Male reproductive traits are differentially affected by dietary macronutrient balance but unrelated to adiposity

Dietary factors influence male reproductive function in both experimental and epidemiological studies. However, there are currently no specific dietary guidelines for male preconception health. Here, we use the Nutritional Geometry framework to examine the effects of dietary macronutrient balance on reproductive traits in C57BL/6 J male mice. Dietary effects are observed in a range of morphological, testicular and spermatozoa traits, although the relative influence of protein, fat, carbohydrate, and their interactions differ depending on the trait being examined. Interestingly, dietary fat has a positive influence on sperm motility and antioxidant capacity, differing to typical high fat diet studies where calorie content is not controlled for. Moreover, body adiposity is not significantly correlated with any of the reproductive traits measured in this study. These results demonstrate the importance of macronutrient balance and calorie intake on reproductive function and support the need to develop specific, targeted, preconception dietary guidelines for males.

Associations of dietary macronutrient composition with cardiometabolic health: data from the National Health and Nutrition Examination Survey (NHANES) 1999–2014

Background

Human nutrition is a leading modifiable risk factor for the prevention of cardiometabolic diseases. However, most nutritional research focuses on the role of specific nutrients rather than compositional analysis of the diet.

Purpose

We aimed to assess the association of dietary macronutrient composition with various markers of cardiometabolic health.

Methods

This study was undertaken using 24-hour food recall data from the National Health and Nutrition Examination Survey from years 1999–2014 (n=36,637). Participants included both males and females ≥20 years of age (49.8±18.3 years; 53% Female). Caloric outliers for males (<800 kcal/day or >4200 kcal/day) and females (<600 kcal/day or >3500 kcal/day) were removed from the analysis (n=1844). Cardiometabolic health markers were collected via mobile examination center and included triglycerides (n=16,444), total cholesterol (n=31,155), LDL cholesterol (n=15,798), HDL cholesterol (n=33,435), blood pressure (n=34,121), body fat percentage (n=4269), body mass index (n=35,187), glucose (n=17,208), insulin (n=16,273), oral glucose tolerance test (n=8280), and HbA1c (n=27,288). Associations of dietary macronutrients with cardiometabolic health markers were assessed using 3-dimensional general additive models (Protein; Carbohydrate; Fat) with adjustment for age, sex, misreporting, ethnicity, education level, household income, physical activity, alcohol intake, and smoking. Response surfaces on right-angled mixture triangles were generated as predictions from absolute macronutrient intake at the 50th percentile of total energy intake. Macronutrient intakes were transformed to a percentage of energy to visualize and interpret associations compositionally.

Results

There was a complex 3-way interactive non-linear association of macronutrient composition with lipid profile (Figure A-D; all p<0.04), blood pressure (Figure E-F; all p<0.001), body fat percentage (Figure G; p<0.001), body mass index (Figure H; p<0.001), and all markers of glycemic control (Figure I-L; all p<0.001). Diets comprised of high protein coupled with low fat were associated with higher triglycerides but generally more favorable total cholesterol, blood pressure, and body fatness. Conversely, diets composed of high protein coupled with high fat were associated with higher HDL cholesterol but worse total cholesterol, body fatness, body mass index, and glycemic control.

Conclusions

These findings display a complex relationship between dietary macronutrient composition and cardiometabolic health. Future research is needed to evaluate how dietary source and quality may modify the observed associations.

Funding Acknowledgement

Type of funding sources: Private company.

Halicin Is Effective Against Staphylococcus aureus Biofilms In Vitro

BACKGROUND

Biofilms protect bacteria from the host immune system and many antibiotics, making the treatment of orthopaedic infections difficult. Halicin, a recently discovered antibiotic, has potent activity against nonorthopaedic infections in mice and the planktonic, free-living forms of many bacterial species, including Staphylococcus aureus , a common cause of orthopaedic infections. Importantly, halicin did not induce resistance in vitro and was effective against drug-resistant bacteria and proliferating and quiescent bacteria. Quiescence is an important cause of antibiotic tolerance in biofilms. However, whether halicin acts on biofilms has not been tested.

QUESTIONS/PURPOSES

(1) Does halicin reduce the viability of S. aureus in less mature and more mature biofilms as it does in planktonic cultures? (2) How do the relative effects of halicin on S. aureus biofilms and planktonic cultures compare with those of conventional antibiotics (tobramycin, cefazolin, vancomycin, or rifampicin) that are commonly used in clinical orthopaedic infections?

METHODS

To measure minimal biofilm eradication concentrations (MBECs) with less mature 3-day and more mature 7-day biofilms, we used 96-well peg plates that provided high throughput and excellent reproducibility. After S. aureus -Xen36 biofilm formation, planktonic bacteria were removed from the cultures, and the biofilms were exposed to various concentrations of halicin, tobramycin, cefazolin, vancomycin, or rifampicin for 20 hours. Biofilm viability was determined by measuring resazurin reduction or by counting colony-forming units after sonication. To determine effects of halicin and the conventional antibiotics on biofilm viability, we defined MBEC 75 as the lowest concentration that decreased viability by 75% or more. To determine effects on bacterial viability in planktonic cultures, minimum inhibitory concentrations (MICs) were determined with the broth dilution method. Each result was measured in four to 10 independent experiments.

RESULTS

We found no differences between halicin's effectiveness against planktonic S. aureus and 3-day biofilms (MIC and MBEC 75 for 3-day biofilms was 25 μM [interquartile range 25 to 25 and 25 to 25, respectively]; p > 0.99). Halicin was eightfold less effective against more mature 7-day biofilms (MBEC 75 = 200 μM [100 to 200]; p < 0.001). Similarly, tobramycin was equally effective against planktonic culture and 3-day biofilms (MIC and MBEC 75 for 3-day biofilms was 20 μM [20 to 20 and 10 to 20, respectively]; p > 0.99). Tobramycin's MBEC 75 against more mature 7-day biofilms was 320 μM (320 to 480), which is 16-fold greater than its planktonic MIC (p = 0.03). In contrast, the MBEC 75 for cefazolin, vancomycin, and rifampicin against more mature 7-day biofilms were more than 1000-fold (> 1000; p < 0.001), 500-fold (500 to 875; p < 0.001), and 3125-fold (3125 to 5469; p = 0.004) greater than their planktonic MICs, respectively, consistent with those antibiotics' relative inactivity against biofilms.

CONCLUSION

Halicin was as effective against S. aureus in less mature 3-day biofilms as those in planktonic cultures, but eightfold higher concentrations were needed for more mature 7-day biofilms. Tobramycin, an antibiotic whose effectiveness depends on biofilm maturity, was also as effective against S. aureus in less mature 3-day biofilms as those in planktonic cultures, but 16-fold higher concentrations were needed for more mature 7-day biofilms. In contrast, cefazolin, vancomycin, and rifampicin were substantially less active against both less and more mature biofilms than against planktonic cultures.

CLINICAL RELEVANCE

Halicin is a promising antibiotic that may be effective against S. aureus osteomyelitis and infections on orthopaedic implants. Future studies should assess the translational value of halicin by testing its effects in animal models of orthopaedic infections; on the biofilms of other bacterial species, including multidrug-resistant bacteria; and in combination therapy with conventional antibiotics.

Animal and translational models of SARS-CoV-2 infection and COVID-19

COVID-19 is causing a major once-in-a-century global pandemic. The scientific and clinical community is in a race to define and develop effective preventions and treatments. The major features of disease are described but clinical trials have been hampered by competing interests, small scale, lack of defined patient cohorts and defined readouts. What is needed now is head-to-head comparison of existing drugs, testing of safety including in the background of predisposing chronic diseases, and the development of new and targeted preventions and treatments. This is most efficiently achieved using representative animal models of primary infection including in the background of chronic disease with validation of findings in primary human cells and tissues. We explore and discuss the diverse animal, cell and tissue models that are being used and developed and collectively recapitulate many critical aspects of disease manifestation in humans to develop and test new preventions and treatments.

