Torpor patterns,arousal rates,and temporal organization of torpor entry in wildtype and UCP1-ablated mice

In eutherian mammals, uncoupling protein 1 (UCP1) mediated non-shivering thermogenesis from brown adipose tissue (BAT) provides a mechanism through which arousal from torpor and hibernation is facilitated. In order to directly assess the magnitude by which the presence or absence of UCP1 affects torpor patterns, rewarming and arousal rates within one species we compared fasting induced torpor in wildtype (UCP1^+/+) and UCP1-ablated mice (UCP^−/−). Torpor was induced by depriving mice of food for up to 48 h and by a reduction of ambient temperature (T _a) from 30 to 18°C at four different time points after 18, 24, 30 and 36 h of food deprivation. In most cases, torpor bouts occurred within 20 min after the switch in ambient temperature (30–18°C). Torpor bouts expressed during the light phase lasted 3–6 h while significantly longer bouts (up to 16 h) were observed when mice entered torpor during the dark phase. The degree of hypometabolism (5–22 ml h⁻¹) and hypothermia (19.5–26.7°C) was comparable in wildtype and UCP1-ablated mice, and both genotypes were able to regain normothermia. In contrast to wildtype mice, UCP1-ablated mice did not display multiple torpor bouts per day and their peak rewarming rates from torpor were reduced by 50% (UCP1^+/+: 0.24 ± 0.08°C min⁻¹; UCP1^−/−: 0.12 ± 0.04°C min⁻¹). UCP1-ablated mice therefore took significantly longer to rewarm from 25 to 32°C (39 vs. 70 min) and required 60% more energy for this process. Our results demonstrate the energetic benefit of functional BAT for rapid arousal from torpor. They also suggest that torpor entry and maintenance may be dependent on endogenous rhythms.     

RETRACTED ARTICLE: Age-dependent Increase in Desmosterol Restores DRM Formation and Membrane-related Functions in Cholesterol-free DHCR24−/− Mice

Cholesterol is a prominent modulator of the integrity and functional activity of physiological membranes and the most abundant sterol in the mammalian brain. DHCR24-knock-out mice lack cholesterol and accumulate desmosterol with age. Here we demonstrate that brain cholesterol deficiency in 3-week-old DHCR24^−/− mice was associated with altered membrane composition including disrupted detergent-resistant membrane domain (DRM) structure. Furthermore, membrane-related functions differed extensively in the brains of these mice, resulting in lower plasmin activity, decreased β-secretase activity and diminished Aβ generation. Age-dependent accumulation and integration of desmosterol in brain membranes of 16-week-old DHCR24^−/− mice led to the formation of desmosterol-containing DRMs and rescued the observed membrane-related functional deficits. Our data provide evidence that an alternate sterol, desmosterol, can facilitate processes that are normally cholesterol-dependent including formation of DRMs from mouse brain extracts, membrane receptor ligand binding and activation, and regulation of membrane protein proteolytic activity. These data indicate that desmosterol can replace cholesterol in membrane-related functions in the DHCR24^−/− mouse. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. An erratum to this article can be found at     

Cholesterol biotransformation to androsta-1,4-diene-3,17-dione by growing cells of <Emphasis Type="Italic">Chryseobacterium gleum</Emphasis>

Cholesterol oxidase activity was studied during biotransformation of cholesterol to androsta-1,4-diene-3,17-dione (ADD) by Chryseobacterium gleum. Spent LB media, containing cholesterol (3 mM≈1 g l⁻¹) where the bacterium was grown for 24 h, at 30°C with constant shaking at 120 rpm, had the highest enzyme activity (167 U mg⁻¹). The growing cells produced 0.076 g ADD from 1 g cholesterol l⁻¹.     

