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C Nelson

Publications and source records attributed to C Nelson.

At least 127 records · Page 7Linked to original sources
PubMed1992

Immunodominant structures of human growth hormone identified by homolog-scanning mutagenesis.

Homolog-scanning mutagenesis has been reported to be useful in elucidating the antigenic epitopes recognized by monoclonal antibodies and hGH binding to its receptor. However, little is known about which structures are recognized as immunodominant by murine serum antibodies. Therefore, the previously published series of hGH homologs and additional mutants of human placental lactogen (hPL), porcine growth hormone (pGH), and human prolactin (hPRL) were examined for their interaction with murine serum derived anti-hGH antibodies. As compared to wild-type hGH, nine of the nineteen segment substituted mutants tested showed a significant reduction in binding to anti-hGH sera. These disruptive substitutions mapped to 5 regions on a structural model of hGH: the length of helix 1 (residues 11-33), the loop between the first disulfide bond and helix 2 (residues 54-74), the beginning of helix 3 (residues 109-112), the carboxyl half of helix 4 (residues 167-182), and the final carboxyl terminus segment of the molecule (residues 184-191). In terms of the current structural model, three of the five immunodominant regions (the loop between residues 54-74, central portion of helix 4 to the carboxyl terminus and part of the amino terminus region of helix 1) closely overlaps the hGH receptor binding epitopes.

Amino Acid Sequence↗
PubMed1992

Agreement between patients and their self-selected surrogates on difficult medical decisions.

BACKGROUND: Several studies have demonstrated that surrogate decision makers often are unable to use substituted judgment when asked to make decisions for incompetent patients. This study further explored this question, using a relatively young, healthy sample of 50 patient/surrogate pairs. METHODS: Patients were randomly recruited from a community family practice clinic and asked to select a surrogate. Five case vignettes were presented to patients and surrogates during separate interviews. Vignettes asked for decisions related to ventilation, resuscitation, and tube feeding for a patient in permanent coma, amputation as life-extending treatment for a mentally confused patient, and chemotherapy for a decisionally incapacitated patient with advanced cancer. Factors considered important to decision making were also investigated. RESULTS: As groups, patients and surrogates were similar as they chose to withdraw or continue treatment in the same proportions. However, within individual pairs, agreement on treatment occurred only 70% of the time even though surrogates were asked to base their treatment decisions on substituted judgment. The kappa coefficients indicated that the rate of agreement in individual vignettes was low. Patients considered "burden on the family" and "time left to live" as the most important factors in choosing among difficult treatment options, while surrogates identified the patients' pain as the most important factor. CONCLUSIONS: The high rate of discrepant decisions underscores the importance of effective patient-surrogate communication before medical decision-making incompetence occurs. The potential of increasing patient-surrogate agreement on difficult medical decisions by educational interventions should be explored.

Adult↗
PubMed1991

Excitation by geniculocortical synapses is not 'vetoed' at the level of dendritic spines in cat visual cortex.

1. We used anatomical methods to examine whether the geniculocortical afferent input to dendritic spines could be gated or 'vetoed' by an inhibitory input to the same spine. 2. Physiologically identified X- and Y-type afferents were injected intra-axonally with horseradish peroxidase (HRP), processed, and drawn under the light microscope. Selected regions of the terminal arbors were then serially sectioned for examination under the electron microscope. 3. Three-dimensional reconstructions of thirty-nine HRP-filled terminal boutons forming fifty asymmetric (type 1) synapses showed that thirty-one synapses were on the heads of dendritic spines. Only two of thirty-one spine heads received an additional symmetric (type 2) synapse, which is presumed to be inhibitory. 4. Examination of twenty-three boutons from two clutch cells (a GABA (gamma-aminobutyric acid)-ergic smooth cell) that form symmetric (type 2) synapses on spines indicated that their preferred location was opposite the asymmetric synapse on the head of the spine. Synaptic input to the necks of spines appears rare. 5. We conclude that most of the excitation provided by the geniculocortical afferent input to the heads of spines cannot be gated or vetoed by inhibition at the level of the spine.

Animals↗
PubMed1991

Virulent human strains of group G streptococci express a C5a peptidase enzyme similar to that produced by group A streptococci.

Specific proteolytic destruction of the human chemotaxin, C5a, is a property of group A and B streptococcal pathogens. Here we show that virulent group G streptococci from human sources also express C5a peptidase activity. The enzyme responsible for this activity is approximately the same size as and is antigenically similar to that produced by group A streptococci. On the basis of Southern hybridization analysis with an internal fragment of the group A C5a peptidase gene (scpA) as a probe, a copy of this gene was found in the genome of all group G human isolates tested. Comparison of partial restriction maps of scpA and scpG revealed significant similarity between the two genes. Group G strains isolated from dogs and cows were found to lack C5a peptidase activity and did not hybridize to the scpA-specific probe. The association of this activity with three streptococcal species suggests that elimination of phagocyte chemotactic attractants is a more universal virulence mechanism than originally anticipated.

