Effects Of Host Age Research Articles

Pathogenicity of Three Avian Influenza Viruses for Leghorn Hens of Different Ages

Pronounced host effects on clinical responses to influenza virus infection were not observed in any of seven trials in which young (26-43 weeks) and olf (65-94 weeks) leghorn hens were inoculated with low pathogenic subtype H5N2, H4N8, or H3N2 virus. In two of seven trials, where hens were infected with H4N8 or H3N2 virus, morbidity rates were slightly higher for old hens than for young hens. These observations indicate that host age effects of the severity of uncomplicated influenza virus infections are likely to be minimal in sexually mature chickens.

Blue Berets or blindfolds? Peacekeeping and the hostage Effect

The hostage effect is a little‐understood aspect of peacekeeping that uses peacekeepers’ inherent vulnerability to harm at the hands of the belligerents as a method of influencing those belligerents. Noting that peacekeepers are increasingly being harmed in civil war operations, this article explores the sources and operation of the hostage effect. It tests the operation of those factors found to attend a hostage effect against three case studies: ONUSAL, a functioning hostage effect; UNOSOM II, a dysfunctional hostage effect; and UNPROFOR II, a malfunctioning hostage effect. The conclusions suggest significant ramifications for the applicability of peacekeeping in different types of conflict situations. Michael Wesley has recently completed a PhD in the Department of International Relations at the University of St. Andrews, Scotland.

Immunity in humans to Necator americanus: IgE, parasite weight and fecundity.

The effect of the humoral immune response on the weight and fecundity of the hookworm Necator americanus was examined in an endemically-infected human population. There was a highly significant negative correlation between total IgE levels and parasite weight and fecundity, after controlling for any effects of host age and hookworm burden. This correlation was present both at initial treatment and after 2 years' reinfection. There was a similar negative correlation between the number of eosinophils and hookworm weight and fecundity at initial treatment. Correlations with levels of specific antibodies to N. americanus excretory-secretory products were weaker and not significant, although there was a trend towards negative correlations with anti-ES IgE. This is the first field evidence for an effective human immune response to N. americanus. Although the mechanism of this effect is not clear, we suggest that total IgE levels reflected the level of Th2 cell activation.

Altered angiogenesis underlying age-dependent changes in tumor growth.

Cancer incidence increases with age, but the growth and spread of tumors is often slow and prolonged in the elderly. Transplantable murine tumors grow and spread less readily in older mice and can be used as models to study the effect of host age. Neovascularization is crucial for the growth of solid tumors, and alterations in the host vascular response may underlie the changes in tumor growth occurring with age. We have used transplantable tumor cells and tumors, and tumor extracts, to better understand differences in the biology of tumor growth and vascularization as a function of host age. Englebreth-Holm-Swarm (EHS) carcinoma and B16-F10 melanoma cells were injected into C57BL mice of different ages. Tumor growth, histology, and cellular DNA synthesis were compared. Vascularization was determined using basic fibroblast growth factor and an in vivo angiogenesis assay. EHS tumor extracts were assayed for biologic activity in vitro using human endothelial cells and in vivo using mouse EHS-BAM carcinoma and human TSU-Pr1 prostate carcinoma cells. EHS tumors formed larger tumors in young than in old C57BL mice. Rapid tumor growth resumed upon transfer of tumor tissue from old animals into young animals. The rate of DNA synthesis of tumor tissue from old animals in organ culture was lower than in tissue from young animals. Histologically, tumors grown in old animals exhibited a threefold higher ratio of extracellular matrix to tumor cells than those grown in young animals. Tumors from adult animals exhibited numerous small blood vessels; those from old animals contained fewer, much larger vessels. Similar results were observed in young mice fed a reduced-calorie diet. Young animals elicited a greater and more rapid angiogenic response than old animals. Extracts of tumors grown in old animals failed to support endothelial cell differentiation in culture. Tumor cells injected together with such old extracts showed reduced tumor growth in nude mice. The rate of growth and morphology of the EHS tumor were altered with age, partly due to a reduced capacity to vascularize the tumors because of a lack of angiogenic factors or the presence of host inhibitors. Alterations in host factors detected in this tumor model may underlie a variety of age-dependent changes that could influence tumor growth and the repair and regeneration of normal tissue. Reducing the vascularization of tumors represents a potential target to reduce their growth and progression.

