DNA composition in South American camelids I. Characterization and in situ hybridization of satellite DNA fractions

The DNA composition and the in situ hybridization of satellite fractions were analysed in the New World camelids llama, alpaca, guanaco and vicuña. In the four camelid forms, it was possible to identify a similar main band DNA and five satellite fractions (I–V) with G+C base contents ranging from 32% to 66%. Satellites II–V from llama were in situ reannealed on chromosomes from the four camelid forms. The results obtained were: (a) the four satellites hybridized with regions of C-banding (centromeric regions of all chromosomes and short arms of some autosomes); (b) in general, homologous hybridizations (llama DNA versus llama chromosomes) were more efficient than heterologous reassociations; there were however three exceptions to this rule (vicuña and alpaca satellite fraction II, chromosome group B; vicuña fraction V, chromosome groups A and B); (c) X chromosomes from the four camelids had satellites III–V but lacked satellite II, (d) no satellite fraction was detected on chromosome Y. The analysis of the in situ hybridization patterns allowed to conclude that most or all C-banded chromosome regions comprise several satellite DNA fractions. It is, moreover, proposed that there is an ample interspecies variation in the number of chromosomes that cross-react with a given satellite fraction. Our data give further support to the close genomic kinship of New World camelids.     

Ag-NOR staining and in situ hybridization of rDNA in the chromosomes of the South American camelids

The location and frequency of Ag-stained NORs and sites of rDNA hybridization were studied in the chromosomes of the South American camelids. In the four camelids these regions occur distally on chromosomes 18, 21, and 27 and the smallest biarmed elements. Quantitative analysis of NOR distribution showed variations between both cells and species. In llama, guanaco and alpaca the NORs number averaged 6 per cell, this being higher than in vicuña where the average was 3. Relative frequencies of NOR-bearing chromosomes in the four camelids were similar. Yet, in vicuña the virtual absence of NOR sites on one of the smallest biarmed pairs was observed. The rDNA sites assessed in llama and vicuña by in situ hybridization with cloned 18S DNA were coincident with the NOR locations and with the frequencies characteristics for each species. Moreover, varying the exposure time of the autoradiographs, labeling patterns specific for each camelid were observed. Grain counts on individual chromosomes indicated that under our conditions one month exposure is enough to demonstrate all the rDNA sites available in the complement of llama. Conversely, at least two months are necessary to show the total sites existing in vicuña. Most probably this finding reflects the presence of variations in the amount of copies of the ribosomal genes per chromosome.     

Oxygen binding properties,capillary densities and heart weights in high altitude camelids

Summary The oxygen binding properties of the blood of the camelid species vicuna, llama, alpaca and dromedary camel were measured and evaluated with respect to interspecific differences. The highest blood oxygen affinity, not only among camelids but of all mammals investigated so far, was found in the vicuna (P₅₀=17.6 Torr compared to 20.3–21.6 Torr in the other species). Low hematocrits (23–34%) and small red blood cells (21–30 m³) are common features of all camelids, but the lowest values are found in theLama species. Capillary densities were determined in heart and soleus muscle of vicuna and llama. Again, the vicuna shows exceptional values (3720 cap/mm² on average in the heart) for a mammal of this body size. Finally, heart weight as percent of body weight is higher in the vicuna (0.7–0.9%) than in the other camelids studied (0.5–0.7%). The possibility that these parameters, measured in New World tylopodes at sea level, are not likely to change considerably with transfer to high altitude, is discussed.In the vicuna, a unique combination of the following features seems to be responsible for an out-standing physical capability at high altitude: saturation of blood with oxygen in the lung is favored by a high blood oxygen affinity, oxygen supply being facilitated by low diffusion distances in the muscle tissue. Loading, as well as unloading, of oxygen is improved by a relatively high oxygen transfer conductance of the red blood cells, which is due to their small size and which compensates the negative effect of a low hematocrit on the oxygen conductance of blood. Blood oxygen transport is presumably favored by two factors: a relatively large heart mass and, as a result of low hematocrit, a low blood viscosity. Both are advantageous for achieving a high maximal cardiac output.     

