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Biomedical subjects

K Lee

Publications and source records attributed to K Lee.

At least 775 records · Page 43Linked to original sources
PubMed1988

Interaction of human parathyroid hormone-related peptide with parathyroid hormone receptors in clonal rat osteosarcoma cells.

Synthetic peptides corresponding to the amino-terminal region of the human parathyroid hormone-related peptide (hPTHrp) were used to characterize the interaction of hPTHrp with parathyroid hormone (PTH) receptors in clonal rat osteosarcoma cells (ROS 17/2.8). Both hPTHrp-(1-34) and [Tyr40]hPTHrp-(1-40) showed full agonist activity in stimulating cyclic AMP accumulation in ROS cells; human PTHrp-(1-34) was approximately 2.5-fold as potent as hPTH-(1-34). Both [Tyr-40]hPTHrp-(3-40) and hPTH-(3-34) inhibited the cyclic AMP increase induced by either hPTHrp or PTH with parallel dose-inhibition curves. Binding to intact ROS cells of a 125I-labeled [Tyr40]hPTHrp-(1-40) (125I-[Tyr40]hPTHrp-(1-40)) which retains full biological activity was time- and temperature-dependent and reversible. Binding of 125I-[Tyr40]hPTHrp-(1-40) and 125I-labeled [Nle8, Nle18, Tyr34]bovine PTH-(1-34)NH2 to ROS cells was competed for, to the same extent and with the comparable potency, by either unlabeled hPTHrp or PTH peptides. The binding capacity and affinity of receptors in ROS cells were strikingly similar for hPTHrp and PTH. Affinity cross-linking with either radioligand resulted in high affinity, specific labeling of an apparently identical macromolecule centering at Mr = 80,000, which was detected in sodium dodecyl sulfate-polyacrylamide gel electrophoresis in both reducing and nonreducing conditions. The data indicate that hPTHrp and PTH, their amino-terminal fragments at least, interact with the identical receptors with regard to affinity, capacity, specificity, and physicochemical characteristics in osteoblastic ROS 17/2.8 cells.

Animals↗
PubMed1988

Nuclease SP: a novel enzyme from spinach that incises damaged duplex DNA preferentially at sites of adenine.

A novel endonuclease has been isolated from extracts of spinach leaves (Spinacia oleracea). The enzyme has been purified by a series of column chromatography steps and has a molecular size of approximately 43,000 daltons. The spinach endonuclease cleaved double stranded DNA damaged by ultraviolet light or cis-diamminedichloroplatinum (II) primarily at sites of adenine when end-labelled DNA fragments of defined sequence were employed as substrates. The nature of the structural distortion contained in damaged, duplex DNA appears to be an important determinant for endonuclease cleavage. DNA helical distortions produced by UV light-induced (6-4) pyrimidine-pyrimidone photoproducts, but not cyclobutane pyrimidine dimers are recognized by the enzyme. The DNA cleavage products generated by the enzyme contain 3'-hydroxyl and 5'-phosphoryl termini. Single stranded DNA and RNA are hydrolyzed by the spinach endonuclease. This enzyme, which we call nuclease SP, is similar in several respects to other single-strand-specific nucleases such as N. crassa and mung bean nucleases and may function in DNA repair and/or recombination events in spinach cells. Nuclease SP should be a useful tool for the analysis of (6-4) photoproducts occurring in duplex DNA.

Base Sequence↗
PubMed1988

Yeast redoxyendonuclease, a DNA repair enzyme similar to Escherichia coli endonuclease III.

A DNA repair endonuclease (redoxyendonuclease) was isolated from bakers' yeast (Saccharomyces cerevisiae). The enzyme has been purified by a series of column chromatography steps and cleaves OsO4-damaged, double-stranded DNA at sites of thymine glycol and heavily UV-irradiated DNA at sites of cytosine, thymine, and guanine photoproducts. The base specificity and mechanism of phosphodiester bond cleavage for the yeast redoxyendonuclease appear to be identical with those of Escherichia coli endonuclease III when thymine glycol containing, end-labeled DNA fragments of defined sequence are employed as substrates. Yeast redoxyendonuclease has an apparent molecular size of 38,000-42,000 daltons and is active in the absence of divalent metal cations. The identification of such an enzyme in yeast may be of value in the elucidation of the biochemical basis for radiation sensitivity in certain yeast mutants.

Base Sequence↗
PubMed1988

Effects of hypoxia on contractile responses of rabbit aortic strips to transmural electrical stimulation.

