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Biomedical subjects

K A Khan

Publications and source records attributed to K A Khan.

At least 37 records · Page 2Linked to original sources
PubMed1995

Transcranial Doppler ultrasonography and transesophageal echocardiography in the investigation of pulmonary arteriovenous malformation in a patient with hereditary hemorrhagic telangiectasia presenting with stroke.

BACKGROUND: Hereditary hemorrhagic telangiectasia (HHT) is associated with a high incidence of pulmonary arteriovenous malformations (PAVMs), which can be the underlying cause for cerebral ischemia or brain abscess. The diagnosis of these malformations may be difficult, as clinical or radiological findings may be absent. Transcranial Doppler ultrasound (TCD) with saline contrast and transesophageal echocardiography (TEE) with saline contrast are useful in identifying patients with right-to-left shunts and may help identify PAVMs. CASE DESCRIPTION: A 68-year-old woman with HHT presented with two strokes over a 1-year period. After the first stroke, a transthoracic echocardiogram with saline contrast demonstrated significant right-to-left shunt that was interpreted as a patent foramen ovale. After the second stroke, a TCD contrast study confirmed this right-to-left shunt; however, a TEE contrast study discovered an extracardiac shunt. Pulmonary angiography revealed a left lower lobe PAVM and three telangiectasias involving the right lung. The PAVM was subsequently embolized. Postembolization radiographic imaging showed complete occlusion of the feeding vessel to the PAVM. However, repeated contrast TCD and TEE demonstrated persistent right-to-left shunting. CONCLUSIONS: In our patient, stroke may have resulted from peripheral venous emboli passing through the PAVM or from endogenous thromboemboli originating within the PAVM. TCD and TEE contrast studies were helpful in judging the efficacy of catheter embolization therapy of PAVM. TCD and TEE with saline contrast may be clinically useful follow-up examinations for recurrence or development of new PAVMs.

Aged↗
PubMed1994

Atypical case of cystic fibrosis.

A patient of cystic fibrosis is hereby reported. He had no family history and presented with chest symptoms, only. There was no evidence of hepatic or pancreatic involvement. To our knowledge this represents the first case of its kind from this part of country.

Adult↗
PubMed1994

In vitro studies of the antibacterial and antifungal activity of oxine and its derivatives.

Twenty-one derivatives of 8-hydroxyquinoline (oxine, 8H, CAS 148-24-3) were prepared and characterized by UV, IR, MS and NMR spectroscopy. Four of these derivatives, N-butyl, 8-butyloxyquinolinium bromide (HBD), 8-pentyloxyquinoline (HPEM), N-pentyl, 8-pentyloxyquinolinium bromide (HPED) and N-benzyl, 8-benzyloxy quinolinium chloride (HBED) are new and reported for the first time. The antimicrobial activity of these compounds was carried out in vitro against 11 Gram positive and 18 Gram negative bacteria, and 18 fungi including 9 dermatophytes, 7 other filamentous fungi and 2 Candida species. Three compounds namely, HPRD, HPED and HBED were found to possess significant antibacterial activity in order of HPED > HPRD > HBED, whereas 4 were found to possess significant antifungal activity in order of 8H > HT > HPEM > 8B.

Anti-Bacterial Agents↗
PubMed1993

Synthesis of alkyl catechols and evaluation of their antibacterial and cyfotoxic activity.

A series of potential biologically active mono-, di- and tetra- alkyl catechols were prepared through Friedel- Crafts alkylation of catechol, and evaluated for their antibacterial and cytotoxic activity. The mono-substituted alkyl derivatives showed maximum antibacterial activity in vitro which increased with the increasing length of the alkyl chains. Primary screening results indicated that all the monoalkyl derivatives except 4- (2-octyl) catechol inhibited the growth of B. bronchoseptica and maximum zones of inhibition were observed in case of monohexyl catechols (both n- and 2-hexyl) and monobenzyl derivative. In case of Gram-negative organisms growth of Kl. pneumoniae and A. calcoaceticus was inhibited by several derivatives. Mono-3-octyl-, monononyl- and monobenzyl catechols markedly inhibited the growth of Kl. pneumoniae. Mono-2-heptyl catechol inhibited the growth of six Gram-negative bacteria. Minimum inhibitory concentration of six most active compounds of the series was determined against Gram-positive and Gram-negative organisms; it ranged from < 100 mug/ml to l0 mug/ml. The antibacterial activity of catechol was not significant. Cytotoxicity test done by brine shrimp assays showed that the order of cytotoxicity decreases in going from mono- to tetra- alkyl catechols, and among the mono- alkyl products, a decrease in order of cytotoxicity was noted in going from mono-methyl catechol (LD(50) = 59) to monopentyl catechol (LD(50) = 173) after which the order of cytotoxicity gradually increased upto the largest alkyl substituent tested i.e. monononyl catechol (LD(50) = 114). Methyl and ethyl catechol, which were almost inactive in respect of their antibacterial activity possessed prononounced cytotoxicity as compared to higher homologues. Catechol itself did not show significant cytotoxicity (LD(50) = 393.27).

Journal Article↗
PubMed1992

Sister chromatid exchange and chromosome aberrations in mice after in vivo exposure of green S--a food colorant.

