Electrical-thermal analytical modeling of monopolar RF thermal ablation of biological tissues: determining the circumstances under which tissue temperature reaches a steady state.

It has been suggested that during RF thermal ablation of biological tissue the thermal lesion could reach an equilibrium size after 1-2 minutes. Our objective was to determine under which circumstances of electrode geometry (needle-like vs. ball-tip), electrode type (dry vs. cooled) and blood perfusion the temperature will reach a steady state at any point in the tissue. We solved the bioheat equation analytically both in cylindrical and spherical coordinates and the resultant limit temperatures were compared. Our results demonstrate mathematically that tissue temperature reaches a steady value in all cases except for cylindrical coordinates without the blood perfusion term, both for dry and cooled electrodes, where temperature increases infinitely. This result is only true when the boundary condition far from the active electrode is considered to be at infinitum. In contrast, when a finite and sufficiently large domain is considered, temperature reaches always a steady state.

Characterization of water reservoirs affected by acid mine drainage: geochemical, mineralogical, and biological (diatoms) properties of the water.

This work presents a combination of geochemical, mineralogical, and biological data obtained in water reservoirs located in one of the most paradigmatic mining regions, suffering from acid mine drainage (AMD) problems: the Iberian Pyrite Belt (IPB). Four water reservoirs located in the Spanish sector of the IBP, storing water for different purposes, were selected to achieve an environmental classification based on the effects of AMD: two mining dams (Gossan and Águas Ácidas), a reservoir for industrial use (Sancho), and one with water used for human supply (Andévalo). The results indicated that the four reservoirs are subject to the effect of metallic loads from polluted rivers, although with different levels: Águas Ácidas > Gossan > Sancho ≥ Andévalo. In accordance, epipsammic diatom communities have differences in the respective composition and dominant taxa. The dominant diatoms in each reservoir indicated acid water: Pinnularia acidophila and Pinnularia aljustrelica were found in the most acidic dams (Gossan and Águas Ácidas, with pH <3), Pinnularia subcapitata in Sancho (pH 2.48-5.82), and Eunotia exigua in Andévalo (pH 2.34-6.15).

[Clinical assessment of a new anesthetic system: the Temel Supra (II)]. / Análisis clínico de un nuevo sistema de anestesia: Temel Supra (II).

OBJECTIVES: To assess the clinical performance of a new anesthetic system developed to provide novel advantages in ventilating the anesthetized patient. PATIENTS AND METHOD: The clinical performance of the Temel Supra was evaluated in 100 adult patients who were anesthetized and ventilated using the device. RESULTS: The patients were adequately oxygenated and ventilated; no adverse events were observed. An open circuit, low flow, or closed circuit could be chosen freely. Ventilation was fully monitored: among the variables measured were rebreathed volume; leaks while the patient was connected; consumption of oxygen, nitrous oxide and anesthetic agents; and cardiac output (noninvasively). CONCLUSIONS: Ventilation and gas exchange were satisfactory in all cases even though some patients developed considerable respiratory impedance. The monitoring of oxygen and other gases consumed and of carbon dioxide produced provided very valuable information about metabolism and pharmacokinetics. The noninvasive monitoring of cardiac output seems to us to be a useful feature for aiding hemodynamic control. The independence of the open and closed circuits means that expired gases do not pass through the canister when the open circuit is used, resulting in savings on soda lime for drying. During pressure-control ventilation, the system maintains a plateau to guarantee better distribution of inspired gases. Other important features are warnings, constant monitoring of leaks, the 100% efficacy of the circuit, and the low internal volume.

Análisis clínico de un nuevo sistema de anestesia: Temel Supra® (II) / Clinical assessment of a new anesthetic system: the Temel Supra® (II)

OBJETIVOS: Realizar la evaluación clínica del nuevo sistema de anestesia Temel Supra® cuyo fin es aportar nuevas ventajas a la ventilación del paciente anestesiado. PACIENTES Y MÉTODOS: Se realiza una evaluación clínica en 100 pacientes adultos anestesiados, y ventilados con este equipo. RESULTADOS: Los pacientes fueron oxigenados y ventilados correctamente sin registrarse incidencia alguna. Se pudo elegir independientemente circuito abierto, bajos flujos y circuito cerrado. La monitorización ventilatoria es completa y el sistema mide, entre otros, el volumen reinhalado, las fugas con el paciente conectado, los consumos de O2, N2O, agentes anestésicos y el gasto cardíaco de manera incruenta. CONCLUSIONES: La ventilación e intercambio gaseoso de los pacientes ha sido satisfactorio en todos los casos, a pesar de que algunos pacientes ofrecían impedancias respiratorias importantes. La monitorización de los consumos de oxígeno y gases así como la producción de carbónico, ofrece una información muy valiosa con respecto al metabolismo y la farmacocinética. La monitorización incruenta del gasto cardíaco nos parece una aportación importante al control hemodinámico del paciente. La independencia del circuito abierto respecto al circular determina que, al emplear el circuito abierto, los gases espirados no pasen por el cánister. Ello tiene como resultado, además de un ahorro en cal sodada, el que no se reseque la misma. Durante la ventilación controlada por presión el sistema permite mantener un nivel de plató que garantiza una mejor distribución del gas inspirado.Otros aspectos importantes son los mecanismos de seguridad, el control permanente de las fugas, la eficacia 100 por ciento del circuito y el bajo volumen interno (AU)

Fertility of beef cattle females with mating stimuli around insemination.

