Microrheology of novel cellulose stabilized oil-in-water emulsions.

Diffusing wave spectroscopy (DWS) is a powerful optical technique suitable to investigate turbid samples in a nondestructive and reproducible way, providing information on the static and dynamic properties of the system. This includes the relative displacement of emulsion droplets over time and changes in the viscoelastic properties. Here, novel and promising cellulose-based oil-in-water (O/W) emulsions were prepared and studied, for the first time, by DWS. Cellulose plays the role of a novel eco-friendly emulsifying agent. The hydrolysis time of cellulose was observed to affect the average size of the emulsion droplets and their stability; the longer the hydrolysis time, the more dispersed and stable the emulsions were found to be. Additionally, a good complementarity between the microrheology (DWS) and macrorheology (mechanical rheometer) data was found. Our work suggests that DWS is a highly attractive method to investigate the stability, aging and microrheology properties of cellulose-based emulsions, providing valuable insights on their microstructure. This technique is thus highly appealing for the characterization and design of novel emulsion formulations.

The pancreatic beta-cell-specific transcription factor Pax-4 inhibits glucagon gene expression through Pax-6.

AIMS/HYPOTHESIS: The paired-homeobox genes pax-4 and pax-6 are crucial for islet development; whereas the null mutation of pax-6 results in the nearly absence of glucagon-producing alpha cells, pax-4 homozygous mutant mice lack insulin and somatostatin-producing beta and delta cells but contain an increased number of alpha cells suggesting that alpha cells could develop by a default mechanism. METHODS: To investigate whether beta-cell specific factors act negatively on glucagon gene transcription, we ectopically expressed pax-4 in glucagon producing InR1G9 cells; Pax-4 inhibited basal transcription of the glucagon gene promoter by 60%. To assess the mechanism of this inhibition, we cotransfected the non-islet cell line BHK-21 with Pax-4 and various transcription factors present in alpha cells. RESULTS: In addition to a general repressor activity on basal glucagon gene promoter activity of 30-50%, a specific 90% inhibition of Pax-6 mediated transactivation was observed. In contrast, Pax-4 had no effect on Cdx-2/3 or HNF3alpha mediated transcriptional activation. Pax-4 showed similar affinity to the Pax-6 binding sites on the glucagon gene promoter compared to Pax-6, but varying with KCl concentrations. CONCLUSION/INTERPRETATION: Pax-4 impairs glucagon gene transcription specifically through inhibition of Pax-6 mediated transactivation. Transcriptional inhibition seems to be mediated by direct DNA binding competition with Pax-6 and potentially additional mechanisms such as protein-protein interactions and a general repressor activity of Pax-4. Glucagon gene expression in alpha cells could thus result from both the presence of islet cell specific transcription factors and the absence of Pax-4.

Factors controlling pancreatic cell differentiation and function.

Diabetes affects 4 to 5% of the population worldwide and is the most common metabolic disorder. The number of individuals diagnosed with diabetes is rapidly increasing, especially in the developed countries and the disorder frequently leads to secondary complications such as retinopathy, nephropathy, neuropathy and cardiovascular disease. Type II (non-insulin-dependent) diabetes mellitus is the most common form of diabetes, more than 90% of diagnosed cases, and results from insulin resistance, pancreatic beta-cell dysfunction, or a combination of both. The beta-cell dysfunction seems to result in part from an inability of the beta cells to produce and secrete sufficient amounts of active insulin in response to an increased demand for insulin. Type I (insulin-dependent) diabetes mellitus is caused by an autoimmune destruction of the insulin producing beta cells, resulting in insulin deficiency. The existing therapies for both types of diabetes are unsatisfactory since they do not offer a cure and are mostly not sufficient for preventing the secondary complications associated with diabetes. Thus, there is a great need for new improved therapies. This search is, however, hampered by our currently limited knowledge of the basic processes that control the proliferation, differentiation, survival and physiology of the beta cell. Over the last 7 to 8 years our knowledge concerning the development of the pancreas has increased substantially due to the use of genetically modified mice. Nevertheless, key questions regarding the control of proliferation and differentiation of pancreatic progenitor cells into fully functional beta cells remain to be solved.

Release rates for pine sawfly pheromones from two types of dispensers and phenology of Neodiprion sertifer.

Comparisons of release rates, duration in the field, and catch efficiency of polyethylene and cotton roll dispensers for the sex pheromones of sawflies (Hymenoptera: Diprionidae) were conducted. The release rates of the Neodiprion sertifer (Geoffr.) and Diprion pini (L.) sex pheromones, the acetates of pentadecanol and (2S,3S,7S)-3,7-dimethyl (2S,3R,7R)-3,7-dimethyl-2-tridecanol from polyethylene dispensers were measured at different temperatures in the laboratory. The release rates for the substances depended on both the temperature and initial load in the vials. The catch from cotton rolls baited with 100 micrograms of the acetate or propionate of 3,7-dimethyl-2-pentadecanol was compared to the catch from regularly renewed cotton rolls baited with 10 micrograms of the same acetate. The catch was higher for the 100-microgram cotton rolls for, at most, 45 days, and there was no significant differences in catch between the acetate and the propionate. The catch in traps baited with polyethylene or cotton roll dispensers loaded with the acetate of 3,7-dimethyl-2-pentadecanol was compared and showed that cotton roll traps mirrored the decreasing release of the substance rather than the actual flight activity. The length of the flight period of N. sertifer in Sweden, the Czech Republic, Italy, and Greece did not exceed 100 days in any of the countries. By adjusting the initial pheromone load of the polyethylene vials to the expected temperatures, it should be possible to get a constant and sufficiently high release rate during the entire flight period.

