[Minimum Caseload Requirements and In-hospital Mortality: Observational Study using Nationwide Hospital Discharge Data from 2006 to 2013]. / Mindestmengen und Krankenhaussterblichkeit ­ Beobachtungsstudie mit deutschlandweiten Krankenhausabrechnungsdaten von 2006 bis 2013.

Background: In order to improve hospital care, minimum caseload requirements for certain elective hospital treatments have been defined by law in Germany. This study analyses retrospectively if adherence to this regulation is associated with the outcome of hospital treatment. Differences in in-hospital mortality were analyzed for complex esophageal and pancreatic surgery, liver and kidney transplantation, stem cell transplantation and total knee replacement. Methods: Within individual inpatient data of the nationwide German hospital discharge data (DRG statistics) all inpatient episodes subject to the minimum volume requirements were identified and annual caseloads per hospital were calculated. Inpatient episodes were assigned to 2 groups: Patients treated in hospitals with a caseload equal to or greater than the minimum caseload (≥ MC) and patients treated in hospitals with a caseload below the minimum caseload (< MC). Logistic regression was used to calculate adjusted in-hospital mortality. Results: In total, 28 931 esophageal surgeries, 78 879 pancreatic surgeries, 7 984 liver transplantations, 21 773 kidney transplantations, 51 064 stem cell transplantations and 1 093 296 total knee replacements were analyzed. Adjusted in-hospital mortality in hospitals with a caseload≥MC was significantly lower than in hospitals with a caseload

[Stroke occurence in Germany - on the comparability of insurance data and registry-based data]. / Schlaganfallgeschehen in Deutschland - Zur Vergleichbarkeit von Krankenkassen-, Register- und DRG-Daten.

PURPOSE: This article presents epidemiological data regarding stroke frequency in Germany based on nationwide statutory health insurance data (Deutsche BKK) and aims to analyse them in the context of current research. The comparability of the most important resources of stroke frequency data - stroke registers, DRG data and insurance data - is initially discussed in order to assess the presented data adequately. METHODS: The study cohort comes from a population of about 1 000 000 people insured with BKK and consists of all persons who were treated for a stroke in an acute care hospital in 2007 (n = 4,843). Data were subjected to statistical secondary analysis including uni- and bivariate statistics and t tests. Reference studies for the observation period include data from GEK and AOK health insurances, from quality assurances Hessen and Bayern, from the ADSR, and hospital DRG data. The different study types are compared regarding their inclusion/exclusion criteria and the resulting effects on reported prevalences. RESULTS: Different inclusion criteria and accordingly different operationalisations of "stroke" impede the comparability of existing German data resources regarding stroke. The inclusion of TIA, non-traumatic subdural haemorrhage (I62), and the frequency of unspecified strokes (I64) is especially inconsistent. In addition, recurrent strokes and the definition of first-ever strokes are treated differently. The study cohort reveals no major discrepancies regarding aetiological subgroups compared to previous results, only the percentage of women (60.3 %) seems exceptionally high. CONCLUSIONS: The gender effect is attributed to the BKK member structure, and especially the high proportion of women in the older age groups. Discussion of stroke frequency in Germany needs to take structural differences between study types into account. There are two vulnerable groups that tend to be underrepresented: TIA patients with a high risk of recurrent strokes, and high-risk patients who have already had a stroke and are care-dependent, which are often unspecifically coded. In the future, study designs should include the whole range of stroke coding, thus enabling differentiated analyses.

[Physio- and occupational therapy pathways of stroke patients and stroke mortality]. / Physio- und ergotherapeutische Versorgungsverläufe und Mortalität im ersten Jahr nach Schlaganfall.

AIMS: This study examines the relationship between adherence to clinical guidelines and survival time in the first year after stroke. METHODS: The sample comprises all clients of the Deutsche BKK, a large German health insurance company, who received acute inpatient care for stroke in 2007, who survived the hospital stay by at least 14 days, and who had motor deficits at the end of their acute treatment (n=1 791). 3 types of treatment that differ in the degree of adherence to clinical guidelines are identified ("Frühreha-Plus">"Standard-Plus">"Nur Akut"). RESULTS: There is a positive relationship between adherence to clinical guidelines and survival time, even when relevant covariates are controlled. The hazard-ratios are 0.49 for "Frühreha-Plus" and 0.65 for "Standard-Plus" compared to "Nur Akut". CONCLUSIONS: Healthcare processes should be organized on the basis of cross-sector collaboration and in line with the recommendations of the guidelines.

