Biomedical subjects

L E Brown

Publications and source records attributed to L E Brown.

At least 19 recordsLinked to original sources

PubMed2003

Effects of chronic cocaine on monoamine levels in discrete brain structures of lactating rat dams.

Chronic gestational cocaine administration has been correlated with high levels of postpartum maternal aggression towards intruders and altered levels of oxytocin in the amygdala. Cocaine may alter both oxytocin and maternal aggression either directly or indirectly through changes in monoamine levels in relevant brain regions. In this study, pregnant female rats were randomly assigned to one of four groups; three cocaine dose groups (7.5, 15 or 30 mg/kg), or a saline-treated group (0.9% normal saline) and given subcutaneous injections twice daily (total volume 2 ml/kg) throughout gestation. Behavioral responses to an inanimate object placed in the homecage were assessed on Postpartum Day (PPD) 6. Immediately following testing, animals were sacrificed and four brain regions implicated in maternal/aggressive behavior (medial preoptic area [MPOA], ventral tegmental area [VTA], hippocampus, and amygdala) were removed for monoamine level analyses using high-performance liquid chromatography. Dams given 30 mg/kg cocaine throughout gestation had significantly higher levels of dopamine (DA) and nonsignificantly elevated serotonin (5-HT) levels relative to saline-treated controls. These dams also exhibited higher frequencies of defensive behavior toward an inanimate object compared to saline-treated controls. Potential mechanisms mediating cocaine-induced increases in responding are proposed.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2001

Preconstancy information can influence visual search: the case of lightness constancy.

Can visual search be based on preconstancy representations of the scene--that is, ones in which accidental characteristics of the scene, such as shadows, point of view, and distance, have not yet been discounted? This question was addressed within the specific context of lightness constancy, the phenomenon that surface lightness is perceived as relatively unchanged despite changes in illumination conditions. Three experiments yielded evidence of preconstancy influence on visual search. This was true even when the preconstancy information that seemed to influence search was unavailable at a reportable level. The results suggest that visual search processes can be engaged before the processing that leads to the experienced perception of the scene is complete.

Adolescent↗

PubMed2001

Functional mobility performance in an elderly population with lumbar spinal stenosis.

OBJECTIVES: To compare the functional mobility (FM) of elderly apparently healthy (AH) subjects and patients with lumbar spinal stenosis (LSS) and to evaluate the reliability and validity of the FM tests. DESIGN: Using the test-retest paradigm, FM performance was assessed in AH subjects. A single FM assessment was conducted on a group of LSS subjects. Between-group performance comparisons were made with the AH subjects and the LSS patients. SETTING: Orthopedic clinical practice (LSS subjects) and university laboratory (AH subjects). PARTICIPANTS: Fifty-seven patients seen in an orthopedic clinical practice for LSS and 96 AH subjects who were volunteers identified from among participants of The Lifelong Learning Society at Florida Atlantic University. INTERVENTIONS: Treadmill walk (TW) test (at 53.6 m/min, 1% increase in grade per min) until 70% of the predicted maximum heart rate was achieved or associated pain made participation uncomfortable. Three trials each of a sit-to-stand (SS, rise from chair as quickly as possible without using arms) and a weight-carrying (WC, walk 20 m as quickly as possible for time carrying 10% of the body weight evenly distributed in hand-held weights) test. The AH group repeated all tests on a separate day. MAIN OUTCOME MEASURES: Time to walk treadmill, stand from sitting position, walk 20 meters, and analysis of variance between groups. RESULTS: Significant between-group differences were found for the TW, SS, and WC tests. Test-retest r values of .839 for the TW, .848 for the SS, and .833 for the WC were observed. CONCLUSIONS: The AH group demonstrated greater FM than the LSS group. The performance disparity between groups may suggest context validity, while the AH groups test-retest stability reflects reliability.

Activities of Daily Living↗

PubMed2001

Differential effect of CD8(+) and CD8(-) dendritic cells in the stimulation of secondary CD4(+) T cells.

