A putative GDP–GTP exchange factor is required for development of the excretory cell in Caenorhabditis elegans

The Caenorhabditis elegans excretory cell extends tubular processes, called canals, along the basolateral surface of the epidermis. Mutations in the exc-5 gene cause tubulocystic defects in this canal. Ultrastructural analysis suggests that exc-5 is required for the proper placement of cytoskeletal elements at the apical epithelial surface. exc-5 encodes a protein homologous to guanine nucleotide exchange factors and contains motif architecture similar to that of FGD1, which is responsible for faciogenital dysplasia. exc-5 interacts genetically with mig-2, which encodes Rho GTPase. These results suggest that EXC-5 controls the structural organization of the excretory canal by regulating Rho family GTPase activities.     

The Gene Encoding Flavanone 3-Hydroxylase is Expressed Normally in the Pale Yellow Flowers of the Japanese Morning Glory Carrying the speckled Mutation Which Produce Neither Flavonol nor Anthocyanin but Accumulate Chalcone, Aurone and Flavanone

The Japanese morning glory carrying the recessive mutable speckledallele with the dominant speckled-activator bears colorlessflowers with fine and round colored spots distributed over thecorolla whereas the plant without the speckled-activator producespale yellow flowers. Previous chemical analysis has indicatedthat a mutation in the gene for flavanone 3-hydroxylase (F3H)is a likely candidate for the speckled allele. However, theF3HmRNA without sequence alteration accumulates normally inthe pale yellow flowers, indicating that the speckled alleleis neither the F3H gene nor a regulatory gene acting on theF3H gene expression. (Received April 4, 1997; Accepted June 2, 1997)     

New PCR-RFLP analysis for the mouse Tnfsf6gld gene caused by a point mutation in the Tnfsf6 [tumor necrosis factor (ligand) superfamily, member 6] locus.

A new polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) analysis was developed for genetic typing of the mouse Tnfsf6gld mutation. An artificial restriction site was introduced to the mouse Tnfsf6gld mutation by PCR amplification using a modified primer. The three genotypes of the Tnfsf6 locus (Tnfsf6gld/Tnfsf6gld, Tnfsf6gld/+, and +Tnfsf6-gld/+Tnfsf6-gld) could be distinguished clearly and easily. This PCR-RFLP analysis was found to be useful for the identification of the mouse Tnfsf6gld mutation.     

Stellate cells storing retinol in the liver of adult lamprey,Lampetra japonica

Summary Distribution, localization and fine structure of the stellate cells in the liver of lamprey, Lampetra japonica, were studied during the spawning migration by use of Kupffer's gold-chloride method, fluorescence microscopy for vitamin A (retinol) and electron microscopy. The stellate cells in the lamprey liver differ in some of their properties from those in mammalian livers. Stellate cells which store abundant retinol in lipid droplets, occur not only in the hepatic parenchyma, but also in the dense perivascular and capsular connective tissue of the liver and in the interstitium of pancreatic tissue. In the hepatic parenchyma these cells are located perisinusoidally or along thick bundles of collagen fibrils. The stellate cells display a number of large retinol-containing lipid droplets, granular endoplasmic reticulum, tubular structures, dense bodies, Golgi complex, microtubules, and microfilaments. In the space of Disse, the stellate cells and extracellular fibrilar components such as collagen fibrils and microfibrils (11–12 nm in diameter) are intervened between the two layers of basal laminae. Differentiation and possible functions of the stellate cells in the lamprey liver are discussed.     

Structure of human phenylethanolamine n-methyltransferase gene: existence of two types of mRNA with different transcription initiation sites

The chromosomal gene for human phenylethanolamine N-methyltransferase (PNMT; EC 2.1.1.28) was isolated from a human genomic library using a cloned human PNMT cDNA as a probe, and the nucleotide sequence was determined. PNMT is encoded in a single gene which consists of three exons. We observed newly the presence of minor PNMT mRNA (type B) besides the major mRNA (type A) as reported previously (Kaneda et al., J. Biol. Chem. 263, 7672–7677, 1988) by Northern hybridization. Type B mRNA carries an approximately 700 nucleotide-long untranslated region in the 5′ terminus. This suggests that two types of mRNA are produced from a single gene through the use of two alternative promoters. A TATA-like sequence locates 30 base pair upstream from the cap site of type A mRNA. Upstream of the cap site, there are several sequences resembling Spl binding sites and glucocorticoid responsive elements, with the latter also found in the first intron.     

Phoresy ofTelenomus sp. (Scelionidae: Hymenoptera), an egg parasitoid of the tussock mothEuproctis taiwana

The phoretic relationship between the egg parasitoidTelenomus sp. cf.euproctidis Wilcox and its host the tussock mothEuproctis taiwana was studied in Okinawa, Japan. One third of the female moths studied in the field carried female parasitoid adults. No male moths carried parasitoids. Parasitoids were observed only in the anal tuft of the moth. Laboratory observation revealed that most of the parasitoids left the body of the moth at the time of the first oviposition of their host and proceeded to lay eggs on the moth egg masses.     

