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Biomedical subjects

E Jacobs

Publications and source records attributed to E Jacobs.

At least 55 records · Page 3Linked to original sources
PubMed1997

Mycoplasma infections of the human respiratory tract.

Mycoplasma pneumoniae represents one of the common etiological agents causing interstitial pneumonia, but more often a long-lasting tracheobronchitis in children and also in adults. The incidence of Mycoplasma pneumoniae diseases varies considerably, major outbreaks being reported every 3 to 5 years. The pathomechanism of this agent is based on a unique, gliding motility, adhesion to respiratory epithelium cells and the induction of a pathological hyperstimulation of cellular response mechanisms of the host. Antigenic similarities between important functional sites of the adhesin of Mycoplasma pneumoniae and various host molecules might be one of the factors responsible for hindering the host-response mechanism and, moreover, failing to protect the host repeated colonization. These are indications of a near perfect adaptation of Mycoplasma pneumoniae to man, its only known host to date.

Adult↗
PubMed1997

A protein disulfide-thiol interchange activity of HeLa plasma membranes inhibited by the antitumor sulfonylurea N-(4-methylphenylsulfonyl)-N'-(4-chlorophenyl) urea (LY181984)

Plasma membrane vesicles isolated from HeLa cells grown in suspension culture contain a protein disulfide-thiol interchange (protein disulfide-like) activity. The activity was estimated from the restoration of activity to inactive (scrambled) pancreatic RNAase. RNAase activity was measured either by hydrolysis of cCMP or by a decrease in acid precipitable yeast RNA. The ability of plasma membrane vesicles to restore activity to inactive (scrambled) pancreatic ribonuclease was inhibited by the antitumor sulfonylurea N-(4-methylphenylsulfonyl)-N'-(4-chlorophenyl)urea (LY181984). The activity correlated with that of a cyanide-resistant NADH oxidase also associated with the plasma membrane vesicles that exhibited a similar pattern of drug response. The activity was stimulated by reduced glutathione and inhibited by oxidized glutathione but did not depend on either for activity. The antitumor sulfonylurea-inhibited activity was greatest in the presence of reduced glutathione and least in the presence of oxidized glutathione. The antitumor sulfonylurea-inhibited activity was unaffected by a monoclonal antibody to protein disulfide isomerase. Also the antitumor sulfonylurea-inhibited activity was unaffected by peptide antisera to the consensus active site sequence of protein disulfide isomerase. Thus the antitumor sulfonylurea-inhibited activity appeared to reside with a novel cell surface protein capable of oxidation of both NADH and protein thiols and of carrying out a protein disulfide isomerase-like protein disulfide-thiol interchange activity in the absence of NADH or other external reductants.

Antineoplastic Agents↗
PubMed1997

Characterization of upstream activating sequences involved in activation and regulation of pho4 expression in Schizosaccharomyces pombe.

In this study, a short region of the pho4 promoter located just upstream of the TATA box, called the upstream activating sequence (UAS), was shown to be responsible for both activation and regulation of pho4 expression in Schizosaccharomyces pombe. This cis-acting sequence is able to activate transcription when placed upstream of the minimal promoter of the constitutively expressed adh gene, and to ensure regulation by thiamine. The organisation of the pho4 promoter is remarkable in that UAS and TATA box are very closely associated. This proximity appears to be essential for efficient transcriptional regulation. Indeed, only slight variations in transcript levels were observed under derepression conditions when the UAS was moved away from the TATA box, while regulation of transcript levels appeared to be strongly affected. This observation suggests the existence of a negative regulatory element whose action requires very close association of UAS and TATA box. Surprisingly, when UAS was moved about 40 bp away from the adh TATA box, residual but very significant repression of gene expression by thiamine, which apparently does not result from transcriptional regulation, was revealed by measuring protein production. These data prompted us to hypothesize the existence of two distinct and cooperative mechanisms of regulation involving specific factor binding to the UAS, the first one controlling transcript levels and the second acting posttranscriptionally.

Amino Acid Sequence↗
PubMed1997

Characteristics of a 20-minute whole blood rapid assay for cardiac troponin T.

