Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The antiviral nucleoside analogue 2',3'-dideoxycytidine (ddC) is a DNA chain terminator and/or inhibitor of human immunodeficiency virus (HIV) reverse transcriptase. We evaluated the effects of ddC in 36 New Zealand white rabbits. Three/sex were assigned to a control group and 5 treatment groups (10-250 mg/kg/day) for 13 or 18 weeks. Blood samples were taken 1 week prior to treatment and weekly thereafter to termination with the exception of the 2 highest dose groups, where blood sample collection was terminated at week 13. Selected hematological analytes were measured weekly with the exception of prothrombin time (PT) and activated partial thromboplastin time (APTT). PT and APTT and selected biochemical analytes were measured prior to treatment, at 7 weeks, and after 13 weeks of treatment. All rabbits were necropsied. Giemsa and hematoxylin and eosin sections were prepared from methacrylate-embedded marrow. Hematological effects included decreases in red blood cell count, hemoglobin, hematocrit, and white blood cell count and increases in mean corpuscular volume and red cell distribution width. Platelets, platelet volume, PT, APTT, and mean corpuscular hemoglobin concentration values were variable or unchanged. Effects were dose-related, most were seen at 1 week, and they persisted to term. Bone marrow histopathologic changes included megalocytosis, erythroid hypoplasia, bizarre erythroid nuclear morphology, nuclear-cytoplasmic asynchrony, and increased mitotic figures. Lymphopenia caused by ddC plateaued at 2 weeks and persisted until termination. Heteropenia (neutropenia) was sporadic. Biochemical values for serum analytes were unchanged by treatment. The principal hematological effect of ddC upon the erythron was characterized as a nonregenerative macrocytic anemia with erythroid hypoplasia and megaloblastic erythropoiesis.(ABSTRACT TRUNCATED AT 250 WORDS)
 ...
PMID:Hematological effects of 2',3'-dideoxycytidine in rabbits. 133 36

Thirty-nine patients from the Nebraska Regional Hemophilia Center were studied for the prevalence and titers of antibodies to HTLV-III/LAV, and for clinical symptoms of possible progression toward the acquired immunodeficiency syndrome (AIDS). Fourteen of 26 (54%) patients with hemophilia A were positive for HTLV-III/LAV antibodies as determined by immunofluorescence and Western blotting. Retrovirus was detected in cultured lymphocytes of two out of three seropositive individuals by reverse transcriptase assay and molecular hybridization with cloned HTLV-III/LAV probe. Of the twelve factor VIII-deficient patients who were seronegative, one had received only heat-treated factor VIII concentrates, six only cryoprecipitate or fresh frozen plasma, two prothrombin complex concentrates, one had not been transfused since 1983, and two had never been transfused. None of the patients treated only with factor IX concentrates, volunteer donor plasma, or cryoprecipitate had HTLV-III/LAV antibodies. In 12 of 14 seropositive hemophiliacs, titers of serum antibodies to HTLV-III/LAV ranged from 1:1,280 to 1:10,240, indicating a strong immune response against HTLV-III/LAV antigens and/or persistent infection with the virus. In spite of the possible exposure to HTLV-III/LAV during the past four years, none of the patients in this group had AIDS. Whether or not this group of patients has developed immunity to the AIDS retrovirus remains to be determined.
 ...
PMID:HTLV-III/LAV antibodies and virus in hemophilia patients in Nebraska: survey and initiation of a prospective study. 242 67

Inactivation of human immunodeficiency virus (HIV) in lyophilised small pool cryoprecipitate, factor VIII concentrate, prothrombin complex and C1-esterase inhibitor concentrate by prolonged heat treatment (72 h, 60 degrees C) was studied. Plasma products, inoculated prior to lyophilisation, had infectious titres ranging from 10(7) to 10(10.5). Residual infectivity (TCID50) was assessed by multiple titrations on H9 cells in a macro system and subsequent detection of virus replication by determining reverse transcriptase activity. Kinetics of inactivation showed a biphasic pattern: during the first 8 h a variable TCID50 reduction up to 10(4.3) was observed, followed by an additional loss of 10(1)-10(2.7) during the next 64 h. Heat treatment for 72 h resulted in a mean TCID50 reduction of 10(5). It is concluded that prolonged heat treatment may lead to the adequate prevention of HIV transmission by lyophilised plasma products.
 ...
PMID:Thermal inactivation of human immunodeficiency virus in lyophilised blood products evaluated by ID50 titrations. 364 79

