Where is my hand in space? The internal model of gravity influences proprioception

Knowing where our limbs are in space is crucial for a successful interaction with the external world. Joint position sense (JPS) relies on both cues from muscle spindles and joint mechanoreceptors, as well as the effort required to move. However, JPS may also rely on the perceived external force on the limb, such as the gravitational field. It is well known that the internal model of gravity plays a large role in perception and behaviour. Thus, we have explored whether direct vestibular-gravitational cues could influence JPS. Participants passively estimated the position of their hand while they were upright and therefore aligned with terrestrial gravity, or pitch-tilted 45° backwards from gravity. Overall participants overestimated the position of their hand in both upright and tilted postures; however, the proprioceptive bias was significantly reduced when participants were tilted. Our findings therefore suggest that the internal model of gravity may influence and update JPS in order to allow the organism to interact with the environment.     

Proportion of soft tissue in selected bone cuts fed primarily as enrichments to large carnivores

Zoos often offer large bones or cuts of meat containing bone (bone cuts) to carnivores to provide oral stimulation and behavioral enrichment. Because of its abrasive action, the act of chewing on a bone can increase the oral health of large felids as well as provide an enriching activity. Unfortunately, because the quantity of edible tissue on the bones is usually unknown, when feeding these cuts one can easily miscalculate an animal's caloric and nutrient intake. To fully comprehend the contribution of bones as a dietary item as opposed to an enrichment item, we removed the soft tissue from a total of 70 samples, representing 14 types of bone cuts commonly used in managed carnivore feeding programs. Across types of cuts, soft tissue averaged 50% of wet weight, with pork knuckles averaging the lowest (23%) and horse shanks the greatest (74%) percent soft tissue. Zoo Biol 27:154–158, 2008. © 2008 Wiley‐Liss, Inc.     

Generation of floxed Spag6l mice and disruption of the gene by crossing to a Hprt-Cre line

Mouse sperm-associated antigen 6 like (SPAG6L) is an axoneme central apparatus protein, essential for the normal function of the ependymal cell and lung cilia, and sperm flagella. Accumulated evidence has disclosed multiple biological functions of SPAG6L, including ciliary/flagellar biogenesis and polarization, neurogenesis, and neuronal migration. Conventional Spag6l knockout mice died of hydrocephalus, which impedes further investigation of the function of the gene in vivo. To overcome the limitation of the short lifespan of conventional knockout mice, we developed a conditional allele by inserting two loxP sites in the genome flanking exon 3 of the Spag6l gene. By crossing the floxed Spag6l mice to a Hrpt-Cre line which expresses Cre recombinase ubiquitously in vivo, mutant mice that are missing SPAG6L globally were obtained. Homozygous mutant Spag6l mice showed normal appearance within the first week after birth, but reduced body size was observed after 1 week, and all developed hydrocephalus and died within 4 weeks of age. The phenotype mirrored that of the conventional Spag6l knockout mice. The newly established floxed Spag6l model provides a powerful tool to further investigate the role of the Spag6l gene in individual cell types and tissues.     

How good is general practice developmental screening?

All developmental screening in Somerset is performed by general practitioners and health visitors. A retrospective review of a cohort of 1504 7 year old children living in semirural Somerset found that the development assessment by a health visitor at age 3 1/2 years had a sensitivity of 45% for identifying the 103 children with special educational needs, whereas the sensitivity of the preschool examination by a general practitioner was 56%. There was no relation between results of preschool developmental assessment and later reading ability. Of the 23 children in special schools, 22 had been identified independently of the developmental screening programme before starting school. Intervention was started at a mean age of 1 year 5 months (range 2 months to 3 years) for children with severe learning difficulties, and 3 years 9 months (2 years 3 months to 6 years 6 months) for children with moderate learning difficulties. The preschool medical examination revealed fairly minor medical problems: 29 of 81 children referred for specialist opinions were shown to be medically normal, and for only seven of the medically abnormal children was information about their conditions given to their teachers. In Somerset screening the development of all children at predetermined ages has not been very useful.