Phosphotransfer reactions as a means of G protein activation

Heterotrimeric guanine nucleotide-binding regulatory proteins (G proteins) serve to transduce information from agonist-bound receptors to effector enzymes or ion channels. Current models of G protein activation-deactivation indicate that the oligomeric GDP-bound form must undergo release of GDP, bind GTP and undergo subunit dissociation, in order to be in active form (GTP bound subunits and free dimers) and to regulate effectors. The effect of receptor occupation by an agonist is generally accepted to be promotion of guanine nucleotide exchange thus allowing activation of the G protein. Recent studies indicate that transphosphorylation leading to the formation of GTP from GDP and ATP in the close vicinity, or even at the G protein, catalysed by membrane-associated nucleoside diphosphate kinase, may further activate G proteins. This activation is demonstrated by a decreased affinity of G protein-coupled receptors for agonists and an increased response of G protein coupled effectors. In addition, a phosphorylation of G protein subunits and consequent phosphate transfer reaction resulting in G protein activation has also been demonstrated. Finally, endogenously formed GTP was preferentially effective in activating some G proteins compared to exogenous GTR The aim of this report is to present an overview of the evidence to date for a transphosphorylation as a means of G protein activation (see also refs [1 and 2] for reviews). (Mol Cell Biochem 157: 593, 1996)Recipient of Servier Investigator Award     

Efficacy of transfer factor in treating patients with recurrent ocular herpes infections

Recurrent ocular herpes is an insoluble problem for the clinician. As cellular immunity plays an important role in controlling herpes relapses, and other studies have shown the efficacy of HSV-specific transfer factor (TF) for the treatment of herpes patients, an open clinical trial was undertaken in 134 patients (71 keratitis, 29 kerato-uveitis, 34 uveitis) suffering from recurrent ocular herpetic infections. The mean duration of the treatment was 358 days, and the entire follow-up period 189121 before, and 64062 days after TF treatment. The cell-mediated immune response to the viral antigens, evaluated by the lymphocyte stimulation test (LST) and the leucocyte migration test (LMT) (P<0.001), was significantly increased by the TF treatment. The total number of relapses was decreased significantly during/after TF treatment, dropping from 832 before, to 89 after treatment, whereas the cumulative relapse index (RI) dropped, during the same period, from 13.2 to 4.17 (P<0.0001). No side effects were observed. It is concluded that patients with relapsing ocular herpes can benefit from treatment with HSV-specific TF.     

Normal rat intestinal cells IEC-18: characterization and transfection with immortalizing oncogenes

IEC-18 cells, a cell line derived from the ileum of rat intestine, have the characteristics of normal cells since they have a contact inhibited cell growth, do not form colonies in soft agar and are not tumorigenic when injected in nude mice. IEC-18 cells were transfected with nuclear oncogenes, c-myc, v-myc and SV40 T antigen in order to obtain immortal cell lines. Independent clones were isolated and characterized for the growth properties. Expression of v-myc altered the morphology of the cells and shortened the doubling time. A slow growth together with a low cloning efficiency was associated with the expression of SV40 T antigen. No changes either in growth or in morphology were observed in c-myc-expressing IEC-18 cells. Expression of these nuclear oncogenes did not result in the neoplastic transformation of the IEC-18 cells, since none of the clones lost the anchorage dependence or were able to form tumors in vivo. The c-myc-containing IEC-18 cells were unable to secrete in the growth medium TGF and exposure to TGF inhibited the growth rate by 30%. All these observations are consistent with the conclusion that the expression of nuclear oncogenes does not lead to the neoplastic transformation of these cells.     

Growth and photosynthetic responses of field-grown sweetgum (Liquidambar styraciflua; Hamamelidaceae) seedlings to UV-B radiation

Very few studies have evaluated the effects of UV-B radiation on trees. especially deciduous species. In this study we evaluate the effects of supplemental UV-B radiation on the growth and photosynthetic capacity of sweetgum (Liquidambar styraciflua L.). Sweetgum seedlings were grown for 2 years in the field under either ambient or supplemental UV-B radiation. Artificial UV-B radiation was supplied by fluorescent lamps at a maximum daily supplementation of either 3.1 or 5.0 kJ of biologically effective UV-B radiation. Over the 2-year period, supplemental UV-B radiation had little effect on total plant biomass or photosynthetic capacity. However, subtle changes in leaf physiology, carbon allocation, and growth were observed. Supplemental UV-B radiation reduced photosynthetic capacity only during the first year, while leaf area and biomass were reduced in the second year. Alterations in carbon allocation included an increase in branch number and root to shoot ratio. While these data do not indicate that the productivity of sweetgum would likely be compromised by an increase in solar UV-B radiation, they do suggest that the UV-B portion of the solar spectrum contributes to the regulation of sweetgum growth and development. Therefore the possibility of significant consequences to sweetgum due to possible increases in UV-B radiation cannot be ruled out.     

Identification of Tuber magnatum Pico DNA markers by RAPD analysis

Summary Different species of truffle were studied in order to identify species-specific markers. The isolation of two Tuber magnatum Pico markers is reported. One of these could be used as a probe in dot blot hybridization, allowing the development of a rapid test able to identify Tuber magnatum species.     

Pigment production from in vitro cultures of Alkanna tinctoria Tausch

Summary An in vitro culture of Alkanna tinctoria Tausch cells was set up in order to investigate the possibility of producing alkannin, a red naphthoquinone naturally present in the root bark of this plant. Furthermore, an in vitro culture of callusderived roots was established and the production of alkannin evaluated. In the different experimental conditions investigated, differences in the production of alkannin derivatives as well as in the type of pigments produced, were observed. The potential use of this technology is discussed.     

Campodimele Study: Blood Pressure and Heart Rate Pattern in Clinically Healthy Elderly Subjects

Noninvasive ambulatory blood pressure (BP) monitoring is a developing method in clinical practice. Its interpretation needs reference standards stratified by age and gender. This study addresses ambulatory BP monitoring in elderly people with the purpose of quantifying the discrete and periodic variability of BP pattern over a 24-h period. The ABPM was performed in 92 clinically healthy subjects (45 men and 47 women) ranging in age from 76 to 102 years. The results refer to the time-qualified mean values with their dispersion, to the circadian rhythm with its parameters, and to the daily baric impact (BI) with its variability. The conclusion is drawn that BP preserves its nychtohemeral variability and circadian rhythmicity despite old age. The daily BP mean level and BI in older people in good health are comparable with those of young subjects, suggesting that humans surviving into old age are characterized by a eugenic control of their pressure regimen.