Dendritic cells (DC), in their role in initiation of the adaptive immune response, have been extensively studied for their capacity to interact and stimulate naive T cells. Subsets of mature murine DC isolated directly from the spleen have been shown to differ in their ability to induce proliferative responses in both primary CD4(+) and primary CD8(+) T cells; the myeloid-related CD8alpha(-) DC induce a more intense or prolonged proliferation of naive T cells than do the lymphoid-related DC bearing CD8alpha despite similar expression of MHC and co-stimulatory molecules. Here we examine the interaction of these DC subpopulations with T cells already in the activated or memory state which are known to have greater sensitivity to antigen stimulation and bear receptors with increased capacity for signal transduction. We show that influenza virus-specific CD4(+) T cell clones and splenic T cells from peptide-primed animals proliferated in response to antigen presented by separated splenic CD8(-) DC. In contrast, these T cells showed only weak, if any, proliferation in response to CD8(+) DC despite observable cluster formation in the cultures. The differential between the two DC types in inducing proliferation was even more pronounced than previously seen with primary T cells and did not reflect differential longevity of the DC in culture, altered response kinetics or deviation from IL-2 to IL-4 induction with CD8(+) DC, but was related to the levels of IL-2 induced. The deficiency in the CD8(+) DC was not overcome by using infectious virus rather than synthetic peptide as the antigen source. These results show that lymphoid-related CD8(+) splenic DC, despite their mature phenotype, fail to provide appropriate signals to secondary CD4(+) T cells to sustain their proliferation.

Animals↗

PubMed2000

B-1 and B-2 cell-derived immunoglobulin M antibodies are nonredundant components of the protective response to influenza virus infection.

We have studied the role of secreted immunoglobulin (Ig)M in protection from infection with influenza virus and delineated the relative contributions of B-1 versus B-2 cell-derived IgM in this process. Mice deficient in secreted IgM but capable of expressing surface IgM and secreting other Ig classes show significantly reduced virus clearance and survival rates compared with wild-type controls. Irradiation chimeras in which only either B-1 or B-2 cells lack the ability to secrete IgM show mortality rates similar to those of mice in which neither B-1 nor B-2 cells secrete IgM. Dependence on both sources of IgM for survival is partially explained by findings in allotype chimeras that broadly cross-reactive B-1 cell-derived natural IgM is present before infection, whereas virus strain-specific, B-2 cell-derived IgM appears only after infection. Furthermore, lack of IgM secreted from one or both sources significantly impairs the antiviral IgG response. Reconstitution of chimeras lacking B-1 cell-derived IgM only with IgM-containing serum from noninfected mice improved both survival rates and serum levels of virus-specific IgG. Thus, virus-induced IgM must be secreted in the presence of natural IgM for efficient induction of specific IgG and for immune protection, identifying B-1 and B-2 cell-derived IgM antibodies as nonredundant components of the antiviral response.

Animals↗

PubMed2000

A fusion DNA vaccine that targets antigen-presenting cells increases protection from viral challenge.

Improving the immunological potency, particularly the Ab response, is a serious hurdle for the protective efficacy and hence broad application of DNA vaccines. We examined the immunogenicity and protective efficacy of a hemagglutinin-based influenza DNA vaccine that was targeted to antigen-presenting cells (APCs) by fusion to CTLA4. The targeted vaccine was shown to induce an accelerated and increased Ab response (as compared with those receiving the nontargeted control) that was predominated by IgG1 and recognized conformationally dependent viral epitopes. Moreover, mice receiving the APC-targeted DNA vaccine had significantly reduced viral titers (100-fold) after a nonlethal virus challenge. The increased protective efficacy was most likely because of increased Ab responses, as cytotoxic T lymphocyte responses were not enhanced. Targeting was demonstrated by direct binding studies of CTLA4 fusion proteins to the cognate ligand (B7; expressed on APCs in vivo). In addition, a targeted protein was detected at 4-fold higher levels in draining lymph nodes within 2-24 h of administration. Therefore, this study demonstrates that targeting DNA-encoded antigen to APCs results in enhanced immunity and strongly suggests that this approach may be useful in improving the protective efficacy of DNA vaccines.

Abatacept↗

PubMed2000

Totally synthetic lipid-containing polyoxime peptide constructs are potent immunogens.

