Cell size and actin architecture determine force generation in optogenetically activated cells.

Adherent cells use actomyosin contractility to generate mechanical force and to sense the physical properties of their environment, with dramatic consequences for migration, division, differentiation, and fate. However, the organization of the actomyosin system within cells is highly variable, with its assembly and function being controlled by small GTPases from the Rho family. To understand better how activation of these regulators translates into cell-scale force generation in the context of different physical environments, here we combine recent advances in non-neuronal optogenetics with micropatterning and traction force microscopy on soft elastic substrates. We find that, after whole-cell RhoA activation by the CRY2/CIBN optogenetic system with a short pulse of 100 ms, single cells contract on a minute timescale in proportion to their original traction force, before returning to their original tension setpoint with near perfect precision, on a longer timescale of several minutes. To decouple the biochemical and mechanical elements of this response, we introduce a mathematical model that is parametrized by fits to the dynamics of the substrate deformation energy. We find that the RhoA response builds up quickly on a timescale of 20 s, but decays slowly on a timescale of 50 s. The larger the cells and the more polarized their actin cytoskeleton, the more substrate deformation energy is generated. RhoA activation starts to saturate if optogenetic pulse length exceeds 50 ms, revealing the intrinsic limits of biochemical activation. Together our results suggest that adherent cells establish tensional homeostasis by the RhoA system, but that the setpoint and the dynamics around it are strongly determined by cell size and the architecture of the actin cytoskeleton, which both are controlled by the extracellular environment.

3D-printed scaffold combined to 2D osteoinductive coatings to repair a critical-size mandibular bone defect.

The reconstruction of large bone defects (12 cm3) remains a challenge for clinicians. We developed a new critical-size mandibular bone defect model on a minipig, close to human clinical issues. We analyzed the bone reconstruction obtained by a 3D-printed scaffold made of clinical-grade polylactic acid (PLA), coated with a polyelectrolyte film delivering an osteogenic bioactive molecule (BMP-2). We compared the results (computed tomography scans, microcomputed tomography scans, histology) to the gold standard solution, bone autograft. We demonstrated that the dose of BMP-2 delivered from the scaffold significantly influenced the amount of regenerated bone and the repair kinetics, with a clear BMP-2 dose-dependence. Bone was homogeneously formed inside the scaffold without ectopic bone formation. The bone repair was as good as for the bone autograft. The BMP-2 doses applied in our study were reduced 20- to 75-fold compared to the commercial collagen sponges used in the current clinical applications, without any adverse effects. Three-dimensional printed PLA scaffolds loaded with reduced doses of BMP-2 may be a safe and simple solution for large bone defects faced in the clinic.

Functional EpoR pathway utilization is not detected in primary tumor cells isolated from human breast, non-small cell lung, colorectal, and ovarian tumor tissues.

Several clinical trials in oncology have reported increased mortality or disease progression associated with erythropoiesis-stimulating agents. One hypothesis proposes that erythropoiesis-stimulating agents directly stimulate tumor proliferation and/or survival through cell-surface receptors. To test this hypothesis and examine if human tumors utilize the erythropoietin receptor pathway, the response of tumor cells to human recombinant erythropoietin was investigated in disaggregated tumor cells obtained from 186 patients with colorectal, breast, lung, ovarian, head and neck, and other tumors. A cocktail of well characterized tumor growth factors (EGF, HGF, and IGF-1) were analyzed in parallel as a positive control to determine whether freshly-isolated tumor cells were able to respond to growth factor activation ex vivo. Exposing tumor cells to the growth factor cocktail resulted in stimulation of survival and proliferation pathways as measured by an increase in phosphorylation of the downstream signaling proteins AKT and ERK. In contrast, no activation by human recombinant erythropoietin was observed in isolated tumor cells. Though tumor samples exhibited a broad range of cell-surface expression of EGFR, c-Met, and IGF-1R, no cell-surface erythropoietin receptor was detected in tumor cells from the 186 tumors examined (by flow cytometry or Western blot). Erythropoiesis-stimulating agents did not act directly upon isolated tumor cells to stimulate pathways known to promote proliferation or survival of human tumor cells isolated from primary and metastatic tumor tissues.

