PubMed Health⌕ Search

Biomedical subjects

M Rizk

Publications and source records attributed to M Rizk.

At least 19 recordsLinked to original sources
PubMed1992

Studies on carbohydrates extracted from native and chemically treated Biomphalaria alexandrina snails.

1. Carbohydrates were extracted from total tissue extracts of Biomphalaria alexandrina snails and were analyzed to their monosaccharides using GLC. 2. The snails were chemically treated with thioxanthone derivatives (compounds I, II, III) and the change in the monosaccharide constituents of their carbohydrates was investigated. 3. The isolated monosaccharides from native and chemically pretreated snails were injected into mice and their protective effects were examined after infection of mice with cercariae of Schistosoma mansoni. 4. The results showed that the main monosaccharides in carbohydrates of snails were galactose, glucose, fucose and mannose and that chemical treatment caused a drop in the galactose content. 5. Moreover, monosaccharide fractions from snails treated with compound III were the most effective in inducing protection against Schistosoma infection in mice.

Animals↗
PubMed1992

Sensitive colorimetric determination of copper (II) ions in some chemicals and multivitamins.

A sensitive and selective colorimetric method has been devised for the micro-determination of copper (II) ions in pure form, some chemicals and multivitamin preparations. The method depends on the formation of stable blue complexes in ammonia medium peaking at 615 nm between copper (II) ions, oxalyldihydrazide and one of the following aldehydes: 4-nitrobenzaldehyde, 2-nitrocinnamaldehyde and formaldehyde with minimum detection limits 0.1, 0.16 and 1.1 ppm, respectively. Several metal ions do not interfere. The optimum reaction conditions were studied and the results obtained were favorably comparable to the diethyldithiocarbamate method.

Aldehydes↗
PubMed1990

Electron microscopic and chemical study of the deposits formed on the copper and inert IUCDs.

The surface of 25 copper IUCDs and 25 inert IUCDs that had been in utero for less than 6 months or more than a year was examined by the scanning electron microscope and the deposits were extracted from another 100 copper and inert IUCDs that had been in utero for less than 6 months or more than a year and examined by the atomic analyser. The most apparent changes were, respectively, amorphous deposits and cellular debris, crystalline deposits, cracks, duplex coating, distortion and corrosion. Duplex coating was found only on inert IUCDs, but corrosion was found on copper IUCDs. The duration of use of the IUCDs had marked effect on the type of the deposits. Bleeding with IUCDs was associated with a thick layer of amorphous deposits. The contraceptive effect of the IUCDs was found to depend on the reaction of the host to the applied IUCDs rather than the type of device. The surface deposits were found to contain mainly calcium, phosphorus and magnesium.

Female↗
PubMed1990

Measurement of some selected enzymatic activities in infected Biomphalaria alexandrina snails.

The activities of aspartate (AST) and alanine (ALT) aminotransferases and that of lactate dehydrogenase (LD) were measured in the homogenate of infected Biomphalaria alexandrina snails, the specific intermediate hosts for the parasite Schistosoma mansoni which is the cause of the disease schistosomiasis. The isoenzymatic pattern of LD was also studied in the infected snails tissue.

Alanine Transaminase↗
PubMed1990

[Apico-aortic shunts. Indications, results].

Seven children or adolescents aged 8 to 20 years (average 13.5 years) underwent implantation of an apico-aortic conduit from 1980 to June 1989. Eleven previous operations under cardiopulmonary bypass had been performed. The indications were recurrence of muscular subaortic stenosis and/or congenital valvular stenosis in 3 cases, and stenotic, previously implanted aortic valve prosthesis of small calibre in 4 cases. The preoperative left ventricular-aortic systolic pressure gradient was between 70 and 130 mmHg. The first two patients had a bioprosthetic valvulation and the 5 succeeding patients a St Jude Medical mechanical prosthesis. The early and late mortality was nil. The average follow-up period is 5, 6 years at present (range 6 months to 9 years). One patient had to undergo repeat valve replacement after 5 years for degenerescence of the porcine bioprosthesis implanted in the conduit. No other complications related to the conduit or valve were observed. At the endpoint of the study all patients were asymptomatic without treatment. Control echocardiographic data showed normalisation of the indices of left ventricular function. Apico-aortic conduits would seem to be a safe and effective technique for the treatment of recurrent severe obstruction of the left ventricular outflow tract.

Adolescent↗
PubMed1989

[Results of coronary surgery in patients over 70 years of age].

