Search PubMed⌕ Search

Biomedical subjects

B Peretz

Publications and source records attributed to B Peretz.

At least 73 records · Page 4Linked to original sources
PubMed1993

Changes in periodontal status of children and young adolescents: a one year longitudinal study.

The purpose of the present study was to describe longitudinal changes in accumulation of dental plaque and gingival inflammation, and their effect on changes in sulcus depth of children and young adolescents. Forty one boys and 37 girls aged 1-12 years living in a rural community in Israel were included in the study. At baseline and 12 months later, Loe's Plaque Index (PlI) and Gingival Index (GI), and sulcus depth were examined. Boys' mean age was significantly lower than girls' mean age (6.04 + 2.76 years, and 7.68 + 2.84 years respectively). PlI, GI and sulcus depth were higher in the 12-month examination compared to baseline. PlI was slightly higher in boys, while GI was slightly higher in girls. These differences however, were not statistically significant. At baseline, sulcus depth was significantly greater in girls than in boys, while at 12 months the difference was not significant. The children were grouped by age as follows: 1-5 years, 6-9 years and 10-12 years. PlI and GI mean scores were significantly higher among the 6-9-year-old individuals. Mean sulcus depth for the 10-12-year-old children was greater than that of the 6-9-year-olds at baseline and after 12 months. The effect of age, PlI and GI on the outcome variable (sulcus depth) was examined using a correlation matrix. At baseline, age showed the highest correlation (r = 0.659) followed by GI (r = 0.364) and PlI (r = 0.123). The same pattern was also observed at the 12 months examination.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Distribution↗
PubMed1992

Effect of age on acetylcholinesterase and other hemolymph proteins in Aplysia.

Hemolymph was examined in young (ca. 86 days old), mature (ca. 163 days old), and old (ca. 294 days old) Aplysia for age-related changes in constituent proteins. In young, mature, and old animals protein concentrations were 1.6 +/- 0.27, 1.41 +/- 0.53, and 1.45 +/- 0.43 mg.ml-1, respectively. The copper-containing respiratory protein, hemocyanin, measured by determining the copper concentration, was found to increase significantly from young (0.98 +/- 0.51 microgram.ml-1) to mature (2.02 +/- 0.95 micrograms.ml-1) Aplysia, with little change between mature and old (1.92 +/- 0.43 micrograms.ml-1) animals. These findings were consistent with the results obtained when hemocyanin was directly measured by spectrophotometric absorption at 340 nm. Acetylcholinesterase (AChE) was present in the hemolymph of Aplysia. Its activity was highest in mature animals (3121 +/- 1627 units.mg-1) and least in old animals (1463 +/- 599 units.mg-1). Young animals had intermediate levels (2080 +/- 762 units.mg-1). SDS-PAGE revealed a distinct pattern of protein bands for hemolymph from each age group; hemolymph from the young group contained six prominent protein bands with molecular weights (MW) from 13 to 300 kDa. Hemolymph of mature and old animals exhibited four and three prominent protein bands, respectively, with MW between 45 and 300 kDa. A prominent band at 97 kDa was present in samples from the mature group, but was faint in samples from the old group and absent in samples from the young group.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase↗
PubMed1992

Differences in aging in two neural pathways: proposed explanations from the nervous system of Aplysia.

A basic question in studies of the neurobiology of aging is to what extent age-related changes are genetically preprogrammed or epigenetically mediated. Our approach to this question is to compare the effect of age on two neural pathways in the marine mollusc, Aplysia. The advantage of Aplysia as a model of neural aging is that age-sensitive properties in the pathways can be studied at the behavioral, physiological, and morphological levels. The two pathways we are investigating respond differently to aging; a comparison of the pathways' properties provides a means of distinguishing the effect of age from other variables in the same animal. Age effects are expressed in the gill withdrawal reflex pathway at the three levels but are minimal in the gill respiratory pathway. The behavioral and physiological expressions of the reflex pathway are weakened in old animals (250 days of age and older) when compared to those in mature ones (ca. 160 days of age). The major differences between the two pathways are: (1) the reflex pathway appears to exhibit more plasticity than the respiratory pathway, and (2) the level of use of the respiratory pathway is more regular and frequent than that of the reflex pathway. The greater plasticity intrinsic to the reflex pathway and its level of use may well be the characteristics upon which age-related changes depend. An interplay between genetic and epigenetic factors is suggested to help explain the differential aging in the two pathways.

Aging↗
PubMed1992

One-year clinical evaluation of an anterior composite resin.

An anterior composite resin was evaluated in a clinical study of 93 Class III and Class IV restorations placed in patients aged 12 to 50 years. The restorations were evaluated at baseline, 6 months, and 1 year. Sixty-four (79%) of the 81 restorations examined at the 1-year recall were unchanged. Marginal discoloration and changes in surface appearance and marginal adaptation accounted for most of the changes. All changes appeared in patients younger than 14 years, which may indicate that the patients had problems in oral hygiene. Replicas of randomly selected restorations showed smooth surfaces and well-sealed margins with a smooth transition from restoration to enamel. Some restorations showed marginal breakdown and a pitted irregular surface.

