Entrainment of the body temperature rhythm in rats: effect of color and intensity of environmental light.

The daily rhythm in body temperature in rats was continuously monitored during exposure to low-intensity environmental illumination of various colors in the visible and near-ultraviolet spectrum. The ability of phase shifts in the lighting schedule to induce concomitant changes in the rhythm was used to determine the spectral sensitivity of the retinal photoreceptor systems mediating rhythm entrainment. Green light (lambda = 530 +/- 45 nanometers) was most potent, and red (lambda = 660 +/- 19 nanometers) and ultraviolet (lambda = 360 +/- 34 nanometers) were least potent in entraining the temperature rhythm.

Maternal, fetal, and amniotic fluid transport of thyroxine, triiodothyronine, and iodide in sheep: a kinetic model.

A mathematical model of iodine kinetics in maternal and fetal sheep has been developed by combining separate iodide, T3, and T4 subsystems. The individual subsystem models were developed from literature studies of maternal-fetal exchange under thyroid-blocked and unblocked conditions. Rates of exchange, concentrations, and spaces of distribution were calculated by the SAAM computer program. The models for each of the subsystems required exchange compartments within the mother and fetus, exchanges between maternal and fetal circulations, and between the fetus and amniotic fluid. The fetal-amniotic fluid exchange was observed directly for iodide and indirectly for T3 and T4. No exchange between mother and amniotic fluid was required. It is possible that the amniotic fluid acts as a reservoir for these and other substances. Maternal-fetal kinetics suggest that low fetal T3 levels are maintained by an active transport of T3 from fetus to mother, a decreased transport from mother to fetus, and a low fetal T3 production. The model also requires that all fetal T3 loss occur via transport to the maternal system rather than via fetal utilization. In contrast, the fetal T4 system is largely autonomous, the small maternal exchange not significantly contributing to the fetal T4 economy. Fetal iodide seems to be supplied by a facilitated bidirectional exchange with the mother.

Effects of estrogen on thyroxine-binding globulin metabolism in rhesus monkeys.

To investigate the effects of estrogen on thyroxine-binding globulin (TBG) metabolism, 4 female Rhesus monkeys were studied before and 3-4 weeks after implantation of beta-estradiol (E2)-containing capsules. In addition, 2 of the animals were also studied for the first 7 days after the start of E2. Serum E2 increased 10-fold from 20 +/- 7 to 212 +/- 41 pg/ml. Serum TBG, initially 20.2 +/- 6 mug/ml, was elevated by 24 h after E2 implantation, and reached a steady level of 46.8 +/- 5.0 mug/ml by 7-10 days. For the turnover studies, highly purified [125I]iodo-TBG was injected iv and serum [125I]PBI and urinary 125I excretion were measured daily. TBG kinetics were evaluated by use of a compartmental model. Although a 2-compartment model was sufficient to fit the control and late E2 data, a 3-compartment model was developed in order to account for the modifications observed during the early E2 period. The final decay rate (k) of TBG was 0.26 +/- 0.01/day during the control period and was slightly lower after E2 (0.23 +/- 0.01/day). In the 2 monkeys studied during the early E2 period, the major effect of E2 was a stimulation of the TBG production rate. This was simulated in the model by a stepwise increase occurring in the last quarter of the first day after E2. There was also an abrupt redistribution of TBG in the compartments defined by the model. The total distribution or serum equivalent volume of TBG after 3-4 weeks of E2 increased 1.4-fold, from 338 +/- 37 ml to 458 +/- 22 ml, and the metabolic clearance rate increased 1.3-fold, from 90 +/- 10 ml/d to 113 +/- 12 ml/d. The increase in the final TBG production rate (2.9-fold) was only slightly greater than the rate calculated for the early E2 period, and was similar to the increase we have recently found in monkey hepatocytes studied in vitro after isolation from E2-treated animals. It appears that stimulation of hepatic synthesis of TBG accounts for the elevated serum levels of TBG observed after estrogen.

A kinetic model of human thyroid hormones and their conversion products.

