Showing papers in "Acta Physiologica Scandinavica in 1984"

Trunk movements in human locomotion

Abstract: Trunk movements in the frontal and sagittal planes were studied in 10 healthy males (18-35 yrs) during normal walking (1.0-2.5 m/s) and running (2.0-6.0 m/s) on a treadmill. Movements were recorded with a Selspot optoelectronic system. Directions, amplitudes and phase relationships to the stride cycle (defined by the leg movements) were analyzed for both linear and angular displacements. During one stride cycle the trunk displayed two oscillations in the vertical (mean net amplitude 2.5-9.5 cm) and horizontal, forward-backward directions (mean net amplitude 0.5-3 cm) and one oscillation in the lateral, side to side direction (mean net amplitude 2-6 cm). The magnitude and timing of the various oscillations varied in a different way with speed and mode of progression. Differences in amplitudes and timing of the movements at separate levels along the spine gave rise to angular oscillations with a similar periodicity as the linear displacements in both planes studied. The net angular trunk tilting in the frontal plane increased with speed from 3-10 degrees. The net forward-backward trunk inclination showed a small increase with speed up to 5 degrees in fast running. The mean forward inclination of the trunk increased from 6 degrees to about 13 degrees with speed. Peak inclination to one side occurred during the support phase of the leg on the same side. Peak forward inclination was reached at the initiation of the support phase in walking, whereas in running the peak inclination was in the opposite direction at this point. The adaptations of trunk movements to speed and mode of progression could be related to changing mechanical conditions and different demands on equilibrium control due to e.g. changes in support phase duration and leg movements.

Vascular permeability changes and smooth muscle contraction in relation to capsaicin-sensitive substance P afferents in the guinea-pig.

Abstract: The occurrence of neurogenic inflammation as indicated by Evans blue extravasation was studied in various organs of the guinea-pig Electrical stimulation of the trigeminal nerve caused Evans blue extravasation due to increased vascular permeability in the nasal mucosa and gingiva Vagal stimulation induced extravasation in the epiglottis, larynx, trachea, bronchial tree and esophagus Splanchnic stimulation induced Evans blue extravasation in the gall bladder, bile ducts and superior mesenteric artery Stimulation of the inferior mesenteric ganglion caused a marked extravasation in the upper and middle part of both ureters, while pelvic activation induced a reaction in the lower ureter, urinary bladder, urethra and vagina Iv substance P (SP) (3 nmol X kg11) or capsaicin (1 mumol X kg-1) both induced extravasation in many tissues including those in which nerve stimulation produced a response The extravasation responses to SP, capsaicin or nerve stimulation all had similar border-line zones, such as esophagus to stomach, bile ducts to duodenum, rectum to anal mucosa, pulmonary artery to heart and vagina to uterus Quantitative determinations showed especially large permeability effects in the trachea, umbilical ligament and ureter The permeability effect of capsaicin and nerve stimulation was abolished in capsaicin-pretreated animals, while the response to SP was still present Capsaicin pretreatment caused an almost total loss of SP in several visceral organs including the respiratory and urinary tracts The SP content in these tissues was correlated (r = 097) to the Evans blue extravasation following nerve stimulation or iv capsaicin SP and capsaicin caused contractions in vitro of the esophagus, ureter, urinary bladder, trachea and gall bladder The capsaicin-induced contraction of the trachea was resistant to tetrodotoxin pretreatment The non-cholinergic, non-adrenergic contraction of the urinary bladder upon field stimulation was still present in capsaicin-pretreated animals In conclusion, neurogenic inflammation occurs in several organs with a highly region-specific distribution, which is accompanied by the presence of capsaicin-sensitive SP neurons Both parasympathetic and sympathetic pathways contain capsaicin-sensitive afferent fibres which mediate an increase in vascular permeability most likely by releasing SP In addition, both capsaicin and SP cause smooth muscle contraction in several visceral organs

The effect of dorsal root transection on the efferent motor pattern in the cat's hindlimb during locomotion.

Abstract: Mesencephalic cats can walk on a treadmill if the midbrain locomotor region is stimulated. The motor pattern of different hindlimb muscles is similar to that of th intact cat. The present experiments in the mesencephalic preparation test if the complex motor pattern in one hindlimb is causally dependent on the afferent signals arising in the same limb during walking. The electromyographical activity and the movement pattern during locomotion were compared before and after transecting all dorsal root fibres originating from one hindlimb. Flexor and extensor muscles at different joints may retain their general pattern after the dorsal root transection. This applies also to muscles such as the knee flexors, which have a short and early flexor burst and a second burst during the extension phase, and the short toe dorsiflexor , which has an early burst in the transition between flexor and extensor activity. After the dorsal root transection the pattern of activity may become more variable and it can even break down altogether. The present results demonstrate that the central nervous system devoid of phasic afferent inflow from one hindlimb can produce a complex motor output to this limb rather than a motor pattern degraded to a simple alternation between flexors and extensors.

