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W L Cruce

Publications and source records attributed to W L Cruce.

At least 37 records · Page 2Linked to original sources
PubMed1988

Evolution of the reticular formation.

The reticular formation of mammals contains numerous nuclei which can be recognized by their projection patterns, cytoarchitectonics, and neuropeptide/neurotransmitter content. We have identified reticular nuclei in representatives from numerous reptilian groups and ascertained presence or absence of these reticular nuclei in an attempt to use neuronal occurrence as a tool to determine phylogenetic relationships. Recently these studies have been extended to two elasmobranchs, a galeomorph shark and a ray. In this report, we concentrate on three medullary spinal projecting reticular nuclei, reticularis gigantocellularis, reticularis magnocellularis, and reticularis paragigantocellularis. We found that all three nuclei were present in rats, lizards, and elasmobranchs, but one nucleus was absent in crocodilians, and two nuclei were absent in turtles. Thus brain organization may give us clues to phylogenetic relationships. Moreover, these three reticular nuclei exhibited remarkably similar cellular morphology in mammals, reptiles, and elasmobranchs.

Animals↗
PubMed1986

Afferent and efferent components of the facial nerve in a frog, Rana pipiens.

The seventh cranial nerve in Rana pipiens is a slender nerve with limited peripheral distribution. We investigated the afferent and efferent components of this nerve by labeling its major branch, the hyomandibular, with horseradish peroxidase. The efferent portion of the seventh nerve originates from a small cell group in the upper medulla which contains two subdivisions. Afferent fibers carried in nerve VII travel in the solitary tract and the dorsolateral funiculus. The solitary component consists of a small number of ascending fibers that reach the level of the trigeminal nucleus and a large descending component that terminates slightly caudal to the obex in the commissural nuclei of the solitary complex. Afferent fibers also descend in the dorsolateral funiculus; many of these fibers cross dorsal to the central canal in the lower medulla. Most of the fibers in the dorsolateral funiculus terminate in the ipsilateral and contralateral dorsal horns and in nuclei of the dorsal column. A few ipsilateral fibers reach lower thoracic levels of the spinal cord.

Afferent Pathways↗
PubMed1985

The dendritic extent of motoneurons in frog brachial spinal cord: a computer reconstruction of HRP-filled cells. With comments on dendritic reconstruction methodologies.

A lateral and a medial motoneuron in the brachial spinal cord of the leopard frog, Rana pipiens, were labeled by horseradish peroxidase applied to the ventral root. Their dendritic trees were traced, analyzed, and plotted using a computer-microscope system. Some dendrites of the medial motoneuron crossed the midline of the spinal cord, but no dendrites of the lateral motoneuron crossed the midline. Nevertheless, the total dendritic length of the lateral motoneuron exceeded that of the medial motoneuron. The peak number of dendritic branch segments of the medial motoneuron was located at a greater distance from its soma than that of the lateral motoneuron. Three-dimensional reconstruction and rotation of the dendritic trees revealed that the dendrites of the medial motoneuron had a greater rostrocaudal extent than those of the lateral motoneuron. When compared to reports of Golgi-impregnated motoneurons, our results suggest that the HRP technique labels dendrites more completely. However, use of the HRP technique may introduce greater errors in the subsequent measurement of dendritic segments due to nonuniform tissue shrinkage.

Animals↗
PubMed1985

Distribution and ultrastructure of primary afferent axons in Lissauer's tract in the northern leopard frog (Rana pipiens).

