Mechanisms underlying the efficacy of a rodent model of vertical sleeve gastrectomy - A focus on energy expenditure.

OBJECTIVE: Bariatric surgery remains the only effective and durable treatment option for morbid obesity. Vertical Sleeve Gastrectomy (VSG) is currently the most widely performed of these surgeries primarily because of its proven efficacy in generating rapid onset weight loss, improved glucose regulation and reduced mortality compared with other invasive procedures. VSG is associated with reduced appetite, however, the relative importance of energy expenditure to VSG-induced weight loss and changes in glucose regulation, particularly that in brown adipose tissue (BAT), remains unclear. The aim of this study was to investigate the role of BAT thermogenesis in the efficacy of VSG in a rodent model. METHODS: Diet-induced obese male Sprague-Dawley rats were either sham-operated, underwent VSG surgery or were pair-fed to the food consumed by the VSG group. Rats were also implanted with biotelemetry devices between the interscapular lobes of BAT to assess local changes in BAT temperature as a surrogate measure of thermogenic activity. Metabolic parameters including food intake, body weight and changes in body composition were assessed. To further elucidate the contribution of energy expenditure via BAT thermogenesis to VSG-induced weight loss, a separate cohort of chow-fed rats underwent complete excision of the interscapular BAT (iBAT lipectomy) or chemical denervation using 6-hydroxydopamine (6-OHDA). To localize glucose uptake in specific tissues, an oral glucose tolerance test was combined with an intraperitoneal injection of 14C-2-deoxy-d-glucose (14C-2DG). Transneuronal viral tracing was used to identify 1) sensory neurons directed to the stomach or small intestine (H129-RFP) or 2) chains of polysynaptically linked neurons directed to BAT (PRV-GFP) in the same animals. RESULTS: Following VSG, there was a rapid reduction in body weight that was associated with reduced food intake, elevated BAT temperature and improved glucose regulation. Rats that underwent VSG had elevated glucose uptake into BAT compared to sham operated animals as well as elevated gene markers related to increased BAT activity (Ucp1, Dio2, Cpt1b, Cox8b, Ppargc) and markers of increased browning of white fat (Ucp1, Dio2, Cited1, Tbx1, Tnfrs9). Both iBAT lipectomy and 6-OHDA treatment significantly attenuated the impact of VSG on changes in body weight and adiposity in chow-fed animals. In addition, surgical excision of iBAT following VSG significantly reversed VSG-mediated improvements in glucose tolerance, an effect that was independent of circulating insulin levels. Viral tracing studies highlighted a patent neural link between the gut and BAT that included groups of premotor BAT-directed neurons in the dorsal raphe and raphe pallidus. CONCLUSIONS: Collectively, these data support a role for BAT in mediating the metabolic sequelae following VSG surgery, particularly the improvement in glucose regulation, and highlight the need to better understand the contribution from this tissue in human patients.

ImpACT+, a coping intervention to improve clinical outcomes for women living with HIV and sexual trauma in South Africa: study protocol for a randomized controlled trial.

BACKGROUND: Addressing sexual trauma in the context of HIV care is essential to improve clinical outcomes and mental health among women in South Africa. Women living with HIV (WLH) report disproportionately high levels of sexual trauma and have higher rates of posttraumatic stress disorder. Adherence to antiretroviral therapy (ART) may be difficult for traumatized women, as sexual trauma compounds the stress associated with managing HIV and is often comorbid with other mental health disorders, further compromising care engagement and adherence. ART initiation represents a unique window of opportunity for intervention to enhance motivation, increase care engagement, and address the negative effects of trauma on avoidant coping behaviors. Mental health interventions delivered by non-specialists in low- and middle-income countries have potential to treat depression, trauma, and effects of intimate partner violence among WLH. This study will examine the effectiveness of Improving AIDS Care after Trauma (ImpACT +), a task-shared, trauma-focused coping intervention, to promote viral suppression among WLH initiating ART in a South African clinic setting. METHODS: This study will be conducted in Khayelitsha, a peri-urban settlement situated near Cape Town, South Africa. Using a hybrid type 1 effectiveness-implementation design, we will randomize 350 WLH initiating ART to the ImpACT + experimental condition or the control condition (three weekly sessions of adapted problem-solving therapy) to examine the effectiveness of ImpACT + on viral suppression, ART adherence, and the degree to which mental health outcomes mediate intervention effects. ImpACT + participants will receive six once-a-week coping intervention sessions and six monthly maintenance sessions over the follow-up period. We will conduct mental health and bio-behavioral assessments at baseline, 4, 8, and 12 months, with care engagement data extracted from medical records. We will explore scalability using the Consolidated Framework for Implementation Research (CFIR). DISCUSSION: This trial is expected to yield important new information on psychologically informed intervention models that benefit the mental health and clinical outcomes of WLH with histories of sexual trauma. The proposed ImpACT + intervention, with its focus on building coping skills to address traumatic stress and engagement in HIV care and treatment, could have widespread impact on the health and wellbeing of individuals and communities in sub-Saharan Africa. TRIAL REGISTRATION: Clinicaltrials.gov NCT04793217 . Retrospectively registered on 11 March 2021.

