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Biomedical subjects

I Schwartz

Publications and source records attributed to I Schwartz.

At least 109 records · Page 6Linked to original sources
PubMed1987

Measurement of cat expression from growth-rate-regulated promoters employing beta-lactamase activity as an indicator of plasmid copy number.

Many promoter-fusion vectors contain an intact beta-lactamase (BLA) gene (bla) to allow measurement of BLA activity as an internal control for plasmid copy number. This approach rests on the assumption that bla is constitutively expressed. To use such vectors for comparison of promoter activity at different growth rates it was necessary to confirm that this is the case under all physiological conditions. The relationship between plasmid copy number and BLA activity at different steady-state growth rates in Escherichia coli HB101 transformed with a ColE1-type plasmid (pBR325) was examined. Both BLA activity and plasmid copy number decreased in a parallel fashion as growth rate increased. This finding was tested further by measuring the growth-rate-regulated expression of the chloramphenicol acetyltransferase (CAT) gene under the control of the rrnB P1 promoter in a plasmid pKK231-1 fusion. The results indicate that BLA activity is a reliable indicator of copy number at a wide range of growth rates and that CAT/BLA ratios can be employed as a valid measure of promoter-specific activity in such plasmid fusions under these different physiological conditions.

Acetyltransferases↗
PubMed1987

Foreign bodies in the tracheobronchial tree.

Between 1972 and 1984, we treated 66 patients with foreign bodies (FBs) in the tracheobronhial tree. Twenty-six patients (39.4 percent) were between one and two years old; 52 (78.8 percent) were under age ten. Forty-four FBs (67 percent) were fruit and vegetable seeds and nuts. Soft organic material (meat, cucumber peels) was found in four patients, chicken bones in six, pins and needles in six, other nonorganic materials (toys, stone, broken thermometer) in six. In 55 patients, the FB was removed at bronchoscopy; three patients coughed up the FB shortly after bronchoscopy. Eight patients were operated on because the impacted FB could not be removed at repeat bronchoscopy trials. In this group, the FB was removed through a bronchotomy in two patients, but in six, pulmonary resection was necessary because of severe bronchiectasis (FBs had been impacted from ten months to 12 years). Stiff bronchoscope was used in all patients. In several cases, the flexible bronchoscope was used initially but proved inadequate. There were three complications, two related to hypoxia, but no deaths. Infants and little children should be prevented from reaching peanuts and seeds. When presence of a FB is suspected, and in children with unresolving pneumonic process, early bronchoscopy is mandatory. Expert anesthesia is essential, and hypoxia must be avoided.

Adolescent↗
PubMed1987

Fine-needle aspiration biopsy in diagnosis of pulmonary masses.

Fine-needle aspiration biopsy (FNAB) is a diagnostic method indicated in patients with pulmonary lesions that cannot be reached with a bronchoscope and when cytologic examinations of the sputum are persistently negative. Cells are aspirated under fluoroscopic control and stained using the Papanicolaou method for cytologic examination. Results are available within hours, and the material can be used for other studies. Between 1975 and 1984, the authors performed 845 FNABs in 342 patients. Diagnosis was established in 306 patients, or 89.5 per cent. Malignant neoplasm was diagnosed in 284 instances, benign disease in 22. In 176 patients with malignant tumors, the diagnosis was based on FNAB exclusively. In 108 patients who were operated on, the results of FNAB matched histology in 97 per cent. The aspiration specimen was inadequate in 36 patients, most of whom had diffuse lung disease. The incidence of complications was extremely low. FNAB is safe and reliable. It is recommended for use in clinical workup of undiagnosed pulmonary masses. FNAB enables rational planning of treatment when other diagnostic methods fail. The authors do not recommend FNAB for use in cases of diffuse pulmonary disease.

Adult↗
PubMed1986

Prostatic cancer after prostatectomy for benign disease.

