Absence Of Animals Research Articles

Fatal myocardial infarct in a Greyhound

ABSTRACTDeath is reported in a 3‐year‐old Greyhound due to an acute myocardial infarction, consequent upon thrombo‐embolic occlusion of the left descending coronary artery, subsequent to dislodgement of a vegetative lesion of the left lateral aortic valve, secondary to sub‐acute bacterial endocarditis. A comparison between some aspects of cardio‐vascular disease in man and dogs is made, and the term ‘heart attack’ as used in the human condition is investigated and its legitimate application to veterinary conditions discussed. The main difference between human and animal coronary disease is the widespread occurrence of atherosclerosis in humans and its absence in animals.

Seed dispersal in a cycad, Macrozamia riedlei

Abstract The influence of animals on patterns of seed dispersal has not been well explored, despite the importance of seed dispersal in plant population biology. Furthermore, the exploitation of animals as dispersal agents has been considered one reason for the replacement of gymnosperms by angiosperms in the Cretaceous. We studied seed dispersal in a cycad, Macrozamia riedlei, and showed that in the absence of animals, ripe seeds drop directly beneath the parent not more than 40 cm from the base. Several animals eat the fleshy outer integument of the seeds, and possums (Trichosurus vulpecula), transport seeds up to 24 m from the parent. The postdispersal positioning of seeds gave a log density‐log distance relationship of y = 7.20 – 2.85x (r2= 0.96, N = 17). Effective local dispersal may have contributed to the persistence of cycads in the world flora for the last 200 million years.

Effects of nutrients and temperature on decomposition of Myriophyllum spicatum L. in a hard‐water eutrophic lake1

Temperature, phosphorus, and nitrogen were investigated as possible factors influencing decay of Myriophyllum spicatum shoots. In laboratory experiments, nitrogen enrichment significantly increased decay rates while phosphorus enrichment did not. Similar increases in decay rate per unit of added nitrogen occurred whether nitrogen was provided as nitrate or was present as additional tissue nitrogen. Exponential decay coefficients depended on temperature with a Q10 of about 3.Predictions of decay rates during litter bag experiments were based on laboratory responses of decay rate to temperature and initial nitrogen concentration of the shoots. Observed decay rates correlated closely with predictions, demonstrating the usefulness of temperature and shoot nitrogen content in explaining variations in decay rates in Lake Wingra. However, predictions underestimated decay rates. Possible explanations for the discrepancies include slow establishment of the detrital microflora, lower nitrogen availability, and absence of animals in the laboratory incubations.

Effects of certain full and partial sterilization treatments on leaf litter

Experiments are described which tested the effects of X-rays, gamma-irradiation, autoclaving, and propylene oxide on the organisms and chemical composition of hazel and oak leaf litter. X-ray treatment at 0.02 Mrad produced no major changes in the composition of the microbial populations, nor significant changes in the chemical composition of the litters. However, this treatment has been used to kill animals in litter, and it is a suggested treatment of litter if micro-organisms are to be studied in the absence of animals, or if a different population of animals is to be introduced. Autoclaving, gamma-irradiation, and propylene oxide, were effective as total sterilizing treatments: a Bacillus species was the only survivor detected. The results confirm that autoclaving is the most drastic of these treatments, and it appears to reduce the content of soluble tannins in the litter. Propylene oxide has certain disadvantages, which are discussed. Gamma-irradiation is at least as effective as autoclaving in killing organisms, and may he more so, as the Bacillus species appeared to be damaged more by irradiation than by the other treatments. Gamma-irradiation appears to leave at least some enzyme systems functioning, but storage of the treated material before use allows free enzyme activity to decline. The effect of storage time on free enzyme systems needs further study.

Observations on striatal connections following total destruction of the nucleus medialis dorsalis in the cat.

SummaryComplete unilateral destruction of the nucleus medialis dorsalis was achieved in 4 cats. Terminal degeneration was found in the caudate nucleus, in contrast to its absence in animals that had only partial destruction of the same structure. Minimal connections with the globus pallidus and putamen were reconfirmed and a definitive connection with the claustrum was also noted.