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Biomedical subjects

A E Davis

Publications and source records attributed to A E Davis.

At least 37 records · Page 2Linked to original sources
PubMed1996

Impaired production of both normal and mutant C1 inhibitor proteins in type I hereditary angioedema with a duplication in exon 8.

In the autosomal dominant disorder type I hereditary angioedema, reduced levels of C1 inhibitor may be due in part to increased turnover and decreased synthesis of normal C1 inhibitor protein. A type I hereditary angioedema patient was recently described in whom the C1 inhibitor mutation consisted of a 20-bp duplication of nucleotides 1414 to 1433 in exon 8 that introduced a frame shift predicting the loss of a normal stop codon and the translation of a protein 52 amino acids longer than normal. In this study, we analyzed the expression of C1 inhibitor in fibroblasts obtained from a skin biopsy of this patient. Two proteins of approximately 78 and 94 kDa were found intracellularly, corresponding to the products of normal and mutated alleles, respectively. Pulse-chase analysis showed a complete lack of secretion of the mutated form. In addition, there was decreased extracellular production of the normal C1 inhibitor, suggesting either decreased secretion or increased intracellular catabolism of the normal protein because of the presence of the mutant allele. The production of other complement proteins was normal. This study provides a model for further analysis of autosomal dominant genetic disorders in which production of the functional protein may be affected by the product of the mutated allele.

Alleles↗
PubMed1996

Evidence for distinct contributions of heavy and light chains to restriction of antibody recognition of the HIV-1 principal neutralization determinant.

We have used phage Ab display technology to analyze two mAbs to HIV-1 envelope proteins gp120 and gp41. From the data obtained we are able to demonstrate that the recognition of the principal neutralization determinant of different strains of HIV-1 by neutralizing mAb M77 is restricted by its heavy and light chains in different ways. Native M77 is able to recognize and neutralize HIV-1 strain IIIB through binding to the gp120 V3 loop. M77 is unable to recognize strains of HIV-1 that differ on either the left or right side of the V3 loop tip. A chain-switched Fab fragment containing the M77 Fd fragment and a different light chain was able to recognize HIV-1 strains that differ from IIIB on the left side but not the right side of the V3 loop tip.

Amino Acid Sequence↗
PubMed1996

Antibody to C1-inhibitor in a patient receiving C1-inhibitor infusions for treatment of hereditary angioneurotic edema with systemic lupus erythematosus reacts with a normal allotype of residue 458 of C1-inhibitor.

Patients with hereditary C4 deficiency are likely to have severe lupus erythematosus. A patient with hereditary angioneurotic edema (HANE) and systemic lupus erythematosus (SLE) had a chronic deficiency in C4 because the hereditary deficiency in C1-inhibitor allowed the C1 in her serum to become activated and then inactivate C4. An attempt was made to repair the C4 deficiency as well as the deficiency in C1-inhibitor by giving infusions of human C1-inhibitor in the hope of inducing remissions of both HANE and SLE. During treatment, antibody to C1-inhibitor developed in the patient; this cleared when the infusions were stopped. During subsequent treatment with danazol alone, measurable C1-inhibitor developed in the patient's serum, but levels of C4 were never significantly increased. Antibody to normal C1-inhibitor was not expected to develop in the patient because she is heterozygous for this autosomal dominant trait. A normal allotype (VAL or MET 458), which would have been in the preparation used but which the patient does not synthesize because she can produce only one allotype (MET 458), appears to have been immunogenic. The antibody isolated from the patient's serum reacted with C1-inhibitor from a normal individual known to be homozygous for 458-VAL but not with one from a homozygote for MET-458.

Adult↗
PubMed1996

An autoantibody to C1-inhibitor recognizes the reactive center of the inhibitor.

An autoantibody to C1-inhibitor produced a clinical disorder resembling that of patients with hereditary angioneurotic edema. The antibody could not interact with C1-inhibitor after exposure to synthetic peptides representing the primary structure of the reactive center region of the protein. Therefore the antibody recognized this domain of the inhibitor, and it probably impaired the function of C1-inhibitor by altering its conformational properties.

Amino Acid Sequence↗
PubMed1996

The catabolism of intact, reactive centre-cleaved and proteinase-complexed C1 inhibitor in the guinea pig.

