Biomedical subjects

S Christensen

Publications and source records attributed to S Christensen.

At least 19 recordsLinked to original sources

PubMed2006

Outcome of peptic ulcer bleeding among users of traditional non-steroidal anti-inflammatory drugs and selective cyclo-oxygenase-2 inhibitors.

BACKGROUND: Few data exist on the impact of non-steroidal anti-inflammatory drug use on peptic ulcer outcome. AIM: To examine the 30-day mortality from peptic ulcer bleeding associated with the use of traditional non-steroidal anti-inflammatory drugs and newer selective cyclo-oxygenase-2 inhibitors. METHODS: Cohort study of patients with a first hospitalization for peptic ulcer bleeding in three Danish counties between 1991 and 2003. Data on pre-admission non-steroidal anti-inflammatory drug use, use of other ulcer-related drugs and comorbidities were obtained from population-based registries. Follow-up data on mortality were obtained from the Danish Civil Registry System. RESULTS: Of 7,232 patients hospitalized for peptic ulcer bleeding, 28% were current non-steroidal anti-inflammatory drug users. Thirty-day mortality was 11% overall, and 13% among current non-steroidal anti-inflammatory drug users. Compared with never-use, the adjusted 30-day mortality rate ratios were 1.4 (95% CI: 1.1-1.9) for current use of non-steroidal anti-inflammatory drugs alone and 1.3 (95% CI: 1.0-1.7) for current use combined with other ulcer-related drugs. For users of celecoxib, alone and in combination, adjusted mortality rate ratios were 1.4 (95% CI: 0.5-3.9) and 2.0 (95% CI: 1.2-3.5), and for users of rofecoxib, 1.2 (95% CI: 0.4-3.9) and 0.9 (95% CI: 0.5-1.6). CONCLUSION: Among patients hospitalized with peptic ulcer bleeding, use of non-steroidal anti-inflammatory drugs, including some newer cyclo-oxygenase-2 inhibitors, is associated with increased short-term mortality.

Aged↗

PubMed2006

Perforated peptic ulcer: use of pre-admission oral glucocorticoids and 30-day mortality.

BACKGROUND: Despite evidence that use of glucocorticoids increases the risk of complicated peptic ulcer disease, limited data exist on how use of oral glucocorticoids affects outcome for patients with peptic ulcer perforation. AIM: To examine 30-day mortality from peptic ulcer perforation among pre-admission oral glucocorticoid users compared with non-users. METHODS: We identified 2061 patients with a first-time hospital discharge diagnosis of perforated peptic ulcer, using population-based discharge registries in three Danish counties. Data on use of glucocorticoids and other ulcer-related drugs, previous hospitalizations for uncomplicated peptic ulcer disease, and comorbidity were obtained from discharge registries and prescription databases. Follow-up data on mortality were provided by the Danish Civil Registry System. RESULTS: A total of 228 patients (11.1%) were exposed to glucocorticoids within 60 days of admission. Overall 30-day mortality rate was 25.2%, the corresponding rate among current glucocorticoid users was 39.4%. Compared with 'never users', the adjusted mortality ratio among current users of oral glucocorticoids alone was 2.1 (95% CI: 1.5-3.1). Among current users of oral glucocorticoids in combination with other ulcer-related drugs the mortality ratio was 1.5 (95% CI: 1.1-2.1). CONCLUSION: Pre-admission use of oral glucocorticoids is associated with up to a twofold increase in 30-day mortality among patients hospitalized with perforated peptic ulcer.

Adult↗

PubMed2006

Rising incidence and persistently high mortality of hospitalized pneumonia: a 10-year population-based study in Denmark.

BACKGROUND: Little is known about temporal trends in the incidence and mortality of pneumonia in the general population. METHODS: We conducted a population-based cohort study in three Danish counties (population 1.4 million) to examine changes in the incidence and 30- and 90-day mortality associated with hospitalized pneumonia between 1994 and 2004. All adults hospitalized with a first-time diagnosis of pneumonia (n = 41 793) were identified in hospital discharge registries and followed for mortality through the Danish Civil Registry System. We determined age-standardized incidence rates and adjusted mortality rates associated with calendar year, gender, age and comorbidity. RESULTS: Between 1994 and 2003, the incidence of hospitalized pneumonia amongst adults increased from 288 per 100 000 person-years to 442 per 100 000 person-years, equivalent to an age-standardized incidence rate ratio of 1.50. The cumulative mortality within 30 and 90 days of admission was 15.2% and 21.9%, respectively, ranging from a 90-day mortality of 2.5% in patients aged 15-39 years to 34.7% in those aged 80 and over. Advanced age was the most important poor prognostic factor, followed by a high comorbidity score and male gender. The adjusted mortality rate ratios amongst patients with hospitalized pneumonia in 1999-2004, when compared with 1994-1998, were 0.89 (95% CI 0.85-0.94) after 30 days and 0.91 (95% CI 0.88-0.95) after 90 days. CONCLUSIONS: The incidence of hospitalized pneumonia in Denmark has increased considerably during the last 10 years and, combined with persistently high mortality rates, is of clinical and public health concern.

