Complete genome sequence of Chlamydia psittaci АМК-16, isolated from a small ruminant in the Middle Volga Region, Russia

We report the complete genome sequence of the Chlamydia psittaci АМК-16, recovered from the aborted caprine fetus during a case of chlamydia infection. This 1,152,497-bp genome with 7,552-bp cryptic plasmid provides novel insights into the genetic diversity of chlamydia agent strains particularly those causing the infection in small ruminants.

Development of Biodegradable Polymer Blends Based on Chitosan and Polylactide and Study of Their Properties

Composite materials of various compositions based on chitosan and polylactide were obtained in the form of films or porous bulk samples. Preliminarily, poly-d,l-lactide was synthesized by ring-opening polymerization of lactide in the presence of Ti(OⁱPr)₄. Polylactide obtained at components molar ratio [lactide]:[Ti(OⁱPr)₄] = 3:1 had the best molecular weight characteristics at a high product yield. Film composition with the weight ratio chitosan-polylactide 50:50 wt. % was characterized by high mechanical properties. The value of the tensile strength of the film was 72 MPa with a deformation of 10% and an elastic modulus of 40 GPa, which is higher than the tensile strength of native chitosan by ~three times. The observed effect is a consequence of the fact that the chitosan-polylactide composite has an amorphous structure in contrast to the native chitosan, which is proved by X-ray phase analysis. An increase in the elastic modulus of the composite in the range of 20–60 °C in contrast to polylactide was found by dynamic mechanical analysis. The observed effect is apparently caused by the formation of hydrogen bonds between functional groups of chitosan and polylactide which is possible through an increase in polylactide segments mobility when its glass transition temperature is reached. The composite material is biocompatible and characterized by high cellular adhesion of fibroblasts (line hTERT BJ-5ta). Their growth on the composite surface was 2.4 times more active than on native chitosan. Bulk porous samples of the composition with the weight ratio chitosan-polylactide 50:50 wt. % were synthesized by original method in ammonium bicarbonate presence. Samples were characterized by a porosity of 82.4% and an average pore size of 100 microns. The biodegradability of such material and absence of inflammatory processes were proven in vivo by the blood parameters of experimental animals. Thus, materials with the weight ratio chitosan-polylactide 50:50 wt. % are promising for potential use in regenerative medicine.

First Detection of Chlamydia trachomatis 'Swedish' Variant (nvCT) in a Russian Couple with Infertility

BACKGROUND

Chronic asymptomatic chlamydial genital infection caused by the wild-type of Chlamydia trachomatis (wtCT) is the most common bacterial infection causing human infertility. The novel 'Swedish' variant of С.trachomatis (nvCT) which contains a 377 bp deletion in a region that is specifically targeted in some nucleic acid amplification tests may impede diagnosis.

OBJECTIVE

The study aimed to investigate whether nvCT may be a possible cause of infertility in a couple undergoing in vitro fertilization (IVF).

METHOD

Clinical specimens from both genital (urethra and cervix) and extra-genital sites (pharynx, conjunctive, blood) of a couple who experienced multiple unsuccessful attempts at pregnancy by natural fertilization and IVF procedures were analyzed before and after antibiotic therapy. Both partners had neither somatic nor endocrinal abnormality nor any clinically apparent genital manifestations of Chlamydia or other STIs.

RESULTS

Before antibiotic therapy all the samples of the Female Partner (FP) contained DNA of only the nvCT. After antibiotic therapy, additionally, DNA of wtCT of genovars E and D was detected in specimens from her conjunctiva and oropharynx. All samples of the Male Partner (MP) revealed co-infection of nvCT and wtCT. Identical SNP within the variable region 4 (VD4) of the ompA gene confirmed the identity of the wtCT strains found in both partners. The FP had a positive anti-chlamydial IgG titer. The sperm characteristics of the MP, motility (immotile spermatozoa was 51.1% versus 21.6%) and vitality (46% versus 68%) declined progressively, and the MP anti-chlamydial IgG titer was negative.

