Vasodilator actions of several N-nitroso compounds

Recent studies have shown that N-nitroso compounds can activate arterial guanylate cyclase and relax isolated arterial smooth muscle; however, the effects of these substances on the cardiovascular system in the anesthetized cat are unknown. The present study was undertaken to compare the effects of several nitrosoguanidines and a nitrosamine, N-nitrosodimethylamine, on arterial guanylate cyclase activity, isolated arterial smooth muscle tone, and systemic vascular resistance in the anesthetized cat. Intravenous injections and infusions of the nitrosoguanidines glyceryl trinitrate (GTN) and sodium nitroprusside (SNP) decreased systemic arterial pressure. During intravenous infusion of the nitrosoguanidines GTN and SNP, cardiac output was unchanged at the peak of the decrease in aortic pressure, indicating that the nitrosoguanidines GTN and SNP both reduced systemic vascular resistance. In addition, intraarterial injections of the nitrosoguanidines produced dose-dependent decreases in perfusion pressure in the feline mesenteric vascular bed perfused at constant flow. These substances were potent relaxants of isolated arterial smooth muscle and markedly activated arterial guanylate cyclase. In contrast, N-nitrosodimethylamine was devoid of vasodilator activity in vivo and exerted only minimal effects on isolated arterial smooth muscle tone or on arterial guanylate cyclase activity. The present data demonstrate a relationship between guanylate cyclase activation and arterial smooth muscle relaxation and suggest that the vasodilator effects on resistance vessels in vivo in response to selected N-nitroso compounds may involve such a mechanism. Although the significance of the presently reported cardiovascular responses to N-nitroso compounds is uncertain, N-nitroso compounds may represent a previously unrecognized class of substances which can be formed in the body and which possess marked vasodilator activity. It is possible that this vasodilator activity may involve the relaxation of vascular smooth muscle through activation of guanylate cyclase.     

The C57BL/6J Mouse Exhibits Sporadic Congenital Portosystemic Shunts

C57BL/6 mice are the most widely used strain of laboratory mice. Using in vivo proton Magnetic Resonance Spectroscopy (¹H MRS), we have repeatedly observed an abnormal neurochemical profile in the brains of both wild-type and genetically modified mice derived from the C57BL/6J strain, consisting of a several fold increase in cerebral glutamine and two fold decrease in myo-inositol. This strikingly abnormal neurochemical “phenotype” resembles that observed in chronic liver disease or portosystemic shunting and appeared to be independent of transgene, origin or chow and was not associated with liver failure. As many as 25% of animals displayed the abnormal neurochemical profile, questioning the reliability of this model for neurobiology. We conducted an independent study to determine if this neurochemical profile was associated with portosystemic shunting. Our results showed that 100% of the mice with high brain glutamine displayed portosystemic shunting by concomitant portal angiography while all mice with normal brain glutamine did not. Since portosystemic shunting is known to cause alterations in gene expression in many organs including the brain, we conclude that portosystemic shunting may be the most significant problem associated with C57BL/6J inbreeding both for its effect on the central nervous system and for its systemic repercussions.     

Phylogeny of the Drosophila saltans species group based on combined analysis of nuclear and mitochondrial DNA sequences

Nucleotide sequences from two nuclear loci, alcohol dehydrogenase and internal transcribed spacer-1 of the nuclear ribosomal DNA repeats, and two mitochondrial genes, cytochrome oxidase I and cytochrome oxidase II, were determined from nine species in the Drosophila saltans species group. The partition homogeneity test and partitioned Bremer support were used to measure incongruence between phylogenetic hypotheses generated from individual partitions. Individual loci were generally congruent with each other and consistent with the previously proposed morphological hypothesis, although they differed in level of resolution. Since extreme conflict between partitions did not exist, the data were combined and analyzed simultaneously. The total evidence method gave a more resolved and highly supported phylogeny, as indicated by bootstrap proportions and decay indices, than did any of the individual analyses. The cordata and elliptica subgroups, considered to have diverged early in the history of the D. saltans group, were sister taxa to the remainder of the saltans group. The sturtevanti subgroup, represented by D. milleri and D. sturtevanti, occupies an intermediate position in this phylogeny. The saltans and parasaltans subgroups are sister clades and occupy the most recently derived portion of the phylogeny. As with previous morphological studies, phylogenetic relationships within the saltans subgroup were not satisfactorily resolved by the molecular data.      

Respiratory allergy to Blomia tropicalis: Immune response in four syngeneic mouse strains and assessment of a low allergen-dose,short-term experimental model

Background

The dust mite Blomia tropicalis is an important source of aeroallergens in tropical areas. Although a mouse model for B. tropicalis extract (BtE)-induced asthma has been described, no study comparing different mouse strains in this asthma model has been reported. The relevance and reproducibility of experimental animal models of allergy depends on the genetic background of the animal, the molecular composition of the allergen and the experimental protocol.

