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Biomedical subjects

B Bengtsson

Publications and source records attributed to B Bengtsson.

At least 145 records · Page 8Linked to original sources
PubMed1979

Effects of nifedipine of pial arteriolar calibre: an in vivo study.

In cats the response of individual pial arterioles to perivascular microapplication of the Ca++-antagonistic drug nifedipine was studied using the image-splitting technique developed by Baez. It has previously been shown that the coefficient of variation for repeated measurements of pial vessel diameter using this system is 1%, under conditions of steady arterial pressure and blood gas tensions. All investigated pial arterioles invariably responded with a dilatation at an injected nifedipine concentration of 10 microM. The dilatatory response was inversely proportional to the resting vessel calibre, i.e., arterioles less tham 70 microns responded with a significantly stronger dilatation as compared with arterioles greater than 100 microns in diameter. In experiments where a minor subarachnoid hemorrhage was made by the injection micropipette injuring capillaries just before the perivascular microapplication of nifedipine, a dilatatory response invariably ensued in spite of the perivascular blood which in itself constricted the arterioles under examination.

Animals↗
PubMed1978

Effects of verapamil and nitroglycerin on contractile responses to potassium and noradrenaline in isolated human peripheral veins.

Isolated ring preparations of human vein were contracted by potassium (127 mM) and noradrenaline (1.8 X 10(-5) M). The potassium-induced contracture developed more rapidly and had a higher maximum amplitude than that produced by noradrenaline. Addition of phentolamine (10(-5) M) reduced the amplitude of the potassium contracture by 22% and abolished the noradrenaline response. Verapamil and nitroglycerin relaxed preparations contracted by potassium and noradrenaline, and, when added prior to stimulation, reduced the contractile responses to these agents. Both verapamil and nitroglycerin inhibited the contractile effect of noradrenaline more strongly than that of potassium. After immersion of the preparations for 30 min. in a calcium-free medium, the responses to potassium and noradrenaline were reduced to 21.3 +/- 2.5% and 7.1 +/- 0.8%, respectively, of the control. Addition of verapamil caused a further reduction of the response to potassium, but not of that to noradrenaline. Nitroglycerin caused a further reduction of the contractions induced by both agents. When the calcium concentration in the extracellular medium was increased from 0 to 4 mM, the contractile responses to potassium and noradrenaline returned to the control level. Both verapmil and nitroglycerin inhibited the contractile responses to calcium; the inhibiting effects of verapamil were significantly more marked than those of nitroglycerin. Tachyphylaxis to nitroglycerin was demonstrated on contractions induced by potassium, but not on noradrenaline-produced responses.

Adult↗
PubMed1978

Estrogen and the relaxant effect of intramural noradrenaline on calcium induced contractures in depolarized rat uterus.

The influence of intramural noradrenaline on calcium induced contractures was studied in isolated preparations of rat uterus. The depolarized (127 mM KCl) myometrium of oophorectomized rats responded with contraction followed by a transient relaxation when exposed to 3 mM calcium. The threshold concentration of calcium, where the transient relaxation began to appear, was between 0.25 and 0.5 mM. Blockade of the beta-adrenoceptors with propranolol or noradrenaline depletion with reserpine completely removed the transient relaxation, indicating that the latter was due to release of intramural noradrenaline. Estrogen treatment abolished the relaxant effect of intramural noradrenaline, whereas progesterone was ineffective in this respect. Preparations from rats in natural estrus responded like estrogenized tissues, and diestrus preparations behaved as uteri of oophorectomized rats without estrogen treatment.

Animals↗
PubMed1978

Estrogen induced inhibition of 3H-noradrenaline release in the uterus and portal vein of the rat.

