Natural Life History Research Articles

Dynamics and development patterns of Pinus sylvestris L. - Fagus sylvatica L. stands in Central Rhodope

The study was conducted in second growth stands in the central Rhodope mountains and (specially) in the region of Xanthi. In order to determine the dynamics and the development patterns of Pinus sylvestris - Fagus sylvatica stands, 39 plots were established, trees were cut, increment cores were taken, and stem analysis was conducted in 4 couples of dominant (competitive) pine and beech trees. The main results of this research indicate that a) The population structures, the regeneration and development patterns are strongly influenced by human and natural disturbances and species 'life history characteristics'. b) The difference in site quality between site types results in differences in the duration of beech invasion (under pine) and in species basal area distribution. c) In good site qualities when individual dominant beech and Scots pine (competitive) trees with a small age difference grew together, the beech trees, in some cases, have almost the same height growth as the pines and the pine trees showed a delayed (for the species) culmination in current annual volume increment which is not followed by a abrupt fall. d) The process of secondary succession is influenced by disturbances regime, environment, propagule availability and species biology.

Divergence in juvenile growth and life history in two recently colonized and partially isolated chinook salmon populations

In 47 families of New Zealand chinook salmon, Oncorhynchus tshawytscha derived from two populations, differing in mean spawning date by 11–17 days and in juvenile life history, neither mean ovum weight nor mean time to hatch differed between the two populations, but substantial differences in mean family weight were apparent from 6 months after fertilization. Differences in growth rates from 12 to 24 months were relatively small, suggesting that most of the divergence in size and growth occurred during the first 6 months of life. There were differences in mean weight for families spawned 11–17 days apart, the approximate interval by which peak spawning date differs between the two populations, but these did not persist beyond 7 months. Differences between the two populations are consistent with their natural life history. The slower growing population experiences cooler temperatures during stream residence and is dominated by fish which spend a year in fresh water before seaward migration, whereas the faster growing population normally experiences warmer temperatures and migrates to sea in the first year of life. These results provide further evidence of life history evolution in partially isolated chinook salmon populations within 90 years (c. 30 generations) of becoming established.

Divergence in juvenile growth and life history in two recently colonized and partially isolated chinook salmon populations

In 47 families of New Zealand chinook salmon, Oncorhynchus tshawytscha derived from two populations, differing in mean spawning date by 11–17 days and in juvenile life history, neither mean ovum weight nor mean time to hatch differed between the two populations, but substantial differences in mean family weight were apparent from 6 months after fertilization. Differences in growth rates from 12 to 24 months were relatively small, suggesting that most of the divergence in size and growth occurred during the first 6 months of life. There were differences in mean weight for families spawned 11–17 days apart, the approximate interval by which peak spawning date differs between the two populations, but these did not persist beyond 7 months. Differences between the two populations are consistent with their natural life history. The slower growing population experiences cooler temperatures during stream residence and is dominated by fish which spend a year in fresh water before seaward migration, whereas the faster growing population normally experiences warmer temperatures and migrates to sea in the first year of life. These results provide further evidence of life history evolution in partially isolated chinook salmon populations within 90 years (c. 30 generations) of becoming established.

HPV typing and HPV16 E6-sequence variations in synchronous lesions of cervical squamous-cell carcinoma from Swedish patients.

We microdissected 15 specimens of invasive cervical cancer co-existing with some of its precursors. Out of 15 cases, 10 carried HPV16, 2 HPV31, 1 HPV18 and 2 were HPV-negative. We found 3 HPV16 E6 variants among the 10 cases; one was A --> G in nt 131 (one case) and a second was A --> G in nt 276. The third, T;--> G in nt 350, was common, and was found in 5 of the 10 patients infected by HPV16. The type of HPV and the E6 variant were identical in all lesions within the same patient. Viral DNA present in normal epithelium was identical in type and E6 variant to HPV in the same patient's lesions. Multiple samples from invasive cancers with HPV were consistently positive. The data suggest that the originally infecting HPV, including its variant type in the E6 gene, persists unaltered in the whole series of CIN that precedes invasive cancer. Our data are compatible with an essential role of HPV manifested by persistence of the viral genome during the entire natural life history of cervical cancer. We did not confirm previous data on the specific association of invasive cancer with an HPV E6 variant (G at nt 350 rather than T). The discrepancy may depend on the relatively few cases investigated or selection of a special sub-set with progression from CIN to invasive cancer already manifest.

