Quantitative relationships between the ingestion of protein-rich material and ovarian development in the Australian sheep blowfly,Lucilia cuprina (Wied.)

The mature ovaries accounted for about 25% of dry weight and 30% of the protein content of wild-type (anautogenous) females of L. cuprina which had fed ad lib. on liver. The protein content of gravid females was 50% greater than at emergence. Protein ingested during the adult stage, therefore, plays an important role in ovarian maturation. The protein content of the ovaries of females fed measured amounts of liver exudate was from 37 to 52% of the amount of protein ingested.

Only limited ovarian development occurred in females fed only protein (high MW fraction of liver exudate or bovine serum albumin). The presence, in addition, of low MW components (low MW fraction of liver exudate or a salt mixture) was necessary for ovarian maturation. Quantitative feeding showed that the high and low MW fractions of liver exudate were, respectively, superior to bovine serum albumin and the salt mixture, which was based on the cation analysis of the low MW fraction of the exudate.     

Bacterivory by starved marine heterotrophic nanoflagellates of two species which feed differently, estimated by uptake of dual radioactive-labelled bacteria

Abstract: The rates of ingestion of bacteria and of accumulation of bacterial biomass by hungry Pteridomonas danica and Paraphysomonas imperforata were measured using dual radioactive-labelled bacteria in experiments lasting 4–8 h. Pteridomonas continuously consumed 4–5 bacteria h⁻¹ throughout experiments lasting 8 h, irrespective of bacterial concentration above a threshold of about 5 × 10⁵ bacteria ml⁻¹, and continued to catch bacteria even below this density. The clearance rate of about 1 nl cell⁻¹ h⁻¹ at higher bacterial concentrations increased three or four times as bacterial numbers fell. Paraphysomonas cells, with only half the biomass of Pteridomonas , ingested up to 10 bacteria h⁻¹ at high bacterial concentrations, and gradually reduced the feeding rate, effectively ceasing to feed at 10⁶ bacteria ml⁻¹; their initial clearance rate of 1–2.5 nl cell⁻¹ h⁻¹ subsequently fell as low as 0.1 nl cell⁻¹ h⁻¹. Estimation of feeding rate by extrapolation from short-term experiments on such flagellates requires extreme caution. These flagellates, starved to levels typical of the natural environment, accumulated ingested bacterial biomass at an efficiency of between 16 and 21%, indicating that in nature they would recycle 80% or more of the nutrients contained in their food.     

Bile salt-dependent lipase in larval turbot, as influenced by density and lipid content of fed prey

Turbot larvae were fed three different densities of rotifers (1000, 3000 and 7500 rotifers 1⁻¹) with a low lipid level (< 15% of dry weight) or 7500 rotifers 1⁻¹ with a high lipid level (∼30% of dry weight). The larval consumption of rotifers increased with increasing prey densities and the content of bile salt-dependent lipase (BSDL) in larvae was correlated positively with the ingestion rate from days 6 to 8. This suggests that BSDL synthesis was stimulated by the amount of ingested prey in the early larval phase. However, growth was highest in larvae receiving the medium prey densities, which indicates that the larvae were not able to digest properly the ingested prey at the higher density. No significant effect on the BSDL content was seen in turbot larvae fed rotifers with a high or low lipid content.     

Ontogenetic changes in potassium transport in xylem of tomato

The influence of plant ontogeny on xylem exudate K⁺ concentrations and K⁺ transport to the shoot was studied in both nutrient-solution and field-grown tomato plants ( Lycopersicon esculentum ).
K⁺ concentrations in xylem exudate from decapitated plants decreased during tomato plant development from a high of 12 m M to a low of 5 m M . In the nutrient-solution plants, the most rapid decline occurred during the vegetative growth phase, while in field-grown plants, the xylem K⁺ concentrations remained high during an-thesis and then subsequently declined. The rapid decline in nutrient-solution plants might be related to a decrease in the absorptive efficiency of the root system. In field-grown plants, a reduction in the availability of assimilates to the root might account in part for the decrease in xylem exudate K⁺ concentrations. The volume (ml h⁻¹ plant⁻¹) and the net rates of K⁺ exudation (mmol h⁻¹ plant⁻¹) decreased dramatically as the fruits approached maturity. Since only a small reduction in xylem exudate K⁺ concentrations occurred during fruiting, the hydraulic conductivity of the root system decreased as the tomato plants aged. It is proposed that the ontogenetic changes in xylem transport of K⁺ contribute to a reduction in leaf free space K⁺ concentration which would explain the decline in tomato leaf K⁺ concentrations.     

