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Biomedical subjects

L Lee

Publications and source records attributed to L Lee.

At least 235 records · Page 13Linked to original sources
PubMed1992

Characterization of two plasmids from Campylobacter jejuni isolates that carry the aphA-7 kanamycin resistance determinant.

Two small plasmids of 11.5 and 9.5 kb, each carrying an aphA-7 kanamycin phosphotransferase gene, were studied. The MICs of kanamycin for the two human Campylobacter jejuni isolates harboring the plasmids were 10,000 and 5,000 micrograms/ml, while the MICs of amikacin were 32 and 8 micrograms/ml, respectively. The MICs of gentamicin and tobramycin were less than or equal to 2 micrograms/ml for both isolates. The restriction endonuclease maps of the plasmids were similar, with the larger plasmid showing two discrete regions of additional DNA. When the aphA-7 gene from each plasmid was cloned into pBR322, the aphA-7 gene expressed the kanamycin resistance phenotype in Escherichia coli. For transformants containing the cloned aphA-7 gene, kanamycin MICs were greater than or equal to 128 micrograms/ml. The aphA-7 gene was also subcloned from the plasmid pFKT4420 into the E. coli-Streptococcus shuttle vector pDL278 and was transformed into Streptococcus gordonii Challis. For streptococcal transformants containing the novel plasmid, kanamycin MICs were 4,000 micrograms/ml. In the presence of a tetracycline resistance plasmid, both small plasmids could be mobilized during conjugal matings to Campylobacter coli recipients.

Amikacin↗
PubMed1992

Endothelium-dependent relaxation and L-arginine metabolism in genetic hypertension.

This study characterizes the effects of L-arginine and NG-monomethyl L-arginine on dilator responsiveness of vascular tissue from Wistar-Kyoto rats and stroke-prone spontaneously hypertensive rats. Rings of abdominal aorta were suspended in tissue baths for measurement of isometric force. After contraction induced by phenylephrine, cumulative addition of acetylcholine, L-arginine, or A23187 to the muscle bath caused a similar relaxation of aortic rings in both animal groups. To test the hypothesis that arginine metabolism is altered in hypertension, aortic rings were incubated with NG-monomethyl L-arginine. NG-monomethyl L-arginine (10-300 microM) did not affect contractile responses to phenylephrine (10(-10) to 10(-4) M) in either animal group (EC50, 10(-7) M). Exposure of aortic rings to NG-monomethyl L-arginine resulted in a greater inhibition of relaxation response to acetylcholine (10(-10) to 10(-6) M) in hypertensive animals. NG-monomethyl L-arginine (300 microM) caused complete inhibition of relaxation to acetylcholine in the hypertension group. Incubation with L-arginine (10-100 microM) overcame the inhibition of acetylcholine-induced relaxation produced by NG-monomethyl L-arginine in both groups. Exposure of aortic ring segments to NG-monomethyl L-arginine attenuated relaxation responses to A23187 (10(-10) to 3 x 10(-6) M) in both groups. L-Arginine-induced reversal of the inhibitory effect of NG-monomethyl L-arginine on the relaxation responses to A23187 was similar between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Comparison of velopharyngeal gap size in patients with hypernasality, hypernasality and nasal emission, or nasal turbulence (rustle) as the primary speech characteristic.

Velopharyngeal insufficiency was assessed using multiview videofluoroscopy on eight patients with hypernasality, 10 patients with hypernasality and audible nasal emission, and 10 patients with nasal turbulence (rustle). Patients demonstrating hypernasality, with or without audible nasal emission, were found to have a significantly larger velopharyngeal gap than those with nasal rustle. This finding suggests that the degree of the velopharyngeal insufficiency can be predicted to some extent based on perceptual assessment. If the presence of a nasal rustle suggests a small velopharyngeal gap, despite the severe distortion of speech, then speech therapy should be considered prior to surgery in those cases.

Adolescent↗
PubMed1992

Retinoblastoma: messenger RNA for interphotoreceptor retinoid binding protein.