Organic reduction of tapioca wastewaters using modified RBC

A modified Rotating Biological Contactor (RBC) was used for the treatability studies of synthetic tapioca wastewaters. The RBC used was a four stage laboratory model and the discs were modified by attaching porous nechlon sheets to enhance biofilm area. Synthetic tapioca wastewaters were prepared with influent concentrations from 927 to 3600 mg/l of COD. Three hydraulic loads were used in the range of 0.03 to 0.09 m³·m^–2·d^–1 and the organic loads used were in the range of 28 to 306 g COD· m^–2·d^–1. The percentage COD removal were in the range from 97.4 to 68. RBC was operated at a rotating speed of 18 rpm which was found to be the optimal rotating speed. Biokinetic coefficients based on Kornegay and Hudson models were obtained using linear analysis. Also, a mathematical model was proposed using regression analysis.List of Symbols A m² total surface area of discs - d m active depth of microbial film onany rotating disc - K _s mg ·l^–1 saturation constant - P mg·m^–2·^–1 area capacity - Q l·d^–1 hydraulic flow rate - q m³·m^–2·d^–1 hydraulic loading rate - S ₀ mg·l^–1 influent substrate concentration - S _e mg·l^–1 effluent substrate concentration - w rpm rotational speed - V m³ volume of the reactor - X _f mg·l^–1 active biomass per unit volume ofattached growth - X _s mg·l^–1 active biomass per unit volume ofsuspended growth - X mg·l^–1 active biomass per unit volume - Y _s yield coefficient for attachedgrowth - Y _A yield coefficient for suspendedgrowth - Y yield coefficient, mass of biomass/mass of substrate removed Greek Symbols hr mean hydraulic detention time - (_max)_A d^–1 maximum specific growth rate forattached growth - (_max)_s d^–1 maximum specific growth rate forsuspended growth - _max d^–1 maximum specific growth rate - d^–1 specific growth rate - _v mg·l^–1·hr^–1 maximum volumetric substrateutilization rate coefficient     

The oxygen uptake-power regression in cyclists and untrained men: implications for the accumulated oxygen deficit

The regression of oxygen uptake (O₂) on power output and the O₂ demand predicted for suprapeak oxygen uptake (O_2peak) exercise (power output = 432 W) were compared in ten male cyclists [C, mean O_2peak = 67.9 (SD 4.2) ml · kg^–1 · min^–1] and nine active, yet untrained men [UT, mean O_2peak = 54.1 (SD 6.5) ml · kg^–1 · min^–1]. The O₂-power regression was determined using a continuous incremental cycle test (CON4), performed twice, which comprised several 4-min exercise periods progressing in intensity from approximately 40%–85% O_2peak. Minute ventilation (_E), heart rate (HR), respiratory exchange ratio (R), blood lactate concentration ([1a^–]_b) and rectal temperature (T _re) were measured at rest and during CON4. The slope of the O₂-power regression was greater (P 0.05) in C [12.4 (SD 0.7) ml · min^–1. W^–1] compared to UT [11.7 (SD 0.4) ml · min^–1 W^–1]; as a result, the O₂ demand (at 432 W) was also higher (P 0.05) in C [5.97 (SD 0.23) l · min^–1] than UT [5.70 (SD 0.15) 1 · min^–1]. ExerciseR and [la^–]_b were lower (P 0.05) in C .in comparison to UT at all power outputs, whereas _E and HR were relatively lower (P 0.05) in C at power outputs approximating 180 W, 220 W and 270 W. Differences in fat metabolism estimated over the first three power outputs accounted for approximately 19% of the difference in O₂-power slopes between the groups and up to 46% of the difference in O₂ at a given intensity. Although the O₂-power regressions were linear for C [r = 0.997 (SD 0.001)] and UT [r = 0.997 (SD 0.001)], the O₂-power slope was higher at power outputs at or above the lactate threshold (13.2 ml · min^–1 · W^–1 than at lower intensities (11.6 ml · min^–1 · W^–1) in C, an effect which was less profound in UT. As a result, the exclusion of O₂ at the highest power outputs completely abolished the difference in O₂-power slopes between C and UT. Thus, the relatively higher O₂ during incremental exercise in C can be almost entirely attributed to the higher O₂ cost of cycling at higher power outputs. In addition, the presence of non-linear responses in O₂ at higher intensities also confirms the invalidity of describing the O₂ response across a wide range of power outputs using a linear function, and challenges the validity of predicting the O₂ demand of more intense exercise by a linear extrapolation of this same function.     

