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PubMed1979

Relation to body fat to age in the Czech population.

Density and percentage of fat in the body were investigated in 403 females and 356 males of Czech population using hydrostatic weighing. The group was divided into four age subgroups ranging from 17 through 22, 23 through 29, 30 through 39 and 40 through 49 years. Fat values were found to increase with age, growing in females and males between the ages of 17 to 49 years from 27.1 to 35.4 and from 16.3 to 26%, respectively. In both sexes, the highest difference in the percentage of fat was observed between the second and third decennium. Body weight was also seen to increase with age up to 40 years of age. On the other hand, from 40 through 49 years a decrease in weight was seen both in male and female means, with the body heights also less in older subjects. The values observed, particularly in females, exceed those reported as a rule in other populations. This is accounted for by nutritional factors such as the amount of calories and composition of food and possibly also by the effect of the genetically given somatotype.

Adipose Tissue↗

PubMed1979

Quantitative characterization of changes in cellularity and collagen fiber size in contracting palatal wounds.

Standard surgical wounds with either plain or undermined margins were created in the hard palates of 15 beagle pups by excising a strip of mucoperiosteum adjacent to molars. Healing was monitored, the pups were sacrificed at intervals from five to 31 days after surgery. Longitudinal data were collected for body weight and wound contraction. Examination of histologic sections of the wounds and adjacent tissues involved visual light microscopic assessments of fibroblast population density and computerized image analysis microscopy for quantification of population densities of three sizes of collagen fibers. Wounds with undermined margins showed less contraction than did those having plain margins. Findings on changes in the morphologic character of the maturing granulation tissues included quantitative documentation of (a) decreases in the population density of fibroblasts, (b) marked decreases in the number of thin (reticular) fibers, (c) marked increases in the number of medium sized fibers, and (d) slight increases in the number of coarse fibers.

Animals↗

PubMed1979

[Effect of cycloheximide, 2,4-dinitrophenol and papaverine on ribosomal RNA synthesis in Ehrlich ascitic carcinoma cells].

The influence of 2,4-dinitrophenol (DNP), papaverine and cycloheximide on RNA synthesis in Ehrlich ascites tumour cells has been investigated. All above mentioned agents inhibit selectively synthesis of high-molecular rRNA precursor, when the cell population density is 3.10(7)--5.10(7) per 1 ml of suspension. When the density of cells decreases as far as 1.10(6) cells per 1 ml. the rRNA synthesis loses the sensitivity to all these agents. The effects of both cycloheximide on the protein synthesis and DNP on ATP level do not depend on the cell population density in suspension. It is suggested that either with a decrease of cell population density the protein synthesis and ATP level cease playing the role of a rate-limiting factor in the rRNA synthesis, or the influence of agents studied is realized by means of their interaction with other cell system.

Adenosine Triphosphate↗

PubMed1976

Place and time aspects of the occurrence of Down's syndrome.

Prevalence rates at birth for Down's syndrome were compared for Massachusetts communities of different population densities. Overall, there was a small positive association between the rate of Down's syndrome and population density, entirely attributable to a strong association for the children of older mothers. An analysis for space and time clustering of births of 2469 children born in Massachusetts with Down's syndrome revealed no aggregation of cases, except for a slight seasonal peak in the summer.

Demography↗

PubMed2026

Weathering the storm: Most maternal and environmental drivers of individual reproductive success do not scale up to population recruitment in a large herbivore.

