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Biomedical subjects

C Urban

Publications and source records attributed to C Urban.

At least 91 records · Page 5Linked to original sources
PubMed1994

The tRNA(Ser)-isoacceptors and their genes in Nicotiana rustica: genome organization, expression in vitro and sequence analyses.

The existence of six serine codons results in a complex pattern of tRNA(Ser) isoacceptors in organisms and organelles. According to the original wobble hypothesis, a minimum of three isoacceptors should be sufficient to read the six serine codons. We have isolated five cytoplasmic tRNAs(Ser) from leaves of Nicotiana rustica. Their nucleotide sequences identify them as four different isoacceptors with the anticodons cm5UGA, CGA, IGA and GCU. For tRNA(Ser) with IGA anticodon, two species have been detected which vary only by one nucleotide in the long extra arm. The first three isoacceptors recognize codons of the type UCN whereas the fourth isoacceptor reads the two serine codons AGC and AGU. The tRNA(Ser) sequences were used to design appropriate primers for the amplification of Nicotiana nuclear tRNA(Ser) genes by the polymerase chain reaction (PCR). A total number of eight tRNA(Ser) genes differing in the coding region were thus identified. Selected PCR DNA fragments were then employed as probes for the isolation of the corresponding genes from a nuclear DNA library of N. rustica. Sequence analyses revealed that five of the isolated seven clones contained tRNA(Ser) genes which are identical in sequence with the five cytoplasmic tRNAs(Ser) mentioned above. None of them contains an intervening sequence. This is the first time that all putative cellular tRNA(Ser) isoacceptors and their corresponding genes have been characterized in an eukaryotic organism. Most of the tRNA(Ser) genes are functional as deduced from in vitro transcription and processing studies. Two of the genes yield pre-tRNAs(Ser) which are not or poorly converted to mature tRNA in a plant extract. The approximate tRNA(Ser) gene number was estimated by hybridization of specific DNA probes to Eco RI-cleaved Nicotiana nuclear DNA. The overall hybridization pattern indicates that members of each particular tRNA(Ser) gene family do not appear to be clustered but distributed randomly throughout the Nicotiana genome.

Anticodon↗
PubMed1994

Follow-up and quality of survival of 67 consecutive children with CNS tumors.

We report the findings at follow-up in 67 consecutive children with central nervous system tumors treated over a 5-year-period at a single institution. The diagnoses were supratentorial astrocytoma (n = 12), cerebellar astrocytoma (n = 10), ependymoma (n = 9), medulloblastoma (n = 9), brain stem glioma (n = 6), optic pathway glioma (n = 5), and others (n = 16). The survival rates were 83% for supratentorial astrocytomas at a median of 46.5 months, 90% for cerebellar astrocytomas and 55% for ependymomas at 40 months, respectively, 55% for medulloblastomas at 22 months, 33% for brain stem gliomas at 23 months, and 80% for optic pathway gliomas at 49 months. With regard to neurological sequelae, 13 patients were treated for epilepsy, 13 patients had mild to moderate neurological deficits, and 4 patients were severely disabled. Seventeen of 37 tested patients performed below average on formal neuropsychometric testing, one-fourth attended special education courses, and at least one-fourth suffered from behavioral and adjustment problems.

Adolescent↗
PubMed1994

Identification of TEM-26 beta-lactamase responsible for a major outbreak of ceftazidime-resistant Klebsiella pneumoniae.

An epidemic of nosocomial ceftazidime-resistant Klebsiella pneumoniae was correlated with production of a ceftazidime-hydrolyzing enzyme with an isoelectric point of 5.6 (BMH-1). BMH-1 was encoded on a large transferable plasmid conferring multiple antibiotic resistance. The gene that encodes BMH-1 was identical to the gene that encodes the TEM-26 extended-spectrum beta-lactamase.

Base Sequence↗
PubMed1993

Editing does not exist for mammalian selenocysteine tRNAs.

