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Biomedical subjects

C M Lee

Publications and source records attributed to C M Lee.

At least 19 recordsLinked to original sources
PubMed1992

Serum-ascites albumin concentration gradient and ascites fibronectin in the diagnosis of malignant ascites.

BACKGROUND: The differential diagnosis between malignant and nonmalignant ascites by using laboratory parameters has not been completely achieved so far. METHODS: The authors studied serum-ascites albumin concentration gradients ([albumin]s - [albumin]a), ascites fibronectin and various parameters in 149 consecutive patients with ascites (including Group 1: 22 patients with intraabdominal malignant lesions; Group 2: 81 patients with chronic liver disease; and Group 3: 46 patients with hepatocellular carcinoma [HCC]). RESULTS: The concentrations of fibronectin, albumin, protein, lactate dehydrogenase, and carcinoembryonic antigen in ascites were significantly higher in Group 1 than in Group 2 (P < 0.001). By contrast, the [albumin]s - [albumin]a was significantly lower in Group 1 than in Group 2 (P < 0.001). None of these parameters was useful in differentiating the ascites of chronic liver disease from that of HCC. In this study, to differentiate malignant ascites from the ascites caused by liver diseases, [albumin]s - [albumin]a (< 1.5 g/dl) and the fibronectin level in the ascites (> 100 micrograms/ml) provided diagnostic accuracy (96.8% and 95.9%, respectively) as precise as those of the levels of albumin (> 1.6 g/dl), protein (> 2.5 g/dl), and lactate dehydrogenase (> 60 U/l; 97.9%, 96.7%, and 94.8%, respectively) in ascites. These results were better than that of carcinoembryonic antigen level (> 1.5 ng/ml, 80.9%). CONCLUSIONS: The authors concluded that [albumin]s - [albumin]a offered the best method to survey malignant ascites because of its sensitivity (100%).

Albumins↗
PubMed1992

Interaction of natriuretic peptides and cGMP production via the same receptor in mouse astrocytes.

Atrial and brain natriuretic peptides have been found previously to bind to specific receptors on cultured mouse astrocytes and to stimulate cyclic guanosine 5-monophosphate (cGMP) production with similar dose dependency although brain natriuretic peptide (BNP) shows a greater maximal stimulatory effect. The present study provides evidence that both peptides work through the same pathway. No additive or synergistic effect was observed when astrocytes were exposed to both peptides. However, human ANF(99-126) at high concentrations partially inhibited porcine BNP induced cGMP production to the level seen with ANF alone. ANF could be viewed as a partial agonist of pBNP competing for the same effector sites. Differences in structure between human ANF(99-126) and porcine BNP may account for the difference in cGMP response. The interaction between the two peptides and the cGMP response does not reflect receptor binding affinities and is likely to be a post-binding event.

Animals↗
PubMed1992

Activation of protein kinase C attenuates the cyclic GMP responses to C-type natriuretic peptide in cultured mouse astrocytes.

C-type natriuretic peptide (CNP), a recently discovered natriuretic peptide, has a potent stimulatory effect on cyclic GMP (cGMP) formation in cultured mouse astrocytes. Pretreatment of astrocytes with phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC), attenuated CNP-induced cGMP responses in a dose-dependent manner, with a half-maximal inhibitory concentration of 6 nM, whereas the inactive phorbol ester analog, 4 alpha-phorbol 12,13-didecanoate, was without effect. In the presence of staurosporine, a PKC inhibitor, the inhibitory effect of PMA on CNP-stimulated cGMP production was reversed. These results suggest that PKC is an inhibitory modulator of CNP-stimulated cGMP responses in astrocytes and that CNP may interact with neuropeptides which stimulate PKC.

Animals↗
PubMed1992

Guanine nucleotide-binding proteins in the intestinal parasite Giardia lamblia. Isolation of a gene encoding an approximately 20-kDa ADP-ribosylation factor.

