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Biomedical subjects

C C Lee

Publications and source records attributed to C C Lee.

At least 19 recordsLinked to original sources
PubMed1992

Inhibitory effect of purines in meiotic maturation of denuded mouse oocytes.

The potential action of purines, such as hypoxanthine and adenosine, in meiotic arrest was examined using denuded mouse oocytes. The spontaneous meiotic maturation of denuded oocytes was significantly inhibited by hypoxanthine and/or adenosine in a dose-dependent manner. Germinal vesicle breakdown (GVBD) was inhibited even at a low concentration (1 nM) of hypoxanthine, when hypoxanthine was microinjected into the cytoplasm of denuded oocytes. This inhibitory action was potentiated by co-injection with allopurinol, a metabolic blocker of hypoxanthine that can block a metabolic pathway to uric acid. By contrast, a microinjection of adenosine was no longer effective in inhibiting GVBD. Inhibitory action of purines in meiotic maturation was correlated with sustaining intracellular cAMP levels. GVBD was resumed by econazole, one of the nitroimidazole derivatives which act as inhibitors of catalytic subunit of adenylate cyclase. This compound was effective in counteracting the effect of adenosine, but not the action of 3-isobutyl-1-methylxanthine (IBMX) on GVBD, indicating that adenosine is probably exerted at the level of oocyte plasmalemma. These data suggest that the inhibitory action of hypoxanthine and adenosine in oocyte meiotic maturation may be involved in the regulation of cAMP metabolism in a differential manner.

1-Methyl-3-isobutylxanthine↗
PubMed1992

Two independent mutational events in the loss of urate oxidase during hominoid evolution.

Urate oxidase was lost in hominoids during primate evolution. The mechanism and biological reason for this loss remain unknown. In an attempt to address these questions, we analyzed the sequence of urate oxidase genes from four species of hominoids: human (Homo sapiens), chimpanzee (Pan troglodytes), orangutan (Pongo pygmaeus), and gibbon (Hylobates). Two nonsense mutations at codon positions 33 and 187 and an aberrant splice site were found in the human gene. These three deleterious mutations were also identified in the chimpanzee. The nonsense mutation at codon 33 was observed in the orangutan urate oxidase gene. None of the three mutations was present in the gibbon; in contrast, a 13-bp deletion was identified that disrupted the gibbon urate oxidase reading frame. These results suggest that the loss of urate oxidase during the evolution of hominoids could be caused by two independent events after the divergence of the gibbon lineage; the nonsense mutation at codon position 33 resulted in the loss of urate oxidase activity in the human, chimpanzee, and orangutan, whereas the 13-bp deletion was responsible for the urate oxidase deficiency in the gibbon. Because the disruption of a functional gene by independent events in two different evolutionary lineages is unlikely to occur on a chance basis, our data favor the hypothesis that the loss of urate oxidase may have evolutionary advantages.

Amino Acid Sequence↗
PubMed1992

Distal motor axonopathy and central nervous system myelin vacuolation caused by cycloleucine, an inhibitor of methionine adenosyltransferase.

Cycloleucine (CL), an inhibitor of methionine adenosyltransferase, has previously been used to produce an experimental model of subacute combined degeneration of the spinal cord. A re-investigation of its effects on the morphology of the nervous system and on brain concentrations of methionine and S-adenosylmethionine (SAM) was undertaken. Cycloleucine was administered as a single dose intraperitoneally (2 mg/g body weight) to young mice aged 21 d and adults aged 6 or 10 wks. The 21-day-old mice showed clinical evidence of toxicity within 24 h and thereafter developed progressive muscle weakness and ataxia. Animals did not survive longer than 1 wk. Light and electron microscopic examination of the central and peripheral nervous systems showed that intramyelinic vacuolation developed in the white matter of brain and cord within 12 h. The intramyelinic vacuolation in the white matter of brain and cord became more severe with longer survival, vacuoles coalescing and secondary axonal degeneration becoming evident. There was no myelin vacuolation in peripheral nerves. Axonal lesions occurred in the distal parts of motor nerves within 12-24 h resulting in degeneration of intramuscular nerve fibres and terminals. Later there was evidence of axonal degeneration in tibial and sciatic nerves. Many dorsal root ganglion cells became vacuolated or necrotic and numerous degenerated fibres were noted in the white matter of the spinal cord, particularly in the gracile funiculus. The optic nerves were not affected at any stage. In adult mice the pathology consisted of distal motor axonal degeneration which developed at 1-2 d. Little or no intramyelinic vacuolation in white matter was noted. Brain concentrations of SAM were reduced and levels of methionine became greatly elevated. The morphological effects of CL are considered to be the result of SAM deficiency impairing transmethylation processes known to be important in the formation and stabilization of myelin through the methylation of myelin basic protein. The immature developing central nervous system is much more vulnerable than the fully myelinated adult brain and spinal cord. The distal, predominantly motor axonopathy is a new observation and may be a reflection of the importance of transmethylation processes in the maintenance of axonal terminal membranes and the mechanisms of release of acetylcholine at the neuromuscular junction.