Muscle glycogen depletion patterns in type I and subgroups of type II fibres during prolonged severe exercise in man.

Abstract: Glycogen depletion of muscle fibre types I, II A, II AB and II B was studied using a histochemical method to quantify glycogen content in individual fibres. The reliability was examined in 29 muscle biopsies, in which total glycogen content was compared to average periodic acid Schiff (PAS) stain intensity in sections from the same samples. Over a wide range of glycogen content (1-252 mmole glucosyl units . kg-1 wet weight) a linear relationship (r = 0.93) was found between the two methods for quantification of muscle glycogen. Glycogen depletion patterns in type I, II A, II AB and II B fibres were studied in 5 subjects during exhaustive bicycle exercise at 75% of VO2 max. At rest before exercise glycogen content was 16% higher in type II subgroups than in type I (p less than 0.05). From start of exercise the same glycogen depletion rate was observed in type I and II A. Glycogen content of Type II AB and II B was unchanged during the first part of exercise. Later a decrease was observed, first in type II AB and finally in II B, suggesting a decrease in threshold force of these fibre types. The results indicate physiological differences between the 3 subgroups of type II fibres in man, whereas at the present exercise intensity type I and II A fibres were recruited simultaneously from start.

Differentiated sympathetic activation during mental stress evoked by the Stroop test.

Abstract: Sympatho-adrenal and hemodynamic responses to mental stress induced by Stroop's color word test (CWT) were examined in 12 healthy volunteers. CWT increased heart rate and blood pressures by 28 beats/min and 29/14 mmHg, on the average. The pressor response was caused by an increase in cardiac output (from 6.3 +/- 0.3 to 10.9 +/- 0.6 l/min, p less than 0.001), since systemic vascular resistance was reduced by approximately 30% during CWT. Calf vascular resistance (mainly muscle) was also reduced. At rest there was a net production of NA and a net removal of adrenaline (ADR) in the forearm tissues. About 45% of the NA in antecubital venous plasma appeared to be derived from the forearm tissues. During CWT arterial NA increased (from 1.53 +/- 0.20 to 2.13 +/- 0.15 nM, p less than 0.001), but antecubital venous NA levels remained unchanged. There was removal of ADR (about 19%) and a calculated production of NA by the lungs at rest, both of which disappeared during stress. CWT caused a "defence reaction"-like hemodynamic response with cardiac activation, but unchanged or reduced peripheral sympathetic nerve activity. This explains the lack of increase in antecubital venous NA, which is markedly influenced by sympathetic activity in the forearm tissues. Arterial plasma catecholamine measurements provide better information concerning sympatho-adrenal activity in the body as a whole than do peripheral venous measurements. Regional sympathetic activity is preferably studied by NA outflow determinations from the target organs.

Effects of neuropeptide Y (NPY) on mechanical activity and neurotransmission in the heart, vas deferens and urinary bladder of the guinea-pig.

Abstract: The effects of preincubation for 10 min with synthetic porcine neuropeptide Y (NPY) on muscle tone and autonomic transmission in the guinea-pig right atrium, vas deferens, urinary bladder, portal vein and trachea were analysed in vitro. NPY induced a metoprolol-resistant, long-lasting, positive inotropic and cronotropic effect per se in the spontaneously beating right atrium. Furthermore, NPY caused a reversible inhibition of both the metoprolol and atropine-sensitive auricle responses to field stimulation (2 Hz or 4 Hz for 2 s) without affecting the response to exogenous noradrenaline (NA) or acetylcholine (ACh). NPY did not induce any contraction of the vas deferens, but inhibited both the rapid twitch response and the sustained tonic contraction induced by field stimulation. The NPY-induced inhibition of the tonic contraction was more long-lasting than that of the twitch response. The tonic contraction was blocked by phentolamine and the twitch response by α-, β-methylene ATP tachyphylaxis. NPY did not inhibit the contractile effects of NA, ATP or α-, β-methylene ATP. NPY also induced a reversible reduction of the non-cholinergic, non-adrenergic contractile response to field stimulation of the urinary bladder. In the portal vein, NPY (up to 5×10–7 M) did not inhibit the spontaneous motility or the phentolamine-sensitive contractile responses to field stimulation and NA. The atropine-sensitive contraction of the trachea or the non-adrenergic, non-cholinergic relaxation induced by field stimulation were not significantly influenced by NPY in doses up to 5×10–7 M. In conclusion, the present data show that in the guinea-pig, NPY exerts positive chronotropic and inotropic effects on the right atrium of the heart. Furthermore, NPY may have presynaptic effects on adrenergic, cholinergic and non-adrenergic—noncholinergic neurotransmission.

