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L Sjödin

Publications and source records attributed to L Sjödin.

At least 37 records · Page 2Linked to original sources
PubMed1990

Quantitation of human chorionic gonadotrophin (hCG) by radioreceptor assay.

A sensitive radioreceptor assay was developed for pharmaceutical preparations of human chorionic gonadotrophin with the use of rat testicular membranes as receptor preparation and human 125I-chorionic gonadotrophin as tracer. The addition of unlabelled human chorionic gonadotrophin or luteinizing hormone inhibited the binding of 125I-chorionic gonadotrophin to the receptors in a concentration dependent way. Concentrations of human chorionic gonadotrophin between 30-300 mIU ml(-1) were normally used for a three-dose assay fulfilling pharmacopoeial statistical requirements for assay validity. The relative standard deviation for five assays was 7%. Estimates of potency of commercial preparations of human chorionic gonadotrophin obtained with the radioreceptor assay correlated well with corresponding estimates from in vivo assays. The proposed radioreceptor assay, however, provides a considerable saving in the number of animals required, requires less technical support, and is more precise than the in vivo method.

Animals↗
PubMed1990

An in vitro bioassay for quantitation of human interferons by measurements of antiproliferative activity on a continuous human lymphoma cell line.

Interferons have, in addition to their antiviral effects, been shown to possess several non-antiviral activities. In this study, an in vitro bioassay for interferon alpha (IFN-alpha) preparations based on their antiproliferative effect in cultured Daudi cells has been developed. Briefly, about 10(5) cells per ml treated with different concentrations of IFN were incubated under standard culture conditions for 3 days. Two different end points, i.e. incorporation of [3H]thymidine and final cell density, were used and responses were evaluated according to established pharmacopoeial principles for quantification of biomolecules. Both methods gave similar results. However, measurement of final cell density yielded the most precise results. The proposed assay, with an effective assay range of 1-10 IU/ml (approximately 0.2-2 x 10(-12)M, had a high sensitivity and precision as well as a good reproducibility. Compared with antiviral assays, it is less resource demanding. In conclusion, the in vitro bioassay described is well suited for potency determinations of IFN-alpha and probably also IFN-beta preparations.

Biological Assay↗
PubMed1990

Binding of cholecystokinin and somatostatin to isolated porcine gastric mucosal cells and effects on aminopyrine uptake.

Mucosal cells were prepared by enzymatic digestion of porcine gastric mucosa with pronase and collagenase. The resulting cell suspension contained 10-15% parietal cells, which responded to histamine stimulation by an up to 20-fold increase in [14C]aminopyrine accumulation over control levels. Cholecystokinin-8 (CCK-8) evoked a more moderate stimulation of [14C]aminopyrine accumulation, whereas somatostatin inhibited histamine-stimulated accumulation. Parietal cells were enriched by elutriation and isopycnic centrifugation on density gradients of Percoll. A fraction with 60% parietal cells bound approximately three times more iodinated CCK-8 than a fraction containing 70% non-parietal cells. Binding of [125I]BH-CCK-8 to preparations containing 30-60% parietal cells was specifically inhibited to about 50% by 10(-9) M unlabelled CCK-8 but not by bombesin. Cell fractions containing about 30% parietal cells also bound [125I]somatostatin. Unlabelled somatostatin at 10(-9) M inhibited tracer binding by about 50%, while CCK-8 did not affect somatostatin binding to such a preparation. The results suggest the existence of specific receptors for CCK and somatostatin on porcine parietal cells exerting a regulatory influence on acid secretion.

Aminopyrine↗
PubMed1990

Vasodepressor activity of pharmaceutical formulations of heparin.