Among the 628 consecutive patients who underwent coronary bypasses performed by the same surgical group between January 1, 1982 and December 31, 1987, 71 (11 p. 100) were aged 70 years or more (mean: 72.5 years; range: 70-83 years). 99 p. 100 of the patients had a history of severe, disabling exertional angina (46 p. 100) or unstable angina (52 p. 100) of 55 months' duration on average; 35 patients (49 p. 100) had already experienced myocardial infarction. Coronary angiography showed a one-vessel disease in 1 case, a two-vessel disease in 1 case, a two-vessel disease in 31 cases and a three-vessel disease in 39 cases; 11 patients (15 p. 100) had stenosis of the left main coronary artery. The ventricular function was considered unaltered in 59 cases (83 p. 100). Altogether, 155 bypasses, including 25 internal mammary grafts, were performed, i.e. an average of 2.2 bypasses per patient. There was only one early (21st day) post-operative death. The post-operative period was uneventful in 57 patients (60 p. 100); 9 developed peri-operative necrosis. Seventy patients have been followed up for a mean period of 24 months: there were 3 late deaths of non-cardiac origin; 60 patients (84.5 p. 100) are now asymptomatic and 3 (4.5 p. 100) are suffering from residual angina. Early mortality excluded, the cumulative probability of survival at 5 years is 94 p. 100.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

[Surgical treatment of complete atrioventricular canal. Value of the "composite double patch" technic].

Between January 1, 1982 and January 1, 1988, 49 complete corrections of complete atrioventricular canal were performed in children aged from 4 months to 8 years. 41 were infants less than 2 years' old and 31 were less than one year old. In the last 35 patients the "composite double patch" technique was used, consisting of closure of the interventricular septal defect with a dacron patch, followed by closure of the ostium primum with a pericardial patch. The mitral cleft was left intact in the last 6 operations. The overall mortality rate was 35 p. 100 (17 patients). It was 23 p. 100 in infants under 1 year and 17 p. 100 in infants aged from 6 to 12 months at the time of surgery (p less than 0.01). Seven of the 35 children in whom the "composite double patch" technique was used died (20 p. 100). Only one early death was recorded among the last 15 children operated upon. Two reoperations were performed: one within one month of the first operation, the other 4 months later for residual mitral regurgitation with haemolysis. 32 children were followed up for periods of 2 months to 6 years, 10 of them for more than 3 years. Two late deaths occurred during the follow-up. Grade 2 or 3/4 residual regurgitation was found in 14 patients who have regular clinical and echocardiographic examinations.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1988

Titrimetric determination of acetylenic hyponotics using organic brominating agents.

A titrimetric method is described for the determination of three acetylenic hypnotics, namely ethchlorvynol, ethinamate, and methylpentynol carbamate, in bulk and in dosage forms. The method involves the use of either 1,3-dibromo-5,5-dimethylhydantoin (DBH), N-bromosuccinimide (NBS) or N-bromophthalimide (NBP) as titrants. A known excess volume of the reagent is added and, after the specified time, the residual reagent is determined iodometrically. This procedure permits semimicro determination (1-15 mg) of the drug. The procedure has been successfully applied to pharmaceutical dosage forms; the results agree well with those given by compendial methods. The stoichiometry of the reaction has been assessed and an explanation of the reaction pathway is presented.

Bromosuccinimide↗
PubMed1988

Evaluation of the side arm of (naphthylvinyl)pyridinium inhibitors of choline acetyltransferase.

A number of quaternary salts of trans-4-(beta-1-naphthylvinyl)pyridine (NVP) were synthesized and evaluated as inhibitors of the enzymes choline acetyltransferase (ChAT) and acetylcholinesterase (AChE). Structural variations in the side arm attached to the pyridine nitrogen atom demonstrate that an inductive effect is small but significant for activity. Inhibition of ChAT by alkylated derivatives decreases when electron-withdrawing groups are placed in the side chain. Substitution of a methyl group on the pyridine ring only slightly affects activities toward ChAT and AChE. When the pyridinium moiety is replaced by an imidazolium ring, no ChAT inhibition was observed. The imidazolium compound, however, was a weak inhibitor of AChE. For design of affinity columns for purification of ChAT, the data also supports the use of long chain alkylated amide derivatives of NVP.

Animals↗
PubMed1987

Calcium-binding proteins in rat skin.

Skin Ca2+-binding protein (SCaBP) was reported to be distinct from the Ca2+-binding parvalbumin (PV), however, more recently its amino acid sequence was shown to be identical to PV. We purified a protein (Mr 12,000; pI4.5) from isolated epidermis (free of other cell layers) of adult rats and whole skin (containing no PV) of newborn rats. This protein is referred to as epidermal protein (EP-12), distinct from PV in its hydrophobicity, amino acid composition and immunological properties. Previously isolated SCaBP was shown to be a mixture of EP-12 and PV. The localization and possible functions of EP-12 and of PV in skin of adult and newborn rat are discussed.

Amino Acids↗
PubMed1986

Colorimetric determination of thioxanthenes with tetracyanoethylene.

A simple and rapid colorimetric method for the quantitative determination of the thioxanthene derivatives, chlorprothixene, tiotixene and metixene has been performed either in their pure form or in tablets. The procedure is based upon the formation of charge transfer complexes with the pi-acceptor tetracyanoethylene. The spectra of the complex show maxima at 415, 410 and 390 nm with a high apparent molar absorptivity which facilitates the determination of 5-100 micrograms X ml-1 of the studied compounds. The mean recoveries are 100.1 +/- 1.4%, 99.8 +/- 0.8% and 100.2 +/- 1.1% for chlorprothixene, tiotixene and metixene, respectively. This procedure is applied to determine these drugs in certain formulations and the results compare favourably to compendial methods.

