A continuous-flow perfusion system for the maintenance and NMR study of small tissue samples in vitro.

To describe and evaluate a novel perfusion system developed to maintain excised tissue in a flowing, oxygenated bathing solution during acquisition of nuclear magnetic resonance (NMR) data, and in addition allow precise data to be acquired continuously while altering the composition of the bathing solution surrounding the tissue. A chamber to house the tissue sample was constructed of interlocking sections of polyethylene tubing, and had approximate internal dimensions of 4 mm in diameter and 4 mm in height. Temperature-controlled, physiologically appropriate buffer solution was pumped via an infusion pump through the chamber, entering and exiting by way of small openings on either end. Immediately surrounding the polyethylene chamber was a tight-fitting four-loop solenoid RF coil. Measured proton NMR parameters were found to be fairly insensitive to the flow rate of the buffer if this coil was used only for reception and a larger-volume transmit-only coil was used for excitation. Temperature control of the sample was successfully implemented between 25 and 40 degrees C. The perfusion system was found to be resistant to the effects of flow rate, as well as a useful tool for the administration of drugs or agents to the tissue. Changes in buffer composition could be performed on the fly without the need to reposition the sample each time a change was made. This avoidance of repositioning was found to yield a fivefold improvement in the precision of T(2) spectral parameters (using frog sciatic nerve as a sample).

Spatial structure and fluctuations in the contact process and related models.

The contact process is used as a simple spatial model in many disciplines, yet because of the buildup of spatial correlations, its dynamics remain difficult to capture analytically. We introduce an empirically based, approximate method of characterizing the spatial correlations with only a single adjustable parameter. This approximation allows us to recast the contact process in terms of a stochastic birth-death process, converting a spatiotemporal problem into a simpler temporal one. We obtain considerably more accurate predictions of equilibrium population than those given by pair approximations, as well as good predictions of population variance and first passage time distributions to a given (low) threshold. A similar approach is applicable to any model with a combination of global and nearest-neighbor interactions.

Socioeconomic differences in Medicare supplemental coverage.

In this study we compare the beneficiaries with various types of Medicare supplemental insurance coverage to examine the impact of socioeconomic characteristics on such coverage. We found that those who are more disadvantaged are less likely to have any coverage, and those who have it are less likely to have it subsidized by a former employer. These findings have direct implications for the fairness of proposed programs to provide prescription drug coverage to Medicare beneficiaries, and for the advisability of various proposals for reforming Medicare, including "premium-support" programs.

Access to medical care reported by Asians and Pacific Islanders in a West Coast physician group association.

This study examines access to medical care for Asians and Pacific Islanders in the United States, using a survey of patients receiving care provided by a physician group practice association concentrated on the West Coast. Asians and Pacific Islanders who had used their health plan in the past year had worse access to health care than whites, blacks, Hispanics, and Native American or other ethnicities. The odds that Asians reported that they had adequate access ranged from about one quarter to three quarters that of whites, depending on the measure. Cultural differences and associated communication problems may explain the access problems experienced by Asians. Interventions need to be developed to address the problems with access to services, and better translation services may play an important role in improving access to care for Asians. Future studies need to clarify why Asians were more vulnerable to the access problems examined than other ethnic groups that might experience similar barriers.

Body composition in nutritionally adequate ambulatory and non-ambulatory children with cerebral palsy and a healthy reference group.

Bone-mineral content (BMC; g) and density (BMD; g/cm2) were measured by dual energy X-ray absorptiometry in the proximal femur, femoral neck, and total body of nutritionally adequate children (n=17; 11 girls, six boys; aged 7.6 to 13.8 years) with spastic cerebral palsy (CP). Bone-mineral-free lean tissue (BMFL; g) and fat mass (FM; g) were obtained from total body scans. Chronological and developmental age-based z scores for the children with CP were derived from a pediatric database (n=894). Children with CP had BMC z scores from -1.8 (total body) to -3.2 (femoral neck) SDs below the normative sample. Non-independent ambulators had lower z scores for total body BMD, femoral neck BMD, and BMC than independent ambulators. The BMFL z score of individuals with CP was 2 SDs below that of the reference group and higher in the independent ambulators than in the non-independent ambulators, whereas FM deviated little. These findings suggest that non-nutritional factors, such as ambulation, account for the low BMC, BMD, and BMFL tissue observed in this population.