Poly(A)-RNA enriched for prothrombin was isolated by specific immunoprecipitation of bovine liver polysomes. Prothrombin consisted of about 8% of the cell-free translation products of this RNA. A double-stranded cDNA was synthesized by using reverse transcriptase (RNA-dependent DNA nucleotidyltransferase) and made blunt-ended with nuclease S1. After tailing with dCTP and terminal transferase, the double-stranded cDNA was annealed to pBR322 DNA that had been cleaved previously at the single Pst I site and similarly tailed with dGTP. The resulting plasmids were used to transform Escherichia coli strain RR1 under P3-EK1 conditions. Sixty-three tetracycline-resistant clones were obtained that hybridized to 32P-labeled cDNA synthesized from prothrombin-enriched mRNA. Recombinants containing cDNA to prothrombin mRNA sequences were screened by a solution hybridization assay with a [3H]cDNA synthesized from mRNA. This enriched mRNA was 50% prothrombin mRNA, as determined by a reticulocyte lysate translation assay. Three positive clones were identified by this assay; they contained bovine DNA inserts of 700, 500, and 400 base pairs. The DNA sequence of the 700-base-pair insert was then determined. This recombinant plasmid contained DNA coding for the carboxyl-terminal 160 residues of bovine prothrombin followed by a noncoding region of 119 base pairs and a poly(A) tail of 60 base pairs.
 ...
PMID:Cloning and analysis of a cDNA coding for bovine prothrombin. 625 59

Rhesus monkey cDNA for tissue factor pathway inhibitor (TFPI) was cloned by means of the reverse transcriptase-polymerase chain reaction, using liver mRNA, and its nucleotide sequence was determined by sequencing five independent clones. Monkey TFPI was found to have a signal peptide of 28 amino acid residues and to be a mature protein of 276 amino acid residues, in which three and seventeen amino acid residue substitutions compared to human TFPI were found, respectively. All the cysteine residues, three putative carbohydrate-linked asparagine residues, and the P1 amino acid residues of each of the three Kunitz inhibitor domains were conserved in the two species. Recombinant monkey TFPI (rTFPI) was isolated from the culture medium of transformed Chinese hamster ovary cells. Amino acid sequence analysis and immunoblotting analysis, using polyclonal and monoclonal antibodies, showed that the carboxyl-terminal basic part of Rhesus monkey rTFPI had been truncated. The inhibitory activity of monkey rTFPI was compared with that of human rTFPI without the carboxyl-terminal basic part. The prothrombin time of human plasma was slightly more prolonged by the addition of monkey rTFPI than by that of human rTFPI. However, no significant differences were found between the potencies of human and monkey rTFPI as to the inhibition of factor Xa and tissue factor-factor VIIa complex.
 ...
PMID:Amino acid sequence and inhibitory activity of rhesus monkey tissue factor pathway inhibitor (TFPI): comparison with human TFPI. 808 87

We addressed the balance between thrombin and its serpin protease nexin I (PNI) after sciatic nerve injury in the mouse. Prothrombin levels increased twofold 24 h after nerve crush, as measured by a specific chromogenic assay, and peaked at day 3. Thrombin activity also increased 2-4 days after injury in distal sciatic nerve segments. Nerve RNA analysis using reverse transcriptase--polymerase chain reaction (RT-PCR) assay confirmed that prothrombin was synthesized locally. We also monitored PNI levels in these injured nerve samples by complex formation with an 125I-labeled target protease and found peak activity occurring later, 6-9 days after the thrombin induction. These data indicate that nerve injury first induces the synthesis of prothrombin, which is subsequently converted to active thrombin. Nerve crush-induced thrombin is followed by the generation of functionally active PNI and may be directly responsible for its induction. By immunocytochemistry with anti-PNI antibody, we found that activated Schwann cells were the source of induced PNI. These results support the concept that the balance between serine proteases and their serpins is dysregulated during nerve injury and suggests a role for its reestablishment in nerve damage repair.
 ...
PMID:Neural thrombin and protease nexin I kinetics after murine peripheral nerve injury. 886 30

Prothrombin, thrombin receptor (ThR), and protease nexin-1 (PN-1) mRNA levels in mouse muscle were quantified using competitive reverse transcriptase-polymerase chain reaction during development and after denervation to examine the possible role of thrombin in activity-dependent synapse elimination at the neuromuscular junction. The results showed that the levels of prothrombin and ThR were maximal at birth and decreased by two orders of magnitude by postnatal day 20 (P20). The level of PN-1 mRNA was fairly constant during development except for a 4-fold to 5-fold downregulation at P10 and P15, the periods of maximal synapse elimination at the rodent neuromuscular junction. The expression of prothrombin mRNA in muscle at birth was 41-fold and 22-fold lower than those of ThR and PN-1, respectively, and the level of difference between prothrombin and PN-1 reached almost three orders of magnitude at adulthood. Denervation of adult muscle resulted in a reversal of the relative expression levels of the three genes. There were rapid 8-fold and 10-fold increases in prothrombin and ThR mRNA, respectively, and a 2-fold decrease in PN-1 mRNA. The changes in mRNA levels of the three genes after denervation indicated that these genes were regulated in a innervation-dependent manner and that nerve activity may play an important regulatory role in the expression of prothrombin, ThR, and PN-1. The concurrent regulation of prothrombin and ThR suggests that thrombin-mediated cellular activities in muscle may be affected via the activation of ThR. An elevated level of local thrombin or thrombin-like activity might result from the decreased inhibitory activity of PN-1 during the period of peak synapse elimination in muscle development.
 ...
PMID:Regulation of prothrombin, thrombin receptor, and protease nexin-1 expression during development and after denervation in muscle. 969 58

