Animal Respiration Research Articles

Impact of Pestarella tyrrhena on benthic metabolism in sediment microcosms enriched with seagrass and macroalgal detritus

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 281:165-179 (2004) - doi:10.3354/meps281165 Impact of Pestarella tyrrhena on benthic metabolism in sediment microcosms enriched with seagrass and macroalgal detritus Sokratis Papaspyrou1,*, Maria Thessalou-Legaki1, Erik Kristensen2 1Department of Zoology-Marine Biology, University of Athens, Panepistimiopolis, 157 84 Athens, Greece 2Institute of Biology, University of Southern Denmark, 5230 Odense M, Denmark *Email: spapasp@cc.uoa.gr ABSTRACT: The impact of Pestarella (= Callianasa) tyrrhena (Decapoda: Thalassinidea), a common burrowing shrimp in the Mediterranean Sea on sediment-water fluxes (O2, TCO2, NH4+ and NO3- + NO2-), sediment characteristics (organic matter, chlorophyll a) and porewater solutes (TCO2, NH4+ and NO3- + NO2-) was investigated in laboratory microcosms over a period of 42 d. Microcosms containing homogenised fine sandy sediment were amended with either dead Posidonia oceanica leaves or fresh Ulva lactuca thalli. Reworking activity by the animal resulted in a rapid burial of surface deposited organic matter into the sediment. Porewater profiles of both TCO2 and NH4+ indicated that P. tyrrhena activities result in a significant flushing of porewater solutes. Total sediment metabolism and carbon mineralisation were enhanced in the presence of P. tyrrhena. Metabolism of P. tyrrhena individuals was approximately 3 times higher in Ulva-amended sediment, probably due to a high activity level when nutritious food sources are in excess. Accordingly, animal respiration explained approximately half of the total enhancement in Ulva-amended sediment, while microbial decomposition of refractory seagrass detritus contributed about 4 times more to the stimulated carbon mineralisation than animal respiration. Despite the higher initial addition of carbon in Posidonia-amended sediment compared to Ulva-amended sediment, the amount of excess carbon mineralised was 4.7 times higher in the latter, indicating that mineralisation processes depend on the degradability rather than the quantity of the organic pool. Although P. tyrrhena excretion constituted only a minor part of the total nitrogen mineralised, macrofaunal activities were the major factor affecting total nitrogen mineralisation, and not the enrichment with organic matter. KEY WORDS: Bioturbation · Pestarella tyrrhena · Posidonia oceanica · Ulva lactuca · Benthic fluxes · Nutrient change Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 281. Online publication date: November 01, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Preclinical Work Leading to the Development of Spinal Analgesia

Preclinical Work Leading to the Development of Spinal Analgesia

William Hasledine Pepys FRS: A Life in Scientific Research, Learned Societies and Technical Enterprise

In a long and many-sided career, William Hasledine Pepys (1775-1856) contributed significantly to the advancement of the chemical and physical sciences during the first half of the nineteenth century. As an original investigator he determined, in collaboration with William Allen, the composition of carbon dioxide, and the density of ammonia, and elucidated the chemical phenomena of respiration in man, animals, and plants. The success of these researches was largely due to the use of ingenious apparatus of his own invention and design. In the field of experimental physics, he investigated several aspects of the recently discovered Voltaic electricity: his 'Voltaic coil', consisting of only two plates, but of very large dimensions, was particularly suited for investigating electromagnetic phenomena and was so used in Davy's researches. Pepys was one of the co-founders of the Mineralogical and Geological Societies, and was elected a Fellow of the Royal Society in 1808. As a prominent member of both the Royal and London Institutions, he held honorary office as Manager and Vice-President, contributing materially to the direction of the affairs of these bodies. Pepys was a friend of Humphry Davy and was acquainted with nearly all the leading scientists and medical men of the day. At the same time, he superintended a notable manufacture of surgical instruments in the City, and promoted by his active directorship the affairs of two public companies, both pioneers in their technological fields, namely the Imperial Continental Gas Association, which was active in introducing the new gas illumination to cities and towns across Europe, and the General Steam Navigation Company, which first maintained a regular passenger and cargo service to Continental ports by the exclusive use of steam-propelled vessels. Pepys' advice in scientific and technical matters was widely sought and freely given; he retained his mental powers to the end of his long life, fulfilling his professional commitments until a few days before his death.

