Spatiotemporal analysis of lake chlorophyll-a with combined in situ and satellite data.

We estimated chlorophyll-a (Chl-a) concentration using various combinations of routine sampling, automatic station measurements, and MERIS satellite images. Our study site was the northern part of the large, shallow, mesotrophic Lake Pyhäjärvi located in southwestern Finland. Various combinations of measurements were interpolated spatiotemporally using a data fusion system (DFS) based on an ensemble Kalman filter and smoother algorithms. The estimated concentrations together with corresponding 68% confidence intervals are presented as time series at routine sampling and automated stations, as maps and as mean values over the EU Water Framework Directive monitoring period, to evaluate the efficiency of various monitoring methods. The mean Chl-a calculated with DFS in June-September was 6.5-7.5 µg/l, depending on the observations used as input. At the routine monitoring station where grab samples were used, the average uncertainty (standard deviation, SD) decreased from 2.7 to 1.6 µg/l when EO data were also included in the estimation. At the automatic station, located 0.9 km from the routine monitoring site, the SD was 0.7 µg/l. The SD of spatial mean concentration decreased from 6.7 to 2.9 µg/l when satellite observations were included in June-September, in addition to in situ monitoring data. This demonstrates the high value of the information derived from satellite observations. The conclusion is that the confidence of Chl-a monitoring could be increased by deploying spatially extensive measurements in the form of satellite imaging or transects conducted with flow-through sensors installed on a boat and spatiotemporal interpolation of the multisource data.

APOE-epsilon4 predicts dementia but not other psychiatric disorders after traumatic brain injury.

The authors studied the association between APOE-epsilon4 genotype and axis I and II psychiatric disorders an average of 30 years after traumatic brain injury. Sixty patients were dichotomized into subjects with and without APOE-epsilon4 allele. Dementia and subclinical dementia were significantly more common with the presence of APOE-epsilon4. The occurrence of other psychiatric disorders did not differ between patients with and without APOE-epsilon4 allele.

Severe somatization in women is associated with altered cerebral glucose metabolism.

BACKGROUND: Somatization is a clinical phenomenon characterized by multiple, medically unexplained somatic symptoms. The pathophysiology remains unknown. We aimed to test the hypothesis of a central nervous system dysfunction in the pathophysiology of this disorder. METHOD: We studied 10 female patients diagnosed as having somatization disorder or undifferentiated somatoform disorder with no current Axis I disorders according to DSM-IV. They were compared with 17 healthy female volunteers using brain [18F]-fluorodeoxyglucose-PET with MRI reference. RESULTS: The patients had lower cerebral metabolism rates of glucose (P<0.05) in both caudate nuclei, left putamen and right precentral gyrus compared with healthy volunteers. CONCLUSIONS: This is the first study to demonstrate changes in brain metabolism in somatizing women. The regional cerebral hypometabolism is probably associated with the pathophysiology of somatization.

Detection of water quality using simulated satellite data and semi-empirical algorithms in Finland.

The aim of the study was to test the feasibility of the band combination of the TERRA MODIS and ENVISAT MERIS instruments for operational monitoring of lakes and coastal waters in Finland. Also simulated LANDSAT TM data were tested. Satellite bands were simulated using airborne measurements with AISA imaging spectrometer. Semi-empirical algorithms with simulated satellite data were tested against field observations using regression analysis. Interpretation of chlorophyll a, suspended matter, turbidity and secchi-disk depth was included in the analyses. The data for this study were gathered in campaigns carried out in May and August 1997 and August 1998 both for lakes in southern Finland and coastal waters of the Baltic Sea. The data set included 85 in situ observations for lakes and 107 for coastal waters. Our results show that the band combination to be included in the ENVISAT MERIS instrument enables the interpretation of water quality, including chlorophyll a concentration using semi-empirical algorithms both for lakes and coastal waters. MERIS band 9 centred at 705 nm is proven to be of vital importance for the detection of chlorophyll a in local surface waters.

Retrieval of water quality from airborne imaging spectrometry of various lake types in different seasons.

