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Biomedical subjects

J J Lin

Publications and source records attributed to J J Lin.

At least 73 records · Page 4Linked to original sources
PubMed1998

Andrographolide suppresses the expression of inducible nitric oxide synthase in macrophage and restores the vasoconstriction in rat aorta treated with lipopolysaccharide.

1. We investigated whether andrographolide, a diterpenoid lactone found at Andrographis paniculata, influences the induction of the inducible nitric oxide synthase (iNOS) in RAW264.7 cells activated by bacterial endotoxin (LPS), as well as in the rats with endotoxic shock and in aortic rings treated with LPS. 2. Incubation of RAW264.7 cells with andrographolide (1 to 50 microM) inhibited the LPS (1 microg ml(-1))-induced nitrite accumulation in concentration- and time-dependent manners. Maximum inhibition was observed when andrographolide was added together with LPS and decreased progressively as the interval between andrographolide and LPS was increased to 20 h. 3. Western blot analysis demonstrated that iNOS expression was markedly attenuated in the presence of andrographolide for 6-24 h, suggesting that andrographolide inhibited iNOS protein induction. 4. Thoracic aorta incubation with LPS (300 ng ml(-1)) for 5 h in vitro exhibited a significant decrease in the maximal contractile response to phenylephrine (10(-9)-10(-5) M). Andrographolide (30 microM) restored the contractile response to control level. 5. In anaesthetized rats, LPS (10 mg kg(-1), i.v.) caused a fall in mean arterial blood pressure (MAP) from 116+/-4 to 77+/-5mmHg. The pressor effect of phenylephrine (10 microg ml(-1), i.v.) was also significantly reduced at 30, 60, 120 and 180 min after LPS injection. In contrast, animals pretreated with andrographolide (1 mg kg(-1), i.v., 20 min prior to LPS) maintained a significantly higher MAP when compared to LPS-rats given with vehicle. Administration of andrographolide 60 min after LPS caused a increase in MAP and significantly reversed the reduction of the pressor response to phenylephrine. 6. Our results indicated that andrographolide inhibits nitrite synthesis by suppressing expression of iNOS protein in vitro. And, this inhibition of iNOS synthesis may contribute to the beneficial haemodynamic effects of andrographolide in endotoxic shock.

Animals↗
PubMed1998

Insulin-like growth factor-I restores microvascular autoregulation in experimental chronic renal failure.

Impairment of autoregulation (AR) is associated with accelerated progression of chronic renal failure (CRF). As the bioavailability of insulin-like growth factor-I (IGF-I) is low in CRF, we investigated the effects of acute luminal application of 10 nM recombinant human IGF-I on AR in juxtamedullary (JM) afferent arterioles (AA) perfused in vitro with a blood solution [(approximately 30% hematocrit (HCT)]. Studies were conducted in AA from adult male rats three to four weeks after five-sixths nephrectomy (Nx) by either surgical excision (N = 7) or infarction (N = 5) of two thirds of the remnant kidney; controls (N = 6) had sham surgery. AA from both Nx groups exhibited marked hypertrophy and impaired AR responses (60 to 140 mm Hg perfusion pressure), features more pronounced in the infarction group. Responses to abluminal acetylcholine (10 microM) were similar in sham and excision groups but were significantly blunted in the infarction group. All groups vasodilated significantly after Ca-channel blockade (10 mM MnCl2). IGF-I restored AR in AA from both Nx groups (P < 0.05, analysis of variance) while it vasodilated AA from controls. These results suggest that IGF-I may protect the glomerulus from injury by maintaining autoregulatory control of renal blood flow, thereby slowing the progression of CRF.

Acetylcholine↗
PubMed1998

Orthodontic treatment planning for inclusion of the third molar in the dental arches: Part II.

