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Biomedical subjects

R Stark

Publications and source records attributed to R Stark.

At least 37 records · Page 2Linked to original sources
PubMed1999

Geophysical variables and behavior: LXXXVIII. Atmospheric electromagnetism: the possible disturbing influence of natural sferics on ESP.

Sferics are electromagnetic impulses generated by electrical discharges during thunderstorms (lightning). One category is comprised of very low frequency electromagnetic waves, traveling over distances up to a thousand kilometers. Sferics have been shown to affect biological responses such as pain syndromes, reaction times, and power in the alpha band of the EEG. In the present study, in which 100 subjects took part, sferics have been studied in their relation to performance on a forced-choice extrasensory perception (ESP) task and to several secondary variables. The general finding is a negative correlation between ESP performance and sferics activity around the time of the session, most notably 24-48 hours prior to the session. Secondary variables appear to modulate this correlation, as has been found in previous research on sferics: the correlation tended to be stronger for persons who scored lower on Neuroticism and higher on the Openness scale of a Five-Factor Personality Questionnaire.

Adolescent↗
PubMed1999

Electrocortical responses of headache patients to the simulation of 10 kHz sferics.

Many headache patients believe that weather changes act as pain triggers. Therefore, the present study investigated the psychophysiological influence of an indicator of atmospheric instability, Very Low Frequency (VLF)-sferics, on 32 subjectively weather-sensitive women suffering from migraine attacks and/or tension-type headaches. It was analyzed if sferics exposure is able to induce electrocortical changes as well as headache symptoms. The subjects, who had been divided into two groups, participated in a sferics simulation study. The experimental group (n = 16) underwent a ten-minute exposure to 10kHz-sferics impulses followed by 20 minutes without treatment in order to examine possible prolonged sferics effects. The control group (n = 16) received no treatment. As dependent measures, EEG spectral power was compared between the two groups at six electrode sites (F3/F4; P3/P4; O1/O2). Sferics exposure provoked increases in absolute alpha and beta power during the treatment. The alpha power enhancement was still present at parietal sites at the end of registration (20 minutes after the end of exposure). The stimulation did not induce headache symptoms.

Adult↗
PubMed1998

Learning from Worked-Out Examples: The Effects of Example Variability and Elicited Self-Explanations

It was investigated to what extent example variability and the elicitation of sophisticated self-explanations foster the acquisition of transferable knowledge by learning from worked-out examples. In addition, it was asked whether the effects of these factors are moderated by the learners' levels of prior topic knowledge. To this end, we had 56 apprentices from a bank learn calculation of compound interest and real interest. They were randomly assigned to the four conditions of a 2 x 2-factorial design (factor 1: uniform vs. multiple examples; factor 2: spontaneous vs. elicited self-explanations). The learning results were measured by a post-test comprising near-transfer problems and far-transfer problems. It was found that the acquisition of transferable knowledge can be supported by eliciting self-explanations. In the case of near transfer, especially learners with low levels of prior topic knowledge profited from the elicitation procedure. On the whole, the findings underline the "causal" relevance of the quality of self-explanations for knowledge acquisition by learning from worked-out examples. The assumption that multiple examples foster transfer performance, at least when sophisticated self-explanations are elicited, was not supported. Copyright 1998 Academic Press.

Journal Article↗
PubMed1998

N-terminal protease of pestiviruses: identification of putative catalytic residues by site-directed mutagenesis.

Pestiviruses are the only members of the Flaviviridae that encode a nonstructural protease at the N terminus of their polyproteins. This N-terminal protease (Npro) cleaves itself off of the nascent polyprotein autocatalytically and thereby generates the N terminus of the adjacent viral capsid protein C. In previous reports, sequence similarities between Npro and the catalytic residues of papain-like cysteine proteases were put forward. To test this hypothesis, substitutions of cysteine and histidine residues within Npro were carried out by site-directed mutagenesis. Translation of the mutagenized Npro-C proteins in cell-free lysates confirmed that only the predicted Cys69 was an essential amino acid for proteolysis, not His130. Further essential residues were identified with His49 and Glu22. While it remains speculative whether Glu22-His49-Cys69 actually build a catalytic triad, these results invalidate the assumption that Npro is a papain-like cysteine protease.

Amino Acid Sequence↗
PubMed1997

Cut out or poke in--the key to the world of single genes: laser micromanipulation as a valuable tool on the look-out for the origin of disease.

