Showing papers on "Population published in 1969"

Assessment of Older People: Self-Maintaining and Instrumental Activities of Daily Living

Abstract: THE use of formal devices for assessing function is becoming standard in agencies serving the elderly. In the Gerontological Society's recent contract study on functional assessment (Howell, 1968), a large assortment of rating scales, checklists, and other techniques in use in applied settings was easily assembled. The present state of the trade seems to be one in which each investigator or practitioner feels an inner compusion to make his own scale and to cry that other existent scales cannot possibly fit his own setting. The authors join this company in presenting two scales first standardized on their own population (Lawton, 1969). They take some comfort, however, in the fact that one scale, the Physical Self-Maintenance Scale (PSMS), is largely a scale developed and used by other investigators (Lowenthal, 1964), which was adapted for use in our own institution. The second of the scales, the Instrumental Activities of Daily Living Scale (IADL), taps a level of functioning heretofore inadequately represented in attempts to assess everyday functional competence. Both of the scales have been tested further for their usefulness in a variety of types of institutions and other facilities serving community-resident older people. Before describing in detail the behavior measured by these two scales, we shall briefly describe the schema of competence into which these behaviors fit (Lawton, 1969). Human behavior is viewed as varying in the degree of complexity required for functioning in a variety of tasks. The lowest level is called life maintenance, followed by the successively more complex levels of func-

Convention: A Philosophical Study

Abstract: Acknowledgements. Foreword by W.V. Quine. Introduction. I. Coordination and Convention. Sample Coordination Problems. Analysis of Coordination Problems. Solving Coordination Problems. Convention. Sample Conventions. II. Convention Refined. Common Knowledge. Knowledge of Conventions. Alternatives to Convention. Degrees of Convention. Consequences of Conventions. III. Convention Contrasted. Agreement. Social Contracts. Norms. Rules. Conformative Behavior. Imitation. Meaning of Signals. IV. Convention and Communication. Sample Signals. Analysis of Signaling. Verbal Signaling. Conventional Meaning of Signals. V. Conventions of Language. Possible Languages. Grammars. Semantics in a Possible Language. Conventions of Truthfulness. Semantics in a Population. Conclusion. Index.

Principles of Systematic Zoology

Abstract: The science of taxonomy the species category species taxa intrapopulational variational variation and the comparison of population samples specification and taxonomic decisions the theory of classification taxonomic characters phenetics cladistics evolutionary classification numerical methods taxonomic collections and identification taxonomic collections and identification taxonomic publications principles of zoological nomenclature

Autoradiographic and histological studies of postnatal neurogenesis. IV. Cell proliferation and migration in the anterior forebrain, with special reference to persisting neurogenesis in the olfactory bulb

Abstract: The properties and fate of the cells of the subependymal layer of the anterior lateral ventricle and its rostral extension into the olfactory bulb were exam­ ined. In one experiment, histological analysis was made of this structure in a large group of rats, ranging in age from newborn to adults. It was established that the ventricular subependymal layer and its rostral extension are present as proliferative and migratory matrices throughout the period studied, with relatively little reduction in size from birth to adulthood. In another, autoradiographic study, the proliferation and migration of cells of this system, and their destination and mode of differentiation, were studied in rats that were injected with thymidine-H3 at 30 days of age and killed at intervals ranging from 1 hour to 180 days. There was a declining gradient in cell proliferation in a caudorostral direction from a high level near the lateral ventricle to the absence of cell proliferation in the olfactory bulb. The labeled cells that were present in high proportion near the lateral ventricle in the rats killed 1-24 hours after injection had further multiplied and moved to the middle portion of the "rostral migratory stream" by the third day, and were located in the subependymal layer of the olfactory bulb by the sixth day after injection. By the twentieth day the labeled ceHs disappeared from the subependymal layer of the olfac­ tory bulb and were distributed throughout the internal granular layer. The differ­ entiated cells were tentatively identified as granular nerve cells and neuroglia cells. These results established that the major target structure of cell production in the subependymal layer of the lateral ventricle in young-adult rats is the olfactory bulb, with only moderate contribution made to the anterior neocortex and basal ganglia. It was postulated that the function of cell migration to the olfactory bulb is the renewal of its cell population. Several investigators (Allen, '12; Bryans, graphic investigation, Smart examined '59; Globus and Kuhlenbeck, '44; Opalski, the morphology of this subependymallayer '34 Rydberg, '32) reported the presence in in infant and adult mice. He established adult animals and man of a mitotically ac­ that the proliferative subependymal layer tive "subependymal layer" (Kershman, '38) extended in adult mice from the anterior around the ependymal wall of the anterior wall of the lateral ventricle rostrally into lateral ventricle. Because techniques were the olfactory bulb. Smart's results indi­ not available for tagging these cells, these cated that these cells give rise, in infant earlier investigators could only speculate mice, to glia and neurons, but he failed to about their fate. The technique of thymi­ obtain evidence of migration in adult mice dine-H" autoradiography, which can be used (excepting a few cells that seemed to for tagging newly-forming cells in order to "leak" into the corpus callosum). He postu­ trace their destiny, was first addressed to lated, in agreement with the hypothesis of this problem by Messier et al. ('58) and previous investigators, that the mitotic ac­ more particularly by Smart ('61). In a tivity of this layer in adults is an abortive combined histological and autoradio- phenomenon and the newly-forming cells