Marked lower anterior crowding (late crowding or post-adolescent crowding) often develops at about the time of third molar eruption. Many studies have implicated the presence of third molars as a cause of this crowding. Despite the fact that there is no clear evidence that this is the case, many orthodontists and their patients' referring dentists routinely remove third molars at the retention stage of treatment to prevent crowding later; Ricketts et al. even advocate enucleation of the third molar while the patient is very young to prevent future crowding. In the following report on two orthodontically-treated patients (the first three cases in this report were published in The Australian Orthodontic Journal, Volume 15, Number 1), the author emphasises the importance of careful consideration of the third molar in the treatment plan.

Adolescent↗
PubMed1998

Diagnosis of cerebral toxoplasmosis by a nested polymerase chain reaction: a case report.

A 24-year-old man infected with human immunodeficiency virus type I rapidly progressed to acquired immune deficiency syndrome. His clinical picture was compatible with a presumptive diagnosis of cerebral toxoplasmosis. Application of a nested polymerase chain reaction (PCR) succeeded in detecting Toxoplasma gondii DNA in both the venous blood and cerebrospinal fluid specimens. This result indicates that PCR is a convenient tool for making a rapid and accurate diagnosis of cerebral toxoplasmosis, especially in developing countries.

Adult↗
PubMed1997

Synthetic scleral reinforcement materials. III. Changes in surface and bulk physical properties.

Changes in the physical properties of polymer materials during implantation in the biological environment can directly affect the ultimate performance of the polymer and/or device. We implanted four types of extraocular bands (porous, solid, composite, and patched) made from 11 types of materials in rabbit eyes and examined the changes in the physical strength and polymer structure of the implanted bands in terms of tensile strength measurements, creep analysis, and attenuated total internal reflectance--Fourier transform infrared spectroscopy (ATR-FTIR) at intervals up to 18 months after implantation. Most of the materials showed increases in tensile strength over the first 6 months in situ in the rabbit eye, followed by significant decreases between 6 and 18 months. Polymer bands that had been implanted for 18 months generally exhibited less creep behavior than unimplanted controls; for most of the bands, creep values ranged from 0% to 10% of the original length. ATR-FTIR of the solid bands and surface coatings showed protein deposition on all of the materials examined, with silicone materials and coatings least affected. Thirty-degree ATR-FTIR scans detected significant changes in the polymer structure for two of the band types: one solid (polyether urethane) and one porous (porous polyacrylate). In general, expanded polytetrafluoroethylene was the most stable in terms of tensile strength and creep. The least stable bands (composite bands made with porous polyurethane) were those that had undergone hydrolytic and/or oxidative degradation and chain scission of the polymer or alteration of the bond between the two materials making up the composite. These changes in physical properties and polymer structure observed after 18 months of implantation support the idea that polymer implant materials should be followed closely over several years in vivo to determine their suitability prior to use in humans.

Animals↗
PubMed1997

Suppression of human ribosomal protein L23A expression during cell growth inhibition by interferon-beta.

Interferons inhibit cell growth in normal and tumor-derived cells. The molecular basis of interferons antiproliferative activity remains to be defined. Using subtraction hybridization, a human melanoma differentiation associated gene, mda-20, has been identified that is down-regulated by treatment with interferon. Sequence analysis indicates that mda-20 is human ribosomal protein L23a (rp L23a). The mRNA levels of rp L23a and growth are diminished in a variety of human tumor cell lines following treatment with human fibroblast interferon, interferon-beta (IFN-beta). Expression of rp L23a is also reduced in human melanoma cells treated with human leukocyte (IFN-alpha) and immune (IFN-gamma) interferons, but not by growth inhibition resulting from serum starvation. These findings suggest that growth suppression alone is not sufficient to reduce rp L23a expression. Instead, reduced rp L23a mRNA results from biochemical changes mediated by interferons. Ectopic expression of an antisense rp L23a sequence in human HeLa cervical carcinoma cells results in a reduction in colony formation indicating a direct antiproliferative effect by inhibiting rp L23a expression. The mechanism underlying inhibition in rp L23a expression in IFN-beta-treated cells may involve antisense rp L23a RNA. These results suggest that rp L23a may be one of the target molecules involved in mediating growth inhibition by interferon.

