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Lamin Type A: A subclass of developmentally regulated lamins having a neutral isoelectric point. They are found to disassociate from nuclear membranes during mitosis.Aging, Premature: Changes in the organism associated with senescence, occurring at an accelerated rate.Farnesyltranstransferase: An enzyme that catalyzes the synthesis of geranylgeranyl diphosphate from trans, trans-farnesyl diphosphate and isopentenyl diphosphate.Cell Nucleus Shape: The quality of surface form or outline of the CELL NUCLEUS.Nuclear Lamina: A lattice of fibrils which covers the entire inner surface of the nuclear envelope and interlinks nuclear pores (NUCLEAR PORE).Werner Syndrome: An autosomal recessive disorder that causes premature aging in adults, characterized by sclerodermal skin changes, cataracts, subcutaneous calcification, muscular atrophy, a tendency to diabetes mellitus, aged appearance of the face, baldness, and a high incidence of neoplastic disease.Prenylation: Attachment of isoprenoids (TERPENES) to other compounds, especially PROTEINS and FLAVONOIDS.Protein PrecursorsProtein Prenylation: A post-translational modification of proteins by the attachment of an isoprenoid to the C-terminal cysteine residue. The isoprenoids used, farnesyl diphosphate or geranylgeranyl diphosphate, are derived from the same biochemical pathway that produces cholesterol.Bone Demineralization, Pathologic: Decrease, loss, or removal of the mineral constituents of bones. Temporary loss of bone mineral content is especially associated with space flight, weightlessness, and extended immobilization. OSTEOPOROSIS is permanent, includes reduction of total bone mass, and is associated with increased rate of fractures. CALCIFICATION, PHYSIOLOGIC is the process of bone remineralizing. (From Dorland, 27th ed; Stedman, 25th ed; Nicogossian, Space Physiology and Medicine, 2d ed, pp327-33)Fibroblasts: Connective tissue cells which secrete an extracellular matrix rich in collagen and other macromolecules.Nuclear Envelope: The membrane system of the CELL NUCLEUS that surrounds the nucleoplasm. It consists of two concentric membranes separated by the perinuclear space. The structures of the envelope where it opens to the cytoplasm are called the nuclear pores (NUCLEAR PORE).Nuclear Proteins: Proteins found in the nucleus of a cell. Do not confuse with NUCLEOPROTEINS which are proteins conjugated with nucleic acids, that are not necessarily present in the nucleus.Skin Abnormalities: Congenital structural abnormalities of the skin.Lamins: Nuclear matrix proteins that are structural components of the NUCLEAR LAMINA. They are found in most multicellular organisms.Protein Modification, Translational: Any of the enzymatically catalyzed modifications of the individual AMINO ACIDS of PROTEINS, and enzymatic cleavage or crosslinking of peptide chains that occur pre-translationally (on the amino acid component of AMINO ACYL TRNA), co-translationally (during the process of GENETIC TRANSLATION), or after translation is completed (POST-TRANSLATIONAL PROTEIN PROCESSING).Lamin Type B: A subclass of ubiquitously-expressed lamins having an acidic isoelectric point. They are found to remain bound to nuclear membranes during mitosis.Organelle Shape: The quality of surface form or outline of ORGANELLES.Contracture: Prolonged shortening of the muscle or other soft tissue around a joint, preventing movement of the joint.Lipodystrophy: A collection of heterogenous conditions resulting from defective LIPID METABOLISM and characterized by ADIPOSE TISSUE atrophy. Often there is redistribution of body fat resulting in peripheral fat wasting and central adiposity. They include generalized, localized, congenital, and acquired lipodystrophy.Maxillofacial Abnormalities: Congenital structural deformities, malformations, or other abnormalities of the maxilla and face or facial bones.Metalloendopeptidases: ENDOPEPTIDASES which use a metal such as ZINC in the catalytic mechanism.Cell Aging: The decrease in the cell's ability to proliferate with the passing of time. Each cell is programmed for a certain number of cell divisions and at the end of that time proliferation halts. The cell enters a quiescent state after which it experiences CELL DEATH via the process of APOPTOSIS.Somatotrophs: Anterior pituitary cells which produce GROWTH HORMONE.Cockayne Syndrome: A syndrome characterized by multiple system abnormalities including DWARFISM; PHOTOSENSITIVITY DISORDERS; PREMATURE AGING; and HEARING LOSS. It is caused by mutations of a number of autosomal recessive genes encoding proteins that involve transcriptional-coupled DNA REPAIR processes. Cockayne syndrome is classified by the severity and age of onset. Type I (classical; CSA) is early childhood onset in the second year of life; type II (congenital; CSB) is early onset at birth with severe symptoms; type III (xeroderma pigmentosum; XP) is late childhood onset with mild symptoms.Cell Nucleus: Within a eukaryotic cell, a membrane-limited body which contains chromosomes and one or more nucleoli (CELL NUCLEOLUS). The nuclear membrane consists of a double unit-type membrane which is perforated by a number of pores; the outermost membrane is continuous with the