Promotion of physical activity by Canadian Registered Dietitians in daily practice.

BACKGROUND: Dietitians are in an opportunistic position to promote healthy eating and active living. The purpose of this study was to determine counselling strategies of dietitians 1 year after attending a workshop designed to strengthen dietitians' self-efficacy for promoting physical activity (PA) as an adjunct to regular nutrition practice. METHODS: A convenience sample of Registered Dietitians (RDs) in Alberta, Canada (n=103) responded to an invitation via an electronic newsletter to complete a web-based survey that asked about counselling practices related to PA. RESULTS: Thirty-seven workshop attendees (n=37) were compared with a group of dietitians (n=66) who completed the survey but who did not attend the workshop. Nearly all (91%) respondents reported promoting PA in daily practice. Those who attended the workshop were more likely to refer clients to PA professionals (chi2=12.68, P<0.05) than those who were not workshop attendees. CONCLUSIONS: Despite a relatively modest response rate, there were clear suggestions that RDs in Alberta, Canada promote PA in daily practice and attending a workshop designed to facilitate the use of specific tools and strategies for promoting PA in daily practice resulted in increased referral of their clients to exercise specialists.

Responses of foliar delta13C, gas exchange and leaf morphology to reduced hydraulic conductivity in Pinus monticola branches.

We tested the hypothesis that branch hydraulic conductivity partly controls foliar stable carbon isotope ratio (delta13C) by its influence on stomatal conductance in Pinus monticola Dougl. Notching and phloem-girdling treatments were applied to reduce branch conductivity over the course of a growing season. Notching and phloem girdling reduced leaf-specific conductivity (LSC) by about 30 and 90%, respectively. The 90% reduction in LSC increased foliar delta13C by about 1 per thousand (P < 0.0001, n = 65), whereas the 30% reduction in LSC had no effect on foliar delta13C (P = 0.90, n = 65). Variation in the delta13C of dark respiration was similar to that of whole-tissues when compared among treatments. These isotopic measurements, in addition to instantaneous gas exchange measurements, suggested only minor adjustments in the ratio of intercellular to atmospheric CO2 partial pressures (ci/ca) in response to experimentally reduced hydraulic conductivity. A strong correlation was observed between stomatal conductance (gs) and photosynthetic demand over a tenfold range in gs. Although ci/ca and delta13C appeared to be relatively homeostatic, current-year leaf area varied linearly as a function of branch hydraulic conductivity (r2 = 0.69, P < 0.0001, n = 18). These results suggest that, for Pinus monticola, adjustment of leaf area is a more important response to reduced branch conductivity than adjustment of ci/ca.

Expression and function of IL-12 and IL-18 receptors on human tonsillar B cells.

IL-12 activates murine and human B cells, but little information is available as to the expression and function of IL-12R on human B lymphocytes. Here we show that the latter cells, freshly isolated from human tonsils, expressed the transcripts of both beta1 and beta2 chains of IL-12R and that beta2 chain mRNA was selectively increased (4- to 5-fold) by incubation with Staphylococcus aureus Cowan I bacteria or IL-12. B cell stimulation with IL-12 induced de novo expression of the transcripts of the two chains of IL-18R, i.e., IL-1 receptor-related protein and accessory protein-like. Functional studies showed that both IL-12 and IL-18 signaled to B cells through the NF-kappaB pathway. In the case of IL-12, no involvement of STAT transcription factors, and in particular of STAT-4, was detected. c-rel and p50 were identified as the members of NF-kappaB family involved in IL-12-mediated signal transduction to B cells. IL-12 and IL-18 synergized in the induction of IFN-gamma production by tonsillar B cells, but not in the stimulation of B cell differentiation, although either cytokine promoted IgM secretion in culture supernatants. Finally, naive but not germinal center or memory, tonsillar B cells were identified as the exclusive IL-12 targets in terms of induction of NF-kappaB activation and of IFN-gamma production.

Cross-linking of the CD40 ligand on human CD4+ T lymphocytes generates a costimulatory signal that up-regulates IL-4 synthesis.

