The role of Kölliker-Fuse nucleus in breathing variability

The Kölliker-Fuse nucleus (KF), which is part of the parabrachial complex, participates in the generation of eupnea under resting conditions and the control of active abdominal expiration when increased ventilation is required. Moreover, dysfunctions in KF neuronal activity are believed to play a role in the emergence of respiratory abnormalities seen in Rett syndrome (RTT), a progressive neurodevelopmental disorder associated with an irregular breathing pattern and frequent apneas. Relatively little is known, however, about the intrinsic dynamics of neurons within the KF and how their synaptic connections affect breathing pattern control and contribute to breathing irregularities. In this study, we use a reduced computational model to consider several dynamical regimes of KF activity paired with different input sources to determine which combinations are compatible with known experimental observations. We further build on these findings to identify possible interactions between the KF and other components of the respiratory neural circuitry. Specifically, we present two models that both simulate eupneic as well as RTT-like breathing phenotypes. Using nullcline analysis, we identify the types of inhibitory inputs to the KF leading to RTT-like respiratory patterns and suggest possible KF local circuit organizations. When the identified properties are present, the two models also exhibit quantal acceleration of late-expiratory activity, a hallmark of active expiration featuring forced exhalation, with increasing inhibition to KF, as reported experimentally. Hence, these models instantiate plausible hypotheses about possible KF dynamics and forms of local network interactions, thus providing a general framework as well as specific predictions for future experimental testing.

Key points

The Kölliker-Fuse nucleus (KF), a part of the parabrachial complex, is involved in regulating normal breathing and controlling active abdominal expiration during increased ventilation. Dysfunction in KF neuronal activity is thought to contribute to respiratory abnormalities seen in Rett syndrome (RTT). This study utilizes computational modeling to explore different dynamical regimes of KF activity and their compatibility with experimental observations. By analyzing different model configurations, the study identifies inhibitory inputs to the KF that lead to RTT-like respiratory patterns and proposes potential KF local circuit organizations. Two models are presented that simulate both normal breathing and RTT-like breathing patterns. These models provide plausible hypotheses and specific predictions for future experimental investigations, offering a general framework for understanding KF dynamics and potential network interactions.

809 An Allogenic Fat-First Approach to Burn Reconstruction Mitigates Adhesion and Soft Tissue Deficit

Introduction

Adipose and adipose-derived stem cell therapies have met success as adjunctive treatment during burn reconstruction with well described benefit in the delayed-treatment of soft-tissue deficits. While the use of allogeneic skin is well-described, adipose tissues have typically remained autologous. Allogenic fat is not commonly used in burn care, however, in large, complex burns where autologous tissue is limited adipose may not be readily available for harvest or use. Understanding the efficacy of allogeneic tissues in this setting is critical to expand our reconstructive options. Here we describe a protocol utilizing allogeneic fat as well as examine the efficacy of this approach on burn-wound contractures, adhesions, and soft-tissue deficits.

Methods

Female, Yorkshire swine received 16, 4x4 cm full-thickness burns. After 48 hours, eschar was removed to fascia. Wounds were stratified to receive either A) No Reconstruction, B) Skin-Only, C) Fat-Only, D) Immediate-Skin, Delayed-Fat, or E) Immediate-Fat, Delayed-Skin. All fat utilized was allogeneic sourced from vendor-matched swine. At 8-weeks post-engraftment animals were sacrificed and all wounds were collected for photography, ultrasound, histology and serum studies.

Results

Use of allogeneic fat significantly improved terminal soft-tissue thickness under both immediate and delayed administration (p< 0.05). Immediate use of allogeneic fat significantly improved tissue mobility vs. untreated and skin graft controls (p< 0.05). Contracture was most significantly affected by timing of skin graft placement, however, could be further mitigated under standard delayed-fat approached with allogeneic tissue.

Conclusions

Here we demonstrate use of allogeneic fat in both traditional-delayed and a fat-first approach with significant mitigation of adhesion when applied as an initial basal layer. Both immediate and delayed allogeneic fat were sufficient to improve on soft tissue deficits.

