Mistletoes and mutant albino shoots on woody plants as mineral nutrient traps.

BACKGROUND AND AIMS: Potassium, sulphur and zinc contents of mistletoe leaves are generally higher than in their hosts. This is attributed to the fact that chemical elements which are cycled between xylem and phloem in the process of phloem loading of sugars are trapped in the mistletoe, because these parasites do not feed their hosts. Here it is hypothesized that mutant albino shoots on otherwise green plants should behave similarly, because they lack photosynthesis and thus cannot recycle elements involved in sugar loading. METHODS: The mineral nutrition of the mistletoe Scurrula elata was compared with that of albino shoots on Citrus sinensis and Nerium oleander. The potential for selective nutrient uptake by the mistletoe was studied by comparing element contents of host leaves on infected and uninfected branches and by manipulation of the haustorium-shoot ratio in mistletoes. Phloem anatomy of albino leaves was compared with that of green leaves. KEY RESULTS: Both mistletoes and albino leaves had higher contents of potassium, sulphur and zinc than hosts or green leaves, respectively. Hypothetical discrimination of nutrient elements during the uptake by the haustorium is not supported by our data. Anatomical studies of albino leaves showed characteristics of release phloem. CONCLUSIONS: Both albino shoots and mistletoes are traps for elements normally recycled between xylem and phloem, because retranslocation of phloem mobile elements into the mother plant or the host is low or absent. It can be assumed that the lack of photosynthetic activity in albino shoots and thus of sugars needed in phloem loading is responsible for the accumulation of elements. The absence of phloem loading is reflected in phloem anatomy of these abnormal shoots. In mistletoes the evolution of a parasitic lifestyle has obviously eliminated substantial feeding of the host with photosynthates produced by the mistletoe.

A prospective study of alcohol expectancies and self-efficacy as predictors of young adolescent alcohol misuse.

AIMS: To test the relative contribution of two key Social Learning Theory constructs, alcohol expectancies (AEs) and drinking refusal self-efficacy (DRSE), in predicting early adolescent drinking behavior and examine the possible mediational role of DRSE over AE. METHODS: High school students (N = 192, mean age 14) were administered measures assessing AE (Drinking Expectancy Questionnaire--Adolescent version; DEQ-A), DRSE (Drinking Refusal Self-Efficacy Questionnaire--Revised Adolescent version; DRSEQ-RA) and indices of alcohol consumption and problem drinking. Age, gender, peer drinking, tobacco use and positive and negative behavioral characteristics were included in the statistical models as known predictors of alcohol misuse. Subjects were followed up at 12 months, with 88.5% retention. RESULTS: Initial confirmatory factor analyses verified factor structures of the DEQ-A and DRSEQ-RA. Prospective structural models controlling for Time 1 drinking behavior, age, gender, peer alcohol use, tobacco use and behavior problems identified that DRSE but not AE was associated with problem drinking 12-month post-initial assessment. DRSE mediated AE in predicting problem drinking. CONCLUSION: Results suggest that DRSE is a more salient cognitive construct than AE in early adolescence alcohol use. In this age group, prevention and treatment strategies that build refusal self-efficacy may be more effective than strategies that challenge AEs.

Somatic in frame deletions not involving juxtamembranous cysteine residues strongly activate the RET proto-oncogene.

Somatic RET mutations have been identified in a variable proportion (about 30-70%) of sporadic Medullary Thyroid Carcinoma (MTC) cases. They are represented by the Met918Thr substitution (exon 16) typical of Multiple Endocrine Neoplasia type 2B (MEN2B) and, to a lesser extent, by nucleotide changes occurring at one of five critical cysteine residues (exons 10 and 11) typical of MEN type 2A (MEN2A). An in vitro transforming activity has already been demonstrated for these mutations. A few different MTC somatic mutations have been reported so far whose biological activity has still to be tested. In this paper we report the identification, in two MTC tumor samples, of two interstitial deletions of 48 bp and 6 bp occurred in exons 10 and 11 respectively. Both were somatic heterozygous in frame mutations, not involving any cysteine residue. Moreover, the expression of a full length RET cDNA carrying one of the two deletions demonstrated a strong transforming capacity in NIH3T3 cells.

