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Biomedical subjects

N Nelson

Publications and source records attributed to N Nelson.

At least 199 records · Page 11Linked to original sources
PubMed1987

Polypeptide-dependent protein kinase from bakers' yeast.

The purification and properties of a protein serine kinase (PK-P) extracted with Triton X-100 from membranes of bakers' yeast are described. The enzyme is virtually inactive unless either a histone or a heat-stable polypeptide from yeast membranes and Mg2+ are added. Other divalent cations substitute for Mg2+ poorly or not at all; most of them, including Mn2+, inhibit when added in the presence of 5 mM Mg2+. The enzyme is unstable but can be stabilized by addition of 0.1% Triton X-100 and 20% glycerol. The final preparation shows, on silver-stained electrophoresis gels, two major bands (Mr 41,000 and 35,000). According to gel filtration the molecular weight of the active protein is about 75,000. Of the two subunits, only the smaller one appears to be autophosphorylated. In addition to casein, the enzyme phosphorylates several proteins including the H+-ATPase (Mr 100,000) in the yeast plasma membrane. In order to demonstrate the phosphorylation of the ATPase (up to 0.9 equivalents), exposure of the latter to an acid phosphatase was required. Other phosphorylated proteins include mRNA cap-binding protein from mammalian erythrocytes and yeast, a glucocorticoid receptor protein, and a preparation of the guanine nucleotide-binding proteins Gi and Go from brain. A partial purification of a natural activator from yeast plasma membranes is described.

Chemical Phenomena↗
PubMed1987

Human salivary gustin is a potent activator of calmodulin-dependent brain phosphodiesterase.

Human salivary gustin stimulated activity of brain calmodulin-dependent cyclic nucleotide phosphodiesterase (cAMP PDEase; 3',5'-cyclic-nucleotide phosphodiesterase, EC 3.1.4.17) in a dose-dependent manner in the absence of calmodulin. At physiological levels found in human saliva, gustin activated cAMP PDEase 5- to 6-fold. Activation of PDEase occurred with as little as 500 ng of gustin. Comparative sensitivity of activation of PDEase by gustin was intermediate between calmodulin and lysophosphatidylcholine with maximal activation and half-maximal activation (indicated in parentheses) at 3 X 10(-8) M (4.3 X 10(-9) M), 3.4 X 10(-6) M (3.4 X 10(-7) M), and 2.5 X 10(-3) M (4.0 X 10(-5) M) for calmodulin, gustin, and lysophosphatidylcholine, respectively. No other major salivary protein activated PDEase. Anticalmodulin antibody completely inhibited calmodulin-activated cAMP PDEase activity, but the antibody had no effect on gustin-activated cAMP PDEase activity. A sensitive calmodulin RIA indicated that no calmodulin was detected in any gustin preparation that activated cAMP PDEase. Both gustin and calmodulin rendered cAMP PDEase thermally labile to a similar extent and increased Vmax without affecting the apparent Km for the substrate cAMP. Activation by gustin and calmodulin was unaffected by lubrol-PX, trypsin inhibitor, pepstatin A, or leupeptin. In the presence of 1 mM EGTA, gustin activated cAMP PDE 5- to 6-fold, but the activating ability was completely lost after gustin was heated at 100 degrees C for 5 min. In contrast, calmodulin lost all activating ability in the presence of 1 mM EGTA, whereas heating calmodulin at 100 degrees C for 5 min did not affect its activation of cAMP PDEase. Lysophosphatidylcholine-activation of cAMP PDEase, like gustin activation, was unaffected by EGTA, but lysophosphatidylcholine-activation of cAMP PDEase, like calmodulin activation, was unaffected by heating at 100 degrees C for 5 min.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1987

Neonatal reference values for ionized calcium, phosphate and magnesium. Selection of reference population by optimality criteria.

