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Biomedical subjects

T M Chen

Publications and source records attributed to T M Chen.

At least 109 records · Page 6Linked to original sources

Extrapulmonary tuberculosis: experience at Veterans General Hospital-Taipei, 1985 to 1987.

From 1985 to 1987, 343 cases of extrapulmonary tuberculosis (TB) were identified, representing about 20% of all the newly diagnosed TB cases at Veterans General Hospital-Taipei. Bacteriological and histopathological examinations were of equal importance in making a diagnosis of extrapulmonary TB. However, 79% of the cases of TB meningitis were diagnosed only by positive cerebrospinal fluid cultures for Mycobacterium tuberculosis. The pleura, lymph nodes, urinary and osteoarticular systems were the most commonly affected locations. Male patients predominated except for TB lymphadenitis. However, female patients with TB are more likely to have non-respiratory TB than are male patients. The peak number of cases by age occurred in the seventh decade of life, and the mean age of male patients was older than that of female patients. Pulmonary lesions suggestive of TB and age over 60 years were the two most common risk factors. Anti-TB chemotherapy alone was enough in many patients. However, more than 50% of the patients with osteoarticular TB, pericardial TB, TB lymphadenitis, and TB enteritis or peritonitis underwent surgical intervention for either diagnosis or treatment. The results of adequate anti-TB chemotherapy or surgical treatment were usually satisfactory. About 32% of the patients were lost to follow-up before completing anti-TB chemotherapy. In this series, 34 deaths occurred, of which 7 were TB-unrelated and 10 occurred before a diagnosis of TB was made or proper therapy initiated. Although TB meningitis was uncommon in this series, it had the highest mortality rate (67%).

Adolescent↗

Interfacing microbore and capillary liquid chromatography to continuous-flow fast atom bombardment mass spectrometry for the analysis of glycopeptides.

This work describes a system to interface either microbore or packed capillary gradient liquid chromatography (LC) to fast atom bombardment mass spectrometry (FAB-MS). The interface incorporates on-line ultraviolet detection and post-column matrix addition to enable independent optimization of both LC and FAB-MS. The glycopeptide antibiotic teicoplanin was chosen as a model system because this group of compounds places severe demands on the chromatographic separation and is difficult to analyze by FAB-MS. For both microbore and capillary LC, high-quality mass spectra of the major components in teicoplanin were obtained; however, the increased sensitivity of the capillary system allowed spectra to be obtained at low picomole concentrations. The sensitivity and ease of use make capillary LC the preferred system for use in LC-FAB-MS.

Amino Acid Sequence↗

Curtatoxins. Neurotoxic insecticidal polypeptides isolated from the funnel-web spider Hololena curta.

Three polypeptide neurotoxins (curtatoxins) were isolated from the venom of the spider Hololena curta by reverse-phase high performance liquid chromatography, gel permeation, and ion-exchange chromatography. The purified toxins induced an immediate paralysis in the cricket Acheta domestica that resulted in desiccation and death of the insect within 24-48 h (LD50 congruent to 4-20 micrograms/g); this toxic effect is consistent with irreversible presynaptic neuromuscular blockade. Curtatoxins are a class of sequence-related, cysteine-rich, carboxyl-terminal amidated polypeptides of 36 to 38 amino acid residues. The cysteine residues are conserved at identical sequence positions among these polypeptides and form 4 intramolecular disulfide bonds. Hydropathy calculations show that the toxins have an internal hydrophobic region flanked by hydrophilic and oppositely charged amino- and carboxyl-terminal ends. By analogy to other cysteine-rich arthropod venom proteins, the folded structure of the curtatoxins is likely important for their target specificity and mode of action at the neuromuscular junction.

Agatoxins↗

Recombinant bivalent live vaccines against neonatal colibacillosis in piglets.

The genes of colonization factor K88 and avirulent heat-labile enterotoxin LT A-B+ of enterotoxigenic E. coli (ETEC) have been ligated, and a vaccine strain containing recombinant plasmid that efficiently expresses two antigens has been obtained. Using the activity of beta-galactosidase as a selection marker instead of drug resistance, another bivalent vaccine strain with the same expression level has also been constructed. The vaccine strains have no toxicity and do not cause any adverse reactions. In challenge study and field trials, a high degree of protection from colibacillosis was afforded to piglets when their dams were immunized orally or parenterally. Practice of bivalent live vaccines including colonization factor and enterotoxin antigens and without antibiotic resistance gene shows effective.

