Biomedical subjects

S W Li

Publications and source records attributed to S W Li.

At least 37 records · Page 2Linked to original sources

PubMed2001

[Amplification and analysis of T-DNA flanking sequences in transgenic rice].

Rice transformation mediated by Agrobacterium tumefaciens has technically matured to some extent, but the mechanics of T-DNA integration in transgenic rice remains largely unknown. Using thermal asymmetric interlaced PCR (TAIL-PCR), we analyzed the flanking sequences of T-DNAs in transgenic rice plants, in which the resistance gene for rice bacterial blight disease, Xa21, had been integrated stably. Sequence analysis of 24 fragments amplified by TAIL-PCR showed that of them 14 were rice genomic DNA, 9 contained vector backbone sequences, and one was a fragment of the exogenous gene Xa21. The characteristics of the 14 rice genomic DNA sequences at T-DNA integrated sites are significantly different from those of the reported rice genomic sequences into which exogenous genes were integrated through direct DNA transformation methods. T-DNA border sequences integrated in rice genome have similar features as those integrated in dicotyledonous genomes. In the backbone containing flanking sequences (37.5%, 9/24) vector backbones appeared in different types.

Base Sequence↗

PubMed2000

Sleep-related injury in the elderly--an epidemiological study in Hong Kong.

OBJECTIVES: Sleep-related injury is a serious but under-recognized condition. We examined the occurrence of sleep-related injuries and REM sleep behavior disorder (RSBD) in a community sample of elderly in Hong Kong. DESIGN: A representative sample of elderly aged 70 years or above were interviewed with a screening question on the presence of sleep-related injuries. Those who answered affirmatively as well as a subsample of negative responders were interviewed by clinicians. Patients with suspected sleep disorders underwent physical and psychiatric assessment as well as sleep studies. SETTING: NA. PATIENTS OR PARTICIPANTS: NA. INTERVENTIONS: NA. RESULTS: In total, 1034 elderly were surveyed and 0.8% reported history of sleep-related injury. Four subjects were confirmed to have RSBD, giving an estimated prevalence of RSBD of 0.38% (95% CI=0.01 to 0.76%). One subject had suspected RSBD but refused investigations while 1 had history suggestive of transient RSBD but could not be confirmed by the sleep studies. The course of RSBD in these subjects was that of a waxing and waning course instead of a progressive deterioration as described in previous literature. Two patients had been hospitalized for sleep-related injury before but their sleep disorder was not recognized. CONCLUSIONS: We found that sleep-related injury and RSBD were not rare in the elderly but were frequently under-recognized. Our study calls for greater attention to elderly who had sustained injury during sleep.

Aged↗

PubMed2000

Reduction of Fe(III), Cr(VI), U(VI), and Tc(VII) by Deinococcus radiodurans R1.

Deinococcus radiodurans is an exceptionally radiation-resistant microorganism capable of surviving acute exposures to ionizing radiation doses of 15,000 Gy and previously described as having a strictly aerobic respiratory metabolism. Under strict anaerobic conditions, D. radiodurans R1 reduced Fe(III)-nitrilotriacetic acid coupled to the oxidation of lactate to CO(2) and acetate but was unable to link this process to growth. D. radiodurans reduced the humic acid analog anthraquinone-2,6-disulfonate (AQDS) to its dihydroquinone form, AH(2)DS, which subsequently transferred electrons to the Fe(III) oxides hydrous ferric oxide and goethite via a previously described electron shuttle mechanism. D. radiodurans reduced the solid-phase Fe(III) oxides in the presence of either 0.1 mM AQDS or leonardite humic acids (2 mg ml(-1)) but not in their absence. D. radiodurans also reduced U(VI) and Tc(VII) in the presence of AQDS. In contrast, Cr(VI) was directly reduced in anaerobic cultures with lactate although the rate of reduction was higher in the presence of AQDS. The results are the first evidence that D. radiodurans can reduce Fe(III) coupled to the oxidation of lactate or other organic compounds. Also, D. radiodurans, in combination with humic acids or synthetic electron shuttle agents, can reduce U and Tc and thus has potential applications for remediation of metal- and radionuclide-contaminated sites where ionizing radiation or other DNA-damaging agents may restrict the activity of more sensitive organisms.

