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Biomedical subjects

A de Jong

Publications and source records attributed to A de Jong.

At least 37 records · Page 2Linked to original sources
PubMed1999

Simultaneous determination of enrofloxacin and its primary metabolite, ciprofloxacin, in plasma by HPLC with fluorescence detection.

A simple and sensitive HPLC method has been developed for the simultaneous determination of enrofloxacin (ENR) and ciprofloxacin (CIP) in plasma. Plasma sample preparation was carried out by adding phosphate buffer (pH 7.4, 0.1 M), followed by extraction with trichloromethane. ENR, CIP and the internal standard, sarafloxacin (SAR), were separated on a reversed-phase column, and eluted with aqueous acetonitrile (80:20). The fluorescence of the column effluent was monitorized at lambda(ex) 338 and lambda(em) 425 nm. The retention times were 2.28, 3.30 and 4.40 min for CIP, ENR and SAR, respectively. The detection limit for the two compounds was 10 ng/mL. Standard curves were linearly related to concentration in the range from 1 to 1500 ng/mL. The recovery was 93% for ENR and 75% for CIP.

Anti-Infective Agents↗
PubMed1999

Heparin-coated circuits for high-risk patients: a multicenter, prospective, randomized trial.

BACKGROUND: Heparin-coated circuits (HCCs) in low-risk cardiac patients who have coronary revascularization have a limited impact on postoperative outcome. In this prospective, randomized investigation, we studied high-risk patients who had cardiac operations with or without HCCs. METHODS: A total of 886 patients who had cardiac operations with cardiopulmonary bypass and at least one patient-related or procedure-related risk factor were enrolled in a multicenter study. They were randomly allocated to have cardiopulmonary bypass with Duraflo II HCCs (HCC group, n = 442) or conventional circuits (control group, n = 444). Postoperative outcome was investigated with respect to the occurrence of organ dysfunction. RESULTS: HCCs are associated with a shorter intensive care unit and postoperative hospital stay and with a lower rate of patients having a severely impaired clinical outcome (stay in intensive care unit for more than 5 days or death) (relative risk 0.66, p = 0.045). Lung dysfunction rate was significantly lower for the patients in HCC group affected by chronic obstructive pulmonary disease or who had mitral procedure (relative risk, respectively, 0.31, p = 0.018 and 0.05, p = 0.02). Renal dysfunction rate was significantly (p = 0.05) lower for diabetics in the HCC group (relative risk 0.28). CONCLUSIONS: When HCCs were used postoperative times decreased and they had a protective effect on lung and kidney function in high-risk patients.

Aged↗
PubMed1999

Subpopulations of Helicobacter pylori are responsible for discrepancies in the outcome of nitroimidazole susceptibility testing.

Metronidazole susceptibility testing by E test was compared to that by disk diffusion for 263 Helicobacter pylori isolates and to that by breakpoint agar dilution for 90 H. pylori isolates. In 5% and 6% of the cases, respectively, results were discrepant. For each of 52 clinical isolates an E test was performed on 10 separate colonies. Subpopulations of resistant and susceptible bacteria were found in five cases. From three isolates, each colony was subcultured and tested up to 10 times. All but 1 of 292 tests showed the same result. We conclude that the E test is reliable and that subpopulations are responsible for discordant results.

Anti-Bacterial Agents↗
PubMed1999

Evaluation of bottlenecks in the late stages of protein secretion in Bacillus subtilis.

Despite a high capacity for secretion of homologous proteins, the secretion of heterologous proteins by Bacillus subtilis is frequently inefficient. In the present studies, we have investigated and compared bottlenecks in the secretion of four heterologous proteins: Bacillus lichenifomis alpha-amylase (AmyL), Escherichia coli TEM beta-lactamase (Bla), human pancreatic alpha-amylase (HPA), and a lysozyme-specific single-chain antibody. The same expression and secretion signals were used for all four of these proteins. Notably, all identified bottlenecks relate to late stages in secretion, following translocation of the preproteins across the cytoplasmic membrane. These bottlenecks include processing by signal peptidase, passage through the cell wall, and degradation in the wall and growth medium. Strikingly, all translocated HPA was misfolded, its stability depending on the formation of disulfide bonds. This suggests that the disulfide bond oxidoreductases of B. subtilis cannot form the disulfide bonds in HPA correctly. As the secretion bottlenecks differed for each heterologous protein tested, it is anticipated that the efficient secretion of particular groups of heterologous proteins with the same secretion bottlenecks will require the engineering of specifically optimized host strains.

Amino Acid Sequence↗
PubMed1999

Mailed, home-obtained urine specimens: a reliable screening approach for detecting asymptomatic Chlamydia trachomatis infections.

