Presence of Dalbulus maidis (Hemiptera: Cicadellidae) and of Spiroplasma kunkelii in the temperate region of Argentina

"Corn stunt" is one of the main corn (Zea mays L.) diseases in the Americas and Dalbulus maidis (DeLong & Wolcott) is the key vector of the pathogen Spiroplasma kunkelii Whitcomb. In Argentina, the corn-producing area is in the temperate region, where vector and pathogen prevalence levels are unknown. In this study, the prevalence and distribution of D. maidis and S. kunkelii in the temperate region of Argentina and D. maidis overwintering ability in this region were determined. Surveys were conducted in 2005-2006 and 2006-2007 seasons to determine D. maidis and S. kunkelii presence, and in winter 2006 to determine the vector overwintering ability. The highest S. kunkelii prevalence and incidence levels were found in the transition area from the temperate to the subtropical region, related to the highest D. maidis prevalence and insects sampled per location. D. maidis adults were found in volunteer corn plants and spontaneous vegetation in autumn and winter months, which were inoculative for the pathogen S. kunkelii. This overwintering ability was related to detection of D. maidis insects in corn crops at early growth stages in the following growing season. This work emphasizes that corn stunt disease is present in the temperate region of Argentina, and this highlights the need to develop proper agronomic practices like monitoring insect vector populations and controlling voluntary plants. This study also indicates that further research is needed to understand the potential yield reduction caused by this pathogen on symptomless plants and population dynamics of the insect vector.

Exitianus obscurinervis (Hemiptera: Cicadellidae), a new experimental vector of Spiroplasma kunkelii

"Corn stunt" caused by the mollicute Spiroplasma kunkelii (Whitcomb) is potentially one of the most severe diseases affecting the corn (Zea mays L.) crop in the Americas, and the leafhopper Dalbulus maidis (DeLong & Wolcott) is considered its most important vector. However, other insects seen quite frequently in corn crops might well be its vectors in Argentina To identify any leafhoppers species other than D. maidis that can transmit S. kunkelii, transmission assays were conducted, using individuals of Exitianus obscurinervis (Stål) collected in field and reared under controlled conditions. S. kunkelii was transmitted to corn plants by E. obscurinervis. The pathogen was transmitted to seven of the 11 plants, which showed characteristic corn stunt symptoms, and the presence of the pathogen was confirmed by DAS-ELISA. The presence of S. kunkelii in the E. obscurinervis individuals used in transmission experiments was confirmed by polymerase chain reaction and electron microscopy. The current study shows the existence of a new experimental vector of S. kunkelii, the leafhopper E. obscurinervis, which acquired spiroplasmas from infected plants and inoculated it to healthy plants.

[The determination of arterial pressure by the physician or the nurse: its relation to ambulatory pressure and left ventricular mass. The MAPA-Madrid Group. Monitorización Ambulatoria de la Presión Arterial (Ambulatory Monitoring of Arterial Pressure)]

BACKGROUND

In the present study we evaluated the influence of the observer's status--physician or nurse--on blood pressure levels and the relationship among clinic blood pressure measurement with ambulatory blood pressure and left ventricle mass.

PATIENTS AND METHODS

Cross sectional study performed in seven primary care centers. Participating physicians and nurses were trained for blood pressure measurement prior to the study and subsequently retrained at 3 month intervals during the study. Patients included in the study were 122 subjects with mild to moderate hypertension who underwent the following study protocol: a) measurement of clinic blood pressure by physician and nurse, in an independent fashion, on 3 visits; b) clinic-epidemiologic questionnaire; c) conventional hematological and biochemical study; d) electrocardiogram; e) 24-hour ambulatory blood pressure monitoring, f) M-mode and Doppler echocardiography (only in 58 subjects).

RESULTS

Nurse-measured blood pressure levels were higher than those determined by physicians (mean differences: 3.9 [6.7] mmHg in systolic blood pressure and 2.6 [5.4] mmHg in diastolic blood pressure). The blood pressure level differences between the two observers were higher in female patients and subjects with low educational level, independently of the observer's gender. Nurse-measured blood pressure was more closely related to ambulatory blood pressure and left ventricle mass than physician-measured blood pressure.

CONCLUSIONS

Nurse-measured blood pressure levels are lower than those determined by physicians and more closely related to ambulatory blood pressure and left ventricle mass than physician-measured blood pressure. These data support that nurses, instead of doctors, should routinely measure blood pressure in primary care centers.

Effect of adenosine and inosine on ureagenesis in hepatocytes

Adenosine and inosine produced a dose-dependent stimulation of ureagenesis in isolated rat hepatocytes. Hypoxanthine, xanthine and uric acid were without effect. Half-maximally effective concentrations were 0.08 microM for adenosine and 5 microM for inosine. Activation of ureagenesis by both nucleosides had the following characteristics: (a) it was observed with either glutamine or (NH4)2CO3, provided that glucose was present; (b) it was not detected when glucose was replaced by lactate plus oleate; (c) it was mutually antagonized by glucagon, but not by adrenaline; and (d) it was dependent on Ca2+. We suggest that the action of adenosine and inosine on ureagenesis might be of physiological significance.