Surgically excised retinoblastomas from 14 patients (age range nine months to two years) were assessed by immunocytochemistry for the expression of photoreceptor-specific proteins and neuronal and glial cell markers. Adjacent tissues were examined for messenger RNA expression of interphotoreceptor retinoid-binding protein (IRBP) using Northern blots. For immunocytochemical stains (ABC method), monoclonal and polyclonal antibodies included S-Ag, rhodopsin, neuron specific enolase (NSE), glial fibrillary acidic protein (GFAP), IRBP, neural adhesion molecule (N-CAM), and rod and cone specific transducin (TR alpha and TC alpha). Histopathology revealed mostly poorly differentiated tumors with necrosis and lack of Flexner-Wintersteiner rosettes. Immunocytochemical staining showed focal IRBP expression in one of the tumors and S-antigen in two cases. Immunoreactivity with rhodopsin was negative. N-CAM, a neural adhesive protein which appears to be involved in the regulation of adhesive interaction during neuronal differentiation, was positive except in two cases. All tumors showed immunoreactivity with NSE, whereas GFAP staining was limited to the perivascular glial tissue confirming the essential neuronal nature of retinoblastoma cells. TC alpha was detected in all tumors and TR alpha in one case. Messenger RNA for IRBP was detected in tumors in which IRBP immunoreactivity could not be detected.

Antibodies, Monoclonal↗
PubMed1992

Eicosapentaenoic acid inhibits endothelium-dependent relaxation to acetylcholine in guinea pig coronary resistance vessels.

Dietary supplementation with eicosapentaenoic acid (EPA) alters arachidonate metabolism. This study characterizes the effect of dietary EPA on endothelium-dependent vasodilation to acetylcholine (ACH) and ATP in guinea pig coronary resistance vessels. Guinea pigs were fed standard chow (n = 6), standard chow+sesame seed oil (n = 6), or standard chow+menhaden fish oil (17% EPA; n = 6). Coronary vasodilations were examined in the isolated, potassium-arrested heart utilizing a modified Langendorff preparation. Coronary vessels were constricted with prostaglandin F2 alpha and relaxed with ACH (5.5 x 10(-9)-10(-6) moles) or ATP (10(-10)-10(-7) moles). Endothelium-dependent dilations to ACH, but not ATP, were attenuated by dietary supplementation with EPA. To assess the role of the endothelium in modulating vascular responses to agonists following dietary manipulation, the perfusate was stimulated by electrolysis (9 V, 4 Hz, 2 msec) in order to generate free radicals, which we have shown to preferentially damage the endothelium. After endothelial damage, responses to ACH, ATP, and nitroprusside were similar between the dietary groups. In an additional group of standard diet animals (n = 6) experiments were performed to assess the role of prostanoid metabolism in affecting coronary vascular reactivity. Perfusion of hearts with indomethacin (14 microM) reduced endothelium-dependent vasodilations to ACH (5.5 x 10(-9)-10(-6) moles), but not to ATP (10(-10)-10(-7) moles). After endothelial damage, infusion of ACH resulted in vasoconstriction, whereas vasodilation responses to ATP were absent. We conclude that dietary supplementation with EPA inhibits endothelium-dependent dilations to ACH in guinea pig coronary microvessels. These diet-related differences in vascular reactivity may be related to the fish-oil-induced alteration of vasodilator prostaglandin metabolism. In the coronary bed, different endothelial factors appear to mediate relaxation to ACH and ATP.

Acetylcholine↗
PubMed1992

Characterization of a class 3 tyrosine kinase.

In an effort to identify unique tyrosine kinases found in human leukemia cell lines, we utilized polymerase chain reaction (PCR) technology and degenerate oligonucleotide primers to produce a cDNA library of kinase catalytic domains found in the human monocytic cell line AML-193. This search yielded a member of the class 3 tyrosine kinases closely related to the murine kinase FD-22. Previous work has identified this kinase as JAK1. This class of tyrosine kinases is characterized by being ubiquitously expressed, lacking both a ligand-binding domain and a SH2 domain, while containing a second domain similar to a degenerate kinase domain. Our studies focused on the further characterization of this class 3 tyrosine kinase using Northern blot analysis to demonstrate an increase in steady-state mRNA by interferon-gamma in human monocytes. A human-hamster somatic cell hybrid panel and linkage mapping was used to assign JAK1 (aml-116) to human chromosome 1.