Effect of host age upon the degree of nigrostriatal dopaminergic system recovery following cografts of adrenal medulla and pretransected peripheral nerve

Accumulation of nerve growth factor (NGF) has been reported to occur at the distal stump of pretransected peripheral nerve. We performed adrenal medullary grafts or cografts of adrenal medulla and distal stump of pretransected peripheral nerve into the striatum of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated young or aging mice. We subsequently compared the survivability of chromaffin cells and the degree of host dopaminergic (DA) fiber recovery in relation to host age. In both young and aging hosts, adrenal medullary chromaffin cells cografted with pretransected peripheral nerve survived better than those in adrenal grafts alone. Host DA fiber recovery, however, showed less recovery and more restriction around the grafted site in aging compared with young hosts. We conclude that pretransected peripheral nerve can enhance the survivability of cografted chromaffin cells both in young and in aging hosts, but that DA fiber recovery is more limited in aging hosts compared to young hosts.

Effect of host age on rate of development of Dinarmus basalis (Rond.) (Hym., Pteromalidae)

AbstractDevelopment time for the parasitoid Dinarmus basalis (Rond.) was shorter on 4th instar larvae and pre‐pupae than on 2nd and 3rd instar larvae of the pulse beetle, Callosobruchus chinensis (L.). This was primarily because of qualitative or quantitative differences between 4th instar larvae or pre‐pupae and 2nd or 3rd instar larvae as hosts. Development time and progeny production was significantly different between the two sexes (P <0.001). Maximum number of males emerged from 2nd or 3rd instar larvae but females from 4th instar larvae or pre‐pupae. The sex‐ratio of D. basalis was strongly female‐biased. Female parasitoids were bigger when developing from 4th instar larvae.

The effect of child abuse and other family violence on the child protection worker and case management

Abstract There is some evidence to suggest that children may be re-abused or killed even after referral to a child protection agency. The traditional response to this has been to improve administrative procedures. This article presents an exploratory study which begins to test an alternative idea, that workers become a hostage to the violence in their clients. They respond to threat by denial and rationalisation. Study findings give tentative support to this theory. It was found that the workers tended to minimise the level of violence in the abusive families, and intervention appeared to be non-provocative. It would seem that this behaviour was largely at an unconscious level as it could not be explained by lack of dedication to work. It is likely that such a ‘hostage effect’ is enhanced by theoretical deficiencies in social work and the prevailing structures of the work environment.

Influence of Helicoverpa zea (Lepidoptera: Noctuidae) Age During the Last Instar on Rates of Parasitization by the Larval-Pupal Parasitoid, Archytas marmoratus (Diptera: Tachinidae)

Effects of host age during each of the 5 d of the last host instar were determined by exposing larvae of Helicoverpa (= Heliothis ) zea (Boddie) to newly larviposited maggots of the larval-pupal parasitoid Archytas marmoratus (Townsend). Based on determinations made in host pupae, lower percentages of older hosts were parasitized and lower percentages of maggots from older hosts developed to the second ins tar. Weights of maggots that parasitized older hosts were lower in 1-d-old host pupae. For older hosts, mean length of the larval stage of A. marmoratus after host pupation was longer; weights of young A. marmoratus larvae revealed that maggots developed very slowly until just before the host pupated. Surviving maggots developing from older hosts used the longer developmental times to overcome the weight differentials, and weights of A. marmoratus pupae were the same regardless of host age and parasitoid weight at the beginning of the host's pupal stage. These and other data indicate that complex behavior allows the A. marmoratus maggot to evade host defenses and grow to a size that enables the parasitoid to avoid encapsulation when it finally enters the host hemocele.

Effect of host age, parasitoid age and temperature on interspecific competition between Chelonus insularis Cresson, Cotesia marginiventris Cresson and Microplitis manilae Ashmead