The optical micromanipulation systems UV(ultraviolet)-Laser Microbeam and Optical Tweezers Trap, already proven to be powerful tools for 'non-contact' micro-manipulation of gametes, cells and organelles, have now made their way into the nanocosmos of genes and molecules. Force measurements of DNA transcription have been performed and selective DNA molecule micromanipulation gives insight into single molecule behaviour. Retrievement of selected single cells without contamination is an import prerequisite for further processing with modern methods of molecular biology. Laser micro-dissection allows to precisely eliminate any unwanted material or to isolate pieces of chromosomes or single cells of interest with high accuracy and efficiency. This enables the cell or chromosome specific molecular analysis of genes and genetic defects underlying disease, such as cancer or infection. This review article gives an overview of current topics of laser microbeam application in biological or medical research and advanced molecular diagnosis.

Animals↗
PubMed1997

Pulmonary illness associated with exposure to Mycobacterium-avium complex in hot tub water. Hypersensitivity pneumonitis or infection?

BACKGROUND: Mycobacterium avium complex is common in water. When aerosolized, it is frequently inhaled but rarely causes illness in healthy people. Hypersensitivity pneumonitis to inhaled aerosols has been described; these aerosols are from several sources of water. The pneumonitis forms are collectively known as humidifier lung; the responsible agent in the water remains uncertain. PURPOSE: To report five cases of respiratory illness in healthy subjects using hot tubs contaminated with M avium complex. DESIGN: Descriptive case reports. SETTING: Consultations in two teaching hospitals. PATIENTS: Five healthy people developed respiratory illnesses characterized by bronchitis, fever, and "flu-like" symptoms after using a hot tub. Acute exacerbations of their illness developed within hours of heavy use of the hot tubs. INVESTIGATIONS: A chest radiograph and sputum culture in all, BAL in one, CT scan and lung biopsy in another were performed. Culture of the water of the two hot tubs also was done. RESULTS: Chest radiographs showed interstitial infiltrates or a miliary nodular pattern. Cultures of all sputum samples, the lung biopsy specimens, lung lavage and water samples were positive for M avium complex. The lung biopsy specimen revealed noncaseating granulomas. All patients recovered with no treatment for M avium complex. CONCLUSION: We conclude that the M avium complex in the water was responsible for the pulmonary illnesses. The symptoms and the results of investigations are more suggestive of a hypersensitivity pneumonitis than of an infection, but no serologic proof of an immunologic reaction to the M avium complex or water was obtained.

Adolescent↗
PubMed1997

Effects of low-frequency magnetic fields on electrocortical activity in humans: a sferics simulation study.

A previously recorded electromagnetic impulse of natural origin, a 10 kHz-sferic, was simulated and presented to 20 subjects. The magnetic component of the signal with a maximum field amplitude of 50 nT and a duration of 500 microseconds was applied over a duration of 10 minutes with a pulse repetition rate that varied statistically between 7 and 20 Hz. After sferics exposure, an additional 20 minutes without treatment were recorded in order to examine possible prolonged effects of sferics stimulation. The control group (n = 20) received no treatment. As a dependent measure, electrocortical changes throughout the course of the experiment were determined by means of EEG spectral analysis and compared between the two groups. Sferics exposure provoked increases in alpha and beta power. The effect was present during stimulation and continued for 10 minutes after the end of treatment. A longer lasting influence of sferics exposure was displayed by subjects with a high degree in weather sensitivity, somatic complaints, and neuroticism, who continued to stay on an enhanced alpha power level until the end of registration (20 minutes after the end of exposure). With these results a general electrocortical sensitivity towards sferics as well as individual differences in sferics reactivity could be demonstrated.

Adult↗
PubMed1996

Simulated micro-gravity and cortical inhibition: a study of the hemodynamic-brain interaction.

The present study was carried out to determine the inhibitory cortical processes induced by changes in hemodynamics. Previous experiments in humans conducted in our laboratory have shown that there is a close relationship between posture and delta and theta EEG activity. The most pronounced effects were obtained during the 6 degrees head-down tilt (HDT) position. In space medicine the HDT procedure is very frequently employed to simulate micro-gravity and to determine the neurohormonal counter-regulations evoked by the expansion of central volume. Twenty male subjects spent 23 h in bed in 6 degrees HDT and 23 h in 6 degrees HUT (head-up tilt) positions during which EEG (frontal, central, parietal, occipital), startle responses, and reaction-times were measured every 2 h (from 10:00 h till 20:00 h). The effects of cardiovascular deconditioning (CD) regularly occurring after HDT were assessed by examining orthostatic tolerance and the physical work capacity (bicycle ergometry). As expected, 23 h HDT led to more pronounced CD than HUT. Spectral power analyses of EEG revealed increases in delta and theta frequency hands similar to those found during HDT in previous EEG studies. In addition, subjects responded more slowly (S1-S2 reaction-time task) during HDT as compared with HUT bedrest. The influence of HDT on startle response, however, was not in keeping with the initial hypothesis (i.e. dampening of reflex activity). The EEG data and the sensorimotor performance indicated that the body fluid shift towards the thoracic cavity induced by HDT resulted in signs of cortical inhibition. In addition to neural mechanisms, other processes must be postulated which are closely related to the counter-regulation evoked by the varying body positions.

