The role of muscle development in the transition to endothermy in nestling bank swallows,Riparia riparia

Summary We examined the transition from ectothermy to endothermy in nestling bank swallows (Riparia riparia) by measuring the peak metabolic response to cold (PMR) in groups of nestlings. Additionally aerobic capacity, as assessed by citrate synthase activity (CS), and contractile function, as assessed by myofibrillar ATPase activity (mATPase) were measured in the pectoralis and mixed leg muscles during development. During the first 65% of their growth (from 2–12 g) bank swallows do not increase their metabolic rate in response to cold (Fig. 1). Between 12 and 16 g the PMR increased from 4 to more than 10 ml O₂ (g·h)^–1. Citrate synthase activity increased throughout development, starting at 20 moles (min·g fresh mass)^–1 in both tissues and increasing to 150 and 50 moles (min·g)^–1 in the pectoralis and leg muscles, respectively (Fig. 5). The augmented aerobic capacity combined with large increases in muscle mass undoubtedly contributes to the improved thermoregulatory abilities of older nestlings. However, muscle mass and aerobic capacity increase continuously and do not show the sharp transition noted in PMR. In the leg muscle mATPase activity is constant throughout growth, but in the pectoralis muscle it undergoes an abrupt increase from 0.5 moles (min·mg myofibrillar protein)^–1 in animals weighing less than 12 g to 0.9 moles (min·mg)^–1 in nestlings weighing more than 15 g (Fig. 6). The similar pattern of development of PMR and mATPase suggests a critical role for muscle development in the transition to endothermy in this species.Abbreviations CS citrate, synthase - mATPase myofibrillar adenosine triphosphatase - PMR peak metabolic rate during cold stress - rate of oxygen consumption     

Der hemmende Einfluß gleichzeitig bewegter Beuteattrappen auf das Beutefangverhalten der Erdkröte (Bufo bufo L.)

Zusammenfassung Durch simultane visuelle Bewegungsreize, die von mehreren Beutetieren (z.B. Mehlkäferlarven) ausgehen, wird der Beutefang der Erdkröte (Bufo bufo L.) gehemmt. An diese Verhaltensheobaehtung anknüpfend, wurde die Abhängigkeit dieses inhibitorischen Umfeldeffektes von verschiedenen visuellen Reizparametern im Attrappen versuch quantitativ gemessen: Im frontalen Gesichtsfeld der Kröte rotierte vor dunklem Hintergrund eine weiße, rechteckige, 2,5 × 20° große Beuteattrappe (Zentralattrappe, z) mit dem Rechteckzentrum im Drehpunkt. Zusätzlich konnten mehrere Kreisscheiben von 5 bzw. 10° (Peripherattrappen, p) um die Zentralattrappe bewegt werden.Die Beutefangaktivität R _z [Beutefangreaktionen x min^–1] auf die allein gebotene Zentralattrappe war bei einer Sehwinkelgeschwindigkeit v _s der distalen Attrappenkanten 10v _s30 [grad x see^–1] maximal und sank für kleinere oder größere Winkelgeschwindigkeiten wieder ab. Eine mit v _s=25 [grad x sec^–1] allein bewegte Peripherattrappe löste maximale Beutefangaktivität R _p aus. Mit zunehmender Anzahl n _p simultan bewegter Peripherattrappen sank die Beutefangaktivität ab.Mehrere, um den gleichen Drehpunkt bewegte Peripherattrappen, deren Abstand untereinander =10° betrug, blieben von der Kröte unbeantwortet. Sie bildeten ein inhibitorisches Umfeld und hemmten dadurch die Reaktion auf die gleichzeitig bewegte Zentralattrappe z. — Die im Simultanreizungsversuch gemessene Beutefangaktivität R _zp war abhängig vom Abstand [grad] zwischen Zentralattrappe und Peripherattrappen ( : Kürzester Abstand zwischen z und p): Für =10° war R _zp0 und stieg für >10° an. — Kontrollversuche, die jeweils auf die Simultanreizung mit z allein folgten (R _z), ließen eine -abhängige Nachhemmung erkennen. — Die hemmende Wirkung auf die Beantwortung von z war auch von der Sehwinkelgeschwindigkeit v _s der Peripherattrappen abhängig; sie war bei derjenigen Sehwinkelgeschwindigkeit (v _s=25 [grad × sec^–1]) maximal, mit der die Zentralattrappe, allein geboten, maximale Beutefangaktivität auslöste; für v _sg25 [grad × sec^–1] nahm die Hemmung wieder ab.Die Versuchsergebnisse lassen auf inhibitorische Verknüpfungen innerhalb des zentralen visuellen Systems schließen. Es wird vermutet, daß die Reiz-Verhaltens-reaktionsbeziehungen in den visuellen Simultanreizungsversuchen durch eine Art zentrale laterale Inhibition bestimmt werden.

