Pheromone responsiveness threshold depends on temporal integration by antennal lobe projection neurons

The olfactory system of male moths has an extreme sensitivity with the capability to detect and recognize conspecific pheromones dispersed and greatly diluted in the air. Just 170 molecules of the silkmoth (Bombyx mori) sex pheromone bombykol are sufficient to induce sexual behavior in the male. However, it is still unclear how the sensitivity of olfactory receptor neurons (ORNs) is relayed through the brain to generate high behavioral responsiveness. Here, we show that ORN activity that is subthreshold in terms of behavior can be amplified to suprathreshold levels by temporal integration in antennal lobe projection neurons (PNs) if occurring within a specific time window. To control ORN inputs with high temporal resolution, channelrhodopsin-2 was genetically introduced into bombykol-responsive ORNs. Temporal integration in PNs was only observed for weak inputs, but not for strong inputs. Pharmacological dissection revealed that GABAergic mechanisms inhibit temporal integration of strong inputs, showing that GABA signaling regulates PN responses in a stimulus-dependent fashion. Our results show that boosting of the PNs’ responses by temporal integration of olfactory information occurs specifically near the behavioral threshold, effectively defining the lower bound for behavioral responsiveness.Olfaction is a key element in many aspects of animal behavior, such as foraging, oviposition, and mate recognition. In many moth species, a special class of odorants called sex pheromones plays a critical role for identification of and orientation to potential mates. Because sex pheromones emitted by females are greatly diluted and dispersed in the air, sophisticated olfactory systems to detect minute amounts of sex pheromones and processing systems to translate subtle peripheral sensory responses into appropriate behavioral responses have evolved in male moths. Theoretical calculations have shown that the detection of 170 molecules of the sex pheromone bombykol [(E,Z)-10,12-hexadecadienol] can trigger sexual behavioral responses in males of the silkmoth Bombyx mori (1). The physical and chemical mechanisms in the antennae, the sensilla, and the olfactory receptor neurons (ORNs) responsible for this remarkably high sensitivity, which can detect even a single molecule, are well understood (2, 3). However, it is unclear how a small number of spikes from a small number of ORNs is processed centrally to allow for high behavioral responsiveness.In moths, pheromone molecules are detected by specialized antennal ORNs that express particular pheromone receptor genes (4–10). The axons of ORNs convey pheromone information to the first olfactory center, the antennal lobe (AL; an analog of the vertebrate olfactory bulb). The AL is composed of a number of glomeruli where ORNs establish connections with two types of neurons: projection neurons (PNs), which relay olfactory information to higher brain regions, and local interneurons (LNs), which are involved in processing olfactory information within the deutocerebrum (11). In particular, male ALs have a specialized pheromone-processing unit called the macroglomerular complex (MGC), which comprises several glomeruli (12). In the silkmoth, the toroid glomerulus in the MGC is known to exclusively process bombykol information (13).Previous reports have shown that the sensitivity of pheromone-responsive ORNs is ∼1,000-fold lower than that of PNs tuned to the same pheromone compound (14, 15), suggesting that the AL network amplifies ORN inputs. One possible source of amplification is the high convergence ratio between ORNs and PNs (16). Considering the small size of most antennae, spatial integration would be likely to occur; however, the fact that weak stimuli activate a few ORNs at best calls for additional mechanisms to explain the high behavioral sensitivity.One candidate explanation is temporal integration, which is a fundamental mechanism for contributing to the amplification of synaptic inputs (17–19). In the olfactory system, the temporal integration properties of AL neurons and their relevance for the initiation of behavior are unknown. Temporal integration in the olfactory system has been challenging to investigate in detail because of the difficulty of accurately controlling olfactory stimuli within a given time period. Under natural conditions, odor molecules are distributed in odor plumes with intermittent local dynamics of odor exposure lasting >100 ms, followed by odor-free air lasting several hundreds of milliseconds (20–24). However, another study showed that “bursts” of odor within a plume structure can be as little 10–20 ms (25, 26). Therefore, the stimulation of pheromone-responsive ORNs must be controlled in the millisecond range.To examine the role of temporal integration in the generation of low thresholds for pheromone-induced behavioral responses, we generated GAL4/UAS transgenic silkmoths expressing channelrhodopsin-2 (ChR2), a light-gated ion channel from green algae, in bombykol-responsive ORNs. The transgenic silkmoths showed light-activated pheromone orientation behavior, and we succeeded in controlling the activity of bombykol-responsive ORNs with single-spike resolution. Using paired-pulse photostimulation at various interstimulus intervals (ISIs), we tested whether temporal integration in the AL network could be the basis of the high behavioral sensitivity.     

Crizotinib administered via nasogastric and percutaneous endoscopic gastrostomy tubes for the successful treatment of ALK-rearranged lung cancer in a patient with poor performance status

Crizotinib—an anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitor—is effective in non-small-cell lung cancers (NSCLCs) that express ALK. Here, we report a patient with ALK-positive lung adenocarcinoma who was administered crizotinib via nasogastric and percutaneous endoscopic gastrostomy (PEG) tubes, with positive results. This case indicates that patients with ALK-positive NSCLC may successfully be treated with crizotinib via nasogastric or PEG tubes. This approach can even be used as a salvage treatment in patients with poor prognoses.     

