Influence of stable iodine on the transfer of131I into cows' milk

The effect of supplying three different stable iodine levels (about 70, 80, and 160 mg day^–1) in the daily feed of four dairy cows has been studied for the excretion pattern of¹³¹I. None of the different treatments had a statistically significant effect. A mean milk transfer coefficient of 0.015 ± 0.001 d 1^–1 was determined for all iodine supply levels investigated.     

Iodine concentration of milk in a dose–response study with dairy cows and implications for consumer iodine intake

Most feed is poor in iodine and iodine supplementation of cow's diets must guarantee milk iodine concentrations for humans that contribute to prevention of the deficiency and minimize the risk of exceeding an upper limit of iodine intake. Five Holstein cows were fed four iodine doses (via Ca(ΙO₃)₂·6H₂O). In four sequential 14-d periods, doses of 0.2 (basal diet), 1.3, 5.1, and 10.1 mg iodine kg^?1 diet dry matter (DM) were administered. Samples of milk were collected during each period; blood was also sampled from each cow for each iodine dosage. In an 18-d depletion period, a non-supplemented diet was provided. Iodine was determined by inductively coupled plasma-mass spectrometry. The iodine content of milk and serum reflected the iodine dosages in feed significantly. The levels for the four doses tested in milk were 101±32, 343±109, 1215±222, and 2762±852 μg iodine kg^?1. The total amount of iodine in milk per day was 30–40% of ingested supplemental iodine. Omitting additional iodine resulted in a short-term reduction of serum and milk iodine following an exponential decay function. The iodine supplementation of 0.5–1.5 mg kg^?1 diet DM represents the requirement of the cow, resulting in 100–300 μg iodine L^?1 milk, which optimally contributes to human supply. The maximum dietary levels of former and present EU legislations (10 and 5 mg iodine kg^?1 cow feed) increase the risk of iodine excess in humans.     

Estimation of cardiac output and stroke volume from thermal equilibration and heartbeat rates in fish

Cardiac output and stroke volume were estimated for a 200 g largemouth blackbass (Micropterus salmoides) by a modified whole-body thermodilution method using the relation between thermal equilibration rates and heartbeat frequencies. The reciprocal of the thermal time constant, k (min^–1), was related to the heartbeat frequency, F (beats min^–1), by the equation k=0.00146 F + 0.309; the slope is the weight-specific stroke volume (ml g^–1) and the intercept is the weight-specific heat transfer constant (cal °C^–1 min^–1 g^–1). Stroke volume was 0.292 ml (0.00146 ml/g body weight), yielding cardiac output values ranging from 44 ml kg^–1 min^–1 (at 30 beats min) to 158 ml kg^–1 min^–1 (at 108 beats min^–1), or 4.4 to 15.8% of body weight. Active (convective) heat transfer due to blood flow constituted an estimated 11 to 34% (mean 22.5%) of total heat transfer, depending on heartbeat frequency; this variability constitutes physiological thermoregulation.     

Translocation and plant availability of radio caesium in an organic soil

¹³⁴Caesium chloride solution was injected into the surface of a peaty podzol at 3 cm depth with 5 cm spacing over a M² at two upland sites, one of which had been fertilized and reseeded. The movement of radio caesium in the soil was subsequently followed by coring and/or taking out 10-cm square blocks at monthly intervals over a period of 2 years. There was very little movement of the caesium down the profile, with more than 95% remaining at the point of application. Lateral movement was also minimal. The caesium did not concentrate in the roots. Samples of herbage collected from the surface during the growing season showed a progressively decreasing concentration of caesium over the period. Total caesium removed in herbage amounted to 3.5 and 0.6% of the original present for the improved and umimproved soils, respectively.The extractability of the caesium from the ¹³⁴Cs-amended peaty soil was compared with that from a low-ash peat which had been treated with the radionuclide for 2 months. Initially 1 M ammonium acetate (pH 7.2) extracted 30 and 56% of the Cs from 0–3 and 3–6 horizous of the improved peaty podzol, respectively. After 5 months only about 12 and 7% of the Cs was extracted by 1 M ammonium acetate and 4 and 1% by 0.1 M sodium pyrophosphate from the 0–3 and 3–6 cm horizons, respectively. After 24 months 1 M ammonium acetate extracted 1.6 and 3.3% of the Cs from the 0–3 and 3–6 cm horizons, respectively. In contrast, the values for the peat after 2 months were 100 and 80% for 1 M ammonium acetate and 0.1 M pyrophosphate, respectively.     