CONCLUSION

Infertility in this couple may have been caused by chronic asymptomatic and persistent nvCT-associated infection that was complicated by re-infection later with wtCT. This study illustrates the importance of including detection methods for nvCT strains in the investigation of infertility cases.

Interaction of hematopoietic CD34+ CD45+ stem cells and cancer cells stimulated by TGF‑β1 in a model of glioblastoma in vitro

The majority of modern treatment methods for malignant brain tumors are not sufficiently effective, with a median survival time varying between 9 and 14 months. Metastatic and invasive processes are the principal characteristics of malignant tumors. The most important pathogenic mechanism is epithelial‑mesenchymal transition (EMT), which causes epithelial cells to become more mobile, and capable of invading the surrounding tissues and migrating to distant organs. Transforming growth factor‑β1 (TGF‑β1) serves a key role in EMT‑inducing mechanisms. The current study presented the interaction between hematopoietic stem cells and glioblastoma cells stimulated by TGF‑β1 in vitro. The materials for the study were hematopoietic progenitor cell antigen CD34+ hematopoietic stem cells (HSCs) and U87 glioblastoma cells. Cell culture methods, automated monitoring of cell‑cell interactions, confocal laser microscopy, flow cytometry and electron microscopy were used. It was demonstrated that U87 cells have a complex communication system, including adhesive intercellular contacts, areas of interdigitation with dissolution of the cytoplasm, cell fusion, communication microtubes and microvesicles. TGF‑β1 affected glioblastoma cells by modifying the cell shape and intensifying their exocrine function. HSCs migrated to glioblastoma cells, interacted with them and exchanged fluorescent tags. Stimulation of cancer cells with TGF‑β1 weakened the ability of glioblastoma cells to attract HSCs and exchange a fluorescent tag. This process stimulated cancer cell proliferation, which is an indication of the ability of HSCs to 'switch' the proliferation and invasion processes in glioblastoma cells.

Personalized regulation of glioblastoma cancer stem cells based on biomedical technologies: From theory to experiment (Review)

Glioblastoma multiforme (GBM) is one of the most aggressive brain tumors. GBM represents >50% of primary tumors of the nervous system and ~20% of intracranial neoplasms. Standard treatment involves surgery, radiation and chemotherapy. However, the prognosis of GBM is usually poor, with a median survival of 15 months. Resistance of GBM to treatment can be explained by the presence of cancer stem cells (CSCs) among the GBM cell population. At present, there are no effective therapeutic strategies for the elimination of CSCs. The present review examined the nature of human GBM therapeutic resistance and attempted to systematize and put forward novel approaches for a personalized therapy of GBM that not only destroys tumor tissue, but also regulates cellular signaling and the morphogenetic properties of CSCs. The CSCs are considered to be an informationally accessible living system, and the CSC proteome should be used as a target for therapy directed at suppressing clonal selection mechanisms and CSC generation, destroying CSC hierarchy, and disrupting the interaction of CSCs with their microenvironment and extracellular matrix. These objectives can be achieved through the use of biomedical cellular products.

Fabrication of digital rainbow holograms and 3-D imaging using SEM based e-beam lithography

Here we present an approach for creating full-color digital rainbow holograms based on mixing three basic colors. Much like in a color TV with three luminescent points per single screen pixel, each color pixel of initial image is presented by three (R, G, B) distinct diffractive gratings in a hologram structure. Change of either duty cycle or area of the gratings are used to provide proper R, G, B intensities. Special algorithms allow one to design rather complicated 3D images (that might even be replacing each other with hologram rotation). The software developed ("RainBow") provides stability of colorization of rotated image by means of equalizing of angular blur from gratings responsible for R, G, B basic colors. The approach based on R, G, B color synthesis allows one to fabricate gray-tone rainbow hologram containing white color what is hardly possible in traditional dot-matrix technology. Budgetary electron beam lithography based on SEM column was used to fabricate practical examples of digital rainbow hologram. The results of fabrication of large rainbow holograms from design to imprinting are presented. Advantages of the EBL in comparison to traditional optical (dot-matrix) technology is considered.

