Spatial transcription of CYP1A in fish liver

Background  

The aim of this work was to study how evenly detoxifying genes are transcribed spatially in liver tissue of fish. Ten Atlantic salmon Salmo salar were intraperitoneally injected with 50 mg/kg of the strong CYP1A inducer β-naphthoflavone and liver tissue harvested seven days later. The liver from 10 control and 10 exposed fish were split into eight sections, RNA extracted and three reference (β-actin, elongation factor 1A_B (EF1A_B)) and two detoxifying genes (CYP1A and GST) quantified with real-time RT-PCR. The cellular localization of the EF1A_B and CYP1A mRNA in the liver of control and β-naphthoflavone treated fish was then determined by in situ hybridization (ISH) using EF1A_B and CYP1A biotinylated oligonucleotide probes.     

毛竹林老竹水平和经营措施对新竹发育质量的影响

毛竹林是我国重要的森林资源类型,在森林固碳和林业应对气候变化中具有不可替代的重要作用。由于毛竹林的持续采伐与自我更新特性,在竹林经营过程中,新竹的发育数量和质量成为评价竹林固碳功能变化的决定性因子。利用两因素随机区组设计,排除地形因子等影响,选取施肥和采伐留养方式这两个因素,研究老竹水平和经营措施对2010年和2013年毛竹林新竹发育质量的影响。结果表明:无论2010年还是2013年,新竹平均胸径、株数和碳储量与3年生和5年生老竹的相关性均高于2年生和4年生老竹。新竹碳储量与3年生和5年生老竹碳储量呈线性相关,建立线性回归模型y=0.675x-2.2491,R~2=0.8561,而新竹碳储量与2年生和4年生老竹碳储量相关性较低,线性回归模型为y=-0.1109x+6.7287,R~2=0.0061。不同经营措施实施后,新老竹之间关系发生了很大的改变,新竹平均胸径与老竹的相关性大幅下降,新竹株数和碳储量与老竹几乎没有相关性,新竹碳储量与3年生和5年生老竹碳储量的线性回归模型为y=0.1036x+3.7539,R~2=0.0981,新竹碳储量与2年生和4年生老竹碳储量的线性回归模型为y=-0.0408x+5.9069,R~2=0.0151。不同经营措施的实施对新竹的平均胸径、株数和地上碳储量产生了很大的影响。处理A_1B_2(大量施肥中度采伐中密度留养)、A_2B_2(中等施肥中度采伐中密度留养)和A_3B_2(不施肥中度采伐中密度留养)新竹平均胸径、新竹株数和新竹碳储量都有所增加,新竹平均胸径增幅为:处理A_2B_2(8.78%)A_1B_2(2.43%)A_3B_2(2.06%),新竹株数增幅为:处理A_1B_2(81.0%)A3B2(35.4%)A2B2(15.2%),新竹地上碳储量增幅为:处理A_1B_2(90.8%)A_3B_2(35.7%)A_2B_2(49.7%),而其余处理基本都会减少,说明适度采伐留养最有利于提高毛竹林新竹的发育质量。仅仅从固碳最大化的角度出发,大量施肥中度采伐中密度留养最有利于新竹碳储量的增加,而从培养大径竹材的角度考虑,中等施肥中度采伐中密度留养能收到更好的效果。     

Complexity of lectins from the hard roe of perch (Perca fluviatilis L.)

Fish eggs are a rich source of lectins, the sugar-binding (glyco)proteins. In this paper we aim to further characterise perch roe lectins using several protein characterisation techniques including affinity chromatography and protein sequencing. Perch roe lectins are comprised of two subunits, subunit A and subunit B which have molecular weights of 12,400 and 12,000, respectively. These subunits form multiple aggregates A_nB_n in which the two subunits are present in differing ratios and, also as an `homogeneous' aggregates of one of the subunits A_n or B_n. Lectins A_n (designated A thereafter) and lectin B_n (designated B thereafter) formed by one type of subunit only (subunit A or B) were isolated in a pure state. Lectin B could also be isolated by spontaneous precipitation occurring during incubation of the perch roe extract at 4°C. Lectin B has a higher affinity for d-glucose than lectin A, whereas both lectins (A and B) have a similar affinity for l-fucose. The N-terminal region of subunit B showed the following amino acid sequence: EPAXPPWGTQFG-, whereas the N-terminus of subunit A was blocked and therefore could not be directly sequenced. Differences between subunits A and B were also found in amino acid composition. This unusual complexity and variability of perch roe lectins is likely to have physiological significance which, as yet, remains to be determined.     

