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Biomedical subjects

A Andersson

Publications and source records attributed to A Andersson.

At least 289 records · Page 16Linked to original sources
PubMed1986

Comparison between pre- and postovulatory distributions of oestradiol and progesterone in the brain of the PMSG-treated rat.

The pre- and postovulatory levels of oestradiol and progesterone were measured in seven brain areas, peripheral fat, muscle tissue and blood plasma in 49 immature female rats which had been given an injection of 4 IU PMSG (Pregnant Mare Serum Gonadotropin) on the 25th day of life. We observed a uniform decline in oestradiol concentration in all the areas of the postovulatory rat. The highest mean concentrations of oestradiol pre- and postovulatory were found in the hypothalamus and the striatum (260 +/- 26, 110 +/- 11, 200 +/- 39 and 75 +/- 13 pg g-1, respectively). The levels of progesterone showed variable increases in all the areas postovulatory. The highest postovulatory concentration was found in the cerebral cortex (29 +/- 2.0 ng g-1) where the increase was six-fold greater than the increases in any of the other areas compared to preovulatory values. The hypothalamus contained high progesterone levels at both times (3.5 +/- 0.68 ng g-1 and 27 +/- 5.2 ng g-1) compared to other areas. We conclude that the female rat brain exhibits differences in the distribution of oestradiol and progesterone both pre- and postovulatory. Since the levels in different brain areas to a large extent varied independently we suggest different uptake mechanisms and/or different binding capacities in various regions of the rat brain.

Animals↗
PubMed1986

Use of genetically marked minicells as a probe in measurement of predation on bacteria in aquatic environments.

Minicells produced by Escherichia coli M2141 were used as probes to measure predation on pelagic bacteria in situ. The minicells, labeled with [S]methionine in one specific protein, were shown to disappear in the presence of a microflagellate (Ochromonas sp.), as seen by a decrease in the amount of labeled marker protein with time. Incubation in filtered (pore size, 0.2 mum) and autoclaved seawater did not affect the amount of labeled marker protein in the minicell. The generation time of flagellates feeding on minicells was determined to be similar to that found for flagellates grown on seawater bacteria or living E. coli NC3. Data indicate that minicells are seen as true food particles by the flagellates. The minicell probe was used in recapture experiments, in which predation in situ on pelagic bacteria was demonstrated. The rate of bacterial production showed a clear covariation with the rate of predation, both in different sea areas and in depth profiles. The obtained results (11 field experiments) showed that the rate of predation, on average, accounts for the consumption of 62% of the bacteria produced.

Journal Article↗
PubMed1986

The human corpus luteum secretes 5 alpha-pregnane-3,20-dione.

A radioimmunoassay for 5 alpha-pregnane-3,20-dione (5 alpha-DHP) in plasma is described. The concentration of 5 alpha-DHP in peripheral plasma during the follicular phase of the menstrual cycle was of the same order of magnitude as that of progesterone (P). During the luteal phase, the plasma 5 alpha-DHP was 8-fold higher than in the follicular phase and about 1/3 of the P concentration. The concentration of 5 alpha-DHP in ovarian venous plasma draining an ovary containing the corpus luteum was 22-fold higher than the concentration in plasma from the contralateral ovarian vein. These results show that the corpus luteum secretes significant amounts of 5 alpha-DHP.

5-alpha-Dihydroprogesterone↗
PubMed1986

Hormonal regulation of the release of plasminogen activators and of a specific activator inhibitor from endometrial tissue in culture.

Two types of plasminogen activator (PA), t-PA (tissue type) and u-PA (urokinase type), are released from endometrial tissue in organ culture, as judged by immunological identification and molecular weight. Addition of estradiol to the medium greatly enhanced the release of u-PA, whereas that of t-PA was not low. Addition of progesterone, on the other hand, after priming of the endometrial tissue with estradiol, resulted in a much lower release of both types of PA. This pattern of PA release in response to hormonal stimulation in vitro agrees with previous observations of the PA activity of endometrial secretion in vivo. Endometrial tissue also released a PA inhibitor with molecular weight of approximately 50,000, which complexed both t-PA and u-PA. In cultures stimulated with estradiol the amount of free u-PA increased gradually during incubation and minor amounts of free t-PA appeared after 4-6 days culture. The amount of complexes, and thus the amount of PA inhibitor also increased under influence of estradiol. In cultures stimulated with progesterone, on the other hand, only minor amounts of free u-PA and no free t-PA was detected. The inhibitor might be of either the endothelial or the placental type, or both.

