Stereoselective routes towards the synthesis of unusual bis(amino acids) and cyclic amino acids

Summary Stereoselective syntheses are described of bridged bis(glycines) as conformationally constrained substitutes for cystine, and of cyclic α-amino acids where the α-carbon of the amino acid is part of a five-, six- or seven-membered ring which may hold a hydroxy group as a threonine analogue.     

The kinetics of diffusion between a spherical cell and a surrounding medium with different diffusion properties

The diffusion equation according to Fick’s law is solved for a spherical cell, surrounded by an infinite medium with different diffusion properties. The method of Laplace transform is used to obtain the formal solution, however, no inversion can be found for all times and an expansion suitable for small times is performed. The final expression found is expanded further to be more suited for the determination of the diffusion coefficient from an experimental curve. Application to a biological problem is dissussed.     

Effects of antalarmin,a CRF receptor 1 antagonist,on fright reaction and endocrine stress response in crucian carp (<Emphasis Type="Italic">Carassius carassius</Emphasis>)

The corticotrophin-releasing factor (CRF) receptors show striking homogeneity throughout the vertebrate subphylum. In mammals, the CRF(1) receptor (CRFR(1)) plays an important role in mediating behavioral and endocrine responses to fear and stress. The specific roles of this receptor subtype in fear and stress reactions in non-mammalian vertebrates are largely unknown. Crucian carp displays the olfactory-mediated fright reaction, a stereotypic behavioral response to waterborne cues from damaged skin of conspecifics. This reaction shows several similarities to basic components of avoidance behavior in mammals. In the present study, we applied the non-peptide CRFR(1) antagonist, antalarmin, to crucian carp 1 h before exposure to conspecific skin extract. This treatment resulted in a suppression of the fright reaction. After skin extract exposure, antalarmin treatment also lead to lower plasma cortisol values, as compared to vehicle treatment. This suppression of the behavioral fright reaction and the stress induced rise in plasma cortisol in crucian carp suggests that the functions of the CRFR(1) are conserved by evolution.     

Fermentation of waste mechanical fibers from a newsprint mill by the rot fungus Sporotrichum pulverulentum

The growth and protein production of Sporotrichum pulverulentum, formerly called Chrysosporium lignorum, have been studied in submerged cultures using lignin-containing waste fibers from a newsprint mill as the only carbon source. The influence of different nitrogen sources on the growth parameters has been particularly investigated. The regulation of the production of extracellular enzymes and their interaction with the fibers is discussed. Experiments with cellulose of different degrees of polymerization and crystallinities showed that the protein content in the residual substance decreased, particularly when the crystallinity increased. When the highly crystalline powder cellulose was used as carbon source, the protein content in the residual substance was only 6% and with the mechanical waste fibers 14%. The results obtained demonstrate that the more complex the carbon source the more difficult it is to digest and the more enzyme has to be produced for its degradation. This puts a heavy burden on the protein synthesizing mechanism. Utilizing results from other work, where the endo- and exo-l, 4-β-glucanases produced by S. pulverulentum for the degradation of cellulose have been quantitatively purified, it has been calculated that the extracellular enzymes under these conditions can together account for approximately 30% of the protein in the mycelium. The endo- and exo-1,4-β-glucanases account for up to 55% of the extracellular protein. Certain possibilities of producing a final product with a high protein content using complex carbon sources are also mentioned.     

Functional Anatomy of the Hearts of Lungfishes and Amphibians

Lungfishes and amphibians have bimodal gas exchange, but variousspecies employ airbreathing with lungs to different degrees.An increased use of pulmonary breathing is correlated with progressivestructural and functional separation of the pulmonary and systemicvascular circuits. Representatives from all genera of lungfishesand several anurans and urodeles utilizing pulmonary breathing,show a preferential distribution of blood tending to minimizerecirculation to the systemic and pulmonary circuits. The degreeof shunting between the two circuits is variable and may expressnormal shifts in regional blood flow. The most important structural and functional features influencingthe preferential circulation through dipnoan and amphibian heartsinclude: (a) Dynamics of inflow in the pulmonary and systemicveins; (b) The extent and localization of atrial septation;(c) The partial ventricular septum in lungfishes and the massiveventricular trabeculation in both amphibians and lungfishes;(d) A laminar ventricular outflow pattern; (e) Structural guidanceof flow in the partially separated bulbus segment of the heart;(f) Vasomotor reactions in the various outflow vessels fromthe heart.     

