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Biomedical subjects

J Petersen

Publications and source records attributed to J Petersen.

At least 217 records · Page 12Linked to original sources
PubMed1987

Occlusion of 22Na+ and 86Rb+ in membrane-bound and soluble protomeric alpha beta-units of Na,K-ATPase.

In this work, we examined occlusion of 22Na+ and 86Rb+ in membranous and detergent-solubilized Na,K-ATPase from outer renal medulla. Optimum conditions for occlusion of 22Na+ were provided by formation of the phosphorylated complex from the beta,gamma-bidentate complex of chromium (III) with ATP (CrATP). Release of occluded cations occurred at equally slow rates in soluble and membrane-bound Na,K-ATPase. Values of 22Na+ occlusion as high as 11 nmol/mg of protein were measured, corresponding to 1.8-2.7 mol of Na+/mol of phosphorylated Na,K-ATPase as determined by 32P incorporation from [gamma-32P]CrATP. Maximum capacity for phosphorylation from [gamma-32P]CrATP was 6 nmol/mg of protein and equal to capacities for binding of [48V]vanadate and [3H]ouabain. The stoichiometry for occlusion of Rb+ was close to 2 Rb+ ions/phosphorylation site. In an analytical ultracentrifuge, the soluble Na+- or Rb+-occluded complexes showed sedimentation velocities (S20,w = 6.8-7.4) consistent with monomeric alpha beta-units. The data show that soluble monomeric alpha beta-units of Na,K-ATPase can occlude Rb+ or Na+ with the same stoichiometry as the membrane-bound enzyme. The structural basis for occlusion of cations in Na,K-ATPase is suggested to be the formation of a cavity inside a monomeric alpha beta-unit constituting the minimum protein unit required for active Na,K-transport.

Adenosine Triphosphate↗
PubMed1987

Purification of Ca2+-activated K+ channel protein on calmodulin affinity columns after detergent solubilization of luminal membranes from outer renal medulla.

A method is developed for purification of the protein of the Ca2+-activated K+ channel from outer renal medulla of pig kidney. The response of this K+ channel to physiological concentrations of Ca2+ is important for regulation of transtubular NaCl transport. In reconstituted vesicles direct addition of calmodulin doubles Ca2+ activation with sufficient affinity (K1/2 0.1 nM) for chromatographic purification of the protein. For purification luminal plasma membrane vesicles are isolated on metrizamide density gradients and solubilized in CHAPS. The fraction of soluble protein retained on calmodulin-Sepharose 4B columns in the presence of Ca2+ and eluted by EGTA is 0.7%. The purified protein has high Ca2+-activated K+ channel activity after reconstitution into phospholipid vesicles. It distributes on two bands of 51 and 36 kDa after gel electrophoresis in SDS. The 36 kDa band is rapidly cleaved by trypsin and may be involved in Ca2+ stimulation of the channel. Phosphorylation from cAMP-dependent protein kinase strongly stimulates Ca2+-activated K+ channel activity and labels the 51 kDa band suggesting that this protein is involved in regulation of K+ channel opening.

Animals↗
PubMed1987

The physical and surgical aspects of silicone oil in the vitreous cavity.

Silicone oil inside the vitreous cavity exerts forces on to the retina as a result of buoyancy, volume displacement, and surface tension. Surface tension rather than viscosity is the key to understanding why the oil seals retinal breaks effectively. The physics of the tamponade was studied quantitatively. Retinal traction can be counteracted by the oil up to a calculated threshold value, depending on the size and shape of the tear, the strength of the surface tension and, most importantly, the distance between the retina and choroid. For a nearly flat retinal hole, the tamponade is very effective. These theoretical results imply straightforward rules for surgery, rules that have been tested in 150 operations. An attempt must be made to fill 100% of the vitreous cavity. Since the air-water boundary has 3 times the surface tension of the water-oil boundary, the most effective procedure is to flatten the retina by means of a fluid-gas exchange and then clamp it in a flat position, implanting the silicone oil. Silicone in the subretinal space or the anterior chamber tends to retract spontaneously, for surface tension causes the smaller bubble to blow up the larger one. Surgical methods are described to make use of it.

