Showing papers by "Autonomous University of Barcelona published in 1997"

Outcome of cord-blood transplantation from related and unrelated donors

Abstract: Background Cord-blood banks have increased the use of cord-blood transplantation in patients with hematologic disorders. We have established a registry containing information on the outcome of cord-blood transplantation. Methods We sent questionnaires to 45 transplantation centers for information on patients receiving cord-blood transplants from 1988 to 1996. Reports on 143 transplantations, performed at 45 centers, were studied, and the responses were analyzed separately according to whether the donor was related or unrelated to the recipient. Results Among 78 recipients of cord blood from related donors, the Kaplan–Meier estimate of survival at one year was 63 percent. Younger age, lower weight, transplants from HLA-identical donors, and cytomegalovirus-negative serologic results in the recipient were favorable prognostic factors. Graft-versus-host disease of at least grade II occurred at estimated rates of 9 percent in 60 recipients of HLA-matched cord blood and 50 percent in 18 recipients of HLA-misma...

Identification of a Genetic Locus for Familial Atrial Fibrillation

Abstract: Background Atrial fibrillation, the most common sustained cardiac-rhythm disturbance, affects over 2 million Americans and accounts for one third of all strokes in patients over 65 years of age. The molecular basis for atrial fibrillation is unknown, and palliative therapy is used to control the ventricular rate and prevent systemic emboli. We identified a family of 26 members of whom 10 had atrial fibrillation that segregated as an autosomal dominant disease. We subsequently identified two additional families in which the disease was linked to the same locus. Methods We screened the human genome with 300 polymorphic dinucleotide-repeat markers using an unconventional strategy of pooling the DNA samples into two groups (affected and unaffected), which reduced the sample size by approximately 90 percent, before performing linkage analysis to map the locus. This made it possible to identify potential loci within a few weeks. Results The lod scores for markers D10S569 and D10S607, located at 10q22–q24, were ...

Primary progressive multiple sclerosis.

Abstract: Patients with multiple sclerosis who develop progressive disability from onset without relapses or remissions pose difficulties in diagnosis, monitoring of disease activity and treatment. There is a need to define the diagnostic criteria for this group more precisely and, in particular, to describe a comprehensive battery of investigations to exclude other conditions. The mechanisms underlying the development of disability and the role of MRI in monitoring disease activity in this clinical subgroup require elucidation, particularly in view of the lack of change on conventional imaging in the presence of continuing clinical deterioration. The prognosis is poor and there are currently no treatment trials for this form of the disease.

Heterogeneous Photocatalysis for Purification, Decontamination and Deodorization of Air

Abstract: A research review of gas–solid heterogeneous photocatalysis is presented, ranging from details of pioneering works, which dealt with basic phenomena like oxygen and water vapor adsorption, to recent applications to pollutant removal in contaminated atmospheres. Special interest is taken in describing the different reactor configurations studied so far in this emerging and promising field. © 1997 SCI

The generalized Cattaneo equation for the description of anomalous transport processes

Abstract: The Cattaneo equation, which describes a diffusion process with a finite velocity of propagation, is generalized to describe anomalous transport. Three possible generalizations are proposed, each one supported by a different scheme: continuous time random walks, non-local transport theory, and delayed flux-force relation. The properties of these generalizations are studied in both the long-time and the short-time regimes. In the long-time limit, we recover the mean-square displacement which is characteristic for these anomalous processes. As expected, the short-time behaviour is modified in comparison to generalized diffusion equations.

Cloning of a gene highly overexpressed in cancer coding for a novel KH-domain containing protein.

Abstract: In a previous large scale screen for differentially expressed genes in pancreatic cancer, we identified a gene highly overexpressed in cancer encoding a novel protein with four K-homologous (KH) domains. KH-domains are found in a subset of RNA-binding proteins, including pre-mRNA-binding (hnRNP) K protein and the fragile X mental retardation gene product (FMR1). By fluorescence in situ hybridization (FISH) the identified gene named koc (KH domain containing protein overexpressed in cancer) was assigned to chromosome 7p11.5. Two pseudogenes were localised on chromosome 6 and 11. The cloned koc cDNA has a 250 bp 5′-UTR, a 1740 bp ORF and a 2168 bp 3′-UTR. The AU-rich 3′-untranslated region of koc contains eight AUUUA and four AUUUUUA reiterated motifs. The deduced koc protein with 580 amino-acids has a relative molecular mass (Mr) of approximately 65 000 (65 K). The koc transcript is highly overexpressed in pancreatic cancer cell lines and in pancreatic cancer tissue as compared to both, normal pancreas and chronic pancreatitis tissue. High levels of expression were as well found in tissue samples of other human tumours. As the KH domain has been shown to be involved in the regulation of RNA synthesis and metabolism, we speculate that koc may assume a role in the regulation of tumour cell proliferation by interfering with transcriptional and or posttranscriptional processes. However, the precise role of koc in human tumour cells is unknown and remains to be elucidated.

