Alternation between attachment mechanisms by limpets in the field

The attachment mechanism used by limpets in the rocky, wave-swept intertidal zone of California was determined during high tide and low tide. The two mechanisms that limpets are known to use, suction and glue-like adhesion, were distinguished by measuring the limpets' attachment forces in shear and by staining for glue-like residues where the limpets had been attached. The results show that ≈ 73% of limpets at high tide use suction, while the rest use glue-like adhesion. Conversely, ≈ 75% of limpets at low tide use glue-like adhesion, while the rest use suction. The normal tenacity of limpets was also measured at high and low tide. The mean tenacity at high tide was significantly less than that at low tide. From these data it was estimated that the mean tenacity of glue-like adhesion is ≈ 0.23 MN·m⁻² and the mean tenacity of suction adhesion is ≈ 0.09 MN·m⁻². It is hypothesized that the cycle of alternating attachment mechanisms is linked to the limpets foraging cycles.     

Biotransformation of cycloalkanones: Controlled oxidative and reductive bioconversions by anAcinetobacter species

Summary Culture conditions have been optimised to enable resting cell cultures ofAcinetobacter calcoaceticus NCIMB 9871 to selectively undertake either oxidative or reductive biotransformations of various bicyclic ketones.     

The use of immobilized porphyrins and corrins to dehalogenate organochlorine pollutants

Porphyrins and corrins have been immobilized onto solid-phase supports and used to dehalogenate organohalides under reducing conditions. One such system has been used to dehalogenate an aqueous solution (10 ppm) of lindane for over 90 days at over 98% efficiency and for a further 150 days in excess of 65% efficiency. Dichloromethane has been shown to be effectively dehalogenated when supplied to immobilized systems in gaseous form. Correspondence to: T. S. Marks     

Passive release of monoclonal antibodies from hybridoma cells

Evidence is presented for the passive release of monoclonal antibodies (MCAB) from hybridoma cells grown in either batch or continuous-flow culture. This release is promoted at room temperature. Passively released MCAB is indistinguishable from that released by actively growing cells, as judged by SDS-polyacrylamide gel electrophoresis. The significance of these observations in relation to the continuous culture of hybridoma cells is discussed.Maximum MCAB content of TB/C3 hybridoma cells is about 55pg per cell, any additional MCAB produced is secreted.Abbreviations MCAB monoclonal antibodies - PBS phosphate buffered saline - RT room temperature - SDS sodium dodecyl sulphate     

Stage-specific cuticular proteins of Ostertagia circumcincta and Ostertagia ostertagi

In this study we have shown that NHS-biotin and I¹²⁵-streptavidin can detect cuticular polypeptides of Ostertagia spp. The labelled polypeptide profile of intact nematodes is simple compared to the profile obtained by labelling homogenates. None of the major internal polypeptides are labelled and the subset of proteins labelled in intact nematodes appears to be mainly surface associated. The results presented here demonstrate that NHS-biotin may be used as a reagent for the analysis of surface polypeptides. The surface polypeptide profiles of the five major developmental stages (L1, L2, L3, L4 and adult) of Ostertagia circumcincta show a series of stage-specific molecules with no polypeptides common to all stages, indicating that the cuticle is a dynamic structure which changes throughout the life cycle. Similarity comparison of Ostertagia ostertagi L3 and L4 stage surface profiles showed that each stage is clearly distinct; comparison of these stages between the two species shows an overall similarity.     

Structural studies of cytochrome b5: complete sequence-specific resonance assignments for the trypsin-solubilized microsomal ferrocytochrome b5 obtained from pig and calf

We report complete sequence-specific proton resonance assignments for the trypsin-solubilized microsomal ferrocytochrome b5 obtained from calf liver. In addition, sequence-specific resonance assignments for the main-chain amino acid protons (i.e., C alpha, C beta, and amide protons) are also reported for the porcine cytochrome b5. Assignment of the majority of the main-chain resonances was rapidly accomplished by automated procedures that used COSY and HOHAHA peak coordinates as input. Long side chain amino acid spin system identification was facilitated by long-range coherence-transfer experiments (HOHAHA). Problems with resonance overlap were resolved by examining differences between the two-dimensional 500-MHz NMR spectra of rabbit, pig, and calf proteins and by examining the temperature-dependent variation of amide proton resonances. Calculations of the aromatic ring-current shifts for protons that the X-ray crystal structure indicated were proximal to aromatic residues were found to be useful in corroborating assignments, especially those due to the large shifts induced by the heme. Assignment of NOESY cross peaks was greatly facilitated by a prediction of intensities using a complete relaxation matrix analysis based on the crystal structure. These results suggest that the single-crystal X-ray structure closely resembles that of the solution structure although there is evidence that the solution structure has a more dynamic character.     

A tubulo-cisternal endoplasmic reticulum system in the potassium transporting marginal cells of the stria vascularis and effects of the ototoxic diuretic ethacrynic acid

Summary Sections of metal impregnated tissue and freeze-fracture have been used to examine intracellular membrane systems in marginal cells of the stria vascularis in mammalian cochleae. A continuous network of elements of the smooth endoplasmic reticulum was revealed. Notable features of this system were a series of flattened cisternae just inside and parallel with the lateral plasma membrane in continuity with an apical network of tubules, cisternae and sheets oriented in parallel with the luminal membrane. The whole system was closely associated with mitochondria. These characteristics suggest that the potassium transporting marginal cells possess a tubulo-cisternal endoplasmic reticulum (TER) like that found in many sodium transporting epithelial cells. The lateral elements of the TER dilated, appearing like vacuoles, and opened to the lateral extracellular space in response to the effects of ethacrynic acid. This diuretic impairs ion transport in the stria vascularis. It is suggested that the TER in marginal cells is involved in the transport of ions and fluid from the cell to the intercellular space when ion balance is disturbed and may play a role in cell volume regulation.This work was supported by the Medical Research CouncilPart of this work was presented at the 18th Workshop on Inner Ear Biology, Montpellier, September, 1981     

Constitutive and mitogen-induced production of T cell growth factor by stable T cell hybridoma lines

Stable T cell growth factor- (TCGF; IL 2) producing cloned T cell hybridoma lines were constructed by fusing murine alloantigen-activated T cells with the 8-azaguanine-resistant lymphoma line, BW5147. Many, but not all, clones of one of these hybridomas, i.e., hybridoma 24, secreted TCGF constitutively, but production was markedly enhanced by stimulation with T cell mitogens. Large numbers of TCGF-secreting hybridoma cells in a stable functional state could be obtained from histocompatible mice inoculated with cloned T cell hybridomas. Moreover, such in vivo-derived hybridoma cells could be stimulated sequentially with mitogen at least twice to secrete their biologically-active product, resulting in larger TCGF yields from the same cells. The secreted product of these T cell hybridoma lines resembled TCGF isolated from other cellular sources in that it: a) supported the growth of a TCGF-dependent T cell line; b) provided help for the induction of alloantigen-reactive cytotoxic T lymphocytes from thymocyte precursors; c) facilitated concanavalin A-induced mitogenic responses of low thymocyte numbers; d) had an apparent m.w. of 30,000 to 40,000 by gel filtration chromatography; and e) was eluted from DEAE-Sephacel ion-exchange chromatography columns by salt concentrations of 30 to 150 mM NaCl. The ability of these T cell hybridomas to grow in vivo and retain their functional characteristics in a stable form should prove useful in terms of providing large numbers of TCGF-secreting cells and studying in vivo aspects of the production of TCGF as well as other immunoregulatory mediators.