Vertebral-body collapse in focal and diffuse disease: patterns of pathologic processes

The radiographic patterns of vertebral-body collapse and/or endplate deformity were examined in 99 autopsy specimens of the thoracolumbar spine with benign and malignant disease. Angling of endplates was found to be highly predictive of underlying malignancy, whereas concavity was more suggestive of benign disease, for both individual vertebral bodies and intact spines (P less than .001). Diffuse-concave, diffuse-angled, and focal-angled patterns were more useful (P less than .001) than the focal-concave pattern (P = .07) in distinguishing between benign and malignant disease for superior endplates, whereas all were equally useful (P less than .025) in inferior endplates. Condition of the adjacent disks, location within the spine, and position of the apex of collapse were not predictive. Although these results and subsequent blinded testing suggest that reliable distinction between benign and malignant vertebral collapse is possible, extrapolation to clinical practice may be inappropriate because of population bias in the study and differences in radiographic quality between autopsy specimens and live subjects.     

Does the perception of downloading speed influence the evaluation of web-based lectures?

Medical schools put little emphasis upon education on public health, even though public health has played an important role in this century. One way to harness its benefit in order to improve global health in the 21st century is to globally share lectures on public health through the Internet. We have developed the Supercourse comprising of web-based learning modules on epidemiology in a standardized format with the size of each web page less than 10 kilobytes. A cross-sectional observational study was conducted to investigate the association of the perception of the access speed to Web-based lectures by teachers with their perception of lecture quality. There were 223 teachers who rated the lectures: 72% were from North America or Western Europe, 40% had taught epidemiology, and 14% reported that the speed of access was slow. Odds ratio of above-average rating among those who reported that the speed of access was fast relative to those who reported that the speed of access was slow was 4.25 (2.03-8.91; P = 0.001). The odds ratios were similar and significant after taking into account several other factors, including the variation of rating across lectures, region, and experiences in teaching epidemiology. The results indicate that the perception of the quality of Web-based lectures is related to the speed of access to a web page. The speed of access may be as important, if not more important, as the content itself. This suggests that, to share educational materials on the Web globally for teachers, one must consider not only the content, but also how people at local sites gain access to the Internet.     

Na+–Ca2+ exchange current from rabbit isolated atrioventricular nodal and ventricular myocytes compared using action potential and ramp waveforms

We measured and compared Na–Ca exchanger current (I_Na–Ca) from rabbit isolated ventricular and atrioventricular (AV) nodal myocytes, using action potential (AP) and ramp voltage commands. Whole cell patch‐clamp recordings were made at 35–37 °C; I_Na–Ca was measured as 5 m M nickel (Ni)‐ sensitive current with major interfering voltage and calcium‐activated currents blocked. In ventricular cells a 2‐s descending ramp elicited I_Na–Ca showing outward rectification and a reversal potential (E_rev) of –13.1 ± 1.2 mV (n = 12; mean ± SEM). With a ventricular AP as the voltage command, the profile of I_Na–Ca followed the applied waveform closely. The current–voltage relation during AP repolarization was almost linear and showed an E_rev of –38.3 ± 5.3 mV (n = 6). As I_Na–Ca depended on the applied voltage waveform, comparisons between the two cell types utilized the same command waveform (a series of AV nodal APs). In ventricular myocytes this elicited I_Na–Ca that reversed near –38 mV and was inwardly directed during the pacemaker potential. This command was also applied to AV node cells; mean I_Na–Ca density at all voltages encompassed by the AP (–70 to +30 mV) did not differ significantly from that in ventricular myocytes (P > 0.05, ANOVA ). This finding was confirmed using brief (250 ms) voltage ramp protocols (P > 0.1 ANOVA ). These data represent the first direct measurements of AV nodal I_Na–Ca and suggest that the exchanger may be functionally expressed to similar levels in the two cell types. They may also suggest a possible role for I_Na–Ca during the pacemaker potential in AV node as inward I_Na–Ca was observed over the pacemaker potential range even with bulk internal Ca buffered to a low level.     

Water legislation in the U.S.: an overview of the Safe Drinking Water Act.

Clearly there is a long history of legislative activity related to water quality in the U.S. Each of the recent legislative provisions in the Safe Drinking Water Act and Clean Water Act will put in motion the adoption of an extensive set of regulations. There is virtual assurance that costly regulations will be promulgated and that these regulations will have a disproportionate impact on small systems, and on the institutional mechanisms for managing and operating water and waste water systems.     

