Hydrogel combined with antimicrobial protease dressing accompanied with emotional support to treat wounds of patients taking immunosuppressive agents: A longitudinal study.

BACKGROUND: This study aimed to evaluate the healing process of chronic wounds treated with hydrogel combined with antimicrobial protease dressing and emotional support intervention in patients taking immunosuppressive agents. CASES: The case series involved 8 patients treated at a tertiary public hospital for 12 weeks. Data were analysed by SPSS version 27.0. The intention-to-treat principle was carried out, without the loss or exclusion of the participants. The subjects had wounds for 70 (98) days, and they consisted of 50% (4/8) males with a mean age of 42.63 years (±16.94). All (100%) subjects had taken immunosuppressive agents, and 62.5% (5/8) had systolic hypertension. The mean initial area of all wounds was 19.54 (5.89) cm2, and the mean final area was 3.0 cm2, with a reduction rate of 89% over the 12 weeks of treatment. In addition, we found that tissue types of these wounds changed by using hydrogel combined with antibacterial protease dressings, especially devitalised tissue (P = 0.011). The amount of exudate did not statistically change (P = 0.083). No participant had severe or local adverse events during the study period. Hence, giving emotional support along with wound care for 12 weeks could significantly reduce anxiety scores (P = 0.012). These results suggested that hydrogel combined with antimicrobial protease dressing and emotional support intervention is a promising method for the healing of wounds in patients who suffer from immunosuppressive diseases or are receiving current immunosuppressive treatment.

Asymmetric interface excited chirality and its applications in reconfiguration.

In this paper, a chiral excitation method based on the asymmetric interface condition is proposed. The chiral characteristics of the metamaterials are affected by the difference in the environmental parameters of the front and rear surfaces. Thus, the device can achieve functional reconfiguration and two applications based on this mechanism are presented, one for sensing and the other for chiral switching. At the same time, a self-calibration measurement method that greatly simplifies the sensing system is proposed. These results have potential applications in the fields of chirality excitation, bio-sensing, and reconfigurable device.

Reconfigurable metamaterial for chirality switching and selective intensity modulation.

A reconfigurable metamaterial for chirality switching and selective intensity modulation is demonstrated experimentally. Through simple folding strategy, nonchiral state, single-band chiral states and dual-bands chiral states can be switched. Circular dichroism up to 0.94 is measured with folding angles of 70°. Meanwhile, selective intensity modulation is realized by the combined effect of folding angle and incident angle. The transmission intensity of circularly polarized waves can be modulated by more than 90% at any selected resonating frequency between 8.97 and 10.73 GHz. This work will benefit the researches of foldable metamaterials and have potential applications in the field of reconfigurable devices.

Fibrinogen and prothrombin complex concentrate in trauma coagulopathy.

BACKGROUND: Coagulopathy after injury contributes to hemorrhage and death. Treatment with specific coagulation factors could decrease hemorrhage and mortality. Our aim was to compare fibrinogen and prothrombin complex concentrate (PCC) in a rabbit model of hemorrhagic shock. MATERIALS AND METHODS: New Zealand white rabbits were anesthetized. Blood was withdrawn to a mean arterial pressure (MAP) of 30-40 mm Hg for 30 min. Animals were resuscitated with lactated Ringer to a MAP of 50-60 mm Hg and randomized to receive 100 mg/kg of fibrinogen, PCC 25 IU/kg, or lactated Ringer. A liver injury was created. A MAP of 50-60 mm Hg was maintained for 60 min. The primary outcome was blood loss, and secondary outcomes were fluid administered and coagulopathy as measured by plasma-based tests. RESULTS: There were eight animals in each group. Median blood loss was significantly higher in the fibrinogen group, at 122 mL (95% confidence interval [CI], 75-194), when compared with that in the control group, 35 mL (95% CI, 23-46; P value = 0.001), and the PCC group, 26 mL (95% CI, 4-54; P value = 0.002). Resuscitation fluid requirement was highest in the fibrinogen group, at 374 mL (95% CI, 274-519), and lowest in the PCC group, at 238 mL (95% CI, 212-309) (P = 0.01). Plasma-based coagulation tests were not different among groups. CONCLUSIONS: In a rabbit model, PCC did not have a significant effect on blood loss. Fibrinogen increased blood loss and fluid requirements.

