Vascular anatomy and tissue osmolality in the filiform and fungiform papillae of the cat's tongue

The vascular anatomy of the filiform and fungiform papillae of the feline tongue was studied by i.a. injection of India ink. Vascular loops of various appearances were found in the types of papillae studied, i.e. the large and the small filiform papillae and the fungiform ones. Such hairpin loops may function as counter-current exchangers and to test this hypothesis tissue osmolality was determined in the papillae, while exposing them to various isotonic electrolyte solutions. The large filiform papillae with a vascular arrangement similar to that of intestinal villi exhibited a marked osmolar gradient from tip to base when exposed to a solution containing both glucose and sodium. If sodium and/or glucose was excluded from the solution, tissue osmolality was significantly decreased. This was also the case when the chloride ions of the solution was substituted with sulphate. The small filiform papillae are only provided with one or a few capillary loops. They exhibited a less marked osmolar gradient than the large ones and none of the different electrolyte solutions decreased the gradient. In the fungiform papillae a tissue hyperosmolality at the tip was also demonstrated. It is proposed that the papillary epithelium is provided with active transport mechanism(s) and that the papillary vessels function as countercurrent multipliers. The functional importance of these mechanisms are tentatively discussed.     

Vascular anatomy and tissue osmolality in the filiform and fungiform papillae of the cat's tongue.

The vascular anatomy of the filiform and fungiform papillae of the feline tongue was studied by i.a. injection of India ink. Vascular loops of various appearances were found in the types of papillae studied, i.e. the large and the small filiform papillae and the fungiform ones. Such hairpin loops may function as countercurrent exchangers and to test this hypothesis tissue osmolality was determined in the papillae, while exposing them to various isotonic electrolyte solutions. The large filiform papillae with a vascular arrangement similar to that of intestinal villi exhibited a marked osmolar gradient from tip to base when exposed to a solution containing both glucose and sodium. If sodium and/or glucose was excluded from the solution, tissue osmolality was significantly decreased. This was also the case when the chloride ions of the solution was substituted with sulphate. The small filiform papillae are only provided with one or a few capillary loops. They exhibited a less marked osmolar gradient than the large ones and one of the different electrolyte solutions decreased the gradient. In the fungiform papillae a tissue hyperosmolality at the tip was also demonstrated. It is proposed that the papillary epithelium is provided with active transport mechanism(s) and that the papillary vessels function as countercurrent multipliers. The functional importance of these mechanisms are tentatively discussed.     

Formation of ectopic neuromuscular junctions in adult rats

The formation of ectopic neuromuscular junctions between a transplanted foreign nerve (the superficial fibular nerve) and the denervated soleus muscle was examined in adult rats. Formation of new junctions was induced by denervating the soleus muscle by cutting the tibial nerve. Junctional transmission began 3 days after denervation when denervation was done 3 weeks after transplantation of the foreign nerve, and progressively later when denervation was done 8, 16 and 24 weeks after transplantation. The rate at which the transmission, once started, acquired mature characteristics was approximately the same in each case. Initially, spontaneous m. e.p. p.s were infrequent, long lasting with a skewed amplitude distribution. The e. p.p. s evoked by stimulation of the foreign nerve were then commonly below threshold for eliciting action potentials and were occasionally no larger than the size of the spontaneous m. e.p. p.s. M.e. p.p. characteristics became normal in the 2nd week after transmission had started. Fully effective evoked transmission with every innervated fibre responding with overshooting action potential occurred 1–3 months after onset of transmission.     

Functional role and angioarchitectural arrangement of the filiform and fungiform papillae on the medial-dorsal surface of the beagle dog tongue.

