Search PubMed⌕ Search

Biomedical subjects

A Colak

Publications and source records attributed to A Colak.

At least 19 recordsLinked to original sources
PubMed2004

Time-level relationship for nitric oxide and the protective effects of aminoguanidine in experimental spinal cord injury.

BACKGROUND: The secondary injury process following spinal cord trauma has been shown to involve different mechanisms such as excessive release of excitatory amino-acids, and induction of free radical induced lipid peroxidation. In this experimental study, the time-level relationship of the nitric oxide and the neuroprotective effects of aminoguanidine were investigated in a rat spinal cord trauma model. METHODS: The experiments were performed on 63 Wistar albino rats divided into three groups; sham-operated control (Group 1), trauma created control (Group 2) and aminoguanidine group (Group 3). In groups 2 and 3, spinal cord trauma was produced at thoracic level by using weight the drop technique (at a severity of 50 gr-cm). After the trauma, the rats in Group 3, received an intraperitoneal injection of 100 mg/kg aminoquanidine twice a day for 3 days. The effects of the injury and the efficacy of aminoguanidine were determined based on biochemical parameters (lipid peroxidation and nitric oxide levels in tissue), and on light microscopy findings in cord tissue collected at different times post-injury. Biochemical parameters were performed one hour, three and five days after injury. Functional recovery was assessed at 3, and 5 days after cord trauma with the inclined-plane technique and Tarlov's motor grading scale. FINDINGS: Although there was no statistically significant difference at the 1(st) hour, the values of the tissue nitric oxide in trauma created controls were 42% higher on the 3(rd) day and 40% higher on the 5(th) day when compared with those in sham controls. The levels of the tissue lipid peroxidation in trauma created controls were 88% higher at the 1(st) hour and 52.8% higher on the 5(th) day when compared with shame controls, but there was no meaningful difference on the 3(rd) day. In the trauma created control group, the mean motor function scores decreased to 1.16 +/- 0.40 and to 1 +/- 0 on the 3(rd) and 5(th) day, respectively. In this group the mean values of the inclined plane were 39.16 +/- 2.04 on the 3(rd) day and 37.91 +/- 1.02 on the 5(th) day. No statistically significant difference was observed in both tissue lipid peroxidation and nitric oxide levels for all time points between the aminoguanidine group and the sham-operated controls (p>0.01). The motor function scores were observed as 2.16 +/- 0.40 on the 3(rd) day and as 3 +/- 0 on the 5(th) day in aminoguanidine group. These values were significantly higher than the trauma created controls (p<0.01). Aminoguanidin treatment also improved the inclined plane performance of the rats; In this group, the mean values of the inclined plane scores were 44.58 +/- 2.92 and 52.91 +/- 1.88 on the 3(rd) and 5(th) days, respectively. These values were significantly higher than the trauma created controls (p<0.01). INTERPRETATION: This study shows that the nitric oxide level does not increase in the spinal cord tissue during the first hour after the spinal cord trauma. It increases significantly in the spinal cord tissue not only three days but also five days following the trauma. Aminoguanidine treatment, which is started just after the trauma, can prevent both the nitric oxide production and lipid peroxidation in spinal cord tissue and it can improve the functional status of the animals. In this respect, aminoguanidine may have a potential role in the treatment of acute spinal cord injury.

Animals↗
PubMed2003

Preoperative oral celecoxib versus preoperative oral rofecoxib for pain relief after thyroid surgery.

BACKGROUND AND OBJECTIVE: The study compared the analgesic efficacy and safety of two preoperatively administered cyclo-oxygenase-2 inhibitors, celecoxib and rofecoxib. METHODS: Ninety adult patients undergoing thyroid surgery were divided into three groups (each n = 30). They were given a single oral dose of placebo, celecoxib 200 mg or rofecoxib 50 mg 1 h before induction of anaesthesia. All patients received a standard anaesthetic. Intraoperative blood loss was measured. Pain scores, sedation scores, heart rate, mean arterial pressure and respiratory rate were noted at 0, 1, 2, 4, 6, 12 and 24 h postoperatively. Analgesic (meperidine) requirements and adverse effects were recorded during the first postoperative 24 h. RESULTS: Compared with placebo, pain scores were significantly lower with rofecoxib at all time points (P < 0.05) and were significantly lower with celecoxib (P < 0.05) during the first 4 h. Pain scores were significantly lower with rofecoxib compared with celecoxib at 6, 12 and 24 h (P < 0.05). The average cumulative 24 h meperidine dose was significantly lower with both celecoxib (54.9 +/- 34.4mg) and rofecoxib (42.8 +/- 40.9 mg) compared with placebo (76.8 +/- 6.2 mg) (P < 0.01 and P < 0.001, respectively). There were no differences in the intraoperative blood loss, heart rate, mean arterial pressure, respiratory rate, sedation scores and incidence of adverse effects among groups. CONCLUSIONS: The preoperative administration of rofecoxib 50 mg and less so of celecoxib 200 mg provide a significant analgesic benefit with regard to postoperative pain relief and decrease in additional opioid requirements after thyroid surgery.

