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Biomedical subjects

M Y Liu

Publications and source records attributed to M Y Liu.

At least 163 records · Page 9Linked to original sources
PubMed1987

Comparative EPR studies on the nitrite reductases from Escherichia coli and Wolinella succinogenes.

Hexaheme nitrite reductases purified to homogeneity from Escherichia coli K-12 and Wolinella succinogenes were studied by low-temperature EPR spectroscopy. In their isolated states, the two enzymes revealed nearly identical EPR spectra when measured at 12 K. Both high-spin and low-spin ferric heme EPR resonances with g values of 9.7, 3.7, 2.9, 2.3 and 1.5 were observed. These signals disappeared upon reduction by dithionite. Reaction of reduced enzyme with nitrite resulted in the formation of ferrous heme-NO complexes with distinct EPR spectral characteristics. The heme-NO complexes formed with the two enzymes differed, however, in g values and line-shapes. When reacted with hydroxylamine, reduced enzymes also showed the formation of ferrous heme-NO complexes. These results suggested the involvement of an enzyme-bound NO intermediate during the six-electron reduction of nitrite to ammonia catalyzed by these two hexaheme nitrite reductases. Heme proteins that can either expose bound NO to reduction or release it are significant components of both assimilatory and dissimilatory metabolisms of nitrate. The different ferrous heme-NO complexes detected for the two enzymes indicated, nevertheless, their subtle variation in heme reactivity during the reduction reaction.

Bacteroidaceae↗
PubMed1987

Kinetic studies of the copper nitrite reductase from Achromobacter cycloclastes and its interaction with a blue copper protein.

Transient state, burst and steady state kinetics of reactions of the blue copper nitrite reductase (NIR) and blue copper protein from Achromobacter cycloclastes are investigated. The two copper-containing species are reacted with each other and where possible with dithionite, ascorbate and nitrite. Both copper proteins are fully reduced by dithionite with both S2O4(2-) and SO2-. species active. NIR is only partially reduced by ascorbate in an unusual biphasic reaction consistent with complete reduction of type-one copper followed by partial reduction of type-two copper. The rate of reduction of the type-one copper is accelerated using phenazine methosulfate as mediator. Nitrite can oxidize dithionite-reduced NIR but cannot reduce oxidized NIR. Rate constants were determined for all observed reactions.

Alcaligenes↗
PubMed1987

Antibodies to Epstein-Barr virus-specific DNase in patients with nasopharyngeal carcinoma and control groups.

Serum samples from 154 patients with nasopharyngeal carcinoma (NPC), 374 with other cancers, 1,000 normal controls from Government Employees' Clinic Center (GECC), and 3,642 individuals of various ethnic-dialect groups living in high-risk areas for NPC were collected and the concentration of antibodies to Epstein-Barr virus (EBV)-specific DNase activity was determined. Taking a serum sample where 1 ml will neutralize two or more units of the DNase activity as positive, 2-4 units as low level, 4-6 units as medium level, and more than 6 units as a high level of antibody, 90.3% of the NPC patients contained significant amounts of antibodies to EBV-specific DNase activity and most of those had high levels of the antibody. In contrast, only 11% of sera from patients with cancers other than NPC contained antibodies to EBV-specific DNase activity, and high levels were very rare (2.1%). The difference in positive rates between these two groups is highly significant according to the chi 2 test (P less than 0.001). The positive rate of this antibody in the control group (GECC) was 5.3% with 0.0%, 0.8%, and 4.5% having high, medium, and low levels of antibodies, respectively. Again, the difference in positive rates between the GECC group and the NPC group is statistically significant (P less than 0.001). Taken separately, the positive rates of anti-EBV DNase activity in the three high-risk groups were 11.7%, 13.0%, and 13.1%. No significant difference in age distribution for the levels of this antibody was observed in the control GECC group or the three high-risk groups. However, the positive rates of the three high-risk groups are more than twice those of the GECC group (11.7% approximately 13.1% vs 5.3%). This ratio coincides with the ratio of the probability of developing NPC in high-risk groups compared to that of the GECC group (also more than two times). The significance of this coincidence is discussed.

Age Factors↗
PubMed1987

Intraventricular morphine produces pain relief, hypothermia, hyperglycaemia and increased prolactin and growth hormone levels in patients with cancer pain.

