A new simplified technique for producing platelet-rich plasma: a short technical note.

A possible strategy to promote the wound-healing cascade in both soft and hard tissues is the preparation of an autologous platelet-rich plasma (PRP) to encourage the release of growth factors from activated platelets. In this process, PRP combines the advantage of an autologous fibrin clot that will aid in hemostasis as well as provide growth factors in high concentrations to the site of a tissue defect. The PRP preparation can be used as a biological enhancer in the healing of fractures and lumbar fusions. The local application of growth factors seems to promote initiation and early maturation of bone formation. Autologous bone or bone substitutes can be added to this mixture to increase the volume of grafting material. A simplified technique utilizing a commercially available separation system (GPS-Gravitational Platelet Separation System) is described. This system provides a less costly alternative to other previously described augmentation techniques and also presents a patient-friendly and operator-safe alternative. Further experimental studies of the actual concentrations of the growth factors in the PRP samples are necessary in order to validate the platelet concentration and growth-factor activation by laboratory evidence. In further prospective clinical trials, the safety and efficacy of PRP, in combination with autologous bone or bone graft substitutes, must be evaluated.

Exploring performance issues for a clinical database organized using an entity-attribute-value representation.

BACKGROUND: The entity-attribute-value representation with classes and relationships (EAV/CR) provides a flexible and simple database schema to store heterogeneous biomedical data. In certain circumstances, however, the EAV/CR model is known to retrieve data less efficiently than conventionally based database schemas. OBJECTIVE: To perform a pilot study that systematically quantifies performance differences for database queries directed at real-world microbiology data modeled with EAV/CR and conventional representations, and to explore the relative merits of different EAV/CR query implementation strategies. METHODS: Clinical microbiology data obtained over a ten-year period were stored using both database models. Query execution times were compared for four clinically oriented attribute-centered and entity-centered queries operating under varying conditions of database size and system memory. The performance characteristics of three different EAV/CR query strategies were also examined. RESULTS: Performance was similar for entity-centered queries in the two database models. Performance in the EAV/CR model was approximately three to five times less efficient than its conventional counterpart for attribute-centered queries. The differences in query efficiency became slightly greater as database size increased, although they were reduced with the addition of system memory. The authors found that EAV/CR queries formulated using multiple, simple SQL statements executed in batch were more efficient than single, large SQL statements. CONCLUSION: This paper describes a pilot project to explore issues in and compare query performance for EAV/CR and conventional database representations. Although attribute-centered queries were less efficient in the EAV/CR model, these inefficiencies may be addressable, at least in part, by the use of more powerful hardware or more memory, or both.

Using a computer database to monitor compliance with pharmacotherapeutic guidelines for schizophrenia.

OBJECTIVE: The study examined whether prescription data from a computerized database could be used to measure conformance with treatment recommendations of the Schizophrenia Patient Outcomes Research Team (PORT). METHODS: Records of an academically affiliated Veterans Affairs medical center were reviewed to identify patients who were hospitalized for schizophrenia and later seen for at least two outpatient visits in the six months after discharge (N=353). RESULTS: Conformance with only three of the 18 PORT pharmacotherapeutic recommendations could be measured with the available data. In regard to the recommendation to use antipsychotics other than clozapine as first-line treatments in acute episodes, 77 percent of the sample filled a prescription for an antipsychotic during the acute episode. Of these, only 6 percent received an antipsychotic regimen that included clozapine. In regard to the PORT recommendation on dosage during acute symptom episodes, 42 percent of the patients on conventional antipsychotics received dosages below the recommended range, 5 percent were above the range, and 53 percent were within it. In contrast, of the 53 patients who received clozapine or risperidone, 87 percent received prescriptions within the recommended dosage range. As for the recommendation to offer a trial of clozapine to patients who do not respond to adequate trials of two different classes of conventional drugs, 10 percent of patients who were switched from conventional regimens to clozapine were receiving dosages of conventional medications below the recommended range. CONCLUSIONS: Patient prescription data can provide preliminary measures to cost-effectively assess conformance with treatment. However, the approach has several limitations, and complementary analyses would enhance its usefulness.

