Lymphocyte populations of Callithrix jacchus marmosets.

A lymphocyte population of common marmosets (Callithrix jacchus) was identified by rosette formation with African green monkey erythrocytes; the rosette-forming cells appeared to be T lymphocytes, as approximately 62% of circulating lymphocytes and 85% of thymus cells formed rosettes with African green monkey erythrocytes. In addition, common marmoset lymphoid cells carrying T-lymphotropic Herpesvirus saimiri or Herpesvirus ateles formed rosettes with African green monkey erythrocytes and treatment of common marmoset circulating lymphocytes with an anti-T cell serum and complement (C′) eliminated rosette-forming cells. Common marmoset T lymphocytes apparently carry a surface receptor for African green monkey erythrocytes, but unlike humans and other closely related nonhuman primates, T lymphocytes of common marmosets fail to form rosettes with sheep erythrocytes.     

Validation of density–elasticity relationships for finite element modeling of human pelvic bone by modal analysis

In total hip arthroplasty and particularly in revision surgery, computer assisted pre-operative prediction of the best possible anchorage strategy for implant fixation would be a great help to the surgeon. Computer simulation relies on validated numerical models. In the current study, three density–elasticity relationships (No. 1–3) from the literature for inhomogeneous material parameter assignment from CT data in automated finite element (FE) modeling of long bones were evaluated for their suitability for FE modeling of human pelvic bone. Numerical modal analysis was conducted on 10 FE models of hemipelvic bone specimens and compared to the gold standard provided by experimental modal analysis results from a previous in-vitro study on the same specimens. Overall, calculated resonance frequencies came out lower than measured values. Magnitude of mean relative deviation of numerical resonance frequencies with regard to measured values is lowest for the density–elasticity relationship No. 3 (−15.9%) and considerably higher for both density–elasticity relationships No. 1 (−41.1%) and No. 2 (−45.0%). Mean MAC values over all specimens amount to 77.8% (No. 1), 78.5% (No. 2), and 83.0% (No. 3). MAC results show, that mode shapes are only slightly influenced by material distribution. Calculated resonance frequencies are generally lower than measured values, which indicates, that numerical models lack stiffness. Even when using the best suited (No. 3) out of three investigated density–elasticity relationships, in FE modeling of pelvic bone a considerable underestimation of model stiffness has to be taken into account.     

Pyrimidine auxotrophy and the complementation map of the Rudimentary locus of Drosophila melanogaster

Summary The complementation pattern of twelve rudimentary mutations has been analyzed at two different levels. When analyzed on the basis of complementation for a wing abnormality the mutations can be divided into three groups, each of which is believed to affect the activity of one of the first three enzymes of pyrimidine synthesis (Norby, 1973; Jarry and Falk, 1974; Rawls and Fristrom, 1975). However, when the mutants are analyzed for complementation on the basis of a second phenotype, pyrimidine auxotrophy, the distinction between two of these three groups is not evident. The disparity in the two patterns probably reflects a different threshold of gene activity required for the detection of an auxotrophic phenotype as compared to that at which a wing abnormality is detectable.The biochemical basis of these results is interpreted in light of recent data suggesting that at least the first two enzymes of pyrimidine synthesis are contained within a single multifunctional protein complex (Soderholm et al., 1975).     

Loads distributed in vivo among vertebrae,muscles, spinal ligaments,and intervertebral discs in a passively flexed lumbar spine

Biomechanics and Modeling in Mechanobiology - The load distribution among lumbar spinal structures—still an unanswered question—has been in the focus of this hybrid experimental and...     

Early host–microbe interaction in a peri‐implant oral mucosa‐biofilm model

The host‐microbe relationship is pivotal for oral health as well as for peri‐implant diseases. Peri‐implant mucosa and commensal biofilm play important roles in the maintenance of host‐microbe homeostasis, but little is known about how they interact. We have therefore investigated the early host‐microbe interaction between commensal multispecies biofilm (Streptococcus oralis, Actinomyces naeslundii, Veillonella dispar, Porphyromonas gingivalis) and organotypic peri‐implant mucosa using our three‐dimensional model. After 24 hr, biofilms induced weak inflammatory reaction in the peri‐implant mucosa by upregulation of five genes related to immune response and increased secretion of IL‐6 and CCL20. Biofilm volume was reduced which might be explained by secretion of β‐Defensins‐1, ‐2, and CCL20. The specific tissue reaction without intrinsic overreaction might contribute to intact mucosa. Thus, a relationship similar to homeostasis and oral health was established within the first 24 hr. In contrast, the mucosa was damaged and the bacterial distribution was altered after 48 hr. These were accompanied by an enhanced immune response with upregulation of additional inflammatory‐related genes and increased cytokine secretion. Thus, the homeostasis‐like relationship was disrupted. Such profound knowledge of the host‐microbe interaction at the peri‐implant site may provide the basis to improve strategies for prevention and therapy of peri‐implant diseases.     

Chromatin modifiers and recombination factors promote a telomere fold-back structure,that is lost during replicative senescence

Telomeres have the ability to adopt a lariat conformation and hence, engage in long and short distance intra-chromosome interactions. Budding yeast telomeres were proposed to fold back into subtelomeric regions, but a robust assay to quantitatively characterize this structure has been lacking. Therefore, it is not well understood how the interactions between telomeres and non-telomeric regions are established and regulated. We employ a telomere chromosome conformation capture (Telo-3C) approach to directly analyze telomere folding and its maintenance in S. cerevisiae. We identify the histone modifiers Sir2, Sin3 and Set2 as critical regulators for telomere folding, which suggests that a distinct telomeric chromatin environment is a major requirement for the folding of yeast telomeres. We demonstrate that telomeres are not folded when cells enter replicative senescence, which occurs independently of short telomere length. Indeed, Sir2, Sin3 and Set2 protein levels are decreased during senescence and their absence may thereby prevent telomere folding. Additionally, we show that the homologous recombination machinery, including the Rad51 and Rad52 proteins, as well as the checkpoint component Rad53 are essential for establishing the telomere fold-back structure. This study outlines a method to interrogate telomere-subtelomere interactions at a single unmodified yeast telomere. Using this method, we provide insights into how the spatial arrangement of the chromosome end structure is established and demonstrate that telomere folding is compromised throughout replicative senescence.