Transanal full-thickness excision for rectal neoplasm: is it advisable to leave the defect open?

PURPOSE

After a full-thickness total wall excision of a rectal tumor, suturing the defect is generally recommended. Recently, due to various contradictory studies, there is a trend to leave the defects open. Therefore, this study aimed to determine whether leaving the defect open is an adequate management strategy compared with suturing it closed based on postoperative outcomes and recurrences.

METHODS

A retrospective review of our prospectively maintained database was conducted. Adult patients who underwent transanal surgery for rectal neoplasm in our institution from 1997 to 2019 were analyzed. Patients were divided into two groups: sutured (group A) or unsutured (group B) rectal defect. The primary outcomes were morbidity (early and late) and recurrence.

RESULTS

In total, 404 (239 men) patients were analyzed, 143 (35.4%) from group A and 261 (64.6%) from group B. No differences were observed in tumor size, distance from the anal verge or operation time. The overall incidence of complications was significantly higher in patients from group B, which nearly double the rate of group A. With a mean follow-up of 58 (range, 12-96) months, seven patients presented with a rectal stricture, all of them from group B.

CONCLUSIONS

We acknowledge the occasional impossibility of closing the defect in patients who undergo local excision; however, when it is possible, the present data suggest that there may be advantages to suturing the defect closed.

Reassessing the evolution of the 1-deoxy-D-xylulose 5-phosphate synthase family suggests a possible novel function for the DXS class 3 proteins

The methylerythritol 4-phosphate (MEP) pathway is of paramount importance for generating plastidial isoprenoids. The first enzyme of the MEP pathway, 1-deoxy-D-xylulose-5-phosphate synthase (DXS), catalyzes a flux-controlling step. In plants the DXS gene family is composed of three distinct classes with non-redundant functions. Although the DXS1 and DXS2 subfamilies have been well characterized, the DXS3 subfamily has been considerably understudied. Here, we carried out in silico and functional analyses to better understand the DXS3 class. Our phylogenetic analysis showed high variation in copy number among the different DXS classes, with the apparent absence of DXS1 class in some species. We found that DXS3 subfamily emerged later than DXS1 and DXS2 and it is under less intense purifying selection. Furthermore, in the DXS3 subfamily critical amino acids positions in the thiamine pyrophosphate binding pocket are not conserved. We demonstrated that the DXS3 proteins from Arabidopsis, Maize, and Rice lack functional DXS activity. Moreover, the Arabidopsis DXS3 protein displayed distinctive sub-organellar chloroplast localization not observed in any DXS1 or DXS2 proteins. Co-expression analysis of the DXS3 from Arabidopsis showed that, unlike DXS1 and DXS2 proteins, it co-expresses with genes related to post-embryonic development and reproduction and not with primary metabolism and isoprenoid synthesis.

Deconvoluting apocarotenoid-mediated retrograde signaling networks regulating plastid translation and leaf development

Signals originating within plastids modulate organelle differentiation by transcriptionally regulating nuclear-encoded genes. These retrograde signals are also integral regulators of plant development, including leaf morphology. The clb5 mutant displays severe leaf morphology defects due to Apocarotenoid Signal 1 (ACS1) accumulation in the developmentally arrested plastid. Transcriptomic analysis of clb5 validates that ACS1 accumulation deregulates hundreds of nuclear genes, including the suppression of most genes encoding plastid ribosomal proteins. Herein, we order the molecular events causing the leaf phenotype associated with the accumulation of ACS1, which includes two consecutive retrograde signaling cascades. Firstly, ACS1 originating in the plastid drives inhibition of plastid translation (IPT) via nuclear transcriptome remodeling of chlororibosomal proteins, requiring light as an essential component. Subsequently, IPT results in leaf morphological defects via a GUN1-dependent pathway shared with seedlings undergoing chemical IPT treatments and is restricted to an early window of the leaf development. Collectively, this work advances our understanding of the complexity within plastid retrograde signaling exemplified by sequential signal exchange and consequences that in a particular temporal and spatial context contribute to the modulation of leaf development.

