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Biomedical subjects

I Lee

Publications and source records attributed to I Lee.

At least 73 records · Page 4Linked to original sources
PubMed2000

Mitochondrial energy metabolism is regulated via nuclear-coded subunits of cytochrome c oxidase.

A new mechanism on regulation of mitochondrial energy metabolism is proposed on the basis of reversible control of respiration by the intramitochondrial ATP/ADP ratio and slip of proton pumping (decreased H+/e- stoichiometry) in cytochrome c oxidase (COX) at high proton motive force delta p. cAMP-dependent phosphorylation of COX switches on and Ca2+-dependent dephosphorylation switches off the allosteric ATP-inhibition of COX (nucleotides bind to subunit IV). Control of respiration via phosphorylated COX by the ATP/ADP ratio keeps delta p (mainly delta psi(m)) low. Hormone induced Ca2+-dependent dephosphorylation results in loss of ATP-inhibition, increase of respiration and delta p with consequent slip in proton pumping. Slip in COX increases the free energy of reaction, resulting in increased rates of respiration, thermogenesis and ATP-synthesis. Increased delta psi(m) stimulates production of reactive oxygen species (ROS), mutations of mitochondrial DNA and accelerates aging. Slip of proton pumping without dephosphorylation and increase of delta p is found permanently in the liver-type isozyme of COX (subunit VIaL) and at high intramitochondrial ATP/ADP ratios in the heart-type isozyme (subunit VIaH). High substrate pressure (sigmoidal v/s kinetics), palmitate and 3,5-diiodothyronine (binding to subunit Va) increase also delta p, ROS production and slip but without dephosphorylation of COX.

Animals↗
PubMed2000

Identification of CD72 as a lymphocyte receptor for the class IV semaphorin CD100: a novel mechanism for regulating B cell signaling.

We have identified the lymphocyte semaphorin CD100/Sema4D as a CD40-inducible molecule by subtractive cDNA cloning. CD100 stimulation significantly enhanced the effects of CD40 on B cell responses. Administration of soluble CD100 markedly accelerated in vivo antigen-specific antibody responses. CD100 receptors with different binding affinities were detected on renal tubular cells (K(d) = approximately 1 x 10(-9)M) and lymphocytes (K(d) = approximately 3 x 10(-7)M). Expression cloning revealed that the CD100 receptor on lymphocytes is CD72, a negative regulator of B cell responsiveness. CD72 thus represents a novel class of semaphorin receptors. CD100 stimulation induced tyrosine dephosphorylation of CD72 and dissociation of SHP-1 from CD72. Our findings indicate that CD100 plays a critical role in immune responses by the novel mechanism of turning off negative signaling by CD72.

Animals↗
PubMed2000

Turkey cytochrome c oxidase contains subunit VIa of the liver type associated with low efficiency of energy transduction.

Cytochrome c oxidase was isolated from turkey liver, heart and breast skeletal muscle and separated by SDS/PAGE. The N-terminal amino-acid sequence of subunit VIa from all tissues and internal sequences from the skeletal muscle enzyme show homology to the mammalian liver-type subunit VIaL, which was verified by isolation and sequencing of the cDNA of turkey subunit VIa. No cDNA corresponding to subunit VIaH (mammalian heart-type) could be found by RACE-PCR with mRNA from all turkey tissues. Measurement of proton translocation with the reconstituted enzymes from turkey liver and heart revealed H+/e- ratios below 0.5 that were independent of the intraliposomal ATP/ADP ratio, as previously found with the bovine liver enzyme. Under identical conditions, the bovine heart enzyme revealed H+/e- ratios of 0.85 at low and 0.48 at high intraliposomal ATP/ADP ratios. The results suggest that in birds the lower H+/e-ratio of cytochrome c oxidase participates in elevated resting metabolic rate and thermogenesis.

Adenosine Diphosphate↗
PubMed2000

Two C-terminal variants of NBC4, a new member of the sodium bicarbonate cotransporter family: cloning, characterization, and localization.

