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Biomedical subjects

C M Lee

Publications and source records attributed to C M Lee.

At least 181 records · Page 10Linked to original sources
PubMed1993

Microbial reduction of sulfur dioxide with pretreated sewage sludge and elemental hydrogen as electron donors.

It has been demonstrated tht heat- and alkali-pretreated-sewage sludge may serve as an electron donor and carbon source for SO2 reduction by Desulfovibrio desulfuricans. A continuous D. desulfuricans culture was operated for 6 mo with complete reduction of SO2 to H2S. The culture required only minor amounts of mineral nutrients in addition to pretreated sewage sludge. It has also been shown that the sulfate-reducing bacterium Desulfotomaculum orientis can be grown on H2 as an energy source, CO2 as a carbon source, and SO2 as a terminal electron acceptor. Complete reduction of SO2 to H2S was observed.

Desulfovibrio↗
PubMed1993

Lithospermic acid B as an antioxidant-based protector of cultured ventricular myocytes and aortic endothelial cells of rabbits.

Lithospermic acid B, an active principle found in a Chinese herbal medicine for treating various heart ailments, was recently isolated, purified and demonstrated by us to salvage the postischemic rabbit heart from reperfusion injury. In this work, we further report that lithospermate B is able to protect each of two types of rabbit cardiocytes, namely ventricular myocytes and aortic endothelial cells against necrosis inflicted by oxyradicals generated pharmacologically with xanthine oxidase and hypoxanthine. Biochemically, the lithospermate B also inhibits the reduction of cytochrome c by superoxide radical anion. Thus, our in vitro data here are in concord with our earlier in vivo finding that lithospermic acid B is most likely an effective antioxidant-based myocardial protector.

Animals↗
PubMed1993

Multiple mitochondrial DNA deletions associated with age in skeletal muscle of rhesus monkeys.

We have examined skeletal muscle for the presence of age-associated mitochondrial DNA (mtDNA) deletions from 16 rhesus monkeys (age range 6-27 years). All animals over 13 years of age contained potential mtDNA deletions, whereas the presence of deletions was greatly reduced or absent in younger animals. The specific deletion patterns varied from individual to individual. Numerous mtDNA deletions accumulate with age in skeletal muscle from a nonhuman primate, indicating that the rhesus monkey may provide an excellent animal model to study mtDNA deletions. Further, the existence of multiple mtDNA deletions supports the possibility that they may contribute to geriatric muscular deficits, which are nearly universal in occurrence yet poorly understood.

Aging↗
PubMed1993

Sequential invasions of pancreatic pseudocysts in pancreatic tail, hepatic left lobe, caudate lobe, and spleen.

A 66-year-old male patient without a history of risk factors for pancreatitis suffered from pancreatitis and developed pseudocyst. During the course of treatment and follow-up, the pseudocyst was found to have migrated through the pancreatic tail, left hepatic lobe, caudate lobe, and spleen on abdominal sonography and computed tomography scan. Finally, emergent laparotomy was done for splenic abscess and removal of infected pseudocyst in the spleen and lesser sac of the abdomen. The patient made a full recovery after operation.

Aged↗
PubMed1993

Conformational study of two substance P hexapeptides by two-dimensional NMR.

The conformation of two substance P (SP) related hexapeptides. Glp-Phe-Phe-(L-Pro)-Leu-Met.NH2 (I) and Glp-Phe-Phe-(D-Pro)-Leu-Met.NH2 (II), in two solvents, chloroform-d and trifluoroethanol(TFE)-d3/H2O, was studied by two-dimensional NMR methods, including COSY, TOCSY, ROESY and HMQC. The study shows that these two peptides exist predominantly in the extended form in TFE/H2O, but in general exhibit a reverse-turn structure in chloroform. I is clearly less ordered than II in both solvents. Furthermore, extensive Phe3-Pro4 cis<==>trans isomerization was found in I but not in II. The differences in the conformational behavior of these two peptides, which are selective agonists for neurokinin NK1 and NK2 receptors, respectively, are discussed.

Amino Acid Sequence↗
PubMed1993

Clinical norms for amplitude of accommodation in Chinese.

Amplitude of accommodation was measured in 121 Hong Kong Chinese subjects between the ages of 11 and 65 years, using the 'push-up' method and the results compared with those previously obtained for Caucasian subjects. The results confirm and quantify clinical experience that Chinese people have lower amplitudes of accommodation than Caucasians. If presbyopia is considered to commence when the amplitude of accommodation declines to less than 5 D, then presbyopia in the Chinese race occurs between the ages of 36 and 40 years. By early in the second decade of life the amplitude of accommodation in the Chinese is already lower than that of Caucasians. This suggests that reduced amplitude of accommodation may be due, at least in part, to factors other than longterm environmental effects.

Accommodation, Ocular↗
PubMed1993

Calcium antagonistic and antiarrhythmic actions of CPU-23, a substituted tetrahydroisoquinoline.

