Biomedical subjects

S L Adams

Publications and source records attributed to S L Adams.

At least 91 records · Page 5Linked to original sources

PubMed1985

Control of types I and II collagen and fibronectin gene expression in chondrocytes delineated by viral transformation.

We have analyzed the effects of transformation by Rous sarcoma virus on expression of types I and II collagen and fibronectin genes in vertebral chondrocytes and compared them with expression of these genes in skin fibroblasts. Transformed chondrocytes display a dramatically decreased amount of type II collagen RNA, which can account fully for the decreased synthetic rate of this protein. Paradoxically, these cells also display greatly increased amounts of type I collagen RNAs, which are translated efficiently in vitro, but not in the intact cells. We show here that the type I collagen RNAs in transformed chondrocytes are nearly indistinguishable from those found in skin fibroblasts, and that they clearly differ from the type I collagen RNAs found in normal chondrocytes. Transformed chondrocytes also display an increased amount of fibronectin RNAs, which can account fully for the increased synthetic rate of this protein. Thus, the effects of transformation by Rous sarcoma virus on type I collagen and fibronectin RNAs in chondrocytes are the opposite of those observed in fibroblasts, which display decreased amounts of these three RNAs. These data indicate that the effects of transformation on the genes encoding type I collagen and fibronectin must be modulated by host cell-specific factors. They also imply that the types I and II collagen genes may be regulated by different mechanisms, the type I genes being controlled at both transcriptional and posttranscriptional levels, and the type II gene being controlled primarily at the transcriptional level.

Animals↗

PubMed1984

Prospective evaluation of syncope.

One hundred seventy patients with syncope presenting to an emergency department were studied prospectively. A checklist was used to supplement the physician's history and physical to ensure adequate recording of potentially useful data. Follow-up data were available in 89% of patients with a mean follow-up period of 6.2 months. Patients were categorized by presumed etiology using specific criteria. Typical vasovagal syncope occurred in 37.1% of patients. Other etiologies included first seizure (8.8%), orthostasis (7.6%), cardiac (4.1%), micturition (2.4%), hypoglycemia (1.8%), and psychogenic (0.6%). Syncope of unknown etiology accounted for 37.6% of the patients. The estimated duration of warning period was significantly shorter in patients with cardiac syncope compared to patients with vasovagal syncope. The yield of laboratory tests was low with the exception of the serum bicarbonate, which was decreased in 70% of our seizure patients. Recommendations regarding initial evaluation and admission are discussed.

Adolescent↗

PubMed1984

Drugs that may exacerbate myasthenia gravis.

Myasthenia gravis is an uncommon disease. The emergency physician should be cautious when prescribing medications to myasthenics for problems not related to myasthenia gravis. We have discussed some of those agents (Figure 3) that are recognized to cause exacerbation of MG or that may have the potential to exacerbate MG. We recommend that management of any medical or surgical problem of the myasthenic be done in consultation with a managing neurologist, and that either early follow-up or admission is necessary when these agents are used in the patient with myasthenia gravis.

Anti-Bacterial Agents↗

PubMed1984

Tissue specificity of type I collagen gene expression is determined at both transcriptional and post-transcriptional levels.

We analyzed the control of type I collagen synthesis in four kinds of differentiated cells from chicken embryos which synthesize very different amounts of the protein. Tendon, skin, and smooth muscle cells were found to have identical amounts of type I collagen RNAs; however, the RNAs had inherently different translatabilities, which were observed both in vivo and in vitro. Chondrocytes also had substantial amounts of type I collagen RNAs, even though they directed no detectable synthesis of the protein either in vivo or in vitro. Type I collagen RNAs in chondrocytes display altered electrophoretic mobilities, suggesting that in these cells the reduction in translational efficiency may be mediated in part by changes in the RNA structure. These data indicate that control of type I collagen gene expression is a complex process which is exerted at both transcriptional and post-transcriptional levels.