Exercise to Mend Aged-tissue Crosstalk in Bone Targeting Osteoporosis & Osteoarthritis

Aging induces alterations in bone structure and strength through a multitude of processes, exacerbating common aging- related diseases like osteoporosis and osteoarthritis. Cellular hallmarks of aging are examined, as related to bone and the marrow microenvironment, and ways in which these might contribute to a variety of age-related perturbations in osteoblasts, osteocytes, marrow adipocytes, chondrocytes, osteoclasts, and their respective progenitors. Cellular senescence, stem cell exhaustion, mitochondrial dysfunction, epigenetic and intracellular communication changes are central pathways and recognized as associated and potentially causal in aging. We focus on these in musculoskeletal system and highlight knowledge gaps in the literature regarding cellular and tissue crosstalk in bone, cartilage, and the bone marrow niche. While senolytics have been utilized to target aging pathways, here we propose non-pharmacologic, exercise-based interventions as prospective "senolytics" against aging effects on the skeleton. Increased bone mass and delayed onset or progression of osteoporosis and osteoarthritis are some of the recognized benefits of regular exercise across the lifespan. Further investigation is needed to delineate how cellular indicators of aging manifest in bone and the marrow niche and how altered cellular and tissue crosstalk impact disease progression, as well as consideration of exercise as a therapeutic modality, as a means to enhance discovery of bone-targeted therapies.

Tailored communication intervention in a Somali community, Sweden, to improve vaccine confidence

Background

Sweden sustains a high and stable vaccination coverage for measles-mumps-rubella (MMR) vaccination (&gt;96%) but despite a high national coverage, there may be local gaps. One example is a Stockholm suburb hosting a population with largely Somali origin that since 1998 has showed low MMR vaccine rates (70%). A baseline study using the Tailoring Immunisation Programme (TIP), child health clinics (CHC) nurses reported poor communication with vaccine hesitant parents who worried that the MMR vaccine may cause autism. Following, a tailored intervention with emphasis on strong and preferred oral communication was designed to address parentś concerns and, seminars to reinforce nurses in improving their encounter with parents.

Methods

The intervention was developed using the TIP guide including an adapted version of the Behaviour Change Wheel model, it included communication tools (films, videos), public seminars in Somali on MMR vaccine, vaccine-preventable diseases and autism, and training of peer parent group. CHC nurses were given tailored seminars with updated information on vaccines with emphasis on how to communicate with vaccine hesitant parents.

Results

Preliminary results suggest that the tools implemented have been well received by all stakeholders and a positive trend in vaccination coverage has been observed. Parents have engaged actively, 32 parents completed the peer-to-peer training and all nurses attended the seminars. Preliminary data of qualitative interviews with 11 nurses indicates that increased knowledge strengthened their confidence to meet the parents and address vaccine hesitancy. The films and information materials facilitated the nursés communication with parents.

Conclusions

Tailored communication interventions need to be tested, implemented and evaluated as tools to motivate change in parental attitudes and to strengthened health care providers role aiming to increase vaccine acceptance and resilience in the immunisation programmes.

Key messages

Tailored communication intervention on vaccination need to be implemented and evaluated as tools to motivate changes in attitudes and behaviours regarding vaccine acceptance. Tailored interventions has been positively received by all target groups and a positive trend in vaccination coverage has been observed.

Union of the European Phoniatricians' position statement on the exit strategy of phoniatric and laryngological services: staying safe and getting back to normal after the peak of coronavirus disease 2019 (issued on 25th May 2020)

BACKGROUND

The following position statement from the Union of the European Phoniatricians, updated on 25th May 2020 (superseding the previous statement issued on 21st April 2020), contains a series of recommendations for phoniatricians and ENT surgeons who provide and/or run voice, swallowing, speech and language, or paediatric audiology services.

OBJECTIVES

This material specifically aims to inform clinical practices in countries where clinics and operating theatres are reopening for elective work. It endeavours to present a current European view in relation to common procedures, many of which fall under the aegis of aerosol generating procedures.

CONCLUSION

As evidence continues to build, some of the recommended practices will undoubtedly evolve, but it is hoped that the updated position statement will offer clinicians precepts on safe clinical practice.