Agile Inverse Design of Polarization-Independent Multi-Functional Reconfiguration Metamaterials Based on Doped VO2.

Increasing attention is being paid to the application potential of multi-functional reconfigurable metamaterials in intelligent communication, sensor networks, homeland security, and other fields. A polarization-independent multi-functional reconfigurable metasurface based on doped vanadium dioxide (VO2) is proposed in this paper. It can be controlled to switch its function among three working modes: electromagnetically induced absorption (EIA), electromagnetically induced transparency (EIT), and asymmetrical absorption. In addition, deep learning tools have greatly accelerated the design of relevant devices. Such devices and the method proposed in this paper have important value in the field of intelligent reconfigurable metamaterials, communication, and sensing.

Nonlinear seismic response analysis of long-span railway cable-stayed bridges crossing strike-slip faults.

Active faults along railways in the mountainous regions of western China pose significant challenges to bridge safety. To ensure the safe operation of long-span railway bridges under complex geological conditions, this study investigates the synthesis of artificial ground motions for bridges crossing strike-slip faults and analyzes their nonlinear seismic response. First, we develop a theoretical method for simulating high- and low-frequency seismic motions using a finite fault and an equivalent velocity pulse model. Next, using a specific long-span railway cable-stayed bridge as a case study, we construct a nonlinear finite element model with OpenSees software. Finally, we assess the seismic response of key bridge components considering various crossing angles, seismic amplitudes, fault rupture directivity, and fling-step effects. The results show that the crossing angle significantly influences the seismic response, with longitudinal and transverse responses exhibiting opposite patterns. Additionally, the scaling factor of seismic motion significantly affects bridge response. For bridges crossing strike-slip faults, the longitudinal response exhibits a sudden increase in displacement due to instantaneous velocity pulses, while the transverse response shows notable residual displacement influenced by the fling-step effect. However, the critical section curvatures of bridge towers and piers remain within the elastic range across all crossing angles, indicating that controlling large displacement deformations is crucial for the seismic design of bridges crossing strike-slip faults.

Mechanism of Iris sibirica and aeration combination on promoting the water purification performance of constructed wetland under low temperature.

Temperature is an important factor affecting the water purification performance of constructed wetland (CW). In the previous study, the combined measures of Iris sibirica and aeration at the bottom of the first quarter filtration chamber could improve the pollutant removal capacity of CW at low temperature. However, the mechanism between the combined measures of Iris sibirica and aeration on enhancing the performance of domestic sewage treatment is unclear. Our study aims to provide scientific validation for the combined measure through monitoring the concentrations of dissolved oxygen (DO), chemical oxygen demand (CODCr), ammonia nitrogen (NH4+-N), and total nitrogen (TN) along the water flow pathway of the CW and measuring the superoxide dismutase (SOD) activities of the plants and the abundance of nitrogen cycle-related microbial functional genes in the substrates of CW to explore the mechanism of combined measures promoting the removal efficiency of the CW under low-temperature stress. Results showed that aerating at the bottom of the first quarter filtration chamber increased DO concentration in the front part of the CW, which benefited the aerobic removal of pollutants and the activities of microorganisms, and the removal CODCr and NH4+-N occurred mainly in the front part of the CW. SOD activities showed that I. sibirica had better resistance to low temperature than Canna indica did. The combined measures of I. sibirica and aeration activated the activities of microorganisms, increased the abundance of the denitrification process genes along the water flow pathway and formed a clear nitrification-denitrification zone in the CW, thus promoted the nitrogen removal efficiency at low temperature. Therefore, this study confirmed the feasibility of the combined measures from a mechanistic perspective.

