Incidence, Mechanisms, and Characteristics of Injuries in Pole Dancers: A Prospective Cohort Study.

OBJECTIVE: Pole dancing is a challenging physical activity. Prospective injury studies in pole dancing are lacking. The aim of this study was to describe the incidence, mechanisms, and characteristics of injuries in pole dancers. METHODS: A total of 66 pole dancers from 41 studios across Australia were prospectively followed over 12 months. An intake questionnaire was administered including items on pole dancers' demographics and training characteristics. Exposure was assessed using a daily online training diary. Self-reported injury data were collected via an incident report form and subsequently coded using the Orchard Sports Injury Classification System. Injuries occurring during pole-specific and pole-related activities were included in the analyses. RESULTS: The sample included 63 females and 3 males, mean age 32.3 ± 8.9 years and mean pole training experience 3.5 ± 2.8 years. 25 of 66 participants completed the full study. The 1-year incidence of all new injuries was 8.95/1,000 exposure hours (95% CI 6.94 - 10.96), 7.65/1,000 hrs (95% CI 5.79 - 9.51) for pole-specific injuries and 1.29/1,000 hrs (95% CI 0.53 - 2.06) for pole-related injuries. A total of 103 injuries occurred, 62.1% of which were sudden onset and 37.9% gradual onset. Mechanism of onset included 54.4% acute and 45.6% repetitive in nature. Shoulder (20.4%) and thigh (11.7%, majority ham¬string) were the most reported anatomic injury sites. Non-contact mechanisms accounted for the majority of injuries (57.3%). The most reported primary contributor to injury onset at the shoulder were manoeuvres characterised by loaded internal humeral rotation (33.3%), and at the hamstring were manoeuvres and postures involving front splits (100.0%). CONCLUSION: The findings indicate that pole dancers are at high risk for injuries. Future research is needed to understand the biomechani¬cal demand of manoeuvres and training characteristics of pole dancing (e.g., workload and recovery) to guide the development of preventative interventions, particularly targeted toward the shoulder and hamstring.

Stellarators Resist Turbulent Transport on the Electron Larmor Scale.

Electron temperature gradient (ETG)-driven turbulence, despite its ultrafine scale, is thought to drive significant thermal losses in magnetic fusion devices-but what role does it play in stellarators? The first numerical simulations of ETG turbulence for the Wendelstein 7-X stellarator, together with power balance analysis from its initial experimental operation phase, suggest that the associated transport should be negligible compared to other channels. The effect, we argue, originates essentially from the geometric constraint of multiple field periods, a generic feature of stellarators.

Oxygen supply by photosynthesis to an implantable islet cell device.

Transplantation of islet cells is an effective treatment for type 1 diabetes with critically labile metabolic control. However, during islet isolation, blood supply is disrupted, and the transport of nutrients/metabolites to and from the islet cells occurs entirely by diffusion. Adequate oxygen supply is essential for function/survival of islet cells and is the limiting factor for graft integrity. Recently, we developed an immunoisolated chamber system for transplantation of human islets without immunosuppression. This system depended on daily oxygen supply. To provide independence from this external source, we incorporated a novel approach based on photosynthetically-generated oxygen. The chamber system was packed sandwich-like with a slab of immobilized photosynthetically active microorganisms (Synechococcus lividus) on top of a flat light source (LEDs, red light at 660 nm, intensity of 8 µE/m(2)/s). Islet cells immobilized in an alginate slab (500-1,000 islet equivalents/cm(2)) were mounted on the photosynthetic slab separated by a gas permeable silicone rubber-Teflon membrane, and the complete module was sealed with a microporous polytetrafluorethylene (Teflon) membrane (pore size: 0.4 µm) to protect the contents from the host immune cells. Upon illumination, oxygen produced by photosynthesis diffused via the silicone Teflon membrane into the islet compartment. Oxygen production from implanted encapsulated microorganisms was stable for 1 month. After implantation of the device into diabetic rats, normoglycemia was achieved for 1 week. Upon retrieval of the device, blood glucose levels returned to the diabetic state. Our results demonstrate that an implanted photosynthetic bioreactor can supply oxygen to transplanted islets and thus maintain islet viability/functionality.

