Metabolic,physiological and kinetic aspects of the alcoholic fermentation of whey permeate by Kluyveromyces fragilis NRRL 665 and Kluyveromyces lactis NCYC 571

Optimum growth conditions for the fermentation of non-concentrated whey permeate by Kluyveromyces fragilis NRRL 665 have been defined. Use of 3.75 g yeast extract l^?1, a growth temperature of 38°C and a pH of 4.0 allowed a maximum productivity of 5.23 g ethanol l^?1 h^?1 in continuous culture with a yield 91% of theoretical. Complete batch fermentation of permeate with 100 g lactose l^?1 was possible with a maximum specific growth rate of 0.276 h^?1 without any change in ethanol yield. Fermentation of concentrated permeate resulted, however, in a general decrease of specific substrate consumption rate, demonstrated by the inability to completely convert an initial 90 or 150 g lactose l^?1 in continuous culture, even at dilution rates as low as 0.05 and 0.08 h^?1, respectively. The decrease could be related to substrate inhibition, to an increase in osmotic pressure caused by lactose and salts, and to ethanol inhibition of both alcohol and biomass yield. The decrease in specific productivity could be counterbalanced by use of high cell density cultures, obtained by cell recycle of K. fragilis. Fermentation of a non-concentrated permeáte at a dilution rate of 1 h^?1 resulted in a productivity of 22 g l^?1 h^?1 at 22 g ethanol l^?1. Cell recycle using flocculating Kluyveromyces lactis NCYC 571 was also tested. With this strain a productivity of 9.3 g l^?1 h^?1 at 45 g product l^?1 was attained at a dilution rate of 0.2 h^?1, with an initial lactose concentration of 95 g l^?1.     

家兔大脑嗅鼻沟后缘皮层对内膝体神经元电活动的下行性影响

在39只用三碘季铵酚麻痹的成年家兔上观察刺激大脑皮层听区对内膝体神经元听反应的影响。刺激 Woolsey 氏 AⅠ、AⅡ区及其周围颞叶皮层,或刺激大脑嗅鼻沟后缘皮层,能抑制一部分 MGB 神经元的听反应,但也有少数神经元受到易化。有效的颞叶皮层刺激点分布范围弥散,而嗅鼻沟后缘皮层的有效刺激点分布得相当集中。根据抑制潜伏期较短以及抑制内膝体早、晚二反应的潜伏期相同等事实,作者认为,刺激嗅鼻沟后缘皮层对 MGB 神经元的下行性影响发生在 MGB 核团之内。     

Composition of Caulobacter crescentus murein synthesized in the presence of glycine

Abstract Glycine added to the growth medium of Caulobacter crescentus was found to substitute Cterminal alanine in the peptide side chains of the murein of this species. Murein synthesized in vivo and in vitro in the presence of glycerine was poorly crosslinked as was new murein formed in the presence of the amino acid. The reduced cross-linkage seems to be due to the effect of glycine on the formation of trimeric muropeptides as revealed by high-performance liquid chromatography (HPLC) muropeptide analysis of murein formed in the presence and absence of the amino acid.     

褐稻虱饲料稻株中数种氨基酸的营养效应

本研究初步证实饲料稻株中甘氨酸、赖氨酸和酪氨酸含量的高低,同褐稻虱(Nilaparvata lugens Stal)的发育进度、存活率、短翅型出现率和单雌产卵量关系极为密切,它们是褐稻虱赖以正常生长发育和繁殖的重要氨基酸。     

The influence of food plant dispersion on caterpillar searching success

Abstract. 1. Collards (Brassica oleracea L.) grown in clumps were more difficult for unstarved, early instar cabbage white caterpillars (Pieris rapae L.) to find than collards spaced at regular intervals, although total plant densities were identical.
2. Early instar, unstarved larvae are less mobile than later instar larvae (our data) or starved larvae (Jones' 1977 data).
3. Starved larvae and late instar larvae tend to find plants more readily than do unstarved or younger larvae.
4. We contend that larval mobility governs the success of searching caterpillars and their sensitivity to variations in plant dispersion.
5. Our results show that the dispersion of targets can influence searching success even though target density is constant. This means that the degree of clumping in host plants is capable of influencing their availability to herbivores.     

How can quantum mechanics of material evolution be possible?: Symmetry and symmetry-breaking in protobiological evolution

Material self-assembly as a self-organizing process is always accompanied by symmetry-breaking in the material configuration. Self-sequencing of amino acids during their thermal polymerization has lost a certain property of permutation symmetry that was observed in the mixture of free amino acids. The evolutionary precursor state is more symmetrical about its internal material configuration and more degenerate due to the multitude of the indistinguishable individuals. The evolution proceeds in the direction along which the degeneracy in the internal states dissolves owing to the symmetry-breaking originating in material flow equilibrium of open material aggregates. Protobiological information is latent in the material system which is highly symmetrical and highly degenerate in its internal states. Evolution of matter is an endogenous process in which the earlier symmetric property is lost and less degenerate states are approached. Quantum-mechanically, the generation of protobiological information is due to the symmetry-breaking of the Hamiltonian originating in the interaction with the exterior through material flow, in contrast to the Schrödinger equation which preserves a symmetry and the associated invariants.     

