California Walnut Research Articles

Urolithin A, Walnut Polyphenol Metabolite, Causes Cell Cycle Arrest and Apoptosis in Prostate and Breast Cancer Cells

The identification of new agents that may modulate the progression of cancer cell growth is of great interest. In this regard, dietary agents can be utilized to identify molecular targets to be used as part of a chemo-preventive strategy. Walnuts contain several bioactive compounds, including pedunculagin, a polyphenol metabolized by microbiota to form urolithins, namely urolithin A (UA). We performed a genomic analysis to study the effect of UA on LNCaP prostate and MCF-7 breast adenocarcinoma cells. Cells were incubated with 40µM UA for 24 hours. Then, RNA was extracted, labeled and hybridized to Affymetrix Human Gene 2.1 ST Array, representing the whole human genome. Microarray results were analyzed using the GeneSpring 12.0 software. Differentially expressed genes (p < 0.05, FC >2) were selected. In both LNCaP and MCF-7 cells, among the differentially expressed genes, we identified a decreased expression of PDK1 and an up-regulation of CDKN1A, both of which have been linked to cancer progression. In MCF-7 cells we also observed an up-regulation of PTEN. The previously mentioned changes in gene expression were validated by RT-real time PCR. Cell cycle distribution and apoptosis were measured by flow cytometry after 24h incubation with UA. An increase in apoptotic cell population and cell cycle arrest were seen in both LNCaP and MCF-7 cells. Our results indicate a potential role of walnuts as a chemo-preventive agent for prostate and breast cancer. Study funded by a grant from the California Walnut Commission

Effects of Walnut Consumption on Mood in Young Adults

Walnuts contain a number of potentially neuroprotective compounds like vitamin E, folate, melatonin, several antioxidative polyphenols and significant amounts of omega‐3 fatty acids. The present study sought to determine the effect of walnuts on mood. Sixty‐four college students were randomly assigned to two treatment sequences in a cross‐over fashion: walnut‐placebo or placebo‐walnut. Baseline data was assessed using Profiles of Mood States (POMS). Data was collected again after eight weeks of intervention. After six‐weeks of washout the intervention groups followed the diets in reverse order. Data was collected once more at the end of the eight‐week intervention period. No significant change in mood was observed in analysis that included both genders on the walnut supplemented diet. However, in gender specific analysis significant improvement was observed in males in the anger/hostility domain (p=0.013) and in the Total Mood Disturbance score (p=0.043). In young males, walnuts seem to have the ability improve some mood domains. The study was in part supported by the California Walnut Commision. The funders had no role in the implementation, data collection, management, analysis, or interpretation of the study or preparation of this publication.

Walnut Consumption Changes the Relative Abundance of Bacteroidetes and Firmicutes in the Gut

Eating walnuts is associated with health benefits that include reducing the risk of heart disease and cancer. These chronic diseases are linked to changes in the gut microbiome; for example, a shift in the abundance of Firmicutes (F) to Bacteroidetes (B). Food is also known to modulate gut microbes. One way walnuts may exert their health benefits is by altering the gut microbiome. This study investigated walnut's effects on the two major gut bacterial phyla, F and B. Male Fischer 344 rats (n=20) were randomly assigned to one of two diets for 6 or 13 weeks: 1) walnut‐enriched (W) containing approximately 2 servings, and 2) replacement (R) in which walnuts were substituted by corn oil, additional protein and fiber. After 6 or 13 weeks, fecal samples were collected from the descending colon, the DNA isolated and analyzed. The V3 hypervariable region of 16S rRNA gene was deep sequenced on an Illumina MiSeq. The data were analyzed using the UPARSE and QIIME pipeline. Body weight (W: 340+24 g vs R: 340+24 g) and food intake (W: 15.4+2.6 g/day vs R: 14.9+2.0 g/day) did not differ significantly. F and B were the most abundant phyla present regardless of diet and constituted about 90% of the microbes detected. The length of time the diet was consumed did not change the relative abundance of F and B. However, inclusion of walnuts in the diet significantly altered the relative abundance of F and B, increasing the ratio of F to B (W: 3.2+0.15 vs R: 1.8+0.18, p&lt;0.002). These data suggest a new mechanism, changing the gut microbial environment, by which walnuts may exert their beneficial health effects. (Support: California Walnut Commission)

Effects of aging and walnut‐rich diet on DNA methylation and expression of immediate‐early genes in critical brain regions.

