Biomedical subjects

C Khan

Publications and source records attributed to C Khan.

12 recordsLinked to original sources

PubMed2001

Estrogenic potency of chemicals detected in sewage treatment plant effluents as determined by in vivo assays with Japanese medaka (Oryzias latipes).

Gonadal intersex and high prevalences of the female phenotype have been observed in fish populations in urbanized areas. Environmental estrogens discharged in sewage treatment plant effluents may be responsible for feminization of fish but many compounds with the potential to induce these responses occur in effluents, including natural and synthetic estrogen hormones, degradation products of alkylphenol ethoxylate surfactants, and plasticizers. In this study, the estrogen hormones 17 alpha-ethinylestradiol, 17 beta-estradiol, estrone, and estriol induced intersex (i.e., testis-ova) and altered sex in Japanese medaka (Oryzias latipes) when these fish were exposed to nanogram per liter concentrations of test compounds from hatch to approximately 100 d after hatch. A mix of nonylphenol mono- and diethoxylate induced a weak response and a mix of nonylphenol mono- and diethoxycarboxylate did not give a response in this assay at microgram per liter concentrations, indicating that these degradation products of nonylphenol ethoxylates have little or no estrogenic activity in fish. Bisphenol A induced testis-ova in medaka exposed to a concentration of 10 micrograms/L, but diethylhexyl phthalate did not induce a response. Results with the medaka assay were consistent with estrogenic responses in the yeast estrogen screening assay. Analyses of monitoring data reported in the literature indicate that concentrations of estrogen hormones detected in the final effluents of sewage treatment plants are generally greater than the lowest-observed-effect levels for alterations to gonadal development in medaka.

Animals↗

PubMed1999

Frequent detection of HIV-1 in the gastric aspirates of neonates born to HIV-infected mothers.

OBJECTIVE: To evaluate the frequency and correlates of oral route exposure of infants born to HIV-1-infected women. METHODS: A multicenter study was performed within the prospective French Perinatal Cohort Study of mother-to-child HIV transmission. Oropharyngeal and gastric aspirates from 122 neonates were studied by reverse transcriptase (RT) polymerase chain reaction (PCR) for the presence of HIV-1, as well as for standard microbiology (Gram staining and culture). RESULTS: Aspirates from 101 neonates were analyzed by RT-PCR; 28% of these were positive for HIV RNA. Another 21 aspirates could not be tested because of PCR inhibition. The median concentration of HIV RNA in the positive aspirates was 126 copies/ml (range: 8-1270). Detection of HIV-1 in the aspirate was significantly related to high maternal plasma-viral load, presence of blood in the aspirate, positive Gram stain or culture, episiotomy or perineal lesions, and sexually transmitted infections during the pregnancy. Most of the mothers received zidovudine prophylaxis during pregnancy and delivery. Among the six infants who were infected with HIV, three had positive aspirates. Of the three assumed to have acquired the infection intrapartum, only one had an HIV RNA-positive aspirate. CONCLUSION: Exposure of the fetus to HIV via the oral route occurs frequently, even in the presence of zidovudine prophylaxis, and is likely to be one of the mechanisms of intrapartum transmission, but not the only one.

Adult↗

PubMed1999

Rubella susceptibility in Jamaican women, 1996.

The 1995 rubella outbreak in Jamaica indicated a need to survey the susceptibility rate in Jamaican antenatal women at risk. In this 1996 study, 389 women in the reproductive age group were investigated for rubella antibodies. In the public sector urban group (A), rubella susceptibility was 20.2%, while in a private sector urban clinic (B) practising routine rubella surveillance and recommending postpartum immunization in seronegatives, the susceptibility rate was 13.8%. The latter rate was significantly lower than that in the rural group (C) (35.9%; p < 0.001). The overall susceptibility rate was 21.3%. Rubella susceptibility has improved overall in women of childbearing age compared with levels in the prevaccine year of 1968. A significant thrust in rubella prevention will still be required before the next rubella epidemic in order to reduce the risk of congenital rubella syndrome.

