Axillary skin crease incision versus conventional posterolateral incision in open repair of patent ductus arteriosus for extremely low birth weight infants: a retrospective study.

BACKGROUND: Thoracotomy with posterolateral incision (PLI) is commonly used for surgical repair of patent ductus arteriosus (PDA) in extremely low birth weight (ELBW) infants. Some reports have described thoracotomy for PDA using an axillary skin crease incision (ASCI) in consideration of cosmetic problems such as surgical wounds and thoracic deformities, but the details remain unclear. METHODS: In this study, we performed clipping ligation by thoracotomy with ASCI for ELBW infants with PDA from 2011 to 2015 for the purpose of improving cosmetic results, and retrospectively compared the results with those for conventional PLI cases performed from 2016 to 2020. RESULTS: ASCI was found to be associated with serious surgical complications and showed a significant difference in outcome parameters only for surgery time, suggesting a safety problem for ASCI. Considering these results, PLI allows clipping of the nearby PDA from the thoracotomy wound while looking straight ahead, whereas the PDA in ASCI is positioned deep and oblique to the thoracotomy wound, so the clipping angle is limited and accurate completion of the procedure is difficult. CONCLUSIONS: Regarding PDA repair in ELBW infants, ASCI shows a high risk of serious surgical complications. Conventional PLI remains preferable for safe and accurate results.

Enhanced enteric neurogenesis by Schwann cell precursors in mouse models of Hirschsprung disease.

Hirschsprung disease (HSCR) is characterized by congenital absence of enteric neurons in distal portions of the gut. Although recent studies identified Schwann cell precursors (SCPs) as a novel cellular source of enteric neurons, it is unknown how SCPs contribute to the disease phenotype of HSCR. Using Schwann cell-specific genetic labeling, we investigated SCP-derived neurogenesis in two mouse models of HSCR; Sox10 haploinsufficient mice exhibiting distal colonic aganglionosis and Ednrb knockout mice showing small intestinal aganglionosis. We also examined Ret dependency in SCP-derived neurogenesis using mice displaying intestinal aganglionosis in which Ret expression was conditionally removed in the Schwann cell lineage. SCP-derived neurons were abundant in the transition zone lying between the ganglionated and aganglionic segments, although SCP-derived neurogenesis was scarce in the aganglionic region. In the transition zone, SCPs mainly gave rise to nitrergic neurons that are rarely observed in the SCP-derived neurons under the normal condition. Enhanced SCP-derived neurogenesis was also detected in the transition zone of mice lacking RET expression in the Schwann cell lineage. Increased SCP-derived neurogenesis in the transition zone suggests that reduction in the vagal neural crest-derived enteric neurons promotes SCP-derived neurogenesis. SCPs may adopt a neuronal subtype by responding to changes in the gut environment. Robust SCP-derived neurogenesis can occur in a Ret-independent manner, which suggests that SCPs are a cellular source to compensate for missing enteric neurons in HSCR.

Mice conditionally expressing RET(C618F) mutation display C cell hyperplasia and hyperganglionosis of the enteric nervous system.

Medullary thyroid carcinoma (MTC) develops from hyperplasia of thyroid C cells and represents one of the major causes of thyroid cancer mortality. Mutations in the cysteine-rich domain (CRD) of the RET gene are the most prevalent genetic cause of MTC. The current consensus holds that such cysteine mutations cause ligand-independent dimerization and constitutive activation of RET. However, given the number of the CRD mutations left uncharacterized, our understanding of the pathogenetic mechanisms by which CRD mutations lead to MTC remains incomplete. We report here that RET(C618F), a mutation identified in MTC patients, displays moderately high basal activity and requires the ligand for its full activation. To assess the biological significance of RET(C618F) in organogenesis, we generated a knock-in mouse line conditionally expressing RET(C618F) cDNA by the Ret promoter. The RET(C618F) allele can be made to be Ret-null and express mCherry by Cre-loxP recombination, which allows the assessment of the biological influence of RET(C618F) in vivo. Mice expressing RET(C618F) display mild C cell hyperplasia and increased numbers of enteric neurons, indicating that RET(C618F) confers gain-of-function phenotypes. This mouse line serves as a novel biological platform for investigating pathogenetic mechanisms involved in MTC and enteric hyperganglionosis.

Contrast-enhanced ultrasonographic findings in torsion of the appendix testis or epididymis in children: a case series.