Recovery of stem cell proliferation by low intensity vibration under simulated microgravity requires LINC complex

Mesenchymal stem cells (MSC) rely on their ability to integrate physical and spatial signals at load bearing sites to replace and renew musculoskeletal tissues. Designed to mimic unloading experienced during spaceflight, preclinical unloading and simulated microgravity models show that alteration of gravitational loading limits proliferative activity of stem cells. Emerging evidence indicates that this loss of proliferation may be linked to loss of cellular cytoskeleton and contractility. Low intensity vibration (LIV) is an exercise mimetic that promotes proliferation and differentiation of MSCs by enhancing cell structure. Here, we asked whether application of LIV could restore the reduced proliferative capacity seen in MSCs that are subjected to simulated microgravity. We found that simulated microgravity (sMG) decreased cell proliferation and simultaneously compromised cell structure. These changes included increased nuclear height, disorganized apical F-actin structure, reduced expression, and protein levels of nuclear lamina elements LaminA/C LaminB1 as well as linker of nucleoskeleton and cytoskeleton (LINC) complex elements Sun-2 and Nesprin-2. Application of LIV restored cell proliferation and nuclear proteins LaminA/C and Sun-2. An intact LINC function was required for LIV effect; disabling LINC functionality via co-depletion of Sun-1, and Sun-2 prevented rescue of cell proliferation by LIV. Our findings show that sMG alters nuclear structure and leads to decreased cell proliferation, but does not diminish LINC complex mediated mechanosensitivity, suggesting LIV as a potential candidate to combat sMG-induced proliferation loss.

Dietary factors and pediatric multiple sclerosis: A case-control study

BACKGROUND

The role of diet in multiple sclerosis (MS) is largely uncharacterized, particularly as it pertains to pediatric-onset disease.

OBJECTIVE

To determine the association between dietary factors and MS in children.

METHODS

Pediatric MS patients and controls were recruited from 16 US centers (MS or clinically isolated syndrome onset before age 18, <4 years from symptom onset and at least 2 silent lesions on magnetic resonance imaging). The validated Block Kids Food Screener questionnaire was administered 2011-2016. Chi-squared test compared categorical variables, Kruskal-Wallis test compared continuous variables, and multivariable logistic regression analysis was performed.

RESULTS

In total, 312 cases and 456 controls were included (mean ages 15.1 and 14.4 years). In unadjusted analyses, there was no difference in intake of fats, proteins, carbohydrates, sugars, fruits, or vegetables. Dietary iron was lower in cases ( p = 0.04), and cases were more likely to consume below recommended guidelines of iron (77.2% of cases vs 62.9% of controls, p < 0.001). In multivariable analysis, iron consumption below recommended guidelines was associated with MS (odds ratio = 1.80, p < 0.01).

CONCLUSION

Pediatric MS cases may be less likely to consume sufficient iron compared to controls, and this warrants broader study to characterize a temporal relationship. No other significant difference in intake of most dietary factors was found.

VP-16, Cyclophosphamide, Adriamycin and Cis-platinum (V:CAP-I) in Patients with Metastatic Adenocarcinoma of the Lung

In an attempt to improve upon the 42% regression rate of the CAP-I regimen in patients with advanced adenocarcinoma of the lung, VP-16 was added to that regimen. VP-16, as a single agent, had a response rate of 12.5% (3/24) in a similar group of patients. The new regimen, V:CAP-I, had a tumor regression rate of 35% (7/20) and an estimated median survival of 171 days. Hence, we were unable to conclude that the addition of VP-16 to the CAP-I regimen statistically improved the regression rate of the CAP-I regimen.

15 Years of Experience with Renal Replacement Therapy in Patients Starting Therapy before Age 20

This study retrospectively evaluates the survival on renal replacement therapy among patients starting dialysis before their twentieth birthday. The cohort included all patients starting therapy from 1972 through August, 1987 at the University of Mississippi or Kidney Care, Inc. Fifty-five patients, median age 17 years, range 5-19 years, underwent 335 patient years of therapy. Nineteen initially received CAPD; 12 home hemodialysis, 2 were transplanted prior to dialysis, and the remaining 22 patients were entered into dialysis in a free standing facility. Thirty-one patients received a cadaveric transplant and four patients received a living related transplant. The median transplant survival was 1360 days. There were 10 patients on renal replacement therapy over 10 years and a survival plot projected a 70% survival at 10 years. Nine patients died. Three percent of the time on renal replacement therapy was spent hospitalized. Although the hospitalization rate is significant, the pediatric patient may be expected to have a long survival on renal replacement therapy.

