Biomedical subjects

M R Emmerling

Publications and source records attributed to M R Emmerling.

43 records · Page 3Linked to original sources

PubMed1990

Acetylcholinesterase-positive innervation in cochleas from two strains of shaker-1 mice.

Shaker-1 is a recessive gene mutation on chromosome 7 in mice, causing both deafness and neurosensory degeneration in the inner ear. A failure of efferent innervation to the outer hair cells is being implicated in the cause of deafness (Green, 1981). To investigate the efferent innervation, we examined the cochleas of two strains of shaker-1 mutants: Sh1/Le (25 and 45 days old) and FS/Ei (28 and 68 days old), using enzymatic staining of acetylcholinesterase (AChE) for the light and electron microscopes, and also by measuring the activities of AChE and of AChE molecular forms. The enzyme levels in the SH1/Le and FS/Ei homozygotes (sh-1/sh-1) were within the range of those in SH1/Le heterozygotes (+/sh-1) and in normal mouse strains (C3H/HeJ, 129/SvJ, ICR). The picture of AChE-positive innervation in both strains differed. In the SH1/Le mutants at 25 days, the innervation appeared normal, but by 45 days it showed a marked atrophy. In the FS/Ei mutants, the degeneration was already evident by the 28th day. In the younger animals of both mutants, large differentiated vesiculated nerve endings were ultrastructurally detected in synaptic contact with outer hair cells. The preservation of AChE activity and of the expression of AChE molecular forms up to 68 days indicate that the shaker-1 cochlea may initially possess a normal input of AChE-positive efferent innervation. The late onset and the slow course of the degeneration of AChE-positive innervation seen in the SH1/Le mutants suggest that the loss of efferent endings may be, contrary to previous suggestions, the consequence rather than the cause of the shaker-1 pathology.

Acetylcholinesterase↗

PubMed1990

Biochemical and morphological differentiation of acetylcholinesterase-positive efferent fibers in the mouse cochlea.

We have compared the biochemical expression of cholinergic enzymes with the morphological differentiation of efferent nerve fibers and endings in the cochlea of the postnatally developing mouse. Choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) are present in the newborn cochlea at specific activities 63% and 25%, respectively, of their mature levels. The relative increases in ChAT, in AChE, and in its molecular forms over the newborn values start about day 4 and reach maturity by about day 10. The biochemical results correlate well with the massive presence of nerve fibers stained immunocytochemically for ChAT and AChE or enzymatically for AChE in the inner and outer hair cell regions. Ultrastructral studies, however, indicate the presence of only few vesiculated fibers and endings in the inner and outer hair cell regions. The appearance of large, cytologically mature endings occurs only toward the end of the third postnatal week. The discrepancy may be resolved in the electron microscopy using the enzymatic staining for AChE. Labeling is seen on many nonvesiculated fibers and endings in the hair cell regions, suggesting that the majority of the efferent fibers in the perinatal organ may be biochemically differentiated but morphologically immature. The results may imply that the efferents to inner and outer hair cells develop earlier than indicated by previous ultrastructral studies. Moreover, the pattern of development suggests that in the cochlea, as in other tissues, the biochemical differentiation of the efferent innervation may precede the morphological maturation.

Acetylcholinesterase↗

PubMed1989

Development of acetylcholinesterase-positive neuronal pathways in the cochlea of the mouse.

Development of the cholinergic enzymes, choline acetyltransferase (ChAT) and AChE, and of the AChE-positive innervation in the cochlea was studied biochemically and morphologically in the postnatal mouse up to 26 days. Both ChAT and AChE are already present at birth in levels comparable to 50 and 20% of near-adult values, respectively. Increases in the enzymatic activities occur mainly during the second postnatal week. ChAT increases primarily in the basal turn; the specific activities in the basal and mid turns become about equal and at least twice of the values found in the apex. AChE increase continues throughout the entire cochlea; at all times its activity is highest in the base and lowest in the apex. In the light microscope, AChE-positive fibres are seen to enter the organ in the intraganglionic bundle during late foetal development and travel upwards via radial bundles. The fibres destined for outer hair cells usually differentiate first and take a separate route. They either cross the prospective tunnel of Corti directly or take a spiral course in front of inner pillar cells to form the inner pillar bundle. The tunnel fibres are radially oriented and provide the innervation to outer hair cells in narrow vertical sectors. In most cases, the outer hair cells are being innervated by the 4th day. Between the 4th and the 6th day, the tunnel fibres reach the outer hair cells in the third row; the first and second outer spiral bundles are formed. The AChE-positive innervation of the inner spiral bundle and plexus forms in short segments, and the bundle may be still discontinuous even by the 6th day. By the 12th day the innervation is complete. In the electron microscope, the stain for AChE may allow identification of growing efferent fibres before their ultrastructural differentiation. Both ChAT and AChE activities are early markers of the differentiating efferent system. An ingrowth of the cholinergic fibres to the entire cochlea occurs before birth. The greatest increase of AChE occurs between the 4th and 10th day, relating in time to efferent synaptogenesis.