Adolescent↗

PubMed2005

Magnesium depletion enhances cisplatin-induced nephrotoxicity.

PURPOSE: Nephrotoxicity and magnesium (Mg)-depletion are well-known side effects to cisplatin (CP) treatment. The purpose of this present study was to investigate the role of Mg on CP induced changes in renal function. CP induced renal dysfunction was achieved by treatment with CP or vehicle (2.5 mg/kg) once weekly for 3 weeks. Since the CP-induced renal damage, including tubular reabsorption defects, is most prominent within the outer medulla (OM), changes in the expression pattern of OM aquaporins and sodium transporters including the Na,K-ATPase (alpha-subunit), type III Na,H-exchanger (NHE3), aquaporin 1 (AQP1) and 2 (AQP2) and the Na,K,2Cl-cotransporter (NKCC2) were investigated by semi-quantitative Western blotting. EXPERIMENTAL DESIGN: Rats had access to either a diet with standard Mg or to a Mg-depleted diet. Cisplatin was administered to female Wistar rats once a week for 3 weeks according to four regimens: (1) Cisplatin 2.5 mg/kg body weight i.p., to rats on a diet with standard Mg, (2) Cisplatin 2.5 mg/kg body weight i.p., to rats on a diet with low Mg, (3) Isotonic NaCl 2.5 ml/kg body weight i.p., to rats on a diet with standard Mg, (4) Isotonic NaCl 2.5 ml/kg body weight i.p., to rats on a diet with low Mg. RESULTS: CP had no effect on plasma creatinine or urea in rats with standard Mg intake, but the expression of all five transporters was significantly reduced when compared to vehicle treated rats on standard Mg-intake. Vehicle treated rats on low Mg-intake had a significant reduction in the expression of Na,K-ATPase, NHE3 and NKCC2, but unchanged expression levels of AQP1 or AQP2 when compared to standard treated controls. Forty percent of the CP-treated rats on low Mg-intake died during the experiment and the remaining animals had marked increased plasma creatinine and urea. Furthermore, the Western blot analysis revealed an almost complete disappearance of all four transporters, suggesting a dramatic synergistic effect of CP and Mg-depletion on renal function including the expression pattern of outer medullary sodium transporters and aquaporins. CONCLUSIONS: This study indicates a substantial additive effect of Mg-depletion on cisplatin induced renal toxicity as evidenced by significant changes in plasma creatinine and urea, renal failure induced mortality and loss of renal transporters. This should give cause for concern since the nephrotoxicity observed during cisplatin treatment might be substantiated by the known Mg-loss associated with cisplatin treatment especially in patients suffering from intense gastro-intestinal side effects.

Animals↗

PubMed2005

HGF is released from buccal fibroblasts after smokeless tobacco stimulation.

To investigate the effect of smokeless tobacco (ST) on (1) HGF, KGF and GM-CSF expression by buccal fibroblasts and (2) on keratinocyte and fibroblast proliferation. Buccal fibroblasts were stimulated with different concentrations of ST extracts in a double dilution from 0.50% w/v to 0.03% w/v. Supernatant was collected after 24/48/72/96 h and assayed for HGF, KGF, and GM-CSF by ELISA. The amount of RNA was used as an indicator of fibroblast cell number. Buccal epithelial cell proliferation was determined by CyQUANT proliferation assay. The amount of HGF and KGF in the supernatant was dependent on exposure time and on concentration of the tobacco extract. High concentration increased production of HGF 4-fold. KGF production was doubled when high concentration of tobacco was used, low concentration did not stimulate cells. GM-CSF production was low in both stimulated and non-stimulated cells. Keratinocytes and fibroblasts showed no increase in proliferation after stimulation with increased concentrations of ST. The results suggest that HGF and KGF may play an important role as a paracrine growth factor in epithelial hyperplasia in ST lesions.

