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Biomedical subjects

S F Nilsson

Publications and source records attributed to S F Nilsson.

35 records · Page 2Linked to original sources
PubMed1987

Comparison of the vasodilatory effects of vasoactive intestinal polypeptide (VIP) and peptide-HI (PHI) in the rabbit and the cat.

In rabbits, intravenous infusion of increasing doses of peptide-HI (PHI), with direct measurement of the uveal blood flow from a cannulated vortex vein, caused a dose-dependent decrease in the uveal vascular resistance. The maximal effect, a 50% decrease, was achieved with about 60 pmol kg-1 min-1. This is similar to what has previously been reported for vasoactive intestinal polypeptide (VIP). Determination of local blood flows, with radioactive microspheres, showed that i.v. infusion of VIP or PHI (60 pmol kg-1 min-1) caused about the same increase in the choroidal blood flow, while the local blood flow in the anterior uvea was unaffected by both peptides. The most marked effect of VIP was observed in glandular tissues, such as the pancreas, submandibular, parotid and thyroid glands. The pancreas was the only one of these tissues in which PHI caused an increased blood flow. In cats, i.v. infusion of VIP (30 pmol kg-1 min-1) during 5-7 min caused a markedly increased blood flow in several tissues. The vasodilation in glandular tissues was even more marked than in rabbits; 3-15 times the normal compared with two to five times the normal in rabbits. The choroidal blood flow was however significantly decreased and the local flow in the anterior uvea tended also to be reduced. Intravenous infusion of either a higher dose of VIP (60 pmol kg-1 min-1) or of PHI (1800 pmol kg-1 min-1) during 2 min had no effect on the uveal vascular resistance. This dose of PHI had only minor effects on local blood flows in other tissues. The results of the present study indicate that porcine VIP is a more potent vasodilator than porcine PHI in most tissues of both the cat and the rabbit, but that there may be exceptions such as the rabbit uvea. The difference in potency may also vary considerably between the species.

Animals↗
PubMed1986

Effects of vasoactive intestinal polypeptide (VIP) on intraocular pressure, facility of outflow and formation of aqueous humor in the monkey.

Stimulation of the facial nerve causes a non-cholinergic vasodilation in the uvea and a rise in the intraocular pressure in rabbits, cats and monkeys. Vasoactive intestinal polypeptide (VIP) has been suggested as the neurotransmitter mediating these effects. In the present investigation, the effects of VIP on aqueous humor dynamics were studied in cynomolgus monkeys. After intracameral injection of 1 microgram VIP, the outflow facility was higher in the experimental eye than in the control; 0.42 +/- 0.46 compared with 0.33 +/- 0.03 microliter cm H20-1 min-1, difference 0.09 +/- 0.04 microliter cm H2O-1 min-1. Intravenous infusion of VIP, 160 ng min-1, increased aqueous humor flow from 1.12 +/- 0.07 to 1.65 +/- 0.09 microliter min-1. Almost the same effect, a 50% increase in aqueous humor flow, was found after intracameral administration of 90 micrograms VIP. This dose of VIP caused a significant increase in intraocular pressure (IOP) in the experimental eye. The maximal difference in IOP between the experimental eye and the control eye was 7.5 +/- 0.4 cm H2O. A lower dose of VIP, 30 micrograms intracamerally, increased aqueous humor flow by about 20%, but had no consistent effect on IOP. The effect of VIP on aqueous humor flow was not affected by pretreatment with indomethacin. The results suggest that most of the rise in IOP caused by intracameral VIP administration is due to a rise in the pressure in the veins into which the aqueous humor is drained. Enhanced formation of aqueous humor plays a smaller role. The effects of VIP on aqueous humor formation and outflow facility suggest that the facial nerve may be involved in nervous control of aqueous humor dynamics, as VIP is most probably released in the eye by stimulation of the facial nerve.

Animals↗
PubMed1985

Characteristics of uveal vasodilation produced by facial nerve stimulation in monkeys, cats and rabbits.