Dorsal roots were transected and filled with horseradish peroxidase to identify the primary afferent axons in Lissauer's tract (LT) of the spinal cord in a ranid frog with light and electron microscopy. Axons in LT could be traced at least 2-3 segments rostral and caudal to the level of the filled root. Some axons in LT entered a nucleus in the dorsal lateral funiculus at brachial and lumbar levels, while other axons terminated in widespread regions of the dorsal horn. Electron microscopy revealed unlabelled terminals with numerous large, dense-cored vesicles in LT. However, large vesicles were rarely observed and were never abundant in labelled primary afferent axons. S type synaptic contacts between labelled axons and unlabelled profiles were observed. The presynaptic axons in these synapses contained many small, spherical vesicles. The cross-sectional area of LT was related to the spinal cord level, with the largest area at the brachial level, and intermediate area at the lumbar level, and the smallest area at the thoracic level. No difference in number of labelled axons was observed in the medial and lateral parts of LT.

Afferent Pathways↗
PubMed1984

Organization within the cranial IX-X complex in ranid frogs: a horseradish peroxidase transport study.

Cranial nerves IX and X in frogs have been described as originating from a nuclear group referred to as the IX-X complex. We studied the central nervous system components of this complex in Rana pipiens and R. catesbiana by labeling peripheral branches of cranial nerves IX and X and identifying the central nervous system contributions of these branches. Various peripheral nerves (IX and the cardiac, gastric, pulmonary, and laryngeal branches of X) were identified and soaked in horseradish peroxidase (HRP). One to 2 weeks later, the frogs were killed and processed for HRP by the tetramethylbenzidine method. Glossopharyngeal efferents originated from a small ventrolateral cell group found at the level of IX root exit. Vagal efferents formed a single column of cells in a ventrolateral position from the level of the brainstem exist of the vagus nerve (approximately 2,000 micrometers above the obex) to 200 micrometers below the obex (values given are for an 80-g frog). This cell group was separate from and just caudal to efferent cells of the glossopharyngeal nerve. Within the vagal portion of the column, cells projecting through the gastric branch were found throughout the rostral-caudal extent of the nucleus. "Cardiac" cells tended to be more rostral than "pulmonary" cells, and both groups of cells were located in the middle of the nucleus. "Laryngeal" cells were located more caudally in the nucleus. This peripheral representation within the vagal nucleus corresponds more closely to the organization found in the mammalian nucleus ambiguus, rather than to the apparent lack of organization found in the mammalian dorsal motor nucleus. Afferents of IX and X entered slightly rostral to the ventral roots of their respective nerves and descended in two tracts. The majority entered the tractus solitarius and descended in a medial position to cervical spinal cord. A portion of the afferents from the vagus nerve crossed the midline in the lower myelencephalon just dorsal to the central canal and ascended a short distance on the contralateral side. Within the solitary tract, vagal afferents were located in a ventrolateral position as they descended to below the obex. Glossopharyngeal afferents filled the remainder of the tract. A smaller portion of afferents from both IX and X did not enter the solitary tract but descended in the spinal tract of V and the dorsolateral funiculus of the spinal cord (Lissauer's tract) to thoracic levels. Afferents of IX also formed a rostral bundle which extended in the solitary tract to the caudal metencephalon.

Animals↗
PubMed1984

Contralateral motoneuron dendritic changes induced by transection of frog spinal nerves.

Changes in dendritic morphology were investigated following lesions of frog spinal nerves. Dendrite length, surface area, and volume, as well as measures of expansion and retraction were examined with the aid of a computer microscope system. We found that dendrites contralateral to the side of transection underwent a distal shift in their branching pattern without changing in total length or total number of branches.

Animals↗
PubMed1983

Afferent and efferent components of the hypoglossal nerve in the grass frog, Rana pipiens.