Adult↗
PubMed1996

Perioperative ischaemia in aortic surgery: combined epidural/general anaesthesia and epidural analgesia vs general anaesthesia and i.v. analgesia.

PURPOSE: The goal of this randomized study was to determine whether combined general and epidural anaesthesia with postoperative epidural analgesia, compared with general anaesthesia and postoperative intravenous analgesia, reduced the incidence of perioperative myocardial ischaemia in patients undergoing elective aortic surgery. METHOD: Patients were randomly assigned to one of two groups. One group (EPI, n = 48) received combined general and epidural anaesthesia and postoperative epidural analgesia for 48 hrs. The other group (GA, n = 51) received general anaesthesia followed by postoperative intravenous analgesia. Anaesthetic goals were to maintain haemodynamic stability (+/- 20% of preoperative values), and a stroke volume > 1 ml.kg-1. A Holter monitor was attached to each patient the day before surgery. Leads 11, V2, and V5 were monitored. Myocardial ischaemia was defined as ST segment depression > 1 mm measured at 80 millisec beyond the J point or an elevation of 2 mm 60 millisec beyond the J point which lasted > 60 sec. An event that lasted > 60 sec but returned to the baseline for > 60 sec and then recurred, was counted as two separate events. The Holter tapes were reviewed by a cardiologist blind to the patient's group. RESULTS: There were no demographic differences between the two groups. Myocardial ischaemia was common; it occurred in 55% of patients. In hospital, preoperative ischaemia was uncommon (GA = 3, EPI = 8). Intraoperative ischaemia was common (GA = 18, EPI = 25). Mesenteric traction produced the largest number of ischaemic (GA = 11, EPI = 11) events. Postoperative ischaemia was most common on the day of surgery. Termination of epidural analgesia produced a burst of ischaemia (60 events in 9 patients). CONCLUSION: Combined general and epidural anaesthesia and postoperative epidural analgesia do not reduce the incidence of myocardial ischaemia or morbidity compared with general anaesthesia and postoperative intravenous analgesia.

Aged↗
PubMed1996

RNase of classical swine fever virus: biochemical characterization and inhibition by virus-neutralizing monoclonal antibodies.

The structural glycoprotein E0 of classical swine fever virus (CSFV) possesses an intrinsic RNase activity. Here we present the first comprehensive biochemical characterization of E0, using a recombinant glycoprotein expressed in insect cells. We were able to show that the presence of neither carbohydrate moieties nor disulfide bonds is a prerequisite for RNase activity. In addition, virus-neutralizing and nonneutralizing anti-E0 monoclonal antibodies were tested for their ability to influence RNase activity. In these experiments, the antibodies which effectively blocked the infection of STE cells also exerted a high degree of E0 RNase inhibition. This correlation suggests that the RNase activity of CSFV E0 plays a role in the viral life cycle.

Animals↗
PubMed1996

Cytopathogenicity of a pestivirus correlates with a 27-nucleotide insertion.

Cytopathogenic (cp) bovine viral diarrhea virus (BVDV) strains are generated in cattle persistently infected with noncytopathogenic (noncp) BVDV.cp BVDV strains are considered crucial for the development of fatal mucosal disease. Comparative analysis of cp and noncp BVDV strains isolated from one animal suffering from mucosal disease revealed that the genomes of the cp BVDV strain (CP7) and the corresponding noncp BVDV strain (NCP7) are highly homologous. However, only the genome of CP7 contains an insertion of 27 nucleotides in the NS2 coding region. The inserted sequence represents a duplication of bases 4064 to 4090 of the viral genome, located between the formerly neighboring nucleotides 4353 and 4354. Parts of the viral polyproteins of CP7 and NCP7 were expressed in the T7 vaccinia virus system. These studies revealed that the insertion identified in the CP7 genome is necessary and sufficient for the induction of NS2-3 cleavage. Since the expression of NS3 is strictly correlated to cp BVDV, the insertion identified in the genome of BVDV CP7 represents most likely the relevant mutation leading to the evolvement of CP7 from NCP7.

Animals↗
PubMed1996

Covariation bias and paranormal belief.

