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Biomedical subjects

L He

Publications and source records attributed to L He.

427 records · Page 24Linked to original sources
PubMedDate not supplied

A high performance liquid chromatographic method for the determination of albuterol enantiomers in human serum using solid phase extraction and chemical derivatization.

A high performance liquid chromatographic method was developed for the simultaneous assay of R(-)- and S(+)-albuterol in human serum. The assay involves solid phase extraction as a sample clean-up step and derivatization of racemic albuterol to its diastereomeric thioureas with 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl isothiocyanate. Chromatographic separation was accomplished under isocratic conditions using an octadecylsilane column and a mobile phase consisting of 29:71 acetonitrile:distilled water containing 0.1% triethylamine, pH 4.0 (adjusted with concentrated phosphoric acid) at a flow rate of 0.8 mL/min. The diastereomers were detected using a fluorescence detector set at 223 nm excitation and no emission filter. Racemic bamethane was used as internal standard. Drug to internal standard peak-height ratios were linear over a 2-20 ng/mL range for each enantiomer. The limit of detection of each analyte was 1.0 ng/mL (S/N = 3).

Albuterol↗
PubMedDate not supplied

Liquid chromatographic separation of praziquantel enantiomers in serum using a cellulose-based chiral stationary phase.

R(-) and S(+) praziquantel (PZQ) in human serum were resolved and quantified using a stereospecific LC method. Each enantiomer and the internal standard 2-methylamino-5-chlorobenzophenone were isolated from serum using a solid-phase extraction procedure on a cyanopropyl column. Recoveries of 98.8, 93.3 and 35.4% were obtained for R(-) PZQ, S(+) PZQ, and the internal standard, respectively. A cellulose-based chiral analytical column (Chiralcel OD) was used with a mobile phase consisting of hexane-2-propanol (70:30, v/v). Linear calibration curves were obtained in the concentration range 50-1000 ng ml-1 for each enantiomer in serum. The detection limit for each enantiomer in serum using UV detection at 212 nm was 5 ng ml-1 (S/N = 3). The limit of quantitation of each enantiomer was 25 ng ml-1.

Cellulose↗
PubMedDate not supplied

Protein phosphorylation signaling mechanisms in carotid body chemoreception.

Chemotransduction in the carotid body occurs in specialized type I cells and likely involves a complex series of regulated events which culminates in the release of neurotransmitter agents and the excitation of afferent nerve fibers. Previous studies have shown that multiple factors, including the levels of calcium and cyclic nucleotide second messengers, are important regulators of the chemoreceptor transduction cascade in type I cells. In addition, increases in electrical excitability induced in type I cells by chronic exposure to hypoxia are mimicked by agents which elevate intracellular cyclic AMP levels [Stea et al., J Neurosci 1995;15:2192-2202]. These and other findings suggest that protein kinases, and the phosphorylation of specific protein targets are important components of the hypoxic transduction machinery. Moreover, protein kinase-mediated cascades may participate in the well-known physiological adjustments which occur in the carotid body during prolonged stimulation. In the current study, our data demonstrate (1) the presence of specific protein kinases and target phosphoproteins in the carotid body, and also in the morphologically similar small intensely fluorescent cells of the superior cervical sympathetic ganglia. (2) Nitric oxide production and efferent inhibition in the chemosensory tissue is reduced in the presence of the specific tyrosine kinase inhibitor, lavendustin A. (3) Hypoxia-induced catecholamine release from type I cells is inhibited by the protein kinase A antagonist, Rp-cAMPs. And finally (4), exposure to chronic hypoxia up-regulates the expression of the tyrosine kinase, fyn, and an important growth regulatory phosphoprotein, growth associated protein-43 (GAP-43). These findings suggest that second messenger-mediated phosphorylation and dephosphorylation of specific protein targets is a mechanism capable of regulating diverse cellular functions in the carotid body during acute and chronic stimulation.

Animals↗
PubMedDate not supplied

Chemosensitivity of the rat type I slowly adapting mechanoreceptor.

An in vitro lateral thoracic skin preparation of the adult rat was used to test the effect of serotonin (5, 50, 500 microM) and control solutions on the response of the type I slowly adapting mechanoreceptor to a standard mechanical stimulus. Serotonin (5-HT) significantly increased the magnitude of the type I response to mechanical indentation: 50 microM 5-HT infusion enhanced responsiveness more effectively than 5 microM 5-HT. In the absence of mechanical stimulation, little or no change in spontaneous discharge relative to control was observed, and recovery to baseline levels occurred within three stimulus trials. In vitro and in vivo control experiments showed no statistically significant change in responsiveness over a similar number of stimulus cycles. It was concluded that 5-HT modulates, but does not activate the rat type I receptor or alter its ability to encode the depth and/or velocity of mechanical displacement.

