Hydrolysis of ribosomes by electrophoretically blotted ribotoxin.
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Electrophoresis, Polyacrylamide Gel↗
Biomedical subjects
A Lin
Publications and source records attributed to A Lin.
The significance of eccentric foci of hyperpigmentation ('small dark dots') within melanocytic nevi. Analysis of 59 cases.
BACKGROUND AND DESIGN: Fifty-nine melanocytic nevi with eccentric foci of hyperpigmentation ("small dark dots") that measured primarily 1 to 2 mm in diameter were prospectively examined to determine the histologic correlates of the dark dots. RESULTS: Forty-one (69%) of the dark dots were due to increased melanin in epidermal melanocytes and/or keratinocytes, usually accompanied by melanophages; of these 41, six (15%) were associated with slight or moderate melanocytic nuclear atypia. Fifteen (25%) of the dark dots were due to increased dermal pigment that was either superficial or deep. Three (5%) of the dark dots were due to melanoma arising within a nevus. CONCLUSIONS: A small percentage of "small dark dots" within melanocytic nevi are due to melanoma. Biopsy specimens of nevi with small dark dots should be sectioned to ensure histologic examination of this focus of hyperpigmentation.
Adolescent↗
Purification and properties of a human platelet inositol 1,4,5-trisphosphate 3-kinase.
An inositol 1,4,5-trisphosphate 3-kinase (Ins(1,4,5)P3 3-kinase) has been purified 943-fold from a 30,000g human platelet extract and has a specific activity of 283 nmol/min/mg protein and an apparent Km for inositol 1,4,5-trisphosphate of 0.76 microM; the optimal pH for the enzymatic activity was 7.2. Under both denaturing and nondenaturing conditions, the kinase preparation contained two polypeptides, both of which exhibited Ca2+/calmodulin-dependent Ins(1,4,5)P3 3-kinase activity. In the presence and absence of calmodulin, Ins(1,4,5)P3 3-kinase exhibited a biphasic response to Ca2+, being stimulated between 10(-7) and 10(-6) M Ca2+ and inhibited when the Ca2+ level was further increased. Ins(1,4,5)P3 3-kinase was stimulated by calmodulin approximately 10-fold, requiring 55 nM calmodulin for a half-maximal effect. Calmodulin stimulation was immediately reversed upon chelation of Ca2+ by ethylene glycol bis (beta-amino-ethyl ether) N,N'-tetraacetic acid consistent with a mechanism of activation involving a direct interaction of calmodulin with Ins(1,4,5)P3 3-kinase. Since we have previously shown that Ins(1,4,5)P3 3-kinase can also be phosphorylated and consequently inactivated by protein kinase C in vitro (Lin, A. N., Barnes, S., and Wallace, R. W., 1990, Biochem. Biophys. Res. Commun. 170, 1369-1376), Ins(1,4,5)P3 3-kinase appears to be a key enzyme in the inositol phosphate signaling pathway and as such may play an important role in human platelet function.
Animals↗
5' distal and proximal cis-acting regulator elements are required for developmental control of a rice seed storage protein glutelin gene.
Using a homologous transgenic rice system it is demonstrated that 5' distal and proximal cis-acting transcriptional regulatory elements are required for developmental control of a rice seed storage protein glutelin gene. Analyses of gene expression of nine progressively truncated 5' promoter sequences in developing endosperm indicated the existence of at least one major positive element located from the -5.1 to -1.8 kb region. The functional importance of proximal elements in the context of 1.8 kb promoter was demonstrated by single substitution mutations in the TATA box (-28/-23), AACA motif (-73/-61), and protein-binding boxes I (-103/-86), II (-124/-110), III (-175/-158) and IV (-200/-217). A simultaneous mutation of five protein-binding sites (-410/-86) essentially eliminated the activity of the 1.8 kb promoter. Although temporal control of the Gt1 gene during endosperm development was retained in plants of constructs from -5.1 kb to -155 bp, spatial control of the glutelin gene was altered when the 5.1 kb promoter was deleted to -507 bp or -154 bp as the reporter gene activities of these constructs were detected in phloem of leaves, and in stems, sheaths and roots of plants.