Vitamin losses during frozen storage of Liza aurata (Risso, 1810), Cyprinus carpio L. 1758, Clupeonella cultriventris caspia (Nordmann, 1840), Rutilus frisii kutum (Kamenskii, 1901) and Sander lucioperca (L., 1758)

The objective of this study was to determine the fat and water‐soluble vitamins contents (A, E, D, K, B₁, B₂, B₆, B₁₂, niacin, biotin, ascorbic, folic and pantethonic acids; in mg kg^?1 fresh weight) lost during frozen storage (?24°C) in time intervals of 0, 1, 2, 3 and 4 months. Studied species included: Liza aurata (golden grey mullet), Cyprinus carpio (common carp), Clupeonella cultriventris caspia (common kilka or sprat), Rutilus frisii kutum (Caspian kutum) and Sander lucioperca (pike perch). Results showed that A, D and K vitamin losses occurred in all samples during storage, but no statistically significant differences were observed. Vitamin E losses under frozen conditions were significant in common kilka, Caspian kutum and pike perch, however, not in golden grey mullet or common carp. A decrease in vitamin C was significant in all fish species, but there were no significant decreases in other water‐soluble vitamins (B₁, B₂, B₆, B₁₂, niacin, folic acid, pantothenic acid, biotin).     

Factors driving spatial and temporal variation in production and production / biomass ratio of stream‐resident brown trout (Salmo trutta) in Cantabrian streams

1. The objective was to identify the factors driving spatial and temporal variation in annual production (P_A) and turnover (production/biomass) ratio (P/B_A) of resident brown trout Salmo trutta in tributaries of the Rio Esva (Cantabrian Mountains, Asturias, north‐western Spain). We examined annual production (total production of all age‐classes over a year) (P_A) and turnover (P/B_A) ratios, in relation to year‐class production (production over the entire life time of a year‐class) (P_T) and turnover (P/B_T) ratio, over 14 years at a total of 12 sites along the length of four contrasting tributaries. In addition, we explored whether the importance of recruitment and site depth for spatial and temporal variations in year‐class production (P_T), elucidated in previous studies, extends to annual production. 2. Large spatial (among sites) and temporal (among years) variation in annual production (range 1.9–40.3 g m^?2 per year) and P/B_A ratio (range 0.76–2.4 per year) typified these populations, values reported here including all the variation reported globally for salmonids streams inhabited by one or several species. 3. Despite substantial differences among streams and sites in all production attributes, when all data were pooled, annual (P_A) and year‐class production (P_T) and annual (P/B_A) and year‐class P/B_T ratios were tightly linked. Annual (P_A) and year‐class production (P_T) were similar but not identical, i.e. P_T = 0.94 P_A, whereas the P/B_T ratios were 4 + P/B_A ratios. 4. Recruitment (Rc) and mean annual density (N_A) were major density‐dependent drivers of production and their relationships were described by simple mathematical models. While year‐class production (P_T) was determined (R² = 70.1%) by recruitment (Rc), annual production (P_A) was determined (R² = 60.3%) by mean annual density (N_A). In turn, variation in recruitment explained R² = 55.2% of variation in year‐class P/B_T ratios, the latter attaining an asymptote at P/B_T = 6 at progressively higher levels of recruitment. Similarly, variations in mean annual density (N_A) explained R² = 52.1% of variation in annual P/B_A, the latter reaching an asymptote at P/B_A = 2.1. This explained why P/B_T is equal to P/B_A plus the number of year‐classes at high but not at low densities. 5. Site depth was a major determinant of spatial (among sites) variation in production attributes. All these attributes described two‐phase trajectories with site depth, reaching a maximum at sites of intermediate depth and declining at shallower and deeper sites. As a consequence, at sites where recruitment and mean annual density reached minimum or maximum values, annual (P_A) and year‐class production (P_T) and annual (P/B_A) and year‐class P/B_T ratios also reached minimum and maximum values.     