Reanalysis of study of pancreatic effects of incretin therapy: methodological deficiencies.

A recently published study by Butler et al. concluded that incretin treatment had adverse effects on the human type 2 diabetic pancreas including 'a marked expansion of the exocrine and endocrine pancreatic compartments, the former being accompanied by increased proliferation and dysplasia and the latter by α-cell hyperplasia with the potential for evolution into neuroendocrine tumours'. Incretin therapy has become widely used for type 2 diabetes, so these conclusions have instigated major concerns with regard to patient safety. We reassessed both the clinical case information and virtual microscopy images of the same 34 cases that were used in the Butler study as well as Network for Pancreatic Organ Donation (nPOD) cases that were not included. Whereas we would like to stress that it is important to investigate in depth any indication that incretin treatment may lead to inflammation or dysplasia in the pancreas, we find that the data presented in the Butler paper have serious methodological deficiencies that preclude any meaningful conclusions.

Islet encapsulation: advances and obstacles.

It has been known for decades that encapsulation can protect transplanted islets from immune destruction in rodents, but it has proved difficult to extend this success to large animals and humans. A new study in this issue by Jacobs-Tulleneers-Thevissen et al (doi: 10.1007/s00125-013-2906-0 ) advances the field by showing that human islets contained in alginate capsules can function very well, not only in the peritoneal cavity of mice, but also in a human with type 1 diabetes. Many obstacles must still be overcome, but this technology has the potential to safely protect transplanted beta cells from autoimmunity and allorejection.

Photo recall reaction following the use of vancomycin.

Drug-induced erythema in the distribution of prior sunburn is called photo recall. Although more commonly induced by chemotherapeutics, it has also been associated with antibiotics such as ampicillin, cephalosporin, and gentamicin. Vancomycin has not been previously reported as a causal agent. This case report describes photo recall in a fifty-three year old woman undergoing treatment with vancomycin for a MRSA infection of the spine. Her eruption followed a photo-distributed pattern on the chest, shoulders, neck and face sparing areas previously protected by her bathing suit. Of note, she reported a similar eruption following vancomycin two years prior.

Rat neonatal beta cells lack the specialised metabolic phenotype of mature beta cells.

AIMS/HYPOTHESIS: Fetal and neonatal beta cells have poor glucose-induced insulin secretion and only gain robust glucose responsiveness several weeks after birth. We hypothesise that this unresponsiveness is due to a generalised immaturity of the metabolic pathways normally found in beta cells rather than to a specific defect. METHODS: Using laser-capture microdissection we excised beta cell-enriched cores of pancreatic islets from day 1 (P1) neonatal and young adult Sprague-Dawley rats in order to compare their gene-expression profiles using Affymetrix U34A microarrays (neonatal, n = 4; adult, n = 3). RESULTS: Using dChip software for analysis, 217 probe sets for genes/38 expressed sequence tags (ESTs) were significantly higher and 345 probe sets for genes/33 ESTs significantly lower in beta cell-enriched cores of neonatal islets compared with those of adult islets. Among the genes lower in the neonatal beta cells were key metabolic genes including mitochondrial shuttles (malate dehydrogenase, glycerol-3-phosphate dehydrogenase and glutamate oxalacetate transaminase), pyruvate carboxylase and carnitine palmitoyl transferase 2. Differential expression of these enzyme genes was confirmed by quantitative PCR on RNA from isolated neonatal (P2 until P28) and adult islets and with immunostaining of pancreas. Even by 28 days of age some of these genes were still expressed at lower levels than in adults. CONCLUSIONS/INTERPRETATION: The lack of glucose responsiveness in neonatal islets is likely to be due to a generalised immaturity of the metabolic specialisation of pancreatic beta cells.

