Islet Density Research Articles

2148-P: Islet Endocrine Cells Shows a Unique Pattern on Development and Growth of Each Cell Type in Human Subjects

Development and growth of islet endocrine cell volume are assumed to mainly depend on cell proliferation. In addition, the partial contribution of islet neogenesis and chromogranin A positive hormone negative cell (CPHN cell) is recently clarified. Detailed evaluation for the islet cell development and growth, however, is not well explored linking to the change of cell replication, neognesis and CPHN cell for each type of endocrine cells in human specimens. For this purpose, we recruited human autopsied pancreata, aged from 24 weeks old to 19 years old (n=32). Formalin-fixed paraffin embedded sections from pancreatic body were used for immunohistochemistry (IHC) and immunofluorescence (IF) analysis. The subjects were divided into 4 groups, Fetus (F: 24-31 weeks), Infant (I : 0-1 years), Child (C : 2-12 years) and Adolescence (A : 13-19 years). Quintuple-IHC with antibodies for glucagon, insulin, somatostatin, pp and Ki-67 was performed for the measurement of islet cell volume density (V) and replication status. Vαand Vβwere increased with age. Vβin A was more abundant than in F (p<0.01). On the other hand, Vδnegatively correlated with age (r=-0.701, p<0.01) and was more in F than in C and A (p<0.01). Ki-67 positive index for αand δ cells showed the highest in F (p<0.01), whereas that of β cells was the highest in I (p<0.01). Neogenic islet density, evaluated in IHC with an antibody for chromogranin A, showed negative correlation with age (r=-0.608, p<0.01). Double-IF with a cocktail of four kinds of antibodies for islet hormones and for chromogranin A was performed to evaluate VCPHN. CPHN cell was identified in both islets and neogenic islets. VCPHNwas more abundant in neogenic islets of F and I than those of C and A. Our results suggest that each kind of islet cell owns a unique pattern of the cell development and growth. In particular, neogenic islet and CPHN cell may play a role as the source of βcells in the later life. Disclosure S. Osonoi: None. H. Mizukami: None. K. Takahashi: None. K. Kudo: None. S. Yagihashi: None.

Endocrinopathy in Pancreatic Cancer Is Characterized by Reduced Islet Size and Density with Preserved Endocrine Composition as Compared to Type 2 Diabetes: Presidential Poster Award

Endocrinopathy in Pancreatic Cancer Is Characterized by Reduced Islet Size and Density with Preserved Endocrine Composition as Compared to Type 2 Diabetes: Presidential Poster Award

Maternal and Paternal Exercise Regulates Offspring Metabolic Health and Beta-Cell Phenotype

Maternal and paternal environment are critical factors in determining risk for obesity and diabetes in offspring. Maternal exercise in mice can prevent the detrimental effects of maternal high-fat feeding on offspring metabolic health, whereas the effects of paternal exercise on offspring are less clear. Little is also known about the effects of maternal or paternal exercise on offspring beta cells, a major factor in glucose homeostasis. We determined the effects of maternal, paternal and maternal+paternal exercise on offspring glucose tolerance and beta cell morphology. Male sires were housed ± running wheels for 3 weeks before breeding (4.4±0.8 km/day) and dams were housed ± running wheels for 2 weeks before breeding (8.4±0.5 km/day) and during gestation (4.7±0.5 km/day). All male and female breeders were fed a high-fat diet. Four groups of male offspring were studied: both parents sedentary (Sed); maternal exercise only (Mat Ex); paternal exercise only (Pat Ex); maternal+paternal exercise (Mat+Pat Ex) (n=5-8 litters/group). Offspring were sedentary and separate cohorts were studied at weaning, 52, and 80 weeks. Post-weaning, offspring were fed a chow diet. There was no effect of parental exercise on offspring glucose tolerance at weaning. At 52 weeks, offspring of exercised parents had ∼25% lower fasting blood glucose concentrations vs. Sed (all p<0.01), and glucose tolerance was improved in Mat Ex (33%), Pat Ex (35%), and Mat+Pat Ex (50%) vs. Sed (p<0.001). Mat Ex, Pat Ex and Mat+Pat Ex had decreased beta cell size (40%) and mass (40%), whereas islet size and density were only decreased in offspring from Mat+Pat Ex parents (28% and 40%, respectively). Older offspring (80 weeks) from all three parental exercise treatments displayed improved glucose tolerance (p<0.05). Maternal and paternal exercise in high-fat fed parents has profound positive effects on offspring glucose tolerance during adulthood and older age that may be linked to adaptations in the endocrine pancreas. Disclosure J. Zheng: None. A.B.A. Wagner: None. N.B. Prince: None. K. So: None. J. Mul: None. E. Dirice: None. M.F. Hirshman: None. K.I. Stanford: None. R. Kulkarni: None. L.J. Goodyear: None.

