Intrinsic and extrinsic wrist ligaments: biomechanical and functional differences

The human wrist is a complex arrangement of bones and ligaments and functions to position the hand and transfer forces between the hand and forearm. The carpal ligaments (extrinsic - connect carpal bones and forearm; and intrinsic - interconnect carpals) are vitally important for wrist function and still incompletely understood biomechanically. Our previous investigations have described the rate-dependent viscoelastic behavior of the scapholunate (intrinsic) ligament. This study demonstrates significant differences in the biomechanical behavior between the intrinsic and extrinsic classes of ligaments. Bone-ligament-bone preparations were obtained by dissecting fresh and fresh-frozen cadaveric specimens. Two intrinsic (IL) [scapholunate (SL, 7) and lunotriquetral (LT, 9)] and two extrinsic (EL) [radiolunate (RL, 2) and radioscaphocapitate (RC, 3)] ligaments were extensively tested on a Monsanto Tensometer testing apparatus in axial loading at 0.5, 1, 5, 10, 50, and 100 mm/min. Significant differences in behavior were noted between the intrinsic and extrinsic ligaments in (1) maximum stress at ultimate yield (IL greater than EL), (2) maximum strain at ultimate yield (IL greater than EL), (3) strain level for onset of plasticity (IL greater than EL), and (4) rate and amount of stress relaxation (IL greater than EL). These results indicate that the intrinsic ligaments are biomechanically quite different than the extrinsic ligaments. These distinctions have important implications for wrist function and pathomechanics.     

Adaptation of cortical NMDA receptors by chronic treatment with specific serotonin reuptake inhibitors

Glycine displaces [3H]CGP-39653 ([3H]D,L-(E)-2-amino-4-propyl-5-phosphono-3-pentenoic acid) binding to the glutamate recognition site with both high and low affinity. We reported previously that chronic treatment with antidepressants reduced the proportion of high to low affinity sites, or, even eliminated the high affinity sites in case of citalopram. Here, we compared the effects of citalopram with another serotonin specific reuptake inhibitor, fluoxetine on this measure. Chronic administration of citalopram or fluoxetine eliminated high affinity glycine-displaceable [3H]CGP-39653 binding to the mouse cortex in 78 and 56% of animals, respectively, indicating that selective serotonin reuptake inhibitors produce qualitatively similar adaptive changes at NMDA receptors, that differ from other antidepressants in this neurochemical measure.     

Cavernous hemangioma of the umbilical cord

We report the case of a cavernous hemangioma with a recently developed hematoma of the umbilical cord. Because of a threatening intrauterine asphyxia an operative vaginal delivery was performed followed by pulmonary disturbance of adaptation and anemia with transfusion. Possible complications are discussed both in terms of the case-history and literature.     

Electrical stimulation of brainstem nuclei: Elicitation, modification, and conditioning of the rabbit nictitating membrane response.

Electrical stimulation of the reticular formation, pars oralis of the spinal trigeminal, abducens, and accessory abducens nuclei was used to assess the role of these sites in the elicitation, reflex modification, and classical conditioning of the rabbit's nictitating membrane response (NMR). Although electrical brain stimulation of the targeted sites revealed comparable levels of unconditioned responses, the spinal trigeminal nucleus was the only site at which reflex modification and conditioned response acquisition occurred reliably. These findings suggest that a locus of conditioned stimulus and unconditioned stimulus interaction, mediating either or both reflex modification and NMR conditioning, is on the sensory side of the reflex arc, at the pars oralis of the spinal trigeminal nucleus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Test of a prototype of the ZEUS backing calorimeter

We have studied the performance of a high resolution uranium-scintillator calorimeter followed by a much coarser backing calorimeter, made out of iron plates interleaved with planes of limited streamer tubes. The test results, obtained at the CERN-SPS hadron beam, show that the backing calorimeter can be used either to veto events with significant energy leakage from the uranium calorimeter or to correct for the energy. In both cases the energy resolution of the combined calorimeters improves significantly compared to the uranium calorimeter alone.     

Evaluating eigenvalues for boundary value problems of heat conduction in rectangular and cylindrical co-ordinate systems

A method of evaluating eigenvalues for any combination of the first, second and third boundary conditions of heat conduction in a plate, a solid cylinder or a hollow cylinder is described. Some general relationships between eigenvalues are derived. Based on these relationships a universal algorithm is developed. A list of a package of computer subroutines is included.     

Effect of mycophenolic acid glucuronide on inosine monophosphate dehydrogenase activity

Mycophenolic acid glucuronide (MPAG) inhibition kinetics were evaluated using purified recombinant human type II inosine monophosphate dehydrogenase (IMPDH). MPAG inhibitory concentrations (IC50) were found to be 532- to 1022-fold higher than those for MPA. As expected, according to tight-binding inhibitor kinetics, mycophenolic acid (MPA) IC50 values increased as IMPDH concentrations increased, whereas IC50 values for xanthosine monophosphate (competitive IMPDH inhibitor used as control), an inhibitor known not to be tight binding, remained independent of enzyme concentration. Although MPAG exhibited only weak inhibition of IMPDH activity, in comparison with MPA, IC50 values increased with increasing enzyme concentration. The presence of trace quantities of MPA (0.2% on a molar basis) in the MPAG preparation, detected by high-performance liquid chromatography analysis, could account for this observation. These data support the proposal that MPAG is a pharmacologically inactive metabolite of MPA.     

Adaptive evolution of highly mutable loci in pathogenic bacteria

Bacteria have specific loci that are highly mutable. We argue that the coexistence within bacterial genomes of such 'contingency' genes with high mutation rates, and 'housekeeping' genes with low mutation rates, is the result of adaptive evolution, and facilitates the efficient exploration of phenotypic solutions to unpredictable aspects of the host environment while minimizing deleterious effects on fitness.