Culture Techniques↗
PubMed1986

Cryopreservation of mouse pancreatic islets. Effects of fast cooling on islet B cell function and on the outcome of islet transplantation.

In most previous studies of cryopreserved isolated pancreatic islets, a slow cooling rate has been employed. We recently observed that faster cooling (5 degrees C/min) resulted in better functional islet preservation than cooling at 0.5 degrees C/min. We found that a culture period after the collagenase isolation of the islets, but prior to freezing, is crucial for the preservation of the islet B cell function. In the present investigation the function of isolated mouse pancreatic islets cooled in Hanks' solution supplemented with 2 M dimethylsulphoxide was compared with that of nonfrozen, cultured islets prepared from the same donors. The islets were cultured in RPMI 1640 + 10% calf serum for 3 days before freezing, and for 3 days after rapid thawing at 37 degrees C. Islets were cooled at rates of 5, 15, or 25 degrees C/min to 70 degrees C and then plunged into liquid nitrogen. All three groups of cryopreserved islets responded with insulin secretion when challenged with high glucose concentrations in batch-type incubations. In further experiments it was found that glucose-stimulated (pro)insulin biosynthesis in islets frozen at 25 degrees C/min was the same as that in the controls. Similar observations were made with respect to glucose-stimulated insulin release in perifusion experiments. However, a 30% reduction in insulin content was observed in the rapidly frozen islets. There was no difference in the replicatory capacity of the islets cells in vitro, as determined by an autoradiographic technique, between control islets and islets cooled at 5 degrees C or 25 degrees C/min. Intrasplenic implantation of 600-800 cryopreserved syngeneic islets into alloxan-diabetic mice led to complete or partial normalization of the hyperglycemia in seven of nine mice. When splenectomy was performed in five animals the serum glucose concentrations increased promptly. We conclude that relatively rapid cooling rates may be useful for cryopreservation of isolated pancreatic islets.

Animals↗
PubMed1985

Influence of cyclooxygenase inhibitors and arachidonic acid on contractile activity of the human Fallopian tube.

Small muscle strips were dissected from the circular and longitudinal muscle layers of the human oviduct. The preparations showed rhythmic spontaneous activity when perfused by Krebs-Ringer buffer. Excitatory effects of the prostaglandin (PG) precursor arachidonic acid were totally blocked by the cyclooxygenase inhibitors 5,8,11,14-eicosatetraynoic acid (ETYA) and indomethacin. The latter drugs also caused a reversible inhibition of spontaneous activity in both muscle layers. After total inhibition produced by ETYA, the initial activity was restored by adding low concentrations of prostaglandin F2 alpha (PGF2 alpha) to the medium. PGE2 was able to reestablish the activity only in the longitudinal layer. It is concluded that isolated smooth muscle of the human oviduct has the capacity of generating PGs from both endogenous and exogenous substrate. The data also suggest that the formation of PGF2 alpha is a prerequisite for maintenance of normal tubal contractions.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1985

Experimental studies of transplantation and regeneration of endocrine pancreatic cells.

