Thermotolerance and heat shock response during early development of the mammalian embryo.
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Animals↗
Biomedical subjects
M Edwards
Publications and source records attributed to M Edwards.
Physical mapping of the human carbonic anhydrase gene cluster on chromosome 8.
A cluster of genes encoding the three cytoplasmic carbonic anhydrase isozymes CAI, CAII, and CAIII lie on the long arm of chromosome 8 (8q22) in humans. These genes have been mapped using pulsed-field gel electrophoresis. The genes lie in the order CA2, CA3, CA1. CA2 and CA3 are separated by 20 kb and are transcribed in the same direction, away from CA1. CA1 is separated from CA3 by over 80 kb and is transcribed in the direction opposite to CA2 and CA3. The arrangement of the genes is consistent with proposals that the duplication event which gave rise to CA1 predated the duplication which gave rise to CA2 and CA3. The order of these three genes differs from that suggested for the mouse based on recombination frequency.
Blotting, Southern↗
Development of radiation protection standards.
Radiation protection standards are based on the best available knowledge, caution, and perception. Dose limits for occupational exposure have decreased as knowledge was gained about radiation effects: from 0.6 Sv (60 rem)/year for 1900-1930 to 50 mSv (5 rem)/year in 1958 (the level still used as of 1990). Current dose limits for public exposure range from 1 mSv to 5 mSv, depending on frequency of exposure. For the embryo and fetus, dose limits are 0.5 mSv/mo and 5 mSv for the entire gestation. In the 1970s, the concept of acceptable risk and that of a non-threshold dose-response relationship became the basis for setting dose limits. Three principles of radiation protection are that (a) dose levels should not exceed acceptable levels, (b) optimal dose levels should be as low as reasonably achievable, and (c) radiation should not be used unless it produces a positive net benefit. Although no dose limits have been set for patients undergoing diagnostic and therapeutic radiologic procedures, such measures must provide a net benefit to patients at optimal dose levels.
History, 20th Century↗
Cloning and characterization of a gene encoding pig epidermal growth factor.
A portion of the pig epidermal growth factor (EGF) gene has been isolated and characterized. The nucleotide sequencies of exons 20 and 21, which encode the EGF region of the precursor protein, show 85% similarity with the human EGF gene sequence. In addition, conservation of the intron-exon boundaries between the two species was generally observed. Although the pig exon 21 appeared to lack a single nucleotide at its 5' end relative to the human gene, sequences obtained by direct amplification of the genomic DNA around the 5' end of this exon using the polymerase chain reaction, and from a pig EGF cDNA recombinant isolated from a kidney library, indicated that the deletion was probably a cloning artifact. Comparison of the predicted amino acid sequence of pig EGF with that of EGF from other species, as well as with several other polypeptides which bind to the EGF receptor, indicated conservation of Gly18, Tyr37, Gly39 and Arg41 in addition to all six cysteine residues and Leu47, which are known to be critical for biological activity. A synthetic gene encoding the predicted amino acid sequence of pig EGF was expressed in yeast. The recombinant polypeptide was shown to compete with 125I-labelled mouse EGF for binding to cells and to stimulate DNA synthesis in quiescent monolayers of Swiss 3T3 cells.
Amino Acid Sequence↗
Airshow disaster plans.
Airshows require careful medical planning. Disaster drills and coordination between all rescue agencies are necessary. Rescue personnel and command post must be highly visible. Good communication includes dedicated radio frequencies at the site, dedicated phone lines to hospitals, and multiple back-ups. Security personnel should use yellow police tape for crowd control, and volunteers must be supervised. Key medical elements include efficient triage and stabilization at the site, adequate medical personnel, equipment dispersed within the crowd, rapid transportation including helicopters, and crisis intervention. Separate areas are needed for persons with minor injuries, relatives and friends, the press, and a morgue. Disaster plans for airshows have unique aspects. A predetermined time benefits planning. Airports often have pre-existing medical facilities, and participating military agencies may have additional resources. Burns and inhalation injuries predominate at airshow accidents. Enlarging spectator safety zones and modifying aerobatic maneuvers can prevent injury.
Aerospace Medicine↗
Autosomal recessive inheritance of myopia in Hong Kong Chinese infants.
Hong Kong Chinese infants were refracted by retinoscopy at regular intervals between the age of approximately 10 and 40 weeks. Cyclopentolate 1% was used to obtain cycloplegia. The spherical equivalent of the refractive error was calculated for each child and analysis of variance carried out according to the refractive status of the parents. From approximately 20 weeks of age a significant difference was found between the mean spherical equivalent of the refractive error of infants of parents both of whom were myopic and that of infants of parents neither of whom was myopic. At 40 weeks of age a good fit with an autosomal recessive probability model was obtained.
Adult↗
The refractive status of Hong Kong Chinese infants.
