investigate the reactions within consecutive vascular sections of the small intestine of the cat during and after a 2–3 h local arterial hypotension at approximately 55 or 30 mm Hg produced by graded arterial occlusion. The sympathetic nerves to the intestine were cut. The resistance vessels were dilated during hypotension, the dilatation being more pronounced the lower the perfusion pressure. In the early phase of hypotension this autoregulation of intestinal blood flow was probably mainly “myogenic” while it was predominantly “metabolic” in the late part of hypotension. When releasing the arterial occlusion, blood flow returned to control after a 55 mm Hg hypotension, while a marked prolonged vasodilatation was observed after the 30 mm Hg hypotension. The capillary filtration coefficient was not changed from control during a hypotension at 55 mm Hg while it was enhanced at 30 mm Hg. Mean capillary hydrostatic pressure seemed to increase in the latter half of most experiments performed at this level. An additional, transient augmentation of capillary pressure seemed to occur after the hypotension. Upon releasing the arterial clamp after a 30 mm Hg hypotension the whole cardiovascular system seemed to derange progressively to judge by a decline of arterial blood pressure.

Centrally mediated effects of sodium and angiotensin II on arterial blood pressure and fluid balance.

Abstract: Four kinds of infusions were made for 1 h periods into the 3rd cerebral ventricle of hydrated, conscious goats: 1) Angiotensin in hypertonic NaCI, 2) angiotensin in slightly hypotonic NaCI, 3) angiotensin in isotonic d-glucose, and 4) hypertonic NaCI. The influence of these infusions on carotid blood pressure and fluid balance was studied. The infusions of angiotensin in hypertonic NaCl had conspicuous hypertensive, dipsogenic, antidiuretic and natriuretic effects. More moderate responses of the same kinds were obtained during the infusions of hypertonic NaCl and of angiotensin in slightly hypotonic NaCI. In contrast, no or only weak effects were obtained by the infusions of angiotensin in isotonic d-glucose. The results are taken as support for the idea that a Na+ sensitive system in the vicinity of the 3rd ventricle may be of importance in the central contml of fluid balance and arterial blood pressure. Such a system may be influenced by the Na+ concentration of the cerebrospinal fluid, and angiotensin may either sensitize it to Na+ or make it more exposed to Na+ ions.

Concentration of noradrenaline in pial vessels, choroid plexus, and iris during two weeks after sympathetic ganglionectomy or decentralization.

Abstract: Changes in the noradrenaline concentration of the sympathetically innervated pial vessels, choroid plexuses, and irides of the rabbit were measured fluorometrically at various periods during the first 2 weeks after pre- or postganglionic denemation (decentralization or excision of the superior cervical ganglia) The noradrenaline values fell to negligible amounts within 2 days after ganglionectomy in all organs, probably somewhat slower in choroid plexuses After decentralization the noradrenaline level increased in the pial vessels, whereas in the choroid plexuses and iris it initially decreased followed by normalization The fall occurred somewhat later in the iris It is suggested that the results of the denervation experiments reflects the presence of functionally different types of sympathetic neurons in one and the same ganglion

Response to Submaximal and Maximal Exercise at Different Levels of Carboxyhemoglobin

Abstract: Five subjects performed submaximal and maximal bicycle and maximal treadmill exercise in normalcy and after carbon monoxide inhalation, giving different levels of carboxyhemoglobin (COHb) in the blood. During maximal treadmill exercise work time on a fixed work load and maximal oxygen uptake were decreased with increasing level of COHb (r = 0.79 and r = 0.85, respectively). Peak blood lactate concentration and pulmonary ventilation were unchanged. Highest measured heart rate was lower in parallell with the increased COHb level compared to control studies. During submaximal work heart rate was increased and oxygen uptake was unchanged at the various levels of COHb. At low submaximal work loads blood lactate concentrations and oxygen deficit was unchanged but increased as work load and COHb-level increased.

Augmented noradrenaline release following nerve stimulation after inhibition of prostaglandin synthesis with indomethacin.

Abstract: The effect of inhibition of prostaglandin synthesis on the release of noradrenaline induced by sympathetic nerve stimulation was studied in the isolated perfused rabbit heart. It was found that indomethacin (Indomee®, Merck, Sharp and Dohme), a drug known to inhibit prostaglandin synthesis, decreased the outflow of prostaglandins normally induced by nerve stimulation. Simultaneously the outflow of noradrenaline in response to nerve stimulation was augmented. Since indomethacin neither caused any release of noradrenaline heart in the absence of nerve stimulation, nor affected the uptake of exogenous noradrenaline, it is concluded, that the increased noradrenaline release reflects disinhibition of a feed-back mechanism, using endogenously formed prostaglandins for limitation of noradrenaline release.

