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Biomedical subjects

S Amini

Publications and source records attributed to S Amini.

At least 73 records · Page 4Linked to original sources
PubMed1989

Clinical associations of variable decelerations during reactive nonstress tests.

Six hundred ninety-three patients at or beyond 30 weeks' gestation with reactive nonstress tests (NSTs) were divided into groups based on the occurrence of variable decelerations of 15 seconds or more in duration and of 20 or more beats per minute in severity. Ultrasound examination within a month of testing showed no increases in nuchal cord localization or decreased amniotic fluid volumes in a subgroup of 181 patients. Fetuses with antepartum variable decelerations were more likely to demonstrate similar decelerations in labor (P less than .001), to undergo operative delivery for a diagnosis of "distress" (P less than .05), to require intensive care nursery admission (P less than .01), and to be small for gestational age (P less than .01). No significant differences were noted in frequency of nuchal or other cord entanglements, overall cesarean section rate, or low pH or Apgar score values. We conclude that variable decelerations in the absence of other alarming NST findings may aid in identifying patients at risk for adverse perinatal occurrences, although factors other than nuchal cord placement or oligohydramnios may be responsible.

Amniotic Fluid↗
PubMed1988

Homograft valve preparation and predicting viability at implantation.

An experimental study was performed using C14 proline uptake in order to: (1) assess the effects of current sterilization and storage methods on fibroblast viability, and (2) establish a control tissue that could be used to determine viability of each homograft valve at the time of implantation in the clinical setting. The results were expressed as disintegrations per minute per milligram of tissue (DPM/mg). Swine aortic (AV), pulmonary (PV), and tricuspid leaflets (TV), and adjacent AV and PV arterial wall were procured sterile and subjected to routine sterilization and storage. Thirty samples of AV were analyzed for incorporation of labeled proline at procurement (208 +/- 7 DPM/mg), following 48-hour antibiotic exposure (87 +/- 6 DPM/mg, P less than .0001), and following controlled rate cryopreservation and storage for 12 days at -80 degrees C (78 +/- 8 DPM/mg, P = .42). Proline uptake of the other tissues at the same intervals disclosed that only the TV resulted in the same degree of viability at implantation (AV 78 +/- 8, PV 68 +/- 3, TV 75 +/- 2, P = NS). The homograft valves were obtained under sterile conditions from brain dead, multiorgan donors (homovital). It has been postulated that these valves are sterile and ready for implantation. Of 17 homovital valves cultured at procurement, 9 had positive cultures within 48 hours (53%). We conclude that: (1) the TV can be processed as a control tissue with each homograft and then utilized to predict viability at the time of implantation in the clinical setting; (2) antibiotic exposure is an essential step in the preparation of all homografts, however, modification of the antibiotic solution is necessary.

Carbon Radioisotopes↗
PubMed1988

Instantaneous risk of events following aortic valve replacement with pericardial valves: a ten-year experience.

Actuarial curves and linearized rates of occurrence are statistical functions that traditionally have been used to evaluate freedom from, or incidence of, valve-related events that occur as a result of aortic valve replacement (AVR); however, the instantaneous risk of an event can be more precisely pinpointed by the use of a time-related hazard function. This function was used to analyze 240 cases involving patients who underwent AVR with the Ionescu-Shiley bovine pericardial valve. Follow-up was for 10 years. The period from 60 to 70 months after implantation was apparently critical, since specific and cumulative events (intrinsic tissue failure, thromboembolism, prosthetic valve endocarditis, cumulated events, and death due to valve-related events) peaked during this period. We suspect important degenerative bioprosthetic changes take place during this period and are the cause, in part, for this pattern. In an effort to reduce the incidence of thromboembolism, close observation, and probably antiplatelet drug administration, should be initiated 60 months after implantation of this valve.

Journal Article↗
PubMed1987

Determining viability of fresh or cryopreserved homograft valves at implantation.

Studies of homograft valves in the past two decades have suggested that "viable" valves, i.e., those maintaining chemical and structural integrity of their leaflet intercellular matrix, have a better long-term function than nonviable valves. The most effective qualitative methods of assessing leaflet viability involve destruction of the valve leaflets; thus, these methods have been limited to random use in selected valves. A study was conducted in swine in an attempt to establish a control tissue which could be tested in place of the homograft leaflets, thereby determining viability levels of every valve clinically implanted and correlating the results with long-term clinical function. Thirty samples each of the aortic and pulmonary artery wall and tricuspid leaflet were compared with aortic and pulmonary leaflets. Utilizing the technique of C14-proline uptake, viability was assessed at procurement, following sterilization, and following cryopreservation and short-term storage. The tricuspid leaflet was found to retain the same level of viability as the aortic and pulmonary leaflets before and after the cryopreservation period. It was concluded that the tricuspid leaflet could be utilized as the control tissue.