Although there is good evidence that the induction of IL-4 synthesis in CD4+ T lymphocytes is favored by Ag presentation by B cells and not macrophages, the precise molecular signals provided by B cells to T cells that enhance IL-4 synthesis are not clear. To examine this issue, we established an APC-independent system to activate highly purified T cells and induce cytokine synthesis, using immobilized mAbs against several T cell surface molecules, including CD3, CD28, and the CD40 ligand (CD40L). The counter-receptors for all three of these molecules are expressed on B cells, and include CD40, which is expressed primarily on B cells, but also on dendritic cells and thymic epithelium. We found that IL-4 synthesis was greatly enhanced by triggering of CD40L on the T cell surface in conjunction with ligation of CD3/TCR and CD28, whereas ligation of CD3/TCR and CD28 in the absence of CD40L triggering resulted in little or no IL-4 synthesis. CD40L costimulation greatly enhanced IL-4 synthesis both in T cells from normal nonallergic adult subjects as well as in naive T cells from cord blood. Furthermore, we demonstrated that IL-4 synthesis was optimally enhanced when the strength of the CD3/TCR signal was limiting, while IL-4 synthesis was inhibited when CD3/TCR stimulation was maximal. These studies confirm that IL-4 synthesis can be induced in normal T lymphocytes in the absence of exogenous IL-4, and demonstrate that CD40L costimulation is of fundamental importance in regulation of IL-4 production. In addition, these findings provide a mechanism by which B cells preferentially enhance IL-4 synthesis in T cells at low Ag concentrations.

Stable carbon isotope discrimination, photosynthetic gas exchange, and growth differences among western larch families.

Photosynthetic gas exchange, stable carbon isotope discrimination (Delta), height and diameter were compared among five open-pollinated families of 12-year-old western larch trees growing in a common garden in Moscow, Idaho, USA. Statistically significant variation was detected among the families in the two growth traits, Delta and stomatal conductance to water vapor (g) (P /= 0.203). Water-use efficiency was strongly correlated with Delta (r = -0.95, P < 0.01). Neither growth trait was correlated with A (r 0.93) and height was not significantly correlated with Delta (r = -0.75, P = 0.15). Tree diameter and Delta were significantly correlated (r = -0.92, P = 0.03). These results were strongly influenced by a single family. Both the variation in Delta and correlation trends between Delta and the growth traits height and diameter suggest the possibility of selecting for high water-use efficiency with the potential for simultaneous gains in height and diameter growth.

Multiple mechanisms of tumorigenesis in E mu-myc transgenic mice.

Transgenic mice bearing a c-myc oncogene under control of the immunoglobulin heavy chain enhancer (E mu-myc mice) reproducibly develop and die from tumors of the B lymphocyte lineage (J.M. Adams, A.W. Harris, C.A. Pinkert, L.M. Corcoran, W.S. Alexander, S. Cory, R.D. Palmiter, and R.L. Brinster, Nature (Lond.), 318: 533-538, 1985; W.Y. Langdon, A. W. Harris, S. Cory, and J.M. Adams, Cell 47: 11-18, 1986; A.W. Harris, C.A. Pinkert, M. Crawford, W.Y. Langdon, R.L. Brinster, and J.M. Adams, J. Exp. Med., 167: 353-371, 1988; reviewed in S. Cory and J.M. Adams, Annu. Rev. Immunol., 6: 25-48, 1988). Analysis of lymphocytes obtained by serial sampling of peripheral blood from individual hemizygous (E mu-myc/0) and homozygous (E mu-myc/E mu-myc) transgenic mice indicates that proliferation in the original host and transplantability into histocompatible recipients are distinct properties that can be acquired independently and in either order. These two types of transgenic mice differ in that homozygous mice have about one-fourth the life span of hemizygous mice and develop polyclonal, non-transplantable tumors in comparison to the oligoclonal, highly transplantable malignancies seen in hemizygous animals. In conclusion, the overall concept of malignancy is best viewed as an aggregate of the separable parameters of cellular proliferation, clonality, tissue invasiveness, metastasis, and (experimental) transplantability. The E mu-myc transgenic mouse represents an attractive model in which to investigate the multistep nature and alternative pathways of tumorigenesis.

Transgenic T cell receptor interactions in the lymphoproliferative and autoimmune syndromes of lpr and gld mutant mice.

