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Biomedical subjects

M Toma

Publications and source records attributed to M Toma.

At least 19 recordsLinked to original sources
PubMed2002

The ultrasonically induced reaction of benzoyl chloride with nitrobenzene: an unexpected sonochemical effect and a possible mechanism.

A mixture of benzoyl chloride and nitrobenzene is not known to be chemically reactive, indeed the mixture is chemically inert when subjected individually to either ultrasonic irradiation or heating. However, if this system is initially subjected to ultrasound and then heated for several hours at 200 degrees C, a reaction does occur and the products are benzoic anhydride, hydrochloric acid, nitrous and nitric acid together with some minor products. To the best of our knowledge, this is the first example of a reaction where the effect of ultrasound does not appear to be the consequence of the direct action of acoustic cavitation bubbles. A possible explanation of this behaviour is advanced which involves an electron transfer reaction in which nitrobenzene is first activated by ultrasound and then acts as oxidant in the thermal stage of reaction.

Journal Article↗
PubMed2001

Cl atom-initiated oxidation of three homologous methyl perfluoroalkyl ethers.

Chlorine atom-initiated photooxidations of three homologous methyl perfluoroalkyl ethers (HFEs), n-C(n)F(2n+1)OCH3 (n = 2, 3, and 5), in air in the absence of NOx were investigated with a long path FTIR/photochemical reaction system to elucidate the degradation mechanisms. The environmental removal processes of these three ethers in the troposphere were estimated. For oxidation of the three ethers, perfluoroalkyl formates (C(n)F(2n+1)OCHO; n = 2, 3 and 5) as relatively stable intermediates were produced at unity of the production ratio, which was independent of the perfluoroalkyl length. The rate constants for the reaction of Cl atoms with C2F5OCHO, C3F7OCHO, and C5F11OCHO were (1.2 +/- 0.5) x 10(-14), (1.2 +/- 0.5) x 10(-14), and (1.8 +/- 0.7) x 10(-14) cm3 molecule(-1) s(-1), respectively. The rate constants of the reaction of Cl with produced perfluoroalkyl formates were larger than these of perfluoroalkyl ethers. The formyl group of the perfluoroalkyl formates was finally converted to carbon dioxide. The -CF2- of the perfluoroalkyl groups for the three ethers was mainly converted to COF2 through the C-C cleavage; the conversion ratios from the carbons of the perfluoroalkyl group to COF2 were 48 +/- 10, 76 +/- 10, and 60 +/- 10% for C2F5OCH3, n-C3F7OCH3, and n-C5F11OCH3, respectively. Sixteen percent of the perfluoroalkyl group for n-C3F7OCH3 was converted to C2F5COF. Similarly, the perfluoroalkyl group of n-C5F11OCH3 was converted to C(n)F(2n+1)COF (n = 2, 3, and/or 4) with the yield of 15-30%, while for C2F5OCH3, the formation of CF3COF was not confirmed. As an oxidation product of the terminal CF3- group, 20, 22, and 16% of the CF3 group for C2F5OCH3, n-C3F7OCH3, and n-C5F11OCH3, respectively, were converted to CF3OOOCF3.

Biodegradation, Environmental↗
PubMed2001

Investigation of the effects of ultrasound on vegetal tissues during solvent extraction.

The paper presents an insight into the mechanism of the ultrasonic enhancement of solvent extraction through the effect of ultrasound on the vegetal material involved. Thus, a series of experiments has been developed to investigate the effect of ultrasonic energy on the vegetal material and the solvent used. Several results concerning the ultrasonic extractive value, ultrasonic swelling index and the effects of frequency on vegetal material are presented.

Plant Extracts↗
PubMed2001

Hepatitis B prevention strategies among pediatric hemodialysis centers.

