The structural architecture of adult mammalian articular cartilage evolves by a synchronized process of tissue resorption and neoformation during postnatal development.

OBJECTIVE: During postnatal development, mammalian articular cartilage acts as a surface growth plate for the underlying epiphyseal bone. Concomitantly, it undergoes a fundamental process of structural reorganization from an immature isotropic to a mature (adult) anisotropic architecture. However, the mechanism underlying this structural transformation is unknown. It could involve either an internal remodelling process, or complete resorption followed by tissue neoformation. The aim of this study was to establish which of these two alternative tissue reorganization mechanisms is physiologically operative. We also wished to pinpoint the articular cartilage source of the stem cells for clonal expansion and the zonal location of the chondrocyte pool with high proliferative activity. METHODS: The New Zealand white rabbit served as our animal model. The analysis was confined to the high-weight-bearing (central) areas of the medial and lateral femoral condyles. After birth, the articular cartilage layer was evaluated morphologically at monthly intervals from the first to the eighth postnatal month, when this species attains skeletal maturity. The overall height of the articular cartilage layer at each juncture was measured. The growth performance of the articular cartilage layer was assessed by calcein labelling, which permitted an estimation of the daily growth rate of the epiphyseal bone and its monthly length-gain. The slowly proliferating stem-cell pool was identified immunohistochemically (after labelling with bromodeoxyuridine), and the rapidly proliferating chondrocyte population by autoradiography (after labelling with (3)H-thymidine). RESULTS: The growth activity of the articular cartilage layer was highest 1 month after birth. It declined precipitously between the first and third months, and ceased between the third and fourth months, when the animal enters puberty. The structural maturation of the articular cartilage layer followed a corresponding temporal trend. During the first 3 months, when the articular cartilage layer is undergoing structural reorganization, the net length-gain in the epiphyseal bone exceeded the height of the articular cartilage layer. This finding indicates that the postnatal reorganization of articular cartilage from an immature isotropic to a mature anisotropic structure is not achieved by a process of internal remodelling, but by the resorption and neoformation of all zones except the most superficial (stem-cell) one. The superficial zone was found to consist of slowly dividing stem cells with bidirectional mitotic activity. In the horizontal direction, this zone furnishes new stem cells that replenish the pool and effect a lateral expansion of the articular cartilage layer. In the vertical direction, the superficial zone supplies the rapidly dividing, transit-amplifying daughter-cell pool that feeds the transitional and upper radial zones during the postnatal growth phase of the articular cartilage layer. CONCLUSIONS: During postnatal development, mammalian articular cartilage fulfils a dual function, viz., it acts not only as an articulating layer but also as a surface growth plate. In the lapine model, this growth activity ceases at puberty (3-4 months of age), whereas that of the true (metaphyseal) growth plate continues until the time of skeletal maturity (8 months). Hence, the two structures are regulated independently. The structural maturation of the articular cartilage layer coincides temporally with the cessation of its growth activity--for the radial expansion and remodelling of the epiphyseal bone--and with sexual maturation. That articular cartilage is physiologically reorganized by a process of tissue resorption and neoformation, rather than by one of internal remodelling, has important implications for the functional engineering and repair of articular cartilage tissue.

The sun and heliosphere at solar maximum.

Recent Ulysses observations from the Sun's equator to the poles reveal fundamental properties of the three-dimensional heliosphere at the maximum in solar activity. The heliospheric magnetic field originates from a magnetic dipole oriented nearly perpendicular to, instead of nearly parallel to, the Sun's rotation axis. Magnetic fields, solar wind, and energetic charged particles from low-latitude sources reach all latitudes, including the polar caps. The very fast high-latitude wind and polar coronal holes disappear and reappear together. Solar wind speed continues to be inversely correlated with coronal temperature. The cosmic ray flux is reduced symmetrically at all latitudes.

Relationship between drug exposure and the efficacy and safety of bupropion sustained release for smoking cessation.

