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Biomedical subjects

G Lee

Publications and source records attributed to G Lee.

At least 163 records · Page 9Linked to original sources
PubMed1997

Variation in coat protein genes among five geographically different isolates of rice tungro spherical virus.

The variation in the sequence of the coat protein genes of four isolates of rice tungro spherical virus from different countries, Malaysia, Thailand, India and Bangladesh, was compared with an isolate from the Philippines. The evidence from RT-PCR, Southern blot hybridization and sequences of the coat protein genes indicated that the isolates appeared to fall into two groups. One comprised the Philippine and Malaysian isolates (about 95% sequence similarity) and the other the Bangladeshi and Indian isolates, the sequences of which differed by about 15% from that of the Philippine isolate. The Thai isolate seemed to be a mixture of these two subgroups.

Amino Acid Sequence↗
PubMed1997

Determination of ocular toxicity in multiple applications of foscarnet iontophoresis.

This is the first study of multiple applications of drug iontophoresis in the eye. We repeated ocular foscarnet iontophoresis in 10 eyes of 10 rabbits every third day at the same paralimbal site for a total of seven applications over a period of 21 days to determine the efficacy and toxicity of multiple applications of ocular foscarnet iontophoresis. Mean vitreous human foscarnet concentration of 189 +/- 50.6 microM (SD) was achieved four hours after the seventh consecutive iontophoretic application over a period of twenty-one days. These levels were within the therapeutic range (25-800 microM) for the treatment of CMV retinitis and comparable to the intravitreal foscarnet concentrations achieved in eyes treated with a only a single application of ocular iontophoresis. Electroretinography (ERG) and Slit-lamp biomicroscopy responses revealed no evidence of ocular toxicity. Indirect ophthalmoscopy of the retinas and gross examinations of the calottes revealed a single, small burn in the retina and choroid corresponding to the application site of the iontophoresis probe similar to the lesion resulting from a single application of iontophoresis. Light and electron microscopy revealed local tissue injury and fibrosis at the iontophoresis site, but adjacent areas were unaffected.

Animals↗
PubMed1997

Genetic homogeneity among methicillin-resistant Staphylococcus aureus strains from Saudi Arabia.

Ninety-four strains of methicillin-resistant Staphylococcus aureus (MRSA) were collected from patients nursed in several hospitals in Saudi Arabia, before they were referred to King Faisal Specialist Hospital and Research Centre for tertiary care. The hospitals were from geographically diverse regions and as such the entirety of Saudi Arabia was covered. All strains were genetically typed by random amplification of polymorphic DNA (RAPD) analysis using three different primers and a representative subset of the strains was analyzed with pulsed-field gel electrophoresis (PFGE) as well. It was concluded that 87 out of 94 (93%) belong to a single clonally related lineage of MRSA. In the other 7 cases, the DNA banding patterns were shown to differ only slightly from those determined for the clonal type. PFGE analysis confirmed the homogeneity of the collection of strains. When the RAPD and PFGE fingerprints obtained for the Saudi clone were compared to those generated for a collection of MRSA with a more diverse geographical background, it was shown that the clonal type from Saudi Arabia was not identical to any of these MRSA strains. Our data provide another example of the capacity of certain MRSA clones to expand through entire nations and establish themselves permanently among large number of hospitals and, consequently, even larger numbers of patients.

DNA, Bacterial↗
PubMed1997

Screening questionnaires for bakers' asthma--are they worth the effort?

The use of a respiratory screening questionnaire is recommended annually to screen bakery workers in the UK. We compared questionnaire screening with other methods of detecting workers with asthmatic symptoms and then assessed the significance of these symptoms with careful investigation and follow-up. Reasons for questionnaire failures were then explored. A questionnaire was issued to 362 flour-exposed workers in a large bakery. All positive respondents to respiratory symptom questions were interviewed by an occupational nurse. Workers with occupationally related symptoms at this interview were referred to the chest clinic. In addition, workers with negative questionnaires were screened using attendance records, sick notes and direct workplace observations. Workers with frequent absence from work or sick notes with respiratory diagnoses were interviewed in the same manner as those answering the questionnaire positively and then referred to clinic. At clinic, a diagnosis was made for each worker on the basis of clinical assessment, spirometry, serial peak expiratory flow rate (PEFR) analysis and radioallergosorbent testing (RAST) testing for specific IgE. Using the clinic diagnoses, the referral routes were audited to assess the rates of case detection of asthma and occupational asthma. The respiratory screening questionnaire identified 68 workers with respiratory symptoms. Of these, 21 proceeded to full assessment. A diagnosis of asthma was made in five cases, one of which was bakers' asthma. In addition, 11 workers not reporting any symptoms by questionnaire were referred to clinic and five were diagnosed as having asthma. Screening questionnaires may lead to an underestimate of the prevalence of asthmatic symptoms and as such should not be used alone in workplace screening.

