A requirement for specific cellular collaboration has been demonstrated for the induction of humoral antibody (1-3), cytotoxic T cells (4,5), and for those helper T cells able to help the induction of B cells (6). Leung and Ada (7) have recently shown that antigen-specific cells can significantly enhance the primary in vitro induction of delayed-type hypersensitivity (DTH)a to influenza virus. We independently developed an in vitro system in which the induction of significant DTH reactivity is dependent on the presence of antigen-specific helper T cells. We used this system to determine the antigen recognition requirements by which these helper T cells act in the induction of DTH precursor cells.A phenomenon referred to as carrier specificity in the elicitation of DTH has been reported in the literature (8, 9), i.e., animals sensitized to a hapten on a given carrier will respond with DTH reactivity only when challenged with the hapten on the same carrier as was used for sensitization. This phenomenon has been insufficiently characterized to ascertain whether it is simply quantitative, in that only a small amount of the DTH reactivity is directed against the hapten, or whether it reflects either a requirement for specific cellular collaboration in the elicitation of DTH and/or that the DTH effector cells are specific for neoantigenic determinants created by coupling the hapten to the carrier. In any case, the phenomenon does not bear on the cellular requirements for inducing DTH and is in this sense different from the classical carrier effects described for the induction of humoral responses.The mechanism by which antigen-specific cells cooperate in the induction of B and helper T cells is known to be most effective when the two specific classes of cells recognize determinants that are physically linked to one another (10,11). With the recent establishment of experimental systems that allow DTH to be induced in vitro (12, 13), it has become possible to determine the cellular requirements for the induction of DTH. The experiments described in this paper were designed to test whether (a) specific cellular collaboration was required for the induction of DTH and * Supported by a grant from the Medical Research Council of Canada to the MRC group on immunoregulation, and a studentship and research allowance from the Alberta Heritage Foundation for Medical Research awarded to M. J. Tucker.1 Abbreviations used in this paper: BRBC, burro erythrocytes; CRBC, chicken erythrocytes; DTH, delayedtype hypersensitivity; FCS, fetal calf serum; FGG, fowl gamma globulin; FGG-BRBC, fowl gamma globulin physically coupled to burro erythrocytes; FGG-MRBC, fowl gamma globulin physically coupled to mouse erythrocytes; i.v., intravenous; MRBC, mouse erythrocytes; RBC, erytbrocytes; s.c., subcutaneous; Thy-1, thymus-derived cell marker.J. Exo. MED.

Muscle strength was assessed from the maximum force that could be exerted voluntarily by triceps brachii muscles of 72 people with chronic cervical spinal cord injury (SCI) at or above C7, and 18 able-bodied (A-B) subjects. The magnitude of co-activation was estimated from the ratio of biceps brachii surface EMG to triceps plus biceps brachii surface EMG (biceps EMG/ triceps + biceps EMG). Maximum voluntary forces exerted by triceps brachii muscles of SCI subjects were significantly lower than those of controls (p < 0.01). Strength differences between muscles of SCI men and women were not evident. Significant positive relationships were found (linear or curvilinear) between triceps surface EMG and force for all control muscles (n = 19) and for 54% of the muscles of SCI subjects (n = 73). The remaining muscle of SCI subjects (n = 63) were either so weak that only one EMG and force value could be measured or EMG occurred without detectable force. For control muscles (n = 19), the mean triceps-biceps EMG ratio was 0.15+/-0.05 for all voluntary contraction force levels. For muscles of SCI subjects, 41 had EMG ratios similar to those of controls, co-activity largely attributed to EMG cross talk; 19 muscles had constant EMG ratios, but these were three standard deviations above the control means; 13 muscles had EMG ratios that decreased or increased as force increased. Muscles of SCI subjects with greater than control levels of co-activity during maximum voluntary contractions (high EMG ratios) were as strong as muscles with EMG ratios similar to controls. These results provide quantitative descriptions of voluntary muscle weakness after SCI and a database from which to evaluate improvements in muscle strength. These data also show that, for many SCI subjects, any triceps-biceps co-activation is similar to that of controls and does not necessarily distort muscle control unduly.

The role of the world's religions may be crucial in rethinking the relationship of humans to the natural world in a mutually enhancing manner. I first acknowledge, although briefly, the scale and complexity of the environmental crisis. Next, I suggest the need for seeking common grounds to work toward a resolution of the crisis. Then I highlight the call for the co-operation and action of the world's religions from particular sectors such as environmental groups, the United Nations, political leaders, scientists, and ethicists. Finally, I document some of the responses and the resources of the world's religions in evoking new attitudes toward nature.

Religious communities are playing an increasingly important role in advancing Earth Stewardship. We briefly summarize the potential of religions and religious values to support this initiative, characterizing its development and acknowledging the inherent tensions between the problems and promise of religious influences. Mobilizing religious believers to contribute to responsible stewardship of the Earth requires a critical appreciation of the complexity of religious traditions and the ways that religious communities view nature, as well as the cultural and spiritual resources that religious teachings provide in confronting change and human suffering. We emphasize religious virtues that favor sustainable resource use and key developments that have prompted fruitful dialogue between ecologists and religious believers. We also describe promising alliances between scientists and spiritual leaders that may help to encourage cooperative Earth Stewardship. Religions have great potential to transform cultures toward improved Earth Stewardship, in collaboration with key scientific, economic, public policy, and education partners.

This paper aims to describe the relation between standard semen analysis parameters (concentration, motility and morphology) and sperm chromatin structure assay (SCSA) results among patients referred for infertility evaluation. Healthy males (n=136) seeking infertility consultation were evaluated prospectively by semen analysis and sperm chromatin structure assay (SCSA). Significant inverse correlations were observed between high sperm concentration and DNA fragmentation index (DFI) and high DNA stainability (HDS) (r=- 0.45; P<0.001, and r=- 0.40; P<0.001, respectively). Both progressive motility and normal morphology were also strongly inversely correlated with DFI and HDS. However, in stratified analysis the correlation between concentration < or =20 M/ml and DFI, and concentration < or =20 M/ml and HDS were not significant (P=0.31 and 0.38, respectively). For men with sperm motility < or =40% the correlation between motility and HDS was not significant (P=0.22), but between motility and DFI the correlation remained significant (P=0.04). Although strong correlations between DFI, HDS and semen analysis findings were noted in the overall study population, when oligozoospermic and asthenozoospermic patients were analysed separately the correlation between concentration and sperm chromatin fragmentation was not significant. For such men, SCSA appears to be a diagnostic variable independent of the semen analysis, providing information about nuclear abnormalities not readily apparent from standard semen analysis alone. Additionally, SCSA data may offer explanations for previous miscarriage, providing closure for some couples contemplating future use of anonymous donor sperm.