OBJECTIVES: A qualitative whole blood rapid assay for cardiac troponin T (cTnT) was examined. The assay uses the same antibodies as for a benchmark ELISA, but the capture and detection roles were switched to enhance specificity. DESIGN AND METHODS: The cTnT Rapid Assay and ELISA were compared in 643 samples from patients having myocardial infarction, coronary artery bypass surgery, ischemic heart disease, musculoskeletal disease, renal failure, or other noncardiac conditions. Concordance between the methods was compared using the McNemar Test and cTnT cutoff of 0.2 micrograms/L. RESULTS: For the "cutoff" of 0.2 micrograms/L, concordance between the cTnT Rapid Assay and ELISA was in the range of 90-95% for each group except the renal failure patients, where concordance was 77.9%. There was no significant difference between the cTnT Rapid Assay and ELISA, except in the renal failure and ischemic heart disease patients, where there was a greater number (p < 0.05) of cTnT Rapid Assay negative results when the ELISA was > 0.2 micrograms/L. Overall concordance between the cTnT Rapid Assay and CK-MBmass was 78%. CONCLUSION: The McNemar test indicated that the cutoff for the cTnT Rapid Assay was 0.2 micrograms/L. Evidently the lower concordance among renal failure and ischemic heart disease patients reflects higher cTnT specificity for the Rapid Assay that was conferred by switching the capture and detection antibodies.

Adolescent↗
PubMed1997

The effect of onapristone, a progesterone antagonist, on the growth of human gastrointestinal cancer xenografts.

Onapristone is a progesterone antagonist which inhibits the growth of mammary tumours in mice. The effect of Onapristone and concomitant oestrogen (E2) supplements on the growth of five human gastrointestinal cancer xenografts was examined. E2 stimulated RD19 (gastric tumour) tumour growth in female mice and tumours grew less well when also treated with Onapristone (P < 0.05). Onapristone had no effect on male mice bearing RD19 tumours or mice of either sex bearing MKN45G (gastric) tumours. PAN-1 (pancreatic) tumours were significantly stimulated by E2 (by 64% of control, P = 0.02) and Onapristone treatment inhibited E2 stimulated growth (52% reduction of E2 control, P > 0.05). C146 (colorectal) tumour growth was not stimulated by E2 nor inhibited by Onapristone. E2 stimulated formation of AP5LV (colorectal) tumour nodules (in lungs) (mean 38-52, P = 0.001). Onapristone significantly reduced the number of nodules (mean 32, P < 0.05) only in female mice not given E2. Xenografts of some GI tumour cell lines grow at different rates in male and female mice. E2 may cause additional growth stimulation and E2 stimulated growth can be reversed by Onapristone to basal levels.

Analysis of Variance↗
PubMed1997

Heterotopic gastric mucosa in the upper esophagus: a prospective study of 33 cases and review of literature.

BACKGROUND AND STUDY AIMS: The prevalence of endoscopically diagnosed heterotopic gastric mucosa in the upper esophagus (HGMUE) has been reported in a few studies, and varies from 0.1 to 10%. Clinical relevance and possible association with other pathological conditions remain a matter of debate. A prospective study was carried out to determine the prevalence of HGMUE, the influence on it of age and sex, and to study the macroscopic and microscopic aspects of the lesion, its clinical relevance and possible association with other pathological conditions. PATIENTS AND METHODS: A total of 674 new patients with upper digestive complaints or alteration of their state of health underwent upper gastrointestinal endoscopy, with special attention paid to the proximal esophagus when withdrawing the gastroscope. They had been carefully questioned, especially regarding possible complaints, which could have drawn attention to the upper esophagus. RESULTS: Heterotopic columnar epithelium in the proximal esophagus was found in 4.9 % of patients. No difference was observed according to age or sex. A mild to moderate chronic inflammatory infiltration of the heterotopic patch was observed in most cases, not related to the presence in the lesion of Helicobacter pylori, which was found in only one case. Pathological conditions of the gastroesophageal junction, especially esophagitis, were slightly more frequent in patients with HGMUE. Mild complaints, possibly related to the presence of the lesion, were observed in three out of the 33 cases. CONCLUSIONS: On the basis of our prospective study we consider that heterotopic columnar epithelium in the proximal esophagus is a rather common, generally asymptomatic, benign congenital anomaly. Malignant transformation of heterotopic gastric mucosa in the upper esophagus and other severe complications are rare. The need for surveillance should be reserved for the rare cases with metaplasia or dysplasia in the heterotopic columnar mucosa.