Function and regulation of the avian caecal bulb: influence of dietary NaCl and aldosterone on water and electrolyte fluxes in the hen (Gallus domesticus) perfused in vivo

Summary The function of the caecal bulb, and its adaptation to chronic high- or low-Na⁺ intake, was investigated by in vivo perfusion of anaesthetised birds. Effects of acute aldosterone injection (125 g·kg^–1 body mass) were also measured.Evidence was found for primary active net absorption of Na⁺, inducing parallel Na-linked absorption of water and Cl^– and secretion of K⁺. Around 20–35% of total Cl^– absorption and K⁺ secretion were independent of Na⁺ fluxes, and these components appear to be driven by passive processes with apparent conductances of 6.3×10^–3 (G _Cl) and 1.1×10^–3 (G _K) S·cm^–2.Acetate (40mM) stimulated Na⁺ fluxes (8.5–9.9 Eq·cm^–2·h^–1) and Na-linked water fluxes (27–44 l·cm^–2·h^–1). Increased coupling ratios (2.9–4.6 l·Eq^–1) and other data indicate that these effects may be due to increased osmotic permeabilities of barriers involved in the Na-linked water transfer pathway.Low-Na⁺ maintenance enhanced EPD (49–69 mV, serosa positive) and all net fluxes:J _Na (6.8–11.6);J _K (–3.2––4.3);J _Cl (4.3–5.6 Eq·cm serosal area^–2·h^–1);J _v (28–43 l·cm^–2·h^–1) (mucosal-serosal fluxes positive).Acute aldosterone enhancedJ _Na (10.8–14.0 Eq·cm^–2·h^–1) and EPD (54–66 mV) by 3 h after injection, but had no effect on the Na-linked components ofJ _K orJ _Cl.Abbreviations ECPD, EPD Electrochemical or electrical potential difference - G _Cl ,G _K ionic conductances (Cl^–, K⁺) - J _v ,J _ion net volume or ion flux rate, mucosa-serosa positive;P _d (Cl) diffusive permeability coefficient (of Cl^–) - SEDM standard error of difference between means     

Photosynthetic production of hydrogen peroxide by Ulva rigida C. Ag. (Chlorophyta)

Production of hydrogen peroxide has been found in Ulva rigida (Chlorophyta). The formation of H₂O₂ was light dependent with a production of 1.2 mol·g FW^–1·h^–1 in sea water (pH 8.2) at an irradiance of 700 mol photons m^–2·s^–1. The excretion was also pH dependent: in pH 6.5 the production was not detectable (< 5 nmol·g FW^–1·h^–1) but at pH 9.0 the production was 5.0 mol·g FW^–1·h^–1. The production of H₂O₂ was totally inhibited by 3-(3,4-dichlorophenyl)-1,1 dimethylurea (DCMU). The ability of U. rigida growing in tanks (7501) under a natural light regime to excrete H₂O₂ was checked and found to be seven times higher at 08.00 hours than other times of the day. The H₂O₂ concentration in the cultivation tank (density: 2 g FW·l^–1) reached the highest value (3 M) at 11.00 hours. Photosynthesis was not influenced by H₂O₂ formation. The H₂O₂ is suggested to come from the Mehler reaction (pseudocyclic photophosphorylation). With an oxygen evolution of 120 mmol·g FW^–1·h^–1 at pH 8.2 and 90 mmol·g FW^–1·h^–1 at pH 9.0, 0.5% and 2.7% of the electrons were used for extracellular H₂O₂ production. The H₂O₂ production is sufficiently high to be of physiological and ecological significance, and is suggested to be a part of the defence against epi and endophytes.Abbreviations ACL artificial, continuous light - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - GNL greenhouse - LDC Luminol-dependent chemiluminescence - SOD Superoxide dismutase This investigation was supported by SAREC (Swedish Agency for Research Cooperation with Developing Countries), Hierta-Retzius Foundation, Marianne and Marcus Wallenberg Foundation, the Swedish Environmental Protection Board, and CICYT Spain.     

