Biomedical subjects

L Y Li

Publications and source records attributed to L Y Li.

At least 19 recordsLinked to original sources

PubMed1992

Purification of opioid receptor in the presence of sodium ions.

Opioid receptor was solubilized from rat brain membranes with a mixture of the detergents CHAPS and digitonin in the presence of protease inhibitors and 1 M NaCl. The solubilized receptor bound mu-opioid agonists and antagonists with affinities similar to those of native membrane receptor. The affinity of solubilized receptor for the agonist PL017 was greatly reduced by GTP gamma S, suggesting the receptor is still associated with G-protein. The solubilized material was passed through an opioid antagonist (10cd) affinity column and a wheat germ agglutinin column, set up in series, to obtain a partially purified receptor preparation. This partially purified material bound mu-agonist with low affinity and the binding affinity was no longer affected by GTP gamma S. The partially purified receptor was further purified by repeating the affinity and lectin chromatography with smaller size column. Binding of opioid antagonist [3H]diprenorphine to the partially or purified receptors was dependent upon the presence of sodium ions. The purified receptor showed saturable and stereospecific binding for opioid ligands, was predominantly of the mu-type, and exhibited as a diffuse band with a medium molecular mass of 62 kD upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The average specific binding activity of the purified receptor was 18.8 +/- 2.3 pmol/micrograms protein, a value close to the theoretical estimation.

Animals↗

PubMed1992

[Pulmonary angitis and granulomatosis].

16 patients of Wegener's granulomatosis, 4 of allergic angiitis and granulomatosis, 3 of lymphomatoid granulomatosis and 1 of necrotizing sarcoid granulomatosis were reported. In this group of different diseases, characteristic pathological manifestations are inflammatory cellular infiltration of vessel wall combined with destruction and necrosis of pulmonary parenchyma. There was little difference in their clinical features. In most of the cases, fever and systemic symptoms related to lung and extrapulmonary organs were present. Correct diagnosis of these diseases is very important, because both the prognosis and therapy are different. As for the prognosis, it ranges from benign (necrotizing sarcoidal granulomatosis) to very malignant (lymphomatoid granulomatosis). The clinical features of each illness were reviewed with emphasis on their histopathologic findings. The therapeutic effect and final outcome were followed.

Adolescent↗

PubMed1992

[The treatment of small cell lung cancer].

Forty-nine cases with small cell lung cancer (SCLC) treated with chemotherapy and radiotherapy were analyzed. Eight of them were of limited disease (LD), and 41(83.7%) had extensive disease (ED). Forty six were treated on a protocol comprising the induction with cyclophosphamide 1g i.v. on days 1st and 8th, vincristine 1-2mg, i.v. on days 1st and 8th, etoposide 100mg i.v. on days 3rd-7th and methotrexate 20mg i.v. on day 3rd, 5th, 9th, 11th and than repeated with the second course of treatment after 21 days. Eight patients (17.4%) responded completely. There were 29 cases with partial response (63%). The total response rate was therefore 80.4%. Then radiotherapy (50 GY Over 4 weeks) was administered to primary cancer area in 36 patients of good response. The CR was increased from 19.4% to 55.6%. Twenty patients had CR. These patients were treated by late intensification with average of six cycles. The median survival period was 10 months. 21 patients (58.3%) were alive more than 1yr. 10 patients (27.8%) survived more than 2 yrs. Six patients (24%) were alive more than 3 yrs. One patient survived over 7 yrs. It was suggested that combined therapy is important for achieving a better response. CR is beneficial for long term remission. Late intensification is a kind of treatment with minimal toxicity and longer remission. Metastases to the central nervous system usually caused death, so prophylactic CNS irradiation (PCI) should be used in patients with ED for achieving a longer remission.

Adult↗

PubMed1991

Codon usage, transfer RNA availability and mistranslation in amino acid starved bacteria.