Adult↗
PubMed1997

Integration specificities of two lambdoid phages (21 and e14) that insert at the same attB site.

It was shown previously that phage 21 and the defective element e14 integrate at the same site within the icd gene of Escherichia coli K-12 but that 21 integrase and excisionase excise e14 in vivo very infrequently compared to excision of 21. We show here that the reverse is also true: e14 excises itself much better than it excises an adjacent 21 prophage. In vitro integrase assays with various attP substrates delimit the minimal attP site as somewhere between 366 and 418 bp, where the outer limits would include the outermost repeated dodecamers suggested as arm recognition sites by S. J. Schneider (Ph.D. dissertation, Stanford University, Stanford, Calif., 1992). We speculate that the reason 21 attP is larger than lambda attP (240 bp) is because it must include a 209-bp sequence homologous to the 3' end of the icd transcript in order to allow icd expression in lysogens. Alteration of portions of 21 attP to their e14 counterparts shows that 21 requires both the arm site and core site sequences of 21 but that replacements by e14 sequences function in some positions. Consistent with Schneider's in vivo results, and like all other known integrases from lambdoid phages, 21 requires integration host factor for activity.

Bacterial Proteins↗
PubMed1997

Severe growth defect in a Schizosaccharomyces pombe mutant defective in intron lariat degradation.

The cDNAs and genes encoding the intron lariat-debranching enzyme were isolated from the nematode Caenorhabditis elegans and the fission yeast Schizosaccharomyces pombe based on their homology with the Saccharomyces cerevisiae gene. The cDNAs were shown to be functional in an interspecific complementation experiment; they can complement an S. cerevisiae dbr1 null mutant. About 2.5% of budding yeast S. cerevisiae genes have introns, and the accumulation of excised introns in a dbr1 null mutant has little effect on cell growth. In contrast, many S. pombe genes contain introns, and often multiple introns per gene, so that S. pombe is estimated to contain approximately 40 times as many introns as S. cerevisiae. The S. pombe dbr1 gene was disrupted and shown to be nonessential. Like the S. cerevisiae mutant, the S. pombe null mutant accumulated introns to high levels, indicating that intron lariat debranching represents a rate-limiting step in intron degradation in both species. Unlike the S. cerevisiae mutant, the S. pombe dbr1::leu1+ mutant had a severe growth defect and exhibited an aberrant elongated cell shape in addition to an intron accumulation phenotype. The growth defect of the S. pombe dbr1::leu1+ strain suggests that debranching activity is critical for efficient intron RNA degradation and that blocking this pathway interferes with cell growth.

Amino Acid Sequence↗
PubMed1997

Cloning and localization of a double-pore K channel, KCNK1: exclusive expression in distal nephron segments.

The K-selective channel, TOK1, recently identified in yeast, displays the unusual structural feature of having two putative pore regions, in contrast to all previously cloned K channels. Using the TOK1 pore regions as probes, we identified a human kidney cDNA encoding a 337-amino acid protein (hKCNK1) with four transmembrane segments and two pore regions containing the signature sequence of K channels. Amino acid identity to TOK1 is only 15% overall but 40% at the pores. Northern analysis indicates high expression of a 1.9-kb message in brain > kidney >> heart. Nephron segment localization, carried out in rabbit by reverse transcription-polymerase chain reaction, reveals that KCNK1 is expressed in cortical thick ascending limb, connecting tubule, and cortical collecting duct. It was not detected in the proximal tubule, medullary thick ascending limb, distal convoluted tubule, and glomerulus. We conclude that KCNK1 is a unique, double-pore, mammalian K channel, distantly related to the yeast channel TOK1, that is expressed in distal tubule and is a candidate to participate in renal K homeostasis.

Amino Acid Sequence↗
PubMed1996

Efficient gene activation system on mammalian cell chromosomes using recombinant adenovirus producing Cre recombinase.

To develop a method for activating genes located on cell chromosomes, an on/off switching unit regulated by the site-specific recombinase Cre was constructed. The switching unit was designed to express firstly the neo gene and secondly the reporter lacZ gene by Cre-mediated excisional deletion of the neo gene. CV1 cell lines bearing the switching unit on a cell chromosome were isolated and activation of the lacZ gene was examined after infection with a Cre-producing recombinant adenovirus. In one cell line virtually 100% of the cells stably expressed the lacZ gene, whereas in another cell line lacZ-expressing cell populations reached only to about 90% and decreased after cell divisions. The Southern blot analyses showed that the latter type of cells contained a head-to-tail array of the switching units, and that consequently the lacZ-expressing units were excised from a cell chromosome and present as extrachromosomal circular DNAs. These results showed that the system offers efficient activation of genes introduced into cell chromosomes and that the organization of the reporter units are important for efficiency and duration of the activated gene expression.