Choline acetyltransferase activity in the hamster central auditory system and long-term effects of intense tone exposure.

Acoustic trauma often leads to loss of hearing of environmental sounds, tinnitus, in which a monotonous sound not actually present is heard, and/or hyperacusis, in which there is an abnormal sensitivity to sound. Research on hamsters has documented physiological effects of exposure to intense tones, including increased spontaneous neural activity in the dorsal cochlear nucleus. Such physiological changes should be accompanied by chemical changes, and those chemical changes associated with chronic effects should be present at long times after the intense sound exposure. Using a microdissection mapping procedure combined with a radiometric microassay, we have measured activities of choline acetyltransferase (ChAT), the enzyme responsible for synthesis of the neurotransmitter acetylcholine, in the cochlear nucleus, superior olive, inferior colliculus, and auditory cortex of hamsters 5 months after exposure to an intense tone compared with control hamsters of the same age. In control hamsters, ChAT activities in auditory regions were never more than one-tenth of the ChAT activity in the facial nerve root, a bundle of myelinated cholinergic axons, in agreement with a modulatory rather than a dominant role of acetylcholine in hearing. Within auditory regions, relatively higher activities were found in granular regions of the cochlear nucleus, dorsal parts of the superior olive, and auditory cortex. In intense-tone-exposed hamsters, ChAT activities were significantly increased in the anteroventral cochlear nucleus granular region and the lateral superior olivary nucleus. This is consistent with some chronic upregulation of the cholinergic olivocochlear system influence on the cochlear nucleus after acoustic trauma.

Evaluation of Social Platform-Based Continuity of Care in Improving Cognitive and Prognostic Effects of Young Patients with Diabetic Retinopathy.

Objective: This study was performed to evaluate the effectiveness of social platform-based continuity of care in improving cognitive and prognostic effects of young age diabetic patients without diabetic retinopathy (DR). Methods: A total of 88 young age diabetic patients admitted to the outpatient clinic of First Affiliated Hospital of Soochow University (Endocrine and Ophthalmology Outpatient) from January 2021 to May 2022 were recruited and assigned via random number table method to receive either routine follow-up care (routine group) or social platform-based continuity of care (WeChat group), with 44 patients in each group. Treatment compliance, cognitive-behavioral ability, self-care ability (self-care responsibility, self-care skills, self-status, knowledge of diabetic retinopathy), quality of life (physical function, psychosocial, symptom and visual function, social activity), and prognosis of the patients were analyzed to investigate the effectiveness of WeChat social platform-based continuity of care. All patients were followed up for one year. Results: Patients receiving WeChat social platform-based continuity of care exhibited obviously higher treatment compliance and better cognitive-behavioral ability, self-care responsibility, self-care skills, self-state, and diabetic retinopathy knowledge follow-up than those with routine care (P<0.05). Patients in the WeChat group had significantly better physical function, mental psychology, symptoms and visual function, and social activity levels than those in the routine group (P<0.05). WeChat-based continuity of care resulted in a significantly lower incidence of visual acuity loss and diabetic retinopathy during follow-up than routine care (P<0.05). Conclusion: WeChat social platform-based continuity of care effectively improves treatment compliance and diabetic retinopathy awareness, and enhances self-care ability of young patients with diabetes mellitus. The life quality of these patients is improved and the risk of poor prognosis has been reduced.

Red Blood Cell Membrane Camouflaged Mesoporous Silica Nanorods as Nanocarriers for Synergistic Chemo-Photothermal Therapy.

