Biomedical subjects

S Bahar

Publications and source records attributed to S Bahar.

At least 19 recordsLinked to original sources

PubMed2006

Inflammatory/demyelinating central nervous system involvement in familial Mediterranean fever (FMF): coincidence or association?

BACKGROUND AND OBJECTIVE: Familial Mediterranean fever (FMF) is an inherited inflammatory disease characterized by recurrent febrile polyserositis. Central nervous system (CNS) involvement in FMF is uncommon, but recently cases with multiple sclerosis (MS) and FMF have been reported. Here we assess patients with both FMF and MS, in order to clarify any relationship between FMF and MS, and to evaluate disease characteristics. PATIENTS AND METHODS: Our MS database between 1986-2005 was screened retrospectively, and patients with both FMF and inflammatory/demyelinating CNS disease were evaluated among a total of 2800 patients including definite MS (n = 2268) and other demyelinating disorders. RESULTS: There were 12 patients with FMF, who developed a CNS disorder with multifocal white matter lesions. Median age at onset of FMF was 7 years, and median age at neurological onset was 26.8 years. Nine patients (including two siblings) had definite MS according to clinical and MRI findings, whereas 3 patients had atypical features suggesting other demyelinating disorders. Disease severity varied among the patients between very mild to a fatal course. All 8 patients evaluated for oligoclonal IgG bands in CSF were positive. CONCLUSION: The rate of FMF among our patients with definite MS is almost 4 times the expected prevalence in Turkey. Our series including a sibling pair concordant for FMF and MS may suggest that similar genetic susceptibility and environmental factors might be responsible, although coincidence still remains a possibility. A prospective study on a larger sample seems to be justified.

Adolescent↗

PubMed2003

Cranial MRI in Behçet's disease: 134 examinations of 98 patients.

Two observers, blinded to the patient's neurological status, reviewed 134 MRI studies of 98 consecutive patients with Behçet's disease (BD), to define imaging patterns and to look for any relationship between the MRI findings and the timing of the examination in patients with differing courses of disease. There were 43 patients with overt parenchymal central nervous system (CNS) involvement, 22 with attacks and remissions, 15 with secondary progressive and six with primary progressive disease; 14 had raised intracranial pressure (RICP). Of the remaining 41 patients without specific neurological complaints, 16 had abnormalities on examination (silent CNS involvement) and 25 did not. During an acute CNS attack, the most common finding was a large lesion in the brain-stem or basal ganglia, extending to the diencephalon. On MRI performed after remission of an acute attack or during secondary progression, the same sites were affected, but the lesions were smaller or scattered, with less clearly defined margins. In primary progressive disease or silent CNS involvement, the cerebral white matter was most commonly involved, but almost half the MRI studies were normal. The brain parenchyma was abnormal in only one of the patients with RICP. MRI was normal in all but three patients without clinical CNS involvement, in whom it showed a few millimetric white-matter lesions. Brain-stem atrophy was seen in 15 patients examined >1 year after an initial parenchymal CNS episode, with secondary progressive cases predominating.

Adult↗

PubMed2003

Effect of light on stochastic phase synchronization in the crayfish caudal photoreceptor.

Phase synchronization between the firing of the crayfish caudal photoreceptor (CPR) and an applied periodic hydrodynamic stimulus is investigated. It is shown that the CPR firing synchronizes with a periodic stimulus over a range of frequencies corresponding to the known sensitivity range of the crayfish to hydrodynamic stimuli. This synchronization is quantified using previously developed measures of synchronization such as the synchronization index; multiple stimulus-response locking ratios occur in this system that are consistent with theoretical predictions based on the theory of synchronization of noisy oscillators. The maximal synchronization for various locking ratios is shifted to higher frequencies in the presence of light.

Animals↗

PubMed2003

Stroke unit versus neurology ward--a before and after study.

