Dimorphism in Pathogenic Fungi

Rippon, John W.

doi:10.3109/10408418009085078

Cited by 41 publications

(31 citation statements)

References 135 publications

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“…The data to be presented in this report demonstrate that P. brasiliensis does contain an estrogen binding protein. We also show that estradiol inhibits the fungal, transformation from mycelial form to yeast form (mycelial-to-yeast transformation), the initial step in the establishment of infection (7). Although the concordance of binding in vitro and bioactivity of hormones in culture is not exact, the findings support our hypothesis-that pathogenic fungi have the capacity to respond to-the hormonal environment of the host through receptor-like steroid binding proteins.…”

supporting

confidence: 68%

“…The data in Table 2 support this hypothesis. Mycelial-to-yeast transformation is an early and, thus, critical step in the development of infection in an individual exposed to P. brasiliensis mycelia (7). The current findings of both an estrogen binding protein and estradiol action to inhibit mycelial-toyeast conversion suggest that this phenomenon is the possible molecular basis for the reduced infection rate in women.…”

Section: Discussionmentioning

confidence: 65%

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Estradiol binds to a receptor-like cytosol binding protein and initiates a biological response in Paracoccidioides brasiliensis.

Loose¹,

Stover²,

Restrepo³

et al. 1983

Proc. Natl. Acad. Sci. U.S.A.

126

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Paracoccidioidomycosis, a disease caused by Paracoccdioides brasilensis, which is endemic to Latin America, is much more common in men than women, suggesting a role for hormonal factors. We recently showed that two other yeasts possess steroid binding proteins and postulated that these receptorlike molecules represented a mechanism by which the hormonal milieu of the host might influence an infecting pathogen. Therefore, we examined P. bralensis for a sex steroid binding protein. Mr of =60,000. Competition experiments revealed that estrone, estriol, and progesterone had 25% of the affinity of estradiol, whereas diethylstilbestrol, androgens, and corticosteroids had low affinity. Investigation of steroid hormone actions in P. brasiienis indicated that estradiol inhibited the fungal transformation from mycelial form to yeast form, the initial step of infection. This suppressive effect was dose-dependent and not found with testosterone. We hypothesize that endogenous estrogens in the host, acting through the cytosol binding protein in the fungus, inhibit mycelialto-yeast transformation, thus explaining the resistance of women *to paracoccidioidomycosis.Paracoccidioides brasiliensis is a pathogenic fungus, the etiologic agent of paracoccidioidomycosis (South American blastomycosis). Although paracoccidioidomycosis is 13-87 times more common in men than women (1), contact with P. brasiliensis is essentially the same for the two sexes (2). The possibility has been considered that the hormonal milieu of the host might directly influence P. brasiliensis, affecting its pathogenicity (1, 3). Although this hypothesis is speculative, our recent findings (4-6) suggest a basis for a mechanism by which host hormones could affect an invading pathogen and alter its infectious properties. We have demonstrated the existence of intracellular proteins in two fungal genera that bind vertebrate steroid hormones with high affinity and specificity. Candida albicans possesses a protein that binds corticosterone and progesterone (4, 5), and Saccharomyces cerevisiae contains a different protein that selectively binds estrogens (6). We have postulated that these macromolecules may represent primitive hormone receptors in fungi. These proteins appear not only to bind endogenous fungal ligands but also to bind vertebrate steroid hormones, a fact we have exploited in selecting the radioprobes for these studies. Therefore, we considered the possibility that P. brasiliensis could possess either an androgen or an estrogen binding protein which, when occupied by the appropriate host sex steroid, might result in altered pathogenicity, thus explaining the predominance of infections in males. The data to be presented in this report demonstrate that P. brasiliensis does contain an estrogen binding protein. We also show that estradiol inhibits the fungal, transformation from mycelial form to yeast form (mycelial-to-yeast transformation), the initial step in the establishment of infection (7). Although the concordance of binding in vitro and bi...

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supporting

confidence: 68%

Section: Discussionmentioning

confidence: 65%

Estradiol binds to a receptor-like cytosol binding protein and initiates a biological response in Paracoccidioides brasiliensis.

