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Biomedical subjects

T You

Publications and source records attributed to T You.

12 recordsLinked to original sources
PubMed2006

Effects of disulfide bridges in domain I of Bacillus thuringiensis Cry1Aa delta-endotoxin on ion-channel formation in biological membranes.

The delta-endotoxin family of toxic proteins represents the major component of the insecticidal capability of the bacterium Bacillus thuringiensis. Domain I of the toxins, which is largely alpha-helical, has been proposed to unfold at protein entry into the membrane of a target insect, following models known as the penknife and umbrella models. We extended the analysis of a previous work in which four disulfide bridges were constructed in domain I of the Cry1Aa delta-endotoxin that putatively prevented unfolding during membrane partitioning. Using bioassays and voltage clamping of whole insect midgut instead of artificial lipid bilayers, it was found that, while toxicity and inhibition of the short-circuit current were reduced, only one of the disulfide bridges eliminated the activity of the toxins in the insect midgut membrane, and in that case, the loss of toxicity was due to the single amino acid substitution, R99C. It is proposed that at least alpha helices 4, 5, 6, and 7 and domain II partition in the midgut membranes of target insects, in support of an insertion model in which the whole protein translocates into the midgut membrane.

Animals↗
PubMed2006

Addition of aerobic exercise to dietary weight loss preferentially reduces abdominal adipocyte size.

OBJECTIVE: To determine if hypocaloric diet, diet plus low-intensity exercise, and diet plus high-intensity exercise differentially influence subcutaneous abdominal and gluteal adipocyte size in obese individuals. DESIGN: Longitudinal intervention study of hypocaloric diet, diet plus low-intensity exercise, and diet plus high-intensity exercise (calorie deficit = 2800 kcal/week, 20 weeks). SUBJECTS: Forty-five obese, middle-aged women (BMI = 33.0+/-0.6 kg/m2, age = 58+/-1 years). MEASUREMENTS: Body composition testing and adipose tissue biopsies were conducted before and after the interventions. Subcutaneous abdominal and gluteal adipocyte size was determined. RESULTS: All three interventions reduced body weight, fat mass, percent fat, and waist and hip girths to a similar degree. Diet only did not change subcutaneous abdominal adipocyte size, whereas both diet plus exercise groups significantly reduced abdominal adipocyte size. Changes in abdominal adipocyte size in the diet plus exercise groups were significantly different from that of the diet group. Gluteal adipocyte size decreased similarly in all three groups. CONCLUSION: Addition of exercise training to dietary weight loss preferentially reduces subcutaneous abdominal adipocyte size in obese women. This may be of importance for the treatment of health complications associated with subcutaneous abdominal adiposity.

Adipocytes↗
PubMed2000

Characterisation of patients with primary biliary cirrhosis responding to long term ursodeoxycholic acid treatment.

BACKGROUND: In some patients with primary biliary cirrhosis, ursodeoxycholic acid causes full biochemical normalisation of laboratory data; in others, indexes improve but do not become normal. AIMS: To characterise complete and incomplete responders. METHODS: Seventy patients with primary biliary cirrhosis were treated with ursodeoxycholic acid 10-15 mg/kg/day and followed up for 6-13 years. RESULTS: In 23 patients (33%) with mainly stage I or II disease, cholestasis indexes and aminotransferases normalised within 1-5 years, except for antimitochondrial antibodies. Histological findings improved. Indexes were not normalised in 47 patients (67%) although the improvement of their biochemical functions parallelled the trend in the first group. In these incomplete responders histological findings improved to a lesser extent. The only difference between the two groups before treatment was higher levels of alkaline phosphatase and gamma glutamyl transpeptidase in the incomplete responders. At onset of treatment the discriminant value separating responders from incomplete responders was 660 U/l for alkaline phosphatase and 131 U/l for gamma glutamyl transpeptidase. One year later it was 239 and 27 U/l (overall predictive value for responders 92%, for incomplete responders 81%). There were no differences between the two groups concerning immune status, antimitochondrial antibody subtypes, liver histology, or any other data. HLA-B39, DRB1*08, DQB1*04 dominated in both groups. CONCLUSIONS: In patients with mainly early stages of primary biliary cirrhosis, higher values of alkaline phosphatase and gamma glutamyl transpeptidase are the only biochemical indexes which allow discrimination between patients who will completely or incompletely respond to ursodeoxycholic acid treatment.

Adult↗
PubMed1999

Detection of hydrazine, methylhydrazine and isoniazid by capillary electrophoresis with a 4-pyridyl hydroquinone self-assembled microdisk platinum electrode.

