Species-dependent features of Dogiel type II neurones in the mammalian enteric nervous system.

Although autonomic gastrointestinal reflex movements, which occur in all mammalian species, have been described almost a century ago, little was known on the mechanisms underlying this behaviour. Recently, however, intrinsic primary afferent neurones, functioning as the first relay in the reflex arches embedded in the intestinal wall, have been identified in the guinea pig ileum. In guinea pig, such neurones display a Dogiel type II morphology and behave electrophysiologically as slow AHP neurones. In other gastrointestinal regions, in both guinea pig and rat, Dogiel type II cells are also encountered, but the strong correlation with slow AHP neuronal features seems less strict. In large mammals, a correlation of the cellular morphology with intracellular el ectrophysiological recordings has only been obtained in the pig small intestine. Surprisingly, in these experiments aberrant electrophysiological behaviour of Dogiel type II neurones is even more striking since the majority of these cells display electrophysiological features considered typical of S neurones. Furthermore, in those rare cases in which a slow afterhyperpolarization (AHP) could be recorded in porcine Dogiel type II cells, its amplitudes were negligible. This has led us to the conclusion that the differences in electrophysiological behaviour of neurones with comparable morphology in different species are most probably due to the modulating influence of the neurotransmitter substances present. This seems to be the most likely hypothesis in view of the considerable differences in neurotransmitter content of neurones with comparable functions throughout the species.     

Nisin stimulates oxygen consumption by Staphylococcus aureus and Escherichia coli.

Nisin stimulated oxygen consumption by nongrowing, glucose-metabolizing Staphylococcus aureus and Escherichia coli cells, indicating a protonophore mode of action. A similar stimulation in E. coli cells osmotically stressed to disrupt the outer cell membrane confirmed the cytoplasmic membrane as the site of nisin action and showed that nisin uptake was not prevented by the outer membrane.     

Heterologous gene expression in Lactococcus lactis subsp. lactis: synthesis, secretion, and processing of the Bacillus subtilis neutral protease

The Bacillus subtilis nprE gene lacking its own promoter sequence was inserted in the lactococcal expression vector pMG36e. Upon introduction of the recombinant plasmid into Lactococcus lactis subsp. lactis strain MG1363, neutral protease activity could be visualized by the appearance of large clearing zones around colonies grown on milk agar plates. By measuring the activities of the neutral protease and the intracellular enzyme lactate dehydrogenase in culture supernatants and cell fractions, it was demonstrated that the neutral protease was actively secreted into the growth medium. This was corroborated by using the Western blot (immunoblot) technique, which showed the presence of the mature form of the neutral protease in the culture supernatant. On the basis of these results, it is concluded that the B. subtilis neutral protease gene was expressed in L. lactis and that the gene product was secreted into the growth medium and was apparently correctly processed to produced a biologically active protein. The secretion of this particular enzyme may be helpful in achieving accelerated cheese ripening.     

Fluorescence banding in four species of Microtidae: an analysis of the evolutive changes of the constitutive heterochromatin

Three different fluorochrome and specific counterstain combination (DAPI/AMD, DA/DAPI and CMA/DA) treatments were applied to the chromosomes of four Microtidae (Rodentia) species. The results complete the data obtained in our previous paper (Burgos, M., Jiménez, R., & Dìaz de la Guardia, R., Genome 30:540–546, 1988) and prove that the changes in the constitutive heterochromatin in the evolution of the karyotypes of these species are not only due to gain or loss of heterochromatin, but are qualitative with respect to their nucleotide composition, repeated base pair organization or DNA-protein complex modification. These variations lead to the differential response to the fluorescence dye combinations used.     

Effects on efficiency in repetitive lifting of load and frequency combinations at a constant total power output.

Boxes were lifted and lowered repetitively at three different combinations of load and frequency. These combinations were chosen such that the total mechanical power generated was constant. Effects of the varying load or frequency conditions (but constant total mechanical power) on the rate of energy expenditure (M) and on the mechanical efficiency (ME) were measured. Mechanical power was determined from film analysis and separated into external power (generated to lift the load) and internal power (to raise the lifter's body mass). The M was determined from oxygen consumption measurements. The ME was calculated in two ways, depending on the definition of mechanical power, including either the external power only (MEext) or the total power output (MEtot). Despite a constant total mechanical power, M increased at higher loads and lower frequencies. This might be explained by the increasing isometric force required in postural and load control. The M increase resulted in a decrease of MEtot. However, at higher loads and lower frequencies MEext increased, indicating that more external work can be done at the same energy costs at higher loads or lower frequencies, which could be of interest from the point of view of occupational physiology. It would seem that at higher loads or lower frequencies the increased costs for isometric muscle action do not outweigh the benefit of raising the body less frequently. Furthermore, it was found that the MEext in lifting was much lower than the values reported for other kinds of activity.(ABSTRACT TRUNCATED AT 250 WORDS)     

Expression patterns of loricrin in various species and tissues

Abstract. In this study we analyzed the expression patterns of loricrin in various species and tissues using immunohistochemistry, immunoblotting and Northern blots. Loricrin is a glycine-, serine- and cysteine-rich protein expressed very late in epidermal differentiation in the granular layers of normal mouse and human epidermis. Later on in differentiation, loricrin becomes cross-linked as a major component into the cornified cell envelope by the formation of N^ɛ -(γ-glutamyl)lysine isopeptide bonds. This process either occurs directly or by the intermediate accumulation in L-keratohyaline granules of mouse epidermis and human acrosyringia. Loricrin was identified in all mammalian species analyzed by virtue of its highly conserved carboxy-terminal sequences revealing an electric mobility of ∼60 kDa in rodents, rabbit and cow and of ∼35 kDa in lamb and human on sodium dodecyl sulfate polyacrylamide gel electrophoresis. Loricrin is expressed in the granular layer of all mammalian orthokeratinizing epithelia tested including oral, esophageal and fore-stomach mucosa of rodents, tracheal squamous metaplasia of vitamin A deficient hamster and estrogen induced squamous vaginal epithelium of ovary ectomized rats. Loricrin is also expressed in a few parakeratinizing epithelia such as BBN [N-butyl-N-(4–hydroxybutyl)nitrosamine]-induced murine bladder carcinoma and a restricted subset of oral and single vaginal epithelial cells in higher mammals. Our results provide further evidence that the program of squamous differentiation in internal epithelia of the upper alimentary tract in rodents and higher mammals differ remarkably. In addition, we also have noted the distinct distribution patterns of human loricrin and involucrin, another major precursor protein of the cornified cell envelope.