Exercise-induced hypoxemia in athletes: role of inadequate hyperventilation

These experiments examined the exercise-induced changes in pulmonary gas exchange in elite endurance athletes and tested the hypothesis that an inadequate hyperventilatory response might explain the large intersubject variability in arterial partial pressure of oxygen (PaO2) during heavy exercise in this population. Twelve highly trained endurance cyclists [maximum oxygen consumption (VO2max) range = 65-77 ml.kg-1.min-1] performed a normoxic graded exercise test on a cycle ergometer to VO2max at sea level. During incremental exercise at VO2max, 5 of the 12 subjects had ideal alveolar to arterial PO2 gradients (PA-aO2) of above 5 kPa (range 5-5.7) and a decline from resting PaO2 (delta PaO2) 2.4 kPa or above (range 2.4-2.7). In contrast, 4 subjects had a maximal exercise PA-aO2 of 4.0-4.3 kPa with delta PaO2 of 0.4-1.3 kPa while the remaining 3 subjects had PA-aO2 of 4.3-5 kPa with delta PaO2 between 1.7 and 2.0 kPa. The correlation between PAO2 and PaO2 at VO2max was 0.17. Further, the correlation between the ratio of ventilation to oxygen consumption vs PaO2 and arterial partial pressure of carbon dioxide vs PaO2 at VO2max was 0.17 and 0.34, respectively. These experiments demonstrate that heavy exercise results in significantly compromised pulmonary gas exchange in approximately 40% of the elite endurance athletes studied. These data do not support the hypothesis that the principal mechanism to explain this gas exchange failure is an inadequate hyperventilatory response.

Optical coherence tomography

A technique called optical coherence tomography (OCT) has been developed for noninvasive cross-sectional imaging in biological systems. OCT uses low-coherence interferometry to produce a two-dimensional image of optical scattering from internal tissue microstructures in a way that is analogous to ultrasonic pulse-echo imaging. OCT has longitudinal and lateral spatial resolutions of a few micrometers and can detect reflected signals as small as approximately 10(-10) of the incident optical power. Tomographic imaging is demonstrated in vitro in the peripapillary area of the retina and in the coronary artery, two clinically relevant examples that are representative of transparent and turbid media, respectively.

Femtosecond pulse generation in Ti:Al(2)O(3) using a microdot mirror mode locker

A new nonlinear intracavity device called a microdot mirror mode locker is demonstrated for ultrashort-pulse generation in solid-state lasers. The microdot mirror produces fast saturable absorber action by using self-focusing. Pulse durations of 190 fs are achieved in a Ti:A1(2)O(3) laser. The microdot mirror mode locker is modular, preserves wavelength tunability, and can be extended to a wide range of solid-state lasers.

Emergence of a virulent clone of Neisseria meningitidis serotype 2a that is associated with meningococcal group C disease in Canada

Multilocus enzyme electrophoresis was used to characterize 378 isolates of Neisseria meningitidis serogroup C recovered during a period of an increase in group C meningococcal disease in Canada. Thirty-four enzyme electrophoretic types were found among the isolates, which were predominantly (96.0%) serotype 2a. One clone (ET 15), characterized by a rarely occurring allele for the enzyme fumarase, was responsible for a focal outbreak in Ontario followed by the spread of group C disease across the province. This clone, which occurred infrequently among strains isolated in 1986, accounted for over 65% of group C strains associated with meningococcal disease in Canada in 1990.

Electrostatic destabilization of the cytochrome b6f complex in the thylakoid membrane

Three of the membrane-spanning polypeptides of the chloroplast cytochrome (cyt) b6f complex were sequentially released from the thylakoid membrane, in the order cyt b6, suIV and Rieske iron-sulfur protein, as the pH was increased from 10 to 12, a protocol usually employed to remove peripheral proteins from membranes. The fourth polypeptide of the cyt b6f complex, cyt f, which spans the membrane once, was apparently not released. The pH values for half-release at low ionic strength were approximately 10.7, 11.1 and 11.3 respectively. The separation of the polypeptides of the complex and the sequential release is readily seen at pH 11, where the loss from the membrane of cyt b6, suIV and Fe iron-sulfur center is approximately 90%, 50% and 20%, respectively. the release of cyt b6 from the membrane was reflected by the absence of its characteristic reduced minus oxidized absorbance signal. The pH values at which the release occurred increased as the ionic strength was raised, implying that the release of the b6f polypeptides arises from extrusion due to repulsive electrostatic interactions probably caused by deprotonation of tyrosine and lysine residues. The lipid content of the released polypeptides was very low, consistent with the observation of a non-membranous state. It is proposed that the pH-dependent extrusion requires two electrostatic effects at alkaline pH higher than approximately 10.5: (i) increased electrostatic repulsion between neighbouring polypeptides of the complex, arising from increased net negative charge in the peripheral segments of these polypeptides, which can cause separation of the polypeptides from the complex; and (ii) ionization of residues such as tyrosine in the membrane-spanning alpha-helices, and neutralization of residues such as lysine which can bind to the negative membrane surface.(ABSTRACT TRUNCATED AT 250 WORDS)

