Biomedical subjects

D A Godfrey

Publications and source records attributed to D A Godfrey.

At least 55 records · Page 3Linked to original sources

PubMed1990

Quantitative distributions of aspartate aminotransferase and glutaminase activities in the guinea pig cochlea.

Distributions of aspartate aminotransferase and glutaminase activities in the guinea pig cochlea have been examined with use of quantitative microchemical techniques to evaluate their roles in cochlear energy metabolism and neurotransmission. Other enzyme activities analyzed were those of choline acetyltransferase and malate dehydrogenase. It is concluded that aspartate aminotransferase activity appears to be especially concerned with cochlear energy metabolism, while glutaminase activity may function in transmitter metabolism in the guinea pig cochlea. Neither enzyme shows a clear association with the olivocochlear bundle.

Animals↗

PubMed1990

Enzymes of transmitter and energy metabolism in cat middle ear muscles.

Activities of the enzymes choline acetyltransferase (ChAT) and acetylcholinesterase (AChE), which metabolize the neuromuscular transmitter acetylcholine, and malate and lactate dehydrogenase (MDH and LDH), enzymes of oxidative and glycolytic energy metabolism, respectively, were measured in the middle ear muscles of the cat. For comparison, the same enzyme activities were measured in extraocular muscle tissue and in three hindlimb muscles rich in either slow oxidative (soleus), fast glycolytic (white part of vastus lateralis), or fast oxidative glycolytic (plantaris) muscle fibers. ChAT and AChE activities were much higher in middle ear muscles than in hindlimb muscles, consistent with a denser neuromuscular innervation, as in extraocular muscles. By contrast, MDH and LDH activities were remarkably low in the middle ear muscles, lower than in any of the hindlimb muscles or the extraocular muscles. Denervation of the stapedius muscle by peripheral transection of the facial nerve resulted in decreases in all four enzyme activities without associated changes in the tensor tympani. Surgical ablation of the peripheral facial nerve supply to the stapedius muscle appears to be a feasible option for producing its denervation. The results suggest some rather specialized chemical characteristics for the middle ear muscles.

Acetylcholinesterase↗

PubMed1989

Quantitative distribution of six amino acids in rat retinal layers.

Concentrations of glutamate, aspartate, glutamine, glycine, GABA, and taurine were determined in samples microdissected from rat retinal layers and assayed by HPLC. Glutamate and glutamine were relatively high in the inner nuclear (INL) and ganglion cell (GCL) layers; aspartate was relatively high in the outer nuclear layer (ONL), outer plexiform layer, and INL. Distributions of glutamate and aspartate did not correlate well with those of enzymes involved in their metabolism. Glycine and GABA were highest in the inner plexiform layer, with increasing concentrations through the INL, and were relatively high in the GCL. Taurine was highest in the ONL.

Amino Acids↗

PubMed1989

Effect of septal ablation on choline acetyltransferase in the paraventricular nucleus.

To determine whether there is a cholinergic projection from the lateral septum to the paraventricular nucleus of the hypothalamus (PVH), a quantitative histochemical analysis of the effects of unilateral ablation (0.5 microliter of a 10 micrograms/ml solution of ibotenic acid) of the lateral septum (LSV) on the choline acetyltransferase (ChAT) activity of the PVH and surrounding perinuclear area was undertaken. Comparisons of the ChAT activity of the PVH region ipsilateral to the LSV lesion (lesioned side) with that of the PVH contralateral (nonlesioned side) to the ablated LSV showed a 20% reduction (p less than 0.05) of ChAT activity in 2 areas of the PVH on the lesioned side. When ChAT activity of LSV-ablated and intact control rats was compared, a 20% difference in activity (p less than 0.05) was noted in four areas on the nonlesioned side and a 35% difference (p less than 0.05) of ChAT activity was noted in five regions of the PVH on the lesioned side of LSV-ablated animals. Taken together these data suggest that the pathway from the LSV to the PVH contains a small, bilateral cholinergic component. However, the data also indicate that this is not the only cholinergic projection to the PVH.

Animals↗

PubMed1987

Quantitative inter-strain comparison of the distribution of choline acetyltransferase activity in the rat cochlear nucleus.

The distribution of choline acetyltransferase activity in the cochlear nucleus of Sprague-Dawley albino rats was quantitatively compared to those in two strains of pigmented rats, Long Evans hooded and Brown Norway, using microdissection and radiometric assay techniques. Although activities tended to be, on the whole, higher in the albino rats, the differences were fairly minor. The relative distributions of choline acetyltransferase activity were generally similar among the 3 rat strains, not only among regions, but also within regions. Stain for acetylcholinesterase activity in the cochlear nucleus also had a similar appearance among the 3 rat strains. These chemical results are consistent with previous anatomical and physiological studies suggesting that auditory differences between albino and pigmented animals may not be as great in the cochlear nucleus as in the superior olivary complex.