Hypothermia - an unusual initial presentation of human immunodeficiency virus infection

We report an unusual case of human immunodeficiency virus (HIV) infection initially presenting with hypothermia and bradycardia associated with an HIV encephalitis. Searches reveal only five reported cases of spontaneous episodic hypothermia in the context of HIV infection. In our case, magnetic resonance imaging revealed the presence of a persistent cavum septum pellucidum (CSP), an anatomical and functional neuro-developmental abnormality, as well as changes compatible with an HIV encephalitis. Episodic hypothermia can occur in association with agenesis of the corpus callosum, known as Shapiro’s syndrome, and the presence of a persistent CSP in our case suggests it may have contributed to the clinical presentation.

Skew in ovarian activation depends on domicile size in phyllode-glueing thrips

Costs and benefits of group living are a fundamental topic in behavioural ecology. Resource availability affects individuals’ breeding prospects alone and in groups, as well as how reproduction is distributed within groups (“reproductive skew”). Here, in facultatively social thrips, we provide correlational evidence that breeding resources are associated with (1) whether solitary or social living is favoured, and (2) the degree of ovarian skew. Dunatothrips aneurae (Thysanoptera, Phlaeothripidae) cooperatively build silk “domiciles” on Australian Acacias, feeding exclusively from internal phyllode surfaces. Per capita productivity scaled differently with group size depending on domicile volume — females in small domiciles did better alone than in groups, whereas in large domiciles single and group-nesting females did equally well. Ovarian dissections revealed that in small domiciles some females were nonreproductive, indicating ovarian (i.e. reproductive) skew. Skew increased as domicile size decreased and group size increased. Breeders had smaller oocyte volume in smaller domiciles, especially those containing nonreproductives. These findings suggest group formation and reproductive skew in D. aneurae may be influenced by reproductive competition for breeding resources. Nonreproductive females in small domiciles may be reproductively suppressed, subfertile, or accumulating resources to reproduce.

Dietary restriction increases variability in longevity

Nutritional environments, particularly those experienced during early life, are hypothesized to affect longevity. A recent cross-taxa meta-analysis found that, depending upon circumstance, average longevity may be increased or decreased by early-life dietary restriction. Unstudied are the effects of diet during development on among-individual variance in longevity. Here, we address this issue using emerging methods for meta-analysis of variance. We found that, in general, standard deviation (s.d.) in longevity is around 8% higher under early-life dietary restriction than a standard diet. The effects became especially profound when dietary insults were experienced prenatally (s.d. increased by 29%) and/or extended into adulthood (s.d. increased by 36.6%). Early-life dietary restriction may generate variance in longevity as a result of increased variance in resource acquisition or allocation, but the mechanisms underlying these largely overlooked patterns clearly warrant elucidation.

Alternative migratory locust phenotypes are associated with differences in the expression of genes encoding the methylation machinery

Despite the importance of locust density-dependent polyphenism as a model system for understanding phenotypic plasticity, there is still much to be learnt about its underlying molecular control. Here we describe the first investigation into the expression of genes encoding the DNA methylation machinery in the migratory locust (Locusta migratoria). We show that the alternative solitarious and gregarious phenotypic states induced by different locust rearing densities are associated with significant differences in the expression of the target genes DNA methyltransferase 1, DNA methyltransferase 2 and methyl-CpG-binding domain protein 2/3. This variation was most pronounced in the embryos of solitarious vs. gregarious mothers. We mapped the embryonic methylation profiles of several intragenic regions and a Long Interspersed Nuclear Element (LINE), each of which is known to be differentially expressed between alternative locust phenotypes or has been directly implicated in phase change. LmI and three genes, adenyl cyclase-associated binding protein 2, choline kinase alpha-like and henna, were methylated. Our results set the stage for future studies investigating the specific role of DNA methylation in the maternal transfer of migratory locust phase polyphenism.

Body condition constrains immune function in field populations of female Australian plague locust Chortoicetes terminifera

The insect innate immune system comprises both humoral and cellular defence responses. In the laboratory, the insect immune system is well characterized. In the field, however, little is known about the role of constitutive insect immune function and how it varies within and between populations. Laboratory studies suggest that host nutrition has significant impact upon insect immune function. Thus, the rationale for this study was to sample natural populations of the Australian Plague Locust Chortoicetes terminifera to establish whether locust body condition (as determined by protein and lipid content) impacted their constitutive immune system and, as a result, has the potential to impact on their capacity to respond to a pathogenic challenge. We found that body condition varied greatly between individual female locusts within sites and that haemolymph protein levels, but not body lipid content, varied between sites. Moreover, our measures of immune function were correlated with the haemolymph levels of protein (in the case of haemocyte density), lipid (prophenoloxidase activity) or both (lysozyme-like antimicrobial activity). We discuss the implications of these findings for the role of biological pesticides in the control of locust populations.

Protein leverage and energy intake

Increased energy intakes are contributing to overweight and obesity. Growing evidence supports the role of protein appetite in driving excess intake when dietary protein is diluted (the protein leverage hypothesis). Understanding the interactions between dietary macronutrient balance and nutrient-specific appetite systems will be required for designing dietary interventions that work with, rather than against, basic regulatory physiology. Data were collected from 38 published experimental trials measuring ad libitum intake in subjects confined to menus differing in macronutrient composition. Collectively, these trials encompassed considerable variation in percent protein (spanning 8-54% of total energy), carbohydrate (1.6-72%) and fat (11-66%). The data provide an opportunity to describe the individual and interactive effects of dietary protein, carbohydrate and fat on the control of total energy intake. Percent dietary protein was negatively associated with total energy intake (F = 6.9, P < 0.0001) irrespective of whether carbohydrate (F = 0, P = 0.7) or fat (F = 0, P = 0.5) were the diluents of protein. The analysis strongly supports a role for protein leverage in lean, overweight and obese humans. A better appreciation of the targets and regulatory priorities for protein, carbohydrate and fat intake will inform the design of effective and health-promoting weight loss diets, food labelling policies, food production systems and regulatory frameworks.

Obesity: lessons from evolution and the environment

The 9th Stock Conference acknowledged the complex background of genetic, cultural, environmental and evolutionary factors of obesity. Gene-environment interactions underlie the flexibility in body-weight and body-fat regulation, illustrated by the hunter-gatherers' feast and famine lifestyle, the variation in physical activity over the lifespan being highest at reproductive age, the variation in energy intake through 'eating in the absence of hunger', while running the risk of exceeding the capacity of triacylglyceride storage, leading to lipotoxicity and metabolic problems. Perinatal metabolic programming for obesity via epigenetic changes in response to a 'Western diet' results in production of lipid-poor milk and metabolically efficient pups, contributing to the perpetuation of obesity throughout generations. Evolutionary insight from comparative physiology and ecology indicates that over generations activity-induced energy expenditure has remained the same compared to wild mammals, that energy balance might be dependant on protein balance, while the function of taste changed from detection of poison or energy to social drinking and social behaviour. At present, the impact of assortative mating on obesity prevalence is unambiguously positive. The complexity that appeared can only be fully appreciated by setting the data into the context of our evolutionary history.

