The influence of environmental temperature on appetite-related hormonal responses

Background

Acute exercise in the heat has been shown to reduce appetite. However, the influence of exercise in the cold on appetite regulation remains unclear. The aim of this study was to compare exercise-induced appetite regulation under three different environmental temperatures.

Methods

Eleven male participants completed three experimental trials on the following separate days: exercise in the heat (36°C), exercise at neutral temperature (24°C), and exercise in the cold (12°C). The exercise trials consisted of pedaling exercises for 30 min at 65% of maximal oxygen uptake (VO_2max). Blood samples were collected repeatedly to determine plasma ghrelin, peptide YY (PYY) and other hormonal concentrations. Subjective feelings of hunger and tympanic temperature were also monitored.

Results

Tympanic temperature was significantly higher in the 36°C trial than that of the other two trials (P < 0.05). The subjective feelings of hunger in the 36°C and 24°C trials were significantly lower than those in the 12°C trial (P < 0.05). Plasma ghrelin concentration decreased significantly with exercise in all conditions (P < 0.05), and the responses were not significantly different among the three conditions. Plasma PYY concentration increased significantly after the exercise in the 24°C trial only (P < 0.05), with no significant difference among the three trials.

Conclusions

These results suggest that exposure to hot or cold temperatures during exercise did not affect exercise-induced plasma ghrelin and PYY responses. However, the exercise-induced reduction of subjective hunger was significantly attenuated in a cold environment.     

Estrous Cycle-Dependent Phasic Changes in the Stoichiometry of Hippocampal Synaptic AMPA Receptors in Rats

Cognitive function can be affected by the estrous cycle. However, the effect of the estrous cycle on synaptic functions is poorly understood. Here we show that in female rats, inhibitory-avoidance (IA) task (hippocampus-dependent contextual fear-learning task) drives GluA2-lacking Ca²⁺-permeable AMPA receptors (CP-AMPARs) into the hippocampal CA3-CA1 synapses during all periods of the estrous cycle except the proestrous period, when estrogen levels are high. In addition, IA task failed to drive CP-AMPARs into the CA3-CA1 synapses of ovariectomized rats only when estrogen was present. Thus, changes in the stoichiometry of AMPA receptors during learning depend on estrogen levels. Furthermore, the induction of long-term potentiation (LTP) after IA task was prevented during the proestrous period, while intact LTP is still expressed after IA task during other period of the estrous cycle. Consistent with this finding, rats conditioned by IA training failed to acquire hippocampus-dependent Y-maze task during the proestrous period. On the other hand, during other estrous period, rats were able to learn Y-maze task after IA conditioning. These results suggest that high estrogen levels prevent the IA learning-induced delivery of CP-AMPARs into hippocampal CA3-CA1 synapses and limit synaptic plasticity after IA task, thus preventing the acquisition of additional learning.     

Structure-activity relationships of endothelin: importance of the C-terminal moiety

The vasoconstrictor activities of various forms of derivatives of endothelin (ET) were characterized in vitro by measuring the contraction of porcine coronary artery strips. The removal of the C-terminal Trp21 reduced the molar potency of the peptide by nearly 3 orders of magnitude. The removal of amino acid residues from the C-terminus of ET(1-20) further attenuated the activity. Replacement of Trp21 with D-Trp, reduction and carboxamidomethylation of the four Cys residues, or cleavage at Lys9 by lysyl endopeptidase all lowered the potency approximately 200 fold. While both native ET and [D-Trp21]ET induced a very slow and sustained vasoconstriction, the other derivatives of ET listed above showed a much more rapid kinetics of vasoconstriction. These results indicate that the C-terminal Trp of ET is especially important for the potent and extremely long-lasting vasoconstrictor activity characteristic to ET.     