Yap regulates skeletal muscle fatty acid oxidation and adiposity in metabolic disease.

Obesity is a major risk factor underlying the development of metabolic disease and a growing public health concern globally. Strategies to promote skeletal muscle metabolism can be effective to limit the progression of metabolic disease. Here, we demonstrate that the levels of the Hippo pathway transcriptional co-activator YAP are decreased in muscle biopsies from obese, insulin-resistant humans and mice. Targeted disruption of Yap in adult skeletal muscle resulted in incomplete oxidation of fatty acids and lipotoxicity. Integrated 'omics analysis from isolated adult muscle nuclei revealed that Yap regulates a transcriptional profile associated with metabolic substrate utilisation. In line with these findings, increasing Yap abundance in the striated muscle of obese (db/db) mice enhanced energy expenditure and attenuated adiposity. Our results demonstrate a vital role for Yap as a mediator of skeletal muscle metabolism. Strategies to enhance Yap activity in skeletal muscle warrant consideration as part of comprehensive approaches to treat metabolic disease.

Agronomic evaluation and molecular characterisation of the acetolactate synthase gene in imazapyr tolerant sugarcane (Saccharum hybrid) genotypes.

KEY MESSAGE: Mutagenesis had no effect on number of stalks/plot, stalk height, fibre and sucrose content of mutants. Imazapyr tolerance is likely due to a S622N mutation in the acetolactate synthase gene. The herbicidal compound imazapyr is effective against weeds such as Cynodon and Rottboellia species that constrain sugarcane production. This study aimed to compare agronomic characteristics of three imazapyr tolerant mutants (Mut 1, Mut 6 and Mut 7) with the non-mutated N12 control after 18 months of growth, and to sequence the acetolactate synthase (ALS) gene to identify any point mutations conferring imazapyr tolerance. There were no significant differences in the number of stalks/plot, stalk height, fibre and sucrose contents of the mutants compared with the N12 control. However, Mut 1 genotype was more susceptible to the Lepidopteran stalk borer, Eldana saccharina when compared with the non-mutated N12 (11.14 ± 1.37 and 3.89 ± 0.52% internodes bored, respectively), making Mut 1 less desirable for commercial cultivation. Molecular characterisation of the ALS gene revealed non-synonymous mutations in Mut 6. An A to G change at nucleotide position 1857 resulted in a N513D mutation, while a G to A change at nucleotide position 2184 imposed a S622N mutation. Molecular dynamics simulations revealed that the S622N mutation renders an asparagine side chain clash with imazapyr, hence this mutation is effective in conferring imazapyr tolerance.

No evidence of white adipocyte browning after endurance exercise training in obese men.

