Relationship between osmoprotection and the structure and intracellular accumulation of betaines by Escherichia coli

Abstract Naturally occuring betaines, especially glycine betaine and proline betaine, were accumulated by Escherichia coli from urine. In synthetic hyperosmotic medium, with an homologous series of added betaines, (CH₃)₃N⁺-(CH₂) _n -COO⁻, osmoprotective activity and intracellular accumulation decreased monotonically as n increased from 1 to 5. In contrast, α -substituted glycine betaines were accumulated in a similar manner to glycine betaine, but with different osmoprotective activities. Arsenobetaine, with a quaternary arsonium group, was also accumulated but amino acids which can become negatively charged in a chemically basic environment were not.     

Regulation of pheromone production in virgin and mated females of two tortricid moths

Sex pheromone titers in females of two tortricid moths, Epiphyas postvittana and Planotortrix octo, did not significantly vary between the scotophase and photophase. Pheromone production in these two species is controlled by a factor located in the head of the respective females, probably the pheromone biosynthesis-activating neuropeptide (PBAN). Unlike that reported for the related tortricid, Argyrotaenia velutinana, the bursa copulatrix in female E. postvittana and P. octo does not appear to contain a factor that stimulates pheromone production. After mating, female E. postvittana permanently shut down pheromone production. In contrast, pheromone titer in mated P. octo females is reduced to a level approximately half that of similar-age virgins. While the abdominal nervous system is involved in the inactivation of pheromone production in mated E. postvittana females and probably acts to stop release of PBAN from the corpora cardiaca, the abdominal nervous system is not involved in effecting the decreased pheromone titers of mated P. octo females. It is possible that in the latter species, a humoral factor(s) is responsible for effecting the decreased pheromone titers, possibly through affecting the release of PBAN from the corpora cardiaca. Bioassaying head extracts allowed changes in PBAN titer in female E. postvittana to be inferred. PBAN titers remain roughly constant in virgins but increase after mating. This suggests that PBAN is biosynthesized throughout the life of an adult virgin female at approximately the same rate as it is released. Furthermore, it appears that the decline in pheromone titer observed in older E. postvittana females is probably due to a decline in competency of the gland to produce pheromone rather than to a decrease in PBAN titer in older females. © 1994 Wiley-Liss, Inc.     

Chiral HPLC with carbohydrate carbamates: Influence of support structure on enantioselectivity

The effect of particle size and pore size of the aminopropylated silica support for cellulose tris(phenylcarbamate) and tris(3,5-dimethylphenylcarbamate) chiral HPLC phases was investigated. It was necessary to reduce phase loading below 20% w/w as pore size and particle size were reduced, but high efficiency columns could be prepared at a 15% w/w loading on 5 and 2.5 μm supports with 120-Å-diameter pores. The 2.5 μm phase permits the use of relatively high flow rates and very efficient enantioselective separations of a range of chiral compounds could be achieved in less than 3 min. © 1994 Wiley-Liss, Inc.     

1H and 15N resonance assignments and secondary structure of the carbon monoxide complex of sperm whale myoglobin

Summary Sequence-specific backbone ¹H and ¹⁵N resonance assignments have been made for 95% of the amino acids in sperm whale myoglobin, complexed with carbon monoxide (MbCO). Many assignments for side-chain resonances have also been obtained. Assignments were made by analysis of an extensive series of homonuclear 2D spectra, measured with unlabeled protein, and both 2D and 3D ¹H-¹⁵N-correlated spectra obtained from uniformly ¹⁵N-labeled myoglobin. Patterns of medium-range NOE connectivities indicate the presence of eight helices in positions that are very similar to those found in the crystal structures of sperm whale myoglobin. The resonance assignments of MbCO form the basis for determination of the solution structure and for hydrogen-exchange measurements to probe the stability and folding pathways of myoglobin. They will also form a basis for assignment of the spectra of single-site mutants with altered ligand-binding properties.     

Comparative physiology and demography of three Neotropical forest shrubs: alternative shade-adaptive character syndromes

A suite of functionally-related characters and demography of three species of Neotropical shadeadapted understory shrubs (Psychotria, Rubiaceae) were studied in the field over five years. Plants were growing in large-scale irrigated and control treatments in gaps and shade in old-growth moist forest at Barro Colorado Island, Panama. Irrigation demonstrated that dry-season drought limited stomatal conductance, light saturated photosynthesis, and leaf longevity in all three species. Drought increased mortality of P. furcata. In contrast, irrigation did not affect measures of photosynthetic capacity determined with an oxygen electrode or from photosynthesis-CO₂ response curves in the field. Drought stress limited field photosynthesis and leaf and plant survivorship without affecting photosynthetic capacity during late dry season. Leaves grown in high light in naturally occurring treefall gaps had higher photosynthetic capacity, dark respiration and mass per unit area than leaves grown in the shaded understory. P. furcata had the lowest acclimation to high light for all of these characters, and plant mortality was greater in gaps than in shaded understory for this species. The higher photosynthetic capacity of gap-grown leaves was also apparent when photosynthetic capacity was calculated on a leaf mass basis. Acclimation to high light involved repackaging (higher mass per unit leaf area) as well as higher photosynthetic capacity per unit leaf mass in these species. The three species showed two distinct syndromes of functionally-related adaptations to low light. P. limonensis and P. marginata had high leaf longevity (3 years), high plant survivorship, low leaf nitrogen content, and high leaf mass per unit area. In contrast, P. furcata had low leaf survivorship (1 year), high plant mortality (77–96% in 39 months), low leaf mass per unit area, high leaf nitrogen content, and the highest leaf area to total plant mass; the lowest levels of shelf shading, dark respiration and light compensation; and the highest stem diameter growth rates. This suite of characters may permit higher whole-plant carbon gain and high leaf and population turnover in P. furcata. Growth in deep shade can be accomplished through alternative character syndromes, and leaf longevity may not be correlated with photosynthetic capacity in shade adapted plants.     

