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Biomedical subjects

J Avery

Publications and source records attributed to J Avery.

At least 19 recordsLinked to original sources
PubMed2000

A cell-free system for regulated exocytosis in PC12 cells.

We have developed a cell-free system for regulated exocytosis in the PC12 neuroendocrine cell line. Secretory vesicles were preloaded with acridine orange in intact cells, and the cells were sonicated to produce flat, carrier-supported plasma membrane patches with attached vesicles. Exocytosis resulted in the release of acridine orange which was visible as a disappearance of labeled vesicles and, under optimal conditions, produced light flashes by fluorescence dequenching. Exocytosis in vitro requires cytosol and Ca(2+) at concentrations in the micromolar range, and is sensitive to Tetanus toxin. Imaging of membrane patches at diffraction- limited resolution revealed that 42% of docked granules were released in a Ca(2+)-dependent manner during 1 min of stimulation. Electron microscopy of membrane patches confirmed the presence of dense-core vesicles. Imaging of membrane patches by atomic force microscopy revealed the presence of numerous particles attached to the membrane patches which decreased in number upon stimulation. Thus, exocytotic membrane fusion of single vesicles can be monitored with high temporal and spatial resolution, while providing access to the site of exocytosis for biochemical and molecular tools.

Acridine Orange↗
PubMed1999

Reconstitution of regulated exocytosis in cell-free systems: a critical appraisal.

Regulated exocytosis involves the tightly controlled fusion of a transport vesicle with the plasma membrane. It includes processes as diverse as the release of neurotransmitters from presynaptic nerve endings and the sperm-triggered deposition of a barrier preventing polyspermy in oocytes. Cell-free model systems have been developed for studying the biochemical events underlying exocytosis. They range from semi-intact permeabilized cells to the reconstitution of membrane fusion from isolated secretory vesicles and their target plasma membranes. Interest in such cell-free systems has recently been reinvigorated by new evidence suggesting that membrane fusion is mediated by a basic mechanism common to all intracellular fusion events. In this chapter, we review some of the literature in the light of these new developments and attempt to provide a critical discussion of the strengths and limitations of the various cell-free systems.

Animals↗
PubMed1998

The psychosocial impact of bone marrow transplantation: a review of the literature.

Bone marrow transplant (BMT) is a procedure used for the treatment of a variety of cancers and malignant diseases. Recovery from this intensive process requires a long-term course, often accompanied by acute morbidity which includes various distressing physical symptoms. Recent literature has begun to explore the impact of this procedure on quality of life and psychosocial issues. While survivorship is often associated with a highly rated global quality of life, recovery from BMT is accompanied by several psychosocial difficulties which negatively impact patients. Fatigue is a common complaint, often hindering recipients for several years following their transplant. As well, reports of psychological distress, psychiatric symptoms, and/or mood disturbances such as anxiety or depression are not uncommon. Many patients also indicate interruption of sexual activity and increased sexual difficulty for several months following BMT. While some investigators have begun to examine hormone replacement therapy (HRT) as a treatment option for reducing sexual dysfunction, there is a general paucity of literature evaluating interventions for BMT survivors. This article reviews the literature examining various quality of life aspects including fatigue, psychosocial difficulties, and sexual functioning of patients during recovery from BMT. Limitations of past research are discussed and directions for future research suggested.

Bone Marrow Transplantation↗
PubMed1997

In vitro exocytosis in sea urchin eggs requires a synaptobrevin-related protein.

Sea urchin eggs provide an efficient in vitro model of exocytosis. We have identified proteins in sea urchin eggs that cross-react with antibodies to mammalian synaptobrevin, synaptotagmin, SNAP-25, syntaxin and rab3a. We show that these proteins are localized to the sea urchin egg cortex, using western blotting and immunocytochemistry. Tetanus toxin light chain cleaves the synaptobrevin-related protein in vitro and inhibits calcium-induced exocytosis. These data demonstrate a conservation between phyla of protein sequence and molecular mechanisms thought to facilitate exocytosis and show that the sea urchin egg provides a unique in vitro exocytotic model with which to study the conserved protein machinery of membrane fusion during secretion.

Animals↗
PubMed1994

Identification and partial sequence analysis of novel annexins in Lytechinus pictus oocytes.

