Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0847097 (acidity)
 15,165 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of specific species of skin bacteria on human sebaceous gland lipids in vitro were analyzed. Isolated dissected sebaceous glands were pooled, homogenized, and sterilized, then incorporated into peptone-yeast extract medium and used as substrate for growth of Propionibacterium acnes, P. granulosum, and Staphylococcus epidermidis subgroup II. The sebaceous lipids were analyzed by thin-layer chromatography before and after bacterial growth. The most striking effect of bacteria on sebaceous gland lipid composition was the hydrolysis of sebaceous triglycerides. The degree of hydrolysis varied with bacterial strain but was most complete with P. acnes and P. granulosum. Staphylococci were not effective in hydrolyzing sebaceous triglycerides at pH 4.5 although, when the pH of the medium was raised to pH 6.4, some strains of staphylococci were as effective as the propionibacteria in hydrolyzing sebaceous triglycerides to free fatty acids. Thus minor changes in acidity may play asignificant role in controlling the lipolytic activity of staphylococci on skin. Another effect of bacterial action on sebaceous gland lipids was the esterification of sebaceous cholesterol to cholesteryl esters. Thus, bacterial action must be taken into account in evaluating studies of alterations in cutaneous cholesterol and cholesteryl esters in skin surface lipids in normal and disease states.
J Invest Dermatol 1975 Jun
PMID:Analysis of lipid composition of isolated human sebaceous gland homogenates after incubation with cutaneous bacteria. Thin-layer chromatography. 23 66

A study was made on the in vitro characteristics and in vivo biological activities of a leukotactic factor derived from psoriatic scale (PLF). Sephadex G-75 chromatography showed that PLF eluted in the region of the 12,500 dalton protein marker. It resisted heating, lyophilization, acidity (pH 3) and alkalinity (pH 11), but was destroyed by trypsin digestion. The substance attracted polymorphonuclear leukocytes (PMNs) in vitro; this ability was inhibited by antiserum to C3a and was partially reduced by antiserum to C5. Although PLF showed strong chemotactic activity for PMNs, its activity for mononuclear cells was only mild. Intradermal injection of PLF into man or guinea-pig produced an erythematous response with dense tissue neutrophilia, the time course of which was similar to that of the Arthus response. PLF also provoked increased vascular permeability in guinea-pig skin. Moreover, repeated intradermal injection of PLF to the same site in guinea-pigs led to moderate acanthosis of the overlying epidermis. These observations strongly suggest that transepidermal migration of leukocytes in psoriatic lesions is provoked by PLF, whose activity appears to reflect that of complement cleavage products, particularly C3a, presumably produced by complement activation in the subcorneal region of the epidermis. Furthermore, it is postulated that PLF may be a factor which plays a crucial role in the production of typical psoriasiform tissue changes.
Br J Dermatol 1977 Nov
PMID:Characterization of a leukotactic factor derived from psoriatic scale. 58 64

In concluding my remarks on structure and function of the skin, I wish to make one additional observation. Most dermatologists have acknowledged the role of the skin and its ability to protect the human organism from invasion by pathogenic organisms. There is good scientific evidence that skin plays an important protective role. Although an intact epidermis is of utmost importance as a protective unit, the contribution of the "acid mantle" is of considerable magnitude. The acidity or alkalinity and stability of this mantle is contributed to, in large measure, by the presence of eccrine gland secretions and sebaceous gland secretions. It is then not logical to assume that if black skin contains larger numbers of large and overly active adnexal glands, it would have a most effective mechanism for control of bacterial, viral, and other infections? That this is not the situation becomes apparent in the discussions that follow on cutaneous infections in black skin.
Dermatol Clin 1988 Jul
PMID:Structure and function of the skin. Are there differences between black and white skin? 304 16

For proper use of systemic GCS, a basic knowledge of the normal HPA axis, as well as knowledge of the pharmacology, clinical usage guidelines, and adverse reactions of these agents is imperative. Both short-term (acute) and long-term side effects should be well known by the physician. The pros and cons of oral and parenteral therapy for various disorders and in various situations should be recognized. For long-term therapy, an intermediate-acting agent such as prednisone in single, early morning doses is most commonly used to minimize suppression of the HPA axis. Alternate-morning doses produce even less suppression if the disease process will respond. A through patient history, including general medical history and medications the patient is taking, is important to anticipate any potential problems. Weight and blood pressure should be checked initially and every 1 to 3 months thereafter. Blood glucose, electrolytes, and lipid studies, including triglycerides, should be done approximately every 6 months. An ophthalmology examination should be performed every year, and stool examination for occult blood and chest radiography can be obtained as indicated. Bone density studies might be necessary in patients who are at high risk for osteoporosis. Specific acute situations may dictate other studies. The patient on long-term GCS should be kept as active as possible, as mild-to-moderate exercise helps prevent certain side effects, such as osteoporosis. The dose of oral GCS is best given with food to prevent gastrointestinal irritation, and agents to decrease gastric acidity might be needed in certain situations. Exposure to infections should be prevented, where possible, and treatment initiated at the first sign of systemic or cutaneous infection. Pain should be evaluated early, especially abdominal pain or bone pain; MRI is indicated if aseptic necrosis of bone is suspected. Both trauma and severe sun exposure should be avoided. Consultation with other specialists is strongly recommended when the situation dictates. Diet is one of the most important strategies to minimize side effects from long-term GCS therapy. Vegetable protein should be increased in the diet, and fats and carbohydrates limited. Adequate calcium is imperative, and calcium supplementation is recommended for high-risk osteoporosis patients. Small amounts of vitamin D may be necessary to increase absorption of calcium. Restriction of sodium is also important, as is maintainance of dietary potassium. Supplemental potassium may be necessary in some patients, and a thiazide diuretic might be useful in patients with hypertension, edema, or osteoporosis. Vitamin C can be given to promote wound healing. A good doctor-patient relationship is important in managing the patient on long-term GCS. The patient must return for regular visits and be encouraged to promptly report any adverse reactions to the physician. If these criteria are maintained and the strategies noted previously are followed, problems from long-term therapy with GCS will be minimized.
Dermatol Clin 1995 Oct
PMID:Minimizing complications from systemic glucocorticosteroid use. 878 96

