Spacing and kinship in the Formosan squirrel living in different habitats

Summary Spacing and kinship of the Formosan squirrel, Callosciurus erythraeus thaiwanensis, were studied in two different habitats. One, native habitat in the woods of Kenting, southern Formosa, was rich in available food throughout the year and had several species of predators. The other, a site in Kamakura, central Japan where squirrels had been introduced, had relatively scanty food and few potential predators. 1. Home ranges among males and between sexes overlapped extensively in both habitats. 2. Females occupied exclusive home ranges in Kamakura but had small overlapping home ranges in Ken-ting. 3. Most males disappeared from their natal areas at 1 year old in both habitats (86% in Kamakura and 93% in Ken-ting), but less females disappeared (36% in Kamakura and 35% in Ken-ting). 4. In Kamakura, daughters settled adjacent to the mother or inherited the home range of the mother, but never shared the mother's home range. In Ken-ting, 35% of daughters shared the home range with their mothers. 5. Tolerance among female kin in Ken-ting was probably facilitated by the richness of available food throughout the year, and functioned to reduce predation risk via alarm calling and mobbing.     

Intra- and interspecific variation in body size ofProtohermes (Megaloptera: Corydalidae)

The life history of three populations ofProtohermes grandis and two populations ofProtohermes immaculatus (Megaloptera: Corydalidae) was compared. In general, the larvae lived in stream riffles for 2 years and the adults appeared in summer. Adult body size differed between these closely related species and also between the populations ofP. grandis. Dwarfism occurred inP. immaculatus, a species that is endemic to the small, isolated island, Amami Island. The population ofP. grandis on Yaku Island, located between Amami Island and the mainland Kyushu, had an intermediate body size between that ofP. immaculatus and the mainland population ofP. grandis. Despite being an insular population,P. grandis on Tsushima Island had a similar body size to mainlandP. grandis. In these populations with large adults, some larvae lived in the streams for 3 years. The size distribution of benthic animals, which are the prey available toProtohermes larvae, differed between the streams studied. The density of large prey was lowest on Amami Island, intermediate on Yaku Island, and highest on the mainland and Tsushima Island. Different size distributions of available prey may be caused by the differences of benthic fauna; most of Ecdyonuridae and Ephemerellidae (large mayflies) and Perlidae (large stoneflies) were not found on Amami and Yaku Islands. Thus, there is a tendency to dwarfism in the populations ofProtobermes inhabiting streams where the density of large prey is low.     

Cloning, Nucleotide Sequences and Differential Expression of the nifH and nifH-Like (frxC) Genes from the Filamentous Nitrogen-Fixing Cyanobacterium Plectonema boryanum

The frxC gene, found in liverwort chloroplast DNA, encodes aprotein of unknown function. The deduced amino acid sequenceof the protein shows significant homology to that of ni-trogenaseFe-protein encoded by the nifH gene. We have cloned the frxCand nifH genes from the nitrogen-fixing cyanobacterium Plectonemaboryanum, using frxC- and nifH-specific probes, and have determinedtheir nucleotide sequences. The amino acid sequence deducedfrom the frxC gene of P. boryanum exhibits 83% homology to thatof the protein encoded by the/rxCgene from liverwort, whereasit exhibits only 34% homology to that encoded by the nifH genefrom the same organism, namely, P. boryanum. Northern blot analysisshowed that the frxC gene was transcribed more actively undernitrogenase-repressed conditions than under nitrogenase-inducedconditions, suggesting that the FrxC protein has a functiondistinct from nitrogen fixation. These results, together withthe phylogenetic relationship between the nifH and frxC genes,indicate that the frxC and nifH genes are derived from a commonancestral gene but have evolved independently to encode proteinswith different functions. (Received April 27, 1991; Accepted August 12, 1991)     

Sequence of three members and expression of a new major subfamily of glutelin genes from rice

Three members have been isolated of an additional glutelin gene subfamily, named subfamily B, consisting of about five members per haploid rice genome. Restriction fragment length polymorphism analysis showed major differences between Japonica and Indica lines, indicating the divergence of the subfamily since the split between the two varieties. While corresponding exons of the subfamily B showed 80 to 88% nucleotide sequence homology, those exons were only 60–65% homologous to those of the glutelin A subfamily [15, 19, 24], distinguishing them from the subfamily A. Intron position and derived polypeptide structure, in addition to the nucleotide sequence, confirm the subfamily B members as glutelins. Analysis of RNA from seeds of different stages of development showed that the subfamily B members were expressed at the same time as those of subfamily A, demonstrating coordinated regulation of the two subfamilies.     

On the hoplonemertean Sagaminemertes nagaiensis (Iwata, 1957), with consideration of its systematics

Summary The polystiliferous hoplonemertean Sagaminemertes nagaiensis (Iwata, 1957) has been redescribed.A distinct pre-cerebral region is wanting. The rhynchocoel opens directly at the tip of the head, whilst the mouth opens seperately below the ventral commissure of the brain which is situated at the anterior end of the head. The dorsal ganglia are well developed and extend posteriorly far behind the ventral ganglia. The cerebral sense organs are situated behind the brain and possess posterior ciliated canals. Cephalic glands are poorly represented, but ocelli are well developed. The sickle-shaped basis of the proboscis bears about 20 central stylets. The caecal appendages of the rhynchocoel are arranged pseudometamerically throughout the body. The foregut is straight, consisting of mouth, oesophagus, stomach and pylorus. Intestinal caeca and lateral diverticula are present. The cephalic lacunae have no anterior anastomosis. A cerebral lacuna is present, there is a rhynchocoel vessel, but transverse vessels are absent. The protonephridia extend throughout the foregut region. Mature spermatogonia are well developed.A systematic discussion of Sagaminemertes nagaiensis suggests that it is taxonomically close to Siboganemertes weberi in the archireptantic family Siboganemertidae.     

