English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The whiskers on the face of mice project through several synapses to anatomically distinct cortical structures called barrels. In this study, the activities of six energy-related enzymes in isolated barrels in layer IV in the somatosensory cortex of adult mice were determined using quantitative histochemical techniques. Data from control barrels and from barrels for which the corresponding whiskers had been damaged were obtained. The analyses were made on freeze-dried cryostat sections. Individual barrels were identified in unstained sections and subsequently, portions of them were dissected out and weighed on a quartz fiber balance. Micromethods for histochemistry, including the use of oil wells and enzymatic cycling amplification, were used. Because only small samples were needed (25 to 40 ng), the levels of several enzymes in the same barrel or the distribution of an enzyme within parts of a single barrel could be determined. The following enzyme levels (given in moles per kg dry weight per hr + SE) were observed in controls: citrate synthase, 5.3 + 0.15; malate dehydrogenase, 20.8 + 0.90; hexokinase, 5.2 & 0.25; lactate dehydrogenase, 10.6 + 0.20; glycogen phosphorylase, 0.374 + 0.031; and glucose-gphosphate dehydrogenase, 0.638 & 0.012. In single barrels, the mitochondrial enzyme, citrate synthase, had a higher activity within the barrel hollowwhich is richer in mitochondria-(7.2 + 0.12) as compared to the barrel side-which is poorer in mitochondria-(4.4 + 0.22). The activities of these six enzymes were determined in particular barrels following cauterization of the related groups of whiskers in adult mice. For example, 60 days after whisker damage, activities expressed as a percentage of control were: citrate synthase, 69%; malate dehydrogenase, 61%; hexokinase, 79%; lactate dehydrogenase, 92%; glycogen phosphorylase, 132%; and glucose-6-phosphate dehydrogenase, 112%. These significant enzymatic changes occurred in the adult mouse brain in spite of the fact that the injury to peripheral tactile organs was three synapses away. Moreover, no anatomical changes in the barrels have been reported after similar damage to the periphery. We interpret the changes in enzyme levels as a manifestation of adaptive “plasticity” in the sense that the metabolic machinery of a neural system is matched to its metabolic need, which, in this case, is reduced as a consequence of reduced neuronal activity. The development of the nervous system can be altered following various types of experimental manipulations. For example, when a sensory system is deprived of input chronically, functional as well as structural changes are observed (Hubel et al., 1977; Woolsey, 1978; Parks, 1979). However, most studies report that the morphological and functional changes can be induced only during a specific “critical” or “sensitive” period in the development of the organism (Jacobson, 1978). Usually after this moment, ’ This work was supported by United States Public Health Service Grants NS 07057, NS 15070, NS 10244, NS 06862, and NS 07129 and American Cancer Society Grant BC4W. We wish to thank Bob Freund for photography and Mary Murphy for typing. ’ To whom correspondence should be addressed at Department of Pharmacology, Washington University School of Medicine, 660 South Euclid Avenue, St. Louis, MO 63110. no major structural changes can be produced (e.g., Woolsey and Wann, 1976; LeVay et al., 1980). Recently, with the use of histochemical staining procedures, regional changes in the levels of enzymes involved in energy metabolism have been demonstrated following chronic sensory deprivation in the adult brain (Wong-Riley et al., 1978). In their study of the mouse somatosensory cortex, Wong-Riley and Welt (1980) demonstrated a decrease in the level of the mitochondrial enzyme, cytochrome oxidase, within barrels for which the corresponding whiskers had been cauterized 80 days previously.3 Anatomically, ” Mice and other rodents have five rows of large whiskers on the face. Each whisker is associated with a single tactile organ or sinus hair which receives a substantial, well segregated afferent innervation from the maxillary division of the trigeminal nerve. The rows of whiskers or mystacial vibrissae are labeled A to E from dorsal to ventral on the 930 Dietrich et al. Vol. 1, No. 9, Sept. 1981 no gross changes in barrel morphology are seen in similar experiments (Woolsey and Wann, 1976). The objective of the present study was to characterize more fully the histochemistry of individual barrels within the posteromedial barrel subfield (PMBSF) through the use of quantitative microtechniques. The levels of enzymes within normal barrels were measured. The activities of various enzymes within barrels for which the corresponding whiskers had been damaged were followed at selected times after whisker damage. These activities were compared directly to the activities within barrels in the same section associated with intact vibrissae. This paper reports base line levels of a number of enzymes related to energy metabolism in normal barrels and quantitates the consequences of chronic sensory deafferentation occurring three synapses away within the adult nervous system. Materials and Methods Preparation of tissue Twenty-two adult Swiss Webster mice of both sexes were used in this study. In 18 mice, the whiskers in rows B and D of both sides of the face were plucked and their follicles were cauterized under Nembutal anesthesia. Experimental animals were allowed to survive for 15,45,60, 90, and 115 days. At this time, facial pads were examined grossly to verify the damage to the whiskers within the treated rows. In some cases, the pattern and the extent of peripheral damage were determined from hematoxylin and eosin-stained paraffin sections of facial skin. In one additional experimental animal, the infraorbital branch of the trigeminal nerve was sectioned surgically on the right side. This animal was sacrificed 60 days later. Mice were decapitated and the heads were frozen directly in liquid nitrogen chilled to its freezing point (-21O’C). The brains were dissected out in a -20°C cold room and the cerebral hemispheres were mounted in a cryostat for tangential sectioning through the PMBSF (Woolsey and Van der Loos, 1970). The sections (20 pm) were dried overnight at -35°C and stored under vacuum at -35°C until the analyses were carried out. Details of the preparation of tissues and sections are described by Lowry and Passonneau (1972). Under a dissecting microscope and with appropriate transmitted illumination, specific barrels could be identified routinely within unstained freeze-dried sections. From these sections, single barrels were isolated and each barrel was subdivided further so that the levels of several enzymes could be determined in the same barrel (Fig. 1) or so that the regional distribution of a single enzyme face. These project to the cortex through three synapses-in the ipsilateral trigeminal nuclei, in the contralateral ventrobasal thalamus, and in the somatosensory (SmI) cortex. The cell bodies in layer IV of this cortex are arranged as cytoarchitectonic units called barrels which extend throughout layer IV and which, when viewed in sections parallel to the pial surface, have a pattern which is “isomorphic” to the whiskers on the face. Thus, in the posteromedial barrel subfield (PMBSF), there are five rows of barrels labeled A to E, from caudal to rostral, which correspond to and receive inputs in a one-to-one fashion from the similarly named five rows of large whiskers on the contralateral face. Figure 1. The method for dissecting individual identified barrels from a 20-pm freeze-dried tangential section is shown. a, In two unstained nonadjacent sections, rows of barrels (A to E) can be seen as are the barrels in each row (i.e., 1 to 3). b, Special dissecting instruments, hair point and razor knife, are shown for scale. Two barrels (I, Cq and 2, E4) have been dissected out of the section. c, These two dissected barrels are shown. Barrel 1 has been quartered and could be used for four separate determinations of the levels of a single enzyme or for the assay of the levels of up to four different enzymes. within a particular barrel could be studied (Fig. 2). Immediately following dissection, samples were weighed on a quartz fiber fishpole balance (Lowry, 1953) and analyzed.

Quantitative histochemical effects of whisker damage on single identified cortical barrels in the adult mouse