Primary Neural Degeneration in the Human Cochlea: Evidence for Hidden Hearing Loss in the Aging Ear

The noise-induced and age-related loss of synaptic connections between auditory-nerve fibers and cochlear hair cells is well-established from histopathology in several mammalian species; however, its prevalence in humans, as inferred from electrophysiological measures, remains controversial. Here we look for cochlear neuropathy in a temporal-bone study of "normal-aging" humans, using autopsy material from 20 subjects aged 0-89 yrs, with no history of otologic disease. Cochleas were immunostained to allow accurate quantification of surviving hair cells in the organ Corti and peripheral axons of auditory-nerve fibers. Mean loss of outer hair cells was 30-40% throughout the audiometric frequency range (0.25-8.0 kHz) in subjects over 60 yrs, with even greater losses at both apical (low-frequency) and basal (high-frequency) ends. In contrast, mean inner hair cell loss across audiometric frequencies was rarely >15%, at any age. Neural loss greatly exceeded inner hair cell loss, with 7/11 subjects over 60 yrs showing >60% loss of peripheral axons re the youngest subjects, and with the age-related slope of axonal loss outstripping the age-related loss of inner hair cells by almost 3:1. The results suggest that a large number of auditory neurons in the aging ear are disconnected from their hair cell targets. This primary neural degeneration would not affect the audiogram, but likely contributes to age-related hearing impairment, especially in noisy environments. Thus, therapies designed to regrow peripheral axons could provide clinically meaningful improvement in the aged ear.

Misdiagnosed paranasal gossypiboma: a 10-year experience with 21 cases at a tertiary center

BACKGROUND

Different from rhinoliths, the paranasal gossypiboma is a foreign body, such as a surgical sponge, left in the nasal cavity. It is a rare, frequently misdiagnosed disease that has rarely been reported. We summarize its clinical characteristics, management, and possible risk factors.

METHODOLOGY

We reviewed medical records of confirmed paranasal gossypibomas at a tertiary medical center between 2005 and 2015. Clinical symptoms, age, sex, anatomic sites, endoscopic photography, computed tomography, intraoperative findings, and past medical history were reviewed.

RESULTS

The study included 21 patients, each of whom had ultimately undergone two operations. Among them, 20 underwent endoscopic nasal surgery in primary hospitals, and 15 had been misdiagnosed during the second surgery. The average interval to discovery of a retained foreign body was 200 days. Predominant occurrence sites were the maxillary and ethmoid sinuses. Computed tomography showed paranasal gossypiboma as a heterogeneous cystic lesion with a thin calcified shell.

CONCLUSIONS

A history of endoscopic nasal surgery, especially performed at a primary hospital, is a warning sign for clinicians. Computed tomography can add to the warning by showing a heterogeneous cystic lesion with a thin calcified shell. Clinicians should be aware of these characteristics to avoid misdiagnosing paranasal gossypiboma.

Genome-wide analysis of the GRAS gene family in physic nut (Jatropha curcas L.)

GRAS proteins play vital roles in plant growth and development. Physic nut (Jatropha curcas L.) was found to have a total of 48 GRAS family members (JcGRAS), 15 more than those found in Arabidopsis. The JcGRAS genes were divided into 12 subfamilies or 15 ancient monophyletic lineages based on the phylogenetic analysis of GRAS proteins from both flowering and lower plants. The functions of GRAS genes in 9 subfamilies have been reported previously for several plants, while the genes in the remaining 3 subfamilies were of unknown function; we named the latter families U1 to U3. No member of U3 subfamily is present in Arabidopsis and Poaceae species according to public genome sequence data. In comparison with the number of GRAS genes in Arabidopsis, more were detected in physic nut, resulting from the retention of many ancient GRAS subfamilies and the formation of tandem repeats during evolution. No evidence of recent duplication among JcGRAS genes was observed in physic nut. Based on digital gene expression data, 21 of the 48 genes exhibited differential expression in four tissues analyzed. Two members of subfamily U3 were expressed only in buds and flowers, implying that they may play specific roles. Our results provide valuable resources for future studies on the functions of GRAS proteins in physic nut.

Staphylococcus aureus causes acute inflammatory episodes in the cornea during contact lens wear

The aim of this investigation was to determine the ability of Staphylococcus aureus to cause keratitis during contact lens wear in the rabbit. Rabbits were fitted with hydrogel lenses and wore them on an extended wear schedule for 7 weeks. At the end of each week of wear, one drop of S. aureus was added to the eyes, and the eyes were monitored using slit lamp bio-microscopy, with subsequent microbial and histological studies of the cornea. In the presence of S. aureus, keratitis occurred after 3 weeks of lens wear, a condition that was characterized by diffuse infiltration of the peripheral cornea and limbal redness. In the absence of bacteria, there was no infiltration until week 6. Contact lens wear also prolonged the retention of bacteria in the eye. Extended contact lens wear and S. aureus caused non-ulcerative keratitis in a rabbit model, and disturbances in the ability of the eye to remove bacteria.

Comparison of potential pathogenic traits of staphylococci that may contribute to corneal ulceration and inflammation

Staphylococcus epidermidis and Staphylococcus aureus are two of the commonest bacteria isolated from corneal ulcers. The aim of the current investigation was to determine the frequency of potentially pathogenic traits in the two staphylococcal species. Strains of both species, some isolated from eyes during active corneal inflammation, were screened for their ability to degrade a variety of proteins and hyaluronic acid and the production of cytotoxins. S. aureus produced more tissue-destructive enzymes than the S. epidermidis. S. aureus strains more commonly synthesized the cytotoxin, alpha-toxin. The production of elastase was more common among S. aureus strains isolated from ulcerative events. The production of alpha-toxin was inversely correlated with isolation from keratitis. This study has demonstrated that S. aureus is better equipped with a range of potentially damaging enzymes and toxins than S. epidermidis and that S. aureus elastase may be involved in the production of corneal ulcers.