Population growth depends upon individual survival and reproduction, but do drivers of individual reproductive success scale up to population recruitment? Factors affecting individuals may have little effect on population dynamics if individuals within a population experience different conditions. When seasonal resource availability is unpredictable and breeding season long, average conditions over a breeding cycle may poorly reflect the environment experienced by many individuals. We compared the drivers of individual reproductive success and population recruitment in an asynchronously breeding large herbivore, the eastern grey kangaroo (Macropus giganteus). We analysed 18 years of individual-based data using multivariate hierarchical Bayesian models to first identify the causal mechanisms relating population density, environmental conditions and maternal traits to individual success. We then assessed whether the drivers of individual reproductive success scaled up to determine population recruitment. Most maternal and environmental covariates strongly influenced individual reproductive success, with distinct effects on juvenile survival before and after pouch exit. Maternal traits had a greater influence in the pouch, whereas environmental conditions became increasingly important once young exited the pouch. Most drivers of individual reproductive success did not affect population recruitment. Recruitment increased with population density and mean body condition of adult females. Weather harshness had a weak positive effect on recruitment, which appeared independent of female age structure, previous recruitment or forage. Most drivers of individual reproductive success did not scale up to population recruitment. Birth asynchrony could buffer population recruitment against environmental variation such that variables affecting individual reproduction have little impact at the population level. Large herbivores that reproduce asynchronously may therefore be more resilient to environmental variability than synchronous breeders.

Bayesian modelling↗

PubMed1978

Nationwide urban noise survey.

Most current knowledge about community response to noise exposure is derived from studies of high-level transportation sources. A nationwide urban noise survey was undertaken to study effects associated with more moderate but far more common sorts of noise exposure. Over 2000 respondents at 24 sites in seven cities of varying noise exposure and population density were interviewed by telephone and in person about their reactions to everyday noises. A brief but comprehensive structured questionnaire was based on direct questioning about annoyance and related effects. Among the major findings of the survey were widespread annoyance and speech interference from exposure to urban noise and strong relationships between the extent of annoyance and exposure level, speech interference, and population density.

Affect↗

PubMed1979

Regulation of RNA synthesis in Tetrahymena pyriformis: secretion of regulatory factors.

The rate of ribosomal RNA synthesis varies greatly with the population density in both exponentially and synchronously growing populations of Tetrahymena pyriformis. Shortly after inoculation of the population - at relatively low cell densities - a gene-dose effect dominates the picture, and a doubling in the gene number is immediately followed by a doubling in the rate of RNA synthesis. However, also other mechanisms are controlling the rate of RNA synthesis. Generally one finds high rates of RNA synthesis in the lag phase of newly inoculated cells, decreasing rate of RNA synthesis during most of the exponential growth phase and very low rate of synthesis in stationary phase cells. We now have results which show that the repression of RNA synthesis in densely populated cultures is caused by a dialysable factor, which is secreted by the cells. If cells are inoculated on a medium which contains this factor the high initial rate of RNA synthesis normally observed is prevented, but the cells multiply and grow with normal generation time until normal stationary-phase population densities are reached.

Animals↗

PubMed1976

On the stability of the stationary state of a population growth equation with time-lag.

If in the Verhulst equation for population growth the reproduction factor depends on the history then the equilibrium may become unstable and oscillations and even non-constant periodic solutions may occur. It is shown that the equilibrium is unstable if the reproduction factor at time t is, up to a sufficiently large factor, an arbitrary average of the population densities in the interval (t-2, t-1).

Mathematics↗

PubMed2026

Mutations in filamentous bacteriophages spark eco-evolutionary feedbacks in Pseudomonas aeruginosa.

