Doxycycline pleurodesis in rabbits: comparison of results with and without chest tube

We have reported previously that there is a high incidence of hemothorax and substantial mortality in rabbits that are given tetracycline derivatives intrapleurally. However, such complications have not been reported in humans when pleurodesis is attempted with tetracycline derivatives. One primary difference in the two situations is that a chest tube is placed only in humans. The objective of this study was to evaluate the hypothesis that chest tube placement would prevent the development of hemothoraces and lead to better pleurodesis in rabbits given doxycycline intrapleurally. Eighty New Zealand White male rabbits received doxycycline, 20 mg/kg, in a total volume of 2 mL. One half of the rabbits were randomized to receive a chest tube at the time of the injection and were subjected to pleural fluid aspiration twice daily. The remaining rabbits (control group) received no chest tube and no aspiration. Ten rabbits from each group were killed on days 4, 7, 14, and 28. The intrapleural injection of doxycycline induced the production of large exudative effusions. The insertion of chest tubes prevented the development of hemothorax (0/20 in chest tube group, 15/20 in control group, p<0.001). The insertion of chest tubes was also associated with a significant reduction in mortality and a significant improvement in pleurodesis. When pleurodesis is attempted in rabbits with intrapleural doxycycline, the insertion of a chest tube will prevent hemothorax and lead to a better pleurodesis.     

Laser in situ keratomileusis for myopia and astigmatism: 6 month results

The increasingly popular immunohistochemical techniques for assay of the estrogen receptor (ER) allow localization of receptor positivity to specific cell populations. Heterogeneity of the ER in tumor cell populations may have important implications for analytic cell selection and for prognosis in ER-positive carcinomas. We studied 84 tissue blocks for level-to-level and geographic heterogeneity within level of the ER and cytokeratin by staining alternate serial sections for ER and cytokeratin. Distribution of ER and cytokeratin positivity was manually assessed. Homogenous positive staining was seen in 63 of 84 cases for ER and 71 of 84 cases for cytokeratin. Distinct geographic variability constant from level to level was seen in 7 cases for ER. In each of these cases, the cell populations stained uniformly for cytokeratin. Artifactual heterogeneity seemed to be uncommon for ER. Automated image analysis and manual ER estimation resulted in more positive cases than did the dextran-coated charcoal (DCC) technique. Interobserver correlation for the manual method seemed high, as did correlation between the manual method and image analysis. Because a majority of the immunohistochemical staining heterogeneity for ER seemed to be biologic, we believe it may mark carcinomas that are less responsive to tamoxifen and more likely to progress than would be predicted by more traditional methods of ER analysis.     

Increased production of amyloid precursor protein provides a substrate for caspase-3 in dying motoneurons

Biochemical and molecular mechanisms of neuronal cell death are currently an area of intense research. It is well documented that the lumbar spinal motoneurons of the chick embryo undergo a period of naturally occurring programmed cell death (PCD) requiring new gene expression and activation of caspases. To identify genes that exhibit changed expression levels in dying motoneurons, we used a PCR-based subtractive hybridization protocol to identify messages uniquely expressed in motoneurons deprived of trophic support as compared with their healthy counterparts. We report that one upregulated message in developing motoneurons undergoing cell death is the mRNA for amyloid precursor protein (APP). Increased levels of APP and beta-amyloid protein are also detected within dying motoneurons. The predicted peptide sequence of APP indicates two potential cleavage sites for caspase-3 (CPP-32), a caspase activated in dying motoneurons. When peptide inhibitors of caspase-3 are administered to motoneurons destined to undergo PCD, decreased levels of APP protein and greatly reduced beta-amyloid production are observed. Furthermore, we show that APP is cleaved by caspase-3. Our results suggest that differential gene expression results in increased levels of APP, providing a potential substrate for one of the cell death-activated caspases that may ultimately cause the demise of the cell. These results, combined with information on the toxic role of APP and its proteolytic by-product beta-amyloid, in the neurodegenerative disease Alzheimer's, suggest that events of developmental PCD may be reactivated in early stages of pathological neurodegeneration.     