Temperature effects on growth, feeding rate and feed conversion of the Pacific white shrimp ( Penaeus vannamei)

Effects of temperature on growth, feeding rate and feed conversion ratio (FCR) of juvenile Pacific white shrimp, Penaeus vannamei (Boone), were quantified in a series of four experiments. In each of experiments 1 to 3, a single size class of shrimp was reared at three constant temperatures (23, 27, 30 °C) and at an ambient temperature control (mean 26.2 °C). In the three experiments, mean shrimp stocking sizes were 3.9, 10.8 and 16.0 g, respectively. Shrimp growth and feeding rate increased directly with temperature in each experiment, but the increases varied among the three size classes so that thermal effects on growth and feeding were size-specific. FCR of small shrimp was not different among the three test temperatures while FCR of medium-and large-sized shrimp varied with temperature. Differences in growth response among size classes was the basis for a fourth experiment, in which two size classes were grown at three temperatures. Growth and feeding rate were again directly related to temperature and varied inversely with size. FCR was primarily related to size; larger shrimp grew less efficiently. Large temperature coefficients, particularly between 23 and 27 °C, demonstrate that P. vannamei growth is extremely sensitive to small changes in temperature. These data also indicate that temperature optima (temperature of fastest growth) is size-specific and decreases as shrimp size increases. For small shrimp (< 5 g), temperature optima may be greater than 30 °C while for large shrimp, the temperature optimum is about 27 °C. These findings appear consistent with the distribution of P. vannamei during its natural life history. For P. vannamei farmers, these data indicate that for all sizes reduced growth and feeding can be expected when pond temperature is below 23 °C and for large shrimp when pond temperature is 30 °C or greater.

Systematics, distribution, genetics and life history of milkfish, Chanos chanos

Chanos chanos belongs to a monotypic gonorynchiform family and is most closely related to the freshwater Ostariophysi. The earliest gonorynchiforms occurred in the Cretaceous of Brazil and west Africa. Chanos occurred in the freshwater Eocene deposits of Europe and North America, and probably invaded the circumtropical Tethys Sea during transgression episodes. At present, milkfish occurs near continental shelves and around oceanic islands throughout the tropical Indo-Pacific. Milkfish populations throughout the range show high genetic variation but low genetic divergence, similar to many other commercially important teleosts. The natural life history of milkfish is one of continual migration. Adults are relatively large (to 1.5 m or 15 kg), long-lived (to 15 years), pelagic and schooling. They spawn offshore near coral reefs or small islands. The eggs, embryos and larvae are pelagic and relatively larger than those of most marine species. Larvae ≥ 10 mm long and 2–3 weeks old move inshore via a combination of passive advection and active migration. Passing shore waters and surf zones, they settle in shallow-water depositional habitats such as mangrove swamps and coral lagoons, where they metamorphose and spend a few months as juveniles. Some juveniles may enter freshwater lakes where they grow into sub-adults but do not mature. Both small juveniles and large sub-adults go back to sea when they reach the size limit supportable by the habitat. Little else is known of the dynamics of wild populations of milkfish. A fishery on inshore larvae supports the centuries-old aquaculture of milkfish in southeast Asia. During the past ten years, milkfish have matured and spawned under various conditions of captivity, and hatcheries have produced larvae to supply the culture ponds. Much remains to be learned concerning the milkfish, particularly its ecology and physiology.

Natural History of Breast Cancer

The natural history of breast cancer has been, and will be, extremely hard to study. Indirect evidence suggests that any cancer cell population may be phenotypically unique with multiple abnormal traits which decisively forge the clinical behavior. Histopathologic grouping will only give a very imperfect reflection of phenotypical individuality. It is proposed that essential determinants of the subsequent behavior have already been fixed during the induction period, i.e. long before the clinical debut. This may to some extent be reflected by the DNA content of the tumor cells. Metastases to axillary lymph nodes is strongly determined by size of primary tumor according to a function which suggests a smooth linear risk for lymphatic spread over a broad size interval. It is suggested that each cell of any given cancer may be endowed with a small chance of dissemination to axillary lymph nodes which may be essentially constant during the entire natural life history. Number of cancer cells of the primary tumor would then be the decisive determinant for risk of metastatic dissemination. It is not necessary to invoke qualitative progression from 'non-metastasibility' to 'metastasibility'. Small differences exist in the natural history of different histological types of breast cancer.

