Testing the Impact of the Whole-Day Good Behavior Game on Aggressive Behavior: Results of a Classroom-Based Randomized Effectiveness Trial.

Three generations of developmental epidemiologically based randomized field trials of the Good Behavior Game (GBG) have been delivered to Baltimore elementary schools. With the collaboration of family and community partners, all three trials were directed at decreasing proximal targets of aggressive behavior and improving learning in first-grade classrooms with distal mental health and substance abuse outcomes. GBG is a group-contingent classroom behavior management strategy that promotes classmate/peer concern for each child's positive behavior by rewarding teams with below-criterion levels of aggressive, disruptive behavior. GBG targets early risk factors for the above distal outcomes: aggressive, disruptive behavior, family/school relationships, and school failure. Here, we report on the third-generation randomized prevention trial of the GBG (whole-day first grade program (WD)), including 12 elementary schools. WD enhanced the standard curriculum in the areas of classroom behavior management; academic instruction, particularly reading; and family-classroom partnerships. Using a within-school classroom randomized trial design, we: 1) evaluate the effectiveness of the WD program by sex and cohort and 2) measure variation in WD impact by the quality of teachers' behavior management practices. Data from 961 first graders were used in general growth mixture modeling that accounts for classroom randomization to identify distinct developmental trajectories of aggressive, disruptive behavior and GBG impact on these trajectories. In the chronic high aggression trajectory of males, ratings of aggression after WD implementation and to the end of third grade were significantly lower in the WD condition than in controls in classrooms with a higher WD dosage (Cohort 2) and especially in classrooms with higher quality of WD implementation. For females, we found a modest but significant benefit of GBG in the low trajectory class when cohorts were combined. Regarding policy implications, embedding GBG into the curricula in teacher's colleges could better support student learning and behavior. Clinical Trials Registration number: NCT00257088.

Statistical properties of four effect-size measures for mediation models.

This project examined the performance of classical and Bayesian estimators of four effect size measures for the indirect effect in a single-mediator model and a two-mediator model. Compared to the proportion and ratio mediation effect sizes, standardized mediation effect-size measures were relatively unbiased and efficient in the single-mediator model and the two-mediator model. Percentile and bias-corrected bootstrap interval estimates of ab/s Y , and ab(s X )/s Y in the single-mediator model outperformed interval estimates of the proportion and ratio effect sizes in terms of power, Type I error rate, coverage, imbalance, and interval width. For the two-mediator model, standardized effect-size measures were superior to the proportion and ratio effect-size measures. Furthermore, it was found that Bayesian point and interval summaries of posterior distributions of standardized effect-size measures reduced excessive relative bias for certain parameter combinations. The standardized effect-size measures are the best effect-size measures for quantifying mediated effects.

Regenerative medicines: A new regulatory paradigm for South Africa.

Clinicians are increasingly using regenerative medicines to repair, replace, regenerate or rejuvenate lost, damaged or diseased genes, cells, tissues or organs. In South Africa, access to these novel gene therapies and cell and tissue-based products is limited. The human leukocyte antigen (HLA) diversity and a paucity of suitable HLA-identical unrelated donors, results in limited access to haematopoietic stem and progenitor cell transplantation (HSPCT). Cell-based products could increase this access. Genetic diversity can also manifest in local or region-specific rare congenital disorders, and in vivo gene therapies hold the promise of developing treatments and cures for these debilitating disorders. South Africa has a disproportionate mortality rate due to non-natural causes, with many surviving with permanent injuries and disabilities. Tissue-engineered cell-based products have the potential to restore many of those affected and improve quality of life and productivity. These factors create an urgency for South Africa to develop regenerative medicines to address the country's unique needs and to provide access to these new and innovative treatment modalities. Achieving this objective requires a well-coordinated effort by multiple stakeholders and role players. A critical component of a regenerative medicine ecosystem is establishing an enabling regulatory framework for these new classes of medicines. Here we provide a brief profile of South Africa, including its genetic diversity, economy, the impact of the burden of disease, health policy and the healthcare system. We address the regulation of medicines, how the existing framework can accommodate regenerative medicines, and the steps needed to establish a future regulatory framework.

COVID-19 in children: Should we be worried?

