Comparison of seasonal growth and polyamine content in shoots of orchard-grown standard and genetic dwarf apple tress

Seasonal variations in growth rate, and polyamine and arginine content were determined in shoots of standard and genetic dwarf apples ( Malus domestica Borkh.) in orchard conditions. Putrescine, spermidine, spermine and arginine exhibited the same seasonal variations. Polyamine titer and arginine content were correlated. Putrescine, spermidine, spermine and arginine levels increased during March and April, reaching the maximum at the end of April. From the onset of May, they decreased gradually until they reached a steady level at the end of July and beginning August. Then the level increased until September when growth stopped. Shoots of both standard and dwarf trees started to grow in April, elongated slowly during the summer and ceased growth in September. Polyamine and arginine content of the shoots of standard apple trees were higher compared to the shoots of genetic dwarfs, but the concentration of polyamine and arginine were not correlated with the growth rate.     

Synthesis and properties of the cyclopentapeptide desthiomalformin

Desthiomalformin, cyclo-d-alanyl-d-alanyl-l-valyl-d-leucyl-l-isoleucyl, was synthesized by conventional methods. Cyclization of the open chain intermediate through the azide produced the cyclopentapeptide in short reaction time and in high yield and was not accompanied by cyclodimerization. The extreme readiness of the pentapeptide azide to form a cyclic structure can be attributed to the presence of alternating d and l residues in the sequence, a feature that should result in reverse turns stabilized by intramolecular hydrogen bonds. Thus the open chain intermediate could have a preferred cyclic conformation.Desthiomalformin has high thermal stability; it can be sublimed in vacuo without decomposition. It lacks, however, the biological activity of its parent compound, malformin.     

Characterization of primary reactants in bacterial photosynthesis. II. Kinetic studies of the light-induced EPR signal (g = 2.0026) and the optical absorbance changes at cryogenic temperatures

We have shown that the rise and decay kinetics of the light-induced EPR signal are identical to the kinetics of the optical changes at 80 °K. This identity provides independent evidence that the EPR signal is due to the oxidized primary electron donor which is bacteriochlorophyll. The EPR and optical changes could be described by a model photochemical reaction scheme that takes into account spin-lattice relaxation. The optical decay rate was found to be temperature independent between 1.5 and 80 °K and to obey approximately first order kinetics. These results are consistent with the hypothesis that the charge recombination occurs via tunneling through a potential barrier. The decay constants at these temperatures were found to be the same for different bacterial species and strains. No differences were found between purified reaction centers of R. spheroides R-26 and whole cells. Reaction centers treated with sodium dodecylsulfate or urea were still photochemically active but showed a markedly different kinetic behavior. The decay constant may, therefore, serve as a probe to investigate the molecular environment of the primary reactants.     

Ecosystem response to earlier ice break‐up date: Climate‐driven changes to water temperature,lake‐habitat‐specific production,and trout habitat and resource use

Climate warming has yielded earlier ice break‐up dates in recent decades for lakes leading to water temperature increases, altered habitat, and both increases and decreases to ecosystem productivity. Within lakes, the effect of climate warming on secondary production in littoral and pelagic habitats remains unclear. The intersection of changing habitat productivity and warming water temperatures on salmonids is important for understanding how climate warming will impact mountain ecosystems. We develop and test a conceptual model that expresses how earlier ice break‐up dates influence within lake habitat production, water temperatures and the habitat utilized by, resources obtained and behavior of salmonids in a mountain lake. We measured zoobenthic and zooplankton production from the littoral and pelagic habitats, thermal conditions, and the habitat use, resource use, and fitness of Brook Trout (Salvelinus fontinalis). We show that earlier ice break‐up conditions created a "resource‐rich" littoral–benthic habitat with increases in zoobenthic production compared to the pelagic habitat which decreased in zooplankton production. Despite the increases in littoral–benthic food resources, trout did not utilize littoral habitat or zoobenthic resources due to longer durations of warm water temperatures in the littoral zone. In addition, 87% of their resources were supported by the pelagic habitat during periods with earlier ice break‐up when pelagic resources were least abundant. The decreased reliance on littoral–benthic resources during earlier ice break‐up caused reduced fitness (mean reduction of 12 g) to trout. Our data show that changes to ice break‐up drive multi‐directional results for resource production within lake habitats and increase the duration of warmer water temperatures in food‐rich littoral habitats. The increased duration of warmer littoral water temperatures reduces the use of energetically efficient habitats culminating in decreased trout fitness.     

