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Biomedical subjects

A Krook

Publications and source records attributed to A Krook.

At least 73 records · Page 4Linked to original sources
PubMed1992

Variability of surface-exposed antigens of different strains of Moraxella catarrhalis.

For serological diagnosis of infection with Moraxella (Branhamella) catarrhalis it is important to determine if there is variability of antigenic properties among different strains. Cross-reactions of nine strains were investigated by an immunofluorescence test using sera from immunized rabbits. All titres but one were 1:256 or higher, the highest being 1:4096. Thus a high degree of antigenic similarity was demonstrated among different strains of Moraxella catarrhalis. However, the homologous titres of six sera were 2 to 16 times higher than the titres for other strains indicating strain variations in antigenic properties of some surface components. There was no correlation between lipopolysaccharide type and titre in the immunofluorescence test.

Animals↗
PubMed1992

Insulin receptor and insulin-responsive glucose transporter (GLUT 4) mutations and polymorphisms in a Welsh type 2 (non-insulin-dependent) diabetic population.

We have recently examined the exons encoding the insulin receptor tyrosine kinase domain and GLUT 4 in 30 subjects with Type 2 (non-insulin-dependent) diabetes mellitus using a molecular scanning approach. The variant sequences Val-Met985 and Lys-Glu1068 of the insulin receptor and Val-Ile383 of GLUT 4 were each separately found in three different diabetic subjects. In a study of a Welsh population, the GLUT 4(383) variant was found in three of 160 diabetic and none of the 80 control subjects. In this study, the same group of Welsh Type 2 diabetic and control subjects was analysed using allele-specific oligonucleotide hybridisation, single nucleotide primer extension and allele-specific restriction digestion to ascertain the frequency of the two insulin receptor mutations. The Val-Met985 mutation was found in none of the 160 Welsh Caucasian Type 2 diabetic subjects and two of 80 control subjects. The Lys-Glu1068 mutation removes a Sty 1 site and digestion of amplified exon 18 with Sty 1 confirmed the presence of the mutation in the heterozygous state in the original subject. None of the Welsh diabetic or control subjects had the Glu1068 mutation. The discovery of a very common silent polymorphism at codon 130 of GLUT 4 allowed examination of the association of this locus with Type 2 diabetes using allele-specific oligonucleotide hybridisation in a subset of the Welsh subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗
PubMed1992

Rapid and simultaneous detection of multiple mutations by pooled and multiplex single nucleotide primer extension: application to the study of insulin-responsive glucose transporter and insulin receptor mutations in non-insulin-dependent diabetes.

The application of molecular scanning techniques to the detection of potentially pathogenic mutations in candidate genes in patients with non-insulin-dependent diabetes has revealed a number of molecular variants of uncertain pathophysiologic significance. The determination of the significance of such variants requires large-scale population studies of the prevalence of the mutant in affected and control groups. Herein, we describe two adaptations of the technique of single nucleotide primer extension (SNuPE) which allow the simultaneous examination of large numbers of alleles at multiple loci. The usefulness of these adaptations is illustrated by their application to the simultaneous detection of three point mutations, two in the tyrosine kinase domain of the insulin receptor and one in the insulin-responsive glucose transporter (GLUT4) in a highly insulin-resistant NIDDM population. By pooling genomic or amplified DNA and performing the SNuPE reactions with three primers of different length we could readily examine 300 alleles on a single 20 lane gel. Using pooled SNuPE, we also examined a large British Caucasian control population for the prevalence of GLUT4 Ile383, a variant which has previously been reported only in NIDDM. GLUT4 Ile383 was detected in 2/42 of the highly insulin-resistant NIDDM subjects and 4/240 middle-aged blood donors. Family studies and examination of the expressed mutant transporter will be necessary to establish whether this mutation is of functional significance. Pooled and multiplex SNuPE are powerful techniques with wide applicability to population genetic studies of specific mutations.

Alleles↗
PubMed1991

Human antibody response to the major adhesin of Mycoplasma pneumoniae: increase in titers against synthetic peptides in patients with pneumonia.

Peptides corresponding to parts of the P1 protein (major adhesin) of Mycoplasma pneumoniae were synthesized. On the basis of predicted antigenicity, seven sequences containing 17 to 21 amino acids were selected. In addition, one peptide containing a sequence of 13 amino acids shown to be related to cytadherence of M. pneumoniae was included. Serum samples from 56 patients with pneumonia were tested for a rise in titers of specific IgG during infection, using the peptides as coating antigens in ELISA. A titer rise against one or more peptides was observed in 10 out of 13 patients with serological evidence of mycoplasmal etiology. Specific antibodies to two or more peptides were demonstrated in three patients, whereas seven patients responded to one peptide only. In the sera from patients with pneumonia of non-mycoplasmal etiology, no titer rises above the cut-off level were observed. Our results indicate that a combination of four peptides would be possible for use as antigen for serological diagnosis of infections with M. pneumoniae.

Adhesins, Bacterial↗
PubMed1991

Cellular ras gene activity is required for full neoplastic transformation by polyomavirus.

