Ants resort to heuristics when facing relational-learning tasks they cannot solve.

We humans sort the world around us into conceptual groups, such as 'the same' or 'different', which facilitates many cognitive tasks. Applying such abstract concepts can improve problem-solving success and is therefore worth the cognitive investment. In this study, we investigated whether ants (Lasius niger) can learn the relational rule of 'the same' or 'different' by training them in an odour match-to-sample test over 48 visits. While ants in the 'different' treatment improved significantly over time, reaching around 65% correct decisions, ants in the 'same' treatment did not. Ants did not seem able to learn such abstract relational concepts, but instead created their own individual strategy to try to solve the problem: some ants decided to 'always go left', others preferred a 'go to the more salient cue' heuristic which systematically biased their decisions. These heuristics even occasionally lowered the success rate in the experiment below chance, indicating that following any rule may be more desirable then making truly random decisions. As the finding that ants resort to heuristics when facing hard-to-solve decisions was discovered post-hoc, we strongly encourage other researchers to ask whether employing heuristics in the face of challenging tasks is a widespread phenomenon in insects.

Private information conflict: Lasius niger ants prefer olfactory cues to route memory.

Foraging animals use a variety of information sources to navigate, such as memorised views or odours associated with a goal. Animals frequently use different information sources concurrently, to increase navigation accuracy or reliability. While much research has focussed on conflicts between individually learned (private) information and social information, conflicts between private information sources have been less broadly studied. Here, we investigate such a conflict by pitting route memory against associative odour cue learning in the ant Lasius niger. Ants were alternatingly trained to find a high-quality scented food source on one arm of a Y-maze, and a differently scented low-quality food source on the opposite arm. After training, ants were presented with a Y-maze in which the high- and low-quality-associated scents were presented on opposite arms than during training. The ants showed an extremely strong preferential reliance on the odour cues, with 100% of ants following the high-quality odour and thus moving towards the side associated with low-quality food. Further experiments demonstrated that ants also learn odour associations more rapidly, requiring only one visit to each odour-quality combination to form a reliable association. Side associations in the absence of odours, by contrast, required at least two visits to each side for reliable learning. While much attention has been focussed on visual route learning in insect navigation and decision-making, our results highlight the overwhelming importance of odour cues in insect path choice.

Tasting the unexpected: disconfirmation of expectations leads to lower perceived food value in an invertebrate.

To make sensible decisions, both humans and other animals must compare the available options against a reference point-either other options or previous experience. Options of higher quality than the reference are considered good value. However, many perceptible attributes of options are value-neutral, such as flower scent. Nonetheless, such value-neutral differences may be part of an expectation. Can a mismatch between the expectation and experience of value-neutral attributes affect perceived value? Consumer psychology theory and results suggest it can. To test this in a non-human animal, we manipulated a value-neutral aspect of a food source-its taste-while keeping its absolute value-its sweetness-the same. Individual ants (Lasius niger) were allowed to drink either lemon- or rosemary-flavoured 1 M sucrose. After three successive visits to the food, we switched the taste in the last, fourth, visit to induce a disconfirmation of expectations. In control trials, ants received the same taste on all four visits. Disconfirmed ants showed lower food acceptance and laid less pheromone on the way back to the nest, even though the molarity of the food was unchanged. As ants recruit nest-mates via pheromone depositions, fewer depositions indicate that the ants valued the food less. Thus, an expectation of value-neutral attributes can influence the perceived value of a resource. Such influences of value-neutral variables on value perception may affect how animals interact with and exploit their environment, and may contribute to phenomena such as flower constancy.

Caloric restriction increases serum testosterone concentrations in obese male subjects by two distinct mechanisms.