PURPOSE: Torsion of the appendix testis or epididymis is a cause of acute scrotum in children. Ultrasonography with color Doppler is the first-choice modality for diagnosis. However, this method requires skill and experience to make a diagnosis with confidence. Recently, contrast-enhanced ultrasonography for diagnosis in various fields has been reported. However, to our knowledge, there has been no report of this method being used to diagnose torsion of the appendix testis or epididymis. The purpose of this study was to retrospectively examine contrast-enhanced ultrasonographic findings in torsion of the appendix testis or epididymis. METHODS: Patients who underwent contrast-enhanced ultrasonography for torsion of the appendix testis or epididymis at our institution between April 2010 and April 2023 were enrolled in this study (n = 12). Contrast-enhanced ultrasonography findings of the affected appendage and the testis parenchyma were examined retrospectively. RESULTS: The parenchyma of the testes was notably enhanced in all the cases. However, 9 of the 12 cases showed that the appendage with torsion was not enhanced at all. In the remaining three cases, only slight enhancement was seen. Nevertheless, it was notably less than that of the parenchyma of the testis. CONCLUSION: Our findings indicated that contrast-enhanced ultrasonography may be an easy and reliable method for diagnosing torsion of the appendix testis or epididymis.

Contrast-enhanced ultrasound findings in testicular torsion and non-testicular torsion.

PURPOSE: Testicular torsion requires emergency surgery; thus, prompt and correct diagnosis is very important. Ultrasound with color Doppler is usually the first-choice modality for diagnosis; however, skill and experience are required for confident diagnosis. Recently, contrast-enhanced ultrasound for the diagnosis of testicular torsion has been reported, but there have been only a few reports. This study aimed to compare contrast-enhanced ultrasound findings in cases of testicular torsion and non-testicular torsion. METHODS: Patients who underwent contrast-enhanced ultrasound for acute scrotum at our institution between April 2010 and January 2023 were divided into testicular torsion (n = 17) and non-testicular torsion (n = 16) groups. The respective contrast-enhanced ultrasound findings were retrospectively examined and compared. RESULTS: In 16 out of 17 cases of testicular torsion, the parenchyma of the affected testis was not enhanced. In the remaining case, reduced contrast enhancement was observed; however, it was still notably less than that observed on the unaffected testis. On the other hand, in all cases of non-testicular torsion (n = 16), the parenchyma of the affected testis was notably enhanced. CONCLUSION: Contrast-enhanced ultrasound is considered an easy and accurate method for diagnosing testicular torsion.

A Case of an Extremely Preterm Infant with Intussusception Triggered by Acquired Cytomegalovirus Infection.

Intussusception is a common cause of intestinal obstruction in infants aged 6-18 months. However, intussusception in preterm neonates (IPN) is an exceedingly rare disorder. The etiology of IPN remains unclear, but common prenatal injuries, such as those causing intestinal hypoxia/hypoperfusion, dysmotility, and strictures, have been proposed as possible contributing factors. Diagnosis is often delayed because the symptoms closely resemble those of necrotizing enterocolitis (NEC). Given the divergent treatments for IPN and NEC, establishing an early and accurate diagnosis is crucial. IPN is predominantly located in the small intestine (91.6%), and ultrasonography proves useful in its diagnosis. We present a case of a very preterm infant who developed intussusception triggered by acquired cytomegalovirus (aCMV) infection, necessitating surgical treatment. The cause of intussusception in this case was diagnosed as aCMV enteritis because no organic lesions were observed in the advanced part of the intussusception. The presence of CMV was confirmed by CMV-DNA-PCR examination of the resected intestinal tract. Intestinal edema and decreased intestinal peristalsis due to aCMV enteritis are likely the primary causes of the intussusception.

Molecular genetic system for regenerative studies using newts.

Urodele newts have the remarkable capability of organ regeneration, and have been used as a unique experimental model for more than a century. However, the mechanisms underlying regulation of the regeneration are not well understood, and gene functions in particular remain largely unknown. To elucidate gene function in regeneration, molecular genetic analyses are very powerful. In particular, it is important to establish transgenic or knockout (mutant) lines, and systematically cross these lines to study the functions of the genes. In fact, such systems have been developed for other vertebrate models. However, there is currently no experimental model system using molecular genetics for newt regenerative research due to difficulties with respect to breeding newts in the laboratory. Here, we show that the Iberian ribbed newt (Pleurodeles waltl) has outstanding properties as a laboratory newt. We developed conditions under which we can obtain a sufficient number and quality of eggs throughout the year, and shortened the period required for sexual maturation from 18 months to 6 months. In addition, P. waltl newts are known for their ability, like other newts, to regenerate various tissues. We revealed that their ability to regenerate various organs is equivalent to that of Japanese common newts. We also developed a method for efficient transgenesis. These studies demonstrate that P. waltl newts are a suitable model animal for analysis of regeneration using molecular genetics. Establishment of this experimental model will enable us to perform comparable studies using these newts and other vertebrate models.