Regional variation in shear strength of the bone—Polymethylmethacrylate interface

Many investigators consider the polymethylmethacrylate-bone interface the weakest link in the bone-cement-implant system. Push-out tests, frequently used for in vitro evaluation of the bone-cement interface, produced inconsistent results of shear strength. Therefore, a more reliable model for testing the shear failure of the interface was developed. Better understanding of intrinsic variations in bone quality and geometry of endosteal bone at the interface may yield important insight into the patterns of clinical failure of cemented total joint prostheses.     

Non-invasive trigeminal evoked potentials: normative aging data

A mild electric shock applied to the lower lip was used to elicit reliable evoked potentials from the trigeminal nerve in 50 normal adults who ranged in age from 20 to 69 years. The waveforms were morphologically similar to those observed with invasive procedures. No substantial effects for subject age, side of stimulation, or recording electrode were obtained for any of the individual trigeminal evoked potential amplitudes or latencies. Female subjects tended to have somewhat larger amplitudes and shorter latencies than male subjects. The results suggest that non-invasive procedures produce reliable evoked potential measures of trigeminal nerve function for patients of all ages.     

Demographic characteristics and prevalence of serologic markers among donors who use the confidential unit exclusion process: the Retrovirus Epidemiology Donor Study

BACKGROUND: Most blood centers utilize a confidential unit exclusion (CUE) process, intended to reduce the risk of transfusion-associated infectious diseases by allowing high-risk donors confidentially to exclude their blood from use for transfusion. The effectiveness of this method remains controversial. STUDY DESIGN AND METHODS: Confirmatory or supplemental test results for antibodies to human immunodeficiency virus, human T-lymphotropic virus type I, and hepatitis C virus, as well as hepatitis B surface antigen and syphilis and screening test results for antibodies to hepatitis B core (antigen) and alanine aminotransferase levels were obtained for approximately 1.8 million units donated during 1991 and 1992 at five blood centers within the United States. The prevalences of these infectious disease markers in units that the donors confidentially excluded (CUE+) and units that the donors did not exclude (CUE-) were calculated and examined within demographic subgroups. RESULTS: Units that were CUE+ were 8 to 41 times more likely to be seropositive for antibodies to human immunodeficiency virus and hepatitis C virus, hepatitis B surface antigen, and syphilis and three to four times more likely to react for antibody to hepatitis B core (antigen) or to have elevated alanine aminotransferase levels than units that were CUE- (p < 0.001). The positive predictive value of CUE (the percentage of CUE+ units that were confirmed seropositive for any marker) was 3.5 percent, and the sensitivity of CUE (the percentage of confirmed-seropositive units that were CUE+) was 2.3 percent. CONCLUSION: The current CUE process has low sensitivity and apparently low positive predictive value, and in many cases, it appeared that donors misunderstood it. Yet, CUE was not a “random process,” as CUE+ units were more likely to be seropositive for any infectious disease marker than CUE- units. This suggests that efforts to improve the CUE system may be warranted. As risk factors for transfusion-transmitted infection become more difficult to identify by history-based screening, however, such efforts may have limited effect.     

CENTRAL NEUROGENIC NEUROPROTECTION: PROTECTION OF BRAIN FROM FOCAL ISCHEMIA BY CEREBELLAR STIMULATION

Electrical stimulation of the cerebellar fastigial nucleus (FN) elevates regional cerebral blood flow (rCBF) independently of cerebral metabolism (rCGU) throughout brain. One hour of FN stimulation also reduces, by up to 50%, the volume of the focal ischemic infarction produced by occlusion of the middle cerebral artery in rat. Protected areas correspond to the ischemic penumbra. Neuroprotection, while reversible, persists for weeks after 1h of stimulation. It cannot be attributed to increasing rCBF and/or reducing rCGU to improve matching of flow and metabolism. Conditional stimulation of FN initiates long-lived inhibition of expression of peri-infarction depolarizing waves, possibly by altering potassium-channel function and suppresses induction of inducible nitric oxide synthase (iNOS) and ICAM in cerebral microvessels. The brain contains intrinsic networks which may protect the brain from ischemic injury, possibly by producing widespread and longterm suppression of electrical excitability and/or and expression of proinflammatory molecules.