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Inhibitory effect of simultaneously moved prey dummies on the prey catching behaviour of the common toad (Bufo bufo L.)

Summary The prey catching behaviour of the toad (Bufo bufo L.) is generally inhibited by simultaneously visual moving stimuli caused by a group of prey animals (mealworms). According to this behavioural observation the dependence of this inhibitory effect on several visual parameters were quantitatively measured in dummy experiments: in the frontal visual field of the toad a white rectangular prey dummy of 2,5×20° (central dummy, z) was rotating in a centre against dark background. In addition several disks of 5 or 10° diameter (peripheral dummies, p) could simultaneously rotate around the central dummy (Figs. 1 and 7).The prey catching activity R _z [catching reactions x min^–1] released by rotation of only the central dummy z increased with increasing angular velocity v _s of the stimulus distal edges, reaching a maximum for 10v_s30 [degrees x sec^–1] and decreasing for v _s>30 [degrees x sec^–1] (Fig. 5).A single peripheral dummy p, moved at v _s=25 [degrees x sec^–1], released maximal catching activity R _p. The activity R _p decreased with the increasing number n _p of simultaneously offered dummies (Fig. 6).The prey catching behaviour of the toad was inhibited, when several peripheral dummies p were moved around the centre with a distance =10° from each other. They caused an inhibitory field and they also inhibited the response to a simultaneously moved central dummy z. The prey catching activity, measured in experiments in which z and p rotated simultaneously, depends on the distance [degrees] between z and p ( being the shortest distance between z and p). For =10°, R _zp was zero; R _zp increased for >10° (Figs. 9 and 10). — Control experiments carried out with z allone — after having applied the simultaneous stimulation — showed a - dependent after-inhibition (Fig. 9). — The inhibitory effect on the response to z also depended on the angular velocity v _s of p; the inhibition was at a maximum for v _s25 [degrees x sec^–1], and it decreased for v _s25 [degrees x sec^–1] (Fig. 11).The experimental results suggest inhibitory interactions within the central visual system. It is supposed that the relation between stimulus and behavioural reaction in simultaneous stimulating experiments results from some kind of central nervous lateral inhibition.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft (Ew 7/4+5).     

Reversed bohr and root shifts in hemocyanin of the marine prosobranch,Buccinum undatum: Adaptations to a periodically hypoxic habitat

Summary Oxygen binding properties of the hemocyanin-containing blood ofBuccinum undatum were examined in vitro and in vivo under normoxic ( 150 mmHg) and hypoxic ( 50 mmHg) conditions at 10°C. Blood pH and showed a decrease in vivo under hypoxic conditions. Oxygen uptake at high water , was about 18 ml O₂/kg·h (wet weight) and the critical oxygen tension between 25 and 50 mm Hg. In vitro the O₂ binding to hemocyanin showedn-values independent of pH, while both O₂ affinity and oxygen carrying capacity were strongly pH dependent. Oxygen affinity increased below pH=8.1 and thus showed a pronounced reversed Bohr shift in the physiological pH range (7.5<pH<8.1). The oxygen carrying capacity similarly increased markedly with falling pH in the physiological pH range (reversed Root shift). Astrup titration curves showed a metabolic and respiratory acidosis under hypoxic conditions ( 50 mm Hg). The role of hemocyanin in the transport of oxygen in relation to ambient O₂ availability is discussed.     