Effect of seawater temperature on the productivity of <Emphasis Type="Italic">Laminaria japonica</Emphasis> in the Uwa Sea,southern Japan

Recent studies on global climate change report that increase in seawater temperature leads to coastal ecosystem change, including coral bleaching in the tropic. In order to assess the effect of increased seawater temperature on a temperate coastal ecosystem, we studied the inter-annual variation in productivity of Laminaria japonica using long-term oceanographic observations for the Uwa Sea, southern Japan. The annual productivity estimates for L. japonica were 2.7 ± 2.5 (mean ± SD) kg wet wt. m⁻¹ (length of rope) (2003/2004), 1.0 ± 0.6 kg wet wt. m⁻¹ (2004/2005) and 12.1 ± 12.5 kg wet wt. m⁻¹ (2005/2006). Our previous study using the same methodology at the same locality reported that the productivity was estimated for the 2001/2002 (33.3 ± 15.2 kg wet wt. m⁻¹) and 2002/2003 (34.0 ± 8.7 kg wet wt. m⁻¹) seasons. Productivity in 2003/2004 and 2004/2005 was significantly lower than in years 2001/2002, 2002/2003 and 2005/2006. A comparison of oceanographic conditions among the 5 years revealed the presence of threshold seawater temperature effects. When the average seawater temperature during the first 45 days of each experiment exceeded 15.5°C, productivity was reduced to about 10 % of that in cooler years. Moreover the analysis of growth and erosion rates indicates that when the seawater temperature was over 17.5°C, erosion rate exceeded growth rate. Thus, an increase of seawater temperature of just 1°C during winter drastically reduces the productivity of L. japonica in the Uwa Sea.     

Change in ammonia-oxidizing microorganisms in enriched nitrifying activated sludge

In this study, sludge was taken from a municipal wastewater treatment plant that contained a nearly equal number of archaeal amoA genes (5.70 × 10⁶ ± 3.30 × 10⁵ copies mg sludge⁻¹) to bacterial amoA genes (8.60 × 10⁶ ± 7.64 × 10⁵ copies mg sludge⁻¹) and enriched in three continuous-flow reactors receiving an inorganic medium containing different ammonium concentrations: 2, 10, and 30 mM NH₄⁺–N (28, 140, and 420 mg N l⁻¹). The abundance and communities of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in enriched nitrifying activated sludge (NAS) were monitored at days 60 and 360 of the operation. Early on, between day 0 and day 60 of reactor operation, comparative abundance of AOA amoA genes to AOB amoA genes varied among the reactors depending on the ammonium levels found in the reactors. As compared to the seed sludge, the number of AOA amoA genes was unchanged in the reactor with lower ammonium level (0.06 ± 0.04 mgN l⁻¹), while in the reactors with higher ammonium levels (0.51 ± 0.33 and 0.25 ± 0.10 mgN l⁻¹), the numbers of AOA amoA genes were deteriorated. By day 360, AOA disappeared from the ammonia-oxidizing consortiums in all reactors. The majority of the AOA sequences from all NASs at each sampling period fell into a single AOA cluster, however, suggesting that the ammonium did not affect the AOA communities under this operational condition. This result is contradictory to the case of AOB, where the communities varied significantly among the NASs. AOB with a high affinity for ammonia were present in the reactors with lower ammonium levels, whereas AOB with a low affinity to ammonia existed in the reactors with higher ammonium levels.     

Biogeochemical conditions and ice algal photosynthetic parameters in Weddell Sea ice during early spring

Physical, biogeochemical and photosynthetic parameters were measured in sea ice brine and ice core bottom samples in the north-western Weddell Sea during early spring 2006. Sea ice brines collected from sackholes were characterised by cold temperatures (range −7.4 to −3.8°C), high salinities (range 61.4–118.0), and partly elevated dissolved oxygen concentrations (range 159–413 μmol kg⁻¹) when compared to surface seawater. Nitrate (range 0.5–76.3 μmol kg⁻¹), dissolved inorganic phosphate (range 0.2–7.0 μmol kg⁻¹) and silicic acid (range 74–285 μmol kg⁻¹) concentrations in sea ice brines were depleted when compared to surface seawater. In contrast, NH₄ ⁺ (range 0.3–23.0 μmol kg⁻¹) and dissolved organic carbon (range 140–707 μmol kg⁻¹) were enriched in the sea ice brines. Ice core bottom samples exhibited moderate temperatures and brine salinities, but high algal biomass (4.9–435.5 μg Chl a l⁻¹ brine) and silicic acid depletion. Pulse amplitude modulated fluorometry was used for the determination of the photosynthetic parameters F _v/F _m, α, rETR_max and E _k. The maximum quantum yield of photosystem II, F _v/F _m, ranged from 0.101 to 0.500 (average 0.284 ± 0.132) and 0.235 to 0.595 (average 0.368 ± 0.127) in the sea ice internal and bottom communities, respectively. The fluorometric measurements indicated medium ice algal photosynthetic activity both in the internal and bottom communities of the sea ice. An observed lack of correlation between biogeochemical and photosynthetic parameters was most likely due to temporally and spatially decoupled physical and biological processes in the sea ice brine channel system, and was also influenced by the temporal and spatial resolution of applied sampling techniques.     

