Drought sensitivity of Amazonian carbon balance revealed by atmospheric measurements.

Feedbacks between land carbon pools and climate provide one of the largest sources of uncertainty in our predictions of global climate. Estimates of the sensitivity of the terrestrial carbon budget to climate anomalies in the tropics and the identification of the mechanisms responsible for feedback effects remain uncertain. The Amazon basin stores a vast amount of carbon, and has experienced increasingly higher temperatures and more frequent floods and droughts over the past two decades. Here we report seasonal and annual carbon balances across the Amazon basin, based on carbon dioxide and carbon monoxide measurements for the anomalously dry and wet years 2010 and 2011, respectively. We find that the Amazon basin lost 0.48 ± 0.18 petagrams of carbon per year (Pg C yr(-1)) during the dry year but was carbon neutral (0.06 ± 0.1 Pg C yr(-1)) during the wet year. Taking into account carbon losses from fire by using carbon monoxide measurements, we derived the basin net biome exchange (that is, the carbon flux between the non-burned forest and the atmosphere) revealing that during the dry year, vegetation was carbon neutral. During the wet year, vegetation was a net carbon sink of 0.25 ± 0.14 Pg C yr(-1), which is roughly consistent with the mean long-term intact-forest biomass sink of 0.39 ± 0.10 Pg C yr(-1) previously estimated from forest censuses. Observations from Amazonian forest plots suggest the suppression of photosynthesis during drought as the primary cause for the 2010 sink neutralization. Overall, our results suggest that moisture has an important role in determining the Amazonian carbon balance. If the recent trend of increasing precipitation extremes persists, the Amazon may become an increasing carbon source as a result of both emissions from fires and the suppression of net biome exchange by drought.

Small global effect on terrestrial net primary production due to increased fossil fuel aerosol emissions from East Asia since the turn of the century.

The global terrestrial carbon sink has increased since the start of this century at a time of growing carbon emissions from fossil fuel burning. Here we test the hypothesis that increases in atmospheric aerosols from fossil fuel burning enhanced the diffuse light fraction and the efficiency of plant carbon uptake. Using a combination of models, we estimate that at global scale changes in light regimes from fossil fuel aerosol emissions had only a small negative effect on the increase in terrestrial net primary production over the period 1998-2010. Hereby, the substantial increases in fossil fuel aerosol emissions and plant carbon uptake over East Asia were effectively canceled by opposing trends across Europe and North America. This suggests that if the recent increase in the land carbon sink would be causally linked to fossil fuel emissions, it is unlikely via the effect of aerosols but due to other factors such as nitrogen deposition or nitrogen-carbon interactions.

Fast high-resolution brain imaging with balanced SSFP: Interpretation of quantitative magnetization transfer towards simple MTR.

Magnetization transfer (MT) reflects the exchange of magnetization between protons bound to macromolecules, such as lipids and proteins, and protons in free liquid, and thus might be an early marker for subtle and undetermined pathologic changes in tissue. Detailed analysis of the entire MT phenomenon, however, commonly requires extensive data acquisition and scanning time, and hence is only of limited clinical interest. Therefore, in practice, magnetization transfer effects are commonly confined into a simple ratio measure, the so-called magnetization transfer ratio (MTR), calculated from a MT-weighted and a non-MT-weighted image. However, subtle physiologic and pathologic changes in tissue, invaluable for specific diagnostic imaging, may be lost since MTR-values depend not only on quantitative magnetization transfer (qMT) parameters but also on sequence parameters and relaxation properties. In order to evaluate and assess the diagnostic specificity of MTR versus qMT, high-resolution whole brain MT data was collected from twelve healthy volunteers using balanced steady-state free precession (bSSFP). In contrast to common MT imaging based on spoiled gradient echo (SPGR) sequences, whole brain qMT imaging can be performed with MT-sensitized bSSFP within a clinically feasible acquisition time. Hence, MT-sensitized bSSFP provides access to both MTR and qMT parameters within a clinical setting. The reliability and possible diagnostic value of MTR are analyzed for twelve white matter (WM) and eleven gray matter (GM) structures of the normal appearing brain. Strong correlations were found within and between longitudinal and transverse relaxation times (T1, T2) and MT parameters (ratio between macromolecular and water protons, F, and magnetization exchange rate, kf), whereas weaker correlations were observed between MTR-values and relaxation times or MT parameters. Structures with highly similar MTR-values, such as the crus cerebri and the anterior commissure in the WM, or the pallidum and the amygdala in the GM, however, were also found that showed significant differences in most quantitative parameters. This observation was confirmed from simulations revealing that the overall effect on MTR from an increase (decrease) in relaxation times may be counterbalanced with a decrease (increase) in MT parameters. These findings corroborate the expectation that qMT is superior to MTR imaging, especially for the evaluation and assessment of pathologic or physiological changes in healthy and pathologic brain tissue.

