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Biomedical subjects

C L Lin

Publications and source records attributed to C L Lin.

155 records · Page 9Linked to original sources
PubMed1985

[The relationship between indicator bacteria and pathogens in food safety].

57 specimens of raw foods and 143 specimens of ready to eat foods were examined for microbial contamination in a period from October, 1982 to September, 1983. The results showed that 26% of the raw foods and 24% of the ready to eat foods didn't meet the government's requirement. When TAPC less than 10(6) CFU/g is used as acceptable level, then 60% of the raw foods and 46% of the ready to eat foods are unsatisfactory. The appearance of pathogenic bacteria in foods increased when the TAPC rised, although only the emergence of S. aureus was statistically significant. The number of indicator bacteria in the foods examined didn't show any correlation with the existence of pathogenic bacteria, indicating that the presence of coliform bacteria and E. coli in foods could hardly serve as parameters for evaluating food safety.

Bacteria↗
PubMedDate not supplied

Reentrant tachyarrhythmias in right atria of cardiomyopathic versus healthy Syrian hamster.

We studied the role of acetylcholine (ACh) and calcium overload in the induction of atrial flutter or atrial fibrillation (AF) in right atria from 34 normal male Syrian hamsters (F1B) and 33 cardiomyopathic Syrian hamsters (BIO 14.6) associated with focal myocardial necrosis. Action potential (AP) was recorded with conventional microelectrode techniques and twitch force by a transducer. ACh (0.1, 1 and 10 microM) induced high-frequency AF (around 33 Hz) along with tension oscillations and contracture in 7 of 12 normal hamster atria. These effects of ACh were abolished by tetrodotoxin or quinidine as well as by atropine. In contrast, ACh induced AF only in 1 of 12 myopathic atria. In both normal and myopathic atria, ACh induced similar changes in AP duration, spontaneous rate and force. The effects of calcium overload were tested by means of a high [Ca(2+)](o) (8.1 mM) low [K(+)](o) (1 mM) solution in another series of experiments. This solution also induced incidence of AF higher in normal (10/12) than in myopathic atria (4/12). The calcium load was also increased by high-frequency pacing (32 Hz for 3 or 30 s): AF occurred in normal atria (5/8), but not in myopathic atria (0/8). Measurement of the refractory period revealed a longer refractory period in myopathic than in control atria. We concluded that the lower incidence of AF in myopathic atria was probably due to their longer refractory period and the associated focal myocardial necrosis which then hindered the establishment of such a reentrant rhythm.

Acetylcholine↗
PubMedDate not supplied

Stresses at the cervical lesion of maxillary premolar--a finite element investigation.

OBJECTIVES: The objective of this study was to use a three-dimensional (3-D) finite element model to investigate normal stress distribution to substantiate the tooth flexure mechanism. The study also compared the changes in the stresses by different occlusal loading sites and directions. METHODS: The 3-D finite element analysis was used. A maxillary premolar was selected to construct the simulation model. The model was constructed step-by-step for convergence and validity. Seven load conditions for various load sites and different directions were simulated to the model. RESULTS: The maximal principal stress and minimal principal stress distributions developed within the structures of seven load conditions were output and their stress distributions on z-plane at the vertical midline were shown. The peak tensile stress of the cervical area for various load conditions were compared and listed. CONCLUSIONS: This study has shown that the presence of tensile stresses in the cervical region of a maxillary premolar by various loading sites and different directions. The results coincided with the stress-induced theory, hence sustaining it. The relationship of the affected factors of leverage to the development of cervical abfraction lesions, was explored.

Bicuspid↗
PubMedDate not supplied

Solid-phase extraction in amphetamine and methamphetamine analysis of urine.

A systematic evaluation that compares the recoveries of methamphetamine and amphetamine from spiked urine using C8, C18, strong cation exchanger (SCX), and C8-SCX mixed procedures (solid-phase extraction) is reported. Optimized experimental conditions including pH of the sample, solvent composition, and urine concentration for different solid-phase extraction sorbents were studied. The largest recoveries--greater than 86% for methamphetamine and greater than 88% for amphetamine--were achieved with a mixed adsorbent (C8-SCX) and mixed elution solvent CH2Cl2-i-propanol-NH4OH (78:20:2) at pH 6. The concentration of the urine matrix did not affect the extraction efficiency. The detection limits of methamphetamine and amphetamine in urine were obtained at 0.03 and 0.07 micrograms/mL, respectively, using gas chromatographic-mass spectrometric analysis operated in the electron impact mode.

