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Biomedical subjects

T Hu

Publications and source records attributed to T Hu.

At least 37 records · Page 2Linked to original sources
PubMed2001

Alcohol consumption patterns and health care costs in an HMO.

We examined the relationship between patterns of alcohol consumption and health care costs among adult members of the Kaiser Permanente Medical Care Program (KPMCP) in Northern California. A telephone survey of a random sample of the KPMCP membership aged 18 and over was conducted between June 1994 and February 1996 (n=10,175). The survey included questions on sociodemographic characteristics, general and mental health status, patterns of past and current alcohol consumption; inpatient and outpatient costs were obtained from Kaiser Permanentes cost management information system. Results showed that current non-drinkers with a history of heavy drinking had higher health costs than other non-drinkers and current drinkers. The per person per year costs for non-drinkers with a heavy drinking history were $2421 versus $1706 for other non-drinkers and $1358 for current drinkers in 1995 US dollars. A history of heavy drinking has a significant effect on costs after controlling for sociodemographic characteristics, health status and health practices. Current drinkers have the lowest costs, suggesting that they may be more likely than non-drinkers to delay seeking care until they are sick and require expensive medical care.

Adolescent↗
PubMed2001

Tbx1, a DiGeorge syndrome candidate gene, is regulated by sonic hedgehog during pharyngeal arch development.

Appropriate interactions between the epithelium and adjacent neural crest-derived mesenchyme are necessary for normal pharyngeal arch development. Disruption of pharyngeal arch development in humans underlies many of the craniofacial defects observed in the 22q11.2 deletion syndrome (del22q11), but the genes responsible remain unknown. Tbx1 is a T-box transcription factor that lies in the 22q11.2 locus. Tbx1 transcripts were found to be localized to the pharyngeal endoderm and the mesodermal core of the pharyngeal arches, but were not present in the neural crest-derived mesenchyme of the pharyngeal arches. Sonic hedgehog (Shh) is also expressed in the pharyngeal arches and is necessary for normal craniofacial development. We found that Tbx1 expression was dependent upon Shh signaling in mouse embryos, consistent with their overlapping expression in the pharyngeal arches. Furthermore, Shh was sufficient to induce Tbx1 expression when misexpressed in selected regions of chick embryos. These studies reveal a Shh-mediated pathway that regulates Tbx1 during pharyngeal arch development.

Amino Acid Sequence↗
PubMed2001

Determination of double decker sandwich structured La-substituted chlorophyll a by EXAFS.

As a representative natural porphyrin derivative, it is interesting to know the chemical form of lanthanide in chlorophyll a. We select the natural fern dicranopteris dichotoma, the most lanthanide-concentrated plant known, to isolate the chlorophyll a for our study. It is found by EXAFS that lanthanum substitutes in the magnesium position in chlorophyll and coordinates with the porphyrin ring. The lanthanum is seen to have a similar coordination structure to a sandwich-type lanthanide complex, with the La surrounded by eight nitrogen atoms from two porphyrin rings with average La-N bond length of 2.65 A.

Chlorophyll↗
PubMed2001

Atp-bound topoisomerase ii as a target for antitumor drugs.

Topoisomerase II (TOP2) poisons interfere with the breakage/reunion reaction of TOP2 resulting in DNA cleavage. In the current studies, we show that two different classes (ATP-sensitive and -insensitive) of TOP2 poisons can be identified based on their differential sensitivity to the ATP-bound conformation of TOP2. First, in the presence of 1 mm ATP or the nonhydrolyzable analog adenosine 5'-(beta,gamma-imino)triphosphate, TOP2-mediated DNA cleavage induced by ATP-sensitive TOP2 poisons (e.g. doxorubicin, etoposide, mitoxantrone, and 4'-(9-acridinylamino)methanesulfon-m-anisidide) was 30-100-fold stimulated, whereas DNA cleavage induced by ATP-insensitive TOP2 poisons (e.g. amonafide, batracylin, and menadione) was only slightly (less than 3-fold) affected. In addition, ADP was shown to strongly antagonize TOP2-mediated DNA cleavage induced by ATP-sensitive but not ATP-insensitive TOP2 poisons. Second, C427A mutant human TOP2alpha, which exhibits reduced ATPase activity, was shown to exhibit cross-resistance to all ATP-sensitive but not ATP-insensitive TOP2 poisons. Third, using ciprofloxacin competition assay, TOP2-mediated DNA cleavage induced by ATP-sensitive but not ATP-insensitive poisons was shown to be antagonized by ciprofloxacin. These results suggest that ATP-bound TOP2 may be the specific target of ATP-sensitive TOP2 poisons. Using Lac repressor-operator complexes as roadblocks, we show that ATP-bound TOP2 acts as a circular clamp capable of entering DNA ends and sliding on unobstructed duplex DNA.