Adenocarcinoma↗
PubMed1997

A contact scoring matrix for qualitative prediction of change in folding of alpha-helices in globular proteins caused by a mutation.

The atomic pairs in contact for atoms from pairs of amino-acid residues on pairs of helices in a protein database consisting of 48 proteins of known tertiary structure from the Brookhaven Protein Data Bank are searched and counted to construct a primary scoring system. Each score in the primary scoring system is weighted further with the possibility of occurrence of each residue pair in the protein database to give a final scoring matrix. Scores for predicting change in folding of alpha-helices in a mutant protein are calculated by assuming that every pair of helices in the protein can closely interact with each other. It is shown that the change in folding of alpha-helices in several mutant proteins are reflected in both the change of the contact scores and the helix geometry calculated.

Databases, Factual↗
PubMed1997

Tropomyosin localization reveals distinct populations of microfilaments in neurites and growth cones.

The functional and structural differences between neurites and growth cones suggests the possibility that distinct microfilament populations may exist in each domain. Tropomyosins are integral components of the actin-based microfilament system. Using antibodies which detect three different sets of tropomyosin isoforms, we found that the vast majority of tropomyosin was found in a microfilament-enriched fraction of cultured cortical neurons, therefore enabling us to use the antisera to evaluate compositional differences in neuritic and growth cone microfilaments. An antibody which reacts with all known nonmuscle isoforms of the alpha Tms gene (Tm5NM1-4) stains both neurites and growth cones, whereas a second antibody against the isoform subset, Tm5NM1-2, reacts only with the neurite. A third antibody which reacts with the Tm5a/5b isoforms encoded by a separate gene from alpha Tms was strongly reactive with both neurites and growth cones in 16-h cultures but only with the neurite shaft in 40-h cultures. Treatment of neurons with cytochalasin B allowed neuritic Tm5NM1-2 to spread into growth cones. Removal of the drug resulted in the disappearance of Tm5NM1-2 from the growth cone, indicating that isoform segregation is an active process dependent on intact microfilaments. Treatment of 40-h cultures with nocodazole resulted in the removal of Tm5NM1-2 from the neurite whereas Tm5a/5b now spread back into the growth cone. We conclude that the organization of Tm5NM1-2 and Tm5a/5b in the neurite is at least partially dependent on microtubule integrity. These results indicate that tropomyosin isoforms Tm5NM1-2, Tm5NM3-4, and Tm5a/5b mark three distinct populations of actin filaments in neurites and growth cones. Further, the composition of microfilaments differs between neurites and growth cones and is subject to temporal regulation.

Actin Cytoskeleton↗
PubMed1997

Tropomyosin isoforms in nonmuscle cells.

Vertebrate nonmuscle cells, such as human and rat fibroblasts, express multiple isoforms of tropomyosin, which are generated from four different genes and a combination of alternative promoter activities and alternative splicing. The amino acid variability among these isoforms is primarily restricted to three alternatively spliced exon regions; an amino-terminal region, an internal exon, and a carboxyl-terminal exon. Recent evidence reveals that these variable exon regions encode amino acid sequences that may dictate isoform-specific functions. The differential expression of tropomyosin isoforms found in cell transformation and cell differentiation, as well as the differential localization of tropomyosin isoforms in some types of culture cells and developing neurons suggest a differential isoform function in vivo. Tropomyosin in striated muscle works together with the troponin complex to regulate muscle contraction in a Ca(2+)-dependent fashion. Both in vitro and in vivo evidence suggest that multiple isoforms of tropomyosin in nonmuscle cells may be required for regulating actin filament stability, intracellular granule movement, cell shape determination, and cytokinesis. Tropomyosin-binding proteins such as caldesmon, tropomodulin, and other unidentified proteins may be required for some of these functions. Strong evidence for the distinct functions carried out by different tropomyosin isoforms has been generated from genetic analysis of yeast and Drosophila tropomyosin mutants.

Animals↗
PubMed1997

XBMP-1B (Xtld), a Xenopus homolog of dorso-ventral polarity gene in Drosophila, modifies tissue phenotypes of ventral explants.