Thirty-four batches of heparin formulations were tested for vasodepressor activity in the anaesthetized cat in accordance with pharmacopoeial requirements. Batches containing chlorobutanol as preservative exerted hypotensive effects, similar to that of 0.1 microgram of histamine/kg, but the average heparin formulation without preservative also caused significant lowering of blood pressure. This effect was reduced by a histamine-H1-receptor antagonist. Heparin formulations, like histamine, caused contraction of the isolated guinea pig ileum which may indicate contamination with up to about 0.1 microgram histamine per 5000 IU of heparin. Using radioligand assays for substance P (SP) and vasoactive intestinal polypeptide (VIP), formulations of heparins of porcine intestinal origin were found not to inhibit 125I-BH-SP binding but some batches moderately reduced binding of 125I-VIP consistent with a maximal contamination with 50-100 ng of VIP per 5,000 IU. The results may have clinical implications for high-dose heparin therapy in connection with thoracic surgery. The results may also provide an argument for retaining the vasodepressor test in pharmacopoeial monographs for heparins.

Animals↗
PubMed1989

In-vitro bioassays for cholecystokinin.

Two in-vitro methods for the bioassay of cholecystokinin (CCK) are described. They should be useful for determinations of potencies of pharmaceutical formulations of CCK. Both are based on the hormone's ability to stimulate exocrine pancreas. The stimulatory effect on 45Ca efflux from preloaded suspended acinar cells or on release of amylase from pancreatic acini from the guinea-pig has been recorded. The assay based on stimulation of 45Ca outflux is more specific and precise than the method using measurements of amylase secretion. Therefore, the calcium assay was further validated against the conventional guinea-pig gall-bladder contraction assay. Both methods gave similar potency readings but the results from the in-vitro assay were more precise.

Amylases↗
PubMed1987

The quantitation of human growth hormone by a radioreceptor assay using an established human cell line.

Membrane receptors on cultured human lymphocytes (IM-9) have been shown to bind human growth hormone (hGH) in a specific manner. The aim of the present study was to develop an in vitro assay of hGH based on this binding. The assay should fulfil established pharmacopoeial requirements for quantitation of hormones. The binding of [125I]hGH was studied as a function of time, temperature, cell density, tracer concentration and the concentration of unlabelled hGH and other related hormones. Also, the dissociation of bound hGH and the chemical stability of hGH in the incubation medium were studied. From these studies, the conditions for an appropriate radioreceptor assay were determined. Briefly, 1.5-3.0 X 10(7) cells ml-1 were incubated with 5-20 X 10(-12) M [125I]hGH and three different concentrations of unlabelled hGH chosen from the linear part of the [125I]hGH displacement curve. The results were analyzed according to general pharmacopoeial principles. The mean values for growth hormone activity tested by radioreceptor assay were within the fiducial limits (P = 0.05) of the corresponding activity determined by the hypophysectomized rat body-weight gain assay. The in vitro assay was found to be more precise and less resource demanding than the in vivo bioassay of hGH. It is concluded that the in vitro bioassay described here is well suited as a screening method for potency determination of hGH preparations.

Animals↗
PubMed1987

Radioreceptor assay for insulin formulations.

A sensitive radioreceptor assay was developed for pharmaceutical insulin formulations with the use of rat liver membranes and 125I-insulin. The addition of unlabeled insulin or insulin analogues inhibited the binding of 125I-insulin to the receptors in a concentration-dependent way. Insulin concentrations between 3 x 10(-9) and 3 x 10(-8) M were used for a three-point assay which fulfilled pharmacopoeial statistical requirements for validity of the assay. The coefficient of variation for five assays was 4%. Potency estimates of insulin preparations obtained with the radioreceptor assay correlated well with corresponding estimates from in vivo assays. Both assays also gave similar potency readings for insulin preparations that were partly degraded during storage at elevated temperatures, but the radioreceptor method was more precise.

Animals↗
PubMed1985

Quantitation of glucagon by radioreceptorassay.

Receptors for glucagon on rat liver membranes were characterized. They bound [125I] glucagon rapidly in a specific and saturable way. Addition of unlabelled glucagon displaced [125I] glucagon from the binding sites in a concentration dependent way. Concentrations from 10(-9) to 10(-8) M of glucagon caused a linear reduction of binding of labelled glucagon. This concentration interval was used for a three-point assay which fulfilled statistical requirements for validity. Individual assays normally resulted in potency estimates of high precision and statistical weight. Mean values for glucagon activity of preparations tested by receptor assay were within the fiducial limits (P = 0.95) for corresponding activity determined by the rabbit blood glucose method. The receptor assay is less time consuming and requires only part of one rat liver while the in vivo assay uses 16 rabbits. Thus, the receptor assay is less resource demanding and should serve well as a screening instrument for control of potency of glucagon preparations.