Proton- and carbamino-linked oxygen affinity of normal human blood.

Abstract: The oxygen affinity of normal human blood was measured at two different pH values and three different pCO2 values over the whole saturation range. From these data, and from data on the interaction of 2,3-diphosphoglycerate with hemoglobin, values were calculated for the proton-linked oxygen affinity at different pCO2 values and for the carbamino-linked oxygen affinity at different pH values. Both the proton-linked and the carbamino-linked oxygen affinity were found to be markedly dependent on the degree of oxygen saturation. The relative contribution of the three ligands, i.e. protons, carbon dioxide and 2,3-diphosphoglycerate, to the classical Bohr effect was estimated and found to be dependant on the oxygen saturation level. The values for the proton-linked oxygen affinity and the carbamino-linked oxygen affinity were found, by applications of Wyman's reciprocal relations and 2,3-diphosphoglycerate binding data, to give good estimates of the oxygen-linked proton binding and the oxygen-linked carbamino binding. The data show that the oxygen-linked carbamino reaction takes place mainly during the binding of the first 2 oxygen molecules with a value of about 0.25 mol per mol of oxygen. The proton release accompanying this reaction was estimated to be 1.3–1.7 mol per mol.

Inhibition by hippurate and probenecid of in vitro uptake of iodipamide and o-iodohippurate. A composite uptake system for iodipamide in choroid plexus, kidney cortex and anterior uvea of several species.

Abstract: Slices of kidney cortex and liver, pieces of lateral choroid plexus and of ciliary body with or without iris were incubated in a potassium-rich medium containing labelled iodipamide often together with labelled o-iodohippurate. Tissues were from rabbits, guinea-pigs, monkeys (3 species), dogs, cats and chicken. Iodipamide at 0.5—2 μM depresses uptake of labelled iodipamide by rabbit kidney cortex wthout affecting uptake of o-iodohippurate. Hippurate at 30 mM suppresses uptake of o-iodohippurate in all tissues tested but leaves a fraction of iodipamide uptake in all tissues and species tested. The findings with o-iodohippurate uptake are compatible with a single uptake system, the findings with iodipamide and the kinetics derived for this substance are incompatible with a single uptake system. Iodipamide seems to be accumulated by one hippurate-sensitive system shared with o-iodohippurate and at least one other, hippurate-insensitive system. This latter system usually is a minority system in kidney cortex and anterior uvea but dominates in liver and choroid plexus and in cat kidney cortex. The hippurate-insensitive system can be suppressed by probenecid but needs a higher concentration than the hippurate-sensitive one.

Chloride Transport across Isolated Frog Skin

Abstract: Kristensen, P. Chloride transport across isolated frog skin. Acta physiol. scand. 1972. 84. 338–346. A net inward transport of chloride was found to occur in isolated skins of Rana temporia. This transport was not dependent on sodium transport and was inhibited by diamox, thio-cyanate and bromide. The active chloride transport was not affected by changes in the transepithelial potential difference. On the other hand, the curve describing efflux as a function of potential difference was found to have a shape resembling the shape of the Goldman equation. Graphical determination of apparent pools showed the influx pool to be about six times greater than the efflux pool. Diamox had no effect on efflux pool size but reduces the apparent influx pool so that it becomes about equal to the efflux pool. This means that at least part of the paths for active and passive chloride movements are different. A working hypothesis is put forward, according to which chloride is actively transported across the outward facing membrane of the outermost living cell layer of the frog skin epithelium, and the main part of the passive flux occurs across the tight seals and via the interspace system.

Microdetermination of free amino acids in pancreatic islets isolated from obese-hyperglycemic mice.

Abstract: Free amino acids were measured with a microtechnique employing labelling with 14C-dansyl-Cl and separation with two-dimensional thin-layer chromatography. Most amino acids occurred in greater amounts in the islets than in the exocrine pancreas. Aspartic acid, valine and leucine were present in tenfold amounts. It is postulated that the β-cells are equipped with binding sites for large amounts of the latter amino acid. Like nervous tissue, the pancreatic islets were characterized by the presence of gamma-aminobutyric acid and high levels of taurine.