Ploidy reduction and genome segregation in cultured carrot cell lines. I. Prophase chromosome reduction

Cytological analysis of different carrot cell lines in culture has shown various cytogenetic anomalies generating new levels of ploidy and novel chromosome numbers. Polyploidy may be considered a reservoir of variability that can be released in the form of distinct new segregants of different ploidy. Mechanisms alternative to mitosis (reductional grouping, prophase chromosome reduction) operate from a polyploid state (possibly reached by means of endopolyploidy, endomitosis, nuclear fusion, or restitution nuclei) to generate new levels of ploidy and novel chromosome numbers necessary for selection to operate in vitro. The segregational phenomena require chromosome recognition in haploid set complements and abnormal behaviour of mitoses; the resulting chromosome variability suggests that chromosomes are arranged, in the resting nuclei, in an orderly and predictable manner.The knowledge of the molecular events governing these mechanisms, and how to control them, would be of great help for future applications of plant cell culture.     

Enzyme-bound pentadienyl and peroxyl radicals in purple lipoxygenase

Samples of purple lipoxygenase prepared by addition of either 13-hydroperoxy-9,11-octadecadienoic acid or linoleic acid and oxygen to ferric lipoxygenase contain pentadienyl and/or peroxyl radicals. The radicals are identified by the g values and hyperfine splitting parameters of natural abundance and isotopically enriched samples. The line shapes of their EPR spectra suggest the radicals are conformationally constrained when compared to spectra of the same radicals generated in frozen linoleic acid. Further, the EPR spectra are unusually difficult to saturate. The radicals are stable in buffered aqueous solution at 4 degrees C for several minutes. All of this implies that these species are bound to the enzyme, possibly in proximity to the iron. Only peroxyl radical is seen when the purple enzyme is generated with either hydroperoxide or linoleic acid in O2-saturated solutions. Addition of natural abundance hydroperoxide under 17O-enriched O2 leads to the 17O-enriched peroxyl radical, while the opposite labeling results in the natural abundance peroxyl radical, demonstrating the exchange of oxygen. Both radicals are detected in samples of purple lipoxygenase prepared with either linoleic acid or hydroperoxide under air. Addition of the hydroperoxide in the absence of oxygen favors the pentadienyl radical. We propose that addition of either linoleic acid or hydroperoxide to ferric lipoxygenase leads to multiple mechanistically connected enzyme complexes, including those with (hydro)peroxide, peroxide, peroxyl radical, pentadienyl radical, and linoleic acid bound. This hypothesis is essentially identical with the proposed radical mechanism of oxygenation of polyunsaturated fatty acids by lipoxygenase.     

Anaerobic metabolism of goldfish,Carassius auratus (L.). Influence of anoxia on mass-action ratios of transaminase reactions and levels of ammonia and succinate

Summary Changes in the concentrations of ammonia, glutamate, alanine, aspartate, -ketoglutarate, oxaloacetate and succinate were measured in freeze-clamped lateralred muscle, dorsal white muscle and liver, and in rapidly cooled blood of goldfish after 12 h of anoxia. Alanine accumulation, succinate accumulation and aspartate depletion are observed in all tissues examined; in the liver the concentrations of glutamate increase and those of ammonia decrease. The mass-action ratio of the glutamate-pyruvate transaminase-catalyzed reaction stays within one order of magnitude from thermodynamic equilibrium in the direction of alanine formation. The mass-action ratio of the glutamate-oxaloacetate transaminase reaction is far from equilibrium when measured oxaloacetate concentrations are used. When levels of free oxaloacetate are calculated from LDH and MDH equilibrium constants, the mass-action ratio of glutamate-oxaloacetate transamination is close to equilibrium in the direction of aspartate formation. Since neither alanine nor glutamate decreases, and since ammonia gradients suggest a continuous ammonia production in all tissues examined, anaerobic proteolysis is assumed. A possible coupling between amino acid catabolism and ethanol production is discussed.Abbreviations ALA alanine - ASP aspartate - EDTA ethylene diamine tetraacetate - FP _ox oxidated flavoprotein - FP _red reduced flavoprotein - FUM fumarate - GLU glutamate - GOT glutamate oxaloacetate transaminase - GPT glutamate pyruvate transaminase - IMP inosine monophosphate - KG -ketoglutarate - LDH lactate dehydrogenase - MAL malate - MAR mass action ratio - MDH malate dehydrogenase - OAA oxaloacetate - PYR pyruvate - sAMP adenylosuccinate - SDH succinate dehydrogenase - SUCC succinate     

