Biomedical subjects

K A Roth

Publications and source records attributed to K A Roth.

At least 37 records · Page 2Linked to original sources

PubMed2000

Mechanisms of programmed cell death in the developing brain.

Programmed cell death (apoptosis) is an important mechanism that determines the size and shape of the vertebrate nervous system. Recent gene-targeting studies have indicated that homologs of the cell-death pathway in the nematode Caenorhabditis elegans have analogous functions in apoptosis in the developing mammalian brain. However, epistatic genetic analysis has revealed that the apoptosis of progenitor cells during early embryonic development and apoptosis of postmitotic neurons at later stage of brain development have distinct roles and mechanisms. These results provide new insight on the significance and mechanism of neural cell death in mammalian brain development.

Animals↗

PubMed2000

Rnx deficiency results in congenital central hypoventilation.

The genes Tlx1 (Hox11), Enx (Hox11L2, Tlx-2) and Rnx (Hox11L2, Tlx-3) constitute a family of orphan homeobox genes. In situ hybridization has revealed considerable overlap in their expression within the nervous system, but Rnx is singularly expressed in the developing dorsal and ventral region of the medulla oblongata. Tlx1-deficient and Enx-deficient mice display phenotypes in tissues where the mutated gene is singularly expressed, resulting in asplenogenesis and hyperganglionic megacolon, respectively. To determine the developmental role of Rnx, we disrupted the locus in mouse embryonic stem (ES) cells. Rnx deficient mice developed to term, but all died within 24 hours after birth from a central respiratory failure. The electromyographic activity of intercostal muscles coupled with the C4 ventral root activity assessed in a medulla-spinal cord preparation revealed a high respiratory rate with short inspiratory duration and frequent apnea. Furthermore, a coordinate pattern existed between the abnormal activity of inspiratory neurons in the ventrolateral medulla and C4 motorneuron output, indicating a central respiratory defect in Rnx mice. Thus, Rnx is critical for the development of the ventral medullary respiratory centre and its deficiency results in a syndrome resembling congenital central hypoventilation.

Abnormalities, Multiple↗

PubMed2000

Amyloid beta-induced neuronal death is bax-dependent but caspase-independent.

Fibrillar amyloid beta (Abeta) peptides are major constituents of senile plaques in Alzheimer disease (AD) brain and cause neuronal apoptosis in vitro. Bax and caspase-3 have been implicated in the pathogenesis of AD and are components of a well-defined molecular pathway of neuronal apoptosis. To determine whether Abeta-induced neuronal apoptosis involves bax and/or caspase-3 activation, we examined the effect of Abeta on wild-type, bax-deficient, and caspase-3-deficient telencephalic neurons in vitro. In wild-type cultures, Abeta produced time- and concentration-dependent caspase-3 activation, apoptotic nuclear changes, and neuronal death. These neurotoxic effects of Abeta were not observed in bax-deficient cultures. Caspase-3 deficiency, or pharmacological inhibition of caspase activity, prevented caspase-3 activation and blocked the appearance of apoptotic nuclear features but not Abeta-induced neuronal death. Neither calpain inhibition nor microtubule stabilization with Taxol protected telencephalic neurons from Abeta-induced caspase activation or apoptosis. These results have potential implications regarding the underlying pathophysiology of AD and towards AD treatment strategies.

Amino Acid Chloromethyl Ketones↗

PubMed2000

Caspase regulation of neuronal progenitor cell apoptosis.

Programmed cell death (apoptosis) of both proliferating neuroblasts and postmitotic neurons is essential for normal nervous system development. To study the molecular regulation of apoptosis in neuronal progenitor cells, we developed a flow cytometric assay capable of distinguishing between viable, apoptotic, and necrotic cell populations. Incubation of freshly dissociated telencephalic cells from gestational day 12-13 mouse embryos with either cytosine arabinoside (AraC) or staurosporine caused a marked increase in the percentage of apoptotic cells. Both drugs induced caspase-3 activation, as determined by in vitro cleavage of a caspase-3 substrate and immunocytochemical detection of activated caspase-3. Treatment of telencephalic cells with the broad caspase inhibitor BAF, blocked caspase-3 activation and protected cells against both AraC and staurosporine-induced apoptotic death. These results indicate that neuronal progenitors possess a caspase-dependent apoptotic pathway, the activation of which may regulate neuronal progenitor cell numbers in vivo.