The concentration of serum testosterone is mainly regulated by the testicular function, which is under control of the central hypothalamic-pituitary-gonadal axis. A certain amount of testosterone is converted into ß-estradiol by adipose tissue. Obesity in men is often associated with decreased androgen levels. The aim of the present study was to examine the effect of caloric restriction on serum testosterone levels in obese men. Dietary intervention study was performed with a very low calorie diet (800 kcal/d) for 12 weeks. Thirteen obese human male subjects (median body mass index: 42.7 kg/m2) were included. Body composition was assessed by impedance analysis. Insulin sensitivity was estimated by leptin-to-adiponectin ratio (LAR). Testosterone (T), ß-estradiol, albumin, sex hormone-binding globulin (SHBG), LH, and FSH serum concentrations were measured by enzyme immunoassays. Statistical analysis was performed on baseline and values after 3 months. Caloric restriction significantly increased total testosterone (6.97 nmol/l to 13.21 nmol/l; p=0.001) and SHBG (22.11 nmol/l to 42.12 nmol/l; p=0.001) concentrations in serum. This is caused by a significant improvement of the testicular function (LH/T: 0.36-0.20; p=0.005) and a significant reduction of the T/ß-estradiol conversion rate (73.59-104.29; p=0.003). There was a significant negative correlation of improvement of testicular function and LAR (rs=-0.683 (p=0.042)). In obese men caloric restriction significantly increases the serum testosterone concentration. This is achieved by 2 distinct mechanisms, that is, improvement of testicular function and reduced conversion of testosterone to ß-estradiol by aromatase activity of the adipose tissue.

Weight loss due to a very low calorie diet differentially affects insulin sensitivity and interleukin-6 serum levels in nondiabetic obese human subjects.

Inflammatory mechanisms are involved in the pathogenesis of type 2 diabetes with interleukin (IL)-6 being particularly important. While long term exercise has been shown to be associated with reduction in IL-6 serum levels in several reports, the discussion on the effect of dietary intervention on IL-6 serum levels is controversial. In the present study, we aimed to investigate the effect of weight loss due to a very low calorie diet (VLCD) on insulin sensitivity and IL-6 serum levels in nondiabetic obese human individuals. 10 patients with obesity were examined during 12 weeks of a VLCD (800 kcal/d). Body composition was measured by impedance analysis. Blood samples were taken before, during, and after the dietary intervention. Leptin, adiponectin, and IL-6 serum levels were measured by ELISA. The body weight decreased significantly from 123.9±6.2-103.5±5.6 kg with a significant reduction in body fat content (43.2±2.3-36.1±3.1%). Leptin levels exhibited a significant decrease from 56.8±5.6-27.9±5.6 ng/ml while adiponectin levels increased significantly from 7.5±0.9-10.6±1.1 µg/ml. Thereby the leptin-to-adiponectin ratio, a novel marker for insulin sensitivity, significantly improved. Mean IL-6 serum concentrations were within the normal range (3.2±0.8 pg/ml) before the study and were not significantly altered by the nutritional therapy. Despite improvement of insulin sensitivity, IL-6 serum levels did not change throughout the study period, suggesting that in nondiabetic obese human subjects IL-6 might have only a minor role in the impairment of insulin sensitivity.

Adipose tissue macrophages inhibit adipogenesis of mesenchymal precursor cells via wnt-5a in humans.

In patients with obesity and type 2 diabetes, adipose tissue is infiltrated by macrophages known to alter adipogenesis of mesenchymal precursor cells via secretion of proinflammatory cytokines. Recently, it has been shown that under certain conditions, immune cells can also express wnt-5a, a factor known to inhibit adipogenesis in humans. Therefore, in this study we aimed to investigate whether macrophages affect adipogenesis of mesenchymal precursor cells via wnt-5a. Wnt-5a was found to be expressed in adipose tissue macrophages in obese and type 2 diabetic human subjects in vivo by immunohistochemistry of adipose tissue biopsies. Furthermore, wnt-5a was detectable in circulating CD14(+) blood monocytes of human subjects with obesity and type 2 diabetes on RNA level by real-time PCR. Besides expression analysis in vivo, we also performed functional studies to explore the role of wnt-5a in low-grade inflammation of adipose tissue. In a cell culture experiment, macrophage-conditioned differentiation medium inhibited adipogenesis of 3T3-L1 cells. This inhibitory effect was restored by adding neutralising anti-wnt-5a antibodies. In conclusion, our data indicate that macrophages alter adipogenesis of 3T3-L1 cells not only via classical proinflammatory cytokines, but also via wnt signalling molecules.