To clarify the effects of hypoxia on adrenergic transmission, we examined the contractile responses of isolated rabbit aortic strips to electrical stimulation, the concentration-response relationships for noradrenaline and KCl, and the electrical stimulation-evoked overflows of total [3H] and [3H]noradrenaline from strips preloaded with [3H]noradrenaline in media equilibrated with gas mixtures containing various concentrations of O2. Contractile responses to electrical stimulation were completely inhibited by tetrodotoxin and alpha-adrenoceptor antagonists such as phentolamine and phenoxybenzamine, but were not affected by indomethacin. When the concentration of O2 in the gas mixture was decreased from 95% to 20%, the contractile responses to electrical stimulation remained unchanged, but as the concentration of O2 was further decreased, the responses were inhibited concentration-dependently. At 0% O2, the response was inhibited by about 80% when compared with control values obtained at 95% O2, and the electrical stimulation-evoked overflows of total [3H] and [3H]noradrenaline into the superfusates were decreased by about 55%. At 0% O2, the concentration-response curve for exogenous noradrenaline was shifted to the right about 50-fold and the maximum response was decreased by 25%. The maximum contractile responses of aortic strips from animals pretreated with reserpine or 6-hydroxydopamine to high KCl were decreased slightly (about 15%). These results suggest that inhibition of adrenergic transmission under hypoxic conditions is mainly the result of a decrease in the stimulus-evoked release of noradrenaline and of a decrease in the affinity of alpha-adrenoceptor for noradrenaline and/or inhibition of signal transduction mechanisms, although hypoxia also causes a slight decrease in the contractility of vascular smooth muscle.

Animals↗
PubMed1988

A nonisotopic method for determination of the in vivo activities of tyrosine hydroxylase in the rat adrenal gland.

A rapid and reliable method for determination of in vivo activities of tyrosine hydroxylase in the rat adrenal gland is presented. This method involves determining the rate of accumulation of 3,4-dihydroxyphenylalanine (Dopa) in the adrenal gland after decarboxylase inhibition by NSD 1015, using HPLC with electrochemical detection after purification of the acid-deproteinized tissue extract with Bio-Rex 70 columns followed by alumina batch method. Purification of the sample with alumina adsorption alone, a method usually used for purification of catecholamines and Dopa, was ineffective: epinephrine and norepinephrine, which are present in high concentrations, interfered with an accurate determination of Dopa, and dopamine, which is retained strongly on the reverse-phase column, interfered with a rapid analysis. Purification with Sephadex G-10 columns followed by alumina adsorption was also ineffective. After purification with columns of weak cation-exchange resins such as Bio-Rex 70 or Amberlite CG-50 followed by alumina adsorption, most of the epinephrine and norepinephrine was removed and dopamine was eliminated. Thus a rapid and accurate determination of Dopa could be made. Of the two cation exchangers, Bio-Rex 70 was more effective. Accumulation of Dopa in the adrenal gland was linear up to 30 min after administration of NSD 1015 and a plateau was reached with doses over 10 mg/kg. Using this method, we investigated the effects of immobilization stress, reserpine, and hypoxia on in vivo activities of tyrosine hydroxylase in the adrenal gland.

Adrenal Glands↗
PubMed1988

Humoral and cell-mediated immune responses in non-pregnant heifers following infection and vaccination with Brucella abortus.

Humoral and cell-mediated-immune responses to Brucella abortus were observed in non-pregnant heifers following infection alone; infection followed by vaccination; vaccination followed by infection; and vaccination alone. The humoral responses, as measured by the Rose Bengal test (RBT), complement fixation test (CFT), indirect haemolysis test (IHLT) and the enzyme-linked immunosorbent assay (ELISA) tended to be immediate and transient following infection alone, infection following vaccination and vaccination alone. However, when vaccination was superimposed on infection, reactions were maintained for at least 2 years. The cell-mediated-immune (CMI) responses were assessed by the lymphocyte stimulation test. The responses occurred after the humoral responses had peaked and were present for periods of 6-22 weeks. However, the level of stimulation was greater following infection than following vaccination, and the response when vaccination was superimposed on infection was present for less than 6 months.

Animals↗
PubMed1988

Sleep patterns and stability in perimenopausal women.

Women between the ages of 40 and 59 years were classified as pre-, peri-, and postmenopausal, with and without hot flash symptoms, for comparison of somnographic sleep variables. Few differences in sleep variables were noted between the groups. However, peri- and postmenopausal women experiencing hot flashes (symptomatic) tended to have lower sleep efficiencies than those not experiencing hot flashes. As well, rapid-eye-movement (REM) latency was longer (p less than 0.05) in the symptomatic women (means = 94.2 min) than in the nonsymptomatic women (means = 71.4 min). Although an age difference existed between the menopausal status groups, it was less than a decade and a main group effect for sleep efficiency and REM latency was seen while controlling for age and/or depression.

Adult↗
PubMed1988

Retinal arteriolar changes in patients with hyperlipidemias.

Hyperlipidemia is a known risk factor for atherosclerosis systemically. To determine whether it causes changes in retinal arterioles, a group of 26 patients with hyperlipidemia (serum cholesterol or triglycerides greater than 95th percentile for age) were compared with 22 "normal" patients (comparison group) and 35 patients with contralateral branch retinal vein occlusion to determine the presence or absence of changes in the retinal arterioles. The arterioles of all groups were evaluated in a masked fashion to determine the presence of arteriovenous nicking, "sclerosis," narrowing, and tortuosity. No differences in the retinal arterioles between the patients with hyperlipidemia and the comparison group were found. Patients with branch retinal vein occlusion in the contralateral eye had significantly more arteriovenous nicking and "sclerosis" than the other groups. These data suggest that hyperlipidemia by itself is not a risk factor for the development of retinal arteriolar changes. Thus examining the retinal arterioles would not be helpful in detecting hyperlipidemia.

