Leydig cell mitoses in human testes bearing early germ cell tumors

Summary Numerous mitoses were noted in testicular tissue from adult men with early germ cell tumors. More than 15 Leydig cells undergoing mitosis were found in the interstitial compartment. The presence of specific crystalline intracytoplasmatic inclusions demonstrated for the first time that differentiated Leydig cells are capable of proliferation. Occasionally cells are difficult to discriminate during mitosis. To establish reference criteria, the light- and electron-microscopic features of the following mitotic cells were examined: Leydig cells, fibroblasts, perivascular cells, peritubular cells, and lymphocytes. Supplementary mitoses in germ cell tumors and in a case of Leydig cell tumor were investigated. In the literature, only single reports of mitoses in Leydig cells are available. The frequent incidence of Leydig cell mitosis in early germ cell tumors may be due to the presence of growth-promoting factors in the testicular tissue.     

No evidence for linkage of autosomal dominant proximal spinal muscular atrophies to chromosome 5q markers

Summary Two recent articles have reported the linkage of a gene for recessive spinal muscular atrophy (SMA) on the chromosome region 5q11.2–13.3. Our data show no linkage of the dominantly inherited forms of SMA to this chromosome region.     

Synthesis patterns of a set of follicle cell proteins in Drosophila melanogaster sibling species

The protein synthesis pattern of a set of stage and tissue specific proteins has previously been described in Drosophila melanogaster. The analysis of this set of follicle cell proteins (Fc proteins) is here extended to cover several sibling species of Drosophila melanogaster, namely D. simulans, D. mauritiana, D. erecta and D. yakuba. Even though a similar set of proteins were synthesized in these species, minor differences in size of the proteins were found between the species. Some of the species exhibited variation within species.     

Optimization of culture conditions for human corneal endothelial cells

Summary Long-term cultivation of human corneal endothelial cells (HCEC) was optimized with respect to different components of the culture system: 25 different nutrient media, different sera, 6 mitogens and various substrates were tested in their ability to influence clonal growth and morphology of HCEC. F99, a 1∶1 mixture of the two media M199 and Ham’s F12, was the most effective basal medium in promoting clonal growth of HCEC. Among various sera, human serum and fetal bovine serum showed optimal growth promoting activities in combination with F99, whereas newborn bovine serum (NBS) was by far superior for the development of a typically corneal endothelial morphology. Crude fibroblast growth factor (FGF), or alternatively endothelial cell growth supplement, was absolutely essential for clonal growth of HCEC at low serum concentrations, for example 5% NBS. Formation of a monolayer with a morphology similar to corneal endothelium in vivo was observed only on culture dishes coated with basal membrane components such as collagen type IV, laminin, or fibronectin. The most pronounced effect on morphologic appearance was obtained by culturing the cells on the extracellular matrix (ECM) produced by bovine corneal endothelial cells. Moreover, ECM could substitute for crude FGF in clonal growth assays.     

Influence of femB on methicillin resistance and peptidoglycan metabolism in Staphylococcus aureus.

The inactivation of FemB by insertion of Tn551 in the central part of the femB open reading frame was shown to increase susceptibility of methicillin-resistant Staphylococcus aureus strains toward beta-lactam antibiotics to the same extent as did inactivation of femA. Strains carrying the methicillin resistance determinant (mec) and expressing PBP 2' were affected to the same extent as were strains selected for in vitro resistance, which did not express PBP 2'. Both femA and femB, which form an operon, are involved in a yet unknown manner in the glycine interpeptide bridge formation of the S. aureus peptidoglycan. FemB inactivation was shown to reduce the glycine content of peptidoglycan by approximately 40%, depending on the S. aureus strain. The reduction of the interpeptide bridge glycine content led to significant reduction in peptidoglycan cross-linking, as measured by gel permeation high-pressure liquid chromatography of muramidase-digested cell walls. Maximum peptide chain length was reduced by approximately 40%. It is shown that the complete pentaglycine interpeptide bridge is important for the sensitivity against beta-lactam antibiotics and for the undisturbed activity of the staphylococcal cell wall-synthesizing and hydrolyzing enzymes, as was also apparent from electron microscopic examinations, which revealed aberrant placement of cross walls and retarded cell separation, leading to a pseudomulticellular phenotype of the cells for both femA and femB mutants.     

Vertically stratified frugivore community composition and interaction frequency in a liana fruiting across forest strata

Vertical stratification is a key feature of tropical forests and structures plant–frugivore interactions. However, it is unclear whether vertical differences in plant-frugivore interactions are due to differences among strata in plant community composition or inherent preferences of frugivores for specific strata. To test this, we observed fruit removal of a diverse frugivore community on the liana Marcgravia longifolia in a Peruvian rain forest. Unlike most other plants, Marcgravia longifolia produces fruits across forest strata. This enabled us to study effects of vertical stratification on fruit removal without confounding effects of plant species and stratum. We found a high number of visits of a few frugivore species in the understorey and a low number of visits of many different frugivores in the canopy and midstorey. Whereas partial and opportunistic frugivores foraged across strata with differing frequencies, obligate frugivores were only found eating fruits in the higher strata. Avian frugivores foraging in the canopy were mainly large species with pointed wings, whereas under- and midstorey avian foragers were smaller with rounded wings. Our findings suggest a continuous shift in the frugivore community composition along the vertical gradient, from a few generalized frugivores in the understorey to a diverse set of specialized frugivores in the canopy. This shift in the frugivore community leads to correlated, reciprocal changes from specialized to generalized plant-frugivore interactions. Thus, we conclude that vertical niche differentiation between species in tropical forests persists even when food resources are available across strata. This highlights its role for promoting biodiversity and ecosystem functioning.     