Zingerone [4-(4-hydroxy-3-methoxyphenyl)-2-butanone] Prevents 6-Hydroxydopamine-induced Dopamine Depression in Mouse Striatum and Increases Superoxide Scavenging Activity in Serum

As superoxide (·O₂^–) and hydroxyl radical (·OH) have been implicated in pathogenesis of Parkinsons disease, free radical scavenging, antioxidant, and neuroprotective agents have attracted attention as ways to prevent progression. We examined effects of zingerone, an alkaloid extracted from ginger root, on 6-hydroxydopamine (6-OHDA)-induced dopamine (DA) reduction in mouse striatum. Zingerone administration 1 h before and for 6 more days following one intracerebroventricular 6-OHDA injection prevented reductions of striatal DA and its metabolites, and increased serum ·O₂^– scavenging activity. Zingerone did not change activities of catalase or glutathione peroxidase in striatum or serum, or ·O₂^– scavenging activity in striatum. Treatment with diethyldithiocarbamate, SOD inhibitor, abolished the protective effect of zingerone against 6-OHDA-induced DA reduction. In vitro, zingerone scavenged ·O₂^– and ·OH and suppressed lipid peroxidation only weakly. Thus, direct antioxidant effects may be a minor component of its putative neuroprotective effect; instead, zingerone acted mainly by increasing systemic superoxide dismutase activity. Effects of zingerone treatment in this model suggest possible value in treatment of Parkinsons disease.     

Maximal oxygen uptake, maximal voluntary isometric contraction and physical activity in young Danish adults

In a randomly selected sample of 88 men and 115 women, aged 23–27 years from Denmark, maximal oxygen uptake ( O_2max), maximal voluntary isometric contraction (MVC) in four muscle groups and physical activity were studied. The O_2max was 48.0 ml · min^–1 kg^–1 and 39.6 ml · min^–1 · kg^–1 for the men and the women, respectively. The MVC was 10% lower than in a comparable group of Danes of the same age and height studied 35 years ago. Only in men was sports activity directly related to O_2max (ml · min^–1 · kg^–1; r=0.31, P<0.01). The MVC of the knee extensors was related to O_2max in the men (r=0.31, P<0.01), but there was no relationship between the other measurements of MVC and O_2max. In the women O_2max (ml · min^–1 · kg^–1) was only related to body size, i.e. body mass index, percentage body fat and body mass [(r= –0.47, –0.48 (both P<0.001) and –0.34. (P<0.01), respectively)]. There were differences in O_2max in the men, according to education and occupation. Blue collar workers and subjects attending vocational or trade schools in 1983 had lower O_2max and more of them were physically inactive. In the women differences were also found, but there was no clear pattern among the groups. More of the women participated regularly in sports activity, but more of the men were very active compared to the women.     

Foraminifera and meiofauna on an intertidal mudflat,Cornwall, England: Populations; respiration and secondary production; and energy budget

A rich and varied meiofauna inhabits a Cornish mudflat near the mouth of the Tamar River in southwestern England. Population densities range from 117 to 943 individuals · g^–1 (wet) sediment (1.4–11.4 × 10⁶ individuals · m^–2), with foraminifera, harpacticoid copepods and nematodes appearing in nearly equal numbers and comprising most of the meiofauna. Seasonally, meiofaunal numbers rise and fall with solar radiation and vary inversely with river discharge. Two species, the atestate allogromiid A and the calcareous Haynesina germanica (Ehrenberg), far outnumber other foraminifera; their population densities and growth rates reach maxima in spring and summer.Monthly rates of sediment respiration are locally variable, but clearly increase from winter (4.13 ml O₂ · m^–2 · h^–1 in December) to spring (38.87 ml O₂ · m^–2 · h^–1 in April). Experiments and calculations ascribe approximately 30% of this total to the meiofauna (including microfauna and microflora), 50% to bacteria and less than 20% to chemical oxidation. A tentative energy budget for the mudflat suggests that secondary production by meiofauna is small as compared with coastal environments elsewhere, and that meiofaunal production (426 Kcal · m^–2 · y^–1) is nearly twice meiofaunal respiration (252 Kcal · m^–2 · yr^–1).     