The effects of host age, age of Cotesia marginiventris Cresson adults and temperature on interspecific competition between fall army worm (FAW), Spodoptera frugiperda (J. E. Smith), larval parasitoids C. marginiventris, Microplitis manilae Ashm. and the egg-larval parasitoid, Chelonus insularis Cresson were studied. All parasitization results for C. marginiventris and M. manilae were from FAW larvae parasitized as eggs by C. insularis. The maximum reproductive potential for C. marginiventris was achieved in hosts initially parasitized by C. insularis and were 36 to 48 hours old and at a temperature of 25°C. No host discrimination was found for C. marginiventris between larvae containing a developing C. insularis and non-parasitized larvae. The optimum parasitoid age for C. marginiventris during the host exposure period was 48 to 96 hr. Younger or older parasitoids were not able to compete as successfully against C. insularis. A sex ratio of approximately 65% males was present in C. marginiventris progeny produced from parents ranging in age from 24 to 108 hr old. Egg to adult development times at 25°C were 17 and 26 days for C. marginiventris and C. insularis, respectively. In multiple parasitized larvae, C. marginiventris appeared to physically attack and destroy the larvae of C. insularis. However, M. manilae larvae died after 6 days without appearing to have been physically attacked in hosts containing C. insularis.

Frequency distribution of Brugia malayi microfilariae in human populations

This study examines the effects of host age and sex on the frequency distribution of Brugia malayi infections in the human host. Microfilarial (mf) counts for a large data base on the epidemiology of brugian filariasis in Shertallai, Kerala, South India are analysed. Frequency distributions of microfilarial counts partitioned by age are successfully described by zero-truncated negative binomial distributions, fitted by maximum likelihood. This analysis provides estimates of the proportion of mf-positive individuals who are identified as negative due to sampling errors, allowing the construction of corrected mf age-prevalence curves, which indicate that the observed prevalence may under-estimate the true figures by between 18 and 47%. There is no evidence from these results for a decrease in the degree of over-dispersion of parasite frequency distributions with host age, such as might be produced by the acquired immunity to infection. This departure from the pattern in bancroftian filariasis (where there is evidence of such decreases in over-dispersion; Das et al. 1990) is discussed in terms of the long history of filariasis control (and consequently low infection prevalence) in Shertallai.

Effect of host age on microenvironmental heterogeneity and efficacy of combined modality therapy in solid tumors

The implications of microenvironmental heterogeneity in solid tumors for combined modality therapy were assessed by comparing the microenvironmental profiles and therapeutic responses of EMT6 tumors implanted into young and aging mice. The radiobiological hypoxic fraction of tumors in aging mice was shown to be 41% (95% CL, 28–60%), while that in young adult hosts is 19% (95% CL, 14–25%). These microenvironmental differences were also seen in perfusion studies and in studies of the intratumoral pH and pO 2 in young and aging mice. The therapeutic importance of microenvironmental factors can be examined in this system, as the tumor cells per se are identical, but the proportions of tumor cells in adverse microenvironments are different. Studies described here show that mitomycin C, an agent with selective toxicity to hypoxic cells, produced greater antineoplastic effects in tumors in aging mice when used alone or as an adjunct to radiation. Combined-modality regimens incorporating agents selectively toxic to hypoxic cells may be especially valuable in improving the results of radiotherapy in tumors in which the tumor-host interactions have resulted in unusually large hypoxic fractions.

Effects of host age on infection of ICR mice with Echinostoma caproni or E. trivolvis

There was no significant difference in the number of E. caproni recovered 21 days post-infection from 1-, 2-, 4-, 5-, 6-, 7-, 12-, or 21-month-old ICR mice infected with 25 metacercarial cysts. A range of 10.8–17.3 worms was recovered from mice in the age groups. In a similar experiment with E. trivolvis, there was no significant difference in worms recovered in young vs old mice. A range of 0–1.7 worms was recovered from mice in each age group. Contrary to a previous study on E. caproni in NMRI mice, our results indicate that host age does not affect establishment of E. caproni or E. trivolvis in the ICR mouse.

Frequency distribution of Wuchereria bancrofti microfilariae in human populations and its relationships with age and sex

This paper examines the effects of host age and sex on the frequency distribution of Wuchereria bancrofti infections in the human host. Microfilarial counts from a large data base on the epidemiology of bancroftian filariasis in Pondicherry, South India are analysed. Frequency distributions of microfilarial counts divided by age are successfully described by zero-truncated negative binomial distributions, fitted by maximum likelihood. Parameter estimates from the fits indicate a significant trend of decreasing overdispersion with age in the distributions above age 10; this pattern provides indirect evidence for the operation of density-dependent constraints on microfilarial intensity. The analysis also provides estimates of the proportion of mf-positive individuals who are identified as negative due to sampling errors (around 5% of the total negatives). This allows the construction of corrected mf age-prevalence curves, which indicate that the observed prevalence may underestimate the true figures by between 25% and 100%. The age distribution of mf-negative individuals in the population is discussed in terms of current hypotheses about the interaction between disease and infection.