Anaerobiosis↗

PubMed2000

Effect of electron donor and solution chemistry on products of dissimilatory reduction of technetium by Shewanella putrefaciens.

To help provide a fundamental basis for use of microbial dissimilatory reduction processes in separating or immobilizing (99)Tc in waste or groundwaters, the effects of electron donor and the presence of the bicarbonate ion on the rate and extent of pertechnetate ion [Tc(VII)O(4)(-)] enzymatic reduction by the subsurface metal-reducing bacterium Shewanella putrefaciens CN32 were determined, and the forms of aqueous and solid-phase reduction products were evaluated through a combination of high-resolution transmission electron microscopy, X-ray absorption spectroscopy, and thermodynamic calculations. When H(2) served as the electron donor, dissolved Tc(VII) was rapidly reduced to amorphous Tc(IV) hydrous oxide, which was largely associated with the cell in unbuffered 0. 85% NaCl and with extracellular particulates (0.2 to 0.001 microm) in bicarbonate buffer. Cell-associated Tc was present principally in the periplasm and outside the outer membrane. The reduction rate was much lower when lactate was the electron donor, with extracellular Tc(IV) hydrous oxide the dominant solid-phase reduction product, but in bicarbonate systems much less Tc(IV) was associated directly with the cell and solid-phase Tc(IV) carbonate may have been present. In the presence of carbonate, soluble (<0.001 microm) electronegative, Tc(IV) carbonate complexes were also formed that exceeded Tc(VII)O(4)(-) in electrophoretic mobility. Thermodynamic calculations indicate that the dominant reduced Tc species identified in the experiments would be stable over a range of E(h) and pH conditions typical of natural waters. Thus, carbonate complexes may represent an important pathway for Tc transport in anaerobic subsurface environments, where it has generally been assumed that Tc mobility is controlled by low-solubility Tc(IV) hydrous oxide and adsorptive, aqueous Tc(IV) hydrolysis products.

Carbonates↗

PubMed2000

[Construction and application of an Escherichia coli high effective expression vector with an enhancer].

In this study, we constructed a high effective fusion expression-vector in E. coli. This vector, pTO-T7, was characterized as: (1) an enhancer from tobacco mosaic virus (TMV), omega sequence, was ligated in front of a T7 promoter in the regulatory sequence; (2) the multi-cloning sites include eight restriction enzyme sites. It can facilitate fusion or nonfusion expression; (3) the N terminal of a fusion protein starts with the first 12 amino acids of T7 gene 10, and the C terminal is the hexahistidine tag; (4) kanmycin resistance gene was used as a selective marker. EGFP gene was inserted into pTO-T7 vector as a reporter gene. Expression data showed that fused-EGFP accounted to more than 50% of the total E. coli protein, and more than 90% of which was soluble. The fluorescence characters of fused-EGFP were also studied. The expression yield of target gene from plasmid pTO-T7 compared with that from pT-T7 without omega sequence suggested that omega sequence in pTO-T7 can improve the expression of target gene significantly.

Base Sequence↗

PubMed1999

Sleep problems in Chinese elderly in Hong Kong.

