Separation of septal influences on lordosis, ultrasound production, and body weight

It is well known that macromolecules like albumin are markedly restricted in their passage across the glomerular capillary wall. However, the relative importance of solute size, charge and shape is currently debated since much of the previous work is based on dextran in neutral or charge-modified forms. These polymers have certain drawbacks that make them less suitable for analysis of capillary permeability and the notion of a glomerular charge barrier has therefore been questioned. Moreover, macromolecules larger than albumin (mol. wt. 69,000) have been suggested to pass through nonselective 'shunt' pathways. In order to study glomerular permeability, isolated rat kidneys were perfused with albumin solutions containing trace amounts of two differently radiolabelled isoenzymes of lactate dehydrogenase (LDH) at low temperature to inhibit tubular function. The isoenzymes have similar size (mol. wt. 140,000) and shape but differ in charge, one carrying a negative net surface charge (LDH1, -19) and the other being slightly cationic (LDH5, +2). The urine and perfusate samples were subjected to high pressure liquid chromatography (HPLC) gel-filtration to allow for measurements of intact LDH. The fractional clearance was 0.11% +/- 0.04% for the anionic LDH1 and 0.56% +/- 0.07% for LDH5, whereas that for albumin was 0.21% +/- 0.03% at a glomerular filtration rate of 0.11 +/- 0.01 mL min-1 g-1 kidney wet weight. The results were analysed using a homogenously charged membrane model and are compatible with a charge density of 35 mEq L-1, with 95% confidence interval of 26-41 mEq L-1. These findings suggest a significant glomerular charge selectivity for proteins substantially larger than albumin. The charge density is, however, far less than estimated from dextran studies.     

A prolonged QRS duration on surface electrocardiogram is a specific indicator of left ventricular dysfunction [see comment

OBJECTIVE: We sought to determine whether a prolonged QRS-interval duration is associated with decreased left ventricular (LV) systolic function. BACKGROUND: The 12-lead electrocardiogram (ECG) is a routine test for suspected cardiac disease. Although several scoring systems have been devised to estimate LV systolic function, no studies have examined the direct relationship between QRS duration alone and LV systolic function. METHODS: We analyzed the standard 12-lead surface ECG of 270 consecutive patients, referred for radionuclide ventriculography. Patients (n = 44) with bundle branch blocks, atrial flutter or fibrillation, pacemaker rhythm, recent myocardial infarction or bypass surgery, and patients on antiarrhythmic drugs were excluded. In the remaining patients (n = 226), we correlated the QRS duration on standard resting ECG, and the resting LV ejection fraction (EF), end-systolic and end-diastolic counts (ESC and EDC, respectively; LV volume indices), as obtained by radionuclide angiography. We used a multivariate analysis to identify independent predictors of reduced ventricular function entering QRS duration, the previously described R-wave score and clinical variables in our model. RESULTS: The QRS duration in the abnormal EF group was significantly longer than in the normal EF group (0.102 vs. 0.091 s, p < 0.0001). A QRS duration >0.10 s was highly specific (83.6%), but modestly sensitive (43.8%), for the prediction of abnormal EF. Furthermore, an abnormal EF was predicted with incrementally increased specificity (83.6% to 99.3%) and a corresponding decrease in sensitivity (43.8% to 13.8%) for each 0.01-s increase in the definition of prolonged QRS (from >0.10 to >0.12 s). Accordingly, the positive likelihood ratio for the prediction of decreased LV function was increased from 2.67 to 19.7 as the definition of prolonged QRS duration was increased from >0.10 to >0.12 s. In the multivariate analysis, a prolonged QRS duration and a low R-wave score were the only independent predictors of decreased LV systolic function. CONCLUSIONS: Prolonged QRS duration (>0.10 s) obtained from a standard resting 12-lead ECG is a specific, but relatively insensitive indicator of decreased LV systolic function. Further prolongation of the QRS had a higher specificity for decreased LV EF and a higher positive likelihood ratio for predicting abnormal LV EF.     

