Interleukin 3 enhances cytotoxic T lymphocyte development and class I major histocompatibility complex "re-presentation" of exogenous antigen by tumor-infiltrating antigen-presenting cells.

We show that interleukin 3 (IL-3) enhances the generation of tumor-specific cytotoxic T lymphocytes (CTLs) through the stimulation of host antigen-presenting cells (APCs). The BALB/c (H-2d) spontaneous lung carcinoma line 1 was modified by gene transfection to express ovalbumin as a nominal "tumor antigen" and to secrete IL-3, a cytokine enhancing myeloid development. IL-3-transfected tumor cells are less tumorigenic than the parental cell line, and tumor-infiltrating lymphocytes isolated from these tumors contain increased numbers of tumor-specific CTLs. By using B3Z86/90.14 (B3Z), a unique T-cell hybridoma system restricted to ovalbumin/H-2b and implanting the tumors in (BALB/c x C57BL/6)F1 (H-2d/b) mice, we demonstrate that the IL-3-transfected tumors contain an increased number of a rare population of host cells that can process and "re-present" tumor antigen to CTLs. Electron microscopy allowed direct visualization of these host APCs, and these studies, along with surface marker phenotyping, indicate that these APCs are macrophage-like. The identification of these cells and their enhancement by IL-3 offers a new opportunity for tumor immunotherapy.

Impaired fetal T cell development and perinatal lethality in mice lacking the cAMP response element binding protein

CREB, the cAMP response element binding protein, is a key transcriptional regulator of a large number of genes containing a CRE consensus sequence in their upstream regulatory regions. Mice with a hypomorphic allele of CREB that leads to a loss of the CREBα and Δ isoforms and to an overexpression of the CREBβ isoform are viable. Herein we report the generation of CREB null mice, which have all functional isoforms (CREBα, β, and Δ) inactivated. In contrast to the CREBαΔ mice, CREB null mice are smaller than their littermates and die immediately after birth from respiratory distress. In brain, a strong reduction in the corpus callosum and the anterior commissures is observed. Furthermore, CREB null mice have an impaired fetal T cell development of the αβ lineage, which is not affected in CREBαΔ mice on embryonic day 18.5. Overall thymic cellularity in CREB null mice is severely reduced affecting all developmental stages of the αβ T cell lineage. In contrast γδ T cell differentiation is normal in CREB mutant mice.

Both apolipoprotein E and A-I genes are present in a nonmammalian vertebrate and are highly expressed during embryonic development

Apolipoprotein E (apoE) is associated with several classes of plasma lipoproteins and mediates uptake of lipoproteins through its ability to interact with specific cell surface receptors. Besides its role in cardiovascular diseases, accumulating evidence has suggested that apoE could play a role in neurodegenerative diseases, such as Alzheimer disease. In vertebrates, apoA-I is the major protein of high-density lipoprotein. ApoA-I may play an important role in regulating the cholesterol content of peripheral tissues through the reverse cholesterol transport pathway. We have isolated cDNA clones that code for apoE and apoA-I from a zebrafish embryo library. Analysis of the deduced amino acid sequences showed the presence of a region enriched in basic amino acids in zebrafish apoE similar to the lipoprotein receptor-binding region of human apoE. We demonstrated by whole-mount in situ hybridization that apoE and apoA-I genes are highly expressed in the yolk syncytial layer, an extraembryonic structure implicated in embryonic and larval nutrition. ApoE transcripts were also observed in the deep cell layer during blastula stage, in numerous ectodermal derivatives after gastrulation, and after 3 days of development in a limited number of cells both in brain and in the eyes. Our data indicate that apoE can be found in a nonmammalian vertebrate and that the duplication events, from which apoE and apoA-I genes arose, occurred before the divergence of the tetrapod and teleost ancestors. Zebrafish can be used as a simple and useful model for studying the role of apolipoproteins in embryonic and larval nutrition and of apoE in brain morphogenesis and regeneration.

Impairment of axonal development and of synaptogenesis in hippocampal neurons of synapsin I-deficient mice.

Synapsin I, the most abundant of all neuronal phosphoproteins, is enriched in synaptic vesicles. It has been hypothesized to regulate synaptogenesis and neurotransmitter release from adult nerve terminals. The evidence for such roles has been highly suggestive but not compelling. To evaluate the possible involvement of synapsin I in synaptogenesis and in the function of adult synapses, we have generated synapsin I-deficient mice by homologous recombination. We report herein that outgrowth of predendritic neurites and of axons was severely retarded in the hippocampal neurons of embryonic synapsin I mutant mice. Furthermore, synapse formation was significantly delayed in these mutant neurons. These results indicate that synapsin I plays a role in regulation of axonogenesis and synaptogenesis.

Temporal and Spatial Patterns of Accumulation of the Transcript of Myo-Inositol-1-Phosphate Synthase and Phytin-Containing Particles during Seed Development in Rice1

Myo-inositol-1-phosphate (I[1]P) synthase (EC 5.5.1.4) catalyzes the reaction from glucose 6-phosphate to I(1)P, the first step of myo-inositol biosynthesis. Among the metabolites of I(1)P is inositol hexakisphosphate, which forms a mixed salt called phytin or phytate, a storage form of phosphate and cations in seeds. We have isolated a rice (Oryza sativa L.) cDNA clone, pRINO1, that is highly homologous to the I(1)P synthase from yeast and plants. Northern analysis of total RNA showed that the transcript accumulated to high levels in embryos but was undetectable in shoots, roots, and flowers. In situ hybridization of developing seeds showed that the transcript first appeared in the apical region of globular-stage embryos 2 d after anthesis (DAA). Strong signals were detected in the scutellum and aleurone layer after 4 DAA. The level of the transcript in these cells increased until 7 DAA, after which time it gradually decreased. Phytin-containing particles called globoids appeared 4 DAA in the scutellum and aleurone layer, coinciding with the localization of the RINO1 transcript. The temporal and spatial patterns of accumulation of the RINO1 transcript and globoids suggest that I(1)P synthase directs phytin biosynthesis in rice seeds.

Ultraviolet-B Radiation Effects on Water Relations, Leaf Development, and Photosynthesis in Droughted Pea Plants1

The effects of ultraviolet-B (UV-B) radiation on water relations, leaf development, and gas-exchange characteristics in pea (Pisum sativum L. cv Meteor) plants subjected to drought were investigated. Plants grown throughout their development under a high irradiance of UV-B radiation (0.63 W m−2) were compared with those grown without UV-B radiation, and after 12 d one-half of the plants were subjected to 24 d of drought that resulted in mild water stress. UV-B radiation resulted in a decrease of adaxial stomatal conductance by approximately 65%, increasing stomatal limitation of CO2 uptake by 10 to 15%. However, there was no loss of mesophyll light-saturated photosynthetic activity. Growth in UV-B radiation resulted in large reductions of leaf area and plant biomass, which were associated with a decline in leaf cell numbers and cell division. UV-B radiation also inhibited epidermal cell expansion of the exposed surface of leaves. There was an interaction between UV-B radiation and drought treatments: UV-B radiation both delayed and reduced the severity of drought stress through reductions in plant water-loss rates, stomatal conductance, and leaf area.