Animals↗
PubMed1992

Induction of ovulation and oocyte maturation of amphibian (Rana dybowskii) ovarian follicles by protein kinase C activation in vitro.

We previously reported that protein kinase C (PKC) activation induced meiotic maturation (germinal vesicle breakdown, GVBD) of Rana dybowskii follicular oocytes cultured in vitro without hormone treatment. The experiments reported here were carried out to establish whether ovarian follicles ovulated in response to PKC activation during culture. A phorbol ester, 12-O-tetradecanoylphorbol-13-acetate (TPA), was used for PKC activation. TPA addition (10 microM) to cultured ovarian fragments induced ovulation and maturation of the oocytes similar to that seen following addition of frog pituitary homogenate (FPH, 0.05 pituitary/ml) or progesterone (0.5 microgram/ml). Such changes were not observed when ovarian fragments were treated with inactive phorbol ester. The time course of TPA-induced ovulation was similar to that produced by FPH-stimulated ovulation. Both TPA- and FPH-stimulated ovulation and maturation were blocked by treatment with cycloheximide, forskolin (an adenylate cyclase stimulator), and 1-(5-isoquinolinylsulfonyl)-2-methyl-piperazine (H-7; a PKC inactivator). FPH treatment markedly increased progesterone levels in the medium during ovarian fragment culture whereas TPA treatment failed to elevate progesterone levels. Thus, TPA treatment mimics FPH and progesterone in inducing ovulation and meiotic maturation in cultured amphibian ovarian fragments. The data strongly suggest that PKC plays an important role in regulating ovulation as well as in modulating amphibian oocyte maturation during follicular differentiation.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1992

Effects of acute oligohydramnios on respiratory system of fetal sheep.

Prolonged oligohydramnios, or a lack of amniotic fluid, is associated with pulmonary hypoplasia and subsequent perinatal morbidity, but it is unclear whether short-term or acute oligohydramnios has any effect on the fetal respiratory system. To investigate the acute effects of removal of amniotic fluid, we studied nine chronically catheterized fetal sheep at 122-127 days gestation. During a control period, we measured the volume of fluid in the fetal potential airways and air spaces (VL), production rate of that fluid, incidence and amplitude of fetal breathing movements, tracheal pressures, and fetal plasma concentrations of cortisol, epinephrine, and norepinephrine. We then drained the amniotic fluid for a short period of time [24-48 h, 30.0 +/- 4.0 (SE) h] and repeated the above measurements. The volume of fluid drained for the initial studies was 1,004 +/- 236 ml. Acute oligohydramnios decreased VL from 35.4 +/- 2.9 ml/kg during control to 22.0 +/- 1.6 after oligohydramnios (P less than 0.004). Acute oligohydramnios did not affect the fetal lung fluid production rate, fetal breathing movements, or any of the other measured variables. Seven repeat studies were performed in six of the fetuses after reaccumulation of the amniotic fluid at 130-138 days, and in four of these studies the lung volume also decreased, although the overall mean for the repeat studies was not significantly different (27.0 +/- 5.2 ml/kg for control vs. 25.5 +/- 5.5 ml/kg for oligohydramnios). Again, none of the other measured variables were altered by oligohydramnios in the repeat studies.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1992

Solitary plasmacytoma of the skull base.

Plasmacytomas involving the skull base are rare lesions that may be well advanced by the time of diagnosis. Because of their anatomic site they may produce a variety of signs and symptoms, some of which may be vague, often resulting in delays in presentation and in appropriate investigations. We present such a patient, discuss the diagnosis and management, and give a review of the literature.

Diplopia↗
PubMed1992

Altered glycosylation and cell surface expression of beta 1 integrin receptors during keratinocyte activation.

