PubMed Health⌕ Search

Biomedical subjects

X H Hu

Publications and source records attributed to X H Hu.

At least 19 recordsLinked to original sources
PubMed2006

Genetic dissection of ethanol tolerance in the budding yeast Saccharomyces cerevisiae.

Uncovering genetic control of variation in ethanol tolerance in natural populations of yeast Saccharomyces cerevisiae is essential for understanding the evolution of fermentation, the dominant lifestyle of the species, and for improving efficiency of selection for strains with high ethanol tolerance, a character of great economic value for the brewing and biofuel industries. To date, as many as 251 genes have been predicted to be involved in influencing this character. Candidacy of these genes was determined from a tested phenotypic effect following gene knockout, from an induced change in gene function under an ethanol stress condition, or by mutagenesis. This article represents the first genomics approach for dissecting genetic variation in ethanol tolerance between two yeast strains with a highly divergent trait phenotype. We developed a simple but reliable experimental protocol for scoring the phenotype and a set of STR/SNP markers evenly covering the whole genome. We created a mapping population comprising 319 segregants from crossing the parental strains. On the basis of the data sets, we find that the tolerance trait has a high heritability and that additive genetic variance dominates genetic variation of the trait. Segregation at five QTL detected has explained approximately 50% of phenotypic variation; in particular, the major QTL mapped on yeast chromosome 9 has accounted for a quarter of the phenotypic variation. We integrated the QTL analysis with the predicted candidacy of ethanol resistance genes and found that only a few of these candidates fall in the QTL regions.

Chromosome Mapping↗
PubMed2003

QTLs for Na+ and K+ uptake of the shoots and roots controlling rice salt tolerance.

An F2 and an equivalent F3 population derived from a cross between a high salt-tolerance indica variety, Nona Bokra, and a susceptible elite japonica variety, Koshihikari, were produced. We performed QTL mapping for physiological traits related to rice salt-tolerance. Three QTLs for survival days of seedlings (SDSs) under salt stress were detected on chromosomes 1, 6 and 7, respectively, and explained 13.9% to 18.0% of the total phenotypic variance. Based on the correlations between SDSs and other physiological traits, it was considered that damage of leaves was attributed to accumulation of Na+ in the shoot by transport of Na+ from the root to the shoot in external high concentration. We found eight QTLs including three for three traits of the shoots, and five for four traits of the roots at five chromosomal regions, controlled complex physiological traits related to rice salt-tolerance under salt stress. Of these QTLs, the two major QTLs with the very large effect, qSNC-7 for shoot Na+ concentration and qSKC-1 for shoot K+ concentration, explained 48.5% and 40.1% of the total phenotypic variance, respectively. The QTLs detected between the shoots and the roots almost did not share the same map locations, suggesting that the genes controlling the transport of Na+ and K+ between the shoots and the roots may be different.

DNA, Plant↗
PubMed2002

In vivo study of intradermal focusing for tattoo removal.

Delivery of intradermally focused nanosecond laser pulses with small energy as an alternate technique applicable to clinical procedures in dermatological and plastic surgery is an area of relatively new interest with multiple potential applications. We assessed this approach on common tattoo pigments in dermis in an in vivo study using a wavelength of 1064 nm. Paired micropigs were tattooed with standard blue, black, green and red pigments. The tattoos were allowed to mature and then treated by 12 ns pulses in a focused beam of 11.4 degrees cone angle. Visual observation and histological analysis of biopsies were performed to evaluate results. Significant reduction in pulse energy and collateral damage was achieved with pulse energy ranging between 38 to 63 mJ. Blue and black tattoos were found to respond well from a clinical standpoint. The depth dependence of tissue response and pigment redistributions at 1 hour, 1 week and 1 month after laser treatment was quantitatively analysed through biopsies and a strong relationship was demonstrated between tattoo response and laser-induced dermal vacuolation. The optical absorption coefficients of the four tattoo pigments were measured to be approximately the same and the laser-induced plasma is suggested to be responsible for the pigment redistribution. As we hypothesised, intradermal focusing of nanosecond pulses significantly reduced required pulse energy for tattoo ablation to about 60 mJ or less. These results stimulate a number of additional questions relevant not only to clinical applications but also to the understanding of the fundamental process of laser-pigment interaction in the dermis as it relates to tattoo removal.

