Distribution, morphology and projections of nitrergic and non-nitrergic submucosal neurons in the pig small intestine

 Sequential nitric oxide synthase immunohistochemistry and nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) histochemistry in pig small intestinal wholemounts revealed a complete colocalisation of the two nitrergic markers in submucous neurons. The external submucous plexus (ESP) contained nitrergic neurons throughout. In the internal submucous plexus (ISP) we found a moderate number of nitrergic neurons in the duodenum, while they were rare in the jejunum and nearly absent in the ileum. Combined NADPHd histochemistry and silver impregnation showed morphological ESP type III and VI neurons to be NADPHd positive whereas ESP type II, IV and V neurons were NADPHd negative. Axons of ESP type III, IV and VI neurons were often observed to enter interconnecting strands directed abluminally. ESP type II neurons projected mainly to the ISP. In special silver-impregnated wholemounts containing both external muscle layers and the abluminal part of the submucous layer, i.e. the myenteric plexus and the ESP, the great majority of impregnated axons within the interconnecting strands were observed to run between both plexuses and did not enter the circular muscle layer. We conclude that ESP type III and VI neurons are nitrergic while ESP type II, IV and V neurons are non-nitrergic. Furthermore, we assume that ESP type III, IV and VI neurons may represent a submucosal input to the myenteric plexus. Accepted: 26 August 1997     

Diagnosis of infantile and juvenile forms of GM2 gangliosidosis variant 0. residual activities toward natural and different synthetic substrates

Summary p-Nitrophenyl-6-sulfo-2-acetamido-2-deoxy--d-glucopyranoside, which is known to be a specific substrate for human hexosaminidase A, has recently been used successfully for diagnosis of variants B and B¹ of G_M2-gangliosidosis (Fuchs et al. 1983; Kytzia et al. 1983; Li et al. 1983). However, it is hydrolyzed by hexosaminidase S as well and is therefore not suitable for detection of patients with variant 0, who reach the normal range of activity toward this substrats. Assay of ganglioside G_M2 cleaving activity in fibroblast extracts in the presence of the natural G_M2 activator protein reveals residual hexosaminidase A activities of less than 2% of normal controls in two infantile and up to 7.5% in two juvenile patients with variant 0.     

Bacteriorhodopsin,boundary lipid and protein conformers. A spin label study

A spin label study, as a function of temperature, has been made with the bacteriorhodopsin membrane using a stearic acid spin label. The ESR spectra show a strong variation with temperature and the presence of isosbestic points. The spectra are interpreted as indicating the presence of a two-component system with an activation energy (approx. 14 kcal/mol) corresponding to a protein conformational change. This activation energy is similar to that deduced from recent flash photolysis studies.It is concluded that the spin label is sensitive to the temperature-dependent protein conformational change in this membrane system.     

A field study on the dependence of the fecundity of Daphnia spec. on food concentration

Summary The dependency of the fecundity of Daphnia spec. on the food concentration was studied in Lake Constance. To eliminate the influence of temperature the number of eggs per adult female was plotted against the concentration of particulate carbon (<50 m) at the estimated time of the production of the eggs. The curve obtained is similar to the results of laboratory investigations. The minimum food concentration for egg production is slightly above 0.2 mg C/1; at 0.7 mg C/1 the curve reaches a plateau. The absolute values of the threshold concentration and the incipient limiting level are compared to laboratory results. It appears that the shift of the field curve to higher concentrations is caused by the imcomplete availability of the 50 m particulate carbon fraction to the daphnids. Daphnia in Lake Constance seem to be food limited during most of the year.     

Auxin-induced H+-pump stimulation does not depend on the presence of epidermal cells in corn coleoptiles

Cell-wall acidification and electrical reactions (depolarization and hyperpolarization) are typical auxin responses in maize (Zea mays L.) coleoptiles. In an attempt to test the role of the outer epidermis in these responses, they have been measured and compared in intact and peeled coleoptile fragments. To exclude interactions between parenchymal and epidermal cells, the coleoptile pieces were completely stripped of their outer epidermis. This preparation was monitored by means of a scanning electron microscope. When externally applied indole-3-acetic acid was tested, we found that neither cell-wall acidification nor the electrical membrane responses depended on the presence of intact epidermal cells.Abbreviations IAA Indole-3-acetic acid - MES 2-[N morpholino-ethane-sulfonic acid - TRIS 2-Amino-2-hydroxymethyl-1,3-propanediol We thank Kuki Kaethner for her excellent technical assistance. This work was supported by the Hessische Graduiertenförderung and the Deutsche Forschungsgemeinschaft.     

