Microbial community structure across a wastewater-impacted riparian buffer zone in the southeastern coastal plain

Riparian buffer zones are important for both natural and developed ecosystems throughout the world because of their ability to retain nutrients, prevent soil erosion, protect aquatic environments from excessive sedimentation, and filter pollutants. Despite their importance, the microbial community structures of riparian buffer zones remains poorly defined. Our objectives for this study were twofold: first, to characterize the microbial populations found in riparian buffer zone soils; and second, to determine if microbial community structure could be linked to denitrification enzyme activity (DEA). To achieve these objectives, we investigated the microbial populations of a riparian buffer zone located downslope of a pasture irrigated with swine lagoon effluent, utilizing DNA sequencing of the 16S rDNA, DEA, and quantitative PCR (qPCR) of the denitrification genes nirK, nirS, and nosZ. Clone libraries of the 16S rDNA gene were generated from each of twelve sites across the riparian buffer with a total of 986 partial sequences grouped into 654 operational taxonomic units (OTUs). The Proteobacteria were the dominant group (49.8% of all OTUs), with the Acidobacteria also well represented (19.57% of all OTUs). Analysis of qPCR results identified spatial relationships between soil series, site location, and gene abundance, which could be used to infer both incomplete and total DEA rates.

Development of a 3-Dimensional Back Contour Imaging System for Monitoring Scoliosis Progression in Children

STUDY DESIGN

Control study.

OBJECTIVES

To present a new surface topography system capable of taking 3-dimensional (3D) spine measurements, to establish baseline values for the measured parameters in a typically developing population, and to determine the intra-rater and inter-rater reproducibility of these parameters.

SUMMARY OF BACKGROUND DATA

Cumulative exposure to radiation from diagnostic radiographs increases patient risk for cancer development. There is a need for noninvasive and non-radiographic tools to accurately and reproducibly measure spine deformity and track scoliosis progression.

METHODS

We measured 10 typically developing subjects with the new Milwaukee Topography System, which is composed of 2 electromagnetic markers, an electronic processing unit, a handheld laser scanner, a software package, and a desktop computer. Two investigators separately scanned the same subjects multiple times, yielding a total of 4 scans per subject per investigator. We measured 17 3D back parameters in each scan. We performed a multivariate analysis of variances to test the hypothesis of no difference for all variables, measured intra-rater and inter-investigator reliability with intra-class correlation (ICC) coefficients, and calculated mean values.

RESULTS

There were highly reproducible ICC values between investigators for 6 parameters (ICC > 0.75), moderate ICC values for 8 parameters (0.75 > ICC > 0.4), and poor ICC values for 3 parameters (ICC < 0.4), all at p < .05. Intra-investigator ICCs were moderate to excellent for almost all parameters.

CONCLUSIONS

The Milwaukee Topography System can be used to monitor and measure 3D back contours in children. The 3D back parameters values measured in the typically developing population can be considered baseline values that can be compared with parameters measured in children with idiopathic scoliosis.

Insights into the molecular mechanism for type 2 diabetes susceptibility at the KCNQ1 locus from temporal changes in imprinting status in human islets

The molecular basis of type 2 diabetes predisposition at most established susceptibility loci remains poorly understood. KCNQ1 maps within the 11p15.5 imprinted domain, a region with an established role in congenital growth phenotypes. Variants intronic to KCNQ1 influence diabetes susceptibility when maternally inherited. By use of quantitative PCR and pyrosequencing of human adult islet and fetal pancreas samples, we investigated the imprinting status of regional transcripts and aimed to determine whether type 2 diabetes risk alleles influence regional DNA methylation and gene expression. The results demonstrate that gene expression patterns differ by developmental stage. CDKN1C showed monoallelic expression in both adult and fetal tissue, whereas PHLDA2, SLC22A18, and SLC22A18AS were biallelically expressed in both tissues. Temporal changes in imprinting were observed for KCNQ1 and KCNQ1OT1, with monoallelic expression in fetal tissues and biallelic expression in adult samples. Genotype at the type 2 diabetes risk variant rs2237895 influenced methylation levels of regulatory sequence in fetal pancreas but without demonstrable effects on gene expression. We demonstrate that CDKN1C, KCNQ1, and KCNQ1OT1 are most likely to mediate diabetes susceptibility at the KCNQ1 locus and identify temporal differences in imprinting status and methylation effects, suggesting that diabetes risk effects may be mediated in early development.

