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Biomedical subjects

J Peters

Publications and source records attributed to J Peters.

At least 379 records · Page 21Linked to original sources
PubMed1993

Otoacoustic emissions from normal-hearing and hearing-impaired subjects: distortion product responses.

Distortion product otoacoustic emissions (DPOAE) were measured in normal-hearing and hearing-impaired human subjects. Analyses based on decision theory were used to evaluate DPOAE test performance. Specifically, relative operating characteristic (ROC) curves were constructed and the areas under these curves were used to estimate the extent to which normal and impaired ears could be correctly identified by these measures. DPOAE amplitude and DPOAE/noise measurements were able to distinguish between normal and impaired subjects at 4000, 8000, and, to a lesser extent, at 2000 Hz. The ability of these measures to distinguish between groups decreased, however, as frequency and audiometric criterion used to separate normal and hearing-impaired ears decreased. At 500 Hz, performance was no better than chance, regardless of the audiometric criterion for normal hearing. Cumulative distributions of misses (hearing-impaired ears incorrectly identified as normal hearing) and false alarms (normal-hearing ears identified as hearing impaired) were constructed and used to evaluate test performance for a range of hit rates (i.e., the percentage of correctly identified hearing-impaired ears). Depending on the desired hit rate, criterion values of -5 to -12 dB SPL for DPOAE amplitudes and 8 to 15 dB for DPOAE/noise accurately distinguished normal-hearing ears from those with thresholds greater than 20 dB HL for the two frequencies at which performance was best (4000 and 8000 Hz). It would appear that DPOAE measurements can be used to accurately identify the presence of high-frequency hearing loss, but are not accurate predictors of hearing status at lower frequencies, at least for the conditions of the present measurements.

Acoustic Stimulation↗
PubMed1993

A comparison of transient-evoked and distortion product otoacoustic emissions in normal-hearing and hearing-impaired subjects.

The ability of transient-evoked otoacoustic emissions (TEOAEs) and distortion product otoacoustic emissions (DPOAEs) to distinguish normal hearing from hearing impairment was evaluated in 180 subjects. TEOAEs were analyzed into octave or one-third octave bands for frequencies ranging from 500 to 4000 Hz. Decision theory was used to generate receiver operating characteristic (ROC) curves for each of three measurements (OAE amplitude, OAE/noise, reproducibility) for each OAE measure (octave TEOAEs, 1/3 octave TEOAEs, DPOAEs), for octave frequencies from 500 to 4000 Hz, and for seven audiometric criteria ranging from 10 to 40 dB HL. At 500 Hz, TEOAEs and DPOAEs were unable to separate normal from impaired ears. At 1000 Hz, both TEOAE measures were more accurate in identifying hearing status than DPOAEs. At 2000 Hz, all OAE measures performed equally well. At 4000 Hz, DPOAEs were better able to distinguish normal from impaired ears. Almost without exception, measurements of OAE/noise and reproducibility performed comparably and were superior to measurements of OAE amplitude, although the differences were small. TEOAEs analyzed into octave bands showed better performance than TEOAEs analyzed into 1/3 octaves. Under standard test conditions, OAE test performance appears to be limited by background noise, especially for the low frequencies.

Acoustic Stimulation↗
PubMed1993

Ontogenetic regulation of mouse Ren-2d renin gene in transgenic hypertensive rats, TGR(mREN2)27.

TGR(mREN2)27 is a new monogenetic rat model with fulminant hypertension, low kidney renin, and high extrarenal renin gene expression. This study characterizes and compares expression of the Ren-2 gene in TGR(mREN2)27 with that in DBA/2 mice and with renin gene expression in rats. Except in the submandibular gland, the tissue-specific expression of Ren-2 is similar in TGR(mREN2)27 and DBA/2. This demonstrates maintenance of tissue specificity. Organs that are involved in cardiovascular regulation, such as the adrenal gland, kidney, and brain, express the Ren-2 gene before hypertension has developed, consistent with the possibility of a causal relationship between transgene expression in these tissues and hypertension. Because these tissues express the renin gene in nontransgenic rats as well, we suggest that this model can be used to study the regulation of renin gene expression and its role in hypertension at these sites. In addition, as an indication that interactions may exist between blood pressure and renin gene expression, we describe reciprocal changes in blood pressure and Ren-2 mRNA levels in the kidney and brain.