INTRODUCTION: Few studies have tested the hypothesis of whether the beneficial effect of Stroke Units (SUs) can be reproduced in routine clinical practice and whether SU are also superior to neurological wards [NWs]. We aimed to compare the outcomes of patients of a newly implemented SU to the outcomes of patients hospitalized in a NW. METHODS: We made a before-after comparison of 352 SUs and 352 NWs patients after adjusting for case-mixes by the multivariate method. Subgroup analyses were also performed to evaluate which patient groups benefit the most. In-hospital case-fatality, proportion of independent patients at discharge, length of hospital stay (LOHS), medical complication rate were the main outcome measures. RESULTS: Adjusted in-hospital case fatality was significantly reduced in the SUs (OR: 0.44, 95 % CI: 0.26-0.76; p = 0.003). The proportion of independent patients at discharge and patients having medical complications was not different. Length of hospital stay was shorter in SU patients (13.76 days vs. 16.72 days, p = 0.003). Treatment in the SUs decreased case fatality in many subgroups [men, elderly, early admitted, severe stroke, co-morbidity present and ischemic stroke groups]. DISCUSSION: The results of randomized trials in favor of SUs can be reproduced in routine clinical practice. The benefit of SU care seems to be more apparent with advancing age and increasing stroke severity. Stroke Unit seems to be a better alternative to an experienced NW.

Activities of Daily Living↗

PubMed2003

Stochastic phase synchronization in the crayfish mechanoreceptor/photoreceptor system.

The two light-sensitive neurons in the crayfish's abdominal sixth ganglion ("caudal photoreceptors," or CPRs), are both primary light sensors and secondary neurons in a mechanosensory pathway. Pei et al. (1996) demonstrated that light enhances the transduction of weak, periodic hydrodynamic stimuli (measured as an increase in the signal-to-noise ratio at the stimulus frequency in the power spectrum of the recorded neural spikes). This has been interpreted as a stochastic resonance effect, in which added light increases the noise intensity of the input to the photoreceptor (possibly through fluctuations in membrane potential), leading to an enhancement of the signal-to-noise ratio (SNR). Here, we discuss the recent demonstration (Bahar et al., 2002) of the correlation between a stochastic-resonance-like effect and an increase in stochastic phase synchronization between the neural response and a periodic mechanical stimulus. We also discuss a novel effect (Bahar et al., 2002) in which light increases the SNR of the second higher harmonic of a periodic input signal, effectively rectifying the input signal. This "second harmonic effect" can also be interpreted in terms of stochastic phase synchronization (Bahar et al., 2002). We review other recent results on the role of stochastic phase synchronization in mediating sensory responses in the crayfish nervous system.

Animals↗

PubMed2001

Entropy and local uncertainty of data from sensory neurons.

We present an empirical comparison between neural interspike interval sequences obtained from two different kinds of sensory receptors. Both differ in their internal structure as well as in the strength of correlations and the degree of predictability found in the respective spike trains. As a further tool in this context, we suggest the local uncertainty, assigning a well-defined predictability to individual spikes. The local uncertainty is demonstrated to reveal significant patterns within the interspike interval sequences, even when its overall structure is (almost) random. Our approach is based on the concept of symbolic dynamics and information theory.

Animals↗

PubMed2001

Cerebral vasculitis and ischaemic stroke in Behçet's disease: report of one case and review of the literature.

INTRODUCTION: Behçet's disease (BD) is a multisystemic, recurrent, inflammatory disorder. Neurological involvement is well-known but cerebral vasculitis and ischaemic stroke are unusual. CASE DESCRIPTION: A 43-year-old male patient presented with acute left hemiparesis, he had recurrent oral aphthae and scrotal ulcerations. Two episodes of transient brainstem ischaemia and an episode of right hemiparesis were reported in the past 2 years. Cranial magnetic resonance (MR) imaging showed a right striatocapsular infarction and multiple segmental stenosis, fusiform enlargement and beading of the arteries of the polygone of Willis were seen on angiography. Cerebro-spinal fluid (CSF) examination disclosed lymphocytic pleocytosis. Skin pathergy test was positive. A diagnosis of BD with cerebral vasculitis was made and immunosuppressive therapy was started. Some improvement of the arterial lesions on MR angiography and normalization of CSF were observed after 1 year of treatment. DISCUSSION: Low grade chronic meningo-encephalitis is the core neuropathological process in neuro-Behçet's disease. Nevertheless BD is a systemic disease known to cause vasculitis and can exceptionally lead to cerebral vasculitis and brain infarction. While BD is usually not part of the differential diagnosis of cerebral vasculitis, it should be borne in mind especially in endemic areas of the disease and in patients from these areas.

