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M Schaefer

Publications and source records attributed to M Schaefer.

At least 55 records · Page 3Linked to original sources
PubMed1986

Modulation of a respiratory motor program by peptide-secreting neurons in Aplysia.

Respiratory pumping of the gill and siphon of Aplysia californica is a fixed-action pattern coordinated by a defined set of interneurons and motor neurons. In semi-intact preparations of the gill and siphon innervated by the abdominal ganglion, respiratory pumping is facilitated for a prolonged period following activation of the peptidergic bag cell neurons. The induced changes in contractile behavior of the gill and siphon correlate with cell-specific actions of the bag cells on motor neurons regulating these organs. Our results suggest that peptidergic neurons can alter the expression of a fixed pattern of behavior by modulating the excitability of motor neurons controlling the behavior.

Animals↗
PubMed1986

Perceptions of quality of life following divorce: a study of children's prognostic thinking.

The general quality of latency-aged children's prognostic thinking and the way in which they view the long-range impact of divorce upon peer adaptation are explored. When interviewed about responses to two fictional peers with marked behavior problems, 80 children in the third and fifth grades displayed an optimism in their prognostic thinking about the future of these peers. In general, peers from divorced homes were perceived as having a more positive future adjustment than peers from intact homes. However, male subjects from disrupted homes revealed a significantly pessimistic orientation regarding the impact of divorce upon the future; females from disrupted homes had a strikingly optimistic view. Implications for school-based interventions are discussed.

Adaptation, Psychological↗
PubMed1986

Functions of purified L3T4+ and Lyt-2+ cells in vitro and in vivo.

The expression of L3T4 and Lyt-2 cell surface molecules separates T cells into two broad, non-overlapping subsets: typical T helper cells are L3T4+ Lyt-2- whereas most T killer cells and their precursors are L3T4- Lyt-2+. This review compares highly purified populations of unprimed L3T4+ and Lyt-2+ cells for their capacity to respond to class I vs. class II H-2 alloantigens. Various parameters are considered, including generation of mixed lymphocyte reactions (MLR) and cell mediated lympholysis (CML) in vitro, proliferative responses in irradiated mice, graft-versus-host reactions and skin allograft rejection. In all of these assays the two T cell subsets exhibit marked specificity in their response to H-2 alloantigens, L3T4+ cells responding only to class II and not class I differences and Lyt-2+ cells showing reciprocal specificity. Contrary to current dogma, the bulk of the evidence suggests that primary responses of Lyt-2+ cells do not depend on exogenous help provided by other T cells.

Animals↗
PubMed1985

Properties of purified T cell subsets. I. In vitro responses to class I vs. class II H-2 alloantigens.

In light of the widely accepted view that Ia-restricted L3T4+ T helper cells play a decisive role in controlling the differentiation of Lyt-2+ cells, experiments were designed to examine whether Lyt-2+ cells can respond to antigen in the absence of L3T4+ cells. The results showed that highly purified Lyt-2+ cells gave high primary mixed lymphocyte reactions (MLR) to various class I differences, including both mutant and allelic differences; responses to class II (Ia) differences were generally undetectable with Lyt-2+ cells. The intensity of MLR to class I differences was not affected by addition of anti-L3T4 monoclonal antibodies (mAb) to the cultures or by removing T cells from the stimulator populations. Negative selection experiments showed that Lyt-2+ cells could respond to class I differences across Ia barriers. MLR of purified Lyt-2+ cells peaked on days 3-4 and then fell sharply; background responses with syngeneic stimulators (auto-MLR) were virtually absent. Parallel experiments with purified L3T4+ cells showed that this subset responded in MLR only to class II (Ia) and not class I differences, reached peak responses only on day 6 rather than days 3-4, and often gave high auto-MLR. Within the first 3-4 d of culture, MLR were generally higher with Lyt-2+ cells than L3T4+ cells. Although no evidence could be found that Ia-restricted L3T4+ cells were required for the response of Lyt-2+ cells, presentation of antigen by Ia+ cells appeared to be essential. Thus, responses were ablated by pretreating stimulator cells with anti-Ia mAb plus C'. Significantly the failure of Lyt-2+ cells to respond to anti-Ia plus C'-treated stimulators could not be restored by adding syngeneic spleen cells; addition of IL-2 led to only a minor (15%) restoration of the response. It is suggested that Ia+ cells provide an obligatory second signal required by Lyt-2+ cells.

Animals↗
PubMed1985

Activity-related changes in protein phosphorylation in an identified Aplysia neuron.

