The immunohistochemical localization of lysozyme in plaice (Pleuronectes platessa L.) tissues

The location of lysozyme in fresh plaice ( Pleuronectes platessa L.) tissues was studied using an immunofluorescent technique. An antiserum to a homogeneous sample of plaice serum lysozyme was prepared in rabbits and was shown to be monospecific by immunodiffusion and inhibition studies. This preparation, used in conjunction with fluorescent labelled sheep anti-rabbit immunoglobulin, demonstrated lysozyme in plaice neutrophils, peritoneal macrophages, gill cartilage and epithelium, spleen, kidney, skin and mucus. The distribution of lysozyme in the skin and secreted mucus was affected by the method of killing the fish.     

The distribution of 0-group flatfish in relation to abiotic factors on the tidal flats in the brackish Dollard (Ems Estuary, Wadden Sea)

The distribution of 0-group flatfish was investigated in 1992 in the Dollard (Ems–Dollard estuary, Wadden Sea). 0-Group plaice, flounder and sole were not evenly distributed over the sampled locations. The spatial distribution pattern of 0-group flatfish in the Dollard changed during the investigation period. In the first week of sole presence, when the mean length of sole was 24–30 mm, salinity correlated significantly with sole density. The distribution of juvenile sole larger than 40 mm total length was affected by the elevation of the location: 0-group sole was restricted to the sampled site with the lowest elevation. The distribution of 0-group plaice was related to sediment: no juvenile plaice were caught at locations with more than 10% mud fraction in the sediment. The distribution of 0-group flounder was also correlated with sediment. Later in the year, salinity correlated negatively with the distribution of 0-group flounder. The influence of sediment composition is probably indirect and linked to the abundance of preferred food items, such as Corophium volutator . Abiotic conditions were suitable to 0-group plaice, flounder and sole.     

Some aspects of the biology of the cercaria and metacercaria of Stephanostomum baccatum (Nicoll, 1907) Manter, 1934 (Digenea: Acanthocolpidae)

Experimental proof is presented that Cercaria neptunae Lebour is the cercaria of Stephanostomum baccatum and that the gastropods Buccinum undatum (L.) and Neptunea antiqua (L.) both act as its first intermediate hosts in the north-east Atlantic. Heavy experimental infections were associated with mortalities of 0+plaice Pleuronectes platessa (L.). The probable effects on plaice of infections at intensities below the lethal level are discussed. Under natural conditions almost all S. baccatum infection of plaice occurs in the first year of life, but newly emerged cercariae were shown experimentally to be capable of encysting in the musculature of plaice up to three years old. The thicker epidermis of older plaice may account for their resistance to infection. Common dabs were more easily infected than plaice. The ability of S. baccatum cercariae to infect plaice and common dabs is inversely related to the length of time between emergence and contact with the host. The differences in skin structure between opposite sides of the plaice body may account for the asymmetrical distribution of metacercariae in the musculature. The potential use of S. baccatum as a biological tag is discussed.     

Effects of solar radiation on the population dynamics of juvenile flatfish in the shallows of the Wadden Sea

During the first days after their arrival in the Wadden Sea, newly settled plaice Pteuronectes platessa L., flounder, Platichthys flesus L., and sole, Solea solea L., stay at low tide in the residual waters on the tidal flats. Here they can be exposed to high levels of solar radiation and extreme temperature conditions. As a result of the extreme temperatures, all settlers eventually leave the shallows and start to exhibit tidally-phased feeding migrations from the tidal channels on to the submerged fiats, In contrast to warm summers, for example 1982, no formation of a hyaline zone could be detected in the otoliths of surviving O-group plaice in 1990, 4 weeks after such a mass emigration, which could be directly observed on particular days in both hot and cold summers. Analysis of UV-B radiation data indicated that in 1990 cloud cover and wind conditions during the settling period protected the post-larvae from high temperature and radiation stress which is necessary to induce hyaline zones in the otoliths. Nevertheless, histological examination of the dorsal skin revealed cellular changes characteristic of sunburn damage in part of-the O-group plaice population in 1990.
Mortality of O-group plaice during and after such a mass emigration, which was directly observed in the drainage gulleys in 1982, was estimated at approximately 14–27%. This rate is assumed to be close to the maximum mortality which can be expected from abiotic factors for O-group plaice in the Wadden Sea.     