Respiratory activity and growth kinetics of Candida yeasts related to carbon sources and available energy

Summary Three yeasts of the genus Candida (Candida intermedia, candida lipolytica and Candida tropicalis) were cultivated batchwise on three different carbon sources: glucose, acetate, and hexadecane. Growth curves, oxygen uptake rates, CO₂ evolution rates and the amount of oxygen required for biomass production were determined. The data were compared and discussed from the point of maximum specific growth rate, maximum oxygen uptake rate, carbon conversion into CO₂ and biomass, consumption of oxygen and available energy for cell synthesis. The results indicated a relationship between _m m, Y_s, Y_O, and for different carbon sources. Y_O and were in the same order of magnitude for acetate (0.58 and 0.38 respectively) and hexadecane (0.45 and 0.40 respectively). These values were remarkably lower than those for glucose (1.26 and 0.54 respectively).Symbols av e^– Available electrons per mol of substrate (dimensionless) - E_av Energy available per mol of substrate (dimensionless) - C_d Dissimilated carbon (%) - m Maximum specific rate of oxygen uptake (mMO₂ h^–1 g^–1) - RQ CO₂ evolved per O₂ consumed - mol. wt. Molecular weight - Y_ATP Biomass mass yield based on mol of ATP generated (g) - Biomass mass yield based on available energy (g) - Y_M Biomass mass yield based on mol of organic substrate (g) - Y_O Biomass mass yield based on oxygen consumed (gg^–1) - 1/Y_O Oxygen consumed for one gram of biomass produced (gg^–1) - Y_s Biomass mass yield based on organic substrate (dimensionless) - b Reductance degree of biomass (equiv. available electrons/g atom carbon) - s Reductance degree of organic substrate (equiv. available electrons/g atom carbon) - Fraction of energy in organic substrate which is converted to biomass - b Weight fraction carbon in biomass (dimensionless) - s Weight fraction carbon in organic substrate (dimensionless) - _m Maximum specific growth rate (h^–1)     

Purification and characterization of β‐methylaspartase from Fusobacterium varium

Methylaspartase (EC 4.3.1.2) was purified 20fold in 35% yield from Fusobacterium varium, an obligate anaerobe. The purification steps included heat treatment, fractional precipitation with ammonium sulfate and ethanol, gel filtration, and ion exchange chromatography on DEAESepharose. The enzyme is dimeric, consisting of two identical 46 kDa subunits, and requires Mg²⁺ (K_m = 0.27 ± 0.01 mM) and K⁺ (K_m = 3.3 ± 0.8 mM) for maximum activity. Methylaspartasecatalyzed addition of ammonia to mesaconate yielded two diastereomeric amino acids, identified by HPLC as (2S,3S)3methylaspartate (major product) and (2S,3R)3methylaspartate (minor product). Optimal activity for the deamination of (2S,3S)3methylaspartate (K_m = 0.51 ± 0.04 mM) was observed at pH 9.7. The Nterminal protein sequence (30 residues) of the F. varium enzyme is 83% identical to the corresponding sequence of the clostridial enzyme.     

Contribution to the genetics of serum β-lipoproteins in man

Summary The genetic behaviour of a human serum -lipoprotein factor, called Ag(a₁), was studied by agar micro-diffusion technique, utilizing an antibody detected in the serum from a transfused thalassemia patient. It behaves as an inherited, dominant, autosomal character, with complete penetrance at birth. It is controlled by a gene and is closely linked to the Ag ^x and Ag ^y genes.The existence of a gene Ag ^b , allelic to , is postulated but the Ag(b) antigen has not so far been detected by specific antisera.The frequency of the gene in a Milan population was found to be 0,43, and in a Berne population was 0,46. The frequencies of the four possible gene combinations in the sample group from Milan were: Ag ^yb =0,53; =0,22; =0,21; Ag ^xb =0,04.The observed frequencies of the factor Ag(a₁) were 0,676 and 0,713, respectively among the Milan and Berne populations.     