Buffer capacity and lactate accumulation in skeletal muscle of trained and untrained men

Abstract: Buffer capacity (beta) of skeletal muscle has been determined in trained (n = 7) and in sedentary subjects (n = 8). The trained subjects were active in ball games where a high degree of anaerobic energy utilization is required. Percentage fibre type occurrence in the thigh muscle was not significantly different in the two groups. However, there was a tendency towards a higher proportion of type I (slow-twitch) fibres (61.5 +/- 11.6% vs. 50.2 +/- 12.5%) and a lower proportion of type IIB fibres (2.1 +/- 3.5% vs 14.1 +/- 16.3%) in the trained subjects. The proportion of the cross-sectional area of the muscle biopsies that was made up of type I or type II fibres was not different in the two groups. All subjects performed an isometric contraction of the knee extensors to fatigue at 61% of their maximal voluntary contraction force. Muscle biopsies were taken from the quadriceps femoris muscle at rest and immediately after contraction. The buffer capacity of muscle was calculated from: beta = (Muscle lactate (work)-Muscle lactate (rest)/(Muscle pH (rest)-Muscle pH (work)). A higher buffer capacity (p less than 0.05) was observed in the trained subjects (beta = 194 +/- 30 mmol X pH-1 X kg-1 dry wt.) compared to the sedentary group (beta = 164 +/- 20) (mean +/- SD). An unexpected finding was that muscle lactate after contraction to fatigue was lower (30%, p less than 0.01) and muscle pH was higher (6.80 +/- 0.06 vs. 6.61 +/- 0.12, p less than 0.01) in the trained subjects than in the sedentary controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuropeptide Y: Immunocytochemical localization to and effect upon feline pial arteries and veins in vitro and in situ

Abstract: Plexuses of nerve fibres containing neuropeptide Y (NPY)-like immunoreactivity invest pial arteries belonging to the circle of Willis, pial arterioles, occasionally penetrating arterioles and large veins. A more sparse supply of NPY-like fibres were observed around pial veins and venules. The NPY-immunoreactive fibres are located within the adventitia or at the adventitia-media border. Only occasional fibres are present in cerebral vessels of animals in which the superior cervical ganglion has been removed one week previously. Administration of NPY resulted in strong, concentration-dependent contractions of isolated feline middle cerebral arteries whereas administration of avian pancreatic polypeptide (APP) elicited weak contractions. In chloraloseanaesthetized cats, perivascular microapplication of NPY in situ resulted in marked concentration-dependent contractions of cerebral pial arterioles (34.7 +/- 6.6%; maximum decrease in calibre with NPY. Perivascular administration of NPY resulted in the constriction of pial veins but the magnitude of the venous calibre reductions was smaller than the response of arterioles at each reductions was smaller than the response of arterioles at each concentration examined. APP did not elicit contraction of pial arterioles or veins during in situ conditions. The pharmacological and immunocytochemical results strongly indicate the existence of a novel perivascular neuronal system containing NPY, which mediates contraction of cerebral blood vessels and NPY is colocalized with NA in sympathetic nerves.

Enzyme levels in pools of microdissected human muscle fibres of identified type. Adaptive response to exercise.

Abstract: Enzyme activities were determined in pools of type I (slow twitch) and II A and II B (fast twitch) fibres of the thigh muscle from individuals engaged to a high degree in physical training of an endurance character and from non-endurance-trained controls. The endurance-trained (ET) group had significantly higher activity levels of the mitochondrial enzymes citrate synthase, malate dehydrogenase, and 3-OH-acylCoA dehydrogenase both in type I (2.1X, 1.7X, 1.4X) and in type II A (2.3X, 1.8X, 1.4X) and II B fibres (2.0X, 1.5X, 1.5X) than the non-endurance-trained (NET) group. Of the glycolytic enzymes, phosphofructokinase (PFK) in type I fibres was significantly higher (1.8X) in the ET than in the NET group whereas glyceraldehydephosphate dehydrogenase (GAPDH) in type I fibres was similar in the two groups. In type II fibres both PFK and GAPDH levels tended to be higher in the ET group. Lactate dehydrogenase (LDH) of both fibre types were not different in the two groups. Type I fibres differed significantly from type II fibres for all the six enzymes measured in both groups. However, no significant difference between fibres of types II A and II B was found. The results indicate that fibres of types I, II A and II B in human skeletal muscle all possess great adaptability with regard to their oxidative capacity. Furthermore, the data suggest that extensive endurance training may enhance the glycolytic capacity in both type I and type II fibres although the glycolytic capacity of the muscle as a whole generally is low in endurance trained subjects owing to a predominance of type I fibres. It is concluded that further studies are needed to determine whether there is a metabolic distinction between fibres of types II A and II B.