Humans↗
PubMed1987

Inhibition of T cell-dependent antibody production by D-penicillamine. Different requirements for Cu2+ in suppression of polyclonal and antigen-specific B cell responses.

The effects of D-penicillamine (D-Pen) on the production of immunoglobulins (Ig) and anti-microbial antibodies (Ab) by human mononuclear cells (MNC) cultured in vitro were analysed by haemolytic plaque forming cell (PFC) assays. Polyclonal Ig and Ab production, induced by pokeweed mitogen (PWM), was not affected by D-Pen in pharmacologically relevant concentrations, unless Cu2+ was added. Likewise, D-Pen + Cu2+, but not D-Pen alone, affected polyclonal Ig production induced by Epstein-Barr virus. The production of interleukin-2 and B cell growth factor by phytohaemagglutinin-stimulated T cells was not inhibited by D-Pen; again D-Pen + Cu2+ markedly reduced the production of these cytokines. By contrast, D-Pen significantly reduced the antigen-induced antibody production without requirement of additional Cu2+. Addition of cytokine-containing supernatant to MNC treated with D-Pen + Cu2+ tended to increase the PWM-induced Ig responses, but had no effect on the antigen-induced Ab production of MNC cultured with D-Pen. Thus, the mechanisms by which D-Pen suppresses polyclonal and antigen-induced B lymphocyte responses are different.

Adult↗
PubMed1986

Pokeweed mitogen-induced secretion of IgG- and IgM-rheumatoid factors by synovial fluid and blood B lymphocytes in rheumatoid arthritis.

Lymphocytes from patients with rheumatoid arthritis (RA) were assayed for their ability to secrete Ig and rheumatoid factors (RF) upon polyclonal activation in vitro. B lymphocytes secreting IgM-RF and IgG-RF were enumerated using hemolytic plaque forming cell (PFC) assays. The sensitivity of RF-PFC formation was similar to that of a reverse PFC assay detecting all cells secreting Ig. Blood mononuclear cells from RA patients generated a median of 12 IgM-RF and 15 IgG-RF-secreting cells/10(6) after 6 days culture with pokeweed mitogen (PWM). Thus a median of approximately 0.5% of IgM- and IgG-secreting cells were identified as RF-PFC. Synovial fluid B lymphocytes co-cultured with autologous blood T lymphocytes in the presence of PWM generated higher numbers of RF-secreting cells; medians of 43 IgM-RF and 441 IgG-RF secreting cells/10(6) were found. Thus, 8-9% of IgM- and IgG-secreting cells from synovial fluid were identified as RF-PFC. In co-cultures containing synovial fluid T cells, PWM-induced RF secretion was low. The data indicate that both blood and SF B cells have the potential for RF secretion.

Antibody Formation↗
PubMed1986

[Fluorosilicone oil heavier than water: a new aid in vitreoretinal surgery].

The specific gravity of fluorosilicone oil (trifluoropropylmethyl siloxane) is greater than that of water, and because of this it opens up new possibilities in vitreoretinal surgery: In cases of PVR detachment, retinal defects at the inferior margin or the posterior pole can be reliably tamponaded. If there is a peripheral retinal hole, the retina is reattached solely by injection of the oil - drainage is unnecessary, since the subretinal fluid is forced back into the vitreous cavity through the retinal defect. Retinal folds resulting from a giant tear will flatten out of their own accord. The present paper communicates initial clinical experience with fluorosilicone oil in 21 eyes (trauma and PVR detachment cases, some of which were considered hopeless). Even though the cases selected for surgery were extreme, reattachment was accomplished intraoperatively in all but one of them. Redetachment occurred in 4 out of 10 eyes following removal of the oil; this was rectified with low-density silicone oil. An immediate side-effect of the new oil was a transient iritis, seen in 5 out of 21 cases. A suspected side-effect after longer-term observation (mean 19 weeks) was that the oil promoted PVR. Out of 4 histologically studied membranes which proliferated under the oil, phagocytosis and foreign body reaction to the oil were found in one of the specimens. No retinal damage due to the oil could be detected by electroretinography. As an intraoperative aid, fluorosilicone oil is thoroughly to be recommended. If a long-term tamponade is essential, the fluorosilicone oil should be replaced with low-density silicone oil (dimethylsiloxane) after a few weeks.