Intrascanner and interscanner variability of magnetization transfer-sensitized balanced steady-state free precession imaging.

Recently, a new and fast three-dimensional imaging technique for magnetization transfer ratio (MTR) imaging has been proposed based on a balanced steady-state free precession protocol with modified radiofrequency pulses. In this study, optimal balanced steady-state free precession MTR protocol parameters were derived for maximum stability and reproducibility. Variability between scans was assessed within white and gray matter for nine healthy volunteers using two different 1.5 T clinical systems at six different sites. Intrascanner and interscanner MTR measurements were well reproducible (coefficient of variation: c(v) < 0.012 and c(v) < 0.015, respectively) and results indicate a high stability across sites (c(v) < 0.017) for optimal flip angle settings. This study demonstrates that balanced steady-state free precession MTR not only benefits from short acquisition time and high signal-to-noise ratio but also offers excellent reproducibility and low variability, and it is thus proposed for clinical MTR scans at individual sites as well as for multicenter studies.

Characterization of normal appearing brain structures using high-resolution quantitative magnetization transfer steady-state free precession imaging.

Compared to standard spoiled gradient echo (SPGR)-methods, balanced steady-state free precession (bSSFP) provides quantitative magnetization transfer (qMT) images with increased resolution and high signal-to-noise ratio (SNR) in clinically feasible acquisition times. The aim of this study was to acquire 3D high-resolution qMT-data to create standardized qMT-values of many single brain structures that might serve as a baseline for the future characterization of pathologies of the brain. QMT parameters, such as the fractional pool size (F), exchange rate (kf) and relaxation times of the free pool (T1, T2) were assessed in a total of 12 white matter (WM) and 11 grey matter (GM) structures in 12 healthy volunteers with MT-sensitized bSSFP. Our results were compared with qMT-data from previous studies obtained with SPGR-methods using MT-sensitizing preparation pulses with significantly lower resolution. In general, qMT-values were in good accordance with prior studies. As expected, higher F and kf and lower relaxation times were observed in WM as compared to GM structures. However, many significant differences were observed within WM and GM regions and also between different regions of the same structure like in the internal capsule where the posterior limb showed significant higher kf than the anterior limb. Significant differences for all parameters were observed between subjects. In contrast to previous studies, bSSFP allowed assessment of even small brain structures due to its high resolution. The observed differences from previous studies can partly be explained by the reduced partial volume effects. MT-sensitized bSSFP is an ideal candidate for qMT-analysis in the clinical routine as it provides high-resolution 3D qMT-data of even small brain structures in clinically feasible acquisition times. The present qMT-data can serve as a reference for the characterization of cerebral diseases.

Consistent land- and atmosphere-based U.S. carbon sink estimates.

