Modelling water use efficiency in a dynamic environment: An example using Arabidopsis thaliana.

Intrinsic water use efficiency (Wi), the ratio of net CO2 assimilation (A) over stomatal conductance to water vapour (gs), is a complex trait used to assess plant performance. Improving Wi could lead in theory to higher productivity or reduced water usage by the plant, but the physiological traits for improvement and their combined effects on Wi have not been clearly identified. Under fluctuating light intensity, the temporal response of gs is an order of magnitude slower than A, which results in rapid variations in Wi. Compared to traditional approaches, our new model scales stoma behaviour at the leaf level to predict gs and A during a diurnal period, reproducing natural fluctuations of light intensity, in order to dissect Wi into traits of interest. The results confirmed the importance of stomatal density and photosynthetic capacity on Wi but also revealed the importance of incomplete stomatal closure under dark conditions as well as stomatal sensitivity to light intensity. The observed continuous decrease of A and gs over the diurnal period was successfully described by negative feedback of the accumulation of photosynthetic products. Investigation into the impact of leaf anatomy on temporal responses of A, gs and Wi revealed that a high density of stomata produces the most rapid response of gs but may result in lower Wi.

A structured observation of behavioral self-regulation and its contribution to kindergarten outcomes.

The authors examined a new assessment of behavioral regulation and contributions to achievement and teacher-rated classroom functioning in a sample (N = 343) of kindergarteners from 2 geographical sites in the United States. Behavioral regulation was measured with the Head-Toes-Knees-Shoulders (HTKS) task, a structured observation requiring children to perform the opposite of a dominant response to 4 different oral commands. Results revealed considerable variability in HTKS scores. Evidence for construct validity was found in positive correlations with parent ratings of attentional focusing and inhibitory control and teacher ratings of classroom behavioral regulation. Hierarchical linear modeling indicated that higher levels of behavioral regulation in the fall predicted stronger levels of achievement in the spring and better teacher-rated classroom self-regulation (all ps < .01) but not interpersonal skills. Evidence for domain specificity emerged, in which gains in behavioral regulation predicted gains in mathematics but not in language and literacy over the kindergarten year (p < .01) after site, child gender, and other background variables were controlled. Discussion focuses on the importance of behavioral regulation for successful adjustment to the demands of kindergarten.

Immunogenicity, safety and lot consistency in adults of a chromatographically purified Vero-cell rabies vaccine: a randomized, double-blind trial with human diploid cell rabies vaccine.

The immunogenicity and safety of a chromatographically purified rabies vaccine (CPRV) was evaluated using US veterinary medical students. In the first study, 242 healthy adults were enrolled in a randomized, modified double-blind, multicenter trial and received five doses of either CPRV or human diploid cell vaccine (HDCV) by intramuscular injection on days 0, 3, 7, 14, and 28 concurrently with human rabies immunoglobulin in a simulated post-exposure prophylaxis regimen. Post-immunization titers in the CPRV and HDCV groups reached 0.5 IU/ml (the WHO-recommended minimally acceptable titer) or greater in all subjects in both vaccine groups by day 14 and remained above that level through day 90. In the second study, 438 healthy adults were enrolled in a randomized, double-blind, multicenter trial and assigned to receive five doses from one of three lots of CPRV by intramuscular injection on days 0, 3, 7, 14, and 28 in a simulated post-exposure prophylaxis regimen to evaluate lot consistency. Post-immunization titers rapidly increased to over 0.5 IU/ml by day 14 for all subjects and remained above that level through day 42 when the study was terminated. The three lots were considered equivalent. The percentage of subjects with at least one local reaction during the five-dose regimen was slightly lower in the CPRV group than in the HDCV group (P=0.06). The most frequently reported local reaction for all doses of vaccine was pain at the injection site. Headache, myalgia, and malaise were the most frequently reported systemic events. The percentage of subjects with at least one systemic event was significantly lower for CPRV (P=0.0084). No vaccine-related serious adverse reaction was reported in these studies. The results of these studies indicate that CPRV administered intramuscularly to healthy adults is immunogenic and is associated with fewer local and systemic reactions than HDCV.