The Diffusion of Innovations among the American States

Abstract: We are now in the midst of a notable revival of interest in the politics of the American states. During the last decade many studies have been conducted of the social, political and economic determinants of state policy outcomes. Several of these writers have argued that the relative wealth of a state, its degree of industrialization, and other measures of social and economic development are more important in explaining its level of expenditures than such political factors as the form of legislative apportionment, the amount of party competition, or the degree of voter participation. It has been claimed that such factors as the level of personal income or the size of the urban population are responsible both for the degree of participation and party competition in a state, and the nature of the system's policy outputs. By making this argument these writers have called into question the concepts of representation and theories of party and group conflict which, in one form or another, are the foundations for much of American political science.There is a growing awareness, however, that levels of expenditure alone are not an adequate measure of public policy outcomes. Sharkansky has shown, for example, that levels of expenditure and levels of actual service are seldom correlated; presumably, some states are able to reach given service levels with much less expenditure than others. Besides establishing the appropriate level of expenditure for a program, policy makers must also decide about the program's relative scope, provisions for appeal from administrative orders, eligibility requirements, the composition of regulatory boards and commissions, and many other matters which have little to do with money.

The Educational and Early Occupational Attainment Process

Abstract: Blau and Duncan (1967:165–172) have recently presented a path model of the occupational attainment process of the American adult male population. This basic model begins with two variables describing the early stratification position of each person; these are his father’s educational and occupational attainment statuses. It then moves to two behavioral variables; these are the educational level the individual has completed and the prestige level of his first job. The dependent variable is the person’s occupational prestige position in 1962. That the model is not without power is attested by the fact that it accounts for about 26 percent of the variance in educational attainment, 33 percent of the variance in first job, and 42 percent of the variance in 1962 level of occupational attainment. Various additions to the basic model are presented in the volume, but none is clearly shown to make much of an improvement in it. These include nativity, migration, farm origin, subgroup position, marriage, and assortative mating. Without detracting from the excellence of the Blau and Duncan analysis, we may make several observations. Because the dependent behaviors are occupational prestige attainments—attainment levels in a stratification system—it is appropriate to single out variables indicating father’s stratification position as the most relevant social structural inputs. It is unfortunate that practical considerations prevented the inclusion of psychological inputs in their model, especially considering the repeated references to one such—mental ability—in the literature on differential occupational attainment (Lipset and Bendix, 1959:203–226; Sewell and Armer, 1966). More recently, this gap has been partially filled (Duncan, 1968). Also omitted are social psychological factors which mediate the influence of the input variables on attainment. This, too, is unfortunate in view not only of the speculative theory but also the concrete research in social psychology, which suggests the importance of such intervening variables as reference groups (Merton, 1957:281–386), significant others (Gerth and Mills, 1953:84–91), self-concept (Super, 1957:80–100), behavior expectations (Gross et al., 1958), levels of educational and occupational aspiration (Haller and Miller, 1963; Kuvlesky and Ohlendorf, 1967; Ohlendorf et al., 1967), and experiences of success or failure in school (Parsons, 1959; Brookover et al., 1965).