Aerobic metabolism of the lizardVaranus exanthematicus: Effects of activity, temperature, and size

Summary Oxygen consumption was measured at rest and during spontaneous activity at body temperatures of 25 and 35°C in 14 fasting Savanna monitor lizards,Varanus exanthematicus ranging in weight from 172 to 7500 g. The allometric relationship between metabolic rate at 25°C and body weight (W) is given by: (ml O₂ STPD·g^–1·hr^–1)=0.88W ^–0.43 (Fig. 2). Although statistical comparisons are equivocal, this intraspecific size dependence exceeds that reported for interspecific comparisons among reptiles and other vertebrate groups (Fig 3). A reproducible diurnal pattern of activity was observed in undisturbed animals with minimum values of between 2400 and 0800 h (Fig. 1). Spontaneous activity and generally reached peak values between 1200 and 2000 hrs. The average ratio of active aerobic metabolic rate (AMR) to minimum (standard) aerobic metabolic rate (SMR) was 8.2. This voluntary AMR/SMR inVaranus exceeds the AMR/SMR for most reptiles stimulated to exhaustion. The high aerobic capacity is consistent with other evidence for efficient exchange and transport of respiratory gases inV. exanthematicus; e.g., low or absent intracardiac shunt flow resulting in high arterial saturation and low ventilation and perfusion requirements.     

Severe hypoxia decreases oxygen uptake relative to intensity during submaximal graded exercise

The effect of severe acute hypoxia (fractional concentration of inspired oxygen equalled 0.104) was studied in nine male subjects performing an incremental exercise test. For power outputs over 125 W, all the subjects in a state of hypoxia showed a decrease in oxygen consumption ( O₂) relative to exercise intensity compared with normoxia (P < 0.05). This would suggest an increased anaerobic metabolism as an energy source during hypoxic exercise. During submaximal exercise, for a given O₂, higher blood lactate concentrations were found in hypoxia than in normoxia (P < 0.05). In consequence, the onset of blood lactate accumulation (OBLA) was shifted to a lower O₂ ( O₂ 1.77 l·min^–1 in hypoxia vs 3.10 l·min^–1 in normoxia). Lactate concentration increases relative to minute ventilation ( _E) responses were significantly higher during hypoxia than in normoxia (P < 0.05). At OBLA, _E during hypoxia was 25% lower than in the normoxic test. This study would suggest that in hypoxia subjects are able to use an increased anaerobic metabolism to maintain exercise performance.     

Water pH and aluminum chemistry in the gill micro-environment of rainbow trout during acid and aluminum exposures

Summary Rainbow trout (Salmo gairdneri) were exposed to acidic soft water (pH_in4.2–6.3) in the presence (93 g·l^–1) or absence of Al. Fish were fitted with latex masks and opercular catheters to measure ventilation , pH changes at the gills, O₂ consumption , ammonia excretion , and Al extraction. During 2–3-h exposures, was generally higher in Al-exposed fish over the pH_in range 4.7–6.3. Alkalinization of expired water was about 0.3 pH units less in Al-exposed fish than in acid-only exposed fish at pH_in 4.5–5.2, an effect attributable to both increased and to buffering by Al. During 44-h exposures to pH_in 5.2 and 4.8 plus Al, increased greatly and expired water pH (pH_ex) decreased with time. There was a small increase in over 44 h at pH 4.4 plus Al, and no changes in pH_ex. In contrast, during 44-h exposures to pH 5.2, 4.8, and 4.4 in the absence of Al, such changes were much smaller or absent. During both short- and longerterm exposures, measured Al accumulation on the gills was only 5–18% of that calculated from cumulative Al extraction from the water, suggesting considerable sloughing of Al. In free-swimming trout, gill Al accumulation was greatest during exposure (2h) to Al at pH 5.2, lower at pH 4.8, and least at pH 4.4 and 4.0. Our results suggest that Al deposition occurs at the gills, causing respiratory and ionoregulatory toxicity, because the pH in the branchial micro-environment is raised above that in the acidic inspired soft water. Higher pH at fish gills may result in Al precipitation due to loss of solubility, or Al accumulation because of shifts in Al species to Al-hydroxide forms which more readily adsorb to the gills.Abbreviations pH _ex expired pH - pH _in inspired pH     

