PubMed Health⌕ Search

Biomedical subjects

T J Yu

Publications and source records attributed to T J Yu.

69 records · Page 4Linked to original sources
PubMed1984

Sequence analysis of derivatized peptides by high-performance liquid chromatography-mass spectrometry.

N-Acetyl-N,O,S-permethylated derivatives of oligopeptides were analyzed by high-performance liquid chromatography-mass spectrometry (HPLC-MS) using a moving belt interface. A heated-gas nebulizer was employed for sample deposition, thus permitting the effective use of a water-methanol gradient covering the range from 5% to 95% water at mobile phase flow-rates of 0.5 ml/min. We demonstrate in this paper that it is possible to sequence the octapeptide derived from the C-chain of glucagon by HPLC-MS analysis of a permethylated enzymatic hydrolysate of this peptide using overlap information from the mass spectral patterns. Moreover, it is shown that peptides not readily amenable to analysis by gas chromatography-MS can be analyzed using this approach. Preliminary results suggest that N-acetyl-methyl ester derivatives of oligopeptides may in specific cases also be a useful alternative for HPLC-MS analysis of complex oligopeptide mixtures.

Amino Acid Sequence↗
PubMed1984

Primary ovarian pregnancy in a cystic teratoma.

Hemoperitoneum was identified by culdocentesis in a 26-year-old woman suffering acute abdominal pain. A pregnancy test was positive. Operation indicated a ruptured ovarian pregnancy, and histologic examination revealed primary intrafollicular ovarian pregnancy in a cystic teratoma. Ovarian pregnancy in an ovarian tumor is exceedingly rare.

Adult↗
PubMed1980

Metal-flavin complexation. A resonance Raman investigation.

Several groups have recently shown that high quality resonance Raman spectra can be obtained for flavin species in spite of their intense fluorescence. We are interested in obtaining the resonance Raman spectra of flavins in various chemical environments in order to determine whether the spectra are useful in probing the chemical interaction between flavins and protein in flavoenzymes. We have obtained the resonance Raman spectrum of a nonfluorescent Ag+ complex of FMN. Several large changes occur in the FMN resonance Raman spectrum upon Ag+ complexation; among these are changes in the 1580 cm-1 region of the FMN spectrum (assigned to nu C=N at N-5 and C-4a), the 1410 cm-1 region and the 1260 cm-1 region (associated with a vibration having some delta N-N-H character at N-3). Similar changes are observed in the same region of a Ru2+-FMN complex. Since these spectral changes occur in two metal flavin complexes with very different electronic spectra, they would seem to be due to vibrational changes induced by metal complexation at N-5 and the oxygen at C-4 of flavin rather than the details of the vibronic interactions which give rise to the resonance enhancement of the spectrum. A structure for the Ag+-FMN complex is suggested. This study has potential physiological significance, because it illustrates the possible role of resonance Raman spectroscopy as a tool for the determination of direct flavin metal interaction in dilute aqueous solution of metalloflavoproteins.

Chemical Phenomena↗
PubMed1976

Effect of cross-linking on the secondary structure of DNA I. Cross-linking by photodimerization.

An investigation has been made into the effect produced by photo-induced pyrimidine cross-links upon the secondary structure of DNA. We have studied the effect of uv irradiation upon the B in equilibrium A transition in DNA brought about by a change of solvent from 70 to 80% ethanol. Circular dichroism (CD) was used to monitor the conformational changes. However, we first showed by means of laser Raman spectroscopy that CD is a reliable monitor of the conformational change, even though the DNA is aggregated in 80% alcohol solutions. It is suggested that this aggregation stabilizes the A form through lateral interaction between the helices. The uv irradiation experiments show that pyrimidine-dimer cross-links induced into the B-form DNA will lock it irreversibly into that conformation and prevent it from going to the A form in 80% EtOH solution. The A-form DNA can tolerate a few cross-links but converts cooperatively to the B form if a larger number of cross-links is introduced. Irradiation-induced pyrimidine cross-links create locally denatured regions in B-form DNA. Upon continued irradiation, the entire DNA moelcule becomes denatured.

Binding Sites↗
PubMedDate not supplied

Renal squamous cell carcinoma: CT findings and clinical significance.

BACKGROUND: To study the biological behavior of renal squamous cell carcinoma (RSCC). METHODS: Fifteen cases of RSCC were retrospectively studied. These cases were classified as central (eight cases) and peripheral (seven cases) types by the tumor location. The clinical data and computed tomographic findings were analyzed and compared. RESULTS: High incidence (87%) of urolithiasis was observed. The prognosis of RSCC was very poor, with a median survival time of 3.5 months. The infectious symptoms, central location, and modified stage IV of the tumor were the poor prognostic factors of RSCC. Two types of RSCC were different in the presenting symptoms, lymph node metastasis, modified tumor staging, and survival time. CONCLUSION: The central and peripheral types of RSCC were different biologically. High index of suspicion should be maintained when identifying the subtle clues of malignancy in patients with urolithiasis.

