Biomedical subjects

T Ha

Publications and source records attributed to T Ha.

53 records · Page 3Linked to original sources

PubMed1996

Probing the interaction between two single molecules: fluorescence resonance energy transfer between a single donor and a single acceptor.

We extend the sensitivity of fluorescence resonance energy transfer (FRET) to the single molecule level by measuring energy transfer between a single donor fluorophore and a single acceptor fluorophore. Near-field scanning optical microscopy (NSOM) is used to obtain simultaneous dual color images and emission spectra from donor and acceptor fluorophores linked by a short DNA molecule. Photodestruction dynamics of the donor or acceptor are used to determine the presence and efficiency of energy transfer. The classical equations used to measure energy transfer on ensembles of fluorophores are modified for single-molecule measurements. In contrast to ensemble measurements, dynamic events on a molecular scale are observable in single pair FRET measurements because they are not canceled out by random averaging. Monitoring conformational changes, such as rotations and distance changes on a nanometer scale, within single biological macromolecules, may be possible with single pair FRET.

Base Sequence↗

PubMed1996

Receptor binding and internalization of a water-soluble (1-->3)-beta-D-glucan biologic response modifier in two monocyte/macrophage cell lines.

Glucan phosphate, a water-soluble, chemically defined (1-->3)-beta-D-glucan biologic response modifier, has been reported to exert antisepsis activity and accelerate wound healing. In this study we describe the specific binding of glucan phosphate to human and murine monocyte/macrophage cell lines, U937 and J774A.1, respectively. At 37 degrees C, equilibrium binding was rapidly achieved, i.e., within 1 min. In U937 cells, binding occurred with an affinity (Kd) of 37 microM and a Bmax of 65 x 106 binding sites/cell at 37 degrees C. In J774A.1 cells, glucan phosphate bound with an affinity (Kd) of 24 microM and a Bmax of 53 x 106 binding sites/cell at 37 degrees C. In both cases there was insignificant nonspecific binding. We further demonstrated that bound glucan phosphate cannot be displaced by a 50-fold excess of unlabeled ligand, suggesting internalization of glucan phosphate. Transmission electron microscopy showed significantly increased cytoplasmic vacuolization and significantly decreased mitotic activity in glucan phosphate-treated U937 cells compared with that in untreated cells. Pullulan, a random coil alpha-(1-->4)-(1-->6)-linked glucose polymer that served as a control, did not compete for the same binding site as glucan phosphate in either cell line, indicating the specificity of the binding site for (1-->3)-beta-D-glucans. We conclude that water-soluble pharmaceutical grade (1-->3)-beta-D-glucan phosphate specifically binds to and is internalized by U937 and J774A.1 cells.

Animals↗

PubMed1996

Microwave and Infrared Spectra, ab Initio Calculation, and Two-Dimensional Model of Amino Group Inversion and Ring Puckering in 2,5-Dihydropyrrole

The microwave spectra of 2,5-dihydropyrrole and 2,5-dihydropyrrole-1-d1 have been measured with Stark and Fourier transform spectrometers in the range 10-39 GHz. Rotational constants, centrifugal distortion constants, and 14N quadrupole coupling constants have been determined from the observed transition frequencies for the ground vibrational state. In addition, two satellites of the normal species and one satellite of the deuterated species have been identified and measured. Splittings of the rotational transitions due to amino group inversion tunneling have been observed and analyzed. Infrared transitions of the amino group inversion mode have been measured in the range 490-720 cm-1. The effect of ring puckering on the inversion motion of the amino group in 2,5-dihydropyrrole and 2,5-dihydropyrrole-N-d1 has been investigated by ab initio calculations and two-dimensional flexible model calculations from the results of microwave and infrared spectroscopy. The observed molecular properties have been reproduced by a model which involved adjustable parameters for the potential energy surface and the structural relaxation of the CCC valence angles. Additional parameters have been transferred from the ab initio calculations. The adjustment of the model to the experimental data has yielded an equatorial equilibrium conformation with slightly larger CCC valence angle than in the most stable axial conformation. Excitation of the first ring puckering state has been found to enhance the inversion tunnel splittings.

Journal Article↗

PubMed1996

A newly developed PCR assay of H. pylori in gastric biopsy, saliva, and feces. Evidence of high prevalence of H. pylori in saliva supports oral transmission.