1. The effects of CPU-23 (1-(1-[(6-methoxyl)-naphth-2-yl])-propyl-2-(1-piperidine)-acetyl-6 ,7- dimethyoxy-1,2,3,4-tetra-hydroisoquinoline) were studied on mechanical and electrical activities, and intracellular free calcium ([Ca2+]i) of isolated cardiac tissues in order to investigate its spectrum and mechanisms of action in the heart. Its antiarrhythmic and haemodynamic effects in pentobarbitone-anaesthetized rats subjected to coronary artery ligation were also evaluated. 2. CPU-23 at 10(-6)-10(-4) M markedly inhibited slow action potential characteristics in guinea-pig papillary muscles and pace-maker action potential of rabbit sinoatrial node. It affected fast action potential only at 10(-4) M. None of the effects of CPU-23 was reversed by washout for up to 2 h. 3. Like nifedipine and diltiazem, CPU-23 decreased the heart rate of the isolated perfused heart of the rat. However, in contrast to these two classical calcium antagonists which dose-dependently inhibited the force of contraction, CPU-23 inhibited and stimulated the force of contraction at 10(-7)-3 x 10(-6) M and 10(-5) M, respectively. 4. CPU-23 at 10(-6)-10(-5) M inhibited the KCl-induced [Ca2+]i increase in the Ca2+ medium, but did not affect the caffeine-induced [Ca2+]i increase in the Ca(2+)-free medium in isolated ventricular myocytes. 5. CPU-23 at 1-5 mg kg-1 reduced dose-dependently ventricular arrhythmias including ventricular ectopic beats, VT and VF as well as mortality during coronary artery ligation. At 2.5-5 mg kg-1 it even abolished VF, which was accompanied by 100% survival. 6. It is suggested that CPU-23 has calcium antagonistic properties in cardiac tissues. It selectively blocks the transmembrane influx of extracellular Ca2+ through Ca2+ channels, thus reducing the heart rate and developed tension, altering the slow action potential characteristics and producing antiarrhythmic effect against ischaemic arrhythmias.

Action Potentials↗
PubMed1993

Hip fracture incidence in Malaysia 1981-1989.

The age-corrected incidence of hip fracture in the city of Kuala Lumpur and the surrounding districts has increased from 1981 to 0.7 per 1,000 population in 1989. Women dominated by a factor of 1.3. The mean age was 73 (50-103) years. The increased rate observed was attributed solely to trochanteric fractures among those 70 years and above. There were differences in the various parameters among the different races. The fracture incidence and woman/man ratio were substantially lower than has been reported from developed countries.

Aged↗
PubMed1993

Case of difficult intubation overcome by the laryngeal mask airway.

A case of difficult intubation is described in which the problem was overcome by use of the laryngeal mask airway (LMA). The patient had difficulty in mouth opening due to severe burn scar contracture around the mouth and limited access prevented tracheal intubation. The use of LMA is shown to have obviated the need for tracheal intubation in the case of a patient whose injuries would have made this technique difficult.

Adult↗
PubMed1993

Effects of neuroactive agents on the isolated heart activities of marine bivalve Meretrix lusoria.

By recording method, we measured simultaneously both the contractile force (CF) and the action potential (AP) of the isolated heart to confirm the chief cardioregulatory transmitters of a marine bivalve. The effects of several neuroactive agents on CF, HR and the amplitude of AP in marine bivalve were investigated. Acetylcholine and carbachol produced inhibitory effects on the heart performance at 1.0 x 10(-11) M. Choline also exhibited inhibitory effects at a higher concentration, but atropine, curare, pilocarpine and hexamethonium bromide (all at 1.0 x 10(-4) M) exerted no significant effects on the spontaneous cardiac activities. 5-HT and 8-OH-DPAT produced positive chronotropic and inotropic effects on the heart at 1.0 x 10(-8) M, whereas adrenaline and dopamine were positively inotropic at 1.0 x 10(-5) M. The perfusion of adrenaline or dopamine typically prolonged the plateau duration of the action potential, and then enhanced CF. However, histamine, GABA and PGF2 alpha all exerted no significant effect on either CF or the amplitude of AP of the isolated heart. The results indicate that 5-HT and acetylcholine are excitatory and inhibitory agents, respectively, that regulate the isolated cardiac performance in a marine bivalve. The mechanism of positively inotropic effects of biogenic amines is discussed.

Acetylcholine↗
PubMed1993

Eosinophilic gastroenteritis: 10 years experience.

Eight patients (five men, three women), mean age 36.9 +/- 13.5 (17-60) yr, were diagnosed to have eosinophilic gastroenteritis. The condition was proved in five patients by biopsies through endoscope, and in three, by operation. All had hypereosinophilia (absolute eosinophil count of 1,337-21,787/cm3). According to Klein classification, two had mucosal disease, three had muscle layer disease, and three, subserosal disease. The most common symptoms were abdominal pain (100%), diarrhea (62.5%), vomiting (62.5%), and nausea (50%). Four patients (50%) had symptoms for more than 1 yr before diagnosis. Barium studies revealed mucosal edema and/or thickening of the small intestinal wall in three cases (including one case with ulceration), partial gastric outlet obstruction in one case, and narrowing of lumen of the terminal ileum in one case. Hypotonic duodenogram revealed double contour in one case. Ultrasound examination revealed thickening of the intestinal wall in two cases; computer tomography revealed thickening of the intestinal wall in one case. All patients were treated with steroid (40 mg/day for initial dose and relapse; 5-10 mg/day for maintenance). The symptoms subsided and the eosinophil counts returned to normal within 2 wk in seven patients and 1 month in one. Of six patients being followed up for 2-10 yr, one had remission, four needed small maintenance dose of steroid, and one suffered from relapse with intestinal perforation.

Adolescent↗
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↗