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Biomedical subjects

N Khan

Publications and source records attributed to N Khan.

At least 181 records · Page 10Linked to original sources
PubMed1993

The effects of a natural disaster on child behavior: evidence for posttraumatic stress.

OBJECTIVES: A prospective study of children examined both before and after a flood disaster in Bangladesh is used to test the hypothesis that stressful events play a causal role in the development of behavioral disorders in children. METHODS: Six months before the disaster, structured measures of selected behavioral problems were made during an epidemiological study of disability among 2- to 9-year-old children. Five months after the disaster, a representative sample of 162 surviving children was reevaluated. RESULTS: Between the pre- and postflood assessments, the prevalence of aggressive behavior increased from zero to nearly 10%, and 45 of the 134 children who had bladder control before the flood (34%) developed enuresis. CONCLUSIONS: These results help define what may be considered symptoms of posttraumatic distress in childhood; they also contribute to mounting evidence of the need to develop and evaluate interventions aimed at ameliorating the behavioral and psychological consequences of children's exposure to extreme and traumatic situations.

Aggression↗
PubMed1993

Community-wide estimation of illicit drug use in delivering women: prevalence, demographics, and associated risk factors.

OBJECTIVE: To determine the community-wide prevalence of illicit drug use in delivering women and to compare rates in women delivering in an urban center serving the medically indigent with those delivering in private hospitals. METHODS: Over 6 weeks, 1062 urine samples were obtained anonymously from women presenting for delivery in seven hospitals in the Jacksonville, Florida area. All urine samples were analyzed blindly for illicit drugs using fluorescent polarized immunoassay. RESULTS: The percentage of women with positive urine toxicology was 7.1%. Positive results were more frequent in the public hospital population (12.7%) than the private hospital population (3.9%). The prevalence of cocaine use was 2.1% and marijuana 5.3%. Urine positivity was similar in black and white women, with cocaine metabolites more prevalent in black women and cannabinoids more common in white women. Women with positive screens for cocaine were more likely to use tobacco and alcohol, admit to substance abuse, and receive limited prenatal care. Women with positive screens for marijuana were difficult to differentiate from the urine-toxicology-negative group. CONCLUSIONS: Urine samples positive for illicit drugs were significantly more common in women delivering in an urban center serving the indigent population than in those delivering in private hospitals. Based on associated factors, cocaine users fit a more indentifiable profile than marijuana users. The overall incidence of positive urine toxicology was no different in black and white pregnant women, but the more frequent finding of cocaine metabolites in black women may lead to biased over-reporting of substance abuse in this population.

Adult↗
PubMed1992

Photosensitization by anticancer agents. 11. Mechanisms of photosensitization of human leukemic cells by diaminoanthraquinones: singlet oxygen and radical reactions.

The synthesis of several aminoanthraquinone derivatives (AAQs), designed to suppress the dark toxicity and to promote more efficient cancer cell photosensitization for potential use in photodynamic therapy (PDT), is described. The following AAQs were synthesized: 1-NH2-4,5-(MeO)2-AQ (1), 1,5-(NH2)2-4,8-(MeO)2-AQ (2), 1,8-(NH2)2-4,5-(MeO)2-AQ (3), and 1,5-(NHPhMe)2-4,8-(MeO)2-AQ (8). The agents exhibit strong absorption in the region 480-620 nm. Possible mechanisms of photosensitization were studied by measuring 1O2 phosphorescence at 1270 nm, detecting superoxide radicals employing an electron paramagnetic resonance (EPR)-spin trapping technique, and measuring oxygen consumption during the photo-oxidation of a representative biological electron donor, NADH. Strong phosphorescence from 1O2 was observed upon illumination of 2 and 3 in C6H6 (quantum yield of 0.25 and 0.5 respectively), and in EtOH (quantum yield of 0.23 and 0.34). The 1-amino-AQ (1) was the weakest 1O2 sensitizer, with quantum yield of 0.13 in benzene. No phosphorescence was observed in EtOH. A superoxide radical was detected as a spin adduct of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) in irradiated benzene solutions of 1, 2 or 3 and DMPO. AAQs 2 and 3 sensitized photo-oxidation of NADH in H2O/EtOH mixture with the intermediacy of singlet oxygen as judged by the effect of sodium azide on the photostimulated oxygen consumption. Evolution of O2 upon addition of catalase to the illuminated solution confirmed the ultimate formation of hydrogen peroxide. These findings suggested that the (di)amino-dimethoxyanthraquinones might exert photosensitization via both Type I and Type II mechanisms. The AAQs were tested for their ability to photosensitize K562 human chronic myeloid leukemic cells in culture. Viability was measured using the 3,4,5-diethylthiazol-2,5-diphenyl tetrazolium blue assay, and DNA and possible membrane damage were assessed. The results from illuminating cells with light > 475 nm show that for the 1,5-compounds, the presence of methoxy substituents at 4,8 positions reduces the dark toxicity from ID50 of 23 to 250 microM and for the 1,8-compounds correspondingly from ID50 of 53 to > 300 microM. In the 1,5-series this decrease of the dark toxicity is accompanied by an increase in light-induced dose modification from 8.85 to 14.4. Differences exist in the mechanisms of cytotoxicity between the prototype phenolic AAQs and their methoxy counterparts. It appears that the cytotoxic action of the latter causes cell damage by the formation of a high proportion of alkali labile sites in addition to frank strand breaks.(ABSTRACT TRUNCATED AT 400 WORDS)