The relationship between long-term electrical activity and protein phosphorylation was investigated in single, identifiable neurons in the abdominal ganglion of Aplysia californica by the intracellular injection of radiolabeled ATP followed by sodium dodecyl sulfate (SDS) gel electrophoresis. Natural and pharmacological treatments that alter the impulse activity of neurons L6 and R15 for prolonged periods did not appear to affect the phosphorylation of most of the 15 major phosphoproteins examined in these cells. Long-term excitation of L6 induced by the phosphodiesterase inhibitor IBMX correlated with phosphorylation of a 29,000-dalton protein. Long-term inhibition of L6 induced by afterdischarge of peptidergic bag-cell neurons appeared to cause dephosphorylation of a 29,000-dalton protein. Burst augmentation of R15 induced by bag-cell afterdischarge did not cause detectable changes in the phosphorylation of the major proteins we examined. These data are consistent with other studies of neural and nonneural tissues which have found a correlation between activity and the level of phosphorylation of a 29,000-dalton protein.

1-Methyl-3-isobutylxanthine↗
PubMed1985

Low molecular weight proteins of Aplysia neurosecretory cells.

The proteins of identified cells from the Aplysia californica central nervous system were labeled with radioactive amino acids and fractionated on SDS acrylamide gels containing 6 M urea. Most of the large cells contain prominent, cell-specific protein products in the molecular weight range between 3 and 30 KD. The molecular weights of the largest specific prevalent protein products are in good agreement with the predicted molecular weights of precursors as determined from an analysis of cDNA clones homologous to mRNA's specifically expressed in several of these neurons. Biologically active peptides have been found in many of these cells. These data, and other indirect evidence suggests that the synthesis of a large amount of a particular protein in this molecular weight range is indicative of the synthesis of a neurosecretory product. We conclude that most, if not all, large neurons in the Aplysia central nervous system are peptidergic.

Animals↗
PubMed1985

Aplysia neurons express a gene encoding multiple FMRFamide neuropeptides.

The neuroactive peptide Phe-Met-Arg-Phe-NH2 (FMRF-amide) has a variety of effects on both mammalian and invertebrate tissues; moreover, FMRFamide-like immunoreactivity is found throughout the animal kingdom. Here we describe the isolation and characterization of a cDNA clone from an Aplysia abdominal ganglion cDNA library that encodes a precursor protein that may give rise to as many as 19 individual FMRFamide peptides. Nearly all of the FMRF sequences are flanked on the amino terminus by Lys-Arg residues and on the carboxy terminus by Gly-Lys residues, suggesting that the single lysine residues function to signal cleavage by processing enzymes. The gene is present in a single copy per haploid genome and gives rise to multiple transcripts, at least some of which appear to arise through alternate RNA splicing. Immunohistochemical analysis suggests that the peptide is present in many neurons throughout the Aplysia nervous system and that these neurons send processes to a variety of different tissues.

Amino Acid Sequence↗
PubMed1985

Affinity-purified interleukin 2 induces proliferation of large but not small B cells.

Immunoaffinity-purified interleukin 2 (IL2) stimulated proliferation of large but not small B cells. Stimulation was observed even when B cells were cultured at very low cell densities (3 X 10(4) per microwell containing 0.2 ml of medium). Addition of small numbers of purified splenic T cells did not enhance the IL2-induced B-cell proliferative response. These results suggest that IL2 was not operating through contaminating T cells. B cells cultured with anti-Ig antibody in vitro showed enhanced proliferation when cultured with EL4 thymoma-derived B-cell growth factor but not when cultured with IL2. A direct role for IL2 in B-cell activation is discussed.

Animals↗
PubMed1985

Moving the 'standards movement'.

Substantial variations found in state implementation of public health service standards were partially explained by information collected from State Health Departments. A number of structural factors, particularly the distribution of service and supervisory responsibilities between state and local agencies, produce role and tactical differences in the process of standards implementation. Patterns and philosophies of intergovernmental funding were also reported to be critical to the process. In that these and related factors have their roots in political decisions, attention to internal and external political constraints is believed to be important to progress on standards implementation. Finally, the extent of variation reported raises the issue of the degree to which a common paradigm of public health exists and guides practice in state and local communities.

Community Health Services↗
PubMed1985

Standards for local public health services: where stand the states?

Of the 47 states that participated in a 1983 survey of State Health Departments, 30 were found to have public health standards in place or started. Most states' standards emphasize the range of services to be provided, but substantial variations were found in how standards are formulated, adopted, and used by state and local agencies.

Health Planning Organizations↗
PubMed1984

Neuropeptides: mediators of behavior in Aplysia.

The Aplysia neuroendocrine system is a particularly advantageous model for cellular and molecular studies because of the relatively small number and large size of its component neurons. Recombinant DNA techniques have been used to isolate the genes that encode the precursors of peptides expressed in identified neurons of known function. The organization and developmental expression of these genes have been examined in detail. Several of the genes encode precursors of multiple biologically active peptides that are expressed in cells which also contain classical transmitters. These studies, as well as immunohistochemical studies and the use of intracellular recording and voltage clamp techniques are the first steps toward revealing the mechanisms by which neuropeptides govern simple behaviors.

