Effects of factors released from eggs and other agents on cyclic nucleotide concentrations of sea urchin spermatozoa.

Factors released from eggs (FRE) of the sea urchin, Strongylocentrotus purpuratus, caused up to 20-fold increases in sperm cyclic AMP levels after a 1-min incubation. Putative cyclic nucleotide phosphodiesterase inhibitors such as theophylline acted in a synergistic manner with FRE to cause even greater increases in sperm cyclic AMP levels. This effect appeared to be specific for egg factors since various hormones (triiodothyronine, norepinephrine, histamine), nucleosides (adenosine, guanosine), nucleophiles (axide), anaesthetics (procaine), ionophores (X537A, A23187), metals (Mn2+) and neurotransmitters (acetylcholine) did not increase sperm cyclic AMP levels. Various mammalian tissue extracts (serum, uterus, adrenal, ovary, lung) also had no effect. We suggest that the activity which elevates the cyclic AMP of sea urchin spermatozoa is specifically associated with sea urchin eggs.     

Chemokines: more than just road signs

Chemokines have long been known to orchestrate dendritic-cell migration in the body. However, recent evidence has shown that chemokines not only direct the trafficking of dendritic cells but also can regulate their maturation status. Here, we propose that this dual function of chemokines ensures that T cells and dendritic cells meet in T-cell regions of lymphoid organs and that antigen is presented in an immunologically optimal context for T-cell priming.     

Lymph node resident rather than skin-derived dendritic cells initiate specific T cell responses after Leishmania major infection

Langerhans cells have been thought to play a major role as APCs for induction of specific immune responses to Leishmania major. Although their requirement for control of infection has been challenged recently, it remains unclear whether they can transport Ag to lymph nodes and promote initiation of T cell responses. Moreover, the role of dermal dendritic cells (DCs), another population of skin DCs, has so far not been addressed. We have investigated the origin and characterized the cell population responsible for initial activation of L. major-specific T cells in susceptible and resistant mice. We found that Ag presentation in draining lymph nodes peaks as early as 24 h after infection and is mainly mediated by a population of CD11c(high)CD11b(high)Gr-1-CD8-langerin- DCs residing in lymph nodes and acquiring soluble Ags possibly drained through the conduit network. In contrast, skin-derived DCs, including Langerhans cells and dermal DCs, migrated poorly to lymph nodes and played a minor role in early T cell activation. Furthermore, prevention of migration through early removal of the infection site did not affect Ag presentation by CD11c(high) CD11b(high) DCs and activation of Leishmania major-specific naive CD4+ T cells in vivo.     

Strong TCR signaling, TLR ligands, and cytokine redundancies ensure robust development of type 1 effector T cells

T cell effector function is a central mechanism of adaptive immunity, and accordingly, protection of the host against pathogens. One of the primary effector molecules produced by T cells in response to such pathogens is the cytokine, IFN-gamma. Although the signaling pathways associated with the production of IFN-gamma are well established, disparate in vivo and in vitro results indicate that distinct pathways may become more prominent dependent upon the nature of the infection, inflammatory milieu and tissue localization. We have examined the roles and requirements of the major IFN-gamma-inducing pathways in vivo and in vitro, specifically: strength of TCR signal; paracrine release of IL-12, IL-23, and IL-18; and autocrine production of IFN-gamma. Our data show a dynamic interaction between these activation pathways, which allows the host a degree of flexibility and redundancy in the induction of IFN-gamma. Upon strong signaling through the TCR, IL-12, IL-18, and IL-23 play negligible roles in the induction of IFN-gamma, whereas autocrine IFN-gamma is an important component in sustaining its own secretion. However, the absence of any one of these factors during a weaker TCR signal, results in strikingly impaired T cell IFN-gamma production. Of note, TLR-activated dendritic cells (DCs) were capable of overcoming the absence of a strong TCR signal, IL-12, IL-23, or IL-18 revealing an important additional mechanism for ensuring a robust IFN-gamma response. Our findings clarify the hierarchical requirements of the major IFN-gamma inducing pathways and highlight the important role TLR ligand-activated DCs have to preserve them.     

Segregation of micron-scale membrane sub-domains in live murine sperm

Lipid rafts, membrane sub-domains enriched in sterols and sphingolipids, are controversial because demonstrations of rafts have often utilized fixed cells. We showed in living sperm that the ganglioside G(M1) localized to a micron-scale membrane sub-domain in the plasma membrane overlying the acrosome. We investigated four models proposed for membrane sub-domain maintenance. G(M1) segregation was maintained in live sperm incubated under non-capacitating conditions, and after sterol efflux, a membrane alteration necessary for capacitation. The complete lack of G(M1) diffusion to the post-acrosomal plasma membrane (PAPM) in live cells argued against the transient confinement zone model. However, within seconds after cessation of sperm motility, G(M1) dramatically redistributed several microns from the acrosomal sub-domain to the post-acrosomal, non-raft sub-domain. This redistribution was not accompanied by movement of sterols, and was induced by the pentameric cholera toxin subunit B (CTB). These data argued against a lipid-lipid interaction model for sub-domain maintenance. Although impossible to rule out a lipid shell model definitively, mice lacking caveolin-1 maintained segregation of both sterols and G(M1), arguing against a role for lipid shells surrounding caveolin-1 in sub-domain maintenance. Scanning electron microscopy of sperm freeze-dried without fixation identified cytoskeletal structures at the sub-domain boundary. Although drugs used to disrupt actin and intermediate filaments had no effect on the segregation of G(M1), we found that disulfide-bonded proteins played a significant role in sub-domain segregation. Together, these data provide an example of membrane sub-domains extreme in terms of size and stability of lipid segregation, and implicate a protein-based membrane compartmentation mechanism.     

All you need to know about p53

A novel protein-based approach has been developed to import a cell-permeable form of the site-specific recombinase Cre into undifferentiated and terminally differentiated mammalian cells     

Free Testosterone Drives Cancer Aggressiveness: Evidence from US Population Studies

Cancer incidence and mortality are higher in males than in females, suggesting that some gender-related factors are behind such a difference. To analyze this phenomenon the most recent Surveillance, Epidemiology and End Results (SEER) database served to access cancer survival data for the US population. Patients with gender-specific cancer and with limited information were excluded and this fact limited the sample size to 1,194,490 patients. NHANES III provided the distribution of physiologic variables in US population (n = 29,314). Cox model and Kaplan-Meier method were used to test the impact of gender on survival across age, and to calculate the gender-specific hazard ratio of dying from cancer five years following diagnosis. The distribution of the hazard ratio across age was then compared with the distribution of 65 physiological variables assessed in NHANES III. Spearman and Kolmogorov-Smirnov test assessed the homology. Cancer survival was lower in males than in females in the age range 17 to 61 years. The risk of death from cancer in males was about 30% higher than that of females of the same age. This effect was present only in sarcomas and epithelial solid tumors with distant disease and the effect was more prominent in African-Americans than Caucasians. When compared to the variables assessed in the NHANES III study, the hazard ratio almost exactly matched the distribution of free testosterone in males; none of the other analyzed variables exhibited a similar homology. Our findings suggest that male sex hormones give rise to cancer aggressiveness in patients younger than 61 years.