Electron-cytochemical localization of alkaline phosphatase to G cells of Necturus maculosus antrum

Summary Electron-cytochemical localization of alkaline phosphatase activity was performed on G cells of Necturus maculosus antral mucosa. Alkaline phosphatase activity was localized to the nuclear membrane, the Golgi/endoplasmic reticulum, and the limiting membranes of G cell peptide-secretion vesicles. There was no specific localization of alkaline phosphatase activity to the plasma membrane. Treatment of the tissues with levamisole (an alkaline phosphatase inhibitor) did not markedly reduce the specific alkaline phosphatase activity. Specific lead deposition was reduced by removal of the substrate from the reaction mixture. The results from this study on N. maculosus G cells demonstrate that alkaline phosphatase activity can be found in a non-mammalian gastric endocrine cell and that specific activity was localized primarily to those intracellular structures involved with protein biosynthesis.     

Land use,soil loss,and sustainable agriculture in Rwanda

The conservation of scarce land resources is essential to the long-term viability of agriculture in Rwanda. High population density, steep slopes, and abundant rainfall prevail in the highland portions of this African country, making the task of erosion control uncommonly difficult for the peasant farmer. The specific use to which land is put, e.g., cultivation, fallow, pasture, woodlots, and, if it is cultivated, the particular combination of crops grown, can be seen as contributing to both the cause and the solution of the land degradation problem. Based on data from a nationwide survey of over 4800 agricultural fields in Rwanda, this study reviews the extent to which the land use and cropping patterns employed by farmers are appropriately suited, in terms of erosion control, to the topographical and environmental characteristics of their landholdings. Analyses of other aspects of the traditional agricultural system, e.g., variations in relative soil fertility, the use of organic fertilizers, and the location of fields relative to the household, are introduced to help explain why farmers often fail to maximize erosion control through land use and cropping practices. Adjustments to current land use practices that can be expected to reduce soil loss are discussed.     

Characterization of sucrose-hydrolyzing enzymes of Zymomonas mobilis

Extracellular proteins of Zymomonas mobilis were analyzed by two-dimensional gel electrophoresis and protein maps drawn up. One of these proteins showed sucrose-hydrolyzing activity, as indicated by activity staining after polyacrylamide gel electrophoresis. It was purified from the extracellular extract of a glucose fermentation by polyacrylamide gel electrophoresis, using a two-step procedure. The molecular mass of the protein was 46 kDa and its isoelectric point 5.0. A rabbit antiserum was raised against this protein. As shown by immunoblotting, the same protein was present in extracellular extracts obtained from glucose, fructose and sucrose fermentations. A cross-reaction was also detected by immunoblotting, with a cellular protein of molecular mass 46 kDa present on the three carbon sources studied. However, activity staining was unsuccessful on gels after electrophoresis of these cellular extracts. The extracellular protein extract obtained from a fermentation run on glucose contained another sucrose-hydrolyzing protein of molecular mass 51 kDa and with an isoelectric point of 4.8. This protein was absent in fructose and sucrose fermentations but showed a positive reaction with the antiserum raised against the 46 kDa extracellular protein. Partially purified sucrose-hydrolyzing proteins also catalyzed transfructosylation reactions, suggesting that they could be of the levansucrase type.     

Tumor-reactive IgE antibodies in plasma of patients with gastrointestinal carcinomas

A total of 208 plasma samples from 115 patients with gastrointestinal carcinomas and nine patients with other intestinal disease were examined for the presence of IgE tumor antibodies by a solid-phase radioimmunoassay. Approximately one-third of the patients gave significant reactions with gastrointestinal carcinoma extracts compared with normal tissue extracts. Absorption with tumor and normal tissue extracts, with type AB human red cells, and with CEA indicated tumor specificity in some of the samples so examined. None of the 50 serum samples tested from normal blood donors contained tumor-specific IgE. IgE tumor antibodies decreased or completely disappeared in the majority of patients 8-13 days after surgical treatment.     

