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Biomedical subjects

N Nelson

Publications and source records attributed to N Nelson.

At least 217 records · Page 12Linked to original sources
PubMed1986

Contribution of formaldehyde to respiratory cancer.

This article reviews the available data on the carcinogenicity of formaldehyde from experimental and epidemiologic studies and makes recommendations for further research. Two definitive chronic inhalation bioassays on rodents have demonstrated that formaldehyde produces nasal cancer in rats and mice at 14 ppm and in rats at 6 ppm, which is within the domain of present permissible human exposure (8-hr time-weighted average of 3 ppm, a 5 ppm ceiling, and a 10 ppm short-term exposure limit). Biochemical and physiologic studies in rats have shown that inhaled formaldehyde can depress respiration, inhibit mucociliary clearance, stimulate cell proliferation, and crosslink DNA and protein in the nasal mucosa. No deaths from nasal cancer have been reported in epidemiologic studies of cohorts exposed to formaldehyde, but three case-control studies suggest the possibility of increased risk. Although excesses of lung cancer deaths have been observed in some studies at industrial plants with formaldehyde exposure, uncertainties in interpretation limit the evaluation of these findings. Excess cancers of the brain and of lymphatic and hematopoietic tissues have been reported in certain studies of industrial groups and in most studies of formaldehyde-exposed professionals, but whether these excesses are related to formaldehyde exposure is not known. Several properties of formaldehyde pose unique problems for future research: the mechanisms responsible for its nonlinear response; its probable mechanism of carcinogenic action as a cross-linking agent; its formation in tissues as a normal metabolite; its possible action as a promoter and/or a cocarcinogen; and the importance of glutathione as a host defense at low exposure.

Air Pollutants↗
PubMed1986

Comparison of the protective effects of three phosphorothioate radioprotectors in the RIF-1 tumor.

Three aminoalkyl phosphorothioates, WR-2721, WR-3689, and WR-77913, were compared as radioprotectors of RIF-1 tumors irradiated in vivo and assayed for cell survival in vitro. The protector doses were 50% of the acute drug LD50. The radiation dose modifying factors for the three drugs were nearly equal, ranging from 1.5 to 1.7 at surviving fractions of 0.1 and 0.05. Using biodistribution data obtained with 35S labeled drugs, the uptake in tumors was calculated as micromoles drug per gram of tumor. On this basis, tumor levels of WR-77913 were 4.5-fold those of WR-2721, and WR-3689 uptake was 2.7-fold greater than uptake of WR-2721. Thus, on a molar basis, WR-2721 appears to be the most effective protector, but all three phosphorothioates protect this tumor moderately well. In diffusible substance autoradiographs of 3H WR-3689 labeled tumors, label was generally distributed over cells with no evidence of preferential localization over nuclei.

Amifostine↗
PubMed1986

Expression of cDNAs for acetylcholine receptor subunits in the yeast cell plasma membrane.

Yeast cells transformed with a plasmid containing cDNA encoding the alpha or delta subunit of the Torpedo californica acetylcholine receptor synthesize a protein. The expected molecular mass, antigenic specificity, and ligand-binding properties (in the case of the alpha subunit) of the subunits in yeast are similar to those of the subunits in T. californica membranes. The subunits are inserted into the yeast plasma membrane, demonstrating for the first time that yeast has the apparatus to express and insert foreign proteins into its plasma membrane. The alpha subunit constitutes approximately 1% of the yeast membrane proteins, and its density is about the same in the plasma membrane of yeast as in the receptor-rich electric organ of Electrophorus electricus. In view of the widely available technology for obtaining large quantities of yeast proteins, yeast cells may prove ideal for amplifying the amounts of interesting membrane-bound proteins available so that physical and biochemical studies can be made easily.

Animals↗
PubMed1985

Ineffectiveness of the trauma score and the CRAMS scale for accurately triaging patients to trauma centers.

Both the Trauma Score (TS) and the CRAMS scale have been advocated for field triage of trauma victims to trauma centers. To determine which scale best serves this purpose, both scores were calculated by computer for 5,130 trauma cases in our statewide computer file of ambulance rescue runs from 1981 through 1983. A total of 3,231 patients (63%) were treated in the ED and released; 1,857 (36.2%) were admitted to the hospital (202 of whom were transferred directly from the ED to the operating room [OR] for immediate operation); and 42 (0.8%) were DOA or died in the ED. Major trauma was defined as a TS of 12 or less or a CRAMS scale of 8 or less. Both scales correctly identified as major trauma all patients who were DOA or died in the ED. The TS identified as major trauma more patients admitted to the hospital than did the CRAMS scale (33% vs 21%; P less than .0001). The TS identified as major trauma more patients transferred from the ED to the OR than did the CRAMS scale (37% vs 21%; P less than .002). Both scales failed to identify as major trauma almost two out of three patients brought directly from the ED to the OR. The paramedics', or emergency medical technicians' qualitative judgements about injury severity, reflected in their coding injuries as life- or limb-threatening, was almost as good (more than 90% sensitive and specific) as either score (100% sensitive and specific) in identifying patients who died, and was better in identifying patients sent from the ED to the OR.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis-Related Groups↗
PubMed1985

Comparison of binding of [3H]misonidazole and [14C]misonidazole in multicell spheroids.

