Activation and accumulation of B cells in TACI-deficient mice

The tumor necrosis factor (TNF)-related ligand B lymphocyte stimulator (BLyS) binds two TNF receptor family members, transmembrane activator and calcium-modulating and cyclophilin ligand interactor (TACI) and B cell maturation molecule (BCMA). Mice that are transgenic for BLyS show B cell accumulation, activation and autoimmune lupus-like nephritis. The existence of at least two distinct BLyS receptors raises the question of the relative contribution of each to B cell functions. We therefore generated mice that were deficient in TACI. TACI-/- mice showed increased B cell accumulation and marked splenomegaly. Isolated TACI-/- B cells hyperproliferated and produced increased amounts of immunoglobulins in vitro. In vivo antigen challenge resulted in enhanced antigen-specific antibody production. Thus, TACI may play an unexpected inhibitory role in B cell activation that helps maintain immunological homeostasis.

TACI-ligand interactions are required for T cell activation and collagen-induced arthritis in mice

Interactions of the tumor necrosis factor superfamily members B lymphocyte stimulator (BLyS) and a proliferation-inducing ligand (APRIL) with their receptors-transmembrane activator and CAML interactor (TACI) and B cell maturation molecule (BCMA)-on B cells play an important role in the humoral immune response. Whereas BCMA is restricted to B cells, TACI is also expressed on activated T cells; we show here that TACI-Fc blocks the activation of T cells in vitro and inhibits antigen-specific T cell activation and priming in vivo. In a mouse model for rheumatoid arthritis (RA), an autoimmune disease that involves both B and T cell components, TACI-Fc treatment substantially inhibited inflammation, bone and cartilage destruction and disease development. Thus, BLyS and/or APRIL are important not only for B cell function but for T cell-mediated immune responses. Inhibition of these ligands might have therapeutic benefits for autoimmune diseases, such as RA, that involve both B and T cells.

On-line detection of sleep-wake states and application to produce intermittent hypoxia only in sleep in rats

Sleep-disordered breathing is associated with adverse clinical consequences such as daytime sleepiness and hypertension. The mechanisms behind these associations have been studied in animal models, especially rats, but intermittent stimuli such as hypoxia have been applied without reference to sleep-wake states. To determine mechanisms underlying the adverse physiological consequences of stimuli associated with sleep-disordered breathing requires criteria for detection of sleep-wake states on-line to trigger stimuli only in sleep. This study aimed to develop such a system for freely behaving rats. Twelve rats with implanted electroencephalogram and neck electromyogram electrodes were studied in the light and dark phases. Electroencephalogram frequencies in the high (20–30 Hz) and low (2–4 Hz) frequency bands distinguished non-rapid eye movement (REM) sleep, whereas neck electromyogram distinguished REM. Using these parameters in a simple algorithm led to detection accuracies of 94.5 ± 1.0 (SE) % for wakefulness, 96.2 ± 0.8% for non-REM sleep, and 92.3 ± 1.6% for REM compared with blinded human judgment. The algorithm was then used to trigger hypoxic stimuli only in sleep. Because frequency and amplitude analysis is readily performed using a variety of commercial systems, incorporation of these parameters into such an algorithm will facilitate studies investigating mechanisms underlying the physiological consequences of sleep-related respiratory stimuli in a fashion that more effectively models clinical disorders.

Anti-IgE efficacy in murine asthma models is dependent on the method of allergen sensitization

BACKGROUND

Murine models used to delineate mechanisms and key mediators of asthma have yielded conflicting results and suggest that the dominant mechanism and mediators required for disease induction differ depending on the model and method of allergen sensitization used.

OBJECTIVE

The goal of this study was to determine whether the mode of allergen sensitization influenced the role that IgE had in allergen-induced pulmonary eosinophilic inflammation.