Modulation of fatty acid-binding capacity of heart fatty acid-binding protein by oxygen — derived free radicals

Summary In this study, we examined the effects of exposure of heart fatty acid-binding protein (h-FABP) to chemically generated O₂ ^– or OH · with respect to its oleate binding and to its electrophoretic properties. Purified rat h-FABP at 40 M scavenged as much as 30% O₂ ^– and 85% OH ·. On the other hand, when 2 nmol (4 M) FABP were exposed to free radicals, the maximum oleate binding capacity as measured by Scatchard analysis was reduced only by 14% and 27% for O₂ ^– and OH ·, respectively. The electrophoretic pattern of free radical-exposed FABP was not markedly different when examined either by the non-denaturing or by denaturing PAGE, suggesting the absence of any degradation or aggregation of FABP by O₂ ^– or OH ·. It is hypothesized that O₂ ^– or OH · in physiological concentration may not alter the function of FABP markedly in the ischemic-reperfused myocardium.Abbreviations h-FABP Heart Fatty Acid Binding Protein - NEFA Non-Esterified Fatty Acids - O₂ ^– Superoxide anions - OH· hydroxyl radicals - OCI hypohalite radicals - H₂O₂ hydrogen peroxide - HPLC High Pressure Liquid Chromatography     

Continuous chemotrophic growth and respiration of Chromatiaceae species at low oxygen concentrations

Endogenous and maximum respiration rates of nine purple sulfur bacterial strains were determined. Endogenous rates were below 10 nmol O₂ · (mg protein · min)^-1 for sulfur-free cells and 15–35 nmol O₂ · (mg protein · min)^-1 for cells containg intracellular sulfur globules. With sulfide as electron-donating substrate respiration rates were considerably higher than with thiosulfate. Maximum respiration rates of Thiocystis violacea 2711 and Thiorhodovibrio winogradskyi SSP1 (254.8 and 264.2 nmol O₂ · (mg protein · min)^-1, respectively) are similar to those of aerobic bacteria. Biphasic respiration curves were obtained for sulfur-free cells of Thiocystis violacea 2711 and Chromatium vinosum 2811. In Thiocystis violacea the rapid and incomplete oxidation of thiosulfate was five times faster than the oxidation of stored sulfur. A high affinity of the respiratoty system for oxygen (K _m =0.3–0.9 M O₂, V _max=260 nmol O₂ · (mg protein · min)^-1 with sulfide as substrate, K _m =0.6–2.4 M O₂, V _max=14–40 nmol O₂ · (mg protein · min)^-1 with thiosulfate as substrate), for sulfide (K _m =0.47 M, V _max=650 nmol H₂S · (mg protein × min)^-1, and for thiosulfate (K _m =5–6 M, V _max =24–72 nmol S₂O ₃ ^2- · (mg protein · min)^-1 was obtained for different strains. Respiration of Thiocystis violacea was inhibited by very low concentrations of NaCN (K _i =1.7 M) while CO concentrations of up to 300 M were not inhibitory. The capacity for chemotrophic growth of six species was studied in continuous culture at oxygen concentrations of 11 to 67 M. Thiocystis violacea 2711, Amoebobacter roseus 6611, Thiocapsa roseopersicina 6311 and Thiorhodovibrio winogradskyi SSP1 were able to grow chemotrophically with thiosulfate/acetate or sulfide/acetate. Chromatium vinosum 2811 and Amoebobacter purpureus ML1 failed to grow under these conditions. During shift from phototrophic to chemotrophic conditions intracellular sulfur and carbohydrate accumulated transiently inside the cells. During chemotrophic growth bacteriochlorophyll a was below the detection limit.     

Temperature insensitive O2 in blood of the tree frogChiromantis petersi

Summary Respiratory gas exchange and blood respiratory properties have been studied in the East-African tree frogChiromantis petersi. This frog is unusually xerophilous, occupies dry habitats and prefers body temperatures near 40°C and direct solar exposure. Total O₂ uptake was low at 81 l O₂·g^–1·h^–1±19.0 (SD) at 25°C increasing to 253.5 l O₂·g^–1·h^–1±94.8 (SD) at 40°C giving aQ ₁₀ value of 2.1. Skin O₂ uptake at 25°C was 38.5% of total. The gas exchange ratio was 0.71 for whole body gas exchange, 0.61 for the lungs and 1.02 for the skin at 25°C.Blood O₂ affinity was low with aP ₅₀ of 47.5 mmHg at 25°C and pH 7.65. Then _H-value at 25°C increased from 2.7 aroundP ₅₀ to 5.0 at O₂ saturations exceeding 70–80%. Surprisingly, blood O₂ affinity was nearly insensitive to temperature expressed by a H value of ±1.0 kcal·mole between 25 and 40°C.The adaptive significance of the low O₂ affinity, the increase ofn _H with O₂ saturation and the temperature insensitive O₂-Hb binding is discussed in relation to the high and fluctuating body temperatures ofChiromantis.     