The annexins are a major class of calcium-binding proteins with unknown functions. In an attempt to define novel model systems in which to study members of the annexin family, we have investigated the expression of annexins in eggs from the sea urchin Lytechinus pictus. Western blot analysis of L. pictus eggs using antisera raised against human annexins I, V and VI revealed the presence of immunoreactive proteins of approximately 34 kDa, 35 kDa and 68 kDa respectively. The sea urchin annexins behaved similarly to their mammalian counterparts, both during purification and in their ability to bind calcium-dependently to anionic phospholipids. Of the three sea urchin annexins, the 34 kDa form was most abundant, yielding sufficient quantities for peptide microsequencing. The amino acid sequences derived in this way showed the L. pictus annexin to be closely related both to mammalian annexin I and to annexins IX, X and XII from Drosophila and Hydra. However, N-terminal sequence from the L. pictus annexin showed it to be a novel member of the annexin super-gene family. The results are interesting in view of the complex evolution of the annexin gene family, and also point to the potential usefulness of echinoderm eggs as a model system in which to study annexin function.

Amino Acid Sequence↗
PubMed1992

Effect of sodium fluoride on bone density in chickens.

In addition to increasing bone volume, fluoride has been demonstrated to increase ash weight and mineral density. To determine whether newly formed or older bone is most affected by fluoride treatment, bone from chickens receiving fluoridated water was fractionated into lower density (recently formed) and higher density (more mature) specific gravity fractions. Fluoride was administered to the chickens for different lengths of time (4 or 13 weeks) or at varying doses for a 4-week period (0, 4.2, 16.8 mmol/liter drinking water). Fluoride treatment caused a shift in the mineral density profile, showing an increased proportion of mineral distribution in the more mature, higher density fractions. To determine whether this density gradient shift was due to increased maturation rate of bone or decreased resorption and mineralization rates, [3H]proline and 45Ca were injected 5 days and 24 hours prior to sacrifice, respectively. The distributions of both 3H or 45Ca, as percentages of total counts incorporated, were shifted by fluoride treatment into more mature, higher density fractions. Expressing the number of counts as a percent of the bone in each fraction (total hydroxyproline or Ca) revealed an increased incorporation of both 3H and 45Ca into the higher specific gravity fractions 2.0-2.2. These results suggest that fluoride treatment increases bone maturation and the rate of secondary mineralization in the cortical bone. Such changes in the quality of more mature, well-mineralized bone, in humans as well as animals, may have a significant influence on brittleness and strength.

Animals↗
PubMed1991

Effect of extended depot fluphenazine treatment and withdrawal on social and other behaviors of Cebus apella monkeys.

To examine whether or not prolonged exposure to a depot neuroleptic has either residual or "tardive pathological" effects on normal behavior, 38 Cebus apella monkeys were observed daily for 108 weeks. The issue of stress influencing such effects was also addressed. During weeks 25-48 half of the monkeys received 0.22 mg/kg fluphenazine decanoate, IM, every 3 weeks, with the dose increased to 0.33 mg/kg during weeks 49-72. Behavioral measures were combined to form composite behavioral variables which quantify four major aspects of behavior: self- and environment-directed behavior, affiliation, aggression, and normal locomotor activity. Mean plasma fluphenazine levels at 48 h post-injection were 0.13 (+/- 0.03) ng/ml for injections 3-8 and 0.24 (+/- 0.07) ng/ml for injections 11-16. The pre-study null hypothesis that the four major aspects of behavior would not be adversely affected by this treatment during the drug-discontinuation phase of the study (weeks 73-108) was not statistically negated. There were highly significant decreases in self- and environment-directed behaviors and affiliation during the treatment periods, implying that treatment may contribute to the negative symptoms of treated schizophrenics. Stress reduced the above effects. Aggression showed some increase during early drug discontinuation, accentuated by stress. Recovery of normal (baseline) behavioral scores began by week 7 after the last treatment. Mild (bucco-lingual) tardive dyskinesias persisted in 30% of the animals for a prolonged time.

Animals↗
PubMed1990

Optimal cardioplegia and 24-hour heart storage with simplified UW solution containing polyethylene glycol.