Three-dimensional structure of endothelial cells in hepatic sinusoids of the rat as revealed by the Golgi method

Summary The three-dimensional structure of endothelial cells in the hepatic sinusoids of the rat was studied by application of light- and electron microscopy on Golgi-impregnated specimens. A number of endothelial cells could thus be individually delineated throughout the hepatic lobules. The cytoplasm, showing heavy silver deposits, consists of two distinct areas, a thick and thin portion. The thick portion, issuing from the region of the perikaryon, branches and tapers toward the cell periphery. The thin portion, occupying the remainder of the cytoplasm, consists largely of highly fenestrated sieve plates. Some intralobular variation can be noted; the thick portion of the endothelial cells is well developed in the periportal zone, while the cells in the centrilobular zone are relatively rich in thin portions. In addition, the area of distribution of an individual endothelial cell is larger in the centrilobular sinusoids than in the periportal zone. Some endothelial cells also possess unique cytoplasmic processes projecting into the intercellular space between hepatocytes and connecting the sinusoidal walls of neighboring sinusoids. These processes may anchor the endothelial cells to the hepatic plates.     

The inner ear of gymnophione amphibians and its nerve supply: A comparative study of regressive events in a complex sensory system (Amphibia,Gymnophiona)

Summary The inner ears of representatives of all six gymnophionan families, as well as an ontogenetic series of one species, were studied in order to understand the origin and changes of the amphibian and basilar papillae. The amphibian papilla is in close proximity to the papilla neglecta in some adult gymnophionans. During ontogeny, both epithelia are adherent before they are separated by the formation of the utriculosaccular foramen. The nerve fibers to both epithelia run together, and both epithelia show a comparable variation in size and position among amphibians (amphibian papilla) and among vertebrates (papilla neglecta). Based on these arguments we propose that the amphibian papilla is a translocation of a part of the papilla neglecta specific to amphibians. Present in all primitive gymnophionans, the basilar papilla is lost in all derived gymnophionans. In contrast to anurans, but similar to some urodeles, amniotes, and Latimeria, the basilar papilla rests partly on a basilar membrane. Because of similarities in structure, topology, and innervation, the basilar papilla is suggested to be homologous in Latimeria and tetrapods. The structural differences of most amphibian basilar papillae, compared to those of amniotes and Latimeria, may be due to the different course of the periotic system and the formation of a basilar papillar recess rather than to a separate evolution of this epithelium. In addition to loss of the basilar papilla, some derived gymnophionans have lost the lagena, presumably independently, and the amphibian papilla is extremely reduced in the only genus without a stapes (Scolecomorphus). The papilla neglecta is, for unknown functional reasons, relatively large in aquatic gymnophionans, whereas it is almost lost in some thoroughly terrestrial gymnophionans. The regressive changes in the inner ear are not reflected in obvious changes in the pattern of eighth nerve projection. However, there is a rearrangement of cell masses in the rhombencephalic alar plate of derived gymnophionans, which may be related to the partial or complete loss of lateral line afferents. We propose that the presence of a basilar papilla is a synapomorphy of tetrapods and Latimeria, that the translocation of the papilla neglecta is related to the unique course of the amphibian periotic canal, and that regressive changes in the inner ear are related to the primitive absence of a tympanic ear.     

Patterns of peripheral innervation of the tongue and hyobranchial apparatus in caecilians (Amphibia: Gymnophiona).

The innervation of the musculature of the tongue and the hyobranchial apparatus of caecilians has long been assumed to be simple and to exhibit little interspecific variation. A study of 14 genera representing all six families of caecilians demonstrates that general patterns of innervation by the trigeminal, facial, glossopharyngeal, and vagus nerves are similar across taxa but that the composition of the "hypoglossal" nerve is highly variable. Probably in all caecilians, spinal nerves 1 and 2 contribute to the hypoglossal. In addition, in certain taxa, an "occipital," the vagus, and/or spinal 3 appear to contribute fibers to the composition of the hypoglossal nerve. These patterns, the lengths of fusion of the contributing elements, and the branching patterns of the hypoglossal are assessed according to the currently accepted hypothesis of phylogenetic relationships of caecilians, and of amphibians. An hypothesis is proposed that limblessness and a simple tongue, with concomitant reduced complexity of innervation of muscles associated with limbs and the tongue, has released a constraint on pattern of innervation. As a consequence, a greater diversity and, in several taxa, greater complexity of neuroanatomical associations of nerve roots to form the hypoglossal are expressed.     

Huntington disease in Finland: a molecular and genealogical study

Summary Huntington disease (HD) is found at exceptionally low frequency in the Finnish population. In this population, linkage disequilibrium was earlier established with markers from the D4S10 and D4S43 loci. We now report a continuation to the restriction fragment length polymorphism haplotype analysis, in combination with a genealogical study of all the Finnish HD families. When the HD pedigrees were systematically traced to the 18th century, only one consanguinity was found, and a high percentage (28%) of the families had foreign ancestors. The majority of the Finnish ancestors were localized to border regions or trade centers of the country following the old postal routes. The observed high risk haplotypes formed with markers from the D4S10 and D4S43 loci were evenly distributed among the HD families in different geographical locations. Consequently, the HD gene(s) has most probably arrived in Finland on several occasions via foreign immigrants during the last few centuries.