Neonatal necrotizing fasciitis with gas gangrene due to peripherally inserted central catheter-related infection.

BACKGROUND: Necrotizing fasciitis in neonates is a rare and life-threatening infection involving necrosis of the skin, subcutaneous tissues, deep fascia, and sometimes underlying muscles, with a fulminant course and high mortality rate. Necrotizing fasciitis with gas gangrene related to infection of a peripherally inserted central catheter is very rare. CASE PRESENTATION: The patient was a full-term female neonate born by vaginal delivery. Following diagnosis of patent ductus arteriosus, indomethacin was administered from a peripherally inserted central catheter for 3 days. Four days after the termination of medical treatment for the patent ductus arteriosus, the patient developed fever and a severely elevated inflammatory response was identified from blood testing. Around the right anterior chest wall, corresponding to the site of the catheter tip, redness was increased and gas crepitus was felt under the skin. Computed tomography revealed emphysema in the anterior chest, in subcutaneous areas and between muscles. Emergency surgical debridement was performed under a diagnosis of necrotizing fasciitis with gas gangrene. With antibiotic treatment, we started to fill the wound with a dialkyl carbamoyl chloride-coated dressing and povidone-iodine sugar ointment after washing with saline once a day. The patient survived and after 3 weeks of treatment with the dressing, the wound had successfully resolved without motor impairments. CONCLUSIONS: In addition to medical treatment and prompt surgical debridement, we used dialkyl carbamoyl chloride-coated dressing and povidone-iodine sugar ointment for antiseptic dressings and successfully treated neonatal necrotizing fasciitis with gas gangrene caused by peripherally inserted central catheter infection with Citrobacter koseri.

Infantile type I pleuropulmonary blastoma presenting with dyspnea due to compression by pneumothorax and an occupying tumor: a case report.

BACKGROUND: Pleuropulmonary blastoma (PPB) is an extremely rare and malignant pediatric lung tumor. Purely cystic PPB has a more favorable prognosis than solid PPB, but may be difficult to distinguish from a certain type of "benign" congenital pulmonary airway malformation before and during surgery. The influence of tumor rupture on long life prognosis has not been clarified in detail. CASE PRESENTATION: A 5-month-old boy underwent emergency transfer from another hospital due to a left thoracic cystic lesion and left pneumothorax detected on chest radiography performed for persistent wheeze and cough. Contrast-enhanced computed tomography of the chest revealed marked deviation of the mediastinum to the right due to a giant cystic lesion and pneumothorax. Thoracotomy was performed on hospital day 2. A cystic lesion had developed from the distal alveolar region of lower lobe of the left lung and the tumor showed a tiny adhesion to the left diaphragm and a tiny rupture near the adhesion. Partial lung excision including the cyst and scraping of the adhesion were performed. Histopathological investigations revealed immature blast cell-like mesenchymal cells and differentiated striated muscle cells in a dense cambium layer were found under the epithelium of the cystic lesion. Type I PPB was diagnosed. CONCLUSIONS: Surgery should be performed with the possibility of type I PPB in mind when an extrapulmonary cystic lung lesion is found. Since issues such as the pathogenesis and long-term prognosis of ruptured cases remain unclear, continued careful follow-up of this case will be required.

Challenging management of a baby with congenital multiple intestinal atresia, trisomy 18 and extremely low birth weight: a case report.