Exploring the degree of concordance of coded and textual data in answering clinical queries from a clinical data repository.

OBJECTIVE: To query a clinical data repository (CDR) for answers to clinical questions to determine whether different types of fields (coded and free text) would yield confirmatory, complementary, or conflicting information and to discuss the issues involved in producing the discrepancies between the fields. METHODS: The appropriate data fields in a subset of a CDR (5,135 patient records) were searched for the answers to three questions related to surgical procedures. Each search included at least one coded data field and at least one free-text field. The identified free-text records were then searched manually to ensure correct interpretation. The fields were then compared to determine whether they agreed with each other, were supportive of each other, contained no entry (absence of data), or were contradictory. RESULTS: The degree of concordance varied greatly according to the field and the question asked. Some fields were not granular enough to answer the question. The free-text fields often gave an answer that was not definitive. Absence of data was most logically interpreted in some cases as lack of completion of data and in others as a negative answer. Even with a question as specific as which side a hernia was on, contradictory data were found in 5 to 8 percent of the records. CONCLUSIONS: Using the data in the CDR to answer clinical questions can yield significantly disparate results depending on the question and which data fields are searched. A database cannot just be queried in automated fashion and the results reported. Both coded and textual fields must be searched to obtain the fullest assessment. This can be expected to result in information that may be confirmatory, complementary, or conflicting. To yield the most accurate information possible, final answers to questions require human judgment and may require the gathering of additional information.

Cost-effectiveness of clozapine in patients with high and low levels of hospital use. Department of Veterans Affairs Cooperative Study Group on Clozapine in Refractory Schizophrenia.

BACKGROUND: This study examined the relationship between pretreatment hospital use and the cost-effectiveness of clozapine in the treatment of refractory schizophrenia. METHODS: Data from a 15-site randomized clinical trial were used to compare clozapine with haloperidol in hospitalized Veterans Affairs patients with refractory schizophrenia (n = 423). Outcomes were compared among those with many days in the hospital use (hereafter, high hospital users) (n = 141; mean = 215 psychiatric hospital days in the year prior to study entry) and those with few days in the hospital use (hereafter, low hospital users) (n = 282; mean = 58 hospital days). Analyses were conducted with the full intention-to-treat sample (n = 423) and with crossovers excluded (n = 291). RESULTS: Clozapine treatment resulted in greater reduction in hospital use among high hospital users (35 days less than controls, P = .02) than among low users (21 days less than controls, P = .05). Patients taking clozapine also had lower health care costs; after including the costs of both medications and other health services, costs were $7134 less than for controls among high hospital users (P = .14) but only $759 less than for controls among low hospital users (P = .82). Clinical improvement in the domains of symptoms, quality of life, extrapyramidal symptoms, and a synthetic measure of multiple outcomes favored clozapine in both high and low hospital user groups. CONCLUSIONS: Substantial 1-year cost savings with clozapine are observed only among patients with very high hospital use prior to initiation of treatment while clinical benefits are more similar across groups. Cost-effectiveness evaluations, and particularly studies of expensive treatments, cannot be generalized across type of use groups.

Possible association of a polymorphism of the tryptophan hydroxylase gene with suicidal behavior in depressed patients.

OBJECTIVE: This study was designed to test the hypothesis that serotonin-system-related genes may be correlated with suicide risk. METHOD: Fifty-one unrelated Caucasian inpatients with major depression, with or without a history of suicidal acts, were genotyped for a biallelic polymorphism at the tryptophan hydroxylase locus. RESULTS: The less common tryptophan hydroxylase U allele occurred with greater frequency in the patients who had attempted suicide. A logistic regression analysis confirmed an association between tryptophan hydroxylase genotype and lifetime history of suicide attempts. CONCLUSIONS: Serotonergic-system-related genes may influence the risk of suicide in persons with major depression.