We report the cloning, characterization, and chromosomal assignment of a new member of the sodium bicarbonate cotransporter (NBC) family, NBC4. The NBC4 gene was mapped to chromosome 2p13 and is a new candidate gene for Alstrom syndrome. Two variants of the transporter have been isolated from human testis and heart, which differ in their C termini. NBC4a encodes a 1137-residue polypeptide and is widely expressed in various tissues, including liver, testis, and spleen. NBC4b is identical to NBC4a except that it has a 16-nucleotide insert, creating a C-terminal frame shift. NBC4b encodes a 1074-residue polypeptide and is highly expressed in heart. Amino acids 1-1046 are common to both NBC4 variants. NBC4a has two protein-interacting domains that are lacking in NBC4b: a proline-rich sequence, PPPSVIKIP (amino acids 1102-1110), and a consensus PDZ-interacting domain, SYSL (1134-1137). NBC4b lacks the stretch of charged residues present in the C terminus of NBC4a and other members of the NBC family. Unlike other members of the NBC family, both NBC4a and NBC4b have a unique glycine-rich region (amino acids 440-469). In comparison with other members of the bicarbonate transport superfamily, NBC4a and NBC4b are most similar structurally to the electrogenic sodium bicarbonate cotransporters (NBC1).

Amino Acid Sequence↗
PubMed2000

Saccharomyces cerevisiae RAI1 (YGL246c) is homologous to human DOM3Z and encodes a protein that binds the nuclear exoribonuclease Rat1p.

The RAT1 gene of Saccharomyces cerevisiae encodes a 5'-->3' exoribonuclease which plays an essential role in yeast RNA degradation and/or processing in the nucleus. We have cloned a previously uncharacterized gene (YGL246c) that we refer to as RAI1 (Rat1p interacting protein 1). RAI1 is homologous to Caenorhabditis elegans DOM-3 and human DOM3Z. Deletion of RAI1 confers a growth defect which can be complemented by an additional copy of RAT1 on a centromeric vector or by directing Xrn1p, the cytoplasmic homolog of Rat1p, to the nucleus through the addition of a nuclear targeting sequence. Deletion of RAI1 is synthetically lethal with the rat1-1(ts) mutation and shows genetic interaction with a deletion of SKI2 but not XRN1. Polysome analysis of an rai1 deletion mutant indicated a defect in 60S biogenesis which was nearly fully reversed by high-copy RAT1. Northern blot analysis of rRNAs revealed that rai1 is required for normal 5.8S processing. In the absence of RAI1, 5.8S(L) was the predominant form of 5.8S and there was an accumulation of 3'-extended forms but not 5'-extended species of 5. 8S. In addition, a 27S pre-rRNA species accumulated in the rai1 mutant. Thus, deletion of RAI1 affects both 5' and 3' processing reactions of 5.8S rRNA. Consistent with the in vivo data suggesting that RAI1 enhances RAT1 function, purified Rai1p stabilized the in vitro exoribonuclease activity of Rat1p.

Amino Acid Sequence↗
PubMed2000

Massive suprachoroidal hemorrhage with retinal and vitreous incarceration; a vitreoretinal surgical approach.

Suprachoroidal hemorrhage(SH) may cause the expulsion of the intraocular contents. Vitreous incarceration in the wound and retinal detachment with SH are extremely poor prognostic signs. Treatment modalities depend on the severity of eye damage. This particular patient had "kissing" hemorrhagic choroidal detachment which completely filled the vitreous cavity after cataract surgery. It seemed to be inoperable. Secondary surgery was delayed 3 days to lower IOP to normal levels. The eye underwent anterior drainage sclerotomy under constantly-maintained limbal or pars plana infusion fluid line pressure. The authors performed a pars plana vitrectomy, followed by perfluorocarbon liquid injection and a silicone oil tamponade. After this surgical approach, the patient attained an attached retina and a visual acuity of 5/200 at the 3 month follow-up.

Aged↗
PubMed1999

Insights into the tetanus toxin model of early-onset epilepsy from long-term video monitoring during anticonvulsant therapy.

Video monitoring studies were undertaken to determine if the anticonvulsant, carbamazepine (CBZ), could prevent seizures in infant rats that had been intrahippocampally injected with tetanus toxin (TNTX). In control rats, seizure frequency peaked 5-6 days after injection and rapidly declined by postinjection day 9. Twice-daily CBZ treatments dramatically suppressed behavioral seizures for 7 days. However, despite increasing the dosage of CBZ, rats experienced more behavioral seizures during the second week after TNTX injection. Paradoxically, tetanus-toxin-injected control rats had very few seizures at this time. Results not only suggest that this TNTX model may be useful in screening drugs for treating intractable focal epilepsy of infancy but also provide some insight into the processes that may contribute to the rapid decline in behavioral seizure frequency that occurs during the acute phase of epileptogenesis in this model.

Age of Onset↗
PubMed1999

Anatomical characteristics and three-dimensional model of the dog dorsal lateral geniculate body.

