Masayuki Sumida

MRI of intracranial germ cell tumors

We reviewed MRI findings in proven intracranial germ cell tumours in 22 cases, 12 of whom received Gd-DTPA. On T1-weighted images, the signal intensity of the tumour parenchyma was moderately low in 19 cases and isointense in 3; on T2-weighted images, it was high in all cases. Regions of different intensity thought to be cysts were found in 17 (77%): 7 of 12 patients with germinoma (58%) and in all other cases. Of the 13 patients with pineal lesions T1-weighted sagittal images showed the aqueduct to be obstructed in 5, stenotic in 7 and normal in 1. Strong contrast enhancement was observed in all 12 cases. Of the 14 patients with suprasellar lesions, 5 were found to have an intrasellar extension, and in 3 of these, the normal pituitary gland, which could be distinguished from the tumour, was displaced anteriorly. Ten patients (45%) had multiple lesions.

Intracranial germ-cell tumor with synchronous lesions in the pineal and suprasellar regions: Report of six cases and review of the literature

The features of intracranial germ-cell tumor with synchronous lesions in the pineal and suprasellar regions (GCTSPS) in six patients were investigated. GCTSPS accounted for 12.8% of all germ-cell tumors (GCT) in our brain tumor study group. In all cases, the initial symptoms were attributable to the suprasellar lesion, and symptoms due to the pineal GCT developed only after admission. Five of the six cases were histologically diagnosed as germinoma. In all cases, tumors of both regions disappeared after irradiation, resulting in no recurrence for an average of 55.3 months. Our experience and reports in the literature suggest that GCTSPS is highly sensitive to radiation in most cases, although some reports indicated that recurrence is frequent after radiation therapy alone. It is suggested that histological diagnosis in one of the GCTSPS lesions is undertaken to make a plan for the following treatment.

Complete mitochondrial DNA sequence of the endangered frog Odorrana ishikawae (family Ranidae) and unexpected diversity of mt gene arrangements in ranids

We determined the complete nucleotide sequence of the mitochondrial (mt) genome of an endangered Japanese frog, Odorrana ishikawae (family Ranidae). We also sequenced partial mt genomes of three other Odorrana and six ranid species to survey the diversity of genomic organizations and elucidate the phylogenetic problems remaining in this frog family. The O. ishikawae mt genome contained the 37 mt genes and single control region (CR) typically found in vertebrate mtDNAs, but the region of Light-strand replication origin (OL) was triplicated in this species. Four protein-encoding genes (atp6, nd2, nd3, and nd5) were found to have high sequence divergence and to be usable for population genetics studies on this endangered species. Among the surveyed ranids, only two species (Rana and Lithobates) manifested the typical neobatrachian-type mt gene arrangement. In contrast, relatively large gene rearrangements were found in Amolops, Babina, and Staurois species; and translocations of single tRNA genes (trns) were observed in Glandirana and Odorrana species. Though the inter-generic and interspecific relationships of ranid taxa remain to be elucidated based on 12S and 16S rrn sequence data, some of the derived mt gene orders were found to have synapomorphic features useful for solving problematic ranid phylogenies. The tandem duplication and random loss (TDRL) model, the traditional model for mt gene rearrangement, failed to easily explain several of the mt gene rearrangements observed here. Indeed, the recent recombination-based gene rearrangement models seemed to be more suitable for this purpose. The high frequency of gene translocations involving a specific trn block (trnH-trnS1) and several single tRNA genes suggest that there may be a retrotranslocation in ranid mt genomes.

MRI of pineal region tumours: relationship between tumours and adjacent structures

A variety of tumours may arise in the pineal region; accurate diagnosis is important in the selection of treatment and prognosis. A retrospective analysis of the MRI studies of 25 patients with pathologically proven pineal region tumours was performed, focused on the relationship between the tumour and neighbouring structures. Compression of the tectal plate was classified as expansive or invasive, and compression of the corpus callosum as inferior, anterior or posterior. In 10 of the 14 patients (71%) with germ cell tumours tectal compression was of the invasive type; 8 patients (57%) had multiple tumours and in 13 (93%) the tumour margins were irregular. Teratomas were readily diagnosed because of characteristic heterogeneous signal intensity. Pineal cell tumours were differentiated from germ cell tumours by their rounded shape, solid nature, sharp margins, and expansive type of tectal compression. Meningiomas were characterised by their falcotentorial attachments, posterior callosal compression, and a low-intensity rim on T2-weighted images. Gd-DTPA injection enabled clear demonstration of the site and extent of tumour spread and was useful in differentiating cystic and solid components. The appearances described, while not pathognomonic, are helpful in the differential diagnosis of pineal region tumours, and valuable in planning appropriate treatment.

Clinical evaluation of 33 patients with histologically verified germinoma

We evaluated 33 patients with histologically verified germinoma between 1978 and 1992. The patients consisted of 23 men and 10 women between 6 and 32 years of age. All patients underwent either biopsy, partial resection, or total resection. All patients received radiotherapy, and all had a complete remission. Recurrence occurred in three patients. Two recurrences were outside of the irradiated area. Though there were four deaths, none were caused by germinoma. Three resulted from the inadequate hormonal replacement. Accurate staging of patients with germinoma using magnetic resonance imaging (MRI), including whole spinal MRI, and development of a radiochemotherapy or chemotherapy method that preserves the hypothalamic-pituitary axis function are needed.