Distinct roles for p42/p44 and p38 mitogen-activated protein kinases in the induction of IL-2 by IL-1.

Interleukin 1 (IL-1) activates p42/p44 and p38 mitogen-activated protein kinases (MAP kinases) in target cells. Here we have used two specific inhibitors, PD98059 which inhibits MAP kinase kinase (MEK), and SB203580 which inhibits p38 MAP kinase to explore the involvement of these kinases in the induction of IL-2 by IL-1 in the murine thymoma cell line EL4.NOB-1. Both kinase inhibitors suppressed IL-1-stimulated IL-2 production. PD98059 blocked IL-2 mRNA accumulation and the induction of a reporter gene linked to the IL-2 promoter. In contrast, SB203580 only marginally inhibited IL-2 promoter-linked reporter gene expression and had no inhibitory effect on IL-2 mRNA levels. Neither PD98059 nor SB203580 had an inhibitory effect on NFkappaB-driven reporter gene expression in response to IL-1. Surprisingly, higher concentrations of SB203580 (30 microM) potentiated the IL-1 responses. PD98059 also inhibited induction of IL-2 by phorbol 12-myristate 13-acetate (PMA), and AP1-linked reporter gene expression in response to PMA but not IL-1. These results indicate that p42/p44 MAP kinase is involved in the regulation of IL-2 gene transcription by IL-1, whilst p38 MAP kinase has a post-transcriptional target. Additional IL-1 signalling pathways can clearly compensate for the lack of p38 MAP kinase which result in potentiation of the IL-1 responses observed at high-dose SB203580.

Staurosporine, but not Ro 31-8220, induces interleukin 2 production and synergizes with interleukin 1alpha in EL4 thymoma cells.

Protein kinase C (PKC) has been implicated in interleukin 1 (IL1) signal transduction in a number of cellular systems, either as a key event in IL1 action or as a negative regulator. Here we have examined the effects of two PKC inhibitors, staurosporine and the more selective agent Ro 31-8220, on IL1 responses in the murine thymoma line EL4.NOB-1. A 1 h pulse of staurosporine was found to strongly potentiate the induction of IL2 by IL1alpha in these cells. In contrast, neither a pulse nor prolonged incubation with Ro 31-8220 affected the response to IL1alpha. Both agents blocked the response to PMA, however. A 1 h pulse of staurosporine was also found to induce IL2 production on its own, activate the transcription factor nuclear factor kappaB (NFkappaB) and increase the expression of a NFkappaB-linked reporter gene. It synergized with IL1alpha in all of these responses. Ro 31-8220 was again without effect, although both staurosporine and Ro 31-8220 blocked the activation of NFkappaB by PMA. Finally, staurosporine caused the translocation of PKC-alpha and -epsilon, and to a lesser extent PKC-beta, but not PKC-θ or -zeta, from the cytosol to the membrane, although a similar effect was observed with Ro 31-8220. The results suggest that PKC is not involved in IL1alpha signalling in EL4 cells. Furthermore, the potentiating effect of staurosporine on IL1alpha action does not involve PKC inhibition, and is likely to be at the level of NFkappaB activation.

Inhibition of prostacyclin release from cultured endothelial cells by nitrovasodilator drugs.

Pretreatment (18 h) of the bovine aortic endothelial cell line AG4762 to 500 microM sodium nitroprusside (SNP), glyceryl trinitrate (GTN) or 3-morpholino-sydnonimine (SIN-1) significantly inhibited 100 nM bradykinin-stimulated prostacyclin (PGI2) release. SIN-1 produced the greatest reduction (67 +/- 6%), followed by SNP (47 +/- 12%) and GTN (45 +/- 9%). Only SIN-1 and GTN inhibited basal PGI2 release where again the effect of SIN-1 (66 +/- 6%) was greater than that of GTN (31 +/- 15%). There was no effect of SNP on basal PGI2 release. We have demonstrated this inhibition of bradykinin-stimulated PGI2 release is not the result of cell death. In addition, 8-bromo-cyclic GMP, whilst having no effect on basal PGI2 release, demonstrated a small but significant inhibition (15 +/- 6%) of the enhanced response to 100 nM bradykinin. These studies may reflect a mechanism by which the release of vasodilators from endothelial cells is altered during therapy with nitrovasodilators and thus may contribute to the development of tolerance to these drugs.

