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Biomedical subjects

C T Ho

Publications and source records attributed to C T Ho.

At least 73 records · Page 4Linked to original sources
PubMed1999

Do flares of systemic lupus erythematosus decline after menopause?

OBJECTIVE: To study whether flares of SLE decline after menopause. METHOD: 34 postmenopausal SLE patients with premenopausal disease onset were studied. The frequency and severity of flares before and after menopause was compared. 17 postmenopausal onset SLE patients were also included for comparison. RESULT: Flares in postmenopausal SLE patients decreased significantly after menopause (total No. of flares/patient-year before and after menopause were 0.50+/-0.10 and 0.14+/-0.05, respectively, p = 0.002). The frequency and proportion of severe flares also dropped significantly. The rate and magnitude of postmenopausal flares in these patients were similar to those of the postmenopausal onset SLE patients, a subset known to run a more benign course. CONCLUSIONS: SLE flares less frequently and seriously after menopause. While this may suggest a protective role of hypoestrogenemia against lupus flares, the contribution of other factors like disease duration and effective treatment to this postmenopausal decline of flares cannot be separated from menopause per se. Further studies are needed.

Adolescent↗
PubMed1999

Suppression of extracellular signals and cell proliferation by the black tea polyphenol, theaflavin-3,3'-digallate.

Previous studies in our laboratory have shown that the major green tea polyphenol, (-)-epigallocatechin-3-gallate (EGCG), suppressed autophosphorylation of epidermal growth factor (EGF) receptor induced by EGF in human A431 epidermoid carcinoma cells. In this study, we examined the inhibitory effects of black tea polyphenols, including theaflavin (TF-1), a mixture (TF-2) of theaflavin-3-gallate (TF-2a) and theaflavin-3'-gallate (TF-2b), theaflavin-3,3'-digallate (TF-3) and the thearubigin fraction on the autophosphorylation of the EGF and PDGF receptors in A431 cells and mouse NIH3T3 fibroblast cells, respectively. First, we examined the effects of these polyphenols on the proliferation of A431 and NIH3T3 cells. Both EGCG and TF-3 strongly inhibited the proliferation of A431 and NIH3T3 cells more than the other theaflavins did. In cultured cells with pre-treatment of tea polyphenol, TF-3 was stronger than EGCG on the reduction of EGF receptor and PDGF receptor autophosphorylation induced by EGF and PDGF, respectively. Other theaflavins slightly reduced the autophosphorylation of the EGF and PDGF receptors; furthermore, TF-3 could reduce autophosphorylation of the EGF receptor (or PDGF receptor) even with co-treatment with EGF (or PDGF) and TF-3, but EGCG was inactive under these conditions. In addition, TF-3 was stronger than EGCG in blocking EGF binding to its receptor. These results suggest that not only the green tea polyphenol, EGCG, but also the black tea polyphenol, TF-3, have an antiproliferative activity on tumor cells, and the molecular mechanisms of antiproliferation may block the growth factor binding to its receptor and thus suppress mitogenic signal transduction.

3T3 Cells↗
PubMed1998

Inhibition of lung carcinogenesis by black tea in Fischer rats treated with a tobacco-specific carcinogen: caffeine as an important constituent.

Here, we examined the effect of black tea and caffeine on lung tumorigenesis in F344 rats induced by the nicotine-derived carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in a 2-year bioassay. NNK was administered s.c. at a dose of 1.5 mg/kg body weight three times weekly for 20 weeks. Animals were given either black tea as drinking water at concentrations of 2%, 1%, or 0.5%, or caffeine in drinking water at concentrations identical to those in 2% and 0.5% tea infusions for 22 weeks. The treatment period began 1 week before and ended 1 week after the NNK administration. The animals were sacrificed on week 101 for the examination of tumors in target organs, including lung, liver, nasal cavity, and other major organs. The NNK-treated group, given 2% black tea, showed a significant reduction of the total lung tumor (adenomas, adenocarcinomas, and adenosquamous carcinomas) incidence from 47% to 19%, whereas the group given 1% and 0.5% black tea showed no change. The 2% tea also reduced liver tumor incidence induced by NNK from 34% in the group given only deionized water to 12%. The tumor incidence in the nasal cavity, however, was not affected by either black tea or caffeine at any of the concentrations tested. The most unexpected finding was the remarkable reduction of the lung tumor incidence, from 47% to 10%, in the group treated with 680 ppm caffeine, a concentration equivalent to that found in the 2% tea. This incidence is comparable to background levels seen in the control group. This study demonstrated for the first time in a 2-year lifetime bioassay that black tea protects against lung tumorigenesis in F344 rats, and this effect appears to be attributed, to a significant extent, to caffeine as an active ingredient of tea.