Drought,warming and soil fertilization effects on leaf volatile terpene concentrations in <Emphasis Type="Italic">Pinus halepensis</Emphasis> and <Emphasis Type="Italic">Quercus ilex</Emphasis>

The changes in foliar concentrations of volatile terpenes in response to water stress, fertilization and temperature were analyzed in Pinus halepensis and Quercus ilex. The most abundant terpenes found in both species were α-pinene and Δ³-carene. β-Pinene and myrcene were also abundant in both species. P. halepensis concentrations were much greater than those of Q. ilex in agreement with the lack of storage in the latter species (15205.60 ± 1140.04 vs. 0.54 ± 0.08 μg g⁻¹ [d.m.]). The drought treatment (reduction to 1/3 of full watering) significantly increased the total terpene concentrations in both species (54% in P. halepensis and 119% in Q. ilex). The fertilization treatment (addition of either 250 kg N ha⁻¹ or 250 kg P ha⁻¹ or both) had no significant effects on terpene foliar concentrations. The terpene concentrations increased from 0.25 μg g⁻¹ [d.m.] at 30°C to 0.70 μg g⁻¹ [d.m.] at 40°C in Q. ilex (the non-storing species) and from 2,240 μg g⁻¹ [d.m.] at 30°C to 15,621 μg g⁻¹ [d.m.] at 40°C in P. halepensis (the storing species). Both species presented negative relationship between terpene concentrations and relative water contents (RWC). The results of this study show that higher terpene concentrations can be expected in the warmer and drier conditions predicted for the next decades in the Mediterranean region.     

The effect of prolonged darkness on the growth, recovery and survival of Antarctic sea ice diatoms

While global climate change in polar regions is expected to cause significant warming, the annual cycle of light and dark will remain unchanged. Cultures of three species of Antarctic sea ice diatoms, Fragilariopsis cylindrus (Grunow) Krieger, Thalassiosira antarctica Comber and Entomoneis kjellmanii (P.T. Cleve) Poulin and Cardinal, were incubated in the dark and exposed to differing temperatures. Maximum dark survival times varied between 30 and 60 days. Photosynthetic parameters, photosynthetic efficiency (α), maximum quantum yield (Fv/Fm), maximum relative electron transport rate (rETRmax) and non-photochemical quenching (NPQ), showed that dark exposure had a significant impact on photoacclimation. In contrast, elevated temperatures had a relatively minor impact on photosynthetic functioning during the dark exposure period but had a considerable impact on dark survival with minimal dark survival times reduced to only 7 days when exposed to 10°C. Recovery of maximum quantum yield of fluorescence (Fv/Fm) was not significantly impacted by temperature, species or dark exposure length. Recovery rates of Fv/Fm ranged from −5.06E−7 ± 2.71E−7 s⁻¹ to 1.36E−5 ± 1.53E−5 s⁻¹ for monthly experiments and from −9.63E−7 ± 7.71E−7 s⁻¹ to 2.65E−5 ± 2.97E−5 s⁻¹ for weekly experiments. NPQ recovery was greater and more consistent than Fv/Fm recovery, ranging between 5.74E−7 ± 8.11E−7 s⁻¹ to 7.50E−3 ± 7.1E−4 s⁻¹. The concentration of chl-a and monosaccharides remained relatively constant in both experiments. These results suggest that there will probably be little effect on Antarctic microalgae with increasing water temperatures during the Antarctic winter.     

