Protease activities in non-embryogenic and embryogenic carrot cell strains during callus growth and embryo formation

Embryogenic and non-embryogenic cell strains of Daucus carota L. were examined for their protease activity using a wide range of chromogenic synthetic peptides as substrates. High arginine-specific activity was present in all strains, but no protease activity "specific" for embryogenic or non-embryogenic strains could be detected with the substrates tested. The specific protease activity was 5–10 times higher in the non-embryogenic as compared to the embryogenic strain for most tested substrates, and this difference was not due to release of proteases in the latter. All strains showed a decrease in protease activity when cultured in media without 2,4-dichlorophenoxyacetic acid, but the embryos had high protease activity in comparison with the nondifferentiated cell aggregates. In the latter aggregates, hydrolyzing activity towards three of the substrates (H-D-Phe-Pip-Arg- p -nitroanilide, Suc-Ala-Pro-Phe- p -nitro-anilide and Bz-Phe-Val-Arg- p -nitroanilide) was absent, whereas the embryos were able to hydrolyze them.     

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.     

Further studies on the involvement of the circadian system in photoperiodic control of antifreeze protein production in the beetle Dendroides canadensis

The role of circadian rhythmicity in the photoperiodic time measuring processes regulating antifreeze protein production in the beetle Dendroides canadensis was further investigated. Using “T” experiments larvae were exposed to environmental light cycle periods close to the period length of the endogenous circadian oscillator. The following light cycles were employed: light/dark 8/13, 8/14, 8/16, 8/18 and 8/19 corresponding to period lengths of 21, 22, 24, 26 and 27 h. Larvae maintained in cycles equal to or less than 24 h displayed a characteristic short-day response, showing significantly (P < 0.01) greater antifreeze protein activity than did those measured on the day of collection in late summer. In contrast, a long-day response was observed in larvae maintained under a 26- or 27-h light cycle in that antifreeze protein activity did not differ from that measured on the initial collection date.

The role of photoperiod and temperature in influencing the photoperiodic timing processes were examined with a series of resonance experiments. The first group consisted of a 24, 36, 48, 60 or 72-h light cycle, each with an 8-h photophase at temperatures of 20 or 17°C. Rhythmic increases in antifreeze protein levels at intervals of 24 h occurred under both temperatures. However, the lower temperature displaced the resonance curve in the vertical direction (i.e. increasing % population response) and reduced the difference between peaks and troughs on the resonance curve. Resonance experiments incorporating a 14-h photophase resulted in low antifreeze protein activity under all conditions except a 36-h light cycle in which a 67% induction was observed.

Eight hour resonance experiments were also conducted with D. canadensis collected in early spring to determine whether the circadian system participates in the photoperiodic timing processes influencing the spring termination of antifreeze protein production. Positive resonance results were obtained in that only larvae maintained in cycles of 36 and 60 h displayed significantly (P < 0.01) lower antifreeze activity when compared to animals on the initial collection date.

The combined results emphasize the involvement of the circadian system in the photoperiodic control of antifreeze protein production by D. canadensis during the fall and spring. Furthermore, the induction of antifreeze protein production is a function of light cycle and its waveform (photoperiod). Temperature appears to modify the photoperiodic response in some manner involving the photoperiodic time measuring processes. It is concluded that the photoperiodic response of antifreeze protein production by D. canadensis is dependent upon the entrainment of the circadian system by the light cycle.     

Nonrandomness of point mutation as reflected in nucleotide substitutions in pseudogenes and its evolutionary implications

Summary We have obtained a revised estimate of the pattern of point mutation by considering more pseudogene sequences. Compared with our previous estimate, it agrees better with expectations based on the double-strand structure of DNA. The revised pattern, like the previous one, indicates that mutation occurs nonrandomly among the four nucleotides. In particular, the proportion of transitional mutations (59%) is almost twice as high as the value (33%) expected under random mutation. The same high proportion of transitions is observed in synonymous substitutions in genes. The proportion of transitional changes observed among electrophoretic variants of human hemoglobin is about the same as that predicted by the revised pattern of mutation. We also show that nonrandom mutation increases, by about 15%, the proportion of synonymous mutations due to single-nucleotide changes in the codon table, and increases, from 10% to 50%, the rate of synonymous mutation in the seven genes studied. However, nonrandom mutation reduces (by about 10%) the proportion of polar changes among nonsynonymous mutations in a gene. As far as single-nucleotide changes (in the codon table) are concerned, nonrandom mutation only slightly favors relatively conservative amino acid interchanges, and has virtually no effect on the proportions of radical changes and nonsense mutations.     