A comparative analysis of the photobiology of zooxanthellae and zoochlorellae symbiotic with the temperate clonal anemone Anthopleura elegantissima (Brandt)

The temperate anemone Anthopleura elegantissima hosts two phylogenetically different symbiotic microalgae, a dinoflagellate Symbiodinium (zooxanthellae, ZX) and a chlorophyte (zoochlorellae, ZC), throughout certain regions of its latitudinal range. Because of the broad intertidal and geographic range of this anemone, we examined the role of irradiance to ascertain which specific symbiotic parameters are affected and whether light intensity governs the observed distributions of natural populations of ZX and ZC. Irradiance appears to be a key factor in regulating both the photophysiology and metabolism of this alga–cnidarian association. Regardless of light intensity, algal densities remained stable for anemones harboring ZX or ZC, whereas the mitotic indices of ZX and ZC both varied directly with light intensity. The chlorophyll content of ZX remained fairly constant regardless of irradiance; in contrast, ZC chlorophyll content was inversely proportional to light intensity. Regardless of irradiance, the carotenoid content of both symbionts was constant; however, ZX carotenoid levels were higher than those of ZC. Net photosynthesis was directly related to light intensity for both algal symbionts and ZX photosynthetic rates were consistently higher than those of ZC. Similarly, the potential carbon contribution of ZX and ZC to animal respiration (CZAR) displayed a direct relationship with light intensity, peaking at 800 µmol·m–2·s–1, then subsequently declined. Lower ZX growth rates, coupled with higher photosynthetic rates and higher CZAR estimates, compared to ZC, suggest that the ZX should be the dominant symbiont as light intensity increases; this may explain the high densities of anemones in the field containing ZX where the levels of irradiance are naturally high. These results support the interpretation that irradiance is a significant environmental parameter that dictates the microhabitat and latitudinal distribution of the two symbiotic algal taxa. This is the second in a series of papers examining the physical parameters that influence the distribution of ZX- and ZC-bearing A. elegantissima.

Chronic Ethanol Exposure Potentiates Lipopolysaccharide Liver Injury Despite Inhibiting Jun N-terminal Kinase and Caspase 3 Activation

Although ethanol is known to sensitize hepatocytes to tumor necrosis factor (TNF) lethality, the mechanisms involved remain controversial. Recently, others have shown that adding TNFalpha to cultures of ethanol-pretreated hepatocytes provokes the mitochondrial permeability transition, cytochrome c release, procaspase 3 activation, and apoptosis. Although this demonstrates that ethanol can sensitize hepatocytes to TNF-mediated apoptosis, the hepatic inflammation and ballooning hepatocyte degeneration that typify alcohol-induced liver injury suggest that other mechanisms might predominate in vivo. To evaluate this possibility, acute responses to lipopolysaccharide (LPS), a potent inducer of TNFalpha, were compared in mice that had been fed either an ethanol-containing or control diet for 5 weeks. Despite enhanced induction of cytokines such as interleukin (IL)-10, IL-15, and IL-6 that protect hepatocytes from apoptosis, ethanol-fed mice exhibited a 4-5-fold increase in serum alanine aminotransferase after LPS, confirming increased liver injury. Six h post-LPS histology also differed notably in the two groups, with control livers demonstrating only scattered apoptotic hepatocytes, whereas ethanol-exposed livers had large foci of ballooned hepatocytes, inflammation, and scattered hemorrhage. No caspase 3 activity was noted during the initial 6 h after LPS in ethanol-fed mice, but this tripled by 1.5 h after LPS in controls. Procaspase 8 cleavage and activity of the apoptosis-associated kinase, Jun N-terminal kinase, were also greater in controls. In contrast, ethanol exposure did not inhibit activation of cytoprotective mitogen-activated protein kinases and AKT or attenuate induction of the anti-apoptotic factors NF-kappaB and inducible nitric oxide synthase. Consistent with these responses, neither cytochrome c release, an early apoptotic response, nor hepatic oligonucleosomal DNA fragmentation, the ultimate consequence of apoptosis, was increased by ethanol. Thus, ethanol exacerbates TNF-related hepatotoxicity in vivo without enhancing caspase 3-dependent apoptosis.