Ant workers die young and colonies collapse when fed a high-protein diet

A key determinant of the relationship between diet and longevity is the balance of protein and carbohydrate in the diet. Eating excess protein relative to carbohydrate shortens lifespan in solitary insects. Here, we investigated the link between high-protein diet and longevity, both at the level of individual ants and colonies in black garden ants, Lasius niger. We explored how lifespan was affected by the dietary protein-to-carbohydrate ratio and the duration of exposure to a high-protein diet. We show that (i) restriction to high-protein, low-carbohydrate diets decreased worker lifespan by up to 10-fold; (ii) reduction in lifespan on such diets was mainly due to elevated intake of protein rather than lack of carbohydrate; and (iii) only one day of exposure to a high-protein diet had dire consequences for workers and the colony, reducing population size by more than 20 per cent.

The price of protein: combining evolutionary and economic analysis to understand excessive energy consumption

Excessive weight gain appears, thermodynamically at least, straightforward: growing energy intake and/or falling energy expenditure create an energetic surplus, resulting in fat accumulation. The situation is, however, far more complex, with genetic, physiological, social, psychological and economic factors all implicated. Thus the causes of excessive weight gain remain difficult to disentangle. We combine two recent developments from different areas of nutrition research: the study of food prices in relation to energy content and the hypothesis that an evolved propensity to regulate protein intake more strongly than non-protein calories exerts powerful leverage on overall energy intake. We partition the energy content of a range of common supermarket foods, and show that increasing overall energy content only modestly raises the cost of foods, largely as a result of macronutrients having very different costs. Higher food prices are associated with higher protein content and lower carbohydrate content, whereas fat content was not significantly associated with food price. We show that the differential costs of energy from protein and carbohydrates may bias consumers towards diets high in carbohydrate energy, leading them to consume excessive energy to meet their dietary protein needs. We review evidence from physiology, evolution and economics that support our suggestion.

Starvation resistance is positively correlated with body lipid proportion in five wild caught Drosophila simulans populations

Stress resistance traits in Drosophila often show clinal variation, suggesting that selection affects resistance traits either directly or indirectly. One of the most common causes of stress for animals is the shortage or suboptimal quality of food, and individuals within many species must survive periods of starvation or exposure to nutritionally imbalanced diets. This study determines the relationship between starvation resistance, body lipid content, and lifespan in five recently collected Drosophila simulans populations from four distinct geographic localities. Despite rearing under standard nutritional conditions, we observed significant differences in starvation resistance between sexes and between localities. If body lipid proportion is included as a covariate in statistical analysis the difference between the sexes remains (slopes are parallel, with males more susceptible than females to starvation across all lipid proportions) but the effect of locality disappears. This result suggests that flies from different localities differ in their susceptibility to starvation because of differences in their propensity to store body lipid. We observed a negative relationship between lifespan and starvation resistance in both males and females, suggesting a fitness cost to increasing lipid reserves. These data raise issues about the role of diet in maintaining life history trait variation within and among populations. In conclusion, we show many similarities and surprising differences in life history traits between D. simulans and Drosophila melanogaster.

Flexible diet choice offsets protein costs of pathogen resistance in a caterpillar

Mounting effective resistance against pathogens is costly in terms of energy and nutrients. However, it remains unexplored whether hosts can offset such costs by adjusting their dietary intake so as to recoup the specific resources involved. We test this possibility by experimentally challenging caterpillars (Spodoptera littoralis) with a highly virulent entomopathogen (nucleopolyhedrovirus), under dietary regimes varying in the content of protein and digestible carbohydrate. We found that dietary protein influenced both resistance to pathogen attack and constitutive immune function to a greater extent than did dietary carbohydrate, indicating higher protein costs of resistance than energy costs. Moreover, when allowed to self-compose their diet, insects surviving viral challenge increased their relative intake of protein compared with controls and those larvae dying of infection, thus demonstrating compensation for protein costs associated with resistance. These results suggest that the change in the host's nutritional demands to fight infection induces a compensatory shift in feeding behaviour.

From disorder to order in marching locusts

Recent models from theoretical physics have predicted that mass-migrating animal groups may share group-level properties, irrespective of the type of animals in the group. One key prediction is that as the density of animals in the group increases, a rapid transition occurs from disordered movement of individuals within the group to highly aligned collective motion. Understanding such a transition is crucial to the control of mobile swarming insect pests such as the desert locust. We confirmed the prediction of a rapid transition from disordered to ordered movement and identified a critical density for the onset of coordinated marching in locust nymphs. We also demonstrated a dynamic instability in motion at densities typical of locusts in the field, in which groups can switch direction without external perturbation, potentially facilitating the rapid transfer of directional information.

Does Bertrand's rule apply to macronutrients?

It has been known for over a century that the dose-response curve for many micronutrients is non-monotonic, having an initial stage of increasing benefits with increased intake, followed by increasing costs as excesses become toxic. This phenomenon, termed Bertrand's rule, is widely assumed not to apply to caloric macronutrients. To date this assumption has been safe, owing to the considerable methodological challenges involved in coaxing animals to over-ingest macronutrients in a way that enables the effects of specific food components to be isolated. Here we report an experiment which overcomes these difficulties, to test whether the second phase (incurring costs with excessive intake) applies to carbohydrate intake by the generalist-feeding caterpillar Spodoptera littoralis. The results showed that excess carbohydrate intake caused increased mortality, thus extending Bertrand's rule to macronutrients.

Obesity: the protein leverage hypothesis

The obesity epidemic is among the greatest public health challenges facing the modern world. Regarding dietary causes, most emphasis has been on changing patterns of fat and carbohydrate consumption. In contrast, the role of protein has largely been ignored, because (i) it typically comprises only approximately 15% of dietary energy, and (ii) protein intake has remained near constant within and across populations throughout the development of the obesity epidemic. We show that, paradoxically, these are precisely the two conditions that potentially provide protein with the leverage both to drive the obesity epidemic through its effects on food intake, and perhaps to assuage it. We formalize this hypothesis in a mathematical model. Some supporting epidemiological, experimental and animal data are presented, and predictions are made for future testing.

Dietary influences over proliferating cell nuclear antigen expression in the locust midgut

We have studied the influence of variations in dietary protein (P) and digestible carbohydrate (C), the quantity of food eaten, and insect age during the fifth instar on the expression of the proliferating cell nuclear antigen(PCNA) in the epithelial cells of the midgut (with special reference to the midgut caeca) in the African migratory locust, Locusta migratoria. Densitometric analysis of PCNA-immunostained cells was used as an indirect measure of the levels of expression of PCNA, and a PCNA cellular index(PCNA-I) was obtained. Measurements of the DNA content of the cells have also been carried out by means of microdensitometry of Feulgen-stained, thick sections of midgut. A comparison between the PCNA nuclear level and the DNA content was performed. The PCNA levels were significantly different among the cells of the five regions studied: caeca, anterior ventricle, medial ventricle, posterior ventricle and ampullae of the Malpighian tubules. We have studied in more detail the region with highest PCNA-I, i.e. the caeca. The quality and the quantity of food eaten under ad libitum conditions were highly correlated with both the PCNA and DNA levels in the caeca cells. Locusts fed a diet with a close to optimal P:C content (P 21%, C 21%) showed the highest PCNA and DNA content. In locusts fed a food that also contained a 1:1 ratio of P to C but was diluted three-fold by addition of indigestible cellulose (P 7%, C 7%), a compensatory increase in consumption was critical to maintaining PCNA levels. Our measurements also showed that the nuclear DNA content of the mature and differentiated epithelial cells was several-fold higher than the levels in the undifferentiated stem cells of the regenerative nests. These results, combined with the low number of mitotic figures found in the regenerative nests of the caeca and the marked variation in PCNA levels among groups, suggest that some type of DNA endoreduplication process may be taking place. Our data also indicate that the DNA synthetic activity in the midgut is related to feeding in locusts. The possible dietary and nutritional regulatory mechanisms and the significance of the differences found are discussed.