Microbial populations strongly shape their environment, which can re-route adaptation toward organism-generated fitness optima. However, the conditions that promote these eco-evolutionary feedbacks are unclear. Here, we used experimental evolution to test whether high population density, by strengthening niche construction, drives eco-evolutionary feedbacks in the bacterial pathogen Pseudomonas aeruginosa (Pa) MPAO1. We tested for adaptation to organism-modified environments by measuring the relative performance of ancestral and endpoint populations in filtrate generated by each evolutionary line sampled across generations. Contrary to expectations, we found that endpoint populations had higher performance than the ancestral strain in filtrate across nearly all evolutionary lines regardless of population density. This was caused by the emergence of hyperactive filamentous bacterio(phage) mutants during experimental passaging that inhibited the ancestral strain but not endpoint populations in modified media. Hyperactive phages emerged from one of two avirulent prophages in MPAO1's genome (Pf4 or Pf6). Hyperactive phages drove the evolution of phage resistance in bacterial populations via mutations in the type IV pilus (TIVP), the phage's binding receptor. In a follow-up experiment, we showed that these TIVP mutations pleiotropically reduced motility and conferred resistance to a TIVP-targeting virulent phage, both of which are important traits for Pa infection and treatment. Overall, this work suggests that filamentous phage evolution can drive eco-evolutionary feedbacks in bacterial populations, causing phenotypic and genetic changes that would not be anticipated from adaptation to the extrinsic environment alone.

Pseudomonas aeruginosa↗

PubMed1976

[World health-related indicators].

Many of the statistics given in this report are estimates based on tentative data and on that extent are not reliable in a strict sense. But the picture they present of gross differences in demographic and social characteristics, in vital statistics, and in resources of medical manpower and hospital beds between major areas of the world is real. More than half of the people of the world live in South Asia and East Asia; population density is highest in Western Europe; and highest rates of population growth are in Middle America and Tropical South America. In Europe less than one-third of the population are aged under 20 years, whereas more than half the population are aged under 20 im Middle and Tropical South America and the Carribbean, in Africa and in South Asia. Urbanization is high in Temperate South America, Northern America, Northern and Western Europe, and Oceania. The daily dietary energy supply per person is 50% higher in Northern America, Europe, USSR, and Ocenia than in Africa (excluding Southern Africa, South and East Asia. The Gross National Product in Northern America is 10 times higher than in Tropical South America and 30 to 40 times higher than in Western Middle and Eastern Africa and in Middle South and South East Asia. Crude birth rates are close to three times higher in Africa, Middle America and South Asia than in Europe, North America and USSR. Differences in crude death rates are less--rates in Western, Middle and Eastern Africa are double these of America Europe, USSR and Oceania. The Expectation of Life is over 70 years for Northern America, Europe, USSR and Oceania. It is under 50 years for Western, Middle and Eastern Africa. In all areas the expectation of life at birth has increased--by up to 10 years--in the past quarter century. Infant mortality is less than 20 per 1 000 in Northern and Western Europe and Northern America. It is over 100 in Africa and South Asia. Number of physicians range from 25 per 10 000 population in USSR to less than 1 per 10 000 in Western, Middle and Eastern Africa. There are over 100 hospital beds per 10 000 population in USSR and in Northern and Western Europe, less than 10 per 10 000 in Western Africa, Middle South Asia and South East Asia.

Age Factors↗

PubMed1979

Ultrastructure and quantitative synaptology of the sacral parasympathetic nucleus.

This study examines the anatomical substrate for the spinal micturition reflex. Light microscopy of pyridine silver-stained sections revealed that the sacral parasympathetic nucleus (SPN) exists as a broken column or chain of cell clusters located along the intermediolateral portion of the dorsal horn in sacral segments S2-S4. Quantitative analysis of neuropil components in electron micrographs provides data for each type of bouton identified in this nucleus. On the somata of these neurons, boutons containing clear spherical vesicles (S type) comprise 70% of the bouton population. Terminals containing three or more dense core vesicles (GS boutons) account for 26% and boutons containing flattened vesicles (F boutons) comprise 4% of the population. F boutons are more common on large dendrites where they comprise 10% of the total bouton population. The actual population density of each bouton type is most evident when the number of boutons is expressed as boutons per 100 micron of membrane length (btn/100 micron). S type boutons are the most frequently encountered type. The population density of S boutons is the same on soma and dendrites at 6.66 btn/100 micron. F boutons are more numerous on large (greater than 2 micron) dendrites (1.28 btn/100 micron) than on small dendrites (0.63 btn/100 micron) or on somata (0.36 btn/100 micron). GS boutons occur more frequently on small dendrites (3.66 btn/100 micron) than on somata (2.29 btn/100 micron), large dendrites (2.88 btn/100 micron) or medium dendrites (2.27 btn/100 micron). These data suggest that the dense core vesicle-containing boutons are applied primarily to small (less than 1 micron) dendrites and that F boutons are associated mostly with large or proximal dendrites. These results provide a quantitative profile of the synaptic input to the sacral autonomic (parasympathetic) neurons which innervate the urinary bladder and demonstrate specific population differences on various postsynaptic structures in this nucleus.

