Search PubMed⌕ Search

Biomedical subjects

E A Mroz

Publications and source records attributed to E A Mroz.

At least 19 recordsLinked to original sources
PubMed1993

Electron-probe analysis of isolated goldfish hair cells: implications for preparing healthy cells.

Electron-probe analysis provides an objective criterion for the physiological status of cells: whether they show the high potassium and low sodium that are expected of healthy animal cells. Preparing isolated goldfish hair cells that were healthy by this criterion required several precautions, including: limited exposure to enzymes and to simple salt solutions, a rest period between enzyme treatment and mechanical disruption of the tissue, and presence of bovine albumin in the medium both during the rest period and during mechanical dispersion and plating. Cells prepared with these precautions from the saccule and lagena and kept in an enriched medium had the following elemental composition (mole percentages with respect to phosphorus): K, 103; Na, 18; Cl, 23; S, 13; Mg, 8; Ca, 1.5. These mole percentages were close to these elements' total millimolar concentrations in the cells. If the precautions were not taken, cells with intact surface membranes (as assessed by exclusion and retention of dyes) could be obtained, but the cells had elevated cell sodium and low cell potassium.

Animals↗
PubMed1990

Purification of a low-molecular-weight excitatory substance from the inner ears of goldfish.

The neurotransmitter released by the hair cell has not been identified; little is known about other neuroactive substances that may be important in hair-cell organ function. To identify neuroactive substances in hair cell tissue, we have examined substances in extracts of the inner ears of goldfish that can excite afferent fibers innervating hair cells. The extracts contain an unidentified low-molecular-weight (LMW) excitatory substance that is a candidate to be the hair-cell neurotransmitter. The LMW excitatory substance has been highly purified by a sequential combination of (1) treatment with cation-exchange resin; (2) gel-permeation chromatography; (3) gradient-elution cation-exchange chromatography; (4) isocratic-elution cation-exchange chromatography; and (5) high-performance anion-exchange chromatography. Based upon its separation behavior in these purification steps, the LMW excitatory substance may be a small, zwitterionic compound with titratable anionic and cationic groups.

Animals↗
PubMed1989

Pharmacological alterations of the activity of afferent fibers innervating hair cells.

To determine whether some of the substances that may be present in hair-cell sensory organs could affect neural activity in afferent fibers, we examined 56 compounds for the ability to alter the discharge rate of afferent fibers innervating hair cells in the lateral line organ of Xenopus laevis, the African clawed frog. These compounds included amino acids, glutamyl dipeptides, standard neurotransmitter candidates, and other constituents of tissues and body fluids. Substances found to be excitatory included some neutral amino acids (alanine, serine, threonine, asparagine, glutamine, and proline), ATP, carnosine, histidine, and barium chloride. Compounds that suppressed discharge included the aromatic amino acids (phenylalanine, tryptophan, and tyrosine), serotonin, and gamma-glutamyl dipeptides. GABA and acidic amino acids (glutamate, aspartate, and cysteine sulfinate) produced a brief excitation followed by a suppression of discharge rate. Several of these substances were active at sufficiently low concentrations that their presence in body fluids may affect afferent fiber discharge rate under normal or pathological conditions.

Amino Acids↗
PubMed1987

A possible neurotransmitter role for CGRP in a hair-cell sensory organ.

We report that calcitonin gene-related peptide (CGRP) increases the discharge rate of afferent fibers innervating hair cells in the lateral line organ of Xenopus laevis. We have localized CGRP-like immunoreactivity in small, presumably efferent, fibers innervating the lateral line organ. In addition to providing evidence for a neurotransmitter role for CGRP in a sensory system, these results may help explain the non-cholinergic excitatory effect seen with efferent stimulation in this and other hair cell organs such as the inner ear.

Action Potentials↗
PubMed1987

Isolation and culture of auditory cells from the goldfish (Carassius auratus).

Large numbers of hair cells and VIIIth nerve ganglion cells are obtained from the inner ears of adult goldfish by a combination of enzymatic and mechanical dissociation. Centrifugation of the dissociated tissue through a discontinuous density gradient produces one fraction enriched in hair cells and another enriched in nerve cells. The fraction of cells enriched in neurons can be put into cell culture and kept for a period of weeks. During that period, the neurons send out processes that can extend for millimeters. The morphology of these cultured neurons is similar to that of the goldfish auditory neurons in histological material.

Animals↗
PubMed1987

Neuroactive substances in inner ear extracts.