Recent work has shown that UW may be better than standard cardioplegic solutions for short-term heart preservation. In this study we have used a rabbit heart model to evaluate a simplified UW solution in which penicillin, dexamethasone, insulin, allopurinol, and adenosine were omitted and 5% polyethylene glycol (PEG20M) was substituted for hydroxyethyl starch. The test systems consisted of 4-hr cardioplegic storage at 15 degrees C with repeated flushing every 30 min for 2 hr and 24-hr hypoxic low-flow microperfusion (3 ml/g/24 hr) at 0 degrees C. Control groups were arrested with a 15-25 ml flush in iced saline and immediately tested. Cardiac output (CO)* after preservation was measured in a working heart model using an acellular perfusate at 37 degrees C at an aortic pressure of 100 cm H2O. The CO (ml/g heart wt/min) were as follows--Controls: St. Thomas II 20.5 +/- 8.3 (5), UW 34.7 +/- 11.7 (16), PEG20M 41.8 +/- 4.4 (14); 4-hr cardioplegia: St. Thomas II 17.4 +/- 0.9 (4), Bretschneider HTK 14.9 +/- 7.0 (4), UW 25.2 +/- 11.5 (9), PEG20M 41.1 +/- 7.8 (8); 24-hr microperfusion: UW 25.4 +/- 11.1 (18), PEG20M 37.1 +/- 8.2 (18). Following cardioplegic or microperfusion preservation, PEG20M hearts functioned at control levels (P greater than 0.05) and were significantly superior to all other solutions, with approximately double the CO (P less than 0.05, all other groups). We conclude that for heart preservation, 5 components can be eliminated from UW and substitution of PEG20M for HES appears to have improved its performance.

Animals↗
PubMed1986

Comparative study of antigen binding T cells separated by Vicia villosa or streptococcal antigen and the effect of HLA class II antigens.

The antigen binding capacity and function of T cells which adhere to the lectin Vicia villosa (VV) or to streptococcal antigen (SA) have been studied. VV-adherent T8+ cells (T8+ VV+) bind 125I-SA whereas VV non-adherent T8+ cells (T8+ VV-) bind little SA. Similarly, SA-adherent T8+ cells (T8+ SA+) bind 125I-SA specifically, whereas SA-non-adherent T8+ cells (T8+ SA-) show little binding of 125I-SA. The SA binding T8+ VV+ or T8+ SA+ cells can present the antigen to T4+ helper cells which generate helper factors and these enhance anti-DNP-antibodies, when incubated with mouse spleen cells and DNP-SA. Parallel reconstitution studies with either T8+ VV- or T8+ SA- cells have revealed that both subpopulations of cells can suppress T4+ helper cell activity. Further reconstitution experiments between the T8+ VV+ (or T8+ SA+) antigen presenting cells and T8+ VV- (or T8+ SA-) suppressor cells suggest that the former can also prevent the latter cells from inhibiting T4 helper cells, so as to function as contrasuppressor cells. Cross-over, reconstitution studies between the VV and SA separated cells have confirmed that the T8+ VV+ and T8+ SA+ cells have similar functions, in SA binding, presenting and contrasuppressor activities. The dose-response curve of binding 125I-SA to T8+ cells is dependent on the HLA-DR type of cells and the binding of 125I-tetanus toxoid was similar to that of 125I-SA. Whereas DRw6- T cells bind predominantly 1,000 ng SA or tetanus toxoid, DRw6+ T cells bind 1 ng and to a lesser extent 1,000 ng of either antigen. HLA-DRw6+ subjects can be considered as high responders for their T cells bind optimally at low concentrations of antigens which induce helper and contrasuppressor functions. In contrast, HLA-DRw6-subjects can be considered as low responders, as their T cells bind optimally at high concentrations of antigens and only the latter induce helper and contrasuppressor functions.

Antigens, Bacterial↗
PubMed1985

The role of a human antigen specific T8+ cell subset in antigen presentation, helper function and contrasuppression.