Alleles↗
PubMed1992

Propionibacterium acnes-enhanced lens-induced granulomatous uveitis in the rat.

Propionibacterium acnes (Corynebacterium parvum) is being implicated more frequently as a cause of intraocular inflammation following cataract surgery. In addition to its role as an infectious agent, P. acnes also may possess adjuvant-like or adjuvant-enhancing properties. The presence of this organism in an eye with residual lens material after extracapsular cataract surgery could augment inflammation resulting from a phacoantigenic (phacoanaphylactic) response. We have modified an established rat model of lens-induced granulomatous uveitis (LIGU) to examine the adjuvant properties of P. acnes. Our results suggest that P. acnes effectively potentiates LIGU.

Adjuvants, Immunologic↗
PubMed1991

Identification of the ATP binding sites of the carbamyl phosphate synthetase domain of the Syrian hamster multifunctional protein CAD by affinity labeling with 5'-[p-(fluorosulfonyl)benzoyl]adenosine.

The ATP analogue 5'-[p-(fluorosulfonyl)benzoyl]adenosine (FSBA) was used to chemically modify the ATP binding sites of the carbamyl phosphate synthetase domain of CAD, the multifunctional protein that catalyzes the first steps in mammalian pyrimidine biosynthesis. Reaction of CAD with FSBA resulted in the inactivation of the ammonia- and glutamine-dependent CPSase activities but had no effect on its glutaminase, aspartate transcarbamylase, or dihydroorotase activities. ATP protected CAD against inactivation by FSBA whereas the presence of the allosteric effectors UTP and PRPP afforded little protection, which suggests that the ATP binding sites were specifically labeled. The inactivation exhibited saturation behavior with respect to FSBA with a K1 of 0.93 mM. Of the two ATP-dependent partial activities of carbamyl phosphate synthetase, bicarbonate-dependent ATPase was inactivated more rapidly than the carbamyl phosphate dependent ATP synthetase, which indicates that these partial reactions occur at distinct ATP binding sites. The stoichiometry of [14C]FSBA labeling showed that only 0.4-0.5 mol of FSBA/mol of protein was required for complete inactivation. Incorporation of radiolabeled FSBA into CAD and subsequent proteolysis, gel electrophoresis, and fluorography demonstrated that only the carbamyl phosphate synthetase domain of CAD is labeled. Amino acid sequencing of the principal peaks resulting from tryptic digests of FSBA-modified CAD located the sites of FSBA modification in regions that exhibit high homology to ATP binding sites of other known proteins. Thus CAD has two ATP binding sites, one in each of the two highly homologous halves of the carbamyl phosphate domain which catalyze distinct ATP-dependent partial reactions in carbamyl phosphate synthesis.

Adenosine↗
PubMed1991

Histidine pKa shifts accompanying the inactivating Asp121----Asn substitution in a semisynthetic bovine pancreatic ribonuclease.

A semisynthetic RNase, RNase-(1-118).(111-124), consisting of a noncovalent complex between residues 1-118 of RNase (obtained from the proteolytic digestion of RNase A), and a synthetic 14-residue peptide containing residues 111-124 of RNase, exhibits 98% of the enzymatic activity of bovine pancreatic ribonuclease A (EC 3.1.27.5). The replacement of aspartic acid-121 by asparagine in this semisynthetic RNase to form the "D121N" analog reduces kcat/Km to 2.7% of the value for RNase A. In the present work, 1H NMR spectroscopy has been used to probe the ionization states of His12, His105, and His119 in this catalytically defective semisynthetic RNase. A comparison of the observed resonances of D121N with those previously determined by others for RNase A enabled us to assign the C2 proton NMR resonances to individual residues; the assignment of His119 was confirmed by titrating D121N with the fully deuterated peptide, [Asn121]-RNase-(111-124). The observed pKa values of His12, His105, and His119 decrease 0.18, 0.16, and 0.02 pH unit, respectively, as a result of the D121N replacement. Values calculated by using a finite difference algorithm to solve the Poisson-Boltzmann equation (the DELPHI program, version 3.0) and a refined 2.0-A coordinate set for the crystal structure of D121N differ significantly for active site residues His12 (delta pKa = -0.58) and His119 (delta pKa = -0.55) but not for His105 (delta pKa = -0.10). The elmination of bound water from the calculations reduced, but did not reconcile, these discrepancies (His12, delta pKa = -0.36; His119, delta pKa = -0.41).

