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Biomedical subjects

D Luo

Publications and source records attributed to D Luo.

At least 127 records · Page 7Linked to original sources
PubMed1994

Molecular control of melanogenesis in malignant melanoma: functional assessment of tyrosinase and lamp gene families by UV exposure and gene co-transfection, and cloning of a cDNA encoding calnexin, a possible melanogenesis "chaperone".

Melanogenesis is a cascade of events significantly controlled by regulatory genes which are associated with the melanosomal membrane. This report introduces our current research efforts dealing with (a) the gene and protein expressions of tyrosinase and Lamp (lysosome-associated membrane protein) families by human melanoma cells after repeated exposures to UV light, (b) the coordinated alterations in the expression of the Lamp family gene and its encoding product after transfection of two genes of the tyrosinase family in human melanoma cells and (c) cloning and sequencing of a Ca(2+)-binding phosphoprotein, calnexin, which could be a candidate as a chaperone for sorting and maturation of tyrosinase and Lamp family glycoproteins in melanogenesis cascade. Our UV exposure study, as well as gene transfection and antisense hybridization experiments, has clearly indicated a marked and coordinated interaction of the Lamp-1 gene with the tyrosinase and TRP-1 genes in this process. We propose that melanogenesis is controlled at least by two major gene family products, i.e., (a) the tyrosinase family of tyrosinase, TRP-1 and TRP-2, and the Lamp family of Lamp-1, Lamp-2 and Lamp-3. These two gene families probably derived from primordial melanogenesis-associated genes which are common or closely related to each other.

Antigens, CD↗
PubMed1994

Coordinated mRNA and protein expression of human LAMP-1 in induction of melanogenesis after UV-B exposure and co-transfection of human tyrosinase and TRP-1 cDNAs.

In order to better understand the cascade of melanogenic events in melanocytes, this report has introduced our two recent approaches for the expression of melanogenesis/or melanosome-associated genes and encoded proteins in melanocytes (melanoma cells) after repeated exposure to UV-B and after cotransfection of two human genes, i.e., tyrosinase and tyrosinase-related protein-1 (TRP-1). Repeated exposure of UV-B (2.5-5.0 mJ/cm2) caused not only upregulation of tyrosinase and TRP-1 genes but also coordinated increase in the gene and protein synthesis expression of Lamp-1 (lysosome-associated membrane protein-1). When COS-7 kidney cells and amelanotic melanoma (C32 and SK-MEL-24) and melanotic melanoma (G361 and SK-MEL-23) cells were exposed to cotransfection of human tyrosinase and TRP-1 cDNAs, there was also an increased expression of Lamp-1 mRNA and protein along with tyrosinase activation and new melanin synthesis. Importantly, single transfectants of human tyrosinase cDNA revealed marked cellular degeneration, whereas this degeneration was not seen in single transfectants of TRP-1 cDNA or cotransfectants of human tyrosinase and TRP-1 cDNAs, indicating that TRP-1 prevented, along with Lamp-1, programmed death of melanocytes after transfection of tyrosinase gene. The coordinated expression of TRP-1 and Lamp-1 was further confirmed by antisense oligodeoxynucleotide hybridization experiment against Lamp-1 gene, showing the decreased expression of TRP-1 as identified by three different types of anti-TRP-1 monoclonal antibodies.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Nitric oxide-dependent efflux of cGMP in rat cerebellar cortex: an in vivo microdialysis study.

The stimulation of excitatory amino acid receptors in the cerebellar cortex results in the Ca2+/calmodulin-dependent activation of nitric oxide synthase. This leads to an increase in tissue levels of cGMP following the interaction of nitric oxide with soluble guanylyl cyclase. The cerebellar cortex has the highest levels of nitric oxide synthase and cGMP in the brain; however, the levels of guanylyl cyclase and cGMP-phosphodiesterase are remarkably low. Thus, the mechanisms regulating cGMP levels in cerebellar cells are unclear. One report has noted that cGMP can be released from cerebellar slices. We have therefore used intracerebellar microdialysis in awake, freely moving rats to test the hypothesis that activation of nitric oxide synthase in the cerebellar cortex results in the release of cGMP. Climbing fibers, which release excitatory amino acids in the cerebellum, were activated with systemic harmaline. This resulted in an immediate increase in extracellular cGMP, which was blocked by TTX or the removal of extracellular Ca2+, and attenuated by prior lesion of the climbing fibers. Blockade of N-type calcium channels with omega-conotoxin also antagonized the harmaline-induced increase. In contrast, blockade of L-type calcium channels, or inhibition of anion transport with probenecid or bromosulfophthalein, potentiated the increase in cGMP seen in response to harmaline. Inhibitors of nitric oxide synthase or guanylyl cyclase prevented the harmaline-induced increase in extracellular cGMP, while phosphodiesterase inhibitors potentiated the increase. Local application of the NMDA antagonist 2-amino-5-phosphonopentanoic acid or the AMPA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione attenuated the effect of harmaline.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Oxidoreductases↗
PubMed1994