Adult↗

PubMed2001

Venous infarction of brainstem and cerebellum.

The authors describe 2 cases of posterior fosa venous infarction. A 56-year-old woman with essential thrombocytemia presented with fluctuating complaints of headache, nausea, vomiting, left-sided numbness-weakness, and dizziness and became progressively stuporous. Cranial magnetic resonance imaging (MRI) showed bilateral parasagittal fronto-parietal and left cerebellar contrast-enhancing hemorrhagic lesions. On magnetic resonance venography, the left transverse and sigmoid sinuses were occluded. The second patient, a 39-year-old woman, presented with acute onset of diplopia, numbness of the tongue, vertigo, and right-sided weakness following a gestational age stillbirth. MRI revealed lesions in the right half of midbrain and pons and in the superior part of the right cerebellar hemisphere. Digital subtraction angiography showed right transverse and sigmoid sinus occlusion. The authors suggest that one should investigate the possibility of venous infarction in the presence of posterior fossa lesions that are often hemorrhagic and are not within any arterial territory distribution but respect a known venous drainage pattern. Recognition of the observed clinical and neuroimaging features can lead to earlier diagnosis and, potentially, more effective management.

Adult↗

PubMed2001

Internuclear ophthalmoplegia and cerebellar ataxia: report of one case.

Deep hemispheric or brainstem small infarcts can lead to atypical lacunar syndromes. Unilateral internuclear ophthalmoplegia (INO) and cerebellar ataxia has not been reported previously. A 57-year-old hypertensive female presented with bilateral appendicular and left truncal cerebellar ataxia and right INO. Cranial MRI showed a right paramedian infarct of lacunar size located in the tegmentum of caudal mesencephalon. At this level the involvement of medial longitudinal fascicle (MLF) led to right INO and the lesion of brachium conjunctivum caused the bilateral cerebellar ataxia. Ipsilateral involvement of both cerebellofugal fibers, before and after decussation, was responsible for bilateral cerebellar ataxia.

Brain Infarction↗

PubMed2000

Existence of bistability and correlation with arrhythmogenesis in paced sheep atria.

INTRODUCTION: Studies of the electrical dynamics of cardiac tissue are important for understanding the mechanisms of arrhythmias. This study uses high-frequency pacing to investigate the dynamics of sheep atria. METHODS AND RESULTS: A 504-electrode mapping plaque was affixed to the right atrium in six sheep. Cathodal pacing stimuli were delivered to the center of the plaque. Pacing period (Tp) was decreased from 275 +/- 25 msec to 75 +/- 25 msec and then increased to 230 +/- 70 msec in steps of either 5 or 10 msec. In all 21 trials in six sheep, the atrium responded 1:1 at longer Tps and 2:1 at shorter Tps. As Tp was decreased, the response switched to 2:1 at a particular Tp. Conversely, as Tp was increased, the response switched back to 1:1 at a particular Tp. Over 21 trials, the 1:1-to-2:1 and 2:1-to-1:1 transitions occurred at 119.5 +/- 18.8 msec and 130.0 +/- 19.1 msec, respectively. This hysteretic behavior yielded bistability windows, 10.5 +/- 7.2 msec wide, wherein 1:1 and 2:1 responses existed at the same Tp. In 15 trials and in all animals, idiopathic wavefronts emanating from outside the mapped region passed through the mapped region. In 13 of those trials, the idiopathic wavefronts occurred at Tps within the bistability window or within 35 msec of its upper or lower limit. CONCLUSION: Bistability windows and idiopathic wavefronts were observed and found to be correlated with each other, suggesting a connection between bistability and arrhythmogenesis.