A New Statistical Approach to Geographic Variation Analysis

Abstract: The authors discuss the problems of describing geographic variation data and develop statistical methods for categorizing sets of populations sampled from different localities. The general approach of the simultaneous test procedures, available with a variety of statistical tests and for continuous as well as for categorical data, is employed with these techniques. Geographical regions are defined as sets of connected localities, with connectedness being defined geometrically. Maximal acceptahle connected sets of localities (defined as regions) or coarsest acceptable connected partitions of the entire set of localities are found by these procedures. These are illustrated with several examples. I. AIMS AND PURPOSES The primary aim of geographic variation anialysis in biological systematics is the description and summarization of patterns of variation and covariation of characteristics of organisms that are distributed over an area. Such analyses are generally applied to species populations to study the variation of diverse characters. The most frequently studied characters are morphological, but recently there have also been such studies of biochemical, physiological, behavioral, cytological, immunological, as well as genetic characters. The basis for studies in geographic variation rests on the existence of populations of comparable organisms at a number of localities in the area under study. Comparisons of these populations are made in terms of one or more observable characters and the analyses relate these comparisons to differences in location. Data for studies in geographic variation consist of samples taken from the populations at a given number of localities, with a set of characteristics observed for each organism sampled. Summary statistics may be computed for each sample, as, for example, means and standard deviations for single measurable characteristics, correlations for pairs of such variables, etc. A summary of the data would then consist of a list of localities, each accompanied by its set of summary statistics for observed characteristics. In most cases, the infornation in such a list would be difficult to grasp and much would be gained by plotting the statistics on a map (or several maps) according to their location. Such graphic representation often reveals a good deal about the geographic variation pattern involved. A step beyond mere description of the pattern of variation of the characteristics of organisms is categorization. Usually, one prefers to group together localities that are geographically adjacent and whose populations are similar in their characteristics. This may be desired merely for purposes of simplification and summarization, or for the formal or semi-formal recognition of a population or series of populations in terms of the Linnean system. The study of patterns of geographic variation will often lead to causal ana:lysis. One may attempt to interpret the variational and correlational patterns of a species as adaptations to variation in known environmental factors, such as climatic, topographic, or edaphic variables. Other possible causes of variation may be differences in associated species populations, such as host plants, parasites, predators, etc. Marked and abrupt changes in characters between close localities may be related to abrupt changes in the above factors, to strong barriers to dispersal of the organisms or to secondary zones of intergradation between allopatrically differentiated populations. Unusual patterns of

Switching in General Predators: Experiments on Predator Specificity and Stability of Prey Populations

Abstract: "Switching" in predators which attack several prey species potentially can stabilize the numbers in prey populations. In switching, the number of attacks upon a species is disproportionately large when the species is abundant relative to other prey, and disproportionately small when the species is relatively rare. The null case for two prey species can be written: P1/P2 = cN1/N2, where P1/P2 is the ratio of the two prey expected in the diet, N1/N2 is the ratio given and c is a proportionality constant. Predators were sea—shore snails and prey were mussels and barnacles. Experiments in the laboratory modelled aspects of various natural situations. When the predator had a strong preference (c) between prey the data and the "null case" model were in good agreement. Preference could not altered by subjecting predators to training regimens. When preference was weak the data did not fit the model replicates were variable. Predators could be trained easily to one or other prey species. From a number of experiments it was concluded that in the weak—preference case no switch would occur in nature except where there is an opportunity for predators to become trained to the abundant species. A patchy distribution of the abundant prey could provide this opportunity. Given one prey species, snails caused a decreasing percentage mortality as prey numbers increased. This occurred also with 2 prey species present when preference was strong. When preference was weak the form of the response was unclear. When switching occurred the percentage prey mortality increased with prey density, giving potentially stabilizing mortality. The consequences of these conclusions for prey population regulation and for diversity are discussed.

New Inductive Population Model for Insect Parasites and its Bearing on Biological Control

Abstract: Mutual interference between searching insect parasites provides theoretical support for current biological control practices.