Adolescent↗

PubMed1997

HIV-1 RNA detection in plasma for the diagnosis of infection in neonates. The French Pediatric HIV Infection Study Group.

The objective of this study was to assess the frequency of detection of HIV-1 RNA in plasma of neonates born to HIV-1-seropositive mothers and to determine the diagnostic value of this method in the neonatal period. The study involved 96 infants among those enrolled in the French National Prospective Study. HIV-1 RNA was detected in the first 10 days of life by nucleic acid sequence-based amplification (NASBA) in 12 of 48 plasma samples of infected infants and in 39 of 39 of the second samples taken before the age of 3 months. On the same samples, peripheral blood mononuclear cell (PBMC) DNA polymerase chain reaction (PCR) or viral culture that had been routinely performed were found to be positive in 11 of 48 samples taken in the first 10 days of life and 39 of 39 second samples. For the noninfected infants, HIV-1 RNA was never detected in the 48 samples taken in the first 10 days of life and was detected in one of the 48 samples taken before the age of 3 months. HIV-1 RNA detection in plasma by NASBA has sensitivity and specificity equal to those of DNA PCR and culture on PBMC for the diagnosis of infection in infants with the clade B virus. This standardized method gives rapid results on a small volume of plasma and seems well suited for diagnosis on a large scale.

CD4 Lymphocyte Count↗

PubMed1995

Stem cell factor binding to retrovirus primer binding site silencers.

Using modified nuclear lysis and binding conditions, we have examined the binding of an embryonal carcinoma (EC) cell factor, binding factor A, to a stem cell-specific silencer which acts at the DNA level and overlaps the Moloney murine leukemia virus (M-MuLV) proline primer binding site (PBS). Following our protocol, we found that in vitro binding of factor A correlated with the in vivo activity of the M-MuLV silencer. Factor A bound specifically to the wild-type silencer element at room temperature and 30 degrees C, but not at 4 degrees C, and bound 10-fold better to the full-length silencer than to a minimal silencer core element. The factor was enriched in nuclear compared with cytosolic extracts and in undifferentiated EC cells compared with differentiated cells in which the silencer is nonfunctional. Salt and ion requirements for factor A binding were investigated, and partial purification steps indicated the factor to be a heparin-Sepharose-binding moiety of greater than 100 kDa. To examine possible relationships between silencer and PBS activities, sequences representing phenylalanine, isoleucine, lysine-1,2, lysine-3, methionine, and tryptophan PBS DNA fragments were tested in vivo for stem cell-specific repression of M-MuLV expression and in vitro in DNA binding assays. Of these PBS elements, only the lysine-1,2 PBS DNA fragment showed consistently high levels of repression. Interestingly, the lysine-1,2 PBS DNA fragment also formed a complex with an EC cell factor with characteristics similar to those of factor A. However, the two factors did not cross-compete in binding studies, suggesting that they may be different but related factors. Our results suggest that expression of Mason-Pfizer monkey virus, visna virus, and spumavirus, which use the lysine-1,2 PBS, may be inhibited in undifferentiated stem cells.

Base Sequence↗

PubMed1992

Heroin addiction and sex hormones in males.

To investigate the effects of illicit heroin abuse on the endocrine system a study was carried out in North West Frontier Province (NWFP) where heroin addiction is prevalent. Sixty-eight subjects were included in this study. Thirty-three were untreated heroin addicts visiting "drug abuse treatment centres" in Peshawar and 35 age matched normal males. Urine samples of all addicts showed the presence of morphine. The serum concentrations of testosterone (T) in addicts was 228 ng/ml, leutinizing hormone (LH) 10.7 mlU/ml and folical stimulating hormone (FSH) 4.9 mlU/ml whereas the corresponding values for control males were T 630 ng/ml, LH 14.3 mlU/ml and FSH mlU/ml, respectively. Heroin exerts a depletion effect on T and FSH levels in more or less all the groups studied irrespective of age, amount of heroin intake per day and period of contact with heroin. LH levels remained affected and are within clinically accepted normal range.

Adolescent↗

PubMed1990