Hip Fractures: Diagnosis and Management

Hip fractures are common causes of disability, with mortality rates reaching 30% at one year. Nonmodifiable risk factors include lower socioeconomic status, older age, female sex, prior fracture, metabolic bone disease, and bony malignancy. Modifiable risk factors include low body mass index, having osteoporosis, increased fall risk, medications that increase fall risk or decrease bone mineral density, and substance use. Hip fractures present with anterior groin pain, inability to bear weight, or a shortened, abducted, externally rotated limb. Plain radiography is usually sufficient for diagnosis, but magnetic resonance imaging should be obtained if suspicion of fracture persists despite normal radiography. Operative management within 24 to 48 hours of the fracture optimizes outcomes. Fractures are usually managed by surgery, with the approach based on fracture type and location; spinal or general anesthesia can be used. Nonsurgical management can be considered for patients who are not good surgical candidates. Pre- and postoperative antistaphylococcal antibiotics are given to prevent joint infection. Medications for venous thromboembolism prophylaxis are also recommended. Physicians should be alert for the presence of delirium, which is a common postoperative complication. Early postoperative mobilization, followed by rehabilitation, improves outcomes. Subsequent care focuses on prevention, with increased physical activity, home safety assessments, and minimizing polypharmacy. Two less common hip fractures can also occur: femoral neck stress fractures and insufficiency fractures. Femoral neck stress fractures typically occur in dancers 20 to 30 years of age, endurance athletes, and military service members, often because of training overload. Insufficiency fractures due to compromised bone strength occur without trauma in postmenopausal women. If not recognized and treated, these fractures can progress to complete and displaced fractures with high rates of nonunion and avascular necrosis.

The Role of Surface Chemistry in the Osseointegration of PEEK Implants

Poly(etheretherketone) (PEEK) implants suffer from poor osseointegration because of chronic inflammation. In this study, we hypothesized that adding NH₂ and COOH groups to the surface of PEEK could modulate macrophage responses by altering protein adsorption and improve its osseointegration. NH₂ and COOH-functionalized PEEK surfaces induced pro- and anti-inflammatory macrophage responses, respectively, and differences in protein adsorption patterns on these surfaces were related to the varied inflammatory responses. The macrophage responses to NH₂ surfaces significantly reduced the osteogenic differentiation of mesenchymal stem cells (MSCs). MSCs cultured on NH₂ surfaces differentiated less than those on COOH surfaces even though NH₂ surfaces promoted the most mineralization in simulated body fluid solutions. After 14 days in rat tibia unicortical defects, the bone around NH₂ surfaces had thinner trabeculae and higher specific bone surface than the bone around unmodified implants; surprisingly, the NH₂ implants significantly increased bone-binding over the unmodified implants, while COOH implants only showed a trend for increasing bone-binding. Taken together, these results suggest that both mineral-binding and immune responses play a role in osseointegration, and PEEK implant integration may be improved with mixtures of these two functional groups to harness the ability to reduce inflammation and bind bone strongly.

Effect of routine first-trimester combined screening for pre-eclampsia on small-for-gestational-age birth: secondary interrupted time series analysis

OBJECTIVE

To evaluate the impact of a first-trimester combined screening program for pre-eclampsia, based on the Fetal Medicine Foundation (FMF) algorithm, on the rate of small-for-gestational age (SGA) at birth and adverse pregnancy outcome.

METHODS

This was a retrospective cohort study of data obtained from a London tertiary hospital between January 2017 and March 2019. The data were derived from a secondary analysis of the cohort evaluated in a clinical-effectiveness study on the implementation of a first-trimester screening program for pre-eclampsia. The cohort included 7720 women screened according to the UK National Institute for Health and Care Excellence (NICE) risk-based approach and 4841 women screened by the FMF multimodal approach, which combines maternal risk factors, blood pressure, pregnancy-associated plasma protein-A and uterine artery Doppler indices. The care package for the FMF-screened group included 150-mg aspirin prophylaxis, ultrasound scans at 28 and 36 weeks' gestation and scheduled delivery at 40 weeks. Outcome measures included the rates of SGA neonates at birth, admission to the neonatal unit, intrauterine demise, neonatal death and hypoxic-ischemic encephalopathy assessed by interrupted time series analysis (ITSA).

RESULTS

There was no significant difference in the rates of intrauterine demise, neonatal death and hypoxic-ischemic encephalopathy between the FMF-screened and NICE-screened cohorts. ITSA showed a significant reduction in the rate of term SGA birth < 10^th percentile at 21 months following implementation of the FMF screening program, with a relative effect reduction of 45.1% (P = 0.004). However, there was no significant relative effect reduction in term SGA birth < 5^th or < 3^rd percentile.

CONCLUSIONS

First-trimester combined screening for pre-eclampsia based on the FMF algorithm accompanied by a care package including serial ultrasound scans for growth evaluation and elective birth from 40 weeks' gestation resulted in a significant 45% relative effect reduction in term SGA birth < 10^th percentile but did not affect term SGA birth < 5^th or < 3^rd percentile. Further screening strategies to detect and improve the outcome of cases with SGA birth < 5^th percentile need to be considered. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Routine first-trimester combined screening for pre-eclampsia: pregnancy-associated plasma protein-A or placental growth factor?