The miRNA profile of human pancreatic islets and beta-cells and relationship to type 2 diabetes pathogenesis

Recent advances in the understanding of the genetics of type 2 diabetes (T2D) susceptibility have focused attention on the regulation of transcriptional activity within the pancreatic beta-cell. MicroRNAs (miRNAs) represent an important component of regulatory control, and have proven roles in the development of human disease and control of glucose homeostasis. We set out to establish the miRNA profile of human pancreatic islets and of enriched beta-cell populations, and to explore their potential involvement in T2D susceptibility. We used Illumina small RNA sequencing to profile the miRNA fraction in three preparations each of primary human islets and of enriched beta-cells generated by fluorescence-activated cell sorting. In total, 366 miRNAs were found to be expressed (i.e. >100 cumulative reads) in islets and 346 in beta-cells; of the total of 384 unique miRNAs, 328 were shared. A comparison of the islet-cell miRNA profile with those of 15 other human tissues identified 40 miRNAs predominantly expressed (i.e. >50% of all reads seen across the tissues) in islets. Several highly-expressed islet miRNAs, such as miR-375, have established roles in the regulation of islet function, but others (e.g. miR-27b-3p, miR-192-5p) have not previously been described in the context of islet biology. As a first step towards exploring the role of islet-expressed miRNAs and their predicted mRNA targets in T2D pathogenesis, we looked at published T2D association signals across these sites. We found evidence that predicted mRNA targets of islet-expressed miRNAs were globally enriched for signals of T2D association (p-values <0.01, q-values <0.1). At six loci with genome-wide evidence for T2D association (AP3S2, KCNK16, NOTCH2, SCL30A8, VPS26A, and WFS1) predicted mRNA target sites for islet-expressed miRNAs overlapped potentially causal variants. In conclusion, we have described the miRNA profile of human islets and beta-cells and provide evidence linking islet miRNAs to T2D pathogenesis.

SSTR2 is the functionally dominant somatostatin receptor in human pancreatic β- and α-cells

Somatostatin-14 (SST) inhibits insulin and glucagon secretion by activating G protein-coupled somatostatin receptors (SSTRs), of which five isoforms exist (SSTR1-5). In mice, the effects on pancreatic β-cells are mediated by SSTR5, whereas α-cells express SSTR2. In both cell types, SSTR activation results in membrane hyperpolarization and suppression of exocytosis. Here, we examined the mechanisms by which SST inhibits secretion from human β- and α-cells and the SSTR isoforms mediating these effects. Quantitative PCR revealed high expression of SSTR2, with lower levels of SSTR1, SSTR3, and SSTR5, in human islets. Immunohistochemistry showed expression of SSTR2 in both β- and α-cells. SST application hyperpolarized human β-cells and inhibited action potential firing. The membrane hyperpolarization was unaffected by tolbutamide but antagonized by tertiapin-Q, a blocker of G protein-gated inwardly rectifying K⁺ channels (GIRK). The effect of SST was mimicked by an SSTR2-selective agonist, whereas a SSTR5 agonist was marginally effective. SST strongly (>70%) reduced depolarization-evoked exocytosis in both β- and α-cells. A slightly weaker inhibition was observed in both cell types after SSTR2 activation. SSTR3- and SSTR1-selective agonists moderately reduced the exocytotic responses in β- and α-cells, respectively, whereas SSTR4- and SSTR5-specific agonists were ineffective. SST also reduced voltage-gated P/Q-type Ca²⁺ currents in β-cells, but normalization of Ca²⁺ influx to control levels by prolonged depolarizations only partially restored exocytosis. We conclude that SST inhibits secretion from both human β- and α-cells by activating GIRK and suppressing electrical activity, reducing P/Q-type Ca²⁺ currents, and directly inhibiting exocytosis. These effects are mediated predominantly by SSTR2 in both cell types.

