A probabilistic model for silver bioaccumulation in aquatic systems and assessment of human health risks.

Silver (Ag) is discharged in wastewater effluents and is also a component in a proposed secondary water disinfectant. A steady-state model was developed to simulate bioaccumulation in aquatic biota and assess ecological and human health risks. Trophic levels included phytoplankton, invertebrates, brown trout, and common carp. Uptake routes included water, food, or sediment. Based on an extensive review of the literature, distributions were derived for most inputs for use in Monte Carlo simulations. Three scenarios represented ranges of dilution and turbidity. Compared with the limited field data available, median estimates of Ag in carp (0.07-2.1 micrograms/g dry weight) were 0.5 to 9 times measured values, and all measurements were within the predicted interquartile range. Median Ag concentrations in biota were ranked invertebrates > phytoplankton > trout > carp. Biotic concentrations were highest for conditions of low dilution and low turbidity. Critical variables included Ag assimilation efficiency, specific feeding rate, and the phytoplankton bioconcentration factor. Bioaccumulation of Ag seems unlikely to result in toxicity to aquatic biota and humans consuming fish. Although the highest predicted Ag concentrations in water (> 200 ng/L) may pose chronic risks to early survival and development of salmonids and risks of argyria to subsistence fishers, these results occur under highly conservative conditions.

Computed tomographic evaluation of the internal structure of the lateral mass of the lower cervical spine.

Axial computed tomography scans with a slice thickness of 2 mm taken from 12 cervical spines were used to study the internal structure of the lateral mass. Images representing the middle of zone I (Heller's classification) and the top of zone III were analyzed. The measurement of zone I involved anterior cortex thickness (ACT) while measurements of zone III included ACT, lateral cortex thickness (LCT), posterior cortex thickness (PCT), lateral mass thickness (LMT), and lateral mass width (LMW). The percentage of the ACT and PCT with respect to the LMT (ACT/LMT and PCT/LMT) were calculated. Results showed the average ACT in zone I ranged from 1.6 to 1.8 mm. In zone III, the average LMT and LMW ranged from 8 to 9 mm and 13 to 15 mm, respectively. The smallest LMT was found at C7. The average ACT and PCT for all levels ranged from 1.8 to 2 mm. The ACT with respect to the LMT (ACT/LMT) was approximately 17% to 19% for C3 to C5 and C7, and 15% for C6 separately. The PCT with respect to the LMT (PCT/LMT) was approximately 16% to 18% for C3 to C6, and 20% for C7. These results show the ventral cortex of the lateral mass is relatively thicker and support the concept of bicortical screw purchase.

The location of the spinal nerve root on plain radiographs of the cervical spine.

Twelve cervical spines from C2 to T1 were harvested from embalmed cadavers to study the location of the nerve root on plain radiographs. After removal of the soft tissue, the spinal nerves just lateral to the transverse processes were exposed and injected with lead oxide. Plain radiographs including anteroposterior (AP) and left and right oblique views were taken. Angular and linear measurements were performed directly on the radiographs. Results showed that the average frontal angle of the nerve root for all levels was 155 degrees on the AP view, 108 degrees on the foraminal side of the oblique view, and 153 degrees on the opposite side of the oblique view. The nerve root height for all levels averaged 4.7 +/- 0.5 mm. The interpedicular space height increased consistently from 7.8 +/- 0.7 mm at C3-C4 to 9.0 +/- 1.3 mm at C6-C7 except at C2-C3. The nerve root height with respect to the interpedicular space height was 56.2% at C2-C3, 57.8% at C4-C5, and 53.7% at C6-C7. A knowledge of the location of the cervical nerve root related to plain radiographs may enhance the value of plain radiographs in the diagnosis and treatment of cervical spinal disorders.

Location of the vertebral artery foramen on the anterior aspect of the lower cervical spine by computed tomography.

Axial computed tomography scans were performed on 14 cadaveric cervical spines to determine the location of the vertebral artery foramen on the anterior aspect of the lower cervical spine. The best scan through the vertebral artery foramen from each level at C3-C6 was selected. Measurements of the vertebral artery foramen included the foramen depth, foramen width, interforaminal distance, the distance from the anterior border of the transverse foramen to the anterior border of the transverse process, the distance from the posterior border of the transverse foramen to the posterior border of the lateral mass, and the distance from the medial border of the vertebral artery foramen to the lateral border of the vertebral body. The results show that the average transverse foramen width was 5.5 +/- 0.4 mm at C3, 5.7 +/- 1.0 mm at C4, 5.9 +/- 0.7 mm at C5, and 5.7 +/- 0.7 mm at C6. The average transverse foramen depth and average interforaminal distance gradually increased from C3 to C6. The distance from the anterior border of the vertebral artery foramen to the anterior border of the transverse process gradually increased from C3 (1.2 +/- 0.4 mm) to C6 (2.7 +/- 0.8 mm) as well. The average distance between the medial border of the transverse foramina and the lateral border of the vertebral body for C3-C6 ranged from 1.8 to 2.2 mm. The average distance between the anterior borders of the vertebral artery foramina and the anterior border of the vertebral body gradually decreased from C3 (8.4 +/- 1.4 mm) to C6 (7.0 +/- 1.6 mm). This study suggested that the lateral border of the vertebral body may be a reliable landmark during anterior cervical decompression. The vertebral artery foramen should be free of violation if vertebrectomy or subtotal vertebrectomy is performed medial to the lateral border of the vertebral body.