Climbing-specific finger endurance: a comparative study of intermediate rock climbers, rowers and aerobically trained individuals.

The aim of this study was to compare the climbing-specific finger endurance of climbers, rowers and aerobically leg trained athletes. Twenty-seven males aged 21.2 +/- 2.2 years (mean +/- s) volunteered for the study. The participants were intermediate rock climbers (n = 9), rowers (n = 9) and leg trained athletes (n = 9). Maximal voluntary contraction (MVC) was determined on climbing-specific finger apparatus. Endurance isometric exercise was performed at 40% MVC in three tests performed in a random order: (1) sustained exercise; (2) 6 s exercise, 4 s rest; and (3) 18 s exercise, 12 s rest. Pre- and post-exercise blood pressure and blood lactate concentration, together with post-exercise pain perception, were measured. The climbers had a significantly greater MVC (383 +/- 35.6 N) than the rowers (321 +/- 49.5 N, P = 0.007) and aerobically leg trained athletes (288 +/- 60.6 N, P = 0.001). There were no significant differences between the groups in terms of endurance times for any of the tests. In the test with 18 s exercise and 12 s rest, the climbers showed a significantly higher increase in blood lactate concentration, on average, than the rowers by 0.01-0.89 mmol x l(-1) (P = 0.006); there were no significant differences, on average, in the comparisons of climbers and the leg trained athletes and rowers and the leg trained athletes. There were no significant differences in the average changes in blood pressure from rest to post-exercise between any of the groups. Although the climbers had greater MVC on average than the other two groups, there were no significant differences in average endurance times amongthe groups. These findings suggest that training for rock climbing and participation in rock climbing may result in some specific adaptations. However, we acknowledge that this study is descriptive and there is the possibility that differences between groups could be attributed to self-selection.

Combinatorial gene expression using multiple episomal vectors.

Episomal vectors offer a powerful alternative to integrative recombination for transgene expression in mammalian cells. In this study, various combinations of G protein-coupled receptors (GPCRs) and the G protein subunit G(i2)alpha, were stably expressed from separate episomal vectors in 293-EBNA (293E) cells. Each episome did not adversely affect the others, as gauged by episomal copy number, steady-state mRNA levels and the presence of functional receptors and G protein. Cell lines expressing genes from multiple autonomously replicating vectors were stable just two weeks after transfection, and remained stable in continuous culture for at least 5months. Co-expression of supplementary G(i2)alpha with receptor amplifies the magnitude of signal transduction thereby permitting the development of more sensitive high throughput functional assays. Given these results, combinatorial transfection is the strategy of choice for generating stable cell lines expressing multiple genes for the study of signal-transduction pathways or the evaluation of receptor ligands.

Small molecule antagonists of the bradykinin B1 receptor.

Screening Pharmacopeia's encoded combinatorial libraries has led to the identification of potent, selective, competitive antagonists at the bradykinin B1 receptor. Libraries were screened using a displacement assay of [3H]-des-Arglo-kallidin ([3H]-dAK) at IMR-90 cells expressing an endogenous human B1 receptor (Bmax = 20,000 receptors/cell, K(D) = 0.5+/-0.1 nM) or against membranes from 293E cells expressing a recombinant human B1 receptor (Bmax = 8,000 receptors/cell, K(D) = 0.5 +/- 0.3 nM). Compound PS020990, an optimized, representative member from the class of compounds, inhibits specific binding of 3H-dAK at IMR-90 cells with a KI of 6 +/- 1 nM. The compound inhibits dAK-induced phosphatidyl inositol turnover (K(Bapp) = 0.4 +/- 0.2 nM) and calcium mobilization (K(Bapp) = 17 +/- 2 nM) in IMR-90 cells. Compounds from the lead series are inactive at the B2 receptor and are > 1000-fold specific for B1 vs. a variety of other receptors, ion channels and enzymes. PS020990 and other related chemotypes therefore offer an excellent opportunity to explore further the role of B1 receptors in disease models and represent a potential therapeutic avenue.

Pharmacists' job satisfaction and perceived utilization of skills.