Renal sympathetic activity in spontaneously hypertensive rats and normotensive controls, as studied by three different methods

Abstract: Recordings of sympathetic activity from multifibre preparations of renal nerves have produced conflicting results concerning the presence or absence of an increased sympathetic discharge in spontaneously hypertensive rat (SHR) compared to normotensive Wistar-Kyoto rats (WKY). Therefore, recordings of single fibre activity to the kidney were performed in anesthetized SHR and WKY in comparison with multifibre recordings in conscious, undisturbed rats. A new method of estimating sympathetic discharge by analyzing the variability of "cycle activity" in multifibre nerve recordings was also used. The average nerve activity in a great number of cardiac cycles was then expressed in relation (in per cent) to the nerve activity in a small number of cardiac cycles with the highest and lowest nerve activity in each rat. Single fibre recordings showed a significantly higher sympathetic activity to the kidneys in SHR (3.8 +/- 0.3 Hz) than in WKY (1.7 +/- 0.2 Hz; p less than 0.001). Also average "cycle activity" was significantly higher in conscious SHR (34 +/- 1%) than in WKY (26 +/- 2%, p less than 0.01). This was due to the larger number of cardiac cycles in SHR with high sympathetic activity while WKY showed more of "silent" cardiac cycles which lacked nerve impulses. Further, the recordings of rectified multifibre renal nerve activity also showed an elevated sympathetic activity in conscious SHR rats. The increased renal sympathetic activity appears to reflect the "primary" central nervous "hyperreactivity" characterizing SHR hypertension. It is suggested that the increased renal sympathetic activity may be of particular importance for the development of primary hypertension in SHR and perhaps also in man.

Contribution of individual organs to total noradrenaline release in humans.

Abstract: Plasma noradrenaline measurements are a fallible guide to sympathetic nervous tone, being dependent on noradrenaline plasma clearance. We have developed radiotracer techniques, based on measurement of the rate of spillover of noradrenaline to plasma, to simultaneously estimate total, and organ-specific, sympathetic nervous activity in humans. In 27 unmedicated subjects without renal or liver disease, or cardiac failure, regional noradrenaline spillover rates were as follows: lungs 138 +/- 36 ng/min (mean +/- SE) (33% of total noradrenaline spillover), kidneys 77 +/- 10 ng/min (22% of total), skeletal muscle 64 +/- 11 ng/min (20%), hepatomesenteric 29 +/- 9 ng/min (9%), skin 18 +/- 4 ng/min (5%), and heart 11 +/- 4 ng/min (3%). Organ-specific noradrenaline spillover measurements are well suited to the elucidation of sympathetic nervous system pathophysiology in human diseases. Since the sympathetic nervous system outflow to individual organs is not activated or suppressed uniformly in different disease states, biochemical measures of "overall sympathetic nervous activity" are insufficiently specific for this purpose.

Changes in neuromuscular performance and muscle fiber characteristics of elite power athletes self‐administering androgenic and anabolic steroids

Abstract: The influence of androgenic-anabolic steroid-induced changes in measures of body composition, muscle fiber characteristics and various aspects of the neuromuscular performance of the leg extensor muscles was investigated in five experimental and six control power athletes during the 24-week programmed strength training followed by the additional six week training without hormone drugs. The mean values of the dosages of self-administration during the 24-week period were 31.0 +/- 14.3 mg/day for anabolic steroids (methandienone, stanozolol, nandrolone) and 178.4 +/- 82.7 mg/week for testosterone. During the 24-week hormone period the experimental group gained in fat-free weight (p less than 0.01) and in the mean muscle fiber areas (p less than 0.01) of the vastus lateralis muscle while the corresponding gains in the control group were minor (NS). The increases of maximal isometric force in the experimental and control groups were 14.7% (p less than 0.01) and 6.1% (NS), respectively, and the values obtained in average load-vertical jumping height curves were improved significantly (p less than 0.05) only in the experimental group. Increases of 18.2% (p less than 0.001) and 12.9% (p less than 0.01) took place in the squat lift in the experimental and control groups, respectively. Both groups demonstrated similar (p less than 0.05) improvements in isometric fast force production. During the additional six week programmed training without hormone drugs significant (p less than 0.05) increases were observed in the experimental group in addition to maximal isometric force and the squat-lift but also in isometric fast force production, while the corresponding changes in the control group were minor (NS). It is suggested that strength training in combination with administration of androgenic-anabolic steroids causes improvements in selected neuromuscular parameters. These changes may be greater than those of caused by the strength training alone.