Adaptation, Physiological↗
PubMedDate not supplied

Role of the liver in alloimmune response following inoculation of donor spleen cells.

The liver is thought to be an immunologically privileged organ in the response to inoculated antigens. We previously demonstrated that it is possible to localize inoculated antigens to the liver alone or only to extrahepatic tissue using orthotopic syngeneic liver transplantation (OSLT). In this study, we analyzed more detailed mechanisms of the anti-alloimmune response in the liver. DA rat spleen cells were systemically injected into WS rats (donor spleen cell inoculation, DSI). In the sensitized liver-grafted (SLG) group, after DSI, liver grafts were retrieved from sensitized WS rats, then transplanted into naive WS rats. In the sensitized liver-removed (SLR) group, after DSI, WS rats were totally hepatectomized and given livers transplanted from naive WS rats. All the rats were challenged with heterotopic heart grafts 10 days after DSI. Mean heart graft survival in the control, DSI, SLG, and SLR groups were 11.6+/-1.6, 10.7+/-2.4, 4.4+/-1.0, and 24.6+/-6.3 days, respectively. Accelerated rejection in the SLG group as well as graft prolongation in the SLR group disappeared when OSLT was performed 2 days after DSI or later. Irradiation of DA splenocytes before inoculation did not alter graft survival in SLG. However, pretreatment with gadolinium chloride prior to DSI attenuated the antidonor response in the SLG group. In conclusion, a vigorous antidonor response occurred in the liver after systemic inoculation of spleen cells. It peaked I day after DSI and disappeared rapidly. Kupffer cells seemed to play an important role in this phenomenon.

Animals↗
PubMedDate not supplied

Expression of c-fos protein in serotonergic neurons of rat brainstem following electro-acupuncture.

The c-fos proto-oncogene encodes a nuclear phosphoprotein, Fos which has been proposed to be a "third messenger" coupling short term extracellular signals to long term alteration in cell function. Using double labeling immunocytochemistry, the present work demonstrated the co-localization of Fos protein and serotonin in the nucleus raphe dorsalis, nucleus raphe centralis superior and rostral ventromedial medulla. The results pose an interesting problem, the possible relation of Fos protein to the biosynthesis of serotonin, awaiting further investigation.

Animals↗
PubMedDate not supplied

Involvement of mu opioid receptors of periaqueductal gary (PAG) in acupuncture inhibition of noxious blood pressure response in rabbits.

Strong electric shock stimulation of the rabbit front paw elicited a pressor blood pressure response regarded as noxious response. Ligands of mu opioid receptors were microinjected into the PAG to observe their effects on acupunture inhibition of the pressor response. (1) Ohmefentanyl (OMF), a mu agonist, significantly attenuated the pressor response. Mu antagonist TCTAP greatly enhanced the pressor response. (2) Electroacupuncture (EA) significantly inhibited the pressor response, the inhibition being readily reversed by TCTAP. The response after TCTAP was significantly greater than that of the control before EA. The results suggest that noxious stimulation is able to activate the mu opioid receptor of the PAG to modulate the noxious response and EA is able to enhance the activation.

Animals↗
PubMedDate not supplied

Release of gonadotropin-releasing hormone (GnRH) from the medio-basal hypothalamus induced by electroacupuncture in conscious female rabbits.

In electroacupuncture (EA) treatment, successful induction of ovulation is usually accompanied with the facilitation of pulsatile secretion of gonadotropin. The present work studied the release of GnRH from the mediobasal hypothalamus (MBH) using push-pull perfusion technique in conscious New Zealand female rabbits before, during and after EA stimulation. EA (4Hz, 5mA, 30 min) of Guanyuan (Ren 4), Zhongji (Ren 3), bilateral Sanyinjiao (SP 6) and Zigong (Extra 16) was given at the end of the 1st, 3rd and 5th hour during 6 hours' perfusion (EA group, n = 6). Cupric acetate (CuAC) was given (1%, 0.9 ml, i.v.) at the end of the 1st hour perfusion (CuAC group, n = 5) as a control since it is known as a stimulant for the release of GnRH. Rabbits in the control group (n = 4) were under the same perfusion condition except with no CuAC injection or EA stimulation. It was found that GnRH level was elevated immediately and significantly (4.64 +/- 0.98 v.s. 2.08 +/- 0.01 pg/ml, P < 0.05) after EA stimulation. In the CuAC group, GnRH level was also significantly elevated (3.84 +/- 0.37 v.s. 2.08 +/- 0.001 pg/ml, P < 0.05) one hour after CuAC injection. In addition, corpus lutein were observed both in the EA group (2/6) and the CuAC group (5/5). No similar changes were found in the control group. The data suggest that EA is capable of facilitating GnRH release from the MBH.

Animals↗
PubMedDate not supplied

Mu opiate receptor antagonist blocks electroacupuncture inhibition on noxious blood pressure response in rabbits.