The morphological and laminar characteristics of the dorsal lateral geniculate nucleus (LGN) and medial interlaminar nucleus (MIN) of the domestic dog (Canis familiaris) were studied by three-dimensional computer reconstruction of labeled retinal afferents following intraocular HRP injections. As previously reported, the dog LGN consisted of layers A, A1, C, C1, C2, and C3. Layers A, C, and C2 receive contralateral-eye inputs, and layers A1 and C1 ipsilateral inputs. The dog MIN was found to have four orderly interdigitating layers; layers 1, 2, 3, and 4, medial to lateral. MIN layers 1 and 3 received contralateral inputs, and layers 2 and 4 ipsilateral inputs. Layer 1 had the largest soma of all LGN/MIN layers. LGN layer A was partially separated into medial and lateral subdivisions by a cleft free of somata. The overall three-dimensional shape of the lateral geniculate body was like the letter C, with the convex part of the C directed posteriorly. The relative volume of the MIN was smaller than in the cat; the canine MIN comprised 8.3% of the combined volume of layers A, A1 and the MIN, while that of the cat comprised 14.2% as estimated from Sanderson's map. The volume of all contralateral-eye layers, combining both LGN and MIN, was 31.2 mm(3) (78%), and that for ipsilateral layers was 8.6 mm(3) (22%). The ratio of ipsilateral to contralateral laminar volumes is much lower in the dog than in the cat.

Animals↗
PubMed1999

Cloning, tissue distribution, genomic organization, and functional characterization of NBC3, a new member of the sodium bicarbonate cotransporter family.

Previous functional studies have demonstrated that muscle intracellular pH regulation is mediated by sodium-coupled bicarbonate transport, Na+/H+ exchange, and Cl-/bicarbonate exchange. We report the cloning, sequence analysis, tissue distribution, genomic organization, and functional analysis of a new member of the sodium bicarbonate cotransporter (NBC) family, NBC3, from human skeletal muscle. mNBC3 encodes a 1214-residue polypeptide with 12 putative membrane-spanning domains. The approximately 7.8-kilobase transcript is expressed uniquely in skeletal muscle and heart. The NBC3 gene (SLC4A7) spans approximately 80 kb and is composed of 25 coding exons and 24 introns that are flanked by typical splice donor and acceptor sequences. Expression of mNBC3 cRNA in Xenopus laevis oocytes demonstrated that the protein encodes a novel stilbene-insensitive 5-(N-ethyl-N-isopropyl)-amiloride-inhibitable sodium bicarbonate cotransporter.

Amino Acid Sequence↗
PubMed1999

Progressive changes of the nuclear matrix protein composition in diethylnitrosamine-induced rat hepatocarcinogenesis.

The nuclear matrix proteins (NMPs) consist of common and tissue-specific nuclear proteins, which can be altered by extracellular environments such as radiation, chemicals and virus infection. Thus, NMP profiles were analyzed in diethylnitrosamine (DEN)-treated rat liver. Male F344 rats (6 weeks old) were treated continuously with DEN (40 ppm) in drinking water. All animals were sacrificed at 10, 20 or 30 weeks during the experiment. The profiles of NMPs and cytoskeletal proteins (CSPs) progressively changed in their number and amount in DEN-treated rats. Four peptides increased in their relative amounts, while three decreased in the 10- and 20-week groups. Many NMPs were detected in DEN-induced hepatocellular carcinomas. These results suggest that the alteration of the NMPs may be involved in DEN-induced hepatocarcinogenesis.

Animals↗
PubMed1999

Induction of nitric oxide synthase mRNA by shear stress requires intracellular calcium and G-protein signals and is modulated by PI 3 kinase.

