Thymosin beta 4 sequesters the majority of G-actin in resting human polymorphonuclear leukocytes.

Thymosin beta 4 (T beta 4), a 5-kD peptide which binds G-actin and inhibits its polymerization (Safer, D., M. Elzinga, and V. T. Nachmias. 1991. J. Biol. Chem. 266:4029-4032), appears to be the major G-actin sequestering protein in human PMNs. In support of a previous study by Hannappel, E., and M. Van Kampen (1987. J. Chromatography. 397:279-285), we find that T beta 4 is an abundant peptide in these cells. By reverse phase HPLC of perchloric acid supernatants, human PMNs contain approximately 169 fg/cell +/- 90 fg/cell (SD), corresponding to a cytoplasmic concentration of approximately 149 +/- 80.5 microM. On non-denaturing polyacrylamide gels, a large fraction of G-actin in supernatants prepared from resting PMNs has a mobility similar to the G-actin/T beta 4 complex. Chemoattractant stimulation of PMNs results in a decrease in this G-actin/T beta 4 complex. To determine whether chemoattractant induced actin polymerization results from an inactivation of T beta 4, the G-actin sequestering activity of supernatants prepared from resting and chemoattractant stimulated cells was measured by comparing the rates of pyrenyl-actin polymerization from filament pointed ends. Pyrenyl actin polymerization was inhibited to a greater extent in supernatants from stimulated cells and these results are qualitatively consistent with T beta 4 being released as G-actin polymerizes, with no chemoattractant-induced change in its affinity for G-actin. The kinetics of bovine spleen T beta 4 binding to muscle pyrenyl G-actin are sufficiently rapid to accommodate the rapid changes in actin polymerization and depolymerization observed in vivo in response to chemoattractant addition and removal.

Biospecific labeling with undecagold: visualization of the biotin-binding site on avidin.

The biotin-binding site on avidin has been labeled with biotin conjugated to undecagold, an organometallic cluster compound containing 11 gold atoms in a core angestroms in diameter. Examination of unstained specimens by scanning transmission electron microscopy reveals the labeled sites directly, without computational averaging or filtering of the images. This approach should be widely applicable for determining the locations of subunits and functional site in biological macromolecules at a resolution at a resolution in range of 15 angstroms.

The control of actin nucleotide exchange by thymosin beta 4 and profilin. A potential regulatory mechanism for actin polymerization in cells.

We present evidence for a new mechanism by which two major actin monomer binding proteins, thymosin beta 4 and profilin, may control the rate and the extent of actin polymerization in cells. Both proteins bind actin monomers transiently with a stoichiometry of 1:1. When bound to actin, thymosin beta 4 strongly inhibits the exchange of the nucleotide bound to actin by blocking its dissociation, while profilin catalytically promotes nucleotide exchange. Because both proteins exchange rapidly between actin molecules, low concentrations of profilin can overcome the inhibitory effects of high concentrations of thymosin beta 4 on the nucleotide exchange. These reactions may allow variations in profilin concentration (which may be regulated by membrane polyphosphoinositide metabolism) to control the ratio of ATP-actin to ADP-actin. Because ATP-actin subunits polymerize more readily than ADP-actin subunits, this ratio may play a key regulatory role in the assembly of cellular actin structures, particularly under circumstances of rapid filament turnover.

Thymosin beta 4 (T beta 4) in activated platelets.

When resting human blood platelets are stimulated with thrombin, 50 to 60% of the G-actin polymerizes to F-actin within 60 seconds. The increase in F-actin is correlated with a corresponding decrease in the complex of G-actin with T beta 4. Within 5 seconds after stimulation, nucleation sites for pyrene actin polymerization increase 1.5 times in Triton-lysed supernatants. Cytochalasin D, known to inhibit the increase in F-actin after thrombin, also inhibits the fall in T beta 4-actin complex and the increase in nucleation sites. Phosphorylation of T beta 4 could not be detected in either control or activated cells. Increased T beta 4 corresponding to that lost from the T beta 4-actin complex is present in lysates from activated platelets and retains the ability to complex with actin. The data, taken together with previous estimates for the dissociation constant of the T beta 4-actin complex, show that actin polymerization following platelet activation could be controlled primarily by the increased availability of free barbed ends of actin filaments which have a higher affinity for G-actin than does T beta 4 and suggest that the increased free T beta 4 may serve to limit the degree of polymerization.