For the period 1980-89, we estimate a carbon sink in the coterminous United States between 0.30 and 0.58 petagrams of carbon per year (petagrams of carbon = 10(15) grams of carbon). The net carbon flux from the atmosphere to the land was higher, 0.37 to 0.71 petagrams of carbon per year, because a net flux of 0.07 to 0.13 petagrams of carbon per year was exported by rivers and commerce and returned to the atmosphere elsewhere. These land-based estimates are larger than those from previous studies (0.08 to 0.35 petagrams of carbon per year) because of the inclusion of additional processes and revised estimates of some component fluxes. Although component estimates are uncertain, about one-half of the total is outside the forest sector. We also estimated the sink using atmospheric models and the atmospheric concentration of carbon dioxide (the tracer-transport inversion method). The range of results from the atmosphere-based inversions contains the land-based estimates. Atmosphere- and land-based estimates are thus consistent, within the large ranges of uncertainty for both methods. Atmosphere-based results for 1980-89 are similar to those for 1985-89 and 1990-94, indicating a relatively stable U.S. sink throughout the period.

Quantitative magnetization transfer imaging using balanced SSFP.

It is generally accepted that signal formation in balanced steady-state free precession (bSSFP) is a simple function of relaxation times and flip angle only. This can be confirmed for fluids, but for more complex substances, magnetization transfer (MT) can lead to a considerable loss of steady-state signal. Thus, especially in tissues, the analytical description of bSSFP requires a revision to fully take observed effects into account. In the first part of this work, an extended bSSFP signal equation is derived based on a binary spin-bath model. Based on this new model of bSSFP signal formation, quantitative MT parameters such as the fractional pool size, corresponding magnetization exchange rates, and relaxation times can be explored. In the second part of this work, model parameters are derived in normal appearing human brain. Factors that may influence the quality of the model, such as B(1) field inhomogeneities or off-resonances, are discussed. Overall, good correspondence between parameters derived from two-pool bSSFP and common quantitative MT models is observed. Short repetition times in combination with high signal-to-noise ratios make bSSFP an ideal candidate for the acquisition of high resolution isotropic quantitative MT maps, as for the human brain, within clinically feasible acquisition times.

[Heifer breeding farms as a source for spreading the BVD virus?]. / Aufzuchtbetriebe als Verbreitungsquelle des BVD-Virus?

It is well known that, in Switzerland, communal grazing of livestock on alpine pastures plays an important role in the spread of BVD virus. Analogously, we might expect that the communal raising on farms specialising in raising heifers of animals born on different farms would also favour the spread of BVDV. This study investigated whether a persistently infected (PI) breeding heifer kept on this type of farm over a period of 26 months would put the other animals at risk of being infected. The PI-animal was in contact with 75 heifers (here defined as contact animals) on this farm. Thirty-two of the contact animals that were probably pregnant (animals at risk of giving birth to a PI-calf) were moved to 8 different breeding farms (here defined as farms at risk). On these 8 farms, 246 calves were found to be at risk of being infected with BVDV. We examined 78 calves and investigated whether the move of the pregnant animals from their original farm had permitted the virus to spread to these 8 other farms. The contact animals had a seroprevalence of 92% and the animals at risk a seroprevalence of 100%. Only one PI-animal was found on the farms at risk. This BVD infection, however, occurred independently of the PI-breeding animal. Seropositive calves were found only on 2 farms. This study did not provide any proof for a spread of BVDV with the PI-breeding animal as a source; likewise, no persistent infection was proven to exist on the farms at risk. This result is likely to be representative for the endemic situation of BVD in Switzerland. Thus, PI-animals present on heifer raising farms infect calves well before servicing. Hence, no new PI-animals are generated, and the infection becomes self-limiting. When we reconstructed the animal movements between the farms and determined the animals to be examined with the aid of the Swiss national animal traffic database (TVD) we found the data of 37% of the heifers to be incomplete and failed to successfully establish the whereabouts of 3 animals.

Feasibility of Flat Panel Detector CT in Perfusion Assessment of Brain Arteriovenous Malformations: Initial Clinical Experience.