Biotic regionalization and climatic controls in western North America

New methods of weather analysis accompanied by microhabitat ‘bioassays’ have been applied in several case studies to demonstrate effects of atmospheric processes on patterns of community composition and structure and potential species evolution. Average spatial and seasonal airmass dynamics which determine regional and elevational patterns of relative microhabitat favorability, were found to vary between a recent global warming trend (ca 1900 to 1940) and the subsequent global cooling trend (ca 1940 to 1970). These apparently systematic spatial and temporal shifts in weather were related to plant establishment patterns and community composition and structure. The proposed causal mechanisms function, in part, through regional shifts in microhabitat size. These effects are similar to larger scale, longer term shifts deduced from the late Quaternary fossil record. By modifying the spatial approach, month-to-month and year-to-year variability of weather has been examined for the last 130 years at individual points in southwestern North America. Three climatic regimes (the end of the Little Ice Age, the recent warming trend and the recent cooling trend) exhibited distinct year-to-year patterns of weather that can be related to the establishment of different kinds of plants (e.g., C₄ grasses versus C₃ shrubs). Oscillations between different temporal climatic regimes appear to promote the episodic establishment of different life forms, but not necessarily their local extinction. The two methods of weather analysis have been combined in a regional assessment of climatic controls of different biomes in space and time with a primary focus on the Chihuahuan desert. Natural ecotones between the Chihuahuan desert and neighboring biomes are clearly related to large scale airmass dynamics associated with seasonal oscillations in jetstream position. The weather patterns controlling ecotonal positions result from seasonal topographic influences on the general circulation of the atmosphere. The apparent stability of these patterns allows causal hypotheses of biogeographic dynamics and the evolution of physiological traits and life history characteristics.     

Temporal Distribution of [3H]-Imipramine Binding in Rat Brain Regions is Not Changed by Chronic Methamphetamine

Specific binding of [³H]-imipramine in the rat suprachiasmatic nuclei, occipital cortex and caudate putamen underwent significant and replicable changes throughout 24 hr under a light-dark cycle or under constant conditions. Daily variations were also found in the medial and dorsal raphe nuclei and the lateral hypothalamus. Methamphetamine, a psychoactive drug with marked effect on circadian rhythms in physiological and hormonal parameters and adrenergic receptors, did not have any significant effect on imipramine binding rhythms in eight discrete brain regions. Thus a drug known to reduce serotoninergic neurotransmission did not change characteristics of the modulatory binding site related to serotonin uptake.     

Development of Adrenocortical Cyclic Nucleotide (Cyclic AMP and Cyclic GMP) and Corticosterone Orcadian Rhythms in Male and Female Rats