Nutrient balancing in grasshoppers: behavioural and physiological correlates of dietary breadth

We examined correlates of nutrient balancing with dietary range by comparing diet selection and ingestive, post-ingestive and performance-related responses to macronutrient imbalance in two species of grasshopper. One of the two species, Locusta migratoria (the African migratory locust), is a specialist grass-feeder, while the other, Schistocerca gregaria (the desert locust), is a generalist herbivore that includes both grasses and forbs in its diet. In ad libitum conditions, both species composed a balanced intake of the two macronutrients protein and carbohydrate from nutritionally complementary synthetic foods, but the composition of the selected diet differed, with the generalist selecting more protein, but not carbohydrate, than the grass-specialist. The grass-specialist, by contrast, retained ingested nitrogen more efficiently on the ad libitum diets. When confined to nutritionally imbalanced foods, both species regulated ingestion in such a way as to mitigate excesses as well as deficits of the two nutrients. The responses were, however, distinct in the two species, with the generalist feeder ingesting greater excesses of protein than the specialist. The species also differed in their post-ingestive responses to ingested excesses of nutrient, with the generalist but not the specialist using protein-derived carbon as an energy source when fed carbohydrate-deficient foods. The generalist also retained a higher level of body protein when confined to protein-deficient diets. The data suggested one functional reason why the generalist species selected a diet with higher protein content in the ad libitum treatment because, when confined to the nutritionally imbalanced foods, development rate peaked on higher protein foods for the generalist compared with the specialist. Many aspects of these data agree with the prediction that generalist-feeding animals should show greater behavioural and physiological flexibility in their responses to nutrient imbalance than do specialists.

A comparison of nutritional regulation in solitarious- and gregarious-phase nymphs of the desert locust Schistocerca gregaria

Nutritional regulatory responses were compared for the cryptic ‘solitarious’ and the conspicuously coloured, aggregating ‘gregarious’ phases of the desert locust Schistocerca gregaria. The desert locust has the genetic potential to exist in either phase, changing between them within a lifetime and epigenetically across generations. Our aim was to compare final-instar nymphs of the two phases with respect to key nutritional variables, including (i) points of regulated intake (the ‘intake target’) for protein and carbohydrate, (ii) the nature of trade-offs between over-eating nutrients in excess and under-eating those in deficit when fed nutritionally unbalanced foods, (iii) diet-related patterns of nutrient utilisation, and (iv) the performance consequences of eating nutritionally unbalanced diets. When provided with pairs of nutritionally unbalanced but complementary foods, both phases regulated their intake of protein and carbohydrate to a similar point. However, when confined to foods that were of unbalanced protein to carbohydrate ratio, gregarious nymphs ate more than solitarious insects. Both phases regulated protein growth, but gregarious insects did so to a lower adult body protein content and converted ingested protein to growth less efficiently. When fed a food high in carbohydrate and low in protein, gregarious nymphs deposited more body lipid and survived less well than did solitarious insects. Solitarious nymphs developed more quickly than gregarious nymphs except on the two most extremely unbalanced diets, on which development time was similar. The results are discussed with respect to the different nutritional ecologies of the two phases and used to develop the hypothesis that animals have evolved to trade-off the cost of eating excess of a nutritionally unbalanced diet against the probability of encountering foods of complementary composition in the future.

High resolution 1H NMR spectroscopic studies of the composition of the haemolymph of crowd- and solitary-reared nymphs of the desert locust, Schistocerca gregaria

High resolution 1H NMR spectroscopy provided a rapid and non-invasive means of establishing a multicomponent profile of the low molecular weight organic metabolites present in the haemolymph of crowd-reared and solitary-reared desert locusts. Assignments of the 1H NMR resonances detected in the one-dimensional (1D) spectra were supported by the comparison of chemical shifts with those of commonly found metabolites, the application of 2D NMR spectroscopy, and spiking of authentic standards into the sample. The haemolymph metabolite profile was found to comprise trehalose, a series of amino acids, organic acids, lipids, ethanol and the polyamine putrescine. In total, it was possible to detect simultaneously and potentially quantify over 20 endogenous compounds. An interesting difference between the phases was the higher putrescine concentrations present in solitary-reared nymphs, which may indicate a role of this compound in phase determination. In addition, differences in the concentrations of trehalose, lipids, acetate and ethanol were also observed between solitary-reared and gregarious-reared nymphs enabling the ready differentiation of the two phases based on the NMR spectra of the haemolymph.

Gregarious behavior in desert locusts is evoked by touching their back legs

Desert locusts in the solitarious phase were repeatedly touched on various body regions to identify the site of mechanosensory input that elicits the transition to gregarious phase behavior. The phase state of individual insects was measured after a 4-h period of localized mechanical stimulation, by using a behavioral assay based on multiple logistic regression analysis. A significant switch from solitarious to gregarious behavior occurred when the outer face of a hind femur had been stimulated, but mechanical stimulation of 10 other body regions did not result in significant behavioral change. We conclude that a primary cause of the switch in behavior that seeds the formation of locust swarms is individuals regularly touching others on the hind legs within populations that have become concentrated by the environment.

The influence of mechanical, visual and contact chemical stimulation on the behavioural phase state of solitarious desert locusts (Schistocerca gregaria)

We investigated the influence of mechanical, visual and contact chemical stimulation on behavioural gregarization of fifth-instar solitarious nymphs of the desert locust. The stimuli were applied in two 2x2 factorial experimental designs, the first with contact chemical and mechanical stimuli, and the second with contact chemical and visual stimulation. Stimulus treatments were applied for a 4-5 h period, after which the behavioural phase state of individual locusts was measured using an assay based on multiple logistic regression analysis of behavioural variables. Mechanical stimulation was provided by showering test insects with millet seeds, thereby excluding the possibility of contact chemical self-stimulation by repeated contact with the same objects. Visual stimulation consisted of the sight of crowd-reared locusts, while contact chemical stimulation was a dichloromethane extract of cuticular hydrocarbons from gregarious nymphs applied to the perch of the test insect. Mechanical stimulation was powerfully gregarizing, whether alone or in combination with contact chemical stimuli. Application of cuticular extract to the perch had no measurable effect on behavioural phase state, either alone or when presented with mechanical or visual stimuli. Visual stimulation alone partly gregarized test locusts. These results appear to conflict with other reports of the gregarizing effect of cuticular hydrocarbons and possible reasons for this discrepancy are discussed.

Is there an intraspecific role for density-dependent colour change in the desert locust?

Attempts to uncover the adaptive significance of density-dependent colour polyphenism in the desert locust, Schistocerca gregaria (Orthoptera: Acrididae), have been unsuccessful. Desert locust juveniles can change colour as part of a phenotypically plastic response to changes in local population density known as phase polyphenism. They are typically cryptic in colour at low rearing density (solitarious phase), but become conspicuous at high density (gregarious phase). Recent evidence indicates that this colour change functions interspecifically as an aposematic signal. Other recent evidence, however, suggests that previous attempts to demonstrate an intraspecific function of gregarious coloration in mediating group interactions among locusts may have been confounded by the effects of multiple sensory cues. We reinvestigated the intraspecific function of density-dependent colour polyphenism and specifically controlled for potentially confounding olfactory and tactile cues. We found no effect of gregarious phase (yellow and black) coloration as either a gregarizing stimulus to behaviourally solitarious locusts or as a visual aggregation stimulus behaviourally to gregarious locusts. We did, however, find that nonmoving solitarious phase (green) coloration significantly increased the activity levels of behaviourally gregarious locusts. We cannot explain this result and its biological relevance remains unknown. In the absence of support for the intraspecific visual cue hypothesis, we favour an aposematic perspective on the function of density-dependent colour polyphenism in the desert locust. The aposematic perspective parsimoniously accounts for density-dependent changes in both colour and behaviour. Copyright 2000 The Association for the Study of Animal Behaviour.

