Feeding rate as valuable information in primate feeding ecology

In this review I outline studies on wild non-human primates using information on feeding rate, which is defined as the food intake per minute on a dry-weight basis; further, I summarize the significance of feeding rate in primate feeding ecology. The optimal foraging theory has addressed three aspects of animal feeding: (1) optimal food patch choice, (2) optimal time allocation to different patches, and (3) optimal food choice. In order to gain a better understanding of these three aspects, the feeding rate itself or its relevance indices (e.g., rates of calorie and protein intake) could be appropriate measures to assess the quality of food and food patches. Moreover, the feeding rate plays an essential role in estimation of total food intake, because it varies greatly for different food items and the feeding time is not a precise measure. The feeding rate could also vary across individuals who simultaneously feed on the same food items in the same food patch. Body size-dependent and rank-dependent differences in the feeding rate sometimes cause individuals to take strategic behavioral options. In the closing remarks, I discuss the usefulness of even limited data on feeding rate obtained under adverse observational conditions in understanding primate feeding ecology.     

Effects of vitamin C intake on gingival oxidative stress in rat periodontitis

Increased levels of oxidative stress due to excessive production of reactive oxygen species are involved in the pathogenesis of periodontitis. Studies suggest a negative association between plasma vitamin C level and the severity of periodontitis. We hypothesized that increases in plasma vitamin C levels after vitamin C intake might clinically reduce gingival oxidative stress in a rat periodontitis model. A ligature was placed around rat mandibular molars for 4 weeks to induce periodontitis, and the rats were then given drinking water with or without 1 g/L vitamin C for 2 weeks after the ligature was removed. The periodontitis-induced rats showed a 149% increase in 8-hydroxydeoxyguanosine level and a 40% decrease in reduced:oxidized glutathione ratio in gingival tissue. Vitamin C intake induced a 175% increase in plasma vitamin C level, resulting in an improvement in the gingival 8-hydroxydeoxyguanosine level (decreased) and in the reduced:oxidized glutathione ratio (increased). Furthermore, in ligature-induced periodontitis lesions, gene expression encoding inflammation, including interleukin-1 alpha and interleukin-1 beta, was more than twofold down-regulated by vitamin C intake. The results suggest that systemic administration of vitamin C could be clinically beneficial in improving periodontitis-induced oxidative stress by down-regulating inflammatory gene expression.     

Cyclic RGD peptide-labeled upconversion nanophosphors for tumor cell-targeted imaging

One of the great challenges of oncology is to improve methods for early tumor detection. Thus tumor cell-targeted optical imaging has been intensively studied. Bioimaging with upconversion (UC) phosphors (UCPs) is of considerable interest due to a variety of possible applications taking advantage of infrared-to-visible luminescence. Here we report for the first time tumor cell-targeted UC imaging using UCPs modified with cyclic RGD peptide (RGD-Y₂O₃). Cyclic RGD peptide binds specifically to integrin α_vβ₃ which is highly expressed in a tumor cell surface of certain cancer types but not in normal tissues. Since UC emission from RGD-Y₂O₃ was observed for U87MG cancer cell (high integrin α_vβ₃ expression), but not for MCF-7 cancer cell (low integrin α_vβ₃ expression), this UC imaging is considered to be integrin α_vβ₃ specific. The non-invasive imaging of integrin α_vβ₃ expression using UCP-based probes will have great potential in cancer imaging in general in living subjects.     

Cloning, expression and characterization of recombinant sweet-protein thaumatin II using the methylotrophic yeast Pichia pastoris

Thaumatin, an intensely sweet-tasting protein, was secreted by the methylotrophic yeast Pichia pastoris. The mature thaumatin II gene was directly cloned from Taq polymerase-amplified PCR products by using TA cloning methods and fused the pPIC9K expression vector that contains Saccharomyces cerevisiae prepro alpha-mating factor secretion signal. Several additional amino acid residues were introduced at both the N- and C-terminal ends by genetic modification to investigate the role of the terminal end region for elicitation of sweetness in the thaumatin molecule. The secondary and tertiary structures of purified recombinant thaumatin were almost identical to those of the plant thaumatin molecule. Recombinant thaumatin II elicited a sweet taste as native plant thaumatin II; its threshold value of sweetness to humans was around 50 nM, which is the same as that of plant thaumatin II. These results demonstrate that the functional expression of thaumatin II was attained by Pichia pastoris systems and that the N- and C-terminal regions of the thaumatin II molecule do not -play an important role in eliciting the sweet taste of thaumatin.     