Thirty-one full-term newborn babies were investigated in order to establish reference values for ionized calcium. Only children fulfilling certain optimality criteria (with best possible maternal and infant conditions and uncomplicated pregnancy and delivery) were included. All infants were breast fed. Capillary blood for analysis of ionized calcium was collected by heel puncture on day 1 (6-36 h post partum, p.p.), day 3 (60-84 h p.p.) and day 5 (108-132 h p.p.). Ionized calcium was measured with a semi-automatic electrode system ICA 1 (Radiometer A/S, Copenhagen, Denmark). The reference ranges (mean +/- 2 SD) for days 1, 3 and 5 were 1.05-1.37, 1.10-1.42 and 1.20-1.48 mmol/l, respectively. The mean ionized calcium concentration on day 1 was significantly lower than on days 3 and 5. Reference values are also given for total calcium, magnesium and phosphate. We emphasize that it is impossible to calculate ionized calcium from total calcium or vice versa.

Calcium↗
PubMed1987

Neonatal hyperexcitability in relation to plasma ionized calcium, magnesium, phosphate and glucose.

Twenty-two full-term babies were examined with a quantitative neurological assessment on days 1, 2 and 5 in order to confirm the clinical impression of hyperexcitability observed at the routine examination on day 1. Ultrasound examination of the head was normal in all cases. Plasma ionized calcium, phosphate and glucose in the hyperexcitability group fell within the neonatal reference ranges, as described previously. However, serum magnesium was significantly lower on day 1, but spontaneously normalized on day 5. Routine check-ups at the well-baby-clinics did not reveal any major illnesses or developmental abnormalities.

Blood Glucose↗
PubMed1987

Perspectives on testing for toxic agents.

A series of observations and comments are made with respect to several areas of toxicology: these are briefly discussed. Some innovative areas receive discussion as representing substantial progress made in the field of toxicology in recent years. Topics included raise a number of questions: what agents should we test, and how should we go about selecting them; what is the importance of allowing for genetic diversity in carrying out tests that are meaningful for humans; and what is the relevance of studies in pharmacokinetics in the laboratory to humans. Human studies, because of ethical considerations, must be indirect, through access to available autopsy and surgical human tissues. Also, drug trials and clinical studies must be exploited. Cancer testing and evaluation is briefly commented on. Systemic toxicity is considered in respect to possible improved ways of determining the "NOEL," that is, the no-observed-effect level. Suggestions for improving study of mixtures of chemicals are considered. The rapid advances in molecular biology have significantly strengthened our ability to trace the action of chemicals in the body from exposure to disease. It is very important that training in toxicology be based on a sound disciplinary training in one of the classic fields of the biomedical sciences, such as biochemistry, pharmacology, molecular biology. It is concluded that advances in the past decade have made the practice of toxicology a much more scientific endeavor, especially in its use of the latest developments in basic biomedical sciences.

Animals↗
PubMed1987

Infectious complications in patients undergoing marrow transplantation: a prospective randomized study of the additional effect of decontamination and laminar air flow isolation among patients receiving prophylactic systemic antibiotics.

99 patients with hematological malignancies underwent allogeneic marrow transplantation from HLA-identical sibling donors and were randomized to receive one of two forms of infection prophylaxis while granulocytopenic: (1) prophylactic systemic antibiotics in a conventional hospital room (PSA, 50 patients) or (2) decontamination, isolation in a laminar air flow room and the administration of prophylactic systemic antibiotics (LAF + PSA, 49 patients). Only 1 patient (3%) in the LAF + PSA group acquired septicemia while granulocytopenic compared to 11 (24%) patients in the PSA group (p less than 0.005). Three patients (6%) in the LAF + PSA group acquired major localized infections compared to 9 (18%) in the PSA group (p = 0.06). There was no significant difference in days in hospital post transplant, days of granulocytopenia, days of fever, incidence of acute graft-versus-host disease, interstitial pneumonitis or overall survival. We conclude that the use of prophylactic systemic antibiotics added to decontamination and laminar air flow isolation of patients undergoing marrow transplantation significantly reduces the incidence of septicemia in the granulocytopenic period.