BACKGROUND: Extremely low birth weight (< 1000 g) still influences postsurgical prognosis in the neonatal and infantile periods. Additionally, the life expectancy of neonates with trisomy 18 is extremely poor owing to various comorbidities. Therefore, it takes courage to perform laparotomy for the purpose of treatment of congenital multiple intestinal atresia in a baby with an unpredictable life prognosis. CASE PRESENTATION: Fetal ultrasonography revealed cardiac malformation, intestinal dilation, and physical characteristics suggestive of a chromosomal abnormality in this case. The patient was diagnosed with trisomy 18 after birth, with an extremely low birth weight. An atrial septal defect, ventricular septal defect, dilated jejunum, and a very thin collapsed small intestine were found on ultrasonography. With a diagnosis of congenital small intestinal atresia, a challenging laparotomy was done at 3 days of age, with jejunal atresia and multiple distal small intestinal atresia were observed. The jejunal end and distal small intestinal stump were separated into stomas at the wound edge. Hypertrophic pyloric stenosis developed at the age of 3 months and resolved with medication. The patient gained weight (2 kg) by daily stool injection into anal side of the intestine and decompression against poor peritonitis of dilated jejunum using enteral feeding tube for the long period. Finally, we could perform intestinal reconstruction safely and successfully at the age of 9 months. Tracheotomy was performed due to difficulty in extubation associated with chronic lung disease. The patient was discharged at the age of 1 year and 3 months, and no major problems were noted at the age of 2 years. CONCLUSIONS: We treat congenital intestinal atresia in extremely low birth weight infants with severe chromosomal abnormalities and severe cardiac malformations as follows: Stoma creation is performed quickly to avoid deterioration of the patient's hemodynamics. After that, while continuing enteric management, palliative cardiovascular surgery is performed as necessary, and the patient's body weight and intestinal tract status are determined to allow safe intestinal reconstruction.

Strategy for surgical treatment of congenital subglottic stenosis in children.

BACKGROUND/PURPOSE: Congenital subglottic stenosis is a rare anomaly caused by thickened cricoid cartilage. We report our surgical techniques, comprising anterior cricoid split (ACS), laryngotracheoplasty (LTP), KTP laser ablation, and application of a tracheal opening retainer (TOR) into the tracheostomy site. METHODS: Nine patients have been treated since 1988. Four patients (median age 85 days; range 5 days to 6 months) underwent ACS. Another four patients (median age, 17 months; range, 5-57 months) underwent LTP using costal cartilage grafts, although two had undergone tracheostomy before LTP. One patient underwent LTP, ablation of the projecting part of the cricoid cartilage with KTP laser (LTP + Laser) and, preservation of the tracheal opening by placement of the TOR. RESULTS: All ACS and LTP patients were successfully extubated at a median of 32 days (range 23-91 days) and 23 days (range 6-31 days) postoperatively, respectively. The LTP + Laser patient was extubated 35 days after surgery and the TOR was removed asymptomatically 20 days after extubation of the stent tube. CONCLUSIONS: Anterior cricoid split is useful for patients ≤ 6 months old and LTP is useful for patients >6 months old and/or with tracheostomy. KTP laser ablation is effective to remove thickened parts of cricoid cartilage protecting the vocal cords. The tracheal opening preserved by the TOR works as an additional channel to safeguard respiration during the extubation process.

Median sternotomy approach for the repair of esophageal atresia: a case report.

BACKGROUND: Repair of esophageal atresia is usually performed through the right thoracic cavity. However, when the upper pouch of the esophagus and tracheoesophageal fistula (TEF) is located in the thoracic inlet and completely on the left side of trachea, it is difficult to dissect and anastomose the esophagus through the right thoracic cavity. We present a case of esophageal atresia, with the esophageal upper pouch located high and completely on the left side of trachea, successfully repaired via the median sternotomy approach. CASE PRESENTATION: A male neonate with a birth weight of 1766 g was prematurely delivered via cesarean section at 34 weeks of gestation. Contrast-enhanced computed tomography (CT) showed that the upper pouch of the esophagus was located at the thoracic inlet and completely on the left side of the trachea; hence, a diagnosis of esophageal atresia was made. Moreover, a TEF was connected to the trachea at the level of the lower end of the upper esophageal pouch. An aberrant right subclavian artery and persistent left superior vena cava were also detected. Esophageal dissection and anastomosis were determined to be very difficult if approached from the right thoracic cavity. Therefore, we performed median sternotomy one day after the neonate was born. The upper pouch of the esophagus and TEF were easily dissected via the median sternotomy approach. Anastomosis of the esophagus was performed, with a good visual field, to the left of the trachea. The postoperative course was uneventful. CONCLUSIONS: This is the first reported case of a median sternotomy approach for esophageal atresia. This technique may be useful when a right thoracic approach is difficult, especially if the esophageal upper pouch is located completely to the left of the trachea or if it is higher than the normal position.