Animals↗

PubMed2000

Dual fluorescent in situ hybridization and immunohistochemical detection with tyramide signal amplification.

To understand the biological relationships among various molecules, it is necessary to define the cellular expression patterns of multiple genes and gene products. Relatively simple methods for performing multi-label immunohistochemical detection are available. However, there is a paucity of techniques for dual immunohistochemical (IHC) and mRNA in situ hybridization (ISH) detection. The recent development of improved non-radioactive detection systems and simplified ISH protocols has prompted us to develop a tyramide signal amplification method for sequential multi-label fluorescent ISH and IHC detection in either frozen or paraffin-embedded tissue sections. We used this method to examine the relationship between glial cell line-derived neurotrophic factor receptor alpha2 (GFRalpha2) mRNA expression and IHC localization of its co-receptor Ret in the trigeminal ganglion of postnatal Day 0 mice. We found that approximately 70% of Ret-immunoreactive neurons possessed GFRalpha2 mRNA and virtually all GFRalpha2-expressing neurons contained Ret-immunoreactive protein. Finally, we used paraformaldehyde-fixed, paraffin-embedded sections and a monoclonal antibody against neuron-specific nuclear antigen (NeuN) to demonstrate the neuronal specificity of GFRalpha2 mRNA expression in adult mouse brain. This multi-labeling technique should be applicable to a wide variety of tissues, antibodies, and probes, providing a relatively rapid and simple means to compare mRNA and protein localization.

Animals↗

PubMed1999

Bid-deficient mice are resistant to Fas-induced hepatocellular apoptosis.

The protein Bid is a participant in the pathway that leads to cell death (apoptosis), mediating the release of cytochrome c from mitochondria in response to signals from 'death' receptors known as TNFR1/Fas on the cell surface. It is a member of the proapoptotic Bcd-2 family and is activated as a result of its cleavage by caspase 8, one of a family of proteolytic cell-death proteins. To investigate the role of Bid in vivo, we have generated mice deficient for Bid. We find that when these mice are injected with an antibody directed against Fas, they nearly all survive, whereas wild-type mice die from hepatocellular apoptosis and haemorrhagic necrosis. About half of the Bid-deficient animals had no apparent liver injury and showed no evidence of activation of the effector caspases 3 and 7, although the initiator caspase 8 had been activated. Other Bid-deficient mice survived with only moderate damage: all three caspases (8 and 37) were activated but their cell nuclei were intact and no mitochondrial cytochrome c was released. We also investigated the effects of Bid deficiency in cultured cells treated with anti-Fas antibody (hepatocytes and thymocytes) or with TNFalpha. (fibroblasts). In these Bid-/- cells, mitochondrial dysfunction was delayed, cytochrome c was not released, effector caspase activity was reduced and the cleavage of apoptosis substrates was altered. This loss-of-function model indicates that Bid is a critical substrate in vivo for signalling by death-receptor agonists, which mediates a mitochondrial amplification loop that is essential for the apoptosis of selected cells.

Animals↗

PubMed1999

Cellular immune responses are essential for the development of Helicobacter felis-associated gastric pathology.

The bacteria Helicobacter pylori is a major human pathogen that infects over half of the world's population. Infection initiates a series of changes in the gastric mucosa, beginning with atrophic gastritis and leading in some patients to peptic ulcer disease, mucosa-associated lymphomas, and gastric adenocarcinoma. Although this cascade of events clearly occurs, little is known about the role of the host immune response in disease progression. We have utilized the C57BL/6 Helicobacter felis mouse model to critically analyze the role of the adaptive immune response in the development of Helicobacter-associated gastric pathology. Infection of B and T cell-deficient RAG-1-/- mice or T cell-deficient TCRbetadelta-/- mice with H. felis resulted in high levels of colonization, but no detectable gastric pathology. Conversely, infection of B cell-deficient microMT mice resulted in severe gastric alterations identical with those seen in immunocompetent C57BL/6-infected mice, including gastric mucosal hyperplasia and intestinal metaplasia. These results demonstrate that the host T cell response is a critical mediator of Helicobacter-associated gastric pathology, and that B cells and their secreted Abs are not the effectors of the immune-mediated gastric pathology seen after H. felis infection. These results indicate that in addition to specific Helicobacter virulence factors, the host immune response is an important determinant of Helicobacter-associated disease.

Animals↗

PubMed1999

Neurokinin B- and substance P-like immunoreactivity are co-localized in enteric nerves of rat ileum.

