Both fasting glucose production and disappearance are abnormal in people with "mild" and "severe" type 2 diabetes

To determine whether regulation of fasting endogenous glucose production (EGP) and glucose disappearance (R(d)) are both abnormal in people with type 2 diabetes, EGP and R(d) were measured in 7 "severe" (SD), 9 "mild" (MD), and 12 nondiabetic (ND) subjects (12.7 +/- 0.6 vs. 8.1 +/- 0.4 vs. 5.1 +/- 0.4 mmol/l) after an overnight fast and during a hyperglycemic pancreatic clamp. Fasting insulin was higher in both the SD and MD than ND subjects, whereas fasting glucagon only was increased (P < 0.05) in SD. Fasting EGP, glycogenolysis, gluconeogenesis, and R(d) all were increased (P < 0.05) in SD but did not differ in MD or ND. On the other hand, when glucose ( approximately 11 mmol/l), insulin ( approximately 72 pmol/l), and glucagon ( approximately 140 pg/ml) concentrations were raised to values similar to those observed in the severe diabetic subjects, EGP was higher (P < 0.001) and R(d) lower (P < 0.01) in both SD and MD than in ND. The higher EGP in the SD and MD than ND during the clamp was the result of increased (P < 0.05) rates of glycogenolysis (4.2 +/- 1.7 vs. 3.5 +/- 1.0 vs. 0.0 +/- 0.8 micromol.kg(-1).min(-1)), since gluconeogenesis did not differ among groups. We conclude that neither glucose production nor disappearance is appropriate for the prevailing glucose and insulin concentrations in people with mild or severe diabetes. Both increased rates of gluconeogenesis (likely because of higher glucagon concentrations) and lack of suppression of glycogenolysis contribute to excessive glucose production in type 2 diabetics.     

Measurement of normal and anomalous diffusion of dyes within protein structures fabricated via multiphoton excited cross-linking

We demonstrate microscale spatial and chemical control of diffusion within protein matrixes created through the use of nonlinear multiphoton excited photochemistry. The mobility of fluorescent dyes of different mass and composition within controlled cross-linked environments has been measured using two-photon excited fluorescence recovery after photobleaching (FRAP). The diffusion times for several rhodamine and sulforhodamine dyes within these fabricated structures were found to be approximately 3-4 orders of magnitude slower than in free solution. The precise diffusion times can be tuned by varying the laser exposure during the fabrication of the matrix, and the diffusion can be correlated with the mesh size determined by TEM and Flory-Rehner analysis. We find that the hydrophobic Texas Red dyes (sulforhodamines) exhibit diffusion that is highly anomalous, indicative of a strong interaction with the hydrophobic cross-linked protein matrix. These results suggests the use of these cross-linked protein matrixes as ideal model systems in which to systematically study anomalous diffusion. Finally, the diffusion can be tuned within a multilayered protein matrix, and this in conjunction with slow diffusion also suggests the use of these structures in controlled release applications.     

Enzymatic activity of alkaline phosphatase inside protein and polymer structures fabricated via multiphoton excitation

We demonstrate micron scale control of bioactivity through the use of multiphoton excited photochemistry, where this technique has been used to cross-link three-dimensional matrixes of alkaline phosphatase, bovine serum albumin, and polyacrylamide and combinations therein. Using a fluorescence-based assay (ELF-97), the enzymatic activity has been studied using a Michaelis-Menten analysis, and we have measured the specificity constants kcat/KM for alkaline phosphatase in both the protein and polymer matrixes to be on the order of 10(5)-10(6) M(-1) s(-1)and are comparable to known literature values in other environments. It is found that the enzyme is simply entrapped in the polymer matrix, whereas it is completely covalently bound in the protein structures. The relative reaction rate of alkaline phosphatase bound to BSA with the ELF substrate was measured as a function of cross-link density and was found to decrease in the more tightly formed matrixes, indicating a decrease in the diffusion in the matrix.     