The Mars Environmental Dynamics Analyzer, MEDA. A Suite of Environmental Sensors for the Mars 2020 Mission

NASA's Mars 2020 (M2020) rover mission includes a suite of sensors to monitor current environmental conditions near the surface of Mars and to constrain bulk aerosol properties from changes in atmospheric radiation at the surface. The Mars Environmental Dynamics Analyzer (MEDA) consists of a set of meteorological sensors including wind sensor, a barometer, a relative humidity sensor, a set of 5 thermocouples to measure atmospheric temperature at ∼1.5 m and ∼0.5 m above the surface, a set of thermopiles to characterize the thermal IR brightness temperatures of the surface and the lower atmosphere. MEDA adds a radiation and dust sensor to monitor the optical atmospheric properties that can be used to infer bulk aerosol physical properties such as particle size distribution, non-sphericity, and concentration. The MEDA package and its scientific purpose are described in this document as well as how it responded to the calibration tests and how it helps prepare for the human exploration of Mars. A comparison is also presented to previous environmental monitoring payloads landed on Mars on the Viking, Pathfinder, Phoenix, MSL, and InSight spacecraft.

Functional analysis of the Chloroplast GrpE (CGE) proteins from Arabidopsis thaliana

The function of proteins depends on specific partners that regulate protein folding, degradation and protein-protein interactions, such partners are the chaperones and cochaperones. In chloroplasts, proteins belonging to several families of chaperones have been identified: chaperonins (Cpn60s), Hsp90s (Hsp90-5/Hsp90C), Hsp100s (Hsp93/ClpC) and Hsp70s (cpHsc70s). Several lines of evidence have demonstrated that cpHsc70 chaperones are involved in molecular processes like protein import, protein folding and oligomer formation that impact important physiological aspects in plants such as thermotolerance and thylakoid biogenesis. Despite the vast amount of data existing around the function of cpHcp70s chaperones, very little attention has been paid to the roles of DnaJ and GrpE cochaperones in the chloroplast. In this study, we performed a phylogenetic analysis of the chloroplastic GrpE (CGE) proteins from 71 species. Based on their phylogenetic relationships and on a motif enrichment analysis, we propose a classification system for land plants' CGEs, which include two independent groups with specific primary structure traits. Furthermore, using in vivo assays we determined that the two CGEs from A. thaliana (AtCGEs) complement the mutant phenotype displayed by a knockout E. coli strain defective in the bacterial grpE gene. Moreover, we determined in planta that the two AtCGEs are bona fide chloroplastic proteins, which form the essential homodimers needed to establish direct physical interactions with the cpHsc70-1 chaperone. Finally, we found evidence suggesting that AtCGE1 is involved in specific physiological phenomena in A. thaliana, such as the chloroplastic response to heat stress, and the correct oligomerization of the photosynthesis-related LHCII complex.

Shedding light on the methylerythritol phosphate (MEP)-pathway: long hypocotyl 5 (HY5)/phytochrome-interacting factors (PIFs) transcription factors modulating key limiting steps

The plastidial methylerythritol phosphate (MEP) pathway is an essential route for plants as the source of precursors for all plastidial isoprenoids, many of which are of medical and biotechnological importance. The MEP pathway is highly sensitive to environmental cues as many of these compounds are linked to photosynthesis and growth and light is one of the main regulatory factors. However, the mechanisms coordinating the MEP pathway with light cues are not fully understood. Here we demonstrate that by a differential direct transcriptional modulation, via the key-master integrators of light signal transduction HY5 and PIFs which target the genes that encode the rate-controlling DXS1, DXR and HDR enzymes, light imposes a direct, rapid and potentially multi-faceted response that leads to unique protein dynamics of this pathway, resulting in a significant difference in the protein levels. For DXS1, PIF1/HY5 act as a direct activation/suppression module. In contrast, DXR accumulation in response to light results from HY5 induction with minor contribution of de-repression by PIF1. Finally, HDR transcription increases in the light exclusively by suppression of the PIFs repression. This is an example of how light signaling components can differentially multi-target the initial steps of a pathway whose products branch downstream to all chloroplastic isoprenoids. These findings demonstrate the diversity and flexibility of light signaling components that optimize key biochemical pathways essential for plant growth.

