New stand magnifiers do not meet rated levels of performance

A new range of stand magnifiers has been released by the COIL company in the United Kingdom. Examination of these magnifiers reveals that they fail to deliver the rated magnifications labelled prominently on the appliances, as a result of the manufacturer's conformance with the requirements of the German DIN standard and the use of back vertex power (F'_v) rather than equivalent dioptric power (F_m) of the magnifier. In this study we provide information on the optometric parameters of these new stand magnifiers that will assist the more accurate specification of improvements in vision expected from their use.     

Required duration of combined annual ivermectin treatment and vector control in the Onchocerciasis Control Programme in west Africa.

In the extension areas of the Onchocerciasis Control Programme in West Africa, aerial larviciding is supplemented with annual ivermectin treatment, mainly to achieve better control of morbidity. The purpose of this study is to determine whether and to what extent the addition of annual ivermectin treatment permits earlier cessation of vector control than originally recommended. The effectiveness of combined ivermectin distribution and vector control was assessed using an epidemiological model. Model predictions suggest that, dependent on the pre-control endemicity of the area and the proportion of persons treated during each ivermectin round, large-scale annual treatment permits a considerable reduction in the duration of vector control. Taking into account uncertainty about the efficacy of ivermectin, our results indicate that, provided treatment coverage is at least 65% and there is no importation of infection from elsewhere, 12 years of combined control will be sufficient to reduce the risk of recrudescence to below 1% in even the most afflicted areas.     

Redeployment of trigeminal motor axons during metamorphosis.

As a consequence of the degeneration and replacement of the jaw muscle fibers in the leopard frog, Rana pipiens, trigeminal motoneurons innervate different targets before and after metamorphosis. This investigation examined the morphological correlates of the reassignment of trigeminal motoneurons during the initial phases of myofiber turnover. Specifically, silver-cholinesterase histochemistry and electron microscopy were used to 1) identify the fate of motor axons within the neuromuscular junctions (NMJs) applied to degenerating larval myofibers and 2) to determine the origin(s) of the motor axons that innervate the postmetamorphic muscle fibers of the jaw. The results demonstrate that the NMJs are retained on larval myofibers throughout their degeneration and are readily identifiable on the residual larval basal laminae that remain after involution of the sarcoplasm. Light and electron microscopic observations provide evidence that both pre- and post-synaptic elements are present on the degenerating fibers. Furthermore, morphometric analyses indicate that the preponderance (86%) of motor axons supplying adult muscle fibers originates from the larval NMJs. This condition suggests that metamorphic redeployment of trigeminal motoneurons occurs through the resumption of growth at the axon terminal supplying larval muscle rather than through the proximal collateralization of these axons and resorption of larval terminals.     

Pheochromocytoma and paraganglioma: comparison of MR imaging with CT and I-131 MIBG scintigraphy

To ascertain the magnetic resonance (MR) imaging characteristics of pheochromocytomas and paragangliomas and to compare MR with computed tomography (CT) and iodine-131 metaiodobenzylguanidine (I-131 MIBG), 19 patients (18 with pheochromocytomas, one with a paraganglioma) were studied. The 18 patients with pheochromocytomas had had positive findings with I-131 MIBG scintigraphy. Abdominal pheochromocytomas were generally hypointense compared with normal liver on T1-weighted MR images and extremely hyperintense on T2-weighted MR images. MR imaging was preferable to CT in the evaluation of primary pheochromocytomas due to superior tissue characterization, particularly in the patient with hypertension and borderline catecholamine levels. For patients with recurrent or metastatic disease, the data suggest that I-131 MIBG scintigraphy is the examination of choice.     

Chaperonin-mediated assembly of wild-type and mutant subunits of human propionyl-CoA carboxylase expressed in Escherichia coli

We developed a bacterial expression system for the human alpha and beta cDNAs of propionyl-CoA carboxylase (PCC). These cDNAs (less the putative mitochondrial matrix targeting presequences) were co-expressed in Escherichia coli on one plasmid vector with each cDNA having its own IPTG-inducible promoter. Only negligible amounts of active PCC were measured despite the presence of both alpha and beta subunits as indicated by Western blot analysis and the almost complete biotinylation of the alpha subunit. Co-expression of this plasmid with a second plasmid vector over-expressing the E. coli chaperonin proteins, groES and groEL, resulted in a several hundred-fold increase in PCC specific activity, to a level comparable with that found in crude human liver extracts. PCC was partially purified on monomeric avidin affinity resin and the presence of both alpha and beta subunits was demonstrated, thereby confirming the assembly of both subunits into an active enzyme. Deficiency of either alpha PCC or beta PCC results in propionic acidemia, an autosomal recessive disorder. We used this expression system to characterize one missense mutation previously described in five Japanese alleles, namely C1283T (Thr428lle) in beta PCC. This mutation, when expressed in E.coli under the same conditions as that of wild-type PCC, had null activity, despite the presence of assembled alpha PCC and beta PCC subunits. This bacterial expression system can be useful for analysis of either alpha PCC or beta PCC mutations. Our findings indicated that the groES and groEL chaperonin proteins were essential for folding and assembly of the human PCC heteromeric subunits.      

Rapid differentiation of the major causative agents of bacterial meningitis by use of frequency-pulsed electron capture gas-liquid chromatograph: analysis of acids.

The major causative agents of bacterial meningitis, Haemophilus influenzae serogroup B, Neisseria meningitidis serogroups B and C, Klebsiella pneumoniae, Streptococcus pneumoniae, and two types of Escherichia coli, were cultured in a modified chemically defined Catlin medium and in a commercial version of the unmodified Catlin medium. The spent media were extracted under acidic conditions, and electron-capturing derivatives were prepared by derivatization with trichloroethanol or haptafluorobutyric anhydride. The derivatives were analyzed on a gas chromatograph equipped with a frequency-pulsed electron capture detector and a PEP-2 computer. The data obtained from the study show that these organisms can be easily distinguished from each other on the basis of metabolic products detected in either type of medium. Three different metabolic groups were detected within two serogroups of N. meningitidis. The methods are practical, and the new technique should offer clinical laboratories and hospitals a better method for rapid identification of this important group of pathogens.