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Biomedical subjects

J M Romeo

Publications and source records attributed to J M Romeo.

32 records · Page 2Linked to original sources
PubMed1990

Role of glucagon in the splanchnic and systemic hemodynamic changes induced by portal-systemic blood shunting.

Portal-systemic blood shunting is often accompanied by hyperglucagonemia and hemodynamic changes. To determine this causal relation, splanchnic and systemic hemodynamics (radioactive microspheres) and plasma glucagon levels (radioimmunoassay) were assessed in conditions of total portal-systemic shunting in portacaval-shunted (PCS) rats and in sham-operated (SO) normal rats. To compare these results, another hemodynamic study was undertaken basally and during glucagon infusion in nonoperated normal rats. PCS rats showed a threefold greater plasma glucagon concentration than SO animals (924 +/- 134 vs. 309 +/- 18 pg/ml, p less than 0.01), and they developed a hyperdynamic splanchnic circulation with higher portal venous inflow than SO rats (8.29 +/- 1.1 vs. 5.09 +/- 0.4 ml/min/100 g, p less than 0.05). Infusion of a pharmacological dose of glucagon in normal rats increased portal venous inflow (from 4.92 +/- 0.33 to 6.24 +/- 0.48 ml/min/100 g, p less than 0.05) so as to imply this hormone in the development of the hyperdynamic splanchnic circulation in conditions of portal-systemic shunting. However, the discrepancies in systemic hemodynamics between PCS and glucagon-infused rats may be a result of the different plasma glucagon levels reached in the two groups.

Animals↗
PubMed1989

Effect of endothelin on systemic and regional hemodynamics in rats.

In this study we analyzed the changes in systemic haemodynamics induced by endothelin, 1 nmol/kg, given as an i.v. bolus to anaesthetized rats. Endothelin induced a dramatic decrease in cardiac output whereas the total peripheral resistance increased more than two times. In addition, renal blood flow decreased while renal vascular resistance increased to a similar extent. A marked decrease in blood flow to the splanchnic organs was also observed. In conclusion, endothelin seems to modulate peripheral vasomotor tone, at least under certain conditions.

Animals↗
PubMed1988

Effect of portacaval surgical anastomosis on systemic and splanchnic hemodynamics in portal hypertensive, cirrhotic rats.

The effect of surgical end-to-side portacaval anastomosis (PCSA) on systemic and splanchnic circulation has been studied in cirrhotic rats with portal hypertension (CCl4-phenobarbital method) and in control animals. Hemodynamics have been measured using the microsphere technique, with a reference sample for the systemic hemodynamic measurements, and intrasplenic injection for portal systemic shunting rate measurements. Compared with controls, sham-operated (SO) cirrhotic rats showed a hyperdynamic circulation with increased cardiac output (CO) and decreased mean arterial pressure and peripheral resistances. PCSA in control rats induced only a small change in systemic hemodynamics, with parallel decreases in arterial pressure and peripheral resistances, and a small, nonsignificant increase in CO. In cirrhotic rats, PCSA induced a decrease of CO to values similar to those of control rats, with an increase in total peripheral resistances. PCSA induced an increase in hepatic arterial blood flow in control and in cirrhotic rats, portal pressure becoming in this latter group not different from that of control rats. Blood flow to splanchnic organs was higher in SO cirrhotic than in SO control animals. Thus portal venous inflow was also increased in SO cirrhotic rats. PCSA induced an increase in portal venous inflow in control rats, which was only significant in cirrhotic rats when expressed as a percentage of CO. In SO control animals, a significant correlation was observed between total peripheral resistances and splanchnic arteriolar resistances and between CO and splanchnic blood flow. These correlations were not observed in cirrhotic rats. These results do not support the hypothesis that hyperdynamic circulation shown by cirrhotic rats is based on increases in splanchnic blood flow and (or) massive portal systemic shunting.

Animals↗
PubMed1987

Cloning of the gene for myxobacterial hemagglutinin and isolation and analysis of structural gene mutations.

Myxobacterial hemagglutinin (MBHA) is a major developmentally induced protein that accumulates during the period of cellular aggregation in the bacterium Myxococcus xanthus. It has been shown that this lectin is targeted to the cell surface and periplasmic space of developmental cells, suggesting that it may play a role in cell-cell recognition or agglutination. We have cloned the structural gene for MBHA by using synthetic deoxyoligonucleotides containing sequences deduced from the amino acid sequence of MBHA and have used the cloned gene to construct strains of M. xanthus that cannot synthesize MBHA. We found that although the MBHA-deficient strains are delayed in their developmental time course, they are otherwise able to aggregate and sporulate normally. Our results suggest that MBHA may function to increase the efficiency of fruiting-body formation but is not a critical component of cellular aggregation.

