Facultative endocrine progenitor cells in the adult pancreas

Using a unique injury model of the pancreas in mouse, Xu et al. (2008) now reveal the involvement of neurogenin3, a marker for embryonic-type endocrine progenitor cells, in the formation of new insulin-producing beta cells. These neurogenin3-positive facultative endocrine progenitor cells in the adult pancreas may be of potential value for treating diabetes.     

Period gene expression in mouse endocrine tissues

Circadian rhythms are generated by the oscillating expression of the Per1 and Per2 genes, which are expressed not only in the central brain pacemaker but also in peripheral tissues. Hormones are likely to coordinate physiological function in time. We performed in situ hybridization to localize mPer1 and mPer2 mRNA to particular cell types and tissue compartments in adrenal, thyroid, and testis. BALB/c mice maintained in a 12:12-h light-dark cycle expressed mPer1 in adrenal medulla, particularly in late afternoon and early night. mPer2 mRNA was more intensely expressed in adrenal cortex, especially in afternoon and evening. mPer1 mRNA was detected in thyroid. mPer1 was found in some but not all seminiferous tubules of each mouse at all times of day. Quantitation in C57BL/6 mice revealed a significant increase in the number of heavily labeled seminiferous tubules early in the night. Consistent with in situ hybridization, immunocytochemistry showed PER1 protein in spermatocytes and spermatids (spermatogenic stages VII-XII). Staining in spermatogonia and interstitial cells was inconsistent. Double labeling with 5'-bromodeoxyuridine showed PER1 expression first occurring 5 days after DNA replication. We conclude that mPeriod genes are expressed in peripheral endocrine glands. Central regulation, adenohypophyseal control, and functional importance of expression and phase remain to be elucidated.     

Identification of the endocrine cells detected by the monoclonal antibody HISL-19 in human tissues.

The human endocrine cells reacting with the monoclonal antibody HISL-19 were identified with hormone antisera of proven specificity using a double immunostaining procedure. The epitope for HISL-19 was found in all types of pituitary cells except ACTH cells, in thyroid C cells, in all types of adrenal medullary and pancreatic islet cells and in somatostatin and pancreatic polypeptide cells of the gastrointestinal mucosa. No staining was found in parathyroid cells and in most gastrointestinal endocrine cells. Either paranuclear focal accumulation or diffuse cytoplasmic distribution of immunoreactive material were found. The spectrum of HISL-19 immunoreactive cells was found to be only in part complementary to that of cells immunoreactive for chromogranin A. Thus, it is concluded that the monoclonal antibody HISL-19 is a useful addition to other immunohistochemical markers for the detection of cells showing neuroendocrine features.     

Colchicine-induced polyploidy in phalaenopsis orchids

Colchicine can induce polyploidy in phalaenopsis orchids. When young protocorms are treated in liquid culture with 50 mg/l colchicine, about 50% of the protocorms develop into tetraploids.     

Roads to polyploidy: the megakaryocyte example.

Polyploidy, recognized by multiple copies of the haploid chromosome number, has been described in plants, insects, and in mammalian cells such as, the platelet precursors, the megakaryocytes. Several of these cell types reach high ploidy via a different cell cycle. Megakaryocytes undergo an endomitotic cell cycle, which consists of an S phase interrupted by a gap, during which the cells enter mitosis but skip anaphase B and cytokinesis. Here, we review the mechanisms that lead to this cell cycle and to polyploidy in megakaryocytes, while also comparing them to those described for other systems in which high ploidy is achieved. Overall, polyploidy is associated with an orchestrated change in expression of several genes, of which, some may be a result of high ploidy and hence a determinant of a new cell physiology, while others are inducers of polyploidization. Future studies will aim to further explore these two groups of genes.     

Facultative Hemi-parasitism in Buchnera hispida Buch.- Ham. ex D. Don

Some aspects of growth in pot cultures of Buchnera hispida seedlings,and variations in their performance in the presence and absenceof a host, Sorghum vulgare, were investigated. It is shown thatB. hispida, planted singly or in groups, can complete its lifecycle in the absence of a foreign host but when one is available,it attacks the host through haustorial connections, and growsmore vigorously. There is no effect on the time of floweringor on seed viability. Anatomical studies of the haustorial connectionbetween host and parasite reveal that actual union of tissuesbetween the two roots occurs at the haustorial bridge. The host-parasiteinteraction often results in the death of the host Sorghum.The potential danger posed by B. hispida to cereal crops inthe tropics is discussed.     

Spontaneous polyploidy in laboratory mice. Embryological and cytogenetic analysis]

The developmental patterns of mice with spontaneous genomic aberrations at the pre- and post-implantation embryonic stages have been studied. The frequency of spontaneous triploidy varies in different strains from 1.7 to 5.8%. Digeny is the principal cytogenetical mechanism for triploidy. The triploid embryos of all the strains under study are characterized by the total delay of development already at the blastocyst stage. The most of triploids die at the stages of neurula and beginning of active organogenesis. A few triploids are resorbed during placentation. In the CBA mice, the triploidization results in the characteristic syndrome: disproportionally reduced amniotic vesicle, hypertrophied allantoic rudiment, reduction of neural plate, absence of head folds, notochord and mesenchyme. The spontaneous tetraploidy in mice occurs very rarely and is accompanied by severe developmental defects already at the preimplantation stages.     

Facultative parthenogenesis discovered in wild vertebrates

Facultative parthenogenesis (FP)—asexual reproduction by bisexual species—has been documented in a variety of multi-cellular organisms but only recently in snakes, varanid lizards, birds and sharks. Unlike the approximately 80 taxa of unisexual reptiles, amphibians and fishes that exist in nature, FP has yet to be documented in the wild. Based on captive documentation, it appears that FP is widespread in squamate reptiles (snakes, lizards and amphisbaenians), and its occurrence in nature seems inevitable, yet the task of detecting FP in wild individuals has been deemed formidable. Here we show, using microsatellite DNA genotyping and litter characteristics, the first cases of FP in wild-collected pregnant females and their offspring of two closely related species of North American pitviper snakes—the copperhead (Agkistrodon contortrix) and cottonmouth (Agkistrodon piscivorus). Our findings support the view that non-hybrid origins of parthenogenesis, such as FP, are more common in squamates than previously thought. With this confirmation, FP can no longer be viewed as a rare curiosity outside the mainstream of vertebrate evolution. Future research on FP in squamate reptiles related to proximate control of induction, reproductive competence of parthenogens and population genetics modelling is warranted.