The number of heterozygous nucleotide sites maintained in a finite population due to steady flux of mutations.

Abstract: N natural populations, it is expected that there is a constant supply of mutaI tions in each generation. These mutations may have different persistence depending on their fitnesses, but collectively, they constitute the ultimate source of genetic variability in the populations. Since the maintenance of genetic variability is an important subject of study in population genetics, it may be worthwhile to investigate, using various models, the effect of mutation on the genetic variability. For example, KIMURA and CROW (1964) studied the number of alleles maintained in a finite population, assuming that each mutant is an allele not preexisting in the population. In the present paper I will use a different model and will investigate the number of heterozygous sites per individual and some related quantities that represent the statistical properties of the mutant frequency distribution, assuming that a very large number of independent sites are available for mutation. In this paper, “site” refers to a single nucleotide pair, although the theory is still appropriate to a small group of nucleotides, such as a codon.

Psychosis and temporal lobe epilepsy. A controlled investigation.

Abstract: UMMARY A controlled investigation comparing a population of 50 temporal lobe epileptics with psychotic episodes with 50 randomly selected temporal lobe epileptics who had never experienced psychotic disturbances, showed that: 1 temporal lobe epilepsy of the dominant hemisphere predisposes to psychotic manifestations; 2 epilepsy of the non-dominant temporal lobe is associated with manic-depressive, of the dominant temporal lobe with schizophrenic disturbances; 3 the presence of psychomotor seizures and frequent temporal fits are inversely correlated with psychosis, suggesting that such seizures and psychosis are antithetical manifestations of the same underlying disturbance of cerebral function: 4 epileptic psychoses are fundamentally related to the epileptic process rather than non-specific psychoses resulting from structural brain damage; 5 in epileptic psychoses periodicity is correlated with minimal chronicity with maximal brain damage. RESUME Une etude controlee comparant 50 epileptiques presentant une epilepsie du lobe temporal avec episodes psychotiques et 50 epileptiques pris au hasard presentant une epilepsie du lobe temporal mais n'ayant jamais presente de troubles psychotiques, a montre que: 1 l'epilepsie du lobe temporal de l'hemisphere dominant predispose aux manifestations psychotiques. 2 l'epilepsie du lobe temporal de l'hemisphere non dominant s'associe a des troubles maniaco-depressifs, celle du lobe temporal de l'hemisphere dominant a des troubles schizophreniques. 3 La presence de crises psycho-motrices et celle de crises temporales frequentes sont en correlation inverse avec les phenomenes psychotiques suggerant que les crises et les psychoses sont des manifestations antithesiques d'un meme dysfonctionnement cerebral. 4 Les psychoses epileptiques sont fondamentalement liees au processus epileptique alors que les psychoses non specifiques resultent d'une lesion organique cerebrale. 5 Les psychoses epileptiques periodiques sont en relation avec une atteinte cerebrale minime, alors que les psychoses epileptiques chroniques sont en relation avec une atteinte cerebrale severe.

Taphonomy and population dynamics of an early Pliocene vertebrate fauna, Knox County, Nebraska