Previously we have isolated a Xenopus cDNA homolog of bone morphogenetic protein-1 (XBMP-1A). In the present report we describe a new cDNA clone called XBMP-1B (or Xtld) from a Xenopus embryonic library. Sequence analysis indicates that these two clones share an indentical N-terminal sequence, including a region of metalloprotease domain, three copies of a repeat first found in complement proteins C1r/s and an epidermal growth factor (EGF)-like sequence. XBMP-1B protein has an additional copy of an EGF-like sequence followed by two copies of complement 1 r/s repeat in the C-terminus. The overall protein structure predicted from the XBMP-1B sequence reveals that it encodes a protein homologous to Drosophila tolloid. Three XBMP-1 transcripts (2.9, 5.2 and 6.6 kb) were detected by northern blot analysis. However, the 2.9 kb transcript hybridized specifically with XBMP-1A and the 5.2 and 6.6 kb transcripts hybridized with XBMP-1B. In Drosophila, a major function of tolloid is to augment the activity of the decapentaplegic gene product, a close relative of tumor growth factor (TGF)-beta superfamily members, BMP-2/4. Although XBMP-1 and XBMP-4 are detected in various adult tissues of Xenopus, the expression pattern of these two genes was not tightly correlated. In the embryo, the expression of XBMP-1 increased gradually from the morula to the swimming tadpole stages. Injection of XBMP-1B RNA into the ventral blastomeres at the 4-cell stage caused an elongation of the ventral marginal zone explants and converted globin-positive blood cells to mesenchymal and muscle tissues at later stages. It was shown that XBMP-1A was less active and a 1A mutant lacking the signal sequence was inactive. Further studies revealed that injection of XBMP-1B RNA into the ventral marginal zone induced up-regulation of dorsal marginal zone markers, such as goosecoid and chordin, at the gastrulation stage. These data indicate that XBMP-1 may have a role in determining dorso-ventral patterning in Xenopus, but in a different way from the dpp/tolloid system demonstrated in Drosophila.

Amino Acid Sequence↗
PubMed1997

A sampling and analytical method for the simultaneous determination of multiple organonitrogen pesticides in air.

An air sampling and analytical method was developed for organonitrogen pesticides using a combined filter and XAD-2 sorbent sampler and high performance liquid chromatography-ultraviolet detection. The method was evaluated for 14 organonitrogen pesticides by National Institute for Occupational Safety and Health evaluation guidelines and procedures. Evaluation experiments addressed limits of detection and quantitation, analytical recovery, sampler capacity, sample stability, and precision and bias over a range of 12 to 240 micrograms per sample. Samples were stable when stored for up to 30 days under either ambient or refrigerated conditions. Based on the finding of this work, 10 of the 14 compounds studied (aldicarb, captan, carbaryl, carbofuran, chlorpropham, diuron, formetanate, methiocarb, oxamyl, propham) can be successfully determined simultaneously using one method with an accuracy of better than +/- 25% of the true value with 95% confidence. Two other compounds (carbendazim/benomyl, methomyl) can be measured with the same accuracy over a more limited concentration range. The remaining two compounds (propoxur, thiobencarb) may meet this criterion, but additional samples would need to be included in the data analysis. With the current data, these two compounds can be determined with an accuracy of better than +/- 27% of the true value with 95% confidence.

Agricultural Workers' Diseases↗
PubMed1997

Differential regulation of neurogenesis by the two Xenopus GATA-1 genes.