Mapping of mglB, the structural gene of the galactose-binding protein of Escherichia coli

Summary The tetracycline resistance transposon Tn10 was inserted into the E. coli chromosome near mglB550, a structural gene for the galactose-binding protein. P1 transductions established the position of these Tn10 insertions (zee-700, 701, 702::Tn10) close to the genes ptsF, fpk, cdd, mglB550, his, and gatA with 85%–95%, 85%, 36%, 20%–40%, 12%–15%, and 0.5% contransduction frequency. Three factor crosses revealed the relative sequence of the genes as: mglB550, zee-700::Tn10, ptsF, fpk, cdd, his. gatA was found to be 1.3% cotransducible with mglB550. Two Tn10 insertions near gatA were isolated and characterized. One, zef-704::Tn10, was 3% cotransducible with fpk, 8% with mglB550, and 42% with gatA. The other, zef-703::Tn10, was 98% cotransducible with gatA but not with mglB550 or fpk. Neither of these two Tn10 insertions was cotransducible with cdd. Four factor crosses revealed the sequence gatA, zef-704::Tn10, mglB550, fpk.Neither zee-700::Tn10 nor zef-703::Tn10 showed any (0/300) contransduction with either glpT or gyrA. The clockwise order of genes is then: his, cdd, fpk, ptsF, zee-700::Tn10, mglB550, zef-704::Tn10, gatA. With a fix-point for his at 44 min, fpk would be placed at 45 min and mglB550 at 45.5 min. During the course of this work we noticed that the cotransduction frequency between Tn10 insertions and nearby markers tended to increase when new P1 lysates were prepared from freshly reisolated strains. This may indicate loss of nonessential genes adjacent to Tn10 insertions. Using insertion zee-702::Tn10, we isolated deletions extending into an mgl gene other than mglB. Crosses between such a deletion mutant and an mglB550 mutant were done. The analysis of the periplasmic proteins of these as well as other transductants or recombinants involving the mglB550 or the mglB551 gene revealed the existence of strains synthesizing both the wild-type as well as the corresponding mutant protein. Strains containing both proteins exhibit either wild-type or mutant phenotype. These strains appeared unstable. Upon reisolation from purified stock cultures kept in glycerol at-20°C, colonies could be isolated that carried only mutant or wild-type protein.     

Peroxidase cytochemistry and ultrastructure of resident macrophages in fetal rat liver: A developmental study

The peroxidase cytochemistry and the ultrastructural characteristics of resident macrophages in fetal rat liver have been investigated. Livers of 10-, 11-, 14-, 17-, and 20-day-old fetuses were fixed by immersion or perfusion, incubated for peroxidase, and processed for transmission electron microscopy. Some 17- and 20-day-old fetuses were injected prior to sacrifice with carbon or 0.8-μm latex particles through the umbilical vein. Some livers were additionally processed for scanning electron microscopy (SEM). The endogenous peroxidase was present in the nuclear envelope (NE) and endoplasmic reticulum (ER) of fetal macrophages with a negative reaction in the Golgi apparatus, a distribution pattern identical to that in Kupffer cells of adult rat liver. Such peroxidase-positive cells avidly took up the injected latex and carbon particles and were the only cell type in fetal liver involved in erythrophagocytosis. Furthermore, they were associated with erythropoietic elements, forming close contacts with such cells, especially normoblasts. The peroxidase pattern in leukopoietic cells differed at all stages of maturation from that in macrophages. By SEM the macrophages exhibited ruffles and lamellopodia on their surfaces and protruded often into the lumen of fetal sinusoids. Macrophages in fetal liver underwent mitotic divisions. The macrophages were first seen on gestation day 11, whereas the first mature monocytes were found on gestation day 17. These observations suggest that resident macrophages in fetal rat liver form a self-replicating cell line independent of the monocytopoietic series, although they may both arise from a common precursor cell.     

A statistical study of the interspike-interval distribution of cortical neurons]

Spontaneous activity was recorded extracellularly by glass microelectrodes from 54 neurons of the Gyrus sigmoideus posterior of unnarcotized and gallamine-immobilazed cats, and the sequential and nonsequential interspike-interval histograms were determined using the multi-channel analyzer CAT 400 C. The interval distributions were characterized by graphic criteria, and it was attempted to describe these distributions mathematically by four biparametric distributions, the Weibull, lognormal, gamma and normal distributions. 80% of the frequency distributions of type I (exponential), II (left skew, gamma-similar) and IV (almost symmetrical) could be assigned to these distributions, namely 43% of the lognormal distribution, 32% of the Weibull distribution, and 5% of the gamma distribution. The interval histograms of the type III (left skew, steep) and V (bimodal) could not be described by any of the distributions selected.