In vitro production of ovarian steroids in yellow perch (Perca flavescens): effects of photothermal manipulation, gonadotropin and phorbol ester

We investigated the capacity of ovaries of yellow perch to produce steroid hormones in vitro and the ovarian response to gonadotropin and phorbol ester during the annual reproductive cycle. The effects of photothermal manipulation on perch gonadal steroidogenesis and its regulation have also been examined. Initially, all females kept indoors were exposed to the same water temperature and photoperiod. By the end of August, following the first sampling, fish were submitted to different photothermal regimes. Group A was maintained under photothermal conditions characteristic for southern Ohio. Group B was submitted to a condensed light/temperature regime designed to accelerate physiological changes that depend on photothermal stimuli. In group A, basal in vitro production of ovarian estradiol (E2) was the highest in October and November, and hCG significantly stimulated E2 secretion during the entire period of vitellogenesis (October-January). In this group, the highest production of basal testosterone (T) was observed before spawning. hCG-stimulated production of T was highest at the beginning of vitellogenesis. Gonadotropin stimulated T production before spawning, a time when gonadotropin was unable to stimulate E2 production. Phorbol ester (PDBu) stimulated E2 and T production during vitellogenesis at the same time points as hCG did (E2: December, January; T: December). hCG-stimulated T production was not mimicked by PDBu in April. Condensing of the photothermal cycle resulted in diminished ovarian production of E2 during vitellogenesis. Moreover, the fish submitted to a condensed photothermal cycle demonstrated augmented T production during the postvitellogenic stage of ovarian development. Ovaries of group B did not respond to PDBu. Generally, the seasonal fluctuations in ovarian capacity to produce E2 and T as well as in gonadal responsiveness to gonadotropin observed in female yellow perch illustrate the dynamic nature of ovarian endocrine function. The lack of response to gonadotropin with regard to E2 production prior to spawning is not due to insensitivity to gonadotropin, but rather due to some deficiency in steroidogenesis (e.g. reduced aromatase activity). It appears also that ovarian steroidogenesis and its regulation are dependent on annual changes of photothermal conditions.     

Cigarette smoke upregulates rat coronary artery endothelin receptors in vivo

Background

Cigarette smoking is a strong cardiovascular risk factor and endothelin (ET) receptors are related to coronary artery diseases. The present study established an in vivo secondhand smoke (SHS) exposure model and investigated the hypothesis that cigarette smoke induces ET receptor upregulation in rat coronary arteries and its possible underlying mechanisms.

Methodology/Principal Findings

Rats were exposed to SHS for 200 min daily for 8 weeks. The coronary arteries were isolated and examined. The vasoconstriction was studied by a sensitive myograph. The expression of mRNA and protein for receptors was examined by real-time PCR, Western blot and immunofluorescence. Compared to fresh air exposure, SHS increased contractile responses mediated by endothelin type A (ET_A) and type B (ET_B) receptors in coronary arteries. In parallel, the expression of mRNA and protein for ET_A and ET_B receptors of smoke exposed rats were higher than that of animals exposed to fresh air, suggesting that SHS upregulates ET_A and ET_B receptors in coronary arteries in vivo. Immunofluorescence staining showed that the enhanced receptor expression was localized to the smooth muscle cells of coronary arteries. The protein levels of phosphorylated (p)-Raf-1 and p-ERK1/2 in smoke exposed rats were significantly higher than in control rats, demonstrating that SHS induces the activation of the Raf/ERK/MAPK pathway. Treatment with Raf-1 inhibitor GW5074 suppressed SHS-induced enhanced contraction mediated by ET_A receptors, and inhibited the elevated mRNA and protein levels of ET_A and ET_B receptors caused by SHS. The results of correlation and regression analysis showed that phosphorylation of Raf and ERK1/2 were independent determinants to affect protein expression of ET_B and ET_A receptors.

Conclusions/Significance

Cigarette smoke upregulates ET_B and ET_A receptors in rat coronary artery, which is associated with the activation of the Raf/ERK/MAPK pathway.     