Theophylline antagonizes cardiovascular responses to dipyridamole in man without affecting increases in plasma adenosine

Abstract: Effects of the vasodilator dipyridamole (Dip) on plasma adenosine levels, heart rate, blood pressure and skin microcirculation were studied in 13 healthy male volunteers. Venous plasma concentrations of adenosine, catecholamines, dipyridamole and theophylline were determined by HPLC. Skin capillary blood cell velocity (CBV) was measured by videophotometric capillaroscopy in the finger nailfold. The adenosine uptake inhibitor Dip (approximately 1-3 microM in plasma) increased plasma adenosine from 0.15 +/- 0.03 to 0.29 +/- 0.03 microM (p less than 0.01) and heart rate (HR) by 13 +/- 2 beats/min (p less than 0.01) and reduced diastolic blood pressure by 6 +/- 2 mmHg (p less than 0.05). Dip did not significantly affect the skin circulation since basal CBV, digital pulse amplitude (DAPA), skin temperature and post-occlusive reactive hyperemia were unchanged. Plasma catecholamine levels were also unaffected. The adenosine receptor antagonist theophylline (45-55 microM in plasma) did not influence basal plasma catecholamine or adenosine levels, HR, blood pressure or skin microcirculation. Following theophylline Dip caused similar elevations of plasma adenosine but no changes in HR or blood pressures. Our results support the hypotheses that Dip dilates blood vessels in man by elevating endogenous adenosine and that theophylline acts as an adenosine antagonist. Under basal conditions, the skin microcirculation appears to be regulated mainly by factors other than adenosine.

Computer-assisted morphometry and microdensitometry of transmitter- identified neurons with special reference to the mesostriatal dopamine pathway. Methodological aspects.

Abstract: New morphometrical and microdensitometrical approaches for evaluation of transmitter-identified neurons in the central nervous system have been developed. These rely at the presynaptic level on the use of immunocytochemistry and at the postsynaptic level on the use of receptor autoradiography. The immunocytochemical analysis involves the indirect immunofluorescence method and the indirect immunoperoxidase method utilizing cryostat and vibratome sections, respectively. In the postsynaptic analysis cryostat sections and tritium-sensitive film were employed. A block diagram representation of the system of the image analyzer used and its connection with its host computer is given. Furthermore, flow charts of the original software developed by our group in presented. The morphometrical analysis has been performed on coronal sections of rat brain resulting in determinations of cell body and cell group parameters. Based on this information, objective criteria have been introduced to assess the existence of a cell group of transmitter-identified neurons in a three-dimensional frame and to give a morphometrical description of this group in the space. Moreover, new quantitative approaches to describe the dendritic and terminal fields have been introduced and for the first time in this type of morphometrical analysis, the Lorenz curves and the Gini index have been utilized in the description of the pattern of dendritic and terminal networks. By means of these morphometrical approaches it became possible to analyze topological and biochemical heterogeneities within cell groups defined in the rostrocaudal frame. In particular, it has been possible to develop a quantitative method for the evaluation of coexistence in nerve cell bodies. This method has been called the overlap method and allows an analysis cell by cell of the possible coexistence of two or more antigens.

Effect of GM1 ganglioside treatment on the recovery of dopaminergic nigro‐striatal neurons after different types of lesion

Abstract: The effect of GM1 ganglioside treatment on the recovery of biochemical and behavioral parameters which define the activity of nigro-striatal dopaminergic systems has been investigated in rats after different types of lesion. GM1 favours the recovery of tyrosine-hydroxylase activity, of the number and affinity of 3H-N-n-propyl-norapomorphine binding sites in the striatum of the lesioned side and reduces the apomorphine-induced rotational behavior after mechanical (i.e. unilateral hemitransection) but not after chemical (i.e. 6-OHDA injected in the substantia nigra) lesion. The source of regrowing dopaminergic nerve terminals in the striatum after hemitransection is mainly a response of intact remaining axons of the ipsilateral side. Moreover the contralateral nigro-striatal systems seems to play, through intrathalamic connections, an important role in regulating the GM1-induced increase of the tyrosine-hydroxylase activity.

Adrenergic nerves and the alpha2-adrenoceptor system regulating melanosome aggregation within fish melanophores

Abstract: Nervous control of melanosome aggregation of melanophores of Labrus ossifagus was studied by electrical field stimulation of isolated scales. Field stimulation elicited a rapid melanosome aggregation which was reversible upon interruption of the stimuli. The response was blocked by guanethidine indicating that adrenergic nerves were stimulated. The melanophore receptors which mediate the nerve-controlled pigment aggregation were characterized to be of the alpha 2-adrenoceptor subtype, since they were inhibited by yohimbine but not by prazosin. Stimulation of the alpha 2-adrenoceptors by noradrenaline was associated with a significant reduction of the cyclic AMP content of the melanophores. It is suggested that adrenergic nerves control melanosome aggregation via alpha 2-adrenoceptors and that these receptors are coupled to the adenylate cyclase-cyclic AMP system of the melanophores.

How to calculate human muscle fibre areas in biopsy samples--methodological considerations.