Animals↗
PubMed2001

Migraine treatment outcomes with rizatriptan in triptan-naive patients: a naturalistic study.

BACKGROUND: The 5-hydroxytryptamine(1B/1D) agonists, or triptans, are the newest class of drugs to become available for the acute treatment of migraine. The class currently includes sumatriptan, zolmitriptan, naratriptan, and rizatriptan. The efficacy of rizatriptan in the acute treatment of migraine has been established against placebo and other oral triptans in controlled comparative trials. OBJECTIVE: The US Migraine Assessment Protocol (USMAP) collected data on the use of rizatriptan in a naturalistic setting reflecting clinical practice. This paper presents results for patients enrolled in the USMAP study who had never taken a triptan before the study. METHODS: At enrollment, 216 patients completed a questionnaire describing their responses to their current nontriptan medications. They were then given specially packaged samples of 4 standard 10-mg rizatriptan tablets and 4 orally disintegrating 10-mg rizatriptan tablets (wafers) and were asked to take a different formulation for each of their next 2 attacks, the sequence to be at their discretion. Within approximately 24 hours after taking rizatriptan, patients were to call a toll-free number to report their responses to rizatriptan using an interactive voice-response system. RESULTS: Within 2 hours after initial dosing of rizatriptan, significantly more patients taking either the rizatriptan tablet or the rizatriptan wafer reported onset of pain relief, had become largely symptom free, and were able to resume usual activities compared with their baseline responses to nontriptans (P < 0.05). In addition, compared with their baseline responses to nontriptans, significantly more patients taking either rizatriptan formulation had mild or no pain 2 hours after dosing (P < 0.05). More than twice as many patients taking the rizatriptan tablets or wafers were either somewhat or very satisfied with the medication compared with their satisfaction with nontriptans (P < 0.05). CONCLUSIONS: In the naturalistic setting of this study, migraineurs who had not previously taken a triptan medication reported more rapid relief of pain, more effective pain relief, and more rapid resumption of normal activities when taking rizatriptan tablets or wafers than when taking a nontriptan medication. Patients dissatisfied with their current nontriptan migraine therapy may benefit from treatment with rizatriptan.

Activities of Daily Living↗
PubMed2001

Optical properties of porcine skin dermis between 900 nm and 1500 nm.

The weak absorption of shortwave infrared light by skin tissues between 700 and 1500 nm offers an important window for diagnosis by optical means. The strong scattering of shortwave infrared light by the skin, however, presents a challenge to the modelling of light propagation through the skin and the understanding of skin optics. We have measured the collimated and diffuse transmittance and diffuse reflectance of porcine skin dermis samples within 30 h post-mortem. Monte Carlo simulations have been performed to inversely determine the absorption coefficient, scattering coefficient and anisotropy factor of the dermis samples in the spectral range from 900 to 1500 nm. We further analyse the sensitivity of the values of the parameters to the experimental errors and inverse calculation procedures. The state of the cellular integrity of the skin samples following optical measurements was verified using transmission electron microscopy. These results were correlated to study post-mortem effects on the in vitro optical properties of porcine dermis. We concluded that for samples stored within crushed ice for up to 30 h post-mortem the wavelength dependence of optical properties of the dermis remains unchanged while the values of the parameters vary moderately due to modification of the water content of the tissue.

Animals↗
PubMed2001

Sequence Analysis of the Bam HI-J Fragment of the Spodoptera litura Multicapsid Nucleopolyhedrovirus.

