PubMed Health⌕ Search

Biomedical subjects

F Yildiz

Publications and source records attributed to F Yildiz.

At least 19 recordsLinked to original sources
PubMed2006

Spin-flop and spin-Peierls transition in doped CuGeO3.

Ni++ ions doped inorganic CuGeO3 sample has been studied by using electron spin resonance (ESR) technique in the temperature range of 3-300 K. The ESR spectrum of Cu++ ion has been observed to be strongly temperature dependent for inorganic spin-Peierls (SP) Cu0.96Ni0.04GeO3 samples. The ESR line width and ESR amplitude exponentially vanishes below a critical temperature, Tsp=14 K. The one-dimensional (1D) antiferromagnetic (AF) spin chain formed of Cu++ is broken by Ni++ (spin-1) ion, giving uncoupled spins at the end of the chains that give extra contribution to the spectra at lower temperature and stabilizes a Néel state. The g-factor is much smaller than the expected value for isolated Cu++ and Ni++ ions and is much more anisotropic than for undoped samples [O. Yalçin, B. Aktaş, J. Magn. Magn. Mater. 258/259 (2003) 137 (reference therein)]. It is shown that the ground state of dimerized spins is singlet. The spin-flop (SF) phenomenon is obtained from AF state mixed condition and then ferromagnetic (FM) state. The spin-flop field slightly increases when increasing temperature in the temperature range 100-300 K. The SF transition is showed almost AF order for Cu0.96Ni0.04GeO3.

Copper↗
PubMed2006

Effect of ticlopidine in the prevention of radiation enteropathy.

Impairment of vascular function is considered to play an important role in chronic radiation enteropathy. In this experimental study, the role of ticlopidine, an inhibitor of ADP-induced platelet aggregation, was investigated in radiation enteropathy. 80 male Wistar albino rats, each weighing 170-200 g, were divided into four groups: (a) radiation alone (n = 20); (b) radiotherapy plus ticlopidine (n = 20); (c) ticlopidine control (n = 20) and (d) control (n = 20). Both radiation groups received 19 Gy radiation to the exteriorized intestinal segments in a single fraction. Ticlopidine or vehicle was administered 12 h after radiotherapy and continued for 1 month. Rats from every group were euthanized randomly at intervals of 6 weeks from 2 weeks to 26 weeks. Histopathological radiation injury was assessed using radiation injury scoring (RIS). Radiation with ticlopidine or radiation alone groups showed significant RIS deterioration compared with controls in all time points studied. Comparison of median RIS of radiotherapy and radiotherapy+ticlopidine groups at the 2nd, 14th and 26th weeks yielded statistically significant RIS in favour of radiotherapy+ticlopidine group (p = 0.05). However, these differences were less pronounced at the 8th and 20th week (p = 0.07). Both radiation groups had poor weight gain when compared with control and ticlopidine groups. The weight gain in radiotherapy+ticlopidine group was significantly superior to only radiation group between 10th and 20th weeks (p = 0.05). This study showed that inhibition of platelet aggregation with ticlopidine might be useful in radiation enteropathy. However, the precise role of antiaggregant therapies on radiation enteropathy should be comprehensively studied before clinical consideration.

Animals↗
PubMed2006

Changes in collagen and elastic fiber contents of the skin, rectus sheath, transversalis fascia and peritoneum in primary inguinal hernia patients.

BACKGROUND: It has been claimed that inguinal hernia is not a local disease; it is a local manifestation of a systemic disorder of collagen metabolism. Previous studies have shown that patients with inguinal hernia have some anomalies in collagen metabolism and changed ratio of collagen types. AIM: To search the changes in collagen and elastic fiber contents of the skin, rectus sheath, transversalis fascia and peritoneum in primary inguinal hernia patients. METHODS AND MATERIALS: Twenty patients operated on for inguinal hernia (HR) included in the study (11 direct and 9 indirect). Nine patients underwent open cholecystectomy served as the control group (CC). A 0.5 x 1 cm. tissue was sampled from skin, rectus sheath, transversalis fascia and peritoneum in HR group. Skin, rectus sheath and peritoneum samples were taken from the patients in CC group. The sections of those samples were submitted to two different staining methods: "Masson's trichrome" for collagen and "van Gieson" for elastin fibers and graded with light microscopy. RESULTS: The rectus sheath samples of CC had higher staining scores for both collagen and elastin fibers in comparison with HR (p = 0.032 and p = 0.026, respectively). CC had a significantly higher score for collagen in peritoneum samples (p = 0.019). There were no statistically significant differences between the patients with direct and indirect inguinal hernias for collagen or elastin fibers scores in skin, rectus sheath, transversalis fascia and peritoneum samples. CONCLUSIONS: These findings, which concur with most of the previous studies, support the theory that inguinal hernia may not be merely a local disease and can be more generalized, at least a regional connective tissue disorder. Regarding the difference between direct and indirect hernias, it could not be possible to report a certain answer, and this issue should be considered together with previous quantitative researches and more sophisticated studies may take place in the future (Tab. 2, Fig. 2, Ref. 23).