A synthetic peptide corresponding to a sequence from influenza hemagglutinin was used as a model antigen to study the immunogenicity of polyoxime constructs. In the absence of any adjuvant, tetrameric forms of different polyoxime constructs did not elicit an antibody response. High and long-lasting levels of antibody were induced, however, by polyoxime constructs to which Pam3Cys (tripalmitoyl-S-glyceryl cysteine) was attached. Comparable serum antibody levels were achieved with Tetraoxime-Pam3Cys administered by the intraperitoneal or intranasal routes to those obtained when the monomeric peptide was administered by the intraperitoneal route in complete Freund's adjuvant (CFA). Mice receiving Tetraoxime-Pam3Cys and Pam3Cys-peptide intranasally developed peptide-specific antibody secreting cells (ASCs) in their lungs and mediastinal lymph nodes. At low dose, the Tetraoxime-Pam3Cys induced higher levels of antibody compared to those elicited by the monomeric Pam3Cys-peptide delivered by either route. These results show that lipo-tetraoxime constructs assembled by polyoxime chemistry can be potent inducers of systemic and mucosal immunity.

Administration, Intranasal↗

PubMed2000

Essential role for the dsRNA-dependent protein kinase PKR in innate immunity to viral infection.

The double-stranded (ds) RNA-dependent protein kinase PKR is considered to play an important role in interferon's (IFN's) response to viral infection. Here, we demonstrate that mice lacking PKR are predisposed to lethal intranasal infection by the usually innocuous vesicular stomatitis virus, and also display increased susceptibility to influenza virus infection. Our data indicate that in normal cells, PKR primarily prevents virus replication by inhibiting the translation of viral mRNAs through phosphorylation of eIF2alpha, while concomitantly assisting in the production of autocrine IFN and the establishment of an antiviral state. These results show that PKR is an essential component of innate immunity that acts early in host defense prior to the onset of IFN counteraction and the acquired immune response.

Animals↗

PubMed2000

Trichostrongylus colubriformis extract upregulates TNF-alpha receptor expression and enhances TNF-alpha sensitivity of L929 cells.

Many pathogens have developed strategies to avoid the host's immune system and hence improve their long-term survival. These strategies include antigenic variation, mimicry of host regulatory proteins and production of immunoregulatory molecules. The ruminant gastrointestinal nematode Trichostrongylus colubriformis produces several factors with homology to human immunoregulatory proteins. However, direct immunomodulation by T. colubriformis proteins has not yet been unequivocally demonstrated. Results in the present paper demonstrate that soluble T. colubriformis factors promote proliferation of the TNF-susceptible mouse fibrosarcoma cell line L929, while inhibiting proliferation of all other cell types tested. In addition, T. colubriformis homogenate enhanced the susceptibility of L929 cells to the cytotoxic action of ovine TNF-alpha. Within 1 h of exposure, T. colubriformis factors bind L929 cells in a stable fashion, yet it takes up to 24 h for the cells to become sensitised to TNF-alpha. Interestingly, the increase of both TNF-alpha sensitivity and proliferation of treated L929 cells correlated with an upregulation in expression of TNF-alpha p55 and p75 receptors.

Animals↗

PubMed2000

The geometry of synthetic peptide-based immunogens affects the efficiency of T cell stimulation by professional antigen-presenting cells.

In the pathway leading to antibody production there are two points at which CD4(+) T(h) cells need to be recruited. The first of these is priming of T cells by their interaction with dendritic cells (DC) bearing antigen presented on MHC class II molecules and the second is the collaborative interaction of these primed T cells with B cells presenting the same antigen. We have previously shown that the configuration of T and B cell determinants within synthetic peptide immunogens can greatly influence the amount of immunogen required to produce an antibody response. Here we investigate whether the difference in potency of different immunogens is related to their ability to be presented by either DC or B cells. We show that determinants in a branched configuration, which are the most efficient at eliciting antibody in vivo, are presented to T cell clones by splenic CD8(-) DC 10-fold more efficiently than the corresponding determinants in a tandem linear arrangement. B cells also showed preferential presentation of branched immunogens to one T cell clone but in contrast to DC, not to a second T cell clone, indicating differences between the two antigen-presenting cell types. We also show that branched immunogens have a greater stability in serum compared to linear peptides, which may further enhance the differences in their in vivo potency.