Twenty of 391 newly diagnosed cases of prostatic cancer (5%) had a prior prostatectomy for benign disease. Digital rectal examination in 16 of 19 patients (84%) revealed a significant prostatic abnormality. Continued serial digital rectal examination should be performed routinely after prostatectomy for benign disease.

Adenocarcinoma↗
PubMed1986

Expression of Escherichia coli infC: identification of a promoter in an upstream thrS coding sequence.

infC, the gene which codes for translation initiation factor 3, is situated in a cluster in the genome of Escherichia coli with genes for several other components of the translation apparatus. Only three nucleotides separate the termination codon of thrS from the initiation codon of infC. This implies that infC is either cotranscribed with thrS from a thrS promoter or that the transcriptional signals for infC are embedded within the upstream thrS coding region. In the present work, several plasmids have been constructed which encompass infC and various amounts of the upstream thrS sequence. The ability of the plasmid DNA, or derived restriction fragments, to direct the synthesis of initiation factor 3 was tested in an in vitro DNA-dependent coupled transcription-translation system and in plasmid-transformed maxicells. The results indicate that initiation factor 3 is synthesized in the absence of the thrS promoter. A promoter whose presence is sufficient for the expression of infC has been localized to an 89-base-pair region which lies 178 to 267 base pairs upstream of the infC initiation codon. S1 nuclease mapping of in vivo transcripts confirms that a transcription initiation site is located in this region. These studies demonstrate that infC can be transcribed from a promoter within the upstream thrS coding sequence.

Amino Acyl-tRNA Synthetases↗
PubMed1986

Association of tumor differentiation with caffeine and coffee intake in women with breast cancer.

Caffeine, which has been linked to benign breast disease, has an antineoplastic effect in experimental animals, whereas in tissue cultures it inhibits mitoses and induces cell differentiation. We examined caffeine and coffee intake in 101 women with breast cancer to determine whether either or both influence cell differentiation in tumors as well. Nutrient analysis was performed by the Nutrition Coding Center of the University of Minnesota with the Nutrition Data system from the National Heart, Lung, and Blood Institute. Stepwise logistic regression, with tumor differentiation (well and moderate versus poor) as the dependent variable, was used. The analysis indicates that caffeine and/or coffee intake has a significant association with tumor differentiation as women with moderately to well-differentiated tumors had higher caffeine and coffee intake. This raises the question whether caffeine or coffee consumption may help induce cell differentiation and slow tumor growth.

Breast Neoplasms↗
PubMed1984

The gene encoding translation initiation factor 3 is highly conserved in gram-negative bacteria.

A 1.1-kb Hp alpha I fragment of the Escherichia coli chromosome containing the gene for translation initiation factor 3 was employed as a probe in heterologous hybridization to chromosomal DNA from a variety of other procaryotes. Positive hybridization was observed to DNA derived from all gram-negative bacteria tested. In contrast, no hybridization to DNA from gram-positive bacteria was detected. In addition, homologous sequences were found in Euglena gracilis chloroplast DNA, while this was not the case with Saccharomyces cerevisiae mitochondrial DNA. These results are discussed in light of existing data on the components and mechanism of translation initiation in the various organisms and organelles employed in this study.

Base Sequence↗
PubMed1984

A radiographic survey of apical root resorption in pulpless permanent teeth.

A radiographic statistical study was performed in order to determine the presence and type of external resorption found in pulpless permanent teeth. Of 1,372 roots evaluated, 49.6% showed resorption. The degree of apical external resorption was significantly related to the presence and size of the periapical lesions in all roots. Much more resorption was found in the roots without root canal filling than in those that were filled.

Adult↗
PubMed1984

Computed tomography of soft-tissue lesions of the extremities, pelvic and shoulder girdles: sonographic and pathological correlations.

