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Biomedical subjects

E C Young

Publications and source records attributed to E C Young.

At least 37 records · Page 2Linked to original sources
PubMed1997

A survey of radon and thoron progeny for dwellings in Hong Kong.

The potential alpha energy concentrations of radon and thoron progeny have been surveyed for dwellings in Hong Kong and the mean values are obtained as 3.58 and 2.29 mWL, respectively. The relative importance of the value for thoron is unexpectedly high, which is attributed to the high 232Th content of the building materials used in Hong Kong. It has also been found that the potential alpha energy concentration values for radon progeny changed dramatically with the season due to the different aerosol contents in the air in different seasons. The factors affecting the potential alpha energy concentration values have also been studied. These factors fall into three categories, namely (1) the building characteristics including age of the buildings, wall coverings and floor coverings; (2) the location of sites including nearby environments and the elevation of the sites; and (3) the meteorological parameters including wind speed, atmospheric pressure, air temperature and relative humidity. For categories (1) and (2), all factors seem to affect the potential alpha energy concentration values, although the effects may be different for radon and thoron progeny, which may be due to the very much different half lives of radon and thoron gas and to the different behavior of radon and thoron progeny in the attachment to aerosols. For category (3), only wind speed has been found to have effects.

Construction Materials↗
PubMed1996

Agonist-induced desensitization and down-regulation of delta opioid receptors alter the levels of their 125I-beta-endorphin cross-linked products in subcellular fractions from NG108-15 cells.

The delta opioid binding sites in subcellular fractions from NG108-15 cells were characterized with respect to their relative molecular size and levels under conditions of receptor adaptation. 125I-beta-Endorphin was cross-linked to preparations enriched in plasma membranes (P20), nuclear membranes or nuclear matrices. Five cross-linked bands appear in all subcellular fractions. The largest molecular size reaction product in nuclear matrix preparations (approximately 72 kDa) differed from that in the other two fractions-(approximately 83 kDa). Immunoblot analyses with an antibody to the delta opioid receptor gave a P20 band pattern similar to that for the corresponding cross-linked products. To determine which cross-linked products in P20 are glycoproteins, labeled membranes were solubilized and purified by wheat germ agglutinin chromatography. The absence of a approximately 36 kDa band after purification suggests that this product is not a glycoprotein. The remaining four bands were present in N-acetyl-D-glucosamine eluates, although their % distribution changes in favor of the largest molecular size band (approximately 83 kDa). Immunoblotting of the eluate gave a single diffuse band at approximately 73 kDa, suggesting the native glycoprotein has a molecular size in the 70-80 kDa range. Etorphine-induced desensitization of cell surface receptors increased the amount of some cross-linked products associated with nuclear membranes. The same treatment did not affect the relative density of the four larger molecular size bands in P20, but increased the density of the approximately 26 kDa product two fold. Etorphine-induced down-regulation evoked an elevation of cross-linked products in nuclear matrix preparations, while all band densities of P20 were diminished. These results suggest that nuclear matrix associated opioid binding sites represent internalized, truncated forms of the glycosylated delta opioid receptor found in P20.

Cell Line↗
PubMed1996

A study of factors affecting indoor radon properties.

The factors affecting indoor radon properties in Hong Kong have been studied, including the radon concentration, the total potential alpha energy concentration of radon progeny, the equilibrium factor, and the fraction of unattached radon progeny. These factors fall into three categories, namely, (1) the building characteristics, including cooling method, age of the buildings, wall coverings and floor coverings; (2) the location of sites, including nearby environments, geological materials of the area, and the elevation of the sites; and (3) the meteorological parameters, including rainfall, relative humidity, pressure, temperature, and wind speeds. For category (1), only the ventilation is found to affect the indoor radon properties. For category (2), only the nearby environments have effects. For category (3), the rainfall and temperature are found to have significant effects.

Air Pollutants, Radioactive↗
PubMed1996

The bioconcentration of 131I in fresh water fish.

The dynamic characteristics of the radionuclide concentration process in fresh water fish have been studied. The experimental data for the tilapias were fitted using a simple compartment model to get characteristic parameters such as concentration factors, elimination rate constants, and initial concentration rates, which are 3.08 Bq kg-1/Bq L-1, 0.00573 h-1, and 12.42 Bq kg-1 h-1, respectively. The relative concentrations of 131I in different parts, i.e., head, gills, flesh, bone and internal organs, of the tilapias are also determined, which are found to be 10.8, 15.4, 26.1, 11.0, and 37.0%, respectively. The effects of different factors on the transfer of radionuclides in fresh water fishes are also discussed. Experiments on the tilapias and the common carp show that the variation of concentration factors for different species may be significant even for the same radionuclide and the same ecological system. On the other hand, the variation in the concentration factors for the flesh of the tilapias is not significant for a certain range of 131I concentrations in the water.