BACKGROUND/OBJECTIVES: The phenomenon of adipocyte 'beiging' involves the conversion of non-classic brown adipocytes to brown-like adipose tissue with thermogenic, fat-burning properties, and this phenomenon has been shown in rodents to slow the progression of obesity-associated metabolic diseases. Rodent studies consistently report adipocyte beiging after endurance exercise training, indicating that increased thermogenic capacity in these adipocytes may underpin the improved health benefits of exercise training. The aim of this study was to determine whether prolonged endurance exercise training induces beige adipogenesis in subcutaneous adipose tissues of obese men. SUBJECTS/METHODS: Molecular markers of beiging were examined in adipocytes obtained from abdominal subcutaneous (AbSC) and gluteofemoral (GF) subcutaneous adipose tissues before and after 6 weeks of endurance exercise training in obese men (n=6, 37.3±2.3 years, 30.1±2.3 kg m-2). RESULTS: The mRNAs encoding the brown or beige adipocyte-selective proteins were very lowly expressed in AbSC and GF adipose tissues and exercise training did not alter the mRNA expression of UCP1, CD137, CITED, TBX1, LHX8 and TCF21. Using immunohistochemistry, neither multilocular adipocytes, nor UCP1 or CD137-positive adipocytes were detected in any sample. MicroRNAs known to regulate brown and/or beige adipose development were highly expressed in white adipocytes but endurance exercise training did not impact their expression. CONCLUSIONS: The present study reaffirms emerging data in humans demonstrating no evidence of white adipose tissue beiging in response to exercise training, and supports a growing body of work demonstrating divergence of brown/beige adipose location, molecular characterization and physiological function between rodents and humans.

Comparing the Efficacy of Triple Nerve Transfers with Nerve Graft Reconstruction in Upper Trunk Obstetric Brachial Plexus Injury.

BACKGROUND: Upper trunk obstetric brachial plexus injury can cause profound shoulder and elbow dysfunction. Although neuroma excision with interpositional sural nerve grafting is the current gold standard, distal nerve transfers have a number of potential advantages. The goal of this study was to compare the clinical outcomes and health care costs between nerve grafting and distal nerve transfers in children with upper trunk obstetric brachial plexus injury. METHODS: In this prospective cohort study, children who underwent triple nerve transfers were followed with the Active Movement Scale for 2 years. Their outcomes were compared to those of children who underwent nerve graft reconstruction. To assess health care use, a cost analysis was also performed. RESULTS: Twelve patients who underwent nerve grafting were compared to 14 patients who underwent triple nerve transfers. Both groups had similar baseline characteristics and showed improved shoulder and elbow function following surgery. However, the nerve transfer group displayed significantly greater improvement in shoulder external rotation and forearm supination 2 years after surgery (p < 0.05). The operative time and length of hospital stay were significantly lower (p < 0.05), and the overall cost was approximately 50 percent less in the nerve transfer group. CONCLUSION: Triple nerve transfer for upper trunk obstetric brachial plexus injury is a feasible option, with better functional shoulder external rotation and forearm supination, faster recovery, and lower cost compared with traditional nerve graft reconstruction. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, II.

A personalized, multi-platform nutrition, exercise, and lifestyle coaching program: A pilot in women.

The aim of this pilot study was to examine if a personalized web-based multi-platform nutrition, exercise, and lifestyle coaching program, supported weight loss and the reduction of chronic disease risk factors in overweight or obese women. Twenty-eight women completed the program, which represented 50% of those who provided baseline data. The program consisted of a one-year curriculum with daily exercise, nutritional habits, and health behaviour lessons along with access to a one-on-one coach. The workouts, habits, and lessons were available via computer, tablet, and mobile device which, along with coaching, facilitated self-monitoring and accountability. At baseline and 12-months, weight, waist circumference, fat mass, muscle mass, blood pressure, total cholesterol, low density lipoproteins, high density lipoproteins, triglycerides, C reactive protein, and fasting glucose were collected. Over the 12 months, women who completed the program, (average age 49.64 (SD 10.99) years), lost 16.52 (SD 13.63) lbs (P < 0.001), and reduced waist circumference by 3.56 (SD 2.31) in (P < 0.0001). Diastolic blood pressure decreased by 3.77 (SD 7.25) mm Hg (P = 0.02) and high density lipoproteins increased by 0.16 (SD 0.28) mmol/L (P = 0.01). No other risk factors changed significantly. Compliance was a significant predictor of weight loss (P < 0.01). In conclusion, women who completed the web-based program experienced significant weight loss (8.62% of initial body weight) coming predominantly from body fat. Chronic disease risk factors also improved.

A multicentre study of the precision and accuracy of the TruSlice and TruSlice Digital histological dissection devices.