A population pharmacokinetic and pharmacodynamic analysis evaluated the relationships of dose, plasma concentrations of bupropion and metabolites, and patient covariates with the safety and efficacy of bupropion sustained release (SR) for smoking cessation. A total of 519 outpatient chronic cigarette smokers were randomized to one of three bupropion SR doses: 100, 150, or 300 mg/day or placebo. The bupropion plasma concentration time data were fit and subject-specific bayesian estimates of clearance were obtained. Logistic regression analyses evaluated the role of dose, concentrations, and covariates in predicting efficacy and safety endpoints. For the evaluation of efficacy, patients were classified as quitters or non-quitters on the basis of a 4-week quit variable (defined as complete abstinence for weeks 4-7 of the study). For the evaluation of safety, patients were classified into two categories for each adverse event evaluated, corresponding to whether the patient ever experienced the adverse event during the course of the study or never experienced the event, regardless of whether the event was treatment-emergent. The efficacy of bupropion SR in facilitating smoking cessation was found to be related to dose and a mean metabolite concentration, and quitting in general was found to be related to the number of cigarettes smoked per day at baseline. Smoking cessation was 1.42, 1.69, and 2.84 times more likely in patients receiving 100, 150, and 300 mg/day of bupropion SR, respectively, as compared to placebo (p = 0.0001). As the baseline number of cigarettes smoked per day increased, the likelihood of quitting decreased regardless of the treatment condition. Insomnia and dry mouth were positively associated with mean metabolite concentrations, and dry mouth was inversely related to patient weight. Anxiety was inversely related to predicted steady-state concentration (Cpss), suggesting a positive effect on this withdrawal symptom. Bupropion SR exhibits a statistically significant dose/plasma level-response relationship for smoking cessation. Dry mouth and insomnia, related to concentrations, may be managed with dose reduction, with the realization that smoking cessation may be impaired.

Interception of comet Hyakutake's ion tail at a distance of 500 million kilometres

Remote sensing observations and the direct sampling of material from a few comets have established the characteristic composition of cometary gas. This gas is ionized by solar ultraviolet radiation and the solar wind to form 'pick-up' ions, ions in a low ionization state that retain the same compositional signatures as the original gas. The pick-up ions are carried outward by the solar wind, and they could in principle be detected far from the coma (Sampling of pick-up ions has also been used to study interplanetary dust, Venus' tail and the interstellar medium.) Here we report the serendipitous detection of cometary pick-up ions, most probably associated with the tail of comet Hyakutake, at a distance of 3.4 AU from the nucleus. Previous observations have provided a wealth of physical and chemical information about a small sample of comets, but this detection suggests that remote sampling of comet compositions, and the discovery of otherwise invisible comets, may be possible.

The effect of bupropion on nicotine craving and withdrawal.

RATIONALE AND OBJECTIVES: Bupropion has demonstrated efficacy for smoking cessation. Given the importance of nicotine craving and withdrawal in the smoking cessation process, the current study examined the effects of bupropion on these parameters during smoking abstinence. METHODS: During a 2-day Baseline phase with ad lib smoking, 91 non-depressed smokers (who were not trying to quit permanently) were administered measures of nicotine craving, withdrawal symptoms, and timed measures of cognitive performance five times daily. Participants were then assigned randomly to a 14-day treatment regimen with bupropion 300 mg/day, bupropion 150 mg/day, or placebo. Thereafter, the above measures were re-administered during 3 days of abstinence on a closed research ward. RESULTS: Relative to placebo, 300 mg bupropion significantly reduced abstinence-associated increases in rated depression, difficulty concentrating, and irritability, and attenuated a decrease in positive affect. The results also suggested that bupropion might have a positive effect on performance measures during the withdrawal period. No effects were observed on craving, anxiety, restlessness, or hunger. The lack of findings on craving measures may be explained by a floor effect; except on the first day of abstinence, neither drug nor placebo groups showed much craving elevation during abstinence. CONCLUSIONS: Study results indicate that bupropion ameliorates some nicotine withdrawal symptoms.

The Brief Social Phobia Scale: a psychometric evaluation.