A comparative analysis of the photobiology of Zooxanthellae and Zoochlorellae symbiotic with the temperate clonal anemone Anthopleura elegantissima (Brandt)

Throughout its geographic range, the temperate-zone anemone Anthopleura elegantissima is the host of one or both of two distinctively different symbiotic microalgae: a dinoflagellate Symbiodinium (zooxanthellae, ZX) and a chlorophyte (zoochlorellae, ZC). Given the broad vertical intertidal and latitudinal range of this anemone, we investigated the role of temperature in determining whether A. elegantissima supports one algal symbiont over the other and whether temperature regulates the observed distributions of natural populations of ZX and ZC. Temperature appears to be a key factor in regulating both the photophysiology and metabolism of this algal–cnidarian association. In anemones containing ZX, neither algal densities nor chlorophyll content varied with temperature (6–24 °C); in contrast, anemones with ZC displayed reduced densities and chlorophyll content at the highest temperature treatment (24 °C). Both ZX and ZC photosynthetic rates were directly related to temperature, as were anemone respiration rates. The higher photosynthetic rates, maintenance of a stable algal density and chlorophyll content, and higher potential contribution of algal carbon toward animal respiration (CZAR) suggest that the ZX are the more viable symbiont as temperature increases, but we suggest alternative reasons why ZC are preserved in this symbiotic association. Elevated temperatures reduce ZC densities and chlorophyll, suggesting that higher temperatures affect this relationship in a negative fashion, presumably due to a higher cost of maintaining ZC by the association; alternatively, these costs may be affiliated with the deterioration of the ZC themselves. These results suggest that temperature may be one of the most significant environmental parameters that sets the intertidal microhabitat and latitudinal distribution patterns of the two algal taxa observed in the field.

Changes in hemodynamics and respiration in animals with different resistance to acute hypoxia

We studied the effects of acute hypoxia on hemodynamics and respiration in cats. The animals were divided into high-, low- and medium-resistant to hypoxia by the time of respiratory arrest after breathing with 3% O2 gas mixture. In high-resistant animals, hemodynamic indices remained at a high level throughout the hypoxic episode, while in low-resistant cats they decreased shortly after the onset of hypoxia. It is suggested that the peculiarities of hemodynamic regulation play an important role in individual resistance to acute hypoxia.

Reversible depression of oxygen consumption in isolated liver mitochondria during hibernation.

The biochemical mechanisms by which hibernators cool as they enter torpor are not fully understood. In order to examine whether rates of substrate oxidation vary as a function of hibernation, liver mitochondria were isolated from telemetered ground squirrels (Spermophilus lateralis) in five phases of their annual hibernation cycle: summer active, and torpid, interbout aroused, entrance, and arousing hibernators. Rates of state 3 and state 4 respiration were measured in vitro at 25 degrees C. Relative to mitochondria from summer-active animals, rates of state 3 respiration were significantly depressed in mitochondria from torpid animals yet fully restored during interbout arousals. These findings indicate that a depression of ADP-dependent respiration in liver mitochondria occurs during torpor and is reversed during the interbout arousals to euthermia. Because this inhibition was determined to be temporally independent of entrance and arousal, it is unlikely that active suppression of state 3 respiration causes entrance into torpor by facilitating metabolic depression. In contrast to the observed depression of state 3 respiration in torpid animals, state 4 respiration did not differ significantly among any of the five groups, suggesting that alterations in proton leak are not contributing appreciably to downregulation of respiration in hibernation.

Measurement of tidal volume by using transthoracic impedance variations in rats.

The application of impedance pneumography for monitoring respiration in small animals has been limited by problems with calibration. With improved instrumentation, we describe the calibration of tidal volume in anesthetized rats. The detection of changes in voltage, reflecting the electrical impedance variations associated with respiration, was optimized by using disposable adhesive silver-silver chloride electrodes, advanced circuitry, and analog-to-digital recording instrumentation. We found a linear relationship between change in impedance and tidal volume in individual rats (R2 >/= 98%), which was strongly influenced by rat weight. Consequently, a calibration equation incorporating change in impedance and rat weight was derived to predict tidal volume. Comparison of the predicted and true tidal volumes revealed a mean R2 >/= 98%, slopes of approximately 1, intercepts of approximately 0, and bias of approximately 0.07 ml. The predicted volumes were not significantly affected by either frequency of respiration or pulmonary edema. We conclude that impedance pneumography provides a valuable tool for the noninvasive measurement of tidal volume in anesthetized rats.

