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K Lucas

Publications and source records attributed to K Lucas.

18 recordsLinked to original sources
PubMed1991

An improved microcomputer program for finding gene- or gene family-specific oligonucleotides suitable as primers for polymerase chain reactions or as probes.

We present here an easy-to-use computer program which finds oligonucleotides suitable as primers in polymerase chain reactions (PCR) or as probes for hybridization. In contrast to other programs used for this purpose, the additional advantage of this one is the possibility of directly detecting gene- as well as gene family-specific oligonucleotides. For this purpose, up to 200 different DNA sequences, of maximally 65,000 nucleotides each, can be scanned in a single search to ensure either single or multiple gene binding of the PCR primers or probes. Specific oligonucleotides for genes carrying internal repetitions and for single genes belonging to a set of highly conserved genes can also be detected. Many parameters such as exclusion of simple sequences, which are known to be highly repeated throughout various genomes or regions of stable secondary structures in both primer-primer and primer-template, can be taken into consideration and avoided. Furthermore, the G + C content and the length of the oligonucleotides can be changed in a broad range by the user.

Animals↗
PubMed1990

cDNA and gene analyses imply a novel structure for a rat carcinoembryonic antigen-related protein.

The gene encoding the human tumor marker carcinoembryonic antigen (CEA) belongs to a gene family which can be subdivided into the CEA and the pregnancy-specific glycoprotein subgroups. The corresponding proteins are members of the immunoglobulin superfamily, characterized through the presence of one IgV-like domain and a varying number of IgC-like domains. Since the function of the CEA family is not well understood, we decided to establish an animal model in the rat to study its tissue-specific and developmental stage-dependent expression. To this end, we have screened an 18-day rat placenta cDNA library with a recently isolated fragment of a rat CEA-related gene. Two overlapping clones containing the complete coding region for a putative 709 amino acid protein (rnCGM1; Mr = 78,310) have been characterized. In contrast to all members of the human CEA family, this rat CEA-related protein consists of five IgV-like domains and only one IgC-like domain. This novel structure, which has been confirmed at the genomic level might have important functional implications. Due to the rapid evolutionary divergence of the rat and human CEA gene families it is not possible to assign rnCGM1 to its human counterpart. However, the predominant expression of the rnCGM1 gene in the placenta suggests that it could be analogous to one of the human pregnancy-specific glycoprotein genes.

Amino Acid Sequence↗
PubMed1989

Identification of a carcinoembryonic antigen gene family in the rat. Analysis of the N-terminal domains reveals immunoglobulin-like, hypervariable regions.

The existence of a carcinoembryonic antigen (CEA)-like gene family in rat has been demonstrated through isolation and sequencing of the N-terminal domain exons of presumably five discrete genes (rnCGM1-5). This finding will allow for the first time the study of functional and clinical aspects of the tumor marker CEA and related antigens in an animal model. Sequence comparison with the corresponding regions of members of the human CEA gene family revealed a relatively low similarity at the amino acid level, which indicates rapid divergence of the CEA gene family during evolution and explains the lack of cross-reactivity of rat CEA-like antigens with antibodies directed against human CEA. The N-terminal domains of the rat CEA-like proteins show structural similarity to immunoglobulin variable domains, including the presence of hypervariable regions, which points to a possible receptor function of the CEA family members. Although so far only one of the five rat CEA-like genes could be shown to be transcriptionally active, multiple mRNA species derived from other members of the rat CEA-like gene family have been found to be differentially expressed in rat placenta and liver.

Amino Acid Sequence↗
PubMed1989

Kinetic implications of structural modification in protein turnover.

It is thought that an important function of protein turnover is to purge the cell of damaged, displaced or unwanted polypeptide molecules. A model combining kinetic equations for synthesis, degradation and alteration is employed to evaluate this proposed role for protein turnover. It is demonstrated that the degradative system need not be aimed exclusively at altered protein molecules for turnover to be capable of controlling the size both of the total population and of the altered subpopulation. These conclusions are relevant to the part played by turnover in metabolic homeostasis, adaptation and catastrophe, and for the notion of control of protein turnover through specific "tagging" of molecules destined for breakdown.

Data Interpretation, Statistical↗
PubMed1987

Russell L. Drake: an historical retrospective.

Russell Drake's career reflects the integral relationship between medical illustration and surgery. During a 44-year association with the Mayo Clinic, he observed pioneering efforts of the most accomplished surgeons of the day. It was his task to portray these breakthroughs visually for journals, books, and slides, thereby disseminating information on new techniques to the entire medical and surgical community. Drake executed the illustrations skillfully and aesthetically, inspiring generations of illustrators. His is a vital chapter in the history of medical communication.

History, 20th Century↗
PubMed1984

[Biotransformation of monolinuron (N-(4-chlorophenyl)-N'-methyl-N'methoxyurea) in isolated perfused chicken liver].

