Biomedical subjects

S B Lee

Publications and source records attributed to S B Lee.

At least 127 records · Page 7Linked to original sources

PubMed1994

Regulation of phospholipase C-beta 4 by ribonucleotides and the alpha subunit of Gq.

The fourth member of mammalian beta-type phospholipase C isozymes, PLC-beta 4, was recently purified from bovine retina, and the corresponding cDNA was cloned from rat brain and sequenced. PLC-beta 4 has now been shown to differ from the other three mammalian beta-type isozymes (PLC-beta 1, -beta 2, and -beta 3) in that it is selectively inhibited by ribonucleotides. The inhibition requires the 5'-phosphate and 2'-hydroxyl groups of ribose as well as the base moiety. Thus, deoxyribonucleotides and ribose 5-phosphate were not inhibitory. The monophosphate, diphosphate, and triphosphate nucleoside derivatives were all inhibitory, whereas cyclic nucleotides were ineffective. Purine nucleotides were more potent inhibitors than pyrimidine nucleotides; the 50% inhibitory concentrations were 20-30 microM for AMP and GMP, and 100-200 microM for UMP and CMP. Unlike the other beta-type isozymes, PLC-beta 4 contains the GX4GKS consensus sequence for the recognition of the phosphoryl group of nucleotides. In the absence of ribonucleotides, the specific activity of PLC-beta 4 toward phosphatidyl-inositol 4,5-bisphosphate was four to five times the average specific activity of PLC-beta 1 and PLC-beta 3. Thus, nucleotide-dependent inhibition may serve to reduce the activity of PLC-beta 4 in the absence of a hormonal signal. The regulation of PLC-beta 4 by G-proteins was also studied. Similar to the other three PLC-beta isozymes, PLC-beta 4 was activated by the alpha subunit of Gq but not by the transducin alpha subunit. However, unlike other PLC-beta isozymes, PLC-beta 4 was not responsive to activation by G beta gamma subunits.

Amino Acid Sequence↗

PubMed1994

The interferon-induced double-stranded RNA-activated protein kinase induces apoptosis.

Interferons (IFNs) exert antitumor activities, but the molecular mechanism underlying these effects is poorly understood. IFN-induced, double-stranded (ds) RNA-activated protein kinase (p68 kinase) has long been implicated in mediating the antiproliferative effects of IFN. In addition, recent studies suggest that p68 kinase may function as a tumor suppressor gene. In this investigation we showed that expression of p68 kinase in HeLa cells resulted in a rapid cell death characteristic of apoptosis. Rapid cell death was not observed in cells which expressed a mutant form of p68 kinase (lys296-->arg) indicating that cell death observed is the result of p68 kinase expression and activation. Moreover, infection of HeLa cells with the mutant vaccinia virus lacking E3L gene, which encodes a dsRNA binding protein that acts as an inhibitor of p68 kinase, also resulted in apoptosis. Thus, we propose that human p68 kinase functions as a tumor suppressor gene by actively participating in apoptosis.

Apoptosis↗

PubMed1994

Ribosomal DNA internal transcribed spacer analysis supports synonomy of Scedosporium inflatum and Lomentospora prolificans.

Scedosporium inflatum is a dematiaceous opportunistic pathogen originally described by D. Malloch and I.F. Salkin (Mycotaxon 21:247-255, 1984). However, E. Gueho and G. S. De Hoog (J. Mycol. Med. 118:3-9, 1991) recently suggested reducing this mold to synonomy with Lomentospora prolificans on the basis of their similar morphological and molecular characteristics. We have investigated the ribosomal DNA internal transcribed spacers (ITS), i.e., ITS I and ITS II, of 18 isolates, including these two fungi and a closely related pathogen, Scedosporium apiospermum, and its telemorph, Pseudallescheria boydii. Identical ITS restriction fragment length polymorphisms were found in eight isolates of S. inflatum and L. prolificans. These results support Gueho and De Hoog's proposal to combine S. inflatum and L. prolificans into the binomial Scedosporium prolificans. However, the ITS I sequence of S. apiospermum and the ITS restriction fragment length polymorphisms of S. apiospermum and P. boydii were found to be significantly different from those of S. inflatum and L. prolificans. The ITS restriction pattern differences may be valuable in clinical settings for distinguishing these fungi.