METHODS

Mice were exposed to dust mite extract in 2 models of allergic inflammation that differed in the method of sensitization. We compared sensitization by aerosol exposure with and without concomitant human respiratory syncytial virus infection with sensitization by means of systemic (intraperitoneal) exposure with adjuvant. After sensitization, animals were similarly challenged with aerosolized allergen. Animals were treated with anti-IgE mAb to deplete IgE and to determine its role in the induction of allergic inflammation and mucosa pathology in these models.

RESULTS

Concomitant respiratory syncytial virus infection significantly enhanced allergen sensitization by aerosol exposure and exacerbated eosinophilic inflammation and airway mucosa pathology. Depletion of IgE in this model significantly reduced lung eosinophilic inflammation and airway mucosa pathology. However, in the model in which animals were sensitized by means of systemic allergen exposure with adjuvant, depletion of IgE had no ameliorative effect on lung inflammation or pathology.

CONCLUSION

We demonstrated that the method of antigen sensitization can delineate the role of IgE in allergen-induced lung inflammation. In a murine model that more closely resembles ambient allergen exposure in human subjects, IgE had a critical role in the pathogenesis of allergic asthma and mucosa pathology. The results parallel the results reported with anti-IgE efficacy in allergic asthmatic human subjects.

A simple, rapid method for HPLC analysis of lycopene isomers

A rapid method for the extraction, separation and quantification of the geometric isomers of lycopene and beta-carotene from tomato fruit is described. Carotenoids in tomato were separated and eluted using a reversed-phase HPLC with a C30 column and a mobile phase consisting of methyl-t-butyl ether, methanol and ethyl acetate. The system provided sharp resolution of cis- and trans-isomers of lycopene within approximately 23 min in contrast to the longer and more complex gradient procedures required by previously described methods. Experiments indicate that the stability of extracts of fresh tomato may be improved if stored at -20 degrees C, and that the presence of the antioxidant BHA has no apparent effect on stability.

Myopia in Singapore kindergarten children

PURPOSE

The purpose of this study was to examine whether close-up work was related to myopia in Singapore kindergarten children.

METHODS

One hundred twenty-eight children, ages 3 to 7 years, from a kindergarten in Singapore were examined by cycloplegic autorefraction. The parents also completed a questionnaire on the different types of close-up work activities each child was engaged in, socioeconomic status, and parental history of myopia.

RESULTS

Myopic children spent 3.0 hours per day (median) on close-up work activity, while nonmyopic children spent 2.0 hours per day (median) on close-up work activity. The prevalence of myopia in the sample was 8.6%.

CONCLUSION

Close-up work activity was not related to myopia in pre-school children.

Cell surface glypicans are low-affinity endostatin receptors

Endostatin, a collagen XVIII fragment, is a potent anti-angiogenic protein. We sought to identify its endothelial cell surface receptor(s). Alkaline phosphatase- tagged endostatin bound endothelial cells revealing two binding affinities. Expression cloning identified glypican, a cell surface proteoglycan as the lower-affinity receptor. Biochemical and genetic studies indicated that glypicans' heparan sulfate glycosaminoglycans were critical for endostatin binding. Furthermore, endostatin selected a specific octasulfated hexasaccharide from a sequence in heparin. We have also demonstrated a role for endostatin in renal tubular cell branching morphogenesis and show that glypicans serve as low-affinity receptors for endostatin in these cells, as in endothelial cells. Finally, antisense experiments suggest the critical importance of glypicans in mediating endostatin activities.

Consistency analysis of similarity between multiple alignments: prediction of protein function and fold structure from analysis of local sequence motifs

A new method to analyze the similarity between multiply aligned protein motifs (blocks) was developed. It identifies sets of consistently aligned blocks. These are found to be protein regions of similar function and structure that appear in different contexts. For example, the Rossmann fold ligand-binding region is found similar to TIM barrel and methylase regions, various protein families are predicted to have a TIM-barrel fold and the structural relation between the ClpP protease and crotonase folds is identified from their sequence. Besides identifying local structure features, sequence similarity across short sequence-regions (less than 20 amino acid regions) also predicts structure similarity of whole domains (folds) a few hundred amino acid residues long. Most of these relations could not be identified by other advanced sequence-to-sequence or sequence-to-multiple alignments comparisons. We describe the method (termed CYRCA), present examples of our findings, and discuss their implications.