OBJECTIVE

To compare the screening performance of serum pregnancy-associated plasma protein-A (PAPP-A) vs placental growth factor (PlGF) in routine first-trimester combined screening for pre-eclampsia (PE), small-for-gestational age (SGA) at birth and trisomy 21.

METHODS

This was a retrospective study nested in pregnancy cohorts undergoing first-trimester combined screening for PE and trisomy 21 using The Fetal Medicine Foundation (FMF) algorithm based on maternal characteristics, nuchal translucency thickness, PAPP-A, free beta-human chorionic gonadotropin, blood pressure and uterine artery Doppler. Women at high risk for preterm PE (≥ 1 in 50) received 150 mg of aspirin per day, underwent serial fetal growth scans at 28 and 36 weeks and were offered elective birth from 40 weeks of gestation. PlGF was quantified retrospectively from stored surplus first-trimester serum samples. The performance of combined first-trimester screening for PE and SGA using maternal history, blood pressure, uterine artery pulsatility index and either PAPP-A or PlGF was calculated. Similarly, the performance of combined first-trimester screening for trisomy 21 was calculated using either PAPP-A or PlGF in addition to maternal age, nuchal translucency thickness and free beta-human chorionic gonadotropin.

RESULTS

Maternal serum PAPP-A was assayed in 1094 women, including 82 with PE, 111 with SGA (birth weight < 10^th centile), 53 with both PE and SGA and 94 with fetal trisomy 21. PlGF levels were obtained retrospectively from 1066/1094 women. Median serum PlGF multiples of the median was significantly lower in pregnancies with PE (1.0 (interquartile range (IQR), 0.8-1.4); P < 0.01), SGA (1.0 (IQR, 0.8-1.3); P < 0.001) and trisomy 21 (0.6 (IQR, 0.5-0.9); P < 0.0001) compared to in controls (1.2 (IQR, 0.9-1.5)). There was no significant difference in the performance of first-trimester screening using PAPP-A vs PlGF for either preterm PE (area under the receiver-operating-characteristics curve (AUC), 0.78 vs 0.79; P = 0.55) or term PE (AUC, 0.74 vs 0.74; P = 0.60). These findings persisted even after correction for the effect of targeted aspirin use on the prevalence of PE. Similarly, there were no significant differences in sensitivity and specificity of combined screening for SGA or trisomy 21 when using PAPP-A vs PlGF.

CONCLUSIONS

Using either PlGF or PAPP-A in routine first-trimester combined screening based on maternal characteristics, blood pressure and uterine artery Doppler does not make a significant clinical difference to the detection of PE or SGA. Depending on the setting, biomarkers should be chosen to achieve a good compromise between performance and measurement requirements. This pragmatic clinical-effectiveness study suggests that combined screening for PE can be implemented successfully in a public healthcare setting without changing current protocols for the assessment of PAPP-A in the first trimester. © 2021 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Protein Adsorption on Surfaces Functionalized with COOH Groups Promotes Anti-inflammatory Macrophage Responses

Implants can induce a foreign body reaction that leads to chronic inflammation and fibrosis in the surrounding tissue. Macrophages help detect the foreign material, play a role in the inflammatory response, and may promote fibrosis instead of the desired tissue regeneration around implants. Implant surface properties impact macrophage responses by changing the nature of the adsorbed protein layer, but conflicting studies highlight the complexity of this relationship. In this study, the effect of surface chemistry on macrophage behavior was investigated with poly(styrene) surfaces containing common functional groups at similar surface densities. The protein layer was characterized to identify the proteins that adsorbed on the surfaces from the medium and the proteins secreted onto the surfaces by adherent macrophages. Of the surface chemistries studied, carboxylic acid (COOH) groups promoted anti-inflammatory responses from unstimulated macrophages and did not exacerbate inflammation upon stimulation. These surfaces also enhanced the adsorption of proteins involved in integrin signaling and promoted the secretion of proteins related to angiogenesis, integrin signaling, and cytokine signaling, which have been previously associated with improved biomaterial integration. Therefore, this study suggests that surface modification with COOH groups may help improve the integration of implants in the body by enhancing anti-inflammatory macrophage responses through altered protein adsorption.

Implementation of routine first trimester combined screening for pre-eclampsia: a clinical effectiveness study

OBJECTIVE

Evaluate clinical effectiveness of the first trimester combined (FMF) pre-eclampsia screening programme when implemented in a public healthcare setting.

DESIGN

Retrospective cohort study.

SETTING

London tertiary hospital from January 2017 to March 2019.

METHODS

7720 women screened for pre-eclampsia according to National Institute for Health and Care Excellence (NICE) risk-based guidance and 4841 by the Fetal Medical Foundation (FMF) algorithm which combined maternal risk factors, blood pressure, PAPP-A and uterine artery Doppler indices in the first trimester. High risk was defined by standard NICE criteria in the pre-intervention cohort (prescribed 75 mg aspirin) or a risk of ≥1:50 for preterm pre-eclampsia from the FMF algorithm in the post-intervention cohort (prescribed 150 mg aspirin).

