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Biomedical subjects

S Passi

Publications and source records attributed to S Passi.

At least 73 records · Page 4Linked to original sources
PubMed1983

Ultrastructural and biochemical observations on the effect of 4-hydroxyanisole plus tyrosinase on normal human melanocytes and keratocytes in tissue culture.

Cultures of melanocytes and keratocytes were exposed to 15 micrograms ml-1 tyrosinase and 4-hydroxyanisole (4-OHA) 5 X 10(-4) M to 5 X 10(-2) M for 1 to 24 h. No damage was suffered by either cell below 5 X 10(-3) M 4-OHA for 6 h, but higher concentrations and longer exposures extensively damaged both cells. Exposure of cells washed free of culture medium to tyrosinase and 4-OHA 1 X 10(-3) M for 1 h resulted also in extensive damage. This indicates that an early-formed toxic product of the reaction between tyrosinase and 4-OHA is inactivated by constituents of the medium. This was confirmed by Liquid Chromatography and Scanning Spectrophotometry which showed that a toxic 4-OHA quinone immediately reacted with nucleophilic substances in the medium resulting in products which, on accumulation, are probably responsible for the later (6 h plus) damage to melanocytes and keratocytes. A possible effect of allegedly specific melanocytotoxic drugs on keratocytes should always be borne in mind with tissue culture experiments.

Anisoles↗
PubMed1983

Stimulation of aflatoxin biosynthesis by lipophilic epoxides.

Epoxy fatty acids added to the culture media either with the inoculum or at the end of exponential growth phase stimulated aflatoxin production by toxigenic strains of Aspergillus flavus and Aspergillus parasiticus. This effect did not appear when the unsaturated fatty acids used for the synthesis of the epoxides and the polyhydroxyacids (which can be considered to be derived from the opening of the oxirane ring) replaced the epoxides in the culture media. No significant differences were detected in the lipid fractions (diglycerides, sterols, triglycerides, free fatty acids, sterol esters) extracted from the mycelia grown in the presence of any of the fatty acid derivates.

Aflatoxins↗
PubMed1983

Beneficial effect of 15% azelaic acid cream on acne vulgaris.

Patients treated with azelaic acid (15%) cream for chloasma reported simultaneous improvement of acne lesions within the treated areas. This prompted an open study of its effect in cases of acne without chloasma. One hundred patients with acne vulgaris were treated for 3-9 months by twice-daily application of the cream with significant improvement in every case.

Acne Vulgaris↗
PubMed1983

Metabolism of straight saturated medium chain length (C9 to C12) dicarboxylic acids.

A method utilizing thin-layer chromatography, high performance liquid chromatography, and mass spectrometry was developed for the quantification of C9, C10, C11, and C12 dicarboxylic acids in serum, urine, and feces of human volunteers and rats after oral administration of the acids. The method allowed good resolution and measurement of the dicarboxylic acids at nanogram levels. In humans, excretion was independent of the dosage; about 60% of C9, 17% of C10, 5% of C11, and 1% of C12 were excreted in the urine during the first 12 hours after administration. The concentration of the acids in serum peaked between 2 and 3 hours. Excretion was also independent of dosage in rats. About 2.5% of C, 2.1% of C10, 1.8% of C11, and 1.6% of C12 were excreted in the urine over a period of 5 days. The serum concentration and the urinary excretion of the diacids reached a maximum at the second day after the oral dose. In both humans and rats, the dicarboxylic acids found in serum and urine were 2, 4, or 6 carbon atoms shorter than the corresponding administered diacid. This indicates that there was beta-oxidation of the ingested diacids to some extent. The administration of [1,9-14C]azeliac acid and of [10,11-3H]dodecandioic acid confirmed the occurrence of beta-oxidation, and led to elucidation of the fate of the ingested diacids that were not excreted as such in the urine.

Administration, Oral↗
PubMed1981

Bile acid content of gallbladder bile and stones in type IIb and IV hyperlipoproteinemia.

We examined the bile acid composition of gallbladder bile using reversed-phase high performance liquid chromatography (HPLC), in normolipemic and hyperlipidemic (types IIb and IV) patients with cholelithiasis and compared them with normal subjects. Similarly, bile acid composition was determined n the gallstones of these patients. No free bile acids were found in any of the samples examined. We observed that gallbladder bile and gallstones of patients with type IV hyperlipidemia showed a significant increase in the percentage of glyco-conjugated bile acids and reduction in taurine conjugates. Based on this finding we postulate that in addition to biliary lipid composition bile acid composition may also play a role in the pathogenesis of cholesterol gallstone formation.

