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J L Jones

Publications and source records attributed to J L Jones.

At least 163 records · Page 9Linked to original sources
PubMed1989

Improved safety factor for triphasic defibrillator waveforms.

Newly developed biphasic waveforms improve defibrillation efficacy both by reduction of defibrillation threshold and by amelioration of shock-induced dysfunction depending on the relative shape of the first and second pulses. Each of these independent effects improves the waveform's safety factor, the ratio between the shock intensity that produces a specific degree of postshock dysfunction and the shock intensity that produces defibrillation (or cellular excitation). Symmetrical waveforms reduce defibrillation threshold to about 60% that of the corresponding monophasic waveform, probably by reduction of excitation threshold for ischemic cells, but increase postshock arrhythmias. Biphasic waveforms with 10% "tails" reduce postshock arrhythmias. This study tests the hypothesis that these independent mechanisms for improvement of defibrillation efficacy can be combined into a single triphasic waveform that will have a higher safety factor than either of the two biphasic waveforms of which it is composed. Cultured myocardial cells were subjected to high-intensity electric-field stimulation with a control monophasic rectangular waveform, a symmetrical biphasic waveform, and a triphasic waveform consisting of the biphasic waveform with an added 10% "tail." Each waveform portion was 5 msec in duration. Photocell mechanograms monitored contractile activity. We found that the duration of postshock arrest of spontaneous contractile activity increased with stimulus intensity for all waveforms. The voltage gradient producing a 4-second arrest after the biphasic waveform shock was 80.6 +/- 1.3% that of the control waveform (100%), while the voltage gradient for the triphasic waveforms was 87.1 +/- 0.73% of control. The difference between biphasic and triphasic waveforms was significant (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Trends in public knowledge and attitudes about AIDS, South Carolina, 1987-1988.

The South Carolina Department of Health and Environmental Control AIDS Program assessed the state population's knowledge and attitudes about AIDS and HIV transmission in 1987 and 1988. Each year approximately 1,800 adults were selected by a random 3-stage cluster design and asked seventeen questions by telephone about AIDS and HIV. Questions addressed attitudes, general knowledge, HIV transmission by casual contact, HIV transmission by sex and IV drug contact, and HIV transmission by blood donation and transfusion. Over 90 percent of respondents were knowledgeable about HIV transmission by high risk behaviors addressed in the questionnaire. Respondents were less knowledgeable about HIV transmission by casual contact (12 to 41 percent gave incorrect answers), HIV testing (45 to 48 percent gave incorrect answers), and transmission by blood donation (43 to 52 percent gave incorrect answers). In general, a higher percentage of correct responses were given in 1988 than in 1987. In regard to responses measured by this survey, we conclude that: (1) there is a high level of knowledge in the state about transmission by high risk behaviors, (2) there are still many misconceptions about casual transmission, HIV testing, and blood donation, and (3) there was improvement in knowledge about AIDS and HIV from 1987 to 1988.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Contact tracing to identify human immunodeficiency virus infection in a rural community.

This report describes a contact investigation conducted in rural South Carolina to identify, counsel, and educate persons infected with or exposed to the human immunodeficiency virus (HIV). Starting with one HIV antibody-positive man and his 19 sex contacts, we identified 83 sex contacts of HIV antibody-positive men. Of these, 64 were residents of the county and 63 (98%) agreed to be tested for evidence of HIV infection. Eight (13%) were HIV antibody positive. Thirty-six initially HIV antibody-negative men were reevaluated at a six-month follow-up visit, and three had seroconverted during this time. Of 25 men who reported practicing anal receptive intercourse, 13 (52%) were HIV antibody positive vs none of 43 men who reported strictly anal insertive intercourse. Comparing reported numbers of sexual contacts for the six-month periods before and after our initial investigation, the mean numbers of named sex contacts decreased by 82% for antibody-positive men and 54% for antibody-negative men. None of the men reported using condoms before entering the study; at the six-month follow-up visit, four (80%) of five of the antibody-positive men and 25 (69%) of 36 of the antibody-negative men reported using condoms at least some of the time.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Looking back. Early occupational therapy education in Wisconsin: Elizabeth Upham Davis and Milwaukee-Downer College.

