Tissue-specific expression and circulating concentrations of nesfatin-1 in domestic animals

Nesfatin-1 is a naturally occurring 82-amino acid protein encoded in the precursor nucleobindin-2 (NUCB2) and has been implicated in multiple physiological functions, including food intake and blood glucose regulation. This study aimed to characterize nesfatin-1 in domestic species, especially cats (Felis catus), dogs (Canis lupus familiaris), and pigs (Sus scrofa). Our in silico analysis demonstrated that the NUCB2/nesfatin-1 amino acid sequence, especially the bioactive core region of the peptide, is very highly conserved (more than 90% identity) in domestic animals. Expression of mRNAs encoding NUCB2/nesfatin-1 was detected in the cat, dog, and pig stomach and pancreas. Immunohistochemistry revealed the presence of nesfatin-1 in the gastric mucosa of the stomach of dogs, cats, and pigs, and in the pancreatic islet β-cells of dogs and pigs. No nesfatin-1 immunoreactivity was found in the cat pancreas. Nesfatin-1 was detected in the serum of dog, cat, pig, bison, cow, horse, sheep, and chicken. Circulating nesfatin-1 in male and female dogs remained unchanged at 60 min after glucose administration, suggesting a lack of meal responsiveness in nesfatin-1 secretion in this species. The presence of nesfatin-1 in the gastric and endocrine pancreatic tissues suggests possible roles for this peptide in the metabolism of domestic animals. Future research should focus on elucidating the species-specific functions and mechanisms of action of nesfatin-1 in health and disease of domestic animals.

Abstract P4-06-02: Germline analysis of breast cancer patients with abnormal somatic results: Ancillary assessment or critical co-diagnostic?

Background: Tumor genetic testing (TGT) is increasingly used for planning cancer treatment and identifying appropriate clinical trials. Emerging literature shows that 4–12% of genetic variants identified on TGT are also present in the germline, conferring hereditary cancer risk. Germline genetic testing (GGT) guidelines were recently expanded to include the identification of a BRCA1/BRCA2 variant on TGT as an indication for germline analysis. We evaluated the diagnostic yield of current GGT guidelines by assessing the rate of pathogenic and likely pathogenic (P/LP) germline findings in a series of patients who had a variant identified on TGT and underwent GGT. Methods: We analyzed de-identified data from 185 sequential patients with various tumor types who had TGT and GGT. Personal and family histories were compared to all available NCCN guidelines for GGT. Results: Sixty-four of 185 patients (34.6%) had at least one P/LP germline variant, and among these patients, 42% (27/64) had variants in BRCA1/BRCA2. Variants in all but one patient (26/27) were also found on TGT. Fourteen of 27 (52%) patients had a personal diagnosis of cancer not typically associated with BRCA1/BRCA2, including colorectal (5), lung (3), and one each of cervical, cholangiocarcinoma, gastric, thymus, thyroid, and uterine. Furthermore, prior TGT results were the only reason GGT guidelines were met in 12 of 27 (44%) patients with germline BRCA1/BRCA2 variants. Among 34 patients with a personal history of breast or ovarian cancer, a P/LP germline variant was identified in nine (26%); the majority (5 of 9) were in non-BRCA1/BRCA2 genes including CDKN2A (1), FANCA (1), MUTYH (1), and PALB2 (2). Notably, the patient with the CDKN2A variant did not meet current breast cancer guidelines for GGT, and one patient with breast cancer and a germline BRCA2 mutation only met GGT guidelines due to prior TGT results. Discussion: Genetic testing guidelines have begun to reflect the opportunity for TGT to identify families at risk for hereditary cancer. Expanding GGT criteria to include TGT results is critical for capturing patients who may not otherwise receive GGT. Our data showed a substantial diagnostic yield in patients—including those with breast or ovarian cancer—who completed GGT after variant identification on TGT. Although current genetic testing guidelines capture the portion of these patients with a BRCA1/BRCA2 mutation identified with TGT, our data suggest that P/LP variants in other genes should also be considered during the evaluation of TGT results for subsequent GTG. Finally, the broad spectrum of tumor types with BRCA1/BRCA2 P/LP variants emphasizes the need for all clinicians, regardless of subspecialty, to be aware of current GTG recommendations when TGT identifies a BRCA1/BRCA2 variant and the potential implications of GTG, including targeted therapy, screening, prevention, and family testing.