We have investigated the signaling pathways by which shear stress induces accumulation of endothelial nitric oxide synthase (eNOS) mRNA in bovine aortic endothelial cells (BAEC). Steady laminar fluid shear stress (20 dyn/cm2) induced a time-dependent increase in eNOS mRNA levels that did not require de novo protein synthesis and was in part transcriptional. Shear responsiveness was conferred on a luciferase reporter by a portion of the eNOS gene promoter encoding the 5'-flanking region between nt -1600 and -779. Shear-mediated induction of eNOS mRNA was abolished by chelation of intracellular calcium ([Ca2+]i) with BAPTA-AM, and inhibited by blockade of calcium entry with SKF96535. In contrast, eNOS mRNA upregulation by shear was potentiated by thapsigargin-mediated depletion of Ca2+i stores. Pertussis toxin (PTX) inhibited both the shear-induced elevation in [Ca2+]i and the subsequent increase in eNOS mRNA, implicating a PTX-sensitive G-protein in both responses. Shear-induced upregulation of eNOS mRNA was unaffected by the calmodulin inhibitor W-7 and by the tyrosine kinase inhibitor herbimycin A, suggesting that neither calmodulin nor tyrosine kinases are required. However, eNOS mRNA upregulation was potentiated by the PI 3-kinase inhibitors wortmannin and LY294002, suggesting that PI 3-kinase inhibits the shear response. Although microtubule integrity is required for the shear-induced regulation of endothelin-1 mRNA and the morphological and cytoskeletal responses to flow, neither microtubule dissolution with nocodazole nor microtubule stabilization with taxol altered shear-induced [Ca2+]i elevation or upregulation of eNOS mRNA. In conclusion, shear stress of BAEC increases eNOS transcriptional rate and upregulates eNOS mRNA levels by a process that requires calmodulin-independent [Ca2+]i signaling and a PTX-sensitive G-protein, is inhibited by PI 3-kinase, and is independent of microtubule integrity and tyrosine kinase activity.

Animals↗
PubMed1999

Lyn dissociation from phosphorylated Fc epsilon RI subunits: a new regulatory step in the Fc epsilon RI signaling cascade revealed by studies of Fc epsilon RI dimer signaling activity.

Cross-linking the heterotrimeric (alpha beta gamma 2) IgE receptor, Fc epsilon RI, of mast cells activates two tyrosine kinases: Lyn, which phosphorylates beta and gamma subunit immunoreceptor tyrosine-based activation motifs, and Syk, which binds gamma-phospho-immunoreceptor tyrosine-based activation motifs and initiates cellular responses. We studied three Fc epsilon RI-dimerizing mAbs that maintain similar dispersed distributions over the surface of RBL-2H3 mast cells but elicit very different signaling responses. Specifically, mAb H10 receptor dimers induce very little inositol 1,4,5-trisphosphate synthesis, Ca2+ mobilization, secretion, spreading, ruffling, and actin plaque assembly, whereas dimers generated with the other anti-Fc epsilon RI mAbs induce responses that are only modestly lower than that to multivalent Ag. H10 receptor dimers activate Lyn and support Fc epsilon RI beta and gamma subunit phosphorylation but are poor Syk activators compared with Ag and the other anti-Fc epsilon RI mAbs. H10 receptor dimers have two other distinguishing features. First, they induce stable complexes between activated Lyn and receptor subunits. Second, the predominant Lyn-binding phospho-beta isoform found in mAb H10-treated cells is a less tyrosine phosphorylated, more electrophoretically mobile species than the predominant isoform in Ag-treated cells that does not coprecipitate with Lyn. These studies implicate Lyn dissociation from highly phosphorylated receptor subunits as a new regulatory step in the Fc epsilon RI signaling cascade required for Syk activation and signal progression.

Animals↗
PubMed1999

Enhanced tumor targeting by an intratumoral injection of colloidal chromic 32P in two human tumors (AsPC-1 pancreas and Ls174T colon) in nude mice.

BACKGROUND AND OBJECTIVES: To find the mechanisms of the ongoing clinical trials in intralesional colloidal chromic 32P (32P-CP) brachytherapy, the cellular uptake of 32P-CP, changes in tumor interstitial fluid pressure (TIFP), and tumor blood flow (TBF) using two (AsPC-1, Ls174T) human tumors were measured. METHODS: After exposure to 32p-CP using exponential and plateau-phase cells, cells were trypsinized at various time intervals, then measured for the levels of radioactivity using a y-counter. Also measured were TIFP using the WIN technique and TBF with laser Doppler flowmetry. RESULTS: The plateau growth-phase of both tumors showed the maximal uptake of 32P-CP at approximately 100 min. TBF decreased within 10 min after an intratumoral (i.t.) injection of 32P-CP, and reached 75% of control value by 1 h. CONCLUSIONS: If 32P-CP was introduced i.t., it maintained highly efficient tumor targeting, mainly due to two physiological mechanisms: the high adherence of 32P-CP to the infused regions and the reduction in TBF by this therapeutic colloid.

Adenocarcinoma↗
PubMed1999

Autologous engineered cartilage rods for penile reconstruction.