Adhesins, Bacterial↗
PubMed1991

Two related helix-loop-helix proteins participate in separate cell-specific complexes that bind the insulin enhancer.

Cell-specific expression of the insulin gene is dependent on a conserved 8-basepair sequence, GCCATCTG, present in two copies in the 5' flanking DNA of the rat insulin 1 gene (Nir and Far elements). A protein factor with well characterized binding affinities binds to this sequence and is unique to the nuclei of insulin-producing cells. Using the Nir element as a probe to screen a hamster insulinoma cDNA expression library, we cloned two cDNA inserts that encode two related helix-loop-helix DNA-binding proteins: Syrian hamster Pan-1 (shPan-1) and Syrian hamster Pan-2 (shPan-2). These clones have minimal differences from the previously reported human E47/E12 and rat PAN (rPan) DNA-binding proteins. In vitro translated protein products of both clones bound the insulin gene promoter Nir and far elements as well as the E2 elements of the mu heavy chain and kappa light chain immunoglobulin genes. Treating insulinoma cell nuclear extract with antiserum selectively directed to each of the two shPan proteins demonstrated the presence of each form of shPan in separate DNA-binding complexes, which together form the previously described, cell-specific, Nir element-binding complex. We conclude that shPan-1 and shPan-2 are the hamster homologs of the ubiquitous E47/E12 and rPan proteins, but form parts of distinct DNA-binding complexes apparently found only in the nuclei of insulin-producing cells.

Amino Acid Sequence↗
PubMed1990

Analysis of the changes in the structure and hydration of the nucleosome core particle at moderate ionic strengths.

In order to better understand the conformational changes induced in the nucleosome core particle by changes in the ionic strength of the media in the range from 0.1 to 0.6 M NaCl, we have conducted a very detailed structural analysis, combining circular dichroism, DNase I digestion, and sedimentation equilibrium. The results of such analysis indicate that the secondary structure of both DNA and histones exhibits small (approximately 5%) but noticeable changes as the salt increases within this range. In the case of DNA, the data are consistent with a trend toward a more relaxed secondary structure. The DNase I pattern of digestion is also altered by the salt and suggests a DNA relaxation around the flanking ends. From the hydrodynamic measurements, we also observe a significant change in the virial coefficients of the particle as the salt increases, which in turn are in very good agreement with the theoretically expected values. Furthermore, the preferential hydration parameter is also found to increase with the salt. We believe that the self-dependent conformational change of the nucleosome core particle is the result of the conjunction of all these subtle changes. Yet, from the present data, their exact relationship to the tertiary structure of the whole particle at the different ionic strengths cannot be exactly defined.

Circular Dichroism↗
PubMed1990

Molecular cloning of a novel splice variant of the alpha subunit of the mammalian Go protein.

We screened a HIT (hamster insulin-secreting tumor) cell cDNA library constructed in lambda gt11 with a Go-specific oligonucleotide probe and isolated six recombinant phages. The inserts of these phages encoded two forms of alpha o, called here alpha o1 and alpha o2. The deduced amino acid sequence of alpha o1 is identical in all of its 354 amino acids to that reported previously for rat and bovine alpha o; that of alpha o2, also of 354 amino acids, is identical to alpha o1 up to and including amino acid 248 and differs thereafter in 26 amino acids. At the nucleotide level, alpha o1 and alpha o2 are identical up to and including the second base of the codon that specifies amino acid 243 and differs thereafter in 88 nucleotides of the remaining open reading frame and has no similarity to alpha o1 in its 3'-untranslated region. We propose that alpha o1 and alpha o2 result as a consequence of alternative splicing of a single alpha o transcript. Northern analysis with specifically designed oligonucleotides indicates that both forms of alpha o are expressed in normal tissues, e.g. brain. After in vitro transcription and translation, the peptides encoded in the alpha o1 and alpha o2 cDNAs could be ADP-ribosylated by pertussis toxin in the presence of added beta gamma dimers. The count of distinct G proteins keeps increasing.

Adenosine Diphosphate Ribose↗
PubMed1990

Splice junction mutations in a yeast tRNA gene which alter the rate and precision of processing.