We have examined the in vivo distribution and metabolism of radiolabeled T4 and T3 in 14 normal subjects using a kinetic model. Tracer amounts of [131I]T4 and [125I]T3 were injected simultaneously, and plasma samples were obtained for up to 7 days thereafter. Separation of these samples by thin layer chromatography yielded kinetic curves for 131I- and 125I-labeled T4, T3, iodide, and iodoprotein, which were then used to develop a kinetic model. The model includes several features. 1) Submodels were developed for T4, T3, iodide, and iodoprotein which simultaneously fit the observed data. 2) Two other submodels were needed for data fit, the first representing rT3, the other representing other intermediates, including the various diiodothyronines. The latter submodel was patterned initially after 3,3'-diiodothyronine kinetics. It was required to account for the delay in appearance of labeled iodide produced from the degradation of T4, and rT3 and proved to be essential for the successful fit of the data. 3) The model accounts for the conversion of T4 to T3 and rT3. Even though rT3 is quantitatively significant as a degradation pathway for T4, its presence does not contribute significantly to total plasma radioactivity after T4 administration because of its rapid turnover in comparison with T4. 4) The small amount of iodoprotein formed is a major contributor to total plasma radioactivity within 3 days after T3 administration. 5) The model permits the elimination of two methodological errors: that due to the presence of labeled iodide, T3, or T4 contaminants in the administered labeled hormones, and that due to the small amount of cross-over between thin layer chromatography peaks. The model provides a concise description of our current understanding of thyroid hormone metabolism and suggests areas where further information is required.

Distribution of subcutaneous thyroxine, triiodothyronine, and albumin in man: comparison with intravenous administration using a kinetic model.

Distributional kinetics of radioiodinated T4 (T4), T3 (T3), and albumin (RISA), after simultaneous administration by the sc and iv routes of 125I- and 131I-labeled compounds, were measured in normal subjects. Data were analyzed by fitting them, using the SAAM technique, to models with three compartments for the iv administered compounds and a fourth compartment for the site of the sc injection. The radiopharmaceuticals administered sc transfered by first order kinetics from the injection site to plasma with half-lives of 20.4, 5.6, and 63.0 h for T4, T3, and RISA, respectively. Percentages of 3.3, 1.2, and 2.1 of the sc dose appeared directly in the vascular compartment. In some, but not all, studies with sc T4 and RISA, a portion of the disappearance from the sc site appeared to be due to in situ deiodination, rather than to transfer of the parent compound into the circulation. After T3 administration, both iv and sc, a product with kinetics similar to RISA appeared, accounting for 3% of the T3 decay for the averaged data and ranging from 0.9--19.4% in individual cases. Comparing T3 kinetic analysis by this technique (in which the iodoprotein byproduct is accounted for by modeling instead of chemical separation), the resulting parameters are similar to those reported by others after chemical separation of T3. Judging by compartment size and distributional kinetics, the model compartments derived for iv administration of these compounds appear to represent the vascular pool (central compartment), the hepatic and renal distribution sites (fast peripheral compartment), and other peripheral tissues (slow peripheral compartment). The latter, which presumably includes the site of sc injection, transfers into the central compartment at approximately the same rate as does the compartment representing the sc injection site itself.

Measurement method for radioactive thyroxine, triiodothyronine, iodide, and iodoprotein in samples with low activity.

A method is described that incorporates resin extraction and thin layer chromatography to isolate and separate radioiodinated thyroxine (T4), triiodothyronine (T3), iodoprotein, and iodide in samples of human plasma up to 3 ml. Tracer studies using this method showed that reverse T3 and 3',5' diiodothyronine (T2), as well as T4, were detected in the "T4 fraction," and that 3-3' T2 and 3' monoiodothyronine, as well as T3, were detected in the "T3 fraction." Monoiodotyrosine and diiodotyrosine (DIT) migrated more slowly than did T4 on the chromatogram, and a large amount of DIT was in the unextracted "iodoprotein fraction." Kinetic studies in 14 normal subjects given intravenous commercial [125I]T3 (T3*) and [131I]T4 (T4*), confirmed the quantitative importance of an iodoprotein in later samples after T3* administration, and its presence after T4*. T4* contamination of commercial T3* also became quantitatively important. On the other hand, despite confirmation of in vivo conversion of T4* to T3*, T3* contributed little quantitatively to the total concentration of radioactivity present even late after T4* injection, due to the more rapid turnover and greater distribution volume of T3*.