Collagen↗
PubMed2005

Effects of magnesium sulphate and clonidine on propofol consumption, haemodynamics and postoperative recovery.

BACKGROUND: This placebo-controlled, double-blind study was designed to assess the effects of magnesium sulphate and clonidine on peroperative haemodynamics, propofol consumption and postoperative recovery. METHODS: Sixty ASA I-II patients undergoing spinal surgery were randomized into three groups. Group M received magnesium sulphate 30 mg kg(-1) as a bolus before induction and 10 mg kg(-1) h(-1) by infusion. Group CL received clonidine 3 microg kg(-1) as a bolus before induction and 2 microg kg(-1) h(-1) by infusion during the operation period. The same volume of isotonic solution was administered to the control group (group CT). Anaesthesia was induced with propofol and was maintained with propofol infusion [dose according to the bispectral index (BIS)], fentanyl and cisatracurium. Analysis of variance and the Bonferroni test were used for statistical analysis. RESULTS: Induction of anaesthesia with propofol was rapid in the presence of magnesium sulphate and clonidine. The time for BIS to reach 60 was significantly shorter in group M and group CL (P<0.0001) but postoperative recovery was slower with magnesium sulphate compared with the clonidine and control groups (P<0.0001). There was no statistical difference in heart rate and arterial blood pressure between the groups. Propofol requirements for induction and maintenance of anaesthesia were significantly lower with magnesium and clonidine (P<0.0001). CONCLUSION: Clonidine caused bradycardia and hypotension and magnesium sulphate caused delayed recovery, but can be used as adjuvant agents with careful management.

Adjuvants, Anesthesia↗
PubMed2005

1,25-Dihydroxy vitamin D3: can it be an effective therapeutic option for aggressive fibromatosis.

Aggressive fibromatosis (AF), also known as desmoid tumor is a monoclonal fibroblastic proliferation in a collagen matrix that arises in musculoaponeurotic structures. Though considered as benign, they are locally invasive and their propensity for recurrence after conservative surgery is well documented. Addition of postoperative adjuvant radiotherapy produces higher local control rates, although recurrence rates are still high in patients with positive margins. The antineoplastic activity of vitamin D has been demonstrated both in vitro and in vivo models of several cancers. The proposed mechanisms for antineoplastic activity include inhibition of proliferation associated with cell cycle arrest, induction of apoptosis and reduction in invasiveness and angiogenesis. It has also been shown that vitamin D has a negative impact on collagen homeostasis by inhibiting the formation and increasing its degradation. Since vitamin D has an antineoplastic activity and negative effect on collagen synthesis and deposition, it is proposed that 1,25-dihydroxy vitamin D3 can be a right therapeutic option for the management of desmoid tumors.

Antineoplastic Agents↗
PubMed2005

Importance of timing of antiaggregant treatment in the prevention of radiation induced enteropathy.

Chronic radiation enteropathy (CRE) is an undesirable radiation-induced toxicity and a common health problem in patients with pelvic or abdominal malignancies. Damage to microvascular endothelial cells and connective tissue is blamed to cause this adverse effect. It is shown that platelets are the first cellular elements that initiate the homeostatic and inflammatory responses and release of several proinflammatory and fibrinogenic mediators. Antiplatelet agents such as ticlopidine and clopidogrel were shown to prevent CRE and this effect is believed to be directed by their activities against thrombocytes. However, recent studies have shown that these drugs also induce apoptosis in endothelial cells and may lead to decreased expression of endothelial prostacyclin and thrombomodulin (TM) and increased release of von Willebrand factor which are shown to be major contributors of coagulation process. Assuming that radiation induced apoptosis occur 6-10h after irradiation, we think that timing of these antiaggregant drugs with irradiation is important and a 6-10h interval between these may be beneficial to avoid this adverse interaction.

Apoptosis↗
PubMed2003

Frontal chondrosarcoma in a cat.