The tachykinins (TKs) substance P (SP), neurokinin A (NKA), and neurokinin B (NKB) have conserved C-terminal sequences and mediate similar physiological responses by activating neurokinin receptors found on neural and smooth muscle cells. Many enteric nerves express preprotachykinin A (PPT A) mRNA and synthesize SP and NKA. However, it is unclear if NKB is synthesized in enteric neurons as many antibodies developed against NKB also recognize other TKs. Therefore, the cellular distribution of NKB-like-immunoreactivity (NKB-ir) in rat ileum was examined using selective antisera raised against either synthetic Cys10-NKB or peptide 2 (P2), a non-tachykinergic peptide sequence in NKB precursor protein. NKB-ir and P2-ir had a similar distribution in varicose nerve fibers in submucosal and myenteric ganglia and almost all ganglia contained immunoreactive nerves. Few submucosal or myenteric neuronal somata contained strong immunoreactivity. Preabsorption of NKB or P2 antisera with their respective cognate peptides, but not with other TK peptides, abolished specific immunostaining. Finally, co-localization of NKB-/P2-ir with SP-ir suggested that most NKB-/P2-ir nerve fibers contain SP-ir, but some SP-ir nerves do not contain detectable NKB-/P2-ir. These results indicate that PPT B products P2 and NKB are localized in a subpopulation of enteric nerves containing TKs encoded by PPT A. Stimulation of these nerves may release NKB to activate local neurokinin receptors.

Animals↗

PubMed1999

In situ immunodetection of neuronal caspase-3 activation in Alzheimer disease.

The mechanism by which cells die in Alzheimer disease (AD) is unknown. Several investigators speculate that much of the cell loss may be due to apoptosis, a highly regulated form of programmed cell death. Caspase-3 is a critical effector of neuronal apoptosis and may be inappropriately activated in AD. To address this possibility, we examined cortical and hippocampal brain sections from AD patients, as well as 2 animal models of AD, for in situ evidence of caspase-3 activation. We report here that senile plaques and neurofibrillary tangles in the AD brain are not associated with caspase-3 activation. Furthermore, amyloid beta (A beta) deposition in the APPsw transgenic mouse model of AD does not result in caspase-3 activation despite the ability of A beta to induce caspase-3 activation and neuronal apoptosis in vitro. AD brain sections do, however, exhibit caspase-3 activation in hippocampal neurons undergoing granulovacuolar degeneration. Our data suggests that caspase-3 does not have a significant role in the widespread neuronal cell death that occurs in AD, but may contribute to the specific loss of hippocampal neurons involved in learning and memory.

Aged↗

PubMed1998

Apaf1 (CED-4 homolog) regulates programmed cell death in mammalian development.

The cytosolic protein APAF1, human homolog of C. elegans CED-4, participates in the CASPASE 9 (CASP9)-dependent activation of CASP3 in the general apoptotic pathway. We have generated by gene trap a null allele of the murine Apaf1. Homozygous mutants die at embryonic day 16.5. Their phenotype includes severe craniofacial malformations, brain overgrowth, persistence of the interdigital webs, and dramatic alterations of the lens and retina. Homozygous embryonic fibroblasts exhibit reduced response to various apoptotic stimuli. In situ immunodetection shows that the absence of Apaf1 protein prevents the activation of Casp3 in vivo. In agreement with the reported function of CED-4 in C. elegans, this phenotype can be correlated with a defect of apoptosis. Our findings suggest that Apaf1 is essential for Casp3 activation in embryonic brain and is a key regulator of developmental programmed cell death in mammals.

Alleles↗

PubMed1998

Trophic support promotes survival of bcl-x-deficient telencephalic cells in vitro.