Giardia lamblia is a protozoan intestinal parasite that has characteristics of both eukaryotes and prokaryotes. To determine whether genes for guanine nucleotide-binding proteins are present in Giardia, genomic DNA and cDNA libraries were screened by polymerase chain reaction and by hybridization with mixed oligonucleotide probes complementary to sequences encoding conserved GTP-binding domains. A gene with a high degree of sequence identity with mammalian ADP-ribosylation factors (ARFs), believed to be important in vesicular transport, was identified. The Giardia ARF gene had a 573-base open reading frame encoding 191 amino acids which are 63-70% identical with known mammalian and yeast ARFs. Sequence conservation among ARFs was greatest in putative GTP-binding domains. A single ARF mRNA species of approximately 750 bases was found in two different Giardia isolates. Primer extension and RNA sequencing of the Giardia ARF transcript revealed a short (6-base) 5'-untranslated region similar in size to those found in other Giardia transcripts. Giardia extracts contained ARF activity, as shown by stimulation of cholera toxin-catalyzed ADP-ribosylation and a Giardia ARF expressed in Escherichia coli as a fusion protein likewise exhibited biochemical activity. Its presence in Giardia is consistent with the view that ARF emerged before the divergence of this protozoan from other eukaryotes (approximately 1.5 billion years ago), and that an ARF-like protein may have been the ancestor of several other classes of signal-transducing guanine nucleotide-binding proteins, including the alpha subunits of the heterotrimeric G proteins.

ADP-Ribosylation Factors↗
PubMed1992

Characterization of the human gene encoding ADP-ribosylation factor 1, a guanine nucleotide-binding activator of cholera toxin.

Mammalian ADP-ribosylation factors (ARFs), approximately 20-kDa guanine nucleotide-binding proteins that stimulate cholera toxin ADP-ribosyltransferase activity, were grouped into three classes based on deduced amino acid sequence. Human ARF 1, a class I ARF, is identical with its bovine counterpart, has a distinctive pattern of tissue and developmental expression, and is encoded by a approximately 1.9-kilobase mRNA. ARF 1 cDNAs were isolated from a human fibroblast cDNA library; one arose via an alternative polyadenylation signal (AA-TACA) 84 nucleotides 5' to the polyadenylation signal (AATAAA) used in the 1815-base pair cDNA. The polyadenylation signals, their respective locations, and the surrounding nucleotide sequences are conserved in human and rat. The human ARF 1 gene, with four introns, spans approximately 16.5 kilobases. Exon 1 (46 base pairs) contains only untranslated sequence. Translation initiates in exon 2, which encodes the sequence GXXXXGK involved in phosphate binding (GTP hydrolysis). The sequence DVGG is encoded in exon 3, and NKQD, which is involved in the interaction with the guanine ring, is interrupted following the codon for Q by intron 4. The carboxyl-terminal 53 amino acids and greater than 1110 base pairs of 3'-untranslated region are encoded in exon 5. Primer extension and mung bean and S1 nuclease mapping indicated multiple transcription initiation sites and were consistent with Northern analyses. The 5'-flanking region has a high GC content but no TATA or CAAT box, as found in housekeeping genes. In addition, the two human class I ARF genes, ARF 1 and ARF 3, have similar exon/intron organizations and use GC-rich promoters.

ADP-Ribosylation Factors↗
PubMed1992

Modification by ketamine on the neuromuscular actions of magnesium, vecuronium, pancuronium and alpha-bungarotoxin in the primate.

The neuromuscular effects of ketamine, at cumulative doses of 2.5 and 10 mg.kg-1 iv, were studied by electromyographically quantifying the thumb response evoked by ulnar nerve stimulation in 25 monkeys anaesthetized with pentobarbital-N2O-O2. Ketamine alone at these doses had no neuromuscular effects. When the EMG response was maintained at 50% of control by a continuous infusion of magnesium, vecuronium, or pancuronium, ketamine depressed the responses by an additional 13 +/- 3%, 34 +/- 7% and 32.5 +/- 3.3% (mean +/- SEM), respectively, at the highest dose, P less than 0.05. In contrast, ketamine had no effect on the neuromuscular block produced by incremental doses of alpha-bungarotoxin. These results indicate that ketamine does not act on the postjunctional acetylcholine receptor. It plays a secondary role in neuromuscular block, possibly by prejunctional or postjunctional effects independent of receptor occupation.

Animals↗
PubMed1992

Evolution of hepatitis delta virus RNA during chronic infection.

