The Rayleigh-Taylor condition for the evolution of irrotational fluid interfaces

For the free boundary dynamics of the two-phase Hele-Shaw and Muskat problems, and also for the irrotational incompressible Euler equation, we prove existence locally in time when the Rayleigh–Taylor condition is initially satisfied for a 2D interface. The result for water waves was first obtained by Wu in a slightly different scenario (vanishing at infinity), but our approach is different because it emphasizes the active scalar character of the system and does not require the presence of gravity.     

Sublinear summation of afferent inputs to the nucleus accumbens in the awake rat

The mechanisms by which the nucleus accumbens integrates afferent input from limbic and cortical structures have been influential in the development of models of psychiatric disorders such as schizophrenia. Previous studies of the response of nucleus accumbens (Nacb) cells to the stimulation of afferent inputs from hippocampus (HC) and prefrontal cortex (PFC) have demonstrated that PFC throughput can be modulated by preceding HC input. Examination of the post-synaptic potential size has suggested, however, that summation of these inputs is sublinear. All studies to date examining Nacb integration of inputs via stimulation of afferents have been performed in the anaesthetized rat. The present experiments compare the response of Nacb cells to different combinations of PFC and HC stimulation in awake and isoflurane-anaesthetized rats that were chronically implanted with both stimulating and recording electrodes. The results of these experiments suggest that summation of afferent input in the Nacb of the awake rat is predominantly sublinear, with only a minority of neurons demonstrating modulation of PFC inputs by the HC in the awake or the anaesthetized animal. The response profile of many cells changed during anaesthesia when compared to the awake condition, and on average showed suppression to PFC input 50 and 150 ms following HC stimulation while under deep isoflurane anaesthesia. These results suggest that sublinear integration of afferent input from the PFC and HC is the dominant mode of integration of Nacb cells in the awake animal, which has implications for corticostriatal models of psychiatric dysfunction.     

Human sperm pattern of movement during chemotactic ＇e-orientation towards a progesterone source

Human spermatozoa may chemotactically find out the egg by following an increasing gradient of attractant molecules. Although human spermatozoa have been observed to show several of the physiological characteristics of chemotaxis, the chemotactic pattern of movement has not been easy to describe. However, it is apparent that chemotactic cells may be identified while returning to the attractant source. This study characterizes the pattern of movement of human spermatozoa during chemotactic re-orientation towards a progesterone source, which is a physiological attractant candidate. By means of videomicroscopy and image analysis, a chemotactic pattern of movement was identified as the spermatozoon returned towards the source of a chemotactic concentration of progesterone (10 pmol l⁻¹). First, as a continuation of its original path, the spermatozoon swims away from the progesterone source with linear movement and then turns back with a transitional movement that can be characterized by an increased velocity and decreased linearity. This sperm behaviour may help the spermatozoon to re-orient itself towards a progesterone source and may be used to identify the few cells that are undergoing chemotaxis at a given time.     

An interactive Internet site for the management of patients with congestive heart failure

BACKGROUND: The Internet is a useful tool for improving communication between patients and their health care providers. However, no study has examined an efficient use of the Internet to improve quality of care for these patients. The purpose of this pilot study is to determine the feasibility of using an Internet-based communication tool with heart failure patients and to assess the effect of this system on the patients' quality of life. METHODS AND RESULTS: A prospective study was conducted among patients (n=16) attending a university-based heart failure clinic. An Internet communication Web site (www.heartfunction.com) was developed for the pilot study. The system was designed to be an information resource for patients and a daily communication method between patients and health care providers. Quality of life scores based on the Minnesota Living with Heart Failure Questionnaire (MLHFQ) were obtained at baseline and at three months. The mean MLHFQ score was 59.75+/-1.5 at baseline and 49.87+/-1.3 at three months (P=0.093). Significant differences were found at three months in the scale items that measured relationships with friends and family (3.062 versus 2.06; P=0.03), working around the house and yard (3.68 versus 2.81; P=0.008) and side effects of medication (2.81 versus 1.93; P=0.048). All patients reported high levels of satisfaction with the Web site. CONCLUSIONS: Internet-based communication is a feasible tool for the management of heart failure patients, providing an effective medium through which health care professionals can interact with their patients. This approach may also improve patient quality of care and quality of life.     

Disruption of beta-catenin pathway or genomic instability define two distinct categories of liver cancer in transgenic mice

BACKGROUND & AIMS: Human liver cancer can be divided into 2 categories that are characterized by activation of beta-catenin and genomic instability. Here we investigate whether similar categories exist among 5 transgenic models of liver cancer, including c-myc, transforming growth factor-alpha, E2F-1, c-myc/transforming growth factor-alpha, and c-myc/E2F-1 mice. METHODS: The random amplified polymorphic DNA method was used to assess the overall genomic instability, and chromosomal loci affected by genomic alterations were determined by microsatellite analysis. beta-Catenin mutations and deletions were analyzed by polymerase chain reaction and sequencing screening. Cellular localization of beta-catenin and expression of alpha-fetoprotein, a prognostic marker of hepatocellular carcinoma, were investigated by immunohistochemistry. RESULTS: Liver tumors from the transgenic mice could be divided into 2 broad categories characterized by extensive genomic instability (exemplified by the c-myc/transforming growth factor-alpha mouse) and activation of beta-catenin (exemplified by the c-myc/E2F-1 mouse). The c-myc/transforming growth factor-alpha tumors displayed extensive genomic instability with recurrent loss of heterozygosity at chromosomes 1, 2, 4, 6, 7, 9, 12, 14, and X and a low rate of beta-catenin activation. The genomic instability was evident from the early dysplastic stage and occurred concomitantly with increased expression of alpha-fetoprotein. The c-myc/E2F-1 tumors were characterized by a high frequency of beta-catenin activation in the presence of a relatively stable genome and low alpha-fetoprotein levels. CONCLUSIONS: We have identified 2 prototype experimental models, i.e., c-myc/transforming growth factor-alpha and c-myc/E2F-1 mice, for the 2 categories of human hepatocellular carcinoma characterized by genomic instability and beta-catenin activation, respectively. These mouse models will assist in the elucidation of the molecular basis of human hepatocellular carcinoma.     

Chagas disease in rural areas of Chaco Province, Argentina: epidemiologic survey in humans, reservoirs, and vectors

We studied the seroprevalence of antibodies against Trypanosoma cruzi in the human population along with domiciliary infestation by triatomine bugs in an area endemic for Chagas disease in the Chaco Province of Argentina. In addition, we carried out parasitologic surveys in patients, dogs, wild mammals, and vectors. The mean seroprevalence in humans was 27.81% (109 of 392) and 24.14% (63 of 261) in 1-15-year-old children. The minimum domiciliary infestation rate was 13.33%, with certain areas reaching 53.85%. The prevalence was 15.09% (16 of 106) in dogs and 35.71% (10 of 28) in opossums. Infection with T. cruzi was detected in 30.10% (59 of 196) of the Triatoma infestans tested. Compared with nationwide studies, our data suggest that 1) there are zones requiring immediate sanitary action, and 2) nationwide estimates are based on very heterogeneous epidemiologic situations. This heterogeneity emphasizes the importance of in-depth studies of restricted areas to provide additional information for a better understanding of the present status of Chagas disease in Argentina.