In recent years, nanoparticles camouflaged by red blood cell membrane (RBCM) have become a potential nano-drug delivery platform due to their good biocompatibility and immune evasion capability. Here, a multifunctional drug nanocarrier based on RBCM camouflaged mesoporous silica nanorods (MSNR) is presented, which can be used in pH and near-infrared (NIR) light triggered synergistic chemo-photothermal killing of cancer cells. To fabricate such a nanocarrier, MSNR and RBCM were prepared by the sol-gel method and modified hypotonic lysis method, respectively. Drugs were loaded into the pores of MSNR. Finally, RBCM was coated on the surface of MSNR by extrusion through a polycarbonate membrane. The advantages of the nanocarrier include: 1) MSNR can induce more cellular uptake than sphere shaped mesoporous silica nanoparticles. 2) The RBCM can reduce drug leakage and prevent clearance of the nanocarriers by macrophages. 3) By simultaneous loading doxorubicin (DOX) and indocyanine green (ICG), pH and NIR triggered synergistic chemo-photothermal therapy can be realized. In the experiment, we studied the drug releasing and cellular uptake of the nanocarriers in a breast cancer cell line (SKBR3 cells), in which a sufficient killing effect was observed. Such a multifunctional drug nanocarrier holds a broad application prospect in cancer treatment.

Optically Transparent, Ultra-Broadband, and Water-Based Microwave Meta-absorber with ITO Metasurfaces.

A transparent in visible wavelengths and ultrabroadband microwave meta-absorber (MMA) based on indium tin oxide (ITO) metasurfaces and a water layer is proposed. After optimizing a series of structural parameters, the proposed MMA can achieve ultrabroadband absorption with an absorption efficiency of more than 90%, covering the frequency range of 9.44-120.92 GHz and a relative absorption bandwidth of 171%. Furthermore, the absorber has many advantages, such as optical transparency, polarization insensitivity, and wide-angle absorption for transverse electric (TE) and transverse magnetic (TM) polarization waves. Moreover, the proposed MMA with 15 × 15 unit cells was fabricated and tested. The fabricated MMA performs well in microwave absorption, as demonstrated by the well-matched experimental results with numerical simulations. These extraordinary advantages mentioned above show that this type of MMAs can be applied in the fields of electromagnetic (EM) stealth, optical windows, and energy collection in the future.

Risk factors for skin injuries in cancer patients with peripherally inserted central catheter: A prospective multicenter cohort study.

BACKGROUND: The risk factors for skin injuries remain poorly understood in cancer patients with peripherally inserted central catheters (PICC). We herein aimed at exploring the effect of clinical factors on the risk of PICC-related skin injuries. METHODS: We included 1245 cancer patients with PICC from 16 hospitals in Suzhou, China. The study outcome was in-hospital skin injuries, including contact dermatitis, skin (epidermal) stripping, tension injury, allergic dermatitis, skin tear, maceration, folliculitis, and pressure injury. RESULTS: During hospitalization, 274 patients (22.0%) developed skin injuries after prolonged use of an indwelling catheter. Univariable logistic regression analysis identified several risk factors for PICC-related skin injuries; multivariable logistic regression analysis showed that the following factors independently and significantly (p < 0.05) associated with the risk of PICC-related skin injuries: body mass index (BMI, >25 kg/m2 versus <18.5 kg/m2: odds ratio (OR), 1.79; 95% confidence interval (CI), 1.03-3.11), skin condition (humid vs normal: OR, 2.96; 95% CI, 1.62-5.43), skin indentation (OR, 4.67; 95% CI, 3.31-6.58), allergic history (OR, 2.11; 95% CI, 1.21-3.66), history of dermatitis (OR, 3.05; 95% CI, 1.00-9.28), history of eczema (OR, 3.36; 95% CI, 1.20-9.43), catheter insertion site (under elbow vs. upper arm: OR, 3.32; 95% CI, 1.12-9.90), and PICC maintenance interval (4-5 days vs ⩽3 days: OR, 0.06; 95% CI, 0.01-0.50; 5-7 days vs ⩽3 days: OR, 0.07; 95% CI, 0.02-0.31; 7-9 days vs ⩽3 days: OR, 0.10; 95% CI, 0.02-0.57). CONCLUSIONS: BMI, skin condition, skin indentation, allergic history, history of dermatitis, history of eczema, catheter insertion site, and PICC maintenance interval were independent risk factors for PICC-related skin injuries in cancer patients. This knowledge will guide future studies with formulating optimal treatment strategies for improving the skin health of cancer patients with PICC.