The relationship between job satisfaction and perceived utilization of skills among pharmacists practicing in institutional and ambulatory care settings in Arizona was studied, and factors thought to influence pharmacists' perceived utilization of skills were evaluated. Questionnaires on job satisfaction and perceived utilization of skills were mailed to a random sample of 600 pharmacists. Information on workplace factors such as hours worked, practice setting, and job title was collected. A 4-item measure of general job satisfaction and a 10-item measure of perceived utilization of skills were used. Responses were measured on a five-point Likert scale ranging from "strongly disagree" to "strongly agree." The response rate was 35%. There was a significant positive relationship between job satisfaction and perceived utilization of skills and between job satisfaction and adequate staffing, where "staffing" referred to factors such as competence of coworkers and workload. Pharmacists with training beyond a B.S. degree in pharmacy were more satisfied with their job than those whose highest degree was a B.S. in pharmacy. Pharmacists practicing in institutional settings, pharmacists with management titles, and older pharmacists perceived that they were utilizing their skills to a greater extent than did pharmacists practicing in ambulatory care settings, pharmacists with a general staff title, and younger pharmacists. Among a sample of Arizona pharmacists in institutional and ambulatory care settings, job satisfaction was influenced by perceived utilization of skills, staffing, and education; practice setting, job title, and age were significantly related to perceived utilization of skills.

Structural basis for the binding specificity of a SSTR1-selective analog of somatostatin.

The availability of subtype-specific agonists and antagonists for somatostatin (SS) receptors (SSTRs) will be important for elucidation of the function of each receptor isoform in vivo. A SS analog, des-AA1,2,5-[D-Trp8, IAmp9]SS (CH275), has been shown previously to bind preferentially to SSTR1. In this report, we identify structural determinants in the ligand and receptor responsible for the selective binding of CH275 to SSTR1 by modifying both the ligand and the receptor. We propose that IAmp9 in CH275, like Lys9 in SS, interacts with Asp137 in the middle of the third transmembrane domain of SSTR1 to form an ion pair, while other residues unique to SSTR1 conbribute to binding selectivity of CH275 for SSTR1. Replacement of Asp137 with Asn resulted in loss of binding of radiolabeled SS and decreased potencies of both SS and CH275 to induce a change in the extracellular acidification rate measured by microphysiometry. The structural determinants for specific binding to SSTR1 were mapped in chimeric SSTR1/SSTR2 receptors. One chimera, 2beta, with the N-terminus to second transmembrane domain (TM2) from SSTR2 and the remainder of the receptor from SSTR1, had low affinity for CH275. Furthermore, when a single residue, Leu107, in TM2 of SSTR1 was replaced with Phe, the corresponding residue in SSTR2, a 20-fold decrease in affinity for CH275 with no significant change in affinity for SS was observed. A reciprocal change from Phe to Leu in the chimeric receptor 2beta resulted in a 10-fold increase in affinity for CH275. Thus, Leu107 is an important determinant for CH275 binding to SSTR1. To identify the moiety in CH275 which could interact with Leu107, a new analog des-AA1,2,5-[D-Trp8, Amp9]SS was prepared. This analog bound to both SSTR1 and SSTR2 with similar affinities; thus, subtype selectivity was lost. Collectively, these data support a binding model for CH275 in which the positively charged IAmp interacts with the negatively charged Asp137 in TM3 of SSTR1 and the isopropyl group of IAmp forms a hydrophobic interaction with Leu107 in TM2.

Formation of a high affinity heregulin binding site using the soluble extracellular domains of ErbB2 with ErbB3 or ErbB4.

ErbB2 functions as a shared signal transducing component for other ErbB receptor family members. Two of these receptors, ErbB3 and ErbB4, bind the heregulin (HRG) or neuregulin family of polypeptide growth factors. Cells expressing ErbB3 alone display a single class of low affinity HRG binding sites, whereas both high and low affinity binding sites can be measured on cells that co-express both ErbB3 and ErbB2. To assess the interaction of the extracellular domains of ErbB receptors, a series of soluble homodimeric and heterodimeric IgG fusion proteins were constructed. Heregulin binding analysis revealed that a heterodimer composed of either ErbB3 or ErbB4 with ErbB2 is sufficient for the formation of a high affinity binding state. In contrast, heterodimeric ErbB3/4-IgG, as well as homodimeric ErbB3-IgG or ErbB4-IgG, contained only low affinity HRG binding sites. Further evidence for the unique specificity of ErbB2 in generating this high affinity binding site was determined by inhibiting HRG binding with an ErbB2 monoclonal antibody.

