Elevated growth temperatures reduce the carbon gain of black spruce [Picea mariana (Mill.) B.S.P.]

We explored the effect of high‐growth temperatures on a dominant North American boreal tree, black spruce [Picea mariana (Mill.) B.S.P.]. In 2004 and 2005, we grew black spruce at either 22 °C/16 °C day/night temperatures [low temperature (LT)] or 30°/24 °C [high temperature (HT)] and determined how temperature affected growth, leaf morphology, photosynthesis, respiration and thermotolerance. HT spruce were 20% shorter, 58% lighter, and had a 58% lower root : shoot ratio than LT trees. Mortality was negligible in the LT treatment, but up to 14% of HT seedlings died by the end of the growing season. HT seedlings had a higher photosynthetic temperature optimum, but net photosynthesis at growth temperatures was 19–35% lower in HT than LT trees. HT seedlings had both a lower apparent maximum ribulose‐1,5‐bisphosphate carboxylation capacity (V_cmax) and a lower apparent maximum electron transport rate (J_max) than LT trees, indicating reduced allocation to photosynthetic components. Consistently, HT needles had 26% lower leaf nitrogen content than LT needles. At each measurement temperature, HT seedlings had 20–25% lower respiration rates than LT trees; however, this did not compensate for reduced photosynthetic rates at growth temperature, leading to a greater ratio of dark respiration to net carbon dioxide assimilation rate in HT trees. HT needles had 16% lower concentrations of soluble sugars than LT needles, but similar starch content. Growth at high temperatures increased the thermotolerance of black spruce. HT trees showed less PSII inhibition than LT seedlings and no increase in electrolyte leakage when briefly exposed to 40–57 °C. While trees that develop at high temperatures have enhanced tolerance for brief, extreme heat events, the reduction in root allocation indicates that seedlings will be more susceptible to episodic soil drying and less competitive for belowground resources in future climates of the boreal region.     

Transcriptome analysis of the response of silkworm to drastic changes in ambient temperature

Bombyx mori is a poikilothermic insect and is economically important for silk production. Drastic changes in the ambient temperature have a negative impact on sericulture. However, the reason as to why high temperature is associated with the occurrence of diseases in silkworm and the response of silkworm to low temperature remain unclear and were the focus of the present study. Dazao silkworm exposed to 13 °C (DZ-13), 25 °C (DZ-25), and 37 °C (DZ-37) were used for RNA-seq analysis. There were 478 and 194 upregulated differentially expressed genes (DEGs) in DZ-13 and DZ-37 while 49 and 273 downregulated DEGs in DZ-13 and DZ-37, respectively. Eight DEGs were co-upregulated, in which seven genes were for heat shock proteins (Hsps), implying that Hsps play important roles in the tolerance of silkworm to high and low temperature. Gene ontology analysis revealed that the developmental process was downregulated in DZ-13. All the DEGs in the oxidative phosphorylation and insulin signaling pathways were upregulated in DZ-13. Several cuticular proteins and ATP synthesis-related genes were upregulated in DZ-13, suggesting that thickening of the cuticle and increase in the ATPase expression would help silkworms to protect themselves from low temperature-induced stress. Several immune-related genes, such as BmRel and BmSerpin-2, were downregulated in DZ-37, revealing that the resistance of silkworm is decreased under high temperature shock resulting in susceptibility to pathogens. Thus, the increase in the thermo-tolerance of silkworm should be related to the enhancement in the pathogen resistance.

     

Leptin and Nitric Oxide Production in Normotensive and Hypertensive Men

Objective: Recent findings have shown that leptin, the product of the obesity gene, may actively participate in the regulation of blood pressure and other cardiovascular functions through the nitric oxide (NO)‐dependent mechanism. Research Methods and Procedures: In this study, to test the hypothesis that leptin regulation of NO metabolism is impaired in hypertension, we examined the possible relationship between circulating leptin and plasma NO metabolite level in normotensive (NT) and hypertensive (HT) men. Results: There were significant correlations between circulating leptin and BMI in both the NT and HT groups (NT: r = 0.64, n = 26, p < 0.01; HT: r = 0.59, n = 22, p < 0.01). The concentration of circulating leptin was similar between the NT and HT men, although the plasma NO metabolite level (nitrite and nitrate) was significantly reduced in the HT men compared with the NT men (NT: 51.0 ± 4.9 μM, n = 26; HT: 37.1 ± 2.5 μM, n = 22, p < 0.05). The circlating leptin was significantly correlated with the plasma NO metabolite level in the overall analysis of the NT and HT men (r = 0.35, n = 48, p < 0.05). When the analysis of the correlation for the NT and HT men was performed separately, there was a significant correlation between circulating leptin and plasma NO metabolites in the NT men (r = 0.45, n = 26, p < 0.05) but not in the HT men (r = 0.15, n = 22). The results of this study are consistent with the hypothesis that leptin‐related metabolism of NO might be altered in HT men.     