Amino acid concentrations in the hamster central auditory system and long-term effects of intense tone exposure.

Exposure to intense sounds often leads to loss of hearing of environmental sounds and hearing of a monotonous tonal sound not actually present, a condition known as tinnitus. Chronic physiological effects of exposure to intense tones have been reported for animals and should be accompanied by chemical changes present at long times after the intense sound exposure. By using a microdissection mapping procedure combined with high-performance liquid chromatography (HPLC), we have measured concentrations of nine amino acids, including those used as neurotransmitters, in the cochlear nucleus, inferior colliculus, medial geniculate, and auditory cortex of hamsters 5 months after exposure to an intense tone, compared with control hamsters of the same age. No very large differences in amino acid concentrations were found between exposed and control hamsters. However, increases of glutamate and γ-aminobutyrate (GABA) in some parts of the inferior colliculus of exposed hamsters were statistically significant. The most consistent differences between exposed and control hamsters were higher aspartate and lower taurine concentrations in virtually all regions of exposed hamsters, which reached statistical significance in many cases. Although these amino acids are not considered likely neurotransmitters, they indirectly have roles in excitatory and inhibitory neurotransmission, respectively. Thus, there is evidence for small, widespread, long-term increases in excitatory transmission and decreases in inhibitory transmission after a level of acoustic trauma previously shown to produce hearing loss and tinnitus.

Differences in the evolution of surface-microstructured silicon fabricated by femtosecond laser pulses with different wavelength.

We experimentally investigate the differences in the evolution of surface-microstructured silicon fabricated by femtosecond laser pulses with different wavelength as a function of irradiated laser energy. The results show that when laser energy absorbed by the silicon material is the same, laser pulses with a shorter wavelength can form the surface-microstructured silicon with less laser energy, while the corresponding spike height is much lower than that of laser pulses with a longer wavelength. This is because the penetration depth of the laser pulses increases exponentially at the increase of the laser wavelength. Additionally, for two laser pulses with the certain wavelength and the certain absorption efficiency of silicon, the proportional relations between their formed spike height and irradiated laser energy should be determined. In particular, the average spike height is 3 times with 8 times corresponding energy for 800 nm laser pulses than that of 400 nm. These results are a benefit for the fast and optimum-morphology preparation of microstructured silicon.

Effects of a novel Mg-C micro-electrolysis system for phenolic wastewater degradation: material characterization, influencing factors, and model optimization.

This study investigated a novel magnesium carbon micro-electrolysis (Mg-C ME) system for strengthening the removal of phenolic compounds in wastewater. The effects of the Mg/C mass ratio, aeration intensity, initial pH and reaction time on the degradation of three phenolic compounds and the COD removal efficiency in the simulated wastewater were evaluated using one-factor-at-a-time (OFAT) method. The optimum values obtained for the Mg/C mass ratio, aeration intensity, initial pH and reaction time were 3:1, 4.0 L/(L·min), 5.0 and 2.5 h, respectively. The experimental removal rates of catechol, resorcinol, and phenol, under the mentioned conditions, were obtained to be 95.6%, 71.5%, and 48.8%, respectively. Meanwhile, the COD removal rates were 63.8%,44.7%,34.0%, respectively. Moreover, experiments were designed and analyzed based on the box-based designing response surface (BBD-RSM) method. According to the results, the Mg/C mass ratio was the most significant variable showing incremental effect on the removal efficiency of catechol in a way that maximum removal efficiency of catechol was achieved in Mg/C mass ratio of 3.23:1. The validation experiments showed that the maximum removal efficiency of catechol was 96.24% under optimization conditions. Resorcinol degradation characteristics analysis indicated that the Mg-C ME system performed a key function in phenolic compounds elimination. Results showed that the Mg-C ME has a considerable capability in removing the phenolic compounds and COD. Thus, it could be considered as an efficient pretreatment choice for treating phenolic wastewater in the future.