Previously, we have shown that the ventralizing factor bone morphogenetic protein 4 (BMP-4) can inhibit Xenopus neurogenesis. The erythroid transcription factor GATA-1 functions downstream of the BMP-4 signaling pathway and mediates BMP-4-induced erythropoiesis. We have found that similar to BMP-4, GATA-1b inhibits neuralization of Xenopus animal cap (AC) cells. The neural inhibition is not seen with GATA-1a, although both GATA-1a and GATA-1b RNAs are translated at the same efficiency and induce globin expression equally in AC cells. GATA-1b RNA injection into AC cells neither induces expression of Xbra (a general mesoderm marker) nor affects expression of XK81 (epidermal keratin) or BMP-4 and Xvent-1 (two ventral markers). These data suggest that GATA-1b retains the epidermal fate of the AC. Intact GATA-1b protein is required for both inhibition of neurogenesis and induction of globin expression. Our findings indicate that GATA-1b can function in ectoderm to specifically regulate neural inducing mechanisms, apparently related to the expression of chordin, a neuralizing gene. Furthermore, tadpole stage embryos injected with GATA-1b are devoid of all dorsoanterior structures including neural tissue. This report provides evidence that the two transcription factors, derived from a recent genome duplication, share a common biological activity (stimulation of erythropoiesis) while also exhibiting a distinct function (inhibition of neurogenesis).

Animals↗
PubMed1997

Xmsx-1 modifies mesodermal tissue pattern along dorsoventral axis in Xenopus laevis embryo.

This study analyzes the expression and the function of Xenopus msx-1 (Xmsx-1) in embryos, in relation to the ventralizing activity of bone morphogenetic protein-4 (BMP-4). Expression of Xmsx-1 was increased in UV-treated ventralized embryos and decreased in LiCl-treated dorsalized embryos at the neurula stage (stage 14). Whole-mount in situ hybridization analysis showed that Xmsx-1 is expressed in marginal zone and animal pole areas, laterally and ventrally, but not dorsally, at mid-gastrula (stage 11) and late-gastrula (stage 13) stages. Injection of BMP-4 RNA, but not activin RNA, induced Xmsx-1 expression in the dorsal marginal zone at the early gastrula stage (stage 10+), and introduction of a dominant negative form of BMP-4 receptor RNA suppressed Xmsx-1 expression in animal cap and ventral marginal zone explants at stage 14. Thus, Xmsx-1 is a target gene specifically regulated by BMP-4 signaling. Embryos injected with Xmsx-1 RNA in dorsal blastomeres at the 4-cell stage exhibited a ventralized phenotype, with microcephaly and swollen abdomen. Histological observation and immunostaining revealed that these embryos had a large block of muscle tissue in the dorsal mesodermal area instead of notochord. On the basis of molecular marker analysis, however, the injection of Xmsx-1 RNA did not induce the expression of alpha-globin, nor reduce cardiac alpha-actin in dorsal marginal zone explants. Furthermore, a significant amount of alpha-actin was induced and alpha-globin was turned off in the ventral marginal zone explants injected with Xmsx-1. These results indicated that Xmsx-1 is a target gene of BMP-4 signaling, but possesses a distinct activity on dorsal-ventral patterning of mesodermal tissues.

Animals↗
PubMed1996

The Saccharomyces CDC13 protein is a single-strand TG1-3 telomeric DNA-binding protein in vitro that affects telomere behavior in vivo.

Saccharomyces telomeres consist of approximately 300 bp of C1-3A/TG1-3 DNA. Cells lacking the activity of the essential gene CDC13 display a cell cycle arrest mediated by the DNA damage sensing, RAD9 cell cycle checkpoint, presumably because they exhibit strand-specific loss of telomeric and telomere-adjacent DNA [Garvik, B., Carson, M. & Hartwell, L. (1995) Mol. Celi. Biol. 15,6128-6138]. Cdc13p expressed in Escherichia coli or overexpressed in yeast bound specifically to single-strand TG1-3 DNA. The specificity of binding displayed by Cdc13p in vitro indicates that in vivo it could bind to both the short, constitutive single-strand TG1-3 tails thought to be present at telomeres at most times in the cell cycle as well as to the long single-strand TG1-3 tails that are intermediates in telomere replication. Genes located near yeast telomeres are transcriptionally repressed, a phenomenon known as telomere position effect. Cells overexpressing a mutant form of Cdc13p had reduced telomere position effect at high temperatures. These data suggest that Cdc13p functions by binding directly to telomeric DNA, thereby limiting its accessibility to degradation and transcription as well as masking it from factors that detect damaged DNA.

Base Sequence↗