Sixty-five patients with various soft-tissue tumours were examined by computed tomography (CT) and ultrasonography. Results were correlated with pathological findings. Although an accurate histological prediction could not be made in most cases, certain patterns appeared to be characteristic of specific types of tumours. A lipoma of uniformly low density may be differentiated from the heterogeneously denser liposarcoma. Multiple irregular linear densities with calcification are characteristic of haemangioma. An echo-free mass on the sonogram with soft-tissue density on CT suggests lymphoma or certain sarcomas. Small isodense subcutaneous lipomas or intramuscular lymphomatous masses may be clearly delineated on sonogram but not seen on CT. Our study indicates that the combined use of CT and ultrasound gives a very detailed basis for planning the surgical approach to the tumour.

Adolescent↗
PubMed1983

Molecular cloning and sequencing of pheU, a gene for Escherichia coli tRNAPhe.

A recombinant plasmid (designated pID2) carrying the E. coli gene for tRNAPhe has been isolated from a plasmid bank constructed by the ligation of a total EcoRI digest of E. coli K12 DNA into the EcoRI site of pACYC184 DNA. The plasmid was selected by virtue of its ability to complement a temperature-sensitive lesion in the gene (PheS) for the alpha-subunit of phenylalanyl-tRNA synthetase. Crude tRNA isolated from such transformants exhibited elevated levels of phenylalanine acceptor activity. The tRNAPhe gene has been localized within the first 300 base pairs of a 3.6 kb SalI fragment of pID2. The sequence of the gene and its flanking regions is presented.

Base Sequence↗
PubMed1983

Photochemical cross-linking of translation initiation factor 3 to Escherichia coli 50S ribosomal subunits.

Translation initiation factor 3 (IF-3) was bound noncovalently to Escherichia coli 50S ribosomal subunits. Irradiation of such complexes with near-ultraviolet light (greater than 285 nm) resulted in covalent attachment of initiation factor 3 to the 50S subunit. Photo-cross-linking attained its maximum level of 40% of that which was noncovalently bound after 90 min of irradiation. Cross-linking was abolished in the presence of either 0.5 M NH4C1 or 0.25 mM aurintricarboxylic acid, indicating that specific binding of initiation factor 3 to the ribosome was a prerequisite for subsequent covalent attachment. Further analysis showed that all the IF-3 was covalently bound to a small number of 50S subunit proteins. The major cross-linked proteins were identified as L2, L7/L12, L11, and L27 by immunochemical techniques. These results are discussed in light of the proposed mechanism for IF-3 function.

Bacterial Proteins↗
PubMed1982

E coli tRNAPhe modified at the 3-(3-amino-3-carboxypropyl) uridine with a photoaffinity label is fully functional for aminoacylation and for ribosomal interaction.

E. coli tRNAPhe was modified at its 3-(3-amino-3-carboxypropyl)uridine residue with the N-hydroxysuccinimide ester of N-(4-azido-2-nitrophenyl) glycine. Exclusive modification of this base was shown by two-dimensional TLC analysis of the T1 oligonucleotide and nucleoside products of nuclease digestion. The fully modified tRNA could be aminoacylated to the same level as control tRNA. The aminoacylated tRNA was as active as control tRNA in non-enzymatic binding to the P site of ribosomes, and in EFTu-dependent binding to the ribosomal A site. The functional activity of this photolabile modified tRNA allows it to be used to probe the A and P binding sites on ribosomes and on the other proteins that interact with tRNA. Crosslinking to the ribosomal P site has been shown.

Affinity Labels↗
PubMed1982

Breast carcinoma in a 46, XX true hermaphrodite.

Muscinous breast carcinoma occurred in a 67-year-old true hermaphrodite who had been reared as a male. The peripheral blood karyotype was 46, XX. A left ovary and right ovotestis were intra-abdominal. Other tumors included an ovarian thecoma and an intestinal leiomyoma. Two previously reported cases of breast cancer in true hermaphrodites are cited.

Adenocarcinoma, Mucinous↗