Age Differences In Susceptibility Research Articles

A heritable component for external apical root resorption in patients treated orthodontically.

External apical root resorption (EARR) is a common and occasionally critical problem in orthodontic patients. Mechanical forces compress the periodontium, leading to localized resorption of cementum that exposes dentin to destruction by clastic activity. Factors controlling occurrence and extent of EARR are poorly understood, but there may be a familial (genetic) factor in susceptibility. A sample of full siblings (103 pairs) was studied, all of whom were treated with the same technique by one orthodontist. Crown and root lengths were measured on cephalograms and panoral films before and after treatment. Six roots were scored on each patient, and decrease in root length was the dependent variable. Generalized linear models were used to quantify within and among sibship variances while controlling for sex, age, and severity of malocclusion (FMA, ANB, AOBO, overjet, NAP) as covariates. Results showed significantly greater among-than within-sibship variances, meaning there is a substantive genetic factor in susceptibility to EARR. Heritability estimates were fairly high, averaging 70% for three roots, although low for the mandibular incisor, probably because of little variation. No evidence was found for a sex or age difference in susceptibility. Quantification of a transmissible component suggests it would be useful to search for the biochemical factors controlling the familial differences in susceptibility.

センダイウイルス感染感受性・抵抗性マウス肺におけるウイルス増殖の比較

Susceptibility of inbred mouse strains to Sendai virus (Mol strain) infection was studied. Although some mouse strains showed age differences in susceptibility between 3-to 4-week-old and 7-to 8-week-old mice, such age differences in susceptibility were not observed in susceptible DBA/2N and resistant BALB/cA mice. In 7-to 8-week-old mice, remarkable strain differences were observed in mortality and intensity of the lung lesions, but not in lung virus titers and serum antibody, between resistant BALB/cA and susceptible DBA/2N mice.

Child Animism: Situational Influences and Individual Differences

Abstract Children's animistic responses were manipulated in two experiments by pictorially varying the motion state of the objects about which they were questioned. Although moving objects elicited more animistic responses, no age difference in susceptibility to the moving-state condition was found between the 4- and 5-year-olds included in Experiment 1. Performance under the two conditions was highly correlated (r = .76) indicating stable individual differences in the tendency to respond in an animistic way. In Experiment 2, a significant Age × Stimulus State interaction was obtained with 5- and 6-year-old subjects. Five-year-olds gave more animistic responses than 6-year-olds in the moving-state condition. Susceptibility to the manipulation was correlated with performance on a Piagetian-type inanimate objects measure (r = .78), further indicating stable individual differences in animistic responding. A negative, but nonsignificant, relationship was found between field independence (CEFT) and susceptibil...

Statistical modeling of animal bioassay data with variable dosing regimens: example--vinyl chloride.

We consider animal bioassay experiments with variable dosing regimens in which groups of animals are dosed beginning at different ages and for varying durations. Two response models are discussed and then applied to data from an experiment on vinyl chloride exposure of F-344 rats, B6C3F1 and Swiss CD-1 mice, and Syrian Golden hamsters. The multistage model of Armitage and Doll, as extended by Whittemore, Day and Brown, and Crump and Howe, is used to estimate the dose effect on the ordered stages of tumor development. The data for all endpoints and species/strains examined consistently indicate a predominant effect on the first stage, suggesting that vinyl chloride is primarily a tumor initiator. This is consistent with evidence from two-stage experiments on this chemical. The second response model, new to this article, adjusts for survival nonparametrically. It is used to test for an age difference in susceptibility, to evaluate alternative exposure durations, and to compare the effectiveness of alternative dosing regimens for detecting carcinogenicity.

Manifestations of experimental leprosy in the armadillo.

Three experiments, using different routes and doses of infection, were conducted using 42 armadillos. Thirty-six of them developed generalized disease. There is no significant sex or age difference in susceptibility. Route and dose of infection make very little difference in the disease prevalence except that the intravenous administration of a large dose reduces the period of development of generalized disease. It is quite possible that in armadillos the resistance to the disease is partly genetic. Although a majority of the armadillos developed lepromatous disease, borderline leproma is fairly common. In skin nodules large colonies of extracellular bacilli are demonstrated. Bacilli are also demonstrated in liver parenchymal cells.

Age difference in the susceptibility to cadmium-induced testicular damage in rats

Since the concentration of cadmium in the testes after cadmium administration to 4-day-old rats is five times that of adults, the objective of this study was to determine if there is an age difference in the susceptibility of Cd-induced testicular damage. Adult rats treated with Cd (1 mg Cd/kg, iv) at 10 weeks of age developed testicular damage and atrophy which persisted for at least 12 weeks. These rats were found to be sterile at the seventh week after injection. For rats treated at 4 days of age, there was no difference in testicular weight, morphology, and fertility between the saline- and Cd-treated groups during 12 weeks after injection. When rats of various ages were examined, it was found that Cd produced no detectable changes in the testes of rats that are 2 weeks of age and younger but slight degenerative changes were observed in rats 3 to 5 weeks of age. However, in rats 6 weeks of age and older, cadmium produced necrosis and atrophy of the testes. Testicular metallothioneins have been proposed to be involved in the protection against Cd-induced testicular damage after cadmium pretreatment in the adult. However, the testicular concentration of metallothioneins in 4-day-old rats was not higher than that of 10-week-old rats, indicating that the age difference in susceptibility to Cd-induced testicular damage is not due to age differences in testicular metallothionein levels. In conclusion, immature rats are resistant to testicular injury produced by Cd and it appears that testicular levels of metallothionein or cadmium do not play an important role in the difference in sensitivity of various aged rats to Cd.