Evaluating the association of allergies with multiple sclerosis susceptibility risk and disease activity in a pediatric population

BACKGROUND

Multiple sclerosis (MS) and allergies are both considered to be related to imbalanced Th1 and Th2 immune responses. Previous studies evaluating the relationship between MS and allergies provide conflicting results.

OBJECTIVE

To assess allergies and asthma as risk factors for MS and as predictors of MS relapses in a pediatric cohort.

METHODS

The environment and genetic risk factors for pediatric MS study is a national case-control project with 16 participating US sites. An environmental questionnaire is used that includes history of allergies in the first five years of life. Case-control data are entered in the pediatric MS Network database and cases at 12 of the 16 sites enter relapse data prospectively. Annualized relapse rate was calculated for patients with follow-up and adjusted for age at disease onset, gender, race, ethnicity, and use of disease-modifying therapy (DMT).

RESULTS

We included 271 cases (mean age at disease onset of 15.7years and 62% female) and 418 controls. Relapse data were available for 193 cases. There was no difference in prevalence of allergies or asthma between cases and controls. Patients with food allergies had fewer relapses compared to patients without food allergies (0.14 vs 0.48, p=0.01).

CONCLUSIONS

While allergies and asthma are not associated with pediatric MS, cases with food allergies have fewer relapses compared to those without food allergies.

Measurements of parity-violating asymmetries in electron-deuteron scattering in the nucleon resonance region

We report on parity-violating asymmetries in the nucleon resonance region measured using inclusive inelastic scattering of 5-6 GeV longitudinally polarized electrons off an unpolarized deuterium target. These results are the first parity-violating asymmetry data in the resonance region beyond the Δ(1232). They provide a verification of quark-hadron duality-the equivalence of the quark- and hadron-based pictures of the nucleon-at the (10-15)% level in this electroweak observable, which is dominated by contributions from the nucleon electroweak γZ interference structure functions. In addition, the results provide constraints on nucleon resonance models relevant for calculating background corrections to elastic parity-violating electron scattering measurements.

New precision limit on the strange vector form factors of the proton

The parity-violating cross-section asymmetry in the elastic scattering of polarized electrons from unpolarized protons has been measured at a four-momentum transfer squared Q2 = 0.624  GeV2 and beam energy E(b) = 3.48  GeV to be A(PV) = -23.80 ± 0.78(stat) ± 0.36(syst) parts per million. This result is consistent with zero contribution of strange quarks to the combination of electric and magnetic form factors G(E)(s) + 0.517G(M)(s) = 0.003 ± 0.010(stat) ± 0.004(syst) ± 0.009(ff), where the third error is due to the limits of precision on the electromagnetic form factors and radiative corrections. With this measurement, the world data on strange contributions to nucleon form factors are seen to be consistent with zero and not more than a few percent of the proton form factors.

No detection of BK virus, JC virus, KI, WU and Merkel cell polyomaviruses in cerebrospinal fluid of patients with neurological complications after hematopoetic stem cell transplantation

Neurological complications, often due to viral reactivation, after allogeneic hematopoetic stem cell transplantation (HSCT) are associated with increased mortality. Here, cerebrospinal fluid from 20 HSCT patients with neurological symptoms were analyzed and found to be negative by PCR for BK virus, JC virus, KI, WU and Merkel cell polyomavirus DNA.

Follicle-stimulating hormone and bioavailable estradiol are less important than weight and race in determining bone density in younger postmenopausal women

The association between follicle-stimulating hormone (FSH) and bone density was tested in 111 postmenopausal women aged 50-64 years. In the multivariable analysis, weight and race were important determinants of bone mineral density. FSH, bioavailable estradiol, and other hormonal variables did not show statistically significant associations with bone density at any site.

INTRODUCTION

FSH has been associated with bone density loss in animal models and longitudinal studies of women. Most of these analyses have not considered the effect of weight or race.

METHODS

We tested the association between FSH and bone density in younger postmenopausal women, adjusting for patient-related factors. In 111 postmenopausal women aged 50-64 years, areal bone mineral density (BMD) was measured at the lumbar spine, femoral neck, total hip, and distal radius using dual-energy X-ray absorptiometry, and volumetric BMD was measured at the distal radius using peripheral quantitative computed tomography (pQCT). Height, weight, osteoporosis risk factors, and serum hormonal factors were assessed.

