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Biomedical subjects

S Jones

Publications and source records attributed to S Jones.

At least 397 records · Page 22Linked to original sources
PubMed1994

Food security reserve policy in Ethiopia: a case study of experience and implications.

Food security reserve policy in Ethiopia since 1982 is reviewed in the light of the limited progress made elsewhere in Africa in establishing and maintaining such reserves. While the reserve played some role in dealing with the crisis of 1987/8, donor confidence was eroded by unauthorised drawings from the reserve and other factors. In 1992, the Ethiopian Food Security Reserve Authority was established to provide a system of management more acceptable to donors. This had led to donor pledges to replenish the reserve, though it remains well below the target level. Despite increased government commitment of funds, donor confidence remains fragile and the reserve remains dependent on donor support. The place of the reserve in national food security policy is not yet fully defined. Conclusions are drawn for food security reserve policy in Ethiopia and elsewhere in Africa.

Attitude to Health↗
PubMed1994

New algorithms to increase the initial rate response in a minute volume rate adaptive pacemaker.

BACKGROUND: Minute volume is a truly physiological sensor for rate adaptive pacing that correlates with metabolic expenditure throughout the range of physical activity. Criticism has centered on the slow initial response compared to less physiological sensors. A new algorithm, consisting of rate augmentation factor and programmable speed of response, has been incorporated in the 1206 META III pacemaker generator and was designed to improve the rate response at lower levels of exertions. Rate augmentation factor increases the programmed rate response factor by 3, 6, or 10 when set to low, medium, or high, respectively; this augmentation lasting to 50% of the maximum programmed rate. Response time can be programmed to medium or fast. METHODS: Nine patients were studied during the first 3 minutes of an exercise test (Bruce protocol) in a single blind manner. The pacemaker generator was randomly programmed with rate augmentation factor at off, low, or high and speed of response to medium or fast, giving six possible combinations. Heart rates were recorded continuously for the duration of the test and until resting heart rate was achieved during recovery. The test was repeated until all six combinations had been tested. RESULTS: During exercise significant differences appeared in response time from 30 seconds onward. Fast response and rate augmentation factor contributed to an improved rate response with greatest speed of response seen with fast response time and high rate augmentation factor. During recovery decreases in recovery time were seen with fast response time but rate augmentation factor prolonged recovery. CONCLUSIONS: Rate augmentation factor improves initial rate response in the early stages of exercise. Fast response gives an improved time to initial rate increase and shortens the duration of inappropriate postexercise tachycardia. These features improve the pattern of response of the minute ventilation sensor.

Aged↗
PubMed1994

Choice autonomy and memory for spatial locations in six-year-old children.

Six-year-old children were presented with 12 identically labelled locations in a room and required to search non-redundantly for the six that contained rewards. On each day they could commit Across-Trial Memory (ATM) errors by visiting non-rewarded locations, or Within-Trial Memory (WTM) errors by revisiting locations previously visited that day. Groups were trained for nine days, either walking or pushed in a wheelchair, and with or without freedom of choice. They were then tested, walking with freedom of choice. Performance of the task improved significantly across training days in groups allowed free choice, whether walking or transported, and was superior at test to that of non-choosing groups. Throughout training and testing, the ATM component of performance was superior in groups allowed free choice. WTM was more accurate than would be expected by chance in all subjects at all stages of the experiment, but did not differ between groups. The problem of comparing WTM scores in groups differing in ATM accuracy was discussed. It was concluded that the primary benefit of free choice in spatial memory tasks is that it promotes accurate environmental segmentation, and that WTM is little affected by training or environmental familiarity.

Child↗
PubMed1994

Conventional and cross-correlation brain-stem auditory evoked responses in the white leghorn chick: rate manipulations.

Rate-dependent changes in the chick brain-stem auditory evoked response (BAER) using conventional averaging and a cross-correlation technique were investigated. Five 15- to 19-day-old white leghorn chicks were anesthetized with Chloropent. In each chick, the left ear was acoustically stimulated. Electrical pulses of 0.1-ms duration were shaped, attenuated, and passed through a current driver to an Etymotic ER-2 which was sealed in the ear canal. Electrical activity from stainless-steel electrodes was amplified, filtered (300-3000 Hz) and digitized at 20 kHz. Click levels included 70 and 90 dB peSPL. In each animal, conventional BAERs were obtained at rates ranging from 5 to 90 Hz. BAERs were also obtained using a cross-correlation technique involving pseudorandom pulse sequences called maximum length sequences (MLSs). The minimum time between pulses, called the minimum pulse interval (MPI), ranged from 0.5 to 6 ms. Two BAERs were obtained for each condition. Dependent variables included the latency and amplitude of the cochlear microphonic (CM), wave 2 and wave 3. BAERs were observed in all chicks, for all level by rate combinations for both conventional and MLS BAERs. There was no effect of click level or rate on the latency of the CM. The latency of waves 2 and 3 increased with decreasing click level and increasing rate. CM amplitude decreased with decreasing click level, but was not influenced by click rate for the 70 dB peSPL condition. For the 90 dB peSPL click, CM amplitude was uninfluenced by click rate for conventional averaging. For MLS BAERs, CM amplitude was similar to conventional averaging for longer MPIs.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1994

Characterization of Listeria monocytogenes pathogenesis in a strain expressing perfringolysin O in place of listeriolysin O.