Immunohistochemical analysis of beta-defensin-2 expression in human lung tumors

AIM

The present research was directed on analysis of the expression patterns of human beta-defensin-2 (hBD-2) in human lung tumors.

MATERIALS AND METHODS

Specimens of surgically resected human lung tumors (n = 31) of different histological type (1 case of small cell lung cancer, and 30 cases of non-small cell lung cancer (1 case of clear cell carcinoma, 9 cases of squamous cell carcinoma (SCC), and 20 cases of adenocarcinoma (AC)) were analyzed for expression of hBD-2 with the use of immunohistochemical analysis.

RESULTS

Immunohistochemical analysis has revealed that all lung tumor samples independently on their histological type express hBD-2 peptide, however at different levels (from < 5% to 100% cells). According to our observations, low-differentiated AC differs from moderately differentiated AC by significantly lower hBD-2 expression levels (p < 0.05). No correlation between hBD-2 expression patterns and PCNA or Bcl-2 expression has been found.

CONCLUSION

Human beta-defensin-2 expression levels may depend on differentiation grade of lung adenocarcinoma.

The spatial dynamics of fibrin clot dissolution catalyzed by erythrocyte-bound vs. free fibrinolytics

SUMMARY BACKGROUND

Coupling fibrinolytic plasminogen activators to red blood cells (RBCs) has been proposed as an effective, yet safe method of thromboprophylaxis, because of increased circulation lifetime and reduced propensity to induce hemorrhage by selectivity for nascent thrombi rather than pre-formed hemostatic clots.

OBJECTIVES AND METHODS

We used confocal microscopy of fluorescently labeled fibrin and erythrocytes in plasma-derived clots to study the spatial dynamics of lysis catalyzed by RBC-coupled vs. free plasminogen activators (RBC-PA vs. PA).

RESULTS

Clot lysis catalyzed by free PA progressed gradually and uniformly. In contrast, distinct holes formed surrounding RBC-PA while the rest of the clot remained intact until these holes enlarged sufficiently to merge, causing sudden clot dissolution. Compared with naïve RBCs within clots lysed by free PA, RBC-PA moved faster inside the fibrin network prior to clot dissolution, providing a potential mechanism for spatial propagation of RBC-PA induced lysis. We also showed the focal nature of fibrinolysis by RBC-PA as dense loading of PA onto RBCs initiates more efficient lysis than equal amounts of PA spread sparsely over more RBCs. In an in vitro model of clots exposed to buffer flow, incorporated RBC-PA increased permeability and formed channels eventually triggering clot dissolution, whereas clots containing free PA remained intact.

CONCLUSIONS

Clot lysis by RBC-PA begins focally, has a longer lag phase when measured by residual mass than homogeneous lysis by PA, is propagated by RBC-PA motility and provides more effective clot reperfusion than free PA, making RBC-PA attractive for short-term thromboprophylaxis.

Differential protein expression in pancreatic islets after treatment with an imidazoline compound

The effects of an imidazoline compound (BL11282) on protein expression in rat pancreatic islets were investigated with a proteomic approach. The compound increases insulin release selectively at high glucose concentrations and is therefore of interest in type 2 diabetes. Whole cell extracts from isolated drug-treated and native pancreatic rat islets were compared after separation by 2-D gel electrophoresis. Differentially expressed proteins were identified by mass spectrometry; 15 proteins were selectively up-regulated and 7 selectively down-regulated in drug-treated islets. Of special interest among the differentially expressed proteins are those involved in protein folding (Hsp60, protein disulfide isomerase, calreticulin), Ca(2+) binding (calgizzarin, calcyclin and annexin I) and metabolism or signalling (pyruvate kinase, alpha enolase and protein kinase C inhibitor 1).

