Synergies in the space of control variables within the equilibrium-point hypothesis

We use an approach rooted in the recent theory of synergies to analyze possible co-variation between two hypothetical control variables involved in finger force production based on the equilibrium-point (EP) hypothesis. These control variables are the referent coordinate (R) and apparent stiffness (C) of the finger. We tested a hypothesis that inter-trial co-variation in the {R; C} space during repeated, accurate force production trials stabilizes the fingertip force. This was expected to correspond to a relatively low amount of inter-trial variability affecting force and a high amount of variability keeping the force unchanged. We used the "inverse piano" apparatus to apply small and smooth positional perturbations to fingers during force production tasks. Across trials, R and C showed strong co-variation with the data points lying close to a hyperbolic curve. Hyperbolic regressions accounted for over 99% of the variance in the {R; C} space. Another analysis was conducted by randomizing the original {R; C} data sets and creating surrogate data sets that were then used to compute predicted force values. The surrogate sets always showed much higher force variance compared to the actual data, thus reinforcing the conclusion that finger force control was organized in the {R; C} space, as predicted by the EP hypothesis, and involved co-variation in that space stabilizing total force.

Task-specific stability of abundant systems: Structure of variance and motor equivalence

Our main goal was to test a hypothesis that transient changes in performance of a steady-state task would result in motor equivalence. We also estimated effects of visual feedback on the amount of reorganization of motor elements. Healthy subjects performed two variations of a four-finger pressing task requiring accurate production of total pressing force (F TOT) and total moment of force (M TOT). In the Jumping-Target task, a sequence of target jumps required transient changes in either F TOT or M TOT. In the Step-Perturbation task, the index finger was lifted by 1cm for 0.5s leading to a change in both F TOT and M TOT. Visual feedback could have been frozen for one of these two variables in both tasks. Deviations in the space of finger modes (hypothetical commands to individual fingers) were quantified in directions of unchanged F TOT and M TOT (motor equivalent - ME) and in directions that changed F TOT and M TOT (non-motor equivalence - nME). Both the ME and nME components increased when the performance changed. After transient target jumps leading to the same combination of F TOT and M TOT, the changes in finger modes had a large residual ME component with only a very small nME component. Without visual feedback, an increase in the nME component was observed without consistent changes in the ME component. Results from the Step-Perturbation task were qualitatively similar. These findings suggest that both external perturbations and purposeful changes in performance trigger a reorganization of elements of an abundant system, leading to large ME change. These results are consistent with the principle of motor abundance corroborating the idea that a family of solutions is facilitated to stabilize values of important performance variables.

Efficacy and safety of flexible-dose oral sildenafil citrate (Viagra) in the treatment of erectile dysfunction in Brazilian and Mexican men

A 12-week, double-blind, placebo-controlled, multicenter study evaluated the efficacy and safety of flexible-dose sildenafil citrate (Viagra) treatment (25, 50 or 100 mg) in Brazilian and Mexican men with erectile dysfunction (ED) of broad-spectrum etiology. Efficacy was assessed on the basis of responses to the 15-item International Index of Erectile Function (IIEF) questionnaire, completed at baseline and after 12 weeks of treatment. At end point, mean scores for all IIEF domains of sexual function (erectile function, orgasmic function, sexual desire, intercourse satisfaction and overall satisfaction) were significantly (P<0.0001) higher in the sildenafil group (n=109) than in the placebo group (n=105). These findings confirm the significant increases in frequency of penetration and frequency of maintained erections reported previously. Sildenafil treatment was well tolerated. The most common adverse events were headache and flushing. In conclusion, sildenafil is a well-tolerated and effective treatment for ED of broad-spectrum etiology in Latin American men.

Dissemination of latent colon adenocarcinoma after laparoscopic cholecystectomy

The seeding of neoplasms at trocar sites has been reported with increasing frequency. A case is presented of a 68 year-old woman with metastatic seeding of nondiagnosed colon cancer at the umbilical trocar site used for a laparoscopic cholecystectomy. Histopathological examination showed metastatic adenocarcinoma probably of gastrointestinal origin. A colonoscopy performed at the same time revealed a 2-cm lesion at the hepatic flexure which was shown histologically to be a differentiated adenocarcinoma. Diffuse peritoneal carcinomatosis was also found on computerised tomography. It is presumed that the primary colon cancer existed prior to cholecystectomy.

Estrogen and progesterone receptors in gastric and colorectal cancer

BACKGROUND/AIMS

Estrogen (ER) and progesterone receptors (PR) have been evaluated in gastrointestinal cancer by several groups with conflicting results. The aim of the study is to examine the presence of these receptors in gastric and colon cancer.

METHODOLOGY

Estrogen (ER) and progesterone (PR) receptors were assayed by the dextran-coated charcoal adsorption method from malignant and normal adjacent tissues in 16 patients with gastric adenocarcinomas and in 10 with colorectal adenocarcinomas.

RESULTS

In gastric cancer, ER were detected in 62.5% and PR in 75% of the patients. In colorectal cancer, the ER and PR were detected in 60% of the patients. The binding activity ranged from 1.14-9.27 fmol/mg protein for estradiol and from 1.43-10.84 fmol/mg protein for progesterone. ER and PR were detected in normal gastric tissue in 62.5% and in 50%, respectively. In the normal colorectal tissue the ER and PR were detected in 30% and 50%. ER ranged from 1.20-16.63 fmol/mg protein for estradiol and from 1.44-9.94 fmol/mg protein for progesterone. There was no statistical difference in levels of ER and PR in both tissues.

CONCLUSIONS

ER and PR were detected in normal and cancer tissues in low levels, suggesting a feature of the tissue rather than a consequence of a malignant process. Eventual role of ER or PR in these cancers remains to be elucidated.

Cholesterolemia in colorectal cancer

BACKGROUND/AIMS

Colorectal cancer incidence is higher in developed countries. High fat intake is one of the risk factors. However, many studies observed lower cholesterol serum levels on diagnosis of colorectal cancer. The aim of this assay was to study the serum cholesterol levels in patients with colorectal cancer and compare these values with individuals of the same age and sex.

METHODOLOGY

Cholesterol serum levels of 85 patients with colorectal cancer were determined. Each of the patients with colorectal cancer were matched with an individual without cancer of the same age and sex. Total cholesterol concentrations were determined using an enzymatic colorimetric method.

RESULTS

The mean serum of cholesterol was 183.4 for the colorectal group and 209.7 for the control group. This difference was statistically significant. This difference was more evident in patients with colon cancer and older than 60 years of age. There was no difference between the different Dukes' stage.

CONCLUSIONS

Our study suggest an association between low blood cholesterol and colorectal cancer. We believe that the lower level of cholesterol observed in these patients is a consequence between the difference of colorectal carcinogenesis.