Abstract: Cross-sectional muscle fibre areas (type I, II A and II B) were determined in duplicate biopsies from the left vastus lateralis (n = 11) and in biopsies from right and left vastus lateralis (n = 8). The SD for the difference in means between duplicate biopsies was 510 microns 2 for type I, 1020 microns 2 for type II A and 860 microns 2 for type II B. Expressed as coefficient of variation (CV) these SD constituted 10, 15 and 15%, respectively. The variation in fibre size within a sample was considerably less than the variation between samples on the assumption that at least 15-20 areas of each fibre type were measured per sample. No difference in mean fibre area for type I, II A and II B fibres was obtained between the right and left muscle. Several artefacts due to the sampling and preparing procedures are discussed and a method for determining muscle fibre areas in biopsy samples is suggested.

Vasoactive intestinal polypeptide (VIP): effects in the eye and on regional blood flows.

Abstract: The effect of vasoactive intestinal polypeptide (VIP) on regional blood flows was studied with labeled microspheres in albino rabbits. Intravenous injection of 500 ng VIP/kg b. w. during 100 s did not change the arterial blood pressure significantly, but caused a rise in intraocular pressure (IOP) and an increase in the choroidal blood flow by 35%, while the blood flow through the anterior uvea was unaffected. The most pronounced vasodilation was observed in the pancreas, the thyroid gland and the parotid gland. In these tissues local blood flow increased by more than 100%. Other tissues, in which this dose of VIP produced vasodilation, were the submandibular gland, the eyelids, the nictitating membrane, the choroid plexus and the heart muscle. Ganglionic or muscarinic blockade had little or no effect on the VIP-induced vasodilation in most of the tissues. Intracameral injection of VIP (1 μg) produced vasodilation in the iris and the ciliary body, but did not affect IOP. VIP had no apparent effect on the pupil size or the blood-aqueous barrier. In experiments with direct blood flow determination from an opened vortex vein intravenous infusion of VIP, 100 ng. kg-1 .min-1 b. w., during five minutes reduced the uveal vascular resistance by about 50%. This study shows that VIP is a potent vasodilator in many tissues at doses hardly affecting the arterial blood pressure and supports the suggestion, that VIP is responsible for the non-cholinergic vasodilation in the eye caused by facial nerve stimulation.

Influence of low muscle temperature on muscle metabolism during intense dynamic exercise.

Abstract: Eight males performed intense leg cycle exercise at a constant rate of work averaging 350 W, according to three different protocols: 1) "Cold exhaustive" exercise (initial muscle temperature (Tm) = 29 degrees C), 2) "Warm non-exhaustive" exercise (initial Tm = 34 degrees C) for the same period of time as in 1), and 3) "Warm exhaustive" (initial Tm = 34 degrees C). In five subjects the concentration of various muscle metabolites was determined before and immediately, 1 min, and 5 min after exercise. Blood lactate concentration was determined before and repeatedly after exercise. At low Tm maximal work time was considerably shorter for all subjects compared to normal Tm, 1.3 and 2.1 min, respectively. Comparing conditions 1) and 2) oxygen deficit and the decrease in ATP and CP content were the same in the two experiments. There was a significantly higher concentration of glucose-6-phosphate 17.6 +/- 10.1 and 8.0 +/- 6.2 mmol X kg dw-1, respectively, and a tendency to higher lactate concentration 60 +/- 36 and 33 +/- 14 mmol X kg dw-1, respectively, immediately after exercise in the "cold exhaustive exercise". Peak blood lactate concentration appeared significantly later after "cold exhaustive" exercise indicating a slower elimination rate of lactate from the muscle compared to "warm non-exhaustive" exercise. The reduction in performance observed at low Tm may partially be explained by an increased accumulation rate of lactate in four of five subjects.

Further studies on renal nerve stimulation induced release of noradrenaline and dopamine from the canine kidney in situ.

Abstract: The renal venous outflow of dopamine and noradrenaline were studied in the canine kidney in situ in connection with renal nerve stimulation (RNS). RNS (0.5-4 Hz) caused frequency-dependent increases in the outflow of both catecholamines, which could be detected already at 0.5 Hz. The ratio dopamine/noradrenaline in renal venous plasma (approximately 0.15) was not influenced by varying the RNS parameters but was significantly enhanced (to about 0.25) by pretreatment with guanethidine according to a procedure previously used to demonstrate renal dopaminergic vasodilatation. The unstimulated kidney removed conjugated dopamine (which represents 98–99% of the total dopamine in plasma). During RNS the conjugated dopamine outflow to renal venous blood increased, but measurements of conjugated dopamine were less reliable than measurements of free dopamine to assess dopamine release from the kidney. When studying the renal nerve contributions to the renal venous outflow of dopamine and noradrenaline more accurate estimates may be obtained by correcting for the removal of catecholamines delivered to the kidney in arterial plasma. Such corrections were performed with endogenous adrenaline or radiolabelled noradrenaline. The two methods of correction yielded similar results and showed that RNS reduced catecholamine extraction in the kidney. The high ratio of dopamine/noradrenaline in kidney tissue (with a preferential distribution of dopamine to the cortex) and the dopamine outflow to renal venous plasma during RNS support the existence of specific dopaminergic nerves in the dog kidney.

