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ATP-sensitive potassium (KATP) Channels are known to be critical in the control of both insulin and glucagon secretion, the major hormones in the maintenance of glucose homeostasis. The involvement of [K.sub.ATP] channels in glucose uptake in the target tissues of insulin, however, is not known. We show here that Kir6.2(-/-) mice lacking Kir6.2, the pore-forming subunit of these channels, have no [K.sub.ATP] channel activity in their skeletal muscles. A 2-deoxy-[[sup.3]H]glucose uptake experiment in vivo showed that the basal and insulin-stimulated glucose uptake in skeletal muscles and adipose tissues of Kir6.2(-/-) mice is enhanced compared with that in wild-type (WT) mice. In addition, in vitro measurement of glucose uptake indicates that disruption of the channel increases the basal glucose uptake in Kir6.2(-/-) extensor digitorum longus and the insulin-stimulated glucose uptake in Kir6.2(-/-) soleus muscle. In contrast, glucose uptake in adipose tissue, measured in vitro, was similar in Kir6.2(-/-) and WT mice, suggesting that the increase in glucose uptake in Kir6.2(-/-) adipocytes is mediated by altered extracellular hormonal or neuronal signals altered by disruption of the [K.sub.ATP] channels. Kir6.2; SUR2; sulfonylurea; insulin; knockout mice

ATP-sensitive [K.sup.+] ([K.sub.ATP]) channels regulate many cellular functions by linking cell metabolism to membrane potential. We have generated [K.sub.ATP] channel-deficient mice by genetic disruption of Kir6.2, which forms the [K.sup.+] ion-selective pore of the channel. The homozygous mice ([Kir6.2.sup.-/-]) lack [K.sub.ATP] channel activity. Although the resting membrane potential and basal intracellular calcium concentrations ([[[Ca.sup.2+]].sub.i]) of pancreatic beta cells in [Kir6.2.sup.-/-] are significantly higher than those in control mice ([Kir6.2.sup.+/+]), neither glucose at high concentrations nor the sulfonylurea tolbutamide elicits a rise in [[[Ca.sup.2+]].sub.i], and no significant insulin secretion in response to either glucose or tolbutamide is found in [Kir6.2.sup.-/-], as assessed by perifusion and batch incubation of pancreatic islets. Despite the defect in glucose-induced insulin secretion, [Kir6.2.sup.-/-] show only mild impairment in glucose tolerance. The glucose-lowering effect of insulin, as assessed by an insulin tolerance test, is increased significantly in [Kir6.2.sup.-/-], which could protect [Kir6.2.sup.-/-] from developing hyperglycemia. Our data indicate that the [K.sub.ATP] channel in pancreatic beta cells is a key regulator of both glucose- and sulfonylurea-induced insulin secretion and suggest also that the [K.sub.ATP] channel in skeletal muscle might be involved in insulin action.

ATP-sensitive [K.sup.+][ (K.sub.KAT]P) channels are known to play important roles in various cellular functions, but the direct consequences of disruption of [K.sub.ATP] channel function are largely unknown. We have generated transgenic mice expressing a dominant-negative form of the [K.sub.ATP] channel subunit Kir6.2 (Kir6.2G132S, substitution of glycine with serine at position 132) in pancreatic beta cells. Kir6.2G132S transgenic mice develop hypoglycemia with hyperinsulinemia in neonates and hyperglycemia with hypoinsulinemia and decreased beta cell population in adults. [K.sub.ATP] channel function is found to be impaired in the beta cells of transgenic mice with hyperglycemia. In addition, both resting membrane potential and basal calcium concentrations are shown to be significantly elevated in the beta cells of transgenic mice. We also found a high frequency of apoptotic beta cells before the appearance of hyperglycemia in the transgenic mice, suggesting that the [K.sub.ATP] channel might play a significant role in beta cell survival in addition to its role in the regulation of insulin secretion.

Abstract Background Nocardiosis is an unusual infection in companion animals characterized by suppurative to pyogranulomatous lesions, localized or disseminated. Cutaneous-subcutaneous, pulmonary and systemic signs are observed in feline nocardiosis. However, osteomyelitis is a rare clinical manifestation in cats. Nocardia cyriacigeorgica (formerly N. asteroides sensu stricto), Nocardia brasiliensis, Nocardia otitidiscaviarum, and Nocardia nova are the most common pathogenic species identified in cats, based on recent molecular classification (16S rRNA gene). The present report is, to our knowledge, the first case of mandibular osteomyelitis in a cat caused by Nocardia africana, diagnosed based upon a combination of methods, including molecular techniques. Case presentation A one-year-old non-neutered female cat, raised in a rural area, was admitted to the Companion Animal Hospital-PUCPR, São José dos Pinhais, State of Paraná, Brazil, with a history a progressive facial lesion, difficulty apprehending food, loss of appetite, apathy and emaciation. Clinical examination showed fever, submandibular lymphadenitis, and a painless, 8 cm diameter mass, which was irregularly-shaped, of firm consistency, and located in the region of the left mandible. The skin around the lesion was friable, with diffuse inflammation (cellulitis), multiple draining sinuses, and exudation of serosanguinous material containing whitish “sulfur” granules. Diagnosis was based initially in clinical signs, microbiological culture, cytological, and histopathological findings, and radiographic images. Molecular sequencing of 16S rRNA of isolate allowed diagnosis of Nocardia africana. Despite supportive care and antimicrobial therapy based on in vitro susceptibility testing the animal died. Conclusion The present report describes a rare clinical case of feline osteomyelitis caused by Nocardia africana, diagnosed based upon a combination of clinical signs, microbiological culture, cytological and histopathological findings, radiographic images, and molecular methods. The use of modern molecular techniques constitutes a quick and reliable method for Nocardia species identification, and may contribute to identification to new species of Nocardia that are virulent in cats.