Reports indicate that children infected with SARS-CoV-2 have thus far presented with less severe disease than adults. Anxiety regarding a greater ability to transmit the virus is largely unfounded and has played a significant role in the decision to allow children to return to school. In some patients, however, especially in infants and in those with underlying comorbidities, severe disease must be anticipated and planned for accordingly. The most relevant severe clinical presentation in addition to the established respiratory complications, is that of a multisystem inflammatory disorder, with features resembling Kawasaki disease. The impact of the pandemic on the economic and social wellbeing of children, including food insecurity and care when parents are ill, cannot be ignored. During this pandemic, it is imperative to ensure access to routine and emergency medical services to sick children. In so doing, potentially devastating medical and socioeconomic consequences can be mitigated.

"Big" growth hormone components from human plasma: decreased reactivity demonstrated by radioreceptor assay.

Plasma as well as pituitary immunoreactive human growth hormone (HGH) comprises at least two discrete components which have been designated as "big" HGH and "little" HGH. Using a newly developed radioreceptor assay, which depends on the ability of a substance to compete with labeled HGH for binding sites on cultured human lymphocytes, we find that the big HGH component from both normal and acromegalic subjects has much less activity in the radioreceptor assay than in the radioimmunoassay, whereas the little HGH component has simnilar activity in both assays.

Estimating drug effects in the presence of placebo response: causal inference using growth mixture modeling.

Placebo-controlled randomized trials for antidepressants and other drugs often show a response for a sizeable percentage of the subjects in the placebo group. Potential placebo responders can be assumed to exist also in the drug treatment group, making it difficult to assess the drug effect. A key drug research focus should be to estimate the percentage of individuals among those who responded to the drug who would not have responded to the placebo ('Drug Only Responders'). This paper investigates a finite mixture model approach to uncover percentages of up to four potential mixture components: Never Responders, Drug Only Responders, Placebo Only Responders, and Always Responders. Two examples are used to illustrate the modeling, a 12-week antidepressant trial with a continuous outcome (Hamilton D score) and a 7-week schizophrenia trial with a binary outcome (illness level). The approach is formulated in causal modeling terms using potential outcomes and principal stratification. Growth mixture modeling (GMM) with maximum-likelihood estimation is used to uncover the different mixture components. The results point to the limitations of the conventional approach of comparing marginal response rates for drug and placebo groups. It is useful to augment such reporting with the GMM-estimated prevalences for the four classes of subjects and the Drug Only Responder drug effect estimate.

[Juvenile hyaline fibromatosis]. / Juvenile hyaline Fibromatose.

Juvenile hyaline fibromatosis is a rare autosomal recessive disease of the connective tissue. We present the case of a 6-year-old normal mental developed boy with confluent pearly papules behind the ears and in the paranasal folds, firm nodules of the scalp, the back and metaphalangs, and severe gingival hypertrophy.

Irradiation induces DNA damage and modulates epigenetic effectors in distant bystander tissue in vivo.

Irradiated cells induce chromosomal instability in unirradiated bystander cells in vitro. Although bystander effects are thought to be linked to radiation-induced secondary cancers, almost no studies have evaluated bystander effects in vivo. Furthermore, it has been proposed that epigenetic changes mediate bystander effects, but few studies have evaluated epigenetic factors in bystander tissues in vivo. Here, we describe studies in which mice were unilaterally exposed to X-irradiation and the levels of DNA damage, DNA methylation and protein expression were evaluated in irradiated and bystander cutaneous tissue. The data show that X-ray exposure to one side of the animal body induces DNA strand breaks and causes an increase in the levels of Rad51 in unexposed bystander tissue. In terms of epigenetic changes, unilateral radiation suppresses global methylation in directly irradiated tissue, but not in bystander tissue at given time-points studied. Intriguingly, however, we observed a significant reduction in the levels of the de novo DNA methyltransferases DNMT3a and 3b and a concurrent increase in the levels of the maintenance DNA methyltransferase DNMT1 in bystander tissues. Furthermore, the levels of two methyl-binding proteins known to be involved in transcriptional silencing, MeCP2 and MBD2, were also increased in bystander tissue. Together, these results show that irradiation induces DNA damage in bystander tissue more than a centimeter away from directly irradiated tissues, and suggests that epigenetic transcriptional regulation may be involved in the etiology of radiation-induced bystander effects.

Coregulation of NADPH oxidase activation and phosphorylation of a 48-kD protein(s) by a cytosolic factor defective in autosomal recessive chronic granulomatous disease.