Adhesins, Escherichia coli↗

The construction of a non-antibiotic resistant ETEC vaccine strain containing K88ac and LT-B antigens.

By inserting the LacZ gene into the plasmid containing ETEC LT-B antigen gene we obtained a recombinant plasmid which could express the beta-galactosidase and LT-B antigen, but has the Tc resistant gene. The K88ac antigen gene was then inserted into the BamHI site of the Tc resistant region in the above plasmid. The final recombinant plasmid has no antibiotic resistance gene but can stably express both LT-B and K88ac antigens, as well as the beta-galactosidase as a tracking marker.

Antigens, Bacterial↗

Thermospray high-performance liquid chromatographic-mass spectrometric characterization of biological macromolecules. I. Analysis of acid hydrolysate of peptides.

A method for the routine analysis of phenylthiocarbamyl (PTC) amino acids by thermospray high-performance liquid chromatography-mass spectrometry (TSP LC-MS) is described. Data were acquired on a small dedicated TSP LC-MS system in which the temperature of the vaporizer and ion source block were optimized. PTC-amino acids exhibited unique TSP mass spectra containing sufficient fragment ions to determine structural data. Therefore, using this method the amino acids contained in the acid hydrolysates of unique and modified peptides were able to be positively identified. Additionally, the amino acid composition of peptides as determined by TSP LC-MS in the selected ion monitoring mode corresponded well with the theoretical value. The detection limits for the PTC-amino acids were at the low picomole level.

Amino Acids↗

Fast atom bombardment mass spectrometric investigation of in vitro degradation within the disulfide-linked core of atrial natriuretic factor.

The use of high-performance liquid chromatography and fast atom bombardment mass spectrometry are shown to be an efficient combination for investigating protease-mediated digestion of synthetic analogs of the peptide hormone ANF (atrial natriuretic factor). As examples of the reported methodology, rANF5-23-NH2 and rANF7-23-NH2 were digested with the endopeptidase thermolysin. These truncated analogs were selected to investigate metabolism within the disulfide-linked core of ANF, particularly at the Cys7-Phe8 bond. While this position was the site of initial hydrolysis for rANF5-23-NH2 (t1/2 = 0.5 min), the Cys7-Phe8 bond remained intact for all observed degradation products of rANF7-23-NH2 (t1/2 = 16 min). These findings suggest that improved stability towards endopeptidase-mediated core hydrolysis may be conferred to analogs of ANF by removal of the first six residues from the N-terminus.

Amino Acid Sequence↗

Receptor binding affinity and thermolysin degradation of truncated and retro-inverso-isomeric ANF analogs.

The peptides H-Phe-Gly-Gly-Arg-Ile-Asp-Arg-Ile-NH2 (rANF8-15-NH2), Ac-Phe-Gly-Gly-Arg-Ile-Asp-Arg-Ile-NH2 (Ac-rANF8-15-NH2), and their corresponding retro-inverso-isomeric peptides H-D-Ile-D-Arg-D-Asp-D-Ile-D-Arg-Gly-Gly-D-Phe-NH2 (D-rANF15-8-NH2), Ac-D-Ile-D-Arg-D-Asp-D-Ile-D-Arg-Gly-Gly-D-Phe-NH2 (Ac-D-rANF15-8-NH2), were evaluated for their ability to compete for the binding of 125I-rANF5-28 to cultured spontaneously hypertensive rat (SHR) aortic smooth muscle cell membranes. Their stability toward hydrolysis by the neutral endopeptidase thermolysin was also studied. The octapeptides rANF8-15-NH2 and Ac-rANF8-15-NH2 bound with IC50's of 367 pM and 1900 pM, respectively, but were rapidly hydrolyzed by thermolysin. Retro-inverso-isomers were prepared to provide molecules with an improved enzymatic stability. The retro-inverso-isomers were completely stable to thermolysin but were virtually inactive in the binding assay (IC50 greater than 1 microM).

