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D Nelson

Publications and source records attributed to D Nelson.

At least 145 records · Page 8Linked to original sources
PubMed1995

An n-allele model for progressive amplification in the FMR1 locus.

An n-allele model is developed for the FMR1 locus, which causes the fragile X syndrome, where n is the number of triplet repeats in the first exon. Frequencies in the general population and in index families are used to generate an n to n + delta transition matrix that predicts specific risks in satisfactory agreement with observation. However, until sequencing distinguishes between stable and unstable alleles with the same value of n, it is premature to infer whether allelic frequencies at the FMR1 locus are at equilibrium or, as some have suggested, are evolving toward higher frequencies of the pathogenic allele.

Alleles↗
PubMed1995

Monoclonal anti-dipeptide antibodies cross-react with detyrosinated and glutamylated forms of tubulins.

Two monoclonal antibodies, GLU-1 and A1.6, raised against gamma-L-glutamyl-L-glutamic acid dipeptide (Glu-Glu) and Ca(2+)-dependent ATPase from Paramecium, respectively, recognized the dipeptide Glu-Glu sequence. Whereas the antibodies immunofluorescently stained very few, if any, cytoskeletal fibers in cultured mammalian cells, almost all interphase as well as mitotic spindle microtubules became visible after treatment of cells with carboxypeptidase A. Immunoblot analysis demonstrated intense cross-reaction of the antibodies to the alpha-tubulin subunit. alpha-Tubulin isotypes produced as fusion proteins in bacteria were labeled by both the antibodies only when the proteins did not contain a tyrosine residue at the C terminus, indicating that GLU-1 and A1.6 specifically recognize the detyrosinated form of alpha-tubulin. When microtubule protein purified from brain was probed, not only alpha-but also, to a lesser extent, beta-tubulin were revealed by the dipeptide antibodies. A synthetic tripeptide YED containing one glutamyl group linked to the second residue of the peptide via the gamma position was also recognized by the antibodies. Since this peptide sequence corresponds to the amino acid sequence of polyglutamyated class III beta isotype at amino acid position 437 to 439, it is suggested that GLU-1 and A1.6 are able to recognize the glutamylated form of beta-tubulin. These results indicate that the C-terminal Glu-Glu sequence displays strong antigenicity, and the antibodies recognize the sequence present in the C terminus of the detyrosinated form of alpha-tubulin and the glutamyl side chain of beta-tubulin. Particularly strong immunoreaction was detected with ciliary and flagellar microtubules; thus, stable axonemal microtubules appear to be rich in post-translationally modified tubulin subunits.

Animals↗
PubMed1995

Research into research practice.

Since the Briggs report of 1972, the debate over whether nursing is a researched based profession continues. This paper attempts to establish whether research performed by practitioners in their own field is being directly utilised in practice. The paper describes a small scale study of registered nurses (n = 22) who have completed the Professional Studies 2 Accident & Emergency module, focusing on the utilisation of their action research and the factors influencing the outcome of its use. Data was collected by self-report questionnaire. The results of the study indicate that many action research projects are not being formally utilised within the clinical area. The main factor stated is the lack of research culture within units, underpinned by a lack of managerial and peer support for research studies. Despite this, research is being utilised, but only by the individuals who conducted it. The results suggest that greater integration between the college of nursing, management and the student is required to improve research utilisation in the clinical area.

Adult↗
PubMed1995

Student nurses' perceptions of accident and emergency nursing: do they match the reality?

This study explores student nurses' perceptions of, and attitudes to, working in an Accident and Emergency (A & E) department prior to allocation there. An assessment of the students' actual experience within the department was then taken. This allowed the students' perceptions to be compared with the reality of the work. The sample consisted of all students training for part 10 of the register who were allocated to the unit over a 4-week period (n = 22). Data was collected by two self completion questionnaires, one given pre-allocation the second post-allocation, a 100% response rate was achieved for each. The results of the study indicate that students' perceptions of the A & E department do not match the reality of the work involved. These perceptions may cause increased anxiety and apprehension for students before they start in the department and this may hinder clinical learning. The results suggest that appropriate preparation prior to the period of clinical experience may help alleviate these difficulties.