We have recently developed a new PCR assay for the detection of H. pylori. In this study, the polymerase chain reaction (PCR) assay was used to detect H. pylori in 88 gastric biopsy, 85 saliva, and 71 fecal specimens from 88 patients. H. pylori infection was confirmed in 71 of 88 patients by culture and/or histological stain of gastric biopsies. Serum IgG antibody to H. pylori was also measured and resulted in 97% sensitivity and 94% specificity. H. pylori DNA was detected by the PCR assay in gastric biopsy specimens from all 71 patients (100% sensitivity) with proven gastric H. pylori infection but not from 17 noninfected patients (100% specificity). In saliva specimens, H. pylori DNA was identified in 57 of the 68 patients (84%) with proven gastric H. pylori infection and in three of the 17 patients without gastric H. pylori infection. However, the PCR assay was only able to detect H. pylori DNA in the feces from 15 of 61 patients (25%) with proven gastric H. pylori infection and one of the 10 patients without gastric H. pylori infection. The results show that the PCR assay is reliable for detecting the presence of H. pylori in gastric biopsy and saliva specimens. The data indicate that H. pylori exists in a higher prevalence in saliva than feces and that the fecal-oral route may be an important means of transmission of this infection in developing countries but not as significant as previously suspected in the developed countries. It is likely that the oral-oral route is more prominent.

Antibodies, Bacterial↗

PubMed1995

High prevalence of Helicobacter pylori in saliva demonstrated by a novel PCR assay.

AIMS: To investigate the prevalence of Helicobacter pylori in the saliva of patients infected with this bacterium. METHODS: A novel polymerase chain reaction (PCR) assay was developed to detect H pylori in saliva and gastric biopsy specimens from patients undergoing endoscopy. RESULTS: Our PCR assay amplified a 417 base pair fragment of DNA from all 21 DNAs derived from H pylori clinical isolates but did not amplify DNA from 23 non-H pylori strains. Sixty three frozen gastric biopsy and 56 saliva specimens were tested. H pylori specific DNA was detected by PCR in all 39 culture positive biopsy specimens and was also identified from another seven biopsy specimens which were negative by culture but positive by histology. H pylori specific DNA was identified by PCR in saliva specimens from 30 (75%) of 40 patients with H pylori infection demonstrated by culture or histological examination, or both, and in three patients without H pylori infection in the stomach. CONCLUSION: The results indicate that the oral cavity harbours H pylori and may be the source of infection and transmission.

Base Sequence↗

PubMed1993

A highly specific and sensitive DNA probe derived from chromosomal DNA of Helicobacter pylori is useful for typing H. pylori isolates.

HindIII-digested DNA fragments derived from an EcoRI-digested 6.5-kb fragment of chromosomal DNA prepared from Helicobacter pylori ATCC 43629 (type strain) were cloned into the pUC19 vector. A 0.86-kb insert was identified as a potential chromosomal DNA probe. The specificity of the probe was evaluated by testing 166 non-H. pylori bacterial strains representing 38 genera and 91 species which included aerobic, anaerobic, and microaerophilic flora of the upper and lower gastrointestinal tracts. None of the 166 non-H. pylori strains hybridized with this probe (100% specificity), and the sensitivity of this probe was also 100% when H. pylori isolates from 72 patients with gastritis and with the homologous ATCC type strain were tested by dot blot hybridization. The capability of this probe for differentiating between strains of H. pylori was evaluated by Southern blot hybridization of HaeIII-digested chromosomal DNA from 68 clinical isolates and the homologous ATCC type strain of H. pylori. Fifty-one unique hybridization patterns were seen among the 69 strains tested, demonstrating considerable genotypic variation among H. pylori clinical isolates. We propose that this probe would be of significant value for conducting epidemiologic studies.

Bacterial Typing Techniques↗

PubMed1992

Inhibition of folate-dependent enzymes by non-steroidal anti-inflammatory drugs.