Uptake of [2-ring-14C]misonidazole and [3H]misonidazole with tritium in the side chain has been compared in 1-mm EMT-6/UW spheroids using liquid scintillation counting and autoradiography. The uptake of both labeled sensitizers as a function of incubation time was virtually identical. Uptake by the spheroids exceeded levels in the medium by 11/2 to 2 hr and was well modeled as a first-order binding process, with rate constants of 0.00324 hr-1 for 3H and 0.00388 hr-1 for 14C. The similar uptake of the two versions of this sensitizer labeled in different positions suggests that the metabolic actions which allow the drug to bind in hypoxic cells do not principally involve metabolites which separate the number 2 carbon of the imidazole ring from the side chain. The pattern of silver grains in autoradiographs was similar for both labeled sensitizers, with most labeled drug bound in an intermediate zone of cells between the necrotic center and the actively proliferating rim of the spheroids. The superior resolution possible with the tritiated compound showed that both nucleus and cytoplasm in viable looking cells were labeled while pycnotic cells were not labeled.

Animals↗
PubMed1984

An immunological method for detecting gene expression in yeast colonies.

A method for detection of cloned, expressed genes in yeast colonies has been developed. The 70-kilodalton (kDa) mitochondrial outer membrane protein of yeast was used as a model protein. Transformation of a strain deficient in the gene for the 70-kDa protein was performed, and transformed colonies were detected with the antibody decoration technique. This technique is based upon gentle lysis of yeast colonies that have been grown on nitrocellulose filters such that the yeast proteins remain bound in discrete spots after lysis. The lysis is carried out by alkaline conditions in the presence of 2-mercaptoethanol and sodium dodecyl sulfate. After lysis, empty sites on the nitrocellulose filter are blocked to eliminate nonspecific binding of proteins by either 0.5% bovine serum albumin or 0.05% Tween 20. Decoration with antibody is visualized by using 125I-labeled protein A or peroxidase-conjugated second antibody. Antigens amounting to less than 0.1% of the total protein in the cell can be readily detected by the assay. The sensitivity of the assay enables detection of 1 positive colony per plate containing about 1000 colonies.

Antigen-Antibody Complex↗
PubMed1984

Bioavailability of iron to rats from processed soybean fractions determined by intrinsic and extrinsic labeling techniques.

Intrinsic and extrinsic labeling techniques were used to measure iron bioavailability from soybean fractions (isolated soy protein, defatted flour, soy hulls, insoluble material and whey) by iron-depleted and non-iron-depleted rats. As expected, absorption of iron was higher in the iron-depleted than in the non-iron-depleted rats. In the iron-depleted group, significantly more iron was absorbed from soy whey than from other fractions. No other significant difference in iron absorption associated with iron source was observed. The higher absorption rate of iron from whey by the iron-depleted rats probably was related to a lower quantity of food consumed during the test meal by this group. Intrinsic and extrinsic labeling techniques produced similar assessments of bioavailability of iron.

Animals↗
PubMed1984

EMS by the numbers.

Explore the source record for details and available documents.

Emergency Medical Services↗
PubMed1983

ATP-driven proton fluxes across membranes of secretory organelles.

The ATP-dependent proton uptake by chromaffin granule membranes, lysosomes, and synaptosomes was examined. In synaptosomes the reaction was absolutely dependent on the presence of chloride, while in chromaffin granules chloride had a profound effect and in lysosomes only a minor effect. The presence of chloride markedly increases the rate of collapse of delta pH by carbonyl cyanide p-trifluoromethoxyphenylhydrazone in all three organelles. Ascorbate with phenazine methosulfate uncoupled the ATP-dependent proton uptake by chromaffin granules, but had no effect on lysosomes and synaptosomes. Proton uptake by submitochondrial particles was about 50-fold more sensitive to dicyclohexylcarbodiimide than the proton uptake by chromaffin granule membranes. Chromaffin granule membranes were treated with 2 M sodium bromide to inactivate the mitochondrial ATPase. The treatment caused a complete inhibition of the ATP-dependent proton uptake. Solubilization of these membranes by sodium cholate, followed by reconstitution by cholate dilution revealed the ATP-dependent proton uptake of the system. It is concluded that the genuine ATPase enzyme of chromaffin granules is a proton translocator.

Adenosine Triphosphate↗
PubMed1983

A novel ATPase in the chromaffin granule membrane.

