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Biomedical subjects

S Jacobsen

Publications and source records attributed to S Jacobsen.

At least 109 records · Page 6Linked to original sources
PubMed1987

Down-regulation of surface beta-adrenoceptors on intact human mononuclear leukocytes. Time-course and isoproterenol concentration dependence.

Incubation of human mononuclear leukocytes (MNL) in vitro with isoproterenol resulted in a rapid loss of surface beta-adrenoceptors, determined by radioligand binding at 4 degrees. Isoproterenol concentrations in the range of 10 nM to 100 microM resulted in significant down-regulation of beta-adrenoceptors. At a concentration of 1 microM isoproterenol, the time-dependent loss of surface beta-adrenoceptors closely paralleled the loss in isoproterenol-stimulated adenylate cyclase activity. If receptor number in intact cells was determined at 32 degrees, hardly any loss in receptor number was observed, due to reversal of down-regulation during the incubation period. When beta-adrenoceptor number in broken cell preparations was determined by [125I]cyanopindolol binding at 37 degrees no significant loss was observed, even after 2 hr of isoproterenol treatment, while [3H]CGP-12177 binding resulted in a similar reduction in binding sites as in intact cells. Reversal of loss in surface beta-adrenoceptors was rapid after 1 hr pretreatment with isoproterenol, but followed a biphasic time course after 4 hr pretreatment, with an initial rapid return of about 40% of the down-regulated receptors, followed by a slow, gradual reappearance of receptors. The results indicate that catecholamine exposure leads to a rapid sequestration of MNL surface beta-adrenoceptors away from the cell surface, to a compartment where they are inaccessible to the hydrophilic ligand [3H]CGP-12177 as well as to the lipophilic ligand [125I]cyanopindolol at 4 degrees. Up to 2 hr of isoproterenol treatment does not lead to any breakdown of sequestered beta-adrenoceptors, as they are still recognized by [125I]cyanopindolol binding in broken cell preparations.

Adenylyl Cyclases↗
PubMed1987

Synergism between thapsigargin and the phorbol ester 12-O-tetradecanoylphorbol 13-acetate on the release of [14C]arachidonic acid and histamine from rat peritoneal mast cells.

Thapsigargin is a potent skin irritating sesquiterpene lactone isolated from the roots of Thapsia garganica L. (Apiaceae). In rat peritoneal mast cells thapsigargin induced a calcium-dependent non-cytotoxic [14C]arachidonic acid and histamine release. A minor amount of the released [14C]arachidonic acid was converted to [14C]prostaglandin D2. A potentiated effect was found between thapsigargin and 12-O-tetradecanoylphorbol 13-acetate, as well as between A23187 and the phorbol ester with respect to release of [14C]arachidonic acid and histamine. It is suggested that the synergistic effect is due to activation of protein kinase C by 12-O-tetradecanoylphorbol 13-acetate and to increased intracellular calcium concentration mediated by A23187 as well as thapsigargin. [14C]arachidonic acid was released mainly from phosphatidylcholine. It is suggested that this release may be due to an action of phospholipase A2, and that protein kinase C is involved in activation of phospholipase A2.

Animals↗
PubMed1987

Modes of determining beta-adrenoceptor number in human mononuclear leucocytes.

Inhibition of total 125I-ICYP binding to intact human mononuclear leucocytes at 32 degrees by propranolol and (+/-) CGP-12177 was biphasic. The high affinity component of 125I-ICYP binding, representing approximately 30% of total, was stereospecific, while the low affinity binding site was inhibited without stereospecificity. (-) Isoproterenol inhibited the high affinity component of 125I-ICYP binding only, with low affinity. By performing binding studies in intact cells at 4 degrees or in broken cell preparations at 37 degrees, the fraction of total 125I-ICYP binding representing specific binding was increased, and agonist affinity was high. Inhibition of 3H-CGP-12177 binding to intact cells at 32 degrees demonstrated a high fraction of specific binding and high agonist affinity. Computer-assisted analysis of total radioligand binding determined over a broad concentration range revealed two populations of saturable 125I-ICYP binding sites in intact cells as well as in broken cell preparations, while 3H-CGP-12177 binding demonstrated only one saturable binding site. The number of high affinity 125I-ICYP binding sites was comparable to the number of saturable 3H-CGP-12177 binding sites. Receptor numbers determined by analysis of total radioligand binding were comparable to receptor numbers determined by subtraction of non-specific binding, determined in the presence of a high concentration of competing ligand. Analysis of total radioligand binding was found to be a better procedure because it eliminates the use of an arbitrary concentration of unlabelled ligand and improves the accuracy of the assay.