Binding interaction of the heregulinbeta egf domain with ErbB3 and ErbB4 receptors assessed by alanine scanning mutagenesis.

Individual residues of the heregulinbeta (HRG) egf domain were mutated to alanine and displayed monovalently on phagemid particles as gene III fusion proteins. Wild type HRGbeta egf domain displayed on phage was properly folded as evidenced by its ability to bind ErbB3 and ErbB4 receptor-IgG fusion proteins with affinities close to those measured for bacterially produced HRGbeta egf domain. Binding to ErbB3 and ErbB4 receptors was affected by mutation of residues throughout the egf domain; including the NH2 terminus (His2 and Leu3), the two beta-turns (Val15-Gly18 and Gly42-Gln46), and some discontinuous residues (including Leu3, Val4, Phe13, Val23, and Leu33) that form a patch on the major beta-sheet and the COOH-terminal region (Tyr48 and Met50-Phe53). Binding affinity was least changed by mutations throughout the Omega-loop and the second strand of the major beta-sheet. More mutants had greater affinity loss for ErbB3 compared with ErbB4 implying that it has more stringent binding requirements. Many residues important for HRG binding to its receptors correspond to critical residues for epidermal growth factor (EGF) and transforming growth factor alpha binding to the EGF receptor. Specificity may be determined in part by bulky groups that prevent binding to the unwanted receptor. All of the mutants tested were able to induce phosphorylation and mitogen-activated protein kinase activation through ErbB4 receptors and were able to modulate a transphosphorylation signal from ErbB3 to ErbB2 in MCF7 cells. An understanding of binding similarities and differences among the EGF family of ligands may facilitate the development of egf-like analogs with broad or narrow specificity.

Gamma-heregulin: a novel heregulin isoform that is an autocrine growth factor for the human breast cancer cell line, MDA-MB-175.

A novel neuregulin isoform, termed gamma-HRG, was cloned and characterized from the human breast cancer cell line, MDA-MB-175. As observed with other neuregulins, gamma-HRG, is a product of alternative mRNA splicing of the neuregulin gene. Gamma-HRG contains the EGF-like and immunoglobulin-like domains that are commonly found in other family members, but lacks a transmembrane and cytoplasmic region. The new isoform possesses a unique N-terminal region that includes a hydrophobic domain that may function as a secretion signal. A purified recombinant version of gamma-HRG competes for binding to soluble ErbB3- and ErbB4-IgG fusion proteins with affinities similar to those observed for rHRGbeta1(177-244). Gamma-HRG has a wide distribution in mesenchymal or neuronal tissues but in contrast to other neuregulins, it is not present in breast, lung, liver and small intestine. Expression of gamma-HRG with its cognate receptors, ErbB3 and ErbB2 suggested that the growth of the MDA-MB-175 cell line might be a result of the autocrine stimulation of a growth factor signaling pathway. Treatment of MDA-MB-175 cells with an anti-ErbB2 monoclonal antibody that interferes with the ligand-dependent formation of ErbB2-ErbB3 heterodimer complexes shows a strong growth inhibitory effect on this cell line. Moreover, incubation with a receptor-IgG fusion protein that neutralizes secreted gamma-HRG, also inhibits cell growth. These data suggest that the secretion of gamma-HRG by MDA-MB-175 cells leads to the formation of a constitutively active receptor complex and stimulates the growth of these cells in an autocrine manner.

Both overlapping and distinct signaling pathways for somatostatin receptor subtypes SSTR1 and SSTR2 in pituitary cells.