Adrenal Glands↗
PubMed1993

Role of muscarinic receptors in renal response to acetylcholine.

Renal arterial infusion of acetylcholine (ACh) (40 micrograms/min) in control dogs produced an ipsilateral increase in renal plasma flow (RPF) and in sodium excretion (UNaV) without a change in glomerular filtration rate (GFR). The increase in RPF and UNaV was maintained during the infusion of ACh. In indomethacin (Indo)-treated dogs (5 mg/kg) ACh produced a transient rise in RPF and UNaV, followed by a progressive decline in RPF and UNaV. The profound renal vasoconstriction was accompanied by a decline in GFR. To determine the role of the muscarinic receptor in the renal vasodilation and in vasoconstriction produced by ACh in Indo-treated dogs, atropine at 6, 60, and 600 micrograms/min was infused into the renal artery before and during the infusion of ACh. In Indo-treated dogs, all dosages of atropine prevented renal vasoconstriction by ACh. Renal arterial infusion of atropine at 600 micrograms/min completely inhibited the renal vasodilation produced by ACh. Atropine infused at 60 micrograms/min partially inhibited, whereas 6 micrograms/min atropine failed to inhibit, the renal vasodilation produced by ACh. Our data suggest that the renal vasodilator and vasoconstrictor effects of ACh in Indo-treated dogs are mediated by two separate types of muscarinic receptors.

Acetylcholine↗
PubMed1993

Regional blood volume distribution during positive and negative airway pressure breathing in supine humans.

To assess the effects of continuous positive (CPAP) or negative airway pressure (CNAP) breathing (+/- 10-12 cmH2O, duration 25 min) on blood content in the body's capacitance vasculature, regional distribution of labeled red blood cells was evaluated in seven spontaneously breathing supine volunteers. Counts were acquired by whole body scans and detectors overlying the liver, intestine, left ventricle, and lower arm, and arterial pressure, heart rate, calf blood flow and vascular resistance, hematocrit, vasopressin, and atrial natriuretic peptide plasma concentrations were also obtained. With CPAP, thoracic, cardiac, and left ventricular counts diminished significantly by 7-10%, were accompanied by significant increases in counts over both the gut and liver, and remained decreased during CPAP but reversed to baseline with zero airway pressure. Calf blood flow and vascular resistance significantly decreased and increased, respectively, whereas limb counts, arterial pressure, heart rate, and hormone concentrations remained unchanged. With CNAP, in contrast, regional counts and other variables did not change. Thus, moderate levels of CPAP deplete the intrathoracic vascular bed and heart, shifting blood toward the gut and liver but not toward the limbs. No short-term compensation increasing cardiac filling during CPAP was seen. In contrast, CNAP did not alter intrathoracic or organ blood content and, therefore, does not simply mirror the effects evoked by CPAP.

Adult↗
PubMed1993

Increased adrenal renin in transgenic hypertensive rats, TGR(mREN2)27, and its regulation by cAMP, angiotensin II, and calcium.

The newly established rat strain TGR(mREN2)27 is a monogenetic model in hypertension research. Microinjecting the mouse Ren-2d renin gene caused it to become a stable part of the genome. The rats are characterized by fulminant hypertension, low plasma active renin, suppressed kidney renin, high plasma inactive renin, and high extrarenal transgene expression, most prominently in the adrenal cortex. Additionally, they exhibit significantly enhanced excretion of corticosteroids. Here we demonstrate that part of the plasma renin and most of the adrenal renin are transgene determined and that the adrenal renin is strongly activated. TGR(mREN2)27 adrenal cells may serve as a new tool to investigate the regulation and processing of Ren-2d-derived renin and its significance in hypertension and steroid metabolism. Adrenal renin in TGR(mREN2)27 is stimulated by 8-bromo-cAMP (8-Br-cAMP), angiotensin II (ANGII), and calcium. 8-Br-cAMP significantly stimulates active renin and prorenin release, as well as Ren-2d mRNA. Interestingly, within 60 min 8-Br-cAMP, ANGII, and calcimycin stimulate active renin, but not prorenin release. This indicates different intracellular pathways. An activated adrenal renin-angiotensin system in TGR (mREN2)27 as well as the lack of negative feedback on renin secretion by ANGII may be of pathophysiological significance in this hypertensive model.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1993

Influence of the earth's magnetic field on resting and activated EEG mapping in normal subjects.