Adult↗
PubMedDate not supplied

Budd-Chiari syndrome due to pacemaker-induced thrombosis.

We report a unique case of Budd-Chiari syndrome caused by pacemaker leads-induced thrombosis. A 34 year old female patient was subjected to a permanent pacemaker insertion because of refractory paroxysmal supraventricular tachycardia attacks related to Wolff-Parkinson-White syndrome. Three years later, another pacemaker was re-implanted because of its dislodgement. Four episodes of skin infections at the implantation site were noted thereafter. The patient developed symptoms of abdominal pain and ascites 5 years after the second pacemaker implantation. Ultrasonography and computerized tomography of the abdomen revealed hepatomegaly with ascites and dilated inferior vena cava. An echocardiogram displayed thrombus formation in the superior vena cava, the right atrium and the inlet of the inferior vena cava into the right atrium. Inferior and superior venacavogram confirmed the above findings. With the impression that Budd-Chiari syndrome was caused by pacemaker-induced thrombus, we removed the pacemaker first and thoracotomy with thrombectomy was then performed. The clinical symptoms resolved after the operation. To our knowledge, this is the first case reported in the literature and this observation supported the thrombosis theory for membranous obstruction of inferior vena cava.

Abdomen↗
PubMedDate not supplied

Bicomponent vascular grafts consisting of synthetic absorbable fibers: Part II: In vivo healing response.

The objectives of this research were (1) to determine whether the use of partially absorbable vascular grafts would improve their nonthrombogenic performance and whether they are more prone to aneurysmal dilation and subsequent failure in vivo, and (2) to find out the relationships, if any, between these in vivo and the previously reported in vitro data with an emphasis on how the in vitro changes in fabric structure and properties related to these in vivo data. Bicomponent vascular fabrics were made from Dacron and polyglycolic acid (PGA) yarns with a range of composition ratios of the PGA to Dacron. Both woven and single Jersey knit fabrics were made, and implanted in dogs for 4 months. The following findings and relationships were obtained. (1) The bicomponent vascular fabrics resulted in a full-wall healing in the thoracic aorta of dogs. All bicomponent vascular grafts in survived dogs exhibited 100% patency, no thrombus or aneurysmal formation, no hematoma or seroma around the grafts, and no fibrin coagula in the inner capsules. The gross morphology of the regenerated tissues was very similar visually to the adjacent original arterial tissue. Histologically, the luminal surface was lined with a layer of endothelial cells with myofibroblasts, fibroblasts, and collagens underneath. (2) The extent of the full-wall healing depended on the type of fabric structure, the concentration of absorbable yarns, the location of absorbable yarns (for the woven group only), and initial water permeability. It is believed that the concentration effect was related to the level of macrophage activation from the degradation products of the absorbable yarns, while the location effect was attributed to the various types of fabric structure change on the degradation of the absorbable yarns. (3) In general, the knitted group (K), was better than the woven group (W). K3 showed the best in vivo performance in the knitted group. (4) In the woven group, W3 was the best. The incorporation of absorbable yarns in the weft direction of the bicomponent fabrics (W3) resulted in a velourlike, loose and porous fabric surface for facilitating tissue ingrowth. The placement of absorbable yarns in the warp direction (W1), however, did not show this unique surface morphology. Calcification was, however, occasionally observed in the woven samples with low initial water permeability. These observed in vivo performances correlated well with our previously reported in vitro study.

Absorption↗
PubMedDate not supplied

Treatment guideline of enuresis in Taiwan.

The treatment guideline of enuresis suggested by the study group of enuresis in Taiwan is reported. Medical consultation and treatment of enuresis are recommended at the age of 5 and 6 years respectively. Evaluation of the enuretic children includes history taking, physical examination and laboratory investigations. A checklist is provided for quick evaluation in busy clinics. Urinalysis, urine specific gravity and office ultrasonography are essential tests. An algorithm of treatment of monosymptomatic enuresis is constructed. The two main options of treatment are behavioral modification with alarm system and pharmacotherapy with desmopressin or imipramine. Imipramine is recommended as one of the treatment options because of its relative safety in Taiwan. However the potential toxicity and mortality of imipramine is highlighted and warned. The responses to treatment are evaluated after a period of treatment for 1 to 3 months. Further evaluation and individualized treatment is suggested for poor responders.

Antidepressive Agents, Tricyclic↗
PubMedDate not supplied

Spontaneous rupture of the bladder in childhood: report of one case.

Perforation of the urinary bladder without history of antecedent trauma is a rare clinical occurrence in children, but should be considered in patients with voiding disorders, abdominal symptoms and unexplained metabolic disturbances. The present report concerns a young infant who presented with irritability, abdominal colic, decreased urine output; blood examinations showing mild leukocytosis, azotemia and metabolic acidosis. Further cystogram and cystoscopy confirmed rupture of the bladder. She had an uneventful recovery after a twelve days of conservative treatment with indwelling catheterization and nutritional support. A subsequent urogram revealed complete healing of the lesion.

Female↗