Many non-steroidal anti-inflammatory drugs (NSAIDs) (including sulphasalazine, sulindac, indomethacin, naproxen, salicylic acid, ibuprofen, piroxicam and mefenamic acid) were found to be competitive inhibitors (with respect to folate) of avian liver phosphoribosylaminoimidazolecarboxamide formyltransferase (AICAR transformylase, EC 2.1.2.3) and bovine liver dihydrofolate reductase (EC 1.5.1.3). In contrast, aspirin and the antipyretic-analgesic drugs acetaminophen and antipyrine were weak inhibitors of these enzymes. Structure-activity correlation suggests that an aromatic ring with a side chain containing a carboxylic acid is a requirement for competitive inhibition of the transformylase. The above-listed NSAIDs also inhibited the folate-coenzyme-mediated biosynthesis of serine from glycine and formate (i.e., the C1 index) by human blood mononuclear cells (BMCs) in experiments where the drug was added to a culture of BMCs. Acetaminophen had a weak inhibitory effect on the C1 index. Consistent with the results obtained in vitro is the observation that the C1 index of BMCs from rheumatoid-arthritis patients treated with drugs which possess little antifolate activity (e.g. acetaminophen) is higher than the C1 index of BMCs from rheumatoid-arthritis patients treated with NSAIDs possessing more potent antifolate activity (e.g. sulindac, sulphasalazine, naproxen and ibuprofen). The mean activity of the transformylase in BMCs taken from healthy humans was 1.98 nmol of product/h per 10(6) cells and the activity was positively correlated with BMC folate levels. These results are consistent with the hypothesis that (1) the antifolate activity of NSAIDs, and hence cytostatic consequences, are important factors in producing anti-inflammatory activity and (2) aspirin exerts its anti-inflammatory effects after its conversion into salicylic acid, which possesses greater antifolate activity than its parent compound.

Acyltransferases↗

PubMed1990

Detection of inhibition of 5-aminoimidazole-4-carboxamide ribotide transformylase by thioinosinic acid and azathioprine by a new colorimetric assay.

The colorimetric assay for 5-aminoimidazole-4-carboxamide ribotide (AICAR) transformylase (phosphoribosylamino-imidazolecarboxamide formyltransferase; EC 2.1.2.3) has been extensively modified. The modified assay is based upon the short-term permanganate oxidation of the folate product, tetrahydrofolate (H4folate) to p-aminobenzoyl glutamate (pABG). The modified assay was used to detect the transformylase activity in crude extracts of peripheral-blood mononuclear cells (PBMCs). Azathioprine and its metabolite, thioinosinic acid (tIMP), are competitive inhibitors (with respect to AICAR) of the chicken liver transformylase and the transformylase from PBMCs of the MRL/lpr mouse, an animal model of systemic autoimmune disease. The Ki values of tIMP and azathioprine for the chicken liver enzyme are 39 +/- 4 microM and 120 +/- 10 microM, whereas the Ki values for the enzyme from PBMCs of the MRL/lpr mouse are 110 +/- 20 microM and 90 +/- 14 microM respectively. The anti-inflammatory drugs ibuprofen and naproxen are also inhibitors of the transformylase.

Acyltransferases↗

PubMed1990

Effect of miso (Japanese soybean paste) and NaCl on DMBA-induced rat mammary tumors.

An AIN-76A diet supplemented with miso (Japanese soybean paste) reduced the incidence (p = 0.05, Fishers exact test) and delayed the appearance (p = 0.04, log rank test) of dimethylbenz[a]anthracene (DMBA)-induced mammary adenocarcinomas in female Sprague-Dawley rats. A NaCl-supplemented AIN-76A diet (containing the same amount of NaCl as in the miso-supplemented diet) also delayed the appearance of tumors (p = 0.02, log rank test) compared with the AIN-76A control diet. The miso- and NaCl-supplemented diet treatment groups showed a trend toward a lower number of cancers per animal, a trend toward a higher number of benign tumors per animal, and a trend toward a lower growth rate of cancers compared with controls. However, no statistical differences in the total number of tumors per animal or growth rate of the cancers were observed in the miso, NaCl, and control groups. Both miso and NaCl supplementation resulted in increased water intake and urine output but no change in the growth of the animals. These data suggest that miso consumption may be a factor producing a lower breast cancer incidence in Japanese women.

9,10-Dimethyl-1,2-benzanthracene↗

PubMed1990

Fed, but not fasted, adrenalectomized rats survive the stress of hemorrhage and hypovolemia.