The Brief Social Phobia Scale (BSPS) is an observer-rated scale designed to assess the characteristic symptoms of social phobia, using three subscales-fear, avoidance, and physiological arousal-which may be combined into a total score. Each of 18 BSPS items is anchored to a 5-point rating scale. Psychometric evaluation of the BSPS in a sample of 275 social-phobia patients yielded a high level of reliability and validity. Test-retest reliability was excellent, as was internal consistency. The fear and avoidance subscales demonstrated highly significant correlations with remaining item totals; however, the physiological subscale did not. The BSPS also demonstrated significant relationships with other established scales that assess anxiety and disability, and it proved sensitive to treatment effects in a trial of a 5-HT3 antagonist and placebo. Factor analysis yielded six meaningful factors. We conclude that the BSPS provides a reliable, valid, and sensitive measure for the evaluation of social phobia.

Cognitive performance on the Alzheimer's Disease Assessment Scale: effect of education.

The cognitive subscale of the Alzheimer's Disease Assessment Scale (ADAS-Cog) is used to monitor disease progression and treatment efficacy in clinical trials of Alzheimer's disease (AD). Using data from a 12-week drug trial, we retrospectively studied the effect of education on ADAS-Cog performance in a group of 444 patients with AD. The effect of education was statistically significant on baseline ADAS-Cog total scores. This effect remained statistically significant after controlling for age, gender, and dementia severity. Education effects were also statistically significant at week 12 for ADAS-Cog total and 10 of 11 subitem scores in 138 AD patients in the placebo arm of the trial. Post hoc analysis showed that non-high school graduates performed worse than those with greater educational levels across a broad range of cognitive domains. Our results, in conjunction with reports linking lower educational level with a higher risk for AD, suggest that educational level of patients be given consideration in the design and interpretation of cognitive tests in AD drug trials.

Psychosis in Parkinson's disease: diagnosis and treatment.

1. This article reviews the prevalence, diagnosis, pathophysiology and management of psychosis in Parkinson's disease. 2. Psychosis in Parkinson's disease has been associated with all antiparkinsonian medications. The most common symptoms are vivid disturbing dreams, visual hallucinations and paranoid delusions. 3. The emergence of psychosis reduces the patient's functional capacity and increases caregiver burden. It also poses a therapeutic dilemma because effective treatment of psychotic symptoms may result in worsening of motor symptoms and vice versa. 4. Increased physician awareness is essential for proper diagnosis and management. Withdrawal of anticholinergic medications and amantadine followed by levodopa dose adjustment is effective in many patients. 5. Atypical neuroleptics, in low doses, may be successful when other measures have failed. However, these agents are not approved for treating Parkinsonian psychosis and must be considered as investigational therapies.

The southern high-speed stream: results from the SWICS instrument on Ulysses.

The high-speed solar wind streaming from the southern coronal hole was remarkably uniform and steady and was confined by a sharp boundary that extended to the corona and chromosphere. Charge state measurements indicate that the electron temperature in this coronal hole reached a maximum of about 1.5 million kelvin within 3 solar radii of the sun. This result, combined with the observed lack of depletion of heavy elements, suggests that an additional source of momentum is required to accelerate the polar wind.

Pharmacologic therapy of obsessive compulsive disorder.

OCD is an anxiety disorder that was once viewed as rare and very difficult to treat. Although the first evidence that a serotonergic drug, clomipramine, might be effective in treating symptoms of OCD was published by Fernandez-Cordoba and Lopez-Ibor Alino in 1967, controlled trials demonstrating the efficacy of pharmacologic treatments in OCD did not appear until the 1980s. The availability of potentially effective treatments, combined with the awareness of prevalence rates for the disorder that are higher than previously believed, led to considerable interest in OCD. Numerous studies have been undertaken to investigate the biology of OCD. The observation that drugs that act by inhibiting serotonin uptake, such as clomipramine, fluvoxamine, sertraline, and fluoxetine, are effective in treating symptoms of OCD has resulted in intense interest in the relationship between serotonin and this disorder. Several lines of investigation support a serotonergic hypothesis for the pathophysiology and treatment of this disorder. Clomipramine, a tricyclic antidepressant that is a potent serotonin uptake inhibitor, was the first pharmacologic treatment for OCD to be studied in large multicenter trials. The successful outcome of these studies resulted in marketing approval by the United States Food and Drug Administration in 1989. Subsequently, similar multicenter trials have been undertaken with the selective serotonin uptake inhibitors fluvoxamine, sertraline, and fluoxetine. Results from these multicenter trials indicate that all these drugs are more effective than placebo in treating OCD. However, meta-analytic techniques applied to the data from controlled trials of these drugs suggest that the effect size for clomipramine is somewhat larger than that of the selective serotonin uptake inhibitors. A number of other drugs that affect serotonin through mechanisms other than uptake inhibition have been tried as treatments for OCD. Because of the small size of many of these studies, it is difficult to evaluate them in the context of the multicenter trials that studied hundreds of patients. Nevertheless, there may be a role for other serotonergic drugs in the treatment of OCD, particularly as adjunctive treatments used to enhance the effect of the serotonin uptake inhibitors. The data supporting the use of adjunctive treatment are limited and cannot be considered to demonstrate definitively the value of augmentation strategies with adjunctive treatment. Nevertheless, the serotonin uptake inhibitors, although effective in a large number of patients, do not appear to provide adequate symptom relief for some patients. Furthermore, among the patients who do respond to serotonin uptake inhibitors, complete remission in uncommon, which leaves a need for improvement of therapies.(ABSTRACT TRUNCATED AT 400 WORDS)