Emerging evidence indicates a direct link between age-associated changes in epigenetic mechanisms and onset of neurodegenerative diseases, and that these genomic modulations are directly affected by the diet. Diets deficient in folate, choline and methionine, or the trace elements zinc and selenium, are reported to induce DNA hypomethylation and are linked to aberrant gene transcription. In a cognitively healthy adult, transcription of immediate-early genes (IEGs), e.g., Arc(activity-regulated cytoskeletal gene),zif268(nerve growth factor inducible-A),bdnf(brain-derived neurotrophic factor) and Reln (plasticity-promoting Reelin) are essential in memory formation and synaptic plasticity. In the current study, we investigated the effect of walnut diets, which are rich in polyunsaturated fatty acids and nutrients such as folates, selenium, magnesium and polyphenolics, on epigenetic mechanisms in critical regions of the brain. Young (3 months, n=30, 10/group) and old (19 months, n=45, 15/group) male Fischer 344 rats were supplemented with control (0%), 6% or 9% walnut diets for 10 weeks. Using LC-MS, absolute amounts of deoxycytidine and methylated cytosine residues in genomic DNA were quantified. Using RT-PCR, expression of bdnf, zif268, reln and arc were measured in hippocampus and frontal cortex. Significant aging effects (p<0.05) were observed for the expression of bdnf, zif268, reln and arc. The 9% walnut diet significantly (p<0.01) increased the expression of zif268 in the hippocampus compared to control animals. The results suggest that dietary walnut may have protective effects on the aging brain. Supported by USDA Intramural and California Walnut Commission.

Luther Burbank’s Contributions to Walnuts

Luther Burbank began making controlled crosses between walnut species in the late 19th century after hearing about a “supposed natural European hybrid walnut.” He crossed Juglans hindsii (northern California black walnut) × J. regia (Persian walnut) and produced progeny that he named ‘Paradox’ because of its extremely fast growth and other “anomalies.” He also crossed two American species, J. hindsii × J. nigra (eastern black walnut), producing ‘Royal’ walnut progeny that were fast-growing and prolific nut producers. A third interspecific hybrid was a cross between J. ailantifolia (Japanese walnut) × J. regia that resulted in extremely vigorous progeny but was not named. He observed segregation in the F2 populations and described giants and dwarfs as reversions to ancestral forms. Luther Burbank also made selections for walnut scion cultivars and was especially interested in thin-shelled nuts. He collected seeds from a J. regia growing in San Francisco because it produced regularly and had very high-quality nuts with relatively thin but poorly sealed shells. He selected one of its seedlings as ‘Santa Rosa Soft-Shell’ and described it as bearing large crops of nuts that were nearly white with thin shells and delicious white meat. Burbank’s contributions to the walnut industry endure to this day, especially through the widespread use of seedling and clonal ‘Paradox’ walnut rootstocks.

Evaluation of microbial loads and the effects of antimicrobial sprays in postharvest handling of California walnuts

Changes in aerobic plate count (APC) and Escherichia coli/coliform count (ECC) of inshell walnuts and walnut kernels were evaluated during commercial harvest and postharvest handling. APC and ECC for inshell walnuts collected from the tree were 6 and 4 log CFU/nut, respectively; counts increased by 1 log during harvest and hulling and decreased by 1 log during drying. Application of up to 200 ppm peracetic acid after hulling with or without a subsequent 2% lauric arginate spray reduced APC and ECC by less than 1 log CFU/nut; counts were not significantly different from the water control. A decrease in shell integrity was evident after drying: visible shell damage increased from 4 to 47% of walnuts after drying. Counts on kernels extracted from visibly intact walnuts from the tree were near the limit of detection (1.7 log CFU/nut). These counts increased by at least 1.4 log CFU/nut after hulling for both thin- and hard-shell cultivars. Microbial populations were 1.6–2.2 log CFU/nut higher for kernels from walnuts with broken shells than for kernels from walnuts with visibly intact shells before, but not after, drying. A better understanding of how microbial populations are affected by postharvest handling practices is important in the development of walnut-specific food safety programs.

