A perceptual memory for low-contrast visual signals

Detection of a visual signal can be facilitated by simultaneous presentation of a similar subthreshold signal. Here we show that the facilitatory effect of a subthreshold signal can persist for more than 16 s. Presenting a near-threshold Gabor signal (prime) produced a phase-independent increase in contrast sensitivity (40%) to similar successive signals (target) for a period of up to 16 s. This effect was obtained only when both prime and target were presented to the same eye. We further show that the memory trace is inactivated by presenting high-contrast signals before the target. These results suggest that activated neurons in the primary visual cortex retain a near-threshold memory trace that persists until reactivated.     

Improving vision in adult amblyopia by perceptual learning

Practicing certain visual tasks leads, as a result of a process termed "perceptual learning," to a significant improvement in performance. Learning is specific for basic stimulus features such as local orientation, retinal location, and eye of presentation, suggesting modification of neuronal processes at the primary visual cortex in adults. It is not known, however, whether such low-level learning affects higher-level visual tasks such as recognition. By systematic low-level training of an adult visual system malfunctioning as a result of abnormal development (leading to amblyopia) of the primary visual cortex during the "critical period," we show here that induction of low-level changes might yield significant perceptual benefits that transfer to higher visual tasks. The training procedure resulted in a 2-fold improvement in contrast sensitivity and in letter-recognition tasks. These findings demonstrate that perceptual learning can improve basic representations within an adult visual system that did not develop during the critical period.     

The role of correction of anaemia in patients with congestive heart failure: a short review

Many patients with Congestive Heart Failure (CHF) are anaemic. This anaemia is associated with more severe CHF and a higher incidence of mortality, hospitalisation and morbidity. The only way to prove that the anaemia is causing this worsening of CHF is to correct it. We review here some of the published papers about correction of anaemia. Many studies show a positive effect of Erythropoietin (EPO) or its' derivatives when administered in combination with oral or IV iron, with improvements in left and right ventricular systolic and diastolic function, dilation and hypertrophy and renal function. In addition, a reduction in hospitalisations, diuretic dose, pulmonary artery pressure, plasma volume, heart rate, serum Brain Natriuretic Peptide levels, the inflammatory marker Interleukin 6, soluble Fas ligand - a mediator of apoptosis, and improvements in New York Heart Association class, exercise capacity, oxygen utilization, caloric intake, Quality of Life and the activity of Endothelial Progenitor Cells, have been observed. Iron deficiency may also play an important role in this anaemia, since improvements in CHF have also been reported following treatment with IV iron alone. However, until the ongoing large placebo-controlled studies of the EPO derivative darbepoetin or IV iron are completed, we will not know whether these treatments really influence CHF outcome.     

Diarrhea in hypothyroidism: bacterial overgrowth as a possible etiology

Constipation is common but diarrhea is very rare in myxedematous patients. We report a young woman with myxedema in whom chronic diarrhea was the dominant symptom. A fasting breath hydrogen test was positive, indicating bacterial overgrowth as the cause of the diarrhea. Antibiotic treatment was successful. We conclude that bacterial overgrowth due to hypomotility may be the etiology of the diarrhea in such patients.     