Clearance rates in the guinea pig were determined for intact guinea pig and human C1 inhibitor, the complexes of both inhibitors with human Cls, beta factor XIIa and kallikrein, and for each inhibitor cleaved at its reactive centre with trypsin. Intact human and guinea pig C1 inhibitor were cleared from the circulation more slowly (t1/2s of 9-7 h and 12.1 h and fractional catabolic rates (FCRs) of 0.09 and 0.117) than any of their cleaved or complexed forms. The reactive centre-cleaved inhibitors were cleared with half-lives of 6.75 h for humans and 10.1 h for the guinea pig. The complexes with target proteases were catabolized much more rapidly, with half-lives ranging from 3-08 h to 4.3 h. The complexes with kallikrein were cleared more slowly than those with Cls and beta factor XIIa. Complexes prepared with the guinea pig and human inhibitors were cleared at equivalent rates. The free inactivated proteases were cleared at rates similar to the equivalent complexes, except for kallikrein, which was cleared more rapidly than its complex. The fact that the complexes with different target proteases differed in their catabolism and that protease and complex catabolism were similar suggests that protease may play a direct role in clearance.

Amino Acid Sequence↗
PubMed1996

Instrument development: getting started.

The four steps involved in instrument development are: concept identification; item construction; validity testing and reliability testing. The clinician who has begun to identify characteristics associated with a patient group has in reality begun the process of instrument development. The challenge for clinicians and researchers is to transform those observable phenomena into a instrument that measures the attribute of the group. Only with reliable and valid measures can true relationships and differences be determined and effective intervention programs be formulated.

Bias↗
PubMed1996

Resistance of human immunodeficiency virus type 1 to neutralization by natural antisera occurs through single amino acid substitutions that cause changes in antibody binding at multiple sites.

The ability of human immunodeficiency virus type 1 (HIV-1) to replicate in the presence of strong immune responses to the virus may be due to its high mutation rate, which provides envelope gene variability for selection of neutralization-resistant variants. Understanding neutralization escape mechanisms is therefore important for the design of HIV-1 vaccines and our understanding of the disease process. In this report, we analyze mutations at amino acid positions 281 and 582 in the HIV-1 envelope, where substitutions confer resistance to broadly reactive neutralizing antisera from seropositive individuals. Neither of these mutations lies within an antibody-binding site, and therefore the mechanism of immune escape in both cases is by alteration of the shape of the envelope proteins. The conformation of the CD4-binding site is shown to be critical with regard to presentation of other discontinuous epitopes. From our analysis of the neutralization of these variants, we conclude that escape from polyclonal sera occurs through alterations at several different epitopes, generally resulting from single amino acid substitutions which influence envelope conformation. Experiments on a double mutant showed that the combination of both mutations is not additive, suggesting that these variants utilized alternate pathways to elicit similar alterations of the HIV-1 envelope structure.

Animals↗
PubMed1996

Primary care management of chronic musculoskeletal pain.

Chronic musculoskeletal pain, a common problem seen in the primary care setting, is often frustrating for both the patient and the clinician. Despite its prevalence, chronic pain is often poorly understood and inconsistently managed by health care providers. Unlike acute pain, chronic pain serves no biologic function and persists long after the tissue has healed from injury. Patients with chronic pain may become isolated from friends and family, lose their jobs, and develop depression. Nonpharmacologic techniques such as acupuncture, massage, and relaxation may be helpful to the patient with chronic pain. In addition to nonsteroidal antiinflammatory drugs, antidepressants and opioid analgesics are useful for treating chronic musculoskeletal pain. This article explains that pathophysiology of chronic pain, lists aspects of chronic pain that distinguish it from acute pain, and develops a general primary care plan for patients with chronic musculoskeletal pain.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1995

C3-independent glomerulonephritis in guinea pigs: dependence upon primary humoral response.