Adult↗
PubMed1997

Spatial relationships in early signaling events of flow-mediated endothelial mechanotransduction.

Blood flow interactions with the vascular endothelium represent a specialized example of mechanical regulation of cell function that has important physiological and pathological cardiovascular consequences. The endothelial monolayer in vivo acts as a signal transduction interface for forces associated with flowing blood (hemodynamic forces) in the acute regulation of artery tone and chronic structural remodeling of arteries, including the pathology of atherosclerosis. Mechanisms related to spatial relationships at the cell surfaces and throughout the cell that influence flow-mediated endothelial mechanotransduction are discussed. In particular, flow-mediated ion channel activation and cytoskeletal dynamics are considered in relation to topographic analyses of the luminal and abluminal surfaces of living endothelial cells.

Animals↗
PubMed1996

Are outbreaks and sporadic respiratory infections by Mycoplasma pneumoniae due to two distinct subtypes?

Thirty-seven clinical isolates of Mycoplasma pneumoniae, cultured from patients' respiratory material between 1986 and 1994, were typed by immunological methods and by polymerase chain reaction (PCR). For immunological typing two monoclonal antibodies (mAb) were used that recognized the P1 adhesion of Mycoplasma pneumoniae strain FH but differed in their ability to inhibit the adherence of Mycoplasma pneumoniae to erythrocytes. The mAb P1.58, which was not able to inhibit adherence, showed reactions with all patients' isolates in immunoblots, whereas the adherence-inhibiting mAb P1.62 reacted with only seven patients' isolates. Due to variations within the P1-adhesin genome of Mycoplasma pneumoniae group 1 (Mycoplasma pneumoniae type strain M129) and group 2 (Mycoplasma pneumoniae type strain FH), two primer sets were designed. According to the size of the PCR-amplification products, all clinical isolates that showed no mAb P1.62 reactivity belonged to Mycoplasma pneumoniae group 1, whereas mAb P1.62-positive-reacting mycoplasma isolates were characterized as group 2 strains. During an outbreak of Mycoplasma pneumoniae diseases in 1992, all 19 clinical isolates showed no cross-reactivity in immunoblots with the mAb P1.62 and were typed by PCR as Mycoplasma pneumoniae group 1 strains. Furthermore, 206 Mycoplasma pneumoniae complement fixation test-positive patient sera (titer > 1:40) from the study period were tested for adherence-inhibiting antibodies towards both type strains. Thirty-two sera showed adherence-inhibiting antibodies towards group 1 and 22 towards group 2 mycoplasmas. In only seven sera were adherence-inhibiting antibodies directed to both Mycoplasma pneumoniae groups. The serological data of the outbreak in 1992 revealed that patients with Mycoplasma pneumoniae group 1 infections developed adherence-inhibiting antibodies more frequently than did patients infected with group 2, which might have implications for the pathogenesis of Mycoplasma pneumoniae diseases and subsequent infections.

Adolescent↗
PubMed1996

Bovine haemoglobin is more potent than autologous red blood cells in restoring muscular tissue oxygenation after profound isovolaemic haemodilution in dogs.