Adolescent↗
PubMed1987

Isometric and isokinetic muscle strength in patients with fibrositis syndrome. New characteristics for a difficult definable category of patients.

A common complaint among patients with fibrositis syndrome is exhaustion and fatique. It was therefore felt desirable to evaluate the muscle strength of these patients compared with normal subjects. Maximum isometric and isokinetic strength of knee extension was measured in 15 patients and 15 healthy matched subjects, using an isokinetic dynamometer (Cybex II). Maximum isometric strength at various knee extension angles (90 degrees, 60 degrees and 30 degrees degrees) was significantly (p less than 0.001) lower in the fibrositis group than in controls, a reduction of approximately 58-66%. Maximum isokinetic strength at various knee extension velocities (30-240 degrees per second) was also significantly (p less than 0.01) lower in the fibrositis group than in controls, the reduction being approximately 41-51%. In conclusion, isometric and isokinetic muscle strength is found to be lower in patients with fibrositis syndrome than in healthy subjects.

Female↗
PubMed1986

Elevated level of beta-adrenergic receptors in hepatocytes from regenerating rat liver. Time study of [125I]iodocyanopindolol binding following partial hepatectomy and its relationship to catecholamine-sensitive adenylate cyclase.

Hepatocytes from regenerating rat liver show an enhanced epinephrine-sensitive adenylate cyclase activity and cAMP response, which may be involved in triggering of the cell proliferation. We have determined adrenergic receptors and adenylate cyclase activity in hepatocytes isolated at various time points after partial hepatectomy. The number of beta-adrenergic receptors, measured by binding of [125I]iodocyanopindolol ([125I]CYP) to a particulate fraction prepared from isolated hepatocytes, increased rapidly after partial hepatectomy as compared with sham-operated or untreated controls. The maximal increase, which was observed at 48 h, was between 5- and 6-fold (from approximately 1 800 to approximately 10 500 sites per cell). Thereafter, the number of beta-adrenergic receptors decreased gradually. Competition experiments indicated beta 2-type receptors. Parallelism was found between the change in the number of beta 2-adrenergic receptors and the isoproterenol-responsive adenylate cyclase activity. The number of alpha 1-adrenergic receptors, determined by binding of [3H]prazosin, was transiently lowered by about 35% at 18-24 h, with no significant change in Kd. Although the results of this study do not exclude the possibility of post-receptor events, they suggest that the increased number of beta 2-adrenergic receptors is a major factor responsible for the enhanced catecholamine-responsive adenylate cyclase activity in regenerating liver.

Adenylyl Cyclases↗
PubMed1986

Effect of serum, alpha-1 acid glycoprotein, lipoproteins and albumin on human mononuclear leucocyte beta-adrenoceptors.

The effects of serum, alpha-1 acid glycoprotein (AAG), serum lipoproteins (SLP) and human serum albumin (HSA) on 3H-(-)-dihydroalprenolol (3H-(-)-DHA) binding and (-)-isoproterenol ((-)-IPR) induced cyclic AMP (cAMP) elevation in human peripheral blood mononuclear leucocytes (MNL) were investigated. The saturable binding of 3H-(-)-DHA was decomposed into two classes of binding sites with maximum binding capacity of approximately 1400 and 30000 sites/cell and with dissociation constants (Kd) of approximately 0.7 and 65 nM. Stimulation of the MNL beta-adrenoceptors by (-)-IPR caused a concentration dependent cAMP accumulation (EC50 approximately 0.2 microM) with maximum level approximately 250% above basal. For all single leucocyte preparations, 30-35 min. exposure to serum, AAG and SLP increased the number of beta-adrenoceptors with 100-200% and the maximal responsiveness to (-)-IPR with 30-90%. The presence of proteins did not change the Kd or the EC50. (-)-Alprenolol inhibited concentration dependently the serum induced increment in (-)-IPR-responsiveness. Serum, AAG and SLP did also increase the number of low affinity binding sites with 25-40% without effect on the Kd. HSA had no consistent effect on beta-adrenergic binding or stimulation. The present study shows that serum, AAG and SLP influence the number and function of MNL beta-adrenoceptors in vitro.

