Biomedical subjects

S K Hwang

Publications and source records attributed to S K Hwang.

At least 19 recordsLinked to original sources

PubMed2000

Molecular cloning and expression analysis of 3-ketoacyl-ACP synthases in the immature seeds of Perilla frutescens.

We report the isolation and expression analysis of two cDNAs encoding 3-ketoacyl-acyl carrier protein synthases (KAS) that are involved in the de novo synthesis of fatty acids in plastids of perilla (Perilla frutescens L.). The cDNAs, designated PfFAB1 and PfFAB24, encoded polypeptides with high sequence identities to those of KAS I and KAS II/IV, respectively, of various plants. Genomic Southern blots revealed that there was a single PfFAB1 gene but two PfFAB24 genes in the perilla genome. Of interest is that the expression of both genes was developmentally regulated in seeds. Their mRNA expression patterns in seeds were also discussed in comparison with the profile of fatty acid accumulation.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗

PubMed2000

Molecular cloning and functional expression of Perilla frutescens 3-ketoacyl-(acyl carrier protein) synthase III.

The 3-ketoacyl-acyl carrier protein synthase III (KAS III) is a condensing enzyme catalyzing the initial step of fatty acid biosynthesis. We isolated two KAS III cDNA isoforms (PfKAS3a and PfKAS3b) from a cDNA library specific to Perilla frutescens immature seeds. Two cDNAs coded for 401 and 400 amino acids, respectively, which showed high degree of sequence similarity to corresponding enzymes from various sources. Results of Southern hybridization indicated that the PfKAS3a gene is present as two copies, whereas the PJKAS3b gene is a single copy. While both genes were equally expressed in high levels during early stages of seed maturation in a development-specific manner, the PfKAS3b transcript showed more prolonged appearance. Expression of the functional recombinant perilla KAS III increased the myristate level in E. coli but it exerted no appreciable effect on cell growth.

3-Oxoacyl-(Acyl-Carrier-Protein) Synthase↗

PubMed2000

Soft drugs. 12. Design, synthesis, and evaluation of soft bufuralol analogues.

In the search for more potent but still short-acting beta-blockers (BB), the methyl, ethyl, isopropyl, tert-butyl, cyclohexyl, 2-(1-adamantyl)ethyl, and methylthiomethyl esters of the acidic inactive metabolite of bufuralol were synthesized based on the "inactive metabolite" approach. The cleavage of the ester bond by blood and tissue esterases rapidly deactivates these compounds, resulting in an ultrashort duration of action. The beta-antagonist potencies and time courses of actions of the new "soft" BBs were characterized by recording ECG and intra-arterial blood pressure (BP) in rats. In the isoproterenol-induced tachycardia model, while bufuralol at an iv dose of 1 mg/kg (3.8 micromol/kg) diminished heart rate (HR) for at least 2 h, the effects of the soft drugs lasted for only 10-30 min at equimolar dose. The inactive metabolite did not decrease HR significantly. The first four members of this series of compounds showed the highest beta-blocking potencies, ranging between 25% and 50% of that of bufuralol. Next, the effects of these most active compounds on resting HR and BP were evaluated in comparison to esmolol. Infused for 10 min at a rate of 20 micromol/kg/min, esmolol decreased HR and mean arterial pressure (MAP) by 40% and 60%, respectively. The soft drugs at doses ranging only between 2 and 4 micromol/kg/min resulted in a 20-40% decrease in HR and a 30-50% reduction in MAP. However, the time courses of both the bradycardic and hypotensive effects of the soft drugs were superimposable to that of esmolol, diminishing within 60 min after the discontinuation of the infusions.

Adrenergic beta-Antagonists↗

PubMed2000

Secondary structural and phylogenetic implications of nuclear large subunit ribosomal RNA in the ectomycorrhizal fungus Tricholoma matsutake.