The fidelity of codon reading was examined in amino acid starved Escherichia coli. In one case the level of misincorporation of methionine was measured at an isoleucine residue encoded by either the commonly used AUU codon or the rarely used AUA codon. In this situation we found the frequency of methionine misincorporation to be very low and to be unaffected by the identity of the isoleucine codon. In other experiments histidine misincorporation for glutamine was measured in glutamine starved cells with normal levels of histidine-specific tRNA and cells overproducing this tRNA. Cells overproducing the tRNA had higher levels of misincorporation.

Amino Acid Sequence↗

PubMed1991

Impact on catalysis of secondary structural manipulation of the alpha C-helix of Escherichia coli dihydrofolate reductase.

The alpha C-helix of Escherichia coli dihydrofolate reductase has been converted to its counterpart in Lactobacillus casei by a triple mutation in the helix (H45R, W47Y, and I50F). These changes result in a 2-fold increase in the steady-state reaction rate (kcat = 26 s-1) that is limited by an increased off rate for the release of tetrahydrofolate (koff = 40 s-1 versus 12 s-1). On the other hand the mutant protein exhibits a 10-fold increase in the KM value (6.8 microM) for dihydrofolate and a 10-fold decrease in the rate of hydride transfer (85 s-1) from NADPH to dihydrofolate. The elevated rate of tetrahydrofolate release upon the rebinding of NADPH, a characteristic of the wild-type enzyme-catalyzed reaction, is diminished. The intrinsic pKa (6.4) of the mutant enzyme binary complex with NADPH is similar to that of the wild type, but the pKa of the ternary complex is increased to 7.3, about on pH unit higher than the wild-type value. Further mutagenesis (G51P and an insertion of K52) was conducted to incorporate a hairpin turn unique to the C-terminus of the alpha C-helix of the L. casei enzyme in order to adjust a possible dislocation of the new helix. The resultant pentamutant enzyme shows restoration of many of the kinetic parameters, such as kcat (12 s-1), KM (1.1 microM for dihydrofolate), and khyd (526 s-1), to the wild-type values. The synergism in the product release is also largely restored. A substrate-induced conformational change responsible for the fine tuning of the catalytic process was found to be associated with the newly installed hairpin structure. The Asp27 residue of the mutant enzyme was found to be reprotonated before tetrahydrofolate release.

Amino Acid Sequence↗

PubMed1991

Microdissection of human high resolution banded chromosome, polymerase chain reaction and microcloning.

A simple technique for microdissection of specific region of human high resolution banded chromosome, followed by polymerase chain reaction (PCR), and microcloning was successfully used to microdissect 4 chromosomal pieces from the distal one third from band 11.2 to the terminal of the short arm of Y chromosome where the testis determining factor is located; 3.6 x 10(4) clones were obtained after 30 cycles of PCR. We analysed 41 clones with insert. The size of insert ranges from 140 to 350 bp (average 250 bp). A Southern blot analysis was done for one of them, and a 2.5 kb Hind III fragment was detected.

Cloning, Molecular↗

PubMed1991

[Clinical use of polysomnography (PSG)].

The clinical diagnoses in 695 cases using PSG were analysed. The results are as follows: Obstructive sleep apnea syndrome (OSAS) in 482 cases (69.4%), chronic obstructive pulmonary diseases with nocturnal hypoxemia in 25 cases (3.6%), epilepsy in 31 cases (4.5%), other sleep disorders in 5 cases (0.7%), and essentially normal in 152 cases (21.9%). Some parameters of PSG in 65 cases with OSAS and those in 2 cases before and after treatment were analysed. It is emphasized that PSG is using for diagnosis of different types of OSAS with appraisable seriousness and of other related sleep disorders. The method and indications of PSG were discussed.

Electroencephalography↗

PubMed1991

[Lymphomatoid granulomatosis. A report of 2 cases].

