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Biomedical subjects

J J Bell

Publications and source records attributed to J J Bell.

At least 19 recordsLinked to original sources
PubMed2005

Low genetic diversity in a marine nature reserve: re-evaluating diversity criteria in reserve design.

Little consideration has been given to the genetic composition of populations associated with marine reserves, as reserve designation is generally to protect specific species, communities or habitats. Nevertheless, it is important to conserve genetic diversity since it provides the raw material for the maintenance of species diversity over longer, evolutionary time-scales and may also confer the basis for adaptation to environmental change. Many current marine reserves are small in size and isolated to some degree (e.g. sea loughs and offshore islands). While such features enable easier management, they may have important implications for the genetic structure of protected populations, the ability of populations to recover from local catastrophes and the potential for marine reserves to act as sources of propagules for surrounding areas. Here, we present a case study demonstrating genetic differentiation, isolation, inbreeding and reduced genetic diversity in populations of the dogwhelk Nucella lapillus in Lough Hyne Marine Nature Reserve (an isolated sea lough in southern Ireland), compared with populations on the local adjacent open coast and populations in England, Wales and France. Our study demonstrates that this sea lough is isolated from open coast populations, and highlights that there may be long-term genetic consequences of selecting reserves on the basis of isolation and ease of protection.

Analysis of Variance↗
PubMed2003

Effect of disturbance on assemblages: an example using porifera.

Extensive sponge assemblages are found in a number of habitats at Lough Hyne Marine Nature Reserve. These habitats are unusual in experiencing a range of environmental conditions, even though they are only separated by small geographic distances (1-500 m), reducing the possibility of confounding effects between study sites (e.g., silica concentrations and temperature). Sponge assemblages were examined on ephemeral (rocks), stable (cliffs), and artificial (slate panels) hard substrata from high- and low-energy environments that were used to represent two measures of disturbance (flow rate and habitat stability). Sponge assemblages varied considerably between habitat types such that only 26% (25 species) of species reported were common to both rock and cliff habitats. Seven species (of a total of 96 species) were found in the least-developed assemblages (slate panels) and were common to all habitats. Sponge assemblages on rocks and panels varied little between high- and low-energy environments, whereas assemblages inhabiting cliffs varied considerably. Assemblage composition was visualized using Bray-Curtis similarity analysis and Multi-Dimensional Scaling, which enabled differences and similarities between sponge assemblages to be visualized. Cliffs from high- and low-energy sites had different assemblage compositions compared to large rocks, small rocks, and panels, all of which had similar assemblages irrespective of environmental conditions. Differences in assemblages were partially attributed to sponge morphology (shape), as certain morphologies (e.g., arborescent species) were excluded from 2-D rock habitats. Other mechanisms were also considered responsible for the sponge assemblages associated with different habitats.

Animals↗
PubMed2001

Neonatal exposure to antigen primes the immune system to develop responses in various lymphoid organs and promotes bystander regulation of diverse T cell specificities.

Neonatal exposure to Ag has always been considered suppressive for immunity. Recent investigations, however, indicated that the neonatal immune system could be guided to develop immunity. For instance, delivery of a proteolipid protein (PLP) peptide on Ig boosts the neonatal immune system to develop responses upon challenge with the PLP peptide later. Accordingly, mice given Ig-PLP at birth and challenged with the PLP peptide as adults developed proliferative T cells in the lymph node that produced IL-4 instead of the usual Th1 cytokines. However, the spleen was unresponsive unless IL-12 was provided. Herein, we wished to determine whether such a neonatal response is intrinsic to the PLP peptide or could develop with an unrelated myelin peptide as well as whether the T cell deviation is able to confer resistance to autoimmunity involving diverse T cell specificities. Accordingly, the amino acid sequence 87-99 of myelin basic protein was expressed on the same Ig backbone, and the resulting Ig-myelin basic protein chimera was tested for induction of neonatal immunity and protection against experimental allergic encephalomyelitis. Surprisingly, the results indicated that immunity developed in the lymph node and spleen, with deviation of T cells occurring in both organs. More striking, the splenic T cells produced IL-10 in addition to IL-4, providing an environment that facilitated bystander deviation of responses to unrelated epitopes and promoted protection against experimental allergic encephalomyelitis involving diverse T cell specificities. Thus, neonatal exposure to Ag can prime responses in various organs and sustain regulatory functions effective against diverse autoreactive T cells.

Animals↗
PubMed2001

Neonatal immunity develops in a transgenic TCR transfer model and reveals a requirement for elevated cell input to achieve organ-specific responses.