Alprenolol↗
PubMed1986

Increased number of beta-adrenoceptors in hepatocytes from rats treated with 2-acetylaminofluorene.

Treatment of rats with chemical carcinogens, including 2-acetylaminofluorene (2-AAF), leads to a strong increase in the hepatic catecholamine-sensitive adenylate cyclase activity. The present study was undertaken to investigate the mechanism for the development of this increase. We report that hepatocytes isolated from rats which had been fed 2-AAF (0.025% w/w) for 8-12 weeks had an increased number of beta-adrenoceptors, as determined by [3H]dihydroalprenolol binding to whole cells and [125I]iodocyanopindolol binding to washed particles. For both ligands the number of binding sites was about 4-fold higher in hepatocytes from 2-AAF-treated rats than in those from controls. The adenylate cyclase activity of the carcinogen-fed animals showed both a general increase manifested in the basal level (2-fold) and in the activities obtained by stimulation with guanine nucleotides (2-3-fold), cholera toxin (1.5-fold), and glucagon (1.3-fold) and a selective, larger increase in the beta-adrenoceptor-linked activity (7-fold increment of the isoproterenol-sensitive activity). The results indicate that the number of hepatocyte beta-adrenoceptors increases during 2-AAF carcinogenesis. This may, at least in part, explain the rise in catecholamine-sensitive adenylate cyclase activity.

2-Acetylaminofluorene↗
PubMed1986

Preparation and characterization of a polyvalent human melanoma antigen vaccine.

A polyvalent melanoma tumor antigen vaccine was prepared from antigens shed by a pool of human melanoma cells cultured in serum-free medium. The vaccine contained multiple melanoma associated antigens (MAAs) and was free of detectable fetal calf serum (FCS) proteins and Dr antigens. Three batches of vaccine prepared several months apart contained the same spectrum of tumor antigens. Thirteen patients with metastatic malignant melanomas were immunized intradermally with escalating doses of the vaccine in a Phase I study. There was no toxicity other than transient urticaria at the injection site. Humoral immunity, assayed by indirect immunoprecipitation, was augmented in five (38%) patients. Cellular immunity, assayed by delayed-type cutaneous hypersensitivity, was induced in four (31%) patients. Skin tests to a control vaccine prepared from pooled allogeneic lymphocytes were negative. Cutaneous metastases regressed completely in one patient who is now disease free after 2 years, and multiple cutaneous metastases have remained stable for 14 months in another patient. These results indicate that active immunization to a partially characterized polyvalent melanoma antigen vaccine is safe and can increase immunity to melanoma in some patients.

Adult↗
PubMed1985

Effect of serum on isoproterenol-induced cyclic AMP accumulation in human lymphocytes.

The effects of autologous serum on basal and isoproterenol (IPR) or prostaglandin E1 (PGE1) stimulated adenosine 3',5' cyclic monophosphate (cAMP) levels were investigated in human lymphocytes. For all blood donors, serum (25% (v/v)) lowered the basal cAMP content. In contrast, the responsiveness of the lymphocyte cAMP accumulation to (-)-IPR was increased. This effect was most clearly demonstrable in bicarbonate buffered incubation medium (40-50% increase of maximal response), but was also seen in phosphate buffered medium (10-20% increase). Serum did not alter the sensitivity of the lymphocytes to IPR. The response to PGE1, which was a considerable more effective stimulator of cAMP accumulation than IPR, was not affected in any consistent way by serum. The results indicate that serum influences the regulation of lymphocyte cAMP and that this effect may partly be exerted at the level of the beta-adrenoceptors.

Alprostadil↗
PubMed1985

pH lability in serum during equilibrium dialysis.

Changes in pH were determined in previously frozen normal human serum during dialysis against sodium phosphate, Krebs Ringer phosphate or Krebs Ringer bicarbonate buffers of pH 7.4. Serum was either untreated (native) or adjusted to pH 7.4 before dialysis. pH in native serum was 7.7-7.9 before dialysis, showed a decrease after 1 h, and an increase after 3 h. pH-adjusted serum showed a continuous pH increase during dialysis. The increase in serum pH during dialysis was larger at 37 degrees C than at 22 degrees C, larger at low than at high buffer molarity, and larger in native than in pH-adjusted serum. The observed changes in serum pH during dialysis are associated with unacceptably large errors in unbound fraction in serum for a number of important drugs. Drug binding determination in serum by equilibrium dialysis should be performed with buffers providing appropriate and stable pH level.