Amino Acid Sequence↗

PubMed1999

The antigenic and immunogenic properties of synthetic peptide immunocontraceptive vaccine candidates based on gamete antigens.

In this study we have investigated the immunogenicity and antigenicity of synthetic immunocontraceptive vaccine candidates containing T- and B-cell epitopes arranged in different geometries. Two epitopes were selected, a B-cell epitope from fox sperm lactate dehydrogenase C(4) and a B-cell epitope from murine zona pellucida protein 3. Both were immunogenic in BALB/c mice when coupled to defined T helper cell determinants, eliciting antibodies which bound to the corresponding B-cell epitope and also to the recombinant protein. Because each of these proteins represent important components in the fertilisation process the results encourage further investigation of synthetic immunocontraceptive vaccines.

Amino Acid Sequence↗

PubMed1999

Preparation and properties of totally synthetic immunogens.

Although the induction of antibodies and T cells by synthetic peptides representing defined antigenic determinants is a routine laboratory procedure, their use as vaccines has not yet been generally realised. There are a number of reasons for this and paramount is the limitation of valency which affects not only immunogenicity, but also the coverage of the antigenic universe. This paper is a review of our own work in which we have assembled synthetic peptides into multivalent artificial proteins and then examined their immunological properties.

Amino Acid Sequence↗

PubMed1999

Mice lacking the transcription factor subunit Rel can clear an influenza infection and have functional anti-viral cytotoxic T cells but do not develop an optimal antibody response.

Rel, a haemopoietic cell-restricted member of the NF-kappaB/Rel family of transcription factors, has recently been shown to be important in the function of B and T lymphocytes. In an attempt to understand the role of this protein in the immune response, we examined the ability of Rel(-/-) mice to counter an influenza virus infection. Normal levels of virus-specific cytotoxic T cells induced in Rel(-/-) mice were able to clear virus from the lungs, albeit with somewhat delayed kinetics compared to normal mice. Rel(-/-) mice did, however, display a markedly reduced T cell proliferative response to the virus, and exhibited impaired local and systemic influenza virus-specific antibody responses. This defect was sufficient to result in an inability of vaccinated mice, but not of previously infected mice, to acquire antibody-dependent protective immunity to reinfection with the same virus. These findings establish that during the response to influenza virus, Rel function allows optimal development of humoral immunity, a role that apparently cannot be fulfilled by other NF-kappaB/Rel proteins.

Animals↗

PubMed1999

No foot in the door: an experimental study of employment discrimination against older workers.

Pairs of testers, one aged 57 and one aged 32, applied for 102 entry-level sales or management jobs in the Washington, DC, metropolitan area. Although their credentials described them as equally qualified, the older applicants received less favorable responses from employers 41.2% of the time. Three quarters of these differences occurred before older applicants could fully present their qualifications. The negative employer assumptions about older workers implied by these differences in outcome were seldom explicitly stated.

Adult↗

PubMed1998

Delivery of multiple CD8 cytotoxic T cell epitopes by DNA vaccination.

Development of CD8 alphabeta CTL epitope-based vaccines requires an effective strategy capable of co-delivering large numbers of CTL epitopes. Here we describe a DNA plasmid encoding a polyepitope or "polytope" protein, which contained multiple contiguous minimal murine CTL epitopes. Mice vaccinated with this plasmid made MHC-restricted CTL responses to each of the epitopes, and protective CTL were demonstrated in recombinant vaccinia virus, influenza virus, and tumor challenge models. CTL responses generated by polytope DNA plasmid vaccination lasted for 1 yr, could be enhanced by co-delivering a gene for granulocyte-macrophage CSF, and appeared to be induced in the absence of CD4 T cell-mediated help. The ability to deliver large numbers of CTL epitopes using relatively small polytope constructs and DNA vaccination technology should find application in the design of human epitope-based CTL vaccines, in particular in vaccines against EBV, HIV, and certain cancers.