To investigate the role of T cell receptor (TcR) expression and interactions in development of lymphoproliferation and autoimmunity in lpr and gld mutant mice, and to determine whether these autoimmune mutations affect T cell selection and repertoire formation, we generated mice homozygous for either the gld or the lpr mutation and containing TcR alpha/beta transgenes (Von Boehmer, H., Annu. Rev. Immunol. 1990. 8: 531) specific for the male (H-Y) antigen in the context of H-2Db. Four main results emerged from analysis of these mice. First, expression of transgenic TcR had no effect on disease incidence and progression. Second, the accumulating T cells reflected normal processes of positive and negative selection. Third, cells expressing the transgenic TcR participated equally in lymphoproliferation regardless of whether their antigenic peptide and/or presenting major histocompatibility complex molecules were present or not. Fourth, expression of the TcR transgenes markedly altered the phenotype of the major accumulating lymphocyte subset. Thus, in these models of lymphoproliferation and autoimmunity. T cell repertoire formation proceeds normally, specific T cell recognition of antigen has no effect on the participation of individual clones, and the phenotype of the cells accumulating is sensitive to either the timing or the amount of TcR expression. These results are discussed in the context of the primary cause vs. secondary manifestations of autoimmunity in these models.

The AXB and BXA set of recombinant inbred mouse strains.

The recombinant inbred (RI) set of strains, AXB and BXA, derived from C57BL/6J and A/J, originally constructed and maintained at the University of California/San Diego, have been imported into The Jackson Laboratory and are now in the 29th to 59th generation of brother-sister matings. Genetic quality control testing with 45 proviral and 11 biochemical markers previously typed in this RI set indicated that five strains had been genetically contaminated sometime in the past, so these strains have been discarded. The correct and complete strain distribution patterns for 56 genetic markers are reported for the remaining RI strain set, which consists of 31 living strains and 8 extinct strains for which DNA is available. Two additional strains, AXB 12 and BXA 17, are living and may be added to the set pending further tests of genetic purity. The progenitors of this RI set differ in susceptibility to 27 infectious diseases as well as atherosclerosis, obesity, diabetes, cancer, cleft palate, and hydrocephalus. Thus, the AXB and BXA set of RI strains will be useful in the genetic analysis of several complex diseases.

Differences defined by bone marrow transplantation suggest that lpr and gld are mutations of genes encoding an interacting pair of molecules.

Homozygosity for either of the lymphoproliferation (lpr) or generalized lymphoproliferative disease (gld) mutations of mice causes the development of systemic lupus erythematosus-like autoimmune syndromes that are characterized by severe lymphadenopathy and highly elevated serum immunoglobulin levels. Although the mutations are nonallelic, analysis of homozygous lpr/lpr and gld/gld mice on the same strain background has indicated that the pathology and severity of the autoimmune syndromes induced by these mutations are indistinguishable. To explain this, it has previously been suggested that lpr and gld may represent mutations in molecules involved in sequential steps of an intracellular metabolic pathway of T cells. We have now investigated the behavior of both lpr and gld in a variety of bone marrow chimeras and have found that functional differences between lpr and gld become apparent after bone marrow transfer. Transfer of lpr/lpr bone marrow to irradiated congenic +/+ recipients caused the development of a graft-vs.-host-like lymphoid wasting syndrome, whereas transfer of gld/gld bone marrow to +/+ recipients resulted in development of a gld-like autoimmune syndrome. Additionally, gld/gld hosts behaved like +/+ hosts irrespective of the genotype of the donor bone marrow, whereas lpr/lpr hosts behaved unlike +/+ hosts when reconstituted with either lpr/lpr, gld/gld, or +/+ bone marrow. These are the first clear differences between these two mutations yet described. Our studies indicate that the molecule altered by the gld mutation is expressed only by bone marrow-derived cells, whereas the molecule altered by the lpr mutation is expressed by both bone marrow-derived cells and by one or more peripheral radioresistant cell populations. To reconcile these differences with the fact that homozygous lpr/lpr and gld/gld mice are indistinguishable, we suggest an alternative model for the relationship between the lpr and gld mutations in which the two molecules affected represent an interacting ligand-receptor pair expressed by different cells.

Bone marrow transplantation from mutant lpr/lpr mice. Functional abnormalities rather than alloantigenic differences appear to determine the development of a graft-vs.-host-like syndrome.