A pressor blood pressure response was elicited by strong electric shock stimulation of the front paw in rabbits anesthetized with chloralose and urethane, immobilized by gallamine triethiodide and maintained by artificial ventilation. The pressor response showed a gradual decline in 3-4 successive trials. Naloxone or TCTAP, a specific mu receptor antagonist, administered intraventricularly (icv) at that time could facilitate the pressor response (n = 8, P < 0.02; n = 7, P < 0.01), suggesting the involvement of mu receptors in the declination of the pressor response. Electroacupuncture could inhibit the pressor response (n = 7, P < 0.01), and the inhibition was readily blocked by TCTAP (n = 7, P < 0.01). No obvious changes were observed in the normal saline control group. The results suggest that acupuncture is able to inhibit the pressor response via the activation of the opioid peptidergic system, of which the mu receptor is an important component.

Animals↗
PubMedDate not supplied

Coexistence of Fos protein and proopiomelanocortin mRNA in hypothalamic arcuate nucleus following electroacupuncture.

The immediate early gene, c-fos encodes a nuclear phosphoprotein, Fos which has been proposed to be a third messenger to regulate the expression of specific target genes. The present work demonstrated the coexistence of Fos protein and proopiomelanocortin (POMC) mRNA in the hypothalamic arcuate nucleus (Arc) using techniques of in situ hybridization and immunocytochemistry. The results suggest the activation of beta-endorphinergic (beta-EP) neurons in the Arc by electroacupuncture (EA) and the possible involvement of Fos in modulating POMC expression.

Animals↗
PubMedDate not supplied

A new cell proliferating marker: cytosolic thymidine kinase as compared to proliferating cell nuclear antigen in patients with colorectal carcinoma.

BACKGROUND: Proliferation markers are necessary for reliable diagnosis. Here we have presented for the first time thymidine kinase 1 (TK1) as a proliferative tumor marker for colorectal carcinoma. PATIENTS AND METHODS: Expression of TK1 in 54 colorectal lesions and 20 colorectal adenoma lesions was detected by immunohistochemistry technique (ABC). Proliferating Cell Nuclear Antigen (PCNA) was run in parallel. RESULTS: TK1-Labelling Index (LI) (65%) was higher than PCNA-LI (52%) in the malignant lesions, although not significantly different (p = 0.1717) between them. TK1-LI as well as PCNA-LI showed significant differences between colorectal carcinoma and colorectal adenoma (TK1 p = 0.0005, PCNA p = 0.0005). Both TK1-LI and PCNA were significantly different in respect to tumor stages (TK1 p = 0.0002, PCNA p = 0.0284). However, only TK1-LI showed significant difference in respect to tumor grades (p = 0.014), but not PCNA-LI (p = 0.132). CONCLUSION: TK1-LI showed more potential as a proliferating marker in colorectal carcinoma than PCNA-LI, especially for evaluating high-risk tumor grade and advanced stage in colorectal carcinoma.

Adenocarcinoma, Papillary↗
PubMedDate not supplied

Prospective randomized study determining whether a 3-day application of ofloxacin results in the selection of fluoroquinolone-resistant coagulase-negative Staphylococcus.

PURPOSE: To determine whether a 3-day application of ofloxacin results in the selection of fluoroquinolone-resistant conjunctival coagulase-negative Staphylococcus. DESIGN: Prospective randomized trial. METHODS: Patients scheduled for ocular surgery were randomized to a control (89 eyes) or study group (70 eyes). The study group received topical ofloxacin (0.3%) four times a day for 3 days. Conjunctival cultures were obtained at baseline (T0) and after 3 days of ofloxacin (T1). Cultures were also obtained at T0 and T1 for the control group, but these eyes did not receive an antibiotic. Bacteria isolated were identified and antibiotic susceptibility was determined. RESULTS: At T0, 53 out of 89 patients (60%) in the control and 48 out of 70 patients (69%) in the study group harbored coagulase-negative Staphylococcus. Among these coagulase-negative Staphylococcus, 12 out of 53 in the control and 11 out of 48 in the study group were resistant to ofloxacin (p>0.9999). At T1, significantly fewer coagulase-negative Staphylococcus (p=0.0003) were isolated from the study group (18 coagulase-negative Staphylococcus), compared the control group (48 coagulase-negative Staphylococcus). Of these, 5 out of 17 coagulase-negative Staphylococcus in the study group and 9 out of 48 coagulase-negative Staphylococcus in the control group were resistant to ofloxacin (p=0.5649). There was no significant difference in the number of coagulase-negative Staphylococcus resistant to ciprofloxacin or norfloxacin in the study group compared to the control group at T1. CONCLUSIONS: Ofloxacin given four times a day for 3 days does not select out for conjunctival fluoroquinolone-resistant coagulase-negative Staphylococcus.

Administration, Topical↗