One hundred and fifty-eight full-term Hong Kong Chinese infants were examined, at the age of approximately 10 weeks, using retinoscopy. Fifty of the subjects were re-examined at the ages of 20, 30 and 40 weeks. Cyclopentolate 1% was used to produce cycloplegia. Photographic methods were used to assess the straightness of the eyes of 122 infants. While the mean spherical equivalent of the refractive error at 10 weeks was within the limits reported in studies of Caucasian infants, a rapid decrease, not previously reported, occurred between the ages of 10 and 40 weeks. The amounts of astigmatism found were in line with results from Caucasian eyes but the direction was overwhelmingly with-the-rule. The prevalence of anisometropia decreased with age and anisometropia was not prevalent at the age of 37 weeks. Two exotropes (1.6%) and no esotropes were identified although this may have been confounded by the use of cyclopentolate.
Astigmatism↗
Neuroimaging of AIDS.
A retrospective review of the neuroimaging procedures of 84 patients with the diagnosis of AIDS was performed. Both computed tomography (CT) and magnetic resonance imaging (MRI) procedures were evaluated for the presence of atrophy, enhancing lesions and focal non-enhancing lesions. The imaging findings in several infectious conditions (toxoplasmosis, cytomegalovirus, papovavirus, HIV virus, tuberculosis and histoplasmosis) are described. Intracranial lymphoma, another complication of AIDS, also is discussed.
Acquired Immunodeficiency Syndrome↗
Structure and methylation patterns of the gene encoding human carbonic anhydrase I.
The gene (CAI) encoding human carbonic anhydrase I (CAI) has been isolated and shown to have a total length of 50 kb. Some 36 kb of this consists of a large intron separating the erythroid-specific promoter from the coding region. A small (54 bp) noncoding exon from within this intron is occasionally found in transcripts. Two different polyadenylation sites have been found, the most distal of which is the most commonly used. Methylation levels near the promoter differ widely in cell lines. In CAI-expressing cells, a region of DNA near the promoter is demethylated in a generally highly methylated background. Surprisingly, non-CAI-expressing cell lines show much lower levels of methylation.
Amino Acid Sequence↗
Expression of a synthetic gene for horseradish peroxidase C in Escherichia coli and folding and activation of the recombinant enzyme with Ca2+ and heme.
A synthetic gene encoding horseradish peroxidase isoenzyme C (HRP C) has been synthesized and expressed in Escherichia coli. The nonglycosylated recombinant enzyme (HRP C*) was produced in inclusion bodies in an insoluble inactive form containing only traces of heme. HRP C* was solubilized and conditions under which it folded to give active enzyme were determined. Folding was shown to be critically dependent upon the concentrations of urea, Ca2+, and heme and on oxidation by oxidized glutathione. Purification of active HRP C* from the folding mixture gave a peroxidase, with about half the activity of HRP C. Glycosylation is thus not essential for correct folding and activity. The C-terminal and N-terminal extensions to HRP identified previously in cloned cDNA sequences are also not required for correct folding. However, Ca2+ appears to play a key role in folding to give the active enzyme. The overall yield of purified active enzyme was 2-3%, but this could be increased by reprocessing material that precipitated during folding.
Amino Acid Sequence↗
On the mechanism by which midazolam causes spinally mediated analgesia.
The electrical current thresholds for pain (ECTP) in the skin of the neck and tail were measured in rats with chronically implanted lumbar subarachnoid catheters. The effects of a benzodiazepine antagonist and a gamma-aminobutyric acid (GABA) antagonist on the analgesic effects of equivalent doses of midazolam, fentanyl, and ketocyclazocine were studied. These were the minimum doses producing maximal segmental analgesia when given intrathecally (i.e., they all caused a significant and maximum increase in ECTP in the tail, which was similar for all three drugs, but no significant change in the ECTP in the neck). Flumazenil (Ro 15-1788) administration caused a parallel shift to the right of the dose-response curve for midazolam spinal analgesia. Segmental analgesia following midazolam was also significantly attenuated (P less than 0.05) when the selective GABA antagonist bicuculline was given intrathecally at the same time as midazolam. The highest dose of bicuculline used (50 pmol) caused no significant attenuation of the segmental analgesic effects of either ketocyclazocine or fentanyl. The authors concluded that the segmental analgesia produced by intrathecal midazolam is mediated by the benzodiazepine-GABA receptor complex that is involved in other benzodiazepine actions.
Analgesia, Epidural↗
Expression of the human carbonic anhydrase I gene is activated late in fetal erythroid development and regulated by stage-specific trans-acting factors.
Using flow cytometric analysis of red cells from different stages of ontogeny with anti-CAI antibody, it was shown that the human carbonic anhydrase I (HCAI) gene product appears in a developmental stage-specific manner. Virtually no CAI protein was detectable in fetal red cells prior to birth. However, at about the time of normal delivery (40 weeks gestation) CAI production is switched on. The proportion of cells containing CAI reaches adult levels during the second half of the first year of life. Northern analysis suggests that the appearance of CAI protein results directly from the activation of the gene and the production of new mRNA. A transient heterokaryon system was set up by fusing the erythroleukaemic cell lines MEL C88 (a mouse cell line in which CAI is expressed) and K562 SAI (a human cell line with an embryonic/fetal phenotype, not expressing CAI). SP6 RNAase mapping of RNA from the fused cells showed activation of the human CAI gene. This shows the developmental stage-specific expression of HCAI to be regulated by trans-acting factors.