The existence of a flux of proton donors from skin (inner part of the forearm) to the electrode was observed in 12 male and female volunteers. This flux was used to collect and identify the ionic species responsible for skin acidity. It was then found that: (i) pK of these proton donors (pK = 6.13 +/- 0.07) was quasi-identical to that of trans-urocanic acid (6.10), and (ii) the amount of urocanic acid present in stratum corneum was sufficient in itself to explain the acidic level as measured with pH meter (R = 0.8484, n = 10, p = 0.00136). As a result, the contribution of other ionic species can be considered as negligible in normal human skin. The data recorded led us to identify three groups (Fast, Medium, and Slow) characterized by different skin surface pH values (low, medium, and close to neutral) and showing a pH gradient in the outer layers of the stratum corneum, or not. Data analysis suggests that these characteristics depend on urocanic acid production rate within the stratum corneum and that this production rate is self-regulated by its urocanic acid content.
J Invest Dermatol 2000 Sep
PMID:Evidence for the existence of a self-regulated enzymatic process within the human stratum corneum -an unexpected role for urocanic acid. 1095 Dec 77

Although dermatology now has the most extensive group of systemic medications available for the treatment of skin diseases at any time, GCSs remain the most important agents for managing inflammatory disorders. It is important that the dermatologist have a broad knowledge of guidelines for clinical use, pharmacology, and adverse effects of these drugs. Acute and chronic side reactions should be well recognized. An understanding of the HPA axis and reasons for administering GCSs in different ways is of great value. A good medical history should be taken on any patient treated with GCSs, including knowledge of conditions that would make GCSs inadvisable and other concomitant systemic medications that might produce drug interactions. During the course of therapy, physical examination should include all systems pertinent to side effects caused by these agents, including frequent evaluations of weight and blood pressure. Blood chemistries should be performed on a regular basis, including glucose, electrolytes, and serum lipids. Osteoporosis is one of the most significant adverse affects to be evaluated, with bone mineral density studies recommended on an annual basis for persons continuing on GCS therapy. If hip or other joint pain develops, MR imaging is the most specific and sensitive radiologic examination for evaluating the possibility of osteonecrosis. An ophthalmology examination should be performed every 6 to 12 months to detect early cataract or glaucoma development. Any early signs of infection should be evaluated by appropriate smears, wet preparations, and cultures. Many other studies, including gastrointestinal and pulmonary examinations, may be dictated by specific acute situations. It is important to begin early prevention of the bone loss that occurs with GCS-induced osteoporosis. The 1996 guidelines of the American College of Rheumatology, including adequate calcium and vitamin D intake, should be followed. Hormonal replacement, a bisphosphonate, calcitonin, or a thiazide diuretic may be indicated. Restriction of sodium in the diet is important, as well as adequate potassium intake. The diet should be low in saturated fat and calories and should be high in vegetable protein. Because osteoporosis is so prevalent with GCSs, keeping the patient as active as possible with mild-to-moderate exercise is important. Whenever possible, exposure to persons with infectious processes should be avoided, and proper treatment should be instituted at the initial signs of systemic or cutaneous infection. Oral doses of GCSs are best taken with food to prevent gastrointestinal irritation, and agents for gastric acidity occasionally may be indicated. Significant trauma should be prevented, as should severe exposure to the sun. Many situations may call for consultation with other medical or surgical subspecialists. The patient must be aware of the importance of regular physician evaluations and reporting of any adverse effects while on long-term GCSs. A good relationship and understanding between the patient and physician are vital in minimizing potential problems from these agents. If the dermatologist maintains the proper guidelines of care, patients on GCSs have the highest benefits and lowest risks possible.
Dermatol Clin 2001 Jan
PMID:Update on systemic glucocorticosteroids in dermatology. 1115 87