Long-term hydrochemical monitoring in an Oyasan Experimental Forest Watershed comprised of two small forested watersheds of Japanese cedar and Japanese cypress

Forest ecosystems are self-fertilizing systems, and development of forest stands depends on nutrient supply via biogeochemical cycling within the ecosystem. Therefore, it is important to clarify the nutrient cycle mediating growth and development. In addition, long-term hydrochemical monitoring is needed to understand the influence of environmental changes on biogeochemical cycling in forest ecosystems. The Oyasan Experimental Forest Watershed (OEFW) is located in the Field Museum Oyasan, the university forest of Tokyo University of Agriculture and Technology, in Gunma prefecture, Japan. OEFW comprises two small adjacent forested watersheds—A-watershed and B-watershed—with respective areas of 1.3 and 1.8 ha. A-watershed is a reestablished forest planted with sugi (Japanese cedar; Cryptomeria japonica) and hinoki (Japanese cypress; Chamaecyparis obtusa) in 1976, and has been managed intensively with fertilizer application. By contrast, B-watershed is an established forest planted with sugi and hinoki in 1907. No forest practices have been carried out except for thinning of suppressed trees in 1983. However, the sugi plantation on the lowest slope (18% of the watershed area) was cut in 2000, and sugi was replanted the following year. In this data paper, we present data on the daily precipitation, discharge, pH, and concentrations of major nutrients (Ca²⁺, Mg²⁺, K⁺, Na⁺, NH₄ ⁺, Cl⁻, NO₃ ⁻, and SO₄ ²⁻) in rainwater and stream water since November 1978. The arithmetical mean pH of precipitation, stream water in A- and B-watershed from the beginning of the monitoring to the present were 4.77 ± 0.67, 6.85 ± 0.41 and 6.88 ± 0.36 (average ± SD), respectively. The arithmetical mean concentrations in precipitation in mmol_c L⁻¹ were 0.030 ± 0.030 for Ca²⁺, 0.010 ± 0.011 for Mg²⁺, 0.009 ± 0.013 for K⁺, 0.020 ± 0.024 for Na⁺, 0.035 ± 0.041 for NH₄ ⁺, 0.026 ± 0.029 for Cl⁻, 0.033 ± 0.038 for NO₃ ⁻, and 0.046 ± 0.043 for SO₄ ²⁻. The mean concentrations in stream water in A-watershed were 0.180 ± 0.032 for Ca²⁺, 0.073 ± 0.013 for Mg²⁺, 0.018 ± 0.009 for K⁺, 0.182 ± 0.024 for Na⁺, 0.010 ± 0.010 for NH₄ ⁺, 0.060 ± 0.008 for Cl⁻, 0.111 ± 0.038 for NO₃ ⁻, and 0.074 ± 0.012 for SO₄ ²⁻; whereas for B-watershed the mean concentrations were 0.169 ± 0.025 for Ca²⁺, 0.079 ± 0.016 for Mg²⁺, 0.018 ± 0.005 for K⁺, 0.192 ± 0.026 for Na⁺, 0.010 ± 0.010 for NH₄ ⁺, 0.065 ± 0.010 for Cl⁻, 0.093 ± 0.025 for NO₃ ⁻, and 0.087 ± 0.011 for SO₄ ²⁻.     

Continuous cultures of <Emphasis Type="Italic">Pseudomonas putida</Emphasis> mt-2 overcome catabolic function loss under real case operating conditions

The long-term performance and stability of Pseudomonas putida mt-2 cultures, a toluene-sensitive strain harboring the genes responsible for toluene biodegradation in the archetypal plasmid pWW0, was investigated in a chemostat bioreactor functioning under real case operating conditions. The process was operated at a dilution rate of 0.1 h⁻¹ under toluene loading rates of 259 ± 23 and 801 ± 78 g m⁻³ h⁻¹ (inlet toluene concentrations of 3.5 and 10.9 g m⁻³, respectively). Despite the deleterious effects of toluene and its degradation intermediates, the phenotype of this sensitive P. putida culture rapidly recovered from a 95% Tol⁻ population at day 4 to approx. 100% Tol⁺ cells from day 13 onward, sustaining elimination capacities of 232 ± 10 g m⁻³ h⁻¹ at 3.5 g Tol m⁻³ and 377 ± 13 g m⁻³ h⁻¹ at 10.9 g Tol m⁻³, which were comparable to those achieved by highly tolerant strains such as P. putida DOT T1E and P. putida F1 under identical experimental conditions. Only one type of Tol⁻ variant, harboring a TOL-like plasmid with a 38.5 kb deletion (containing the upper and meta operons for toluene biodegradation), was identified.     