We surveyed pediatric hemodialysis centers (PHDCs) concerning their hepatitis B virus (HBV) prevention strategies. One hundred thirty-one patients were being dialyzed in these PHDCs in December 1996. Although all centers immunized HBV-susceptible hemodialysis patients and had infection control policies to curtail the spread of HBV infection, most centers were not in compliance with all of the Centers for Disease Control and Prevention recommendations for isolating hepatitis B surface antigen-positive patients.

Adolescent↗
PubMed2001

Development of a new method to induce angiogenesis at subcutaneous site of streptozotocin-induced diabetic rats for islet transplantation.

The subcutaneous space is a potential site for clinical islet transplantation. Even though there are several advantages, poor blood supply at this site mainly causes failure of islet survival. In this study, angiogenesis was induced in advance at the diabetic rats subcutis for islet transplantation by implanting a polyethylene terephthalate (PET) mesh bag containing gelatin microspheres incorporating basic fibroblast growth factor (bFGF) (MS/bFGF) and a collagen sponge. The bFGF was incorporated into gelatin microspheres for controlled release of bFGF. As controls, a PET mesh bag with or without either collagen sponges or MS/bFGF was implanted at the subcutaneous site of diabetic rats. Macroscopic and microscopic examinations revealed the formation of capillary network in and around the PET mesh bag containing MS/bFGF and collagen sponges 7 days after implantation when compare with other control groups. When tissue hemoglobin level was also measured, a significantly high level of hemoglobin amount was observed compared with that of control groups. When allogeneic islets mixed with 5% agarose were transplanted into the prevascularized rat subcutis, normoglycemia was maintained for more than 40 days, while other control groups were ineffective. This study demonstrated that combination of gelatin microspheres incorporating bFGF and collagen sponges enabled the mesh to induce neovascularization even at the subcutaneous site of streptozotocin-induced diabetic rats, resulting in improved function of islet transplantation.

Animals↗
PubMed2000

The effect of osmo-induced stress on product formation by Zymomonas mobilis on sucrose.

The intensification of biosynthesis of fructooligosaccharides in the presence of high salt concentrations was observed during sucrose (10%) fermentation by Zymomonas mobilis 113S. A 0.6 M NaCl concentration led to an increase of oligosaccharide productivity by 3.5-fold. Sorbitol formation was increased in the presence of 0.16 M NaCl and was inhibited at highest salt concentrations. In a medium with high (65%, w/w) sucrose content the salts gave inhibitory effects on fructooligosaccharide production by lyophilised Z. mobilis cells. Influence of salts on gluconic acid and sorbitol formation under these conditions was studied. The ratio of oligosaccharides and gluconic acid productivity (Qolig./Qglucon.) was increased approximately 2 times at 1% KCl. Sorbitol formation was not significantly influenced in the presence of KCl (up to 2%).

Oligosaccharides↗
PubMed1999

Initial and long-term results of angioplasty in unprotected left main coronary artery.

Angioplasty of the unprotected left main coronary artery (LMCA) has been controversial. Although recent single-center studies suggest that new devices may change the situation, many questions and problems remain. Therefore, the results of unprotected left main coronary angioplasty of 175 procedures in 107 patients were analyzed to evaluate its feasibility and effectiveness. The treatment of the initial 107 cases included balloon angioplasty (39 cases, 36%), directional coronary atherectomy (53 cases, 50%), and stents (15 cases, 14%). They were divided into 3 major subgroups: (1) acute group (n = 14), in which LMCA angioplasty was performed in patients with acute myocardial infarction; (2) emergency group (n = 10); and (3) elective group (n = 83). In-hospital mortality was higher in the acute (35.7%) and emergency (40.0%) groups than in the elective group (3.6%; p <0.0001). Angiographic follow-up was routinely performed and the restenosis rate including in-hospital restenosis was 70% in the acute group, 37.5% in the emergency group, and 40% in the elective group (p = NS). The mean clinical follow-up period was 2.9 years, and the estimated 5-year survival rates of the acute and emergency groups were 50% and 48.2%, respectively. However the 5-year survival rate of the elective group was higher than that seen in the acute or emergency group (77.5%; p <0.05). Repeat LMCA angioplasty was performed in 37 of 68 patients with 8.8% mortality (38.5% of acute and emergency cases and 1.8% of elective cases). The results indicated that elective unprotected LMCA angioplasty is relatively feasible and effective under scheduled angiographic follow-up.

