Benzene and the risk of non-Hodgkin lymphoma: A review and meta-analysis of the literature

Benzene, an accepted leukemogen, has been suggested to cause other hemato- and lymphopoietic cancers. Here we review the published literature for non-Hodgkin lymphoma (NHL) and occupational exposure to benzene. Six cohorts, sixteen case–control studies and two studies of other designs were identified through keyword searches of bibliographic databases. Twenty-two of twenty-four studies found no association between NHL and ever exposed to benzene compared to never; a random-effects meta-analysis gave a pooled risk estimate of 1.11 (95% confidence interval 0.94–1.30). Our finding of no effect agrees with one of two previous meta-analyses. The other meta-analysis examined if high benzene exposure increased NHL risk but a lack of consistent exposure categories within the same metric should have precluded pooling risks by exposure level. Instead, we reviewed whether dose–response relationships existed. The best available data came from six studies where exposure was estimated from historical measurements and on the whole, no trends in risks of NHL with rising cumulative, average, peak, or duration of benzene exposure were found. NHL is a heterogeneous group of malignancies and although less well-studied, benzene was not associated with any NHL subtype. In conclusion, benzene at either low or high doses does not increase the risk of NHL.     

Improving the clinical efficiency of T2 mapping of ligament integrity

Current MR methods use T₂^? relaxation time as a surrogate measure of ligament strength. Currently, a multi-echo voxel-wise least squares fit is the gold standard to create T₂^? maps; however, the post-processing is time-intensive and serves as a stopgap for clinical use. The study objective was to determine if an alternative method could improve post-processing time without sacrificing fidelity of T₂^? values for eventual translational use in the clinic. Using a 6 echo FLASH sequence, three different methods were used to determine intact posterior cruciate ligament (PCL) median T₂^? Two of these methods utilized a voxel-wise method to establish T₂^? maps: (1) a current “gold standard” method using a voxel-wise 6 echo least-squares fit (6LS) and (2) a voxel-wise 2 echo point T₂^? determination (2MM). The third method used median ligament signal intensity and a single nonlinear least-squares fit (6LS_ROI) instead of a voxel-wise basis. The resulting median T₂^? values of the PCL and computational time were compared. The median T₂^? values were 42% higher using the 2MM compared to the 6LS method (p<0.0001). However, a strong correlation was found for the median T₂^? values between the 2MM and 6LS methods (R²=0.80). The median T₂^? values were not significantly different between the 6LS and 6LS_ROI methods (p=0.519). Using the 2MM (which provides a regional map) and the 6LS_ROI (which efficiently provides the median T₂^? value) methods in tandem would take only minutes of post-processing computational time compared to the 6LS method (~540 min), and hence would facilitate clinical application of T₂^? maps to predict ligament structural properties as a patient outcome measure.     

Identification of mitochondrial proteins on two-dimensional electrophoresis gels of extracts of adult Drosophila melanogaster

Several hundred proteins have been resolved on two-dimensional gels of extracts of [³⁵S]methionine-labeled adult Drosophila melanogaster. 27 of these polypeptides disappear from the gel pattern after feeding the K⁺ ionophore nonactin. These proteins have been identified as mitochondrial, since the two-dimensional gel pattern of extracts of isolated mitochondria correlates well with the pattern of the proteins missing from that of nonactin-treated flies. Nine new proteins also appear on the two-dimensional gels of the extracts from the nonactin-treated flies. Apparently, these nine proteins are precursors of the mature mitochondrial forms. These particular data support the concept that processing of many of the cytoplasmically synthesized mitochondrial proteins requires a specific membrane potential, and that some of these proteins are modified intramitochondrially. However, using [³⁵S]methionine incorporation techniques, not all labeled polypeptides disappear from mitochondria during such treatment. Feeding similarly radiolabeled flies with chloramphenicol, an inhibitor of mitochondrial protein synthesis, results in the disappearance of only one protein from the gel pattern with the concurrent appearance of a ‘new’ high-molecular-weight polypeptide. Collectively, these data show that a specific group of [³⁵S]methionine-labeled mitochondrial proteins can be identified by selective inhibition of mitochondrial function in whole cell protein maps of adult D. melanogaster.     

A differential medium for the enumeration of homofermentative and heterofermentative lactic Acid bacteria

A medium was developed for the differential enumeration of homofermentative and heterofermentative lactic acid bacteria. Essential components of the medium included fructose (14 mM), KH(2)PO(4) (18 mM), bromcresol green (as a pH indicator), and other nutrients to support growth. In agar medium, homofermentative colonies were blue to green, while heterofermentative colonies remained white. A total of 21 Lactobacillus, Pediococcus, Leuconostoc, and Streptococcus species were correctly classified with the medium.     

Characterization of the structural proteins of the murine coronavirus strain A59 using monoclonal antibodies

Monoclonal antibodies reacting with the A59 strain of mouse hepatitis virus (MHV-A59) were characterized and those specific to the E2 major envelope glycoprotein were studied in detail. Antibodies were tested for their ability to neutralize viral infectivity (N+ characteristic) and prevent viral-induced cell-to-cell fusion (F+ characteristic). All four possible combinations of activities reflecting E2 functions were found, i.e., N+F+, N-F-, N+F-, and N-F+. In addition, competitive binding studies with these monoclonal antibodies revealed two nonoverlapping antigenic regions. The first region, designated A, was recognized by antibodies which included each of the four functional types. Region B was identified by a single monoclonal antibody with N-F- activities. The existence of antibodies which only neutralize virus or only block viral-induced fusion implies that the structures on E2 which serve as targets for neutralization and which induce fusion are not identical. The critical determinants for neutralization and fusion must be closely related topographically on E2 since both N+F- and N-F+ antibodies recognize the same antigenic region.     

Purified cytochrome b561 catalyzes transmembrane electron transfer for dopamine beta-hydroxylase and peptidyl glycine alpha-amidating monooxygenase activities in reconstituted systems

Cytochrome b561 from bovine adrenal medulla chromaffin granules has been purified by fast protein liquid chromatography chromatofocusing. The purified cytochrome was reconstituted into ascorbate-loaded phosphatidylcholine vesicles. With this reconstituted system transmembrane electron transfer for extravesicular soluble dopamine beta-hydroxylase activity was demonstrated. In accordance with the model proposed by Njus et al. (Njus, D., Knoth, J., Cook, C., and Kelley, P. M. (1983) J. Biol. Chem. 258, 27-30), catalytic amounts of a redox mediator were necessary to achieve electron transfer between cytochrome and soluble dopamine beta-hydroxylase. Our observations also showed that when membranous dopamine beta-hydroxylase was reconstituted on cytochrome containing vesicles, electron transfer occurred only in the presence of a redox mediator. Since cytochrome b561 has been found in secretory vesicles associated with peptidyl glycine alpha-amidating monooxygenase, electron transfer to this enzyme was also examined. Analogous to the results obtained for dopamine beta-hydroxylase, transmembrane electron transfer to peptidyl glycine alpha-amidating monooxygenase appears to require a redox mediator between cytochrome and this monooxygenase. These observations indicate that purified cytochrome b561 is capable of providing a transmembrane supply of electrons for both monooxygenases. Since no direct protein to protein electron transfer occurs, the results support the hypothesis that the ascorbate/semidehydroascorbate redox pair serves as a mediator for these enzymes in vivo.