Animals↗

PubMed1982

Regulation of the synthesis of extracellular matrix components in chondroblasts transformed by a temperature-sensitive mutant of Rous sarcoma virus.

Regulation of cartilage extracellular matrix synthesis has been examined in chondroblasts infected with a temperature-sensitive mutant of Rous sarcoma virus. Cells grown at the nonpermissive temperature synthesized large amounts of several chondroblast-specific polypeptides (type IV proteoglycan core protein, type II procollagen, a proteoglycan link protein(s) and a 60 kd protein) and very low levels of fibronectin. At the permissive temperature, synthesis of chondroblast-specific proteins was coordinately reduced, while fibronectin synthesis was greatly increased. These changes reflected comparable alterations in levels of translatable mRNAs encoding these proteins. This analysis also revealed the unexpected presence in the transformed cells of type I collagen mRNAs, which are not used in intact cells, indicating that a posttranscriptional control (or controls) may be acting in transformed chondroblasts.

Animals↗

PubMed1980

Isolation and characterization of genomic DNA coding for alpha 2 type I collagen.

We have isolated and characterized a segment of the chick alpha 2 collagen gene by screening a library of chick genomic fragments using as hybridization probe an alpha 2 collagen cDNA clone. Several clones were isolated and one of them, lambda gCOL 204, was used for further studies. The DNA of lambda gCOL 204 hybridizes to a unique species of mRNA the size of alpha 2 collagen mRNA. This mRNA can be translated into a unique polypeptide which comigrates in SDS-gel electrophoresis with pro-alpha 2 collagen. Electron microscopic analysis by R-loop technique indicates that lambda gCOL 204 contains 7Kb of the alpha 2 collagen gene. This 7 Kb piece constitutes the 3' end of the gene. The same clone also contains 9 Kb of DNA that is immediately adjacent to the 3' end of the alpha 2 collagen gene. The cloned segment of the alpha 2 collagen gene is interrupted by 8 intervening sequences of various lengths. The coding sequences for collagen in this clone add up to approximately 1,800 bp, which correspond to about 1/3 of alpha 2 collagen mRNA. DNA sequence analysis of a small coding segment of lambda g COL 204 reveals a characteristic collagen type sequence which encodes for an amino acid sequence identical to a sequence found in calf alpha 2 collagen. The sequence of this region of the protein has not yet been determined for the chick alpha 2 collagen.

Animals↗

PubMed1980

Construction of a recombinant bacterial plasmid containing pro-alpha 1(I) collagen DNA sequences.

A partially purified mRNA preparation enriched for chick collagen messenger RNA activity was used as template for the synthesis of double stranded cDNA. The cDNA was ligated into the HindIII site of the plasmid vector pBR322 and used to transform Escherichia coli x1776. One plasmid with an 800-base pair insert was shown to contain DNA sequences corresponding to Type I pro-alpha 1 collagen.

Animals↗

PubMed1979

Use of recombinant plasmids to characterize collagen RNAs in normal and transformed chick embryo fibroblasts.

Two recombinant plasmids containing chick collagen DNA sequences have been used to characterize messenger RNAs for pro-alpha1 (type I) and pro-alpha2 collagen. Poly(A)-containing RNA from chick embryo calvaria and long bones, tissues which are very active in collagen synthesis, were electrophoresed on agarose gels containing methylmercuric hydroxide and transferred to diazobenzyloxymethyl paper; these covalently bound RNAs were hybridized to 32P-labeled pro-alpha1 or pro-alpha2 collagen DNA sequences derived from the recombinant plasmids. The pro-alpha1 collagen probe identified two RNAs, a major species of 5000 bases and a minor species of 7100 bases; the pro-alpha2 collagen probe hybridized to a major species very similar in size to the pro-alpha1 mRNA, about 5200 bases, and a minor species of 5700 bases. It is possible that the 7100 and 5700 base RNAs represent precursors of pro-alpha1 and pro-alpha2 collagen mRNA, respectively. When similar hybridization experiments were performed with RNA from chick embryo fibroblasts, both the pro-alpha1 and pro-alpha2 collagen mRNAs were observed, as well as their corresponding larger species. With RNAs from fibroblasts transformed by Rous sarcoma virus, however, the levels of all RNA species which hybridized with the pro-alpha1 and pro-alpha2 collagen DNA probes were significantly reduced.