BACKGROUND: Five key factors enabling a good surgical grossing technique include a flat uniformly perpendicular specimen cutting face, appropriate immobilisation of the tissue specimen during grossing, good visualisation of the cutting tissue face, sharp cutting knives and the grossing knife action. TruSlice and TruSlice Digital are new innovative tools based on a guillotine configuration. The TruSlice has plastic inserts whilst the TruSlice Digital has an electronic micrometre attached: both features enable these dissection factors to be controlled. The devices were assessed in five hospitals in the UK. MATERIAL AND METHODS: A total of 267 fixed tissue samples from 23 tissue types were analysed, principally the breast (n = 32) skin (30), rectum (28), colon (27) and cervix (17). Precision and accuracy were evaluated by measuring the defined thickness, and the consistency of achieving the defined thickness of tissue samples taken respectively. Both parameters were expressed as a total percentage of compliance for the cohort of samples accessed. RESULTS: Overall, the mean (standard deviation) score for precision was 81 (11) % whilst the accuracy score was 82 (11) % (both p < 0.05, chi-squared test), although this varied with type of tissue. Accuracy and precision were strongly correlated (rp = 0.83, p < 0.001). CONCLUSION: The TruSlice Digital devices offer an assured precision and accuracy performance which is reproducible across an assortment of tissue types. The use of a micrometre to set tissue slice thickness is innovative and should comply with laboratory accreditation requirements, alleviating concerns of how to tackle issues such as the 'measurement of uncertainty' at the grossing bench.

Economic assessment of fidaxomicin for the treatment of Clostridium difficile infection (CDI) in special populations (patients with cancer, concomitant antibiotic treatment or renal impairment) in Spain.

The objective of this paper was to assess the cost-utility of fidaxomicin versus vancomycin in the treatment of Clostridium difficile infection (CDI) in three specific CDI patient subgroups: those with cancer, treated with concomitant antibiotic therapy or with renal impairment. A Markov model with six health states was developed to assess the cost-utility of fidaxomicin versus vancomycin in the patient subgroups over a period of 1 year from initial infection. Cost and outcome data used to parameterise the model were taken from Spanish sources and published literature. The costs were from the Spanish hospital perspective, in Euros (€) and for 2013. For CDI patients with cancer, fidaxomicin was dominant versus vancomycin [gain of 0.016 quality-adjusted life-years (QALYs) and savings of €2,397 per patient]. At a cost-effectiveness threshold of €30,000 per QALY gained, the probability that fidaxomicin was cost-effective was 96 %. For CDI patients treated with concomitant antibiotic therapy, fidaxomicin was the dominant treatment versus vancomycin (gain of 0.014 QALYs and savings of €1,452 per patient), with a probability that fidaxomicin was cost-effective of 94 %. For CDI patients with renal impairment, fidaxomicin was also dominant versus vancomycin (gain of 0.013 QALYs and savings of €1,432 per patient), with a probability that fidaxomicin was cost-effective of 96 %. Over a 1-year time horizon, when fidaxomicin is compared to vancomycin in CDI patients with cancer, treated with concomitant antibiotic therapy or with renal impairment, the use of fidaxomicin would be expected to result in increased QALYs for patients and reduced overall costs.

Improved nitrogen use efficiency in transgenic sugarcane: phenotypic assessment in a pot trial under low nitrogen conditions.

KEY MESSAGE: Sugarcane lines transformed with an alanine aminotransferase gene demonstrated an improved nitrogen use efficiency compared with untransformed controls in a pot trial under low nitrogen conditions.

Serotonin in the ventral hippocampus modulates anxiety-like behavior during amphetamine withdrawal.

Withdrawal from amphetamine is associated with increased anxiety and sensitivity to stressors which are thought to contribute to relapse. Rats undergoing amphetamine withdrawal fail to exhibit stress-induced increases in serotonin (5-HT) release in the ventral hippocampus and show heightened anxiety-like behaviors. Therefore, we tested the hypothesis that reducing 5-HT levels in the ventral hippocampus is a causal mechanism in increasing anxiety-like behaviors during amphetamine withdrawal. First, we tested whether reducing 5-HT levels in the ventral hippocampus directly increases anxiety behavior. Male rats were bilaterally infused with 5,7-dihydroxytryptamine (5,7-DHT) into the ventral hippocampus, which produced a 83% decrease in ventral hippocampus 5-HT content, and were tested on the elevated plus maze (EPM) for anxiety-like behavior. Reducing ventral hippocampus 5-HT levels decreased the time spent in the open arms of the maze, suggesting that diminished ventral hippocampus 5-HT levels increases anxiety-like behavior. Next, we tested whether increasing 5-HT levels in the ventral hippocampus reverses anxiety behavior exhibited by rats undergoing amphetamine withdrawal. Rats were treated daily with either amphetamine (2.5-mg/kg, i.p.) or saline for 2weeks, and at 2weeks withdrawal, were infused with the selective serotonin reuptake inhibitor paroxetine (0.5µM) bilaterally into the ventral hippocampus and tested for anxiety-like behavior on the EPM. Rats pre-treated with amphetamine exhibited increased anxiety-like behavior on the EPM. This effect was reversed by ventral hippocampus infusion of paroxetine. Our results suggest that 5-HT levels in the ventral hippocampus are critical for regulating anxiety behavior. Increasing 5-HT levels during withdrawal may be an effective strategy for reducing anxiety-induced drug relapse.