The sequence of large subunit (LSU) and 5.8S rRNA genes has been determined for Tricholoma matsutake. A secondary structure model was predicted for both LSU and 5.8S rRNAs, showing most of the structural features consistent with those of the consensus secondary structure model proposed for the eukaryotic cytoplasmic LSU rRNAs. With a reconstructed eukaryotic phylogeny based on full-length LSU rDNA sequences, T. matsutake was placed on the same branch with Cryptococcus neoformans as its closest neighbor. We proposed that T. matsutake be considered as one of the representative members of the division Basidiomycota. Here we report for the first time the complete LSU rRNA gene sequence in T. matsutake, a member of Homobasidiomycetes.

Base Sequence↗

PubMed2000

Infantile head injury, with special reference to the development of chronic subdural hematoma.

An infantile head injury has unique features in that infants are totally helpless and dependent on their parents, and biomechanical characteristics of the skull and brain are very different from those of other age groups. The authors reviewed a total of 16 infant head injury patients under 12 months of age who were treated in our hospital from 1989 to 1997. Birth head injury was excluded. The most common age group was 3-5 months. Early seizures were noted in 7 cases, and motor weakness in 6. Three patients with acute intracranial hematoma and another 3 with depressed skull fracture were operated on soon after admission. Chronic subdural hematomas (SDHs) developed in 3 infants. Initial CT scans showed a small amount of SDH that needed no emergency operation. Resolution of the acute SDH and development of subdural hygroma appeared on follow-up CT scans within 2 weeks of injury. Two of these infants developed early seizures. Chronic SDH was diagnosed on the 68th and 111th days after the injuries were sustained, respectively. The third patient was the subject of close follow-up with special attention to the evolution of chronic SDH in view of our experience in the previous 2 cases, and was found to have developed chronic SDH on the 90th day after injury. All chronic SDH patients were successively treated by subduro-peritoneal shunting. In conclusion, the evolution of chronic SDH from acute SDH is relatively common following infantile head injury. Infants with head injuries, especially if they are associated with acute SDH and early development of subdural hygroma, should be carefully followed up with special attention to the possible development of chronic SDH

Chronic Disease↗

PubMed1998

Small-subunit ribosomal DNA of an ectomycorrhizal fungus tricholoma matsutake: sequence, structure and phylogenetic analysis.

A 2861 bp nucleotide sequence containing Tricholoma matsutake SSU rRNA gene and its flanking regions was determined and analyzed. Comparison with known SSU rDNA sequences and primer extension analysis revealed that the SSU rRNA coding region and intergenic spacer 2 (IGS2) are 1805 bp and 1043 bp in length, respectively. The IGS2 has an imperfect direct repeat (type 1) homologous to the region downstream to the 5S rRNA gene and the three imperfect tandem direct repeats (type 2) upstream to the SSU rRNA-encoding sequence. Structural analysis by a comparative method showed that the overall secondary structure of the SSU rRNA is generally similar to that of S. cerevisiae, whereas the secondary structures of the V4 regions predicted by the thermodynamics-based method showed different configurations between distantly related taxa, implying that these structural differences can provide phylogenetically informative features. Phylogenetic trees based on both the aligned SSU rRNA sequences with almost full-length sequences and V4 sequences revealed that T. matsutake is very closely related to other basidiomycetes belonging to Agaricales. Thus we propose that the V4 region is also a good source for the inference of phylogeny to support the SSU rRNA phylogeny.

Base Sequence↗

PubMed1998

Syntheses and cytotoxicities of four stereoisomers of muricatacin from D-glucose.

Four stereoisomers of muricatacin 1a-d were prepared by the reaction of corresponding aldehydes 4a-d, which in turn were prepared from D-glucose, with the anion of triethylphosphonoacetate followed by reduction and cyclization under acidic conditions. Cytotoxicities of four stereoisomers were tested against in vitro A-549 cell line as well as MCF-7 cell line. Stereochemistry at C4 and C5 position of muricatacin did not affect the cytotoxicities significantly.

Antineoplastic Agents↗

PubMed1997

Prolonged ethanol intake increases D2 dopamine receptor expression in the rat brain.