Cross‐talk between monocyte invasion and astrocyte proliferation regulates scarring in brain injury

Scar formation after brain injury is still poorly understood. To further elucidate such processes, here, we examine the interplay between astrocyte proliferation taking place predominantly at the vascular interface and monocyte invasion. Using genetic mouse models that decrease or increase reactive astrocyte proliferation, we demonstrate inverse effects on monocyte numbers in the injury site. Conversely, reducing monocyte invasion using CCR2^?/? mice causes a strong increase in astrocyte proliferation, demonstrating an intriguing negative cross‐regulation between these cell types at the vascular interface. CCR2^?/? mice show reduced scar formation with less extracellular matrix deposition, smaller lesion site and increased neuronal coverage. Surprisingly, the GFAP⁺ scar area in these mice is also significantly decreased despite increased astrocyte proliferation. Proteomic analysis at the peak of increased astrocyte proliferation reveals a decrease in extracellular matrix synthesizing enzymes in the injury sites of CCR2^?/? mice, highlighting how early key aspects of scar formation are initiated. Taken together, we provide novel insights into the cross‐regulation of juxtavascular proliferating astrocytes and invading monocytes as a crucial mechanism of scar formation upon brain injury.     

The role of lemming herbivory in the sex ratio and shoot demography of willow populations

We investigated the role of lemming herbivory on the age structure and physical form of a stand of willows ( Salix lanata ) using lemming scars on stems as an indication of past herbivory. Salix lanata had a female-biased sex ratio comparable to that found in other willow species and it has been proposed that such a sex ratio may be due to selective herbivory on male genets. There was, however, no difference in the degree of scarring in male and female plants. Scarring did not appear to change the overall physical structure of the willows including the number of stems, the proportion of dead stems and the degree of branching. However, 72% of scarred 7 mm stems were dead, compared to only 22% of non-scarred stems, suggesting that lemming herbivory may play a role in ramet death. There was a significant positive correlation between stem ages and the lemming cycle as determined by the frequency of scars. With experimental scarring, S. lanata increased its production of new shoots in relation to the degree of scarring. We suggest that this demonstrates a pattern of compensatory growth in willows, whereby they take advantage of a period of relatively low herbivory following the crash of the lemming populations in order to compensate for damage that occurred during the lemming peak.     

New methods to evaluate colocalization of fluorophores in immunocytochemical preparations as exemplified by a study on A2A and D2 receptors in Chinese hamster ovary cells.

An important aspect of the image analysis of immunocytochemical preparations is the evaluation of colocalization of different molecules. The aim of the present study is to introduce image analysis methods to identify double-labeled locations exhibiting the highest association of two fluorophores and to characterize their pattern of distribution. These methods will be applied to the analysis of the cotrafficking of adenosine A2A and dopamine D2 receptors belonging to the G protein-coupled receptor family and visualized by means of fluorescence immunocytochemistry in Chinese hamster ovary cells after agonist treatment. The present procedures for colocalization have the great advantage that they are, to a large extent, insensitive to the need for a balanced staining with the two fluorophores. Thus, these procedures involve image processing, visualization, and analysis of colocalized events, using a covariance method and a multiply method and the evaluation of the identified colocalization patterns. Moreover, the covariance method offers the possibility of detecting and quantitatively characterizing anticorrelated patterns of intensities, whereas the immediate detection of colocalized clusters with a high concentration of labeling is a possibility offered by the multiply method. The present methods offer a new and sensitive approach to detecting and quantitatively characterizing strongly associated fluorescence events, such as those generated by receptor-receptor interaction, and their distribution patterns in dual-color confocal laser microscopy.