We studied the mechanism by which cell adhesiveness becomes activated when keratinocytes are removed from skin and placed into cell culture. Our results suggest that activation involves altered beta 1 integrin subunit glycosylation accompanied by an increase in cell surface beta 1 integrin receptors. Activated keratinocytes contained two forms of the beta 1 integrin subunit, approximately 93 kDa and approximately 113 kDa. As shown by pulse-chase experiments, the smaller represented the cytoplasmic precursor of the larger, and only the 113 kDa mature form was detected in integrin receptors expressed at the cell surface. Pre-activated keratinocytes contained beta 1 integrin subunits ranging from approximately 97 to 110 kDa. These beta 1 subunits had been processed through the Golgi, based on resistance to endoglycosidase-H treatment, and were not converted to 113 kDa subunits during subsequent cell culture. Experiments with endoglycosidase-F showed that differences in the apparent sizes of beta 1 integrin subunits observed in pre-activated and activated keratinocytes could be attributed to differences in subunit glycosylation. Smaller beta 1 subunits found in pre-activated keratinocytes, like the precursor beta 1 subunits of activated cells, appeared to be less efficient in reaching the cell surface. Overall, a approximately 10-fold increase in the level of cell surface integrin receptors occurred concomitant with the increased proportion of 113 kDa beta 1 subunits found in activated cells. Endoglycosidase-F experiments also indicated that there were changes in keratinocyte alpha subunits associated with beta 1. In related experiments, keratinocytes cultured in low Ca2+, serum-free MCDB medium for 4 days proliferated but their adhesiveness did not become activated. Therefore, keratinocyte proliferation and activation of adhesion are regulated separately. Finally, substantial activation of keratinocytes was observed when serum was added to cells cultured in MCDB with serum, indicating a role for serum factors in the activation process.

Animals↗
PubMed1992

Initial predictors of survival in patients with systemic sclerosis (scleroderma).

We conducted a retrospective study of 86 patients with systemic sclerosis (SSc) to clarify the initial predictors of survival at the first visit to the hospital. A life-table analysis of survival was performed concerning 137 items from their histories, physical examinations, and laboratory data. The observed cumulative survival rates were 78.0 percent at 5 years and 68.2 percent at 10 years. Ten items were found to be the initial predictors of survival in patients with SSc. Of these 10 items, 9 items showed significant differences within 5 years of the first visit to the hospital. Patients with resting electrocardiographic abnormalities, such as atrial or ventricular arrhythmias, or conduction disturbances, pulmonary fibrosis on the chest x-ray films, or decreased vital capacity had significantly lower survival rates. However, patients with anti-centromere antibody had a significantly better survival rate. In addition, males, aged patients over 65 years old, and patients with proteinuria, leucopenia, or hypergammaglobulinemia had significantly lower survival rates. Only patients with proximal scleroderma at the first visit to the hospital had a significantly lower survival rate after 8 years. These results are useful in predicting individual patients at risk of shortened survival and in managing these patients.

Adolescent↗
PubMed1992

Chronic progressive external ophthalmoplegia with NADH-CoQ reductase deficiency: report of a case.

A thirty-two year old female had chronic progressive external ophthalmoplegia (CPEO), exertional fatigue, dysarthria, dysphagia, and bilateral hearing impairment. Histochemical stains, obtained from the right vastus lateralis, showed ragged-red fibers and wide-spread abnormalities in the number, size, and the structure of mitochondria under electronomicroscopic examination. A biochemical analysis showed a low activity of NADH-cytochrome C reductase, NADH dehydrogenase and a normal activity of succinate cytochrome C reductase and cytochrome C oxidase. This data suggests a specific defect in the NADH dehydrogenase of complex I (NADH CoQ reductase). We believe that this is the first biochemically defined mitochondrial myopathy reported in Taiwan and provides additional evidence for the existence of biochemical heterogeneity in mitochondrial disorders of CPEO.

Adult↗
PubMed1992

Primary medullary hemorrhage: report of a case.

A 40-year-old normotensive man suddenly developed dizziness, vomiting, hoarseness and swallowing disturbance. Neurologic examinations showed bilaterally decreased palatal elevation and gag reflex, upbeat nystagmus and gait ataxia. The diagnosis of medullary hemorrhage was first established by computed tomography (CT). Magnetic resonance imaging study further showed a hematoma in the paramedial medulla oblongata extending dorsorostrally to the pontomedullary junction. It gave the precise anatomic boundary of the intramedullary hematoma and was well correlated with the clinical findings. This patient's subsequent prognosis was good with gradual improvement of the clinical signs and symptoms. A follow-up CT scan showed resolution of the hematoma, and the prognosis was consistent with a good neurologic recovery.

Adult↗
PubMed1992

Hypothalamic amenorrhea in a case of mitochondrial encephalomyopathy.

A 26-year-old female with myoclonus epilepsy associated with ragged-red fibers is reported. Clinically, she had myoclonus epilepsy, cerebellar ataxia, a bilateral neurosensory type hearing loss, retinitis pigmentosa and short stature. She also presented with primary amenorrhea and poor development of secondary sexual characteristics. Endocrinologic studies revealed that hypothalamic dysfunction was the most plausible cause of her primary amenorrhea. Magnetic resonance imaging showed marked dilatation of the third ventricle indicating thalamic and hypothalamic degeneration. We conclude that hypothalamic dysfunction may be one of the characteristic features of mitochondrial encephalomyopathies.

