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1.
Various workers, including T. D. Stewart, claim that the aboriginal Americas were relatively disease-free because of the Bering Strait cold-screen, eliminating many pathogens, and the paucity of zoonotic infections because of few domestic animals. Evidence of varying validity suggests that precontact Americans had their own strains of treponemic infections, bacillary and amoebic dysenteries, influenza and viral pneumonia and other respiratory diseases, salmonellosis and perhaps other food poisoning, various arthritides, some endoparasites such as the ascarids, and several geographically circumscribed diseases such as the rickettsial verruca (Carrion's disease) and New World leishmaniasis and trypanosomiasis. Questionably aboriginal are tuberculosis and typhus. Accordingly, virtually all the “crowd-type” ecopathogenic diseases such as smallpox, yellow fever, typhoid, malaria, measles, pertussis, polio, etc., appear to have been absent from the New World, and were only brought in by White conquerors and their Black slaves. My hypothesis is that native American medical care systems—especially in the more culturally advanced areas—were sufficiently sophisticated to deal with native disease entities with reasonable competence. But native medical systems could not cope with the “crowd-type” disease imports that struck Indian and Eskimos as “virgin field” populations. Reanalysis of native population losses through a genocidal combination of disease, war, slavery and attendant cultural disruption by Dobyns, Cook and others strongly suggest that traditional estimates underplayed the death toll by a factor of the general order of ten. This would make for an immediately pre-contact Indian population of some 90–111 million instead of the traditional 8–11 million. Evidence is growing that Indians may have been no more susceptible to new pathogens than are other “virgin soil” populations, and thus their immune systems need not be considered less effective than those in other people. Present-day high mortality rates in Indians of both continents from infectious disease imports may be more socioeconomic than anything else.  相似文献   

2.
A disease with symptoms similar to palm lethal yellowing was noticed in the early 2013 in Khuzestan Province (Iran) in date palm (Phoenix dactylifera). Infected trees displaying symptoms of streak yellows and varied in the incidence and severity of yellowing. A study was initiated to determine whether phytoplasma was the causal agent. Polymerase chain reaction–restriction fragment length polymorphism (PCR‐RFLP) methods using universal phytoplasma primers pairs R16mF1/mR1 and M1/M2 were employed to detect putative phytoplasma(s) associated with date palm trees. Nested PCR using universal primers revealed that 40 out of 53 trees were positive for phytoplasma while asymptomatic date palms from another location (controls) tested negative. RFLP analyses and DNA sequencing of 16S rDNA indicated that the presence of two different phytoplasmas most closely related to clover proliferation (CP) phytoplasma (group 16SrVI) and ash yellows (AY) phytoplasma (group 16SrVII). Sequence analysis confirmed that palm streak yellows phytoplasmas in each group were uniform and to be phylogenetically closest to “CandidatusP. fraxini” (MF374755) and “Ca. P. trifolii” isolate Rus‐CP361Fc1 (KX773529). Result of RFLP analysis of secA gene of positive samples using TruI and TaqI endonuclease is in agreement with rDNA analysis. On this basis, both strains were classified as members of subgroups 16SrVI‐A and 16SrVII‐A. This is the first report of a phytoplasma related to CP and AY phytoplasma causing date palm yellows disease symptoms.  相似文献   

3.
A large‐scale survey was conducted on pistachio plants exhibiting foliar symptoms including scorch, little leaf, yellows and reddish in pistachio growing areas in the Qom, Yazd and Qazvin provinces of Iran. Total DNA was extracted from symptomatic and symptomless pistachio and used in nested PCR assays with phytoplasma universal primers. Nested PCR products were obtained for symptomatic plant samples while the symptomless plants yielded no PCR products. Virtual restriction fragment length polymorphism, phylogenetic and DNA homology analyses of partial 16S ribosomal sequences of phytoplasma strains associated with symptomatic plants revealed the presence of phytoplasmas referable to two ribosomal groups; in particular, “Candidatus Phytoplasma solani” and “Ca. P. phoenicium” were identified. The presence of these phytoplasmas in pistachio is of great phytosanitary significance due to its commercial interest.  相似文献   

4.
The results of a detailed morphological analysis of the skull attributed to Mozart are presented which refute a recent claim that the skull as well as several of Mozart's portraits show indications of uncomplicated trigonocephaly. These indications according to the present analysis are within the limits of normal variation and derive from retention of part of the long arm of the anterior fontanelle.  相似文献   