Candidemia in non-neutropenic critically ill patients: analysis of prognostic factors and assessment of systemic antifungal therapy

Abstract: Objective: To determine the incidence and prognosis of candidemia in non-neutropenic critically ill patients, to define mortality-related factors, and to evaluate the results of systemic antifungal therapy. Design: A prospective multicenter survey in which medical and/or surgical intensive care units (ICUs) in 28 hospitals in Spain participated. Patients: All critically ill patients with positive blood cultures for Candida species admitted to the participating ICUs over a 15-month period were included. Interventions: Candidemia was defined as the presence of at least one positive blood culture containing Candida species. The follow-up period was defined as the time elapsed from the first positive blood culture for Candida species to discharge or death during hospitalization. Antifungal therapy was considered to be “early” when it was administered within 48 h of the date when the first positive blood culture was obtained and “late” when it was administered more than 48 h after the first positive blood culture. Measurements and main results: Candidemia was diagnosed in 46 patients (mean age 59 years), with an incidence of 1 critically ill patient per 500 ICU admissions. The species most frequently isolated were Candida albicans (60%) and C. parapsilosis (17%). Fluconazole alone was given to 27 patients, amphotericin B alone to 10, and sequential therapy to 6. Three patients did not receive antifungal therapy. The overall mortality was 56% and the attributable mortality 21.7%. In the univariate analysis, mortality was significantly associated with a higher Acute Physiology and Chronic Health Evaluation (APACHE) II score at the onset of candidemia (p=0.04) and with the time elapsed between the episode of candidemia and the start of antifungal therapy 48 h or more later (p<0.02). Patients with an APACHE II score lower than 21 at the onset of candidemia had a higher probability of survival than patients who were more seriously ill (p=0.04). Patients with “early” antifungal therapy (≤48 h between the onset of candidemia and the start of antifungal therapy) had a higher probability of survival compared with patients with late therapy (p=0.06). No significant differences were noted between the two groups on different antifungal therapy. Conclusions: The incidence of candidemia in ICU patients was very low. An APACHE II score >20 at the time of candidemia was associated with a higher mortality. Further studies with a large number of patients are needed to assess the effect of early antifungal therapy on the decrease in mortality associated with candidemia and to determine the appropriate dosage of fluconazole and duration of treatment.

Socioeconomic differences in cancer survival: a review of the evidence.

Abstract: In the discussion of social inequalities in health there has been much debate on the role of medical care. Large differences in cancer incidence and mortality from cancer have been consistently observed. To understand the potential importance of socioeconomic differences in prompt detection and treatment of cancer it is essential to have data on cancer survival. These have been examined less extensively than differences in cancer incidence. We have reviewed 42 studies on social class differences in cancer survival. Twenty-three studies were conducted in North America, and 15 in western European countries. Twenty-three studies were carried out through population-based cancer registries and 17 through hospitals or hospital-based registries. Seven studies examined survival differences for multiple cancer sites. Social class differences in cancer survival appear remarkably general. Patients in low social classes had consistently poorer survival than those in high social classes. The magnitude of the differences for most cancer sites was fairly narrow, with most relative risks falling between 1 and 1.5. The widest differences were observed for cancers of good prognosis and specifically cancers of the female breast, corpus uteri, bladder and colon. The pattern of the social differences in survival did not vary consistently by sex, country, or source of the study population and did not depend on the socioeconomic indicator used.