Base Sequence↗

PubMed1994

Initial and follow-up brain MRI findings and correlation with the clinical course in Wilson's disease.

We performed pretreatment brain MRIs in 25 patients with neurologically symptomatic Wilson's disease (WD) and clinical and MRI follow-up in 16 of them. All 25 pretreatment MRIs revealed abnormalities, with abnormal high-signal intensity (HSI) in bilateral thalami being the most common (92%). HSI lesions in the brainstem (84%) and the basal ganglia (72%) were also common. Brain atrophy was present in 88% of the 25 patients. In the follow-up period of 5 to 24 months, during which the patients were treated with D-penicillamine, both HSI lesions and neurologic symptoms improved in 88% of the 16 patients, but the brain atrophy did not change.

Adolescent↗

PubMed1994

A clinical study of benign focal amyotrophy.

We reviewed the clinical, electrophysiological, radiological, and histopathological findings in 25 patients with benign focal amyotrophy. There were 14 patients with upper limb type and 11 with lower limb type. 18 patients had unilateral involvement and 7 had bilateral involvement asymmetrically. The characteristics clinical features were sporadic occurrence, predominance in young males, nonprogressive course or initial progression for 1 to 3 years followed by stationary state, segmental distribution of muscle weakness and atrophy localized to one limb or both homologous limbs markedly asymmetrically, and absence of any definite sensory loss or central nervous system involvement. The electrophysiological, radiological, and muscle histopathological findings suggested chronic focal anterior horn cell disease. Although the prevalence of this disease is still unknown, the importance of recognition is being emphasized because of its common occurrence in our country and the benign prognosis.

Adolescent↗

PubMed1994

[An analysis of Korean women's reproductivity].

An analysis of reproductivity is mainly concerned with the measurement of net force of fertility expressed in terms of a generation rather than in a given year. The present study examined current trends of Korean Women's reproductivity interpreting general reproduction and net reproduction rates, intrinsic rate of natural increase and mean length of gestation. The data used for this analysis were drawn from the national fertility surveys from 1970 through 1990 conducted by the Korea Institute for Population and Health. The figures of the present study revealed that the reproduction rates of Korea during the last 20 years decreased from 2.22 in 1970 to 0.71 in 1990 and net reproduction rates also dropped from 1.9 to 0.69 during the same period of time. Furthermore, from this study, it is noticed that the replacement level of fertility had been reached since the early 1980s. The intrinsic rate of natural increase as measure of population growth under existing conditions of fertility and mortality and free of the influence of the current age distribution, is computed. The level of rate was not much changed and was 0.3 in 1970 compared with 0.25 in 1990, which is still higher than other developed countries. The mean age of mother at the birth of their daughters defined as the length of generation has been slightly changed from 23.9 in 1971 to 25.8 in 1990.

Age Factors↗

PubMed1993

Activation of phospholipase C-beta 2 mutants by G protein alpha q and beta gamma subunits.

The beta- but not the gamma- and delta-type isozymes of inositol phospholipid-specific phospholipase C (PLC) are activated by G protein alpha q and beta gamma subunits. The beta-type PLC isozymes differ from other isozymes in that they contain a long carboxyl-terminal region downstream of the Y catalytic domain and a region rich in acidic amino acids between the two separated X and Y catalytic domains. To determine the sites on PLC-beta 2 that participate in the interaction of the enzyme with alpha q and beta gamma subunits, we introduced specific truncations and substitutions in the PLC-beta 2 cDNA at positions corresponding to the carboxyl-terminal and acidic amino acid-rich regions, respectively. After transient expression of these cDNA clones in CV-1 cells, the mutant enzymes were partially purified and their capacity to be activated by alpha q and beta gamma subunits determined. Substitution of glutamine residues for three or all seven of a stretch of consecutive glutamic acids in the acidic domain of PLC-beta 2 affected neither alpha q- nor beta gamma-dependent activation significantly. Carboxyl-terminal truncation to residue Gly-934 or to residue Ala-867 resulted in enzymes that were activated by beta gamma but not by alpha q. This result suggests that the carboxyl-terminal region of PLC-beta 2 is required for activation by alpha q, and that beta gamma subunits interact with a different region of the enzyme. Thus, alpha q and beta gamma subunits may independently modulate a single PLC-beta 2 molecule concurrently.