Threats of future climate change and land use to vulnerable tree species native to Southern California

SUMMARYClimate and land-use changes are expected to drive high rates of environmental change and biodiversity loss in Mediterranean ecosystems this century. This paper compares the relative future impacts of land use and climate change on two vulnerable tree species native to Southern California (Juglans californica and Quercus engelmannii) using species distribution models. Under the Intergovernmental Panel for Climate Change's A1B future scenario, high levels of both projected land use and climate change could drive considerable habitat losses on these two already heavily-impacted tree species. Under scenarios of no dispersal, projected climate change poses a greater habitat loss threat relative to projected land use for both species. Assuming unlimited dispersal, climate-driven habitat gains could offset some of the losses due to both drivers, especially in J. californica which could experience net habitat gains under combined impacts of both climate change and land use. Quercus engelmannii, in contrast, could experience net habitat losses under combined impacts, even under best-case unlimited dispersal scenarios. Similarly, projected losses and gains in protected habitat are highly sensitive to dispersal scenario, with anywhere from &gt; 60% loss in protected habitat (no dispersal) to &gt; 170% gain in protected habitat (unlimited dispersal). The findings underscore the importance of dispersal in moderating future habitat loss for vulnerable species.

THE CALIFORNIA WALNUT IMPROVEMENT PROGRAM: SCION BREEDING AND ROOTSTOCK DEVELOPMENT

The goals of the University of California-Davis Walnut Improvement Program are to develop improved scion and rootstock cultivars for the California walnut industry and to utilize emerging genomic tools to increase breeding efficiency. Scion breeding objectives include new cultivars with early harvest dates, light kernel color, and resistance to blight and the development of scions with resistance to Cherry leaf roll virus. Rootstock development is directed at genetic resistance to soil-borne pathogens including Phytophthora, nematodes, and crown gall. Advances in clonal propagation methods, particularly micropropagation, have allowed replicated testing of genotypes of interest and have facilitated an expanding commercial production of improved clonal rootstocks. RX1, a Juglans microcarpa × Juglans regia hybrid with resistance to Phytophthora, and VX211, a very vigorous Juglans hindsii × J. regia hybrid exhibiting nematode tolerance, have been released for commercial use. Phenotyping, DNA mapping, and bioinformatic analyses are being combined to generate markers for traits of interest, including lateral bearing, kernel color, and harvest date, and will be used to improve selection efficiency. The Walnut Improvement Program is an integrated effort that depends on research cooperation with pathologists, molecular biologists, and UC Extension farm advisors, and relies on the assistance of commercial nurseries and walnut growers for planting and evaluation of statewide trials.

Modelling the effect of pyrethroid use intensity on mite population density for walnuts.

Published studies relating pyrethroid use and subsequent mite outbreaks have largely been based on laboratory and field experiments, with some inferring a result of increased miticide use. The present study derived a mathematical model proposed to quantify the effect of pyrethroid use intensity on mite population density. The model was validated against and parameterized with actual field-level pyrethroid and miticide use data from 1995 to 2009 for California walnuts, where the miticide use intensity was a proxy of the mite population density. The parameterized model was MI = 1.61 - 0.89 · exp(-93.31PI) (RMSE = 0.13; R(2) = 0.69; P < 0.01), where PI and MI are the average pyrethroid and miticide use intensity in small intervals respectively. A three-range scheme was presented to quantify pesticide applications based on the change rate of MI to PI. Specific for California walnuts, the PI range of 0-0.025 kg ha(-1) was identified as the rapidly increasing range where MI increased vastly when PI increased. Results confirmed that more miticide was used, presumably to prevent or control mite resurgence when pyrethroids were applied, a practice that is not only costly but might be expected to aggravate mite resistance to miticides and increase risk associated with these chemicals to the environment and human health.

