Occupational lead exposure and hearing loss

Studies of adults, children, and laboratory animals suggest an association between lead exposure and hearing loss. A causal relationship might direct mandated medical surveillance of lead-exposed workers to include audiometric testing. A cross-sectional, computerized dataset was obtained from a private occupational health screening company to examine the relationship between blood lead level and hearing loss. Audiometry and blood lead results were available for 183 workers. A statistically significant correlation was found between blood lead level and an elevated hearing threshold at 400 Hz (P = 0.03); no other frequencies showed such a correlation. This finding suggests either an interaction between nose exposure and lead, interaction of other exposure factors (such as cigarette smoking), or that factors other than biomechanical ones render the organ of Corti more susceptible at 4000 Hz. Further evaluation of these questions should be undertaken. Computerized databases created for worker surveillance may be a source for data useful for examining other causal connections in occupational settings.     

Spectral and mode characteristics of InAsSbP/InAsSb/InAsSbP lasers in the spectral region near 3.3 µm

The characteristic features of the continuous-wave lasing spectra near 3.3 μm of multimode InAsSbP/InAsSb/InAsSbP double-heterostructure diode lasers are shown. The observation of mode switching to longer and shorter wavelengths at cryogenic temperatures is reported. It is shown that suppression of the longitudinal side modes closest to the main mode results in large mode jumps in energy during mode tuning by current. The characteristics which were observed are explained by gain spectrum inhomogeneity due to spectral hole burning in narrow-gap semiconductors. The intraband charge-carrier relaxation times in the active region are estimated. Fiz. Tekh. Poluprovodn. 39, 1139–1144 (September 1998)     

Circular stereotactic callosotomy: a preliminary report. Technical note

The authors propose a new method for performing stereotactic callosotomy, which they have named circular callosotomy. The operating device is the original Riechert-Mundinger's string electrode, which can be protruded through a side window and by rotating the probe it is possible to cut the commisural pathways to the extent required. The anatomical results of the operation can be checked using MRI scanning.     

Relationships between H-NS, sigma S, SpvR and growth phase in the control of spvR, the regulatory gene of the Salmonella plasmid virulence operon

We propose that chronically denervated Schwann cells may be less able to respond to axonal signals than their acutely denervated counterparts, and that this lack of sensitivity may be one reason why axons fail to regenerate into chronically denervated nerve stumps. To test this proposal we have used in situ hybridization, and quantitative and qualitative immunohistochemistry to compare the expression of c-erbB2 and c-erbB4 receptors in Schwann cells denervated for up to 6 months in vivo, with that seen in Schwann cells denervated for similar periods of time but then exposed to regenerating axons. The results were correlated with the extent of axonal regeneration in each experimental group as assessed from transverse sections which had been double-immunolabelled using anti S-100 and anti-beta tubulin III antibodies. Since c-erbBs are receptors for neuronally derived neuregulins we probed the appropriate axotomised DRG neurons for expression of GGF2 mRNA. When the denervated distal stumps were anastomosed to acutely transected proximal stumps, GGF expression in DRGs increased transiently during the first week: we assume that secreted GGF2 derived from regrowing axon sprouts would have been available to Schwann cells in all distal stumps. Endoneurial cell proliferation (predominantly Schwann cell proliferation); levels of expression of c-erbB receptors by Schwann cells, and the degree to which axons regenerated into the distal stumps all decreased as the period of prior denervation increased: the longer the time of denervation, the lower the expression of c-erbBs in Schwann cells, and the smaller the percentage of bands of Bungner which were re-innervated.     

Perturbation in the 240Pu/239Pu global fallout ratio in local sediments following the nuclear accidents at Thule (Greenland) and Palomares (Spain)

Diabetes complicates 2-3% of all pregnancies and is associated with an increase in both perinatal morbidity and mortality, though reasons for these adverse outcomes are unknown. Estrogen biosynthesis is a critical factor during pregnancy and is carried out in the placenta via aromatase (cytochrome P450 19A1), which catalyzes the conversion of C-19 androgens to C-18 estrogens. Previous studies have shown that hormones such as insulin-like growth factors and insulin regulate aromatase activity when studied in vitro. Interestingly, levels of these hormones are altered in patients with diabetes. Thus, we hypothesized that the presence of maternal diabetes may alter placental aromatase activity and thus estrogen biosynthesis, possibly serving as one factor in the adverse outcomes of babies born to mothers with diabetes. To this end, we measured the production of 19-hydroxyandrostenedione, 19-oxoadrostenedione and estrone in 30 placental tissues from diabetic patients, using [7-3H]androst-4-ene-3,17-dione as a model substrate for aromatase (P450 19A1). A statistical difference was detected in the percentage of 19-oxoandrostenedione formed between the overt and control groups (P < 0.05). Additionally, NADPH P450-reductase levels were measured in these same tissues to determine whether alterations in this enzyme necessary for aromatase activity could be affected by diabetes. No differences in reductase levels were detected among the patient groups. However, a statistical correlation was found between NADPH P450-reductase activity and the formation velocities of all three estrogen products (P < 0.05). Thus, it appears that the presence of diabetes does not affect placental aromatase activity.     

