Search PubMed⌕ Search

Biomedical subjects

E B Hansen

Publications and source records attributed to E B Hansen.

At least 37 records · Page 2Linked to original sources
PubMed1993

Cloning of the lysA gene from Mycobacterium tuberculosis.

The lysA and proC genes of Mycobacterium tuberculosis were cloned by screening of a recombinant lambda gt11 M. tuberculosis DNA library for phages able to complement lysA and proC Escherichia coli mutants. The lysA gene encodes diaminopimelic acid decarboxylase which catalyzes the conversion of diaminopimelic acid (DAP) to lysine. The lysA gene from M. tuberculosis encodes a 44-kDa protein, as determined by maxicell experiments. The nucleotide sequence of the structural gene was established. The deduced amino acid sequence was found to exhibit significant homology (from 55% to 73% similarity, and from 27% to 53% identity) to DAP decarboxylase sequences from other bacterial species.

Amino Acid Sequence↗
PubMed1993

Characterization of three rifamycins via electrospray mass spectrometry and HPLC-thermospray mass spectrometry.

Rifamycins are a class of antibiotic compounds of which rifampicin is the most commonly prescribed. Conventional electron-impact mass spectrometry of rifampicin has not been found to provide useful data. Thermospray and electrospray mass spectrometry are studied as potential tools for the analysis of rifampicin, rifamycin SV, and rifamycin B. Using thermospray and electrospray ionization, all three compounds provide significant ion intensity for either the [MH]+ or [MNa]+ ions. In addition, combined high-performance liquid chromatography-thermospray mass spectrometry provides useful analytical data for a mixture of the three rifamycins.

Chromatography, High Pressure Liquid↗
PubMed1993

Insertion of Transposon Tn917 Derivatives into the Lactococcus lactis subsp. lactis Chromosome.

Two transposition vectors, pTV32 and pLTV1, containing transposon Tn917 derivatives TV32 and LTV1, respectively, were introduced into Lactococcus lactis subsp. lactis MG1614. It was found that pTV32 and pLTV1 replicate and that TV32 and LTV1 transpose in this strain. A protocol for production of a collection of Tn917 insertions in L. lactis subsp. lactis was developed. The physical locations of TV32 on the chromosomal SmaI fragments of 62 independent transpositions were established by pulsed-field gel electrophoresis. These transpositions could be divided into at least 38 different groups that exhibited no Tn917-dominating hot spots on the L. lactis subsp. lactis chromosome. A total of 10 of the 62 transpositions resulted in strains that express beta-galactosidase. This indicates that there was fusion of the promoterless lacZ of the Tn917 derivatives to a chromosomal promoter. Thus, the Tn917-derived transposons should be powerful genetic tools for studying L. lactis subsp. lactis.

Journal Article↗
PubMed1992

Cementless total knee arthroplasty in unselected cases of osteoarthritis and rheumatoid arthritis. A 3-year follow-up study of 103 cases.

The authors reviewed 103 cementless AGC 2000 total knee arthroplasties in unselected cases of osteoarthritis and rheumatoid arthritis with a follow-up period of 3 years. Excellent or good clinical results were obtained in 96%. The median maximal flexion was 110 degrees. Two aseptic loosenings of the tibial components had been revised prior to this evaluation. Two other patients showed radiographic signs of tibial loosening but were asymptomatic. Undersizing of the tibial component predisposes to subsidence and loosening. One had septic tibial loosening planned for revision. Four had nonprogressive lucent lines beneath the tibial tray but were asymptomatic. No patellar or femoral component loosening was revealed. Undercorrection of preoperative varus deformity did not dispose to tibial loosening or radiolucency, nor influence the clinical result. In terms of survival of the prosthesis the cumulative success rate was 97.1%. When pain and radiographic loosening was also considered, the success rate was 90.7%. These results encourage uncemented use of this prosthesis, but emphasize the importance of good primary prosthetic fit at the tibial side.

Adult↗
PubMed1991

Diffusion and binding of monoclonal antibody TNT-1 in multicellular tumor spheroids.

Tumor spheroids of HT-29 human colon adenocarcinoma and A375 melanoma were established to investigate the uptake and clearance kinetics of TNT-1, a monoclonal antibody that targets necrotic cells of tumors. Our data reveal that there was rapid uptake of TNT-1 and its F(ab')2 fragment in both spheroid models, whereas an antibody of irrelevant specificity, Lym-1, and its F(ab')2 fragment bound poorly to the spheroids. Unlike previously reported monoclonal antibodies to tumor cell-surface antigens, TNT-1 showed 1) a linear uptake that increased over time without saturation in tumor spheroids and 2) an unexpected uptake by a subpopulation of cells in the viable outer rim of the spheroids. These preclinical studies provide important information concerning the therapeutic potential of TNT monoclonal antibodies for the treatment of cancer and micrometastases.