Morphological parameters affecting false lumen thrombosis following type B aortic dissection: a systematic study based on simulations of idealized models

Type B aortic dissection (TBAD) carries a high risk of complications, particularly with a partially thrombosed or patent false lumen (FL). Therefore, uncovering the risk factors leading to FL thrombosis is crucial to identify high-risk patients. Although studies have shown that morphological parameters of the dissected aorta are related to FL thrombosis, often conflicting results have been reported. We show that recent models of thrombus evolution in combination with sensitivity analysis methods can provide valuable insights into how combinations of morphological parameters affect the prospect of FL thrombosis. Based on clinical data, an idealized geometry of a TBAD is generated and parameterized. After implementing the thrombus model in computational fluid dynamics simulations, a global sensitivity analysis for selected morphological parameters is performed. We then introduce dimensionless morphological parameters to scale the results to individual patients. The sensitivity analysis demonstrates that the most sensitive parameters influencing FL thrombosis are the FL diameter and the size and location of intimal tears. A higher risk of partial thrombosis is observed when the FL diameter is larger than the true lumen diameter. Reducing the ratio of the distal to proximal tear size increases the risk of FL patency. In summary, these parameters play a dominant role in classifying morphologies into patent, partially thrombosed, and fully thrombosed FL. In this study, we point out the predictive role of morphological parameters for FL thrombosis in TBAD and show that the results are in good agreement with available clinical studies.

     

Individualistic responses of bird species to environmental change

We investigated how the population dynamics of the same bird species varied in different environments, and how the population dynamics of different species varied in the same environment, by calculating long-term population trends for 59 insectivorous songbird species in 22 regions or strata of eastern and central North America using data from the North American Breeding Bird Survey. Of the 47 species that occurred in more than one region 77% increased in some regions and declined in others. Of the 22 regions 91% had some species that increased and others that decreased. There were only slightly more significant correlations between strata in species trends and between species for stratum trends than would be expected by chance. Because of nonlinearities in the data, the actual patterns of population fluctuations of the same species in different regions and of different species in the same region were even more heterogeneous than suggested by our analyses of linear trends. We conclude that these bird species respond to spatial and temporal variation in their environment in a very individualistic fashion. These individualistic responses show that the extrapolation of population trends gained from a few local studies to a larger spatial scale, and the use of a few indicator species to monitor the status of a broader community, are suspect.     

Cloning of the amphibolic Calvin cycle/OPPP enzyme d-ribulose-5-phosphate 3-epimerase (EC 5.1.3.1) from spinach chloroplasts: functional and evolutionary aspects

Exploiting the differential expression of genes for Calvin cycle enzymes in bundle-sheath and mesophyll cells of the C4 plant Sorghum bicolor L., we isolated via subtractive hybridization a molecular probe for the Calvin cycle enzyme d-ribulose-5-phosphate 3-epimerase (R5P3E) (EC 5.1.3.1), with the help of which several full-size cDNAs were isolated from spinach. Functional identity of the encoded mature subunit was shown by R5P3E activity found in affinity-purified glutatione S-transferase fusions expressed in Escherichia coli and by three-fold increase of R5P3E activity upon induction of E. coli overexpressing the spinach subunit under the control of the bacteriophage T₇ promoter, demonstrating that we have cloned the first functional ribulose-5-phosphate 3-epimerase from any eukaryotic source. The chloroplast enzyme from spinach shares about 50% amino acid identity with its homologues from the Calvin cycle operons of the autotrophic purple bacteria Alcaligenes eutrophus and Rhodospirillum rubrum. A R5P3E-related eubacterial gene family was identified which arose through ancient duplications in prokaryotic chromosomes, three R5P3E-related genes of yet unknown function have persisted to the present within the E. coli genome. A gene phylogeny reveals that spinach R5P3E is more similar to eubacterial homologues than to the yeast sequence, suggesting a eubacterial origin for this plant nuclear gene.Abbreviations R5P3E d-ribulose-5-phosphate 3-epimerase - RPI ribose-5-phosphate isomerase - TKL transketolase - PRK phosphoribulokinase - GAPDH glyceraldehyde-3-phosphate dehydrogenase - FBP fructose-1,6-bisphophatase - FBP fructose 1,6-bisphosphate - G6PDH glucose-6-phosphate dehydrogenase - 6PGDH 6-phosphogluconate dehydrogenase - OPPP oxidative pentose phosphate pathway - Rubisco ribulose-1,5-bisphosphate carboxylase/oxygenase - FBA fructose-1,6-bisphophate aldolase - IPTG isopropyl -d-thiogalactoside - GST glutathione S-tranferase - PBS phosphate-buffered saline - TPI triosephosphate isomerase     

Dielectric relaxation in lecithin/cholesterol/water-mixtures

The dielectric spectrum of aqueous solutions of dimyristoyl-l-3-phosphatidylcholine and dipalmitoyl-l-3-phosphatidylcholine with admixed cholesterol has been determined by means of a pulse reflection method which was used to measure the complex permittivity of the solutions as a function of frequency between 100 kHz and 50 MHz. Measurements have been performed at various concentrations of cholesterol in dependence of temperature around the crystal-line/liquid-crystalline phase transition temperature of the solutions.The measured dielectric spectra are treated in terms of a Debye-function. The dielectric relaxation strength and the relaxation time decrease distinctly with increasing cholesterol concentration. In addition, the data are treated on the basis of a theoretical solution model in order to allow for conclusions concerning the lecithin head group motion in the lipid bilayer surface. One important result is that increasing cholesterol concentration affects the interaction of the lecithin head groups and increases their mobility. These effects already occur at small concentrations of cholesterol.