[Evaluation of API Coryne System, version 2.0, for diphteroid gram-positive rods identification with clinical relevance]. / Evaluación del sistema API coryne, versión 2.0, para la identificación de bacilos gram-positivos difteroides de importancia clínica.

The ability of the API Coryne system, version 2.0, to identify 178 strains of gram-positive rods was evaluated. Seventy eight isolates belonged to genus Corynebacterium and one hundred to related genera, all strains were isolated from clinical samples at the Laboratory of Bacteriology, Hospital de Clínicas José de San Martin (UBA) between 1995 and 2004. The isolates were identified according to von Graevenitz and Funke's scheme. One hundred and sixty two out of 178 strains (91%) were correctly identified at genus and species level (IC95 = 85.6-94.6), in 44 of them (24.7%) additional tests were needed to final identification. Sixteen strains (9%) were not correctly identified (IC95 = 5.4-14.4); none of the 178 strains remained unidentified. The API Coryne system, version 2.0, is useful to identify the majority of Cory-nebacterium species with clinical relevance: Corynebacterium jeikeium, Corynebacterium urealyticum, Corynebacterium striatum, Corynebacterium pseudodiphtheriticum, Corynebacterium amycolatum and related species such as Arcanobacterium haemolyticum, Dermabacter hominis, Listeria monocytogenes, among others. Nevertheless for yellow-pigmented diphteroid gram-positive rods (Aureobacterium spp., Leifsonia aquatica, Microbacterium spp. and Cellulomonas spp.) and for acid fast gram-positive rods (Rhodococcus, Gordonia, Tsukamurella and Nocardia) the identification usefulness the system is limited.

Phenotypic and genotypic characterization of macrolide resistant Streptococcus pneumoniae recovered from adult patients with community-acquired pneumonia in an Argentinian teaching hospital.

Streptococcus pneumoniae isolates (n = 262) were recovered from adult patients with community-acquired pneumonia. Erythromycin-resistance levels increased from 9% (1997-1998) to 16% (2000-2002). Sampling for resistance mechanisms prevalent within 19 erythromycin-resistant S. pneumoniae showed mef(E) in 13/19 isolates while 4/19 carried the erm(B) gene (3/19 cMLS(B) and 1/19 iMLS(B) phenotype). MIC ranges for erythromycin and clindamycin were 0.5-16 mg/l and <0.008-0.063 mg/l for the M phenotype, 128-512 mg/l and 128-256 mg/l for the cMLS(B) phenotype, and 4 and <0.008 mg/l for the iMLS(B) phenotype. This is the first report studying the prevalence of macrolide resistance determinants in S. pneumoniae in our country.

Neumonia por Legionella pneumophila. Experiencia en un Hospital Universitario de Buenos Aires / Pneumonia due to Legionella pneumophila. Experience gathered in a University Hospital in Buenos Aires

Legionnaires disease is a well recognized cause of community acquired pneumonia (CAP) all around the world. In Latin America its incidence remains unknown. This study analyzed a cohort of 9 patients with CAP due to Legionella pneumophila observed from 1997 to 2001, in the Hospital de Clínicas José de San Martin, University of Buenos Aires. Clinical history included recent illnesses, work exposure, physical exam, prior antibiotic use and severity of illness criteria. None of the 9 patients had a history of recent travels, and 4 of them required admission in intensive care unit (ICU). Seven patients had a cigarette smoking history, four of them also had COPD, and one patient had a non-Hodgkin lymphoma. This study confirms the low specificity of clinical and general laboratory criteria to predict this etiology. Legionella isolation is difficult, and serological testing allows retrospective diagnosis but takes several weeks, while urinary antigen test gives a bed-side diagnosis. When Legionella appears in isolated cases, as happens in Argentina, it should be necessary to have a high index of suspicion to successfully arrive at an etiological diagnosis. Legionella pneumophila is a pathogen causing CAP in our area. A surveillance should be established preferably focused on selected populations including severe CAP, immunocompromised hosts and patients with chronic obstructive pulmonary disease.(AU)