Animals↗
PubMed1984

Binding and internalization of 125I-Bolton-Hunter-substance-P by pancreatic acinar cells.

Binding of 125I-labelled Bolton-Hunter substance P (125I-BH-SP) to dispersed pancreatic acinar cells from guinea pigs was studied. Association of 125I-BH-SP to acinar cells was rapid, specific, and temperature-dependent. Dissociation of bound 125I-BH-SP was slow and 60 min after dilution only 12% of cell-associated radioactivity had dissociated from cells. Various c-terminal fragments of SP as well as structurally related substances inhibited binding. Bound 125I-BH-SP partly resisted acid washes of cells. After lysis of cells, cell-associated radioactivity was chromatographed on a Sephadex G-25 column. Part of radioactivity was eluted as apparently intact 125I-BH-SP. It is suggested that this material has been internalized into acinar cells.

Animals↗
PubMed1984

Interaction of substance P with dispersed pancreatic acinar cells from the guinea pig. Relationships between structure, binding and biological activity.

Binding of 125I-[Tyr8]-SP to isolated pancreatic acinar cells was inhibited in a concentration-dependent way by SP, [Tyr8]-SP and longer C-terminal fragments of SP. SP6-11 was the shortest sequence to bind significantly to SP-receptors as well as to stimulate amylase release from dispersed pancreatic acini. SP7-11 and shorter fragments did not inhibit binding of 125I-[Tyr8]-SP and did not stimulate secretion of amylase significantly. SP augmented the stimulatory effect of cholecystokinin on amylase release. Two SP-antagonists, [D-Pro2, D-Trp7,9]-SP and [D-Pro2,4, D-Lys3, D-Gln5,6, D-Trp7,9]-SP inhibited binding of 125I-[Tyr8]-SP in a concentration dependent manner and tended at a high concentration to reduce release of amylase evoked by submaximal concentrations of SP.

Amylases↗
PubMed1984

Effects of gastric inhibitory polypeptide on dispersed pancreatic acinar cells from the guinea pig.

Purified natural porcine gastric inhibitory polypeptide (GIP), in high concentrations, was found to stimulate outflow of 45Ca, increase cellular accumulation of cyclic GMP and cyclic AMP and cause release of amylase from dispersed pancreatic acinar cells. Synthetic GIP increased cellular cyclic AMP levels, but did not affect outflux of calcium, cellular levels of cyclic GMP or release of amylase. The discrepancy between results with natural and synthetic preparations of porcine GIP may be explained by a possible contamination of natural GIP with cholecystokinin. Other examined pancreatic secretory stimulating peptides which induce cyclic AMP accumulation in acinar cells, also increase release of amylase. Synthetic GIP increased levels of cyclic AMP without affecting amylase release. This suggests that the correlation between amylase release and total cellular accumulation of cyclic AMP in response to GIP is not close.

Amylases↗
PubMed1984

Insulin receptors on pancreatic acinar cells in guinea pigs.

The characteristics of interaction of insulin with specific receptors on exocrine pancreatic cells of the guinea pig have been studied. Insulins from different species as well as certain insulin analogs were found to have affinities to receptors on pancreatic acinar cells which are similar to what have been described for insulin receptors in other organs of different mammalian species. Binding was rapid and reversible at 37 C but dissociation was markedly slower at 12 C. Clear indications of negative cooperativity between binding sites were not seen. Bovine and chicken insulin bound with approximately a 100-fold higher affinity to guinea pig insulin receptors than guinea pig insulin itself. The number of insulin receptors per acinar cell were comparable with what has been described for other mammalian cells. Part of cell-associated insulin was internalized. After 60 min of incubation the major part of radioactivity in the incubation medium as well as in cells appeared as intact [125I] iodoinsulin on a Sephadex G-50 column and less than 12% of radioactivity was eluted as breakdown products together with Na 125I.

Aminoisobutyric Acids↗
PubMed1980

Interaction of substance P with dispersed pancreatic acinar cells from the guinea pig. Binding of radioiodinated peptide.