The role of female accessory glands in maternal inheritance of phase in the desert locust Schistocerca gregaria

Accessory glands of crowd-reared females of Schistocerca gregaria were ligatured from the lateral oviducts. Hatchlings resulting from egg pods laid after the treatment showed a significant shift towards solitarious behaviour as compared to hatchlings from control-treated females. Morphometric measurement of hatchlings revealed no consistent difference between ligatured and control females, however, one ratio (hind femur length/vertex width) was approaching significance. Hatchlings from eggs of crowd-reared females behaved solitariously when freshly laid eggs were washed with a saline solution. Gregarious behaviour could be restored when washed eggs were treated with a saline extract of the accessory glands. The colouration of hatchlings was not affected by any treatment. Our findings implicate the accessory glands in the production, release or activation of the recently reported gregarizing factor found in the egg pod foam [McCaffery, A.R., Simpson, S.J., Islam, M.S., Roessingh, P., 1998. A gregarizing factor present in the egg pod foam of the desert locust Schistocerca gregaria. Journal of Experimental Biology 201, 347-363].

The role of food distribution and nutritional quality in behavioural phase change in the desert locust

The behaviour of herbivorous insects is influenced by their nutritional state. Nutrition-induced behavioural changes are often interpreted as adaptive mechanisms for controlling nutrient intake; however, their influence on other life history traits has received far less attention. We investigated the effect of food quality and distribution on the behaviour and phase state of desert locusts, Schistocerca gregaria Forskål (Orthoptera, Acrididae), which change from the 'solitarious' to the 'gregarious' phase in response to population density. Phase change involves many morphological, physiological and behavioural changes. Solitarious insects are cryptic whereas gregarious locusts aggregate. Individual phase change is stimulated by mechanical contact with other locusts. A clumped resource distribution promotes change to the gregarious phase by increasing crowding and contact between individuals. In this study, we found that the effect of food distribution on locust phase depended on the nutritional quality of the food. We used three synthetic food treatments: near optimal, dilute and a choice of two unbalanced but complementary foods. Clumped resource distribution led to increased gregarization in the dilute and the complementary diet treatments. This effect was particularly pronounced on the complementary foods, owing to the interaction of crowding and locomotion. Gregarization was most pronounced in the dilute diet treatment, owing to increased activity. These diet-induced effects are explained in terms of behavioural changes in locomotion, quiescence and feeding that are consistent with what is known from earlier work on locust feeding behaviour and behavioural phase change. Copyright 2000 The Association for the Study of Animal Behaviour.

Density-dependent aposematism in the desert locust

The ecological processes underlying locust swarm formation are poorly understood. Locust species exhibit phenotypic plasticity in numerous morphological, physiological and behavioural traits as their population density increases. These density-dependent changes are commonly assumed to be adaptations for migration under heterogeneous environmental conditions. Here we demonstrate that density-dependent nymphal colour change in the desert locust Schistocerca gregaria (Orthoptera: Acrididae) results in warning coloration (aposematism) when the population density increases and locusts consume native, toxic host plants. Fringe-toed lizards (Acanthodactylus dumerili (Lacertidae)) developed aversions to high-density-reared (gregarious-phase) locusts fed Hyoscyamus muticus (Solanaceae). Lizards associated both olfactory and visual cues with locust unpalatability, but only gregarious-phase coloration was an effective visual warning signal. The lizards did not associate low rearing density coloration (solitarious phase) with locust toxicity. Predator learning of density-dependent warning coloration results in a marked decrease in predation on locusts and may directly contribute to outbreaks of this notorious pest.

Assuaging nutritional complexity: a geometrical approach

We have introduced a framework that enables the identification of the important elements in complex nutritional systems, and the quantification of the interactions among them. These interactions include those among the multiple constituents of the ingesta, as well as between behavioural (ingestive) and physiological (post-ingestive) components of nutritional homeostasis. The resulting descriptions provide a powerful means to generate and test hypotheses concerning the mechanisms, ecology and evolution of nutritional systems. We provide an overview of the key concepts involved in our scheme, and then introduce four examples in which the framework is used to develop and test hypotheses. In the first example we use comparative methods based on a data set of 117 insect species to test a prediction about the relationship between evolving an association with bacterial endosymbionts and the composition of the optimal diet. Second, using two species of locusts (a grass specialist and a generalist), we consider the relationship between an animal's diet breadth and the decision rules employed when feeding on foods containing suboptimal protein: carbohydrate values. Third, we introduce a mathematical model that predicts the dose-response properties of gustatory systems in the context of nutritional homeostasis. Finally, we consider the interaction between tannic acid and macronutrient balance in the diet of locusts.

High- and low-affinity single-peptide/MHC ligands have distinct effects on the development of mucosal CD8alphaalpha and CD8alphabeta T lymphocytes

In this study, we compared the influence of two peptides on the selection of CD8alphaalpha and CD8alphabeta intraepithelial lymphocytes (IELs) of the intestine, which develop by a unique and partially thymus-independent process. Mice were used in which all T cells carried one transgenic T cell antigen receptor (TCR) (F5), and in which only well defined transgenic peptides were presented by H-2Db. The first peptide, for which the F5 TCR has a high affinity, derives from the influenza virus nucleoprotein (NP68). The second peptide, NP34, is an antagonistic variant of NP68 and is recognized by the F5 TCR with low affinity. To avoid presentation of endogenous peptides or production of T cells carrying alternative TCRs, F5 TCR transgenic mice were generated that were deficient for Tap-1 and Rag-1. In these mice, no CD3(+)CD8(+) cells were found in lymph nodes, spleen, or intestine. Introduction of transgenes encoding either NP34 or NP68 along with an endoplasmic reticulum signal sequence enabled Tap-1-independent expression of each peptide in these mice. Positive selection of F5TCR+CD8(+) thymocytes was not rescued by these transgenic peptides. However, the high-affinity NP68 peptide induced maturation of CD8alphaalpha IEL, whereas the low-affinity NP34 peptide stimulated development of both CD8alphabeta and CD8alphaalpha IEL, but in smaller numbers. When both peptides were present, CD8alphabeta T cells failed to develop and the number of CD8alphaalpha IELs was lower than in mice carrying the NP68 transgene alone. These data demonstrate that single ligands with a high or low affinity for TCR are capable of inducing or inhibiting the maturation of alternative subsets of IELs.

Both the lymphotoxin and tumor necrosis factor pathways are involved in experimental murine models of colitis

BACKGROUND & AIMS

Membrane lymphotoxin (LT) alpha/beta, a member of the tumor necrosis factor (TNF) family of immune regulatory molecules, is involved both in the development of secondary lymphoid tissues and the maintenance of organized lymphoid tissues in the adult. Defects observed in the mucosal immune system in animals with a genetically disrupted LTalpha/beta pathway coupled with the expression of LTalpha/beta in activated T cells motivated an examination of the importance of this pathway in experimental colitis.

METHODS

Soluble LTbeta receptor (LTbetaR) immunoglobulin fusion protein was used to inhibit the LTalpha/beta/light axis in two independent rodent models of colitis: CD45RBhi CD4(+)-reconstituted SCID mice and bone marrow-transplanted tg26 mice (BM --> tg26).

RESULTS

Treatment with LTbetaR immunoglobulin attenuated the development of both the clinical and histological manifestations of the disease in these two murine models of colitis. Given the success of TNF inhibitors in the treatment of human Crohn's disease, the effects of LTbetaR immunoglobulin have been compared with antibody to TNF in the BM --> tg26 model, and both treatments were equally efficacious.

CONCLUSIONS

The LT pathway plays a role in the development of colitis as important as that of the TNF system and, therefore, represents a potential novel intervention point for the treatment of inflammatory bowel disease.