We have introduced mutations into a tRNALeu3 gene which alter the intron boundaries and examined their effects on RNA splicing. Our results show that the 5'-proximal splice junction is not specified by the position of an adjacent base-paired stem present in all naturally occurring tRNA precursors. Also, efficient cleavage of 5'-splice junctions unique to these mutants, -CpU-, -UpA- and -UpG-, indicates the purine found at the 5'-side of this site in all natural precursors is dispensable. Some alterations of the sequence and structure at the 5'-proximal splice site reduce the rate of cleavage therein and result in accumulation of molecules composed of the 5'-half of the tRNA plus the intron. The precise position of the 5'-proximal cleavage site can vary +/- 1 base in these mutants. The 3'-proximal splice junction is rendered inactive by changing the prospective splice junction sequence from -ApC- to -CpC- and reducing the size of an unpaired loop at this site from six to two bases. Very small amounts of RNA composed of the 3'-half of the tRNA plus the intron accumulate from this precursor. We conclude that splice junction sequence and structure affect both the rate and precision of intervening sequence removal.

Base Sequence↗
PubMed1990

Transactivation of the p53 oncogene by E1a gene products.

Infection of quiescent rat kidney cells with human adenovirus is shown to transcriptionally stimulate (transactivate) the p53 oncogene. The increased transcription results in an accumulation of p53-specific mRNA in parallel with an increase in p53 protein levels, although there is a considerable delay between transcriptional activation and the detection of stable p53 mRNA and protein. The induction of p53 is detectable with two monoclonal antibodies recognizing different epitopes. The induction of p53 by adenovirus is delayed compared to induction by serum, and it occurs after the onset of adenovirus-induced cellular DNA replication. Thus, adenovirus-induced DNA replication bypasses a G0/G1 control point. Experiments with hydroxyurea show that p53 activation does not require continued cell cycling and thus is likely to be a direct consequence of viral gene expression. Finally, the induction of p53 is shown to be dependent on expression of the 289-residue product encoded by the viral E1a gene.

Adenovirus Early Proteins↗
PubMed1990

Pan: a transcriptional regulator that binds chymotrypsin, insulin, and AP-4 enhancer motifs.

Two cDNAs were cloned that encode proteins (Pan-1 and Pan-2, with predicted molecular masses of 67.4 and 67.7 kD, respectively) that bind to a conserved transcriptional regulatory element present in pancreatic exocrine genes. The cDNAs are virtually identical in the region that encodes the amino-terminal 525 amino acids; they differ only by a 3-nucleotide insertion that results in the addition of a single amino acid. The cDNAs, however, code for related, but divergent, carboxy-terminal regions. Expression of the cloned cDNAs in HeLa cells activates expression of a cotransfected chimeric gene containing multimers of the pancreatic conserved element linked to a minimal promoter. Pan-1 and Pan-2 bind to the consensus sequence CAC/GCTGT/C, the CACCTGTC motif, which is present in transcriptional control elements of several genes. Both Pan-1 and Pan-2 bind to related motifs present in the rat insulin enhancer as well as a DNA segment containing the SV40 AP-4 element. The Pan-1 and Pan-2 cDNAs display extensive sequence identity with partial cDNA clones encoding E12 and E47, which bind to the immunoglobulin kappa E2 cis-active element, and may be derived from the same gene. These factors belong to a set of genetically distinct molecules, including AP-4 and MLTF, that bind to the CACCTGTC motif or related sequences. The Pan/E12,E47 proteins also show structural similarity with the Drosophila daughterless protein, MyoD, Myogenin, and Myf-5.

Amino Acid Sequence↗
PubMed1990

Resource use and cost of initial coronary revascularization. Coronary angioplasty versus coronary bypass surgery.

Although there is intense interest in the cost-saving potential of therapeutic alternatives, most studies have analyzed hospital charges rather than actual economic costs. To analyze cost differences rigorously, we studied 115 patients undergoing initial elective angioplasty (percutaneous transluminal coronary angioplasty, PTCA) and 274 patients undergoing initial elective surgery (coronary artery bypass graft surgery, CABG). Detailed resource consumption profiles were constructed and used to estimate the cost savings from switching a patient from CABG to PTCA. Four cost-accounting methods were used in the analysis; each method made different assumptions about the costs that would vary and the costs that would be fixed according to the number of procedures performed. The variable costs in the four methods were the 1) cost of supplies, 2) cost of personnel and supplies, 3) average direct costs, and 4) average direct costs plus allocated hospital overhead. The mean hospital charges for CABG patients were $19,644 versus $9,556 for PTCA patients (p less than 0.0001). The estimated cost difference between CABG and PTCA was substantially less than the $10,088 difference in charges, however, with net savings of 19%, 46%, 53%, and 78% of charges using cost-accounting methods 1-4, respectively. Thus, although the initial hospital charges for PTCA are significantly less than for CABG, the actual economic cost savings may be significantly overestimated by the use of hospital charge data.