Mafa expression enhances glucose-responsive insulin secretion in neonatal rat beta cells.

AIM/HYPOTHESIS: Neonatal beta cells lack glucose-stimulated insulin secretion and are thus functionally immature. We hypothesised that this lack of glucose responsiveness results from a generalised low expression of genes characteristic of mature functional beta cells. Important glucose-responsive transcription factors, Mafa and Pdx1, regulate genes involved in insulin synthesis and secretion, and have been implicated in late beta cell development. The aim of this study was to assess whether Mafa and/or Pdx1 regulates the postnatal functional maturation of beta cells. METHODS: By quantitative PCR we evaluated expression of these and other beta cell genes over the first month compared with adult. After infection with adenovirus expressing MAFA, Pdx1 or green fluorescent protein (Gfp), P2 rat islets were evaluated by RT-PCR and insulin secretion with static incubation and reverse haemolytic plaque assay (RHPA). RESULTS: At P2 most beta cell genes were expressed at about 10% of adult, but by P7 Pdx1 and Neurod1 no longer differ from adult; by contrast, Mafa expression remained significantly lower than adult through P21. Overexpression of Pdx1 increased Mafa, Neurod1, glucokinase (Gck) mRNA and insulin content but failed to enhance glucose responsiveness. Similar overexpression of MAFA resulted in increased Neurod1, Nkx6-1, Gck and Glp1r mRNAs and no change in insulin content but, importantly, acquisition of glucose-responsive insulin secretion. Both the percentage of secreting beta cells and the amount of insulin secreted per beta cell increased, approaching that of adult beta cells. CONCLUSIONS/INTERPRETATION: In the process of functional maturation acquiring glucose-responsive insulin secretion, neonatal beta cells undergo a coordinated gene expression programme in which Mafa plays a crucial role.

Per-arnt-sim (PAS) domain-containing protein kinase is downregulated in human islets in type 2 diabetes and regulates glucagon secretion.

AIMS/HYPOTHESIS: We assessed whether per-arnt-sim (PAS) domain-containing protein kinase (PASK) is involved in the regulation of glucagon secretion. METHODS: mRNA levels were measured in islets by quantitative PCR and in pancreatic beta cells obtained by laser capture microdissection. Glucose tolerance, plasma hormone levels and islet hormone secretion were analysed in C57BL/6 Pask homozygote knockout mice (Pask-/-) and control littermates. Alpha-TC1-9 cells, human islets or cultured E13.5 rat pancreatic epithelia were transduced with anti-Pask or control small interfering RNAs, or with adenoviruses encoding enhanced green fluorescent protein or PASK. RESULTS: PASK expression was significantly lower in islets from human type 2 diabetic than control participants. PASK mRNA was present in alpha and beta cells from mouse islets. In Pask-/- mice, fasted blood glucose and plasma glucagon levels were 25 ± 5% and 50 ± 8% (mean ± SE) higher, respectively, than in control mice. At inhibitory glucose concentrations (10 mmol/l), islets from Pask-/- mice secreted 2.04 ± 0.2-fold (p < 0.01) more glucagon and 2.63 ± 0.3-fold (p < 0.01) less insulin than wild-type islets. Glucose failed to inhibit glucagon secretion from PASK-depleted alpha-TC1-9 cells, whereas PASK overexpression inhibited glucagon secretion from these cells and human islets. Extracellular insulin (20 nmol/l) inhibited glucagon secretion from control and PASK-deficient alpha-TC1-9 cells. PASK-depleted alpha-TC1-9 cells and pancreatic embryonic explants displayed increased expression of the preproglucagon (Gcg) and AMP-activated protein kinase (AMPK)-alpha2 (Prkaa2) genes, implying a possible role for AMPK-alpha2 downstream of PASK in the control of glucagon gene expression and release. CONCLUSIONS/INTERPRETATION: PASK is involved in the regulation of glucagon secretion by glucose and may be a useful target for the treatment of type 2 diabetes.

