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Biomedical subjects

H Nilsson

Publications and source records attributed to H Nilsson.

At least 145 records · Page 8Linked to original sources
PubMed1984

Effects of low and high Na diets on cardiovascular dynamics in normotensive and hypertensive rats: neuroeffector characteristics of the resistance vessels.

The aim of the study reported was to explore differences in neuro-effector characteristics of the resistance vessels from normotensive and hypertensive rats (WKY and SHR), which from five to twelve weeks of age had been exposed to either low-sodium (0.5 mM/100 g food), control-sodium (5 mM/100 g) or high-sodium (50 mM/100 g) diet. Isolated small mesenteric arteries (diameter 150-200 microM) were mounted in a two-vessel Mulvany-Halpern myograph. Noradrenaline sensitivity was similar in all arteries. Frequency-response curves of SHR arteries were steeper than in WKY. In both strains low-sodium curves were displaced to higher frequencies with little difference between control and high-sodium curves. Inhibition of the Na-K-ATPase with ouabain enhanced neurogenic responses more than noradrenaline responses, but to similar extents in all sodium groups. The results suggest that chronic low-sodium diet substantially reduces the total adrenergic transmitter release per impulse.

Animals↗
PubMed1984

Boston thoracic brace in the treatment of idiopathic scoliosis. Initial correction.

The Boston thoracic brace, i.e., a Boston brace with axillary support, was used to treat thoracic scoliosis in 44 patients. The mean initial correction for curves with the apex at T8-T9 was 15.9 degrees +/- 6.1 degrees (54%). This was a great and significant improvement over results obtained with both the Boston brace and the Boston Milwaukee brace. This degree of correction confirms earlier observations that the increased efficiency of the brace outweighs the disadvantages of the axillary component and encourages further efforts in the direction of nonsurgical treatment of the early stages of scoliosis.

Adolescent↗
PubMed1983

Intestinal vascular responses to dopamine during fentanyl-nitrous oxide anaesthesia, supplemented with dixyrazin.

Intestinal haemodynamics in response to continuous i.v. administration of dopamine were investigated in cats anaesthetized with fentanyl-nitrous oxide either with or without supplement of dixyrazin. A dose-dependent vasodilatation was observed in the dopamine dose range 2.5-35 micrograms . kg-1 . min-1 and the subsequent maximal intestinal blood flow increase was 121%. No net intestinal vasoconstriction was evident even at the largest dopamine doses, although the vascular response reached a plateau at 17.5 micrograms . kg-1 . min-1. Control experiments during chloralose anaesthesia gave similar results. Changes in mean arterial pressure and heart rate were small. Renal blood flow was virtually unchanged at dopamine doses below 10 micrograms . kg-1 . min-1, while renal vasoconstriction was evident following dopamine doses above that level. The addition of i.v. dixyrazin (0.15-0.30 mg . kg-1) to the fentanyl-nitrous oxide anaesthesia substantially potentiated the intestinal vasodilator response to i.v. dopamine and the maximal blood flow increase was 183% at 10-15 micrograms . kg-1 . min-1. In vitro experiments using mesenteric resistance vessels from the rat demonstrated a dose-dependent relaxation to dopamine. At very large doses this response was counteracted, but not reversed into vasoconstriction by dopamine-induced alpha-adrenergic stimulation.

Animals↗
PubMed1983

Effects of B-HT 920 and B-HT 933 on dopamine and noradrenaline autoreceptors in the rat brain.

B-HT 920 at low doses inhibited the accumulation of DOPA following treatment with reserpine and a DOPA decarboxylase inhibitor in the dopamine-, but not in the noradrenaline-predominant regions of the rat brain. B-HT 933 selectively inhibited this DOPA accumulation in the noradrenaline-predominant regions. These effects of B-HT 920 and B-HT 933 were completely antagonized by haloperidol and yohimbine, respectively. The rat motor activity was reduced by B-HT 920 and it was restored following apomorphine. B-HT 933 decreased the motor activity by a yohimbine-sensitive mechanism. The results indicate that B-HT 920 can selectively and potently stimulate the dopamine autoreceptors whereas B-HT 933 can selectively stimulate the noradrenaline autoreceptors.