Adult↗
PubMed1995

Metabolic and energetic changes during apoptosis in neural cells.

Changes in cellular energetic and metabolic parameters were analyzed at several time points during apoptosis of differentiated PC12 cells following removal of nerve growth factor (NGF). As approximately 60% of the population died during the period of study (24 h), most of the measured metabolic indicators declined over time. However, this decline paralleled the overall decrease in cellular viability, suggesting that, in individual cells, a compromised metabolic state occurred suddenly and very late in the death process. For example, when expressed as a function of viable cells, protein and RNA synthesis did not decrease until 24 h. Glucose utilization in live cells was never significantly reduced relative to control levels; lactate production decreased slightly within 4-8 h after NGF removal, but eventually rebounded to 122% of control levels by 24 h. ATP levels dropped 27% in an early predeath period, but then returned to near control levels (on a per-live-cell basis) once the population actively began to die. The ATP/ADP ratio remained at least 84% of control throughout. UTP/UDP and GTP/GDP ratios did not change significantly at any time point.

Animals↗
PubMed1995

Effects of NO-generating compounds on synaptosomal energy metabolism.

The effects of nitroprusside and S-nitrosocysteine, compounds that generate nitric oxide (NO), on synaptosomal energy-producing pathways and energy level were investigated. The decrease in respiration was much faster and more pronounced with S-nitrosocysteine than with nitroprusside. S-Nitrosocysteine, at 10 microM, inhibited by 80% respiration with glucose and succinate (plus rotenone) in intact synaptosomes and with ascorbate/cytochrome c in broken preparations. Oxygenated hemoglobin reversed and/or prevented the inhibition, whereas glutathione (GSH) prolonged it. Under aerobic conditions, the synaptosomal energy level (creatine phosphate/creatine and ATP/ADP ratios) was reduced by the presence of S-nitrosocysteine, whereas lactate generation was enhanced. The effects on energy parameters were greater at 5 min than at 15 min of incubation and were more pronounced in the presence of GSH. Under strictly anaerobic conditions, lactate production was reduced by the NO-generating compounds in a concentration-dependent manner. It is concluded that (a) inhibition of oxidative phosphorylation by NO leads to a fall in the synaptosomal energy level, which in turn stimulates glycolysis; (b) glycolysis can be inhibited by higher concentrations of the radical; and (c) inhibitory effects on the energy-generating pathway and ATP level could contribute to NO toxicity under some in vivo situations.

Animals↗
PubMed1995

Overexpression of the human NFM subunit in transgenic mice modifies the level of endogenous NFL and the phosphorylation state of NFH subunits.

Neurofilaments (NFs), the major intermediate filaments of central nervous system (CNS) and peripheral nervous system (PNS) neurons, are heteropolymers formed from the high (NFH), middle (NFM), and low (NFL) molecular weight NF subunits. To gain insights into how the expression of NF subunit proteins is regulated in vivo, two transgenes harboring coding sequences for human NFM (hNFM) with or without the hNFM multiphosphorylation repeat domain were introduced into mice. Expression of both hNFM constructs was driven by the hNFM promoter and resulted in increased levels of hNFM subunits concomitant with an elevation in the levels of mouse NFL (mNFL) proteins in the CNS of both lines of transgenic mice. The increased levels of mNFL appear specific to NFM because previous studies of transgenic mice overexpressing either NFL or NFH did not result in increased expression of either of the other two NF subunits. Further, levels of the most heavily phosphorylated isoforms of mouse NFH (mNFH) were reduced in the brains of these transgenic mice, and electron microscopic studies showed a higher packing density of NFs in large-diameter CNS axons of transgenic versus wild-type mice. Thus, reduced phosphorylation of the mNFH carboxy terminal domain may be a compensatory response of CNS neurons to the increase in NFs, and reduced negative charges on mNFH sidearms may allow axons to accommodate more NFs by increasing their packing density. Taken together, these studies imply that NFM may play a dominant role in the in vivo regulation of the levels of NFL protein, the stoichiometry of NF subunits, and the phosphorylation state of NFH. NFM and NFH proteins may assume similar functions in regulation of NF packing density in vivo.