Sugar regulation of SUGAR TRANSPORTER PROTEIN 1 (STP1) expression in Arabidopsis thaliana

Sugars regulate the expression of many genes at the transcriptional level. In Arabidopsis thaliana, sugars induce or repress the expression of >1800 genes, including the STP1 (SUGAR TRANSPORTER PROTEIN 1) gene, which encodes an H(+)/monosaccharide cotransporter. STP1 transcript levels decrease more rapidly after the addition of low concentrations of sugars than the levels of other repressed genes, such as DIN6 (DARK-INDUCED 6). We found that this regulation is exerted at the transcriptional level and is initiated by phosphorylatable sugars. Interestingly, the sugar signal that modulates STP1 expression is transmitted through a HEXOKINASE 1-independent signalling pathway. Finally, analysis of the STP1 5' regulatory region allowed us to delimit a region of 309bp that contains the cis elements implicated in the glucose regulation of STP1 expression. Putative cis-acting elements involved in this response were identified.

An Uncharacterized Apocarotenoid-Derived Signal Generated in ζ-Carotene Desaturase Mutants Regulates Leaf Development and the Expression of Chloroplast and Nuclear Genes in Arabidopsis

In addition to acting as photoprotective compounds, carotenoids also serve as precursors in the biosynthesis of several phytohormones and proposed regulatory signals. Here, we report a signaling process derived from carotenoids that regulates early chloroplast and leaf development. Biosynthesis of the signal depends on ζ-carotene desaturase activity encoded by the ζ-CAROTENE DESATURASE (ZDS)/CHLOROPLAST BIOGENESIS5 (CLB5) gene in Arabidopsis thaliana. Unlike other carotenoid-deficient plants, zds/clb5 mutant alleles display profound alterations in leaf morphology and cellular differentiation as well as altered expression of many plastid- and nucleus-encoded genes. The leaf developmental phenotypes and gene expression alterations of zds/clb5/spc1/pde181 plants are rescued by inhibitors or mutations of phytoene desaturase, demonstrating that phytofluene and/or ζ-carotene are substrates for an unidentified signaling molecule. Our work further demonstrates that this signal is an apocarotenoid whose synthesis requires the activity of the carotenoid cleavage dioxygenase CCD4.

Characterization of evolutionarily conserved motifs involved in activity and regulation of the ABA-INSENSITIVE (ABI) 4 transcription factor

In recent years, the transcription factor ABI4 has emerged as an important node of integration for external and internal signals such as nutrient status and hormone signaling that modulates critical transitions during the growth and development of plants. For this reason, understanding the mechanism of action and regulation of this protein represents an important step towards the elucidation of crosstalk mechanisms in plants. However, this understanding has been hindered due to the negligible levels of this protein as a result of multiple posttranscriptional regulations. To better understand the function and regulation of the ABI4 protein in this work, we performed a functional analysis of several evolutionarily conserved motifs. Based on these conserved motifs, we identified ortholog genes of ABI4 in different plant species. The functionality of the putative ortholog from Theobroma cacao was demonstrated in transient expression assays and in complementation studies in plants. The function of the highly conserved motifs was analyzed after their deletion or mutagenesis in the Arabidopsis ABI4 sequence using mesophyll protoplasts. This approach permitted us to immunologically detect the ABI4 protein and identify some of the mechanisms involved in its regulation. We identified sequences required for the nuclear localization (AP2-associated motif) as well as those for transcriptional activation function (LRP motif). Moreover, this approach showed that the protein stability of this transcription factor is controlled through protein degradation and subcellular localization and involves the AP2-associated and the PEST motifs. We demonstrated that the degradation of ABI4 protein through the PEST motif is mediated by the 26S proteasome in response to changes in the sugar levels.