The effect of a weight-bearing physical activity program on bone mineral content and estimated volumetric density in children with spastic cerebral palsy.

After an 8-month physical activity intervention in children with cerebral palsy, increases in femoral neck bone mineral content (BMC) (9.6%), volumetric bone mineral density (v BMD) (5.6%), and total proximal femur BMC (11.5%) were observed in the intervention group (n = 9) compared with control subjects (n = 9; femoral neck BMC, -5. 8%; v BMD, -6.3%; total proximal femur BMC, 3.5%).

Quantitative MR imaging of carpal tunnel syndrome.

OBJECTIVE: Previous MR imaging studies have produced evidence of changes to structures within the wrist believed to be associated with carpal tunnel syndrome. In an attempt to resolve the conflicting and inconclusive results of these studies, we report here the results of an MR imaging study at a field strength of 3.0 T, which is higher than that previously reported. SUBJECTS AND METHODS: Patients with carpal tunnel syndrome and control groups of asymptomatic subjects were studied using MR imaging. We evaluated electrophysiologically the median nerve function of the affected wrists of all patients. A gradient-recalled echo pulse sequence was used to study 13 3-mm-thick slices within the wrist of each patient or asymptomatic subject. Spatial resolution was approximately 0.3 x 0.3 mm2. The median nerve and other structures associated with the carpal tunnel, which were clearly shown on the MR images, were analyzed to yield structural data. RESULTS: Analysis revealed that the cross-sectional area of the nerve within and proximal to the carpal tunnel was approximately 50% larger in patients with carpal tunnel syndrome than in asymptomatic subjects. We found no significant difference in the area of the nerve within the carpal tunnel compartment compared with the area of the nerve proximal to the carpal tunnel either in patients or in asymptomatic subjects. Also, flattening of the nerve on entering the carpal tunnel was not significantly different in patients than in asymptomatic subjects. In patients an increase in the palmar bowing of the flexor retinaculum was found only at the level of the hamate compared with that found in asymptomatic subjects. The cross-sectional area of the carpal tunnel was of a similar size in patients and in asymptomatic subjects. Comparison of electrodiagnostic results indicated no correlations between the MR parameters and electrophysiologic dysfunction of the median nerve for patients. CONCLUSION: The only statistically significant differences found between patients with carpal tunnel syndrome and asymptomatic subjects were that the median nerve was approximately 50% larger within and proximal to the carpal tunnel in patients with carpal tunnel syndrome and palmar bowing of the flexor retinaculum occurred in patients only at the level of the hamate.

Multi-component T1 relaxation and magnetisation transfer in peripheral nerve.

We report here a study of longitudinal relaxation (T1) and magnetisation transfer (MT) in peripheral nerve. Amphibian sciatic nerve was maintained in vitro and studied at a magnetic field strength of 3 T. A CPMG pulse sequence was modified to include either a saturation pulse to measure T1 relaxation or an off-resonance RF irradiation pulse to measure MT. The resulting transverse relaxation (T2) spectra yielded four components corresponding to three nerve compartments, taken to result from myelinic, axonal, and inter-axonal water, and a fourth corresponding to the buffer solution water in which the nerve sample was bathed. Each nerve component was analysed for T1 relaxation and MT. All three nerve T2 components exhibited unique T1 relaxation and MT characteristics, providing further support for the assignment of the components to unique physical compartments of water. Numerical investigation of T1sat measurements of each of the three nerve T2 components indicates that while the two shorter-lived exhibit similar steady-state magnetisation transfer ratios (MTRs), their respective MT properties are quite different. Simulations demonstrate that mobile water exchange between these two components is not necessary to explain their similar steady-state MTR. In the context of the assignment of these two components to signal from myelinic and axonal water, this is to say that these two microanatomical regions of nerve may exhibit similar steady-state MTR characteristics despite possessing widely different MT exchange rates. Therefore, interpreting changes in MTR solely to reflect a change in degree of myelination could lead to erroneous conclusions.