Tyr8-SP has been radioactively labeled with 125I to a specific activity of 200 microCI/microgram. This tracer has been found to be rapidly and reversibly bound in a specific way to dispersed pancreatic acinar cells. The specific binding is saturable and dependent on incubation temperature. At 37 degrees C 125I-tyr8-SP is bound to a less degree than at lower temperatures since the peptide is rapidly degraded at 37 degrees C. Native SP inhibits binding of tracer. Results have been analyzed according to Scatchard and suggest 2 functionally distinct types of binding sites; a small number of sites with high affinity and a larger number of sites with low affinity for SP. SP-sites also bind eledoisin and physalaemin which are peptides similar to SP in terms of chemical structure and biological activities. The concentration range in which SP, physalaemin, nd eledoisin inhibit binding of 125I-tyr8-SP correlates well with the range in which these peptides stimulate biochemical processes like outflux of 45Ca, accumulation of cyclic GMP and release of amylase from acinar cells.

Animals↗
PubMed1980

Interaction of substance P with dispersed pancreatic acinar cells from the guinea pig. Stimulation of calcium outflux, accumulation of cyclic GMP and amylase release.

In dispersed acinar cells from the guinea pig pancreas, substance P (SP) was found to stimulate outflux of 45Ca, cellular accumulation of cyclic GMP, and release of amylase. Maximal effects on accumulation of cyclic GMP and release of amylase were obtained with 3 x 10(-8) M of SP, 10(-7) M of Sp caused maximal outflux of 45Ca. These effects corresponded to 30-50% of the maximal effects obtained with caerulein, a cholecystokinin-like decapeptide. The concentrations of SP required for stimulation of 45Ca outflux, accumulation of cyclic GMP, and release of amylase correspond well with those which affect binding of 125I-tyr8-SP to pancreatic acinar cells.

Amylases↗
PubMed1980

Effect of intraluminal pH on the release of somatostatin and gastrin into antral, bulbar and ileal pouches of conscious dogs.

Experiments were performed on conscious dogs with chronic pouches of the antrum, the duodenal bulb or the ileum, which were perfused with solutions of varying pH. Gastrin and somatostatin levels were measured in the perfusates. When the pouches were perfused with 0.15 M NaCl only small amounts of gastrin and somatostatin (1 pmol/min) were released into the lumen of the antrum and of the duodenal bulb. By lowering pH of the perfusion fluid a pH dependent release of somatostatin was induced into the lumen of the antrum and the duodenal bulb. Perfusion with 0.1 M HCl caused a large output of somatostatin (6--60 pmol/min) into the pouches. The upper pH limit for stimulation of the intraantral or intrabulbar somatostatin release appeared to be approximately pH 3--4. Somatostatin was also released into ileal perfusates at intraluminal pHs below 3--4. Lowering of pH in the antral pouches caused an increased intraluminal gastrin release, which was quantitatively less impressive than that of somatostatin. Occasionally also the gastrin release into the duodenal bulb increased during perfusion with 0.1 M HCl, whereas no such release was induced by acidification of the lumen of the ileum. It is suggested that the inhibition of gastrin release observed at low intraantral pH is mediated by a local effect of somatostatin, since this peptide is released in a pH dependent manner in the antropyloric region. It is also suggested that acidification of any region of the gastrointestinal tract will stimulate the release of peptides from all endocrine cells of the open type, probably by an unspecific effect on the membrane. Thus both gastrin and somatostatin are released by acidification of the antrum, but in the presence of high local levels of somatostatin, the release of gastrin is substantially inhibited.

Animals↗
PubMed1980

Inhibition of acid secretion from vagally innervated and denervated gastric pouches by (Gln4)-neurotensin.

In dogs with innervated fundic pouches an intravenous infusion of (Gln4)-neurotensin, 60 pmol X kg-1 X min-1, reduced the pentagastrin-stimulated acid secretion to 40% of the control secretory rate. After vagal denervation of the fundic pouches the same dose of (Gln4)-neurotensin did not significantly change the secretion. These findings suggest that (Gln4)-neurotensin does not act directly on parietal cells but inhibits acid secretion at a presynaptic level.

Animals↗