Analysis of oxygen evolution during photosynthetic induction and in multiple-turnover flashes in sunflower leaves

Exchange of CO₂ and O₂ and chlorophyll fluorescence were measured in the presence of 360 1 · 1^–1 CO₂ in nitrogen in Helianthus annuss L. leaves which had been preconditioned in the dark or at a photon flux density (PFD) of 24 mol · m^–2 · s^–1 either in 21 or 0% O₂. An initial light-dependent O₂ outburst of 6 mol · m^–2 was measured after aerobic dark incubation. It was attributed to the reduction of electron carriers, predominantly plastoquinone. The maximum initial rate of O₂ evolution at PFD 8000 mol · m^–2 · s^–1 was 170 mol · m^–2 · s^–2 or about four times the steady CO₂-and light-saturated rate of photosynthesis. Fluorescence measurements showed that the rate was still acceptor-limited. Fast O₂ evolution ceased after electron carriers were reduced in the dark-adapted leaf, but continued for a short time at the lower rate of 62 mol · m^–2 · s^–1 in the light-adapted leaf. The data are interpreted to show that enzymes involved in 3-phosphoglycerate reduction are dark-inhibited, but were fully active in low light. In a dark-adapted leaf, respiratory CO₂ evolution continued under nitrogen; it was partially inhibited by illumination. Prolonged exposure of a leaf to anaerobic conditions caused reducing equivalents to accumulate. This was shown by a slowly increasing chlorophyll fluorescence yield which indicated the reduction of the PSII acceptor Q_A in the dark. When the leaf was illuminated, no O₂ evolution was detected from short light pulses, although transient O₂ production was appreciable during longer light pulses. This indicates that an electron donor (pool size about 2–3 e/PSII reaction center) became reduced in the dark and the first photons were used to oxidise this donor instead of water.Abbreviations Chl chlorophyll - CRC carbon reduction cycle - GAPDH NADP-glyceraldehyde-phosphate dehydrogenase - PFD photon flux density - PGA 3-phosphoglycerate - RuBP ribulose bisphosphate - TCA tricarboxylic acid cycle To whom correspondence should be addressedThis work received support by the Estonian Academy of Sciences, the Gottfried-Wilhelm-Leibniz Program of the Deutsche For-schungsgemeinschaft and the Sonderforschungsbereich 251 of the University of Würzburg.     

Simultaneous oxygen production and nitrogenase activity of an ammonia-excreting mutant of the cyanobacterium Anabaena variabilis in a co-culture with wheat

Summary A mutant strain of Anabaena variabilis, strain SA-1 that supported growth of wheat plants in a hydroponic co-culture in nitrogen (N) free medium also produced enough oxygen (O₂) to support root respiration. The steady-state concentration of net O₂ in the co-culture was dependent on incident light intensity. At an incident photosynthetic photoflux (PPF) of 1000 mol photons·m^–2·s^–1, net O₂ evolution by the co-culture in the root zone reached a maximum value of about 220 mol O₂ evolved·h^–1·mg chlorophyll (Chl)^–1. The O₂ concentration in the rhizosphere of the co-culture stayed above the ambient air level. O₂ uptake in the dark by strain SA-1-supplemented wheat roots washed free of cyanobacterium was higher than the root respiration of nitrate-grown plants. Nitrate-grown plants required aeration for maximum growth while the wheat-cyanobacterial co-culture can be cultured without aeration. These results show that O₂ produced by strain SA-1 can be used to supply the O₂ needs for root respiration of wheat. Respiration reduced net O₂ evolution by the mutant SA-1, decreasing the partial pressure of O₂ at the sites of cyanobacterial attachment to the roots. This led to an increase in the specific activity of nitrogenase of the co-culture at the high light intensities used to support wheat growth. This activity of about 30 mol ethylene produced·mg Chl^–1·h^–1 was three-fold higher than the activities obtained with the free-living strain SA-1 assayed at the same light intensity. In the co-culture, ammonia produced by the mutant strain SA-1 was not detectable. The NH _inf4 ^sup+ produced by strain SA-1 was used by the wheat plants and, under these conditions, the total N content of the plants reached as high as 85% of the total N content of nitrate-grown plants. In the co-culture system the metabolism of wheat and the cyanobacterium complemented each other, leading to higher plant growth in N-free medium. Offprint requests to: M. Gunasekaran     