The positive influence of a cholinergic–anticholinergic pretreatment and antidotal treatment on rats poisoned with supralethal doses of soman

The influence of pretreatment with the drug mixture (pyridostigmine, benactyzine and trihexyphenidyle), and antidotal treatment (the oxime HI-6 in combination with benactyzine) on respiration, circulation and survival of experimental animals poisoned with supralethal doses of soman (2×LD 50) was investigated in a rat model with on-line monitoring of respiratory and circulatory parameters. Untreated soman poisoning caused rapid respiratory depression, progressive bradycardia and a short-term increase in the mean arterial pressure, followed immediately by hypotension. The poisoned rats died on average within 10 min from respiratory and circulatory insufficiency. A cholinergic–anticholinergic pretreatment alone partially prevented changes in monitored physiological variables, caused by soman, but only for a few minutes; post-poisoning treatment with antidotes, also alone, had similar effects. The rats died on average within 30 min from respiratory and circulatory failure. When rats were pretreated by the drug mixture and treated by antidotes, respiration as well as circulation were completely restored and the rats survived at least 120 min following soman challenge. The results of the investigation suggest that cholinergic–anticholinergic pretreatment seems able to enhance the efficacy of antidotal treatment in restoring respiratory and circulatory changes induced by soman.

Acute effects of nitric oxide blockade with L-NAME on arterial haemodynamics in the rat.

1. We employed the technique of impedance spectral analysis to investigate the role of endogenous nitric oxide (NO) in the regulation of steady and pulsatile haemodynamics in Wistar Kyoto rat (WKY). 2. A total of 12 WKYs was anaesthetized with pentobarbitol sodium (40 mg kg-1, i.p.) and artificially ventilated with an animal respirator. The aortic pressure wave was monitored with a high fidelity Millar sensor, and aortic flow wave with an electromagnetic flow probe. The pressure and flow waves were subjected to Fourier transform for the analysis of impedance spectra. 3. The baseline cardiovascular parameters were mean arterial pressure (APm) 95 +/- 9 mmHg, heart rate (HR) 338 +/- 9 b.p.m., stroke volume (SV) 0.23 +/- 0.01 ml, cardiac output (CO) 77.8 +/- 1.6 ml min-1, total peripheral resistance (TPR) 98 +/- 11 (x10(3)) dyne s cm-5, characteristic impedance (Zc) 2046 +/- 141 dyne s cm-5, arterial compliance at mean AP (Cm) 3.78 +/- 0.22 microliters mmHg-1 and backward pulse wave (Pb) 12.9 +/- 0.6 mmHg. 4. An NO synthase inhibitor, NG-nitro-L-arginine monomethyl ester (L-NAME) was administered at graded intravenous doses. This agent caused dose-dependent increases in AP and TPR with decreases in HR. At an accumulative dose of 10 mg kg-1, APm was increased by 29 +/- 3 mmHg (+31%) and TPR by 49 +/- 6 (x10(3)) dyne s cm-5 (+50%), while HR was reduced by 37 +/- 5 b.p.m. (-11%) and CO by 10.4 +/- 0.8 ml min-1 (-14%). The pulsatile haemodynamics including Zc and Pb were slightly increased by 14-15%. Cm was decreased by 1.09 microliters mmHg-1 (-29%). L-NAME also did not significantly affect the ventricular work including the steady, oscillatory and total work. 5. Aminoguanidine, a specific inhibitor for inducible NO synthase (iNOS), in dose 10-60 mg kg-1 i.v. did not alter the AP, HR and other parameters. The result indicated that blockade of constitutive NOS, but not iNOS is involved in these changes. 6. Angiotensin II (Ang) in various infusion doses was used to produce a profile of AP increase similar to that caused by L-NAME. Ang remarkably increased Zc, while TPR was moderately elevated. The pattern of haemodynamic changes was different from that following L-NAME. 7. The results suggest that blockade of the endogenous NO affects predominantly the arterial pressure and peripheral resistance. The Windkessel functions such as arterial impedance and pulse wave reflection are slightly increased. Ventricular works are not significantly altered.

