Maternal GABAergic and GnRH/corazonin pathway modulates egg diapause phenotype of the silkworm Bombyx mori

Diapause represents a major developmental switch in insects and is a seasonal adaptation that evolved as a specific subtype of dormancy in most insect species to ensure survival under unfavorable environmental conditions and synchronize populations. However, the hierarchical relationship of the molecular mechanisms involved in the perception of environmental signals to integration in morphological, physiological, behavioral, and reproductive responses remains unclear. In the bivoltine strain of the silkworm Bombyx mori, embryonic diapause is induced transgenerationally as a maternal effect. Progeny diapause is determined by the environmental temperature during embryonic development of the mother. Here, we show that the hierarchical pathway consists of a γ-aminobutyric acid (GABA)ergic and corazonin signaling system modulating progeny diapause induction via diapause hormone release, which may be finely tuned by the temperature-dependent expression of plasma membrane GABA transporter. Furthermore, this signaling pathway possesses similar features to the gonadotropin-releasing hormone (GnRH) signaling system for seasonal reproductive plasticity in vertebrates.

To ensure survival under unfavorable environmental conditions and synchronize populations, most insect species enter diapause, which is a seasonal adaptation that evolved as a specific subtype of dormancy (1, 2). Diapause is not a passive response to changing conditions but rather an actively induced state that precedes adverse natural situations. Therefore, this diapause phenotype is accompanied by changes in energy metabolism or storage to improve cold/stress tolerance in later life stages, or progeny via reproductive switch (3). Although it has been generally suggested that brain/neuroendocrine systems are associated with this seasonal reproductive plasticity in both vertebrates and invertebrates (3, 4), the hierarchical relationship of the molecular mechanisms involved in the perception of environmental signals to integration into morphological, physiological, behavioral, and reproductive responses, known as the diapause syndrome, remains unclear (3).The silkworm Bombyx mori is a typical insect that arrests normal development during early embryogenesis, which is accompanied by metabolic changes in diapause (5, 6). The development of diapause-destined embryos is arrested during the G2 cell cycle stage immediately after the formation of the cephalic lobe and telson and sequential segmentation of the mesoderm (7). The bivoltine strain of B. mori has two generations per year, and progeny diapause is transgenerationally induced as a maternal effect and is determined by the environmental temperature, photoperiod, and nutrient conditions during embryonic and larval development of the mother (5, 6). The temperature signal during the mother’s embryonic development predominantly affects diapause determination, even if silkworms of the bivoltine Kosetsu strain are exposed to all cases of photoperiods during embryonic and larval development. In the Kosetsu strain, when eggs are incubated at 25 °C under continuous darkness, the resultant female moths (25DD) lay diapause eggs in almost all cases. In contrast, incubation of eggs at 15 °C in dark condition results in moths (15DD) that lay nondiapause eggs in almost all cases (6).Embryonic diapause is induced by the diapause hormone (DH) signaling pathway, which consists of highly sensitive and specific interactions between a neuropeptide, DH, and DH receptor (DHR) (6, 8). DH is exclusively synthesized in seven pairs of neurosecretory cells (DH-PBAN–producing neurosecretory cells [DHPCs]) located within the subesophageal ganglion (SG) in the mother’s generation (6). DH is released into the hemolymph during pupal–adult development and acts on the DHR, which belongs to the G protein-coupled receptors (GPCRs) (9). DH levels in the hemolymph are higher in the 25DD than 15DD pupae in the middle of pupal–adult development when the developing ovaries are sensitive to DH (6). Furthermore, the embryonic Bombyx TRPA1 ortholog (BmTRPA1) acts as a thermosensitive channel that is activated at temperatures above ∼21 °C and affects diapause induction through DH release (10). However, there remain questions about the thermal information that is received by BmTRPA1 and linked to DH signaling to induce diapause.From the 1950s, it has been suggested that the DH release was controlled by signals derived from certain region(s) in the brain based on surgical experiments, such as midsagittal bisection or transection (11–13). Especially, the operation in nondiapause producers changed them to diapause producers while transection of the protocerebrum had no effect on the diapause producers. These surgical results suggested the involvement of the protocerebrum in the inhibitory control of DH secretion (12, 14). Furthermore, the accumulation of the ovarian 3-hydroxykynurenine (3-OHK) pigment that accompanies the diapause syndrome was affected by injection with γ-aminobutyric acid (GABA) and the plant alkaloid picrotoxin (PTX), which is a widely used ionotropic GABA and glycine receptor antagonist (15, 16), and the selective ionotropic GABA receptor (GABAR) antagonist bicuculline. This suggests that a GABAergic neurotransmission via ionotropic GABAR is involved in DH secretion, which may be active in nondiapause producers but inactive in diapause producers throughout the pupal–adult development (14, 17). In general, ionotropic GABAR is composed of homo- or hetero-pentameric subunits. All known GABAR subunits display a similar structural scheme, with a large N-terminal extracellular domain involved in the formation of a ligand-binding pocket and a pore domain made of four transmembrane alpha-helices (TM1–TM4) (16, 18). Four homologous sequences of the ionotropic GABAR subunit genes were identified as RDL, LCCH3, GRD, and a GRD-like sequence named 8916 in various insects (19). However, the in vivo physiological roles of both signals derived from the brain and the GABAergic pathway in diapause induction have not been previously investigated.Corazonin (Crz) is an undecapeptide neurohormone sharing a highly conserved amino acid (a.a.) sequence across insect lineages and is involved in different physiological functions, such as heart contraction (20), stress response (21, 22), various metabolic activities (23–25), female fecundity (26), melanization of locust cuticles (27), regulation of ecdysis (28, 29), and control of caste identity (30). Moreover, Crz belongs to the gonadotropin-releasing hormone (GnRH) superfamily alongside adipokinetic hormone (AKH) and AKH/Crz-related peptide (ACP). Duplicates of an ancestral GnRH/Crz signaling system occurred in a common ancestor of protostomes and deuterostomes through coevolution of the ligand receptor (31, 32).Herein, we demonstrated that the hierarchical pathway consists of a GABAergic and Crz signaling system modulating progeny diapause induction by acting on DH release. We propose that the PTX-sensitive GABAergic signal may act to chronically suppress Crz release in dorsolateral Crz neurons (under nondiapause conditions) and that diapause conditions (or PTX injection) inhibits GABAergic signaling, resulting in accelerated Crz release, which in turn induces DH release. GABA signaling may be finely tuned by the temperature-dependent expression of the plasma membrane GABA transporter (GAT), which differs between the 25DD and 15DD conditions. Furthermore, this signaling pathway possesses similar features to the GnRH signaling system with respect to seasonal reproductive plasticity in vertebrates.     