The complete RNA sequences of hepatitis delta virus (HDV) isolated at three different time points from a chronic delta hepatitis patient were determined. These time points represented three different periods of clinical flare-ups. The sequence analysis showed that these three different HDV isolates evolved at a rate ranging from 3.0 x 10(-2) to 3.0 x 10(-3) substitutions/nucleotide/year, depending on the period of infection. The evolution rates appeared to correlate with the changes of clinical pictures of hepatitis, i.e., the more drastic the change in the symptom of hepatitis was, the more nucleotide changes were detected. Except during the transition from the acute phase to chronic phase of delta hepatitis, when there was a much larger number of changes in HDV RNA sequence, the overall evolution rate of HDV RNA in the chronic phase appeared to be similar to those of other RNA viruses. Sequence relationship of these HDV RNAs suggested that acute exacerbations in chronic delta hepatitis were associated with the evolution of the persistently infected HDV, rather than resulting from new viral infections. However, some of the mutations were not cumulative, suggesting that HDV isolated at a later time was not directly evolved from the immediately previous one. Thus, HDV at any time point was a mixture of viruses with slight sequence variations, and a specific HDV RNA species was selected from this virus population under different environments. These findings indicate that HDV RNA is heterogeneous and evolves at a fast rate. The evolution rates in different parts of HDV RNA also varied. The evolution rate of HDV RNA determined here was higher than the ones determined previously from partial RNA sequences of two Japanese HDV isolates.

Adult↗
PubMed1992

Surgical management of subfoveal choroidal neovascularization.

BACKGROUND: Subfoveal choroidal neovascularization (CNV) usually is associated with a poor visual prognosis. Laser photocoagulation of certain subfoveal membranes secondary to age-related macular degeneration (ARMD) appears preferable to observation based on recent Macular Photocoagulation Study (MPS) findings but is associated with decreased vision. The authors explored the use of vitreoretinal surgical techniques as an alternative method of eradicating subfoveal CNV. METHODS: After vitrectomy, a small retinotomy technique was used to extract or disconnect from the choroidal circulation subfoveal CNV in 58 eyes. There were 33 eyes with ARMD, 20 eyes with presumed ocular histoplasmosis, and 5 eyes with miscellaneous etiologies. Five eyes also received subfoveal RPE patches. RESULTS: With limited follow-up, significant improvement in vision (defined as 2 Snellen lines) was achieved in 7 of 22 eyes with ARMD CNV removal (1 eye 20/20), 0 of 4 eyes with ARMD CNV removal and RPE patches, and 1 of 7 eyes with ARMD CNV disconnection. Significant improvement was achieved in 6 of 16 eyes with presumed ocular histoplasmosis removal and 0 of 4 eyes with presumed ocular histoplasmosis CNV disconnection. In 5 eyes with miscellaneous CNV, 2 improved (20/20 and 20/40). CNV recurred in 29%. CONCLUSIONS: Some patients with subfoveal CNV appear to benefit from surgical removal. Only rarely do eyes with ARMD improve. Longer-term follow-up and refined case selection are required before this approach can be widely recommended.

Aged↗
PubMed1992

Tachykinin-stimulated inositol phospholipid hydrolysis and taurine release from human astrocytoma cells.

The activation of NK1 receptors on U373 MG human astrocytoma cells by substance P (SP) and related tachykinins was accompanied by an increase in taurine release and an accumulation of inositol phosphates. Both of these effects could be inhibited by spantide, a SP receptor antagonist. The relative potency of tachykinins in stimulating 3H-inositol phosphate accumulation correlated very well with their effects in stimulating the release of [3H]-taurine and inhibition 125I-Bolton-Hunter reagent-conjugated SP binding. The effect on [3H]taurine release was mimicked by a protein kinase C (PKC) activator, phorbol 12-myristate 13-acetate (PMA). The inactive phorbol ester analogue 4-alpha-phorbol 12,13-didecanoate, however, was without effect. Both SP- and PMA-induced releases of [3H]-taurine were markedly inhibited by staurosporine, a potent PKC inhibitor. Pretreatment of U373 MG cells with 10 microM PMA for 19 h to down-regulate PKC activity also markedly inhibited both SP- and PMA-induced releases of [3H]-taurine. Treatment of cells with 100 nM SP induced a time-dependent translocation of PKC from the cytosolic fraction to the membrane fraction. These findings are consistent with the hypothesis that an activation of NK1 receptors on U373 MG cells results in the release of inositol phosphates and activation of PKC, which in turn may regulate the release of taurine.

Alkaloids↗
PubMed1992

C-type natriuretic peptide is a potent stimulator of cyclic GMP production in cultured mouse astrocytes.