Longitudinal assessment in COPD patients: multidimensional variability and outcomes

The value and timing of multidimensional assessments in chronic obstructive pulmonary disease (COPD) remains unclear because there is little information about their variability and relationship to outcome. The aim of this study was to determine the progression of COPD using clinical and spirometric variability over time with mortality as the outcome. We determined the annual intra-individual variability of forced expiratory volume in 1 s (FEV1) and BODE (body mass index, airflow obstruction, dyspnoea, exercise capacity) index in 403 patients with at least five measurements. The pattern was defined as "stable" if the annual change remained constant in ≥66% of the observations and "unstable" if it did not meet that threshold. We explored the minimum number of yearly observations that related to mortality in the 704 patients of the cohort. The "unstable" pattern of FEV1 was seen in 53% and 40% of patients using a threshold of 40 mL·year(-1) and 100 mL·year(-1), respectively. There was a slightly more "stable" pattern in the BODE index (62% for 1 point). A profile associated with mortality was defined by a baseline measurement followed by annual measurements for 2 years of the BODE index, but not its individual components, including FEV1 (p<0.001). Progression of COPD measured using FEV1 is inconsistent and relates poorly to outcome. Monitoring the more stable BODE index better assesses disease progression.

Inflammatory and repair serum biomarker pattern: association to clinical outcomes in COPD

Background

The relationship between serum biomarkers and clinical expressions of COPD is limited. We planned to further describe this association using markers of inflammation and injury and repair.

Methods

We studied lung function, comorbidities, exercise tolerance, BODE index, and quality of life in 253 COPD patients and recorded mortality over three years. Serum levels of Interleukins 6,8 and16, tumor necrosis factor alpha (TNF α) [inflammatory panel], vascular endothelial growth factor (VEGF), and matrix metalloproteinase 9 (MMP-9) [injury and repair panel] and pulmonary and activation-regulated chemokine (PARC/CCL-18) and monocyte chemotactic protein 1 (MCP-1/CCL2) [chemoattractant panel] were measured. We related the pattern of the biomarker levels to minimal clinically important differences (MCID) using a novel visualization method [ObServed Clinical Association Results (OSCAR) plot].

Results

Levels of the inflammatory markers IL-6, TNF α were higher and those of injury and repair lower (p < 0.01) with more advanced disease (GOLD 1 vs. 4). Using the OSCAR plot, we found that patients in the highest quartile of inflammatory and lowest quartile of injury and repair biomarkers level were more clinically compromised and had higher mortality (p < 0.05).

Conclusions

In COPD, serum biomarkers of inflammation and repair are distinctly associated with important clinical parameters and survival.

ABI4 and its role in chloroplast retrograde communication

The acquisition of plastids is a landmark event in plant evolution. The proper functionality of these organelles depends on strict and continuous communication between the plastids and the nucleus to precisely adjust gene expression in response to the organelle's requirements. Signals originating from the plastids impact the expression of a variety of nuclear genes, and this retrograde communication is essential to couple the nuclear expression of plastid-localized products with organelle gene expression and, ultimately, functionality. Major advances have been made in this field over the past few years with the characterization of independent retrograde signaling pathways and the identification of some of their components. One such factor is the nuclear transcriptional factor ABI4 (ABA-INSENTIVE 4). ABI4, together with the plastid PPR GUN1 protein, has been proposed to function as a node of convergence for multiple plastid retrograde signaling pathways. ABI4 is conserved among plants and also plays important roles in various critical developmental and metabolic processes. ABI4 is a versatile regulator that positively and negatively modulates the expression of many genes, including other transcriptional factors. However, its mode of action during plastid retrograde signaling is not fully understood. In this review, we describe the current evidence that supports the participation of ABI4 in different retrograde communication pathways. ABI4 is regulated at the transcriptional and post-transcriptional level. A known regulator of ABI4 includes the PTM transcription factor, which moves from the chloroplast to the nucleus. This transcription factor is a candidate for the transmission of retrograde signals between the plastid and ABI4.

