Risk factors for nosocomial pneumonia in critically ill trauma patients

OBJECTIVE

To determine risk factors for nosocomial pneumonia in critically ill trauma patients.

DESIGN

Prospective cohort study.

SETTING

The trauma intensive care unit (ICU) of a 1500-bed tertiary-care hospital.

PATIENTS

All critically ill trauma patients (n = 103) admitted consecutively between November 1995 and October 1996.

INTERVENTIONS

A comparison of data recorded at the time of ICU admission and during the clinical evolution in patients with (n = 23) and without (n = 80) nosocomial pneumonia was made. Data referred mainly to possible risk factors were recorded; they also included factors related to pneumonia etiology and evolutive factors. Predictors of nosocomial pneumonia were assessed by logistic regression analysis.

MEASUREMENTS AND MAIN RESULTS

The presence of significant growth on quantitative cultures of the protected specimen brush (> or = 103 colony forming units/mL) was required to accept pneumonia as microbiologically proven, as well as the concurrence of a cohort of clinical and radiologic signs. Twenty-three (22.3%) patients developed nosocomial pneumonia. The mean age of these patients was 41.7 yrs; 18 of them (78.3%) were men. The microorganisms isolated in significant concentrations were Acinetobacter baumanii (ten cases), Staphylococcus aureus (11 cases), Pseudomonas aeruginosa (five cases), Haemophilus influenzae (two cases), and Klebsiella pneumoniae, Citrobacter freundii, Serratia marcescens, Enterococcus spp., Enterobacter spp., coagulase-negative Staphylococcus, and Streptococcus intermedius (one case each one). Risk factors for pneumonia by univariate analysis included nasogastric tube; continuous enteral feeding; prolonged mechanical ventilation (>1 day); use of H2-receptor antagonist, sucralfate, muscle relaxants, corticosteroids, barbiturates, and inotropic agents; positive end-expiratory pressure; intense sedation; re-intubation; tracheotomy; urgent brain computed tomography (CT) scan; craniotomy; iatrogenic event; and hyperventilation. The mortality rate was 43.5% (10 of 23) in the nosocomial pneumonia group and 18.8% in patients without nosocomial pneumonia (p =.02). Also, the mean stay in the ICU, the therapeutic charge (measured with total and mean punctuation of the Therapeutic Intervention Scoring System) and the complications, infectious and noninfectious, of the clinical evolution were significantly more frequent in patients with nosocomial pneumonia than in those without pneumonia (p <.05). In the multivariate analysis, continuous enteral feeding, craniotomy, prolonged mechanical ventilation (>24 hrs), use of positive end-expiratory pressure, and corticotherapy were independent predictors of nosocomial pneumonia.

CONCLUSIONS

It seems that factors related to the patient's clinical course, rather than variables registered on the first days of ICU admission, are those that would exert an influence on the development of nosocomial pneumonia in critically ill trauma patients. In this way, from our point of view, in our study the main risk factors are the use of prolonged mechanical ventilation (>4 hrs) and positive end-expiratory pressure. At the same time, we can conclude that the reduction of this infection incidence could decrease the mean stay in the ICU, the therapeutic charge, and the prognosis in terms of mortality and morbidity.

Assessment of the effectiveness of descending aortomyoplasty for nonischemic cardiac failure by means of the subendocardial viability index

INTRODUCTION

Paraaortic or external aortic counterpulsation is been investigated as a definitive ventricular assistance in cases of terminal congestive heart failure and when heart transplantation is counterindicated. Our aims is to assess the haemodynamic effects of an descending aortomyoplasty in a biological model of congestive heart failure.

MATERIALS AND METHODS

As specimens, we used 10 "Large White" pigs. Mean weight was 25,3+/-2,14 Kg. After the administration of conventional anaesthesia, dissection of the latissimus dorsi muscle was performed. Then we performed a thoracotomy at the level of the fourth intercostal space to reach the thoracic aorta. The aorta is dissected 7 centimetres from the output of the subclavia artery and it is wrapped by the dissected muscle. A cardiomyostimulator is provided in order to allow the synchronization between the diastole and the muscle contraction. The model of heart failure was provoked using Verapamil plus Propanolol i.v.

