Search PubMed⌕ Search

Biomedical subjects

A Siddiqui

Publications and source records attributed to A Siddiqui.

At least 127 records · Page 7Linked to original sources
PubMed1987

In vivo phosphorylation and protein analysis of hepatitis B virus core antigen.

The C open reading frame of the hepatitis B virus contains two in-frame ATG codons that are separated by the precore region and encodes two major polypeptides that are antigenically distinct and that are probably synthesized from individual mRNAs. The precore region directs the secretion of the e antigen, whereas the core antigen can be expressed in the absence of these sequences. In this report a transient expression system was used to study the hepatitis B virus core antigen. By using a chimeric complex of adenovirus major late promoter-simian virus 40 enhancer sequences, we were able to achieve high levels of core antigen expression in transfected cells, permitting characterization of this protein and analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The core polypeptide is a 20.9-kilodalton protein, and we show in this study that it is phosphorylated in vivo. Cell fractionation studies, the results of which are supported by indirect immunofluorescence, localized the phosphocore in the cytosol and the nucleus and indicated that it is associated with the membrane of transfected cells. Results of Triton X-114 solubilization studies indicated that the phosphocore is peripherally associated with cytoplasmic membranes. Expression of the membrane-associated phosphocore occurred in the absence of the precore sequences. The phosphocore also assembled into particles in the absence of other viral gene products or intact DNA.

Amino Acids↗
PubMed1986

Transcriptional control elements of hepatitis B surface antigen gene.

A series of recombinant plasmid vectors containing hepatitis B virus (HBV) DNA sequences was constructed to study the biosynthesis of the hepatitis B virus surface antigen (HBsAg) RNA and to locate transcriptional control elements involved in the regulation of the S and pre-S DNA sequences. We examined the transcription of the HBsAg gene in permanent cell lines that were developed by transfecting with recombinant vectors containing HBV sequences and the neomycin gene followed by G418 selection. We further defined the promoter activities upstream of and within the pre-S sequences using the assayable chloramphenicol acetyltransferase gene. Results obtained from S1 nuclease digestion and primer extension suggest that HBsAg transcripts are initiated at multiple sites in the pre-S region and from a site upstream of the pre-S region. Chloramphenicol acetyltransferase assays indicate that DNA sequences within and upstream of the pre-S region contain promoter activities and that the "TATA" sequence-containing promoter and the internal promoter show similar levels of activities in CV-1 cells and several other cell lines tested.

Animals↗
PubMed1986

The human hepatitis B virus enhancer requires trans-acting cellular factor(s) for activity.

The activity of the hepatitis B viral enhancer element was studied in various cell lines. This enhancer shows strict host and tissue specificity in that it is functional only in liver cells of human origin. Further, it requires trans-acting factor(s) present in liver cells for activity, and this activity is independent of hepatitis B virus gene products in the cell lines tested.

Acetyltransferases↗
PubMed1986

Expression of hepatitis B viral core region in mammalian cells.

We studied the expression of the core region of the hepatitis B virus genome in mammalian cells with recombinant plasmid vectors. Stably transformed rat fibroblast cell lines were established by transfection with vectors containing subgenomic and genome-length hepatitis B virus DNA, followed by G418 selection. The RNA transcripts directed by the core region were characterized by Northern blot hybridization and S1 nuclease mapping. Using the chloramphenicol acetyltransferase gene expression system, the promoter activity located upstream of the core open reading frame was confirmed. The synthesis of core and e polypeptides was studied with a commercial radioimmunoassay. These studies show that partial deletion of the precore sequences abolished secretion of the e antigen, but there was pronounced synthesis of the core antigen in transfected cells.

Animals↗
PubMed1986

Hodgkin disease and non-Hodgkin lymphomas in children: utilization of radiological modalities.

If costs of medical care are to be reduced, the choice of which imaging modality to use must be made as carefully as possible. This study was done to show how radiological modalities were used to evaluate patients with Hodgkin disease and non-Hodgkin lymphoma. We kept a record of every radiological study performed on 66 children with both diseases seen in the past 6 1/3 years. The results of these studies were analyzed to see which areas of the body were studied, which imaging modality was used, how frequently the studies were repeated, and how frequently the studies gave abnormal results. Our findings disclosed that radiological studies have been appropriately performed in anatomic regions of the body in which disease is present. New imaging modalities have been introduced, and the use of some of the older modalities has been decreased. With some modalities, such as skeletal survey, liver/spleen scan, whole-lung tomography, contrast studies of the bowel, and excretory urography, utilization is higher than it ought to be in view of the fact that the yield of positive results is low and the information is obtainable in many cases from other more sensitive procedures. These studies should not be performed as a routine on initial evaluation or follow-up of all patients with Hodgkin or non-Hodgkin lymphomas. On initial presentation all patients should undergo chest radiography and CT scanning of both chest and abdomen. A problem area is that the timing of follow-up studies has been somewhat erratic, with some inappropriate studies particularly 3 or 4 years after diagnosis. Too many imaging procedures have probably been done in follow-up of our patients.