Increased cell proliferation and associated expression of PDGFRbeta causing hypercellularity in patellar tendinosis

OBJECTIVE

This study assessed cellularity in patellar tendinosis with respect to cell proliferation and the expression of platelet-derived growth factor receptor beta (PDGFRbeta).

METHODS

Surgical samples were taken from 11 patients fulfilling criteria of patellar tendinosis and from 12 matched controls. Standard immunohistochemistry methods were used to detect expression of PDGFRbeta and proliferation cell nuclear antigen (PCNA). Results were analysed by computer-assisted microscopy. Tendon cells were isolated from nine tendinosis and eight control tissues for cell culture.

RESULTS

Increased cellularity (P<0.001) was observed in tendinosis tissues compared with controls, and also a higher proliferative index (P:<0.001). Increased expression of PDGFRbeta was demonstrated (P<0.001). Cultured tendinosis cells showed a higher proliferation rate than controls (P<0.001). This was maintained when the cells were cultured under various conditions of serum supplementation (P<0.01). Tendinosis cells also showed a higher proliferation rate (P<0.01) in medium containing 10 ng/ml PDGF.

CONCLUSION

Hypercellularity in patellar tendinosis is caused by increased cell proliferation and is associated with increased expression of PDGFRbeta.

The financial performance of hospitals belonging to health networks and systems

The U.S. health industry is experiencing substantial restructuring through ownership consolidation and development of new forms of interorganizational relationships. Using an established taxonomy of health networks and systems, this paper develops and tests four hypotheses related to hospital financial performance. Consistent with our predictions, we find that hospitals in health systems that had unified ownership generally had better financial performance than hospitals in contractually based health networks. Among health network hospitals, those belonging to highly centralized networks had better financial performance than those belonging to more decentralized networks. However, health system hospitals in moderately centralized systems performed better than those in highly centralized systems. Finally, hospitals in networks or systems with little differentiation or centralization experienced the poorest financial performance. These results are consistent with resource dependence, transaction cost economics, and institutional theories of organizational behavior, and provide a conceptual and empirical baseline for future research.

Evolutionary coadaptation of the motif 2--acceptor stem interaction in the class II prolyl-tRNA synthetase system

Known crystal structures of class II aminoacyl-tRNA synthetases complexed to their cognate tRNAs reveal that critical acceptor stem contacts are made by the variable loop connecting the beta-strands of motif 2 located within the catalytic core of class II synthetases. To identify potential acceptor stem contacts made by Escherichia coli prolyl-tRNA synthetase (ProRS), an enzyme of unknown structure, we performed cysteine-scanning mutagenesis in the motif 2 loop. We identified an arginine residue (R144) that was essential for tRNA aminoacylation but played no role in amino acid activation. Cross-linking experiments confirmed that the end of the tRNA(Pro) acceptor stem is proximal to this motif 2 loop residue. Previous work had shown that the tRNA(Pro) acceptor stem elements A73 and G72 (both strictly conserved among bacteria) are important recognition elements for E. coli ProRS. We carried out atomic group "mutagenesis" studies at these two positions of E. coli tRNA(Pro) and determined that major groove functional groups at A73 and G72 are critical for recognition by ProRS. Human tRNA(Pro), which lacks these elements, is not aminoacylated by the bacterial enzyme. An analysis of chimeric tRNA(Pro) constructs showed that, in addition to A73 and G72, transplantation of the E. coli tRNA(Pro) D-domain was necessary and sufficient to convert the human tRNA into a substrate for the bacterial synthetase. In contrast to the bacterial system, base-specific acceptor stem recognition does not appear to be used by human ProRS. Alanine-scanning mutagenesis revealed that motif 2 loop residues are not critical for tRNA aminoacylation activity of the human enzyme. Taken together, our results illustrate how synthetases and tRNAs have coadapted to changes in protein-acceptor stem recognition through evolution.

