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Biomedical subjects

M A Hassan

Publications and source records attributed to M A Hassan.

At least 19 recordsLinked to original sources
PubMed2006

Are the demographics for squamous cell cancer in the head and neck changing in the United Kingdom?

Head and neck squamous cell carcinoma is well known to be more common in men than women. Smoking and alcohol are the key risk factors causing such malignancies and there are several publications which have suggested that the prevalence of these diseases is increasing more in women than in men in western countries due to increased smoking and alcohol use. We collected our data at the Institute of Laryngology and Otology from the last 45 years and analysed the disease ratios in male to female patients in different sites within the head and neck. Our results revealed a decreasing male to female ratio, though this was not statistically significant. However, it draws attention to the increasing number of women with head and neck cancer, which may reflect their increasing use of cigarettes and alcohol.

Aged↗
PubMed2003

Effect of new poly 2-acryloyl-N,N'-bis (4-nitrophenyl) propandiamide and poly 2-acryloyl-N,N'-bis (4-methylphenyl) propandiamide and their synergistic action on the stability of nitrocellulose.

The stability of nitrocellulose can be significantly improved by incorporating two novel polymeric compounds as new stabilizers, each has two p-substituted phenyl rings in its repeating unit. The two prepared polymers were used independently and in three different blend ratios in comparison with the conventional propellant stabilizer, diphenylamine. The efficiency of the prepared stabilizers and their synergistic effect were evaluated using thermo gravimetric analysis (TGA), Bergmann-Junk test and differential scanning calorimetry (DSC). It was found that both polymers and their 50%:50% blend ratio are more efficient nitrocellulose stabilizers than diphenylamine.

Collodion↗
PubMed2002

A prospective randomized comparison of sequential versus monoculture systems for in-vitro human blastocyst development.

BACKGROUND: Extending the period of in-vitro culture to the blastocyst stage may improve implantation rates in IVF treatment. Recognition of the dynamic nature of early embryo metabolism has led to the development of commercially available sequential culture systems. However, their improved efficacy over monoculture systems remains to be demonstrated in prospective studies. METHODS: Embryos obtained from 158 women undergoing IVF treatment were randomized by sealed envelopes to culture in one of three systems: (A) culture for 5 days in our own monoculture medium (Rotterdam medium); (B) culture for 3 days in Rotterdam medium followed by 2 days in fresh Rotterdam medium; (C) culture for 5 days using the commercially available G1/G2 sequential culture system. RESULTS: There were no significant differences in blastulation, implantation or pregnancy rates between the three tested culture systems. CONCLUSION: The employed monoculture system is as effective as the G1/G2 sequential system for the culture of blastocysts for IVF.

Blastocyst↗
PubMed2002

Differential scanning calorimetry to investigate the compatibility of ciprofloxacin hydrochloride with excipients.

The compatibility between ciprofloxacin hydrochloride (CFX) and some excipients was evaluated using differential scanning calorimetry (DSC). Physical mixture, coground mixture, compressed mixture and kneaded mixture were prepared to study the effect of sample manipulation. In addition, the samples of physical mixture were also accelerated at 55 degrees C for three weeks to obtain more reliable conclusions. Different types of excipients currently used in tablet or capsule formulations namely, calcium phosphate dibasic dihydrate (Emcompress), magnesium stearate lactose, sorbitol, mannitol, croscarmellose sodium (Ac-Di-Sol), sodium carboxymethyl starch (Primojel), microcrystalline cellulose (Avicel PH 101, Emcocil) were examined. The DSC scan of CFX displayed two endothermic peaks probably as a result of a fusion process followed by a decomposition process. CFX appeared to interact with sorbitol, mannitol, Ac-Di-Sol, Primojel, Avicel PH 101 and Emcocil.

Anti-Infective Agents↗
PubMed2001

Effect of malonyl malonanilide dimers on the thermal stability of nitrocellulose.

Three malonanilide dimers (MA2-MA4) were prepared by the reaction of ethyl malonate with malonanilide derivatives (M2-M4). These dimers were investigated as new stabilizers for nitrocellulose. The evaluation process has been performed through Bergman-Junk (BJ) test, thermal analysis measurements (TGA and DSC) and kinetic parameters calculations (E(a)). The comparative study between mass spectra and thermal analysis of the new dimers helped in resolving the thermal decomposition mechanisms for the new dimers. It was found that the new dimers especially (MA2 and MA4) showed better stabilizing effect for the nitrocellulose than the centralite 1 (C1) which is the common stabilizer.

Anilides↗
PubMed2001

Synthesis, chemical and enzymatic hydrolysis, and bioavailability evaluation in rabbits of metronidazole amino acid ester prodrugs with enhanced water solubility.

