Effect of sex on counterregulatory responses to exercise after antecedent hypoglycemia in type 1 diabetes

A marked sexual dimorphism exists in healthy individuals in the pattern of blunted neuroendocrine and metabolic responses following antecedent stress. It is unknown whether significant sex-related counterregulatory differences occur during prolonged moderate exercise after antecedent hypoglycemia in type 1 diabetes mellitus (T1DM). Fourteen patients with T1DM (7 women and 7 men) were studied during 90 min of euglycemic exercise at 50% maximal O(2) consumption after two 2-h episodes of previous-day euglycemia (5.0 mmol/l) or hypoglycemia of 2.9 mmol/l. Men and women were matched for age, glycemic control, duration of diabetes, and exercise fitness and had no history or evidence of autonomic neuropathy. Exercise was performed during constant "basal" intravenous infusion of regular insulin (1 U/h) and a 20% dextrose infusion, as needed to maintain euglycemia. Plasma glucose and insulin levels were equivalent in men and women during all exercise and glucose clamp studies. Antecedent hypoglycemia produced a relatively greater (P < 0.05) reduction of glucagon, epinephrine, norepinephrine, growth hormone, and metabolic (glucose kinetics) responses in men compared with women during next-day exercise. After antecedent hypoglycemia, endogenous glucose production (EGP) was significantly reduced in men only, paralleling a reduction in the glucagon-to-insulin ratio and catecholamine responses. In conclusion, a marked sexual dimorphism exists in a wide spectrum of blunted counterregulatory responses to exercise in T1DM after prior hypoglycemia. Key neuroendocrine (glucagon, catecholamines) and metabolic (EGP) homeostatic responses were better preserved during exercise in T1DM women after antecedent hypoglycemia. Preserved counterregulatory responses during exercise in T1DM women may confer greater protection against hypoglycemia than in men with T1DM.     

Secretory traffic triggers the formation of tubular continuities across Golgi sub-compartments

The organization of secretory traffic remains unclear, mainly because of the complex structure and dynamics of the secretory pathway. We have thus studied a simplified system, a single synchronized traffic wave crossing an individual Golgi stack, using electron tomography. Endoplasmic-reticulum-to-Golgi carriers join the stack by fusing with cis cisternae and induce the formation of intercisternal tubules, through which they redistribute their contents throughout the stack. These tubules seem to be pervious to Golgi enzymes, whereas Golgi vesicles are depleted of both enzymes and cargo. Cargo then traverses the stack without leaving the cisternal lumen. When cargo exits the stack, intercisternal connections disappear. These findings provide a new view of secretory traffic that includes dynamic intercompartment continuities as key players.     

The solution structure of ChaB,a putative membrane ion antiporter regulator from <Emphasis Type="Italic">Escherichia coli</Emphasis>

Background  

ChaB is a putative regulator of ChaA, a Na⁺/H⁺ antiporter that also has Ca⁺/H⁺ activity in E. coli. ChaB contains a conserved 60-residue region of unknown function found in other bacteria, archaeabacteria and a series of baculoviral proteins. As part of a structural genomics project, the structure of ChaB was elucidated by NMR spectroscopy.     

Platelet aggregation and antibacterial effects of an l-amino acid oxidase purified from Bothrops alternatus snake venom

The isolation and biochemical/enzymatic characterization of an L-amino acid oxidase, Balt-LAAO-I, from Bothrops alternatus snake venom, is described. Balt-LAAO-I is an acidic glycoprotein, pI approximately 5.37, homodimeric, Mr approximately 123,000, whose N-terminal sequence is ADVRNPLE EFRETDYEVL. It displays a high specificity toward hydrophobic and basic amino acids, while deglycosylation does not alter its enzymatic activity. Balt-LAAO-I induces platelet aggregation and shows bactericidal activity against Escherichia coli and Staphylococcus aureus. In addition, this enzyme is slightly hemorrhagic and induces edema in the mouse paw. Balt-LAAO-I is a multifunctional enzyme with promising relevant biotechnological and medical applications.     

In vitro effect of indomethacin and interferon-alpha on Th1 and Th2 cytokine synthesis in patients with chronic hepatitis C