A molecular throttle: the recombination hotspot chi controls DNA translocation by the RecBCD helicase

RecBCD enzyme is a heterotrimeric helicase/nuclease that initiates homologous recombination at double-stranded DNA breaks. Several of its activities are regulated by the DNA sequence chi (5'-GCTGGTGG-3'), which is recognized in cis by the translocating enzyme. When RecBCD enzyme encounters chi, the intensity and polarity of its nuclease activity are changed, and the enzyme gains the ability to load RecA protein onto the chi-containing, unwound single-stranded DNA. Here, we show that interaction with chi also affects translocation by RecBCD enzyme. By observing translocation of individual enzymes along single molecules of DNA, we could see RecBCD enzyme pause precisely at chi. Furthermore, and more unexpectedly, after pausing at chi, the enzyme continues translocating but at approximately one-half the initial rate. We propose that interaction with chi results in an enzyme in which one of the two motor subunits, likely the RecD motor, is uncoupled from the holoenzyme to produce the slower translocase.     

Difference in food selection between patas monkeys (Erythrocebus patas) and tantalus monkeys (<Emphasis Type="Italic">Cercopithecus aethiops tantalus</Emphasis>) in Kala Maloue National Park,Cameroon, in relation to nutrient content

Phytochemical or nutrient analyses of primate diets have revealed clues to their food selection in a single species. On the other hand, few interspecific comparisons of phytochemical or nutrient composition of primate diets have been made, although diets are considered to differ in phytochemical or nutrient content from primate species to species, since different species have different body weights and different morphological and physiological characteristics. I compared the nutrient content of diet between patas monkeys (Erythrocebus patas) and tantalus monkeys (Cercopithecus aethiops tantalus) living sympatrically in Cameroon. Patas subsisted on a smaller number of food items, most of which were also tantalus food items. Then, I compared the protein–fiber ratio and the available energy content of the food items eaten by patas (patas foods) with those items eaten only by tantalus (tantalus foods). Both variables were higher in patas than tantalus foods, although there was no significant difference in available energy of plant foods. Next, when I performed discriminant analysis for patas foods and tantalus foods, employing the above two variables, a discriminant function with positive coefficients for both variables was obtained. The mean discriminant-function score of patas foods was higher than that of tantalus foods. Despite being somewhat larger in weight, patas selectively fed on a smaller number of foods of higher quality than did tantalus. I discuss why the results are inconsistent with a well known body weight–diet relationship (Jarman–Bell principle). Energy-efficient locomotion enables patas to exploit not only small dispersed food items of high quality but also areas where high-quality foods are distributed in clumps. Electronic Publication     

Multiplication of a restriction-modification gene complex

Previous works have suggested that some gene complexes encoding a restriction (R) enzyme and a cognate modification (M) enzyme may behave as selfish mobile genetic elements. RM gene complexes, which destroy 'non-self' elements marked by the absence of proper methylation, are often associated with mobile genetic elements and are involved in various genome rearrangements. Here, we found amplification of a restriction-modification gene complex. BamHI gene complex inserted into the Bacillus chromosome showed resistance to replacement by a homologous stretch of DNA. Some cells became transformed with the donor without losing BamHI. In most of these transformants, multiple copies of BamHI and the donor allele were arranged as tandem repeats. When a clone carrying one copy of each allele was propagated, extensive amplification of BamHI and the donor unit was observed in a manner dependent on restriction enzyme gene. This suggests that restriction cutting of the genome participates in the amplification. Visualization by fluorescent in situ hybridization revealed that the amplification occurred in single cells in a burst-like fashion that is reminiscent of induction of provirus replication. The multiplication ability in a bacterium with natural capacity for DNA release, uptake and transformation will be discussed in relation to spreading of RM gene -complexes.     

Effects of fasting on growth hormone/insulin-like growth factor I axis in the tilapia,Oreochromis mossambicus

Effects of fasting on the growth hormone (GH)-insulin-like growth factor I (IGF-I) axis were examined in the tilapia (Oreochromis mossambicus) acclimated to fresh water. Fasting for 2 weeks resulted in significant reductions in body weight, specific growth rate and hepatosomatic index in both males and females. Significant reductions in specific growth rates were observed after 1 and 2 weeks in both sexes, although the decrease in body weight was not significant in the female. A significant reduction was also seen in the condition factor of females after 2 weeks. No change was seen in the gonadosomatic index in either sex. Two weeks of fasting also produced a significant reduction in plasma IGF-I but not in plasma GH, prolactin (PRL(188)) or cortisol. Significant reductions in the hepatic IGF-I mRNA were seen in both sexes. On the other hand, a significant increase was observed in cortisol receptor mRNA in the female liver. Plasma IGF-I levels were correlated significantly with specific growth rate, condition factor and hepatosomatic index, indicating that plasma IGF-I is a good indicator of growth in the tilapia. No change was seen in plasma glucose or osmolality after 2 weeks of fasting. During fasting, tilapia appears to convert metabolic energy from growth to basal metabolism including maintenance of ion and water balance.