Aging effects on vestibulo-ocular responses in C57BL/6 mice: comparison with alteration in auditory function

Age-related changes in auditory function are well documented in animal models; however, this is not the case as regards vestibular function. In this study, we evaluated age-related changes in vestibulo-ocular responses in C57BL/6 mice that are considered as a model of presbycusis. The functional data were substantiated by the findings of histological analysis of vestibular and auditory peripherals. The gain in vestibulo-ocular reflex, which reflects functionality of the vestibular system, increased in an age-dependent manner until 12 weeks and exhibited limited functional loss due to aging after 24 weeks. By contrast, no alteration in the thresholds of the auditory brainstem response (ABR) was observed from 3 to 12 weeks of age; however, ABR thresholds were significantly elevated from age 24 weeks and onwards. Histological analysis demonstrated that the degeneration of auditory peripherals was closely related with functional loss due to aging. Vestibular peripherals also exhibited age-related degeneration morphologically, although age-related dysfunction was not apparent. Age-related changes in the vestibular function of C57BL/6 mice followed a different time course when compared to changes in auditory function. These findings indicate that mechanisms for age-related changes in vestibular function differ from those of auditory function.     

Renal oncocytosis

Renal oncocytosis is a rare disorder in which numerous oncocytic nodules develop in the kidney. An additional case is reported here. The patient was a 51-year-old woman who had received hemodialysis for 27 years. Nineteen years previously she had developed a tumorous lesion in the right kidney, which had been diagnosed as oncocytoma with laparotomic biopsy. Recently the kidney was removed because of enlargement of the tumor. The renal parenchyma was entirely replaced with numerous brownish nodules. Histologically, the nodules were composed of nests of uniform oncocytic cells. Ultrastructurally, the oncocytic cells contained numerous mitochondria. Immunohistochemical features of the nodules were identical to those of sporadic oncocytomas, that is, immunophenotypes similar to the distal nephron and reactivity with antimitochondrial antigen. Based on these findings, the lesion was diagnosed as renal oncocytosis. It was not possible to determine whether the larger nodules should be diagnosed as oncocytoma or a part of oncocytosis. Additionally, the germ line mutation of the Birt-Hogg-Dubé (BHD) syndrome gene was examined using the genomic DNA obtained from the peripheral lymphocytes, which failed to show any gene alteration. Despite the rare occurrence pathologists and urologists should be aware of renal oncocytosis, as a precursor lesion of renal oncocytoma and chromophobe renal cell carcinoma.     

Explicit knowledge and intention to learn in sequence learning: an event-related potential study

The present study was performed to examine how intention to learn and explicit knowledge in sequence learning are reflected in event-related potentials. Participants responded to numerals presented in a repeating order, which were replaced infrequently by deviant numerals. The participants were given incidental or intentional learning instructions. Sequence parts for which they acquired explicit knowledge were identified for each participant by post-task memory tests. Reaction times indicated that sequence learning occurred under both types of instruction. The N2 enhancement for deviants was primarily associated with explicit sequence knowledge, and the P3 enhancement showed a weak association. These results suggested that N2 and P3 reflect different aspects of explicit learning.     

Neural mechanisms controlling jaw-jerk reflex in the cat

Signal substances of axon terminals presynaptic to jaw spindle Ia afferents and their ultrastructural features were examined using a combination of intra-axonal horseradish peroxidase injection and postembedding immunogold-labeling techniques in cats. A total of 35 axon terminals presynaptic to 22 horseradish peroxidase-labeled Ia boutons were examined. Of the 35 presynaptic axon terminals, 14 (40%) were immunoreactive for both gamma-aminobutyric acid and glycine, 9 (26%) for gamma-aminobutyric acid alone and 9 (26%) for glycine alone. The bouton volume, mitochondrial volume, active zone area, and apposed surface area were larger for Ia boutons than for presynaptic axon terminals, while each of the values is similar among the three types of presynaptic axon terminals. These results suggest that gamma-aminobutyric acid and glycine play an important role for modulating the jaw-jerk reflex presynaptically and that the smaller size of presynaptic axon terminals is important to prevent action potential generation from Ia afferents.     

The relationship between sleep disturbance and morale in Japanese elderly people

BACKGROUND: Complaints of sleep disturbance are common in elderly individuals. The quality of life (QOL) for people who have insomnia is thought to be worse than for those who do not have insomnia. In this study we investigated the influence of disturbed sleep on morale in elderly people who live independently. METHODS: A survey of the necessity of public nursing care for all those aged over 65 years was performed in Kumamoto city, Japan. Three hundred subjects from the elderly population living at home without special care were sampled at random and they filled out a questionnaire regarding sleep, psychiatric symptoms and attitudes towards their own aging. RESULTS: A logistic regression analysis found psychiatric symptoms and problems keeping awake to be independently related to a negative attitude towards one's own aging. Neither sleep, sex nor age demonstrated any relationship with the negative attitudes of elderly individuals. CONCLUSION: Excessive daytime sleepiness is related to poor morale regardless of both the quality and quantity of sleep and psychiatric symptoms.     

A critical increase in right-to-left shunt after acute myocardial infarction in a 68-year-old male with tetralogy of Fallot

A male patient with tetralogy of Fallot accompanied by aortic regurgitation had maintained sufficient exercise capacity for a number of decades with the status of acyanotic tetralogy of Fallot. When he was 67 years old, he suffered a posterior wall acute myocardial infarction and direct percutaneous coronary angioplasty successfully revascularised the target lesion in the left circumflex artery. However, a few months after the onset of the myocardial infarction, his shortness of breath became clinically significant and was associated with increased right-to-left shunt and increased right ventricular end-diastolic pressure, as well as hypoxia. At 68 years old, therefore, total corrective repair of the tetralogy with replacement of the aortic and pulmonary valves was performed. The patient was asymptomatic after the successful operation. This report suggests that coronary artery disease can be one of the potential factors in inducing critical hemodynamic changes in aging patients with congenital heart disease, especially those who have a shunt between the right and left chambers. The unique clinical course is described with some discussion of the repair of tetralogy in adults.     

Effects of body posture on local sweating and sudomotor outflow as estimated using sweat expulsion

To estimate the effects of changes in body posture on sudomotor function, sweat rates on the forearm, chest and thigh, tympanic temperature (Tty), and skin temperatures were recorded in an upright sitting and a supine position under a hot environment of 40 degrees C Ta and 40% relative humidity for 60 min. Sweat expulsions were identified on sweat rate curves and their rates (Fsw) were calculated. Tty was higher, and its initial fall was greater, in the supine position than in the sitting position. On the forearm and the chest, the regression line relating sweat rate to mean body temperature (Tmb) had a gentler slope in the supine position, whereas on the thigh, it showed a steeper slope. The regression line relating Fsw to Tmb had a steeper slope in the supine position than in the sitting position, suggesting that the gain in the mechanisms for central integration and rhythm-generation was enhanced in the supine position. The parameter of sweat rate divided by Fsw was lower on the forearm and the chest, whereas it was higher on the thigh in the supine position than in the sitting position, suggesting that sudomotor outflow was modified at the spinal cord in association with skin pressure. It was concluded that body posture affects sudomotor functions through both brain and spinal mechanisms.