Aging↗
PubMed1995

Recombinant endotoxin neutralizing protein improves survival from Escherichia coli sepsis in rats.

OBJECTIVE: A recombinant endotoxin neutralizing protein was evaluated for its ability to ameliorate the effects of Escherichia coli sepsis in rats. DESIGN: Prospective, controlled animal trial. SETTING: Hospital animal research laboratory. SUBJECTS: Wistar rats, treated with gentamicin 1 hr after challenge with intraperitoneal E. coli O18ac. INTERVENTIONS: The animals received a recombinant endotoxin neutralizing protein, in doses of 5, 25, or 50 mg/kg, either 30 or 60 mins after challenge; controls received saline. MEASUREMENTS AND MAIN RESULTS: Geometric mean serum endotoxin concentrations in endotoxin neutralizing protein-treated animals did not differ from control animals. Tumor necrosis factor concentrations in animals treated with endotoxin neutralizing protein 30 mins after challenge were significantly lower than controls. Animals treated with 25 or 50 mg/kg of endotoxin neutralizing protein 30 mins after E. coli challenge had significant improvements in survival compared with controls. Animals treated with 50 mg/kg of endotoxin neutralizing protein 60 mins after E. coli challenge had significant improvements in survival compared with controls. CONCLUSION: Endotoxin neutralizing protein significantly reduces mortality from Gram-negative sepsis in an antibiotic-treatment model of E. coli peritonitis and bacteremia in rats, mediated by a neutralization of the biological effects of endotoxin.

Animals↗
PubMed1995

Molecular detection of a common mutation in coagulation factor V causing thrombosis via hereditary resistance to activated protein C.

More than half of all patients with familial or recurring venous thrombosis have hereditary resistance to activated protein C (HRAPC) as the result of specific missense mutation in the gene for coagulation factor V. Because the mutant factor Va (with an Arg to Gln substitution at codon 506) cannot be cleaved and inactivated by activated protein C, carriers of this mutation are at significantly increased risk of venous thrombosis. We have recently introduced a direct polymerase chain reaction (PCR)-based clinical diagnostic test for the factor V codon 506 mutation based on the destruction of an Mnl I restriction site by the causative nucleotide substitution. To assess the accuracy of this PCR-based assay, we compared a functional clotting time test for HRAPC with the direct mutation test. Of 47 patients dually tested, only five had discrepant values for the functional test versus the DNA test. Either of these two complementary assays is useful for the accurate diagnosis of HRAPC. The DNA-based test is, however, specifically recommended for evaluation of anticoagulated patients or patients with borderline functional tests and confirmation of genotype in HRAPC families. In an additional analysis of 287 normal individuals, we found an extremely high prevalence of the mutated codon 506 allele-- approximately 4% in each of two different populations. The absence of disease in the majority of heterozygous carriers suggests that symptomatic thrombosis requires the simultaneous presence of both a mutated factor V protein and additional synergistic factors.

Codon↗
PubMed1995

Molecular genetics in pediatric training: how much do we really know?

A questionnaire was designed to assess the degree of knowledge among 44 residents and medical students in a pediatric residency program about recent advances in medical genetics. The mean score was 40% (4 correct answers per individual). There were no significant differences among the groups. The mean number of correct responses to each question was 13, but topics that had been highly publicized, especially in the lay press, were associated with more correct answers. Among residents and medical students, knowledge of the exact genetic defects of inherited diseases and their implications at the molecular and clinical levels may be limited.

District of Columbia↗
PubMed1995

Celiac sprue in an asymptomatic elderly man.

The authors discuss the case of an asymptomatic patient with celiac sprue presenting with hematologic abnormalities on screening laboratory examination. The patient was initially treated for vitamin B-12 and folate deficiency, and subsequently for iron deficiency with limited success until the diagnosis was established. The absence of such classic features of celiac disease as steatorrhea and diarrhea is not an uncommon presentation. Unexplained iron deficiency should alert the clinician to the possibility of celiac sprue.