Assessment of hemodynamic response during focal neural activity in human using bolus tracking, arterial spin labeling and BOLD techniques

In this study, the hemodynamic response and changes in oxidative metabolism during functional activation were measured using three functional magnetic resonance imaging (fMRI) techniques: the blood oxygenation level-dependent (BOLD) technique, flow-sensitive alternating inversion recovery (FAIR), and bolus tracking (BT) of an MR contrast agent. With these three techniques we independently determined changes in BOLD signal, relative cerebral blood flow (rCBF), and cerebral blood volume (rCBV) associated with brain activation in eight healthy volunteers. In the motor cortex, the BOLD signal increased by 1.8 +/- 0.5%, rCBF by 36.3 +/- 8.2% (FAIR), and 35.1 +/- 8.6% (BT), and rCBV by 19.4 +/- 4.1% (BT) in response to simultaneous bilateral finger tapping. In the visual cortex, BOLD signal increased by 2.6 +/- 0.5%, rCBF by 38.5% +/- 7.6 (FAIR), and 36.9 +/- 8.8% (BT), and rCBV by 18.8 +/- 2.8% (BT) during flickering checkerboard stimulation. Comparing the experimentally measured rCBV with the calculated rCBV using Grubb's power-law relation, we conclude that the use of power-law relationship results in systematic underestimate of rCBV.

Microvascular reconstruction and tracheotomy are significant determinants of resource utilization in head and neck surgery

BACKGROUND

Successful "critical pathway" design and implementation are dependent on appropriate patient stratification according to those factors that are primary determinants of resource utilization.

OBJECTIVES

To test the validity of our previously reported critical pathway design and to determine whether tracheotomy and microvascular reconstruction (MR) are primary determinants of resource utilization.

DESIGN

Cost-effectiveness analysis.

SETTING

Tertiary referral academic institution.

METHODS

Retrospective analysis of data from 133 head and neck surgery cases in which the treatment regimen was based on critical pathways over a 26-month period.

OUTCOME MEASURES

Length of stay and total patient charges were used as indices of resource utilization. One-way analysis of variance and t tests were used for statistical analysis of significance.

RESULTS

Ninety patients (67.7%) underwent MR; 43 (32. 3%) did not. Seventy-five patients (56.4%) underwent tracheotomy; 58 (43.6%) did not. Four patient groups were constructed in decreasing order of complexity as follows: group 1, patients who underwent both tracheotomy and MR (n = 58); group 2, patients who underwent MR alone (n = 32); group 3, patients who underwent tracheotomy alone (n = 17); and group 4, patients who did not undergo either procedure (n = 26). Both tracheotomy and MR were found to be independent determinants of resource utilization and were additive when both were present. The length of stay varied from 8.4 days (in patients who underwent both procedures) to 6.7 days (in patients who did not undergo either procedure), with intermediate values in cases in which only 1 procedure was performed. The total charges varied in a similar manner from a high of $33,371 to a low of $19,994. Subanalysis with respect to intensive care unit, ward, and operating room charges showed a similar stratification.

CONCLUSION

Tracheotomy and MR are both significant determinants of charges and length of stay in head and neck surgery cases and must be considered in the design of strategies to promote efficient resource utilization.