Theoretical studies on the necessary number of components in mixtures

Summary Theoretical studies on the optimal numbers of components in mixtures (for example multiclonal varieties or mixtures of lines) have been performed according to phenotypic yield stability (measured by the parameter variance). For each component i, i = 1, 2,..., n, a parameter u_i with 0 u_i 1 has been introduced reflecting the different survival and yielding ability of the components. For the stochastic analysis the mean of each u_i is denoted by u ₁ and its variance by _i ² For the character total yield the phenotypic variance V can be explicitly expressed dependent on 1) the number n of components in the mixture, 2) the mean of the _i ² 3) the variance of the _i ² 4) the ratio and 5) the ratio _i ² /² where denotes the mean of the u _i and _u ² is the variance of the u _j. According to the dependence of the phenotypic stability on these factors some conclusions can be easily derived from this V-formula. Furthermore, two different approaches for a calculation of necessary or optimal numbers of components using the phenotypic variance V are discussed: A. Determination of optimal numbers in the sense that a continued increase of the number of components brings about no further significant effect according to stability. B. A reduction of b % of the number of components but nevertheless an unchanged stability can be realized by an increase of the mean of the u _i by 1% (with and _u ² assumed to be unchanged). Numerical results on n (from A) and 1 (from B) are given. Computing the coefficient of variation v for the character total yield and solving for the number n of components one obtains an explicit expression for n dependent on v and the factors 2.-5. mentioned above. In the special case of equal variances, _i ² = _o ² for each i, the number n depends on v, x = (₀/)² and y = (_u/)². Detailed numerical results for n = n (v, x, y) are given. For x 1 and y 1 one obtains n = 9, 20 and 79 for v = 0.30, 0.20 and 0.10, respectively while for x 1 and arbitrary y-values the results are n = 11, 24 and 95.This publication is an extended version of a lecture given at the 1984-EUCARPIA meeting (Section Biometrics in Plant Breeding) in Stuttgart-Hohenheim (Federal Republic of Germany)     

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.     

Selective synthesis of cerebrosides: (2S, 3R, 4E)-1-O-β-d-galactopyranosyl-N-(2′R and 2′S)-2′-hydroxytetracosanoyl-sphingenine

The cerebrosides were first isolated by Thudicum in 1874 and the structures were established by Carteret al. in 1950 (for review, see [2]). In 1961 Shapiro and Flowers [3] reported the first total synthesis of a cerebroside1 (Fig. 1) which was identified with the natural sample, only through comparison of their i.r. data. In order to confirm the absolute configuration at C-2 of natural cerebroside1, we describe here an unambiguous synthesis of two stereoisomeric cerebrosides1 and2, and found that the¹H-NMR spectra of the synthetic1 (Fig. 2) was completely identical with that of the natural cerebroside reported recently by Dabrowskiet al. [4].In planning the synthetic route, the target structures1 and2 were disconnected at the dotted lines to give three key synthetic intermediates3, 4 and5 or6 (Fig. 1).Abbreviations Bu butyl - Ph phenyl - t-BuPh₂SiCl t-butyldiphenylsilyl chloride - MTPA -methoxy--trifluoromethylphenylacetic acid - THF tetrahydrofuran Part 36 in the series Synthetic Studies on Cell-surface Glycans, for part 35, see [1]     

Enhancement of mycobactericidal activity of glutaraldehyde with α,β-unsaturated and aromatic aldehydes

Summary Several ,-unsaturated and aromatic aldehydes were evaluated for antimicrobial activity usingMycobacterium bovis as the test strain. Activity of most of the compounds was determined in the presence and absence of 2% glutaraldehyde. Several compounds highly active against this organism, e.g. 2-pentenal, benzaldehyde, ando-phthalaldehyde showed rapid kill of >10⁵ CFU ml^–1 in 5 min. Activity of ,-unsaturated compounds substituted in the ₁ position showed increasing activity with increasing chain length. Of the aromatic aldehydes tested, benzaldehyde andp-dimethylamino benzaldehyde showed little activity alone, but when combined with 2% glutaraldehyde showed increased activity. Substituents added to the benzaldehyde ring (nitro, chloro, methyl, and methoxy) all detracted from the synergism, but still showed increased activity over the activity of 2% glutaraldehyde. The same affect was noted with disubstituted benzaldehyde compounds but not with substitutedo-phthaladehyde (2-formylformaldehyde).     

