Studies of alveolar cell morphometry and mass clearance in the rat lung following inhalation of an enriched uranium dioxide aerosol

Summary Seventy-three rats were exposed to an aerosol of enriched uranium dioxide (UO₂), giving initial lung burdens of 26 to 447 µg at 6 days post-inhalation (PI). At 7 days PI 35 of these rats were further exposed to thermalised neutrons at a fluence of 1 x 10¹² neutrons CM^–2. There was no significant difference between the two groups in the clearance rate of the UO₂ particles from the lung, up to 590 days PI. The particles cleared relatively slowly over this period with a retention halftime in the lung of 160 to 176 days.Transmission electron microscope (TEM) studies of tissue from the alveolar region at 8 days PI showed that inhalation of UO₂ particles significantly increased the sizes of macrophage and type II cells, and the number of macrophage and type I cells. There was also a significant increase in the size of lysosomal granules within the macrophages after exposure to the UO₂ particles. The exposure to UO₂, neutrons and²³⁵U fission fragments had no significant effect on any of the cells above that observed in the animals exposed to UO₂ alone.Additional rats were exposed to the same neutron fluence without prior UO₂ inhalation. The alveolar cells of neutron-only exposed rats were, in size and number, typically no different from those in the completely unexposed control rats.     

Development, survival and fecundity of the urine fly, Scatella (Teichomyza) fusca and predation by the black dumpfly, Hydrotaea aenescens

Development, survival and fecundity for Scatella (Teichomyza) fusca Maquart (Diptera: Ephydridae) were studied at 20 ± 1 °C and 85 ± 10% r.h. Mean (± S.E.) developmental times of eggs, larvae and pupae were 4.0 ± 0.06, 14.9 ± 0.19 and 14.6 ± 0.11 days, respectively, the mean (± S.E.) survival of the original egg cohort to the start of larval, pupal and adult stage being 77.2 ± 3.2%, 54.5 ± 2.6% and 47.9 ± 3.5%, respectively. Females and males displayed approximately straight survivorship curves during adult life, implying constant mortality rates. Mean (± S.E.) adult longevity was 41.6 ± 2.98 days for females and 51.2 ± 3.91 days for males. Assuming a stable age distribution the population consisted of 56% eggs, 31% larvae, 6% pupae and 7% adults. Oviposition peaked when females were 25 days old, and the highest reproductive values (RV_x) (mean ± S.E.) ranged from 129.1 ± 7.57 to 138.5 ± 6.83 for individuals 17–27 days old. A female deposited a mean (± S.E.) of 614.7 ± 35.9 female eggs over a maximum life span of 93 days. The basic reproductive rate (R ₀) (mean ± S.E.) was 173.0 ± 14.2 female offspring per female and the intrinsic rate of natural increase of female individuals (r) (mean ± S.E.) was 0.088 ± 0.001 day^-1. The mean (± S.E.) generation time (T) was 57.8 ± 0.78 days. In cultures with equal numbers of first instar S. fusca larvae and predacious third instar larvae of Hydrotaea aenescens (synonymous Ophyra aenescens) Wiedemann, mean (± S.E.) survival to the adult stage of S. fusca (16.7 ± 8.8%) was significantly lower than in controls with S. fusca alone (58.3 ± 7.4%). The potential significance of predation by H. aenescens on S. fusca in pig farms is discussed.     

Attachment of Blastomyces dermatitidis conidia to murine bronchoalveolar macrophages: Characterization of binding the elicitation of respiratory burst

We studied the mechanisms of adherence of Blastomyces dermatitidis conidia to murine bronchoalveolar macrophages and the ability of the conidia to elicit an increase in macrophage O _inf2 ^sup- production, using an avirulent fungal strain. The number of cell associated conidia was counted by visual inspection of 2 hour macrophage monolayers incubated with conidia and O _inf2 ^sup- was measured by reduction of ferricytochrome c. Adherence of conidia to bronchoalveolar macrophages was time dependent and reached a plateau after 30 min (36±5%, 51±22%, and 36±17% macrophages with adherent conidia after 15, 30, and 60 min, respectively). Both Ca⁺² and Mg⁺² were required. The carbohydrates mannose, mannan, fucose, alpha-methylmannoside, beta-glucan, galactose, N-acetylglucosamine and chitotriose (100–1000 g/ml) did not inhibit adherence of conidia to macrophages. Trypsin treatment of macrophages or conidia did not affect binding. Conidia did not stimulate bronchoalveolar macrophage production of O _inf2 ^sup- above baseline concentrations (2.0±0.9 vs 0.8±0.5 nmol O _inf2 ^sup- , p>0.05). We conclude that murine bronchoalveolar macrophage-B. dermatitidis conidia interactions occur primarily by a non-lectin-like attachment and do not result in the production of macrophage derived O _inf2 ^sup- .     