Why pancreatic islets should be regarded and regulated like organs.

There are strong reasons to say that pancreatic islets are organs before they are isolated and that they should be considered to be organs once transplanted. Thus, taking into account how much we have learned about the structure and function of islet micro-organs, it seems highly illogical to on one hand consider autologous islets be regulated as organ transplants and alloislets to be regulated with the very restrictive rules used for cell transplantation. It is particularly problematic that this policy has led to restrictions that have made it next to impossible for transplants of alloislets to be carried out in the US, which is a very sad situation for the country that made so many of the advances that brought islet transplantation to the clinic.

Rat islet cell aggregates are superior to islets for transplantation in microcapsules.

AIMS/HYPOTHESIS: Islet transplantation is a promising treatment for type 1 diabetes but is hampered by a shortage of donor human tissue and early failure. Research on islet cell transplantation includes finding new sources of cells and immunoisolation to protect from immune assault and tumourigenic potential. Small islet cell aggregates were studied to determine if their survival and function were superior to intact islets within microcapsules because of reduced oxygen transport limitation and inflammatory mediators. METHODS: Islet cell aggregates were generated by dispersing rat islets into single cells and allowing them to re-aggregate in culture. Rat islets and islet cell aggregates were encapsulated in barium alginate capsules and studied when cultured in low (0.5% or 2%) or normal (20%) oxygen, or transplanted into mice. RESULTS: Encapsulated islet cell aggregates were able to survive and function better than intact islets in terms of oxygen-consumption rate, nuclei counts, insulin-to-DNA ratio and glucose-stimulated insulin secretion. They also had reduced expression of pro-inflammatory genes. Islet cell aggregates showed reduced tissue necrosis in an immunodeficient transplant model and a much greater proportion of diabetic xenogeneic transplant recipients receiving islet cell aggregates (tissue volume of only 85 islet equivalents) had reversal of hyperglycaemia than recipients receiving intact islets. CONCLUSIONS/INTERPRETATION: These aggregates were superior to intact islets in terms of survival and function in low-oxygen culture and during transplantation and are likely to provide more efficient utilisation of islet tissue, a finding of importance for the future of cell therapy for diabetes.

Palmitate induces a pro-inflammatory response in human pancreatic islets that mimics CCL2 expression by beta cells in type 2 diabetes.

AIMS/HYPOTHESIS: Beta cell failure is a crucial component in the pathogenesis of type 2 diabetes. One of the proposed mechanisms of beta cell failure is local inflammation, but the presence of pancreatic islet inflammation in type 2 diabetes and the mechanisms involved remain under debate. METHODS: Chemokine and cytokine expression was studied by microarray analysis of laser-capture microdissected islets from pancreases obtained from ten non-diabetic and ten type 2 diabetic donors, and by real-time PCR of human islets exposed to oleate or palmitate at 6 or 28 mmol/l glucose. The cellular source of the chemokines was analysed by immunofluorescence of pancreatic sections from individuals without diabetes and with type 2 diabetes. RESULTS: Microarray analysis of laser-capture microdissected beta cells showed increased chemokine and cytokine expression in type 2 diabetes compared with non-diabetic controls. The inflammatory response in type 2 diabetes was mimicked by exposure of non-diabetic human islets to palmitate, but not to oleate or high glucose, leading to the induction of IL-1beta, TNF-alpha, IL-6, IL-8, chemokine (C-X-C motif) ligand 1 (CXCL1) and chemokine (C-C motif) ligand 2 (CCL2). Interference with IL-1beta signalling abolished palmitate-induced cytokine and chemokine expression but failed to prevent lipotoxic human islet cell death. Palmitate activated nuclear factor kappaB (NF-kappaB) in human pancreatic beta and non-beta cells, and chemically induced endoplasmic reticulum stress caused cytokine expression and NF-kappaB activation similar to that occurring with palmitate. CONCLUSIONS/INTERPRETATION: Saturated-fatty-acid-induced NF-kappaB activation and endoplasmic reticulum stress may contribute to IL-1beta production and mild islet inflammation in type 2 diabetes. This inflammatory process does not contribute to lipotoxicity ex vivo, but may lead to local chemokine release.

