Histamine formation in human wound tissue

Zusammenfassung Wund- und Granulationsgewebe bildet beim Menschen nach Hautschnitt in den ersten Tagen erhebliche Mengen von Histamin durch Dekarboxylierung von Histidin. Diese Fähigkeit zur gesteigerten Histaminbildung kann dabei nicht den Mastzellen zugeschrieben werden.     

Intracellular free calcium rise triggers nuclear envelope breakdown in the sea urchin embryo

Cytosolic free calcium has recently been implicated in the regulation of mitosis in plant and animal cells. We have previously found correlations between increases in the levels of intracellular free calcium [Ca2+]i and visible transitions of structure at nuclear envelope breakdown (NEBD) and the onset of anaphase during mitosis in sea urchin embryos and tissue culture cells. To go beyond correlations it is necessary to manipulate [Ca2+]i, and in sea urchin embryos this requires the injection of calcium-chelator buffer solutions as the changes in free calcium in the cell cycle are dependent on intracellular stores. We report here that blocking the increase in [Ca2+]i which just precedes NEBD prevents this from taking place and halts mitosis. Subsequent injections which momentarily increase [Ca2+]i, or a natural recovery of the higher calcium levels, result in NEBD and the successful continuation of mitosis. Similarly, artificially increasing calcium by early injections results in early NEBD. We conclude that the increase in [Ca2+]i preceding NEBD is an essential regulatory step required for entry into mitosis.     

Experimental measurement of the photonic properties of icosahedral quasicrystals

Quasicrystalline structures may have optical bandgap properties-frequency ranges in which the propagation of light is forbidden-that make them well-suited to the scientific and technological applications for which photonic crystals are normally considered. Such quasicrystals can be constructed from two or more types of dielectric material arranged in a quasiperiodic pattern whose rotational symmetry is forbidden for periodic crystals (such as five-fold symmetry in the plane and icosahedral symmetry in three dimensions). Because quasicrystals have higher point group symmetry than ordinary crystals, their gap centre frequencies are closer and the gaps widths are more uniform-optimal conditions for forming a complete bandgap that is more closely spherically symmetric. Although previous studies have focused on one-dimensional and two-dimensional quasicrystals, where exact (one-dimensional) or approximate (two-dimensional) band structures can be calculated numerically, analogous calculations for the three-dimensional case are computationally challenging and have not yet been performed. Here we circumvent the computational problem by doing an experiment. Using stereolithography, we construct a photonic quasicrystal with centimetre-scale cells and perform microwave transmission measurements. We show that three-dimensional icosahedral quasicrystals exhibit sizeable stop gaps and, despite their quasiperiodicity, yield uncomplicated spectra that allow us to experimentally determine the faces of their effective Brillouin zones. Our studies confirm that they are excellent candidates for photonic bandgap materials.     

Intracellular pH and the sodium requirement at fertilisation.

Several lines of evidence suggest that ionic messengers are primary agents in the metabolic derepression which occurs at fertilisation. The derepression at fertilisation or parthenogenetic activation of the sea urchin egg occurs in two main phases. The first phase, which triggers the early events of fertilisation, is mediated by transitory increase of intracellular free calcium. The second, which triggers the late events of fertilisation, is mediated by a rise in the intracellular pH (refs 4-6). The transition from the early events of fertilisation of sea urchin eggs to the late events requires a minimal concentration of sodium in the external medium. External Na+ is required for the acid effux which follows fertilisation. Na+ requirement and the acid effux have been correlated in a hypothesis which proposes that internal protons are exchanged for external Na+ (refs 8, 9). By using pH-sensitive microelectrodes, we have examined the relationship between external Na+ and internal pH more closely. We demonstrate here that the increase of the intracellular pH following egg activation does require external Na+. However, the relative insensitivity of the alkalisation of the egg cytoplasm to large reductions of external Na+ is evidence against the Na-H exchange hypothesis.     

Elevated histidine decarboxylase activity in the kidney of the pregnant mouse

Zusammenfassung Die Fähigkeit,¹⁴C-Histamin aus¹⁴C-Histidin zu bilden, steigt in der Niere der schwangeren Maus enorm an. Dieses Organ ist deshalb eine der reichsten Quellen von tierischer Histidindecarboxylase.     

Absorption of protein in the early postoperative period in chronic conscious dogs

Postoperative alterations in amino acid exchange across the intestinal tract and in the capacity for protein absorption were investigated in a chronic canine model. Changes in postoperative splanchnic amino acid exchange consisted of a temporary decrease of total splanchnic amino acid release, including a significant reduction in alanine production, and an increase in glutamine consumption. Contrary to results under stable metabolic conditions, branched chain amino acids were also taken up by the intestine in the early postoperative period. The changes in postoperative amino acid exchange were not, however, reflected by a corresponding alteration in protein transport capacity. The absorptive capacity for a protein hydrolysate remained stable during the early postoperative period.