Animals↗

PubMed1987

Separate enzymatic microassays for aspartate aminotransferase isoenzymes.

The properties of the cytosolic and mitochondrial isoenzymes of aspartate aminotransferase were studied using a commercial preparation of the cytosolic isoenzyme, a mitochondrial preparation, and whole brain homogenate. Based on these properties, microassays were developed and shown to be highly specific and quantitatively accurate for measuring the activity of either the cytosolic or mitochondrial isoenzyme in microgram quantities of tissue. The assays have been successfully applied to homogenates of a wide variety of tissues. They can be used to measure the activities of aspartate aminotransferase isoenzymes in sub-microgram samples of freeze-dried tissue.

Animals↗

PubMed1987

Distributions of the activities of aspartate aminotransferase isoenzymes in rat retinal layers.

Distributions of the activities of the cytosolic (cAAT) and mitochondrial (mAAT) isoenzymes of aspartate aminotransferase were determined in rat retinal layers. cAAT was highest in the photoreceptor inner segments, inner nuclear layer and inner plexiform layer; mAAT was highest in the inner segments. The high activity in the inner segments indicates that both isoenzymes are involved in energy metabolism in addition to a possible role in neurotransmission.

Animals↗

PubMed1987

Distribution of glutaminase activity in retinal layers of rat and guinea pig.

The glutaminase activity in rat and guinea pig retina is twice as high in photoreceptor inner segments as in any other layer. Since the inner segments are involved in non-transmitter-related metabolic functions, it is suggested that glutaminase should not necessarily be taken to imply glutamatergic neurotransmission until the function of the high activity in regions such as the inner segments is better understood.

Animals↗

PubMed1987

Effect of olivocochlear bundle transection on choline acetyltransferase activity in the rat cochlear nucleus.

Using a microdissection and quantitative microassay approach, choline acetyltransferase activities were mapped in the cochlear nuclei of rats having complete transections of the olivocochlear bundle on one side in the brain stem. In rats in which the trapezoid body was not significantly damaged by the lesion, consistent reductions of choline acetyltransferase activity in subregions of the lesion-side cochlear nucleus, as compared to the control side, averaged about 20%. Nevertheless, a profound lesion-side reduction of choline acetyltransferase activity was found in a branch connection from the olivocochlear bundle to the cochlear nucleus. The results suggest that branches from the olivocochlear bundle are cholinergic, but contribute a relatively minor proportion of the cholinergic synapses in all regions of the rat cochlear nucleus. In the light of previous results with more extensive lesions, it can be proposed that synapses in all regions of the rat cochlear nucleus. In the light of previous results with more extensive lesions, it can be proposed that most cholinergic input into the rat cochlear nucleus enters by a ventral route along the trapezoid body. It is noted that this represents a quantitatively somewhat different situation from that in the cat.

Acetylcholinesterase↗

PubMed1987

Effects of trapezoid body and superior olive lesions on choline acetyltransferase activity in the rat cochlear nucleus.

Using a microdissection and quantitative microassay approach, choline acetyltransferase activities were mapped in the cochlear nuclei of rats having either transection of the trapezoid body or destruction of the superior olivary complex on one side in the brain stem. Lateral trapezoid body transection resulted in dramatic loss of choline acetyltransferase activity in all parts of the ipsilateral cochlear nucleus, while more medial transection had little effect. Destruction of the superior olivary complex resulted in dramatic loss of choline acetyltransferase activity in the ipsilateral cochlear nucleus, and detectable loss also contralaterally. The results suggest that most of the centrifugal cholinergic projections to the rat cochlear nucleus derive from or traverse the vicinity of the superior olivary complex bilaterally and enter the cochlear nucleus ventrally from the region of the trapezoid body.

Animals↗

PubMed1987

Distribution of activities of aspartate aminotransferase isoenzymes and malate dehydrogenase in guinea pig retinal layers.