MAIN OUTCOME MEASURES

Screening effectiveness, rates of pre-eclampsia.

RESULTS

The FMF screening programme resulted in a significant reduction in the screen-positive rate (16.1 versus 8.2%, odds ratio [OR] 0.50, 95% confidence interval [CI] 0.41-0.53) with a concurrent increase in targeted aspirin use in women classified as high risk for pre-eclampsia (28.9 versus 99.0%, OR 241.6, 95% CI 89.6-652.0). Screening indices were uniformly improved for the FMF algorithm with receiver operating characteristic (ROC) analysis demonstrating excellent discrimination for preterm pre-eclampsia (area under the curve [AUC] = 0.846, 95% CI 0.778-0.915, P value <.001). Interrupted time series analysis showed that the FMF screening programme resulted in a significant 21-month relative effect reduction of 80% (P = .025) and 89% (P = .017), for preterm and early pre-eclampsia, respectively.

CONCLUSIONS

First trimester combined screening for pre-eclampsia is both feasible and effective in a public healthcare setting. Such an approach results in a two-fold de-escalation of risk, doubling of pre-eclampsia detection, near total physician compliance of aspirin use and a significant reduction in the prevalence of preterm pre-eclampsia.

TWEETABLE ABSTRACT

Implementation of 1st trimester combined pre-eclampsia screening effectively reduces prevalence of the disorder.

New Male Specific Markers for Hop and Application in Breeding Program

Male specific DNA sequences were selected from a Diversity Arrays Technology (DArT) mapping study to evaluate their suitability for determination of the sex phenotype among young seedlings in a hop (Humulus lupulus L.) breeding program. Ten male specific DArT markers showed complete linkage with male sex phenotype in three crossing families. Following optimization, four were successfully converted into PCR markers and a multiplex PCR approach for their use was developed. Among 197 plants (97 from the world collection; 100 from three segregating families), 94-100% positive correlation with sex phenotypic data was achieved for the single PCR amplification, whereas the multiplex approach showed 100% correlation. To develop a fast and low-cost method, crude sample multiplex PCR was evaluated in 253 progenies from 14 segregating populations without losing accuracy. The study describes, for the first time, the routine application of molecular markers linked to male sex in an intensive Slovenian hop breeding program. The methods described could be employed for screening of sex at the seedling stage in other hop programs worldwide, thereby saving resources for desirable female plants.

Surface phosphonation enhances hydroxyapatite coating adhesion on polyetheretherketone and its osseointegration potential

Polyetheretherketone (PEEK) has excellent mechanical properties, biocompatibility, chemical resistance and radiolucency, making it suitable for use as orthopedic implants. However, its surface is hydrophobic and bioinert, and surface modification is required to improve its bioactivity. In this work, we showed that grafting phosphonate groups via diazonium chemistry enhances the bioactivity of PEEK. Decreased contact angle indicated reduced hydrophobicity as a result of the treatment and X-ray photoelectron spectroscopy (XPS) confirmed the attachment of phosphonate groups to the surface. The surface treatment not only accelerated hydroxyapatite (HA) deposition after immersion in simulated body fluid but also significantly increased the adhesion strength of HA particles on PEEK. MC3T3-E1 cell viability, metabolic activity and deposition of calcium-containing minerals were also enhanced by the phosphonation. After three months of implantation in a critical size calvarial defect model, a fibrous capsule surrounded untreated PEEK while no fibrous capsule was observed around the treated PEEK. Instead, mineral deposition was observed in the region between the treated PEEK implant and underlying bone. This work introduces a simple method to improve the potential of PEEK-based orthopedic implants.

STATEMENT OF SIGNIFICANCE

We have introduced phosphonate groups on the surface of PEEK substrates using diazonium chemistry. Our results show that the treatment not only increased the adhesion strength of hydroxyapatite particles deposited on PEEK in vitro by approximately 40% compared to unmodified PEEK, but also improved the metabolic activity and mineralization of MC3T3-E1 cells. When implanted in cranial defects in rats, the phosphonate coating enhanced the osseointegration of PEEK by successfully preventing the formation of a fibrous capsule and favoring mineral deposition between the implant and the surrounding bone. This work introduces a simple method to improve the potential of PEEK-based orthopedic implants, particularly those with complex shapes.