Structural abnormalities in islets from very young children with cystic fibrosis may contribute to cystic fibrosis-related diabetes

Cystic fibrosis (CF)-related diabetes (CFRD) is thought to result from beta-cell injury due in part to pancreas exocrine damage and lipofibrosis. CFRD pancreata exhibit reduced islet density and altered cellular composition. To investigate a possible etiology, we tested the hypothesis that such changes are present in CF pancreata before the development of lipofibrosis. We evaluated pancreas and islet morphology in tissues from very young CF children (<4 years of age), and adult patients with CF and CFRD. The relative number of beta-cells in young CF tissues was reduced by 50% or more when compared to age-matched controls. Furthermore, young CF tissues displayed significantly smaller insulin-positive areas, lower proportion of beta-cells positive for the proliferation marker Ki67 or the ductal marker CK19 vs. control subjects, and islet inflammatory cell infiltrates, independently of the severity of the exocrine lesion and in the absence of amyloid deposits. CFRD pancreata exhibited greater islet injury with further reduction in islet density, decreased relative beta-cell number, and presence of amyloid deposits. Together, these results strongly suggest that an early deficiency in beta-cell number in infants with CF may contribute to the development of glucose intolerance in the CF pediatric population, and to CFRD, later in life.

Androgen signaling expands β-cell mass in male rats and β-cell androgen receptor is degraded under high-glucose conditions

A deficient pancreatic β-cell mass increases the risk of type 2 diabetes mellitus. Here, we investigated the effects of testosterone on the development of pancreatic β-cell mass in male rats. The β-cell mass of male rats castrated at 6 wk of age was reduced to ~30% of that of control rats at 16 wk of age, and castration caused glucose intolerance. Loss of β-cell mass occurred because of decreases in islet density per pancreas and β-cell cluster size. Castration was negatively associated with the number of Ki-67-positive β-cells and positively associated with the number of TUNEL-positive β-cells. These β-cell changes could be prevented by testosterone treatment. In contrast, castration did not affect β-cell mass in male mice. Androgen receptor (AR) localized differently in mouse and rat β-cells. Testosterone enhanced the viability of INS-1 and INS-1 #6, which expresses high levels of AR, in rat β-cell lines. siRNA-mediated AR knockdown or AR antagonism with hydroxyflutamide attenuated this enhancement. Moreover, testosterone did not stimulate INS-1 β-cell viability under high d-glucose conditions. In INS-1 β-cells, d-glucose dose dependently (5.5-22.2 mM) downregulated AR protein levels both in the presence and absence of testosterone. The intracellular calcium chelator (BAPTA-AM) could prevent this decrease in AR expression. AR levels were also reduced by a calcium ionophore (A23187), but not by insulin, in the absence of the proteasome inhibitor MG132. Our results indicate that testosterone regulates β-cell mass, at least in part, by AR activation in the β-cells of male rats and that the β-cell AR is degraded under hyperglycemic conditions.

Comprehensive analysis of in vitro to field transition of micromorphology and leaf architecture in Passiflora edulis Sims. f. flavicarpa Deg.