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Previously, we demonstrated the requirement for a minimum coherence time of an applied, small amplitude (10 μT) ELF magnetic field if the field were to produce an enhancement of ornithine decarboxylase activity in L929 fibroblasts. Further investigation has revealed a remarkably similar coherence time phenomenon for enhancement of ornithine decarboxylase activity by amplitude-modulated 915 MHz microwaves of large amplitude (SAR 2.5 W/kg). Microwave fields modulated at 55, 60, or 65 Hz approximately doubled ornithine decarboxylase activity after 8 h. Switching modulation frequencies from 55 to 65 Hz at coherence times of 1.0 s or less abolished enhancement, while times of 10 s or longer provided full enhancement. Our results show that the microwave coherence effects are remarkably similar to those observed with ELF fields. © 1993 Wiley-Liss. Inc.  相似文献   

8.
A polyphasic PCR-DGGE approach was used to describe the microbial population occurring in natural whey cultures (NWCs) for water-buffalo Mozzarella cheese production. Total microbial community was assessed without cultivation by analyzing DNA directly extracted from the original samples of NWC. In addition, DNA extracted from bulks of cells formed by harvesting colonies from the serial dilution agar plates of a variety of culture media was used to profile the "cultivable" community. The 16S rDNA V3 region was amplified using DNA from NWC as well as DNA from bulks as templates and the amplicons were separated by DGGE. The microbial entities occurring in NWCs were identified by partial 16S rDNA sequencing of DGGE bands: four lactic acid bacteria (LAB) closest relative of Streptococcus thermophilus, Lactococcus lactis, Lactobacillus delbrueckii and Lactobacillus crispatus were revealed by the analysis of DNA directly extracted from NWC while two other LAB, Lactobacillus fermentum and Enterococcus faecalis, were identified by analyzing DNA from the cultivable community. The developed PCR-DGGE analysis of the "cultivable" community showed good potential in evaluating microbial diversity of a dairy environment: it usefully highlighted the bias introduced by selective amplification when compared to the analysis of the total community from NWC and allowed suitability of media and growth conditions to be evaluated. Moreover, it could be used to complete the culture independent study of microbial diversity to give information on concentration ratios among species occurring in a particular environment and can be proposed for rapid identification of dominant microorganisms in alternative to traditional tools.  相似文献   

9.
The reproductive patterns (birth seasonality, litter size, litters per year) of two sympatric species of galago (Galago zanzibaricus and G. garnettii) were studied in a coastal forest in Kenya for a two-year period. Trap-retrap and radio tracking methods were employed. G. zanzibaricus has one infant twice per year; G. garnettii has one infant once per year. Both species are seasonal breeders. These East African galagos are intermediate in reproductive patterns when compared with galagos from South African woodland (G. senegalensis moholi and G. crassicaudatus umbrosis) and West African rainforest (G. alleni and G. demidovii). Climatic patterns (total annual rainfall, seasonal variability of rainfall, variability in total annual rainfall, and annual temperature variability) are also compared for the three regions. Climatically, East Africa is intermediate between West and South Africa in total annual rainfall and in seasonality of rainfall, but not in year-to-year variability in rainfall. East Africa shows the highest variability in annual rainfall. South Africa has the coldest dry seasons and highest variability in temperatures. The results of this study suggest that “r-selection” and “K-selection” do not provide adequate explanations of galago reproductive patterns.  相似文献   

10.
Biophysical methods allow quantitative deductions as to the “bending effectivity” of various stele types and the contribution of different tissues to the stability of upright plant axes. Considering the first occurrence of the different stele types in geological history, a strong tendency towards a higher “bending effectivity” can be observed. It can be shown that Rhynia gwynne-vaughanii, Aglaophyton major (Rhynia major) and Asteroxylon mackiei as well as probably the vast majority of early “vascular” land plants were turgor systems, i.e. that the parenchyma (when fully turgescent) is by far the most important contributory factor towards the bending stability of the upright axes.  相似文献   