Adult↗
PubMed1992

Adult-onset, autosomal dominant, rimmed vacuolar myopathy with limb-girdle distribution--a preliminary report.

Adult-onset, autosomal dominant myopathy with limb-girdle distribution in a Chinese family is reported. Nine members were affected with characteristic proximal weakness and pelvifemoral-preceded scapulohumeral involvement. The facial, extraocular and bulbar muscles were spared. Rimmed vacuoles were the most obvious characteristics in the myopathologic study of the biopsy specimens from four patients. In a review of the previous literature, we found three reported families with clinical and myopathologic features identical to ours, and these families are viewed as a distinct subgroup of myopathy.

Adult↗
PubMed1992

Controlled reperfusion of the regionally ischemic myocardium with leukocyte-depleted blood reduces stunning, the no-reflow phenomenon, and infarct size.

Open-chest sheep underwent 90 minutes' occlusion of the diagonal branch of the left anterior descending coronary artery, followed by vented cardiopulmonary bypass. After 30 minutes of cardioplegic arrest, simulating distal anastomoses, the occlusion on the coronary artery branch was released. Controlled reperfusion (40 to 50 mm Hg, 135 to 150 ml/min) for the first 20 minutes was delivered at the aortic root with either unmodified whole blood (control, n = 7) or blood passed through leukocyte filters (filters, n = 7). Serial measurements were made during 3 additional hours reperfusion off cardiopulmonary bypass. During ischemia, the major determinants of infarct size, which include area at risk, collateral myocardial blood flow, and rate-pressure product were not significantly different between groups. Overall, during reperfusion, mean left ventricular stroke work index in the filter group was greater than in the control group (28.7 +/- 5.8 versus 12.6 +/- 6.4 x 10(3) erg/gm, p less than 0.05), as was mean rate of rise of left ventricular pressure (1900 +/- 260 versus 1348 +/- 279 mm Hg/sec, p less than 0.05). Myocardial blood flow to the area at risk at 3 1/2 hours of reperfusion in the filter group was also significantly better than in the control group (0.57 +/- 0.15 versus 0.27 +/- 0.05 ml/min/gm, p less than 0.05), as was necrotic area as a percentage of area at risk (40% +/- 6% versus 70% +/- 5%, p less than 0.05). These results demonstrate amelioration of myocardial stunning and the no-reflow phenomenon, as well as decreased infarct size. We conclude that controlled reperfusion with leukocyte-depleted blood is superior to whole-blood reperfusion for the surgical treatment of acute regional ischemia.

Animals↗
PubMed1991

Expression of recombinant dystrophin and its localization to the cell membrane.

Duchenne's muscular dystrophy (DMD) is an X-linked progressive myopathy caused by a defect in the DMD gene locus. The gene corresponding to the DMD locus produces a 14-kilobase (kb) messenger RNA that codes for a large cytoskeletal membrane protein, dystrophin. DMD and Becker's muscular dystrophy are the consequences of dystrophin mutations. The exact biological function of dystrophin remains unknown but it has been demonstrated that it is localized to the cytoplasmic face of the cell membrane and has direct interaction with several other membrane proteins. We report here the synthesis of a 14-kb full-length complementary DNA for the mouse muscle dystrophin mRNA and the expression of this cDNA in COS cells. The recombinant dystrophin is indistinguishable from mouse muscle dystrophin by western blot analysis with anti-dystrophin antibodies and was shown by an immunofluorescent technique to be localized in the cell membrane. Our successful construction of a functional full-length cDNA opens opportunities for the study of structure and function of dystrophin and provides an opportunity to initiate gene therapy studies.

Animals↗
PubMed1991

Intraamniotic detection of Chlamydia trachomatis deoxyribonucleic acid sequences by polymerase chain reaction.

The presence of Chlamydia trachomatis in cervicovaginal cells and amniotic fluid of pregnant women was examined by culture and by polymerase chain reaction deoxyribonucleic acid amplification methods. Chlamydial deoxyribonucleic acid sequences were found in nine of 31 (29.0%) cervicovaginal cell specimens, five of which also were positive by culture method. Amniotic fluid specimens from two of the nine (22.2%) cervicovaginal chlamydial deoxyribonucleic acid-positive women and none from the remaining 22 cervicovaginal chlamydial deoxyribonucleic acid-negative women were found to contain chlamydial deoxyribonucleic acid. The results underscore the significance and frequency of intraamniotic chlamydial infection in women with urogenital chlamydial infections.

Amniotic Fluid↗