PURPOSE: This study compares the effects of stored red cells, freshly donated blood and ultrapurified polymerized bovine haemoglobin (HBOC) on haemodynamic variables, oxygen transport capacity and muscular tissue oxygenation after acute and almost complete isovolaemic haemodilution in a canine model. METHODS: Following randomization to one of three groups, 24 anaesthetized Foxhounds underwent isovolaemic haemodilution with 6% hetastarch to haematocrit levels of 20%, 15% and 10% before they received isovolaemic stepwise augmentation of 1 g.dl-1 haemoglobin. In Group 1, animals were given autologous stored red cells which they had donated three weeks before. In Group 2, animals received freshly donated blood harvested during haemodilution. In Group 3, animals were infused with HBOC. Skeletal muscle tissue oxygen tension was measured with a polarographic 12 mu needle probe. RESULTS: In all groups, heart rate and cardiac index were increased with decreasing vascular resistance during haemodilution (P < 0.05). Haemodynamic variables showed a reversed trend during transfusion when compared to haemodilution but remained below baseline (P < 0.05). Arterial and venous oxygen content were changed in parallel to changes of haematocrit and haemoglobin concentrations but were lower in Group 3 than in Groups 1 and 2 (P < 0.05) during transfusion. In contrast, the oxygen extraction ratio was higher in Group 3 (59 +/- 8%, P < 0.01) at the end of transfusion than in Group 1 (37 +/- 13%) and 2 (32 +/- 5%). In Group 3, mean tissue oxygen tension increased from 16 +/- 5 mmHg after haemodilution to 56 +/- 11 mmHg after transfusion (P < 0.01) and was higher than in Group 1 (41 +/- 9, P < 0.01) and Group 2 (29 +/- 11, P < 0.01). While in Group 3 an augmentation of 0.7 g.dl-1 haemoglobin resulted in restoring baseline tissue oxygenation, higher doses of 2.7 g.dl-1 and 2.1 g.dl-1 were needed in Groups 1 and 2 to reach this level (P < 0.01). CONCLUSION: The results show a higher oxygenation potential of HBOC than with autologous stored red cells because of a more pronounced oxygen extraction.

Animals↗
PubMed1996

Response of a protein disulfide isomerase-like activity of transitional endoplasmic reticulum to all-trans retinol.

Isolated membrane fractions enriched in vesicles of transitional endoplasmic reticulum from rat liver exhibited protein disulfide isomerase-like activity of low specific activity. Activity was measured as the ability to restore activity to reduced, denatured and oxidized (scrambled) RNase. Submicromolar concentrations of retinol either stimulated or inhibited this activity depending on the composition of the redox buffer. In the presence of 1 microM reduced glutathione, micromolar concentrations of retinol stimulated the activity while higher or lower concentrations were less effective. With scrambled RNase, retinol was largely without effect in the absence of reduced glutathione or in the presence of oxidized glutathione. In the presence of NADH, retinol inhibited the protein disulfide-like activity over the same range of concentrations where retinol stimulated in the presence of reduced glutathione. These responses were observed with scrambled and inactive RNase and with reduced and inactive RNase as substrates. Also inhibited by retinol in these membrane preparations was their ability to oxidize NADH. Thus the retinol-modulated protein disulfide isomerase activity appears to correlate with the presence in transitional endoplasmic reticulum of an activity capable of oxidizing NADH in the presence of potassium cyanide that also was inhibited by submicromolar concentrations of retinol.

Animals↗
PubMed1996

Oestrogen and progesterone receptors in gastrointestinal cancer cell lines.

Expression of sex steroid receptors by gastrointestinal (GI) tumours may indicate a role for hormonal manipulation in their management. A panel of seven established cell lines derived from primary human GI tumours were assayed for oestrogen and progesterone receptor (ER and PgR) expression by ligand binding, immunocytochemistry and enzyme-immunoassay methods. It was possible to demonstrate very low levels of both ER and PgR in the GI cell lines using enzyme immunoassay (EIA), with levels of PgR generally higher than those for ER. Neither ER nor PgR were detected in cytosols made from the GI cell lines in a classical dextran coated charcoal ligand binding assay. Similarly, immunohistological analysis (Abbott ERICA, PgRICA) of cultured cell preparations or of frozen and paraffin sections of xenograft tumour failed to demonstrate receptors. This confirms that low PgR levels are measurable by EIA in GI tumour cell lines. Upregulation of PgR expression in tumours by exposure to oestradiol in vitro was not observed.

Animals↗
PubMed1996

Molecular characterization of hybrid Tbp2 proteins from Neisseria meningitidis.