Monovalent—divalent cation ratios and the occurrence of phytoplankton, with special reference to the desmids

SUMMARY. We have analysed data from ninety-nine Scottish freshwater lochs, to explore the relationship between water chemistry and phytoplankton assemblages. Our results confirm that there are strong correlations both between the phytoplankton quotient and divalent cation concentrations, particularly Ca⁺⁺, and also between the phytoplankton quotient and the (Na⁺+ K⁺)/(Ca⁺⁺+ Mg⁺⁺) ratio. However, the latter is evidently a spurious relationship, arising from the former association, together with an association between Ca⁺⁺ and the (Na⁺+K⁺)/ (Ca⁺⁺+ Mg⁺⁺) ratio. The observed correlation does not persist if account is taken of concomitant variations in the Ca⁺⁺concentration. This conclusion is suggested both by relatively informal analyses (median polish, partial correlation coefficients) and by more formal modelling and testing (stepwise regression, all-subsets regression).     

The Impact of Sheep Grazing on Net Nitrogen Mineralization Rate in Two Temperate Salt Marshes

Abstract: Nitrogen mineralization rate was studied in grazing trials with three different stocking rates (0, 3, 10 sheep ha^-1) in two man-made salt marshes, viz. a Puccinellia maritima -dominated low salt marsh and a high salt marsh dominated by Festuca rubra. Mineralization rates were derived from the amounts of mineral N which accumulated in situ during six-week incubation periods in tubes containing undisturbed soil cores from the upper 10 cm soil layer. The annual rates of net N mineralization were significantly higher in the better drained, high salt marsh (71 - 81 kg ha^-1 yr^-1) than in the low salt marsh (39 - 49 kg ha^-1 yr^-1). High amounts of belowground litter accumulated in the low salt marsh due to frequent water logging. Both N mineralization and nitrification rate were negatively correlated with soil water content. In the Puccinellia maritima salt marsh, grazing had neither an effect on N mineralization rates during any of the incubation periods nor on annual mineralization rates. In the Festuca rubra salt marsh, N mineralization rates increased earlier during spring at the intensively grazed site than at the moderately grazed and the ungrazed site. N mineralization and nitrification rates were significantly higher at the ungrazed site than at the intensively grazed site during the period of peak net N mineralization from the end of April until mid-June. Although sheep grazing affected the seasonal pattern of N mineralization in the high marsh, grazing did not affect the annual rate of net N mineralization.     

Effect of potassium status on K+ (Rb)+ uptake and transport in sunflower roots

Young sunflower plants ( Helianthus annuus L. cv. Halcón), grown in nutrient solution at two K⁺ levels (0.25 and 2.5 m M ) were used to study the effect of K⁺ content in the root on uptake and transport of K⁺ to the exuding stream of decapitated plants. Roots of plants grown in low K⁺ gave higher exudation flux, higher K⁺ concentration in exudate and higher K⁺ flux than high K⁺ roots. After 6 h of uptake the K⁺ flux in low K⁺ roots was about three times that in high K⁺ roots. When the roots were kept in a nutrient solution in which Rb⁺ replaced K⁺, low K⁺ roots exuded much more Rb⁺ than K⁺ after the first 2 h, whereas high K⁺ roots exuded about similar amounts of K⁺ and Rb⁺. In intact plants grown at three different K⁺ levels (0.1, 1.0 and 10.0 m M ), there was an inverse relationship between the K⁺ level in the nutrient solution and the Rb⁺ accumulated in the roots or transported to the shoot. The results suggest that the transport of ions from xylem parenchyma to stele apoplast may be controlled by ions coming down from the shoot in sieve tubes.     