The BamHI-J fragment located at 25.8--9.9 map units of the Spodoptera litura multicapsid nucleopolyhedrovirus (SpltMNPV) genome was sequenced. The fragment contained four ORFs, one partial ORF potentially encoding C-terminal of chitinase gene and one partial homologous region (hr). The four ORFs included lef-8 gene, J domain protein gene (bjdp gene), ORF570 and ORF165. The ORF570 revealed 31% identity to the helicase-2 of Lymantria dispar MNPV. The ORF165 was unique to the SpltMNPV. The bjdp gene, reported here for the first time in baculoviruses, was one of J domain family protein genes, and the predicated amino acid sequence possessed a characteristic of J domain protein of other DnaJ proteins at its N-terminus. The lef-8 showed high identities to the homologs of reported baculovirus genomes. As a component of virus-encoded RNA polymerase, the LEF-8 of SpltMNPV had the conserved motif GIKICGIHGQKG near the C-terminal end. Analysis of the LEF-8 phylogenic tree demonstrated SpltMNPV was very closely related to SpliMNPV.

Journal Article↗
PubMed2000

Survey of migraineurs referred to headache specialists: care, satisfaction, and outcomes.

The authors report a survey of 281 migraineurs recently referred to headache specialists by primary care physicians. Compared with care before referral, specialists spent substantially more time with patients and were more likely to ask patients to take a prophylactic drug and to keep a headache diary, to discuss migraine triggers, and to prescribe 5-hydroxytryptamine1B/1D agonists (triptans). After referral, patients reported improved satisfaction with care and significant decreases in frequency, duration, and severity of attacks.

Adult↗
PubMed1999

Burden of migraine in the United States: disability and economic costs.

BACKGROUND: Migraine is a common disabling disease but its economic burden has not been adequately quantified. OBJECTIVE: To estimate the burden of migraine in the United States with respect to disability and economic costs. METHODS: The following data sources were used: published data, the Baltimore County Migraine Study, MEDSTAT's MarketScan medical claims data set, and statistics from the Census Bureau and the Bureau of Labor Statistics. Disability was expressed as bedridden days. Charges for migraine-related treatment were used as direct cost inputs. The human capital approach was used in the estimation of indirect costs. RESULTS: Migraineurs required 3.8 bed rest days for men and 5.6 days for women each year, resulting in a total of 112 million bedridden days. Migraine costs American employers about $13 billion a year because of missed workdays and impaired work function; close to $8 billion was directly due to missed workdays. Patients of both sexes aged 30 to 49 years incurred higher indirect costs compared with younger or older employed patients. Annual direct medical costs for migraine care were about $1 billion and about $100 was spent per diagnosed patient. Physician office visits accounted for about 60% of all costs; in contrast, emergency department visits contributed less than 1% of the direct costs. CONCLUSIONS: The economic burden of migraine predominantly falls on patients and their employers in the form of bedridden days and lost productivity. Various screening and treatment regimens should be evaluated to identify opportunities to reduce the disease burden.

Absenteeism↗
PubMed1997

Absorption spectra of corneas in the far ultraviolet region.

PURPOSE: To study the corneal absorption in the far ultraviolet (UV) region between 260 and 190 nm. METHODS: Thirty-four corneal samples of thickness near 20 microns were obtained from 18 porcine corneas and six human corneas with a microtome-cryostat. The authors conducted absorbance measurements of the sectioned corneal samples supported by two UV optical windows from 350 to 190 nm using a dual-beam spectrophotometer. Three whole porcine corneas were used to study the effect of freezing on the absorbance from 350 to near 290 nm. RESULTS: The absorption spectra of porcine and human corneas from 350 to 190 nm were measured and three segments in the spectrum between 260 and 190 nm have been identified. The linear absorption coefficients were determined to be 2300 +/- 330 (cm-1) at 210 nm and 2410 +/- 370 (cm-1) at 193 nm for the porcine corneas and 2320 +/- 470 (cm-1) at 210 nm and 2340 +/- 150 (cm-1) at 193 nm for the human corneas. CONCLUSIONS: A "window of ablation" in the far UV region between 220 and 190 nm has been identified in which short laser pulses of similar durations and different wavelengths may be interchangeable to ablate the corneal surface with similar characteristics.