The different results from flat panel detector CT in various pathologies have provoked some discussion. Our aim was to assess the role of flat panel detector CT in brain arteriovenous malformations, which has not yet been assessed. Five patients with brain arteriovenous malformations were studied with flat panel detector CT, DSC-MR imaging, and vessel-encoded pseudocontinuous arterial spin-labeling. In glomerular brain arteriovenous malformations, perfusion was highest next to the brain arteriovenous malformation with decreasing values with increasing distance from the lesion. An inverse tendency was observed in the proliferative brain arteriovenous malformation. Flat panel detector CT, originally thought to measure blood volume, correlated more closely with arterial spin-labeling-CBF and DSC-CBF than with DSC-CBV. We conclude that flat panel detector CT perfusion depends on the time point chosen for data collection, which is triggered too early in these patients (ie, when contrast agent appears in the superior sagittal sinus after rapid shunting through the brain arteriovenous malformation). This finding, in combination with high data variability, makes flat panel detector CT inappropriate for perfusion assessment in brain arteriovenous malformations.

On the propionibacteria in the pilosebaceous ducts of uninvolved skin of acne patients.

In 24 persons with a severe inflammatory acne and 48 control subjects, bacteria were sampled from the sebaceous gland exretory ducts with the glass sampling head method according to Holland et al. After anaerobic culture bacterial counts were performed. The total numbers of P. acnes and the frequency of detection of P. granulosum were determined. The bacterial counts of P. acnes were almost idendical in the two collectives. P. granulosum was detected at a significantly higher frequence in the acne patients than in the control subjects. It can be assumed on the basis of the results that an increase in the bacterial counts of P. acnes is not to be regarded as a pathogenetic factor in the inflammatory acne of older patients. On the other hand, they suggest that P. granulosum may have an appreciable role in acne.

The feasibility of replacing antibiotics by quaternary ammonium compounds in topical antimicrobial acne therapy.

Determinations of the minimum inhibitory concentrations for various antimicrobial surfactants with reference to the bacteria P. acnes, P. granulosum, and St. epidermidis are reported. The results show that quaternary ammonium compounds can display minimum inhibitory concentrations corresponding to those of relevant antibiotics. With the especially effective substance fractionated dimethylcocobenzalkoniumchloride )ARQUAD DMMCD-B), it could be further shown that with in vivo application in 70% isopropanol or in an ethanol-containing film mask ointment suppression can be obtained of P. acnes, all propionibacteria added, and all pilosebaceous duct bacteria which can be cultured under anaerobic conditions. The studies may point out a way of replacing antibiotics in the antimicrobial therapy of acne by quaternary ammonium compounds.

Influence of cyproterone acetate and estradiol on cell kinetics in the sebaceous gland of the golden hamster ear.

The cell kinetics of the sebaceous gland of the hamster ear were analysed in untreated animals, in animals treated with cyproterone acetate, and in animals treated with estradiol. Both active substances lead to a reduction in the size of the sebaceous gland (measurement with the integration plate), to a reduction of mitoses (colcemide method), to a reduction in the 3H-thymidine labelling index, to a prolongation of the S-phase (double labelling technique with 3H- and 14C-thymidine), and to a decrease in the number of cells labelled with 3H-thymidine which remain in contact with the basal lamina of the sebaceous gland 6 days after application of the isotope. The results indicate that, like cyproterone acetate, estradiol reduces the effect of androgens on cell kinetics in the sebaceous gland under the test conditions chosen, even if in an entirely different way.

On the use of infrared spectroscopy for the in vivo measurement of the water content of the horny layer after application of dermatologic ointments.