The effect of C-type natriuretic peptide (CNP), a novel member of the natriuretic peptide family, on cyclic GMP (cGMP) generation was studied in primary cultures of mouse astrocytes. CNP stimulated cGMP production by mouse astrocytes in a dose-dependent fashion, with an EC50 of 32 nM and a maximal stimulatory concentration of greater than 1 microM, which induced a rise of cGMP level from a baseline of 1.0 +/- 0.1 pmol/mg of protein to 196.2 +/- 22.0 pmol/mg of protein. Compared with our previously reported atrial and brain natriuretic peptide-induced cGMP responses, CNP had a lower EC50 and was 10-20 times more efficacious in its maximal effect on cGMP stimulation. These data lend support to the concept of a significant role of CNP in neuromodulation/neurotransmission.

Animals↗
PubMed1992

Cardiovascular effects of substituted tetrahydroisoquinolines in rats.

1. A series of substituted tetrahydroisoquinolins derived from the cleavage products of tetrandrine were found to inhibit [3H]-nitrendipine binding to rat cerebral cortical membranes. Those compounds which displaced [3H]-nitrendipine binding were also able to inhibit high KCl-induced contraction of rat aorta in vitro. 2. There was a significant correlation between the ability of these tetrahydroisoquinolines to inhibit [3H]-nitrendipine binding and KCl-induced contraction (r = 0.99, P less than 0.001). 3. CPU-23 (1-(1-[(6-methoxy)-naphth-2-yl])-propyl-2-(1-piperidine)-acetyl- 6,7- dimethoxy-1,2,3,4-tetrahydroisoquinoline), one of the most potent compounds identified in this series, behaved as a simple competitive inhibitor at the [3H]-nitrendipine binding site and reduced the apparent affinity but not the maximal number of binding sites in saturation analysis. 4. In contrast to nifedipine which caused hypotension and tachycardia, CPU-23 induced both hypotension and bradycardia in a dose-dependent manner in pentobarbitone-anaesthetized Sprague-Dawley rats, spontaneously hypertensive and age-matched normotensive WKY rats. 5. It is suggested that CPU-23 may exert its cardiovascular effects via interaction with the dihydropyridine binding site on the L-type calcium channel.

Alkaloids↗
PubMed1992

Various sonographic patterns of smooth muscle tumors of the gastrointestinal tract: a comparison with computed tomography.

To evaluate the sonographic patterns of smooth muscle tumors of the gastrointestinal tract, we analyzed 25 patients with histologically confirmed smooth muscle tumors. Sonography revealed no abdominal mass in seven patients (sonogram-negative), and abdominal masses in 18 patients (sonogram-positive). The mean size of tumors in the sonogram-negative group (4.5 +/- 1.5 cm) was smaller than that in the sonogram-positive group (11.4 +/- 3.5 cm). We classified the various sonograms into three patterns. Comparing the sonograms with the computed tomographic pictures of each pattern, we theorized that the different patterns on sonograms may be caused by tumor necroses of different sizes with or without gas in the necrotic cavity. For the necrotic tumors, the size of the necrotic area did not correspond to the size of the tumor. However, the tumors with necroses were significantly larger than those without necroses. A central necrosis was found in cases exhibiting both leiomyosarcoma and leiomyoma. On comparing the sonogram-positive and sonogram-negative groups, we found that the size and location of a tumor may affect the detection rate of that tumor by sonography.

Adult↗
PubMed1992

[Proliferation of lymphocytes T and B by prehispanolone LC-5504 of Leonurus hereterophyllus Sweet].

Leonurus hereterophyllus Sweet is a traditional Chinese herbal medicine used to treat menstrual disturbances in woman. A new labdane diterpene, prehispanolone LC-5504, namely 9 alpha, 13R,15,16-diepoxy-labdane-14-en-7-one, had been isolated. The authors studied the synergism of labdane diterpene, prehispanolone LC-5504 and Con A and LPS on T cells and B cells proliferation of BALB/c female mice in vitro. They showed that: (1) proliferation of T cells was demonstrated by administration of LC-5504 of various concentrations together with Con A. This proliferation was 5-8 times stronger than that observed when Con A was used alone. Such effect on T cells was not observed when LC-5504 was used alone. (2) Proliferation of B cells was not observed whether LC-5504 was used alone or together with LPS.

Animals↗
PubMed1992

Circumaortic left renal vein: report of a case.

