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J A Kessler

Publications and source records attributed to J A Kessler.

At least 55 records · Page 3Linked to original sources
PubMed1996

Interleukin-7 is trophic for embryonic neurons and is expressed in developing brain.

Interleukin-7 (IL7) is a hematopoietic cytokine with critical functions in both B- and T-lymphocyte development. In this study, we find that IL7 exhibits trophic properties in the developing brain as well. Treatment of cultures of embryonic brain with exogenous IL7 increases neuronal survival and results in greater numbers of cells manifesting neurite outgrowth. As demonstrated with single-cell cultures, IL7 acts directly to promote neuronal survival. Expression of the mRNA encoding the high-affinity IL7 receptor (IL7R) is observed in vitro in neurons as well as in subventricular zone progenitor cells. Phosphorylation of p59fyn, which is activated by IL7 in pre-B cells and is thought to be important in neural development, occurs rapidly following IL7 treatment of cultured embryonic neurons. Additionally, the expression of c-myc mRNA, which is modulated by IL7 in lymphoid cells, is upregulated by IL7 in the same CNS cultures. Finally, the messenger RNAs encoding IL7 and IL7R are expressed in vivo in developing brain. The direct neurotrophic properties of IL7 combined with the expression of ligand and receptor in developing brain suggest that IL7 may be a neuronal growth factor of physiological significance during central nervous system (CNS) ontogeny.

Animals↗
PubMed1996

Microglial lineage species are expressed in mammalian epidermal growth factor-generated embryonic neurospheres.

The epigenetic signals and progenitor cell species involved in progressive neural maturation in the mammalian brain are poorly understood. Although these complex developmental issues can be examined in cultures of generative zone progenitor cells, analysis of signaling relationships in complex progenitor cell systems requires the meticulous definition of the cellular complement at each developmental stage. The presence of microglia within the generative zone cultures would further complicate these developmental analyses. Utilizing the microglial markers Griffonia simplicifolia B4 isolectin, carbocyanine dye-acetylated low density lipoprotein, F4/80, and Mac-1 we now report the presence of microglia within cultures of late embryonic murine epidermal growth factor-derived generative zone progenitor cells. Cytokine treatment of serially passaged epidermal growth factor-generated neurospheres altered the phenotype of the microglia in culture. Macrophage colony-stimulating factor treatment promoted the expression of spindle-shaped microglia, whereas granulocytemacrophage colony-stimulating factor treatment promoted the elaboration of flat and amoeboid microglia. Treatment with microglial-conditioned medium or 10% non-heat inactivated fetal calf serum led to an increased complement of both phenotypes. Microglia could be generated from single isolated neurospheres, and there were differences in the number of microglial lineage species obtained from distinct oligopotent progenitor cells, raising the possibility that a complement of this cellular lineage may be derived from a progenitor cell present within the generative zones. These observations indicate that microglia are present within the generative zone progenitor cell system, and this system thus represents an important experimental resource to examine the progenitor cell maturation and the origin of the microglial lineage.

Animals↗
PubMed1996

Neurotrophic factors in the treatment of peripheral neuropathy.

Peripheral neuropathies are common and frequently debilitating disorders which may include various subpopulations of motor, sensory or autonomic neurons depending on the underlying aetiology. They are likely to be the first group of neurological disorders to be successfully treated with growth factors since peripheral nerves are accessible to proteins given systemically. Preclinical and ongoing clinical trials of nerve growth factor (NGF) suggest that it will be useful for the treatment of diabetic, toxic and compressive sensory neuropathies. At appropriate doses NGF has no significant side effects in humans. Since NGF administration to mature animals stimulates synthesis of brain-derived neurotrophic factor and perhaps other neurotrophins in peripheral nerves, the spectrum of neuropathies treatable with NGF is wider than might be predicted. Preclinical studies suggest that insulin-like growth factor 1 (IGF-1) will be useful for the treatment of mixed motor and sensory neuropathies. For example, IGF-1 treatment can prevent the experimental motor and sensory neuropathies caused by the antitumour drugs, vincristine and cisplatin. Other neurotrophic factors have also shown promise in preclinical trials. The successful use of growth factors in the treatment of peripheral neuropathies may provide the first true therapy for this previously untreatable and devastating group of neurological disorders.

