Induced helical chirality of perylenebisimide aggregates allows for enantiopurity determination and differentiation of α-hydroxy carboxylates by using circular dichroism.

We have developed a working strategy for accurate enantiomeric excess (ee) determination based on induced helical aggregation of achiral perylenebisimide (PBI) dyes. PBI dyes functionalized with boronic acid moieties were shown to be effective chirality sensors for α-hydroxy carboxylates. Seven α-hydroxy carboxylates tested showed strong induced Cotton effects in the perylene absorption region around λ=500 nm, which were utilized for enantiomeric excess determination and chemo-discrimination of the analytes, with an average absolute error of 2 % in ee determination and 100 % correctness in analyte classification. Responses in the absorption spectra, which arise from the guest-enhanced aggregation, allow the determination of the sample concentration, thus enabling analysis of samples of unknown concentration and ee. The simplicity of the strategy, the ease of sample preparation, and the accuracy demonstrated, can potentially facilitate screening procedures in asymmetric synthesis.

[Anatomical study of auditory brainstem implantation through retrosigmoid approach].

OBJECTIVE: To provide anatomic data for auditory brainstem implantation (ABI) through the retrosigmoid approach. METHODS: Simulated operations were performed on 30 web adult head specimens and the structure around the foramen of luschka was observed. Both microscope and endoscope were employed. RESULTS: (1)The bony window, the most adjacent but not overlapping with sigmoid sinus, was a circle with a radius of 20 mm. Its center was located behind midpoint of the line from parietal notch to mastoid apex with a distance of (26.42 +/- 1.29) mm. The distance between bony window and transverse sinus, mastoid apex, foramen of luschka, jugular foramen, posterior edge of internal auditory meatus and root entry zone of the IX cranial nerve were (22.45 +/- 1.41) mm, (35.51 +/- 1.65) mm, (43.86 +/- 2.20) mm, (16.56 +/- 1.64) mm, (15.01 +/- 0.63) mm and (46.27 +/- 1.70) mm respectively; (2) The foramen of luschka can be spotted by using microscope or endoscope, especially 30 degrees angled endoscope. By this way, we could obtain a more distinct visual field without over-retraction of cerebellum and achieve the goal of minimally invasive surgery. The distance between the foramen of luschka and internal acoustic porus was (15.01 +/- 0.53) mm; (3) The foramen of luschka lies in the triangle formed by flocculus and root entry zone of glossopharyngeal nerve and rostral margin of biventer lobule. Choroids plexus acts as a direct landmark. the length of lateral recess was (17.53 +/- 1.03) mm. The distance between acoustic tubercle and the foramen of luschka and the root of cochlea never was (16.52 +/- 1.67) mm and (13.77 +/- 1.66) mm respectively. CONCLUSION: Adjustment of the angle of skull bone window and clarification of cerebellopontine angle are the keys to positioning the foramen of luschka. The usage of 30 degrees angled endoscope can identify the angle are the keys to positioning the foramen of luschka. The usage of 30 degrees angled endoscope can identify the foramen of luschka more accurately and expose the operation area more clearly.

Effects of delayed brain-derived neurotrophic factor application on cochlear pathology and auditory physiology in rats.

