EMG study on the effect of ageing on the human masseteric jaw-jerk reflex

The effect of age on the masseteric jaw-jerk reflex was investigated in 22 young (11 males and 11 females with mean age 23.2 years) and 22 older dentate subjects (11 males and 11 females with mean age 61.3 years). Electromyographic (EMG) recordings were obtained, after chin taps, from the relaxed masseter muscle of the preferred chewing side, by use of a computerised recording and analysis system. With increasing age the occurrence of the reflex was reduced, the latency was increased, while the amplitude was decreased. Those findings are probably related to the general age related changes in the muscular tissue, the sense organs, the peripheral nerves and especially the central nervous system, Increased biological variance was also observed in the older subjects, as in most aspects of performance in the latent years. Furthermore, the effects of ageing were generally similar in men and women. The age-related decrement in the monosynaptic reflex response is indicative of a generalised decline in the motor performance of the stomatognathic system and the decreased ability of the older dental patient to easily adapt to any dramatic changes in the sensory input.     

Difference in apolipoprotein E type 4 allele (APOE epsilon 4) among dentate and edentulous subjects

Objectives: To evaluate the frequency of apolipoprotein (APOE) alleles and determine whether APOE type 4 allele (?4) was associated with edentulousness even when certain factors were controlled. Background: The APOE are important in lipid homeostasis, and APOE ?4 has been found in many diseases and to have a negative impact on longevity. Tooth loss is more common in ill aged subjects with low income and education. Materials and methods: In a population‐based study involving 1860 subjects between 35 and 85 years 1321 dentate (mean age = 54; 54% women, 46% men) and 539 edentulous (mean age = 72; 62% women, 38% men) subjects were studied. Logistic regression was performed with dentate/edentulous as dependent variables and years of education, socio‐economic status, social network, stress level, handicap from birth, 23 various diseases and APOE ?4 as covariates. Thereafter, APOE ?4 frequencies were studied in 342 dentate and 336 edentulous subjects 50–85 years of age. The subjects were matched with regard to age, gender, years of education, living condition, stress level, handicap from birth and 23 various diseases. Results: APOE allele frequency in the total group was ?2 = 7.8%, ?3 = 76.4% and ?4 = 15.8%. Age, living condition, years of education and APOE ?4 were significant covariates in edentulous subjects (p ≤ 0.001). APOE ?4 in the matched groups revealed significant differences between the dentate group and the edentulous group (χ² = 5.68; p = 0.017). There was no group effect (F_(29,648) = 0.849; p < 0.696; Wilks’ lambda = 0.963). In the dentate group, the frequencies of APOE were: ?2 = 8.8%, ?3 = 77.9% and ?4 = 13.3%. Corresponding frequencies of APOE in the edentulous group were: ?2 = 6.6%, ?3 = 75.4% and ?4 = 18.0%. Conclusion: Despite matching both groups with regard to different background factors, the edentulous group had a higher frequency of APOE ?4 than the dentate group. Thus, genetic factors might contribute to greater risk in developing complex oral diseases leading to tooth loss or just be an indication that the subjects in our study carrying APOE ?4 are more fragile.     

Incidental and intentional flavor memory in young and older subjects

Incidental and intentional learning and memory for 2 novel flavors were compared in young and elderly subjects. Incidental and intentional learning groups rated 2 new soups on acceptability for different occasions and were tested for memory the next day. On the first day, only the intentional group was asked to memorize the stimuli. With incidental learning, elderly and young were equally good, but the young performed better with intentional than with incidental learning, whereas the elderly did not. There were no age-related differences in perceptual discrimination. When comparing perceived flavor with the memory of it, the elderly tend to overrate intensities of remembered flavor attributes, whereas the young tend to underrate them. Memory was not related to flavor pleasantness or neophobia. Like memory for taste and texture, flavor memory seems to be mainly tuned at detecting changes and based on "feelings of not knowing" rather than on precise identification and recognition of previously encountered stimuli.     