Bone age and growth in fetal alcohol syndrome.

We have found delayed mean bone age in 63 children with fetal alcohol syndrome (FAS). The mean bone age Z-score for boys (n = 31) was -2.12 SDs and for girls (n = 32) was -1.62 SDs. This might suggest that they have potential for catch-up growth. However, experience with children with intrauterine growth retardation suggests that this will not be the case and that FAS children will be of reduced height at maturity. Further support for this assumption was gained from a sample of 26 patients who were followed until at least the age of 14 years for females and 16 years for males. There was no significant change in height Z-scores from early childhood to early adulthood, the mean score being -2.16 SDs and -2.11 SDs at mean ages of 4.83 years and 18.69 years, respectively. On the other hand, there were significant changes in weight and head circumference. The mean weight Z-score changed from -2.10 SDs to -1.14 SDs (p < 0.001). The head circumference mean Z-score in 16 patients was -3.13 SDs at a mean age of 2.79 years and -2.63 SDs at a mean age of 17.37 years (p = 0.013). Short stature can continue to be used as a diagnostic criterion for FAS beyond childhood.

Multiecho imaging with suboptimal spoiler gradients.

Although multiecho imaging may be used to measure transverse relaxation (T2), B1 and B0 inhomogeneity generally gives rise to unwanted coherence pathway signals which result in erroneous T2 measurements. One approach to suppressing this unwanted signal is to center each rf refocusing pulse between spoiler gradients which dephase the unwanted signal; however, hardware limitations often dictate the use of suboptimal spoiler gradients, that is, gradients that cannot provide sufficient dephasing strength. Using simulations, this work demonstrates that by means of a small additional spoiler gradient prior to the first rf refocusing pulse it is possible to reduce substantially the contribution from unwanted coherence pathways in multiecho imaging studies that use suboptimal spoiler gradients. This reduction of unwanted signal results in measured T2 values within approximately 1% of values obtained using spoiler gradients of optimal strength. These results were found for a wide range of biologically relevant T1 and T2 values, missettings of the rf refocusing pulse as large as 5%, and frequency offsets of up to 25 Hz. Multiecho image data agreed with the simulations. Using the additional spoiler gradient it is possible to reduce spoiler gradient strengths by up to 75%.

Changes in water diffusion due to Wallerian degeneration in peripheral nerve.

The authors report NMR measurements of the changes in water diffusion brought about by in vivo Wallerian degeneration due to either crush- or tie-injuries in the sciatic nerve of the frog. Using a pulsed-gradient spin-echo sequence with a diffusion measurement time of 28 ms, the degree of diffusion coefficient anisotropy ¿D(longitudinal)/D(transverse)¿ 4 weeks after injury in both crush- and tie-injured nerves (2.3 +/- 0.4 and 1.7 +/- 0.1, respectively) is significantly less than in normal frog sciatic nerve (3.9 +/- 0.4). The decrease of anisotropy in the degenerated nerves is due to both a decrease in longitudinal diffusion and an increase in transverse diffusion. The changes in diffusion coefficients are compared with the degree of axonal and myelin breakdown observed in light and electron micrographs of the nerves.

Foetal alcohol syndrome in Saskatchewan: unchanged incidence in a 20-year period.

Despite major initiatives in public and professional education about foetal alcohol syndrome (FAS) in Saskatchewan in the last 20 years, its incidence rate has not fallen. The rate was 0.515 per 1,000 live births in 1973-1977 and 0.589 in 1988-1992. Two hundred and seven (207) cases were ascertained, the majority being patients of the Alvin Buckwold Child Development Program in Saskatoon. These individuals were severely handicapped: 72% had at least one malformation, the mean intelligence quotient was 67.8 (range 35-106) and 45.9% had a behaviour problem. Only 25.6% still lived with their biological parents when last seen, and only 27 of 108 cases were in a regular class at school without additional support being necessary. New approaches are needed to reduce the incidence of FAS. Emphasis should be placed on individual case-finding, counselling for high-risk women, and community development programs. We are currently attempting this through a provincial coordinating committee.