Cation fluxes in the saps of Sinapis alba during the floral transition

Plants of Sinapis alba L. were induced to flower by either a single long day or a single displaced short day. The levels of three cations. Ca²⁺, Mg²⁺ and K⁺, were measured by atomic absorption spectrophotometry in exudates from roots, leaves and apical stem tips. The export of all three cations out of the root system (root exudate) was increased in induced as compared to non-induced plants. No changes were observed in cation export out of the mature leaves (leaf exudate). The supply of cations to the apical bud (apical exudate) did not originate from the phloem and, so, should mainly be of apoplastic origin. Only the supply of Ca²⁺ to the apical bud was increased, not the supply of Mg²⁺ or K⁺. The increase in Ca²⁺ supply was transient and occurred at about the same time as a conspicuous stimulation of cell division, previously detected in the apical bud.     

Ontogenesis of Ca++ and Mg++ Contents of Embryonic Chick Heart

The Ca⁺⁺ and Mg⁺⁺ contents of embryonic chick heart were studied by atomic absorption spectrophotometry during a period from 48 h of foetal development until 2-3 days post-hatching. The hearts were isolated and incubated for 40 min at 22°C in three different media aerated with 95% 0₂-5% C0₂. The media included: normal Ringer's; Ca⁺-free Ringer's with 3 mM EGTA; and Ca⁺⁺-free Ringer's with 3 mM EDTA. At 48 h, the tubular myocardium contained 7-3 mM Ca⁺⁺ per wet weight which decreased rapidly to 1-2 mM by 10 days of development and remained between 0-9 and 1-1 mM until hatching. The Ca⁺⁺ content paralleled the changes in Na⁺ content reported earlier. Treatment with excess chelators, EGTA or EDTA, resulted in removal of 65-75% of the Ca⁺⁺ content throughout development until the time of hatching, when 50% of the Ca⁺⁺ became firmly bound. In contrast to the results with Ca⁺⁺, myocardial Mg⁺⁺ content rose rapidly from an initial value of 3.2 mM at 48 h to 6.7 mM by the 5th day of development, and then gradually declined throughout the remaining foetal development to 4.8 mM 2-3 days post-hatching. The Mg⁺⁺ contents closely paralleled changes in K⁺ content during development, which were reported earlier. Treatment with EGTA and EDTA removed 13-22% and 19-28% of the myocardial Mg⁺⁺, respectively, during development until just prior to hatching, when only 10-12% could be removed by chelation.     

Bacterivory by the ciliate Euplotes in different states of hunger

Abstract: The feeding of the marine ciliate Euplotes mutabilis was studied using bacteria ( Vibrio natriegens ) doubly labelled with ³H-thymidine and ¹⁴C-leucine. In the presence of abundant bacteria (30 × 10⁶ bacteria ml⁻¹), an average Euplotes cell (initially without food vacuoles) with a protein content of 12 ng consumed 16 × 10³ bacteria in the first hour and 27 × 10³ bacteria over four hours, accumulating about 60% of the bacterial protein into ciliate macromolecules. Euplotes which had been starved or under-fed to reduce cell protein biomass to 7 or 9 ng consumed significantly fewer bacteria, but the gross growth efficiency for protein did not change. The rate of consumption of bacteria by large Euplotes of protein content 15 ng was initially less than that of 12 ng cells, and it decreased markedly before the end of a 4-hour experiment. Recently divided cells ingested bacteria rapidly, but showed a reduced gross growth efficiency of about 40%. At low bacterial concentrations (6 × 10⁶ bacteria ml⁻¹) the rates of ingestion were markedly reduced to between     and     of maximal levels; the smallest cells could not sustain feeding activity at the low prey concentration and gross growth efficiency fell from 43 to 20% during a 4-hour experiment. The strategy adopted by Euplotes in response to local fluctuations in food supply involves rapid consumption with high growth efficiency in times of plenty, but slow shrinkage without cell division to survive in times of shortage.     

