Biomedical subjects
Publications and source records attributed to A Boyd.
Two patients with postoperative pneumothorax following open-heart surgery are described. The diagnostic usefulness of computed tomography and chest roentgenogram in this complication is discussed.
It has been shown using ELISA and affinity chromatography, that extracts from heat-shocked Drosophila melanogaster larvae and cultured cells react with monoclonal antibodies raised against bovine alpha-crystallin. It is suggested that this cross-reactivity is associated with the region of the sequence corresponding to residues 98-108 of the bovine alpha A-crystallin chain. This region may be important for the functions of both alpha-crystallin and the heat-shock proteins.
Forty-four patients with non-small cell carcinoma of the lung were treated every 3 weeks with vinblastine (4 mg/m2/day iv X 2) and cisplatin (20 mg/m2/day iv X 3). Of the 28 patients with metastatic disease, eight (29%; 90% confidence interval of true response, 17%-47%) achieved objective response, for a median duration of 27 weeks. Median survival in this group was 47 and 28 weeks for responders and nonresponders, respectively. Of the 16 patients with advanced regional disease, 11 (69%; 90% confidence interval of true response, 49%-86%) achieved objective response. Thirteen of these patients received consolidation radiotherapy (4500 cGy/25 fractions/5 weeks), with a boost of 1000 cGy/5 fractions/1 week in those patients who achieved response. In the three patients who did not receive radiotherapy, two died during the induction phase, one from grade 4 leukopenia and sepsis and the second from unrelated factors. The third patient had systemic progression of disease during induction chemotherapy. Six patients experienced overall improvement in their chemotherapy response from the radiotherapy. Two patients who did not respond to the chemotherapy achieved partial response with irradiation. Four patients who had partial response to the chemotherapy achieved complete response with irradiation, and seven patients had no further change in their degree of response to irradiation. The overall median survival of this group was 81 weeks. Maintenance chemotherapy was not given. After radiotherapy, the site of first failure was outside the radiation field in nine of 13 patients (69%). Hematologic toxicity was dose-limiting. Other toxic effects that were not dose-limiting included nephrotoxicity, neurotoxicity, and acute nausea and vomiting. In the patients with advanced regional disease, there was no increase in the radiation toxicity attributable to the chemotherapy. We conclude that: (a) this dose schedule of vinblastine and cisplatin has reproducible activity in non-small cell carcinoma of the lung; (b) the response and median survival of patients with advanced regional disease are superior to those of patients with metastatic disease; and (c) in patients with advanced regional disease, treatment with chemotherapy followed by radiotherapy yielded an overall response rate of 81% (90% confidence interval of true response, 60%-93%) and improved survival compared to a similar group of patients studied by others receiving radiotherapy alone. We recommend further testing of this concept.
The tar and tsr genes of Escherichia coli encode homologous transducer proteins that mediate distinct chemotactic responses. We report here the construction of two tasr chimeric genes in which the 5' coding region of the tar gene is fused to the 3' coding region of the tsr gene at either of two conserved restriction sites. Both chimeric genes code for chemotactically functional proteins. Results of analyses of behavior and methylation in cells carrying the chimeric genes support existing models for the disposition of transducer domains across the cell membrane and reveal that the receptors for internal pH map in a specific region of the COOH-terminal (cytoplasmic) domain.
In an attempt to identify stages of mu gene activation subsequent to VHDHJH assembly, we investigated two pre-B cell lines (A1 and A8) that have both alleles of the JH locus rearranged but do not make mu polypeptides. The block in A1 reflects incorrect VHDHJH assembly on both alleles. In A8, although an out-of-phase VHDHJH-C mu allele is transcribed, the properly assembled allele is silent, despite having a normal VH promoter and mu enhancer. Thus, transcription can be restricted to a single mu allele. Low level mu transcription in both lines was associated with demethylation of the VHDHJH and enhancer regions but not of the C mu gene. Markedly elevated mu transcription ensued on lipopolysaccharide stimulation or fusion to a plasmacytoma, but only fusion induced C mu demethylation. Hence stepwise demethylation is implicated in mu gene regulation, but enhanced expression can also occur independently of, or prior to, demethylation.