Quality of isolated pig islets is improved using perfluorohexyloctane for pancreas storage in a split lobe model

Pancreas transportation between donor center and islet production facility is frequently associated with prolonged ischemia impairing islet isolation and transplantation outcomes. It is foreseeable that shipment of pig pancreases from distant centralized biosecure breeding facilities to institutes that have a long-term experience in porcine islet isolation is essentially required in future clinical islet xenotransplantation. Previously, we demonstrated that perfluorohexyloctan (F6H8) is significantly more efficient to protect rat and human pancreata from ischemically induced damage compared to perfluorodecalin (PFD). To evaluate the effect of F6H8 on long-term stored pig pancreases in a prospective study, we utilized the split lobe model to minimize donor variability. Retrieved pancreases were dissected into the connecting and splenic lobe, intraductally flushed with UW solution and immersed alternately in either preoxygenated F6H8 or PFD for 8-10 h. Prior to pancreas digestion, the intrapancreatic pO2 and the ratio of ATP-to-inorganic phosphate was compared utilizing 31P-NMR spectroscopy. Isolated islets were cultured for 2-3 days at 37°C and subjected to quality assessment. Pancreatic lobes stored in preoxygenated F6H8 had a significantly higher intrapancreatic pO2 compared to pancreata in oxygen-precharged PFD (10.11 ± 3.87 vs. 1.64 ± 1.13 mmHg, p < 0.05). This correlated with a higher ATP-to-inorganic phosphate ratio (0.30 ± 0.04 vs. 0.14 ± 0.01). No effect was observed concerning yield and purity of freshly isolated islets. Nevertheless, a significantly improved glucose-stimulated insulin response, increased viability and postculture survival (57.2 ± 5.7 vs. 39.3 ± 6.4%, p < 0.01) was measured in islets isolated from F6H8-preserved pancreata. The present data suggest that F6H8 does not increase islet yield but improves quality of pig islets isolated after prolonged cold ischemia.

Human β cell transcriptome analysis uncovers lncRNAs that are tissue-specific, dynamically regulated, and abnormally expressed in type 2 diabetes

A significant portion of the genome is transcribed as long noncoding RNAs (lncRNAs), several of which are known to control gene expression. The repertoire and regulation of lncRNAs in disease-relevant tissues, however, has not been systematically explored. We report a comprehensive strand-specific transcriptome map of human pancreatic islets and β cells, and uncover >1100 intergenic and antisense islet-cell lncRNA genes. We find islet lncRNAs that are dynamically regulated and show that they are an integral component of the β cell differentiation and maturation program. We sequenced the mouse islet transcriptome and identify lncRNA orthologs that are regulated like their human counterparts. Depletion of HI-LNC25, a β cell-specific lncRNA, downregulated GLIS3 mRNA, thus exemplifying a gene regulatory function of islet lncRNAs. Finally, selected islet lncRNAs were dysregulated in type 2 diabetes or mapped to genetic loci underlying diabetes susceptibility. These findings reveal a new class of islet-cell genes relevant to β cell programming and diabetes pathophysiology.

SUMO-1: Ubiquitin gains weight

The highly conserved ubiquitin polypeptide functions by covalently modifying other proteins. This modification has a well-established role in facilitating substrate degradation by the proteasome and can regulate some proteins by ways other than targeting them to the proteasome. It has now emerged that proteins bearing only distant similarity to ubiquitin can also be attached to specific proteins. The consequences of most of these modifications are not yet understood. However, two recent papers on one ubiquitin-like protein, SUMO-1, demonstrate a role in targeting a protein crucial for nucleocytoplasmic trafficking to the nuclear pore complex. These and other recent findings suggest a much wider influence of the 'ubiquitin system' on cell biology and raise intriguing regulatory and mechanistic questions.