Objectives

This work had two objectives. The first was to study the anti-B. tropicalis allergic responses in different mouse strains using a short-term model of respiratory allergy to BtE. This study included the comparison of the allergic responses elicited by BtE with those elicited by ovalbumin in mice of the strain that responded better to BtE sensitization. The second objective was to investigate whether the best responder mouse strain could be used in an experimental model of allergy employing relatively low BtE doses.

Methods

Groups of mice of four different syngeneic strains were sensitized subcutaneously with 100 μg of BtE on days 0 and 7 and challenged four times intranasally, at days 8, 10, 12, and 14, with 10 μg of BtE. A/J mice, that were the best responders to BtE sensitization, were used to compare the B. tropicalis-specific asthma experimental model with the conventional experimental model of ovalbumin (OVA)-specific asthma. A/J mice were also sensitized with a lower dose of BtE.

Results

Mice of all strains had lung inflammatory-cell infiltration and increased levels of anti-BtE IgE antibodies, but these responses were significantly more intense in A/J mice than in CBA/J, BALB/c or C57BL/6J mice. Immunization of A/J mice with BtE induced a more intense airway eosinophil influx, higher levels of total IgE, similar airway hyperreactivity to methacholine but less intense mucous production, and lower levels of specific IgE, IgG1 and IgG2 antibodies than sensitization with OVA. Finally, immunization with a relatively low BtE dose (10 μg per subcutaneous injection per mouse) was able to sensitize A/J mice, which were the best responders to high-dose BtE immunization, for the development of allergy-associated immune and lung inflammatory responses.

Conclusions

The described short-term model of BtE-induced allergic lung disease is reproducible in different syngeneic mouse strains, and mice of the A/J strain was the most responsive to it. In addition, it was shown that OVA and BtE induce quantitatively different immune responses in A/J mice and that the experimental model can be set up with low amounts of BtE.     

Role of HLA DRB1*15 and HLA DRB1*16alleles in the genetic susceptibility to develop systemic lupus erythematosus (SLE) after Chikungunya and Zika viruses infection in México

Systemic lupus erythematosus (SLE) is a clinically and genetically heterogeneous disease particularly prevalent in Mexico. Althoughits etiology is unknown, genetic factors strongly influence its presenceas well as triggering factors, such as viral infections, including Cytomegalovirus and Epstein-Barr virus. Here,the study presents the appearance of de novoSLE (patients who did not present SLE before de virus infection, corroborated by serological analysis and negative for antinuclear antibodies) cases in Mexicans who live near the southern border of Mexico, who presented clinical symptoms of arthritic, hematological, mucocutaneous and renal SLE, after Zika and/ or Chikungunya virus infection. Low resolution class Ⅱ HLA typing was performed, which found a significantly increased frequency of HLA DRB1*02 (15 and 16)when compared to a group of 99 healthy individuals (P =0.001, OR=4.5, IC95% 1.8~11.0). All the patients were diagnosed with SLE 1 to 3 years after being confirmed with the Zika, and/or Chikungunya infection. At the point of acute viral infection, none of the patients presented clinical signs or symptoms of autoimmunity or were negative for antinuclear antibodies. In genetically susceptible individuals, Zika and Chikungunya viral infection can trigger SLE.     

Localized 13C NMR Spectroscopy in the Human Brain of Amino Acid Labeling from d-[1-13C]Glucose

Abstract: Cerebral metabolism of d [1-¹³C]glucose was studied with localized ¹³C NMR spectroscopy during intravenous infusion of enriched [1-¹³C]glucose in four healthy subjects. The use of three-dimensional localization resulted in the complete elimination of triacylglycerol resonance that originated in scalp and subcutaneous fat. The sensitivity and resolution were sufficient to allow 4 min of time-resolved observation of label incorporation into the C3 and C4 resonances of glutamate and C4 of glutamine, as well as C3 of aspartate with lower time resolution. [4-¹³C]Glutamate labeled rapidly reaching close to maximum labeling at 60 min. The label flow into [3-¹³C]glutamate clearly lagged behind that of [4-¹³C]glutamate and peaked at t = 110–140 min. Multiplets due to homonuclear ¹³C-¹³C coupling between the C3 and C4 peaks of the glutamate molecule were observed in vivo. Isotopomer analysis of spectra acquired between 120 and 180 min yielded a ¹³C isotopic fraction at C4 glutamate of 27 ± 2% (n = 4), which was slightly less than one-half the enrichment of the C1 position of plasma glucose (63 ± 1%), p < 0.05. By comparison with an external standard the total amount of [4-¹³C]glutamate was directly quantified to be 2.4 ± 0.1 µmol/ml-brain. Together with the isotopomer data this gave a calculated brain glutamate concentration of 9.1 ± 0.7 µmol/ml, which agrees with previous estimates of total brain glutamate concentrations. The agreement suggests that essentially all of the brain glutamate is derived from glucose in healthy human brain.