In amphibians, the spinomedullary region of the central nervous system is compressed rostrocaudally because of the absence of a neck. In Ranid frogs, the hypoglossal nerve emerges as the ventral ramus of the second spinal nerve. The first spinal nerve, though present in tadpoles, is absent as a separate nerve in adults. To investigate the central nervous system components of the hypoglossal nerve in Rana pipiens, we soaked identified, transected branches of this nerve in horseradish peroxidase, a retrograde and anterograde tracer. We found that the hypoglossal nerve in these frogs originates from two efferent nuclei located in the caudal medulla, a medial and a lateral one. Afferent fibers, primarily from the tongue, are also found in the hypoglossal nerve and travel in the dorsolateral funiculus of the spinal cord, descending to thoracic levels of the cord. Efferents to intrinsic tongue muscles and the genioglossus muscle originate in the medial medullary nucleus. Efferents to the sternohyoid muscle, which travel through the hypoglossal nerve, originate in the lateral medullary nucleus. Since in mammals the sternohyoid muscle is innervated by the first spinal nerve, we have obtained experimental evidence that the hypoglossal nerve in Rana pipiens contains components of this spinal nerve.

Afferent Pathways↗
PubMed1983

The sources of supraspinal afferents to the spinal cord in a variety of limbed reptiles. I. Reticulospinal systems.

Horseradish peroxidase was injected into various levels of the spinal cord of turtles (Pseudemys and Chrysemys), lizards (Tupinambis, Iquana, Gekko, Sauromelus, and Gerrhonotus), and a crocodilian (Caiman). The results suggest that brainstem reticulospinal projections in limbed reptiles rival mammalian reticulospinal systems in complexity. The reptilian myelencephalic reticular formation can be divided into four distinct reticulospinal nuclei. Reticularis inferior pars dorsalis (RID) contains multipolar neurons which project bilaterally to the spinal cord. Reticularis inferior pars ventralis (RIV), which is only found in lizards and crocodilians, contains fusiform neurons with horizontally running dendrites and it projects ipsilaterally to the spinal cord. Reticularis ventrolateralis (RVL), which is found only in field lizards, contains triangular neurons whose dendrites parallel the ventrolateral edge of the brainstem and it projects ipsilaterally to the spinal cord. The myelencephalic raphe (RaI) varies considerably. RaI of turtles contains large reticulospinal neurons which form a continuous population with more laterally situated RID cells. RaI of lizards contains a few small reticulospinal neurons. RaI of the crocodilian Caiman contains giant reticulospinal neurons with laterally directed dendrites. The caudal metencephalic reticular formation of reptiles can be divided into two distinct reticulospinal nuclei. Reticularis medius (RM) contains large neurons with long, ventrally directed dendrites; it projects ipsilaterally to the spinal cord. Reticularis medius pars lateralis (RML) contains small neurons with laterally directed dendrites; it projects contralaterally to the spinal cord. The rostral mesencephalic and caudal mesencephalic reticular formation of reptiles can be divided into three distinct reticulospinal nuclei. Reticularis superior pars medialis (RSM) consists mostly of small, spindle-shaped neurons which project bilaterally to the spinal cord. In the lizard Tupinambis, however, large multipolar, ipsilaterally projecting neurons are occasionally seen in RSM. Reticularis superior pars lateralis (RSL) contains large, ipsilaterally projecting neurons with long, ventrolaterally directed dendrites. SRL in lizards can be divided into a dorsomedial portion, which projects ipsilaterally to the spinal cord, and a ventrolateral portion which projects contralaterally. The locus ceruleus-subceruleus field (LC-SC) contains small spindle-shaped neurons which project bilaterally to the spinal cord. Labelled reticulospinal neurons were also observed in the rostral metencephalic raphe (RaS) of the turtle brainstem. These cells are small, spindle-shaped neurons which resemble the small cells of the adjacent RSM field.

Afferent Pathways↗
PubMed1982

The organization of the reptilian formation: a comparative study using Nissl and Golgi techniques.