Adenoviridae↗
PubMed1996

Tau binds to the distal axon early in development of polarity in a microtubule- and microfilament-dependent manner.

Microtubule-associated protein tau is localized to the axon in situ and has been implicated in the development of neuronal polarity. Here we report that tau is extracted differentially in cultured hippocampal neurons yielding an axon-specific localization under conditions that keep the integrity of the plasma membrane. The amount of bound tau increases toward the distal axon and is highest at the transition from the axonal shaft to the growth cone. This distribution is significantly different from the distribution of axonal microtubules that are most concentrated at the proximal axon. Distal binding of tau to one process appears early in development of polarity in culture and correlates with the onset of axon formation (day 2 in culture). Binding to the distal axon requires intact microtubules and microfilaments. Distal tau binding does not stabilize microtubules selectively against drug-induced disassembly, because colchicine-induced microtubule depolymerization is highest distally. We conclude that binding of tau to the distal axon follows a complex mechanism, is an early event in the development of polarity, and reproduces the axon-specific localization of tau in situ.

Actin Cytoskeleton↗
PubMed1996

Abnormal peripheral lymphocyte function in c-abl mutant mice.

The proto-oncogene c-abl encodes a tyrosine kinase that is hypothesized to function in proliferation-stimulatory signaling pathways. Previous work on mice homozygous for targeted mutations in the c-abl gene (ablml and abl2 mutant strains) has demonstrated multiple defects, including a susceptibility to infections that results in a high mortality rate after weaning. FACS analysis of the hemopoietic system of c-abl mutants demonstrated variable reductions in B and T lymphocytes in adult bone marrow, thymus, spleen, and peripheral blood. In addition, bone marrow from mutants showed a decreased ability to respond to interleukin-7. We further found that B cells from ablm1 mice had a reduced ability to respond to lipopolysaccharide (decreased to 10% of control response) that was dependent on the culture conditions and the tissue of origin of B cells. Peripheral blood from the mutants also had a reduced response to the T cell mitogen concanavalin A. Immune response in ablm1 mice as determined by the mixed lymphocyte response and the sheep red blood cell plaque-forming assay was grossly normal. These findings suggest that although specific signaling pathways in lymphocytes may involve c-Abl, the immune system can function in the absence of a normal c-abl gene product.

Animals↗
PubMed1996

Differential use of protein 4.1 translation initiation sites during erythropoiesis: implications for a mutation-induced stage-specific deficiency of protein 4.1 during erythroid development.

Expression of multiple protein 4.1 isoforms in erythroid progenitors and in a variety of nonerythroid tissues results from alternative pre-mRNA splicing. In 4.1 pre-mRNA, several translation initiation sites are present; synthesis of isoforms larger than 80 kD occurs when an upstream 5' AUG is spliced in, whereas the 80-kD mature erythroid isoform is produced when the upstream AUG is spliced out and translation is initiated at the downstream AUG. During erythropoiesis, this splicing switch is developmentally regulated. We studied this developmental switch in hereditary elliptocytosis 4.1Alg, in which a DNA rearrangement involving the exon containing the downstream AUG results in loss of coding capacity for the 80-kD 4.1, leading to mature red blood cells deficient in 4.1 with decreased membrane mechanical stability. Analysis of erythroblast RNA by reverse transcriptase-polymerase chain reaction showed that, although it retained the upstream AUG, its coding region was approximately 2.2 kb, compared with approximately 2.5 kb of normal 4.1 mRNA, because of the deletion of exons, including the one that codes for the downstream AUG. Immunofluorescent microscopy and Western blot analysis documented protein 4.1 expression in HE 4.1Alg erythroblasts. These studies emphasize the crucial role of differentiation-regulated RNA splicing because, within the same erythroid tissue, the HE 4.1Alg phenotype did not appear until after the differentiation-associated splicing event.

Base Sequence↗
PubMed1996

Inhibition of the association of RNA polymerase II with the preinitiation complex by a viral transcriptional repressor.

Transcriptional repression is an important component of regulatory networks that govern gene expression. In this report, we have characterized the mechanisms by which the immediate early protein 2 (IE2 or IE86), a master transcriptional regulator of human cytomegalovirus, down-regulates its own expression. In vitro transcription and DNA binding experiments demonstrate that IE2 blocks specifically the association of RNA polymerase II with the preinitiation complex. Although, to our knowledge, this is the first report to describe a eukaryotic transcriptional repressor that selectively impedes RNA polymerase II recruitment, we present data that suggest that this type of repression might be widely used in the control of transcription by RNA polymerase II.

Base Sequence↗
PubMed1996

Basic thermoanalytical studies of insoluble collagen matrices.