A scanning electron microscopic study has been performed on the three-dimensional morphological structure and functional arrangement in microvascular cast specimens (MVCS) of the filiform (FiP) and fungiform papillae (FuP) of the entire medial-dorsal surface of the caudal portion of the beagle dog tongue. The characteristics and functional arrangements of each FiP and FuP were as follows: The FiPs densely and geometrically covered the entire medial-dorsal surface. The outer structure of the FiPs was composed of both the main process (mp) and accessory process (ap). These were formed by both the ascending and descending branches and originating in their tributaries was a spoon-like capillary micronetwork structure with a sharp arrowhead-like top. The mp inclined posteriorly and the ap anteriorly. On the other hand, the outer structure of the FuPs was a rounded papillary body composed of a capillary microvascular network consisting of the ascending and descending branches just as the FiPs. They were distributed sporadically along the oblique eines of FiPs in a V running from both peripheral edges in the posterocentral direction. It has been conjectured that the FiPs play a concentric functionally important role in transporting food and liquid from both the peripheral edges to the postero-central part or towards the pharynx, and on the other hand the FuPs play an assisting role in receiving gustatory sensations from the masticated food and liquid on the medial-peripheral and central-dorsal surface of the caudal portion of the beagle dog tongue.     

Limited survival of adult human testicular tissue as ectopic xenograft

BACKGROUND: Grafting of testicular tissue into immunodeficient mice has become an interesting and promising scientific tool for the generation of gametes and the study of testicular function. This technique might potentially be used to generate sperm from patients whose testes need to be removed or are destroyed due to therapeutic intervention or as a consequence of disease. Here we explore whether adult human testicular tissue from patients with different testicular pathologies survives as xenograft. METHODS AND RESULTS: Testis tissue from adult patients with varying degrees of spermatogenesis was grafted into two strains of immunodeficient mice (severe combined immunodeficiency, Nu/Nu). Tissue with active spermatogenesis prior to grafting largely regressed. However, testicular tissue survival was better in cases where spermatogenesis was suppressed prior to grafting and occasionally spermatogonial stem cells survived. Cases with spermatogenic disruption were not corrected by the xenografting. CONCLUSION: Superior survival of the germinal epithelium and spermatogonia when spermatogenesis was suppressed prior to grafting could provide a novel strategy for germline preservation in pre-pubertal cancer patients. This approach could also be valuable to study the early stages of human spermatogenesis.     

Morphological studies for retrusive movement of the human adult tongue

This study identified the anatomical and close functional relationship between the transverse lingual and superior pharyngeal constrictor muscle. Two en bloc samples (including the tongue and mid-pharyngeal wall) and four whole tongues were obtained from adult human cadavers. We found that fibers of the superior pharyngeal constrictor muscle connected with fibers of the transverse lingual muscle, forming a ring of muscle at the base of the tongue. The average diameters of the transverse muscle fibers increased in size gradually as they approached the base of the tongue. Distribution of the muscle spindles in the transverse lingual muscle and the genioglossus muscle also increased as they reached posteriorly near the base of the tongue. These findings suggest that a ring of muscle formed by the postero-inferior portion of the transverse lingual muscle and the superior pharyngeal constrictor may be largely responsible for the retrusive movement of the tongue and the constrictive movement of the pharyngeal cavity as an antagonist of the genioglossus muscle.     

Neural control of ovulation

Pituitary gonadotrophin function is controlled to a great extentby the central nervous system and by the feedback action (positiveand negative) of sex steroids. Neural structures involved inthis mechanism may be divided into two levels. The first levelis represented by the nervous structures releasing gonadotrophin-releasinghormone (GnRH) in a pulsatile manner into the portal circulation.The gene encoding the precursor protein for GnRH has been descnbedrecently. The precursor protein appears to be composed of 92amino acids, in which the GnRH decapeptide is preceded by asignal pep-tide and followed by a peptide termed GAP for GnRH-associatedpeptide. The GnRH-syntheslzing neurones and the nervous structuressynchronizing the GnRH discharge (pulse generator) in the monkey,and probably also in the human, reside in the medial basal hypothalamus,which appears to have a highly integrated structure. The GnRHpulse generator is influenced by nervous structures outsidethe medial basal hypothalamus (second level of control) as wellas by ovarian and other hormones. These influences probablyimpinge directly or indirectly on the hypothalamic oscillator.Concerning the chemical nature of the substances mediating theaction, a large number of neurotransmitters and neuropeptideshave been reported to influence GnRH secretion.     