Signal role for activation of caspase-3-like protease and burst of superoxide anions during Ce<Superscript>4+</Superscript>-induced apoptosis of cultured <Emphasis Type="Italic">Taxus cuspidata</Emphasis> cells

The signal events of 1 mM Ce⁴⁺ (Ce(NH₄)₂(NO₃)₆)-induced apoptosis of cultured Taxus cuspidata cells were investigated. The percentage of apoptotic cells increased from 0.82% to 51.32% within 6 days. Caspase-3-like protease activity became notable during the second day of Ce⁴⁺-treatment, and the maximum activity was 5-fold higher than that of control cells at the fourth day. When the experiment system was pretreated with acetyl-Asp-Glu-Val-Asp-aldehyde (Ac-DEVD-CHO) at 100 M, caspase-3-like activity resulted in distinct inhibition by 70% and 77.3% after 3 and 4 days of induction. Furthermore, 100 M Ac-DEVD-CHO partially reduced the apoptotic cells by 58.6% and 60.8% at day 4 and 5 respectively. Ce⁴⁺ induced superoxide anions (O₂·–) transient burst, and the first peak appeared at around 3.7–4 h, the second appeared at about 7 h. Both O₂·– burst and cell apoptosis were effectively suppressed by application of diphenyl iodonium (NADPH oxidase inhibitor). Inhibition of O₂·– production attenuated caspase-3-like activation by 49% and 53.6% during day 3 and 4 respectively. In addition, a total of 15 protein spots changed in response to caspase-3-like protease activation were identified by two-dimensional gel electrophoresis. These results suggest that Ce⁴⁺ of 1 mM induces apoptosis in suspension cultures of T. cuspidata through O₂·– burst as well as caspase-3-like protease activation. The burst of O₂·– exerts its activity as an upstream of caspase-3-like activation. Our results also implicate that other signal pathways independent of an O₂·– burst possibly participate in mediating caspase-3-like protease activation.     

Model aided design of repeated fed-batch penicillin fermentation

Structured models of antibiotic fermentation that quantify maturation and aging of product forming biomass are fitted to experimental data. Conditions of superiority of repeated fed batch cultivation are characterized on the basis of a performance criterion that includes penicillin productivity and costs of operation. Emphasis is placed on the relevance of such research to the model aided design of optimal cyclic operation.List of Symbols c IU/mg cost factor - D s^–1 dilution rate - J IU · cm^–3 · h^–1 net productivity - k _p IU · mg^–11 · h^–1 specific product formation rate - k _pm IU · mg^–1 · h^–1 maximum specific product formation rate - p IU/cm³ concentration of penicillin - T s final time of fermentation - t s fermentation time - X kg/m³ concentration of biomass dry weight - X ₁kg/m³ concentration of young, immature biomass - X ₂ kg/m³ concentration of mature product forming biomass - X _c kg/m³ biomass concentration of the end of growth phase - X _mkg/m³ maximum biomass concentration Greek Letters s^–1 specific maturation rate - s^–1 specific aging rate - s^–1 specific growth rate - _m s^–1 maximum specific growth rate - _p s^–1 specific growth rate during the product formation phase - s cycle time - % volume fraction of draw-off Abbreviations CC chemostat culture - RFBC repeated fed batch culture - RBC repeated batch culture     

Oxygen and carbon dioxide transport by the haemocyanin of an amphibious crab,Holthuisana transversa