Survival of immature neurons is regulated by Bcl-xL, as targeted disruption of bcl-x significantly increases cell death in vivo and in vitro. Death of cultured bcl-x-deficient and wild-type telencephalic cells can be prevented by fetal calf serum or chemically-defined medium (ITS), suggesting trophic factors in these media potentiate survival through a pathway independent of Bcl-xL. Addition of trophic factors to basal medium revealed that insulin and insulin-like growth factors (IGFs), but not other trophic factors, reduced apoptosis of wild-type and bcl-x-deficient telencephalic cells. Antibodies raised against IGF-I receptors and wortmannin both attenuated the effects of IGF-I, indicating survival was mediated by IGF-I receptors and phosphatidylinositol 3'-kinase signaling, whereas effects of ITS were only partially reduced by these agents. The survival promoting effects of ITS were reduced in cells lacking both bcl-x and bcl-2, indicating Bcl-2 plays a supportive role to Bcl-xL in maintaining telencephalic cell survival. Furthermore, the ratio of expression of the pro-apoptotic bax gene to the anti-apoptotic bcl-2 gene was reduced in bcl-x-deficient cultures grown in ITS, suggesting that the interaction between these bcl-2 family members may, in part, regulate a Bcl-xL independent survival pathway. Finally, the pro-apoptotic bad gene does not appear to play a role in these interactions as targeted disruption of bad did not alter apoptosis in telencephalic cultures.

Animals↗

PubMed1998

In situ immunodetection of activated caspase-3 in apoptotic neurons in the developing nervous system.

Activation of caspase-3 requires proteolytic processing of the inactive zymogen into p18 and p12 subunits. We generated a rabbit polyclonal antiserum, CM1, which recognizes the p18 subunit of cleaved caspase-3 but not the zymogen. CM1 demonstrated an apparent specificity for activated caspase-3 by specifically immunolabelling only apoptotic but not necrotic cortical neurons in vitro. In the embryonic mouse nervous system, CM1 immunoreactivity was detected in neurons undergoing programmed cell death and was markedly increased in Bcl-xL-deficient embryos and decreased in Bax-deficient embryos. CM1 immunoreactivity was absent in the nervous system of caspase-3-deficient mouse embryos and in neurons cultured from caspase-3-deficient mice. Along with neuronal somata, extensive neuritic staining was seen in apoptotic neurons. These studies indicate that caspase-3 is activated during apoptosis in the developing nervous system in vivo and that CM1 is a useful reagent for its in situ detection.

Animals↗

PubMed1998

Neurotrophin sensitivity of prevertebral and paravertebral rat sympathetic autonomic ganglia.

Prevertebral and paravertebral sympathetic autonomic ganglia respond differently to a large number of experimental and clinical insults. The selective involvement of subpopulations of sympathetic neurons may reflect differences in their response to neurotrophic substances. To test this hypothesis, we investigated the response of prevertebral and paravertebral rat sympathetic ganglia to selected neurotrophic substances in vivo and in vitro and identified the ganglionic distribution of neurons expressing high affinity neurotrophin receptor mRNAs. Dissociated cultures of embryonic prevertebral and paravertebral ganglionic neurons showed comparable responses to NGF deprivation and only small differences in their response to rescue with other trophic substances. In situ hybridization studies of adult rat sympathetic ganglia using probes specific for the high-affinity neurotrophin receptor transcripts trks A, B, and C demonstrated that neurons in both prevertebral and paravertebral sympathetic ganglia express predominantly trkA receptors in vivo. In addition, increased tyrosine hydroxylase (TOH) activity was induced only by doses of neurotrophic substances that activate trkA and showed only small differences between neonatal prevertebral and paravertebral ganglia. Although small differences in the sensitivity of pre- and paravertebral sympathetic neurons to various neurotrophins have been identified in our studies, they are unlikely, in isolation, to explain major differences in the sensitivity of these ganglia to neuropathologic processes.

Aging↗

PubMed1997

Bax deficiency prevents the increased cell death of immature neurons in bcl-x-deficient mice.

The intracellular balance between pro- and antiapoptotic members of the Bcl-2 gene family is thought to regulate cell death. Targeted disruption of bcl-x, a death repressing member, causes massive cell death of immature neurons in the developing mouse CNS, whereas targeted disruption of bax, a proapoptotic member, blocks the death of specific populations of sympathetic and motor neurons. In the present study, mice deficient in both Bcl-xL and Bax (bcl-x-/-/bax-/-) are used to examine the relative significance and potential interactions of Bcl-xL and Bax during early CNS development. bcl-x-/-/bax-/- mice demonstrate greatly reduced levels of apoptosis both in vivo and in vitro compared with the CNS of Bcl-xL-deficient mice, as assessed by histology and terminal deoxytransferase-mediated deoxyuridine triphosphate nick end-labeling. Bax-deficient mice, however, contain occasional apoptotic cells in the developing CNS, and cultures of bax-deficient telencephalic cells demonstrate similar levels of apoptosis as wild-type cultures. These results suggest that Bax critically interacts with Bcl-xL to regulate survival of immature neurons, but indicate that other cell death regulating proteins, in addition to Bcl-xL and Bax, also function during CNS development.