The life history of dendritic leukocytes (DL).

Although the Langerhans cells were detected more than a century ago, it has only recently been realized that they belong to a family of cells, here referred to as dendritic leukocytes (DL), continuously seeded out from the bone marrow to most tissues in the body. Our knowledge about the natural life history of DL and their participation in inflammatory reactions is still fragmentary. A review of their life history and kinetics might therefore seem premature. However, during the last few years this family of cells has received widespread attention as accessory cells for the initiation of T-cell responses. A volume on the cellular kinetics of the inflammatory reaction would therefore be incomplete without a chapter devoted to these cells. Because many of the readers may not be well acquainted with this cell family, I shall first give some background information about the historical development of the dendritic leukocyte concept, and about the proposed functional roles of these cells.

Population Dynamics of a Montane Conifer Forest, Western Cascade Range, Oregon, USA

Size and age structure were used to reconstruct the population dynamics of two forested stands in the western Cascade Range, Oregon, USA. Trees with different growth rates and size—age relationships occurred in the same stand. The relationships between diameter and age of 939 aged trees of four species, although statistically significant, were often weak. Data on both age and spatial dispersion added critical information on stand dynamics not available from size alone. The population structures and regeneration patterns described were strongly influenced by natural disturbances and species' life history characteristics. Periodic fires of variable intensity and extent have produced a mosaic of relatively even—aged patches of different conifer species. The early establishment and dominance by a species on a site was a determinant of subsequent forest regeneration. If Pseudotsuga menziesii dominated early, regeneration of Tsuga heterophylla, and often Abies amabilis, was rapid. If, however, Tsuga heterophylla established first, further regeneration of other species was absent or minimal until canopy openings formed.

Classifying hazardous events

Classification is an information management technique that helps achieve the goals of scientific and applied research by simplifying and ordering complex and varied observations. This paper is intended as a guide to the use and application of classifications of hazardous events. Proposed classifications are reviewed and evaluated in terms of their purposes, methods, supportive evidence and the scientific and applied goals of classification. The review is structured according to the metaphor of the natural life history of a hazard that distinguishes three stages of human-environment interaction: (a) hazard causes, (b) physical and psychosocial characteristics of hazards, and (c) individual and aggregate responses to hazards. The life history perspective has the advantage of being multidimensional and transactional. The structure highlights the relationship between proposed classifications, identifies needed areas of conceptual and empirical development, and provides a general guideline for the selection and use of classifications for hazard management.

Manipulation of the amygdala noradrenergic system impairs extinction of passive avoidance

In a consolidation paradigm, noradrenergic manipulation of the rat amygdala results in disruption of extinction for passive avoidance. These results are discussed in light of a recent controversy concerning the role of central norepinephrine systems in general extinction behavior. The discussion is cast primarily within the gramework of rodent natural life history, the presence of innate behavioral strategies, and the organization of information processing as an integration of experiential attributes.

Natural history of glioma.

The natural life history of gliomas is discussed from the viewpoint of early diagnosis of so-called "silent" gliomas and postoperative follow-up study of "inactive gliomas, both types easily detectable by CT scan. On the basis of their functional status, about 10% of 150 histologically proven intracranial gliomas were judged to be silent or inactive gliomas. They were inactive for an average of 8.5 years, and most were fibrillary or gemistocytic astrocytomas except for one grade 3 astrocytoma. cystic formation was seen in two thirds of the cases and calcification in one half. Also, among highly malignant gliomas, a significant difference in the period of survival was seen between the group with very long intervals of 2-3 years, from onset to operation and that with relatively short periods of 2-3 months. Accordingly, treatment policy regarding such silent or inactive gliomas should be carefully determined case by case. Monitoring during postoperative progression-freed intervals is especially useful.

Success in a Hatchery Program with Fall Chinook Salmon by Simulating the Natural Life History of the Stock

Abstract Life histories of juvenile fall chinook salmon (Oncorhynchus tshawytscha) vary among and within stocks. In Elk River on the southern coast of Oregon, most juveniles live in fresh water for 6 to 7 months, grow to a large size, and migrate to sea in autumn. When this life history was simulated in the rearing program at Elk River Hatchery for the 1968, 1969, and 1970 broods, esimates of survival back to the river of five different hatchery releases averaged 4.3% and ranged from 3.3 to 5.8%. A release of 1968-brood fish reared until they were yearlings had a survival of 2.2%. However, when fish from the 1970 brood were reared in the hatchery for only a short period and released in early summer, as in a more traditional hatchery rearing program for fall chinook salmon, survival to return was only 0.3%. These results suggest that simulating the natural life history of native stocks in hatchery programs can have substantial benefit.