The Cambrian origin of the circulatory system of crustaceans

The carapace of Recent crustaceans such as myodocope ostracodes and phyllocarids is pervaded with well-developed anastomosing sinuses conveying hemolymph from the metabolizing organs to the dorsal heart. The inner lamella cuticle, which separates the sinuses from seawater, is thin enough to allow gaseous diffusion (e.g., O2 uptake) over its surface. Comparable radiating and/or anastomosing features, of possible vascular origin, are herein recognized in several possible Crustacea from the Cambrian: cambriid, svealutiid, hipponicharionid and beyrichonid Bradoriida and in Carnarvonia from the middle Cambrian Burgess Shale. The vascular network is basically the same in these groups, consisting of sinuses radiating from supposed adductorial areas or from inferred areas of dorsal attachment of the body. The integumental (carapace sinuses) and branchial (gills) systems of respiration in crustaceans and crustacean-like animals were probably already differentiated by the middle Cambrian. The oldest record of probable integumental circulation is in the bradoriid Petrianna from the early Cambrian of Greenland. Similar circulatory systems may be represented by radiating ridges on the cephalon of other Cambrian arthropod groups such as the arachnomorphs (Burgessia) and trilobites (Naraioa) and may also be manifest in the carapaces of Ordovician-Devonian leperditicope ostracodes. Organs on the thoracopods of Cambrian supposed crustaceans, such as Canadaspis, resemble the foliaceous thoracic gills of Recent nebaliid phyllocarids and therefore may have served the same (respiratory) function.

The Closed Equilibrated Biological Aquatic System: general concept and aspects of botanical research.

The Closed Equilibrated Biological Aquatic System (CEBAS) consists of four subcomponents which form a closed (artificial) aquatic ecosystem initially designed to study the long-term influence of space conditions on several successive generations of aquatic organisms. Teleost fishes and water snails in the zoological component produce CO2 ammonium ions and waste compounds which can be utilized after ammonium is oxidised in a microbial component by the botanical component consisting of a rootless, aquatic higher plant species which eliminates ions, i.e. nitrate, and produces oxygen for animal respiration. An electronic component serves as a data-acquisition and regulation device for temperature and oxygen-dependent illumination of the plant chamber. A comprehensive interdisciplinary research programme, focused around the CEBAS, is especially well developed in the field of zoology. It covers a ground laboratory and preparations for two scheduled space flight projects, as well as aspects of combined animal-plant food production modules for human nutrition in bioregenerative space life-support systems and for terrestrial production sites. In the botanical research programme, morphological investigations on Ceratophyllum demersum L. performed with light and electron microscopy have demonstrated a gas lacuna system which, in addition to starch grains in the plastids, might regulate the buoyancy of the plant and/or serve as a 'gas skeleton'. Also, a remarkable symmetry in the arrangement of tissues was observed in stems and older leaves. The photosynthetic capacities of Ceratophyllum in the CEBAS-MINI MODULE proved to be more than sufficient for life support, and experiments on nitrate uptake into the plants showed their capacity to utilize ions from the water.

An ex vivo model of the rat trachea to study the effect of inhalable toxic compounds.

Different cell culture and organ systems are used to evaluate the physiological responses of the airways to the effects of carcinogenic [e.g., benzo(a)pyrene] and anticarcinogenic (e.g., retinoids) compounds on cellular growth and differentiation. However, in contrast to in vivo conditions dissociated epithelial cells or tracheal ring cultures are covered with medium. Therefore, we developed an ex vivo perfusion model enabling evaluation of morphology and metabolism of different compounds under near-physiological conditions. The trachea was surrounded with culture medium and perfused with air by means of a small animal respirator. To test the viability of the system under various experimental conditions tracheal probes were incubated with either retinoids (retinol 10(-5) mol/l; retinyl palmitate 10(-5) mol/l) or benzo(a)pyrene (10(-7) mol/l) for up to 7 days. At the end of the incubation period metabolites in the trachea and in the medium were measured by means of high-performance liquid chromatography. Samples were examined by light microscopy, and by scanning and transmission electron microscopy for cell morphology. Glycoconjugate expression was assessed by lectin histochemistry. Specimens incubated in a retinoid-supplemented medium revealed no alterations in the distribution of cell types and characteristics of the epithelial layer compared with tracheal biopsies assessed immediately after removal from the animals. Glycoconjugate patterns especially remained intact. Histological changes after incubation with benzo(a)pyrene resembled in vivo morphology of vitamin A-deficient rats. An important advantage of this in vitro model compared with common cell or organ cultures is the preservation of the original phenotype and environment of the tracheobronchial surface. In addition, carcinogenic substances, such as benzo(a)pyrene, can easily be applied by airway or through the medium.

Design of an Electronically Operated Flow-Through Respirometer and Its Use to Investigate the Effects of Copper on the Respiration Rate of the Amphipod Gammarus pulex (L.)