Effects of host age, host density and parent age on reproduction of the filth fly parasite Urolepis rufipes (Hymenoptera: Pteromalidae)

Urolepis rufipes Ashmead, a pteromalid wasp, was recently discovered parasitizing house fly and stable fly pupae in eastern Nebraska dairies. Studies have been conducted on the biology of this parasite to evaluate its potential as a biological control agent of stable flies (Stomoxys calcitrans (L.] and house flies (Musca domestica L.). House fly pupae were suitable as hosts for U.rufipes at all ages; however, significantly higher parasitism occurred on host pupae aged 96-120 h. Parasite-induced mortality (host mortality without progeny production) was higher than for other pteromalid parasites of filth flies under similar conditions. Parasitism increased with parasite--host ratio at 20 degrees C; however, the opposite was noted at 30 degrees C for parasite--host ratios ranging from 5:50 to 50:50. Fly eclosion decreased as parasite--host ratio increased at 20 degrees C, and no host eclosion occurred at the highest parasite--host ratios (20:50 and 50:50) at 30 degrees C. Females produced an average of 18.6 female and 7.6 male progeny. 88% of the progeny were produced during the first 6 days post parental eclosion. The short life span, low progeny emergence rate and high per cent host eclosion, in comparison with other parasite species, suggests that the Nebraska strain of U.rufipes may not an effective biological control agent of house flies.

Effect of host age upon interleukin-2-mediated anti-tumor responses in a murine fibrosarcoma model.

The age-associated decline in immune function may be an important factor in both the pathogenesis of neoplastic diseases and the response to immunopharmacological therapies. With the increased efforts to develop immunotherapy with such agents as interferon and interleukin-2 (IL-2), the question of the effect of host age upon response is of practical importance. Phase I and phase II clinical trials of IL-2 have included primarily young patients, and toxicity and efficacy have not been reported with specific reference to host age. In this study, we examined young and old mice with regard to in vitro natural killer and lymphokine-activated killer (LAK) cell functions. We also assessed the effects of exogenously administered recombinant human IL-2 in tumor-bearing mice of various ages. We found that natural killer cell function was demonstrably lower in old mice but that LAK cell function was comparable (young versus old). Furthermore, IL-2 treatment was successful in increasing survival time in old mice, similar to results in young mice. Our observations allow the prediction that immune senescence per se does not preclude successful anti-neoplastic treatment with IL-2.

Population dynamics of Trichostrongylus colubriformis in sheep: The effect of host age on the establishment of infective larvae

Sheep, reared worm-free in pens and aged 12–36 weeks, were infected each weekday with 2000 infective T. colubriformis larvae (L3). Establishment was measured at various times during the course of infection and the rate of development of resistance to new infection was found to be faster in older than in younger hosts. In addition arrested development at the exsheathed L3 stage was found to be less marked in older hosts. Sheep which had experienced natural infection on pasture up to 20 weeks of age before exposure, in pens, to the same experimental infections as their worm-free counterparts showed similar immune responses. However, at 36 weeks of age, pasture-reared sheep had acquired a high level of resistance to infection with T. colubriformis.

Sex ratio manipulation by the parasitoid waspSpalangia cameroni in response to host age: A test of the host-size model

A sex ratio response to host resources as measured by external host dimensions has been demonstrated in many parasitoid wasps, includingSpalangia cameroni. The responses generally are in the direction predicted by sex ratio theory, specifically the host-size models. Here I show that femaleS. cameroni also respond to differences in resource availability not associated with changes in external host dimensions, and this response is in the direction predicted by host-size models. When given old and young hosts simultaneously, femaleS. cameroni oviposit a greater proportion of sons in old than in young host pupae, at least for 0-day old versus 3-day old hosts. Old hosts weigh less than young hosts but are not significantly different in external width. Thus it appears that the offspring sex ratio response may result from mothers detecting physical or chemical changes within the host which are associated with host age. No evidence is found that the manipulation in response to host age has been selected for via an effect of host age on wasp size; there was no significant effect of host age on either male of female wasp size. A second prediction of the host-size models is also supported by this study: when each female is presented with only a single host age, rather than two host ages simultaneously, host age has no effect on offspring sex ratio.