Neural control of erection

Penile erection is a vascular event controlled by the autonomic nervous system. The spinal cord contains the autonomic preganglionic neurons that innervate the penile erectile tissue and the pudendal motoneurons that innervate the perineal striated muscles. Sympathetic pathways are anti-erectile, sacral parasympathetic pathways are pro-erectile, and contraction of the perineal striated muscles upon activity of the pudendal nerves improves penile rigidity. Spinal neurons controlling erection are activated by information from peripheral and supraspinal origin. Both peripheral and supraspinal information is capable of either eliciting erection or modulating or inhibiting an erection already present. Sensory information from the genitals is a potent activator of pro-erectile spinal neurons and elicits reflexive erections. Some pre-motor neurons of the medulla, pons and diencephalon project directly onto spinal sympathetic, parasympathetic and pudendal motoneurons. They receive in turn sensory information from the genitals. These spinal projecting pathways release a variety of neurotransmitters, including biogenic amines (serotonin, dopamine, noradrenaline, and adrenaline) and peptides that, through interactions with many receptor subtypes, exert complex effects on the spinal network that controls penile erection. Some supraspinal structures (e.g. the paraventricular nucleus and the medial preoptic area of the hypothalamus, the medial amygdala), whose roles in erection have been demonstrated in animal models, may not project directly onto spinal pro-erectile neurons. They are nevertheless prone to regulate penile erection in more integrated and coordinated responses of the body, as those occurring during sexual behavior. The application of basic and clinical research data to treatment options for erectile dysfunction has recently proved successful. Pro-erectile effects of phosphodiesterase type 5 inhibitors, acting in the penis, and of melanocortin agonists, acting in the brain, illustrate these recent developments.     

Morphogenesis of rat lingual filiform papillae

The morphogenesis of filiform papillae on rat tongue was investigated with the electron microscope. Tongue rudiments were first seen on the 12th day of gestation. At 15–17 days, dermal papillae had formed and were arranged in hexagonal array on the dorsal lingual surface. Capping each dermal papilla was a two-layered epithelium that protruded slightly above the lingual surface, thus forming the early filiform papilla. In the next stage of development, at 18–19 days of gestation, the epithelium lining the papilla had differentiated into two cell populations, one producing hard keratin, the other producing soft keratin. Some of the keratinized epithelial cells assumed a position at an acute angle to the tongue surface and extended deep into the epithelium. In the next stage, 20–21 days, a cleft appeared within these angularly oriented cells. This resulted in the division of the epithelium into keratin-lined individual filiform papillae. Finally, the individual papillae increased in size to the adult form.     

Neural circuits underlying tongue movements for the prey-catching behavior in frog: distribution of primary afferent terminals on motoneurons supplying the tongue

The hypoglossal motor nucleus is one of the efferent components of the neural network underlying the tongue prehension behavior of Ranid frogs. Although the appropriate pattern of the motor activity is determined by motor pattern generators, sensory inputs can modify the ongoing motor execution. Combination of fluorescent tracers were applied to investigate whether there are direct contacts between the afferent fibers of the trigeminal, facial, vestibular, glossopharyngeal-vagal, hypoglossal, second cervical spinal nerves and the hypoglossal motoneurons. Using confocal laser scanning microscope, we detected different number of close contacts from various sensory fibers, which were distributed unequally between the motoneurons innervating the protractor, retractor and inner muscles of the tongue. Based on the highest number of contacts and their closest location to the perikaryon, the glossopharyngeal–vagal nerves can exert the strongest effect on hypoglossal motoneurons and in agreement with earlier physiological results, they influence the protraction of the tongue. The second largest number of close appositions was provided by the hypoglossal and second cervical spinal afferents and they were located mostly on the proximal and middle parts of the dendrites of retractor motoneurons. Due to their small number and distal location, the trigeminal and vestibular terminals seem to have minor effects on direct activation of the hypoglossal motoneurons. We concluded that direct contacts between primary afferent terminals and hypoglossal motoneurons provide one of the possible morphological substrates of very quick feedback and feedforward modulation of the motor program during various stages of prey-catching behavior.     