To investigate the role of ras gene activity in cellular transformation by polyomavirus, murine C3H10T1/2 cells were rendered ras deficient by transfection with an antisense ras gene construct. Ras deficiency resulted in a partial suppression of the polyomavirus-induced transformed phenotype. The production of viral middle T antigen and its association with pp60c-src, increased membrane-associated protein kinase C activity, and morphological transformation were unaffected by the downregulation of c-ras gene expression. On the other hand, stimulated proliferation, focus formation on confluent monolayers of normal cells, and colony formation in soft agar were all greatly reduced in cells containing reduced p21ras levels. It is concluded that ras gene activity is needed for full cell transformation by polyomavirus.

Animals↗
PubMed1990

Rapid aetiological diagnosis of pneumonia based on routine laboratory features.

The values of some basic laboratory features on admission to hospital were recorded and compared in 418 adult patients with community-acquired pneumonia, namely erythrocyte sedimentation rate, C-reactive protein, white blood cell (WBC) count, serum lactate dehydrogenase (S-LD), serum alanine-aminotransferase, and serum sodium. Discriminant analysis was performed to obtain an aetiological diagnosis. WBC value of greater than 15 x 10(9)/l strongly indicated a bacterial and, especially a pneumococcal aetiology, whereas increased S-LD could imply a mycoplasmal infection. For patients less than 50 years of age the equation C2 = -1.788 + 0.204 x WBC-0.0909 X S-LD was constructed, in which C2 greater than 0 indicated a pneumococcal aetiology. This function correctly classified 31/33 (93.9%) patients with a mycoplasmal and 20/31 (64.5%) patients with a pneumococcal infection. Patients with viral, Haemophilus influenzae or chlamydial infection could not be discriminated from each other. The age of the patient, WBC and possibly S-LD on admission are easily accessible parameters and these results could therefore be of value in daily clinical practice in hospitals.

Adolescent↗
PubMed1990

Minimal criteria for identification of Moraxella (Branhamella) catarrhalis.

A study was performed which aimed at testing the reliability of our routine diagnostic tests for identification of Moraxella (Branhamella) catarrhalis in clinical samples from the respiratory tract. A preliminary diagnosis of 122 isolates as Moraxella catarrhalis was obtained by using colony morphology and results of Gram stain and oxidase test as the sole diagnostic criteria. By using additional tests we could show that the preliminary diagnosis was incorrect for 21 isolates, which were classified as different Neisseria species. 20 of these were isolated from sputum samples. We propose that at least a test for DNA hydrolysis should be included in the routine procedure for identification of Moraxella catarrhalis in sputum.

Deoxyribonucleases↗
PubMed1989

Comparison of three methods for detection of pneumococcal antigen in sputum of patients with community-acquired pneumonia.

In a prospective study of 249 patients with community-acquired pneumonia, three tests for the detection of pneumococcal antigen in sputum were compared: a coagglutination test for detecting capsular antigens (Cap-CoA), a sandwich enzyme immunoassay (PnC-EIA) and a coagglutination test (PnC-CoA), both the latter detecting the pneumococcal C-polysaccharide common to all pneumococcal types. Sixty-three patients had culture-positive pneumococcal pneumonia, 45 pneumonia caused by other bacteria and 141 pneumonia of viral or unknown etiology. The sensitivity of Cap-CoA (63%) and PnC-CoA (65%) was somewhat higher than that of PnC-EIA (49%), but not significantly so. The specificity was 96-98% for all three methods. Using PnC-CoA 66 patients with possible pneumococcal infection were detected, the diagnosis being verified by culture in 41. Using Cap-CoA 59 such patients were detected, the diagnosis being verified in 40, and using the PnC-EIA 47 such patients were detected, the diagnosis being verified in 31. Antigen was found almost as often in non-purulent as in purulent samples, and as often in washed as in non-washed purulent samples. However, antibiotic treatment before the sputum sample was obtained resulted in significantly lower sensitivity of both PnC-CoA and Cap-CoA. This study confirms the high sensitivity and specificity of methods for pneumococcal antigen detection in sputum. Since CoA is easier and quicker to perform, and cheaper than the EIA, either PnC-CoA or Cap-CoA would seem to be the technique of choice for detection of pneumococcal antigen, whereby all sputum samples, including non-purulent samples, can be used.

Adolescent↗
PubMed1988

Enzyme-linked immunosorbent assay for detection of Mycoplasma pneumoniae specific immunoglobulin M.

An ELISA was developed for the detection of IgM antibodies to Mycoplasma pneumoniae in human sera, using microtiter plates coated with rabbit antiserum to human IgM selecting for IgM antibodies in the first reaction step. The specific antibodies were detected using enzyme-labelled, detergent-solubilized antigen. The complement fixation test was used as reference method. In a prospective study of 59 patients with community-acquired pneumonia, 13 of whom had evidence of mycoplasmal etiology, the ELISA was shown to have high specificity (97%). In samples taken seven days after onset of the disease all complement-fixation positive samples (n = 20) but one were positive, demonstrating the diagnostic value of a positive test in samples taken after that period.