To identify the neurotransmitter released by sensory hair cells, as well as to find other substances that might influence neural function of the inner ear, we have prepared extracts from inner ears of fishes (which have large numbers of hair cells), fractionated the extracts, and studied the effects of the fractionated extracts on the discharge rate of afferent fibers innervating hair cells in the lateral line organ of the African clawed frog Xenopus laevis. The extracts contain active substances that do not bind to a cation-exchange resin at neutral pH. Gel-permeation chromatography suggests that at least 2 unidentified excitatory substances are present in the extracts: one of low molecular weight (Mr about 200) and one of high molecular weight (Mr less than or equal to 5000). Some extracts also contain a high-molecular-weight inhibitory substance (Mr greater than 5000). The low-molecular-weight active substance is detected in extracts of inner ear, but not in brain or muscle. The high-molecular-weight excitatory substance is present both in brain and in inner ear.

Action Potentials↗
PubMed1986

Pancreatic zymogen granules differ markedly in protein composition.

The activities of both chymotrypsin and amylase in individual zymogen granules of rat pancreas were measured by means of micromanipulation and microfluorometric methods. The enzyme content and the ratio of amylase to chymotrypsin varied widely among granules taken from the same animal. These results are compatible with short-term nonparallel bulk secretion of the two enzymes through exocytosis. The distribution of each enzyme activity in a population of granules suggests quantal packaging of amylase and chymotrypsinogen into the granules.

Amylases↗
PubMed1984

Nucleotides in a single mammalian ovum or preimplantation embryo.

ATP, ADP, and AMP have been measured jointly on a single mouse ovum or preimplantation embryo using an ultramicrofluorescence technique. The method uses the traditional approach of enzymatic analysis based on changes in the concentrations of nucleotide cofactors, but eliminates the need for enzymatic recycling. It permits the measurement of as little as 10 fmol, and may be adapted for numerous metabolites.

Adenine Nucleotides↗
PubMed1983

An NADH-coupled assay for femtogram or nanogram quantities of chymotrypsin.

Chymotrypsin can be determined with an NADH-coupled assay. Hydrolysis of the substrate benzoyltyrosine ethyl ester is monitored by coupling the liberation of ethanol to the production of NADH and determining the NADH spectrophotometrically or fluorometrically. Nanogram quantities of chymotrypsin can be determined in milliliter volumes. With these microfluorescence methods this assay can be performed in a final volume of less than a nanoliter, allowing determination of femtogram quantities of chymotrypsin, the amount present in an individual zymogen granule.

Animals↗
PubMed1977

On the origin of substance P and glutamic acid decarboxylase (GAD) in the substantia nigra.

Knife cuts in the frontal plane separating the anterior part of the caudate-putamen from the globus pallidus resulted in marked decreases in substances P levels in the reticular part of the substantia nigra. More caudal knife cuts were required in order to effect maximal decreases in nigral glutamic acid decarboxylase levels. Thus, there is a clear anatomical dissociation between the striatal neurons which project to the reticular part of the substantia nigra and which contain SP, and the more caudally located GAD-containing striatal and pallidal neurons, all of which travel through the globus pallidus on their way to the substantia nigra.

Animals↗
PubMed1977

Evidence for substance P in the striato-nigral tract.

The highest concentration of substnace P yet found in the mammalian brain is in the reticular part of the substantia nigra. The effect of various lesions on the substance P content of that region has been examined in the rat in order to determine the possible sources and paths of nigropetal substance P-containing fibers. Unilateral knife cuts which transect the medial forebrain bundle and medial portion of the crus cerebri at a premammillary level lead to a 90% reduction in substance P in the ipsilateral reticular part of substantia nigra, with no significant effect on contralateral values. Incomplete electrolytic lesions of the globus pallidus lead to a 50% decrease. These data indicate that descending uncrossed pathways provide most of the substance P in the reticular part of the substantia nigra, with the striato-nigral tract providing an important component.

Afferent Pathways↗
PubMed1977

Substance P.

Explore the source record for details and available documents.

Animals↗
PubMed1976

Regional distribution of substance P in the brain of the rat.

Using a sensitive radioimmunoassay we have studied the regional distribution of substance P. The level of substance P is higher in the mesencephalon, hypothalamus and preoptic area than in other regions of the brain. Substance P is found in especially high concentrations in the reticular part of the substantia nigra and the interpeduncular nucleus. It is present in large amounts in several septal, preoptic and hypothalamic nuclei as well.

Animals↗