No link between handedness and spatial navigation: evidence from over 400 000 participants in 41 countries.

There is an active debate concerning the association of handedness and spatial ability. Past studies used small sample sizes. Determining the effect of handedness on spatial ability requires a large, cross-cultural sample of participants and a navigation task with real-world validity. Here, we overcome these challenges via the mobile app Sea Hero Quest. We analysed the navigation performance from 422 772 participants from 41 countries and found no reliable evidence for any difference in spatial ability between left- and right-handers across all countries. A small but growing gap in performance appears for participants over 64 years old, with left-handers outperforming right-handers. Further analysis, however, suggests that this gap is most likely due to selection bias. Overall, our study clarifies the factors associated with spatial ability and shows that left-handedness is not associated with either a benefit or a deficit in spatial ability.

Cultural determinants of the gap between self-estimated navigation ability and wayfinding performance: evidence from 46 countries.

Cognitive abilities can vary widely. Some people excel in certain skills, others struggle. However, not all those who describe themselves as gifted are. One possible influence on self-estimates is the surrounding culture. Some cultures may amplify self-assurance and others cultivate humility. Past research has shown that people in different countries can be grouped into a set of consistent cultural clusters with similar values and tendencies, such as attitudes to masculinity or individualism. Here we explored whether such cultural dimensions might relate to the extent to which populations in 46 countries overestimate or underestimate their cognitive abilities in the domain of spatial navigation. Using the Sea Hero Quest navigation test and a large sample (N = 383,187) we found cultural clusters of countries tend to be similar in how they self-rate ability relative to their actual performance. Across the world population sampled, higher self-ratings were associated with better performance. However, at the national level, higher self-ratings as a nation were not associated with better performance as a nation. Germanic and Near East countries were found to be most overconfident in their abilities and Nordic countries to be most under-confident in their abilities. Gender stereotypes may play a role in mediating this pattern, with larger national positive attitudes to male stereotyped roles (Hofstede's masculinity dimension) associated with a greater overconfidence in performance at the national level. We also replicate, with higher precision than prior studies, evidence that older men tend to overestimate their navigation skill more than other groups. These findings give insight into how culture and demographics may impact self-estimates of our abilities.

Reported sleep duration reveals segmentation of the adult life-course into three phases.

Classically the human life-course is characterized by youth, middle age and old age. A wide range of biological, health and cognitive functions vary across this life-course. Here, using reported sleep duration from 730,187 participants across 63 countries, we find three distinct phases in the adult human life-course: early adulthood (19-33yrs), mid-adulthood (34-53yrs), and late adulthood (54+yrs). They appear stable across culture, gender, education and other demographics. During the third phase, where self-reported sleep duration increases with age, cognitive performance, as measured by spatial navigation, was found to have an inverted u-shape relationship with reported sleep duration: optimal performance peaks at 7 hours reported sleep. World-wide self-reported sleep duration patterns are geographically clustered, and are associated with economy, culture, and latitude.

Entropy of city street networks linked to future spatial navigation ability.

The cultural and geographical properties of the environment have been shown to deeply influence cognition and mental health1-6. Living near green spaces has been found to be strongly beneficial7-11, and urban residence has been associated with a higher risk of some psychiatric disorders12-14-although some studies suggest that dense socioeconomic networks found in larger cities provide a buffer against depression15. However, how the environment in which one grew up affects later cognitive abilities remains poorly understood. Here we used a cognitive task embedded in a video game16 to measure non-verbal spatial navigation ability in 397,162 people from 38 countries across the world. Overall, we found that people who grew up outside cities were better at navigation. More specifically, people were better at navigating in environments that were topologically similar to where they grew up. Growing up in cities with a low street network entropy (for example, Chicago) led to better results at video game levels with a regular layout, whereas growing up outside cities or in cities with a higher street network entropy (for example, Prague) led to better results at more entropic video game levels. This provides evidence of the effect of the environment on human cognition on a global scale, and highlights the importance of urban design in human cognition and brain function.

Discrimination reversal conditioning of an eyeblink response is impaired by NMDA receptor blockade.

In the present study we examined the effects of the specific NMDA receptor antagonist CPP on discrimination reversal learning in rabbits. We report two primary findings. First, the institution of NMDA receptor blockade had no effect on a learned discrimination. Second, after stimulus reversal, CPP treatment impaired acquisition of the discrimination reversal. This impairment manifested itself early in training as a retardation in acquisition of a CR to the new CS+ and late in training as an inability to suppress responsiveness to the new CS-. Given the comparability of the present results with previously published results for phenytoin-treated rabbits, we suggest that the effects of phenytoin on learning in this paradigm is at least in part mediated by its effects on NMDA receptors. We further suggest that these findings emphasize the need to better define the role of NMDA receptor activation and hippocampally-mediated circuits in a variety of associative learning paradigms.