Adenocarcinoma↗
PubMed1990

Direct analysis of microbial extracts containing metabolites of ethylenediamine-type antihistamines via high-performance liquid chromatography-thermospray mass spectrometry.

The utility of high-performance liquid chromatography-thermospray mass spectrometry (HPLC-TSMS) for the characterization of the ethylenediamine-type antihistamines, pyrilamine, methapyrilene, tripelennamine, and thenyldiamine, and their methylene chloride-extractable microbial metabolites from a biological matrix is demonstrated. Typically, the [M + H]+ ion was detected as the base peak in the TS mass spectra of these compounds. The ethylenediamine-type antihistamine metabolites were detected in an extract of a fungal culture grown in the presence of 5 mg of the antihistamine. A detection limit of 200 ng was observed for the HPLC-TSMS analysis of pyrilamine.

Chromatography, High Pressure Liquid↗
PubMed1990

Application of thermospray liquid chromatography-mass spectrometry for the analysis of chloramphenicol and three related compounds.

The thermospray (TS) liquid chromatographic-mass spectrometric analysis of the antibiotic chloramphenicol and three related compounds is presented. The three additional compounds are dehydrochloramphenicol, aminodehydrochloramphenicol, and nitrophenylaminopropanediol. Baseline separation of the four compounds is achieved. The TS mass spectrum of each of the four compounds includes a prominent [MH]+ ion plus some fragment ion peaks.

Chloramphenicol↗
PubMed1989

Structure and regulation of the lytic replicon of phage P1.

Three replicons, R, L and P1dR, have been previously identified in bacteriophage P1, but only the R (or plasmid) replicon has been functionally and structurally characterized. Evidence is provided here that the L-replicon is the principal replicon used for DNA replication during the lytic cycle. The L-replicon (exclusive of its promoter) is shown to be contained within a 1093-base-pair DNA segment that includes a 281-codon open reading frame, designated repL. L-replicon function requires transcription in the direction that should generate translatable repL message. This transcription is normally under the control of the phage c1 repressor, but a deletion that places the functional L-replicon under alternative control can be constructed. The DNA sequence of the replicon and surrounding regions was established. The sequenced region contains the c4 and ant genes and a hitherto unidentified gene, kilA, which is immediately upstream of repL and is controlled by the c1-regulated promoter. The kilA gene was shown to be non-essential for both replication and lytic development whereas the repL gene probably encodes an essential replication protein.

Amino Acid Sequence↗
PubMed1989

Structure and mapping of antigenic domains of protein antigen b, a 38,000-molecular-weight protein of Mycobacterium tuberculosis.

Only a limited number of proteins from Mycobacterium tuberculosis have so far been shown to possess species-specific epitopes as defined by monoclonal antibodies. One such protein is protein antigen b (Pab) of molecular weight 38,000, which binds the monoclonal antibodies HYT 28, HAT 2, HBT 12, HGT 3, TB 71, and TB 72. The gene encoding this protein was isolated from a lambda gt11 M. tuberculosis DNA library. The nucleotide sequence of the recombinant mycobacterial insert was determined, and an open reading frame of 374 amino acids was identified. The amino acid sequence exhibited 30% homology to a phosphate-binding protein, PstS, from Escherichia coli. The pab gene was subcloned into pBR322 in conjunction with the lacZ gene, and deletions were obtained from the 3' end. The anti-Pab monoclonal antibodies were used to probe crude protein lysates of E. coli transformed with the deletion plasmids. The monoclonal antibodies showed two reactivity patterns; one group of antibodies were dependent on the presence of the ultimate 91 amino acids of the protein, whereas another group of antibodies recognized an antigenic domain located on the middle portion of the molecule. None of the antibodies bound to the N-terminal 117-amino-acid peptide.

Amino Acid Sequence↗
PubMed1989

Participation of the lytic replicon in bacteriophage P1 plasmid maintenance.