Anthraquinones↗
PubMed1992

Estimates of the prevalence of childhood seizure disorders in communities where professional resources are scarce: results from Bangladesh, Jamaica and Pakistan.

Although numerous estimates of the prevalence of seizure disorders in populations in the less developed world have now been published, these estimates are difficult to interpret due to lack of comparability of study methods and criteria for case definition. The results reported in this paper are from a large, collaborative study of disabilities in 2- to 9-year-old children in which standard research procedures and case definitions were used in three diverse populations (located in Bangladesh, Jamaica and Pakistan). A two-phase study design (screening followed by professional evaluations) was used in this study allowing for the professional evaluation to serve as the criterion in the estimation of prevalence, even for rare disorders. As a result, the prevalence estimates reported here have a high degree of comparability across populations and exhibit unusually strong validity for population surveys. Febrile seizures were the most common type of seizure history in all three populations, with point estimates of lifetime prevalence ranging from 10.9 to 62.8 per 1000. The lifetime prevalence rates of epilepsy (recurrent unprovoked seizures) ranged from 5.8 to 15.5 per 1000. Lifetime prevalence rates of neonatal, all provoked and all unprovoked seizures, as well as estimates of the prevalence of active epilepsy, are also reported.

Age Factors↗
PubMed1992

Comparison of serum fructosamine and blood glucose concentrations as indices of glycaemic control in non-insulin dependent diabetic out-patients.

The usefulness and validity of blood glucose measurement as an index of diabetic control were assessed with reference to serum fructosamine. Two hundred and twenty-eight non-insulin dependent diabetic out-patients were studied in the usual clinical setting. Fasting blood glucose (FBG) concentration was positively correlated with serum fructosamine (r = 0.42, t = 6.78 p less than 0.01). On the basis of their serum fructosamine concentrations, patients were divided into 3 groups. They were good control (fructosamine less than or equal to 288 umol/l), acceptable control (fructosamine less than or equal to 320 umol/l) and poor control groups (fructosamine greater than 320 umol/l). The mean fasting blood glucose concentration was significantly higher in the latter than the former 2 groups. However, at each level of control, there was a wide range of FBG concentrations. Thus, the value of FBG in predicting glycaemic control is limited. Its positive predictive value was only 32%, and its overall accuracy as an index of diabetic control was only 58% though its negative predictive value was high (93%). In 162 patients with poor diabetic control as indicated by their serum fructosamine concentrations, 81 (50%) of them had FBG less than 10 mmol/l on their clinic visit day. Fasting blood glucose is therefore not a reliable measure of good diabetic control, though it is useful in predicting poor control. FBG is simple to measure, cheap and rapidly available on clinic day, thus ensuring its continuing use. Doctors should be aware of its limitations and should not rely solely on FBG to assess diabetic control.

Adult↗
PubMed1991

The solution structure of motilin from NMR distance constraints, distance geometry, molecular dynamics, and an iterative full relaxation matrix refinement.

A model of the structure of the 22 amino acid residue gastrointestinal peptide hormone motilin in 30% hexafluoro-2-propanol has been obtained by using distance constraints obtained from two-dimensional nuclear Overhauser enhancements. A set of initial structures have been generated by using the distance geometry program DIANA, and 10 of these structures have been refined by using restrained molecular dynamics (AMBER). The resulting structures are virtually indistinguishable in terms of constraint violations and energies and display less than 0.5-A root mean square deviations (RMSD) of the backbone atom positions from Tyr7 to Lys20. A comparison of back-calculated and experimental NOE intensities indicates that RMSD's are not the best indicators of the goodness of fit or of the precision with which the structure is defined. The structure was further refined by fitting the experimental NOE data using an iterative full relaxation matrix analysis. The mean error between the observed and calculated backbone NOE intensities for the final refined structure was 0.23 for the full length of the molecule, 0.18 for the region from Glu9 to Lys20, and 0.29 for the region from Phe1 to Gly8. R factors for the same regions were 0.27, 0.19, and 0.43, respectively. All of the NOE-determined structures consistently display an alpha-helix which extends from Glu9 to Lys20. Considerable lack of definition of structure exists at the amino and carboxyl ends of the molecule and also in the vicinity of Thr6-Tyr7-Gly8. A tendency to form a wide turn appears to exist over the sequence Pro3-Ile4-Phe5-Thr6, but the structure in this region is not well defined by the NOE data.

