Cryo-electron tomography of neurospora mitochondria.

Cryo-electron tomography was used to study the structural organization of whole frozen-hydrated mitochondria from Neurospora crassa. Unlike mitochondria from many other species and tissues, in this case the cristae form a three-dimensional network of interconnected lamellae. Basically, the three-dimensional structure of ice-embedded mitochondria from this species is consistent with previous descriptions of mitochondria prepared by chemical fixation and resin embedding. Nonetheless, ice-embedded mitochondria display some important differences: the outer surface of the mitochondria was found to be rather smooth, the intermembrane space was constant in width, and distinct contact sites between the membranes were clearly revealed. Furthermore ATP synthase particles on the outer surface of an "inside-out vesicle" were visible in 3-D reconstructions. Thus, cryo-electron tomography can provide detailed insights into these organelles with minimal perturbations of the physiological state. This indicates that it is a realistic goal to achieve "molecular resolution" with rather large biological specimens in the near future, ultimately allowing the identification and localization of macromolecules in their cellular context.

Larva-adult relationships in an ancestral dipteran: A re-examination of sensillar pathways across the antenna and leg anlagen of Chaoborus crystallinus (DeGeer, 1776; Chaoboridae).

In one of his classical studies on insect metamorphosis, Weismann compared the imaginal anlagen of the ancestral phantom midge, Chaoborus, with those of advanced brachycerans. We have expanded his findings on the relationships between larval and imaginal organs using electron microscopy and cobalt backfilling of the antenna and leg anlagen and the axonal trajectories of corresponding larval sensilla. We show that both primordia are confluent with the larval antennae and "leg" sensilla (an ancestral Keilin organ), respectively. These fully developed larval organs represent the distal tips of the imaginal anlagen rather than separate cell clusters. The axons of the larval antenna and leg sensilla project across the corresponding anlagen to their target neuromeres within the central nervous system (CNS). Within the discs, nerves composed of these larval axons, developing afferent fibres and efferences ascending from the CNS are found. Both the structure of the primordia and the axonal trajectories thus relate the situation found in advanced brachycerans with that seen in more ancestral insects. In addition, the larval antennae, legs, wings and even the eyes possess very similar afferent pioneer trajectories supporting the idea that the described pattern is generally used in the ontogeny of sensory systems.

The epidemiology of medical care utilization by severely-disabled independently-living adults.

A prospective study of the medical care utilization experience of 205 severely-disabled independently-living adults in Eastern Massachusetts shows that there was a mean of 0.83 +/- 1.26 hospital admissions, 9.9 +/- 22.7 hospital days, 1.5 +/- 2.31 emergency room (ER) visits, and 26.88 +/- 44.4 outpatient contacts per person per year. Among those hospitalized, the mean experience was 16.2 +/- 27.1 days per person per year; mean length-of-stay was 9.3 +/- 14.7 days per admission. Regression analysis indicates that those with spinal cord injuries as major disabling conditions were significantly more likely to be hospitalized. So were those with lower self-assessments of health, higher levels of depressions, and more baseline ER visits. Self-assessment of health is a significant predictor of hospital days for the total cohort (including those with no admissions); so are age at onset of disability (greater age; higher risk), and bed disability days in the month before the baseline survey (more disability days; higher risk). Among those hospitalized, the total number of days hospitalized is significantly related to both age at onset of disability (later onset; more days) and baseline days hospitalized (greater number; more days). Lengths-of-stay are significantly related to two factors; age and age at onset of disability (in both cases, greater age associated with longer stays). Prior ER visits are a significant predictor of subsequent ER visits (more baseline; more subsequent); so are respondents' reported satisfaction with their participation in their medical care (lower reported satisfaction; more ER visits), organizational affiliations, and frequencies of contacts with friends or relatives. Higher levels of social interaction (i.e. organizational affiliation and more frequent social contacts) were associated with more ER visits. Prior contacts with physicians, nurse-practitioners, or physician-assistants was the most powerful predictor of subsequent outpatient contacts (more baseline; more subsequent). There were also significant relationships between subsequent contacts and respondents' assessments of their health relative to others with similar disabilities (relatively worse health; more contacts), age (greater age; more contacts), and baseline ER visits (more visits; more contacts).

A prospective evaluation of the effect of managed care on medical care utilization among severely disabled independently living adults.

We conducted an 18-month longitudinal evaluation of a model-managed medical care program for severely disabled, independently living adults. Regression analyses using an additive model (no interaction effects) suggest that persons in the study group did not have statistically significantly different utilization experiences than members of the comparison group. Regression analyses that include interaction effects suggest that, for certain segments of the cohort, the study group's utilization experience was significantly lower than that of members of the comparison group. Persons in the study group with higher baseline emergency room (ER) utilization had significantly fewer hospital admissions (P = 0.0055). The participants with better self-assessments of health experienced significantly fewer hospital days per person (P = 0.0075) and days per person hospitalized (P = 0.0056), and persons with organizational affiliations reported significantly fewer ER visits (P = 0.0264).

Rehospitalization and spinal cord injury: cross-sectional survey of adults living independently.

A cross-sectional survey of 96 people living independently with spinal cord injuries (SCI) in Eastern Massachusetts shows that 57% had been hospitalized at least once in the year before the survey. Sample means were 1.0 admissions and 16.0 days/person/year. Eight percent of the sample (eight persons) accounted for 22% of admissions and 59% of total hospital days. For those hospitalized, the mean was 1.7 admissions and 45.1 days/person/year. Mean length-of-stay was 34.7 days/admission. Multiple regression analysis shows that three variables appear to be independently related to increased numbers of admissions: self-assessment of health; place of residence; and age (younger respondents at higher risk). One variable is independently associated with total days of hospitalization: leaving home at least once daily (as opposed to less frequently) is associated with lower risk. There were no statistically significant relationships between either numbers of hospitalizations or total days hospitalized and ADL or IADL status, education, employment, medical insurance, household composition, gender, age at onset of disability, time since onset of disability, substance use (alcohol, cannabis, or tobacco), level of SCI lesion, or social supports.