Development of a Rapid and Efficient Method for Non-Lethal DNA Sampling and Genotyping in Scallops

Non-lethal DNA sampling has long appealed to researchers studying population and conservation genetics, as it does not necessitate removing individuals permanently from their natural environment or destroying valuable samples. However, such an approach has not yet been well established in bivalves. In this study, we demonstrate that the gill represents a good source of tissue for non-lethal sampling in scallops. Removal of a few gill filaments caused no noticeable behavioral abnormalities or increased mortality rates in Zhikong scallop (Chlamys farreri) during a three-month period of observation. To facilitate rapid gill-based DNA extraction, six methods (MA-MF) were designed and evaluated, each requiring less than one hour of processing time. The optimal method was identified as MF, in terms of maintaining DNA integrity and genotyping accuracy. Further optimization of MF method by orthogonal experimental design suggested that the utilization of gills could be limited to 2 mg of sample, which is sufficient for performing up to 20,000 PCR reactions. We also demonstrate the excellent cross-species utility of MF in two additional scallop species, Yesso scallop (Patinopecten yessoensis) and bay scallop (Argopecten irradians). Taken together, our study provides a rapid and efficient approach for applying non-lethal DNA sampling in bivalve species, which would serve as a valuable tool for maintaining bivalve populations and conservation genetics, as well as in breeding studies.     

Characterization of new Caenorhabditis elegans strains with high and low thermotolerance

The strains of Caenorhabditis elegans displaying low (LT) and high (HT1, HT2, and HT3) thermotolerance were obtained from the wild-type N2 strain by artificial selection for thermostability of locomotion and by natural selection in laboratory for thermotolerance of fertility under tolerable environmental temperature elevation. All these strains are new genetic variants that emerged during the experiment. The worms of strains HT2 and HT3 displayed an elevated upper temperature limit for reproduction (from 26 to 27.5°C), thermostability of locomotion at 36°C, and survival at 37°C as compared with the strain N2. The results have demonstrated that adaptation of C. elegans to high tmeperatures is an appropriate laboratory model for studying the mechanisms involved in the evolution of thermotolerance of poikilothermic Metazoa.     

Purification and characterization of a chloride ion-dependent α-glucosidase from the midgut gland of Japanese scallop (Patinopecten yessoensis)

Marine glycoside hydrolases hold enormous potential due to their habitat-related characteristics such as salt tolerance, barophilicity, and cold tolerance. We purified an α-glucosidase (PYG) from the midgut gland of the Japanese scallop (Patinopecten yessoensis) and found that this enzyme has unique characteristics. The use of acarbose affinity chromatography during the purification was particularly effective, increasing the specific activity 570-fold. PYG is an interesting chloride ion-dependent enzyme. Chloride ion causes distinctive changes in its enzymatic properties, increasing its hydrolysis rate, changing the pH profile of its enzyme activity, shifting the range of its pH stability to the alkaline region, and raising its optimal temperature from 37 to 55 °C. Furthermore, chloride ion altered PYG’s substrate specificity. PYG exhibited the highest V_max/K_m value toward maltooctaose in the absence of chloride ion and toward maltotriose in the presence of chloride ion.     

Assessment of the state of the Japanese scallopMizuhopecten yessoensis in Alekseeva Bight (Peter the Great Bay, Sea of Japan) based on morphological and biochemical parameters

The results of an integrated examination of the state of the scallopMizuhopecten yessoensis in Alekseeva Bight (Peter the Great Bay, Sea of Japan) are presented. In mollusks of different ages, shell height was measured; in animals of commercial size (over 100 mm), some size and weight characteristics (annual increment of shell and adductor muscle and soft tissue weight) were determined. The morphology of the digestive gland and gills was studied. In the adductor muscle and digestive gland, the concentration of heavy metals (HMs) (Hg, Cu, Zn, Mn, Pb, Cd, Ni, Co, and Cr) was determined. In the digestive gland, metallothionein and reduced glutathione concentration was also determined, as was the activity of glutathione-dependent enzymes (glutathione peroxidase and glutathione reductase). In scallops collected outside Alekseeva Bight, the linear growth rate and adductor muscle weight were on average 1.3 and 1.7 times greater, respectively, than in those collected in the bight. In scallop organs, numerous histomorphological alterations were revealed: digestive cell vacuolization and hemocyte infiltration of the digestive gland, hyperplasia and vacuolization of the respiratory epithelium, and connective tissue hypertrophy in gill filaments. The biochemical parameters of scallops from Alekseeva Bight differed substantially from those of mollusks collected outside the bight. We conclude that one of the factors negatively affecting the state of theM. yessoensis population in Alekseeva Bight is the contamination of the bight with HMs, especially mercury. This is consistent with the results of chemical analysis of bottom sediments and tissues of two mytilid species,Modiolus kurilensis andCrenomytilus grayanus, specimens of which were collected in the bight together with the scallops [3].     