The mechanisms regulating activation of the respiratory burst enzyme, NADPH oxidase, of human neutrophils (PMN) are not yet understood, but protein phosphorylation may play a role. We have utilized a defect in a cytosolic factor required for NADPH oxidase activation observed in two patients with the autosomal recessive form of chronic granulomatous disease (CGD) to examine the role of protein phosphorylation in activation of NADPH oxidase in a cell-free system. NADPH oxidase could be activated by SDS in reconstitution mixtures of cytosolic and membrane subcellular fractions from normal PMN, and SDS also enhanced phosphorylation of at least 16 cytosolic and 14 membrane-associated proteins. However, subcellular fractions from CGD PMN plus SDS expressed little NADPH oxidase activity, and phosphorylation of a 48-kD protein(s) was selectively defective. The membrane fraction from CGD cells could be activated for NADPH oxidase when mixed with normal cytosol and phosphorylation of the 48-kD protein(s) was restored. In contrast, the membrane fraction from normal cells expressed almost no NADPH oxidase activity when mixed with CGD cytosol, and phosphorylation of the 48-kD protein(s) was again markedly decreased. Protein kinase C (PKC) activity in PMN from the two patients appeared to be normal, suggesting that a deficiency of PKC is not the cause of the defective 48-kD protein phosphorylation and that the cytosolic factor is not PKC. These results demonstrate that the cytosolic factor required for activation of NADPH oxidase also regulates phosphorylation of a specific protein, or family of proteins, at 48 kD. Although the nature of this protein(s) is still unknown, it may be related to the functional and phosphorylation defects present in CGD PMN and to the activation of NADPH oxidase in the cell-free system.

National Institutes of Health Consensus Development Conference Statement: adjuvant therapy for breast cancer, November 1-3, 2000.

OBJECTIVE: Our goal was to provide health-care providers, patients, and the general public with an assessment of currently available data regarding the use of adjuvant therapy for breast cancer. PARTICIPANTS: The participants included a non-Federal, non-advocate, 14-member panel representing the fields of oncology, radiology, surgery, pathology, statistics, public health, and health policy as well as patient representatives. In addition, 30 experts in medical oncology, radiation oncology, biostatistics, epidemiology, surgical oncology, and clinical trials presented data to the panel and to a conference audience of 1000. EVIDENCE: The literature was searched with the use of MEDLINE(TM) for January 1995 through July 2000, and an extensive bibliography of 2230 references was provided to the panel. Experts prepared abstracts for their conference presentations with relevant citations from the literature. Evidence from randomized clinical trials and evidence from prospective studies were given precedence over clinical anecdotal experience. CONSENSUS PROCESS: The panel, answering predefined questions, developed its conclusions based on the evidence presented in open forum and the scientific literature. The panel composed a draft statement, which was read in its entirety and circulated to the experts and the audience for comment. Thereafter, the panel resolved conflicting recommendations and released a revised statement at the end of the conference. The panel finalized the revisions within a few weeks after the conference. The draft statement was made available on the World Wide Web immediately after its release at the conference and was updated with the panel's final revisions. The statement is available at http://consensus.nih.gov. CONCLUSIONS: The panel concludes that decisions regarding adjuvant hormonal therapy should be based on the presence of hormone receptor protein in tumor tissues. Adjuvant hormonal therapy should be offered only to women whose tumors express hormone receptor protein. Because adjuvant polychemotherapy improves survival, it should be recommended to the majority of women with localized breast cancer regardless of lymph node, menopausal, or hormone receptor status. The inclusion of anthracyclines in adjuvant chemotherapy regimens produces a small but statistically significant improvement in survival over non-anthracycline-containing regimens. Available data are currently inconclusive regarding the use of taxanes in adjuvant treatment of lymph node-positive breast cancer. The use of adjuvant dose-intensive chemotherapy regimens in high-risk breast cancer and of taxanes in lymph node-negative breast cancer should be restricted to randomized trials. Ongoing studies evaluating these treatment strategies should be supported to determine if such strategies have a role in adjuvant treatment. Studies to date have included few patients older than 70 years. There is a critical need for trials to evaluate the role of adjuvant chemotherapy in these women. There is evidence that women with a high risk of locoregional tumor recurrence after mastectomy benefit from postoperative radiotherapy. This high-risk group includes women with four or more positive lymph nodes or an advanced primary cancer. Currently, the role of postmastectomy radiotherapy for patients with one to three positive lymph nodes remains uncertain and should be tested in a randomized controlled trial. Individual patients differ in the importance they place on the risks and benefits of adjuvant treatments. Quality of life needs to be evaluated in selected randomized clinical trials to examine the impact of the major acute and long-term side effects of adjuvant treatments, particularly premature menopause, weight gain, mild memory loss, and fatigue. Methods to support shared decision-making between patients and their physicians have been successful in trials; they need to be tailored for diverse populations and should be tested for broader dissemination.