Effect of whole body vibration frequency on neuromuscular activity in ACL-deficient and healthy males

Whole-body vibration (WBV) has been shown to enhance muscle activity via reflex pathways, thus having the potential to contrast muscle weakness in individuals with rupture of the anterior cruciate ligament (ACL). The present study aimed to compare the magnitude of neuromuscular activation during WBV over a frequency spectrum from 20 to 45 Hz between ACL-deficient and healthy individuals. Fifteen males aged 28±4 with ACL rupture and 15 age-matched healthy males were recruited. Root mean square (RMS) of the surface electromyogram from the vastus lateralis in both limbs was computed during WBV in a static half-squat position at 20, 25, 30, 35, 40 and 45 Hz, and normalized to the RMS while maintaining the half-squat position without vibration. The RMS of the vastus lateralis in the ACL-deficient limb was significantly greater than in the contralateral limb at 25, 30, 35 and 40 Hz (P<0.05) and in both limbs of the healthy participants (dominant limb at 25, 30, 35, 40 and 45 Hz, P<0.05; non dominant limb at 20, 25, 30, 35, 40 and 45 Hz, P<0.05). The greater neuromuscular activity in the injured limb compared to the uninjured limb of the ACL-deficient patients and to both limbs of the healthy participants during WBV might be due to either augmented excitatory or reduced inhibitory neural inflow to motoneurons of the vastus lateralis through the reflex pathways activated by vibratory stimuli. The study provides optimal WBV frequencies which might be used as reference values for ACL-deficient patients.     

The multi-herbal formula Chong-Myung-Tang improves spatial memory and increases cell genesis in the dentate gyrus of aged mice

Chong-Myung-Tang (CMT) is a multi-herbal formula that has been used to improve memory. However, the potential mechanism remains unknown. The present study investigated the effects of CMT (50, 100, and 200?mg/kg) on spatial memory of aged mice. The behavioral training tests indicated that 200?mg/kg CMT treatment can significantly improve spatial memory of aged mice in the Morris water maze. Moreover, cell survival was examined by injecting bromodeoxyuridine (BrdU) on the first three days. The result showed that 200?mg/kg CMT treatment significantly increased cell survival in the dentate gyrus. Cell proliferation was determined by injecting BrdU 2?h before the mice were killed. The result suggested that CMT treatments had no influence on cell proliferation in the dentate gyrus. Thus, an increase in cell survival in the dentate gyrus stimulated by CMT may be involved in the effect of CMT on spatial memory improvement.     

Calcium-ion movement and contractility in atrial strips of frog heart are not affected by low-frequency-modulated, 1 GHz electromagnetic radiation

Calcium efflux from electrically stimulated, ⁴⁵Ca²⁺-preloaded atrial strips of the frog heart was measured from samples of the rinsing perfusate collected at 2-min intervals for 32 min in a continuous perfusion chamber. Contractile force was simultaneously monitored. The specimen chamber was located in a stripline apparatus in which the atrial strips were exposed for 32 min to constant (CW) or amplitude-modulated (AM), 1 GHz electromagnetic (EM) fields at specific absorption rates (SAR) ranging from 3.2 μW/kg to 1.6 W/kg. Amplitude modulation was either at 0.5 Hz, in synchrony with the electrical stimulus applied to the preparation, or at 16 Hz. Neither unmodulated nor 0.5 Hz or 16 Hz modulated 1 GHz waves affected the movement of calcium ions or the contractile force in isolated atrial strips of the frog heart. © 1993 Wiley-Liss, Inc.     

Midazolam and theN-methyl-d-aspartate (NMDA) receptor antagonist 2-amino-7-phosphonoheptanoic acid (AP-7) attenuate stress-induced expression of c-fos mRNA in the dentate gyrus

Summary 1. The effects of restraint stress on c-fos mRNA expression in the dentate gyrus were investigated byin situ hybridization.2. Confirming previous findings, c-fos mRNA expression increased after 30 min of forced restraint.3. This effect was attenuated by a previous i.c.v. injection of the anxiolytic benzodiazepine midazolam (20 nmol/2 µl) or theN-methyl-d-aspartate (NMDA) receptor antagonist 2-amino-7-phosphonoheptanoic acid (AP-7; 5 nmol/2 µl).4. These results suggest that the dentate gyrus is activated during restraint stress and that this activation may be modulated by benzodiazepine -aminobutyric acid_A (GABA_A) or NMDA receptors.