Abstract: The principal purpose of this study is to determine from geological and biological evidence how a concentration of fossil bones originated. The Verdigre quarry of earliest Pli— ocene age in the Valentine Formation, northeastern Nebraska forms the basis for the investi— gation. Some 40 genera of mammals, 7 of reptiles, 2 of amphibians, and 6 of fishes are rep— resented in a collection of over 20,000 identifiable specimens recovered from a small exca— vation in a 4-5 foot-thick lens of extremely poorly sorted, gravelly, silty, clayey sand. The open framework and textural inversion of the fossiliferous stratum indicate very rapid deposition, probably in a single flood. Preferred orientation of long bones shows that the depositional current flowed from the NNW. The site of deposition was an off-channel de— pression on a broad floodplain which was subaerially exposed (mudcracked)prior to the flood. The great majority of the fossil remains do not represent animals killed by the flood as they are completely disarticulated and often somewhat abraded, except for 7 articulated skele— tons. Stream table experiments suggest that current sorting is probably responsible for the scarcity of elements such as ribs, vertebrae, sacra, and phalanges compared with rami, meta— podia, tibiae, etc. Discrete age groups, distinguished on the basis of tooth eruption and wear.(Kurten, 1953), are present in Verdigre mammals represented by large samples. Four hundred seventy-five Mery— aodus (antilocaprid)individuals fall into 7 year-classes: one juvenile (.8 year)and 6 adult (1.8- 6.8 years). Burrs on the horns of Meryaodus males are annual but cannot be used in population dynamics studies of collections of transported remains because they are easily re— moved by abrasion. Fifty-seven Protohippus (3-toed horse)individuals fall into 3 juvenile (-.2, .8, and 1.8 years)and at least 7 adult age classes.The lack of individuals of inter— mediate ages and the large proportion of animals of reproductive age in the samples indicate that non-selective catastrophic death accounts for most, and possibly nearly all, of the dis— articulated mammal remains in the quarry. Merycodus and Protohippus at least, died in the winter –– about 2-3 months before the season of giving birth. Growth ring study of catfish vertebrae and gar scales indicates that these aquatic forms were also winterkilled. Shotwell's (1955)method of determining the proximity of various habitats to vertebrate quarry sites is not applicable to the Verdigre assemblage, and probably not to other collections, because it fails to consider e.g.: 1. sedimentary evidence, such as indications of size-sorting 2. the possibility different effects of catastrophic and attritional mortality on the composition of quarry faunas 3. the great mobility of grazing mammals. There is evidence that size sorting is responsible for differences in ‘completeness’ of various mammals in Shotwell's published samples as well as in the Verdigre quarry. Sites of deposition of late Tertiary quarry faunas were in stream valleys; the interstream grassland habitat was probably rarely if ever directly sampled by depositional processes. Mass occurrences of grazing animals such as in the Verdigre bonebed are interpreted as resulting from mortalities which occurred down on floodplains at times of environmental stress. Early Pliocene vegetation in the Verdigre area resembled that of parts of the Gulf Coast of southern Texas and northern Mexico; forests occupied the broad floodplains and savannas the interfluves (MacGinitie, 1962). Crocodiles and giant land tortoises in the fauna indicate a normally frost-free climate. The presence of sharks and batoids suggests marine influence; stream gradients may have been significantly lower and the shoreline of the Gulf may have been closer to Nebraska in the early Pliocene than at present.

Experimental Zoogeography of Islands: The Colonization of Empty Islands

Abstract: We report here the first evidence of faunistic equilibrium obtained through controlled, replicated experiments, together with an analysis of the immigration and extinction processes of animal species based on direct observations. The colonization of six small mangrove islands in Florida Bay by terrestrial arthropods was monitored at frequent intervals for 1 year after removal of the original fauna by methyl bromide fumigation. Both the observed data and climatic considerations imply that seasonality had little effect upon the basic shape of the colonization curves of species present vs. time. By 250 days after defaunation, the faunas of all the islands except the most distant one ("EI") had regained species numbers and composition similar to those of untreated islands even though population densities were still abnormally low. Although early colonists included both weak and strong fliers, the former, particularly psocopterans, were usually the first to produce large populations. Among these same early invaders were the taxa displaying both the highest extinction rates and the greatest variability in species composition on the different islands. Ants, the ecological dominants of mangrove islands, were among the last to colonize, but they did so with highest degree of predictability. The colonization curves plus static observations on untreated islands indicate strongly that a dynamic equilibrium number of species exists for any island. We believe the curves are produced by colonization involving little if any interaction, then a gradual decline as interaction becomes important, and finally, a lasting dynamic equilibrium. Equations are given for the early immigration, extinction, and colonization curves. Dispersal to these islands is predominantly through aerial transport, both active and passive. Extinction of the earliest colonists is probably caused chiefly by such physical factors as drowning or lack of suitable breeding sites and less commonly by competition and predation. As population sizes increase it is expected that competition and predation will become more important. Observed turnover rates showed wide variance, with most values between 0.05 and 0.50 species/day. True turnover rates are probably much higher, with 0.67 species/day the extreme lower limit on any island. This very high value is at least roughly consistent with the turnover equation derived from the MacArthur—Wilson equilibrium model, which predicts turnover rates on the order of 0.1—1.0 species/day on the experimental islands.

