Nonrandom nature of in vivo methylation of dimethylnitrosamine and the subsequent removal of methylated products from rat liver chromatin DNA.

This investigation was designed to study whether methylation of liver chromatin DNA by dimethylnitrosamine (DMN) and the subsequent in vivo removal of DNA-bound methylated products are random. Liver chromatin DNA was fractionated into nuclease-digestible and nondigestible material 4 hr following the administration of [3H]DMN (0.5 mg/250 muCi/100 g body weight). Digestion of such methylated liver chromatin with pancreatic DNase I or micrococcal nuclease and analysis of nuclease-digested acid-soluble products revealed a discrepancy between the radioactivity released (72%) and the nucleotides released (50%) as measured by the absorbance at 260 nm. This discrepancy disappeared, and the rate and extent of release of both the radioactivity and the absorbance at 260 nm were identical when the total purified DNA isolated from methylated chromatin was used as the substrate instead of chromatin DNA in the nuclease reaction. These results, together with the fact that guanine contents of the DNA of the two fractions of the chromatin isolated by nuclease digestion were identical, suggest that methylation of the nuclease-accessible region of hepatic chromatin DNA is relatively greater than that of the inaccessible region. The study of the removal of methylated products in the accessible region of the chromatin DNA further reveals that, of the methylated products present at 4 hr, 62% is lost by 3 days, 87% is lost by 1 week and 94% is lost by 2 weeks. However, loss from the nuclease-inaccessible region of chromatin DNA is only 27% by 3 days, 49% by 1 week, and 86% by 2 weeks, thereby suggesting that the removal of methylated products from this region of chromatin DNA is relatively slower compared with that from the nuclease-accessible region of chromatin-DNA. The results of this study thus indicated (a) an increased methylation and faster rate of removal of DMN-induced methylated products in nuclease-accessible regions of chromatin DNA and (b) decreased methylation and slower rate of removal from the nuclease-inaccessible regions of chromatin DNA. It is concluded that the distribution and removal of DMN-induced methylated products in liver chromatin DNA is nonrandom as measured by this technique.     

Prevalence and correlates of tobacco use among 10-12 year old school students in Patna District, Bihar, India

In order to assess the prevalence and correlates of tobacco use among school students (10-12 years), information on tobacco use and socio-demographic variables was collected from 1626 students (male 1027) using a questionnaire. Bivariate and multiple regression analysis were done. Ever users in the sample were 16.6% (95 % CI 14.8, 18.4) and current users were 5.1 % (95 % CI 4.1, 61). Current use was significantly associated with male sex (OR 2.3, CI 1.09 5.14), students not participating in sports (OR 2, CI 1.04 4.04), tobacco use among friends (OR 4, CI 2.02 8.25), unaware of harmful effects of tobacco (OR 2.6, CI 1.1 6.14) and students who were used by parents and teachers to buy tobacco for them (OR 2.1, CI 1.4 4.19). Tobacco control programs focusing on male students, those who do not participate in sports, those whose friends use tobacco and those who are used by parents and teachers to buy tobacco are warranted.     

Fatal case of Naegleria fowleri meningo-encephalitis in an infant: case report

Primary amoebic meningo-encephalitis (PAM) is extremely rare and is caused by Naegleria fowleri. It is ?commonly seen in older children who swim in water contaminated with Naegleria species. It is very rare to contract the illness by any other means. We report a case of PAM in an infant aged 6 months. To the best of our knowledge, only one other case of PAM in an infant has been reported from India. A high index of suspicion is required in infants who manifest similarly to pyogenic meningitis but whose CSF shows no bacterial organisms so that a wet mount of a CSF sample can be done for early detection of Naegleria fowleri infection and appropriate intervention.     

Electro-clinical characteristics and postoperative outcome of medically refractory tumoral temporal lobe epilepsy

BACKGROUND: Very few studies have specifically addressed surgical treatment and outcome of patients with tumor-related temporal lobe epilepsy (TLE). AIM: To define the postoperative seizure outcome and the factors that influenced the outcome of patients with tumor-related TLE. MATERIALS AND METHODS: We selected patients whose surgical pathology revealed a temporal lobe neoplasm and who had completed > 1 year of postoperative follow-up. We reviewed the clinical, EEG, radiological and pathological data, and the seizure outcome of these patients and assessed the factors that influenced the outcome. RESULTS: Out of the 409 patients who underwent surgery for refractory TLE during the 8-year study period, there were 34 (8.3%) patients with temporal lobe neoplasms. The median age at surgery was 20 years and the median duration of epilepsy prior to surgery was 9.0 years. MRI revealed tumor in the mesial location in 21 (61.8%) patients. Interictal and ictal epileptiform EEG abnormalities were localized to the side of th lesion in the majority. Mesial temporal lobe structures were included in the resection, if they were involved by the tumor; otherwise, lesionectomy alone was performed. During a median follow-up of 4 years, 27 (79%) patients were completely seizure-free. The only factor that predicted long-term seizure-free outcome was being seizure-free during the first two postoperative years. CONCLUSIONS: Our results emphasize the fact that in patients with tumoral TLE, when the seizures are medically refractory, surgery offers potential for cure of epilepsy in the majority.     