Phylogeny, Morphology, Distribution, and Pathogenicity of Botryosphaeriaceae and Diaporthaceae from English Walnut in California.

Species of family Botryosphaeriaceae and genus Diaporthe (anamorph: genus Phomopsis, family Diaporthaceae) were reported and caused diseases on various fruit and nut trees in California. In the last several years, diseases on English walnut (Juglans regia) caused by species of Botryosphaeriaceae and Diaporthe were observed frequently in California. Disease symptoms include stem canker; shoot canker and blight; twig, leaf, and fruit blight; and necrotic leaf lesions. Isolates of the pathogen were collected from English walnut in 13 counties in California. The aims of this study were to identify these isolates and to test their pathogenicity to English walnut cultivars. In total, 159 California isolates were identified based on comparisons of DNA sequence data of the internal transcribed spacer, translation elongation factor 1-α, and β-tubulin gene regions, and combined with the morphological features of the cultures and conidia. Research results revealed that isolates represent 10 species of Botryosphaeriaceae and two species of Diaporthe. These species include Botryosphaeria dothidea, Diplodia mutila, D. seriata, Dothiorella iberica, Lasiodiplodia citricola, Neofusicoccum mediterraneum, N. nonquaesitum, N. parvum, N. vitifusiforme, Neoscytalidium dimidiatum, Diaporthe neotheicola, and D. rhusicola. Pathogenicity on three English walnut cultivars ('Chandler', 'Tulare', and 'Vina') using a mycelium plug inoculation method revealed that all these species are pathogenic to all the tested cultivars, with L. citricola and N. parvum being the most pathogenic species, followed by N. mediterraneum, N. dimidiatum, and B. dothidea. Chandler was more tolerant to infection than Tulare and Vina. Results in this study determined that multiple numbers of the Botryosphaeriaceae fungi and two Diaporthe spp. cause cankers and blights of English walnut and vary in their virulence from highly to slightly virulent, respectively.

Atwater factors overestimate the calorie content of walnuts (371.1)

Walnuts are a good source of magnesium, a shortfall nutrient, and contain a significant source of alpha‐linolenic acid. Their unique fatty acid profile likely contributes to their beneficial effect on cardiovascular health, with walnuts being the first whole food for which the US FDA permitted a qualified health claim. These health benefits make walnuts an important part of a healthful dietary pattern; however, their perceived high energy density may be a barrier to consumption. Recent research has shown that Atwater calculations overestimate the energy content of other tree nuts by 5‐20%; however accuracy of the Atwater estimated energy content of walnuts has not been investigated. A RCT was conducted in which 18 subjects were fed 2 diets, a base diet (0 g/d walnuts) and the base diet with all foods reduced and 42 g/d of walnut pieces added. After adaptation to both diets, subjects collected all urine and feces voided for 7 to 10 d at the end of each 3‐wk diet period. These samples and diets were freeze dried and gross energy was measured by bomb calorimetry. The metabolizable energy (ME) content of walnuts was found to be 5.22 kcal/g (146 kcal/serv) as compared to the Atwater‐calculated amount of 6.61 kcal/g (185 kcal/serv). Thus, Atwater factors overestimate by 21% the ME content of walnuts. These data will better inform consumers about the energy content of their foods.Grant Funding Source: USDA and California Walnut Commission

Demographic determinants of body mass index in healthy elderly men and women (1026.2)

