Chikako Saiki

Angioarchitectural comparison of the filiform papillae of the cat and rabbit using scanning electron microscopic specimens

The functional and morphological characteristics of the fungiform papillae (FuP) on the anterior dorsal surface of the cat and rabbit tongues were studied and compared using a scanning electron microscope (SEM), because the comparison of the functional and morphological relationship of FuP in microvascular cast specimens (MVCS) between these tongues is as yet not clear. In both species, FuP were found to be distributed sporadically among the numerous filiform papillae (FiP). In the cat, in particular, FuP were classified into four types (FuP I-IV) according to the shape and size of a main process (MP) and the number of accessory processes (AP). Each FuP, (FuP I-III lay along oblique lines of FiPs) contained a MP and many APs lying at the anterior basal margin of the MP, whereas FuP IV contained only the small fishnet-ball-shaped MP. In the rabbit, however, only the similar size and shape of the capillary loops, resembling the carnation flower, were scattered among FiPs on the anterior dorsal surface of the fore-tongue. These results suggest that in comparing the functional sense mechanism in both species, the FuP of the rabbit tend to be more simple than those of the cat in respect to taste sense.

ANGIOARCHITECTURAL CLASSIFICATION OF THE FUNGIFORM PAPILLAE IN THE CAT TONGUE

Abstract Three-dimensional structures of the microvascular network of the fungiform papillae (FuP) of the cat tongue were observed by the corrosion cast method under a scanning electron microscope (SEM). FuP were found to be distributed sporadically among the different types of numerous filiform papillae (FiP). A single FuP consisted of the main process (MP) and the accessory process (AP) which were arranged at the anterior basal margin of the MP. FuP can be classified into four types (I∼IV) according to the shape and size of the MP and the number of AP within each FuP. FuP-I to FuP-III contained a large, medium and small MP, showing the small fishnet-ball and oval-ball shapes, and these were surrounded at the anterior basal margin by AP inclining toward the anterior part of the tongue. FuP-IV contained only the small fishnet-ball-shaped MP.

EXCITATORY MECHANISM OF VERATRIDINE ON SLOWLY ADAPTING PULMONARY STRETCH RECEPTORS IN ANESTHETIZED RABBITS

The excitatory effects of veratridine on slowly adapting pulmonary stretch receptors (SARs) were studied before and after administration of ouabain (a Na+-K+ ATPase inhibitor) in anesthetized, artificially ventilated rabbits after vagus nerve section. Administration of veratridine (40 microg/kg) stimulated SAR activity but did not significantly alter tracheal pressure. Administration of ouabain (50 microg/kg) initially stimulated SAR activity during both inflation and deflation, but after 20 min, two different types of SAR responses were observed; one became silent at the peak, of inflation only, and the other maintained excitatory activity during both inflation and deflation phases. Veratridine usually inhibited SAR activity in ouabain-treated animals, irrespective of the difference of ouabain effects. These results suggest that veratridine-induced stimulation of SARs is closely related to the change in the Na+ ion gradient, which is regulated by Na+ pump activity.

Stem cell therapy for central nerve system injuries: glial cells hold the key.

Mammalian adult central nerve system (CNS) injuries are devastating because of the intrinsic difficulties for effective neuronal regeneration. The greatest problem to be overcome for CNS recovery is the poor regeneration of neurons and myelin-forming cells, oligodendrocytes. Endogenous neural progenitors and transplanted exogenous neuronal stem cells can be the source for neuronal regeneration. However, because of the harsh local microenvironment, they usually have very low efficacy for functional neural regeneration which cannot compensate for the loss of neurons and oligodendrocytes. Glial cells (including astrocytes, microglia, oligodendrocytes and NG2 glia) are the majority of cells in CNS that provide support and protection for neurons. Inside the local microenvironment, glial cells largely influence local and transplanted neural stem cells survival and fates. This review critically analyzes current finding of the roles of glial cells in CNS regeneration, and highlights strategies for regulating glial cells’ behavior to create a permissive microenvironment for neuronal stem cells.

Effects of ouabain and flecainide on CO2-induced slowly adapting pulmonary stretch receptor inhibition in the rabbit

The inhibitory effect of CO2 on slowly adapting pulmonary stretch receptors (SARs) was examined before and after administration of ouabain, a Na+-K+ ATPase inhibitor, and flecainide, a Na+ channel blocker. The experiments were performed in anesthetized, artificially ventilated rabbits after vagus nerve section. CO2 inhalation (maximal tracheal CO2 concentration ranging from 9.2 % to 10.4%) for about 60 sec decreased the receptor activity during both inflation and deflation. The magnitude of decreased SAR activity during deflation was greater than that seen during inflation. Administration of ouabain (25 microg/kg) initially stimulated SAR activities during inflation and deflation, and after 20 min, the SAR response was still kept excitatory in both inflation and deflation phases. Under these conditions, CO2 inhalation inhibited SAR activities during inflation and deflation. Flecainide treatment (3 mg/kg) that abolished veratridine (30 microg/kg)-induced SAR excitation had no significant effect on the inhibitory responses of SAR activity to CO2. These results suggest that the inhibitory effect of CO2 occurs when ouabain results in intracellular Na+ concentration ([Na+]i) increases in the SAR endings, and that CO2-induced SAR inhibition may not be related to the reduction of influx of Na+ through voltage-gated Na+ channels.