RESULTS

FSH inversely correlated with weight, bioavailable estradiol, areal BMD at the lumbar spine and hip, and volumetric BMD at the ultradistal radius. In the multivariable analysis, no hormonal variable showed a statistically significant association with areal BMD at any site. Weight was independently associated with BMD at all central sites (p < 0.001), but not with BMD or pQCT measures at the distal radius. Race was independently associated with areal BMD at all sites (p ≤ 0.008) and with cortical area at the 33% distal radius (p = 0.004).

CONCLUSIONS

Correlations between FSH and bioavailable estradiol and BMD did not persist after adjustment for weight and race in younger postmenopausal women. Weight and race were more important determinants of bone density and should be included in analyses of hormonal influences on bone.

Steady and oscillatory fluid flows produce a similar osteogenic phenotype

Mechanical loading induces positive changes in the skeleton due to direct effects on bone cells, which may include regulation of transcription factors that support osteoblast differentiation and function. Flow effects on osteoblast transcription factors have generally been evaluated after short exposures. In this work, we assayed flow effects on osteogenic genes at early and late time points in a preosteoblast (CIMC-4) cell line and evaluated both steady and oscillatory flows. Four hours of steady unidirectional flow decreased the level of RANKL mRNA 53 ± 7% below that of nonflowed cells, but increases in Runx2 and osterix mRNA (44 ± 22% and 129 ± 12%, respectively) were significant only after 12-19 h of continuous flow. Late flow effects on RANKL and osterix were also induced by an intermittent flow-rest protocol (four cycles of 1 h on/1 h off + overnight rest). Four hours of oscillatory flow decreased RANKL mRNA at this early time point (63 ± 2%) but did not alter either osterix or Runx2. When oscillatory flow was delivered using the intermittent flow-rest protocol, Runx2 and osterix mRNA increased significantly (85 ± 19% and 161 ± 22%, respectively). Both β-catenin and ERK1/2, known to be involved in RANKL regulation, were rapidly activated by steady flow. Inhibition of flow-activated ERK1/2 prevented the increase in osterix mRNA but not Runx2; Runx2 phosphorylation was increased by flow, an effect which likely contributes to osterix induction. This work shows that both steady and oscillatory fluid flows can support enhancement of an osteogenic phenotype.

Study of arsenopyrite weathering products in mine wastes from abandoned tungsten and tin exploitations

Arsenopyrite-rich wastes from abandoned tungsten and tin exploitations were studied to determine the composition and characteristics of the secondary phases formed under natural weathering conditions so as to assess their potential environmental risk. Representative weathered arsenopyrite-bearing rock wastes collected from the mine dumps were analysed using the following techniques: X-ray powder diffraction (XRD) analysis, polarizing microscopy analysis, electron microprobe analysis (EMPA) and microRaman and Mössbauer spectroscopies. Scorodite, pharmacosiderite and amorphous ferric arsenates (AFA) with Fe/As molar ratios in the range 1.2-2.5 were identified as secondary arsenic products. The former showed to be the most abundant and present in the different studied mining areas. Its chemical composition showed to vary in function of the original surrounding rock mineralogy in such a way that phosphoscorodite was found as the mineral variety present in apatite-containing geoenvirons. Other ever-present weathering phases were goethite and hydrous ferric oxides (HFO), displaying, respectively, As retained amounts about 1 and 20% (expressed as As(2)O(5)). The low solubility of scorodite, the relatively low content of AFA and the formation of compounds of variable charge, mostly of amorphous nature, with high capacity to adsorb As attenuate importantly the dispersion of this element into the environment from these arsenopyrite-bearing wastes.