P1 bacteriophage carries at least two replicons: a plasmid replicon and a viral lytic replicon. Since the isolated plasmid replicon can maintain itself stably at the low copy number characteristic of intact P1 prophage, it has been assumed that this replicon is responsible for driving prophage replication. We provide evidence that when replication from the plasmid replicon is prevented, prophage replication continues, albeit at a reduced rate. The residual plasmid replication is due to incomplete repression of the lytic replicon by the c1 immunity repressor. Incomplete repression was particularly evident in lysogens of the thermoinducible P1 c1.100 prophage, whose replication at 32 degrees C remained almost unaffected when use of the plasmid replicon was prevented. Moreover, the average plasmid copy number of P1 in a P1 c1.100 lysogen was elevated with respect to the copy number of P1 c1+. The capacity of the lytic replicon to act as an auxiliary in plasmid maintenance may contribute to the extraordinary stability of P1 plasmid prophage.

Alleles↗
PubMed1988

Microbial transformation of the antihistaminic drug triprolidine hydrochloride.

The production of a known mammalian metabolite of the antihistamine triprolidine through fungal metabolic transformation has been demonstrated. The filamentous fungus Cunninghamella elegans ATCC 9245 was grown in Sabouraud dextrose broth containing triprolidine hydrochloride monohydrate. One major metabolite was extracted with methylene chloride, isolated by high-performance liquid chromatography, and identified by its proton-nuclear magnetic resonance and desorption chemical ionization mass spectral properties as hydroxymethyl triprolidine (2-[1-(4-hydroxymethylphenyl)-3-(1-pyrrolidinyl-1-propenyl)] pyridine). After 240 h of incubation, the hydroxymethyl derivative represented approximately 55.0% of the initial dose. Fungal oxidation of hydroxymethyl triprolidine to the corresponding carboxylic acid triprolidine derivative (also a known mammalian triprolidine metabolite) was not observed. No mutagenic activity was observed for triprolidine and hydroxymethyl triprolidine by reversion of Salmonella typhimurium strains TA97, TA98, TA100, and TA104 at concentrations up to 1000 and 200 micrograms/plate, respectively. These results suggest that the fungal metabolism of triprolidine to the hydroxymethyl derivative occurs predominantly through pathways which do not result in mutagenic activation. Incubation of C. elegans with triprolidine under an 18O2 atmosphere and subsequent electron impact mass spectral analysis of the hydroxymethyl triprolidine formed indicate that molecular oxygen was incorporated into the methyl group and suggest a mono-oxygenase catalyzed reaction. This study parallels previous studies on the mammalian metabolism of triprolidine and clearly indicates that the microbial transformation of triprolidine is a useful alternative for the synthesis of potential mammalian metabolites.

Animals↗
PubMed1988

Fungal transformations of antihistamines: metabolism of methapyrilene, thenyldiamine and tripelennamine to N-oxide and N-demethylated derivatives.

1. Strains of the fungus Cunninghamella elegans ATCC 9245 and 36112 were tested for their ability to transform the antihistamines methapyrilene (I), thenyldiamine (II) and tripelennamine (III). 2. Antihistamine metabolites were isolated by h.p.l.c., and identified by their 1H-n.m.r. and mass spectral properties. 3. All three drugs were transformed by both C. elegans strains to N-oxidized and N-demethylated derivatives. Metabolism during 96 h of incubation amounted to 85% for (I), 64% for (II), and 83% for (III). Metabolites soluble in organic solvents amounted to 62% to 86% of the total metabolism; approximately 88% to 95% of the organic-soluble metabolites were N-oxide derivatives of each antihistamine.

Aminopyridines↗
PubMed1986

Use of bullfrogs (Rana catesbeiana) as biological markers for 2,3,7,8-tetrachlorodibenzo-p-dioxin contamination in the environment.

Adult bullfrogs were collected along the Rockey Branch Creek in Arkansas. This area is known to be contaminated with 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD). The levels of 2,3,7,8-TCDD found in livers from these bullfrogs ranged from 0.64 to 48 ppb. These results suggest the utility of bullfrogs as a biological marker for 2,3,7,8-TCDD in the environment.

Animals↗
PubMed1986

Host participation in plasmid maintenance: dependence upon dnaA of replicons derived from P1 and F.

Nonparticipation of the bacterial dnaA gene in plasmid replication has been assumed to be the general rule. In conditional dnaA mutants of Escherichia coli, only plasmid pSC101 has been shown to have a dnaA requirement. Experiments with dnaA null mutants of E. coli, presented here, show that dnaA plays a critical and direct role in the replication of miniplasmids derived from P1 and F as it does in the initiation of bacterial replication. Evidence is also presented for the existence of a dnaA-independent secondary replicon of P1 that is able to drive bacterial chromosome replication but is inadequate to support the maintenance of P1 as a plasmid in E. coli.

DNA Replication↗