Choosing staff members reduces time in mechanical restraint due to self-injurious behaviour and requesting restraint

BACKGROUND

Using mechanical restraints to protect a person who engaged in dangerous self-injury was decreased by manipulation of an establishing operation involving the client choosing the staff person who would work with her.

MATERIALS AND METHODS

The client was a 28-year-old woman diagnosed with autism, bipolar disorder, static cerebral encephalopathy, moderate intellectual disabilities, hypotonia and musculoskeletal deformities. She had a history of biting herself and further bites could produce irreversible nerve damage. Mechanical restraints were applied when she bit, tried to bite herself or asked for them.

RESULTS

When she was allowed to choose staff members, the use of mechanical restraint decreased.

CONCLUSION

Reducing the time spent in mechanical restraint by giving the client a choice of staff members who would work with her demonstrates that such a choice may be an establishing operation. The usefulness of cumulative records and scatterplots to evaluate changes in the occurrence of self-injurious behaviour (SIB) and associated mechanical restraint is shown as are the advantages of using alternating treatment designs to assess the effectiveness of treatment conditions for someone who exhibits long-term cyclic behaviour.

Membrane potential-dependent inactivation of voltage-gated ion channels in alpha-cells inhibits glucagon secretion from human islets

OBJECTIVE

To document the properties of the voltage-gated ion channels in human pancreatic alpha-cells and their role in glucagon release.

RESEARCH DESIGN AND METHODS

Glucagon release was measured from intact islets. [Ca(2+)](i) was recorded in cells showing spontaneous activity at 1 mmol/l glucose. Membrane currents and potential were measured by whole-cell patch-clamping in isolated alpha-cells identified by immunocytochemistry.

RESULT

Glucose inhibited glucagon secretion from human islets; maximal inhibition was observed at 6 mmol/l glucose. Glucagon secretion at 1 mmol/l glucose was inhibited by insulin but not by ZnCl(2). Glucose remained inhibitory in the presence of ZnCl(2) and after blockade of type-2 somatostatin receptors. Human alpha-cells are electrically active at 1 mmol/l glucose. Inhibition of K(ATP)-channels with tolbutamide depolarized alpha-cells by 10 mV and reduced the action potential amplitude. Human alpha-cells contain heteropodatoxin-sensitive A-type K(+)-channels, stromatoxin-sensitive delayed rectifying K(+)-channels, tetrodotoxin-sensitive Na(+)-currents, and low-threshold T-type, isradipine-sensitive L-type, and omega-agatoxin-sensitive P/Q-type Ca(2+)-channels. Glucagon secretion at 1 mmol/l glucose was inhibited by 40-70% by tetrodotoxin, heteropodatoxin-2, stromatoxin, omega-agatoxin, and isradipine. The [Ca(2+)](i) oscillations depend principally on Ca(2+)-influx via L-type Ca(2+)-channels. Capacitance measurements revealed a rapid (<50 ms) component of exocytosis. Exocytosis was negligible at voltages below -20 mV and peaked at 0 mV. Blocking P/Q-type Ca(2+)-currents abolished depolarization-evoked exocytosis.

CONCLUSIONS

Human alpha-cells are electrically excitable, and blockade of any ion channel involved in action potential depolarization or repolarization results in inhibition of glucagon secretion. We propose that voltage-dependent inactivation of these channels underlies the inhibition of glucagon secretion by tolbutamide and glucose.

Gamma-aminobutyric acid (GABA) is an autocrine excitatory transmitter in human pancreatic beta-cells

OBJECTIVE

Paracrine signaling via gamma-aminobutyric acid (GABA) and GABA(A) receptors (GABA(A)Rs) has been documented in rodent islets. Here we have studied the importance of GABAergic signaling in human pancreatic islets.

RESEARCH DESIGN AND METHODS

Expression of GABA(A)Rs in islet cells was investigated by quantitative PCR, immunohistochemistry, and patch-clamp experiments. Hormone release was measured from intact islets. GABA release was monitored by whole-cell patch-clamp measurements after adenoviral expression of alpha(1)beta(1) GABA(A)R subunits. The subcellular localization of GABA was explored by electron microscopy. The effects of GABA on electrical activity were determined by perforated patch whole-cell recordings.