Animals↗

Cloning and expression of heat-labile enterotoxin operon of an enterotoxigenic human Escherichia coli strain.

Plasmid pJY11 of the Escherichia coli H10407 strain was isolated and completely digested with restriction endonuclease PstI in order to isolate the heat-labile enterotoxin (LT) operon. The resulting fragments were then separated by electrophoresis on agarose gel, and the location of the LT region in pJY11 was determined by Southern hybridization. The LT region was found to be located on a 5.3 kb fragment of pJY11. This fragment was recovered and subsequently ligated to PstI-linearized pUC8 DNA. After transformation and selection, a clone that effectively expressed LT was obtained. Biological and immunological assays showed the LT synthesized by this clone to be biologically and immunologically identical to that synthesized by the parent E. coli strain H10407; the LT production level of this recombinant strain was 15 times greater.

Animals↗

[Lateral calcaneal artery flap].

The lateral calcaneal artery flap provides a simple and reliable option for reconstructing the posterior heel defect. In our 10 cases including 3 diabetic patients, there was no flap necrosis, but one had the problem of wound healing. In another case, the skin graft over the flap donor site failed to take. All patients have protective sensation on the flap area, and 7 ambulatory patients can engage in a normal daily activity. Numbness over the lateral foot does not cause any trouble. There are a lot of spoke injuries in our 6-million-motorcycle country. When the conservative treatments do not achieve a satisfactory result, the lateral calcaneal artery flap should be the best surgical intervention for the defect less than 5 cm in diameter with bone or tendon exposure.

Adolescent↗

Design and synthesis of metabolically stable atrial natriuretic factor analogs. Amino- and carboxy-terminal stabilization.

Two analogs of rat atrial natriuretic factor, rANF7-28-NH2 and [Mpr7,Ala20,D-Arg27]rANF7-27-NH2, were prepared by the solid-phase method. These peptides had 2-fold and 7-fold less affinity, respectively, than rANF1-28 in binding to membranes prepared from cultured aortic smooth muscle cells, and both peptides were 5-fold less potent than rANF1-28 in relaxing serotonin-contracted rabbit aortic rings. rANF7-28-NH2 was rapidly degraded by rat kidney homogenates but [Mpr7,Ala20,D-Arg27]rANF7-27-NH2 had enhanced stability against rat kidney homogenate degradation. However, this in vitro stability did not translate into an extended duration of action in vivo.

Amino Acid Sequence↗

High-pressure liquid chromatographic assay of dextromethorphan hydrobromide, guaifenesin, and sodium benzoate in an expectorant syrup.

An ion-pair reversed-phase high-pressure liquid chromatographic assay is developed that allows simultaneous quantitation of guaifenesin, dextromethorphan hydrobromide, and sodium benzoate in an expectorant syrup. The method is rapid and accurate. Average recoveries of 99.6, 99.8, and 99.7% with relative standard deviations of 0.5, 0.9, and 0.2% are obtained for guaifenesin, dextromethorphan hydrobromide, and sodium benzoate, respectively, from laboratory prepared samples. Chromatographic conditions are selected to afford a pH that provides adequate separation of guaifenesin, dextromethorphan hydrobromide, sodium benzoate, and sodium saccharin and a detection wavelength that effectively compensates for the great disparity in quantity between guaifenesin and dextromethorphan hydrobromide present in syrups. The relationships between the retention volume of dextromethorphan hydrobromide and the alkyl chain length as well as the concentration of the counterion are studied. The retention profiles for sodium saccharin, guaifenesin, sodium benzoate, and dextromethorphan hydrobromide in the apparent pH range of 2.5 to 6.6 are established.

Benzoates↗

In vitro processing of rANF7-28-NH2 by rat kidney homogenates.

The major rat kidney in vitro degradation products of the rat atrial natriuretic factor analog, H-Cys7-Phe-Gly-Gly-Arg-Ile-Asp-Arg-Ile-Gly-Ala-Gln-Ser-Gly-Leu-Gly -Cys-Asn-Ser-Phe-Arg-Tyr28-NH2 (with a Cys27-Cys23 disulfide bridge), have been identified. The degradation products are the C-terminal modified compounds rANF7-27, rANF7-26, and rANF7-25.

Amino Acid Sequence↗