FIZZ1, a novel cysteine-rich secreted protein associated with pulmonary inflammation, defines a new gene family

Bronchoalveolar lavage fluid from mice with experimentally induced allergic pulmonary inflammation contains a novel 9.4 kDa cysteine-rich secreted protein, FIZZ1 (found in inflammatory zone). Murine (m) FIZZ1 is the founding member of a new gene family including two other murine genes expressed, respectively, in intestinal crypt epithelium and white adipose tissue, and two related human genes. In control mice, FIZZ1 mRNA and protein expression occur at low levels in a subset of bronchial epithelial cells and in non-neuronal cells adjacent to neurovascular bundles in the peribronchial stroma, and in the wall of the large and small bowel. During allergic pulmonary inflammation, mFIZZ1 expression markedly increases in hypertrophic, hyperplastic bronchial epithelium and appears in type II alveolar pneumocytes. In vitro, recombinant mFIZZ1 inhibits the nerve growth factor (NGF)-mediated survival of rat embryonic day 14 dorsal root ganglion (DRG) neurons and NGF-induced CGRP gene expression in adult rat DRG neurons. In vivo, FIZZ1 may modulate the function of neurons innervating the bronchial tree, thereby altering the local tissue response to allergic pulmonary inflammation.

A mixed-penalty biphasic finite element formulation incorporating viscous fluids and material interfaces

The fluid viscosity term of the fluid phase constitutive equation and the interface boundary conditions between biphasic, solid and fluid domains have been incorporated into a mixed-penalty finite element formulation of the linear biphasic theory for hydrated soft tissue. The finite element code can now model a single-phase viscous incompressible fluid, or a single-phase elastic solid, as limiting cases of a biphasic material. Interface boundary conditions allow the solution of problems involving combinations of biphasic, fluid and solid regions. To incorporate these conditions, the volume-weighted mixture velocity is introduced as a degree of freedom at interface nodes so that the kinematic continuity conditions are satisfied by conventional finite element assembly techniques. Results comparing our numerical method with an independent, analytic solution for the problem of Couette flow over rigid and deformable porous biphasic layers show that the finite element code accurately predicts the viscous fluid flows and deformation in the porous biphasic region. Thus, the analysis can be used to model the interface between synovial fluid and articular cartilage in diarthrodial joints. This is an important step toward modeling and understanding the mechanisms of joint lubrication and another step toward fully modeling the in vivo behavior of a diarthrodial joint.

Effects of humanized monoclonal antibody to rhesus CD11a in rhesus monkey cardiac allograft recipients

INTRODUCTION

Leukocyte function-associated antigen-1 (LFA-1, CD11a) monoclonal antibody (mAb) affects many leukocyte functions without cell depletion. We hypothesized that the use of a humanized, anti-rhesus modified LFA-1 mAb (H2C12) in rhesus monkeys would cause: (1) prolonged heart allograft survival, (2) inhibition of primary but not secondary antibody responses, and (3) minimal drug toxicity.

METHODS AND RESULTS

Control (n=5) and H2C12-treated (n=7) (8-20 mg/kg i.v. on day -1 followed by 10 mg/kg/day) adult male rhesus recipients were inoculated with GP120 protein antigen on day -28 and -1 and grafted with heterotopic abdominal hearts (day 0). Donor-recipient pairs were equally MLR mismatched (4329.8+/-1124.1 CPM controls vs. 7289.0+/-1926.5 treated, P=NS). Mean heart allograft survival as evaluated by daily abdominal palpation was significantly prolonged in high dose recipients (23.0+/-2.6, n=4) vesus controls (8.2+/-1.3, n=5, P<0.02, Mann-Whitney U test). H2C12 treatment did not produce signs of cytokine release or toxicity, was nondepleting, but down-modulated PBL CD11a expression to 43.4+/-3.6% (n=4) of control levels (n=5) at day 7 as demonstrated by flow cytometry. It had no effect on postoperative Con A or MLR and did not prevent mAb clearance due to the rhesus-antihuman antibody response. The addition of mycophenolate mofitil prevented rhesus-antihuman antibody response with therapeutic H2C12 levels seen for >35 days.

CONCLUSIONS

The use of this mAb to block CD11a had the benefit of being a well tolerated, highly targeted therapy. These are the first results showing that monotherapy with anti-leukocyte function-associated antigen-1 mAb prolonged survival of MLR mismatched allogenic cardiac grafts in primates.

