Temporal and spatial differences in glycosaminoglycan synthesis by fetal lung fibroblasts

In studies of the ontogeny of fibroblast-epithelial interactions during late fetal lung rat lung development, we have identified two subpopulations of fibroblasts which differed in their ability to promote epithelial cell proliferation or differentiation. As glycosaminoglycans (GAGs) have been implicated in the regulation of these processes we have tested whether the two fibroblast populations synthesize different GAGs and whether the GAG pattern changes with development. Fibroblasts incorporate more [3H]glucosamine and Na2 35SO4 into GAGs than epithelial cells. Both cell types deposited a significant amount of newly synthesized GAGs in the cell-matrix layer. GAGs were lost faster from the cell-matrix layer of fibroblasts (t1/2 = 12 h) than from that of epithelial cells (t1/2 = 48 h). Total GAG synthesis by fibroblasts did not change with advancing gestation, but synthesis of sulfated GAGs by epithelial cells declined with advancing gestation. Independent of gestational age epithelial cells synthesized predominantly heparan sulfate. Depending on their proximity to the epithelium, fibroblasts differed in their production of GAGs. Fibroblasts in close proximity to the epithelium mainly produced and secreted hyaluronan. More distant fibroblasts, from the pseudoglandular stage of lung development synthesized primarily heparan sulfate and chondroitin sulfate. This same population of fibroblasts from the canalicular stage of lung development, produced more hyaluronan. As the shift to hyaluronan occurs with the thinning of the alveolar septal wall, this finding suggests that developmentally regulated GAG production by fibroblasts may facilitate epithelial-fibroblast interaction, thus influencing fetal lung growth and differentiation.     

Low hydration phase properties of phospholipid mixtures

An experimental investigation of the low hydration phase properties of phospholipid mixtures is described. ²H (D₂O) NMR, X-ray diffraction and differential scanning calorimetry have been used to elucidate the phase properties of mixtures of the mixed chain phospholipids palmitoyloleoylphosphatidylcholine (POPC) and palmitoyloleoylphosphatidylethanolamine (POPE). At 10% hydration pure POPE exhibited a H_II phase above 330 K, a fluid lamellar phase below 315 K, and a minimally hydrated crystalline phase below 300 K. For the 1:1 mixture, the samples exhibited only gel or fluid phases between 270 K and 360 K for hydrations in the range 15% to 30%. Below 15% hydration the mixture exhibited two fluid phases with different repeat spacings, as predicted previously.     

Stage-specific cuticular proteins of Ostertagia circumcincta and Ostertagia ostertagi

In this study we have shown that NHS-biotin and I¹²⁵-streptavidin can detect cuticular polypeptides of Ostertagia spp. The labelled polypeptide profile of intact nematodes is simple compared to the profile obtained by labelling homogenates. None of the major internal polypeptides are labelled and the subset of proteins labelled in intact nematodes appears to be mainly surface associated. The results presented here demonstrate that NHS-biotin may be used as a reagent for the analysis of surface polypeptides. The surface polypeptide profiles of the five major developmental stages (L1, L2, L3, L4 and adult) of Ostertagia circumcincta show a series of stage-specific molecules with no polypeptides common to all stages, indicating that the cuticle is a dynamic structure which changes throughout the life cycle. Similarity comparison of Ostertagia ostertagi L3 and L4 stage surface profiles showed that each stage is clearly distinct; comparison of these stages between the two species shows an overall similarity.     

Wood excavations of three species of subterranean termites

We compared the feeding excavations on wood blocks of three species of subterranean termites, Coptotermes formosanus Shiraki, Reticulitermes flavipes (Kollar), and R. virginicus (Banks). Feeding rate followed the order C. formosanus > R. flavipes > R. virginicus. Wood surface area (mm²) exposed per unit feeding was higher for C. formosanus and R. flavipes than for R. virginicus. This was caused by the tendency of C. formosanus and R. flavipes to make internally penetrating tunnels, thereby increasing surface area, whereas R. virginicus made trough- and bowl-like depressions on the outside of blocks, sometimes decreasing the size of blocks outwardly without a corresponding high increase in surface area typical with the tunnels of the other species. Consequently, wood surface area was sometimes reduced, rather than increased as a result of feeding by R. virginicus. Different patterns of wood excavation suggest that these termites have divergent roles in wood decay processes.