[A cross-sectorial analysis of physio and occupational therapy pathways after stroke]. / Physio- und ergotherapeutische Versorgungsverläufe bei Schlaganfallbetroffenen - von der Akut- über die Rehabilitationsbehandlung bis zur ambulanten Heilmittelversorgung.

PURPOSE: This article examines the provision of physiotherapy and occupational therapy for stroke patients from a cross-sectorial perspective, from acute to rehabilitative care to outpatient services. METHODS: The sample comprises all clients of the Deutsche BKK, a large German health insurance company, who received acute care for stroke in 2007, who survived the initial hospital stay, and who had a secondary diagnosis of motor deficits (n = 1 929). RESULTS: For 60.4% of these stroke patients, no further treatment was provided after acute care. The odds of receiving early rehabilitation treatment while in hospital stay decreased by 1% with each year of life. Only 18.8% of patients received a form of treatment that was largely in line with current recommendations for stroke care, beginning with early rehabilitation and including further treatment in the context of rehabilitation measures or outpatient care. Patients who were in long-term nursing care before stroke were at increased risk of not being placed on this treatment pathway, which has been positively evaluated. 20.7% of patients did not receive any early rehabilitation treatment, but received further rehabilitation treatment and/or outpatient services after hospital discharge. CONCLUSIONS: We recommend that receipt of long-term nursing care should routinely be regarded as a risk factor for underprovision of treatment after stroke (yellow flag).

Did the gradual loss of GLUT2 cause a shift to diabetic disorders in the New Zealand obese mouse (NZO/Hl)?

The New Zealand obese mouse (NZO/Hl) is characterised by hereditary obesity and type-2 diabetes, including insulin resistance, hyperinsulinaemia, and glucose intolerance. In other diabetic models, it has been revealed that the proper functioning of the glucose transporter isoform 2 (GLUT2) is essential for adequate secretion of insulin. The aim of this study was to compare the distribution of islet cells and GLUT2, as well as the expression of GLUT2-mRNA, in the pancreas of NZO mice and metabolically unimpaired NMRI (Naval Medical Research Institute) mice. Pancreas tissue was obtained from different stages of development. For molecular determination of the expression level of GLUT2-mRNA, total-RNA was extracted from the pancreas and analysed by quantitative real-time RT-PCR. All investigated NZO mice displayed increased weight, elevated hyperinsulinaemia, and slightly enhanced blood glucose levels compared with the NMRI control mice. By means of immunofluorescence microscopy drastically reduced insulin levels were detected, which might be compensated by the observed islet cell hyperplasia and hypertrophy. Furthermore, the normally peripheral localisation of the alpha-cells within islets was disturbed. By contrast, there were no changes in somatostatin cell distribution. However, considerable differences appeared with regard to GLUT2: whereas the beta-cells of NMRI mice showed dense immunostaining of the GLUT2 transporter on the cell surface, in all age groups of NZO mice, GLUT2 on the plasma membranes was reduced and dispersed in the cytoplasm. These findings agree with the molecular biological results, which displayed decreased mRNA-expression of GLUT2. In summary, the observed alteration of islet morphology and of GLUT2 expression in diabetic mice complements our previous results from a superfusion protocol and further clarifies the mechanisms of diabetogenesis in NZO mice.

Indication of circadian oscillations in the rat pancreas.

The central circadian oscillator of the suprachiasmatic nucleus controls diurnal rhythmicity of the body with light as its dominant zeitgeber. Recently, peripheral oscillators have been detected in liver and heart, which follow as yet unidentified cues. In this study real-time reverse transcription-polymerase chain reaction (RT-PCR) was used in analysis of the expression of the major clock genes Per1, Per2, Bmal1, Cry1, Tim (timeless) and Clock, as well as of the output genes Dbp and Rev-erbalpha in the pancreatic tissue of rats. The results presented here indicate a robust circadian expression of clock genes (e.g. Per1 and Bmal1) and the probable existence of a peripheral oscillator in the pancreas. Whether this oscillator regulates the diverse functions of the islets of Langerhans remains to be elucidated.