The use of mailed, home-obtained urine specimens could facilitate screening programs for the detection of asymptomatic Chlamydia trachomatis infections. Since transport time could have an adverse effect on the sensitivity of C. trachomatis detection by PCR, the influence of DNA degradation on amplification was monitored over the course of 1 week. Therefore, urine specimens were aliquoted on the day of collection or arrival. Two groups of urine specimens were investigated. Group I contains first-void C. trachomatis-positive and -negative urine samples. DNA degradation was monitored in group I samples for 7 days at room temperature (RT) and at 4 degrees C by amplifying different lengths of the human beta-globin gene and the C. trachomatis plasmid target. DNA degradation was observed only for the larger human beta-globin fragments at days 5 to 7 at RT. In contrast, at 4 degrees C all targets could be amplified. Urine specimens were also frozen and thawed before aliquoting to mimic freezing during transport. This resulted in a lower sensitivity for the detection of C. trachomatis after thawing and 3 to 4 days at RT. In addition, mailed, home-obtained C. trachomatis-positive urine specimens (group II) were analyzed for 7 days after arrival by two commercially available C. trachomatis detection systems (PCR and ligase chain reaction [LCR]). The C. trachomatis plasmid target in mailed, home-obtained urine specimens could be amplified by both PCR and LCR after 1 week of storage and/or transport at RT. In conclusion, our findings indicate that mailed, home-obtained urine specimens are suitable for the sensitive detection of asymptomatic C. trachomatis infections by amplification methods, even if the transport time is up to 1 week at RT. These findings support the feasibility and validity of screening programs based on mailed, home-obtained urine specimens. Larger studies should be initiated to confirm our results.

Base Sequence↗
PubMed1998

[Reading: a source of information. Study of motivational factors, influencing the reading of professional literature in nursing].

A qualitative research among 13 Dutch nurses working in different areas of nursing investigated which factors might influence nurses' motivation (not) to read specialist literature. Two central subjects were identified: nurses' personal interests and the influence of the environment at work. Analysis of the data shows a great influence of the work environment on the individual nurse's choice to read specialist literature: the more stimulating the environment is towards developing and discussing knowledge, the more nurses make use of specialist literature. An individual reason to consult such literature is formed by the presence of "search questions", based on incidents in a person's actual work situation. Informants report little or no interest in research or studies: they only incidentally read abstracts of research findings, and only concerning subjects directly linked with their own practice situation. Influence of the work environment seems to play an important role on the choice made.

Education, Nursing, Continuing↗
PubMed1997

Gas chromatographic-mass spectrometric analysis of the loop diuretic torasemide in human urine.

A fast and reliable gas chromatographic-mass spectrometric (GC-MS) method for the identification and determination of the loop diuretic torasemide in human urine is described. The usefulness of different derivatization procedures and reagents was studied. Flash methylation using trimethylanilinium hydroxide was the most convenient and appropriate procedure. The optimal urine isolation method comprised alkaline liquid-liquid extraction with ethyl acetate. After evaporation of the organic layer to dryness, the solid residue was reconstituted in the derivatizing reagent and was directly injected into the GC-MS system. Samples were analysed in the multiple ion detection mode using electron impact ionization. No interferences from other urinary compounds were found. Torasemide gave rise to a derivative that was identified by GC with Fourier transform infrared detection. There was a 70 +/- 5% recovery of torasemide. The coefficient of variation was 5% at a concentration of 0.05 microgram/ml. The method was used for the determination of torasemide in urine samples obtained from a healthy volunteer that had received a single, 10 mg dose of torasemide.

Diuretics↗
PubMed1997

Comparative susceptibilities of various animal-pathogenic mycoplasmas to fluoroquinolones.

The in vitro activities of six antimicrobial agents were tested against 162 mycoplasma strains of eight species isolated from poultry and livestock at different geographic sites. Tiamulin was most active (MICs at which 90% of the isolates were inhibited [MIC90s], 0.025 to 0.25 microg/ml); enrofloxacin and danofloxacin had near equivalent activities (MIC90s, 0.05 to 1.0 microg/ml), but were much more active than flumequine (MIC90s, 1 to 50 microg/ml). The MIC90s of tylosin and oxytetracycline were 0.25 to > 100 microg/ml and 0.25 to 100 microg/ml, respectively.

Animals↗
PubMed1997

The Drosophila melanogaster RAD54 homolog, DmRAD54, is involved in the repair of radiation damage and recombination.