Animals↗

PubMed2000

Mitochondrial and intrinsic optical signals imaged during hypoxia and spreading depression in rat hippocampal slices.

During hypoxia in the CA1 region of the rat hippocampus, spreading-depression-like depolarization (hypoxic spreading depression or HSD) is accompanied by both a negative shift of the extracellular DC potential (DeltaV(o)), and a sharp decrease in light transmittance (intrinsic optical signal or IOS). To investigate alterations in mitochondrial function during HSD and normoxic spreading depression (SD), we simultaneously imaged mitochondrial depolarization, using rhodamine-123 (R123) fluorescence, and IOS while monitoring extracellular voltage. Three major phases of the R123 signal were observed during hypoxia: a gradual, diffuse fluorescence increase, a sharp increase in fluorescence coincident with the HSD-related DeltaV(o), primarily in the CA1 region, and a plateau-like phase if reoxygenation is delayed after HSD onset, persisting until reoxygenation occurs. Two phases occurred following re-oxygenation: an abrupt and then slow decrease in fluorescence to near baseline and a slow secondary increase to slightly above baseline and a late recovery. Parallel phases of the IOS response during hypoxia were also observed though delayed compared with the R123 responses: an initial increase, a large decrease coincident with the HSD-related DeltaV(o), and a trough following HSD. After reoxygenation, there occurred a delayed increase in transmittance and then a slow decrease, returning to near baseline. When Ca(2+) was removed from the external medium, resulting in complete synaptic blockade, the mitochondrial response to hypoxia did not significantly differ from control (normal Ca(2+)) conditions. In slices maintained in low-chloride (2.4 mM) medium, a dramatic reversal in the direction of the IOS signal associated with HSD occurred, and the R123 signal during HSD was severely attenuated. Normoxic SD induced by micro-injection of KCl was also associated with a decrease in light transmittance and a sharp increase in R123 fluorescence but both responses were less pronounced than during HSD. Our results show two mitochondrial responses to hypoxia: an initial depolarization that appears to be caused by depressed electron transport due to lack of oxygen and a later, sudden, sharp depolarization linked to HSD. The depression of the second, sharp depolarization and the inversion of the IOS in low-chloride media suggest a role of Cl(-)-dependent mitochondrial swelling. Lack of effect of Ca(2+)-free medium on the R123 and IOS responses suggests that the protection against hypoxic damage by low Ca(2+) is not due to the prevention of mitochondrial depolarization.

Animals↗

PubMed1999

Masked assessment of MRI findings: is it possible to differentiate neuro-Behçet's disease from other central nervous system diseases? [corrected].

Two neuroradiologists reviewed MRI studies of 34 patients with neuro-Behcet's disease (NBD), 22 with multiple sclerosis (MS) and 7 with systemic lupus erythematosus (SLE) with central nervous system involvement, masked to the clinical diagnosis, age and sex of the patients. Of the patients with NBD 12 were in an acute attack; the others had chronic disease. MRI was assessed using a set of criteria, looking at atrophy, the site of discrete parenchymal lesions, regions of predominant involvement and the extent of the lesion(s). The observers also made a guess at the clinical diagnosis. The brain stem and/or basal ganglia were the most predominantly involved sites in all patients with acute NBD; 75% of these lesions were large and confluent, mainly extending from the brain stem to the diencephalon and basal ganglia. However, in chronic cases, the predominant involvement was in the brain stem and/or basal ganglia in only 36%, and in cerebral hemisphere white matter in another 36%; 27% of these patients showed no parenchymal lesion. Hemisphere white-matter lesions were equally distributed between periventricular and other areas in NBD, while in MS more were periventricular, and in SLE more were nonperiventricular. Brain-stem atrophy was seen in 21% of patients with NBD, with a specificity of 96.5%. In the absence of cortical atrophy, its specificity was 100%. The attempt at making a radiological diagnosis was successful in all cases of acute NBD and 95.5% of patients with MS, but in only 40% of patients with chronic NBD. Most of this latter groups MRI studies were interpreted as MS. An extensive lesion involving the brain stem and basal ganglia seemed to be diagnostic of acute NBD. However, hemisphere white-matter lesions could not be differentiated from those in MS.