Formation of compound 305 requires the simultaneous generation of both alloxan and GSH radicals.

This in vitro study investigates the conditions under which "compound 305" is formed. Using HPLC, ESR as well as UV spectroscopy, "compound 305" was largely separated and characterized. It has an absorption peak at 314 nm, which changes after reoxygenation to shorter wavelengths within hours. The retention time of "compound 305" amounts to 10.93 +/- 0.042 min. The formation of "compound 305" does not depend on alloxan (ALX) or reduced glutathione (GSH), but most likely on the steady-state concentration of the paramagnetic derivatives of both reactants (ALX* and GS*). The alloxan radical (ALX*) is formed by either a one-electron transfer from e. g. GSH to alloxan or oxidation of dialuric acid. The concentration of the ALX* was determined to be 12 +/- 3.6 micromol/l using the stable ultramarine radical as an ESR standard. ALX* is stable only under anaerobic conditions. It disappears within 2 min in air. Since formation of "compound 305" needs both ALX* as well as GS*, which are also necessary for the generation of reactive oxygen species (ROS), it is assumed that formation of "compound 305" diminishes the toxicity of alloxan.

Simultaneous quantitative determination of alloxan, GSH and GSSG by HPlc. Estimation of the frequency of redox cycling between alloxan and dialuric acid.

This in vitro study compares the frequency of redox cycling between alloxan and dialuric acid at different initial ratios of glutathione and alloxan. Alloxan oxidizes GSH to GSSG. The rate of GSH oxidation at a given initial GSH concentration of 2.0 mmol/L depends on the initial concentration of alloxan added. The higher the concentration of alloxan in relation to the initial concentration of GSH, the faster GSH oxidation proceeds, as well as oxygen consumption, and therefore, formation of reactive oxygen species. The highest rates of GSH oxidation, i.e. GSSG formation, were found at concentration ratios of between 2.0 mmol/L GSH and 0.2 and 0.04 mmol/L alloxan, respectively. Because 0.04 mmol/L alloxan oxidizes 2.0 mmol/L GSH completely, a frequency of at least 25 cycles between alloxan and dialuric acid within 3 hours can be assumed. During each redox cycle, two molecules of GSH are oxidized to one molecule of GSSG, and during each cycle one molecule of oxygen is reduced simultaneously to one molecule of hydrogen peroxide. In total, therefore, one molecule of alloxan oxidizes at least 50 molecules of GSH and forms about 25 molecules of hydrogen peroxide.

Comparison between xanthine oxidases from buttermilk and microorganisms regarding their ability to generate reactive oxygen species.

Xanthine oxidase (XO) forms uric acid from xanthine. It is assumed that at the same time oxygen is reduced by the XO to reactive oxygen species (ROS), mainly to .O2- and to H2O2. Under certain conditions such ROS can be highly damaging to cellular structures. Therefore, XO was frequently used as a model system, in which the impact of ROS on cellular compounds and structures has been investigated. In this in vitro study xanthine oxidases from buttermilk and from microorganisms were compared regarding their ability to generate ROS. It could be shown that both enzymes are able to transform xanthine to uric acid but differ significantly in their reductive properties to oxygen. XO from buttermilk reduces oxygen to both .O2- and H2O2 whereas XO from microorganisms generates H2O2, but fails to form .O2-. Since .O2- are involved in maintaining transition metal-mediated formation of hydroxyl radicals (.OH) from H2O2, we conclude that XO from microorganisms is therefore largely unsuitable in studies investigating just the interaction of .O2- with other ROS on cellular compounds.

Scavenging effect of melatonin on hydroxyl radicals generated by alloxan.