Cymelarsan in the treatment of buffaloes naturally infected with Trypanosoma evansi in south China

Forty buffaloes naturally infected with Trypanosoma evansi in the South of China were treated with a single dose of a new arsenical. Cymelarsan (Mel Cy) at 0.25 mg/kg to 3.0 mg/kg by intramuscular injection. All animals were cured, with the exception of two out of four animals treated with 0.25 mg/kg Mel Cy which relapsed two months after drug administration. Two out of eight buffaloes in control groups treated with a single dose of diminazene aceturate (Berenil), 3.5 mg/kg, relapsed two months after treatment. All cured animals showed no trypanosomes in their blood when tested within one to three years after administration. A scleroma about 2 to 3.5 cm in diameter was found at the site of injection at the dose of 1.5 mg/kg Mel Cy in three of eight animals. At a dose of 3 mg/kg, Mel Cy induced obvious necrosis of the tissue at the site of injection. The results of field application proved that Mel Cy is a very active trypanocidal drug against T. evansi.

Micron-resolution ranging of cornea anterior chamber by optical reflectometry

Noncontact, high resolution measurements of anterior eye structures using optical coherence domain reflectometry are described. Distances between intraocular structures are measured by directing a beam of short coherence length light onto the eye and performing an interferometric measurement on the optical group delay of reflected signals. Measurements of corneal thickness, corneal excision depth, and anterior chamber depth are demonstrated in vitro, and the location of tissue boundaries is resolved to within +/- 2 microns. The full-width-half-maximum longitudinal resolution is 10 microns. Sensitivities to reflected signals as small as 10(-10) of the incident power are achieved by heterodyne detection.

Preliminary studies of serum glycoconjugates in patients with cancer using the enzyme-linked lectin assay

After primary analyses on the serum glycoconjugates of lung cancer and normal individual using the enzyme-linked lectin assay (ELLA) with 12 kinds of lectins, PHA and LCA were selected for further study in the sera of 8 kinds of cancers, 4 kinds of non-malignant diseases and a kind of postoperative cancer. It was found that the test values of 7 kinds of cancers with PHA or LCA were significantly higher than those of the normal (P less than 0.01); the values of 4 kinds of non-malignant diseases with PHA were not higher (P greater than 0.05); the values of the postoperative cancer with PHA were obviously lower than those of the preoperative (P less than 0.02). The results showed that the serum glycoconjugates which can bind to PHA seemed related to the cancerous existence in human bodies. The significance of the findings was discussed.

Epstein-Barr virus (EBV)-containing nasopharyngeal carcinoma cells express the B-cell activation antigen blast2/CD23 and low levels of the EBV receptor CR2

Anaplastic nasopharyngeal carcinoma (NPC) cells invariably harbor the Epstein-Barr virus (EBV) genome, an association that is unique among human virus-associated cancers. Although EBV is able to replicate in epithelial cells, results with expression of the EBV receptor (complement receptor type 2 [CR2]; also called CD21) in normal and malignant epithelial cells are conflicting. We grew five different EBV-associated NPC tumors in nude mice, and by using a sensitive transcriptional assay, we detected a very weak transcription signal of the EBV receptor CR2 gene in these cells. This suggests that low levels of EBV receptor may be expressed by malignant epithelial nasopharyngeal cells. The gene coding for Blast2/CD23, a B-cell activation molecule induced by EBV, was transcribed in three of the transplanted NPC tumors. The soluble form of the Blast2/CD23 protein was also detected in medium taken from short-term cultures of the same NPC cell lines. In contrast to the lymphoid system, in which Blast2/CD23 expression is associated with EBV nuclear antigen (EBNA2) expression, no EBNA2 protein could be detected in these NPC epithelial cells. Our study represents the first demonstration of Blast2/CD23 expression in epithelial cells. As the soluble form of the Blast2/CD23 protein possesses growth factor activity associated with EBV-induced B-cell immortalization, these results suggest a possible role for this molecule in the pathogenesis of NPC.

Dose parameters of 125I and 192Ir seed sources

As mandated by an NCI brachytherapy contract, we measured dosimetric parameters for 192Ir seeds and two models of 125I seeds. Measurements were with LiF powder in a water-equivalent phantom. Data were corrected for background, sample mass, and finite detector volume. Selected parameters were also investigated through Monte Carlo calculations. Results are presented in terms of a dose parametrization that is described in detail, and are compared to published data. Our results agreed well with published data for relative quantities such as radial and angular dose dependence. Our measured value for the 192Ir dose factor was 4.55 cGy(H2O) cm2 mCi-1 h-1, also in good agreement with commonly used values. However, the measured dose factors for 125I seed models 6702 and 6711 were 1.18 and 1.06 cGy(H2O) cm2 mCi-1 h-1, values well below those in general use.