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T Gilbert

Publications and source records attributed to T Gilbert.

69 records · Page 4Linked to original sources
PubMed1990

Endocytosis via coated pits mediated by glycoprotein receptor in which the cytoplasmic tail is replaced by unrelated sequences.

Rat 6 fibroblast cell lines expressing wild-type chicken liver glycoprotein receptor (CHL) or chimeric receptors with alternate cytoplasmic tails were produced to study the role of the cytoplasmic tail in mediating receptor localization in coated pits and endocytosis of ligand. Cells expressing CHL or cells expressing a hybrid receptor that contains the cytoplasmic tail of the asialoglycoprotein receptor display high-efficiency endocytosis of N-acetylglucosamine-conjugated bovine serum albumin in experiments designed to measure an initial internalization step, as well as in studies of continuous uptake and degradation. Substitution of the cytoplasmic tail by the equivalent domain of rat Na,K-ATPase beta subunit or by a stretch of Xenopus laevis globin beta chain does not abolish endocytosis but decreases the endocytosis rate constant from 15%-16%/min to 2.4% and 6.5%/min, respectively. Electron microscopy was used to visualize the glycoprotein binding sites at the surface of Rat 6 cells transfected with the various receptors. The percentage of receptors found in coated areas ranged from 32% for CHL to 9% for the Na,K-ATPase hybrid, indicating that clustering in coated pits correlates with efficiency of endocytosis. We concluded that replacement of the CHL cytoplasmic tail with unrelated sequences does not prevent, but decreases to varying extents, coated-pit localization and endocytosis efficiency. The construct with NH2-terminal globin tail lacks a signal for high-efficiency localization in coated pits but nevertheless is directed to the pits by an alternative mechanism.

Amino Acid Sequence↗
PubMed1989

Nucleotide sequence of a novel kanamycin resistance gene, aphA-7, from Campylobacter jejuni and comparison to other kanamycin phosphotransferase genes.

A novel kanamycin phosphotransferase gene, aphA-7, was cloned from a 14-kb plasmid obtained from a strain of Campylobacter jejuni and the nucleotide sequence of the gene was determined. The presumed open reading frame of the aphA-7 structural gene was 753 bp in length and encoded a protein of 251 amino acids with a calculated weight of 29,691 Da. A 29-kDa protein was demonstrated in Escherichia coli maxicells containing the cloned aphA-7 gene. A ribosomal binding site corresponding to 5 of 8 bases of the 3' end of the E. coli 16S rRNA was 8 bp upstream of the start codon. Sequences corresponding to the -35 and -10 regions of the consensus promoter sequences of E. coli were upstream of the presumed initiation codon of the gene. The DNA sequence was most closely related to the aphA-3 gene from Streptococcus faecalis, showing 55.4% sequence similarity. There was 45.6% identity at the amino acid level between the aphA-3 and the aphA-7 proteins. Of the three conserved regions noted previously in phosphotransferase genes, the aphA-7 amino acid sequence was identical to the six conserved amino acids in motif 3, but differed in one of the five conserved amino acids in motif 1 (if gaps are permitted) and 3 of the 10 conserved residues in motif 2. The 32.8% G + C ratio in the open reading frame of the aphA-7 kanamycin resistance gene, which is similar to that of the C. jejuni chromosome, suggests that the aphA-7 may be indigenous to Campylobacters.

Amino Acid Sequence↗
PubMed1989

Development of a DNA probe from the deoxyribonucleotide sequence of a 3-N-aminoglycoside acetyltransferase [AAC(3)-I] resistance gene.