To elucidate the signaling events mediated by specific somatostatin receptor (SSTR) subtypes, we expressed SSTR1 and SSTR2 individually in rat pituitary GH12C1 and F4C1 cells, which lack endogenous somatostatin receptors. In transfected GH12C1 cells, both SSTR1 and SSTR2 coupled to inhibition of Ca2+ influx and hyperpolarization of membrane potential via a pertussis toxin (PTx)-sensitive mechanism. These effects reflected modulation of ion channel activities which are important for regulation of hormone secretion. Somatostatin analogs MK678 and CH275 acted as subtype selective agonists as expected. In transfected F4C1 cells, both SSTR1 and SSTR2 mediated somatostatin-induced inhibition of adenylyl cyclase via a PTx-sensitive pathway. In addition, activation of SSTR2 in F4C1 cells, but not SSTR1, stimulated phospholipase C (PLC) activity and an increase in [Ca2+]i due to release of Ca2+ from intracellular stores. Unlike adenylyl cyclase inhibition, the PLC-mediated response was only partially sensitive to PTx. To determine the structural determinants in SSTR2 necessary for activation of PLC, we constructed chimeric receptors in which domains of SSTR2 were introduced into SSTR1. Chimeric receptors containing only the third intracellular loop, or all three intracellular loops from SSTR2, mediated inhibition of adenylyl cyclase, but failed to stimulate PLC activity as did wild-type SSTR2. Furthermore, the C-terminal tail of SSTR2 was not required for coupling to PLC. Thus, by expressing individual somatostatin receptor subtypes in pituitary cells, we have identified both overlapping and distinct signaling pathways for SSTR1 and SSTR2, and have shown that sequences other than simply the intracellular domains are required for SSTR2 to couple to the PLC signaling pathway.

Randomized, double-blind, placebo-controlled dose-ranging study of tirofiban (MK-383) platelet IIb/IIIa blockade in high risk patients undergoing coronary angioplasty.

OBJECTIVES: The objectives of this double-blind, placebo-controlled, randomized dose-ranging study were 1) to examine the safety and tolerability of tirofiban (MK-383), a new nonpeptide platelet IIb/IIIa receptor antagonist, on a background of intravenous heparin and aspirin therapy; 2) to study the pharmacodynamics and pharmacokinetics of tirofiban; and 3) to evaluate the incidence of adverse cardiac outcomes (urgent repeat revascularization, myocardial infarction and death) with tirofiban versus placebo in a high risk subset of patients undergoing coronary angioplasty. BACKGROUND: Abrupt vessel closure complicates 4% to 8% of angioplasty procedures. Recent data have suggested that agents that antagonize the platelet glycoprotein IIb/IIIa receptor may reduce the incidence of adverse ischemic outcomes after coronary angioplasty. METHODS: Seventy-three patients received tirofiban in three sequential dose panels and 20 patients received placebo. Patients within each panel were randomized to receive either tirofiban or placebo in a 3:1 randomization design. Bolus doses of 5, 10 and 10 microg/kg and continuous infusion (16 to 24 h) doses of 0.05, 0.10 and 0.15 microg/kg per min were administered in panels I, II and III, respectively. Patients received concomitant heparin and aspirin for the angioplasty procedure. Data on patients receiving placebo (heparin and aspirin only) were pooled across panels for comparisons. The pharmacodynamic effect of tirofiban on ex vivo platelet aggregation to 5 micromol/liter adenosine diphosphate (ADP) and bleeding times were measured. Clinical outcomes were assessed in all patients, but the power to detect clinically meaningful differences (a one-third reduction in clinical events) between groups was limited (5%). RESULTS: Tirofiban was associated with a dose-dependent inhibition of ex vivo ADP-mediated platelet aggregation that was sustained during intravenous infusion and resolved rapidly after drug cessation. Adverse bleeding events, largely related to vascular access site hemorrhage, were slightly increased at the highest dose. Adverse clinical outcomes were infrequent in all patients and were not different among the small number of patients within each group. CONCLUSIONS: This study establishes a rational and generally well tolerated dosing regimen for administration of tirofiban as adjunctive therapy in high risk angioplasty patients. The impact of tirofiban on adverse clinical outcomes after angioplasty awaits definition by a larger clinical trial.