Alloxan can act as a generator of reactive oxygen species (ROS) as long as sufficient suitable reducing agents (e.g. reduced glutathione) and oxygen are available. Using electron spin resonance-spectroscopy and the oxygen-centered spin trap DEPMPO, we demonstrate that hydroxyl radicals (OH.) are formed in vitro by alloxan in the presence of glutathione (GSH) and chelated divalent iron. Furthermore, peroxidation of polyunsaturated fatty acids from phosphatidylcholine-containing liposomes with concomitant formation of malondialdehyde (MDA) was used as a further indicator for a preceding OH. formation. Melatonin, the main secretory product of the pineal gland, is an effective scavenger of OH.. The 50%-inhibitor concentration (IC50-value) for melatonin to scavenge OH. generated from the alloxan/GSH-reaction in the presence of ferrous ions was 23 micromol/L. In contrast to the ability to effectively scavenge OH., the potential of melatonin to prevent lipid peroxidation is considerably less pronounced.

'Classical' and 'new' diabetogens--comparison of their effects on isolated rat pancreatic islets in vitro.

This study compares functional and morphological alterations caused by application of alloxan, streptozotocin, xanthine oxidase/hypoxanthine (generation of reactive oxygen species), or S-nitroso-N-acetyl-D,L-penicillamine (SNAP, liberation of nitric oxide) to isolated rat pancreatic islets in vitro. In perifusion experiments, membrane leakage--detected by non-stimulated insulin release--was found after application of all drugs, but showed a substance-specific time pattern. Twenty-four hours after application of the classical diabetogens (alloxan or streptozotocin), potassium chloride- and glucose-stimulated insulin secretion were markedly reduced, while a persistent reduction was observed neither after exposure to xanthine oxidase/hypoxanthine, nor to SNAP. Morphological analysis of the islets revealed that nearly all beta-cells were destroyed following alloxan or streptozotocin treatment, while the majority of beta-cells were configured regularly after application of xanthine oxidase/hypoxanthine or SNAP. Necrotic cells found after xanthine oxidase/hypoxanthine usually differed in morphology from those observed after application of the classical diabetogens. While the former cells were characterised by swollen nuclei, the latter had shrunken nuclei with irregular condensed chromatin. Apoptosis was found only following nitric oxide exposure. Due to these differences, it seems unlikely that alloxan, streptozotocin, xanthine oxidase/hypoxanthine, and nitrix oxide have a common major feature in their toxic action.

A neuroendocrine releasing effect of melatonin in the brain of an insect, Periplaneta americana (L.).

Melatonin exists in nearly all organisms, but little is known of its function in non-vertebrates. Long-term perifusions as well as short-term batch incubations of brains and molting glands of the cockroach Periplaneta americana were used to test the influence of melatonin on the prothoracicotropic hormone, a glandotropic neuropeptide in the brain, which stimulates the production of the molting hormone ecdysone in the molting gland. Changes of ecdysteroid production in molting glands were determined by radioimmunoassay as ecdysone equivalents. Melatonin (10 nmol/L) was without effect on the prothoracic gland but stimulated the prothoracicotropic effect of brains in both in vitro investigations, long-term perifusions and short-term batch incubations. The effect was dose-dependent. The melatonin effect on the release of prothoracicotropic hormone in the brain was suppressed by luzindole (10 nmol/L), a pre-synaptic receptor antagonist of melatonin. The retro-cerebral complex (corpora cardiaca-corpora allata) did not seem to be involved in the effect of melatonin on the brain. Serotonin (10 nmol/L) suppressed the release of prothoracicotropic hormone. This is the first experimental evidence of a neurohormonal releasing effect of melatonin in the insect nervous system.

Evidence for a melatonin receptor within pancreatic islets of neonate rats: functional, autoradiographic, and molecular investigations.

In a recent perifusion investigation, we showed that the pineal secretory product melatonin reduces insulin secretion from isolated pancreatic islets of neonate rats stimulated with potassium chloride (KCl), glucose, and forskolin. This effect of melatonin was reproduced with doses ranging from 200 pmol/L to 5 micromol/L. Because it is generally accepted that melatonin exerts some of its biological effects through specific, high-affinity pertussis-toxin-sensitive G-protein-coupled receptors, we blocked the putative melatonin receptor of pancreatic islets using both the non-hydrolyzable guanosine triphosphate analog guanosine 5'-O-(3-thiotriphosphate) (GTPgammaS, 30 micromol/L) and the melatonin antagonist luzindole (10 micromol/L). Both GTPgammaS and luzindole caused a near normalization of the melatonin-induced inhibition of the forskolin-stimulated insulin secretion. To localize putative melatonin receptors within the pancreatic islets autoradiographic studies were additionally carried out. These investigations showed specific binding of 2-[125I]iodomelatonin, which were in exact correspondence with the localization of the islets. In addition, gray-level analysis showed that unlabeled melatonin was able to reduce the binding of 2-[125I]iodomelatonin in a dose-dependent manner. Concentrations of unlabeled melatonin of 10(-9) mol/L produced a 50% reduction in specific binding, whereas concentrations of 10(-6) mol/L displaced the binding completely. Likewise, the results of molecular investigations showed that the rat pancreas contains a melatonin receptor, since reverse transcription polymerase chain reaction (RT-PCR) experiments, using specific primers for the rat melatonin receptor Mel1a, showed that mRNA for this melatonin receptor type is expressed in pancreatic tissue of newborn rats. In summary, it may be said that our functional. autoradiographic, and molecular results indicate that the Mel1a receptor is located on the pancreatic islets, possibly in the beta cells.