Animals↗
PubMed1995

Subunit interactions in dimeric kinesin heavy chain derivatives that lack the kinesin rod.

The N-terminal residues of the two heavy chains of the motor enzyme kinesin form two globular "heads"; the heads are attached to a "rod" domain which is a two-stranded alpha-helical coiled-coil. Interaction between the heads is thought to be important to kinesin function. The rod may not be necessary for head-head interactions because a heavy chain N-terminal fragment containing only residues from the head and adjacent region forms dimers (Huang, T.-G., Suhan, J., and Hackney, D. D. (1994) J. Biol. Chem. 269, 16502-16507). However, the nature and stability of the subunit-subunit interactions in such derivatives are unclear. To examine the physical properties of heavy chain interaction in and near the head domains, we characterized the self-association behavior of two dimeric kinesin derivatives predicted (Lupas, A., van Dyke, M., and Stock, J. (1991) Science 252, 1162-1164) to lack the rod. Derivative K448-BIO contains the 448 N-terminal residues of Drosophila kinesin heavy chain fused at the C terminus to a 2-residue linker and a C-terminal fragment from Escherichia coli biotin carboxyl carrier protein; derivative K448-L is the same except that it lacks the biotin carboxyl carrier protein fragment. Both derivatives expressed in insect cells display microtubule-stimulated ATPase activity; K448-BIO also displays microtubule motility. Equilibrium sedimentation and gel filtration indicate that purified K448-BIO and K448-L at 0.02-0.4 mg/ml form homogeneous solutions of homodimers with no detectable formation of monomers or higher order oligomers. Derivative self-association is non-covalent but extremely stable with an association constant > or = 2 x 10(8) M-1. Stable subunit-subunit association induced by structures in and near the kinesin heads may be necessary for full mechanochemical function.

Animals↗
PubMed1995

Failure of a single-headed kinesin to track parallel to microtubule protofilaments.

Kinesin, a two-headed motor enzyme molecule, hydrolyses ATP to direct organelle transport along microtubules. As it moves along a microtubule, kinesin remains associated with, or 'tracks', microtubule protofilaments. We have prepared truncated kinesin derivatives that contain either two mechanochemical head domains or only a single head. Unlike intact kinesin and the two-headed derivatives, the one-headed enzyme frequently fails to track protofilaments, suggesting that it detaches from microtubules during movement. In this way, the one-headed kinesin derivative is similar to the motor enzyme myosin, which frequently detaches from the actin filament during movement. For myosin (which has two heads), the consequence of this detachment is that single molecules do not appear to drive continuous movement along the filament. Our observations suggest that the ability of single two-headed kinesin molecules to drive continuous movement results from a 'hand-over-hand' mechanism in which one head remains bound to the microtubule while the other detaches and moves forwards.

Animals↗
PubMed1995

The variation of radon exhalation rates from building surfaces of different ages.

Standardized activated charcoal canisters (according to the U.S. EPA) have been used to collect radon exhaled from concrete surfaces covered with thin plaster (categorically different from thick plaster) of 32 buildings of different ages (0.5-31 y) in Hong Kong. Concrete surfaces covered with thin plaster is the commonest wall configuration in Hong Kong. The canisters are analyzed using gamma spectroscopy to obtain the radon exhalation rates. The results show that the radon exhalation rate decreases with the building age.

Air Pollution, Indoor↗
PubMed1995

A comparison of two photon planning algorithms for 8 MV and 25 MV X-ray beams in lung.

We report results of a comparison of two photon planning algorithms, the Clarkson Scatter Integration algorithm and the Equivalent Tissue-air Ratio algorithm, using a simple lung phantom for 8 MV and 25 MV X-ray beams of field sizes 5 cm x 5cm and 10 cm x 10 cm. Central axis depth-dose distributions were measured with a thimble chamber or a Markus parallel-plate chamber. Dose profile distributions were measured with TLD rods and films. Measured dose distributions were then compared to predicted dose distributions. Both agorithms overestimate the dose at mid-lung as they do not account for the effect of electronic disequilibrium. The Clarkson algorithm consistently shows less accurate results in comparison with the ETAR algorithm. There is additional error in the case of the Clarkson algorithm because of the assumption of a unit density medium in calculating scatter, which gives an overestimate in the effective scatter-air ratios in lung. For a 5 cm x 5 cm field, the error of dose prediction (Dpredicted-Dmeasured) for 25 MV x-ray beam at mid-lung is 15.8% and 12.8% for Clarkson and ETAR algorithm respectively. At 8 MV the error is 9.3% and 5.1% respectively. In addition, both algorithms underestimate the penumbral width at mid-lung as they do not account for the penumbral flaring effect in low density medium. It is very important for medical physicists, radiation therapists and clinicians to be aware of the limitation of their radiotherapy treatment planning systems.