Listeriolysin O (LLO) is a pore-forming cytolysin that enables Listeria monocytogenes to escape from a host cell vacuole. The structural gene for the related cytolysin perfringolysin O (pfo) was cloned downstream from the promoter for hly, the gene encoding LLO, both on a plasmid and on the L. monocytogenes chromosome. Both strains secreted active PFO, although regulation was not identical to that of LLO. The chromosomal PFO-expressing strain was characterized for intracellular growth and cell-to-cell spread. It escaped from a host cell vacuole with 64% efficiency compared with the wild type as determined by immunofluorescent staining of bacteria for F-actin, a marker for entry into the cytoplasm. In addition, it replicated intracellularly with a doubling time similar to that of the wild type for 5 h, after which growth was aborted because of a cytotoxic effect on the host cell and influx of extracellular gentamicin. The chromosomal PFO strain was able to plaque in mouse L2 fibroblasts, but it did so at 20% efficiency compared with the wild type and the plaques were significantly smaller. Both strains expressing PFO were completely avirulent in mice. These results indicate that PFO can mediate escape from a host cell vacuole but cannot complement an hly deletion strain for virulence.

Animals↗
PubMed1994

Antilisterial immunity includes specificity to listeriolysin O (LLO) and non-LLO-derived determinants.

Subclinical infection of BALB/c mice with virulent Listeria monocytogenes leads to the generation of Listeria-specific T-cell populations required for the expression of protective immunity. The L. monocytogenes-produced hemolysin listeriolysin O (LLO) is a virulence factor which appears to be crucial for the induction of protective antilisterial immunity. Analysis of the specificity of antilisterial cytotoxic cells from Listeria-immune BALB/c donors has shown a dominant response to an epitope corresponding to amino acids 91 to 99 of LLO. Demonstration of antilisterial T cells with specificity to non-LLO-derived epitopes has been difficult to achieve because of the requirement of LLO in facilitating escape of the bacteria to the cytoplasm of the host cell and the apparent dominance of an anti-LLO response in antilisterial immunity. In this study we show that antilisterial immunity also includes specificity to non-LLO-derived determinants. We used as an immunogen an LLO- mutant of L. monocytogenes which expresses the hemolysin perfringolysin O (PFO). The LLO- PFO+ L. monocytogenes mutant possesses invasive properties similar to those of wild-type L. monocytogenes and escape from the phagocytic vacuole because of the activity of PFO. We found that J774 target cells infected with the LLO- PFO+ L. monocytogenes mutant were lysed by antilisterial cytotoxic T cells obtained from BALB/c mice immunized with wild-type L. monocytogenes. In addition, BALB/c mice immunized with the LLO- PFO+ L. monocytogenes mutant were immune to challenge with LLO+ wild-type L. monocytogenes, a finding indicative of protective antilisterial immunity specific to Listeria-derived epitopes other than LLO. Spleen cells from BALB/c mice immunized with the LLO- PFO+ L. monocytogenes mutant adoptively transferred antilisterial protection to a subsequent challenge with wild-type L. monocytogenes. This splenocyte population also contained cytotoxic cells which lysed target cells infected with either the LLO- PFO+ L. monocytogenes mutant or wild-type LLO+ L. monocytogenes but did not lyse target cells infected with an LLO-expressing Bacillus subtilis transformant. These results establish that during the immune response to L. monocytogenes, immune splenocytes with specificity for LLO and other, non-LLO-derived epitopes develop. These non-LLO epitopes serve as targets for antilisterial cytotoxic cells and for lymphocytes which adoptively transfer antilisterial immunity.

Animals↗
PubMed1994

Appropriateness of paediatric admission.

A study of the 'appropriateness' of 267 consecutive emergency admissions to a district paediatric department showed that admission was at a peak in the evening and night time. Breathing difficulty, head injury, and fever were the commonest presenting problems. Sixty three per cent of admissions occurred between 6 pm and 8 am and these were more likely to be after self referral to the accident and emergency department and were evenly distributed through the social classes. Overall 80.5% of admissions were considered to be necessary on medical grounds by the consultants at the time of discharge. Parental assessment of severity of illness and need for admission correlated well with that of the doctors. Fifty two per cent of all admissions took place though the accident and emergency department, and although a higher number of these were from disadvantaged families these were equally appropriate on medical grounds to those sent for admission by the general practitioner. Altogether 26.5% of admissions were for less than 24 hours and half of these were judged to be unnecessary. Implications for the organisation of inpatient care are discussed.

Asthma↗
PubMed1994

Developing effective editorial boards for hospital-based newsletters and magazines.

Editorial boards can be of tremendous help to a busy editor of a hospital-based newsletter or magazine. This article shows you how to develop the role of the editorial board member, make certain all members know and can achieve the editor's expectations, and chair a board that shares with you a commitment to excellence in publishing. These strategies apply to other in-house publications, such as school of nursing and association newsletters as well.