Base Sequence↗
Identification of an oncoprotein- and UV-responsive protein kinase that binds and potentiates the c-Jun activation domain.
The activity of c-Jun is regulated by phosphorylation. Various stimuli including transforming oncogenes and UV light, induce phosphorylation of serines 63 and 73 in the amino-terminal activation domain of c-Jun and thereby potentiate its trans-activation function. We identified a serine/threonine kinase whose activity is stimulated by the same signals that stimulate the amino-terminal phosphorylation of c-Jun. This novel c-Jun amino-terminal kinase (JNK), whose major form is 46 kD, binds to a specific region within the c-Jun trans-activation domain and phosphorylates serines 63 and 73. Phosphorylation results in dissociation of the c-Jun-JNK complex. Mutations that disrupt the kinase-binding site attenuate the response of c-Jun to Ha-Ras and UV. Therefore the binding of JNK to c-Jun is of regulatory importance and suggests a mechanism through which protein kinase cascades can specifically modulate the activity of distinct nuclear targets.
3T3 Cells↗
Protein phosphatase 2A potentiates activity of promoters containing AP-1-binding elements.
The involvement of serine/threonine protein phosphatases in signaling pathways which modulate the activity of the transcription factor AP-1 was examined. Purified protein phosphatase types 1 (PP1) and 2A (PP2A) were microinjected into cell lines containing stably transfected lacZ marker genes under the control of an enhancer recognized by AP-1. Microinjection of PP2A potentiated serum-stimulated beta-galactosidase expression from the AP-1-regulated promoter. Similarly, transient expression of the PP2A catalytic subunit with c-Jun resulted in a synergistic transactivation of an AP-1-regulated reporter gene. PP2A, but not PP1, potentiated serum-induced c-Jun expression, which has been previously shown to be autoregulated by AP-1 itself. Consistent with these results, PP2A dephosphorylated c-Jun on negative regulatory sites in vitro, suggesting one possible direct mechanism for the effects of PP2A on AP-1 activity. Microinjection of PP2A had no effect on cyclic AMP (cAMP)-induced expression of a reporter gene containing a cAMP-regulated promoter, while PP1 injection abolished cAMP-induced gene expression. Taken together, these results suggest a specific role for PP2A in signal transduction pathways that regulate AP-1 activity and c-Jun expression.
Animals↗
Control of AP-1 activity by signal transduction cascades.
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Enzyme Activation↗
Casein kinase II is a negative regulator of c-Jun DNA binding and AP-1 activity.
c-Jun, a major component of the inducible transcription factor AP-1, is a phosphoprotein. In nonstimulated fibroblasts and epithelial cells, c-Jun is phosphorylated on a cluster of two to three sites abutting its DNA-binding domain. Phosphorylation of these sites inhibits DNA binding, and their dephosphorylation correlates with increased AP-1 activity. We show that two of these sites, Thr-231 and Ser-249, are phosphorylated by casein kinase II (CKII). Substitution of the third site, Ser-243, by Phe interferes with phosphorylation of the inhibitory sites in vivo and by purified CKII in vitro. Microinjection into living cells of synthetic peptides that are specific competitive substrates or inhibitors of CKII results in induction of AP-1 activity and c-Jun expression. Microinjection of CKII suppresses induction of AP-1 by either phorbol ester or an inhibitory peptide. These results suggest that one of the roles of CKII, a major nuclear protein kinase with no known functions, is to attenuate AP-1 activity through phosphorylation of c-Jun.
Amino Acid Sequence↗
Ultraviolet-B irradiation of platelets: a preliminary trial of efficacy.
Prior studies established that ultraviolet-B light (UVB) irradiation of platelet concentrates (PCs) at appropriate doses can eliminate the mixed lymphocyte culture-stimulating and -responding capacity of lymphocytes in the PCs without adversely affecting in vitro platelet function. The in vivo recovery and survival and in vitro characteristics of UVB-irradiated platelets were investigated in paired studies. PCs were stored for 1 day and then exposed to UVB. Platelet recovery, survival, and function were comparable to those of nonirradiated platelets. Recovery and survival of platelets stored for 5 days before UVB exposure were decreased relative to controls, although they were considered clinically acceptable. Paired transfusion studies were also performed in seven thrombocytopenic patients by using platelets obtained by apheresis. Comparable posttransfusion platelet increments and bleeding time corrections were obtained with both irradiated and control (nonirradiated) platelets. It can be concluded that platelets survive and function relatively normally in vivo after UVB irradiation sufficient to abolish lymphocyte reactivity in mixed lymphocyte culture. Long-term studies of UVB-irradiated PCs are needed to assess their potential in reducing recipient alloimmunization.