The effect of electrical stimulation of the facial nerve on ocular blood flow and intraocular pressure (IOP) was studied in monkeys, cats and rabbits. Ocular blood flow was determined with radioactive microspheres or by direct measurement of uveal blood flow from a cannulated vortex vein in rabbits. Frequency-response relationships were determined in monkeys (intraocular pressure) and rabbits (uveal blood flow). Stimulation of the facial nerve produced a marked increase (greater than 100%) in choroidal blood flow in all three species. The effect in the anterior uvea appeared the same, but less pronounced. Retinal blood flow was not affected by the stimulation in any of the species. In cats, local blood flow in the optic nerve was significantly increased by the stimulation. As there was no significant change in mean arterial blood pressure, the increase in blood flow must have been due to decreased vascular resistance. The uveal vasodilation was resistant to muscarinic blockade in all three species, excluding acetylcholine as the principal peripheral transmitter. Stimulation of the facial nerve also caused a moderate increase in IOP (range 1-11 cmH2O), only investigated in monkeys. This increase in IOP seems to be secondary to the intraocular vasodilation. The maximal increase in intraocular pressure, in monkeys, and vasodilation, in rabbits, was obtained at 15-20 Hz. At these frequencies, the vasodilation was always abolished by ganglionic blockade. In rabbits, stimulation at high frequencies (greater than 40 Hz) sometimes produced uveal vasodilation even after ganglionic blockade. This vasodilation was always less pronounced than before the ganglionic blockade and could be abolished by muscarinic blockade. The increase in uveal blood flow, in rabbits, was not affected by administration of indomethacin, indicating that prostaglandins are not critically involved in the vasodilation produced by facial nerve stimulation. The vasodilatory nerve fibers in the facial nerve are likely to be involved in regulation of choroidal blood flow to control the environmental temperature for the retina. The present study establishes the existence of efferent vasodilatory nerve fibers of facial nerve origin to the uvea. The peripheral transmitter causing the vasodilation is suggested to be vasoactive intestinal polypeptide (VIP).

Animals↗
PubMed1985

Control of ocular blood flow.

The eye has a dual vascular supply. The uveal vessels are distributed within the choroid, the ciliary body, and the iris; and the retinal vessels within the inner parts of the retina. The vascularization of the uvea is very rich and the blood flow is high, which stabilizes the temperature of the eye. The vascularization of the retina is relatively sparse, which is an obvious advantage for the optics. The perfusion pressure in the eye can be defined as the local arterial blood pressure minus the intraocular pressure. Reductions in perfusion pressure, caused by increments in intraocular pressure, or reductions in mean arterial pressure reduce the blood flow in the choroid. In the retina, there are efficient autoregulatory mechanisms that prevent changes in flow within a wide range of perfusion pressures. Stimulation of the cervical sympathetic chain causes vasoconstriction in the uvea, with near-maximal effects as 10 Hz. The sympathetic nerves are not activated during moderate hemorrhage. They apparently prevent overperfusion and breakdown of intraocular barriers under conditions of acute elevation of the arterial blood pressure. Electrical stimulation of the oculomotor nerve causes cholinergic vasoconstriction in the anterior uvea. Near-maximal vasoconstriction is obtained between 10 and 20 Hz. In conscious animals, muscarinic blockade causes vasodilatation in the iris, indicating that there is a basal traffic in the vasomotor fibers of the oculomotor nerve. Electrical stimulation of the facial nerve causes vasodilatation in the uvea that cannot be prevented by muscarinic blockade: near-maximal vasodilatation is obtained between 10 and 20 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

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

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 microgram) 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 X kg-1 X 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.

Animals↗
PubMed1980

Characterization of human lymphocyte surface receptors for mitogenic and non-mitogenic substances.