The challenge of practice based research: a group approach.

Social work research has long been an area overlooked by direct practice clinicians for several reasons. Some clinicians are uncomfortable with research and tend to avoid it, while others feel they do not have time to generate quality research material and still serve clients adequately. The Social Work Services Department in a university teaching hospital accepted the challenge of combining direct practice and research. By drawing on internal levels of expertise, while collaborating with other area professionals, the Research Committee has adopted a group approach of individuals conducting practice-based research. This method of generating research has yielded many positive results.

Effect of multiple doses of losartan on the pharmacokinetics of single doses of digoxin in healthy volunteers.

1. Losartan (DuP 753, MK-954) is a novel, potent and highly selective AT1 angiotensin II receptor antagonist. The effect of multiple oral doses of losartan on digoxin pharmacokinetics was evaluated in healthy male subjects. 2. In a double-blind and randomized fashion, subjects received 50 mg losartan or placebo once daily for 15 days in each period. At least 7 days elapsed between the two treatment periods. On days 4 and 11 of each period, subjects also received a single 0.5 mg dose of digoxin intravenously and orally respectively. 3. Eleven of 13 subjects completed the study. Side effects were mild and transient (12 out of 13 subjects reported at least one adverse experience). During the study, no laboratory abnormalities were noted. 4. Multiple oral doses of losartan (50 mg daily) did not affect the pharmacokinetic parameters of 0.5 mg of digoxin i.v. AUC(0.48h) of immunoreactive digoxin during losartan 28.8 +/- 2.9 vs 28.5 +/- 3.9 ng ml-1 h during placebo; not significant, and 96 h urinary excretion [% dose] during losartan 54.0 +/- 7.2 vs 51.9 +/- 6.5% during placebo; not significant). Geometric mean ratios (90% confidence interval) for AUC and urinary excretion were respectively, 1.03 (0.98, 1.08) and 1.09 (0.98, 1.21). 5. Multiple oral doses of losartan did not affect the pharmacokinetic parameters of oral digoxin AUC(0.48 h) during losartan 23.6 +/- 3.7 ng ml-1 h vs 22.4 +/- 2.6 ng ml-1 h during placebo; not significant, Cmax 3.5 +/- 0.7 ng ml-1 with vs 3.1 +/- 0.5 ng ml-1 without losartan; not significant and tmax 0.6 +/- 0.2 h with vs 0.9 +/- 0.7 h without losartan; not significant, and 96 h urinary excretion [% dose] during losartan 51.2 +/- 6.3 vs 46.3 +/- 2.4% during placebo; not significant). Geometric mean ratios (90% confidence interval) for AUC and urinary excretion were respectively, 1.06 (0.98, 1.14) and 1.12 (0.97, 1.28). 6. We conclude that multiple oral doses of losartan (50 mg daily) do not alter the pharmacokinetics of immunoreactive digoxin, following either intravenous or oral digoxin. Furthermore, the co-administration of digoxin with losartan is well tolerated by healthy male volunteers.

Losartan potassium as initial therapy in patients with severe hypertension.

This 12-week, open-label study was conducted to gain experience with losartan potassium, an angiotensin II receptor antagonist, in patients with severe hypertension. Patients were either untreated or withdrawn from current therapy for at least 48 h before initiation of losartan 50 mg once daily. Patients were titrated to 100 mg as needed to achieve a goal of sitting diastolic blood pressure (SiDBP) 90 or 95 mm Hg. Hydrochlorothiazide (12.5 mg once daily titrated to 25 mg) was added and followed by either a dihydropyridine calcium channel blocker (CCB) and/or atenolol, if BP was not controlled. A total of 179 patients with a pretreatment mean baseline BP of 172 +/- 17/112 +/- 18 mm Hg enrolled in the trial and BP was recorded 24 h after dosing at baseline and weeks 2, 4, 8 and the final week (10-12 weeks). The mean reductions in SiDBP from baseline were 7.3, 9.3, 15.9 and 18.9 mm Hg, respectively, and these changes from baseline were statistically significant, P < 0.001. At the end of the trial, 22% of patients remained on losartan monotherapy, 30% required the addition of hydrochlorothiazide (HCTZ) and 31% required both HCTZ and a CCB; 11% required HCTZ and atenolol while 4% required HCTZ, a CCB and atenolol; 2% of patients were on regimens not specified by the protocol. SiDBP < 90 mm Hg was achieved in 68 patients by the final visit; 24% of these patients were treated with losartan monotherapy (50 or 100 mg), 41% achieved control with the addition of HCTZ (12.5 or 25 mg) and 24% required triple therapy which included losartan, HCTZ and a CCB. As assessed by the investigator, 25% of the patients in the study had drug-related clinical adverse experiences. Headache was the most frequently reported clinical adverse event (26% of patients). No clinically significant changes in laboratory parameters were observed. It is concluded that losartan potassium can be used as initial therapy for patients with severe hypertension and can be administered concurrently with hydrochlorothiazide, calcium channel blockers and atenolol.