Capillary electrophoresis (CE)/electrochemical detection (EC) for the simultaneous detection of hydrazine, methylhydrazine, and isoniazid has been developed with a 4-pyridyl hydroquinone self-assembled microdisk platinum electrode. Such an electrode has very high catalytic ability for hydrazines and they could be detected even at 0.0 V. The responses for hydrazine, methylhydrazine, and isoniazid are linear over 3 orders of detected concentration and of magnitude of 0.2-400 microM, 0.2-400 microM, 0.5 microM-2 mM, with correlation coefficients of 0.9998, 0.9991, and 0.9982, respectively. And they could be detected to levels of 0.1, 0.1 and 0.2 microM, respectively. This modified electrode was found to be very stable and reproducible when continuously used as detector for capillary electrophoresis for period of at least 4 weeks with no apparent loss of response.

Electrochemistry↗
PubMed1998

Determination of sulfadiazine and sulfamethoxazole by capillary electrophoresis with end-column electrochemical detection.

Capillary electrophoresis (CE) with end-column electrochemical detection (EC) of sulfadiazine (SDZ) and sulfamethoxazole (SMZ) is described. Under the optimum conditions, SDZ and SMZ were separated satisfactorily, and a highly sensitive and stable response was obtained at a potential of 1.1 V versus Ag/AgCl. Optimized end-column detection provides detection limits as low as 0.1 microM for both compounds, which corresponds to 0.024 and 0.021 fmol with peak efficiencies of 394,000 and 335,000 theoretical plates for SDZ and SMZ, respectively. The calibration graph was linear over three order of magnitude. The relative standard deviations (n = 12) of peak currents and migration times were 2.3 and 2.7%, and 0.8 and 1.3%, respectively, for the two compounds. The proposed method was applied to the analysis of tablets and human urine samples with satisfactory results.

Anti-Infective Agents↗
PubMed1996

Ursodeoxycholic acid and prednisolone versus ursodeoxycholic acid and placebo in the treatment of early stages of primary biliary cirrhosis.

BACKGROUND: Ursodeoxycholic acid probably is not able to cure primary biliary cirrhosis. Therefore in this study ursodeoxycholic acid was administered together with prednisolone, since monotherapy with glucocorticoids has been shown to have some positive effects. METHODS: Thirty patients with primary biliary cirrhosis (stages I-III) were entered into the study. Fifteen were treated with ursodeoxycholic acid 10 mg.kg-1.day-1 and placebo (group A), 15 with ursodeoxycholic acid and 10 mg prednisolone (group B) for 9 months. Apart from the usual laboratory examinations, liver biopsies were taken from 29 patients before and after therapy. RESULTS: Liver enzymes decreased significantly compared to the initial values in both groups (p < 0.001), but in group B cholestasis-indicating enzymes and the immunoglobulins G and A improved more rapidly. Between both groups the differences for AP, GGT, IgG, IgA and gamma-globulins were significant (p < 0.05), but only for short terms. In group B, liver histology improved significantly (p < 0.003), which correlated with the decrease of IgG. Ursodeoxycholic acid became the predominant bile acid in the serum. Toxic bile acids did not increase. Bone densitometry revealed a slight deterioration of preexisting osteoporosis in one patient. CONCLUSIONS: Although combination therapy with ursodeoxycholic acid and prednisolone was not superior to monotherapy with ursodeoxycholic acid with regard to liver function tests, it had a highly beneficial influence on liver histology. In our previous trials with monotherapy histology remained unchanged. An early decrease in IgG during combination therapy seems to be an indicator of an amelioration of liver histology.

Adult↗
PubMed1995

TUDCA and UDCA are incorporated into hepatocyte membranes: different sites, but similar effects.

The aim of this paper is to point out that: 1) CDCA and DCA increase the polarity of cell membranes and cause the release of cholesterol and phospholipid from the membranes; 2) the extent of this damage is inversely correlated with the cholesterol content of the membrane investigated; 3) UDCA, TUDCA and GUDCA decrease membrane polarity; 4) they prevent membrane damage when added prior to CDCA or DCA; 5) UDCA appears to be incorporated into the apolar domain of the membrane, TUDCA, GUDCA into the interface; 6) UDCA decreases HLA class I expression on hepatocyte membranes; 7) CDCA induces GLDH-release from liver mitochondria and increases mitochondrial membrane polarity and mobility; and 8) UDCA reduces the release of GLDH from mitochondria caused by CDCA.

Animals↗
PubMed1993

High performance liquid chromatographic determination of free and conjugated bile acids in serum, liver biopsies, bile, gastric juice and feces by fluorescence labeling.

Separation and measurement of commonly occurring free and conjugated bile acids in serum, liver biopsies, bile, gastric juice and feces have been successfully accomplished using high performance liquid chromatography with fluorescence labeling. Free and conjugated bile acids were extracted from pretreated samples using Sep-Pak C18 cartridges and then fractionated on a piperidinohydroxypropyl Sephadex LH-20 column. Free and glycine conjugated bile acids were labelled with 4-bromomethyl-7-methoxycoumarin. Taurine conjugated bile acids were hydrolysed with cholylglycine hydrolase prior to derivatization with 4-bromomethyl-7-methoxycoumarin. Labelled bile acids were eluted using an acetonitrile/methanol/water gradient on an ultrasphere ODS column. The eluate was monitored by a fluorophotometer at 360 nm (excitation) and 410 nm (emission). Linearity was obtained between 50 and 400 nmol. Recoveries from serum, gastric juice and feces were greater than 87%. This is therefore a sensitive method for the precise quantification of bile acids in serum, liver biopsies, bile, gastric juice and feces.