Multiexponential T2 relaxation in degenerating peripheral nerve.

The multiexponential T2 relaxation spectrum of peripheral nerve undergoing Wallerian degeneration has been measured both in vivo and in vitro. Degeneration of the sciatic nerve of the amphibian Xenopus laevis was induced by crush injury, and T2 relaxation spectra of the nerve were measured at several times up to 35 days following injury. Histologic evidence verified that the nerve underwent Wallerian degeneration. Relaxation spectra were observed to undergo measurable changes as degeneration progressed, the most evident being a reduction from three well-resolved T2 components to one and a decline in the fraction of the spectra associated with the shortest T2 component. The former appears to reflect the collapse and loss of myelinated fibers, while the latter a combination of interstitial edema and myelin loss.

Physician awareness of fetal alcohol syndrome: a survey of pediatricians and general practitioners.

OBJECTIVE: To determine the knowledge, clinical experience and perceived needs for resource materials of Saskatchewan physicians in regard to fetal alcohol syndrome (FAS) and alcohol-related birth defects. DESIGN: Mailed survey. SETTING: Saskatchewan. PARTICIPANTS: All 48 pediatricians and half (394) of the family physicians (FPs) and general practitioners (GPs) practising in Saskatchewan received a questionnaire. The numbers of physicians who completed it were 24 and 249 respectively. RESULTS: The pediatricians were more likely than the other physicians to be aware of FAS and to have diagnosed at least one case of FAS. Among the FPs and GPs, the year of graduation from medical school was a significant factor in their knowledge of FAS and their diagnostic practices. Those who graduated before 1974, the year FAS was first described in the medical literature, were less likely than the more recent graduates to be aware of FAS and to ask their patients about alcohol use during pregnancy but were more likely to feel comfortable discussing alcohol-related issues in families. All of the groups reported a need for more information about FAS and for resources on alcohol-related issues in general. CONCLUSIONS: Saskatchewan physicians are aware of FAS but have expressed a need for more information about FAS, particularly for parents, as well as physician training materials and information about where to refer patients with FAS and parents with alcohol-related problems.

Anterograde to retrograde reversal of fast axonal transport within cold blocked and rewarmed intact axons.

The possibility that anterograde to retrograde reversal of axonal transport might take place in mid axon at a site distant from any nerve termination was investigated in sciatic nerve preparations from Xenopus laevis. The nerve, containing a pulse of anterogradely transported protein labeled with [35S]methionine, was kept in a two-compartment temperature controlled chamber. One compartment containing the proximal nerve was maintained at room temperature throughout the duration of an experiment while the second compartment containing the distal nerve, and separated from the first by a thermal barrier, was initially cooled to 3-4 degrees C and later warmed to room temperature. Transport of labeled proteins in the nerve was detected with a position-sensitive detector of ionizing radiation. With the distal portion of the nerve cold, the pulse of labeled protein transported up to the thermal barrier and stopped. When the distal part of the nerve was warmed to room temperature, retrograde and anterograde pulses of label propagated away from the thermal barrier with no time delay. The retrograde pulse could be collected on the distal side of a proximally placed tie and could be eliminated by treatment of the proximal nerve with vinblastine or dinitrophenol. Functional and structural evidence indicated that the cold block and thermal barrier were not destructive to the axons. Electron microscopy showed that the numerical density of axonal microtubules distal to the cold block was decreased about seven fold during the cold treatment and that this decrease could be prevented by 10 mumol/l taxol.(ABSTRACT TRUNCATED AT 250 WORDS)

T2 relaxation of peripheral nerve measured in vivo.