Soil coring at multiple field environments can directly quantify variation in deep root traits to select wheat genotypes for breeding.

We aim to incorporate deep root traits into future wheat varieties to increase access to stored soil water during grain development, which is twice as valuable for yield as water captured at younger stages. Most root phenotyping efforts have been indirect studies in the laboratory, at young plant stages, or using indirect shoot measures. Here, soil coring to 2 m depth was used across three field environments to directly phenotype deep root traits on grain development (depth, descent rate, density, length, and distribution). Shoot phenotypes at coring included canopy temperature depression, chlorophyll reflectance, and green leaf scoring, with developmental stage, biomass, and yield. Current varieties, and genotypes with breeding histories and plant architectures expected to promote deep roots, were used to maximize identification of variation due to genetics. Variation was observed for deep root traits (e.g. 111.4-178.5cm (60%) for depth; 0.09-0.22cm/°C day (144%) for descent rate) using soil coring in the field environments. There was significant variation for root traits between sites, and variation in the relative performance of genotypes between sites. However, genotypes were identified that performed consistently well or poorly at both sites. Furthermore, high-performing genotypes were statistically superior in root traits than low-performing genotypes or commercial varieties. There was a weak but significant negative correlation between green leaf score (-0.5), CTD (0.45), and rooting depth and a positive correlation for chlorophyll reflectance (0.32). Shoot phenotypes did not predict other root traits. This study suggests that field coring can directly identify variation in deep root traits to speed up selection of genotypes for breeding programmes.

Exercise training does not enhance hypothalamic responsiveness to leptin or ghrelin in male mice.

The detection of hormone and nutrient signals by the hypothalamus is blunted in obesity and contributes to dysregulated energy homeostasis. We investigated whether aerobic exercise training would improve long-term hypothalamic sensitivity to both leptin and ghrelin, independent of acute exercise-induced signalling. Male C57Bl/6J mice were fed either a chow or high-fat diet for 6 weeks, then remained sedentary on their respective diet, or completed 6 weeks of treadmill exercise training with a progressive increase in exercise volume and intensity. Food intake and hypothalamic signalling were assessed in mice injected with leptin or ghrelin at least 24 h after the last exercise bout. Exercise training reduced body mass, increased daily food intake and improved glucose tolerance. Intraperitoneal leptin administration reduced food intake in lean and obese mice, and this was not enhanced after exercise training. Leptin-mediated activation of phosphorylated signal transducer and activator of transcription 3 in the arcuate nucleus and ventromedial nucleus of the hypothalamus was not enhanced with exercise training. Ghrelin increased food intake and c-Fos positive neurones in the hypothalamus in lean and obese mice, and these physiological and molecular responses were not enhanced with exercise training. This suggests that the previously reported exercise effects on sensitising hypothalamic signalling and food intake responses may be limited to the period immediately after an exercise bout, and are not a result of stable structural or molecular changes that occur with exercise training.

Distal nerve transfers are effective in treating patients with upper trunk obstetrical brachial plexus injuries: an early experience.