Potentiation of aggregation and inhibition of adenylate cyclase in human platelets by prostaglandin E analogues.

1. The 16-phenoxy prostaglandin E analogue sulprostone consistently potentiates primary aggregation waves induced by adenosine 5'-diphosphate (ADP), PAF and 11,9-epoxymethano PGH2 (U-46619) in platelet-rich plasma from human donors. The effect is not blocked by the TP-receptor antagonists, EP 092 and GR 32191. The high potency of sulprostone (threshold concentration = 4-10 nM) and the weak block of sulprostone potentiation by the EP1-receptor antagonist, AH 6809 (pA2 = 4.3) suggest the involvement of EP3-receptors as opposed to EP1- or EP2-subtypes. 2. Eight prostaglandin E (PGE) analogues were compared against sulprostone for their effects on PAF-induced aggregation in human platelet-rich plasma (PRP) in the presence of GR 32191 and the DP-receptor antagonist, BW A868C. PGE2 and 11-deoxy PGE2-1-alcohol showed evidence of both potentiating and inhibitory actions and butaprost showed only inhibitory activity at high concentrations. The remaining analogues always elicited potentiation, with the following potency ranking: sulprostone = 16,16-dimethyl PGE2 > MB 28767 > misoprostol > GR 63779X = 17-phenyl-omega-trinor PGE2. The results again indicate that EP3- rather than EP1- or EP2-receptors are involved. However, relative potentiating potency could be affected by differences in plasma protein binding and the very high sensitivity of the human platelet to prostacyclin (IP)-receptor-mediated inhibition (IC50 for the specific IP-receptor agonist cicaprost = 0.8 nM). 3. On human washed platelet suspensions the PGE analogues, with the exception of butaprost,inhibited the rise in adenosine 3':5'-cyclic monophosphate (cyclic AMP) induced by cicaprost (8 nM).PGE2 produced a monophasic inhibition curve (IC50 = 5.4 nM, 92% inhibition at 600 nM). The potency ranking was 16,16-dimethyl PGE2> sulprostone>MB 28767 = PGE2> misoprostol> GR 63778X>17-phenyl-w-trinor PGE2> 1 1-deoxy PGE2-1-alcohol. AH 6809 inhibited the effect of sulprostone and 17-phenyl-c-trinor PGE2 with pA2 values of 5.75 and 5.32 respectively; these values are at least one log unit lower than those found for EP1-receptor block in smooth muscle.4. There is a statistically significant correlation between IC50 values for the PGE analogues on the human platelet cyclic AMP assay and the guinea-pig vas deferens (standard EP3 preparation): slope =1.00, r = 0.80, P <0.05. However the correlation is far from ideal and GR 63779X in particular has a lower potency in the cyclic AMP assay. At this time we suggest that it is prudent to describe the human platelet receptor as 'EP3-like'.5. We believe that our results provide further evidence for linking PGE-induced potentiation of aggregation to inhibition of adenylate cyclase. Sulprostone is a suitable agonist for further study of this system and in particular the nature of the G-protein linkage(s) involved. In addition the necessity to consider potentiation of platelet aggregation in -relation to the clinical use of PGE analogues in man is emphasised.

Mechanisms involved in the stimulation by cycloheximide of prostaglandin production in the guinea-pig uterus.