Bone Marrow↗
PubMed1985

Ocular blood flow after experimental alkali burns and prostaglandin administration.

Ocular blood flow was determined using radioactive strontium 85 microspheres after an alkali (sodium hydroxide [NaOH]) burn to the eye. With 20 microL of NaOH, blood flow was significantly increased in the iris, ciliary processes, and choroid from two through four hours. This correlated well with the sustained increase in intraocular pressure (IOP) seen after a 20-microL burn. A 50-microL burn increased blood flow at one hour, but it returned toward normal levels beyond two hours. In general terms, there appeared to be a meaningful correlation between IOP changes and altered blood flow following ocular alkali burns. The blood flow changes paralleled those occurring after the topical application of prostaglandins and supported the concept that ocular blood flow dynamics are mediated by prostaglandins.

Alkalies↗
PubMed1985

Molecular cloning and characterization of the cDNA coding for hepatitis B virus surface antigen.

Hepatitis B virus surface antigen (HBsAg) mRNA has been enriched from a hepatoma cell line (PLC/PRF/5) by specific polysome immunoprecipitation and used for cDNA cloning. A HBsAg cDNA clone was identified by in situ hybridization with a cloned viral probe. It was characterized by restriction endonuclease mapping and DNA sequence analysis. Molecular hybridization of PLC/PRF/5 cellular DNA and RNA to [32P]-labeled HBsAg cDNA revealed the integration of at least six copies of the hepatitis B virus (HBV) DNA into the host genome and expression of three DNA species containing HBsAg-specific sequences. The possible role of HBV in the oncogenesis of primary hepatocellular carcinoma is discussed.

Carcinoma, Hepatocellular↗
PubMed1984

Magnetic resonance imaging of bone marrow disease in children.

Seven children underwent magnetic resonance imaging (MRI) of the bone marrow: results showed that it is technically feasible to obtain good MR images of marrow in children. MR has detected abnormality in the bone marrow of a child who had metastatic neuroblastoma. The extent of abnormality in the femur correlated well with findings of a bone marrow isotope scan. In one child who had idiopathic aplastic anemia, diseased marrow could not be distinguished from normal marrow on MR images. MRI identified abnormality of the marrow in osteogenic sarcoma, and demonstrated change in response to chemotherapy. It displayed marrow spread of tumor as well as CT. MRI showed marrow abnormality in four children who had leukemia.

Anemia, Aplastic↗
PubMed1984

Magnetic resonance imaging of neuroblastoma with a 0.15-T magnet.

Magnetic resonance imaging (MRI) in nine children with neuroblastoma showed that MRI can effectively demonstrate primary and metastatic disease and aid in predicting tumor resectability. MRI can show changes in tumor size and intensity in response to chemotherapy or radiation therapy. Neuroblastomas have an image intensity much lower than that of liver and muscle on inversion-recovery scans. On spin-echo 500/30 scans, the tumors have a greater intensity than muscle and a similar or slightly greater intensity than liver. On spin-echo 1000/60 scans, they are always of greater intensity than liver or muscle. At this stage, the overall accuracy of MRI as compared with other imaging methods is not known.

Adrenal Gland Neoplasms↗
PubMed1984

Calcification and uptake of Tc-99m diphosphonates in neuroblastomas: concise communication.

Sixty-six percent of 54 patients with neuroblastoma demonstrated uptake of bone-seeking radioagents by the primary tumor. This is a higher incidence than previously reported. Uptake was slightly more common in abdominal than thoracic tumors. There was a significant correlation between the size of the tumor and tracer uptake. Calcification was demonstrated in the primary tumor in almost 90% of the 54 patients. This is a much higher incidence of calcification than previously reported. Microscopy shows that the calcification is not always due to tumor necrosis; it also occurs in areas of viable tumor cells. Tracer uptake is believed to be related to calcium metabolism. The rate of metabolic activity rather than the total amount of calcium present within the tumor may be the most important factor in determining the amount of uptake. No significant relationship was found between tracer uptake and tumor stage or homovanillic acid and vanillylmandelic acid metabolic activity.

Abdominal Neoplasms↗
PubMed1983

Hepatitis B virus DNA in Kaposi sarcoma.