Animals↗
PubMed1996

Nerve growth factor regulates the expression of brain-derived neurotrophic factor mRNA in the peripheral nervous system.

Neurotrophins are profound regulators of neuronal survival in the developing peripheral nervous system and are synthesized by peripheral neurons themselves both during development and in maturity. Neuronal neurotrophin expression may be importantly related to survival of mature neurons, both in normal and pathological states. We show here that brain-derived neurotrophic factor (BDNF) gene expression in dorsal root ganglia is strongly stimulated in vivo by another neurotrophin, nerve growth factor (NGF). Furthermore, colocalization studies show that many BDNF-expressing sensory neurons also express trk A, the high-affinity NGF receptor. These results demonstrate a novel regulatory mechanism for neurotrophin gene expression and suggest a paracrine function for neurotrophins in mature animals.

Animals↗
PubMed1996

TNF alpha inhibits Schwann cell proliferation, connexin46 expression, and gap junctional communication.

Schwann cell responses to nerve injury are stimulated, in part, by inflammatory cytokines. This study compares changes in the phenotype of cultured Schwann cells after exposure to the cytokine tumor necrosis factor (TNF)-alpha or the mitogen neu differentiation factor (NDF)-beta. TNF alpha inhibited proliferation in a dose-dependent manner without altering Schwann cell survival. TNF alpha also reduced both gap junctional conductance and Lucifer yellow dye coupling between Schwann cells. Moreover, both Po and glial fibrillary acidic protein (GFAP) immunoreactivity were reduced. By contrast, NDF beta initially had little effect on cell division although it reduced junctional coupling within 8 h. However, by 48 h, NDF beta stimulated proliferation with a concomitant increase in coupling. Dividing Schwann cells (BrdU+) were preferentially dye coupled compared to nondividing cells, indicating an association between proliferation and coupling. Moreover, cultured Schwann cells expressed connexin46 mRNA and protein, and changes in the levels of the protein correlated with the degree of proliferation and coupling. The data thus provide evidence for cytokine-induced modulation of Schwann cell antigenic phenotype, proliferation, and gap junction properties. These observations suggest that enhanced gap junctional communication among Schwann cells after nerve injury could help to coordinate cellular responses to the injury, and that TNF alpha may be a signal which terminates proliferation as well as junctional communication.

Animals↗
PubMed1996

Altered connexin expression after peripheral nerve injury.

The identification of connexin32 (Cx32) in myelinating Schwann cells and the association of Cx32 mutations with peripheral neuropathies suggest a functional role for gap junction proteins in the nerve. However, after nerve crush injury, Cx32 expression dramatically decreases in Schwann cells in the degenerating region, returning to control levels at newly formed nodes of Ranvier and Schmidt-Lantermann incisures by 30 days. The present study examined increases in expression of other connexins that occur after peripheral nerve injury. A 56/58-kDa connexin46 (Cx46) protein species was detected in adult rat sciatic nerve, along with very low levels of Cx46 mRNA. However, by 3 days after crush injury, coincident with changes in Schwann cell phenotype, Cx46 mRNA rapidly increased in the degenerating regions. Additionally, the 56/58-kDa Cx46 protein species present in adult nerve decreased and a 53-kDa Cx46 species, which was also present in cultured Schwann cells, became apparent. Connexin43 (Cx43) mRNA and protein, which was localized to perineurial cells in adult nerve, dramatically increased in endoneurial fibroblasts in the crush and distal regions by 3 days, coincident with macrophage infiltration. By 12 days after injury, Cx43 decreased and was comparable to normal nerve. These results suggest that enhanced expression of Cx46 and Cx43, by nonneuronal cells, may be important for the injury and regenerative responses of peripheral nerves.