It has been reported that selenocysteine tRNA from bovine liver is completely edited to two isoacceptor species, called tRNA([Ser]SecNCA) and tRNA([Ser]SecCmCa), which differ from the gene sequence. We used direct tRNA sequencing, mobility shift analyses, primer extension, restriction enzyme digestion and single strand conformational polymorphism (SSCP) analyses of products from reverse transcription coupled with polymerase chain reaction (RT/PCR), sequencing of RT/PCR products and HPLC-coupled mass spectrometry to reproduce this result and show here that editing of these tRNAs does not occur.

Animals↗
PubMed1993

Nosocomial outbreak of Klebsiella infection resistant to late-generation cephalosporins.

OBJECTIVE: To describe the epidemiology, antimicrobial susceptibility, and control of widespread ceftazidime-resistant Klebsiella pneumoniae infections in a North American hospital and circumstances that led to delayed detection. DESIGN: A 2-year epidemiologic, microbiologic, and clinical cohort study. SETTING: A 487-bed general hospital in New York City. PATIENTS AND CLINICAL ISOLATES: Patient records were reviewed retrospectively and prospectively. Isolates were obtained from the Clinical Microbiology Laboratory. RESULTS: Four hundred thirty-two isolates of ceftazidime-resistant Klebsiella pneumoniae were recovered during a 19-month study period. The peak incidence reached 17.3% of all Klebsiella isolates. One hundred fifty-five patients were colonized or infected, representing more than 70 per 1000 average daily census. Infections occurred in 39% of patients from whom ceftazidime-resistant Klebsiella was isolated. These included 14 bacteremias and 17 pulmonary infections among 52 infected patients. The outbreak coincided with increasing use of ceftazidime therapy for multiresistant Acinetobacter infections. Reduction in ceftazidime use and barrier precautions markedly reduced the incidence of colonization and infection. Ceftriaxone, ceftizoxime, cefotaxime, and cephamycins were inhibitory, but not bactericidal, against ceftazidime-resistant Klebsiella and appeared effective by routine disc diffusion tests. In contrast, imipenem provided consistent bactericidal activity. Preliminary studies indicated that the outbreak was caused by one or more plasmid-mediated beta lactamases. CONCLUSIONS: Nosocomial ceftazidime-resistant Klebsiella pneumoniae may be resistant to the bactericidal activity of all cephalosporins and cephamycins. Such isolates appear susceptible to cephalosporins other than ceftazidime by routine disc diffusion testing. Ineffective therapy, delayed detection of resistance, and epidemic spread are potential consequences. Imipenem provides consistent bactericidal activity. Ceftazidime restriction and barrier precautions for colonized and infected patients are effective control measures.

Aged↗
PubMed1993

Prognostic significance of myeloid-associated antigen expression on blast cells in children with acute lymphoblastic leukemia. The Austrian Pediatric Oncology Group.

The prognostic significance of expression of myeloid-associated antigens in childhood acute lymphoblastic leukemia (myA+ALL) was evaluated. From 1984 to 1990, 251 children with immunologically verified ALL were treated in two prospective consecutive Austrian studies. Complete immunophenotyping was performed in 206 cases (82%). Out of these 175 cases were classified as B-cell precursor ALL, 31 cases as T-ALL. Expression of myeloid-associated antigens was demonstrated in 23 cases (13.1%) of childhood B-cell precursor ALL, particularly in immature (CD10 negative) forms (P < .0001), and in 1 case (3.2%) of T-ALL. CDw65 was expressed most frequently (12 cases), followed by CD13 and CD15 (5 cases each), CD33 (4 cases), and blood-group H (3 cases). Compared to myA- ALL prognosis of children with myA+ B-cell precursor ALL was poor, despite intensive multiagent chemotherapy according to BFM protocols. Remission rates were not impaired, but pEFS was 74.6% for myA- ALL, and only 37.8% for myA+ ALL (P = .0001). As demonstrated by multivariate analysis the expression of myeloid-associated antigens was the most important prognostic variable for EFS in B-cell precursor ALL, whether or not CD10 was expressed.

