The role in cell binding of a beta-bend within the triple helical region in collagen alpha 1 (I) chain: structural and biological evidence for conformational tautomerism on fiber surface

Dystrophin is a plasma membrane-associated cytoskeletal protein of the spectrin superfamily. The dystrophin cytoskeleton has been first characterized in muscle. Muscular 427 kDa dystrophin binds to subplasmalemmal actin filaments via its amino-terminal domain. The carboxy-terminus of dystrophin binds to a plasma membrane anchor, beta-dystroglycan, which is associated on the external side with the extracellular matrix receptor, alpha-dystroglycan, that binds to the basal lamina proteins laminin-1, laminin-2, and agrin. In the muscle, the dystroglycan complex is associated with the sarcoglycan complex that consists of several glycosylated, integral membrane proteins. The absence or functional deficiency of the dystrophin cytoskeleton is the cause of several types of muscular dystrophies including the lethal Duchenne muscular dystrophy (DMD), one of the most severe and most common genetic disorders of man. The dystrophin complex is believed to stabilize the plasma membrane during cycles of contraction and relaxation. Muscular dystrophin and several types of dystrophin variants are also present in extramuscular tissues, e.g. in distinct regions of the central nervous systems including the retina. Absence of dystrophin from these sites is believed to be responsible for some extramuscular symptoms of DMD, e.g. mental retardation and disturbances in retinal electrophysiology (reduced b-wave in electroretinograms). The reduced b-wave in electroretinograms indicated a disturbance of neurotransmission between photoreceptors and ON-bipolar cells. At least two different dystrophin variants are present in photoreceptor synaptic complexes. One of these dystrophins (Dp260) is virtually exclusively expressed in the retina. In the neuroretina, dystrophin is found in significant amounts in the invaginated photoreceptor synaptic complexes. At this location dystrophin colocalizes with dystroglycan. Agrin, an extracellular ligand of alpha-dystroglycan, is also present at this location whereas the proteins of the sarcoglycan complex appear to be absent in photoreceptor synaptic complexes. Dystrophin and dystroglycan are located distal from the ribbon-containing active synaptic zones where both proteins are restricted to the photoreceptor plasma membrane bordering on the lateral sides of the synaptic invagination. In addition, some neuronal profiles of the postsynaptic complex also contain dystrophin and beta-dystroglycan. These profiles appear to belong at least in part to projections of the photoreceptor terminals into the postsynaptic dendritic complex. In view of the abnormal neurotransmission between photoreceptors and ON-bipolar cells in DMD patients the dystrophin/beta-dystroglycan-containing projections of photoreceptor presynaptic terminals into the postsynaptic dendritic plexus might somehow modify the ON-bipolar pathway. Another retinal site associated with dystrophin/beta-dystropglycan is the plasma membrane of Müller cells where dystrophin/beta-dystroglycan appear to be present at particular high concentrations. At this location the dystrophin/dystroglycan complex may play a role in the attachment of the retina to the vitreous, and, under pathological conditions, in traction-induced retinal detachment.     

A comparison of placebo response with major depressive disorder in patients recruited through newspaper advertising versus consultation referrals

Recent evidence indicates few differences between patients recruited through advertising and by consultation referral, and there is some suggestion that those recruited through advertising are more representative of the target community population. However little has been reported on differences in placebo response and compliance in these two patient groups. We conducted a retrospective chart review of 49 patients with major depressive disorder (MDD), recruited through advertising or consultation, randomized to placebo in five clinical trials. Variables included demographics, clinical history, efficacy, compliance, and completion data. Homogeneity was demonstrated for most variables. Differences in placebo groups included significantly lower Hamilton Rating Scale for Depression (HAM-D) scores for the advertisement group throughout the trials. Advertisement patients were also more likely to be early placebo responders and in remission at Days 14 and 28. No differences were found in completion rates or reasons for early termination. Compliance was excellent for both groups. Early placebo response of the advertisement group reinforces the need for trials of at least 8 weeks. In addition, consultation patients may have a more severe illness and be treatment resistant, suggesting they are less generalizable to community practice populations.     

Embryotoxic doses of vitamin A to rabbits result in low plasma but high embryonic concentrations of all-trans-retinoic acid: risk of vitamin A exposure in humans

Retinoid pharmacokinetics were examined in plasma, placenta and embryos of gestational d 12 rabbits following application of an embryotoxic dosing regimen (10 mg retinyl palmitate/kg body wt per day from gestational d 7 to 12). Vehicle-treated or untreated rabbits served as controls. Physiological concentrations of all-trans-retinoic acid (all-trans-RA) and 13-cis-RA in rabbit plasma (5-8.33 nmol/L) were very close to the endogenous levels in human plasma. In addition, we identified endogenous all-trans-RA, 3,4-didehydroretinol and 3,4-didehydroretinoic acid in rabbit embryo. Following the last retinyl palmitate administration, apparent steady-state concentrations of all retinoids were reached in the examined compartments of rabbits. The major polar retinoid in plasma was 9, 13-di-cis-RA, but its embryonic concentrations were only about 6% of those in plasma. In the embryo, retinol and its esters were found at high concentrations; lower amounts of all-trans-4-oxo-RA and the newly identified 14-hydroxy-4, 14-retro-retinol could also be measured. Embryonic concentrations of all-trans-RA were about 100% higher than endogenous levels. The overall exposure of the embryo to this retinoid was, however, substantial. Embryonic area under the concentration time curve values strongly suggest that the embryotoxicity of the applied dosing regimen is mainly due to the action of all-trans-RA. A very remarkable finding of this study is the marginal increase of plasma concentrations of all-trans-RA over their endogenous levels, which is comparable to the human situation after vitamin A intake. This analogy indicates that high vitamin A intake may be associated with a higher risk for teratogenic effects in humans even in the absence of high elevation of plasma all-trans-RA levels.     