Differences in osmoacclimation between sporophytes and gametophytes of the brown alga Ectocarpus siliculosus

The osmoacclimation of Ectocarpus siliculosus isolates known to have different salt tolerances was investigated. Included were isolates originating from 5 different locations in the northern hemisphere, and sporophyte and gametophyte phases of different ploidy from two of the locations were compared. The effect of salinity treatment (8–64%₀) on inorganic ions (K⁺, Na⁺, Mg²⁺, Cl⁻, SO²⁻₄, phosphate) and the low molecular weight carbohydrate mannitol was measured, together with complimentary measurements of cell viability. Very different responses between isolates were obtained, both between isolates of different geographic origin and between sporophytes and gametophytes from the same parent material. A similarity in response between haploid and diploid gametophytes, and diploid and triploid sporophytes indicates that physiological differences between gametophyte and sporophyte generations are not necessarily based on ploidy changes alone. There were no identifiable differences in the responses of male and female gametophytes. K⁺ is the major osmolyte within the species, and differences in the regulation of K⁺ largely account for the observed variation in osmoacclimation, both between life history phases and between isolates from different localities. Isolates with broader salt tolerances had the higher concentrations of mannitol. There were differences between isolates in the amounts and regulation of Cl⁻ and phosphate, the latter being present in unusually high concentrations. There were also isolate differences in the concentrations of Mg²⁺ and SO²⁻₄, although these divalent ions were present only in low concentrations.     

Divalent cations enhance ammonia excretion in Lahontan cutthroat trout in highly alkaline water

The Lahontan cutthroat trout lives under highly alkaline and saline conditions in Pyramid Lake, Nevada (pH 9.4; 0.2 mmol 1⁻¹ Ca⁺⁺; 7.3 mmol 1⁻¹ Mg⁺⁺). These experiments were conducted to study the possible roles of water Ca⁺⁺ and Mg⁺⁺ concentrations on ammonia excretion in the Lahontan cutthroat trout under highly alkaline conditions. The basic protocol of the experiments was to determine ammonia excretion rates during the following three exposure periods (each of 3-h duration) in sequence: (a) in normal lake water; (b) in soft lake water with the divalent cation concentrations reduced; and (c) in the soft lake water with either Ca⁺⁺ or Mg⁺⁺ (or no divalent cations added) added back at the appropriate lake water concentration. The soft-water exposure caused a significant reduction in ammonia excretion to about half of the control (original lake water) levels. When either Ca⁺⁺ or Mg⁺⁺ was added to the soft water in the third exposure period, the ammonia excretion rates were increased more than twofold back to lake water levels.     

ATPase Activity in Isolated Flagella from Euglena gracilis

SYNOPSIS. The ATPase activity of isolated flagella was studied in Euglena gracilis strain Z in the presence of Mg⁺⁺ or Ca⁺⁺. With Mg⁺⁺, the optimum activity was at pH 7 and with Ca⁺⁺, at pH 9. The K _m values were respectively 6.6 × 10⁻⁴ and 3.6 × 10⁻⁴. Activity was influenced also by temperature and ionic strength. Results with inhibitors of membrane ATPase suggest the presence of a specific contractile system in the flagella. Our results are compatible with a multicomponent enzymic system containing 2 active ATPases.     

