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Biomedical subjects

D Oliver

Publications and source records attributed to D Oliver.

At least 73 records · Page 4Linked to original sources
PubMed1995

Competition between ribosome and SecA binding promotes Escherichia coli secA translational regulation.

SecA protein, the protein translocation ATPase of Escherichia coli, autogenously regulates its translation during normal protein secretion by binding to a secretion-responsive element located near the 5' end of its gene on geneX-secA mRNA. In order to characterize this autoregulation further, RNA footprinting and primerextension inhibition (toeprinting) studies were carried out with a segment of geneX-secA RNA, 30S ribosomal subunits and tRNAfMet along with purified SecA protein. The results show that ribosome and SecA-binding sites overlap, indicating that a simple competition for binding of geneX-secA mRNA presumably governs the translation initiation step. Further analysis showed that SecA protein was able to specifically dissociate a preformed 30S-tRNAfMet-geneX-secA RNA ternary complex as indicated by the disappearance of its characteristic toeprint after SecA addition. These findings are consistent with secA autoregulation, and they suggest a novel mechanism for the autoregulatory behavior of this complex protein.

Adenosine Triphosphatases↗
PubMed1994

SecA protein is exposed to the periplasmic surface of the E. coli inner membrane in its active state.

E. coli cells harboring pCG169 containing the secD secF locus possessed SecA protein almost entirely in an integral membrane form in which it displayed normal protein translocation activity. These results imply that integral membrane SecA is the catalytically active form of this enzyme and that products of the secD secF locus regulate SecA association with the inner membrane. Protease and biotinylation accessibility studies of right side-out and inside-out membrane vesicles derived from this strain revealed that SecA was exposed to the periplasmic surface of the inner membrane. These studies suggest a model of bacterial protein secretion, whereby insertion of SecA into the inner membrane and its association with SecY/E/G promotes assembly of active protein-conducting channels comprised in part of integral membrane SecA protein, and products of the secD secF locus regulate the channel assembly-disassembly reaction by modulating the SecA insertion-deinsertion step.

Adenosine Triphosphatases↗
PubMed1994

Carboxy-terminal region of Escherichia coli SecA ATPase is important to promote its protein translocation activity in vivo.

The role of the carboxy-terminal region of E. coli SecA ATPase was investigated by using genetic methods to construct a truncated SecA protein missing the last 66 amino acid residues and by systematically substituting serine for each of four cysteine residues present in this protein. Truncation of SecA or alteration of any of the carboxy-terminal cysteine residues resulted in poor growth and a protein secretion defect, indicating that this region of SecA is important in its protein translocation activity. Biochemical analysis of the altered proteins revealed a modest increase in translocation ATPase activity, suggesting that the carboxy-terminal region of SecA may facilitate the coupling of its ATPase activity to cycles of protein translocation.

Adenosine Triphosphatases↗
PubMed1994

Analysis of the DNA-binding domain of the HSV-1 origin-binding protein.

In order to understand DNA-protein interactions at the origin of DNA replication in herpes simplex virus type 1 (HSV-1), we have undertaken an analysis of the DNA-binding domain of the origin-binding protein (OBP) and its mechanism of binding to the Oris sequence of HSV-1. Mutant DNA-binding domains were constructed, expressed in vitro, and used to test for binding by gel shift analysis. A C-terminal deletion mutant was functional in binding, thereby redefining the C-terminal boundary of the DNA-binding domain at amino acid 822. Fifteen insertion mutants were also constructed across the DNA-binding domain. Several of these mutants were unable to bind DNA. Interestingly, 4 mutants that destroy DNA binding fall within a region that has a particularly high degree of sequence similarity to the varicella zoster virus gene 51 product. A second objective was to define how the DNA-binding domain interacts with the origin. Results of gel shift analysis using contranslated proteins of different sizes suggest that the DNA-binding domain can interact with a single binding site as a monomer. Binding to the wild-type Oris template indicated that the binding domains can interact with both binding sites I and II independent of any cooperative effect mediated by the amino-termini. This suggests that the basic unit of recognition involved in OBP/Oris interactions may contain a single DNA-binding domain of OBP in association with a single binding site.