Adolescent↗
PubMed1991

Age-related differential expression of neuropeptide mRNAs in Aplysia.

The basis of aging in the Aplysia nervous system is unknown. We now report age-related changes in mRNA expression of phe-met-arg-phe-NH2 (FMRFamide) and egg-laying hormone (ELH) in the abdominal ganglion, a part of the CNS, in young, mature and old Aplysia. Northern blot analysis revealed two mRNA species of 1.4 and 3.2 kb for RMRFamide and a single mRNA species of 0.8 kb for ELH. FMRFamide mRNA level increased 1.5-fold from young to mature and then decreased 3-fold in old animals. ELH mRNA gradually increased between young and mature animals and then escalated 25-fold in old animals. Age differentially affected the mRNA of these two peptides, which may contribute to behavioral changes previously reported.

Aging↗
PubMed1990

Caries protective aspects of saliva and enamel.

Saliva may be considered as being similar to enamel but in a liquid phase. Saliva, the mechanics of remineralization and demineralization, the acquired pellicle and the enamel surface all act to maintain the status quo, resisting mineral loss from the enamel.

Dental Caries↗
PubMed1989

Age sensitivity of osmoregulation and of its neural correlates in Aplysia.

Osmoregulation was studied in the marine mollusc Aplysia californica in young, mature, and old adults. To monitor volume and osmoregulation, we measured body weight, hemolymph osmolality, and chloride concentration. These parameters were measured at regular intervals with animals in 90% artificial seawater (90% ASW) for up to 36 h. They showed that the rates at which Aplysia osmo- and volume regulate were significantly slowed with increased age. However, no age effect was found in osmoregulation when the hemolymph was diluted to 90% of control in animals without an external stress, i.e., by injection of distilled H2O and keeping animals in 100% ASW. Because the dilution bypassed the sensory receptors that detect external changes of osmolality, this finding suggested that the slowed osmoregulation involved age-impaired functioning of the neural pathway mediating osmoregulation. Other evidence was from mature adults whose osmoreceptive organ, the osphradium, was lesioned; they mimicked osmoregulation measured in old adults. In preparations containing a portion of the osmoregulatory pathway, the osphradium was stimulated by 90% ASW, and the responsiveness of neuron R15, which putatively regulates antidiuresis, was tested. The stimulus inhibited spiking in R15 from mature adults but not in R15 from old adults or from osphradiallesioned mature ones. In old Aplysia the refractoriness of R15 to osphradial stimulation demonstrated that the effecacy of the pathway was impaired with increased age; it helped explain the slower rate of osmoregulation. Possible changes of osmoregulatory mechanisms and behavior compensating for the age sensitivity of osmoregulation are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1987

Motor neuronal function in old Aplysia is improved by long-term stimulation of the siphon/gill reflex.

As Aplysia age, motor neuronal (L7) elicited gill-pinnule contractions are significantly decreased, as is transmission at pinnule junctions. To determine whether this reduced function of L7 with increased age could be altered, the siphon/gill reflex, which involves the L7-pinnule pathway, was stimulated regularly in unrestrained old animals. Aplysia, more than 240 days old, were assigned randomly into trained and untrained groups. For more than 3 weeks, a 1-s, 25-g water jet stimulus was administered to the siphon of the trained animals 10 times per day at 20-min intervals. The duration of siphon withdrawal increased significantly during training. In semi-intact preparations, pinnule contractions and junctional transmissions were then measured during 3-s depolarized pulses to L7 (frequency range = 1-44 per 3-s interval). The trained animals had (a) significantly higher pinnule contractions, (b) a significantly greater increase in pinnule contractions elicited by increasing L7 spike rates, (c) significantly higher double-spike facilitation, and (d) significantly higher facilitation per spike across the four spike trains below or at pinnule contraction threshold. Long-term stimulation of the siphon/gill reflex in old Aplysia did not produce the same functional efficiency observed in mature Aplysia; nevertheless, the significant training-induced increases in both pinnule contraction and junction transmission indicate that a considerable level of plasticity still exists in an aging nervous system. Whether this long-term training of Aplysia retards the same processes responsible for the age-related decline in neuromuscular transmission or produces a compensatory change in other neuronal processes is discussed.

Aging↗
PubMed1986

Properties of muscle cells and remodeling of neuromuscular junctions as related to age in Aplysia.