Background: Aging and obesity impose a high burden on health care system. An understanding of the determinants of body mass index (BMI) can be helpful in targeted intervention and education in this population. Objective: We assessed the demographic determinants of BMI in healthy elderly men and women, using cross‐sectional data. Methods: A total of 240 healthy participants (63‐79 years) recruited for a clinical trial on cognition was selected for this study. We used the data collected at baseline from these subjects including body weight, height, BMI, age, gender, ethnicity, physical activity level (assessed by a physical activity questionnaire) and years of education. We used a multiple linear regression model to analyze the predictors of BMI. Results: There were 74 males and 166 females in our study of which 77.1% were Caucasians, 6.7% Asians, 5.4% Blacks and 4.6% Hispanics. 32.5% of participants were normal weight, 37.5% and 24.2% were overweight and obese (BMI &gt;30 kg/m2), respectively. Preliminary analyses showed that those engaged in moderate physical activity had lower BMI than those that participated only in mild physical activity (β=‐2.97, P=0.002). Other demographic variables considered in the study were not associated with BMI. Conclusion: Our preliminary findings suggest that physical activity is an important predictor of BMI in this elderly population.Grant Funding Source: California walnut commission

English

The invasive forb Brassica nigra (black mustard) and the native tree Juglans californica (black walnut) are allelopathic species that suppress the growth of neighboring plants. This study evaluates how allocation to root, reproductive, and photosynthetic biomass in B. nigra was affected with proximity to J. californica.&nbsp; We hypothesized that a joint suppressive effect would lead to lower root biomass allocation in B. nigra near J. californica due to reduced interspecific competition. Our results indicate that B. nigra plants growing near J. californica had significantly lower root : total biomass ratios, and provide insights into how to effectively control this invasive species. &nbsp; Key words:&nbsp; Allelopathy, competition, invasive species biology, principle of allocation, Santa Monica Mountains.

Stacking resistance to crown gall and nematodes in walnut rootstocks

BackgroundCrown gall (CG) (Agrobacterium tumefaciens) and the root lesion nematodes (RLNs) (Pratylenchus vulnus) are major challenges faced by the California walnut industry, reducing productivity and increasing the cost of establishing and maintaining orchards. Current nematode control strategies include nematicides, crop rotation, and tolerant cultivars, but these methods have limits. Developing genetic resistance through novel approaches like RNA interference (RNAi) can address these problems. RNAi-mediated silencing of CG disease in walnut (Juglans regia L.) has been achieved previously. We sought to place both CG and nematode resistance into a single walnut rootstock genotype using co-transformation to stack the resistance genes. A. tumefaciens, carrying self-complimentary iaaM and ipt transgenes, and Agrobacterium rhizogenes, carrying a self-complimentary Pv010 gene from P. vulnus, were used as co-transformation vectors. RolABC genes were introduced by the resident T-DNA in the A. rhizogenes Ri-plasmid used as a vector for plant transformation. Pv010 and Pv194 (transgenic control) genes were also transferred separately using A. tumefaciens. To test for resistance, transformed walnut roots were challenged with P. vulnus and microshoots were challenged with a virulent strain of A. tumefaciens.ResultsCombining the two bacterial strains at a 1:1 rather than 1:3 ratio increased the co-transformation efficiency. Although complete immunity to nematode infection was not observed, transgenic lines yielded up to 79% fewer nematodes per root following in vitro co-culture than untransformed controls. Transgenic line 33-3-1 exhibited complete crown gall control and 32% fewer nematodes. The transgenic plants had thicker, longer roots than untransformed controls possibly due to insertion of rolABC genes. When the Pv010 gene was present in roots with or without rolABC genes there was partial or complete control of RLNs. Transformation using only one vector showed 100% control in some lines.ConclusionsCG and nematode resistance gene stacking controlled CG and RLNs simultaneously in walnuts. Silencing genes encoding iaaM, ipt, and Pv010 decrease CG formation and RLNs populations in walnut. Beneficial plant genotype and phenotype changes are caused by co-transformation using A. tumefaciens and A. rhizogenes strains. Viable resistance against root lesion nematodes in walnut plants may be accomplished in the future using this gene stacking technology.