Surgical removal of unilateral vestibular schwannomas after failed Gamma Knife radiosurgery

One of the primary criticismes of vestibular schwannoma (VS) radiosurgery is that the risk of surgical morbidity is increased for patients whose tumor progresses after the procedures. We reviewed the French experience of operated patients after failed Gamma Knife radiosurgery. From July 1992 to January 2002, 25 out of the 1000 treated patients underwent another treatment procedure for a gamma knife failure. Excluding the NF2 patients, 21 patients have been operated and the present study shows the data collected for 20 of them. In order to analyze the difficulties observed during the surgery, a questionnaire was filled by the surgeons. The mean interval between radiosurgery and removal was 36 Months, from 10 to 83 Months. The mean increase in Volume was 559% (37 to 3036%, median 160%). Evolution of the Koos grading was found from 8 grade II, 10 grade III et 2 grade IV to 10 grade III and 10 grade IV. Patients have been operated for radiological tumor growth in 7 cases and for clinico-radiological evolution in 13 cases. In 9 cases, the surgeon considered that he had to face unusual difficulties mainly because of adhesion of the tumor to neurovascular structures. Tumor removal was total in 14 cases, near total in 4 cases and subtotal in 2 cases. One case of venous infarction was noticed at the second day following surgery responsible of hemiparesis and aphasia that gradually recovered. At last follow-up examination, facial nerve was normal (House and Brackmann grade I and II) in 10 cases while it was a grade III in 7 cases and grade IV and V in 3 cases. We recommend that the decision for surgical removal of growing vestibular schwannoma after Gamma Knife treatment should be done after a sufficiently long follow-up period. Our results show that the quality of removal and of facial nerve preservation might be impaired by radiosurgery in half of cases. However these results do not support a change in our policy of radiosurgical treatment of small to medium size vestibular schwannoma.     

Functional characterization of the pentapeptide QYNAD on rNav1.2 channels and its NMR structure

The endogenous pentapeptide QYNAD (Gln-Tyr-Asn-Ala-Asp) is present in human cerebrospinal fluid (CSF), and its concentration is increased in demyelinating diseases. QYNAD was synthesized and its action on the rNa_v1.2 voltage-gated sodium channel -subunit was studied using whole-cell recordings in a heterologous expression system. The effects were seen only upon equilibration of the peptide in the external bath solution for at least 10 min before the commencement of whole-cell experiments. The steady-state activation curve showed a rightward shift of 10 mV, while the steady-state inactivation curve showed a leftward shift of 5 mV. Frequency-dependent inhibition of the sodium current amplitude was observed at 2–10 Hz, in the presence of external QYNAD, but was not seen when applied internally. Fits of the whole-cell sodium current traces by Hodgkin-Huxley equations revealed subtle changes in the voltage-dependent rate constants governing the transition of the activation and the inactivation gates. Two dimensional NMR spectroscopy revealed the absence of medium and long-range Nuclear Overhauser effects (NOEs), which indicates that the peptide does not adopt any canonical secondary structure in solution. In summary, our studies show that although the pentapeptide QYNAD does not have a defined structure in solution, it has defined actions on the rNa_v1.2 voltage-gated sodium channel isoform.     

Coronavirus-induced demyelination occurs in the absence of CD28 costimulatory signals

Infection of mice with mouse hepatitis virus (MHV) strain A59 results in acute encephalitis, hepatitis, and chronic demyelinating disease. T lymphocytes play an important role in MHV infection, and costimulatory signals are an important component of T cell function. To elucidate the role of the main costimulatory molecule, CD28, in MHV pathogenesis and demyelination, we examined the kinetics of MHV-A59 infection in CD28 knockout mice. MHV-A59-infected CD28 knockout mice developed acute encephalitis and hepatitis, and the same degree of chronic demyelination as normal C57Bl/6 (B6) mice. Thus, CD28, the costimulatory T cell molecule, is not required for MHV infection and MHV-induced demyelination.     

Reversal of restricted diffusion in cerebral venous thrombosis: case report

We report a patient with extensive cerebral venous thrombosis who showed complete reversal of restricted diffusion on MRI, accompanied by excellent clinical recovery. The implications of these findings in relation to interpretation of diffusion changes in cerebral venous thrombosis are discussed, and differences with arterial stroke are highlighted.