The efficacy of Japanese encephalitis vaccine in Henan, China: a case-control study.

A population based case-control study to evaluate Japanese encephalitis (JE) vaccine efficacy was carried out in Gusi County, Henan Province, China from June to September in 1991. This study showed that the JE vaccine had a strong protective effect. The estimate of the vaccine efficacy was 78% (95% CI = 16-94%). An unimmunized child was at 4.54 times greater risk of developing JE than were fully immunized children during the study period. The present study may have underestimated the vaccine efficacy due to evaluation based on routine vaccination which might have been affected by vaccination management and the local cold chain system.

Antibodies, Viral↗
PubMed1994

[Laparoscopic cholecystectomy performed in 235 cases of cholecystitis with impacted gallstones].

During the past 2 years, 235 cases of cholecystitis with impacted gallstones were treated with laparoscopic technique. There were 221 chronic cases and 14 acute cases accounting altogether for 15.19% of a total of 1475 patients undergoing laparoscopic cholecystectomy during the same period. As a result, 9 of these patients were converted to open surgery. Severe adhesion around the gallbladder or/and in the Calot triangle in 7, acute impacted gallstone, gallbladder necrosis along with obscure anatomy in the calot triangle in 1, and gallstone impacted at the junction of the common hepatic and cystic duct in 1 were observed. Conversion rate was 3.8%. Postoperative bile leakage developed in 2 cases and healed spontaneously. There were no intraperitoneal sepsis and perioperative death in our patients. The diagnosis, classification, and management for acute or chronic impacted gallstone are discussed.

Adult↗
PubMed1994

Symptom Questionnaire anxiety and depression scales: reliability and validity.

Many instruments have been developed with college students and used primarily with students or younger adults. Thus, researchers face challenges in selecting measures of psychological state that are valid and reliable for use with elders. This article describes a measure of psychological state, the Symptom Questionnaire; provides information about its reliability and validity; and details the steps used to evaluate reliability and validity of its anxiety and depression scales for elders hospitalized for an acute episode of a chronic condition. The findings suggest that a short version of the Symptom Questionnaire, consisting of the depression and anxiety scales, is valid and reliable for elders. The findings also revealed small differences between the means of data collected using the short version and those obtained using the full instrument.

Age Factors↗
PubMed1994

Plutonium-catalyzed oxidative DNA damage in the absence of significant alpha-particle decay.

Plutonium is considered to be a carcinogen because it emits alpha particles that may result in the irradiation of stem cell population. In the present study we show that plutonium can also catalyze reactions that induce hydroxyl radicals in the absence of significant alpha-particle irradiation. Using the low specific activity isotope, 242Pu, experiments were performed under conditions in which chemical generation of hydroxyl radicals was expected to exceed the radiolytic generation by one hundred thousand-fold. The results showed that markers of oxidative DNA base damage, thymine glycol and 8-oxoguanine could be induced from plutonium-catalyzed reactions of hydrogen peroxide and ascorbate similarly to those occurring in the presence of iron catalysts. Plutonium-242, as a neutralized nitrate in phosphate buffer, was 4.8-fold more efficient than iron at catalyzing the oxidation of ascorbate at pH 7. The results suggest that plutonium complexes could participate in reactions at pH 7 that induce oxidative stress--a significant tumor-promoting factor in generally accepted models of carcinogenesis.

Alpha Particles↗
PubMed1993

Identification of a cDNA coding for a Ca(2+)-binding phosphoprotein (p90), calnexin, on melanosomes in normal and malignant human melanocytes.