The influence of estrogen treatment on 3H-noradrenaline release, induced by potassium or calcium, was studied in isolated preparations of the uterus and the portal vein of the rat. Uterine strips of oophorectomized rats responded with contraction followed by transient relaxation when immersed in a medium containing 127 mM potassium. The transient relaxation was accompanied by an increased rate of 3H-noradrenaline efflux. When the uterine strips were bathed in calcium-free potassium solution, addition of calcium (3 mM) evoked an increased outflow of 3H-noradrenaline coinciding with a relaxation phase of the contractile response to calcium. After estrogen treatment of the rats the pattern of response was altered. The uterus then responded to potassium and calcium with sustained contractures and with a relatively small (potassium) or with no (calcium) increase of 3H-noradrenaline efflux. Normetanephrine (5 X 10(-5) M) did not influence the uptake or release of 3H-noradrenaline in either non-estrogenized or estrogen treated rats uterus. Calculations, based on the amounts of 3H-noradrenaline released by potassium and on the inhibitory effects of desipramine (10(-5) M) on neuronal uptake of noradrenaline, suggested that similar amounts of tracer were accumulated in the adrenergic nerves of both non-estrogenized treated preparations. Tyramine (10(-4) M) had a weaker stimulatory effect on 3H-noradrenaline release than potassium, and the tyramine induced release was not inhibited by estrogen treatment. Strips of the rat portal vein responded to potassium with an increased rate of 3H-noradrenaline efflux. As in the uterus, estrogen treatment reduced the release of 3H-noradrenaline in response to potassium. The adrenolytic effect of estrogen is possibly due to reduced entry of calcium ions into the nerve terminal.

Animals↗
PubMed1978

Effects of diethylstilboestrol and ovarian steroids on the contractile responses and calcium movements in rat uterine smooth muscle.

1. The synthetic oestrogen diethylstilboestrol had a potent inhibitory effect on the mechanical responses of the rat uterus. The spontaneous contractions were reduced in amplitude by 2 microgram and were completely abolished by 20 microgram diethylstilboestrol. The amplitude of contractions induced by acetylcholine (ACh) was also considerably reduced in the presence of 20 microgram of the compound. 2. Oestradiol (oestradiol-17 beta) had a weaker, and progesterone a negligible, effect on the spontaneous contractions. 3. In the depolarized (induced by high potassium) uterus, the log concentration response curve for contraction induced by Ca was sigmoidal and reached its maximum at about 1 mM-Ca. These responses to Ca were greatly depressed by oestradiol and progesterone and were again completely abolished by diethylstilboestrol. All three compounds were also able to induce a relatively rapid relaxation in preparations contracted by Ca. 4. Inhibition of the ACh contraction in the depolarized uterus by diethylstilboestrol, oestradiol and progesterone had the characteristic of blocking the second, and relatively slow, phase of the contraction without influencing the first rapid response. A similar pattern of inhibition was observed in the presence of D-600 or EGTA. 5. The lanthanum method gave only an approximate measure of cellular Ca in the rat uterus, since La failed to block 45Ca efflux and was unable effectively to displace extracellular 45Ca. 6. Diethylstilboestrol reduced the influx of 45Ca both in normal and depolarizing media but did not affect 45Ca efflux. 7. These results indicate that oestrogens and progesterone are able to decrease Ca entry into the uterine cells, which probably accounts for their inhibitory effect on the contractile activity. The mechanism by which these agents induce relaxation of a contracted uterus also seems to depend on the inhibition of Ca influx.

Acetylcholine↗
PubMed1977

The role of intramural noradrenaline in the potassium induced contracture of non-estrogenized smooth muscle.

The influence of intramural noradrenaline on potassium induced contractures was studied in isolated preparations of the uterus and the portal vein of the rat. Uterine strips of oophorectomized rats responded with contraction followed by transient relaxation when immersed in a medium containing 127 mM potassium chloride. Reserpinization or blockade of beta-adrenoceptors with propranolol greatly diminished the transient relaxation. In the isolated portal vein, both noradrenaline depletion with reserpine and alpha-adrenoceptor blockade (phentolamine) reduced the active tension produced in response to the isotonic potassium solution. These results suggest that intramural noradrenaline plays a significant role in the development of contractures evoked by potassium in the uterus and the portal vein of the rat. In the uterus, the released noradrenaline counteracts the development of active tension, whereas in the portal vein, noradrenaline has a contractile effect which is added to that of potassium. Estrogen treatment reduced (portal vein) or abolished (rat uterus) the contractile effects of intramural noradrenaline. The adrenolytic effect of estrogen is possibly due to reduction in the release of noradrenaline from the sympathetic nerve-endings.