Animals↗

PubMed1976

Dynamics of submerged growth of Mycobacterium tuberculosis under aerobic and microaerophilic conditions.

When Mycobacterium tuberculosis is grown in detergent-containing medium under continous agitation, multiplication is known to follow a logarithmic mode. When the cultures are not continuously shaken, but only agitated a few times a week to resuspend the bacilli and permit turbidity to be measured, the net increase suggests an arithmetic growth mode. It is shown here that a single pulse of aeration of an unshaken submerged culture of M. tuberculosis causes an almost instantaneous acceleration of growth, followed rapidly by a cessation of growth. Whether or not the bacilli will subsequently resume growth depends on the bacillary population density of the cuture at the time of application of the pulse of aeration. If the bacilli are permitted to grow in the depths of Dubos Tween Albumin broth without any agitation, they exhibit net arithmetic growth and attain a maximal population density greater than is seen in cultures exposed to occasional pulses of aeration. By the use of isotopically labeled cells, it has been shown that replication occurs ar a logarithmic rate amoung the small proportion of the bacilli that remain suspended in nonagitated cultures. This replication is balanced by settling of cells, resulting in a net appearance of arithmetic multiplication. The cells that have settled into the sediment replicate at a very slow rate, if at all, but do retain their viability for 4 weeks or longer. This suggests a possible analogy to quiescent tubercle bacilli in vivo.

Aerobiosis↗

PubMed1978

Organelle pathology in primary and secondary haemochromatosis with special reference to lysosomal changes.

The organelle pathology of liver biopsy specimens from patients with either primary or secondary haemochromatosis was investigated by analytical subcellular fractionation in combination with enzymic microanalysis. The most striking changes were found in the lysosomes. Increased total activities but decreased latent activities of enzymes selectively localized to the high density population of lysosomes was demonstrated in the iron overloaded biopsies. Depletion of the iron, where possible, by venesection was accompanied by a return to normal of these changes. The other subcellular organelles, plasma membrane, endoplasmic reticulum, biliary canaliculi, mitochondria, peroxisomes and the low density population of lysosomes appear to be relatively unaffected. The minor changes demonstrated are similar to those seen in other forms of chronic liver disease. It is suggested that iron mediated lysosomal disruption is implicated in the pathogenesis of the tissue damage in haemochromatosis.

Biopsy↗

PubMed1977

[The decline of fertility in Western Europe. II. Which fertility rate would be desirable in France? (author's transl)].

A way to try and assess the significance of such or such level in long term fertility is to work out population projections based on a variety of assumptions and to compare their different implications. The age pyramids of France until 2100 that derive from four contrasted evolutions of fertility are studied in the present article: completed fertility in birth cohorts ranging from 1.4 to 2.6 children per woman. While some demographic parameters are not much sensitive to the assumption made for the fertility level (e.g. percent of economically active people in total population), others are closely related to fertility (such as total number of inhabitants, percent of younger people or of older people in total population, annual rate of entry into economically active population). In France, where population density is much lower than in most neighbouring countries, a fertility level that would lay at -- or a little higher than -- replacement (i.e. 2.1 children per woman) can be considered as a desirable target.

Adolescent↗

PubMed1977

Changes in phosphatidylinositol metabolism correlated to growth state of normal and Rous sarcoma virus-transformed Japanese quail cells.