Energy allocation for reproduction in a marsupial arboreal folivore,the common ringtail possum (Pseudocheirus peregrinus)

This study examines the annual energetics of a small folivorous marsupial, Pseudocheirus peregrinus. Particular attention was given to the energy and time allocated to reproduction by the females. Daily energy expenditure was measured directly using the doubly labelled water technique. Energy transferred to the young via the milk was estimated from information on milk composition and production. There was no significant seasonal variation in the energy expenditure or water influx of males or females. The mean daily energy expenditure of a 1-kg non-lactating adult ringtail possum was 615 kJ day^–1 or 2.2 times standard metabolic rate. Females showed significant changes in daily energy expenditure according to their reproductive status. Without the burden of lactation the total annual energy expenditure of an adult female was estimated as 212.4 MJ kg^–1 year^–1. The total annual energy expenditure of a female rearing two young was 247.5 MJ kg^–1 year^–1, with the late stage of lactation constituting the most energetically expensive period accounting for 30% of the total yearly energy expenditure during 24% of the time. Total metabolisable energy allocation during reproduction (22 MJ kg) was similar to estimates available for other herbivores, although, the peak metabolisable energy allocation during lactation (759 kJ day^–1) was lower than values available for other herbivores. The total energy requirement for reproduction (metabolisable energy plus potential energy exported to young via milk) suggests that the ringtail possum also has a relatively low overall energy investment in reproduction. It is suggested that the lactational strategy of the ringtail possum has been selected in order to spread the energy demands of reproduction over time due to constraints on the rate of energy intake imposed by a leaf diet and/or to prolong the mother-young bond. The strategies a female ringtail possum may employ to achieve energy balance when faced with the energy demands of reproduction are discussed.     

Ticks (Acari: Ixodidae) infesting the Arabian Camel (Camelus dromedarius) in the Sinai,Egypt with a note on the acaricidal efficacy of Ivermectin

In this study, tick burdens on camels (Camelus dromedarius) were determined in the vicinity of the St. Catherine monastery, Sinai, Egypt. In total 2,545 ticks (1,491 adults and 1,054 nymphs) were collected and identified. Mean tick burdens were relatively heavy and the range in number of ticks per camel was very broad (6–173). Hyalomma dromedarii was the predominant tick species and accounted for 95.6% of the adult ticks. Other ticks found were H. marginatum subspp. and H. anatolicum excavatum. All nymphs collected were Hyalomma spp.In addition, the effect of ivermectin (Ivomec MSD AGVET) on tick burdens, when given subcutaneously at 0.2 mg/kg¹, was evaluated in nine camels in the date-palm plantation of Kibbutz Yahel in the Arava valley, Israel. Initial tick burdens on these camels (half-body tick counts) ranged from 20–105 ticks per camel. Seven camels from the same herd with half-body tick counts ranging from 40–107 ticks per camel were not treated and served as a control group. Ivermectin was not effective against Hyalomma tick infestation in camels under these conditions.     

Application of the STICS crop model to predict nitrogen availability and nitrate transport in a tropical acid soil cropped with maize