Refilling of embolized vessels in young stems of laurel. Do We need a new paradigm?

Recovery of hydraulic conductivity after the induction of embolisms was studied in woody stems of laurel (Laurus nobilis). Previous experiments confirming the recovery of hydraulic conductivity when xylem pressure potential was less than -1 MPa were repeated, and new experiments were done to investigate the changes in solute composition in xylem vessels during refilling. Xylem sap collected by perfusion of excised stem segments showed elevated levels of several ions during refilling. Stem segments were frozen in liquid N2 to view refilling vessels using cryoscanning electron microscopy. Vessels could be found in all three states of presumed refilling: (a) mostly water with a little air, (b) mostly air with a little water, or (c) water droplets extruding from vessel pits adjacent to living cells. Radiographic probe microanalysis of refilling vessels revealed nondetectable levels of dissolved solutes. Results are discussed in terms of proposed mechanisms of refilling in vessels while surrounding vessels were at a xylem pressure potential of less than -1 MPa. We have concluded that none of the existing paradigms explains the results.

Proprotein convertases (PC1/PC3 and PC2) in normal and neoplastic human tissues: their use as markers of neuroendocrine differentiation.

By immunocytochemistry and immunoblotting, we examined normal and neoplastic human tissues with polyclonal antibodies raised against selected peptide regions of proprotein convertase-2 and -3 (PC2 and PC3), two proteases that have been shown to selectively cleave neuroendocrine precursor molecules at pairs of basic residues. Immunoreactivity for both enzymes was detected in neuroendocrine cells of pituitary, gut, pancreas, thyroid, and adrenals and in tumors thereof, but was absent in thyroid follicular cells, parathyroids, adrenal cortex, testes, and a number of nonneuroendocrine tissues, both normal and tumorous. Although both PCs were virtually universal concomitants of the neuroendocrine system, cells with a neural phenotype (e.g. pheochromocytes and Merkel cells) predominantly contained PC2, whereas classic endocrine cells contained mostly PC3. PC3 immunoreactive cells were abundant all along the gastrointestinal tract, whereas PC2 was highly expressed only in the pyloric antrum and proximal third of duodenum. Double immunostaining experiments revealed colocalization of PC3 with virtually all gastrointestinal peptides, whereas PC2 immunoreactivity was mostly expressed in gastrin, cholecystokinin, and somatostatin cells. Noticeably, the proportion of glucagon-producing cells immunoreactive for PC3 was high in the gut and low in pancreatic islets and glucagonomas, whereas the reverse occurred for PC2. At the ultrastructural level, immunostaining was confined to the mature dense core granules, the site of storage of granins and peptide hormones. With the exception of parathyroid cells, PC2 and/or PC3 expression correlated with the occurrence of granins, canonical markers of the secretory granules. Immunoblotting experiments confirmed the identity of the immunocytochemical reactivities. It is concluded that PC2 and PC3 are highly sensitive markers of neuroendocrine differentiation and have distinct distribution patterns, and that antibodies to these enzymes may play an important role in the analysis of tumors.

Different strategies of drought resistance in three Mediterranean sclerophyllous trees growing in the same environmental conditions.

Measurements have been made of leaf conductance to water vapour, relative water content and water potential in Olea oleaster Hoffmgg et Link, Ceratonia siliqua L. and Laurus nobilis L., three evergreen sclerophyllous trees growing in Sicily at sea level. Measurements were made hourly in May and September 1986. Although all the three species are regarded as components of a homogeneous group (sclerophylls) and they all showed a high degree of sclerophylly, the strategies they adopted to withstand drought were completely different. Olea oleaster behaved as a 'drought-tolerating' species. Drought was 'avoided' by Ceratonia siliqua by a 'water-spending' strategy and by Laurus nobilis by a 'water-saving' strategy combined with the capability of recovering even minimal water losses by dropping leaf water potential drastically. Such differences in drought resistance are discussed in terms of differences in the bulk elastic modulus of leaf cells and wood anatomy.