Age-related morphologic properties of muscle cells and of their innervation in the gill were sought to explain reduced contractility in old Aplysia. As a consequence of previous physiological findings, properties of two muscle groups were examined: one group, MPn, innervated by motor neuron, L7, whose ability to elicit muscle contraction was reduced during aging, and the other group, LEV, innervated by motor neuron, LDG1, whose ability was not. In neither group did muscle properties, such as cell diameter and density and thick filament diameter and density, and resting potential, change with age. In contrast, age-related remodeling of nmjs did occur. The results show that remodeling is expressed differently in the two types of junctions: In L7-nmjs contact between terminals and muscle cells significantly increased with age; in LDG1-nmjs the terminal perimeter was enlarged significantly and not the contact between terminals and muscle cells. With increased age, the proportion of the terminal perimeter in contact with muscle in L7-nmjs increased significantly, and in LDG1-nmjs it remained essentially the same. Accompanying the remodeling of LDG1 terminals was a significant increase of vesicles in them; no significant change in vesicle number was measured in L7 terminals. The effect on transmission of the age-related presynaptic changes in the two types of junctions is discussed.

Aging↗
PubMed1984

Survival and aging of a small laboratory population of a marine mollusc, Aplysia californica.

In an investigation of the postmetamorphic survival of a population of 112 Aplysia californica, five animals died before 100 days of age and five after 200 days. The number of survivors among the 102 animals which died between 100 and 220 days declined approximately linearly with age. The median age at death was 155 days. The animals studied were those that died of natural causes within a laboratory population that was established to provide Aplysia for sacrifice in an experimental program. Actuarial separation of the former group from the latter was justified by theoretical consideration. Age-specific mortality rates were calculated from the survival data. Statistical fluctuation arising from the small size of the population was reduced by grouping the data in bins of unequal age duration. The durations were specified such that each bin contained approximately the same number of data points. An algorithm for choosing the number of data bins was based on the requirement that the precision with which the age of a group is determined should equal the precision with which the number of deaths in the groups is known. The Gompertz and power laws of mortality were fitted to the age-specific mortality-rate data with equally good results. The positive values of slope associated with the mortality-rate functions as well as the linear shape of the curve of survival provide actuarial evidence that Aplysia age. Since Aplysia grow linearly without approaching a limiting size, the existence of senescence indicates especially clearly the falsity of Bidder's hypothesis that aging is a by-product of the cessation of growth.

Aging↗
PubMed1984

Functional history of two motor neurons and the morphometry of their neuromuscular junctions in the gill of Aplysia: evidence for differential aging.

Because the viability of the gill withdrawal reflex is dependent on age in Aplysia, we examined physiologic and morphometric properties of two motor neurons, L7 and LDG1, involved in the reflex in three postmetamorphic age groups: young, mature, and old. L7's capability to elicit pinnule contraction, a major component of the reflex, was reduced markedly in old gills; facilitation at old L7 terminals, upon which contraction is dependent, was significantly reduced. The morphology of the pinnule neuromuscular junctions changed with increased age. In contrast, LDG1's capability to elicit efferent vessel contraction, a major component of respiratory movements, was not significantly altered by age; facilitation also was relatively unaffected; and morphologic changes at neuromuscular junctions were poorly correlated with age. Aging occurs differentially in two motor neurons innervating the gill. The dissimilarity in function and in frequency of activation of L7 and LDG1 may help explain the greater vulnerability of L7 to the effects of aging. The possibility that disuse is involved in the aging process is discussed.

Animals↗
PubMed1982

Age-diminished motor neuronal function of central neuron L7 in Aplysia.

The efficacy of central neuron L7 to elicit gill pinnule contractions was tested in mature and old Aplysia. The difference in age between groups was no less than 70 days and as much as 150 days. Spike in L7 were necessary to elicit pinnule contractions in both age groups. Spike rates of 8 spikes per second and higher elicited pinnule contractions that were significantly smaller in old than in mature animals. Synaptic activity in the pinnule muscles innervated by L7 was recorded extracellularly during contractions, and it was significantly less facilitated by spike trains in old compared to that in mature Aplysia. This suggests that the reduction of facilitated synaptic transmission between L7 and pinnule muscles results in diminished motor neuron function.

Aging↗
PubMed1981

Age-dependent anatomical changes in an identified neuron in the CNS of Aplysia californica.

Neurons of Aplysia californica are naturally pigmented and the pigment accumulates with age. In the present study the pigment was examined in the same neuron from Aplysia of three postmetamorphic ages: young, sexually mature, and old. The large central neuron, R2, was examined by light and electron microscopy to determine if the pigment possessed properties similar to lipofuscin pigment seen in aging mammalian neurons. We used the same microscopic techniques that demonstrate the presence of lipofuscin in mammalian neurons. Light microscopic studies demonstrated a regional correlation between autofluorescence, staining with Sudan Black, and the naturally occurring pigment in old R2s. Electron microscopic studies revealed the presence of large vacuolated and lamellated membrane-bound bodies in the peripheral cytoplasm of old R2s, similar to those found in mammalian neurons. The bodies were located in the same region in which autofluorescence and Sudan Black staining were observed. Although the naturally occurring pigment accumulates with age, it acquires characteristics of lipofuscin pigment in the neurons of older sexually mature animals. The presence of these pigment characteristics can be used as an index of aging in Aplysia neurons as they are in mammalian neurons.

Aging↗