The effect of cytokinins on nitrate reductase activity

Cytokinins in addition to nitrate induce nitrate reductase activity (NRA) in some plants. Effects of cytokinins onNRA was investigated in stem pith parenchyma of kale, intact wheat and barley seedlings and isolated cucumber cotyledons. The most profound effect onNRA was found in barley and wheat seedlings.NRA in seedlings sprayed with 100 μM 6-benzylaminopurine (BAP) for three subsequent days was increased in leaves and decreased in roots. These changes were further enhanced in seedlings grown in nutrient solution lacking nitrate:NRA in wheat and barley leaves was increased by 57% and 202%, respectively, in plants supplied with nitrate theNRA increase was not significant: in wheat and barley leaves by 22% and 9%, respectively. Similar effect of BAP and kinetin was found in kale stem parenchyma and cucumber cotyledons. The cytokinin kinetin or BAP alone increasedNRA about twice in kale and three times in cucumber. Addition of nitrate to the medium enhanced the effect of kinetin in kale discs, but the two effects were not additive. Additive effect of nitrate and BAP onNRA was found in cucumber cotyledons in light. In general NRA was more affected by cytokinins in intact seedlings of wheat and barley as compared to explanted tissue of kale and cucumber, and lack of nitrogen made their effect more expressive.     

Insertion of a MalE β-Galactosidase Fusion Protein into the Envelope of Escherichia coli Disrupts Biogenesis of Outer Membrane Proteins and Processing of Inner Membrane Proteins

The synthesis of a membrane-bound MalE β-galactosidase hybrid protein, when induced by growth of Escherichia coli on maltose, leads to inhibition of cell division and eventually a reduced rate of mass increase. In addition, the relative rate of synthesis of outer membrane proteins, but not that of inner membrane proteins, was reduced by about 50%. Kinetic experiments demonstrated that this reduction coincided with the period of maximum synthesis of the hybrid protein (and another maltose-inducible protein, LamB). The accumulation of this abnormal protein in the envelope therefore appeared specifically to inhibit the synthesis, the assembly of outer membrane proteins, or both, indicating that the hybrid protein blocks some export site or causes the sequestration of some limiting factor(s) involved in the export process. Since the MalE protein is normally located in the periplasm, the results also suggest that the synthesis of periplasmic and outer membrane proteins may involve some steps in common. The reduced rate of synthesis of outer membrane proteins was also accompanied by the accumulation in the envelope of at least one outer membrane protein and at least two inner membrane proteins as higher-molecular-weight forms, indicating that processing (removal of the N-terminal signal sequence) was also disrupted by the presence of the hybrid protein. These results may indicate that the assembly of these membrane proteins is blocked at a relatively late step rather than at the level of primary recognition of some site by the signal sequence. In addition, the results suggest that some step common to the biogenesis of quite different kinds of envelope protein is blocked by the presence of the hybrid protein.     

Postnatal Changes in the Activity Ratio of Specific and Nonspecific Cholinesterases from Neuronal Perikarya

Abstract: A soluble fraction from rat brain neuronal perikarya was shown to contain both the specific and nonspecific forms of the enzyme acetylcholines-terase (EC's 3.1.1.7. and 3.1.1.8., respectively). The ratio of the enzyme activities varied along the course of brain development: the nonspecific form being predominant from 1 to 15 days of age and the specific one showing the pattern of rising activity from day 15 onward. We suggest a possible relationship between this changing in cholinesterase activities and the establishment of synapses within the rat cerebral cortex.     

Photosynthetic preparation and characterization of 13C-labeled carbohydrates in agmenellum quadruplicatum

The blue-green alga Agmenellum quadruplicatum (strain PR6) has been used to prepare photobiosynthetically ¹³C-labeled d-glucose, 2-O-(α-d-glucopyranosyl)-glyceric acid (glucosylglycerate), 2-hydroxy-1-(hydroxymethyl)ethyl α-d-gluco-pyranoside (glucosylglycerol), and α-d-glueopyranosyl β-d-fructofuranoside (sucrose). When grown to a cell density of 4.4 g.L^-1 (dry weight) under nitrate-nitrogen limiting growth conditions for 120 h, the algal cells contained 38% of the dry-cell weight as(1 → 4)-α-d-glucan (amylose). About 1% of the dry-cell weight was glucosylglycerol, glucosylglycerate, and sucrose. Glutamate was obtained, together with carbohydrates of low molecular weight, when the cells were extracted with chloroform-methanol; d-glucose was recovered from the extracted cells by acid hydrolysis of the starch. The algae were grown by using 20 mol% [¹³C] carbon dioxide for preparation of labeled carbohydrates and for cellular component identification by whole-cell n.m.r. spectroscopy.     