Social work in pediatric oncology: a family needs assessment.

When a child is diagnosed with cancer, the family is confronted with meeting both the physical and psychosocial needs of the child and maintaining normal family functioning. This study assessed the perceived psychosocial needs of 77 families who have a child diagnosed with cancer. Preliminary results suggest practical application for social work interventions in specific areas such as the development of an informal support network, enhancement of communication within families concerning the disease, the need for adequate information at various stages of the disease, and continued supportive services for the family.

Relationship of self-effecacy to cholesterol lowering and dietary change in hyperlipidemia.

This study examined whether self-efficacy was associated with lipid lowering and dietary change among men undergoing dietary counseling to lower cholesterol levels. Twenty-five hyperlipidemic men (total cholesterol ≧220 mg/dL) participated in four weeks of dietary instruction. Plasma lipids were measured prior to treatment, at posttreatment, and at three- and twelvemonth follow-up. Dietary intake and self-efficacy as measured by the revised Eating Self-Efficacy Scale (ESES-R) were assessed at pretreatment, posttreatment, and three-month follow-up. Pre-treatment to posttreatment increases in self-efficacy in situations characterized by negative affect were related to extent of lipid lowering and dietary change. Although subjects showed significant reductions in cholesterol levels following treatment, by one year, lipid levels had returned to pretreatment values. Factors related to long-term maintenance of dietary change and lipid lowering among hyperlipidemics merit further research.

6agonist selectivity determinants in somatostatin receptor subtypes I and II.

The biological activities of the peptide hormone somatostatin are mediated through a recently identified family of G-protein-linked receptors. A number of somatostatin analogs have been characterized with selective affinities for particular somatostatin receptor subtypes. Using one such molecule (MK-678), we have delineated receptor regions that determine analog selectivity in the murine Type 1 and Type 2 somatostatin receptors. We find that the regions about the second and third extracellular loops of these two receptors contain the determinants for MK-678 selectivity and affinity.

Coexpression of erbB2 and erbB3 proteins reconstitutes a high affinity receptor for heregulin.

The heregulin/neu differentiation factor gene products were purified and cloned based on their ability to stimulate the phosphorylation of a 185-kDa protein in human breast carcinoma cell lines known to express erbB2. However, not all cells that express erbB2 respond to heregulin, indicating that other components besides erbB2 may be required for heregulin binding. Cells that are transfected with the closely related receptor, erbB3, display a single class of lower affinity heregulin binding sites than has been previously observed on breast carcinoma cell lines. Little or no stimulation of tyrosine phosphorylation in response to heregulin occurs in cells that are transfected with erbB3 alone. Transfection of cells with erbB3 and erbB2 reconstitutes a higher affinity binding receptor, which is also capable of generating a tyrosine phosphorylation signal in response to heregulin. A monoclonal antibody to erbB2 will inhibit heregulin activation of tyrosine phosphorylation and binding in cells transfected with both receptors but not with erbB3 alone. In cells expressing erbB2 and erbB3, both proteins become tyrosine-phosphorylated upon interaction with heregulin. Direct interaction between heregulin and the two proteins was demonstrated by chemical cross-linking experiments using 125I-heregulin followed by immunoprecipitation with antibodies specific for erbB2 or erbB3.