BMP inhibition-driven regulation of six-3 underlies induction of newt lens regeneration.

Lens regeneration in adult newts is a classic example of how cells can faithfully regenerate a complete organ through the process of transdifferentiation. After lens removal, the pigment epithelial cells of the dorsal, but not the ventral, iris dedifferentiate and then differentiate to form a new lens. Understanding how this process is regulated might provide clues about why lens regeneration does not occur in higher vertebrates. The genes six-3 and pax-6 are known to induce ectopic lenses during embryogenesis. Here we tested these genes, as well as members of the bone morphogenetic protein (BMP) pathway that regulate establishment of the dorsal-ventral axis in embryos, for their ability to induce lens regeneration. We show that the lens can be regenerated from the ventral iris when the BMP pathway is inhibited and when the iris is transfected with six-3 and treated with retinoic acid. In intact irises, six-3 is expressed at higher levels in the ventral than in the dorsal iris. During regeneration, however, only expression in the dorsal iris is significantly increased. Such an increase is seen in ventral irises only when they are induced to transdifferentiate by six-3 and retinoic acid or by BMP inhibitors. These data suggest that lens regeneration can be achieved in noncompetent adult tissues and that this regeneration occurs through a gene regulatory mechanism that is more complex than the dorsal expression of lens regeneration-specific genes.

Increased RET Activity Coupled with a Reduction in the RET Gene Dosage Causes Intestinal Aganglionosis in Mice.

Mutations of the gene encoding the RET tyrosine kinase causes Hirschsprung's disease (HSCR) and medullary thyroid carcinoma (MTC). Current consensus holds that HSCR and MTC are induced by inactivating and activating RET mutations, respectively. However, it remains unknown whether activating mutations in the RET gene have adverse effects on ENS development in vivo We addressed this issue by examining mice engineered to express RET51(C618F), an activating mutation identified in MTC patients. Although Ret51(C618F)/51(C618F) mice displayed hyperganglionosis of the ENS, Ret51(C618F)/- mice exhibited severe intestinal aganglionosis because of premature neuronal differentiation. Reduced levels of glial cell-derived neurotrophic factor (GDNF), a RET-activating neurotrophic factor, ameliorated the ENS phenotype of Ret51(C618F)/- mice, demonstrating that GDNF-mediated activation of RET51(C618F) is responsible for severe aganglionic phenotype. The RET51(C618F) allele showed genetic interaction with Ednrb gene, one of modifier genes for HSCR. These data reveal that proliferation and differentiation of ENS precursors are exquisitely controlled by both the activation levels and total dose of RET. Increased RET activity coupled with a decreased gene dosage can cause intestinal aganglionosis, a finding that provides novel insight into HSCR pathogenesis.

Regeneration of retinotectal projections after optic tectum removal in adult newts.

PURPOSE: When injured, the adult newt possesses the remarkable capability to regenerate tissues and organs with return of function and physiology. One example is the newt eye, in which regeneration can restore normal vision if the retina or lens has been removed. We wanted to examine how the retinotectal projections regenerate after removal of the brain's optic tectum and establish this animal as a model for retinal projection as well as a central nervous system regeneration model. METHODS: A major portion of the left optic tectum was removed in several adult newts, and the animals were monitored postoperatively for eight months to observe regeneration and innervation. Cell proliferation was examined by histological methods and by BrdU incorporation. RESULTS: We observed that adult newts have the capability to the excised optic tectum. As indicated by horseradish peroxidase staining, 80% of the retinotectal projection area was regenerated eight months after the operation, even though the wound closed much earlier. Our study provides the first quantitation of regeneration of the retinotectal projections. The ependymal cells that line the ventricle were the most likely source of the regenerated tectum. After removal, cell proliferation was detected only in the ependymal cells layer. Double staining of proliferating cells and neurons was limited, indicating that direct transition of ependymal cells is a possibility. CONCLUSIONS: The retinotectal projections after removal of the adult newt optic tectum can be readily re-established. Thus, this model can become indispensable for the study of vision restoration and neurogenesis.

FGF2 triggers iris-derived lens regeneration in newt eye.