An experiment was conducted to test the hypothesis that sterile mounts around insemination improves pregnancy rate to artificial insemination (AI) and to define the effects of age, season, time to complete AI and time of day of insemination. A total of 178 Simbrah females were randomly assigned by calving date and body condition to one of three treatments during two consecutive years: (1) mating stimuli with a sterile bull at the time the cows were detected in estrus; (2) mating stimuli immediately after completing AI; (3) without mating stimuli. All cows and heifers were maintained under the same conditions of handling and feeding within the two breeding seasons (winter 1995 and summer 1996). Vasectomized bulls were used for the sterile mounts. Cows and heifers that were given a sterile mount at the time of detection of estrus, had an increased pregnancy rate (60.0%) compared with females given a sterile mount after completing AI (25.4%) or females without the sterile mount (35.6%) (P < 0.01). Age, season, time to complete AI and time of day of AI were all non-significant (P > 0.05). Therefore, there is a biostimulatory effect of mating at the time beef cattle females are detected in estrus, on pregnancy rates to AI.

Molecular and epidemiological study of Salmonella clinical isolates.

A survey of Salmonella infections was carried out over a 1-year period in the rural community covered by the Hospital Reina Sofía (Tudela, Spain). The 255 strains that were collected were studied by serotyping, antimicrobial resistance, and plasmid profile analysis. The predominant serotype was S. enteritidis (85.90%), followed by S. typhimurium (7.06%) and S. virchow (2.36%). Only 7.84% of the strains were resistant to antimicrobial agents. The most common resistance was to beta-lactam antibiotics. This resistance was due to the presence of one of two types of beta-lactamases, TEM-1 or TEM-2. Resistance to kanamycin was associated with the synthesis of a 3'-O-phosphotransferase. The resistance to streptomycin and chloramphenicol was either not enzymatic or was due to a 3"-O-phosphotransferase and a chloramphenicol acetyltransferase, respectively. Analysis of total plasmid DNA content revealed the presence of plasmids in 96.08% of the isolates. According to their plasmid profile, the strains could be classified into different groups. The three main groups, which accounted for 50.19, 20.78, and 4.70% of the isolates, respectively, corresponded to the antimicrobial-susceptible S. enteritidis serotype. These results suggested that plasmid profile analysis in conjunction with antimicrobial resistance determination can be useful for subtyping resistant Salmonella isolates.

Resistance to apramycin in two enterobacterial clinical isolates: detection of a 3-N-acetyltransferase IV.

Considering the possible role of farm animals in the contamination of human consumers by plasmid-mediated apramycin-resistant enterobacteria strains, this type of resistance should be tested more systematically in human isolates. Very recently we isolated in Zaragoza one apramycin-resistant Escheria coli strain obtained from the blood of a hospitalized patient; this clinical isolate produced a plasmid-mediated 3-N-aminoglycoside acetyltransferase IV. We describe also the isolation in Madrid of one multiresistant Klebsiella pneumoniae clinical strain. This isolate harbored a single plasmid and carried determinants for apramycin, gentamicin, tobramycin, hygromycin B, streptomycin, and ampicillin, which could be transferred en bloc to E. coli K-12 J62. Extracts from donor and transconjugant strains carrying pUZ6776 plasmid produce acetyltransferase activity AAC(3)-IV and double phosphotransferase activity (HPH and APH(3'')).

Stability of dactimicin to aminoglycoside-modifying enzymes produced by 341 bacterial clinical isolates.

The stability of dactimycin to aminoglycoside-modifying enzymes produced by 341 bacterial clinical isolates has been studied. Enzymatic activities were measured by the phosphocellulose binding assay. The results demonstrated that dactimicin was stable to the following enzymes: (i) AAC(3)-II,-III,-IV and -V. (ii) AAC(2'); (iii)AAC(6')-I and -II;(iv) ANT(2"); (v)ANT(4'); (vi) APH(3')-I,-II,-III and -IV. In contrast, dactimicin was only inactivated by two enzymes, AAC(3)-I and the bifunctional AAC(6')/APH(2"). This staphylococcal enzyme modified and inactivated dactimicin by acetylation but not by phosphorylation, suggesting the possibility of a second target amino group, such as 6'-NH2, in addition to the C4 amino group, which is the target for AAC(3)-I.

Characterization of an hospital disseminated plasmid encoding resistance to gentamicin and other antimicrobial agents.