Metabolic rate and cost of growth in juvenile pike (Esox lucius L.) and perch (Perca fluviatilis L.): the use of energy budgets as indicators of environmental change

Summary Energy budgets of juvenile pike and perch (weighing approximately 3 g) were determined in experiments lasting up to 4 days, by simultaneously measuring oxygen consumption, food consumption, and growth of individual fish. Although the basic pattern of energy allocation was identical in the two species, perch subjected to constant light (PEL) showed faster growth, higher assimilation and conversion efficiency, and higher oxygen consumption than perch subjected to a short daylength regime (PED). The efficiency with which food energy was converted into body mass was 39±5% in PED but 49±4% in PEL. However, the “work coefficient” (increment of body mass/post-prandial increase of oxygen consumption: mg · μmol O _inf2 ^sup−1 ) differed only insignificantly between the two groups of perch, indicating that the metabolic cost of growth was unaffected by the manipulation of experimental conditions. This identifies the higher assimilation efficiency, i.e. the increased flow of food energy into the tissues as being the cause of accelerated growth of perch under the constant-light regime. In both species the maximum feeding-induced metabolic rate was 4 times higher than the lowest preprandial rate. In perch (which were kept on low rations before the experiments) the post-prandial metabolic rate increased steadily from day to day during the 4-day experiments, so that on the last day the rate of oxygen consumption exceeded the rate on the first day by about 41%. This investigation provides further evidence that the allocation of metabolic energy in fish is based on a flexible strategy which responds sensitively to changes in both internal and external conditions.     

Retina-specific LDH isozyme in blueback herring, Alosa aestivalis (Mitchell), and alewife, Aiosa pseudoharengus (Wilson)

The retina of 390 Alosa aestivalis and 410 Alosa pseudoharengus have been examined by means of starch-gel electrophoresis. The retina-specific E₄ isozyme has been found to occur in all the fish examined. This study demonstrates for the first time that the E₄ isozyme occurs in A. aestivalis. Because the E₄ isozyme is not polymorphic and has an identical mobility in A. pseudoharengus and in A. aestivalis it is neither suitable for use as a species identification characteristic nor a population marker. Alosa aestivalis and Alosa pseudoharengus are two commercially important ana-dromous species of fish in New Brunswick, Canada. These two species may occur together in the same spawning runs but w^rhile A. pseudoharengus has a wide distribution along the East coast of North America (Leim & Scott, 1966) A. aestivalis occurs in a very limited area in Canada where it is at the northern limit of its range and because of increasing threat of pollution has been listed by McAllister (1970) as one of 17 endangered species. These two species of fish are morphologically very similar and can only be separated by the colour of the abdominal peritoneum (Leim & Scott, 1966). McKenzie (1973) has compared these two species by means of protein electrophoresis and found that while the muscle myogen patterns were species specific, the LDH patterns were the same in both species. He described these two species as five isozyme fish showing the LDH isozymes A₄, A₃B, A₂B₂, AB₃ and B₄. Since Horowitz & Whitt (1972) have reported the presence of the E₄ isozyme in the retina of some teleosts including. A. pseudoharengus but not including A. aestivalis, I considered it worth-while to re-examine A. aestivalis and A. pseudoharengus to find out whether A. aestivalis possessed this isozyme and, if so, whether the mobility of the isozyme could be used as a species identification characteristic and as a population marker. The fish used in this study were collected from five different locations during the 1971 spring migration period and held deep frozen for eight months before they were examined. They were identical to the specimens used for the study reported by McKenzie (1973) where the collection dates, numbers of fish and geographic locations are given. One eyeball from each of 390 A. aestivalis and 410 A. pseudoharengus was removed. Each eyeball was homogenized in 10 drops of distilled water and allowed to stand for one hour at 4^oC. The samples were then centrifuged for 10 min at 12 000 g. The supernatants were used immediately for vertical starch-gel electrophoresis. The apparatus used was that described by Boyer & Hiner (1963). The conditions of electrophoresis were the same as used by Saunders & McKenzie (1971). The LDH bands were stained by the deposition of blue formazan dyes in the regions of LDH activity. The stain formula and details of methods are given in Whitt (1970). The LDH isozyme patterns of all the fish examined were identical. The location of the isozymes A₄, A₃B, A₂B₂, AB₃ and B₄ are indicated in Fig. 1. A₄ is abundant in muscle while B₄ is abundant in heart. Because the LDH subunits assemble preferentially into homodimeric pairs before forming tetramers (Markert & Ursprung, 1971). A₄. A₂B₂ and B₄ show up in electropherograms as strong bands while A₃B and AB₃ show up as weak bands. The retina-specific isozyme E₄ is shown between B₄ and AB₃. Whitt (1970) has already demonstrated that A. pseudoharengus is a five isozyme fish. This has been confirmed by McKenzie (1973) who also compared both A. pseudoharengus and A. aestivalis and found these five isozymes had identical mobilities in both species of fish. The present study demonstrates for the first time that the retina-specific E₄ occurs in A. aestivalis where it has the same electro-phoretic mobility as that of A. pseudoharengus. The patterns are the same and do not appear to vary with geographic origin of the fish. The reason why the presence of the E₄ isozyme was demonstrated in the present study and not in the previous one (McKenzie, 1973) is because of the method used. In that study the migration length was not long enough to sufficiently separate the enzymes. In the present study vertical starch-gel electrophoresis which allows for long migration distances was used. As has already been shown for the A-B isozymes (McKenzie, 1973), the E₄ isozyme is not polymorphic in these two species of fish. It therefore has no use as apopulation marker. Because the E₄ isozyme has an identical mobility in both species of fish, it cannot be used as a species identification characteristic.     