La enfermedad de los legionarios es una causa de neumonía adquirida en la comunidad (NAC)reconocida en todo el mundo. En Latinoamérica su incidencia es desconocida. En este estudiose analizó a 9 pacientes con NAC por Legionella pneumophila atendidos entre 1997 y 2001 en el Hospital deClínicas José de San Martín de la Universidad de Buenos Aires. Se registraron datos de antecedentes, enfermedad actual, contactos, exposición laboral, examen físico, pruebas de laboratorio y uso previo de antibióticos, y se tomó en cuenta la presencia de criterios de gravedad. Nueve pacientes presentaron diagnóstico de NAC por Legionella, ninguno refirió antecedentes de viajes recientes; cuatro de ellos debieron ser internados en unidades de cuidado intensivo. Siete pacientes tenían antecedentes de tabaquismo, 4 tenían EPOC y un paciente linfoma no-Hodgkin. Nuestra casuística corrobora la baja especificidad de la clínica y estudios complementarios para predecir esta etiología. El aislamiento de Legionella es dificultoso, la seroconversión permite eldiagnóstico retrospectivo y requiere plazos prolongados y el antígeno urinario aporta un diagnóstico inmediato.Cuando la legionelosis aparece en casos aislados, como ocurriría en Argentina, si no se piensa en esta etiologíano se llegará al diagnóstico. Legionella pneumophila es un patógeno de NAC en nuestro medio, debe buscarsemejor, particularmente en pacientes graves, inmunodeprimidos y en fumadores con enfermedad pulmonarobstructiva crónica (EPOC).(AU)

Neumonia por Legionella pneumophila. Experiencia en un Hospital Universitario de Buenos Aires / Pneumonia due to Legionella pneumophila. Experience gathered in a University Hospital in Buenos Aires

Legionnaires' disease is a well recognized cause of community acquired pneumonia (CAP) all around the world. In Latin America its incidence remains unknown. This study analyzed a cohort of 9 patients with CAP due to Legionella pneumophila observed from 1997 to 2001, in the Hospital de Clínicas José de San Martin, University of Buenos Aires. Clinical history included recent illnesses, work exposure, physical exam, prior antibiotic use and severity of illness criteria. None of the 9 patients had a history of recent travels, and 4 of them required admission in intensive care unit (ICU). Seven patients had a cigarette smoking history, four of them also had COPD, and one patient had a non-Hodgkin lymphoma. This study confirms the low specificity of clinical and general laboratory criteria to predict this etiology. Legionella isolation is difficult, and serological testing allows retrospective diagnosis but takes several weeks, while urinary antigen test gives a bed-side diagnosis. When Legionella appears in isolated cases, as happens in Argentina, it should be necessary to have a high index of suspicion to successfully arrive at an etiological diagnosis. Legionella pneumophila is a pathogen causing CAP in our area. A surveillance should be established preferably focused on selected populations including severe CAP, immunocompromised hosts and patients with chronic obstructive pulmonary disease.

La enfermedad de los legionarios es una causa de neumonía adquirida en la comunidad (NAC)reconocida en todo el mundo. En Latinoamérica su incidencia es desconocida. En este estudiose analizó a 9 pacientes con NAC por Legionella pneumophila atendidos entre 1997 y 2001 en el Hospital deClínicas José de San Martín de la Universidad de Buenos Aires. Se registraron datos de antecedentes, enfermedad actual, contactos, exposición laboral, examen físico, pruebas de laboratorio y uso previo de antibióticos, y se tomó en cuenta la presencia de criterios de gravedad. Nueve pacientes presentaron diagnóstico de NAC por Legionella, ninguno refirió antecedentes de viajes recientes; cuatro de ellos debieron ser internados en unidades de cuidado intensivo. Siete pacientes tenían antecedentes de tabaquismo, 4 tenían EPOC y un paciente linfoma no-Hodgkin. Nuestra casuística corrobora la baja especificidad de la clínica y estudios complementarios para predecir esta etiología. El aislamiento de Legionella es dificultoso, la seroconversión permite eldiagnóstico retrospectivo y requiere plazos prolongados y el antígeno urinario aporta un diagnóstico inmediato.Cuando la legionelosis aparece en casos aislados, como ocurriría en Argentina, si no se piensa en esta etiologíano se llegará al diagnóstico. Legionella pneumophila es un patógeno de NAC en nuestro medio, debe buscarsemejor, particularmente en pacientes graves, inmunodeprimidos y en fumadores con enfermedad pulmonarobstructiva crónica (EPOC).