Amino Acid Sequence↗

PubMed1993

The interferon-induced double-stranded RNA-activated human p68 protein kinase potently inhibits protein synthesis in cultured cells.

The role of the interferon-induced double-stranded RNA (dsRNA)-activated human p68 protein kinase as an inhibitor of protein synthesis has been inferred from work with cell-free systems, but direct proof in animal cells is lacking. To document the action of p68 protein kinase in vivo, we have used an infection-transfection system where expression of p68 is driven by a vaccinia virus promoter regulated by the lacl repressor/operator controlling elements. In cultured cells infected with vaccinia virus and transfected with a plasmid containing the p68 gene, there is synthesis of p68 when lacl repressor is inhibited with isopropyl-beta-D-thiogalactoside. When infection-transfections are carried out with the p68 gene together with the luciferase (LUC) reporter gene, a strong inhibition of LUC expression developed with time postinfection. This inhibition was not observed with a mutant form of the kinase (Lys-->Arg at position 296) and it was reversed by antisense expression of the p68 gene. During inhibition of LUC expression the protein kinase was phosphorylated, possibly as a result of autophosphorylation activated by the dsRNA forms which are known to accumulate in vaccinia virus-infected cells. Inhibition of LUC expression was at the level of translation. Our findings demonstrate that expression and activation of the human p68 protein kinase in vivo potently inhibits protein synthesis.

Cells, Cultured↗

PubMed1993

The interferon-induced double-stranded RNA-activated human p68 protein kinase inhibits the replication of vaccinia virus.

The interferon-induced, double-stranded RNA (dsRNA)-activated protein kinase (p68 kinase) has long been implicated as one of the antiviral agents responsible for overcoming virus infections. To investigate the antiviral potential of p68 kinase, we have generated a recombinant vaccinia virus that expresses human p68 kinase under the control of lac operator/repressor element. Upon induction of p68 kinase gene with the inducer isopropyl-beta-D-thiogalactoside (IPTG), we observed in cultured cells a severe (> 90%) inhibition of virus protein synthesis; this inhibition correlated with autophosphorylation of p68 kinase. As a result of inhibition in the synthesis of virus polypeptides, there was a 100-fold decrease in virus yields. When cells were infected with the recombinant virus expressing lys296-->arg296 mutant p68 kinase there was no reduction in virus yields. Our findings demonstrate that human p68 kinase once activated severely inhibits vaccinia virus replication as a result of inhibition of protein synthesis.

Animals↗

PubMed1993

Uniparental inheritance and replacement of mitochondrial DNA in Neurospora tetrasperma.

This study tested mechanisms proposed for maternal uniparental mitochondrial inheritance in Neurospora: (1) exclusion of conidial mitochondria by the specialized female reproductive structure, trichogyne, due to mating locus heterokaryon incompatibility and (2) mitochondrial input bias favoring the larger trichogyne over the smaller conidium. These mechanisms were tested by determining the modes of mitochondrial DNA (mtDNA) inheritance and transmission in the absence of mating locus heterokaryon incompatibility following crosses of uninucleate strains of Neurospora tetrasperma with trichogyne (trichogyne inoculated by conidia) and without trichogyne (hyphal fusion). Maternal uniparental mitochondrial inheritance was observed in 136 single ascospore progeny following both mating with and without trichogyne using mtDNA restriction fragment length polymorphisms to distinguish parental types. This suggests that maternal mitochondrial inheritance following hyphal fusions is due to some mechanism other than those that implicate the trichogyne. Following hyphal fusion, mutually exclusive nuclear migration permitted investigation of reciprocal interactions. Regardless of which strain accepted nuclei following seven replicate hyphal fusion matings, acceptor mtDNA was the only type detected in 34 hyphal plug and tip samples taken from the contact and acceptor zones. No intracellular mtDNA mixtures were detected. Surprisingly, 3 days following hyphal fusion, acceptor mtDNA replaced donor mtDNA throughout the entire colony. To our knowledge, this is the first report of complete mitochondrial replacement during mating in a filamentous fungus.