This study elucidate the micromorphological changes and leaf architectural developments of in vitro (multiplication phase) and in vivo transferred (acclimatized plants in the field) micropropagated plantlets of Passiflora edulis Sims. f. flavicarpa Deg. The in vitro leaves were small, ovate and pale green in color; but glossy, bright green colored leaves with conspicuous midrib were observed in field transferred plants. Constantly opened stomata throughout the culture period were found under in vitro conditions, these were fully functional after field transfer of the plantlets. In vitro environment favoured increased stomatal density (80.5), stomatal index (28.8), under-developed trichomes, reduced vein islet density (7.0) and irregular venation pattern. Reduced stomatal density (63.4) and index (25.3), well developed trichomes, increased vein islet density (22.0) and regular venation pattern were observed in field acclimatized plantlets. Crystals were absent in the in vitro grown leaves but well developed rhombohedral and sphaerocrystals were observed throughout the major and minor veins in the cells of field plants. The foliar micromorphological study revealed that the in vitro environmental conditions favoured the development of abnormal features. These anomalies have been adjusted and plants developed structural and morphological changes needed for successful adaptation in the field conditions.

Critical role of β1 integrin in postnatal beta-cell function and expansion.

β1 integrin is essential for pancreatic beta-cell development and maintenance in rodents and humans. However, the effects of a temporal beta-cell specific β1 integrin knockout on adult islet function are unknown. We utilized a mouse insulin 1 promoter driven tamoxifen-inducible Cre-recombinase β1 integrin knockout mouse model (MIPβ1KO) to investigate β1 integrin function in adult pancreatic beta-cells. Adult male MIPβ1KO mice were significantly glucose intolerant due to impaired glucose-stimulated insulin secretion in vivo and ex vivo at 8 weeks post-tamoxifen. The expression of Insulin and Pancreatic and duodenal homeobox-1 mRNA was significantly reduced in MIPβ1KO islets, along with reductions in insulin exocytotic proteins. Morphological analyses demonstrated that beta-cell mass, islet density, and the number of large-sized islets was significantly reduced in male MIPβ1KO mice. Significant reductions in the phosphorylation of signaling molecules focal adhesion kinase, extracellular signal-regulated kinases 1 and 2, and v-Akt murine thymoma viral oncogene were observed in male MIPβ1KO islets when compared to controls. MIPβ1KO islets displayed a significant increase in protein levels of the apoptotic marker cleaved-Poly (ADP-ribose) polymerase and a reduction of the cell cycle marker cyclin D1. Female MIPβ1KO mice did not develop glucose intolerance or reduced beta-cell mass until 16 weeks post-tamoxifen. Glucose intolerance remained in both genders of aged MIPβ1KO mice. This data demonstrates that β1 integrin is required for the maintenance of glucose homeostasis through postnatal beta-cell function and expansion.

Effects of Obesity and Diabetes on α- and β-Cell Mass in Surgically Resected Human Pancreas.

Context:The ethnic difference in β-cell regenerative capacity in response to obesity may be attributable to different phenotypes of type 2 diabetes among ethnicities.Objective:This study aimed to clarify the effects of diabetes and obesity on β- (BCM) and α-cell mass (ACM) in the Japanese population.Design, Setting, and Participants:We obtained the pancreases of 99 individuals who underwent pancreatic surgery and whose resected pancreas sample contained adequate normal pancreas for histological analysis. Questionnaires on a family history of diabetes and history of obesity were conducted in 59 patients. Pancreatic sections were stained for insulin or glucagon, and fractional β- and α-cell area were measured. Islet size and density as well as β-cell turnover were also quantified.Results:In patients with diabetes, BCM was decreased by 46% compared with age- and body mass index-matched nondiabetic patients (1.48% ± 1.08% vs 0.80% ± 0.54%, P < .001), whereas there was no difference in ACM between the groups. There was no effect of obesity or history of obesity on BCM and ACM irrespective of the presence or absence of diabetes. There was a negative correlation between BCM, but not ACM, and glycated hemoglobin before and after pancreatic surgery. In addition, reduced BCM was observed in patients with pancreatic cancer compared with those with other pancreatic tumors.Conclusions:These findings suggest that the increase in BCM in the face of insulin resistance is extremely limited in the Japanese, and BCM rather than ACM has a major role in regulating blood glucose level in humans.

Islet Volume and Indexes of β-Cell Function in Humans.