Xylem recovery from cavitation-induced embolism in young plants of Laurus nobilis: a possible mechanism.

Xylem recovery from cavitation-induced embolism was studied in l-yr-old twigs of Laurus mibilis L. Cavitation was induced by applying pre-established pressure differentials (AP0,1 ) across the pit membranes of xylem conduits. ΔP0 ) were 1.13, 1.75 and 2.26 MPa, corresponding to about 50, 77 und 100% of the measured leaf water potential at the rurgor loss point ΔP0,1 were obtained either by increasing xylem tensions or by applying positive pressures from outside, or by a combination of the two. The percentage loss of hydraulic conductivity (PLC) did not change, regardless of how the ΔP0-1 were obtained. This confirmed that xylem cavitation was nucleated by microbubbles from outside the vessels. Positive pressures, however, amplified (up to 75%) and sped up the xylem refilling (20 min) in comparison with that measured in unpressurized twigs (c.50% in 15 h). Twigs girdled proximally to their pressurized segment 1 nun after the desired pressure value had been reached, did not recover from embolism. The later the twigs were girdled with respect to when they were tested for PLC, the higher was their recovery from embolism, suggesting that some messenger was transported in the phloem which stimulated xylem refilling. Indol-3-acetic acid (1AA] applied to the exposed cortex of both pressurized and unpressurized twigs, induced an almost complete recovery from PLC. We hypothesize that the refilling of cavitated xylem might be a result of an auxin-induced increase in the phloem loading with solutes. This would cause radial transport of solutes to cavitated xylem conduits via the rays, thus decreasing their osmotic potential and making them refill. No positive xylem pressure potentials were measured during xylem recovery from PLC.

Ca2+ and Ca2+ channel antagonists in the control of human small cell lung carcinoma cell proliferation.

Small cell lung carcinoma cells possess voltage-dependent calcium channels (VDCCs) of the L, omega-conotoxin-sensitive and P-like type. We hypothesized that these VDCCs might regulate the secretion of autocrine growth factors and thus influence the proliferation of these cells. We found that extracellular Ca2+ plays a stimulatory role in the proliferation of the GLC8 cell line. L-type calcium channel blockers of the dihydropyridine, phenylalkylamine and benzothiazepine classes inhibited [3H]thymidine incorporation in these cells, however at concentrations higher than those required to block L-type channel function. Moreover, the growth of murine Swiss 3T3 fibroblasts which do not possess L-type Ca2+ channels, was inhibited by the Ca2+ channel antagonists at the same effective concentrations as in small cell lung carcinoma cells. omega-conotoxin and omega-agatoxin IVA, which block the N- and P-type channel respectively, had no effect on GLC8 cell proliferation. It is concluded that the presence of extracellular Ca2+ is a positive stimulus for small cell lung carcinoma cell growth. However, under our experimental conditions, the calcium channel blockers inhibited DNA synthesis most probably by a mechanism other than VDCC antagonism.

Candida humilis--dominant species in sourdoughs for the production of durum wheat bran flour bread.

Yeasts present in the sourdough that is generally used for the production of durum wheat bran flour bread wereisolated and identified. Samples were taken during the rebuilding phase and at different intervals of time in order to monitor the population dynamics. The results obtained from the phenotypic studies were further confirmed by the molecular studies and enabled us to affirm that most of the strains, more than 95%, belong to the species Candida humilis. The dominance of C. humilis was steady in time. The isolations were carried out at sufficiently long intervals so that it was possible to ascertain that the conditions in which the sourdough is kept are fundamental to the microbiological stability of the dough.

Drought resistance of Ailanthus altissima: root hydraulics and water relations.