Services and prevention: pharmacoepidemiology of antidepressant use.

Between 1988 and 1994, data from 3 large sites revealed a 3-5 fold increase in the prevalence of antidepressant (ATD) treatment for U.S. youths aged 2-19 years. In 1994, the ATD prevalence for youths of this age ranged from 13 per 1000 (in the HMO) to 18 per 1000 (in 2 state Medicaid systems). Males predominated in the 10-14-year-olds treated with ATDs, whereas females predominated among 15-19-year-olds. Caucasians were more than twice as likely to receive ATD therapy than their African-American counterparts. Primary care providers were the major source of ATD prescriptions for youths. The leading diagnoses in primary care were ADHD followed by depression, whereas the diagnostic order was reversed for youths who received psychiatric services. This review provides details concerning these patterns and trends in ATD treatment of youths from community-based clinical data sources. In addition, the role of these data in an expanded, comprehensive psychotropic knowledge base is discussed. Finally, the implications of an expanded knowledge base for ATD treatments are discussed in regard to generating research questions on effectiveness and safety and to improve treatment consensus within a public-health perspective.

Dialectical behavior therapy for bulimia nervosa.

OBJECTIVE: The effects of dialectical behavior therapy adapted for the treatment of binge/purge behaviors were examined. METHOD: Thirty-one women (averaging at least one binge/purge episode per week) were randomly assigned to 20 weeks of dialectical behavior therapy or 20 weeks of a waiting-list comparison condition. The manual-based dialectical behavior therapy focused on training in emotion regulation skills. RESULTS: An intent-to-treat analysis showed highly significant decreases in binge/purge behavior with dialectical behavior therapy compared to the waiting-list condition. No significant group differences were found on any of the secondary measures. CONCLUSIONS: The use of dialectical behavior therapy adapted for treatment of bulimia nervosa was associated with a promising decrease in binge/purge behaviors.

The increased rate of stimulant treatment for hyperactive/inattentive students in secondary schools.

OBJECTIVE: To describe trends in medication use for hyperactive/inattentive (HA/I) secondary school students from 1975 through 1993 and to present differences in the treatment of HA/I relative to school grade. DESIGN: A comprehensive survey of the HA/I treatment of public elementary and secondary school students has been conducted biennially by school nurses in Baltimore County, MD since 1975. RESULTS: Although only 11% of all public school students on medication for HA/I were in secondary schools in 1975, the proportion gradually rose such that in the 1990s, 30% of all medicated students were attending secondary schools. Also in secondary schools, the gender ratio for students on medication for HA/I narrowed from a 1:12 female/male ratio in 1981 to a 1:6 female/male ratio in 1993. CONCLUSIONS: Many more elementary school students are now remaining on stimulant medication for HA/I into their teens. Compared with a decade ago, relatively more girls are on stimulant treatment for HA/I during their secondary school years.

Increased methylphenidate usage for attention deficit disorder in the 1990s.

OBJECTIVE: To estimate the increased use and the prevalence of methylphenidate (Ritalin) treatment of youth with attention deficit disorder (ADD) during the 1990s. DESIGN: Using time-trend findings from two large population-based data sources, three pharmaceutical databases, and one physician audit, a best-fit estimate of the usage and the usage trends for methylphenidate treatment over the half decade from 1990 through 1995 was sought. SETTING: Five regions in the United States (US) and the nation as a whole. PATIENTS: Youths on record as receiving methylphenidate for ADD. RESULTS: The findings from regional and national databases indicate that on average, there has been a 2.5-fold increase in the prevalence of methylphenidate treatment of youths with ADD between 1990 and 1995. In all, approximately 2.8% (or 1.5 million) of US youths aged 5 to 18 were receiving this medication in mid-1995. The increase in methylphenidate treatment for ADD appears largely related to an increased duration of treatment; more girls, adolescents, and inattentive youths on the medication; and a recently improved public image of this medication treatment. CONCLUSION: The database findings presented serve to correct exaggerated media claims of a 6-fold expansion of methylphenidate treatment, although they do not clarify the issue of the appropriateness of this treatment.