Perfil da automedicação no Brasil

Abstract: INTRODUCAO: Os dados apresentados fazem parte de um estudo multicentrico sobre automedicacao na America Latina realizado pela Organizacao Mundial de Saude (OMS). Objetivou-se tracar um perfil da automedicacao atraves da analise da procura de medicamentos em farmacias sem prescricao medica ou aconselhamento do farmaceutico/balconista. MATERIAL E METODO: As especialidades farmaceuticas foram classificadas pelo codigo "Anatomical Therapeutical Classification" e analisadas sob quatro aspectos qualitativos: valor intrinseco, essencialidade (lista da OMS e Relacao Nacional de Medicamentos Essenciais (RENAME), combinacao em dose fixa e necessidade de prescricao medica. RESULTADOS: Foram solicitadas 5.332 especialidades farmaceuticas (785 diferentes principios ativos), sendo 49,5% combinacoes em dose fixas, 53,0% de valor intrinseco nao elevado, 44,1% sujeitos a prescricao medica, 71,0% nao essenciais e 40,0% baseados em prescricoes medicas anteriores. Os medicamentos mais solicitados foram analgesicos (17,3%), descongestionantes nasais (7,0%), antiinflamatorio/antireumatico e antiinfecciosos de uso sistemico, ambos com 5,6%. CONCLUSOES: Os dados sugerem que a automedicacao no Brasil reflete as carencias e habitos da populacao, e consideravelmente influenciada pela prescricao medica e tem a sua qualidade prejudicada pela baixa seletividade do mercado farmaceutico.

Carboplatin-based versus cisplatin-based chemotherapy in the treatment of surgically incurable advanced bladder carcinoma

Abstract: BACKGROUND The carboplatin-based chemotherapeutic regimen M-CAVI (methotrexate, carboplatin, and vinblastine) is active against bladder carcinoma and can be administered to patients who are ineligible to receive cisplatin or doxorubicin. The authors designed a randomized study to evaluate whether M-CAVI offers a therapeutic advantage over the cisplatin-based regimen M-VAC (methotrexate, vinblastine, doxorubicin, and cisplatin) in the treatment of patients with surgically incurable advanced bladder carcinoma. METHODS Patients with surgically incurable advanced bladder carcinoma were enrolled on a randomized trial comparing M-CAVI, which consists of carboplatin (300 mg/m2 on Day 2, adjusted using Calvert's formula for an area under the curve of 5), methotrexate (30 mg/m2 on Days 1, 15, and 22), and vinblastine (3 mg/m2 on Days 2, 15, and 22) administered every 28 days, versus standard M-VAC. The eligibility criteria included histologically proven bladder carcinoma, surgically incurable disease, and no prior chemotherapy. Patients were treated until disease progression or unacceptable toxicity occurred. RESULTS From January 1989 to January 1994, 47 assessable patients were included. Seventeen patients had lymph node disease and 30 had distant metastatic disease. Twenty-three patients were randomized to receive M-CAVI and 24 to receive M-VAC. Patient characteristics in the two groups were similar. Overall response rates were 39% (95% confidence interval [CI], 20-62%) for M-CAVI and 52% (95% CI, 30-73%) for M-VAC (P = 0.3), with 3 complete responses observed among patients treated with M-VAC and none among those in the M-CAVI group. M-VAC was associated with more gastrointestinal toxicity, stomatitis, alopecia, and Grade 4 neutropenia than M-CAVI. One toxicity-related death occurred in the M-VAC group. There was a statistically significant difference in median disease-related survival time favoring M-VAC (16 months; range, 6 to 22+) versus M-CAVI (9 months; range, 6 to 14+) (P = 0.03). CONCLUSIONS M-CAVI is less toxic but less active than M-VAC in the treatment of patients with advanced bladder carcinoma. Carboplatin-based regimens in which carboplatin is administered at the dose range used in the current study should be reserved for patients who cannot tolerate cisplatin treatment. Further research is required to assess the impact of high dose carboplatin in the treatment of this disease. Cancer 1997; 80:1966-72. © 1997 American Cancer Society.

Recombination and Gene Flux Caused by Gene Conversion and Crossing Over in Inversion Heterokaryotypes

Abstract: A theoretical analysis of the effects of inversions on recombination and gene flux between arrangements caused by gene conversion and crossing over was carried out. Two different mathematical models of recombination were used: the Poisson model (without interference) and the Counting model (with interference). The main results are as follows. (1) Recombination and gene flux are highly site-dependent both inside and outside the inverted regions. (2) Crossing over overwhelms gene conversion as a cause of gene flux in large inversions, while conversion becomes relatively significant in short inversions and in regions around the breakpoints. (3) Under the Counting model the recombination rate between two markers depends strongly on the position of the markers along the inverted segment. Two equally spaced markers in the central part of the inverted segment have less recombination than if they are in a more extreme position. (4) Inversions affect recombination rates in the uninverted regions of the chromosome. Recombination increases in the distal segment and decreases in the proximal segment. These results provide an explanation for a number of observations reported in the literature. Because inversions are ubiquitous in the evolutionary history of many Drosophila species, the effects of inversions on recombination are expected to influence DNA variation patterns.