Animals↗
PubMed1982

Are isolated femoral resistance vessels or tail arteries good models for the hindquarter vasculature of spontaneously hypertensive rats?

We have investigated the extent to which the properties of small arteries from the hindquarters of spontaneously hypertensive rats (SHRs) are consistent with the characteristics of perfused SHR hindquarter preparations (for which the relaxed vascular resistance, the reactivity and the sensitivity are reported to be increased). We have therefore compared the in vitro morphological and pharmacological properties of a femoral resistance vessel (i.d. ca 200 microns) and of the tail artery (i.d. ca 600 microns) from SHRs with those from control Wistar-Kyoto rats (WKYs). When relaxed, for any given wall tension, the internal circumference of the SHR resistance vessels was reduced, but that of the SHR tail artery was normal. When activated with 10 microM noradrenaline, the SHR resistance vessels had an increased calcium sensitivity, but the calcium sensitivity of the SHR tail arteries was normal. However, the maximum response of both types of SHR vessels was such that the vessels would have been able to contract against increased transmural pressure. The noradrenaline sensitivity of the SHR resistance vessels was normal but the SHR tail arteries had a decreased sensitivity. The results suggest that the femoral resistance vessel is in general a better model for the hindquarter vasculature than the tail artery.

Animals↗
PubMed1982

Role of membrane potential in the response of rat small mesenteric arteries to exogenous noradrenaline stimulation.

1. We have made simultaneous measurements of membrane potential and wall tension in rat 200 microns mesenteric arteries. 2. The resting membrane potential was -59.2 +/- 0.4 mV and stable (218 measurements, fifty-two vessels). 3. With maximal exogenous noradrenaline stimulation (10 microM) the membrane depolarized to about -34 mV. During the onset of tension development oscillations (period about 6 sec) in both tension and membrane potential were often seen; the membrane potential changes led the tension changes by about 1.2 sec. 4. In the presence of increased K+ (e.g. 40 mM), vessels had an increased noradrenaline sensitivity, and here noradrenaline stimulation produced little change in membrane potential. 5. With maximal K+ stimulation (85 mM), in the presence of phentolamine (1 microM), the membrane depolarized to about -17 mV, the tension being about 70% of the maximal noradrenaline response. 6. In the presence of phentolamine (1 microM), noradrenaline caused hyperpolarization without tension development. The hyperpolarization was inhibited by propranolol and mimicked by isoprenaline. 7. The results suggest that in these small vessels membrane potential variations are not essential to, but have an important modulating influence on, the tension response to exogenous noradrenaline.

Animals↗
PubMed1982

Potentiating and depressive effects of ouabain and potassium-free solutions on rat mesenteric resistance vessels.

We have investigated the in vitro effects of ouabain and K-free solutions on some pharmacological and electrophysiological properties of rat mesenteric resistance vessels (internal diameter approximately 190 micrometers). Vessels were mounted as ring preparations on a myograph capable of measuring their isometric wall tension. In normal saline solutions, vessels did not exhibit any tone and had a membrane potential of -54 mV. Both 1 mM ouabain and K-free solutions caused a transient depolarization of 5-8 mV; thereafter the membrane slowly depolarized to about -45 mV after 30 minutes. There was no mechanical response to ouabain, but K-free solutions caused a transient development of tension which could be inhibited by phentolamine (1 microM). In norepinephrine-activated vessels, exposure to ouabain or K-free solutions caused a small depolarization and an increase in tension. Long-term (30-minute) exposure to 1 mM ouabain or K-free solutions reduced the amplitude of norepinephrine responses and, for the lower (but not the higher) norepinephrine concentrations, the membranes were about 14 mV more depolarized than control. The mechanical responses to a cocktail of norepinephrine in a high potassium solution were, however, unaffected. Re-exposure to normal saline solution produced a transient hyperpolarization and transiently eliminated the norepinephrine response, but thereafter the membrane potential and response returned to normal. The results indicate that ouabain and K-free solutions can have both short-term potentiating and long-term depressive effects on the mechanical response of rat mesenteric resistance vessels to norepinephrine.