Tobacco plants expressing the Cry1AbMod toxin suppress tolerance to Cry1Ab toxin of Manduca sexta cadherin-silenced larvae

Cry toxins produced by Bacillus thuringiensis bacteria are insecticidal proteins used worldwide in the control of different insect pests. Alterations in toxin-receptor interaction represent the most common mechanism to induce resistance to Cry toxins in lepidopteran insects. Cry toxins bind with high affinity to the cadherin protein present in the midgut cells and this interaction facilitates the proteolytic removal of helix α-1 and pre-pore oligomer formation. Resistance to Cry toxins has been linked with mutations in the cadherin gene. One strategy effective to overcome larval resistance to Cry1A toxins is the production of Cry1AMod toxins that lack helix α-1. Cry1AMod are able to form oligomeric structures without binding to cadherin receptor and were shown to be toxic to cadherin-silenced Manduca sexta larvae and Pectinophora gossypiella strain with resistance linked to mutations in a cadherin gene. We developed Cry1AbMod tobacco transgenic plants to analyze if Cry1AMod toxins can be expressed in transgenic crops, do not affect plant development and are able to control insect pests. Our results show that production of the Cry1AbMod toxin in transgenic plants does not affect plant development, since these plants exhibited healthy growth, produced abundant seeds, and were virtually undistinguishable from control plants. Most importantly, Cry1AbMod protein produced in tobacco plants retains its functional toxic activity against susceptible and tolerant M. sexta larvae due to the silencing of cadherin receptor by RNAi. These results suggest that CryMod toxins could potentially be expressed in other transgenic crops to protect them against both toxin-susceptible and resistant lepidopteran larvae affected in cadherin gene.

Functional characterization of the three genes encoding 1-deoxy-D-xylulose 5-phosphate synthase in maize

The 1-deoxy-D-xylulose 5-phosphate synthase (DXS) enzyme catalyses the first biosynthetic step of the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway. In plants the MEP pathway is involved in the synthesis of the common precursors to the plastidic isoprenoids, isopentenyl diphosphate and dimethylallyl diphosphate, in plastids. DXS is recognized as limiting this pathway and is a potential target for manipulation to increase various isoprenoids such as carotenoids. In Zea mays three dxs genes exist that encode plastid-targeted functional enzymes. Evidence is provided that these genes represent phylogenetically distinctive clades conserved among plants preceding monocot-dicot divergence. There is differential accumulation for each dxs gene transcript, during development and in response to external signals such as light. At the protein level, the analysis demonstrates that in Z. mays, DXS protein is feedback regulated in response to the inhibition of the pathway flow. The results support that the multilevel regulation of DXS activity is conserved in evolution.

Microalbuminuria and hypoxemia in patients with chronic obstructive pulmonary disease

RATIONALE

Microalbuminuria (MAB), a marker of endovascular dysfunction, is a predictor of cardiovascular events and all-cause mortality in the general population. There is evidence of vascular dysfunction in patients with chronic obstructive pulmonary disease (COPD).

OBJECTIVES

To assess the prevalence and relationship of MAB with clinical and physiological parameters in stable patients with COPD.

METHODS

We measured urinary albumin rate (urinary albumin to creatinine ratio: UACR), smoking history, arterial blood pressure, gas exchange, body mass index, lung function, BODE index (body mass index, airflow obstruction, dyspnea, exercise performance), and comorbidity index in 129 patients with stable COPD and 51 smokers with normal spirometry without known cardiovascular disease. MAB levels were compared between groups. A multivariate analysis was performed to determine the best determinants of MAB levels.

MEASUREMENTS AND MAIN RESULTS

MAB was higher in patients with COPD than in control smokers (8 [5th-95th percentile (P₅₋₉₅), 2.9-113] vs. 4.2 [P₅₋₉₅, 1.8-22.7] mg/g, P < 0.001]). The difference remained significant even after using the standard pathologic threshold (MAB, 30-299 mg/g in women and 20-299 mg/g in men; 24% in patients with COPD vs. 6% in control smokers; P = 0.005). In patients with COPD, there was a negative correlation between Pa(O₂) and MAB (r = -0.40, P < 0.001). Using multivariate analysis, MAB was only associated with the Pa(O₂) (relative risk, 0.934; 95% confidence interval, 0.880-0.992; P < 0.001) and with the systolic arterial blood pressure (relative risk, 1.034; 95% confidence interval, 1.011-1.057; P = 0.003).