Replacement of destroyed B-cells with new "healthy" ones appears to be the most physiological approach to treatment of insulin-dependent (type 1) diabetes. This could be achieved either by transplantation of isolated islets or pancreatic segments or by stimulation of the replicatory activity in the islet cells surviving the acute toxic or infectious insult. The results of our experimental investigations indicate that adult, mature insulin-producing cells can replicate very actively when challenged with a proper stimulus, such as when implanted into obese-hyperglycaemic mice. The growth of transplanted islets is, however, dependent on the site of implantation. Thus, the subcapsular space of the kidney is more favourable than the spleen. Furthermore, immunosuppressive therapy may impair islet cell replicatory activity, as demonstrated in this study for Cyclosporin A. In a search for factors stimulating islet cell replication, we found that the hepatotoxic agent galactosamine enhanced this process as observed autoradiographically one week after the injection. This fits in with previous case reports demonstrating increased mitotic activity in islets of patients suffering from various acute liver diseases. Altogether this series of experiments demonstrates that islet cell replication is a more dynamic process than has hitherto been believed. Obviously many conditions influence this process so significantly that an impact on the diabetic state of the patients can well be expected.

Animals↗
PubMed1985

Modulation of streptozotocin-induced insulitis and hyperglycaemia in the mouse.

Multiple low-dose injections of streptozotocin (SZ) induce a gradually developing hyperglycaemia and pancreatic insulitis in certain inbred mouse strains. In the present investigation nicotinamide, which is known to protect against SZ-induced diabetes, was given prior to a single diabetogenic dose of SZ to C57BL/KsJ mice. Nicotinamide protected against SZ-induced hyperglycaemia in the acute phase but 13 of the 18 animals in this group became diabetic during the second week of observation. Nine of these mice had insulitis, seven of which showed overt diabetes. Since nicotinamide increased the serum glucose concentration at the time of the SZ-administration ten minutes later, the possibility that glucose mediated the protective action was evaluated. Glucose-pretreatment, however, was found to potentiate the diabetogenic action of SZ. It is obvious from the present data that another type of diabetes than that induced by a single high dose of SZ can be evoked if the immediate B-cytotoxic effects of SZ are reduced. It may be speculated that islet B-cells of mice given nicotinamide before SZ, for a time retain SZ-induced DNA injuries, which may lead to the expression of neoantigens and an autoimmune reaction.

Animals↗
PubMed1985

Tissue culture of human fetal pancreas. Development and function of B-cells in vitro and transplantation of explants to nude mice.

The present study evaluates the development and function of human fetal B-cells in vitro with a view to using such cells in future attempts for transplantation of human fetal pancreas to diabetic patients. A method previously described in our laboratory for preparing islets in vitro from the fetal rat pancreas has been applied and modified for use with human fetal pancreas. Pancreatic glands of different gestational ages were obtained from 37 consecutive prostaglandin-induced abortions. After a mild collagenase treatment, the partially disintegrated tissue was maintained in culture for 7 days in tissue culture medium RPMI 1640 plus 20% fetal calf serum to permit cell attachment and out-growth of endocrine cells. In 17 of the 37 consecutively cultured fetal pancreatic glands, islet-like cell clusters were formed. The 20 remaining glands were lost because of either bacterial contamination or lack of viability already before dissection had occurred. Sections of the newly formed cell clusters revealed well-preserved pancreatic cells showing frequent mitotic figures. The tissue exhibited a high rate of (pro)insulin biosynthesis and a modest insulin response to secretory stimuli, suggesting that the mechanism of glucose regulation by the fetal B-cells is not yet fully developed. Electron micrographs showed a large number of granule-containing cells, some of which were identified as B-cells. In nine cases, harvested cell clusters were implanted beneath the kidney capsule of nude mice. When these animals were killed after 2 mo, seven mice showed a considerable growth of the grafts with numerous islet-like structures containing insulin- and glucagon-positive cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Direct evidence for the cytomembrane derivation of Birbeck granules: the membrane-sandwich effect.

Digitonin, which is known to cause extensive damage to cytomembranes in general, was found to have a most remarkable effect on epidermal Langerhans' cells. Thus, it generates a membrane-sandwiching process resulting in the formation of large discs which except for the differences in size have the same morphology as ordinary Birbeck granules. This demonstrates that the cytomembrane of the Langerhans' cell has the inherent ability to superimpose upon itself, leaving little doubt that the normal Birbeck granules derive from the cytomembrane.

