489 research outputs found
Stable carbon and radiocarbon isotope compositions of particle size fractions to determine origins of sedimentary organic matter in an estuary
Stable and radioactive carbon isotopic compositions of particle size fractions of a surface sediment from the Ems-Dollard estuary vary considerably with particle size. The organic material in the fine fractions (<20 µm) has considerably higher 14C values (14a~80%) than that in the coarse fractions (52%) and has higher δ13C values (average of -23‰ and -25.6‰, respectively). This shows that OM in the fine and the coarse fractions has different sources. The organic carbon in the fractions with particle sizes <20 µm is mainly imported from the North Sea. The contribution of material from the Ems river appears negligible. The carbon isotopic composition of the coarse fractions points to a terrestrial contribution. Discrete organic fragments are found of both terrestrial and marine/estuarine origin.
Life-threatening hypokalaemia and quadriparesis in a patient with ureterosigmoidostomy
We report quadriparesis as a result of severe hypokalaemia and acidosis in
a 50-year-old man who had undergone ureterosigmoidostomy for bladder
extrophy 48 years earlier. Aggressive suppletion with intravenous
potassium and bicarbonate combined with potassium-sparing diuretics and
ACE inhibitors resulted in complete restoration of the serum potassium and
resolution of the neurological symptoms. The underlying mechanism as well
as the treatment of hypokalaemia and hyperchloraemic metabolic acidosis
after ureterosigmoidostomy are briefly discussed
Poverty, Housing, and Market Processes
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68441/2/10.1177_107808747200800108.pd
Origin and palaeoenvironmental significance of C<sub>25</sub> and C<sub>27</sub>n-alk-1-enes in a 25,000-year lake-sedimentary record from equatorial East Africa
We studied the distribution of long-chain alkenes (n-C23 to n-C31) in well-dated sediments from Lake Challa, a deep crater lake near Mt. Kilimanjaro in equatorial East Africa, to reveal signatures of palaeo-environmental and palaeo-climatic changes affecting the production of these compounds during the last 25 kyr. The apolar fractions of organic sediment extracts dated to the last 16 kyr showed an unusual dominance of d13C-depleted n-C25:1 and n-C27:1 alk-1-enes. These alkenes were not detected in soil and litter from near the shoreline and from the inner rim of the crater, pointing to an autochthonous, aquatic source. Analysis of suspended particulate matter indicated that the n-alk-1-enes are produced in the well-oxygenated upper 30 m of the water column, indicating a phytoplanktonic origin. Sedimenting particles collected monthly from December 2006 to November 2007 showed increased fluxes of n-alk-1-enes following the locally prominent short rain season in November–December. Green algae and/or cyanobacteria were identified as candidate sources of these alkenes. Production of the n-C25:1 and n-C27:1 alkenes in Lake Challa was much reduced during the Last Glacial Maximum and early late-glacial period, suggesting a temperature or CO2 effect on habitat suitability. We explored the potential of n-alk-1-ene accumulation rates, and of a derived Alkene Index [n-C27:1]/([n-C25:1] + [n-C27:1]), to record longer-term climatic changes. The Alkene Index record of Lake Challa over the past 25 kyr shows clear periodicity with a dominant frequency of ~2.3 kyr, potentially indicative of monsoon variability directly or indirectly forced by variation in solar radiation
Stem cell factor receptor (c-KIT) codon 816 mutations predict development of bilateral testicular germ-cell tumors
Testicular germ-cell tumors (TGCTs) of adolescents and adults originate
from intratubular germ cell neoplasia (ITGCN), which is composed of the
malignant counterparts of embryonal germ cells. ITGCN cells are
characterized, among others, by the presence of stem cell factor receptor
c-KIT. Once established, ITGCN will always progress to invasiveness.
Approximately 2.5-5% of patients with a TGCT will develop bilateral
disease and require complete castration, resulting in infertility, a need
for lifelong androgen replacement, and psychological stress. To date, the
only way to predict a contralateral tumor is surgical biopsy of the
contralateral testis to demonstrate ITGCN. We did a retrospective study of
224 unilateral and 61 proven bilateral TGCTs (from 46 patients, in three
independently collected series in Europe) for the presence of activating
c-KIT codon 816 mutations. A c-KIT codon 816 mutation was found in three
unilateral TGCT (1.3%), and in 57 bilateral TGCTs (93%; P < 0.0001). In
the two wild-type bilateral tumors for which ITGCN was available, the
preinvasive cells contained the mutation. The mutations were somatic in
origin and identical in both tumors. We conclude that somatic activating
codon 816 c-KIT mutations are associated with development of bilateral
TGCT. Detection of c-KIT codon 816 mutations in unilateral TGCT identifies
patients at risk for bilateral disease. These patients may undergo
tailored treatment to prevent the development of bilateral disease, with
retention of testicular hormonal function
POU5F1 (OCT3/4) identifies cells with pluripotent potential in human germ cell tumors
Human germ cell tumors (GCTs) may have variable histology and clinical
behavior, depending on factors such as sex of the patient, age at clinical
diagnosis, and anatomical site of the tumor. Some types of GCT, i.e., the
seminomas/germinomas/dysgerminomas and embryonal carcinomas (the stem cell
component of nonseminomas), have pluripotent potential, which is
demonstrated by their capacity to differentiate into somatic and/or
extraembryonic elements. Although embryonal carcinoma cells are
intrinsically pluripotent, seminoma/germinoma/dysgerminoma cells, as well
as their precursor carcinoma in situ/gonadoblastoma cells, have the
phenotype of early germ cells that can be activated to pluripotency. The
other types of GCT (teratomas and yolk sac tumors of infants and newborn,
dermoid cyst of the ovary, and spermatocytic seminoma of elderly) are
composed of (fully) differentiated tissues and lack the appearance of
undifferentiated and pluripotent stem cells. OCT3/4, a transcription
factor also known as OTF3 and POU5F1, is involved in regulation of
pluripotency during normal development and is detectable in embryonic stem
and germ cells. We analyzed the presence of POU5F1 in GCT and other tumor
types using immunohistochemistry. The protein was consistently detected in
carcinoma in situ/gonadoblasto
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