The energy balance of the Australian brine shrimp, Parartemia zietziana (Crustacea : Anostraca)

SUMMARY. Assimilation budgets (i.e. assimilation = respiration + excretion + production) are presented for cohorts of P. zietziana in two salt lakes. Shrimps in Pink Lake had an assimilation rate of 1631.6 kJ m⁻² year ⁻¹, those in Lake Cundare 212.1 kJ m⁻² year⁻¹. In both lakes, respiration accounted for 60–80% of assimilation. Assimilation rates for individuals (derived as assimilation = ingestion minus faecal output) are also given and compared with respiratory rates of individuals. The comparisons indicated that energy was often consumed at a higher rate by respiration than it could be supplied by assimilation. Starvation due to a low assimilation efficiency was suggested as a cause of the consistent mortality, variable growth rate of individuals and unpredictable recruitment which were characteristic of the cohorts of P. zietziana in both lakes. An analysis of mortality showed that the young had the poorest survival, as predicted by a theoretical model of a starving zooplankter and a comparison of the increase with weight of ingestion and respiration. Gross growth efficiency (production: assimilation) was 15–30%, about the same as published data on Anostracans. Net growth efficiency (production : consumption) was 5–12% and generally lower than published values reflecting the difficulty P. zietziana has in balancing its budget.     

Chlorate-resistant rose cells: influx, efflux and reduction of [36Cl]-chlorate

Clones of Rosa damascena Mill. cv. Gloire de Guillan, selected for growth in solid medium containing 56 m M NaClO₃, were studied to determine the reason for their resistance to this toxic salt. The cells grew on medium containing nitrate as the only nitrogen source, and they synthesized nitrate reductase (EC 1.6.6.2) in the presence of nitrate. The cells were resistant in the presence of nitrate. However, their resistance was greatly increased by the presence of glutamate in the medium. The cells took up [³⁶Cl]-ClO₃- and reduced it to ClO₂⁻, but the fraction of ClO₃⁻ that they reduced under our experimental conditions was less than that reduced by wild type. The slower production of ClO₂⁻ apparently accounted for the resistance of the cells to ClO₃⁻. We suggest several possible reasons for the low rate of reduction of ClO₃⁻.     

Examination of the role of the proteolytically-activated form of protein kinase C in the differentiation of human haemopoietic cells

Abstract. In neutrophils, the phorbol ester 12- O -tetrade-canoylphorbol-l3-acetate (TPA) induced the translocation of the Ca⁺⁺- and phospholipid-dependent protein kinase, protein kinase C (PK-C) from the soluble to the particulate fraction. At the same time there was a corresponding increase in the amount of Ca⁺⁺- and phospholipid-independent protein kinase activity recovered in the soluble fraction. This soluble Ca⁺⁺- and phospholipid-independent protein kinase presumably reflects proteolytic activation of the particulate associated PK-C. Bone marrow and undifferentiated HL-60 cells also translocated PK-C to the particulate fraction in response to TPA but did not accumulate the soluble Ca⁺⁺- and phospholipid-independent form of the enzyme. Similar results were obtained using HL-60 cells induced to differentiate with dimethyl sulphoxide (DMSO), recombinant human granulocyte-macrophage colony-stimulating factor (rh GM-CSF) or la,25-dihydroxyvitamin D₃. There was also no significant change in either the number or time of expression of differentiation-specific cell surface antigens observed on HL-60 cells induced to differentiate with either DMSO, 1α,25-dihydroxyvitamin D3 or TPA in the presence of cyclosporin A, an agent reported to inhibit the proteolytic breakdown of PK-C to the Ca⁺⁺- and phospholipid-independent form. Likewise, cyclosporin A did not affect the rate or extent of differentiation of primary bone marrow cell cultures. These results suggest that the proteolytically activated and phospholipid-independent form of PK-C is probably not involved in haemopoietic cell differentiation.     

Changes in sodium and potassium in Nitellopsis cells treated with transient salt stress

Abstract. Nitellopsis cells grown in fresh water have a relatively low cytoplasmic Na⁺ (11 mol m⁻³) and high cytoplasmic K⁺ (90 mol m⁻³) content. A 30-min treatment with 100 mol m⁻³ external NaCl resulted in a high [Na⁺]_c (90 mol m⁻³) and a low [K⁺]_c (33 mol m⁻³), Subsequent addition of external Ca²⁺ (10 mol m⁻³) prevented Na⁺ influx and then [Na⁺]_c decreased slowly. Changes in [K⁺]_c were opposite to [Na⁺]_c. During the recovery time vacuolar Na⁺ increased, while vacuolar K⁺ decreased. Since all these processes proceeded also under ice-cold conditions, the restoration of original cytoplasmic ion compositions is suggested to be a passive nature. The notion that the passive movement of ions across the tonoplast can act as an effective and economic mechanism of salt tolerance under transient or under mild salt stress conditions is discussed.     