The use of oxygen consumption as a measure of metabolism has resulted in the development of many types of respirometer. These can be classified into three types. Firstly, there is the closed system in which oxygen concentration is measured at the beginning and end of the experiment and an organism`s respiratory rate calculated from the decrease in oxygen concentration and the volume of the vessel. Secondly, there is a system in which respired oxygen is replaced by oxygen from the surrounding air and the resultant change in air volume is measured gasometrically. A third approach, and the one employed in this study, utilises an open flow-through system in which water passes through a chamber containing an animal and the oxygen concentration is measured and compared to that of a reference chamber without an animal. The difference in oxygen concentration is then used to determine the respiration rate of the test animal. In open flow-through systems excretory products are washed away and water is not left stagnant as may occur in closed techniques. In addition, the open flow technique provides a constant oxygen concentration, avoids stress to animals with oxygen concentration-dependent metabolism and allows the simulation of low oxygen tension environments.more » Despite these obvious advantages the use of flow-through respirometers has been somewhat limited due to difficulties in calibration and complexity in construction and operation (Edwards and Learner 1960). The purpose of this investigation was to design a flow-through respirometer which is sufficiently sensitive to detect pollutant-induced respiratory changes in freshwater invertebrates and which permits automated continuous recording of the respiration of several animals maintained individually. In order to evaluate the system the effect of copper (prepared form cupric sulphate, CuSO{sub 4}.5H{sub 2}O) on the respiration of the shrimp Gammarus pulex was studied. 26 refs., 2 figs., 1 tab.« less

Photosynthesis and respiration of two species of algal symbionts in the anemone Anthopleura elegantissima (Brandt) (Cnidaria; Anthozoa)

In parts of its range, the anemone Anthopleura elegantissima (Brandt) is populated by two different symbiotic algae: zoochlorellae and zooxanthellae. Anemones with exclusively one or the other symbiont were compared under identical conditions. A zooxanthella was about twice the volume and carbon content of a zoochlorella, and contained more chlorophyll. Zooxanthellae population density was 24% less than zoochlorellae, consequently zooxanthellae protein biomass per unit animal was only 58% greater than zoochlorellae. The mitotic index (MI) of zoochlorellae was almost 22 times greater than zooxanthellae, and the diel cell division pattern was asynchronous in both algae. Using duration of cytokinesis times ( t d ) of 28 and 69 h for zooxanthellae and zoochlorellae, respectively, we estimated that zoochlorellae grew eight times faster than zooxanthellae. with a commensurately shorter population doubling time. Zooxanthella respiration was two and a half times and net photosynthesis twice that of a zoochlorella; this coupled with a comparatively low growth rate allows the zooxanthellae population to potentially translocate almost five times as much carbon to its host as do zoochlorellae. The contribution of carbon to animal respiration (CZAR) was estimated at 48% for the zooxanthellate and only 9% for zoochlorellate anemones. It is suggested that these associations may be similar to ancestral symbioses.

Subchronic toxicity of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5 H)-furanone (MX) in Wistar rats

The subchronic (14–18 wk) toxicity of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), a mutagenic by-product in chlorinated drinking water, was evaluated in Wistar rats. In a range-finding study, MX was administered daily for 14 days by gavage in deionized water to male rats (five animals per group) at doses of 12.5, 25, 50, 100 or 200 mg/kg body weight. The doses above 50 mg/kg were lethal and three out of five animals also died during treatment at 50 mg/kg. The range-finding study was repeated with doses of 5, 10 and 20 mg MX/kg, given on 5 days a week, to both males and females (10 animals per group). These doses were not overtly toxic but caused several changes in plasma clinical chemistry at 10 and 20 mg MX/kg in comparison with the controls. These included increased urea, creatinine and bilirubin and decreased inorganic phosphate and potassium in females and increased cholesterol in males. In the subchronic toxicity study, rats (15 per group) were given MX by gavage, on 5 days a week, at doses of 0 (controls) or 30 mg/kg (low dose) for 18 wk, or, in the high-dose group, at doses increasing from 45 to 75 mg/kg over 14 wk. The high dose was finally lethal (two males and one female died) and caused hypersalivation, wheezing respiration, emaciation and tangled fur in animals. The body weights of the high-dose males decreased by 15%, and food consumption was decreased by 15 to 20%, but the water consumption increased by 15% to 60%. Plasma cholesterol and triglycerides were elevated and urine excretion was increased. Urine specific gravity was decreased and the relative weights of the liver and kidneys were increased in both sexes at both doses in comparison with the controls. At both doses, duodenal hyperplasia occurred in males and females, and slight focal epithelial hyperplasia in the forestomach was observed in males. Splenic atrophy and haemosiderosis were seen in two high-dose females, and epithelial cell atypia in the urinary bladder of one high-dose male and female. The frequency of bone marrow polychromatic erythrocytes with micronuclei was slightly increased in low-dose males. The results indicate that repeated administration of MX disturbs the fluid-electrolyte balance and induces diuresis, causes mucosal hyperplasia in the gastro-intestinal tract as a local effect, and affects lipid metabolism.

