Muscle fibre types in the suprahyoid muscles of the rat.

Five muscle fibre types (I, IIc, IIa, IIx and IIb) were found in the suprahyoid muscles (mylohyoid, geniohyoid, and the anterior and posterior bellies of the digastric) of the rat using immuno and enzyme histochemical techniques. More than 90% of fibres in the muscles examined were fast contracting fibres (types IIa, IIx and IIb). The geniohyoid and the anterior belly of the digastric had the greatest number of IIb fibres, whilst the mylohyoid was almost exclusively formed by aerobic fibres. The posterior belly of the digastric contained a greater percentage of aerobic fibres (83.4%) than the anterior belly (67.8%). With the exception of the geniohyoid, the percentage of type I and IIc fibres, which have slow myosin heavy chain (MHCbeta), was relatively high and greater than has been previously reported in the jaw-closing muscles of the rat, such as the superficial masseter. The geniohyoid and mylohyoid exhibited a mosaic fibre type distribution, without any apparent regionalisation, although in the later MHCbeta-containing fibres (types I and IIc) were primarily located in the rostral 2/3 region. In contrast, the anterior and posterior bellies of the digastric revealed a clear regionalisation. In the anterior belly of the digastric 2 regions were observed: both a central region, which was almost exclusively formed by aerobic fibres and where all of the type I and IIc fibres were located, and a peripheral region, where type IIb fibres predominated. The posterior belly of the digastric showed a deep aerobic region which was greater in size and where type I and IIc fibres were confined, and a superficial region, where primarily type IIx and IIb fibres were observed.

Muscle fibre types and their distribution in the biceps and triceps brachii of the rat and rabbit.

Muscle fibre type composition and distribution in the biceps brachii (long head) and triceps brachii (long head) of the rat and rabbit were investigated using the following histochemical techniques: myosin ATPase, with preincubation at pH 10.4 and 4.35; succinate dehydrogenase (SDH) and glycogen phosphorylase. The muscle fibres were classified into slow-twitch (SO), fast-twitch glycolytic (FG), fast-twitch oxidative glycolytic (FOG and FOg) and fast-twitch oxidative fibres (FO). Significant differences in the regional distribution of muscle fibre types have been observed between the rat and the rabbit. In the rat, SO fibres were restricted to the deep regions of both biceps and triceps brachii, whereas FG fibres were located in the intermediate and superficial regions (the superficial regions contained the highest percentages of FG fibres). In the rabbit, SO and FG fibres were spread over the entire muscle, although SO and FG fibres were most abundant in the deep and superficial regions respectively. These findings indicate that the biceps and triceps brachii are more regionalised in the rat than in the rabbit.

Fos expression in the trigeminal sensory nuclei after a chemical lesion of the lower lip mucosa.

C-fos containing neurons were investigated in the trigeminal sensory nuclear complex and in the dorsal horns of the cervical spinal cord (C1-C2) of the rat after a chemical noxious stimulus was applied to the lower lip mucosa. Numerous labelled neuronal nuclei were detected in the dorsolateral area of the caudal half of the trigeminal nucleus interpolaris, and in Rexed's laminae I-IIo of the dorsomedial area of the trigeminal nucleus caudalis and rostral C1. A few c-fos-labelled neurons were observed in laminae IIi and V. No Fos expression was detected in the trigeminal oral and principal nuclei.

Ultrastructure of the organum vasculosum laminae terminalis in the advanced teleost Chelon labrosus (Risso, 1826).

The advanced teleost Chelon labrosus shows a well-developed organum vasculosum laminae terminalis (OVLT). Together, the vascular organization and ultrastructure have many similarities with those found in mammals, though it is somewhat simpler. To date, the dense network of fenestrated capillaries in the nervous parenchyma of the OVLT observed in Chelon labrous has not been reported in other fishes, and resembles the porta system of mammals. However, the OVLT does not present intraventricular neuronal processes, as occurs in the corresponding organ of most vertebrates. Moreover, between the numerous neurons and the neuropil that surround these capillaries, terminal buttons with clear and dense-core vesicles can be appreciated. Most striking is the contact of neurons and even terminal buttons with the basal lamina of the external limiting membrane without interpose glial prolongations that separate the nervous parenchyma from the perivascular space; this represents windows in the blood brain barrier. The above characteristics and the absence of cilaited or chemorecptors structures suggest that neurohemal function of the OVLT, possibly under the control of neurotransmiters secreted by the terminal buttons dispersed throughout the whole organ.

A comparative study of the transganglionic transport of cholera toxin-horseradish peroxidase (CT-HRP) and wheat germ agglutinin-horseradish peroxidase (WGA-HRP) in the trigeminal system of the guinea pig.