We have recently shown that conscious adrenalectomized rats exhibit nearly normal recovery of arterial blood pressure during the 5 h after hemorrhage. In those experiments, it appeared that a previous reduction in food intake might have compromised the recovery of blood pressure and increased mortality. These experiments were designed to test in conscious sham-adrenalectomized (control) and adrenalectomized rats prepared with indwelling arterial and venous cannulae 1) the effects of a 20- to 24-h fast (compared to rats fed ab libitum) on the mobilization of plasma substrates and recovery of arterial blood pressure after a 15 ml/kg.5 min hemorrhage, and 2) vascular responsivity to pressor agents in fed or fasted groups before or 2 h after hemorrhage. In all rats hemorrhage resulted in decreased arterial pressure and heart rate. Arterial pressure recovered to near normal in both fed and fasted control groups and in the fed adrenalectomized rats, and all of these rats survived for 24 h after stress. By contrast, in the fasted adrenalectomized rats, arterial pressure recovered only during the first 1.5-2 h and then failed, resulting in 100% mortality by 3-5 h. Compared to the other three groups, in which substrate levels either increased or remained fairly stable, plasma glucose and beta-hydroxybutyrate concentrations fell steadily from 1.5-2 h after hemorrhage until death occurred in the fasted adrenalectomized rats. Basal ACTH concentrations were elevated compared to control values in both adrenalectomized groups (fed and fasted). Hemorrhage caused increases in plasma ACTH in all groups; the magnitude of the responses did not differ among the groups. The dilution of Evans' blue dye after hemorrhage (used as an index of fluid movement into the vascular space) was not different in control and adrenalectomized rats (either fed or fasted). There were no differences in pressor responses to phenylephrine, vasopressin, or angiotensin-II between the fed and fasted conditions in the control rats either before or after hemorrhage. There was a fasting-associated decrease in vascular responsivity to vasopressin, but normal responsivity to phenylephrine and angiotensin-II, in the adrenalectomized rats both before and after hemorrhage.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenalectomy↗

PubMed1990

Corticosterone, but not glucose, treatment enables fasted adrenalectomized rats to survive moderate hemorrhage.

Fed adrenalectomized rats survive the stress of hemorrhage and hypovolemia, whereas fasted adrenalectomized rats become hypotensive and hypoglycemic after the first 90 min and die within 4 h. We have studied the effects of glucose and corticosterone (B) infusions after hemorrhage as well as treatment with B at the time of adrenalectomy on the capacity of chronically prepared, conscious, fasted, adrenalectomized rats to survive hemorrhage. We have also measured the magnitudes of vasoactive hormone responses to hemorrhage. Maintenance of plasma glucose concentrations did not sustain life; however, treatment of rats at the time of adrenalectomy with B allowed 100% survival, and acute treatment of adrenalectomized rats at the time of hemorrhage allowed about 50% survival during the 5-h posthemorrhage observation period. Rats in the acute B infusion group that died exhibited significantly increased plasma B and significantly decreased plasma glucose concentrations by 2 h compared to the rats that lived. Plasma vasopressin, renin, and norepinephrine responses to hemorrhage were markedly augmented in the adrenalectomized rats not treated with B, and plasma vasopressin concentrations were significantly elevated at 1 and 2 h in all of the rats that subsequently died compared to values in those that lived. We conclude that: 1) death after hemorrhage in fasted adrenalectomized rats is not a result of lack of glucose; 2) chronic and, to an extent, acute treatment of fasted adrenalectomized rats with B enables survival; 3) fasted adrenalectomized rats exhibit strong evidence of hepatic insufficiency which is not apparent in either fed adrenalectomized rats or B-treated fasted adrenalectomized rats; 4) death after hemorrhage in fasted adrenalectomized rats may result from hepatic failure as a consequence of marked splanchnic vasoconstriction mediated by the actions of extraordinarily high levels of vasoactive hormones after hemorrhage; and 5) B appears to act to decrease the magnitude of response of vasoactive hormones after hemorrhage in fasted adrenalectomized rats.

Adrenalectomy↗

PubMed1989

Upper esophageal sphincter opening and modulation during swallowing.

Studies were done on 8 normal subjects with synchronized videofluoroscopy and manometry to facilitate a biomechanical analysis of upper esophageal sphincter opening and volume-dependent modulation during swallowing. Movements of the hyoid and larynx, dimensions of sphincter opening, and intraluminal sphincter pressure were determined at 1/30th-s intervals during swallows of 1, 5, 10, and 20 ml of liquid barium. Our analysis subdivided upper esophageal sphincter activity during swallowing into five phases: (a) relaxation, (b) opening, (c) distention, (d) collapse, and (e) closure. Sphincter relaxation occurred during laryngeal elevation and preceded opening by a mean period of 0.1 s. Opening occurred as the sphincter was pulled apart via muscular attachments to the hyoid such that the hyoid coordinates at which sphincter opening and closing occurred were constant among bolus volumes. Sphincter distention after opening was modulated by intrabolus pressures rather than graded hyoid movement. The generation of intrabolus pressure coincided with the posterior thrust of the tongue that culminated in pharyngeal wall contact and the initiation of pharyngeal peristalsis. Larger volume swallows were associated with greater intrabolus pressure and increased bolus head velocity. The duration of sphincter opening increased in conjunction with a prolongation of the anterior-superior excursion of the hyoid and a delay in the onset of pharyngeal peristalsis (the event that determined the timing of sphincter closure). We conclude that transsphincteric transport of increasing swallow bolus volumes is accomplished by modulating sphincter diameter, opening interval, and flow rate (reflected by bolus head velocity). Furthermore, upper esophageal sphincter opening is an active mechanical event rather than simply a consequence of cricopharyngeal relaxation.