RESULTS

PCR analysis detected relatively high levels of the mRNAs encoding GABA(A)R alpha(2), beta(3,) gamma(2), and pi subunits in human islets. Patch-clamp experiments revealed expression of GABA(A)R Cl(-) channels in 52% of beta-cells (current density 9 pA/pF), 91% of delta-cells (current density 148 pA/pF), and 6% of alpha-cells (current density 2 pA/pF). Expression of GABA(A)R subunits in islet cells was confirmed by immunohistochemistry. beta-Cells secreted GABA both by glucose-dependent exocytosis of insulin-containing granules and by a glucose-independent mechanism. The GABA(A)R antagonist SR95531 inhibited insulin secretion elicited by 6 mmol/l glucose. Application of GABA depolarized beta-cells and stimulated action potential firing in beta-cells exposed to glucose.

CONCLUSIONS

Signaling via GABA and GABA(A)R constitutes an autocrine positive feedback loop in human beta-cells. The presence of GABA(A)R in non-beta-cells suggests that GABA may also be involved in the regulation of somatostatin and glucagon secretion.

Somatostatin release, electrical activity, membrane currents and exocytosis in human pancreatic delta cells

AIMS/HYPOTHESIS

The aim of this study was to characterise electrical activity, ion channels, exocytosis and somatostatin release in human delta cells/pancreatic islets.

METHODS

Glucose-stimulated somatostatin release was measured from intact human islets. Membrane potential, currents and changes in membrane capacitance (reflecting exocytosis) were recorded from individual human delta cells identified by immunocytochemistry.

RESULTS

Somatostatin secretion from human islets was stimulated by glucose and tolbutamide and inhibited by diazoxide. Human delta cells generated bursting or sporadic electrical activity, which was enhanced by tolbutamide but unaffected by glucose. Delta cells contained a tolbutamide-insensitive, Ba(2+)-sensitive inwardly rectifying K(+) current and two types of voltage-gated K(+) currents, sensitive to tetraethylammonium/stromatoxin (delayed rectifying, Kv2.1/2.2) and 4-aminopyridine (A current). Voltage-gated tetrodotoxin (TTX)-sensitive Na(+) currents contributed to the action potential upstroke but TTX had no effect on somatostatin release. Delta cells are equipped with Ca(2+) channels blocked by isradipine (L), omega-agatoxin (P/Q) and NNC 55-0396 (T). Blockade of any of these channels interferes with delta cell electrical activity and abolishes glucose-stimulated somatostatin release. Capacitance measurements revealed a slow component of depolarisation-evoked exocytosis sensitive to omega-agatoxin.

CONCLUSIONS/INTERPRETATION

Action potential firing in delta cells is modulated by ATP-sensitive K(+)-channel activity. The membrane potential is stabilised by Ba(2+)-sensitive inwardly rectifying K(+) channels. Voltage-gated L- and T-type Ca(2+) channels are required for electrical activity, whereas Na(+) currents and P/Q-type Ca(2+) channels contribute to (but are not necessary for) the upstroke of the action potential. Action potential repolarisation is mediated by A-type and Kv2.1/2.2 K(+) channels. Exocytosis is tightly linked to Ca(2+)-influx via P/Q-type Ca(2+) channels. Glucose stimulation of somatostatin secretion involves both K(ATP) channel-dependent and -independent processes.

JW. CXCL13-CXCR5 interactions support prostate cancer cell migration and invasion in a PI3K p110-, SRC- and FAK-dependent fashion (98.5)