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Résumé Les organismes pionniers qui modifient le bois et le rendent acceptable par les insectes qui le perforent sont généralement des champignons du bois pourri. Cependant, une fois que les termites ou autres insectes perforant le bois ont pénétré, leurs galeries favorisent les bactéries fixatrices d'azote, permettent l'invasion d'autres organismes décomposeurs, et de ce fait régularisent la décomposition du bois (Ausmus, 1977). L'exposition de la surface à l'intérieur des perforations jouant un rôle très important dans le processus de pourrissement, il est souhaitable de pouvoir quantifier la surface des galeries dues à l'alimentation des termites. Une courbe type permettant de prédire l'aire de la surface perforée a été construite en perçant 109 morceaux de bois de trous cylindriques de différents diamètres, en calculant l'aire de la surface des morceaux de bois, en appliquant et pesant une couche de vernis pour bois au polyuréthane, et en divisant la masse de polyuréthane par l'aire de la surface. Le modèle prédictif qui en découle est: Y=0,01443×-3,51825 (P=0,0001; r=0,68), y étant la masse de polyuréthane (en g) et x la surface (en mm²) du morceau de bois. En traitant de la même façon au polyuréthane les morceaux de bois perforés par les termites, nous pourrions déduire leur surface.Une expérience a été effectuée avec 3 espèces de rhinotermitides,- Coptotermes formosanus Shiraki, Reticulitermes flavipes (Kollar) et R. virginicus (Banks). Des groupes de chaque espèce se sont alimentés pendant 11 ou 12 jours sur des morceaux de bois non contaminés par des champignons. Nous avons déterminé la survie, la consommation, la modification de la surface du morceau de bois (par utilisation du modèle prédictif) et le changement de surface par terminte.La survie est la même, mais la consommation est dans l'ordre suivant: C. formosanus > R. flavipes > R. virginicus. L'aire de la surface exposée par unité d'alimentation était plus élevée pour C. formosanus et R. flavipes que pour R. virginicus (Tab. 1). Ceci est dû à la tendance de C. formosanus et R. flavipes de creuser des galeries vers l'intérieur, tandis que R. virginicus fait des cuvettes à la surface du bois. Les attaques superficielles de R. virginicus réduisent parfois le volume du morceau de bois sans accroître proportionnellement la surface comme le font les espèces creusant des galeries. Ainsi, avec R. virginicus la surface peut être réduite au lieu d'augmenter. Des différences entre colonies s'observent avec toutes les variables (Tab. 2).Nos résultats suggèrent que C. formosanus et R. flavipes contribuent plus que R. virginicus à exposer le bois aux autres organismes décomposeurs. Cependant, ces résultats peuvent être modifiés par un conditionnement préalable du bois par des champignons.

     

Primary cultures and the levels of cytochromeP450 in hepatocytes from mouse,rat, hamster,and rabbit liver

Summary Hepatocyte primary cultures (HPC) derived from rat, mouse, hamster, and rabbit liver were characterized for a variety of parameters. The conditions that maximized recovery, attachment, and survival varied between species. Hepatocytes from all four species were capable of attaching in serum-free Williams’ medium E (WME), but optimal attachment as monolayer cultures was achieved for mouse and hamster HPC in medium receiving 1% calf serum supplementation. Hamster hepatocytes required additional cations, whereas rabbit and rat hepatocytes displayed maximal attachment in medium supplemented with 10% calf serum. Survival of mouse and rabbit hepatocytes after 24 h in serum supplemented media was in the order of 90%. Rat and hamster hepatocyte 24 h survival was approximately 70 and 60%, respectively, and was not significantly affected by serum supplementation. Hepatocytes from each species varied in their content of cytochromeP450 at the time of isolation and in the rate of reduction during culture. Mouse and rat hepatocytes demonstrated the most rapid decline in content during the initial 24 h in culture, whereas concentrations in rabbit hepatocytes were virtually unchanged. The rate of decline inP450 concentrations in hamster hepatocytes was intermediate between those displayed by rat and rabbit hepatocytes. These studies have delineated conditions useful for the culture of hepatocytes from four species and have documented the status of an important parameter of their functional capability. This study was supported by EPA contract 68-01-6179. C. J. Maslansky was a recipient of a Monsanto Fund Fellowship in Toxicology.     