[Evaluation of API 20 NE (version 6.0) in rare Gram-negative non-glucose-fermenting bacilli]. / Evaluación de API 20 NE (versión 6.0) en bacilos gram-negativos no fermentadores de glucosa infrecuentes.

The ability of the API 20 NE method (6.0 version, bio-Mérieux, Marcy L'Etoile, France) to identify 188 strains of gram negative nonfermentative bacilli (NFB) was evaluated (Fenazinic pigment producing Pseudomonas aeruginosa and Acinetobacter spp. were excluded). These were isolated from patients treated at the Hospital de Clínicas José de San Martín of the University of Buenos Aires during the period 1996-2001. Strains were identified according to the Schreckenberger P testing method. Out of 188 NFB strains, 175 (93.09%) were correctly identified by the API 20 NE method at the genus and species level (IC95 = 88.47-96.27) while 61 (32.45%) required additional testing for correct identification. Thirteen strains (6.91%; IC95 3.73-11.53) could not be correctly identified and none of them were classified as "non identified". The API 20 NE method is a practical, easy to handle, fast and useful system for the identification of NFB since conventional manual methods take longer and require many biochemical, enzymatic and physiological tests which are sometimes not available depending on the size and capability of the laboratory. Although it is easy to handle, the API 20 NE identification system must be interpreted by an expert microbiologist who must compare the results obtained by this system with the information provided by the distinctive cultures and mobility patterns of these organisms.

Evaluación de API 20 NE (versión 6.0) en bacilos gram-negativos no fermentadores de glucosa infrecuentes. / [Evaluation of API 20 NE (version 6.0) in rare Gram-negative non-glucose-fermenting bacilli]

The ability of the API 20 NE method (6.0 version, bio-Mérieux, Marcy LEtoile, France) to identify 188 strains of gram negative nonfermentative bacilli (NFB) was evaluated (Fenazinic pigment producing Pseudomonas aeruginosa and Acinetobacter spp. were excluded). These were isolated from patients treated at the Hospital de Clínicas José de San Martín of the University of Buenos Aires during the period 1996-2001. Strains were identified according to the Schreckenberger P testing method. Out of 188 NFB strains, 175 (93.09

) were correctly identified by the API 20 NE method at the genus and species level (IC95 = 88.47-96.27) while 61 (32.45

) required additional testing for correct identification. Thirteen strains (6.91

; IC95 3.73-11.53) could not be correctly identified and none of them were classified as [quot ]non identified[quot ]. The API 20 NE method is a practical, easy to handle, fast and useful system for the identification of NFB since conventional manual methods take longer and require many biochemical, enzymatic and physiological tests which are sometimes not available depending on the size and capability of the laboratory. Although it is easy to handle, the API 20 NE identification system must be interpreted by an expert microbiologist who must compare the results obtained by this system with the information provided by the distinctive cultures and mobility patterns of these organisms.

Evaluación de API 20 NE (versión 6.0) en bacilos gram-negativos no fermentadores de glucosa infrecuentes / [Evaluation of API 20 NE (version 6.0) in rare Gram-negative non-glucose-fermenting bacilli]

The ability of the API 20 NE method (6.0 version, bio-Mérieux, Marcy L’Etoile, France) to identify 188 strains of gram negative nonfermentative bacilli (NFB) was evaluated (Fenazinic pigment producing Pseudomonas aeruginosa and Acinetobacter spp. were excluded). These were isolated from patients treated at the Hospital de Clínicas José de San Martín of the University of Buenos Aires during the period 1996-2001. Strains were identified according to the Schreckenberger P testing method. Out of 188 NFB strains, 175 (93.09