Adult↗
Multiple GF-1 binding sites flank the erythroid specific transcription unit of the human carbonic anhydrase I gene.
Six potential GF-1 sites which bind an erythroid factor are present in the 5' and 3' regions flanking the erythroid-specific transcription unit of the human carbonic anhydrase I (HCAI) gene. When two of these sites are placed upstream of a minimal eukaryotic promoter they confer up-regulated expression in erythroid over non-erythroid cells. The presence of the erythroid factor in TPA-treated HEL cells in which the level of HCAI transcript has greatly decreased and in non-HCAI-expressing K562 cells suggests that in these cases the presence of the factor is not sufficient for HCAI expression.
Base Sequence↗
Crystallization and preliminary X-ray studies of an aspartate aminotransferase mutant from Escherichia coli.
Mutant aspartate aminotransferase V39L (Val39 replaced by Leu) from Escherichia coli has been crystallized into a monoclinic cell from a polyethylene glycol solution (pH 7.5) by vapor diffusion. The space group and the unit cell dimensions have been determined using a precession camera, a CAD4 diffractometer and a Nicolet Xentronics area detector to be P2(1) with a = 86.8 A, b = 79.9 A, c = 89.4 A, beta = 118.74 degrees. The crystals diffract to better than 2.3 A and are suitable for X-ray structure analysis.
Aspartate Aminotransferases↗
Expression of recombinant horseradish peroxidase C in Escherichia coli.
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Escherichia coli↗
Transformation of murine melanocytes by basic fibroblast growth factor cDNA and oncogenes and selective suppression of the transformed phenotype in a reconstituted cutaneous environment.
Constitutive expression of basic fibroblast growth factor (bFGF), a common characteristic of metastatic melanomas, was reproduced in vitro by infection of normal murine melanocytes with a recombinant retrovirus carrying a cDNA for bFGF. Expression of bFGF in these cells conferred autonomous growth in culture and extinguished differentiated functions, such as the synthesis of melanin and formation of dendrites. Independence from exogenous bFGF and loss of differentiated functions in vitro were induced also by transformation of melanocytes with the oncogenes myc, Ela, ras, and neu, although bFGF was not expressed by the respective transformants. As shown in skin reconstitution experiments onto syngeneic mice and subcutaneous injections into nude mice, the various transformants differed in their behavior in vivo. The bFGF transformants did not form tumors. They reverted to having a normal, melanotic phenotype and restricted growth. Myc and Ela transformants grew as tumors in nude mice but not in syngeneic, immunocompetent animals. Ras-transformed melanocytes were always tumorigenic, whereas the formation of tumors by neu transformants was suppressed by the concomitant grafting of keratinocytes in reconstituted skin of syngeneic mice. These data show that melanocytes genetically manipulated to produce bFGF acquire properties in vitro similar to those of metastatic melanoma cells or those induced by various oncogenes but that constitutive production of bFGF by itself is insufficient to make melanocytes tumorigenic. The experiments also show that melanocytes transformed by the selected oncogenes respond differentially to various environments in vivo.
Animals↗
Oculogyric crisis after metoclopramide therapy.
Oculogyric crisis developed in a 21-year-old girl after 5 oral doses of 10 mg of metoclopramide. The symptoms were relieved by i.v. administration of diphenhydramine hydrochloride. Although ocular side effects of metoclopramide are rare, it can induce an alarming oculogyric crisis in some sensitive subjects. The mechanism of oculogyric crises is unclear but the characteristics of the condition and some known causes are discussed. Advice is given on optometric management.
Adult↗
Neurofibromatosis types 1 and 2: cranial MR findings.
Neurofibromatosis 1 (NF-1) (von Rekhlinghausen disease) and neurofibromatosis 2 (NF-2) (bilateral acoustic neurofibromatosis) have been recently recognized to be distinct disorders through genetic linkages. The authors compared the cranial magnetic resonance (MR) images of 53 patients with NF-1 and 11 with NF-2. In the NF-1 group, MR imaging revealed 19 patients with optic gliomas and eight with parenchymal gliomas. In 32 patients, foci of prolonged T2, similar to those reported previously as hamartomas, were identified in the cerebellar peduncles, globus pallidus, midbrain, and other locations. The frequency of these foci was related to both age and the presence of optic gliomas. In the NF-2 group, MR imaging revealed eight patients with cranial nerve schwannomas and six with meningiomas (in addition to acoustic schwannomas in all 11). These findings demonstrate that NF-1 and NF-2 are different diseases requiring different imaging protocols. NF-1 seems to be associated with tumors of astrocytes and neurons and NF-2 with tumors of meninges and Schwann cells.
Adolescent↗