On population growth in a randomly varying environment

Abstract: If a population is growing in a randomly varying environment, such that the finite rate of increase per generation is a random variable with no serial autocorrelation, the logarithm of population size at any time t is normally distributed. Even though the expectation of population size may grow infinitely large with time, the probability of extinction may approach unity, owing to the difference between the geometric and arithmetic mean growth rates.

Attitudes and Attraction

Abstract: Publisher Summary This chapter describes research on interpersonal attraction in relation to a philosophy of science in terms of the historical antecedents and current developments. The co relational studies of attraction and similarity of attitudes, opinions, beliefs, and values have essentially involved attempts to determine the validity and to extend the generality of this formulation. With minor variations, these studies involved the identification of pairs of individuals who indicate mutual attraction (spouses, fiances, and sociometrically identified friends), an assessment of these individuals on one or more attitudinal measures, and a statistical determination of the pairs' similarity. Often, this similarity is evaluated not only in terms of departure from a theoretical base line of chance pairings but also by comparison with the similarity of random pairs or mutually antagonistic pairs from the same population. The study of attitude similarity between pairs of friends has fed to results parallel to those involving married couples. Misunderstandings and confusions about research goals and research methods in personality and social psychology occur frequently. There are several issues involved when research interest moves from “real-life” studies closely tied to naturalistic observations into laboratory research in which some variables are manipulated and others controlled. A possible research paradigm for the study of attitude similarity–dissimilarity and attraction has been discussed. The chapter also mentions the generality of the similarity–attraction relationship and theory of attraction as reinforcement model.

Overweight and Hypertension A Review

Abstract: The interrelationships between hypertension and obesity, two common and major health hazards, are reviewed. Comparisons of simultaneous intra-arterial and cuff blood pressure measurements indicate in general that the association between blood pressure and body weight is real and independent of arm circumference. Hypertension is more common among the obese than among the nonobese and, conversely, a significant proportion of hypertensive persons in the population are overweight. Obese hypertensive subjects experience a greater risk of coronary heart disease than the nonobese, and mortality rates for obese hypertensive persons are higher than for those with obesity alone or hypertension alone. Weight reduction has been shown to lower blood pressure, and it may bring about a more favorable prognosis in obese hypertensive persons. Possible mechanisms that may be responsible for the frequent association between obesity and hypertension have been discussed. Irrespective of the underlying pathophysiologic mechani...

On the Kolmogorov-Smirnov Test for the Exponential Distribution with Mean Unknown

Abstract: The standard tables used for the Kolmogorov-Smirnov test are valid when testing whether a set of observations are from a completely specified continuous distribution If one or more parameters must be estimated from the sample then the tables are no longer valid A table is given in this note for use with the Kolmogorov-Smirnov statistic for testing whether a set of observations is from an exponential population when the mean is not specified but must be estimated from the sample The table is obtained from a Monte Carlo calculation

Microtus Population Biology: Demographic Changes in Fluctuating Populations of M. Ochrogaster and M. Pennsylvanicus in Southern Indiana

Abstract: Microtus pennsylvanicus and M. ochrogaster are sympatric in southern Indiana grasslands. From June 1965 to August 1967 four populations were lived trapped, three of them in 0.8—hectare (2—acre) outdoor pens. Both species increased during 1965 and reached peak densities in summer 1966. Microtus ochrogaster declined abruptly that fall and remained low; M. pennsylvanicus declined the following spring. One of the fenced populations increased to a density about three times that of its unfenced control. By early fall 1966 it had nearly destroyed its food resources and then suffered a severe decline associated with obvious overgrazing and starvation. No such overgrazing has been seen on any unfenced grasslands in this area. Dispersal is probably necessary for normal population regulation in these voles, since fenced populations seem unable to regulate their density below the limit set by starvation. Both species bred extensively in the winter of 1965—66 during the phase of population increase. There was little or no breeding during the winter after the peak. Survival of females in the trappable population of both species was high and relatively constant until the end of the cycle. In males, periods of low survival punctuated the increase and peak phases, and these periods of low male survival did not occur at the same time in the two Microtus species. Some mortality processes are thus highly specific for sex and species. In the fenced populations survival rates were very high and no sporadic male losses occurred. Increasing and peak populations of M. pennsylvanicus and M. ochrogaster are characterized by adults of large body size. During the increase and peak phases some voles stopped growing at low weights (30—40 g) while others reached high asymptotic weights (45—55 g). The demography of these Microtus species in southern Indiana is similar to that of other cycle voles and lemmings in temperate and arctic areas.