Forward mutation assay of V79 cells to 6-thioguanine resistance in a soft agar technique that eliminates effects of metabolic co-operation

A technique involving culture in soft agar was used for the assay of forward mutation of V79 cells to 6-thioguanine (6TG) resistance. The main reason for the use of soft agar was to prevent reduction in recovery of mutants depending on the cell density plated for mutation selection, which is the chief problem in the liquid method, and which results mainly from metabolic co-operation due to cell-to-cell contact.V79 cells grew well in fortified soft agar medium (DMEM + 20% FBS) showing cloning efficiencies (>80%) as high as in liquid culture. Therefore, V79/HGPRT mutagenesis could be assayed quantitatively in soft agar culture.The frequency of 6TG-resistant colonies in agar selective medium increased linearly with increase in concentration of EMS. Toxicity and mutagenic responses were greater in soft agar than in liquid culture.In cultures of untreated and EMS-treated cells, more than 95% of the 6TG-resistant colonies isolated were aminopterin-sensitive.Use of soft agar for selection prevented the reduction in the number of mutants with increase in the size of incula on plating up to 1?2 × 10⁶ cells per 9-cm dish: in liquid culture, even with a lower plating number (2 × 10⁵ cells per 9-cm dish), a notable reduction in numbers of mutants was observed. This character was re-examined in a reconstruction experiment. The results show that, when up to 2 × 10⁶ cells were plated per 9-cm dish, 6TG-resistant cells were almost completely recovered from the soft agar medium, whereas only 10% were recovered from liquid culture.     

Persistence of Bacillus thuringiensis parasporal crystal insecticidal activity in soil

Spores and parasporal crystals of a Bacillus thuringiensis var. aizawai (H-serotype 7), strain HD137, streptomycin-resistant mutant were added to acidic (pH 5.0) natural and autoclaved soil and incubated at ?0.10 MPa, 25°C. Populations of B. thuringiensis in both soil treatments showed exponential rates of mortality which were represented by linear regression, the loss of viability being greater in natural than autoclaved soil. In natural soil, parasporal crystal insecticidal activity was lost at a complex, nonexponential rate. The initial, rapid decrease of activity gradually slowed, and the level of activity stabilized at 10% of the original inoculum level after 250 days incubation, until the cessation of sampling at >2 years. In autoclaved soil no significant (P > 0.2) loss of parasporal crystal insecticidal activity was detected over the same period, which suggested that soil microorganisms were responsible for the loss of crystal insecticidal activity in the natural, nonsterilized soil. The rate of loss of crystal activity in natural soil correlated well with assay data reported in the literature using Galleria mellonella, which measures the combined activity of spore and crystal. In autoclaved soil correlation was poor, probably due to variability in the bioassay data.     

Bluelight-induced,flavin-mediated transport of redox equivalents across artificial bilayer membranes

Summary This paper continues our studies of physico-chemical properties of vesicle-bound flavins. Based on previous results, an advanced model system was designed in order to study the mechanisms underlying bluelight-induced redox transport across artificial membranes. The lumen of single-shelled vesicles was charged with cytochromec, and amphiphilic flavin (AF1 3, AF1 10) was bound to the membrane. Upon bluelight irradiation redox equivalents are translocated from exogeneous 1e ^–(EDTA)-and 2e ^–(BH₃CN^–) donors across the membrane finally reducing the trapped cytochromec both under aerobic and anaerobic conditions. The mechanisms involved are explored and evidence for the involvement of various redox states of oxygen, dihydroflavin and flavosemiquinone is presented.     

Neopterin Retards Loss of Serotonin N-Acetyltransferase Activity from Cultured Chick Pineal Glands

Abstract: d -Neopterin at 10 μ M delayed start of the decline of serotonin N -acetyltransferase (NAT) activity from the peak level in the cycle exhibited by chick pineal glands cultured under standard conditions in the dark. A less marked retardation of decline of NAT activity was found with glands cultured under diurnal illumination or those exposed prematurely to light. There were no significant effects of neopterin on the increases of NAT activity or peak levels of activity developed. The pteridine also retarded loss of NAT activity from the peak level developed in the dark when the time of explanting into culture was later in the (solar) day, but not when it was earlier. Neopterin had no effect on the cycle in cyclic GMP content of cultured chick pineal glands.