Crack Front Interaction with Self-Emitted Acoustic Waves.

The interaction of a propagating crack in implanted silicon with self-emitted acoustic waves results in periodic patterns on fractured surfaces. Direct measurement of the acoustic emission ahead of the fracture front shows the emergence of dominant acoustic frequency related to the crack velocity. It is shown that the surface modifications are made of roughness modulations due to periodic deviations of the crack front. A physical mechanism explaining the pattern formation is proposed, well in agreement with the observed pattern wavelengths.

Nucleolar-persistence phenomenon during spermatogenesis in genus Meccus (Hemiptera, Triatominae).

The Triatominae subfamily consists of 150 species in 18 genera, grouped into six tribes. In cytogenetics, triatomines are important biological models because they have holocentric chromosomes and nucleolar persistence in meiosis. The phenomenon of nucleolar persistence has been described for 23 species of triatomine in three genera: Triatoma, Rhodnius, and Panstrongylus. However, new species and genera should be analyzed to assess whether nucleolar persistence is a peculiarity of Triatominae. Thus, this study aimed to analyze nucleolar behavior during spermatogenesis of Meccus pallidipennis and M. longipennis, focusing on the nucleolar-persistence phenomenon. Through the analysis of spermatogenesis, more specifically of meiotic metaphase, we observed the phenomenon of nucleolar persistence in M. pallidipennis and M. longipennis, represented by remnants of nucleolar material in metaphase. Thus, although nucleologenesis of new species, and, especially, new genera, should be analyzed, this study confirms for the first time the phenomenon of nucleolar persistence in the genus Meccus. Therefore, we emphasize the importance of new studies in this area in order to assess whether this phenomenon is truly a synapomorphy of these hematophagous insects.

Blood lactate removal during recovery at various intensities below the individual anaerobic threshold in triathletes.

AIM: Optimal lactate removal was reported to occur at work-rate between 30% and 70% VO2max. However, it has been recently recommended to quantify exercise intensity not in percentage of VO2max but in relation to validated metabolic reference points such as the individual anaerobic threshold (IAT) and the individual ventilatory threshold (IVT). The purpose of this study was to examine the effect on lactate removal of different recovery work-rates below the IAT defined calculating the difference (DT) between IAT and IVT, then choosing the IVT+50%DT, the IVT and the IVT-50%DT work-rates. METHODS: Eight male triathletes (VO2max 69.7+/-4.7, VO2IAT 52.9+/-4, VO2IVT 41.1+/-4.7 mL x kg(-1) x min(-1)), after a 6-min treadmill run at 75% of difference between IAT and VO2max, performed in a random order the following 30-min recovery treatments: 1) run at IVT(plus;50%DT), 2) at IVT, 3) at IVT(-50%DT), 4) passive. Blood lactate was measured at 1, 3, 6, 9, 12, 15, 20, 25, 30 minutes of recovery. RESULTS: All active recovery work-rates (from 50+/-5% to 67+/-4% VO2max) were within the range previously reported for optimal lactate removal, and significantly more efficient than passive recovery on lactate removal curve (% of accumulated lactate above rest value). However, significant differences (P<0.01) were found among active recovery intensities: the IVT(-50%DT) was the most efficient work-rate from the 9th minute to 30th minute. CONCLUSIONS: In triathletes, the IVT(-50%DT) was the optimal work-rate for lactate removal; moreover none of the studied active work-rate showed further lactate decrease after the 20th minute of recovery.

[Prognosis of postoperative aortic dissection. Assessment with magnetic resonance]. / Prognóstico da dissecção da aorta após cirurgia. Avaliação por ressonância magnética.