Citation Format: Blanco AM, Yang S, Michalski ST, Ouyang K, Hamlington B, Fulbright J, Erhard K, Kang HC, Jacobs M, Koptiuch C, Vig H, Silver E, Benson C, Massingham L, Lincoln SE, Nussbaum RL, Hampel H, Esplin ED. Germline analysis of breast cancer patients with abnormal somatic results: Ancillary assessment or critical co-diagnostic? [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-06-02.

Brain glycogen supercompensation after different conditions of induced hypoglycemia and sustained swimming in rainbow trout (Oncorhynchus mykiss)

Brain glycogen is depleted when used as an emergency energy substrate. In mammals, brain glycogen levels rebound to higher than normal levels after a hypoglycemic episode and a few hours after refeeding or administration of glucose. This phenomenon is called glycogen supercompensation. However, this mechanism has not been investigated in lower vertebrates. The aim of this study was therefore to determine whether brain glycogen supercompensation occurs in the rainbow trout brain. For this purpose, short-term brain glucose and glycogen contents were determined in rainbow trout after being subjected to the following experimental conditions: i) a 5-day or 10-day fasting period and refeeding; ii) a single injection of insulin (4 mg kg(-1)) and refeeding; and iii) sustained swimming and injection of glucose (500 mg kg(-1)). Food deprivation during the fasting periods and insulin administration both induced a decrease in glucose and glycogen levels in the brain. However, only refeeding after 10 days of fasting significantly increased the brain glycogen content above control levels, in a clear short-term supercompensation response. Unlike in mammals, prolonged exercise did not alter brain glucose or glycogen levels. Furthermore, brain glycogen supercompensation was not observed after glucose administration in fish undergoing sustained swimming. To our knowledge, this is the first study providing direct experimental evidence for the existence of a short-term glycogen supercompensation response in a teleost brain, although the response was only detectable after prolonged fasting.

Prediction of reproductive outcomes according to different serum anti-Müllerian hormone levels in females undergoing intracystoplasmic sperm injection

Background and aim of the study

Serum anti-Müllerian hormone (AMH) is a reliable marker of ovarian reserve, and it has been shown to be correlated with reproductive outcomes in grouped analyses. However, practical data is scarce for the physician and the patients to predict these outcomes in an individual couple according to serum AMH measured prior to assisted reproduction technology (ART) procedures.

Study Design

To address this question, we performed an analytic observational study including 145 females undergoing intracytoplasmic sperm injection (ICSI) in a single center. Results were analyzed according to serum AMH; subgroup analyses were performed by grouping patients according to patient’s age and FSH levels.

Results

The risk of cycle cancelation decreased from 64% in patients with serum AMH ≤3 pmol/L (0.42 ng/mL) to 21% with AMH ≥15 pmol/L (2.10 ng/mL). Cycle cancelation occurred in approximately two-thirds of the patients with AMH ≤ 3 pmol/L irrespective of the FSH level. However, with higher AMH values the risk of cycle cancelation decreased more significantly in patients with normal FSH. The rate of good response increased from almost null in patients with AMH ≤3 pmol/L to 61% in those with AMH ≥15 pmol/L. The positive correlation between good response and AMH was also significant, but with lower absolute rates, when patients were grouped according to their age or FSH levels. Pregnancy rate increased moderately, but significantly, from 31% with AMH ≤3 pmol/L to 35% with AMH ≥15 pmol/L.

Conclusions

We provide estimates of reproductive outcomes according to individualized values of serum AMH, in general and in subgroups according to patient’s age or serum FSH, which are helpful for the clinician and the couple in their decision making about starting an assisted reproductive treatment.

De novo assembly and functional annotation of the olive (Olea europaea) transcriptome

Olive breeding programmes are focused on selecting for traits as short juvenile period, plant architecture suited for mechanical harvest, or oil characteristics, including fatty acid composition, phenolic, and volatile compounds to suit new markets. Understanding the molecular basis of these characteristics and improving the efficiency of such breeding programmes require the development of genomic information and tools. However, despite its economic relevance, genomic information on olive or closely related species is still scarce. We have applied Sanger and 454 pyrosequencing technologies to generate close to 2 million reads from 12 cDNA libraries obtained from the Picual, Arbequina, and Lechin de Sevilla cultivars and seedlings from a segregating progeny of a Picual × Arbequina cross. The libraries include fruit mesocarp and seeds at three relevant developmental stages, young stems and leaves, active juvenile and adult buds as well as dormant buds, and juvenile and adult roots. The reads were assembled by library or tissue and then assembled together into 81 020 unigenes with an average size of 496 bases. Here, we report their assembly and their functional annotation.