Preinduction of HSP70 promotes hypoxic tolerance and facilitates acclimatization to acute hypobaric hypoxia in mouse brain

It has been shown that induction of HSP70 by administration of geranylgeranylacetone (GGA) leads to protection against ischemia/reperfusion injury. The present study was performed to determine the effect of GGA on the survival of mice and on brain damage under acute hypobaric hypoxia. The data showed that the mice injected with GGA survived significantly longer than control animals (survival time of 9.55 ± 3.12 min, n = 16 vs. controls at 4.28 ± 4.29 min, n = 15, P < 0.005). Accordingly, the cellular necrosis or degeneration of the hippocampus and the cortex induced by sublethal hypoxia for 6 h could be attenuated by preinjection with GGA, especially in the CA2 and CA3 regions of the hippocampus. In addition, the activity of nitric oxide synthase (NOS) of the hippocampus and the cortex was increased after exposure to sublethal hypoxia for 6 h but could be inhibited by the preinjection of GGA. Furthermore, the expression of HSP70 was significantly increased at 1 h after GGA injection. These results suggest that administration of GGA improved survival rate and prevented acute hypoxic damage to the brain and that the underlying mechanism involved induction of HSP70 and inhibition of NOS activity.     

Effect of prebiotics on bacteriocin production and cholesterol lowering activity of <Emphasis Type="Italic">Pediococcus acidilactici</Emphasis> LAB 5

The in vitro influence of three prebiotics viz. mannitol, maltodextrin and sorbitol was evaluated on probiotic aspects like bile salt tolerance, cholesterol lowering efficiency and bacteriocin production of the strain, Pediococcus acidilactici LAB 5 which was isolated from vacuum packed fermented meat product. Optimum temperature for bacteriocin production in MRS medium was 37°C. The strain deconjugated bile salt (sodium taurocholate) to 607.66 ± 10.894 μg/ml from initial bile salt concentration 3 mg/ml. In vitro cholesterol removal capability of the strain P. acidilactici LAB 5 was 62 ± 2.742 μg/ml. Prebiotic sorbitol had a positive influence on the probiotic parameters like better cell growth, bacteriocin production and cholesterol removal capability. Anaerobic condition had influenced largely on bile salt deconjugation, cholesterol removal and bacteriocin production. Synbiotic treatment of P. acidilactici LAB 5 with sorbitol for 1 month lowered the plasma cholesterol level to 176.34 ± 12.66 μg/ml in comparison to untreated one (208.76 ± 20.27 μg/ml) in Swiss albino mice. Intestinal adherence of P. acidilactici LAB 5 was also more in synbiotic condition than only in probiotic and control treatments.     

Development of adrenal chromaffin cells in Sf1 heterozygous mice

Adrenal medullary chromaffin cells are derivatives of the neural crest and are widely believed to share a common sympathoadrenal (SA) progenitor with sympathetic neurons. For decades, the adrenal cortical environment was assumed to be essential for channelling SA progenitors towards an endocrine chromaffin cell fate. Our recent analysis of steroidogenic factor 1(Sf1) −/− mice, which lack an adrenal cortex, has challenged this view: in Sf1 −/− mice chromaffin cells migrate to the correct “adrenal” location and undergo largely normal differentiation. In contrast to Sf1 homozygous mutants, heterozygous animals have an adrenal cortex, which, however, is smaller than in wildtype littermates. We show here that the Sf1 +/− adrenal cortical anlagen attract normal numbers of chromaffin progenitor cells into their vicinity by embryonic day 13.5 (E13.5). Two days later, however, only a few scattered cells with highly immature features have immigrated into the adrenal cortex, whereas the remainder form a coherent cell assembly ectopically located at the medial surface of the gland. These cells appear more mature than the scattered intracortical chromaffin progenitors and express the adrenaline synthesizing enzyme PNMT with a delay of 1 day in comparison with wildtype littermates. Nevertheless, chromaffin progenitor cells undergo a numerical reduction of approximately 30% by E17.5. Together, our data suggest that normal adrenocortical development is critical for the correct immigration of chromaffin progenitors into the cortical anlagen, for the timing of PNMT expression and for the regulation of chromaffin cell numbers.This work was supported by a grant from the Deutsche Forschungsgemeinschaft (SFB 488, TP A6).     