Psychotherapeutic medication patterns for youths with attention-deficit/hyperactivity disorder.

OBJECTIVES: (1) To describe temporal patterns of office visits for attention-deficit/hyperactivity disorder (ADHD) and stimulant treatment for 5- to 14-year-old US youths; (2) to compare youth visits for ADHD with and without melication according to patient demographics, physician specialty, reimbursement source, and comorbid diagnoses; and (3) to compare office visits for youths with ADHD in relation to common medication patterns (stimulants alone, stimulants with other psychotherapeutic medication, and nonstimulant psychotherapeutic medications alone). DESIGN: Survey based on a national probability sample of office-based physicians in the United States. SETTING: Physician offices. PARTICIPANTS: A systematically sampled group of office-based physicians. MAIN OUTCOME MEASURES: National estimates of office visits for ADHD and psychotherapeutic drug visits for ADHD for each year and for a combined 8-year period. RESULTS: Youth visits for ADHD as a percentage of total physician visits had a 90% increase, from 1.9% in 1989 to 3.6% in 1996. Stimulant therapy within ADHD youth visits rose from 62.6% in 1989 to 76.6% in 1996. While the majority of non-ADHD youth visits were conducted by primary care physicians, one third of ADHD youth visits were managed by psychiatry and neurology specialists. Health maintenance organization insurance was the reimbursement source for 17.9% of non-ADHD youth visits but only 11.7% of ADHD youth visits. Complex medication therapy was more likely to be prescribed by psychiatrists and less likely to be related to visits with health maintenance organization reimbursement. CONCLUSIONS: National survey estimates in the 1990s confirm the substantial increase in visits for youths diagnosed as having ADHD, with more than three quarters of these visits associated with psychotherapeutic medication treatment. Physician specialty and reimbursement source variables identify distinct patient populations with a gradient in psychotherapeutic medication patterns from single-drug standard (stimulant) therapy to complex multidrug treatment regimens for which evidence-based scientific information is lacking.

Central Stimulant Treatment of Childhood Attention Deficit Hyperactivity Disorder : Issues and Recommendations from a US Perspective.

The use of CNS stimulants for the treatment of attention deficit hyperactivity disorder (ADHD) in children has steadily increased in most areas of the world over the last 30 years. In mid-1995, at least 1.5 million US children were receiving methylphenidate or dexamphetamine (dextroamphetamine). However, in other countries these agents are not used as widely.Specific stimulant-induced benefits for children with ADHD include: improved school grades, more completed classroom work, fewer reprimands for disruptive behaviour, improved handwriting, and improved behaviour at home and in social situtions. Stimulants benefit at least 75% of children with ADHD and are remarkably well tolerated, having few (for the most part minor and temporary) adverse effects.However, the benefits of stimulants that are obvious in most patients with ADHD during a brief clinical trial are primarily symptomatic. Although the behavioural benefits of stimulants are generally present during each period of treatment for as long as the ADHD condition exists (and children with ADHD are now often staying on stimulant medication into their mid-teens), the treatment has not been shown to change the long term outcome of the disorder.Before prescribing stimulants, paediatric physicians need to perform a careful diagnostic assessment for ADHD using multiple sources of information, including detailed ratings of the child's behaviour from his/her teachers and from a parent. If at baseline, the child's academic and behavioural adjustment in the classroom is good, stimulant medication would be inappropriate. However, if the child's pattern of ADHD has consistently and seriously interfered with his/her classroom and home adjustment, stimulant treatment should be actively considered. Should stimulant therapy be initiated, knowledgeable medical follow-up is required.

Pemoline hepatotoxicity and postmarketing surveillance.

