Showing papers by "Urban Lendahl published in 1996"

Fetal ventral mesencephalon of human and rat origin maintained in vitro and transplanted to 6-hydroxydopamine-lesioned rats gives rise to grafts rich in dopaminergic neurons

Abstract: Free-floating roller tube cultures of human fetal (embryonic age 6-10 weeks post-conception) and rat fetal (embryonic day 13) ventral mesencephalon were prepared. After 7-15 days in vitro, the mesencephalic tissue cultures were transplanted into the striatum of adult rats that had received unilateral injections of 6-hydroxydopamine into the nigrostriatal bundle 3-5 weeks prior to transplantation. Graft survival was assessed in tyrosine hydroxylase (TH)-immunostained serial sections of the grafted brains up to post-transplantation week 4 for the human fetal xenografts and post-transplantation week 11 for the rat fetal allografts. D-amphetamine-induced rotation was monitored up to 10 weeks after transplantation in the allografted animals and compared with that of lesioned-only control animals. All transplanted animals showed large, viable grafts containing TH-immunoreactive (ir) neurons. The density of TH-ir neurons in the human fetal xenografts and in rat fetal allografts was similar. A significant amelioration of the amphetamine-induced rotation was observed in the animals that received cultured tissue allografts. These results promote the feasibility of in vitro maintenance of fetal human and rat nigral tissue prior to transplantation using the free-floating roller tube technique.

Cerebrospinal Fluid of Newborn Infants Contains a Deglycosylated Form of the Intermediate Filament Nestin

Abstract: Nestin is an intermediate filament protein found in CNS progenitor cells. Nestin reappears in CNS tumor cells and reactive astrocytes after CNS injury. In this study we investigated whether nestin could be detected in the cerebrospinal fluid (CSF) of newborn infants and whether expression levels change with gestational age (GA) and/or brain injury. Using Western blot analysis, we examined the expression of nestin in the CSF of newborn infants (GA 25-42 wk) with asphyxia (n = 14), periventricular leukomalacia and peri(intra)ventricular hemorrhage (n = 7), and in a control group (n = 11). Protein extract from the periventricular brain tissue of a 1-wk-old infant was also analyzed. Nestin was detected in all the CSF samples and in the protein extract from the periventricular brain tissue. Although the CSF levels of nestin expression did not change with increasing GA, the asphyxia group had significantly lower levels of nestin in the CSF. An unexpected finding was that brain-derived nestin had an apparent molecular mass of approximately 240 kD, whereas all analyzed CSF samples contained two nestin-immunoreactive proteins at 200 and 220 kD. Experimental deglycosylation of the 240-kD form reduced the molecular mass to 220 kD, indicating that nestin undergoes a specific deglycosylation upon release into the CSF.

Elevated expression levels of an Ig transgene in mice links the IgH 3' enhancer to the regulation of IgH expression.

Abstract: To delineate the role of the IgH 3' enhancer in the regulation of Ig heavy (IgH) chain gene expression, mice harbouring rearranged IgH transgenes, with (PSV>3) and without (PSvyi) this element, were produced. RNA and protein analysis from the different transgenic lines revealed a 5to 7-fold increase in the expression level of the transgene containing the IgH 3' enhancer. This difference is also reflected at the protein level in hybridomas generated from the two transgenic lines. The elevation of transgene Ig expression In the PSV|x3 lines is restricted to activated B lymphocytes, an observation which is further supported by the ability of this transgene to be reactivated upon immunization. Interestingly, although the up-regulation of transgene expression In PSVn3 animals Is considerably higher in comparison to the PSV^.1 animals, a significant response is still observed in the PSVp.1 mice. We speculate therefore that the IgH locus is subject to transcriptional modification in late B cell development Our data suggest that both the E^ enhancer and the IgH 3' enhancer can up-regulate transgene Ig expression, but the presence of the 3' enhancer results in elevated levels of transgene Ig production. It therefore appears that the expression level of IgH genes is subject to transcriptlonal modification during B cell development. Additional control elements are most likely required for optimal Ig expression, since our expression data from the transgene in PSV|i3 animals are incompatible with endogenous Ig levels. The recent identification of additional enhancer elements in the far 3' end of the IgH locus supports this possibility. The data presented here provides a sound basis for the production of high levels of mAb, possibly tailored to suit the needs of the researcher.

H-2Dp transgene alters natural killer cell specificity at the target and effector cell levels. Comparison with an H-2Dd transgene.

