Yuko Suzuki

Distinct expression pattern of insulin-like growth factor family in rodent taste buds.

The insulin‐like growth factor (IGF) system is an important regulator of growth and differentiation in a variety of tissues. In the present study, the expression of IGF family members in the taste buds of mice and rats was examined. By reverse transcriptase polymerase chain reaction (RT‐PCR) analysis, mRNA of IGF‐I and ‐II, IGF‐I receptor (IGF‐IR), insulin receptor (insulin R), and IGF‐binding protein (IGFBP)‐2, ‐3, ‐4, ‐5, and ‐6 was detected in the taste bud‐containing epithelium of the circumvallate papillae of mice. As suggested by the study using degenerate PCR (McLaughlin [2000] J. Neurosci. 20:5679–5688), IGF‐IR was expressed in most of the taste bud cells of adult mice, as found by immunohistochemistry, and in those of postnatal day (P) 6 mice by in situ hybridization. Insulin R, which has strong homology to IGF‐IR, was also detected in most of the taste bud cells of mice by immunohistochemistry and in situ hybridization. IGF‐I immunoreactivity was detected in a few taste bud cells and in the epithelium surrounding taste buds. Northern blot analysis revealed that the amount of IGF‐I mRNA in taste bud‐containing epithelium was very low compared with that in liver. IGF‐II immunoreactivity was weakly detected in mouse taste buds and the surrounding epithelium. In the rat tissue, a subset of the taste bud cells was positive for IGF‐II. Among the six IGFBPs, IGFBP‐2, ‐5, and ‐6 were detected in the mouse taste buds: IGFBP‐2 and ‐5 immunoreactivity was seen in the majority of the taste bud cells, whereas IGFBP‐6 immunoreactivity was found in the nerve fibers innervating the taste buds. In situ hybridization study also revealed that IGFBP‐2 and ‐5 mRNA was synthesized in the taste buds of P6 mice and that the expression of these mRNAs overlapped in von Ebners glands. These data reveal that IGF‐I and ‐II might be produced in taste bud cells and (or) surrounding lingual epithelium and act through IGF‐IR and insulin R locally in a paracrine and autocrine manner. The activity of these IGFs may be modulated through their interaction with IGFBP‐2, ‐5, and 6. J. Comp. Neurol. 482:74–84, 2005.

Abdominal abductor muscle in crayfish: Physiological properties and neural control—II. Abdominal movements

1. 1. Activities of crayfish abdominal abductor muscles accompanying the abdominal movements in response to footboard tilts were studied. 2. 2. The asymmetrical activation of aad, aam and aav by footboard tilts about a longitudinal axis produced an abdominal rotation, whereas the symmetrical activation of aad and aam by footboard tilts about a transverse axis produced a slight raise of abdomen. 3. 3. These equilibrium responses were mediated only by the inputs from leg proprioceptive organs. Neither the statocyst nor the eye inputs affected the responses.

Abdominal abductor muscle in crayfish: Physiological properties and neural control—III. Tonic system

1. 1. The tonic system associated with rotational movement of the abdomen of crayfish was investigated electrophysiologically. 2. 2. The medial (aam) and ventral (aav) abdominal abductor muscles consisted exclusively of “slow” fibers. A distinct gradient of fiber diameter distribution observed in aam reflected directly the gradient of fiber property distribution in the muscle. 3. 3. Aam was innervated by 6 exciter motoneurons and 2 inhibitors, while aav was innervated by 5 excitors and 1 inhibitor. There was a functional matching between the properties of the muscle fiber and the innervating motoneuron. 4. 4. The feedback loop consisting of the stretch receptor N cell having no specific receptor muscle in aam and of the innervating motoneuron suggests the existence of different kind of length servo control system from the one utilizing the abdominal MRO.

Computer simulations for a site-specific modeling of indoor radio wave propagation

Modeling of the indoor radio wave propagation accurately is important in order to design and plan wireless LAN (WLAN) networks in the indoor environment. Computer simulations are convenient methods for the purpose. Until now, it was reported that large-scale electromagnetic simulations using the finite difference time domain (FDTD) method could assess characteristics precisely because of its high ability to model an indoor environment numerically. Although they require rich computer resources and longer running times than the other methods, these problems can be solved by using cluster computer systems. During the work it was found that numerical results depended considerably upon the numerical models of indoor environment. An office building consists of primary structures such as concrete walls and floors, and includes furniture in rooms and reinforcing rods in the concrete walls. All components of the structure can be considered in the numerical model. However, it is desirous that a precise modeling of the indoor propagation is carried out using the simpler numerical model. The paper carries out numerical electromagnetic simulations for an indoor radio wave propagation in a whole floor with a WLAN access point at the frequency of 2.4 GHz, and discusses a relationship between the numerical model and the simulation result. It is showed from the consideration that the measured result of received signal strength indicator is almost similar to the numerical result for only the primary structure such as concrete walls and floors. On the other hand, assessments of electric field distributions and Poynting vectors clarify that besides the primary structure, the furniture should be taken into account to predict propagation paths, delay profiles and signal arrival angles precisely.

Stem Cells of Olfactory Cells During Development

There are two types of basal cell in the basal region of the olfactory epithelium of mice: (1) The basal cells proper, which are in direct contact with the basement membrane, are positive for keratin as detected with anti-keratin antibodies [1–4]. (2) The globose basal cells, which lie between basal cells proper and olfactory cell nuclei, or often close to the basement membrane, are stained positively with antineural cell adhesion molecule (N-CAM) antibody [5,6] and are devoid of keratin [2]. An earlier study using [3 H]thymidine autoradiography revealed that basal cells proper divide and give rise to new olfactory cells via globose basal cells because olfactory cells are continuously replaced by stem cells [7]. We reported in a previous study combining immunohistochemistry of keratin with the bromodeoxyuridine (BrdU) method for labeling dividing cells that globose basal cells increase their mitotic activity after axotomy but that basal cells proper do not show any change in their mitotic rate, suggesting that globose basal cells are stem cells of olfactory cells [8]. These two types of basal cell have been shown to differentiate in the basal region of the olfactory epithelium at birth [2]; however, the changes in the mitotic activity of these cells during postnatal development have not been investigated.

Lamellar Bodies of Mouse Taste Buds

It has been reported that fixation with tannic acid preceding osmication preserves saturated phospholipids. Tannic acid reacts with the choline base of phosphatidylcholine and sphingomyelin to form a complex, which is then stabilized by treatment with OsO4 and survives during embedding procedures. Thus, the ordered lamellar structures of phospholipids can be demonstrated under an electron microscope [1].