Sister chromatic exchanges (SCE) and chromosome aberrations (CA) in mice after in vivo exposure of Green S were carried out following single acute treatment. Except for the lowest dose (25 mg/kg body weight) a significant increase in the SCEs were observed in all the other doses (50, 100, and 200 mg/kg) tested. In CA study two higher doses (200 and 400 mg/kg) showed a significant increase in CA when compared with control. The minimum effective dose which induced SCE and CA was 50 and 200 mg/kg of body weight, respectively. The trend tests for the evidence of dose response effects were also significant for both SCE and CA. No significant differences were observed in cell replication kinetic (RI) analysis. A significant increase in the mitotic index (MI) was also observed in the highest dose (400 mg/kg) tested when compared with control. Thus the present study indicates that Green S can induce both SCE and CA in vivo in bone marrow cells of mice.

Animals↗
PubMed1992

Sister-chromatid exchange and chromosome aberrations induced by paracetamol in vivo in bone-marrow cells of mice.

Sister-chromatid exchange (SCE) and chromosome aberrations (CA) induced by paracetamol (PC), a common analgesic, were studied in vivo on bone-marrow cells of mice. The trend tests for the evidence of dose-response effects for both SCE and CA were significant. The significant increase in SCE as well as CA induced by PC may be attributed to the fact that PC can induce genotoxicity through DNA damage. Thus, the present study indicates that PC was genotoxic in vivo in bone-marrow cells of mice.

Acetaminophen↗
PubMed1992

Evaluation of the genotoxicity of 4-N-butylamino-1,2,3,4-tetrahydroacridine hydrochloride (centbucridine): a new local anaesthetic.

Centbucridine, a new local anaesthetic, was tested in in vivo genotoxicity assays. Three different endpoints were selected for this purpose. Chromosome aberrations (CA) and sister chromatid exchange (SCE) were analysed in bone marrow cells and DNA-strand breaks (SB) were measured in liver cells of mice following a single acute exposure. No significant differences were observed in the CA, SCE and SB studies, when compared with respective controls. An increase in the mitotic indices (MI) was observed only with the lowest dose tested in the CA study. No significant differences in the MI were observed with the two higher doses tested when compared with solvent controls. Trend tests for linear dose response were negative in all the parameters examined including MI. The overall results of the three endpoints tested indicated that centbucridine was not genotoxic in the mouse.

Anesthetics, Local↗
PubMed1991

A simple and rapid method for the quantification of Eudragit RS100 and RL100 poly(methacrylates) in sustained-release dosage forms.

A colorimetric ion-pair complexation method has been developed which provides a simple and rapid way of quantifying Eudragit RS100 and RL100 in pharmaceutical dosage forms. The quaternary ammonium groupings in these polymers appear to form an ion-pair complex with the dye tropaeolin OOO. When extracted into an organic phase, the optical density at 484 nm is linearly related to polymer concentration. Control of pH is important, and it should be maintained within the range 4.5 to 9.0. A wide range of pharmaceutical excipients commonly used in tablet, pellet, and film-coating formulations did not interfere with formation of the complex, but certain drugs were found to significantly enhance or decrease the assay response. Good reproducibility, precision, and accuracy were demonstrated when the method was applied to a film-coated pellet formulation containing an interfering drug (promethazine hydrochloride). However, removal of interfering substances must be optimized. The method was sufficiently sensitive for the determination of polymer on a single dose unit of encapsulated beads.

Acrylic Resins↗
PubMed1989

Genotoxicity studies on mice after short term inhalation exposure to methyl isocyanate.

Mutagenicity testing is an important aspect of the toxicological evaluation of environmental chemicals for safety. Methyl isocyanate (MIC), a very hazardous chemical used for the manufacture of insecticides, was studied for its genotoxic effects on the somatic cells of mice after inhalation exposure by means of an in vivo micronucleus test and chromosomal analysis of bone marrow cells. Animals were exposed for 10 min to different concentrations (2.40, 4.80 or 7.20 microliters) of MIC in a 22 litre chamber at 0 and 24 h. Bone marrow smears prepared 6 h after the second treatment were examined for the occurrence of micronuclei (MN) in polychromatic (P) and normochromatic (N) erythrocytes. The frequencies of cells with MN and the P/N ratio did not differ significantly from those of the control at all the exposure levels. Chromosomal preparations revealed few structural and numerical abnormalities. Aberrations encountered were of the chromatid type only. Quantitative analyses failed to exhibit any significant increase in aberration rates in the three treated groups. Numerical abnormalities were within the control range.

Administration, Inhalation↗
PubMed1986

Argon laser trabeculoplasty in a residency program.

The following article discusses the outcome of 60 eyes with various forms of glaucoma undergoing resident-performed argon laser trabeculoplasty (ALT). The majority (46/60) of eyes had primary open-angle glaucoma. Decrease in intraocular pressure (IOP) was not as great as reported in the literature. Our results suggest that initially treating 180 degrees of the angle is associated with improved overall results. ALT has proved to be a safe and effective alternative to conventional surgery for glaucoma in a residency training setting.

Adult↗