Exploring common ground in the stem cell ethical debate—A perspective for scientists

The purpose of this special issue of Stem Cell Reviews is to address some of the most difficult ethical debates surrounding the derivation of pluripotent stem cell lines. The possible benefits of stem cells are widely discussed, but the scientific community is particularly aware that research in this area is still at an early, but essential, stage of development. With this research at such an early stage, it is noteworthy that the media, the public, religious leaders, politicians, policy makers, and regulators have had as much interest in stem cell research as for any other area of scientific inquiry. The central issue that has made this area so controversial has been the use of the human embryo for deriving stem cell lines.     

Selective vulnerability of unmyelinated fiber Schwann cells in nerves exposed to local anesthetics

When peripheral nerves of experimental rats are exposed to local anesthetics, distinctive and reproducible pathologic changes occur involving the perineurial sheath and endoneurial contents. Application of intermediate strength concentrations of the local anesthetics, 2-chloroprocaine, lidocaine, etidocaine, and intermediate or high concentrations of procaine to the surface of rat sciatic nerves resulted in the following changes. By 48 hours, the perineurial sheath exposed to the drug was disrupted and became permeable to granulocytes which infiltrated the subjacent endoneurium in conjunction with edema formation in the endoneurial interstitium. Application of 10% procaine to exposed nerve resulted in extensive demyelination. The most striking pathologic change occurring with either intermediate or high doses was accumulation of lipid droplets in Schwann cells, a phenomenon that occurred often in myelin-producing Schwann cells but much less frequently in unmyelinated fiber Schwann Cells. Lipid accumulation appears to be one of several reactive changes that affect Schwann cells of myelinated fibers and is dose-dependent. On the other hand, while reactive changes were infrequently seen in unmyelinated fiber Schwann cells, these cells appeared more susceptible to injury as shown by electron microscopy. Injury to Schwann cells by local anesthetics is temporary because these cells can replicate quickly. Autoradiographic studies of thymidine incorporation 1 week after procaine administration to the sciatic nerve showed intense proliferation of Schwann cells, but no such activity in controls. These findings support the view that their neurotoxic properties may account in some part for the function of local anesthetics, that Schwann cells of small unmyelinated fibers are more vulnerable to these agents than those of myelinated fibers, and that destruction of their supporting cells is followed by vigorous mitotic activity in the endoneurium.     

Visualisation of the extent of damage in a rat spinal cord injury model using MR microsopy of the water diffusion tensor

Magnetic Resonance Diffusion Tensor Imaging (DTI) of the control and traumatic injured spinal cord of a rat in vitro is reported. Experiments were performed on excised spinal cords from 10 Wistar rats, using a home-built 6.4 T MR microscope. MRI and histopathological results were compared. Presented results show that DTI of the spinal cord, perfused with formalin 10 minutes after the injury, can detect changes in water diffusion in white matter (WM) and in gray matter (GM), in areas extending well beyond the region of direct impact. Histology of neurons of the GM shows changes that can be attributed to ischemia. This is in agreement with the observed decrease of diffusion in the injured regions, which may be attributed to the cytotoxic edema due to ischemia. However, the diffusion changes in highly anisotropic WM seem to be caused by a direct action of mechanical force of impact, which significantly distorts the nerve fibers.     

Nuclear receptor NR2E3 gene mutations distort human retinal laminar architecture and cause an unusual degeneration

Mutations in the nuclear receptor gene, NR2E3, cause a disorder of human retinal photoreceptor development characterized by hyperfunction and excess of the minority S (short wavelength or blue) cone photoreceptor type, but near absence of function of the majority rod receptor. NR2E3 disease can also progress to blindness. How the human retina accommodates mis-specified types and numbers of neurons and advances to retinal degeneration are unknown. We studied the retinal organization in vivo of patients with NR2E3 mutations. Early human NR2E3 disease with S cone hyperfunction showed thickened retinal layers within an otherwise normally structured retina. With visual loss, however, lamination was coarse and there was a strikingly thick and bulging appearance to the retina, localized to an annulus encircling the central fovea. This pattern was not found in other retinal degenerations. The abnormal laminar retinal architecture of early NR2E3 disease may be due in part to larger cells with an S cone phenotype in place of rods that failed to differentiate. The later-stage dysplastic appearance suggests a previously unrecognized proliferative response in human retinal degeneration.     