The potential of children as eyewitnesses: A comparison of children and adults on eyewitness tasks.

This study examined children's capabilities in an eyewitness task. Subjects aged five to twenty-two years viewed a confederate interacting with the experimenter and later were asked to tell what had happened, to answer objective questions (including a leading question), and to identify the confederate from 6 photos. The results indicated that although young children were unable to freely narrate what they had observed as thoroughly as adults, they were as accurate as adults in answering objective questions and in identifying the confederate from 6 photos. Additionally, there were no age differences in susceptibility to leading questions.

The influence of age on the toxicity and metabolism of methyl parathion and parathion in male and female rats

To determine the mechanisms responsible for the variations in toxicity of methyl parathion and parathion, the in vitro metabolism of these insecticides and cholinesterase sensitivity to their respective oxygen analogs methyl paraoxon and paraoxon were studied in male and female rats of several ages. For rats of five ages studied (1, 12–13, 23–24, 35–40, and 56–63 days), there was a gradual decrease in susceptibility to poisoning by both insecticides with increasing age up to 35–40 days for both sexes. Age differences in susceptibility were not related to differences in sensitivity of cholinesterase to inhibition by paraoxon or methyl paraoxon in vitro. Oxidative formation of the oxygen analogs, oxidative aryl cleavage, and glutathione-dependent dealkylation and dearylation of methyl parathion and parathion were assayed in liver homogenates of male and female rats of the five ages. Rates of enzymatic detoxification of their corresponding oxygen analogs by A-esterase, glutathione- S-aryl-, and - S-alkyl-transferase and inactivation by binding were also investigated. Correlation coefficients for rates of metabolism versus LD50 values for the different ages were calculated. In general, changes in LD50 values with age for methyl parathion and parathion correlated better with changes in rates of reactions which represented detoxification pathways for methyl paraoxon and paraoxon than for reactions which represented direct metabolism of the parent insecticides. Both male and female rats became much less sensitive to the acute lethal effects of methyl paraoxon and paraoxon with increasing age. This is consistent with a hypothesis that changes in LD50 values of methyl parathion and parathion with age are due to changes in rates of metabolism of the oxygen analogs.

Studies on the enzyme inducing effect of polychlorinated biphenyls

Aroclor 1260 was fed to weanling male and female rats in the diet at levels of 1, 5, 25 and 50 ppm to determine its enzyme inducing capacity over various feeding periods. Dose-dependent increases in the activity of 3 hepatic microsomal enzymes were observed; maximal induction occurred in the first 3 weeks of the feeding period. Among the 3 enzyme systems studied, N-demethylase was the most sensitive to the inducing effect of Aroclor 1260. The enzyme induction was more pronounced in male rats than in females. An age difference in susceptibility of male rats to the enzyme inducing effect was also noted, young rats being more susceptible than adults. Data obtained by simultaneously feeding PCB and DDT to rats showed that these compounds have additive inducing effects on N-demethylase activity. However, PCB and DDT were not, when combined, additive on the O-demethylase and EPN-detoxification systems under the test conditions employed. Comparison of enzyme inducing effects of three Aroclor compounds, Aroclor 1221, 1254 and 1260, clearly indicates that both microsomal N-demethylase and EPN detoxification activity were increased in proportion to the chlorine content of the Aroclor compounds. Maximal induction of O-demethylase occurred at 54% chlorination.

Age differences in susceptibility to hypnosis

Abstract Hypnotic susceptibility scores were compared in a crosssectional sample of 1,232 Ss, ranging in age from 5 to 78 years. The sample was comprised of 579 high school and college students, and a family sample of 653 parents and children. A peak of hypnotizability in the age interval 9-12 years, with a gradual decline thereafter, confirms earlier studies. A comparison of scores by age and sex showed a significant difference (p = .001) for ages 21-32; this difference was produced by a significant rise in scores for the young mothers of the family sample and was not found for students at the same age level. It was concluded that this finding demands replication before too much can be made of it.