Conservation and chromosomal localization of DNA satellites in balenopterid whales

DNA satellites were isolated from three balenopterid species, viz. the minke, sei, and fin whales. In each of them at least two DNA satellites were recognizable with buoyant densities in neutral CsCl of =1.702/1.703 and =1.710/1.711, respectively. cRNAs from each satellite group were used for filter and in situ hybridisations. Homo- and heterologous DNA-cRNA hybrids within each satellite group yielded virtually identical melting curve profiles showing conservation of at least a considerable part of the DNA satellite sequences. There was no evident sequence homology between the =1.702/1.703 and the =1.710/1.711 satellites by filter hybridisation. — The in situ hybridisation showed that in each species the =1.702/1.703 satellite was located in centromeric-paracentromeric C-bands in a few pairs, whereas the =1.710/1.711 satellite was located in terminal C-bands throughout the karyotypes. — The data on the whale DNA satellites indicate that the quantitative evolution of the satellite DNA sequences preceded species divergence of the balenopterids and that the satellite sequences have remained relatively unaltered since the divergence took place. The function of satellite DNA is considered to imply the introduction of both chromosomal and genic polymorphisms and thus being of great importance in speciation. Based upon these concepts a model is postulated for the function of satellite DNA. According to this model at meiotic pairing euchromatin-heterochromatin overlapping between homologous chromosomes is considered to be of a general occurrence. This overlapping is presumed to be accentuated by the size heteromorphism frequently observed between homologous heterochromatic segments (C-bands). In the region of such euchromatin-heterochromatin overlapping, crossing-over would be excluded. The overlapping is suggested to be rectified progressively in the chromosome arms, leaving unaffected crossing-over distant to the euchromatin-heterochromatin junctions. The consequence of this will be that genes in the proximity of the junctions are collectively inherited and selected, whereas genes distant to the heterochromatin will be independently assorted and selected.     

The specificity of the effect of 2,4-D and NAA of the growth,micromorphology, and occurrence of starch in long-termNicotiana tabacum L. Cell strains

The characteristic micromorphology of the tobaoco cell strains, or its cyclic changes in the course of the subcultivation interval can be affected by auxin composition of the medium,i.e. by the application of either 2,4-D alone, or NAA, or their combination. On omitting one of the auxins, the over-all growth of the cultures is not substantially affeoted; however, the participation of various oell types, as well as the occurrenoe of starch grains are altered. The presenoe of 2,4-D alone results in an inhibition of starch occurrence, NAA alone causes a stimulation. There is no causal dependence of the occurrence or absence of starch grains on the stimulation of elongation (volume) growth, or, on the contrary, on cell division.     

External mass transfer in a biological film reactor

A method for calculating the mass transfer coefficient in a biological film system, under turbulent flow conditions, is presented. It is experimentally found that fluid velocity has a positive effect on the rate of substrate utilization when the system is operated in other than the kinetic regime. A correlation is developed which indicates a dependence of the mass transfer coefficient on the fluid velocity raised to the 0.7 power.     

Alcohol:NAD oxidoreductase in brain of rats from a colony fed dilute ethanol for many generations.

—Alcohol:NAD oxidoreductase (EC 1.1.1.1) was studied in brain cortex, hypothalamus, cerebellum and midbrain of adult and immature rats, and in the whole encephalon of neonatal rats. The rats used in this study were (i) from a colony which has been given 12% (v/v) aqueous ethanol as the only fluid for 54 generations (‘E.F.’ rats); (ii) rats removed from this colony after the forty-eighth generation and thereafter fed water instead of the alcohol solution (‘E.F./H₂O’ rats); and (iii) normal rats. Enzyme activity in the 20,000 g supernatant of tissue homogenates was measured by the method of Raskin and Sokoloff. Activity was found to be highest in neonatal rat brain and to decrease as the age increased. Activity in the hypothalamus of adult E.F. rats was significantly higher than that found in the same region of adult E.F./H₂O rats. Immature rat cerebellum alcohol:NAD oxidoreductase activity was higher both in ‘E.F.’ and ‘E.F./H₂O’ suggesting a possible genetic change be involved in this CNS region. It may be concluded that, with the exception of neonatal rats, ethanol consumption induces an increase in rat CNS alcohol :NAD oxidoreductase activity.     

Social grooming between squirrel monkeys and uakaris in a seminatural environment

Young squirrel monkeys (Saimiri sciureus) were reported grooming an adult female uakari (Cacajao calvus rubicundus) on four different occasions. Furthermore, the uakari was noted grooming two squirrel monkeys in separate instances. These observations took place in a seminatural rainforest (The Monkey Jungle; Goulds, Florida, U.S.A.) where provisions are provided. Some possible hypostheses tendered to account for this unusual behavior included (a) the unaverted interaction of food-seeking and fur-cleaning behavior, and (b) the compatibility of play-curiosity activities by squirrel monkeys with the uakaris' need for social contact.     

Nomenclatural adjustments in some European monocotyledons

New nomenclatural combinations are validated for fifteen taxa belonging to the generaDanthonia, Stipa, Lolium, Phippsia, Elymus, Schoenoplectus andAllium.