Loose¹,

Stover²,

Restrepo³

et al. 1983

Proc. Natl. Acad. Sci. U.S.A.

126

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“…It is clear that P haeckeli is an eucaryotic organism, but it is still an open question whether it is a fungus, an alga or a protozoan. The plant hypothesis issupported-by the lack of movement within the spore and similarities of the spore's architecture to conidia of the histopathogenic fungus Blastomyces dermatitidis (Rippon 1980) a s emphasized by Nylund & Westman (1983). Further contributions to the resolution of the taxonomic position of P haeckeli can be expected from electron microscopic investigations and molecular analysis of the parasite.…”

Section: Discussionmentioning

confidence: 99%

Microscopic anatomy and histochemistry of the crayfish parasite Psorospermium haeckeli

Vogt¹,

M²

1995

Dis. Aquat. Org.

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Psorospemum haeckeli, a common parasite of the European noble crayfish Astacus astacus, occurs as an egg-shaped spore of ca 100 X 60 X 60 pm, particularly within the collagenous layer of the thoracic arteries and the surrounding subepidermal connective tissue. Smaller numbers are also found within the connective tissues of virtually all organs. The morphology and histology of these spores was investigated by microscopic techniques and the composition of their major structural components was identified by histochemistry. Each spore is enveloped by a layer of connective tissue which is assumed to derive from the host. It varies in thickness and composition among the infected organs. The spore proper consists of a 3-layered shell enclosing many globules. The outer shell layer is composed of solid, collagen-and elastin-negative, proteinaceous plates separated by sutures. The medial shell layer appears less compact and includes glycoprotelns or neutral mucopolysaccharides. The inner layer is composed of 2 membranous structures including glycoproteins, glycolipids, and collagen-and elastin-like proteins. The interior of the spore contains lipid globules of variable size, intensely staining nonlipid globules with crystalline and vacuolar inclusions, and 2 closely associated nuclei. In most of the crayfish investigated some of the spores were encapsulated by haemocytes and melanized.

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“…Saprophytic fungi' are the commonest agents of mycotic keratitis as they gain entry following trauma [2]. Aspergillus spp have been the commonest isolate from various part of India, followed by Acremonium spp, Fusarium spp and Candida spp [3][4][5][6].…”

Section: Discussionmentioning

confidence: 99%

“…Ocular surgery and use of contact lenses also increase the chance of fungal keratitis [1,2], The aetiological agents are commonly introduced from an exogenous source and most are normally saprophytic fungi. Some pathogenic fungi like Histoplasma capsulatum have also been known to cause primary keratomycosis [2]. Injudicious use of topical corticosteroids and antibacterial agents enhance the risk of mycotic keratitis.…”

mentioning

confidence: 99%

Mycotic Keratitis

Gokhale

Joshi

Haider

et al. 1995

Medical Journal Armed Forces India

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Mycotic keratitis is a distressing infection and may lead to permanent blindness. Fifty two cases of suspected mycotic keratitis were studied from Jan 91 to Sep 94. Specimens were collected on swabs in 2 0 cases and by corneal scraping in 32 cases. Wet mount examination of the specimens revealed fungal elements in 8 (15.4%) cases, of which 3 specimens were collected on swabs and 5 by corneal scraping. Fungi were isolated from a total of 12 (23.1%) specimens 5 of which were obtained by swabs while 7 by corneal scraping. Important pathogens were Fusarium spp, Aspergillus spp, Candida albicans and Cephalosporium spp. Direct examination of the specimens was found to be less sensitive than culture for the diagnosis of mycotic keratitis. M J A F I 1 9 9 5 ; 51 : 267-269

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Dimorphism in Pathogenic Fungi

Cited by 41 publications

References 135 publications

Estradiol binds to a receptor-like cytosol binding protein and initiates a biological response in Paracoccidioides brasiliensis.

Estradiol binds to a receptor-like cytosol binding protein and initiates a biological response in Paracoccidioides brasiliensis.

Microscopic anatomy and histochemistry of the crayfish parasite Psorospermium haeckeli

Mycotic Keratitis

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