Animals↗
PubMed1987

Analysis of middle tumor antigen and pp60c-src interactions in polyomavirus-transformed rat cells.

The relative abundance of pp60c-src molecules associated with polyomavirus (Py) middle tumor antigen (MTAg) and the relative abundance of MTAg associated with pp60c-src in a variety of Py-transformed rat cells was determined by quantitative immunoblot analyses which detect pp60c-src or Py MTAg. The results demonstrate that approximately 5 to 10% of the total immunoprecipitable pp60c-src molecules in Py-transformed rat cells are stably associated with MTAg and have elevated protein kinase activities. In these same cells, it was found that approximately 10 to 15% of the detectable MTAg molecules are stably associated with pp60c-src. Other results presented in this report demonstrate that approximately 50 to 75% of the total MTAg-associated cellular tyrosine kinase activity potentially represents the enzymatic activity of pp60c-src, while the remaining 25 to 50% represents the activity of other cellular tyrosine kinases. Our results also show that most pp60c-src molecules associated with Py MTAg do not possess electrophoretic mobilities that are altered from those of pp60c-src molecules not associated with MTAg or pp60c-src molecules obtained from normal rodent cells.

Animals↗
PubMed1987

Analysis of polyomavirus middle-T-antigen-transformed rat cell variants expressing different levels of pp60c-src.

We characterize two independent variant cellular clones which arose following in vitro passage of polyomavirus middle-T-antigen (MTAg)-transformed FR3T3 cells expressing RNA complementary to c-src mRNA. These clones were initially flat and underwent morphologic transformation at a high frequency to a phenotype indistinguishable from that of parental MTAg-transformed FR3T3 cells. Biochemical analysis of the flat clones prior to phenotypic conversion revealed that these cells synthesized little detectable pp60c-src and had correspondingly low levels of pp60c-src protein kinase activity and MTAg-associated protein kinase activity. The flat cell clones did not possess detectable focus-forming activity, were not capable of detectable anchorage-independent growth, and had saturation densities and doubling times below those normally observed for FR3T3 cells. Following conversion of the flat clones to a shape resembling that of typical MTAg-transformed cells, the abundance of pp60c-src, pp60c-src kinase activity, and MTAg-associated in vitro protein kinase activity were all restored to the levels found in the parental MTAg transformants. These cells had growth rates, focus-forming activities, anchorage-independent growth rates, and saturation densities similar to those of the parental MTAg-transformed rat cells. These data provide additional evidence that maintenance of a transformed phenotype by polyomavirus MTAg in established rat cell lines depends, at least in part, on a minimal threshold level of pp60c-src.

Animals↗
PubMed1987

Analysis of the c-src gene product structure, abundance, and protein kinase activity in human neuroblastoma and glioblastoma cells.

We have compared in different human neuroblastoma cell lines and human glioblastoma cells the expression level, structure, and tyrosine-specific protein kinase activity of pp60c-src. Our results show that not all human neuroblastoma cell lines express pp60c-src molecules with amino-terminal structural alterations. In neuroblastoma cells which possess pp60c-src with altered gel migration, the diminished polyacrylamide gel mobility of pp60c-src was found not to be dependent upon amino-terminal phosphorylations since extensive treatment of these molecules with phosphatase did not significantly change their gel migration properties. Similar differences in gel migration were observed when RNA from the various neuroblastoma and glioblastoma cells was translated in vitro using either rabbit reticulocyte or wheat germ lysates. White the level of c-src mRNA in the different cells analyzed was found to be similar, the abundance of pp60c-src in these same cells was found to vary by as much as 12-fold. This suggests that the abundance of pp60c-src in human neuroendocrine tumors is regulated through post-transcriptional and/or post-translational events which may be related to the stage of neuronal differentiation of the cells. Based upon determination of pp60c-src abundance by immunoblot analysis, we demonstrate that pp60c-src molecules derived from human neuroblastoma and glioblastoma cells have very similar in vitro protein kinase activities.

Antibodies, Monoclonal↗
PubMed1986

Analysis of pp60c-src protein kinase activity in hamster embryo cells transformed by simian virus 40, human adenoviruses, and bovine papillomavirus 1.

We have examined the effect of DNA tumor virus transformation of primary hamster embryo cells on the tyrosyl kinase activity of pp60c-src. Our present study demonstrates that some clones of hamster embryo cells transformed by simian virus 40, adenovirus type 2, adenovirus type 12, or bovine papillomavirus 1 can possess elevated pp60c-src kinase activity when compared with normal hamster embryo cells. However, other clones of hamster embryo cells transformed by these same viruses were found to have normal levels of pp60c-src kinase activity. In those clones of transformed cells where pp60c-src kinase activity was elevated, the increased levels of kinase activity were the result of an apparent increase in the specific activity of the pp60c-src phosphotransferase rather than an increase in the amount of the src gene product. Additionally, pp60c-src was not found to be physically associated with tumor antigens known to be encoded by these viruses. These results indicate that elevated levels of pp60c-src kinase activity can be found in hamster embryo cells transformed by several different DNA tumor viruses and suggest that the molecular mechanism by which pp60c-src kinase activity is elevated may differ from that previously observed in polyomavirus-transformed cells. These results also imply that elevation of pp60c-src kinase activity is not required for the transformation of hamster cells by these viruses.

