Terminal Stage Of Infection Research Articles

STUDIES ON THE METABOLISM OF LEAVES WITH LOCALIZED VIRUS INFECTIONS: MITOCHONDRIAL ACTIVITY IN TMV-INFECTED NICOTIANA GLUTINOSA L.

An increase in the number of mitochondria in leaf tissues of Nicotiana glutinosa soon after inoculation with tobacco mosaic virus was indicated by examination of ultrathin sections, and verified by nitrogen assays of mitochondrial preparations. The succinoxidase activity of mitochondria from locally infected tissues was much higher than that of mitochondria from healthy tissues. Enzyme activity continued at increased levels until the terminal stages of infection, when low succinoxidase activity accompanied degenerative changes in the mitochondria. An early effect of localized virus infection appears to be an increase in the number of mitochondria, and therefore an increase in total enzyme per infected cell. This explains, at least in part, the overall increase in respiration of locally infected tissues previously observed.

CYTOCHEMICAL OBSERVATIONS ON INTRANUCLEAR INCLUSION OF FELINE VIRAL RHINOTRACHEITIS VIRUS.

SummaryExamination of feline renal cell cultures infected with feline viral rhinotracheitis virus and stained by the May-Grunwald-Giemsa, acridine orange, and the Feulgen techniques showed that there were definite morphological alterations with biochemical changes within the cell. The evidence suggests that the cytologic changes occurred in the nucleus first. The development of the inclusion body was accompanied by an increase in staining reaction for desoxyribonucleic acid in the nucleus. The Feulgen technique revealed a decrease in staining intensity of the nucleus in the later stages of inclusion development. Such results were not obtained with the May-Grunwald-Giemsa and acridine orange stains. With these latter 2 staining methods the terminal stages of infection were characterized by an increased accumulation or redistribution of desoxyribonucleic acid-staining material in the cytoplasm.

The behaviour of a mutant strain of Salmonella typhimurium in experimental mouse typhoid.

A streptomycin-resistant mutant of a virulent strain ofSalm. typhimuriumwas less virulent to mice than the parent strain. The difference in virulence was only observed when mice were infected with small numbers of organisms. Although the mutant strain caused fewer deaths than the parent strain it remained capable of establishing persistent infection in the majority of animals.The significant difference in the behaviour of the two strainsin vivowas that after clearance from the blood multiplication in the tissues began more rapidly with the virulent strain and was progressive, whereas multiplication of the mutant was delayed, was less in degree and was apparently suppressed within a few days of infection.The mutant strain was apparently identical antigenically with the parent strain, and was equally toxic. The mice dying of infection with this strain did so when the bacterial population had reached a level similar to that in the terminal stage of infection with the virulent strain.The essential difference between the two strains was the speed and probability of attaining a critical final population. The mutant strain ofSalm. typhimurium, bothin vitroandin vivo, had a slower growth rate than the parent strain. A possible hypothesis to explain the importance of this finding in relation to the outcome of infection has been discussed.I am indebted to the Medical Research Council for the provision of a grant towards the expenses of this investigation and to Mr T. Norris and Miss Italia S. Alderton for technical assistance.

A Physiological Study of Virus Parasitism

Summary The experimental data herein presented have demonstrated that the rates of oxygen consumption of embryonated eggs vary directly with the temperature of incubation. Thus, ten-day-old embryos incubated at 32.2 C have a Qeo2 amounting to about 50 per cent of that obtained with eggs incubated at 37.8 C. The experiment performed at an elevated temperature of 39.4 C yielded slight, but not statistically significant evidence of an increased rate of oxygen consumption. It is interesting to note that eggs injected with the NJ-KD strain of Newcastle disease virus (NDV) and incubated under standard conditions (37.8 C at 52 per cent relative humidity) do not exhibit any appreciable deviation in their Qeo2 from normal eggs or from embryonated eggs, injected with an equivalent amount of normal allantoic fluid, until near the terminal stage of the infection. At that time, there appears to be a rapid reduction in the rate of oxygen consumption, to the low level established for infertile eggs. Eggs inoculated with NDV and incubated (32.2 C) approximately 10 degrees below the standard environmental temperature responded to the infection as above, except that the survival time was increased from approximately 40 hours to 70 hours; furthermore, the slope of the drop in the Qeo2 at the terminal stage of infection appeared to be far more gradual. Repeated experiments with control and NDV-infected eggs incubated at 39.4 C failed to show any significant difference in the mean Qeo2 or in the survival time, from that observed with eggs incubated under standard conditions. The results presented tend to support the hypothesis that the rates of virus multiplication within a host cell may be regulated by the over-all respiratory quotient of that system. That is to say, a reduced Qeo2 of the embryonated egg is presumably accompanied by a reduction in the rate of virus proliferation. In the case of the hens' egg, the variation of environmental temperatures constitutes an easy mechanism for altering the Qeo2 to any desired level. We have been unable to demonstrate any significant stimulation in the oxygen uptake of infected eggs. This has been observed to be true also in the case of eggs infected with Western equine encephalitis virus3. It is appreciated that these results are not in accordance with those reported by Parodi, et al. (1) and Pinkerton et al. (2). A possible discrepancy between our findings and those of the above authors may be due to the entirely different types of technique employed.