Animals↗
PubMed1977

Some essential optical features of the Zeiss fundus camera.

The imaging system of the Zeiss fundus camera comprises a front lens and a mirror with a central opening in the anterior focus of a camera objective. Focusing is achieved by changing the distance between the film and the camera objective. The principal point of the examined eye is imaged in the central opening of the mirror when the camera is correctly positioned. By applying reasoning current in elementary geometrical optics it was found 1) that both the absolute and the relative magnification depend on the "reduzierte Axenlängenkonvergenz" only, 2) that it is possible to correct the influence of refraction on magnification and 3) that the relation between the camera extension needed to provide sharp pictures and the principal point refraction of the examined eye is linear. The validity and practical importance of those findings as well as transcleral illumination and theoretical resolving power are briefly discussed.

Fundus Oculi↗
PubMed1976

Resemblance between tonometer readings on relatives and spouses.

The resemblance between tonometer readings on relatives and spouses was studied in a material derived from a population survey and consisting of 1042 unique individuals forming 365 nuclear families and 1333 pairs divided into groups with different sex-composition and type of connection. Persons in whom glaucoma was suspected were excluded. The general level of resemblance in the present study was similar to that in previous studies. Differences between groups with different sex-composition conformed to a pattern expected from environmental effects. The resemblance between husbands and their wives was highly significant and of the same order of magnitude as that in relatives sharing a common genetic background. We concluded that a common environment contributes materially to the resemblance between tometer readings on relatives. The possibility of a cumulative environmental effect was suggested by an increase in resemblance with age.

Adolescent↗
PubMed1976

The variation and covariation of cup and disc diameters.

The variation and covariation of cup and disc diameters were studied in a material derived from a population survey and consisting of 2,334 fundus photographs from as many eyes in 1,322 subjects. A simple device was used to facilitate focusing of the camera. The colour slides were projected on to a screen at a fixed distance and measured on ruled paper. The effect of refraction on the magnification in the eye-camera system was compensated by the use of a simple correcting factor. Some apparently quite normal discs, nevertheless, had an area more than four times larger than that of other equally normal ones. The sizes of discs and cups covaried, however, to a suprisingly great extent (r = 0.8) and changes in disc diameter were in general parallelled by similar changes in cup diameter. The amount of tissue in the optic nerve head therefore varied somewhat less than the disc size. Cup diameters were widely dispersed, unevenly distributed and heavily dependent on disc size. The "average rim breadths", on the other hand, were much less dispersed, normally distributed and independent on the disc diameter. By taking the covariation of cup and disc diameters into account the detection of any enlargement or diminution of the optic cup ought to be facilitated.

Adolescent↗
PubMed1975

Expression and segregation of HL-A antigens in D98/AH-2 by lymphocyte and fibroblast hybrids.

Somatic cell hybrids between D98/AH-2 and fibroblasts or peripheral blood lymphocytes were analysed for the expression of HL-A antigens. The hybrids express the antigens of the donor lymphocytes or fibroblasts as well as other HL-A specificities from D98/AH-2, a HeLa derivative on which no HL-A could be detected by direct cytotoxicity. Segregant hybrid clones could be used to determine HL-A haplotypes and define the linkage relationships between these haplotypes and the PGM3 alleles expressed in the hybrids. An analysis of the HL-A antigens on D98/AH-2 and other HeLa derivates was done using absorption and a modified cytotoxicity assay.

Alleles↗