Amino Acid Sequence↗
PubMed1994

ssaD1, a suppressor of secA51(Ts) that renders growth of Escherichia coli cold sensitive, is an early amber mutation in the transcription factor gene nusB.

Complementation analysis of the ssaD1 mutation, isolated as a suppressor of the secA51(Ts) mutation that renders growth of Escherichia coli cold sensitive, was used to show that ssaD corresponds to nusB, a gene known to be important in transcription antitermination. DNA sequence analysis of the ssaD1 allele showed that it creates an amber mutation in the 15th codon of nusB. Analysis of the effect of different levels of NusB protein on secA transcription and translation suggested that NusB plays little or no role in the control of secA expression. Accordingly, mechanisms by which nusB inactivation can lead to suppression of secA51(Ts) and secY24(Ts) mutations without affecting secA expression need to be considered.

Adenosine Triphosphatases↗
PubMed1993

Two distinct ATP-binding domains are needed to promote protein export by Escherichia coli SecA ATPase.

Six putative ATP-binding motifs of SecA protein were altered by oligonucleotide-directed mutagenesis to try to define the ATP-binding regions of this multifunctional protein. The effects of the mutations were analysed by genetic and biochemical assays. The results show that SecA contains two essential ATP-binding domains. One domain is responsible for high-affinity ATP binding and contains motifs A0 and B0, located at amino acid residues 102-109 and 198-210, respectively. A second domain is responsible for low-affinity ATP binding and contains motifs A3 and a predicted B motif located at amino acid residues 503-511 and 631-653, respectively. The ATP-binding properties of both domains were essential for SecA-dependent translocation ATPase and in vitro protein translocation activities. The significance of these findings for the mechanism of SecA-dependent protein translocation is discussed.

Adenosine Triphosphatases↗
PubMed1993

Ethical issues in palliative care--an overview.

There are many ethical decisions to be made during palliative care of a patient with motor neurone disease. These may concern the physical and psychosocial care of the patient and will become highlighted when death approaches. By close involvement of the patient and his/her family with the interdisciplinary team the most appropriate decisions on the patient's care can be made.

Amyotrophic Lateral Sclerosis↗
PubMed1993

Bereavement--whose responsibility?

Bereavement care begins during the terminal phase of motor neurone disease as the family prepare for the death. Due to the long-term nature of the illness there is a need to allow the expression of painful feelings and to ensure that the family is adequately supported. The responsibility for care in bereavement lies not only with the family but with the health care professions, bereavement support groups and the whole community.

Amyotrophic Lateral Sclerosis↗
PubMed1993

Prostitution and HIV risk behavior.

The authors discuss prostitution as a high-risk behavior for HIV infection and transmission, using data from interviews with prostitutes in Bridgeport, Connecticut, and New York City. "The primary objective is to share some of the information gained in research interviews and street work so that it can be utilized to assist efforts at reaching such high risk behavior populations with appropriate AIDS prevention information, testing, counseling and health services." Factors considered include prostitute characteristics, the pimp, perceived roles of the prostitute, power and control, risky sexual practices, and knowledge, attitudes, and behavior relating to AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1992

The baboon model under anesthesia for in vivo cerebral blood flow studies using single photon emission computed tomographic (SPECT) techniques.

Single photon emission computed tomography of the brain can be useful in animal experimentation directed toward cerebral conditions. A well established and understood baboon model, necessarily under anesthesia, could be especially valuable in such investigations. Six normal baboons were studied under various anesthetic agents and their combinations: ketamine, thiopentone, pentobarbitone, and halothane. Cerebral blood flow (CBF) studies were performed with 99mTc-HMPAO. CBF effects from various anesthesia were detected, requiring careful choice of the anesthesia for cerebral investigations.