RESULTS

A significant increase of the systolic and diastolic aortic pressure (54,2+/-4,05 and 27.5+/-6.77 mmHg versus 76.5+/-6.25 and 56.4+/-5.2 mmHg, p<0,001) and a significant decrease of the left ventricle telediastolic pressures were observed (12.9+/-9 versus 2.6+/-1.57 mmHg, p<0,001). An increase of the cardiac output (0.363+/-0.11 versus 0.846+/-0.08 L/min, p<0,001) and the Subendocardial Viability Index (0.968+/-0.076 versus 1.351+/-0,107, p<0,001)were observed in a model of non-ischemic heart failure.

CONCLUSION

Descending Aortomyoplasty as a technique to support circulation in cases of acute heart failure, improves the parameters of ventricular function, aiding the functional recovery of the left ventricle and improving significantly cardiac output as well as diastolic and systolic cardiac pressure. In addition to this, improves the Subendocardial Viability Index in cases of acute heart failure, which indirectly reflects an improvement of the Transmural and Subendocardial Perfusion of the failing heart.

[Motor impairment, in patients with severe Parkinson's disease, associated with dopaminergic hyperstimulation (entacapone)]

OBJECTIVE

[corrected] Entacapone was given to try to improve the motor complications in eight patients with Parkinson's disease (PD) treated chronically with levodopa, with daily severe motor fluctuations and dyskinesias.

PATIENTS AND METHODS

We introduced entacapone (200 mg added to every dose of levodopa) to 8 parkinsonian patients (mean age: 68.25 +/- 2.3; range: 68-72; mean PD duration: 10.4 +/- 2.7 years) treated with oral levodopa, plus a dopa-decarboxylase inhibitor (mean dose: 706.25 +/- 2.3 mg/day; mean period of levodopa-treatment; 9 +/- 2.3 years). Dyskinesias were present in all patients (chorea: 8 patients; "off"--dystonia: 4; byphasic dyskinesias: 3). The type and duration (time "on" and "off") of fluctuations was categorized on the "on-off" charts drawn up by the patients or their relatives, and observation by the investigators after the introduction of entacapone. One patient, with severe impairment with entacapone, was evaluated (motor response) during i.v. apomorphine infusion (40 mg, during 3 hours).

RESULTS

The combination of levodopa and entacapone was associated with a net increase in "off" time in all patients (from 5.8 +/- 1.2 h to 12.4 +/- 4.4 h) without change in the URPD. In the patient studied with i.v. apomorphine, "off" periods appeared during the infusion.

CONCLUSION

These findings suggest that increased daily levodopa consumption may reduce striatal responsiveness to dopaminergic stimulation in severe parkinsonian patients. These data should be considered when planning the treatment strategy of complex parkinsonian patients.

Liquid chromatographic determination of the total available free and intrachain lysine in various foods

A method for the quantitative determination of the total available lysine in various foods is developed. The method is based on the reaction of the amino groups on the lysine molecule with fluorodinitrobenzene and is capable of furnishing simultaneous determination of the available intrachain lysine (known as N-epsilon-[2,4-dinitrophenyl]-L-lysine) or the available free and/or N-terminal lysine (known as N,N'-di-[2,4-dinitrophenyl]-L-lysine). Optimum conditions for separation and quantitation are studied. The results show the proposed method to be both accurate and precise and suitable for food samples containing hydrolyzed proteins.