Acute Disease↗

PubMed1999

Persistence of external chloride and DIDS binding after chemical modification of Glu-681 in human band 3.

Although its primary function is monovalent anion exchange, the band 3 protein also cotransports divalent anions together with protons at low pH. The putative proton binding site, Glu-681 in human erythrocyte band 3, is conserved throughout the anion exchanger family (AE family). To determine whether or not the monovalent anion binding site is located near Glu-681, we modified this residue with Woodward's reagent K (N-ethyl-5-phenylisoxazolium-3'-sulfonate; WRK). Measurements of Cl(-) binding by (35)Cl-NMR show that external Cl(-) binds to band 3 even when Cl(-) transport is inhibited approximately 95% by WRK modification of Glu-681. This indicates that the external Cl(-) binding site is not located near Glu-681 and thus presumably is distant from the proton binding site. DIDS inhibits Cl(-) binding even when WRK is bound to Glu-681, indicating that the DIDS binding site is also distant from Glu-681. Our data suggest that the DIDS site and probably also the externally facing Cl(-) transport site are located nearer to the external surface of the membrane than Glu-681.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1996

Seven-year follow-up of neurologic involvement in Behçet syndrome.

OBJECTIVE: To determine the long-term prognosis of neurologic involvement in Behçet syndrome. DESIGN: Forty-six patients with Behçet syndrome, who had been the subjects of a previous report with short-term follow-up, were reexamined 7 years later; 42 of them could be reexamined neurologically. Neuropsychological testing, magnetic resonance imaging, electromyography, and evoked potential studies were performed when available. RESULTS: Of the 27 patients who had had headaches without any neurologic symptoms or signs previously, 2 had developed an acute neurologic attack. In addition, 7 patients in this group showed minor abnormalities on neurologic examination and/or other laboratory investigations, without history of any attacks. Among the previous neuro-Behçet group (n = 15), as defined by the presence of neurologic signs or symptoms, other than headache, 7 had a stationary course, while 8 had been progressive. Three of the latter group had died. Patients with progressive course had had abnormal cerebrospinal fluid findings at the time of the previous report, whereas patients with a stationary course had not. CONCLUSIONS: Silent neurologic involvement may occur in Behçet syndrome. Patients should undergo periodic neurologic evaluation. The long-term prognosis in neuro-Behçet syndrome does not seem to be as favorable as we observed in short-term follow-up. Cerebrospinal fluid findings may predict prognosis.

Adult↗

PubMed1996

A controlled study of reliability and validity of MRI findings in neuro-Behçet's disease.

Our aim was to test the reliability of interpreting MRI studies in neuro-Behçet's disease (NBD) and to determine the sensitivity and specificity of different MRI findings. We prospectively studied 50 patients: 24 had chronic NBD, 12 multiple sclerosis, 5 vasculitis other than Behçet's disease (BD) and 9 patients had BD without neurological involvement. MRI studies were performed according to a standard protocol with a 0.2 T imager. Two neuroradiologists, blinded to the diagnosis, age and sex of the subjects, reviewed the films independently, twice. Separate assessments were made for a set of items: dural sinus pathology, widening of ventricles and sulci, brain stem atrophy, lesions of the cerebral cortex, discrete lesions of deep white matter, basal ganglia, brain stem and cerebellum and the presence of smooth periventricular high-signal foci. Intraobserver agreement was substantial or better, and interobserver agreement moderate to substantial for most items. In these patients with chronic NBD we found low sensitivity on all assessed items. Dural sinus pathology or brain stem atrophy were highly specific, but parenchymal lesions in different sites had uniformly low specificity.