Adolescent↗
PubMed1993

Treatment of aplastic anemia with a monoclonal antibody directed against the interleukin-2 receptor.

Severe aplastic anemia (SAA) has been related in most cases to underlying autoimmune conditions. Various immunosuppressive regimens have been recommended in the absence of an HLA-identical bone marrow donor. Prednisolone, antithymocyte globulin, and cyclosporin A have been shown to be effective. This report describes the successful treatment of a 23-year-old woman suffering from severe aplastic anemia who had become multiresistant against previously administered immunosuppressive agents, using a monoclonal IL-2-receptor blocking antibody. The patient responded within 4 weeks. The time to the next relapse was 8 months; however, another remission with a second course of horse-antithymocyte globulin was achieved and has been maintained for 27 months to date with low doses of cyclosporin A. Although this is an anecdotical report, IL-2-receptor blockade using a monoclonal antibody might be considered as a further alternative in multi-resistant SAA, perhaps increasing the susceptibility to further immunosuppressive trials.

Adult↗
PubMed1993

Effect of sulbactam on infections caused by imipenem-resistant Acinetobacter calcoaceticus biotype anitratus.

A recent outbreak of multiresistant strains of Acinetobacter calcoaceticus biotype anitratus was observed mostly, but not exclusively, in the surgical intensive care unit in our hospital. Disk diffusion and microdilution susceptibility studies demonstrated resistance to imipenem, all aminoglycosides, and all individual beta-lactam antibiotics. Only ampicillin plus sulbactam, cefoperazone plus sulbactam, and polymyxin produced zone sizes and MICs in the susceptible ranges. Determination of MICs and MBCs demonstrated that sulbactam was the antimicrobial agent responsible for the killing of these organisms. Nine of 10 patients who were infected with imipenem-resistant Acinetobacter strains and received ampicillin plus sulbactam for > 3 days improved clinically, and in many cases organisms were eradicated from the site of isolation.

Acinetobacter Infections↗
PubMed1993

Single dose of filgrastim (rhG-CSF) increases the number of hematopoietic progenitors in the peripheral blood of adult volunteers.

Hematopoietic progenitor cell levels were monitored in the peripheral blood of ten healthy adults receiving a single dose of recombinant human granulocyte colony-stimulating factor (rhG-CSF). The objective was to determine the time and number of progenitor cells released into the peripheral blood, induced by a single dose of 15 micrograms/kg rhG-CSF administered intravenously. In all cases the absolute number of circulating progenitor cells including granulocyte-macrophage and erythroid lineages increased up to 12-fold (median 9.4-fold) 4 days after treatment. These findings were based on flow cytometric quantification of CD34+ cells and on progenitor assays. The relative distribution of granulocyte/macrophage and erythroid progenitors remained unchanged. rhG-CSF was well tolerated; mild to moderate bone pain was the most common side-effect and was noted in 6 of 10 subjects. Thus a single dose of rhG-CSF is effective in mobilizing progenitor cells into the peripheral blood in healthy adults. If these progenitors are capable of reconstituting bone marrow, peripheral progenitor cell separation following rhG-CSF administration could be a reasonable alternative to conventional bone marrow harvest in healthy adults.

Adult↗
PubMed1992

Hyperfractionated radiotherapy and polychemotherapy in brain stem tumors in children.

Between October 1989 and January 1991 five children with brain stem tumors were treated with sequential chemo- and radiotherapy. The polychemotherapy consisted of procarbazine, ifosfamide, etoposide, methotrexate, cisplatin and cytosine arabinoside. Locally, hyperfractionated radiotherapy was delivered at a total dose of 63.8 Gy (1.1 Gy twice daily, 10 fractions per week). After a median observation time of 11.8 (range 4-23) months from diagnosis three children are alive and without evidence of tumor progression. Two patients died from tumor progression 11 and 16 months respectively after initiation of therapy.