The Kinetics of Hydrolysis of Animal Fat by Pancreatic Lipase

Hydrolysis of lipids from beef fat by pancreatic lipase was studied. The maximum release of free fatty acids was shown to occur at 40°C for the first 3 h of the experiment. After this, transetherification was predominant. The main kinetic parameters were the following: maximum hydrolysis rate, V = 1.25 ± 0.1 mg fat/ml min; Michaelis constant, K _M ^H = 100 ± 12 mg fat/ml; constant of substrate inhibition, K _S = 10.0 ± 0.8 mg fat/ml; equilibrium constant, K _P = 277 ± 170 mg fat/ml; and activation energy of beef fat hydrolysis by pancreatic lipase, E _a = 19.1 ± 1.1 kJ/mole. The kinetic method used could be applied to development of the method for biotransformation of poorly assimilated fats into more valuable products.     

Mechanism of Mg Binding in the Na,K-ATPase

The Mg²⁺ dependence of the kinetics of the phosphorylation and conformational changes of Na⁺,K⁺-ATPase was investigated via the stopped-flow technique using the fluorescent label RH421. The enzyme was preequilibrated in buffer containing 130 mM NaCl to stabilize the E1(Na⁺)₃ state. On mixing with ATP, a fluorescence increase was observed. Two exponential functions were necessary to fit the data. Both phases displayed an increase in their observed rate constants with increasing Mg²⁺ to saturating values of 195 (± 6) s⁻¹ and 54 (± 8) s⁻¹ for the fast and slow phases, respectively. The fast phase was attributed to enzyme conversion into the E2MgP state. The slow phase was attributed to relaxation of the dephosphorylation/rephosphorylation (by ATP) equilibrium and the buildup of some enzyme in the E2Mg state. Taking into account competition from free ATP, the dissociation constant (K_d) of Mg²⁺ interaction with the E1ATP(Na⁺)₃ state was estimated as 0.069 (± 0.010) mM. This is virtually identical to the estimated value of the K_d of Mg²⁺-ATP interaction in solution. Within the enzyme-ATP-Mg²⁺ complex, the actual K_d for Mg²⁺ binding can be attributed primarily to complexation by ATP itself, with no apparent contribution from coordination by residues of the enzyme environment in the E1 conformation.     

Effect of external K+, Ca2+, and Ba2+ on membrane potential and ionic conductance in rat astrocytes

Summary 1. The purpose of this study was (a) to identify if astrocytes show a similar non-Nernstian depolarization in low K⁺ or low Ca²⁺ solutions as previously found in human glial and glioma cells, and (b) to analyze the influence of the K⁺ conductance on the membrane potential of astrocytes.2. The membrane potential (E_m) and the ionic conductance were studied with whole-cell patch-clamp technique in neonatal rat astrocytes (5–9 days in culture) and in human glioma cells (U-251MG).3. In 3.0 mM K⁺, E_m was –75 ± 1.0 mV (mean ± SEM,n=39) in rat astrocytes and –79 ± 0.7 mV (n=5) in U-251MG cells. In both cell types E_m changed linearly to the logarithm of [K⁺]₀ between 3.0 and 160 mM K⁺. K⁺ free medium caused astrocytes to hyperpolarize to –93 ± 2.7 mV (n=21) and U-251MG cells to depolarize to –27 ± 2.1 mV (n=3).4. The I-E curve did not show inward rectification in astrocytes at this developmental stage. The slope conductance (g) exhibited only a small decrease (–19%) in K⁺ free solution and no significant change in 160 mM K⁺.5. Ba²⁺ (1.0 mM) depolarized astrocytes to –45 ± 2.9 mV (n=11), decreasing the slope conductance (g) by 42.4 ± 8.3% (n=11). Ca²⁺ free solution depolarized astrocytes to –53 ± 3.4 mV (n=12) and resulted in a positive shift of the I-E curve, increasing g by 15.3 ± 8.2% (n=8).6. Calculations indicated that a block of K⁺ channels explains the depolarizing effect of Ba²⁺. The effects of K⁺ free or Ca²⁺ free solutions on E_m can be explained by a transformation of K⁺ channels to non-specific leakage channels. That astrocytes show a different reaction to low K⁺ than glioma cells can be related to the lack of inwardly rectifying K⁺ channels in astrocytes at this developmental stage.     