) were correctly identified by the API 20 NE method at the genus and species level (IC95 = 88.47-96.27) while 61 (32.45

) required additional testing for correct identification. Thirteen strains (6.91

; IC95 3.73-11.53) could not be correctly identified and none of them were classified as [quot ]non identified[quot ]. The API 20 NE method is a practical, easy to handle, fast and useful system for the identification of NFB since conventional manual methods take longer and require many biochemical, enzymatic and physiological tests which are sometimes not available depending on the size and capability of the laboratory. Although it is easy to handle, the API 20 NE identification system must be interpreted by an expert microbiologist who must compare the results obtained by this system with the information provided by the distinctive cultures and mobility patterns of these organisms.

Cefotaxime-hydrolysing beta lactamases in Morganella morganii.

The frequency of enterobacterial isolates with high resistance to expanded-spectrum beta-lactam antibiotics (mainly cefotaxime or ceftriaxone) has increased notoriously in Argentina, mainly because of the spread of extended-spectrum beta-lactamases. The aim of this work was the study of extended-spectrum beta-lactamases in several Morganella morganii isolates with unusually high resistance to ceftriaxone. These strains produced at least two beta-lactamases, of apparent pIs of 5.4 and 8.2, molecular weight 23 000, well inhibited by clavulanate, compatible with a broad-spectrum beta-lactamase - perhaps TEM-1 - and an extended-spectrum beta-lactamase, respectively. The extended-spectrum beta-lactamase was identified as a CTX-M-type beta-lactamase - probably CTX-M-2 - by polymerase chain reaction, restriction profile analysis and DNA-DNA hybridisation. The remaining isolates studied produced either the broad-spectrum beta-lactamase plus the ubiquitous AmpC beta-lactamase (13 strains), or the AmpC beta-lactamase only (10 strains).

Effects of age and gender on the cardiovascular responses to isoproterenol.

We studied the effects of age and gender on cardiovascular responses to beta-adrenergic stimulation with the use of two-dimensional echocardiography in 16 young (aged 20-31) and 20 older (aged 60-75) healthy individuals. Following administration of atropine, each subject was given an infusion of isoproterenol at incremental doses from 0.010 to 0.030 microgram kg-1 min-1. The slopes of the fractional shortening-end-systolic wall stress (FS-sigma es) relationships were steeper in the young men (-0.87 +/- 0.28, n = 8) compared to the older men (-0.41 +/- 0.13, n = 10), and in the young women (-0.55 +/- 0.14, n = 8) compared to the older women (-0.38 +/- 0.13, n = 10). Furthermore, the magnitude of the age-associated differences in these slopes was larger in the men (old vs young) than in the women (old vs young) which, in the absence of changes in preload, suggests a greater decline in the contractile response to isoproterenol with advancing age in men compared to women. Furthermore, the men exhibited a greater attenuation of chronotropic response to isoproterenol than did the women. These observations suggest that gender plays a significant role in the age-associated decline in inotropic and chronotropic responses to beta-adrenergic stimulation, with men exhibiting a greater decline with aging than women.

Effects of age and gender on cardiovascular responses to phenylephrine.

BACKGROUND: The age-associated impairment in left ventricular (LV) systolic function appears to be mostly detectable during exercise or sympathetic stimulation. We hypothesized that the decline in cardiac function could be unmasked by an acute increase in afterload induced by phenylephrine. We further sought to examine whether the deterioration in cardiac function is influenced by gender. METHODS: We studied 17 young (20-31 years old) and 21 older healthy subjects (60-75 years old) who were given infusions of incremental doses of phenylephrine following cardiac muscarinic receptor blockade with atropine. Left ventricular systolic function was assessed with 2-D echocardiography. RESULTS: The young subjects exhibited a paradoxical increase in heart rate in response to alpha-adrenergic stimulation, but the older subjects did not (p < .01). The increase in systolic blood pressure in response to phenylephrine was influenced by age and gender (i.e., greater in the younger men and older women), whereas the increase in diastolic blood pressure was greater in the younger than the older subjects of both sexes. The changes in LV end-diastolic diameter with phenylephrine were unaffected by age or gender. The slope of the systolic shortening-end systolic wall stress relationship was significantly steeper in the older subjects, suggesting a decline in the contractile response to an acute increase in afterload with aging. CONCLUSIONS: This study's findings suggest that age can significantly influence the cardiovascular responses to alpha-adrenergic stimulation and that phenylephrine, by acutely increasing afterload, is effective in unmasking the age-associated deterioration in left ventricular systolic function. Further, it appears that the increase in systolic blood pressure in response to an alpha-adrenergic challenge is significantly influenced not only by age but also by gender.