Adolescent↗
PubMed1992

Paraparesis secondary to a spinal mass as the presenting feature of erythroleukaemia in a 10-month-old child.

Severe neurological impairment as the first symptom of acute leukaemia is a rather uncommon finding. We report the case of a 10-month-old infant who presented with acute paralysis of the lower extremities due to cord compression by an epidural tumour composed of malignant erythrocyte precursor cells. Diagnosis of erythroleukaemia (EL) was made by needle biopsy of the spinal epidural mass and confirmed by bone marrow aspiration. Antileukaemic treatment in combination with radiotherapy to the epidural tumour led to haematological remission and neurological recovery with disappearance of the mass lesion as demonstrated by MRI. However, haematological relapse occurred with death of the patient 7 months after diagnosis. This is the first reported case of EL presenting with paraparesis due to an epidural tumour. The clinical symptoms, results of cytogenetic and immunological studies and the clinical course are described.

Biopsy, Needle↗
PubMed1992

Reduction of the dose to the lens in prophylactic cranial irradiation: a comparison of three different treatment techniques and two different beam qualities.

Three treatment techniques using two beam qualities have been compared on the basis of dose to the lens in prophylactic cranial irradiation. The dose to the lens and the globe was measured with thermoluminescent crystals in an anthropomorphic phantom and calculated by a computer-assisted planning system. A comparison was made of large field and small field techniques using 60Co and 8 MV photons. Modifications to the basic techniques studied included angulation of the gantry, angulation of the couch, and placement of an additional eye block close to the surface. The dose to the lens could be reduced to four percent of the midplane dose by applying the small-field technique combined with the use of 8 MV energy photons, by placing an additional block close to the surface, and by five degree occipitally angling the gantry, as well as rotating the treatment couch to account for the divergence of the beam. The use of 60Co produced an underdosage of the posterior segment of the globe in angled treatment techniques.

Cataract↗
PubMed1992

Congenital sideroblastic anemia successfully treated by allogeneic bone marrow transplantation.

Allogeneic bone marrow transplantation (BMT) was carried out on a 34-month-old boy with congenital sideroblastic anemia. The patient had been red blood cell transfusion dependent since the age of 7 weeks. He did not respond to therapy with pyridoxine and developed secondary progressive hemosiderosis. The preparatory regimen consisted of busulfan (3.5 mg/kg for 4 days) and cyclophosphamide (50 mg/kg for 4 days). Full engraftment of donor bone marrow was achieved and effective hemopoiesis is still maintained 3 years after BMT.

Anemia, Sideroblastic↗
PubMed1992

ABO-incompatible bone marrow transplantation: prevention of hemolysis by alkaline hydration with mannitol diuresis in conjunction with red cell reduced buffy coat bone marrow.

Bone marrow transplantation (BMT) in the presence of major ABO incompatibility presents the risk of a potentially fatal hemolytic transfusion reaction at the time of marrow infusion. We describe the use of a forced alkaline hydration/mannitol diuresis regimen in combination with red blood cell (RBC) reduced bone marrow given as buffy coat in 5 patients undergoing allogeneic BMT from ABO incompatible donors. Three patients had ABO antibody titers of 1:32 and were not subjected to antibody removal procedures. Two patients with respective antibody titers of 1:512 and 1:128 underwent plasmapheresis to reduce the antibody titers to below 1:64. The forced diuresis/mannitol regimen was well tolerated. Although the RBC content was still high in the buffy coat preparation a significant hemolytic transfusion reaction was successfully prevented. No patient had back pain, hyperbilirubinemia or renal impairment despite clinical and laboratory evidence of hemoglobinuria. These data indicate that patients with antibody titers below 1:64 might be spared the risks and cost associated with plasmapheresis or complete RBC depletion of the bone marrow transplant.

ABO Blood-Group System↗