We used C3-deficient (C3D) guinea pigs to evaluate the role of C3 in an active model of experimental nephritis. Normal strain 2 (C3N, n = 13) and C3D (n = 6) guinea pigs were immunized with cationized bovine gamma-globulin (CBGG). Fourteen days later (Day 0), daily intravenous injections of CBGG were given for 3 to 7 days and the animals were sacrificed on Day 10 or 21. Immunofluorescence (IF) microscopy of renal tissue revealed two patterns of glomerular IgG deposition: granular loop (11/13 C3N, 3/6 C3D), and predominantly mesangial (2/13 C3N, 3/6 C3D). Codeposited C3 was seen in all C3N and in no C3D animals. Electron microscopy showed subepithelial deposits in all. A significant correlation (P < 0.005) was seen between an animal's IF pattern and its level of serum antibodies to CBGG; those with lower antibody levels exhibited the mesangial pattern. C3D animals had lower mean antibody levels than C3N (P < 0.01), but both IF patterns were represented. Urine protein concentration, which was increased relative to controls, did not differ between C3N and C3D groups, but was significantly greater in those with loop IF. Serum albumin was significantly reduced in animals with loop IF. C3N animals showed a significant reduction in mean serum C3. In this model, immune deposit location and degree of proteinuria are independent of C3 deposition and dependent upon the level of antibody response to CBGG. Induction of antibody to CBGG is impaired in the absence of C3.

Animals↗
PubMed1995

V-region and class specific RT-PCR amplification of human immunoglobulin heavy and light chain genes from B-cell lines.

We have designed and tested primers that amplify complete human kappa and lambda light chain genes, and human Fd fragments from gamma, mu and alpha heavy chain genes. These primers were tested for efficiency and specificity on monoclonal sources of human immunoglobulin RNA, obtained from human B-cell lines of known immunoglobulin gene expression. Analysis of the sequences derived from these B-cells confirms the specificity of the PCR primers and the extent of somatic mutation seen in different B-cell malignancies supports existing concepts for differing aetiologies in the tumours concerned.

Amino Acid Sequence↗
PubMed1995

Vitamin A trafficking in Caco-2 cells stably transfected with cellular retinol binding proteins.

During intestinal vitamin A absorption, retinol is esterified by long-chain fatty acids and secreted in chylomicron particles. Stable transfectants of the human intestinal Caco-2 cell line overexpressing cellular retinol binding protein II (CRBP II) or coexpressing CRBP II and CRBP were established to study their role in intestinal vitamin A trafficking. Compared with control cell lines, retinol uptake increased up to twofold by overexpression of CRBP II and up to 2.9-fold by coexpression of CRBP and CRBP II. Retinyl ester synthesis was increased proportionate to the increase in retinol absorption in all cell lines. Retinyl ester secretion was directly correlated with retinyl ester synthesis in control and CRBP II-transfected cell lines. However, transfection with CRBP increased the proportion secreted. Expression of CRBP and CRBP II also affected the polarity of retinyl ester secretion by increasing the proportion secreted basolaterally. Thus these studies provide evidence that intestinal retinol uptake, retinyl ester synthesis, and retinyl ester secretion are correlated with levels of CRBP and CRBP II and that the effects of CRBP on retinyl ester secretion can be distinguished from those of CRBP II.

Cell Line↗
PubMed1995

Unique C1 inhibitor dysfunction in a kindred without angioedema. II. Identification of an Ala443-->Val substitution and functional analysis of the recombinant mutant protein.

We have determined the cause of an unusual C1 inhibitor abnormality in a large kindred. We previously found that half of serum C1 inhibitor molecules in affected kindred members are normal. The other half complexed with C1s but showed little complex formation with C1r. These molecules also appeared to be relatively resistant to digestion by trypsin. Taken together, the findings suggested that members of this kindred are heterozygous for an unusual C1 inhibitor mutation. Sequencing of genomic DNA from the kindred revealed that thymine has replaced cytosine in the codon for Ala443 (P2 residue) in one C1 inhibitor allele, resulting in substitution with a Val residue. To test the effect of this substitution, a mutant C1 inhibitor containing Ala443-->Val was constructed by site-directed mutagenesis and expressed in COS-1 cells. Both the Ala443-->Val mutant and the wild-type C1 inhibitor complexed completely with C1s, kallikrein, and coagulation Factor XIIa after incubation at 37 degrees C for 60 min. In contrast, the mutant inhibitor failed to complex completely with C1r under the same conditions. Time course analysis showed that the ability of the mutant to complex with C1s is also impaired: although it complexed completely in 60 min, the rate of complex formation during a 0-60-min incubation was decreased compared with wild-type C1 inhibitor. The mutant inhibitor also formed a complex with trypsin, a serine protease that cleaves, and is not inhibited by, wild-type C1 inhibitor. The Ala443-->Val mutation therefore converts C1 inhibitor from a substrate to an inhibitor of trypsin. These studies emphasize the role of the P2 residue in the determination of target protease specificity.