Detection of interstellar pick-up hydrogen in the solar system.

Interstellar hydrogen ionized primarily by the solar wind has been detected by the SWICS instrument on the Ulysses spacecraft at a distance of 4.8 astronomical units from the sun. This "pick-up" hydrogen is identified by its distinct velocity distribution function, which drops abruptly at twice the local solar wind speed. From the measured fluxes of pick-up protons and singly charged helium, the number densities of neutral hydrogen and helium in the distant regions of the solar system are estimated to be 0.077 +/- 0.015 and 0.013 +/- 0.003 per cubic centimeter, respectively.

Full-thickness mucous membrane grafts from the vestibular (oral labial) mucosa of the lip.

BACKGROUND: Full thickness mucous membrane coverage is desired for a variety of reconstructive tasks involving the oral cavity and vermilion area of the lips. OBJECTIVE: This article will inform the readership that the vestibular (oral labial) mucosal area of the lower lip close to the sulcus may provide adequate full-thickness mucous membrane graft tissue for such purposes. METHOD: A series of photographs from a number of representative cases with accompanying commentary will enable the surgeon to easily incorporate this technique into his/her practice. CONCLUSION: The lips vestibular mucosa will be found to be an invaluable ally in accomplishing non-deforming coverage of superficial mucosal defects without unnecessary surgical invasion of visible lip/chin structures.

Diagnosis and treatment of obsessive compulsive disorder.

Obsessive compulsive disorder (OCD) is a common anxiety disorder that appears to be due to a disturbance in central serotonergic functioning. Drugs, such as clomipramine, that inhibit neuronal reuptake of serotonin are effective in treating OCD. Behavioral therapy techniques are also effective.

Plasma Composition in Jupiter's Magnetosphere: Initial Results from the Solar Wind Ion Composition Spectrometer.

The ion composition in the Jovian environment was investigated with the Solar Wind Ion Composition Spectrometer on board Ulysses. A hot tenuous plasma was observed throughout the outer and middle magnetosphere. In some regions two thermally different components were identified. Oxygen and sulfur ions with several different charge states, from the volcanic satellite lo, make the largest contribution to the mass density of the hot plasma, even at high latitude. Solar wind particles were observed in all regions investigated. Ions from Jupiter's ionosphere were abundant in the middle magnetosphere, particularly in the highlatitude region on the dusk side, which was traversed for the first time.

Clomipramine hydrochloride in childhood and adolescent obsessive-compulsive disorder--a multicenter trial.

Children and adolescents with obsessive compulsive disorder were studied in an 8-week, multicenter, double-blind, parallel groups trial of clomipramine hydrochloride (CMI) versus placebo. Efficacy assessments included the child version of the Yale-Brown Obsessive Compulsive Scale and the National Institute of Mental Health Global rating scale. At the end of 8 weeks, CMI-treated patients showed a mean reduction in Yale-Brown Obsessive Compulsive Scale score of 37% compared to 8% in the placebo group. Side effects were typical of tricyclic antidepressants. In a 1-year open label treatment, CMI continued to be effective and well tolerated.