Adult↗
PubMed1990

[Efficacy of combined therapy using coronary reperfusion and elective percutaneous transluminal coronary angioplasty for acute myocardial infarction].

The effects of elective percutaneous transluminal coronary angioplasty (PTCA) performed one month after coronary reperfusion therapy in patients with acute myocardial infarction (AMI) were observed using exercise Tl-201 myocardial scintigraphy performed before and after PTCA. Myocardial perfusion in Tl-201 scintigraphy was significantly greater in the early (less than 4 hours) and late (4-9 hours) reperfusion groups than in the total occlusion group one month after the onset of AMI. Both reperfusion groups showed significant improvement in myocardial perfusion after elective PTCA; whereas, the total occlusion group showed no significant improvement. In the early reperfusion group, there were no significant differences in myocardial perfusion between those with well developed and those with poorly developed collateral circulations one month after the onset of AMI. However, in the late reperfusion group, myocardial perfusion was greater in those with well developed collateral circulations compared to those with poorly developed collateral circulations. The grade of myocardial perfusion in the late reperfusion group with poorly developed collateral circulations did not differ significantly from that of the total occlusion group. There was significant improvement of myocardial perfusion in the early and late reperfusion groups with well developed collateral circulations after elective PTCA; whereas, no significant improvement was observed in the late reperfusion group with poorly developed collateral circulations. These findings indicate that the time interval from the onset of AMI to reperfusion and the grade of development of collateral circulations are the major determinants of myocardial perfusion after elective PTCA and after reperfusion therapy.

Adult↗
PubMed1986

Poorly encapsulated Cryptococcus neoformans from patients with AIDS. I: Preliminary observations.

Ten isolates of Cryptococcus neoformans recovered from individual patients with the acquired immunodeficiency syndrome (AIDS) were studied in conjunction with three other isolates from non-AIDS patients. On primary culture nine out of ten of the AIDS isolates grew as nonmucoid, dry, pasty colonies resembling those produced by "diphtheroids." One isolate formed moist colonies. In contrast, the three non-AIDS Cryptococcus neoformans isolates produced highly mucoid colonies. India ink mounts of primary cultures of the ten AIDS isolates after 48 hours incubation in 5% CO2 showed markedly smaller capsules than the three non-AIDS isolates. India ink preparations of fresh cerebrospinal fluid of two specimens from AIDS patients in which capsule sizes were systematically determined showed a few moderately encapsulated cells dispersed among numerous others that were poorly encapsulated. This observation was confirmed in mucicarmine-stained smears of cerebrospinal fluid. Poorly encapsulated Cryptococcus neoformans seem to be associated with infections in AIDS patients.

Acquired Immunodeficiency Syndrome↗
PubMed1982

Structural characterization of myosin from bovine brain.

Myosins isolated from bovine brain, rabbit skeletal muscle, and chicken gizzard smooth muscle and their heavy meromyosin and light meromyosin fractions were studied in the electron microscope by negative staining with uranyl acetate. Under similar conditions of preparation and polymerization, the three myosins formed paracrystals of different structures. The light meromyosin portion of the skeletal muscle myosin also assembled in a different fashion than the brain or smooth muscle light meromyosins; the latter two assembled similarly. The heavy meromyosin portion from each of the three myosins was shown to interact with the actins isolated from each of the three tissue sources by the formation of the characteristic arrowhead patterns with similar periodicities. The brain heavy meromyosin attachment to both skeletal and brain actins was dissociated by ATP. It is suggested that differences in the light meromyosin portions of the three myosins may account in part for their differences in assembly in vivo.

Actins↗