The daily rhythm of the adrenocortical cyclic nucleotides (cyclic AMP and cyclic GIMP) was studied in infant male and female Wistar rats before and after the establishment of an adult-like daily rhythm of plasma corticosterone. As in this strain the rhythm of corticosterone is known to be present on postnatal day 18, pups of 2 and 3 weeks of age were studied. The dams and the pups as well as the young adult animals were kept on a controlled 12L-12D photoperiod. Groups of 8-10 pups were killed at 4-hr intervals throughout the day. Plasma corticosterone levels and adrenal cyclic AMP and cyclic GMP concentrations were simultaneously measured and the daily patterns established. Pups of 2 weeks of age showed neither plasma corticosterone nor adrenal cyclic AMP rhythms whereas pups of 3 weeks of age exhibited a typical adult-like circadian rhythm for both variables. The patterns for adrenal cyclic GMP differed according to sex: In female pups no cyclic GMP circadian rhythm could be detected at either 2 or 3 wk. In male pups of 3 wk a typical mature rhythm for adrenal cyclic GMP was evident whereas in younger male pups (2 wk) a circadian rhythm was detected. This circadian rhythm, however, differed from mature circadian rhythm in that its peak was located at 1300 hr instead of 0700 hr. These results demonstrate that, unlike that of cyclic AMP the adrenal cyclic GMP circadian rhythm does not appear at the same time as the plasma corticosterone circadian rhythm. Moreover, a circadian rhythmicity for adrenal cyclic GMP can be found in the absence of any corticosterone circadian rhythm. These facts argue against the view of cyclic GMP being a mediator of ACTH-stimulated steroidogenesis.     

The Circadian Rhythm of Plasma Thyrotropin in Depression and Recovery

The 24-hr patterns of plasma thyrotropin have been observed in 12 endogenous depressed patients in both depressed and recovered states and in 13 normal subjects. A clear circadian rhythm was detected in controls with high values at night. In depression, the circadian rhythm was altered with amplitude reduction and blunted nocturnal secretion, abnormalities particularly relevant in bipolar patients. This flattened profile could be linked to the blunted response of TSH to TRH administration reported in depressed patients. Normal nyctohemeral patterns have been restored after recovery. These chronobiological abnormalities as well as their normalization under antidepressant drugs seem to be similar to those reported for various parameters (e.g. temperature, Cortisol, etc) in depression which could support the chronobiological hypothesis for affective disorders.     

Flavonoids in the leaves of twenty-eight polygonaceous plants

Flavonoids in the leaves of twenty-eight species belonging to the Polygonaceae were studied. Thirty-three kinds of flavonoids were isolated, and eighteen kinds were obtained as crystals. Quercetin glycosides were commonly found in the family. In the quercetin glycosides, 3-O-rhamnoside was most frequently found: 3-O-glucuronide is also distributed widely. Myricetin glycosides were rare. Methylated flavonols were found in some species of the sectionsEchinocaulon andPersicaria. Eleven kinds ofC-glycosylflavones were found in the present survey, andC-glycosylflavones were distributed in all species of the genusRheum and in almost all species of the section Tiniaria.Rumex Acetosella andPolygonum suffultum are exceptional, the former contains flavone glycoside and the latterC-glycosylflavones only, as main components.     

α-1,4-glucan phosphorylase forms from leaves of spinach (Spinacia oleracea L.)

Peptide patterns and immunological properties of the cytoplasmic and chloroplastic -1,4-glucan phosphorylase (EC 2.4.1.1) from spinach leaves have been studied and were compared with those of phosphorylases from other sources. The two spinach leaf phosphorylases were immunologically different; a limited cross-reactivity was observed only at high antigen or antibody concentrations. Peptide mapping of the two enzymes resulted in complex patterns composed of more than 20 fragments; but no peptide was electrophoretically identical in both proteins. Approximately 13 to 15 of the fragments exhibited antigeneity but no cross-reactivity of any peptide was observed. Therefore, the two compartment-specific phosphorylase forms from spinach leaves represent isoenzymes possessing different primary structures. Peptide patterns of potato tuber and rabbit muscle phosphorylase were different from those of the two spinach leaf enzymes. Although the potato tuber phosphorylase resides in the plastidic compartment and is kinetically closely related to the chloroplastic spinach enzyme, it reacted more strongly with the anti-cytoplasmic-phosphorylase immunoglobulin G. Similar results were obtained with rabbit muscle phosphorylase. These observations support the assumption that the chloroplast-specific phosphorylase isoenzyme has a higher structural diversity than does the cytoplasmic counterpart.Abbreviations EDTA ethylenediaminetetraacetic acid - Hepes 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid - PEG polyethylene glycol (approx. MW 8000) I=Schächtele and Steup 1986