Inter- and intraspecific evolutionary relationships of the rice frog Rana limnocharis and the allied species R. cancrivora inferred from crossing experiments and mitochondrial DNA sequences of the 12S and 16S rRNA genes

The rice frog Rana limnocharis is widely distributed in Southeast Asia and the rest of the Asian region extending from India to Japan. In Japan, the Sakishima-island populations of this species were regarded as a distinct species based on morphological and genetic divergences. The main purposes of this study were to confirm the presence of intraspecific reproductively isolating mechanisms in the Sakishima-island populations of R. limnocharis, and to clarify molecular inter- and intraspecific relationships of R. limnocharis and an allied species, Rana cancrivora. The hybridization experiments revealed that there were no reproductively isolating mechanisms between the Sakishima-island populations and other populations of R. limnocharis. The molecular evolutionary relationships were investigated by analyzing nucleotide sequences of the mitochondrial 12S and 16S rRNA genes using 12 populations of R. limnocharis from Japan and Taiwan, and two populations of R. cancrivora from Thailand and the Philippines. The phylogenetic trees constructed by the NJ method showed that the two populations of R. cancrivora were clearly separated from the 12 populations of R. limnocharis, and that the 12 populations of R. limnocharis were broadly divided into three clades; the first comprising eight populations from the main islands of Japan, the second comprising the Sakishima-island populations, and the third comprising the Okinawa-island and Taiwan populations. Interestingly, the Okinawa-island and Taiwan populations of R. limnocharis showed a close relationship that possibly reflected a secondary contact between the two populations. Based on the present crossing experiments and molecular data, it seems reasonable to regard the Sakishima-island populations as a single subspecies of R. limnocharis.

Concomitant pituitary adenoma and Rathke's cleft cyst.

Abstract We reviewed the clinical, radiological and surgical findings in patients with both pituitary adenoma and Rathkes cleft cyst. We retrospectively selected patients with both lesions from the 374 patients in whom a sellar/juxtasellar lesion was detected on MRI at 1.5 tesla. All patients received intravenous contrast medium. Concomitant pituitary adenoma and Rathkes cleft cyst were found in eight patients (2.1 %). The frequency of the combination was 3.5 % of pituitary adenomas and 11 % of Rathkes cleft cysts. Symptoms were always due to the adenoma, secreting adrenocorticotrophin in two patients and growth hormone in six. The adenoma was larger in five patients, and the cyst in three. The cysts gave variable signal. The adenoma was adjacent to the cyst in seven patients, and enclosed it in the other patient. As a result of experience with MRI, concomitant pituitary adenoma and Rathkes cleft cyst are now known not to be as rare as thought previously. When a nonenhancing cyst-like structure is demonstrated in a patient with pituitary adenoma, the possibility of a coexisting Rathkes cleft cyst should be considered.

Evolutionary Relationships and Reproductive Isolating Mechanisms in the Rice Frog (Fejervarya limnocharis) Species Complex from Sri Lanka, Thailand, Taiwan and Japan, Inferred from mtDNA Gene Sequences, Allozymes, and Crossing Experiments

Abstract The rice frog (Fejervarya limnocharis) species complex is widely distributed, from India to Japan, and most prevalently in Southeast Asia. Conspicuous morphological variation has been reported for this species complex throughout its distribution range. In the present study, we used mtDNA gene sequence and allozyme analyses to infer evolutionary affinities within this species complex using eight populations (Sri Lanka; Bangkok and Ranong in Thailand; Taiwan; and Hiroshima, Okinawa, Ishigaki and Iriomote in Japan). We also conducted crossing experiments among four populations from Japan, Thailand, and Sri Lanka in order to find out more about the reproductive isolating mechanisms that might exist among the East, Southeast, and South Asian populations of this species complex. The crossing experiments revealed that the Sri Lanka population is reproductively isolated from the Hiroshima, Bangkok, and Ranong populations by complete hybrid inviability, and that the Bangkok population may be reproductively isolated from the Hiroshima population by partial hybrid inviability. Thus, it is not unreasonable to regard the Sri Lanka population as a species separated from F. limnocharis. The mtDNA and allozyme data showed that the Ranong population is most closely related to the Bangkok population in nuclear genome, but more similar to the Okinawa and Taiwan populations in mtDNA genome. The present, preliminary survey may raise questions about the species status of these particular populations and also about the nature of the biological species concept.

Sex-linked genes and linkage maps in amphibians.

This paper reviews sex-linked genes and linkage maps in amphibians. It appears that there is no common ancestral or conserved sex-linkage group in amphibians, whereas an important proportion of other linkage groups has been conserved in amphibians. Comparisons of amphibian linkage maps with those of fishes and mammals reveal several syntenic associations apparently conserved over a very long period of vertebrate divergence.

The Genus Fejervarya (Anura: Ranidae) in Central Western Ghats, India, with Descriptions of Four New Cryptic Species

ABSTRACT We compared six taxa of the genus Fejervarya from central Western Ghats, southwestern India, including F. rufescens, F. sahyadris, and four taxa that possess distinct mtDNA haplotypes as demonstrated by our previous studies. Morphological comparisons with F. brevipalmata, F. keralensis, F. nilagirica, and F. syhadrensis on the basis of literature descriptions and museum specimens revealed that the four haplotypes do not correspond to any of the previously described species. Therefore, they are named herein as new species. Although each of these new species was separated clearly by discriminant analyses, two large-bodied species, as well as two small-bodied species, occurring sympatrically or parapatrically in many collecting sites, were very similar to each other in external appearance. Acoustic characteristics available for five of the six species were most conspicuous and diagnostic features. This study revealed the occurrence of active speciation in Fejervarya in the Western Ghats, one of the hot spots of biodiversity in the world.