Cloning, Molecular↗
PubMed1986

Activity of a phage-modified RNA polymerase at hybrid promoters. Effects of substituting thymine for hydroxymethyluracil in a phage SP01 middle promoter.

Transcription of bacteriophage SP01 middle promoters is specifically initiated by a complex of the Bacillus subtilis host's RNA polymerase core (E) with the SP01 gene 28 transcription-regulating protein, gp28. Normal SP01 DNA contains hydroxymethyluracil (hmUra) in place of thymine and E . gp28 preferentially transcribes hmUra-containing DNA. Hybrid DNA molecules containing an SP01 middle promoter, PM25 . 1, have been constructed in which one DNA strand contains T and the other hmUra. The major feature of these reciprocal hybrid promoters is that one has, predominantly, T substituted for hmUra in the central -35 recognition sequence in the transcribed strand, while the other has, predominantly, T substituted for hmUra in the -10 recognition sequence in the non-transcribed strand. Binding by the E . gp28 RNA polymerase and transcription of these hybrid promoters and of the normal, all-hmUra, promoter have been compared. Both hybrid promoters are weaker than the normal PM25 . 1 promoter, but the hybrid promoter with T substituted in the -10 sequence is the weakest of the set. The DNase I footprint of the normal PM25 . 1 promoter shows temperature-dependent protection of a relatively long stretch of DNA downstream from the transcriptional start site, correlating with a thermal transition of transcriptional activity of promoter complexes. The stronger of the hybrid promoters also undergoes this transition, but the weaker does not. We discuss these findings in terms of protein-DNA interactions determining specificity for a modified nucleotide at this promoter.

Bacillus subtilis↗
PubMed1986

The phage SPO1-specific RNA polymerase, E.gp28, recognizes its cognate promoters in thymine-containing DNA.

The bacteriophage SPO1 gene 28-encoded protein, gp28, directs specific recognition of viral middle promoters in hydroxymethyluracil-containing DNA by the Bacillus subtilis host's RNA polymerase core. Using appropriately sensitive methods of detection, we have shown that discrimination against thymine-containing DNA is not absolute and that the gp28-containing RNA polymerase precisely initiates transcription at two thymine-containing SPO1 middle promoters.

Bacteriophages↗
PubMed1986

Nucleotide sequence of the myxobacterial hemagglutinin gene contains four homologous domains.

Myxococcus xanthus, a Gram-negative bacterium, has a complex life cycle that includes fruiting-body formation, a primitive form of multicellular development. Myxobacterial hemagglutinin (MBHA) is a lectin that is induced during the aggregation phase of fruiting-body formation. We have cloned the gene for MBHA and determined its sequence by the dideoxy chain-termination technique. The sequence data show the probable sites for translational initiation and termination and suggest that MBHA does not contain a cleaved leader signal peptide. The DNA sequence shows four strong internal homologies. The deduced amino acid sequence shows that the protein (Mr 27,920) consists of four highly conserved domains each consisting of 67 amino acids. Thus MBHA is physically multivalent in structure, a requirement for all hemagglutinins.

Amino Acid Sequence↗
PubMed1976

Biosynthesis of ribothymidine in the transfer RNA of Streptococcus faecalis and Bacillus subtilis. A methylation of RNA involving 5,10-methylenetetrahydrofolate.

The methyl moiety of ribothymidine in the tRNA of Streptococcus faecalis, Bacillus subtilis, and probably Bacillus cereus is dervied from a 1-carbon folate derivative and not S-adenosylmethionine. Micrococcus luteus (M. lysodeikticus) tRNA appears to be almost devoid of ribothymidine. S. faecalis tRNA lacking ribothymidine can be methylated in vitro with formation of ribothymidine. 5,10-Methylenetetrahydrofolate has been identified as the 1-carbon donor involved in ribothymidine formation in S. faecalis and implicated in the analogous reaction in B. subtilis. The reaction requires FADH2 and/or another reducing agent present in cell extracts for the reduction of the methylene moiety.

Bacillus subtilis↗