22 believers and 20 skeptics of extrasensory perception (ESP) participated in a telepathy experiment. Subjects were asked to judge the covariation between transmitted symbols and the corresponding feedback given by a receiver. Believers overestimated the number of successful transmissions ('hits'). Skeptics were characterized by accurate hit judgments. For believers, positive correlations between hit-responses, their heart rates, and their experienced arousal were found. In addition, subjective arousal was positively associated with the hit estimates given at the end of the experiment. This response pattern was absent in the group of skeptics. It is concluded that covariation bias as a psychophysiological concept plays an important role in the maintenance of paranormal belief.

Adult↗
PubMed1996

Ethical considerations in rural health nursing.

Nurses are the health workers most frequently found providing primary health care services in rural communities throughout the world. In these settings, often with limited resources and far from professional support systems, nurses may encounter ethical dilemmas quite different from those experienced by their colleagues in urban hospital settings. Consider the following example from a remote island community. A young nurse with two years experience in an urban hospital is posted to a remote village. In this country there are very few doctors, so nurses diagnose and treat common health problems. On this day a traditional political leader, a middle-age man, is brought to the small clinic by his adult son to be treated for his cough. Other patients are waiting to be seen, but the son makes it clear that he expects his father to be cared for immediately. The nurse doesn't think it is right to give preferential treatment, but the other patients back away and she defers to the son's demands. The nurse examines the man and concludes that he has a common viral infection requiring only symptomatic treatment. When she tries explaining this to the patient, he becomes annoyed and insists that what he needs is a penicillin injection. That's how the last nurse working in this clinic had treated him when he was sick and he had recovered within days. Finally, the young nurse overwhelmed by his age and status and under pressure from his family gives the injection. Shortly afterwards the patient collapses in shock and very nearly dies. The family blamed the nurse, and the community council demanded that she be removed. The case was eventually investigated by the authorities, and the nurse was formally reprimanded for giving the patient an unnecessary injection which caused him harm. Rural nurses-indeed all rural health workers-need support in order to maintain ethical standards in practice. The purpose of this paper is to examine four potential sources of such support: nursing education programs; the Ministries of Health; the law; and the professional nursing organization.

Community Health Nursing↗
PubMed1996

[Investigations of raw milk for Shiga-like toxin producing Escherichia coli by the polymerase chain reaction].

This is a report about the occurrence of Shiga-like toxin (SLT) producing Escherichia coli in milk in southern Sachsen-Anhalt. Samples were taken from tanks of milk at the farms. The samples were investigated by polymerase chain reaction as recommended by the "Bundesinstitut für gesundheitlichen Verbraucherschutz und Veterinärmedizin". Using PCR, in 11% of the tank samples sequences coding for SLT I and/or SLT II were detected. 75% of the as positive detected samples had eae gen. Some cows in these farms spread potentially enterohemorrhagic E. coli. These farms should not sell milk for raw consumption.

Animals↗
PubMed1995

Classical swine fever virus: independent induction of protective immunity by two structural glycoproteins.

To study which proteins of classical swine fever virus (CSFV) are able to confer protective immunity in swine, N-terminal autoprotease, viral core protein, and the three structural glycoproteins were expressed via vaccinia virus recombinants (VVR). CSFV proteins synthesized in cells infected with VVR showed migration characteristics on sodium dodecyl sulfate gels identical to those of their respective CSFV counterparts. Apparently authentic dimerization of the recombinant glycoproteins was observed. The glycoproteins E0 and E2 were detected on the surfaces of VVR-infected cells. In protection experiments, swine were immunized with the different VVR, and the generation of humoral immune response was monitored. Only animals vaccinated with VVR expressing E0 and/or E2 resisted a lethal challenge infection with CSFV. Glycoprotein E0 represents a second determinant for the induction of protective immunity against classical swine fever.

Animals↗
PubMed1995

Evaluation of the enzyme-linked immunosorbent assay for the rapid screening and detection of classical swine fever virus antigens in the blood of pigs.

A workshop was convened, at which seven enzyme-linked immunosorbent assays (ELISAs) were compared with virus isolation for the detection of viraemia in serial blood samples collected from six pigs at up to fourteen days after inoculation with classical swine fever virus. All ELISAs were of the double antibody sandwich type, using monoclonal and/or polyclonal antibodies to detect a variety of viral proteins in leukocytes, or in anti-coagulated blood or serum. Compared to virus isolation, specificity of the ELISA was good: only one sample found negative by virus isolation yielded a positive result in a single ELISA. Some false-negative results occurred with samples collected at up to eight days after inoculation, but all tests found samples collected between nine and fourteen days post-inoculation to be positive. The ELISAs require less-specialised facilities and can be performed much more rapidly than virus isolation. They are therefore extremely promising tools for screening large numbers of live pigs.

African Swine Fever↗