Animals↗
PubMed1996

Study of corneal ablation with picosecond laser pulses at 211 nm and 263 nm.

BACKGROUND AND OBJECTIVE: Corneal ablation has been studied by picosecond laser pulses in the far-UV region. STUDY DESIGN/MATERIALS AND METHODS: Laser pulses of 25 ps duration at 211 nm and 263 nm wavelengths and a 1 kHz repetition rate have been used to ablate human and rabbit corneas. The dependence of the etch rate on laser fluence has been measured at both wavelengths. The collateral tissue damage has been investigated by electron microscopy. RESULTS: The ablation threshold for human cornea is determined to be about 3.0 mJ/cm2 at 211 nm, while the thresholds for rabbit cornea are about 2.3 mJ/cm2 at 211 nm and 8.0 mJ/cm2 at 263 nm. The slopes of the ablation curves and the dimensions of the damage zones have also been determined. CONCLUSION: We compare these results to the existing data on corneal ablation by nanosecond UV pulses and discuss the deficiency of the photochemical model. Experimental results are analyzed in terms of a model that features plasma ablation assisted by chromophore absorption.

Animals↗
PubMed1995

[Hand grip strength as a nutritional indicator of patients with oral and maxillofacial malignancies to predict post-operative complications]

The correlation between hand grip strength(HGS),arm muscle circumference(AMC) and creatinine-height index (CHI) were studied in 127 patients with oral and maxillofacial malignancies.Prediction of postoperative complications by using HGS was also attempted in the patients undergoing surgical treatment.The results showed:(1)HGS correlated well with AMC and CHI,indicating that HGS can be used as a nutritional parameter to reflect the skeletal muscle condition(depletion or repletion);(2)comparison of the operative patients whose HGS<85% of the standard value(Group I)with those HGS>/=85% of the standard value(Group II)demonstrated that Group I hand a much higher incidence of postoperative complication(48.4%) than that of Group II (18.5%)(X=9.30;P<0.005),which means that HGS can be served as a nutritional prognostic indicator to predict postoperative complications.

Journal Article↗
PubMed1995

Alterations of monoamine metabolites and neurobehavioral function in lead-exposed workers.

Neurobehavioral and neurochemical effects of occupational lead exposure were investigated by WHO Neurobehavioral Core Test Battery (NCTB) testing and a series of monoamine neurotransmitters and their metabolites analyzing in workers from lead smeltery and storage-battery manufacturing factory and matched controls. Indicators of lead exposure, the blood lead (PbB) and zinc protophorphyrin (ZPP) levels were found significantly higher in the exposed group compared with that of the controls (70.55 micrograms/dL vs 3.67 micrograms/dL; and 294.92 micrograms/dL vs 38.32 micrograms/dL, respectively). Furthermore, elevated urinary homovanillic acid (HVA) and impairment of certain neurobehavioral performances were also found in the lead exposed workers; the latter included attention/response speed, manual dexterity, perceptual-motor speed, visual perception/memory, and motor speed/steadiness. Positive or negative correlations were observed between certain parameters. Thus, homovanillic acid (HVA) is positively correlated with PbB and ZPP; dopamine (DA) negatively correlated with Benton visual retention (BVR); and HVA negatively correlated with digit symbol (DSy), BVR, and pursuit aiming (PA). It is suggested that the alterations of dopamine and its metabolites HVA in urine associated with impairment of neurobehavioral function might be served as biomarkers of lead-induced neurotoxicity.

Adult↗
PubMed1994

Central mechanism of indomethacin analgesia.