Genetic analyses in consecutive israeli jewish colorectal cancer patients

OBJECTIVES: Two APC germline mutations, E1317Q and I1307K, have been linked to colorectal cancer (CRC) risk. Whereas the I1307K variant is almost exclusively encountered in (Ashkenazi) Jews, E1317Q is not restricted to certain ethnic populations. Data on its contribution to CRC risk in Jewish patients are sparse. AIMS: To assess the contribution of E1317Q to CRC development in the Jewish population. METHODS: A total of 538 consecutive Israeli Jewish CRC patients and 440 controls were genotyped for E1317Q. In addition, the rate of the I1307K APC missense mutation and the two predominant Jewish mutations in hMSH2, A636P, and 324delCA, associated with hereditary nonpolyposis colon cancer (HNPCC), were determined. RESULTS: The E13117Q missense mutation was detected in 6/538 (1%) of CRC patients and 5/440 (1%) of controls. The I1307K variant was found in 8% of all patients and in 11% (35/322) of patients of Ashkenazi Jewish descent. Carriers and noncarrier CRC patients did not differ in age of onset or associated colonic adenomatous polyps. The carrier rate among controls was 5% among Ashkenazim and 1.6% among non-Ashkenazi individuals. The 324delCA hMSH2 mutation was not observed in this cohort, and 4 of 322 Ashkenazi patients (1.2%) displayed the A636P mutation. CONCLUSION: In Jewish CRC patients the E1317Q variant plays little if any role in colorectal cancer susceptibility and genetic testing for this variant is not warranted. The I1307K mutation is associated with a moderate excess risk for CRC, but age of onset seems not to be earlier and this variant is not associated with a multiple colonic polyp phenotype. Founder mutations in hMSH2 are rare in consecutive CRC patients.     

Soluble egg antigens from Schistosoma mansoni induce angiogenesis-related processes by up-regulating vascular endothelial growth factor in human endothelial cells

Schistosomiasis mansoni is characterized by hepatic granuloma formation. Endothelial cell activation within these granulomas may contribute to their development and to increased vascularization in the granuloma periphery. The earliest event in granuloma formation is the lodging of schistosome eggs within presinusoidal capillaries. The eggs secrete factors that may activate endothelial cells. This study investigated the effects of Schistosoma mansoni soluble egg antigen (SEA) on angiogenic processes: proliferation, tube formation, and apoptosis of human umbilical vein endothelial cells (HUVECs). HUVECs require serum and growth factors to proliferate in vitro. Proliferation occurred when SEA or live eggs were substituted for growth factors, but not for serum. SEA increased HUVEC tube formation and decreased HUVEC apoptosis after serum and growth factor deprivation. Messenger RNA for vascular endothelial growth factor (VEGF) increased 2-fold in SEA-treated HUVECs. These findings suggest that products secreted by schistosome eggs may promote angiogenesis within hepatic granulomas by up-regulating endothelial cell VEGF.     

Between the Subjective and the Objective: How Informative Is Subjective Evaluation of Memory Among the Old-Old?

This study addresses the relationship between subjective evaluation of memory and objective cognitive dysfunction in old-old age. In a sample of 164 participants (mean age 91.9, range 87–106) drawn from a nationwide Israeli survey, 42% evaluated their memory positively and 30% negatively. Participants were no more concerned about being forgetful than younger adults. Subjective memory and concern about forgetfulness were not significantly correlated with cognitive dysfunction. Sociodemographic, physical, and well-being characteristics explained three times more variance of cognitive dysfunction than of subjective memory. The study suggests that subjective memory among old-old people who can undergo a survey interview may not reflect actual cognitive dysfunction. Apparently, the role of subjective evaluation resides in other areas of adaptation to very old age.     

Incorporating vessel taper and compliance properties in Navier-Stokes based blood flow models

A popular and useful technique used to model blood flow in cardiovascular simulations is to divide each blood vessel into a series of segments, each with its own lumped resistance, intertance, and compliance parameters. The values of these parameters are usually obtained through a simplification of the Navier-Stokes equations for fluid flow. However, the simplification often ignores the nonlinear and convective terms of the equations, resulting in errors in the parameter values, especially in the value found for resistance per unit length. We report a new method for the calculation of vessel resistance per unit length which takes into account the effects of vessel taper and wall compliance. It is shown that these effects can be addressed by the addition of two time-varying terms to the calculation of resistance per unit length. One term, due to vessel taper, is proportional to volumetric flow rateQ. The other term, due to vessel compliance, is proportional to ∂p/∂t. These variables are readily available in computer simulations of blood flow in lumped parameter systems. Using data for the descending aorta, the new parameter values, when averaged over a cardiac cycle, compare favorably with results in the literature.