Identification of bacterial chemoattractants for oyster (Crassostrea virginica) hemocytes

The cytoplasmic and cell wall components of the Gram-positive bacterium Bacillus megaterium and the cytoplasmic and cell envelope components of the Gram-negative bacterium Escherichia coli were assayed for chemotactic activity for the hemocytes of Crassostrea virginica. The cellular components were separated by differential centrifugation and gel filtration was used to determine the approximate molecular weights of the chemoattractant molecules. Active fractions were assayed for glycoproteins and lipoproteins. As a result, it is known that hemocytes are chemotactically attracted to proteins of approximately 10,000 daltons which are associated with the cell wall of B. megaterium and the cell envelope of E. coli.     

Isolation and properties of Tn10 insertions in the rac locus of Escherichia coli

Summary Two Tn10 insertions that are in the rac locus of the chromosome of Escherichia coli have been isolated and characterized. These insertions are located at min 29.7 and min 30.0. The insertions are stable when an F123 rac::Tn10 episome is transferred to an F^- rac ⁺ recipient, but they are lost at a high frequency when transferred to an F^- rac ^- recipient. This latter condition has been previously, demonstrated to cause the excision of the rac locus. The Tn10 insertions are also lost at a high frequency when strains containing them are lysogenized with reverse. If the lysogens that have lost the Tn10 insertion are subsequently cured of reverse, the cells no longer contain sequences homologous with rac locus DNA. These strains were rac ^- when tested for recombination activation (Low 1973), and this procedure consequently provides a simple means to make isogenic rac ^- and rac ^- strains.     

Validation of a primary production model of the desert shrub Larrea tridentata using soil-moisture augmentation experiments

Summary In previous papers we have described and verified a primary production model of the desert shrub Larrea tridentata. Here we address the validation phase of the evaluation of this model. Two versions of the model which differ in the priority scheme used for allocating carbon to reproductive or vegetative organs were compared on the basis of their usefulness and reliability over a range of soil-moisture conditions. Over an entire growing season when soil-moisture conditions were near normal both versions of the model were adequate predictors of total above-ground vegetative growth and one was an adequate predictor of reproductive growth as well. A more detailed analysis revealed that the versions varied in the range of soil-moisture conditions over which they were adequate and that neither was adequate when soil-moisture had remained high for extended periods. The validation process has revealed some likely areas for model improvement to increase adequacy.     

Stereochemical aspects of forcing special substrate hydrazides to behave either as electrophiles or as nucleophiles during catalysis by crude papain

Restriction of hydrazides of N-blocked amino acids mainly to electrophilic action, in acylating crude papain, has been achieved by means of a large amount of aniline, with formation of insoluble anilides of N-acylamino acids. Similarly, nucleophilic behavior, on the part of a hydrazide, has been promoted by introducing a large proportion of an N-acylamino acid to produce an insoluble N¹,N²-diacylhydrazine. Achiral, chiral and racemic hydrazides and their corresponding N-acylamino acids were utilized in the study. Among the more informative combinations of reactants were Z-dl-alanine hydrazide with aniline and then with Z-glycine. A stereospecific response in the former situation produced Z-l-alanine anilide. In the latter case, a stereoselective interaction produced Z-Gly-NHNH-lAla-Z more rapidly than Z-Gly-NHNH-d-Ala-Z. The final incubation period yielded an optically pure D product. Differences in stereochemical control have been delineated in terms of different spatial aspects for interactions at the S and S′ subsites of sulfhydryl proteolytic enzymes. A racemic reactant encountered firm stereospecificity as an electrophile at the S subsite but only modest stereoselectivity as a nucleophile at the S′ subsite. The ready availability of crude papain allows an effective procedure for the synthesis of substantial quantities of diacylhydrazines.