Hybrid approach with laparoscopic wall-inversion surgery and single-incision intragastric surgery for intraluminal gastrointestinal stromal tumor: A case report

Laparoscopic wedge resection (LWR) for intraluminal gastrointestinal stromal tumor (GIST) leads to excessive resection of normal gastric wall. We report a case of GIST around the cardia successfully treated with full-thickness partial resection using a hybrid approach of laparoscopic surgery and single-incision intragastric surgery (SIIGS). A 69-year-old woman had a 5 cm intraluminal GIST at the posterior wall around the cardia. Submucosal injection of glycerin and indigo carmine was performed with transoral endoscopy. Circumferential seromuscular incision followed by placement of seromuscular sutures to invert the lesion into the stomach was performed under laparoscopy. By SIIGS, resection of the inverted mucosa and retrieval of the tumor were completed. A hybrid approach consisting of laparoscopic wall-inversion surgery and SIIGS was useful for intraluminal GIST and may expand the indications for laparoscopic wall-inversion surgery by removing size limitations.     

Primary esophageal mucosa‐associated lymphoid tissue lymphoma treated by endoscopic submucosal dissection

Primary esophageal mucosa‐associated lymphoid tissue (MALT) lymphoma is rare. There have been few reports about early primary esophageal MALT lymphoma being treated endoscopically. The clinical profile of primary esophageal MALT lymphoma is currently unclear, so it is important to accumulate more information about early esophageal MALT lymphoma. To achieve early detection of esophageal MALT lymphoma, we need more accurate knowledge and information about the macroscopic and morphological features of this tumor. Endoscopic resection is one of the most effective treatments. With respect to the lateral andvertical margins of the resected specimen, endoscopic submucosal dissection (ESD) may be superior to endoscopic mucosal resection for treating early esophageal MALT lymphoma. Here we report the macroscopic appearance of the tumor which is the first successful case of ESD for early esophageal MALT lymphoma.     