K-ras mutations in mucinous ovarian tumors : A clinicopathologic and molecular study of 95 cases

Abstract: BACKGROUND To assess the role of K-ras mutations in the pathogenesis of mucinous ovarian tumors, the authors looked for K-ras point mutations at codons 12 and 13 in 95 mucinous ovarian neoplasms. The results were subsequently correlated with the clinicopathologic data. METHODS Benign, borderline, and malignant mucinous ovarian tumors were identified microscopically. DNA was extracted from formalin fixed, paraffin embedded tissue, and target sequences were amplified in vitro by polymerase chain reaction. Mutations were detected by the presence of restriction fragment length polymorphisms artificially introduced by the use of mutant amplimers. In tumors containing areas that exhibited different histologic grade, precise microdissection of each of these areas was performed. The results were correlated with the clinical data and the morphologic features of the neoplasms. RESULTS The overall frequency of codon 12/13 ras gene mutations was 68%. Codon 12 point mutations were present in 63% of the cases (55.7% of mucinous cystadenomas, 73% of borderline tumors, and 85% of carcinomas). Codon 13 mutations were detected in 11.5% of the tumors (five cystadenomas, three borderline tumors, and three carcinomas). Eight tumors (three benign, two borderline, and three malignant) exhibited mutations at codons 12 and 13. In 12 of the 15 tumors with 2 areas showing different histologic grade, identical point mutations were detected separately in both areas. CONCLUSIONS The results of this study confirm that K-ras mutations do occur in benign and particularly in malignant mucinous ovarian tumors. The authors' findings support the hypothesis that K-ras mutational activation is an early event in mucinous ovarian tumorigenesis. Cancer 1997; 79:1581-6. © 1997 American Cancer Society.

Neonatal Handling and Environmental Enrichment Effects on Emotionality, Novelty/Reward Seeking, and Age-Related Cognitive and Hippocampal Impairments: Focus on the Roman Rat Lines

Abstract: Roman high- and low-avoidance (RHA/Verh and RLA/Verh) rats are selected and bred for extreme divergence in two-way active avoidance acquisition. In addition, compared to RLA/Verh rats, RHA/Verh rats are (behaviorally and physiologically) less anxious or reactive to stressors, show increased novelty (sensation)-seeking behavior as well as a higher preference for rewarding substances, and are usually less efficient in learning tasks not involving shock administration. The present article reviews evidence showing that neonatal handling and/or environmental enrichment leads to enduring effects (their magnitude frequently depending upon the rat line) on those behaviors. For example, it has been found that neonatal handling reduces most of the (behavioral and physiological) signs of emotionality/anxiety in RLA/Verh rats, while environmental enrichment increases their novelty seeking (also the case with RHA/Verh rats), saccharin and ethanol intake, and sensitivity to amphetamine. Finally, initial results (currently being further elaborated upon) support a preventive action of both environmental treatments on age-related impairments in learning a spatial, water maze task as well as on hippocampal neuronal atrophy.

PD153035, a tyrosine kinase inhibitor, prevents epidermal growth factor receptor activation and inhibits growth of cancer cells in a receptor number-dependent manner.