Morphological studies of rat lingual filiform papillae

In an attempt to elucidate the functions of three types of filiform papillae in the rat's tongue, corrosive resin casts of the microvessels in the filiform papillae were observed under the scanning electron microscope. The filiform papillae were also examined by light and transmission electron microscopy. The three dimensional architecture of the microvessel loops in the small conical filiform papillae was relatively simple with limited divergence and anastomosis in the papillae, whereas that in the large conical filiform papillae formed a complex network which resulted from repeated divergence and anastomosis. The microvessels in the thready filiform papillae branched several times in the primary papillae and then formed a hairpin-like loop in each of the secondary papillae. Under the light and transmission electron microscope, the small and large conical filiform papillae revealed remarkably similar tissue architectures, with the exception of their sizes. However, these two types of filiform papillae were arranged in quite opposite directions. In the large conical filiform papillae, the epithelium on the anterior side of the papillae lacked a granular layer, whereas the epithelium on the posterior side contained a well-developed granular layer. Based on these findings, we presume that the functions of the three type of filiform papillae are as follows. That of the small conical filiform papillae is to take food efficiently into the oral cavity. That of the large conical filiform papillae is to grind further the food which has been crushed with the teeth in coordination with the palate. The thready filiform papillae might function as a heat-releasing organ and be involved in the control of body temperature.     

Neural control of limb coordination

Summary This study examines the effect of removing input descending from the brain on the production of the distinctive leg motor patterns of walking and hatching by spinal circuitry of 0- to 3-day old posthatching chicks. Transection of the cervical spinal cord was performed and chicks were tested between 2 and 28 h after surgery. Walking with good weight support could be elicited from many spinal chicks when placed on a moving treadmill belt. In some cases, sensory stimulation resulting from tail and/or wing pinch was also used. Placing spinal chicks in the hatching position in glass eggs was sufficient to elicit hatching-like leg movements in some animals. Wing pinch was used to elicit more or longer episodes of leg movements. Quantitative analyses of EMG recordings from 6 leg muscles were used to evaluate the changes in motor patterns after cervical spinal transection. Most of the characteristic features of walking and hatching are maintained after descending input from the brain is eliminated. Each muscle is activated in the double or single bursting pattern typical of the normal behavior. Characteristic phase relationships are also preserved. In addition, burst duration versus cycle period relationships seen during the normal behaviors are maintained in the spinal animals. This shows that circuitry located in the spinal cord can produce these distinctive aspects of the hatching and walking motor patterns in the absence of brain input. While many features of walking and hatching patterns were maintained in spinal animals, some changes were noted. For example, although interlimb patterns of coordination are unchanged during spinal hatching and in many sequences of spinal walking, they do become more variable during some sequences of spinal walking. This suggests that descending input from the brain normally plays a role in stabilizing interlimb alternation during walking. An increase in cycle period is seen during walking in spinal chicks. In addition, the relative durations of hip and ankle flexor bursts (expressed as percent of cycle period) increase in both behaviors. Because these changes are also seen in chicks with lumbosacral deafferentations, they may represent the response of the pattern generating circuitry to any reduction in input. In some animals, cervical spinal transection was combined with lumbosacral deafferentation so that both brain input and sensory input from the legs were removed from the spinal cord. Results from these animals were similar to those from animals with deafferentation alone in that the walking and hatching patterns converged, but did not become identical (Bekoff et al. 1987). The remaining differences may be due to the use of some unique elements of pattern generating circuitry in each behavior, or to differences in the remaining input to the same pattern generating circuitry. A possible source for such differences in input is the undeafferented neck region.     

Neural control of gene recruitment in metazoans

Gene recruitment played a critical role in metazoan evolution. Yet, there is no consensus on whether it is an accidental event or a result of an inherent “gene recruiting” mechanism. The prevailing opinion among biologists is that gene recruitment results from random changes in genes or their regulatory regions, but the supporting evidence is poor and controversial. Herein, I present a mechanism in which gene recruitment is a neurally determined event, an adaptive response to changes in environmental conditions. In support of the hypothesis, I present evidence on the manipulative expression of genes in the central nervous system, as well as neurally determined examples of gene recruitment in transgenerational developmental plasticity and in evolution of metazoans Developmental Dynamics 240:1–8, 2011. © 2010 Wiley‐Liss, Inc.