There is considerable interest in determining the role of prothrombin fragments, especially urinary prothrombin fragment 1 (UPTF1), in the pathogenesis of calcium oxalate (CaOx) urinary calculi. This fragment is present in abundance in the matrix of CaOx crystals generated in human urine in vitro and has also been detected in human urinary stones containing calcium. More recently, prothrombin gene expression has been reported in the human kidney. However, studies examining the renal biosynthesis of prothrombin or perhaps only its fragments during experimental lithogenesis, and in consequence, the role of UPTF1 in stone formation, cannot be carried out in humans. The aim of this investigation therefore was to determine whether prothrombin gene expression is present in the rat kidney. Total RNA was isolated from the kidneys and livers of 12 rats. Using reverse transcriptase PCR, mRNAs corresponding to the thrombin and fragment 1 + 2 (F1+2) regions of prothrombin were analysed by agarose gel electrophoresis. The expression of glyceraldehyde 3-phosphate dehydrogenase was also examined to determine whether the quality of the tissue mRNAs was adequate for analyses. The amplified products were identified by sequence analysis. All kidneys displayed evidence of expression of the thrombin and F1+2 domains of the prothrombin gene. Furthermore, the sequences of these PCR-derived products from kidney were identical to those from liver. This suggests that the prothrombins secreted by these two organs are identical. The fact that prothrombin biosynthesis occurs in both the human and rat kidney presents an opportunity for using established rat models of stone disease to evaluate the influence of lithogenic conditions on prothrombin gene expression, and the potential role of UPTF1 in vivo.
 ...
PMID:The prothrombin gene is expressed in the rat kidney: Implications for urolithiasis research. 1060 51

Thrombin appears to underlie myometrial contractions in response to intrauterine bleeding. In a similar fashion, thrombin generated within the uterus in the absence of active bleeding could also produce contractions. These studies sought to determine whether functionally active prothrombin is expressed in the pregnant and nonpregnant rat uterus. Uteri were obtained from proestrus/estrus and timed-pregnant Sprague-Dawley rats. Western blots were performed using antithrombin antibodies. Immunohistochemical studies were performed using the same antibodies along with the Vector Elite ABC kit. Qualitative reverse transcriptase-polymerase chain reaction studies were performed using rat prothrombin-specific oligonucleotide primers. In vitro uterine contraction studies were performed using Taipan snake venom (an exogenous prothrombinase) and components of the plasma prothrombinase complex (Factors Xa and V) with and without pretreatment with thrombin inhibitors (heparin or hirudin). The Western blots demonstrated prothrombin peptides in myometrial tissue from estrus and pregnant rats. The immunohistochemical studies confirmed prothrombin peptides in both the circular and longitudinal myometrium, along with the endometrium. The reverse transcriptase-polymerase chain reaction studies demonstrated prothrombin mRNA in the endometrium and placenta, but not in the myometrial smooth muscle. The Taipan snake venom stimulated a significant increase in contractions, which were suppressed by pretreatment with heparin and hirudin. The Factor Xa and V complex also significantly stimulated uterine contractions, which were likewise inhibited by hirudin. These studies provide evidence supporting the expression of functionally active prothrombin in the pregnant and nonpregnant rat uterus. Based on the presence of its mRNA, prothrombin appears to be synthesized in the endometrium and placenta; in contrast, the myometrial smooth-muscle cells appear to sequester preformed prothrombin. These results support the hypothesis that intrauterine thrombin could play an autocrine/paracrine role in the regulation of contractile activity.
 ...
PMID:Intrauterine expression of prothrombin in the sprague-dawley rat. 1238 11

Breakthroughs during lamivudine therapy were assessed according to hepatitis flares and mutational polymorphism of hepatitis B virus (HBV) infecting patients. Of 42 patients with chronic hepatitis B and positive for hepatitis B e antigen in serum, 13 (30%) harbored HBV mutants with lamivudine resistance after a mean duration of 29 months on lamivudine. The virological breakthrough occurred 14.5 months after the start of lamivudine treatment, and all the patients with it developed breakthrough hepatitis 3 months later. The clinical course of breakthrough hepatitis was self-limited except in one patient who had already developed cirrhosis at the baseline. One year after breakthrough hepatitis, serum ALT, albumin, prothrombin time and platelet counts were maintained well on conventional treatments without resorting to interferon. Major HBV mutants during breakthrough hepatitis were those with M552I in the YMDD motif of viral DNA polymerase/reverse transcriptase in 7 patients (54%), M552I/L528M in 4 patients (31%) and M552V/L528M in 2 patients (15%). There were no patients in whom mutations at nucleotide 529 occurred including the 2 who later developed hepatocellular carcinoma. There was no clear relationship between distinct mutational patterns and clinical courses. Further studies are needed for making out the effects of lamivudine-resistant mutants on clinical outcomes, taking into considerations genotypes of HBV.
 ...
PMID:Subclones of drug-resistant hepatitis B virus mutants and the outcome of breakthrough hepatitis in patients treated with lamivudine. 1468 51


1 2 Next >>