Effects of moderate hyperthyroidism and time relative to feeding on tissue responsiveness to insulin in sheep

The effects of moderate hyperthyroidism and time relative to feeding on tissue responsiveness to insulin were determined in four sheep using a hyperinsulinemic euglycemic clamp procedure, because thyroid hormones have glucoregulatory function in ruminants and non-ruminant animals. The sheep were fed alfalfa hay cubes and corn-based concentrates. They were intravenously injected in turn with saline (control treatment) and then with triiodothyronine (1.5 nmol d(-1); T3 treatment) once daily for 23 days for each treatment. The glucose clamp procedure was performed at four different times relative to feeding (before, during and after feeding) in both treatments. Insulin was intravenously infused at a constant rate of 6.0 mU (kgxmin)(-1) for 2 h and a glucose solution was infused to maintain euglycemia. Plasma T3 concentrations were higher (P=0.0001) for the T3 treatment than for the control treatment (4.0 and 1.3 nmol l(-1), respectively). For the glucose clamp procedure, glucose infusion rates were greater (P=0.0001) for the T3 treatment than for the control treatment, and were greater (P<0.05) during feeding than before feeding and after the end of feeding, but no interaction was detected. In conclusion, tissue responsiveness to insulin in sheep was independently enhanced by moderate hyperthyroidism induced by intravenous T3 injection and feeding.     

Interaction of elongation factor-1alpha and pleckstrin homology domain of phospholipase C-gamma 1 with activating its activity

The pleckstrin homology (PH) domain is a small motif for membrane targeting in the signaling molecules. Phospholipase C (PLC)-gamma1 has two putative PH domains, an NH(2)-terminal and a split PH domain. Here we report studies on the interaction of the PH domain of PLC-gamma1 with translational elongation factor (EF)-1alpha, which has been shown to be a phosphatidylinositol 4-kinase activator. By pull-down of cell extract with the glutathione S-transferase (GST) fusion proteins with various domains of PLC-gamma1 followed by peptide sequence analysis, we identified EF-1alpha as a binding partner of a split PH domain of PLC-gamma1. Analysis by site-directed mutagenesis of the PH domain revealed that the beta2-sheet of a split PH domain is critical for the interaction with EF-1alpha. Moreover, Dot-blot assay shows that a split PH domain specifically binds to phosphoinositides including phosphatidylinositol 4-phosphate and phosphatidylinositol 4, 5-bisphosphate (PIP(2)). So the PH domain of PLC-gamma1 binds to both EF-1alpha and PIP(2). The binding affinity of EF-1alpha to the GST.PH domain fusion protein increased in the presence of PIP(2), although PIP(2) does not bind to EF-1alpha directly. This suggests that EF-1alpha may control the binding affinity between the PH domain and PIP(2). PLC-gamma1 is substantially activated in the presence of EF-1alpha with a bell-shaped curve in relation to the molar ratio between them, whereas a double point mutant PLC-gamma1 (Y509A/F510A) that lost its binding affinity to EF-1alpha shows basal level activity. Taken together, our data show that EF-1alpha plays a direct role in phosphoinositide metabolism of cellular signaling by regulating PLC-gamma1 activity via a split PH domain.     

Microdistribution of alpha particles in pathological sections of tissues from thorotrast patients detected by imaging plate autoradiography

Thorotrast is a colloidal suspension of radioactive (232)ThO(2) that naturally emits alpha particles (90%), beta particles and gamma rays (10%). Thorotrast was used as a radiographic contrast agent in the 1930s-1950s; it caused liver cancer several decades after injection because of its life-long deposition and exposure. Determination of the amount and the distribution of radioactive thorium are essential for assessment of radiation risks. We visualized alpha particles on ordinary archival tissue sections using an imaging plate and a BAS5000 image analyzer. Furthermore, we confirmed that the imaging system is sensitive enough to detect alpha particles and accurate in measuring the total amount of thorium deposited in the organ from a single tissue section. This method revealed that the amount of thorium deposited in tumor tissue is correlated to that in non-tumor tissue. Thorotrast deposition was not associated with DNA damage determined by histochemistry. In combination with histological findings, it is suggested that radioactive thorium always migrates within the deposited organs by macrophages, and that the organs are evenly exposed to alpha particles.     

A reaction-diffusion model for interference in meiotic crossing over

One crossover point between a pair of homologous chromosomes in meiosis appears to interfere with occurrence of another in the neighborhood. It has been revealed that Drosophila and Neurospora, in spite of their large difference in the frequency of crossover points, show very similar plots of coincidence-a measure of the interference-against the genetic distance of the interval, defined as one-half the average number of crossover points within the interval. We here propose a simple reaction-diffusion model, where a "randomly walking" precursor becomes immobilized and matures into a crossover point. The interference is caused by pair-annihilation of the random walkers due to their collision and by annihilation of a random walker due to its collision with an immobilized point. This model has two parameters-the initial density of the random walkers and the rate of its processing into a crossover point. We show numerically that, as the former increases and/or the latter decreases, plotted curves of the coincidence vs. the genetic distance converge on a unique curve. Thus, our model explains the similarity between Drosophila and Neurospora without parameter values adjusted finely, although it is not a "genetic model" but is a "physical model," specifying explicitly what happens physically.     