In this case, chondrosarcoma, detected on the frontal bone of a 12-year-old female cross-bred cat was examined clinically and histopathologically. After being processed routinely, specimens were stained with Hematoxylin & Eosin and Crossman Modification of Mallars Triple Stain. The neoplasm was composed of numerous fusiform mesenchymal cells intimately associated with the formation of lobular structure, separated by thin fibrous septae. In the center there were observed atypical chondrocytes, forming the matrix of the tumoral mass, surrounded by round-ovoid, fusiform mesenchymal cells having interference with the septal tissue at the periphery. Few mitotic figures were detected in these areas. The tumors pattern, localization, the species and the age of the animal were consistent with those of multilobular chondroma known as chondroma rodens. Although the mitotic figures and the wide atypia indicated that the entity was a neoplasm of malign type, it was more likely considered to be the malign transformation of chondroma rodens. The post-surgical outcome of the patient was observed, and recurrence on the same site was reported within 2 months.

Animals↗
PubMed2001

Impaired neurogenic and endothelium-dependent relaxant responses of corpus cavernosum smooth muscle from hyperthyroid rabbits.

We investigated the effect of hyperthyroidism on the responsiveness of the rabbit corpus cavernosum smooth muscle. In male albino rabbits, hyperthyroidism was established by oral feeding of L-thyroxine at increasing dosages (150-450 microg/kg) over an 8-week period. This treatment produced a stable hyperthyroid state as indicated by the increased serum T4 levels. The reactivity of corpus cavernosum tissue from hyperthyroid animals and euthyroid control animals was studied in organ chambers. Hyperthyroidism caused impaired neurogenic and endothelium-dependent relaxant responses with decreased Emax and pD2 values. However, hyperthyroidism had no effect on both phenylephrine- and KCl-induced contractile responses and sodium nitroprusside- and papaverine-induced endothelium-independent relaxant responses, and there was no change in agonist potency. These data indicate that hyperthyroidism may impair both neurogenic and endothelium-dependent relaxation of corporal smooth muscle, and may contribute to the etiology of impotence.

Acetylcholine↗
PubMed2001

Antidepressant, anxiogenic, and antinociceptive properties of levofloxacin in rats and mice.

Levofloxacin, an optically active isomer of ofloxacin, is a fluorinated quinolone with a broad spectrum of antibacterial activity. Fluoroquinolones have been used for the treatment of bacterial infections for many years. Although they were considered as relatively safe drugs, various adverse effects have recently been reported along with increase in the usage of new-generation fluoroquinolones. In the present study, some of the central nervous system (CNS)-related side effects of levofloxacin were clarified in animals. Our results suggested that: levofloxacin (10-20-40 mg/kg i.p.) had no depression-like effect in the forced swimming test (FST) in rats; exerted anxiety-like effect in the elevated plus maze test in rats; did not alter the locomotor activity in rats; had no apparent effect on sleep latency but shortened the sleeping time on pentobarbital sleeping time in mice; and showed analgesic activity in acetic acid writhing and hot plate test in mice.

Analgesics↗
PubMed2001

Chronic ethanol consumption impairs adrenoceptor- and purinoceptor-mediated relaxations of isolated rat detrusor smooth muscle.

OBJECTIVE: To investigate the effects of chronic ethanol consumption on the reactivity of detrusor smooth muscle. MATERIALS AND METHODS: Eight male rats received ethanol (7.2% v/v) in a modified liquid diet for 4 weeks. Two control groups were assessed; eight rats in one group were fed sucrose and received a liquid diet, and 12 rats in the second group received standard rat chow and water for 4 weeks. The reactivity of detrusor smooth muscle strips from ethanol-fed animals and control animals was evaluated in organ chambers. RESULTS: The relaxation response elicited by isoprenaline or adenosine was unaffected in the both control groups while it was significantly inhibited, with decreased maximum responses and pD2 values, in the ethanol-fed group. Contractile responses of detrusor smooth muscle to carbachol or 80 mmol/L KCl and relaxant responses to papaverine were similar in the control groups and the ethanol-fed group. There was no change in agonist potency among the groups. CONCLUSION: Chronic ethanol consumption impairs beta-adrenoceptor- and purinoceptor-mediated relaxation but not cholinoceptor-mediated contraction of the rat detrusor smooth muscle. Thus, it appears that different regulatory mechanisms are involved in ethanol-induced alterations in beta-adrenergic, purinergic and muscarinic receptors in detrusor strip.

Adenosine↗
PubMed2001

Blood pressure and vascular reactivity to endothelin-1, phenylephrine, serotonin, KCl and acetylcholine following chronic alcohol consumption in vitro.