We found in a former investigation that by measuring sleep parameters, the REM latency is shortened in the E-W position of sleepers compared with the N-S position. This paper reports on a further neurological observation in humans concerning the influence of the earth's magnetic field: there are statistically significant differences in the EEG of normal subjects, depending on whether the subjects sit facing the N-S or E-W direction. The difference is especially pronounced in the alpha-power.

Adult↗
PubMed1993

Infrequent mutation of the p53 gene in fibrous tumors of infancy and childhood.

Mutations in the p53 tumor suppressor gene occur in > 50% of human malignancies, but are exceedingly rare in benign tumors. The malignant potential of fibrous tumors of children may be unpredictable at microscopic examination. We therefore sought to determine whether malignant fibrous tumors could be distinguished from their benign counterparts by the presence of mutations in p53. We screened 27 fibrous tumor samples from 20 young patients. Tumors were classified as benign, borderline, or malignant by conventional microscopic criteria. RNA extracted from each specimen was used as the template for reverse transcription followed by polymerase chain reaction (PCR) amplification, with six pairs of primers covering the whole coding region of the p53 gene. All PCR products were screened for the presence of mutations using single-strand conformation polymorphism analysis. In addition, PCR products encompassing exons 5-9, the sites of the most frequent mutations in human tumors, were sequenced directly. Both methods detected a single point mutation in a highly malignant tumor (malignant fibrous histiocytoma). The mutation was a silent one at codon 36 (CCG-CCA, Pro-Pro). We conclude that p53 mutations are infrequent in childhood fibrous tumors, consistent with previous observations of low malignant potential (< 10%) and better prognosis in this tumor group. Therefore, screening for p53 mutations is not a useful prognostic indicator in fibrous tumors with borderline pattern at microscopic examination.

Adolescent↗
PubMed1993

[Determination of the microporosity and the microbe permeability of sterilized packs. Comparison of the bubble pressure method, testing of microbe permeability according to DIN 58953 part 6 and the particle count test].

Three different methods (the germ impermeability test according to the guidelines of DIN 58953 part 6, paragraph 2.15 (3), bubble-point method according to CEN EN AA 002 Annex C (1), and particle-penetration test (2)) were tested for their suitability to prove the microporosity and germ impermeability of sterilization packs. The results of the bubble-point method and the particle-penetration test differed from each other to a certain extent. The results of the germ impermeability test according to DIN do not agree with those of the other methods. The DIN method has the advantage of giving practice orientated conditions. Therefore we recommend for the germ impermeability test of sterilization packs the method according to the guidelines of the DIN.

Permeability↗
PubMed1993

[Superheating of germ carriers falsifies the steam resistance of bioindicators].

In the course of experiments on the resistance of bioindicators in saturated steam the authors noticed that carriers made of filter paper showed superheating by hygroscopic condensation. The differences in temperature between the bioindicators and the saturated steam amounted to about 5 Kelvin. Even after 20 minutes temperature equilibrium has not been reached. As a result of overheating and reduced water activity the frequency of bioindicators with surviving test organisms was increased. Beyond that, the microbiologic results depended on storage conditions of the bioindicators before putting them into the resistometer. The lower (higher) the-relative humidity, the higher (lower) the superheating, and the higher (smaller) the frequency of indicators with test organisms having survived. Carriers made of glass fibre fleece did not show any superheating and related effects. But carriers onto which small amounts of a suspension of test organisms in blood have been dried on, gave a superheating of about 1.7 Kelvin. Under identical conditions t50% values of bioindicators made of filter paper and bioindicators made of glass fibre fleece differed considerably. Experiments with Enterococcus faecium as test organism at 75 degrees C resulted in 14.4 and 1.7 minutes, respectively. Therefore, the high resistance of test organisms dried onto filter paper is an artefact caused by superheating. The experimental results should have consequences on the manufacture and use of bioindicators as well as chemoindicators and on the evaluation of results got with them.