Behcet Syndrome↗

PubMed1996

Production of cyclomaltodextrin glucanotransferase from an alkalophilic Bacillus sp. in rice and corn flakes.

Cyclomaltodextrin glucanotranferase (CGTase) catalyzes the degradation of starch to form alpha-, beta- and gamma-cyclodextrin. Based on cyclodextrin formation, an alkalophilic Bacillus sp. ATCC 21783 was used for its high CGTase production ability, using corn and rice flakes as substrates. Maximum enzyme production was achieved after 96 hours at pH 9.0, temperature 37 degrees C, and 1% (w/v) of either substrate together with the addition of trub. The specific enzyme activity was determined by High Pressure Liquid Chromatography (HPLC) and expressed as using International Units based on total cyclodextrin formation. Optimum conditions for this determination were studied, finding that the best results are obtained at pH 5.0, 7.0 and 9.0, temperature 55 degrees C and 3 hours of incubation in 1% (w/v) of rice flakes as starch source.

Bacillus↗

PubMed1995

High-yield production of diphtheria toxin mutants by high-density culture of C7 (beta)tox+ strains grown in a non-deferrated medium.

A high-density growth approach was utilized to produce mutated diphtheria toxin from two strains of Corynebacterium diphtheria: C7 (beta)(tox-201,tox-9) and C7 (beta)(tox-107). The cross-reacting mutants (CRM) of the diphtheria toxin are CRM9 and CRM107; both of them carry the mutation in their binding site and, as a result, have 1/300 of the systemic toxicity of the wild-type diphtheria toxin. Since iron inhibits diphtheria toxin production, the traditional approach has been to grow the bacteria in a very low iron concentration. The procedure described here involved the use of a modified, non-deferrated, growth medium that provided fast and high-density growth of the bacteria, and which, when associated with simultaneous depletion of glucose and iron, enhanced the toxin production. Oxygen-enriched air was supplied to enable the bacteria to grow to a cell density giving an absorbance of 70 at 600 nm (15-20 g/l dry weight). The maximum toxin concentration in the culture supernatant was 150 mg/l. The CRM products, which remained stable following microfiltration and ultrafiltration, could be easily purified using a two-step chromatography procedure.

Corynebacterium diphtheriae↗

PubMed1995

Evaluation of response to postradiation eight in one chemotherapy in childhood brain tumors.

Ten children, 3 to 15 years of age with high risk primary brain tumors were treated with postradiation 'eight in one' chemotherapy; vincristine, lomustine, procarbazine, hydroxyurea, cisplatin, cytosine arabinoside, cyclophosphamide and methylprednisolone. The tumors comprised of three medulloblastomas, two primitive neuroectodermal tumors, one ependymoblastoma and four anaplastic ependymomas. Treatment involved surgery (two total resection, six subtotal and two biopsy only) followed by conventional radiotherapy (primary tumor: 50-54 Gy, whole brain: 30-45 Gy, and spinal axis: 25-36 Gy). Objective tumor response with radiotherapy was achieved in 7 of 9 patients (78%) (6/8 patients with residual tumor and one patient with complete resection but positive cerebrospinal fluid cytology). Complete response was attained in 4 of 9 patients (44%). 'Eight in one' chemotherapy was initiated four weeks after radiation and repeated at 4 weekly intervals for 5-8 courses. Postradiation 'eight in one' failed to show any additional effect on tumor responses. Median survival was 34 months (range 9-48 months) with five of ten patients alive: four in complete and one in partial remission. All the five survivors were among the patients who had achieved response to initial treatment. This result suggested that degree of response to initial treatment might determine subsequent outcome and thus the choice of modality for initial therapy might be important.

Adolescent↗