Using a biological indicator to detect potential sources of cross-contamination in the dental operatory

The authors conducted a study using surveillance monitoring methodology to identify operatory contamination and to evaluate the effectiveness of infection control procedures. Viridans streptococci were evaluated as biological indicators of oral contamination. Viridans streptococci, abundant in human saliva, were detected on operatory surfaces after dental treatments were finished and surfaces were disinfected. The findings validate current concepts of infection control as demonstrated in barrier methods.     

Risk of severe malaria among African infants: direct evidence of clinical protection during early infancy

Little empirical evidence from field-based studies exists on the relative magnitude or duration of clinical protection from Plasmodium falciparum malaria in infancy. A prospective study was undertaken to examine the age distribution of hospital admissions in four geographically and demographically well-defined areas with differing intensities of P. falciparum transmission. Where transmission was perennial, significant clinical protection from severe morbidity was observed up to the third month of life; in the seasonal transmission area, disease rates rose after the sixth month of life. Infants exposed to the highest rates of P. falciparum exposure demonstrated significant declines in the risks of severe malaria from 6 months of age. These data provide direct evidence for the very early acquisition of clinical immunity and for the existence of a period of clinical protection, which together may explain why, in these communities, the cumulative risk of malarial disease throughout childhood appears to decline with increasing transmission intensity.     

Comparison of performances of displacement and mixing ventilations. Part II: indoor air quality

A numerical simulation using a validated computational fluid dynamics model is used to investigate and compare the performances of displacement and mixing ventilations (MVs), under different boundary conditions. A companion paper will report the results in terms of thermal comfort, while this paper investigates the indoor air quality (IAQ). The IAQ will be measured in terms of carbon monoxide, mean age of air and the three volatile organic compounds, toluene, benzene and formaldehyde, which are commonly found in indoor room furnishings. The case studies include offices, classrooms, retail shops and industrial workshops, under typical Hong Kong thermal boundary conditions. Compared with conventional MV, displacement ventilation may provide better IAQ in the occupied zone.     

An automatic tracking system for phase-noise measurement

A low cost, automatic tracking system for phase noise measurement has been implemented successfully. The tracking system is accomplished by applying a charge pump phase-locked loop as an external reference source to a digital spectrum analyzer. Measurement of a 2.5 GHz, free-running, voltage-controlled oscillator demonstrated the tracking accuracy, thus verifying the feasibility of the system.     

Enhancement of a genetic algorithm for affine invariant planar object shape matching using the migrant principle

The use of the migrant principle has proved to be effective in reducing the impact of the initial populations of genetic algorithms in optimising simple linear functions. Analytical and empirical results have also suggested that the method could be applied to locate an optimal solution in larger search space with more complex landscape. In the paper, an attempt has been made to develop an enhanced object matching technique that is based on the integration of the migrant principle and an existing genetic algorithm for affine invariant object recognition. As the latter had been taken as the foundation of a series of research works, any improvement on the scheme will directly benefit subsequent developments. The problem being addressed is highly nonlinear, which requires well-formed initial populations to attain successful matching of object shapes. Experimental results reveal that, for the same population size and mutation rate, the proposed method demonstrates significant improvement, as compared with its precedent, and that it is insensitive to the initial population.     

Gain and carrier lifetime measurements in AlGaAs multiquantum well lasers

We have measured the gain and the carrier lifetime at threshold in shallow proton stripe AlGaAs multiquantum well lasers with several different active layer structures. The lasers studied had active layers with two wells, four wells, six wells, and the modified multiquantum well. The net gainGis found to vary almost linearly with the injection currentIfor all the laser structures studied. The slopedG/dIis largest for the modified multiquantum well (MMQW) laser which is consistent with the observed lowest threshold current of these devices. We find that the carrier density at threshold for the MMQW laser is about a factor of 4 lower than that for a single quantum well laser. Thus, the effect of a nonradiative mechanism (e.g., Auger effect) which varies superlinearly with the injected carrier density is considerably reduced in MMQW lasers compared to that in single quantum well (SQW) lasers or the conventional double heterostructure lasers. The reduced threshold carrier density of the MMQW lasers has important implications for high temperature performance of lasers fabricated from the InGaAsP/InP material systems which are believed to have nonradiative mechanisms that vary superlinearly with carrier density, particularly for those laser structures for which the high temperature operation is not limited by leakage current.