In recent years, it has become clear that neonatal exposure to Ag induces rather than ablates T cell immunity. Moreover, rechallenge with the Ag at adult age can trigger secondary responses that are distinct in the lymph node vs the spleen. The question addressed in this report is whether organ-specific secondary responses occur as a result of the diversity of the T cell repertoire or could they arise with homogeneous TCR-transgenic T cells. To test this premise, we used the OVA-specific DO11.10 TCR-transgenic T cells and established a neonatal T cell transfer system suitable for these investigations. In this system, neonatal T cells transferred from 1-day-old DO11.10/SCID mice into newborn (1-day-old) BALB/c mice migrate to the host's spleen and maintain stable frequency. The newborn BALB/c hosts were then given Ig-OVA, an Ig molecule carrying the OVA peptide, and challenged with the OVA peptide in CFA at the age of 7 wk; then their secondary responses were analyzed. The findings show that the lymph node T cells were deviated and produced IL-4 instead of IFN-gamma and the splenic T cells, although unable to proliferate or produce IFN-gamma, secreted a significant level of IL-2. Supply of exogenous IL-12 during Ag stimulation restores both proliferation and IFN-gamma production by the splenic T cells. This restorable form of splenic unresponsiveness referred to as IFN-gamma-dependent anergy required a transfer of a high number of neonatal DO11.10/SCID T cells to develop. Thus, the frequency of neonatal T cell precursors rather than repertoire diversity exerts control on the development of organ-specific neonatal immunity.

Amino Acid Sequence↗
PubMed2001

Neonatal exposure to antigen induces a defective CD40 ligand expression that undermines both IL-12 production by APC and IL-2 receptor up-regulation on splenic T cells and perpetuates IFN-gamma-dependent T cell anergy.

T cell deletion and/or inactivation were considered the leading mechanisms for neonatal tolerance. However, recent investigations have indicated that immunity develops at the neonatal stage but evolves to guide later T cell responses to display defective and/or biased effector functions. Although neonatal-induced T cell modulation provides a useful approach to suppress autoimmunity, the mechanism underlying the biased function of the T cells remains unclear. In prior studies, we found that exposure of newborn mice to Ig-PLP1, a chimera expressing the encephalitogenic proteolipid protein (PLP) sequence 139-151, induced deviated Th2 lymph node cells producing IL-4 instead of IL-2 and anergic splenic T cells that failed to proliferate or produce IFN-gamma yet secreted significant amounts of IL-2. However, if assisted with IFN-gamma or IL-12, these anergic splenic T cells regained full responsiveness. The consequence of such biased/defective T cells responses was protection of the mice against experimental allergic encephalomyelitis. In this study, investigations were performed to delineate the mechanism underlying the novel form of IFN-gamma-dependent splenic anergy. Our findings indicate that CD40 ligand expression on these splenic T cells is defective, leading to noneffective cooperation between T lymphocytes and APCs and a lack of IL-12 production. More striking, this cellular system revealed a requirement for IL-2R expression for CD40 ligand-initiated, IL-12-driven progression of T cells into IFN-gamma production.

Animals↗
PubMed2001

Multi-modal antigen specific therapy for autoimmunity.

Peripheral tolerance, represents an attractive strategy to down-regulate previously activated T cells and suppress an ongoing disease. Herein, immunoglobulins (Igs) were used to deliver self and altered self peptides for efficient peptide presentation without costimulation to test for modulation of experimental allergic encephalomyelitis (EAE). Accordingly, the encephalitogenic proteolipid protein (PLP) sequence 139-151 (referred to as PLP1) and an altered form of PLP1 known as PLP-LR were genetically expressed on Igs and the resulting Ig-PLP1 and Ig-PLP-LR were tested for efficient presentation of the peptides and for amelioration of ongoing EAE. Evidence is presented indicating that Ig-PLP1 as well as Ig-PLP-LR given in saline to mice with ongoing clinical EAE suppresses subsequent relapses. However, aggregation of both chimeras allows crosslinking of Fcgamma receptors (FcgammaRs) and induction of IL-10 production by APCs but does not promote the up-regulation of costimulatory molecules. Consequently, IL-10 displays bystander suppression and synergizes with presentation without costimulation to drive effective modulation of EAE. As Ig-PLP1 is more potent than Ig-PLP-LR in the down-regulation of T cells, we conclude that peptide affinity plays a critical role in this multi-modal approach of T cell modulation.

Animals↗
PubMed2000

Coupling of peripheral tolerance to endogenous interleukin 10 promotes effective modulation of myelin-activated T cells and ameliorates experimental allergic encephalomyelitis.