Blood Component Transfusion↗
Studies on the adhesion of glass-ionomer cements to dentin.
This study investigated the bonding mechanisms of glass-ionomer cement to dentin. The approaches included mechanical determination of bond strengths, analysis of surface morphology by means of scanning electron microscopy (SEM) and confocal microscopy, and measurement of chemical changes of fracture bond sites by means of x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The highest bond strengths were obtained with light-cured glass-ionomer cement. SEM and confocal images showed evidence of mechanical interlocking of cement in dentinal tubules. SIMS depth profiles confirmed the ion-exchange process between the light-cured glass-ionomer cement and the dentin surface. From corresponding XPS results, it was clear that the adhesion characteristics were significantly affected by light-curing and the chemical structure of the polymer.
Adhesiveness↗
The paperless essay: one way to teach writing and computer skills in medical school.
We designed an assignment for first-year medical students that included instruction in writing and in computer use, two important subjects that are usually neglected in the traditional curriculum. As part of a neuroscience course, students wrote an essay using a word processor and submitted it to the instructor via the campus computer network. If requested by the instructor, the students submitted a revision of their essays without a grade penalty. As a result of completing the assignment, students learned the importance of revision and were stimulated to learn more about computers. With only slight modification of medical school courses, faculty can place more emphasis on writing skills and computer literacy.
Computer Literacy↗
Genetic etiology of lung cancer.
Although the clinical management of lung cancer has not changed substantially over the past decade, this same time period has witnessed exciting new developments concerning the origins of this disease. These findings support the hypothesis that lung cancer, as well as other common adult tumors, arise as a result of somatic mutations to a specific group of cellular genes referred to as oncogenes and tumor suppressor genes. New strategies for the prevention and treatment of lung cancer will emerge as we identify the mechanisms that control mutation rates for these target genes and gain a better understanding of the role these genes play in coordinating normal cell growth and differentiation.
Genes, Retinoblastoma↗
A role for sunlight in skin cancer: UV-induced p53 mutations in squamous cell carcinoma.
Sunlight is a carcinogen to which everyone is exposed. Its UV component is the major epidemiologic risk factor for squamous cell carcinoma of the skin. Of the multiple steps in tumor progression, those that are sunlight-related would be revealed if they contained mutations specific to UV. In a series of New England and Swedish patients, we find that 14/24 (58%) of invasive squamous cell carcinomas of the skin contain mutations in the p53 tumor suppressor gene, each altering the amino acid sequence. Involvement of UV light in these p53 mutations is indicated by the presence in three of the tumors of a CC----TT double-base change, which is only known to be induced by UV. UV is also implicated by a UV-like occurrence of mutations exclusively at dipyrimidine sites, including a high frequency of C----T substitutions. p53 mutations in internal malignancies do not show these UV-specific mutations. The dipyrimidine specificity also implicates dipyrimidine photoproducts containing cytosine as oncogenic photoproducts. We believe these results identify a carcinogen-related step in a gene involved in the subsequent human cancer.
Aged↗
A metabotropic glutamate receptor agonist does not mediate neuronal degeneration in cortical culture.
In light of the evidence that calcium plays a critical role in excitotoxic neuronal death, it has been speculated that the metabotropic glutamate receptor may also contribute to excitotoxic damage through the mobilization of Ca2+ from intracellular stores. In the present study we examined this possibility by studying the neurotoxicity of trans-1-amino-cyclopentyl-1,3-dicarboxylate (trans-ACPD), a selective agonist of the metabotropic glutamate receptor. Exposure of cortical neurons to 100 microM trans-ACPD substantially increased phosphoinositide hydrolysis and intraneuronal free calcium in the presence of CPP and CNQX. Despite the presence of functional metabotropic receptors on cultured neurons, however, exposure of cultures to as high as 1 mM trans-ACPD for 24 h failed to produce any morphological or chemical signs of neuronal damage. Furthermore, trans-ACPD did not potentiate submaximal neurotoxicity produced by other non-N-methyl-D-aspartate (NMDA) agonists, kainate and D,L-alpha-amino-3-hydroxy-5-methyl-4-isoxazole-4-propionic acid (AMPA).