IPF1/PDX1 deficiency and beta-cell dysfunction in Psammomys obesus, an animal With type 2 diabetes.

The homeodomain transcription factor IPF1/PDX1 is required in beta-cells for efficient expression of insulin, glucose transporter 2, and prohormone convertases 1/3 and 2. Psammomys obesus, a model of diet-responsive type 2 diabetes, shows markedly depleted insulin stores when given a high-energy (HE) diet. Despite hyperglycemia, insulin mRNA levels initially remained unchanged and then decreased gradually to 15% of the basal level by 3 weeks. Moreover, insulin gene expression was not increased when isolated P. obesus islets were exposed to elevated glucose concentrations. Consistent with these observations, no functional Ipf1/Pdx1 gene product was detected in islets of newborn or adult P. obesus using immunostaining, Western blot, DNA binding, and reverse transcriptase-polymerase chain reaction analyses. Other beta-cell transcription factors (e.g., ISL-1, Nkx2.2, and Nkx6.1) were expressed in P. obesus islets, and the DNA binding activity of the insulin transcription factors RIPE3b1-Act and IEF1 was intact. Ipf1/Pdx1 gene transfer to isolated P. obesus islets normalized the defect in glucose-stimulated insulin gene expression and prevented the rapid depletion of insulin content after exposure to high glucose. Taken together, these results suggest that the inability of P. obesus islets to adapt to dietary overload, with depletion of insulin content as a consequence, results from IPF1/PDX1 deficiency. However, because not all animals become hyperglycemic on HE diet, additional factors may be important for the development of diabetes in this animal model.

Developmental biology of the pancreas.

All pancreatic cell types (endocrine, exocrine, and ductal) are derived from the same endodermal dorsal and ventral anlage, which grow together to form the definitive pancreas. Golosow and Grobstein were pioneers in the field of pancreatic developmental research, as were Wessells and Cohen, who already in the 1960s performed classic embryological experiments describing the morphogenesis of the pancreas and the epithelio-mesenchymal interactions that are instrumental for proper pancreas development. Recent findings suggest that follistatin and fibroblast growth factors represent some of these key mesenchymal factors that actively promote at least pancreatic exocrine development. The true endodermal origin of the pancreatic endocrine cells became evident by experiments performed by the groups of LeDouarin and Rutter in the 1970s. The newly acquired insights regarding the specification of pancreatic endocrine cells as controlled by the notch signaling pathway (i.e., similar to the mechanisms by which neurons are specified during neurogenesis) have provided a novel understanding of the long acknowledged similarities between neurons and the pancreatic endocrine cells. Last, the identification of a number of distinct transcription factors operating at various levels of pancreatic development and in different cell types has provided useful information both on pancreas development and on various pancreatic disorders such as diabetes. Interestingly, four of the hitherto defined five different maturity-onset diabetes of the young (MODY) genes correspond to transcription factors, and, in addition, several transcription factors have also been linked to type 2 diabetes.

Persistent expression of Hlxb9 in the pancreatic epithelium impairs pancreatic development.

The homebox gene Hlxb9, encoding Hb9, exhibits a dual expression profile during pancreatic development. The early expression in the dorsal and ventral pancreatic epithelium is transient and spans from embryonic day (e) 8 to e9-e10, whereas the later expression is confined to differentiating beta-cells as they appear. We previously showed that Hlxb9 is critically required for the initiation of the dorsal, but not the ventral, pancreatic program. Here, we demonstrate the requirement for a stringent temporal regulation of Hlxb9 expression during early stages of pancreatic development. In transgenic mice, where Hlxb9 expression, under control of the Ipf1/Pdx1 promoter, was extended beyond e9-e10, the development of the pancreas was drastically perturbed. Morphological analyses showed that the growth and morphogenesis of the pancreatic epithelium was impaired. Moreover, differentiation of pancreatic endocrine and exocrine cells was diminished and instead the pancreatic epithelium with its adjacent mesenchyme adopted an intestinal-like differentiation program. Together, these data point to a need for a tight temporal regulation of Hlxb9 expression. Thus, a total loss of Hlxb9 expression results in a block of the initiation of the dorsal pancreatic program, while a temporally extended expression of Hlxb9 results in a complete impairment of pancreatic development.

Attenuation of FGF signalling in mouse beta-cells leads to diabetes.

Fibroblast growth factor (FGF) signalling has been implicated in patterning, proliferation and cell differentiation in many organs, including the developing pancreas. Here we show that the FGF receptors (FGFRs) 1 and 2, together with the ligands FGF1, FGF2, FGF4, FGF5, FGF7 and FGF10, are expressed in adult mouse beta-cells, indicating that FGF signalling may have a role in differentiated beta-cells. When we perturbed signalling by expressing dominant-negative forms of the receptors, FGFR1c and FGFR2b, in the pancreas, we found that that mice with attenuated FGFR1c signalling, but not those with reduced FGFR2b signalling, develop diabetes with age and exhibit a decreased number of beta-cells, impaired expression of glucose transporter 2 and increased proinsulin content in beta-cells owing to impaired expression of prohormone convertases 1/3 and 2. These defects are all characteristic of patients with type-2 diabetes. Mutations in the homeobox gene Ipf1/Pdx1 are linked to diabetes in both mouse and human. We also show that Ipf1/Pdx1 is required for the expression of FGFR1 signalling components in beta-cells, indicating that Ipf1/Pdx1 acts upstream of FGFR1 signalling in beta-cells to maintain proper glucose sensing, insulin processing and glucose homeostasis.