A comparative study of cholera toxin (CT) and wheat germ agglutinin (WGA) conjugated with horseradish peroxidase (HRP) was made on trigeminal central projections of the lower incisor gingiva afferent neurons in the guinea pig. Considerably more CT-HRP-labeled endings were observed in the trigeminal sensory nuclear complex (TSNC) and in the cervical spinal cord (C1-C8). The substantia gelatinosa (lamina II) of both the caudal nucleus of the TSNC and C1-C2 was the only area where WGA-HRP labeled more terminals. CT-HRP-labeled fibers and endings were traced up to C7-C8, whereas with WGA-HRP were rare caudal to C5. A comparison of the two methods currently in use, i.e. the 2-step glutaraldehyde and sodium periodate, showed that the latter yields conjugates which are more sensitive as neuroanatomical tracers.

[Scanning electron microscope study of unerupted enamel surface in adult patients]. / Estudio con microscopia electrónica de barrido de la superficie del esmalte no erupcionado en pacientes adultos.

We have undertaken a scanning electron microscope study of the enamel surface of the third molar in adult patients. The enamel surface are partially covered by a thin cuticle. The arrangement of the enamel prisms was clearly observed in the basal region of the cusps.

Location of the motoneurons innervating the transverse mandibular muscle in the guinea pig.

Motoneurons supplying the transverse mandibular muscle (TMM) in the guinea pig have been traced by injecting wheat germ agglutinin-horseradish peroxidase (WGA-HRP) in the TMM, and after applying HRP to the mylohyoid nerve. The TMM is bilaterally innervated by 22-36 motoneurons in each trigeminal motor nucleus, forming a column located ventrolaterally along the entire length of the superficial masseter motoneuron group. The axons are incorporated to the mylohyoid nerve. The location, the axon pathways in the brainstem and the pattern of the dentritic tree suggest that in the guinea pig the TMM motoneurons are involved in the masticatory movements in coordination with other jaw-closing muscles.

Modifications of clinical methodology in Class I restoration with composite resins.

This work describes modifications of clinical methodology for the use of composite resins (changes in the isolation of the operating field, in the preparation of the cavities to be occluded and in the way the resin is applied), and relates them to studies of the fine structure of dental enamel and of the adverse side-effects of resins.

Distribution of postganglionic parasympathetic fibers originating in the pterygopalatine ganglion in the maxillary and ophthalmic nerve branches of the trigeminal nerve; HRP and WGA-HRP study in the guinea pig.

The distribution of the postganglionic parasympathetic fibers originating in the pterygopalatine ganglion (PTPG) has been traced in the guinea pig by means of the HRP and WGA-HRP methods. The greatest number of labeled cells were observed when WGA-HRP was injected in the lacrimal gland. After applying HRP to all the ramifications of the maxillary and ophthalmic divisions of the trigeminal nerve, labeled neurons were found in the PTPG. Numerous PTPG fibers were detected in the ethmoidal and sphenopalatine nerves. The presence of PTPG fibers in the supraorbital, infratrochlear, zygomaticotemporal, zygomaticofacial-inferior palpebral, sphenopalatine and infraorbital-superior alveolar nerves has not hitherto been reported in mammals.

Contralateral projections of trigeminal mandibular primary afferents in the guinea pig as seen by transganglionic transport of horseradish peroxidase.

Transganglionic transport of horseradish peroxidase (HRP) was used to investigate contralateral projections of trigeminal mandibular fibers in the guinea pig. After application of HRP to the buccal, lingual, auriculotemporal, mylohyoid, mental and inferior alveolar nerves, crossing fibers and contralateral endings were found in the caudal region of the nucleus of the solitary tract (most of these belonging to the buccal and lingual nerves), the dorsomedial region of the subnucleus caudalis of the trigeminal sensory nuclear complex (TSNC), and the dorsal horns of the first 5 cervical spinal cord segments (C1-C5). The greatest numbers of crossing fibers in the medullary and cervical dorsal horn segments belonged to the mental and mylohyoid nerves, though these nerves did not project contralaterally to C4-C5. Contralateral buccal and lingual endings were scattered sparsely from the subnucleus caudalis to C5, and only very few contralateral auriculotemporal terminals were observed. Though laminae I-V of the dorsomedial region of the medullary and cervical dorsal horns all exhibited contralateral endings of the mental and mylohyoid nerves, most such endings were found in laminae IIi-III, followed by lamina IV, which suggests their involvement in the reception of mechanical stimuli and in the sensory motor reflexes of the orofacial region. The contralateral buccal and lingual terminals were distributed somatotopically in the first 5 cervical cord segments, with the lingual endings rostral to the buccal terminals within each segment. In C4 and C5 lingual endings appeared exclusively in laminae I and IIo, suggesting that like the ipsilateral lingual projections at this level, which also terminate in these laminae, they may be involved in pain and temperature sensation.

A scanning electron microscope study of the iatrogenic fractures produced by intra-radicular dental techniques.

Iatrogenic fractures are frequently produced by certain dental techniques, such as lateral condensation or the use of intra-radicular screws or pins. In the present study, we have described these fractures by means of the scanning electron microscope. Although several authors have pointed out the difficulty to visualize the iatrogenic fractures, they can be easily showed under the scanning electron microscope.