Current evidences suggest that non-steroidal anti-inflammatory drugs could enhance the antiviral activity of interferon-alpha in chronic HCV infection. In this study, we investigated the effect of indomethacin, a non-steroidal anti-inflammatory drug, and interferon-alpha on cytokine production by peripheral blood mononuclear cells from 12 untreated patients with chronic hepatitis C. We evaluated the effect of incubation with indomethacin, interferon-alpha or both on synthesis of Th1- (interleukin-2, interferon-gamma) and Th2-associated cytokines (interleukin-4, interleukin-10), and of the antiviral protein 2',5'-oligoadenylate synthetase. Interferon-alpha induced a significant increase in production of interleukin-2. Smaller increases were also seen in the presence of indomethacin, while incubation with both indomethacin and interferon-alpha leads to a synergistic effect. Incubation with indomethacin decreased both interleukin-4 and interleukin-10, whereas interferon-alpha increased these cytokines. The addition of indomethacin to interferon-alpha significantly reversed this interferon-induced increase. Finally, both indomethacin and the association interferon-alpha plus indomethacin determined a significant increase in 2',5'-oligoadenylate synthetase production compared to both baseline and interferon-alpha alone. In conclusion, indomethacin was able to enhance the antiviral activity of interferon-alpha and to modulate the interferon-induced Th1 and Th2 cytokine response by increasing the Th1-response, fundamental for sustained clearance of HCV, and by decreasing the Th-2 type response, associated with HCV persistence.     

IS<Emphasis Type="Italic">Rm31</Emphasis>, a new insertion sequence of the IS<Emphasis Type="Italic">66</Emphasis> family in<Emphasis Type="Italic"> Sinorhizobium meliloti</Emphasis>

Sinorhizobium meliloti natural populations show a high level of genetic polymorphism possibly due to the presence of mobile genetic elements such as insertion sequences (IS), transposons, and bacterial mobile introns. The analysis of the DNA sequence polymorphism of the nod region of S. meliloti pSymA megaplasmid in an Italian isolate led to the discovery of a new insertion sequence, ISRm31. ISRm31 is 2,803 bp long and has 22-bp-long terminal inverted repeat sequences, 8-bp direct repeat sequences generated by transposition, and three ORFs (A, B, C) coding for proteins of 124, 115, and 541 amino acids, respectively. ORF A and ORF C are significantly similar to members of the transposase family. Amino acid and nucleotide sequences indicate that ISRm31 is a member of the IS66 family. ISRm31 sequences were found in 30.5% of the Italian strains analyzed, and were also present in several collection strains of the Rhizobiaceae family, including S. meliloti strain 1021. Alignment of targets sites in the genome of strains carrying ISRm31 suggested that ISRm31 inserts randomly into S. meliloti genomes. Moreover, analysis of ISRm31 insertion sites revealed DNA sequences not present in the recently sequenced S. meliloti strain 1021 genome. In fact, ISRm31 was in some cases linked to DNA fragments homologous to sequences found in other rhizobia species.     

Does tumor growth follow a "universal law"?

A general model for the ontogenetic growth of living organisms has been recently proposed. Here we investigate the extension of this model to the growth of solid malignant tumors. A variety of in vitro and in vivo data are analysed and compared with the prediction of a "universal" law, relating properly rescaled tumor masses and tumor growth times. The results support the notion that tumor growth follows such a universal law. Several important implications of this finding are discussed, including its relevance for tumor metastasis and recurrence, cell turnover rates, angiogenesis and invasion.     

The conserved glutamate residue adjacent to the Walker-B motif is the catalytic base for ATP hydrolysis in the ATP-binding cassette transporter BmrA

ATP-binding cassette (ABC) proteins constitute one of the widest families in all organisms, whose P-glycoprotein involved in resistance of cancer cells to chemotherapy is an archetype member. Although three-dimensional structures of several nucleotide-binding domains of ABC proteins are now available, the catalytic mechanism triggering the functioning of these proteins still remains elusive. In particular, it has been postulated that ATP hydrolysis proceeds via an acid-base mechanism catalyzed by the Glu residue adjacent to the Walker-B motif (Geourjon, C., Orelle, C., Steinfels, E., Blanchet, C., Deléage, G., Di Pietro, A., and Jault, J. M. (2001) Trends Biochem. Sci. 26, 539-544), but the involvement of such residue as the catalytic base in ABC transporters was recently questioned (Sauna, Z. E., Muller, M., Peng, X. H., and Ambudkar, S. V. (2002) Biochemistry, 41, 13989-14000). The equivalent glutamate residue (Glu504) of a half-ABC transporter involved in multidrug resistance in Bacillus subtilis, BmrA (formerly known as YvcC), was therefore mutated to Asp, Ala, Gln, Ser, and Cys residues. All these mutants were fully devoid of ATPase activity, yet they showed a high level of vanadate-independent trapping of 8-N3-alpha-32P-labeled nucleotide(s), following preincubation with 8-N3-[alpha-32P]ATP. However, and in contrast to the wild-type enzyme, the use of 8-N3-[gamma-32P]ATP unequivocally showed that all the mutants trapped exclusively the triphosphate form of the analogue, suggesting that they were not able to perform even a single hydrolytic turnover. These results demonstrate that Glu504 is the catalytic base for ATP hydrolysis in BmrA, and it is proposed that equivalent glutamate residues in other ABC transporters play the same role.