In order to have a proper biosynthesis and secretion of the melanin-pigment granules (melanosomes) the melanocyte may require a melanosome-associated molecule that provides a signal for assembly and organization of melanogenic enzymes and proteins within the compartment of melanosomes. This study reports the presence of a Ca(2+)-binding phosphoprotein, p90, which can be engaged in such melanogenic function, located on the melanosomal membrane of human melanocytes. A human melanoma cDNA expression library in lambda Zap II was screened with a rabbit polyclonal antibody raised against human melanosomes isolated from cultured human melanoma cells, SK MEL 23. A cDNA encoding a melanosomal protein, M(r) 90 kDa, was identified through this immunoscreening. A partial sequencing of nucleotides (822 bp from the N-terminal domain) of this clone (3.8 kb) and predicted amino acids showed more than 90% homology with dog calnexin, a previously reported endoplasmic reticulum (ER) transmembrane protein. A fusion protein of this p90 with beta-galactosidase expressed in Escherichia coli revealed both the immuno-cross-reactivity with anti-dog calnexin and anti-human melanosome antibodies and the Ca(2+)-binding property. Upon immunohistochemistry, the anti-dog calnexin antibody revealed the positive immunoreactivities with both normal and malignant human melanocytes, showing a much higher expression of antigenic epitope than nonmelanocytic human cells. The laser scanning confocal immunofluorescence, using an antibody against a human melanosome-specific antigen (HMSA-5), and immunoelectron microscopy, using immunogold, confirmed the major localization of anti-dog calnexin antibody epitope on the melanosomes and ER.

Amino Acid Sequence↗
PubMed1993

N-methyl-D-aspartate-induced nitric oxide release: an in vivo microdialysis study.

Increasing evidence indicates that nitric oxide acts as an intercellular signal transduction molecule in the nervous system. In particular, in vitro studies have demonstrated that nitric oxide is produced in the cerebellar cortex and is responsible for the increases in cyclic GMP seen in response to glutamate receptor activation. In this study, we have combined the technique of intracerebellar microdialysis with a sensitive assay for nitric oxide oxidation products nitrate and nitrite, to assess nitric oxide release directly in awake, freely moving animals. We have found that infusion of N-methyl-D-aspartate via the microdialysis probe results in a dose-dependent increase in cerebellar nitric oxide release. This increase was prevented by prior administration of an N-methyl-D-aspartate receptor antagonist, or the nitric oxide synthase inhibitor NG-nitroarginine. Both these pretreatments also reduced the basal extracellular nitrite and nitrate levels, suggesting that there is a tonic glutamate-induced nitric oxide production in the cerebellum of awake, freely moving animals. These results provide direct evidence for nitric oxide release in response to N-methyl-D-aspartate receptor activation in the adult cerebellar cortex, in vivo. This new approach, coupling microdialysis with the azo dye detection method of Griess, should thus prove useful for the in vivo study of nitric oxide release from various brain regions in response to pharmacological, physiological or behavioral manipulations.

Amino Acid Oxidoreductases↗
PubMed1993

Characterization of melanosome-associated proteins by establishment of monoclonal antibodies and immunoscreening of a melanoma cDNA library through an anti-melanosome antibody.

Monoclonal antibodies against melanosomal components (human melanosome specific antigens; HMSAs) have been developed in our laboratory. HMSA-1-4 recognizes structural matrix proteins of melanosomes. HMSA-5 is identical to TRP-1, equivalent to the b (brown) locus of murine melanocytes and expressed in early stages of melanosomal maturation. HMSA-6 is a protein associated with melanosomes but its role is still unclarified, and HMSA-7 is identical to the lysosomal protein CD63. We have also recently identified p90 calnexin-like, Ca(2+)-binding protein p97 melanotransferrin, and p64 beta-D-galactosidase-like protein associated with melanosomes through immunological screening of our melanocytes (melanoma cells) cDNA library. Approximately 150 genes and 60 loci are known to influence eye, skin and hair colour in mammals. Tyrosinase is a rate-limiting enzyme responsible for melanin synthesis. In addition, tyrosine-related proteins (TRPs) and their genes have been identified and cloned. Tyrosinase and TRPS (e.g., TRP-1; b-locus protein identical to HMSA-5 and TRP-2; dopachrome tautomerase) are synthesized according to underlying genetic programmes, and are up- and/or down-regulated to create various forms of abnormal melanin pigmentation. We herein propose the importance of investigating the role of non-tyrosinase related proteins such as those which we have recently identified.

