Novel HMO-Glasses with Sb2O3 and TeO2 for Nuclear Radiation Shielding Purposes: A Comparative Analysis with Traditional and Novel Shields

The radiation shielding characteristics of samples from two TeO₂ and Sb₂O₃-based basic glass groups were investigated in this research. TeO₂ and Sb₂O₃-based glasses were determined in the research as six samples with a composition of 10WO₃-(x)MoO₃-(90 − x)(TeO₂/Sb₂O₃) (x = 10, 20, 30). A general purpose MCNPX Monte Carlo code and Phy-X/PSD platform were used to estimate the radiation shielding characteristics. Accordingly, the linear and mass attenuation coefficients, half value layer, mean free path, variation of the effective atomic number with photon energy, exposure and built-up energy factors, and effective removal cross-section values were determined. It was determined that the results that were produced using the two different techniques were consistent. Based on the collected data, the most remarkable findings were found to be associated with the sample classified as T80 (10WO₃ + 10MoO₃ + 80TeO₂). The current study showed that material density was as equally important as composition in modifying radiation shielding characteristics. With the T80 sample with the greatest density (5.61 g/cm³) achieving the best results. Additionally, the acquired findings were compared to the radiation shielding characteristics of various glass and concrete materials. Increasing the quantity of MoO₃ additive, a known heavy metal oxide, in these TeO₂ and Sb₂O₃-based glasses may have a detrimental impact on the change in radiation shielding characteristics.     

The mismatch repair pathway functions normally at a non-AID target in germinal center B cells

Deficiency in Msh2, a component of the mismatch repair (MMR) system, leads to an approximately 10-fold increase in the mutation frequency in most tissues. By contrast, Msh2 deficiency in germinal center (GC) B cells decreases the mutation frequency at the IgH V region as a dU:dG mismatch produced by AID initiates modifications by MMR, resulting in mutations at nearby A:T base pairs. This raises the possibility that GC B cells express a factor that converts MMR into a globally mutagenic pathway. To test this notion, we investigated whether MMR corrects mutations in GC B cells at a gene that is not mutated by AID. Strikingly, we found that GC B cells accumulate 5 times more mutations at a reporter gene than during the development of the mouse. Notably, the mutation frequency at this reporter gene was approximately 10 times greater in Msh2(-/-) compared with wild-type GC B cells cells. In contrast to the V region, the increased level of mutations at A:T base pairs in GC B cells was not caused by MMR. These results show that in GC B cells, (1) MMR functions normally at an AID-insensitive gene and (2) the frequency of background mutagenesis is greater in GC B cells than in their precursor follicular B cells.     

Bioassay-guided fractionation and in vivo antiplasmodial effect of fractions of chloroform extract of Artemisia maciverae Linn

In the search for new plant-derived anti-malarial compounds, chromatographic fractions of chloroform extract of whole plants of Artemisia maciverae were tested in vivo using chloroquine resistant and chloroquine sensitive Plasmodium berghei NK 65 infected Swiss albino mice. One fraction and a sub-fraction of this were most active at 10/mg and cleared parasitemia in mice within 3 days. The different fractions and sub-fractions were tested with different reagents to determine the broad classes of compounds present. The active fraction tested positive for triterpenes and alkaloids, and the sub-fraction for only triterpenes. These tests suggest that the anti-malarial activities observed with these fractions may be due to these classes of compounds in the chloroform extract of the A. maciverae. Further chemical work is however required to characterize the active constituents.     

Seroprevalence of Helicobacter pylori antibodies in medical students and residents in Recife,Brazil

BACKGROUND: The epidemiology of Helicobacter pylori (Hp) still constitutes a relevant subject of investigation. GOAL: The goal of this study was to determine the seroprevalence rate of Hp antibodies in medical students and residents, and its relationship with medical practice, age, gender and parents' formal education level. STUDY: The study was carried out from March 1999 to March 2000, on a population of 1,119 medical students and residents, from which a randomized and stratified sample was drawn. Each stratum comprised students attending the basic training level, students attending the professional training level, and residents. Independent samples were calculated for each group, making a total of 405 subjects. Each participant was interviewed using a questionnaire. After the interview, serum samples were collected and stored at -20 degrees C for detecting IgG antibodies against Hp by an enzyme-linked immunosorbent assay. RESULTS: A 31.4% seroprevalence rate of Hp antibodies was observed, which significantly increased during the graduation course according to the medical practices, ranging from 23.4% in students up to 38.6% in residents. Seroprevalence rate increased according to the age (p = 0.002), where older individuals had spent more time in practical activities. Seroprevalence was higher in males and was smaller among those whose parents had a university degree. CONCLUSION: The seroprevalence rate of Hp antibodies amongst medical students and residents increases from the basic up to residence level, suggesting that contact with patients during clinical practice may constitute a risk factor for acquiring Hp infection.     

An immunochemical marker for goldfish Mauthner cells

The Mauthner (M-) cells are pair of large reticulospinal neurons that mediate tail-flip escape responses in fish. Exploring the co-localization of scaffold and gap junction proteins at mixed (electrical and chemical) synapses, we found that the use of a particular antibody against the scaffold protein Zonula Occludens-2 (ZO-2) resulted in labeling of these cells. We show here that this staining is restricted to the Mauthner cell and evenly distributed along its dendrites and axon, also prominent in small dendritic and axonal processes. Because the observed labeling is non-specific, we suggest that the antibody might recognize a soluble protein that is primarily expressed in the Mauthner cells. While the identity of this protein is presently unknown, the use of this antibody should facilitate the identification of the Mauthner cell and its fine processes during anatomical and immunohistochemical studies, which otherwise require intracellular injection of tracer molecules during electrophysiological recordings.     

Epidural cylinder electrodes for presurgical evaluation of intractable epilepsy: technical note

BACKGROUND: This is a technical report describing a different technique for the insertion of epidural electrodes in the preoperative evaluation of epilepsy surgery. Our experience in 67 cases using this technique is analyzed. METHODS: Cylinder electrodes with multiple recording nodes spaced 1 cm apart along a Silastic core are placed into the epidural space under general anesthesia through single or multiple burr holes. We reviewed the data on 67 cases of medically intractable epilepsy requiring intracranial monitoring that had epidural cylinder electrodes placed. The electrodes were placed bilaterally or contralateral to subdural grids in 64 of the 67 cases. Continuous monitoring was performed from 1 to 3 weeks. RESULTS: This method was most useful when used bilaterally or contralateral to subdural grids. Definitive surgery was rendered in 48 of 67 cases. After monitoring, all electrodes were removed at bedside or upon return to the operating room for definitive surgery. There were no mortalities, infections, cerebrospinal fluid leaks, neurologic deficits, or electrode malfunctions. Two patients (2/67, 3%) did develop subdural hematomas early in our series after dural injury near the pterion; however, these patients did not sustain permanent deficit. CONCLUSIONS: Epidural cylinders are another option for preoperative monitoring, useful for determining lobe or laterality of seizure genesis. They offer an alternate method to EPEs in cases where epidural recording is desirable. The cylinder electrodes are easy to place and can be removed without a return to the operating theater. The electrodes' minimal mass effect allows them to be safely placed bilaterally or contralateral to subdural grids. The epidural cylinders can monitor cortex with a greater density of nodes and can access regions not amenable to EPEs.