Islet volume and endocrine pancreas architecture (islet size distribution) may be independent determinants of β-cell function. Furthermore, the accuracy of homeostatic model assessment (HOMA) indexes in predicting β-cell mass has never been assessed. Here we investigated the relationships between islet volume, islet density, and islet size distribution, estimated after pancreatic tissue digestion, with established indexes of β-cell function in humans. We included in this study 42 patients who were candidates for islet autotransplantation and had well-characterized glucose metabolism. Indexes of insulin secretion were calculated and compared with the islet volume, as a surrogate of β-cell mass, obtained after digestion of pancreas. Islet counting analysis showed considerable interindividual variation in islet density and size. Islet volume, but not density nor size, was the only independent determinant of β-cell function assessed by insulin HOMA β-cell. Islet volume was significantly reduced in the patients with overt hyperglycemia, but not in patients with impaired fasting glucose. Insulin HOMA β-cell predicted islet volume better than other measures of fasting insulin secretion. In conclusion, the present study documented a close direct relationship between indexes of β-cell function and islet volume in humans. The insulin HOMA β-cell provides a more reliable estimate of pancreatic islet volume than fasting glucose before islet isolation.

Impact of Pancreatic Rat Islet Density on Cell Survival during Hypoxia.

In bioartificial pancreases (BP), the number of islets needed to restore normoglycaemia in the diabetic patient is critical. However, the confinement of a high quantity of islets in a limited space may impact islet survival, particularly in regard to the low oxygen partial pressure (PO2) in such environments. The aim of the present study was to evaluate the impact of islet number in a confined space under hypoxia on cell survival. Rat islets were seeded at three different concentrations (150, 300, and 600 Islet Equivalents (IEQ)/cm2) and cultured in normal atmospheric pressure (160 mmHg) as well as hypoxic conditions (15 mmHg) for 24 hours. Cell viability, function, hypoxia-induced changes in gene expression, and cytokine secretion were then assessed. Notably, hypoxia appeared to induce a decrease in viability and increasing islet density exacerbated the observed increase in cellular apoptosis as well as the loss of function. These changes were also associated with an increase in inflammatory gene transcription. Taken together, these data indicate that when a high number of islets are confined to a small space under hypoxia, cell viability and function are significantly impacted. Thus, in order to improve islet survival in this environment during transplantation, oxygenation is of critical importance.

Phenotypic Characterization of MIP-CreERT1Lphi Mice With Transgene-Driven Islet Expression of Human Growth Hormone.

There is growing concern over confounding artifacts associated with β-cell–specific Cre-recombinase transgenic models, raising questions about their general usefulness in research. The inducible β-cell–specific transgenic (MIP-CreERT1Lphi) mouse was designed to circumvent many of these issues, and we investigated whether this tool effectively addressed concerns of ectopic expression and disruption of glucose metabolism. Recombinase activity was absent from the central nervous system using a reporter line and high-resolution microscopy. Despite increased pancreatic insulin content, MIP-CreERT mice on a chow diet exhibited normal ambient glycemia, glucose tolerance and insulin sensitivity, and appropriate insulin secretion in response to glucose in vivo and in vitro. However, MIP-CreERT mice on different genetic backgrounds were protected from high-fat/ streptozotocin (STZ)-induced hyperglycemia that was accompanied by increased insulin content and islet density. Ectopic human growth hormone (hGH) was highly expressed in MIP-CreERT islets independent of tamoxifen administration. Circulating insulin levels remained similar to wild-type controls, whereas STZ-associated increases in α-cell number and serum glucagon were significantly blunted in MIP-CreERT1Lphi mice, possibly due to paracrine effects of hGH-induced serotonin expression. These studies reveal important new insight into the strengths and limitations of the MIP-CreERT mouse line for β-cell research.

Pancreatic Islet APJ Deletion Reduces Islet Density and Glucose Tolerance in Mice.