Cell Nucleus↗

PubMed1993

Phosphorylation of ribosomal protein S6 and its regulation during differentiation of human leukemic cells.

We attempted to study the role of protein tyrosine kinase (PTK) and protein kinase C (PKC) in the cascade of phosphorylation of ribosomal protein S6 during differentiation of leukemic cells (HL-60, THP-1, and RWLeu-4). Neither activation nor inhibition of colony stimulating factor-1 (CSF-1) receptor's PTK activity with CSF-1 or genistein respectively affected the phosphorylation of S6. However, vanadate which is a protein tyrosine phosphatase (PTP) inhibitor showed enhancement of S6 phosphorylation. Dimethylsulfoxide which does not affect either PTK or PKC demonstrated no change in S6 phosphorylation. PKC activation by acute 12-0-tetradecanoyl phorbol-13-acetate (TPA) treatment induced monocytic differentiation and S6 phosphorylation. Surprisingly, the more prominent phosphorylation of S6 protein was observed in PKC-depleted cells by prolonged TPA treatment. Our results suggest that PTK/PTP play a lesser role in S6 phosphorylation of HL-60 cells than PKC does. In addition, two different mechanisms seem to be involved in TPA-induced S6 phosphorylation during HL-60 differentiation: PKC activation by acute TPA treatment and PKC depletion which may lead to the synthesis of some endogenous protein responsible for the differentiation by chronic TPA treatment.

Cell Differentiation↗

PubMed1993

Microwave miniprep of total genomic DNA from fungi, plants, protists and animals for PCR.

A rapid procedure for the isolation of total DNA from various eukaryotic organisms is described. This method uses a common microwave oven for the alteration of cellular walls and membranes. The procedure is rapid and can be completed in as little as 15 minutes. The method has been used to isolate DNA from reptiles, plants, slime molds and other protists, and this DNA has been used for successful amplification of ribosomal genes from these organisms. The procedure is a time-saving and cost-effective process that helps to eliminate several sources of contamination that can be found in other DNA isolation procedures.

DNA↗

PubMed1992

Periodontal changes following coronal/root perforation and formocresol pulpotomy.

A clinical case report is presented which describes the sequelae of an iatrogenic lateral crown/root perforation and a formocresol pulpotomy. The post-operative course of the initial therapy included significant hard and soft tissue destruction and eventual tooth loss. The possible implication of the role of formocresol is discussed.

Adult↗

PubMed1992

Phylogeny of five fungus-like protoctistan Phytophthora species, inferred from the internal transcribed spacers of ribosomal DNA.

Ribosomal DNA variation was used to study evolutionary relationships among five fungal-like protoctistan Phytophthora species. On the basis of morphological and ecological characteristics, four of these species--P. palmivora, P. megakarya, P. capsici, and P. citrophthora--were once thought to be related. Variation within a species was extensively studied in a fifth, outgroup species--P. cinnamomi--known, on the basis of ecological, isozyme, and mitochondrial DNA studies, to be variable. Internal transcribed spacer regions (ITS I, between the 18S and 5.8S rDNAs; and ITS II, between the 5.8S and 25S rDNAs) from 27 isolates of these five species were analyzed by polymerase chain reaction amplification and direct sequencing. Intraspecific variability was undetected or low. Interspecific nucleotide difference was 0.3%-14.6%, and comparisons of variable regions permitted the evaluation of phylogenetic relationships among species. Both neighbor-joining and parsimony analysis of ITS variability support a close relationship between cacao isolates of P. capsici and P. citrophthora and a common lineage for P. palmivora and P. megakarya. Large distance values were estimated between P. cinnamomi and the other species. Inferred relationships based on ITS variability were compared with those based on other characters. The catalog of sequences provides the information necessary to design taxon-specific probes potentially useful in taxonomic, ecological, and population-level studies.