Binding of lipopeptide to CD14 induces physical proximity of CD14, TLR2 and TLR1

Lipoproteins or lipopeptides (LP) are bacterial cell wall components detected by the innate immune system. For LP, it has been shown that TLR2 is the essential receptor in cellular activation. However, molecular mechanisms of LP recognition are not yet clear. We used a FLAG-labeled derivative of the synthetic lipopeptide N-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2R,S)-propyl]-(R)-cysteinyl-seryl-(lysyl)(3)-lysine (Pam(3)CSK(4)) to study the roles of CD14, TLR2 and TLR1 in binding and signaling of LP and their molecular interactions in human cells. The activity of Pam(3)CSK(4)-FLAG was TLR2 dependent, whereas the binding was enabled by CD14, as evaluated by flow cytometry and confocal microscopy. Using FRET and FRAP imaging techniques to study molecular associations, we could show that after Pam(3)CSK(4)-FLAG binding, CD14 and Pam(3)CSK(4)-FLAG associate with TLR2 and TLR1, and TLR2 is targeted to a low-mobility complex. Thus, LP binding to CD14 is the first step in the LP recognition, inducing physical proximity of CD14 and LP with TLR2/TLR1 and formation of the TLR2 signaling complex.     

Situational factors associated with AIDS risk behavior lapses and coping strategies used by gay men who successfully avoid lapses

While most gay men have reduced behavior practices at high risk for HIV infection, there is growing evidence that many also lapse to unsafe sex. This study examined situational factors related to risk behavior lapses as well as coping strategies used by men who successfully resist lapse urges. A convenience sample of 470 men patronizing gay bars or attending social organization meetings in four cities was surveyed. Forty-five percent of men were classified as "lapsers" (those who had had unprotected anal intercourse in the previous 6 months) and 24% were classified as "resisters" (those who successfully resisted urges to engage in this behavior). All provided information concerning the importance of factors related to the most recent occurrence of either unsafe sex or resisting unsafe urges. Most episodes of unsafe sex occurred outside monogamous relationships and with partners of unknown HIV serostatus, although simply inquiring about partner serostatus was relatively common. Lapsers rated affectionate feelings and wishing to please a partner as well as spontaneity of unsafe sex as the most important situational factors surrounding high-risk behavior. Resisters of unsafe sex urges reported active cognitive self-guidance, experience in safe sex, and recall of both AIDS fears and safety benefits as their most important coping strategies. Gay men who continue high-risk behavior may be overrelying on partner reports of negative serostatus. Lapse prevention approaches tailored to situations that create increased risk vulnerability must be developed. Teaching skills already used by men who successfully resist unsafe sex urges might be one approach.     

Effectiveness of diaphragmatic stimulation with single-channel electrodes in rabbits

Every year, a large number of individuals become dependent on mechanical ventilation because of a loss of diaphragm function. The most common causes are cervical spinal trauma and neuromuscular diseases. We have developed an experimental model to evaluate the performance of electrical stimulation of the diaphragm in rabbits using single-channel electrodes implanted directly into the muscle. Various current intensities (10, 16, 20, and 26 mA) produced tidal volumes above the baseline value, showing that this model is effective for the study of diaphragm performance at different levels of electrical stimulation     

Współwystępowanie dwóch rzadkich chorób genetycznych: fenyloketonurii oraz zespołu Pradera i Williego. Opis przypadku

Phenylketonuria (PKU) is an autosomal recessive metabolic disease caused by an error of phenylalanine metabolism. Delayed treatment or treatment performed unsystematically might lead to neurological disorders and progressive intellectual disability. In the Prader-Willi syndrome (PWS) clinical manifestations change with age. Feeding difficulties resulting from the poor suck and hypotonia are typical in the neonatal period and early infancy. As patients grow their activities increase, muscle tone improves, the extreme hyperphagia appears – the main cause of obesity. Mental development of patients is usually mildly retarded. We report the case of a patient affected by two genetic diseases: PKU and PWS. Variety of clinical symptoms and abnormal results of laboratory analyses make the correct diagnosis difficult. Elevated phenylalanine level in screening newborn test, disorders of muscle tone, poor suck, and low urine biopterin concentration did not allow to clearly rule out the hyperphenylalaninemia caused by a tetrahydrobiopterin deficiency (BH₄). Data from obstetric anamnesis and the early postnatal clinical findings suggested the PWS. Hyperphagia and the increased risk of carbohydrates tolerance disorders in patients with PWS make it very difficult to balance properly the low-phenylanine diet necessary in PKU treatment. The patient presented by us needs well-coordinated multidisciplinary medical care which aims to provide proper physical development and to support the boy's mental potential as well as appropriate functioning in the society.