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Biomedical subjects

J Kaiser

Publications and source records attributed to J Kaiser.

At least 55 records · Page 3Linked to original sources
PubMed2001

Genotoxic effect of monocrotophos to sentinel species using comet assay.

Monocrotophos is the single largest selling agrochemical in India. Sensitive biomarkers to study the genotoxic effects caused by monocrotophos in aquatic organisms, especially fish, are lacking. The fish used in this study are Tilapia mossambica, which are edible, commercially valuable and distributed all over India. The objective of this study was to study DNA strand breaks induced by monocrotophos in T. mossambica in vivo using single-cell micro gel electrophoresis/comet assay. Tilapia were treated orally with 0.313, 0.625, 1.25, 1.875, 2.5, 3.125, 3.75 and 4.375 ppm of monocrotophos and the assay was performed on nucleated erythrocytes after 24, 48, 72 and 96 h. A significant increase in mean comet tail-length (5.21-7.46 microM), indicating DNA damage, was observed at all the doses with monocrotophos when compared to controls (3.36 microM). The mean tail-length showed a dose-related increase and time-dependent decrease. The maximum increase in mean comet tail-length was observed at 24 h. Relative to these effects, reductions in mean comet tail-length were seen at 48 and 72 h. By 96 h, values had returned to control levels at all doses, indicating repair of the damaged DNA and/or loss of heavily damaged cells. The study reveals that the comet assay is a sensitive and rapid method to detect genotoxicity of monocrotophos and other environmental pollutants in sentinel species.

Animals↗
PubMed2001

Self-initiation of EEG-based communication in paralyzed patients.

OBJECTIVES: Severely paralyzed patients could learn to voluntarily generate slow cortical potential (SCP) shifts in their electroencephalogram and to use these signals to operate a communication device. To enhance the patients' autonomy, the present study describes the development of a permanently available communication system that can be turned on and off by locked-in patients without external assistance. A skill necessary for turning the system on is the ability to regulate one's slow potentials in the absence of continuous feedback. METHODS: A stepwise learning approach was employed to train two paralyzed patients to regulate their SCPs without continuous feedback. Elements of the original communication system were gradually removed and elements of the new stand-by mode were introduced. RESULTS: At the end of the learning procedure, both patients achieved correct response rates of above 84% in training sessions without continuous feedback. This skill enabled them to turn the communication device on and off without assistance from others. CONCLUSIONS: These findings suggest that severely paralyzed individuals can learn to operate an EEG-based communication device autonomously.

Adult↗
PubMed2001

Brain-computer communication: unlocking the locked in.

With the increasing efficiency of life-support systems and better intensive care, more patients survive severe injuries of the brain and spinal cord. Many of these patients experience locked-in syndrome: The active mind is locked in a paralyzed body. Consequently, communication is extremely restricted or impossible. A muscle-independent communication channel overcomes this problem and is realized through a brain-computer interface, a direct connection between brain and computer. The number of technically elaborated brain-computer interfaces is in contrast with the number of systems used in the daily life of locked-in patients. It is hypothesized that a profound knowledge and consideration of psychological principles are necessary to make brain-computer interfaces feasible for locked-in patients.

Brain↗
PubMed2001

Brain-computer communication: self-regulation of slow cortical potentials for verbal communication.

OBJECTIVE: To test a training procedure designed to enable severely paralyzed patients to communicate by means of self-regulation of slow cortical potentials. DESIGN: Application of the Thought Translation Device to evaluate the procedure in patients with late-stage amyotrophic lateral sclerosis (ALS). SETTING: Training sessions in the patients' homes. PARTICIPANTS: Two male patients with late-stage ALS. INTERVENTIONS: Patients learned voluntary control of their slow cortical potentials by means of an interface between the brain and a computer. Training was based on visual feedback of slow cortical potentials shifts and operant learning principles. The learning process was divided into small steps of increasing difficulty. MAIN OUTCOME MEASURES: Accuracy of self-control of slow cortical potentials (percentage of correct responses). Learning progress calculated as a function of training session. RESULTS: Within 3 to 8 weeks, both patients learned to self-regulate their slow cortical potentials and to use this skill to select letters or words in the Language Support Program. CONCLUSIONS: This training schedule is the first to enable severely paralyzed patients to communicate without any voluntary muscle control by using self-regulation of an electroencephalogram potential only. The protocol could be a model for training patients in other brain-computer interface techniques.

Adult↗
PubMed2001

The position dependent 15N enrichment of nitrous oxide in the stratosphere.

The position dependent 15N fractionation of nitrous oxide (N2O), which cannot be obtained from mass spectrometric analysis on molecular N2O itself, can be determined with high precision using isotope ratio mass spectrometry on the NO+ fragment that is formed on electron impact in the source of an isotope ratio mass spectrometer. Laboratory UV photolysis experiments show that strong position dependent 15N fractionations occur in the photolysis of N2O in the stratosphere, its major atmospheric sink. Measurements on the isotopic composition of stratospheric N2O indeed confirm the presence of strong isotope enrichments, in particular the difference in the fractionation constants for 15N14NO and 14N15NO. The absolute magnitudes of the fractionation constants found in the stratosphere are much smaller, however, than those found in the lab experiments, demonstrating the importance of dynamical and also additional chemical processes like the reaction of N2O with O(1D).

Air Pollutants↗
PubMed2000

Environmental toxicology. Treaty takes a POP at the dirty dozen.

Last month's talks to mitigate global warming may have flopped, but this week brought some consolation to those concerned about the planet's environmental health: the first-ever global agreement to abolish a class of dangerous industrial chemicals. The treaty, finalized by representatives of 122 countries meeting in Johannesburg, South Africa, also spells out a process to determine the next chemicals to be proscribed.

DDT↗
PubMed2000

NIH. Higher profile for minority health.

For years, some biomedical groups and health activists have pushed the National Institutes of Health (NIH) to devote more attention to factors affecting the health of U.S. minorities. Last week, President Bill Clinton signed into law a measure that elevates NIH's office of minority health to the National Center on Minority Health and Health Disparities. The move comes with the promise of a bigger budget and greater autonomy to pursue studies on why blacks, Hispanics, and other groups suffer disproportionately high rates of diseases such as heart disease, prostate cancer, and diabetes.

Budgets↗