Intercellular CO2 concentration and water-use efficiency of temperate plants with different life-forms and from different microhabitats

Summary Photosynthesis and transpiration were measured simultaneously, under near-optimum and constant environmental conditions, in intact leaves of plants native to the temperate forest region. A linear relationship between photosynthetic rate and stomatal conductance was found in every species tested irrespective of leaf age or season, indicating that the calculated intercellular CO₂ concentration and water-use efficiency were fairly constant within a species. The values of intercellular CO₂ concentration and water-use efficiency ranged from 221 to 271 l l^–1 and 4.46 to 8.20 mol CO₂ mmolH₂O^–1 (6.24±0.90 mol CO₂ mmolH₂O^–1), respectively. The variations in intercellular CO₂ concentration and water-use efficiency were not directly related to photosynthetic capacities, life-forms, or microhabitat preferences. The intercellular CO₂ concentrations found in this study were close to values reported from cultivated plants and plants native to more arid regions, suggesting a common mechanism to maintain the stomatal conductance proportional to photosynthetic capacity over a wide variety of C₃ plants.     

Binding and crosslinking of 125I-labeled recombinant human tumor necrosis factor to cell surface receptors

Highly purified recombinant human tumor necrosis factor (TNF) (molecular mass determined as 17 kilodaltons (kDa) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and as 36 kDa by Sephadex G-100 gel chromatography) was labeled with 125I to a specific activity of 5 microCi/micrograms without appreciable loss of activity. The binding of 125I-TNF to eighteen human and twelve animal cell lines was examined. The binding varied considerably among different cell lines. In most cell lines, the binding was inhibited up to greater than 90% by the addition of a 100-fold excess of unlabeled TNF. Some human and mouse cell lines showed no significant binding above background levels, suggesting that these cell lines had no receptors for TNF. Among the TNF receptor-positive cell lines, there was no direct correlation between the level of specific TNF binding and the level of sensitivity to the cytotoxic or cytostatic effect of TNF. Some cell lines were sensitive to TNF, whereas others were not affected at all by TNF. The TNF receptor-negative cell lines were also resistant to TNF. Therefore, although the existence of TNF receptor seems to be necessary, it does not alone determine cellular sensitivity to TNF. Scatchard analysis of the binding data revealed that human HeLa S3 and THP-1 had about 50,000 and 10,000 receptors/cell with a dissociation constant (KD) of 0.3-0.5 nM, respectively. Similarly, mouse L-929 and L-M cells had about 5,000 receptors/cell with KD of 3-5 nM. 125I-TNF bound to HeLa S3 cells was rapidly internalized at 37 degrees C, presumably by receptor-mediated endocytosis, and degraded to acid-soluble products. The turnover of TNF receptors on HeLA S3 cells seemed to be rapid, since the level of specific binding quickly decreased after treatment with 100 micrograms/ml of cycloheximide at 37 degrees C with a half-life of about 1.5 h. The crosslinking of the cell-bound 125I-TNF with the use of disuccinimidyl suberate yielded a complex of 105 kDa for HeLa S3 and THP-1 cells, and a complex of 100 kDa for U937 cells. The crosslinking was completely inhibited by the addition of a 100-fold excess of unlabeled TNF. Assuming that the complex was due to a one-to-one association of the dimeric form of TNF (34 kDa) with the receptor, we estimated the molecular size of the human TNF receptor to be 71 kDa for HeLa S3 and THP-1, and 66 kDa for U937.     

Calcium- and Calmodulin-Dependent Phosphorylation of Diphosphoinositide in Acetylcholine Receptor-Rich Membranes from Electroplax of Narke japonica

The phosphorylation of phosphoinositides in the acetylcholine receptor (AChR)-rich membranes from the electroplax of the electric fish Narke japonica has been examined. When the AChR-rich membranes were incubated with [gamma-32P]ATP, 32P was incorporated into only two inositol phospholipids, i.e., tri- and diphosphoinositide (TPI and DPI). Even after the alkali treatment of the membrane, AChR-rich membranes still showed a considerable DPI kinase activity upon addition of exogenous DPI. It is likely that the 32P-incorporation into these lipids was realized by the membrane-bound DPI kinase and phosphatidyl inositol (PI) kinase. Such a membrane-bound DPI kinase was activated by Ca2+ (greater than 10(-6) M), whereas the PI kinase appeared to be inhibited by Ca2+. The effect of Ca2+ on the DPI phosphorylation was further enhanced by the addition of ubiquitous Ca2+-dependent regulator protein calmodulin. Calmodulin antagonists such as chlorpromazine (CPZ), trifluoperazine (TFP), and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7) inhibited the phosphorylation of DPI in the AChR-rich membranes. It is suggested that the small pool of TPI in the plasma membrane is replenished by such Ca2+- and calmodulin-dependent DPI kinase responding to the change in the intracellular Ca2+ level.