OBJECTIVE: To evaluate operated type A aortic dissection by Magnetic Resonance Imaging (MRI), in order to detect long-term complications and identify prognostic indexes of evolution. DESIGN: Prospective study with a three-year period of follow-up. Prognosis evaluation. SETTINGS: Outpatient Clinic at Hospital de Santa Maria and Magnetic Resonance Imaging Center at Hospital da Cruz Vermelha. PATIENTS: A sample of 37 patients submitted to type A aortic dissection surgery, included sequentially, after exclusion of those with contraindication to MRI. METHODS: Initial evaluation (clinical and MRI study) at 3 to 4 months and at 1, 2 and 3 years after surgery. The mean follow-up time was 39.3 +/- 2.9 months. We evaluated the following complications over the aorta (aortic graft and five segments of residual aorta) and the aortic valve: aneurysm, pseudoaneurysm, rupture, re-dissection, progressive aortic valve regurgitation, reoperation and death. The prognostic indexes analysed were: presence of residual flap; false lumen patency; presence of re-entry points; false lumen to aorta dimension ratio; initial aortic dimension; increase of aortic dimension. RESULTS: All patients, with the exception of three that died, remained asymptomatic. COMPLICATIONS: Aneurysm was detected in 45.9% of patients, located in one or more segments; rupture occurred in three patients, preceded by aneurysm and pseudoaneurysm development; moderate or severe aortic regurgitation was detected in 47.8% of patients. Prognostic indexes: 1. Aneurysm development in each segment yeilded a significant association with: presence of residual flap in the same and other segments; higher initial dimension of the same and other segments, with the exception of the abdominal segment; higher increase in dimension of the same and other segments, with the exception of the abdominal segment; 2. Moderate or severe aortic regurgitation development showed a tendency to association with higher increase in dimension of proximal ascending aorta. 3. No association was found between aneurysm and aortic regurgitation development. CONCLUSIONS: Patients operated for type A aortic dissection had a high incidence of late complications which lead to reoperation and in some cases death. The presence of a residual flap, increased aortic dimensions and higher increase rate of aortic dimensions were associated with a complicated evolution. MRI was a very useful technique for long-term monitoring and to identify prognostic indexes of evolution.

Pulmonary transvalvular and venous flows in the estimation of left ventricular diastolic pressures. A comparative Doppler-catheterization study.

OBJECTIVES: To evaluate the association between patterns of pulmonary transvalvular and venous flows in patients with ischemic heart disease, assessed by Doppler echocardiography, and invasive measurements of left ventricular (LV) diastolic pressures. POPULATION: Thirty-seven patients with clinical diagnosis or suspicion of coronary heart disease and referred for coronary angiography; all were in sinus rhythm, and had no known valvular heart or chronic pulmonary disease. METHODS: The following were recorded during transthoracic Doppler echocardiography: acceleration time (AT) and total ejection time (ET) of right ventricular outflow; duration of the flow at atrial contraction (a duration) and duration of the "A" wave of mitral inflow (A duration). These data were correlated with the values of LV filling pressures previously obtained by cardiac catheterization. RESULTS: We found a significant correlation of LV end-diastolic pressures with the difference a-A duration (r = 0.75; p < 0.001) and also with the ratio AT/ET (r = -0.73;.

[The implantation of VDD pacemakers with a single electrode--a comparative study. The experience of the last 5 years]. / Implantação de pacemakers VDD com um único eléctrodo--estudo comparativo. Experiência dos últimos cinco anos.