A series of amino acid esters (3a-e) have been synthesized and evaluated as potential prodrugs of metronidazole with the aim of improving aqueous solubility and therapeutic efficacy. The aqueous solubility and the lipophilicity (expressed as the log P value) of metronidazole and its esters were investigated. In general the prodrugs revealed enhanced water solubility compared with metronidazole. N,N-diethylglycinate hydrochloride (3a) and 4-ethylpiperazinoacetate (3e) derivatives displayed higher aqueous solubility, which exceeded that of the parent drug by factors of approximately 140 and 100, respectively. All the esters revealed lower log P values than metronidazole except for the 4-phenylpiperazinoacetate derivative (3f), which was 6.5-times more lipophilic than metronidazole. The hydrolysis kinetics of the esters were studied in aqueous phosphate buffer (pH 7.4) and 80% human plasma at 37 degrees C. In all cases the hydrolysis followed pseudo-first-order kinetics and resulted in a quantitative reversion to metronidazole as evidenced by HPLC analysis. The prodrugs exhibited adequate chemical stability (half-life, t1/2, 4-16 h) in aqueous phosphate solution of pH 7.4. In 80% human plasma they were hydrolysed within a few minutesto metronidazole. The esters 3d (methylpiperazinoacetate derivative) and 3f were exempted since their t1/2 values were approximately 2.5 and 8.5 h, respectively. A comparative pH-rate profile study of N,N-diethylglycinate hydrochloride (3a) and 4-ethyl-piperazinoacetate (3e) derivatives in aqueous buffer solution over the pH range 2.2-10 was investigated. The results indicated that 3a showed marked stability at pH 2-6 followed by accelerated hydrolysis at pH 7.4. The basic ester 3e was found to be less stable at lower pH values but exhibited comparative stability at physiological pH. Moreover, in-vivo experiments in rabbits revealed a higher metronidazole plasma level with sustained release characteristics within the prodrug-treated animals (10- and 2.5-fold) as compared with the parent drug-treated group. In conclusion, the designed amino acid esters 3a and 3c-e might be considered as good candidates for water-soluble prodrug forms of metronidazole.

Amino Acids↗
PubMed2000

Evaluation of malonanilides as new stabilizers for double-base propellants.

Five malonanilide derivatives (M1-M5) were prepared by the reaction of ethyl malonate with aniline derivatives. These compounds were investigated as new stabilizers for double-base propellants (DBPs). The evaluation process has been performed through thermal stability tests, thermal analyses measurements (TGA and DSC) and kinetic parameters calculations (E(a)). The results of the new stabilizers were compared with the results of the classical stabilizer N, N-diethyldiphenyl urea. It has been found that o- and p-dinitromalonanilides, in particular, showed better stability effect for DBPs than the classical one.

Aerosol Propellants↗
PubMed2000

Improvement of availability of allopurinol from pharmaceutical dosage forms I - suppositories.

Solid dispersion and crystallization of a very slightly water-soluble drug, allopurinol, were prepared using urea, sodium salicylate and beta-cyclodextrin (beta-CD) as carriers. The spectroscopic infra-red (IR), differential scanning calorimetry (DSC) and powder X-ray diffractometry (PXRD) data indicate a role of these carriers in decreasing the crystallinity of allopurinol and complexing abilities. Solid dispersion and crystallization of the drug with these carriers were used in suppository formulations to investigate their role in enhancement of drug release through the membrane barrier. The bases used included Suppocire AM and the mixture of polyethylene glycols (PEGs). The release rates of allopurinol from lipophilic and hydrophilic suppository bases were examined and compared with those obtained for their inclusion compounds incorporated in the same bases. The prepared suppositories were evaluated for in-vitro drug release, when fresh and on storage. The release of pure allopurinol from the lipophilic base was remarkably higher than that from the hydrophilic one. The release of allopurinol from lipophilic as well as hydrophilic bases was significantly enhanced by crystallization of the drug from 5% w/v of sodium salicylate. Allopurinol crystallized from sodium salicylate, showed enhanced release reaching about 100% in 1 h from the Suppocire AM base. The obtained data from these experiments proved the superiority of the PEG formulations containing coevaporates of the drug to sodium salicylate, ratio 1:1, or of the drug to beta-CD, ratio 1:2; T(90%),12 and 36 min, respectively. A significant decrease of uric acid excretion in rabbits was observed after rectal administration of suppositories containing allopurinol crystallized from sodium salicylate.

Allopurinol↗
PubMed1999

Respiratory complications after thyroidectomy and the need for tracheostomy in patients with a large goitre.