Animals↗
PubMed1998

Green tea epigallocatechin gallate shows a pronounced growth inhibitory effect on cancerous cells but not on their normal counterparts.

(-)-Epigallocatechin gallate (EGCG), a catechin polyphenol compound, represents the main ingredient of green tea extract. Although EGCG has been shown to be growth inhibitory in a number of tumor cell lines, it is not clear whether the effect is cancer-specific. In this study we compared the effect of EGCG on the growth of SV40 virally transformed WI38 human fibroblasts (WI38VA) with that of normal WI38 cells. The IC50 value of EGCG was estimated to be 120 and 10 microM for WI38 and WI38VA cells, respectively. Thus, EGCG at 40 microM completely inhibited the growth of WI38VA cells, but had little or no inhibitory effect on the growth of WI38 cells. Similar differential growth inhibition was also observed between a human colorectal cancer cell line (Caco-2), a breast cancer cell line (Hs578T) and their respective normal counterparts. EGCG at a concentration range of 40-200 microM induced a significant amount of apoptosis in WI38VA cultures, but not in WI38 cultures, as determined by terminal deoxynucleotidyl transferase assay. After exposure to EGCG at 200 microM for 8 h, more than 50% of WI38VA cells in a confluent culture became apoptotic. In contrast, less than 1% of WI38 cells displayed apoptotic labeling under the same condition. EGCG did not affect the serum-induced expression of c-fos and c-myc genes in normal WI38 cells. However, it significantly enhanced their expression in transformed W138VA cells. It is possible that differential modulation of certain genes, such as c-fos and c-myc, may cause differential effects of EGCG on the growth and death of cancer cells.

Anticarcinogenic Agents↗
PubMed1998

Process-induced chemical changes in foods. An overview.

Processing of foods induces changes in their physical, chemical and sensory characteristics. Many researchers have shown the chemical consequences of food processing on acceptability and sensory attributes, nutritive value and wholesomeness of foods. A cursory account of these changes is provided.

Dietary Carbohydrates↗
PubMed1998

Flavor generation during extrusion cooking.

Extrusion cooking is a high temperature-short time process which is ideal for the production of flavor volatiles. However, due to the nature of this process there are many opportunities for these volatiles to be lost. This has led many researchers to study the formation and retention of volatiles during extrusion. This review will focus on-the flavor related reactions which may occur during extrusion and their occurrence in various flours and due to the addition of reactive precursors.

Amino Acids↗
PubMed1998

Photochemical reactions of flavor compounds.

Photochemical reaction is a chemical reaction which is initiated by light. In addition to light, photosensitizer and oxygen are the two important factors which contribute to the formation of photochemical products. In this contribution, photochemical reactions of flavor compounds are classified into four categories according to the factors of photosensitizer and oxygen. Photochemical reaction with or without sensitizer in the absence of oxygen and unsensitized photochemical reaction in the presence of oxygen usually involve free radical reactions; while in the presence of oxygen and sensitizer, the singlet oxygen can be generated that then reacts with flavor compounds which contain double bonds to give the oxygenated products.

Dimerization↗
PubMed1998

Inhibitory activity of boswellic acids from Boswellia serrata against human leukemia HL-60 cells in culture.