Adult↗

PubMed1988

Hemoglobin-catalyzed transformation of elliptinium acetate into electrophilic species. Evidences for oxidative activation of the drug in human red blood cells.

The anti-tumor drug N2-methyl-9-hydroxyellipticinium acetate (NMHE, Celiptium) after incubation with various N or S containing amino acids (alanine, histidine, aspartic acid, cysteine, glutathione) with hemoglobin and hydrogen peroxide or an organic peroxide (terbutylhydroperoxide) leads to the formation of the corresponding covalent binding adducts, via an oxidative activation. The formation of the covalent adduct glutathione-elliptinium was also demonstrated in human red blood cells. The importance of such process under in vivo conditions is discussed.

Alkaloids↗

PubMed1988

Neurite extension on dibutyryl cyclic AMP-stimulated astrocytes.

Although both central and peripheral neurons successfully regenerate cut axons along peripheral nerve and other suitable substrates, axonal elongation through the mature central nervous system (CNS) is limited. It has been proposed that the presence of reactive astrocytes formed in response to CNS injury act as a barrier to axonal regeneration. In contrast, in vitro, astrocytes in a flat or unstimulated state have been shown to be a preferred substrate for neurite extension. We have investigated whether induced modifications of astrocytes alter the capacity of these cells to act as a substrate for axonal elongation. Treatment with dibutyryl cyclic AMP (dBcAMP) results in a marked morphological and biochemical change in astrocytes, considered by some to be a model of reactive astrocytosis. Retinal and dorsal root ganglia explants from embryonic mice were cultured on top of untreated glial monolayers and those treated with dBcAMP. The subsequent neuritic growth was measured at 48 h. No difference was found between the groups, indicating that astrocytes are an excellent substrate for axonal growth, even after they develop a stellate shape and high levels of glial fibrillary acidic protein.

Animals↗

PubMed1986

Ribose as the preferential target for the oxidized form of elliptinium acetate in ribonucleos(t)ides. Biological activities of the resulting adducts.

The covalent binding of the oxidized form of elliptinium acetate, an antitumor drug, to various ribonucleos(t)ides is described. In the absence of a strong nucleophile on the bases, e.g., a sulfhydryl group, the main target of this quinone imine derivative is the sugar moiety. With unmodified regular bases, the first electrophilic addition always occurs on the 2'-oxygen of ribose (more slowly for pyrimidine than for purine); in a second step, cyclization of the reoxidized product leads to a spiro derivative: only one stereoisomer is detected with purine nucleoside; the other stereoisomer appears as a minor product (10-20%) with nucleotides and pyrimidine nucleosides. With modified bases, no change is observed except for bases exhibiting an additional strong nucleophilic center: oxidized elliptinium alkylates thioguanine and thioguanosine on the sulfur atom and in this last case not on the ribose moiety. All spiro derivatives are less cytotoxic than the parent compound even if the base is an antimetabolite (azauridine); however, thio-elliptinium adducts maintain high cytotoxicity.

Alkaloids↗

PubMed1985

Characterisation of a new cell line (CJ18) from a patient with 'hairy' cell leukaemia.

A cell line (CJ18) has been established from the peripheral blood of a patient with hairy cell leukaemia (HCL) in a leukaemic phase. They grow slowly in large clumps with a doubling time of 3-4 d. 8% show positivity for surface immunoglobulin G and a small percentage (5%) are positive for intracytoplasmic immunoglobulin. They are B1,Ia1 positive and CALL, TdT and OKM1 negative. Although they are Epstein Barr Virus Nuclear Antigen (EBNA) positive they have several features not found in other EBNA positive B lymphoblastoid cell lines which suggest they may be derived from the patient's leukaemic hairy cells. They are strongly positive for tartrate resistant acid phosphatase, esterase positive, contain numerous lysosomes and are able to phagocytose sheep red blood cells after exposure to tetradecanoyl-12, 13-phorbol acetate (TPA). Following exposure to retinoic acid and TPA they adhere to plastic with numerous slender processes, a feature seen in HCL cells.

Antibodies, Monoclonal↗

PubMedDate not supplied

Keeping genetics simple.

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Genetic Predisposition to Disease↗