The brainstem reticular formation has been studied in 16 genera representing 11 families of reptiles. Measurements of Nissl-stained reticular neurons revealed that they are distributed along a continuum, ranging in length from 10 micrometer to 95 micrometer. Reticular neurons in crocodilians and snakes tend to be larger than those found in lizards and turtles. Golgi studies revealed that reticular neurons possess long, rectilinear, sparsely branching dendrites. Small reticular neurons (less than 31 micrometers length) possess fusiform or triangular somata which bear two or three primary dendrites. These dendrites have a somewhat simpler ramification pattern when compared with those of large reticular neurons ( greater than 30 micrometers length). Large reticular neurons generally possess perikarya which are triangular or polygonal in shape. The somata of large reticular neurons bear an average of four primary dendrites. The dendrites of reptilian reticular neurons ramify predominantly in the transverse plane and are devoid of spines or excrescences. The dendritic ramification patterns observed in the various repitilian reticular nuclei were correlated with known input and output connections of these nuclei. Nissl and golgi techniques were used to divide the reticular formation into seven nuclei. A nucleus reticularis inferior (RI) is found in the myelencephalon, a reticularis medius (RM) in the caudal two-thirds of the metencephalon, and a reticularis superior (RS) in the rostral metencephalon and caudal mesencephalon. Reticularis inferior can be subdivided into a dorsal portion (RID) and a ventral portion (RIV). All reptilian groups possess RID and RM but RIV is lacking in turtles. Reticularis superior can be subdivided into a large-celled lateral portion (RSL) and a small-celled medial portion (RSM). All reptilian groups possess RSM and RSL, but RSL is quite variable in appearance, being best developed in snakes and crocodilians. The myelencephalic raphe nucleus is also quite variable in its morphology among the different reptilian families. A seventh reticular nucleus, reticularis ventrolateralis (RVL), is found only in snakes and in teiid lizards. It was noted that the reticular formation is simpler (fewer numbers of nuclei) in the representative of older reptilian lineages and more complex (greater numbers of nuclei) in the more modern lineages. Certain reticular nuclei are present or more extensive in those families which have prominent axial musculature.

Alligators and Crocodiles↗
PubMed1981

Brain stem origins of spinal projections in the lizard Tupinambis nigropunctatus.

In order to study brainstem origins of spinal projections, ten Tegu lizards (Tupinambis nigropunctatus) received complete or partial hemisections of the spinal cord at the first or second cervical segment. Their brains were processed for conventional Nissl staining. The sections were surveyed for the presence or absence of retrograde chromatolysis. Based on analysis and comparison of results from lesions in the various spinal cord funiculi, the following conclusions were reached: The interstitial nucleus projects ipsilaterally to the spinal cord via the medial longitudinal fasciculus, as does the middle reticular field of the metencephalon. The red nucleus and dorsal vagal motor nucleus both project contralaterally to the spinal cord via the dorsal part of the lateral funiculus. The superior reticular field in the rostral metencephalon and the ventrolateral vestibular nucleus project ipsilaterally to the spinal cord via the ventral funiculus. The dorsolateral metencephalic nucleus and the ventral part of the inferior reticular nucleus of the myelencephalon both project ipsilaterally to the spinal cord via the dorsal part of the lateral funiculus. Several brainstem nuclei in Tupinambis project bilaterally to the spinal cord. The ventrolateral metencephalic nucleus, for example, projects ipsilaterally to the cord via the medial longitudinal fasciculus and contralaterally via the dorsal part of the lateral funiculus. The dorsal part of the inferior reticular nucleus projects bilaterally to the spinal cord via the dorsal part of the lateral funiculus. The nucleus solitarius complex projects contralaterally via the dorsal part of the lateral funiculus but ipsilaterally via the middle of the lateral funiculus. The inferior raphe nucleus projects bilaterally to the spinal cord via the middle part of the lateral funiculus. These data suggest that supraspinal projections in reptiles, especially reticulospinal systems, are more highly differentiated than previously thought. On the other hand, recent findings in cat, opossum, and monkey reveal that the organization of supraspinal pathways in the Tegu lizard bears a striking resemblance to that observed in mammals.

Animals↗
PubMed1980

Normal dendritic morphology of frog spinal motoneurons: a Golgi study.