Amino Acid Sequence↗
PubMed1991

Early measurement of systemic lipid peroxidation products in the plasma of major blunt trauma patients.

We sought evidence of oxidant-induced biological membrane damage in 43 resuscitated blunt trauma patients (average ISS, 36.9) within 2-6 hours of injury and before anaesthesia and surgery. The plasma levels of the lipid peroxidation products (conjugated dienes, CDs A 233 nm) and malondialdehyde (MDA, nMol/ml) and the oxidant-inducing effect of the trauma plasma on normal FMLP-stimulated neutrophils were compared to those of control subjects. No differences were observed in the plasma levels of MDA (1.73 +/- 2.15 vs. 1.45 +/- 0.70 nMol/ml) and CDs (2.07 +/- 2.16 vs. 1.28 +/- 0.60 A 233nm), or on stimulated neutrophil superoxide production (26.4 +/- 6.9 vs. 29.0 +/- 6.2 nMol O2-/2 x 10(6) PMNs). These observations persisted when the patients were analyzed based on injury severity, the presence of long bone fractures, and the class of shock at presentation. We conclude that there is no evidence of oxidant-induced membrane damage manifested by increased plasma levels of CDs or MDA within 2 to 6 hours of blunt injury.

Adolescent↗
PubMed1991

Diagnostic and prognostic significance of serum cholinesterase and lactate dehydrogenase in breast cancer.

Serum cholinesterase (ChE) and Lactate dehydrogenase (LDH) activities were estimated in 40 cases of carcinoma breast, 25 cases of benign tumours and compared with healthy controls (30 cases). Significant difference in enzyme activities were obtained between benign and malignant neoplasms of the breast when compared with each other as well as when compared with healthy controls. Also, there were significant enzyme changes between non-metastatic cases and those with metastasis and when Stage I and Stage II cancers were compared with those in Stage III and Stage IV. No difference in enzyme levels were recorded between pre and post-operative cases and in different types of breast cancers. While ChE was depressed in 80 per cent cases of malignancy breast, serum LDH was raised in 73.3 per cent cases.

Breast Diseases↗
PubMed1990

Sequence-specific 1H NMR assignments and secondary structure of porcine motilin.

The solution structure of the 22-residue peptide hormone motilin has been studied by circular dichroism and two-dimensional 1H nuclear magnetic resonance spectroscopy. Circular dichroism spectra indicate the presence of alpha-helical secondary structure in aqueous solution, and the secondary structure can be stabilized with hexafluoro-2-propanol. Sequence-specific assignments of the proton NMR spectrum of porcine motilin in 30% hexafluoro-2-propanol have been made by using two-dimensional NMR techniques. All backbone proton resonances (NH and alpha CH) and most of the side-chain resonances have been assigned by using double-quantum-filtered COSY, RELAYED-COSY, and NOESY experiments. Simulations of NOESY cross-peak intensities as a function of mixing time indicate that spin diffusion has a relatively small effect in peptides the size of motilin, thereby allowing the use of long mixing times to confidently make assignments and delineate secondary structure. Sequential alpha CH-NH and NH-NH NOESY connectivities were observed over a significant portion of the length of the peptide. A number of medium-range NOESY cross-peaks indicate that the peptide is folded into alpha-helix from Glu9 to Lys20, which agrees favorably with the 50% helical content determined from CD measurements. The intensities of selected NOESY cross-peaks relative to corresponding diagonal peaks were used to estimate a rotational correlation time of approximately 2.5 ns for the peptide, indicating that the peptide exists as a monomer in solution under the conditions used here.

Amino Acid Sequence↗
PubMed1990

Hanging leg weight--a rapid technique for estimating total body weight in pediatric resuscitation.

The accuracy of two methods of rapidly estimating total body weight in children was assessed. The first method correlated patient length to known total body weight, and the second correlated the weight of both legs weighted together to known total body weight. One hundred children undergoing general anesthesia in the operating rooms of Childrens Hospital of Los Angeles were entered into the study. Each child had a known preoperative body weight. After induction of anesthesia, each child's supine length was measured and hanging (inert) legs were weighted. There was excellent linear correlation between hanging leg weight and total body weight (correlation coefficient [r2], 0.95) for all patients, and good linear correlation between supine length and total body weight, r2, 0.86). Range restriction analysis for both techniques showed poor correlation for total body weights of less than 10 kg and poor correlation for the supine length technique when total body weight was more than 25 kg. The hanging leg weight of an inert child has excellent correlation to total body weight for children weighing more than 10 kg.

Adolescent↗
PubMed1989

Liver biopsy.

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Biopsy, Needle↗