Dopamine via interaction with its receptor is known to be involved in the behavioral and endocrine actions in the mammalian brain. Behavioral effects produced by ethanol appear to be due to its actions on the dopaminergic system. In the present study using in situ hybridization histochemistry and RNase protection assay, the effect of prolonged ethanol intake on the expression of D2 dopamine receptor mRNA was examined in the rat brain. Specific D1 and D2 receptor mRNA signals were detected in the caudate putamen, nucleus accumbens, olfactory tubercle, hippocampus, dentate gyrus, and amygdaloid complex of the rat brain. Within the hypothalamus, the level of receptor mRNA was low in most nuclei with a somewhat higher level in the arcuate nucleus. Only the supurachiasmatic nucleus showed moderate to dense dopamine receptor mRNAs. Prefrontal cortex showed hybridization signals but their intensity was very low. A considerable amount of D2 mRNA was localized in the substantia nigra but D1 mRNA was not. Ethanol (10%) intake for 5 weeks increased both the density of hybridization signal and number of cells expressing D2 dopamine receptor mRNA in the caudate putamen, and nucleus accumbens, but not in the olfactory tubercle. RNase protection assay revealed about a 1.5-fold increase in the D2 dopamine receptor mRNA level in the corpus striatum. These results provide a basis for the involvement of dopamine D2 receptor expression in alcoholism.

Alcohol Drinking↗

PubMed1995

Cementless total hip arthroplasty with AML, PCA and HGP prostheses.

Two hundred and fourteen patients who had 270 cementless hip prostheses were followed for 2 to 8 years. PCA (Porous-Coated Monatomic), AML (Monatomic Medullary Locking) and HGP (Harris-Galante-Porous) femoral stems and acetabular cups were used without any preference for the prostheses. The overall clinical results were similar for the three prostheses with average Harris hip scores of 93, 93 and 91 respectively. Four PCA prostheses had radiological aseptic loosening and one was revised because of polyethylene wear. There was no loosening in the AML and HGP prostheses. Pain in the thigh, usually slight, occurred in 17% of AML, 21% of PCA and 19% of HGP prostheses. Five years after operation, radiological changes such as migration, calcar remodelling and radiolucent lines were the same for the 3 prostheses, but bony ingrowth was greater with the AML femoral stems.

Adult↗

PubMed1994

Vascular injury during total hip arthroplasty: the anatomy of the acetabulum.

We encountered a massive retroperitoneal haemorrhage due to perforation of the external iliac vein by a drill tip passing through the antero-superior quadrant of the acetabulum during cementless total hip arthroplasty. An anatomical study of the acetabulum was undertaken to determine the safe zones for transacetabular screw fixation. Five cadavera were studied to find the proper locations for screws using acetabular quadrants. The postero-superior and postero-inferior acetabular quadrants have good bone stock and are safe for the transacetabular replacement of screws. The antero-superior and inferior quadrants should be avoided. Screws placed in these quadrants may damage the external iliac artery and vein or the obturator vessels.

Acetabulum↗

PubMed1994

Growth hormone replacement therapy in adults with growth hormone deficiency; thrice weekly low dose administration.

Recent reports on growth hormone (GH) therapy have shown that GH has various beneficial effects in GH deficient adults. In most of these studies, GH was administered daily. Because GH is still expensive and has to be delivered by subcutaneous injection, we studied the 6-month therapeutic effects of thrice weekly GH injection therapy and compared it with daily therapy. Twenty eight adult patients with GH deficiency were randomly assigned into group 1 (ten cases, thrice weekly injections of GH), group 2 (nine cases, daily injections), and group 3 (nine cases, placebo injections). Lean body mass, serum basal GH levels, and insulin-like growth factor 1 levels significantly increased after six months of GH therapy in both groups 1 and 2. According to computed tomography, the mean mid-thigh muscle mass significantly increased in group 1, while the visceral fat mass significantly decreased in group 2. GH levels significantly increased exercise rate-pressure product and hand grip strength only in group 1. These results suggest that thrice weekly injections of GH are as effective as daily injections in GH deficient adults.