Animals↗
PubMed1996

Bone morphogenetic proteins promote astroglial lineage commitment by mammalian subventricular zone progenitor cells.

The epigenetic signals that regulate lineage development in the embryonic mammalian brain are poorly understood. Here we demonstrate that a specific subclass of the transforming growth factor beta superfamily, the bone morphogenetic proteins (BMPs), cause the selective, dose-dependent elaboration of the astroglial lineage from murine embryonic subventricular zone (SVZ) multipotent progenitor cells. The astroglial inductive effect is characterized by enhanced morphological complexity and expression of glial fibrillary acidic protein, with concurrent suppression of neuronal and oligodendroglial cell fates. SVZ progenitor cells express transcripts for the appropriate BMP-specific type I and II receptor subunits and selective BMP ligands, suggesting the presence of paracrine or autocrine developmental signaling pathways (or both). These observations suggest that the BMPs have a selective role in determining the cell fate of SVZ multipotent progenitor cells or their more developmentally restricted progeny.

Animals↗
PubMed1996

The consequence of passive administration of an anti-human immunodeficiency virus type 1 neutralizing monoclonal antibody before challenge of chimpanzees with a primary virus isolate.

The anti-gp41 virus neutralizing monoclonal antibody 2F5 was infused into chimpanzees, which were then given an intravenous challenge with a primary human immunodeficiency virus type I (HIV-1) isolate. In two control animals, the infection was established immediately, as evidenced by positive cell-associated DNA PCR and serum RNA PCR tests within 1 week, seroconversion by 4 weeks, and development of lymphadenopathy in this acute phase. Serum RNA PCR tests were negative in one of the two antibody-infused animals until week 8 and in the other antibody-infused animal until week 12; both animals seroconverted at week 14. The peak of measurable virus-specific serum RNA was delayed until week 16 in one antibody-infused animal. Virus-specific RNA in the other animal did not reach levels comparable to those in the other animals through 1 year of follow-up studies. Virus was isolated from the week 16 blood sample from one infused animal. Virus was not isolated from peripheral blood of the second animal but was isolated from lymph node cells taken at week 36. The infection of untreated chimpanzees with this primary isolate appears robust. Use of this isolate should widen the scope of possible experiments in the chimpanzee model. This antibody infusion study indicates that neutralizing antibody, when present at the time of challenge, affects the timing and level of infection and remains influential after it can no longer be detected in the peripheral circulation. It is possible that preexisting, neutralizing antibodies (passively administered or actively elicited) affect the course of acute-phase virus replication in humans. It remains to be established whether these immunologically mediated early effects will influence the course of HIV-1 disease.

Amino Acid Sequence↗
PubMed1996

CSF-1 deficiency in mice results in abnormal brain development.

Colony stimulating factor-1 (CSF-1) was initially identified as a growth factor for mononuclear phagocytes. This study examines the role of CSF-1 in the development of the central nervous system (CNS). CSF-1 treatment of neurons cultured from embryonic brain promoted survival and process outgrowth in a dose-dependent manner. By contrast, CSF-1 treatment of neurons cultured from the osteopetrotic (op/op) mouse, a null mutant for CSF-1, promoted significantly less process outgrowth, suggesting that there are neural abnormalities in op/op animals. Nuclease protection assays were used to determine whether CSF-1 and its receptor are expressed at times appropriate to regulate neural development. Both CSF-1 and its receptor are expressed in developing mouse brain, with a unique pattern of CSF-1 mRNA splice variant expression encoding secreted, and not membrane-bound, growth factor. To determine whether brain function is altered by null mutation of CSF-1, op/op mice were examined using electrophysiologic assays. Brainstem auditory and visual evoked potentials were both abnormal in op/op mice. Further, intracortical recordings revealed aberrant neuronal function within visual cortex and alterations in the cortical circuitry that balances excitation and inhibition. Daily CSF-1 injection of postnatal op/op mice largely rescued the abnormal neural phenotype, confirming that the absence of CSF-1 during development is responsible for the abnormalities. The effects of CSF-1 on cultured embryonic neural cells, the developmentally appropriate expression of CSF-1 and its receptor, and the neurological abnormalities in op/op mice suggest a role for CSF-1 in brain development.