Single photon emission computerized tomography imaging of amphetamine-induced dopamine release in drug-free schizophrenic subjects.

The dopamine hypothesis of schizophrenia proposes that hyperactivity of dopaminergic transmission is associated with this illness, but direct observation of abnormalities of dopamine function in schizophrenia has remained elusive. We used a newly developed single photon emission computerized tomography method to measure amphetamine-induced dopamine release in the striatum of fifteen patients with schizophrenia and fifteen healthy controls. Amphetamine-induced dopamine release was estimated by the amphetamine-induced reduction in dopamine D2 receptor availability, measured as the binding potential of the specific D2 receptor radiotracer [123I] (S)-(-)-3-iodo-2-hydroxy-6-methoxy-N-[(1-ethyl-2-pyrrolidinyl) methyl]benzamide ([123I]IBZM). The amphetamine-induced decrease in [123I]IBZM binding potential was significantly greater in the schizophrenic group (-19.5 +/- 4.1%) compared with the control group (-7.6 +/- 2.1%). In the schizophrenic group, elevated amphetamine effect on [123I]IBZM binding potential was associated with emergence or worsening of positive psychotic symptoms. This result suggests that psychotic symptoms elicited in this experimental setting in schizophrenic patients are associated with exaggerated stimulation of dopaminergic transmission. Such an observation would be compatible with an abnormal responsiveness of dopaminergic neurons in schizophrenia.

Rhodopsin and the retinal G-protein distinguish among G-protein beta gamma subunit forms.

The beta gamma subunits of G-proteins are composed of closely related beta 35 and beta 36 subunits tightly associated with diverse 6-10 kDa gamma subunits. We have developed a reconstitution assay using rhodopsin-catalyzed guanosine 5'-3-O-(thio)triphosphate (GTP gamma S) binding to resolved alpha subunit of the retinal G-protein transducin (Gt alpha) to quantitate the activity of beta gamma proteins. Rhodopsin facilitates the exchange of GTP gamma S for GDP bound to Gt alpha beta gamma with a 60-fold higher apparent affinity than for Gt alpha alone. At limiting rhodopsin, G-protein-derived beta gamma subunits catalytically enhance the rate of GTP gamma S binding to resolved Gt alpha. The isolated beta gamma subunit of retinal G-protein (beta 1, gamma 1 genes) facilitates rhodopsin-catalyzed GTP gamma S exchange on Gt alpha in a concentration-dependent manner (K0.5 = 254 +/- 21 nM). Purified human placental beta 35 gamma, composed of beta 2 gene product and gamma-placenta protein (Evans, T., Fawzi, A., Fraser, E.D., Brown, L.M., and Northup, J.K. (1987) J. Biol. Chem. 262, 176-181), substitutes for Gt beta gamma reconstitution of rhodopsin with Gt alpha. However, human placental beta 35 gamma facilitates rhodopsin-catalyzed GTP gamma S exchange on Gt alpha with a higher apparent affinity than Gt beta gamma (K0.5 = 76 +/- 54 nM). As an alternative assay for these interactions, we have examined pertussis toxin-catalyzed ADP-ribosylation of the Gt alpha subunit which is markedly enhanced in rate by beta gamma subunits. Quantitative analyses of rates of pertussis modification reveal no differences in apparent affinity between Gt beta gamma and human placental beta 35 gamma (K0.5 values of 49 +/- 29 and 70 +/- 24 nM, respectively). Thus, the Gt alpha subunit alone does not distinguish among the beta gamma subunit forms. These results clearly show a high degree of functional homology among the beta 35 and beta 36 subunits of G-proteins for interaction with Gt alpha and rhodopsin, and establish a simple functional assay for the beta gamma subunits of G-proteins. Our data also suggest a specificity of recognition of beta gamma subunit forms which is dependent both on Gt alpha and rhodopsin. These results may indicate that the recently uncovered diversity in the expression of beta gamma subunit forms may complement the diversity of G alpha subunits in providing for specific receptor recognition of G-proteins.