Adenosine Triphosphate↗
PubMed2001

Does willingness to pay vary by race/ethnicity? An analysis using mammography among low-income women.

As part of a population-based intervention to improve periodic mammogram screening, we examined WTP for mammography in five ethnic groups. Through random digit dialing, we contacted households in low-income census tracts of Alameda County, California (San Francisco Bay area). Women who met the ethnicity, age and cancer-free eligibility criteria were invited to participate. For the baseline assessment, women were surveyed over the phone in their preferred language. Of the 1465 surveyed women, 499 identified themselves as African-American, 199 were Chinese, 167 were Filipino, 300 were Latina, and 300 were non-Hispanic white. Bivariate and multivariate analysis showed that WTP varied significantly by ethnicity (P<0.05). We also found that when Filipino and Chinese women had a female relative with breast cancer, they were willing to pay less money for a mammogram. African-American, Latino, and non-Hispanic white women, however, were willing to pay more money for a mammogram if a female relative had had breast cancer. This ethnic difference, when there is a familial link to breast cancer, needs further study as it has implication for genetic testing. Nevertheless, WTP studies that do not account for ethnic differences may be overstating net benefits to society.

California↗
PubMed2001

Characterization of spirolides a, c, and 13-desmethyl c, new marine toxins isolated from toxic plankton and contaminated shellfish.

Three additional marine toxins, spirolides A (1), C (3), and 13-desmethyl-C (7), were isolated from contaminated scallops and phytoplankton collections obtained from a Nova Scotian aquaculture site, as well as from batch cultures of the dinoflagellate Alexandrium ostenfeldii obtained as a single-cell isolate from these phytoplankton assemblages. The structures of these new spirolide derivatives, characterized by mass spectrometry and NMR, indicate a close relationship with spirolides B (2) and D (4) isolated previously from contaminated shellfish in the same area. All of these compounds display "fast-acting" toxicity in the traditional bioassay used for monitoring shellfish, and this is related to the presence of a cyclic imine function in all these compounds. Those spirolides containing a vicinal dimethyl group in the seven-membered ring are resistant to oxalic acid hydrolysis, whereas those that do not are readily hydrolyzed. These observations suggest that the extra methyl group on the seven-membered imine ring of 3, 4, and 7 appears to block the process of imine hydrolysis perhaps by stereochemical interference.

Animals↗
PubMed2001

The biomechanical, morphologic, and histochemical properties of the costal cartilages in children with pectus excavatum.