Heterogeneous reduction of 239PuO2 by aqueous Fe(II) in the presence of hematite

The reduction of PuO2(am) by Fe(II) in the presence and absence of hematite was studied over a range of pH values and oxidation/reduction potentials. In contrast to thermodynamic predictions, the presence of hematite did not have a major effect on the overall reduction of PuO2(am) to aqueous Pu(III). Instead the aqueous Pu(III) concentrations at longer time frames were accurately predicted using the measured Fe(II) concentration and existing thermodynamic data for the reaction: H2O + H++ Fe2++ PuO2(am) ⇌ Pu3++ Fe(OH)3(am) with log K =− 0.6. The accuracy of this approach in all solutions containing aqueous Fe(II), coupled with the apparent lack of oxidation of Fe(II) by O2(g), suggests that the Fe(OH)3(am) is formed by the oxidation of Fe(II) to Fe(III) by radiolysis. The continued generation of reactive amorphous iron hydroxide by radiolysis prevents thermodynamic equilibrium from being reached with more stable ferric oxide compounds, except possibly under acidic conditions where amorphous ferric hydroxide is soluble. The use of measured pe values, instead of aqueous Fe(II) measurements, also yields reasonable predictions of the final Pu(III) concentrations although the predictions are more uncertain.

Genetic diversity of Iranian soft-seed pomegranate genotypes as revealed by fluorescent-AFLP markers

The amplified fragment length polymorphism (AFLP) technique was used to examine the genetic relationships among 21 Iranian soft-seeded pomegranate (Punica granatum L.) genotypes. Out of 72 fluorescent-AFLP primer combinations screened, 31 were selected to produce the 503 polymorphic markers used in this study. Genetic similarity estimates between genotypes, calculated by the Jaccard's similarity coefficient, ranged from 0.17 to 1.00, while the cophenetic correlation coefficient between the genetic similarities and the unweighted pair group method of arithmetic averages (UPGMA) dendrogram was 0.98. The AFLP-based UPGMA dendrogram revealed two groups within the genotypes at 0.33 similarity coefficient, which reflect fruit traits such as peel and aril color, and seed firmness, as well as region of origin. Our study shows that the use of molecular markers is essential during all steps of germplasm management to avoid genotype redundancy and mislabeling. The present study will be used as a reliable reference to discriminate among these genotypes, to aid management of germplasm collections used to breed new varieties for the Iranian pomegranate industry.

A drug resistance screen using a selective MET inhibitor reveals a spectrum of mutations that partially overlap with activating mutations found in cancer patients

The emergence of drug resistance is a primary concern in any cancer treatment, including with targeted kinase inhibitors as exemplified by the appearance of Bcr-Abl point mutations in chronic myeloid leukemia (CML) patients treated with imatinib. In vitro approaches to identify resistance mutations in Bcr-Abl have yielded mutation spectra that faithfully recapitulated clinical observations. To predict resistance mutations in the receptor tyrosine kinase MET that could emerge during inhibitor treatment in patients, we conducted a resistance screen in BaF3 TPR-MET cells using the novel selective MET inhibitor NVP-BVU972. The observed spectrum of mutations in resistant cells was dominated by substitutions of tyrosine 1230 but also included other missense mutations and partially overlapped with activating MET mutations that were previously described in cancer patients. Cocrystallization of the MET kinase domain in complex with NVP-BVU972 revealed a key role for Y1230 in binding of NVP-BVU972, as previously reported for multiple other selective MET inhibitors. A second resistance screen in the same format with the MET inhibitor AMG 458 yielded a distinct spectrum of mutations rich in F1200 alterations, which is consistent with a different predicted binding mode. Our findings suggest that amino acid substitutions in the MET kinase domain of cancer patients need to be carefully monitored before and during treatment with MET inhibitors, as resistance may preexist or emerge. Compounds binding in the same manner as NVP-BVU972 might be particularly susceptible to the development of resistance through mutations in Y1230, a condition that may be addressed by MET inhibitors with alternative binding modes.

Corrosion Mechanisms of Spent Fuel Under Oxidizing Conditions

The release of99Tc can be used as a reliable marker for the extent of spent oxide fuel reaction under unsaturated high-drip-rate conditions at 90°C. Evidence from leachate data and from scanning and transmission electron microscopy (SEM and TEM) examination of reacted fuel samples is presented for radionuclide release, potential reaction pathways, and the formation of alteration products. In the ATM-103 fuel, 0.03 of the total inventory of99Tc is released in 3.7 years under unsaturated and oxidizing conditions. Two reaction pathways that have been identified from SEM are 1) through-grain dissolution with subsequent formation of uranyl alteration products, and 2) grain-boundary dissolution. The major alteration product identified by X-ray diffraction (XRD) and SEM, is Na-boltwoodite, Na[(UO2)(SiO3OH)]H20, which is formed from sodium and silicon in the water leachant.

A Type I Insulin-Like Growth Factor Receptor Kinase Inhibitor (PQIP) Enhances the Cytotoxicity of Doxorubicin in Human Cancer Cell Lines

