Effects of naloxone on the oestradiol-induced LH surge and cortisol release in transported cows

Four control cows released a normal LH surge in response to 1 mg oestradiol benzoate i.m. Compared to controls, 30 min transport of 5 cows 16-18 h after oestradiol significantly delayed the onset (P less than 0.05), suppressed the amplitude (P less than 0.01) and reduced the total LH release (P less than 0.001) in 4 cows and totally blocked the surge in the 5th cow. Just before the onset of transport, 5 cows were given 250 mg naloxone i.v. In 3 cows, the LH surge was delayed and reduced in amplitude and duration and was totally blocked in the other two, i.e. naloxone did not avert the detrimental effects of transport. Transport stimulated cortisol release in cows. Cows given naloxone + transport released significantly more (P less than 0.001) cortisol than did those subjected to transport alone. In conclusion, naloxone appeared to have further stimulated the hypothalamopituitary-adrenal axis of cows under stress.     

Role for endocytosis of a constitutively active GPCR (GPR185) in releasing vertebrate oocyte meiotic arrest

Vertebrate oocytes are naturally arrested at prophase of meiosis I for sustained periods of time before resuming meiosis in a process called oocyte maturation that prepares the egg for fertilization. Members of the constitutively active GPR3/6/12 family of G-protein coupled receptors represent important mediators of meiotic arrest. In the frog oocyte the GPR3/12 homolog GPRx (renamed GPR185) has been shown to sustain meiotic arrest by increasing intracellular cAMP levels through Gα_Sβγ. Here we show that GPRx is enriched at the cell membrane (~80%), recycles through an endosomal compartment at steady state, and loses its ability to signal once trapped intracellularly. Progesterone-mediated oocyte maturation is associated with significant internalization of both endogenous and overexpressed GPRx. Furthermore, a GPRx mutant that does not internalize in response to progesterone is significantly more efficient than wild-type GPRx at blocking oocyte maturation. Collectively our results argue that internalization of the constitutively active GPRx is important to release oocyte meiotic arrest.     

Knockdown of HPRT for Selection of Genetically Modified Human Hematopoietic Progenitor Cells

The inability to obtain sufficient numbers of transduced cells remains a limitation in gene therapy. One strategy to address this limitation is in vivo pharmacologic selection of transduced cells. We have previously shown that knockdown of HPRT using lentiviral delivered shRNA facilitates efficient selection of transduced murine hematopoietic progenitor cells (HPC) using 6-thioguanine (6TG). Herein, we now extend these studies to human HPC. We tested multiple shRNA constructs in human derived cell lines and identified the optimal shRNA sequence for knockdown of HPRT and 6TG resistance. We then tested this vector in human umbilical cord blood derived HPC in vitro and in NOD/SCID recipients. Knockdown of HPRT effectively provided resistance to 6TG in vitro. 6TG treatment of mice resulted in increased percentages of transduced human CD45⁺ cells in the peripheral blood and in the spleen in particular, in both myeloid and lymphoid compartments. 6TG treatment of secondary recipients resulted in higher percentages of transduced human cells in the bone marrow, confirming selection from the progeny of long-term repopulating HPCs. However, the extent of selection of cells in the bone marrow at the doses of 6TG tested and the toxicity of higher doses, suggest that this strategy may be limited to selection of more committed progenitor cells. Together, these data suggest that human HPC can be programmed to be resistant to purine analogs, but that HPRT knockdown/6TG-based selection may not be robust enough for in vivo selection.     

Experimental diabetes in cats induced by partial pancreatectomy alone or combined with local injection of alloxan

Experimental diabetes was produced in cats by partial pancreatectomy using a short and technically simple surgical procedure. Electrocautery was used to cauterize pancreatic blood vessels and seal free edges of remaining pancreatic tissue to prevent secretion of pancreatic enzymes into the peritoneal cavity. In a second group of animals, partial pancreatectomy was followed by local injection of alloxan into an arterial branch of the cranio-mesenteric artery. The combined procedure resulted in diabetes mellitus in 100% (8 of 8) animals as compared to only 70% (14 of 20) in those subjected to partial pancreatectomy alone. In addition, the alloxan-pancreatectomized cats had a reduced latency period prior to onset of chronic hyperglycemia (4.8 days compared to 19.3 days postoperatively in pancreatectomized cats). The diabetic cats were maintained in poor metabolic control (blood glucose approximately 300 mg/dl) by daily injections of low doses of long-acting insulin. Pancreatic enzyme supplementation was given by mouth. Weight changes and blood glucose levels were monitored carefully to maintain the health of the animals while keeping them in poor metabolic control.