Noise squeezing in a nanomechanical Duffing resonator

We study mechanical amplification and noise squeezing in a nonlinear nanomechanical resonator driven by an intense pump near its dynamical bifurcation point, namely, the onset of Duffing bistability. Phase sensitive amplification is achieved by a homodyne detection scheme, where the displacement detector's output, which has a correlated spectrum around the pump frequency, is down-converted by mixing with a local oscillator operating at the pump frequency with an adjustable phase. The down-converted signal at the mixer's output could be either amplified or deamplified, yielding noise squeezing, depending on the local oscillator phase.

P-glycoprotein effect on the properties of its natural lipid environment probed by Raman spectroscopy and Langmuir-Blodgett technique

Behavior of P-glycoprotein (Pgp) natural lipid environment within the membrane of CEM cells expressing Pgp in the quantities varying from 0% to 32% of the total amount of all membrane proteins is described for the first time. Observed cooperative effect of Pgp-induced increase of membrane stability, decrease of the temperature of gel-to-crystal lipids transition and predominance of the lipid liquid crystalline phase at physiological temperatures should have an impact in development of multidrug resistance phenotype of tumor cells by favoring the Pgp intercellular transfer and Pgp ATPase activity.

Polyelectrolyte Nanoparticles Mediate Vascular Gene Delivery

PURPOSE

The purpose is to develop a non-viral gene delivery system that meets the requirements of colloidal stability of DNA complexes expressed in terms of no particle aggregation under physiologic conditions. The system should be used to transfect cardiovascular tissues.

METHODS

We used a strategy based on the formation of polyelectrolyte nanoparticles by deposition of alternatively charged polyelectrolytes onto a DNA core. Polyelectrolytes were transfer RNA as well as the synthetic polyanion, polyvinyl sulfate (PVS), and the polycation polyethylenimine (PEI). The PEI/DNA complex formed the DNA core.

RESULTS

We observed that the DNA is condensed by polycations and further packaged by association with a polyanion. These nanoparticles exhibited negative surface charge and low aggregation tendency. In vivo rat carotid artery experiments revealed high transfection efficiency, not only with the reporter gene but also with the gene encoding human urokinase plasminogen activator (Hu-uPA). Hu-uPA is one of the proteins involved in the recovery of the blood vessels after balloon catheter injury and therefore clinically relevant.

CONCLUSIONS

A strategy for in vivo gene transfer is proposed that uses the incorporation of polyanions as RNA or PVS into PEI/DNA complexes in order to overcome colloidal instability and to generate a negative surface charge. The particles proved to be transfectionally active in vascular gene transfer.

Polycation-mediated transfection: how to overcome undesirable side effects of sticky DNA complexes

Using polycationic transfection one encounters undesired persistent binding to cells of sticky polycation/DNA complexes. These complexes simulate transfection under conditions where no uptake is expected e.g. at 4 degrees C if the uptake is by endocytosis. To overcome this problem, using H1/DNA complexes, we developed an easy and nontoxic method for removing the sticky complexes not taken up during the transfection phase. The cells are simply washed with isotonic (0.1 M) MgCl2 solution, which enables the complete removal of the complexes by their rapid dissolution.

Structure of transfection-active histone H1/DNA complexes

Relationships between the structure of transfecting complexes of histone H1 and DNA and their transfection efficiency were studied. Transfection activity proved to be connected to complex aggregates. Low speed centrifugation of the complexes resulted in loss of the transfection activity. The complexes/aggregates were active with high efficiency in a broad range of weight input ratios r(i) (0.1 < r(i) < 30). Using atomic force microscopy (AFM), the complexes were imaged at negative, nearly electroneutral and positive charge conditions. Electroneutral complexes at r(i) = 1 showed a multitude of different complex forms. Fibrillar, network-like and branched structures were frequently present in one complex. Strongly positive charged complexes had a toroidal appearance. All these different forms contributed to the high transfection efficiency. Cellular uptake is supposed to be by phagocytosis.