OBJECTIVE: To review the numerous reports of hepatotoxic adverse drug reactions (ADRs) ascribed to pemoline that were sent to the U.S. Food and Drug Administration (FDA) between 1975 and 1996 and to describe the medical community's lack of awareness of these reports. METHOD: All ADR reports from 1975 through 1996 wherein pemoline was the suspect agent were obtained from the FDA MedWatch Internet site, and some details of nine pemoline-related deaths in youths were obtained directly from the FDA. The published literature on this subject was fully reviewed. RESULTS: (1) In premarketing clinical trials with pemoline in the early 1970s, hepatic abnormalities were noted in enzyme levels (1%-3% of youths receiving maintenance treatment), during rechallenges (6 of 6), and in biopsies (2 of 2). (2) Between 1975 and 1989, 12 cases of jaundice and 6 deaths in youths ascribed to pemoline hepatotoxicity were reported to the FDA. (3) The first medical literature report of a serious ADR ascribed to pemoline was in a 1989 letter to the editor. (4) Physicians generally only became aware of serious pemoline hepatotoxicity in December 1996. (5) Pemoline use increased until 1997. CONCLUSION: Limitations in postmarketing surveillance and public reporting in the United States, particularly in the 1980s, largely accounted for delays in an appropriate response to pemoline hepatotoxicity.

Racial disparity in psychotropic medications prescribed for youths with Medicaid insurance in Maryland.

DESIGN: A retrospective analysis was conducted using state Medicaid prescription drug reimbursement claims for youths aged 5 through 14 years according to the race of the recipients of psychotropic and medical drugs. METHOD: A person-based data set was created from Medicaid administrative data for fiscal year 1991 from the state of Maryland to yield the following: (1) estimates of prevalence of prescription recipients per 100 eligible enrollees; (2) relative prescription use ratios according to race (African-American versus Caucasian); and (3) the interrelation of race and geographic region on prescription prevalence. RESULTS: Five major findings were observed: (1) African-American youths with Medicaid insurance aged 5 through 14 were less than half (39% to 52%) as likely to have been prescribed psychotropic medications as Caucasian youths with Medicaid insurance; (2) the relative difference for nonpsychotropic medication classes was much less pronounced: African-American youths were prescribed nonpsychotropic medications at a rate 60% to 87% of the Caucasian youths' rate; (3) the stimulants (essentially methylphenidate) had the most disparate African-American/Caucasian ratio (1:2.5); (4) the racial disparity for psychotropics was not altered by partial (noncontinuous enrollment) eligibility status; and (5) although geographic variation reduced the racial disparity, the substantial racial difference (1:2.0) remained. CONCLUSION: Compared with Caucasians, African-American youths aged 5 through 14 with Medicaid insurance coverage showed a distinctly lower rate of treatment with psychopharmacological agents.

A quantitative analysis of G-actin binding proteins and the G-actin pool in developing chick brain.

The large G-actin pool in individual actively motile cells has been shown to be maintained primarily by the actin sequestering protein thymosin beta four (Tbeta4). It is not clear whether Tbeta4 or an isoform also plays a primary role in neural tissue containing highly motile axonal growth cones. To address this question we have made a definitive analysis of the relative contributions of all the known G-actin sequestering proteins: Tbeta4, Tbeta10, profilin, and phosphorylated (inactive) and unphosphorylated (potentially active) forms of both ADF and cofilin, in relation to the G-actin pool in developing chick brain at embryonic days 13 and 17. From our measurements we estimate the intracellular concentration of G-actin as 30-37 microM and of Tbeta4 as 50-60 microM in an 'average' brain cell in embryonic chick brain. No other beta thymosin isoforms were detected in these brain extracts. The ratio of soluble, unphosphorylated ADF to Tbeta4 is only 1:7 at 13 embryonic days, but increases to 1:4 at 17 days. Profilin and cofilin concentrations are an order of magnitude lower than Tbeta4. Combining the contributions of Tbeta4, unphosphorylated ADF and unphosphorylated cofilin, we estimate a mean G-actin critical concentration of approximately 0.45 microM and approximately 0.2 microM, respectively, in day 13 and day 17 embryonic brain extracts, suggesting a significant developmental decrease. We conclude that (a) Tbeta4 is the major actin sequestering protein in embryonic chick brain and the only beta thymosin isoform present; (b) ADF may play a significant developmental role, as its concentration changes significantly with age; (c) the known G-actin binding proteins can adequately account for the G-actin pool in embryonic chick brain.