[The molecular epidemiology of the rotavirus in Spanish children. The Rotavirus Study Group (GER)]. / Epidemiología molecular de rotavirus en niños españoles. Grupo de Estudio de Rotavirus (GER).

BACKGROUND: Rotavirus are the most common etiologic agent of acute gastroenteritis in childhood. The knowledge of the circulating antigenic types is important in development of future vacunes. METHODS: Faeces from children (age < 4 years) with acute gastroenteritis admitted in the two hospitals (Hospital Severo Ochoa-Madrid and Hospital General Vic-Barcelona) have been studied prospectively during one year (October-1996 to October-1997). The detection of rotavirus was performed by ELISA (IDEIA, Dako). All samples were G-serotyping by EIA-Mabs (Silenius Laboratories) and the indeterminate or non-serotypable samples were G-genotyping by RT-PCR. P genotypes were identified by RT-PCR. RESULTS: 322 (45%) patients with acute diarrhoea causing for rotavirus were confirmed, 242 coming from the Madrid metropolitan area and other 80 from the Barcelona area. The EIA-Mabs technique made it possible to identify the G serotypes in 287 cases (89%), corresponding 207 to G1 serotype, 70 to G4 serotype and 6 to G3 serotype. In 4 patients both G1 and G4 serotypes were detected. The EIA-Mabs could not determined the serotype in 35 (11%) patients, all of whom were confirmed by RT-PCR (12 belonged to serotype G1 and 23 to serotype G4). Analysis of P genotypes was carried out in 25 patients obtained from Madrid and 17 from Barcelona; all cases were classified in the P[8] genotype. CONCLUSIONS: The most frequent serotype in both hospitals was G1. The EIA-Mabs technique were showed a high sensitivity, however, the RT-PCR technique used were even more efficient, making it possible for us to identify all the non-serotypable EIA-Mabs cases. The temporal study of circulating serotypes/genotypes of rotavirus is necessary to evaluate the efficiency of vaccines.

Argentinian collaborative study on prevalence of erythromycin and penicillin susceptibility in Streptococcus pyogenes. The Argentinian Streptococcus Study Group.

Two monthly studies on the prevalence of penicillin and erythromycin susceptibility of Streptococcus pyogenes were performed in May and October of 1994 in Argentina. A total of 58 centers from 27 cities participated in these studies. A total of 1072 isolates were tested by a diffusion method, although 595 isolates were tested both by the diffusion and an agar dilution method (n = 1767 isolates). No penicillin-resistant streptococci were found in our study (MIC100 = 0.03 microgram/ml). Only four isolates were confirmed as erythromycin resistant S. pyogenes (prevalence 0.14 and 0.28% in May and October 1994, respectively). Resistance in three isolates was due to an inducible mechanism, although in one strain a different phenotype was observed.

Muscle glycogen accumulation after endurance exercise in trained and untrained individuals.