Animals↗
Localization of surface peptide from ribosomal protein L7 on 80 S ribosome by biotinylation.
A surface topography of ribosomal peptides on ribosome particles was conducted by using N',Hydroxysuccinimido-biotin (NHS-biotin) modification. All rat ribosomal proteins, except proteins L3 and L8, are biotinylated when the ribosome particle is the substrate. A surface peptide from protein L7 was determined from biotinylated ribosomes by high performance liquid chromatography and cyanogen bromide peptide mapping. It was found that only the tandem repeats of the NH2-terminal segment of protein L7 are accessible to biotinylation. It is concluded that the NH2-terminal-end of protein L7 should be exposed on the surface of ribosomal particles.
Animals↗
Revised clinical and laboratory criteria for subtypes of inherited epidermolysis bullosa. A consensus report by the Subcommittee on Diagnosis and Classification of the National Epidermolysis Bullosa Registry.
Inherited epidermolysis bullosa encompasses a number of diseases, with the common finding of blister formation after minor mechanical trauma to the skin. In some forms significant, if not eventually fatal, extracutaneous disease activity may occur. In recent years application of newer technologies has contributed substantially to an overall understanding of this collection of inherited diseases. Concurrently, many new phenotypes have been recognized, in part the result of ongoing prospective patient registries in the United States and abroad. Unfortunately, this has resulted in a massive literature that may appear to be confounded by seemingly excessive or arbitrary subdivision of epidermolysis bullosa variants. With these concerns in mind a subcommittee was established by the National Epidermolysis Bullosa Registry to summarize the current literature and to make recommendations as to the best clinical and laboratory criteria for the practical diagnosis and subclassification of patients with inherited epidermolysis bullosa.
Epidermolysis Bullosa↗
Molecular action of tricholin, a ribosome-inactivating protein isolated from Trichoderma viride.
An extracellular protein was isolated from a species of soil-borne fungi (Trichoderma viride) and its amino acid composition has been determined. The protein is acidic with a molecular mass of 14,200 daltons and is given the trivial name tricholin. Tricholin is a potent inhibitor of cell-free protein synthesis. When rabbit reticulocyte lysate was incubated with tricholin at a concentration of 6.3 x 10(-7) M, it completely abolished the capacity of the lysate to support protein synthesis. The inhibition appears to be due to its reaction to ribosomes, since it generates a specific cleavage product, an alpha-sarcin RNA fragment, from reticulocyte ribosomal RNA. This reaction to ribosomes mimics that of alpha-sarcin. The antibody of alpha-sarcin strongly cross-reacts with tricholin, while the antibody of tricholin shows a weak reaction with alpha-sarcin.
Cell-Free System↗
Sequence specificity of mRNA N6-adenosine methyltransferase.
The sequence specificity of chicken mRNA N6-adenosine methyltransferase has been investigated in vivo. Localization of six new N6-methyladenosine sites on Rous sarcoma virus (RSV) virion RNA has confirmed our extended consensus sequence for methylation: RGACU, where R is usually a G (7/12). We have also observed A (2/12) and U (3/12) at the -2 position (relative to m6A at +1) but never a C. At the +3 position, the U was observed 10/12 times; an A and a C were observed once each in weakly methylated sequences. The extent of methylation varied between the different sites up to a maximum of about 90%. To test the significance of this consensus sequence, it was altered by site-specific mutagenesis, and methylation was assayed after transfection of mutated RSV DNA into chicken embryo fibroblasts. We found that changing the G at -1 or the U at +3 to any other residue inhibited methylation. However, inhibition of methylation at all four of the major sites in the RSV src gene did not detectably alter the steady-state levels of the three viral RNA species or viral infectivity. Additional mutants that inactivated the src protein kinase activity produced less virus and exhibited relatively less src mRNA in infected cells.
Animals↗