Age-Related Changes of the Susceptibility to Infection with Brugia pahangi in Male and Female BALB/c Mice

Effects of host age and sex on murine Brugia pahangi infection were examined. In female BALB/c mice, partial resistance to B. pahangi developed rapidly with age. In animals inoculated at 5-6 wk of age, resistance was about 2 times higher than in the youngest group (2-3 wk) and remained at a similar level through the study period (12 wk). Male BALB/c mice showed a similar tendency until 5-6 wk of age, but afterward their susceptibility increased with age. Significant difference in the susceptibility was detected between sexes after sexual maturation. After macrophage blockade by an injection of carbon particles into the mice, the age- and sex-related differences were completely abolished. This suggests that macrophages might have an important role(s) in the age- and sex-related changes of susceptibility to B. pahangi in BALB/c mice.

Effect of Host Age on Tumor-Associated Angiogenesis in Mice

Previous reports on the slower growth of tumors in senescent mice have suggested a decrease in tumor angiogenesis in these animals, but such an observation has not yet been documented quantitatively. In this study, we report the relative amount of tumor angiogenesis and tumor volume for two different types of tumor in 11 young (8-9-wk old) versus nine older (19-mo old) male C57BL/10 mice. B16 melanoma or SP1 methylcholanthrene-induced fibrosarcoma cells were injected into the ventral skin of mice. After 3 days, the mice were killed and the injection sites were examined for angiogenesis surrounding the tumor (centrally directed tumor angiogenesis), nerve-associated angiogenesis, and tumor volume. In the older mice, there was significantly less centrally directed tumor angiogenesis for both tumors tested, and nerve-associated angiogenesis was decreased for B16 melanoma. The mean tumor volume for the B16 implants was smaller for the older animals, but the mean SP1 tumor volumes were identical for both age groups. These findings support the hypothesis that tumor growth in older animals is associated with less formation of new blood vessels, and this may explain the slower tumor growth observed in aged animals with certain experimental tumors.

Encapsulation of eggs of the encyrtid wasp, Metaphycus swirskii, by the hemispherical scale, Saissetia coffeae: Effects of host age and rearing temperature

AbstractThe combined effects of host age and rearing temperature upon the encapsulation of eggs of Metaphycus swirskii Annecke & Mynhardt (Hymenoptera: Encyrtidae) by the hemispherical scale, Saissetia coffeae (Walker) (Homoptera: Coccidae), were determined. Encapsulation incidence at 16, 20, 24 and 28 °C increased with the age of the host, being 5.5–19.6% in 3rd instar nymphs, 45.4–74.2% in young female scales and 88.8–100% in preovipositing female scales. Within each host physiological age range, encapsulation frequency was not materially influenced by most of the temperatures. At 32 °C, regardless of host age, S. coffeae encapsulated 99.5 to 100% of parasitoid eggs. Complete immunity to successful parasitism by M. swirskii occurred at 20, 24, 28 and 32 °C in preovipositing female scales and at 32 °C in 3rd‐instar nymphs and young female scales of S. coffeae.RÉSUMÉEncapsulation des oeufs de Metaphycus swirskii par Saissetia coffeae: influence de l'âge de l'hôte et de la température.Cette étude a déterminé les effets combinés de l'âge de l'hôte et de la température sur l'encapsulation des oeufs de M. swirskii Annecke & Mynhardt (Hym. Encyrtidae) par S. coffeae Walker (Homopt. Coccidae). La fréquence d'encapsulation à 16, 20, 24 et 28 °C a augmenté avec l'âge de l'hôte, 5,5–19,6% dans les larves de 3ème stade, 45,4–74,2% chez les jeunes femelles et 88,8–100% chez les femelles avant la ponte. Dans chaque gamme d'âge physiologique de l'hôte, la fréquence d'encapsulation n'est pas influencée par la plupart des températures. A 32 °C, quel que soit l'âge de l'hôte, S. coffeae a encapsulé 99,5–100% des oeufs du parasitoïde. Une immunité complète au parasitisme par M. swirskii a été obtenue à 20, 24, 28 et 32 °C pour les femelles de cochenilles dans la période précédant la ponte, et à 32 °C pour les larves de 3ème stade et les jeunes femelles de S. coffeae.