Several immune-based approaches are being considered for modulation of inflammatory T cells and amelioration of autoimmune diseases. The most recent strategies include simulation of peripheral self-tolerance by injection of adjuvant free antigen, local delivery of cytokines by genetically altered T cells, and interference with the function of costimulatory molecules. Although promising results have been obtained from these studies that define mechanisms of T cell modulation, efficacy, practicality, and toxicity, concerns remain unsolved, thereby justifying further investigations to define alternatives for effective downregulation of aggressive T cells. In prior studies, we demonstrated that an immunoglobulin (Ig) chimera carrying the encephalitogenic proteolipid protein (PLP)1 peptide corresponding to amino acid sequence 139-151 of PLP, Ig-PLP1, is presented to T cells approximately 100-fold better than free PLP1. Here, we demonstrate that aggregation endows Ig-PLP1 with an additional feature, namely, induction of interleukin (IL)-10 production by macrophages and dendritic cells, both of which are antigen-presenting cells (APCs). These functions synergize in vivo and drive effective modulation of autoimmunity. Indeed, it is shown that animals with ongoing active experimental allergic encephalomyelitis dramatically reduce the severity of their paralysis when treated with adjuvant free aggregated Ig-PLP1. Moreover, IL-10 displays bystander antagonism on unrelated autoreactive T cells, allowing for reversal of disease involving multiple epitopes. Therefore, aggregated Ig-PLP1 likely brings together a peripheral T cell tolerance mechanism emanating from peptide presentation by APCs expressing suboptimal costimulatory molecules and IL-10 bystander suppression to drive a dual-modal T cell modulation system effective for reversal of autoimmunity involving several epitopes and diverse T cell specificities.

Animals↗
PubMed1998

Lack of correlation between growth hormone provocative test results and subsequent growth rates during growth hormone therapy.

OBJECTIVES: To determine whether there is a relationship between the peak GH level in pituitary stimulation tests and the growth rate in response to treatment with recombinant human growth hormone (GH). METHODS: We identified 24 843 patients in the National Cooperative Growth Study database who had not been treated previously with GH therapy and divided them into three groups according to the peak GH level in pituitary stimulation testing: 1) <10 microg/L (n = 14 132); 2) >/=10 microg/L (n = 7476); and 3) no test results reported (n = 3235). Growth rates in each group in response to GH therapy were examined. RESULTS: The children in each of the groups responded to GH therapy with a vigorous increase in growth rates (means, 8.4 to 9.5 cm/y) in the first year, followed by a gradual decline and then stabilization at 1.0 to 1.9 cm/y greater than the pretreatment values. There were large overlaps in the growth rates among the groups, but the differences were significant. The growth rates in a smaller group of children (n = 187) who had normal GH responses and normal growth rates before GH therapy increased similarly in the first year of therapy (to 7.7 to 9.2 cm/y), but then declined rapidly to the pretreatment values or lower. CONCLUSION: Because the GH response to pituitary stimulation testing is inadequate for diagnosing GH deficiency, such testing also is inadequate for determining whether GH treatment should be prescribed in a child with short stature. In addition, the waning response to GH therapy in normally growing short children suggests that this treatment may not have a sustained benefit in these children.

Body Height↗
PubMed1996

Gender change from female to male in classical congenital adrenal hyperplasia.

The psychoendocrinology of the development of normal gender identity and its variations is poorly understood. Studies of gender development in individuals born with endocrinologically well-characterized intersex conditions are heuristically valuable for the disaggregation of factors that are acting in concert during normal development. Four 46,XX individuals with classical congenital adrenal hyperplasia (CAH) and atypical gender identity entered a comprehensive research protocol including systematic interviews and self-report inventories on gender role behavior and identity, sexual history, and psychiatric history. Some of the data on gender variables were compared to data from 12 CAH women with the salt-wasting variant (CAH-SW) with female gender identity. The four patients (ages 28, 35, 38, and 30 years) represented three different subtypes of classical early-onset CAH: 21-OH deficiency, simple virilizing (CAH-SV); 21-OH deficiency, salt-wasting (CAH-SW); and 11-beta-OH deficiency. Their medical histories were characterized by delay beyond infancy or lack of surgical feminization of the external genitalia and progressive virilization with inconsistent or absent glucocorticoid replacement therapy. Although three patients had undergone one or more genital surgeries, all had retained at least some orgasmic capacity. In regard to childhood gender-role behavior, the four gender-change patients tended to be more masculine or less feminine than (behaviorally masculinized) CAH-SW controls. All patients were sexually attracted to females only. The process of gender change was gradual and extended well into adulthood. The most plausible factors contributing to cross-gender identity development in these patients appeared to be neither a particular genotype or endocrinotype nor a sex-typing bias on the part of the parents but a combination of a gender-atypical behavioral self-image, a gender-atypical body image, and the development of erotic attraction to women. Implications for psychosocial management are also discussed.