The RAD54 gene of Saccharomyces cerevisiae plays a crucial role in recombinational repair of double-strand breaks in DNA. Here the isolation and functional characterization of the RAD54 homolog of the fruit fly Drosophila melanogaster, DmRAD54, are described. The putative Dmrad54 protein displays 46 to 57% identity to its homologs from yeast and mammals. DmRAD54 RNA was detected at all stages of fly development, but an increased level was observed in early embryos and ovarian tissue. To determine the function of DmRAD54, a null mutant was isolated by random mutagenesis. DmRADS4-deficient flies develop normally, but the females are sterile. Early development appears normal, but the eggs do not hatch, indicating an essential role for DmRAD54 in development. The larvae of mutant flies are highly sensitive to X rays and methyl methanesulfonate. Moreover, this mutant is defective in X-ray-induced mitotic recombination as measured by a somatic mutation and recombination test. These phenotypes are consistent with a defect in the repair of double-strand breaks and imply that the RAD54 gene is crucial in repair and recombination in a multicellular organism. The results also indicate that the recombinational repair pathway is functionally conserved in evolution.

Amino Acid Sequence↗
PubMed1997

Latest population projections for the European Union.

This article presents the results of Eurostat's latest population projections for the 15 countries of the European Union. Under the Eurostat baseline scenario, the EU population will continue to grow slowly until around the year 2025 before starting to decline. The number of young people will continue to fall, while the number of older people will increase. To greater or lesser extents, all EU countries will experience declining population growth and an ageing population.

Adolescent↗
PubMed1996

Assessment of the need for care 15 years after onset of a Dutch cohort of patients with schizophrenia, and an international comparison.

Assessment of needs for care is crucial in the evaluation of ongoing changes from institutional care to various forms of day- and outpatient treatment. Do patients really do better in the community and are they adequately cared for? The 15-year follow-up of a Dutch incidence cohort of patients with schizophrenia and other functional non-affective psychoses showed that 47 (out of 63) patients had positive ratings of symptoms and disabilities. They were assessed by means of the Needs for Care Assessment Schedule, which articulates the problems and corresponding interventions resulting in a judgement of met or unmet need for treatment or assessment. There was a mean of 2.1 clinical problems and 2.1 social problems per patient. Few problems were considered to generate unmet needs: 14% of the clinical problems and only 7% of the social problems. Nevertheless, 32% of the patients had one or more unmet needs. These results were compared with data from six research centres in the United Kingdom (Camberwell, Oxford and South Glamorgan), Canada (Montreal), Italy (Verona) and Finland (Tampere). Despite differences in health care settings in the four countries, the ratio of met to unmet needs (about 4-5 to 1) among chronic, mostly schizophrenic patients is more or less the same with the exception of an apparently underserved hostel population in Oxford and the Finnish patient population probably due to high expectations with respect to independent community living.

Adolescent↗
PubMed1996

Bacillus subtilis can modulate its capacity and specificity for protein secretion through temporally controlled expression of the sipS gene for signal peptidase I.

Bacillus subtilis contains three chromosomally encoded type I signal peptidases (SipS, SipT and SipU), which remove signal peptides from secretory precursor proteins. In the present study the biological function of SipS and the regulation of its synthesis were analysed. Unlike the type I signal peptidase of Escherichia coli, SipS was essential neither for protein secretion nor viability of the cell. However, in the absence of SipS the rate of processing of several preproteins was reduced, and four of the seven major secreted proteins of B. subtilis were hardly detectable in the growth medium. Surprisingly, the processing of Bacillus amyloliquefaciens alpha-amylase and the secretion of at least two endogenous B. subtilis proteins was improved in the absence of SipS. These findings indicate that the substrate preference of SipS differs from that of SipT and SipU, and that SipS is an important factor determining the efficiency of protein secretion in B. subtilis. SipS is transcribed in a growth phase- and medium-dependent manner. In minimal medium, the growth phase-dependent transcription of sipS is controlled by the DegS-DegU two-component regulatory system, indicating that the expression of sipS is regulated by the same factors that control the expression of most genes for secreted degradative enzymes. Our observations suggest that B. subtilis can modulate its capacity and specificity for protein secretion through the controlled expression of sipS.

Bacillus subtilis↗
PubMed1995

A novel human c-sis mRNA species is transcribed from a promoter in c-sis intron 1 and contains the code for an alternative PDGF B-like protein.

The human platelet-derived growth factor (PDGF) B chain precursor is usually translated from a 3.5 kb c-sis/PDGF B gene transcript. The first exon of the c-sis/gene contains the code for the signal peptide of the PDGF B chain precursor, preceded by a 1 kb long untranslated sequence with potent translation inhibitory activity. In this paper we show that a novel 2.6 kb c-sis mRNA present in the human choriocarcinoma cell line JEG-3 initiates at an alternative exon 1, which we refer to as exon 1a. The 90 bp long exon 1a is located in the center of the first intron of the gene. It coincides with a very pronounced DNase-I-hypersensitive site and is preceded by a functional promoter. Of the three ATG codons present in exon 1a, the third one perfectly matches the criteria of a consensus start codon. It initiates an open reading frame that is continuous with the code for the PDGF B chain precursor but lacks the code for a signal peptide. We conclude that this novel 2.6 kb c-sis mRNA species lacks the strong translation inhibitory potential of the regular exon 1 and contains the code for a PDGF B-like protein that may be targeted to the cell nucleus.