Effect of P-glycoprotein expression on the accumulation and cytotoxicity of topotecan (SK&F 104864), a new camptothecin analogue.

Topotecan (TPT, 9-dimethylaminomethyl-10-hydroxycamptothecin) is the first topoisomerase I-directed cytotoxic agent to enter clinical trials in the United States in two decades. The effect of P-glycoprotein (Pgp) overexpression on TPT cytotoxicity was examined in CHRC5 (colchicine-resistant) and AuxB1 (parental) Chinese hamster ovary cells. Examination of the IC50 values observed in colony-forming assays revealed that the CHRC5 cells were 15-fold (SD, +/- 3; n = 3) resistant to TPT after a 1-h exposure and 3.2-fold (SD, +/- 1.4; n = 4) resistant in continuous exposure experiments. Band depletion immunoblotting revealed that 4-fold higher concentrations of extracellular TPT were required to induce the formation of topo I-DNA complexes in CHRC5 cells as compared to AuxB1 cells. To assess the role of Pgp in this resistance, drug accumulation and cytotoxicity assays were repeated in the absence and presence of quinidine. Addition of quinidine enhanced TPT accumulation (measured by high-performance liquid chromatography) and diminished the IC50 for TPT to a greater extent in CHRC5 cells than in AuxB1 cells. To examine whether similar effects could be detected in Pgp-expressing human cells, MCF-7/Adriar breast cancer cells and KG1a human acute myelogenous leukemia cells were examined. Quinidine or verapamil enhanced TPT accumulation in both of these cell lines but had no effect in parental MCF-7 cells or a variety of human leukemia cell lines that do not overexpress Pgp. Cytotoxicity measurements performed by counting the number of surviving cells (MCF-7/Adriar) or employing a modified, highly stable tetrazolium dye reduction assay (leukemia cell lines) revealed that quinidine diminished the IC50 for TPT in the Pgp-overexpressing cell lines but not in the control lines. These results suggest that Pgp overexpression diminishes TPT accumulation and TPT cytotoxicity in hamster and human cells. It should be stressed, however, that these effects were substantially smaller than the effects of Pgp overexpression on the accumulation and cytotoxicity of the anthracycline daunorubicin and the epipodophyllotoxin etoposide in the same cell lines.

Phase I and pharmacokinetic study of hepsulfam (NSC 329680).

Hepsulfam (NSC 329680), a bifunctional alkylating agent structurally related to busulfan, has entered clinical trial based on its broader preclinical antitumor activity compared with that of busulfan and its i.v. formulation which may circumvent the many problems arising from the p.o. administration of busulfan, such as significant individual differences in bioavailability. In this Phase I study, 53 patients received 95 courses of hepsulfam at doses ranging from 30 to 480 mg/m2 administered i.v. over 30 min every 28 days. Hematological toxicity was dose limiting. Leukopenia and thrombocytopenia were dose related, delayed in onset, and sustained for long durations. Toxicity was cumulative in most patients receiving more than one course. This pattern of myelosuppression suggests that hepsulfam is cytotoxic to hematopoietic stem cells. Although hematological toxicity was not particularly severe during most courses, its lengthly duration precluded the prompt administration of subsequent courses. Minimal nonhematological effects were observed. Pharmacokinetic studies revealed that the clearance rate of hepsulfam is linear over the dose range studied and that its plasma disposition is biphasic with mean alpha and beta half-lives of 19 +/- 18 (SE) min and 337 +/- 248 (SE) min, respectively. The area under the plasma clearance curve correlated with the percentage of change in WBC using a sigmoidal Emax model and with the duration of thrombocytopenia in patients with hematological toxicity. Based on the protracted duration of the toxicity of multiple doses that were greater than 210 mg/m2, the recommended starting dose for Phase II trials is 210 mg/m2. However, these trials should be pursued with caution because of the protracted nature of hepsulfam's myelosuppression. Because hepsulfam produced minimal nonhematological toxicity, substantial dose escalation above 480 mg/m2 may be possible with hematopoietic stem cell support.