Cycloheximide produced a large increase in prostaglandin (PG) E2 output and smaller increases in PGF2 alpha and 6-keto-PGF1 alpha when superfused over the guinea-pig uterus for 20 min. This stimulation of the outputs of these 3 PGs by cycloheximide did not require extracellular calcium. TMB-8 (an intracellular calcium antagonist) had no effect on the stimulation of PGE2 output by cycloheximide, but it completely prevented the stimulation of PGF2 alpha and 6-keto-PGF1 alpha outputs. W-7 (a calmodulin antagonist) had no effect on the stimulation of PGE2 and PGF2 alpha outputs by cycloheximide, but it partially reduced and delayed the stimulation of 6-keto-PGF1 alpha output. Neomycin (a phospholipase C inhibitor) did not prevent the increases in PGE2 and 6-keto-PGF1 alpha outputs produced by cycloheximide. However, neomycin (5 and 10 mM, but not 1 mM) inhibited the small increases in PGF2 alpha caused by cycloheximide. On its own, neomycin produced a dose-dependent, transient increase in 6-keto-PGF1 alpha output without affecting the outputs of PGF2 alpha and PGE2. It is concluded that different mechanisms are involved in the processes by which cycloheximide stimulates the syntheses of PGE2, PGF2 alpha and 6-keto-PGF1 alpha in the guinea-pig uterus.

Parasite detection efficiencies of five stool concentration systems.

Fresh fecal material that was free of ova and parasites was pooled with 10% Formalin in a 1:4 ratio to prepare a standard specimen. Portions of 100 ml of this specimen were individually seeded with Cryptosporidium oocysts, Entamoeba coli, Entamoeba histolytica, and Giardia lamblia cysts; ova of Necator americanus; and Strongyloides larvae. Appropriate volumes of each parasite suspension were used to evaluate the Fecal Concentrator Kit (Remel, Lenexa, Kans.), Fecal Parasite Concentrator (Evergreen Scientific, Los Angeles, Calif.), Para-Pak Macro-Con (Meridian Diagnostics, Inc., Cincinnati, Ohio), and Trend FeKal CON-Trate (Trend Scientific, Inc., St. Paul, Minn.). A standardized gauze filtration method was used as the reference procedure. Tests were performed in triplicate with each individual parasite-concentrator combination, with three slides examined from each sediment. All of the systems effectively concentrated parasites compared with direct examination of unconcentrated fecal material. The Fecal Concentrator Kit provided the best overall performance. Clarity of sediment, lack of debris, and uniformity of background material were found to be important considerations for microscopic detection of parasites in concentrated specimens.

Rapid species identification and biotyping of respiratory isolates of Haemophilus spp.

Three commercially available systems, the 4-h Minitek Enterobacteriaceae III, the Haemophilus Trio-Tube, and the Micro-ID, were evaluated for their capacities to identify and biotype 308 respiratory isolates of Haemophilus spp. When compared with aminolevulinic acid test results, the definitive identification method used in this study, these systems demonstrated no significant differences in their capacities to differentiate Haemophilus influenzae from Haemophilus parainfluenzae. They were in agreement with the standard method of species identification approximately 50% of the time. When sucrose was added to the Minitek and Trio-Tube configurations, the efficiency rate of species identification increased to more than 95%. The Micro-ID could not be modified to incorporate this additional biochemical parameter. The performance of the sucrose-supplemented Minitek and Trio-Tube systems, compared to the combined results of Micro-ID and aminolevulinic acid, produced correlations of 94 and 90%, respectively. Rapid and accurate methodologies are available for combined species identification and biotyping of Haemophilus spp.

Evaluation of leukocyte esterase activity as a rapid screening technique for bacteriuria.

Microscopy and leukocyte esterase activity, both employed as screening techniques for urine cultures, were evaluated with respect to two distinct populations, male and female. When 424 urine specimens from males were examined, 95% of the Gram-stained smears and 91% of the leukocyte esterase tests correctly correlated with culture results, indicating significant bacteriuria. There were no significant differences between the Gram stain and leukocyte esterase activity in predicting a negative culture: 99% and 98%, respectively. Neither microscopy nor esterase activity proved as sensitive or as efficient in predicting a negative culture with the female population.