Abscisic acid and mefluidide in the regulation of cold hardiness development in Solanum tuberosum L. potato

Plants of Solanum tuberosum L. potato do not cold acclimate when exposed to low temperature such as 5°C, day/night. When ABA (45 M) was added to the culture medium, stem-cultured plantlets of S. tuberosum, cv. Red Pontiac, either grown at 20°C/15°C, day/night, or at 5°C, increased in cold hardiness from –2°C (killing temperature) to –4.5°C. The increase in cold hardiness could be inhibited in both temperature regimes if cycloheximide (70 M) was added to the culture medium at the inception of ABA treatment. Cycloheximide did not inhibit cold hardiness development, however, when it was added to the culture medium 3 days after ABA treatment.When pot-grown plants were foliar sprayed with mefluidide (50 M), ABA content increased from 10 nmol to 30 nmol g^–1 dry weight and plants increased in cold hardiness from –2°C to about –3.5°C. The increases in free ABA and cold hardiness occurred only in plants grown at 20°C/15°C; neither ABA nor cold hardiness increased in plants grown at 5°C.The results suggest that an increase in ABA and a subsequent de novo synthesis of proteins are required for the development of cold hardiness in S. tuberosum regardless of temperature regime, and that the inability to synthesize ABA at low temperature, rather than protein synthesis, appears to be the reason why S. tuberosum does not cold acclimate.     

Psychiatry and ethics: The problematics of respect for religious meanings

Over the past two decades American psychiatrists have had to address the emergence of an increasingly fervent religious pluralism. Particularly in cases of socially controversial new religious movements (NRMs), distressed families have pressured psychiatrists to assess the mental state of recruits to such sects, often labeled cults. At this inevitably acrimonious interface between family values and religious liberties, psychiatrists have for the most part resisted pressures to medicalize religious conversions. This article provides an historical review of American psychiatric response to NRMs with respect to nosology and practice. It introduces this response in the more general context of ethics and the problematics of respect for religious meanings.     

Spectroscopic studies of the manganese complex of Photosystem II

Our recent EPR and EXAFS experiments investigating the structure of the oxygen-evolving complex of PS II are discussed. PS II treatments which affect the cofactors calcium and chloride have been used to poise samples in modified forms of the S-states, S₁, S₂ and S₃. X-ray absorption studies indicate a similar overall structure for the manganese complex between treated and native samples although the influence of the treatments and cofactors is observed. Manganese oxidation (or oxidation of a ligand to the manganese cluster) is indicated to occur on each of the transitions S₁ S₂ and S₂ S₃ in these modified samples. The cluster appears to contain at least two inequivalent Mn-Mn pairs. In the native samples the Mn-Mn distance is 2.7 Å, but in samples where the calcium site is affected, one of the pairs has a 3.0 Å Mn-Mn distance. The intensity of the 3.3/3.6 Å interaction is reduced on sodium chloride treatment (calcium depletion) perhaps indicating calcium binding close to the manganese cluster. From EPR data we also propose that treatments which affect calcium and chloride binding cause a modification of the native S₂ state, slow the reduction of Y_z and allow an S3 EPR signal to be observed following illumination. The origin of the S3 EPR signal, a modified S₃ or S₂ X where X is an organic radical of unknown charge, is discussed in relation to the results from the EXAFS studies.Abbreviations EPR electron paramagnetic resonance spectroscopy - EXAFS extended X-ray absorption fine structure - HTG n-heptyl -d-thioglucoside - MES 2(N-morpholino)ethanesulfonic acid - OEC oxygen evolving complex - PPBQ phenyl-1,4-benzoquinone - PS II Photosystem II - Y_z redox active tyrosine     

Confocal laser scanning microscopy reveals voltage-gated calcium signals within hippocampal dendritic spines

The induction of long-term potentiation (LTP) is generally assumed to be triggered by Ca²⁺ entry into dendritic spines via NMDA receptor-gated channels. A previous computational model proposed that spines serve several functions in this process. First, they compartmentalize and amplify increases in [Ca²⁺]_i. Second, they augment the nonlinear relationship between synaptic strength and the probability or magnitude of LTP induction. Third, they isolate the metabolic machinery responsible for LTP induction from increases in [Ca²⁺]_i produced by voltage-gated Ca²⁺ channels in the dendritic shaft. Here we examine this last prediction of the model using methods that combine confocal microscopy with simultaneous neurophysiological recordings in hippocampal brain slices. Either of two Ca²⁺-sensitive dyes were injected into CA1 pyramidal neurons. Direct depolarization of the neurons via the somatic electrode produced clear increases in Ca²⁺ signals within the dendritic spines, a result that was not predicted by the previous spine model. Our new spine model suggests that some of this signal could theoretically result from Ca²⁺-bound dye diffusing from the dendritic shaft into the spine. Dye diffusion alone cannot, however, explain the numerous cases in which the Ca²⁺ signal in the spine was considerably larger than that in the adjacent dendritic shaft. The latter observations raise the possiblity of voltage-gated Ca²⁺ entry directly into the spine or else perhaps via Ca²⁺-dependent Ca²⁺release. The new spine model accommodates these observations as well as several other recent experimental results. 1994 John Wiley & Sons, Inc.