Oxisols have a high likelihood of NO₃ ^– leaching which may strongly reduce N availability for tropical crops. The aim of this work was to evaluate the N and the water submodels of the STICS crop model for its ability to estimate N availability in N-fertilised field maize crops on two oxisols in Guadeloupe (French West Indies) with and without Al toxicity: a non-limed plot (NLI, pH_KCl 3.9, 2.1 cmol Al³⁺ kg^–1), and a limed plot (LI, pH_KCl 4.5, 0 cmol Al³⁺ kg^–1). An uncropped plot (UC, pH_KCl 4.5, 0 cmol Al³⁺ kg^–1) was used in order to fit some model parameters for soil evaporation, nitrification and NO₃ ^– transport. The model was modified in order to describe nitrification as a partially inhibited process in acid soils, and to take into account NO₃ ^– retention in oxisols. Nitrification was described as the result of the multiplicative effects of soil acidity, temperature and soil water content. Soil moisture and NO₃ ^– and NH₄ ⁺ content up to 0.8 m soil depth, above-ground biomass and N uptake by crops, and their leaf area index (LAI), were measured from sowing to the beginning of grain filling. The model described correctly the changes in soil water content during the moist and the dry periods of the experiment, and there was some evidence that capillary rise occurred in the dry period. Nitrogen mineralization, nitrification in UC, NO₃ ^– transport and plant uptake were satisfactorily simulated by the model. Because of the effect of Al toxicity on plant growth, LAI at flowering was three times higher in LI than in NLI. Some discrepancies between observed and simulated data were found for the distribution of NO₃ ^– and NH₄ ⁺ in the cropped plots. This was probably due to the change of the ionic N form absorbed by the crops as a function of soil acidity and available P in the soil. No leaching was observed below 0.8 m depth and this was associated with NO₃ ^– retention in the soil. The results showed that partial inhibition of nitrification and NO₃ ^– retention should be taken into account by crop models to obtain realistic estimates of N availability for plants in tropical acid soils.     

Control of renal and extrarenal salt and water excretion by plasma angiotensin II in the kelp gull (Larus dominicanus)

Summary The osmoregulatory effects of intravenously (i.v.) administered angiotensin II (AII) at dose rates of 5, 15 and 45 ng · kg^–1 · min^–1 were examined in kelp gulls utilizing salt glands and/or kidneys as excretory organs.In birds given i.v. infusion of 1200 mOsmolal NaCl at 0.3 ml · min^–1 and utilizing only the salt glands to excrete the load, infusion of AII for 30 min consistently inhibited salt gland function in a dose-dependent manner.In birds given i.v. infusion of 500 mOsmolal NaCl at 0.72 ml · min^–1 and utilizing both salt glands and kidneys to excrete the load, each dose of AII given for 2 h inhibited salt gland function but stimulated the kidney, so that the overall outputs of salt and water were enhanced and showed significant (2P<0.01) positive correlations with plasma AII.In birds given i.v. infusion of 200 mOsmolal glucose at 0.5 ml · min^–1 and utilizing only the kidneys to excrete the load, low doses of AII (5 and 15 ng · kg^–1 · min^–1) caused renal salt and water retention, whereas a high dose (45 ng · kg^–1 · min^–1) stimulated salt and water output.The actions of plasma AII in kelp gulls support the concept that this hormone plays a vital role in avian osmoregulation, having effects on both salt gland and kidney function. Elevation of plasma AII consistently inhibits actively secreting salt glands, but its effects upon renal excretion depend primarily on the osmotic status as well as on the plasma AII concentration. In conditions of salt and volume loading doses of AII stimulate sodium and water excretion. With salt and volume depletion, the action of AII is bi-phasic with low doses promoting renal sodium and water retention but high circulating levels causing natriuresis and diuresis.     

Bioventing of diesel oil-contaminated soil: Comparison of degradation rates in soil based on actual oil concentration and on respirometric data

The effects of bioventing, nutrient addition and inoculation with an oil-degrading bacterium on biodegradation of diesel oil in unsaturated soil were investigated. A mesocosm system was constructed consisting of six soil compartments each containing 6 m³ of naturally contaminated soil mixed 11 with silica sand, resulting in a diesel oil content of approximately 2000 mg kg^–1. Biodegradation was monitored over 112 days by determining the actual diesel oil content of the soil and by respirometric tests. The best agreement between calculations of degradation rates based upon the two methods was in July, when venting in combination with nutrient addition resulted in degradation rates of 23 mg kg^–1 day^–1 based on actual oil concentration in the soil and 33 mg kg^–1 day^–1 calculated from respirometric data. In September, these rates decreased to 9 and 1.4 mg kg^–1 day^–1, and in October the degradation rates were 5 and 0.7 mg kg^–1 day^–1 based upon the two methods. The average ambient temperature during the respirometric tests was 14,10 and 2°C in July, September and October, respectively. The combination of venting and nutrient addition resulted in an average residual oil content of the soil of 380 mg kg^–1. Neither venting alone nor inoculation enhanced oil degradation. The respiratory quotient averaged 0.40. The oil composition changed following degradation resulting in the unresolved complex mixture constituting up to 96% of the total oil content at the end of the experimental period.     

