PubMed Health⌕ Search

Biomedical subjects

T C Fletcher

Publications and source records attributed to T C Fletcher.

At least 19 recordsLinked to original sources
PubMed1991

Immunocompetence as a measure of the biological effects of sewage sludge pollution in fish.

1. Dab, Limanda limanda, exposed to nominal concentrations of 0 (control), 0.0032% (low) and 0.032% (high) sewage sludge in seawater for 12 weeks, were assessed for their immunological competence. 2. No effect upon total blood leucocyte and erythrocyte numbers was found, although significantly fewer thrombocytes were seen in the high-exposure group. 3. A decreased serum protein level was found in the high exposure group, but lysozyme and immunoglobulin levels showed non-significant differences between the groups. 4. Melano-macrophage centres were also affected in the high-exposure dab, which had increased numbers in the spleen and kidney. No effect upon spleen weights or oxygen free radical production by splenocytes was noted. However, oxygen free radical production by kidney leucocytes was inhibited in the low-exposure dab.

Animals↗
PubMed1987

The enhanced induction of metallothionein by zinc, its half-life in the marine fish Pleuronectes platessa, and the influence of stress factors on metallothionein levels.

Intraperitoneal injection of zinc raised levels of a hepatic metallothionein-like species. Assuming that this species was metallothionein (MT) then levels were raised from approximately 20 micrograms/g to 300 micrograms/g in 7 days, and levels thereafter remained high for the next 4 weeks. The half-lives of the protein in liver and kidney from starved fish, measured using in vivo incorporation of 35S cysteine at 11 degrees C, were approximately 27 days and 32 days respectively. The following agents failed to stimulate synthesis of MT in plaice: stress (due to catching), endotoxin, dexamethasone, cortisol and turpentine.

Animals↗
PubMed1987

Effect of opsonization on oxidative metabolism of plaice (Pleuronectes platessa L.) neutrophils.

The effect of serum opsonization on Vibrio alginolyticus (heat-killed)-stimulated chemiluminescence (CL) by plaice kidney- and peritoneal exudate-derived neutrophils was investigated. Peritoneal neutrophils only recognized heat-labile and kidney neutrophils only heat-stable opsonic activity in normal serum. Specific antibody did not show opsonic activity nor any synergism with the normal serum opsonins for either neutrophil population. Evidence was found for the production, by plaice neutrophils, of H2O2, O2-, OH. and two or more, as yet unidentified, reactive oxygen species (ROS).

Animals↗
PubMed1986

Modulation of nonspecific host defenses in fish.

Seasonal, nutritional and hormonal effects on fish nonspecific protective mechanisms have been reviewed, together with the influence of some environmental pollutants. In the plaice (Pleuronectes platessa L.), the serum concentration of lysozyme and the acute phase reactant, C-reactive protein (CRP) and in vitro neutrophil migration have been used as indicators of the ability of test substances to modulate nonspecific defense mechanisms. Cortisol and adrenalin appear to be implicated in the production of CRP, and cortisol, at concentrations found in naturally stressed plaice, significantly reduces the migration of peritoneal neutrophils. Exposure to sub-lethal concentrations of inorganic mercury reduce circulating levels of lysozyme. The results provide further support for an association between environmental stressors and the disease susceptibility of fish populations. Phagocytic cell function, as measured by chemiluminescence, migration or phagocytic index, emerges as a useful test system.

Animals↗
PubMed1986

Migration of fish leucocytes in vitro: the effect of factors which may be involved in mediating inflammation.

