Evolutionary Patterns of Axial Muscle Systems in Some Invertebrates and Fish

SYNOPSIS. Axial muscles used for oscillatory swimming are foundnot only in fish and other vertebrates but also in some protochordatesand invertebrates. Chaetognaths have unsegmented locomotor musculaturewith some unusual features, but larvacean tunicates and thetadpole larvae of ascidians show the simplest variant of thechordate segmented axial muscle arrangement for flexing a notochordalcolumn, where all muscle cells along one side are electricallycoupled. With amphioxus, the basic fish myotomal layout is established,with two main fibre types probably used for different patternsof swimming (as in fish). There are, however, several uniquefeatures, including the flattened fibre shape and the paramyosinsystem of the notochord. Agnatha have two fibre types in themyotomes, a third type perhaps being a developmental stage inthe ontogeny of fast fibres. In lampreys, the central fibresof the characteristic fibre sandwiches in the myotomes are flattened(though less so than in amphioxus); they have a dual innervationof unknown function seen also in the fast fibre system of manyGnathostome fish groups. Hagfish fast fibres are not flattenednor do they have a dual innervation. Gnathostome fish axialmuscles are strikingly uniform in design with two possible exceptions:(1) higher teleost fast fibres which, unlike those of othergroups, are multiply-innervated and (2) tonic fibres in a fewfish, which seem not to be involved in locomotion.     

Identification of distinct T cell receptor (TCR)-gamma delta heterodimers using an anti-TCR-gamma variable region serum

T cell hybridomas were generated from CD3+, CD4-, CD8- splenocytes and fetal thymocytes. V gamma 1-expressing proteins present on these murine TCR-gamma delta hybridomas were identified by using an anti-TCR V gamma 1 peptide serum. This antiserum specifically immunoprecipitated 41-kDa TCR V gamma-C gamma 4 chains and 31-kDa TCR V gamma-C gamma 1/2 chains from distinct heterodimers expressed on the TCR-gamma delta T cell hybridomas. The RNA from a hybridoma with a 31-kDa TCR-gamma chain hybridized with a V gamma 1 probe but failed to hybridize with a V gamma 2 probe. In contrast, the RNA from a hybridoma with a 32-kDa TCR-gamma chain hybridized with a V gamma 2 probe. This 32-kDa TCR-gamma chain was not immunoprecipitated by the anti-V gamma 1 serum. These data were consistent with the conclusion that the 31-kDa protein was the product of a V gamma 1 to C gamma 2 rearrangement, whereas the 32-kDa protein was the product of a V gamma 2 to C gamma 1 rearrangement. Furthermore, Southern analyses confirmed that the 32-kDa protein was the product of a V gamma 1.2-J gamma 2 rearrangement, and all three of the 41-kDa TCR-gamma chains were the results of V gamma 1.1-J gamma 4 rearrangements. This was the first demonstration at the clonal level of TCR-gamma proteins which use members of the V gamma 1 gene family, as well as the C gamma 2 constant region. Additional biochemical analyses of the TCR-gamma and -delta proteins from three independently derived C gamma 4-bearing T cell hybridomas suggested that most of the molecular mass diversity observed in the bulk subpopulation of peripheral C gamma 4-containing heterodimers may be contributed by the TCR-delta chains.     

Otolith microstructure indicating growth and mortality among plaice, Pleuronectes platessa L., post-larval sub-cohorts

Growth and mortality of post-metamorphosed plaice were studied by means of daily increments in the sagittal otoliths. The Gompertz model was the best fit to length-at-age data and there were no significant differences between length-at-age and back-calculated lengths. The microstructure pattern of the otoliths at metamorphosis was also used to estimate hatching and settlement distributions. Differential growth and mortality occurred among sub-cohorts; growth rates and mortality were higher in fish that settled earlier. In 1986, the best survival was for a sub-cohort settling in late May to early June. In contrast, in the warmer season of 1987, survival was highest for the second and third sub-cohorts settling in late April and mid May.     

Unimpaired formation of hormone-stimulated inositol trisphosphate in human mesangial cells under hyperglycemic conditions.

The relationship between bulk cellular myo-inositol content and phosphatidylinositol metabolism was evaluated in a human mesangial cell line under euglycemic and hyperglycemic conditions. Mesangial cells maintained in high glucose medium displayed a concentration-dependent fall in myo-inositol as measured by gas-liquid chromatography. Measurements of phosphatidylinositol, phosphatidylinositol 4-monophosphate and phosphatidylinositol 4,5-bisphosphate mass revealed slight but statistically insignificant increases in cells exposed to high glucose containing medium. CDP-diacylglycerol: myo-inositol 3-phosphatidylinositol transferase activity, measured in plasma membranes from mesangial cells grown under control and hyperglycemic conditions, was kinetically similar with Michaelis constants (Km values) for myo-inositol of 2.9 and 2.1 mM, respectively. Finally, hormone-stimulated intracellular calcium mobilization and myo-inositol 1,4,5-trisphosphate mass was measured from mesangial cells grown under normal and hyperglycemic conditions. Both intracellular calcium and inositol trisphosphate formation were unchanged in cells previously exposed to high glucose conditions (400 mg/dl) compared to cells grown under normal glucose concentration (100 mg/dl). These data indicate that bulk changes in myo-inositol induced by hyperglycemia are neither associated with alterations in basal levels of inositol containing glycerolipids nor with changes in hormone-stimulated calcium mobilization and inositol trisphosphate formation under conditions of short term changes in extracellular glucose.     

Scrapie I. Transmission and Pathogenesis

Homogenized brain, extracts, and residues of brain from normal and scrapie sheep were inoculated into 116 sheep. Of 72 sheep inoculated with scrapie material 27 developed the disease, whereas four of 44 inoculated with ;normal' brain material showed symptoms similar to those of scrapie. The scrapie agent survived extraction for 18 hours with diethyl ether followed by water for 24 hours. Similarly the agent survived extraction in a Soxhlet apparatus with 95 per cent ethanol containing 2.0 per cent 4 M HC1 for 24 hours. There was no evidence of demyelination in sections of brain and spinal cord supporting the view that allergic encephalomyelitis is not responsible for the scrapie symptoms. Liver function, as measured by the bromsulfalein test, remained normal until just before death. These results preclude that liver dysfunction contributes to the disease but do not exclude the possibilities of other metabolic derangements.