Spanish intercomparisons for individual monitoring

The Spanish Nuclear Safety Council (CSN) carries out an intercomparison programme for individual monitoring every 5 years. The objective is to acquire valuable information on the performance of the dosimetry systems of the participating Spanish approved dosimetry services and to assess precision and accuracy as quality indicators of overall dosimetry performance. CSN has carried out two intercomparison programmes, the last one in 1995, in which 18 approved dosimetry services participated. The dosemeters were exposed to photon fields (137Cs gamma rays and two X ray beams of different qualities), at two standard laboratories in Spain. The irradiations were done for evaluating personal dose equivalent, Hp(10), using the ICRU 47 phantom. Presently, CSN is carrying out a new intercomparison, which will be finished in 2001. Twenty-three dosimetry services will participate; 22 from Spain and one from Cuba. The irradiations will be done in reference photon radiation fields.

The outlook for the application of electronic dosemeters as legal dosimetry

This study analyses new trends of a set of 12 electronic personal dosemeters in order to gain an overview of their main advantages and limitations. Physical characteristics and radiological, mechanical and environmental performance were tested according to IEC-61526 Standard requirements. The study highlights the different behaviour of the selected dosemeters. In particular, it is demonstrated that three of the tested devices fulfilled most of the established requirements, whereas another three of them presented important faults. The parameters that need more development are, in general, the response at low energy photon and beta radiation, and the dose rate alarm features. In some cases, mechanical problems as well as interference in the response due to external electromagnetic fields were also found. However, the results of the study foresee a promising future for the application of the newest personal electronic dosemeters as legal personal dosemeters and show the need for internationally agreed technical requirements within the European countries.

The Spanish National Dose Registry and Spanish radiation passbooks

The Spanish National Dose Registry (BDN) is the Nuclear Safety Council's (CSN) national database of occupational exposure to radiation. Each month BDN receives records of individual external doses from approved dosimetry services. The dose records include information regarding the occupational activities of exposed workers. The dose information and the statistical analysis prepared by the BDN are a useful tool for effective operational protection of occupationally exposed workers and a support for the CSN in the development and application of the ALARA principle. The Spanish radiation passbook was introduced in 1990 and since then CSN, as regulatory authority, has required that all outside workers entering controlled areas should have radiation passbooks. Nowadays, CSN has implemented improvements in the Spanish radiation passbooks, taking into account previous experience and Directive 96/29/EURATOM.

An integrated anaerobic--physico-chemical treatment concept for wool scouring wastewater

The strong flow wastewater from a wool scouring industry is treated by a combination of anaerobic digestion and physico-chemical postreatment. Based on previous laboratory results (Gutiérrez et al., 1999), three anaerobic baffled reactors (ABR) of 300 m3 each were built, processing 60% of the strong flow of a wool scouring mill for about two years. COD and grease removal in the anaerobic reactors were 47-50% and 50-55% respectively, with an organic load between 8.9 and 6.7 kg COD/m3 d. The effluent of the anaerobic reactors was assayed with additives in an industrial decanter centrifuge. As results of these assays, all the effluent of the three reactors was sent to the decanter centrifuge after dosing additives. Overall COD and grease removal of the integrated system were 87% and 93% respectively. Dosage of coagulation-flocculation additives was optimized in a continuous flocculation device. The proposed treatment is cheaper and easier to control than others alternatives with COD removal higher than 93%.

[Falling backward: atypical sign of iodiopathic Parkison's disease. Use of intravenous apomorphine as a diagnostic test]

INTRODUCTION

The differential diagnosis of a parkinsonian syndrome is extensive and complex. In most cases, however, a detailed clinical examination will help to differentiate between idiopathic Parkinson's disease (IPD) and other causes of parkinsonism.

PATIENTS AND METHODS

10 patients with an average age of 65.1 years (range 60-70), of whom 6 were men and 4 women were referred to our department with a diagnosis of IPD and history of backwards falls. The average duration of disease was 4.7 years (range 4-7). All 10 patients had at presentation a severe akinetic-rigid syndrome with no other symptoms of IPD. I.v. apomorphine (APO) was administered to each of them at a rate of 8.9 mg/hr (range 15.3 mg/hr) for an average time of 5.4 hours (range: 3-10 hours).

