PubMed Health⌕ Search

Biomedical subjects

J Kuzma

Publications and source records attributed to J Kuzma.

12 recordsLinked to original sources
PubMed2000

A silastic positioner for a modiolus-hugging position of intracochlear electrodes: electrophysiologic effects.

HYPOTHESIS: It was postulated that an electrode array that achieved a close modiolar proximity would result in reduced threshold levels and amplitude slopes, as measured with electrically evoked auditory brainstem responses (EABRs). BACKGROUND: Quality and quantity of auditory information transmitted by a cochlear implant to patients with sensorineural hearing loss depend on spatial and temporal resolution achieved by the electrical intracochlear stimulation. METHODS: To improve spatial resolution, a new electrode system was developed by Advanced Bionics Corp., with the intention of obtaining greater modiolar proximity. The implant version specified for animal experiments consists of a straight electrode array of seven embedded platinum discs and a so-called Silastic-positioner. The Silastic positioner is shaped to follow the dimensions of the scala tympani with a concave (triangular) inner side, which fits the form of the electrode array. The aim of the study was to evaluate the influence of a modiolus-hugging electrode position in contrast to a conventional electrode position on EABR in short-term animal experiments. Short-term electrophysiologic studies were performed on six adult cats. After local intracochlear application of neomycin solution (50 mg/mL), electrodes were inserted into the scala tympani. Electrically evoked auditory brainstem response threshold levels and EABR amplitude slopes were systematically investigated with and without the positioner. RESULTS: Electrically evoked auditory brainstem response measurements revealed a distinct apicobasal threshold shift, with increasing thresholds toward the basal end of the electrode. After insertion of the positioner, this shift diminished or was inverted and EABR thresholds and amplitude slopes were reduced significantly. CONCLUSIONS: Threshold and amplitude slope data emphasize the functional benefit of the positioner system, especially for the stimulation of electrodes in the more basal channels.

Animals↗
PubMed2000

New Clarion electrode with positioner: insertion studies.

A new straight thin electrode array (universal electrode) was designed to be used together with a positioner, which will place the electrode array at the medial wall (modiolus) of the cochlea. The study objectives were to demonstrate safety and ease of insertion, tissue trauma, electrode position, and depth for universal and standard electrodes in human temporal bones; to test functional properties in cats; and to determine the surgical procedure and electrophysiological benefits in a clinical study. The cadaver study demonstrated the ease of insertion for the universal electrode and the positioner without tissue damage. An average gain of insertion depth of 180 degrees was achieved with the positioner. Animal studies demonstrated a reduction in threshold of 6 dB for the electrical auditory brain stem response (EABR). Neither additional cochlear damage nor additional connective tissue formation was found. The intraoperative human study findings showed a marked reduction of threshold for both EABR and stapedius reflex thresholds. Impedances were increased. Plain x-rays demonstrated modiolus proximity of the electrode with the positioner. The new Clarion electrode with positioner is a relatively safe design for providing modiolus proximity. The electrophysiological benefits include reduction of threshold and power consumption.

Adult↗
PubMed1997

Abscisic acid signaling through cyclic ADP-ribose in plants.

Abscisic acid (ABA) is the primary hormone that mediates plant responses to stresses such as cold, drought, and salinity. Single-cell microinjection experiments in tomato were used to identify possible intermediates involved in ABA signal transduction. Cyclic ADP-ribose (cADPR) was identified as a signaling molecule in the ABA response and was shown to exert its effects by way of calcium. Bioassay experiments showed that the amounts of cADPR in Arabidopsis thaliana plants increased in response to ABA treatment and before ABA-induced gene expression.

Abscisic Acid↗
PubMed1995

Bacteria produce the volatile hydrocarbon isoprene.

Various bacterial species, both Gram-negative and Gram-positive, were found to produce the volatile hydrocarbon isoprene (2-methyl-1,3-butadiene). Out of the tested cultures, Bacillus produced the most isoprene. The production of isoprene from bacteria was confirmed by gas chromatography-mass spectrometry. Media and growth effects on isoprene production were investigated: growth in rich media led to higher levels of isoprene than growth in minimal media, and highest isoprene emission rates were seen in log-phase cultures. Temperature profiles for bacterial isoprene production showed an optimum of 45 degrees C and were suggestive of an enzymatic mechanism for isoprene formation.

Bacillus↗
PubMed1995

Marine Vibrio species produce the volatile organic compound acetone.

While screening aerobic, heterotrophic marine bacteria for production of volatile organic compounds, we found that a group of isolates produced substantial amounts of acetone. Acetone production was confirmed by gas chromatography, gas chromatography-mass spectrometry, and high-performance liquid chromatography. The major acetone producers were identified as nonclinical Vibrio species. Acetone production was maximal in the stationary phase of growth and was stimulated by addition of l-leucine but not the other common amino acids, suggesting that leucine degradation leads to acetone formation. Acetone production by marine vibrios may contribute to the dissolved organic carbon associated with phytoplankton, and some of the acetone produced may be volatilized to the atmosphere.

Journal Article↗
PubMed1986

Significant determinants of susceptibility to alcohol teratogenicity.

Typically, the rate of abusive drinking during pregnancy considerably exceeds the rates of fetal alcohol syndrome (FAS) and alcohol-related birth defects, suggesting that other factors may modify the impact of alcohol on the developing organism. Data in the literature supporting this susceptibility hypothesis are sparse. In this paper, two studies in different samples, using different analytic strategies to examine susceptibility to different adverse outcomes are presented. Among 176 pregnancies in which lowered birth weight for gestational age was detected as an effect attributable to frequent beer drinking, 27 infants weighted less than 2,700 grams and 149 weighed more. Using discriminant analysis to contrast these groups, lowered birth weight for gestational age was associated with black race and lower maternal weight and weight gain. The effects of these factors were additive with that of persistent alcohol exposure; no interactions were detected, but pregnancies with risks in addition to alcohol were more likely to yield growth-retarded infants. In a second study, pregnancies resulting in 25 FAS cases were contrasted with 50 controls. A four-factor model accounted for nearly two-thirds of the explainable variance in the occurrence of FAS. Adjusted for frequency of maternal drinking, chronic alcohol problems and parity, there was a sevenfold increase in risk for FAS among black infants. The findings from both studies are consistent with the susceptibility hypothesis and have potentially important implications for public health and clinical approaches to prevention, as well as for future research.

Abnormalities, Drug-Induced↗