Animals↗

PubMed1978

Decreased levels of collagen mRNA in rous sarcoma virus-transformed chick embryo fibroblasts.

We have found that double-stranded cDNA synthesized in extended reactions by avian myeloblastosis virus reverse transcriptase is suitable substrate for a variety of restriction endonucleases. Experiments in which rabbit reticulocyte mRNA was reverse-transcribed and restricted to generate beta-globin-specifihe nucleotide sequence of beta-globin mRNA. This method has been applied to study collagen mRNA synthesis in normal and Rous sarcoma virus (RSV)-transformed chick embryo fibroblasts. Characteristic sets of collagen cDNA restriction fragments were produced from RNA fractions rich in collagen message activity. These sets of cDNA fragments, generated by the restriction endonucleases Hae III and Hap II, provided a convenient marker for the presence of collagen mRNA sequences. Equal quantities of high molecular weight mRNA from chick embryo fibroblasts (CEF) and RSV-CEF were reverse-transcribed and the resulting cDNA was restricted. The relative yields of collagen cDNA fragments from such reactions strongly suggest that the decrease in functional collagen RNA following RSV-induced transformation of CEF represents a decrease in the copy number of collagen messenger sequences. The potential of this approach for the study of regulation in other systems is discussed.

Animals↗

PubMed1978

Construction of a recombinant bacterial plasmid containing a chick pro-alpha2 collagen gene sequence.

A recombinant plasmid containing chick pro-alpha2 collagen gene sequences has been constructed and cloned in Escherichia coli. Using partially purified collagen mRNA as template, we synthesized double-stranded DNA by the successive action of reverse transcriptase (RNA-directed DNA nucleotidyltransferase) from avian myeloblastosis virus and the Klenow A fragment of E. coli DNA polymerase I. From this complex mixture of double-stranded DNAs, a specific 200-base-pair restriction fragment was generated by cleavage with the restriction endonucleases BamHI and EcoRI. These enzymes also make unique cuts in the plasmid vector pBR322. The restriction fragment was inserted into pBR322 via these BamHI and EcoRI sites and cloned in E. coli chi1776. The cloned recombinant plasmid was shown to contain pro-alpha2 collagen DNA by its specific hybridization to chick pro-alpha2 collagen mRNA, as assayed in an in vitro translation system. Thus, a clone containing pro-alpha2 collagen DNA was constructed without first obtaining highly purified collagen mRNA.

Animals↗

PubMed1977

Levels of translatable mRNAs for cell surface protein, collagen precursors, and two membrane proteins are altered in Rous sarcoma virus-transformed chick embryo fibroblasts.

Transformation of chick embryo fibroblasts by Rous sarcoma virus results in decreased amounts of a major cell surface protein and of collagen. To determine the mechanism accounting for the decreased production of these proteins, we have measured the relative amounts of functional mRNAs for these and other transformation-sensitive proteins. Total cellular RNAs extracted from normal cells and from cells transformed by the Schmidt-Ruppin strain of Rous sarcoma virus were translated in a cell-free system derived from wheat germ. Analysis of the in vitro translation products of RNAs from normal and transformed chick embryo fibroblasts shows a 5-fold reduction in the translatable mRNA for cell surface protein and a 10-fold reduction in translatable mRNA for two collagen precursors. In addition, increases in functional mRNA are observed for myosin and for two membrane polypeptides with molecular weights of 95,000 and 78,000; the latter two proteins increase on transformation, but the increases are in large part secondary to the depletion of glucose from the medium of transformed cells. Our data suggest that some of the major cellular changes induced by oncogenic viruses are due to changes in the activity of specific cellular genes.