Regulation of G proteins by chronic morphine in the rat locus coeruleus.

A possible role for G proteins in contributing to the chronic actions of opiates was investigated in the rat locus coeruleus (LC). The LC is a relatively homogeneous brain region that appears to play an important role in mediating acute and chronic opiate action in animals, as well as in humans. It was found that chronic, but not acute, treatment of rats with morphine, under conditions known to induce states of opiate tolerance and dependence, produced an increase in the level of pertussis toxin-mediated ADP-ribosylation of G proteins in the LC. The morphine-induced increase in ADP-ribosylation occurred in both Gi and Go, and was observed over a 30-fold range of NAD concentrations used. Concomitant treatment of rats with the opiate receptor antagonist naltrexone blocked the ability of morphine to produce this effect. In contrast, chronic morphine had no effect on pertussis toxin-mediated ADP-ribosylation of Gi and Go in the other brain regions studied, including the neostriatum, frontal cortex, and dorsal raphe. Chronic morphine also had no effect on cholera toxin-mediated ADP-ribosylation of Gs in the LC and these other brain regions. Preliminary immunoblot analysis revealed that increased ADP-ribosylation levels of the alpha subunit of Go in the LC were associated with equivalent increases in the immunoreactivity of this protein in this brain region. It is possible that the observed regulation of G-proteins by morphine in the LC represents part of the changes that underlie opiate addiction in these neurons.

International social security agreements: the U.S. experience.

International social security agreements are advantageous both for persons who are working now and for those whose working careers are over. For current workers, the agreements eliminate the dual contributions they might otherwise be paying to the social security systems of both the United States and another country. They also favorably affect the profitability and competitive position of American companies with foreign operations by reducing their cost of doing business. For persons who have worked both in the United States and abroad, and who are now retired, disabled, or deceased, the agreements often result in the payment of benefits to which the worker or the worker's family members would not otherwise have become entitled. Credit for social security coverage the worker earned in the United States and the other country can be combined, if necessary, to meet eligibility requirements, and partial benefits can be paid by one or both countries. Because international social security agreements benefit both workers and employers, the agreements program is supported by organized labor and the international business community. Since the first agreement was signed 15 years ago, every Presidential administration has endorsed the program. In view of this support, and the fact that the agreements enhance the image of the United States as a socially progressive member of the international community, it is expected that totalization agreements will be concluded with additional countries in the future.

Hormone-sensitive magnesium transport in murine S49 lymphoma cells: characterization and specificity for magnesium.