Undecagold clusters for site-specific labeling of biological macromolecules: simplified preparation and model applications.

We report simple and rapid procedures for the synthesis of a variety of stable, water-soluble undecagold cluster, and model applications of a thiol-reactive gold cluster for the specific labeling of cysteine residues in proteins.

Relative cardiovascular safety of psychostimulants used to treat attention-deficit hyperactivity disorder.

ABSTRACT The pertinent literature was reviewed on cardiovascular changes induced by psychostimulant medication treatment of hyperactive children. An assessment of 15 controlled studies using test doses of methylphenidate revealed a significant elevation of the resting heart rate in previously unmedicated children (mean + 11 beats/min) but, with continued drug treatment, only a minor insignificant increase (mean + 4 BPM) is observed. Methylphenidate resulted in no consistent or clinically meaningful blood pressure changes (8 studies) and no EKG irregularities (4 studies). Available data for dextroamphetamine and pemoline were less extensive, but showed essentially no significant cardiovascular changes in hyperactive youth. Stimulant overdoses in nonhyperactive children often led to hypertension and tachycardia, but were associated with only one cardiovascular fatality (amphetamine). Comparable studies of these stimulants in adults revealed: (1) tachycardia and hypertension following high test doses of methylphenidate, (2) hypertension but no tachycardia following high test doses of dextroamphetamine, (3) far greater cardiovascular changes following the parenteral administration of stimulants, (4) the development of a prominent degree of tolerance to the cardiovascular effects of stimulants with continued use, (5) very infrequent cardiovascular changes (3%) in medically ill, older adults following stimulant treatment for depression, and (6) infrequent cardiomyopathy and arteritis in association with amphetamine abuse, but not with pemoline or methylphenidate use. The stimulant-induced changes in children are modest in comparison with changes in cardiovascular functioning associated with normal daily activities, and are not comparable to the risks that can occur with tricyclic antidepressants. There appears to be a wide margin of cardiovascular safety when standard psychostimulants are taken orally in customary doses for long periods by hyperactive children. In view of the numerous negative studies, it probably is not essential to monitor heart rate, blood pressure, or EKG prior to or during routine psychostimulant treatment of children and adolescents with ADHD, unless there are comorbid cardiovascular abnormalities.

Changing patterns of psychotropic medications prescribed by child psychiatrists in the 1990s.

The active (1994) and closed (1988 to 1992) outpatient records of youths seen in four separate community mental health centers (CMHC) in Baltimore County, Maryland were reviewed in mid-1994 to document recent changes in the medication-prescribing practices of local child psychiatrists. Inpatient summaries of previously hospitalized CMHC youths were also reviewed to supplement the outpatient medication assessment with hospital data. This regional survey of medication treatments in child psychiatry revealed that, during the half decade before 1994, there was an increase in overall psychotropic medication treatment, multiple concurrent medication treatments (polypharmacy), and antidepressant treatment with serotonin reuptake inhibitors (SRIs). Inpatient youths were consistently prescribed more psychotropic medications and diagnosed more frequently with major depressive disorder than outpatients. Medications typically used to first treat mood disorders became the predominant medication prescribed for both outpatients and inpatients by child psychiatrists in 1994, leading to a proportional decline in prescribed stimulant treatment. The shift from tricyclic antidepressants to SRI antidepressants in the 1990s by child psychiatrists matches the same recent practice shift by adult psychiatrists. Likewise, the increased prescription of drugs to treat mood disorders and the increased rate of polypharmacy notable of late among child psychiatrists now also mirrors adult psychiatry practice. Wide geographic variations in neuroleptic and antidepressant medication patterns were noted, even among facilities in the same metropolitan region. After psychiatric hospitalization, most youths who continued treatment at a CMHC outpatient clinic discontinued their inpatient medications within 3 months; the sole exception were children who had been placed on psychostimulants.

Sources of data for pharmacoepidemiological studies of child and adolescent psychiatric disorders.