Actins↗

PubMed1976

Purification and characterization of two initiation factors required for maximal activity of a highly fractionated globin mRNA translation system.

Two additional initiation factors (IF-M4 and IF-M5) have been purified and characterized both physically and biologically. IF-M4 is active as a single polypeptide chain with a molecular weight of 48,000. In contrast, IF-M5 is active as a complex with a molecular weight of about 500,000 and consists of seven major and several minor polypeptide components. Analysis of IF-M5 in two polyacrylamide gel electrophoresis systems indicated that one of the major polypeptide chains of IF-M5 was the 35,000 dalton subunit of IF-MP. This analysis also revealed that IF-M2A, IF-M3, and elongation factor 2 were present as minor components. Both IF-M4 and IF-M5 are required to achieve maximal activity in an assay system dependent on exogenous globin mRNA, but neither factor has been observed to stimulate model reactions that utilize artificial templates [poly(U) or AUG].

Animals↗

PubMed1975

Binding of MET-TRNAf and GTP to homogeneous initiation factor MP.

Homogeneous initiation factor MP forms a stable complex with Met-tRNAf which binds to nitrocellulose filters in the absence of ribosomal subunits. Complex formation is rapid at 0 degrees and the rate of reaction is stimulated 20-fold by GTP when freshly prepared initiation factor MP is used. Under optimal assay conditions, a 1:1:1 stoichiometry for initiation factor MP, GTP, and Met-tRNAf is indicated, based on a molecular weight for initiation factor MP of 180,000. Kinetic analysis of ternary complex formation suggests an ordered reaction sequence with binding of GTP followed by binding of Met-tRNAf. However, binding of GTP appears to produce an unstable state which leads to rapid inactivation of initiation factor MP in the absence of Met-tRNAf. Formation of a stable binary complex of initiation factor MP and Met-tRNAf occurs in the absence of GTP. The binary complex cannot subsequently bind GTP. While storage of initiation factor MP at 0 degrees for several weeks has no effect on the rate or extent of Met-tRNAf binding in the presence of GTP, the rate of binary complex formation is increased 10-fold. The binary and ternary complexes appear to bind to 40 S ribosomal subunits with equal efficiency.

Animals↗

PubMed1975

Eukaryotic initiation complex formation. Evidence for two distinct pathways.

Two distinct pathways have been elucidated which lead to the formation of an AUG-dependent initiation complex. One pathway involves the use of initiation factor M1 (IF-M1) to promote AUG-dependent binding of the initiator tRNA to the 40 S subunit, followed by joining of the 60 S subunit in the presence of IF-M2A, IF-M2B, and GTP. The second pathway involves the IF-MP-directed binding of initiator tRNA to the 40 S subunit via a ternary complex of IF-MP-GTP-Met-tRNAf. This reaction does not require AUG codon. However, subsequent formation of an 80 S initiation complex (as determined by methionyl-puromycin synthesis) required AUG as well as IF-M2A, IF-M2B, and GTP. Since both pathways require the same complementary initiation factors (at the same level), it would appear that the only difference is the manner in which the initiator tRNA is bound to the 40 S subunit, either by IF-M1 or IF-MP. Examination of the requirements for endogenous mRNA-directed methionyl-puromycin synthesis indicates a greater difference between IF-MP and IF-M1 in that only IF-MP was capable of forming an 80 S initiation complex which was sensitive to puromycin.

Animals↗

PubMed1975

Comparison of fMet-tRNAf and Met-tRNAf from Escherichia coli and rabbit liver in initiation of hemoglobin synthesis.