Adult↗
PubMed2003

Protective effect of melatonin on experimental spinal cord ischemia.

STUDY DESIGN: Experimental animal model to assess ischemic spinal cord injury following occlusion of the thoraco-abdominal aorta. OBJECTIVES: To measure whether melatonin administered to rabbits before and after occlusion exerts an effect on the repair of ischemia-reperfusion (IR) injury. SETTING: Medical Biology Laboratory, Inonu University, Malatya, Turkey. METHODS: Rabbits were divided into three IR treatment groups and one sham-operated (ShOp) control group. The three treatment groups had their infrarenal aorta temporarily occluded for 25 min, while the ShOp group had laparotomy without aortic occlusion. Melatonin was administered either 10 min before aortic occlusion or 10 min after the clamp was removed. Physiologic saline was administered to the control animals. After treatment, the animals were euthanized and lumbosacral spinal cord tissue was removed for the determination of relevant enzyme activities. RESULTS: Malondialdehyde levels, indicating the extent of lipid peroxidation, were found to be significantly increased in the nonmelatonin treated (IR) group when compared to the ShOp group. Melatonin, whether given to pre- or post occlusion groups, suppressed malondialdehyde levels below that of the ShOp group. Catalase (CAT) and glutathione peroxidase (GSH-Px) enzyme activities were increased in the IR group compared to the ShOp group. Melatonin given preocclusion resulted in a significant decrease in both CAT and GSH-Px enzyme levels. The superoxide dismutase (SOD) enzyme activity was decreased in the ischemia-reperfusion treatment group. However, the melatonin treatment increased SOD enzyme activity to levels approximating that of the ShOp group. CONCLUSION: To our knowledge, this is the first study that shows the effects of melatonin administered both pre- and postischemia on induced oxidative damage to injured spinal cords. Our data also expands on reports that melatonin administration may significantly reduce the incidence of spinal cord injury following temporary aortic occlusion.

Animals↗
PubMed2002

Progesterone profiles of fat-tailed tuj ewes following tactile and visual separation of rams at the beginning of the breeding season.

The aim of this study was to determine the level and duration of progesterone secretion during the sequential oestrous cycles in fat-tailed Tuj ewes following tactile and visual separation of rams during the breeding season. For these purposes, rams were separated from the main flock for 50 days starting from the beginning of the breeding season and 21 ewes were randomly selected for the current experiment. In order to assess luteal activity and the length of oestrous cycles, the ewes were blood-sampled thrice or twice weekly for the measurement of progesterone in plasma. The data showed that 3 +/- 0.2 oestrous cycles were observed in this time window, and the first oestrous cycle observed was shorter (P < 0.05) than the following cycles (mean +/- SEM, 14.6 +/- 0.82, 16.5 +/- 0.48 and 17.0 +/- 0.54 days, respectively, for cycles 1, 2 and 3). Progesterone production was significantly lower in the first oestrous cycle compared with the second and third cycles on days 9, 12 and 14 of the cycles. The follicular periods of ewes showed four accumulations (maximum values using a 3-day moving average technique) throughout the study and the percentages of ewes at each accumulation (peak day +/- 1 day) were 50, 35, 65 and 80% for the first, second, third and fourth accumulations, respectively (P < 0.05). It was concluded that progesterone production was lower and the oestrous cycles were shorter during the first oestrous cycle and that tactile and visual separation of rams at the beginning of the breeding season might enhance the synchronizing effect towards the end of the breeding season in the fat-tailed Tuj ewes.

Animals↗
PubMed2002

Effect of aminophylline on recovery from sevoflurane anaesthesia.