Cerebellum-related characteristics of Scn8a-mutant mice.

Among ten sodium channel alpha-subunit genes mapped in human and mouse genomes, the SCN8A gene is primarily expressed in neurons and glia. Mice with two types of Scn8a null mutations--Scn8a ( med ) and Scn8a ( medTg )--live for only 21-24 days, but those with incomplete mutations-Scn8a ( medJ ) and Scn8a ( medJo )--and those with knockout of Scn8a only in cerebellar Purkinje cells live to adult age. We review here previous work on cerebellum and related regions of Scn8a mutant mice and include some newer immunohistochemical and microchemical results. The resurgent sodium current that underlies the repeated firing of Purkinje cells is reduced in Scn8a mutant and knockout mice. Purkinje cells of mutant mice have greatly reduced spontaneous activity, as do the analogous cartwheel cells of the dorsal cochlear nucleus. Up-regulation of GABA(A) receptors in regions to which Purkinje cells project may partially compensate for their decreased activity in the mutant mice. The somata of cerebellar Purkinje cells of Scn8a ( medJ ) and Scn8a ( medJo ) mice, as revealed by PEP-19 immunoreaction, are slightly smaller than normal, and their axons, especially in Scn8a ( medJo ) mice, sometimes show enlargements similar to those in other types of mutant mice. Density of GABA-like immunoreactivity is decreased in Purkinje somata and regions of termination in deep cerebellar and vestibular nuclei of Scn8a ( medJ ) mice, but measured GABA concentration is not significantly reduced in microdissected samples of these regions. The concentrations of taurine and glutamine are significantly increased in cerebellar-related regions of Scn8a ( medJ ) mice, possibly suggesting up-regulation of glial amino acid metabolism.

Effectiveness of 4-hydroxy phenyl N-tert-butylnitrone (4-OHPBN) alone and in combination with other antioxidant drugs in the treatment of acute acoustic trauma in chinchilla.

Acute acoustic trauma (AAT) results in oxidative stress to the cochlea through overproduction of cellular reactive oxygen, nitrogen, and other free radical species appearing from 1 h to 10 days after noise exposure. It has been shown that N-acetyl-L-cysteine (NAC), a glutathione prodrug, and acetyl-L-carnitine (ALCAR), a mitochondrial biogenesis agent, are effective in reducing noise-induced hearing loss. Phenyl N-tert-butylnitrone (PBN), a nitrone-based free radical trap, appears to suppress oxidative stress in a variety of disorders and several biological models. In this study, we tested whether 4-hydroxy PBN (4-OHPBN), a major metabolite of PBN, administered 4 h after noise exposure is effective in treating noise-induced hearing loss and whether a combination of antioxidant drugs (4-OHPBN plus NAC and 4-OHPBN plus NAC plus ALCAR) provides greater efficacy in attenuating AAT since each agent addresses different injury mechanisms. Chinchilla were exposed to a 105 dB octave-band noise centered at 4 kHz for 6 h. 4-OHPBN and combinations of antioxidant drugs were intraperitoneally administered beginning 4 h after noise exposure. Hearing threshold shifts in auditory brainstem responses and missing outer hair cell counts were obtained. 4-OHPBN reduced threshold shifts in a dose-dependent manner while both drug combinations showed greater effects. These results demonstrate that 4-OHPBN and combinations of antioxidants can effectively treat acute acoustic trauma and drug combinations may increase the effectiveness of treatment and decrease the required individual medication dose.

Comparison of gamma-aminobutyrate receptors in the medial vestibular nucleus of control and Scn8a mutant mice.