Infrared-spectroscopic investigations of the water content of the stratum corneum after application of emulsions and wash solutions are reported. As a methodologic variation infrared spectroscopy is applied after stripping the skin to determine the hydration of various depths of the stratum corneum by ointments. Using soap as an example, a method of correcting the overlap effects between the ointment and skin spectrums is presented which expands the application possibilities of infrared spectroscopy. An o/w emulsion with plenty of water and a w/o emulsion containing less water produce to almost the same degree a hydration of the deeper layers of the stratum corneum which lasts for at least 40 min. The report in the literature that soap solutions produced a stronger hydration of the stratum corneum and surfactant solutions is not supported.

Infrared-spectroscopic determination of the water content of the horny layer in healthy subjects and in patients suffering from atopic dermatitis.

Infrared spectroscopic measurements of hydration of the stratum corneum before and after stripping the skin five and ten times with scotch tape are reported. Investigations on 64 healthy persons show that for individuals over 45 and under 15 years of age the range of the measurement values is strikingly larger than for persons in the age group 15 - 45 years of age. A small, but not significant reduction in the measurement values is found in females as compared to males. A comparison of the clinically unaffected skin of atopic dermatitis patients with the skin of normal persons points to an increase in the hydration of the stratum corneum of atopic dermatitis patients, which is especially evident in patients who show clinical evidence of "dry" and rough skin.

On the influence of an external therapy with dexamethasone-21-sodium-m-sulfobenzoate on the amount of free fatty acids in the skin surface lipids.

A lipid-free preparation containing 0.076% dexamethasone-21-sodium-m-sulfobenzoate (corresponding to 0.05% dexamethasone) has been applied to the right side of the back and the same vehicle without the agent to the left side of the back of 16 male subjects without any skin diseases. The applications were made twice daily over a period of 26 days. Two days after the final application the skin surface lipids were analysed quantitatively by means of the direct extraction method and the paper absorption method. Thin layer chromatograpical analyses were also carried out. The sum of skin surface lipids is not altered by dexamethasone-21-sodium-m-sulfobenzoate. This agent does, however, induce a significant increase in the free fatty acids at the expense of the triglycerides. The importance of this result is discussed with reference to the pathogenesis of steroid acne.

Propionibacteria in patients with acne vulgaris and in healthy persons.

A total of 375 anaerobic and microaerophilic coryneform rods, isolated from the pilosebaceous ducts of 26 healthy persons (71 strains) and from comedones (93 strains), pustules (107 strains), and the unaffected skin (104 strains) of 36 acne patients were classified according to the species key in Bergey's manual, the biotyping scheme of Pulverer and ko, the serotyping schedule of Höffer et al., and the phage typing schedule of Jong et al. The statistical evaluation demonstrated certain differences in the frequencies of the Propionibacterium species and types between the different groups tested. Thus, the species P. granulosum was isolated only from acne patients (50.0% of patients examined) and was found more frequently in comedones and pustules than in unaffected follicles in acne patients. The majority of P. granulosum strains belonged to serotype II (95). Biotype A propionibacteria were more frequently found in strains from healthy controls (52.1% of strains) than in strains from healthy controls (52.1% of strains) than in strains from comedones (17.2%), pustules (27.1%) and unaffected skin (38.5%) of the acne patients. The results of phage-typing showed that the P. acnes lysotype I was more frequent in acne patients (total: 73.2% of strains), especially in the inflamed pustules (88.5%), than in healthy controls (55.1%).

The effect of systemic treatment with 5-fluorouracil on the epidermis of the guinea pig.

The thymidine labelling index and the mitosis rate (blocked by colcemid) in the basal cell layer of the guinea pig were determined before and during treatment with 5-fluorouracil (1 mg i.p. in 2 day's interval/100 g body weight). Additionally, the epidermal area and thickness and the number and size of cells were measured. 5-Fluorouracil equally reduces the thymidine labelling index and the mitosis rate with the full effect after treatment of at least 22 days. From these findings it is concluded that the S-phase--calculated from the end of the thymidine synthesis--is not altered. Furthermore atrophy of the epidermis runs parallel with the reduction of the 3H thymidine labelling index and the mitosis rate.