The neurotoxicity of sulfur-containing amino acids in energy-deprived rat hippocampal slices

The rat hippocampal slice preparation and its electrophysiology were used to assess the toxicity of two sulfur-containing amino acids, L-cysteate (CA) and L-cysteine (CYS). Both compounds were innocuous under normal conditions but became toxic in energy-deprived (lack of oxygen or glucose) slices. CA and CYS toxicity was apparent as both reduced the number of slices that normally recover their neuronal function (evoked CA1 population spike) after a standardized period of hypoxia or glucose deprivation (GD). The competitive N-methyl-D-aspartate (NMDA) antagonist DL-2-amino-5-phosphonovalerate blocked the toxicity of both CA and CYS in hypoxic slices, but it was effective only against CYS toxicity in glucose-deprived slices. The glycine antagonist 7-chlorokynurenate blocked CA and CYS toxicity in hypoxic slices but was unable to block their toxicity in glucose-deprived tissue. Perfusing slices with medium containing a high magnesium concentration blocked the toxicity of CA in both hypoxic and glucose-deprived slices, a treatment that was ineffective against CYS toxicity under either condition. Calcium depletion from the perfusion medium completely blocked the damaging effect of both amino acids in hypoxic slices, but it only partially blocked the toxicity of CA and did not block that of CYS in glucose-deprived slices. These results suggest that CA and CYS activate different NMDA receptor subsets and other glutamate receptor subtypes. Moreover, the results indicate a possible difference between the mechanism that lead to hypoxic neuronal damage and the one that lead to hypoglycemic neuronal damage.     

Rational use of rubella vaccine for prevention of congenital rubella syndrome in the Americas

Seventy-three spinal cord injured patients with central cord syndrome who had undergone inpatient rehabilitation, were studied retrospectively with regard to their demographic, neurologic and functional characteristics. There were 67 males and six females with a mean age of 53.5 years. Falls was the commonest mechanism of injury (54.8%) followed by motor vehicle accidents. Eleven patients sustained cervical fractures and 41 had radiological evidence of cervical spondylosis. Seventeen patients had sensory impairment and significant spasticity was present in 14 patients. Significant improvements in the admission/discharge ASIA motor scores and Modified Barthel Index (MBI) scores (P < 0.001) were noted after rehabilitation. Ninety-two percent of patients were continent of bladder on discharge compared to 64.4% on admission. Multiple regression analysis revealed three factors associated with a better functional outcome, namely, higher admission MBI scores, absence of spasticity and younger age (P < 0.05).     

Residues Val254, His256, and Phe259 of the angiotensin II AT1 receptor are not involved in ligand binding but participate in signal transduction

The role of the external third of helix VI of the angiotensin II (AII) AT1 receptor for the interaction with its ligand and for the subsequent signal transduction was investigated by individually replacing residues 252-256 by Ala, and residues 259 or 261 by Tyr, and permanently transfecting the resulting mutants to Chinese hamster ovary (CHO) cells. Binding experiments showed no great changes in affinity of any of the mutants for AII, [Sar1]-AII, or [Sar1, Leu8]-AII, but the affinity for the nonpeptide antagonist DuP753 was significantly decreased. The inositol phosphate response to AII was remarkably decreased in mutants V254A, H256A, and F259Y. These results indicate that AT1 residues Val254, His256, and Phe259 are not involved in ligand binding but participate in signal transduction. Based in these results and in others from the literature, it is suggested that, in addition to the His256 imidazole ring, the Phe259 aromatic ring interacts with the AII's Phe8, thus contributing to the signal-triggering mechanism.     

Overview of health-related quality-of-life measures for pediatric patients: application in the assessment of pharmacotherapeutic and pharmacoeconomic outcomes

Health-related quality of life (HRQOL) is an important dimension in assessing health care. Several methodologic considerations are related to the manner in which these data are obtained in children. Few multidimensional generic measures of quality of life (QOL) have been developed for children and adolescents. Most published research concerns the development of tools to be used in a disease-specific manner for clinical trials. Although several authors point out numerous advantages in assessing HRQOL in clinical practice, several barriers must be overcome for this to occur. In the current era of economic restraint, HRQOL measures must be integrated into pharmaco-economic analyses to assess fully the impact of a drug on health care resources and outcomes.     

Cerebral blood flow relationships associated with a difficult tone recognition task in trained normal volunteers

Tone recognition is partially subserved by neural activity in the right frontal and primary auditory cortices. First we determined the brain areas associated with tone perception and recognition. This study then examined how regional cerebral blood flow (rCBF) in these and other brain regions correlates with the behavioral characteristics of a difficult tone recognition task. rCBF changes were assessed using H2(15)O positron emission tomography. Subtraction procedures were used to localize significant change regions and correlational analyses were applied to determine how response times (RT) predicted rCBF patterns. Twelve trained normal volunteers were studied in three conditions: REST, sensory motor control (SMC) and decision (DEC). The SMC-REST contrast revealed bilateral activation of primary auditory cortices, cerebellum and bilateral inferior frontal gyri. DEC-SMC produced significant clusters in the right middle and inferior frontal gyri, insula and claustrum; the anterior cingulate gyrus and supplementary motor area; the left insula/claustrum; and the left cerebellum. Correlational analyses, RT versus rCBF from DEC scans, showed a positive correlation in right inferior and middle frontal cortex; rCBF in bilateral auditory cortices and cerebellum exhibited significant negative correlations with RT These changes suggest that neural activity in the right frontal, superior temporal and cerebellar regions shifts back and forth in magnitude depending on whether tone recognition RT is relatively fast or slow, during a difficult, accurate assessment.