Amino Acid Sequence↗

PubMed1998

Immunopotentiation of humoral and cellular responses to inactivated influenza vaccines by two different adjuvants with potential for human use.

Two quite different adjuvants, currently under development for use in humans, have been examined for their effects on the magnitude and type of immunity elicited in response to inactivated influenza vaccine. Immunostimulating complexes (ISCOM adjuvant) contain the saponin ISCOPREP 703, and SPT is an oil-in-water emulsion of squalane, non-ionic block copolymer (L121) and Tween 80. Influenza virus vaccines formulated in either adjuvant were far superior to the non-adjuvanted aqueous vaccine in eliciting antibody and T-cell responses in mice, particularly at lower doses of antigen. In addition, the vaccines containing adjuvant were superior in eliciting protective immunity. One of the shortcomings of the unadjuvanted inactivated influenza vaccine was its inability to elicit a primary proliferative T-cell response. However, after one dose of either adjuvanted vaccine, strong proliferative responses were achieved. We also show that subcutaneous vaccination with inactivated vaccines is capable of modulating the isotype profile of antibody secreting cells generated in the lungs of mice in response to intranasal challenge with live virus. In this system, the isotype of antibody elicited after challenge of mice that had received ISCOM vaccine more closely mimicked that of animals vaccinated with live virus.

Adjuvants, Immunologic↗

PubMed1998

Effect on blood pressure of potassium, calcium, and magnesium in women with low habitual intake.

In populations, dietary intakes of potassium, calcium, and magnesium each have been inversely associated with blood pressure. However, most clinical trials in normotensive populations have not found that dietary supplements of these minerals lowered blood pressure. We tested the hypothesis that normotensive persons who have low habitual intake of these minerals would be particularly responsive to supplementation. Three hundred normotensive women in the Nurses Health Study II (mean age, 39 years), whose reported intakes of potassium, calcium, and magnesium were between the 10th and 15th percentiles, received for 16 weeks' duration daily supplements of either potassium 40 mmol, calcium 30 mmol (1200 mg), magnesium 14 mmol (336 mg), all three minerals together or placebos. At baseline, mean (+/-SD) 24-hour ambulatory blood pressures were 116+/-8 and 73+/-6 mm Hg systolic and diastolic, respectively, and mean dietary intakes of potassium, calcium, and magnesium were 62+/-20 mmol/d, 638+/-265 mg/d, and 239+/-79 mg/d, respectively. The mean differences (with 95% confidence intervals) of the changes in systolic and diastolic blood pressures between the treatment and placebo groups were significant for potassium, -2.0 (-3.7 to -0.3) and -1.7 (-3.0 to -0.4), but not for calcium, -0.6 (-2.2 to 1.0) and -0.7 (-2.0 to 0.6), or for magnesium, -0.9 (-2.6 to 0.8) and -0.7 (-2.2 to 0.8). The administration of calcium and magnesium with potassium did not enhance the effect of potassium alone, and the changes in blood pressure were not significant -1.3 (-3.0 to 0.4) and -0.9 (-2.2 to 0.4). In conclusion, potassium, but not calcium or magnesium supplements, has a modest blood pressure-lowering effect in normotensive persons with low dietary intake. This study strengthens evidence for the importance of potassium for blood pressure regulation in the general population.

Adult↗

PubMed1997

Free radical induced polymerization of synthetic peptides into polymeric immunogens.

Free radical induced polymerization of vinyl monomers such as the acryloyl peptides described here is a facile and rapid reaction used routinely, for example, in the polymerization of acrylamide and bisacrylamide for the assembly of polyacrylamide gels. The technology allows the incorporation of many of the same or different peptide determinants into a single polymer chain. In this study large polymers containing multiple copies of peptides representing T- and B-cell determinants of influenza haemagglutinin were constructed. The determinants retained antigenicity after the polymerization procedure and the polymers were highly immunogenic; the levels of antibody obtained after a single dose of polymeric immunogen were at least as great as those achieved only after repeated doses of the equivalent monomeric peptide. The technology has a wide range of potential applications, not the least significant of which is the construction of designer immunogens for third generation vaccine candidates.

Amino Acid Sequence↗