Kainate receptor modification in the fetal guinea pig brain during hypoxia

The present study tests the hypothesis that hypoxia alters the high-affinity kainate receptors in fetal guinea pig brain. Experiments were conducted in normoxic and hypoxic guinea pig fetus at preterm (45 days of gestation) and term (60 days of gestation). Hypoxia in the guinea pig fetus was induced by exposure to maternal hypoxia (FiO₂=7%) for 60 min. Brain tissue hypoxia in the fetus was documented biochemically by decreased levels of ATP and phosphorreatine. [³H]-Kainate binding characteristics (Bmax=number of receptors, Kd=dissociation constant) were used as indices of kainate receptor modification. P₂ membrane fractions were prepared from the cortex of normoxic and hypoxic fetuses and were washed six times prior to performing the binding assays. [³H]kainate binding was performed at 0°C for 30 min in a 500 l medium containing 50 mM Tris-HCl buffer, 0.1 mM EDTA (pH 7.4), 300 g protein and varying concentrations of radiolabelled kainate ranging from 1 to 200 nM. Non-specific binding was determined in the presence of 1.0 mM glutamate. During brain development from 45 to 60 days gestation, Bmax value increased from 330±16 to 417±10 fmoles/mg protein; however, the Kd was unchanged (8.2±0.4 vs 8.8±0.5 nM, respectively). During hypoxia at 60 days, the Kd value significantly increased as compared to normoxic control (15.5±0.7 vs 8.8±0.5 nM, respectively), whereas the Bmax was not affected (435±12 vs 417±10 fmol/mg protein, respectively). At 45 days, hypoxia also increased the Kd (11.9±0.6 vs 8.2±0.4 nM) without affecting the Bmax (290±15 vs 330±16 fmol/mg protein, respectively). The results show that the number of kainate receptors increase during gestation without change in affinity and demonstrate that hypoxia modifies the high-affinity kainate receptor sites at both ages; however the effect is much stronger at 60 days (term). The decreased affinity of the site could decrease the kainate receptor-mediated fast kinetics of desensitization and provide a longer period for increased Na⁺-influx, leading to increased accumulation of intracellular Ca²⁺ by reversal of the Na⁺–Ca²⁺ exchange mechanism. In addition, Kd values for kainate-type glutamate receptor sites are 30–40 fold lower (i.e. higher affinity) than those for NMDA-displaceable glutamate sites. The higher affinity suggests that the activation of the kainate-type glutamate receptor during hypoxia could precede initiation of NMDA receptormediated excitotoxic mechanisms. We propose that hypoxia-induced modification of the high affinity kainate receptor in the fetus is a potential mechanism of neuroexcitotoxicity.     

Daily milk intake and body water turnover in suckling mink (Mustela vison) kits

Daily (24 h) milk intake and body water turnover were measured in eight litters of suckling mink (Mustela vison) kits (6–9 kits litter⁻¹) during weeks 1–4 post partum using the tritiated water (³HHO) dilution technique. The biological half-life of body water turnover in the mink kits increased linearly from 0.9 days in week 1 (3–5 days post partum) to 1.9 days in week 4 (22–24 days post partum). The daily milk intake varied markedly among the mink kits within a litter and increased significantly with increasing body mass from (mean±SEM) 10.9±0.4 g per kit during week 1 to 27.7±1.0 g per kit during week 4. Throughout the study, male kits were ∼10% heavier and had a significantly higher milk intake than female kits. The results were corrected for water recycling between the dam and her kits, ranging from ∼4 to 15% of the daily milk water intake, and the calculated daily milk yield of the 2 year old lactating mink dams increased from 87±7 g day⁻¹ in week 1 to 190±15 g day⁻¹ in week 4 post partum. The average body growth rate of the mink kits ranged from 2.9 g kit⁻¹ per day in week 1 to 5.4 g kit⁻¹ per day in week 4, and the calculated mean intake of mink milk per unit of body weight gain was remarkably stable at 4.0 (g g⁻¹) during weeks 1–3 post partum, but increased to 5.6 (g g⁻¹) in week 4 post partum. The amount of metabolizable energy supplied to the kits by the daily milk yield of the dam increased from ≈450 to ≈990 kJ day⁻¹, which corresponded well with the calculated daily energy requirements of the kits. The tritiated water dilution technique was found feasible and reliable for repeated measurements of milk intake in suckling mink kits up to 4 weeks of age.     