Adult↗

PubMed2004

Magnesium and potassium homeostasis during cisplatin treatment.

PURPOSE: Administration of cisplatin causes changes in magnesium and potassium metabolism. The purpose of this study was to investigate day-to-day changes in renal and intestinal homeostasis of magnesium (Mg) and potassium (K) during repeated cisplatin treatments in rats to provide guidelines for human supplementation studies. EXPERIMENTAL DESIGN: Rats were housed in metabolic cages with access to a diet containing excess Mg and K. Treatment was administered once a week for 3 weeks and comprised either cisplatin 2.5 mg/kg body weight i.p or, as sham treatment, isotonic NaCl 2.5 ml/kg body weight i.p. Urine and feces were collected every 24 h. Blood samples for measurement of plasma Mg and K were obtained from a permanent arterial catheter prior to each treatment cycle and at the termination of the study. RESULTS: Cisplatin exerted a significant negative effect on total Mg balance. This effect was cumulative with repeated doses of cisplatin. The observed difference was mainly due to the difference in Mg balance between the treatment day and the following 2-3 days. The cumulated urinary excretion of Mg did not differ significantly between the two groups at the end of follow-up. A significant decrease was observed in cumulated intestinal absorption in treated rats compared to control rats at the end of follow-up. Lowered intestinal absorption accounted for 90% of the difference in total Mg balance between the two groups as compared to the renal loss. Cisplatin treatment also exerted a negative effect on total K balance, although the difference between cisplatin-treated and control rats was not significant at the end of follow-up. CONCLUSIONS: The Mg loss associated with cisplatin treatment was mainly the result of lowered intestinal absorption and not, as presently thought, the result of increased renal elimination. Instead, an increased renal reabsorption capacity was observed in response to decreased intestinal absorption. The study further showed that Mg and K metabolism are subject to predictable changes in intestinal absorption and renal excretion with each cisplatin treatment, and that knowledge of these changes can be used in planning supplementation. Thus, the experimental observations support intravenous supplementation on the day of treatment and 2-3 days after treatment followed by oral supplementation until the next treatment.

Animals↗

PubMed2003

Pharmacological monitoring of azathioprine therapy.

BACKGROUND: Studies on azathioprine (Aza) treatment in Crohn disease have indicated a positive correlation between clinical remission and a concentration in erythrocytes of the metabolites 6-thioguanine nucleotides (E-6-TGN) above 230 pmol/8 x 10(8) RBC. A concentration of the methylated Aza metabolites (E-6-MMP) above 5000 pmol/8 x 10(8) RBC has been correlated to hepatotoxicity. Thiopurine methyltransferase (TPMT) is responsible for the formation of methylated metabolites and lower E-TGN levels, and TPMT genotyping has been proposed as guidance for dosage. In a cross-sectional study we investigated relationships between the clinical outcome and Aza dose, the TPMT genotype and the Aza metabolite levels among patients with Crohn disease. METHODS: TPMT genotype (PCR assay), azathioprine metabolite levels (HPLC analysis) and xanthine oxidase (XO) activity were determined once in 71 randomly selected Crohn patients on an unaltered Aza dose for at least 3 months. RESULTS: None of the doses of Aza, TPMT genotype, E-6-TGN-, E-6-MMP levels or XO activity were significantly related to disease activity (H-B score), (P = 0.18, P = 0.69, P = 0.90, P = 0.54, P = 0.29, respectively). Leucopenia and/or hepatotoxicity were not demonstrated in any patient. Four patients had a heterozygous TPMT genotype (6.1%; 95% CI: 1.68%-14.80%). The 4 TPMT heterozygous patients had higher E-6-TGN levels than did the 67 remaining patients (P = 0.008). CONCLUSIONS: To explore the applicability of TPMT genotyping, E-6-TGN and E-6-MMP levels for therapeutic drug monitoring, large prospective studies with patient entry at the start of Aza therapy are needed. Until the results of such studies are available, the dose adjustments of Aza should be guided primarily by clinical response and blood counts; metabolite level measurements can only be applied to identify therapeutic non-compliance.

Adult↗

PubMed2003

CARD4/NOD1 is not involved in inflammatory bowel disease.

