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T Chaudhuri

Publications and source records attributed to T Chaudhuri.

At least 19 recordsLinked to original sources
PubMed2005

The theaflavin fraction is responsible for the facilitatory effect of black tea at the skeletal myoneural junction.

The effect of various fractions of black tea [(Camellia Sinensis) (L) O. Kuntze (Theaceae)] on the function of mammalian skeletomotor apparatus was studied. The theaflavin fraction (Tfs) produced a concentration- dependent facilitation of indirect twitch responses of the rat phrenic nerve diaphragm preparation and the facilitation was dependent on the amount of calcium present in the bathing fluid. Nifedipine reduced the facilitatory effect of Tfs as a function of its concentration. Tfs failed to produce facilitation when the twitch height was reduced to about 50% of the control value in presence of magnesium chloride. Tfs completely antagonized the submaximal paralytic effect of d- tubocurarine and decamethonium bromide. Tfs did not have any effect on direct twitch responses or on acetylcholine (Ach) and potassium chloride (KCl) induced contractures of denervated diaphragm. The results revealed that the site of action of Tfs is on the contractile mechanism of the voluntary muscle and point to a critical role of calcium in the mechanism of action of Tfs. N omega-nitro-L-arginine-methyl ester (L-NAME), a nitric oxide synthase (NOS) inhibitor, antagonized both the facilitatory and inhibitory effects on indirect twitch responses of rat diaphragm induced by L-arginine and Tfs when the phrenic nerve was stimulated at 5 Hz and 50 Hz respectively. The thearubigin (Trs) fraction of black tea and the aqueous part which is completely devoid of Tfs, did not potentiate the twitch responses. The findings suggest that Tfs have a potentiating effect on the contractile mechanism of skeletal muscle and that calcium and nitric oxide may modulate this action of Tfs.

Animals↗
PubMed2002

Antimutagenic effects of black tea (World Blend) and its two active polyphenols theaflavins and thearubigins in Salmonella assays.

Almost two thirds of the world population consume tea everyday. Tea is processed differently in different parts of the world to give green (20%), black (78%) or oolong tea (2%). The antimutagenic and anticarcinogenic activities of green tea were extensively investigated compared with those of black tea. Considering the potent antimutagenic effects of green tea we recognized the need to evaluate the antimutagenic effects of black tea (World Blend Tea, Southern Tea Co., Marietta, GA) in Salmonella strains TA97a, TA98, TA100 and TA102 in preincubation tests, both with and without S9 activation. Attempts have also been made to compare the results of the tea extracts with their two active polyphenols theaflavins and thearubigins. Antimutagenicity assays were carried out in bacterial plates treated with different concentrations (1%, 2.5%, 5%, 10% and 20%) of tea extracts against known bacterial mutagens sodium azide, 4-nitro-o-phenylenediamine, cumine hydroperoxide, 2-aminofluorene and danthron. A significant decrease in the number of revertant colonies was observed in the plates treated with 1% to 20% of tea extract plus positive mutagen when compared with positive mutagen only. Both the active polyphenols theaflavins and thearubigins extracted from the black tea (World blend) also showed significant antimutagenic effects against known positive compounds in these strains. In the experiments with S9 activation, the antimutagenic effects were significantly higher. These results indicate that black tea and its two polyphenols have significant antimutagenic effects in Ames Salmonella assays.

Animals↗
PubMed2002

Studies with black tea and its constituents on leukemic cells and cell lines.

The anticancer effect of black tea (BT) and its polyphenols theaflavin (TF) and thearubigin (TR) has been evaluated on U-937 cell line, a myeloid leukemic cell line and on leukemic cells isolated from peripheral blood of chronic myeloid leukemia (CML) patients. In both types of cells, cell growth inhibition was observed 24 hrs after treatment with BT, TF and TR. MTT assay showed growth inhibition of metabolically active cells and inhibition of DNA synthesis was observed by 3H-Thymidine incorporation after treatment with the compounds. In all cases TF and TR were more effective than BT, suggesting that these are possibly the active components in BT responsible for its antileukemic activity. Superoxide dismutase (SOD), a free radical scavenger, was found to be increased by TF, whereas BT and TR lowered the level in comparison to the control. The present study is the first report of antileukemic effect of BT and its polyphenols.

Anticarcinogenic Agents↗
PubMed2001

Anticlastogenic effects of black tea (World blend) and its two active polyphenols theaflavins and thearubigins in vivo in Swiss albino mice.

