Effect of inhibitors of polyamine biosynthesis on primary differentiation of mouse egg]

Alpha-Methylornithine, an inhibitor of the synthesis of putrescine does not affect the cleavage of Mouse eggs, cultured in vitro from the 2-cell stage, before blastocyst formation, whereas methylglyoxal-Bis (guanylhydrazone), an inhibitor of the syntheses of spermidine and spermine induces the embryos to become quiescent at about the 8-cell stage; resumption of their development, after transfer to fresh medium, is followed by a delay in cavitation. These results may be related to the biological clock theory for primary differentiation.     

Pancreatic islet β-cell deficit and glucose intolerance in rats with uninephrectomy

This study was performed to examine the effect of chronic renal impairment and renin-angiotensin system (RAS) activation induced by unilateral nephrectomy (UNX) on the development of pancreatic islet β-cell deficit and glucose intolerance. Sprague-Dawley rats were randomized into three groups: untreated UNX (n = 10), UNX treated with the angiotensin-converting enzyme inhibitor lisinopril (n = 8) and sham operation (n = 10). Blood glucose, serum insulin, renal function and histological changes of kidney and pancreas were examined 8 months postoperation. Compared with the sham rats, UNX rats developed renal impairment, insulin deficiency and glucose intolerance. Histological staining revealed an islet β-cell deficit associated with increased immunoreactivity for angiotensin and angiotensin type 1 receptor in UNX rats. Treatment with lisinopril significantly improved renal dysfunction, hyperglycemia, insulin secretion and islet RAS expression. These data suggest that chronic renal impairment and RAS activation may contribute to islet β-cell loss and glucose intolerance. RAS blockade may therefore prevent these disorders. Received 29 August 2007; received after revision 25 September 2007; accepted 27 September 2007     

La vitellogenesi inArbacia lixula eSphaerechinus granularis (Echin. Echin.)

Summary The researches carried out both under the light and electron microscopes permitted us to ascertain that, in EchinodermataArbacia lixula andSphaerechinus granularis, yolk globules form by aggregation of ribonucleoproteic particles. It appears that the globules themselves in the first stage of their formation show such physico-chemical conditions as to condition the precipitation of silver in the method used to reveal Golgi apparatus.     

Receptor-mediated transport and deposition of complement component C3 into developing chicken oocytes

Immunological resistance of the chick embryo is dependent upon IgG present in the yolk of the layed egg. Here we show that complement factor 3 (C3), a key component of the humoral complement system, is a yolk component of chicken eggs. C3 is transported into oocytes by LR8-mediated endocytosis. LR8 also binds and transports other major yolk components such as vitellogenin, very-low-density lipoprotein, and α₂-macroglobulin. Expression studies of LR8 during chicken development and oocyte maturation, in combination with studies on the uptake of individual yolk components, suggest the following model for oocyte maturation in the chicken: all oocytes present in the ovary contain high levels of LR8 mRNA and protein long before the onset of oocyte maturation. Selected oocytes gain access to yolk precursors, and LR8 binds, internalizes, and deposits the major yolk components in the ratio of their relative abundance in the accessible pool.Received 9 May 2005; received after revision 6 June 2005; accepted 13 June 2005     

Correlation between ovarian growth,vitellogenin titer,and yolk polypeptide pattern in the haemolymph ofCalliphora vicina

Summary During the first egg maturation cycle ofCalliphora vicina changes in the vitellogenin titer and yolk polypeptide pattern of the haemolymph are correlated with the intensity of follicular growth, and the rate of yolk deposition.Acknowledgments. Support from The Danish Natural Science Research Council (grant: 11-0423) and access to facilities at the laboratory of Dr Bente L. Hansen (Institute of Medical Microbiology) is gratefully acknowledged.     

Über die Entstehung spezifischer bioaktiver Stoffe in der frühembryonalen Entwicklung der Tiere

Summary The autor studied the reaction of stage ontogenins with different proteids, isolated from the embryos at the moment of formation of the respective ontogenin. Not all fractions (least of all the yolk) fix the ontogenins. The DNA-proteids fix them; such a mixture specifically stimulates the development. In these mixtures, new substances are discovered: Ontogens.     

Immunochemical identification of vitellogenin in the serum of the newtTriturus cristatus

Summary The hematic yolk precursor — vitellogenin — has been identified immunochemically in the serum of estrogenized females of the newtTriturus cristatus by employing an antiserum prepared against yolk proteins.     

Vitellogenesis in the air breathing fish,Channa punctatus (Bloch)

Summary Two types of yolk develop in the oocyte ofChanna punctatus. The carbohydrate yolk, which develops from the material present in the ooplasm, breaks up for the use of the growing oocyte before ovulation takes place. The proteid yolk, developing from the extraoocytic material, finally crams the fully mature oocyte, perhaps to participate in the process of embryogenesis.Acknowledgments. The authors are grateful to Professor C.C. Das, for his encouragement and the laboratory facilities. The award of a U.G.C. junior fellowship to one of us (U.R.A.) by the Berhampur University is thankfully acknowledged.     