Chlorprothixene↗
PubMed1986

Skin calcium binding protein: effect of ultraviolet B irradiation.

Skin calcium binding protein (SCaBP) has been found in the epidermal basal layer but not in the suprabasal layers, suggesting that its presence is correlated with the position of the cell and/or the cells' low degree of differentiation and high proliferation capacity. Rats were exposed to ultraviolet B (UVB) irradiation (280-320 nm, 0.1 J/cm2) to dissociate these two main characteristics of basal layer cells. Skin biopsy specimens were taken 24 and 48 h after UVB exposure. The [3H]thymidine labeling index, SCaBP localization (indirect immunofluorescence), and SCaBP levels monitored by radioimmunoassay were investigated. The [3H]thymidine labeling index was significantly increased after UVB treatment, and the [3H]thymidine-labeled cells were present not only in the basal layer but also in the suprabasal epidermal layers. Anti-SCaBP immunofluorescence was observed in both suprabasal and basal layers (rather than exclusively in the basal layer, as in control conditions). The radioimmunoassay indicated an overall increase in skin SCaBP content. No evidence was obtained that this increase was due to humoral factors, as no changes in SCaBP concentration on cell proliferation were observed in nonirradiated epidermal areas. Topical application of a single dose of vitamin D3, equivalent to the amount synthesized by UVB exposure, was also without effect. Thus the presence of this marker is correlated with the low degree of cell maturity and the cells' ability to proliferate rather than their basal position.

Animals↗
PubMed1985

Regulation of bile-acid synthesis. Role of sterol carrier protein 2 in the biosynthesis of 7 alpha-hydroxycholesterol.

Sterol carrier protein2 (SCP2) is known to stimulate utilization of cholesterol in enzymic reactions in which cholesterol is the substrate. Substantial recent experimental evidence indicates that SCP2: activates enzymic conversion of intermediates between lanosterol and cholesterol; stimulates the microsomal conversion of cholesterol into cholesterol ester in rat liver; and enhances mitochondrial utilization of cholesterol for pregnenolone formation in the adrenals. The conversion of cholesterol into 7 alpha-hydroxycholesterol is the rate-limiting step in bile-acid synthesis. We therefore investigated the effect of SCP2 on this physiologically critical reaction by using a gas-chromatography-mass-spectrometry procedure that measures the mass of 7 alpha-hydroxycholesterol formed. The results show that SCP2 enhances 7 alpha-hydroxycholesterol formation by rat liver microsomes (microsomal fractions), utilizing either endogenous membrane cholesterol, cholesterol supplied exogenously in serum or in the form of cholesterol/phospholipid liposomes. Microsomes immunotitrated with anti-SCP2 antibody exhibited considerably less capacity to synthesize 7 alpha-hydroxycholesterol, which was restored to control levels on addition of purified SCP2. These data are consistent with the suggestion that SCP2 may be of physiological significance in the overall metabolism of cholesterol.

Animals↗
PubMed1984

Skin calcium-binding protein: effect of vitamin D deficiency and vitamin D treatment.

The amount of skin calcium-binding protein, evaluated using a sensitive radioimmunoassay and indirect immunofluorescence, was decreased in vitamin-D deficient rats and increased after one week vitamin D3 or 1 alpha-hydroxyvitamin D3 treatment. In vitamin D replete and in vitamin D-deficient animals, skin calcium-binding protein was not sensitive to changes in dietary and/or serum calcium concentrations. These results indicate that this protein is different from other calcium-binding proteins such as parvalbumin and calmodulin which are not vitamin D-dependent, and also different from intestinal calcium-binding protein which, in D replete animals, is sensitive to changes in dietary and serum calcium concentrations. Skin calcium-binding protein may, therefore, represent a new class of vitamin D-dependent protein.

Animals↗
PubMed1984

Polarographic behaviour and determination of some penicillins after bromometric oxidation.

The direct current polarographic behaviour of the bromometric oxidation product of certain penicillins has been investigated. The oxidized products give a well defined cathodic wave with E1/2 = 0.6 V vs saturated calomel electrode (SCE). The nature of the wave and the electrode reaction have been evaluated. A procedure was developed for investigation of the penicillins either in the pure state or in dosage forms. The results were compared with those obtained with the official methods.

Ampicillin↗
PubMed1984

Properties of cholesterol 7 alpha-hydroxylase in rat liver microsomal acetone powder.

Rat liver microsomes were extracted with acetone, and a microsomal powder preparation was obtained. The cholesterol 7 alpha-hydroxylase activity of acetone powder was linear with time, the amount of protein, and the amount of cholesterol in human or rat serum. Unesterified lipoprotein cholesterol was also an effective substrate, and the Km values increased progressively from high-density lipoprotein (HDL) to low-density lipoprotein (LDL) to very-low-density lipoprotein (VLDL), suggesting that HDL-free-cholesterol was the better substrate.

Acetone↗