A2B adenosine receptor blockade inhibits growth of prostate cancer cells

The role of the A_2B adenosine receptor (AR) in prostate cell death and growth was studied. The A_2B AR gene expression quantified by real-time quantitative RT-PCR and Western blot analysis was the highest among four AR subtypes (A₁, A_2A, A_2B, and A₃) in all three commonly used prostate cancer cell lines, PC-3, DU145, and LNCaP. We explored the function of the A_2B AR using PC-3 cells as a model. The A_2B AR was visualized in PC-3 cells by laser confocal microscopy. The nonselective A_2B AR agonist NECA and the selective A_2B AR agonist BAY60-6583, but not the A_2A AR agonist CGS21680, concentration-dependently induced adenosine 3′,5′-cyclic monophosphate (cyclic AMP) accumulation. NECA diminished lactate dehydrogenase (LDH) release, TNF-α-induced increase of caspase-3 activity, and cycloheximide (CHX)-induced morphological changes typical of apoptosis in PC-3 cells, which were blocked by a selective A_2B AR antagonist PSB603. NECA-induced proliferation of PC-3 cells was diminished by siRNA specific for the A_2B AR. The selective A_2B AR antagonist PSB603 was shown to inhibit cell growth in all three cell lines. Thus, A_2B AR blockade inhibits growth of prostate cancer cells, suggesting selective A_2B AR antagonists as potential novel therapeutics.     

Cerebrospinal Fluid from Patients with Subarachnoid Haemorrhage and Vasospasm Enhances Endothelin Contraction in Rat Cerebral Arteries

Introduction

Previous studies have suggested that cerebrospinal fluid from patients with subarachnoid hemorrhage (SAH) leads to pronounced vasoconstriction in isolated arteries. We hypothesized that only cerebrospinal fluid from SAH patients with vasospasm would produce an enhanced contractile response to endothelin-1 in rat cerebral arteries, involving both endothelin ET_A and ET_B receptors.

Methods

Intact rat basilar arteries were incubated for 24 hours with cerebrospinal fluid from 1) SAH patients with vasospasm, 2) SAH patients without vasospasm, and 3) control patients. Arterial segments with and without endothelium were mounted in myographs and concentration-response curves for endothelin-1 were constructed in the absence and presence of selective and combined ET_A and ET_B receptor antagonists. Endothelin concentrations in culture medium and receptor expression were measured.

Results

Compared to the other groups, the following was observed in arteries exposed to cerebrospinal fluid from patients with vasospasm: 1) larger contractions at lower endothelin concentrations (p<0.05); 2) the increased endothelin contraction was absent in arteries without endothelium; 3) higher levels of endothelin secretion in the culture medium (p<0.05); 4) there was expression of ET_A receptors and new expression of ET_B receptors was apparent; 5) reduction in the enhanced response to endothelin after ET_B blockade in the low range and after ET_A blockade in the high range of endothelin concentrations; 6) after combined ET_A and ET_B blockade a complete inhibition of endothelin contraction was observed.

