Evaluation of candidate spermatogonial markers ID4 and GPR125 in testes of adult human cadaveric organ donors

The optimal markers for human spermatogonial stem cells (SSCs) are not known. Among the genes recently linked to SSCs in mice and other animals are the basic helix-loop-helix transcription factor ID4 and the orphan G-protein-coupled receptor GPR125. While ID4 and GPR125 are considered putative markers for SSCs, they have not been evaluated for coexpression in human tissue. Furthermore, neither the size nor the character of the human spermatogonial populations that express ID4 and GPR125, respectively, are known. A major barrier to addressing these questions is the availability of healthy adult testis tissue from donors with no known reproductive health problems. To overcome this obstacle, we have employed healthy testicular tissue from a novel set of organ donors (n = 16; aged 17-68 years) who were undergoing post-mortem clinical organ procurement. Using immunolabelling, we found that ID4 and GPR125 are expressed on partially overlapping spermatogonial populations and are more broadly expressed in the normal adult human testis. In addition, we found that expression of ID4 remained stable during ageing. These findings suggest that ID4 and GPR125 could be efficacious for identifying previously unrecognized human spermatogonial subpopulations in conjunction with other putative human stem cell markers, both in younger and older donors.

Characterization of the EP receptor subtype that mediates the inhibitory effects of prostaglandin E2 on IgE-dependent secretion from human lung mast cells

BACKGROUND

Prostaglandin E2 (PGE2 ) has been shown to inhibit IgE-dependent histamine release from human lung mast cells. This effect of PGE2 is believed to be mediated by EP2 receptors. However, definitive evidence that this is the case has been lacking in the absence of EP2 -selective antagonists. Moreover, recent evidence has suggested that PGE2 activates EP4 receptors to inhibit respiratory cell function.

OBJECTIVE

The aim of this study was to determine the receptor by which PGE2 inhibits human lung mast cell responses by using recently developed potent and selective EP2 and EP4 receptor antagonists alongside other established EP receptor ligands.

METHODS

The effects of non-selective (PGE2 , misoprostol), EP2 -selective (ONO-AE1-259, AH13205, butaprost-free acid) and EP4 -selective (L-902,688, TCS251) agonists on IgE-dependent histamine release and cyclic-AMP generation in mast cells were determined. The effects of EP2 -selective (PF-04418948, PF-04852946) and EP4 -selective (CJ-042794, L-161,982) antagonists on PGE2 responses of mast cells were studied. The expression of EP receptor subtypes was determined by RT-PCR.

RESULTS

Prostaglandin E2 , EP2 agonists and EP4 agonists inhibited IgE-dependent histamine release from mast cells. PGE2 and EP2 agonists, but not EP4 agonists, increased cyclic-AMP levels in mast cells. EP4 -selective antagonists did not affect the PGE2 inhibition of histamine release, whereas EP2 -selective antagonists caused rightward shifts in the PGE2 concentration-response curves. RT-PCR studies indicated that mast cells expressed EP2 and EP4 receptors.

CONCLUSIONS AND CLINICAL RELEVANCE

Although human lung mast cells may express both EP2 and EP4 receptors, the principal mechanism by which PGE2 inhibits mediator release in mast cells is by activating EP2 receptors.

Direct imaging of 3D atomic-scale dopant-defect clustering processes in ion-implanted silicon

The fabrication of nanoscale semiconductor devices for use in future electronics, energy, and health is among others based on the precise placement of dopant atoms into the crystal lattice of semiconductors and their concurrent or subsequent electrical activation. Dopants are built into the lattice by fabrication processes like ion implantation, plasma-based doping, and thermal annealing. Throughout the fabrication processes fundamental phenomena like dopant diffusion, activation, and clustering occur concurrently with damaging and subsequently recovering the crystal lattice. These processes are described by atomic-scale mechanisms of ion-host atom interaction and have an immense impact on the electrical performance of the resulting devices. Insight in their fundamental nature is of utmost importance for optimizing the performance of nanoscale technologies. In this paper, we demonstrate direct three-dimensional imaging of boron clusters and atoms in crystal defects using field ion microscopy. Our approach allows for the first time the complete characterization of the size and crystallographic orientation of boron-decorated crystal defects. This new method opens a path to image a wide variety of dopant-cluster forms and hence to study the formation and dissolution of boron clusters in silicon on the atomic scale.

Prophylactic penicillin after 5 years of age in patients with sickle cell disease: a survey of sickle cell disease experts

BACKGROUND

Since the publication of the Prophlyactic Penicillin Study II in 1995, the management of penicillin prophylaxis for children with sickle cell disease (SCD) after 5 years of age has been controversial. In this study, we sought to describe current practice patterns of pediatric hematologists related to cessation of penicillin prophylaxis for children with SCD after 5 years of age.

PROCEDURE

We performed a cross-sectional, electronic survey of pediatric hematologists with expertise in SCD to examine practices regarding penicillin prophylaxis in children with SCD after 5 years of age. We also investigated factors potentially associated with continuation of penicillin prophylaxis using the Jonckheere-Terpstra test and Fisher's exact test.

RESULTS

Of the 106 physicians surveyed from 76 centers, 84% completed the survey. Among respondents, 76% routinely recommended cessation of penicillin prophylaxis after 5 years of age. The practice of routinely continuing penicillin after 5 years of age was associated with decreased concern about antibiotic resistance in Streptococcus pneumoniae (P = 0.01), with the usage of prophylactic penicillin in mild SCD genotypes (sickle hemoglobin-C disease and sickle β(+) thalassemia, P = <0.001), and with increasing use of other preventive evaluations (e.g., MRI for silent stroke) in childhood (P = 0.05).

CONCLUSION

Most pediatric hematologists with an SCD expertise recommend cessation of prophylactic penicillin after 5 years of age.