Ciliary neurotrophic factor blocks rod photoreceptor differentiation from postmitotic precursor cells in vitro

The development of photoreceptors in the mammalian retina is thought to be controlled by extrinsic signals. We have shown previously that ciliary neurotrophic factor (CNTF) potently inhibits photoreceptor differentiation in cultures of rat retina. The present study analyzes which developmental processes are affected by CNTF. Rod differentiation as determined by opsin and recoverin immunocytochemistry was effectively blocked by CNTF and leukemia inhibitory factor, but not by other neurotrophic agents tested. CNTF did not influence proliferation, cell death, or survival, and had no effect on the downregulation of nestin immunoreactivity in progenitor cells. Opsin-positive rods could be reverted to an opsin-negative state initially, but became unresponsive to CNTF later. No compensatory increase in the number of other cell types was observed. Application of neutralizing antibodies against CNTF revealed that rod development was partially blocked by an endogenous CNTF-like molecule in control cultures. Our results suggest that CNTF can act as a specific negative regulator of rod differentiation. Its action on photoreceptor precursor cells could serve to synchronize the maturation of photoreceptors, which are born over an extended period of time. Together with other stimulatory signals, CNTF may thus control the temporally and numerically correct integration of photoreceptors into the retinal network.     

Synthesis of medium-chain fatty acids and their incorporation into triacylglycerols by cell-free fractions fromCuphea embryos

During their rapid maturation period, seeds of Cuphea wrightii A. Gray mainly accumulate medium-chain fatty acids (C₈ to C₁₄) in their storage lipids. The rate of lipid deposition (40–50 mg·d^–1·(g fresh weight)^–1) is fourfold higher than in seeds of Cuphea racemosa (L. f.) Spreng, which accumulate long-chain fatty acids (C₁₆ to C₁₈). Measurements of the key enzymes of fatty-acid synthesis in cell-free extracts of seeds of different maturities from Cuphea wrightii show that malonyl-CoA synthesis may be a triggering factor for the observed high capacity for fatty-acid synthesis. Experiments on the incorporation of [1-¹⁴C]acetate into fatty acids by purified plastid preparations from embryos of Cuphea wrightii have demonstrated that the biosynthesis of medium-chain fatty acids (C₈ to C₁₄) is localized in the plastid. Thus, in the presence of cofactors for lipid synthesis (ATP, NADPH, NADH, acyl carrier protein, and sn-glycerol-3-phosphate), purified plastid fractions predominantly synthesized free fatty acids, 30% of which were of medium chain length. Transesterification of the freshly synthesized fatty acids to coenzyme A and recombination with the microsomal fraction of the embryo homogenate induced triacylglycerol synthesis. It also stimulated fatty-acid synthesis by a factor 2–3 and increased the relative amount of medium-chain fatty acids bound to triacylglycerols, which corresponded to about 60–80% in this lipid fraction.Abbreviations ACP acyl carrier protein - FW fresh weight This work was supported by the Bundesminister für Forschung und Technologie. The authors thank S. Borchert for her suggestions for plastid preparation.     

Identification of a novel senolytic agent,navitoclax, targeting the Bcl‐2 family of anti‐apoptotic factors

Clearing senescent cells extends healthspan in mice. Using a hypothesis‐driven bioinformatics‐based approach, we recently identified pro‐survival pathways in human senescent cells that contribute to their resistance to apoptosis. This led to identification of dasatinib (D) and quercetin (Q) as senolytics, agents that target some of these pathways and induce apoptosis preferentially in senescent cells. Among other pro‐survival regulators identified was Bcl‐xl. Here, we tested whether the Bcl‐2 family inhibitors, navitoclax (N) and TW‐37 (T), are senolytic. Like D and Q, N is senolytic in some, but not all types of senescent cells: N reduced viability of senescent human umbilical vein epithelial cells (HUVECs), IMR90 human lung fibroblasts, and murine embryonic fibroblasts (MEFs), but not human primary preadipocytes, consistent with our previous finding that Bcl‐xl siRNA is senolytic in HUVECs, but not preadipocytes. In contrast, T had little senolytic activity. N targets Bcl‐2, Bcl‐xl, and Bcl‐w, while T targets Bcl‐2, Bcl‐xl, and Mcl‐1. The combination of Bcl‐2, Bcl‐xl, and Bcl‐w siRNAs was senolytic in HUVECs and IMR90 cells, while combination of Bcl‐2, Bcl‐xl, and Mcl‐1 siRNAs was not. Susceptibility to N correlated with patterns of Bcl‐2 family member proteins in different types of human senescent cells, as has been found in predicting response of cancers to N. Thus, N is senolytic and acts in a potentially predictable cell type‐restricted manner. The hypothesis‐driven, bioinformatics‐based approach we used to discover that dasatinib (D) and quercetin (Q) are senolytic can be extended to increase the repertoire of senolytic drugs, including additional cell type‐specific senolytic agents.     