A preliminary report has shown the existence of an endemic R plasmid in the University Hospital of Zaragoza. The results presented in this paper demonstrate the dissemination of a new 73 kilobases plasmid into multiple strains and species of gram-negative bacilli. This transferable plasmid belongs to Incompatibility group P and mediates resistance to ampicillin, tetracycline, gentamicin, kanamycin, streptomycin, chloramphenicol and sulfamethoxazole, synthesizing the aminoglycoside-modifying enzymes 3-acetyltransferase, 3'phosphotransferase, and 3"nucleotidyltransferase, and a TEM-1 beta-lactamase. These results and the previous findings show that a family of gentamicin-resistance plasmids exists among the gram-negative bacteria in the University Hospital. Resistance to gentamicin in all these plasmids is associated with the formation of 3-N-acetyltransferases.

Chromosomal origin of acetyltransferase AAC(6') specifying amikacin resistance in Serratia marcescens.

Two clinical isolates of Serratia marcescens resistant to aminoglycoside-aminocyclitols and other antibiotics have been examined for aminoglycoside-modifying enzymes. Both strains were amikacin-resistant, and this resistance was mediated by an acetyltransferase AAC(6'). S. marcescens 737 contains a single conjugative plasmid, pUZ 737, of 135 kilobases, which confers resistance to gentamicin and tobramycin by a nucleotidyltransferase, ANT(2"), and to kanamycin, neomycin, butirosin and lividomycin by a phosphotransferase, APH(3'). S. marcescens 1830 does not contain extrachromosomal DNA, and it produced only the above mentioned AAC(6'). The presence of AAC(6') and associated aminoglycoside resistance are not dependent on the presence of a detectable plasmid, not transferred by conjugation, and not cured. Therefore, this enzyme is probably encoded by a chromosomal gene.

[APH(3')-II phosphotransferase determination using protein transfer (western blotting)]. / Estudio de la fosfotransferasa APH(3')-II mediante trasferencia de proteínas ("western blotting").

The APH(3')-II aminoglycoside-phosphotransferase has been studied by protein blotting. This technique allowed the detection of the enzyme in the crude extracts from clinical isolates of Enterobacteriaceae, and the molecular weight determination of the APH(3')-II. The obtained molecular weight of 25,000 is coincident with the previously reported value determined by a different method. These results demonstrate that this technique is useful for the study of aminoglycoside-modifying enzymes.

Enzymatic modification of aminoglycoside antibiotics by Branhamella catarrhalis carrying an R factor.

Fifteen out of 89 clinical strains of Branhamella catarrhalis isolated from patients at the University Hospital of Zaragoza were resistant to aminoglycosides and other antimicrobials. In two strains, B. catarrhalis 220 and B. catarrhalis 115, the resistance to aminoglycosides was associated with synthesis of aminoglycoside-modifying enzymes, namely 3"-O-phosphotransferase [APH(3")] and 3'-O-phosphotransferase [APH(3')]. B. catarrhalis 115 was resistant to ampicillin, streptomycin, kanamycin, neomycin, butirosin, lividomycin, ribostamycin, paromomycin and trimethoprim-sulfamethoxazole and harboured a 32 megadalton (Md) plasmid. The resistance determinants of the latter were transferred to Neisseria subflava by conjugation and to Escherichia coli by transformation. The transconjugant strain presented an antibiotic resistance pattern similar to the donor strain and carried the same plasmid. The transformant strain acquired the 32 Md plasmid but presented, besides the resistance pattern already mentioned, resistance to tetracycline, gentamicin and tobramycin. Resistance to gentamicin and tobramycin was mediated by the synthesis of a 3-N-acetyltransferase. This resistance and the related enzyme were expressed neither in the donor B. catarrhalis strain nor in the transconjugant N. subflava strain.

Aminoglycoside-phosphotransferases APH(3')-IV and APH(3") synthesized by a strain of Campylobacter coli.

Campylobacter coli strain 981 of animal origin was resistant to erythromycin, tetracycline, streptomycin, kanamycin, ribostamycin, neomycin, paromomycin, lividomycin, and butirosin. Resistance to aminoglycosides of strain 981 was mediated by phosphotransferases APH (3') type-IV and APH (3"). C. coli 981 harboured three plasmids of 24, 34, and 40 Megadaltons respectively. None of these plasmids were transferable to Escherichia coli K-12 by conjugation.

A growing clinical problem: plasmid-determined resistance to aminocyclitol-aminoglycosides in enterobacteria.

The contents of this paper include the following items: Incidence of R+ gentamicin-resistant enterobacteria and gentamicin usage. Aminocyclitol-modifying enzymes produced by 719 R+ isolates of enterobacteria belonging to different genera. Epidemiology of some plasmids (so-called pUZ) determining resistance to aminocyclitol in enterobacteria. Comparison of AAC (3) classes.

Expression of bacteriophage M13 DNA in vivo. Localization of the transcription initiation and termination signal of the mRNA coding for the major capsid protein.

During the infection cycle of the filamentous bacteriophage M13 a phage specific RNA species is made which selectively directs in vitro the synthesis of the precursor of the major capsid protein encoded by gene VIII. This RNA is unstable (its mean half-life is 11 min) and is made in amounts representing at least 2% of the newly synthesized RN. Nucleotide sequence analysis have indicated that the synthesis of this RNA species is initiated and terminated at the same promoter (G0.18) and termination signal (T0.25) of the M13 genome as the 8S RNA species made in vitro under the direction of M13 replicative form DNA.