Myopathy-dependent changes in activity of ATPase, SDH and GPDH and NOS expression in the different fibre types of hamster muscles

Proximal (vastus lateralis) and distal (gastrocnemius) muscles of 100-day-old normal and myopathic BIO TO-2 hamsters were analysed to study the effects of myopathy on the different muscle fibre types: SO (slow oxidative), FOG (fast oxidative glycolytic) and FG (fast glycolytic). Cytophotometric measurements of enzyme activities (myofibrillic adenosine triphosphatase, succinate dehydrogenase and glycerol-3-phosphate dehydrogenase), Western blot analysis of nitric oxide synthase (NOS) I, II, III isoforms and NOS II immunohistochemistry were performed. The following alterations were found in myopathic muscle fibres: all fibre types of both proximal and distal myopathic muscles showed decreased myofibrillic adenosine triphosphatase activity indicating depressed contractility. This was associated with depressed oxidative activity of the muscle fibres. A shift to more glycolytic metabolism was observed, mainly in FG fibres of proximal muscle. We found an increased NOS II expression in both myopathic muscle types investigated. It means that increased NO production inhibits force generation in myopathic muscle. NOS II immunoreactivity was found mainly in the cytoplasm of FG fibres. NOS I and NOS III expression was not significantly effected by this form of myopathy. Our findings demonstrate that muscle fibres of proximal and distal skeletal muscles of 100-day-old cardiomyopathic BIO TO-2 hamsters are altered with respect to contractility, metabolism and NOS II expression. FG fibres of the proximal muscle were effected most strongly.

Cytophotometrical and immunohistochemical analysis of soft palate muscles of children with isolated cleft palate and combined cleft lip and palate

Palatal muscle biopsies from the cleft margin of children were subjected to cytophotometrical and immunohistochemical analysis. Muscle fiber types were classified according to the enzyme activity of myofibrillic adenosine triphosphatase, glycerol-3-phosphate-dehydrogenase and succinate dehydrogenase assessed cytophotometrically. Fiber type-related immunoreactivity of nitric oxide synthase (NOS) isoforms I, II, III, as a physiological modulator of skeletal muscle function, was related to the oxidative and glycolytic activity of the muscle fibers. Fast oxidative glycolytic fibers with high oxidative activity showed strong NOS I immunoreactivity, whereas fast glycolytic fibers with high glycolytic activity were stronger immunolabelled for NOS III. NOS II expression was similar in all fiber types. No differences in NOS immunoreactivity were found between the two investigated forms of deformity. Additionally to the usual skeletal muscle fiber types, a slow tonic fiber type was for the first time identified in cleft palate muscles. Comparison of two forms of cleft palate, isolated cleft palate and combined cleft lip and palate has shown decreased enzyme activities in muscle fibers of palatal muscles from combined cleft lip and palate. Fast oxidative glycolytic fibers were mainly effected. Cytophotometrical and immunohistochemical analysis indicated a depressed performance of the cleft palatal muscles from combined cleft lip and palate as a stronger deformity compared with isolated cleft palate.

Nitric oxide synthase isoforms I, III and protein kinase-Ctheta in skeletal muscle fibres of normal and streptozotocin-induced diabetic rats with and without Ginkgo biloba extract treatment

The expression of nitric oxide synthase (NOS) isoforms I, III and protein kinase-Ctheta (PKCtheta) in rat vastus lateralis muscle was demonstrated immunohistochemically and then correlated to the physiological metabolic fibre types: SO (slow-oxidative), FOGI, FOGII (fast-oxidative glycolytic; I more glycolytic, II more oxidative), and FG (fast-glycolytic). NOS expression in muscles from different experimental groups (normal and diabetic rats, with and without Ginkgo biloba extract treatment) was assayed by Western blotting. Generally, NOS I and PKCtheta were co-expressed in fibres with predominantly oxidative metabolism (SO, FOGII). This suggests an interplay of PKCtheta and NOS I in nitric oxide production by oxidative fibres. NOS III was more highly expressed in fibres with predominantly glycolytic metabolism (FOGI, FG). A somewhat lower NOS I immunoreactivity was also found in NOS III positive fibres suggesting that NOS III and NOS I are co-expressed in these fibres. Western blotting revealed that NOS I as well as NOS III expression in the vastus lateralis muscle was down-regulated in diabetes and increased after Ginkgo biloba extract treatment. These effects may be associated with a diminished glucose uptake by myocytes of diabetic musclesand with an improved muscle function after Ginkgo biloba treatment.