Use of immunochemical methods for characterization and purification of tissue-specific inhibitors of mitotic activity (chalones)]

The 81% ethanol-precipitable fraction of water-soluble proteins from skin inhibiting the proliferation of epidermal tissues was shown to contain 9 protein components according to acrylamide gel disk-electrophoresis. Seven of these were identical to homologous serum proteins and could be adsorbed on the corresponding immunosorbents. Two proteins remained in the solution after immunoadsorption. Their electrophoretic properties were the same as those in the total 81% ethanol fractions. These proteins like the 81% ethanol fraction inhibited the entering of cells into mitosis and DNA synthesis phase.     

Cutaneous oxygen uptake and its relation to skin blood perfusion and ambient salinity in the plaice, Pleuronectes platessa

Oxygen uptake across plaice skin was unaffected by temporary arrest of skin blood flow. This indicates that oxygen taken up across the skin is consumed by the skin itself. Weight specific rate of O2-consumption of skin is estimated to be 1.7-1.9 times that of the entire fish. Total resting O2-consumption increased from 0.43 to 0.58 mg X kg-1 X min-1 when salinity was raised from 8.5 to 25%. The relative increase in O2-uptake across the skin following an increase in salinity was smaller than the increase in total O2-uptake. This is taken to indicate that the high O2-consumption of skin is not specifically related to an osmoregulatory function of the skin.     

桐花树叶醇提取物乙酸乙酯部位对大鼠皮肤抗氧化与抗衰老能力的影响

萃取法获得桐花树叶75%乙醇提取物的石油醚、二氯甲烷、乙酸乙酯、正丁醇和水部位(醇沉),从中筛选出多酚与总黄酮含量均较高、DPPH自由基清除能力较强的乙酸乙酯部位作为辅料试配成膏状体,并通过对SD大鼠背部皮肤进行连续外涂实验,测定其皮肤组织匀浆的总超氧化物歧化酶(T-SOD)活性、羟基自由基清除能力、丙二醛(MDA)含量、羟脯氨酸(HYP)和胶原蛋白含量。结果表明:2.0%桐花树叶乙酸乙酯部位膏状体处理组的皮肤组织T-SOD活性、羟基自由基清除能力、HYP和胶原蛋白含量均极显著高于,但MDA含量极显著低于阴性对照组(仅含化妆品基质的膏状体)、阳性对照组(2.0%熊果苷膏状体)与1.0%、0.5%乙酸乙酯部位膏状体处理组(P0.01)。说明桐花树叶乙酸乙酯部位是一种潜在的抗氧化或抗衰老化妆品辅料,2.0%乙酸乙酯部位含量是试配该化妆品的有效添加剂量。增强T-SOD活性、提高自由基清除能力、降低MDA含量、促进胶原蛋白合成可能是桐花树叶乙酸乙酯部位预防或延缓皮肤衰老的作用机制。     

Sex differences in the gonadotropins of the Black Sea plaice Scophthalmus maeoticus

No quantitative differences in the effect of acetone-dried pituitaries from male and female plaice upon loach-recipients (Misgurnus fossilis) have been found in testing the activity of the glands on plaice-recipients. This fact suggests the existence of qualitative differences between gonadotropins from plaice males and females. This conclusion was supported in the experiments on the effect of purified gonadotropic fractions, isolated separately from male and female hypophyses, on maturation of the loach. Three gonadotropic fractions obtained by preparative disc-electrophoresis in polyacrylamide gel, differ in their biological activity and electrophoretic mobility. The activity of gonadotropic fractions in males is higher, than in females; electrophoretic mobility of two fractions is also higher in males, whereas the third fraction does not exhibit sexual differences.     

