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F Kirchhoff

Publications and source records attributed to F Kirchhoff.

82 records · Page 5Linked to original sources
PubMed1990

Highly sialylated N-CAM is expressed in adult mouse optic nerve and retina.

The localization of the neural cell adhesion molecule (N-CAM) and its highly sialylated form, which is prevalent in young tissues and has therefore been called embryonic neural cell adhesion molecule, was studied in the developing and adult mouse optic nerve and retina immunohistologically and immunochemically. At embryonic and early postnatal ages, neuroblasts and young postmitotic neurons, Müller cells and astrocytes in the retina, and retinal ganglion cell axons and all glial cells in the optic nerve express highly sialylated neural cell adhesion molecule. Beginning with the third postnatal week, highly sialylated neural cell adhesion molecule disappears from retinal ganglion cell axons in the optic nerve and from neuronal cell bodies and processes in the retina. In addition, it is not detectable on oligodendrocytes in 3-week-old animals. However, highly sialylated neural cell adhesion molecule continues to be expressed in the adult optic nerve and retina by astrocytes and Müller cells. On these cells it is only absent from cell membranes contacting basal lamina. Weakly sialylated neural cell adhesion molecule, in contrast, is expressed by all cell types of retinal and optic nerve during development and in the adult. The loss of highly sialylated neural cell adhesion molecule from neurons and oligodendrocytes must therefore be considered as a cell type-specific conversion of the so-called embryonic to the adult form of neural cell adhesion molecule and does not simply reflect the disappearance of neural cell adhesion molecule from these cells. Weakly sialylated neural cell adhesion molecule, however, is absent from outer segments of photoreceptor cells and, as is the case for the highly sialylated form, from glial cell surfaces contacting basal lamina. Thus, the expression of highly sialylated neural cell adhesion molecule by pre- and postmitotic neurons and by oligodendrocytes is restricted mainly to the period of histogenetic events in retina and optic nerve, i.e. cell division, cell migration, dendritic and axonal growth and synaptogenesis. In addition to the observation that this form of neural cell adhesion molecule is less adhesive than the weakly sialylated, adult form, it is likely that highly sialylated neural cell adhesion molecule plays an important role during dynamic morphogenetic events. Furthermore, the expression of highly sialylated neural cell adhesion molecule by astrocytes and Müller cells in adult optic nerves and retinae suggests some histogenetically plastic functions for these cells in the adult mouse visual system.

Animals↗
PubMed1990

A novel proviral clone of HIV-2: biological and phylogenetic relationship to other primate immunodeficiency viruses.

Infectious molecular clones of the human immunodeficiency virus type 2 (HIV-2) will be valuable tools for the study of regulatory gene functions and the development of an animal model for the human acquired immunodeficiency syndrome (AIDS). To this end, we have cloned and sequenced a novel HIV-2 isolate, HIV-2BEN. One clone, designated MK6, is infectious for various human T-cell lines and for human and macaque peripheral blood lymphocytes (PBL), allowing molecular studies of HIV-2 infection and replication. Since MK6 is highly cytopathic in MT-2 and Molt-4 clone 8 cells, antiviral agents and neutralizing sera may be tested. Cluster analysis of HIV-1, HIV-2, and simian immunodeficiency virus (SIV) env and gag genes revealed that HIV-2BEN yielded the earliest node of phylogenetic divergence for all reported HIV-2 sequences. Noise analysis showed that, with the current data, no specification of any branching order can be made among the four groups of primate lentiviruses, HIV-1, HIV-2/SIVSMM/MAC, SIVAGM, and SIVMND.

Animals↗
PubMed1990

Isolation and characterization of HIV-2ben obtained from a patient with predominantly neurological defects.