Animals↗
PubMed1995

LIF-and IL-1 beta-mediated increases in substance P receptor mRNA in axotomized, explanted or dissociated sympathetic ganglia.

Regulation of substance P receptor (SPR) mRNA was examined in the rat sympathetic superior cervical ganglion (SCG) in vitro and in vivo after axotomy. Interleukin-1 beta (IL-1 beta) treatment of explanted ganglia elevated levels of SPR mRNA. By contrast, dissociated cultures of purified sympathetic neurons, purified fibroblasts, and purified Schwann cells each expressed only low levels of SPR mRNA, and treatment with the cytokine did not alter levels of the receptor mRNA. Treatment of Schwann cell or fibroblast cultures with leukemia inhibitory factor (LIF) also did not alter SPR mRNA. However, treatment of pure neuronal cultures with LIF significantly elevated levels of the receptor mRNA. Further, SPR mRNA increased in pure sympathetic neurons cultured in the presence of conditioned medium from IL-1 beta treated fibroblasts or Schwann cells; this effect was blocked in the presence of LIF antibody. This suggests that the stimulatory effects of IL-1 beta on SPR mRNA in explants is mediated by LIF release. Axotomy of the SCG in vivo resulted in a significant increase in LIF mRNA. Further, axotomy resulted in a significant increase in SPR mRNA, suggesting that LIF may mediate the increase in SPR mRNA. In view of the known effects of substance P (SP) on inflammatory responses, these observations suggest that coordinated expression of SP and SPR mRNA in neurons after nerve injury may participate in inflammatory and repair processes in the ganglion.

Animals↗
PubMed1995

Enhancing the avidity of a human recombinant anti-HIV-1 monoclonal antibody through oligomerization.

The oligomerization by chemical cross-linking of a recombinant human antiviral monoclonal antibody (MAb), r447-1, and its characterization are described. This MAb binds to an epitope residing in the hypervariable V3 region of the envelope protein (gp120/160) of HIV-1. A dimeric form of this MAb displays enhanced avidity and was found to be capable of neutralizing a greater variety of lymphoid cell culture-adapted HIV-1 variants and HIV-1 primary isolates than its monomeric form. The superior binding and breadth of reactivity of this antibody suggests it may have utility as a therapeutic and/or prophylactic agent, if it possesses an appropriate safety and immunogenicity profile.

Antibodies, Monoclonal↗
PubMed1995

Differentiation of hippocampal progenitor cells in vitro: temporal expression of intercellular coupling and voltage- and ligand-gated responses.

Mechanisms regulating the expression of intercellular coupling, development of membrane excitability, and cellular responsiveness to neurotransmitters during neuronal ontogeny are largely unknown. To define the temporal relationship among these properties during neurogenesis, murine embryonic hippocampal progenitor cells immortalized with a temperature-sensitive allele of the SV40 large T-antigen were examined during successive stages of neuronal differentiation in vitro using patch clamp, dye coupling, and Ca2+ imaging techniques. Electrotonic and dye coupling between untreated neuroblasts were frequent in cells maintained at the temperature (39 degrees C) nonpermissive for T-antigen expression. However, as neuroblasts differentiated into neurons under the influence of interleukin-7 added alone or concurrently with transforming growth factor-alpha after basic fibroblast growth factor, both junctional conductance and the extent of dye coupling progressively decreased. Voltage-dependent inward currents were present within 2 to 6 days after differentiating treatments began. During intermediate developmental stages (3 to 5 days in culture), cells became responsive to GABA (> or = 100 microM) but not to glutamate, glycine, or to acetylcholine (< or = 1 mM), as indicated by [Ca2+]i measurements and patch clamp recordings. In contrast, voltage- and ligand-gated responses but not electronic coupling were frequently observed in mature neuronal primary cultures. Together, these results indicate that certain cytokines may orchestrate the progressive expression of functional neuronal phenotypes in vitro, in which the gradual disappearance of intercellular coupling parallels the onset of voltage-dependent responses and both of which precede the expression of neurotransmitter chemosensitivity.