The analgesic effect of indomethacin was investigated by using the visceral pain model in rabbits. After intravenous administration of indomethacin (2 mg/kg), the maximum increase of the visceral pain threshold was 0.42 +/- 0.31 mA (P < 0.05). The analgesic effect lasted 40 min. After intraventricular microinjection of indomethacin (50 micrograms), the maximum increase of the visceral pain threshold was 0.37 +/- 0.43 mA. After intravenous administration of indomethacin, the content of norepinephrine in perfusates of rabbit fourth ventricle was significantly increased from 18.10 +/- 8.05 to 32.16 +/- 6.15 mg/40 microliters (P < 0.05), compared with data for the control group. The content of beta-endorphin in the perfusate after indomethacin administration was decreased from 5-25 min and slightly increased from 25-35 min, compared with the data for the control group, but there was no significant difference (P > 0.05). Furthermore, intraventricular microinjection of phentolamine (50 micrograms) could block the analgesic effect of an intravenous injection of indomethacin, while naloxone could not. The results imply that prostaglandins of the central nervous system could induce hyperalgesia. Indomethacin injected centrally and peripherally has an analgesic effect on visceral pain. This analgesic effect is mediated by alpha-adrenoceptors. beta-Endorphin does not participate in the analgesic action of indomethacin.

Analgesics↗
PubMed1994

Dynamics of shock waves and cavitation bubbles generated by picosecond laser pulses in corneal tissue and water.

Time-resolved flash photography was used to investigate the dynamics of shock waves and cavitation bubbles generated by picosecond optical breakdown in bovine corneal tissue and water. A picosecond Nd:YLF laser was employed. A rapid decay of the shock waves was observed in both materials, with similar temporal characteristics, indicating that water serves as a good model for shock wave studies. In contrast, differences in the cavitation bubble dynamics were found between cornea and water, which are related to differences in the mechanical and thermal properties of the two media, suggesting that water should not be used to model cavitation dynamics in cornea. The experimental results also suggest that the efficiency of intrastromal ablation may be increased by using short pulses and moderate pulse energies in order to avoid the creation of large cavitation bubbles. The experiment indicates that the optimum laser repetition rate for intrastromal ablation is between 1 and 5 kHz.

Animals↗
PubMed1994

Effects of low level lead exposure on behavior of young rats.

Dam rats were given Pb (0.58, 1.76, and 5.27 mmol.L-1), containing water ad lib from d 16 of gestation to weaning of the offspring on d 21 postpartum. The pups continued drinking the same water till the postnatal d 30. The neurobehavioral function of pups was tested. The second step-down latencies (SDL2) were shortened and the number of step-downs in 5 min (NSD) were increased in step-down test. The prolongation of the lapse of time in passing through the whole course (LTPWC) and the increase in number of entries into the blind alley (NEBA) were measured in water maze test. The number of ambulations and rearings were increased in locomotor activity. The results indicated that Pb exerts adverse effects on the learning ability and memory function, and induces hyperactivity in young rats.

Animals↗
PubMed1992

Measuring exposure for the epidemiologic study of acute effects.

This report explores the importance of characterizing short-term (peak) exposures for successful epidemiologic study of acute reversible effects. By selecting upper respiratory tract irritation, which is time-limited, reversible, and not critically affected by host factor sensitivities, the illustrated approach (directed at an acute respiratory irritant) provides insights on issues important in the general study of acute effects. The fundamental concern in a study of acute irritant effects is that such events occur in response to abrupt increases in exposure. This calls for a closer examination of how to distinguish bursts, or peaks, of exposure from continuous exposures measured simply as time weighted averages. Three parameters of peak exposures are discussed: duration, magnitude, and frequency. The importance of duration is illustrated by contrasting exposure patterns relevant for the study of acute vs. chronic health effects. The minimum magnitude of a peak relevant to the study of a specific physiologic response requires knowledge of the threshold below which no detectable response occurs. For any identified threshold level, only exposures exceeding that level are defined as relevant peaks for an exposure-response analysis. Finally, the issue of frequency, the minimum length of time between successive exposures necessary for the subject to return to baseline risk, is explored. A study of respiratory irritation associated with sodium borates is used to illustrate these issues.

Acute Disease↗