Structural studies of a phosphatidyl serine-amorphous calcium phosphate complex

A phosphatidyl serine-amorphous calcium phosphate complex has been synthesized as a model of the matrix vesicle system that is associated with the induction of mineral deposition in bone, cartilage and dentine. The complex has been studied using a novel technique of subtractive extended X-ray absorption fine structure (EXAFS). This enables spectra of the components of the molecules to be subtracted from the complex so as to identify the sites of interaction. The results suggest there is a movement in the nitrogen atom of the phosphatidyl serine which approaches the calcium atom in the mineral phase. This interpretation would link the membrane structure of the vesicle to the structure of the mineral in a way that could explain some of its roles in biomineralization.

Large-scale preparation of biologically active recombinant ovine obese protein (leptin)

Prokaryotic expression vector pMON3401 encoding full size A(-1) ovine leptin was prepared by polymerase chain reaction (PCR) of previously described cDNA. E. coli cells transformed with this vector overexpressed large amounts of ovine leptin upon induction with nalidixic acid. The expressed protein found in the inclusion bodies was refolded and purified to homogeneity on Q-Sepharose and SP-Sepharose columns, yielding two electrophoretically pure fractions (leptin-Q and leptin-SP), composed respectively of 90 and 95% of monomeric protein of the expected molecular mass of 16 kDa. The purified protein was capable of interacting with antibodies raised against (GST-ovine leptin and to bind specifically to ventromedial hypothalamus of ewes. The biological activity of both fractions resulting from proper renaturation was further evidenced by their ability to stimulate DNA synthesis in leptin-sensitive BAF/3 cells transfected with a long form of human leptin receptor construct.

Maximizing AIDS expertise

Breakthroughs in treatments for HIV/AIDS are offering new hope. Health plans are identifying the right professionals to coordinate these promising but complex new treatments.

Tetracycline demineralization of dentin: the effects of concentration and application time

The current investigation was initiated to study the effect concentration and application time has on the rate of tetracycline demineralization of dentin. Buccal and lingual surfaces of extracted bovine molars were ground to a smooth flat dentin surface using wetted silicon carbide discs. Standardized depressions were made in the dentin surface with a #909-055 diamond round wheel. Fresh tetracycline HCl (TTC-HCl) (Flavine Int. Inc.) solutions, i.e., 0, 25, 50, 75, 100, 125 and 150 mg/ml were prepared. A 30% citric acid solution was used as a positive control. The pH of each solution was recorded. 7 microl of each solution were pipetted into a depression and remained undisturbed for 1, 3, or 5 min. At the end of each application time period a fresh #3 cotton pellet was placed in the depression, once every 20 s for 1 min, to soak up the solution. The 3 pellets were placed in a 2.00 ml of 18 M omega H2O sample. As a measure of the rate of demineralization, the parts per million calcium (ppm Ca++) found in each sample were determined using atomic absorption spectrophotometry. Two-way analysis of variance was used to determine effects of TTC-HCI concentration and time on the rate of demineralization. No significant differences were found in the mean ppm Ca++ released at 1-, 3- and 5-min application times for 0, 25, or 50 mg/ml TTC. No significant differences were found in the mean ppm Ca++ released (i) between 3- and 5-min application times for 75, 100, 125 and 150 mg/ml TTC-HCl solutions and (ii) between 75, 100, 125 and 150 mg/ml TTC-HCl solutions within either the 3- or 5-min application times. The mean ppm Ca++ released at 3- and 5-min application times for 75, 100, 125 and 150 mg/ml TTC-HCI solutions were all significantly greater than the respective readings at the 1-min application time. The mean ppm Ca++ recorded for the 30% citric acid solution for all 3 application times were 3 to 5.5 x greater than the highest mean ppm Ca++ recording for TTC-HCl. The results of this study show that a 3-min application time of 75 mg/ml TTC-HCl solution is equally as effective at demineralizing dentin as is higher concentrations and/or longer application times, but was far less effective than a 30% citric acid solution.

Who needs to know?

Health plans need to collect data on mental health services to ensure quality and improve care. But can they do this and protect patient confidentiality at the same time?

Assay for valproic acid and its E-delta2 metabolite in rat plasma by capillary gas chromatography without prior derivatization

A new and improved gas chromatographic assay method for valproic acid and a metabolite, E-delta2 valproic acid, in rat plasma has been developed. The assay has sufficient sensitivity to measure free levels of the parent drug and metabolite. By employing a Stabilwax-DA capillary column, symmetrical chromatographic peaks were obtained without the need for prior derivatization. Standard curves for valproic acid were linear from 0.1 to 640 microg/ml. Standard curves for the metabolite were linear from 0.1 to 556 microg/ml.

4 x 4 vertical-cavity surface-emitting laser (VCSEL) and metal-semiconductor-metal (MSM) optical backplane demonstrator system

We describe a system demonstrator based on vertical-cavity surface-emitting lasers, metal-semiconductor-metal detectors, printed circuit board (PCB) level optoelectronic device packaging, a compact bulk optical relay, and novel barrel/PCB optomechanics. The entire system was constructed in a standard VME electrical backplane chassis and was capable of operating at >1.7 Gbit/s of aggregate data capacity. In addition to the component technologies developed, we describe operational testing and characterization of the demonstrator.