A multi-mutant herpes simplex virus vector has minimal cytotoxic effects on the distribution of filamentous actin, alpha-actinin 2 and a glutamate receptor in differentiated PC12 cells

To develop effective gene therapy techniques that target populations of neurons in the spinal cord, suitable vectors must be developed that will undergo efficient, retrograde transport from an appropriate peripheral site and will not be cytotoxic. Our previous work (LeVatte et al, 1998a) has demonstrated that a replication defective herpes simplex virus vector 14Hdelta3vhsZ, that has been substantially detoxified, is retrogradely transported from peripheral sites and can infect large numbers of the targeted spinal neurons. We plan to develop targeted gene therapy approaches designed to modulate the excitatory glutamatergic methyl-D-aspartate (NMDA) receptor in spinal cord neurons as a means of ameliorating a form of episodic high blood pressure that occurs after spinal cord injury. In this report, we demonstrate that, in differentiated PC12 cells, a neuronal-like cell line, the virus vector does not appear to alter aspects of the cytoskeletal architecture important to the proper distribution of the NMDA receptor. In turn, the distribution of endogenous NMDA receptor 1 subunit protein (NMDAR1) or a transfected NMDAR1-green fluorescent fusion protein was also found to be unaltered after vector infection. However, whereas endogenous NMDAR1 distribution was maintained, vector infection did tend to reduce the level of its expression. This drop in endogenous NMDAR1 expression coincided with the expression of the HSV immediate early genes ICP0 and ICP27 over the first 24-48 h. These results indicate that the 14Hdelta3vhsZ herpes simplex virus vector is suitable to use in future strategies to alter the level of gene expression in targeted populations of spinal cord neurons.

Cloning of mouse prostaglandin transporter PGT cDNA: species-specific substrate affinities

We recently identified and/or cloned the PG transporter PGT in the rat (rPGT) (Kanai, N., R. Lu, J. A. Satriano, Y. Bao, A. W. Wolkoff, and V. L. Schuster, Science 268: 866-869, 1995) and the human (hPGT) (Lu, R., and V. L. Schuster, J. Clin. Invest. 98: 1142-1149, 1996). Here we have cloned and expressed the mouse PGT (mPGT) cDNA. The tissue distribution of mPGT mRNA expression is significantly more restricted than that of rPGT and hPGT mRNA. Although the deduced amino acid sequence of mPGT is similar to the rat (91% identity) and human (82% identity) homologues, it has three regions of dissimilarity: amino acids 128-163 and 283-298, and valine 610 and isoleucine 611 (predicted to lie within putative transmembrane span 12). Affinities of hPGT, rPGT, and mPGT for several PG substrates differed, with hPGT having the highest [low Michaelis constant (K(m))] and mPGT the lowest affinity. A chimeric protein, linking the N-terminal domain of mPGT with the C-terminal domain of hPGT, had affinity for PGE2 indistinguishable from that of hPGT, indicating that the C-terminal domain dictates K(m). We mutagenized mouse valine 610 and isoleucine 611 to their corresponding human residues (methionine and glycine, respectively); however, these changes did not convert the inhibition constant of mPGT to that of hPGT. The mouse gene was localized to chromosome 9 in a region syntenic with the region of human chromosome 3 containing the hPGT gene. These studies highlight the species-dependence of tissue expression and function of PGT and lay the groundwork for the use of the mouse as a model system for the study of PGT function.

American Society for Microbiology--99th general meeting. 30 May-3 June 1999, Chicago, IL, USA

The American Society for Microbiology (ASM) celebrated its centenary at this meeting, which aimed to appeal to an audience with diverse microbiological interests. The program comprised six colloquia, division lectures and award sessions, division sessions, poster and special interest sessions, as well as pre-meeting workshops. The colloquia topics, selected by the ASM members advisory committee, were: pathogenesis; microbes and public health; microbial diversity; beyond the recombinant RNA revolution; molecular dissection of complex biological processes; and, host defenses. The divisional groups were: diagnostic microbiology and epidemiology; pathogenesis and host response mechanisms; general microbiology; and, molecular microbiology, physiology and virology. Each group highlighted a topic of importance to scientists from all divisions within that group and the divisional lecture was given by a distinguished scientist within one of the division's sessions.