11.
We present phylogenetic analyses (parsimony, maximum likelihood and Bayesian inference) for 69 lineages of anthoathecate hydroids based on 18 morphological characters (12 proposed for the first time) plus mitochondrial (16S and COI) and nuclear (18S and 28S) molecular markers. This study aims to test the monophyly of the present concept of the family Bougainvilliidae, assessing its phylogenetic position within Hydroidolina. Our working hypothesis is used as a context for inferring the evolution of certain morphological characters, focusing on the exoskeleton. Our results shed light on some phylogenetic uncertainties within Hydroidolina, delimiting eight well‐supported linages, viz. Hydroidolina, Siphonophorae, Leptothecata, Aplanulata, Filifera II, Filifera III, Capitata and Pseudothecata taxon novum, the latter supported by four morphological synapomorphies. The monophyly of several families was not supported, viz. Bougainvilliidae, Cordylophoridae, Oceaniidae, Rathkeidae and Pandeidae. Some of the genera typically considered in Bougainvilliidae, including Bougainvillia, fell into the clade Pseudothecata, which is consistently reconstructed as the sister group of Leptothecata. We formally suggest that Dicoryne be removed from Bougainvilliidae and placed in the resurrected family Dicorynidae. The exoskeleton was a key feature in the diversification of Hydroidolina, especially with the transition from the bare hydranth to one completely enveloped within the exoskeleton. In this context, bougainvilliids exhibit several intermediate states in the development of the exosarc. Although the concatenated analysis unravels some interesting hypotheses, taxon sampling is still deficient and therefore more data are necessary for achieving a more complete understanding of the evolution and ecology of bougainvilliids and their allies.  相似文献   

12.
Preliminary observations were made between October 1982 and May 1983 on the nature, taxonomic composition, spatial distribution, buoyancy behaviour and nutrient requirements of some unusual planktonic algal “jellies” in Oguta Lake in Southeastern Nigeria. These “jellies” are macroscopic, blue-green algal masses whose excessive mucilage of high consistency acts as substrata for other epiphytic components viz. diatoms and green algae. They are more abundant in the lentic areas of the lake, undergo diurnal vertical movements and have their growth enhanced by spikes of nitrogen and phosphorus salts into their aquatic medium. The effects of these “jellies” on the ecology and general water use of the lake are discussed. Speculations on the reasons for their occurrence are given and possible control measures outlined.  相似文献   

13.
SYNOPSIS. A defined medium for an insect trypanosomatid, “Leptomonas pessoai” (probably a member of the genus Herpetomonas) isolated from the reduviid Zelus leucogrammus, allows growth up to 37 C. No marked differences were evident for growth at 37 C. The requirements for amino acids, vitamins, purine, and hemin, and pH range were like those established for Crithidia fasciculata. Again like C. fasciculata, it remains alive at 4 C for at least 3 months in a çlycerolated defined medium.  相似文献   

14.
BARTLETT, SUSAN J., MYLES S. FAITH, KEVIN R. FONTAINE, LAWRENCE J. CHESKIN, AND DAVID B. ALLISON. Is the prevalence of successful weight loss and maintenance higher in the general community than the research clinic? Obes Res. Objective: The prevalence of successful weight loss remains unclear. In 1982, Schachter concluded that in the general population, the rate of “self-cured” obesity approached 63%–much higher than the rate from clinical trials. Several subsequent studies have addressed this issue. Research Methods and Procedures: Our initial goal was to meta-analyze these studies to evaluate the validity of the original hypotheses and the extent to which additional investigations supported the findings. We began by restating Schachter's hypotheses in precise, testable terms. Results: A systematic review of these studies found many methodological limitations and much heterogeneity among the samples studied, hypotheses addressed, and operational definitions. Some of these limitations appear to stem from the lack of clear, precise statements of the exact hypotheses tested. Differences among studies are delineated, and we outline why meta-analytic pooling of these data appears inappropriate. Conclusions: The current data are inadequate to draw any definite conclusions regarding the cure rate of obesity. Criteria for the adequate study of success rates with “self-cure” in the general population are proposed.  相似文献   

15.
Proboscis monkey (Nasalis larvatus) social organization was studied at the Tanjung Puting National Park in Kalimantan Tengah, Indonesia, for 12 months. Data were collected on one-male groups and all-male groups by using scan sampling and event sampling while following groups. Evening census surveys were also conducted. Proboscis monkeys were found to follow the typical Asian colobine pattern of one-male social groups, with extra-group males forming all-male groups. These groups appear stable, with few changes in membership. One-male groups appear to be “female bonded”; adult females direct affiliative behaviors towards their offspring and other adult females, not towards the male. Nearest-neighbor data indicate some peripheralization of juvenile animals.  相似文献   