A HIV-2 strain named HIV-2ben was isolated from peripheral blood lymphocytes of a patient who, since 1984, had developed neurological symptoms such as Raynaud's syndrome, followed by paresthesia of extremities and ataxia, and finally paraparesis of the legs and incontinence. This new isolate could be distinguished from HIV-2rod by antibody-binding epitopes, peptide maps of core p24 and p18 polypeptides and restriction endonuclease cleavage pattern.

Animals↗
PubMed1990

Experimental infection of macaques with HIV-2ben, a novel HIV-2 isolate.

Ten rhesus (Macaca mulatta) and six fascicularis (Macaca fascicularis) macaques were inoculated with HIV-2ben using three different virus preparations and two routes of inoculation. Thirteen of the 16 inoculated macaques seroconverted 2-6 weeks after infection. Three M. mulatta remained seronegative. The seroconverted animals developed antibody titres from 80 to 40,000. Their antibodies reacted with gp160 and gp130 and, in varying degrees, with gp32 and core proteins. Virus could be re-isolated from 11 of the 16 macaques. M. mulatta were transiently viraemic 6-14 weeks after infection whereas all M. fascicularis were persistently viraemic 2-7 weeks after infection onwards. In the 6-18 months after infection one M. mulatta lost 20% of its body weight and two M. fascicularis showed transient lymphadenopathy and splenomegaly; the other animals remained clinically normal. A re-isolated virus from a M. mulatta was indistinguishable from the inoculated HIV-2ben by genomic restriction enzyme analysis. M. mulatta and M. fascicularis are infectable by a single intravenous injection of cell-free HIV-2ben. Persistent viraemia in M. fascicularis represents a valuable and reliable parameter for studies on antivirals and vaccines.

Animals↗
PubMed1990

Genomic divergence of an HIV-2 from a German AIDS patient probably infected in Mali.

The complete nucleotide sequence of an HIV-2 isolate derived from a German AIDS patient with predominantly neurological symptoms is reported. The HIV-2BEN sequence is highly divergent from those of previously described HIV-2 and SIV strains. Evolutionary tree analysis of eight HIV-2 sequences reveals the existence of three HIV-2 groups. HIV-2BEN belongs to a group with two isolates from Ghana and The Gambia. Based on a comparison of HIV-2BEN with six HIV-2 isolates, SIVsmm and SIVmac, the variability of the structural env and gag proteins is similar within the HIV-2/SIVsmm/mac and HIV-1 groups. In contrast, the regulatory HIV-1 proteins are more highly conserved than those from HIV-2 strains. Multiple sequence alignments reveal that some domains of the envelope and regulatory proteins are well conserved among HIV-1, HIV-2/SIVsmm/mac, SIVagm and SIVmnd. The identification of conserved domains within the external glycoprotein could help to develop broadly active vaccines.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Immunohistological localization of the adhesion molecules L1, N-CAM, and MAG in the developing and adult optic nerve of mice.

The localization of the cell adhesion molecules L1, neural cell adhesion molecule (N-CAM), and myelin-associated glycoprotein (MAG) was studied immunohistologically at the light and electron microscopic levels and immunochemically in the developing and adult mouse optic nerve and retina. The neural adhesion molecule L1 is strongly expressed on the shafts of fasciculating unmyelinated axons at all ages studied from embryonic day 15 through adulthood. Growth cones of retinal ganglion cell axons were weakly L1-positive or L1-negative when contacting glial cells. Unmyelinated axons were not only L1-positive when contacting each other but also when contacting glia, whereas contacts between glial cells were L1-negative at all developmental unmyelinated retinal nerve fiber layer or in the unmyelinated optic nerve head became L1-negative when enwrapped by myelin in the optic nerve proper. At all stages of development N-CAM showed profuse labeling on fasciculating axons, growth cones, and their contact sites with glial cells as well as contacts between glial cells. In contrast to L1, axons remained N-CAM-positive when becoming myelinated. Sometimes, N-CAM was found in compact myelin. However, N-CAM was absent from glial surfaces contacting basement membranes at the interface to meninges, blood vessels, and the vitreous body of the eye. MAG was first detectable intracellularly in oligodendrocytes associated with the endoplasmic reticulum and Golgi apparatus before it became apparent at the cell surface. There it was present on oligodendrocytes prior and during the first stages of ensheathment of axons, both on cell body and processes. After formation of compact myelin MAG remained strongly expressed periaxonally and was only weakly detectable in noncompacted myelin including inner mesaxon and paranodal loops. None of the adhesion molecules was detectable on extracellular matrix, in the meninges, or on endothelial cells. Immunochemical analysis of antigen expression at different developmental stages was in agreement with the immunohistological data. We infer from these observations that L1 is involved in stabilization not only of axon-axon, but also axon-glia contacts, while the more dynamic structure of the growth cone generally expresses less L1. A differential expression of L1 along the course of an axon--being present on its unmyelinated, but absent on its myelinated part--further supports the notion that L1 may be involved in the stabilization of axonal fascicles but not of axon-myelin contacts.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1989