The ATPase activity of the chromaffin granule membrane was found to differ profoundly from that of the mitochondrial inner membrane. First, mitochondrial ATPase is much more sensitive to low concentrations of dicyclohexylcarbodiimide than the chromaffin granule ATPase. Second, analysis of chromaffin granule preparations by immune replication revealed that mitochondrial contamination (as measured with an antibody against cytochrome c oxidase) could account for the presence of mitochondrial-type ATPase. Third, exposure of chromaffin granule preparation to sodium bromide removed the mitochondrial-type ATPase, but left over 70% of the total ATPase activity of the chromaffin granules intact. Finally, after solubilization of the chromaffin granule membranes with detergents, a novel ATPase could be separated from the mitochondrial-type ATPase. It is proposed that this novel ATPase represents most of the ATPase activity of the chromaffin granules and that the mitochondrial-type ATPase reflects contamination by mitochondria.

Adenosine Triphosphatases↗
PubMed1983

Genes and transcripts for the polypeptides of the cytochrome b6/f complex from spinach thylakoid membranes.

Cytochrome b6/f complex was prepared from washed thylakoid membranes by a procedure involving detergent treatment and centrifugation in sucrose gradients. The complex is composed of at least four polypeptide species, cytochrome f which occurs in two variant forms (mol. wt. 34/33 kd), cytochrome b6 (23 kd), the high-potential Rieske iron-sulfur protein (19 kd) and a fourth subunit (17 kd) of unknown function. Transcripts for the cytochromes f, b6 and subunit 4 were found in plastid RNA, those for the Rieske iron-sulfur protein in cytosolic poly(A) RNA. Transcripts for cytochrome b6 and subunit 4 are translated in rabbit reticulocyte lysates into products of correct length. The Rieske iron-sulfur protein and the cytochrome f apoprotein appear to be made as precursors with excess sequences of 7 and 4 kd, respectively. Cytochrome f, cytochrome b6 and subunit 4 are encoded by uninterrupted plastid genes that are located in the large single-copy region of the circular DNA molecule. Each of these genes is present once per chromosome. Their location and direction of transcription have been determined by hybrid-selection mapping and by cell-free transcription/translation of various recombinant DNAs. The genes for cytochrome b6 and for subunit 4 lie near each other, but do not overlap. They are transcribed into a single message. The gene for cytochrome f maps 15 kbp away from this cluster, close to the 3' end of the gene for the large subunit of ribulosebisphosphate carboxylase/oxygenase, and is transcribed into a separate 4 kb long RNA. All these genes have the same polarities with respect to each other.

Journal Article↗
PubMed1983

Yeast mitochondrial outer membrane specifically binds cytoplasmically-synthesized precursors of mitochondrial proteins.

The precursor of cytochrome b(2) (a cytoplasmically-synthesized mitochondrial protein) binds to isolated mitochondria or to isolated outer membrane vesicles. Binding does not require an energized inner membrane, is diminished by trypsin treatment of the membranes and is not observed with the partially processed (intermediate) form of the cytochrome b(2) precursor or with non-mitochondrial proteins. Upon energization of the mitochondria, the bound precursor is imported and cleaved to the mature form. Similar results were obtained with the precursor of citrate synthase. This receptor-like binding activity was present in isolated outer, but not inner membrane. It was solubilized from outer membrane with non-ionic detergent and reconstituted into liposomes.

Journal Article↗
PubMed1983

Improved maxillary stability with modified Lefort I technique.

This modification of the LeFort I osteotomy places the horizontal bony cut higher and into the dense cortical bone of the maxillozygomatic complex. It gives greater stability and also provides a more solid bony base for intraosseous wiring of the mobilized segment. This usually eliminates the need for dento-osseous or maxillomandibular fixation, and the segments appear to solidify more quickly. Over the last year, we have used this technique in 23 cases (four maxillary advancements, seven one-piece maxillary intrusions, and 12 segmental maxillary intrusions) with very favorable results. This modification has given us greater control and stability, especially in combined maxillary and mandibular osteotomies.

Humans↗
PubMed1983

Digital nerve sensory potentials in lesions of cervical roots and brachial plexus.

Normal values for the amplitudes of digital sensory nerve action potentials were obtained from 190 control subjects, using an orthodromic surface-recording technique. Lower limits were calculated, taking into account laterality, age and sex; the ratios of amplitudes between different digits were also estimated. The results in control subjects were compared with those of 20 cases of trauma involving root avulsion or extraspinal injury, 38 patients with intraspinal disease, 6 patients with extraspinal disorder and 9 cases of neuralgic amyotrophy. The variability of the dermatomes is discussed and it is concluded that digital sensory potential amplitudes offer a useful method of determining the site of a nerve lesion, provided certain limitations are recognized.

Adult↗