Drought resistance of Ailanthus altissima (Mill.) Swingle is a major factor underlying the impressively wide expansion of this species in Europe and North America. We studied the specific mechanism used by A. altissima to withstand drought by subjecting potted seedlings to four irrigation regimes. At the end of the 13-week treatment period, soil water potential was -0.05 MPa for well-watered control seedlings (W) and -0.4, -0.8 and -1.7 MPa for drought-stressed seedlings (S) in irrigation regimes S1, S2 and S3, respectively. Root and shoot biomass production did not differ significantly among the four groups. A progressively marked stomatal closure was observed in drought-stressed seedlings, leading to homeostasis of leaf water potential, which was maintained well above the turgor loss point. Root and shoot hydraulics were measured with a high-pressure flow meter. When scaled by leaf surface area, shoot hydraulic conductance did not differ among the treated seedlings, whereas root hydraulic conductance decreased by about 20% in S1 and S2 seedlings and by about 70% in S3 seedlings, with respect to the well-watered control value. Similar differences were observed when root hydraulic conductance was scaled by root surface area, suggesting that roots had become less permeable to water. Anatomical observations of root cross sections revealed that S3 seedlings had shrunken cortical cells and a multilayer endodermal-like tissue that probably impaired soil-to-root stele water transport. We conclude that A. altissima seedlings are able to withstand drought by employing a highly effective water-saving mechanism that involves reduced water loss by leaves and reduced root hydraulic conductance. This water-saving mechanism helps explain how A. altissima successfully competes with native vegetation.

Malignant pheochromocytoma in multiple endocrine neoplasia type 2B syndrome. Case report and review of the literature.

A malignant behavior (i.e., distant metastatic spread) has been recorded in 3-4% pheochromocytomas occurring in the context of multiple endocrine neoplasia type 2A syndrome, but has never been documented in patients with the type 2B form. In this report we describe a case of malignant pheochromocytoma arising in the latter syndrome setting. The patient, a white young male, had the full-blown syndrome, including multicentric, bilateral medullary thyroid carcinoma metastatic to regional lymph nodes, mucosal neuromas, digestive ganglioneuromatosis, marfanoid habitus, and bumpy lips. Three and a half years after surgical resection of an apparently benign adrenal pheochromocytoma he developed widespread osseous metastases. The presence of hypertensive crises and high urinary catecholamine excretion rates, coupled to moderate hypercalcitoninemia, normal circulating carcinoembryonic antigen levels, negative whole-body 99mTc-(V) dimercaptosuccinic acid scan, and absence of neck or mediastinal disease by magnetic resonance imaging, proved that the metastases were from his previous adrenal and not thyroid tumor. Furthermore, since the bone metastases strongly accumulated 131I-metaiodobenzylguanidine, several courses of the radiocompound were given, which resulted in an objective, though partial, tumor regression.

Neuronal repair. Asynchronous therapy restores motor control by rewiring of the rat corticospinal tract after stroke.

The brain exhibits limited capacity for spontaneous restoration of lost motor functions after stroke. Rehabilitation is the prevailing clinical approach to augment functional recovery, but the scientific basis is poorly understood. Here, we show nearly full recovery of skilled forelimb functions in rats with large strokes when a growth-promoting immunotherapy against a neurite growth-inhibitory protein was applied to boost the sprouting of new fibers, before stabilizing the newly formed circuits by intensive training. In contrast, early high-intensity training during the growth phase destroyed the effect and led to aberrant fiber patterns. Pharmacogenetic experiments identified a subset of corticospinal fibers originating in the intact half of the forebrain, side-switching in the spinal cord to newly innervate the impaired limb and restore skilled motor function.

Occurrence and dominance of yeast species in sourdough.

