Early spiral arteriole remodeling in the uterine-placental interface: A rat model.

The mammalian placenta's interface with the parent is a richly vascularized tissue whose development relies upon communication between many different cell types within the uterine microenvironment. The uterine blood vessels of the interface are reshaped during pregnancy into wide-bore, flaccid vessels that convey parental blood to the exchange region of the placenta. Invasive trophoblast as well as parental uterine macrophages and Natural Killer cells are involved in the stepwise remodeling of these vessels and their respective contributions to this crucial process are still being delineated. However, the earliest steps in arteriole remodeling are understudied as they are difficult to study in humans, and other species lack the deep trophoblast invasion that is so prominent a feature of placentation in humans. Here, we further characterize the rat, with deep hemochorial placentation akin to humans, as a model system in which to tease apart the earliest, relatively understudied events in spiral arteriole remodeling. We show that the rat uterine-placental interface increases in size and vascularity rapidly, before trophoblast invasion. The remodeling stages in the arterioles of the rat uterine-placental interface follow a sequence of anatomical changes similar to those in humans, and there are changes to the arterioles' muscular tunica media prior to the marked influx of immune cells. The rat is a tractable model in which to better understand the cell/cell interactions occurring in vivo in an intact tissue microenvironment over time.

Intra-horn insemination in the alpaca Vicugna pacos: Copulatory wounding and deep sperm deposition.

Alpacas (Vicugna pacos) are reported to be the rare mammal in which the penis enters the uterus in mating. To date, however, only circumstantial evidence supports this assertion. Using female alpacas culled for meat, we determined that the alpaca penis penetrates to the very tips of the uterine horns, abrading the tract and breaking fine blood vessels. All female alpacas sacrificed one hour or 24 hours after mating showed conspicuous bleeding in the epithelium of some region of their reproductive tract, including the hymen, cervix and the tips of each uterine horn, but typically not in the vagina. Unmated females showed no evidence of conspicuous bleeding. Histological examination of mated females revealed widespread abrasion of the cervical and endometrial epithelium, injuries absent in unmated females. Within one hour of mating, sperm were already present in the oviduct. The male alpaca's cartilaginous penis tip with a hardened urethral process is likely responsible for the copulatory abrasion. The entire female reproductive tract interacts with the penis, functioning like a vagina. Alpacas are induced ovulators, and wounding may hasten delivery of the seminal ovulation-inducing factor beta-NGF into the female's blood stream. There is no evidence of sexual conflict in copulation in alpaca, and thus wounding may also be one of a variety of mechanisms devised by mammals to induce a beneficial, short-term inflammatory response that stimulates blastocyst implantation, the uterine remodeling associated with placental development, and thus the success of early pregnancy.

Areal and synaptic interconnectivity of prelimbic (area 32), infralimbic (area 25) and insular cortices in the rat.

This study investigated the interconnectivity of areas in the medial prefrontal and insular cortices in the rat. The areas studied were the prelimbic (PL, area 32) and infralimbic (IL, area 25) cortices and the dorsal anterior agranular insular (AId) and regions of posterior insular cortex (PI-comprising the agranular, dysgranular and granular fields). Following injections of the anterograde tracer biotinylated dextran amine (BDA) into layers 2-5 of each area, labelled axonal varicosities were found ipsilaterally in the other cortical areas. The most prominently labelled pathways were PL-->AId, AId-->PL, IL-->AId/PI, and PI-->IL. Qualitative and quantitative examinations of the laminar distribution of labelled axonal varicosities in the terminal fields indicated the existence of topographically organised 'feed-forward' (insular to PL/IL) and 'feed-back' (PL/IL to insular) pathways. The identity of the post-synaptic targets innervated by the PL/IL to AId pathways were investigated ultrastructurally. An analysis of 250 anterogradely labelled synaptic boutons (taken from layers 2/3) indicated that spine heads (presumed to originate from pyramidal cells) were the principal (88-93%) targets; all identified synaptic junctions were asymmetric. The results define an interconnected network of reciprocal pathways between cortical areas processing general and specific 'viscerosensory' information (AId and PI) and medial areas involved in cognitive (PL) and visceromotor (IL) functions. The data provide important aspects of the cortical circuitry underlying the integration of cognitive and emotional processing mechanisms, not only in rats, but also in primates.