Masticatory function in patients with xerostomia

The effects of reduced salivary output in patients suffering from xerostomia on masticatory function has not been previously studied. This study compares masticatory performance and kinematic activity of patients suffering from xerostomia with age-, sex-, and number of occluding pairs-matched healthy controls. Masticatory function was evaluated by assessment of chewing motion and muscle activity during chewing an artificial food (CutterSil), chewing gum and swallowing a bolus of almond. Chewing motion was recorded with the Optotrak computer system. Bilateral muscle activity of both masseter and anterior temporalis was recorded using surface electrodes. Results of this study revealed significant differences between patients and controls in their ability to process food and masticatory muscle activity. The majority of patients could not break down the artificial food, others had a larger median particle size than the controls. A significant difference was also observed in the number of chewing cycles required to swallow almonds, the patients required more than twice as many chews as the controls, P < 0.001. The right masseter muscle displayed significantly less activity for the patient than the controls. These findings suggest that patients with xerostomia exhibit reduced ability to process food. The observed decline in masticatory performance is probably due to reduced activity of the muscles of mastication.

Acute myocardial infarction. Then and now

Dramatic changes in the management of acute myocardial infarction (AMI) have occurred in the past decade. While previous management strategies were primarily supportive, current strategies focus on achieving and maintaining patency of the infarct-related artery restoring blood flow to jeopardized myocytes, preserving left ventricular function, and preventing recurrences and complications in addition to promoting healing. Restoration of blood flow can be achieved pharmacologically with thrombolytic agents or mechanically with percutaneous transluminal coronary angioplasty (PTCA). Early use of antiplatelet agents and anticoagulants helps maintain patency of the infarct-related arteries and prevents thromboembolic complications. Administration of beta-blockers and angiotensin enzyme inhibitors are more specific means of conserving myocardium and preserving ventricular function. Additionally, several strategies for preventing arrhythmias such as prophylactic lidocaine use and routine long-term suppression of premature ventricular contractions with antiarrhythmic drugs are no longer routinely advocated. Basically, in the era prior to the eighth decade of this century, the primary direction of the therapeutic strategy for AMI was to reduce the oxygen demands in the infarcted myocardium; whereas in the subsequent years, the emphasis shifts to improvement in oxygen delivery, via thrombolysis, PTCA, and coronary artery bypass graft surgery. These interventional changes, when added to greater sophistication in the use of drugs to reduce oxygen demands, resulted in significant lowering of myocardial mortality.

The interpersonal relationship in clinical practice. The Barrett-Lennard Relationship Inventory as an assessment instrument

The biomedical model that has long been central to medical practice is gradually being expanded to a broader biopsychosocial model. Relationship-building skills commensurate with the new paradigm need to be understood by educators and taught to medical practitioners. The person-centered, or humanistic, model of psychologist Carl Rogers provides a theoretical approach for the development of effective biopsychosocial relationships. The Barrett-Lennard Relationship Inventory (BLRI) was developed in 1962 as an assessment instrument for the person-centered model. In this article, the person-centered model and the use of the BLRI as an assessment instrument of this model are discussed. Current and potential uses of the BLRI are explored.

Pure motor demyelinating neuropathy: deterioration after steroid treatment and improvement with intravenous immunoglobulin

Within one month of starting oral prednisolone treatment weakness unexpectedly increased in four patients aged 34 to 75 years with purely motor forms of acquired chronic demyelinating neuropathy. By contrast, steroids produced the expected improvement in 11 other patients with symmetric sensorimotor chronic inflammatory demyelinating polyneuropathy. Two of the patients with purely motor demyelinating neuropathy were subsequently treated with high dose IVIg (0.4 g/kg/day for five days) with prompt improvements in strength measurements and motor nerve conduction. Thus IVIg seems to be the treatment of choice and steroids should be used with extreme caution, if at all, in patients with purely motor forms of acquired demyelinating polyneuropathy.

Excessive daytime somnolence in women with abnormal respiratory efforts during sleep

An abnormal level of respiratory efforts, indicated by significant increase in peak negative esophageal pressure (Pes), can be associated with daytime somnolence in snoring pre-menopausal women. No drop in oxygen saturation (SaO2) or visual evidence of transient electroencephalographic (EEG) arousals can be found at repeat polysomnography. Nasal continuous positive airway pressure (CPAP) titrated on Pes measurements eliminates somnolence.

Cardiac failure, snoring, ventricular arrhythmias and nasal bilevel positive pressure ventilation

Patients with stable cardiac failure who snore may present sleep hypopnea and cardiac arrhythmias. Nasal continuous positive airway pressure (CPAP) may worsen the disordered breathing. Nasal bilevel positive airway pressure (BiPAP), however, may help alleviate the breathing problem and eliminate sleep-related arrhythmias.

Pure red cell aplasia and hepatitis A

A patient with pure red cell aplasia associated with hepatitis A showed a dramatic and rapid recovery after initiation of oral prednisone therapy. The response to corticosteroid therapy suggests an immune etiology for this life-threatening disorder.