Conclusions

Our experimental findings showed that in intact rat basilar arteries exposed to cerebrospinal fluid from patients with vasospasm endothelin contraction was enhanced in an endothelium-dependent manner and was blocked by combined ET_A and ET_B receptor antagonism. Therefore we suggest that combined blockade of both receptors may play a role in counteracting vasospasm in patients with SAH.     

Synthesis of novel 1-alkyl-8-substituted-3-(3-methoxypropyl) xanthines as putative A2B receptor antagonists

In order to identify a high-affinity, selective antagonist for the A_2B subtype adenosine receptor, more than 40 1,8-disubstituted-3-(3-methoxypropyl) xanthines were prepared and evaluated for their binding affinity at recombinant human adenosine receptors, mainly of the A_2A and A_2B subtypes. Some of the 1-ethyl-3-(3-methoxypropyl)-8-aryl substituted derivatives 15(a–m) showed moderate-to-high affinity at human A_2B receptors, with compound 15d showing A_2B selectivity over the other A receptors assayed (A₁, A_2A, A₃) of 34-fold or over.     

Postendocytic vitellin processing in ovarian follicles of the stick insect Carausius morosus (Br.)

Newly laid eggs of the stick insect Carausius morosus contain two native vitellins (Vit A and Vit B). Under denaturing conditions, these vitellins resolved into 3 (A₁, A₂, and A₃) and 2 (B₁ and B₂) polypeptides. All of these polypeptides had counterparts in the female hemolymph from which they were shown to be derived by in vivo labelling. During ovarian development, the 2 vitellins changed both in charge and polypeptide composition. In EV and LV follicles, Vit A resolved into 4 distinct vitellin polypeptides (A₀, A₁, A₂ and A₃). Using a panel of monoclonal antibodies, polypeptide A₀ proved to be immunologically related to polypeptide A₂. In follicles about to begin choriongenesis, polypeptide A₃ was gradually replaced by a lower M_r polypeptide. Over the same time period, polypeptide B₁ changed in charge, but not in M_r. To confirm the existence of a polypeptide processing in C. morosus, ovarian follicles of different developmental stages were exposed in vivo to [³⁵S]-methionine from 6 to 72 h. Data showed that A₀ and B₁ were the polypeptides most heavily labelled after short time exposures to the radioisotope. Polypeptides B₂ and A₃ were also labelled to some extent. With progressively longer exposures, polypeptides A₁ and A₂ also became labelled. In vivo exposure to [³H]-GlcNAc caused all vitellin polypeptides to become heavily labelled. Autoradiographic analysis of ovarian follicles labelled this way showed that, during development, radioactivity was gradually transferred from newly formed yolk spheres in the cortical ooplasm to the central ooplasm. Data were interpreted as suggesting a causal relationship between polypeptide processing and progressive yolk sphere fusion to yield the central ooplasm. © 1993 Wiley-Liss, Inc.     

Laboratory evaluation of two bioenergetics models applied to yellow perch: identification of a major source of systematic error

Laboratory growth and food consumption data for two size classes of age 2 year yellow perch Perca flavescens , each fed on two distinct feeding schedules at 21° C, were used to evaluate the abilities of the Wisconsin (WI) and Karas–Thoresson (KT) bioenergetics models to predict fish growth and cumulative consumption. Neither model exhibited consistently better performance for predicting fish body masses across all four fish size and feeding regime combinations. Results indicated deficiencies in estimates of resting routine metabolism by both models. Both the WI and KT models exhibited errors for predicting growth rates, which were strongly correlated with food consumption rate. Consumption-dependent prediction errors may be common in bioenergetics models and are probably the result of deficiencies in parameter values or assumptions within the models for calculating energy costs of specific dynamic action, feeding activity metabolism or egestion and excretion. Inter-model differences in growth and consumption predictions were primarily the result of differences in egestion and excretion costs calculated by the two models. The results highlighted the potential importance of parameters describing egestion and excretion costs to the accuracy of bioenergetics model predictions, even though bioenergetics models are generally regarded as being insensitive to these parameters. The findings strongly emphasize the utility and necessity of performing laboratory evaluations of all bioenergetics models for assurance of model accuracy and for facilitation of model refinement.     