Proton translocation during denitrification in Rhodopseudomonas sphaeroides f. denitrificans

Proton translocation during the reduction of NO ₃ ^- , NO ₂ ^- , N₂O and O₂, with endogenous substrates, in washed cells of Rhodopseudomonas sphaeroides f. denitrificans was investigated by an oxidant pulse method. On adding NO ₂ ^- to washed cells, anaerobically in the dark, an alkalinization occurred in the reaction mixture followed by acidification. When NO ₃ ^- , N₂O or O₂ was added to cells in the dark or with these compounds and NO ₂ ^- in light an acidification only was observed. Proton translocation was inhibited by carbonyl cyanide-m-chlorophenyl hydrazone.Valinomycin treated cells produced acid in response to the addition of either NO ₃ ^- , NO ₂ ^- , N₂O or O₂. The proton extrusion stoichiometry ( ratios) in illuminated cells were as follows: NO ₃ ^- 0.5N₂, 4.82; NO ₂ ^- 0.5N₂, 5.43; N₂ON₂, 6.20; and O₂H₂O, 6.43. In the dark the comparable values were 3.99, 4.10, 4.17 and 3.95. Thus, illuminated cells produced higher values than those in the dark, indicating a close link between photosynthesis and denitrification in the generation of proton gradients across the bacterial cell membranes.When reduced benzyl viologen was the electron donor in the presence of 1 mM N-ethylmaleimide and 0.5 mM 2-n-heptyl-4-hydroxyquinoline-N-oxide in the dark, the addition of either NO ₃ ^- , NO ₂ ^- or N₂O to washed cells resulted in a rapid alkalinization of the reaction mixture. The stoichiometries for proton consumption, ratios without a permeant ion were NO ₃ ^- NO ₂ ^- ,-1.95; NO ₂ ^- 0.5 N₂O,-3.03 and N₂ON₂,-2.02. The data indicate that these reductions occur on the periplasmic side of the cytoplasmic membrane.Abbreviations BVH reduced benzyl viologen - CCCP carbonyl cyanide m-chlorophenyl hydrazone - DIECA N, N-diethyl-dithiocarbamate - HOQNO 2-n-heptyl-4-hydroxyquinoline-N-oxide - NEM N-ethylmaleimide     

Inhibition of ADP-ribosylation of histone H1 by analogs of diadenosine 5′, 5‴-p1,p4-tetraphosphate

The effects of analogs of diadenosine 5,5-p¹,p⁴-tetraphosphate (Ap4A) were examined on the ADP-ribosylation reaction of histone Hl catalysed by purified bovine thymus poly(ADP-ribose)transferase. Among the compounds tested, Ap4A and ApCH₂PPPA were shown to be the most efficient inhibitors of the enzyme. From kinetic studies of their action, it appears that Ap4A and ApCH₂pppA might be mixed type inhibitors.Abbreviations ADP-ribose adenosine diphosphate ribose - ADPRT poly-(ADP-ribose)transferase - Ap4A diadenosine 5,5-p₁,p₄-tertraphosphate - Ap4A diadenosine 5,5-p¹,p⁴(-1,N⁶-ethenyl-)tetra-phosphate - ApAA diadenosine 5,5-p¹,p⁴(-N⁶(-1,N⁶-)bisethenyl-)tetraphosphate - ApCH₂pppA diadenosine 5,5-p¹,p⁴(-p¹,p²-methylene-)tetraphosphate - AppCH₂ppA diadenosine 5,5-p¹,p⁴(-p²,p³methylene-)tetraphosphate - AppNHppA diadenosine 5,5-p¹,p⁴(-p²,p³-amino-)tetraphosphate - AppCHBrppA diadenosine 5,5-p¹,p⁴(-p²,p³-bromine methyno-)tetraphosphate - CpCH₂ppCH₂PC dicytidine 5,5-p¹,p⁴(-p¹,p²-p³,p⁴-bismethylene-)tetraphosphate - ApCH₂ppCH₂pA diadenosine 5,5-p¹,p⁴(-p¹,p²-p³,p⁴-bismethylene-)tetraphosphate.     