Smurf2 induces ubiquitin-dependent degradation of Smurf1 to prevent migration of breast cancer cells

Ubiquitin-dependent protein degradation is involved in various biological processes, and accumulating evidence suggests that E3 ubiquitin ligases play important roles in cancer development. Smad ubiquitin regulatory factor 1 (Smurf1) and Smurf2 are E3 ubiquitin ligases, which suppress transforming growth factor-beta (TGF-beta) family signaling through degradation of Smads and receptors for TGF-beta and bone morphogenetic proteins. In addition, Smurf1 has been reported to promote RhoA ubiquitination and degradation and regulate cell motility, suggesting the involvement of Smurf1 in cancer progression. However, the regulation and biological function of Smurf1 and Smurf2 in cancer development remain to be elucidated. In the present study, we show the post-translational regulation of Smurf1 by Smurf2 and the functional differences between Smurf1 and Smurf2 in the progression of breast cancer cells. Smurf2 interacted with Smurf1 and induced its ubiquitination and degradation, whereas Smurf1 failed to induce degradation of Smurf2. Knockdown of Smurf2 in human breast cancer MDA-MB-231 cells resulted in increases in the levels of Smurf1 protein, and enhancement of cell migration in vitro and bone metastasis in vivo. Of note, knockdown of Smurf1, but not of Smurf2, enhanced TGF-beta signaling in MDA-MB-231 cells, suggesting that increased an protein level of Smurf1 offsets the effect of Smurf2 knockdown on TGF-beta signaling. These results indicate that two related E3 ubiquitin ligases, Smurf1 and Smurf2, act in the same direction in TGF-beta family signaling but play opposite roles in cell migration.     

An avian transforming retrovirus isolated from a nephroblastoma that carries the fos gene as the oncogene.

A new avian transforming retrovirus, NK24, was isolated from a chicken with a nephroblastoma. This transforming virus induced fibrosarcomas with osteogenic cell proliferation and nephroblastomas in vivo and transformed fibroblast cells in vitro. From extracts of NK24-transformed cells, anti-gag serum immunoprecipitated a 100-kilodalton nonglycosylated protein with no detectable protein kinase activity. An NK24 provirus present in infected quail cells was molecularly cloned and subjected to nucleotide sequence analysis. The genome of NK24 was 5.3 kilobases long and had a 1,126-base-pair sequence of cellular origin in place of a viral sequence of avian leukosis virus containing the 3' half of the gag gene and the 5' half of the pol gene. Although the entire env gene was retained, it appeared to be inactive, possibly owing to the loss of function of its splice acceptor site as a result of a second deletion of 1,598 bases in the 3' half of the pol gene that extended to the acceptor site. Nucleotide sequence analysis revealed that the NK24 virus contained the fos gene, previously identified as the oncogene of FBJ and FBR murine osteosarcoma viruses. Unlike the v-fos gene products of FBJ and FBR, which suffer a structural alteration at their carboxyl termini, the NK24 v-fos gene product seemed to have the same carboxyl-terminal structure as the chicken c-fos gene product. A comparison of the structures of the products of the NK24 v-fos and mouse c-fos genes suggested that the fos gene product consists of highly conserved regions and relatively divergent regions.     

Distribution by sex of mouse fetuses in the intrauterine position

We examined whether or not the sex of the fetuses of polytocous animals distributes randomly in the position along the uterine horn in 255 mouse litters. The fetal sex ratio did not differ significantly among the three intrauterine segments (ovarian, middle, and cervical). Based on the number of fetuses examined in this study, it can be stated that even if sex ratio differences exist among the segments, the ratio in individual segments would fall mostly inside the ±0.1 range, when the overall sex ratio (M/(M+F)) is around 0.5.     