Influence of melatonin on free radical-induced changes in rat pancreatic beta-cells in vitro.

Free radicals may produce cytotoxicity to pancreatic islets under pathophysiological conditions. The aim of our in vitro investigations was to compare functional and morphological changes in pancreatic beta-cells induced by reactive oxygen species (ROS) generated by alloxan or xanthine oxidase/hypoxanthine (XO/HX), respectively. We demonstrate that short-term exposure to alloxan or to XO/HX leads to a temporarily elevated insulin release from isolated pancreatic islets. On application of alloxan, this effect is caused by beta-cell necrosis and can be prevented by administration of melatonin, while in contrast, XO/HX did not lead to long-term morphological changes in the majority of the cells. Among the cells destroyed by alloxan, only necrosis could be detected, while in contrast, some apoptotic cells were identified by the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) reaction and electron microscopic examinations of cells treated with XO/HX. Melatonin was able to prevent the changes caused by alloxan, but failed to influence the alterations caused by XO/HX. Using electron spin resonance and lipid peroxidation assay, respectively, it was confirmed that melatonin effectively detoxifies hydroxyl radicals. Therefore, we believe that hydroxyl radicals are the toxic principle of alloxan, but not of XO/HX toxicity.

Pineal influence on annual nuclear volume changes in ventromedial hypothalamic nucleus (VMH) neurons of the male Wistar rat.

The ventromedial hypothalamic nucleus (VMH) regulates various autonomic, endocrine, and behavioral activities. These activities show annual changes, and the pineal gland is involved in their adjustment to environmental cues. Therefore, this study investigated whether the VMH belongs to the effector structures of the pineal gland. To abolish the rhythmic melatonin release, male Wistar rats were subjected to pinealectomy (PX) or ganglionectomy (sympathetic denervation of the pineal gland, GX) regularly at the beginning of any of the four seasons. Brains from animals of PX-, GX-, and sham-operated control groups were prepared 3 months later for measurement of the nuclear volume, which changes according to the general gene activity. At each of the four seasons, 2000 nuclei of VMH neurons stemming from 18 animals per group were measured to obtain both seasonal daily mean values and annual mean values, respectively, as well as to calculate annual curves of the nuclear volume using empirical regression and locally adjusted polynomial approximation. The major findings are the following. First, inactivation of the pineal function influences the nuclear activity of VMH neurons, (2) PX and GX mainly depress the nuclear activity, indicating that the pineal influence on the VMH may predominantly be a stimulatory one. Third, size and direction of the changes caused by PX and GX vary in a seasonally dependent manner. Fourth, the annual rhythm of the nuclear activity of the VMH is modified by PX and GX. To explain how the pineal effects on the VMH may be mediated, a possible inhibitory influence of the suprachiasmatic nucleus (SCN), which has been activated in the same animals following both PX and GX, is discussed. In conclusion, the results confirm that the nuclear activity of VMH neurons underlies pineal influences. This also indicates an involvement of the pineal gland in many VMH-regulated functions.

Alloxan acts as a prooxidant only under reducing conditions: influence of melatonin.