Muscle glycogen accumulation was determined in six trained cyclists (Trn) and six untrained subjects (UT) at 6 and either 48 or 72 h after 2 h of cycling exercise at approximately 75% peak O2 uptake (VO2 peak), which terminated with five 1-min sprints. Subjects ate 10 g carbohydrate . kg-1 . day-1 for 48-72 h postexercise. Muscle glycogen accumulation averaged 71 +/- 9 (SE) mmol/kg (Trn) and 31 +/- 9 mmol/kg (UT) during the first 6 h postexercise (P < 0.01) and 79 +/- 22 mmol/kg (Trn) and 60 +/- 9 mmol/kg (UT) between 6 and 48 or 72 h postexercise (not significant). Muscle glycogen concentration was 164 +/- 21 mmol/kg (Trn) and 99 +/- 16 mmol/kg (UT) 48-72 h postexercise (P < 0.05). Muscle GLUT-4 content immediately postexercise was threefold higher in Trn than in UT (P < 0.05) and correlated with glycogen accumulation rates (r = 0.66, P < 0.05). Glycogen synthase in the active I form was 2.5 +/- 0.5, 3.3 +/- 0.5, and 1.0 +/- 0.3 micromol . g-1 . min-1 in Trn at 0, 6, and 48 or 72 h postexercise, respectively; corresponding values were 1.2 +/- 0.3, 2.7 +/- 0.5, and 1.6 +/- 0.3 micromol . g-1 . min-1 in UT (P < 0.05 at 0 h). Plasma insulin and plasma C-peptide area under the curve were lower in Trn than in UT over the first 6 h postexercise (P < 0.05). Plasma creatine kinase concentrations were 125 +/- 25 IU/l (Trn) and 91 +/- 9 IU/l (UT) preexercise and 112 +/- 14 IU/l (Trn) and 144 +/- 22 IU/l (UT; P < 0.05 vs. preexercise) at 48-72 h postexercise (normal: 30-200 IU/l). We conclude that endurance exercise training results in an increased ability to accumulate muscle glycogen after exercise.

Cardiovascular adaptations to 10 days of cycle exercise.

We hypothesized that 10 days of training would enhance cardiac output (CO) and stroke volume (SV) during peak exercise and increase the inotropic response to beta-adrenergic stimulation. Ten subjects [age 26 +/- 2 (SE) yr] trained on a cycle ergometer for 10 days. At peak exercise, training increased O2 uptake, CO, and SV (P < 0.001). Left ventricular (LV) size and function at rest were assessed with two-dimensional echocardiography before (baseline) and after atropine injection (1.0 mg) and during four graded doses of dobutamine. LV end-diastolic diameter increased with training (P < 0.02), whereas LV wall thickness was unchanged. LV contractile performance was assessed by relating fractional shortening (FS) to the estimated end-systolic wall stress (sigmaES). Training increased the slope of the FS-sigmaES relationship (P < 0.05), indicating enhanced systolic function. The increase in slope correlated with increases in CO (r = -0.71, P < 0.05) and SV (r = -0.70, P < 0.05). The increase in blood volume also correlated with increases in CO (r = 0.80, P < 0.01) and SV (r = 0.85, P < 0.004). These data show that 10 days of training enhance the inotropic response to beta-adrenergic stimulation, associated with increases in CO and SV during peak exercise.

Changes in stroke volume with beta-blockade before and after 10 days of exercise training in men and women.

We sought to determine whether 10 days of training would be a sufficient stimulus for cardiac adaptations that would allow a greater compensatory stroke volume during beta-blockade. We also sought to determine whether men and women had a similar cardiac reserve capacity for increasing stroke volume with beta-blockade during submaximal exercise. Eight men (age 29 +/- 2 yr, mean +/- SE) and eight women (25 +/- 2 yr) cycled at 65% of peak O2 consumption (unblocked) under placebo-control and beta-blockade (100 mg atenolol) conditions performed on separate days. These tests were repeated at the same power output after training (10 consecutive days, 1 h of cycling per day). Before training, beta-blockade significantly (P < 0.05) decreased heart rate (HR) and cardiac output and increased stroke volume in both men and women. After training, the increase in stroke volume and decrease in HR with beta-blockade was significantly less while cardiac output was reduced more. There were no gender differences in the effects of beta-blockade on HR, stroke volume, or cardiac output. These data indicate that, during exercise with beta-blockade, exercise training for 10 days does not enhance the compensatory increase in stroke volume and that men and women have a similar cardiac reserve capacity for increasing stroke volume.

Changes in stroke volume and maximal aerobic capacity with increased blood volume in men women.