Bile↗
PubMed1993

Neurons derived from a human teratocarcinoma cell line establish molecular and structural polarity following transplantation into the rodent brain.

Studies of neurons grafted into the brains of experimental animals have been limited by the lack of suitably homogeneous populations of neurons for transplantation. Here we describe the transplantation and survival of pure, postmitotic human neurons (NT2N cells) into the rat brain. NT2N cells were derived from a human teratocarcinoma line (NTera2/clone D1 or NT2 cells) in vitro by retinoic acid treatment. Approximately 5-10 x 10(4) NT2N cells (including previously frozen aliquots of NT2N cells) were injected into the neocortex, subjacent white matter, or hippocampus of adult (N = 51) or neonatal (N = 17) Sprague-Dawley rats. Cyclosporine (7-10 mg/kg) was administered daily to 13 adult rats for up to 12 weeks post-transplant prior to sacrifice. Untreated rats survived for up to 21 weeks post-transplant. Injection sites were serially sectioned and NT2N grafts were analyzed immunohistochemically using antibodies to diverse neuronal and glial proteins to assess the lineage of the grafted cells and their ability to establish molecular and structural polarity. NT2N cells transplanted into untreated adult and neonatal rat brains were committed exclusively to the neuronal phenotype and survived for as long as 8 weeks, although most were rejected after 4 weeks. However, cyclosporine prolonged survival of the NT2N grafts for up to 12 weeks. Further, grafted NT2N cells exhibited an asymmetric geometry (with long axons and simplified dendrites), as well as molecular polarity (with highly phosphorylated neurofilament proteins segregated in axons and microtubule associated protein 2 confined to perikarya and dendrites) by 4 weeks post-transplant. However, the grafted neurons did not become fully mature as evidenced by their failure to express the most highly phosphorylated heavy neurofilament proteins. Finally, previously frozen NT2N cells survived in the rat brain, and none of the grafts formed neoplasms. We conclude from these studies that transplanted NT2N cells represent a highly advantageous model system for studies of the developmental biology of neurons.

Animals↗
PubMed1993

Molecular aspects of membrane stabilization by ursodeoxycholate [see comment].

BACKGROUND: Ursodeoxycholate, used for therapy in biliary liver diseases, prevents bile salt damage in animal experiments. Using isolated red blood cell and both canalicular and basolateral hepatocyte membranes, the present study examined this protective effect. METHODS: Membranes were incubated with chenodeoxycholate, with chenodeoxycholate and ursodeoxycholate simultaneously, and first with ursodeoxycholate followed by chenodeoxycholate. Changes in membrane structure were investigated by electron paramagnetic resonance spectroscopy, using different spin labels. Data were confirmed by analysis of membrane lipids and studies with 14C-labeled bile acids. RESULTS: The increase of polarity in the apolar domain of the membrane caused by chenodeoxycholate corresponded to the amount of solubilized lipids. After preincubation with ursodeoxycholate or its conjugates, membrane damage by subsequent chenodeoxycholate incubation was prevented. This effect was caused by binding of ursodeoxycholate in the apolar domain, of its conjugates in the interface of the membrane. CONCLUSIONS: Chenodeoxycholate solubilizes membrane lipids and permits water to permeate into plasma membranes. The steroid nucleus of ursodeoxycholate is bound to the apolar domain and that of the conjugates to the interface of the membrane, thus stabilizing membrane structure.

Animals↗
PubMedDate not supplied

Illuminated lens fixator for bimanual pars plana lensectomy.

Pars plana vitrectomy and lensectomy are effective methods for removing posteriorly dislocated lens material. We describe an illuminated nucleus fixator that assists in the removal of posteriorly dislocated lens fragments. We tested the efficacy of the illuminated nucleus fixator compared to a standard endoilluminator in removing lens nuclei from the vitreous cavity of a cadaveric eye model. Use of the illuminated nucleus fixator as compared to a standard endoilluminator significantly reduced the time needed to remove lens nuclei from the vitreous cavity. This instrument could penetrate and fixate lens nuclei and could safely stabilize small and intermediate-sized lens fragments against the activated fragmatome. Bimanual lensectomy using the illuminated nucleus fixator significantly shortens the surgical time needed to remove posteriorly dislocated lens fragments. Shortening the surgical time for lensectomy may minimize such complications as retinal tears, trauma, and phototoxicity.

Humans↗