Animals↗

PubMed1997

Enx (Hox11L1)-deficient mice develop myenteric neuronal hyperplasia and megacolon.

The isolated homeobox gene Enx (Hox11L1) is expressed in enteric neurons innervating distal ileum, and proximal and distal colon. Enx-deficient mice develop megacolon with massive distension of the proximal colon. The number of myenteric ganglia, total neurons per ganglion, and NADPH diaphorase presumptive inhibitory neurons per ganglion are increased in the proximal and distal colon, but decreased in the distal ileum of all Enx-/- mice. Enx-/- mice provide a model for human neuronal intestinal dysplasia (NID), in which myenteric neuronal hyperplasia and megacolon are seen. These results suggest that Enx is required for the proper positional specification and differentiative cell fate of enteric neurons.

Animals↗

PubMed1997

Murine gamma-herpesvirus 68 causes severe large-vessel arteritis in mice lacking interferon-gamma responsiveness: a new model for virus-induced vascular disease.

Fundamental issues remain unresolved regarding the possible contribution of viruses to vascular pathology, as well as the role of the immune system in regulating these processes. Here we demonstrate that infection of mice with gamma-herpesvirus 68 (gammaHV68) provides a novel model for addressing these issues. Interferon-gamma receptor-deficient (IFNgammaR-/-) mice died weeks to months after gammaHV68 infection from a severe large-vessel panarteritis. GammaHV68-infected B cell-deficient and normal weanling mice exhibited milder large-vessel arteritis. Immunohistochemical analyses demonstrated gammaHV68 antigen in arteritic lesions and revealed a striking tropism of gammaHV68 for smooth muscle cells. These studies demonstrate that IFN-gamma is essential for control of chronic vascular pathology induced by gammaHV68 and suggest gamma-herpesviruses as candidate etiologic agents for human vasculitis.

Animals↗

PubMed1997

Dystrophic axonal swellings develop as a function of age and diabetes in human dorsal root ganglia.

Neuroaxonal dystrophy, characterized by swollen axon terminals and, to a lesser degree, enlarged initial segments of axons or perikaryal projections, develops in human dorsal root sensory ganglia as a function of aging and diabetes. Lesions are typically located within the satellite cell capsule and are intimately applied to sensory neuronal perikarya, which are compressed and distorted but are otherwise normal. Swollen axons contain large numbers of neurofilaments that are immunoreactive with antisera to highly phosphorylated neurofilament epitopes but fail to stain with antisera directed against hypophosphorylated neurofilament epitopes. Other dystrophic swellings contain collections of tubulovesicular profiles admixed with neurotransmitter granules. Neuroaxonal dystrophy involves subpopulations of intraganglionic axons and apparent terminals, notably those containing CGRP, while apparently sparing others, including noradrenergic sympathetic axons. Diabetic subjects develop lesions prematurely and in greater numbers than in aged subjects. Individual dystrophic axons in diabetics and aged human subjects are identical in their light microscopic, immunohistochemical and ultrastructural appearance, suggesting the possibility of shared pathogenetic mechanisms.

Adolescent↗

PubMed1997

Enzyme-based antigen localization and quantitation in cell and tissue samples (Midwestern assay).

Quantitation of antigen concentration in cell and tissue samples typically requires antigen extraction, which precludes antigen localization in the same sample. Similarly, antigen immunolocalization in fixed cells or tissue sections provides limited information about antigen concentration. We have developed a rapid and sensitive assay for simultaneous antigen localization and quantitation in cell and tissue samples that does not involve antigen extraction, radioactive materials, or image analysis. Fixed cells and/or tissue sections are used with antigen-specific enzyme-linked probes to generate soluble reaction products that are spectrophotometrically quantifiable and deposited reaction products that are microscopically localizable. The amount of soluble reaction product is dependent on several variables, including antigen concentration, probe specificity and sensitivity, sample size, and enzyme reaction time. These variables can be experimentally controlled so that soluble reaction product is proportional to antigen concentration in the sample. This assay was used in multiple applications including detection of Ki-67 nuclear antigen immunoreactivity in human brain tumors, in which it showed a clear relationship with visually determined Ki-67 cell labeling indexes. This assay, termed the Midwestern assay, should be applicable to a wide variety of antigens in both clinical and research samples.

Alzheimer Disease↗