Organizational and administrative factors influencing the adoption of consortia programs by rural hospitals

This study was designed to assess the effects of various hospital and environmental characteristics on the involvement of rural hospitals in forming and governing consortia and adopting consortia programs. The study focused on the 127 hospitals that are members of the nine rural consortia developed by grants from the Robert Wood Johnson Foundation during 1989 under its Hospital-Based Rural Hospital Consortia Program. Hospital involvement in the formation and governance of the consortia was found to be far less than expected for these grass-roots organizations. Only 38 percent of the administrators said that their hospitals were involved in developing the consortia, and 44 percent said that they played a role in determining the program menu. Governing board and medical staff involvement was even more limited. Program adoption rates were found to be related to both the types of programs offered by the consortia and the characteristics of the hospitals. In general, greater involvement of physicians and governing board members in hospital decisions was found to enhance program adoption rates, but the influence varied by type of involvement in the hospital and program content.

The effects of group size and group economic factors on collaboration: a study of the financial performance of rural hospitals in consortia

STUDY QUESTIONS

To determine factors that distinguish effective rural hospital consortia from ineffective ones in terms of their ability to improve members' financial performance. Two questions in particular were addressed: (1) Do large consortia have a greater collective impact on their members? (2) Does a consortium's economic environment determine the degree of collective impact on members?

DATA SOURCES AND STUDY SETTING

Based on the hospital survey conducted during February 1992 by the Robert Wood Johnson Hospital-Based Rural Health Care project of rural hospital consortia. The survey data were augmented with data from Medicare Cost Reports (1985-1991), AHA Annual Surveys (1985-1991), and other secondary data.

STUDY DESIGN

Dependent variables were total operating profit, cost per adjusted admission, and revenue per adjusted admission. Control variables included degree of group formalization, degree of inequality of resources among members (group asymmetry), affiliation with other consortium group(s), individual economic environment, common hospital characteristics (bed size, ownership type, system affiliation, case mix, etc.), year (1985-1991), and census region dummies.

PRINCIPAL FINDINGS

All dependent variables have a curvilinear association with group size. The optimum group size is somewhere in the neighborhood of 45. This reveals the benefits of collective action (i.e., scale economies and/or synergy effects) and the issue of complexity as group size increases. Across analyses, no strong evidence exists of group economic environment impacts, and the environmental influences come mainly from the local economy rather than from the group economy.

CONCLUSION

There may be some success stories of collaboration among hospitals in consortia, and consortium effects vary across different collaborations.

RELEVANCE/IMPACT

When studying consortia, it makes sense to develop a typology of groups based on some performance indicators. The results of this study imply that government, rural communities, and consortium staff and steering committees should forge the consortium concept by expanding membership in order to gain greater financial benefits for individual hospitals.

Increased dependence of glucose production on peripheral insulin in diabetic depancreatized dogs