Human λ light chain locus: Organization and DNA sequences of three genomicJ regions

Evidence for the genomic organization of human lambda light chain joining (J) region gene segments is presented. A mouse J probe was used in Southern hybridizations to localize joining region sequences in a cosmid clone containing the genomic cluster of six human lambda constant (C) region gene segments. The results of these hybridizations suggest the presence of at least one J gene segment upstream from each constant region gene segment. The DNA sequences indicate that the human JI, J2, and J3 gene segments have consensus nonamer and heptamer sequences, proposed to be involved in V-J joining, are capable of encoding the known amino acid sequences for the respective J peptides, and have a sequence which could give functional RNA splice site at the end of their coding regions. Our data show that a single functional J is located 1.3 or 1.6 kb upstream of each of the C gene segments known to encode the Mcg, Kern^– Oz^–, and Kern^–Oz⁺ isotypes. Therefore, the gene organization of this region of the human lambda locus is J1 CI -J2C2-J3C3. The DNA sequences ofJ 1,J 2, andJ 3 presented in this paper establish that a singleJ gene segment precedes each expressed C gene segment, and support a model for the evolution of the human JC clusters where JICI andJ2C2-J3C3. arose from different ancestral JC units.     

Characterization of microbial NO production, N2O production and CH4 oxidation initiated by aeration of anoxic rice field soil

Intermittent drainage of rice fields isdiscussed as an option to mitigate emission ofCH₄, an important greenhouse gas. HoweverN₂O, a potentially more effective greenhouse gas,may be emitted during the aeration phase. Therefore,the metabolism of NO, N₂O, NH ,NO and NO and the kinetics ofCH₄ oxidation were measured after aeration ofmethanogenic rice field soil. Before aeration, thesoil contained NH in relatively highconcentrations (about 4 mM), while NO andNO were almost undetectable. Immediatelyafter aeration both NO and N₂O were produced withrates of about 15 pmol h^-1 gdw^-1 and 5 pmolh^-1 gdw^-1, respectively. Simultaneously,NH decreased while NO accumulated. Later on, NO was depletedwhile NO concentrations increased.Characteristic phases of nitrogen turnover wereassociated with the activities of ammonium oxidizers,nitrite oxidizers and denitrifiers. Oxidation ofNH and production of NO and N₂O wereinhibited by 10 Pa acetylene demonstrating thatnitrification was obligatory for the initiation ofnitrogen turnover and production of NO and N₂O.Ammonium oxidation was not limited by the availableNH and thus, concomittant production of NOand N₂O was not stimulated by addition ofNH . However, addition of NO stimulated production of NO and N₂O in bothanoxic and aerated rice soil slurries. In this case,10 Pa acetylene did not inhibit the production of NOand N₂O demonstrating that it was due todenitrification which was obviously limited by theavailability of NO . In the aerated soilslurries CH₄ was only oxidized if present atelevated concentrations >50 ppmv CH₄). Atatmospheric CH₄ concentrations (1.7 ppmv)CH₄ was not consumed, but was even slightly produced.CH₄ oxidation activity increased afterpreincubation at 20% CH₄, and then CH₄was also oxidized at atmospheric concentrations. CH₄oxidation kinetics exhibited sigmoid characteristicsat low CH₄ concentrations presumably because ofinhibition of CH₄ oxidation by NH .     

KCl transport across an insect epithelium: II. Electrochemical potentials and electrophysiology

Summary The cellular mechanism of K-stimulated Cl transport in locust hindgut was studied using double-barrelled ionsensitive microelectrodes and electrophysiological techniques. Steady-state net electrochemical potentials for Cl and K and the conductances of apical and basal membranes and paracellular pathway were determined under control conditions, during exposure to 1mm cAMP, and following ion substitutions. Under control open-circuit conditions, intracellular Cl activity (a _Cl ^c ) was 3.5 times that predicted for passive equilibrium across the apical membrane. The net electrochemical potential opposing Cl entry from the mucosal side increased by 50% during cAMP stimulation of transepithelial Cl absorption whereas the net electrochemical potential favoring Cl exit across the basal membrane was unchanged. No correlation was observed between and the net electrochemical potential across the apical membrane for Na. The net electrochemical potential favoring K entry across the apical membrane was negligible underI _sc conditions when Cl transport rate was approximately 10 eq cm^–2 hr^–1. Locust rectal cells showed electrical and dye coupling. The results also indicate that most transepithelial diffusion of ions is transcellular and that epithelial tightness effectively increases during exposure to cAMP becauseR _a andR _b both decrease, by 80% whileR _j is unchanged. The cAMP-induced R _b was abolished in Cl-free saline whereas R _a was insensitive to Cl removal, but was blocked by removing K from the saline. Based on these findings, our model for Cl absorption in locust hindgut features i) an active entry step for Cl at the apical membrane which is stimulated by cAMP and by low levels of K on the mucosal side, but is not energized by or a large cAMP-stimulated Cl conductance in the basal membrane and a similar cAMP-stimulated K conductance in the apical membrane. cAMP dose-response curves are similar for the stimulation of active Cl absorption and Cl-independent (i. e. K) conductance, indicating that cAMP exerts dual control over active Cl transport and counter-ion permeability.     

