Educational Forum with Clinical Studies Current Science and Research

February 27, 2011

FREQUENCY SPECIFIC EFFECTS OF DOPAMINE IN THE NUCLEUS ACCUMBENS

The action of dopamine was evaluated in the nucleus accumbens of acutely prepared rabbits. It was found that the effect of iontophoretically applied dopamine depended upon the frequency of stimulation of an afferent pathway; in this case the ipsilateral fimbria. Dopamine had a marked suppressive effect on field responses evoked by fimbria stimulation at 0.5 Hz, but not those responses evoked at 6.0 Hz. Dopamine was also effective in activating adenylate cyclase. Both the physiological and the biochemical effects of dopamine could be blocked by appropriate antagonists, suggesting that the phenomena observed were receptor mediated. It is suggested that dopamine serves to enhance information arriving from the hippocampal formation within the theta range by the suppression of competing non-theta activity.

Xanya Sofra Weiss

Xanya Sofra Weiss

Multiple Sclerosis: Low-Frequency Temporal Blood Oxygen Level– Dependent Fluctuations Indicate Reduced Functional Connectivity —Initial Results

PURPOSE: To study the correlation of low-frequency blood oxygenation level– dependent (BOLD) fluctuations on magnetic resonance (MR) images obtained of the left- and right-hemisphere primary motor regions in healthy control subjects and patients with multiple sclerosis (MS). MATERIALS AND METHODS: Sixteen healthy volunteers and 20 patients with MS underwent MR imaging with a 1.5-T imager by using a protocol designed to monitor low-frequency BOLD fluctuations. Data for low-frequency BOLD fluctuations were
acquired with subjects at rest and during continuous performance of a bilateral fingertapping task. These data were low-pass filtered (<0.08 Hz), and cross correlations of all acquired pixels to a region of interest in the left precentral gyrus were calculated. Confidence levels were calculated from the cross correlations. The fraction of pixels in the right precentral gyrus above a confidence level of 95% for correlation with the precentral gyrus was calculated for each subject. RESULTS: A plot of the fraction of the right precentral gyrus with high correlation with the left precentral gyrus for the finger-tapping state versus the resting state showed a clear discrimination between patients with MS and control subjects. Compared with control subjects, patients with MS generally had a smaller fraction of the pixels in the right precentral gyrus above the confidence level. This finding indicates that our method results in greater than 60% sensitivity and 100% specificity for discriminating patients with MS from control subjects. No significant correlation was found between clinical measures of MS disease and correlations of low-frequency BOLD fluctuations between left and right precentral gyri. CONCLUSION: On the basis of the connectivity measure of low-frequency BOLD fluctuations, patients with MS exhibited lower functional connectivity between rightand left-hemisphere primary motor cortices when compared with that in control subjects.

Xanya Sofra Weiss

Xanya Sofra Weiss

Pulsed short-wave diathermy effects on human fibroblast proliferation. Xanya Sofra Weiss

Filed under: Xanya Sofra Weiss — Tags: — Dr. Xanya @ 7:32 pm

Hill J, Lewis M, Mills P, Kielty C. Pulsed short-wave diathermy effects on human fibroblast proliferation. Arch Phys Med Rehabil 2002;83:832-6. Objectives: To investigate the influence of pulsed short-wave diathermy (PSWD) on fibroblast and chondrocyte cell proliferation rates and to establish the influences of different dosages applied. Design: Four single-blind trials. Setting: Laboratory, in vitro study. Specimens: Human adult dermal fibroblast and chondrocyte cells were plated at known concentrations and incubated for 5 days. Intervention: Exposure to PSWD, twice daily, on days 2, 3, and 4. Main Outcome Measure: After crystal violet staining (day 5), optical density (cell number) was determined spectrophotometrically. Results: PSWD, given at mean power of 48W for 10 minutes, increased fibroblast proliferation compared with control groups (P[lt ].001). There was a relationship between cell proliferation and the amount of energy given (P[lt ]0.001). The optimal mean power for proliferation was estimated to be 13.8W. While keeping mean power constant at 6W, altering pulse duration and pulse repetition rate dosage parameters did not have a significant effect on proliferation (P=.519). Chondrocyte proliferation also increased with PSWD exposure of 6W at 10 minutes duration (P=.015). In addition, treatment time was significantly associated with chondrocyte proliferation (P[lt ].001). Conclusion: PSWD is associated with increased rates of fibroblast and chondrocyte proliferation in vitro, which is dose dependent. These results contribute to an understanding of the physiologic mechanisms underlying the therapeutic effects of PSWD.

Xanya Sofra Weiss

Xanya Sofra Weiss

Growth hormone: uses and abuses. Xanya Sofra Weiss

Filed under: Xanya Sofra Weiss — Tags: — Dr. Xanya @ 7:30 pm

Raymond L Hintz; 2004

Unconvincing and therefore called for raising the price and limiting availability.1 The prime minister’s strategy unit, with access to the same evidence, concluded that controlling average consumption through the mechanism of raising the price and limiting access would have unwanted side effects and was not a viable option. They therefore called for education, more policing, improved treatment, and the alcohol industr y entering into voluntar y agreements to behave reasonably.7 The academy working group would agree that all of these actions were necessar y. But they took the view, based on evidence, that such actions should complement measures to control overall level of consumption. Two reports, same evidence, and yet such different conclusions. As scientists, steeped in alcohol (as it were), we who prepared the academy’s report no doubt came to the issue with our own set of prejudices. The prime minister’s strategy unit had a different set. It is reasonable to surmise that they found the prospect of raising the tax on alcohol unattractive, as they did reversing the trend of making it ever easier to buy alco- hol. The policy implications of the science may well have influenced their view of the evidence. This leads me, naively perhaps, to want to separate two issues: what the science shows and its policy implications. It is perfectly reasonable for governments to balance a number of interests in forming policies. Scientific evidence on dose response relations between exposure and risk is only one consideration. Others include analysis of costs and benefits, risk analysis, and appreciation of the degree to which policies fit with public values.8 It is helpful, however, to keep these distinct. Public values are important. There is much discus- sion now of individual responsibility for behaviour. This informs the government’s call for consultation as it develops a white paper on public health. A healthy tension exists in a democratic society between individual responsibility and the role of government. Smoking is a matter of individual responsibility but successive British governments have taken beneficial action by raising the price for health reasons, restricting advertising and promotion, and restricting smoking in public places. Unlike smoking, the healthi- est amount of alcohol is not zero. Nevertheless, the 50% rise in alcohol consumption in Britain means that as a population we are drinking well above the optimal level for health. As it develops its white paper on public health the government has another opportunity to look at the evidence linking harm with average alcohol consumption and consider that government has a responsibility alongside that of individual citizens.

Xanya Sofra Weiss

Xanya Sofra Weiss

Endothelin. Xanya Sofra Weiss

Filed under: Xanya Sofra Weiss — Tags: — Dr. Xanya @ 7:27 pm
endothelin (ET): any of a group of vasoconstrictive peptides produced by endothelial cells. Three known endothelins, designated ET-1, ET-2, and ET-3, are chemically related to asp venom. ET-1 is the most potent vasoconstrictor yet discovered, being 10 times stronger than the second-most potent vasoconstrictor known, angiotensin II.
Xanya Sofra Weiss
« Newer PostsOlder Posts »

Powered by WordPress