The problematic cemented Devonian brachiopod Schuchertellopsis durbutensis Maillieux, 1939

The Devonian cemented brachiopod Schuchertellopsis durbutensis has proved difficult to classify and its possible taxonomic relationships are unknown. Morphologically Schuchertellopsis resembles more closely members of the Orthotetidina than the Davidsoniidina. Examination of the shell structure, a key diagnostic feature of the Orthotetidina, shows that Schuchertellopsis has the cross laminar secondary shell typical of all orthotetidines. However, the presence of both pseudopunctate and incipient an extropunctate fabric within the ventral valve is unique amongst orthotetidine brachiopods and is thought to represent a phase of shell fabric experimentation. Schuchertellopsis probably fits most comfortably within the Schuchertellidae, and is the earliest representative of that family.     

Preface to Mechanisms of neuromuscular control. A Theme organized and edited by J. L. van Leeuwen

Preface to Mechanisms of neuromuscular control. A Theme organized and edited by J. L. van Leeuwen.     

Repetitive excitation of bursts of action potentials in the rat hippocampus following single shock stimulation

1. Post-stimulus time (PST) histograms of rat hippocampal cells were recorded in vivo following single-shock stimulation of the fornix. 2. The PST histograms displayed a series of peaks of decreasing amplitude, similar to damped oscillatory responses previously recorded in cats and rabbits. 3. The effect of increased background activity was investigated by recording histograms with concurrent pulse train stimulation of the contralateral hippocampus. The histograms showed a decreased latency to the onset of the second peak. 4. Damped oscillatory activity seen in the in vivo rat preparation could not be elicited in the in vitro rat slice preparation. Thus species differences cannot account for the absence in slice studies of this type of damped oscillatory activity. 5. We conclude that the level of spontaneous activity is one factor contributing to the genesis of multiple peaks in histograms in the in vivo preparation.     

Cloning and expression of the 3' portion of the T4 denV gene as a lacZ fusion gene

Polyclonal antibodies have been raised against endonuclease V from the bacteriophage T4. This rabbit serum, from which endemic E. coli antibodies have been removed, reacts with a single protein from T4-infected E. coli with a molecular weight of 16078 dalton. It was confirmed that these antibodies were directed against endonuclease V through the inhibition of the pyrimidine dimer specific nicking activity of endonuclease V in an in vitro nicking assay. A phage lambda gt11 T4 dC DNA library was screened for phage which produced a beta-galactosidase-endonuclease V fusion protein. Immunopositive clones were detected at a frequency of 0.25% of the plaques in the library. Restriction enzyme analyses of the DNA from 45 of these phage showed that all contained a 1.8 kb T4 EcoRI fragment which had been inserted within lambda gt11 in a single orientation. Western analysis of proteins which were produced from an induction of lysogens made from these phage reveals a single fusion protein band with a molecular weight slightly larger than native beta-galactosidase.     

Vitamin K epoxidase activity of rough and smooth microsomes from rat liver

The distribution of vitamin K epoxidase activity in rough and smooth microsomes has been studied and compared to the prothrombin precursor and vitamin K-dependent carboxylase activity. All three activities were high in rough microsomes as compared to the low levels found in smooth microsomes. The results are in agreement with the suggestion that there might be a linkage between the vitamin K-dependent carboxylation and epoxidation reaction in vivo.     

Effects of industrial respirators on breathing pattern at different work levels

The effects of a filtering device and an air-line apparatus on breathing pattern were studied in healthy men with different physical characteristics and work capacity. The subjects comprised nine construction workers aged 35-44, and nine firemen aged 21-35. The construction workers' mean maximal oxygen consumption (VO2max) was 34.5 ml min-1 kg-1, the firemen's 66.9 ml min-1 kg-1. Breathing pattern was analyzed for its components, inspiratory time, expiratory time, breathing frequency, tidal volume, and pulmonary ventilation at rest, during two submaximal treadmill walks when the subjects' absolute work load was equal, and during recovery. Neither the filtering device nor the air-line apparatus had a significant effect on breathing pattern when compared with the control values measured twice with a low-resistance breathing valve. A significantly longer expiratory time, lower breathing frequency, and smaller pulmonary ventilation were found for the firemen with the breathing valve and the industrial respirators. The breathing pattern of the construction workers and the firemen differed, but the alterations were not induced by the use of the filtering device or the air-line apparatus when studied at aerobic work levels up to 60% VO2max.