Adult↗
PubMed1985

A rapid fixation technique of epidermis for electron microscopy.

A rapid processing technique for ultrastructural studies of human epidermis has been devised in order to reduce dislocation of soluble compounds and to make available sections for diagnostic purposes within reasonable time (ca 4 hours). The morphology of cellular components agreed with or improved upon that obtained after commonly used methods. Thus, for example, the substance in the intercorneal space was better preserved and the cytomembrane and certain of its specializations appeared more distinct.

Adult↗
PubMed1984

Effects of chloroquine on lipid metabolism of mouse pancreatic islets.

Pancreatic islets accumulate the amphiphilic drug, chloroquine, which leads to a marked impairment of the insulin production of the B-cells in vitro. In this study the effects of the drug on islet lipid metabolism in vitro were investigated. It was found that exposure of islets to chloroquine (10(-5) M) for one week induced an increase of D-[U-14C]glucose incorporation into phospholipids and triacylglycerols of about two-fold and into diacylglycerols of about six-fold. Furthermore, two-dimensional thin-layer chromatography showed an increased rate of D-[U-14C]glucose incorporation into all major phospholipid classes. A 17% increase of the total islet phospholipid content indicated that an accumulation of islet cell phospholipids occurred. Pulse-chase experiments with D-[U-14C]glucose showed that the rate of degradation of islet phospholipids was decreased after prolonged exposure to chloroquine. No short-term effects of chloroquine upon either the de novo biosynthesis of islet lipids or upon phospholipid degradation could be demonstrated. The present data therefore suggest that chloroquine impairs the rate of islet lipid degradation in long-term experiments, which may be a primary lesion in the sequence of events leading to functional impairment of the B-cell.

Animals↗
PubMed1984

Metal ion and drug binding to proteolytic fragments of calmodulin: proteolytic, cadmium-113, and proton nuclear magnetic resonance studies.

Tryptic fragmentation of Ca2+-saturated calmodulin (CaM) takes place mainly at Lys-77; however, proteolysis can occur instead at Arg-74 or Lys-75. This cleavage pattern results in the production of three peptides each of the amino- and carboxy-terminal halves of CaM of slightly different length. A purification scheme for the three carboxy-terminal half-peptides is reported. Proton nuclear magnetic resonance (1H NMR) studies of peptides comprising the amino- or carboxy-terminal half of CaM reveal the great structural similarity between these two proteolytic fragments and the intact protein. Since this was observed for the apoprotein as well as the Ca2+-saturated protein, this means that the two halves of the protein are independently folded. A comparison of the changes in the 1H NMR spectra observed for the intact protein and the fragments upon addition of Ca2+ clearly identified sites III and IV as the two high-affinity binding sites. Furthermore, addition of Ca2+ or Cd2+ induces qualitatively similar changes in the spectra, thus indicating that Cd2+ is a reliable replacement for Ca2+ in these studies. Subsequent 113Cd NMR studies of trifluoperazine (TFP) binding to tryptic and thrombic fragments of calmodulin revealed the presence of two distinct drug binding sites, one located in the amino-terminal half and one located in the carboxy-terminal half. The spectral changes, induced upon addition of the antipsychotic drug, were similar to those observed upon binding of TFP to intact calmodulin. The strongest TFP binding site is located in the carboxy-terminal half.

Animals↗
PubMed1984

Effect of genetic background on the capacity for islet cell replication in mice.