The aacC1 gene encoding the 3-N-aminoglycoside acetyltransferase [AAC(3)-I] was cloned from enteric plasmid pJR88, and its deoxyribonucleotide sequence was determined. Significant nucleotide homology was noted in the region extending from the proposed -35 sequences through the first 59 base pairs of the aacC1 gene open reading frame (ORF) and the upstream flanking regions and ORFs of several other antibiotic resistance genes. Sequences were noted to be homologous with the 6'-N-aminoglycoside acetyltransferase [AAC(6')-I], 2''-O-aminoglycoside adenylyltransferase [AAD(2'')], and 3''-O-aminoglycoside adenylyltransferase [AAD(3'')] resistance genes; the OXA-1, OXA-2, and PSE-2 beta-lactamase genes; and several dihydrofolate reductase genes. Small regions of homology were noted in the 3'-flanking regions of these resistance genes as well. A DNA probe for the aacC1 gene was selected from the nucleotide sequence information and was tested against a series of genetically and enzymatically defined strains. The probe, which proved specific for the aacC1 gene, was then tested against a series of 58 gentamicin-susceptible and 219 gentamicin-resistant gram-negative bacilli isolated from patients at the Seattle Veterans Administration Medical Center. Only six clinical isolates were noted to carry the aacC1 gene. Each was resistant to gentamicin but susceptible to kanamycin, tobramycin, and amikacin. The presence of homologous regions of DNA at both the 3' and 5' ends of the aacC1 gene reinforces the importance of choosing probes from within the ORFs of genes and of avoiding flanking sequences. When the homology with other sequences extends into the ORF, as it does with the aacC1 gene, development of a specific probe may require determination of the nucleotide sequence.

Acetyltransferases↗
PubMed1989

Characterization of a human-mouse chimeric antibody reactive with a human melanoma associated antigen.

The data presented demonstrate that a human-murine chimeric antibody has been generated that retains the immunoreactivity and has similar pharmacokinetic properties of its parent murine monoclonal antibody NRML-05. A competitive ELISA assay demonstrated that antigen reactivity of both parent and chimera were nearly identical. In a direct cell binding assay, NRML-05 and chimeric antibodies were immunoreactive, 81% and 83%, respectively. Scatchard Analysis of the antibodies indicate very similar affinities for NRML-05 (4.4 x 10(9) M-1) and chimera (2.7 x 10(9) M-1). Localization of the two antibodies to tumor xenografts in nude mice were very similar in biodistribution studies. The chimeric antibody is not as well recognized by antiglobulin from patients who have responded to non-idiotypic murine antibody determinants. Although this data does not predict how immunogenic a chimera would be in the clinical setting, it does suggest that patients without significant anti-idiotypic antiglobulin response could benefit from second and subsequent administrations with chimeric antibody. Even though anti-idiotypic responses may occur with the chimera, these may be reduced as a result of the presentation of these epitopes on the less immunogenic human constant domains.

Animals↗
PubMed1988

Light- and electron-microscopic analysis of the kidney in newborn rats exposed to gentamicin in utero.

Kidneys of newborn rats, whose mothers were given 75 mg/kg of gentamicin daily from the tenth day of gestation to its term, were examined by light and electron microscopy, as were kidneys of control rats whose mothers were given saline during the same period. In the gentamicin-treated group, the numbers of differentiated glomeruli and of S-shaped bodies counted in a median cross-section of the kidney were reduced, compared with those in the control group, but the glomerular volume was the same. In newborn rats issued from gentamicin-treated mothers, the proximal tubular lumen of the mature nephron lying in the deepest cortex was dilated, and their proximal tubular cells exhibited extensive damage, resembling that described in tubular cells of adult rats exposed to gentamicin. The subcapsular nephrogenic zone exhibited focal alterations of cytoplasmic organelle membranes, as well as nuclear lesions of several types, in cells of the nephron anlagen of the undifferentiated metanephric blastema, which were otherwise of normal appearance.

Animals↗
PubMed1987

Effects of prenatal and postnatal exposure to gentamicin on renal differentiation in the rat.