Single pancreatic beta cells co-express multiple islet hormone genes in mice.

AIMS/HYPOTHESIS: It is widely accepted that production of insulin, glucagon, somatostatin and pancreatic polypeptide in islet cells is specific to beta, alpha, delta and pancreatic polypeptide cells, respectively. We examined whether beta cells express other genes encoding islet hormones. METHODS: Nested RT-PCR was performed on single beta cells of transgenic mice with green fluorescent protein (GFP) driven by mouse insulin I promoter (MIP-GFP). RESULTS: Only 55% of adult beta cells expressed the insulin gene alone, while others expressed two or more islet hormone genes; 4% expressed all four hormone genes. In embryonic and neonatal cells, 60% to 80% of GFP(+) cells co-expressed pancreatic polypeptide and insulin genes in contrast to 29% in adult. To clarify cell fate, we conducted lineage tracing using rat insulin II promoter-cre mice crossed with reporter mice Gt(ROSA)26Sor-loxP-flanked STOP-cassette-GFP. All GFP(+) cells expressed insulin I and II genes, and showed similar heterogeneity of co-expression to that seen in MIP-GFP mice. Although we report expression of other hormone genes in a significant proportion of beta cells, our lineage tracing results demonstrate that after inducing InsII (also known as Ins2) expression, beta cell progenitors do not redifferentiate to non-beta cells. CONCLUSIONS/INTERPRETATION: This study shows co-expression of multiple hormone genes in beta cells of adult mice as well as in embryos and neonates. This finding could: (1) represent residual expression from beta cell precursors; (2) result from alternative developmental pathways for beta cells; or (3) denote the differentiation potential of these cells. It may be linked to functional heterogeneity. This heterogeneity in gene expression may provide a means to characterise the functional, cellular and developmental heterogeneity seen in beta cells.

Reformation of the Electron Internal Transport Barrier with the Appearance of a Magnetic Island.

When realising future fusion reactors, their stationary burning must be maintained and the heat flux to the divertor must be reduced. This essentially requires a stationary internal transport barrier (ITB) plasma with a fast control system. However, the time scale for determining the position of the foot point of an ITB is not clearly understood even though its understanding is indispensable for fast profile control. In this study, the foot point of the electron ITB (eITB) was observed to be reformed at the vicinity of a magnetic island when the island started to form. In addition, the enhanced confinement region was observed to expand during the eITB formation according to the radial movement of the magnetic island toward the outer region. Compared to the time scales of the local heat transport, the faster time scales of the movement of the eITB foot point immediately after island formation (~0.5 ms) suggest the importance of the magnetic island for plasma profile control to maintain stationary burning.

Differentiation of COPAS-sorted non-endocrine pancreatic cells into insulin-positive cells in the mouse.