Possible role of prostacyclin synthase in altered prostacyclin generation in DOCA-salt hypertensive rats

Prostacyclin (PGI2) synthase is one of the key enzymes for vasodepressor PGI2 biosynthesis in the vascular wall. In this study, we attempted to define the alterations in PGI2 synthase and its role in the PGI2 generation in the vascular wall of deoxycorticosterone acetate (DOCA)-salt rats. The PGI2-generating capacity was enhanced significantly when DOCA-salt rats established hypertension, whereas the generation of other arachidonate metabolites, eg, PGE2, PGF2 alpha, and thromboxane, was unaltered. Moreover, the increase in PGI2 generation was associated with an increase in PGI2 synthase activity in the vascular wall. Indeed, the averaged PGI2 generating capacity was closely correlated to the averaged PGI2 synthase activity in DOCA-salt hypertensive rats and three lines of control rats. Incontrast, phospholipase C and phospholipase A2, both of which liberate arachidonate for PGI2 synthesis, were rather lowered in DOCA-salt hypertensive rats. These data clearly indicate that vascular PGI2 generation is increased in the development of DOCA-salt hypertension and that PGI2 synthase is mainly responsible for this enhancement. The increased PGI2 synthase may be relevant to the blood pressure elevation and is expected to have beneficial effects on the vascular protection in hypertension.     

Determination of thiosulfate in body fluids by GC and GC/MS

A simple and sensitive method to determine thiosulfate in human blood and urine was devised. Thiosulfate was first alkylated with pentafluorobenzyl bromide, with L-ascorbic acid as the stabilizer and sodium chloride as the catalyst. The alkylated thiosulfate was oxidized with iodine to obtain bis(pentafluorobenzyl)disulfide, which was then subjected to gas chromatography and gas chromatography/mass spectrometry. Mass fragmentography was used to identify the disulfide, and gas chromatography with an electron capture detector was used for quantitative determination. The lower limit of detection was 0.003 mumol/mL.     

Evidence for medial-mass regression in the vascular wall of Dahl hypertensive rats by cicletanine treatment.

We designed experiments to investigate the effects of cicletanine, a novel antihypertensive drug, on medial hypertrophy in Dahl rats susceptible to salt-induced hypertension (Dahl S rats). Cicletanine treatment (500 mg of cicletanine/kg of chow) for 6 weeks lowered blood pressure by 19% in Dahl S rats challenged with a high-salt (4%) diet. The blood pressure reduction was associated with a significant decrease in weight of the aortic vessels. Morphological examination revealed that this treatment decreased medial hypertrophy and expansion of intimal tissue, in concert with resolution of the periarteritis in the intrarenal arteries. In fact, the content of actin in the aortic wall, analyzed by SDS-PAGE, was decreased significantly with this treatment and myosin content was reduced to the same extent as well. Moreover, cicletanine per se lowered protein synthesis in randomly cycling cultured vascular smooth muscle cells (VSMCs) from Sprague-Dawley rats. Actin formation by VSMCs was decreased with cicletanine. Thus, these data indicate that chronic cicletanine treatment produces regression of the medial hypertrophy in Dahl S rats. Direct inhibitory effects on cytoskeleton protein synthesis, as well as its antihypertensive action, are partly responsible for this regression in vivo.     

Effect of estrogen treatment on testicular gonadotropin receptors in prostatic cancer patients

Effects of estrogen treatment on testicular human chorionic gonadotropin (hCG) and follicle-stimulating hormone (FSH) receptors in man were investigated. Ten patients (aged 58 to 75, mean 67 years) with prostatic cancer were treated with diethylstilbestrol diphosphate (DESDP) (300 mg daily, oral administration). They were divided into two groups: 5 of them (aged 58 to 74, mean 67 years) were orchiectomized after 7 days of treatment and the remainder (aged 60-75, mean 67 years) after 6 months of treatment. hCG and FSH receptors in the resected testes of each group were measured and compared with those of age-matched prostatic cancer patients without any treatment (controls). After 7 days and 6 months of DESDP treatment, the number of hCG receptors decreased to approximately 53% and 24%, respectively, of that of the controls. FSH receptors in the testes of the patients treated with DESDP did not differ significantly from those of the controls.     

Assessment of myocardial damage in dilated-phase hypertrophic cardiomyopathy by using indium-111-antimyosin Fab myocardial scintigraphy

For the detection of myocardial cell damage, an 111In-antimyosin Fab study was carried out on seven patients (Group A) in the dilated phase of hypertrophic cardiomyopathy, seven patients (Group B) with dilated cardiomyopathy, and eight control patients (Group C). Imaging was done 48 hr after intravenous injection of 74 MBq of 111In-antimyosin Fab. Myocardial antimyosin uptake was visually graded as 0, +1, +2 or +3. A score of +2 or +3 was considered positive. The heart/lung ratio of antimyosin uptake (antimyosin index) also was determined. Antimyosin uptake was positive in seven (100%), nine (90%) and no (0%) patients in Groups A, B, and C, respectively. The antimyosin index in Groups A and B was 2.46 +/- 0.49 and 2.04 +/- 0.24, respectively, findings were significantly higher than that in Group C (1.51 +/- 0.13) (p less than 0.01). Positive biopsy findings were noted in only two patients in Group A. Thus, antimyosin uptake was increased in dilated phase hypertrophic cardiomyopathy and dilated cardiomyopathy, which suggests ongoing necrotic changes in these patients.