Lens regeneration in newts occurs exclusively from the dorsal aspect of the iris pigment epithelium. Although the phenomenon has been a paradigm of experimental tissue regeneration, little is understood about how it is initiated and restricted to the dorsal iris. Here we show among various growth factors injected in an intact eye, a single injection of FGF2 specifically caused morphological changes of the iris characteristic of lens regeneration, induced expression of transcription factor genes Pax6, Sox2 and MafB, as well as endogenous Fgf2 in both dorsal and ventral halves, and provoked second lens development only from the dorsal iris. FGF2 protein accumulated in the iris tissue after the lens was removed, and injection of a soluble form of FGF receptor titrating FGF2 inhibited all reactions observed after the lens removal or after administration of FGF2. These results indicate that FGF2 and/or related molecules trigger lens regeneration from the dorsal iris in the newt. The observations also indicate that the absence of lens regeneration from the ventral iris is due to a block in a later phase of lens developmental pathway.

A METHOD FOR THE REMOVAL OF THE JELLY AND VITELLINE MEMBRANE FROM THE EMBRYOS OF XENOPUS LAEVIS.

A simple procedure is described for removing the jelly and vitelline membrane of Xenopus laevis embryos. The method is based on the observation that incubation of the embryos in the mixed solution of trypsin and sodium thioglycolate at pH 8.0 causes effective dissolution of these structures. This solution is equally effective in this respect on the embryos at different developmental stages. Normal development is obtained from all of the denuded neurulae and from many of the denuded earlier embryos. Some chemical properties of the jelly and the vitelline membrane of Xenopus laevis are discussed based upon these observations.

Inhibition of Lens Regeneration by Nickel Subsulfide in the Japanese Common Newt, Cynops pyrrhogaster: (newt/lens regeneration/nickel subsulfide/carcinogenesis).

To investigate the effects of nickel subsulfide (Ni3 S2 ) on lens regeneration, Ni3 S2 was administered to the lentectomized newt eye by a single injection into the eye chamber. Lens regeneration was inhibited in the early stage of regeneration with about 60% of the treated eyes after 25 days, while all control eyes had a regenerating lens. The size of the regenerating lens in the treated eyes was the same as in controls. Lens regeneration was inhibited in all treated eyes containing Ni3 S2 particles within the eye chamber. Inhibition of lens regeneration in the treated eyes was about 80% at 3 months, when all control eyes had already completed lens regeneration. Although the tendency toward pupil disappearance was prominent in the eyes having no regenerating lens, there were also a few eyes which had no regenerating lens and no signs of pupil disappearance. The significance of these results was discussed in relation to the regeneration and carcinogenesis.

A UNIQUE JUNCTIONAL STRUCTURE FOUND IN BLASTULA CELLS OF THE NEWT, TRITURUS PYRRHOGASTER.

The outermost cell layer of the animal half of the newt blastula (Triturus pyrrhogaster) was examined to investigate intercellular junctions by transmission and scanning electron microscopy. A unique structure is observed at the terminal region of the intercellular junction. The structures are cytoplasmic ridges elevated from the cell surfaces, and their inner part is filled with spaces of various sizes. It is supposed that these ridges result from the encounter of cytoplasmic folds protruding from two neighboring cells. Below the ridges, there is a short close junctional area which is followed by a long region of intercellular space intermittently bridged by cytoplasmic projections. Microvillus-like cytoplasmic processes on the apical cell surfaces, and microfilaments and microtubules in subsurface regions are observed in this material as in many other embryonic cells of amphibians.

Accumulation of Annulate Lamellae in the Subcortical Layer during Progesterone-induced Oocyte Maturation in Xenopus Laevis: (annulate lamellae/oocyte maturation/Xenopus laevis).

Changes in the fine structure, the location and the number of stacks of annulate lamellae during progesterone-induced maturation of oocytes of Xenopus were determined by electron microscopy. longitudinal sections of full-grown oocytes, about 260 stacks of annulate lamellae were observed with marked concentration in the subcortical layer, particularly in the vegetal hemisphere. After exposure to. progesterone, annulate lamellae increased and accumulated further in the subcortical layer. A significant increase of annulate lamellae around the vegetal side of the germinal vesicle seen 3 h after progesterone application. In oocytes 6 h after progesterone application, an average of 320 stacks of annulate lamellae were seen in longitudinal sections and more than two-thirds of the pore complexes of annulate lamellae were localized in the subcortical layer less than 50 from the oocyte surface, the rest being distributed in the deeper ooplasm. At the time of ger- minal vesicle breakdown, all the annulate lamellae underwent complete decomposition. The results were discussed from the view point of comparative developmental biology.