BACKGROUND AND AIMS: Inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are complex genetic disorders. CARD15/NOD2, a member of the Ced4 superfamily which includes Apaf-1 and CARD4/NOD1, has recently been associated with genetic predisposition to CD but additional genetic factors remain to be identified. Because CARD4/NOD1 shares many structural and functional similarities with CARD15, we tested its putative role in IBD. PATIENTS AND METHODS: The 11 exons of CARD4 were screened for the presence of variants in 63 unrelated IBD patients. The only non-private genetic variation encoding for a substitution in the peptidic chain was genotyped in 381 IBD families (235 CD, 58 UC, 81 mixed, and seven indeterminate colitis families) using a polymerase chain reaction-restriction fragment length polymorphism procedure. Genotyping data were analysed by the transmission disequilibrium test. RESULTS: Five of nine sequence variations identified in the coding sequence of the gene encoded for non-conservative changes (E266K, D372N, R705Q, T787M, and T787K). Four were present in only one family. The remaining variant (E266K), which exhibited an allele frequency of 0.28, was not associated with CD, UC, or IBD. Furthermore, IBD patients carrying sequence variations in their CARD4 gene had a similar phenotype to those with a normal sequence. CONCLUSION: Our results suggest that CARD4 does not play a major role in genetic susceptibility to IBD.

Adaptor Proteins, Signal Transducing↗

PubMed2002

The diversity and function of soil microbial communities exposed to different disturbances.

To improve understanding of the relationship between the diversity and function of the soil ecosystem, we investigated the effect of two different disturbances on soil bacterial communities -- long-term exposure to the heavy metal mercury and transient exposure to the antibiotic tylosin. In the mercury-contaminated soil the diversity (Shannon index) was reduced as assessed from denaturing gradient gel electrophoresis (DGGE) of amplified 16S rDNA sequences from the soil community DNA and from colony morphology typing of the culturable bacterial population. However, analysis of the substrate utilization profiles did not reveal any differences in diversity. In the tylosin-treated soil, DGGE revealed a small difference in the diversity of 16S rDNA compared to the control soil, whereas analysis of the colony morphology typing or substrate utilization results did not reveal any differences in diversity. Soil function was also affected by mercury contamination. The lag time before soil respiration increased following addition of glucose or alfalfa substrate was longer in the mercury-contaminated soil than in the control soil. Moreover, it was markedly prolonged in mercury-contaminated soil subjected to heat treatment prior to substrate addition, thus indicating reduced resistance to a new disturbance in the mercury-contaminated soil as compared to the control soil. Tylosin treatment did not have any significant effect on any of the respiration parameters measured, either with or without prior heat treatment of the soil.

Bacteria↗

PubMed2002

Collecting duct function in liver cirrhotic rats with early sodium retention.

Liver cirrhosis is a chronic disease associated with sodium retention due to increased tubular sodium reabsorption. However, the exact tubular site of increased sodium reabsorption in uncertain. We have recently demonstrated selective hypertrophy of the inner stripe of the outer medulla (ISOM) in rats with liver cirrhosis induced by common bile duct ligation (CBL). The present study was designed in order to measure Na-K-ATPase activity in the two major tubular segments located in the ISOM: the thick ascending limb of henles (MTAL) and the collecting ducts (OMCD) in CBL rats. Sham-operated rats were used as controls. In addition, the natriuretic response to amiloride (0.2 mg kg(-1) h(-1) i.v) was examined in conscious, chronically instrumented rats during conditions where amiloride-induced volume losses were replaced continuously using a servo-controlled i.v. volume replacement system. For 4-5 weeks after CBL, cirrhotic rats showed sodium retention relative to control rats without any sign of ascites. Plasma levels of sodium and aldosterone were normal, but plasma vasopressin was increased. Effective renal plasma flow was significantly increased, whereas glomerular filtration rate (GFR) and renal lithium handling were normal. The CBL rats showed a blunted natriuretic response to amiloride (DeltaFE(Na): 1.17 +/- 0.15% vs. 1.65 +/- 0.13%; P < 0.05). In rats with CBL, Na-K-ATPase activity per mm tubular length was decreased in the OMCD and unchanged in the TAL segment. These results suggest that increased tubular sodium reabsorption in liver cirrhotic rats with early sodium retention is localized in segments proximal to the collecting ducts.

Amiloride↗

PubMed2001

[Angiotensin II antagonists versus ACE inhibitors in the treatment of raised blood pressure].