PURPOSE: Conditions such as inadequate and ambiguous genitalia that are caused by rudimentary penis, severe hypospadias or traumatic injury require surgical intervention. Although silicone penile prostheses are an accepted treatment modality, biocompatibility issues may be a problem in select cases. We previously demonstrated that rods composed of cartilage could be created using chondrocytes seeded on biodegradable polymer scaffolds. We showed that the cartilage rods engineered ex situ were readily elastic and withstood high degrees of pressure. We investigated the feasibility of applying the engineered cartilage rods in situ in an animal model. MATERIALS AND METHODS: Autologous chondrocytes harvested from rabbit ears were grown and expanded in culture. Cells were seeded onto biodegradable poly-L-lactic acid coated polyglycolic acid polymer rods at a concentration of 50 x 10(6) chondrocytes per cm3. A total of 18 chondrocyte polymer scaffolds were implanted into the corporal spaces in 10 rabbits. As controls, 1 corpus in each of 2 rabbits was not implanted. The animals were sacrificed 1, 2, 3 or 6 months after implantation. Histological analysis was performed using hematoxylin and eosin, aldehyde fuschin-alcian blue and toluidine blue staining. RESULTS: All animals tolerated the implants for the duration of the study without any complications. Gross examination after retrieval at 1 month showed well formed, milky white cartilage structures within the corpora. All polymers were fully degraded by 2 months. There was no evidence of erosion or infection at any of the implant sites. Histological analysis using alcian blue and toluidine blue staining revealed mature and well formed chondrocytes in the retrieved implants. CONCLUSIONS: Autologous chondrocytes seeded on preformed biodegradable polymer structures form cartilage structures within the rabbit corpus cavernosum. This technology appears to be useful for creating autologous penile prostheses.

Animals↗
PubMed1999

Acute inflammation of the proliferative zone of gastric mucosa in Helicobacter pylori gastritis.

The neutrophilic infiltration has been regarded to represent the activity of Helicobacter pylori gastritis. It may involve the epithelium and/or lamina propria. The incidence and degree of the two types of infiltration do not correlate with each other frequently. We correlated the two types of neutrophilic infiltration with H. pylori infection and other pathologic parameters respectively in 300 randomly selected gastric biopsies as well as serial biopsies from a separate group of 95 patients who were treated for H. pylori infection. The "random biopsies" had chronic gastritis of various degrees, and the organisms were identified in 239 cases (79.7%); in the "treated group," the organisms disappeared completely in 62 cases (65.3%). Characteristically, the intraepithelial neutrophilic infiltration was predominantly localized to the proliferative zone of the gastric mucosa (zone 2) where the density of H. pylori was considerably lower than the surface epithelium. In the "random biopsies," both acute epithelial and interstitial neutrophilic infiltration correlated significantly (p < 0.01) with the H. pylori infection. In the "treated group," however, only acute epithelial inflammation correlated significantly (p < 0.01) with the eradication of infection while acute interstitial inflammation did not. Acute epithelial inflammation was no less frequently present in advanced chronic gastritis than in early chronic gastritis. Acute epithelial inflammation of the proliferative zone is a characteristic pathologic finding of H. pylori gastritis, and appears to be directly associated with the pathogenesis of H. pylori gastritis and its progression.

Biopsy↗
PubMed1999

Portal vein embolization with use of a new liquid embolic material: an experimental study.

PURPOSE: To evaluate the efficacy and safety of a new liquid embolic material in portal vein embolization (PVE). MATERIALS AND METHODS: A new embolic material (Embol) was percutaneously injected into the left portal vein of 13 swine, using a balloon catheter to prevent reflux. The swine were killed immediately (n = 6), 2 weeks (n = 4), and 4 weeks (n = 3) after the PVE, and the volumes of the right and left lobes were measured. The changes in body temperature, aspartate aminotransferase (AST) (formerly SGOT), alanine aminotrasferase (ALT) (formerly SGPT), and bilirubin levels after the PVE were studied, and the histopathologic changes in the embolized and nonembolized lobes were examined with light microscopy. RESULTS: The average volume ratio of the right:left lobe immediately after the PVE was 55(+/-2):45(+/-1), and changed to 71(+/-3):29(+/-3) at 2 weeks and 82(+/-3):18(+/-3) at 4 weeks after embolization. There were only mild changes in AST, ALT, and bilirubin levels, and only one pig showed a significant elevation in body temperature after PVE. Microscopically, the embolized lobe showed contraction of hepatocyte without any sign of necrosis and the nonembolized lobe expansion of hepatocyte. CONCLUSIONS: The new embolic material seems effective and safe for PVE.

Animals↗