Acetylcholinesterase↗

PubMed1986

Identification of the chick neural retina cell surface N-acetylgalactosaminyltransferase using monoclonal antibodies.

Intact embryonic chick neural retina cells have at their surface an N-acetylgalactosaminyltransferase which catalyzes the incorporation of N-acetylgalactosamine from UDP-N-acetylgalactosamine into endogenous macromolecular acceptors. The enzyme along with its endogenous acceptors can be isolated as a particulate complex following treatment of membrane-enriched fractions with Triton X-100. In this paper we report on two separate fusions generating monoclonal antibodies: one using as immunogen the particulate complex and the second using as immunogen a soluble N-acetylgalactosaminyltransferase found in tissue-culture-conditioned medium which lacks endogenous acceptor activity. Antibodies from both fusions recognize an antigen which is tightly associated with the particulate transferase/acceptor complex and a soluble antigen having N-acetylgalactosaminyltransferase activity toward exogenously added acceptors. The antibodies recognize a component of ca Mr 220,000, which shows N-acetylgalactosaminyltransferase activity after SDS-gel electrophoresis and transfer to nitrocellulose. This component comigrates on two-dimensional gel electrophoresis with an iodinatable cell surface component whose presence at the cell surface correlates with endogenous transferase activity. We conclude that the antibodies recognize the transferase enzyme itself. Immunohistochemical analysis shows that the enzyme is initially localized throughout the embryonic neural retina in a pattern indicative of a cell surface disposition but becomes restricted to the outer plexiform layer and to outer segments in the adult.

Animals↗

PubMed1981

Cross-linking and binding of fibronectin with asymmetric acetylcholinesterase.

The similarities between the tail of asymmetric acetylcholinesterase (AcChE) and collagen prompted us to investigate if asymmetric AcChE, like collagen, can interact with fibronectin. Gradient centrifugation studies revealed that asymmetric, but not globular, AcChE bound to fibronectin and could be cross-linked covalently to fibronectin by plasma transglutaminase. The interaction of asymmetric AcChE with fibronectin paralleled the interaction of fibronectin with collagen. These results raise the possibility that fibronectin may be involved in attaching asymmetric AcChE to cell surfaces.

Acetylcholinesterase↗

PubMedDate not supplied

PD 142676 (CI 1002), a novel anticholinesterase and muscarinic antagonist.

Inhibition of brain acetylcholinesterase (AChE) can provide relief from the cognitive loss associated with Alzheimer's disease (AD). However, unwanted peripheral side effects often limit the usefulness of the available anticholinesterases. Recently, we identified a dihydroquinazoline compound, PD 142676 (CI 1002) that is a potent anticholinesterase and a functional muscarinic antagonist at higher concentrations. Peripherally, PD 142676, unlike other anticholinesterases, inhibits gastrointestinal motility in rats, an effect consistent with its muscarinic antagonist properties. Centrally, the compound acts as a cholinomimetic. In rats, PD 142676 decreases core body temperature. It also increases neocortical arousal, as measured by quantitative electroencephalography, and cortical acetylcholine levels, measured by in vivo microdialysis. The compound improves the performance of C57/B10j mice in a water maze task and of aged rhesus monkeys in a delayed match-to-sample task involving short-term memory. The combined effect of AChE inhibition and muscarinic antagonism distinguishes PD 142676 from other anticholinesterases, and may be useful in treating the cognitive dysfunction of AD and produce fewer peripheral side effects.

Animals↗

PubMedDate not supplied

Differentiation and distribution of acetylcholinesterase molecular forms in the mouse cochlea.

The activities of the globular and asymmetric forms of acetylcholinesterase (AChE) were measured in the whole cochlea and cochlear turns of the developing postnatal mouse. The globular AChE forms (G4, G2 and G1) were present in each cochlear turn at birth. An asymmetric AChE form (A12) was detected in the midturn on the 4th postnatal day, and in the base and apex on the 7th postnatal day. The activities of all AChE molecular forms increased rapidly during the second postnatal week and reached a plateau by the 19th postnatal day. In the 26-day old mouse, G4 constitutes the largest proportion of total cochlear AChE (57%), G2/G1 being 37% and A12 being 6%. The distribution of the AChE forms among the different turns is as follows: the combined value of the activities of G2 and G1 AChE was the same in each turn; G4 was the major form in the base and midturn; and A12, the least abundant AChE form of all, was localized mainly in the base. Our results indicate that in the cochlea (1) the content of molecular forms is similar to that of other neuronal systems, (2) the expression of AChE molecular forms is developmentally regulated, and (3) the AChE isoenzymes develop and are distributed differentially along the cochlear length; resulting near maturity in the greater proportional expression of G4 and A12 in the base and midturn and G2/G1 in the apex.

Acetylcholinesterase↗