Animals↗
PubMed1983

Establishment of an inbred line of mice that express a synergistic immune defect precluding in vitro responses to type 1 and type 2 antigens, B cell mitogens, and a number of T cell-derived helper factors.

Introduction of the CBA/N X-linked gene into C3H mice has resulted in the establishment of a new strain of mice that has profound immunologic defects. B cells from these mice show significantly impaired in vitro immune responses to the T cell-independent type 1 antigen trinitrophenyl-Brucella abortus (TNP-BA) as well as markedly reduced proliferative responses to a number of B cell mitogens when compared with the responses of the parental control mice. The in vivo response of such mice to TNP-BA is, however, comparable to that of CBA/N mice. Furthermore, B cells from C3.CBA/N mice are unresponsive to the plaque-forming cell enhancing effects induced by EL4-derived supernatant in the presence of TNP-BA, unlike B cells obtained from CBA/N or C3H/Hen mice whose responsiveness to TNP-BA can be significantly enhanced in the presence of EL4-derived supernatant. The model we have presented to best explain these results suggests that B cells from C3.CBA/N mice can be stimulated only under conditions in which they can interact with carrier-specific T cell help and not under conditions where factor-dependent responses are dominant.

Animals↗
PubMed1983

Lyb-5- B cells of CBA/N mice can be induced to synthesize DNA by culture with insolubilized but not soluble anti-Ig.

The use of anti-immunoglobulin (anti-Ig) antibodies to stimulate B cell proliferation (1-4), and to stimulate B cell differentiation in the presence of T cell derived-lymphokines (5-8), has simplified investigations into the mechanisms of B cell growth and maturation that are dependent on the cross-linking of surface Ig (sIg). It is only the ontogenetically late appearing Lyb-5+ murine splenic B cells, however, that proliferate in response to anti-Ig antibodies, whereas B cells of the Lyb-5- phenotype obtained from neonatal mice or from mice with the xid immune defect cannot be induced to proliferate in response to this stimulus (1, 9, 10). Thus, the analysis of B lymphocyte physiology of the Lyb-5- B cell population has been hampered by the unavailability of B cell stimulants that mimic an antigen-induced sIg cross-linking event that leads to B cell activation. The inability of soluble anti-Ig antibodies to induce the proliferation of Lyb-5- cells has been particularly difficult to explain because these cells can be induced to increase in size (11) and to show an increase in their expression of surface Ia (sIa) after exposure to anti-Ig (12). Apparently, therefore, these cells are not entirely refractory to this stimulus but are simply unable to progress to the latter stages of cell activation. In view of our observations that the cells of CBA/N mice cannot respond to soluble trinitrophenyl-(TNP) dextran or TNP-polyacrylamide (13) but can respond to insolubilized forms of these antigens, we evaluated their ability to respond to insolubilized anti-Ig. In this paper we report that B cells from CBA/N mice can be stimulated to proliferate in response to anti-Ig conjugated to Sepharose beads, but in contrast to normal B cells they need to be stimulated with beads expressing a high-epitope density of anti-Ig antibodies.

Animals↗
PubMed1983

T cell dependence and factor reconstitution of in vitro antibody responses to TNP-B. Abortus and TNP-Ficoll: restoration of depleted responses with chromatographed fractions of a T cell-derived factor.

In vitro anti-trinitrophenyl (TNP) antibody responses to TNP conjugates of killed Brucella abortus organisms (TNP-BA), an antigen previously designated as a type 1 thymus-independent (TI-1) antigen, are markedly diminished after vigorous depletion of T cells, as are the responses to the type 2 TI (TI-2) antigen, TNP-Ficoll. We, therefore, propose that these antigens be redesignated as type 1 and type 2, respectively, to reflect their T cell dependence but to differentiate them from classical T cell-dependent (TD) antigens. T cell-depleted responses to type 1 and type 2 antigens can be restored by the addition of a) EL4 supernatant, b) phenyl-sepharose-purified fractions of EL4 supernatant that are rich in interleukin 2(IL2), and c) pl 4.5-5.5 isoelectric focused (IEF) fractions of EL4 supernatant which are also rich in IL2 activity. Removal of IL2 activity from EL4 supernatant by absorption on IL2-dependent T cells substantially reduced its restorative ability. Whether the active principle in EL4 supernatant activity responsible for restoring responses to type 1 and type 2 antigens is IL2, and whether it acts directly on B cells or by acting on contaminating T cells, is unresolved.

Animals↗