BACKGROUND: Current surgical management of obstetrical brachial plexus injury is primary reconstruction with sural nerve grafts. Recently, the nerve-to-nerve transfer technique has been used to treat brachial plexus injury in adults, affording the benefit of distal coaptations that minimize regenerative distance. The purpose of this study was to test the hypothesis that nerve transfers are effective in reconstructing isolated upper trunk obstetrical brachial plexus injuries. METHODS: Ten patients aged 10 to 18 months were treated with three nerve transfers: spinal accessory nerve to the suprascapular nerve for shoulder abduction and external rotation; a radial to axillary nerve for shoulder abduction; and ulnar or median nerve transfer to the musculocutaneous nerve for elbow flexion. Patients were assessed preoperatively and postoperatively using the Active Movement Scale. All patients were followed regularly for up to 2 years. RESULTS: Improvement in elbow and shoulder function was observed between 6 and 24 months. By 6 months, all patients passed the cookie test. At 24 months, shoulder abduction improved from 3.7 ± 0.6 to 5.0 ± 0.5, shoulder external rotation from 1.8 ± 0.4 to 4.3 ± 0.6, shoulder flexion from 3.7 ± 0.5 to 5.4 ± 0.5, elbow flexion from 3.7 ± 0.6 to 6.3 ± 0.2, and forearm supination from 2.1 ± 0.4 to 5.9 ± 0.2. There was no clinically appreciable donor-site morbidity. CONCLUSIONS: Nerve transfers reduced operative times compared with traditional nerve grafting procedures. Those patients showed significant gains in Active Movement Scale score by 24 months postoperatively, comparable to results achieved by nerve grafting. These findings support nerve transfers as a potential alternative treatment option for upper trunk obstetrical brachial plexus injuries. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, IV.

A rapid, controlled-environment seedling root screen for wheat correlates well with rooting depths at vegetative, but not reproductive, stages at two field sites.

BACKGROUND AND AIMS: Root length and depth determine capture of water and nutrients by plants, and are targets for crop improvement. Here we assess a controlled-environment wheat seedling screen to determine speed, repeatability and relatedness to performance of young and adult plants in the field. METHODS: Recombinant inbred lines (RILs) and diverse genotypes were grown in rolled, moist germination paper in growth cabinets, and primary root number and length were measured when leaf 1 or 2 were fully expanded. For comparison, plants were grown in the field and root systems were harvested at the two-leaf stage with either a shovel or a soil core. From about the four-leaf stage, roots were extracted with a steel coring tube only, placed directly over the plant and pushed to the required depth with a hydraulic ram attached to a tractor. KEY RESULTS: In growth cabinets, repeatability was greatest (r = 0.8, P < 0.01) when the paper was maintained moist and seed weight, pathogens and germination times were controlled. Scanned total root length (slow) was strongly correlated (r = 0.7, P < 0.01) with length of the two longest seminal axile roots measured with a ruler (fast), such that 100-200 genotypes were measured per day. Correlation to field-grown roots at two sites at two leaves was positive and significant within the RILs and cultivars (r = 0.6, P = 0.01), and at one of the two sites at the five-leaf stage within the RILs (r = 0.8, P = 0.05). Measurements made in the field with a shovel or extracted soil cores were fast (5 min per core) and had significant positive correlations to scanner measurements after root washing and cleaning (>2 h per core). Field measurements at two- and five-leaf stages did not correlate with root depth at flowering. CONCLUSIONS: The seedling screen was fast, repeatable and reliable for selecting lines with greater total root length in the young vegetative phase in the field. Lack of significant correlation with reproductive stage root system depth at the field sites used in this study reflected factors not captured in the screen such as time, soil properties, climate variation and plant phenology.

Response of millet and sorghum to a varying water supply around the primary and nodal roots.

BACKGROUND AND AIMS: Cereals have two root systems. The primary system originates from the embryo when the seed germinates and can support the plant until it produces grain. The nodal system can emerge from stem nodes throughout the plant's life; its value for yield is unclear and depends on the environment. The aim of this study was to test the role of nodal roots of sorghum and millet in plant growth in response to variation in soil moisture. Sorghum and millet were chosen as both are adapted to dry conditions. METHODS: Sorghum and millet were grown in a split-pot system that allowed the primary and nodal roots to be watered separately. KEY RESULTS: When primary and nodal roots were watered (12 % soil water content; SWC), millet nodal roots were seven times longer than those of sorghum and six times longer than millet plants in dry treatments, mainly from an 8-fold increase in branch root length. When soil was allowed to dry in both compartments, millet nodal roots responded and grew 20 % longer branch roots than in the well-watered control. Sorghum nodal roots were unchanged. When only primary roots received water, nodal roots of both species emerged and elongated into extremely dry soil (0.6-1.5 % SWC), possibly with phloem-delivered water from the primary roots in the moist inner pot. Nodal roots were thick, short, branchless and vertical, indicating a tropism that was more pronounced in millet. Total nodal root length increased in both species when the dry soil was covered with plastic, suggesting that stubble retention or leaf mulching could facilitate nodal roots reaching deeper moist layers in dry climates. Greater nodal root length in millet than in sorghum was associated with increased shoot biomass, water uptake and water use efficiency (shoot mass per water). Millet had a more plastic response than sorghum to moisture around the nodal roots due to (1) faster growth and progression through ontogeny for earlier nodal root branch length and (2) partitioning to nodal root length from primary roots, independent of shoot size. CONCLUSIONS: Nodal and primary roots have distinct responses to soil moisture that depend on species. They can be selected independently in a breeding programme to shape root architecture. A rapid rate of plant development and enhanced responsiveness to local moisture may be traits that favour nodal roots and water use efficiency at no cost to shoot growth.

