Epineurial Window Is More Efficient in Attracting Axons than Simple Coaptation in a Sutureless (Cyanoacrylate-Bound) Model of End-to-Side Nerve Repair in the Rat Upper Limb: Functional and Morphometric Evidences and Review of the Literature

End-to-side nerve coaptation brings regenerating axons from the donor to the recipient nerve. Several techniques have been used to perform coaptation: microsurgical sutures with and without opening a window into the epi(peri)neurial connective tissue; among these, window techniques have been proven more effective in inducing axonal regeneration. The authors developed a sutureless model of end-to-side coaptation in the rat upper limb. In 19 adult Wistar rats, the median and the ulnar nerves of the left arm were approached from the axillary region, the median nerve transected and the proximal stump sutured to the pectoral muscle to prevent regeneration. Animals were then randomly divided in two experimental groups (7 animals each, 5 animals acting as control): Group 1: the distal stump of the transected median nerve was fixed to the ulnar nerve by applying cyanoacrylate solution; Group 2: a small epineurial window was opened into the epineurium of the ulnar nerve, caring to avoid damage to the nerve fibres; the distal stump of the transected median nerve was then fixed to the ulnar nerve by applying cyanoacrylate solution. The grasping test for functional evaluation was repeated every 10–11 weeks starting from week-15, up to the sacrifice (week 36). At week 36, the animals were sacrificed and the regenerated nerves harvested and processed for morphological investigations (high-resolution light microscopy as well as stereological and morphometrical analysis). This study shows that a) cyanoacrylate in end-to-side coaptation produces scarless axon regeneration without toxic effects; b) axonal regeneration and myelination occur even without opening an epineurial window, but c) the window is related to a larger number of regenerating fibres, especially myelinated and mature, and better functional outcomes.     

Mathematical Modeling Predicts Enhanced Growth of X-Ray Irradiated Pigmented Fungi

Ionizing radiation is known for its cytotoxic and mutagenic properties. However, recent evidence suggests that chronic sub-lethal irradiation stimulates the growth of melanin-pigmented (melanized) fungi, supporting the hypothesis that interactions between melanin and ionizing photons generate energy useful for fungal growth, and/or regulate growth-promoting genes. There are no quantitative models of how fungal proliferation is affected by ionizing photon energy, dose rate, and presence versus absence of melanin on the same genetic background. Here we present such a model, which we test using experimental data on melanin-modulated radiation-induced proliferation enhancement in the fungus Cryptococcus neoformans, exposed to two different peak energies (150 and 320 kVp) over a wide range of X-ray dose rates. Our analysis demonstrates that radiation-induced proliferation enhancement in C. neoformans behaves as a binary “on/off” phenomenon, which is triggered by dose rates <0.002 mGy/h, and stays in the “on” position. A competing dose rate-dependent growth inhibition becomes apparent at dose rates >5000 mGy/h. Proliferation enhancement of irradiated cells compared with unirradiated controls occurs at both X-ray peak energies, but its magnitude is modulated by X-ray peak energy and cell melanization. At dose rates <5000 mGy/h, both melanized and non-melanized cells exposed to 150 kVp X-rays, and non-melanized cells exposed to 320 kVp X-rays, all exhibit the same proliferation enhancement: on average, chronic irradiation stimulates each founder cell to produce 100 (95% CI: 83, 116) extra descendants over 48 hours. Interactions between melanin and 320 kVp X-rays result in a significant (2-tailed p-value = 4.8×10⁻⁵) additional increase in the number of radiation-induced descendants per founder cell: by 55 (95% CI: 29, 81). These results show that both melanin-dependent and melanin-independent mechanisms are involved in radiation-induced fungal growth enhancement, and implicate direct and/or indirect interactions of melanin with high energy ionizing photons as an important pro-proliferative factor.     

Using Low Levels of Stochastic Vestibular Stimulation to Improve Balance Function

Low-level stochastic vestibular stimulation (SVS) has been associated with improved postural responses in the medio-lateral (ML) direction, but its effect in improving balance function in both the ML and anterior-posterior (AP) directions has not been studied. In this series of studies, the efficacy of applying low amplitude SVS in 0–30 Hz range between the mastoids in the ML direction on improving cross-planar balance function was investigated. Forty-five (45) subjects stood on a compliant surface with their eyes closed and were instructed to maintain a stable upright stance. Measures of stability of the head, trunk, and whole body were quantified in ML, AP and combined APML directions. Results show that binaural bipolar SVS given in the ML direction significantly improved balance performance with the peak of optimal stimulus amplitude predominantly in the range of 100–500 μA for all the three directions, exhibiting stochastic resonance (SR) phenomenon. Objective perceptual and body motion thresholds as estimates of internal noise while subjects sat on a chair with their eyes closed and were given 1 Hz bipolar binaural sinusoidal electrical stimuli were also measured. In general, there was no significant difference between estimates of perceptual and body motion thresholds. The average optimal SVS amplitude that improved balance performance (peak SVS amplitude normalized to perceptual threshold) was estimated to be 46% in ML, 53% in AP, and 50% in APML directions. A miniature patch-type SVS device may be useful to improve balance function in people with disabilities due to aging, Parkinson’s disease or in astronauts returning from long-duration space flight.     