Osmolality and volume factors in salt gland control of pekin ducks after adaptation to chronic salt loading

Summary Pekin ducks were adapted to permanent osmotic stress by rearing them on a NaCl solution of increasing concentration up to 2% as drinking water. Their salt and water balance was compared with that of non-adapted ducks maintained on tap water. Amounts and osmolalities of salt gland secretion and cloacal discharges, plasma osmolality and electrolytes were measured during stepwise osmotic loading by intravenous infusion of NaCl solution of about 740 mosm·kg^–1, at rates of 0.25, 0.45 and 0.65 ml·min^–1. Before loading, the plasma osmolality of the adapted ducks was about 22 mosm·kg^–1 higher than in non-adapted animals. The initial step of loading induced salt gland secretion in the adapted ducks after an average rise of plasma osmolality of 3.6 mosm·kg^–1 and in the non-adapted animals after a rise of 7.8 mosm·kg^–1. The method of osmotic loading enabled both groups of animals to balance their water input and output. However, only the adapted ducks were able to balance NaCl input and output, predominantly by salt gland secretion, thus maintaining a stable plasma osmolality. The nonadapted ducks retained 42% of the salt load which resulted in a rise of plasma osmolality of 49 mosm·kg^–1, more salt being excreted by the kidneys than by the salt glands.In the salt-adapted ducks, salt gland activity, plasma osmolality and Na⁺ concentration did not correlate during balanced states of salt input and output. The involvement of tonicity receptors in salt gland control was confirmed by the stimulating effects of various hypertonic solutions. On the other hand, continuous loading by a constant infusion of NaCl solution of 1,300 mosm·kg^–1 induced a steady salt gland secretion at a rising plasma osmolality and thus suggested that a volume factor is involved in salt gland control. Inhibition of salt gland activity by withdrawing blood and activation by blood infusion confirmed this assumption. While a direct cause and effect relationship between volume changes and salt gland secretion cannot be demonstrated, the results indicate that volume changes in one or more extracellular compartments do affect salt gland secretion.Supported by Deutsche Forschungsgemeinschaft (Si 320/2)     

Heavy metal and PCB contamination of Bryozoan colonies in the River Meuse (Belgium)

In the Meuse River (Liège area, Belgium), large amounts of three species of Bryozoans, Fredericella sultana (BLUM.), Plumatella emarginata ALL. and Plumatella fungosa (PALL.) occur. They cover 3 to 40% of the bank walls and their biomass ranges from 12 to 293 g m^–2 (dry weight). In the heated waters of a nuclear power plant (Tihange) and of industries lined up along the river, colony development occurs 3 to 4 weeks earlier than at an upstream station. The heavy metal content of living colonies ranges from 4 to 21 mg kg^–1 Cd, 45 to 182 mg kg^–1 Cu, 803 to 2232 mg kg^–1 Zn, 150 to 483 mg kg^–1 Pb and 21 to 138 mg kg^–1 Cr (DW). The mean concentration of PCBs was 925 µg kg^–1 (DW). Heavy metal and PCB concentrations in the sediments were close to those of colonies, suggesting that most of the pollutants found in the Bryozoans is in fact in the sediment trapped by the colonies.     