We have previously shown that CXCR5 is significantly expressed by the prostate cancer (PCa) tissue than compared to high grade prostatic intraepithelial neoplasia and benign prostatic hyperplasia. We have also demonstrated PCa cell lines significantly express functional CXCR5, which promote cell invasion, migration, and active matrix metalloproteinase expression. In the present study, we elucidate the molecular mechanisms of PCa cell migration and invasion mediated by CXCL13-CXCR5. Using phospho-specific antibody microarray and Western blot analyses, we have delineated the pathways involved in CXCL13-CXCR5 signaling by PCa cell lines. For the first time, we show Gα, Gβ, and Gγ protein isoforms are differentially expressed by normal prostatic epithelial cell lines (PrEC and RWPE-1) versus PCa cell lines (PC3, DU145, LNCaP, and C4-2b). We also illustrate LNCaP cells express PI3K-p110α, -p110β, and -p110δ, while PC3 cells express PI3K-p110α, -p110β, -p110γ, and DOCK2. Migration and invasion assays revealed that both PC3 and LNCaP cell lines invade and migrate toward CXCL13 in a PI3K-dependent fashion. Src-FAK were required for this CXCL13-mediated migration and invasion. PC3 cells were capable of exploiting both PI3K-p110α/β /γ- and PI3K-p110γ-integrin β3-mediated events for migration and invasion, while LNCaP cells were only able to use PI3K-p110α/β /δ-dependent mechanisms for progression. In conclusion, the diversity of G protein and PI3K p110 isoforms along with Src- and FAK-signaling dictate the potential of PCa cell lines to migrate and invade in response to CXCL13.

Exocytotic properties of human pancreatic beta-cells

Pancreatic beta-cells secrete insulin in response to elevated blood glucose via Ca(2+)-dependent fusion of secretory granules with the plasma membrane (regulated exocytosis). While exocytosis has been extensively investigated in rodent beta-cells, studies on human beta-cells are scarce. We have characterized the exocytotic properties of human beta-cells by insulin release measurements, carbon fiber amperometry, and capacitance measurements using the patch-clamp technique. Voltage-clamp depolarizations evoked capacitance increases in single beta-cells in a time- and voltage-dependent manner. The capacitance responses as well as insulin release from intact islets were strongly amplified by elevation of intracellular cAMP levels. Exocytosis was more dependent on Ca(2+) influx through P/Q-type than L-type Ca(2+) channels, reflecting the relative contribution of these channels to the total Ca(2+) current. Exocytosis (as monitored by capacitance or amperometric measurements) decreased during repetitive stimulation as a result of inactivation of Ca(2+) channels as well as depletion of a readily releasable pool of granules. These results reveal both similarities and differences between human and rodent beta-cells.

Voltage-gated ion channels in human pancreatic beta-cells: electrophysiological characterization and role in insulin secretion

OBJECTIVE

To characterize the voltage-gated ion channels in human beta-cells from nondiabetic donors and their role in glucose-stimulated insulin release.

RESEARCH DESIGN AND METHODS

Insulin release was measured from intact islets. Whole-cell patch-clamp experiments and measurements of cell capacitance were performed on isolated beta-cells. The ion channel complement was determined by quantitative PCR.

RESULTS

Human beta-cells express two types of voltage-gated K(+) currents that flow through delayed rectifying (K(V)2.1/2.2) and large-conductance Ca(2+)-activated K(+) (BK) channels. Blockade of BK channels (using iberiotoxin) increased action potential amplitude and enhanced insulin secretion by 70%, whereas inhibition of K(V)2.1/2.2 (with stromatoxin) was without stimulatory effect on electrical activity and secretion. Voltage-gated tetrodotoxin (TTX)-sensitive Na(+) currents (Na(V)1.6/1.7) contribute to the upstroke of action potentials. Inhibition of Na(+) currents with TTX reduced glucose-stimulated (6-20 mmol/l) insulin secretion by 55-70%. Human beta-cells are equipped with L- (Ca(V)1.3), P/Q- (Ca(V)2.1), and T- (Ca(V)3.2), but not N- or R-type Ca(2+) channels. Blockade of L-type channels abolished glucose-stimulated insulin release, while inhibition of T- and P/Q-type Ca(2+) channels reduced glucose-induced (6 mmol/l) secretion by 60-70%. Membrane potential recordings suggest that L- and T-type Ca(2+) channels participate in action potential generation. Blockade of P/Q-type Ca(2+) channels suppressed exocytosis (measured as an increase in cell capacitance) by >80%, whereas inhibition of L-type Ca(2+) channels only had a minor effect.

