Cross-Epithelial Hydrogen Transfer from the Midgut Compartment Drives Methanogenesis in the Hindgut of Cockroaches

In the intestinal tracts of animals, methanogenesis from CO₂ and other C₁ compounds strictly depends on the supply of electron donors by fermenting bacteria, but sources and sinks of reducing equivalents may be spatially separated. Microsensor measurements in the intestinal tract of the omnivorous cockroach Blaberus sp. showed that molecular hydrogen strongly accumulated in the midgut (H₂ partial pressures of 3 to 26 kPa), whereas it was not detectable (<0.1 kPa) in the posterior hindgut. Moreover, living cockroaches emitted large quantities of CH₄ [105 ± 49 nmol (g of cockroach)⁻¹ h⁻¹] but only traces of H₂. In vitro incubation of isolated gut compartments, however, revealed that the midguts produced considerable amounts of H₂, whereas hindguts emitted only CH₄ [106 ± 58 and 71 ± 50 nmol (g of cockroach)⁻¹ h⁻¹, respectively]. When ligated midgut and hindgut segments were incubated in the same vials, methane emission increased by 28% over that of isolated hindguts, whereas only traces of H₂ accumulated in the headspace. Radial hydrogen profiles obtained under air enriched with H₂ (20 kPa) identified the hindgut as an efficient sink for externally supplied H₂. A cross-epithelial transfer of hydrogen from the midgut to the hindgut compartment was clearly evidenced by the steep H₂ concentration gradients which developed when ligated fragments of midgut and hindgut were placed on top of each other—a configuration that simulates the situation in vivo. These findings emphasize that it is essential to analyze the compartmentalization of the gut and the spatial organization of its microbiota in order to understand the functional interactions among different microbial populations during digestion.     

Cupin: A candidate molecular structure for the Nep1-like protein family

Background  

NEP1-like proteins (NLPs) are a novel family of microbial elicitors of plant necrosis. Some NLPs induce a hypersensitive-like response in dicot plants though the basis for this response remains unclear. In addition, the spatial structure and the role of these highly conserved proteins are not known.     

Erythropoietin--a review

Erythropoietin is one of the members of the growth factor family. It is a glycoprotein. The sialic acid residues of the carbohydrate part prevent the elimination of the molecule from the circulation. The protein moiety is responsible for its biological activity. The main locus of synthesis of erythropoietin is the kidney, but there exist different concepts about its exact localisation. Most of the erythroid cells will be influenced by erythropoietin, except of the erythrocytes, which do not bind this factor. Besides short latency effects like the stimulation of the hemoglobin synthesis, there also occur long latency effects like the stimulation of the synthesis of different membrane proteins.     

Inhibition of 3H-thymidine incorporation of lymphocytes by a soluble factor from macrophages

Supernatants of peritoneal macrophages cocultivated with spleen cells or thymocytes contain a factor suppressing the ³H-thymidine (³H-TdR) incorporation of PHA-stimulated lymphocytes. The suppressing activity is not due to cytotoxicity and does not affect the rate of cell transformation or cell proliferation. The factor reduces only the ³H-TdR incorporation and not the DNA synthesis of lymphocytes. It does not show target cell specificity. The factor is dialysable, heat stable, and generated by macrophages.     

Preliminary studies on streptomutin A

Summary Supplementation of the culture medium with 2-deoxystreptidine allowsStreptomyces griseus MIT-5, an idiotrophic mutant, to produce an antibiotic which we have called streptomutin A. Degradation studies on the antibiotic showed that the aminocyclitol moiety is different from streptidine. Streptomutin A also is distinct from streptomycin in having a much different ratio of biological to chemical activity.This paper is Contribution No. 2746 from the Department of Nutrition and Food Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, U.S.A.     

From Positivism to Interpretivism and Beyond: Tales of Transformation in Educational and Social Research

From Positivism to Interpretivism and Beyond: Tales of Transformation in Educational and Social Research. Louis Heshusius and Keith Ballard, eds. New York: Teachers College Press, 1996. 197 pp.     

No neonates without adults

With the potential to process the world's agricultural and food waste, provide sustainable fodder for livestock, aquaculture, and pet animals, as well as act as a source of novel biomolecules, the black soldier fly, Hermetia illucens, has been launched into the leading position within the insects as feed industry. Fulfilment of these goals, however, requires mass-rearing facilities to have a steady supply of neonate larvae, which in-turn requires an efficient mating process to yield fertile eggs; yet, little is known about adult reproductive behavior, nor what physiological factors lead to its emergence. Moreover, fertile egg production tends to be highly variable in colony. Therefore, this review brings together what is currently known of the organismal biology of H. illucens, compiling information on adult morphology, physiology, biogeography, genomics, and behavioral ecology. As a holistic synthesis, it highlights several directions of interest for research to follow.