This review describes the role of pH in cutaneous structure and function. We first describe the molecules that contribute to the acidity or alkalinity of the skin. Next, differences in cutaneous pH among species, among individuals of the same species and within individuals are described. The potential functions of cutaneous pH in normal and diseased skin are analysed. For example, cutaneous pH has a role in the selection and maintenance of the normal cutaneous microbiota. In addition, cutaneous acidity may protect the skin against infection by microbes. Finally, there is evidence that a cutaneous pH gradient activates pH-dependent enzymes involved in the process of keratinization.
Vet Dermatol 2002 Dec
PMID:A comparative review of cutaneous pH. 1246 61

Alpha-hydroxy acids (AHAs) such as glycolic acid (GA) and lactic acid (LA) have been reported to be effective in treating pigmentary lesions such as melasma, solar lentigines, and postinflammatory hyperpigmentation. The mechanism of this effect might be due to epidermal remodeling and accelerated desquamation, which would result in quick pigment dispersion. However, the direct effect of AHAs on melanin synthesis has not yet been well studied. To elucidate such a direct effect of AHAs on melanogenesis, we performed melanin assays, growth curve determinations, Northern and Western blotting for melanogenic proteins [tyrosinase, tyrosinase related protein (TRP)-1 and TRP-2], and tyrosinase and, 4-dihydroxyphenylalaninechrome tautomerase enzyme activity assays using mouse B16 and human melanoma cells. GA or LA (at doses of 300 or 500 microg/ml) inhibited melanin formation in similar dose-dependent manner, without affecting cell growth. Although the mRNA and protein expression or molecular size of tyrosinase, TRP-1 and TRP-2 were not affected, tyrosinase activity was inhibited. To see whether GA and/or LA directly inhibit tyrosinase catalytic function, the effect of GA and LA on human tyrosinase purified from the melanosome-rich large granule fraction of human melanoma cells was performed. GA or LA were shown to inhibit tyrosinase enzyme activity directly, but this effect was not due to the acidity of GA or LA, because adjusting the pH to 5.6 (the pH of GA and LA at concentrations of 2500 microg/ml), did not affect tyrosinase activity. Taken together, these results show that GA and LA suppress melanin formation by directly inhibiting tyrosinase activity, an effect independent of their acidic nature. GA and LA might work on pigmentary lesions not only by accelerating the turnover of the epidermis but also by directly inhibiting melanin formation in melanocytes.
Exp Dermatol 2003
PMID:The inhibitory effect of glycolic acid and lactic acid on melanin synthesis in melanoma cells. 1475 23

Aged skin commonly is afflicted by inflammatory skin diseases or xerosis/eczema that could be triggered or exacerbated by impaired epidermal permeability barrier homeostasis. This defect is linked to reduced epidermal lipid synthesis in humans and in mice of advanced age (i.e., >75 years in human or >18-24 months in mice). We now report that barrier defects in moderately aged humans (50-80 years) or analogously aged mice (12-15 months) are linked instead to defective stratum corneum (SC) acidity. In moderately aged mouse epidermis, we find that abnormal acidification, in turn, is linked to decreased Na+/H+ antiporter (NHE1) expression. Decreased NHE1 levels lead to increased SC pH, which results in defective lipid processing and delayed maturation of lamellar membranes, due to suboptimal activation of the pH-sensitive essential, lipid-processing enzyme, beta-glucocerebrosidase. Conversely, impaired SC integrity in moderately aged mice is due to increased pH-dependent activation of serine proteases, leading to premature degradation of corneodesmosomes. These abnormalities were normalized by exogenously acidifying the SC, suggesting a basis for the well-known acidification therapies that are widely used to treat the pathologic xerosis/eczema seen in moderately aged humans.
J Invest Dermatol 2007 Dec
PMID:Stratum corneum acidification is impaired in moderately aged human and murine skin. 1755 64

To determine whether pigment type determines differences in epidermal function, we studied stratum corneum (SC) pH, permeability barrier homeostasis, and SC integrity in three geographically disparate populations with pigment type I-II versus IV-V skin (Fitzpatrick I-VI scale). Type IV-V subjects showed: (i) lower surface pH (approximately 0.5 U); (ii) enhanced SC integrity (transepidermal water loss change with sequential tape strippings); and (iii) more rapid barrier recovery than type I-II subjects. Enhanced barrier function could be ascribed to increased epidermal lipid content, increased lamellar body production, and reduced acidity, leading to enhanced lipid processing. Compromised SC integrity in type I-II subjects could be ascribed to increased serine protease activity, resulting in accelerated desmoglein-1 (DSG-1)/corneodesmosome degradation. In contrast, DSG-1-positive CDs persisted in type IV-V subjects, but due to enhanced cathepsin-D activity, SC thickness did not increase. Adjustment of pH of type I-II SC to type IV-V levels improved epidermal function. Finally, dendrites from type IV-V melanocytes were more acidic than those from type I-II subjects, and they transfer more melanosomes to the SC, suggesting that melanosome secretion could contribute to the more acidic pH of type IV-V skin. These studies show marked pigment-type differences in epidermal structure and function that are pH driven.
J Invest Dermatol 2009 Jul
PMID:pH-regulated mechanisms account for pigment-type differences in epidermal barrier function. 1917 37


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