BACKGROUND/PURPOSE: The cause of the pectus excavatum (PE) remains unclear, although some results of research have indicated that the disturbance of the sternum or costal cartilage might be responsible for this deformity. But no decisive evidence has been gained. The authors have analyzed the biomechanical, morphologic, and histochemical properties of the cartilage in PE and intend to support the belief that the disturbance of the cartilage might contribute to the development of PE. METHODS: Thirty-eight specimens of the sixth cartilage were obtained at operation for the PE group (aged from 3 to 6 years; mean, 4.2 years). And 28 specimens of the control group (aged from 3 to 6 years; mean, 4.4 years) were gained from routine postmortem examinations in which the cause of death was unlikely to have affected the cartilage. The biomechanical test was carried out in a material testing machine (Shimadzu AG-10TA, Tokyo, Japan). The relation curve of load-deformation in tensile and compressive tests and the curve of load-time in the flexuous test were recorded automatically. The values of the ultimate strength and strain were calculated from this relation curve. The specimens also underwent H&E staining. The values of the area, circumference, mean diameter, maximal diameter, and morphologic factor of the cell and the nucleus of the cartilage in superficial and deep area were determined with the help of image analysis software (GT-2 model, China). The superficial zone (SZ) and deep zone (DZ) of the cartilage were examinated with electron microscopy (JEM-100SX, Japan). The distribution and intensity of type II collagen was shown by immunohistochemistry staining and analyzed with the image analysis software (GT-2 model, Huakang Co, Chengdu, China). The extent and distribution of proteoglycan were analyzed after Safranin-O and periodic acid shiff (PAS) staining. RESULTS: The mean strength of the costal cartilage in the experimental group was less than that in the control group in terms of tension, compression, and flexure (P <.05). The shape of the stress-strain curve for tension and compression in the experimental group was different from the control group. The fracture load in the experimental group was less than in the control group in tension (1.5 MPa versus 2.8 MPa) and in compression (.2 MPa versus 8.3 MPa). The time of fracture in experimental group was 30 seconds compared with 38 seconds in control group. No denaturation or necrosis could be found in light microscopical examination. There was no manifestation of hyperplasia or hypoplasia in the costal cartilage of the PE group. In SZ and DZ areas, the pattern and the number of mitochondria, endoplasmic reticulum, and Golgi in the experimental group were the same as the control group in transmission electron microscopy. Furthermore, the distribution and the number of proteoglycan in the 2 groups did not show a significant difference both in SZ and DZ areas. Although the distribution of the collagen in SZ areas was normal, this pattern was disturbed in DZ areas in the experiment group. The results of type II collagen immunohistochemistry examination was concordant with that change. No significant difference between control and experimental group could be seen in Safranin-O and PAS staining for proteoglycan. CONCLUSIONS: The biomechanical stability of the cartilage was decreased in the PE group. This might be caused by the disorderly arrangement and distribution of the collagen in the cartilage of PE patients. J Pediatr Surg 36:1770-1776.

Biomechanical Phenomena↗
PubMed2001

[Survey on the high risk behaviors related to acquired immunologic deficiency syndrome and sexually transmitted diseases among men who have sex with men in mainland China].

OBJECTIVE: To understand the high risk behaviors related to acquired immunologic deficiency syndrome (AIDS) and sexually transmitted diseases (STDs) among men who have sex with men (MSM) in mainland China. METHODS: A self-administrated anonymous mail survey was carried out in MSM throughout the mainland of China in 1999. RESULTS: One thousand eight hundred questionnaires were mailed out and 729 effective questionnaires were collected. The response rate was 40.5%. The average age of subjects was 31 years old. Their average age at first sexual intercourse with a man was 18.6 years old. Average number of male sexual partners were 39.2 out of which 75.7% reported having had anus-intercourse. In the latest year, 63.6% reported ever having sex with strange men, 39.8% reported ever having group sex, 9.3% reported having sold sex and 3.8% having bought sex. 50% of them reported ever having sex with women. One hundred thirty-three reported having been diagnosed STD. Sixty-two reported having tested for HIV antibody and 11 were positive. Two-thirds reported ever using a condom when having sex. CONCLUSION: High risk sexual behaviors were prevalent among MSM in mainland China with HIV infection rate already reaching a high level. Women having sex with MSM are at a greater risk of HIV infection.

Acquired Immunodeficiency Syndrome↗
PubMed2001

[Effect of para-aminobenzoic acid on the adhesion of Streptococcus mutans].

OBJECTIVE: To investigate the effects of Para-aminobenzoic acid (PABA) on the adhesion of Streptococcus mutans to saliva-coated hydroxyapatite (S-HA). METHODS: The adhesion model in vitro established by Gibbons was adopted in this study to quantify adsorptive cells through [3H] thymidine labelling. RESULTS: PABA solution over a range of concentration from 10(-9) to 10(-3) g/L could inhibit the attachment of S. mutans to S-HA effectively, and the inhibition declined when the concentration of PABA solution was 10(-3) g/L. CONCLUSION: PABA can inhibit the adherence of Streptococcus mutans to S-HA effectively.

4-Aminobenzoic Acid↗
PubMed2001

[A study on bacterial contamination of dental handpieces].