Transfer of bone marrow (BM) from autoimmunity-prone mice homozygous for the lymphoproliferation (lpr) mutation to irradiated congenic +/+ recipients has previously been shown to result in a syndrome similar to chronic graft-vs.-host (GVH) disease. It has been suggested that this syndrome may be due to an antigenic difference caused by the lpr mutation itself or to antigenic differences at loci closely linked to the lpr locus (Theofilopoulos, A. N. et al., J. Exp. Med. 1985. 162:1; Mosbach-Ozmen, L. and Loor, F., Thymus 1987. 9:197). However, the results presented here indicate that alloantigenic differences do not play a role in this syndrome. Instead, the chronic disease observed in lpr/lpr----(+/+) BM chimeras appears to develop as a result of a functional defect associated with the lpr mutation which is expressed shortly after transfer of lpr/lpr BM to irradiated recipients. This defect causes an increase in the levels of serum IgG1 and IgG2, which peak at 4-5 weeks post-transfer and then decline to normal levels by 9-10 weeks post-transfer. Inflammation similar to that observed in classic GVH reactions accompanies excess IgG production in congenic +/+ recipients but not in lpr/lpr recipients of lpr/lpr BM. We demonstrate that the GVH-like response occurring in lpr/lpr----(+/+) chimeras is dependent on mature T cells, but that either lpr/lpr or (+/+) T cells can support this reaction. These results suggest that transfer of lpr/lpr BM to normal mice causes immunoregulatory disturbances which lead to nonspecific activation of T cells. We speculate that lpr/lpr BM causes a GVH-like reaction in +/+ recipients but a systemic lupus erythematosus-like syndrome in lpr/lpr recipients because of intrinsic differences in the +/+ and lpr/lpr host environments. Considering these findings, the lpr/lpr----+/+ GVH model may be useful for analysis of factors capable of inducing undesirable reactions in clinical BM transplantation between nominally histocompatible donors and recipients, in addition to being informative about the nature of the lpr mutation itself.

Spontaneous Pneumocystis carinii pneumonia in immunodeficient mutant scid mice. Natural history and pathobiology.

The opportunistic pathogen Pneumocystis carinii (Pc) poses a major clinical health problem in individuals with immune deficiency, including those patients with human immunodeficiency (HIV)-associated acquired immune deficiency disease (AIDS). Heretofore, in vivo investigations of the biology of Pc and pathogenesis of pneumocystosis have generally employed steroid-induced immune suppression with antibiotic prophylaxis and protein deprivation. This approach has many drawbacks, chief among them being the widespread, multiple interacting effects caused by the inducing agents. Athymic (nude) mice and rats have been used, but are less than ideal, as the immune defect primarily affects T lymphocytes. This article describes the natural history, pathobiology, and environmental effects on Pc pneumonitis in nonaxenically housed mice homozygous for the autosomal recessive mutation 'severe combined immunodeficiency' (scid), which almost totally lack both cell-mediated and antibody-mediated immune functions. The predictability, unequivocal expression, high morbidity, and well-defined genetic basis make scid/scid mutant mice the model of choice for in vivo studies of spontaneous pneumocystosis.

Murine "viable motheaten" mutation reveals a gene critical to the development of both B and T lymphocytes.

In lethally irradiated normal mice reconstituted with both normal and autoimmune mutant viable motheaten (mev) bone marrow, the mev-derived B and T cells display aberrant behavior, while those derived from the normal bone marrow develop and function normally. The observed developmental abnormalities of mev B and T lymphocytes are therefore intrinsic to these cell types, rather than being determined by defective influences from the cells' environment. These data bring into question the in vivo significance of reported intercellular regulatory defects in motheaten (me) and mev mice and suggest that these mutations affect a gene whose product acts cell autonomously in the development of several hematopoietic cell lineages including B and T lymphocytes.

Novel B-cell maturation factor from spontaneously autoimmune viable motheaten mice.