Symmetric molecules with 1,4-triazole moieties as potent inhibitors of tumour-associated lactate dehydrogenase-A

A series of symmetric molecules incorporating aryl or pyridyl moieties as central core and 1,4-substituted triazoles as a side bridge was synthesised. The new compounds were investigated as lactate dehydro-genase (LDH, EC 1.1.1.27) inhibitors. The cancer associated LDHA isoform was inhibited with IC₅₀?=?117–174 µM. Seven compounds exhibited better LDHA inhibition (IC₅₀ 117–136 µM) compared to known LDH inhibitor – galloflavin (IC₅₀ 157 µM).     

DNA or RNA Oligonucleotide 2′-Hydrazides for Chemoselective Click-Type Ligation with Carbonyl Compounds

An efficient method for the synthesis of DNA or RNA oligonucleotide 2′-hydrazides is described. Fully deprotected oligonucleotides containing a hydrazide group at the 2′-position of a uridine residue were obtained by a novel two-step procedure: periodate cleavage of an oligonucleotide with 1,2-diol group followed by conversion of the aldehyde to hydrazide with an extended linker arm using a homobifunctional reagent succinic dihydrazide and NaBH₃CN. The resulting oligonucleotide 2′-hydrazides were efficiently conjugated by a click-type reaction at acidic pH to aliphatic or aromatic aldehydes with or without NaBH₃CN reduction to afford novel 2′-conjugates.     

Preparation, characterization and reactivity of 1-benzylpyridinium-4-aldoxime chloride and 1-phenacylpyridinium-4-aldoxime chloride and their complexes with the aquapentacyanoferrate(II) ion

A detailed structural characterization of the biologically active 1-benzylpyridinium-4-aldoxime chloride and 1-phenacylpyridinium-4-aldoxime chloride was performed using NMR and vibrational and electronic spectroscopy, as well as X-ray diffraction. The complexes of these compounds with the aquapentacyanoferrate(II) ion were examined in solution, isolated as solids and characterized by elemental analysis, electronic, FT-IR and NMR spectral data. They were found to be mononuclear substituted pentacyanoferrates(II) containing the aldoxime group coordinated to the iron through the nitrogen atom. The complexes were also precipitated in the form of the respective zinc salts; the analysis of these complexes revealed a molar Fe/Zn ratio of 1, thus confirming the charge of the complex anions to be −2. The ionization constants of the aldoxime group in the free ligands and in the respective cyano complexes were also determined. Despite the presence of two donor sites in 1-phenacylpyridinium-4-aldoxime chloride, only the aldoxime group was found to be reactive.     

Asymmetric block of the plant vacuolar Ca2+-permeable channel by organic cations

In this work we have analysed the voltage-dependent block of the slow activating channel from red beet vacuoles by Tris, quaternary ammonium ions and the natural polyamines putrescine, spermidine and spermine. All these organic cations when applied from the cytosolic side blocked the channel by binding apparently deep (zδ values in the range of 0.65–1.35) within the pore. Tetraethylammonium ion did not pass the selectivity filter, whereas the cations with a smaller cross-section and Tris could pass across the entire pore, as evidenced by a relief of block at high positive voltages. Voltage dependence of the establishment of block from cytosolic side and of its relief was anomalously strong in the sense that the total charge moved across the pore for all blockers tested, with a notable exception of spermine, was in excess of their actual valence. This behaviour is consistent with the existence of multiple binding sites within a long pore, their simultaneous occupancy and interaction between different ions. In contrast, binding of blockers from the vacuolar (lumenal) side appears to follow a single-ion handling rule, with a common binding site for all amines located at approximately 30% of the electrical distance from the lumenal side. Received: 22 February 1999 / Revised version: 6 July 1999 / Accepted: 8 July 1999     

A Model of Hydrodynamic Interaction Between Swimming Bacteria

We study the dynamics and interaction of two swimming bacteria, modeled by self-propelled dumbbell-type structures. We focus on alignment dynamics of a coplanar pair of elongated swimmers, which propel themselves either by “pushing” or “pulling” both in three- and quasi-two-dimensional geometries of space. We derive asymptotic expressions for the dynamics of the pair, which complemented by numerical experiments, indicate that the tendency of bacteria to swim in or swim off depends strongly on the position of the propulsion force. In particular, we observe that positioning of the effective propulsion force inside the dumbbell results in qualitative agreement with the dynamics observed in experiments, such as mutual alignment of converging bacteria.