Animals↗
PubMed1993

Molecular and biological characteristics of avian polyomaviruses: isolates from different species of birds indicate that avian polyomaviruses form a distinct subgenus within the polyomavirus genus.

The isolation and characterization of two avian polyomaviruses, from chicken (BFDV-2) and a parrot (BFDV-3), is reported. Both isolates are closely related to the non-mammalian polyomavirus budgerigar fledgling disease virus (BFDV) isolated from budgerigars (now called BFDV-1), and all three viral genomes are shown to have the same basic size of 4981 bp. A 151 bp insertion was, however, observed in the non-coding region of BFDV-2 which represented an exact duplication of the left half of the non-coding region, including the putative early promoter and amino terminus of the large T antigen. With a further 15 base pairs exchanged elsewhere throughout the three genomes, these viruses have distinct degrees of tropism for various avian species. The production of antibodies directed against a beta-galactosidase-large T antigen fusion protein of BFDV-1 is described. These antibodies detected the large T antigen, with an M(r) of approximately 80K, and the small t antigen, with an M(r) of approximately 24K, in cells infected with BFDV isolates. Whereas these antibodies bind with low affinity to the large T antigen of simian virus 40 (SV40), SV40- or mouse polyomavirus-specific antibodies will not bind to the BFDV large T antigen. Antibodies directed against BFDV structural polypeptides exhibit broad, reciprocal cross-reactivities with all three structural proteins of mammalian polyomaviruses. The significance of polyomavirus infections in various avian species is discussed. Based on unique structural and biological properties we propose that these viruses should be placed in a distinct subgenus (Avipolyomavirus) within the polyomaviruses.

Animals↗
PubMed1993

[Effects of the stimulating point and non-point on human cerebral evoked potential and spinal cord evoked potential].

The experiments were carried out on 36 normal subjects. Pain stimulation points are at Neiguan or Hegu and pain stimulation nonpoints are nearby Neiguan or Hegu. The Record locations are at cortex and cervical vertebrae. The feature of evoked cerebral potential (ECP) and spinal cord evoked potential (ESP) by pain stimulation the points or non-points were studied. The results have been obtained. 1. Pain stimulation point ECP generally consists of wave P1, N1, P2, N2, P3, N3, P4 and N4. There is a certain amplitude and latency of each wave. 2. The elements of pain stimulation non-point ECP are Similar to point ECP in the feature. Comparing Pain stimulation Point ECP with non-point ECP, the amplitude of wave P3-N3 of stimulation point ECP increases (P < 0.05). 3. Pain stimulation Point ESP and non-point ESP consist of wave P1, N1 and P2, N3. Comparing Pain stimulation point with non-point there are no significant changes in the amplitude and the latency of ESP.

Acupuncture Points↗
PubMed1993

[Changes in TXB2/6-keto-PGF1 alpha ratio and their relation to blood lipids of Type A behavioral patterns].

To study the pathophysiological relation between Type A behavioral pattern and coronary artery disease, we analyzed the Type A behavioral pattern, serum triglycerides (TG), cholesterol (TC), high density lipoprotein cholesterol (HDLc), and TXB2, 6-keto-PGF1 alpha in 60 patients with coronary artery disease and 60 age-sex-matched healthy subjects. All of them had normal blood pressure. The results showed Type A behavioral pattern was more prevalent than Type B behavioral pattern in coronary artery diseased patients and the reverse was true in the controlled subjects (P < 0.025); TG, TC and TXB2/6-keto-PGF1 alpha ratio increased significantly in Type A behavioral pattern compared with Type B behavioral patients, but HDLc/(TC+TG) and the level of HDLc decreased significantly in the Type A behavioral pattern than in the Type B behavioral pattern (P < 0.05). The TG, TC increased significantly and 6-keto-PGF1 alpha HDLc decreased significantly in the coronary artery diseased patients (P < 0.05). However, the ratio of TXB2/6-keto-PGF1 alpha was inversely related to HDLc/(TC+TG) among the coronary artery diseased patients. The results of this cross-sectional study suggest that coronary artery disease is associated with Type A behavioral pattern through the metabolism of lipids and prostaglandins in various ways.