Genomic organization and mutational analysis of KVLQT1, a gene responsible for familial long QT syndrome

To elucidate the role of the KVLQT1 gene in the pathogenesis of long QT syndrome (LQTS), we have established a screening system for detecting KVLQT1 mutations by the polymerase chain reaction-single strand conformation polymorphism technique (PCR-SSCP). We first determined exon/intron boundaries and flanking intronic sequences, and found that the KVLQT1 gene consists of 17 coding exons. Subsequently, we synthesized oligonucleotide primers to cover the coding region and the flanking intronic sequences, and searched for mutations in 31 Japanese LQTS families. When genomic DNA from each proband was examined by PCR-SSCP followed by direct DNA sequencing, mutations were detected in five families; two independent families carried the same mutation and three of the four were novel. Each mutation was present in affected relatives of the respective proband. This work will enable us to search more thoroughly for LQTS mutations associated with KVLQT1, and eventually will help us in finding genotype/phenotype relationships. Received: 20 March 1998 / Accepted: 30 April 1998     

Alteration of the LIS1 gene in Japanese patients with isolated lissencephaly sequence or Miller-Dieker syndrome

LIS1 is a genetic entity that is responsible for lissencephaly. Previously we have reported isolated lissencephaly sequence(ILS) in a Japanese patient carrying a balanced chromosomal translocation that disrupted the LIS1 gene. We examined mutations of LIS1 in 12 additional Japanese patients, 8 of them with ILS and 4 with Miller-Dieker syndrome (MDS). Fluorescence in situ hybridization (FISH) analysis disclosed deletions of part of the LIS1 gene or of the chromosomal region surrounding it in three of the ILS cases and in three of the MDS cases. In one of the remaining five ILS cases, SSCP analysis and subsequent sequence analysis identified a 1-bp deletion in exon IV, which can be expected to result in premature termination of the gene product. Our results indicate that in Japan, as elsewhere, abnormality of the LIS1 gene is a common cause of MDS/ILS. Received: 20 April 1998 / Accepted: 28 July 1998     

The light/dark cycle operation with an hour-scale period enhances caffeine production by Coffea arabica cells

The intermittent light irradiation with an hour-scale period is used for producing caffeine by Coffea arabica cells. Three factors concerning the light/dark cycle operation such as light intensity, the length of the cycle (period), and the ratio of the illumination time to the dark time (light/dark ratio) were investigated to optimize the caffeine production efficiency regarding light consumption. The light/dark ratio of 1/1 enhanced caffeine production, reaching the same level as continuous light; thus, the intermittent light irradiation improved the production efficiency twofold. The production was not influenced by the period, but was determined by light intensity regardless of intermittent or continuous light irradiation.     

Role of tachykinins in airway responses to ozone in rats

Previousstudies that used neonatal capsaicin (Cap) treatment toablate C fibers indicate that C fibers act to inhibit lung damage andairway hyperresponsiveness after ozone(O₃) exposure in rats. Thepurpose of this study was to determine1) the role of tachykinins in theseprotective effects and 2) whetherdifferences in minute ventilation (E)during O₃ exposure might accountfor the effect of Cap. In the first study, male Sprague-Dawley rats were exposed to 1 part/million O₃or air for 3 h. Four hours later, a bronchoalveolar lavage (BAL) wasperformed or airway responsiveness was measured. Rats were treated withCP-99994 and SR-48968, selective neurokinin-1- and -2-receptorantagonists, respectively, or with vehicle (Veh).O₃ caused an increase in thenumber of neutrophils recovered from BAL fluid in both the Veh-treatedand tachykinin-receptor antagonist (TKRA)-treated rats, but the numberof neutrophils was approximately twofold greater in the TKRA-treatedrats. In contrast, TKRA treatment had no effect on baseline pulmonarymechanics or airway responsiveness. AfterO₃ exposure, the number ofneutrophils in BAL fluid was also greater in Cap- than in Veh-treatedrats. O₃ reducedE in both Veh- and Cap-treated rats,but the response was greater (reduction of 44.7 ± 3.7 vs. 27.8 ± 6.8%) and occurred earlier (10 vs. 70 min) in Cap- than inVeh-treated rats (P < 0.02). Theseresults suggest that tachykinins mediate protective effects of C fibersagainst O₃-induced lunginflammation. The results also indicate that the more pronounced effectof O₃ on BAL neutrophils inCap-treated rats is not the result of a greater inhaled dose ofO₃ resulting from greaterE.

     

Selective Foraging Behavior in Nest-Provisioning Females of Parastrachia japonensis (Hemiptera: Cydnidae): Cues for Preferred Food

Females of Parastrachia japonensis (Hemiptera: Cydnidae) provision nymph-containing nests with drupes of the single host tree, Schoepfia jasminodora (Rosidae: Santales). P. japonensis feeds on the endosperm of these drupes. Foraging females approached and accepted only a few selected drupes for transport to their nests from among the hundreds of drupes scattered on the ground. The characteristics of the drupes that elicited an acceptance response under field conditions were examined. Females estimated the degree of endosperm development using volatile and nonvolatile chemicals in the outer skin as cues and selected only those drupes which had a well-developed endosperm. Although the cues that prompted approach and inspection of a drupe are in the fleshy outer skin, females presented with various substitute drupes coated with outer skin juices of acceptable drupes selected only those they could recognize as a solid mass, suggesting that they used volatile chemicals in the outer skin as cues for approaching and inspecting a drupe and then taste and tactile stimuli as cues for acceptance. Thus, this bug possesses a complex, ecologically sensitive cognitive system that enables it to recognize valuable food items by using reliable cues. The importance of selective foraging by P. japonensis females and the evolutionary significance of this behavior are discussed.