Four major triterpene acids including beta-boswellic acid (1), 3-O-acetyl-beta-boswellic acid (2), 11-keto-beta-boswellic acid (3), and 3-O-acetyl-11-keto-beta-boswellic acid (4) were isolated from the gum resin of Boswellia serrata and examined for their in vitro antitumor activity. They inhibited the synthesis of DNA, RNA and protein in human leukemia HL-60 cells in a dose dependent manner with IC50 values ranging from 0.6 to 7.1 microM. Among them, compound 4 induced the most pronounced inhibitory effects on DNA, RNA and protein synthesis with IC50 values of 0.6, 0.5, and 4.1 microM, respectively. The effect of 4 on DNA synthesis was found to be irreversible. Compound 4 significantly inhibited the cellular growth of HL-60 cells, but did not affect cell viability.

Antineoplastic Agents, Phytogenic↗
PubMed1998

Safety of hormonal replacement therapy in postmenopausal patients with systemic lupus erythematosus.

It remains controversial whether administration of exogenous estrogens is safe in systemic lupus erythematosus (SLE). The current study was undertaken to determine the effect of hormone replacement therapy (HRT) on the rate and magnitude of flares in a cohort of postmenopausal SLE patients. Thirty-four patients were prospectively followed. The frequency and severity of disease exacerbations in 11 patients who received HRT was compared with 23 patients who did not receive HRT. Our results showed that both users and non-users of HRT had a comparable age of disease onset, duration of disease, clinical manifestations, and duration of follow-up. No significant increase in the rate (0.12 relapses/patient-year in HRT group vs 0.16 relapses/patient-year in the non-HRT group, p = 0.90) or magnitude (total SLEDAI score increase during flares/patient-year in the HRT and non-HRT groups were 0.55 and 1.22, respectively, p = 0.57) of flares could be demonstrated in patients who received HRT over a median follow-up period of 35 months. We concluded that HRT appeared to be well tolerated and safe in postmenopausal SLE patients. Its potential beneficial effect may outweigh its deleterious effect on disease activity.

Adult↗
PubMed1998

Dietary administration of an extract from rosemary leaves enhances the liver microsomal metabolism of endogenous estrogens and decreases their uterotropic action in CD-1 mice.

We evaluated the effects of a methanol extract from the leaves of the plant Rosmarinus officinalis L. (rosemary) on the metabolism and action of estradiol and estrone. Treatment of female CD-1 mice with 2% rosemary in AIN-76A diet for 3 weeks increased the liver microsomal 2-hydroxylation of estradiol and estrone by approximately 150%, increased their 6-hydroxylation by approximately 30% and inhibited the 16alpha-hydroxylation of estradiol by approximately 50%. Treatment of female CD-1 mice with 2% rosemary diet for 3 weeks also stimulated the liver microsomal glucuronidation of estradiol and estrone by 54-67% and 37-56%, respectively. In additional studies, feeding 2% rosemary diet to ovariectomized CD-1 mice for 3 weeks inhibited the uterotropic action of estradiol and estrone by 35-50% compared with animals fed a control diet. The results of this study showed that feeding female mice a 2% rosemary diet increased the liver microsomal oxidation and glucuronidation of estradiol and estrone and inhibited their uterotropic action.

Animals↗
PubMed1998

Effect of dietary curcumin and dibenzoylmethane on formation of 7,12-dimethylbenz[a]anthracene-induced mammary tumors and lymphomas/leukemias in Sencar mice.

Female Sencar mice (6 weeks old) were administered 1 mg of 7,12-dimethylbenz[a]anthracene (DMBA) by oral gavage once a week for 5 weeks. At 20 weeks after the first dose of DMBA, 68% of mice developed mammary tumors (the average 1.08 tumors per mouse) and 45% had lymphomas/leukemias. Feeding 1% dibenzoylmethane (DBM) in AIN 76A diet, starting at 2 weeks before the first dose of DMBA and continuing until the end of the experiment, inhibited both the multiplicity and incidence of DMBA-induced mammary tumor by 97%. The incidence of lymphomas/leukemias was completely inhibited by 1% DBM diet. In contrast, feeding 2% curcumin diet had little or no effect on the incidence of mammary tumors, and the incidence of lymphomas/leukemias was reduced by 53%.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1998

Late onset systemic lupus erythematosus in southern Chinese.