Hospitals↗
PubMed1994

Oral vinorelbine (Navelbine) in the treatment of advanced non-small cell lung cancer: a preliminary report.

Vinorelbine (Navelbine; Burroughs Wellcome Co, Research Triangle Park, NC; Pierre Fabre Médicament, Paris, France) is a novel semisynthetic vinca alkaloid with antitumor activity in non-small cell lung cancer. An oral preparation of this drug is under investigation and was tested in a multicenter phase II study in patients with stage IV measurable or evaluable non-small cell lung cancer. The initial vinorelbine dose was 100 mg/m2/wk (80 mg/m2/wk for patients with prior radiotherapy). Following an initial 37% incidence of grade 3 or 4 neutropenia, the dose was reduced by 40 mg/dose. Nausea, vomiting, diarrhea, and mucositis were other frequently observed toxicities. A preliminary analysis indicated a response rate of 14%, suggesting activity of this drug when administered orally.

Administration, Oral↗
PubMed1993

Anti-erythropoietin receptor (EPO-R) monoclonal antibodies inhibit erythropoietin binding and neutralize bioactivity.

We have generated six high affinity monoclonal antibodies (MoAbs) to the human erythropoietin receptor (hEPO-R) polypeptide. All six MoAbs bind to the extracytoplasmic domain of the hEPO-R, and all immunoprecipitate 35S-labeled hEPO-R from metabolically labeled Ba/F3-hEPO-R cells. Four of the MoAbs neutralize the EPO-dependent growth of Ba/F3-hEPO-R cells, whereas two MoAbs are non-neutralizing. None of the MoAbs inhibit the EPO-dependent growth of Ba/F3 cells expressing the murine EPO-R (mEPO-R), even though the hEPO-R and mEPO-R share 82% amino acid identity. All six of the anti-EPO-R MoAbs bind to the cell surface human EPO-R but none bind to the cell surface murine EPO-R. Of the four neutralizing MoAbs, the one-half maximal inhibition occurs at MoAb concentrations ranging from 1 nmol/L to 50 nmol/L. These MoAbs also compete with radiolabeled EPO for hEPO-R binding. The two non-neutralizing MoAbs fail to inhibit EPO-dependent growth or compete with EPO-binding, even at antibody concentrations as high as 500 nmol/L. The four neutralizing MoAbs, designated group I, compete with each other for an epitope of the hEPO-R polypeptide required for EPO-binding. The two non-neutralizing MoAbs recognize discrete epitopes, and are designated group II and group III MoAbs. In conclusion, this is the first description of MoAbs specific for the hEPO-R. The MoAbs, which recognize three discrete epitopes, may be useful in characterizing the spectrum of cells that display the hEPO-R and in further defining the role of EPO in hematopoiesis.

Antibodies, Monoclonal↗
PubMed1993

The lux autoinducer regulates the production of exoenzyme virulence determinants in Erwinia carotovora and Pseudomonas aeruginosa.

Erwinia carotovora and Pseudomonas aeruginosa secrete exoenzymes that contribute to the pathogenesis of plant and mammalian infections respectively. E.carotovora mutants defective in synthesis of the pectinase, cellulase and protease exoenzymes were isolated and classified into two groups. Group 2 mutants were found to be defective in the production of a small freely diffusible molecule, N-3-(oxohexanoyl)-L-homoserine, lactone (HSL), and were avirulent. Addition of exogenous HSL to these group 2 mutants restores synthesis of the exoenzymes and virulence in planta. Of the exoenzymes of P.aeruginosa the metalloprotease, elastase, is an established virulence determinant. Mutants of P.aeruginosa that are defective in elastase production have been isolated and were again found to fall into two groups. Analogous to the group 2 mutants of E.carotovora, group 2 mutants of P. aeruginosa are defective in the synthesis of HSL and exogenous HSL restores elastase production. HSL has now been linked to the control of bioluminescence in Vibrio fischeri, carbapenem antibiotic production of E.carotovora and the above exoenzyme virulence determinants. This information significantly enhances our understanding of the extent and nature of pheromone mediated gene expression control in prokaryotes.

4-Butyrolactone↗
PubMed1993

Zn2+ potentiates ATP-activated currents in rat sympathetic neurons.

The ATP-activated inward current (IATP) in cultured rat superior cervical ganglion neurons and its modulation by extracellular Zn2+ were examined. ATP activated a non-specific cation conductance and caused a transient rise in intracellular Ca2+. The current response was specifically activated by ATP and was blocked by the P2-purinoceptor antagonist, suramin. Low concentrations of extracellular Zn2+ rapidly and reversibly potentiated both IATP and the intracellular Ca2+ rise. The potentiation by 10 microM Zn2+ was dependent on the concentration of agonist; Zn2+ increased the sensitivity of activation without potentiating the maximum response. Higher concentrations of Zn2+ reduced and prolonged the current, consistent with open-channel block. We hypothesize that there exist two sites of action for Zn2+: a positively acting allosteric site that enhances current amplitude and a site, possibly within the pore, that blocks conductance through the channel.

Adenosine Triphosphate↗