0-group flatfish growth conditions on a nursery ground (Bay of Canche, Eastern English Channel)

The settlement and growth conditions of three 0-group flatfish species, sole (Solea solea L.), plaice (Pleuronectes platessa L.) and dab (Limanda limanda L.) in the Bay of Canche, French coast of the Eastern English Channel, were investigated during summer 1997. 0-group dab were the more abundant of the three species (75.4%) followed by plaice (21%) and sole (3.6%). Analyses of fish size distribution indicated that settlement of plaice occurred before sole and dab. Growth of sole was faster than that of plaice, which in turn was faster than that of dab (0.68, 0.43 and 0.33 mm d^?1 respectively). Sole differed from plaice and dab by their larger mean length attained at the end of their first summer stay in the nursery ground. Growth performances of 0-group sole and plaice were analysed by comparing estimated growth in the field with predicted maximum growth according to temperature-growth rate models from experimental studies of growth with unlimited food supply. The data of this study suggest that plaice growth may have been limited during late summer, whereas sole growth does appear to have been determined only by water temperature.     

Enhancement of polyphenol bio-activities by enzyme reaction

Using β-glucosidase to hydrolyze glycosides into aglycones, the present study attempted to improve the bio-activity of the extract from mulberry leaves. When varying the ethanol fraction, pH, and temperature of the extract, the optimum conditions for the enzyme reaction were identified as a 10% ethanol fraction in the extract, pH 5.0, and 40 °C temperature. Under these optimum conditions, the enzyme reaction produced a remarkable increase in the anti-oxidation and tyrosinase inhibition activities of the extract by as much as 219.5% and 230.9%, respectively. This improved bio-activity of the extract was due to the hydrolysis of the glycoside polyphenols rutin, isoquercitrin, and astragalin into the aglycone polyphenols quercetin and kaempferol. Furthermore, the enzymatic hydrolysis of the extract by β-glucosidase also produced some additional benefits that are critical factors for the skin absorption of bio-active ingredients, including an improved hydrophobicity (239.41%) and reduced mean molecular weight (from 387.3 to 291.4), resulting in a significantly enhanced skin permeability (513%).     

Biochemical changes occurring during final maturation of eggs of some marine and freshwater teleosts

Biochemical changes which occur during post-vitellogenic meiotic maturation of oocytes were investigated by measuring the concentrations of various phosphorus-containing fractions of the ovaries and mature eggs of four marine species with pelagic eggs, plaice, Pleuronecles platessa , cod, Gadus morhua , haddock, Melanogrammus aeglefinus , and whiting, Merlangius merlangus , and three freshwater species with demersal eggs, rainbow trout, Salmo gairdneri , pike, Esox lucius , and powan, Coregonus lavarelus . In the former group, protein phosphate was deposited at normal vertebrate levels in the ovaries during vitellogenesis but was exhausted during maturation, its decrease correlating with the uptake of water which rendered the mature egg buoyant in sea water. In plaice, phospholipid phosphate declined slightly during maturation, while inorganic phosphate increased by an amount slightly less than that which disappeared from the protein fraction. No such changes occurred on maturation in these three fractions in the freshwater species, in which little or no water uptake occurred. In plaice, the approximately five-fold increase in the water content of the oocyte was accompanied by a corresponding five-fold increase in the amount of potassium, the major inorganic cation of the oocyte. These pelagic eggs appear to be unique among the eggs of vertebrates in their high water content ( c . 92%) and in the fact that the protein phosphate is almost entirely utilized before fertilization, while, in those freshwater fishes and other oviparous vertebrates that have been examined, the egg is of much lower water content (50–70%) and most of the protein phosphate, like the other major yolk constituents, is used during embryonic growth. This utilization at such an early stage in the life cycle constitutes an extreme example of heterochrony.     

Monoaminergic nerves in the skin of plaice Pleuronectes platessa (L.)

1. The fluorescent histochemical technique of Falck and Hillarp was applied to plaice skin. The presence of monoaminergic nerve terminals, containing predominantly stores of adrenaline, forming a plexus in and around the melanophore layer was demonstrated. 2. Such stores were enriched by noradrenaline in the presence of monoamine oxidase inhibitor, unaffected by spinal section, depleted by spinal nerve section or ligatures and abolished by reserpine. 3. The observations support the view that teleost sympathetic melanophore aggregating nerves are truly adrenergic.     