Adult↗
PubMed1981

Ultrastructural observations on the effect of 4-hydroxyanisole on normal human melanocytes in tissue culture.

Riley's classic 1970 experiment showing a specific cytotoxic effect of 4-hydroxyanisole (4-OHA) on tissue-cultured melanocytes of black guinea pig ear skin was repeated on normal human melanocytes, and the results were examined by electron microscopy. In dispersed tissue culture, no specific toxic effect on human melanocytes was observed following equally timed exposures to similar (10(-3) M) or even higher (10(-2) M) concentrations of the drug; plasma membrane, nucleus, and cytoplasmic organelles, including melanosomes were unaffected. The same applied to melanocytes of whole epidermis exposed for 5 hr to the same concentrations of 4-OHA in culture medium. Melanocytes of PUVA treated skin similarly exposed for up to 24 hr to 10(-2) and 10(-3) M 4-OHA, likewise exhibited no evident morphological damage at the ultrastructural level. The discrepancy of results between guinea pig and man could have a variety of explanations, one of which could be due to a possible relatively low level of active tyrosinase in the human melanocytes (Riley believes the cytotoxic effect of 4-OHA to be due to the fact that it acts as a substrate for tyrosinase, toxic intermediates being liberated as a result). However, the lack of effect on the PUVA-activated melanocytes indicates that this cannot be the entire explanation.

Anisoles↗
PubMed1981

Molecular basis of substrate and inhibitory specificity of tyrosinase: phenolic compounds.

In order to investigate the molecular basis of substrates, and the inhibitory specificity of tyrosinase, a large series of phenolic compounds have been analysed by using a High Performance Liquid Chromatographic-Scanning Spectrophotometric system. Depending on their chemical structure, phenolic compounds may act as substrates or as competitive inhibitors of tyrosinase. The ability to act as substrates requires the presence in the molecule of electron donor groups, while competitive inhibition on the contrary requires the presence of powerful electron acceptor groups. Certain phenolic compounds used as therapeutic agents or as food preservatives are chemically capable of acting as alternative substrates or competitive inhibitors of tyrosinase in vitro; their effect on melanocytes in vivo therefore merits investigation.

Catechol Oxidase↗
PubMed1981

Analysis of lipids and dioxin in chloracne due to tetrachloro-2,3,7,8-p-dibenzodioxin.

Biochemical investigations on the lipid and dioxin content of the cysts and comedo-like lesions of three children exposed to tetrachloro-2,3,7,8-p-dibenzodioxin (TCDD) have been performed. Gas chromatography and mass spectrometry failed to demonstrate the presence of dioxin despite the high sensitivity of the method. Further investigation by thin layer and gas chromatography-mass spectrometry showed that the lipids of the chloracne lesions in these children were exclusively epidermal in origin. These findings support the hypothesis that exposure to dioxin produces a hyperproliferative reaction of the cutaneous epithelium with squamous metaplasia of the cells lining the ducts of skin glands.

Acne Vulgaris↗
PubMed1981

An application of high performance liquid chromatography to analysis of lipids in archaeological samples.

Five samples from three different types of 1500-year-old Mediterranean amphorae, as well as from a contemporary oil lamp found in the same deposit, were analyzed for the presence of lipid residues. Each sample of finely ground amphorae powder weighed 1-2 g. The abundance of interfering secondary products makes thin-layer chromatography (TLC) an essential step of the procedure. The fractionation of the extract into its various lipid components by means of TLC was followed by quantitative recovery of the triglyceride (TG) and free fatty acid (FFA) fractions from the plates and by the measurement of their components by high performance liquid chromatography (HPLC) after esterification. The minimum detectable level is 1 ng. The amphorae samples revealed a more abundant FFA fraction than a TG fraction, which is the reverse of what we know about the composition of fresh oil. Despite the considerable age of the amphorae and their preservation under non-ideal conditions, the lipid residues have retained certain identifiable characteristics that enable one to make valid suggestions as to the type of commodity originally transported in the amphorae. The results of these experiments yield important information that enables the biochemist to observe an aging process irreproducible in the laboratory and provides the archaeologist with previously unavailable information about trade 15 centuries ago.