Proliferation of islet cells may compensate for both an increased peripheral insulin resistance and islet cell destruction but the capacity for regeneration may be genetically determined. For the latter reason, glucose-stimulated islet cell replication was estimated in both inbred C57BL/6J (BL/6) and C57BL/KsJ (BL/Ks) mice. Islets isolated from both strains were exposed to high concentrations of glucose in vitro or in vivo for a prolonged time period. This was achieved either by culturing the islets free-floating in a high glucose concentration medium for 3 days or implanting the islets intrasplenically in insufficient numbers to cure alloxan-diabetic syngeneic recipients. In both strains high glucose concentration culture was found to increase the autoradiographic labelling index of the islets but the replicatory activity decreased with age. The proliferative rate of the islet cells of the BL/6 mice was about twice as high as that of the BL/Ks mice irrespective of age and glucose concentration. Likewise, the labelling index of intrasplenic BL/6 islets implanted into alloxan-diabetic mice was twice as high as that of the islets implanted into alloxan-diabetic BL/Ks mice. The replicatory activity of the latter islets did not differ statistically from that of islets implanted into non-diabetic control BL/Ks mice. No differences in the rates of proinsulin and total protein biosynthetic rates were observed between high glucose concentration-cultured islets of the two mouse strains. The present results indicate that the proliferative response of pancreatic islets to a prolonged glucose stimulation may be genetically determined. This may play a significant role in the development of different diabetic syndromes both in laboratory animals and man.

Aging↗
PubMed1984

Long-term effects of cyclosporin A on cultured mouse pancreatic islets.

In the light of recent attempts to treat newly-diagnosed Type 1 (insulin-dependent) diabetic patients with cyclosporin A, and reports suggesting an impaired glucose tolerance following immunosuppression therapy with cyclosporin A, we investigated the long-term effects of cyclosporin A on islet beta-cell morphology and function in vitro. Collagenase-isolated mouse pancreatic islets were cultured free-floating for 7 days in medium RPMI 1640 + 10% calf serum in the presence of cyclosporin A (0.1 or 1.0 mg/l). Islets cultured in the presence of the higher cyclosporin A concentration had impaired islet proinsulin biosynthesis and insulin release when challenged with high glucose concentration. Moreover, the insulin content of the drug-exposed islets was decreased and so was the rate of DNA synthesis. The glucose oxidation and respiratory rates, however, remained unaffected, suggesting that the impaired insulin production was not a result of defective oxidative metabolism. There were no changes in the ultrastructure or phospholipid biosynthesis of the islets after the drug treatment. These data indicate that cyclosporin A affects islets in culture, the clinical implications of which are so far difficult to assess. The inhibitory effect of cyclosporin A on islet cell DNA synthesis must nevertheless be considered in attempts to ameliorate Type 1 (insulin-dependent) diabetes, and when grating islet cells in numbers primarily insufficient to cure the recipient.

Animals↗
PubMed1984

The significance of culture for successful cryopreservation of isolated pancreatic islets of Langerhans.

It was the aim of the present study to investigate the significance of culture before and after freeze-thawing of isolated mouse pancreatic islets. To evaluate the impact of culture before freezing (5 degrees C/min; 2 M dimethyl sulfoxide), islets were frozen either directly after isolation or after 2, 4, or 7 days of culture in medium RPMI 1640. The culture period after thawing was 7 days. Islets immediately frozen exhibited virtually no (pro)insulin biosynthesis and also a severe inhibition of glucose-stimulated insulin release. The precultured (2-7 days), frozen islets synthesized and released insulin at rates comparable to those of nonfrozen, cultured islets. Studies of the effects of culture after freeze-thawing were performed after a 3-day culture period prior to freezing. The (pro)insulin biosynthetic rates did not differ between islets cultured for 0-7 days after thawing. There was an apparent increase of glucose-stimulated insulin release when the islets were cultured for more than 2 days after thawing. It may be that the decreased viability of islets frozen immediately after isolation was due to minor cell damage induced by the collagenase incubation. During culture the islets may recover and become more resistant to freeze-damage. The beneficial effect of culture after thawing may reflect the loss of damaged cells, which otherwise would influence the results of the viability tests.

Animals↗
PubMed1984

The ciliated human keratinocyte.

Human keratinocytes were investigated for the presence of single cilia. Almost all basal keratinocytes were found to carry a single cilium in normal, occluded, and psoriatic skin. The ciliary structure was progressively reduced in keratinocytes approaching the surface. No remnants of the ciliary apparatus were found in the granular layer. In one case of nickel-allergic dermatitis (patch test), the keratinocytes had lost their cilia; the significance of this surprising finding remains to be elucidated.

Adult↗