Increased removal capacity for 1,2-dichloroethane by biological modification of the granular activated carbon process

The removal of 5 mg 1^–1 1,2-dichloroethane [(CH₂Cl)₂] was studied in two granular activated carbon (GAC) reactors run with hydraulic retention times of below 1 h. One reactor was operated abiotically. The other one was inoculated with microorganisms able to degrade (CH₂Cl)₂. While the (CH₂Cl)₂-adsorption capacity of the non-inoculated GAC reactor was exhausted after 20 days, it apparently did not exhaust for at least 170 experimental days in the biologically activated system because (CH₂Cl)₂ was removed to over 95% as a result of the microbial degradation. The biodegradation was quantified: during the passage through the biologically activated GAC reactor, (CH₂Cl)₂ (5± mg l^–1) disappeared, chloride ions (3.3±0.2 mg l^–1) were produced, and oxygen (4 to 6 mg l^–1) was consumed. Removal of 30% of GAC at the entrance of the reactor, which visibly carried most of the biomass, and its replacement by virgin GAC at the end of the column did not change the apparent (CH₂Cl)₂removal capacity of the GAC column, indicating that still enough biomass was available to degrade most of the chemical fed. After the addition of the virgin carbon, the effluent concentration fell for a short period of time from about 200 g l^–1 to below 100 g l^–1, indicating partial adsorption of the non-degraded (CH₂Cl)₂ at the end of the reactor by the virgin carbon. Thus, the modification of the adsorption process by inoculation and maintenance of bacteria with special degradation capabilities resulted in a lower consumption of GAC and thus led to an extended service life of the GAC columns.     

Ionic and osmotic regulation capabilities of juvenile Gulf of Mexico sturgeon, Acipenser oxyrinchusde sotoi

The salinity tolerance, and hydromineral regulation capabilities of three size groups (small 110–170 g; medium 230–290 g, large 460–700 g; n=48 for each group) of 13-month-old juvenile Gulf of Mexico sturgeon were investigated. Fish (n=6 for each salinity) were transferred directly from freshwater (FW) to a series of experimental salinity treatments (0, 5, 10, 15, 20, 25, 30, and 35 parts per thousand (ppt)). Fish were also acclimated in brackish water (20 ppt) for 2 weeks and transferred to a salinity of 34 ppt. In this condition juvenile Gulf of Mexico sturgeon adapted to saltwater (SW) and maintained their hydromineral balance. FW adapted sturgeon (n=6) had an average blood hemotocrit of 28.2±0.8%, plasma osmolality of 260.7±1.6 mOsm kg⁻¹ H₂O, and plasma ion concentrations of 135.7±1.2 mM l⁻¹ Na⁺, 106.9±1.9 mEq l⁻¹ Cl⁻, and 2.9±0.1 mM l⁻¹ K⁺. In SW adapted sturgeon (n=8) blood parameters averaged 26.9±0.7% for hematocrit, 294.2±2.3 mOsm kg⁻¹ H₂O for osmolality, 152.0±1.7 mM l⁻¹ Na⁺, 149.2±1.4 mEq l⁻¹ for Cl⁻, and 3.1±0.1 mM l⁻¹ K⁺. The method of transfer (abrupt or slow acclimation) directly affected fish survival and the time they took to achieve ionic and osmotic regulation. This SW adaptation appears to be related to body size, the larger the fish the easier the adaptation process. A threshold size of about 170 g was apparent for the fish to adapt to saltwater after 2 weeks of acclimation. Chloride cells were present in both FW and SW adapted sturgeon with SW and brackish water fish having chloride cells significantly (P<0.05) more numerous (561±53 and 598±45 cells mm⁻²) and larger in size (41.0±3.85 and 34.2±4.49 μm²) than FW adapted sturgeon (10±1.0 cells mm⁻² and 22±2.53 μm²). Few chloride cells were observed in the opercular membrane, however, none were found in the pseudobranch and spiracle.     