To compare the receptor patterns for mitogenic and non-mitogenic substances, surface glycoproteins of human lymphocytes were labelled with the lactoperioxidase-catalysed iodination technique and with a galactose oxidase-tritiated sodium borohydride technique. Labelled cells were detergent-solubilized, and the lysates were allowed to react with insolubilized purified mitogenic lectins, phytohaemagglutinin, leucoagglutinin and an insolubilized non-mitogenic lectin, oxidized leucoagglutinin. Lectin-reactive proteins were eluted with sodium dodecyl sulphate (SDS) buffer. Cell membrane components reactive with anti-lymphocyte globulin (ALG) were retrieved by indirect immunoprecipitation with protein-A-bearing staphylococcus Cowan I strain (SaCI). Lectin- and ALG-reactive proteins were analysed by SDS polyacrylamide gel electrophoresis. Iodinated glycoproteins regularly showed four major components with molecular weights of 120,000, 70,000, 60,000 and 43,000 daltons, respectively, on 7% gels. An additional broad peak in the molecular weight range 20,000--35,000 daltons was found on 10% gels. Tritiated glycoproteins also showed four major components with MW 120,000, 70,000, 60,000 AND 42,000, RESPECTIVely, which reacted with lectin and ALG. In addition, ALG reacted with some glycoproteins with MW between 150,000 and 230,000 daltons. On 10% gels additional lectin- and ALG-binding glycoproteins with MW around 30,000 daltons were found. The similarity in structures bound by mitogenic and non-mitogenic substances indicates that lymphocyte activation may depend on some property conferred by the mitogen.

Antilymphocyte Serum↗
PubMed1980

The retinol-binding protein.

Vitamin A is transported from its storage site in the liver to the epithelial tissues by a carrier protein, the Retinol-binding protein (RBP). In plasma RBP forms a complex with thyroxine-binding prealbumin. The present article reviews available data on the RBP system. The complete primary structure of RBP has been determined. The plasma concentration of RBP is regulated by the vitamin A status so that in vitamin A deficiency RBP molecules are not secreted from the liver. RBP molecules interact with a cell membrane receptor, probably a protein component present on epithelial cells. Vitamin A is thereby delivered to the cells. The uptake of vitamin A by the cells causes a reduction of the affinity of RBP for prealbumin. The RBP molecules which no longer are able to interact efficiently with prealbumin are excreted through the kidney glomerulus and degraded.

Amino Acid Sequence↗
PubMed1979

Concanvalin-A-binding proteins on the surface of human malignant and normal lymphocytes.

The concanavalin-A-binding cell surface glycoproteins from normal and certain leukaemic human lymphocytes were radiolabelled and then solubilized with detergent, isolated by affinity chromatography on Con A insolubilized on agarose beads, and subsequently analysed by SDS-polyacrylamide gel electrophoresis. Leukaemic T cells from patients with Sezary syndrome were found to express major concanavalin-A-binding glycoproteins on their outer surface similar to those of normal T lymphocytes. Leukaemic B cells from patients with chronic lymphocytic leukaemia expressed Con-A-binding proteins similar to those of B-cell lines. HLA antigens were predominant among the major Con-A-binding proteins on the surface of the normal and the malignant T cells studied. Human Ia-like antigens, HLA antigens, and the cell surface immunoglobulins IgD and IgM represented the major Con-A-binding proteins on the B cells studied. beta 2-microglobulin was found associated with HLA antigens on both leukaemic and non-leukaemic T and B cells. The presence of additional Con-A-binding proteins expressed on the surface of the different cell types studied is discussed along with some physical characteristics of the human Ia-like antigens isolated.

B-Lymphocytes↗
PubMed1976

Isolation and identification of the major concanavalin A binding glycoproteins from murine-lymphocytes.

The major glycoproteins which bind concanavalin A have been isolated and identified from murine spleen cells, thymocytes,and purified thymus-derived (T) lymphocytes, and from the spleen cells of congenitally athymic (nude) mice. The cells were radiolabeled by lactoperoxidase catalyzed 125I iodination or by culturing the cells in media containing [3H]leucine or [3H]fucose. The cell membrane was solubilized with Nonidet P-40 and the concanavalin A binding proteins were isolated by affinity chromatography and analyzed according to their mobility on polyacrylamide gel electrophoresis in sodium dodecyl sulfate. The major proteins from various lymphocyte preparations were identified by immunoprecipitation with specific antisera. The molecules coded by the histocompatibility-2 complex acted as concanavalin A binding proteins H-2K and H-2D were isolated from T lymphocytes, thymocytes, and bone marrow derived (B) lymphocytes. The Ia antigens were identified from B lymphocytes and tentatively identified from T lymphocytes. In addition to these H-2 complex proteins, immunoglobulin M and D on B lymphocytes also bound concanavalin A binding. All these glycoproteins have previously been identified as cell surface molecules. The presence of certain minor unidentified concanavalin A binding proteins on lymphoid cells is indicated.