Pregnant rats were injected daily, from the 10th day of gestation to term, with 75 mg/kg of gentamicin. They gave birth about 15 h later than control pregnant rats injected with saline to pups with various degrees of growth retardation. In pups born of gentamicin-treated mothers, the number of nephrons present at birth, as well as the final number of nephrons, were reduced by at least 20%. Observation of the kidneys by light microscopy showed focal tubular lesions on the mature nephrons. The intrarenal concentration of gentamicin was higher in the severely growth retarded pups than in the others. In another series of experiments, rats were given 75 mg/kg of gentamicin daily from days 1 to 13 after birth. Although under these conditions the concentration of gentamicin reached in the postnatal kidney was higher than that reached after exposure in utero, no reduction of the final number of nephrons was observed. It is concluded that administration of gentamicin to pregnant rats caused focal tubular lesions in the developing kidney and a reduced rate of early nephrogenesis. The latter was probably due to growth retardation, though a more direct effect of gentamicin on early nephrogenesis may also have been involved.

Animals↗
PubMed1987

Effect of fetal exposure to gentamicin on kidneys of young guinea pigs.

Clearance experiments were performed with young pups born of guinea pigs given a daily injection of 4 mg of gentamicin per kg (body weight) from days 48 to 54 of gestation (term, 68 days). For 3-day-old animals, the glomerular filtration rate was similar to that measured in control guinea pigs of the same age whose mothers were given saline during the same period of gestation. The same applied to fractional excretion of water, urea, total solutes, Na, K, Ca, and Mg but not to fractional phosphate excretion, which increased significantly in the gentamicin group when compared with the controls (mean +/- standard error, 21.7 +/- 4.9 versus 7.3 +/- 1.8%; P less than 0.05; n = 6 for both). The glomerular volume of the juxtamedullary nephrons diminished by about 40%, and their proximal tubule length decreased by about 20%. The glomerular volume of the superficial nephrons also diminished, by about 30%, but their proximal tubule length did not change. The gentamicin concentration was higher in the renal cortex than in the medulla (13.1 +/- 2.6 versus 5.7 +/- 2.2 micrograms/g [dry wt]; P less than 0.01; n = 6 for each). It decreased significantly from days 3 to 20 in both tissues. No functional impairment of the kidney was found in 10-day-old animals, and normal or even supranormal morphometry of the nephrons was observed in the 20-day-old animals. It is concluded that fetal exposure to gentamicin impairs proximal tubular function in the developing animal and might also adversely affect glomerular and tubular growth. However, both the functional and morphometric impairments of nephrons are transitory.

Animals↗
PubMed1986

Molecular analysis of the argB gene of Aspergillus nidulans.

The transcriptional organization and sequence of the Aspergillus nidulans argB gene, encoding ornithine carbamoyl transferase (OCTase; E.C. 2.1.3.3.), was determined. Transcription of the gene begins within a methionine-initiated open translation reading frame, indicating that a second methionine codon of the open reading frame is used for translation initiation. The predicted length of the OCTase precursor peptide is 359 amino acids, and it contains a highly basic amino terminus that is probably involved in mitochondrial targeting. There is extensive homology between Aspergillus OCTase and mammalian and bacterial OCTases and weaker homology between the Aspergillus polypeptide and bacterial arginine carbamoyl transferase.

Amino Acid Sequence↗
PubMedDate not supplied

MR imaging of low signal intensity pulmonary lesions using flow-sensitive techniques.

Various spin echo techniques can be used to define the nature of low signal intensity lesions of the lung. A pulmonary arteriovenous malformation and a chronic pulmonary hematoma had a similar appearance on standard spin echo magnetic resonance (MR) images. Both lesions demonstrated central absence of signal surrounded by a thin rim of tissue, suggesting a vascular lesion. For further characterization of these lesions, a rotating gated MR technique was used in which images are obtained at different points in the cardiac cycle, such that pulsatile flow alters signal intensity with velocity changes during the cardiac cycle. Phase images also discriminated flowing blood in the arteriovenous malformation from stationary lung tissues, whereas the hematoma was not distinguished from lung parenchyma. Rotating gated sequences and reconstructed phase images may be useful in determining the etiology of low signal intensity pulmonary lesions.

Adult↗
PubMedDate not supplied

Ward manager systems in learning disability services.

Drawing on two separate research projects, this article examines the ward manager system within learning disability services and highlights issues for consideration by services about to embark on such systems.

Clinical Competence↗