Out-of-plane distortion of the iron in ferrohemoglobin due to pseudo-Jahn-Teller effect

The large out-of-plane distortion of the iron atom of deoxyform ferrous hemoglobin is attributed to the pseudo-Jahn-Teller effect, which is caused by the odd parity vibrational mode and the electronic states of different parity. It is suggested that this effect in general may be seen in transition metal or rare earth ion compounds.     

Chromosaponin I increases mechanical extensibility of lettuce root cell walls

Chromosaponin I (CSI), at 3 m M , stimulates the growth of lettuce roots ( Lactuca sativa L. cv. Grand Rapids) with increasing fresh weight and decreasing root diameter compared with control. To analyze the mechanism of action of CSI, mechanical properties of lettuce root cell walls were examined with a tensiometer and the osmotic potential of the cell sap was measured with a vapor pressure osmometer. The mechanical extensibility of the cell wall was increased by CSI treatment, while the osmotic potential remained constant. Under osmotic stress, through addition of 0.225 M mannitol, the mechanical extensibility of the cell wall was increased before stimulation of growth was observed. These results suggest that cell wall-loosening is involved in the growth stimulation induced by CSI.     

Synthesis of appropriately functionalized vancomycin CD and DE ring systems

Synthesis of appropriately and fully functionalized 16-membered CD and DE ring systems of vancomycin is detailed.     

n-Amyl alcohol as a substrate for the production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by bacteria

Abstract n -Amyl alcohol was examined as a source for the synthesis of the 3-hydroxyvalerate (3HV) unit of the biopolyester, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HB-co-3HV)), by Alcaligenes sp., Pseudomonas sp. and several methylotrophic bacteria. A. eutrophus and Ps. lemoignei synthesized P(3HB-co-3HV) from glucose and n -amyl alcohol under nitrogen-deficient conditions. Many of methylotrophic bacteria grown on methanol synthesized the copolyester from methanol and n -amyl alcohol under nitrogen-deficient conditions. The content and composition of the polyester varied from strain to strain. Paracoccus denitrificans differed from all others in having a higher content of 3-hydroxyvalerate units in the copolyester synthesized.     

A Hydrophilic Peptide Comprising 18 Amino Acid Residues of the Prosaposin Sequence Has Neurotrophic Activity In Vitro and In Vivo

Abstract: Prosaposin, a 517-amino-acid glycoprotein, not only acts as the precursor of saposin A, B, C, and D but also possesses neurotrophic activity to rescue hippocampal CA1 neurons from ischemic damage in vivo and to promote neurite extension of neuroblastoma cells in vitro. Recently, the trophic activity of prosaposin on human neuroblastoma cells has been shown to reside in the NH₂-terminal hydrophilic sequence (LIDNNRTEEILY) of the human saposin C. Here we show that prosaposin, saposin C, and a peptide comprising the 18-amino-acid sequence (18-mer peptide; LSELIINNATEELLIKGL) located in the NH₂-terminal hydrophilic sequence of the rat saposin C-domain promoted survival and neurite outgrowth of cultured rat hippocampal neurons in a dose-dependent manner. Moreover, infusion for 7 days of the 18-mer peptide into the lateral ventricle of gerbils, starting either 2 h before or immediately after 3 min of forebrain ischemia, protected ischemia-induced learning disability and hippocampal CA1 neuronal loss. Thus, we ascribe the in vitro and in vivo trophic actions of prosaposin on hippocampal neurons to the linear 18-mer sequence and raise the possibility that this peptide can be used as an agent for the treatment of forebrain ischemic damage.     

Glucose-stimulated Single Pancreatic Islets Sustain Increased Cytosolic ATP Levels during Initial Ca2+ Influx and Subsequent Ca2+ Oscillations

In pancreatic islets, insulin secretion occurs via synchronous elevation of Ca²⁺ levels throughout the islets during high glucose conditions. This Ca²⁺ elevation has two phases: a quick increase, observed after the glucose stimulus, followed by prolonged oscillations. In these processes, the elevation of intracellular ATP levels generated from glucose is assumed to inhibit ATP-sensitive K⁺ channels, leading to the depolarization of membranes, which in turn induces Ca²⁺ elevation in the islets. However, little is known about the dynamics of intracellular ATP levels and their correlation with Ca²⁺ levels in the islets in response to changing glucose levels. In this study, a genetically encoded fluorescent biosensor for ATP and a fluorescent Ca²⁺ dye were employed to simultaneously monitor the dynamics of intracellular ATP and Ca²⁺ levels, respectively, inside single isolated islets. We observed rapid increases in cytosolic and mitochondrial ATP levels after stimulation with glucose, as well as with methyl pyruvate or leucine/glutamine. High ATP levels were sustained as long as high glucose levels persisted. Inhibition of ATP production suppressed the initial Ca²⁺ increase, suggesting that enhanced energy metabolism triggers the initial phase of Ca²⁺ influx. On the other hand, cytosolic ATP levels did not fluctuate significantly with the Ca²⁺ level in the subsequent oscillation phases. Importantly, Ca²⁺ oscillations stopped immediately before ATP levels decreased significantly. These results might explain how food or glucose intake evokes insulin secretion and how the resulting decrease in plasma glucose levels leads to cessation of secretion.