Oxygen mass transfer in a bubble column bioreactor containing lysed yeast suspensions

Summary Liquid-phase volumetric oxygen transfer coefficients were evaluated in a bubble column containing yeast suspensions, using the instationary oxygen absorption method and a polarographic oxygen electrode. The electrode time lag was found to be independent of both the system studied and the operating conditions. The volumetric oxygen mass transfer coefficients k _L a could be reasonably predicted by calculating k _L from the equation derived by Bhavaraju et al. or the empirical equation of Calderbank and Moo-Young and a from the experimental gas hold-up values.Nomenclature a Exponent in Eq.6 or specific gas-liquid interfacial area based on reactor volume m - b Exponent in Eq. 6 - C Constant in Eq 6 or oxygen concentration in the liquid phase g/ml - C ^* Equilibrium oxygen concentration g/ml - C ₀ Oxygen concentration in the liquid phase at t=0 g/ml - C _E Oxygen concentration as determined by the polarographic electrode g/ml - D _B Bubble equivalent diameter mm - D _l Oxygen diffusivity in the liquid phase m²/s - g Acceleration of gravity m/s² - K Consistency index Pasⁿ - K _L Liquid-phase mass transfer coefficient m/s - n Power law exponent - Pe _sw Peclet number based on bubble swarm velocity - S _C Schmidt number - Sh Sherwood number - i Time s - U _B Bubble rise velocity in infinite medium m/s - U _g Superficial air velocity based on column cross-sectional area m/s - U _sw Bubble swarm velocity defined by Eq.15 m/s - Y _MSW Mass transfer coeficient correction factor for mobile interfaces in pseudo-plastic fluids Eq. 7 - Y _MSW Mass transfer coefficient correction factor for immobile interface in pseudo-plastic fluids Eq. 8 Greek letters _l Density of liquid g/ml - _sus Density of unaerated suspension g/ml - _{wet cell} Density of yeast wet cells g/ml - _l Viscosity of the liquid Pas - _app Apparent viscosity of power law fluid Pas - _E Electrode time lag s - _l Time lag due to resistance of the gas-liquid interface s - _g Gas hold-up, volume fraction occupied by the gas phase - _l Liquid hold-up - _c Wet cell volume fraction     

Mode of uptake of sterol by Arthrobacter simplex

The mechanism of uptake of water-insoluble -sitosterol by a newly isolated strain of Arthrobacter simplex SS-7 was studied. The production of an extracellular sterol-pseudosolubilizing protein during growth of A. simplex on -sitosterol was demonstrated by isolating the factor from the cell-free supernatant and its subsequent purification by Sephadex G-150 column chromatography. The M _r of the purified sterol-pseudosolubilizing protein determined by SDS–PAGE was 19kDa. The rate of sterol pseudosolubilization (5.2×10^–3g l^–1h^–1) could not adequately account for the rate of sterol uptake (72×10^–3g l^–1h^–1) and the specific growth rate (56×10^–3 h^–1). However in the unfavourable growth condition, when the cells were treated with sodium azide at the level of 30–60% of MIC, the sterol pseudosolubilization accounted for nearly 74% of the total growth containing 96% free cells. Cellular adherence to substrate particles was found to play an active role in the normal growth of the strain on -sitosterol. Unlike sodium acetate-grown cells, whose surface activity was negligible (60mNm^–1), the sterol-grown cells had strong surface activity (40mNm^–1). The high lipid content and long chain fatty acids in the cell-wall of -sitosterol-grown cells probably contribute to the high sterol adherence activity of the cells.