BACKGROUND AND OBJECTIVE: In this randomized, double-blind study, we aimed to investigate the effect of aminophylline on recovery from sevoflurane. METHODS: One-hundred ASA I-II patients scheduled for elective surgery were randomly divided into two groups receiving either NaCl 0.9% (Group 1, n = 50) or aminophylline 5mg kg(-1) (Group 2, n = 50). All patients were premedicated with atropine 0.01 mgkg(-1) and midazolam 0.06mgkg(-1) intramuscularly. Anaesthesia was induced with propofol 2mg kg(-1) for muscle relaxation, and atracurium 0.5 mg kg(-1) was maintained with sevoflurane 2% in 50% oxygen and nitrous oxide. Further atracurium (0.1 mgkg(-1) was given when needed. Aminophylline or saline was given after sevoflurane was discontinued. Heart rate, mean arterial pressure, peripheral oxygen saturation, the duration of anaesthesia and recovery times (eye opening, verbal response, extubation and successful performance of arithmetical calculations) were recorded. RESULTS: There were no statistically significant differences in mean arterial pressure, peripheral oxygen saturation and anaesthesia time between the two groups. Heart rate increased significantly (P < 0.05) after aminophylline and was also higher than in the placebo group. Recovery times were significantly shorter (P < 0.001) in the patients receiving aminophylline. CONCLUSIONS: Aminophylline speeded recovery after sevoflurane anaesthesia and it may have some advantage in anaesthesia practice for patients.

Adolescent↗
PubMed2000

Increased cell proliferation and R.Msp1 fragmentation induced by 5-aza-2'-deoxycytidine in rat testes related to the gene imprinting mechanism.

DNA methylation is one of the crucial mechanisms for cellular and tissue differentiation during developmental stages in mammals. 5-aza-2'-deoxycytidine, a specific cytosine DNA Methyltransferase inhibitor, is known to cause DNA hypomethylation in CpG, CpNpG and CCGG sequences. Therefore the present study was designed to determine the effects of 5-aza-2'-deoxycytidine on the germinal cells of the adult rat testicular tissue. Rat testicular tissues from the 5-aza-2'-deoxycytidine treated experimental and non-treated control groups were processed for light microscopy and also for genomic DNA isolation assays. The isolated genomic DNAs were digested with R.Msp1 in order to determine the methyl pattern differences in the enzyme cognate CCGG sequence. Testicular tissues from treated rats showed increased cell proliferation when investigated at the light microscopical level. On the other hand, genomic DNA of these proliferative tissue showed high fragmentation sizes of R.Msp1 digestion when compared to controls. While the R.Msp1 digested control group DNA fragmentation condensed at approximately 4700-5100 bps size, the experimental group DNA fragmentation was condensed at 700-900 bps size. In addition, 5-aza-2'-deoxycytidine has effects on increased cell proliferation via the loss of somatic de novo gene imprinting. These results imply that abnormally imprinted normal somatic cells in mammals are susceptible to epigenetic modification. These results also suggest that the genomic DNA of testicular tissues from control rats is resistant to R.Msp1 while DNA from the experimental group testicular cells demonstrating high proliferation rate could not resist to R.Msp1 digestion due to DNA hypomethylation in CCGG sequence. In conclusion, it could be suggested that the reversal of gene imprinting in germinal cells may cause an increased cellular proliferation and R.Msp1 fragmentation when induced by 5-aza-2'-deoxycytidine.

Animals↗
PubMed2000

Effect of hyperbaric oxygen therapy on fetal spinal grafts: an experimental study.

In neural transplantation, lack of oxygen supply to the graft in acute stage is an important problem. This study was undertaken to evaluate the effects of hyperbaric oxygen (HBO2) on fetal spinal grafts. Spinal cord tissues obtained from 16-day fetal rats were transplanted into the spinal cord of adult Wistar rats (n = 30). After transplantation, they were randomly divided into two groups (n = 15 for each group); Group 1 received transplant alone, group 2 received transplant and HBO2 therapy consisting of 100% oxygen at 2.5 atm abs for 90 min twice a day for 7 days. Seven days after their surgery, all animals were killed for histologic examination. Degenerative changes, parenchymal integrity, host spinal cord edema, and vascularization of the graft were scored on a 3-point scale. Scores of these parameters were statistically analyzed. The graft survival rates in groups 1 and 2 were 54.5% and 71.4%, respectively. Animals treated with HBO2 showed statistically less spinal cord edema than the untreated groups (P < 0.05). Parenchymal integrity was also significantly better in this group (P < 0.05). The results indicate that edema reduction effect of HBO2 prevents the displacement of graft from the gap and contributes to the integration between the graft and host.

Animals↗
PubMed1999

MR imaging for early complications of transpedicular screw fixation.