Summary The oxygen and carbon dioxide transporting properties of the haemolymph from an amphibious Australian crab,Holthuisana transversa were investigated. Within the temperature range 15 to 35°C increasing temperature markedly decreased oxygen affinity (H=–54 kJ·mol^–1). The Bohr effect was small at all temperatures with a mean value of –0.13. Over the temperature range 15–35°C there was a significant increase in the cooperativity of oxygen binding. Changing the concentration of Ca,l-lactate or haemocyanin in the haemolymph could elicit no significant change in either O₂ affinity or cooperativity of O₂ binding. There was no evidence in support of a specific effect of CO₂ on oxygen affinity of either non-dialysed or dialysed haemolymph.The amount of CO₂ that could be carried byH. transversa haemolymph was significantly reduced by increased temperature (approx. 14 to 12.5 mmol·l^–1 CO₂). Comparisons of oxygenated and deoxygenated haemolymph at a fixed pH were unable to demonstrate the presence of a significant Haldane effect. Combining data from oxygenated and deoxygenated haemolymph the buffer value was calculated to be in the range –6.2 to –8.5 mmol·l^–1 HCO ₃ ^– ·pH unit^–1.The insensitivity ofH. transversa haemocyanin function to all modulating influences except temperature is discussed with respect to the ecology of this crab.     

Elektron-Spin-Resonanz-Untersuchungen der Reaktionskinetik strahleninduzierter freier Radikale des Cholesterins

Zusammenfassung Die Reaktionskinetik strahleninduzierter freier Radikale des Cholesterins wurde in flüssiger Phase bei Raumtemperatur mittels ESR-Spektroskopie untersucht. Mit Hilfe eines geeigneten photochemischen Initiationssystems ließen sich in Cyclohexanlösung unter UV-Bestrahlung (235 nm265 nm) genau dieselben freien Radikale des Cholesterins darstellen, die schon früher [9, 7] in röntgenbestrahltem Cholesterinpulver beobachtet worden waren. Bei ausreichendem O₂-Partialdruck (3·10⁴Torr) über der Probenlösung trat das ESR-Spektrum eines Peroxyradikals auf, das mittels der Analyse seiner Reaktionsprodukte (7-Hydroxy-Cholesterin und 7-Keto-Cholesterin) mit dem Cholesteryl-7-peroxyradikal identifiziert wurde. Die Kinetik sowohl der Bildung als auch des Zerfalls des Radikals entsprachen einer Reaktion von 2. Ordnung. Die Geschwindigkeitskonstante für den bimolekularen Zerfall, eine Disproportionierung in Alkohol und Keton unter Abgabe eines Moleküls O₂, wurde bei Raumtemperatur zuk ₂=(1,8 _–0,6 ^+0,9 )·10⁶ sec^–1M^–1·l bestimmt. Ferner wurde gezeigt, daß das Cholesteryl-7-peroxyradikal aus dem freien Radikal Cholesteryl-7 durch Anlagerung eines Moleküls O₂ entsteht. Für die Geschwindigkeitskonstante dieser Reaktion ergab sich eine untere Schranke vonk ₁=0,40·10¹⁰ sec^–1M^–1·l.

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Electron spin resonance investigations on radiation-induced free radicals of cholesterol in liquid phase

Summary The reaction kinetics of radiation-induced free radicals of cholesterol was studied in liquid phase at room temperature by means of e.s.r. spectroscopy on a solution of cholesterol in cyclohexane. Using a convenient photochemical initiation system, just those free radicals of cholesterol could be generated by the filtered u.v. radiation from a Xe high pressure lamp (235 nm265 nm) as were observed already a decade ago by Gordy [9] and by Ehrenberg, Löfroth [7] in X-irradiated cholesterol powder. At sufficiently high O₂-pressures (3·10^–4 Torr) over the sample solution a peroxy radical e.s.r. spectrum arose during u.v. irradiation which was identified by product analysis (7-hydroxy-cholesterol and 7-keto-cholesterol) to be dueto a cholesteryl-7-peroxyradical. The radical'sgeneration and decay kinetics was governed by a second order reaction. The velocity constant for bimolecular decay of the cholesteryl-7-peroxyradical was found to be k₂=(1.8 _–0,6 ^+0,9 )·10⁶sec^–1M^–1·l at room temperature. Furthermore it could be shown that the cholesteryl-7-peroxyradical was built up by the addition of one molecule of O₂ to a cholesteryl-7 free radical. For this reaction a value ofk ₁=0.4·10¹⁰ sec^–1 M^–1·l was estimated as a lower limit of the velocity constant.

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Die Arbeit stellt einen Auszug aus einer Dissertation an der Technischen Hochschule München dar.