Inter-laboratory comparison of plasma catecholamine determinations using several different assays

Abstract: Thirty-four laboratories performed altogether 41 plasma catecholamine assays on each of four samples. Various radioenzymatic assays, high performance liquid chromatographic (HPLC) assays with electrochemical detection and fluorimetric assays were used. There was reasonable agreement that the levels of adrenaline and noradrenaline in a basal plasma pool were about 0.2 and 1.8 nM, respectively. The levels in a pool of plasma obtained after exercise were about 0.7 and 11 nM, respectively. The study, however, revealed a sometimes considerable variability between methods as well as between laboratories using the same method. Results from duplicate determinations of noradrenaline suggest frequent problems with intra-laboratory reproducibility. Results concerning the recoveries of 0.7 or 3.0 nM adrenaline or 2.0 nM noradrenaline (added to the basal plasma pool) showed a rather frequent need for improved precision. Fluorimetric assays gave unacceptable results. Plasma free dopamine measurements showed a basal level of 0.1-0.2 nM with most HPLC assays and a tendency towards higher levels and greater scatter with radioenzymatic methods. On the whole, reverse phase HPLC methods and an inhomogeneous group of single-isotope derivative radioenzymatic assays showed the largest variability. Less variability was found with the radioenzymatic assay of Peuler & Johnson (1977), provided that a few obviously erroneous results were excluded. The smallest variability was found with microparticulate cation exchange HPLC. It is concluded that plasma catecholamine assays would benefit from better standardization and a continuous quality control. Problems associated with validation of new assays, as well as modifications of old assays are discussed.

Relationship between arterial and venous adenosine levels and vasodilatation during ATP- and adenosine-infusion in dogs.

Abstract: The hemodynamic effects of ATP and adenosine (i.v. infusions) were studied in dogs in parallel with quantitative determination of purines in plasma by HPLC. In two experiments, infusion were performed during treatment with dipyridamole, an uptake inhibitor of adenosine. A 50-60% reduction of mean arterial blood pressure (MABP) was induced by both ATP and adenosine at infusion rates ranging between 17-290 mumoles/min. Cardiac output was unaffected by the purine infusions, indicating that the reduction of MABP was caused by a reduction of the systemic vascular resistance. Elevated ATP and adenosine concentrations were seen in venous plasma (pulmonary artery) during infusion, while only approximately 10% recovered ATP had been degraded to adenosine. On the other hand, in arterial plasma, virtually all nucleotides had been eliminated whereas the adenosine concentrations in plasma ranged between 5 and 20 microM. The magnitude of the vasodilatation was strictly related to the arterial plasma adenosine level irrespective of whether ATP or adenosine was infused. Thus, adenosine probably mediates the vasodilatory effect of ATP.

Cardiovascular responses to face immersion and apnea during steady state muscle exercise. A heart catheterization study on humans.

Abstract: The cardiovascular adjustments to face immersion and apnea (FIA) in human beings during steady-state muscle exercise (163 and 98 watt) have been investigated. Using a triple lumen flow directed catheter inserted into the pulmonary artery we were able to measure cardiac output (CO) by thermodilution technique, pulmonary arterial pressure (PPA) right atrial pressure (PRA) and left ventricular filling pressure (PAD). Phasic arterial blood pressure (BP) was measured via a cannula in the radial artery. A 12 lead ECG was recorded continuously. FIA caused an immediate rise in BP (median 61 %), the highest level being 25.33 kPa. CO during the last half of FIA was reduced by 49% (range 46–59, n=7) systemic vascular resistance increased by median 200% (range 111–280). Myocardial oxygen demand determined by the heart rate pressure double product fell from median 33.6 to 16.8 (163 W) and 28.5 to 19.1 (98 W) given as beats/min · kPa ·4 102. Mean reduction was by 42%. PPA and PRA immediately increased and remained constant until a further pronounced increase was seen towards the end of FIA when pulmonary vascular resistance (PVR) went up. PACO2 and PAO2 at the end of 30 sec FIA (163 W) was 10.0 and 5.6 kPa, respectively, values which expectedly would cause pulmonary vasoconstriction. Our findings demonstrate that humans are able to make principally the same cardiovascular adjustments to diving as aquatic mammals, although the response patterns are slower and less efficient. The marked increase in systemic arterial blood pressure which we observed is in contrast to that in e.g. diving seals. In humans the rises in SVR and PVR is not so closely adjusted to the reduction in CO. This will reduce the oxygensaving potential by causing a rise in cardiac afterloads.