Adenoviruses, Human↗
PubMed1986

Regulation of pp60c-src synthesis by inducible RNA complementary to c-src mRNA in polyomavirus-transformed rat cells.

To determine the potential role of pp60c-src in polyomavirus-transformed cells, we constructed a recombinant plasmid with the mouse metallothionein-I promoter upstream of a src gene in an anti-sense orientation. We cotransfected this plasmid into middle tumor antigen-transformed FR3T3 cells with a plasmid containing the neomycin resistance gene, and G418 resistant colonies were selected. Analysis of these cells for pp60c-src expression revealed that 50 of the 200 cellular clones screened were found to have decreased levels of c-src expression when compared with the parental middle tumor antigen-transformed cells. Three independent clones which transcribed the expected 3.6-kilobase src complementary RNA and had levels of pp60c-src kinase activity comparable to that of normal FR3T3 cells were further analyzed. In the presence of Cd2+, these clones grew significantly slower in monolayer cultures than either the parental transformed cells (FR18-1) or FR18-1 cells transfected with the neomycin resistance gene alone. The morphology of these clones in the presence of Cd2+ was distinct from that of either the parental FR18-1 cells or normal FR3T3 cells. The clones expressing the complementary src RNA were found to form fewer colonies in soft agar, form fewer foci on monolayers of normal rat cells, and form tumors more slowly following injection into syngenic rats when compared with parental FR18-1 cells. The results of these studies suggest that the level of pp60c-src kinase activity affects the growth characteristics and transformation properties of polyoma virus-transformed rat cells.

Animals↗
PubMed1983

Association of pp36, a phosphorylated form of the presumed target protein for the src protein of Rous sarcoma virus, with the membrane of chicken cells transformed by Rous sarcoma virus.

A cellular protein with a molecular mass of approximately 36 kilodaltons is the presumed target protein of the src protein [the transforming protein encoded by Rous sarcoma virus (RSV)]. The cellular location of the phosphorylated 36-kilo-dalton protein (pp36) in chicken embryo fibroblasts transformed by the Schmidt-Ruppin strain of RSV has been investigated. In these studies, two-dimensional electrophoresis was used for detection of the phosphoproteins in total cell extracts and also in fractionated subcellular components. We conclude that pp36 is localized in the plasma membrane, on the basis of the following observations. (i) Fractionation of 32P-labeled cell extracts showed that pp36 is almost exclusively localized in the crude membrane fraction and no appreciable amount was found in nuclear or cytoplasmic fractions. (ii) On further fractionation of the crude membrane fraction, pp36 was localized mostly in the plasma membrane rather than in other membranous fractions. (iii) Isolated plasma membrane by itself phosphorylated the 36-kilodalton protein on incubation with [gamma-32P]ATP.

Animals↗
PubMed1981

Specificity of an immunoprecipitin test for non-A non-B hepatitis.

An immunodiffusion system detecting an antigen showing immunological identity with international laboratory reference sera was developed by use of acute-phase and recovery sera from patients with transmission-proven non-A, non-B acute hepatitis. In other liver diseases the antigen was also present in a high proportion of patients and there were similar findings in conditions with high levels of circulating immune complexes in the serum. Fractionation of antigen-containing sera by column chromatography, polyethylene glycol treatment, and reduction and alkylation also suggested that immune complexes may be responsible for antigenic activity. The precipitation lines did not develop in the presence of 10 mmol/l EDTA or at a pH less than 8.0 and the reactant in "antibody" containing sera was shown not to be an immunoglobulin. Although the transmission of non-A, non-B hepatitis by blood and blood products shows that viral antigens are likely to be present in the circulation, this study shows that immune reactions apparently closely associated with the infection may be detecting immune complexes rather than specific viral components and emphasises the need for careful evaluation of the specificity of other reported serological tests for non-A, non-B hepatitis.

Acute Disease↗
PubMed1981

Ultrastructural changes in the liver in experimental non-A, non-B hepatitis.