Adolescent↗
PubMed1987

The effect of prophylactic intravenous immune globulin on the incidence of septicemia in marrow transplant recipients.

Ninety-seven patients randomized to receive (45 patients) or not to receive (52 patients) intravenous cytomegalovirus immune globulin before and after allogeneic marrow transplantation were evaluated retrospectively for the occurrence of bacterial and fungal septicemia in the first 100 days post-transplant. In a proportional hazards regression test, infection prevention regimens, immunoglobulin administration, age and occurrence of acute graft-versus-host disease were tested simultaneously for the occurrence of septicemia in the pre- and post-engraftment period. Of these factors, only patients receiving immunoglobulin had significantly fewer episodes of septicemia following engraftment with 11 (26%) patients in the globulin group having 14 episodes compared to 22 (42%) patients in the control group having 27 episodes (p = 0.039). None of the patients experienced complications with the immunoglobulin infusions. These results suggest that the administration of intravenous immunoglobulin may be a practical and effective method to decrease the incidence of septicemia following marrow transplantation.

Bone Marrow Transplantation↗
PubMed1987

Occupational cancer.

Cancer resulting from occupational exposure is now receiving major attention, focusing on identification, regulation, and control of cancer-causing agents. Such cancer can result from exposure to chemicals and ionizing and nonionizing radiation. Extended exposure (often years) and an extended latent period of perhaps decades may intervene before tumor appearance. Although the actual extent of occupational cancer is in debate, estimates have ranged from 4 to 15 per cent of all cancer.

Humans↗
PubMed1986

Photosystem I reaction centers from maize bundle-sheath and mesophyll chloroplasts lack subunit III.

Photosystem I reaction centers were isolated from mesophyll and bundle-sheath chloroplasts of the C4 maize plant. Both preparations were found to be free of chlorophyll b and to have the same spectral properties and chlorophyll/P700 ratio as photosystem I reaction centers isolated from C3 plants. Photosystem I reaction centers from both mesophyll and bundle sheath were found to consist of six subunits with apparent molecular masses of about 70 kDa, 20 kDa, 17 kDa, 16 kDa, 10 kDa and 8 kDa, corresponding to photosystem I reaction center subunits I, II, IV, V, VI and VII of spinach, as tested by their immunological cross-reactivity with antibody raised against the respective spinach subunits. No cross-reactivity was found with antibodies raised against subunit III of spinach, either in whole thylakoids or purified reaction centers of both bundle-sheath and mesophyll chloroplasts. It is concluded that photosystem I reaction centers of bundle-sheath and mesophyll thylakoids of maize are identical and lack the polypeptide corresponding to subunit III present in all C3 plants so far tested.

Centrifugation, Density Gradient↗
PubMed1986

Purification of N-ethylmaleimide-sensitive ATPase from chromaffin granule membranes.

An N-ethylmaleimide-sensitive ATPase was purified 100-fold from chromaffin granule membranes. The purification procedure included solubilization with polyoxyethylene 9 lauryl ether, chromatography on hydroxylapatite and DEAE-cellulose columns, and glycerol gradient centrifugations. Inclusion of phosphatidylserine and a mixture of protease inhibitors during the purification procedure was necessary to maintain the activity of the preparation. The purified preparation contained four major polypeptides with molecular masses of about 115, 72, 57, and 39 kDa, which were copurified with the ATPase activity. The 115-kDa subunit binds [14C]dicyclohexylcarbodiimide and the subunits of 115 and 39 kDa bind [14C]N-ethylmaleimide. The ATP-dependent proton uptake activity of chromaffin granule membranes is inhibited 50% with about 20 microM N-ethylmaleimide, while over 5 mM concentrations of the inhibitor were required to block the ATPase activity of the membranes. The ATPase activity of the purified enzyme was inhibited via two different affinities: a high affinity site with a Ki in the microM range and a low affinity site in the mM range, each contributing to about 50% inhibition of the enzyme. It is concluded that the proton-ATPase of chromaffin granule membranes contains at least four subunits with the 115-kDa polypeptide being the main subunit having the active site for the ATPase activity of the enzyme.