BACKGROUND: The development and maintenance of spiral ganglion cells (SGCs) appear to be supported by neurotrophins. Removal of this support leads to their gradual degeneration. Intracochlear infusion with neurotrophins can provide trophic support to SGCs in animal deafness models if given shortly after deafening. However, it is not known whether delayed intervention will provide similar protection, which might be clinically relevant. The present research was conducted to determine the effects of brain-derived neurotrophic factor (BDNF) administration on the capacity of the peripheral processes to resprout. METHODS: The left cochlea of 20 profoundly deafened rats, which were divided into 2 groups equally, was implanted with an electrode and drug-delivery system 30 days after deafening. Either BDNF or artificial perilymph (AP) was delivered continuously for 28 days. Electrically evoked auditory brainstem responses (EABRs) were recorded during the period. SGC body and peripheral process density were measured. RESULTS: The EABR thresholds of AP increase continually. Those of BDNF increase slowly at the beginning then decrease, and were significantly less than those of the AP group from day 14 to 28 (P < 0.01). In terms of SGC and peripheral process density, the difference between the treated and control ears of BDNF group was clearly significant (P < 0.01), but not in AP group (P > 0.05). Analysis of the left cochlea between the two groups demonstrated that SGC/peripheral process density of the BDNF group was significantly greater than that of the AP group. Finally, a functional formula was developed relating the last EABR threshold and SGC density and process density, which was as follows: T = 466.184 - 2.71 (F.B.L). CONCLUSIONS: Under the conditions of delayed intervention following 30 days after deafening in rats, it can be concluded that BDNF enhances SGC bodies and peripheral processes survival after differentiation and so improves auditory sensitivity. SGC peripheral processes influence the auditory sensitivity.

Multicomponent covalent dye assembly for tight binding and sensitive sensing of L-DOPA.

A mixture of two simple perylene-containing receptors was found to bind bifunctional L-DOPA synergistically and tightly via orthogonal boronate ester and imine bond formation in neutral aqueous solutions, the resulting three-component assembly forming optically active long fibrous aggregates.

Direct sensing of fluoride in aqueous solutions using a boronic acid based sensor.

Binding of the fluoride ion triggers aggregation of a pyreneboronic acid-catechol ensemble in acidic aqueous solutions, giving rise to intense excimer emission, allowing for sensitive fluoride ion sensing at ppm levels, with an apparent fluoride binding constant higher than 10(3) M(-1) which is unprecedented for boronic acid sensors in water.

Delayed electrical stimulation and BDNF application following induced deafness in rats.

CONCLUSION: Under the condition of delayed intervention (30 days after deafening) following gentamicin+furosemide deafening in rats, we conclude that chronic intracochlear electrical stimulation (ES) and continuous intracochlear administration of brain-derived neurotrophic factor (BDNF) enhance spiral ganglion cell (SGC) body and peripheral process survival and improve auditory sensitivity. Moreover, the combination of ES and BDNF has a synergistic protective effect rather than an additive effect. Both SGC body and peripheral process influence the auditory sensitivity, and the latter appears to be more important. OBJECTIVE: To determine the influence of delayed application of combined ES and neurotrophins on the survival of SGC body and peripheral processes after induced deafness in the rat. This study also explored the relationship between auditory sensitivity and SGC/peripheral process density. MATERIALS AND METHODS: The left cochlea of profoundly deafened rats was implanted with an electrode and drug-delivery system 30 days after deafening. BDNF or artificial perilymph (AP) was delivered continuously for 28 days. Experimental animals received ES with or without BDNF (BDNF+ES and ES+AP), and control animals received BDNF or AP without ES (BDNF and AP). The right cochleae of the animals served as deafened untreated controls. Electrically evoked auditory brainstem responses (EABRs) were recorded immediately after surgery and every 7 days. RESULTS: In the AP group, EABR thresholds demonstrated a systematic and rapid increase throughout the treatment period after the deafening procedure and electrode implantation. However, in the other three treatment groups, EABR thresholds showed a slow increase at the beginning and then slow decrease. The thresholds of the BDNF and ES+AP groups were significantly less than those of the AP group from day 7 to 28 and those of the BDNF+ES group were significantly less than those of other three groups from day 21 to 28, indicating that BDNF infusion and chronic ES have a synergistic effect rather than an additive effect. In terms of SGC and peripheral process density, the difference between the treated and control ears of BDNF, ES+AP, and BDNF+ES groups was clearly significant. Analysis of the SGC/peripheral process density of the left cochlea across the treatment groups demonstrated that SGC/peripheral process density of the BDNF and ES+AP groups was significantly greater than that of the AP group and the density of the BDNF+ES group was significantly greater than that of the other three groups, indicating that BDNF infusion and chronic ES have a synergistic effect rather than an additive effect. Finally, a functional formula was developed relating the last EABR threshold and SGC density and process density.