Regulation of the human immune response was studied by sequential separation of subsets of T cells, followed by assessment of their helper and suppressor functions in a series of reconstitution experiments. T8+ lymphocytes were separated by panning on streptococcal antigen (SA) coated plates into T8+ SA-adherent cells (T8+SA+) and T8+ SA-non-adherent cells (T8+SA-). The helper and suppressor functions of the T8+SA+ and T8+SA- cells, reconstituted with T4+ helper cells were then studied by a direct antibody forming cell assay. T4+ cells will not induce helper activity by 1000 ng SA alone but require the accessory function of monocytes (Mo). However, replacing Mo by T8+SA+ cells will elicit a similar helper activity by T4+ cells and SA as that induced by Mo. In addition to the antigen-specific presentation and induction of helper activity, the T8+SA+ subset displays the properties of antigen-specific contrasuppressor cells. Thus, reconstitution of T4+ cells and T8+SA- (suppressor cells) with T8+SA+ and 1000 ng SA induces helper and no suppressor activity. Substitution of Mo for the T8+SA+ cells converts the helper to a predominantly suppressor-cell function. T8+SA- cells elicit suppression with 1 ng SA in the absence of accessory cells and reconstitution with Mo, T8+SA+ or T4+ cells failed to affect the suppressor activity. Total reconstitution of the four principle subsets of T4+, T8+SA+, T8+SA- cells and Mo elicited similar antigen dose-dependent responses as those of the unseparated mononuclear cells. It seems that all four cell subsets are required for optimal immunoregulation. We suggest that the T8+SA+ can present antigen to T4+ helper cells and induce helper activity, but in addition these cells can prevent the suppressor subset of T8+ cells from inhibiting T4+ helper cells and function as contrasuppressor cells. The mechanism of these functions is not known but HLA class II antigens might play an essential role in antigen binding, presentation and contrasuppression of the T8+SA+ cells, as the latter are significantly enriched in Ia+ cells.

Antibody Formation↗
PubMed1985

Separation and characterization of a subset of human T8+ cells which function as antigen-presenting and contrasuppressor cells.

The lectin Vicia villosa (VV) binds preferentially a subset of T cells. Separated VV-adherent cells (AC) do not generate helper function alone, but when added to VV-non-adherent cells (NAC), they can present streptococcal antigen (SA) and induce helper function as effectively as monocytes, at a ratio of 1 VV-AC to 4 VV-NAC. Further separation into a T8+ subset of VV-AC and reconstitution with T4+ helper cells (HC) has established that the T8+ VV-AC induces T4+ cells to helper activity. However, in addition to antigen presentation, the T8+ subset of VV-AC has a contrasuppressor function, for it can prevent T8+ suppressor cells from inhibiting T4+ HC function. The results suggest that a T8+ subset can present antigen to T4+ HC, activate helper function and prevent suppression. The T8+ VV-AC may have considerable biological significance in its dual function of countering the dominant suppressor activity and presenting antigen to induce helper activity.

Antibodies, Monoclonal↗
PubMed1985

Helper and suppressor functions of human mononuclear cells depleted of antigen-binding T8+ cells.

We have utilized the antigen-binding function of a subset of T8+ cells to remove these cells in vitro from human peripheral blood mononuclear cells. This was carried out by treating the cells with streptococcal antigen (SA), monoclonal anti-SA antibody and complement. The concentration of SA binding to T8+ cells differs with the HLA-DR type of the cells: 1 ng SA binds to DRw6+ cells and elicits T helper activity, whereas 1000 ng SA elicits T suppressor activity, in an assay for antibody-forming cells. After depletion of the antigen-binding cells by the SA-specific complement-dependent killing technique, the helper function of the DRw6+ cells was lost but suppression was elicited not only by 1000 ng but also by 1 ng SA. Similarly, DRw6- cells which bind 1000 ng SA to elicit helper activity and 1 ng to elicit suppression, when depleted of the SA-binding cells, resulted in loss of helper activity but again, suppression could be elicited by both 1000 and 1 ng SA. We suggest that treatment of mononuclear cells with antigen, the specific antibody and complement removes the T8+ antigen-binding cells which present antigen to T helper cells and results in the loss of helper function. Suppressor function is however, not only retained with the original concentration of SA but also expressed with that required to elicit helper function in the untreated cells. These findings are consistent with our hypothesis that the antigen-binding and presenting T8+ cells also function as contrasuppressor cells. Thus, the T8+ subset of cells have a dual function, to present antigen and to activate T helper cell function, and to prevent suppressor cells from inhibiting the helper cells.

Antibodies, Bacterial↗
PubMed1985

The helper and suppressor functions of primate T cells elicited by a 185K streptococcal antigen, as compared with the helper function elicited by a 4K streptococcal antigen.