Dipeptidyl-peptidase 4 and attractin expression is increased in circulating blood monocytes of obese human subjects.

Dipeptidyl-peptidase (DPP)-4, which catalizes the degradation of the insulinotropic incretin glucagon-like-peptide (GLP)-1, and the DPP-4 like enzyme attractin are involved in activation of T-lymphocytes and monocytes. Recently, it has been demonstrated, that the risk for certain infections is increased in type 2 diabetic patients under DPP-4 inhibitor treatment. The aim of the present study was to examine the expression of DPP-4 and attractin in circulating blood monocytes of obese and type 2 diabetic subjects. Monocytes were isolated by CD14-antibody based magnetic cell sorting from blood samples of 17 lean controls, 20 obese, non-diabetic subjects and 19 obese patients with type 2 diabetes. FACS analysis was performed to test purity of the cell preparations. Expression was measured by multiplex RT-PCR on RNA-level. DPP-4 and attractin were detectable in human circulating monocytes with attractin being expressed at higher levels compared to DPP-4. Both enzymes were significantly higher expressed in circulating blood monocytes of obese subjects compared to lean controls. In contrast, type 2 diabetes did not significantly affect expression levels. Finally, neither DPP-4 nor attractin expression was altered by sitagliptin or insulin treatment. In conclusion, our data demonstrate, that expressions of DPP-4 and attractin in circulating blood monocytes of human subjects are influenced by metabolic abnormalities with obesity being an important factor.

Visfatin/PBEF/Nampt and resistin expressions in circulating blood monocytes are differentially related to obesity and type 2 diabetes in humans.

Low-grade inflammation is important in the development of obesity related pathologies such as insulin resistance and type 2 diabetes, and also cardiovascular disease. Visfatin/PBEF/Nampt and resistin are proinflammatory adipokines secreted from adipocytes, monocytes, and macrophages, and have been linked to atherosclerotic plaque formation, recently. The aim of the present study was to investigate if the expression of these molecules in circulating blood monocytes is altered in obese and/or type 2 diabetic human subjects. Monocytes were isolated by CD14-antibody based magnetic cell sorting from blood samples of 17 lean controls, 20 obese nondiabetic subjects, and 19 obese patients with type 2 diabetes. FACS analysis was performed to test purity of the cell preparations. Expression of the different adipokines was measured by multiplex real-time PCR on RNA-level. Visfatin/PBEF/Nampt was found to be very strongly expressed in monocytes, whereas resistin levels were significantly lower. Furthermore, visfatin/PBEF/Nampt expression was significantly upregulated in obese type 2 diabetic patients, whereas obese nondiabetics exhibited similar levels compared to lean controls, indicating that visfatin/PBEF/Nampt levels are related to type 2 diabetes rather than to obesity. In contrast, resistin expression displayed a different pattern being significantly increased in obese subjects compared to controls but not related to type 2 diabetes. These data suggest a differential role for these two proinflammatory adipokines in linking metabolic diseases to atherosclerosis with visfatin/PBEF/Nampt being more important in patients with type 2 diabetes and resistin in obese but nondiabetic human subjects.

Human fetal adiponectin and retinol-binding protein (RBP)-4 levels in relation to birth weight and maternal obesity.

Recent studies suggest that the perinatal period is a sensitive part in human development with respect to the pathogenesis of metabolic diseases in adulthood. Neonates, who are either small or large for gestational age (SGA or LGA) have a greater risk of developing obesity and insulin resistance in later life. The term "perinatal priming" is used to describe this phenomenon. Therefore, in the present study we first aimed to investigate if birth weight influences fetal adiponectin and RBP-4 metabolism. Umbilical cord blood was obtained form 40 neonates born on term+/-4 weeks and the adipokine concentrations in the serum were measured. In this analysis adiponectin but not RBP-4 levels showed a positive significant correlation to birth weight. Since maternal preconceptional obesity is associated with an increased birth weight and the risk for LGA neonates, we further aimed to investigate, if the maternal nutritional state influences fetal adiponectin and RBP-4. Therefore umbilical cord blood levels of the adipokines were correlated to maternal preconceptional BMI. In this analysis, neither adiponectin nor RBP-4 levels showed a significant correlation. Taken together, in the present study for the first time we directly compare fetal adiponectin and RBP-4 levels in respect to birth weight and maternal preconceptional BMI. Our data suggest that (1) adiponectin is more likely to have a role in perinatal priming of obesity and insulin resistance than RBP-4 and (2) that birth weight has a greater impact on fetal adipokine serum levels than maternal preconceptional obesity.

