Academic Impact of Qualitative Studies in Healthcare: Bibliometric Analysis

Context

Although qualitative studies are becoming more appreciated in healthcare, the number of publications of quality studies remains low. Little is known about the frequency and characteristics of citation in qualitative studies.

Objective

To compare the academic impact of qualitative studies to that of two quantitative studies: systematic reviews and randomized controlled trials.

Methods

Publications in BMJ between 1997 and 2006 (BMJ’s median impact factor was 7.04 during this period) employing qualitative methods were matched to two quantitative studies appearing the same year using PubMed. Using Web of Science, citations within a 24-month publication period were determined. Additionally, three hypotheses were examined: qualitative studies are 1) infrequently cited in original articles or reviews; 2) rarely cited by authors in non-English-speaking countries; and 3) more frequently cited in non-medical disciplines (e.g., psychology or sociology).

Results

A total of 121 qualitative studies, 270 systematic reviews, and 515 randomised controlled trials were retrieved. Qualitative studies were cited a total of 1,089 times, with a median of 7.00 times (range, 0–34) for each study. Matched systematic reviews and randomized controlled trials were cited 2,411times and 1,600 times, respectively. With respect to citing documents, original articles and reviews exceeded 60% for each study design. Relative to quantitative studies, qualitative studies were cited more often by authors in English-speaking countries. With respect to subject area, medical disciplines were more frequently cited than non-medical disciplines for all three study designs (>80%).

Conclusion

The median number of citations for qualitative studies was almost the same as the median of BMJ’s impact factor during the survey period. For a suitable evaluation of qualitative studies in healthcare, it will be necessary to develop a reporting framework and include explicit discussions of clinical implications when reporting findings. Coordination between researchers and editors will be needed to achieve this goal.     

Production of Erythritol by n-Alkane-grown Yeasts

In the course of study on citric acid fermentation by Candida zeylanoides, in which n-alkane (a mixture of C–12 to C–15) was used as the sole source of carbon, we found that a polyol-like substance was accumulated when the medium-pH fell down to below 4.0. This was isolated in crystalline forms and identified as meso-erythritol. Comparing erythritol production among fifty yeast strains, Candida zeylanoides, particularly its glycerol-requiring mutant KY 6166, was found to be an excellent producer.

Erythritol production was also observed with ethanol or acetic acid as the sole carbon source but not with glucose. An efficient condition for large production of erythritol was to keep the medium-pH at low level (2.5 to 4.0) and the concentration of NaCl or KCl at high level (1 to 3%). Under conditions established in this work, more than 55 mg/ml of erythritol was successfully produced in 120 hr incubation in 300-ml flasks, which corresponded to 55% of the alkane used.     

A Novel Nectin-mediated Cell Adhesion Apparatus That Is Implicated in Prolactin Receptor Signaling for Mammary Gland Development

Mammary gland development is induced by the actions of various hormones to form a structure consisting of collecting ducts and milk-secreting alveoli, which comprise two types of epithelial cells known as luminal and basal cells. These cells adhere to each other by cell adhesion apparatuses whose roles in hormone-dependent mammary gland development remain largely unknown. Here we identified a novel cell adhesion apparatus at the boundary between the luminal and basal cells in addition to desmosomes. This apparatus was formed by the trans-interaction between the cell adhesion molecules nectin-4 and nectin-1, which were expressed in the luminal and basal cells, respectively. Nectin-4 of this apparatus further cis-interacted with the prolactin receptor in the luminal cells to enhance the prolactin-induced prolactin receptor signaling for alveolar development with lactogenic differentiation. Thus, a novel nectin-mediated cell adhesion apparatus regulates the prolactin receptor signaling for mammary gland development.     

Spatial heterogeneity in induced defense of Brachionus calyciflorus within a single lake caused by a bed of floating-leaved macrophyte Trapa species

Limnology - While induced defense of aquatic organisms against predators has been considerably studied by both laboratory and field research, our understanding is still limited about, for example,...     

Effects of hydrogen bonds in association with flavin and substrate in flavoenzyme d-amino acid oxidase. The catalytic and structural roles of Gly313 and Thr317.

According to the three-dimensional structure of a porcine kidney D-amino acid oxidase-substrate (D-leucine) complex model, the G313 backbone carbonyl recognizes the substrate amino group by hydrogen bonding and the side-chain hydroxyl of T317 forms a hydrogen bond with C(2)=O of the flavin moiety of FAD [Miura et al. (1997) J. Biochem. 122, 825-833]. We have designed and expressed the G313A and T317A mutants and compared their enzymatic and spectroscopic properties with those of the wild type. The G313A mutant shows decreased activities to various D-amino acids, but the pattern of substrate specificity is different from that of the wild type. The results imply that the hydrogen bond between the G313 backbone carbonyl and the substrate amino group plays important roles in substrate recognition and in defining the substrate specificity of D-amino acid oxidase. The T317A mutant shows a decreased affinity for FAD. The steady-state kinetic measurements indicate diminished activities of T317A to substrate D-amino acids. The transient kinetic parameters measured by stopped-flow spectroscopy revealed that T317 plays key roles in stabilizing the purple intermediate, a requisite intermediate in the oxidative half-reaction, and in enhancing the release of the product from the active site, thereby optimizing the overall catalytic process of D-amino acid oxidase.     

Transformation of Polyoxins D,E, and F with Sodium Bisulfite

Polyoxins D, E, and F which possess 5-carboxyuracil as the nucleobase were reacted selectively with sodium bisulfite at pH 4.0 resulting in facile decarboxylation to afford corresponding 5,6-dihydrouracil-6-sulfonates and uracil type polyoxins (polyoxins L, M, and K) in good yield. The former compounds were also converted to the latter almost quantitatively with mild alkali treatment. Biological activities of the transformed compounds were described.     

The conversion of phosphoserine residues to selenocysteine residues on an opal suppressor tRNA and casein

This study has been undertaken in order to elucidate the mechanisms of incorporation of Se into glutathione peroxidase (GSHPx), in which selenocysteine corresponds to the opal termination codon UGA on the mRNA. We studied the above mechanisms using an opal suppressor tRNA, prepared from bovine liver, and casein as a model protein for the GSHPx apo-enzyme which might contain phosphoserine. The results showed that opal suppressor tRNA did not accept selenocysteine (lower than 0.1 mmol/mol) under the standard conditions. A trace amount of phosphoseryl-tRNA was converted to selenocysteyl-tRNA by incubation with H2Se and some enzymes. Meanwhile, a number of phosphoserine residues in casein were converted to selenocysteine residues by incubation with H2Se and enzymes. These results suggest that opal suppressor tRNA plays a role in synthesizing GSHPx via co- and/or post-translational mechanisms.