Gibberellins in Embryo-Suspensor of Phaseolus coccineus Seeds at the Heart Stage of Embryo Development

Gibberellins (GAs) in suspensors and embryos of Phaseolus coccineus seeds at the heart stage of embryo development were analyzed by combined gas chromatography-mass spectrometry (GC-MS). From the suspensor four C₁₉-GAs, GA₁, GA₄, GA₅, GA₆, and one C₂₀ GA, GA₄₄, were identified. From the embryo, five C₁₉-GAs GA₁, GA₄, GA₅, GA₆, GA₆₀ and two C₂₀ GAs, GA₁₉ and GA₄₄ were identified. The data, in relation to previous results, suggest a dependence of the embryo on the suspensor during early stages of development.     

Gibberellins in suspensor,embryo and integument from very young seeds of Phaseolus coccineus L.

Endogenous gibberellins (GAs) were extracted from suspensor, embryo and integument of very young seeds of Phaseolus coccineus L. and detected by combined gas chromatography-mass spectrometry (GC-MS). Results show the presence of one C₂₀-GA, GA₄₄ and five C₁₉-GAs in the suspensor: GA₁, GA₄, GA₅, GA₆ and GA₈, and four C₁₉-GAs in the integument: GA₁, GA₅, GA₆ and GA₈. Only traces of GA₁ and GA₅ were identified in the embryo. A compound structurally related to GAs was identified as tetrahydroxy-Kauranoic acid in suspensor, integument and, only in trace amounts, in the embryo.     

Evaluation of hepatitis C virus serotypes and IgM anti-HCV antibodies in two groups of anti-HCV positive subjects in south-east Italy

We investigated the relation between the presence of IgM antibodies to hepatitis C virus (HCV) and serotypes of HCV, in particular when a high level of IgM antibodies are present in patients infected with HCV serotype I and may be associated with the source, duration and evolution of infection. The study involved two anti-HCV positive groups with chronic liver disease from the same area, one of which was a group of haemodialysis patients attending the same haemodialysis centre.     

Channel formation by salmon and human calcitonin in black lipid membranes.

In this study we investigated the interaction of salmon and human calcitonin (Ct) with artificial lipid bilayer membranes. Both peptides were able to form either transient or permanent channels in the model membranes. The channels formed by salmon Ct at concentration (125 nM) had, on average, a single-channel conductance of 0.58 +/- 0.04 nS in 1M KCl (+10 mV), which is voltage-dependent at lower voltages. Human Ct forms at the same concentration channels with a much lower probability, and high voltages of up to +150 mV were needed to initiate channel formation. The estimated single-channel conductance formed under these conditions was approximately 0.0119 +/- 0.0003 nS in 1 M KCl. Both salmon and human Ct channels were found to be permeable to calcium ions. The possibility is discussed that the superior therapeutic effect of salmon Ct as a tool to treat bone disorders, including Paget disease, osteoporosis, and hypercalcemia of malignancy, rather than human Ct is related to the lack of the fibrillating property of salmon Ct. Preliminary data indicate that also eel and porcine Ct and carbocalcitonin form channels in model membranes.     

Effect of calcium ions on human calcitonin. Possible implications for bone resorption by osteoclasts

Calcium ions (Ca²⁺) are indispensable for life and are involved in important physiological actions, which makes maintaining a constant level of blood Ca²⁺ essential. Ca²⁺ is mainly stored in bones which serve as a reservoir and its homeostasis is modulated by various hormones. Human calcitonin (hCt) is a small peptide hormone that exerts its physiological effect on Ca²⁺ metabolism by means of osteoclast-mediated bone resorption inhibition. Most of these actions are mediated through peptide/receptor interaction that acts via a second messenger. However, in vitro studies have shown that hCt can interact with membrane lipids to form ion channels in membrane models. This ability is due to the peptide’s secondary structure and aggregation state, that can be modulated by different molecules. In our study, we evaluated the effect of Ca²⁺, at different concentrations, both on the hCt ion channel incorporated into a planar lipid membrane made up of phosphatidylcholine containing 15 % phosphatidylglycerol and on the secondary structure of hCt in an aqueous environment. Ca²⁺ is able to interact with the hCt peptide by acting on the channel incorporated into the membrane as well as on the peptide in solution, both by increasing hCt channel frequency and in solution promoting α-helix formation, that counteracts the fibrillating process. These experimental observations, suggesting that hCt senses Ca²⁺ concentration variations, strengthen the hypothesis that channel formation represents an extra source of Ca²⁺ entry into osteoclasts in addition to the well-known interaction of the monomer with the specific receptor.     

A monoclonal antibody for the detection of conjugated forms of abscisic acid in plant tissues

A mouse monoclonal antibody against abscisic acid (ABA) was produced and characterized. It was raised using ABA conjugated to the carrier protein through the carboxyl (Cl) group as immunogen. It did not discriminate between free ABA or its ester derivatives. This antibody, which is the first monoclonal against Cl-conjugated ABA, shows interesting characteristics. It has high affinity (K_a=1.5 × 10⁹ L/mol) and specificity. Compounds structurally similar to ABA, such as phaseic acid, dihydrophaseic acid, and both the 2,trans-isomer and the (R)-enantiomer of ABA, are not reactive. The narrow linear range of the standard curve (0.018–1.8 pmol) ensures great precision of the assay. This monoclonal antibody has been used for the quantification of ABA conjugates in crude aqueous extracts of bean leaves by radioimmuno-assay (RIA). The fractionation of the extracts by high-performance liquid chromatography (HPLC) confirmed the absence of cross-reacting compounds. Because of its affinity and specificity, in combination with antibodies against free ABA, this antibody should be a sound tool for studying the metabolism and immunolocalization of ABA in plant tissues.