Alternative Splicing↗
PubMed1995

Identification of the potential active site of the signal peptidase SipS of Bacillus subtilis. Structural and functional similarities with LexA-like proteases.

Signal peptidases remove signal peptides from secretory proteins. By comparing the type I signal peptidase, SipS, of Bacillus subtilis with signal peptidases from prokaryotes, mitochondria, and the endoplasmic reticular membrane, patterns of conserved amino acids were discovered. The conserved residues of SipS were altered by site-directed mutagenesis. Replacement of methionine 44 by alanine yielded an enzyme with increased activity. Two residues (aspartic acid 146 and arginine 84) appeared to be conformational determinants; three other residues (serine 43, lysine 83, and aspartic acid 153) were critical for activity. Comparison of SipS with other proteases requiring serine, lysine, or aspartic acid residues in catalysis revealed sequence similarity between the region of SipS around serine 43 and lysine 83 and the active-site region of LexA-like proteases. Furthermore, self-cleavage sites of LexA-like proteases closely resembled signal peptidase cleavage sites. Together with the finding that serine and lysine residues are critical for activity of the signal peptidase of Escherichia coli (Tschantz, W.R., Sung, M., Delgado-Partin, V.M., and Dalbey, R.E. (1993) J. Biol. Chem. 268, 27349-27354), our data indicate that type I signal peptidases and LexA-like proteases are structurally and functionally related serine proteases. A model envisaging a catalytic serine-lysine dyad in prokaryotic type I signal peptidases is proposed to accommodate our observations.

Amino Acid Sequence↗
PubMed1995

The endogenous Bacillus subtilis (natto) plasmids pTA1015 and pTA1040 contain signal peptidase-encoding genes: identification of a new structural module on cryptic plasmids.

Various strains of Bacillus subtilis (natto) contain small cryptic plasmids that replicate via the rolling-circle mechanism. Like plasmids from other Gram-positive bacteria, these plasmids are composed of several distinct structural modules. A new structural module was identified on the B. subtilis plasmids pTA1015 and pTA1040. It is composed of two genes: one specifies an unidentified protein with a putative signal peptide; and the other (sipP) specifies a functional type 1 signal peptidase (SPase). The homologous, but non-identical, sipP genes of the two plasmids are the first identified plasmid-specific SPase-encoding genes. With respect to structure and activity, the corresponding enzymes (denoted SipP) are highly similar to the chromosomally encoded SPase, SipP, of B. subtillis and several newly identified SPases of other bacilli. Our findings suggest that plasmid-encoded SPases have evolved because, of under certain conditions, SPase can be a limiting factor for protein secretion in B. subtilis.

Amino Acid Sequence↗
PubMed1992

Signal peptidase I of Bacillus subtilis: patterns of conserved amino acids in prokaryotic and eukaryotic type I signal peptidases.

Signal peptidases (SPases) remove signal peptides from secretory proteins. The sipS (signal peptidase of subtilis) gene, which encodes an SPase of Bacillus subtilis, was cloned in Escherichia coli and was also found to be active in E.coli. Its overproduction in B.subtilis resulted in increased rates of processing of a hybrid beta-lactamase precursor. The SipS protein consisted of 184 amino acids (mol. wt 21 kDa). The protein showed sequence similarity with the leader peptidases of E.coli and Salmonella typhimurium, and the mitochondrial inner membrane protease I of Saccharomyces cerevisiae. Patterns of conserved amino acids present in these four proteins were also detected in the Sec11 subunit of the SPase complex of S.cerevisiae and the 18 and 21 kDa subunits of the canine SPase complex. Knowledge of the sequence of SipS was essential for the detection of these similarities between prokaryotic and eukaryotic SPases. The data suggest that these proteins, which have analogous functions, belong to one class of enzymes, the type I SPases.

Amino Acid Sequence↗
PubMed1991

Lack of specific hybridization between the lep genes of Salmonella typhimurium and Bacillus licheniformis.

This paper describes an attempt to clone the Bacillus licheniformis lep gene, encoding signal peptidase, using the Salmonella typhimurium lep gene as a hybridization probe. Although a hybridizing fragment was obtained, DNA sequence analysis indicated that it did not contain the lep gene. Instead, the protein encoded by the cloned fragment showed similarity with a variety of L-asparaginases.

Amino Acid Sequence↗