The vasoactive intestinal peptide (VIP): VI. The 17-norleucine analog of the sequence 14–28

A pentadecapeptide amide with the C-terminal sequence (14–28) of the vasoactive intestinal peptide (VIP), but with the methionine residue in position 17 replaced by l-norleucine, was synthesized. The synthesis was carried out through stepwise chain lengthening, by the in situ technique. The norleucine-containing pentadecapeptide, l-arginyl-l-lysyl-l-glutaminyl-l-norleucyl-l-alanyl-l-valyl-l-lysyl-l-lysyl-l-tyrosyl- l-leucyl-l-asparaginyl-l-seryl-l-isoleucyl-l-leucyl-l-asparaginamide, was as active in relaxing different smooth-muscle preparations as the methionine-containing parent sequence.     

On the question of the primary acceptor in bacterial photosynthesis: Manganese substituting for iron in reaction centers of Rhodopseudomonas spheroides R-26

Iron was partially replaced by manganese in a reaction center preparation of Rhodopseudomonas spheroides R-26. The reaction centers containing manganese were distinguished spectroscopically (EPR) from those containing iron. The low-temperature photochemical activities were found to be identical for both species. This makes it unlikely that the transition metal by itself is the primary electron acceptor.     

Studies on the subcellular localization of the membrane-bound fraction of intestinal calcium-binding protein

Sorbitol density gradient centrifugation applied to intestinal mucosa homogenates resulted in a complete separation of soluble calcium-binding protein from the bound fraction of calcium-binding protein, providing further documentation of the bound pool of calcium-binding protein. The peak of the bound calcium-binding protein was not associated with the major peaks of any of the markers used, but was associated with minor peaks of alkaline phosphatase, RNA, and glucose-6-phosphatase. Lack of association of bound calcium-binding protein with (Na⁺ + K⁺)-ATPase indicated that the bound calcium-binding protein is not on the basolateral membrane. Differential centrifugation fractionation indicated that the bound calcium-binding protein is not associated with nuclei or mitochondria. The bound calcium-binding protein also could not be detected in partially pyrified brush borders. Exclusion of the brush border and basolateral membranes as the location of the bound calcium-binding protein suggests an intracellular locate.     

Release of dopamine and norepinephrine by hypoxia from PC-12 cells

We examined the effects of hypoxia on the release of dopamine(DA) and norepinephrine (NE) from rat pheochromocytoma 12 (PC-12) cellsand assessed the involvement ofCa²⁺ and protein kinases instimulus-secretion coupling. Catecholamine release was monitored bymicrovoltammetry using a carbon fiber electrode as well as by HPLCcoupled with electrochemical detection (ECD). Microvoltammetricanalysis showed that hypoxia-induced catecholamine secretion(PO₂ ofmedium ~40 mmHg) occurred within 1 min after the onset of thestimulus and reached a plateau between 10 and 15 min. HPLC-ECD analysisrevealed that, at any level of PO₂, therelease of NE was greater than the release of DA. In contrast, inresponse to K⁺ (80 mM), DA releasewas ~11-fold greater than NE release. The magnitude ofhypoxia-induced NE and DA releases depended on the passage, source, andculture conditions of the PC-12 cells. Omission of extracellularCa²⁺ or addition of voltage-gatedCa²⁺ channel blockers attenuatedhypoxia-induced release of both DA and NE to a similarextent. Protein kinase inhibitors, staurosporine (200 nM) andbisindolylmaleimide I (2 µM), on the other hand, attenuatedhypoxia-induced NE release more than DA release. However, proteinkinase inhibitors had no significant effect onK⁺-induced NE and DA releases.These results demonstrate that hypoxia releases catecholamines fromPC-12 cells and that, for a given change inPO₂, NErelease is greater than DA release. It is suggested that proteinkinases are involved in the enhanced release of NE during hypoxia.