Hypothyroid state and membrane fatty acid composition influence cardiac mitochondrial pyruvate oxidation

Pyruvate oxidation was measured in cardiac mitochondria from euthyroid and hypothyroid rats fed diets enriched with either to ω − 6 or ω − 3 fatty acids. Both State 4 and State 3 rates of pyruvate-dependent respiration were markedly reduced in hypothyroid mitochondria, regardless of diet consumed, compared to euthyroid controls. Respiratory control ratios and ADP/O ratios were the same under all treatments. While there was no significant effect of diet on respiration in euthyroid mitochondria, pyruvate oxidation was 28% higher in hypothyroid mitochondria from animals fed the ω − 3 diet compared to those fed the ω − 6 diet. Depressed respiration in the hypothyroid state was correlated with 18% more phosphatidylcholine in the inner mitochondrial membrane whereas phosphatidylethanolamine was 17% lower and cardiolipin 32% lower compared to controls. The total phospholipid fatty acid composition was not affected by the hypothyroid state. However, enhanced respiration in hypothyroid animals fed the ω − 3 diet was associated with a 3-fold increase in monounsaturated fatty acids in the cardiolipin fraction, and a 12-fold increase in ω − 3 fatty acids, primarily 22:5(ω − 3) and 22:6(ω − 3). The data suggest that membrane levels of cardiolipin and its ω − 3 fatty acid content modulate pyruvate transport in hypothyroid mitochondria.

Metalimnetic Oxygen Depletion: Organic Carbon Flux and Crustacean Zooplankton Distribution in a Quarry Embayment

Metalimnetic Oxygen Depletion: Organic Carbon Flux and Crustacean Zooplankton Distribution in a Quarry Embayment

Algal Symbiosis in Bunodeopsis: Sea Anemones with "Auxiliary" Structures.

This study describes the photobiology of two tropical species of the symbiotic sea anemone genus Bunodeopsis from Discovery Bay, Jamaica, B. antilliensis was found in shallow water (0.3m) and experienced higher irradiance levels than B. globulifera from deeper water (3 m). Both species contained symbiotic dinoflagellates of the genus Symbiodinium within the endodermal cells. The external morphology and expansion-contraction behavior of the two anemone species were closely linked to symbiont distribution. B. antilliensis had large vesicles (2.6 mm3), with 88.5% of the symbiont population in the lower column and basal disk and 11.5% in the tentacles and upper column, and was contracted under normal daylight illumination. In contrast, B. globulifera had small vesicles (0.2 mm3), with 55.5% of the symbionts in the lower column and basal disk and 44.5% in the tentacles and upper column, and was expanded under illumination. The photosynthetic physiology of the symbionts indicated that those from B. globulifera were adapted to lower host habitat irradiances than were those from B. antilliensis. The symbionts from B. globulifera had a significantly higher chlorophyll a content (7.34 +/- 0.77 pg·cell-1) and photosynthetic efficiency (0.24 μgO2·106 cells.h-1/μmol photons·m-2·s-1) and lower saturation irradiance (277 +/- 18 μmol photons·m-2·s-1) than those from B. antilliensis, 4.51 +/- 0.29 pg.cell-1, 0.17 μgO2.106 cells· h-1/μmol photons·m-2·s-1 and 436 +/- 78 μmol photons·m-2·s-1, respectively. The calculated rate of carbon translocation in both species of Bunodeopsis (97%) was high and reflected the low algal protein biomass ratios (2%) and population growth rates (<0.1·day-1). The CZAR values in B. antilliensis (109%) and B. globulifera (92%) suggest that both species are potentially autotrophic with respect to carbon available for animal respiration.