Quantitative molecular monitoring of residual tumor cells in chronic lymphocytic leukemia.

New therapeutic approaches for the treatment of B-cell chronic lymphocytic leukemia (B-CLL) can induce remarkable responses. Molecular remissions have been observed occasionally after high-dose chemotherapy. Thus, new improved techniques to monitor residual tumor cells on a molecular basis in CLL are warranted. For this purpose, a real-time quantitative allele-specific oligonucleotide polymerase chain reaction (ASO-PCR) for patients with B-CLL was designed. In the present study, the PCR assay was standardized with identical cycling parameters as well as primer, probe, and MgCl(2) concentration for each patient. Ten patients were monitored with DNA samples obtained at 52 time points (median: 5.2 per patient). The median follow-up per patient was 11.4 months. Nine of ten patients had PCR-detectable residual tumor cells in the peripheral blood after therapy. One patient became PCR negative with a combination of fludarabine and rituximab after the end of treatment. The MRD levels in patients with detectable disease ranged from 0.002% to 10.1% after therapy. We conclude that real-time quantitative ASO-PCR can be utilized for quantitative molecular monitoring of minimal residual disease (MRD) in B-CLL patients in complete remission (CR), that new effective treatment approaches such as combined chemo/immunotherapy can render CLL patients PCR negative, and that different MRD levels in PCR-positive patients were observed warranting further investigation into possible correlation with clinical outcome.

Increase of anti-inflammatory cytokines in patients with esophageal cancer after perioperative treatment with G-CSF.

Granulocyte colony-stimulating factor (G-CSF) has been shown to effectively stimulate granulopoiesis, in both neutropenic and in non-neutropenic patients. Recently, other effects of G-CSF on the immune system have attracted interest in treating non-neutropenic patients with a high risk of severe infection. In this phase II trial, we measured the effects of G-CSF on the serum cytokine levels in patients with esophageal cancer undergoing esophagectomy. Twenty subsequent patients (study group, 19 evaluable) received G-CSF (rhG-CSF, Filgrastim) at standard doses (300 microg or 480 microg) subcutaneously 2 days before and up to 7 days after surgery. G-CSF was well tolerated. Leukocytes increased from 7600/microl at study entry (day -2) to a maximum of 45 100/microl (day 6). In the study patients, we found a highly significant (P<0.001) postoperative increase of G-CSF, IL-1ra, sTNFRp55 and sTNFRp75 as compared with the baseline level. In contrast, IL-8 levels were decreased by a factor of 6.8; there were no changes in the very low TNF-alpha levels. The comparison of the study group with a control group of 21 cancer patients undergoing major surgery who were not treated with G-CSF showed significant differences in the serum levels of G-CSF, sTNFRp55, sTNFRp75, and IL-1ra, respectively. There was no infection in the study group up to 10 days after surgery as compared with 29.9% in a historical control group (P=0.008). Thus, the induction of anti-inflammatory cytokines and the downregulation of pro-inflammatory cytokines by G-CSF might be a promising adjuvant treatment of infectious complications in patients undergoing esophagectomy.

Perioperative treatment with filgrastim stimulates granulocyte function and reduces infectious complications after esophagectomy.