Ethanol has been reported to cause hypertension, the mechanism of which is unknown. Therefore, the effect of chronic ethanol consumption on vascular responsiveness and blood pressure was investigated. Systolic blood pressure was recorded weekly by tail-cuff method. Aortic rings from rats fed chow ad libitum or pair-fed liquid diets containing either ethanol (7.2% v/v) or isocaloric carbohydrate for 4 weeks were placed in organ chambers for isometric tension measurement. There was a mild but significant elevation of the systolic blood pressure in the alcohol-fed rats by week 1 compared to baseline measurements and this remained higher. No significant changes in reactivity of rat isolated aortas to phenylephrine, serotonin, endothelin-1 (ET-1) and KCl were seen in chronic ethanol consumption. In addition, the sensitivity (i.e. pD2) of alcohol-fed aortic rings to the vasoconstrictors was also unchanged compared to controls. Chronic ethanol consumption, however, increased relaxation to acetylcholine with increased pD2 values, but did not alter relaxation to sodium nitroprusside, a cyclic guanosine monophosphate (cGMP)-dependent direct smooth muscle dilator. The results indicate that chronic ethanol consumption significantly potentiates endothelium-dependent relaxations in aortic rings, probably through interference with the production and/or the release of nitric oxide (NO) or adaptive alterations in muscarinic receptors on the endothelial cells, and that increased vascular responsiveness to several vasoconstrictors is not a mechanism responsible for the blood pressure elevation in the chronic alcohol consumption in rats.

Acetylcholine↗
PubMed2001

Impaired esophageal reactivity in adriamycin-induced rat esophageal atresia: an in vitro study.

PURPOSE: The aim of this study was to investigate the reactivity of lower esophageal smooth muscle in the Adriamycin-induced esophageal atresia (EA) rat model. METHODS: The fetuses were divided into 3 groups. The control group was exposed to saline. The second group comprised fetuses that were exposed to Adriamycin but in whom EA did not develop. The third group comprised of fetuses that were exposed to Adriamycin and EA was observed. The reactivity of distal esophageal strips was studied in organ chambers. RESULTS: The tension was similar in all groups precontracted with carbachol for the study of relaxation to serotonin. Relaxation of lower esophageal strips to serotonin was comparably unaffected in the control and Adriamycin-no EA groups, whereas it was significantly inhibited in the EA group with decreased E(max) and pD(2) values. Contractile responses of esophageal smooth muscle to carbachol or 80 mmol/L KCl and relaxant responses to papaverine were similar in all groups. No change in agonist potency was observed among the groups. CONCLUSIONS: Our study showed impairment of serotonin-receptor-mediated relaxation; but not of cholinoceptor-mediated contraction of the lower esophageal smooth muscle in the EA. Thus, impaired relaxant responses may be, at least in part, a contributing factor in the esophageal dismotility seen in EA.

Animals↗
PubMed2001

Dermatofibrosarcoma protuberans metastasizing to cavernous sinuses and lungs: a case report.

Dermatofibrosarcoma protuberans (DFSP) is a locally aggressive tumor with a low potential for distant metastases. We report a 22-year-old female patient with a typical cutaneous DFSP who developed five local recurrences followed by left cavernous sinus metastasis at the eighth year and right cavernous sinus and lung metastases at the ninth year. In each local recurrence the tumor showed histological signs of progression as being more cellular, having higher mitotic index and being aggressively invasive through the underlying soft tissues. The histopathological evaluation of the metastatic tumor resected from the left cavernous sinus revealed dedifferentiation from low-grade DFSP to higher grade fibrosarcomatous morphology. Immunohistochemical studies of the primary tumor and also the recurrent and metastatic tumors showed diffuse CD34 positivity in all specimens and p53 positivity was detected in the metastatic tumor resected from left cavernous sinus.

Adult↗
PubMed2001

Prognostic value of auditory brainstem response for neurologic outcome in patients with neonatal indirect hyperbilirubinemia.

To investigate the value of the auditory brainstem response as a reliable test for the neurologic prognosis of infants with neonatal indirect hyperbilirubinemia, auditory brainstem response studies were performed in 22 infants. The patients were followed up until 12 months of age. Two patients demonstrated pathologic auditory brainstem response consistent with auditory neuropathy but had no neurologic finding except a lack of speech at 12 months of age. Two other patients had neurologic sequelae, one showing severe dyskinetic cerebral palsy, the other mild hypotonia and motor retardation, but their auditory brainstem response results were normal. These results suggested that auditory brainstem response examination might not provide reliable information for the neurologic prognosis. Neurologic disturbances resulting from bilirubin neurotoxicity can be seen in patients with a normal auditory brainstem response, but patients with an abnormal auditory brainstem response may not have any neurologic dysfunction apart from speech retardation.