Among the early influences on the profession of occupational therapy were the founding schools and those who helped create them. The Midwest was energized by Elizabeth Upham Davis, who was instrumental in establishing the occupational therapy education program at Milwaukee-Downer College in 1918. This paper relates Mrs. Davis's efforts on behalf of occupational therapy both in the development of the program at Milwaukee-Downer and on a national level during the early years of the profession.

History, 20th Century↗
PubMed1987

The assessment of in vitro modulation of milk fat globule membrane expression by human breast carcinomas.

Although knowledge of functional differentiation and tumour-associated changes of breast carcinomas can be gained by the application of antibodies directed against the milk fat globule membrane, more significant information may be obtained by assessment of the potential of breast carcinomas to modulate their antigenic phenotype. In this study, the extend to which primary tumours can undergo modulation in vitro has been investigated, with consideration of the suitability of organ culture in combination with the immunohistochemical detection of two milk fat globule membrane epitopes, HMFG1 and HMFG2, as methods for detecting this. The preservation of three of the 30 carcinomas assessed, all poorly differentiated, was poor after 3 days of culture. The viability of the other 27 was variable, and was greater in the better differentiated tumours and with the addition of insulin. Expression of the milk fat globule membrane epitopes was generally well maintained. Six of the carcinomas showed a significant change in antigen expression, with this being more frequent in tissues incubated with insulin. Hence, a small group of carcinomas have been identified which appear to have a greater capacity to undergo functional differentiation. Organ culture is considered to be a suitable method for maintaining the tissues in vitro for such evaluation, but the problems encountered in quantifying the immunohistochemical staining, because of antigenic heterogeneity, were such that it is suggested that other approaches be employed.

Adenocarcinoma, Mucinous↗
PubMed1987

Microlesion formation in myocardial cells by high-intensity electric field stimulation.

Arrhythmias, S-T segment changes, immediate refibrillation, and other signs of dysfunction are often observed after clinical and experimental transthoracic defibrillation. In vitro studies suggested that shock-induced dysfunction is induced by sarcolemmal dielectric breakdown accompanied by ionic exchanges through transient, shock-induced microlesions in the sarcolemma. To test this hypothesis, cultured chick embryo myocardial cells were shocked in media containing fluorescein isothiocyanate-labeled dextrans (FITC-dextrans) ranging in molecular mass from 4 to 70 kDa, using electric field stimulation 5 ms in duration and ranging in intensity from 0 to 200 V/cm. Results showed that the percentage of cells incorporating 4- to 20-kDa dextrans increased in a dose-dependent manner. The 4- and 10-kDa dextrans were incorporated beginning at intensities of 50-100 V/cm. Dextran incorporation corresponded with shock intensities which produced a shock-induced arrest of spontaneous contraction lasting 1 min. The 20-kDa dextrans were incorporated following 150- and 200-V/cm shocks. Shocks of these intensities also produced a transient postshock contracture. Larger dextrans (40 and 70 kDa) were not incorporated. These results suggest the formation of transient sarcolemmal microlesions having a diameter of 45-60 A during high-intensity electric field stimulation.

Animals↗
PubMed1987

Improved cardiac cell excitation with symmetrical biphasic defibrillator waveforms.

