Sharp Increase In Mortality Research Articles

Influence of exposure duration on the toxicity of triclopyr ester to fish and aquatic insects

Flow-through toxicity tests were conducted to determine the effects of exposure time on the toxicity of triclopyr butoxyethyl ester (Garlon® 4) to fish (rainbow trout and chinook salmon) and stream insects (Hydropsyche sp. and Isonychia sp.). The toxicity of triclopyr ester to fish increased with exposure time, but the rate of increase in toxicity declined with increasing exposure duration. Median lethal concentrations for rainbow trout exposed for 1, 6, or 24 h were 22.5, 1.95, and 0.79 mg/L triclopyr ester (expressed as acid equivalent, nominal concentrations), respectively. Comparable values for chinook salmon were 34.6, 4.7, and 1.76 mg/L. The toxicity of triclopyr ester to aquatic insects also increased with increasing exposure time, but was considerably less than the toxicity to fish. There was no significant mortality (chi-square p>0.05) of insects following 3-h exposures to the maximum test concentration of approximately 110 mg/L. Median lethal concentrations following 9- and 24-h exposures were 14.9 and 4.0 ml/L for Hydropsyche sp., and 37.0 and 8.8 mg/L for Isonychia sp., respectively. At each exposure time in the toxicity tests, there was a sharp increase in mortality over relatively small increases in concentration, resulting in extremely steep slopes of the probit lines (6.3–33.8), and indicating an apparent response threshold. The herbicide exhibited delayed lethal effects, particularly in fish, but only at short term exposures to higher concentrations. The risk of adverse effects on fish and aquatic insects from triclopyr ester contamination, based on the results of these time-toxicity tests, is discussed.

Slowing of age-specific mortality rates in Drosophila melanogaster

We have studied age-dependent mortality in large cohorts of male and female D. melanogaster from four inbred lines. Average longevity varies substantially between genotypes (broad-sense heritability = 22%). Contrary to the predictions of the Gompertz model, mortality rates tend to decelerate at the most advanced ages. Fitting Gompertz, Weibull, Logistic, and Two-stage Gompertz mortality models to the data, we find that the best fit is obtained with the two-stage model, with exponentially increasing mortality at early ages, and zero or nearly zero increase at older ages. There is little microenvironmental effect from cage to cage. There is a sex-dependent mortality crossover: males and females differ in initial mortality rate and degree of acceleration of mortality rate, but the ordering of the sexes according to mortality parameters depends on genotype. Model fitting can be affected by gaps between deaths in the tail of the survivorship distribution. The observations are inconsistent with the limited life-span paradigm, which predicts sudden and well-defined drops in survivorship and corresponding sharp increases in mortality at advanced ages for large cohorts of genetically identical individuals.

Parkinsonism mortality in the US, 1. Time and space distribution

We studied the time-space variations of mortality for parkinsonism in the US during the periods 1962-1985 and 1971-1978 from statistics on primary cause-of-death and multiple causes-of-death, respectively. Linear regression analysis and a test for significance of spatial clustering were used. For parkinsonism as a primary cause-of-death, up to the late 1970's there was a decrease in mortality for the age groups below 75 and stable rates for the age group 75 years and over. A moderate decrease among those below 75 years, and a sharp increase in mortality among those over 74, were observed for the period since the late 1970s. The variation of the age-specific mortality during the period 1962-1985 ranged from 100% in the age group 35-44 years to +98% in those aged over 84 years. Within the same age group, the variations across time of mortality due to, and related to parkinsonism, for the period 1971-1978, were similar. In the spatial analysis, an association between mortality related to parkinsonism and geographical latitude was found. We conclude that: 1) parkinsonism at death is widely distributed; 2) the changes across time can not be explained by a reduction in general mortality; 3) improvements in diagnostic ascertainment and reporting among the elderly may have particularly occurred during the last decade; and 4) the disorder has been progressively confined to the elderly by diminishing in the younger birth cohorts.