RESULTS

The improvement of the akinetic-rigid state in six of the patients during the i.v. infusion with APO helped to elicit signs that are atypical of IPD (ataxia and postural instability). Three of the patients did not respond to i.v. APO and one of them could not be evaluated, as he did not tolerate the infusion. Oral Dopa challenge or s/c APO bolus has not been as successful in helping to differentiate IPD from other parkinsonian syndromes.

CONCLUSIONS

The prompt detection of postural instability or retropopulsion is necessary in order to diagnose atypical parkinsonian syndromes. In difficult cases, continuous i.v. APO will improve the akinetic-rigid state and facilitate the detection of atypical signs. The pharmacokinetic characteristics of APO, and the advantage of it being possible to administer the drug i.v. in a few hours increases the viability of this test.

Evaluation of a new serodiagnostic tuberculosis test based on immunoglobulin A detection against Kp-90 antigen

We evaluated a new serological test for tuberculosis (TB) diagnosis, an enzyme-linked immunosorbent assay which detects the presence of immunoglobulin A (IgA) antibodies in human serum, the Kreatech TB IgA EIA test. The study was performed using 166 serum samples collected in the city of Barcelona, Spain. Fifty-six serum samples were from TB patients and 111 from controls, 40 of which were non-TB pneumonia patients. The test sensitivity was 70.58% in the adult group with pulmonary TB and 50% in the group with extra-pulmonary TB. These sensitivities were similar to those previously reported by others. However, we found that the test had a low specificity of only 68.68%, while specificities of 90% and 95% have been reported. This discrepancy may be attributable to differences in the respective study populations. In our control group we included 40 non-TB pneumonia patients (36% of the entire control group), in whom test specificity dropped to 47.22%. In those studies in which specificities of 90% and above were achieved, very few serum samples from non-TB pneumonia patients were tested (6-12% of the entire control group).

Thrombocytopenia associated with liver cirrhosis and hepatitis C viral infection: role of thrombopoietin

BACKGROUND/AIMS

Thrombocytopenia in chronic liver diseases has traditionally been considered a consequence of platelet pooling and destruction in spleen. We tried to evaluate the influence of thrombopoietin, the physiological regulator of thrombopoiesis, on the origin of this thrombocytopenia.

METHODOLOGY

We determined serum thrombopoietin levels by ELISA in thrombocytopenic patients with liver cirrhosis (n = 32) and with chronic hepatitis C viral infection (n = 23). A group of 43 healthy subjects was used as a control.

RESULTS

Liver cirrhosis patients presented slightly, but not significantly, lower serum thrombopoietin levels (104 +/- 56 pg/mL) than controls (121 +/- 58 pg/mL) or patients infected with chronic hepatitis C virus (125 +/- 40 pg/mL). No correlations were found between serum thrombopoietin concentrations and liver tests or hematological parameters.

CONCLUSIONS

We conclude that low thrombopoietin production may play a role, along with hypersplenism, in the development of thrombocytopenia in patients with liver cirrhosis. Normal thrombopoietin levels exclude a defect in thrombopoietin production as a possible etiology for the thrombocytopenia in patients with chronic hepatitis C viral infection. However, a direct viral megakaryocyte infection or an immune mechanism could explain this thrombocytopenia, according to the thrombopoietin levels detected.

RET genotypes comprising specific haplotypes of polymorphic variants predispose to isolated Hirschsprung disease

BACKGROUND

Hirschsprung disease (HSCR), which may be sporadic or familial, occurs in 1:5000 live births and presents with functional intestinal obstruction secondary to aganglionosis of the hindgut. Germline mutations of the RET proto-oncogene are believed to account for up to 50% of familial cases and up to 30% of isolated cases in most series. However, these series are highly selected for the most obvious and severe cases and large familial aggregations. Population based studies indicate that germline RET mutations account for no more than 3% of isolated HSCR cases. Recently, we and others have noted that specific polymorphic sequence variants, notably A45A (exon 2), are over-represented in isolated HSCR.