[Morphology of cracks in enamel surface produced experimentally using high and low temperature]. / Morfologia de las grietas en la superficie del esmalte producidas experimentalmente mediante bajas y altas temperaturas.

A scanning electron microscope study was made to study the morphological changes in the human enamel surface produced by low and high temperatures. Cracked dental enamel was observed when the teeth were exposed at low and high temperatures. When the time of exposition was increased, there are more enamel cracks which may be considered as enamel fractures.

[Scanning electron microscope study of dentin treated with sodium N-monochloro-DL2-aminobutyrate (NMAB)]. / Estudio al microscopio electrónico de barrido de la dentina tratada con N-monocloro-DL2-aminobutirato sódico (NMAB).

This paper report a scanning electron microscope study of the dentinal surface after treatment with sodium N-monochloro-DL2-aminobutyrate (NMAB). The carious cavity shows a rugous and irregular surface. There are detaching plates of the dentin dissolved by the NMAB. At high magnification the compact dentin and the detaching plates show a acid-etched surface.

An experimental study of the colour changes in composite resins.

The composite resins are the most frequently materials employed in restorative odontology. One of the shortcomings is the colour stability. Several workers have reported that colour changes can be considerably avoided with use of photo-polymerized composite resins. However, the present investigation demonstrates that several agents, such as coffee, tea and cola, stain photo-polymerized composite resin samples. The maximum staining was observed in the case of coffee followed by tea, cola being the less chromatic agent of the three.

Otic ganglion parasympathetic neurons innervate the pulp of the mandibular incisor of the guinea pig.

Neurons innervating the pulp of the lower incisor of the guinea pig have been traced using the fluorochrome Fast blue. Besides those located in the ipsilateral Gasser's ganglion, a small number of parasympathetic cells in the ipsilateral otic ganglion were also found to innervate the pulp (chiefly the deepest region) via the inferior alveolar nerve. This is the first anatomical evidence of the presence of parasympathetic fibers in the teeth of mammals. It is suggested that these parasympathetic neurons stimulate the vasodilation of the arterioles supplying the tooth pulp.

Identification of abducens motoneurons, accessory abducens motoneurons, and abducens internuclear neurons in the chick by retrograde transport of horseradish peroxidase.

The location of the motoneurons innervating the lateral rectus, pyramidalis, and quadratus muscles of the chick has been determined by application of horseradish peroxidase (HRP) to these muscles and their nerve branches, and internuclear neurons in the abducens nucleus have been identified by injection of HRP into the oculomotor nucleus. Quantitative results were obtained by means of a semiautomatic image analyzer. Lateral rectus motoneurons were observed only in the ipsilateral principal abducens nucleus, where they numbered 500-550, and quadratus and pyramidalis motoneurons only in the ipsilateral accessory abducens nucleus. The 325-375 internuclear neurons that appeared in the principal abducens nucleus contralateral to the oculomotor nucleus injected with HRP were practically confined to the rostral two thirds of the nucleus, where they tended to surround the lateral rectus motoneurons in dorsal or lateral positions, though a minority of interneurons also mingled with the motoneurons in the center or at the medial face of the nucleus. Most interneurons were small and elongated, but a minority of larger interneurons morphologically similar to the lateral rectus motoneurons were also distinguishable. The 100-110 quadratus motoneurons and the 45-55 pyramidalis motoneurons mingled in the accessory abducens nucleus were larger than the lateral rectus motoneurons and sent their axons into the ipsilateral abducens nerve.

The postganglionic parasympathetic fibers originating in the otic ganglion are distributed in several branches of the trigeminal mandibular nerve: an HRP study in the guinea pig.

Application of HRP to the proximal stumps of the ramifications of the trigeminal nerve shows that all those belonging to the mandibular branch contain parasympathetic fibers originating in the otic ganglion. The nerve with the largest proportion of these fibers is the auriculotemporal nerve (50-60% of all labeled neurons), while the smallest percentages are found in the lingual nerve and motor root (about 5% each). The presence of otic fibers in the inferior alveolar, mylohyoid, buccal and motor branches of the trigeminal nerve has not hitherto been reported.

Pyrocatechol as a stabilizing agent for o-tolidine and o-dianisidine: a sensitive new method for HRP neurohistochemistry.

A new procedure for detecting HRP in nerve tissue is described which is based on the use of pyrocatechol to stabilize the oxidation products of o-tolidine and o-dianisidine in citric acid/ammonium acetate buffer of pH 4.85. In both cases the precipitate obtained is insoluble, stable and more visible than when any variant of the diaminobenzidine method is employed, and the morphological image of neurons and nerve fibres labelled with HRP is superior to that produced by the tetramethylbenzidine/sodium nitroprusside method. There is no non-specific precipitation, and no retraction of nerve tissue has been observed. The performance of the method is improved further using either o-tolidine/pyrocatechol or o-dianisidine/pyrocatechol in conjunction with glucose oxidase, which may be useful if it is desired to obtain Golgi-like images of HRP-bearing cells or to display weakly HRP-labelled nerve fibres.