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.     

A controlled trial of scheduled replacement of central venous and pulmonary-artery catheters.

BACKGROUND. The incidence of infection increases with the prolonged use of central vascular catheters, but it is unclear whether changing catheters every three days, as some recommend, will reduce the rate of infection, It is also unclear whether it is safer to change a catheter over a guide wire or insert it at a new site. METHODS. We conducted a controlled trial in adult patients in intensive care units who required central venous or pulmonary-artery catheters for more than three days. Patients were assigned randomly to undergo one of four methods of catheter exchange: replacement every three days either by insertion at a new site (group 1) or by exchange over a guide wire (group 2), or replacement when clinically indicated either by insertion at a new site (group 3) or by exchange over a guide wire (group 4). RESULTS. Of the 160 patients, 5 percent had catheter-related bloodstream infections, 16 percent had catheters that became colonized, and 9 percent had major mechanical complications. The incidence rates (per 1000 days of catheter use) of bloodstream infection were 3 in group 1, 6 in group 2, 2 in group 3, and 3 in group 4; the incidence rates of mechanical complications were 14, 4, 8, and 3, respectively. Patients randomly assigned to guide-wire-assisted exchange were more likely to have bloodstream infection after the first three days of catheterization (6 percent vs. 0, P = 0.06). Insertions at new sites were associated with more mechanical complications (5 percent vs. 1 percent, P = 0.005). CONCLUSIONS. Routine replacement of central vascular catheters every three days does not prevent infection. Exchanging catheters with the use of a guide wire increases the risk of bloodstream infection, but replacement involving insertion of catheters at new sites increases the risk of mechanical complications.     

Surgical alterations of the pancreas and insulin-independent glucose disposal.

Systemic drainage of pancreatic venous effluent and denervation of the pancreas that follows pancreatic transplantation has been shown to alter postoperative glucose disposal despite elevated levels of peripheral insulin in response to a glucose challenge. Since an appreciable fraction of postprandial glucose disposal takes place in the absence of insulin (insulin-independent glucose disposal--IIGD), we have investigated potential changes in this aspect of carbohydrate metabolism before and after bladder-drained pancreatic auto-transplantation (PAT/B) as well as partial pancreatectomy (PPx). The hyperglycemic clamp protocol with a background infusion of somatostatin was performed on control (PREOP) dogs as well as PAT/B and PPx animals. The rate of glucose disposal (M Value) during the period of hypoinsulinemia induced by Somatostatin (SST) was measured and reported. Whereas glucose disposal during steady state hyperglycemia was significantly diminished for both PPx and PAT/B in the absence of SST, IIGD was unaltered across all three groups studied. We therefore conclude that surgical alteration of the pancreas results in abnormal glucose disposal during steady state hyperglycemia despite apparently normal to supranormal levels of peripheral insulin, and that alterations in IIGD are not responsible for these differences.     

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.     

Status of percutaneous catheter drainage of abscesses

The definitive role of catheter drainage in the therapy of abscesses has not yet been totally elucidated. The resolution rate of intra-abdominal infection with catheter drainage is highly variable, depending on the inclusion criteria employed. Certain infections are very effectively treated (i.e., abscesses that are single, not communicating with abdominal viscera, noncancerous, and bacterial) with simple catheter drainage, whereas others (i.e., infected pancreatic tumor phlegmon) prove to be much more resistant to simple catheter drainage. When all intra-abdominal "abscesses" are collected, the success of catheter drainage ranges from 47 per cent to 73 per cent. The wide variation should be seen not so much as a reflection of differences in technical ability of the radiologist to introduce a catheter, but rather as emblematic of the highly variable nature of the cause of intra-abdominal infection and the definition of an abscess. Hospitals with a large number of complex problems such as malignancy, transplant and other immunosuppressed patients, and referrals of patients with complex long-standing intra-abdominal infections are likely to have a much lower rate of success with percutaneously placed catheters than are those institutions that derive their series from post-traumatic or primary diseases such as appendiceal or diverticular disease. In the former series, a higher morbidity and mortality rate would be expected from any form of treatment when compared to a series from a practice based on more primary care problems. Intra-abdominal infections are a heterogeneous set of processes, and the role of interventional radiology in the diagnostic and therapeutic approach cannot be underestimated. In planning for the care of a patient with a presumed intra-abdominal infectious process, percutaneous aspiration of a fluid mass is an effective tool for establishing the diagnosis of an abscess. The brief introduction of a catheter has rarely led to contamination of an otherwise sterile collection. However, it often effects dramatic symptomatic relief if the fluid collection is infected. It has therefore been an evolving recommendation to employ the techniques of interventional radiology aggressively in a diagnostic capacity. Subsequently, therapeutic interventions can be undertaken in joint agreement among the physician, surgeon, and radiologist. The diagnosis and treatment of intra-abdominal infections can often times be carried out in a relatively easy and non-morbid manner that effects cure in a significant percentage of patients.(ABSTRACT TRUNCATED AT 400 WORDS)     

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.