Adenosine Triphosphatases↗
PubMed1986

Polypeptides of the oxygen-evolving photosystem II complex. Immunological detection and biogenesis.

Oxygen-evolving photosystem II complex was isolated from spinach chloroplasts. The individual polypeptides of the complex were isolated from sodium dodecyl sulfate (SDS)-polyacrylamide gels and antibodies were raised in rabbits against these polypeptides. After washing of the isolation complex by 0.8 M Tris to release the extrinsic proteins, a distinct diffused protein band was revealed at the position of 33 kDa in SDS gels containing 4 M urea. When this band was electroeluted from the gel and subsequently electrophoresed on SDS gels, three distinct protein bands became apparent. Antibodies raised against each one of these polypeptides cross-reacted with the other two polypeptides to varying degrees but not with the other subunits of the complex. The three polypeptides were denoted as "34," "33," and "32" kDa and the 33 being the herbicide-binding protein. Using the antibodies, the relative amounts of the photosystem II polypeptides were followed during greening of etiolated spinach seedlings. While all three extrinsic polypeptides were present in etiolated leaves at relatively high amounts, the other polypeptides could not be detected prior to an approximate 6-h illumination period. Further illumination induced the appearance of all of the rest of the subunits in a relatively similar rate. The oxygen evolution activity was developed parallel to the increase in the amounts of these polypeptides. Therefore, the assembly of the active photosystem II during greening is a two-step process in contrast with the photosystem I reaction center, which is assembled step by step, and the rest of the chloroplast protein complexes, which are assembled by a concerted mechanism.

Antibody Specificity↗
PubMed1986

Biosynthesis of the Torpedo californica acetylcholine receptor alpha subunit in yeast.

Yeast cells were transformed with a plasmid containing complementary DNA encoding the alpha subunit of the Torpedo californica acetylcholine receptor. These cells synthesized a protein that had the expected molecular weight, antigenic specificity, and ligand-binding properties of the alpha subunit. The subunit was inserted into the yeast plasma membrane, demonstrating that yeast has the apparatus to express a membrane-bound receptor protein and to insert such a foreign protein into its plasma membrane. The alpha subunit constituted approximately 1 percent of the total yeast membrane. The alpha subunit constituted approximately 1 percent of the total yeast membrane proteins, and its density was about the same in the plasma membrane of yeast and in the receptor-rich electric organ of Electrophorus electricus. In view of the available technology for obtaining large quantities of yeast proteins, it may now be possible to obtain amplified amounts of interesting membrane-bound proteins for physical and biochemical studies.

Animals↗
PubMed1986

The 5'-flanking sequences of human globin genes contribute to tissue specific expression.

The specificity of expression of the isolated 5'-flanking sequences of the human beta- and epsilon-globin genes was examined in the K562 human erythroleukemia cell line, the murine erythroleukemia (MEL) cell, and in nonerythroid cell lines CV-1, HeLa-S3, and WI-38. Globin flanking sequences were active only in the erythroid K562 and MEL cell lines. Furthermore, the upstream sequence of the adult, beta-globin gene was active in MEL cells which express adult globin and not in K562 cells which express embryonic and fetal globins suggesting that tissue specificity resides in these upstream sequences. No expression was observed in K562 cells which have an embryonic-fetal hemoglobin phenotype.

Acetyltransferases↗
PubMed1986

Airborne particles, their use in the respiratory system to measure air flow, function, and clearance.

Nonhygroscopic monodisperse particles can be used to estimate airway dimensions within chosen regions of the respiratory tract. These dimensions correspond well with those measured in inflation-fixed lungs. The dispersion of a bolus of airborne particles on inhalation and exhalation is very sensitive to the dimensions of the airways through which the bolus passes, yielding indices of dispersion that provide sensitive indicators of changes in airway dimensions, eg, with smoking. The rates of clearance of particles from the lungs are determined using gamma-labelled particles whose lung retention is determined by external measurements. There are major differences between the deep lung and the ciliated airways. Changes in clearance rates are caused by disease or inhaled intoxicants such as cigarette smoke. At lower levels of irritant exposure, an acceleration of clearance rate is observed, while higher doses and longer periods of exposure produce decreased rates. It is suggested that aerosol techniques may have useful clinical applications; approaches are suggested for such applications.