Increase in acid phosphatase activity during fertilization of a teleost egg

Summary Acid phosphatase activity was localized at the periphery of the yolk globules in the egg of the teleost,Catostomus commersoni. In addition, a 3-fold increase in acid phosphatase activity was associated with fertilization and pronucleus formation.I thank Dr C. W. Huver for use of facilities.     

Survival of rabbit embryos after rapid freezing and thawing

Summary Frozen storage of rabbit embryos at the 16-cell stage in 2.0 M dimethylsulfoxide (DMSO) in phosphate-buffered saline (PBS) was achieved by a 2-step procedure. After storage for 10 days at–196°C they were revived by rapidly thawing at 500°C/min. On transfer of these embryos to pseudopregnant foster mothers, 50% survived to term. The difference in in vivo survival between frozen-thawed and frozen-thawed-cultured embryos was not significant.Acknowledgment. The authors thank the Director for the facilities. VHR is supported by Council of Scientific and Industrial Research (India).     

Mitocondri,zone del Golgi e globuli vitellini negli ovociti in accrescimento diPlanorbis corneus L. (Moll. Gast. Polm.)

Summary The authors observed, in the oocytes ofPlanorbis corneus, that the yolk globules are formed from the mitochondria, which first swell up and then are filled with proteic particles (of a probably ribosomal nature). Such a process is in relation to the formation of the Golgi zones.     

Acid phosphatase in eggs of the zebrafish,Brachydanio rerio

Summary 2 isozymes of acid phosphatase have been identified by polyacrylamide disc gel electrophoresis in the ovary and mature, unfertilized eggs ofB. rerio. Histochemically, the enzyme appears to be localized in preyolk bodies of previtellogenic oocytes and in yolk platelets of vitellogenic and postvitellogenic oocytes. The contents of the cortical granules at all stages of oocyte differentiation were acid phosphatase negative.     

Transthyretin binds to glucose-regulated proteins and is subjected to endocytosis by the pancreatic β-cell

Transthyretin (TTR) is a functional protein in the pancreatic β-cell. It promotes insulin release and protects against β-cell death. We now demonstrate by ligand blotting, adsorption to specific magnetic beads, and surface plasmon resonance that TTR binds to glucose-regulated proteins (Grps)78, 94, and 170, which are members of the endoplasmic reticulum chaperone family, but Grps78 and 94 have also been found at the plasma membrane. The effect of TTR on changes in cytoplasmic free Ca²⁺ concentration ([Ca²⁺]_i) was abolished if the cells were treated with either dynasore, a specific inhibitor of dynamin GTPase that blocks clathrin-mediated endocytosis, or an antibody against Grp78, that prevents TTR from binding to Grp78. The conclusion is that TTR binds to Grp78 at the plasma membrane, is internalized into the β-cell via a clathrin-dependent pathway, and that this internalization is necessary for the effects of TTR on β-cell function.     

Comparison of the in vitro development of mouse single blastomeres with and without the zona pellucida

No difference was observed during in vitro development between mouse single blastomeres with and without the zona pellucida, isolated from 2- and 4-cell stage eggs.     

Comparison of the in vitro development of mouse single blastomeres with and without the zona pellucida

Summary No difference was observed during in vitro development between mouse single blastomeres with and without the zona, pellucida, isolated from 2- and 4-cell stage eggs.     

Histopathological effect of thiourea on the ovarian tissues ofSarcophaga ruficornis (Fabr.)

Summary The primary target of thiourea in femaleSarcophaga are the follicles in the ovarioles. The follicle cells as a result become syncytial and their nuclei get pycnotic, inhibiting the transport of nutrient material into the nurse cells and of yolk into the oocytes. The subnormal eggs produced are not viable.     

Explantationsin vitro de blastodermes de Poissons(Salmo,Esox)

Summary Blastula of trout (Salmo irideus) and pike (Esox lucius), deprived of their yolk, are cultivated in the Holtfreter solution. The differenciation of the germ of the trout stops; that of the pike germ is carried on almost normally. That difference might be due to the influence of nucleic acids contained in it.     

The effect of proctolin on the adenylate and guanylate cyclases in theLocusta brain at various developmental stages

Summary Proctolin at concentrations 10^–8–10^–7 M elevated by 40% brain adenylate cyclase activity of adultLocusta migratoria migratorioides R.F. In moulting individuals, proctolin caused a decrease in brain adenylate cyclase activity, and it proved to be ineffective in the larvae. Proctolin caused only a slight decrease on guanylate cyclase activity of the brain at every developmental stage.     

AfricanClarias catfish elicits long-lasting weak electric pulses

The African catfishClarias is generally considered to possess electroreceptors but not electric organs. It is reported here that at least one species of the genus,C. gariepinus, can produce weak monophasic discharges during aggressive interactions with conspecifics. These irregular pulse discharges are substantially longer than the electric organ discharges (EODs) of all other pulse-generating freshwater electric fishes. It is also shown that the optimal sensitivity ofClarias' ampullary receptors just corresponds to the modal pulse duration. TheClarias catfish, with its very specific EOD, may be of special interest in the evolution of the electrogenic system in the siluriforms, comprising many electroreceptive but nonelectrogenic catfish species.