Acidification affects the perch,Perca fluviatilis,populations in small lakes,of southern Finland

Synopsis Characteristics of perch were studied in 4 recently acidified lakes in southern Finland. The densities of the populations were 0–250 ha^–1 compared with 1400–3300 ha^–1 in two circumneutral reference lakes. The perch were close to extinction in one acidic lake and dominated by 7 year old fish in two other acidic lakes, suggesting decreased reproduction. Individual fecundity was not reduced by the acidity, but high mortality (close to 100%) of eggs in two acidic lakes indicated recruitment failure. In one of the acidified lakes reproduction had continued resulting in a population dominated by younger fish. However, increased egg mortality, low density, and the resulting high growth rate of perch in this lake were considered to be consequences of the acidity. These findings are the first documentation on the possible decrease of fish populations in Finland due to acid precipitation.     

The population dynamics of pike,Esox lucius,and perch,Perca fluviatilis,in a simple predator-prey system

Synopsis The population dynamics and predator-prey relationship of pike, Esox lucius, and perch, Perca fluviatilis, were examined in simple fish communities in two adjacent shallow lakes, Lochs Kinord and Davan, Deeside, Scotland. Few perch survive to age 3 but Z is low for fish > 3 years and perch live up to 17 years. Population fecundity remained relatively high and constant in perch because of the multi-age spawning stock and the presence of older more fecund perch. Growth rates of perch in both lochs are relatively high as a consequence of low stock abundance. The N, B, and P of adult perch were unusually low. The age range of pike, and N, B, P, and growth were in the range of values reported elsewhere. There was little variation in the strength of pike year classes and the importance of cannibalism and low occurrence of alternative prey in the lochs suggest that the populations were self-regulating. Cannibalism by adults was responsible for most of mortality in perch larvae, and predation by pike and adult perch was responsible for the majority of juvenile losses. This conclusion is supported by the high biomass ratios of pike:juvenile perch of 1.0–30.8. While the number of adult fish was almost equal, the biomass of adult pike was 2–3 × that of perch in Kinord and 6 × in Davan. In L. Kinord, where year class strength was stable, high predation pressure from perch and pike reduced perch abundance rather than eliminated year classes. Perch year classes fluctuated in abundance in L. Davan and were eliminated in the first summer in two sampling years. The pike, and particularly the perch populations, have features characteristic of fish communities in unperturbed ecosystems: namely, a wide range of age classes, stability in biomass with variation dampened by longevity, and low production.     

Subunit Structure of Soybean 11S Globulin

The acidic and the basic subunits were shown to be present in equimolar amounts in the 11S globulin molecule by the densitometric scanning of the SDS gel and the molecular weight consideration. The four acidic subunits (A₁, A₂, A₃ and A₄) were found to be present in the approximate molar ratio of 1:1:2:2. Four basic subunits separated and designated as B₁, B₂, B₃ and B₄ based on the relative mobilities in the acidic gel in 7 m urea were found to be present in the approximate molar ratio of 1:1:2:2. The four basic subunits were fractionated in approximately same amounts into three different peaks, peak I (B₁ and B₂), peak II (B₃) and peak III (B₄) by CM-Sephadex C–50 column chromatography in the presence of 6 m urea. Three kinds of intermediary subunits of 11S globulin were fractionated with DEAE-Sephadex A–50 in the absence of reducing agents in 6 m urea, and disulfide bonds appeared to participate in the binding between the acidic and the basic subunits in the molar ratio of 1: 1 with the following combinations; A₁ and A₂ combined with B₃, A₃ with B₁ and B₂, and A₄ with B₄. In view of the above results and molecular weight consideration, a new model of subunit structure was proposed for 11S globulin.     