Adsorption↗
PubMedDate not supplied

The expression of rac1 pseudogene in human tissues and in human brain tumors.

BACKGROUND: Recent studies have demonstrated that Rac is a regulator of cell morphology and growth. Rac1 gene appears to have involvement in tumorigenesis and metastatic potential. In our previous study of rac1 gene in 45 human brain tumors, rac1 pseudogene was found. The rac1 pseudogene is an intronless pseudogene and has a similarity of 86% with rac1 nucleotide sequence. The rac1 pseudogene contains 579 nucleotides and only 46 amino acids can be translated. Little is known about the expression of rac1 pseudogene in human tissues or tumors. MATERIALS AND METHODS: The expression of rac1 gene and rac1 pseudogene in different human tissues and brain tumors was investigated by the use of reverse transcriptase-polymerase chain reaction and Northern blotting. RESULTS: The rac1 gene is apparently expressed in these 8 human tissues. The rac1 pseudogene is also apparently expressed in human tissues except for brain tissue. The overexpression of rac1 gene in brain tumors was 8% (2/25) and the overexpression of rac1 pseudogene was 76.9% (20/26). Only two astrocytomas had overexpression of rac1 gene, compared with normal brain tissues. The overexpression of rac1 pseudogene was 6 of 9 in meningiomas, 7 of 9 in astrocytomas, and 7 of 8 in pituitary adenomas. CONCLUSIONS: High frequency of overexpression of rac1 pseudogene was detected in the human brain tumors when compared with that expressed in the normal brain tissues. Our study suggested that the rac1 pseudogene may play an important role of the tumorigenesis of brain.

Astrocytoma↗
PubMedDate not supplied

Simulation and fabrication of subwavelength structures for a nanometer feature enabling lens-less laser writers.

A set-up was proposed to propagate submicrometer light beams without resorting to the conventional approach of using a lens. The main target was to develop a method of either by passing or circumventing the diffraction limit to develop a new optical head for a laser writer system with submicrometer resolution. Starting from using surface plasma theory to explain the mechanism of extraordinary transmission phenomenon, we move to discuss the fabrication processes for free-standing metal films and the corresponding transmission light beam images in the far field. A finite difference time domain (FDTD) method was adopted to simulate the electromagnetic field distribution of transmission light beams from the near field to the far field. The experimental results confirm that surface structures on the incident side of incoming light beams can excite surface plasma and enhance the throughput energy of transmission light beams. In addition, we also established that surface structures on the exit side can suppress the diffraction effect and make transmission light beams directional. The experimental and simulation results were found to agree well with each other, which validates the effectiveness of the FDTD simulation approach. As a free-standing film was too fragile to be of practical use, a proposition to develop a substrate-based nanostructured film to ease the construction of an optical head for a laser writer was developed.

Journal Article↗
PubMedDate not supplied

Proinsulin level in diabetes mellitus measured by a new immunochemiluminometric assay.

Proinsulin, the precursor of insulin and C-peptide, is detectable in the circulation and is a potential marker of beta-cell dysfunction. Currently, circulating proinsulin can be measured accurately without the interference of insulin or C-peptide by immunometric assays and a few specific radioimmunoassays. An immunochemiluminometric assay was developed in our laboratory by using two immunopurified polyclonal antibodies of C-peptide and insulin from two goats. The C-peptide antiserum was labeled with acridinium ester. The insulin antiserum was immobilized onto a plastic bead. With this assay, proinsulin levels found in noninsulin-treated patients with noninsulin-dependent diabetes mellitus (63 +/- 58 pmol/L; n = 19) were significantly higher (p < 0.05) than levels in insulin-treated patients with noninsulin-dependent diabetes mellitus (30 +/- 24 pmol/L; n = 43), and both were significantly higher (p < 0.001) than proinsulin levels in patients with insulin-dependent diabetes mellitus. In addition, there was a negative correlation between proinsulin levels and duration of years on insulin therapy in patients with noninsulin-dependent diabetes mellitus (r = -0.4795; p < 0.01).

Adult↗