The type-I insulin like growth factor (IGF-IR) is either activated and/or overexpressed in a wide range of tumor types and contributes to tumorigenicity, proliferation, survival, metastasis and drug resistance. Disruption of IGF-IR signaling alone or in combination with other cytotoxic agents has emerged as an important strategy in cancer therapy. Our laboratory has shown that sequentially combining doxorubicin with anti-IGF-IR antibodies significantly enhances the response of chemotherapy, while the opposite sequence causes cells resistant to chemotherapy. Here, we show that a novel small-molecule IGF-IR kinase inhibitor, cis-3-[3-(4-methyl-piperazin-l-yl)-cyclobutyl]-1-(2-phenyl-quinolin-7-yl)-imidazo[1,5-a]pyrazin-8-ylamine (PQIP) inhibited IGF-IR and insulin receptor (IR) kinase activity and proliferation in MCF-7 and MDA435/LCC6 cell lines. Moreover, PQIP treatment blocked both IGF-I and insulin stimulated activation of mitogen-activated protein kinase and phosphatidylinositol 3-kinase in both cell lines. At doses that inhibited monolayer cell growth, the compound also inhibited cell motility, blocked IGF-I stimulated S-phase progression and induced autophage; at higher doses, it also caused PARP cleavage. Combining PQIP with doxorubicin significantly enhanced cytotoxicity but did not further enhance doxorubicin-induced PARP cleavage in monolayer cell growth. Furthermore, our sequencing studies showed that combining PQIP with doxorubicin simultaneously or doxorubicin followed by PQIP significantly inhibited the anchorage-independent growth in both MCF-7 and MDA435/LCC6 cells. In contrast, pre-treatment with PQIP followed by doxorubicin did not enhance the cytotoxicity of doxorubicin in anchorage-independent growth, which is similar as anti-IGF-IR antibodies in combination with doxorubicin. In summary, these results suggest that the IGF-IR tyrosine kinase inhibitor PQIP can be used alone or in combination with chemotherapy to enhance cytotoxicity of human tumor cell lines, and the timing of IGF-IR inhibition may affect responses to doxorubicin.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6110.

Preventive effects of the EGFr inhibitor erlotinib in ER+ methylnitrosourea (MNU) induced and in ER- MMTV/Neu/P53KO mammary cancer models

Abstract #1112

The preventive/therapeutic efficacies of Erlotinib in both ER+ and ER- models of breast cancer in rats and mice, respectively, were evaluated. For the ER+ model, female Sprague-Dawley rats were administered MNU at 50 days of age. Beginning five days later, Erlotinib was administered 7x/week for the remainder of the study. Daily administration of Erlotinib in a prevention setting at 4 and 1.33 mg/kg BW/day reduced tumor multiplicity by 72 and 35%, respectively; doses &gt;6 mg/kg BW/day decreased cancers by &gt;90%. When rats with palpable mammary cancers were treated for six weeks with 4 mg/kg BW/day of Erlotinib, most of the tumors showed highly significantly regressions. Similarly, when rats bearing palpable mammary cancers were treated with Erlotinib for 5 days (3 or 1 mg/kg BW/day), large decreases in tumor cell proliferation and alterations in expression of phosphorylated EGFr, AKT, ERK and SHC were observed. In additional studies, the preventive effect of Erlotinib in a MMTV/Neu/P53KO bitransgenic model was examined. These mice develop ER- cancers which overexpress Neu and have an alteration in P53. These changes are characteristic of ER- human breast cancers. An initial experiment showed that Erlotinib (50 mg/Kg BW/day) was also effective as a preventive agent in this model. Effects of this agent on proliferation and altered expression of phosphorylated EGFr, AKT, ERK and SHC are in progress. Our results showing efficacy of the EGFr inhibitor Erlotinib in ER+ mammary cancers are in agreement with a clinical study of early stage human ER+ breast cancer showing that the EGFr inhibitor Gefitinib is highly effective in ER+/EGFr+ tumors (Polychronis, et al., Lancet Oncolo.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 1112.

Analysis of inhibitory action of modified U1 snRNAs on target gene expression: discrimination of two RNA targets differing by a 1 bp mismatch

The modified U1 snRNA gene can suppress expression of a target transgene. In the present study, its potential utility to inhibit a dominant negative/gain of function mutation is explored. Using a green fluorescent protein (GFP) target gene, inhibition was achieved in all cells transduced with U1antiGFP directed at multiple sites within GFP. Using a chloramphenicol acetyltransferase (CAT) target gene, inhibition was not increased by increasing the hybridization domain from 10 to 16 bp or when a site in an upstream exon or intron was targeted. To determine if a U1 anti-target design could discriminate between two transcripts that differ by a 1-2 bp mismatch, GFPtpz and GFPsaph were chosen as targets because they share sequence homology except for three regions where a 1, 2 or 3 bp mismatch exists. The results demonstrated that U1antiGFP correctly reduced its cognate GFP expression by >90% and therefore U1 anti-target constructs are able to discriminate a 1 or 2 bp mismatch in their target mRNA. Thus, these U1 anti-target constructs may be effective in a strategy of somatic gene therapy for a dominant negative/gain of function mutation due to the discreteness of its discrimination. It may complement other anti-target strategies to reduce the cellular load of a mutant transcript.