Abstract: The expression of MHC class I molecules is an important determinate of natural killer (NK) cell specificity. The missing self hypothesis proposes that NK cells express receptors for self-MHC class I molecules so that target cells that share MHC class I alleles with the NK cells are not killed by those NK cells. However, some effector cells fail to kill some allogeneic target cells suggesting that shared motifs between different MHC class I alleles can interact with the effector cell class I receptors and prevent lysis. We have used transgenic mice to critically assess whether different MHC class I alleles can exert common influences on NK cell specificity at the host/effector and target cell levels. The specificity of NK cells have been compared between C57BL/6 (H-2b) mice and B6DP (H-2b, H-2Dp) and D8 (H-2b, H-2Dd) transgenic mice. The data indicate that H-2Dp and H-2Dd confer similar protection and specific lysis, such that NK cells from either of the H-2Dp or H-2Dd transgenic mice kill nontransgenic target cells yet they do not kill either of the transgenic target cells. The expression of an H-2Dp transgene also provides protection for C57BL/6 lymphoblasts from allogeneic BALB/c (H-2d) NK cells. Furthermore, H-2Dp and H-2Dd transgenic target cells are lysed to a similar extent by H-2k effector cells. These data suggest that H-2Dp and H-2Dd may be able to inhibit the same NK cell population. This may occur through a shared motif recognized by the same receptor, or different motifs recognized by different, but co-expressed receptors.

Influence of glycosylphosphatidylinositol‐linked H‐2Dd molecules on target cell protection and natural killer cell specificity in transgenic mice

Abstract: The expression of certain major histocompatibility complex (MHC) class I ligands on target cells is one important determinate of their susceptibility to lysis by natural killer (NK) cells. NK cells express receptor molecules that bind to MHC class I. Upon binding to their MHC class I ligand, the NK cell is presumed to receive a signal through its receptor that inhibits lysis. It is unclear what role the MHC class I molecules of the effector and target cells play in signaling to the NK cell. We have investigated the role of the cytoplasmic and transmembrane domains of MHC class I molecules by producing a glycosylphosphatidylinositol (GPI)-linked H-2Dd molecule. The GPI-linked H-2Dd molecule is recognized by H-2Dd-specific antibodies and cytotoxic T lymphocytes. Expression of the GPI-linked H-2Dd molecule on H-2b tumor cells resulted in protection of the tumor cells after transplantation into D8 mice (H-2b, H-2Dd) from rejection by NK cells. In addition, NK cells from mice expressing the GPI-linked H-2Dd molecule as a transgene were able to kill nontransgenic H-2b lymphoblast target cells. The GPI-linked MHC class I molecule was able to alter NK cell specificity at the target and effector cell levels. Thus, the expression of the cytoplasmic and transmembrane domains of MHC class I molecules are not necessary for protection and alteration of NK cell specificity.

Expression of Trk Receptors during Cartilage Differentiation

Abstract: The products of the tyrosine kinase trk family of proto-oncogenes bind neurotrophins (NTFs) and are components of their high-affinity receptors. The trk gene encodes for the TrkA transmembrane glycoprotein, which functions as a receptor for nerve growth factor (NGF). Brain-derived neurotrophic factor (BDNF) and neurotrophin-4 (NT-4) are the preferred ligands for TrkB. and neurotrophin-3 (NT-3) for TrkC (reviewed in reference 1). The presence of Trk receptors in nonneuronal cells of developing tissues and organs indicates that these molecules may play a role in embryonic development that would be distinct from a neurotrophic function. Cartilage development involves mesoderm-derived cells (chondrocytes) that contribute to appositional growth of the limb skeleton. Chondrocytes synthesize macromolecules characteristic of cartilage such as collagen type I1 and sulfated proteoglycans. The majority of studies dealing with cartilage cell differentiation have been carried out on mesenchymal cells isolated from limb buds.* However, the molecular mechanisms regulating cartilage formation are not filly understood. In the present study we analyzed the expression of Trk receptors during mouse limb development in vivo and in micromass cultures in vitro. Because little is known about their regulation, we studied the effects of various growth factors on expression of Trk receptors in vitro. F 1 (CBA x NMRI) and Balb C mouse embryos (E 10-El 8) were used. Immunohistochemistry was performed according to Mitsiadis et aL3 Fivepm sections were incubated with TrkA (B. B. Rudkin), TrkB (Santa Cruz Biotechnology, USA), and TrkC (D. Martin-Zanca) affinity purified antibodies against the extracellular domain of the receptors, and cTrk (Santa Cruz Biotechnology, USA) an-

Mouse Serrate-1 and Notch genes differ in their response to signaling molecules during odontogenesis

Abstract: Serrate--like genes encode transmembrane ligands to Notch receptors and control cell fate decisions during development. This signaling system appears to function in most multicellular organisms since Notch receptors and Delta/Serrate ligands have been found in both invertebrates and vertebrates (Artavanis-Tsakonas et aI., 1995). Highly conserved homologue of the Drosophila Serrate have been recently identified in rat (Lindsell et aI., 1995) and in mouse. Jagged, the rat Serrate-I homologue, is believed to participate in Notch signaling as it seems to activate Notch in myoblasts in culture, as reflected by an inhibition of their differentiation (Lindsell et aI., 1995). Little is known about regulation of vertebrate Notch receptors and ligands. As a step towards addressing this issue, we have analysed the expression and regulation of the mouse Serrate-1 (Ser-1) gene during tooth development. Tooth develops as a result of sequential and reciprocal interactions between neural crest-derived mesenchyme and the oral ectoderm. Particular emphasis was given to tissue interactions, since it was previousry shown that such interactions and exposure to specific signaling molecules are critical in organizing the expression of Notch receptors during odontogenesis (Mitsiadis et aI., 1995),