Fluctuations in spring climate in the western United States over the last 4-5 decades are described by examining changes in the blooming of plants and the timing of snowmelt-runoff pulses. The two measures of spring's onset that are employed are the timing of first bloom of lilac and honeysuckle bushes from a long-term cooperative phenological network, and the timing of the first major pulse of snowmelt recorded from high-elevation streams. Both measures contain year-to-year fluctuations, with typical year-to-year fluctuations at a given site of one to three weeks. These fluctuations are spatially coherent, forming regional patterns that cover most of the west. Fluctuations in lilac first bloom dates are highly correlated to those of honeysuckle, and both are significantly correlated with those of the spring snowmelt pulse. Each of these measures, then, probably respond to a common mechanism. Various analyses indicate that anomalous temperature exerts the greatest influence upon both interannual and secular changes in the onset of spring in these networks. Earlier spring onsets since the late 1970s are a remarkable feature of the records, and reflect the unusual spell of warmer-than-normal springs in western North America during this period. The warm episodes are clearly related to larger-scale atmospheric conditions across North America and the North Pacific, but whether this is predominantly an expression of natural variability or also a symptom of global warming is not certain.

The San Francisco Bay estuary has been rapidly modified by human activity. Diking and filling of most of its wetlands have eliminated habitats for fish and waterfowl; the introduction of exotic species has transformed the composition of its aquatic communities; reduction of freshwater inflow by more than half has changed the dynamics of its plant and animal communities; and wastes have contaminated its sediments and organisms. Continued disposal of toxic wastes, the probable further reduction in freshwater inflow, and the possible synergy between the two provide the potential for further alteration of the estuary's water quality and biotic communities.

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BACKGROUND CONTEXT There have been no full-scale trials of the optimal number of visits for the care of any condition with spinal manipulation. PURPOSE To identify the dose-response relationship between visits to a chiropractor for spinal manipulation and chronic low back pain (cLBP) outcomes; to determine the efficacy of manipulation by comparison to a light-massage control. STUDY DESIGN/SETTING Practice-based randomized controlled trial. PATIENT SAMPLE Four hundred participants with cLBP. OUTCOME MEASURES The primary cLBP outcomes were the100-point Modified Von Korff pain intensity and functional disability scales evaluated at the 12 and 24-week primary endpoints. Secondary outcomes included days with pain and functional disability, pain unpleasantness, global perceived improvement, medication use, and general health status. METHODS One hundred participants with cLBP were randomized to each of four dose levels of care: 0, 6, 12, or 18 sessions of spinal manipulation from a chiropractor. Participants were treated three times per week for six weeks. At sessions when manipulation was not assigned, they received a focused light massage control. Covariate-adjusted linear dose effects and comparisons to the no-manipulation control group were evaluated at 6, 12, 18, 24, 39, and 52 weeks. RESULTS For the primary outcomes, mean pain and disability improvement in the manipulation groups was 20 points by 12 weeks and sustainable to 52 weeks. Linear dose-response effects were small, reaching about two points per six manipulation sessions at 12 and 52 weeks for both variables (P < .025). At 12 weeks, the greatest differences from the no-manipulation control were found for 12 sessions (8.6 pain and 7.6 disability points, P < .025); at 24 weeks, differences were negligible. At 52 weeks, the greatest group differences were seen for 18 visits (5.9 pain and 8.8 disability points, P < .025). CONCLUSIONS The number of spinal manipulation visits had modest effects on cLBP outcomes above those of 18 hands-on visits to a chiropractor. Overall, 12 visits yielded the most favorable results, but was not well distinguished from other dose levels.

The McCulloch retractor generates a higher IMP than the Norfolk and Norwich retractor. However, postoperative improvement in VAS, ODI, and SF-36 scores in these patients was associated with a shorter duration of muscle retraction and not the degree of IMP or IPP generated. In this respect, periodic relaxation of the paraspinal muscle retractors during surgery to allow muscle perfusion may help to reduce postoperative back pain and disability.