In view of the dramatic shift to managed care models for United States health care delivery, reliable information on the prevalence and variations in psychopharmacological drug therapies for youth in community practice settings is essential. Pharmacoepidemiology, the study of medication use in large populations, aims to accomplish that challenging task. This article offers child psychopharmacologists a brief introduction to data sources for pharmacoepidemiology. Knowledge of these data sources combined with epidemiological methods for data analysis is a beginning step to assess the psychotropic medication prescribing patterns of community physicians. This review is organized in the following sequence: (1) characteristics of the "usual practice environment" according to setting, patient population, and physician characteristics; (2) validity issues related to data sources and their potential for outcomes research; (3) data sources divided into primary and secondary types that are described in terms of their features, advantages, and limitations, followed by examples of selected applied studies using such information; (4) procedures for analyzing secondary data; (5) data analytic and longitudinal approaches; and (6) access, confidentiality, and funding. A goal for future investigators in this emerging field is to develop applied research that is clinically sophisticated, methodologically sound, and public health-minded.

Prevalence variations in psychotropic treatment of children.

This study was undertaken to clarify several aspects of the estimation of prevalence of three commonly use pediatric psychotropic agents, namely, methylphenidate, desipramine, and imipramine. The study aims are threefold: (1) to show the variability of drug prevalence by comparing estimates from three data sources; (2) to show the misleading impression that can be created by reporting drug prevalence estimates based on counts of prescriptions rather than persons; (3) to show the utility of gender-by-age-specific prevalence of drug use as a marker for diagnosis. Two data sources that yield population-based prescription estimates were available: 1991 Medicaid administrative claims data for prescriptions from a mid-Atlantic state and 1991 prescription records of the northwest region of Kaiser Permanente, a staff-model health maintenance organization (HMO). Another source of data consists of the 1991 National Ambulatory Medical Care Survey, which records medication information reported during physician office visits. Data analysis consists of quantitative estimates of (1) drug prevalence from each source; (2) the ratio of prescription claims to persons; and (3) the proportion of drug use according to age and gender. Methylphenidate and desipramine prevalence had a twofold greater use among state Medicaid enrollees compared with HMO enrollees. Average claims-to-person ratios of 5:1 suggest better accuracy using persons with medication rather than prescription counts. Gender-by-age-specific prevalence rates showed that 75% of the drug use for desipramine among those less than 15 years old was found among males, whereas 75% of the desipramine use among those 15 or older was found among females, suggesting its use for the treatment of attention deficit-hyperactivity disorder among young males and for depression among older females. The variability of community physician decision making in pediatric psychopharmacology is better understood by observing drug prevalence rates from different settings. National sampling efforts should be undertaken to verify regional and setting-specific prevalence findings and to learn the reasons for their fluctuation.

A behavioral program for disruptive Junior High school students: results and follow-up.

The 5-year annual and 4-year follow-up results of a collaborative community mental health center--junior high school program for disruptive students are presented. The program is a comprehensive, behavioral, in-school, regular education project characterized by a token economy, parent contracting, major subjects taught in the morning, small class enrollment, small group and individualized instruction, an early release from school contingency option and frequent parent-school communications. Annual controlled outcome results revealed that the program led to significant and consistent reductions in expulsions, suspensions, and grade failure, and variable, often significant, gains in attendance and achievement. Follow-up findings indicated that former program students in senior high school achieved a significantly higher entry rate, greater attendance, better classroom conduct, and a lower frequency of withdrawal from school.

A motivational environment for behaviorally deviant junior high school students.

A contingency management program was established in a junior high school to better manage and educate students having histories of severe misconduct. School administration selected 46 eighth-graders having multiple suspensions for misbehavior. Students (N = 32) in two of the schools remained in traditional programs, serving as controls, whereas students (N = 14) in the third school participated in a token reinforcement program. Reinforcers provided in the afternoon were contingent upon achievement and discipline during morning academic periods. Home-based reinforcers were established to support school behavior. Compared with the control group, significant reductions in negative school behavior as well as greater increases in academic achievement were obtained for the treatment group, thus supporting the efficacy of contingency management for adolescents school misbehavior.