Protection and replenishment of a functional pancreatic β-cell mass (BCM) are key goals of all diabetes therapies. Apelin, a small regulatory peptide, is the endogenous ligand for the apelin receptor (APJ) receptor. The apelin-APJ signaling system is expressed in rodent and human islet cells. Apelin exposure has been shown to inhibit and to stimulate insulin secretion. Our aim was to assess the influence of a selective APJ deletion in pancreatic islet cells on islet homeostasis and glucose tolerance in mice. Cre-LoxP strategy was utilized to mediate islet APJ deletion. APJ deletion in islet cells (APJ(Δislet)) resulted in a significantly reduced islet size, density and BCM. An ip glucose tolerance test showed significantly impaired glucose clearance in APJ(Δislet) mice. APJ(Δislet) mice were not insulin resistant and in vivo glucose-stimulated insulin secretion was reduced modestly. In vitro glucose-stimulated insulin secretion showed a significantly reduced insulin secretion by islets from APJ(Δislet) mice. Glucose clearance in response to ip glucose tolerance test in obese APJ(Δislet) mice fed a chronic high-fat (HF) diet, but not pregnant APJ(Δislet) mice, was impaired significantly. In addition, the obesity-induced adaptive elevations in mean islet size and fractional islet area were reduced significantly in obese APJ(Δislet) mice when compared with wild-type mice. Together, these findings demonstrate a stimulatory role for the islet cell apelin-APJ signaling axis in regulation of pancreatic islet homeostasis and in metabolic induced β-cell hyperplasia. The results indicate the apelin-APJ system can be exploited for replenishment of BCM.

Islet Number Rather Than Islet Size Is a Major Determinant of β- and α-Cell Mass in Humans

The objective of the study was to clarify the relative contribution of islet number and islet size to β- and α-cell mass in humans. We obtained the pancreas at autopsy from 72 Japanese adults with no history of diabetes or pancreatitis (aged 47 ± 12 years, body mass index 24.1 ± 5.0 kg/m(2)). Pancreatic sections were stained for insulin or glucagon, and fractional β-cell area (%BCA) and α-cell area (%ACA) were measured. Islet number and islet size as well as β-cell turnover were also quantified. Glycosylated hemoglobin measured within 1 year prior to death was obtained in 38 individuals. There was considerable interindividual variation in islet density and mean islet size, with a significant negative correlation between the two (r = -0.25, P = .03). There were significant positive correlations between islet density and %BCA or %ACA (r = 0.63, P < .001, and r = 0.41, P = .001), whereas mean islet size correlated with neither of them. Islet density as well as %BCA, but not mean islet size, was negatively correlated with glycosylated hemoglobin (r = -0.37, P = .02, and r = -0.36, P = .03). The present study suggests that islet number rather than islet size is a major determinant of β- and α-cell mass in humans. Interindividual difference in islet number may contribute to susceptibility to development of glucose intolerance.

Age-associated changes of islet endocrine cells and the effects of body mass index in Japanese.

Impaired growth and premature death of β-cells are implicated in the progression of islet pathology in type 2 diabetes. It remains unclear, however, how aging affects islet cells, or whether the islet change in diabetes is an augmented process of aging. We studied age-related changes of the islet structure in Japanese non-diabetic subjects and explored the underlying mechanism of the changes. A total of 115 non-diabetic autopsy cases were subjected to morphometric analysis for volume densities of islets, β- and non-β-cells, as well as their masses. Proliferation activity identified by Ki67, and expressions of pancreatic and duodenal homeobox (PDX)-1, cell cycle inhibitor P16, and oxidative stress marker γH2AX were also examined. There was a gradual and marginal decline of volume densities of islets, β- and non-β-cells with aging, while masses of these components were increased during maturation and slowly decreased after the 40s. Islet density was high in the young, but reduced after maturation. There was only a minimal influence of increased body mass index (BMI) on the increase in β-cell mass, but not on the other variables. Ki67 positivity and PDX-1 expressions were high in the young, but low after maturation, whereas expressions of P16 and γH2AX were elevated in the aged. Age-associated decline of β-cell mass is marginal after maturation, and the reduction of β-cell mass could be a specific process in diabetes. The impact of BMI on the islet structure is limited in Japanese with normal glucose tolerance.

You are what you eat-Do not blame your mother.

You are what you eat-Do not blame your mother.

