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Biomedical subjects

S Karakas

Publications and source records attributed to S Karakas.

5 recordsLinked to original sources
PubMed2005

Circulating leptin and body composition in chronic obstructive pulmonary disease.

Nutritional depletion and weight loss are two features of chronic obstructive pulmonary disease (COPD), and the association between low body mass index (BMI) and poor prognosis in patients with COPD is a common clinical observation. Mechanisms of weight loss are still unclear in COPD. Excessive energy expenditure partly due to increased work of breathing was shown, but other mechanisms have been searched for. Leptin is a hormone secreted by adipocytes that plays an important role in energy homeostasis and regulates body weight through control of appetite and energy expenditure. The aim of this study was to evaluate the association of circulating leptin levels and measures of body composition in COPD patients. Thirty male COPD outpatients (mean age 66.3 +/- 8.4) and 20 controls (mean age 65.9 +/- 10.8) were included in the study. After standard spirometry and body composition measurements, serum leptin concentration was measured by ELISA assay. COPD patients were grouped according to BMI. Mean BMI was 19.01 +/- 2.26 kg/m2 in group 1 (COPD patients with low BMI), 26.85 +/- 4.51 in group 2 COPD (COPD patients with normal/high BMI) and 27.64 +/- 2.75 kg/m2 in healthy controls (group 3). Mean serum leptin concentration was 1.41 +/- 1.86 ng/ml in group 1, 2.60 +/- 1.38 ng/ml in group 2 and 2.82 +/- 1.46 ng/ml in group 3 (p = 0.002). Leptin correlated to not only BMI but also body weight, waist circumference, triceps and biceps skinfold thickness and body fat percent (p < 0.05 for all). Results of this study suggest that the cause of weight loss is not increased circulating leptin in COPD. Instead, leptin remains regulated in COPD and further decreased in patients with low BMI, probably as a compensatory mechanism to preserve body fat content, which should be evaluated in further studies.

Aged↗
PubMed1993

Development of a memory trace for a complex sound in the human brain.

The development of a memory trace for a complex, unfamiliar sound in the human brain was studied by repeatedly presenting reading subjects with this sound ('standard') which was occasionally replaced by a slightly different sound ('deviant'). Deviants did not elicit the mismatch negativity, an index of automatic change detection in auditory cortex, in the beginning but did later during the session. This result reflects a gradual 'sharpening' of sensory information encoded in the memory trace: the representation of the standard stimulus eventually became precise enough to enable the cortical change-detector mechanism to detect a slight different stimulus.

Acoustic Stimulation↗
PubMed1989

Specificity of auditory evoked potentials from rat hypothalamus: differential recording by lateral and ventromedial electrodes.

Evoked potentials recorded from ventromedial nucleus (VMH) and lateral area (LHA) of the hypothalamus were studied in freely moving rats with respect to specificity of the components to recorded areas and to peripheral stimuli utilized. This study attempts to circumvent some methodological problems and contamination in data with respect to origin of recorded components by comparing monopolar and differential recordings made in VMH and LHA, areas accepted as being involved in food-intake behavior. Of the stable components, the complex with 15-20 ms latency was evaluated as of extra-hypothalamic origin. Meanwhile, those with 25-ms (positive) and 40-ms (negative) average peak latencies were considered as specific to recorded areas. Hypothalamic responses appeared not to be specific to stimulus modality, indicating convergence of different sensory modalities on studied areas. Hunger and satiety appeared to influence the amplitude of the specified components similarly, the study not providing evidence for the reciprocal relation stated in the dual center hypothesis between VMH and LHA.

Action Potentials↗