OBJECTIVE: To compare the epidemiological characteristics and immediate results of all first single lead VDD pacemaker (PM) implantations with those of an equal number of dual chamber DDD PM, implanted during a 5-year period in a tertiary-care hospital. POPULATION AND METHODS: A total of 41 patients (pts) (25 males, mean age of 69.0 +/- 11.8 years) underwent a VDD PM implantation, from 30-11-92 to 15-9-97. This group was compared with an equal number of patients (28 males, mean age of 69.9 +/- 7.31 years) with a DDD PM implanted in the same period, selected by a criterion of immediate temporal proximity of procedure. For each patient we collected the clinical and electrocardiographic (ECG) indications for PM implantation, parameters of atrial (AS) and ventricular (VS) sensing and ventricular pacing (VP), X-ray exposure time (XRT) and complications. RESULTS: In the VDD group, 46.3% of the patients had syncope, 51.2% had complete AV block on the ECG, and 14.6% were PM-dependent. Analyzed procedure-related parameters were as follows: P-wave amplitude: 2.1 +/- 0.6 V; AS threshold: 1.2 +/- 0.7 V; R-wave amplitude: 9.1 +/- 3.3 V; VS threshold: 7.0 +/- 2.0 V; VP thresholds: 0.68 +/- 0.24 mA, 0.43 +/- 0.12 V (for a spike duration of 0.5 ms); ventricular impedance: 644.9 +/- 132.0 ohm; XRT; 7' 43" +/- 8' 23". There were two minor complications, for an incidence of 4.9% (one local hematoma and a vagal reaction). In the DDD group the clinical and ECG characteristics were similar, but there was a 22.0% prevalence of sinus-node dysfunction, VS 0% in the VDD group). The P-wave amplitude and AS threshold were significantly (p < 0.005) better (2.8 +/- 0.9 V and 2.8 +/- 0.9 V respectively). The other parameters were similar to those of the VDD group. CONCLUSIONS: The immediate results of VDD PM implantation are good and comparable with those of DDD PM, although with worse acute AS parameters.

Effect of alum on free-living and copepod-associated Vibrio cholerae O1 and O139.

The effects of alum [KAl(SO4)2] on free-living and copepod-associated Vibrio cholerae O1 and O139 were investigated by using plate counts and immunofluorescence direct viable counting (DVC). Growth of alum-treated cells in 0.5/1000 Instant Ocean seawater was inhibited, i.e., no growth was obtained on Luria-Bertani (LB) agar or thiosulfate-citrate-bile salt-sucrose (TCBS) agar. However, a significant number of the inhibited cells maintained viability, as measured by DVC. In comparison, a significant number of V. cholerae organisms associated with zooplankton, most of which were crustacean copepods, were viable but nonculturable, with only a small number of cells retaining culturability on LB and TCBS agar. Both DVC and viable plate counts (CFU) were significantly greater for V. cholerae O1 and O139 associated with zooplankton than for V. cholerae in water alone, i.e., without copepods. It is concluded that alum is an effective coagulant but not an effective killing agent for V. cholerae and that association with copepods offers protection for V. cholerae O1 and O139 against alum and chlorine treatments.

Trypanosoma cruzi in the opossum Didelphis marsupialis: a study of the correlations and kinetics of the systemic and scent gland infections in naturally and experimentally infected animals.

The genus Didelphis (Marsupialia, Didelphidae) has the unique capacity of supporting both multiplication cycles of Trypanosoma cruzi simultaneously; besides the intracellular forms, the epimastigotes can be found multiplying and differentiating abundantly in the lumen of the scent glands. The biological significance of the life cycle of T. cruzi within the scent glands of Didelphis marsupialis, as well as its contribution to the epidemiology of the disease, is presently unclear. In order to clarify the mechanisms involved in the colonization of this singular habitat by T. cruzi, as well as to understand its biological role, we have carried out a serological and parasitological follow-up of both natural and experimental infections of young and adult opossums. Although all natural infections were stable and long lasting, no infected scent glands were found, indicating that the stability of the systemic infections does not depend on the presence of flagellates in the scent gland. In 84% of the experimentally infected animals the colonization of the scent glands was preceded by a period of patent parasitemia. Parasitism of the scent glands was essentially permanent and bilateral, and its maintenance was independent of circulating parasites. Moreover, the course of the infection differed depending on the source (scent glands versus axenic culture-derived) of the metacyclic forms. Our results suggest that parasitism of the SG of D. marsupialis is most likely a secondary acquisition, a step toward independence from the insect vector, similarly to what is accepted for Trypanosoma equiperdum.

[Demographic discontinuities in Brazil and the state of Sao Paulo]. / Discontinuidades demograficas en Brasil y el estado de Sao Paulo.