Adolescent↗
PubMed1986

Functional capacities of T lymphocyte subsets from synovial fluid and blood in rheumatoid arthritis.

A reverse haemolytic plaque forming cell (PFC) assay was employed to analyse the impact of T suppressor/cytotoxic and T helper cells on B cell function in 10 patients with rheumatoid arthritis (RA). In all cases T8-enriched cells from synovial fluid and blood suppressed the pokeweed mitogen (PWM) induced IgM, IgG, and IgA secretion by autologous lymphocytes to the same degree. The suppression was partly abolished by irradiation of T8-enriched cells. T4-enriched cells from blood increased the PWM induced Ig secretion by autologous blood B cells. In six of 10 patients responses 1.2 to four times higher were obtained with T4-enriched cells from synovial fluid, but in four of 10 patients synovial fluid T4-enriched cells did not increase the PWM responses of blood B cells. T4- and T8-enriched T cells from synovial fluid comprised more Ia+ cells than did T cells from blood (36% v 3% and 43% v 6%). Ia+ T helper and suppressor/cytotoxic cells may modulate in vivo activation of synovial B cells in RA.

Arthritis, Rheumatoid↗
PubMed1986

An epidemic of cirrhosis in Danish women revisited.

Between 1944 and 1947 the mortality statistics for the Danish population show an epidemic increase of liver diseases: subacute necrosis and cirrhosis. The epidemic only affected female mortality rates. Mortality due to cirrhosis remained at a higher rate for women than men until 1970 as a result of an excess mortality in the cohort of women who in 1945 were over the age of 45. Up to 1981 this group showed an excess of 4,000 fatalities. A reevaluation of medico-statistical data shows that the disease cannot be explained by the epidemic hepatitis occurring in 1942-1944 or by increased consumption of alcohol. Possible causes could be pharmaceutical products or additives, perhaps hormone preparations.

Adult↗
PubMed1986

Autoreactive lymphocytes in thyroid disorders. Quantitation of anti-thyroglobulin antibody formation by a specific haemolytic plaque forming cell (PFC) assay.

Blood mononuclear cells (MNC) from 21 patients with autoimmune thyroiditis were assayed for secretion of immunoglobulins in vitro by a reverse haemolytic plaque forming cell (PFC) assay. An antigen-specific assay was employed to quantify anti-thyroglobulin antibody (TgAb) secreting cells. The sensitivities of the two PFC assays were similar. The antigen specificity of the Tg-PFC assay was demonstrated by the ability of free Tg to inhibit PFC formation. The number of spontaneous TgAb-secreting cells was low (median 3 IgG-Tg-PFC/10(6), range 0-35/10(6)); TgAb activity was found in 3% (range 0-11%) of total IgG-PFC. The number of spontaneous IgG-TgAb-secreting cells correlated positively to TgAb titres in serum. MNC from most patients secreted IgG-TgAb upon polyclonal stimulation in vitro for six days with pokeweed mitogen (52 IgG-Tg-PFC/10(6), range 0-478/10(6)); TgAb activity was found among 2% (range 0-8%) of total IgG-PFC. Again, pokeweed mitogen-induced TgAb secretion correlated positively to TgAb titres in serum. Finally, MNC from most patients secreted TgAb after culture with Tg. The Tg-induced response was about 1/3 of the pokeweed mitogen-induced TgAb response. Tg did not increase the production of total IgG indicating that Tg is not a polyclonal stimulus. Few TgAb-secreting MNC were discovered in euthyroid sex and age-matched control patients.