Bama miniature pigs’ liver possess great heat tolerance through upregulation of Nrf2-mediated antioxidative enzymes

The liver is one of the most crucial organs affected by high ambient temperature. Bama miniature pig show a heat tolerance in hot summer months. However, the physiological condition of liver under high ambient temperature has not been well elucidated in Bama miniature pig. Here we performed an experiment to investigate the effects of high ambient temperature on liver function, redox status and Nrf2 antioxidant pathway in Bama miniature pigs. Twelve pigs were randomly divided into two groups and separately exposed to the neutral temperature (NT, 25 °C) and high temperature (HT, 40 °C) for 8 days. The hepatic damage marker, such as total bilirubin (TBIL), alkaline phosphatase (AKP), γ-glutamyl transpeptidas (γ-GT), alanine transaminase (ALT) and aspartase transminase (AST), didn’t reach statistical significance between NT and HT group. Moreover, abnormal observation of hepatic histology and hepatocyte ultrastructure were not detected in HT group. The activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) as well as glutathione (GSH) content, were dramatically increased after heat exposure. Heat treatment didn’t increase hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) concentrations. The expression of Nrf2-regulated genes, such as nuclear factor erythroid 2-related factor 2 (Nrf2), NAD(P)H: quinine oxidoreductase 1 (NQO1), superoxide dismutase 1 (SOD1), heme oxygenase-1 (HO-1) and glutamate cysteine ligase catalytic subunit (GCLC), were significantly increased in HT group. Nrf2 protein was accumulated in HT group through immunohistochemical analysis. The current data provide clear evidence that Bama miniature pigs’ liver possess great capacity of heat tolerance, which related to activation of Nrf2 antioxidant pathway.     

High environmental temperature and low pH stress alter the gill phenotypic plasticity of Hoven's carp Leptobarbus hoevenii

Climate warming and low pH environment are known to negatively impact all levels of aquatic organism from cellular to organism and population levels. For ammonotelic freshwater species, any abiotic factor fluctuation will cause disturbance to the fish, specifically at the gills which act as a multifunctional organ to support all biological processes. Therefore, this study was designed to investigate the effect of temperature (28 vs. 32°C) and pH (7.0 vs. 5.0) stress on the gill plasticity of Hoven's carp after 20 days of continuous exposure. The results demonstrated that high temperature and low pH caused severe changes on the primary and secondary lamellae as well as the cells within lamellae. An increasing trend of the proportion available for gas exchange was noticed at high temperature in both pH exposures, which resulted from a reduction of the primary lamellae width with elongated and thinner secondary lamellae compared to fishes at ambient temperature. Following exposure to high temperature and acidic pH, Hoven's carp experienced gill modifications including aneurysm, oedema, hypertrophy, curling of secondary lamellae, epithelial lifting, hyperplasia and lamellae fusion. These modifications are indicators of the coping mechanism of Hoven's carp to the changing environment in order to survive.     

Temperature-dependent changes in energy metabolism, intracellular pH and blood oxygen tension in the Atlantic cod

The effect of acute increase in temperature on oxygen partial pressure (Po ₂) was measured in the gill arches of Atlantic cod Gadus morhua between 10 and 19° C by use of oxygen microoptodes. Oxygen saturation of the gill blood under control conditions varied between 90 and 15% reflecting a variable percentage of arterial or venous blood in accordance with the position of each optode in the gill arch. The data obtained suggested that arterial Po₂ remained more or less constant and arterial oxygen uptake did not become limiting during warming. A progressive drop in venous Po₂, however, was observed at >10° C indicating that excessive oxygen uptake from the blood is not fully compensated for by circulatory performance, until finally, Po₂ levels fully collapse. In a second set of experiments energy and acid–base status of white muscle of Atlantic cod in vivo was measured by magnetic resonance (³¹P‐NMR) spectroscopy in unanaesthetized and unimmobilized fish in the temperature range between 13 and 21° C. A decrease in white muscle intracellular pH (pH_i) with temperature occurred between 10 and 16° C (ΔpH per ° C = ?0·025 per ° C). In white muscle temperature changes had no influence on high‐energy phosphates such as phosphocreatine (PCr) or ATP except during exposure to high critical temperatures (>16° C), indicating that white muscle energy status appears to be relatively insensitive to thermal stress if compared to the thermal sensitivity of the whole animal. The data were consistent with the hypothesis of an oxygen limitation of thermal tolerance in animals, which is set by limited capacity of oxygen supply mechanisms. In the case of Atlantic cod circulatory rather than ventilatory performance may be the first process to cause oxygen deficiency during heat stress.     