A comparison of hematological and serum biochemical values between two groups of female cynomolgus monkeys reared under different conditions

The influence of long term rearing conditions on the hematological and serum biochemical values in laboratory-bred female cynomolgus monkeys (Macaca fascicularis) was studied under the following two conditions. Group A: New born infants were nursed by their mothers for at least 12 weeks after birth. After weaning, four monkeys of approximately equal age and body weight were kept in a relatively small cage (90 cm W x 60 cm D x 60 cm H) and reared to five years of age. These rearing conditions are commonly used in the breeding program of our primate center. Group B: One male and five females of wild origin were introduced into a relatively large cage (180 cm W x 180 cm D x 160 cm H). Female monkeys born in these cages were used in this study. All of them were reared by their own mothers and grew well in these cages. Male monkeys born in these cages were removed at about 3.5 years of age. Hematological and serum biochemical values between the two groups in each age class were compared and analyzed by the canonical discriminant analysis (the discriminant analysis with reduction of dimensionality). Age correlated highly with the value of the first canonical variate. The second canonical variate detected a difference in the blood hematology and biochemistry probably induced by the difference in rearing conditions.     

In vitro establishment of tumorigenic human B-lymphoblastoid cell lines transformed by Epstein-Barr virus

We studied tumorigenic and phenotypic characteristics of pre- and postimmortal human B-lymphoblastoid cell lines (LCLs) transformed by Epstein-Barr virus (EBV): preimmortal LCLs showed low telomerase activity and a normal diploid karyotype while postimmortal LCLs showed much higher telomerase activity and maintained a clonal aneuploidic state. Among five postimmortal LCLs tested, LCLs N0005 and N6803 formed colonies in agar medium and showed marked aneuploidy, and N6803 was transplantable into nude mice indicating that it had a complete malignant phenotype, but all preimmortal LCLs and the remaining three postimmortal LCLs lacked these characteristics. The products of tumor suppresser genes, p16(INK4A) and pRb, were downregulated in these two LCLs, and the p53 gene was mutated in N0005 LCL. We believe these results showed for the first time that some postimmortal EBV-transformed LCLs can become tumorigenic, contrary to previous reports, and that these LCLs provide an in vitro model of tumorigenesis induced by EBV.     

15-deoxy-delta 12,14-prostaglandin J2 and laminar fluid shear stress stabilize c-IAP1 in vascular endothelial cells

Laminar shear stress strongly inhibits vascular endothelial cell apoptosis by unknown mechanisms. We reported that shear stress stimulates endothelial cells to produce 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) by elevating the expression level of lipocalin-type prostaglandin D synthase. To investigate the role of 15d-PGJ2 produced in the vascular wall, we examined the effect of 15d-PGJ2 on endothelial cell apoptosis. We induced apoptosis in human umbilical vein endothelial cells (HUVECs) by growth factor deprivation. 15d-PGJ2 strongly inhibited DNA ladder formation, nuclear fragmentation, and caspase-3-like activity in HUVECs. To elucidate the mechanism by which 15d-PGJ2 inhibits endothelial cell apoptosis, we examined expression of the inhibitor of apoptosis proteins (IAP) cellular-IAP1 (c-IAP1), c-IAP2, x-linked IAP, and survivin in HUVECs. In parallel with the inhibition of apoptosis, 15d-PGJ2 elevated the expression level of c-IAP1 protein in a dose- and time-dependent manner without changing the mRNA level. Laminar shear stress also induced c-IAP1 expression. Chase experiments with the use of cycloheximide revealed that 15d-PGJ2 and shear stress both inhibited the proteolytic degradation of c-IAP1 protein. These results suggested that 15d-PGJ2 inhibits endothelial cell apoptosis through, at least in part, c-IAP1 protein stabilization. This mechanism might be involved in the antiapoptotic effect of laminar shear stress.     

Spectral characteristics of the bioluminescence induced in the marine fish,Porichthys notatus,byCypridina (ostracod) luciferin

Summary Specimens ofPorichthys notatus, which are naturally luminous along the coast of California, are non-luminous in Puget Sound. However, luminescence capability may be induced in the adult Puget SoundPorichthys by the administration of purifiedCypridina (ostracod) luciferin, syntheticCypridina luciferin, orCypridina organisms. The bioluminescence emission spectra produced by the Puget Sound fish following induction is similar, if not identical, to that of the naturally luminousPorichthys notatus from California waters (maxima: 485 and 507 nm).