Zinc phytotoxicity to oilseed rape grown on zinc-loaded substrates consisting of Fe oxide-coated and calcite sand

The risk of zinc (Zn) phytotoxicity in soils has increased in various regions following application of different anthropogenic materials. In order to assess the relative efficiency of Fe oxide and calcite in sorbing Zn and hence alleviating Zn phytotoxicity, we grew oilseed rape for 28 days in pots containing Zn-loaded model substrates consisting of Fe oxide (ferrihydrite)-coated sand (FOCS, 0.2–0.5 mm, 0.3 m² ferrihydrite g^–1 sand) and calcium carbonate (calcite) sand (CCS, 0.2–0.5 mm, 0.3 m² calcite g^–1 sand). Five substrates containing 5, 10, 20, 40, and 80% FOCS and supplied with ZnSO₄ at a rate of 30, 100, 300, and 1000 mg Zn kg^–1 were used in the cropping experiment and in an in vitro study of Zn desorption for 62 days. Plants exhibited good growth and a similar dry matter yield (DMY) at the 30 and 100 mg Zn kg^–1 rates. On the other hand, DMY was markedly reduced at the 300 and, especially, at the 1000 mg Zn kg^–1 rate, particularly for the substrates with the higher FOCS proportions. Symptoms of phytotoxicity (viz. chlorosis, purple colouration due to P deficiency) were apparent at such rates and were accompanied by high Zn concentrations in both shoot (average values >1000 and >1500 mg Zn kg^–1 dry matter for the 300 and 1000 mg Zn kg^–1 rate, respectively) and root (average values >2500 and >6000 mg Zn kg^–1 dry matter for the 300 and 1000 mg Zn kg^–1 rate, respectively). Total Zn uptake was maximal at 300 mg Zn kg^–1. The results of water extractable Zn in the substrate after cropping and the dissolved Zn concentrations measured in substrate–water systems (desorption experiment) suggest that, on a surface area basis, calcite is more effective than Fe oxide to retain Zn and thus alleviate phytotoxicity at high Zn loadings. However, the Zn-sorption capacity of the Fe oxide cannot be neglected, particularly at low Zn loadings, where Fe oxide seems to exhibit a higher affinity for Zn – but not a higher Zn-sorption capacity – than does calcite.     

Influence of L-tryptophan and auxins applied to the rhizosphere on the vegetative growth of Zea mays L.

Glasshouse experiments were conducted to evaluate the influence of L-TRP in comparison with indole-3-acetamide (IAM), tryptophol (TOL) and indole-3-acetic acid (IAA) on the growth of Zea mays L. var. Early Sunglow. L-TRP (25 to 2.5×10^–5 mg kg^–1 soil), IAM (22 to 2.2×10^–5 mg kg^–1 soil), TOL (20 to 2.0×10^–5 mg kg^–1 soil), and IAA (22 to 2.2×10^–5 mg kg^–1 soil) were applied as a soil drench to established uniform seedlings. All treatments were applied in a completely randomized design with 10 replicates. IAM had no significant effect on the plant growth parameters. Shoot height, uppermost leaf collar base distance, internodal distance, and shoot dry and fresh weights were significantly improved upon the addition of TOL (2.0×10^–2 mg kg^–1 soil), however, the highest concentration (20 mg kg^–1 soil) caused a 14.6% reduction in leaf width. L-TRP (2.5×10^–3 mg kg^-1 soil) also had a significant influence on shoot height, uppermost leaf collar base distance, internodal distance and fresh weight of shoot compared with the control. The highest concentration of L-TRP (25=mg kg^–1 soil) had a negative effect on leaf width and dry weight of the shoot. The most pronounced response on the corn growth parameters was observed with the application of IAA at lower concentrations (2.2×10^–5 to 2.2×10^–2 mg kg^–1 soil) specifically improving root growth. The highest concentration (22 mg kg^–1 soil) of IAA had a significant negative effect on plant height, leaf width, stem diameter, shoot fresh and dry weight. These findings indicate that L-TRP applied at the appropriate concentrations can have positive effects on corn growth comparable to pure auxins (TOL and IAA).     