Effects of changing temperature regimes on resistance to races of Melampsora medusae in a cultivar of poplar

Leaf discs of Populus deltoides cv. W-79/307 inoculated with race 4–C of Melampsora medusae, give a compatible reaction when incubated at 16°C (LT), but an incompatible reaction at 26°C (HT). When, over a 12–day period, sets of inoculated leaf discs were reciprocally transferred between the temperature regimes (LT to HT, or HT to LT), incubation for as short as 15 h at HT resulted in incompatibility which was not reversed by subsequent incubation at LT. In contrast, incubation of the inoculated discs at LT for at least 4 days was necessary for the development of a compatible reaction following transfer to HT. Further, incompatibility induced in discs by inoculation with race 4–C and incubation at HT is epistatic to expected compatibility following subsequent inoculation with race 4–M, a temperature non-sensitive biotype. The rapidity, irreversibility and epistatic nature of the temperature-induced incompatibility suggests that initial recognition in this pathosystem may be for incompatibility. The significance of these results in this host/pathogen system is discussed.     

Quantitative histopathology of Oreochromis niloticus gills after copper exposure

In order to test whether histopathological changes of gills demonstrated a good dose–response relationship with water copper levels, juvenile Nile tilapia Oreochromis niloticus, of both sexes and similar mass (36·3 + 7·7 g), were kept in dechlorinated tap water (temperature 25° C, range ±1° C; pH 6·5–7·5; hardness 74·5 mg l^?1 CaCO₃) and exposed to 40 and 400 μg l^?1 of copper. Gill samples were collected after 3, 7, 14 and 21 days. Six major histopathological changes (oedema, lifting, changes in filament epithelium thickness, lamellar fusion, vasodilatation and aneurisms) and three minor ones (proliferation of the lamellar epithelium, necrosis and adjacent lamellar fusion) were found and their prevalence estimated. The extent and severity of each histopathological change were used to develop a severity gradation scale (SGS). Semi‐quantitative analysis of the histopathological changes and measurements of gill copper deposition levels revealed a good dose– and time–response relationship. Oedemas and aneurisms were significantly correlated with acute exposure periods and lamellar fusion with chronic exposure. Epithelial lifting and changes in filament epithelial thickness were seen at lower and higher metal concentrations, respectively. The data also revealed that the SGS profile of each lesion was dependent of gill copper burden.     

The distribution, size and age compositions, and growth of the scallop Mizuhopecten yessoensis (Bivalvia: Pectinidae) in the northwestern Tatar Strait

The distribution patterns, size, age structure, and growth of the scallop Mizuhopecten yessoensis were studied in the northwest of the Tatar Strait, Sea of Japan. We determined that the northern boundary of the species range occurred in the region of Tabo Bay, at 51°37?? N. The distribution of the mollusk, depending on latitude, depth, substrate, and age, was determined. The maximum depth of M. yessoensis habitat is 138 meters, the maximum shell height is 200 mm, and the maximum age is 14 years. The differences in the growth rate of the Japanese scallop in different areas are discussed in relation to the conditions of its habitat in the northern part of its range.     

The effects of gill remodeling on transepithelial sodium fluxes and the distribution of presumptive sodium-transporting ionocytes in goldfish (Carassius auratus)

Goldfish, Carassius auratus, adaptively remodel their gills in response to changes in ambient oxygen and temperature, altering the functional lamellar surface area to balance the opposing requirements for respiration and osmoregulation. In this study, the effects of thermal- and hypoxia-mediated gill remodeling on branchial Na⁺ fluxes and the distribution of putative Na⁺-transporting ionocytes in goldfish were assessed. When assessed either in vitro (isolated gill arches) or in vivo at a common water temperature, the presence of an interlamellar cell mass (ILCM) in fish acclimated to 7°C clearly decreased Na⁺ efflux across the gill relative to fish maintained at 25°C and lacking an ILCM. However, loss of the ILCM in 7°C-acclimated fish exposed to hypoxia led to a decrease in Na⁺ efflux (assessed under hypoxic conditions) despite the apparent large increases in functional lamellar surface area. Goldfish possessing an ILCM were able to sustain Na⁺ uptake, albeit at a lower rate matched to efflux, owing to the re-distribution of ionocytes expressing genes thought to be involved in Na⁺ uptake [Na⁺/H⁺ exchanger isoform 3 (NHE3) and V- type H⁺-ATPase] to the edge of the ILCM where they can establish contact with the surrounding environment. NHE-expressing cells co-localized with Na⁺/K⁺-ATPase expression, suggesting a role for NHE in Na⁺-uptake in the goldfish. Implications of the ILCM on ion fluxes in the goldfish are discussed.