Modular design of Gbeta as the basis for reversible specificity in effector stimulation

The G protein Gbetagamma subunit complex stimulates effectors by direct interactions utilizing extensive Gbeta regions over the surface of its propeller structure that faces the Galpha subunit. Our previous experiments have shown the resolved functions of signal transfer and general binding for Gbeta regions involved in stimulation of the effector phospholipase C-beta2, PLC-beta2, within the region Gbeta-(86-135), which comprises three beta strands arranged in a structurally contiguous fashion (Buck, E., Li, J., Chen, Y., Weng, G., Sacarlata, S., and Iyengar, R. (1999) Science 283, 1332-1335). This raises an important question as to why mutagenesis studies indicate that an extensive set of sites all over the Gbeta propeller structure and outside the 86-135 region are involved in Gbeta regulation of PLC-beta2. Using peptides to define functions of these Gbeta regions, we find that Gbeta signaling to PLC-beta2 relies on a collection of modular signal transfer and general binding units, each with lower apparent affinity relative to Gbetagamma-PLC interactions. Gbeta-(42-54) functions as a signal transfer region, Gbeta-(228-249) and Gbeta-(321-340) function in general binding, and Gbeta-(64-84) and Gbeta-(300-313) seem to play a structural role rather than a direct contact with the effector. A substitution within the Gbeta-(42-54) signal transfer region that increases the K(act) of this peptide for PLC-beta2 is accompanied by an increase in the observed maximal extent of signal transfer. We conclude that the lower K(act) for individual signal transfer regions may result in a decrease in the maximal effect of signal transfer. The spatial resolution of the signal transfer and general binding regions over a wide surface of Gbeta allow geometrical constraints to achieve specificity even with relatively low affinity interactions.

Falsifying mental models: testing the predictions of theories of syllogistic reasoning

Four experiments are reported that tested the claim, drawn from mental models theory, that reasoners attempt to construct alternative representations of problems that might falsify preliminary conclusions they have drawn. In Experiment 1, participants were asked to indicate which alternative conclusion(s) they had considered in a syllogistic reasoning task. In Experiments 2-4, participants were asked to draw diagrams consistent with the premises, on the assumption that these diagrams would provide insights into the mental representation being used. In none of the experiments was there any evidence that people constructed more models for multiple-model than for single-model syllogisms, nor was there any correlation between number of models constructed and overall accuracy. The results are interpreted as showing that falsification of the kind proposed by mental models theory may not routinely occur in reasoning.

Resolution of a signal transfer region from a general binding domain in gbeta for stimulation of phospholipase C-beta2

Signaling by guanine nucleotide-binding proteins (G proteins) involves sequential protein-protein interactions. G protein-betagamma subunit (Gbetagamma) interactions with phospholipase C-beta2 (PLC-beta2) were studied to determine if all Gbeta contacts are required for signaling. A peptide encoding Gbeta amino acid residues 86 to 105 stimulated PLC-beta2. Six residues (96 to 101) within this sequence could transfer signals and thus constitute a core signal transfer region. Another peptide, encoding Gbeta amino acid residues 115 to 135, did not substantially stimulate PLC-beta2 by itself but inhibited Gbetagamma stimulation, indicating that residues 115 to 135 constitute a general binding domain. Resolution of signal transfer regions from general binding domains indicates that all protein-protein contacts are not required for signal transfer and that it may be feasible to synthesize agonists and antagonists that regulate intracellular signal flow.

Exercise and dietary cholesterol alter rat myocardial capillary ultrastructure

The effects of a cholesterol-rich diet and exercise training on the myocardial capillary network and capillary ultrastructure were examined using Sprague-Dawley rats subjected to a 7-week exhaustive swimming scheme. A total of 16 animals were randomly divided into four groups consisting of normal dietinactive, normal dietexercise, cholesterol dietinactive, and cholesterol dietexercise. Following the experimental regimen the largest heart-mass-to-body-mass ratios were measured for the exercised rats fed a normal diet and the smallest ratios were found for the cholesterol-fed inactive rats. The capillary-to-fiber ratios and the capillary densities of the exercise-trained animals fed normal and cholesterol-containing diets were higher than those of either of the inactive groups. Diet and exercise had significant and opposing effects on the number of capillary pinocytotic vesicles and no significant effect on vesicle size. The capillary endothelium of the exercise-trained animal groups occupied a smaller proportion of the capillary area when compared to diet-matched inactive groups. The results of this study imply that exercise training and a cholesterol-containing diet have opposite effects on the heart-mass-to-body-mass ratio and capillary pinocytotic vesicle number. Furthermore, exercise increases the capillary network of the myocardium and may facilitate receptor-mediated transport in heart capillaries.

Porphyrin induced calcium release from skeletal muscle sarcoplasmic reticulum

Micromolar concentrations of the porphyrin mesotetra(4-N-methylpyridyl)porphine tetraiodide is shown to induce rapid release of Ca2+ from skeletal muscle sarcoplasmic reticulum vesicles. Porphyrin-induced Ca2+ release is stimulated by ATP (KdATP = 100 microM) and Ca2+ (KdCa = 1 microM) and is inhibited by Mg2+ (KI = 220 microM) and ruthenium red (KI = 7 nM). The porphyrin is also shown to stimulate high affinity [3H]ryanodine binding by decreasing the dissociation constant (kd) and increasing the binding capacity (Bmax). Moreover, in the presence of Mg2+, receptor binding is sensitized to activation by Ca2+, and porphyrin-stimulated channel activity is sensitized to activation by Ca2+. These observations show that porphyrin-induced Ca2+ release is due to a direct interaction with the Ca2+ release protein from sarcoplasmic reticulum.

