PubMed Health⌕ Search

Biomedical subjects

D M Lowe

Publications and source records attributed to D M Lowe.

28 records · Page 2Linked to original sources
PubMed1978

Responses of lysosomes in the digestive cells of the common mussel, Mytilus edulis, to sex steroids and cortisol.

Estradiol-17beta and progesterone at physiological concentrations in vivo induced a reduction in lysosomal stability in the digestive cells of Mytilus edulis. Estradiol-17beta (10(-8) M) also reduced lysosomal stability within 15 min in vitro. Lysosomal stability was determined cytochemically as the labilisation period for latent N-acetyl-beta-hexosaminidase and this was shown to be inversely related to microdensitometric measurements of staining intensity for this enzyme. Estradiol-17beta did not appear to induce complete labilisation or cytochemical activation of lysosomal hexosaminidase and a second, much longer labilisation period could be determined for this hormone. The effects of estradiol-17beta were partially counteracted by cortisol (10(-2) M). There was an increase in PAS staining of secondary lysosomes and an increase in alcian blue staining of residual bodies in digestive cells of animals exposed to estradiol-17beta, while no changes could be observed in basophil cells. The significance of these results is discussed in terms of the physiological role of digestive cells and their possible function as target cells for estradiol-17beta and progesterone.

Animals↗
PubMed1978

Cytology and quantitative cytochemistry of a poliferative atypical hemocytic condition in Mytilus edulis (Bivalvia, mollusca).

Proliferative lesions were found in 16 of 994 Mytilus edulis mussels obtained from the mouth of the River Lynher at Plymouth, England. These lesions were characterized by infiltration and replacement of the connective tissue by enlarged, atypical, mitotically active, basophilic, hemocyte-like cells. Cytologic examination indicated the involvement of two cell types in this disorder, both of which were similar in appearance to the much smaller, normal basophallic agranular hemocyte. The abnormal cells were rich in cytoplasmic RNA and had significantly higher DNA levels than normal hemocytes as determined by scanning microdensitometry. A few of the atypical cells contained small cytoplasmic granules that were positive for lysosomal hydrolases. This condition was observed sequentially from what is believed to be the earliest stage of the disease, in which only a few atypical cells were present, to the terminal stage, in which the connective tissue was almost completely replaced and the digestive gland cells were necrotized. Some potentially carcinogenic aromatic hydrocarbons have been identified in the substrate of the mussel bed by gas-liquid chromatography-mass spectrometry analysis.

Animals↗
PubMed1974

Studies on the structure and activity of rabbit Clq (a subcomponent of the first component of complement).

1. The subunit structure of rabbit subcomponent C1q was examined in a previous publication (Reid et al., 1972). The present paper describes some aspects of the structure of the polypeptide chains derived from the molecule. 2. The three polypeptide chains, produced by performic oxidation, of rabbit subcomponent C1q were isolated by ion-exchange chromatography in 8m-urea on DEAE-cellulose. 3. Each chain was found to contain 15-18% glycine and significant amounts of the amino acids hydroxyproline and hydroxylysine. 4. By means of collagenase digestion it was shown that all three chains of rabbit subcomponent C1q contain collagen-like sequences of amino acids which constitute about 40% of each chain. 5. By use of carboxypeptidase A it was established, indirectly, that the collagen-like sequences, in one of the chains, are probably located near, or at, the N-terminal end of the chain. 6. Collagenase digestion and heating at 52 degrees C (but not at 49 degrees C) caused rapid loss of native rabbit subcomponent C1q haemolytic activity.

Amino Acids↗
PubMed1972

Isolation and characterization of C1q, a subcomponent of the first component of complement, from human and rabbit sera.

1. C1q, a subcomponent of the first component of complement, has been isolated, in a haemolytically active and soluble form, by ion-exchange chromatography and gel filtration, from human and rabbit sera. Yields ranged from 10 to 25mg/litre of serum and the activity of final preparations was consistently in the range 5x10(3)-15x10(3) C1qH(50) units/mg. 2. The molecular weights of human and rabbit subcomponent C1q were 409600 and 417600, as determined by sedimentation equilibrium studies. 3. Subcomponent C1q from both species was shown to be composed of non-covalently linked subunits of approximately 57000 molecular weight as determined by gel-filtration or sedimentation equilibrium studies in 5.3m-guanidinium chloride. Reduction or oxidation of human and rabbit subcomponent C1q yielded three chains each having a molecular weight of approximately 23000 and which differed slightly in amino acid composition but markedly in carbohydrate content. The oxidized chains were separated, on a preparative scale, by ion-exchange chromatography in 8m-urea on DEAE-cellulose. 4. Both human and rabbit subcomponent C1q contained hydroxyproline, hydroxylysine, a high percentage of glycine and approximately 8% carbohydrate. Glutamic acid and aspartic acid were the free N-terminal amino acids of human subcomponent C1q whereas only serine was found in rabbit subcomponent C1q. 5. Collagenase digestion of human or rabbit subcomponent C1q caused a rapid loss of haemolytic activity which correlated with the breakdown of collagenous regions in the molecule.