OBJECTIVE: The aim of this study is to evaluate the effects of different factors, including concentration of the bacterial suspension, number of stops set on handpieces, and different disinfectants, on bacterial contamination of handpieces and their clinical significance. METHODS: Bacterial contamination of 20 handpieces were analyzed in different concentration of bacterial suspension, number of stops set on handpieces and after using different out surface disinfectants. RESULTS: Statistical increment (P < 0.05) of handpieces inside contamination was observed relevant to increment of the bacterial suspension concentration. No statistical relevance was seen between handpiece inside contamination and the number of stops set on handpieces(P > 0.05). Disinfection with different disinfectants significantly decreased out surface contamination(P < 0.05), but no statistical change of bacteria (P > 0.05) was observed inside handpieces. CONCLUSION: As the concentration of bacterial suspension is the key factor affecting the inside contamination of handpieces, oral cavity cleanness is essential before dental therapy. The surface disinfection of handpieces is necessary after dental therapy, but cannot prevent cross-contamination between patients.

Cross Infection↗
PubMed2001

[Effects of para-aminobenzoic acid (PABA) on growth of Streptococcus mutans].

OBJECTIVE: The aim of this study is to examine effects of para-aminobenzoic acid (PABA) on the growth of Streptococcus mutans (S. mutans). METHODS: Different concentrations of PABA (10(-10)-10(-3) g/L) were separately transferred to modified Carlsson medium. S. mutans (ATCC 25175) grew in modified Carlsson medium with different concentrations of PABA. All cultures were incubated at 37 degrees C anaerobically in an atmosphere of 80% of nitrogen (v/v), 10% of hydrogen (v/v) and 10% of carbon dioxide (v/v) for 48 hours. The absorbance values of S. mutans were measured by using a spectrometer (UV-1601). The colony forming units (CFU) were obtained by growing S. mutans in media with different concentrations of PABA (10(-10)-10(-3) g/L). RESULTS: Different concentrations of PABA had different stimulating effects on the growth of S. mutans (P < 0.05). But this kind of stimulating effects declined when the concentration of PABA was 10(-3) g/L. CONCLUSION: This experiment indicates PABA has stimulating effects on the growth of S. mutans, and PABA can promote growth of S. mutans.

4-Aminobenzoic Acid↗
PubMed2001

[Effects of different disinfectants on levels of endotoxin in canals of chronic periapical periodontitis].

OBJECTIVE: The objective of this study is to compare effects of formocresol, camphorated phenol and Ya Kan (metronedazole) on endotoxin levels in canals of chronic periapical periodontitis. METHODS: A total of 30 patients with chronic periapical periodontitis were selected from outpatients, and 10 cases each were randomly picked out to treat by sealing with formocresol, camphorated phenol and Ya Kan respectively. All patients were both sampled before and after sealing of these disinfectants, and chromogenic substrate method of limulus amebocyte lysate (LAL) test was used to measure levels of endotoxin. RESULTS: The effects of Ya Kan, formocresol and camphorated phenol on levels of endotoxin did not showed significant difference. CONCLUSION: Some anti-anaerobic bacterial drugs can be used to treat chronic periapical periodontitis.

Anti-Infective Agents, Local↗
PubMed2000

Members of the HRT family of basic helix-loop-helix proteins act as transcriptional repressors downstream of Notch signaling.

The Hairy-related transcription-factor (HRT) genes encode three related basic helix-loop-helix transcription factors that show sequence similarity to the Hairy and Enhancer of split family of transcriptional repressors. HRT proteins are expressed in specific regions of the developing heart, vasculature, pharyngeal arches and somites, and the periodicity of their expression in somitic precursors mirrors that of Notch signaling-related molecules. In the present study, we show that the intracellular domain of the Notch1 receptor (Notch1 IC), which is constitutively active, up-regulates HRT2 expression in 10T(1/2) fibroblasts. Luciferase reporter assays using the regulatory regions of the mouse HRT genes revealed that transcription of all three genes is stimulated by Notch1 IC. The promoters of the HRT genes share homology in a binding site for Suppressor of Hairless [Su(H)], a transcriptional mediator of Notch signaling. A dominant-negative Su(H) mutant abolished Notch-activated HRT2 expression, and mutation of the conserved Su(H) consensus site in the HRT2 promoter attenuated transcriptional activation by Notch. Ectopic expression of HRT proteins also blocked activation of HRT2 expression by Notch1 IC through a mechanism requiring the basic region, but not the conserved carboxyl-terminal YQPW-TEVGAF motif of HRT2. These findings identify HRT genes as downstream targets for Notch signaling and reveal a negative autoregulatory loop whereby HRT proteins repress their own expression through interference with Notch signaling.