Algorithms↗
PubMed1995

Structural and functional features of one- and two-headed biotinated kinesin derivatives.

The oligomeric structure was determined for four recombinant kinesin derivatives containing N-terminal fragments of the kinesin alpha-subunit. Some of the proteins were dimeric (two-headed) molecules with mechanochemical properties similar to those of intact kinesin. Comparison of the primary and quaternary structures of the derivatives with those of intact kinesin suggests that structures distinct from the long alpha-helical coiled-coil rod domain contribute to subunit self-association. Three of the proteins contain a single engineered site for post-translational biotination in vivo; this facilitates analysis of motility in experiments in which the proteins are specifically bound to streptavidin-conjugated microscopic plastic beads. One of the derivatives is monomeric (one-headed); like the two-headed derivatives, it is functional in the motility assay and is a microtubule-dependent ATPase. Unlike intact kinesin and the two-headed derivatives, the one-headed enzyme fails to track microtubule protofilaments. This confirms a prediction of proposed "hand-over-hand" mechanisms of kinesin movement. The ability of molecules with a one-headed solution structure to generate movement is consistent with a translocation-generating conformational change internal to the kinesin head. A simple set of coupling rules can be used to formulate consistent mechano-chemical mechanisms that explain movement by both one- and two-headed kinesin molecules.

Adenosine Diphosphate↗
PubMed1994

A preliminary study on the radon concentrations in water in Hong Kong and the associated health effects.

Tap water, flushing water and drinking water including natural mineral water, artificial mineral water and distilled water have been investigated for their radon concentrations. It has been found that the radon concentration in natural mineral water samples is the highest and that in tap water is the second highest, while other categories have values very near to the detection limit. From these the corresponding annual effective doses for the stomach and the lung are determined. It is found that annual effective dose due to direct consumption of water (mineral and tap water) is far greater than that due to inhalation of radon emanated from tap water and flushing water. Moreover, it is also shown that the annual effective doses due to inhalation of radon emanated from tap water and flushing water is negligible when compared to the total annual effective dose for indoor radon in Hong Kong.

Hong Kong↗
PubMed1992

Salivary antibody titers in adults challenged with a human rotavirus.

To determine whether salivary antibody is a reliable indicator of rotavirus infection and mucosal rotavirus antibody concentrations, salivary rotavirus antibody titers were determined as a function of time following inoculation of 24 adult volunteers with a virulent strain of human rotavirus (CJN). Twenty of the subjects became infected and all produced detectable amounts of salivary rotavirus IgA. These antibody concentrations remained undetectable in the four uninfected subjects. Rises of greater than or equal to fourfold in either salivary rotavirus IgA or neutralizing antibody to the challenge virus were detected in all but two subjects. The titers of both antibodies were maximal at 13 days after inoculation and decreased significantly (p less than .02) by 27 days, a result very similar to that previously found with stool rotavirus IgA in CJN-infected subjects. These results suggest that salivary rotavirus antibody titers are an accurate reflection of mucosal rotavirus antibody and a possible surrogate for intestinal rotavirus antibody.

Adolescent↗
PubMed1991

Prevention of surface-to-human transmission of rotaviruses by treatment with disinfectant spray.

A model was developed to examine the effects of disinfectants on the transmission of infectious rotavirus from a dried surface to humans. The initial experiments were designed to find a method of preserving rotavirus infectivity during drying. Culture-adapted human rotavirus (CJN strain) was dried at room temperature in different organic suspensions, including fecal matter, several laboratory media, and nonfat dry milk (NDM). Recoveries of infectious virus were then compared. Fecal matter provided little protection in this study relative to distilled water, but the other suspensions were quite protective, especially NDM, which consistently allowed recoveries of greater than 50%. When 10(3) focus-forming units of unpassaged CJN virus were dried in NDM and administered to subjects who licked the dried material, 100% (8 of 8) became infected. The effect of Lysol brand disinfectant spray (LDS) was next examined. Although NDM provided some protection against inactivation by LDS, spraying under conditions recommended by the manufacturer consistently caused the CJN virus titer to decrease greater than 5 log10. Consumption of CJN virus (10(3) focus-forming units) sprayed with LDS caused no infection in 14 subjects, whereas 13 of 14 subjects who consumed the unsprayed virus became infected (P less than 0.00001). The methods developed in this study could be used to test the effects of other disinfectants on the spread of infectious rotavirus from inanimate surfaces to humans.