Adolescent↗
PubMed1988

Septicemia caused by Staphylococcus saprophyticus.

Staphylococcus saprophyticus is a common cause of acute urinary tract infection (UTI) in young women. Septicemia has not been reported in patients without signs of immunodeficiency. We report 2 such cases in previously healthy 19- and 33-year-old women. Thus, this microbe may give rise to invasive infection and should be considered when coagulase-negative staphylococci are isolated from blood cultures in patients with symptoms of UTI.

Adult↗
PubMed1988

Detection of specific IgM antibodies for the diagnosis of Mycoplasma pneumoniae infections: a clinical evaluation.

The diagnostic value of detection of specific IgM antibodies was analysed in Mycoplasma pneumoniae infections. In a retrospective clinical and serological study, M. pneumoniae IgM antibodies were determined by a mu-capture ELISA using enzyme-labelled antigen. The study group consisted of 91 patients with significantly raised titers in paired sera or a single high titer of complement fixation antibodies. About 40% of the patients had been treated with antibiotics ineffective against M. pneumoniae infections prior to admission to hospital. Treatment with erythromycin or tetracycline was shown to give a shorter period of fever compared to if no or ineffective therapy was given. Specific IgM antibodies were detected in about 80% of sera sampled 9 days or more after onset of symptoms. In sera sampled at 7-8 days after onset IgM antibodies were found in about 40% of the sera but only occasionally in sera sampled earlier. In the age group 0-20 years 88% of the patients developed an IgM response. In the higher ages (greater than 60 years) a significantly lower rate of IgM responders was observed.

Adolescent↗
PubMed1988

IgG response to Mycoplasma pneumoniae in patients with community-acquired pneumonia determined by ELISA.

In a prospective study of community-acquired, radiologically verified pneumonia, a solubilized mycoplasma antigen was used in an enzyme-linked immunosorbent assay (ELISA) for the detection of IgG-antibodies to Mycoplasma pneumoniae in paired sera from 60 patients. All of the 13 patients with a positive complement fixation (CF) test for M. pneumoniae were positive in the ELISA, and 46 out of 47 patients with a negative CF test were negative. The only false positive test was recorded from a patient with a positive CF test for Chlamydia. Specific IgG antibodies were also determined in paired sera from 50 pneumonia patients, all positive in the CF test for M. pneumoniae, and collected over a period of 10 years. Of these 50 patients, 45 were recorded as positive in the ELISA for IgG antibodies to M. pneumoniae. In the prospective as well as in the retrospective study, the time for admission to hospital after onset of disease showed considerable variation (1-14 days), with the consequence that high titers were recorded in the CF as well as in the ELISA in some of the first serum samples. A tendency to earlier detection of significant titers was noted in the CF test as compared to the ELISA.

Adolescent↗
PubMed1987

A new coagglutination test for detecting pneumococcal C-polysaccharide.

A new coagglutination test (PnC-CoA) for detecting pneumococcal C-polysaccharide (PnC) was compared with a commercial kit for detecting capsular polysaccharide using sputum samples from 105 patients with pneumonia. The sensitivity obtained with PnC-CoA was 95.8% and with the commercial kit 83.3%; the specificity was 96.5% and 91.2%, respectively. The PnC-CoA is simple to perform and it is a rapid, sensitive and specific test for detecting Streptococcus pneumoniae in sputa from adult patients with pneumonia.

Agglutination Tests↗
PubMed1987

Etiologic diagnosis of pneumonia by antigen detection: crossreactions between pneumococcal C-polysaccharide and oral microorganisms.

Crossreactions between bacteria occurring more or less frequently in the respiratory tract were investigated using an enzyme-linked immunosorbent assay (ELISA) developed for the detection of pneumococcal C-polysaccharide. A collection of 218 strains was investigated: 30 Streptococcus pneumoniae, 120 alpha-streptococci, and 68 strains representing other species. Strong crossreactions were observed with 36% of the alpha-streptococci and with two of 11 Staphylococcus aureus strains. The collection of alpha-streptococci consisted of 90 fresh clinical isolates and 30 stock strains. Almost all crossreactions of alpha-streptococci were found among the clinical isolates. Among the stock strains only one of four Streptococcus mitis strains was positive. Pneumococcal C-polysaccharide and phosphorylcholine inhibited the reactions in ELISA with monoclonal antibodies against pneumococcal C-polysaccharide, as well as with a polyclonal antiserum against pneumococcal C-polysaccharide. We suggest that the cross reactions between alpha-streptococci and pneumococci depend on the presence of phosphorylcholine as a common antigenic determinant. The crossreaction in the ELISA with some Staphylococcus aureus strains may be explained by the presence of protein A binding to the Fc portion of the antibodies. When the 10 alpha-streptococci that showed the strongest crossreactions and ten pneumococci representing different types were tested in different concentrations the absorbance values were lower for most alpha-streptococci compared with the pneumococci. This explains that false positive results with alpha-streptococci do not seem to constitute a practical problem in this ELISA developed for detection of pneumococcal C-polysaccharide in samples from patients with pneumonia.

Antigens, Bacterial↗