In killer strains of the yeast Kluyveromyces lactis, production of a protein toxin which inhibits the growth of sensitive yeast cells is associated with the presence of two linear DNA plasmids, k1 and k2. We have determined the nucleotide sequence of the smaller plasmid k1 (8.9kb) which is thought to carry the structural gene(s) encoding the toxin. The plasmid has a low G + C content (26.8%) and contains four long open reading frames which account for over 95% of the total sequence. The longest open reading frame (1146 amino acids) probably corresponds to a structural gene for the killer toxin. Transcripts from three of the putative genes have been detected in K.lactis by Northern hybridisation.
Thirteen patients with acute myeloid leukaemia aged from 19 to 81 were treated with low dose cytosine arabinoside (ARA-C) in a dose of 10-15 mg/m2 twice daily subcutaneously. Three complete remissions were obtained. Partial responses were observed in a further two patients. To analyse the action of low dose ARA-C freshly isolated leukaemic cells and cells from the cloned promyelocytic leukaemia cell line (HL60) were cultured in vitro in the presence of cytosine arabinoside. Minimal evidence of differentiation induction was observed when compared with the cytotoxic effects of the drug. These results suggest that ARA-C does not exert its anti-leukaemic effects by halting proliferation through differentiation induction. Rather, it appeared that the capacity of this agent to kill cells in S-phase produced a progressive depletion of the cycling leukaemic cells. This resulted in a corresponding steady decline in the total leukaemic cell population.
The value and accuracy of a scoring system applied to clinical examination, aspiration cytology and mammography has been assessed in the diagnosis of 224 consecutive 'new' patients attending a breast clinic with a breast lump. In 72 of 99 patients with breast cancer (80%) the scores were high enough to allow definitive surgery without formal histology; all were subsequently confirmed as breast carcinomas. Cytology proved the most accurate investigation with no false positives and a correct diagnosis in 146 of 148 adequate specimens (98.6%). This system reduced the frozen section rate by 74% and allowed for a more appropriate counselling of patients prior to mastectomy.
Attempts were made to functionally map antigenic expression of the Epstein-Barr virus (EBV) to specific regions on the EBV genome, using the B95-8 strain. Experiments were performed to map the expression of early antigen (EA), both restricted and diffuse (R and D, respectively), and the EBV nuclear antigen (EBNA), using intact B95-8 DNA, cloned BamHI fragments or Charon 4A fragments. DNA preparations were microinjected into two EBV genome-negative epithelial tumor cell lines. Expression of EBV antigens was monitored using precharacterized human sera, as well as monoclonal antibodies to EA-R and EA-D. The data suggest that EA-R maps to the BamHI H fragment, and EA-D maps to the Charon 4A fragment 7. A previous report that BamHI K is associated with the expression of a nuclear neoantigen tentatively identified as EBNA (W.P. Summers, E.A. Grogan, D. Shedd, M. Robert, C.R. Liu, and G. Miller, Proc. Nat. Acad. Sci. USA 79, 5688-5692, 1982) was also confirmed.
The tar and tsr genes of E. coli encode functionally analogous transducer proteins that mediate two distinct classes of chemotactic response. The tap gene lies adjacent to tar, and is thought to encode another transducer protein. We present here the complete nucleotide sequence of the tar-tap region of the E. coli genome, together with a comparative analysis of the sequences of the Tar, Tap, and Tsr proteins. The proteins appear to have a simple transmembrane structure consisting of an extracytoplasmic amino-terminal domain, a membrane-spanning domain, and an intracellular carboxy-terminal domain. The carboxy-terminal domains of three proteins possess highly homologous sequences and contain sites of methylation involved in sensory adaptation, while the amino-terminal sequences are only distantly related to one another, consistent with their serving as chemoreceptor domains that have diverged functionally.
The title compound and its antipode with natural steroid configuration were synthesized and tested. Both compounds showed equal potency as anti-arrhythmic compounds. An additional effect found for the steroid with natural configuration was its plasma cholesterol lowering activity in the rat. This suggests that enantiosteroids may have a more selective action than the steroids with natural configuration.