BACKGROUND: To examine the sleep habits and one-year prevalence of sleep disturbance (difficulty in falling asleep, broken sleep and early morning wakening) as well as insomnia (subjectively inadequate or poor sleep) in an elderly Chinese population in Hong Kong. METHOD: In Phase 1, a representative sample of elderly aged 70 years or above were interviewed with a sleep questionnaire, and Cantonese versions of the Mini-Mental State Examination (CMMSE) and Geriatric Depression Scale(CGDS). In Phase 2, those with scores suggestive of cognitive impairment on CMMSE or depression on CGDS were interviewed by psychiatrists for making clinical diagnoses according to DSM IV. RESULTS: 1,034 elderly were interviewed in Phase 1. Occasional or persistent sleep disturbance were reported by 75% and insomnia in 38.2% of elderly. Slightly less than half of elderly with sleep disturbance complained of insomnia. Advancing age was associated with a higher rate of sleep disturbance while females had a higher rate of insomnia. Factors associated with sleep disturbance and insomnia included poor perceived health, past history of smoking, current depressive disorders, more chronic physical illness, more life events and more somatic complaints. Only 2.8% of the sample had taken sleeping pills within a one-year period. CONCLUSIONS: Sleep disturbance and insomnia are two separate but overlapping constructs and should be differentiated. Sleep disturbance is very common in the elderly and may be due to physiological changes with ageing. In contrast, those with a concommitant complaint of insomnia have impaired physical and mental health and may merit more medical attention.

Aged↗

PubMed1999

Quantitation of 3,4-dihydroxyphenylacetaldehyde and 3, 4-dihydroxyphenylglycolaldehyde, the monoamine oxidase metabolites of dopamine and noradrenaline, in human tissues by microcolumn high-performance liquid chromatography.

We recently described the chemical synthesis of 3, 4-dihydroxyphenylacetaldehyde and 3,4-dihydroxyphenylglycolaldehyde, the monamine oxidase metabolites of dopamine and noradrenaline, respectively. We demonstrated the neurotoxicity of these compounds. Catecholamine nerve cells which synthesize these aldehydes die in degenerative brain diseases, such as Parkinson's and Alzheimer's. Here we describe a sensitive method for separating these catecholaldehydes from catecholamines and their other oxidative and methylated metabolites by microcolumn high-performance liquid chromatography with electrochemical detection. We then quantitate catecholamines and their major metabolites in human brain, plasma, and urine. The method can be used to determine the role of these catecholaldehydes in human disease.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1999

Accumulation of 3,4-dihydroxyphenylglycolaldehyde, the neurotoxic monoamine oxidase A metabolite of norepinephrine, in locus ceruleus cell bodies in Alzheimer's disease: mechanism of neuron death.

3,4-Dihydroxyphenylglycolaldehyde (DOPEGAL) is the neurotoxic monoamine oxidase A (MAO-A) metabolite of norepinephrine (NE). NE neurons in the locus ceruleus (LC) die in Alzheimer's disease (AD). To determine if DOPEGAL could contribute to NE neuron death in AD we measured levels of DOPEGAL, NE and their synthesizing enzymes in LC from AD and matched controls. We found 2.8- and 3.6-fold increases in DOPEGAL and MAO-A in AD LC neuronal cell bodies compared to controls. NE and dopamine beta-hydroxylase were increased by 3.8- and 10.7-fold, respectively. Implications for the mechanism of neuron death in AD are discussed.

Aged↗

PubMed1999

Mutations in COL11A2 cause non-syndromic hearing loss (DFNA13).

We report that mutation of COL11A2 causes deafness previously mapped to the DFNA13 locus on chromosome 6p. We found two families (one American and one Dutch) with autosomal dominant, non-syndromic hearing loss to have mutations in COL11A2 that are predicted to affect the triple-helix domain of the collagen protein. In both families, deafness is non-progressive and predominantly affects middle frequencies. Mice with a targeted disruption of Col11a2 also were shown to have hearing loss. Electron microscopy of the tectorial membrane of these mice revealed loss of organization of the collagen fibrils. Our findings revealed a unique ultrastructural malformation of inner-ear architecture associated with non-syndromic hearing loss, and suggest that tectorial membrane abnormalities may be one aetiology of sensorineural hearing loss primarily affecting the mid-frequencies.

Amino Acid Sequence↗

PubMed1999

Human Ehlers-Danlos syndrome type VII C and bovine dermatosparaxis are caused by mutations in the procollagen I N-proteinase gene.