A laboratory study on the short-term zonal oscillations of the trochid Monodonta turbinata (Born) (Mollusca: Gastropoda)

Zonal oscillations of Monodonta turbinata (Born) were monitored with an actographic device which precluded clustering behaviour. Unfed snails maintained their cyclic pattern of behaviour for up to 8 days under a light-dark cycle which simulated the natural one. Under constant conditions of light or dark, however, the snails ceased migration and occupied a zonal position typical of day and night, respectively. Experiments in diffuse light and with light from below the floor of the experimental tank showed that the downward migration of M. turbinata in the daytime depends on positive geotaxis combined with negative phototaxis whilst the upward migration at night depends on a negative geotaxis. This mechanism is similar to that described in other littoral molluscs. There was no evidence of an endogenous control of rhythmic zonal activity.     

Dose dependent stimulation of hepatic oxygen consumption and alanine conversion to CO2 and glucose by 3,5,3'-triiodo-L-thyronine (T3) in the isolated perfused liver of hypothyroid rats

The effect of increasing concentration of T3 (10 × 10^?12 – 2000 × 10^?6 M) on O₂-consumption and [¹⁴C]-alanine conversion into [¹⁴C]-CO₂ and [¹⁴C]-glucose was investigated in the isolated perfused liver of hypothyroid starved rats. T3 induced within 1 h an increase (i) in the oligomycine-sensitive O₂-consumption (+ 50–85 %), (ii) in the [¹⁴C]-CO₂-production (+55–102 %), and (iii) in the [¹⁴C]-glucose synthesis (+ 40?80 %). These effects were dose dependent and significant at a concentration as low as 10 × 10^?12 M, reported to represent the free hormone concentration in rat serum under in vivo conditions. The results demonstrate a direct and rapid stimulatory action of T3 in the physiological range on hepatic energy metabolism and glucose production. The effects could not be explained by the thyroid hormone induced nuclear activity.     

Metabolism of propionic acid by golden delicious apples

The headspace of whole Golden Delicious apples treated with propionic acid vapour, was analysed by means of GC, after enrichment on Tenax GC, and its c     

Evidence for distinct polygenic regulation of antibody responses to some unrelated antigens in lines of mice selected for high or low antibody responses to somatic antigen of Salmonella

The effect of the selective breeding of mice for high or low antibody production to complex immunogens is largely nonspecific, since it modifies the responsiveness of high (H) and low (L) lines to many antigens unrelated to the selection antigen. However, the nonspecific effect of the polygenic control operating in these lines is not a general feature. For example, the group of genes in selection IV, carried out for responsiveness to somatic antigen of Salmonella, does not modify the responses to sheep erythrocytes (SE). Despite equivalent responses in H and L mice of selection IV, a large variability was found in individual responses of F₂ interline hybrids, which demonstrates the presence of alleles with high or low effect on responses to SE. A selective breeding (Selection IV-A) was therefore initiated from this F₂ population for responsiveness to SE. A progressive interline divergence occurred during the first seven generations of selection; the interline separation was due to polygenic regulation (about four independent loci from a preliminary estimate).Equivalent responses to the s antigen of Salmonella are observed in the two lines. This constitutes additional evidence for distinct polygenic regulation of responses to SE and to somatic antigen. Moreover, the pattern of responses to several unrelated antigens (nonspecific effect) also differs between Selections IV and IV-A.Abbreviations H high responder lines - L low responder lines - s somatic antigen of Salmonella - f flagellar antigen of Salmonella - R response to selection - S selection differential - F₀ foundation population - h² heritability (realized) - RGG rabbit gamma globulin - CE chicken erythrocyte - HE human erythrocyte - PE pigeon erythrocyte - SE sheep erythrocyte