Effect on airways resistance of prostaglandin E1 given by aerosol to healthy and asthmatic volunteers

The forced expiratory volume in one second (F.E.V.₁) was measured in healthy and asthmatic volunteers and the inhalation of prostaglandin E₁ (PGE₁) was compared with that of isoprenaline, using metered aerosols.In healthy volunteers PGE₁, either as the free acid or the neutral triethanolamine salt, did not affect the F.E.V.₁; the free acid was irritant to the upper respiratory tract. In five out of six asthmatic volunteers with reversible airways obstruction, inhalation of 55 μg of PGE₁ (triethanolamine salt) produced an increase in F.E.V.₁ comparable in both degree and duration to that produced by an inhalation of 550 μg. of isoprenaline sulphate.Though the triethanolamine salt was well tolerated in most of the asthmatic subjects studied, in one asthmatic subject this preparation caused coughing and there was a progressive reduction in the F.E.V.₁ associated with bronchospasm.     

Technical considerations for assessing alterations in skeletal muscle sarcoplasmic reticulum Ca++-sequestration functionin vitro

A multiple measurement system for assessing sarcoplasmic reticulum (SR) Ca⁺⁺-ATPase activity and Ca⁺⁺-uptake was used to examine the effects of SR fractionation and quick freezing on rat white (WG) and red (RG) gastrocnemius muscle.In vitro measurements were performed on whole muscle homogenates (HOM) and crude microsomal fractions (CM) enriched in SR vesicles before and after quick freezing in liquid nitrogen. Isolation of the CM fraction resulted in protein yields of 0.96±0.1 and 0.99±0.1 mg/g in WG and RG, respectively. The percent Ca⁺⁺-ATPase recovery for CM compared to HOM was 14.5% (WG) and 10.1% (RG). SR Ca⁺⁺-activated Ca⁺⁺-ATPase activity was not affected by quick freezing of HOM or CM, but basal ATPase was reduced (P<0.05) in frozen HOM (5.12±0.18–3.98±0.20 mole/g tissue/min in WG and from 5.39±0.20–4.48±0.24 mole/g tissue/min in RG). Ca⁺⁺-uptake was measured at a range of physiological free [Ca⁺⁺] using the Ca⁺⁺ fluorescent dye Indo-1. Maximum Ca⁺⁺-uptake rates when corrected for initial [Ca⁺⁺]_f were not altered in HOM or CM by quick freezing but uptake between 300 and 400nM free Ca⁺⁺ was reduced (P<0.05) in quick frozen HOM (1.30±0.1–0.66±0.1 mole/g tissue/min in WG and 1.04±0.2–0.60±0.1 mole/g tissue/min in RG). Linear correlations between Ca⁺⁺-uptake and Ca⁺⁺-ATPase activity measured in the presence of the Ca⁺⁺ ionophore A23187 were r=+0.25, (P<0.05) and r=+0.74 (P<0.05) in HOM and CM preparations, respectively, and were not altered by freezing. The linear relationships between HOM and CM maximum Ca⁺⁺-uptake (r=+0.44, P<0.05) and between HOM and CM Ca⁺⁺-ATPase activity (r=+0.34, P<0.05) were also not altered by tissue freezing. These data suggest that alterations in maximal SR Ca⁺⁺-uptake function and maximal Ca⁺⁺-ATPase activity may be measured in both HOM and CM fractions following freezing and short term storage. (Mol Cell Biochem139, 41–52, 1994)     