Blockade of the renin-angiotensin system has proved an important principle in the pharmacotherapy of cardiovascular diseases. There is now overwhelming documentation on the beneficial effect of angiotensin converting enzyme inhibitors (ACE inhibitors) on mortality and morbidity in patients with cardiovascular risk factors. Such documentation is still lacking for the angiotensin II receptor antagonists which, in 1999, sold for 77% of the amount spent on ACE inhibitors in Denmark. This review assesses the therapeutic effects of angiotensin II antagonists compared with the ACE inhibitors in patients with uncomplicated essential hypertension. From 21 comparative studies with a duration of up to one year, it can be concluded that the lowering of the blood pressure with the two classes is similar. Both showed relatively few side effects, the only difference being a higher incidence of cough after ACE inhibitors. Until larger comparative long-term studies on mortality and morbidity have been conducted, angiotensin II antagonists should only be used in hypertensive patients experiencing unacceptable side effects with ACE inhibitors.

Angiotensin II↗

PubMed2001

Humicola insolens cellobiose dehydrogenase: cloning, redox chemistry, and "logic gate"-like dual functionality.

1Cellobiose dehydrogenase is a hemoflavoenzyme that catalyzes the sequential electron-transfer from an electron-donating substrate (e.g. cellobiose) to a flavin center, then to an electron-accepting substrate (e.g. quinone) either directly or via a heme center after an internal electron-transfer from the flavin to heme. We cloned the dehydrogenase from Humicola insolens, which encodes a protein of 761 amino acid residues containing an N-terminal heme domain and a C-terminal flavin domain, and studied how the catalyzed electron transfers are regulated. Based on the correlation between the rate and redox potential, we demonstrated that with a reduced flavin center, the enzyme, as a reductase, could export electron from its heme center by a "outer-sphere" mechanism. With the "resting" flavin center, however, the enzyme could have a peroxidase-like function and import electron to its heme center after a peroxidative activation. The dual functionality of its heme center makes the enzyme a molecular "logic gate", in which the electron flow through the heme center can be switched in direction by the redox state of the coupled flavin center.

Journal Article↗

PubMed2001

Prospective evaluation of cancer clinical trial accrual patterns: identifying potential barriers to enrollment.

PURPOSE: Well-conducted cancer clinical trials are essential for improving patient outcomes. Unfortunately, only 3% of new cancer patients participate in clinical trials. Barriers to patient accrual in cancer clinical trials must be identified and overcome to increase patient participation. MATERIALS AND METHODS: We prospectively tracked factors that potentially affected patient accrual into cancer clinical trials at the University of California Davis Cancer Center. Oncologists seeing new outpatients were asked to complete questionnaires regarding patient characteristics and the physician's decision-making on patient eligibility, protocol availability, and patient opinions on participation. Statistical analysis was performed to correlate these parameters with subsequent protocol accrual. RESULTS: There were 276 assessable patients. At the initial visits, physicians did not consider clinical trials in 38% (105/276) of patients principally because of a perception of protocol unavailability and poor performance status. Physicians considered 62% (171/276) of patients for participation in clinical trials. Of these, only 53% (91/171) had an appropriate protocol available for site and stage of disease. Seventy-six of 90 patients (84%) with available protocols met eligibility criteria for a particular study. Only 39 of 76 patients (51%) agreed to participate in cancer clinical trials, for an overall accrual rate of 14% (39/276). The remainder (37/76, 49%) declined trial participation despite meeting eligibility criteria. The most common reasons were a desire for other treatment (34%), distance from the cancer center (13%), patient refusal to disclose reason (11%), and insurance denial (8%). Patients with private insurance were less likely to enroll in clinical trials compared to those with government-funded insurance (OR, 0.34; P =.03; 95% CI, 0.13 to 0.9). CONCLUSION: Barriers to cancer clinical trial accrual can be prospectively identified and addressed in the development and conduct of future studies, which may potentially lead to more robust clinical trials enrollment. Investigation of patient perceptions regarding the clinical trials process and the role of third party-payers is warranted.

Adolescent↗

PubMed2001

[Severely injured patients after the initial phase--vegetative state or remaining cognitive functions?].

BACKGROUND: We wanted to quantify improvements in the subacute rehabilitation phase in patients with severe brain injuries classified as vegetative or minimal brain consciousness. MATERIAL AND METHODS: Five patients were studied during a 12 months period using a method called Coma Recovery Scale (CRS) as described by Giacino et al. (1991). The parameters measured included visual and hearing functions, motor functioning, oromotor/verbal function, communication, and arousal. The observations of the patients and commandos given were standardised in a manual, and the responses achieved from the patients were recorded according to a scale for each parameter. RESULTS: This procedure for measuring closely the progress over time in these severely brain injured patients, was used for planning a realistic rehabilitation program. It was found to be very practical in communication with relatives of the patients and with the other therapists involved. INTERPRETATION: By decomposing the cognitive functions by this method using all the available possibilities for inputs, even minimal improvement in the cognitive functions mentioned could be uncovered and recorded.