K/Na selectivity at the plasmalemma of cortical root cells and preferential release of sodium to the xylem vessels in roots of Atriplex hortensis

Using excised roots of Atriplex hortensis L., cv. Gelbe Gartenmelde, the uptake, accumulation and xylem transport of K⁺ and Na⁺ have been measured. Influx as well as xylem transport proved to discriminate little between K⁺ and Na⁺, when considered in relation to the external solution. Both K⁺ and Na⁺ inhibited the uptake and xylem transport of each other to about the same degree. Measurements of intracel-lular Na⁺ fluxes by means of compartment analysis indicated that the low degree of K/Na discrimination during uptake was due to low influx selectivity. Moreover, K⁺/Na⁺ exchange at the plasmalemma was not very efficient in Atriplex roots. In order to establish the basis of the low K/Na discrimination in xylem transport, the rates of K⁺ and Na⁺ transport were related to the cytoplasmic K⁺ and Na⁺ concentrations to yield the selectivity ratio of transport, S(transport) = (φ_cx(K) × [Na⁺]_c)/(φ_cx(Na) × [K⁺]_c). Under all conditions this ratio was far below one indicating that Na⁺ was favoured during xylem release in excised roots of Atriplex at low external concentrations. The implications of this discrimination in favour of Na+ are discussed with respect to salt tolerance of A. hortensis .     

Some observations of rainbow trout, Salmo gairdneri, Richardson, infected with Cryptobia salmositica

Rainbow trout ( Salmo gairdneri ) were infected with an inoculum of infected blood containing 10⁶ Cryptobia salmositica. Parasitaemia was cyclical with a major peak at 14–21 days and a smaller peak at 42 days. The first peak of parasitaemia was correlated with low glucose, plasma proteins, and haematocrit levels. During this time clinical symptoms (exophthalmia, ascites, pale liver and gills) of the pathogenic condition were observed. The partial disappearance of the parasites from the blood was corrrelated with their appearance in the peritoneal cavity. As plasma glucose, proteins, and haematocrit levels returned towards control values, the oedema and gill paleness declined. Examination of the liver and spleen showed an exudate of fibrous matrix on their exterior surfaces. In addition, the presence of 2–4×10³ mm⁻³ Cryptobia in asymptomatic surviving fish suggests that a chronic parasitaemia can be tolerated.     

Distribution and metabolism of root-applied cytokinins in Pisum sativum

When N ⁶ [8–¹⁴C] furfuryladenine was applied to the intact root system of Pisum sativum L. cv. Meteor seedlings it was almost completely metabolised to other compounds within 24 h. Of the total activity recovered from the plants 94.5% was retained in the root system itself. ¹⁴C was recovered in a number of ethanol-soluble compounds and in ribonucleic acid, deoxyribonucleic acid and protein fractions of roots, stems, leaves and axillary buds. In rapidly growing axillary buds released from apical dominance by removal of the shoot apex the combined nucleic acid fractions accounted for 63.3% of the total ¹⁴C recovered from these organs. Xylem exudate collected from decapitated plants 0 to 12 h after supplying N ⁵[8–¹⁴C]furfuryladenine to the roots consistently contained a single major ¹⁴C-labelled compound which, in three different solvent systems, had the same Rf values as a major endogenous cytokinin isolated from the xylem of unlabelled plants. The content of N ⁶ [8–¹⁴C] furfuryladenine itself in the xylem exudate was always low and in some experiments it could not be detected.
It is suggested that part of the label from N ⁶ [8- ¹⁴CJfurfuryladenine taken up by the intact root system may have become incorporated in an endogenous cylokinin before export to the shoot.