In vitro generation of somaclonal variant plants of sugarcane for tolerance to Fusarium sacchari.

KEY MESSAGE : A combination of in vitro culture and mutagenesis using ethyl methanesulfonate (EMS) followed by culture filtrate-mediated selection produced variant sugarcane plants tolerant and resistant to Fusarium sacchari. Eldana saccharina is a destructive pest of the sugarcane crop in South Africa. Fusarium sacchari PNG40 (a fungal strain harmful to E. saccharina) has the potential to be an endophytic biological control agent of the stalk borer. However, the fungus causes Fusarium stalk rot in sugarcane. In the current study, sugarcane plants tolerant and resistant to F. sacchari PNG40 were produced by exposing embryogenic calli to the chemical mutagen ethyl methanesulfonate (EMS), followed by in vitro selection during somatic embryogenesis and plantlet regeneration on media containing F. sacchari culture filtrates (CF). The incorporation of 100 ppm CF in the culture media at the embryo maturation stage, at germination, or at both, resulted in callus necrosis and consequent reduced plantlet yield. Subsequent trimming of the roots of regenerated plants and their exposure to 1,500 ppm CF served as a further selection treatment. Plants produced from EMS-treated calli displayed improved root re-growth in the presence of CF pressure compared with those from non-treated calli. The tolerance of CF-selected plants was confirmed in greenhouse tests by inoculation with F. sacchari PNG40, re-isolation of Fusarium spp. from undamaged tissue of asymptomatic plants and establishment of the identity of fungal isolates as PNG40 using molecular analysis. The restriction of PNG40 presence to the inoculation lesion in some plants suggested their resistance to the fungus. Genotypes exhibiting symptomless endophytic colonization by PNG40 were identified and will be utilised for testing biological control strategies against E. saccharina.

Regulation of plasma ceramide levels with fatty acid oversupply: evidence that the liver detects and secretes de novo synthesised ceramide.

AIMS/HYPOTHESIS: Plasma ceramide concentrations correlate with insulin sensitivity, inflammation and atherosclerotic risk. We hypothesised that plasma ceramide concentrations are increased in the presence of elevated fatty acid levels and are regulated by increased liver serine C-palmitoyltransferase (SPT) activity. METHODS: Lean humans and rats underwent an acute lipid infusion and plasma ceramide levels were determined. One group of lipid-infused rats was administered myriocin to inhibit SPT activity. Liver SPT activity was determined in lipid-infused rats, and obese, insulin resistant mice. The time and palmitate dose-dependent synthesis of intracellular and secreted ceramide was determined in HepG2 liver cells. RESULTS: Plasma ceramide levels were increased during lipid infusion in humans and rats, and in obese, insulin-resistant mice. The increase in plasma ceramide was not associated with changes in liver SPT activity, and inhibiting SPT activity by ~50% did not alter plasma ceramide levels in lipid-infused rats. In HepG2 liver cells, palmitate incorporation into extracellular ceramide was both dose- and time-dependent, suggesting the liver cells rapidly secreted the newly synthesised ceramide. CONCLUSIONS/INTERPRETATION: Elevated systemic fatty acid availability increased plasma ceramide but this was not associated with changes in hepatic SPT activity, suggesting that liver ceramide synthesis is driven by substrate availability rather than increased SPT activity. This report also provides evidence that the liver is sensitive to the intracellular ceramide concentration, and an increase in liver ceramide secretion may help protect the liver from the deleterious effects of intracellular ceramide accumulation.