Aged↗
PubMed1986

Autoreactive lymphocytes in thyroid disorders. II. Comparison of anti-thyroglobulin antibody production by plaque-forming cell, radio-immunological and enzyme-linked immunosorbent assays.

Blood mononuclear cells (MNC) from 9 randomly selected patients with autoimmune thyroiditis were stimulated in vitro with pokeweed mitogen (PWM), a polyclonal B lymphocyte activator. The secretion of immunoglobulins (Ig) and anti-thyroglobulin antibodies (TgAb) was assayed by means of haemolytic plaque-forming cell (PFC) assays, radio-immune assay (RIA) and enzyme-linked immunosorbent assays (ELISA). Total Ig and TgAb production was maximal using MNC cultured at 1.0 X 10(6)/ml as estimated by PFC, RIA and ELISA. The Ig and TgAb production as measured by RIA and ELISA was 1.5 - 3 times higher after 12 days' culture compared to 6 days' culture. Ig and TgAb production measured by PFC-assays at day 6 correlated positively to the results obtained by RIA and ELISA at day 12. PWM-induced TgAb secretion correlated positively to TgAb titres in serum. As judged by PFC, TgAb production was found in 8/9 patients; about 5% (range 0 - 7.9%) of the total PWM-stimulated IgG-secreting cells were involved in TgAb secretion. TgAb production as measured by ELISA and RIA was found in 6/9 patients. By reference to an affinity-purified human TgAb preparation, the TgAb secretion was about 0.7% (range 0 - 21.3%) of the total PWM-induced IgG secretion.

Antibody Formation↗
PubMed1985

Chymotryptic cleavage of alpha-subunit in E1-forms of renal (Na+ + K+)-ATPase: effects on enzymatic properties, ligand binding and cation exchange.

Chymotrypsin in NaCl medium at low ionic strength rapidly cleaves a bond in the N-terminal half of the alpha-subunit of pure membrane-bound (Na+ + K+)-ATPase from outer renal medulla. Secondary cleavage is very slow and the alpha-subunit can be converted almost quantitatively to a 78 kDa fragment. The sensitive bond is exposed to cleavage when the protein is stabilized in the E1 form by binding of Na+ or nucleotides. The bond is protected in medium containing KCl (E2K form), but it is exposed when ADP or ATP are added (E1KATP form). Fluorescence analysis and examination of ligand binding and enzymatic properties of the cleaved protein demonstrate that cleavage of the bond stabilizes the protein in the E1 form with sites for tight binding of nucleotides and cations exposed to the medium. About two 86Rb ions are bound per cleaved alpha-subunit with normal affinity (Kd = 9 microM). The bound Rb+ is not displaced by ATP or ADP. The nucleotide-potassium antagonism is abolished and ATP is bound with high affinity both in NaCl and in KCl media. Na+-dependent phosphorylation is quantitatively recovered in the 78 kDa fragment, but the affinity for binding of [48V]vanadate is very low after cleavage. ADP-ATP exchange is stimulated 4-5-fold by cleavage; while nucleotide dependent Na+-Na+, K+-K+, or Na+-K+ exchange are abolished. Cleavage with chymotrypsin in NaCl at the N-terminal side of the phosphorylated residue thus stabilizes the E1 form of the protein and abolishes cation exchange and conformational transitions in the protein although binding of cations, nucleotides and phosphate is preserved. In contrast, cleavage with trypsin in KCl at the C-terminal side of the phosphorylated residue does not interfere with E1-E2 transitions and Na+-Na+ or K+-K+ exchange. This data support the notion that cation exchange and E1-E2 transitions are thightly coupled.

Adenosine Diphosphate↗