INFLUENCE OF UV-B RADIATION ON NITROGEN UTILIZATION BY A NATURAL ASSEMBLAGE OF PHYTOPLANKTON

A 7‐day mesocosm experiment was conducted in July 1996 to investigate the effects of ambient UV‐B radiation (UVBR) exclusion and two UVBR enhancements above ambient levels on NO₃^?, NH₄⁺ and urea utilization in a natural plankton community (<240 μm) from the Lower St. Lawrence Estuary. The phytoplankton community was dominated by diatoms during the first 3 days and, afterward, by flagellates and dinoflagellates. The results of 4‐h incubations just below the water surface show that, compared with ambient UVBR conditions, UVBR exclusion generally increased NO₃^?, NH₄⁺, and urea uptakes. During the last 4 days of the experiment, the percent increase in the specific uptake rate of urea under excluded UVBR conditions varied between 17% and 130% and was a linear function of the ambient UVBR dose removed. During the first 3 days, the phytoplankton community dominated by diatoms was able to withstand UVBR enhancements without any perceptible effect on nitrogen uptake. However, during the post‐diatom bloom period, UVBR enhancements resulted in decreases in NO₃^?, NH₄⁺, and urea uptake compared with ambient UVBR conditions. The reduction of urea uptake under UVBR enhancements during the last 3 days varied between 23% and 64% and was linearly related to the enhanced UVBR dose. However, the different UVBR treatments did not affect the internal organic nitrogen composition (internal urea, free amino acids, and proteins) of the phytoplankton community experiencing vertical mixing in the mesocosms. The discrepancy between short‐term uptake measurements at the surface and long‐term effects in the mesocosms emphasizes the importance of vertical mixing on UVBR effects in natural ecosystems. This suggests that an increase in ambient UVBR would have a minimal effect on nitrogen utilization by natural phytoplankton assemblages if these are vertically mixed.     

Detection of ischemia-reperfusion cardiac injury by cardiac muscle chemiluminescence

Various methods have been used in the past to assess the implication of oxygen free radicals (OFR) in ischemia-reperfusion-induced cardiac injury. Luminol-enhanced tert-butyl-initiated chemiluminescence in cardiac tissue reflects oxidative stress and is a very sensitive method. It was used to elucidate the role of OFR in cardiac injury due to ischemia and reperfusion. Studies were conducted on perfused isolated rabbit hearts in three groups (n = 8 in each): I, control; II, submitted to global ischemia for 30 min; III, submitted to ischemia for 30 min followed by reperfusion for 60 min. The heart tissue was then assayed for chemiluminescence (CL); content of malondialdehyde (MDA), an indicator of OFR-induced cardiac injury; and activity of tissue levels of antioxidants [superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px)].The control values for left and right ventricular CL and malondialdehyde were 81.1 ± 15.4 (S.E.) and 182.4 ± 50.3 (S.E.), mv-min-mg protein^–1; and 0.024 ± 0.006 (S.E.) and 0.324 ± 0.005 (S.E.) nmoles-mg protein^–1 respectively. Ischemia produced an increase in the cardiac CL (3.3 to 4.4 fold) and MDA content (2 to 2.6 fold). Reperfusion following ischemia also produced similar changes in CL and MDA content. The control values for activity of left ventricular SOD, catalase, and GSH-Px were 45.77 ± 1.73 (S.E.) U-mg protein^–1 5.35 ± 0.51 (S.E.) K-10^–3-sec^–1-mg protein^–1, and 77.50 ± 7.70 (S.E.) nmoles NADPH-min^–1-mg protein^–1 respectively. Activities of SOD and catalase decreased during ischemia but were similar to control values in ischemic-reperfused hearts. The GSH-Px activity of left ventricle was unaffected by ischemia, and ischemia-reperfusion. GSH-Px activity of the right ventricle increased with ischemia, and ischemic-reperfusion.These results indicate that cardiac tissue chemiluminescence would be a useful and sensitive tool for the detection of oxygen free radical-induced cardiac injury.     

