Biomedical subjects

M F Towle

Publications and source records attributed to M F Towle.

5 recordsLinked to original sources

PubMed1998

Deprivation of leukemia inhibitory factor by its function-blocking antibodies augments T cell activation.

Leukemia inhibitory factor (LIF) is a cytokine that acts on a wide range of cell types in vitro, but knowledge of its physiological role is limited. High levels of LIF protein have been selectively detected in the thymus throughout postnatal development. LIF-deficient mice have shown impaired thymic T cell maturation, suggesting the possibility that T cells require LIF for maturation. We have used highly specific antibodies raised against native rat LIF to inhibit LIF function during a defined and restricted period of thymic T cell maturation (first postnatal week). Surprisingly, we observed increased T cell activation in the LIF-deprived wild-type rat. The increased T cell response is retained even 4 weeks after anti-LIF treatment when the level of LIF in the thymic microenvironment has returned to normal. Our results are in contrast to findings with LIF knockout mice, where decreased T cell activation was observed. These observations suggest that LIF may have alternative effects on various phases of T cell development and that LIF may be involved in the restriction of the T cell repertoire during maturation occurring in the first postnatal week.

Animals↗

PubMed1997

Distribution of cholinergic neuronal differentiation factor/leukemia inhibitory factor binding sites in the developing and adult rat nervous system in vivo.

Cholinergic neuronal differentiation factor/leukemia inhibitory factor (CDF/LIF) is a multifunctional cytokine that affects neurons as well as many other cell types. Toward elucidating its neural functions in vivo, we previously investigated the distribution of CDF/LIF binding sites with iodinated native CDF/LIF in embryonic to postnatal day 0 (P0) rats. In the present study, we have extended our examination to postnatal ages and find that specific CDF/LIF binding sites are present at defined developmental stages in additional brain regions not previously exhibiting binding by P0. High levels of binding are detected in all P7 sensory and autonomic ganglia examined, but only in restricted postnatal central nervous system structures. Cranial motor and mesencephalic trigeminal neurons maintain high levels throughout, while binding to spinal motor neurons, which decreases to low levels at P0, reappears by P14 and increases with age. Most other structures, which show detectable binding by P0, exhibit higher levels at postnatal ages, including the red, deep, ventral cochlear, trapezoid, superior olivary, vestibular, ventral tegmental, and ventral posterior thalamic nuclei as well as the glomerular layer of the olfactory bulb. High levels are also detected in several structures for the first time after P0, including the cerebellar cortex (molecular and Purkinje cell layers), lateral reticular nucleus of the medulla and reticular formation, as well as the reticulotegmental, medial geniculate, solitary (rostral, dorsomedial, and commissural regions), medial septal, lateral mammillary, and lateral habenular nuclei. These results not only identify regions of potential CDF/LIF-responsive neurons and glia throughout development but suggest new CDF/LIF roles in the nervous system.

Animals↗

PubMed1997

Tissue-specific and ontogenetic regulation of LIF protein levels determined by quantitative enzyme immunoassay.

To define the physiological role of leukemia inhibitory factor (LIF), it is essential to localize sites of LIF synthesis in vivo. We generated polyclonal antibodies specific for native rat LIF, and developed a two-site immunoassay to detect 10 pg LIF/ml. Using this immunoassay, we determined LIF content of 18 organs, CNS regions, and ganglia throughout postnatal development of rats. High levels of LIF protein (1.0-11.0 ng/g tissue) are present in relatively few tissues: the uterus at late proestrus to estrus and on day 5 of pregnancy, ovary at estrus to early metestrus-1, footpads during early postnatal development and thymus throughout. Intermediate levels (0.5-1.0 ng) are detected in the gut, skin, skeletal muscle, pancreas and lung at one or more postnatal ages. Low levels (0.1-0.5 ng) are observed in most other non-nervous and nervous tissues. LIF protein levels do not completely correspond to reported LIF mRNA levels.

Age Factors↗

PubMed1992

Function-blocking antibodies against cholinergic neuronal differentiation factor.

Cholinergic neuronal differentiation factor, CDF, causes a transition from noradrenergic to cholinergic phenotype in cultured sympathetic neurons. Moreover, its identification with leukemia inhibitory factor has shown that CDF is a multifunctional cytokine. To examine the physiological role of CDF and to further elucidate the as yet unknown effects of CDF on the nervous system, two kinds of function-blocking antibodies were generated. One type, raised against whole native CDF, completely blocks CDF activity, whereas the other type, raised against a synthetic peptide corresponding to the N-terminal amino acid region of CDF, blocks activity partially. All three anti-CDF and two antipeptide polyclonal antibodies tested in this study significantly inhibit CDF function.

Animals↗

PubMed1991

Immunoaffinity purification and dose-response of cholinergic neuronal differentiation factor.

A glycoprotein from heart cell-conditioned medium, cholinergic neuronal differentiation factor (CDF), causes a transition from noradrenergic to cholinergic phenotype in cultured rat sympathetic neurons. Although the transition has been known to occur in a dose-dependent manner and CDF has been purified, the examination of a complete dose-response of neurons to CDF has not been possible because sufficient quantities of pure CDF have not been available. A complete dose-response curve is essential for evaluating the biological response of the neurons, for assessing the physiological role of CDF and for understanding the mechanism of action of CDF. We report here an immunoaffinity-purification procedure for CDF with a 73.1% recovery using antibodies raised against a synthetic peptide homologous with the N-terminal region of CDF. This method produced pure CDF in quantities sufficient for examination of the full dose-response range of the neurons. Our main findings are the following. The dose-responses of acetylcholine and catecholamine metabolisms to CDF are different, although the same molecule affects both transmitters. While the half-maximal concentrations for acetylcholine induction (0.20 nM) and for catecholamine suppression (0.28 nM) are similar, the response of catecholamine metabolism begins slowly and saturates at a CDF concentration (5-20 nM) considerably higher than that of acetylcholine (0.6 nM). This may indicate that CDF affects multiple processes in catecholamine metabolism.

Amino Acid Sequence↗