Dietary cholesterol enhances torpor in a rodent hibernator

Dietary cholesterol can affect both body lipid composition and steroid hormone concentration. We investigated whether a diet rich in cholesterol influences torpor patterns of hibernating chipmunks (Tamias amoenus) and, if so, whether these changes are better explained by diet-induced changes in body lipid composition or the concentration of testosterone, which at high levels inhibits torpor. Two groups of chipmunks were maintained either on a cholesterol diet (rodent chow containing 10% cholesterol) or a control diet (rodent chow) during pre-hibernation fattening and throughout the hibernation season. Torpid chipmunks on the cholesterol diet had significantly lower minimum body temperatures (−0.2 ± 0.2 vs +0.6 ± 0.2 °C), lower metabolic rates (0.029 ± 0.002 ml O₂ g⁻¹h⁻¹ vs 0.035 ± 0.001 ml O₂ g⁻¹h⁻¹), and longer torpor bouts at −1 °C (6.8 ± 0.5 vs 4.1 ± 1.0 days) than chipmunks on the control diet. Dietary cholesterol resulted in a significant increase in blood plasma cholesterol (sevenfold), liver cholesterol content (6.9-fold) and liver triglyceride content (3.5-fold) in comparison to controls. In contrast, dietary cholesterol had no detectable effect on the concentration of plasma testosterone, which was very low in both groups. Since torpor was deeper and longer in animals on the cholesterol diet our study suggests that torpor patterns of chipmunks were either directly affected by the dietary cholesterol or via changes in body lipid composition. Accepted: 22 January 1997     

Anaerobic co-digestion of dairy manure with mulched switchgrass for improvement of the methane yield

The owners of farm-scale anaerobic digesters are relying on off-farm wastes or energy crops as a co-digestion feedstock with animal manure in order to increase their production of methane and thus revenues. Switchgrass represents an interesting feedstock for Canadian digesters owners as it is a high-yielding low-maintenance perennial crop, well adapted to northern climate. Methane potential assays in batch tests showed methane production of 19.4 ± 3.6, 28.3 ± 1.7, 37.3 ± 7.1 and 45.7 ± 0.8 L kg⁻¹, for raw manure, blended manure, manure and mulched switchgrass, manure and pretreated switchgrass, respectively. Two 6-L lab-scale anaerobic digesters were operated for 130 days in order to assess the benefit of co-digesting switchgrass with bovine manure (digester #2), at a 20% wet mass fraction, compared with a manure-only operation (digester #1) The digesters were operated at an hydraulic retention time of 37 ± 6 days and at loads of 2.4 ± 0.6 and 2.6 ± 0.6 kg total volatile solids (TVS) L⁻¹ day⁻¹ for digesters #1 (D1) and #2 (D2), respectively. The TVS degradation reached 25 and 39%, which resulted in a methane production of 1.18 ± 0.18 and 2.19 ± 0.31 L day⁻¹ for D1 and D2, respectively. The addition of 20% on a wet mass ratio of switchgrass to a manure digester increased its methane production by 86%. The co-digestion of switchgrass in a 500 m³ manure digester could yield up to 10.2 GJ day⁻¹ of purified methane or 1.1 MWh day⁻¹ of electricity.     