A comparison has been made of the ability of the formylated and unformylated initiator tRNAs of Escherichia coli and rabbit liver to participate in a number of model reactions of protein synthesis. These reactions include: (a) formation of a ternary complex composed of the initiator tRNA, GTP, and initiation factor MP; (b) ApUpG-directed binding of the initiator tRNA to 40 S subunits with initiation factor Ml; (c) formation of the artificial dipeptide, methionylpuromycin; (d) formation of the natural initial globin dipeptide, methionylvaline; and (e) synthesis of sheep alpha and betaB-globin chains on reticulocyte polysomes from a type BB sheep. The results of these studies indicate that although the prokaryotic initiator tRNA species function efficiently in the partial reactions which involve only binding, the methionine donated by the prokaryotic tRNA is not incorporated efficiently into peptide linkage. This suggests that the initial high level of binding of the E. coli initiator tRNAs may be nonspecific, and that the structure of the tRNA itself is important for specific recognition by eukaryotic initiation factors. The effect of formylation on the effectiveness of the initiator tRNA is not clear; it reduces activity in ternary complex formation, does not affect ApUpG-directed binding to 40 S subunits, and increases the rate or extent of incorporation of methionine, or both, into methionylpuromycin and globin chains.

Animals↗

PubMed1973

Hemogloblin switching in sheep and goats: erythropoietin-dependent synthesis of hemoglobin C in goat bone-marrow cultures.

The anemia-induced switch from hemoglobin A (alpha(2)beta(2) (A)) to hemoglobin C (alpha(2)beta(2) (C)) synthesis occurring in vivo in sheep and goats has been reproduced in tissue culture of goat bone-marrow cells. Cultivation of primary cultures of goat bone marrow in the presence of erythropoietin results in the appearance of detectable amounts of beta(C) globin after 48-72 hr, as well as in a decrease in beta(A) globin. A population of proerythroblasts, as well as active heme and globin synthesis, are maintained for at least 3 days in erythropoietin-treated, but not in erythropoietin-deficient, cultures. These findings demonstrate (i) maintenance of erythropoietin-responsive cells from bone marrow in vitro, and (ii) switching in vitro from the synthesis of a globin chain coded by one gene to that coded by a different, nonallelic gene. Bone-marrow culture might be a useful model system for study of the mechanism of action of erythropoietin and for study of the activation (and inactivation) of specific genes in vitro.

Anemia↗

PubMedDate not supplied

Massive ethylene glycol poisoning without evidence of crystalluria: a case for early intervention.

A case of severe ethylene glycol poisoning is presented, characterized by protracted delirium, coma, and delayed adult respiratory distress syndrome. This patient never demonstrated evidence of calcium oxalate crystalluria or renal insufficiency. Ethylene glycol intoxication should be considered in the patient who presents with an altered mental status, unexplained metabolic acidosis, and elevated anion and osmolal gaps with or without crystalluria. Early empiric ethanol therapy and consideration of dialysis are recommended for those patients with such a presentation without evidence of abnormal levels of ketones, lactate, salicylate, or ethanol. It is proposed that early ethanol therapy may prevent the formation of ethylene glycol metabolites to the extent that calcium oxalate crystalluria is not seen.

Acid-Base Equilibrium↗

PubMedDate not supplied

Emergency medical recognition and management of idiopathic anaphylaxis.

Idiopathic anaphylaxis (IA) is a diagnosis of exclusion that is made when no identifiable causative factors can be found for an episode of anaphylaxis. IA is a potentially life-threatening disease that is the result of a nonimmunologic mast cell activation syndrome. Acute presentation and treatment of these patients is most often in the emergency department and is clinically the same as anaphylaxis from allergens. Since these episodes are unpredictable and often recurrent, these patients are at risk of death if not identified on acute presentation and managed appropriately. As an increasing number of patients are being diagnosed with IA, they will be presenting to emergency departments with initial and recurrent episodes of IA. Therefore, increased awareness of IA and coordinated care is needed so that the morbidity and mortality of this potentially fatal disease can be kept at a minimum.

Acute Disease↗