This study determined whether the effects of acute plasma volume expansion (PVX) or 10 days of training on stroke volume during submaximal cycling and on treadmill maximal oxygen uptake (VO2max) were similar between men and women. Subjects performed a submaximal cycle test and a treadmill test to exhaustion under three conditions: control, PVX, and after training. Cycle peak VO2 (VO2peak) and blood volume were measured before and after training. Training consisted of daily 1-h bouts [30 min at 80% peak heart rate (HRpeak) and ten 2-min intervals at 95% HRpeak alternating with 1-min low-intensity pedaling] on a cycle ergometer for 10 consecutive days. Training increased cycle VO2peak in men [P < 0.05; 3.14 +/- 0.13 vs. 3.42 +/- 0.13 (SE) l/min] and women (2.11 +/- 0.10 vs. 2.37 +/- 0.12 l/min) and increased blood volume in men (67.6 +/- 3.0 vs. 72.3 +/- 3.1 ml/kg) and women (62.7 +/- 2.2 vs. 65.6 +/- 2.4 ml/kg). As a result of the greater blood volume with PVX and with training, stroke volume (ml) during submaximal cycling increased in men (control 110 +/- 4; PVX 123 +/- 4; trained 121 +/- 4) and women (control 87 +/- 5; PVX 95 +/- 6, trained 96 +/- 7). Treadmill VO2max (ml.kg-1.min-1) did not change with PVX despite a 6-7% reduction in hemoglobin concentration, whereas training resulted in an increase in VO2max in men (control 47.9 +/- 2.8; PVX 46.7 +/- 2.8; trained 49.9 +/- 2.6) and women (control 38.0 +/- 1.2; PVX 36.9 +/- 1.2; trained 39.2 +/- 1.2). The effects of PVX or training on stroke volume or VO2max did not differ between men and women. An additional finding was an increase in diastolic and mean blood pressures at 65% of cycle VO2peak with PVX and with training in women. Thus men and women hold similar cardiac reserve capacities for increasing stroke volume and, as a result, VO2max is maintained despite a reduction in hemoglobin concentration. However, gender differences in blood pressure regulation with increased blood volume might exist.

RNA-mediated specificity of DNA packaging into hybrid lambda/phi 29 proheads.

A small RNA (pRNA, 174 nt) is known to be essential for DNA packaging in bacteriophage phi 29. However, in an in vitro DNA packaging system based on hybrid lambda/phi 29 proheads (made up of head proteins from phage lambda and connectors from phage phi 29), the specificity of DNA packaging is lost, and different RNA molecules fulfil the requirements for DNA packaging, albeit with less efficiency than phi 29 pRNA. Competition assays with RNAs from different sources have shown that phi 29 connectors bind preferentially pRNA. An increase in the efficiency of phi 29 DNA packaging into hybrid proheads induced by phi 29 pRNA is observed because, when phi 29 pRNA is incubated with hybrid proheads, phi 29 DNA is packaged more efficiently than other DNAs of similar length. Furthermore, when hybrid proheads carrying phi 29 pRNA are incubated with a mixture of DNAs from different sources, phi 29 DNA is selectively packaged, thus indicating that phi 29 pRNA determines the specificity of DNA packaging.

Characterization of an RNA-binding domain in the bacteriophage phi 29 connector.

The connector of bacteriophage phi 29 is known to promote the viral prohead assembly, to bind DNA, and to drive DNA packaging into preformed viral shells in an RNA-dependent process. In this report, the phi 29 connector protein, p10, is shown to bind RNA in a sequence-independent fashion, and to possess an RNA recognition motif comprised approximately the region between residues 21 and 94 of the p10 sequence. Substitution mutants in specific amino acids of the RNA-binding domain obtained by site-directed mutagenesis showed that amino acids Phe23, His57, Phe59, and Tyr61 are critical for RNA binding and, subsequently, for DNA packaging into proheads. Proteolytic modified forms of the phi 29 connector have allowed us to conclude that the DNA- and RNA-binding domains are separated within the p10 sequence. It is also shown that RNA is stably associated to DNA-filled proheads during the DNA-packaging process.