The Influence of Age of Host on Infection with Eimeria tenella

Excystation of E. tenella sporozoites was more rapid in chicks aged 4, 5, and 6 weeks than in those of 0, 1, 2, and 3 weeks. A greater proportion of unexcysted sporulated oocysts was found in the feces of birds aged 0 and 1 week than in any of the other age-groups studied, indicating less successful excystation in these birds. Oocyst production to a dose of 500 oocysts increased with age of host. Older birds tended to be more resistant to second and third infections than the younger birds but direct comparisons are difficult to make. Chickens of different ages are known to differ in their susceptibility to infection with Eimeria spp. (Tyzzer, Theiler, and Jones, 1932; Brackett and Bliznick, 1952; Gardiner, 1955; Long, 1959; Krassner, 1963; Doran and Farr, 1965). Various reasons for the age differences in susceptibility, such as length of intestine, availability of cells, and physiological conditions for sporozoite penetration have been advanced by the authors quoted above. Some earlier work in this laboratory which involved the excystation of E. tenella in very young chicks indicated that the percentage excystation increased with age of host. Consequently, we have examined the excystation of E. tenella in chicks of different ages and also the extent of the subsequent infection as shown by oocyst

Comparison of Acute Toxicity of Anticholinesterase Insecticides to Weanling and Adult Male Rats

SummaryA comparison was made of the acute toxicity of a number of anticholinesterase insecticides in weanling and adult male rats. The results indicate that weanlings are about twice as susceptible as adults to parathion, methyl parathion, Systox, Di-Syston, Guthion, Malathion, Delnav, and Folex. A smaller increase in susceptibility of weanlings was noted with Ethion, Phosdrin, Dipterex and Sevin. Weanlings were about 5 times more susceptible to EPN and about 4 times more susceptible to Trithion than adult male rats. In the case of OMPA adults were about 5 times more susceptible than weanlings. The age differences in susceptibility are probably due to incomplete development of enzymes which catalyze the metabolism of anticholinesterase insecticides in the livers of young animals.

COMPARISON OF ACUTE TOXICITY OF ANTICHOLINESTERASE INSECTICIDES TO WEANLING AND ADULT MALE RATS.

SummaryA comparison was made of the acute toxicity of a number of anticholinesterase insecticides in weanling and adult male rats. The results indicate that weanlings are about twice as susceptible as adults to parathion, methyl parathion, Systox, Di-Syston, Guthion, Malathion, Delnav, and Folex. A smaller increase in susceptibility of weanlings was noted with Ethion, Phosdrin, Dipterex and Sevin. Weanlings were about 5 times more susceptible to EPN and about 4 times more susceptible to Trithion than adult male rats. In the case of OMPA adults were about 5 times more susceptible than weanlings. The age differences in susceptibility are probably due to incomplete development of enzymes which catalyze the metabolism of anticholinesterase insecticides in the livers of young animals.

The age factor in the susceptibility of man and animals to radiation. II. Age differences in susceptibility to carcinogenesis in man.

Variation in man's susceptibility to the induction of cancer at different ages is of considerable interest both theoretically and practically. In the past, very little information on the subject has been available and it has not been possible to use human data to test any particular hypothesis about the mechanism of carcinogenesis. Recently, however, the situation has begun to change and it may, perhaps, be of interest to review the data to see whether any useful conclusions can be drawn from them. The theoretical interest of the question lies principally in the fact that in most of the common types of human cancer the incidence increases very rapidly with age. This increase begins at about the age of 20 years and continues at least until the age of 80 years and probably beyond. It occurs characteristically in cancer of the skin, in most of the epithelial cancers of the respiratory and digestive tracts and in such different types as chronic lymphatic leukaemia and chronic myelomatosis. In these types of cancer a rough working rule is that the incidence is approximately proportional to the 5th or 6th power of the age—for example, when the age is doubled the incidence increases about 25 or 26 times. In some other types of cancer, however, the relationship with age is quite different.

INFLUENCE OF AGE ON SUSCEPTIBILITY OF MICE TO ST. LOUIS ENCEPHALITIS VIRUS AND ON THE DISTRIBUTION OF LESIONS

1. Young mice are more susceptible than older mice to the virus of St. Louis encephalitis inoculated intraperitoneally, but with virus inoculated intracerebrally or intranasally, there is no significant age difference in susceptibility. The greatest change in the resistance to the virus inoculated intraperitoneally occurs between the 2nd and 3rd weeks of life. 2. The distribution of the lesions of St. Louis encephalitis in the C.N.S. of young and of old animals following intraperitoneal inoculation indicates that the virus may reach the brain either by the ascending pathway from the spinal cord or by the olfactory pathway irrespective of the age of the animal. However the ascending pathway is most frequently concerned. 3. The distribution of lesions does not offer evidence that the virus enters the C.N.S. of young animals directly from the blood stream following intraperitoneal inoculation. 4. Although widespread lesions occur earlier in the C.N.S. of young mice than in that of older mice inoculated intraperitoneally with large doses of virus, this fact is not satisfactorily explained by assuming the more rapid increase of the virus in the C.N.S. of young animals, since the latter are not more susceptible to virus inoculated directly into the brain. 5. The observations can be explained by the hypothesis that a greater amount of virus survives and reaches the portals of the C.N.S. in young animals following intraperitoneal inoculation and that this is an important factor in the influence of age on susceptibility to the virus.