Abstract: PD153035 is reported to be a specific and potent inhibitor of the epidermal growth factor (EGF) receptor tyrosine kinase and, to a lesser degree, of the closely related HER2/neu receptor. We show that PD153035 inhibits EGF-dependent EGF receptor phosphorylation and suppresses the proliferation and clonogenicity of a wide panel of EGF receptor-overexpressing human cancer cell lines. EGF receptor autophosphorylation in response to exogenous EGF was completely inhibited at PD153035 concentrations of >75 nM in cells overexpressing the EGF receptor. In contrast, PD153035 only reduced heregulin-dependent tyrosine phosphorylation in HER2/neu-overexpressing cell lines at significantly higher concentrations (1400-2800 nM). PD153035 exposure did not affect the expression of either EGF receptors or HER2/neu. PD153035 caused a dose-dependent growth inhibition of EGF receptor-overexpressing cell lines at low micromolar concentrations, and the IC50 in monolayer cultures was less than 1 microM in most cell lines tested. At doses of up to 2.5 microM, the IC50 for HER2/neu-overexpressing cells was not reached. In colony-forming assays, the PD153035 growth-inhibitory activity in cultures driven by endogenous (autocrine) ligand was correlated with EGF receptor number, with higher activity in cells expressing higher numbers of EGF receptors and only minimal activity in cells expressing normal numbers of EGF receptors but high HER2/neu levels. PD153053 also abolished all growth effects mediated by the addition of exogenous EGF; this condition could be reversed upon removal of the compound. Cotreatment with C225, an anti-EGF receptor-blocking monoclonal antibody, further enhanced the antitumor activity of PD153035, suggesting mechanisms of action for C225 other than competition with ligand binding. This latter finding also suggests that combined anti-EGF receptor strategies may be of enhanced benefit against tumors with high levels of EGF receptor expression.

Biosystematics of entomopathogenic nematodes: current status, protocols and definitions.

Abstract: COST Action 819: Entomopathogenic nematodes, supercedes Action 812: Cold active lines of insect parasitic nematodes in Agriculture and Biotechnology. It functions in the field of Agriculture and Biotechnology and began in July 1994 and will end in May, 1999. The main objective is to combine interrelated European expertise to increase the use of entomopathogenic nematodes (EPNs) in integrated pest management and to reduce the need for chemical control. Coordination of the Action is the responsibility of a management committee in accordance with a Memorandum of Understanding, which has been signed by representatives of 17 countries: Austria, Belgium, Czech Republic, Finland, France, Germany, Hungary, Ireland, Italy, The Netherlands, Norway, Poland, Portugal, Spain, Sweden, Switzerland and the UK. A research institute in Israel is also participating. Over 40 research institutions and 10 commercial companies participate in Action 819. The EU funding meets the costs related to coordination including the scientific secretariat, workshops, management committee and working group meetings, publications, short term scientific missions and evaluations.

Cortisol and glucose responses after acute stress by net handling in the sparid red porgy previously subjected to crowding stress

Abstract: In red porgy Pagrus pagrus subjected to 3 weeks of chronic stress by crowding, plasma cortisol remained significantly higher in crowded fish compared to controls. There was no significant effect of crowding on plasma glucose levels. When the crowded fish were subjected to an acute handling the plasma cortisol response was similar to that of the uncrowded fish. No significant differences were found between the groups. The changes in plasma glucose following acute handling were also similar in both crowded and uncrowded fish.

Flowering phenology, floral traits and pollinator composition in a herbaceous Mediterranean plant community

Abstract: The relationships between flowering plants and their insect visitors were studied in a Mediterranean grassland in north-east Spain. Floral traits (size, shape, symmetry, and colour), floral rewards (pollen and nectar), flowering period, and floral visitors were recorded for the 17 most abundant plants in the community. Flowering was year-round, but most species flowered in spring. The three species that flowered after spring had small flowers, but the distribution of floral features (including rewards offered) did not show a strong seasonality. Ants contributed 58.5% to the flower visits recorded. Other frequent visitors were beetles (12%), flies (9.5%), honey bees (6.4%), wild bees (6.4%), and wasps (5.2%). Honey bees were most abundant in April, wild bees from April to July, beetles from May to July, and ants from May to September. The lack of tight plant-insect associations was the rule, with most plant species visited by a rather diverse array of insects representing two or more orders. The plant species having narrower spectra of visitors either had flower rewards exposed or attracted mostly illegitimate visitors. By means of correspondence analysis four categories of plants were defined according to their main groups of visitors: (1) honey bees and large wild bees; (2) large wild bees; (3) ants and beetles; and (4) beetles and small-sized bees. The Mantel test was used to calculate correlations among four matrices representing similarities in visitors attracted, floral morphological traits, pollen-nectar rewards, and blooming time, respectively. In spite of seasonality shown by the different insect groups, results indicate that the observed patterns of visitor distribution among plants were most affected by pollen-nectar rewards.