Ryanodine induces persistent inactivation of the Ca2+ release channel from skeletal muscle sarcoplasmic reticulum

Junctional sarcoplasmic reticulum (SR) membranes isolated from rabbit skeletal muscle were pretreated with 0.1-500 microM ryanodine under equilibrium conditions optimal for receptor binding, followed by the removal of bound alkaloid by several washes in Ca(2+)- and ryanodine-free buffer. Pretreatment with > 100 nM ryanodine results in a concentration-dependent decrease in the Bmax of the high affinity sites and a complete loss of measurable low affinity binding sites that persist for > 48 hr. Quantitative analysis of residual ryanodine using three different methods demonstrates that the inhibition is not the result of residual ryanodine bound to its receptor. Ca2+ transport measurements made with antipyrylazo III show that actively loaded ryanodine-pretreated SR exhibits a persistent insensitivity to ryanodine- and daunomycin-induced Ca2+ release that is not seen with washed control vesicles. Lipid bilayer membranes fused with SR vesicles exhibit rapidly fluctuating single-channel events with a conductance of 468 pS in asymmetric CsCl solutions. Ryanodine (10 microM) produces a unidirectional transition to a slowly fluctuating half-conductance state that is not reversed by perfusion of the bilayer with Ca(2+)-free buffer and subsequent addition of dithiothreitol. However, dithiothreitol added in the ryanodine pretreatment medium offers marked protection against ryanodine-induced loss of binding sites and allows complete restoration of native gating behavior of single channels in bilayer lipid membrane. Using three different experimental approaches, the data demonstrate that the alkaloid at micromolar concentration persistently alters SR Ca2+ release channel function, perhaps by uncoupling four negatively cooperative binding sites. The oxidation of critical receptor thiols is implicated in the process.

Ryanodine stabilizes multiple conformational states of the skeletal muscle calcium release channel

Nanomolar to micromolar ryanodine alters the gating kinetics of the Ca2+ release channel from skeletal sarcoplasmic reticulum (SR) fused with bilayer lipid membranes (BLM). In the presence of asymmetric CsCl and 100 microM CaCl2 cis, ryanodine (RY) (5-40 nM) activates the channel, increasing the open probability (po; maximum 300% of control) without changing unitary conductance (468 picosiemens (pS)). Statistical analyses of gating kinetics reveal that open and closed dwell times exhibit biexponential distributions and are significantly modified by nanomolar RY. Altered channel gating kinetics with low nanomolar RY is fully reversible and correlates well with binding kinetics of nanomolar [3H]RY with its high affinity site (Kd1 = 0.7 nM) under identical experimental conditions. RY (20-50 nM) induces occasional 1/2 conductance fluctuations which correlate with [3H]RY binding to a second site having lower affinity (Kd2 = 23 nM). RY (5-50 nM) in the presence of 500 mM CsCl significantly enhances Ca(2+)-induced Ca2+ release from actively loaded SR vesicles. Ryanodine > or = 50 nM stabilizes the channel in a 234-pS subconductance which is not readily reversible. RY (> or = 70 microM) produces a unidirectional transition from the 1/2 to a 1/4 conductance fluctuation, whereas RY > or = 200 microM causes complete closure of the channel. The RY required for stabilizing 1/4 conductance transitions and channel closure do not quantitatively correlate with [3H]RY equilibrium binding constants and is attributed to significant reduction in association kinetics with > 200 nM [3H]RY in the presence of 500 mM CsCl. These results demonstrate that RY stabilizes four discrete states of the SR release channel and supports the existence of multiple interacting RY effector sites on the channel protein.

Rose bengal activates the Ca2+ release channel from skeletal muscle sarcoplasmic reticulum

The photooxidizing xanthene dye rose bengal (10 nM to 1 microM) stimulates rapid Ca2+ release from skeletal muscle sarcoplasmic reticulum vesicles. Following fusion of sarcoplasmic reticulum (SR) vesicles to an artificial bilayer, reconstituted Ca2+ channel activity is stimulated by nanomolar concentrations of rose bengal in the presence of a broad-spectrum light source. Rose bengal does not appear to affect K+ channels present in the SR. Following reconstitution of the sulfhydryl-activated 106-kDa Ca2+ channel protein into a bilayer, rose bengal activates the isolated protein in a light-dependent manner. Ryanodine at a concentration of 10 nM is shown to lock the 106-kDa channel protein in a subconductance state which can be reversed by subsequent addition of 500 nM rose bengal. This apparent displacement of bound ryanodine by nanomolar concentrations of rose bengal is also directly observed upon measurement of [3H]ryanodine binding to JSR vesicles. These observations indicate that photooxidation of rose bengal causes a stimulation of the Ca2+ release protein from skeletal muscle sarcoplasmic reticulum by interacting with the ryanodine binding site. Furthermore, similar effects of rose bengal on isolated SR vesicles, on single channel measurements following fusion of SR vesicles, and following incorporation of the isolated 106-kDa protein strongly implicates the 106-kDa sulfhydryl-activated Ca2+ channel protein in the Ca2+ release process.