Ehlers-Danlos syndrome (EDS) type VIIC is a recessively inherited connective-tissue disorder, characterized by extreme skin fragility, characteristic facies, joint laxity, droopy skin, umbilical hernia, and blue sclera. Like the animal model dermatosparaxis, EDS type VIIC results from the absence of activity of procollagen I N-proteinase (pNPI), the enzyme that excises the N-propeptide of type I and type II procollagens. The pNPI enzyme is a metalloproteinase containing properdin repeats and a cysteine-rich domain with similarities to the disintegrin domain of reprolysins. We used bovine cDNA to isolate human pNPI. The human enzyme exists in two forms: a long version similar to the bovine enzyme and a short version that contains the Zn++-binding catalytic site but lacks the entire C-terminal domain in which the properdin repeats are located. We have identified the mutations that cause EDS type VIIC in the six known affected human individuals and also in one strain of dermatosparactic calf. Five of the individuals with EDS type VIIC were homozygous for a C-->T transition that results in a premature termination codon, Q225X. Four of these five patients were homozygous at three downstream polymorphic sites. The sixth patient was homozygous for a different transition that results in a premature termination codon, W795X. In the dermatosparactic calf, the mutation is a 17-bp deletion that changes the reading frame of the message. These data provide direct evidence that EDS type VIIC and dermatosparaxis result from mutations in the pNPI gene.

Alternative Splicing↗

PubMed1999

Gradual withdrawal of long-term anticholinergic antiparkinson medication in Chinese patients with chronic schizophrenia.

Previous antiparkinson drug withdrawal studies involving white subjects have yielded inconclusive findings, whereas there is a paucity of data concerning Asian patients. A double-blind, placebo-controlled, randomized trial using gradual withdrawal of antiparkinson medication was conducted to evaluate the need for maintenance antiparkinson therapy for clinically stable Chinese patients with chronic schizophrenia. Seventy-five schizophrenic subjects who had received a diagnosis according to DSM-IV who had been ill for at least 5 years and on antipsychotic and antiparkinson medication for a minimum of 2 years entered the study. After baseline assessment, 58 subjects were matched according to age, sex, age at onset, length of illness, dose and length of antipsychotic and antiparkinson medication, and the presence of various extrapyramidal side effects. Randomly assigned dose-reduction and control groups were formed consisting of 29 subjects each. Trihexyphenidyl (THP), the only oral antiparkinson drug used in the study, was reduced by 1 mg every 2 weeks, whereas other psychotropic medication remained unchanged. Monthly assessment was performed using the Brief Psychiatric Rating Scale, Hamilton Rating Scale for Depression, Abnormal Involuntary Movement Scale, Simpson-Angus Scale, Barnes Akathisia Rating Scale, and the Nursing Observation Scale for Inpatient Evaluation-30. Complete withdrawal of THP was possible in 25 (90%) of the 28 subjects who completed the study, whereas considerable dose reduction was achieved in the remaining 3 subjects. There were no significant differences between dose reduction and control groups on any of the rating scales at the completion of the study. Our results suggest that long-term prophylactic administration of antiparkinson medication is unnecessary in the treatment of the majority of Chinese patients with chronic schizophrenia because withdrawal was accomplished without adverse mental or motor effects.

Adult↗

PubMed1999

Dissimilatory reduction of Fe(III) and other electron acceptors by a Thermus isolate.