Animals↗
PubMed1991

1H-NMR studies of bovine platelet factor 4: histidine assignments and interactions with heparin.

1H-NMR spectroscopy has been used to assign and to characterize the two histidine C2H resonances of the heparin binding protein, bovine platelet factor 4. One histidine has a pKa value of 6.51 at 27 degrees C; the second histidine exhibits 2 pKa values of 5.52 and 5.66 at 27 degrees C. The two histidine resonances have been assigned by an analysis of their deuterium exchange kinetics. Both resonances are solvent accessible with half-times of exchange at pH 8.8 of 3.3 and 4.0 days. These two resonances have been assigned by digesting partially deuterated protein with Staphylococcus aureus V-8 proteinase, separating and purifying the resulting peptides, and determining their relative and residual hydrogen content by NMR. The results indicate that His-38 has the lower pKa value and the slower deuterium exchange rate, whereas His-50 has the higher pKa value and the faster deuterium exchange rate at pH 8.8. The 1H-NMR resonance of His-38 of bovine platelet factor 4 is preferentially perturbed by the introduction of heparin. This observation and the presence of His-38 within the belt of positively charged residues around the platelet factor 4 tetramer supports the model of the platelet factor 4-heparin complex in which the polysaccharide crosses over each of the 2 alpha-helices of the 2 dimers at right angles.

Animals↗
PubMed1991

Refined crystal structure of ytterbium-substituted carp parvalbumin 4.25 at 1.5 A, and its comparison with the native and cadmium-substituted structures.

The crystal structure of carp parvalbumin 4.25 containing a 1:1 molar ratio of ytterbium chloride to protein has been refined at 1.5 A resolution by restrained least-squares methods to a crystallographic R value of 0.199. The crystal structure confirms the NMR studies, which suggest that low concentrations of ytterbium cause an extensive displacement of calcium from the EF metal binding site. A comparison of the ytterbium-substituted model with the native and cadmium-substituted structure show no significant differences, except around the substituted EF metal-binding region. The displacement of calcium by ytterbium at the EF site has caused a movement in the polypeptide backbone of Ser-91 and Asp-92. This movement resulted in an increase in the number of oxygen ligands bound to ytterbium in the EF site from seven to eight.

Amino Acid Sequence↗
PubMed1991

Acute effects of diisopropyl fluorophosphate (DFP) on autonomic and behavioral thermoregulatory responses in the Long-Evans rat.

Experiments were designed to assess the mechanisms of diisopropyl fluorophosphate (DFP)-induced changes in thermoregulation of the rat. In one study, male rats of the Long-Evans strain were injected with DFP (s.c.) at doses ranging from 0 to 2.0 mg/kg while maintained at an ambient temperature (Ta) of 20--24 degrees C. Body (Tb) and tail skin (Tt) temperatures were recorded for 5 h post-injection. DFP doses of greater than or equal to 1.0 mg/kg resulted in significant decreases in Tb lasting up to 5 h and increases in Tt lasting up to 1 h post-injection. In a second study, metabolic rate (MR), evaporative water loss (EWL), motor activity (MA), Tb, and Tt were measured at 2 h post-injection of 0, 0.5, 1.0, and 1.5 mg/kg DFP (s.c.) at Ta values of 10, 20, and 30 degrees C. DFP treatment resulted in hypothermia at all three Ta values, but the effect was attenuated at 30 degrees C. MR was significantly reduced at a Ta of 20 degrees C following 1.5 mg/kg, unaffected by DFP at a Ta of 30 degrees C, and stimulated at 10 degrees C following 0.5 mg/kg DFP. EWL was significantly elevated at 30 degrees C following 1.5 mg/kg DFP. MA was significantly reduced following greater than or equal to 1.0 mg/kg DFP at 20 and 30 degrees C and 1.5 mg/kg at 10 degrees C. Tt was elevated and reduced by DFP at Ta values of 30 and 10 degrees C, respectively. In a third study, rats were injected with DFP and placed in a temperature gradient for 1 to 2 h post-injection while selected Ta and Tb were monitored. While both control and DFP-treated rats remained in the cool end of the gradient, rats administered DFP at doses of 1.0 and 1.5 mg/kg were significantly hypothermic. It was also found that Ta values of 10, 20, and 30 degrees C had no effect on DFP-induced inhibition of cholinesterase activity of plasma and erythrocyte fractions of whole blood. Overall, these data support the hypothesis that acute DFP may lower the set-point for the control of body temperature in the rat and demonstrates that the toxicity of DFP is modified by changes in Ta.