A protein kinase activity is associated with and specifically phosphorylates the neural cell adhesion molecule L1.

The neural cell adhesion molecule L1 is a phosphorylated integral membrane glycoprotein that is recovered from adult mouse brain by immunoaffinity chromatography as a set of polypeptides with apparent molecular masses of 200, 180, 140, 80, and 50 kilodaltons (L1-200, L1-180, L1-140, L1-80, and L1-50, respectively). In the present study, we show that two kinase activities are associated with immunopurified L1: One specifically phosphorylates L1-200 and L1-80 but not L1-180, L1-140, or L1-50. This pattern of phosphorylation corresponds to the one described for L1 after metabolic phosphate incorporation into cultures of cerebellar cells. In both cases, serine is the main amino acid that is labeled by radioactive phosphate. The kinase activity is not activated by Ca2+, calmodulin, phosphatidylserine, diolein, cyclic AMP, or cyclic GMP, a result suggesting that the enzyme is distinct from Ca2+/calmodulin-dependent kinases, from protein kinase C, or from cyclic AMP/cyclic GMP-dependent kinases and may belong to the independent kinase group. The other kinase phosphorylates only casein but not L1, utilizes GTP as well as ATP, and is strongly inhibited by heparin. Because the primary structure of the L1 protein does not contain consensus sequences characteristic for known kinases, we believe that the catalytic activities detectable in immunopurified L1 are due to kinases that are strongly enough associated with L1 to withstand the stringent purification procedures.

Animals↗
PubMedDate not supplied

Idiotypic vaccine for treatment of human B-cell lymphoma. Construction of IgG variable regions from single malignant B cells.

Immunoglobulin idiotypes (Id) of malignant B cells represent highly specific markers which can be used for vaccination. PCR-amplification of immunoglobulin genes enables the rapid production of large amounts of Id vaccines. However, the separate amplification and subsequent recombination of heavy and light chains can lead to a loss of the relevant Id. To preserve the original chain pairs, we used single malignant B cells derived from an immunocytoma patient. Cytoplasm was extracted and the mRNA transcribed into cDNA. The VH and VL genes were then amplified by PCR and cloned into a vector for expression in E. coli. Id production was checked using an anti-Id mouse monoclonal Ab raised against the patient's tumor-specific IgG. One out of 3 constructs expressed the relevant Id. Analysis of the first 31 light chain residues revealed an identical sequence for the malignant B cells' IgG and the recombinant Id construct. Exchange of either the heavy or light chain with an unrelated chain resulted in loss of the Id. An unrelated sequence derived from the c-myc protein is coupled to the Id vaccine. The lymphoma patient was shown to have Abs to the c-myc sequence. This sequence therefore, increases the Id+ Ab's antigenicity. CD spectroscopy showed an alpha-helical structure for the c-myc epitope. In conclusion, a B-cell lymphoma autovaccine was produced containing immunogenic sequences that do not alter the steric conformation of the tumor-specific Id.

Animals↗