Two patients with lymphomatoid granulomatosis were diagnosed by postmortem autopsy or exploratory thoracotomy. The lung, skin, spleen, renal and lymph nodes were involved. The most common presenting complaints are fever, cough, expectoration shortness of breath. The radiographic manifestations are multiple, bilateral nodular shadows. The histologic features is a unique form of pulmonary angiitis and granulomatosis, which is a necrotizing angiocentric and angio-destructive infiltrative process composed of small lymphocytes and atypical lymphoreticular cells.

Adult↗

PubMed1991

[An analysis of 30 cases of chylothorax and chyloperitoneum].

Thirty patients diagnosed as chylothorax and chyloperitoneum (13 of chylothorax, 9 of chyloperitoneum and 8 of both) in PUMC Hospital from 1923 to 1989 were reported. Thus, the incidence rate of these two diseases is rather low. The commonest causes were iatrogenic trauma (9 cases) and malignant tumor (7 cases). Other causes were tuberculosis (5 cases), lymphangioma (2 cases), Behcet's syndrome (1 case) and non-iatrogenic trauma (1 case). The etiology was not known in 5 cases. Acute episode was observed in patients with traumatic chylous effusion; it was usually manifested as dyspnea or abdominal distention. Patients with nontraumatic chylous effusion usually run a chronic course. The characteristics of chylous effusion were analyzed. Lymphangiography and lymphoscintigraphy with 99m TC-labeled dextran play important roles in diagnosis and treatment. It has been suggested that the changes in T-cell immunocompetence is important in determining whether the treatment should be conservative or operative. If chylous effusion is due to tuberculosis, antituberculosis treatment should be instituted.

Adolescent↗

PubMed1990

A reliable method for obtaining high-resolution banded chromosome preparations from chorionic villus samples.

A reliable method for obtaining high-resolution banded chromosome preparations from chorionic villus samples (CVS) is described, in which a synchronization cell-culture technique with the use of thymidine is introduced. After culturing a suspension of chorionic villus cells in a medium supplemented with 0.3 mg/ml thymidine for 13-17 hr, cells were washed twice, and recultured for further 8 hr. The cells were then treated with 10 micrograms/ml ethidium bromide or 1 microgram/ml actinomycin D for 1 hr and subsequently with 0.01 microgram/ml Colcemid for 30 min. The average mitotic index obtained was more than 60 mitoses/mg CVS, and more than 60% of mitoses proceeded to the prometaphase stage, the later prophase stage, or in between. The application of this method for prenatal diagnoses in five CVS in the first trimester pregnancies proved that it is a simple, practical and efficient prenatal diagnostic method.

Cell Cycle↗

PubMed1990

Economic effects of nosocomial infections in cardiac surgery.

A study of 60 infected patients and matched controls showed that nosocomial infection in cardiac surgery cost each patient an additional 2207 yuan (pounds 290). The cost of multisite infection was much higher. Infected patients were in hospital for a mean of 14 extra days.

Adolescent↗

PubMed1990

A prospective study of nosocomial infections in cardiac surgery patients in China.

A prospective survey of postoperative nosocomial infections (NI) in cardiac surgery was carried out in a cardiovascular specialty hospital in Beijing, China. During the period from December 1986 to December 1987, 1208 cardiovascular surgery patients were surveyed for NI. The overall incidence of NI was found to be 7.5%. The incidence of lower respiratory tract and wound infections were 4.5% and 2.9%, respectively. These two kinds of infection accounted for 78.1% of the total infections. After effective control measures were taken at the end of the first 6 months (December 1986 to May 1987) of the study, the incidence fell from 10.6% to 5.1% in the next 7-month period (June to December 1987). The pathogens causing NI were mostly gram-negative bacteria, and they were mainly opportunistic. The contribution of fungal infection was significant in the hospitals. The majority of the pathogenic isolates were highly resistant to the antibiotics commonly used in the hospital.

Adolescent↗

PubMed1990

[Clinical analysis of 90 cases of eosinophilia and pulmonary infiltrates with peripheral eosinophilia].