Insoluble collagen has been utilized as a base material for parenteral drug carrier systems. Information on its physicochemical properties was obtained by focussing on thermoanalytical methods. On the way from the raw material to the matrices, the acidic aqueous dispersion represents an important intermediate state. DSC and FTIR revealed its complete denaturation at 43 degrees C. Dense homogeneous collagen matrices were prepared by air-drying at 25 degrees C and became denatured at 103.5 degrees C, far above normal storage temperatures. Dielectrical Thermal Analysis demonstrated transitions in the dielectrical storage and loss moduli, reflecting the dissipation of electrical energy and increased molecular mobility caused by collapse of the triple helical structure. Cross-linking of the collagen dispersion with glutaraldehyde induced no alteration in the thermoanalytical properties of dry matrices. However, in the swollen state, after incubation of the devices in phosphate buffer the transition temperature increased from 50 to 70 degrees C as cross-linking was intensified. This indicated stronger interactions between the collagen fibre structures. Dissolution tests with cytochrome c-loaded matrices showed that higher amounts of the model protein were trapped inside the matrices as more glutaraldehyde was added.

Animals↗
PubMed1996

Gender differences in health: evidence from the Czech Republic.

Gender differences in health have been linked to gender stratification in the United States. Women's relation to production, paid and unpaid work, and their experience of this gender inequality disadvantage their self-rated health compared to men. Men's consumption or health lifestyles disfavors their comparative health. This formulation is tested in the Czech Republic with a sample of matched wives and husbands (N = 577 households). This extends previous research in the United States on gender differences in health in two ways: into post-communist Europe and by comparing paired wives and husbands. Respondents completed questionnaires in 1994 on their health and well-being, jobs and finances, non-economic life events, marriage, psychological states, opinions about the changes in the Czech Republic, and socioeconomic background. Wives and husbands filled out separate questionnaires. The relation to production (both the objective relation and its subjective experience) did not impair wives' self-reported health any more than that of their husbands, and husbands' consumption or health lifestyles did not put them at a health disadvantage. Interpretations of these findings rest on both the extension of the study into post-communist Europe and by comparing matched wives and husbands.

Adult↗
PubMed1996

Ocular iontophoretic supplementation of intravenous foscarnet therapy.

PURPOSE: Reactivation of cytomegalovirus retinopathy during intravenous antiviral therapy is usually treated with higher doses of drug. We sought to determine whether ocular iontophoresis increases the intravitreal foscarnet concentration attained by intravenous injection. METHODS: We injected foscarnet (120 mg/kg or 180 mg/kg) intravenously into 24 rabbits and determined the time of maximal concentrations in serum and vitreous humor. We injected the same doses into 24 additional rabbits and administered ocular foscarnet iontophoresis one hour later. Vitreous humor concentrations were assayed at one, four, eight, 24, 60, and 120 hours after iontophoresis and compared with those from injection alone. RESULTS: Maximum serum and vitreous humor concentrations were achieved one hour after each intravenous dose. Maximum vitreous humor concentrations were achieved four hours after 120 mg/kg intravenous doses plus iontophoresis and eight hours after 180-mg/kg intravenous doses plus iontophoresis. Vitreous humor levels were significantly higher in eyes receiving intravenous foscarnet (120 mg/kg, P < .0001; 180 mg/kg, P < .0001) plus ocular Foscarnet iontophoresis than in those receiving intravenous foscarnet alone. Vitreous humor foscarnet levels in eyes receiving 120 mg/kg intravenously did not differ significantly from those in the group receiving 180 mg/kg intravenously (P < .1). The intravenous dose did not significantly affect vitreous humor levels after iontophoresis (P < .1). Vitreous concentrations fell below therapeutic levels (25 microM) in all eyes 60 hours after intravenous foscarnet and ocular foscarnet iontophoresis. CONCLUSIONS: Ocular iontophoresis significantly increased intravitreous foscarnet concentrations above those attained by intravenous injection alone and may be an effective alternative to increasing the intravenous drug dose in patients with reactivated cytomegalovirus retinopathy.

Animals↗
PubMed1996

Regulation of the phosphorylation state and microtubule-binding activity of Tau by protein phosphatase 2A.

Recently, we reported that a pool of protein phosphatase 2A (PP2A) is associated with microtubules. Here, we demonstrate that specific isoforms of PP2A bind and dephosphorylate the neuronal microtubule-associated protein tau. Coexpression of tau and SV40 small t, a specific inhibitor of PP2A, in CV-1, NIH 3T3, or NT2 cells induced the phosphorylation of tau at multiple sites, including Ser-199, Ser-202, Thr-205, Ser-396, and Ser-404. Immunofluorescent and biochemical analyses revealed that hyperphosphorylation correlated with dissociation of tau from microtubules and a loss of tau-induced microtubule stabilization. Taken together, these results support the hypothesis that PP2A controls the phosphorylation state of tau in vivo.

3T3 Cells↗