Arterioles↗
PubMed1988

Left ventricular function during chronic endotoxemia in swine.

Cardiac performance was studied in 15 chronically instrumented awake pigs during chronic endotoxemia (CET) induced by intravenous infusion of low doses of endotoxin. We sought to test the hypothesis that left ventricular inotropic state was depressed during the stage of chronic endotoxemia when cardiac output, heart rate, and left ventricular systolic pressures are elevated, termed "hyperdynamic sepsis". Left ventricular pressure, internal short axis diameter (SAX), pulmonary artery blood flow, and electrocardiogram were recorded. After initial surgical preparation, each pig was observed for 7-10 days to measure representative basal values. Each pig was then reoperated on day 10 to implant an endotoxin-loaded osmotic pump whose output, infused Salmonella enteritidis endotoxin at a rate calculated to be 10 micrograms.kg-1.h-1 for up to 7 days. Cardiac performance was monitored by measuring dP/dt, heart rate, stroke volume, end-diastolic diameter, percent change in diameter, and the slope of the end-systolic pressure diameter relationship (ESPDR). Data from the basal days were pooled and compared with the data obtained each day of CET by two-way analysis of variance. Ten of 15 pigs survived more than 2 days of CET; 5 died before the morning of the second CET day. The surviving pigs demonstrated elevated systolic pressures, left ventricular maximum rate of pressure development (+dP/dtmax and -dP/dtmax), heart rates, and cardiac output. However, both ESPDR and percent SAX shortening were significantly depressed during both CET days. We conclude that cardiac inotropic state is depressed during hyperdynamic sepsis as indicated by the load-independent parameter ESPDR and confirmed by depressed percent SAX shortening.

Analysis of Variance↗
PubMed1988

Cytogenetic study of silver-staining NOR in 8-cell-stage mouse blastomeres fused to 1-cell-stage embryos.

Isolated blastomeres from 8- to 16-cell-stage embryos were fused by standard micromanipulatory means with either unfertilized eggs or fertilized or haploid parthenogenetically activated pronuclear-stage embryos. The hybrid eggs/embryos were incubated overnight in the presence of Colcemid until they had entered the first cleavage division. Air-dried chromosome preparations were then stained with silver nitrate in order to detect active nucleolar organizing regions (NOR). While control unfertilized eggs and 1-cell-stage fertilized and parthenogenetically activated embryos showed no evidence of silver-staining NOR-positive regions, the metaphase plates from 8- to 16-cell embryos showed characteristic NOR-positive regions, while their interphase nuclei also showed a characteristic reticular staining appearance. When hybrids between blastomere nuclei and unfertilized eggs were examined, none of the blastomere nuclei entered mitosis. However, when hybrids between blastomere nuclei and fertilized embryos were examined, in two thirds of the embryos, a single blastomere-derived diploid metaphase plate was present in association with two pronuclear-derived haploid metaphase plates. In most instances, the blastomere-derived chromosomes did not display silver-nitrate-staining NOR. Similar findings were observed when the blastomere-derived chromosomes in hybrids between blastomere nuclei and haploid parthenogenetic embryos were analysed. In the majority of cases, when blastomere nuclei remained in interphase, the characteristic silver-nitrate-staining fine reticular material either was not seen, or the nuclear contents were dispersed into clumps of chromatin-like material. Occasionally, the diploid chromosomes in the hybrids displayed morphological abnormalities. Our findings suggest that the cytoplasm of activated (but not nonactivated) 1-cell embryos is capable of influencing the nucleolar activity of the introduced 8- to 16-cell nuclei, effectively erasing from their chromosomes the memory of at least three previous rounds of rRNA synthesis.

Animals↗
PubMed1988

Assessment of the need for a home intravenous antibiotic program.

Home intravenous antibiotic programs (HIAP) have been in existence for more than 12 years. The feasibility of such a program at the UBC-HSCH was assessed. The health records of all patients discharged between April 1, 1985 to March 31, 1987 with a diagnosis of septic arthritis, osteomyelitis, pyelonephritis, skin and soft tissue infections in the diabetic, prostatitis or infective endocarditis were reviewed retrospectively. Selection criteria to determine eligibility of patients for a HIAP were derived from the literature and grouped into three areas: patient, disease, and treatment criteria. From a total of 184 patients identified, 14 diabetic patients were excluded. The exclusion of patients with hospital stays of less than five days or those that did not have the appropriate diagnosis resulted in 77 patients available for more extensive review. Sixteen of 77 patients (20.8%) were judged eligible for a HIAP: 1 of 22 with pyelonephritis; 4 of 12 with septic arthritis; 5 of 21 with prostatitis; 2 of 12 with infective endocarditis; 4 of 10 with osteomyelitis. A total of 81 hospital bed days ($20,250.00) might have been saved if a HIAP was in place.

British Columbia↗