This study investigated the inhibition of cyclophosphamide (CP) and dimethylbenz(a)anthracene (DMBA) induced genetic damage by black tea (World blend) and its two active polyphenols theaflavins (TF) and thearubigins (TR) in Swiss albino mice as measured by chromosome aberrations (CA) and sister chromatid exchanges (SCE). Three different concentrations (5, 10 and 20%) of tea and a single dose of TF and TR were tested for their anticlastogenic effects against DMBA (50 mg/kg body weight) and CP (20 mg/kg for CA and 10 mg/kg for SCE). A significant decrease in CA was observed in all the three concentrations of tea extract plus DMBA treated groups when compared with the respective DMBA treated group alone. Similarly a significant decrease in CA was observed in all the three concentrations of tea extracts plus CP treated series when compared with the group treated with CP alone. In SCE assay, a significant decrease in SCE was observed in 5, 10 and 20% black tea extract plus CP and 10 and 20% tea extracts plus DMBA treated groups when compared with the CP or DMBA treated group alone. In the single dose of TF and TR treated groups a significant decrease in both CA and SCE was observed in both the TF and TR plus both the carcinogen treated groups when compared with their positive controls. The protective effects of black tea extracts were more significant than that of its two polyphenols. This study indicates that both black tea and its active polyphenols TF and TR have significant anticlastogenic effects in bone marrow cells of mice.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed2001

Antiinflammatory and antioxidant property of saponins of tea [Camellia sinensis (L) O. Kuntze] root extract.

Two groups of saponins, TS-1 and TS-2, isolated from tea root extract (TRE) were tested for antiinflammatory and in vitro antioxidant activity. Both TS-1 and TS-2 inhibited carrageenan-induced paw oedema in rats. The antioxidant activity of these compounds was evaluated using the xanthine-xanthine oxidase system. The study indicated that the previously observed antitumour activity of TRE might be mediated through scavenging of free radicals by saponins and their antiinflammatory activity.

Animals↗
PubMed2000

Prokinetic effect of black tea on gastrointestinal motility.

The gastrokinetic effects of hot water extract of black tea [Camellia sinensis, (L) O. Kuntze (Theaceae)] on gastrointestinal motility were studied both in vivo and in vitro. The extract significantly accelerated the gastrointestinal transit (GIT) in vivo in mice. These facilitatory effect was reduced after pretreatment with atropine, hemicholinium-3, morphine, indomethacin, McN-A-343 and L-arginine. In guinea pig ileum, the extract facilitated the peristaltic reflex in response to pressures in normal preparation. The black tea extract and L-NMMA (nitric oxide synthase inhibitor) significantly reduced the electrical field stimulated nonadrenergic, noncholinergic (NANC) relaxation of isolated rat fundal strips. The extract markedly enhanced the tonic ('hump') responses to transmural stimulation in longitudinal muscle of guinea pig ileum which was unaltered in the presence of atropine. These findings suggest a cholinergic involvement and a partial role of prostaglandin and nitric oxide in the mechanism of action of black tea extract on gastrointestinal motility. To determine the effective constituents in black tea responsible for this activity, the effect of black tea polyphenols on GIT were also studied. Thearubigin fraction (but not theaflavin) accelerated GIT significantly which suggests its involvement in the prokinetic effect of black tea.

Animals↗
PubMed2000

Triterpenoid saponins from the roots of tea plant (Camellia sinensis var. assamica).

Three olean-12-ene type triterpenoid saponins, named TR-saponins A, B and C, were isolated as methyl esters from tea roots (Camellia sinesis var. assamica) after treatment with diazomethane. Their structures were established as the methyl esters of 3-O-alpha-L-arabinopyranosyl (1-->3)-beta-D-glucuronopyranosyl-21, 22-di-O-angeloyl-R1-barrigenol-23-oic acid, 3-O-alpha-L-arabinopyranosyl (1-->3)-beta-D-glucuronopyranosyl-21-O-angeloyl-22-O-2-me thylbutanoyl-R1- barrigenol-23-oic acid and 3-O-alpha-L-arabinopyranosyl (1-->3)-beta-D-glucuronopyranosyl-16 alpha-O-acetyl-21-O-angeloyl-22-O-2-methylbutanoyl-R1-bar rigenol-23-oic acid, by extensive 1D and 2D-NMR as well as FABMS and HR-MS analyses.

Magnetic Resonance Spectroscopy↗
PubMed1994

Saponins from Barringtonia acutangula.