Angioarchitectural structure of the fungiform papillae on rabbit tongue anterodorsal surface

The relationships between the functional and morphological characteristics and the positional difference of the microvascular cast specimen (MVCS) of the fungiform papillae (FuP) on the antero-dorsal surface of the rabbit tongue were examined and compared using a scanning electron microscope (SEM). The sporadic FuPs scattered among the numerous small filiform papillae (SfP) were found to be distributed irregularly over the antero-dorsal surface. FuPs consisted of the ascending and descending capillary loops, forming margins of the central opening at the top of FuP. They resembled flower-like configurations (carnations), the petals of which ranged from eight to twelve, and they were larger in width and more complex in shape than SfPs with morphological differences. FuPs can be classified into three types: type I (consisting of eight petals), type II (ten petals), type III (twelve petals) according to the shape of FuP, and to the petal number of the flower-like aspect on the eight points of MVCS of FuPs observed by SEM. These results suggest that the petals of the ascending and descending capillary loops of FuP expanded the flower-like figure, increased in the surface areas and effectively play a role in receiving the sense of taste.

Functional and morphological observations on the microvascular structure of the filiform and fungiform papillae in the cat tongue

The purpose of this study was to undertake a three-dimensional comparative observation of the microvascular cast specimen (MVCS) of the filiform papillae (FiP) and fungiform papillae (FuP) on the dorsal surface of the cat tongue. By means of the corrosive resin casting technique, the MVCS of the FiP and FuP of the cat tongue were prepared and examined in detail under the scanning electron microscope (SEM). The numerous FiP and FuP distributed sporadically among the different types of the FiP were found on the entire dorsal surface of each cat tongue. A single FiP consisted of a main process (MP) which contained a large spoon-shaped concave network process and the accessory process (AP) contained a bundle of spine-like processes, arranged in a circle at the basal margin of the MP. The FiP can be classified into five types (Type I-V) according to the shape and size of the MP and numbers of the AP. Each FuP consisted of a single MP which contained an ovoid head and many AP surrounding the basal margin of the MP. The FuP can be classified into four types (FuP I-IV) according to the shape and size of the MP and numbers of the AP. The MP of the FuP, a sense organ for taste, of the cat tongue was considered to be a transformed type from the MP of the FiP, which acquires the ability to masticate and swallow functionally.

Inhibitory mechanism of slowly adapting pulmonary stretch receptors after release from hyperinflation in anesthetized rabbits

In anesthetized, artificially ventilated rabbits with vagus nerve section, release from 10 consecutive hyperinflations (inflation volume = 3 tidal volume) caused an inhibition of the slowly adapting pulmonary stretch receptor (SAR) activity for 16-22 sec. Intravenous administration of tetraethylammonium (TEA, 10 and 20 mg/kg), a K+ channel blocker, did not significantly alter either basal SAR discharge or tracheal pressure (PT). Although TEA treatment at 10.0 mg/kg had no significant effect on the magnitude and duration of inhibited SAR activity seen after release from hyperinflation, the increasing dose of this K+ channel blocker up to 20 mg/kg inhibited these effects of the receptor activity but this inhibition was small. The Na+ -K+ ATPase inhibitor ouabain (5 and 10 microg/kg) that had no significant effect on SAR activity and P(T) in the control abolished or attenuated the inhibitory action of SARs in a dose-dependent manner. Furthermore, the changes in dynamic lung compliance (Cdyn) and P(T) in response to post-hyperinflation were not significantly influenced by pretreatment with either TEA or ouabain. These results suggest that the inhibitory action of receptors seen during post-hyperinflation corresponded with the induction of slow afterhyperpolarization (sAHP), and that the mechanism of generating the sAHP of SARs is mainly mediated by the activation of Na+ -K+ pump activity.

Angioarchitectural structure of the fungiform papillae on the anterodorsal surface of the rat tongue

To ascertain whether the microvascular morphological differences of fungiform papillae (FuP) on the anterodorsal surface of the rat tongue are locationally and functionally related, this study aimed at examining and comparing, in greater detail, the comparative morphological characteristics of FuP. FuP were sporadically and consistently scattered among numerous filiform papillae (FiP) in three parts: the apical, central and in front of the intermolar eminence on the anterodorsal surface. We studied these by means of the microvascular cast specimen (MVCS) of FuP using scanning electron microscopy (SEM). The results obtained in this study showed that in all three parts on the anterodorsal region, the capillary bed of FuP presented as a netbasket-like and cylindrical figure with a central hole consisting of 4-5 horizontal rings of several ascending and descending roots. FuP in the central part on the anterodorsal region were relatively larger in size and more cylindrical in shape than those of both the other parts, and they play the leading part as sensory organs for the taste sense and were regarded as taste receptive organs.

Numerical variation and distributive pattern on micro vascular cast specimens of vallate papillae in the crossbred Japanese cat tongue

In order to examine in detail the numerical variation and distributive pattern of vallate papillae (VaP) on the lingual posterior dorsal surface of the crossbred Japanese cat tongue, macroscopic, stereoscopic and scanning electron microscopic studies by means of a microvascular cast specimen (MVCS) were carried out under the scanning electron microscope (SEM). Regardless of sex, there were 4-8 VaPs in number, with an average of 6, forming 2-4 pairs arranged by type which could be observed symmetrically or asymmetrically on both sides of the posterior dorsal region of the tongue surface. The results of this study showed that the distributive pattern of VaP can be classified into six forms: typical forms I (2 left and 2 right), II (3:3) and III (4:4); and forms IV (2:3), V (2:4) and VI (3:2) were atypical. It seems that there is every probability that statistically another atypical form (3:4), (4:2), (4:3) will appear in the future. Nevertheless, in a large number of studies on the lingual papillae of the cat tongue, 8 VaPs arranged in pairs by type have been found (form III (4:4)) has not yet been reported in the crossbred Japanese cat tongue.