Base Sequence↗

PubMed1992

MR imaging of the internal carotid artery in ischemic cerebrovascular disorders--clinical and angiographic correlation.

This study was intended to correlate the appearance of the cavernous segment of the carotid artery on MR images with the presence of significant stenosis or occlusion of the cervical carotid artery as seen on angiograms in 37 patients with cerebrovascular disorders who had brain MRI and arteriography. Three patients demonstrated an isointense signal within the carotid artery's cavernous segment, correlating with complete carotid occlusion as seen angiographically. Ten patients had variable signal intensity and/or luminal narrowing in the carotid siphon; seven of these findings correlated with angiographic evidence of carotid occlusion, while carotid branch occlusion was seen angiographically in the other three. The demonstration of normal signal void within a normal-appearing cavernous segment of the internal carotid artery in the remaining 24 patients correlated with an absence of significant stenosis within the cervical segment in 21 patients. In the remaining three, significant disease of the internal carotid artery was found. Isointensity or luminal irregularity within the intracranial carotid artery can indicate complete occlusion or slow flow. The presence of normal flow void in the intracranial segment does not exclude significant abnormality of the cervical segment of the carotid artery.

Adolescent↗

PubMed1992

Arthroscopic subacromial decompression.

A study group composed of 11 shoulders in 10 patients underwent arthroscopic subacromial decompression for impingement syndrome. There were no biceps tendon ruptures, acromioclavicular arthritis or glenohumeral instability. Eight men and two women ranging in age from 17 to 65 years (mean age 38.7) with dominant arm involvement in 9/10 were evaluated for an average follow-up of 19.4 months (range 12-26) postoperatively. Based on the University of California at Los Angeles shoulder rating scale, nine (82%) shoulders had satisfactory results and the remaining two (18%) had unsatisfactory results. This is a preliminary report of our early experience in this rather new method of treatment, but the results are encouragingly good.

Acromion↗

PubMed1992

Passive exercise system: effect on muscle activity, strength, and lean body mass.

There is little information concerning the effects of passive exercise training in healthy humans. This prompted an investigation to evaluate muscle activity and the associated changes in strength and lean body mass resulting from a passive exercise program. Twenty-eight healthy volunteers, aged 26 to 44 years, participated in this six-week study. Lean body mass changes were evaluated by tetrapolar bioelectric impedance measurements, strength changes by isokinetic strength evaluation, and muscle activity by surface EMG techniques. Reproducible muscle activity was recorded in all three muscles studied during two of three preselected exercises. This involuntary muscle activity was attributed to fusimotor and postural reflexes. No significant change (p greater than .05), however, occurred in muscle strength or lean body mass at the end of the six weeks. Lack of these physiologic changes in light of the documented muscle activity is attributed to insufficient training effect.

Adult↗

PubMed1991

Cardiovascular regulation by cholinergic mechanisms in rostral ventrolateral medulla of spontaneously hypertensive rats.

This study aimed to demonstrate the role of acetylcholine receptors in the rostral ventrolateral medulla (RVL) in the central regulation of the cardiovascular system in normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). The effects of cholinergic drugs, microinjected into the rostral ventrolateral medullary vasopressor area, on blood pressure and heart rate in anesthetized and artificially ventilated rats were investigated. Unilateral microinjection of carbachol (1 nmol/site), physostigmine (300 pmol/site) or 3,4-diaminopyridine (500 pmol/site) into the RVL elicited a pressor and tachycardiac response, of which only the pressor response was significantly greater in SHR than in WKY. Bilateral microinjection of atropine (1 nmol/site) caused a depressor and bradycardiac response. The depressor response produced by atropine injected in the RVL was also significantly greater in SHR than in WKY. These results suggest that there are tonic cholinergic mechanisms in the RVL of the rats, which exert an excitatory cardiovascular action, and that the enhanced responsiveness to acetylcholine receptor stimulation in the RVL may contribute to the sustained elevation of blood pressure in the SHR.

4-Aminopyridine↗