According to the most commonly accepted hypothesis, ventricular defibrillation is produced by exciting cells in a critical mass of the ventricle. For monophasic defibrillator waveforms, this hypothesis correctly predicts a direct correlation between defibrillation threshold in the transthoracic calf model and excitation threshold for extracellular field stimulation in the cultured cell model. To further test the hypothesis, we determined whether symmetrical biphasic waveforms, which reduce defibrillation threshold in the calf to approximately 65% of that of the corresponding monophasic waveform (14), decrease excitation threshold in the cultured cell model. Experiments were performed on 100- to 250-microns aggregates from 10- to 12-day-old chick embryos. Excitation threshold strength-duration curves obtained at extracellular potassium (Ko) = 6.5 mM and pacing interval of 1,000 ms showed a significant reduction for symmetrical biphasic rectangular waveforms, when compared with the corresponding monophasic waveforms for durations greater than 3 ms. At the rheobase, the threshold ratio between the biphasic and monophasic waveforms was 0.63 (SE = 0.02). Transmembrane potentials during stimulation showed that excitation takes place during the second portion of the biphasic waveform for intensities that are subthreshold for the monophasic waveform. The relative effectiveness of the biphasic waveform (5-ms duration) increases under "fibrillation conditions" of short pacing interval (300 ms) and high extracellular potassium (10.5 mM). These results show that symmetrical biphasic waveforms decrease excitation threshold in the cultured cell model and that the degree of threshold reduction is dependent on Ko and beat rate.

Animals↗
PubMed1986

Performance correlates of self-reported cognitive failure and of obsessionality.

In six experiments, two performance tests, measuring a number of aspects of attention, were administered to 129 people from the general population. Self-reported cognitive failure, and a measure of obsessional personality, were related to one particular measure of attention. There was evidence that individuals with low cognitive failure show different patterns of attention when anxious, as compared with high scorers; this may underlie differences in vulnerability to environmental stresses.

Adolescent↗
PubMed1985

Studies of synthetic peptide analogs of the amphipathic helix. Structure of complexes with dimyristoyl phosphatidylcholine.

The amphipathic helix hypothesis for the lipid-associating domains of exchangeable plasma apolipoproteins has been further studied by analysis of the structure of the complexes formed between four synthetic peptide analogs of the amphipathic helix and dimyristoyl phosphatidylcholine (DMPC). Density gradient ultracentrifugation, negative stain electron microscopy, nondenaturing gradient gel electrophoresis, 1H NMR, high sensitivity differential scanning calorimetry, and circular dichroism were the techniques used in these studies. The two analogs Asp-Trp-Leu-Lys-Ala-Phe-Tyr-Asp-Lys-Val-Ala-Glu-Lys-Leu-Lys-Glu-Ala-Phe (18A) and 18A-Pro-18A whose sequences most strongly mimic native amphipathic sequences were found also most strongly to mimic apolipoprotein A-I in DMPC complex structure. The covalently linked dimer of the prototype amphipathic analog 18A, 18A-Pro-18A, appears to have greater lipid affinity than 18A. This presumably is the result of the cooperativity provided by two covalently linked lipid-associating domains in 18A-Pro-18A. The studies further suggest that the charge-reversed analog of the prototype 18A, reverse-18A, has the lowest lipid affinity of the four analogs studied and forms only marginally stable discoidal DMPC complexes. We postulate that this low lipid affinity is due predominantly, but not necessarily exclusively, to the lack of a hydrophobic contribution of lysine residues at the polar-nonpolar interface of reverse-18A versus 18A. The intermediate lipid affinity of des-Val10-18A, the fourth analog peptide, to produce a rank order of 18A-Pro-18A greater than 18A greater than des-Val10-18A greater than reverse-18A, supports this interpretation. Des-Val10-18A which has Val deleted from 18A has an amphipathic helical structure partially disrupted by the shift of 2 lysine residues away from the polar-nonpolar interface.

Amino Acid Sequence↗
PubMed1985

Neurophysiology.

Explore the source record for details and available documents.

Brain↗
PubMed1984

Structural studies of apolipoprotein A-I/phosphatidylcholine recombinants by high-field proton NMR, nondenaturing gradient gel electrophoresis, and electron microscopy.