Effects of food nutrient content, insect age and stage in the feeding cycle on the FMRFamide immunoreactivity of diffuse endocrine cells in the locust gut

We have studied the influence of variations in dietary protein and digestible carbohydrate content, of insect age and of time during the feeding cycle on the endocrine cells of the ampullar region of the midgut in the African migratory locust Locusta migratoria L. Morphometric analysis of FMRFamide-like immunoreactivity was used as an indirect measure of the amount of FMRFamide-related peptides (FaRPs) stored in the gut endocrine cells. There was a highly significant correlation between FaRP content and the nutritional quality of the food, measured relative to the concentrations and ratio of protein to digestible carbohydrate in a nutritionally optimal diet. The direction of the relationship between FaRP content and diet quality varied with age during the fifth stadium. On day 1, FaRP levels increased with the nutritional quality of the food, while on day 4 the opposite relationship was observed. Release of peptide was triggered by the onset of a meal during ad libitum feeding, with cell FaRP levels returning to premeal values within 15 min of the meal ending. The results also suggested that cell contents were released during food deprivation beyond the normal intermeal interval. Locusts switched for a single meal during ad libitum feeding on day 4 from a low- to a high-carbohydrate food did not respond by reducing endocrine cell FaRP content. Our results show a relationship between the diffuse gut endocrine system and feeding and nutrition in locusts. The ampullar endocrine cells are in three-way contact with the midgut luminal contents, with the primary urine from the Malpighian tubules and with the haemolymph. They are thus ideally positioned to play an integrative receptor-secretory function in the regulation of a variety of post-ingestive processes, such as enzyme secretion, absorption, gut motility or nutrient metabolism.

Spatial scales of desert locust gregarization

Central to swarm formation in migratory locusts is a crowding-induced change from a "solitarious" to a "gregarious" phenotype. This change can occur within the lifetime of a single locust and accrues across generations. It represents an extreme example of phenotypic plasticity. We present computer simulations and a laboratory experiment that show how differences in resource distributions, conspicuous only at small spatial scales, can have significant effects on phase change at the population level; local spatial concentration of resource induces gregarization. Simulations also show that populations inhabiting a locally concentrated resource tend to change phase rapidly and synchronously in response to altered population densities. Our results show why information about the structure of resource at small spatial scales should become key components in monitoring and control strategies.

Diet quality influences the (&dgr ;)13C and (&dgr ;)15N of locusts and their biochemical components

To determine whether relative enrichments of 15N and 13C in locusts are influenced by diet, locust nymphs were raised from hatchlings to adults on either seedling wheat or maize. Maize provided less hexose sugars and protein per gram than did wheat. Maize also depends on the C4 form of photosynthesis, while wheat uses the C3 form; this difference in photosynthetic pathways produces two distinguishable ranges of 13C values.The lower-quality maize diet corresponded to a 5.1 increase in animal 15N, relative to diet, whereas the wheat diet corresponded to an increase of only 2.3 . The maize-fed animals were more 13C-depleted in lipid, trehalose and chitin than those fed wheat. The results for 15N and 13C suggest that substrate recycling occurred on the low-quality maize diet. Consequently, we examined the variations in the isotopic differences between locusts and their diet at the biochemical level.

Consequences of Fas-ligand and perforin expression by colon T cells in a mouse model of inflammatory bowel disease

BACKGROUND & AIMS

We describe a type of colitis that develops after transplantation of nonallogeneic wt bone marrow cells into T cell- and natural killer cell-deficient Tg26 mice (BM-->Tg26). In these animals, severe wasting and inflammation of the colon correlates with the expansion of mucosal T lymphocytes that displays cytotoxic activity. The aims of this study were to determine the relative contribution of perforin and Fas ligand (Fas-L) expression to the cytotoxic action of these T cells and to examine the influence of each pathway in this model of colitis.

METHODS

Colonic T cells were tested for their ability to mediate Fas- and perforin-dependent killing in redirected cytotoxicity assays. Bone marrow cells from donor mice lacking either Fas-L (gld mice) or perforin (PFPnull mice) or both molecules were used to reconstitute Tg26 mice.

RESULTS

Colon cytotoxic T lymphocyte displayed both Fas- and perforin-dependent killing. Deficiency in perforin, but not Fas-L, resulted in reduced incidence of wasting and, to a lesser extent, severe colitis in BM-->Tg26 animals.

CONCLUSIONS

Colon T cells from BM-->Tg26 mice express both perforin and Fas-L. Although neither pathway is critical in the development of colitis, perforin does have a measurable influence on disease in the BM-->Tg26 colitis model.

Effects of sensory stimuli on the behavioural phase state of the desert locust, Schistocerca gregaria

The nature of stimuli, emanating from other locusts, which are effective in inducing gregarization in the desert locust was investigated. Isolated-reared fifth-instar nymphs were subjected to tactile, visual and olfactory stimuli, presented singly and in combination, and the effect on the behavioural phase state was quantified using logistic regression analysis. Tactile stimulation provided by rolling paper spheres proved to be highly gregarizing, whether presented alone or in combination with the other stimuli. Olfactory and visual stimuli together caused partial behavioural gregarization. Visual stimulation alone was weakly gregarizing after prolonged exposure, while olfactory stimuli alone were ineffective. Nymphs and pre-reproductive and reproductive adults of both sexes were also treated with synthetic adult male `aggregation' pheromone blend (Torto et al., 1994, Journal of Chemical Ecology 20, 1749). No effect of this blend was found on the behavioural phase state, even when visual stimuli were present. Non-locust related stimuli, including wheat odour and flashing lights, were also tested on nymphs. Neither induced any change in the behavioural phase state, indicating that increased sensory flow is not a sufficient explanation for locust-induced behavioural phase change.

Development of colonic adenocarcinomas in a mouse model of ulcerative colitis

Mice deficient in both interleukin-2 and beta 2-microglobulin expression (Beta 2mullnull x IL-2null mice) develop an inflammatory disease of the colon resembling ulcerative colitis. To examine long-term complications of disease in these mice, a group of 34 Beta 2mnull x IL-2null mice was monitored for 6-12 months. Development of clinical disease was assessed by wasting, general appearance, and diarrhea. Further analysis included histologic examination of the distal colon for colitis, staining of CD4+ T cells for surface activation markers, and cytoplasmic staining of CD4+ T cells for IFN-gamma and TNF-alpha. These older Beta 2mnull x IL-2null mice had activated CD4+ T cells as assessed by surface markers on flow cytometry. Cytoplasmic staining revealed IFN-gamma production, but not TNF-alpha production by CD4+ T cells. The majority of these older Beta 2mnull x IL-2null mice continued to have colitis on histology. However, they lived much longer and had less wasting in comparison to IL-2null mice. At necropsy, 11 (32%) of 34 of the Beta 2mnull x IL-2null mice had tumors in the proximal half of the colon. Histologic examination confirmed these tumors to be adenocarcinomas. These mice may be useful as a model for studying carcinogenesis in chronic colitis.

