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Biomedical subjects

M Yavuz

Publications and source records attributed to M Yavuz.

31 records · Page 2Linked to original sources
PubMed2000

The relationship between tumor necrosis factor (TNF)-alpha and survival following granulocyte-colony stimulating factor (G-CSF) administration in burn sepsis.

Blood levels of tumor necrosis factor (TNF)-alpha were determined in 78 patients with burn sepsis. Of these patients, 51 were managed with additional administration of granulocyte colony-stimulating factor (G-CSF) in addition to routine treatment procedures (group A), while 27 received only routine treatment (group B). G-CSF was administrated for at least nine and at most 14 days; doses were gradually decreased in each 3 day period. On the 1st, 4th, 7th, 10th and 15th days, blood levels of TNF-alpha were determined. We sought to determine whether TNF alpha levels had a prognostic value in the management of burn induced sepsis that was treated with G-CSF. In our study, patients with gradually decreasing TNF-alpha levels in the second 3 day period, were strong candidates for survival, because TNF-alpha levels decreased little in nonsurvivors but decreased greatly in survivors. The survival rate was 42/51 (82.3%) in group A and 9/27 (33.3%) in group B. In conclusion, G-CSF had positive effects on survival, and TNF-alpha was a predictor of prognosis in burn-induced sepsis.

Adolescent↗
PubMed1999

Characterization of the Hansenula polymorpha CPY gene encoding carboxypeptidase Y.

We have isolated the Hansenula polymorpha CPY gene encoding carboxypeptidase Y (Hp-CPY). The deduced amino acid sequence revealed that Hp-CPY consists of 541 amino acids and has a calculated Mr of 60,793. The protein is highly similar to Saccharomyces cerevisiae CPY (61.8% identity). At the N-terminus of Hp-CPY signals for the entry into the secretory pathway and subsequent sorting to the vacuole were identified. Immunocytochemically, using monospecific antibodies raised against Hp-CPY, the protein was localized to the vacuole. On Western blots, a diffuse protein band was observed in extracts of H. polymorpha cells, suggesting that the protein is glycosylated. This was confirmed by endoglycosidase H treatment, which resulted in a strong reduction of the apparent Mr of the protein. We have investigated the effect of CPY deletion on the degradation of peroxisomes, an autophagous process that occurs when the organelles become redundant for growth. In deltacpy cells peroxisomal proteins were degraded in the vacuole as efficiently as in wild-type H. polymorpha cells, indicating that CPY is not a major proteinase in this pathway.

Amino Acid Sequence↗
PubMed1999

Penalized-likelihood estimators and noise analysis for randoms-precorrected PET transmission scans.

This paper analyzes and compares image reconstruction methods based on practical approximations to the exact log likelihood of randoms-precorrected positron emission tomography (PET) measurements. The methods apply to both emission and transmission tomography, however, in this paper we focus on transmission tomography. The results of experimental PET transmission scans and variance approximations demonstrate that the shifted Poisson (SP) method avoids the systematic bias of the conventional data-weighted least squares (WLS) method and leads to significantly lower variance than conventional statistical methods based on the log likelihood of the ordinary Poisson (OP) model. We develop covariance approximations to analyze the propagation of noise from attenuation maps into emission images via the attenuation correction factors (ACF's). Empirical pixel and region variances from real transmission data agree closely with the analytical predictions. Both the approximations and the empirical results show that the performance differences between the OP model and SP model are even larger, when considering noise propagation from the transmission images into the final emission images, than the differences in the attenuation maps themselves.

Image Processing, Computer-Assisted↗
PubMed1999

Callotasis in a fasciosteal flap model in rabbits: part II. a new contribution to the concept of distraction osteogenesis.

The basis of lengthening bones at their anatomic locations has been defined in detail by many authors. The possibility of distraction osteogenesis in vascularized bone grafts and the role of periosteum was investigated in 35 growing New Zealand White rabbits in four experimental groups: group 1, the scintigraphic assessment group (N = 4); group 2, the distraction group with intact periosteum (N = 15); group 3, the control group without periosteum in the distraction area (N = 6); and group 4, the control group in which the flaps were wrapped in silicone leaves (N = 10). Scintigraphy was used to evaluate the survival of the bone graft. Metatarsal fasciosteal flaps were fixed by external fixators and then subjected to osteotomy. Distraction was started after 10 days of osteotomy and continued at 0.5 mm/24 hr for 10 days, with a total elongation of 4 to 6 mm. Radiological examination at day 10 of starting the distraction, and both radiological and histological examinations at days 15, 20, and 30 were performed. In group 1, positive scintigraphic images of the flaps were obtained. In group 2, progressive calcification was detected radiologically and mixed-type ossification was observed histologically. However, in group 3, distraction failed. Group 4 was excluded from the study due to silicone exposition. The authors demonstrated that vascularized bone segments can be lengthened, and provided information about the importance of periosteum in distraction osteogenesis.

Animals↗
PubMed1998

Upper extremity salvage procedure with flow-through free flap transfer taken from the amputated part.

An alternative free flap technique in a patient presenting with an incomplete amputation in the right cubital region, resulting from a gunshot wound, is introduced. The defect area was repaired using a flow-through fasciocutaneous free flap, which, when following a cubical or popliteal region amputation, is a suitable option for revascularisation and salvage of the extremity.

Adolescent↗
PubMed1998

Statistical image reconstruction methods for randoms-precorrected PET scans.

Positron emission tomography (PET) measurements are usually precorrected for accidental coincidence events by real-time subtraction of the delayed-window coincidences. Randoms subtraction compensates on average for accidental coincidences but destroys the Poisson statistics. We propose and analyze two new approximations to the exact log-likelihood of the precorrected measurements, one based on a 'shifted Poisson' model, the other based on saddle-point approximations to the measurement of probability mass function (PMF). The methods apply to both emission and transmission tomography; however, in this paper we focus on transmission tomography. We compare the new models to conventional data-weighted least-squares (WLS) and conventional maximum-likelihood methods [based on the ordinary Poisson (OP) model] using simulations and analytic approximations. The results demonstrate that the proposed methods avoid the systematic bias of the WLS method, and lead to significantly lower variance than the conventional OP method. The saddle-point method provides a more accurate approximation to the exact log-likelihood than the WLS, OP and shifted Poisson alternatives. However, the simpler shifted Poisson method yielded comparable bias-variance performance to the saddle-point method in the simulations. The new methods offer improved image reconstruction in PET through more realistic statistical modeling, yet with negligible increase in computation time over the conventional OP method.

Abdomen↗
PubMed1997

The reversed-flow temporoparietal fascial flap.

A patient is reported whose forehead soft-tissue defect was reconstructed by a reversed-flow temporoparietal fascial flap. This procedure can shorten the operating time. The blood circulation of the flap is satisfactory. The only drawback is the resulting scar of the skin-grafted area.

Adult↗
PubMed1989

Effects of sublingual administration of nifedipine on arterial pressure, plasma renin activity, and glomerular filtration rate in essential hypertension.

Effects of sublingual administration of nifedipine on systemic arterial pressure (BP), plasma renin activity (PRA), aldosterone level (AL), and serum sodium (Na) and potassium (K) levels, have been determined. A significant decrease was observed in systolic and diastolic blood pressure five minutes after the sublingual administration of nifedipine in 21 patients with mild or moderate essential hypertension. Furthermore, in an observation period of six hours, it was also established that the effect of nifedipine on systolic and diastolic blood pressure continued. An increase was observed in glomerular filtration rate, whereas there were no changes in PRA, AL, or serum Na and K levels.

Administration, Sublingual↗