The Major Respiratory Diseases of American Indians

The most prominent respiratory diseases of American Indian adults are pneumonia, cancer of the lung, chronic obstructive pulmonary disease (COPD), and tuberculosis. Mortality and hospitalization rates of these diseases were compared with those for the rest of the U.S. population and between Indian groups in the various Indian Health Service Areas. Pneumonia and influenza constitute the sixth leading cause of death among Indians and the fifth leading cause of death among the U.S. All Races population. Chronic obstructive pulmonary disease is the fourth leading cause of death among U.S. All Races, but only the tenth leading cause of death among Indians. Pneumonia and tuberculosis are more significant causes of death and disability for Indians than are COPD and cancer of the lung. The explanation for these differences in mortality rates between Indians and the general population are not known. Respiratory system diseases are responsible for 10.6% of Indian hospitalizations. The most frequent is pneumonia, which accounts for approximately 4% of all Indian hospitalizations. Differences in respiratory diseases between Indian groups are sometimes striking, with a sharp increase in mortality and hospitalization in the Areas across the northern border of the lower 48 states. There is also a much higher prevalence of cigarette smoking in those same Areas.

A time-course study of chronic paternal cyclophosphamide treatment in rats: effects on pregnancy outcome and the male reproductive and hematologic systems.

We have found previously that daily treatment of male rats for 11 wk with low doses of the anticancer drug cyclophosphamide had no apparent effect on male reproductive organ weights, epididymal sperm counts, or serum hormones at the end of the treatment period; yet, upon breeding to untreated females, these males produced a high rate of post-implantation loss and fetal anomalies. The present study was designed to investigate the time course and dose response of the effects of chronic cyclophosphamide treatment on the male reproductive and hematologic systems. Male Sprague-Dawley rats were gavage-fed for 1, 3, 6 and 9 wk with saline (control), or 5.1 (low dose) or 6.8 (high dose) mg/kg/day of cyclophosphamide. After each of the treatment periods, males were mated to determine the effect on pregnancy outcome, then killed, and the effects on the male reproductive and hematologic systems were assessed. After 6 wk of treatment, a sharp increase in mortality was found between the 5.1 and 6.8 mg/kg/day doses of cyclophosphamide. The high dose of cyclophosphamide induced higher levels of pre- and post-implantation loss but fewer fetal anomalies than did the low dose. The low dose of cyclophosphamide did not affect reproductive organ weights; in contrast, the high dose caused decreases in epididymal, ventral prostate, and seminal vesicle weights after 3, 6, and 9 wk. Testicular and epididymal sperm counts were decreased in a dose-dependent manner after 3 wk; in addition, the high dose led to a decrease in epididymal sperm counts after 6 wk of treatment. Another rapidly proliferative tissue, the bone marrow, was dramatically affected by both doses of cyclophosphamide at all time points, with leukocyte counts decreasing to 40% of control by 1 wk. After 9 wk of treatment, effects on the male reproductive system were less marked, compared to earlier time points, whereas those on the hematologic system and pregnancy outcome persisted. Thus chronic low-dose treatment of male rats with cyclophosphamide not only had early and striking effects on the bone marrow and the pregnancy outcome but also affected the male reproductive system in a clear time- and dose-dependent manner.

Demographic Structure of Ceanothus Megacarpus Chaparral in the Long Absence of Fire

Wildfires have had a major influence on the struc? tural and functional adaptations that have evolved in species of mediterranean-type ecosystems. In Califor? nia chaparral, for example, shrubs regenerate after fires from basal sprouts or seed germination cued to the first postfire season. Certain species of Ceanothus and Arctostaphylos produce abundant seed throughout their lifespan, and the seeds lie dormant in the soil for many years until germination is stimulated by fire. These species do not resprout after fire, and thus are often referred to as obligate seeding shrubs. In the absence of fire, these species neither rejuvenate their canopy from basal sprouts as sprouting shrubs do, nor do they recruit new seedlings. The demographic patterns for one such species, Ce? anothus megacarpus Nutt. ssp. megacarpus, have been documented in studies by Schlesinger and Gill (1978, 1980). This shrub is distributed on the coastal front of the Coast Ranges from Santa Barbara County to San Diego County, often forming nearly pure, even-aged stands dating back to a previous fire. As with other obligate-seeding species, seedling populations are high in the first postfire year, but nil in later years. Mortality in the 1st yr is typically quite high. The causes of mor? tality probably include drought, predation, and com? petition from the dense herbaceous vegetation. After the 1st yr, mortality is relatively low during the first decade. However, as the shrub canopy closes in, Schle? singer and Gill (1978) found another sharp increase in mortality, and they attributed this stand-thinning to increased competition for water (Schlesinger and Gill 1980). After stand-thinning in the second decade, mortality in Ceanothus megacarpus was shown to level offonce again. Schlesinger and Gill's studies, however, did not extend much beyond the second decade. It is not known what happens after this time. Anecdotal observations in the literature suggest that after ?30-40 yr another sharp increase in mortality is to be expected due to stand senescence.