Evidence for the laryngeal source of ultrasonic and audible cries of rodents

The audible cries of three species of young myomorph rodents were found to be emitted through the nose and the mouth, buccal and nasal cavity resonances being involved in the production of the formant structures of the emitted cries. Ultrasonic cries were found to be emitted mainly through the mouth, with no evidence for the involvement of cavity resonances. Nerve sectioning experiments on adult and young rats implicated the larynx as the source of both their audible and their ultrasonic cries. However, consideration of the considerable differences in physical structure between the typically "vocal" audible cries and the ultrasonic cries, as well as other differences noted in the experimental conditions here and elsewhere, leads to the conclusion that the rodent larynx may operate in two quite different sound production modes.     

Interactions between Sympathomimetic Amines and Antidepressant Agents in Man

Intravenous infusions of phenylephrine, noradrenaline, adrenaline, and isoprenaline were given to healthy human volunteers after five to seven days on phenelzine, tranylcypromine, or imipramine, and cardiovascular responses were compared with those observed under control conditions. With monoamine oxidase inhibitors there was a 2-2½ fold potentiation of the pressor effect of phenylephrine, but no clinically significant potentiation of cardiovascular effects of noradrenaline, adrenaline, or isoprenaline. With imipramine there was potentiation of the pressor effects of phenylephrine (2-3 fold), noradrenaline (4-8 fold), and adrenaline (2-4 fold); there were dysrhythmias during adrenaline infusions, but no noticeable or consistent changes in response to isoprenaline.Noradrenaline and adrenaline in amounts contained in local anaesthetics used in dentistry are not likely to be significantly potentiated in otherwise healthy patients receiving monoamine oxidase inhibitors. Hazardous potentiation of their cardiovascular effects might occur in patients receiving tricyclic antidepressants.Our observations do not indicate that the hazards associated with isoprenaline inhalation by bronchial asthmatics would be increased by coincident therapy with a monoamine oxidase inhibitor or tricyclic antidepressant.     

Factors Affecting Virulence of Shigella flexneri: Defective Methionine Synthesis in an Escherichia coli-Shigella Hybrid

An Escherichia coli-Shigella flexneri hybrid of intermediate virulence was studied to determine whether its shorter survival in host cells might be due to a metabolic defect. Investigation of its growth in minimal glucose medium showed that the hybrid, like its E. coli parent, had a longer lag phase and a slower growth rate than its virulent Shigella parent. Methionine was found to increase the growth rate of the hybrid. The Shigella parent of the hybrid can synthesize methionine normally, but the E. coli parent has a point mutation in its metA gene. Since it synthesizes enough methionine to grow slowly, it is postulated that the hybrid strain has a hybrid metA gene, that is, a gene composed partly of deoxyribonucleic acid (DNA) from E. coli, with the balance of the DNA from S. flexneri. Phage P1-mediated transduction, with the metA(-)E. coli parent as recipient and the Shigella parent as donor, yielded a few transductants that responded to methionine in the same way the hybrid did. Many more transductants of the hybrid type were produced when the hybrid strain was used as a donor. It is suggested that this poorly functioning gene acts synergistically with the hybrid strain's relaxed synthesis of ribonucleic acid to prevent its survival in the host.     

Escherichia coli Mutant with Elevated Nicotinamide Adenine Dinucleotide Phosphate (Reduced) Oxidase Activity

A slow-growing mutant of Escherichia coli with greatly elevated nicotinamide adenine dinucleotide phosphate (reduced; NADPH) oxidase activity has been isolated. The oxidase activity of the wild-type organism, normally low at pH 7.5, was increased when the assay was performed at pH 6.0. Sucrose density gradients of sonic extracts of the mutant and wild-type strains revealed several peaks of NADPH oxidase activity at pH 6.0. The parent organism had a peak of activity of high molecular weight which was absent from the mutant. The mutant strain had an activator capable of increasing the activity of all wild-type density gradient peaks, especially the one of high molecular weight. The activator was either missing or masked in the wild type. Agar gel electrophoresis of the extracts uncovered a rapidly moving band from the wild type, missing from the mutant; the material in this band had weak NADPH-diaphorase activity and strongly inhibited the activity of the mutant NADPH oxidase. It was concluded that, in wild-type E. coli, NADPH oxidase activity is regulated by a proper balance of an activator and an inhibitor. The absence of the inhibitor, as in the mutant, or the inactivation of the inhibitor at acid pH levels, results in a high level of NADPH oxidase activity. The relation of high NADPH oxidase levels and subsequent decrease of the NADPH pool to the decrease in growth rate is considered.