Amelioration of Neurosensory Structure and Function in Animal and Cellular Models of a Congenital Blindness

1. Download high-res image (129KB)
2. Download full-size image

     

Role of neuronal activity and kinesin on tract tracing by manganese-enhanced MRI (MEMRI)

MEMRI offers the exciting possibility of tracing neuronal circuits in living animals by MRI. Here we use the power of mouse genetics and the simplicity of the visual system to test rigorously the parameters affecting Mn2+ uptake, transport and trans-synaptic tracing. By measuring electrical response to light before and after injection of Mn2+ into the eye, we determine the dose of Mn2+ with the least toxicity that can still be imaged by MR at 11.7 T. Using mice with genetic retinal blindness, we discover that electrical activity is not necessary for uptake and transport of Mn2+ in the optic nerve but is required for trans-synaptic transmission of this tracer to distal neurons in this pathway. Finally, using a kinesin light chain 1 knockout mouse, we find that conventional kinesin is a participant but not essential to neuronal transport of Mn2+ in the optic tract. This work provides a molecular and physiological framework for interpreting data acquired by MEMRI of circuitry in the brain.     

Ku86 preserves chromatin integrity in cells adapted to high NaCl

Cells adapted to high NaCl have many DNA breaks both in cell culture and in the renal inner medulla in vivo; yet they survive, function, and even proliferate. Here, we show that Ku86 is important for maintaining chromosomal integrity despite the continued presence of DNA breaks. The Ku heterodimer is part of DNA-dependent PK (DNA-PK), a complex that contributes by nonhomologous end joining to repair of double-strand breaks. We demonstrate that cells deficient in Ku86, but not cells deficient in DNA-PKcs (the catalytic subunit of DNA-PK), are hypersensitive to high NaCl as manifested by profound inhibition of proliferation, aberrant mitosis, and increased chromosomal fragmentation. Lower eukaryotes, including the soil nematode Caenorhabditis elegans, lack a DNA-PKcs homologue but are able to adapt to high NaCl. We show that cells of C. elegans adapted to high NaCl have many DNA breaks, similar to the mammalian cells adapted to high NaCl. Ku86 mutant C. elegans as well as C. elegans fed with cku86 dsRNA also display hypersensitivity to high NaCl, characterized by a reduced number of progeny and prolonged generation time in high NaCl. We propose that Ku86 ameliorates the effects of high NaCl-induced DNA breaks in adapted cells by supporting alignment of the broken ends of the DNA and thus maintaining integrity of the fragmented chromatin.     

Fibula lengthening using a modified Ilizarov method

A combination of external and internal fixation techniques for a fibular lengthening procedure using the Ilizarov method is described. The technique is minimally invasive, allows precise deformity correction, enables early weight bearing, and minimizes the time that the patient wears the external fixator.     

Minimal principle for rotor filaments

Three-dimensional rotors, or scroll waves, provide essential insight into the activity of excitable media. They also are a suspected cause in the formation and maintenance of ventricular fibrillation, whose lethality is well known. It is therefore of considerable interest to find out what configurations can be adopted by such pathologies. A scroll's behavior is embodied in its organizing center or filament, a largely quiescent tube about which the scroll rotates. Predicting filament shape has normally required computer-intensive simulations of the whole scroll in time. We have found a fast and robust principle that yields the prediction for stationary filaments on a purely geometrical basis, blind to the reaction parameters of the medium. The procedure is to calculate the filament shape as a minimal path. We work in singly diffusive media whose diffusivity tensor--and no other feature--varies spatially. Mathematical and numerical evidence is presented for the proposition that a stable filament is a geodesic in a three-dimensional space whose metric is given by the inverse diffusivity tensor of the medium. Away from the boundaries, a stable filament is unaffected by the reaction parameters. The algorithmic aspects of this work are subsidiary to our main purpose of drawing attention to the universal and unexpectedly exact fit of an elementary geodesic principle within reaction-diffusion theories.     

The Role of Apoptosis in Normal and Abnormal Embryonic Development

Programmed cell death or apoptosis is a widespread biological phenomenon. Apoptosis is characterized by typical cell features such as membrane blebbing, chromatin condensation, and DNA fragmentation. It involves a number of membrane receptors (e.g., Fas, TNFR) and a cascade of signal transduction steps resulting in the activation of a number of cysteine proteases known as caspases. Disordered apoptosis may lead to carcinogenesis and participates in the pathogenesis of Alzheimer disease, Parkinson disease, or AIDS. Programmed cell death plays an important role in the processes of gamete maturation as well as in embryo development, contributing to the appropriate formation of various organs and structures. Apoptosis is one of the mechanisms of action of various cytotoxic agents and teratogens. Teratogen-induced excessive death of embryonic cells is undoubtedly one of the most important events preceding the occurrence of structural abnormalities, regardless of their nature. Therefore understanding the mechanisms involved in physiological as well as in disturbed or dysregulated apoptosis may lead to the development of new methods of preventive treatment of various developmental abnormalities. The present review summarizes data on the mechanisms of programmed cell death and concentrates on apoptosis involved in normal or disturbed gametogenesis and in normal and abnormal embryonic development.     

Experimental approach to improving early postirradiation restoration in the hemopoietic system of irradiated canines

Experiments on mongrel canines exposed to total body irradiation in free-in-air dose of 3.85 (LD 95/45) or 4.05 Gy were carried out to evaluate the therapeutic effectiveness of some of bone marrow immediate-after-irradiation extraction, incubation in the presence of protein synthesis inhibitor and reimplantation in the organism (the reimplantation method) or bone marrow extraction alone (the extraction method). There were tested various kinds of methods that differed in bone marrow-blood mix volume extracted, in large or in small volumes. It has been determined that the reimplantation method in large volumes and the extraction method in small volumes are equally effective. Being supplemented with supportive therapy by antibiotics during d8-d24, the methods allowed the rescue at 4.05 Gy irradiation significantly more animals than in the case of therapy alone or its combination with ineffective variants of the methods. The positive effect of the methods manifested in a higher level of leukocyte nadir on d17, earlier reaching 0.5 x 10(9) and 1 x 10(9) leukocytes per liter, and increasing 45 days survival.The mechanism of positive influence of the methods on the radiation injury of hemopoesis seems to be related to increased cytokine producing because of the irritation of bone marrow stromal cells and thus favorable interference in the early restoration processes.     

Prevention of Staphylococcus aureus biofilm on dialysis catheters and adherence to human cells

BACKGROUND: Dialysis patients, often carriers of Staphylococcus aureus in their nares, are at high risk of S. aureus infections. METHODS: We examined whether RNAIII inhibiting peptide (RIP), which interferes with quorum sensing mechanisms, reduces adherence of S. aureus to host cells and to dialysis catheter polymers in vitro. Adherence was tested by spectroscopy using safranin staining, by confocal scanning laser microscopy and by atomic force microscopy. RESULTS: RIP inhibited bacterial adherence to HaCat and HEp-2 cells and reduced adherence and biofilm formation not only on polystyrene, but also on both polyurethane- and silicone-made dialysis catheters, with a preponderant effect on silicone, to which bacteria were more adherent. CONCLUSION: RIP opens a new perspective in anti-S. aureus prophylaxis, particularly in dialysis patients.