Angioedema↗
PubMed1995

Innovative sensory input for the comatose brain-injured patient.

Coma following brain injury may last days or months and is associated with decreased quality of life for survivors and families. One intervention postulated to improve coma recovery is sensory stimulation. This article critically examines current theoretical perspectives and empirical data related to sensory stimulation, discusses the usefulness of sensory stimulation programs (SSP) in critical care settings, and poses strategies for implementation of an SSP. Future directions for nursing practice and research also are addressed.

Brain Injuries↗
PubMed1995

Preventing feeding-associated aspiration.

Aspiration and its sequela aspiration pneumonia are frequent complications associated with enteral feeding. The purpose of this article is to provide a framework for recognizing aspiration events, identifying at-risk patients, and developing research-based strategies to prevent aspiration.

Eating↗
PubMed1994

Functional analysis of the serpin domain of C1 inhibitor.

To analyze the role of the heavily glycosylated amino-terminal domain of C1 inhibitor in protease inhibitory activity, two truncated C1 inhibitor molecules were constructed. The abilities of the recombinant truncated inhibitors to complex with target proteases were compared with that of the wild-type recombinant protein. One recombinant truncated molecule consisted of amino acid residues 76 to 478 (C-serp(76)) and the other of residues 98 to 478 (C-serp(98)). The recombinant proteins were each expressed in similar quantities. The thermal denaturation profiles of the two truncated proteins were similar to that of the wild-type protein. Identical binding of C1s, C1r, kallikrein, and beta factor XIIa was observed with the three molecules. Furthermore, the truncated molecules also effectively inhibited C1 activity in hemolytic assays. These studies therefore clearly demonstrate that the amino-terminal domain of C1 inhibitor does not influence complex formation with target proteases.

Complement C1 Inactivator Proteins↗
PubMed1994

A cluster of mutations within a short triplet repeat in the C1 inhibitor gene.

Mutations in the C1 inhibitor gene that result in low functional levels of C1 inhibitor protein cause hereditary angioneurotic edema. This disease is characterized by episodic edema leading to considerable morbidity and death. Among 60 unreported kindred with the disease, four patients were discovered to have mutations clustered within a 12-bp segment of exon 5 from nucleotide 8449 to nucleotide 8460. This short segment of DNA contains three direct repeats of the triplet CAA and is immediately preceded by a similar adenosine-rich sequence (CAAGAACAC). These triplet repeats make this region susceptible to mutation by a slipped mispairing mechanism. There are two other short triplet repeat elements in the coding region for this gene, but they have not become mutated in any kindred examined. This suggests that the apparent enhanced mutation rate in this region of exon 5 may be influenced by DNA structural characteristics.

Amino Acid Sequence↗
PubMed1994

Acquired C1 inhibitor deficiency as a result of an autoantibody to the reactive center region of C1 inhibitor.

An autoantibody that we hypothesize to react with the reactive center of the plasma serine proteinase inhibitor, C1 inhibitor (C1INH), has been found in a patient with acquired C1INH deficiency. The Ab blocks the ability of C1INH to inhibit the hydrolysis of N-carbobenzyloxy-L-lysine thiobenzylester by purified C1s. A cryoprecipitate from the patient's plasma as well as the Ig fraction were able to block C1INH inhibition of C1s. The immunoaffinity purified Ab to C1INH from the patient's plasma Ig fraction neutralizes the inhibitory activity of C1INH in a dose-dependent manner and blocks the ability of normal C1INH to form a complex with C1s. The neutralizing activity of the purified Ab is reversed by a synthetic peptide that corresponds to the amino acid sequence in the P1 to P15 positions of the reactive center of C1INH but not by a 34-amino-acid trypsin peptide or 37-amino-acid elastase peptide derived from the C-terminus of C1INH. Western blot analysis indicated that the Ab is an oligoclonal Ig with kappa light chains.

Adult↗