It is demonstrated that multi-exponential transverse (T2) relaxation components can be estimated from multi-echo images of peripheral nerve. Three T2-relaxation components with T2 values +/- standard deviations (populations +/- standard deviations) of 19 +/- 7 ms (26 +/- 9%), 63 +/- 31 ms (29 +/- 11%) and 241 +/- 24 ms (45 +/- 7%) have been identified in vivo in the sciatic nerve of the amphibian Xenopus laevis. The longer-lived component, not identified previously in vivo, provides a significant contrast-to-noise ratio (CNR) between nerve and muscle in the latter-echo images. It is shown that the CNR can be further improved by the averaging of selected images from the multi-echo set.

Action of brefeldin A on amphibian neurons: passage of newly synthesized proteins through the Golgi complex is not required for continued fast organelle transport in axons.

The relation between the availability of newly synthesized protein and lipid and the axonal transport of optically detectable organelles was examined in peripheral nerve preparations of amphibia (Rana catesbeiana and Xenopus laevis) in which intracellular traffic from the endoplasmic reticulum to the Golgi complex was inhibited with brefeldin A (BFA). Accumulation of fast-transported radio-labeled protein or phospholipid proximal to a sciatic nerve ligature was monitored in vitro in preparations of dorsal root ganglia and sciatic nerve. Organelle transport was examined by computer-enhanced video microscopy of single myelinated axons. BFA reduced the amount of radiolabeled protein and lipid entering the fast-transport system of the axon without affecting either the synthesis or the transport rate of these molecules. The time course of the effect of BFA on axonal transport is consistent with an action at an early step in the intrasomal pathway, and with its action being related to the observed rapid (< 1 h) disassembly of the Golgi complex. At a concentration of BFA that reduced fast-transported protein by > 95%, no effect was observed on the flux or velocity of anterograde or retrograde organelle transport in axons for at least 20 h. Bidirectional axonal transport of organelles was similarly unaffected following suppression of protein synthesis by > 99%. The findings suggest that the anterograde flux of transport organelles is not critically dependent on a supply of newly synthesized membrane precursors. The possibilities are considered that anterograde organelles normally arise from membrane components supplied from a post-Golgi storage pool, as well as from recycled retrograde organelles.

Reversal of rapidly transported protein and organelles at an axonal lesion.

The time required for both rapid axonally transported organelles (vesicles and tubulo-vesicular structures) and proteins to undergo anterograde to retrograde reversal at a crush site was examined using sciatic nerve preparations obtained from Xenopus laevis. The transport and reversal of a pulse of newly synthesized 35S-labeled proteins was studied with a position-sensitive detector of ionizing radiation. Organelle transport and reversal were studied using video microscopy. Both protein and organelle reversal were assessed in two bathing media: a physiological saline and a medium that was compatible with the intracellular environment (internal medium). The time required for protein transport to reverse at a ligature was determined as a function of the time interval between the application of the ligature and the arrival of the pulse at the ligature (lesion time). In physiological saline, reversal times were greatest, about 3.5 h, when the lesion time was 1 h or less and decreased to approximately 1.5 h for lesion times of 4-12 h. When corrected for the approximately 2 mm length of degeneration caused by the saline, the results were similar to those obtained in internal medium and indicated a minimal reversal time for proteins of about 2 h. Organelle transport was examined close to narrow lesions in single myelinated axons. That the organelles moving away from the lesion represented organelles that had undergone reversed transport was suggested by observation of the reversal of individual organelles, and by a correlation between the flux of organelles towards and away from the lesion. Analysis of organelle flux within and adjacent to a segment of axon isolated by two lesions indicated that 70-80% of organelles moving away from a lesion represented reversed transport. Observations in internal medium were consistent with a reversal time of < 15 min, and in physiological saline < 30 min. The substantially smaller reversal time for organelle transport as compared to protein transport is consistent either with the existence of two types of organelles with different reversal times and hence different reversal mechanisms, or with the possibility that during reversal proteins are off-loaded from carrier organelles and subsequently up-loaded to different organelles.