AIMS: The aim of this work is to identify the dominant yeast species in homemade sourdoughs. METHODS AND RESULTS: PCR/restriction fragment length polymorphism analysis of internal transcribed spacer regions was used for the identification of isolates and the data were confirmed with phenotypic tests. The strains belonging to Saccharomyces cerevisiae were identified to strain level by analysis of inter-delta regions. CONCLUSION: This work shows that the dominant species in homemade sourdoughs can differ from each other. Saccharomyces cerevisiae was found to be the dominant species, followed by the Candida milleri, C. humilis, S. exiguus and Issatchenkia orientalis. The inter-delta regions of S. cerevisiae strains showed high polymorphism. SIGNIFICANCE AND IMPACT OF THE STUDY: Occurrence of single, non-Saccharomyces species and S. cerevisiae polymorphism in the yeast populations of sourdough samples.

Hydraulic architecture of plants of Helianthus annuus L. cv. Margot: evidence for plant segmentation in herbs.

The hydraulic architecture of sunflower (Helianthus annuus L. cv. Margot) was studied in terms of the partitioning of the hydraulic conductance (Kleaf) of leaves inserted at progressively more apical nodes both in growing plants (GP) and in plants at full anthesis (mature plants, MP). Leaf conductance to water vapour (gL), leaf water potential (PsiL), leaf water potential at zero turgor (Psi tlp), and leaf osmotic potential at full turgor (pi0) were also measured. Sunflower plants showed gL and Kleaf values significantly increasing in the acropetal direction, while PsiL of basal leaves was significantly more negative than that of distal leaves; Psi tlp markedly decreased in the acropetal direction in MP so that leaves of MP retained increasingly more turgor the more apical they were. This hydraulic pattern, already present in very young plants (GP), strongly favours apical leaves. These data suggest that the progressive leaf dieback starting from the stem base, as observed when the inflorescence of sunflower reached maturity, might be due to time-dependent loss of hydraulic conductance. In fact, Kleaf loss was correlated with PsiL drop and stomatal closure. Leaf dehydration was aggravated by solute exportation from the basal towards the apical leaves, as revealed by the acropetal decrease of pi0. Kleaf was shown to be linearly and positively related to the prevailing ambient irradiance during plant growth, thus suggesting that leaf hydraulics is very sensitive to environmental conditions. It was concluded that the pronounced apical dominance of some sunflower cultivars is determined, among other factors, by plant hydraulic architecture.

Multivariate analysis of prognostic factors in sporadic medullary carcinoma of the thyroid. A retrospective study of 109 consecutive patients.

BACKGROUND: Because of the rarity of medullary thyroid carcinoma, adequate information for determination of the prognostic characteristics and clinical course of this disease can be obtained only from a database that serves a large population. METHODS: A retrospective review of 109 patients with sporadic medullary thyroid carcinoma was conducted; all were diagnosed and treated at a single institution over a 30-year period. The series included 57 males and 52 females with a median follow-up of 5.3 years. Statistical univariate analysis of relapse free survival and overall survival was done for 18 clinicopathologic variables, including sex, age, TNM staging, completeness of surgical resection, postoperative calcitoninemia, histologic subtype, tumor size, thyroid capsule invasion, amyloid, katacalcin, calcitonin, and calcitonin gene-related peptide immunostaining patterns of the primary tumor. RESULTS: Risk factors for unfavorable outcome were male sex, age > 60 years, incomplete tumor resection, mixed cell subtype, tumor size > 4 cm, extrathyroid tumor invasion, lack of amyloid, N1 and M1 categories, and heterogeneous calcitonin and katacalcin immunostaining pattern. In the multivariate analysis, only capsule status, M category, and age at diagnosis remained in the final model for overall survival. In the final model for relapse free survival, capsule status remained, together with sex and amyloid status. CONCLUSIONS: Extrathyroid tumor invasion, the presence of distant metastases, and age > 60 years are characteristic of patients at high risk of death from disease sooner, whereas extrathyroid invasion, male sex, and the absence of amyloid characterize patients who are at high risk for recurrence. Extrathyroid tumor invasion appears to be the worst prognostic factor and may allow for the breakdown of patients into two categories, amenable to different therapeutic regimens.