Adolescent↗
PubMed1991

Characteristics of age-related language decline in adults with Down syndrome.

Age-related declines in language and other neuropsychological variables were examined in 60 adults with Down syndrome. Researchers have found that deterioration in functioning is present in most adults with Down syndrome if they live to be 35 years of age. Declines have typically been interpreted as symptoms of Alzheimer disease; however, the declines are not well-understood, and alternative explanations have been suggested. Our results showed significant relations between aging and language comprehension and aging and self-help skills. Verbal skills were not significantly related to aging and little variation occurred between the youngest and the oldest subjects. Guidelines for choosing appropriate criteria to examine the loss of language skills in this population were discussed.

Adult↗
PubMed1990

Developing a dysphagia program in an acute care hospital: a needs assessment.

A needs assessment for a hospital-based dysphagia program was conducted to determine incidence, management procedures, and outcome for stroke patients with swallowing disorders. Using a chart review of 225 patients, it was found that 28% had documented evidence of dysphagia. When dysphagia co-occurred with stroke, significantly more functional problems and medical complications were reported, as well as increased need for dietary modifications and alternative feeding methods. The dysphagic patients were more often aphasic and dysarthric and less able to communicate. Mental status was more likely to be reduced and the need for staff supervision during mealtime was increased. Dysphagic patients had significantly longer hospital stays, thus increasing the cost of their care. At discharge, almost half of them continued to need feeding modifications, which may have delayed rehabilitation or transfer to facilities with other levels of care. The dysphagia group clearly displayed a wide range of clinical symptoms that would alert staff to their risk for medical complications because of swallowing problems. We believe that this needs assessment clearly showed that a multidisciplinary dysphagia management program has the potential to enhance patient care while decreasing the cost of health care delivery for the hospital.

Aged↗
PubMed1990

Influenza-specific ELISA IgA and IgG predict severity of influenza disease in subjects prescreened with hemagglutination inhibition.

Four influenza A challenge studies were performed over a period of three years using the same dose of one virus pool. The first three studies were conducted two influenza seasons apart from the last study. In all four studies only subjects with screening hemagglutination inhibition (HAI) antibody titers less than or equal to 1:8 in sera were accepted as study subjects. The rate of infection after influenza challenge was 96% (25 of 26) in the first three studies, and only 73% (8 of 11) in the last study (P less than 0.04). The rate of influenza illness in the first three studies was 62% (16 of 26), and only 9% (1 of 11) in the last study (all subjects: P = 0.003; infected subjects: P = 0.01). Even though screening HAI titers were comparable between groups, prechallenge serum influenza-specific IgG titers correlated inversely with respiratory symptoms (P = 0.04). Prechallenge nasal wash influenza-specific IgA titers were lower in subjects who developed influenza illness (P = 0.03). Prechallenge influenza-specific nasal wash ELISA-IgA titers and serum ELISA-IgG titers predicted influenza severity in patients prescreened by HAI during influenza challenge studies.

Adolescent↗
PubMed1990

Protection of adults rechallenged with a human rotavirus.

Previous studies of adults challenged with human rotavirus (CJN strain) showed that 74% became infected and 55% of those infected experienced illness. Protection against infection correlated with rotavirus antibody, most significantly (P = .005) serum rotavirus IgG. In this study, 20 previously challenged subjects were reinoculated with the same virus 9-12 months after their initial challenge. Only 1 of 8 subjects not infected after the initial challenge and 2 of 12 infected after the first inoculation became infected after reinoculation; none became ill. Titers of rotavirus antibodies (serum, jejunal, and stool) at the time of reinoculation were about as high as or higher than they were before the initial inoculation. This correlated with greater protection, but the extent of protection was significantly greater (P less than .0001) than predicted based on a previous model relating protection and preinoculation titers of serum rotavirus IgG. Thus, inoculation with human rotavirus provided homotypic protection for at least 9-12 months, and protection remained correlated with higher concentrations of rotavirus antibody. However, the specific relationship between protection and rotavirus antibody was altered after the initial inoculation.

Adult↗