Adult↗

PubMed1993

[Evaluation of radiation doses in mammography].

A dedicated X-ray mammography was introduced to our hospital from 1987 and an imaging receptor of xeroradiography was applied. We reported previously that the average air exposure was 0.79R and that the absorption dose of skin was 1.00 rad. These data are similar to literature reports. Screen-film mammography was introduced recently. To select the best breast imaging and the least radiation exposure, diverse methods were investigated. A dosimetry (Capintec model 192) and a PS-033 parallel ionization chamber were applied to compare the absorption dose on polystyrene phantom between various exposure factors, the application of breast clamp and the size of exposure field. Retrospective estimation of the radiation dose was obtained from the exposure factors of previous mammography since July, 1990 to May, 1992. There were 1035 xeromammographic examinations and 358 examinations with medium-speed screen-film mammography. Another 61 craniocaudal and 96 mediolateral projections with high-speed screen-film mammography were recruited during the recent two months. An ionization chamber (Exradin, Shonka-Wyckoff A5) with an electrometer (Keithley 617) wer selected to obtain the dose equivalent from air exposure between selected exposure factors. The radiation dose of mammography is linearly correlated with voltage/kV and current/mAs. The application of a breast clump reduces 10% of the skin dose. The average exposure factors of xeromammography are 45.6 kV, 163.5 mAs. These results remain the same as in our previous report. Xeromammography has a greater exposure to air, estimated average glandular dose and absorbed dose than screen-film mammography. The mean exposure factor of rapid screen-film mammography gains half the value of medium screen-film mammography, ie. 26.6 kV, 87.0 mAs vs. 26.0 kV, 164.5 mAs.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗

PubMed1992

Permeability of arachidonic acid metabolites through the round window membrane in chinchillas.

Our previous studies showed that samples of middle ear effusion contain high concentrations of arachidonic acid metabolites (AAMs); both prostaglandins (PGs) and leukotrienes (LTs). Since abnormal levels of AAMs in the perilymph seem to be associated with salicylate ototoxicity and the round window membrane (RWM) is the most likely route of entry from the middle ear to the inner ear, it would be important to know the permeability of AAMs through the RWM. Permeability of AAMs was determined by applying labeled and standard representatives AAMs on the RWM and counting radioactivity or measuring concentrations of AAMs in perilymph at different time intervals. Using chinchillas as experimental animals, samples of perilymph were obtained through a fenestration made at the helicotrema of the cochlea after 0.5, 1, 2, and 4, hours from placing tritiated or standard PGE2, 6-keto-PGF1 alpha, LTB4, LTC4 and 15-hydroxyeicosatetraenoic acid (HETE) over RWMs. Radioactivity in the perilymph was determined by a scintillation counter and concentrations of AAMs were measured by reverse phase high performance liquid chromatography (RP-HPLC) and radioimmunoassay. AAMs, which are twenty carbon fatty acids, were found to cross the RWM readily. Radioactivity and concentrations of AAMs in perilymph were detected in 30 minutes and peaked by one hour from the application of AAMs on the RWM. The results of this study suggest that AAMs such as PGs and LTs present in the middle ear fluid can cross the RWM readily and enter into the perilymphatic space of the cochlea. Sensorineural hearing loss observed in chronic otitis media could be mediated by PGs and LTs in the middle ear effusion crossing over to the inner ear through the RWM.

Adrenal Cortex Hormones↗

PubMed1991

Changes of cardiac output during treadmill exercise by impedance cardiography.