Relevance of bacterioplankton abundance and production in the oligotrophic equatorial Indian Ocean

Bacterioplankton abundance and production, chlorophyll a (Chl a) concentrations and primary production (PP) were measured from the equatorial Indian Ocean (EIO) during northeast (NEM), southwest (SWM) and spring intermonsoon (SpIM) seasons from 1°N to 5°S along 83°E. The average bacterial abundance was 0.52 ± 0.29, 0.62 ± 0.33 and 0.46 ± 0.19 (× 10⁸ cells l⁻¹), respectively during NEM, SWM and SpIM in the top 100 m. In the deep waters (200 m and below), the bacterial counts averaged ∼0.35 ± 0.14 × 10⁸ cells l⁻¹ in SWM and 0.39 ± 0.16 × 10⁸ cells l⁻¹ in SpIM. The 0–120 m column integrated bacterial production (BP) ranged from 19 to 115 and from 10 to 51 mg C m⁻² d⁻¹ during NEM and SWM, respectively. Compared with many open ocean locations, bacterial abundance and production in this region are lower. The bacterial carbon production, however, is notably higher than that of phytoplankton PP (BP:PP ratio 102% in SWM and 188% in NEM). With perpetually low PP (NEM: 20, SWM: 18 and SpIM: 12 mg C m⁻² d⁻¹) and Chl a concentration (NEM: 16.5, SWM: 15.0 and SpIM: 20.9 mg m⁻²), the observed bacterial abundance and production are pivotal in the trophodynamics of the EIO. Efficient assimilation and mineralization of available organics by bacteria in the euphotic zone might serve a dual role in the ultra-oligotrophic regions including EIO. Thus, bacteria probably sustain microheterotrophs (micro- and meso-zooplankton) through microbial loop. Further, rapid mineralization by bacteria will make essential nutrients available to autotrophs.     

Microcapsules and Transdermal Patch: A Comparative Approach for Improved Delivery of Antidiabetic Drug

Glibenclamide (GL)-loaded microcapsules (MC) and transdermal patches (TDP) were formulated and in vitro and in vivo parameters compared to find out the best route of drug administration. The formulation TDP1 having a drug–polymer ratio 1:1 showed comparatively higher GL release and better permeation across mice skin (p < 0.05). From the comparative study, it was concluded that the transdermal system of GL produced better improvement compared to oral microcapsule administration (p < 0.05). The transdermal system exhibited comparatively slow and continuous supply of GL at a desired rate to systemic circulation avoiding metabolism, which improved day-to-day glycemic control in diabetic subjects. Transdermal system of GL exhibited better control of hyperglycemia and prolonged plasma half-life by transdermal systems (9.6 ± 1.2 h) in comparison with oral microcapsule (5.84 ± 2.1 h), indicating that the drug, when administered by transdermal systems, will remain in the body for a longer period. From the glucose tolerance test, transdermal route effectively maintained the normoglycemic levels in contrast to the oral group (MC1), which produced remarkable hypoglycemia ranging from −12.6 ± 2.1% to −18 ± 2.3%. The significantly high (p < 0.05) area under the curve values observed with transdermal system (1,346.2 ± 92.3 ng ml⁻¹ h⁻¹) also indicate increased bioavailability of the drug from these systems compared to the oral route (829.8 ± 76.4 ng ml⁻¹ h⁻¹).     

Light colour influences the behaviour and stress physiology of captive tench (<Emphasis Type="Italic">Tinca tinca</Emphasis>)

Groups of juvenile tench (7.02 ± 0.28 g) were reared under four different light regimes; blue light, red light (80 Wm⁻² 12L:12D photoperiod) white light (912 ± 210 lux, 80 Wm⁻², 12L:12D photoperiod) and no light (0 lux) (0L:24D). Visibility of fish out of shelters was used as an indicator of activity and was monitored by video recording. Blood plasma cortisol concentrations were also measured. Fish under blue or white light were significantly less active during the photophase than those under red or no light (P < 0.01). Red light produced similar activity patterns to fish receiving 24 h darkness. Plasma cortisol concentrations were also significantly influenced (P < 0.05) with the fish under white light having the highest plasma cortisol concentration (317 ± 62 ng cm⁻³) compared to fish in the dark treatment (106 ± 36 ng cm⁻³). Thus, the provision of coloured light filters increases activity in juvenile tench and may reduce their intrinsic stress level.     