Comparison of the structure of ribosomal 5S RNA from E. coli and from rat liver using X-ray scattering and dynamic light scattering

The structures of eukaryotic ribosomal 5S RNA from rat liver and of prokaryotic 5S RNA from E. coli (A-conformer) have been investigated by scattering methods. For both molecules, a molar mass of 44,500±4,000 was determined from small angle X-ray scattering as well as from dynamic light scattering. The shape parameters of the two rRNAs, volume V _c, surface O _c, radius of gyration R _s, maximum dimension of the molecule L, thickness D, and cross section radius of gyration R _sq, agree within the experimental error limits. The mean values are V _c=57±3 nm³, O _c=165±10 nm², R _s=3.37±0.05 nm, L=10.8±0.7 nm, D=1.57±0.07 nm, R _sa=0.92±0.01 nm.Identical structures for the E. coli 5S rRNA and the rat liver 5S rRNA at a resolution of 1 nm can be deduced from this agreement and from the comparison of experimental X-ray scattering curves and of experimental electron distance distribution function. The flat shape model derived for prokaryotic and eukaryotic 5S rRNA shows a compact region and two protruding arms. Double helical stems are eleven-fold helices with a mean base pair distance of 0.28 nm. Combining the shape information obtained from X-ray scattering with the information about the frictional behaviour of the molecules, deduced from the diffusion coefficients D _20,w ⁰ =(5.9±0.2)·10^-7 cm²s^-1 and (6.2±0.2)·10^-7 cm²s^-1 for rat liver 5S rRNA and E. coli 5S rRNA, respectively, a solvation shell of about 0.3 nm thickness around both molecules is determined. This structural similarity and the consensus secondary structure pattern derived from comparative sequence analyses suggest that all 5S rRNAs may indeed have conserved essentially the same type of folding of their polynucleotide strands during evolution, despite having very different sequences.     

Catecholamines in fetal pig plasma and the response to acute hypoxia and chronic fetal decapitation

Summary Dopamine, norepinephrine and epinephrine were measured by radioenzymatic assay in blood plasma samples drawn from the umbilical arteries of 30 anaesthetised Landrace pig fetuses. Just prior to term, the concentrations of dopamine (0.46±0.14 ng·ml^–1) and norepinephrine (1.74±0.60 ng·mg^–1) were lower than earlier in gestation, whereas epinephrine concentrations at term (0.80±0.31 ng·ml^–1) were similar to those at mid-gestation, intervening stages of gestation having higher levels of plasma epinephrine. Fetal hypoxia was induced by clamping the umbilical cord for 2 min and the catecholamines determined in arterial blood samples immediately thereafter, then again 3 min after removal of the clamp. Inconsistent effects of cord clamping on catecholamine levels were seen at 55 days, but thereafter, in all but one instance, the hormone levels were increased. Fetuses near term tended to respond less than fetuses at 75 and 96 days gestation (term=114±1 day). Catecholamines were also present in the circulation of fetuses decapitated at 42 days gestation and studied at 109±1 days. The average concentrations of dopamine (1.12±0.27 ng·ml^–1) and norepinephrine (8.23±3.04 ng·ml^–1) were greater than in intact fetuses, the plasma epinephrine levels being comparable to, or slightly higher than, those in intact fetuses. The results demonstrate that catecholamines are present in the circulation of the intact and decapitated pig fetus and that the actual concentrations and the type of response to umbilical cord clamping are dependent on gestation age.     

Imipramine-Induced Changes in 5-HT2 Receptor Sites and Inositoltrisphosphate Levels in Rat Brain

The effect of chronic administration of Imipramine on [³H]Spiperone binding to 5-HT₂ sites and inositoltrisphosphate (IP₃) levels in rat cerebral cortex was studied. Our data shows that treatment with imipramine (5 mg/kg body weight, intraperitoneally) for 30 days significantly down regulates 5-HT₂ receptors sites (262 ± 29 fmol/mg protein) in cerebral cortex (38%), compared to control rats (425 ± 60 fmol/mg protein., P < 0.001). However there was no significant change in the affinity of [³H]-Spiperone binding (kd) to 5-HT₂ sites in cerebral cortex after exposure to imipramine (Kd = 0.84 ± 0.11 nM). It is also observed that imipramine treatment significantly reduces 5-HT stimulated [³H]IP₃ formation in cerebral cortex (6,411 ± 708 dpm/mg protein), compared to the saline treated rats (12,238 ± 1,544 dpm/mg protein; P < 0.001), with concomitant decrease in Pdtlns-4–5-P₂. This study suggests that the therapeutic action of imipramine in brain might be by reducing hypersensitivity of 5-HT₂ receptors by down regulation, which leads to reduced levels of inositolphospholipids. This inturn reduces the levels of IP₃. In conclusion, imipramine acts at presynaptic site by blocking the reuptake of serotonin and at post synaptic site it downregulates 5-HT₂ sites with decreased IP₃ levels after chronic exposure.     