Circumaortic left renal vein is an uncommon anomaly which has not been previously reported in Taiwan. We describe a case of circumaortic left renal vein in a 15-year-old girl who presented with intermittent hematuria. Angiogram revealed double left renal veins in the form of a venous collar. Computed tomography depicted the preaortic and retroaortic left renal veins clearly. In a survey of hematuria, circumaortic renal vein should be taken into consideration in a differential diagnosis, and an appreciation of the specific radiologic findings can help to establish the diagnosis easily. In addition, preoperative recognition of this uncommon anomaly is of supreme importance in a retroperitoneal operation in order to avoid massive bleeding.

Adolescent↗
PubMed1992

Molecular cloning and sequence analysis of an isolate of hepatitis C virus from Southern California, U.S.A.

We obtained a cDNA clone representing a partial RNA sequence of a human hepatitis C virus (HCV) isolate from Southern California. RNA was extracted from the liver tissue of a patient with post-transfusion hepatitis, and used for cDNA synthesis and polymerase chain reaction (PCR) amplification using oligonucleotide primers specific for the prototype HCV RNA. The cDNA clone obtained contains 585 base pairs of HCV sequences and represents the region encoding the putative nonstructural protein NS3 of HCV. Sequence analysis of this clone showed that it shares 93.8%, 78.7% and 79.6% similarity, respectively, with the previously published American, Japanese and Taiwanese isolates at the nucleotide level, indicating the heterogeneity of HCV RNA in different geographic areas. By contrast, it shares 97.3%, 92.9% and 92.9% with these respective isolates at the amino acid level, suggesting the functional conservation of viral genes.

Amino Acid Sequence↗
PubMed1991

Miltirone, a central benzodiazepine receptor partial agonist from a Chinese medicinal herb Salvia miltiorrhiza.

Ten diterpene quinones, which inhibited the binding of [3H]flunitrazepam to central benzodiazepine receptors with IC50s ranging from 0.3 to 36.2 microM, were isolated from the ethereal extract of the roots of Salvia miltiorrhiza. Among these natural products, miltirone has the highest potency (IC50 = 0.3 microM). It was orally active in an animal model used to predict clinical tranquilizing effects. Unlike diazepam, miltirone behaved as a partial agonist in the central benzodiazepine receptor binding and behavioural tests. Moreover, it produced no acute muscle relaxant effect and did not induce drug dependence and withdrawal reactions after chronic administration in mice.

Abietanes↗
PubMed1991

Heterogeneity of chromogranin A-derived peptides in bovine gut, pancreas and adrenal medulla.

Chromogranin A is produced in many endocrine cell types, and is widely used as a marker in endocrine-cell pathology and secretory-cell biology. There is some evidence that it may be proteolytically processed to yield the putative pancreatic regulatory peptide, pancreastatin, and, in order to characterize the relevant pathways in gastrointestinal and pancreatic endocrine cells, we have used, in radioimmunoassay, site-directed antibodies to pancreastatin itself (L331) and to a sequence of chromogranin A immediately C-terminal to pancreastatin (L300). The latter antibody revealed three major forms of immunoreactivity of 8 kDa and five peptides of approx. 3 kDa in bovine pancreas and gut extracts. The 8 kDa peptides were characterized as chromogranin A-(248-313)-peptides, i.e. C-terminally extended forms of pancreastatin; two of the 8 kDa variants differed in two positions, confirming a polymorphism predicted from cDNA sequencing. One of the 3 kDa peptides was characterized as chromogranin A-(297-313)-peptide, i.e. the C-terminal heptadecapeptide of the 8 kDa peptide that would be liberated after cleavage to yield pancreastatin. On the basis of chromatographic studies, immunohistochemistry and the stoichiometry of different immunoreactive peptides, three different pathways of chromogranin A processing were identified: in adrenal chromaffin cells chromogranin A existed mainly as the unmodified intact protein, in pancreatic islet and gastric antral endocrine cells pancreastatin and the 3 kDa peptides were major products, but in small intestine and gastric corpus endocrine cells there was little nor no pancreastatin and the 8 kDa cleavage product predominated. There are therefore important differences in the distribution of chromogranin A-derived peptides between quite closely related populations of endocrine cells that are attributable not only to variable post-translational cleavage but also to the expression of different primary sequences. It seems possible that in different cell types chromogranin A-derived peptides might subserve a variety of different functions.

Adrenal Medulla↗