The suitability of the AISA airborne imaging spectrometer for monitoring lake water quality was tested in four surveys carried out in southern Finland in 1996-1998. Altogether, 11 lakes were surveyed and the total number of stations with concurrent remote sensing and limnological measurements was 127. The ranges of the water quality variables were: the sum of chlorophyll a and phaeophytin a 1-100 microg l(-1), turbidity 0.4-26 FNU, total suspended solids 0.7-32 mg l(-1), absorption coefficient of aquatic humus at 400 nm 1.2-14 m(-1) and secchi disc transparency 0.4-7 m. For the retrieval analyses, 24 AISA channels in the 450-786 nm range with a channel width of 6-14 nm were used. The agreement between estimated and observed water quality variables was generally good and R2 for the best algorithms was in the range of 0.72-0.90 over the whole dataset. The channels used for May were, in most cases, the same as those for August, but the empirical parameters of the algorithms were different. After seasonal grouping, R2 varied from 0.84 to 0.95. The use of apparent reflectance instead of radiance improved the estimation of water quality in the case of total suspended solids and turbidity. In the most humic lake, the empirical algorithms tested were suitable only for the interpretation of total suspended solids and turbidity.

A semi-operative approach to lake water quality retrieval from remote sensing data.

A semi-operative approach to retrieve chlorophyll-a concentration from airborne/spaceborne spectrometer observations has been developed and tested using the airborne imaging spectrometer (AISA) data from 11 lakes located in southern Finland. The retrieval approach is empirical and requires nearly simultaneous in situ training data on water quality for the determination of regression coefficients. However, the training data does not have to be collected from every lake under investigation. Instead, the results obtained indicate that reliable estimates on the level of chlorophyll-a (chl-a) for an individual lake can be achieved without employing in situ data representing this specific lake. This enables the estimation of water quality from remotely sensed data for numerous lakes with the aid of reference data only for a few selected lakes representing the region under investigation. In addition, it is shown that the remotely sensed spectrum shape characteristics are highly affected by the trophic and humic state of the lake water.

Analysis on the feasibility of multi-source remote sensing observations for chl-a monitoring in Finnish lakes.

Chlorophyll-a (chl-a) concentration of lake water can be measured with airborne (or spaceborne) optical remote sensing instruments. The rmse obtained here with empirical algorithms and 122 measurement points was 8.9 microg/l (all points used for training and testing). Airborne Imaging Spectrometer for Applications (AISA) was used in four lake water quality measurement campaigns (8 measurement days) in southern Finland during 1996-1998 with other airborne instruments and extensive in situ data collection. As empirical algorithms are employed for chl-a retrieval from remote sensing data, temporally varying factors such as surface reflection and atmospheric effects degrade the estimation accuracy. This paper analyzes the quantitative accuracy of empirical chl-a retrieval algorithms available as methods to correct temporal disturbances are either included or excluded. The aim is to evaluate the usability of empirical chl-a retrieval algorithms in cases when no concurrent reference in situ data are available. Four methods to reduce the effects of temporal variations are investigated. The methods are: (1) atmospheric correction; (2) synchronous radiometer data; (3) wind speed data; and (4) bidirectional scattering model based on wind speed and sun angle data. The effects of different correction methods are analyzed by using single-date test data and multi-date training data sets. The results show that the use of a bidirectional scattering model and atmospheric correction reduces the bias component of the measurement error. Radiometer data also appear to improve the accuracy. However, if concurrent in situ reference data are not available, the retrieval algorithms and correction methods should be improved for reducing the bias error.

Transgenic mice overexpressing truncated trkB neurotrophin receptors in neurons show increased susceptibility to cortical injury after focal cerebral ischemia.

It has been suggested that the increased production of endogenous BDNF after brain insults supports the survival of injured neurons and limits the spread of the damage. In order to test this hypothesis experimentally, we have produced transgenic mouse lines that overexpress the dominant-negative truncated splice variant of BDNF receptor trkB (trkB.T1) in postnatal cortical and hippocampal neurons. When these mice were exposed to transient focal cerebral ischemia by occluding the middle cerebral artery for 45 min and the damage was assessed 24 h later, transgenic mice had a significantly larger damage than wild-type littermates in the cerebral cortex (204 +/- 32% of wild-type, P = 0.02), but not in striatum, where the transgene is not expressed. Our results support the notion that endogenously expressed BDNF is neuroprotective and that BDNF signaling may have an important role in preventing brain damage after transient ischemia.

Induction of protein kinase Cdelta subspecies in neurons and microglia after transient global brain ischemia.