The effects of analgesic, thermoregulatory and endocrine functions of administering morphine sulphate (0.3 mg) into the lateral cerebral ventricle via an Ommaya catheter were assessed in eight patients with cancer pain. Satisfactory control of intractable pain was obtained in these patients, without any change in other sensory modalities. The delay in the onset of pain relief and the duration of analgesia ranged, respectively, from 20 to 40 min and from 12 to 16 h after drug injection. In addition, intraventricular administration of morphine caused a reduction in rectal temperature in these patients at an ambient temperature of 24 degrees C. The hypothermia in response to the injection of morphine was due to cutaneous vasodilation and sweating. There was no change in metabolism or in respiratory evaporative heat loss after morphine injection. Further, 10 to 20 min after intraventricular administration of morphine, the blood levels of prolactin, growth hormone and glucose were elevated in these patients. The changes in temperature and endocrine levels lasted for 1-3 h. In addition to the pain relief, these side-effects of morphine treatment were short-lasting and disappeared as the morphine treatment continued. The results indicate that activation of opiate receptors in the brain produced pain relief, hypothermia (due to cutaneous vasodilation and sweating), and increased blood levels of prolactin, growth hormone and glucose in patients with cancer pain.

Adult↗
PubMed1987

Preliminary studies on antigenic variation of poliovirus using neutralizing monoclonal antibodies.

Cross-neutralization assays were done using 85 strains of poliovirus type 1 with five groups of monoclonal antibodies. These strains were classified into 10 subgroups which had marked differences in antigenicity. Subgroups P1-2 (28%) and P1-5 (43%) were dominant and have been epidemic in China in recent years. These two subgroups were antigenically different from the Sabin-1 strain, but according to their responses to one group of monoclonal antibodies they had antigenic epitopes in common with the Mahoney and Brunhilde strains. Similarly, 91 strains of type 3 poliovirus were classified into six subgroups with another five groups of monoclonal antibodies. The results showed that strain P3/Yunnan/2/84, which was isolated from cases of poliomyelitis in a local epidemic in the Yunnan province of China in 1984, and strain P3/Finland/23127/84, which was isolated in Finland in 1984, were both antigenically different from the Sabin-3 strain and the reference virulent strain.

Animals↗
PubMed1987

Long-term treatment of hyperprolactinaemia with bromocriptine: effect of drug withdrawal.

Fifty-one patients with hyperprolactinaemia (23 with macroadenoma, 23 with microadenoma, and five with idiopathic hyperprolactinaemia) were treated with bromocriptine for 2-12 years (4.9 +/- 2.9 years, mean +/- SD). During therapy, the serum PRL levels were suppressed into the normal range in all but five patients. In these five patients, despite the high circulating PRL, gonadal function returned to normal in three, while in the other two gonadotrophin reserve was impaired even before therapy. Gel chromatography showed that one of these patients had a high proportion of a large molecular weight form of PRL. Twenty-four patients received bromocriptine as the sole method of treatment for over 2 years (3.4 +/- 2.3 years). In five out of the 24 subjects (21%), serum PRL remained normal with no clinical symptoms after prolonged drug withdrawal (1-4 years). Twenty-one patients received radiotherapy in conjunction with bromocriptine therapy. Of these 11 had prior surgery. After a follow-up of 6.0 +/- 3.0 years after radiotherapy, serum PRL remained within the normal range in 6 out of 21 subjects (29%), 1-4 years after bromocriptine withdrawal. One of the patients had impaired GH response to insulin hypoglycaemia developing after radiotherapy. We conclude that prolonged bromocriptine treatment is an effective treatment for prolactinomas.

Adenoma↗
PubMed1986

Properties and electron transfer specificity of copper proteins from the denitrifier "Achromobacter cycloclastes".

A blue copper protein (Mr 12,000) was purified from cells of "Achromobacter cycloclastes" grown as a denitrifier. When reduced, the blue copper protein transferred electrons to the copper protein nitrite reductase purified from the same cells, whereas a variety of cytochromes from denitrifiers failed to do so. Inclusion of a protease inhibitor, phenylmethylsulfonyl fluoride, in the buffers employed during preparation yielded purified blue copper protein with 18 more amino acid residues and two times more specific enzyme activity than other researchers have found.

Alcaligenes↗
PubMed1986

Effects of certain atmospheric pollutants (SO2, NO2 and CO) on the soluble amino acids, molecular weight and antigenicity of some airborne pollen grains.