The Purkinje cells of the cerebellum provide inhibitory input to vestibular nucleus neurons, with gamma-aminobutyrate (GABA) as neurotransmitter. Using extracellular recordings and bath application of agonists and antagonists, we compared GABA receptors in the medial vestibular nucleus of brain slices from Scn8a mutant mice of med(J) type, in which there is greatly reduced spontaneous and evoked activity of Purkinje cells, to those in slices from control mice. Muscimol, an agonist at GABA(A) receptors, produced a larger reduction of firing rate in neurons of mutant mice than in neurons of control mice, whereas there was no difference for baclofen, an agonist at GABA(B) receptors. In most cases tested, the effects of muscimol and baclofen remained similar when synaptic transmission was blocked, suggesting that the effects were predominantly directly upon GABA receptors of the neurons being recorded from. The up-regulation of GABA(A) receptors was similar in magnitude to that previously found for rats with bilateral transection of the inferior cerebellar peduncle. It may relate in both cases to reduced Purkinje cell input to medial vestibular nucleus neurons. The lack of effect on GABA(B) receptors suggests that the changes found with peduncle transection may have resulted from something more than reduced Purkinje cell activity, such as reduced concentrations of GABA, or that reduction of Purkinje cell activity in Scn8a mutant mice was insufficient to affect GABA(B) receptors. Other possible explanations of the results cannot be excluded since the Scn8a mutation affects other neuron types besides Purkinje cells.

Amino acid and acetylcholine chemistry in the central auditory system of young, middle-aged and old rats.

Older adults generally experience difficulties with hearing. Age-related changes in the chemistry of central auditory regions, especially the chemistry underlying synaptic transmission between neurons, may be of particular relevance for hearing changes. In this study, we used quantitative microchemical methods to map concentrations of amino acids, including the major neurotransmitters of the brain, in all the major central auditory structures of young (6 months), middle-aged (22 months), and old (33 months old) Fischer 344 x Brown Norway rats. In addition, some amino acid measurements were made for vestibular nuclei, and activities of choline acetyltransferase, the enzyme for acetylcholine synthesis, were mapped in the superior olive and auditory cortex. In old, as compared to young, rats, glutamate concentrations were lower throughout central auditory regions. Aspartate and glycine concentrations were significantly lower in many and GABA and taurine concentrations in some cochlear nucleus and superior olive regions. Glutamine concentrations and choline acetyltransferase activities were higher in most auditory cortex layers of old rats as compared to young. Where there were differences between young and old rats, amino acid concentrations in middle-aged rats often lay between those in young and old rats, suggesting gradual changes during adult life. The results suggest that hearing deficits in older adults may relate to decreases in excitatory (glutamate) as well as inhibitory (glycine and GABA) neurotransmitter amino acid functions. Chemical changes measured in aged rats often differed from changes measured after manipulations that directly damage the cochlea, suggesting that chemical changes during aging may not all be secondary to cochlear damage.

Amino acid concentrations in chinchilla cochlear nucleus at different times after carboplatin treatment.

Amino acid concentrations were measured in the cochlear nucleus for a group of 20 chinchillas: four each of control and 4, 8, 29, and 85 days after treatment with the ototoxic anti-tumor drug carboplatin (100 mg/kg, i.p.). The treated chinchillas showed various extents of inner hair cell loss, generally more complete at longer survival times, but little loss of outer hair cells. Aspartate concentration in rostral anteroventral cochlear nucleus (AVCN) showed a decline to 28% less than the control value at 29 and 85 days after treatment, whereas glutamate concentration showed little change through 29 days, then dropped by 22% at 85 days after treatment. In caudal posteroventral cochlear nucleus (PVCN), the aspartate concentration decreased by 32% at 29 days, in animals with significant inner hair cell loss, and 48% at 85 days after treatment, while the glutamate concentration showed no decrease through 29 days and 40% decrease at 85 days. The concentration of gamma-aminobutyrate (GABA) was about 18% lower than control in caudal PVCN at all survival times. Significant correlations were found between the proportion of inner hair cells remaining and glutamate and aspartate concentrations in PVCN and AVCN, but not GABA or other amino acids.