T cell-mediated pathology in two models of experimental colitis depends predominantly on the interleukin 12/Signal transducer and activator of transcription (Stat)-4 pathway, but is not conditional on interferon gamma expression by T cells

The requirements for interleukin (IL)-12/signal transducer and activator of transcription (Stat)-4 signaling and induction of T cell-specific interferon (IFN)-gamma expression in the development of T helper cell (Th)1-type pathology were examined in two different models of experimental colitis. In each model, abnormal reconstitution of the T cell compartment in immunodeficient mice by adoptive cell transfer leads to a wasting syndrome and inflammation of the colon, induced by IFN-gamma and tumor necrosis factor (TNF)-alpha-producing T cells. We show here that treatment with anti-IL-12 antibodies in one of the models, or reconstitution with T cells from Stat-4-deficient (Stat-4(null)) mice in both models resulted in a milder disease in the majority of recipient animals, compared with those that were left untreated or that had been reconstituted with wt cells. Protected mice in each group also harbored lower frequencies of IFN-gamma-producing T cells than did diseased mice, suggesting that effects on wasting and colitis resulted from the attenuation of IFN-gamma expression by T cells. To test whether the development of pathogenic T cells in the two colitis models was directly dependent on T cell-specific IFN-gamma expression, IFN-gammanull donors were used for T cell reconstitution in each system. Surprisingly, large numbers of IFN-gammanull-reconstituted mice developed wasting and colitis, which in many cases was of comparable severity to that seen in animals reconstituted with wt cells. Furthermore, T cells from these animals expressed TNF-alpha, demonstrating that they had retained the ability to produce another proinflammatory cytokine. Taken together, these results demonstrate that in some forms of chronic experimental colitis the development of pathogenic T cells is influenced predominantly, though not exclusively, by IL-12 via the actions of Stat-4 proteins. Furthermore, our data suggest that in the models of colitis studied here the effects of IL-12/Stat-4 or other Th1 promoting pathways are not limited to the induction of IFN-gamma gene expression in T lymphocytes.

Strategies for comprehensive nurse managed occupational health services: focusing on work related health problems while maintaining comprehensive care delivery

1. Occupational health nurses can position themselves to be valuable assets as human resources become more important in the complicated world of producing products, services, managing employees, and making a profit. 2. An on-site nurse managed occupational health unit provides opportunities for positively influencing employees' health while affording multiple opportunities for the occupational health nurse to impact the bottom line of the business unit. Exploring the opportunities can lead to exciting program development and implementation. 3. The nursing process (assessment, planning, implementation, and evaluation) can be applied to occupational health programs and service development. This technique assists the nurse in identifying an organization's strengths and weaknesses and in developing the strategies for the implementation of a coordinated program.

The Effect of Diet Quality on δ(13)C and δ(15)N in the Tissues of Locusts, Locusta migratoria L

Abstract Locust nymphs were raised from hatching to adult locusts on either seedling wheat (C(3)) or maize (C(4)), to determine whether relative enrichments/depletions of (15)N and (13)C within body tissues are influenced by diet. The maize contained less hexose sugars and protein per gram than wheat. The isotopic spacing between the food and the whole insect was found to differ between the two diets. The lower quality maize diet showed an overall +5.1‰ enrichment in δ(15)N compared to + 2.8‰ for wheat, possibly due to increased fractionation due to protein recycling. The maize diet resulted in increased depletion in lipid and trehalose and depletion in chitin relative to diet. The results for both δ(15)N and δ(13)C suggest that substrate recycling was occurring on the low quality maize diet. Therefore diet quality determines the enrichment/depletion in δ(15)N and δ(13)C within organisms.

Geometric analysis of macronutrient selection in the rat

A conceptual framework is introduced which has been derived from work on insects. The scheme is intended to integrate studies of diet selection, regulation of amounts eaten, nutrient utilization, body composition and animal performance. Aspects of framework are illustrated with published data on macronutrient selection in the rat. An animal is viewed as moving through a multidimensional nutrient space, which is bounded by axes representing each required nutrient and within which lie optimal points of intake and nutrient allocation ("targets"). The aim is first to estimate the location of these functional optima experimentally, and then to interpret the responses of animals which are constrained from reaching them ("decisions of best compromise"). The framework can then be used to interpret data from animals reared under differing environmental conditions and to compare animals of differing developmental stage, genotype or nutritional state.

Development and function of T lymphocytes and natural killer cells after bone marrow transplantation of severely immunodeficient mice

Bone marrow (BM) transplantation experiments were performed in a strain of CD3 epsilon-transgenic mice, termed tg epsilon 26, which are completely deficient in T-cell and natural killer (NK) cell development. We found that an interaction of stromal cells and prothymocytes is required for the induction of a cortical thymic microenvironment. This induction takes place in a time window from fetal development to early neonates. Although the thymic environment is not required for NK-cell development, we found that aberrantly educated alpha beta or gamma delta T lymphocytes can influence NK-cell ontogeny. Surprisingly, BM transplantation of tg epsilon 26 fetuses and neonates results in normal T-cell development, but very low levels of NK cells. The poor NK-cell reconstitution in fetal and neonatal stages could be explained by an inefficient migration of hematopoietic progenitor cells to the BM. By contrast, migration of the progenitor cells to the thymus was efficient to initiate T-cell development. BM transplantation of adult tg epsilon 26 mice resulted in abnormal T-cell development which, in turn, caused an inflammatory bowel disease (IBD) in the recipient mice. Studies in these BM chimeras have revealed that both alpha beta and gamma delta T cells can be pathogenic and, further, that Th1-like cytokines produced by these cells are causal factors in the pathogenesis of IBD.

Glutathione reductase turned into trypanothione reductase: structural analysis of an engineered change in substrate specificity

Trypanosoma and Leishmania, pathogens responsible for diseases such as African sleeping sickness, Chagas' heart disease, or Oriental sore, are two of the very few genera that do not use the ubiquitous glutathione/glutathione reductase system to keep a stable cellular redox balance. Instead, they rely on trypanothione and trypanothione reductase to protect them from oxidative stress. Trypanothione reductase (TR) and the corresponding host enzyme, human red blood cell glutathione reductase (GR), belong to the same flavoprotein family. Despite their closely related three-dimensional structures and although their natural substrates share the common structural glutathione core, the two enzymes are mutually exclusive with respect to their disulfide substrates. This makes the parasite enzyme a potential target for antitrypanosomal drug design. While a large body of structural data on GR complexes is available, information on TR-ligand interactions is very limited. When the two amino acid changes Ala34Glu and Arg37Trp are introduced into human GR, the resulting mutant enzyme (GRTR) prefers trypanothione 700-fold over its original substrate, effectively converting a GR into a TR [Bradley, M., Bücheler, U. S., & Walsh, C. T. (1991) Biochemistry 30, 6124-6127]. The crystal structure of GRTR has been determined at 2.3 A resolution and refined to a crystallographic R factor of 20.9%. We have taken advantage of the ease with which ligand complexes can be produced in GR crystals, a property that extends to the isomorphous GRTR crystals, and have produced and analyzed crystals of GRTR complexes with glutathione, trypanothione, glutathionylspermidine and of a true catalytic intermediate, the mixed disulfide between trypanothione and the enzyme. The corresponding molecular structures have been characterized at resolutions between 2.3 and 2.8 A with R factors ranging from 17.1 to 19.7%. The results indicate that the Ala34Glu mutation causes steric hindrance leading to a large displacement of the side chain of Arg347. This movement combined with the change in charge introduced by the mutations modifies the binding cavity, forcing glutathione to adopt a nonproductive binding mode and permitting trypanothione and to a certain degree also the weak substrate glutathionylspermidine to assume a productive mode.