Depending on the availability of suitable reducing agents, alloxan can be either a prooxidant or an antioxidant. Alloxan and its reduced derivative, dialuric acid, act as a redox couple, driven by reduced glutathione (GSH) or L-cysteine, generating in vitro in the presence of oxygen, both superoxide radical and hydrogen peroxide. The production of superoxide radicals was shown by the appearance of lucigenin chemiluminescence (CL) as well as by the generation of formazan from nitroblue tetrazolium (NBT). The lucigenin CL as well as the NBT reduction was inhibited by superoxide dismutase and partially by catalase. Melatonin inhibited alloxan-mediated CL. In contrast, in the absence of reducing agents, alloxan is a scavenger of superoxide radicals formed by other reactions. Because of the high content of reducing compounds in the cell (e.g. glutathione), it is suggested that alloxan acts in vivo mainly as a generator of reactive oxygen species.

Evidence for a circadian rhythm of insulin release from perifused rat pancreatic islets.

This study aims to analyse a circadian rhythm of insulin secretion from isolated rat pancreatic islets in vitro and its potential modulation by melatonin, the concentrations of which change in vivo inversely to that of insulin. The circadian rhythm was evaluated in a perifusion system, adapted to the specific conditions of pancreatic islets. To determine rhythmicity of insulin secretion, 30-min fractions were collected continuously for investigative periods of 44 to 112 h. Insulin secretion in 10 experiments was analysed by using the MacAnova-program for period length (tau), the chi2-periodogram for test of significance (p < 0.001), and additionally the empirical cosine adaptation for amplitude and goodness-of-fit. Thereby a circadian pattern was observed with periods (tau) between 21.8 and 26.2 h. The period duration (mean +/- SEM) was 23.59 +/- 0.503 h, the overall mean insulin release 1038 +/- 13 pmol/l and the mean amplitude 88 +/- 17 pmol/l. Adding melatonin (10 nmol/l, t = 2 h) as a hormonal Zeitgeber during analysis of circadian insulin secretion phase-response studies show phase-shifts with approximately 9 h phase advance. Thereafter the circadian period was maintained, while the amplitude was enhanced. From this it is concluded that an endogenous circadian oscillator is located within the pancreatic islets of the rat that regulates circadian insulin secretion of the insulin-producing beta cells. The pacemaker is remarkably stable, because its periodicity is not affected by factors altering insulin secretion. In agreement with inhibitory influences of melatonin (range 0.5 nmol/l to 5 micromol/l) on the insulin response in vitro, the phase-responses support the contention that pancreatic beta cells may be targets for melatonin action.

Dynamic insulin secretion from perifused rat pancreatic islets.

Insulin secretion from isolated pancreatic islets of 8- to 12-day-old rats was investigated in a dynamic in vitro (perifusion) system. The aims of the study were (i) to describe a carefully controlled in vitro method to study the mechanism of insulin secretion and to analyse the effects and dynamic interactions of bioactive compounds on isolated rat pancreatic islets, (ii) to validate the method by comparing fundamental data on the functions of the islets obtained with this method to those collected with other techniques; and (iii) to find novel features of the control of insulin secretion. The method was carefully designed to maintain the functional capacity of the explanted cells. A functional standardization system was elaborated consisting of (i) analysis of the changes in the basal hormone secretion of the cells; (ii) evaluating responses to a standard, specific stimuli (50 mM glucose for 3 min); (iii) determining the alteration of the momentary size of the hormone pool with responses to KCl; and (iv) direct determination of the total intracellular hormone content from the extract of the column. The technique provides accurate quantitative data on the dynamic responses to biologically active compounds that act directly on the pancreatic islets. The islets maintained their full responsiveness for up to 7 days, and responses as close as in 1-min intervals could be distinguished. A linear dose-response relationship was found on the glucose-induced insulin release in case of 3-min stimulation with 4 and 500 mM of glucose (lin-log graph). Utilizing this method, we showed that no desensitization to glucose-induced insulin release can be observed if the responsiveness of the cells is properly maintained and the parameters of the stimulation are carefully designed. Exposure of the explanted islets to 10 microM acetylcholine or 30 mM arginine (Arg) induced a transitory elevation of insulin release similar in shape to that experienced after glucose stimulation. Norepinephrine (NE), dopamine (DA) and somatostatin (SS) did not induce any detectable alteration on the basal insulin secretion of the islets. However, 100 nM SS given together with 50 mM glucose, 30 mM Arg or 10 microM acetylcholine significantly reduced the insulin-releasing effect of these substances (by 75.5, 71.5 and 72.5%, respectively). At the same time, SS did not alter the insulin response of the islets to 100 mM elevation of K+ concentration. SS also inhibited glucose-induced insulin release in a dose-dependent way (ED50 = 22 nM). A similar dose-dependent inhibitory effect on glucose-induced insulin release was found with NE (ED50 = 89 nM) and DA (ED50 = 2.2 microM). gamma-Aminobutyric acid (GABA) did not influence insulin release under similar circumstances.