The effect of Bromelia pinguin extract on the pregnant rat uterus

A non proteinaceous extract of Bromelia pinguin fruit was examined for activity on the rat uterus in vivo and in vitro. The in vivo experiments involved pregnant rats given the extract intraperitoneally. These rats did not abort nor were any foetal deformities observed. The extract inhibited spontaneous activity of the pregnant rat uterus in vitro. The extract of Bromelia pinguin fruit may have some utero-active compound which inhibits uterine motility.(AU)

Psychiatric mental health nursing: thriving in a changing environment through outcomes-based measurements.

This article focuses on the necessity of outcomes-based measurements in the behavioral health care field. The authors describe the reasons why outcomes research is essential to the survival of behavioral services and, even more specifically, psychiatric mental health nursing. An actual outcome study process using psychiatric patients treated by a clinical nurse specialist is described in detail. The authors reflect their orientation to outcomes-based measurements through their perspectives as a manager and an outpatient therapist.

Streptozotocin alters pancreatic beta-cell responsiveness to glucose within six hours of injection into rats

A 24-hour glycaemic profile following streptozotocin (80 mg/kg. ip) injection was investigated in fasted rats. The most prominent changes in blood glucose were hyperglycaemia associated with low levels of plasma insulin after two hours followed by hypoglycaemia associated with high levels of plasma insulin after six hours; subsequently hyperglycaemia progressively developed and this was associated with decreasing levels of plasma insulin. Further probing revealed that at two hours after streptozotocin injection, the pancreatic á-cells could not respond to an oral glucose load while, at six hours after, there was an apparent return of á-cell responsiveness, but subsequently á-cell responsiveness was progressively lost and histological examination revealed cellular damage. From these results, it is concluded that within six hours of injection, stretozotocin initiates pancreatic á-cell damage which leads to the development of diabetes mellitus. (AU)

Streptozotocin alters pancreatic beta-cell responsiveness to glucose within six hours of injection into rats

A 24-hour glycaemic profile following streptozotocin (80 mg/kg. ip) injection was investigated in fasted rats. The most prominent changes in blood glucose were hyperglycaemia associated with low levels of plasma insulin after two hours followed by hypoglycaemia associated with high levels of plasma insulin after six hours; subsequently hyperglycaemia progressively developed and this was associated with decreasing levels of plasma insulin. Further probing revealed that at two hours after streptozotocin injection, the pancreatic ß-cells could not respond to an oral glucose load while, at six hours after, there was an apparent return of ß-cell responsiveness, but subsequently ß-cell responsiveness was progressively lost and histological examination revealed cellular damage. From these results, it is concluded that within six hours of injection, stretozotocin initiates pancreatic ß-cell damage which leads to the development of diabetes mellitus.

An overview of current research on the biological effects of extracts from the unripe ackee (Blighia sapida L.) - abstract

It has been demonstrated that subacute intraperitoneal administration of high doses of the lipid fraction of the unripe ackee resulted in marked neutropaenia, pulmonary toxicity and changes in the blood chemistry in rats. This study has been carried out to further isolate the neutropaenic principle by testing both aqueous and lipid fractions and to see if this effect could be demonstrated in a different animal species. In mice, intraperitoneal administration of aqueous and lipid extracts of the ackee at a dose regimen of 300mg/kg thrice weekly for six weeks showed an initial rise, followed by a lowering of the neutrophil count, red blood cell count, haemoglobin, platelet count, serum albumin and alkaline phosphatase also decreased. It is concluded that in addition to it's hypoglycaemic principle, both aqueous and lipid extracts of unripe ackee, when adminstered separately, have neutropaenic activity. Further research involving characterization and testing is in progress. (AU)

Unstable diabetic state produced by a small dose of streptozotocin in rats

A diabetic state was induced with a single intraperitoneal dose (45 mg/kg) of streptozotocin in rats. Their fasting blood glucose concentrations oscillated between 12.7 ñ 1.9 mmol/l and 4.6 ñ 0.6 mmol/l during 35 days of monitoring. Their body weights were also reduced, while controls gained weight, although food consumption was not significantly different. Also, within the first «-hour of the oral glucose tolerance test, blood glucose concentration increased in the diabetic and the control rats, but only in the control rats was there a simultaneous increase in serus IRI concentration (7.2 ñ 8 x 10 to the 2nd power pmol/l to 27.0 ñ 5.2 x 10 to the 2nd power pmol/l) which, like the blood glucose concentration, subsequently fell to fasting level in the control rats. In the diabetic rats, however, it was not until the following hour of the tolerance test that serum IRI concentration increased (3.4 ñ 0.3 x 10 to the 2nd power pmol/l to 65.0 ñ 12.5 x 10 to the 2nd power pmol/l) and blood glucose concentration began to fall. By the end of the test in the diabetic rats, blood glucose concentration fell but remained significantly higher than the control value. Additionally, no pancreatic tumours were identified in these diabetic rats. The results therefore suggest that an unstable diabetic state was produced by streptozotocin because the treshold for insulin secretion by glucose was increased, while the production of insulin by the pancreas was not significantly affected (AU)