Distributions of activity of the cytosolic (cAAT) and mitochondrial (mAAT) isoenzymes of aspartate aminotransferase and of malate dehydrogenase (MDH) were determined in guinea pig retinal layers. The distribution of total AAT activity (tAAT = cAAT + mAAT) and of mAAT activity correlated well (r = 0.88-0.91) with the distribution of MDH activity. mAAT activity was highest in the inner segments of the photoreceptors; there was a greater than twelve-fold difference between activity in that layer and in the inner retinal layers. cAAT activity was also highest in the inner segments, but the difference between the activity in the inner segments and the other layers was not nearly as great as with mAAT. cAAT activity was also relatively high in the outer nuclear layer, outer plexiform layer, and part of the inner plexiform layer. The high activity of cAAT, mAAT, and MDH in the inner segments indicates that all of these enzymes are involved in metabolic reactions related to energy production and/or to photoreceptive processes in the outer segments and, therefore, that the enzymes are probably involved in energy-related metabolism at synapses. However, other functions, including those related to neurotransmission, are not excluded.

Animals↗

PubMed1986

The distribution of choline acetyltransferase in the rat amygdaloid complex and adjacent cortical areas, as determined by quantitative micro-assay and immunohistochemistry.

The distribution of choline acetyltransferase (ChAT) within the amygdaloid complex has been studied to evaluate what should primarily represent the terminal field of the cholinergic projection from the basal forebrain. Two currently available methods have been combined for the comparison: immunohistochemistry with a monoclonal antibody against ChAT, by a double peroxidase-antiperoxidase procedure, and quantitative histochemistry involving micro-assay of the ChAT activity of contiguous microdissected samples. Both methods indicate prominent ChAT activity in the basolateral amygdaloid nucleus (especially rostrally), the nucleus of the lateral olfactory tract (especially layer II), and the amygdalohippocampal area. Regions of lower ChAT activity were not accurately represented by the immunohistochemistry, but could be discriminated by the quantitative assays. Lowest activity was found in the medial nucleus of the amygdala. Most other regions had activities at least as high as average brain or neocortex. Gradients of enzyme activity were found within several regions, including the basolateral and lateral amygdaloid nuclei and the nearby posterior piriform cortex. In the piriform cortex, a region of particularly high ChAT activity was found at its medial edge near the nucleus of the lateral olfactory tract. The immunohistochemical method shows a few intensely reactive somata in layer III within this zone. Comparison of the results seen with immunohistochemistry and quantitative histochemistry suggests an advantage in using them together, since their respective strengths and weaknesses tend to complement each other.

Amygdala↗

PubMed1986

Effect of enucleation on choline acetyltransferase activity in layers of goldfish optic tectum.

Choline acetyltransferase (ChAT) activity was determined in layers of optic tectum in control goldfish and in goldfish 4-20 days following unilateral enucleation. Significant changes in activity were found in the periventricular (PV) and superficial gray and white (SGW) layers. Within 4 days, ChAT activity in the PV layer on the lesioned side was about 75% of that on the control side. By 20 days, ChAT specific activity in the SGW layer on the lesioned side was about 150-160% of that on the control side. This increase in specific activity in the SGW layer was accounted for by the decrease in volume and in density of the layer after enucleation, so that the total amount of activity in the layer did not change significantly, indicating that the optic terminals contain little to no ChAT activity. ChAT activity in the optic tract was very low and did not decrease after enucleation. These data strongly indicate that the retinotectal pathway in goldfish is not cholinergic and, therefore, that the ChAT activity in the SGW layer is related to sources other than retinal ganglion cells. It is suggested that one such source might be neurons with somata in the PV layer.

Acetylcholinesterase↗

PubMed1986

Quantitative distributions of aspartate aminotransferase and glutaminase activities in the rat cochlea.

The intra-cochlear distributions of aspartate aminotransferase and glutaminase, prominent enzymes of aspartate and glutamate metabolism, have been studied by quantitative microchemical techniques. Also measured was choline acetyltransferase, the enzyme synthesizing acetylcholine, and a marker for the olivocochlear bundle. Aspartate aminotransferase activity was highest in the stria vascularis, about half this high in the organ of Corti synaptic (hair cell) zones, somewhat lower in the organ of Corti non-synaptic (Hensen's cell) zones, lower yet in Reissner's and lowest in the tectorial membrane. Glutaminase, on the other hand, had its highest activity in synaptic zones, about a third of that activity in the organ of Corti non-synaptic zones, and a barely detectable activity in Reissner's and tectorial membranes, and stria vascularis. Seven days after transection of the olivocochlear bundle, no significant difference was found between lesion- and control-side aspartate aminotransferase or glutaminase activities, even though no choline acetyltransferase activity remained in the lesion-side of the organ of Corti. Both the distribution of aspartate aminotransferase activity and the lesion results would seem to implicate it in energy more so than neurotransmitter metabolism. The distribution of glutaminase activity could be consistent with a role in neurotransmission; however, the lesion data were unable to demonstrate a specific association with the olivocochlear bundle.