Animals↗
PubMed1991

Multicenter registry of angioplasty therapy of cardiogenic shock: initial and long-term survival.

This retrospective multicenter study reviews the role of acute percutaneous transluminal coronary angioplasty in the treatment of cardiogenic shock complicating acute myocardial infarction to determine whether early reperfusion affects in-hospital and long-term survival. From 1982 to 1985, 69 patients were treated with emergency angioplasty to attempt reperfusion of the infarct-related artery. Balloon angioplasty was unsuccessful in 20 patients (group 1) and successful in 49 patients (group 2). Initial clinical and angiographic findings in the groups with unsuccessful and successful angioplasty were similar with respect to age (60.5 +/- 2.3 versus 57 +/- 1.8 years), infarct location (65% versus 65% anterior) and gender (65% versus 67% male). Hemodynamic variables in the two groups, including systolic blood pressure (68 +/- 4.3 versus 73 +/- 1.6 mm Hg), left ventricular end-diastolic pressure (24.4 +/- 2.4 versus 27 +/- 1.0 mm Hg) and initial ejection fraction (28.5 +/- 4% versus 32 +/- 2%), were also similar. Twenty-nine patients received thrombolytic therapy with streptokinase; the overall rate of reperfusion was 34%. Group 1 patients had a short-term survival rate of 20%, compared with 69% in group 2 patients (p less than 0.0005). Thirty-eight patients survived the hospital period and were followed up for 24 to 54 months (mean 32.5 +/- 2.4). Five patients (all in group 2) died during follow-up. The long-term incidence rate of congestive heart failure was 19%, arrhythmia 21%, need for repeat angioplasty 17% and coronary artery bypass grafting 26%. Twenty-four month survival was significantly better in group 2 patients (54%) versus group 1 patients (11%, p = 0.003).(ABSTRACT TRUNCATED AT 250 WORDS)

Angioplasty, Balloon, Coronary↗
PubMed1991

Evidence against a role for insulin-like growth factor II in the autonomous growth of rat 18,54-SF cells.

The 18,54-SF rat cell line multiplies in serum-free medium and has been reported to produce insulin-like growth factor II (IGF-II) and to possess IGF-II/mannose 6-phosphate (Man-6-P) receptors, raising the possibility of autocrine growth stimulation by IGF-II acting through this receptor. When serum-free medium was changed every 24 h the 18,54-SF cells multiplied at the same rate as when the medium was not changed. An antibody (No. 3637) which blocks the binding of IGF-II to the IGF-II/Man-6-P receptor did not decrease or increase the growth rate of the 18,54-SF cells when medium was changed every 24 h. When the medium was changed every 12 h the rate of accumulation of cells in the culture was decreased. Addition of IGF-I or IGF-II at 10, 50, and 100 ng/ml every 12 h did not correct this decrease in cell number. When the medium was replaced every 12 h, cells in the periphery of the cultures gradually became nonviable as assessed by trypan blue uptake. However, the percentage of cells synthesizing DNA in the center of the cultures (approximately 50% during a 3 h pulse with tritiated thymidine) was the same whether the medium was changed every 12 h or left unchanged. Addition of IGF-I or IGF-II to the fresh medium change every 12 h did not increase the percentage of cells synthesizing DNA.

Animals↗