OBJECTIVE: Systemic lupus erythematosus (SLE) is a multisystem disorder that predominately affects women of the reproductive age. Onset of the disease beyond the age of 50 years is unusual. This study was undertaken to compare retrospectively the clinical and laboratory features between early and late onset (onset of disease beyond the age of 50 years) SLE patients in a Chinese population. METHODS: Case records of all SLE patients who attended our rheumatology clinics between 1971 and 1997 were reviewed. Patients with a disease onset beyond the age of 50 years were identified. One hundred consecutive SLE patients who had their disease onset before the age of 50 were recruited as controls. The presenting clinical features, autoantibody profile, number of major organs involved, number of major relapses, and the use of cytotoxic agents in the two groups of patients were obtained and compared. RESULTS: 25 patients with late onset SLE were identified. All the female patients in the late onset group were postmenopausal. The female to male ratio was 3.2 to 1, compared with 13.3 to 1 in the control group (p < 0.02). Both groups had a comparable duration of disease. There were no significant differences in the presenting features between the two groups except for a lower prevalence of malar rash (24% v 86%, p < 0.0001) and a higher prevalence of rheumatoid factor (32% v 1%, p < 0.0001) in the late onset patients. On subsequent visits, the late onset group had a lower prevalence of lupus nephritis (4% v 51%, p < 0.001), fewer major organs involved (mean number of major organs involved; 0.3 v 0.9, p < 0.02), fewer major relapses (mean number of major relapses/patient; 0.08 v 0.47, p < 0.002, number of major relapses/patient year; 0.009 v 0.12, p < 0.001), and required fewer cytotoxic agents for disease control (percentage of patients on cytotoxic agents; 32% v 79%, p < 0.002). CONCLUSION: Late onset SLE in Chinese tends to run a more benign course with fewer major organ involvement and fewer major relapses. The significantly higher incidence of male sex in late onset SLE and the milder disease course in the postmenopausal female patients suggest that oestrogen status may influence disease activity.

Adolescent↗
PubMed1997

Inhibition of inducible nitric oxide synthase gene expression and enzyme activity by epigallocatechin gallate, a natural product from green tea.

Chronic inflammation has been implicated as the underlying factor in the pathogenesis of many disorders. In the past decade, inflammation-related endogenous production of reactive nitrogen species, similar to oxygen free radicals, has also been suggested as a risk factor for cancer, in addition to the well-studied exogenous nitroso compounds. Epidemiological, in vitro, and animal model studies have implicated green tea to be protective against nitroso compound-induced and inflammation-related cancer. Therefore, we investigated the effect of epigallocatechin-3-gallate (EGCG), one of the known biologically active catechins contained in green tea, on the production of nitric oxide (NO.). We have shown previously that EGCG reduces NO. production as measured by nitrite accumulation in the culture medium. Expanding on this finding, in this report we show that EGCG may do so by two mechanisms: reduction of inducible nitric oxide synthase (iNOS) gene expression and inhibition of enzyme activity. Addition of 1-10 microM EGCG to lipopolysaccharide- and interferon-gamma-activated mouse peritoneal cells reduced iNOS mRNA expression concentration dependently, to 82-14%, as measured by relative reverse transcription-polymerase chain reaction. Addition of 50-750 microM EGCG, in a concentration-dependent manner, inhibited the enzyme activity of iNOS, to 85-14%, and neuronal nitric oxide synthase (nNOS), to 93-56%, as measured by citrulline formation. EGCG competitively inhibited binding of arginine and tetrahydrobiopterin, and the gallate structure is important for this action.

Animals↗
PubMed1997

Effects of tea, decaffeinated tea, and caffeine on UVB light-induced complete carcinogenesis in SKH-1 mice: demonstration of caffeine as a biologically important constituent of tea.