Changes in Myocardial Electrical Impedance Induced by Coronary Artery Occlusion in Pigs With and Without Preconditioning: Correlation With Local ST-Segment Potential and Ventricular Arrhythmias

Abstract: Background Myocardial ischemia increases tissue electrical resistivity leading to cell-to-cell uncoupling, and this effect is delayed by ischemic preconditioning in isolated myocardium. Alterations in myocardial resistivity elicited by ischemia in vivo may influence arrhythmogenesis and local ST-segment changes, but this is not well known. Methods and Results Myocardial impedance (resistivity [Ω · cm] and phase angle [°]), epicardial ST segment, and ventricular arrhythmias were analyzed during 4 hours of coronary artery occlusion in 11 anesthetized open-chest pigs; these were compared with 13 other pigs submitted to a similar coronary occlusion preceded by ischemic preconditioning. Myocardial resistivity rose slowly during the first 34±7 minutes of occlusion (237±41 to 359±59 Ω · cm), increased rapidly to 488±100 Ω · cm at 60 minutes, and reached a plateau value (718±266 Ω · cm, ANOVA; P<.01) at 150±69 minutes. By contrast, phase-angle changes began after 17 minutes of ischemia (−3.0±1.6° to −4.2±1.2° at ...

Chromosome studies in human sperm nuclei using fluorescence in-situ hybridization (FISH)

Abstract: The use of chromosome specific DNA probes labelled with fluorochromes and especially the combination of several probes has been used to indirectly study the chromosome constitution of decondensed sperm nuclei by fluorescence in-situ hybridization (FISH), and has allowed to include this test in the protocol of study of infertile males. Still, if the test is to be valid, several strict conditions must be met, and some specific characteristics have to be taken into account. This becomes evident when comparing earlier results with more recent ones. The basic technical factors to be taken into account are the methods of chromatin decondensation, the number of spermatozoa and of individuals to study, the use of internal controls, the scoring criteria, the specificity of the probes and the possible existence of polymorphisms that may interfere with the detection of fluorescent signals. In the last 7 or 8 years, a large number of papers has been published, describing the incidence of aneuploidies in controls, in individuals in whom a tendency to non-disjunction was suspected and in infertile males. Studies in controls have shown a considerable intra- and inter-individual variability in the frequency of aneuploidies, the tendency of some chromosomes to undergo non-disjunction (chromosome 21 and the sex chromosomes) and the importance of alpha-satellite polymorphisms when using centromere probes. In the control population, the frequency of aneuploidy per haploid set has been estimated at approximately 6%. The incidence of aneuploidies in sperm nuclei for some of the chromosomes more frequently involved in trisomies is considerably higher than the incidence of these trisomies established through epidemiological data using the global incidence of chromosome abnormalities during the peri-implantation stage. In infertile males and in males with sex-chromosome abnormalities (usually with very low numbers of spermatozoa) the results show an increased incidence of sex chromosome aneuploidies and diploid (multi-aneuploid?) sperm nuclei. The results could be related to the higher incidence of chromosome abnormalities (especially sex-chromosome aneuploidies) observed in children conceived by intracytoplasmic sperm injection (ICSI).

Primary Sjögren's syndrome and associated lung disease: CT findings in 50 patients

Abstract: OBJECTIVE: We prospectively evaluated the high-resolution CT findings in 50 nonsmoking patients with proven primary Sjogren's syndrome. CONCLUSION: High-resolution CT is a sensitive technique in assessing pulmonary involvement in patients with primary Sjogren's syndrome. Interstitial lung disease and bronchiolar inflammatory changes are common abnormal findings seen on CT scans in primary Sjogren's syndrome.

Theoretical Study of the Low-Barrier Hydrogen Bond in the Hydrogen Maleate Anion in the Gas Phase. Comparison with Normal Hydrogen Bonds

Abstract: Relative strengths of normal and low-barrier hydrogen bonds (LBHBs) in the gas phase were analyzed by means of quantum-mechanical and thermodynamic calculations on the mesaconic/citraconic and several maleic/fumaric cis/trans isomerization equilibria. All geometries were fully optimized with correlation effects included via second-order Moller−Plesset perturbation theory. The cis isomer of the maleic monoanion (also known as hydrogen maleate) is greatly stabilized in the gas phase owing to the formation of an intramolecular low-barrier hydrogen bond more than 20 kcal/mol stronger, in free energy terms, than the corresponding normal intramolecular hydrogen bond in maleic diacid. The very short internuclear distance (2.41 A) obtained at the MP2 level between the hydrogen donor and the hydrogen acceptor in hydrogen maleate, as well as the high value of the NMR chemical shift for the participating proton, are two other characteristics experimentally attributed to the formation of an LBHB. The transition state...