Segmental and interganglionic projections from primary fibres of insect mechanoreceptors

The tertiary shell of the eggs of anostracan crustaceans consists of two layers, an outer cortex and an inner alveolar layer. Scanning electron microscope studies show that, in most species, these layers are separated by a subcortical space which intercommunicates with spaces in the cortex and with the meshwork of the alveolar layer. No evidence was found for direct communication between pores on the surface of Branchipus stagnalis eggs and the subcortical space. No surface pores were found in the eggs of Branchinecta packardi, Chirocephalus diaphanus, Artemia salina, nor in eggs of the notostracan Triops cancriformis. Similarities in structure and possible functions of the egg shells of anostracan crustaceans and certain insects are discussed in relation to similarities in certain features of their environments.     

The projections of chemically identified nerve fibres in canine ileum

Summary The projections of nerve fibres with immunoreactivity for the peptides enkephalin (ENK), gastrin-releasing peptide (GRP), neuropeptide Y (NPY), somatostatin (SOM), substance P (SP) and vasoactive intestinal peptide (VIP) were studied in canine small intestine by analysing the consequences of lesions of intrinsic and extrinsic nerves. Of peptides present in fibres supplying myenteric ganglia, GRP, SOM and VIP were in anally directed nerve pathways, whereas ENK and NPY were in orally directed pathways. Pathways ran for up to about 30 mm. SP fibres ran for short distances in both directions in the myenteric plexus. The circular muscle was supplied with ENK, NPY, SP and VIP fibres arising from the myenteric ganglia, whereas most mucosal SP and VIP fibres were deduced to arise from submucous ganglia. There were projections of fibres reactive for ENK, GRP, SOM, SP and VIP from myenteric ganglia to submucous ganglia. Antibodies to tyrosine hydroxylase were used to locate noradrenaline nerve fibres supplying the intestine; these fibres all disappeared when extrinsic nerves running through the mesentery to the small intestine were cut. It is deduced that there is an ordered pattern of projections of peptide-containing fibres in the canine intestine.     

Some central nervous actions of centrophenoxine (Meclofenoxat) in animals.

In experiments with rats and mice it was been found that centrophenoxine in acute experiments in large doses has inhibitory effects on the central nervous system. Centrophenoxine has no analgesic action. When administered subchronically, centrophenoxine aggravates both the pentetrazol and the maximal electroshock seizures.     

Some implications of helical fibres in worm cuticles

The cuticles of many worms contain a cylindrical trellis made of layers of collagen fibres wound round the body in left- and right-hand helices. This kind of extensible skeletal structure imposes various constraints on a worm's behaviour, and some of these are examined, using the nematomorph Parachordodes woltersforffii as the main example. Upon extension or shortening of the cuticle, neighbouring fibres in one layer will eventually touch and so limit further movement; this in turn affects the extent of shortening, elongation, bending and coiling of the whole worm. Simple equations relate: the angle between a fibre and the worm's long axis; fibre spacing and radius; worm body radius and radius of curvature. The relevance to the life of the worm of fibre arrangement, matrix properties and volume changes is discussed.     

Some current problems in amphibian limb regeneration.

Limb regeneration in adult urodele amphibians proceeds by formation of a blastema at the amputation plane. This paper discusses how the blastema forms, and how its positional identity on the proximodistal axis is manifest. Retinoic acid is able to reset axial specification and there is particular interest in determining how it acts. Although limb regeneration is restricted among vertebrates to the urodeles, its mechanism poses fundamental questions in development biology.     

Some problems in the measurement of stress and social readjustment.

Although the Social Readjustment Rating Scale has been a useful stimulant to the study of life change and illness, it has important limitations. The existing scale cannot be used to determine the role of varying types of life changes (e.g., favorable or adverse) in the occurrence of illness. Other problems discussed are ambiguity of items, the confounding of independent and dependent variables, and lack of item specification. Suggestions are made for improved measurement of life change and for more effective study of life change and illness.