Animals↗
PubMed1982

Factors influencing the release of cyclic AMP from mouse thyroid tissue stimulated by TSH in vitro.

The accumulation of cyclic AMP (cAMP) in mouse thyroid tissue in response to TSH in the presence of 1 mM theophylline was accompanied by a release of the nucleotide from the tissue into the incubation medium. This cAMP release was almost rectilinearly related to the time of exposure to TSH, and rectilinearly related to the log concentration of TSH in the range 0.1-5 mU/ml. The cAMP release proved to be independent of the pre-incubation time up to 4 h, and took place also in the absence of methylxanthines when the cAMP level was low. The total cAMP accumulation in response to TSH was augmented by different inhibitors of protein synthesis but the fraction of the nucleotide that was retained intracellularly was increased only by puromycin. Dipyridamole had an effect similar to that of puromycin. Depolarization or treatment with ouabain did not change the distribution of cAMP between tissue and medium. It is concluded that the release of cAMP from thyroid tissue stimulated by TSH may take place under physiological conditions, that it seems to be regulated by the actual concentration of TSH, and that it may be of significance for the regulation of the intracellular cAMP level.

Animals↗
PubMed1981

Extent of structurally reduced venous distensibility in rats.

1. Venous pressure--volume relations were studied in maximally vasodilated whole-body preparations after cardiac arrest, as well as in fully vasodilated, perfused hindquarter preparations of spontaneously hypertensive rats (SHR) and normotensive controls. Central venous pressures were measured also in the anaesthetized animals before cardiac arrest. 2. Central venous pressure in intact, anaesthetized SHR was 1.9 +/- 0.20 mmHg compared with 0.75 +/- 0.25 in controls (P less than 0.001). 3. In both preparations SHR showed a nearly 20% reduction in venous compliance, whereas calculated 'unstressed' volumes (volumes at zero transmural pressure) were largely equal in SHR and controls. 4. SHR capacitance vessels thus appear to have a structurally reduced wall distensibility of about 10% with no change in overall size. It probably reflects a structural adaptation to a modest increase of average transmural pressure that also affects the low-pressure side.

Animals↗
PubMed1981

Portable emergency ventilators. Sensitivity to environment.

The function in various types of climate of three ventilators which are commercially available in Sweden: Motivus, Pneupac 2 and Logic 07, was tested as well as their sensitivity to vibration. The ventilators functioned in subzero temperatures only if the driving gas had a low humidity content. They also required an increased driving gas pressure. Only Logic 07 would function below -20 degrees C. In a hot climate there were no functional disturbances. Motivus and Pneupac 2 had few resonance frequencies during the vibration tests. Logic 07 had a very marked resonance frequency at 60 Hz, as well as in other ranges, which disturbed the ventilatory function since the vibration affected the ventilatory frequency regulator. All three ventilators functioned without any complaints after being subjected to vibration tests for at least 15 min at the observed resonance frequencies, or to shock tests. The results suggest that a through scrutiny should be carried out of the function of compact ventilators in various environments.

Climate↗
PubMed1981

Structurally reduced distensibility of cardiovascular low-pressure' compartments in primary hypertension, as studied in spontaneously hypertensive rats (SHR).