Overdiagnosis and Overtreatment of Pulmonary Embolism: The Emperor May Have No Clothes

Pulmonary embolism is being overdiagnosed and overtreated, especially in previously normal women using oral contraceptives, with undesirable consequences in heparin treatment. This is in part a consequences of high estimates of its occurrence based on postmortem data and in part of technologic developments in diagnostic methods. Blood gas data are not diagnostically very helpful. Perfusion scans should be used, largely to exclude the diagnosis. Ventilation scans are only occasionally helpful and are expensive. Pulmonary angiography is the most accurate diagnostic means currently available. Further studies are needed to elucidate the prevalence and natural life history of pulmonary embolism in the previously healthy person.

Epidemiology Abuse: Epidemiological and Psychosocial Models of Drug Abuse

Epidemiological and psychosocial approaches to drug abuse are discussed, with specific reference to the limits of the narrow epidemiological model when applied to the dynamics of heroin addiction, especially the elimination of heroin supply. During the early sixties there was much controversy between medical and psychosocial models of drug abuse with respect to methadone maintenance treatment programs versus drug free treatment programs. Frequently drug abuse treatment facilities would refuse to have both types of programs available, but after some time the differences which were thought to be irreconcilable were in fact reconciled and the field moved towards a synthesis of drug free and methadone maintenance approaches. The same thing needs to occur with respect to epidemiological and psychosocial approaches to drug abuse. The current narrow epidemiological approaches to drug abuse focus on heroin itself and ways of eliminating heroin supply. Psychosocial models are concerned with alienation, societal inadequacies, and psychological deficiencies of addicts. Psychosocial approaches define heroin addiction as a symptom of a more widespread social and psychological malaise, while narrow epidemiological approaches consider the heroin addiction itself the sole problem. Epidemiological and psychosocial approaches to drug abuse should be integrated so that much valuable information produced by epidemiologists such as the dynamics of the spread of heroin addiction, the period of time that addicts remain infectious, and the natural life-history of epidemics can be combined with knowledge produced by psychosocial approaches to fashion a more comprehensive approach to drug abuse. An epidemiologically based approach calling for stringent control of heroin distribution to non-addict populations coupled with easy access to low cost heroin for addicted persons would reflect an appreciation of the psychological/social/political realities involved in addiction as well as a grounding in epidemiological principles and data.

Epidemiology Abuse: Epidemiological and Psychosocial Models of Drug Abuse

Epidemiological and psychosocial approaches to drug abuse are discussed, with specific reference to the limits of the narrow epidemiological model when applied to the dynamics of heroin addiction, especially the elimination of heroin supply. During the early 60's there was much controversy between medical and psychosocial models of drug abuse with respect to methadone maintenance treatment programs versus drug free treatment programs. Frequently drug abuse treatment facilities would refuse to have both types of programs available, but after some time the differences which were thought to be irreconcilable were in fact reconciled and the field moved towards a synthesis of drug free and methadone maintenance approaches. The same thing needs to occur with respect to epidemiological and psychosocial approaches to drug abuse. The current narrow epidemiological approaches to drug abuse focus on heroin itself and ways of eliminating heroin supply. Psychosocial models are concerned with alienation, societal inadequacies, and psychological deficiencies of addicts. Psychosocial approaches define heroin addiction as a symptom of a more widespread social and psychological malaise, while narrow epidemiological approaches consider the heroin addiction itself the sole problem. Epidemiological and psychosocial approaches to drug abuse should be integrated so that much valuable information produced by epidemiologists such as the dynamics of the spread of heroin addiction, the period of time that addicts remain infectious, and the natural life-history of epidemics can be combined with knowledge produced by psychosocial approaches to fashion a more comprehensive approach to drug abuse. An epidemiologically based approach calling for stringent control of heroin distribution to non-addict populations coupled with easy access to low cost heroin for addicted persons would reflect an appreciation of the psychological/social/political realities involved in addiction as well as a grounding in epidemiological principles and data.

A clinicopathologic study of 92 cases of granulosa cell tumor of the ovary with special reference to the factors influencing prognosis.