PURPOSE

In order to determine if it is the variant per se, a combination thereof, or another locus in linkage disequilibrium which predisposes to HSCR, we looked for association of RET haplotype(s) and disease in HSCR cases compared to region matched controls.

METHODS

Seven loci across RET were typed and haplotypes formed for HSCR cases, their unaffected parents, and region matched controls. Haplotype and genotype frequencies and distributions were compared among these groups using the transmission disequilibrium test and standard case-control statistic.

RESULTS

Twelve unique haplotypes, labelled A-L, were obtained. The distributions of haplotypes between cases and controls (chi(11)(2) =81.4, p<<0.0001) and between cases and non-transmitted parental haplotypes were significantly different (chi(2)(11)=53.1, p<0.0001). Genotypes comprising pairs of haplotypes were formed for cases and controls. There were 38 different genotypes among cases and controls combined. Inspection of the genotypes in these two groups showed that the genotype distribution between cases and controls was distinct (chi(37)(2)=93. 8, p<<0.0001). For example, BB, BC, BD, and CD, all of which contain at least one allele with the polymorphic A45A, are prominently represented among HSCR cases, together accounting for >35% of the case genotypes, yet these four genotypes were not represented among the population matched normal controls. Conversely, AA, AG, DD, GG, and GJ, none of which contains A45A, are commonly represented in the controls, together accounting for 43% of the control genotypes, and yet they are never seen among the HSCR cases.

CONCLUSIONS

Our data suggest that genotypes comprising specific pairs of RET haplotypes are associated with predisposition to HSCR either in a simple autosomal recessive manner or in an additive, dose dependent fashion.

Pharmacological treatment of Alzheimer disease: from psychotropic drugs and cholinesterase inhibitors to pharmacogenomics

For the past 20 years the scientific community and the pharmaceutical industry have been searching for treatments to neutralize the devastating effects of Alzheimer disease (AD). During this period important changes in the etiopathogenic concept of AD have occurred and, as a consequence, the pharmacological approach for treating AD has also changed. During the past 2 decades only 3 drugs for AD have been formally approved by the FDA, although in many countries there are several drugs which are currently used as neuroprotecting agents in dementia alone or in combination with cholinesterase inhibitors. The interest of the pharmaceutical industry has also shifted from the cholinergic hypothesis which led to the development of cholinesterase inhibitors to enhance the bioavailability of acetylcholine at the synaptic cleft to a more "molecular approach" based on new data on the pathogenic events underlying neurodegeneration in AD. In our opinion, the pharmacological treatment of AD should rely on a better understanding of AD etiopathogenesis in order to use current drugs that protect the AD brain against deleterious events and/or to develop new drugs specifically designed to inhibit and/or regulate those factors responsible for premature neuronal death in AD. The most relevant pathogenic events in AD can be classified into main categories: primary events (genetic factors, neuronal apoptosis), secondary events (beta-amyloid deposition in senile plaques and brain vessels, neurofibrillary tangles due to hyperphosphorylation of tau proteins, synaptic loss), tertiary events (neurotransmitter deficits, neurotrophic alterations, neuroimmune dysfunction, neuroinflammatory reactions) and quaternary events (excitotoxic reactions, calcium homeostasis miscarriage, free radical formation, primary and/or reactive cerebrovascular dysfunction). All of these pathogenic events are potential targets for treatment in AD. Potential therapeutic strategies for AD treatment include palliative treatment with nonspecific neuroprotecting agents, symptomatic treatment with psychotropic drugs for noncognitive symptoms, cognitive treatment with cognition enhancers, substitutive treatment with cholinergic enhancers to improve memory deficits, multifactorial treatment using several drugs in combination and etiopathogenic treatment designed to regulate molecular factors potentially associated with AD pathogenesis. This review discusses the conventional cholinergic enhancers (cholinesterase inhibitors, muscarinic agonists), noncholinergic strategies that have been developed with other compounds, novel combination drug strategies and future trends in drug development for AD treatment. Stem-cell activation, genetically manipulated cell transplantation, gene therapy and antisense oligonucleotide technology constitute novel approaches for the treatment of gene-related brain damage and neuroregeneration. The identification of an increasing number of genes associated with neuronal dysfunction along the human genome together with the influence of specific allelic associations and polymorphisms indicate that pharmacogenomics will become a preferential procedure for drug development in polygenic complex disorders. Furthermore, genetic screening of the population at risk will help to identify candidates for prevention among first-degree relatives in families with transgenerational dementia.