AIMS/HYPOTHESIS: The regenerative process in the pancreas is of particular interest, since insulin-producing beta cells are lost in diabetes. Differentiation of new beta cells from pancreatic non-endocrine cells has been reported in vivo and in vitro, a finding that implies the existence of pancreatic stem/progenitor cells. However, while tissue-specific stem cells are well documented in skin, intestine and testis, pancreatic stem cells have been elusive. We hypothesised that pancreatic stem/progenitor cells within the non-endocrine fraction could be a source of new islets in vitro. METHODS: To test if there were such cells within the pancreas, we generated pancreatic cell aggregates from tissue remaining after islet isolation from mouse insulin promoter 1-green fluorescent protein (MIP-GFP) mice. To eliminate any contamination of insulin-positive cells, we deleted all GFP-positive aggregates using COPAS Select and cultured with Matrigel. Immunohistochemistry, quantitative real-time PCR and single-cell nested RT-PCR were performed to confirm formation of insulin-producing cells. RESULTS: The GFP-negative cells were expanded as monolayers and then differentiated into three-dimensional cystic structures. After 1 week of culture, GFP-positive cells were found as clusters or single cells. By quantitative real-time PCR, no insulin mRNA was detected immediately after COPAS sorting, but after differentiation insulin mRNA of the whole preparation was 1.91 +/- 0.31% that of purified MIP-GFP beta cells. All GFP-positive cells expressed insulin 1; most expressed insulin 2, pancreas duodenum homeobox-1 and cytokeratin 19 by single cell nested RT-PCR. CONCLUSIONS/INTERPRETATION: Our data support the concept that within the exocrine (acinar and ductal) pancreas of the adult mouse there are cells that can give rise to insulin-positive cells in vitro.

Towards better understanding of the contributions of overwork and glucotoxicity to the beta-cell inadequacy of type 2 diabetes.

Type 2 diabetes (T2D) is characterized by reduction of beta-cell mass and dysfunctional insulin secretion. Understanding beta-cell phenotype changes as T2D progresses should help explain these abnormalities. The normal phenotype should differ from the state of overwork when beta-cells compensate for insulin resistance to keep glucose levels normal. When only mild hyperglycaemia develops, beta-cells are subjected to glucotoxicity. As hyperglycaemia becomes more severe, so does glucotoxicity. beta-Cells in all four of these situations should have separate phenotypes. When assessing phenotype with gene expression, isolated islets have artefacts resulting from the trauma of isolation and hypoxia of islet cores. An advantage comes from laser capture microdissection (LCM), which obtains beta-cell-rich tissue from pancreatic frozen sections. Valuable data can be obtained from animal models, but the real goal is human beta-cells. Our experience with LCM and gene arrays on frozen pancreatic sections from cadaver donors with T2D and controls is described. Although valuable data was obtained, we predict that the approach of taking fresh samples at the time of surgery is an even greater opportunity to markedly advance our understanding of how beta-cell phenotype evolves as T2D develops and progresses.

Malic enzyme is present in mouse islets and modulates insulin secretion.

AIMS/HYPOTHESIS: The pyruvate-malate shuttle is a metabolic cycle in pancreatic beta cells and is important for beta cell function. Cytosolic malic enzyme (ME) carries out an essential step in the shuttle by converting malate to pyruvate and generating NADPH. In rat islets the pyruvate-malate shuttle may regulate insulin secretion and it has been shown to play a critical role in adaptation to obesity and insulin resistance. However, ME has not been demonstrated in mouse islets and three reports indicate that mouse islets contain no ME activity. If mouse islets lack ME, rat and mouse islets must regulate insulin secretion by different mechanisms. METHODS: We measured ME activity by a fluorometric enzymatic assay and Me mRNA by real-time PCR. ME activity was also measured in streptozotocin-treated mouse islets. FACS-purified beta cells were obtained from MIP-GFP mouse islets, agouti-L obese mouse islets and mouse beta cell line MIN-6. Insulin secretion and NADPH/NADP(+) ratios were measured in Me siRNA-treated beta cells. RESULTS: ME activity and Me mRNA were present in C57BL/6 mouse islets. ME activity was reduced in streptozotocin-treated mouse islets. ME activity was also measurable in FACS-purified mouse beta cells. In addition, ME activity was significantly increased in obese agouti-L mouse islets and the mouse MIN-6 cell line. Me siRNA inhibited ME activity and reduced glucose-stimulated insulin secretion and also inhibited NADPH products. CONCLUSIONS/INTERPRETATION: Mouse islets contain ME, which plays a significant role in regulating insulin secretion.