Mariculture potential of the spot prawn, Pandalus platyceros Brandt

Biological characteristics and culture methods were investigated for the spot prawn, Pandalus platyceros Brandt. Ovigerous adults were caught in the local fishery; six of these produced 2 628 to 4 669 larvae. The larval period ranged from 26 to 35 days (9.5–12.0°C). Maximum larval survival was about 70%, with mortalities being most frequent during ecdysis. The relation of wet weight (g) to carapace length (mm) for the first 26 months was calculated as log W = −3.0843 + 2.9308 log L. Prawns showed good survival between 9.5 and 21.0°C. Mortality increased sharply when temperatures exceeded 21.0°C. Salinities below 22‰ resulted in a sharp increase in mortality. A diet of brine shrimp nauplii sufficed for newly hatched larvae. Growth was enhanced when larvae were fed a unicellular algal supplement ( Phaeodactylum tricornutum), although mortality was somewhat higher. Larvae progressed rapidly to foraging on larger brine shrimp and diced foods. Six-month-old spot prawns raised on a squid diet averaged 3.4 g, and at 1 year the mean weight was 6.3 g. A feeding experiment, incorporating 12 diets, disclosed that highest growth rates and best food conversion ratios were achieved on a combined California seamussel and giant red sea urchin diet. However, the best growth rate achieved was considered marginal for mariculture. It was concluded that unless the growth rate could be accelerated by other food formulations or culture techniques, a monoculture system for mass cultivation would not be feasible. The spot prawn may have potential in a polyculture system.

Oxygen Toxicity in the Newborn Lung: Reversal of Inhibition of DNA Synthesis in the Mouse

Continuous exposure to 100% oxygen at atmospheric pressure for two weeks causes significant alterations in the growth of the lung and the body of newborn mice. These changes can be divided into three phases. The initial phase, which lasts 96 hours, is characterized by inhibition of lung DNA synthesis, diminished total lung DNA, and a decrease in the ratio of lung DNA to body weight. The intermediate phase from 96 to 144 hours is characterized by a sharp increase in mortality, a plateau in body weight, and a minimal lung DNA/body weight ratio. During this period, however, surviving animals show a reversal of the inhibition of DNA synthesis and thus an increase in total lung DNA. The third phase, occurring after 144 hours, is characterized by a continued increase in DNA synthesis and total lung DNA, a gain in body weight, a return of the lung DNA/body weight ratio to control levels, and a sharp decline in mortality. The survival rate of 54% in newborn mice over two weeks contrasts with the near total mortality reported for adult experimental animals similarly exposed. The reversal of the inhibition of lung DNA synthesis in surviving mice suggests either that some newborn animals are inherently resistant to pulmonary oxygen toxicity or that they develop, during a critical exposure period, an adaptive process necessary for their survival.

Perforated peptic ulcer in Auckland and Glasgow.

A retrospective study is presented of the incidence of perforated peptic ulcer diagnosed at laparotomy or autopsy in the Auckland area for the decade 1954 to 1963. During this period 408 perforations, comprising 345 pyloro-duodenal, 59 gastric and four stomal ulcers, were treated in hospital. The total mortality rate for the treated patients was 8.3%, rising to 13.7% for the whole series. Approximately 60% of the perforations occurred after the age of 60 years, there being a sharp increase in mortality with advancing age; the death rate was higher for gastric ulcer perforations for both sexes at all ages. Pyloro-duodenal ulcer perforations were considerably more frequent in the male, but the differences were much less striking in the case of gastric ulcer. In the female, both pyloro-duodenal and gastric ulcers perforated at a later age and carried a higher mortality rate. Despite a linear increase in the population during the decade under study, there has been no change in the annual frequency of perforations. The figures presented suggest a low incidence of perforation in the Maori race. The main features of the survey have been compared with those of a similar study carried out in the west of Scotland.

NEONATAL GASTRIC PERFORATION WITH SURVIVAL

A case report of an infant with neonatal gastric perforation is presented, together with a review of the English literature. Almost two-thirds of cases of this condition occur in premature infants. Abdominal distention, absent bowel sounds, and dyspnea are the commonest clinical signs, each occurring in 70% or more of the cases. Seventeen of 39 reported patients who were treated surgically within 12 hours of onset of signs or symptoms survived. Operation more than 12 hours after onset has resulted in a sharp increase in mortality. No survivals have been reported without surgery.