Oral administration of green or black tea inhibited UVB light-induced complete carcinogenesis in the skin of SKH-1 mice. Green tea was a more effective inhibitor than black tea. Oral administration of decaffeinated green or black tea resulted in substantially less inhibitory activity than did administration of the regular teas, and in one experiment, administration of a high-dose level of the decaffeinated teas enhanced the tumorigenic effect of UVB. Oral administration of caffeine alone had a substantial inhibitory effect on UVB-induced carcinogenesis, and adding caffeine to the decaffeinated teas restored the inhibitory effects of these teas on UVB-induced carcinogenesis. In additional studies, topical application of a green tea polyphenol fraction after each UVB application inhibited UVB-induced tumorigenesis. The results indicate that caffeine contributes in an important way to the inhibitory effects of green and black tea on UVB-induced complete carcinogenesis.

Administration, Oral↗
PubMed1997

In vitro and in vivo protective effect of honokiol on rat liver from peroxidative injury.

Honokiol, a compound extracted from the Chinese medicinal herb Magnolia officinalis, has a strong antioxidant effect on the inhibition of lipid peroxidation in rat heart mitochondria. To investigate the protective effect of honokiol on hepatocytes from peroxidative injury, oxygen consumption and malondialdehyde formation for in vitro iron-induced lipid peroxidation were assayed, and the mitochondrial respiratory function for in vivo ischemia-reperfusion injury were evaluated in rat liver, respectively. The inhibitory effect of honokiol on oxygen consumption and malondialdehyde formation during iron-induced lipid peroxidation in liver mitochondria showed obvious dose-dependent responses with a concentration of 50% inhibition being 2.3 x 10(-7) M and 4.96 x 10(-7) M, respectively, that is, 550 times and 680 times more potent than alpha-tocopherol, respectively. When rat livers were introduced with ischemia 60 min followed by reperfusion for 60 min, and then pretreated with honokiol (10 micrograms/kg BW), the mitochondrial respiratory control ratio (the quotient of the respiration rate of State 3 to that of State 4) and ADP/O ratio from the honokiol-treated livers were significantly higher than those of non-treated livers during reperfusion. The dose-dependent protective effect of honokiol on ischemia-reperfusion injury was 10 microgram-100 micrograms/Kg body weight. We conclude that honokiol is a strong antioxidant and shed insight into clinical implications for protection of hepatocytes from ischemia-reperfusion injury.

Animals↗
PubMed1997

Triterpenoid saponins from Aster lingulatus.

Two new triterpenoid saponins named asterlingulatosides A and B were isolated from the whole plants of Aster lingulatus. Their structures were determined by spectroscopic data and chemical transformations to be 3-O-beta-D-glucopyranosyl-3 beta,16 alpha-dihydroxyolean-12-en-28-oic acid-28-O-alpha-L-O-arabinopyranoside and 3-O-beta-D-glucopyranosyl-3 beta,16 alpha-dihydroxyolean-12-en-28-oic acid-28-O-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranoside++ +. They showed inhibitory activity on DNA synthesis in human leukaemia HL-60 cells.

Antineoplastic Agents, Phytogenic↗
PubMed1997

Asterlingulatosides C and D, cytotoxic triterpenoid saponins from Aster lingulatus.

A further investigation of Aster lingulatus has led to the isolation of two additional novel triterpene saponins, asterlingulatoside C [3-O-beta-D-glucopyranosyl-3 beta, 16 alpha-dihydroxyolean-12-en-28-oic acid 28-O-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-alpha- L- arabinopyranoside] (1) and asterlingulatoside D [3-O-beta-D-glucopyranosyl-3 beta,16 alpha-dihydroxyolean-12-en-28-oic acid 28-O-beta-D-xylopyranosyl-(1-->3)-beta-D-xylopyranosyl-(1-->4)-alpha-L- rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranoside] (2). Elucidation of the structures of 1 and 2 was mainly based on FABMS and 1D and 2D homonuclear and heteronuclear NMR techniques. Compounds 1 and 2 showed good inhibitory activity against DNA synthesis in human leukemia HL-60 cells with IC50 values of 8.8 and 6.1 microM, respectively.

Antineoplastic Agents, Phytogenic↗