Vulnerability of newly settled plaice (Pleuronectes platessa L.) to predation: effects of habitat structure and predator functional response

Plaice (Pleuronectes platessa) nursery grounds on the Swedish west coast have been subject to increasing cover of annual green macroalgae during recent years, with growth of algae starting at the time of plaice settlement in April to May. A laboratory experiment was performed to investigate how the vulnerability to predation of metamorphosing plaice was affected by the presence of filamentous algae. Predation by shrimps (Crangon crangon) on settling plaice larvae was higher on sand than among algae, whereas predation by crabs (Carcinus maenas) was unaffected by habitat type, suggesting a lower overall mortality of plaice in the vegetated habitat. When predators and prey were presented with a combination of the two habitats, predation by shrimps was as high as that in the sand treatment alone, whereas predation by crabs was lower than that in the two treatments with one habitat. Based on these results, an additional experiment was performed, investigating the functional response of shrimps to six densities of juvenile plaice in a sand habitat with alternative prey present. The proportional mortality of juvenile plaice (12-16 mm total length (TL)) was density-dependent and was best described by a type III (sigmoid) functional response of the predatory shrimps. The results suggested that the combined predation pressure from shrimps and crabs was lower among algae than on sand, but settling plaice and predatory shrimps chose the sand habitat. Plaice densities in the sigmoid part of the obtained functional response curve represented normal to high field densities of plaice on the Swedish west coast, suggesting that shrimp predation could have a stabilising effect on plaice recruitment. The formation of macroalgae mats could therefore lead to a concentration of plaice juveniles in the remaining sand habitat and increased mortality through density-dependent predation by shrimps.     

Susceptibility of Atlantic herring and plaice larvae to predation by juvenile cod and herring at two constant temperatures

Predation encounters were staged in the laboratory to compare prey responsiveness, predator error rate, and predator capture success for juvenile cod Gadus morhua (a suction feeder) and herring Clupea harengus (a biting predator) preying on herring and plaice Pleuronectes platessa larvae. Trials were conducted at near natural temperature extremes for the larvae (8 and 13°C) to assess the importance of water temperature to the interaction. Herring larvae were significantly more responsive to attacks by herring than were plaice larvae (5·7 vs 0'0%). The two prey species were equally responsive to attacks by cod (2–6 vs 10%). Cod caught 91% of herring larvae attacked and juvenile herring caught 87%. Cod were successful in 96% of attacks on plaice, but juvenile herring caught significantly fewer (83%) plaice larvae. For each predator species, capture success did not vary significantly with prey species. Overall capture success for herring was significantly lower than that for cod. Responsiveness of herring larvae to attacks by juvenile herring increased with temperature, but predator error rate and capture success were not altered by water temperature.     

The effect of ethanol on ion transport in frog skin.

Frog skin has been used as a model epithelial sodium-transporting system to study the effect of ethanol on ion transport. Treatment of the outside of frog skin with ethanol decreased the net sodium transport due to inhibition of 22Na+ influx. Ethanol did not alter sodium outflux when bathin the outside of the skin. The inhibition was in proportion to the concentration of ethanol, 0.25 M resulting in 50% inhibition. The chloride permeability of the skin was increased several-fold when the skin was exposed to ethanol in either bathing solution. With 0.4 M ethanol in the inner bathing solution, all the unidirectional fluxes of Na+ and C1- were increased. The movement of C1- was evaluated by comparison of C1- flux with urea flux, since urea is thought to move passively across frog skin via an extracellular (shunt) pathway. Chloride flux was increased to a greater extent than urea flux. These experiments indicate that ethanol affects chloride permeability beyond an increase in extracellular ion flow and independent of its effect of Na+ transport.     

Chronic ethanol consumption enhances internalization of alpha1 subunit-containing GABAA receptors in cerebral cortex