Biochemical properties of pigeon milk and its effect on growth

Summary The avian juvenile food pigeon milk was studied for its chemical composition and effect on growth in vivo and in vitro. Pigeon milk on a wet weight basis consisted of 9–13% protein, 9–11% fat, 0.9–1.5% carbohydrate, 0.8–1.1% ash, 0.10–0.12% non-protein nitrogen, energy content 5.6–6.8 kcal·g^-1. Except for proteins there was little or no decrease in pigeon milk constitutents during the first week of secretion. Pigeon milk proteins consisted of trichloroacetic acid (precipitable), trichloroacetic acid (soluble), and free amino acid components in the ranges 8.4–12.1%, 0.5–0.7% and 1.4–2.5%, respectively; whereas the level of trichloroacetic acid (precipitable) and trichloroacetic acid (soluble) components decreased by about 30%, that of the free amino acids increased by 9% in the first week. About 0.6–1.0% of pigeon milk sugar was found in the trichloroacetic acid (soluble) fraction and increased by 67% in the first week. The remainder was found in the trichloroacetic acid (precipitable) fraction and did not change during this period. Major lipids of pigeon milk were the neutral lipids (7.8–8.4%); the minor lipids were glycolipids (0.9–1.6%), phospholipids (0.5–1.4%) and cholesterol (0.5–0.6%). Squabs fed pigeon milk increased their body weight by 22-fold in the first 3 weeks after hatching, and crude extracts of pigeon milk stimulated the growth of cultured hamster ovary cells. These results reflect the ability of pigeon milk to stimulate growth both in vivo and in vitro.Abbreviations AOAC association of official analytical chemists - BRIT board of radiation and isotope technology - CHO chinese hamster ovary - DNA deoxyribonucleic acid - EDTA ethylenediaminetetra-acetic acid - FCS foetal calf serum - GF growth factor - GS goat serum - MEM minimum essential medium - NPN nonprotein nitrogen - PBS phosphate-buffered saline - PM pigeon milk - TCA(P) trichloroacetic acid precipitable fraction - TCA(S) trichloroacetic acid soluble fraction     

Energy requirements of the red kangaroo (<Emphasis Type="Italic">Macropus rufus</Emphasis>): impacts of age,growth and body size in a large desert-dwelling herbivore.

Generally, young growing mammals have resting metabolic rates (RMRs) that are proportionally greater than those of adult animals. This is seen in the red kangaroo (Macropus rufus), a large (>20 kg) herbivorous marsupial common to arid and semi-arid inland Australia. Juvenile red kangaroos have RMRs 1.5–1.6 times those expected for adult marsupials of an equivalent body mass. When fed high-quality chopped lucerne hay, young-at-foot (YAF) kangaroos, which have permanently left the mother's pouch but are still sucking, and recently weaned red kangaroos had digestible energy intakes of 641±27 kJ kg^–0.75 day^–1 and 677±26 kJ kg^–0.75 day^–1, respectively, significantly higher than the 385±37 kJ kg^–0.75 day^–1 ingested by mature, non-lactating females. However, YAF and weaned red kangaroos had maintenance energy requirements (MERs) that were not significantly higher than those of mature, non-lactating females, the values ranging between 384 kJ kg^–0.75 day^–1 and 390 kJ kg^–0.75 day^–1 digestible energy. Importantly, the MER of mature female red kangaroos was 84% of that previously reported for similarly sized, but still growing, male red kangaroos. Growth was the main factor affecting the proportionally higher energy requirements of the juvenile red kangaroos relative to non-reproductive mature females. On a good quality diet, juvenile red kangaroos from permanent pouch exit until shortly after weaning (ca. 220–400 days) had average growth rates of 55 g body mass day^–1. At this level of growth, juveniles had total daily digestible energy requirements (i.e. MER plus growth energy requirements) that were 1.7–1.8 times the MER of mature, non-reproductive females. Our data suggest that the proportionally higher RMR of juvenile red kangaroos is largely explained by the additional energy needed for growth. Energy contents of the tissue gained by the YAF and weaned red kangaroos during growth were estimated to be 5.3 kJ g^–1, within the range found for most young growing mammals.Abbreviations BMR basal metabolic rate - DEI digestible energy intake - MER maintenance energy requirement - MER_g maintenance plus growth energy requirement - PPE permanent pouch exit - RMR resting metabolic rate - YAF young-at-foot Communicated by I.D. Hume     

Comparison of soil nitrogen mineralization and nitrification in a mixed grassland and forested ecosystem in central Taiwan

