Ascorbic acid as a factor controlling "in vivo" its biosynthetic pathway

The capacity of ascorbic acid biosynthesis in potato tuber tissue is closely correlated with the ascorbic acid content of the cells: the lower the endogenous content of ascorbic acid, the greater its biosynthesis. At the highest level of ascorbic acid found in the cells, the biosynthetic capacity is virtually zero. In these conditions, adding glucose (the first precursor of ascorbic acid) has no effect whatsoever, whereas adding galactono-gamma-lactone (the last precursor) induces a high rate of ascorbic acid synthesis. It is suggested that AA biosynthesis is subject to a regulatory mechanism "in vivo" which controls an initial step in the biosynthetic pathway. The last step in this pathway, catalyzed by galactone oxidase, is never blocked and, moreover, its activity is greater than that of the preceding steps.     

Immunohistochemical absence of adrenergic neurons in the dorsal part of the solitary tract nucleus in sudden infant death

The immunohistochemical distribution of TH and PNMT containing neuronal elements was investigated utilizing peroxidase anti-peroxidase methods in newborn control and sudden infant death syndrome (SIDS) brainstems. The TH immunoreactive neurons, within the medulla oblongata, displayed a similar distribution in both control and SIDS tissue. However, PNMT immunoreactive neurons seen in the dorsal part of the nucleus of tractus solitarius in control tissue were not observed in SIDS tissue. This alteration of adrenergic neurons in the dorsal part of NTS (region reported to be implicated in the control of blood pressure and respiration) could explain the cardiorespiratory disorders in SIDS.     

K-Opioid Agonist Modulation of [3H]Thymidine Incorporation into DNA: Evidence for the Involvement of Pertussis Toxin-Sensitive G Protein-Coupled Phosphoinositide Turnover

Abstract: A body of evidence has indicated that μ-opioid agonists can inhibit DNA synthesis in developing brain. We now report that K -selective opioid agonists (U69593 and U50488) modulate [³H]thymidine incorporation into DNA in fetal rat brain cell aggregates in a dose- and developmental stage-dependent manner. K agonists decreased thymidine incorporation by 35% in cultures grown for 7 days, and this process was reversed by the K -selective antagonist, norbinaltorphimine, whereas in 21-day brain cell aggregates a 3,5-fold increase was evident. Cell labeling by [³H]thymidine was also inhibited by the K -opioid agonist as shown by autoradiography. In addition, U69593 reduced basal rates of phosphoinositide formation in 7-day cultures and elevated it in 21-day cultures. Control levels were restored by norbin-altorphimine. Pertussis toxin blocked U69593-mediated inhibition of DNA synthesis. The action of K agonists on thymidine incorporation in the presence of chelerythrine, a protein kinase C (PKC) inhibitor, or in combination with LiCl, a noncompetitive inhibitor of inositol phosphatase, was attenuated in both 7- and 21-day cultures. These results suggest that K agonists may inhibit DNA synthesis via the phosphoinositide system with a pertussis toxin-sensitive G protein as transducer. In mixed glial cell aggregates, U50488 increased thymidine incorporation into DNA 3.1-fold, and this stimulation was reversed by the opioid antagonist naltrexone.     

The influence of parasitic water mites on the instantaneous death rate of their hosts

Summary The effect of 2 species of water mites on the instantaneous death rate of their hosts was measured on the basis of laboratory experiments. In both parasite-host association — the parasitic water mite Hydryphantes tenuabilis on the aquatic insect host Hydrometra australis and the parasitic water mite Arrenurus pseudotenuicollis on the mosquito Anopheles crucians — the effect of mite load on the instantaneous death rate of the host appeared to be linear. Also, the impact of a single parasite on the host's death rate was apparently related to the ratio of parasite to host body weight. The results of this study are in general agreement with recent theoretical investigations of the regulation of host populations by parasites.     

Asymmetry of the cerebral hemispheres in man: a bridge binding the 1st and the 2d temporal gyri, superior face of the 2d temporal gyrus, and fusiform gyrus]

The autors study 76 human brains, 36 of which are dissected. They observe a "T1 T2 bridge" over the first temporal and second temporal gyri more often on the left side than on the right. They find the maximal width of the superior face of the second temporal gyrus predominant on the right side in 70% of cases, on the left side in 15% and equivalent on both sides in 15%. The fusiform gyrus is found wider on the left side in 53% of cases, on the right in 22% and equivalent on both sides in 25%.     

Gas exchange and leaf metabolism of irrigated maize at different growth stages

Abstract

Net ecosystem exchange (NEE), leaf gas exchange and biochemical traits were investigated in an irrigated maize crop grown under Mediterranean conditions. Sub-optimal irrigation water supply determined a drought stress during the early vegetative growth stage (45–49 days after swing) that decreased NEE. Drought, in the late vegetative stage, also caused a reduction of leaf gas exchange. In the latter period, proline, glycine and serine, as well as sucrose leaf contents increased, while starch, proteins and glucose contents decreased. In the early reproductive stage, the crop experienced a longer dry spell that induced a reduction in canopy as well as in leaf gas exchanges, while protein and free amino acid contents decreased with respect to the late vegetative stage. Both ecophysiological and biochemical data demonstrate a good capacity of cultivar Pioneer PR32D99 to endure the environmental stress, related to Mediterranean summer drought, leading to an elevated dry matter yield at harvest. Photosynthetic apparatus appeared fairly resistant to soil water shortage due likely to the increased leaf content of organic solutes, such as amino acids and soluble sugars.     

Germinability and fungal occurrence in seeds of Abies alba Mill. populations in southern Italy

Abstract

Germination tests were carried out on seeds from three Italian populations of Abies alba. Seed germinability was up to 38%. HgCl₂, NaClO and plant preservative mixture were used as seed‐sterilising agents. Despite chemical treatments, Papulaspora rubida and Chaetomium globosum were isolated. The possible role of these fungi in the physiology of silver fir seed germination process was discussed.     

Mitochondria and Familial Predisposition to Breast Cancer

Mitochondrial genome and functional alterations are related to various diseases including cancer. In all cases, the role of these organelles is associated with defects in oxidative energy metabolism and control of tumor-induced oxidative stress. The present study examines the involvement of mitochondrial DNA in cancer and in particular in breast cancer. Furthermore, since mitochondrial DNA is maternally inherited, hereditary breast cancer has been focused on.