Adult male spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) were compared to explore to what extent venous "unstressed" volume, compliance and wall distensibility are structurally altered in primary hypertension. The perfused, maximally vasodilated hindquarters and the entire, completely relaxed cardiovascular system during cardiac arrest were used for comparisons of "initial" volumes and pressure volume characteristics of the respective low-pressure compartments. In both preparations SHR and WKY showed identical "unstressed" venous volumes, computed by extrapolation to zero pressure from initial volumes and the nearly linear pressure-volume relationships, while venous compliance (delta V/delta P) was in each case about 20% reduced iun SHR. Consequently, the structurally determined wall distensibility of the low-pressure compartment, calculated as the square root of volume compliance/unstressed (or initial) volume, was significantly reduced in SHR; about 10%. Such venous "structural resetting" has important hemodynamic consequences, not least because it reinforces increase of venous return and cardiac filling pressure in SHR, caused by given sympathetic activations. Evidently, not only resistance, cardiac and barostat functions but also the venous capacitance function are structurally reset early in primary hypertension, implying a redesign of the entire cardiovascular system to operate at a higher pressure equilibrium.

Animals↗
PubMed1981

Enzyme thermistor analysis of penicillin in standard solutions and in fermentation broth.

Immobilized penicillinase was applied in an enzyme thermistor for calorimetric analysis of samples containing penicillin G. Standard solutions as well as extracts from fermentation broth were analyzed. The enzyme was applied bound either to porous glass or, when dealing with crude preparations, to the inner surface of nylon tubing. In the fermentation system studied, high concentrations of penicillin were present, thus allowing dilution to reduce the influence of the composition of the medium on the analysis. The useful linear concentration range was from 0.1 to 100 mM. The coefficient of correlation between analytical results obtained with the present method and those from conventional assays was 0.997.

Journal Article↗
PubMed1981

Effect of inhibition of protein synthesis on thyroid cyclic AMP accumulation in vitro.

When thyroid cells in vitro are stimulated by TSH for 2 h cyclic AMP (cAMP) is synthesized at a high rate during the first 25 min of stimulation, thereafter at a lower rate. The mechanism for this reduction of adenyl cyclase activity was studied in vitro using mouse thyroid tissue. As some of the cAMP formed is released from the cells the sum of cAMP in tissue and incubation medium was studied and considered to reflect the accumulated cAMP synthesis as breakdown synthesis as breakdown by phosphodiesterase was minimized by 1 mM theophylline. The TSH stimulated tissue did not release any adenyl cyclase inhibiting factor into the incubation medium. Cycloheximide, 5 micrograms/ml, enhanced the cAMP response to a single or repeated stimulation by TSH. Its effect was visible after 25 min of incubation and remained at about the same size for 2 h, but the levelling off of cAMP synthesis was not prevented but took place at a higher level. The effect of puromycin, 500 microgram/ml, was similar to that of cycloheximide. Also actinomycin D, 1 microgram/ml, enhanced the cAMP response to TSH. It is concluded that a protein synthesis dependent inhibitor of adenyl cyclase is activated by TSH, but it accounts only for a minor part of the adenyl cyclase inhibition that takes place in the later part of a TSH stimulation of the thyroid. Additional adenyl cyclase inhibiting mechanisms must be considered.

Animals↗
PubMed1980

Effect of sodium-potassium-dependent ATPase inhibition on noradrenaline-activated calcium sensitivity of mesenteric resistance vessels in adult spontaneously hypertensive rats.

1. We have investigated the noradrenaline-activated calcium sensitivity of 150 micrometer mesenteric resistance blood vessels from spontaneously hypertensive and control Wistar-Kyoto rats. 2. Under control conditions the spontaneously hypertensive rat blood vessels had a greater calcium sensitivity than the Wistar-Kyoto rat vessels. 3. In the presence of 1 mmol of ouabain/l, a treatment known to inhibit the sodium-potassium-dependent ATPase, the responses of the spontaneously hypertensive rat blood vessels were reduced more than those of the Wistar-Kyoto rat blood vessels, so that the responses of spontaneously hypertensive rat and Wistar-Kyoto rat blood vessels were then similar. 4. Similar results were obtained by removing external potassium, a procedure which should also inhibit the sodium-potassium-ATPase. 5. The results suggest that the greater noradrenaline-activated calcium sensitivity of spontaneously hypertensive rat blood vessels may be associated with an increased sodium-potassium-ATPase activity.

Animals↗