Biomarkers↗
PubMed1992

Forensic psychiatry and prison liaison services in Auckland: the first twelve months.

AIMS: to assess referrals to a prison liaison service of regional forensic services in Auckland. METHODS: data on forensic psychiatric referrals from Auckland prisons 1 October 1989 to 30 September 1990 were collected. This was the first year of the service. RESULTS: there were 127 forensic psychiatric referrals in the period. The characteristic profile of such a case was that of a 28.5 year old male, unemployed remanded of Maori ethnic background. The commonest charge was nonsexual assault together with a prominent history of polysubstance misuse. Schizophrenia was the most frequent diagnosis. CONCLUSIONS: these findings have implications for regional forensic psychiatry services and other mental health providers, and the community in general.

Adult↗
PubMed1992

Comparative mapping of mouse chromosome 4 and human chromosome 9: Lv, Orm, and Hxb are closely linked on mouse chromosome 4.

The genes for orosomucoid (ORM-1 and ORM-2), delta-aminolevulinate dehydratase (ALAD), and hexabrachion or tenascin (HXB) all map to the q31-qter region of human Chromosome (Chr) 9. The mouse homolog of each of these genes has been mapped to Chr4, but hexabrachion has not previously been mapped by linkage analysis. We have now ordered Orm-1, Lv (the mouse homolog of ALAD), and Hxb in an interspecific backcross panel, by use of tyrosinase related protein-1, Tyrp-1, whose human homolog maps to 9p13-pter (Abbott et al., Genomics 1991) as a reference locus. No recombinants were identified in 124 animals between Lv and Orm-1. Hxb was found to be 1.6 cM distal to Lv and Orm-1, and 4.8 cM proximal to Tyrp-1, or b. These data therefore contribute to our knowledge of the conserved synteny between HSA 9q and MMU 4.

Animals↗
PubMed1992

Mapping of the structural gene for S-adenosyl homocysteine hydrolase to mouse chromosome 2, and related sequences to chromosomes 8 and X.

Comparative mapping studies in human and mouse have shown that, to date, human Chromosome (Chr) 20 is completely syntenic with distal mouse Chr 2. The structural locus for S-adenosyl-L-homocysteine hydrolase (EC 3.3.1.1) in human, AHCY, maps to 20 qter-->q13.1, and we report here that the homologous locus in the mouse, Ahcy, maps to distal mouse Chr 2 with gene order Pcna-Ahcy-Ada. Analysis of 123 progeny of an interspecific backcross between a laboratory stock, AN, and Mus spretus using a rat cDNA probe revealed the presence of at least two other Ahcy-related sequences segregating independently in the mouse genome. One, Ahcy-rs1, was mapped to Chr 8 in the BXH recombinant inbred strains, and the other, Ahcy-rs2, shows a pattern of inheritance consistent with X-linkage.

Adenosine Deaminase↗
PubMed1992

Comparative mapping of mouse chromosome 2 and human chromosome 9q: the genes for gelsolin and dopamine beta-hydroxylase map to mouse chromosome 2.

The mapping of human chromosome 9 (HSA9) and mouse chromosome 2 (MMU2) has revealed a conserved syntenic region between the distal end of the long arm of chromosome 9 and proximal mouse chromosome 2. Two genes that map to human chromosome 9q34, gelsolin (GSN) and dopamine beta-hydroxylase (DBH), have not previously been located in the mouse. We have used an interspecific backcross to map each of these genes, by Southern blot analysis, to mouse chromosome 2. Gelsolin (Gsn) is tightly linked to the gene for complement component C5 (Hc), and dopamine beta-hydroxylase (Dbh) is just proximal to the Abelson leukemia virus oncogene (Abl) and alpha-spectrin 2 (Spna-2). The loci for gelsolin and dopamine beta-hydroxylase therefore form part of the conserved synteny between HSA9q and MMU2.

Animals↗