The pure pollen grains of Red Oak (Quercus rubra), Meadow Fescue (Festuca elatior) and Chinese Elm (Ulmas pumila) were exposed to carbon monoxide (CO), sulphur dioxide (SO2) and nitrogen dioxide (NO2). After exposure, the soluble free amino acids were determined from the extracts using two-dimensional thin layer chromatography, and the molecular weight of the extracts were determined by SDS-gel electrophoresis (PAGE). The results indicated that after contamination, both the amino acids and molecular weight profiles were changed. In addition, the double immunodiffusion method was used against rabbit-antisera to determine the antigenicity of contaminated and non-contaminated pollen grain extracts. The results also showed that there were antigenic changes after contamination.

Air Pollutants, Occupational↗
PubMed1985

Antibody to Epstein-Barr virus-specific DNase as a marker for the early detection of nasopharyngeal carcinoma.

We have previously shown that high levels of antibody to Epstein-Barr virus (EBV)-specific DNase may be a useful marker for the early diagnosis of nasopharyngeal carcinoma (NPC). Sera from 3,368 males in an area with a high risk for the development of NPC were examined for the presence of antibody to EBV-specific DNase activity. Significant levels of the antibody were found in 430 of these sera. As a result, 32 individuals have attended the out-patient department of otolaryngology for clinical examination. Among them, one individual was found to have a stage II nasopharyngeal carcinoma. This result supports the value of determination of antibody to EBV-specific DNase as a marker for the early detection of NPC.

Adult↗
PubMed1985

Traumatic intracavernous carotid aneurysm with massive epistaxis.

Five cases of traumatic intracavernous carotid aneurysm are presented. All of the patients were young men with a history of severe head injury. The clinical manifestations were massive epistaxis and an ipsilateral cavernous sinus syndrome. The diagnosis was made correctly by carotid angiography. All of the patients developed another episode of massive epistaxis after admission. Emergency trapping of the internal carotid artery was performed. An urgent rescue method was used in one of our patients to prevent exsanguination before definitive surgical treatment. One patient died of exsanguination in spite of emergency ligation of the internal carotid artery. In the other four patients, no epistaxis was experienced after the operation.

Adult↗
PubMed1985

Spinal intramedullary pseudocyst. Case report.

The authors describe a case of a spinal intramedullary pseudocyst at T-1 that did not communicate with the surrounding spaces. The cystic wall was composed of dense connective tissue without epithelial or neoplastic cells. The patient's condition improved dramatically after surgical removal of the cyst. The literature on spinal intramedullary cystic lesions is reviewed and the etiology of pseudocysts is discussed. This case is believed to be the first in which a pseudocyst has been demonstrated within the spinal cord.

Adult↗
PubMed1984

Activity of DNase associated with replication of Epstein-Barr virus in NPC-204 cells.

A deoxyribonuclease derived from Epstein-Barr virus (EBV)-producing lymphoblastoid cell line (NPC-204 cells) treated with IUdR was purified by DEAE cellulose, phospho-cellulose, and DNA-cellulose columns with 45% recovery. The activity of the DNase was neutralized by serum of patient with nasopharyngeal carcinoma (NPC). The DNase had a strong requirement for divalent cations and an alkaline pH optimum. Its activity was inhibited by highly ionic strength and polyamines.

Cell Line↗
PubMed1984

Antibody to Epstein-Barr virus specific DNase in sera of nasopharyngeal carcinoma and other nine most common cancer patients in Taiwan.

Sera from 119 patients with nasopharyngeal carcinoma (NPC), 33 patients with other cancers of the head and neck, 220 normal subjects and various numbers of patients with each of the other nine most common cancers in Taiwan were examined for their serum antibody response to Epstein-Barr virus (EBV)-specific DNase. The positive rate (neutralizing activity greater than 2 units) in normal subjects was 5.5%; 12.1% in patients with other cancers of the head and neck, 87.4% in NPC patients and 0% (colon or rectal cancer) to 30% (lung cancer) in the other nine cancer patients. There is statistically significant difference of positive rates between NPC patients and lung cancer patients (p less than 0.001). Briefly, the test has 87% sensitivity and 95% specificity for NPC patients. Therefore titration of the serum antibody reactivity to EBV-specific DNase can be used as a method for massive screening for the early diagnosis of NPC.

Adult↗