Anesthesia↗
PubMed1992

Quality of life improvements in CAPD patients treated with subcutaneously administered erythropoietin for anemia.

Twenty-two continuous ambulatory peritoneal dialysis (CAPD) patients, mean age 48 years, at 3 U.K. renal units were assessed with the Nottingham Health Profile (NHP) before and after treatment with recombinant human erythropoietin (r-HuEPO). Mean (SD) hemoglobin (Hb) at baseline was 7.5 (1.0) gm/dL and 10.8 (1.5) gm/dL at retest. There were significant improvements in energy (p less than 0.0001), social life (p less than 0.005), relationships at home (p less than 0.05) and leisure pursuits (p less than 0.05). Twelve patients, mean age 51 years, who had already completed more than 9 months on r-HuEPO treatment were reassessed to determine the changes sustained. Mean (SD) Hb at second retest was 12.8 (1.3) gm/dL. Improvement in energy continued to be significant, and emotional wellbeing showed further improvement. Problems with household tasks, which had not shown significant improvement at Test B, were now considerably reduced (p = 0.016). The study showed far-reaching benefits similar to those reported in hemodialysis patients, in a population with a higher mean age and higher potential coexisting illness or disability than most reported hemodialysis studies.

Activities of Daily Living↗
PubMed1991

The value of anticarcinoembryonic antigen, human milk factor globulin, and antikeratin antibodies in differentiating mesothelioma from lung carcinoma.

Monoclonal anticarcinoembryonic antigen (antiCEA), human milk factor globulin (HMFG2), and antikeratin antibodies were assessed for their value in the differential diagnosis of pleural mesothelioma (53 cases) and carcinoma of the lung (60 cases) in material from necropsies. In 40 of the cases pleural biopsies were also studied in the same manner. AntiCEA was found to be the best discriminating antibody for most types of mesothelioma; HMFG2 was slightly less valuable but a useful additional tool. Antikeratin was the least useful. For both antiCEA and HMFG2 antibodies, however, the proportion of carcinomas staining was smaller than in previous studies and this, combined with the positive staining of some mesotheliomas, reduces the value of the reactions in the individual case. Medical panels adjudicating compensation claims should not use these reactions as the sole criteria in deciding the origin of the tumours in these cases.

Antigens, Neoplasm↗
PubMed1991

Stereotactic fine needle aspiration biopsy (SFNB) of breast: preliminary results in Perth with the TRC mammotest machine. Cytological aspects.

Stereotactic fine needle aspiration biopsy (SFNB) was carried out on 404 mammographically detected impalpable breast lesions from 389 women between October 1988 and January 1990. Seventy-three lesions were excised, and 38 were carcinomas. Thirty-six of the 38 carcinomas had been diagnosed as atypical, suspicious or malignant by cytology; in the remaining 2 only fat and fibrous tissue were present in smears. The sensitivity of cytological diagnosis in detecting malignancy was therefore 94.8% (36 of 38 cases). A cytological diagnosis of malignancy was made in 23 cases (5.7%) and in 5 (1.2%) the findings were suspicious of malignancy. All of these were confirmed as carcinoma histologically; the predictive value of a positive cytological diagnosis was therefore 100%. In 32 cases (7.9%) the cytological findings were atypical but inconclusive. Twenty-three of these lesions were excised, and 8 proved to be carcinoma (34.8%). No case assessed radiologically and cytologically as benign has subsequently proven to be malignant. Twenty-two of 28 cases of invasive carcinoma were given an unequivocal cytological diagnosis of malignancy; 2 were suspicious of malignancy, and in 3 the findings were atypical but inconclusive. Of the 10 pure duct carcinoma-in-situ (DCIS) lesions, (26.3% of the cancers) 1 was diagnosed cytologically as malignant, 3 as suspicious of malignancy, and 5 as atypical. The sensitivity of SFNB in detecting DCIS lesions was therefore similar to invasive carcinomas, but cases of DCIS were more likely to be given a suspicious or atypical diagnosis rather than a definite diagnosis of malignancy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