Platelet ultrastructural morphometry for diagnosis of partial delta-storage pool disease in patients with mild platelet dysfunction and/or thrombocytopenia of unknown origin. A study of 24 cases

BACKGROUND AND OBJECTIVE

Exact diagnosis is sometimes difficult in patients presenting with a slight bleeding diathesis, prolonged bleeding times, non-specific aggregometric abnormalities, and/or mild thrombocytopenia. The objective of this study was to evaluate the use of platelet ultrastructural morphometry in detecting a partial d-storage pool disease in such patients.

DESIGN AND METHODS

Platelets from 52 patients and 15 controls were fixed immediately in glutaraldehyde in White's saline without anticoagulant and processed for transmission electron microscopy. Using computer-assisted morphometry, the size and shape of the platelets were measured, as were the size and number per platelet of the dense- and a-granules. Ultrastructural morphology of the above and other intraplatelet structures was observed.

RESULTS

Twenty-four cases were diagnosed as having a partial d-storage pool disease. Mean platelet area (2.28 microm(2)) and maximum diameter (2.58 microm) were significantly greater in patients than in control subjects (1.64 microm(2) and 2. 25 microm, respectively) but discoid shape was preserved. Mean dense-granule number was decreased, both per platelet and per microm(2) of platelet area (patients 0.22 and 0.09; controls 0.42 and 0.24). Seven patients also had a marked decrease in a-granules, resulting in a significantly lower mean number of granules per microm(2 )(patients 2.43; controls 3.15). Additionally, the patients' platelets had significant increases in both lipid droplets and surface-connected canalicular system.

INTERPRETATION AND CONCLUSIONS

A partial dense-granule deficiency, sometimes associated with partial a-granule deficiency, should be borne in mind faced with patients who have a slight bleeding diathesis, non-specific platelet dysfunction tests and/or mild thrombocytopenia of unknown origin. Platelet ultrastructural morphometry is useful in diagnosing this condition.

[Perfusion SPECT with (99m)Tc-HMPAO in type I diabetics with no background of central neurologic symptoms. A study of activation with acetazolamide]

OBJECTIVE

This study aimed to assess if activation with acetazolamide increases the diagnostic capacity of baseline SPECT with (99m)Tc-HMPAO in the study of brain perfusion in type I diabetic patients with no history of neurological symptoms.

MATERIAL AND METHODS

A baseline SPECT was carried out in 11 diabetes mellitus type I patients with no neurological symptoms with 555 MBq of (99m)Tc-HMPAO; 1 g of acetazolamide was administered during the examination and a second SPECT was obtained 20' later with the same methodology used in the baseline SPECT. The images were visually analyzed. The post-acetazolamide studies were analyzed with (CBS) and without (WBS) baseline image subtraction and both methods were compared.

RESULTS

The baseline SPECT showed 48 hypoperfused cortical areas. The post-acetazolamide SPECT analyzed without baseline image subtraction detected 14 new hypoperfused areas and those analyzed with it detected 26 areas. 69% of the baseline hypoperfused areas were hyporeactive in the WBS analysis and 54% in the CBS analysis.