This series comprises ten patients treated with transpedicular screw fixation, who suffered early postoperative problems such as radicular pain or motor weakness. Besides plain radiographs, all patients were also evaluated with MR imaging. Three patients were reoperated for either repositioning or removal of the screws. MR images, especially T1-weighted ones, were very helpful for visualizing the problem and verifying the positions of the screws. In cases of wide areas of signal void around the screws, the neighboring axial MR images at either side, which have fewer artifacts, gave more information about the screws and the vertebrae.

Adult↗
PubMed1998

The use of near infrared spectroscopy (NIRS) in children after traumatic brain injury: a preliminary report.

Children commonly develop diffuse cerebral swelling after traumatic brain injury (TBI) which is believed due to a secondary response to the injury. Near infrared spectroscopy (NIRS), a continuous, direct, and noninvasive monitor of cerebral oxygenation and cerebral blood volume (CBV), could be helpful in understanding these secondary responses. The aims of our study were to determine whether NIRS used in children with severe TBI will provide insight into the pathophysiology of injury. Ten children (1 mo to 15 years old) with severe TBI (admission GCS < or = 7) were continuously monitored by NIRS by placing optodes over the frontalparietal region. Relative values of oxyhemoglobin (HbO2), deoxyhemoglobin (Hb), and total hemoglobin (THb) were obtained and compared to intracranial pressure (ICP), mean arterial pressure (MAP), electroencephalography (EEG), and arterial PCO2 (PaCO2). Episodes of intracranial hypertension (ICP > 20 Torr [T]), changes in ICP > 10 T, changes in PaCO2 > or = 8 T, and changes in MAP > 20 T frequently resulted in changes in HbO2, Hb, and THb. Hyperventilation with decreased PaCO2 always resulted in cerebral oxygen desaturation irregardless of ICP. Often, high ICP correlated with increased THb and HbO2 indicating increased CBV and cerebrovascular dilatation. In two children, posttraumatic seizures were preceded by an unexplained rapid cerebral hyperoxygenation several hours prior to the onset of the clinical seizures. NIRS reliably detects changes in cerebral hemodynamics in children and may be used to further understand the etiology of the diffuse cerebral swelling seen in children after severe TBI.

Adolescent↗
PubMed1998

Unusual presentation of a sinonasal carcinoma mimicking an aneurysm rupture.

Although the association of subarachnoid hemorrhage (SAH) and tumoral lesions in adult is well known, hemorrhage from a sinonasal carcinoma extending to the intracranial cavity is exceedingly rare. In this paper, the authors report on a 12-year-old girl who presented with SAH caused by a sinonasal carcinoma located in the anterior skull base area. To our knowledge, this is the first report of a sinonasal carcinoma concomitant with SAH.

Aneurysm, Ruptured↗
PubMed1998

Surgical management of spinal cord compression from plexiform neurofibromas in patients with neurofibromatosis 1.

OBJECTIVE: Plexiform neurofibromas with sizable intraspinal extensions and resultant spinal cord compromise pose challenging management problems, because these lesions may involve multiple nerves and engulf adjacent vascular and visceral structures. In this report, we review our experience with the surgical treatment of these lesions. METHODS: Patients were identified by a detailed review of hospital medical records and the database of our multidisciplinary neurofibromatosis clinic. Ten patients had large plexiform neurofibromas that extended intraspinally, producing a combination of myelopathy and radiculopathy. Two patients exhibited single-level intraspinal growth, and eight showed multilevel involvement. Four patients showed bilateral plexiform neurofibromatous growth intraspinally, with "hourglass" compression of the spinal cord. Operative approaches and outcomes were reviewed in detail. RESULTS: Gross total resection of the symptomatic intraspinal tumor component was achieved for nine patients. The management of the extraspinal component was individualized, depending on the pattern and extent of involvement of the surrounding structures. Nine patients experienced complete recovery of neurological function postoperatively; the remaining patient demonstrated significant functional improvement. With a median follow-up period of 4 years, only one patient has developed recurrent intraspinal compression, in this case from tumor involvement by the same plexiform lesion at a lower spinal level. Two patients treated early in the series using standard laminectomy approaches developed significant kyphotic deformities, necessitating subsequent fusion. Based on these initial results, osteoplastic laminotomy techniques were used in the last five cases, allowing anatomic reconstruction of the involved levels; none of these latter patients has developed significant kyphosis, with a median follow-up period of 3 years. CONCLUSION: Radical resection of intraspinal tumor components in patients with neurofibromatosis 1 and large plexiform neurofibromas can help to preserve excellent neurological function. Technical factors in the management of these lesions are presented.

Adolescent↗
PubMed1998

Iatrogenic arachnoid cyst with distinct clinical picture as a result of bone defect in the floor of the middle cranial fossa: case report.