CONCLUSIONS

Voltage-gated T-type and L-type Ca(2+) channels as well as Na(+) channels participate in glucose-stimulated electrical activity and insulin secretion. Ca(2+)-activated BK channels are required for rapid membrane repolarization. Exocytosis of insulin-containing granules is principally triggered by Ca(2+) influx through P/Q-type Ca(2+) channels.

Preparing and probing atomic number states with an atom interferometer

We describe the controlled loading and measurement of number-squeezed states and Poisson states of atoms in individual sites of a double well optical lattice. These states are input to an atom interferometer that is realized by symmetrically splitting individual lattice sites into double wells, allowing atoms in individual sites to evolve independently. The two paths then interfere, creating a matter-wave double-slit diffraction pattern. The time evolution of the double-slit diffraction pattern is used to measure the number statistics of the input state. The flexibility of our double well lattice provides a means to detect the presence of empty lattice sites, an important and so far unmeasured factor in determining the purity of a Mott state.

The male obese Wistar diabetic fatty rat is a new model of extreme insulin resistance

The male obese Wistar Diabetic Fatty (WDF) rat is a genetic model of obesity and non-insulin dependent diabetes (NIDDM). The obese Zucker rat shares the same gene for obesity on a different genetic background but is not diabetic. This study evaluated the degree of insulin resistance in both obese strains by examining the binding and post binding effects of muscle insulin receptors in obese rats exhibiting hyperinsulinemia and/or hyperglycemia. Insulin receptor binding and affinity and tyrosine kinase activity were measured in skeletal muscle from male WDF fa/fa (obese) and Fa/? (lean) and Zucker fa/fa (obese) and Fa/Fa (homozygous lean) rats. Rats were fed a high sucrose (68% of total Kcal) or Purina stock diet for 14 weeks. At 27 weeks of age, adipose depots were removed for adipose cellularity analysis and the biceps femoris muscle was removed for measurement of insulin binding and insulin-stimulated receptor kinase activity. Plasma glucose (13.9 vs. 8.4 mM) and insulin levels (14,754 vs. 7440 pmol/L) were significantly higher in WDF obese than in Zucker obese rats. Insulin receptor number and affinity and TK activity were unaffected by diet. Insulin receptor number was significantly reduced in obese WDF rats ( 2.778 +/- 0.617 pmol/mg protein), compared to obese Zucker rats (4.441 +/- 0.913 pmol/mg potein). Both obese strains exhibited down regulation of the insulin receptor compared to their lean controls. Maximal tyrosine kinase (TK) activity was significantly reduced in obese WDF rats (505 +/- 82 fmol/min/mg protein) compared to obese Zucker rats (1907 +/- 610 fmol/min/mg protein). Only obese WDF rats displayed a decrease in TK activity per receptor. These observations establish the obese WDF rat as an excellent model for exploring mechanisms of extreme insulin resistance, particularly post-receptor tyrosine kinase-associated defects, in non-insulin dependent diabetes.

Use of glycated hemoglobin to assess Glycemic control in Wistar diabetic fatty rats and Zucker fatty rats

The Wistar Diabetic Fatty rat (WDF fafa) is a congenic strain of the Wistar Kyoto rat. Studies using blood glucose reveal that only fatty male (not female) WDF rats spontaneously develop hyperglycemia when fed a stock diet. Blood glucose values have not provided consistent results for evaluation of glycemic status in fatty male WDF rats. Zucker fatty (fafa) rats, while sharing the fa gene and the development of hyperinsulinemia and hyperlipemia, do not spontaneously become hyperglycemic. In order to examine strain differences and the effects of age on long-term average glycemic status in WDF and Zucker rats, glycated hemoglobin (GHb) was analyzed. Glycated hemoglobin was measured in male lean and obese WDF and Zucker rats at 2, 3, 6, and 12 months of age. Nonfasted plasma glucose was measured in male lean and obese WDF rats at 2, 3, 6, and 12 months of age and in lean and obese Zucker rats at 3, 6, and 12 months of age. Plasma insulin was measured in lean and obese WDF and Zucker rats at 3, 6, and 12 months of age. Obese WDF rats had significantly elevated GHb compared to lean controls at 3, 6, and 12 months of age. Glycated hemoglobin was substantially above the normal range (3.8-6.5%) at 3 months of age (14.1%). Glycated hemoglobin significantly declined in the obese WDF rats between 6 and 12 months of age. Nonfasted plasma glucose was significantly elevated in the obese WDF rats at 3 months (14.1 +/- 2.1 mM/L) and 6 months of age (16.2 +/- 2.3 mM/L) compared to lean controls. At 12 months of age there was no difference in plasma glucose between obese and lean WDF rats. Obese and lean Zucker rats had similar levels of GHb and plasma glucose at all ages. In conclusion, GHb provides more integrated data for classifying disease status of WDF rats and evaluation of potential long-term complications associated with hyperglycemia.