Africa, Northern↗
PubMed1980

Effect of azelaic acid on human malignant melanoma.

In 23 patients with malignant melanoma, including some with metastases and terminal patients, topical and oral (10--15 g daily) azelaic acid given for 1--12 weeks before surgical excision of the lesions was followed by arrest and subsequent regression of the advancing edge of lesions, reduction in size and flattening of nodular areas, and progressive lightening of pigmentation. Histological and ultrastructural effects included: degeneration and disappearance of malignant epidermal and dermal melanocytes with reduction of junctional activity; epidermal proliferation and return towards normal organisation; reappearance of papillary dermis, pilosebaceous units, and sweat glands; separation of dermal melanoma tumour masses into smaller collections of cells by regenerating connective tissue; and increase in number of dermal mast cells, macrophages, and round cells. These preliminary results indicate a direct cytotoxic effect of azelaic acid on melanocytes of human melanoma.

Administration, Oral↗
PubMed1979

Effect of dicarboxylic acids on lentigo maligna.

Dicarboxylic acids from C8 to C14 are competitive inhibitors of tyrosinase in vitro, and here, the effect of a cream containing 15% azelaic acid (C9) on 3 cases of lentigo maligna is described. The lesions were treated for 90 days, with remarkable clinical and histological effect, maintained for up to 2 yr after cessation of treatment. Progress during treatment of one case was additionally monitored by electron microscopy, which revealed progressive elimination of abnormal melanocytes both basally and suprabasally, and their replacement by essentially normal cells engaged in normal melanogenesis. There was also progressive diminution in the general disorganization of the epidermis, and disappearance of lymphocyte response. It is concluded that dicarboxylic acids have a direct inhibitory and cytotoxic effect on abnormally active or structurally disordered melanocytes in lentigo maligna, but further investigations are required to establish their precise mode of action. Similar application of dicarboxylic acids to normal skin affects only a small proportion of melanocytes, suggesting that some phasic factor, or individual states of activity, may be concerned in their susceptibility.

Aged↗
PubMed1979

Effect of dicarboxylic acids on normal human melanocytes in dispersed tissue culture.

Since dicarboxylic acids are competitive inhibitors of tyrosinase, and effective in treatment of hyperpigmentary disorders, such as chloasma and lentigo maligna, probably due to a cytotoxic effect on abnormal melanocytes, it is of interest to examine their effect on normal melanocytes in tissue culture. Azelaic or dodecandioic acids were added (150-200 micrograms/ml) to dispersed cultures of epidermal cells, and melanocytes were examined by electron microscopy after 7, 10, 15, 20 and 30 days. Apart from a stimulation of melanogenesis, the presence of dicarboxylic acids in the culture medium caused no detectable damage to melanocytes, nor did they prevent growth of a second generation of cells.

Culture Techniques↗
PubMed1978

Identification of tyrosinase inhibitors in cultures of Pityrosporum.

Lipid fractions capable of inhibiting the dopa-tyrosinase reaction in vitro were isolated by thin-layer chromatography from submerged cultures of Pityrosporum supplemented with oleic acid or vaccenic acid. Analysis of these fractions by gas chromatography-mass spectrometry revealed the presence mainly of C(9) and C(11) dicarboxylic acids. Standard dicarboxylic acids from C(8) to C(13) were capable of inhibiting tyrosinase in vitro to varying extents. Enzymatic kinetic studies showed that they act as competitive inhibitors of tyrosinase. These observations suggest that dicarboxylic acids could be used in the treatment of people with hyperpigmentary disorders.

Catechol Oxidase↗
PubMed1977

Induction of hyphae in cultures of Pityrosporum by cholesterol and cholesterol esters.

The effect of cholesterol and cholesterol esters on Pityrosporum cultures has been studied. A mixture of 0.25% to 2.0% of cholesterol:cholesteryl stearate:glyceryl monostearate (2.0:1.5:2.0) added to Bacto Yeast Morphology Agar plus oleic acid was able to induce hyphae in cultures of both Pityrosporum orbiculare and P. ovale. This result is discussed with respect to the cholesterol effect on cell membranes and to the occurrence of cholesterol and cholesterol esters in the scaling patches of Pityriasis versicolor.

Cell Membrane↗