Animals↗
PubMed2000

A novel mechanism of cell killing by anti-topoisomerase II bisdioxopiperazines.

Bisdioxopiperazines are a unique class of topoisomerase II inhibitors that lock topoisomerase II at a point in the enzyme reaction cycle where the enzyme forms a closed clamp around DNA. We examined cell killing by ICRF-187 and ICRF-193 in yeast cells expressing human topoisomerase II alpha (htop-IIalpha). Expression of htop-IIalpha in yeast cells sensitizes them to both ICRF-187 and ICRF-193, compared with cells expressing yeast topoisomerase II. ICRF-193 is still able to exert growth inhibition in the presence of genes encoding both ICRF-193-resistant and ICRF-193-sensitive htop-IIalpha enzymes, indicating that sensitivity to bisdioxopiperazines is dominant. Killing by ICRF-193 occurs more rapidly, than the killing in yeast cells due to a temperature-sensitive yeast topoisomerase II incubated at the non-permissive temperature. These results are reminiscent of a top-II poison such as etoposide. However, the killing caused by ICRF-193 and ICRF-187 is not enhanced by mutations in the RAD52 pathway. The levels of drug-induced DNA cleavage observed with htop-IIalpha in vitro is insufficient to explain the sensitivity induced by this enzyme in yeast cells. Finally, arrest of cells in G(1) does not protect cells from ICRF-193 lethality, a result inconsistent with killing mechanisms due to catalytic inhibition of top-II or stabilization of a cleavable complex. We suggest that the observed pattern of cell killing is most consistent with a poisoning of htop-II by ICRF-193 by a novel mechanism. The accumulation of closed clamp conformations of htop-II induced by ICRF-193 that are trapped on DNA might interfere with transcription, or other DNA metabolic processes, resulting in cell death.

Alleles↗
PubMed2000

Cigarette consumption and sales of nicotine replacement products.

BACKGROUND: The first nicotine replacement product, Nicorette Gum, was marketed in 1984 as an adjuvant to help smokers quit smoking. In 1992, sales of nicotine patches were begun. Before 1996, nicotine gums and nicotine patches were prescribed by physicians and supplemented with behavioural counselling. Since 1996, nicotine gums and patches became available over the counter. OBJECTIVES: To examine the effect of sales of nicotine replacement products on national cigarette consumption. DESIGN: National time series quarterly cigarette consumption, sales of nicotine gums and patches data between 1976 and 1998 are used to estimate a time series autoregressive moving average intervention model. PARTICIPANTS: National reported statistics. MAIN OUTCOME MEASURES: Per capita cigarette sales. RESULTS: A 10% increase in sales of nicotine replacement products will lead to a 0.04% reduction in cigarette sales. The model indicates that a 0.076% reduction in cigarette consumption is associated with the availability of nicotine patches after 1992. The over the counter dummy variable (after 1996) has a negative sign, but is not significant, perhaps due to only a few quarters of data in the study period. CONCLUSIONS: Nicotine replacement products (nicotine gums and nicotine patches) play a significant role in reducing cigarette consumption, in addition to the negative effect of increasing cigarette price and the overall trend of declining cigarette consumption (as reflected by the time trend variable). The findings of this study suggest that additional efforts for promoting sales of nicotine replacement products will be another effective alternative to discouraging cigarette consumption.

Adolescent↗
PubMed2000

Help seeking by persons of Mexican origin with functional impairments.

OBJECTIVE: Mexican Americans have low rates of service utilization for mental health problems. This study examined the use of health services by persons who have symptoms of mental distress that they say impair their ability to function. METHODS: A stratified field survey was conducted in central California to select a probabilistic sample of persons of Mexican origin. A multinomial logistic regression was used for the analysis. RESULTS: Among respondents who reported functional impairments attributable to their symptoms, 58 percent met diagnostic criteria for a mental disorder. Of that group, 69 percent did not use any health services. Respondents who sought medical services for mental health symptoms were more likely to be women and to meet diagnostic criteria for a mental disorder. Respondents who sought mental health services for their symptoms were more likely to be female, to be unmarried, and to have had 12 or more years of education. Health insurance status was not associated with type of service used. CONCLUSIONS: Even among Mexican Americans who met diagnostic criteria for a mental illness, most did not use services of any sort, and many of those who sought treatment for their symptoms turned to medical and informal services.

Adult↗