1. The hormone-sensitive transport of Mg(2+) into murine S49 lymphoma cells and its relationship to other divalent cation transport systems have been investigated.2. Mg(2+) influx, measured with (28)Mg(2+), is saturable with an apparent extracellular ion concentration at half-maximal influx (K(in)) for Mg(2+) of 330 muM and a maximal influx rate of 360 p-mole/min.10(7) cells (2.9 n-mole/min.mg cell protein or a flux rate of about 0.12 p-mole/sec.cm(2)). Efflux of Mg(2+) is biphasic with half-times of 55 and 240 min at 37 degrees C and is temperature-sensitive.3. beta-Adrenergic agonists inhibit influx but not efflux of Mg(2+) in S49 cells. Efflux of Mg(2+) is also unaffected by extracellular [Mg(2+)] or [Ca(2+)]. These results imply that the mechanism of the transport system does not involve Mg-Mg exchange.4. Mn(2+) is a non-competitive inhibitor of Mg(2+) influx with an inhibition constant, K(i), of about 200 muM. The weak inhibition exhibited by Ca(2+) (K(i) > 5 mM) is also non-competitive. La(3+) inhibits Mg(2+) transport half-maximally at about 100 muM; Ni(2+), Zn(2+), Co(2+) and Sc(3+) are all less effective than La(3+). The Ca(2+)-channel blockers cis-diltiazem, verapamil, and nifedipine and the monovalent cations Na(+) and K(+) also have no effect on Mg(2+) influx. However, increasing the extracellular pH stimulates Mg(2+) influx.5. Total cellular Mg(2+) is about 85 n-mole/10(7) cells; however, at apparent isotopic equilibrium with (28)Mg(2+) less than 3% of total cellular Mg(2+) has been exchanged. This indicates that cellular Mg(2+) is highly compartmented and that recently transported Mg(2+) exchanges very slowly with bulk intracellular Mg(2+).6. Ca(2+) influx has a K(in) of 80 muM and is much slower than Mg(2+) influx. V(max) varied in different experiments from 3 to 15 p-mole/min.10(7) cells (25-125 p-mole/min.mg cell protein). Efflux of Ca(2+) is biphasic with half-times of 22 and 200 min and is temperature-sensitive. Hormonal stimulation has no effect on either influx or efflux of Ca(2+). Mg(2+) is a competitive inhibitor of Ca(2+) influx (K(i) = 3 mM).7. Two kinetic components of Mn(2+) influx are present with apparent K(in)s of 4 muM and 100 muM. Maximal influx rates are 5 and 60 p-mole/min.10(7) cells (40 and 480 p-mole/min.mg cell protein), respectively. Influx of Mn(2+) is not altered by beta-adrenergic agonist.8. Uptake of Na(+) or K(+) is unaltered by beta-adrenergic stimulation. These data in the S49 lymphoma cell indicate that (a) Mg(2+) is translocated by a transport system independent of those that transport other divalent cations, (b) hormonal inhibition of divalent ion transport is specific for Mg(2+) and (c) cellular Mg(2+) is highly compartmented.

Software balancing of multiple detectors during CT scanning.

The general requirements for balancing of detectors in a multiple detector CT scanner are discussed, and the specific requirements for software balancing using data acquired within the body section during the scan are outlined. A particular technique which can be implemented in a scanner employing a simultaneous translation and rotation of the source/detector package is presented. The technique produces an exact balancing offset and gain factors, to within accuracy limits imposed by the statistical uncertainty due to noise in the measurements. However, the technique admits a redundancy of solutions with allows the statistical sample to be expanded to include virtually all data acquired during the scan, thereby suppressing detector imbalance artifacts to the same level as overall quantum noise in the image.

Magnesium but not calcium accumulation is inhibited by beta-adrenergic stimulation in S49 lymphoma cells.

The uptake of 28Mg and 45Ca was measured in S49 lymphoma cells. The beta-adrenergic agonist (-)-isoproterenol markedly inhibited the rate of 28Mg accumulation but had no effect on 45Ca accumulation. The effect of (-)-isoproterenol was blocked by (-)-propranolol. In variants of the S49 cell line deficient in adenylate cyclase activity (cyc-) or in hormone receptor-adenylate cyclase coupling (unc), (-)-isoproterenol had no effect on 28Mg accumulation. The S49 lymphoma cells also possess prostaglandin E1 receptors coupled to adenylate cyclase, and, like (-)-isoproterenol, prostaglandin E1 decreased the rate of 28Mg uptake. Experiments with the mouse erythroleukemia cell line GM86 also showed a beta-adrenergic-mediated decrease in the rate of accumulation of 28Mg. Previous work has shown that Mg2+ increases the affinity of agonists for the beta-adrenergic receptor (Bird, S.J., and Maguire, M.E. (1978) J. Biol. Chem. 253, in press). In view of these effects of Mg2+, it is suggested that Mg2+, but not Ca2+, may regulate the sensitivity of S49 cell adenylate cyclase to stimulation by catecholamines.