FERMENTATIVE AND PHOTOCHEMICAL PRODUCTION OF HYDROGEN IN ALGAE

1.. After 2 hours of fermentation in nitrogen the metabolism of those algae which were found capable of photoreduction with hydrogen changes in such a way that molecular hydrogen is released from the cell in addition to carbon dioxide. 2. The amount of hydrogen formed anaerobically in the dark depends on the amount of some unknown reserve substance in the cell. More hydrogen is formed in presence of added glucose, but no proportionality has been found between the amount of substrate added and that of hydrogen formed. This is probably due to the fact that two types of fermentation reactions exist, with little or no connection between them. Whereas mainly unknown organic acids are formed during the autofermentation, the addition of glucose causes a considerable increase in the production of lactic acid. 3. Algae which have been fermenting for several hours in the dark produce upon illumination free hydrogen at several times the rate observed in the dark, provided carbon dioxide is absent. 4. Certain concentrations of dinitrophenol strongly inhibit the evolution of hydrogen in the dark. Fermentation then continues mainly as a reaction leading to lactic acid. In such poisoned algae the photochemical liberation of hydrogen still continues. 5. If the algae are poisoned with dinitrophenol the presence of carbon dioxide will not interfere with the photochemical evolution of hydrogen. 6. The amount of hydrogen released in this new photochemical reaction depends on the presence of an unknown hydrogen donor in the cell; it can be increased by the addition of glucose but not in proportion to the amount added. 7. The results obtained allow for a more correct explanation of the anaerobic induction period previously described for Scenedesmus and similar algae. The possibility of a photochemical evolution of hydrogen had not been taken into account in the earlier experiments. 8. The origin of the hydrogen released under the influence of light is discussed.

Observation of the naive-T-odd Sivers effect in deep-inelastic scattering

Azimuthal single-spin asymmetries of leptoproduced pions and charged kaons were measured on a transversely polarized hydrogen target. Evidence for a naive-T-odd, transverse-momentum-dependent parton distribution function is deduced from nonvanishing Sivers effects for pi(+), pi(0), and K(+/-), as well as in the difference of the pi(+) and pi(-) cross sections.

Pancreatic neuroendocrine tumors (PNETs): incidence, prognosis and recent trend toward improved survival

BACKGROUND

Pancreatic neuroendocrine tumors (PNETs) are uncommon neoplasms that can present with symptoms of hormone overproduction. We evaluated the incidence, prognosis, and temporal trends of PNETs.

PATIENTS AND METHODS

We analyzed all cases of PNETs registered in the Surveillance, Epidemiology, and End Results database from 1973 to 2000. Age-adjusted incidence and survival rates were calculated and survival trends over time were evaluated.

RESULTS

We identified 1483 cases of PNETs. The crude annual incidence per 1,000,000 was 1.8 in females and 2.6 in males and increased with advancing age. The incidence increased over the study period. Most patients (90.8%) had nonfunctional tumors. Advanced stage, higher grade, and age were the strongest predictors of worse survival. Patients with functional tumors had better outcomes than patients with nonfunctional tumors in both univariate and multivariate analysis (P = 0.004). Survival time increased over the period from 1973 to 2000. No differences were seen in the distribution of stage or age at diagnosis among time periods.

CONCLUSION

PNETs are uncommon neoplasms but the incidence may be increasing. Age, grade, stage, and functional status predict survival in patients with PNETs. Survival has improved over time, but this is not explained by earlier diagnosis or stage migration.

Fine-scale genetic mapping of two Pierce's disease resistance loci and a major segregation distortion region on chromosome 14 of grape

A refined genetic map of chromosome 14, which contains the Pierce's disease (PD) resistance locus, was created from three grape mapping populations. The source of PD resistance in these populations was b43-17, a male form of Vitis arizonica Engelm. that is homozygous resistant. The resistance locus segregated as a single dominant gene and mapped as PdR1a in the F1 selection F8909-17 (9621 population) and as PdR1b in a sibling F1 selection F8909-08 (04190 population). These two full sibs inherited either allele of the Pierce's disease resistance locus from the b43-17 parent, which is homozygous at that locus. The 9621 population consisted of 425 progeny and PdR1a mapped between markers VvCh14-56/VvCh14-02 and UDV095 within a 0.6 cM genetic distance. The 04190 population consisted of 361 progeny and PdR1b mapped between markers VvCh14-02 and UDV095/VvCh14-10 within a 0.4 cM distance. Many of the markers present on chromosome 14 were distorted with an excess of female alleles in the 04190 and 04373 population (developed from a cross of V. vinifera L. F2-35 x b43-17) indicating that potential gametophytic factors are present in this region. Common markers from this region within the 9621 population were not distorted except Scu15. When these markers were compared to V. vinifera-based maps of chromosome 14 they were also distorted suggesting the involvement of gametophytic factors, and prompting the identification of this region as Vitis-segregation distortion region 1 (V-SDR1). The refined genetic maps developed from this study can be used to identify and clone genes that confer resistance to Pierce's disease.