Usefulness of ploidy, AgNOR and immunocytochemistry for differentiating benign and malignant cells in serous effusions

OBJECTIVE

The objective of this study was to establish the value of different markers in differentiating reactive mesothelial cells from metastatic adenocarcinomatous cells in serous effusions (SE).

METHODS

Forty-five SE were processed for morphological examination (Papanicolaou stain), assessment of ploidy, AgNOR counting and immunocytochemical assay of carcinoembryonic antigen (CEA), epithelial membrane antigens (EMA), Ber-EP4 and Leu-M1. Ploidy was established in an image-analyser in smears stained by the Feulgen stain method. AgNOR dots were counted in the smears stained with the silver nitrate assay for non-histone proteins present in the nucleolar organizer region. CEA, EMA, Ber-EP4 and Leu-M1 were evaluated by immunocytochemistry using the streptavidin-biotin complex method.

RESULTS

All the smears with positive cytology were aneuploid. Three false negatives by morphological studies were aneuploid, with AgNOR values in two of them corresponding to the neoplastic group. CEA and Leu-M1 showed a low specificity; EMA and Ber-EP4 showed moderate sensitivity.

CONCLUSIONS

The assessment of ploidy and the study of AgNOR were better methods than immunocytochemistry for distinguishing between reactive mesothelial cells and adenocarcinomatous cells in serous fluid.

Ethanol intake enhances inflammatory mediators in brain: role of glial cells and TLR4/IL-1RI receptors

The brain is one of the major target organs of ethanol actions, and its chronic and acute intoxication results in significant alterations in brain structure and function, and in some cases to neurodegeneration. Glial cells and Toll-like receptors (TLRs) are vital players in CNS immune response; dysregulation of this response plays an important role in brain damage and neurodegeneration. Ethanol has immunomodulatory effects and induces specific alterations in the TLRs response in many tissues. These actions depend on the cell type, ethanol dose and treatment duration, as well as the concomitant presence of pathogens and their characteristics. Recent findings indicate that low concentrations of ethanol (10 mM) promote inflammatory processes in brain and in glial cells by up-regulating cytokines and inflammatory mediators (iNOS, NO, COX-2), and by activating signaling pathways (IKK, MAPKs) and transcriptional factors (NF-kappaB, AP-1) implicated in inflammatory injury. TLR4/IL-1RI receptors may be involved in ethanol-mediated inflammatory signaling, since blocking these receptors abolishes the production of ethanol-induced inflammatory mediators and cell death. We propose that at low physiologically relevant concentrations, ethanol facilitates TLR4/IL-1RI recruitment into lipid rafts microdomains, leading to the activation and signaling of these receptors. In summary, current results suggest that TLR4/ IL-1RI are important targets of ethanol-induced inflammatory brain damage.

Usefulness of AgNOR technique and CEA expression in atypical metaplastic cells from cervical smears

OBJECTIVE

To evaluate the proliferating capacity of atypical metaplastic cells in cervical smears by AgNOR technique and image analysis and investigate the probable relation with squamous intraepithelial lesions (SIL) using immunocytochemical assay for carcinoembryonic antigen (CEA).

STUDY DESIGN

Eight cervical smears were stained with Papanicolaou stain for diagnosis of atypical metaplastic cells. After removal of the stain the smears were processed with a silver colloidal solution and the AgNOR area determined by image cytometry. Differences in the mean AgNOR protein area between reactive metaplastic cells and controls were tested by Student's t test. The CEA was investigated by immunocytochemical staining in smears with atypical metaplastic cells and smears from high-grade squamous intraepithelial lesions (HSIL).

RESULTS

The mean AgNOR areas from atypical metaplastic cells (4.55, 6.66, 4.68, 5.30, 4.97, 6.20, 6.28, and 7.35) were significantly greater those that of intermediate metaplastic cells and cells from low-grade squamous intraepithelial lesions (LSIL) (0.77, 0.99, and 0.82, respectively). The atypical metaplastic cells showed values of mean AgNOR area intermediate between that of basal cells (3.28) and HSIL cells (7.73) or neoplastic cells (16.12). The CEA was strongly expressed by the atypical metaplastic cells.