Amino Acids↗
PubMedDate not supplied

Impact of the Sea Empress oil spill on lysosomal stability in mussel blood cells.

Coastal zones are among the most productive and vulnerable areas on the planet. An example of impact on these fragile environments was shown in the case of the "Sea Empress" oil tanker, which ran aground in the Bristol Channel in 1996, spilling 72,000 tons of "Forties" crude oil. The objective was to investigate the sub-lethal cellular pathology and tissue hydrocarbon contamination in marine mussel populations, 4 months after the initial spill, using the neutral red retention (NRR) assay for lysosomal stability in blood cells. NRR was reduced in mussels, and indicative of cell injury, from the two sites closest to the spill in comparison with more distant and reference sites. Lysosomal stability was inversely correlated with polycyclic aromatic hydrocarbon concentrations in mussel tissues. Reduced lysosomal stability has previously been shown to contribute to impaired immunocompetence and to autophagic loss of body tissues. The use of this type of technique is discussed in the context of cost-effective, ecotoxicological tools for Integrated Coastal Zone Management.

Animals↗
PubMedDate not supplied

Engineering of tyrosyl tRNA synthetase.

The gene encoding the enzyme tyrosyl tRNA synthetase from Bacillus stearothermophilus has been systematically altered using synthetic oligonucleotides as mutagens. The construction of mutations has been facilitated by using strains of bacteria defective in mismatch repair and also by utilising a genetic marker in the M13 strain (such as an amber mutation, or an EcoK or EcoB site) which allows selection for the progeny of M13 replication derived from the minus (mutagenized) strand. Several mutations have been constructed in the ATP binding site to elucidate the roles of individual residues in catalysis and substrate binding and it has even been possible to construct mutants which have improved affinity for ATP. Mutations in various surface lysine and arginine residues have allowed us to identify potential contacts with the tRNA, and indicate that a cluster of basic residues close to the C-terminus of the enzyme probably makes important interactions with the tRNA.

Amino Acyl-tRNA Synthetases↗
PubMedDate not supplied

Hydrogen bonding and biological specificity analysed by protein engineering.

The role of complementary hydrogen bonding as a determinant of biological specificity has been examined by protein engineering of the tyrosyl-tRNA synthetase. Deletion of a side chain between enzyme and substrate to leave an unpaired, uncharged hydrogen-bond donor or acceptor weakens binding energy by only 0.5-1.5 kcal mol-1. But the presence of an unpaired and charged donor or acceptor weakens binding by a further approximately 3 kcal mol-1.

Amino Acyl-tRNA Synthetases↗
PubMedDate not supplied

Pethidine pharmacokinetics after intramuscular dose: a comparison in Caucasian, Chinese and Nepalese patients.

The pharmacokinetics of pethidine after a single intramuscular injection were studied in 30 male patients of Caucasian, Chinese and Nepalese extraction. There were no significant differences between the three ethnic groups in the mean time for maximum absorption (tmax) and peak plasma concentration (Cmax) of pethidine. The mean (+/- S.D.) elimination half life (t1/2) of pethidine was shorter in Caucasians (4.5 +/- 1.3 h) compared with Nepalese (6.3 +/- 1.6 h) and Chinese (8.1 +/- 3.1 h) (p < 0.01). The plasma clearance of pethidine was greater in Caucasians (14.2 +/- 4.8 ml.min-1.kg-1) than in Nepalese (12.6 +/- 2.9 ml.min-1.kg-1) and Chinese (10.0 +/- 2.9 ml.min-1.kg-1) (p < 0.05); yet the apparent renal clearance was similar (64.1 +/- 22.9, 86.7 +/- 44.5 and 61.4 +/- 30.1 ml.min-1.kg-1, respectively, for the Chinese (n = 6), Caucasian (n = 6) and Nepalese (n = 9) patients). No apparent ethnic differences were found in the tmax and Cmax of norpethidine which emerged as the major metabolite in the plasma in the three races. An apparently higher area under plasma concentration-time curve (AUC infinity [symbol: see text]) and longer elimination t1/2 of the metabolite were observed in the two Asian patient groups. It appears that both the Chinese and Indian groups did not eliminate pethidine as effectively as the Caucasians after a single intramuscular injection, which may be the result of interethnic variability in the metabolism of pethidine. Caution may be required on multiple dosing of pethidine in Asian patients due to the possible accumulation of the parent drug and its toxic metabolite, norpethidine.

Adolescent↗