A thermophilic bacterium that can use O2, NO3-, Fe(III), and S0 as terminal electron acceptors for growth was isolated from groundwater sampled at a 3.2-km depth in a South African gold mine. This organism, designated SA-01, clustered most closely with members of the genus Thermus, as determined by 16S rRNA gene (rDNA) sequence analysis. The 16S rDNA sequence of SA-01 was >98% similar to that of Thermus strain NMX2 A.1, which was previously isolated by other investigators from a thermal spring in New Mexico. Strain NMX2 A.1 was also able to reduce Fe(III) and other electron acceptors. Neither SA-01 nor NMX2 A.1 grew fermentatively, i.e., addition of an external electron acceptor was required for anaerobic growth. Thermus strain SA-01 reduced soluble Fe(III) complexed with citrate or nitrilotriacetic acid (NTA); however, it could reduce only relatively small quantities (0.5 mM) of hydrous ferric oxide except when the humic acid analog 2,6-anthraquinone disulfonate was added as an electron shuttle, in which case 10 mM Fe(III) was reduced. Fe(III)-NTA was reduced quantitatively to Fe(II); reduction of Fe(III)-NTA was coupled to the oxidation of lactate and supported growth through three consecutive transfers. Suspensions of Thermus strain SA-01 cells also reduced Mn(IV), Co(III)-EDTA, Cr(VI), and U(VI). Mn(IV)-oxide was reduced in the presence of either lactate or H2. Both strains were also able to mineralize NTA to CO2 and to couple its oxidation to Fe(III) reduction and growth. The optimum temperature for growth and Fe(III) reduction by Thermus strains SA-01 and NMX2 A.1 is approximately 65 degrees C; their optimum pH is 6.5 to 7.0. This is the first report of a Thermus sp. being able to couple the oxidation of organic compounds to the reduction of Fe, Mn, or S.

Biodegradation, Environmental↗

PubMed1999

Apoptosis in rat erectile tissue induced by castration.

AIM: To investigate the effect of androgen on the structure of corpus cavernosum. METHODS: Thirty mature rats were randomized into 3 groups, i.e., simple castration, castration with testosterone (T) supplementation and sham-operated controls. One week after operation, the animals were sacrificed and corpora cavenosa harvested. Apoptosis was detected with the in situ end labeling (ISEL) techniques and DNA fragment analysis. RESULTS: The apoptotic rate was 4.19% in the simple castrated rats, 0. 2% in castrated rats supplemented with T and 0.14% in the controls. Significant difference was found between the simple castrates and other two groups (P < 0.01). When comparing the T-supplementation group with the controls, there was no statistical difference (P > 0.05). CONCLUSION: Castration induced apoptosis in rat corpus cavernosum, that could be prevented by T supplementation. It suggests that androgen plays an important role in maintaining the structure of corpus cavernosum.

Animals↗

PubMed1999

Regeneration of neuronal nitric oxide synthase (nNOS)-containing nerve fibers in rat corpus cavernosum.

AIM: To investigate the effect of cavernous nerve injury on the nNOS-containing nerve fibers in rat corpus cavernosum. METHODS: Thirty-three male SD rats were randomized into 3 groups: 5 rats underwent pelvic exploration without transection of cavernous nerve as the sham-operated controls, the unilateral injury group (14 rats) had the cavernous nerve cut on one side, and the bilateral injury group (14 rats) had the nerves cut on both sides. Corpora cavernosa were harvested at the 3rd week and 6th month after surgery. nNOS-positive nerve fibers were examined with strepavidin peroxidase immunohistochemistry techniques (SP method). RESULTS: After bilateral ablation, the nNOS-positive nerve fibers were significantly decreased at both the 3rd week (17 +/- 4) and the 6th month (16 +/- 4). For the unilateral injury group, the nNOS-positive nerve fibers were similarly decreased on the side of the neurotomy at the 3rd week (18 +/- 6), but by the 6th month, the number increased significantly (61 +/- 9) and approximated the level on the contralateral side (81 +/- 13). CONCLUSION: In rats after unilateral cavernous nerve ablation, nNOS-containing nerve fibers might regenerate 6 months after operation, but regeneration did not occur in animals with bilateral cavernous nerve injury. Results suggest that during pelvic radical surgery, the cavernous nerve should be preserved at least on one side in order to accomplish adequate regeneration.

Animals↗

PubMed1998

Norepinephrine transmitter metabolite generates free radicals and activates mitochondrial permeability transition: a mechanism for DOPEGAL-induced apoptosis.