The effect of systemic treatment with 5-fluorouracil on the epidermis of the guinea pig.

The thymidine labelling index and the mitosis rate (blocked by colcemid) in the basal cell layer of the guinea pig were determined before and during treatment with 5-fluorouracil (1 mg i.p. in 2 day's interval/100 g body weight). Additionally, the epidermal area and thickness and the number and size of cells were measured. 5-Fluorouracil equally reduces the thymidine labelling index and the mitosis rate with the full effect after treatment of at least 22 days. From these findings it is concluded that the S-phase--calculated from the end of the thymidine synthesis--is not altered. Furthermore atrophy of the epidermis runs parallel with the reduction of the 3H thymidine labelling index and the mitosis rate.

Qualitative and quantitative investigations on the resident bacterial skin flora in healthy persons and in the non-affected skin of patients with seborrheic Eczema.

The composition of the aerobic and anaerobic bacterial skin flora was investigated quantitatively and qualitatively in 25 patients with seborrheic eczema (SE) and in 35 healthy persons. In SE patients, the geometric mean count for propionibacteria in the pilosebaceous ducts of the forehead was reduced to a statistically significant extent in comparison with the control group. There was the same tendency with regard to the geometric mean count of the superficial anaerobic bacterial flora of the back, whereas the geometric mean counts of the coagulase-negative staphylococci were the same in the two groups. These results may explain earlier findings of a reduction of free fatty acids in the surface lipids in SE patients. According to the results of differentiation in 295 propionibacteria and 157 micrococcaceae, 7 biotypes and 10 phage types of propionibacteria which were so far unknown could be demonstrated. Significant differences between the groups with regard to the frequency of different biotypes, serotypes, and phage types could be demonstrated neither in propionibacteria nor in coagulase-negative staphylococci. The results of typing, however, showed that patients with SE displayed much more frequently several different propionibacterial species and types as well as different micrococcal species and types than persons with healthy skin.

Effects of microemulsions on the stratum corneum and hydrocortisone penetration.

We tested a high-water-content hydrophilic microemulsion (ME 1) and a low-water-content lipophilic microemulsion (ME 2) for their suitability for use in dermatology, in general, and as alternative hydrocortisone (HC) vehicles, in particular. The lipophilic component of both study products was isopropyl myristate. The surfactant/cosurfactant system of ME 1 consisted of two sucrose esters and that of ME 2 was a mixture of Tagat S and Plurololeat. Both MEs showed no in vitro irritability in the hen's egg test on chorioallantoic membranes. In 14 subjects, stratum corneum water content was determined by corneometry and transepidermal water loss (TEWL) by the Tewameter before and after 3 days use of ME 1 or ME 2 as well as on two untreated control sites. ME 1 produced dehydration and increased TEWL as evidence of barrier compromise. ME 2 also produced an increase in TEWL but had no dehydrating effect. Subjects then underwent standardized washing with a surfactant solution. Under these conditions, pretreatment with ME 2 also produced dehydration, but to a lesser extent than did pretreatment with ME 1. In the same subjects, the impact of the two MEs on HC penetration (0.5%, 24h occlusion) was evaluated in terms of the chromameter-determined blanching effect compared with that on a site treated only with an occlusive film dressing. The comparator was an ambiphilic cream (Basiscreme (BC) Deutscher Arzneimittel Codex (German Formulary)). Irritative skin redness produced by ME 1 was significant and that produced by ME 2 was slight but visible, compared with BC. HC penetration was demonstrable from all the study products via the blanching effect and was significantly greater from ME 1 and slightly greater from ME 2 than from BC. However, neither ME would improve HC therapy because the irritative effects were so great that the blanching effect of HC formulated in ME 1 was significantly smaller and that of HC in ME 2 slightly smaller than that of HC formulated in BC.