Prevalence, natural history, and relationship of wheezy bronchitis and asthma in children. An epidemiological study

Abstract: Three randomly selected groups of 7-year-old schoolchildren in Melbourne with mild wheezy bronchitis, with moderate wheezy bronchitis, and with asthma were compared with a control group, and the patients followed up until 10 years of age. Comparison showed that if there was any significant difference between the study groups and the controls it was usually present in all these study groups. It was considered that children with wheezy bronchitis and asthma were from the same population with the same underlying basic disorder, and that there was a wide spectrum in various aspects of the natural history of the disorder.About 11% of all children aged 10 years had had some asthmatic episodes. Seventy per cent. of these children ceased having asthma before 10 years of age, while about 30% (3.7% of the whole community) continued to have episodes. There was a highly significant correlation between early age of onset, the frequency of episodes in the first year of symptoms, and the persistence of asthmatic episodes up to 10 years of age.Ten per cent. of all children with asthmatic episodes continued to have symptoms as severely at 10 years as at an earlier period. In this group the onset of symptoms was almost always before 3 years of age, there was a high frequency of episodes in the first year of symptoms, and boys and girls were affected in the ratio of 7:3.

Heterogeneity of human Platelets: I. Metabolic and kinetic evidence suggestive of young and old platelets

Abstract: Human platelets have been separated into two extreme density populations by centrifugation in specific density media. A large-heavy platelet population with specific gravity > 1.055 and a light-small population with specific gravity < 1.046 were obtained, each representing approximately 15-20% of the total population volume. The average volume per platelet of the separated large-heavy and light-small platelet populations was 12 and 5 mu(3) respectively. When data are expressed per milliliter platelets or per gram wet weight, the large-heavy platelet population had a 2-fold greater glycogen content, 1.3-fold greater orthophosphate content, 1.3-fold greater total adenine nucleotide content, 4.2-fold greater rate of glycogenolysis, 2.6-fold greater rate of glycolysis, 2.9-fold greater rate of protein synthesis, and 5.7-fold greater rate of glycogen synthesis. Significant differences were not obtained with respect to total lipid content or total lipid synthesis. The large-heavy platelet had a 2.5-fold greater resistance to osmotic shock as measured by adenosine triphosphate (ATP) or adenosine diphosphate (ADP) release. These data, as well as diisopropyl fluorophosphate (DFP(32)) survival curves in rabbits, indicate that large-heavy platelets have a greater metabolic potential and suggest that they may be the young platelets which progress with age to light-small platelets with a diminished metabolic potential.

On Models of Commercial Fishing

Abstract: 1. A fishery resource, although conceivably exhaustible, is replenishable; that is, it is subject to laws of natural growth which define an environmental biotechnological constraint on the activities of the fishing industry. 2. The resource and the activity of production from it form a stock-flow relationship. The new growth in the population fish mass depends upon the harvest rate relative to natural recruitment to the stock. If the harvest rate exceeds the recruitment rate, the stock declines, and vice versa. 3. The recovery or harvesting process is subject to various possible external effects all of which represent external diseconomies to the firm: (a) Resource stock externalities result if the cost of a fishing vessel's catch decreases as the population of fish increases. (b) Mesh externalities result if the mesh size (or other kinds of gear selectivity variables) affects not only the private costs and revenues of the fisherman but also the growth behavior of the fish population. (c) Crowding externalities occur if the fish population is sufficiently concentrated to cause vessel congestion over the fishing grounds and, thus, increased vessel operating costs for any given catch. All of these various types of externalities arise fundamentally because

Certain Histological and Chemical Responses of the Vascular Interface to Acutely Induced Mechanical Stress in the Aorta of the Dog