Adolescent↗

PubMed2001

Genetic refinement and physical mapping of a chromosome 16q candidate region for inflammatory bowel disease.

Crohn's disease (CD) is a complex genetic disorder for which a susceptibility gene, IBD1, has been mapped within the pericentromeric region of chromosome 16. In order to refine the location of IBD1, 77 multiplex CD families were genotyped for 26 microsatellite markers evenly spaced by approximately 1 cM. Nonparametric linkage analyses exhibited a maximum NPL score of 3.49 (P=2.37x10(-4)) in a region centred by markers D16S3136, D16S3117 and D16S770. Simulation studies showed that the probability for IBD1 to be located in a 5 cM region around these markers was 70%. A 2.5 Mb YAC and BAC contig map spanning this genetic region on chromosome band 16q12 was built. TDT analyses demonstrated suggestive association between the 207 bp allele of D16S3136 (P<0.05) and a new biallellic marker hb27g11f-end (P=0.01). These markers were located in the hb27g11 and hb87b10 BAC clones from the contig. Taken together, the present results provide a crucial preliminary step before an exhaustive linkage disequilibrium mapping of putatively transcribed regions to identify IBD1.

Alleles↗

PubMed2001

A novel carbohydrate:acceptor oxidoreductase from Microdochium nivale.

A Microdochium nivale carbohydrate:acceptor oxidoreductase was purified, cloned, heterologously expressed, and characterized. The gene encoding the protein showed one intron, and the ORF showed a sequence with low homology (< or = 25% identity or 65% similarity) to other known flavin-containing carbohydrate oxidases. The maturation of the protein required the cleavage of a tetrameric propeptide in addition to an 18 amino-acid signal peptide. The enzyme was found to have a relative molecular mass of 55 000 Da, an isoelectric point of 9, and one FAD per protein. It could oxidize mono-, oligo-, or polymeric saccharides, and transfer their electrons to O2 or other acceptors. When D-glucose served as electron-donating substrate, an activity of 2 s(-1) was observed at pH 5.5 and 23 degrees C. Among various oligosaccharides, the enzyme preferred tetrameric dextrins, indicating a favorable interaction of four linked glucose units with the substrate pocket. The unique structure and ability of oxidizing oligo/polymeric saccharides suggest a promising prospect of this enzyme for various industrial/medicinal applications.

Alcohol Oxidoreductases↗

PubMed2001

Origins of phytochrome-modulated Lhcb mRNA expression in seed plants.

The levels of Lhcb mRNA in higher plants are regulated by phytochrome, cryptochrome, and an endogenous circadian oscillator. To determine whether similar regulatory mechanisms operate in the ancient gymnosperm Ginkgo biloba, we measured Lhcb mRNA levels in seedlings in response to different light conditions. Removal of a diurnally oscillating light stimulus caused dampening of maximal Lhcb mRNA accumulation levels, with little change in periodicity. Although low fluence pulses of both red and blue light given to etiolated seedlings caused maximal accumulation of Lhcb mRNAs characteristic of the phasic/circadian response seen in flowering plants, the additional initial acute response seen in flowering plants was absent. The induction of Lhcb gene expression in both cases was at least partially reversible by far-red light, and appeared biphasic over a range of red fluences. Together, these data indicate that Lhcb genes in G. biloba appear to be regulated in a manner similar to that of flowering plants, whereas signaling and attenuation of mRNA levels through the photoreceptor systems and circadian clock show features distinct from those characterized to date. The implications for these findings are discussed in light of the evolution of circadian clock input signaling.

Arabidopsis Proteins↗

PubMed2001

Evidence for two components of object-based selection.

A wealth of research has shown that observers can bias visual processing toward specific locations, but the role of object-based selection is less clear In support of object-based selection, previous research has shown that when two objects are presented simultaneously, observers are better at reporting two attributes from one of the objects than one attribute from each object. However there has been controversy over whether this effect is best explained by object-based selection or spatial selection. Our work suggests that there are two separate components of selection in this task: (Ca) a spatial component that is observed when the relevant targets are cued for observers before the onset of the stimulus display and (b) an object-based component that can still be observed when the first component has been eliminated. The latter effect replicates the initial evidence in favor of object-based selection, and can be demonstrated even when the relevant targets are cued after the offset of the target stimuli.

Attention↗