2-Cyano-4-fluoro-1-thiovalylpyrrolidine analogues as potent inhibitors of DPP-IV

We report the synthesis and biological activity of a series of 2-cyano-4-fluoro-1-thiovalylpyrrolidine inhibitors of DPP-IV. Within this series, compound 19 provided a potent, selective, and orally active DPP-IV inhibitor which demonstrated a very long duration of action in both rat and dog.

The contribution of proficiency testing to improving laboratory performance and ensuring quality patient care

The idea of comparing laboratories' test results against one another predated federal regulations by decades (1) and was initially used as an educational tool. The introduction of federal regulations altered the proficiency testing (PT) environment (2,3) and today there is concern that the regulatory requirements do not address extraneous factors that may adversely affect a laboratory's PT performance (6). This article aims to address these concerns and hopes to convince the reader that while the scope of PT has expanded beyond its original intent as an educational tool for the laboratory, PT can still function in that capacity. Improvements in laboratory performance and laboratory medicine as a whole continue to be supported by proficiency testing for numerous reasons. Several mistakes laboratories have made in the past are addressed and suggestions for improvement are given. Laboratory managers who take proactive steps to ensure quality patient test results should experience fewer PT failures, and in turn can focus more attention on the educational benefits that participating in PT can offer.

Non-uniform distribution of mitochondria in pancreatic acinar cells

The distribution of mitochondria in pancreatic acinar cells was investigated using confocal fluorescence microscopy and transmission electron microscopy (EM). Acinar cells were studied either after enzymatic isolation or in small segments of undisassociated pancreatic tissue. Loading of isolated acinar cells with Mito Tracker Green or Red, a fluorescence mitochondrial probe, showed that mitochondria are predominantly situated in the perigranular, subplasmalemmal and perinuclear regions. Subsequent applications of EM fixatives induced a leak of the fluorescent indicator to the cytosol but did not change the distribution of mitochondria. EM was then performed on isolated acinar cells and on acinar cells of pancreatic tissue segments. The intracellular distribution of mitochondria was quantified by calculating the percentage of the cross-sectional area that was occupied by mitochondria. In isolated acinar cells the highest density of mitochondria was seen in the perigranular region, where mitochondria occupied 25.69+/-1.58% of the area, then the subplasmalemmal region with 12.61+/-0.77% and the perinuclear region with 9.07+/-0.97% ( n=26). Similar results were obtained from acinar cells of pancreatic tissue segments: the perigranular 22.9+/-1.95%, subplasmalemmal 12.45+/-0.78% and perinuclear regions 9.07+/-0.97% ( n=26). The outer mitochondrial membranes were frequently positioned close to membranes of the ER, which followed the outer contour of mitochondria. Mitochondria were never found in direct contact with the nuclear envelope: there were usually layers of ER between the mitochondrial and nuclear membranes. Subplasmalemmal mitochondria were found in a very close proximity to the plasma membrane with no ER layers between the mitochondrial and the corresponding plasma membranes. We conclude that in pancreatic acinar cells mitochondria are preferentially distributed to perigranular, subplasmalemmal and perinuclear regions and this distribution is not affected by isolation or fixation procedures.