Effect of Exercise on Pancreatic Islets in Zucker Diabetic Fatty Rats

Exercise and physical activity improve the glycemic control in people with type 2 diabetes (T2D). It is known that activity improves muscle utilization of glucose, and that exercise can spare islets if initiated prior to the onset of diabetes. However, any effect of exercise on pancreatic islet function after the diagnosis of overt diabetes is unknown. The aim of the study was to investigate the effects of exercise training on pancreatic islets in a rodent model of overt T2D. 12-week old male Zucker Diabetic Fatty (ZDF) rats and control lean rats were divided into 4 groups: sedentary control exercised control, sedentary diabetic and exercised diabetic. Exercised rats were trained with moderate intensity running on a treadmill for 7 weeks. Assessment of plasma insulin levels, islet cell composition (relative proportion of α, β and δ cells), islet density, insulin content and islet core diameter was conducted at the end of the study. Diabetes in ZDF rats lead to high HbA1c and BGLs, which was not reversed by exercise. Diabetes caused destruction of the islet structure and significant loss of β-cells, with an increased proportion of α- and δ-cells. Exercise improved islets morphology in the diabetic group, while islet density and islet cell composition were not affected by exercise. Increased insulin immunostaining of the pancreatic islets was identified in the diabetic animals after exercise. Although exercise did not affect the diabetes-induced decrease in the proportion of islet β cells, there appeared to be an improvement in the islet architecture and in β-cell insulin content.

PACAP Inhibits β-cell Mass Expansion in a Mouse Model of Type II Diabetes: Persistent Suppressive Effects on Islet Density

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a potent insulinotropic G-protein-coupled receptor ligand, for which morphoregulative roles in pancreatic islets have recently been suggested. Here, we evaluated the effects of pancreatic overexpression of PACAP on morphometric changes of islets in a severe type II diabetes model. Following cross-breeding of obese-diabetic model KKAy mice with mice overexpressing PACAP in their pancreatic β-cells, the resulting KKAy mice with or without PACAP transgene (PACAP/+:Ay/+ or Ay/+ mice) were fed with a high-fat diet up to the age of 11 months. Pancreatic sections from 5- to 11-month-old littermates were examined. Histomorphometric analyses revealed significant suppression of islet mass expansion in PACAP/+:Ay/+ mice compared with Ay/+ mice at 11 months, but no significant difference between PACAP/+ and +/+ (wild-type) mice, as previously reported. The suppressed islet mass in PACAP/+:Ay/+ mice was due to a decrease in islet density but not islet size. In addition, the density of tiny islets (<0.001 mm2) and of insulin-positive clusters in ductal structures were markedly decreased in PACAP/+:Ay/+ mice compared with Ay/+ mice at 5 months of age. In contrast, PACAP overexpression caused no significant effects on the level of aldehyde-fuchsin reagent staining (a measure of β-cell granulation) or the volume and localization of glucagon-positive cells in the pancreas. These results support previously reported inhibitory effects of PACAP on pancreatic islet mass expansion, and suggest it has persistent suppressive effects on pancreatic islet density which may be related with ductal cell-associated islet neogenesis in type II diabetes.

TCF7L2 rs7903146 impairs islet function and morphology in non-diabetic individuals

Transcription factor 7-like 2 (TCF7L2) is a Wnt-signalling-associated transcription factor. Genetic studies have clearly demonstrated that DNA polymorphisms within TCF7L2 confer the strongest known association with increased risk of type 2 diabetes. However, the impact of the TCF7L2 type-2-diabetes-associated rs7903146 T allele on biological function and morphology of human pancreatic islets is unknown. Paraffin sections of pancreases from 187 brain-deceased donors (HbA(1c) <6.5% [48 mmol/mol]) were used to genotype the TCF7L2 variant rs7903146 and evaluate its impact on islet morphology and alpha and beta cell subpopulations following immunostaining for glucagon and C-peptide. Following islet isolation, we investigated the correlation between TCF7L2 genotype and in vitro islet functional variables from our in-house pancreatic database. TCF7L2 rs7903146 (T/T) was associated with reduced basal and glucose-stimulated insulin secretion in isolated human islets, and reduced islet density in whole pancreas. Morphological analysis demonstrated islet size was increased in T/T carriers. Furthermore, rs7903146 was associated with an increased glucagon/C-peptide ratio, especially in bigger islets. The TCF7L2 variant rs7903146 risk allele is associated with impaired insulin secretion, reduction of total islet number and quantitative as well as qualitative morphological changes in human islets. Understanding how the TCF7L2 genotype modulates its activity and how TCF7L2 impacts the islet morphology may aid the design of new therapeutic approaches for the treatment of type 2 diabetes.