BACKGROUND: Thyroidectomy for a large goitre carries a relatively high risk of postoperative respiratory obstruction which may necessitate tracheostomy. METHODS: One hundred and three patients with a large goitre who underwent thyroidectomy were studied prospectively. The presence or absence of six preoperative predictive factors for the development of serious postoperative respiratory obstruction was recorded. These factors were: goitre for more than 5 years, preoperative recurrent laryngeal nerve palsy, significant tracheal narrowing and/or deviation, retrosternal extension, difficult endotracheal intubation and thyroid cancer. Tracheostomy was performed on the basis of clinical judgement. RESULTS: Postoperative respiratory complications occurred in 32 patients (31 per cent), and were obstructive in 24 patients and not obstructive in eight. Tracheostomy was necessary in 13 patients (13 per cent). Tracheomalacia was the most common indication (n = 5). There were no deaths. At least four of the six risk factors were present in nine of the 13 patients who underwent tracheostomy compared with two of the 90 patients who did not. CONCLUSION: Multiple preoperative risk factors in a patient with a large goitre may be useful in predicting the need for planned tracheostomy following thyroidectomy.

Adolescent↗
PubMed1998

Synthesis of 2,5-disubstituted-1,4-benzoquinone derivatives as potential antimicrobial and cytotoxic agents.

A number of 2,5-disubstituted-1,4-benzoquinone derivatives were prepared and characterized by elemental analysis, infrared (IR), nuclear magnetic resonance (1H-NMR), and mass spectra (MS). These compounds and their synthetic precursors were evaluated for their in vitro antimicrobial and cytotoxic activity. The most potent antimicrobial compound was the thiadiazolyl derivative 4b, which was 2- to 4 times more active than the antimicrobial drug sulfathiazole. All the tested compounds were active in the Brine Shrimp Lethality (BS) Test. Compound 4e which was the most active in the BS test was also found to possess a significant cytotoxicity against two tumor cell lines. Some of the compounds were found to be mutagenic at relatively high concentration.

Animals↗
PubMed1998

Kojic acid production by Aspergillus flavus using gelatinized and hydrolyzed sago starch as carbon sources.

Direct conversion of gelatinized sago starch into kojic acid by Aspergillus flavus strain having amylolytic enzymes was carried out at two different scales of submerged batch fermentation in a 250-mL shake flask and in a 50-L stirred-tank fermentor. For comparison, fermentations were also carried out using glucose and glucose hydrolyzate from enzymic hydrolysis of sago starch as carbon sources. During kojic acid fermentation of starch, starch was first hydrolyzed to glucose by the action of alpha-amylase and glucoamylase during active growth phase. The glucose remaining during the production phase (non-growing phase) was then converted to kojic acid. Kojic acid production (23.5 g/L) using 100 g/L sago starch in a shake flask was comparable to fermentation of glucose (31.5 g/L) and glucose hydrolyzate (27.9 g/L) but in the 50-L fermentor was greatly reduced due to non-optimal aeration conditions. Kojic acid production using glucose was higher in the 50-L fermentor than in the shake flask.

Aspergillus flavus↗
PubMed1997

Dissolution kinetics of glibenclamide glass.

This work examines the dissolution kinetics of glibenclamide crystalline state, form I, and glibenclamide glassy state, form II. This required determination of the pH-solubility profiles of the two forms, dissolution at different stirring rates, temperatures, and pHs. It was found that form II exhibited higher solubility and dissolution rate at all the studied pHs. However, a significant increase in dissolution and solubility of form II was noted at pH 6. Dissolution studies at different stirring rates confirmed that the dissolution process is diffusion controlled, zero order in nature and adheres to the Noyes and Whitney and Levich equations. Dissolution studies at different temperatures enabled calculation of the heat of dissolution, Ea, of both forms. Ea for form I and form II was found to be almost identical. Storing of form II for one week at different temperatures resulted in the partial transformation of form II to form I as indicated from dissolution studies. The extent of transformation and hence reduction in dissolution rate increased with the increase in storage temperature.

Buffers↗
PubMed1996

Pattern of postoperative pyrexia in Khartoum.

The pattern of postoperative pyrexia in Khartoum was prospectively studied in 260 patients who underwent a variety of surgical operations. Ninety four patients (36.1%) developed postoperative pyrexia. The commonest causes of pyrexia encountered were wound sepsis (10%), malaria (9.6%) and respiratory tract infection (7.3%). Less frequent causes were urinary tract infection, thrombophlebitis, intra-abdominal sepsis and deep vein thrombosis. In 14.6% of the patients, the cause of pyrexia was undetermined. The risk factors for postoperative pyrexia were the patient's age, diabetes mellitus, obesity, preoperative chest infection, smoking, duration of surgery, operator's surgical experience and urethral catheterisation. The postoperative pyrexia was associated with 7.4% mortality rate which was due to intra-abdominal sepsis and pulmonary embolism. The incidence of postoperative pyrexia can be minimised by adequate preoperative preparation, meticulous surgical technique and good postoperative care.

Adolescent↗
PubMed1995

Schistosomal glomerulopathy: a putative role for commonly associated Salmonella infection.