Phase I and pharmacologic study of topotecan: a novel topoisomerase I inhibitor.

PURPOSE: A phase I and pharmacologic study was undertaken to determine the maximum-tolerated dose (MTD), describe the principal toxicities, and characterize the pharmacologic behavior of topotecan, which is a semisynthetic analog of camptothecin with broad preclinical antitumor activity and the first topoisomerase I-targeting agent to enter clinical development in the United States since studies of sodium camptothecin over 2 decades ago. PATIENTS AND METHODS: Thirty-minute infusions of topotecan were administered daily for 5 consecutive days every 3 weeks to patients with advanced solid malignancies at doses ranging from 0.5 to 2.5 mg/m2/d. RESULTS: At doses of 1.5 and 2.0 mg/m2, grade 3 and 4 neutropenia occurred in most courses; however, neutropenia was brief and rarely associated with fevers or treatment delays. Neutropenia was more severe in patients with extensive prior treatment than in minimally pretreated patients, but these differences were not substantial. At 2.5 mg/m2, topotecan induced profound and prolonged neutropenia that was frequently associated with fever and treatment delays in minimally pretreated patients. Topotecan also induced mild depressions in the hematocrit level in the majority of courses; however, precipitous drops requiring transfusional therapy occurred in 14% of courses and suggested a drug-induced hemolytic effect. Unlike sodium camptothecin, hemorrhagic cystitis was not observed. Thrombocytopenia, skin rash, diarrhea, and vomiting occurred infrequently and were modest in severity. Responses were observed in non-small-cell lung carcinoma and platinum-refractory ovarian carcinoma. Drug disposition in plasma was described by a biexponential model, with renal elimination accounting for 38.7% of drug disposition. Topotecan was rapidly hydrolyzed in vivo to a less active, open-ring form. CONCLUSIONS: Neutropenia is the dose-limiting toxicity, and 1.5 mg/m2 is the recommended starting dose of topotecan for both minimally and heavily pretreated patients in future phase II trials, with escalation to 2.0 mg/m2 if treatment is well tolerated. Non-small-cell lung and platinum-refractory ovarian carcinomas should be among those evaluated in phase II trials of topotecan.

The S. cerevisiae Mag1 3-methyladenine DNA glycosylase modulates susceptibility to homologous recombination.

DNA glycosylases, such as the Mag1 3-methyladenine (3MeA) DNA glycosylase, initiate the base excision repair (BER) pathway by removing damaged bases to create abasic apurinic/apyrimidinic (AP) sites that are subsequently repaired by downstream BER enzymes. Although unrepaired base damage may be mutagenic or recombinogenic, BER intermediates (e.g. AP sites and strand breaks) may also be problematic. To investigate the molecular basis for methylation-induced homologous recombination events in Saccharomyces cerevisiae, spontaneous and methylation-induced recombination were studied in strains with varied MAG1 expression levels. We show that cells lacking Mag1 have increased susceptibility to methylation-induced recombination, and that disruption of nucleotide excision repair (NER; rad4) in mag1 cells increases cellular susceptibility to these events. Furthermore, expression of Escherichia coli Tag 3MeA DNA glycosylase suppresses recombination events, providing strong evidence that unrepaired 3MeA lesions induce recombination. Disruption of REV3 (required for polymerase zeta (Pol zeta)) in mag1 rad4 cells causes increased susceptibility to methylation-induced toxicity and recombination, suggesting that Pol zeta can replicate past 3MeAs. However, at subtoxic levels of methylation damage, disruption of REV3 suppresses methylation-induced recombination, indicating that the effects of Pol zeta on recombination are highly dose-dependent. We also show that overproduction of Mag1 can increase the levels of spontaneous recombination, presumably due to increased levels of BER intermediates. However, additional APN1 endonuclease expression or disruption of REV3 does not affect MAG1-induced recombination, suggesting that downstream BER intermediates (e.g. single strand breaks) are responsible for MAG1-induced recombination, rather than uncleaved AP sites. Thus, too little Mag1 sensitizes cells to methylation-induced recombination, while too much Mag1 can put cells at risk of recombination induced by single strand breaks formed during BER.

Plasma clearance of intravenously administered pituitary human growth hormone: gel filtration studies of heterogeneous components.