Effects of serum from patients with type 1 diabetes on primary cerebellar granule cells

Type 1 diabetes is an autoimmune disease of unknown etiology. Our previous work has shown that a factor present in serum from type 1 diabetic patients causes increased Ca2+ channel activity and apoptotic DNA fragmentation in pancreatic beta-cells. Here we examined the effects of type 1 diabetic serum on primary cerebellar granule cells (CGCs). In CGCs, exposure to type 1 diabetic serum did not cause increased apoptosis or changes in Ca2+ channel activity. However, patient serum did cause modulation of Ca2+ signals in a cell type with triangular soma that exhibited low voltage-gated Ca2+ currents. This cell was present primarily in cultures exposed to type 1 diabetic serum. The presence of low voltage-gated Ca2+ currents and long neuronal dendrites indicated that this unique cell was of neuronal origin and not of glial origin.

Role of apoptosis in pancreatic beta-cell death in diabetes

Apoptosis is a physiological form of cell death that occurs during normal development, and critical mediators of this process include caspases, reactive oxygen species, and Ca2+. Excessive apoptosis of the pancreatic beta-cell has been associated with diabetes. Consequently, apoptosis research has focused on how infiltrating macrophages or cytotoxic T-cells might kill pancreatic beta-cells using cytokines or death receptor triggering. Meanwhile, the intracellular events in the target beta-cell have been largely ignored. Elucidation of such targets might help develop improved treatment strategies for diabetes. This article will outline recent developments in apoptosis research, with emphasis on mechanisms that may be relevant to beta-cell death in type 1 and type 2 diabetes. Several of the models proposed in beta-cell killing converge on Ca2+ signaling, indicating that the pancreatic beta-cell may be an ideal system in which to carefully dissect the role of Ca2+ during apoptosis.

Munc-18 associates with syntaxin and serves as a negative regulator of exocytosis in the pancreatic beta -cell

The Munc-18 protein (mammalian homologue of the unc-18 gene; also called nSec1 or rbSec1) has been identified as an essential component of the synaptic vesicle fusion protein complex. The cellular and subcellular localization and functional role of Munc-18 protein in pancreatic beta-cells was investigated. Subcellular fractionation of insulin-secreting HIT-T15 cells revealed a 67-kDa protein in both cytosol and membrane fractions. Immunohistochemistry showed punctate Munc-18 immunoreactivity in the cytoplasm of rat pancreatic islet cells. Direct double-labeling immunofluorescence histochemistry combined with confocal laser microscopy revealed the presence of Munc-18 immunoreactivity in insulin-, glucagon-, pancreatic polypeptide-, and somatostatin-containing cells. Syntaxin 1 immunoreactivity was detected in extracts of HIT-T15 cells, which were immunoprecipitated using Munc-18 antiserum, suggesting an intimate association of Munc-18 with syntaxin 1. Administration of Munc-18 peptide or Munc-18 antiserum to streptolysin O-permeabilized HIT-T15 cells resulted in significantly increased insulin release, but did not have any significant effect on voltage-gated Ca(2+) channel activity. The findings taken together show that the Munc-18 protein is present in insulin-secreting beta-cells and implicate Munc-18 as a negative regulator of the insulin secretory machinery via a mechanism that does not involve syntaxin-associated Ca(2+) channels.

Immunocytochemical visualization of transfected DNA in cultured cells

Nonviral transfection is one of the modern methods for the incorporation of foreign genes into cells. This process involves uptake of foreign genetic material by the cell and further trafficking through the cytoplasm to the nucleus. Elucidation of cytoplasmic pathways of transfection complexes can be useful to improve already existing gene delivery systems or to establish new systems. To monitor transfection complexes in the cell during transfection, we elaborated a method for the visualization of transfection complexes by introducing digoxigenin-labelled nucleotides into foreign DNA followed by detection of digoxigenin label with the use of antibodies directed against digoxigenin. This procedure allowed the visualization of DNA in transfection complexes and to monitor these complexes in cells during transfection.