Plaice (Pleuronectes platessa L.) neutrophils were isolated from the kidney on a discontinuous Percoll gradient and from the peritoneal cavity at the peak of a glycogen-elicited inflammatory response. The migratory ability of neutrophils was assessed using a 48-well microchemotaxis chamber, with an incubation of 1.5 h at 12 degrees C. The two neutrophil populations showed different responses to N-formylmethionyl-leucyl-phenylalanine (FMLP). Whereas kidney neutrophils only showed a significant enhancement of migration at 10(-7) M, inflammatory neutrophils exhibited a bimodal response, with one peak of migratory activity at 10(-9) M and a second at greater than 10(-6) M. Kidney neutrophils showed a consistent response with various concentrations of a 24 h culture supernatant of Vibrio alginolyticus. In every case increased migration was observed with 5-, 10- and 100-fold dilutions, with the latter two conditions producing a significant enhancement (p less than 0.01 and p less than 0.05 respectively). The undiluted and 2-fold diluted supernatant caused a decreased cell migration compared with control values. The supernatant from kidney neutrophils cultured with serum-opsonized, heat-killed V. alginolyticus produced greater migratory activity than neutrophils or the treated bacteria incubated alone (the controls). In each case, the enhanced activity of the supernatant was detectable by 1 h of incubation. By 4 h, the activity of the neutrophil/bacteria supernatant was significantly higher than that of the controls (p less than 0.01), but by 24 h had fallen to control levels. There was no evidence for a chemotactic response with FMLP, the bacterial supernatant or the neutrophil-derived factor and the responses were therefore assumed to be chemokinetic.

Animals↗
PubMed1986

Serum cortisol, glucose and lipids in plaice (Pleuronectes platessa L.) exposed to starvation and aquarium stress.

Plaice were maintained in the aquarium (11-12 degrees C) during May for 15 days without feeding. Within 48 hr, there was a decline in serum total lipids (P less than 0.001), phospholipids (P less than 0.01), triglycerides (P less than 0.001), cortisol (P less than 0.01) and glucose (P less than 0.001), but an increase in nonesterified fatty acids (NEFA; P less than 0.01). There was a significant inverse correlation between NEFA and glucose over 15 days (P less than 0.001) and between NEFA and cortisol over the first 5 days (P less than 0.01). Cortisol and glucose showed a significant correlation over 15 days (P less than 0.01). Serum cortisol and glucose were not apparently affected by starvation. Only cortisol provided a sensitive indicator of aquarium disturbance. Exposure of the fish to agitation or reduced O2 for 1 hr significantly elevated cortisol (P less than 0.001) but only the latter treatment elevated glucose (P less than 0.01); neither treatment affected the lipids.

Animals↗
PubMed1985

Isolation of substances with vascular permeability-increasing activity from the skin of the plaice (Pleuronectes platessa L.).

A methanolic extract of plaice skin, from which lipids had been removed, was chromatographed on alumina, eluted with decreasing concentrations of ethanol. Only the 60% ethanol fraction exhibited smooth muscle activity, with bradykinin-like properties. The 20% ethanol fraction increased vascular permeability in rat skin, as measured by dye-leakage. This was not due to the degranulation of mast cells. Intradermal injection of either fraction into the plaice caused localized erythema.

Animals↗
PubMed1985

The influence of hormones and inflammatory agents on C-reactive protein, cortisol and alanine aminotransferase in the plaice (Pleuronectes platessa L.).

Endotoxin stimulates production of both C-reactive protein (CRP) and cortisol in the plaice within 24 hr. Cortisol alone (optimum dose i.p. 500 micrograms/300 g wt fish) also stimulates CRP production and the possibility that endotoxin acts through cortisol was examined. Dexamethasone suppresses cortisol production but elevates CRP. Cortisol levels are restored to normal within 24 hr of endotoxin injection. Turpentine and ACTH which stimulate cortisol do not affect CRP. Endotoxin and cortisol have no significant effect on alanine aminotransferase activity in the serum and liver although it is elevated in the serum within 24 hr of the administration of adrenalin or turpentine.

Adrenocorticotropic Hormone↗
PubMed1979

The release of prostaglandin E2 from the skin of the plaice, Pleuronectes platessa L.