Evidence for interaction between transmembrane segments in assembly of Kv1.3

Previously, we showed that the N-terminal recognition domain (T1) of Kv1.3 was not required for assembly of functional channels [Tu et al. (1996) J. Biol. Chem. 271, 18904-18911]. Moreover, specific Kv1.3 peptide fragments including regions of the central core are able to inhibit expression of current produced from a channel lacking the T1 domain, Kv1.3(T1-). To elucidate the mechanism whereby Kv1.3 peptide fragments suppress Kv1.3(T1-) current, we have studied the ability of peptide fragments containing the transmembrane segments S1, S1-S2, or S1-S2-S3 to physically associate with the Kv1.3(T1-) polypeptide subunit in vitro in microsomal membranes. Using c-myc (9E10) epitope-labeled peptide fragments and anti-myc antibody as well as antisera to the Kv1.3 C-terminus, we now demonstrate specific association of these peptide fragments with Kv1.3(T1-). Association of peptide fragments with Kv1.3(T1-) was correlated with integration of both proteins into the membrane. Furthermore, the relative strength and kinetics of this association directly correlated with the ability of fragments to suppress Kv1.3(T1-) current. The rate-limiting step in the sequential synthesis, integration, and formation of a complex was the association of integrated polypeptides within the plane of the lipid bilayer. These results strongly suggest that the physical association of transmembrane segments provides the basis for suppression of K+ channel function by K+ channel peptide fragments in vivo. Moreover, the S1-S2-S3 peptide fragment potently suppressed full-length Kv1.3, thus implicating a role for the S1-S2-S3 region of Kv1.3 in the assembly of the Kv1.3 channel. We refer to these putative association sites as IMA (intramembrane association) sites.     

Guidelines for management of left-sided prosthetic valve thrombosis: a role for thrombolytic therapy. Consensus Conference on Prosthetic Valve Thrombosis

OBJECTIVES: We sought to form a consensus recommendation for management of prosthetic valve thrombosis (PVT) from previous case and uncontrolled reports from a consensus of international specialists. BACKGROUND: PVT and thromboembolism relate to inadequate anticoagulation and valve type and location. PVT is suspected by history (dyspnea) and auscultation (muffled valve sounds or new murmurs) and confirmed by Doppler echocardiography showing a marked valve gradient. METHODS: A consensus conference was held to recommend management of left-sided PVT. RESULTS: Transesophageal Doppler echocardiography is used to visualize abnormal leaflet motion and the size, location and mobility of thrombus. Thrombolysis is used for high risk surgical candidates with left-sided PVT (New York Heart Association functional class III or IV) because cerebral thromboembolism may occur in 12% of patients. Duration of thrombolysis depends on resolution of pressure gradients and valve areas to near normal by Doppler echocardiography performed every few hours. Lysis is stopped after 72 or 24 h if there is no hemodynamic improvement (operation indicated). Heparin infusion with frequent measurement of activated partial thromboplastin time (aPTT) begins when aPTT is more than twice control levels and can be converted to warfarin (international normalized ratio [INR] 2.5 to 3.5) plus aspirin (81 to 100 mg/day). Patients in functional class I or II have lower surgical mortality, and those with large immobile thrombi on the prosthetic valve or left atrium have responded to endogenous lysis with combined subcutaneous heparin every 12 h (aPTT 55 to 80 s) plus warfarin (INR 2.5 to 3.5) for 1 to 6 months. Operation is advised for nonresponders or patients with mobile thrombi. CONCLUSIONS: Thrombolysis, followed by heparin, warfarin and aspirin, is advised for high risk surgical candidates with left-sided PVT.     

1.04 GBd low EMI digital video interface system using small swingserial link technique

In a high-resolution flat panel system, a conventional interface that directly connects a liquid crystal display (LCD) controller to a flat panel cannot overcome the problems of excess EMI (electromagnetic interference) and power caused by full-swing transmission signals in parallel lines. This paper presents a high-speed digital video interface system implemented with a low-cost standard CMOS (complimentary metal-oxide-semiconductor) technology that can mitigate EMI and power problems in high-resolution flat panel display systems. The combined architecture of the high-speed, small number of parallel lines and low-voltage swing serial interface can support resolutions from VGA (640×480 pixels) up to XGA (1024×768 pixels) with significant power improvement and drastic EMI reduction. To support high-speed, low-voltage swing signaling and overcome channel-to-channel skew problems, a robust data recovery system is required. The proposed digital phase-locked loop enables robust skew-insensitive data recovery of up to 1.04 GBd     

A Metallographic Study of the High-Temperature Decomposition of Austenite in Alloy Steels Containing Mo and Cr

Optical and electron microscopy have been used to study the complex microstructures developed during the isothermal decomposition of austenite above 550°C in Fe-4Mo-0.2C and Fe-10Cr-0.4C alloy steels. As the transformation temperature is decreased, the decomposition products change from the disordered growth of nodular alloy pearlites to blocky ferrite structures containing fine dispersions of alloy carbide, and finally to acicular ferrite structures also containing alloy carbide. The branched M₆C and M₂₃C₆ of the high-temperature pearlite is replaced by Mo₂C and M₇C₃ with a fibrous or lath morphology in the lower temperature structures. The decomposition microstructures are explained in terms of a model which takes account of the growth of particular alloy carbides at the interfaces of ferrite allotriomorphs, where the growth mechanism, and hence the morphology, is sensitive to transformation temperature.     

Electrophysiological properties and cholinergic responses of rat ventral oral pontine reticular neurons in vitro

This study analyses the relationship between the use of rotating instruments, the production of a smear layer and the presence of alterations to enamel microstructures. The rotating instruments used were carbide (8-12 blade) and diamond tipped (30-15 m) cutters. Cavities were made in extracted teeth. Subsequently, half the sample was analysed using the rugosimeter before and after the application of ortophosphoric acid at 35% for 15 and the other half suing a Scansion Electronic microscope (SEM). The results obtained showed on the one hand that carbide cutters leave a smoother surfacer than diamond tipped cutters, and on the other that the smear layer is eliminated better by carbide cutters compared to diamond tipped cutters. Moreover, there are no major traumatic-type alterations at the level of the enamel affecting the microstructure after the use of carbide cutters.