The delayed death of CA1 neurons after global brain ischemia is associated with induction of apoptosis genes and is inhibited by protein synthesis inhibitors, suggesting that the degeneration of CA1 pyramidal neurons is an active process that requires new gene expression. The transient global ischemia model has been extensively used to identify enzymes and other proteins underlying delayed neuronal cell death. The expression of protein kinase C (PKC) subspecies after 20 minutes of global brain ischemia produced by a four-vessel occlusion model in the rat was studied. From the multiple PKC subspecies studied, only PKCdelta mRNA was significantly up-regulated in CA1 pyramidal neurons at 24 hours and in activated microglia at 3 to at least 7 days after ischemia. The induction of PKCdelta mRNA was also found in the cortex at 8 hours and 3 days after ischemia. This cortical but not hippocampal induction was regulated by an alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid/kainate receptor antagonist, 6-nitro-7-sulfamobenzo[f]quinoxaline-2,3-dione, and glucocorticoids. An N-methyl-D-aspartate receptor antagonist, MK-801, was without effect on the induction of PKCdelta subspecies. The selective and prolonged induction of the PKCdelta mRNA and protein first in CA1 pyramidal neurons and at a later stage in activated microglia suggests that the PKCdelta isozyme may take part in regulation of the delayed death of CA1 neurons after transient global brain ischemia.

Expression of cyclooxygenase-2 mRNA after global ischemia is regulated by AMPA receptors and glucocorticoids.

BACKGROUND AND PURPOSE: Cyclooxygenase-2 (COX-2) is implicated in ischemic neuronal death. In focal ischemia, its mRNA induction is mediated through N-methyl-D-aspartic acid (NMDA) receptors and phospholipase A(2). Because mechanisms of neuronal death involving COX-2 in global ischemia are unclear, we studied the time course and regulation of COX-2 expression in rat brain global ischemia. METHODS: Global ischemia was induced by a 4-vessel occlusion method. COX-2 mRNA levels were demonstrated with in situ hybridization and COX-2 protein with immunocytochemistry. Several animals were pretreated with MK-801, an NMDA receptor antagonist; 2, 3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX), an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist; and dexamethasone. RESULTS: In the cortex, the CA3 hippocampal region and dentate gyrus expression of COX-2 mRNA peaked at 4 to 8 hours, while in the CA1 region COX-2 mRNA levels were high at 4 to 24 hours. COX-2 protein was induced in the corresponding regions at 12 to 24 hours, but in the CA1 neurons the protein was still seen at 3 days. COX-2 mRNA induction in the cortex was inhibited by NBQX and dexamethasone and in CA1 neurons was inhibited by NBQX. MK-801 did not suppress COX-2 induction. CONCLUSIONS: COX-2 is differentially induced in the cortex and hippocampal structures after global ischemia. The prolonged COX-2 expression in the vulnerable CA1 neurons is regulated by AMPA receptors, suggesting that COX-2 expression is likely to be associated with AMPA receptor-mediated neuronal death in global ischemia. Glucocorticoids may not be efficiently used to inhibit ischemia-induced COX-2 expression in the hippocampus.

Spreading depression induces expression of calcium-independent protein kinase C subspecies in ischaemia-sensitive cortical layers: regulation by N-methyl-D-aspartate receptors and glucocorticoids.

Spreading depression is a wave of sustained depolarization challenging the energy metabolism of the cells without causing irreversible damage. In the ischaemic brain, sreading depression-like depolarization contributes to the evolution of ischaemia to infarction. The depolarization is propagated by activation of N-methyl-D-aspartate receptors, but changes in signal transduction downstream of the receptors are not known. Because protein phosphorylation is a general mechanism whereby most cellular processes are regulated, and inhibition of N-methyl-D-aspartate receptors or protein kinase C is neuroprotective, the expression of protein kinase C subspecies in spreading depression was examined. Cortical treatment with KCl induced an upregulation of protein kinase Cdelta and zeta messenger RNA at 4 and 8 h, whereas protein kinase Calpha, beta, gamma and epsilon did not show significant changes. The gene induction was the strongest in layers 2 and 3, and was followed by an increased number of protein kinase Cdelta-immunoreactive neurons. Protein kinase Cdelta and zeta inductions were inhibited by pretreatment with an N-methyl-D-aspartate receptor antagonist, dizocilpine maleate, which also blocked spreading depression propagation, and with dexamethasone, which acted without blocking the propagation. Quinacrine, a phospholipase A2 inhibitor, reduced only protein kinase C5 induction. In addition, N(G)(-nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, did not influence protein kinase Cdelta or zeta induction, whereas 6-nitro-7-sulphamoylbenzo[f]quinoxaline-2,3-dione, an alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate/kainate receptor antagonist, and the cyclo-oxygenase inhibitors indomethacin and diclophenac tended to increase gene expression. The data show that cortical spreading depression induces Ca2(+)-independent protein kinase C subspecies delta and zeta, but not Ca(2+)-dependent subspecies, through activation of N-methyl-D-aspartate receptors and phospholipase A2. Even though the signal pathway is similar to the induction described previously in ischaemia for genes implicated in delayed neuronal death, the gene inductions observed here are not necessarily pathogenetic, but may represent a general reaction to metabolic stress.