Regulation of intracellular calcium in human esophageal smooth muscles

We have investigated sources of Ca2+ contributing to excitation of human esophageal smooth muscle, using fura 2 to study cytosolic free Ca2+ concentration ([Ca2+]i) in dispersed cells and contraction of intact muscles. Acetylcholine (ACh) caused an initial peak rise of [Ca2+]i followed by a plateau accompanied by reversible contraction. Removal of extracellular Ca2+ or addition of dihydropyridine Ca2+ channel blockers reduced the plateau phase but did not prevent contraction. Caffeine also caused elevation of [Ca2+]i and blocked responses to ACh. Undershoots of [Ca2+]i were apparent after ACh or caffeine. Blockade of the sarcoplasmic reticular Ca(2+)-ATPase by cyclopiazonic acid (CPA) reduced the ACh-evoked increase of [Ca2+]i and abolished the undershoot, indicating involvement of Ca2+ stores. When contraction was studied in intact muscles, removal of Ca2+ or addition of nifedipine reduced, but did not abolish, carbachol (CCh)-induced contraction. Elevation of extracellular K+ caused contraction that was inhibited by nifedipine, although CCh still elicited contraction. CPA caused contraction and suppressed the CCh-induced contraction, whereas ryanodine reduced CCh-induced contraction. Our studies provide evidence that muscarinic excitation of human esophagus involves both release of Ca2+ from intracellular stores and influx of Ca2+.

[The culture of TMJ condylar cartilage cells and study on their biological behaviors in vitro]

To investigate the behavoir of TMJ condylar cartilage cells in vitro, the mandibular condylar cartilage cells were harvested from a 5-month-old human fetus by dissection and sequential digestion with 0.25% trypsin and 0.2% collagenase (type II). The isolated cells were cultured in DMEM medium and identified by histochemical and immunohistochemical methods. Cell proliferation, morphology and ultrastructure were observed by phase-contrast microscope, cytologic staining and electronic microscope. In primarily cultured cells, polygonal chondroblast-like cells dominated and they were confirmed by the positive result of immunohistochemical examination for type II collagen and Toludin blue staining. In conclusion, the TMJ cells in this culture system kept their phenotype in vivo.

C-peptide does not alter carbohydrate metabolism in isolated mouse muscle

The effects of C-peptide on carbohydrate metabolism in isolated mouse soleus muscle were studied. C-peptide, at concentrations up to 1,000 nM, had no effect on [14C]glucose incorporation into glycogen, glycogen synthase activity, or 2-deoxyglucose uptake. These data demonstrate that C-peptide has no direct effect on the measured parameters of carbohydrate metabolism in isolated mouse muscle.

Intracellular calcium stores in isolated tracheal smooth muscle cells

We investigated the effects of acetylcholine (ACh) and histamine on intracellular calcium concentration ([Ca2+]i) and contraction of freshly isolated guinea pig tracheal smooth muscle cells. Previous electrophysiological studies revealed that agonists elicit cation and Cl- currents, but a role for Ca2+ in mediating these effects remains unresolved. Here we characterize agonist-induced changes of [Ca2+]i, using fura 2, and examine the contribution of the sarcoplasmic reticulum (SR) to regulation of [Ca2+]i. We provide evidence that the rise of [Ca2+]i and the contraction elicited by ACh or histamine are largely due to release of Ca2+ from stores. Agonists elicited Ca2+ transients in Ca(2+)-free solution with 0.5 mM ethylene glycol-bis (beta-aminoethyl ether)-N, N, N',N'-tetraacetic acid (EGTA), whereas prolonged exposure to Ca(2+)-free solution diminished the rise of [Ca2+]i. In addition, blockade of SR Ca(2+)-adenosinetriphosphatase (ATPase) by cyclopiazonic acid (CPA) or thapsigargin caused elevation of [Ca2+]i and reduction of ACh-evoked increase of [Ca2+]i. In many cells, [Ca2+]i fell below baseline (undershoot) after ACh or caffeine. CPA abolished this undershoot and reduced the rate of recovery of [Ca2+]i to basal levels. Furthermore, oscillations of [Ca2+]i were elicited in the presence or absence of extracellular Ca2+, and these too were reversibly abolished by CPA. Our results provide evidence that Ca2+ stores play a significant role in agonist-mediated increase of [Ca2+]i in tracheal muscle and that the SR contributes to the restoration of basal Ca2+ levels.

Development of an anthropometric database for Hong Kong Chinese CAD operators

With the increasing popularity of using computer-aided design (CAD) in Hong Kong, it is time to look into the design of a suitable workplace for the CAD operators working in the industries. This can be achieved by applying anthropometric data into the design for enhancing performance and reducing musculoskeletal problems. In order to avoid any mismatches in anthropometric dimensions, which is believed to be one of the main causes of fatigue and occupational illness among workers, in the workplace design for them, eleven relevant body dimensions from a group of 150 Hong Kong male adults with ages ranging from 18 to 28 years were collected and analyzed to develop a computerized anthropometric database for Hong Kong CAD operators. The eleven anthropometric dimensions measured were: shoulder rest height, elbow-fingertip length, shoulder breadth, hip breadth, sitting eye height, elbow rest height, third lumbar disc-pan length, thigh clearance height, popliteal height, buttock-popliteal length, and stature. The computerized database can provide some useful statistics such as mean, standard deviation and relevant percentiles of all the measured dimensions. With the aid of these statistics, a new workplace for CAD operators was designed which improved performance substantially.

[Experimental studies on Uncaria sinensis (Oliv.) Havil and Achyranthes bidentata Blume and their compacibility]

Pharmacological studies were conducted on Uncaria sinensis and Achyranthes bidentata both separately and combined. Comparison was made on the hypotensive effect on normal and renal-type hypertensive rats as well anti-spasmodic and sedative effects in mice. The results showed that Uncaria sinensis and Achyranthes bidentata have obvious synergic action in compatibility.

Identification of ochratoxin A in food samples by chemical derivatization and gas chromatography-mass spectrometry

The contamination of foods with ochratoxin A can be determined very sensitively by high-performance liquid chromatography (HPLC) with fluorescence detection. A novel procedure is described to confirm OA-positive results quantitatively down to the HPLC detection limit of 0.1 ppb. For this, ochratoxin A in the sample extract is converted into its O-methylochratoxin A methyl ester derivative, which is identified subsequently by gas chromatography-mass spectrometry negative-ion chemical ionization and multiple ion detection modes using the hexadeuterated O-methyl-d3-ochratoxin A methyl-d3 ester derivative as internal standard for quantification. In the analysis of more than 60 contaminated samples, the procedure was found to be very accurate.