90 patients diagnosed as eosinophilia and pulmonary infiltrates with peripheral eosinophilia in PUMC Hospital from 1957 to 1986 were reported. The cause of the eosinophilia was unknown in 42% of the patients. Among these patients, hypereosinophilic syndromes (HES) were suspected in 11 patients. The most common presenting symptoms of HES were fever, skin lesions gastrointestinal symptoms and hepatosplenomegaly, the mean peripheral blood eosinophil count was as high as 25.6 x 10(9) cells/L. Biopsies of bone marrow and involved organs revealed extensive eosinophilic infiltration and severe necrosis. In the past ten years, eosinophilia and pulmonary infiltrates caused by parasitic infections obviously decreased. The most common parasites were ascaris Lumbricoides, Ancylostoma duodenale and Clonorchis sinesis. The other main causes which induced pulmonary infiltrates were allergic bronchopulmonary mycosis (ABPM) and chronic eosinophilic pneumonia. The prevalence of ABPM increased recently; early diagnosis and effective therapy could prevent the irreversible damage resulting in airways obstruction and fibrosis.

Ancylostomiasis↗

PubMed1990

[Diagnosis of cyanosis and digital clubbing caused by liver cirrhosis].

Six cases of cyanosis and digital clubbing caused by liver cirrhosis were reported. The mean levels of PaO2 and PaCO2 were 6.4 +/- 0.8 kPa (48.3 +/- 6.2 mmHg) and 3.9 +/- 0.8 kPa (29.5 +/- 6.1 mmHg) respectively. The cause of cyanosis and digital clubbing in liver cirrhosis was discussed. Abnormal intrapulmonary shunting (IPS), which was proved in 4 cases by whole-body radionuclide scanning with 99mTc-MAA, is suggested as the major cause of cyanosis in liver cirrhosis. Clinically IPS is usually associated with debilitating conditions characterized by hyperventilation, abnormality of lung diffusion and orthodeoxia or platypnea. The authors suggest that whole-body radionuclide scanning with 99mTc-MAA may be performed for establishing IPS if liver cirrhosis is highly suspected to be the cause of severe hypoxemia.

Adult↗

PubMed1990

[Mesothelioma and mesothelial hyperplasia].

Twenty cases of pleural mesothelioma (2 localized and 18 diffuse malignant pleural mesothelioma), 6 cases of diffuse malignant peritoneal mesothelioma and 1 case of mesothelial hyperplasia were reported. The prominent clinical manifestations of malignant mesothelioma was serosal effusion. The exudate was bloody, mucinous and of high specific gravity. It contained numerous mesothelial cells. The diagnosis is difficult because mesothelial hyperplasia and other malignant tumors may mimic mesothelioma in some clinical aspects. Roentgenography, CT scan, cytology of serosal fluid and biopsy world help to establish the diagnosis of mesothelioma. Immunohistochemical features of 4 cases of mesothelioma is negative immunostaining for carcino embryonic antigen (CEA) and positive for keratin antigen. In one case ultrastructural examination showed characteristic features of epithelial mesothelioma cells. The average survival period in case of chemotherapy and/or surgical intervention in patients of this series was 31.3 months. Mesothelial hyperplasia has rather good prognosis; but the strategy of therapy may be conservative.

Adult↗

PubMed1989

Study of the 5-oxoprolinase reaction by 13C NMR.