Influence of melatonin and serotonin on glucose-stimulated insulin release from perifused rat pancreatic islets in vitro.

Insulin plays a key role in the control of glucose homeostasis in mammals. Insulin secretion is regulated by a coordinated interplay of several factors. The role of the indoleamines in the control of insulin secretion has not been fully elucidated yet. The present study was addressed to investigate the function of melatonin and serotonin in the direct control of insulin secretion from the pancreatic islets. Explanted rat Langerhans' islets were treated with melatonin or serotonin while also being exposed to specific (glucose) or non-specific (KCl) stimulus either in a pulsatile or long-term manner in a perifusion system. Insulin content from the effluent tissue culture media was analyzed with RIA. Pulsatile administration of melatonin and serotonin alone did not alter the basal insulin secretion from the explanted islets even at pharmacological (5 microM) level. However, insulin response to specific (glucose) or non-specific (KCl) stimulus was significantly reduced while the islets were treated with melatonin (3 to 12 hr, 10 nM to 5 microM). This effect was reversible and repeatable. Both the start and end of the effect was rapid, evolving and disappearing within 10 min. On the other hand, under similar experimental protocol, serotonin (at 5 microM concentration) significantly enhanced both glucose and KCl stimulated insulin release. Since the effect of the non-specific stimulation (with KCl) was also altered, melatonin and serotonin seem to alter not only the release but also the synthesis of the insulin. Our data show that melatonin and serotonin have a direct effect on the insulin secretion from the pancreatic islets.

Circannual morphometric investigations of the rat suprachiasmatic nucleus after pinealectomy, ganglionectomy and thyroidectomy.

We karyometrically investigated the nucleus suprachiasmaticus (SCN) which had been manipulated in several ways in order to analyze the functional importance of the pineal gland on the primary pacemaker of mammals in the course of the year. The manipulation modes were (i) pinealectomy (PX), and (ii) sympathetic denervation of the pineal by bilateral extirpation of the upper cervical ganglia (ganglionectomy, GX). Additionally, the influence of the inactivated pineal, obtained through hypothyroidism which was realized by (iii) subtotal thyroidectomy (TX), was also investigated. With respect to annual oscillations the results of our investigations were able to illustrate the following. (1) The SCN consists of at least two parts (ventrolateral and dorsomedial) each with different functions and relationships. The nuclei of the ventrolateral cells are bigger and there are many indications both in our own research and from literature that the neurons of this part are involved in the generation of rhythms. (2) The size of the cell nuclei of the ventrolateral part shows annual patterns. In the course of the year the maxima of the nuclear volume were registered in March and September (bimodal pattern, equinox, L:D = 12:12). PX, GX or TX only negligibly changed the bimodal annual pattern. However, in comparison the smallest cell nuclei were registered in the winter (short day). The much smaller cell nuclei of the dorsomedial part likewise show bimodal patterns but only in the experimental groups. The control group of this part shows an unimodal annual curve with a minimum at long-day conditions (June, L:D = 16:8). (3) All manipulations which inactivated the pineal or reduced the content of melatonin (PX, GX, and TX) were followed by an increase (activation) of cell nuclei of the SCN. In contrast to these effects, an increase of thyroxine (by exposure to cold), has an opposite effect (not documented here). In conclusion these results indicate, without a doubt, that a negative correlation exists, functionally, between the SCN and the pineal (in the same annual experiment the nuclear size of the pinealocytes was increased, under short-day conditions in December, and decreased under long-day circumstances in June). Additionally, it could be shown that the degree of negative correlation between the pineal and the SCN was seasonally dependent. The lowest effects of PX, GX and TX were registered at short-day conditions (December, L:D = 8:16).