Abstract: The purpose of this study is to quantify certain histologic and chemical responses of the intimal tissues in vivo to acutely induced mechanical stresses. Evans blue dye was given to tag serum albumin and an artificial fat emulsion was infused so that altered fluxes of either serum proteins or the artificial chylomicrons across the vascular interface into the intimal region could be detected. Special histologic and photodensimetric techniques were developed to estimate these fluxes as well as the architectural changes in the endothelial cell population. Architectural changes were quantified by doing endothelial cell counts to quantify the "normal" and "abnormal" endothelial cell population density as a function of stress exposure. The stress corresponding to the greatest rate of change of normal to abnormal cell forms is defined as the acute critical yield stress (τc) and was found to average < 420 dynes/cm2. Similarly the stress at which the greatest number of cells are being eroded is defined as the erosion stress (τe). The flux of Evans blue dye into the intima increased with pressure or wall strain, with shearing stress, and with increased turbulence. The flux of artificial chylomicrons into the intimal region never occurred in the presence of a normal endothelial cell population and was found to be most heavy in areas of total cellular erosion.

Physical separation of hemopoietic stem cells from cells forming colonies in culture.

Abstract: Mouse bone marrow cells in suspension were separated into a number of fractions on the basis of cell density by equilibrium density gradient centrifugation, or on the basis of cell size by velocity sedimentation. After each type of separation, the cells from the various fractions were assayed for their ability to form macroscopic spleen colonies in irradiated recipient mice, and for their ability to form colonies in a cell culture system. The results from either separation technique demonstrate that cells in some fractions formed more colonies in vivo than in the culture system, while cells in other fractions formed more colonies in culture than in the spleen. The results of control experiments indicate that this separation of the two types of colony-forming cells was not an artifact of the separation procedures. From these experiments it was concluded that the population of cells which form colonies in culture under the conditions used is not identical to the population of cells detected by the spleen colony assay.

Theta isoantigen as a marker of thymus-derived lymphocytes in mice.

Abstract: THERE is an obvious need for a marker that will differentiate one type of lymphocyte from another. The need has become urgent in view of recent evidence suggesting that there are at least two populations of lymphocytes, one thymus-derived and one bone marrow-derived, which participate in different ways in the immune response1. The theta (θ) isoantigen (θ is determined by a single locus with two alleles: θAKR found in AKR and RF mice and θC3H present in most other inbred strains of mice tested), described by Reif and Allen2,3, which is found chiefly in thymus lymphocytes and brain, and to a lesser extent in peripheral lymphocytes in mice, seemed a possible antigenic marker of thymus-derived lymphocytes. To establish that θ is such a marker, it is necessary to demonstrate that there is a discrete population of peripheral lymphocytes which carry the antigen and that these cells are thymus-dependent.

INTESTINAL CAPILLARIES I. Permeability to Peroxidase and Ferritin

Abstract: Horseradish peroxidase (mol. diam. ≃50 A) and ferritin (mol. diam. ≃110 A) were used as probe molecules for the small and large pore system, respectively, in blood capillaries of the intestinal mucosa of the mouse. Peroxidase distribution was followed in time, after intravenous injection, by applying the Graham-Karnovsky histochemical procedure to aldehyde-fixed specimens. The tracer was found to leave the plasma rapidly and to reach the pericapillary spaces 1 min post injection. Between 1 min and 1 min 30 sec, gradients of peroxidase reaction product could be demonstrated regularly around the capillaries; their highs were located opposite the fenestrated parts of the endothelium. These gradients were replaced by even distribution past 1 min 30 sec. Ferritin, followed directly by electron microscopy, appeared in the pericapillary spaces 3–4 min after i.v. injection. Like peroxidase, it initially produced transient gradients with highs opposite the fenestrated parts of the endothelium. For both tracers, there was no evidence of movement through intercellular junctions, and transport by plasmalemmal vesicles appeared less efficient than outflow through fenestrae. It is concluded that, in the blood capillaries of the inintestinal mucosa, the diaphragms of the endothelial fenestrae contain the structural equivalents of the small pore system. The large pore system seems to be restricted to a fraction of the fenestral population which presumably consists of diaphragm-free or diaphragm-deficient units.