Ninety-two cases of granulosa cell tumor of the ovary have been studied. The clinical and pathologic data from this group were similar to that obtained in previous series. Because of the long natural history of many granulosa cell tumors, crude death rates over a relatively short period give little indication of the true malignant potential of these neoplasms and hence corrected survival rates were calculated; these show that, if no patient died from any other disease, approximately half of the women with this neoplasm would die, as a result of the tumor, within 20 years. Factors indicating a relatively poor survival rate were: age over 40 at the time of diagnosis, a presentation with abdominal symptoms, a palpable mass, a solid large tumor, bilateral tumors, extraovarian spread, and numerous mitotic figures in the tumor. It is suggested that all granulosa cell tumors should be considered as malignant and that the factors pointing to a poor prognosis are those indicating that a particular tumor has been diagnosed at a late stage in its natural history, either because it has been present for a long time or because it is highly malignant. There are no definite criteria for defining the prognosis in a case in which the tumor has been removed at any early stage in its natural life history.

Play it Again Sam — an Essay on Salmon Enhancement

For more than 100 years efforts have been made to increase the abundance of the various species of Pacific salmon. The success of these ventures is largely a matter of conjecture because the scale of natural fluctuations is sufficient to mask the effect of human intervention. No well-defined program for salmon enhancement has yet been developed for British Columbia as a whole. This is mainly attributable to the pressures for providing protection for the existing stocks in the circumstances of an intensive fishery and increasing effects of other resource uses.From a social point of view, salmon enhancement is a highly desirable activity. Salmon occupy a special place in the culture of residents of the Pacific coast. Salmon arc economically valuable and salmon fishing provides a rich source of employment. Recreational fisheries are valuable but their true economic worth is difficult to judge. Benefit:cost ratios for salmon enhancement should be calculated for whole programs rather than for individual projects to obtain an approach consistent with the desirable strategy of development.From a biological point of view, salmon enhancement is feasible. There is potential in the ocean for growing more salmon; many historic runs can be rebuilt and there are many opportunities for colonizing watersheds that are currently inaccessible to salmon. Harvesting of increased stocks of salmon could pose risks for natural stocks that are relatively unproductive. More effective management and development of new strains of salmon may be required in these circumstances. Predator-control programs may in some instances be useful adjuncts to salmon-enhancement projects.The types of enhancement activity that will most likely be rewarding are those that interfere least with the natural life history. Removal of obstructions, regulation of stream flow, construction of artificial spawning channels, are typical simple measures that involve less research information and less risk than rearing hatcheries.Priorities for different salmon-enhancement projects involve consideration of the regional economic and social conditions as well as appreciation of the biological and physical problems. Regardless of priorities it is essential to a successful program that there be a commitment to continuity. Additionally, the total administrative complex for salmon enhancement should involve research components.The execution of a successful salmon-enhancement program depends on the establishment of an agency with the single responsibility of salmon enhancement. The financing of a successful program should depend partly on revenues generated from the resource users, such as a tax on commercially caught salmon, a license for saltwater angling. Special grants from federal and provincial governments would also be appropriate. Regardless of the administrative arrangements, it is urgently necessary that provincial government involvement be more substantial than it is at present. With their control over resource management practices, the provincial government is in a vital position for maintenance of freshwater environments.An investment of at least $100 million, and probably twice that amount, could be undertaken in a salmon-enhancement program that could be executed within 10 years. There are compelling reasons for starting on this enhancement program immediately.

Lymphocyte Phytohemagglutinin Responsiveness, Immunoglobulins and Autoantibodies in Aging Humans

Abstract Phytohemagglutinin responsiveness of peripheral blood lymphocytes declines in aged humans. Older humans exhibit a rise in the incidence of autoantibodies. The incidence of autoantibodies becomes significantly greater among older subjects over 80 years of age and is most significant in humans with low lymphocyte phytohemagglutinin responses. Serum levels of IgG and IgA were increased in subjects surviving beyond the 7th decade. Correlations could not be detected between serum immunoglobulin levels, titers of individual autoantibodies and the lymphocyte response to phytohemagglutinin. These observations suggest that hyperglobulinemia, impaired lymphocyte phytohemagglutinin responsiveness, and increased frequency of autoantibodies are characteristic of surviving older humans and represent associated events in the natural history of human life.

The natural life history of children with minimal brain dysfunction.

The natural life history of children with minimal brain dysfunction.