Biomedical subjects

L Adam

Publications and source records attributed to L Adam.

6 recordsLinked to original sources

PubMed1992

Transient expression in Physarum of a chloramphenicol acetyltransferase gene under the control of actin gene promoters.

We cloned and sequenced two actin promoters from Physarum, and constructed plasmids carrying these promoters upstream of a bacterial chloramphenicol acetyltransferase (cat) gene. We then tested the plasmids for their ability to express cat in Physarum amoebae. We present reliable methods for introducing plasmid DNA into Physarum amoebae by electroporation, and show that expression of the cat gene in amoebae occurs in the presence, but not the absence, of one or the other Physarum actin promoter.

Actins↗

PubMed1992

Prognostic implications of p53 protein, epidermal growth factor receptor, and Ki-67 labelling in brain tumours.

The expression of p53 protein, epidermal growth factor receptor (EGFR), and Ki-67 nuclear antigen was examined by immunohistochemistry in biopsies of 16 types of human brain tumours, including 43 astrocytomas. P53 protein, almost certainly its mutant form, was expressed in seven of the 16, and EGFR in 11 of the 16 types of tumours. In astrocytomas both the proportion of tumours which expressed p53 or EGFR increased with grade of malignancy as did the mean Ki-67 labelling index (LI): p53-0% in grade 1, 17% in grade 2, 38% in grade 3, 65% in grade 4; EGFR-0% in grade 1, 33% in grade 2, 85% in grade 3, 95% in grade 4; mean Ki-67 L1-1.1% in grades 1 and 2, 8.3% in grade 3, and 13.4% in grade 4. Astrocytomas which expressed p53 or EGFR had a significantly higher Ki-67 LI at P less than 0.05 (11.8% and 10.7%, resp.) than those that did not (6.2% or 4.1%, resp.). Patients with astrocytomas expressing p53 or EGFR had a significantly reduced survival (P = 0.035 and P = 0.007, resp.): only 11% of the p53 + ve and 13% of the EGFR + ve patients were alive at 100 weeks following diagnosis compared to 36% of p53-ve or 60% of EGFR-ve patients. Patients with Ki-67 LI greater than 5% had a reduced survival (P less than 0.0001)--none survived beyond 86 weeks following diagnosis, whilst 63% of patients with less than 5% positive cells were still alive at 100 weeks. The univariate analysis showed that in astrocytomas expression of p53 mutants, EGFR protein, and Ki-67 greater than 5% are associated with malignant progression and poor prognosis. The multivariate analysis revealed that only tumour grade and Ki-67LI were independent prognostic factors for survival.

Adolescent↗

PubMed1991

An unusual actin-encoding gene in Physarum polycephalum.

Actin is one of the most conserved proteins in eukaryotic organisms. In the present work, we cloned and determined the nucleotide sequence of an unusual actin-encoding gene, ardD, from the slime mold, Physarum polycephalum. The ardD gene encodes an ArdD protein containing 367 amino acids (aa) instead of the 375-376 aa found in a typical actin. The nine missing aa are accounted for by deletions of three aa in the first exon, five in the fifth exon and one in the sixth exon. These deletions in the coding sequence were observed in a polymerase chain reaction (PCR)-generated cDNA fragment, which excludes the possibility of a cloning artifact. In addition, ArdD contains numerous aa substitutions distributed throughout the protein. The ArdD aa sequence was compared with published actin sequences. The most identity is seen with the P. polycephalum ArdA, ArdB and ArdC (84%) and Acanthamoeba (82%) actins, while the least identity is found with Tetrahymena actin (67%). The expression of the ardD gene is developmentally regulated. The highest levels of ardD mRNA were found in spherules, less was seen in plasmodia and no detectable transcripts were observed in amoebae. The PCR amplification of an ardD cDNA from spherules confirmed the presence of mRNA in this developmental stage. The aa deletions and substitutions in the predicted ArdD aa sequence make it one of the most distinctive actins known.

Actins↗

PubMed1991

Characterization of an Escherichia coli gene encoding betaine aldehyde dehydrogenase (BADH): structural similarity to mammalian ALDHs and a plant BADH.

An open reading frame of 1476 nucleotides, cloned from a region of the Escherichia coli genome encoding betaine biosynthesis functions, was shown to encode a betaine aldehyde dehydrogenase (BADH; EC 1.2.1.8). Either of two adjacent codons (5'-GTGATG) could function as a start codon, producing a presumptive polypeptide of 491 or 490 amino acids. The deduced primary structure of the E. coli BADH showed 39-43% positional identity, over its entire length, to aldehyde dehydrogenases (ALDH: EC 1.2.1.3) of mammalian origin. This similarity increased to 75-77% when conservative aa substitutions were also taken into consideration. Spinach BADH was also similar to the bacterial BADH, showing 38% identity and 80% overall similarity. Other homologs included a fungal and a putative bacterial ALDH. Although E. coli BADH was specific for the substrate, betaine aldehyde, it showed the highest levels of similarity to the prototype human ALDH-2. Only one gap in each sequence had to be introduced for optimal alignment. The conservation between E. coli BADH and the ALDHs was also evident in the predicted secondary structures and hydrophilicity profiles of the polypeptides, suggesting a similarity in the overall folding patterns of ALDH and BADH. These observations suggest a common ancestry for BADH and ALDH, preceding prokaryote-eukaryote divergence.

Aldehyde Dehydrogenase↗

PubMed1977

Computerized brain impedograph.

Design of an on-line system utilizing a minicomputer and a specific dedicated hardware for 2T brain tissue impedance is provided. The prototype system, which can operate from 2 Hz to 10 kHz, covers most of the frequency range of interest in the encephalographic research. Driving the brain tissue with constant current and sampling the response current and voltage, the coefficients for a Fourier series expansion can easily be obtained. Real (resistance) and imaginary (capacitance) impedance components at each chosen frequency are printed on a Teletype printer.

Brain↗

PubMed1976

'Self-correcting' spherical bioelectrode.

Most of the widely used biopotential macroscopic and microscopic bioelectrodes do not enable proper measurements while in contact with 'problematic' tissues, such as myocardial and other muscular tissues, cortical and intracavital tissues. A quantitative spherical electrode was designed as an example in the family of bioelectrodes enabling application in moving or vibrating media. The electrode developed is insensitive to its contact area. Decreasing the contact area to 40% causes 25% increase in measured resistance only. The electrode shows excellent performance in alternating current conditions combined with well-defined direct current characteristics.

Electrochemistry↗