Helper and suppressor functions of human T lymphocytes that act on antibody-forming B cells were elicited by a large 185K streptococcal cell wall antigen. However, a small 4K streptococcal peptide elicited helper but no suppressor function. These differences in the functional activities of the large and small m.w. streptococcal antigens (SA) were confirmed by direct immunisation of rhesus monkeys with the 185K-SA and 4K-SA. Sequential studies have shown that whereas the 185K-SA elicits dose-dependent helper and suppressor activities, the 4K-SA elicits only helper function. Cell-depletion studies with human cells suggest that removal of T8+ cells by killing with OK.T8 and complement leads to a loss of suppressor and a broadening in the concentration of 185K-SA, which elicits helper activity. Because the 4K-SA does not elicit suppression, removal of T8+ cells does not affect this function. However, similar depletion of T4+ cells results in loss of the helper activities, both with the 185K-SA and 4K-SA, and again a broadening in the concentration of the 185K-SA, which elicits suppression. Direct comparison by autoradiography between 125I-labeled 185K-SA and 4K-SA suggests that both antigens can bind directly to monocytes or T8+ VV+ cells. Furthermore, both antigens can induce helper function if T4+ cells are reconstituted with either monocytes or T8+ VV+ cells. Attempts will now be made to sequence the amino acid determinants of the 185K-SA, so as to define the epitopes responsible for the two major regulating functions elicited by this antigen.

Animals↗
PubMed1984

Sequential development of helper and suppressor functions, antibody titers and functional avidities to a streptococcal antigen in rhesus monkeys.

Sequential development of antibody titer, functional avidity, helper and suppressor activities were investigated in rhesus monkeys. These were immunized with a single dose of 0.1 microgram to 10 mg of a streptococcal protein antigen (SA) in aluminium hydroxide. The IgG antibody titers followed the classical pattern first established in mice, of high-dose and low-dose tolerance with intermediate doses of immunity. This was correlated with a similar pattern of functional avidity of IgG antibodies, as measured by a dissociation assay. Helper and suppressor functions were assayed in parallel by inducing the corresponding factors from monkey lymphocytes in Marbrook flasks and testing the factors which cross the species barrier in cooperative cultures with CBA mouse spleen B cells. A progressive modulation of helper and suppressor activities was elicited by the increasing doses of SA, during the initial 28 days after immunization. Thus, dominant suppressor with minimal helper activity, IgG antibody titer and functional avidity were elicited by 0.1 microgram SA. However, 1 or 10 micrograms SA induced dominant helper with minimal or transient suppressor activity and high IgG antibody titers and functional avidity. Somewhat intermediate responses were elicited by 100 micrograms SA, but 1 mg and especially 10 mg SA induced dominant suppressor and minimal helper activity, with low IgG antibody titers and functional avidities. When the immune response was established, about 28 days after immunization, the intermediate dose of SA elicited IgG antibodies with high titer and functional avidity, high T cell helper but low suppressor activities. In contrast, both high- and low-dose SA induced partial tolerance, with low IgG antibody titer, functional avidity and T cell helper activity. These studies suggest cyclical development of helper and suppressor functions during the 4 weeks after immunization. The emergence of a dominant helper or suppressor function is antigen dose dependent.

Animals↗
PubMed1984

Detection of cross-reacting murine I-J like determinants on a human subset of T8+ antigen binding, presenting and contrasuppressor cells.

Murine I-J gene products have been found in T suppressor cells (SC) and factors, macrophages and contrasuppressor cells (CSC). However, a human counterpart of the murine I-J has not been reported. As there is strong evidence that some murine anti-Ia antisera cross-react with human Ia antigens, the possibility was tested that mouse anti-I-J antibodies might cross-react with corresponding human class II determinants. Indeed, this revealed that three anti-I-J monoclonal antibodies (MoAb) and two antisera tested react with human mononuclear cells and that a significantly greater proportion of T8+ than T4+ cells or monocytes (Mo) react with the I-J antibodies. This was corroborated by autoradiography with significant inhibition of 125I-SA (streptococcal antigen) binding to T8+ cells but not to Mo by the MoAb or antisera to murine I-J. Functional reconstitution experiments of T4+ helper cells with the SA binding and presenting T8+ Vicia villosa adherent cells (VV-AC) and assessment of specific antibody forming cells to SA suggest that the antigen presenting function of this T8+ subset can be significantly inhibited by killing with the MoAb to I-J and complement. Furthermore, the subset of T8+ VV-AC also functions as CSC, for killing with MoAb to I-J and complement significantly inhibited the contrasuppressor function. This is consistent with the presence of I-J gene products in murine CSC. However, similar treatment of T8+ VV-NAC (non-adherent cells) or monocytes (Mo) failed to affect the suppressor or accessory helper function of these cells, respectively. Phenotypic characterization, inhibition of 125I-SA binding and reconstitution experiments for helper and suppressor functions, suggest that a subset of T8+ antigen binding, presenting and CSC may express determinants cross-reacting with murine I-J molecules.

Animals↗