Diabetes and nutrition recommendations: a practical perspective.

Nutritional management is a major therapeutic tool in the care of persons with diabetes. Goals for insulin-dependent and noninsulin-dependent diabetes mellitus (IDDM and NIDDM) differ due to the underlying pathophysiology of the conditions. This article discusses the nutrition management goals for IDDM and NIDDM and provides practical recommendations to achieve them. The authors supply a sample meal plan, a list of high-fiber and low-fat foods, a sample diet history, and a food record to facilitate assessment and patient behavior changes. NPs can use this information in practice when nutrition consultation is not available.

Managing diabetes in the home: a model approach.

The Diabetes Home Care Program has been an effective means of providing diabetes management and education to homebound, usually elderly, persons with diabetes. The program appears to be cost effective, the average cost per patient is less than one day of hospitalization. Reimbursement of the program has been good as patients have qualified for reimbursement under Medicare guidelines. Improved diabetes control has been demonstrated following the home care intervention. Since elderly persons with diabetes are frequently referred for home care, it would be appropriate for home care agencies to provide specialized care for persons with diabetes. The Diabetes Home Care Program can serve as a model of diabetes management and education for homebound persons with diabetes.

Head-temperature effects on physiology, comfort, and performance during hyperthermia.

This study assessed the effects of head temperature on subjects under hyperthermic conditions. Six volunteers were trained to plateau on a manikin task that tested cognitive performance and reaction time. A subject's core temperature was driven with a full-length, liquid-conditioned garment perfused with water at 30 degrees or 43 degrees C, and head temperature was controlled by a cap with an inlet temperature of 8 degrees or 43 degrees C. Heavy insulation was worn overall; ambient temperature was 30 degrees C. Subjects were heated and cooled twice during each experiment to include all possible cap/suit temperature combinations. Each subject did one control and four stress experiments. Comfort and performance were measured as the subject's esophageal temperature (Tes) rose and fell through the range 37.5-39.0 degrees C. Cap temperature did not affect rectal temperature (Tre) but significantly altered the Tes rate of change; a cool head sometimes truncated the peak Tes value. Although the cap covered only 3-4% of the body surface, the head was a major determinant of subjective comfort. Body heating tended to shorten reaction time and diminish performance accuracy, while head cooling largely reversed these trends. Possible mechanisms include 1) change in overall heat balance; 2) countercurrent exchanges in the neck, and 3) change in sensory output. Head cooling deserves serious consideration for machinery operators where whole-body thermoneutrality is impractical.

Head acceleration and psychomotor performance.

Concussion resulting from head acceleration could explain the poor survival rates in some types of accidents. Experiments have been conducted on a decelerator using a tracking task to determine whether high head acceleration could affect psychomotor performance. Human subjects were exposed to impact acceleration of O (sham), 5, 10 and 12 -Gx facing forwards. Measurements were made of the linear and angular accelerations experienced at the head and a step tracking task was used to examine psychomotor performance. Electroencephalographs were also recorded. Both the linear and angular accelerations at the head were increased at the higher levels of impact acceleration. At -5Gx there were no significant differences in psychomotor performance when compared with controls, but at -10Gx, and especially -12Gx, significant differences were found. The EEG activity did not vary significantly and no concussive effects were observed in any subject. These results suggest that impairment of psychomotor performance severe enough to jeopardise survival could be produced by high accelerations of the head, though neither linear nor angular acceleration appear to have special significance.

Joint Committee on Aviation Pathology: III. Some influences of restraint harness design on accident pathology.

Careful investigation of restraint harness function can reveal the mechanism of failure and, by rectification, prevent repetition of such failures. The investigation can also lead to alteration in the specification for restraint harnesses, and so eliminate weaknesses in future design. The aviation pathologist can play an important part in the assessment of the efficiency of a restraint system in use. His assessment can sometimes be more revealing than laboratory tests, as the unforeseen event often reveals unknown weaknesses.