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Biomedical subjects

M Zakrzewski

Publications and source records attributed to M Zakrzewski.

At least 19 recordsLinked to original sources
PubMed2001

Investigation of solid-state reactions using variable temperature X-ray powder diffractrometry. I. Aspartame hemihydrate.

PURPOSE: The object of this study was to demonstrate the applicability of variable temperature X-ray powder diffractometry (XRD) to investigate solid-state reactions using aspartame as a model compound. METHODS: Aspartame exists as a hemihydrate (ASH) under ambient conditions and converts to aspartame anhydrate (ASA) at approximately 130 degrees C. ASA on further heating to approximately 180 degrees C undergoes decomposition (intramolecular cyclization) to form a diketopiperazine derivative (DKP). The dehydration as well as the decomposition kinetics were studied isothermally at several temperatures. The unique feature of this technique is that it permits simultaneous quantification of the reactant as well as the product. RESULTS: While the dehydration of ASH appeared to follow first-order kinetics, the cyclization of ASA was a nucleation controlled process. The rate constants were obtained at various temperatures, which permitted the calculation of the activation energies of dehydration and cyclization from the Arrhenius plots. The activation energy of dehydration was also calculated according to the method described by Ng (Aust. J. Chem., 28:1169-1178, 1975) and the two values were in good agreement. CONCLUSIONS: The study demonstrates that XRD is an excellent complement to thermal analysis and provides direct information about the solid-states of various reaction phases.

Algorithms↗
PubMed2000

Identifying male college students' perceived health needs, barriers to seeking help, and recommendations to help men adopt healthier lifestyles.

Seven focus groups at a university campus were formed to identify college men's health concerns, barriers to seeking help, and recommendations to help college men adopt healthier lifestyles. Content analysis was used to identify and organize primary patterns in the focus-group data. Results of the study revealed that the college men were aware that they had important health needs but took little action to address them. The participants identified both physical and emotional health concerns. Alcohol and substance abuse were rated as the most important issues for men. The greatest barrier to seeking services was the men's socialization to be independent and conceal vulnerability. The most frequently mentioned suggestions for helping men adopt healthier lifestyles were offering health classes, providing health information call-in service, and developing a men's center. Implications of the results are discussed.

Adaptation, Psychological↗
PubMed2000

[Clinical classification of diabetic foot as a guideline for selection of treatment].

Foot ulceration in patients with diabetes mellitus is always a serious risk factor for lower limb amputation. To amputate or to continue conservative treatment is usually a very difficult decision and not without mistakes. The main objective of the study was assessment of the diabetic wound depth as a clinical guideline for decision-making of conservative or aggressive surgical treatment. Local foot ulceration and results of management of 62 diabetics were analysed. Lower leg amputations were performed in 40% of the patients. The foot wound was evaluated according to University of San Antonio or Wagner's scoring system. Conservative treatment resulted in failure in 19% of patients of grade I, 54% of grade II, 60% of grade III and 87% of grade IV according to Wagner's. Using the San Antonio classification there were 20% of amputations in grade I, 58% in grade II and 65% in grade III. Taking into account infection and peripheral vascular disease there were 37% of amputations in stage B, 41% in stage C and 80% in stage D. Data analysis of the study suggests better clinical usefulness of the San Antonio classification system in prognosis of limb salvage. There is high probability of failure in conservative treatment of diabetic foot lesion of grade II and III and in stage D according to University of San Antonio scoring system.

Adult↗
PubMed1995

Hemostatic activity of organs in declamping shock.

The aim of the study was to determine the haemostatic components activity of organs in declamping shock. The abdominal aorta was cross-clamped below or above renal arteries. No significant changes in tromboplastic and antithrombin activities were found in the kidney, liver, lung, heart and skeletal muscle. Renal cortex and medulla as well as the lungs show higher plasminogen activator activity and considerably higher antiplasmin activity. Diminished fibrinolysis in the kidney and the lung may promote thrombotic complications.

Animals↗
PubMed1995

Activity of membrane, cytosol and lysosome enzymes in organs and blood serum during declamping shock.

The aim of the study was to evaluate the enzyme activity of cellular membranes (GGT), cytosol (ALT, AST) and lysosome (AP, AcP) in the cytosol, whole homogenate and blood serum during declamping shock, following release of abdominal aorta cross-clamping. The aorta was clamped for 60 minutes. An increase in GGT, AP and AcP activities in the cytosol and whole homogenate of the renal cortex, renal medulla, liver, lung, heart and the skeletal muscle occurs after declamping. Rise in the enzymatic activity, especially of acid phosphatase is higher when the aorta above renal arteries was clamped. However, its activity in the blood serum remains unchanged. Alterations in the distribution and the activity of the studied enzymes may indicate that aortic clamping damages the endoplasmic reticulum and lysosomal membranes. Yet, cellular membranes preserve their structural and functional integrity.

Acid Phosphatase↗
PubMed1977

An objective indicant of binocular vision in humans: size-specific interocular suppression of visual evoked potentials.

Evoked cortical potentials (VEPs) to grid patterns flashed to one eye were suppressed in amplitude when grid patterns were continuously presented to the other eye. The degree of interocular suppression of VEPs was influenced by the stereoacuity of the subjects. VEPs were obtained to each of two grid sizes flashed to one eye (individual squares subtending 15 and 60 min of arc) and changes in amplitude of these VEPs were considered as a function of four stimuli continuously presented to the other eye (diffuse light, 15, 30, and 60 min of arc squares in grids). Interocular suppression of VEPs was greater (a) when the continuously presented grid was of high (38.00 mL) as compared to low (00.38 mL) intensity, (b) when the continuous and flashed grids were of the same as compared to different sizes, and (c) in six subjects who had good as compared to six subjects who had poor binocularity. Eleven of the twleve subjects could be classified correctly as having good or poor binocularity on the basis of statistically significant interocular suppression of VEPs. The results were interpreted in terms of centrally located binocular neurons responsive to specific grid sizes or spatial frequencies and the decreased functioning of such neurons in subjects with poor binocularity.

Evoked Potentials↗
PubMed1972

[Chyluria].

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Chyle↗