Adrenal Hyperplasia, Congenital↗
PubMed1991

Cognitive ability and everyday functioning in women with Turner syndrome.

This paper presents results from an assessment of cognitive ability and everyday functioning in a group of adult women with Turner syndrome (TUS). Twenty-three TUS women were compared with 23 matched controls with constitutional short stature (CSS). A subgroup of 10 TUS women were compared with their nondisabled female siblings. On the Wechsler Adult Intelligence Test-Revised (Wechsler, 1981), no significant group differences were found in Verbal IQ. There were significant group differences for Performance IQ and Full Scale IQ, largely due to specific deficits in the area of spatial and mathematical ability. These difficulties were also evident on the Benton Visual Retention Test-Revised (Benton, 1974). TUS individuals had significantly lower educational attainment than CSS controls but did not differ from their siblings. TUS individuals had significantly lower occupational attainment than the women in both comparison groups.

Achievement↗
PubMed1989

Psychopathology and social functioning in women with Turner syndrome.

Turner syndrome (TUS) in women is associated with sex chromosome abnormalities, ovarian dysgenesis with estrogen deficiency, and short stature. The goal of this study was to assess the long-term effects of these sex chromosome and hormonal anomalies on psychopathology and social functioning. We report interview and questionnaire data concerning lifetime history of mental disorders and current psychiatric symptoms. Also reported are data from questionnaires and interviews evaluating social functioning as measured by education, occupation, personal resources, and sexual behavior. Twenty-three TUS women were studied and compared with 23 closely matched women with constitutional short stature (CSS) and with 10 normal sisters of the TUS women. TUS women reported generally less mental disorder and comparable rates of psychiatric symptoms. On the other hand, they had lower overall functioning on a measure of global psychological health and had more impairment in social functioning as measured by achievement of adult milestones. We conclude that TUS women display less mental illness by positive symptom-oriented criteria but also less mental health when day-to-day functioning is considered. Our data suggest that differences in TUS women cannot be explained solely by short stature and may be related to other psychosocial, genetic, endocrine, or CNS effects of the syndrome.

Achievement↗
PubMed1987

Dichotic listening following idiopathic precocious puberty: speech processing capacity and temporal efficiency.

Eleven right-handed adolescent females with a history of idiopathic precocious puberty (IPP) were compared to 11 pair-matched normal controls of similar maturational status. They were tested on a dichotic consonant-vowel (CV) discrimination task in which syllables were presented simultaneously to the two ears or with an interaural delay of 30 or 60 msec. The IPP and control groups did not differ: (1) in right-ear advantages; (2) in double-correct or total correct measures of accuracy; or (3) in "lag effects." The findings provide further evidence that timing of puberty--maturation rate--is not related to verbal ability or lateralization in adolescent females.

Adolescent↗
PubMed1986

Clinical studies with recombinant-DNA-derived methionyl human growth hormone in growth hormone deficient children.

Thirty-six children with growth hormone deficiency were treated for up to 48 months with methionyl human growth hormone (hGH) synthesised by DNA recombinant methods. The growth rate for these children increased from 3.2 +/- 1.1 cm/yr to 10.5 +/- 2.2 cm/yr (mean +/- SD). This was similar to the effect of pituitary hGH in ten GH deficient children, 3.8 +/- 1.0 to 10.1 +/- 1.1 cm/yr. Serum somatomedin C rose from 0.26 +/- 0.23 U/ml to 0.79 +/- 0.53 U/ml after 6 months of methionyl-hGH therapy, similar to the effect of pituitary hGH. The incidence of antibody formation to methionyl-hGH was higher than that observed with pituitary hGH (Kabi) but poor growth was observed only in the one patient on methionyl-hGH who acquired high-titre high-binding-capacity antibodies to hGH. No consistent changes in levels of antibodies to Escherichia coli proteins were detected. No other allergic manifestations or systemic side-effects were demonstrable.

Adolescent↗
PubMed1980

Effect of growth hormone on human drug metabolism: time course and substrate specificity.

Replacement therapy for six weeks with human growth hormone (hGH) in deficient children has been shown to produce a significant lengthening of amobarbital t1/2. Studies to define the time course of this effect were carried out and indicate either no change or a minimal change after one to eight days of treatment. The increased t1/2 noted at six weeks persists for at least one year. In contrast to amobarbital, theophylline was found to exhibit a shortening of t1/2 from a mean of 7.52 +/- 4.44 (SD) to a mean of 3.38 +/- 1.23 hours in four subjects. Thus, replacement therapy with hGH results in quantitatively large but opposite changes in the elimination of these two drugs. For both substrates, however, t1/2 after hGH replacement more closely resembles values reported for normal subjects. This suggests that hGH may be a major determinant of in vivo drug elimination.

Adolescent↗