Ethanol reduces tolerance, sensitization, and up-regulation of D2-receptors after subchronic haloperidol

To study the interrelationships between dopamine D2-receptor density and behavioral responses after chronic treatment with neuroleptics female Wistar rats received haloperidol (HP; 14 mg/l), ethanol (ETOH; 5 vol.%), a combination of both, or tap water as drinking fluids for one or two weeks. Mean intake doses ranged between 1.28 and 1.48 mg/kg/day (HP) and between 3.7 and 4.8 g/kg/day (ETOH). HP administered for one or two weeks raised the number of [3H]spiroperidol binding sites in the striatum by 55%. Concomitant administration of ETOH diminished the increase of Bmax to 23%. The up-regulation was even reversed when ETOH was added with a delay of one week, although the drug alone had no effect on dopamine-D2-receptor density. KD values were not substantially affected. During HP treatment the rats established a tolerance to the motor sedation which was measured by circadian motility recordings. Coadministration of ETOH reduced the development of tolerance, the activity remained at a depressed level. Acute applications of HP (0.3, 0.6, and 0.9 mg/kg, or saline, respectively) also revealed tolerance to the drug for various behavioral responses (exploratory locomotion, rearing, rotarod performance, catalepsy). The tolerance was reduced in all those animals which had received combinations of ETOH and HP. The reduction was most pronounced for the cataleptic response. Pretreatment with ETOH alone had no effect. Sensitization to dopamine agonists was studied by apomorphine-induced stereotypies (licking, sniffing, and forepaw scratching). As expected, chronic HP enhanced the responses. The increased number of stereotypies was reduced in rats pretreated with the combination, although ETOH alone did not affect the response. The reduction was most pronounced for licks.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism of anthraquinone-induced calcium release from skeletal muscle sarcoplasmic reticulum

The anthraquinones, doxorubicin, mitoxantrone, daunorubicin and rubidazone are shown to be potent stimulators of Ca2+ release from skeletal muscle sarcoplasmic reticulum (SR) vesicles and to trigger transient contractions in chemically skinned psoas muscle fibers. These effects of anthraquinones are the direct consequence of their specific interaction with the [3H] ryanodine receptor complex, which constitutes the Ca2+ release channel from the triadic junction. In the presence of adenine nucleotides and physiological Mg2+ concentrations (approximately 1.0 mM), channel activation by doxorubicin and daunorubicin exhibits a sharp dependence on submicromolar Ca2+ which is accompanied by a selective, dose-dependent increase in the apparent affinity of the ryanodine binding sites for Ca2+, in a manner similar to that previously reported with caffeine. Unlike caffeine, however, anthraquinones increase [3H]ryanodine receptor occupancy to the level observed in the presence of adenine nucleotides. A strong interaction between the anthraquinone and the caffeine binding sites on the Ca2+ release channel is also observed when monitoring Ca2+ fluxes across the SR. Millimolar caffeine both inhibits anthraquinone-stimulated Ca2+ release, and reduces anthraquinone-stimulated [3H]ryanodine receptor occupancy, without changing the effective binding constant of the anthraquinone for its binding site. The degree of cooperativity for daunorubicin activation of Ca2+ release from SR also increases in the presence of caffeine. These results demonstrate that the mechanism by which anthraquinones stimulate Ca2+ release is caused by a direct interaction with the [3H]ryanodine receptor complex, and by sensitization of the Ca2+ activator site for Ca2+.

Behavior of somatostatin-immunoreactive cells in the gastric mucosa before and after selective proximal vagotomy and pyloroplasty in treatment of gastric and duodenal ulcers

Antral somatostatin-immunoreactive cells (D cells) were counted pre- and postoperatively in 20 patients with duodenal ulcer and in 8 patients with gastric ulcer. Counts were obtained either over a 2-yr postoperative period (duodenal ulcer patients) at intervals of 0.5, 1, and 2 yr or over a greater than or equal to 4-yr postoperative period (gastric ulcer patients) at intervals of 1-2 yr. In patients with a normal population of gastrin-immunoreactive cells (G cells), the D cells were within the normal range (mean value 0.53% in duodenal ulcer patients and 0.67% in gastric ulcer patients). High G-cell values were accompanied by high D-cell values (e.g., in gastrin-cell hyperplasia) and low G-cell values were accompanied by low D-cell values. The G-cell to D-cell ratio was 8:1 and 6.6:1 in duodenal and gastric ulcer patients, respectively. After selective proximal vagotomy and pyloroplasty, the following observations were made: the relation of number of G cells to number of D cells remained unchanged; the postoperative rise in G-cell population was accompanied by a rise in D-cell population; hypertrophy of the D cells was apparent as was postoperative hyperplasia, with a postoperative increase in D-cell size. Morphologic coupling of the gastrin-somatostatin system in the antrum is assumed. This is constant in ulcer disease both before and after vagotomy.