Ligand-histone H1 conjugates: increased solubility of DNA complexes, but no enhanced transfection activity

We introduced galactose and a short RGD sequence as ligands into H1 histone to target the asialoglycoprotein receptor or integrins on cells expressing these receptors. The efficiency of the gene transfer mediated by galactosylated H1 histone was strongly affected by the transfection conditions. Galactosylation of H1 led to an increase of the basic H1-mediated gene transfer activity only, when H1 itself did not develop its optimal transfection activity. Under other conditions any specific gene transfer mediated by the asialoglycoprotein receptor was covered by the high transfection efficiency of H1 itself. Similar results of a marginal increase in the transfection efficiency were obtained by conjugates of a short RGD sequence and H1. This unexpected failure in the receptor specificity of both conjugates could be due to the unspecific cell-binding capacity of the H1 moiety and to increasing solubility of the complexes as shown by gel shift and solubility measurements.

A new efficient method for transfection of neonatal cardiomyocytes using histone H1 in combination with DOSPER liposomal transfection reagent

Although cationic lipids are successfully used for gene transfer in vitro, primary cells such as neonatal cardiomyocytes frequently resist efficient transfection. We show here that the polycationic lipid DOSPER in combination with histone H1 was much more efficient in transfection of neonatal cardiomyocytes than DOSPER alone or other cationic lipids. This has been shown for transfection with the reporter plasmids pSV beta-gal and pCMV luc. If viral transfections are not possible, this mild method is an alternative to transfect cardiomyocytes.

Delayed Ca2+ response to glucose in diabetic GK rat

The spontaneously diabetic non-obese GK (Goto-Kakizaki) rat exhibits high basal plasma glucose and insulin levels and poor glucose-induced insulin secretion, which makes it a suitable model for non-insulin dependent diabetes mellitus, NIDDM. The aim of this study was to investigate the handling of cytosolic free Ca2+ concentration ([Ca2+]i), the key regulator of insulin secretion, in GK rat single pancreatic islets. For this purpose the influence of high glucose (16.7 mM) and arginine (20 mM) on [Ca2+]i was studied in GK and Wistar rat islets, which served as controls. The data obtained suggest that glucose which through its metabolism generates ATP needed for closure of the KATP channels and membrane depolarization, induces a delayed [Ca2+]i response in the GK rat pancreatic islet. This delay in [Ca2+]i response is likely to result from a defective metabolism of glucose in the diabetic islet.

Galparan: a powerful insulin-releasing chimeric peptide acting at a novel site

Galparan is a 27-amino acid long chimeric peptide, GWTLNSAGYLLGP-INLKALAALAKKIL amide, consisting of galanin-(1-13) linked to mastoparan amide via a peptide bond to provide the mastoparan and galanin effector parts of the molecules. Galparan (10 microM) powerfully stimulates insulin secretion from isolated rat pancreatic islets in a reversible and dose-dependent manner; the stimulation is 26-fold at 3.3 mM glucose and 6-fold at 16.7 mM glucose. Galparan also enhances insulin secretion to a similar extent from islets of diabetic GK rats. The stimulatory effect of galparan on insulin release is not directly dependent on extracellular Ca2+, nor can it be explained only by changes in free cytosolic Ca2+ concentrations. Furthermore, galparan is effective in evoking insulin release in B cells depolarized by 25 mM KCl when ATP-sensitive K+ channels are kept open by diazoxide. Thus, galparan, like mastoparan, stimulates exocytosis of insulin at a distal site in the stimulus-secretion coupling of the B cell. This distal site is not identical to that used by mastoparan, as pertussis toxin pretreatment does not influence the insulinogenic effect of galparan. In conclusion, galparan evokes a large and reversible insulin secretion, acting at a yet unknown distal site and also promoting exocytosis in depolarized B cells from normal rats as well as diabetic GK rats.