ENDOPLASMIC RETICULUM. A cell may contain more than one nucleus. (From Singleton & Sainsbury, Dictionary of Microbiology and Molecular Biology, 2d ed)Aging: The gradual irreversible changes in structure and function of an organism that occur as a result of the passage of time.Bone Diseases, DevelopmentalPhenotype: The outward appearance of the individual. It is the product of interactions between genes, and between the GENOTYPE and the environment.Mutation: Any detectable and heritable change in the genetic material that causes a change in the GENOTYPE and which is transmitted to daughter cells and to succeeding generations.Syndrome: A characteristic symptom complex.Alkyl and Aryl Transferases: A somewhat heterogeneous class of enzymes that catalyze the transfer of alkyl or related groups (excluding methyl groups). EC 2.5.Progeria: An abnormal congenital condition, associated with defects in the LAMIN TYPE A gene, which is characterized by premature aging in children, where all the changes of cell senescence occur. It is manifested by premature greying; hair loss; hearing loss (DEAFNESS); cataracts (CATARACT); ARTHRITIS; OSTEOPOROSIS; DIABETES MELLITUS; atrophy of subcutaneous fat; skeletal hypoplasia; elevated urinary HYALURONIC ACID; and accelerated ATHEROSCLEROSIS. Many affected individuals develop malignant tumors, especially SARCOMA.Heterochromatin: The portion of chromosome material that remains condensed and is transcriptionally inactive during INTERPHASE.Longevity: The normal length of time of an organism's life.Cells, Cultured: Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others.Membrane Proteins: Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.Skin: The outer covering of the body that protects it from the environment. It is composed of the DERMIS and the EPIDERMIS.Disease Models, Animal: Naturally occurring or experimentally induced animal diseases with pathological processes sufficiently similar to those of human diseases. They are used as study models for human diseases.Enzyme Inhibitors: Compounds or agents that combine with an enzyme in such a manner as to prevent the normal substrate-enzyme combination and the catalytic reaction.DNA Repair: The reconstruction of a continuous two-stranded DNA molecule without mismatch from a molecule which contained damaged regions. The major repair mechanisms are excision repair, in which defective regions in one strand are excised and resynthesized using the complementary base pairing information in the intact strand; photoreactivation repair, in which the lethal and mutagenic effects of ultraviolet light are eliminated; and post-replication repair, in which the primary lesions are not repaired, but the gaps in one daughter duplex are filled in by incorporation of portions of the other (undamaged) daughter duplex. Excision repair and post-replication repair are sometimes referred to as "dark repair" because they do not require light.Heterozygote: An individual having different alleles at one or more loci regarding a specific character.Mitosis: A type of CELL NUCLEUS division by means of which the two daughter nuclei normally receive identical complements of the number of CHROMOSOMES of the somatic cells of the species.DNA Damage: Injuries to DNA that introduce deviations from its normal, intact structure and which may, if left unrepaired, result in a MUTATION or a block of DNA REPLICATION. These deviations may be caused by physical or chemical agents and occur by natural or unnatural, introduced circumstances. They include the introduction of illegitimate bases during replication or by deamination or other modification of bases; the loss of a base from the DNA backbone leaving an abasic site; single-strand breaks; double strand breaks; and intrastrand (PYRIMIDINE DIMERS) or interstrand crosslinking. Damage can often be repaired (DNA REPAIR). If the damage is extensive, it can induce APOPTOSIS.Bone and Bones: A specialized CONNECTIVE TISSUE that is the main constituent of the SKELETON. The principle cellular component of bone is comprised of OSTEOBLASTS; OSTEOCYTES; and OSTEOCLASTS, while FIBRILLAR COLLAGENS and hydroxyapatite crystals form the BONE MATRIX.Mice, Transgenic: Laboratory mice that have been produced from a genetically manipulated EGG or EMBRYO, MAMMALIAN.Cell Line: Established cell cultures that have the potential to propagate indefinitely.Mice, Knockout: Strains of mice in which certain GENES of their GENOMES have been disrupted, or "knocked-out". To produce knockouts, using RECOMBINANT DNA technology, the normal DNA sequence of the gene being studied is altered to prevent synthesis of a normal gene product. Cloned cells in which this DNA alteration is successful are then injected into mouse EMBRYOS to produce chimeric mice. The chimeric mice are then bred to yield a strain in which all the cells of the mouse contain the disrupted gene. Knockout mice are used as EXPERIMENTAL ANIMAL MODELS for diseases (DISEASE MODELS, ANIMAL) and to clarify the functions of the genes.Protein Binding: The process in which substances, either endogenous or exogenous, bind to proteins, peptides, enzymes, protein precursors, or allied compounds. Specific protein-binding measures are often used as assays in diagnostic assessments.