CONCLUSIONS

MAB is frequent in patients with COPD and is associated with hypoxemia independent of other cardiovascular risk factors. Further studies are necessary to investigate whether MAB could be an early simple biomarker of cardiovascular compromise in patients with COPD.

Heterologous expression of yeast Hxt2 in Arabidopsis thaliana alters sugar uptake, carbon metabolism and gene expression leading to glucose tolerance of germinating seedlings

The hexose transporter 2 gene (Hxt2) from Saccharomyces cerevisiae was expressed in Arabidopsis thaliana under control of the 35S promoter. Several independent transgenic lines were selected after confirming single gene insertion by southern blot analysis in the T4 generation. Northern blots revealed the presence of heterologous transcript. Radiolabeling experiments revealed an increased rate of incorporation of the non-metabolizable analog 3-O-methyl-[U-14C]-glucose. This confirmed that the yeast Hxt2 transporter was functional in Arabidopsis. No phenotypic changes at the vegetative and reproductive stages could be detected in the transgenic lines when compared to wild type plants. Shortly after germination some differences in development and glucose signaling were observed. Transgenic seedlings cultivated in liquid medium or on solid agar plates were able to grow with 3% glucose (producing bigger plants and longer roots), while development of wild type plants was delayed under those conditions. Metabolite analysis revealed that the Hxt2 transgenic lines had higher rates of sugar utilization. Transcriptional profiling showed that particular genes were significantly up- or down-regulated. Some transcription factors like At1g27000 were repressed, while others, such as At3g58780, were induced. The mRNA from classical sugar signaling genes such as STP1, Hxk1, and ApL3 behaved similarly in transgenic lines and wild type lines. Results suggest that the Hxt2 transgene altered some developmental processes related to the perception of high carbon availability after the germination stage. We conclude that the developmental arrest of wild type plants at 3% glucose not only depends on Hxk1 as the only sugar sensor but might also be influenced by the route of hexose transport across the plasma membrane.

The Arabidopsis ABA-INSENSITIVE (ABI) 4 factor acts as a central transcription activator of the expression of its own gene, and for the induction of ABI5 and SBE2.2 genes during sugar signaling

The transcription factor ABA INSENSITIVE 4 (ABI4), discovered nearly 10 years ago, plays a central role in a variety of functions in plants, including sugar responses. However, not until very recently has its mechanism of action begun to be elucidated. Modulating gene expression is one of the primary mechanisms of sugar regulation in plants. Nevertheless, the transcription factors involved in regulating sugar responses and their role(s) during the signal transduction cascade remain poorly defined. In this paper we analyzed the participation of ABI4, as it is one of the main transcription factors implicated in glucose signaling during early seedling development. Our studies show that ABI4 is an essential activator of its own expression during development, in ABA signaling and in sugar responses. It is also important for the glucose-mediated expression of the genes ABI5 and SBE2.2. We demonstrate that ABI4 binds directly to the promoter region of all three genes and activates their expression in vivo through at CE1-like element. Previous studies found that ABI4 also functions as a transcriptional repressor of sugar-regulated genes, therefore this transcription factor is a versatile protein with dual functions for modulating gene expression.

Unravelling the regulatory mechanisms that modulate the MEP pathway in higher plants

The methyl-D-erythritol 4-phosphate pathway is responsible for the biosynthesis of a substantial number of natural compounds of biological and biotechnological importance. In recent years, this pathway has become an obvious target to develop new herbicides and antimicrobial drugs. In addition, the production of a variety of compounds of medical and agricultural interest may be possible through the genetic manipulation of this pathway. To this end, a complete understanding of the molecular mechanisms that regulate this pathway is of tremendous importance. Recent data have accumulated that show some of the multiple mechanisms that regulate the methyl-D-erythritol 4-phosphate pathway in plants. In this review we will describe some of these and discuss their implications. It has been demonstrated that 1-deoxy-D-xylulose-5-phosphate synthase (DXS), the first enzyme of this route, plays a major role in the overall regulation of the pathway. A small gene family codes for this enzyme in most of the plants which have been analysed so far, and the members of these gene families belong to different phylogenetic groups. Each of these genes exhibits a distinct expression pattern, suggesting unique functions. One of the most interesting regulatory mechanisms recently described for this pathway is the post-transcriptional regulation of the level of DXS and DXR proteins. In the case of DXS, this regulation appears conserved among plants, supporting its importance. The evidence accumulated suggests that this regulation might link the activity of this pathway with the plant's physiological conditions and the metabolic demand for the final products of this route.