Complexes formed between apolipoprotein A-I (apo A-I) and dimyristoylphosphatidylcholine (DMPC) or egg phosphatidylcholine have been studied by high-field 1H NMR, nondenaturing gradient gel electrophoresis, electron microscopy, and gel filtration chromatography. Emphasis has been placed on an analysis of the particle size distribution within the micellar complexes produced at lipid/protein molar ratios of 40-700. As determined by electron microscopy and gel filtration of DMPC/apo A-I complexes, the size of the discoidal micelles produced appears to increase uniformly with an increasing lipid/protein ratio. By electron microscopy, the diameters of isolated DMPC/apo A-I discoidal micelles range from approximately 89 A at a 40 molar ratio to 205 A at a 700 molar ratio. Analysis of the micellar complexes by 1H NMR shows that concomitant with the increase in size is the progressive downfield shift of the choline N-methyl proton resonance of the complex which is observed from 3.245 to 3.267 ppm over the above molar ratio range. The relationship between chemical shift and micelle size is most simply interpreted as arising from a weighted averaging of two lipid environments--lipid-lipid and lipid-protein. In contrast to the above interpretation of the gel filtration experiments on DMPC/apo A-I complexes, nondenaturing gradient gel electrophoresis analysis of particle size distribution leads to an unexpected observation: as the DMPC/apo A-I ratio increases, discrete complexes of increasing size are formed in an apparently quantized manner.(ABSTRACT TRUNCATED AT 250 WORDS)

Apolipoprotein A-I↗
PubMed1984

Decreased defibrillator-induced dysfunction with biphasic rectangular waveforms.

High-intensity electric shocks used for cardiac defibrillation produce arrhythmias, S-T segment changes, and a low percent success in situ. Cultured myocardial cells exhibit similar postshock arrhythmias that are caused by a prolonged depolarization of the cell membrane. Since this dysfunction is ameliorated by biphasic RLC-type waveforms, we examined rectangular biphasic waveforms to maximize this beneficial effect and clarify the dysfunction-inducing mechanism. Cultured myocardial cells were subjected to electric field stimulation with monophasic 5-ms rectangular waveforms of about 80 V/cm to produce a postshock arrest of contractile activity lasting 4 s. Shocks given with this control waveform were alternated with biphasic test waveforms having the same initial portion followed by negative "tails" 1-100 ms in duration and 5-100% of the initial positive portion in amplitude. Results from 31 biphasic waveforms demonstrated significant alterations in postshock dysfunction. Waveforms with up to 10% undershoot and ranging from 5 to 100 ms in duration decreased arrest time by up to 50%; waveforms with greater than 20% undershoot led to protracted postshock arrest times. These results strengthen the hypothesis that electromechanical breakdown of the myocardial cell membrane underlies postshock dysfunction and show that biphasic waveforms with low amplitude tails ameliorate this dysfunction.

Animals↗
PubMed1983

Improved defibrillator waveform safety factor with biphasic waveforms.

Excitation thresholds and arrhythmias were studied in "adult-type" cultured chick embryo myocardial cells after electric field stimulation with biphasic, truncated, and rectified underdamped RLC (resistance-inductance-capacitance) type waveforms, to test the hypothesis that the negative phase of biphasic waveforms ameliorates membrane dysfunction induced by the initial positive portion. Photocell mechanograms and intracellular microelectrodes monitored extrasystoles and depolarization-induced arrhythmias. Rectifying or truncating biphasic waveforms did not alter the excitation threshold. However, shock intensities producing specific postshock arrhythmias or a specific severity of postshock prolonged depolarization differed significantly when biphasic waveforms were truncated or rectified. The voltage gradient producing a specific dysfunction was 12-14% lower for the truncated version than for the biphasic; that for the rectified version was 17-27% lower than for the biphasic version (although both contained the same energy). Safety factor, the ratio between shock intensity producing specific dysfunction and that producing excitation, was determined for each waveform. Biphasic waveforms had larger safety factors than truncated or rectified waveforms. Since safety factor, as measured in cultured myocardial cells, closely corresponds with in situ defibrillating effectiveness (14), the significantly higher safety factors of biphasic waveforms suggest that carefully shaped biphasic waveforms might improve the efficacy and safety of cardiac defibrillation procedures.

Animals↗