Accounting↗
PubMed1990

Comparisons of female and male early adolescent sex role attitude and behavior development.

This study contrasted female and male early adolescent sex role attitude and behavior development in an ecological context as defined by Bronfenbrenner. Data were the results of a state-wide survey of early adolescents and their parents. Hierarchical multiple regression was used to test both sex role attitude development and behavior development models. Only the models for attitude development were significant. The level of traditionalism of female sex role attitude development was significantly influenced by maternal employment, the level of traditionalism of the father's sex role attitudes in interaction with the amount of time he spent with his daughter, and chronological age. In contrast, the level of traditionalism of male sex role attitude development was significantly influenced by the level of traditionalism of the mother's sex role attitudes in interaction with the level of closeness to the mother that was reported by the son, and both mother's and father's perception of pubertal age. The implications of the findings for human development theory, early adolescence as a stage of development, and sex role theory and research are discussed.

Adolescent↗
PubMed1989

The chymotrypsin enhancer core. Specific factor binding and biological activity.

A 20-base pair (bp) conserved sequence present in the 5'-flanking regions of genes highly expressed in the exocrine pancreas forms part of the enhancers of the rat amylase 2A, chymotrypsin B, and elastase I genes. Factor(s) that interact with the conserved DNA sequence of the rat chymotrypsin B gene in vitro have been detected in extracts from acinar cells but not in three other cell lines tested. Transfection experiments suggest that the acinar cell factor(s) recognizing this enhancer core sequence are transcriptional activators. Multimers of a 28-bp sequence located by DNase I protection are capable of activating heterologous promoters in acinar cells. In vitro competition binding and methylation interference analyses indicate protein-DNA interactions at two distinct sites 10 base pairs apart on the DNA. This interaction is identical in extracts from cultured acinar cells as well as from whole pancreas tissue. The presence of two contiguous binding motifs on the same face of the DNA suggests that two (multiple) factors cooperate in the transcriptional regulation of this gene. We term these factors CACCTG pan-1 and TTTCCC pan-1. A factor with the binding specificity of the adenovirus major late transcription factor (MLTF) cross-reacts with the factor CACCTG pan-1 in vitro. However, the distribution of this factor in the various cells does not correlate with the activity of the enhancer core element in vivo. Further, conversion of the chymotrypsin sequence into a consensus MLTF site by three-point mutations abolished enhancer activity in acinar cells. Thus, the MLTF-like factor cannot substitute functionally for the factor CACCTG pan-1 and may act as an inhibitor of chymotrypsin enhancer function.

Animals↗
PubMed1989

A pituitary POU domain protein, Pit-1, activates both growth hormone and prolactin promoters transcriptionally.

The anterior pituitary gland provides a model for investigating the molecular basis for the appearance of phenotypically distinct cell types within an organ, a central question in development. The rat prolactin and growth hormone genes are expressed selectively in distinct cell types (lactotrophs and somatotrophs, respectively) of the anterior pituitary gland, reflecting differential mechanisms of gene activation or restriction, as a result of the interactions of multiple factors binding to these genes. We find that when the pituitary-specific 33-kD transcription factor Pit-1, expressed normally in both lactotrophs and somatotrophs, is expressed in either the heterologous HeLa cell line or in bacteria, it binds to and activates transcription from both growth hormone and prolactin promoters in vitro at levels even 10-fold lower than those normally present in pituitary cells. This suggests that a single factor, Pit-1, may be capable of activating the expression of two genes that define different anterior pituitary cell phenotypes. Because a putative lactotroph cell line (235-1) that does not express the growth hormone gene, but only the prolactin gene, appears to contain high levels of functional Pit-1, a mechanism selectively preventing growth hormone gene expression may, in part, account for the lactotroph phenotype.

Animals↗
PubMed1989

Maternal age and screening for gestational diabetes: a population-based study.

The American College of Obstetricians and Gynecologists (ACOG) has recommended screening for gestational diabetes, using a 50-g, 1-hour glucose challenge (threshold for further testing 140 mg/dL or higher), for all pregnant women aged 30 or older and for younger women with risk factors. In order to assess these recommendations, we collected demographic and historic data on 6214 pregnant women representing a population of universally screened individuals. Of 125 cases of gestational diabetes diagnosed (ACOG criteria), 70 patients (56%) were under the age of 30. In addition, 44% of gestational diabetics had no risk factors. The cost per case diagnosed would be $190 with the ACOG recommendations, $192 if the age for routine screening were lowered to 25 years or more, and $222 if universal screening were practiced. Using the ACOG recommendations, 35% of gestational diabetes would go undiagnosed, with little cost savings.

Adult↗