Nine athletes and ten nonathletes were selected randomly to study the changes of cardiac function during exercise by impedance cardiography. The speed of the treadmill was maintained at 3.4 mph, and its grade was increased by 1% (Balke protocol). The exercise was continued until the target heart rate (THR), 85% of maximum oxygen uptake (VO2max). The measured parameters for pre- and post-exercise were stroke volume (SV), heart rate (HR), and cardiac output (CO). Average stroke volume of athletes at pre-exercise, 71.1 ml, was higher than that of nonathletes, 64.6 ml, and stroke volume of the former at post-exercise, 97.0 ml, was also higher than that of the latter, 85.2 ml. Therefore, despite the lower heart rate, cardiac outputs of athletes at pre- and post-exercise, 4.98 and 16.3 L/min, were higher than those of nonathletes, 4.87 and 14.2 L/min. For the second phase of the study, cardiac outputs of three subjects were measured during the continuous treadmill exercise with newly developed electrodes and shoes for minimizing motion artifact. Though there were several studies measuring cardiac output during continuous bicycle exercise, this is thought to be the first study in the world measuring cardiac output during continuous treadmill exercise without aid of ensemble averaging.

Adult↗

PubMed1991

Induction of osteochondromas by periosteal resection.

Forty immature and 40 mature rabbits which received periosteal resection from the proximal metaphyses or diaphyses of tibiae were evaluated for the occurrence of osteochondromas at the sites of periosteal defects. Thirteen of 20 immature tibiae with the periosteal defects at their proximal metaphyses showed osteochondromas covered by hyaline cartilage caps. We assume that the occurrence of osteochondroma at the metaphyseal region of growing long bone, where the periosteal defects were made, is due primarily to a decrease in the power of the periosteum to control the circumferential growth of the metaphysis, and is due secondarily to an abnormal proliferation of cartilage progenitors located in Ranvier's groove.

Animals↗

PubMed1991

Cementless total hip arthroplasty with PCA prosthesis.

Eighty-one cases of cementless porous-coated total hip arthroplasties in 74 patients were analyzed. Hip rating scores as described by Harris were used, and AP and lateral radiographs were made serially: preoperatively, 3 months, 6 months, 1 year, and 2 years postoperatively. The average postoperative hip rating score was 91 points (range: 76 to 100 points) at 1 year and 93 points (range: 74 to 100 points) at 2 years. The overall clinical results were satisfactory in these patients at both 2 and 4 years. However, slight to mild thigh pain was observed in 16 (19.8%) of 81 hips at 2 years, and 10 (21.3%) of 47 hips at 4 years postoperatively. Moderate to severe limp was seen in 11 (13.6%) of 81 hips at 2 years and seven (14.9%) of 47 hips at 4 years postoperatively.

Adult↗

PubMed1991

Bilateral fracture-dislocation of the sacroiliac joint: a case report.

Bilateral fracture-dislocation of the sacroiliac joint with intrapelvic displacement of the sacrum is a rare and extremely severe injury. We treated a patient with bilateral fracture-dislocation of the sacroiliac joint using a nonoperative method and obtained an excellent functional result.

Adult↗

PubMed1990

Effects of ketamine on contractile responses in vascular smooth muscle.

This study was designed to determine the effects of ketamine on contractions induced by norepinephrine (NE), K+ or histamine (Hist) and on agonist-induced calcium mobilization, in rabbit thoracic aorta with or without endothelium. Contractile responses to NE, K+ or Hist were markedly attenuated by prior exposure to ketamine. Subsequent addition of ketamine to the rabbit aorta undergoing an isometric contraction induced by NE, K+ or Hist also decreased the contractile responses in a calcium ion concentration-dependent manner. Preincubation with ketamine produced a concentration-dependent inhibition of contractile responses elicited by the addition of calcium ion (1.6 mM) to a Ca(++)-free depolarizing solution. However, the phasic contraction produced by NE with 2mM lanthanum pretreatment, which is release of intracellular calcium, was also inhibited by ketamine. Moreover, the tonic contraction produced by NE after depletion of the agonist-releasable pool of intracellular calcium, which is thought to be due to calcium influx, was depressed by ketamine. These data suggest that ketamine relaxes NE-contracted rings of rabbit thoracic aorta by decreasing calcium entry and by producing an extracellular calcium-independent relaxant effect.

Animals↗