Drift-ice and under-ice water communities in the Gulf of Bothnia (Baltic Sea)

The algal, protozoan and metazoan communities within different drift-ice types (newly formed, pancake and rafted ice) and in under-ice water were studied in the Gulf of Bothnia in March 2006. In ice, diatoms together with unidentified flagellates dominated the algal biomass (226 ± 154 μg ww l⁻¹) and rotifers the metazoan and protozoan biomass (32 ± 25 μg ww l⁻¹). The under-ice water communities were dominated by flagellates and ciliates, which resulted in lower biomasses (97 ± 25 and 21 ± 14 μg ww l⁻¹, respectively). The under-ice water and newly formed ice separated from all other samples to their own cluster in hierarchical cluster analysis. The most important discriminating factors, according to discriminant analysis, were chlorophyll-a, phosphate and silicate. The under-ice water/newly formed ice cluster was characterized by high nutrient and low chlorophyll-a values, while the opposite held true for the ice cluster. Increasing trends in chlorophyll-a concentration and biomass were observed with increasing ice thickness. Within the thick ice columns (>40 cm), the highest chlorophyll-a concentrations (6.6–22.2 μg l⁻¹) were in the bottom layers indicating photoacclimation of the sympagic community. The ice algal biomass showed additional peaks in the centric diatom-dominated surface layers coinciding with the highest photosynthetic efficiencies [0.019–0.032 μg C (μg Chl-a ⁻¹ h⁻¹) (μE m⁻² s⁻¹)⁻¹] and maximum photosynthetic capacities [0.43-1.29 μg C (μg Chl-a ⁻¹ h⁻¹)]. Rafting and snow-ice formation, determined from thin sections and stable oxygen isotopic composition, strongly influenced the physical, chemical and biological properties of the ice. Snow-ice formation provided the surface layers with nutrients and possibly habitable space, which seemed to have favored centric diatoms in our study.     

Reflex bradycardia does not influence oxygen consumption during hypoxia in the European eel (Anguilla anguilla)

Most teleost fish reduce heart rate when exposed to acute hypoxia. This hypoxic bradycardia has been characterised for many fish species, but it remains uncertain whether this reflex contributes to the maintenance of oxygen uptake in hypoxia. Here we describe the effects of inhibiting the bradycardia on oxygen consumption (MO₂), standard metabolic rate (SMR) and the critical oxygen partial pressure for regulation of SMR in hypoxia (Pcrit) in European eels Anguilla anguilla (mean ± SEM mass 528 ± 36 g; n = 14). Eels were instrumented with a Transonic flow probe around the ventral aorta to measure cardiac output (Q) and heart rate (f _H). MO₂ was then measured by intermittent closed respirometry during sequential exposure to various levels of increasing hypoxia, to determine Pcrit. Each fish was studied before and after abolition of reflex bradycardia by intraperitoneal injection of the muscarinic antagonist atropine (5 mg kg⁻¹). In the untreated eels, f _H fell from 39.0 ± 4.3 min⁻¹ in normoxia to 14.8 ± 5.2 min⁻¹ at the deepest level of hypoxia (2 kPa), and this was associated with a decline in Q, from 7.5 ± 0.8 mL min⁻¹ kg⁻¹ to 3.3 ± 0.7 mL min⁻¹ kg⁻¹ in normoxia versus deepest hypoxia, respectively. Atropine had no effect on SMR, which was 16.0 ± 1.8 μmol O₂ kg⁻¹ min⁻¹ in control versus 16.8 ± 0.8 μmol O₂ kg⁻¹ min⁻¹ following treatment with atropine. Atropine also had no significant effect on normoxic f _H or Q in the eel, but completely abolished the bradycardia and associated decline in Q during progressive hypoxia. This pharmacological inhibition of the cardiac responses to hypoxia was, however, without affect on Pcrit, which was 11.7 ± 1.3 versus 12.5 ± 1.5 kPa in control versus atropinised eels, respectively. These results indicate, therefore, that reflex bradycardia does not contribute to maintenance of MO₂ and regulation of SMR by the European eel in hypoxia.