Vocal reaction times to unilaterally presented concrete and abstract words: towards a theory of differential right hemispheric semantic processing.

Previous studies investigating hemispheric organization for processing concrete and abstract nouns have provided conflicting results. Using manual reaction time tasks some studies have shown that the right hemisphere is capable of analyzing concrete words but not abstract. Others, however, have inferred that the left hemisphere is the sole analyzer of both types of lexicon. The present study tested these issues further by measuring vocal reaction times of normal subjects to unilaterally presented concrete and abstract items. Results were consistent with a model of functional localization which suggests that the minor hemisphere is capable of differentially processing both types of lexicon in the presence of a dominant left hemisphere.

Comparison of stability provided to the unstable spine by the kinetic therapy table and the Stryker frame.

Loss of spinal alignment can lead to neurological compromise in individuals with unstable spine injuries. We compared the ability of the Roto-Rest bed and the Stryker frame to immobilize an unstable cervical and lumbar segment in a cadaver. The Roto-Rest bed was superior to the Stryker frame in the immobilization of both cervical and lumbar fractures.

Severe cervical kyphotic deformities in patients with plexiform neurofibromas: case report.

Two patients with cervical plexiform neurofibromas are presented. Each of these patients had severe cervical kyphosis and has undergone anterior decompression, anterior reconstruction, and posterior stabilization. We discuss the surgical management of cervical kyphotic deformities associated with plexiform neurofibromas and review the factors associated with bony changes in neurofibromatosis.

The use of primary internal fixation in spondylolisthesis.

A prospective randomized study was designed to examine differences in the primary fusion rate between two surgically treated groups of patients with spondylolisthesis. Twenty-seven patients underwent L5 laminectomy (Gill procedure) and L5 nerve root decompression. Fourteen patients (group I) underwent in-situ posterolateral fusion, thirteen patients (group II) received internal stabilization with the Steffee plate and screw system. All patients were followed for a minimum of two years. Ten of fourteen (72%) patients treated with non-instrumented fusion went on to union. Ten of thirteen (78%) patients treated with internal fixation achieved union. No statistically significant increase in the primary fusion rate occurred with addition of internal fixation compared to non-instrumented posterolateral grafting alone.

Evaluation of current extrication orthoses in immobilization of the unstable cervical spine.

An experiment was designed to evaluate the comparative stabilizing efficacy of several widely used semi-rigid orthoses applied to unstable fresh cadaver cervical spines subject to load. Cadaver specimens were surgically destabilized at the C4-5 segment. Lateral radiographs of the destabilized spine were obtained before and after collar placement and after the application of a 5-pound flexion force. Data analysis employing a one-way analysis of variance showed no statistically significant difference in the Necloc's, Philadelphia Collar's, or the Stifneck's ability to stabilize the cervical spine against a deforming flexion force (P greater than 0.05). They all provide translational stability while allowing angular changes to occur with application of the flexion force. The Philadelphia Collar Halo System is statistically superior to all three of the aforementioned collars in prevention of both translation and sagittal rotation (P less than 0.05).

Analysis of the torque applied to bone screws by trauma surgeons. Comparisons based on years of experience and material of implant construction.

Stability of an internal fixation construct is dependent on the torque placed on the screws holding the plate, the number of screws in the construct, and the number of cortices purchased by each screw. This study addresses the ability of surgeons to apply uniform torque and the variability between stainless steel and titanium. A total of 630 measurements were made by trained orthopedists using a device to measure the torque applied to 3.5 mm screws when tightening them to a plate. Variations were found to be significant depending on the number of years the orthopedist was in practice and the type of construct material used. The average torque applied to a stainless steel construct is 5.82 in-lb, while the torque applied to titanium is 5.41 in-lb (P < 0.01). The longer an orthopedist is in practice, the more torque will be applied to the screw/plate construct.