Adult↗
PubMed1986

Prevention of nosocomial infections in marrow transplant patients: a prospective randomized comparison of systemic antibiotics versus granulocyte transfusions.

One hundred twelve patients with hematologic malignancies underwent marrow transplantation from HLA-matched sibling donors and were randomized to receive either prophylactic granulocyte transfusions (PG, 67 patients) or prophylactic systemic antibiotics (PSA, 45 patients) as prophylaxis against nosocomial infections. Patients were treated in conventional hospital rooms and studied until day 100 post-transplant. For the entire study period, 26 patients (39%) in the PG group developed septicemia compared to 15 patients (33%) in the PSA group. Twenty-eight patients (42%) in the PG group developed local major infections compared to 19 patients (42%) in the PSA group. Ten patients (15%) in the PG group developed viral interstitial pneumonitis compared to 6 patients (13%) in the PSA group. None of these differences were statistically significant. There was no difference in the incidence of bacterial or fungal infections or viral interstitial pneumonitis between the two groups during the granulocytopenic or post-engraftment period. There was no difference in the incidence and severity of graft-versus-host-disease (GVHD). Inability to carry out the prophylaxis was frequent in the PG group, with complications necessitating discontinuance of transfusion in 24% of the recipients and 13% of the donors. The use of PG as an infection prophylaxis modality in marrow transplantation is not supported by this study, as it is difficult to carry out and because PG did not show any advantage over the use of PSA in preventing nosocomial infections.

Adolescent↗
PubMed1986

The diagnostic and predictive value of cerebrospinal fluid lactate in children with meningitis. Its relation to current diagnostic methods.

One hundred and thirty-three children with suspected meningitis aged from 11 days to 16 years were investigated with routine cerebrospinal fluid (CSF) laboratory methods: microscopy of a Gram-stained smear, bacterial culture, determination of leukocytes, lactate, and the CSF/blood glucose ratio. On the basis of bacterial cultures and clinical course, the children were classified into three groups: bacterial meningitis (n = 18), aseptic meningitis (n = 28), and a control group (n = 87). The main intention was to study the relation between current diagnostic methods and lactate. CSF lactate levels and cell counts, related significantly (p less than 0.01) better to the presence of bacterial meningitis than CSF/blood glucose ratios. Lactate levels exceed 2.4 mmol/l in all children with bacterial meningitis, but in none of the control group. Of 28 children with aseptic meningitis 3 had lactate in the range 2.5-2.7 mmol/l, while the others had values of 2.4 mmol/l or less. We consider CSF lactate to be the best predictor in the clinical decision to institute antibiotic treatment of children with suspected bacterial meningitis.

Adolescent↗
PubMed1986

Isolation of Pathogenic Bacillus circulans from Callus Cultures and Healthy Offshoots of Date Palm (Phoenix dactylifera L.).

Pure cultures of a gram-negative, rod-shaped bacterium, which produced endospores after 3 to 5 days on solid medium, were isolated exclusively from tissue cultures of the date palm Phoenix dactylifera L. Electron microscopic examination of thin sections of the bacteria revealed the bilayer membrane typical of gramnegative bacteria and confirmed the nature of the spores as true endospores. Biochemical and physiological tests indicated that the bacteria were Bacillus circulans. B. circulans was consistently isolated from the internal tissues, including the meristem, of apparently healthy offshoots of date palm. When meristem and embryo callus tissue culture samples were injected with B. circulans isolated from similar tissue culture samples and from offshoots, the majority of the isolates produced a rapid, destructive soft rot of the tissues.

Journal Article↗