Transferrin-binding protein 2 (Tbp2) from Neisseria is an outer membrane-associated extracellular lipoprotein that is involved in iron capture within the infected host. The analysis of tbp2 clones isolated from various bacterial strains revealed extensive divergences throughout the open reading frame (ORF), with predicted amino acid (aa) sequences displaying 47% to 83% identity. Such a variability is likely to have resulted from the selective pressure exerted by the host immune system, but raises questions regarding the existing constraints for conservation of protein function. Indeed, the neisserial Tbp2s include a large structured domain, extending throughout the N-terminal half of the protein (approximately 270-290 aa), which is extremely stable and whose conformational integrity is required for efficient binding to human transferrin (hTf). In this work, a functional study of Tbp2s encoded by hybrid genes constructed by reassorting highly divergent tbp2 sequences in the region of the ORF encoding this structured domain was performed. The data demonstrate that the determinant intramolecular interactions allowing formation of a stable Tbp2 structure able to interact efficiently with hTf or/and that the Tbp2 residues involved in the interaction with hTf are not well conserved. However, a number of rearrangements appeared to generate genes encoding proteins which have retained structural stability and hTf-binding capacity. This suggested that despite the extreme aa sequence divergence and the conformational constraints, horizontal genetic exchanges, which are known to occur in neisserial populations, may have contributed significantly to the generation of sequence variation within tbp2 ORFs. The analysis of two tbp2 clones characterized in this work supports this hypothesis.

Amino Acid Sequence↗
PubMed1995

Production of lipidated meningococcal transferrin binding protein 2 in Escherichia coli.

Neisseria meningitidis strains grown under iron starvation conditions produce transferrin binding proteins (Tbp1 and Tbp2) which have been shown to play a major role in iron acquisition. Recent studies performed with Tbp2 purified from N. meningitidis suggest that this surface protein is a potential vaccine component. In order to further evaluate the immunogenicity of Tbp2, it was essential to develop a heterologous expression system to generate high amounts of purified protein. Tbp2 is produced in Neisseria as a precursor with a signal peptide whose cleavage follows a lipidation step on a cysteine residue which is the first amino acid in the mature protein. When produced in Escherichia coli with its natural signal peptide, a high amount of Tbp2 (about 10% of total cell proteins) was detected. However, most of the protein was nonlipidated precursor and only a small fraction was mature Tbp2. In order to optimize the maturation of the precursor, the natural signal sequence was replaced by several E. coli lipoprotein signal peptides. Expression levels and maturation of the precursor were highly variable depending on the signal peptide used. With one of these, an efficient maturation and a high amount of mature lipidated Tbp2 were obtained (about 3% of total cell proteins). A large-scale production process was then established for this E. coli-produced Tbp2.

Amino Acid Sequence↗
PubMed1995

Molecular mimicry by Mycoplasma pneumoniae to evade the induction of adherence inhibiting antibodies.

Specific regions of adherence binding sites and epitopes of the P1 adhesin of Mycoplasma pneumoniae were synthesised as octapeptides and used as targets in a modified enzyme-linked immunosorbent assay. Acute phase and convalescent sera from 10 patients with M. pneumoniae infection were tested for antibody reactivity to these octapeptides. In convalescent sera, antibody activities were directed against octapeptides of the epitope regions, whereas no antibody activity was found in acute or convalescent sera to octapeptides of adherence-mediating binding sites could be explained partially from the results of cross-reactivity experiments with adherence-inhibiting anti-P1 adhesin monoclonal antibodies (MAbs). Two of these MAbs showed cross-reactions with intracellular antigens of eukaryotic cell lines in immunofluorescence microscopy experiments. The cross-reacting antigens were isolated and characterised as glyceraldehyde-3-phosphate dehydrogenase and 2-phospho-D-glycerate hydrolyase. Antigenic mimicry of eukaryotic structures by functional sites of the P1 adhesin of M. pneumoniae may influence the pathogenesis of M. pneumoniae infection.

Adhesins, Bacterial↗
PubMed1995

The satellite laboratory and point-of-care testing. Integration of information.

Laboratory testing is returning to the point of care, where it started in the 19th century. This decentralization of testing is occurring because of the many advantages it brings to the practice of critical care medicine, such as faster turn-around time and better patient management in inpatient and outpatient settings. However, decentralization of testing is decentralizing laboratory information. In addition, bedside analytical systems are causing a quality assurance dilemma in which data can be seen and acted on before the appropriate quality checks are completed. Current information technology allows these data to be integrated and thus patient care processes to be enhanced through tracking of clinical outcomes and reducing costs. Because the goal of point-of-care testing is to provide data in a timely manner, the future success of any point-of-care/satellite testing system will depend on the ease with which it can be integrated into the medical information system.

Clinical Laboratory Information Systems↗