A total of 190 patients were selected after being subjected to hemoculture for detecting Salmonella spp, coproscopy for Schistosoma mansoni eggs and ELISA testing for anti schistosomal sero-reactivity. They made up 4 group; The first comprised 31 febrile patients with positive hemoculture, coproscopy and ELISA, 13 of them with hepatic fibrosis and received combined anti- typhoid and antibilharzial therapy. The second comprised 53 febrile patient with the same criteria; 18 with hepatic fibrosis, and received anti typhoid & antibilharzial alternatively. The third group comprised 46 febrile patients with positive hemoculture and negative coproscopy but with positive ELISA 20 were hepatosplenic & received anti typhoid treatment. The fourth comprised 60 afebrile patients with negative hemoculture and positive coproscopy and ELISA 35 were hepatosplenic, and received anti-bilharzial treatment. 50 healthy individuals were selected as control. The controls and the patients; before and after treatment underwent investigation for determining levels of serum complement3 as a marker of immune complex precipitation activity and creatinine clearance, and urinary proteins excretion in 24 hours as measurements of glomerular function. The specific treatment either combined or alternative or single in the first 3 groups consequently showed marked improvement in the above criteria with insignificant additive pattern in the second. The fourth group showed non-significant difference in the above criteria after anti-bilharzial therapy among the hepatosplenic, meanwhile it improved these criteria significantly among the non-hepatosplenic--in the four groups--whose criteria were significantly higher than among the hepatosplenic before treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Knowledge of sexually transmitted diseases, HIV infection and AIDS among sexually active adolescents in Nairobi, Kenya and its relationship to their sexual behaviour and contraception.

A total of 675 male and female adolescents, aged 10 to 19 years, who were attending the adolescent antenatal clinic at the Kenyatta National Hospital and the Special STD and Skin Disease Clinic in Nairobi, between April 1, 1991 and July 31, 1991, were interviewed by means of partially structured questionnaire, to determine their level of awareness on sexually transmitted diseases, HIV infection, AIDS and contraception with its relationship to their sexual behaviour and contraceptive practice. Adolescents formed 27.6% of people attending the STD and Skin diseases clinic, of whom 52.9% were females and 41.2% were males. Majority of them were not in any formal employment. A few were students in schools in the city. 70.4% of the total group mentioned gonorrhoea as a sexually transmitted disease, as compared to only 54.3% who mentioned AIDS as a sexually transmitted disease. They only mentioned three diseases, namely gonorrhoea, syphilis, and AIDS (HIV infection). Majority of them had started coitus very early. They were involved with many and different partners, some of whom belonged to the high risk groups for HIV infection as well as STD's. As a reflection of their low awareness on AIDS, most of these sexually active adolescents had not changed their sexual behaviour, nor were they using any protective measure against STD's or HIV infection. The implications of these findings are discussed and possible remedial measures suggested.

Adolescent↗
PubMed1994

Abdominal tuberculosis.

The abdomen is involved in 10% to 30% of patients with pulmonary tuberculosis. The diagnosis is not difficult in societies where the disease is common and clinicians are aware of it. While previously rare in Western countries, the incidence is now rising among immigrants, and patients with AIDS. In HIV-infected patients, the disease is of a rapidly progressive nature, often fatal through usually treatable, but the diagnosis is difficult and often delayed. Treatment is essentially medical but occasionally surgical operation is necessary.

Abdomen↗
PubMed1993

Isolation and characterization of simian immunodeficiency virus from African white-crowned mangabey monkeys (Cercocebus torquatus lunulatus).

Forty-eight of 236 sera from seven species of African non-human primates in Kenya, including those of white-crowned mangabey monkeys (Cercocebus torquatus lunulatus) had antibodies to simian immunodeficiency viruses (SIVs). Isolates of simian lentivirus were obtained from seropositive white-crowned mangabey monkeys which are indigenous in West Africa. This virus, designated as SIVWCM, appeared morphologically similar to HIV by electron microscopy, showed Mg(2+)-dependent reverse transcriptase activity, and induced cytopathic effects in human CD4-positive cells. Western blotting analysis revealed that env products of SIVWCM cross-reacted with those of SIVAGM more strongly than with those of HIV-1 and SIVMAC, and clear hybridization bands were detected with an SIVAGM probe. For comparison of the virus sequence with those of other primate lentiviruses, part of the pol gene and the long terminal repeats (LTRs) were amplified and cloned. Sequencing showed that SIVWCM isolates were closely related to SIVAGM isolates. This study suggested that SIVAGM from the Cercopithecus genus and SIVWCM from the Cercocebus genus may be members of an SIV group that is genetically distinct from the SIV from a sooty mangabey monkey (SIVSMM) of the genus Cercocebus, to which the white-crowned mangabey monkey also belongs.

Animals↗