Dynamics of the Serine Chemoreceptor in the Escherichia coli Inner Membrane: A High-Speed Single-Molecule Tracking Study

We investigated the mobility of the polar localized serine chemoreceptor, Tsr, labeled by the fluorescent protein Venus in the inner membrane of live Escherichia coli cells at observation rates up to 1000 Hz. A fraction (7%) of all Tsr molecules shows free diffusion over the entire cell surface with an average diffusion coefficient of 0.40 ± 0.01 μm² s⁻¹. The remaining molecules were found to be ultimately confined in compartments of size 290 ± 15 nm and showed restricted diffusion at an inner barrier found at 170 ± 10 nm. At the shortest length-scales (<170 nm), all Tsr molecules diffuse equally. Disruption of the cytoskeleton and rounding of the cells resulted in an increase in the mobile fraction of Tsr molecules and a fragmenting of the previously polar cluster of Tsr consistent with a curvature-based mechanism of Tsr cluster maintenance.     

Influence of daylength on metabolic rate and daily water loss in the male prosimian primate Microcebus murinus

In its natural habitat, Microcebus murinus, a small malagasy prosimian primate, is exposed to seasonal shortage of water and resources. During the winter dry season, animals enter a pronounced fattening period with concurrent decrease in behavioural/physiological activities, whereas the breeding season is restricted to the rainy summer months. To determine the role of daylength on metabolic rate and water loss in this nocturnal primate, we measured body mass, oxygen consumption at 25°C (RMR), circadian water loss through urine output (UO) and evaporation (EWL) in eight males exposed to either short days (8L:16D SD) or long days (14L:10D LD), under controlled captive conditions. Exposure to SD led to a ponderal increase (maximal body mass: 125±4 g, N=8), and to significant changes in RMR and water loss, both reaching lowest values after 3 months under SD (0.84±0.04 ml O₂ h⁻¹ g⁻¹ and 38±0.3 mg H₂O g⁻¹ day⁻¹, respectively). Following exposure to LD, body mass decreased to 77±3 g (N=8), whereas both RMR and water loss, mainly through EWL, significantly increased (P<0.001), the highest value occurring after 2 months (1.51±0.08 ml O₂ h^.−1 g⁻¹ and 87±7 mgH₂O g⁻¹ day⁻¹, respectively). Moreover, independent of daylength, circadian changes in EWL were characterized by significantly reduced values during the diurnal rest. The results demonstrate that daylength variations affect the physiology of this tropical primate, allowing anticipatory adaptation to seasonal environmental constraints.     

Evaluation of cefquinome's efficacy in controlling avian colibacillosis and detection of its residues using high performance liquid chromatography (HPLC)

This study aimed to evaluate the efficacy of cefquinome in treatment and controlling of Escherichia coli experimentally infected broiler chickens, in addition of detection of its residues using High performance liquid chromatography (HPLC). In this study, 150 one-day old Cobb broiler chicks were used. On the 14^th day chicks experimentally infected and divided into 3 equal groups (50 each); control group (G1) non-infected, non-treated, (G2) infected with E. coli O₇₈ non treated, (G3) infected with E. coli O₇₈, cefquinome treated. Cefquinome was administrated 5^th day post infection, intramuscularly by a dose of (2 mg/ kg b w.t) for 3 consecutive days. Experimental E. coli infection in broilers induced weakness, loss of appetite, depression, cough and watery diarrhea in addition to a recorded mortality (30%) with reduction in growth performance, erythrogram, total proteins, albumin, antioxidants and haemagglutination inhibition (HI) titers. In addition, a significant increase in feed conversion rate (FCR), leukocytic count, liver enzymes, kidney functions, total globulins, malondialdehyde, nitric oxide and lysozyme activity. Treatment with cefquinome led to decreased mortality rate, improvement in clinical signs, growth performance and modulated most of these altered parameters. Cefquinome's residues was not detected in breast muscles 3^rd day and liver and kidneys 7^th days post treatment. Therefore, it's recommended that cefquinome is a good choice for controlling of colibacillosis in broilers and its withdrawal time 3 days in breast muscles and 7 days in liver and kidney post treatment.