Antisense inhibition of NADH glutamate synthase impairs carbon/nitrogen assimilation in nodules of alfalfa (Medicago sativa L.)

Legumes acquire significant amounts of nitrogen for growth from symbiotic nitrogen fixation. The glutamine synthetase (GS)/NADH-dependent glutamate synthase (NADH-GOGAT) cycle catalyzes initial nitrogen assimilation. This report describes the impact of specifically reducing nodule NADH-GOGAT activity on symbiotic performance of alfalfa (Medicago sativa L.). Four independent transgenic alfalfa lines, designated GA89, GA87, GA88, and GA82 (for GOGATantisense), containing an antisense NADH-GOGAT cDNA fragment under the control of the soybean leghemoglobin (lbc3) promoter were evaluated. The GA plants were fertile and showed normal growth in non-symbiotic conditions. The NADH-GOGAT antisense transgene was heritable and the T1 plants showed phenotypic alterations - similar to primary transformants. Clonally propagated plants were inoculated with Sinorhizobium meliloti after rooting and the symbiotic phenotype was analyzed 21 days post-inoculation. Nodules of each GA line had reduced NADH-GOGAT activity, ranging from 33 to 87% of control plants, that was accompanied by comparable decreases in RNA and protein. Plants from the GA89 line, with the lowest NADH-GOGAT activity (c. 30%), presented a strikingly altered symbiotic phenotype: concomitantly activities of key enzyme for carbon and nitrogen assimilation decreased; nodule amino acids and amides were reduced while sucrose accumulated. Antisense GOGAT plants were chlorotic, reduced in fresh weight, and had a lower N content than control plants. Photosynthesis was also impaired in antisense plants. Specifically, reducing NADH-GOGAT in nodules resulted in plants having impaired nitrogen assimilation and altered carbon/nitrogen metabolic flux.

Comparison of the effects of acetazolamide and aminophylline on apnea incidence and on ventilatory response to CO2 in preterm infants

Acetazolamide (ACTZ) reduces sleep apnea in adults exposed to high altitude and augments the ventilatory response to CO2. In order to determine the effect of ACTZ on the ventilatory response to CO2 and the incidence of apnea in preterm infants, 7 infants (BW, 1070 +/- 191 g; postnatal age, 9 +/- 7 days) were randomized to receive ACTZ (5 mg/kg/dose Q6h for 36 hr) and 7 infants (BW, 1092 +/- 292 g; post-natal age, 5 +/- 2 days) received aminophylline (AMINO; 8 mg/kg bolus then 2.5 mg/kg Q12h for 36 hr). Minute ventilation (VE), end-tidal CO2 (PETCO2), ventilatory response to CO2, number of apneic episodes (> or = 15 sec duration), and arterial blood gases were measured before and 24-36 hr after starting therapy. In the AMINO group there was a significant decrease in apnea frequency from 6 +/- 1 to 2 +/- 2 episodes over an 8 hr epoch (P < 0.05), while no significant change was observed in the ACTZ group. The end-tidal CO2 decreased significantly from 44 +/- 7 to 38 +/- 6 mmHg in the AMINO group and from 47 +/- 5 to 36 +/- 5 mmHg in the ACTZ (P < 0.05), which lead to a shift to the left of the CO2-response curve in both groups. The slope of the CO2 response curve did not change significantly in the AMINO group and decreased in the ACTZ group. There was a significant decrease of pH from 7.43 to 7.26 in the ACTZ group, whereas in the AMINO group pH increased from 7.38 to 7.44.(ABSTRACT TRUNCATED AT 250 WORDS)