We investigated the effects of recombinant G-CSF (Filgrastim) on the function of neutrophils and the rate of infectious complications in an open-label, nonrandomized study of patients with esophageal cancer undergoing esophagectomy. In this single-center phase-II trial 20 sequential patients (19 evaluable) received Filgrastim at standard doses (300 microg or 480 microg) subcutaneously for 2 days prior to and up to 7 days after surgery. The phagocytotic activity of neutrophils and the oxidative burst in the study group and in an experimental control group (n=27) were measured on days -2, 2, and 10. Neutrophil function was enhanced in the Filgrastim-treated group by factor 1.2 for phagocytosis (p=0.016) and 1.4 for oxidative burst (p)=0.154). Leukocyte counts increased from 7.6 x 10(9)/l (day -2) to a maximum of 45 x 10(9)/l on day 6. No infection was reported in the study group (mean age 59.7 years; 13 men, seven women) up to 10 days after surgery. In contrast, 23 patients (29.9%) in a historical control group (mean age 56 years; 67 men, ten women) treated at the same center developed infections within the first 10 days (p = 0.008). In addition, no postoperative deaths occurred in the study group, compared with 9.1% in the group of historical controls. Thus, in this study, administration of Filgrastim stimulated neutrophil function in patients undergoing esophagectomy, and it might be effective in reducing infectious complications related to the surgical procedure.

A real-time PCR assay for the quantification of residual malignant cells in B cell chronic lymphatic leukemia.

Several new therapeutic approaches for the treatment of monoclonal B cell lymphomas are currently being investigated. In parallel with new therapeutic modalities, more sensitive diagnostic methods are needed. These methods should be highly sensitive in detecting very low amounts of malignant cells and should be specific for the malignant clone. In addition, these methods should allow the quantification of residual tumor cells. In this study a new real-time polymerase chain reaction (LightCycler) was evaluated to quantify residual tumor cells in monoclonal B cell malignancies. This technology combines the advantages of rapid cycling PCR with the online detection of PCR products using fluorescent dyes. Our assay is based on immunoglobulin heavy chain (IgVH)-specific PCR with allele-specific primers complementary to hypervariable CDRII and CDRIII regions. A set of framework region III (FRIII)-specific hybridization probes was used for detection of the specific amplification product, and IgVH copy number was quantified with the cloned IgVH sequence as an external standard. The approach was evaluated with the Hodgkin lymphoma cell line L428 in order to quantify L428 dilutions. L428 cells mixed with peripheral blood mononuclear cells (PBMNCs) were detected and quantified with a sensitivity of one cell within 1 x 10(5) PBMNCs. Sample DNA from the peripheral blood and from the bone marrow of two patients with B-CLL was analyzed in the new set up at different time points before and after therapy. Statistically significant changes in IgVH copy numbers were documented in both patients. We conclude that this technology offers an additional opportunity to detect and quantify residual tumor cells in B-CLL over several log steps with a high sensitivity. The kinetics of residual tumor cell counts in B-CLL can be analyzed by this method.

Suppressed neutrophil function as a risk factor for severe infection after cytotoxic chemotherapy in patients with acute nonlymphocytic leukemia.

Severe infections are a major problem in patients suffering from acute nonlymphocytic leukemia (ANLL) undergoing myeloablative chemotherapy. Possible factors leading to infectious complications in these patients are suppressed immune defense mechanisms existing prior to therapy, including those involving the neutrophil granulocyte department. In this study we investigated whether neutrophil function as measured by oxidative burst and phagocytosis before the start of treatment correlates with the severity of infection after therapy. Forty-four patients were included, 27 men and 17 women. Their median age was 46 years (range 20-70 years). According to the development of infectious complications the patients were assigned retrospectively to group 1 (no or only mild infections, n = 29) or to group 2 (severe infection or death due to infection, n = 15). The phagocytic activity was significantly reduced in group 2 as compared with group 1 [113.7+/-13.7 (SEM) vs 170.0+/-19.2, mean channel fluorescence; p =0.04]. In contrast, the oxidative burst as measured by FMLP stimulation was pronounced but not significantly enhanced in group 2 (24.8+/-6.1 vs 14.5+/-3.4, mean channel fluorescence). In conclusion, patients with severe infections after chemotherapy might already have preactivated neutrophils with suppressed function prior to treatment. Thus, evaluating function parameters could help to estimate the individual risk of infection for a patient with ANLL.