"Given the importance of information on the population age structure when planning short, medium and long-term needs within the different social strata, this paper is a proposal to deepen...the study of changes in the population pyramids.... Based on the most recent methodologies a study of age discontinuities is carried out and a method of follow-up by cohorts is suggested, taking the 15-19 and 20-24 age groups as an example. The purpose is to show that, as a...cohort ascends in the age pyramid, new and different necessities arise and also different responses are demanded on the part of the social system." Data are for Brazil as a whole and for the state of Sao Paulo. (SUMMARY IN ENG)

Trypanosoma cruzi infection in the opossum Didelphis marsupialis: absence of neonatal transmission and protection by maternal antibodies in experimental infections.

The high rate of natural Trypanosoma cruzi infection found in opossums does not always correlate with appreciable densities of local triatomid populations. One alternative method which might bypass the invertebrate vector is direct transmission from mother to offspring. This possibility was investigated in five T. cruzi infected females and their litters (24 young). The influence of maternal antibodies transferred via lactation, on the course of experimental infection, was also examined. Our results show that neonatal transmission is probably not responsible for the high rate of natural T. cruzi infection among opossums. In addition antibodies of maternal origin confer a partial protection to the young. This was demonstrated by the finding of a double prepatency period and 4, 5 fold lower levels of circulating parasites, in experimentally infected pouch young from infected as compared to control uninfected mothers. On the other hand, the duration of patent parasitemia was twice as long as that observed in the control group.

Preliminary study of the relationship between plasma and erythrocyte magnesium variations and some circulating pro-oxidant and antioxidant indices in a standardized physical effort.

The aim of this preliminary study was to determine the relationship between exercise, magnesium (Mg) status, oxidative stress, and antioxidant defence systems. Some corresponding indices have been evaluated: plasma Mg, ascorbate, uric acid, adrenaline, creatine kinase (CK), thiobarbiturate reactive substances, adrenochrome; and in erythrocytes (RBC): reduced and oxidized glutathione (GSH and GSSG) and Mg. Venous blood samples were withdrawn before and 3 min after completion of a 40 min run. Only two significant changes were observed after effort: plasma Mg decreased (P < 0.009) and plasma adrenaline increased (P < 0.005). There was a non-significant tendency for indices of oxidative stress and antioxidant capacity to increase. The significant correlations between plasma Mg and CK (r = -0.88) and between RBC Mg and plasma ascorbate (r = -0.76) disappeared after the effort. Further research is necessary, with a larger number of subjects and variables, to obtain a better understanding of these interactions.

[Population and labor force: the case of coffee growing in the West Paulista]. / Populacao e forca de trabalho: o caso da cafeicultura no oeste paulista.

PIP: Fertility rates in Brazil have dropped at an increasingly rapid rate since 1940; this has occurred in the absence of an explicit, official policy on population control, and without a notable increase in quality of life. The context for analysis of this change in population dynamics is the colonato, the coffee plantation labor system which was prevalent in the Western portion of the state of Sao Paulo, or Paulista West unitl 1930; work organization here was based on the family as a unit of labor force. This study reconsiders the importance of the family in the labor force under the colonato, and the demographic implications of this organizational pattern. European immigrant colonists contracted with coffee growers to do subsistence farming; in exchange, they were granted land in proportion to the number of coffee trees tended. An increase in the number of family members resulted in an increase in productive capacity of the head of the family. The high fertility rate among these immigrants may have been a natural response to the existing institutional control of the labor system, high mortality rates and abundance of land; however, it may not have been a deliberate, planned response based on economic essentials. Also significant is the fact that the average family size in the Paulista West has changed little in the last 60 years. Immigrant families may have received contracts based on their favorable demographic composition rather than on their size alone. The elimination of contracted, guaranteed land-for-subsistence farming is sufficient to explain the changes in fertility patterns. Additional research is needed and should be based on empirical evidence.^ieng