By appropriate placement of two electrodes on the epicardiac surface of Langendorff-perfused hearts, His-bundle and preatrial signals can be recorded by the surface electrogram (S-ECG). These signals are difficult to detect because of their low amplitude of a few microvolts. To improve the monitoring of these low-level potentials we studied the His-bundle spike as detected by intracardiac electrodes and by epicardial records (S-ECG) and compared these signals in the time and frequency domain. The frequency spectra of these cardiograms were used to develop appropriate filters and high-gain amplifiers for a continuous monitoring of the His-bundle signal from the epicardiac surface. By means of such a monitoring system, high-frequency components of preatrial activities could be resolved also. The time coincidence of these spikes to the simultaneously recorded intraatrial electrogram from electrodes positioned near the sinus node and near the His-bundle is demonstrated. Hence, the early atrial signals likely yield information about sinoatrial conduction. Application examples of monitoring His-bundle signals and preatrial signals in a beat-to-beat manner are described also for various conduction blocks or arrhythmias. With this monitor the evaluation of characteristic parameters of the conduction system of the heart like HV-, AH- and A'H-time, and likely, SACT can easily be performed for every heartbeat on a digital oscilloscope with low resolution or a two-channel chart recorder. Small and intact hearts can be used with this system to detect intracardiac low-level potentials during the heart beat.

Animals↗

PubMedDate not supplied

Continuous ECG measurements of intracardiac activity from the surface of Langendorff-perfused guinea pig hearts.

The present paper describes a method by which it is possible to continuously detect early atrial and His-bundle activity from the surface of intact Langendorff-perfused guinea-pig hearts, by appropriate placement of two electrodes and the use of a custom designed instrumentation-amplifier. In some experiments the surface ECG recordings were compared with intracardiac ECG recordings. No difference in ECG durations could be observed between intracardiac and extracardiac measurements. In further experiments changes in ECG durations and heart rate were measured for 2 h. After 30 min equilibration time, no changes in heart rate and conduction time could be observed. In order to locate the best surface electrode positions to detect His-bundle activity, vector ECG recordings were taken at high gain. This vector ECG signal contained a His-loop which was split into a larger and a smaller part. The main and initial vector was directed to the left and the smaller to the right ventricle. The best recordings of the His-bundle activity could be observed when the electrodes were positioned as follows; one in a posterior position, near the valve plane and the other one in the opposite position near the initial part of the anterior interventricular artery and in the direction of the large His-loop. We conclude that the ECG surface recordings are a valuable tool for measuring impulse propagation through various segments of the cardiac conduction system in preparations of guinea-pig hearts, perfused by the Langendorff method.

Animals↗

PubMedDate not supplied

Effect of saliva composition on experimental root caries.

The aim of this study was to determine the effect of saliva composition on caries lesion development independently of the flow rate of unstimulated whole saliva (UWS) and other caries-related variables such as lesion progression time, oral hygiene level, and fluoride exposure. We hypothesized that this could be done by developing experimental root caries under carefully controlled conditions in situ in test subjects with UWS flow rates within a narrow window of normalcy. Fifteen female and 5 male subjects (66 +/- 6 years) were selected for the study according to their UWS flow rates between 0.2 and 0.4 ml/min. All subjects developed experimental root caries lesions during a 62-day period in which UWS as well as stimulated whole saliva (SWS) were repeatedly collected and analysed for flow rate, pH, buffer capacity, inorganic, and organic composition. Caries lesion development was determined by quantitative microradiography. The mean UWS flow rate was 0.30 +/- 0.05 ml/min. Significant negative correlations were obtained between UWS total phosphate concentration and mineral loss (DeltaZ; r(s) = -0.72, p < 0.001) and UWS total protein concentration and DeltaZ (r(s) = -0.70, p < 0.01). SWS and its constituents had only limited or no effect on DeltaZ. Qualitative UWS protein analysis (SDS-PAGE) revealed that subjects with low DeltaZ values had broader and more stained amylase bands than subjects with high DeltaZ values. These findings were confirmed quantitatively by HPLC. We conclude that, within a group of subjects with normal UWS flow rates, the UWS composition was more important for caries lesion development than the SWS composition. Furthermore, high UWS concentrations of phosphate, protein, and amylase were caries-protective.

Aged↗

PubMedDate not supplied

Salmonella serovars in food poisoning episodes recorded in Brazil from 1982 to 1991.

The Salmonella serovars involved in 25 food poisoning episodes which occurred in the Southeast and South of Brazil from 1982 to 1991 were identified. The most frequently detected serotype was S. Typhimurium (13/25, 52%), and the food most frequently involved in the transmission of Salmonella was homemade mayonnaise. The need to set up a permanent program of epidemiologic alert for food poisoning is emphasized.

Brazil↗

PubMedDate not supplied

Evaluation of phenotypic markers associated with pathogenicity in the genus Listeria.

A total of 130 Listeria strains were tested in order to evaluate lecithinase production and capacity for Congo red adsorption as markers of pathogenicity. The strains were identified according to acid production from sugars and by the CAMP test and the data were correlated with the ability to produce keratoconjunctivitis in guinea pigs. L. monocytogenes cultures presented 51.8% and 88.8% positivity rates for Congo red adsorption and lecithinase production, respectively, whereas 80.8% and 100% for L. innocua cultures were negative for the two test, respectively.

Animals↗

PubMedDate not supplied

Lysotypes and plasmidial profile of Salmonella serovar typhimurium isolated from children with enteric processes in the cities of Rio de Janeiro, RJ, and Salvador, BA - Brazil.

The lysotypes, plasmidial profiles, and profiles of resistance to antimicrobial agents were determined in 111 Salmonella Typhimurium strains isolated from feces and blood of children treated in Rio de Janeiro and in Salvador. Six distinct lysotypes (19, 41, 97, 105, 120 and 193) were recognized, with a predominance of lysotype 193 (59.7%) in Rio de Janeiro and of phage type 105 (38.4) in Salvador. Approximately 86.7% of the lysotype 193 strains presented multiple resistance to more than six antimicrobial agents, whereas 93% of lysotype 105 strains were fully susceptible. More than 90% of the strains presented plasmids distributed into 36 different profiles in Rio de Janeiro and into 10 profiles in Salvador. A 40 MDa plasmid was the most frequent (47%) in the strains from Rio de Janeiro, whereas a 61 MDa plasmid predominated (14.5%) in Salvador. Combined analysis of plasmid profile and classification into lysotypes (especially those belonging to types 105 and 103, proved to be more discriminatory than the other methods applied).

Bacterial Typing Techniques↗

PubMedDate not supplied

Listeria monocytogenes in renal transplant recipients.

Five cases of Listeria monocytogenes bacteremia were observed from April to December 1985, among renal transplant recipients from the same hospital in São Paulo, Brazil. The patients were adults (mean age: 40.6 years), and the basic complaint was fever, with no report of meningeal syndrome. Laboratory tests revealed the presence of two serovars, (1/2)a and 4b, which were classified into three lysotypes. The four strains of serovar 4b showed the same antibiotype, with resistance to cefoxitin, clindamycin, oxacillin and penicillin.

Adult↗