DNA extracted from Kaposi sarcoma biopsies was analyzed for the presence of hepatitis B viral (HBV) DNA sequences by Southern blot hybridization. The probes used were (i) molecularly cloned subgenomic fragments of HBV DNA and (ii) HBV DNA extracted from Dane particles that included DNA sequences that encode hepatitis B surface antigen and core antigen. The limited study reported here demonstrates that HBV DNA exists mainly in an episomal state in the Kaposi sarcoma tissue and that these DNA forms are different from those found in hepatitis B virion. The presence of various DNA forms suggests that HBV DNA is engaged in DNA replication, which implies that the tissue is infected with HBV.

Cloning, Molecular↗
PubMed1983

Expression of hepatitis B virus surface antigen gene in cultured cells by using recombinant plasmid vectors.

By using a new host-vector system, expression of the gene coding for hepatitis B surface antigen has been studied. A subgenomic fragment of cloned hepatitis B viral DNA was inserted into the plasmid vector pSV010. Transfection of COS cells with the recombinant plasmid vector containing hepatitis sequences leads to the synthesis of hepatitis B surface antigen, which is released in the culture medium in the form of 22-nm particles similar to those found in the sera of hepatitis carriers.

Animals↗
PubMed1983

The effect of amniotic fluid aspiration on pulmonary function in the adult and newborn rabbit.

Aspiration of uncontaminated human amniotic fluid was investigated in adult and newborn rabbits and compared with three other experimental groups: 10% meconium solution, saline, and sham-injected controls. Fluids were injected into the trachea of adult animals (4 or 6 ml/kg body weight), newborn vaginally-delivered animals (a mean volume of 8 ml/kg), and cesarean-delivered animals before their first breath (a mean volume of 11 ml/kg). In adult animals aspirating amniotic fluid or saline, arterial PO2 measured over a 24-h period showed a mean difference between groups of less than 5% for both 4 and 6 ml/kg. Meconium aspiration produced a greater depression in PO2 than amniotic fluid aspiration (a mean difference of 16 and 31% for 4 and 6 ml/kg, respectively) and animals aspirating meconium showed a deteriorating trend over 24 h, whereas animals aspirating amniotic fluid improved. One of eight adult animals aspirating amniotic fluid died versus four of five aspirating meconium. All five animals aspirating saline 6 ml/kg survived. Lung weight and resting volume of adult animals aspirating amniotic fluid were not significantly different from animals aspirating saline or nothing. Lung pressure volume curves from adult animals aspirating amniotic fluid were nearly identical to controls. Histology showed significantly greater atelectasis in adult animals that received 6 ml/kg amniotic fluid than controls, but this was not different from saline. There was no association between the number of cells in amniotic fluid and arterial PO2 after aspiration or any other aspect of pulmonary function measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Amniotic Fluid↗
PubMed1983

Expression of hepatitis B surface antigen in mammalian cells and identification of a precursor form of HBsAg.

The purpose of this study was to program the synthesis of hepatitis B surface antigen in cultured mammalian cells from defined DNA sequences derived from the Hepatitis B viral DNA. The product of this system used in the present study is the 22-nm hepatitis B surface antigen particles released in the culture medium with biophysical properties identical to the 22-nm HBsAg particles found in the serum of hepatitis B carriers. Additionally, preliminary results are presented concerning the synthesis of a precursor polypeptide bearing hepatitis B surface antigenic determinants.

Animals↗
PubMed1982

Liver metastases in Wilms' tumour.

Fifty patients with Wilms' tumour have been reviewed to evaluate the incidence of liver metastasis in order to identify the optimum time and frequency for radiological investigation. Liver involvement occurred in 12% of our cases. The most rewarding periods for the diagnosis of liver metastasis are the first few months of the illness, the period immediately after stopping chemotherapy, or any time that lung metastases are identified. Liver scintigraphy is recommended as the initial investigation, and abnormal cases should proceed to ultrasound or computed tomography.

Child↗
PubMed1982

High-contrast film copying for thallium 201 cardiac image processing.

To evaluate the usefulness of high-contrast film copying as an economical means of enhancing contrast in thallium 201 cardiac images, stress and rest studies of 47 patients with and 19 patients without coronary artery disease were evaluated. A total of 66 sets of four different image formats were independently interpreted by five observers. The analysis of the receiver operating characteristic curves suggested that the high-contrast film copies were superior to their original analog images and comparable with computer-processed images in diagnostic yield. It appears that contrast enhancement by simple film copying can improve the accuracy of 201Tl image interpretation.

Coronary Disease↗