The hypoglycaemic effect of annatto (bixa orellana) - abstract

In West Indian folklore, a number of plant extracts are utilised for medicinal purposes. One common malady so treated is diabetes mellitus. Some twenty (20) folk medicines (bush tea) were investigated as to their efficacy in lowering blood sugar levels in the anaesthetised dog model. The annatto (bixa orellana) when prepared as an oil suspension of the red seed coat was found to be quite a potent hypoglycaemic agent. It was further studied in order to purify the crude extract and possibly identify the pharmacologically active agent(s). The annatto seeds were percolated with chloroform until the bright red colour of the seed coat was removed. This extract was concentrated in vacua and the residue extracted selectively with 60 percent ethanol/water and petroleum ether. A final wine-red to orange viscous extract was used in the biological experiments. This partially purified petroleum ether extract was dissolved in corn oil (80 mg/kg body weight animal) and given to anaesthetized dogs via a stomach tube. After a residence time of one (1) hour, oral glucose tolerance tests were performed. The results showed hypoglycaemia in both the normal and streptozotocin diabetic dogs when compared to controls. Its effect is to delay the peaking of glucose after a meal and to increase the release of insulin in relation to blood glucose levels. The possibility of an effective hypoglycaemic principle in this extract increases pharmacological curiosity into this form of 'lay' treatment of diabetes mellitus. Detailed studies are continuing to identify and isolate the active component(s) (AU)

Extraction of an hyperglycaemic principle from the annatto (Bixa orellana)

The red powdery extract from the seeds of the annatto, Bixa orellana, is a well known food colouring. In an oil suspension it is used as a folk remedy (bush tea) in the West Indies, for diabetes mellitus. Detailed investigations on this extract, yielded a methyl ester, trans-bixin, molecular weight 394 and molecular formula C24 H30 O4. This purified substance was demonstrated, in anaaesthetised mongrel dogs, to cause hyperglycaemia. Concomitant electron microscopy of tissues biopsies, revealed damage to mitochrondria and endoplasmic reticulum mainly in liver and pancreas. When dogs were fed on a diet fortified with riboflavin, there was neither demonstratable tissue damage nor associated hyperglycaemia. These findings point to: (i) the potential dangers of informal medications such as 'bush teas'; (ii) the possible role of plant extracts/food additives in the development of diabetes mellitus especially in the undernourished state. (AU)

Isolation, purification and identification of the hyperglycaemic principle of the annatto (Bixa orellana) - abstract

The crude extract eluted from the seed of Bixa orellana was seen to cause hyperglycaemia in anaesthetized dogs. Further investigation was carried out to find the biologically active component. Column chromatography, PLC and recrystallizations yielded a pure residue with m.p. 220. The experimental dogs in quantities below one gram, it caused sustained hyperglycaemia and severe damage to tissues of the liver, kidney and pancreas. The level of toxicity associated with this plant is of interest, since its extract is widley used in various goods (AU)

Polyethylene glycol-induced heteroassociation of malate dehydrogenase and citrate synthase.

Studies by dynamic and total intensity light scattering, ultracentrifugation, electron microscopy, and chemical crosslinking on solutions of the pig heart mitochondrial enzymes, malate dehydrogenase and citrate synthase (separately and together) demonstrate that polyethylene glycol induces very large homoassociations of each enzyme, and still larger heteroenzyme complexes between these two enzymes in the solution phase. Specificity of this heteroassociation is indicated by the facts that heteroassociations with bovine serum albumin were not observed for either the mitochondrial dehydrogenase or the synthase or between cytosolic malate dehydrogenase and citrate synthase. The weight fraction of the enzymes in the mitochondrial dehydrogenase-synthase associated particles in the solution phase was less than 0.03% with the dilute conditions used in the dynamic light scattering measurements. Neither palmitoyl-CoA nor other solution conditions tested significantly increased this weight fraction of associated enzymes in the solution phase. Because of the extremely low solubility of the associated species, however, the majority of the enzymes can be precipitated as the heteroenzyme complex. This precipitation is a classical first-order transition in spite of the large particle sizes and broad size distribution. Ionic effects on the solubility of the heteroenzyme complex appear to be of general electrostatic nature. Polyethylene glycol was found to be more potent in precipitating this complex than dextrans, polyvinylpyrrolidones, ficoll, and beta-lactoglobulin.

Toxicity of the hyperglycaemic-inducing extract of the Annatto (Bixa orellana) in the dog

The Annatto seed coat extract, which is commonly used in folklore in treating diabetes mellitus, has been investigated for its effects on blood sugar levels in the dog. An alkali-soluble hyperglycaemia-inducing fraction was detected, and detailed studies revealed toxic effects in the pancreas and liver accompanied by hyperglycaemia and apparent tendency to increased insulin levels. The toxicity was diminished by feeding riboflavin. The relevance of this finding points to a possible aetiological role in the development of malnutrition-related diabetes mellitus and also to the potential toxicity inherent in the widespread use of folklore medicines (AU)