5-Oxoprolinase catalyzes the ATP-dependent decyclization of 5-oxo-L-proline to L-glutamate. Previous studies provided evidence for the intermediate formation of a phosphorylated form of 5-oxoproline (Seddon, A. P., and Meister, A. (1986) J. Biol. Chem. 261, 11538-11541) and of a tetrahedral intermediate (Li, L., Seddon, A. P., and Meister, A. (1987) J. Biol. Chem. 262, 11020-11025). A new approach to the study of the reaction mechanism using the 18O isotope effect on the 13C NMR signals for 5-oxoproline and glutamate is reported here. The 13C chemical shifts induced by 18O substitution for the carbonyl group of 5-oxoproline and the gamma-carboxyl group of glutamate are about 0.03 ppm with respect to the corresponding 16O-compounds. Using 5-[18O]oxo[5-13C]proline (97 and 79.5 atom % excess, 13C and 18O, respectively), the disappearance of the 18O-labeled and unlabeled 5-oxoproline and formation of the corresponding glutamate species were followed in the reactions catalyzed by purified preparations of 5-oxoprolinase isolated from Pseudomonas putida and from rat kidney. This procedure permits simultaneous determinations of the rates of 18O exchange and of the overall decyclization reaction. The ratios of 18O exchange rates to the overall reaction rates for the bacterial and kidney enzyme catalyzed-reactions were 0.28 and 0.14, respectively. The findings support the view that the coupling of ATP hydrolysis to 5-oxoproline decyclization involves formation of a phosphorylated tetrahedal intermediate. Although the exchange phenomena are consistent with the mechanistic interpretations, they seem not to be required for catalysis.

Adenosine Diphosphate↗

PubMed1989

Structural analysis of a rat renal kallikrein gene.

A renal kallikrein gene has been isolated, sequenced and characterized from a rat genomic library using a kallikrein cDNA probe. The kallikrein gene is 4160 bases in length and consists of 5 exons and 4 introns. The deduced sequence of the gene encodes an 18 amino acid (a.a.) signal peptide, a 6 a.a. propeptide and a 237 a.a. active enzyme with an N-terminal valine. A sequence comparison of this and tissue kallikrein (pancreatic kallikrein) indicates the key a.a. residues for serine protease activity (HIS-ASP-SER) and cleavage specificity at basic a.a. Northern blot analysis using a specific oligonucleotide probe reveals that this gene is expressed specifically in the kidney but not in the pancreas. This gene is also expressed non-specifically in the submandibular gland which expresses all kallikrein family genes. The expression of this kidney-specific kallikrein gene is regulated by steroid hormones.

Adrenalectomy↗

PubMed1989

Spermatogenic cell-somatic cell interactions are required for maintenance of spermatogenic cell glutathione.

Sertoli cells play a major role in the regulation of spermatogenic cell energy metabolism and differentiation. This study demonstrates that Sertoli cells are essential for the maintenance of spermatogenic cell glutathione (GSH), an important intracellular reductant and detoxicant. Primary spermatocytes and round spermatids isolated from Xenopus laevis contained 1.5 +/- 0.1 mM GSH, but sperm lacked detectable GSH. During a 5-day culture period, isolated spermatocytes and spermatids lost 80% of the initial GSH (t 1/2 = 55 h). The levels of GSH were unaffected by L-buthionine-SR-sulfoximine (BSO), a selective inhibitor of GSH synthesis. Cultures of testicular lobules and spermatocysts (composed of germ cells and Sertoli cells) depleted of interstitial tissue lost only 30% of their initial GSH in 4.5 days; the GSH levels decreased during treatment with BSO. Spermatogenic cells in cultured testes maintained their GSH levels for 7 days by a BSO-sensitive mechanism. These results demonstrate that the intracellular GSH levels of spermatogenic cells are dependent upon germ cell-somatic cell interactions. Spermatogenic cells were shown to possess gamma-glutamyl transpeptidase, glutathione synthetase, 5-oxoprolinase, and gamma-glutamylcysteine synthetase activities. [35S] Cysteine incorporation and distribution as analyzed by high performance liquid chromatography (HPLC) showed that isolated spermatogenic cells are capable of GSH synthesis. The rate of GSH synthesis, however, was insufficient to compensate for GSH turnover. These results demonstrate that production of spermatogenic cell GSH is dependent upon Sertoli cells. To our knowledge, this is the first evidence that interactions between different cell types may be of significance in GSH metabolism.

Animals↗