Bilirubin↗
PubMed2000

Antidepressant-like effect of 7-nitroindazole in the forced swimming test in rats.

RATIONALE: There is some strong evidence about the role of nitric oxide (NO) as an intercellular messenger in central physiological mechanisms. NO is synthesized from L-arginine by nitric oxide synthase (NOS), as a response to activation of N-methyl-D-aspartate (NMDA) receptors by excitatory amino acids. NMDA receptor antagonists also produce antidepressant-like actions in preclinical models. OBJECTIVE: In the present study, the involvement of NO in the mechanism of depression was investigated. 7-Nitroindazole (7-NI) (15, 30, 60, 90 mg/kg IP), a selective inhibitor of neuronal NOS was examined. METHODS: The Porsolt forced swimming test (FST) has been used as a test for screening new antidepressant agents. RESULTS: 7-NI dose-dependently decreased the immobility time in FST, but produced no significant change in locomotor activity in naive rats. Neither L-arginine, nor D-arginine (100 mg/kg) affected the immobility time in the FST or revealed any effect on locomotion. L-Arginine but not D-arginine, given 10 min before 7-NI, reversed the 7-NI-induced effect on immobility time. CONCLUSIONS: Our findings suggest that NO might be an important modulator of depression in rats.

Animals↗
PubMed2000

Conventional external radiotherapy in the management of clivus chordomas with overt residual disease.

Cranial chordomas are uncommon tumors accounting for less than 1% of all intracranial neoplasms. Although they are slowly growing, rarely metastasizing tumors, cranial chordomas are challenging to treat due to their critical location, invasive nature and aggressive recurrence. The aim of this retrospective study was to evaluate the role of conventional irradiation in the treatment of clival chordomas with overt residual disease after incomplete surgery. Between January 1979 and December 1997, 18 patients with histologically confirmed clival chordoma were treated with radiotherapy. Median age at the time of diagnosis was 32 years. The mean duration of the symptoms before diagnosis was 33.9 months. Median tumor diameter at initial presentation was 5 cm (range, 3-7 cm). The type of surgical procedure was subtotal excision in 11 patients and biopsy in 7. Radiation treatment was delivered with megavoltage units, and total doses between 50 Gy and 64 Gy (median, 60 Gy) were administered with conventional daily fractions. One patient received additional 12.50 Gy with linear accelerator-based stereotactic radiosurgery after subtotal excision and external irradiation. The mean follow-up time was 43.2 months. Overall survival at 5 years was 35%. Eleven patients showed progression after radiotherapy. The median time to progression after radiotherapy was 40.8 months (38.4-43.2) with a 5-year progression-free survival of 23%. Five patients (29.4%) showed symptomatic relief after radiotherapy while persistent symptoms were recorded for 6 patients. Incomplete surgery and conventional external radiotherapy with a dose of around 60 Gy seem to be inadequate in the treatment of clival chordomas.

Adult↗
PubMed2000

Anxiolytic-like effects of 7-nitroindazole in the rat plus-maze test.

It is considered that nitric oxide (NO) is one of the most interesting research subjects. Because the actual role of NO in the mechanism of anxiety is still unclear, in this study, the involvement of NO in the mechanism of anxiety was investigated, using the plus-maze test. 7-Nitroindazole (7-NI) (15, 30, 60, 90, and 120 mg/kg), a new nitric oxide synthase (NOS) inhibitor was studied. The time spent on open arms and open-arm visits was evaluated. 7-NI, at 15-120 mg/kg doses potently increased the time spent on open arms and open-arm visits. However, at 120 mg/kg it attenuated the time spent on the open arms, compared to at 90 mg/kg. This effect was attributed to decreased locomotor activity in the higher dose group. Neither L-arginine, nor D-arginine (100 mg/kg) significantly affected any of the behavioral parameters measured in the rat elevated plus-maze test. Neither drugs revealed any effect on locomotion. L-Arginine but not D-arginine given 10 min before 7-NI, reversed the 7-NI induced anxiolytic-like effects. These data support an involvement of NO in the process of anxiety, and further suggest that the anxiolytic-like effect of 7-NI may be attributable to the inhibition of NO synthesis.

Animals↗