Both pituitary and plasma human GH (hGH) comprise heterogeneous components, exhibiting similar patterns when gel filtered on Sephadex G-100. To determine at what rate the components are cleared from the circulation, blood was obtained at specific intervals following a bolus injection of pituitary hGH in hypopituitary patients. Each sample was gel filtered to determine its component profile of RIA values, which, when plotted vs. the time interval it represented, yielded a means of monitoring its disappearance from the plasma. Total hGH was cleared with a t 1/2 of 21.5 min, the little component was cleared at 19.0 min, the big component was cleared at 26.5 min, and the pre-big component was cleared at 45 min. These data indicate that the larger the hGH component, the longer it takes to be cleared from the plasma.

Evidence for higher proportion of "little" growth hormone with increased radioreceptor activity in acromegalic plasma.

Plasma growth hormone (GH) from both normal and acromegalic patients comprises multiple immunoreactive components that can be separated by G-100 Sephadex gel filtration and measured by radioimmunoassay (RIA) and radioreceptor assay (RRA). The higher molecular weight immunoreactive components, from both normal and acromegalic subjects, have a lower RRA/RIA than does the lower molecular weight "little" GH component. The "little" GH component comprises a higher proportion of the total immunoreactive GH in acromegalic plasma than in normal plasma whether the data are expressed only in terms of the "big" and "little" components (89 vs. 71%), or as a function of total immunoreactive GH (76 vs. 55%), or whether the plasma is obtained in the basal or stimulated state for the acromegalic patients. When the RRA/RIA x 100 is determined for the isolated "little" component, the acromegalic has a significantly greater ratio than the normal (110 vs. 75%). We conclude that acromegalic plasma contains a higher proportion of the more radioreceptor active "little" GH component than does the normal and, in addition, that the "little" component from the acromegalic is more radioreceptor-active than the normal.

Properties of human growth hormone polypeptides: purified from pituitary extracts and synthesized in monkey kidney cells and bacteria.

Several forms of human GH (hGH) have been elucidated by extraction of human pituitary and recombinant DNA techniques. In the present study we have characterized five of these hGH polypeptides by gel filtration, RIA, and radioreceptor assays. These include extractable pituitary hGH and its naturally occurring 20K variant. Two hGH polypeptides were produced from naturally occurring human genes in simian kidney cells (SV-hGH 1 and 2) and another preparation was produced from a partially synthesized gene in bacteria (E. coli-hGH). As predicted from their known DNA sequences, naturally occurring pituitary hGH, SV-hGH 1, and E. coli-hGH migrated as a single peak on Sephadex G-100 column and had the same immunological and receptor-binding properties. By contrast, SV-hGH 2 (14 dispersed amino acid substitutions) and the 20K variant (amino acid residues 32-46 deleted from hGH) contained more higher molecular weight components and had diminished immunological and receptor-binding potency. SV-hGH 2 differed from the 20K variant by having even lower immunological potency and containing more of the higher molecular weight component. These variant forms of hGH may provide an explanation for the heterogeneity of both pituitary and plasma hGH.

Visual field constriction caused by colored contact lenses.

Goldmann visual field testing was performed on ten patients while they were wearing the recently released DuraSoft 3 colored soft contact lenses. All patients but one had visual field constriction ranging from 5 degrees to 20 degrees. When the areas inside the three tested isopters were averaged, the amount of field loss ranged from 21% to 47%. Contact lens fitters as well as wearers should be warned of this potential complication.

Failure of bromocriptine to alter the qualitative characteristics of human growth hormone in acromegaly.

The role of bromocriptine as a therapeutic agent for acromegaly is uncertain. In the present study we have attempted to determine whether bromocriptine therapy causes qualitative changes in plasma human growth hormone (hGH) in acromegaly. When eight paired samples obtained before and during bromocriptine therapy were filtered over Sephadex G-100 there was no difference in the elution profiles. When the "little" hGH peak from each of the eight paired samples was pooled, lyophilized, and assayed in both radioreceptor assay (RRA) and radioimmunoassay (RIA), the RRA/RIA before treatment was not different than during treatment. When bromocriptine in pharmacologically significant concentrations was incubated with cultured human lymphocytes in vitro, there was no alteration in hGH binding properties. These results demonstrate directly that bromocriptine does not change the form or receptor-reactive properties of plasma hGH and, further, that the drug does not alter at least one form of human growth-hormone receptor.