Factor VIII, a blood-clotting derivative prepared from pooled human plasma, previously shown to cause a short-incubation-period non-A, non-B hepatitis in patients and in chimpanzees, was studied further to establish the nature of the pathological lesions associated with this infection. Percutaneous liver biopsy specimens were examined in detail. Cytoplasmic changes in the hepatocytes were observed on the 7th day after inoculation in one instance and after 13 days in the second, and persisted in the biopsy specimens for 13 weeks after infection. Abnormalities in hepatocyte nuclei, including aggregates of irregularly shaped particles 15-20 nm in size, were observed about 1 week after the onset of the cytoplasmic changes. The ultrastructural changes are described and their nature and significance discussed. Attention is drawn to somewhat similar cytoplasmic and nuclear changes occurring in other disease entities.

Animals↗
PubMed1977

Physicochemical studies of non-histone protein HMG17 with DNA.

Non-histone protein high mobility group-17 (HMG17) isolated from calf thymus consists of 89 amino acids and the complete sequence is known (Walker, J.M., Hastings, J.R.B. and Johns, E.W. (1977) Eur. J. Biochem. 176, 461-468). We have studied its conformation and interaction with DNA by a variety of technics. The results show that the protein has a random structure. It binds non-cooperatively, non-specifically and reversibly to DNA. It is estimated that each molecule of protein binds to 57 nucleotides of calf thymus DNA. The equilibrium constant for binding is approx. 1 - 10(6) M-1. HMG17 induces conformational changes in DNA similar to some of the histones in particular H1.

Animals↗
PubMedDate not supplied

Impact of oligohydramnios on maternal and perinatal outcomes of spontaneous premature rupture of the membranes at 18-28 weeks.

OBJECTIVE: We compare the maternal and perinatal outcomes between 69 patients with oligohydramnios and 49 patients with adequate fluid at the time of initial evaluation for PROM. METHODS: One hundred and eighteen patients with spontaneous premature rupture of the membranes (PROM) at 18-28 weeks are included in the study. Inclusion criteria are singleton gestation, normal fetal anatomical survey and normal amniotic fluid prior to PROM, and absence of labor or abruption at the time of PROM. Oligohydramnios is defined as an amniotic fluid index (AFI) <5 cm of measurable pockets of amniotic fluid which are free of umbilical cord. Expectant management was carried during the 3-year period. The overall perinatal survival is 66%. Pulmonary hypoplasia is present in 18%, and skeletal deformities in 3% of all neonates. RESULTS: There is no significant difference between the two groups in the mean gestational ages at PROM (172+/-17 d vs. 171+/-14 d), latency periods (9+/-14 d vs. 8+/-13 d), incidences of chorioamnionitis (48 vs. 39%), endometritis (19 vs. 14%), neonatal sepsis (11 vs. 13%), or skeletal deformities (6 vs. 0%). Patients with oligohydraminos have significantly higher incidences of fetal heart rate decelerations (59 vs. 38%) and C-section (38 vs. 16%) (P < 0.05) than patients with adequate amniotic fluid. CONCLUSIONS: After adjusting for confounding variables, neonates with oligohydramnios are twice as likely to develop pulmonary hypoplasia (20 vs. 10%) and more likely to experience neonatal death (30 vs. 20%) when compared to those with adequate fluid, even though the difference is not statistically significant.

Adult↗
PubMedDate not supplied

HIV-1 regulatory protein tat induces RNA binding proteins in central nervous system cells that associate with the viral trans-acting-response regulatory motif.

OBJECTIVES: To investigate some of the cellular consequences of HIV-1 Tat expression in human astrocytic cells. This study is based on evidence that cellular factors play a critical role in facilitating transcriptional activation by Tat through its interaction with the trans-acting-response (TAR) RNA element and upstream HIV-1 long terminal repeat (LTR) promoter binding site. STUDY DESIGN-METHODS: Using the previously established astrocytic cell line of human origin stably transfected with Tat cDNA, we analyzed the formation of a nucleoprotein complex consisting of three cellular proteins associated with TAR RNA using ultraviolet (UV) crosslinking and glutathione-S-transferase (GST) pull-down assays. RESULTS: UV crosslinking experiments reveal that the molecular masses of the proteins range from 50 to 62 kd. Transient transfection studies demonstrate that the presence of these proteins correlates with the ability of Tat to transactivate the HIV-1 LTR in the absence of the trinucleotide bulge, a region within TAR that has been shown to be important for Tat-TAR interaction. A combination of GST pull-down assays and RNA binding studies demonstrates that the 50-kd protein interacts with both Tat and TAR and is likely to be NF-kappa B p50. CONCLUSIONS: Taken together, these data suggest that in the absence of a functional Tat binding site such as TAR (which tethers the viral protein to the RNA), cellular protein NF-kappa B p50 may be able to bring Tat into the RNA binding complex Tat has been shown to activate expression of a variety of cellular genes that may not contain a binding site for Tat but do contain binding sites for NF-kappa B family members. The results presented in this study may be relevant for Tat-mediated transactivation of cellular as well as viral genes, both of which might contribute to the central nervous system damage associated with HIV-1 infection.

Astrocytes↗