Collection Protocol for Human Pancreas

This dissection and sampling procedure was developed for the Network for Pancreatic Organ Donors with Diabetes (nPOD) program to standardize preparation of pancreas recovered from cadaveric organ donors. The pancreas is divided into 3 main regions (head, body, tail) followed by serial transverse sections throughout the medial to lateral axis. Alternating sections are used for fixed paraffin and fresh frozen blocks and remnant samples are minced for snap frozen sample preparations, either with or without RNAse inhibitors, for DNA, RNA, or protein isolation. The overall goal of the pancreas dissection procedure is to sample the entire pancreas while maintaining anatomical orientation. Endocrine cell heterogeneity in terms of islet composition, size, and numbers is reported for human islets compared to rodent islets. The majority of human islets from the pancreas head, body and tail regions are composed of insulin-containing β-cells followed by lower proportions of glucagon-containing α-cells and somatostatin-containing δ-cells. Pancreatic polypeptide-containing PP cells and ghrelin-containing epsilon cells are also present but in small numbers. In contrast, the uncinate region contains islets that are primarily composed of pancreatic polypeptide-containing PP cells. These regional islet variations arise from developmental differences. The pancreas develops from the ventral and dorsal pancreatic buds in the foregut and after rotation of the stomach and duodenum, the ventral lobe moves and fuses with the dorsal. The ventral lobe forms the posterior portion of the head including the uncinate process while the dorsal lobe gives rise to the rest of the organ. Regional pancreatic variation is also reported with the tail region having higher islet density compared to other regions and the dorsal lobe-derived components undergoing selective atrophy in type 1 diabetes. Additional organs and tissues are often recovered from the organ donors and include pancreatic lymph nodes, spleen and non-pancreatic lymph nodes. These samples are recovered with similar formats as for the pancreas with the addition of isolation of cryopreserved cells. When the proximal duodenum is included with the pancreas, duodenal mucosa may be collected for paraffin and frozen blocks and minced snap frozen preparations.

Pressure Hyperalgesia in Hind Limb Suspended Rats

Spaceflight and simulated microgravity often associate with pain and prediabetes. Streptozotocin (STZ)-induced moderate insulinopenia rat models of prediabetes result in pressure hyperalgesia. The current study was designed to determine whether or not simulated microgravity induced by hind limb suspension (HLS) in rats lead to insulinopenia and pressure hyperalgesia. Adult male rats were divided into HLS (N = 20) and control, non-suspended (N = 16) groups, respectively. Bodyweight and hind limb pressure-pain withdrawal threshold (PPT) were measured at regular 2-5 d intervals for 7 d before and 12-13 d after HLS. Bodyweights and PPT of control and HLS animals measured on the day of suspension were not different. During the experiment, control rats gained 61 +/- 5 g, but maintained their PPT at the baseline level. Suspended rats gained 26 +/- 3 g of weight during the same time period and their PPT declined from 105 +/- 6 g to 84 +/- 6 g. Neither blood glucose nor pancreatic islet density and area were affected by HLS. However, the random plasma insulin of HLS rats was significantly lower than that of control animals (1.6 +/- 0.2 vs. 2.7 +/- 0.2 ng ml(-1)). The observed relationship between insulin and PPT levels in the HLS rats was similar to that observed in rats with STZ-induced insulinopenia. These data suggest that moderate insulinopenia may affect the rat's sensitivity to deep pressure directly, without affecting glucose homeostasis. In addition, our data suggest that HLS rats may develop peripheral neuropathy.