16.
Honeybee colonies exposed under a 765-kV, 60-Hz transmission line at 7 kV/m show the following sequence of effects: 1) increased motor activity with transient increase in hive temperature; 2) abnormal propolization; 3) impaired hive weight gain; 4) queen loss and abnormal production of queen cells; 5) decreased sealed brood; and 6) poor winter survival. When colonies were exposed at 5 different E fields (7, 5.5, 4.1, 1.8, and 0.65–0.85 kV/m) at incremental distances from the line, different thresholds for biologic effects were obtained. Hive net weights showed significant dose-related lags at the following exposures: 7 kV/m, one week; 5.5 kV/m, 2 weeks; and 4.1 kV/m, 11 weeks. The two lowest exposure groups had normal weight after 25 weeks. Abnormal propolization of hive entrances did not occur below 4.1 kV/m. Queen loss occurred in 6 of 7 colonies at 7 kV/m and 1 of 7 at 5.5 kV/m, but not below. Foraging rates were significantly lower only at 7 and 5.5 kV/m. Hive weight impairment and abnormal propolization occur at lower E-field intensity than other effects and limit the “biological effects corridor” of the transmission line to approximately 23 m beyond a ground line projection of each outer phase wire. Intrahive E fields of 15–100 kV/m were measured with a displacement current sensor. Step-potential-induced currents up to 0.5 μA were measured in an electrically equivalent bee model placed on the honeycomb in a hive exposed at 7 kV/m. At 1.8 kV/m body currents were a few nanoamperes, or two orders of magnitude lower, and these colonies showed no effects. E-field versus electric shock mechanisms are discussed.  相似文献   

17.
Insect societies have traditionally been considered as harmonious, peaceful superorganisms in which all individuals altruistically cooperate to increase the reproductive success of the society as a whole. Over the last decade, this view has changed dramatically. Individual group members can pursue their egoistic interests at a cost to the whole society. The integrity of the society is sustained usually by the suppression of egoistic reproduction by workers, either through direct interference by the queen, the establishment of dominance hierarchies, or mutual policing and punishment. A detailed analysis of the processes in insect societies helps to understand which processes maintain the cooperation among egoistic individuals.  相似文献   

18.
Phototherapy Miniaturization of electronics, small enough to be integrated into textiles, offer new opportunities for medical technology and phototherapy. Measuring physiological body functions and the use of semiconductors like light emitting diodes (LEDs) actively influencing physiology are examples for these kinds of innovations.  相似文献   

19.
“Bryndza” is a traditional Slovak dairy product (type of soft cheese) made from sheep cheese which was ripened for 14 days. Because its manufacture, transporting and/or storing represent conditions which facilitate contamination, the effect of enterocin CCM4231 in “bryndza” was investigated with the aim to reduce the contaminant agents. “Bryndza” was divided into equal portions (50 g). The experimental sample (ES) as well as the control sample one (C1) were inoculated with Listeria innocua Li1 strain. The other control samples C2 and C3 were without Li1 strain. C3 control was selected as a reference control. ES and C2 portions were treated with purified enterocin CCM4231 in a concentration of 6400 AU/ml. Before the experimental inoculation, “bryndza” was checked for the presence of contaminant agents. The experiment lasted 1 week and the samples were stored in the refrigerator at 4 °C. Sampling was performed on day 1, on day 4 and on day 7. The control samples C2 and C3 were checked only on day 1 and then after 1 week. The following contaminant agents were detected in “bryndza” before its experimental inoculation with L. innocua Li1 strain: Escherichia coli in the amount 103 cfu/ml/g, Staphylococcus aureus (102 cfu/ml/g) and enterococci (104 cfu/ml/g). In the control sample C2, the number of E. coli was reduced to 102 cfu/ml/g. Enterococci and staphylococci were totally eliminated there. Concerning C3 control, natural decrease of bacteria was found and/or their unchanged counts. The value of pH (5) was stable during the whole experiment. In the experimental sample inoculated with Li1 strain, its counts were decreased immediately after enterocin CCM4231 addition approximately by one order of magnitude. This inhibitory effect was also detectable on day 4 by the difference of one order of magnitude between ES and C1. On day 7, 103 cfu/ml/g of Li1 strain were detected in both samples (ES, C1). The difference by one order of magnitude indicated, an inhibitory effect of enterocin CCM4231 in “bryndza”. However, bacteriocin activity was not determined by laboratory analyses.  相似文献   

20.
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