6-Ketoprostaglandin F1 alpha↗
PubMed1992

[Preventive effect of green tea on MNNG-induced lung cancers and precancerous lesions in LACA mice].

Three hundred and ninety LACA mice of seven weeks old were used in 2 batches (96.4 wks and 106 wks) for studying the preventive effect of green tea on MNNG-induced lung cancers and precancerous lesions. These mice (within each batch) were randomly allocated to four groups, namely, positive control (MNNG), green tea (GT), complex (MNNG + GT), and blank control (C) group. In MNNG group, MNNG 250 micrograms) was injected intravenously every five days for seven times in each mouse; the total dosage of MNNG was 1.75mg. In GT group, according to W/W, 5% GT dust was well mixed into 95% common diet for long-term breeding. In complex group, MNNG was given as that in MNNG group and the mice were reared as those in GT group. The mice in MNNG group and in C group were all reared by common diet. The mean amount of daily intake of feed was 10g. The number of effective animals was 354. The results of experiments showed different degrees of preventive effect of green tea on MNNG-induced lung cancers and precancerous lesions in LACA mice. Green tea exerted an effect on the number of induced cancers and precancerous lesions, causing a drop of the cancerous rate from 79.75% to 13.59% and the number of lung tumor down to 1/7-1/16 that of the MNNG group, i.e. down to less than one tumor nodule per mouse.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma↗
PubMed1992

Full-valve annuloplasty in treatment of primary deep venous valvular incompetence of the lower extremities.

Full-valve annuloplasty of superficial femoral venous valves was performed successfully in 139 extremities affected with primary deep venous incompetence of the lower limb. Chronic ulcerations in 43 affected extremities healed after operation. Postoperative venography showed that the recovery rate of valvular function was 97%, and no serious complication was noted. Follow-up for a mean of 3.5 years showed no varicosed vein and no recurrence of ulceration. The principles of operation, the optimum site, number and degree of annuloplasty, indications and results of the operation were discussed.

Adult↗
PubMed1991

The effect of thyroid hormone and glucocorticoids on carp growth hormone-releasing factor (GRF)-induced growth hormone (GH) release in rainbow trout (Oncorhynchus mykiss).

1. The effect of thyroid hormone and glucocorticoids on carp growth hormone-releasing factor (GRF)-induced growth hormone (GH) secretion was studied on rainbow trout using a dispersed pituitary cell culture system. 2. A combined administration of lower doses (0.01 microM) of 3,5,3'-triiodo-L-thyronine (T3) and dexamethasone (Dex) significantly increased spontaneous as well as carp GRF-induced GH release. 3. Lower doses of Dex alone had no effect, and T3 had a marginal effect on GH release. Higher doses of either Dex or T3 potentially reduced GH release. 4. This study indicates an important role of thyroid hormone and/or glucocorticoids in the hypothalamic regulation of GH secretion in fish.

Animals↗
PubMed1991

Interaction of carp growth hormone-releasing factor and somatostatin on in vitro release of growth hormone in rainbow trout (Oncorhynchus mykiss).

Possible antagonism between somatostatin (SS) and carp growth hormone-releasing factor (GRF) on growth hormone (GH) secretion was examined by radioimmunoassay in a dispersed rainbow trout pituitary cell culture system. SS (3 nM) significantly antagonized carp GRF(1-29; 1 nM, 10 nM)-induced GH secretion. The slope of the dose-response curve for carp GRF(1-29) with SS was statistically different from that of carp GRF(1-29) alone (p less than 0.05) suggesting a noncompetitive antagonism of SS to carp GRF. The carp GRF(1-29) was also indicated to be a noncompetitive antagonist to SS (p = 0.056). Carp GRF(1-29; 100 nM) was unable to restore the inhibitory effect of SS on GH release after pre-exposure of SS (30 nM) to the pituitary cells. We conclude that SS antagonizes carp GRF on GH release at the pituitary level in rainbow trout and this antagonism is noncompetitive. SS has a postantagonism to carp GRF which may implicate some important physiological adaptations in teleosts.

Animals↗