CONCLUSION

The expression of CEA in the atypical metaplastic cells underlies the probable relation to SIL. Although the organizer region areas raised high values, it would be necessary to use a greater number of cases to define whether the AgNOR area is indicative of the proliferative activity of the atypical metaplastic cells.

Asthenozoospermia: analysis of a large population

Spermatozoa travel a long distance to meet and fertilize the oocyte, so sperm motility is a requisite for normal fertilization. Asthenozoospermia, or low sperm motility, is a common cause of human male infertility. This is a retrospective study (1992-1999) to document the prevalence of this pathology in infertile men and to clarify the probable factors associated to its etiology. The prevalence was 18.71% for asthenozoospermia and 63.13% for asthenozoospermia associated with oligo- and/or teratozoo-spermia; thus, 81.84% of the studied samples had altered motility. Leukocytospermia, the ratio of germ cells/sperm, anti-sperm antibodies, consistency, biochemical markers of accessory sex glands, and sperm response after swim-up were studied in normospermic (N), asthenozoospermic (A), and combined asthenozoospermic (C) samples. No significant difference was found in the frequency of leukocytospermia among groups. The rate of germ cells/(spermatozoa + germ cells) between C and N (p < .01) and C and A (p < .01) was statistically different, while no difference was found on comparing N and A. MAR-test over 40% was found in 6% of the A samples and 7.6% of the C, while no positive values were observed in the N group. The percentage of hyperviscous samples was higher in the low sperm motility samples than in the normal group. Data on concentration of the biochemical markers seem to be decreased in asthenozoospermia. Pure and combined asthenozoo-spermia showed different behavior in sperm recovery after swim-up. Two different asthenozoospermias could be defined: the pure one where sperm environment is involved (immunological factor, hyperviscosity, and secretory gland function) and the combined, where the testis is comprised.

Epididymal cytology changes in hypothyroid rats

The purpose of this research was to investigate, using light, transmission, and scanning electron microscope, the effect of hypothyroidism on the ultrastructure of the rat epididymis. Thyroidectomy was obtained by ip injection of 270 microCi of (131)I per rat. One month later, several portions of cauda epididymis were examined. Morphological differences were detected in the epididymis of the hypothyroid animals when compared to the control normal rats. The hypothyroid conditions were associated with important changes in the epididymis. The light observations showed cells with clearing of the chromatin and increased density and thickness of the chromatic rim, chromatinic net, and disappearance of the segment of the chromatin rim. In the scanning electron microscope broken, oblique, denuded epithelial cells with loss of stereocilia were observed, as well as flattening of the tubule. The hypothyroid condition under transmission electron microscope was associated with a decrease in the height of the cells, diminution of the internal lumen and number of mitoses, and decreased chromatin decondensation. Results obtained confirmed that hypothyroidism causes marked structural changes in the ductus epididymis and could adversely affect the maturation and motility of sperm.

Shedding of immature germ cells

The immature germ cells (IGC) constitute the highest percentage (90%) of nonsperm cells (NSpC) in ejaculates from fertile or infertile men. The objective of this study was to evaluate IGC concentration and the IGC/(IGC + Sp) ratio, in normozoospermia and dispermia. Normozoospermia from men with proven fertility (NPF). nonproven fertility (NNPF). dispermia (D) and semen samples with excessive shedding of immature germ cells (GI 1.7 x 10(6) to 5 x 10(6) IGC/mL and GII > 5.0 x 10(6) IGC/mL) were used in this study. The mean value +2 SD for the NNPF (1.7 x 10(6)/mL) and the value proposed by WHO (5 x 10(6)/mL) were employed to define GI and GII groups. IGC concentration is statistically different in the studied groups. The IGC/Sp ratio showed a significant difference only between the NNPF and the D. When comparing semen parameters (Sp/ejaculate. grade (a) motility and morphology) there was a highly significant difference between NNPF and GI and GII: no difference was found between GI and GII. While studying 200 cases of dispermias 83% showed a high shedding of immature germ cells. The cytological study of nonsperm cells and the count and identification of the immature germ cells could be used to evaluate the dispermic disorders.