1 A fungal extract which produces a cutaneous hypersensitivity reaction in the plaice, Pleuronectes platessa L., was incubated in vitro with the skin of this teleost fish. Samples of incubation media were assayed for smooth muscle stimulating activity. 2 Prostaglandin E2 was identified by bioassay, thin-layer chromatography, ultraviolet absorption spectroscopy and gas chromatography--mass spectrometry. Release from challenged skin was maximum after 60 min incubation. 3 Analysis of the fatty acid composition of plaice skin showed that although arachidonic acid was present (3% of total fatty acids), the precursor of prostaglandin E3, eicosapentaenoic acid contributed 9% of total. 4 Indomethacin (50 mg/kg i.p) did not inhibit the erythema induced by the fungal extract, whilst a dose of 1 mg/kg maximally inhibited prostaglandin release from skin on incubation in vitro. 5 It is concluded that prostaglandins do not have an exclusive role in the mediation of the hypersensitivity reaction.

Animals↗
PubMed1977

A haemagglutinin in the tissue fluid of the Pacific oyster, Crassostrea gigas, with specificity for sialic acid residues in glycoproteins.

An agglutinin for human red cells has a specificity for sialic acid and a high affinity for bovine salivary glycoprotein. Digestion of the glycoprotein with Pronase or neuraminidas indicated that binding of sialic acid to receptors in the agglutinin is the first step in the mechanism of formation of a stable complex between ligand and receptor.

Agglutinins↗
PubMed1977

Isolation of a peptido-polysaccharide from the dermatophyte Epidermophyton floccosum and a study of its reaction with human C-reactive protein and a mouse anti-phosphorylcholine myeloma serum.

Culture filtrate extracts from a number of dermatophyte and Aspergillus species precipitate with human C-reactive protein (CRP) and the lectin Con A. Using immobilized Con A, a peptidopolysaccharide (PPS) has been isolated from Epidermophyton floccosum culture filtrate by affinity chromatography and shown to precipitate with Con A, human CRP sera and a mouse myeloma serum with specificity for phosphorylcholine (PC). The PPS contains carbohydrate (60%), protein (35%), choline and phosphate. The carbohydrate portion consists almost entirely of D-mannose with only 2% hexosamine. Amino acid analysis revealed that serine, threonine, proline and glycine accounted for over 50% of the total amino acids present. Precipitation of E. floccosum PPS and pneumococcal C substance with human CRP sera and mouse anti-PC serum were compared in quantitative precipitin studies. Inhibition studies demonstrated that PC is a potent inhibitor of the serum CRP-PPS and myeloma protein-PPS precipitation reactions. The involvement of 'C substances' in a variety of biological processes is discussed.

Animals↗
PubMed1976

Identification of glycoproteins in goblet cells of epidermis and gill of plaice (Pleuronectes platessa L.), flounder (Platichthys flesus (L.)) and rainbow trout (Salmo gairdneri Richardson).

A quantitative analysis has been made of the glycoproteins present in the goblet cells of the epidermis, gill filaments and gill lamellae of three species of teleost fish. The glycoproteins have been identified by a combination of techniques, including the use of the enzyme sialidase followed by Alcian Blue staining, at PH 2.6 or 1.0, in combination with periodic acid-Schiff. The selected fish were representative of species living in marine, freshwater and estuarine environments. The range of glycoproteins identified in these fish was similar to that found in mammalian tissue in that both neutral and acid glycoproteins were present, the latter included both sialomucins sensitive and resistant to sialidase, and sulphomucin. A single goblet cell contained either neutral or acid glycoproteins alone or in combination. Only the epidermis of the plaice and rainbow trout contained uniform cell populations producing acid glycoproteins, the former sulphomucin and the latter mainly sialomucin. At each site in the flounder and in the gill epithelia of the plaice and rainbow trout, the goblet cell population was mixed, with cells producing each type of glycoprotein. The number of goblet cells producing each type of glycoprotein varied at each tissue site.

Alcian Blue↗