CONCLUSION

The perfusion SPECT with acetazolamide improves the diagnostic capacity of the baseline perfusion (99m)Tc-HMPAO SPECT, and makes it possible to classify the abnormalities as metabolic or vascular, with a preference for the post-acetazolamide CBS imaging analysis.

[Spatial distribution of sharks captures in the Pacific of Nicaragua and its relationship with several oceanographic variables]

Between August 1995 and August 1997 long line fishing techniques and a bathythermograph were used to correlate some physical variables with the spatial distribution of four shark species in 26 fishing cruises off the Nicaraguan Pacific Coast. They were the thresher (Alopias vulpinus), blue (Prionace glaucea), gray (Carcharhinus falciformis) and hammer (Sphyra lewini). All species concentrated in the southeastern Nicaraguan Pacific, at the seasonal upwelling area of Papagayo Gulf. The range of sea surface temperatures in which the sharks were captured was 25-28 degrees C. We could clearly associate this physical parameter with shark availability. The vertical distribution of the captured sharks suggests that they occupy termocline levels above the 15 degrees C isotherm. Although these species are oceanic, the blue shark was captured in ocean waters over the 1800 m isobar, while the grey and thresher sharks where close to the continental shelf. Body length in decreasing order are: thresher (210-290 cm, SN = 21), blue (60-240 cm, SN = 13) and gray (80-200 cm, SN = 17).

Neuronal correlates of sensory discrimination in the somatosensory cortex

Monkeys are able to discriminate the difference in frequency between two periodic mechanical vibrations applied sequentially to the fingertips. It has been proposed that this ability is mediated by the periodicity of the responses in the quickly adapting (QA) neurons of the primary somatosensory cortex (S1), instead of the average firing rates. We recorded from QA neurons of S1 while monkeys performed the vibrotactile discrimination task. We found that the periodic mechanical vibrations can be represented both in the periodicity and in the firing rate responses to varying degrees across the QA neuronal population. We then computed neurometric functions by using both the periodicity and the firing rate and sought to determine which of these two measures is associated with the psychophysical performance. We found that neurometric thresholds based on the firing rate are very similar to the animal's psychometric thresholds whereas neurometric thresholds based on periodicity are far lower than those thresholds. These results indicate that an observer could solve this task with a precision similar to that of the monkey, based only on the firing rate produced during the stimulus periods.

Comparison of drought tolerance in nitrogen-fixing and inorganic nitrogen-grown common beans

In this work, we evaluated how the use of alternative N sources affects drought-stress tolerance in common beans. To this end, plants were cultivated employing either N(2) fixation or two levels of inorganic nitrogen: 1 mM NH(4)NO(3) (limiting) or 10 mM NH(4)NO(3) (sufficient). Drought was imposed by withholding watering at 30 days after planting (DAP) - coinciding with flowering. At 20 DAP, growth and N content were significantly higher in NH(4)NO(3)-sufficient plants than in N(2)-fixing and NH(4)NO(3)-limited beans. At later times, only N(2)-fixing and NH(4)NO(3)-sufficient plants continued assimilating N and growing, with the NH(4)NO(3)-sufficient plants being consistently bigger. After 10 days of stress (40 DAP), desiccation was evident, but only NH(4)NO(3)-sufficient plants suffered drought-induced senescence. After 20 days of stress (50 DAP), N content increased in NH(4)NO(3)-sufficient but not in N(2)-fixing beans, despite the latter's lesser state of wilt. Pod dry weight dropped 43% in NH(4)NO(3)-sufficient beans with respect to well-watered plants, while remaining constant in N(2)-fixing beans. Under drought conditions, the number of pods limited pod yield regardless of the nitrogen source used; nevertheless, the translocation of soluble matter to pods continued in both NH(4)NO(3)-sufficient and N(2)-fixing beans. We conclude that common beans grown under conditions of N(2) fixation were more drought tolerant than those provided with sufficient levels of NH(4)NO(3). The most stress-sensitive traits in these plants were the incorporation of N into their shoots and the number of pods remaining on them.