Epididymal scanning electron microscopy study in hypothyroid rats

The purpose of this research was to investigate, using scanning electron microscopy, the effect of hypothyroidism on the ultrastructure of the rat cauda epididymis. Thyroidectomy was obtained by ip injection of 270 muCi of 131I per rat. One month later, several portions of cauda epididymis were examined. Morphological and physiological differences were detected in the cauda epididymis of the hypothyroid animals when compared to the control normal rats. The hypothyroid condition was associated with important changes in the luminal surface of the cauda epididymis epithelium. Broken, oblique, and loss of stereocilia, denuded epithelial cells, and flattening of the tubule were observed. The results confirm that hypothyroidism causes marked structural changes in the cauda ductus epididymis and could be adversely affect sperm maturation motility.

[Usefulness of AgNOR technique in the interpretation of serous effusions]

BACKGROUND

AgNOR technique detects, using silver salts, argyrophylic proteins of the nucleolar organizer region (NOR). The number and size of NOR reflect cell activity, proliferation and transformation and may help to differentiate benign from malignant cells.

AIM

To assess the value of AgNOR assay to differentiate reactive mesothelial cells from malignant cells in serous effusions.

MATERIAL AND METHODS

Thirty one fluids obtained from 16 pleural, 14 peritoneal and one pericardial effusion, were studied. The fluids were processed with Giemsa and Papanicolau stains and with the AgNOR technique. The number of AgNOR dots were counted (only when it was possible to distinguish each individual dot) and the mean value per nucleus was calculated for each smear.

RESULTS

Mesothelial cells had a mean of 4.88 +/- 1.5 dots compared with 13.78 +/- 3.88 dots in the malignant cells (p < 0.001).

CONCLUSIONS

AgNOR assay can be useful for the differentiation of benign and malignant cells in serous effusions.

High-affinity binding of T3 to epididymis nuclei

Thyroid hormones play an important role in epididymal function. Hypothyroid animals experience a significant decrease in the number and forward motility of sperm and a remarkable impairment of epididymal morphology. However, it is yet unknown if such activity is due to direct actions of iodothyronines on the target epididymis. The eventual identification of T3 receptors in the nucleous of epididymal cells becomes relevant. For this reason, the authors searched for specific high-affinity binding of T3 to these nuclei. Twenty prepuberal male Wistar rats were used. The testes and epididymis were approached as one unit through a scrotal incision. The fat-free epididymides were subjected to standard techniques to prepare the nuclei for incubations with 125I-T3 concentrations, ranging from 0.5 x 10(-9) to 2.0 x 10(-11) M. Calculations of association constants and binding capacities were performed according to Scatchard. A single binding site with a Ka of 3.06 +/- 0.6 x 10(9) M(-1) or Kd of 3.26 +/- 0.6 x 10(10) M and a maximal binding capacity of 0.11 +/- 0.02 pmol T3/microg DNA were observed. It is concluded that these nuclei contain a specific T3 receptor. This finding strongly suggests that thyroid hormones have direct effects on the epididymis.

Changes in the epididymal ultrastructure in hypothyroid rats

The purpose of this research was to investigate the effect of hypothyroidism on the ultrastructure of the rat cauda epididymis. Thyroidectomy was obtained by i.p. injection of 270 microCi of 131I per rat. One month later, several portions of cauda epididymis were examined in an electron microscope. Morphological and physiological differences were detected in the cauda epididymis of the hypothyroid animals when compared to the control normal rats. The hypothyroid condition was associated with a decrease in the height of the cells and diminution of the internal lumen, number of mitoses, and chromatin decondensation. Hypothyroidism produces a remarkable impairment of epididymal morphology that could be mainly responsible for the functional alterations that lead to the dramatic slowing of spermatozoa motility, commonly seen in severe thyroid insufficiency.

Thyroid gland and epididymal sperm motility in rats

The purpose of this research was to investigate the effect of hypofunction of the thyroid gland, caused by radioactive suppression of the gland, on the pattern of spermatozoa motility in different segments of the rat epididymis. Thyroidectomy was obtained by i.p. infection of 270 microCi of I-131. After about 30 days, the animal reached hypothyroidism as determined by serum level of T4. When the motility pattern of the sperm obtained from the epididymis of normal rats was compared to that of hypothyroid animals, a drop in the parameter of path velocity (VAP), progressive velocity (VSL), and track speed (VCL) were detected. Hypofunction was associated with decreasing sperm motility in the epididymis. In thyroidectomized rats injected with T4, no sperm motility changes were observed.