We used the buried bag incubation method to study temporal patterns of net N mineralization and net nitrification in soils at Ta-Ta-Chia forest in central Taiwan. The site included a grassland zone, (dominant vegetation consists of Yushania niitakayamensis and Miscanthus transmorrisonensis Hayata) and a forest zone (Tsuga chinensis var. formosana and Yushania niitakamensis). In the grassland, soil concentration NH₄ ⁺ in the organic horizon (0.1–0.2 m) ranged from 1.0 to 12.4 mg N kg^–1 soil and that of NO₃ ^– varied from 0.2 to 2.1 mg N kg^–1 soil. In the forest zone, NH₄ ⁺ concentration was between 2.8 and 25.0 mg N kg^–1 soil and NO₃ ^–varied from 0.2 to 1.3 mg N kg^–1 soil. There were lower soil NH₄ ⁺ concentrations during the summer than other seasons. Net N mineralization was higher during the summer while net nitrification rates did not show a distinct seasonal pattern. In the grassland, net N mineralization and net nitrification rates were between –0.1 and 0.24 and from –0.04 to 0.04 mg N kg^–1 soil day^–1, respectively. In the forest zone, net N mineralization rates were between –0.03 and 0.45 mg N kg^–1 soil day^–1 and net nitrification rates were between –0.01 and 0.03 mg N kg^–1 soil day^–1. These differences likely result from differing vegetation communities (C₃ versus C₄ plant type) and soil characteristics.     

Clinoptilolite zeolite and cellulose amendments to reduce ammonia volatilization in a calcareous sandy soil

Leaching of nitrate (NO₃ ^–) below the root zone and gaseous losses of nitrogen (N) such as ammonia (NH₃) volatilization, are major mechanisms of N loss from agricultural soils. New techniques to minimize such losses are needed to maximize N uptake efficiency and minimize production costs and the risk of potential N contamination of ground and surface waters. The effects of cellulose (C), clinoptilolite zeolite (CZ), or a combination of both (C+CZ) on NH₃ volatilization and N transformation in a calcareous Riviera fine sand (loamy, siliceous, hyperthermic, Arenic Glossaqualf) from a citrus grove were investigated in a laboratory incubation study. Ammonia volatilization from NH₄NO₃ (AN), (NH₄)₂SO₄(AS), and urea (U) applied at 200 mg N kg^–1 soil decreased by 2.5-, 2.1- and 0.9-fold, respectively, with cellulose application at 15 g kg^–1 and by 4.4-, 2.9- and 3.0-fold, respectively, with CZ application at 15 g kg^–1 as compared with that from the respective sources without the amendments. Application of cellulose plus CZ (each at 15 g kg^–1) was the most effective in decreasing NH₃ volatilization. Application of cellulose increased the microbial biomass, which was responsible for immobilization of N, and thus decreased volatilization loss of NH₃–N. The effect of CZ, on the other hand, may be due to increased retention of NH₄ in the ion-exchange sites. The positive effect of interaction between cellulose and CZ amendment on microbial biomass was probably due to improved nutrient retention and availability to microorganisms in the soil. Thus, the amendments provide favorable conditions for microbial growth. These results indicate that soil amendment of CZ or CZ plus organic materials such as cellulose has great potential in reducing fertilizer N loss in sandy soils.     

Recent evolution of sedimentary heavy metals in a coastal lagoon contaminated by industrial wastewaters (Pialassa Baiona,Ravenna, Italy)