Second-passage Japanese quail embryo cell cultures, normal or quantitatively transformed by Rous sarcoma virus, were investigated for phospholipid composition and metabolism. Cells cultivated at low and high population density as well as in the presence or absence of serum, have been compared by chemical analysis and in pulse-chase experiments. No differences in the lipid compositions between the normal and the tumor cells or between cells under different culture conditions were detected. In no case was the metabolism of phosphatidylserine or sphingomyelin affected by culture conditions. The metabolism of the choline and ethanolamine glycerophospholipids, however, differed according to culture conditions, whether cells were normal or transformed. Significantly, in normal cells, the breakdown of [32P]phosphate-labeled phosphatidylinositol was slowed when cell growth was restricted, i.e., at high population density or in medium without serum. This effect was not observed in tumor cells under such culture conditions, and cells were not growth inhibited. Hence, release of [32P]phosphate from phosphatidylinositol is the only parameter in the metabolism of phospholipids observed to correlate with growth.

Animals↗

PubMed1975

Studies on the rumen flagellate Neocallimastix frontalis.

The vast increase in the population density of the rumen flagellate Neocallimastix frontalis shortly after the host animal has commenced eating is caused by stimulation of a reproductive body on a vegetative phase of the organism to differentiate and liberate the flagellates. The stimulant is a component of the host's diet. The vegetative stage of N. frontalis bears a strong morphological resemblance to that of certain species of aquatic phycomycete fungi, and consists of a reproductive body borne on a single, much branched rhizoid. The flagellates liberated in vivo within 15 to 45 min of feeding lose their motility within I h and develop into the vegetative phase, thus producing a rapid decrease in population density of the flagellates. Conditions for maximum flagellate production are similar to those occurring in the rumen: pH 6-5, 39 degrees C, absence of O2, presence of CO2. Differentiation of the reproductive body is inhibited by compounds affecting membrane structure and function, but not by inhibitors of protein synthesis. The organism was cultured in vitro in an undefined medium in the absence of bacteria or other flagellates.

Animals↗

PubMed1977

Intramembranous particles and chlorophyll complexes in chloroplasts.

The size and population density of large and small particles from freeze-fractured chloroplasts of three wild-type algae and of normal spinach were determined. Computer analyses of low-temperature absorption spectra of chloroplast preparations from these species were performed, and a possible correlation between the occurrence of seven chlorophyll complexes and the aforementioned properties of the intramembranous particles was studies. It was found that only single-sized particles occur in a species containing neither chlorophyll b nor chlorophyll a-685 complexes. The three remaining species carry particles of two sizes, termed large and small particles. However, from quantitative considerations it is concluded that the chlorophyll content of none of the various pigment complexes is related to the size and the population density of the studied particles. If such a relationship exists, it seems likely to be due to the carrier moiety of the chorophyll b-chlorophyll a-685 complex.

Chlorophyll↗

PubMed1977

Some characteristics of tribal peoples.

The study of health and disease in distinctive human groups is an important source of knowledge, and ultimately of understanding. Tribal societies are at the polar extreme from modernized communities. However, with the breakdown of isolation this distinctiveness is being eroded, slowly for genes, more rapidly for ideas and behaviour, and fastest for infective agents of disease. Though comtemporary tribal men cannot be equated with prehistoric men, they resemble them more than do modernized men. Therefore the study of tribal peoples not only widens the range of circumstances in which human adaptability is observed, it throws some light on the evolution of human diseases. This is particularly the case with regard to the study of 'diseases of modern life'. Tribal life is characterized by comparative physical and cultural isolation, simplicity, small group size, low population density and closeness to nature, both physically and conceptually. In spite of rapid change, which itself needs study, there are still situations where what is studied has shown little recent change. In a world where dissatisfaction with life and medicine grows in spite of unparalleled technical success, we should look again at tribal men. There is much to learn from each other's successes and failures.

Animals↗