Three monodesmosidic glucuronide saponins of barringtogenol C, named barringtosides A, B and C have been isolated as their methyl esters from the dried seeds of Barringtonia acutangula. On the basis of chemical and spectral evidence, the structures of these new saponins were elucidated to be as follows: barringtoside A, 3-O-beta-D-xylopyranosyl(1-->3)-[beta-D-galactopyranosyl(1-->2)]-beta-D- glucuronopyranosyl barringtogenol C; barringtoside B, 3-O-beta-D-xylopyranosyl(1-->3)-]beta-D-galactopyranosyl(1-->2)]-beta-D- glucuronopyranosyl-21-O-tigloyl-28-O-isobutyryl barringtogenol C; barringtoside C, 3-O-alpha-L-arabinopyranosyl(1-->3)-[beta-D-galactopyranosyl(1-->2 )]-beta-D - glucuronopyranosyl barringtogenol C.

Carbohydrate Sequence↗
PubMed1987

HLA status following fetal liver transplantation in aplastic anaemia and acute myeloid leukaemia.

Fetal liver infusion (FLI) was tried as an alternate mode of therapy in 40 patients with aplastic anaemia and in 16 patients with acute myeloid leukaemia. The fetal HLA typing carried out on spleen and thymus cells revealed that, while it was more difficult to HLA type the thymus than the spleen cells, 'full house' antigens could be determined only in fetuses of 18 weeks or older. No special effort was made to transfuse HLA- matched or partially matched donor cells into the recipient. The recipients were HLA typed at varying time intervals following FLI in an attempt to document a possible chimerism. None of the patients revealed a 'shift' in their HLA antigen profile and there was no evidence of any donor cell engraftment. No relationship between the HLA match of donor and recipient, and the general condition, the prognosis or the total survival of the patient was evidenced. These data indicate that, even though fetal liver cells express HLA antigens, these cells are functionally incompetent to cause an apparent graft-versus-host disease in the host.

Anemia, Aplastic↗
PubMed1986

Thallium-201 myocardial imaging during coronary vasodilation induced by oral dipyridamole.

Myocardial perfusion imaging of 201TI injected during maximum exercise has been an important diagnostic tool for coronary artery disease. Pharmacologic coronary vasodilation by i.v. infusion of dipyridamole may be used in lieu of exercise stress for purposes of diagnostic perfusion imaging. However, i.v. dipyridamole is not currently available from commercial sources for widespread routine use. Accordingly, this study was carried out in order to determine whether high dose, oral dipyridamole would be useful as a coronary vasodilator for purposes of diagnostic perfusion imaging. Fifty-eight patients undergoing diagnostic coronary arteriography also had myocardial perfusion imaging with 201TI under conditions of rest, maximum exercise stress, and high dose oral dipyridamole. Of those patients who had a defect on exercise thallium images, 75% also had a perfusion defect on thallium images after high dose oral dipyridamole. These results indicate that oral dipyridamole causes sufficient coronary arteriolar vasodilation and increase of coronary flow in nonstenotic arteries to identify perfusion defects comparable to those seen on maximum exercise stress in at least 75% of cases. In 25% of patients with exercise defects, no perfusion defect was seen after oral dipyridamole. Thus, oral dipyridamole is a potent coronary vasodilator, comparable to exercise stress in most cases, but in a minority of patients may not be comparable to exercise stress.

Administration, Oral↗
PubMed1979

Association of respiratory tract colonization with adherence of gram-negative bacilli to epithelial cells.

Factors that promote oropharyngeal colonization of seriously ill patients with gram-negative bacilli are as yet poorly understood. In this investigation, 34 subjects who required intensive care were studied; 18 (53%) were colonized with gram-negative bacilli. Oropharyngeal epithelial cells of all colonized patients contained adherent bacilli. Fewer alpha-hemolytic streptococci but greater numbers of Pseudomonas aeruginosa and Klebsiella pneumoniae (P less than or equal to 0.01) adhered in vitro to buccal epithelial cells from colonized patients than to cells from noncolonized patients. Adherence of bacilli to buccal cells was inhibited in vitro by concanavalin A but not by bovine serum albumin or phytohemagglutinin. Brief exposure of buccal cells to trypsin increased adherence of bacilli. Prior adherence of one species of bacilli inhibited subsequent adherence of a second species. These findings suggested that epithelial cells of the upper respiratory tract contain binding sites for gram-negative bacilli. Factors associated with serious illness appear to increase the availability of these binding sites, thus facilitating colonization of the upper respiratory tract with gram-negative bacilli.

Binding Sites↗