The formation of improved tetraploid population of red crucian carp × common carp hybrids by androgenesis

Bisexual fertile diploid androgenetic individuals (A₀) (2n=100) were formed by androgenesis. In this way, the diploid spermatozoa from male allotetraploid hybrids (AT) (4n=200) of red crucian carp (Carassius auratus red var.) (♀) × common carp (Cyprinus carpio L.) (♂) were used to fertilize the UV-treated haploid eggs of goldfish (Carassius auratus), and living androgenetic diploid fish were developed. The A₀ became sexually mature at the age of 2 years, and they fertilized with each other to form their offspring (A₁). In this study, we observed the chromosomal number, gonadal structure and appearance of A₁ fish. The results are as follows: (1) In A₁, there were 85% tetraploids (A₁-4n), 10% triploids (A₁-3n) and 5% diploids (A₁-2n), suggesting that diploid A₀ could produce diploid gametes. It was concluded that the formation of diploid gametes generated from diploid A₀ was probably related to the mechanism of pre-meiotic endoreduplication. (2) Among A₁, only A₁-4n possessed normal ovaries and testes. The mature males of A1-4n produced white semen. Under the electron microscope, the head of diploid sperm generated by A₁-4n was bigger than that of haploid sperm generated by red crucian carp. In the testes of the A₁-4n, there were many mature normal spermatozoa with a head bearing plasma membrane and a tail having the typical structure of “9+2” microtubules. Between the head and the tail, there were some mitochondria. The ovaries of A₁-4n developed well and mainly contained II, III and IV-stage oocytes. The IV-stage oocytes were surrounded by inner and outer follicular cells. The micropyle was observed on the oolemma of follicular cells. There were abundant yolks and plenty of endoplasmic reticulum in the cytoplasm of IV-stage oocytes. Because A₁-2n and A₁-3n were distant crossing diploid hybrids and triploid hybrids respectively, they possessed abnormal gonads, and no mature semen and eggs were observed. (3) Compared with allotetraploids, the A₁-4n fish not only had advantages such as fast growth rate and strong resistibility but also showed some new good performances such as high ratio of body width to body length, smaller heads and shorter tails. These results indicated that androgenesis could produce bisexual fertile tetraploids and improve the shape of allotetraploid hybrids as well, which will be of great significance in both the cell genetics research and fish breeding.     

The formation of improved tetraploid population of red crucian carp × common carp hybrids by androgenesis

Bisexual fertile diploid androgenetic individuals (A0) (2n=100) were formed by androgenesis. In this way, the diploid spermatozoa from male allotetraploid hybrids (AT) (4n=200) of red crucian carp (Carassius auratus red var.) (♀) × common carp (Cyprinus carpio L.) (♂) were used to fertilize the UV-treated hap- loid eggs of goldfish (Carassius auratus), and living androgenetic diploid fish were developed. The A0 became sexually mature at the age of 2 years, and they fertilized with each other to form their offspring (A1). In this study, we observed the chromosomal number, gonadal structure and appearance of A1 fish. The results are as follows: (1) In A1, there were 85% tetraploids (A1-4n), 10% triploids (A1-3n) and 5% diploids (A1-2n), suggesting that diploid A0 could produce diploid gametes. It was concluded that the formation of diploid gametes generated from diploid A0 was probably related to the mechanism of pre-meiotic endoreduplication. (2) Among A1, only A1-4n possessed normal ovaries and testes. The mature males of A1-4n produced white semen. Under the electron microscope, the head of diploid sperm generated by A1-4n was bigger than that of haploid sperm generated by red crucian carp. In the testes of the A1-4n, there were many mature normal spermatozoa with a head bearing plasma mem- brane and a tail having the typical structure of "9 2" microtubules. Between the head and the tail, there were some mitochondria. The ovaries of A1-4n developed well and mainly contained II, III and IV-stage oocytes. The IV-stage oocytes were surrounded by inner and outer follicular cells. The micropyle was observed on the oolemma of follicular cells. There were abundant yolks and plenty of endoplasmic reticulum in the cytoplasm of IV-stage oocytes. Because A1-2n and A1-3n were distant crossing diploid hybrids and triploid hybrids respectively, they possessed abnormal gonads, and no mature semen and eggs were observed. (3) Compared with allotetraploids, the A1-4n fish not only had advantages such as fast growth rate and strong resistibility but also showed some new good performances such as high ratio of body width to body length, smaller heads and shorter tails. These results indicated that an- drogenesis could produce bisexual fertile tetraploids and improve the shape of allotetraploid hybrids as well, which will be of great significance in both the cell genetics research and fish breeding.