Intranasal administration of an Escherichia coli-expressed codon-optimized rotavirus VP6 protein induces protection in mice

We are developing rotavirus vaccines based on the VP6 protein of the human G1P[8] [corrected] [J. Virol. 73 (1999) 7574] CJN strain of rotavirus. One prototype candidate consisting of MBP::VP6::His6, a chimeric protein of maltose-binding protein, VP6 and hexahistidine, was expressed mainly as truncated polypeptides in Escherichia coli BL21(DE3) cells. A possible reason for this extensive truncation is the high frequencies of rare bacterial codons within the rotavirus VP6 gene. Expression of truncated recombinant VP6 was found to be reduced, and expression of complete VP6 protein was simultaneously increased, when the protein was expressed in Rosetta(DE3)pLacI E. coli cells that contain increased amounts of transfer RNAs for a selection of rare codons. The same observation was made when a synthetic codon-optimized CJN-VP6 gene was expressed in E. coli BL21 or Rosetta cells. To increase protein recovery, recombinant E. coli cells were treated with 8M urea. Denatured, full-length MBP::VP6::His6 protein was then purified and used for intranasal vaccination of BALB/c mice (2 doses administered with E. coli heat-labile toxin LT(R192G) as adjuvant). Following oral challenge with the G3P[16] [corrected] [J. Virol. 76 (2002) 560] EDIM strain of murine rotavirus, protection levels against fecal rotavirus shedding were comparable (P>0.05) between groups of mice immunized with denatured codon-optimized or native (not codon-optimized) immunogen with values ranging from 87 to 99%. These protection levels were also comparable to those found after immunization with non-denatured CJN VP6. Thus, expression of complete rotavirus VP6 protein was greatly enhanced by codon optimization, and the protection elicited was not affected by denaturation of recombinant VP6.     

Isoprostanes, prostaglandins and tocopherols in pre-eclampsia, normal pregnancy and non-pregnancy

This study is designed to evaluate whether oxidative stress and inflammation are involved in severe pre-eclampsia compared to normal pregnancy and non-pregnancy. We have measured plasma and urinary levels of 8-iso-PGF2alpha, a major isoprostane as an indicator of oxidative stress; plasma and urinary 15-keto-dihydro-PGF2alpha, a major metabolite of cyclooxygenase-catalysed PGF2alpha as an indicator of inflammatory response, and plasma -alpha-and -gamma-tocopherol in 18 pre-eclamptic, 19 normal pregnancy and 20 non-pregnant women. Pregnant women had significantly higher levels of 8-iso-PGF2alpha and PGF2alpha metabolite as compared to the non-pregnancy. Levels of 8-iso-PGF2alpha in the pre-eclamptic women did not differ from the normal pregnancy but PGF2alpha metabolite levels were significantly higher in normal pregnancy. On the other hand, gamma-tocopherol levels were significantly lower in pre-eclampsia than normal pregnancy. In contrast, the concentration of alpha-tocopherol was very similar between the groups. alpha-and gamma-tocopherol levels were significantly lower in pregnancy compared to non-pregnancy. Although no direct evidence of oxidative stress and inflammatory response was observed in severe pre-eclampsia, a reduction of gamma-tocopherol suggests the possible precedence of oxidative stress in this condition. Higher levels of isoprostanes and prostaglandin metabolite in late pregnancy suggest the importance of both free radicals and cyclooxygenase-catalysed oxidation products in normal biological processes of pregnancy.     

Allosteric regulation of tRNA import: interactions between tRNA domains at the inner membrane of Leishmania mitochondria

Import of nucleus-encoded tRNAs into the mitochondria of the kinetoplastid protozoon Leishmania involves recognition of specific import signals by the membrane-bound import machinery. Multiple signals on different tRNA domains may be present, and further, importable RNAs interact positively (Type I) or negatively (Type II) with one another at the inner membrane in vitro. By co-transfection assays, it is shown here that tRNA^Tyr (Type I) transiently stimulates the rate of entry of tRNA^Ile (Type II) into Leishmania mitochondria in transfected cells, and conversely, is inhibited by tRNA^Ile. Truncation and mutagenesis experiments led to the co-localization of the effector and import activities of tRNA^Tyr to the D domain, and those of tRNA^Ile to the variable region–T domain (V-T region), indicating that both activities originate from a single RNA–receptor interaction. A third tRNA, human tRNA^Lys, is imported into Leishmania mitochondria in vitro as well as in vivo. This tRNA has Type I and Type II motifs in the D domain and the V-T region, respectively, and shows both Type I and Type II effector activities. Such dual-type tRNAs may interact simultaneously with the Type I and Type II binding sites of the inner membrane import machinery.