The biotransformation of radioactively labelled monolinuron (N-(4-chloro[U-14C]phenyl)-N'-methyl-N'-methoxyurea) was studied in the isolated perfused liver of the chicken. After a 4-hr perfusion, 83.1% of the added radioactivity was recovered, 56.6% in the perfusion medium and 26.5% in the liver and bile. The fraction of radioactivity extractable from the perfusion medium into ethyl acetate amounted to 47.8% of the added dose. In addition to monolinuron, five breakdown products were identified in this extract, namely N-(4-chlorophenyl)-N'-hydroxymethyl-N'-methoxyurea, N-(4-chlorophenyl)-N'-methoxyurea, N-(4-chlorophenyl)-N'-methylurea, 4-chlorophenylurea and 4-chloroacetanilide. Of particular interest was the absence of arylhydroxylated monolinuron derivatives, since in monolinuron-metabolism studies in the laying hen 2-hydroxy-4-chlorophenylurea and 3-hydroxy-4-chlorophenylurea were both detected. This differing metabolism corresponds to earlier findings in the rat, in which arylhydroxylated breakdown products were detected only in in vivo studies and not in rat-liver perfusion. Possible reasons for the differing metabolism of monolinuron in vivo and in vitro are discussed.

Animals↗
PubMed1983

Uricase from soybean root nodules: purification, properties, and comparison with the enzyme from cowpea.

A 45-fold purification of uricase (urate:O2 oxidoreductase, EC 1.7.3.3) from soybean root nodules by ammonium sulfate fractionation, gel filtration, and affinity chromatography is described. Electrophoresis on nondenaturing gels using an activity stain or on sodium dodecyl sulfate (SDS) gels demonstrated that the enzyme obtained was nearly homogeneous. The subunit molecular weight of uricase estimated from SDS gels was 32,000 +/- 3000. Gel-filtration studies indicated that the native enzyme is a monomer at pH 7.5 which associates to form a dimer at pH 8.8. Enzyme activity was stabilized by the addition of dithiothreitol. The pH dependence of the enzyme showed an optimum of 9.5. Initial rate kinetics showed Km values of 10 and 31 microM for uric acid and oxygen, respectively, with an intersecting pattern of substrate dependence. Uricase activity was inhibited strongly by xanthine, which was competitive with respect to uric acid (Ki = 10 microM). No significant inhibition was observed in the presence of a variety of amino acids, ammonium, adenine, or allopurinol, in contrast with results reported for the cowpea enzyme. Gel-filtration chromatography and SDS-gel electrophoresis of uricase purified by the same method from cowpea nodules indicated that the native enzyme exists as a monomer of Mr 50,000 at pH 7.5.

Hydrogen-Ion Concentration↗
PubMed1980

Hepatic necrosis in rats following halothane administration: protective effect of diethyldithiocarbamate.

Foci of necrosis have been observed in the liver of 50% of enzyme-induced rats treated with halothane. The frequency of liver necrosis was significantly reduced by treatment with the free radical scavenger diethyldithiocarbamate. The severity of the lesion was not increased by repeated exposures to the anesthetic, and, although the frequency of liver necroses may be greater, the differences were not statistically significant.

Anesthesia, Inhalation↗
PubMedDate not supplied

Relapse in acute lymphoblastic leukemia as a function of white blood cell and absolute neutrophil counts during maintenance chemotherapy.

Several reports document an inverse correlation between bioavailability of maintenance chemotherapeutic agents and the likelihood of relapse in childhood. White blood cell counts (WBC) and absolute neutrophil counts (ANC) are easily ascertainable parameters which might be expected to reflect plasma levels of chemotherapy. To determine whether WBC and ANC predict outcome of children with acute lymphoblastic leukemia (ALL), we did a multivariate analysis of means of these values during maintenance therapy in patients with ALL treated on a single protocol. Of the 52 patients, 15 (29%) relapsed. For those still disease-free, minimum time of follow-up is 7-8/12 years. During the first year of maintenance therapy, mean WBC (x 10(3)/mm3) in the relapsed and nonrelapsed groups were 4.5 +/- 0.9 and 3.9 +/- 0.7, respectively (p = 0.03); mean ANC (x 10(3)/mm3) were 3.0 +/- 0.9 and 2.5 +/- 0.6 (p = 0.05). However, the range of values was large with considerable overlap between the two groups. There was no obvious difference in distribution of values when confounding prognostic features were adjusted for in the analysis. No significant differences were seen between WBC or ANC during the second year of therapy. Larger numbers of patients will be needed to ascertain whether specific guidelines for dosage modifications can be made on the basis of serial WBC. Future pharmacokinetic studies should look at possible correlations with mean WBC and ANC.

Antineoplastic Combined Chemotherapy Protocols↗