Differential responses of trees to temperature variation during the chilling and forcing phases

Temperate-zone trees must fulfill cultivar-specific chilling and heat requirements during the dormant period, in order to produce leaves and flowers in the following growing season. Timing and accumulation rate of chill and heat are understood to determine the timing of spring events, but both processes are difficult to observe in dormant tree buds. Where long-term phenological observations are available, Partial Least Squares (PLS) regression offers a statistical opportunity to delineate phases of chill and heat accumulation and determine the climatic requirements of trees. This study uses PLS regression to explore how the timing of spring events of chestnut in China, cherry in Germany and walnut in California is related to variation in the daily rates of chill and heat accumulation, as calculated with horticultural models. Dependent variables were 39 years of flowering dates for chestnuts in Beijing (China), 25 years of cherry bloom in Klein-Altendorf (Germany) and 54 years of walnut leaf emergence in Davis (California, USA). These were related to daily accumulation rates of chill, calculated with the Dynamic Model, and heat, calculated with the Growing Degree Hours Model. Compared to an earlier version of the procedure, in which phenological dates were related to unprocessed temperature data, delineation of chilling and forcing phases was much clearer when using horticultural metrics to quantify chill and heat. Chestnut bloom in the cold-winter climate of Beijing was found to depend primarily on the rate of heat accumulation, while cherry bloom in the temperate climate of Germany showed dependence on both chill and heat accumulation rates. The timing of walnut leaf emergence in the mild-winter climate of California depended much more strongly on chill accumulation rates. Chilling (in Chill Portions=CP) and heat (in Growing Degree Hours=GDH) requirements determined based on PLS regression were 79.8±5.3 CP and 13,466±1918 GDH for chestnut bloom in Beijing, 104.2±8.9 CP and 2698±1183 GDH for cherry bloom in Germany, and 37.5±5.0 CP and 11,245±1697 GDH for walnut leaf emergence in California. Spring phases of cherry in Klein-Altendorf and especially chestnut in Beijing will likely continue to advance in response to global warming, while for walnut in California, inadequate chilling may cause delays in flowering and leaf emergence. Such delays could serve as an early-warning indicator that future productivity may be threatened by climate change. The R package ‘chillR’ makes the method used in this study available for wider use.

Induction of Cell Cycle Arrest and Apoptosis by an Extract Created from California Walnuts (JUGLANS SP.) in MDA‐MB‐231, MCF7, and HeLa Cells

Walnuts contain components that may slow cancer growth including omega 3 fatty acids, phytosterols, polyphenols, carotenoids, and melatonin. Previous reports have shown that feeding mice a diet that contains walnuts was able to inhibit growth of MDA‐MB‐231 human breast cancers implanted in nude mice. However, the compounds which elicit this action have yet to be elucidated. We have conducted a pilot to begin characterization compounds isolated from walnuts and their ability to kill cancer cells. A methanol extract was prepared from the kernel of walnuts, solvent evaporated and the powder was dissolved in DMSO to a concentration of 100mg/ml and was used in subsequent assays. The extract induced cell death as measured by the trypan blue exclusion assay in a dose and time dependent manner. Mitochondrial outer membrane potential decreased rapidly with treatment. Phosphatidyl serine flipping increased in a dose‐dependent manner. Our results suggest that compounds isolated from walnuts are capable of inducing cell cycle arrest and apoptosis in a variety of cancer cell lines. Current studies are underway to identify the specific components of the methanol extract which are responsible for these activities. This work was supported by a grant from the California Walnut Commission to JBW.