Animals↗
PubMed1995

Kappa opioid receptors participate in nerve growth factor-induced hyperalgesia.

It has recently been observed that nerve growth factors induces the rapid onset of thermal hyperalgesia, and the more delayed onset of mechanical hyperalgesia when administered to mature rats. Though several mechanisms have been proposed to explain this phenomenon, it is still not well understood. Previous studies have shown that nerve growth factor can directly excite nociceptive sensory ganglion neurons in culture via activation of kappa excitatory opioid receptors. The possible involvement of these excitatory opioid receptors in mediating the hyperalgesia was investigated. Nerve growth factor-induced thermal hyperalgesia in rodents was prevented by co-administration of the non-selective opiate antagonist naloxone, as well as by the kappa-selective antagonist nor-binaltorphimine. Addition of the long-acting opioid antagonist, naltrexone, partially prevented mechanical hyperalgesia. Administration of low dose dynorphin to mice (a selective kappa-receptor agonist) mimicked the hyperalgesia effects of nerve growth factor. Opiate antagonists and anti-nerve growth factor antibody both interfered with Freund's adjuvant-induced inflammatory hyperalgesia. Altogether, these observations suggest that activation of excitatory opioid receptors plays a role in mediating nerve growth factor-induced hyperalgesia and that, in turn, nerve growth factor contributes to the hyperalgesia associated with inflammatory states. Since opioid receptor antagonists are well tolerated clinically, they may be useful for patients receiving nerve growth factor as part of ongoing trials of the factor in peripheral neuropathy.

Animals↗
PubMed1995

A human monoclonal antibody to a complex epitope in the V3 region of gp120 of human immunodeficiency virus type 1 has broad reactivity within and outside clade B.

We have used virus neutralization and antibody-binding techniques to define the epitope for a human monoclonal antibody, designated 19b, within the V3 region of the gp120 surface glycoprotein of human immunodeficiency virus type 1. Unusually, the 19b epitope encompasses residues on both flanks of the V3 loop. However, 19b binding to gp120 is independent of sequences at the crown of the V3 loop, provided that they are compatible with the formation of a type II beta turn that is presumably necessary to juxtapose the antigenic residues on the V3 flanks. By comparing the V3 sequences of virus gp120s able and unable to bind 19b, we were able to define the canonical 19b epitope as -I----G--FY-T, where residues at the positions indicated by the gaps do not contribute directly to the 19b-binding site. A few conservative substitutions at the more critical residues are also compatible with 19b binding. Inspection of V3 sequences in the human immunodeficiency virus database indicated that the canonical 19b epitope is well conserved among isolates from the North American-European clade B and also among clade E isolates from Thailand and clade F isolates from Brazil. A minority of gp120s from clades A and C also possess the 19b epitope. Consistent with the theoretical predictions of its cross-clade reactivity, 19b was found to bind to gp120s from clades A, B, C, E, and F in immunoassays. However, 19b was not able to reduce the infectivity of primary viruses from clades A, E, and F that were predicted to possess the 19b epitope and only modestly reduced the infectivity of a clade C virus at low input virus concentrations. Cross-clade neutralization via V3-directed antibodies may, therefore, be difficult, even if the antibodies show broad reactivities in binding assays and the viruses theoretically possess the relevant binding site.

Amino Acid Sequence↗
PubMed1995

A vaccine-elicited, single viral epitope-specific cytotoxic T lymphocyte response does not protect against intravenous, cell-free simian immunodeficiency virus challenge.