Viscosity of human seminal fluid: role of lysozyme

The aim of this research was to evaluate the role of lysozyme in the phenomenon of seminal hyper-viscosity. The enzyme was determined in 142 samples of seminal plasma either leucospermic or not, with or without active macrophages classified according to their consistency (normal or high). The kinetic method with Micrococcus lysodeikticus as substrate was employed. No difference was found in enzymatic concentration expressed in nmol/L of enzymatic protein (mean +/- 2 SEM) on comparing normal and high seminal consistency groups, while differences proved highly significant in batches either leucospermic or not (n = 44, 197.2 +/- 51.3 vs. n = 98, 108.3 +/- 12.8; p < .0005). On subdividing the normal and high-consistency groups according to the count of polymorphonuclear leucocytes and the macrophagic responses, differences were also significant (p < .005 in both cases). Lysozyme concentration increases in presence of leucospermic reaction. In vitro lysozyme addition showed no significant effect on samples with high consistency. The results indicate that lysozyme plays no direct role in the phenomenon of seminal hyperviscosity, although its deficiency in cases of chronic infections may prove a factor aggravating the clinical picture.

'Ciliated' tumour cells in ascitic fluid from two cases of cystadenocarcinoma of the ovary

We report two cases of primary carcinoma of the ovary in which 'ciliated' adenocarcinoma cells were found in the ascitic fluid. Transmission electron microscopy revealed that these were not true cilia but rather a prolific growth of abnormal microvilli. The cytological findings were compared with the histological appearances of the primary tumour. No ciliated cells were seen in the primary tumour, suggesting that the formation of the microvilli represented an independent proliferation of the cells in the fluid. Special staining reactions for mucin, alkaline phosphatase and epithelial membrane antigen were identical in the primary tumour and the cells in the ascitic fluid.

Phagocytosis of ejaculated spermatozoa

In patients with accessory gland infections or subjects who have sperm antibodies in their semen, the presence of macrophages with phagocytic activity on ejaculated spermatozoa is significant. Light microscopy cannot certify phagocytosis because it does not give a three-dimensional view of the cells and can lead one to mistake superficial adherence of the spermatozoa to the macrophage for phagocytic activity. For that reason, scanning electron microscopy was used in this study. The samples, fixed with 2.5% glutaraldehyde in phosphate-buffered saline, were processed for observation with light microscopy (Giemsa or Papanicolaou stain) or with scanning electron microscopy (cell selection, critical point drying and paladium-platinum sputtering). With scanning electron microscopy, inactive macrophages had large membrane folds and a globular structure similar to those seen in ascites, whereas when active, they decreased in volume and developed a surface with granules or blebs. Inactive macrophages were rarely seen. A few minutes after mixing the different fractions of the ejaculate, phagocytosis reached such a level of activity that the spermatozoa partly covered the macrophages. Thus, we observed that the spermatozoa were caught by the head first in some instances but by the main-piece fragment of the tail first in other instances; very rarely were they taken by the midportion, between the head and tail. The presence in the ejaculate of macrophages with phagocytic activity on living, motile spermatozoa thus indicates that the encounter between the macrophages and spermatozoa was a result of the assemblage of components that make up the ejaculate. In this way the contributions of the prostatic gland and seminal vesicles play an important part in the spermiophagy of spermatozoa.

Human seminal biochemistry: fructose, ascorbic acid, citric acid, acid phosphatase and their relationship with sperm count

Seminal concentration of fructose, ascorbic acid, citric acid and acid phosphatase were measured in azoospermic, oligozoospermic and control males. No significant differences were found among the groups evaluated. The data obtained in the present study suggest that in the absence of infection and androgen deficiency, the failure of the germinal line of the testis is not correlated with alterations of the adnexal glands.

Development of mouse semilunar valves

The development of the semilunar valves of the great arteries of the mouse is studied by light and scanning electron microscopy. The earliest anlage of the valves is observed at day 11.5 of gestation, as three pairs of tubercles protruding towards the lumen of the truncus arteriosus. These early cusps consist of a core of mesenchymal tissue covered by the endocardium. From day 12.5 to 14 a process of excavation takes place in the arterial face of the cusps resulting in the achievement of their final shape. Our observations suggest that the excavation process is produced by a selective growth of the free edges of the cusps. Numerous pieces of evidence are reported suggesting that the selective growth of the cusps is due to an inductive interaction between the endocardium of the arterial face of the cusps and the underlying mesenchyme. The histogenesis of the cusps takes place very late in development and possibly continues into the postnatal period. The results are compared with studies made in other vertebrates.