Animals↗

PubMed1985

Laminar distributions of choline acetyltransferase and acetylcholinesterase activities in the inner plexiform layer of rat retina.

Choline acetyltransferase and acetylcholinesterase activities were measured in samples taken at 7-micron increments through the inner plexiform layer of rat retina. These enzyme activities were not uniformly distributed through the depth of the inner plexiform layer. Peaks of choline acetyltransferase activity occurred at about one-third and peaks of acetylcholinesterase activity at about one-fifth of the depth into the inner plexiform layer from either side. The positions of the two peaks of choline acetyltransferase activity most likely correspond to the locations of processes from cholinergic amacrine somata in the inner nuclear layer, which spread in sublamina a, and processes from cholinergic amacrine somata "displaced" in the ganglion cell layer which spread in sublamina b of the inner plexiform layer. The peaks of acetylcholinesterase activity may in addition correspond to the processes of cholinoceptive amacrine and ganglion cells. The magnitudes of choline acetyltransferase and acetylcholinesterase activities are as high as found anywhere in rat brain, emphasizing the important role of cholinergic mechanisms in visual processing through the rat inner plexiform layer.

Acetylcholinesterase↗

PubMed1985

Distributions of aspartate aminotransferase and malate dehydrogenase activities in rat retinal layers.

Aspartate aminotransferase (AAT), an enzyme interconverting glutamate and aspartate, has been suggested to be a marker for glutamatergic and/or aspartatergic neurons. However, AAT, glutamate, and aspartate are also involved in cellular metabolism, e.g., the malate-aspartate shuttle. To investigate the extent to which AAT might be involved in these several functions in retina, the distribution of AAT activity in rat retinal layers was compared to that of malate dehydrogenase (MDH), an enzyme of aerobic metabolism proposed to be physically complexed with AAT in the malate-aspartate shuttle mechanism. The distribution of AAT activity in retinal layers closely paralleled that of MDH (correlation coefficient AAT versus MDH = 0.93). AAT activity was proportionately higher than MDH in the photoreceptor inner segments, containing a high density of mitochondria, and in the outer plexiform layer (OPL), containing photoreceptor terminals and bipolar and horizontal cell processes. The amount of total AAT activity in the inner segments related to the mitochondrial isoenzyme is almost twice that in the other layers tested, including the OPL. The correlation between AAT and MDH activities is consistent with AAT involvement in retinal energy metabolism, although other functions, such as neurotransmission, are possible.

Animals↗

PubMed1985

Distributions of choline acetyltransferase and acetylcholinesterase activities in layers of rat superior colliculus.

Choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities were assayed in samples dissected from sagittal sections through rat superior colliculus. The magnitude of ChAT activity was about half to equal that found in rat whole brain in all layers except stratum griseum intermediale, where the average activity was higher than whole brain. AChE activity was three to four times that found in rat whole brain in superficial layers and about the same as average brain in deeper layers, except in the statum griseum intermediale, where the average activity was about twice whole brain. Rostral-caudal gradients in both ChAT and AChE activities occurred in stratum griseum intermediale, with activities in the caudal region of some animals as high as four times those in the rostral. ChAT activity in samples associated with locations of patches or spots of AChE staining product in stratum griseum intermediale was significantly higher than in samples from "nonpatch" regions. Results are discussed relative to inputs into the colliculus, whose terminations may correlate in location with the distributions of the enzyme activities.

Acetylcholinesterase↗

PubMed1984

Choline acetyltransferase and acetylcholinesterase in centrifugal labyrinthine bundles of rats.

Activities of choline acetyltransferase and acetylcholinesterase were measured for the acetylcholinesterase-positive fiber bundles containing axons projecting from the brainstem to the labyrinth of the rat. These activities were compared to those of a well-established cholinergic tract: the facial motor root. The choline acetyltransferase activities were roughly similar between the tracts, consistent with a conclusion that the centrifugal labyrinthine fibers are all cholinergic. The acetylcholinesterase activities were much higher in the centrifugal labyrinthine bundle than in the facial motor root, probably relating to the smaller diameters of the labyrinthine fibers. Transection of the centrifugal labyrinthine bundle led to virtually total loss of its choline acetyltransferase activity lateral to the cut, consistent with a centrifugal direction of all the fibers, but loss of only half its acetylcholinesterase activity, even after 34 days. These results agree with those for well-established cholinergic pathways, including the facial motor root in the present study, and with previous suggestions that a component of the acetylcholinesterase in cholinergic tracts might be synthesized by cells other than the neurons in the tract.

Acetylcholinesterase↗