449 research outputs found
PTEN hamartoma tumor syndromes in childhood: description of two cases and a proposal for follow-up protocol
PTEN hamartoma tumor syndromes (PHTS) are a spectrum of
hamartomatous overgrowth syndromes associated with germline
mutations in the tumor suppressor PTEN gene located on
10q23.3. It is widely accepted that two of these disorders,Cowden
syndrome and BannayanâRileyâRuvalcaba syndrome, are allelic
conditions. BecausePTENmutations are not identifiable in every
case of the PHTS phenotype, the inability to detect a mutation
within thePTENgene does not invalidate the clinical diagnosis of
Cowden syndrome, or BannayanâRileyâRuvalcaba syndrome, in
patients who meet diagnostic criteria for these disorders. PTEN
mutations are associated with an increased risk for developing
breast, thyroid, endometrial, and sometimes renal cancers. Thus,
cancer surveillance is the cornerstone of PHTS patient management.
Although a consensus cancer surveillance protocol has not
been formally instituted, all PTEN mutation carriers should
adopt the cancer surveillance strategies proposed for patients
with Cowden syndrome. In addition, because gastrointestinal
and vascular complications can be more severe in Bannayanâ
RileyâRuvalcaba syndrome than in Cowden syndrome, patients
with BannayanâRileyâRuvalcaba syndrome should be monitored
from this point of view too. In this study, we report on
two cases with BannayanâRileyâRuvalcaba phenotype that
showed two different PTEN mutations.Wealso propose practice
recommendations for management of PHTS patient
The Diversity of Poisonous Plant Patches in the Arid Rangelands of Namaqualand, South Africa
The Namaqualand region in South Africa is part of the richest arid biodiversity hotspot in the world. Plant distribution and diversity here are impacted by various biophysical and anthropogenic factors. In these landscapes, poisonous plant patches, which pose serious threats to livestock, are widespread but their contribution to the regions biodiversity are not fully understood. This study assessed their plant diversity and compared its matrix. This study was conducted in the semi-arid to arid Steinkopf pastoral area located in Namaqualand where livestock is still herded daily. Twenty-five paired sites were selected based on the dominance of poisonous plants within the genera Tylecodon, Euphorbia and Adromischus. Within these sites, the number and abundance of different plant species were recorded and categorised into different plant functional types. Results showed a significant difference in Shannon Wiener plant diversity where poisonous plant patches displayed a greater diversity compared to sites sampled in the matrix. We interpret these findings as a consequence of herding in the region, where herders do not allow their animals to graze on or near poisonous plant patches. As such, palatable plants, which are absent or low in abundance in the surrounding landscape have a refuge where they can survive and set seed. This study provides evidence that the ethnobotanical knowledge of herders and palette of livestock are also major contributors to the spatial distribution and diversity of plant species in the arid biodiversity hotspot
Observation of a New Type of Low Frequency Waves at Comet 67P/Churyumov-Gerasimenko
We report on magnetic field measurements made in the innermost coma of
67P/Churyumov-Gerasimenko in its low activity state. Quasi-coherent,
large-amplitude (), compressional magnetic field
oscillations at 40 mHz dominate the immediate plasma environment of the
nucleus. This differs from previously studied comet-interaction regions where
waves at the cometary ion gyro-frequencies are the main feature. Thus classical
pick-up ion driven instabilities are unable to explain the observations. We
propose a cross-field current instability associated with newborn cometary ion
currents as a possible source mechanism.Comment: 6 pages, 3 Figure
Spatial distribution of low-energy plasma around 2 comet 67P/CG from Rosetta measurements
International audienceWe use measurements from the Rosetta plasma consortium (RPC) Langmuir probe (LAP) and mutual impedance probe (MIP) to study the spatial distribution of low-energy plasma in the near-nucleus coma of comet 67P/Churyumov-Gerasimenko. The spatial distribution is highly structured with the highest density in the summer hemisphere and above the region connecting the two main lobes of the comet, i.e. the neck region. There is a clear correlation with the neutral density and the plasma to neutral density ratio is found to be âŒ1-2·10 â6 , at a cometocentric distance of 10 km and at 3.1 AU from the sun. A clear 6.2 h modulation of the plasma is seen as the neck is exposed twice per rotation. The electron density of the collisonless plasma within 260 km from the nucleus falls of with radial distance as âŒ1/r. The spatial structure indicates that local ionization of neutral gas is the dominant source of low-energy plasma around the comet
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