The role of anterior surgery in the treatment of thoracolumbar fractures.

Operative treatment of thoracolumbar burst fractures or fracture dislocations is a relatively modern development. Anterior decompression and stabilization play a significant role in the treatment of thoracolumbar burst fractures. This article reviews the clinical indications and describes a one-staged operative technique for anterior instrumentation following anterior decompression.

Modification of technique and results of atlantoaxial transfacet stabilization.

A modification of the C1 C2 transfacet stabilization is reported. This technique allows a smaller incision to be made and provides a method for easier screw insertion.

Complex dislocation of first metatarsophalangeal joint.

Dislocation of the first metatarsophalangeal joint is rare. Closed reduction is often impossible due to soft tissue interposition. A case is presented and the literature is reviewed with emphasis on normal and pathologic anatomy. Treatment recommendation is open reduction performed as soon as possible following injury if the dislocation cannot be reduced by closed methods.

Hemispheric processing strategies for lexical decisions among elderly persons.

Lexical decision vocal reaction times were obtained in 1990 for 30 young adult and 18 elderly subjects to tachistoscopically presented concrete and abstract words by Rastatter and McGuire. The young adults' data suggested differential right-hemispheric processing, while the elderly subjects' data were interpreted as suggesting that the right hemisphere loses its processing function. Here we reinterpret the elderly subjects' data based on visual information-processing theory and suggest that variations in processing strategy account more completely for their data.

Do the hemispheres interact during object naming? Evidence from tachistoscopic viewing and time-sharing paradigms.

Here we report an experiment in which 16 right-handed young adults named a series of unilaterally presented pictures during concurrent unimanual finger tapping with the right and left hands at separate times. A multivariate analysis of variance showed no significant differences in picture-naming reaction time between left versus right visual-field stimulations. Also the test for finger tapping was nonsignificant, with the magnitude of disruption being symmetrical for the right and left hands as a function of visual fields. It was proposed that the two cerebral hemispheres interact with each other at later processing stages when performing tasks requiring both left and right hemispheric processing resources.

Naming reaction times to tachistoscopically presented pictures: some evidence of right hemisphere encoding.

The present study measured naming reaction times by normal subjects to unilaterally presented picture stimuli. Significant differences in picture-naming reaction time did not exist between left and right visual-field stimulations. The right hemisphere in the intact brain is capable of generating a verbal label for pictured stimuli. A psychological model suggests that a possible processing synergy between the two hemispheres may be tied to spatial processing and elementary linguistics.

EMG activity of the orbicularis oris superior, orbicularis oris inferior, and masseter muscles of a cleft-palate child.

The peak amplitude of EMG activity was measured from the orbicularis oris superior (OOS), orbicularis oris inferior (OOI), and masseter muscles of a cleft-palate child and compared to data obtained from a normal child. Both children evidenced similar levels of average peak EMG activity and variability of performance across the three muscles. These data were interpreted to suggest that limitations in the function of the OOS, OOI, and masseter muscles do not contribute to the articulatory anomalies exhibited by the cleft-palate child.

Speech-motor equivalence in aging subjects'.

The peak amplitude of EMG activity was measured from the orbicularis oris superior (OOS), orbicularis oris inferior (OOI), and masseter muscles for three normal, geriatric women (range 70 to 75 yr.) and compared with prior data for a group of normal, 4- and 8-yr.-old children and young adults (range 21 to 29 yr.). The elderly groups' variability across the three muscles paralleled that of the 4-yr.-olds, suggesting that speech-motor equivalence returns to an earlier level of operation in aging speakers. Also, the elderly subjects evidenced reduced levels of average peak EMG activity as compared to those of the other groups. This finding was interpreted as reflecting a loss of general muscle function, a possible concomitant of facial muscle atrophy that accompanies advanced age.