Protection against simian immunodeficiency virus (SIV) challenge was assessed in rhesus monkeys with a vaccine-elicited, single SIV epitope-specific cytotoxic T-lymphocyte (CTL) response in the absence of SIV-specific antibody. Strategies were first explored for eliciting an optimal SIV Gag epitope-specific CTL response. These studies were performed in rhesus monkeys expressing the major histocompatibility complex (MHC) class I gene Mamu-A*01, a haplotype associated with a predominant SIV CTL epitope mapped to residues 182 to 190 of the Gag protein (p11C). We demonstrated that a combined modality immunization strategy using a recombinant Mycobacterium bovis BCG-SIV Gag construct for priming, and peptide formulated in liposome for boosting, elicited a greater p11C-specific CTL response than did a single immunization with peptide-liposome alone. Vaccinated and control monkeys were then challenged with cell-free SIVmne by an intravenous route of inoculation. Despite a vigorous p11C-specific CTL response at the time of virus inoculation, all monkeys became infected with SIV. gag gene sequencing of the virus isolated from these monkeys demonstrated that the established viruses had no mutations in the p11C-coding region. Thus, the preexisting CTL response did not select for a viral variant that might escape T-cell immune recognition. These studies demonstrate that a potent SIV-specific CTL response can be elicited by combining live vector and peptide vaccine modalities. However, a single SIV Gag epitope-specific CTL response in the absence of SIV-specific antibody did not provide protection against a cell-free, intravenous SIV challenge.

Animals↗
PubMed1995

Turnover of circulating virion RNA and of cell-associated viral DNA reflects active viral replication in human immunodeficiency virus type 1-infected individuals.

A quantitative assessment of human immunodeficiency virus type 1 turnover in patient cell-free virion and infected-cell compartments under the dynamic conditions imposed by an effective antiviral therapy was performed. The turnover was rapid, and following a temporal lag, the extent of viral population replacement was eventually similar in both compartments. Each compartment therefore reflects considerable active virus replication.

Antiviral Agents↗
PubMed1995

Transforming growth factor-beta 1 and forskolin modulate gap junctional communication and cellular phenotype of cultured Schwann cells.

Following peripheral nerve injury, Schwann cells undergo a series of cellular alterations that are thought to assist the regenerative process. Some of these changes are stimulated by the local release of cytokines and mitogenic factors. To test the hypothesis that cytokine regulation of gap junctional communication between cells helps to coordinate Schwann cell responses, cultured rat Schwann cells, from sciatic nerve, were utilized to study phasic changes induced by transforming growth factor-beta 1 (TGF beta 1), a cytokine released after nerve injury, or forskolin in combination with bovine pituitary extract (F-BPE), known for its mitogenic effects in vitro. In mitotically quiescent cultures, TGF beta 1 significantly decreased both electrical and dye coupling mediated by gap junctions. Single-channel analysis revealed that cultured Schwann cells expressed gap junctions with two distinct channel sizes of about 26 pS and 44 pS. TGF beta 1 treatment reduced coupling due to both populations of channels. Exposure to TGF beta 1 had a minimal effect on proliferation but significantly altered cellular morphology; cell bodies became flattened with multipolar processes within 72 hr. Additionally, immunolabeling for both low-affinity nerve growth factor receptor (L-NGFR) and glial fibrillary acidic protein (GFAP) were reduced, suggesting increased differentiation. In contrast, treatment with F-BPE significantly enhanced both electrical and dye coupling and stimulated Schwann cell proliferation. Additionally, cell bodies became more rounded with polarized, cytoplasmic processes contiguously aligned with adjacent cells. F-BPE reduced immunolabeling for L-NGFR but increased expression of both GFAP and the major peripheral myelin protein, P0. These data indicate that TGF beta 1 and/or F-BPE induce phenotypic changes in Schwann cells, including the coordinated regulation of proliferation and modulation of intercellular communication via gap junctions. Such mechanisms may underlie phasic responses that orchestrate recovery from nerve injury, indicating that Schwann cell gap junctions may be critical for peripheral nerve function.

Animals↗