Animals↗
PubMed1975

Studies on thyroid hormone-binding proteins. I. The subunit structure of human thyroxine-binding globulin and its interaction with ligands.

Thyroxine-binding globulin was isolated from human plasma by ammonium sulfate fractionation, chromatographic separations on diethylaminoethyl-Sephadex, gel chromatography, and two different electrophoretic procedures. The highly purified was homogeneous when subjected to polyacrylamide gel electrophoresis, ultracentrifugation analyses, and immunochemical determinations. The weight average molecular weight as determined by sedimentation equilibrium ultracentrifugations was 54,000 and by sedimentation diffusion data 55,000. Amino acid analyses indicated a minimum of 110 amino acid residues per molecule. By determination of the minimum in the curve for the fraction of maximum deviation from the amino acid analyses it was found that the minimum molecular weight for the polypeptide was 12,200. Carbohydrate analyses demonstrated the presence f equimolar amounts of amnnose, galactose, and glucosamine, and the carbohydrate portion constituted 7.5% of the total weight. The amino acid analyses suggested that thyroxine-binding globulin is composed of 4 subunits. Molecular weight determinations by gel chromatography in 6 M guanidine hydrochloride indicated the presence of three species of globulin with apparent molecular weights 52,000, 25,000, and 13,500, respectively. Prolonged storage in guanidine hydrochloride promoted a more than 60% yield of the monomeric species. Moreover, a half-molecule of thyroxine-binding globulin was isolated and shown to consist of two polypeptide chains of similar molecular weight...

Amino Acids↗
PubMed1975

Studies on thyroid hormone-binding proteins. II. Binding of thyroid hormones, retinol-binding protein, and fluorescent probes to prealbumin and effects of thyroxine on prealbumin subunit self association.

Vitamin A in human plasma is transported by its specific carrier protein, the retinol-binding protein. Under physiological conditions the protein forms a stable protein-protein complex with the tetrameric plasma protein, the thyroxine-binding prealbumin. Human prealbumin was shown to interact with the fluorescent probes 1,8-anilinonaphthalene sulfonate (ANS) and 2-p-toluidinylnaphthalene-6-sulfonate (TNS). ANS bound to the protein at two independent sites with the apparent association constant 3 X 10(5) M-1, whereas TNS interacted with a single site with the binding constant 5 X 10(k) M-1. The fluorescent yield of protein-bound ANS was 0.95, a more than 200-fold enhancement compared with that of ANS in aqueous solutions. TNS enhanced its quantum yield nearly 500-fold to 0.37. On addition of thyroid hormones the fluorescent probes could be quantitatively displaced from the protein. This finding suggested that triiodthyronine, thyroxine, and the probes bound to a common site in prealbumin, which is likely to have a strongly hydrophobic character. The association constants for the interaction between prealbumin and the thyroid hormones could be calculated by using the hormones as competitive inhibitors in the TNS-prealbumin titrations. The data from the competition experiments together with those obtained from equilibrium dialysis revealed one major hormone binding site on the protein. The calculated association constant were 9 X 10(6) M-1 and 1 X 10(8) M-1 for triiodothyronine and thyroxine, respectively. Prealbumin monomers were bound to Sepharose by covalent attachment, and their properties were examined. Evidence was obtained demonstrating that the retinol-binding protein could interact with a single subunit of prealbumin. The estimated apparent association constant for the interaction of the protein and the matrix-bound monomeric prealbumin was 3 X 10(4) M-1, approximately 250-fold lower than that measured for protein and matrix-bound tetrameric prealbumin. The data, however, strongly suggest that there are four retinol-binding protein sites per prealbumin molecule. Using the technique of sedimentation equilibrium ultracentrifugation the prealbumin subunit self-association has been studied. The energy of the interaction for the prealbumin subunits is very high, and various concentrations of guanidine hydrochloride has to be used to perturb the equilibrium. All experiments indicated that prealbumin dissociates directly into monomers without the presence of intermediate forms. Thyroxine perturbed the chemical equilibrium of the prealbumin monomer-tetramer system by strengthening the interaction between the subunits.

Anilino Naphthalenesulfonates↗