CD16-expressing CD8alpha alpha+ T lymphocytes in the intestinal epithelium: possible precursors of Fc gammaR-CD8alpha alpha+ T cells

T lymphocytes normally express their Ag receptors in association with the CD3 proteins, which include CD3zeta. In CD3zeta eta(null) mice thymic and peripheral T lymphocytes do not express the TCR/CD3 complex on their surface due to retention in the endoplasmic reticulum of the remaining polypeptide chains. However, intestinal intraepithelial lymphocytes (iIEL) of CD3zeta eta(null) mice do express surface TCR, because the Fc epsilonRI gamma chain replaced the CD3zeta chain in the TCR/CD3 complex. Here we report that in a subset of CD8alpha alpha+ iIEL the presence of the Fc epsilonRI gamma chain could be accounted for by the surface expression of the Fc gammaRIII(CD16) complex. Because in wild-type (wt) mice only CD16+ iIEL coexpressed Fc epsilonRI gamma and CD3zeta, we concluded that the presence of Fc epsilonRI gamma was dictated by its required participation of CD16 complex. CD8alpha alpha+ iIEL bearing CD16 and B220 were also detected in the intestinal mucosa of RAG-2(null) mice from 12 days after birth onward. Two independent experimental settings were used in an attempt to demonstrate that CD16+ iIEL matured into CD16- T cells. First, in the RAG-2(null) mice, iIEL responded to in vivo administration of an anti-CD3epsilon mAb by progression to a more mature stage of development, characterized by a loss of CD16 and B220. Secondly, a conversion to CD16- iIEL occurred upon transfer of wt CD16+ iIEL into RAG-2(null) mice. We conclude from these experiments that in both RAG-2(null) and wt mice, a precursor/progeny relationship may exists between CD16+ B220+ CD8alpha alpha+ and CD16- B220- CD8alpha alpha+ iIEL.

CD16-expressing CD8alpha alpha+ T lymphocytes in the intestinal epithelium: possible precursors of Fc gammaR-CD8alpha alpha+ T cells

T lymphocytes normally express their Ag receptors in association with the CD3 proteins, which include CD3zeta. In CD3zeta eta(null) mice thymic and peripheral T lymphocytes do not express the TCR/CD3 complex on their surface due to retention in the endoplasmic reticulum of the remaining polypeptide chains. However, intestinal intraepithelial lymphocytes (iIEL) of CD3zeta eta(null) mice do express surface TCR, because the Fc epsilonRI gamma chain replaced the CD3zeta chain in the TCR/CD3 complex. Here we report that in a subset of CD8alpha alpha+ iIEL the presence of the Fc epsilonRI gamma chain could be accounted for by the surface expression of the Fc gammaRIII(CD16) complex. Because in wild-type (wt) mice only CD16+ iIEL coexpressed Fc epsilonRI gamma and CD3zeta, we concluded that the presence of Fc epsilonRI gamma was dictated by its required participation of CD16 complex. CD8alpha alpha+ iIEL bearing CD16 and B220 were also detected in the intestinal mucosa of RAG-2(null) mice from 12 days after birth onward. Two independent experimental settings were used in an attempt to demonstrate that CD16+ iIEL matured into CD16- T cells. First, in the RAG-2(null) mice, iIEL responded to in vivo administration of an anti-CD3epsilon mAb by progression to a more mature stage of development, characterized by a loss of CD16 and B220. Secondly, a conversion to CD16- iIEL occurred upon transfer of wt CD16+ iIEL into RAG-2(null) mice. We conclude from these experiments that in both RAG-2(null) and wt mice, a precursor/progeny relationship may exists between CD16+ B220+ CD8alpha alpha+ and CD16- B220- CD8alpha alpha+ iIEL.

Expression of pro-inflammatory cytokines by TCR alpha beta+ and TCR gamma delta+ T cells in an experimental model of colitis

An inflammatory bowel disease (IBD) comparable to human ulcerative colitis is induced upon transfer of T cell-depleted wild-type (F1) bone marrow into syngeneic T cell-deficient (tg epsilon26) mice (F1 --> tg epsilon26). Previously we have shown that activated CD4+ T cells predominate in transplanted tg epsilon26 mice, and adoptive transfer experiments verified the potential of these cells to cause disease in immunodeficient recipient mice. Using flow cytometry for the detection of intracellular cytokine expression, we demonstrate in the present study that large numbers of CD4+ and CD8+ TCR alphabeta+ T cells from the intraepithelial region and lamina propria of the colon of diseased, but not from disease-free mice, produced interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha). Large numbers of T cells from peripheral lymphoid tissues of these animals also expressed IFN-gamma and TNF-alpha, but few expressed interleukin-4, demonstrating a strong bias towards Th1-type T cell responses in these animals. TCR gammadelta+ T cells, typically minor constituents of the inflammatory infiltrate of the colon in F1 --> tg epsilon26 mice, also expressed IFN-gamma at a high frequency upon CD3 stimulation. In light of these findings we examined the potential involvement of TCR gammadelta+ T cells by testing their ability to induce colitis in tg epsilon26 mice. We report here that tg epsilon26 mice transplanted with T cell-depleted bone marrow from TCR alpha(null) and TCR beta(null) animals developed IBD. Furthermore, disease in these mice correlated with the development of peripheral and colonic TCR gammadelta+ T cells capable of IFN-gamma production. These results suggest that IFN-gamma may be a common mediator of IBD utilized by pathogenic T cells of distinct phenotype.

Natural killer cell development is blocked in the context of aberrant T lymphocyte ontogeny

Over-expression of human or mouse CD3-epsilon transgenes profoundly disturbs T lymphocyte and natural killer (NK) cell development. One of these transgenic strains, termed tgepsilon26, displays a very early block in T lymphocyte and NK cell development. We showed previously that the absence of early thymocyte progenitors results in an abnormal thymic microenvironment. Due to this thymic defect, T cell development could not be restored by bone marrow (BM) transplantation in adult tgepsilon26 mice but could in fetal tgepsilon26 mice. Here we examine the effect of this abnormal thymic environment on NK cell development. We demonstrate that NK cell maturation in tgepsilon26 mice was reconstituted by BM derived from completely T cell-deficient mice, i.e. RAG-2(-/-) and TCRbeta x delta-/-, but not from wild-type mice. Moreover, tgepsilon26 mice transplanted with BM from partially T cell-deficient mice, i.e. TCRalpha-/-, TCRbeta-/- and TCRdelta-/- mice, did not reconstitute their NK cell compartment. We conclude from these studies that the thymic environment is not required for NK cell development, but that aberrantly educated alphabeta or gammadelta T lymphocytes can influence NK cell ontogeny. Furthermore, high serum levels of tumor necrosis factor (TNF) were detected in the vast majority of tgepsilon26 mice transplanted with BM cells derived from partially T cell-deficient mice, but never from tgepsilon26 mice transplanted with BM cells derived from completely T cell-deficient mice. The high levels of TNF may play an important role in the observed inhibition of NK cell development, since in vivo treatment with an anti-TNF antibody restored NK cell development.

Detection of tumor cells in the bone marrow, peripheral blood, and apheresis products of breast cancer patients using flow cytometry

One of the possible drawbacks to autologous bone marrow (BM) and peripheral blood progenitor cell (PBPC) transplantation in breast cancer patients is the potential for tumor cell contamination in the transplanted product. To assess the presence of breast cancer cells, we have developed a flow-cytometric method using cytokeratin-FITC and CD45-phycoerythrin (PE) to detect very low levels of cytokeratin-positive (CK+) tumor cells in mononuclear cell (MNC) preparations. In a model system using PBMNC and the breast cancer cell line CAMA, the sensitivity of detection of this flow-cytometric method was one tumor cell in 200,000 MNC. This method was used to evaluate BM, PB, and apheresis products (AP) from 44 patients with metastatic breast cancer. When possible, stained cytologic examination was performed on smears of the unprocessed specimens and on flow cytometry-sorted cells. Results indicated that CK+ tumor cells could be detected by flow cytometry in all three specimen types. When present, however, the tumor content (per MNC) tended to be higher in BM than in PB or AP. Samples from a given patient taken serially over the course of chemotherapy revealed variable results, suggesting that the presence of tumor contamination may be sporadic and requires evaluation of each stem cell product. Of 75 samples tested with both flow cytometry and cytology, the results were concordant in 54 cases (72%). In the remaining samples, flow cytometry only was positive in 15 cases (20%), and cytology only was positive in six cases (8%). This flow-cytometric technique is useful in the evaluation of transplant products for CK+ tumor cell contamination.