We have recently found that in nondiabetic dogs and humans, suppression of glucose production (GP) is mediated by both peripheral and hepatic effects of insulin. We have also found that both nonesterified fatty acids (NEFA) and glucagon are important determinants of the peripheral effect of insulin on GP. However, in moderately hyperglycemic depancreatized dogs, suppression of GP appeared to be mediated by peripheral but not hepatic insulin. In this latter study, insulin concentrations were in the high postprandial range (approximately 300 pmol/L) and suppression of GP may have been close to maximum. The aim of the present study was to determine whether GP can be regulated by hepatic insulin in depancreatized dogs at low insulin concentrations in the postabsorptive range. Depancreatized dogs were maintained at moderately hyperglycemic levels (approximately 10 mmol/L) by subbasal insulin infusions. In paired experiments, additional low-dose equimolar insulin infusions (0.75 pmol/kg x min) were administered peripherally (PER, n = 6) or portally (POR, n = 6) during glucose clamps. This resulted in a minimal increase in peripheral insulin levels, which was greater in PER versus POR, 29.0 +/- 3.7 versus 11.7 +/- 2.2 pmol/L. Also, we infused insulin peripherally at half this rate (1/2 PER, n = 6) to match the increase in peripheral insulin levels in POR (1/2 PER, 14.6 +/- 2.2) and thus obtain a selective POR versus 1/2 PER difference in hepatic sinusoidal insulin levels. PER suppressed GP more than POR (45.4% +/- 4.0% v 35.3% +/- 6.8%, P < .001), whereas POR did not suppress GP more than 1/2 PER (35.6% +/- 6.3%). Therefore, suppression of GP was proportional to peripheral rather than hepatic sinusoidal insulin levels, as in our previous study at higher insulin concentrations. In conclusion, during glucose clamps in moderately hyperglycemic depancreatized dogs, (1) suppression of GP was dominated by insulin's peripheral effects not only at postprandial but also postabsorptive insulin levels, and (2) we found no evidence for a hepatic effect of insulin in suppressing GP. We hypothesize that this effect is reduced in the depancreatized dog model of diabetes due to hepatic insulin resistance and/or hyperglycemia.

Intra-tRNA distance measurements for nucleocapsid proteindependent tRNA unwinding during priming of HIV reverse transcription

We report here the direct measurement of intra-tRNA distances during annealing of the tRNA primer to the HIV RNA genome. This key step in the initiation of retroviral reverse transcription involves hybridization of one strand of the acceptor arm of a specific lysine tRNA to the primer binding site on the RNA genome. Although the mechanism of tRNA unwinding and annealing is not known, previous studies have shown that HIV nucleocapsid protein (NC) greatly accelerates primer/template binary complex formation in vitro. An open question is whether NC alone unwinds the primer or whether unwinding by NC requires the RNA genome. We monitored the annealing process in solution by using fluorescence resonance energy transfer (FRET). Distance measurements demonstrate unequivocally that the tRNA acceptor stem is not substantially unwound by NC in the absence of the RNA genome, that is, unwinding is not separable from hybridization. Moreover, FRET measurements show that both heat- and NC-mediated annealing result in an approximately 40-A increase in the separation of the two ends of the tRNA acceptor arm on binding to the template. This large increase in separation of the two ends suggests a complete displacement of the nonhybridized strand of the acceptor stem in the initiation complex.

Human Immunodeficiency Virus Reverse Transcriptase and Protease Sequence Database

The HIV RT and Protease Sequence Database is an on-line relational database that catalogues evolutionary and drug-related human immunodeficiency virus reverse transcriptase (RT) and protease sequence variation (http://hivdb.stanford.edu). The database contains a compilation of nearly all published HIV RT and protease sequences including International Collaboration database submissions (e.g., GenBank) and sequences published in journal articles. Sequences are linked to data about the source of the sequence sample and the anti-HIV drug treatment history of the individual from whom the isolate was obtained. The database is curated and sequences are annotated with data from 180 literature references. Users can retrieve additional data and view alignments of sequences sets meeting specific criteria (e.g., treatment history, subtype, presence of a particular mutation).

Medicaid TEFRA option in Minnesota: implications for patient rights

This research studied a special-needs population under age 18 who had both private insurance and Medicaid coverage through the Tax Equity and Fiscal Responsibility Act of 1982 (TEFRA) option. We found that children with managed care plans, particularly health maintenance organizations (HMOs), tended to incur higher total expenses to TEFRA than children with indemnity plans. Our findings also show that managed care in Minnesota tends to provide the same or marginally better coverage as indemnity plans do for core medical items but much less coverage for ancillary items such as home care, therapies, and durable medical equipment.