The molecular mechanisms that underlie ethanol dependence involve alterations in the functional properties and subunit expression of GABAA receptors. Chronic ethanol exposure decreases GABAA receptor alpha1 subunits and increases alpha4 subunit levels in cerebral cortical membranes. This study explored the effect of chronic ethanol exposure on internalization of GABAA/benzodiazepine receptors. Chronic ethanol exposure increased alpha1 subunit levels by 46 +/- 12% and [3H]flunitrazepam binding by 35 +/- 9% in the clathrin-coated vesicle (CCV) fraction. There was a corresponding 34 +/- 8% decrease in alpha1 peptide expression and 37 +/- 6% decrease in [3H]flunitrazepam binding in the synaptic fraction. Chronic ethanol consumption also increased the alpha1 subunit immunoprecipitate in the cytosolic fraction (77 +/- 22%), measured by western blot analysis. Moreover, co-immunoprecipitation of both clathrin and adaptin-alpha with alpha1 subunits was increased in the cytosolic fraction, suggesting that alpha1 subunit endocytosis is enhanced by chronic ethanol consumption. In contrast, alpha4 subunit peptide levels were not altered in the CCV fraction despite a 39 +/- 13% increase in peptide levels in the synaptic fraction of cortex. Moreover, acute ethanol exposure did not alter alpha1 subunit peptide expression or [3H]flunitrazepam binding in the synaptic or CCV fractions. These results suggest that chronic ethanol consumption selectively increases internalization of alpha1 subunit-containing GABAA receptors in cerebral cortex.     

Analysis of the enzyme polymorphism in a plaice, Pleuronectes platessa L., population from the north-west coast of Brittany, France

A study of enzyme polymorphism by electrophoretical techniques permitted the genetic structure and the homogeneity degree of the plaice population present in the Abers Wrac'h and Benoit along the north-west coast of Brittany to be determined. Thirteen enzymic systems encoded by 21 loci were analysed and nine of these loci were polymorphic at the 5% level. The comparison of allelic frequencies and of observed heterozygosity h _obs did not show significant differences between these two individual groups. Nei's genetic identity ( I = 0.998) and distance ( D = 0.002) as estimated from allelic frequencies showed that the plaice of the two estuaries are very similar.
Thus, the plaice of A. Wrac'h and of A. Benoit belong to the same population in which the average level of polymorphism per locus P is 47% and the observed average heterozygosity per individual H _obs is 0.163 ± 0.094.     

Seasonal Ichthyodiversity and Growth Patterns of Juvenile Flatfish on a Nursery Ground in the Southern Bight of the North Sea (France)

The demersal fish community on a flatfish nursery ground, of the Southern Bight of the North Sea, was sampled monthly between May 1998 and 1999. The studied coastal area is a multispecific nursery area. Although 32 fish species were caught, only nine species had a major influence on the variation in total densities through the year and can be considered as key species. Juvenile sole and plaice exhibited similar seasonal growth patterns with rapid growth during late spring and summer, a growth arrest during autumn and winter and a restart of growth in March. Comparisons of observed growth in length with predicted maximal growth under optimal food conditions suggested that during the summer, growth of 0-group sole and plaice was only determined by prevailing mean water temperature. During autumn and winter, while growth in length of sole followed model predictions, observed length of plaice was less than model predictions, suggesting growth limitation. Analyses of the factors that may be responsible for differences between observed and expected length growth indicated that autumn and winter growth arrest of plaice was not only related to low winter water temperature. It is suggested that for visual feeders such as plaice, the interaction of decreasing food availability and day length during autumn and winter can reduce the access to food resource and therefore feeding success and growth.     

Aspects of leucocyte migration in the plaice, Pleuronectes platessa L.

Histological studies on plaice tissues revealed mononuclear phagocytes emigrating through capillary endothelium in response to bloodborne foreign erythrocytes, with a >50% increase in circulating leucocytes within 2 h. Despite this rapid influx of leucocytes, cellular accumulation during peritoneal inflammatory responses was significantly slower than in mammals. In vitro studies with chemotaxis chambers revealed that random leucocyte migration was enhanced in the presence of endogenous chemostimulatory substances (inflammatory exudate fluid and endotoxin-activated plaice serum) although directional migration was not demonstrated. It is suggested that, compared with mammals, the slower accumulation of teleostean leucocytes at sites of injury is not due to a locomotory defect but possibly results from lower levels of endogenous chemoattractants being generated.     

Precipitating activity in the sera of plaice, Pleuronectes platessa L. to a helminth antigen

An antigen abstract of Proleptus obtusus an intestinal nematode of the common dogfish has been shown to precipitate with a serum component of plaice. As the parasite has never been shown to infect plaice it is suggested that perhaps the serum component might be C–reactive protein (CRP). However, characterization of the component revealed that it was specific immunoglobulin analagous to antibody of the IgM class. It is suggested the helminth antigen involved is cross–reacting with a common antigen to which the plaice is normally exposed.