Both in vivo and in vitro, mice homozygous for the viable motheaten mutation show severe immunodeficiency, polyclonal B-cell activation and Ig secretion, and spontaneous production of a lymphokine [B-cell maturation factor (BMF)] that directly drives the maturation of normal or tumor B cells to the state of active Ig secretion. BMF from motheaten mice is distinct from previously identified forms in its cells of origin (B cells) and biochemical characteristics (apparent Mr 15,000 by gel filtration and NaDodSO4/PAGE; pI 4.3 by chromatofocusing). Among the known murine single-gene models of autoimmunity, only motheaten mice show high levels of spontaneous BMF production, which therefore may be an important component in the development of this form of autoimmunity/immunodeficiency disease. The coincidence of spontaneous BMF production and uncontrolled Ig secretion within the same mutant mouse constitutes the strongest evidence to date for a significant physiological (in vivo) role for BMFs.

Gamma-interferon is one of several direct B cell-maturing lymphokines.

Two classes of molecules often released after the interaction of T lymphocytes, macrophages and antigen are B-cell maturation factors (BMF)1-3 and immune (gamma) interferon (IFN-gamma)4-7. BMFs directly induce the maturation of resting B lymphocytes to the state of active immunoglobulin secretion, while IFN-gamma is defined by the reduction of viral infectivity in vitro. However, interferons have been shown to have a variety of effects and they have also been reported both to increase and decrease B-cell differentiation in intact animals and complex cellular mixtures in vitro. Here we show that murine IFN-gamma produced by recombinant DNA technology shows similar biological effects to BMFs from two other sources. All three preparations induce immunoglobulin secretion by both normal resting murine splenic B cells and the comparable B-cell tumour line WEHI-279.1 (refs 1, 3). IFN-gamma and the other two BMFs are not identical, however, as anti-IFN-gamma antibodies block the effects on B cells of IFN-gamma, but not those of the other two lymphokines. IFN-gamma may be one of several molecules with a direct role in driving the maturation of resting B cells to active immunoglobulin secretion.

B cell maturation factor: effects on various cell populations.

B cell maturation factor (BMF) is a lymphokine that promotes the maturation of resting murine splenic B lymphocytes, and the analogous B cell tumor line WEHI-279, to the state of active immunoglobulin (Ig) secretion. All subsets of normal B cells examined, including neonatal and adult B cells, B cells from various organs, and B cells from CBA/N mice, are inducible by BMF. Induction of Ig secretion is independent of thymus-derived cells, LPS receptors, and MHC haplotype, because nude, C3H/He, and mice of many strains are equally responsive to BMF. Purified B cells prepared by using a fluorescence-activated cell sorter also respond to BMF, showing that BMF directly interacts with and triggers Ig secretion by B cells. In limiting dilution cultures, most normal resting splenic B cells or WEHI-279 B tumor cells are inducible by BMF. By using the WEHI-279 cells as a model system, specific aspects of the BMF response have been analyzed. In terms of the degree of stimulation observed, the primary mechanism for the induction of Ig secretion by BMF is an enhanced and balanced synthesis of Ig heavy (H) and light (L) chains. A less significant component of the induced Ig secretion is an increase in the ratio of secretory to membrane H chains produced. Kinetically, the shift in the ratio of secretory to membrane H chain forms occurs first, and this is followed by the increased synthesis of both L and H chains. Responding B cells also die during this induction process. Although the changes in the ratio of H chain forms, H and L synthesis, and cell viability take several days to occur, BMF will program significant later responses after only 1 or a few hr of interaction with target B cells.

Cholesterol synthesis in polyclonally activated cytotoxic lymphocytes and its requirement for differentiation and proliferation.

The kinetics of sterol synthesis and DNA synthesis in polyclonally activated, concanavalin A-stimulated spleen cell cultures were analyzed. Inhibition of DNA synthesis by 1-beta-D-arabinofuranosylcytosine (Ara-C) did not abrogate the formation of cytotoxic effector cells. However, inhibition of sterol synthesis by 25-hydroxycholesterol inhibited formation of cytotoxic effector cells as well as cellular proliferation. The inhibition of cytotoxicity correlated well with the dose of 25-hydroxycholesterol administered and was dependent on the time of administration. The agent had to be present when sterol synthesis occurred normally during the time lapse before DNA synthesis began. Compactin had the same effect as 25-hydroxycholesterol. The effects of inhibition of sterol biosynthesis on cytotoxicity could be counteracted by addition of cholesterol-containing liposomes. Based on these experiments, the links between proliferation and differentiation in lymphocytes are discussed.