Four-level cervical corpectomy

STUDY DESIGN: Retrospective analysis of 31 cases of cervical spondylotic myelopathy treated by four-level subaxial cervical corpectomy. OBJECTIVE: To determine whether extremes of anterior decompression and fusion have inordinate or unique levels of morbidity. SUMMARY OF BACKGROUND DATA: There is a paucity of data on experience with four-level corpectomy. However, counsel against such surgery can be found. MATERIALS AND METHODS: The records and studies of 31 consecutive cases of cervical spondylotic myelopathy, treated by four-level corpectomy, were retrospectively analyzed. Patients in 26 cases were observed longer than 2 years. No hardware was used in the procedures. External orthosis, worn for 6 months, was a Philadelphia-type collar in 25 patients and a halo vest in 6. RESULTS: Three patients died within 3 weeks of surgery (9.7%). Delayed radiculopathy occurred in four patients after surgery, three had acute graft complications, and one had pseudomeningocele, for a morbidity rate of 25.8%. There was no infection or worsened myelopathy. CONCLUSIONS: No unique morbidity is associated with extremes of subaxial decompression when compared with surgery of lesser extent.     

Breast disease: dynamic spiral MR imaging

The cochleo- and tonotopic organization of the second auditory area (AII) was investigated in cats anaesthetized with pentobarbital using a combination of macro- and microelectrode recording technique. The results obtained following electrical stimulation of the neural fibres innervating different regions of the organ of Corti indicate the existence of two complete representations of the cochlea in area AII: one in the dorsocaudal portion, the other in its ventrorostral portion. These two cortical representations of the cochlea differ in size and spatial orientation. The dorsocaudal projection area extends over a distance of 2.6-3.2 mm from the basal to the apical focus and is arc-shaped. The spatial orientation of cochlea representation within the dorsocaudal region of AII is similar to that described in AI, in that stimulation of the cochlea base results in maximal responses in the more rostral portion of AII and stimulation of the apex evokes cortical responses more caudally. The ventrorostral region within AII is smaller (1.4-2.5 mm length), and has the opposite cochleotopic orientation (base and apex stimulation represented caudally and rostrally, respectively). In both AII zones, there was a proportionally greater cortical representation of basilar membrane than of middle and apical portions. Although two distinct zones with the overall cochleotopic pattern described above were noted in all cats, their precise size and location considerably varied in different animals. Using microelectrode recordings, a cortical tonotopic organization can be observed that was consistent with and expanded on the earlier cochleotopic data. Within the dorsocaudal region of AII, neurons with higher best frequency responses were located in more rostral regions, while those with lower best frequencies were located caudally. An orderly progression of best frequency responses was noted as serial recordings carried out along the full extent of the representation. Neurons within the ventrorostral region of AII also displayed an orderly progression of best frequencies, but in the opposite direction, with higher best frequencies noted more caudally and lower best frequencies more rostrally.     

Cyclooxygenase-2 inhibition prevents delayed death of CA1 hippocampal neurons following global ischemia

The inducible isoform of the enzyme cyclooxygenase-2 (COX2) is an immediate early gene induced by synaptic activity in the brain. COX2 activity is an important mediator of inflammation, but it is not known whether COX2 activity is pathogenic in brain. To study the role of COX2 activity in ischemic injury in brain, expression of COX2 mRNA and protein and the effect of treatment with a COX2 inhibitor on neuronal survival in a rat model of global ischemia were determined. Expression of both COX2 mRNA and protein was increased after ischemia in CA1 hippocampal neurons before their death. There was increased survival of CA1 neurons in rats treated with the COX2-selective inhibitor SC58125 [1-[(4-methylsulfonyl) phenyl]-3-trifluoro-methyl-5-[(4-fluoro)phenyl] pyrazole] before or after global ischemia compared with vehicle controls. Furthermore, hippocampal prostaglandin E2 concentrations 24 h after global ischemia were decreased in drug-treated animals compared with vehicle-treated controls. These results suggest that COX2 activity contributes to CA1 neuronal death after global ischemia.     

"Death by proxy": ethics and classification in epidemiology

Epidemiology is reductionist in that it usually relies on creating categories of people or risk factors. Classification must be undertaken as part of any study, however by the act of choosing groups, individuals are (potentially) consigned to either a higher or lower risk group. We discuss this from an ethical perspective and consider: (a) whether the groupings commonly chosen genuinely represent the risk factor of interest, (b) the implications for individuals when consigned to groups and (c) the implications for epidemiology.     

Coronary artery disease in women. How customary expectations can interfere with interpretation of test results

Although one in three women in the United States will die of heart disease, traditionally coronary artery disease (CAD) in women has received less recognition as a public health problem than has the disease in men. To assist practicing physicians in recognizing CAD in women, this article reviews sex differences in risk factors and manifestations of CAD as well as strengths and weaknesses of various diagnostic tests in women.