Identification of Malassezia species isolated from Iranian seborrhoeic dermatitis patients

BACKGROUND AND OBJECTIVES

In recent years, the genus Malassezia has come to be considered important in the etiology of seborrhoeic dermatitis (SED). The aim of present study was identification of Malassezia species on the lesions of Iranian SED patients.

METHODS

100 patients with SED were enrolled in the study. The patients were evaluated both clinically for the severity of SED and microscopically for the presence of the yeast Malassezia. Diagnosis of Malassezia was made after the yeast Malassezia was microscopically observed on skin scales stained with methylene blue. All samples were also cultivated on Leeming and Notman and Sabouraud's dextrose agar culture media. The agar plates were incubated at 32 degrees C for 2 weeks and evaluated for the existence of growth every day for one week. Identification of isolated yeast was based on morphological and physiological characteristics.

RESULTS

From 100 patients with SED, 60% were female. The age range was 12-65 years with median 27.3 years. The highest prevalence of SED was seen in 20-29 years age group. 59% and 41% of patients had local and generalized lesions, respectively. 58% of patients showed lesion on scalp. Microscopic examination of skin scales was positive in 100% of SED lesions. 96% of patients showed more than 1-3 yeasts in each microscopic field whereas only 4% patients showed 1-3 yeasts in whole slide. Totally, 77% of the specimens yielded Malassezia in culture. Malassezia globosa was the most commonly isolated Malassezia species (55.8%). Malassezia globosa had also most frequencies on scalp and face lesions. Malassezia furfur had most frequency on trunk lesions.

CONCLUSION

The results of our study showed high recovery rate of Malassezia species on lesions of patients with SED. So it might be playing a causative role in the etiology of this disease.

Oxytocin and its receptors are synthesized in the rat vasculature

Produced and released by the heart, oxytocin (OT) acts on its cardiac receptors to decrease the cardiac rate and force of contraction. We hypothesized that it might also be produced in the vasculature and regulate vascular tone. Consequently, we prepared acid extracts of the pulmonary artery and vena cava of female rats. OT concentrations in dog and sheep aortae were equivalent to those of rat aorta (2745 +/- 180 pg/mg protein), indicating that it is present in the vasculature of several mammalian species. Reverse-phase HPLC of aorta and vena cava extracts revealed a single peak corresponding to the amidated OT nonapeptide. Reverse-transcribed PCR confirmed OT synthesis in these tissues. Using the selective OT receptor ligand compound VI, we detected a high number of OT-binding sites in the rat vena cava and aorta. Furthermore, OT receptor (OTR) mRNA was found in the vena cava, pulmonary vein, and pulmonary artery with lower levels in the aorta, suggesting vessel-specific OTR distribution. The abundance of OTR mRNA in the vena cava and pulmonary vein was associated with high atrial natriuretic peptide mRNA. In addition, we have demonstrated that diethylstilbestrol treatment of immature female rats increased OT significantly in the vena cava but not in the aorta and augmented OTR mRNA in both the aorta (4-fold) and vena cava (2-fold), implying regulation by estrogen. Altogether, these data suggest that the vasculature contains an intrinsic OT system, which may be involved in the regulation of vascular tone as well as vascular regrowth and remodeling.

Rat heart: a site of oxytocin production and action

We report here that the rat heart is a site of oxytocin (OT) synthesis and release. Oxytocin was detected in all four chambers of the heart. The highest OT concentration was in the right atrium (2128 +/- 114 pg/mg protein), which was 19-fold higher than in rat uterus but 3.3-fold lower than in the hypothalamus. OT concentrations were significantly greater in the right and left atria than in the corresponding ventricles. Furthermore, OT was released into the effluent of isolated, perfused rat heart (34.5 +/- 4.7 pg/min) and into the medium of cultured atrial myocytes. Reverse-phase HPLC purification of the heart extracts and heart perfusates revealed a main peak identical with the retention time of synthetic OT. Southern blots of reverse transcription-PCR products from rat heart revealed gene expression of specific OT mRNA. OT immunostaining likewise was found in atrial myocytes and fibroblasts, and the intensity of positive stains from OT receptors paralleled the atrial natriuretic peptide stores. Our findings suggest that heart OT is structurally identical, and therefore derived from, the same gene as the OT that is primarily found in the hypothalamus. Thus, the heart synthesizes and processes a biologically active form of OT. The presence of OT and OT receptor in all of the heart's chambers suggests an autocrine and/or paracrine role for the peptide. Our finding of abundant OT receptor in atrial myocytes supports our hypothesis that OT, directly and/or via atrial natriuretic peptide release, can regulate the force of cardiac contraction.