Aged↗
PubMed1994

Tricarboxylic acid cycle in rat brain synaptosomes. Fluxes and interactions with aspartate aminotransferase and malate/aspartate shuttle.

The flux through different segments of the tricarboxylic acid cycle was measured in rat brain synaptosomes with gas chromatography-mass spectrometry using either deuterated glutamine or [13C]aspartate. The flux between 2-oxoglutarate and oxaloacetate was estimated to be 3.14 and 4.97 nmol/min/mg protein with and without glucose, respectively. These values were 3-5-fold faster than the flux between oxaloacetate and 2-oxoglutarate (0.92 nmol/min per mg protein) measured in the presence of glucose. The pattern of intermediates labeling suggests that the overall rate-controlling reaction involves either citrate synthase or pyruvate dehydrogenase but not 2-oxoglutarate or isocitrate dehydrogenase. The enrichment in [3,3,4,4-2H4]glutamate from [2,3,3,4,4-2H5]glutamine was as rapid as in [2,3,3,4,4-2H5]glutamate, which indicates that the aspartate aminotransferase reaction is severalfold faster than the flux through the tricarboxylic acid cycle. [13C]Aspartate was rapidly converted to [13C]malate, suggesting that in intact synaptosomes aspartate entry into the mitochondrion is very slow. The finding that aspartate is taken up by mitochondria as malate, along with the observed high enrichment in [3-2H]malate (from [2,3,3,4,4-2H5]glutamine), is consistent with the substantial synaptosomal activity of the malate/aspartate shuttle.

Animals↗
PubMed1994

Glutamine catabolism by heart muscle: regulation of phosphate-activated glutaminase by ATP, citrate, and chloride.

Production of glutamate from glutamine by rat heart mitochondria was stimulated by citrate and ATP in a dose-dependent manner. Citrate required phosphate for manifestation of its stimulatory action, whereas ATP enhanced glutaminase activity with and without phosphate. At low concentrations (1-50 mM) ATP was more potent than citrate, whereas the opposite was true at high (50-150 mM) levels of these anions. Both citrate and ATP decreased the concentration of phosphate required for half-maximal stimulation of glutamate production (EC50) and reduced the value of the Hill coefficient. Phosphate lowered the EC50 for ATP. Chloride and other anions of chaotropic series inhibited glutamine catabolism, most likely by causing depolymerization of the enzyme. Rupture of mitochondrial membranes by freeze-thawing decreased the responsiveness of glutaminase to phosphate, ATP, and especially to citrate but it did not alter the inhibition of the enzyme by chaotropic anions. It is concluded that phosphate, ATP, and citrate act in concert to modulate glutaminase activity in heart in vivo. Chloride, which exhibits a small inhibitory effect at a concentration normally present in cardiac muscle, may assume a greater regulatory role in situations accompanied by a rise in the internal level of this anion.

Adenosine Triphosphate↗
PubMed1994

Rapid dendritic cell recruitment is a hallmark of the acute inflammatory response at mucosal surfaces.

Immunohistochemical analysis of challenge sites such as skin and the peritoneal cavity has identified neutrophils as virtually the sole cellular participants in acute bacterial inflammation, peak influx occurring 24-48 h in advance of mononuclear cell populations associated with adaptive immunity. This study challenges the general applicability of this paradigm. We demonstrate here that the earliest detectable cellular response after inhalation of Moraxella catarrhalis organisms is the recruitment of putative class II major histocompatibility complex-bearing dendritic cell (DC) precursors into the airway epithelium, the initial wave arriving in advance of the neutrophil influx. Unlike the neutrophils which rapidly transit into the airway lumen, the DC precursors remain within the epithelium during the acute inflammatory response where they differentiate, and develop the dendriform morphology typical of resident DC found in the normal epithelium. During the ensuing 48-h period, these cells then migrate to the regional lymph nodes. No comparable DC response was observed after epidermal or intraperitoneal challenge, and it may be that mucosal surfaces are unique in their requirement for rapid DC responses during acute inflammation. We hypothesize that the role of the DC influx during acute inflammation may be surveillance for opportunistic viruses, and that this covert protective mechanism is operative at a restricted number of mucosal tissue sites.

Animals↗