Several of the gene products required for bacterial motility and chemotaxis are integral components of the cytoplasmic membrane. Amplification of the expression of one of these genes, motB, using in vitro recombinant DNA techniques, has allowed us to initiate a study of the assembly of this protein into the membrane. The identical sizes of the motB gene products synthesised in vivo and in vitro strongly suggest that assembly is achieved without the involvement of a proteolytically processed leader peptide. Further analysis of this system should yield valuable insights into the specific determinants of the cellular localisation of the motB gene product. Two other membrane proteins, the tsr and tar products have been studied in relation to their role as integrating channels for the transfer of sensory information into the bacterial cell. A model of the functional properties of these proteins is presented and discussed in terms of recent findings that they are subject to multiple covalent modifications during sensory adaptation.
The tsr and tar genes, which are widely separated in the E. coli genome, encode functionally analogous transducer proteins that focus and integrate two distinct classes of chemosensory information. Physical mapping of these genes was achieved by use of transposon Tn5 mutagenesis of cloned DNA fragments. The polar effects of Tn5 insertions in the tar-cheR-cheB-cheY-cheZ region indicated that these genes are cotranscribed from a promoter upstream of tar and revealed the existence of a new gene, tap (taxis-associated protein), lying between tar and cheR. DNA hybridization studies demonstrated that the tsr gene possesses sequence homologies with the tar and tap genes, suggesting that they have all evolved from a common ancestor. The tap gene encoded a polypeptide of apparent molecular weight of 65,000, which may constitute a transducer protein of unknown specificity.
A series of defective lambda transducing phage carrying genes from the lip-leuS region of the Escherichia coli chromosome (min 14 on the current linkage map) has been isolated. The phage defined the gene order as lac---lip-dacA-rodA-pbpA-leuS---gal. These included the structural genes for penicillin-binding protein 2 (pbpA) and penicillin-binding protein 5 (dacA) as well as a previously unidentified cell shape gene that we have called rodA. rodA mutants were spherical and very similar to pbpA mutants but were distinguishable from them in that they had no defects in the activity of penicillin-binding protein 2. The separation into two groups of spherical mutants with mutations that mapped close to lip was confirmed by complementation analysis. The genes dacA, rodA, and pbpA lie within a 12-kilobase region, and represent a cluster of genes involved in cell shape determination and peptidoglycan synthesis. A restriction map of the lip-leuS region was established, and restriction fragments were cloned from defective transducing phage into appropriate lambda vectors to generate plaque-forming phage that carried genes from this region. Analysis of the proteins synthesized from lambda transducing phage in ultraviolet light-irradiated cells of E. coli resulted in the identification of the leuS, pbpA, dacA, and lip gene products, but the product of the rodA gene was not identified. The nine proteins that were synthesized from the lip-leuS region accounted for 57% of its coding capacity. Phage derivatives were constructed that allowed about 50-fold amplification of the levels of penicillin-binding proteins 2 and 5 in the cytoplasmic membrane.
The tsr and tar genetic loci of Escherichia coli determine the presence in sodium dodecyl sulfate-polyacrylamide gel electrophoresis of methyl-accepting chemotaxis proteins (MCPs) I and II, respectively, each of which consists of a distinct group of multiple bands. Synthesis of the tsr and tar products was directed in ultraviolet-irradiated bacteria by lambda transducing phages. The addition of appropriate chemotactic stimuli to these cells resulted in the appearance of additional, faster migrating electrophoretic forms of the Tsr and Tar polypeptides which disappeared upon removal of the stimulus. The stimulus-elicited forms comigrated with component bands of the corresponding MCPs. These results indicate that methylation itself caused shifts in electrophoretic mobility and hence led to the observed MCP band patterns. The number of Tsr species suggested that there were at least three methylated sites on the Tsr polypeptide. The conclusion that methylation generates multiplicity was supported by the results of experiments in which the tsr product was synthesized in mutant bacteria defective in specific chemotaxis functions concerned with methylation or demethylation of MCPs. Thus, the presence of a cheX defect blocked the stimulus-elicited appearance of faster migrating forms of the tsr product; conversely, the presence of a cheB defect resulted in a pronounced shift toward these forms in the absence of a chemotactic stimulus.
Evidence from pulse-chase experiments indicates that the outer membrane matrix protein or porin of Escherichia coli B/r passes through a Sarkosyl-soluble membrane pool on the way to its eventual Sarkosyl-insoluble state in the outer membrane.
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