Blood↗
PubMed1985

A 24-m3 direct heat-sink calorimeter with on-line data acquisition, processing, and control.

The construction and performance of a 24-m3 direct heat-sink calorimeter for continuous measurement of evaporative and sensible heat loss in human subjects are described. Extensive use of real-time processing for compensation of physical time constants and delays made it possible to solve response-time and stability problems associated with the large volume. The performance characteristics of the calorimeter are 1) a linear response between 0 and 320 W (471 g . h-1) for evaporative heat with a precision of 4.0-0.6% in the range 25-100 W, 2) a linear response between 0 and 280 W for sensible heat with a precision of 1.4-0.2% in the range 50-200 W, 3) a stability corresponding to a drift of less than 0.6 W (24 and 72 h) on both evaporative and sensible heat outputs and 24- and 72-h standard deviations (values every 2 min) of 0.3 and 0.4 W for evaporative heat and 0.6 and 0.7 W for sensible heat, 4) response times (95%) of 15 min for both evaporative and sensible heat, 5) independency on the position of the calibration source within the chamber, 6) no measurable "cross talk" between evaporative and sensible heat inputs, 7) negligible dependency of the external air humidity between 14 and 70%, and 8) operating temperature range from 18 to 30 degrees C. More than 40 experiments of 25-h duration with human subjects have been carried out. In no case was any discomfort recorded. An example of the 25-h continuous evaporative and sensible heat output tracing of one experiment is given.

Body Temperature↗
PubMed1984

A comparison of the binding characteristics of the beta-adrenoceptor antagonists 3H-dihydroalprenolol and 125I-iodocyanopindolol in rat liver.

The binding characteristics of 3H-dihydroalprenolol and 125I-iodocyanopindolol have been compared in a particulate fraction from regenerating rat liver. When total 3H-dihydroalprenolol binding and inhibition of total 3H-dihydroalprenolol binding by (-)isoprenaline, (-)alprenolol and (+/-)cyanopindolol was investigated, it was found that all agents were bound to two classes of saturable binding sites. In the inhibition studies, the presence of two binding components was not obvious until the data were transformed into Hofstee plots and these were decomposed, except in the case of (+/-)cyanopindolol. Only (+/-)cyanopindolol was found to distinguish clearly between the two saturable binding sites identified by 3H-dihydroalprenolol, as indicated by a broad plateau in the inhibition curve. When 125I-iodocyanopindolol was used as radioligand, only one saturable binding site was identified, even in the presence of less selective inhibiting ligands. The lower affinity component of 3H-dihydroalprenolol binding could be inhibited by 10 microM phentolamine. However, binding experiments with 3H-prazosin indicated that the lower affinity component was not identical with the alpha-adrenoceptor. Phentolamine did not influence 125I-iodocyanopindolol binding. Thus, due to its higher specific activity and a high degree of selectivity, 125I-iodocyanopindolol appears to be the ligand of choice.

Adrenergic beta-Antagonists↗
PubMed1983

Mechanisms for the emergence of catecholamine-sensitive adenylate cyclase and beta-adrenergic receptors in cultured hepatocytes. Dependence on protein and RNA synthesis and suppression by isoproterenol.

Adult male rat hepatocytes, which normally respond poorly to beta-adrenergic agents, acquire such responsiveness during primary monolayer culture. We here show that the rise in catecholamine-sensitive adenylate cyclase activity in hepatocytes in vitro is closely paralleled by an increase in the ability to bind the beta-adrenoceptor ligand [125I]cyanopindolol. The emergence of beta-adrenergic responsiveness did not require cell attachment or serum. Addition of dexamethasone, insulin, thyroxine or dihydrotestosterone to the cultures, singly or in combination, did not prevent the augmented beta-adrenergic responsiveness. The increase in catecholamine-sensitive adenylate cyclase activity and [125I]cyanopindolol binding could be blocked by cycloheximide or actinomycin D. Exposure of the cultures to isoproterenol at 3-hourly intervals led to a dose-dependent suppression of the rise in isoproterenol-responsive adenylate cyclase and prevented the increase in beta-adrenoceptor binding.

Adenylyl Cyclases↗