Comparison between famciclovir and valacyclovir for acute pain in adult Japanese immunocompetent patients with herpes zoster

Famciclovir is a guanine analog antiviral drug used commonly for herpes zoster. Efficacy of famciclovir treatment has been reported to be comparable to valacyclovir treatment. Both of these medications reduce the time to complete cessation of zoster‐associated pain including post‐herpetic neuralgia, as compared to acyclovir. We conducted a multicenter, randomized, open clinical trial in order to evaluate the extent of pain relief afforded by these two antiviral drugs during the acute disease phase of herpes zoster. The study group comprised 86 immunocompetent adult patients suffering from herpes zoster, who were treated with either famciclovir or valacyclovir for 7 days. Of these, 55 patients enrolled in this study within 72 h of the onset of the rash and 31 patients after 72 h of the onset. There was a significant reduction in acute herpes zoster pain with famciclovir on day 7 and at 2–3 weeks in both of these patient groups, while with valacyclovir, there was not significant reduction in pain on day 7. Of patients aged 50 years or older, there was a significantly earlier reduction in pain with famciclovir than with valacyclovir. In addition, a significant reduction in the number of patients with pain was observed as early as days 3–4 with famciclovir treatment as compared with valacyclovir treatment. We conclude that famciclovir was superior to valacyclovir in the relief of acute pain of herpes zoster. Accordingly, famciclovir is recommended for herpes zoster patients with moderate symptoms and a visual analog scale score of under 50 mm.     

A case of adult congenital laryngeal cleft asymptomatic until hypopharynx cancer treatment

Laryngeal cleft is an anomaly of failed posterior closure of the larynx. Most cases are diagnosed and need treatment early in life due to respiratory and swallowing problems. We report an unusual case of a 66-year-old man with an asymptomatic laryngeal cleft until treatment for hypopharyngeal cancer. During concurrent chemoradiotherapy (CCRT), despite reduced tumor volume, he presented severe dysphagia and dyspnea, followed by severe pneumonia twice. Because CCRT had to be discontinued, a pharyngolaryngectomy was performed for the cancer treatment. The resected specimen showed total removal of the tumor and a total longitudinal cleft of the cricoid cartilage, classified as a type III laryngeal cleft by the Benjamin and Inglis’ classification. A review of computed tomography images indicated that the redundant mucosa from bilateral edges closed the separation of the posterior cricoid cartilage and narrowed the laryngeal airway during CCRT. Adult presentations of laryngeal cleft are quite rare with only ten reported cases in English literature; the present case is of the oldest patient. Undiagnosed cases with laryngeal cleft may exist asymptomatically or without severe symptoms. The awareness of this condition may increase its diagnosis as a cause of diseases such as aspiration and recurrent pneumonia even in adult patients.     

Pulmonary metastasectomy for metachronous metastasis of esophageal cancer after esophagectomy

Background and objective

Pulmonary metastasectomy is a standard therapy for some types of metastatic lesions in the lung. Although the prognosis for esophageal cancer patients with pulmonary metastasis is poor, it has been reported that some post-esophagectomy patients have good prognosis after pulmonary metastasectomy. We investigated the role of resecting pulmonary metastases arising from esophageal cancer at our institution.

Patients and methods

Seven patients with primary squamous cell carcinoma or adenocarcinoma of the thoracic esophagus who underwent resection of metachronous pulmonary metastases at our institution between 2006 and 2012 were identified from a retrospective database. All patients had undergone curative resection of their primary esophageal carcinoma.

Results

Six patients had unilateral and solitary lung metastasis. One patient presented with one metastatic lesion on each side, and he underwent 4 metastasectomy for pulmonary metastasis 3 times. There was no perioperative morbidity or mortality. The disease-free interval after esophagectomy ranged from 191 to 559 days (median, 463 days). Survival after pulmonary metastasectomy ranged from 357 to 3191 days (median, 1803 days). Three patients received systemic chemotherapy before metastasectomy. Currently, 5 patients are alive without evidence of recurrent disease.

Conclusion

Pulmonary metastasectomy may be acceptable as a part of multimodal treatment for solitary metachronous pulmonary metastasis in esophageal carcinoma.