From 2000 to 2002, sediment contamination by Cd, Cu, Hg, Pb and Zn was analysed in the Pialassa Baiona salt marsh, which receives petrochemical wastewaters from the industrial district of Ravenna (Italy). The recent contamination levels were compared with data of previous studies carried out in 1982, in order to assess whether environmental policies and remedial measures reduced sediment pollution. Sedimentary profiles of Cu and Pb were homogeneous along the uppermost 0–10 cm horizon, which corresponded to the sedimentation in the last 30 years. Concentrations of Zn attained a peak (up to 800 mg kg⁻¹ dry weight) in the 0–4 cm sediment horizon, which was assumed to correspond to the last 10–15 years. A wide-spread contamination by Hg was detected in the salt marsh as well as in the main channel with peaks up to 20–40 mg kg⁻¹ dry weight. Nonetheless, recent sediments resulted less contaminated, since Hg discharge from industrial plants ceased about 20 years ago. Contamination levels by Hg values were two orders of magnitude higher than the international sediment quality standards. Cadmium, which was analysed for the first time in 2000–2002, attained a peak in the surface layers (1–2.5 mg kg⁻¹ d.w.), with a progressive decline along the sediment column. Through comparison with pre-industrial values detected in the deeper sediment horizons (before 1920), Hg showed the highest enrichment factor, up to 300 times. Cd and Zn concentrations in recent sediments were from 2 to 10 times higher than background values. In terms of possible adverse effects, Hg posed the highest risk, and Cd and Zn were frequently above the recommended thresholds.     

Adaptation of renal function to hypotonic medium in the winter flounder (Pseudopleuronectes americanus)

Summary The kidneys of winter flounders transferred to hypotonic medium were investigated for glomerular and tubular handling of fluid and electrolytes and for the urinary excretion of proteins. Media were sea water (925 mosm·kg^–1) and brackish water (70 mosm·kg^–1).In sea water, the urine was hypertonic to the plasma in 7 fish of this study. Urine flow rate was correlated with the GFR. After adaptation to brackish water a delay of 1 to 3 days was observed until the kidneys switched from fluid retention to the excretion of large amounts of dilute urine. GFR and urine flow rate were increased from 0.61±0.08 to 1.58±0.29 ml·h^–1·kg^–1 and from 0.14±0.02 to 0.68±0.08 ml·h^–1·kg^–1, respectively . With increased filtered load the tubular reabsorption of fluid decreased from 74±2.4% to 45±11.2%. The excretion rates of sodium and potassium were increased due to decreased fractional sodium and potassium reabsorption. The urinary excretion of divalent cations, however, was reduced because the net tubular reabsorption of calcium was increased and the net secretion of magnesium was diminished.Both the urinary total protein concentration and the protein pattern showed no significant change, but the rate of protein excretion was increased from 0.21±0.04 to 0.60±0.05 mg·h^–1·kg^–1. The comparison of protein patterns obtained from urine and serum samples revealed that high molecular weight (HMW) proteins prevail in the serum whereas low molecular weight (LMW) proteins dominate in the urine. The diminished quantity of the HMW-protein fraction in the urine thus may reflect size selectivity of the glomerular filtration barrier for serum proteins also in the winter flounder.Abbreviations BW brackish water - SW sea water - GFR glomerular filtration rate - HMW heigh molecular weight - LMW low molecular weight     

Pulmonary diffusing capacity in reptiles (Relations to temperature and O2-uptake)

Summary Pulmonary CO-diffusing capacity (D l _CO), lung volume, pulmonary perfusion and O₂-uptake were measured by non-invasive techniques in the lizardsVaranus exanthematicus andTupinambis teguixin (mean body weight 2.2 kg for both species).The CO-diffusing capacity was at 25–27°C 0.059 mlstpd·kg^–1·min^–1·Torr^–1 inVaranus, which is 47% greater than the value of 0.040 mlstpd·kg^–1·min^–1·Torr^–1 inTupinambis. The lung volume ofVaranus was 36 ml·kg^–1 and that ofTupinambis 20 ml·kg^–1. At 35–37°C the diffusing capacity of lizard lungs are about 25% of those for mammals of comparable size.InVaranus pulmonary CO-diffusing capacity increased with temperature from 0.027 mlstpd·kg^–1·min^–1·Torr^–1 at 17–19 °C to 0.075 mlstpd·kg^–1·min^–1·Torr^–1 at 35–37 °C. This change closely matched a concomitant increase of O₂-uptake. Pulmonary perfusion increased from 27 ml·kg^–1·min^–1 to 55 ml·kg^–1·min^–1 within this temperature range.The study emphasizes that pulmonary diffusing capacity cannot be fully evaluated without information on pulmonary perfusion and O₂-uptake. In reptiles and other ectotherms diffusing capacity must be reported at specified body temperature.