Effects of methoxamine, an alpha-1 adrenoceptor agonist, and prazosin, an alpha-1 antagonist, on the stages of the sleep—waking cycle in the cat

Abstract: In these experiments the effects of alpha 1-adrenoceptor agonism and antagonism were studied on the stages of the sleep-waking cycle of the cat, in order to determine optimal levels of alpha 1-adrenergic transmission for these stages. Polygraphic 16-h recordings showed that prazosin, an alpha 1-adrenoceptor antagonist, at 1 mg/kg i.p., increased paradoxical sleep (PS) time from 15.3% to 26.4% (p less than 0.001) of total time, and the number of PS episodes from 30.4 to 43.6 (p less than 0.001). The effect was prompt, reaching a maximum during the first 4 h with a shortening of PS latency from 40.4 min to 11.0 min (p less than 0.001). Prazosin at doses of 0.5 and 3.0 though not at 10.0 mg/kg also slightly, but significantly, increased PS. Methoxamine, and alpha 1-adrenoceptor agonist, at doses of 0.5 and 3.0 mg/kg, increased aroused waking time (low voltage mixed frequency EEG) during the first 4 h from 23.5% to 33.3% (p less than 0.05) and to 50.3% (p less than 0.01), and decreased PS. Prazosin potentiated dose-dependently clonidine-induced drowsiness ( hypersynchronized 4-8 Hz EEG), whereas the decrease in deep slow wave sleep and PS were potentiated only at the largest dose of it. These results indicate that moderate inhibition of cerebral alpha 1-adrenergic transmission facilitates paradoxical sleep in the cat. Furthermore, they suggest that the level of cerebral alpha 1-adrenergic transmission is high during aroused waking and low during drowsy waking.

Spontaneous running in wheels. A microprocessor assisted method for measuring physiological parameters during exercise in rodents.

Abstract: When examining physiological parameters during exercise in rodents most techniques use forced exercise on treadmills or forced swimming which undoubtedly will employ stress to the animals. This paper describes a convenient method to measure physiological parameters during spontaneous exercise in rodents. Hamsters and rats develop a spontaneous running pattern in wheels. The hamsters are reaching maximal activity almost immediately. In contrast, rats increase their running activity with time and need about 4 weeks to reach an average of about 7 km/day. The amount of running is measured by a microprocessor system. With this technique pain threshold, blood pressure and heart rate for example could be measured for extended periods of time, without changing the environment of the animals.

Age‐ and pressure‐dependent changes of systemic resistance vessels concerning the relationships between geometric design, wall distensibility, vascular reactivity and smooth muscle sensitivity

Abstract: The resistance vascular function in normotension, and its alterations in primary hypertension and ordinary aging, was analysed concerning the interactions between (1) geometric vascular design, (2) wall distensibility, (3) transmural pressure and (4) smooth muscle activity. Paired hindquarter perfusions were used, comparing hemodynamic resistance characteristics in young, adult and old normotensive (WKY) and spontaneously hypertensive rats (SHR). From the experimental data pressure-resistance diagrams were constructed, which quantitatively interrelate the four factors in all SHR-WKY groups. The diagrams show, over a wide pressure range, how altered smooth muscle activity as well as structural adaptation affect resistance vessel distensibility: likewise how distensibility considerably interferes with “active” resistance adjustments. They also show how markedly the range of active resistance responses during ordinary constant-pressure perfusion is affected whenever pressure is reset to new levels. Finally, the diagrams illustrate the fundamental hemodynamic difference between hypertensive and normotensive resistance vessels, mainly because of factors 1 and 2, which render the hypertensive vessels stronger, stiffer and hyperreactive. Thereby they are capable of a widened response range despite the higher pressure level, which is further accentuated on acute pressure normalization. In contrast, ordinary aging alters resistance vascular behaviour only little, smooth muscle contractility and sensitivity remaining almost unchanged. However, vascular reactivity is moderately enhanced at lower pressures, presumably a geometric consequence of age-dependent, intimal-interstitial endowment.

Skeletal muscle sympathetic activity at rest in trained and untrained subjects.

Abstract: The effect of physical training on muscle sympathetic activity (MSA) was studied by comparing resting levels of MSA in 8 well-trained racing cyclists and in 8 age-matched untrained subjects (mean age 22 yrs). In addition, MSA was determined for 5 untrained subjects before and after an 8-week training program on cycle ergometers (training group). Recordings were made from the peroneal nerve at the knee with the subject in recumbent position. The well-trained cyclists were characterized by a clearly higher maximal oxygen uptake (VO2 max) and lower heart rate at submaximal exercise (180 W) than their untrained counterparts. These variables were also significantly changed with training in the training group. In contrast, there were no training-related effects on MSA. Thus, MSA expressed as either the number of sympathetic bursts/100 heart beats (+2%, NS) or bursts/min (-10%, NS) did not differ between the well-trained cyclists and the untrained controls. Furthermore, no changes in MSA occurred with training in the training group (bursts/100 heart beats: +8%, NS; bursts/min -2%, NS). Individual variations in MSA were large and independent of training state. It is concluded that differences in physical conditioning do not account for the large inter-individual differences in MSA in resting man.