Evaluating Paradox Walnut Rootstocks for Resistance to Armillaria Root Disease

The most common rootstock for Juglans regia (Persian or “English” walnut) in California is Paradox, typically a hybrid of J. hindsii (Northern California black walnut) × J. regia. Unfortunately, Paradox is very susceptible to Armillaria root disease. The relative resistance to Armillaria mellea of six clonally propagated Paradox rootstocks (AX1, Px1, RR4 11A, RX1, Vlach, VX211) was evaluated and compared with that of clonally propagated J. hindsii rootstock selection W17, J. regia scion cultivar Chandler, and Pterocarya stenoptera (Chinese wingnut). In a growth-chamber assay, plants were micropropagated and rooted in vitro before inoculating the culture medium with A. mellea. At two months post-inoculation, the most resistant and susceptible Paradox rootstocks were AX1 and VX211, respectively, with 9% vs. 70% mortality, and this finding was consistent across three isolates of A. mellea and three replicate experiments. This broad range of resistance within Paradox is consistent with past field trials that tested other genotypes. Our finding of similarly high susceptibility of ‘Chandler’ and W17 (61% vs. 69% mortality) is in contrast to two field trials, in which other J. regia genotypes were more susceptible than those of J. hindsii. A third trial, however, identified some J. regia genotypes as more resistant than those of J. hindsii. Therefore, it is possible that W17, which was not previously tested, is an Armillaria-susceptible genotype of J. hindsii. Based on our findings of repeatable mortality levels across three isolates of A. mellea and three replicate experiments, the growth-chamber assay has promise, albeit with confirmed resistant and susceptible controls, for identifying putative resistant rootstocks (e.g., AX1) in preparation for a field trial with controlled inoculations.

Anticancer metabolistes from California walnuts (Juglans sp.)

Anticancer metabolistes from California walnuts (Juglans sp.)

An analysis of the larval instars of the walnut twig beetle, Pityophthorus juglandis Blackman (Coleoptera: Scolytidae), in northern California black walnut, Juglans hindsii, and a new host record for Hylocurus hirtellus

By measuring and analyzing larval head capsule widths, we determined that a northern California population of the walnut twig beetle, Pityophthorus juglandis Blackman (Coleoptera: Scolytidae), has three larval instars. We also developed rules to classify P. juglandis larval instars. Overlap in the ranges of widths among consecutive instars was addressed by fitting a distribution model to the data and determining limits for head capsule width classes and probabilities of instar misclassification. Growth ratios for laboratory and field samples of P. juglandis were consistent with the Brooks-Dyar rule and with results in the literature for other bark and ambrosia beetle species. As a consequence of branch dissection to retrieve larvae of P. juglandis, we established that northern California black walnut, Juglans hindsii (Jeps.) Jeps. ex R.E. Sm., is a host for the xylophagous “California hardwood bark beetle,” Hylocurus hirtellus (LeConte) (Coleoptera: Scolytidae), and that H. hirtellus is associated with P. juglandis beneath the bark of small diameter branches. It appears that in northern California, univoltine H. hirtellus is active in flight from early March through early May, with the majority of the adults dispersing in April. The females are the colonizing sex.

Effects of whole walnuts and walnut components on postprandial triglyceride response, plasma measures of antioxidant activity, and endothelial function in overweight and obese adults

Walnuts beneficially affect endothelial function and oxidative stress. Mechanisms specific to walnut components are not known. We evaluated acute, postprandial effects of walnut components [separated nut skins (5.6 g), de‐fatted nutmeat (34 g), and nut oil (51 g)] versus whole walnuts (85 g) on metabolic parameters. Overweight/obese adults (9 women/6 men) with moderate hypercholesterolemia were randomized to a 4‐period crossover study design. There was a treatment by time interaction (P &lt; 0.01) for TG. Post hoc tests showed that oil increased TG versus nutmeat and skins at 120 min and 240 min versus skins; the whole nut increased TG versus skins at 120 min and 240 min (P &lt; 0.01 for all). Ferric reducing antioxidant power was different between nutmeat and oil and nutmeat and skins (P &lt; 0.01 for both). Skins decreased the reactive hyperemia index (RHI) versus baseline (P &lt; 0.01), and oil improved RHI versus skins (P &lt; 0.01). For the Framingham RHI (fRHI), oil was greater than skins and the whole nut (P &lt; 0.01 for both). For the oil treatment, ex vivo cholesterol efflux correlated with RHI and fRHI (r = 0.35, P = 0.07; r = 0.39, P = 0.04). There were no differences in total thiols or malondialdehyde. Walnut oil improved endothelial function compared to the skins, and these changes were associated with improved reverse cholesterol transport. Measurement timing, extraction method, and/or bioavailability may help explain these effects.Grant Funding Source: California Walnut Commission and the GCRC, PSU (NIH grant M01RR10732); ClincalTrials.gov identifier: NCT00938340