Normal dendritic morphology of frog (Rana pipiens) lumbar motoneurons was studied using Golgi silver impregnation. Branching characteristics and quantitative measurements of dendrites were obtained using computer-aided serial reconstruction of a typical lumbar motoneuron over seven adjacent 80-micrometer transverse sections. Dendrites were classified based upon site of dendrite origin from the soma and distribution of the dendritic array within the spinal cord. Eight possible sites of dendritic origin from the soma were identified. Two dendrites, D1 and D2, are planar dendrites which arise from the dorsal aspect of the soma. They are moderately complex, reaching branch order 5-6, and are oriented predominantly in the transverse plane. Input to these dendrites is primarily segmental via dorsal root projections. Three dendrites, D3, D4, and D5, arise laterally from the soma and extend through the lateral funiculus toward the subpial region. Two dendrites, D6 and D7, arise ventrally. D6 extends ventrolaterally and is a simple dendrite reaching branch order 3-4. D7 aborizes extensively in the ventral funiculus and in the central gray, reaching a branch order of 8-9. This dendrite extends rostrally and caudally over a distance of at lest 560 micrometer. Another dendrite (D8) arises from the medial aspect of the soma and projects toward the central canal. Four sites (D1, D2, D6, and D7) almost invariably give rise to dendrites. Dendrites arise at D4 in 66% of the cells examined. Dendrites are found at D3, D5, and D8 much less frequently (6-21%). Total dendritic length (12,043 micrometer) and lengths of the individual dendrites, branch length versus branch order, and number of branches at increasing radii were examined, and Sholl analysis was performed.

Animals↗
PubMed1980

A Golgi impregnation technique for thin brain slices maintained in vitro.

A technique for using routine rapid Golgi impregnation procedures on very thin freshly fixed slices (less than 0.5 mm) of brain tissue is described. The technique was particularly successful with hippocampal slices that were maintained and stimulated in vitro prior to fixation. Thin tissue slices were surrounded by thicker sections of tissue to form a 5 mm thick bundle. The tissue bundle was then processed by a rapid Golgi procedure, 5 days each in chromate osmium and silver nitrate solutions. At the end of this time the thin tissue slices were unwrapped from their thicker protecting tissue sections, embedded in celloidin, cut at 60-100 micrometer thickness on a sliding microtome and mounted in permount under cover glass. Qualitative light microscopic analysis of the rapid Golgi impregnated slices revealed fully impregnated cell bodies, dendrites, dentritic spines, axons and axonal varicosities with minimal background artifact. In contrast, unprotected thin tissue slices showed only a dense black artifact without cells or processes.

Animals↗
PubMed1975

Termination of supraspinal descending pathways in the spinal cord of the tegu lizard, Tupinambis nigropunctatus.

Descending fiber projections to the lizard spinal cord were studied using anterograde axonal degeneration. Following hemisection of the cord at the first spinal segment, degeneration was found in the white and gray matter as far down as the 31st (caudal) segment. Degenerating fibers in the white matter were confined to the ipsilateral side and were found in the medial longitudinal fasiculus and the outer half ot the lateral and ventral funiculi. Degeneration was more intense in the dorsolateral and ventromedial funiculi than in the ventrolateral funiculus. In the gray matter, REXED's criteria were applied to Nissl-stained material to delimit boundaries of ten laminae. Degeneration of suprospinal axons was most intense in the medial part of VII, dorsal and ventral commissures to ramify contralaterally in the medial part of VII, in VII, and in medial IX. No degeneration was present in the lateral part of the spinal gray on the contralateral side. In Golgi-stained material, dendrites of lateral IX cells were seen to extend into lamina VII, the dorsolateral part of VII, and the lateral funiculus. Thus, fibers of the ventromedial supraspinal pathway may make axodendritic contact with motoneurons of lateral IX as well as medial IX, ipsilaterally. In addition, there is a possibility of a crossed connection to contralateral motoneurons.

Afferent Pathways↗