OBJECTIVE AND IMPORTANCE: This kind of arachnoid cyst has not previously been described as a complication of a cranial base bone defect. Recognition of this rare complication may be delayed, because clinicians are unaware of its possibility. CLINICAL PRESENTATION: A 22-year-old man presented with severe headache and increasing difficulty in breathing and swallowing. A physical examination revealed a pulsatile mass in the oral cavity, arising from the parapharyngeal area. A cystic mass that protruded into the oral cavity, through a dural and bony defect in the left middle fossa, was detected on neuroimages. INTERVENTION: A left frontotemporal craniotomy was made, and the cyst was decompressed. Duraplasty was performed with lyophilized dura. The bone defect was managed with a calvarial free bone graft and a pedicled myofacial flap. Serial neuroimaging studies performed postoperatively showed that the cyst had decreased in size. CONCLUSION: This report describes an unusual complication of a cranial base bone defect. Although not all bone defects in the cranial base require reconstruction, management of the large bone defect, particularly in the middle fossa, should preferably be accomplished with the help of a bone graft to support the dural graft.

Adult↗
PubMed1998

An unusual variant of a growing skull fracture in an adolescent.

A great majority of growing skull fractures occur in infancy and earlychildhood. Since the growth of brain is necessary as a driving force for these lesions to occur, almost all reported cases have been before the first 3 years of life. Although a number of uncommon locations, such as basiooccipital and skull base areas, have been reported, they are commonly located on calvaria. The authors report a growing skull fracture on the orbital roof in a 16-year-old female admitted to hospital with complaints of headache and seizures. She had had an orbital trauma 8 years before. CT scan revealed a hypodense lesion in the right frontal lobe and a diastatic fracture line on the right orbital roof. A right craniotomy was performed. Excision of arachnoid loculations and duraplasty were carried out. This is an unusual condition with respect to the location of the lesion, as well as the age of the patient.

Adolescent↗
PubMed1998

Recurrent tethering: a common long-term problem after lipomyelomeningocele repair.

The authors reviewed the records of 94 patients who underwent initial repair of a lipomyelomeningocele between 1982 and July 1996 at the Children's Hospital of Pittsburgh to determine the incidence and time course of symptomatic retethering. In each of these patients, the initial operative goals were to microsurgically debulk as much of the lipoma as possible to allow the conus to move freely within the spinal canal, to divide any tethering arachnoidal adhesions, to close the pia if possible and to reconstitute a capacious thecal sac, using a dural graft if necessary. With a median follow-up of 58 months, 19 of these patients (20.2%) required 28 subsequent operations for symptomatic retethering. Median time between the initial procedure and reoperation for retethering was 52 months. The primary complaint of 12 patients was intractable low-back or leg pain. Other common symptoms were progressive bowel and/or bladder dysfunction, deterioration of motor function and foot deformities. The decision to reoperate was based predominantly on the clinical situation of the patient; magnetic resonance imaging was used to confirm the location and extent of tethering. Patients with transitional lipomas had a significantly higher frequency of symptomatic retethering than those with caudal or dorsal lesions (p < 0.05). No other clinical or technical feature correlated with an increased frequency of retethering. In particular, none of a variety of types of dural graft materials appeared to entirely prevent symptomatic retethering. Following reoperation, pain complaints resolved and many of the other symptoms improved partially or resolved completely. Although the long-term results were also favorable in the majority of patients, a small subgroup (n = 6) exhibited repetitive symptomatic tethering that proved increasingly difficult to treat. We concluded that symptomatic retethering is a common problem in children with lipomyelomeningoceles, even after an adequate initial operation. To date, no type of graft material has been shown to entirely prevent this problem. Close long-term surveillance of such patients is required to allow detection and treatment of symptomatic retethering.

Adolescent↗
PubMed1998

Characterization of microsomal aniline hydroxylase of rainbow trout, Salmo gairdneri.

Aniline hydroxylase from liver microsomes of rainbow trout Salmo gairdneri converted aniline to p-aminophenol, the specific activity being 0.068 nmoles/min/mg protein in potassium phosphate buffer, pH 7.4 at 25 degrees C. The maximal rate of the enzyme reaction was found at aniline concentrations above 5 mM and in the presence of NADPH. Vmax and K(m) were 0.048 nmoles/min/mg and 0.105 mM respectively. The Hill plot showed the Hill constant to be 1.02 indicating one substrate binding site with no cooperativity. Ca2+ and Mg2+ at concentrations ranging between 1-10 mM stimulated the enzyme activity.

Aniline Hydroxylase↗