A hidden beneficial: biology of the tick‐wasp Ixodiphagus hookeri in Germany

The parasitic wasp Ixodiphagus hookeri parasitizes hard ticks and is therefore considered as a potential candidate for biological control of ticks. However, there are still considerable gaps of knowledge about the biology of I. hookeri, especially for European populations. Thus, the present study was performed to assess important life‐history parameters of the parasitoid in Germany. Field studies accomplished in three successive years revealed that unfed Ixodes ricinus nymphs are infested by the parasitoid at a low but constant rate of 1.9–3.8% and that adult wasps are present only during a short period in late summer. The mean developmental time of wasps in I. ricinus nymphs ranged from 28 to 70 days under constant laboratory conditions and was prolonged in the second half of the year. Bioassays on parasitization and host preference behaviour showed that unfed nymphs of the host species I. ricinus are significantly preferred in experiments, in which unfed and engorged larvae as well as fully engorged nymphs were offered as alternatives. The marsh tick Dermacentor reticulatus was not accepted as an alternative host. Our data show that the investigated I. hookeri populations differ markedly from populations in other regions of the world in many aspects. The adaptation of different strains to local conditions explains the limited success of imported strains in earlier biological control attempts and highlights the importance of doing research to enhance the control potential of native strains.     

A cytogenetic study of recurrent abortion

Summary Chromosomal analysis was performed in a series of 27 women with repeated spontaneous abortions and in 16 of the husbands. In one woman a balanced translocation of the type 13q/15q was detected, and a pericentric inversion of a chromosome A₁ was found in the husband of another proband. The significance of these findings is discussed.

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Zusammenfassung Bei 27 Frauen mit wiederholten Aborten und bei 16 zugehörigen Ehemännern wurden Chromosomenanalysen durchgeführt. Bei einer Probandin fand sich eine balancierte Translokation 13q/15q, bei dem Ehemann einer anderen Probandin eine perizentrische Inversion eines Chromosoms A₁. Die Bedeutung der Befunde wird diskutiert.

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The study was supported by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 35.     

GM1 binding-deficient exotoxin is a potent noninflammatory broad spectrum intradermal immunoadjuvant

Intradermal (i.d.) immunization is a promising route of vaccine administration. Suitable i.d. adjuvants are important to increase vaccine efficacy in poorly responding populations such as the elderly or for dose-sparing strategies in the face of vaccine shortages. Bacterial exotoxins, such as Escherichia coli heat-labile enterotoxin (LT), exert strong immunostimulatory effects through binding to monosialoganglioside (GM1) cell surface receptors; however, injection is hampered by local inflammation. We demonstrate that the injection of LT formulations deficient in GM1 binding by mutation (LT(G33D)) or in vitro ligand coupling does not cause localized edema and inflammation in mice, yet these formulations retain potent adjuvant activity by enhancing functional Ab and cellular immune responses to coadministered Ags. Complete protection against in vivo lethal tetanus toxin challenge and the induction of Ag-specific CTL responses capable of killing target cells in vivo indicated in vivo efficacy of the induced immune responses. LT(G33D) proved superior to standard alum adjuvant regarding the magnitude and breadth of the induced immune responses. Immunizations in complex ganglioside knockout mice revealed a GM1-independent pathway of LT adjuvanticity. Immunostimulation by i.d. LT(G33D) is explained by its ability to induce migration of activated APCs to the proximal draining lymph nodes. LT(G33D) is a promising candidate adjuvant for human trials of parenteral vaccines in general and for current i.d. vaccine development in particular.