3,4-Dihydroxyphenylglycolaldehyde (DOPEGAL) is the monoamine oxidase A metabolite of norepinephrine (NE) and epinephrine. DOPEGAL, but neither NE nor its other metabolites induces apoptosis in differentiated PC-12 cells by an unknown mechanism. To study the mechanism of DOPEGAL-induced apoptosis, we tested DOPEGAL and NE for their capacity to generate free radicals and to induce mitochondrial permeability transition (PT). Results show that DOPEGAL but not NE forms reactive free radical intermediates under oxidative stress and enhances Ca2+-mediated induction of the mitochondrial PT. Linkage of these events to apoptosis is described. Implications for degenerative diseases are discussed.

Aldehydes↗

PubMed1998

Procollagen N-proteinase and procollagen C-proteinase. Two unusual metalloproteinases that are essential for procollagen processing probably have important roles in development and cell signaling.

As soon as procollagen precursors of fibrillar collagens were discovered in the early 1970s, it became apparent that connective tissues must contain proteolytic activities that cleave the N-propeptides and the C-propeptides from procollagens. Isolation and characterization of the enzymic activities, however, proved to be unexpectedly difficult. Both proteinases are large and are synthesized in several different forms with polypeptide chains ranging in size from 70 kDa to about 130 kDa. The N-proteinase has the unusual property of cleaving the N-propeptides from type I and type II procollagens if the proteins are in a native conformation, but not if the proteins are partially unfolded so that the N-telopeptides are no longer in a hair-pin configuration. The C-proteinase specifically cleaves native and denatured types I, II and III procollagens. It also specifically cleaves a precursor of lysyl oxidase and laminin 5. Both enzymes and their variants have structures that place them in a large and expanding super-family of over 200 zinc-binding metalloproteinases. The larger of two forms of the N-proteinase contains an RGD sequence for binding through integrins and properdin repeats similar to those found in thrombospondin. The shorter 70 kDa form of the C-proteinase is identical to the protein that was previously identified as bone morphogenic protein-1. Both the 70 kDa C-proteinase and two larger forms are homologous to proteins that are expressed early in development in a variety of organisms, including Drosophila, sea urchin, and fish. Therefore, the data suggest that both the N- and C-proteinases have important biological functions in addition to the roles in the processing of procollagens.

Animals↗

PubMed1998

A 1,064 bp fragment from the promoter region of the Col11a2 gene drives lacZ expression not only in cartilage but also in osteoblasts adjacent to regions undergoing both endochondral and intramembranous ossification in mouse embryos.

We isolated a 1,064 bp promoter fragment that extended from the 3'-end of the adjacent gene for retinoic X receptor-beta to beyond the most clearly defined start site of the mouse Col11a2 gene. The fragment was then joined to a beta-galactosidase gene and used to prepare transgenic mice. Three independent lines of transgenic mice were generated. The reporter beta-galactosidase gene was expressed in essentially all cartilaginous tissues in 15.5-day-old mouse embryos. In addition, the construct was expressed in osteoprogenitors within developing periosteum and in osteoblasts within mineralized bone. This pattern of expression was evident during both endochondral and intramembranous bone formation. Therefore, the results suggest that 1,064 bp promoter fragment can drive tissue-specific expression of the Col11a2 gene.

Animals↗

PubMed1998

Clock-face drawing, reading and setting tests in the screening of dementia in Chinese elderly adults.

Comprehensive neuropsychological batteries focus on the subtle cognitive deficits in dementia, but a brief screening instrument is also of immense practical value. As the clock-drawing test encompasses a number of cognitive domains frequently disturbed by the dementing process, it is considered to be a suitable screening instrument for the disorder. We documented the usefulness of a new scoring method of the clock-drawing test for screening of dementia in the elderly Chinese in Hong Kong. Fifty-three demented individuals and 53 healthy elderly controls were assessed. At a cutoff score of 3/4, the sensitivity and specificity of the clock-drawing test in screening of dementia was 83% and 79%. With a composite test of clock reading and clock setting, the positive predictive value of the clock face test was 98%. This new scoring method of clock-drawing proved to be a valid measure for screening of dementia. It is applicable in non-English speaking populations and should be a useful adjunct for quick screening assessment of dementia.

Aged↗