Phased array Doppler reflectometry at Wendelstein 7-X.

A passive phased array Doppler reflectometry system has recently been installed in the Wendelstein-7X stellarator. In contrast to conventional Doppler reflectometry systems, the microwave beam can be steered on short time scales in the measurement plane perpendicular to the magnetic field in the range of ±25° without mechanical steering components. This paper characterizes the design and properties of the phased array antenna system and presents the first measurement results from the latest OP1.2a campaign.

Adrenergic modulation of pancreatic A, B, and D cells alpha-Adrenergic suppression and beta-adrenergic stimulation of somatostatin secretion, alpha-adrenergic stimulation of glucagon secretion in the perfused dog pancreas.

The effects of adrenergic substances on pancreatic insular secretions were studied in a completely isolated canine pancreas with exclusion of the duodenum from the perfusion circuit. To ensure adequate blockade, blockers were infused before agonists. A dose range of beta-receptor blockade was tested, and putative alpha-adrenergic effects were confirmed by combined alpha- and beta-adrenergic receptor blockade.beta-Adrenergic agonism (2 ng/ml isoproterenol) induced a mean integrated increase of 79+/-20% in somatostatin secretion, whereas glucagon and insulin secretion were increased by 185+/-45 and 495+/-146%, respectively. The stimulations of D, A, and B cells were abolished by propranolol.alpha-Adrenergic agonism (10 ng/ml epinephrine) after beta-adrenergic blockade) moderately decreased somatostatin (-37+/-7%) secretion, moderately increased glucagon (91+/-19%), and markedly decreased insulin (-85+/-3%) release. Similar effects on D-, A-, and B-cell secretion were induced with 2 ng/ml epinephrine or 10 ng/ml norepinephrine after beta-adrenergic blockade. The alpha-adrenergic effects on the D and A cell were abolished by either phentolamine or by phenoxybenzamine. This study showed that there are indeed alpha-adrenergic receptors on A cells and that the secretion of glucagon, a "stress" hormone, was stimulated either by alpha- or beta-adrenergic receptor agonism. D-cell secretion, like that of the B cell, was inhibited by alpha-adrenergic agonism and was stimulated by beta-adrenergic agonism. However, beta-adrenergic-induced changes in D-cell secretion were smaller in magnitude than those of B-cell secretion.

Sustained oscillations of insulin, glucagon, and somatostatin from the isolated canine pancreas during exposure to a constant glucose concentration.

Canine pancreata were perfused in vitro to examine whether hormone cycles could be demonstrated without hepatic or central nervous influence. Insulin, glucagon, and somatostatin demonstrated regular sustained cyclic secretion from the in vitro canine pancreas. Oscillations were noted for over 200 min during the infusion of a constant glucose concentration. Insulin demonstrated a 10-min period with a range of 8-12 min/cycle. Somatostatin had a 10-min period with a range of 8-11 min. Glucagon had a period of 8.6 min with range of 6-10 min. These periods do not allow glucagon to be consistently 90 degrees out of phase with insulin and somatostatin. When glucose was increased from 88 to 200 mg/dl, insulin cycles persisted but on an elevated base line, demonstrating that cycles react to glucose changes but are not dependent upon them. Cycles were disrupted by infusions of dopamine, apomorphine, epinephrine, and acetylcholine, but were reestablished. Autonomic blockade by both single and combined infusions of atropine (cholinergic), propranolol, and dibenzyline (adrenergic) had no effect on cycles. These results suggest that, in vitro, there is an intrinsic rhythm of hormone secretion by the pancreas despite a constant glucose level. The production of in vitro cycles requires the presence of a driving oscillator or pacemaker within the pancreas and the coordination of islets by pace-maker-islet communication, presumably by a non-adrenergic neural system. In vitro oscillations may Indicate that the pancreas is the driver or Zeitgeber of in vivo glucose-insulin cycles.