Changes In Host Resistance Research Articles

Changes in host resistance to cancer during chemical carcinogenesis

Changes in host resistance to cancer during chemical carcinogenesis

Multiple systems failure and circulatory support.

As our knowledge of and capabilities in surgery improve, the problems that we encounter change. We have learned to better support the circulation and the heart, the kidneys, the lungs and other organs in patients after trauma or after operation and failure of any one of these organs alone has been less of a problem. In the early 1970's, there was a simultaneous or sequential development of problems or failure of several organs. We called this syndrome multiple, progressive or sequential systems or organ failure (MOF). It is truly a syndrome related to surgical progress. By defining the problem and developing an understanding of it, we can better prevent its occurrence and increase the survival and well-being of those under our care. Common factors in patients who develop this syndrome include some or all of following: A) A multiple systems injury or extensive soft tissue injury and/or a major or extensive operation. These can lead to MOF, even in a previously normal patient. In patients with limited systems such as with prior vascular disease or emphysema, the problem is intensified. B) A period of shock accompanying the injury or operation and/or later circulatory instability with a marginal cardiac output. C) Requirement for multiple and perhaps continuous blood transfusions. D) Renal injury or an alteration in renal blood flow that may not be evident initially. E) Marginal ventilatory function with atelectasis, aspiration, fat embolism or other problems. F) Early problems such as continued or recurrent bleeding requiring reoperation, large hematomas, tissue necrosis, peritoneal contamination, pulmonary injury or head injury. G) Catabolism with all of its attendant problems. H) Failure of rapid return of gastrointestinal function and discontinuation of intravenous infusions to enable oral intake and spontaneous adequate ventilation for extubation. I) There are often clinical or technical errors or problems such as a leaking anastomosis or wound separation. J) Depressed host resistance leading to invasive sepsis or abscesses. As this occurs, ventilatory failure ensues or there is a worsening of previously abnormal ventilation, right heart failure secondary to increased pulmonary vascular resistance or myocardial depression with increased venous pressure, progressive evidence of hepatic failure with a rising bilirubin, renal failure and problems with an altered sensorium, coagulation and stress ulceration. The key factor in most reports on this problem has been infection. Attention to the problems of cell injury and a better definition of changes in host resistance, the relationship fsepsisto to pulmonary, renal and hepatic failure and other organ relationships should help to prevent this problem. The injured or surgically-treated patient who has experienced a severe metabolic insult may have multiple systems or organ failure. Careful evaluation, a well-planned operative procedure, and excellent supportive postoperative care with elimination of clinical or technical errors and prevention of sepsis should result in survival of most of these patients.

Use of viral infections in animal models to assess changes in the immune system.

Viral infections in animal models appear to be ideal systems for determining toxicity to the immune system by environmental substances. Since many viral infections that are utilized in animals produce systemic disease, these models provide an opportunity to evaluate the interaction between virus and components of host resistance. In these infections it is possible to delineate the role of antibody, interferon, cell-mediated immunity, neutrophils and macrophages in response to infection. A change in any of these components responsible for resistance to a particular virus may be correlated with an alteration of mortality an pathogenesis of the viral infection. Three experimental viral infections in mice that are potential candidates for use in determining immunotoxicity are discussed in terms of the response of individual components of resistance to infection and how changes in there components result in alterations of viral pathogenesis. The resistance to encephalomyocarditis virus infection in mice appears to be primarily mediated by antibody and interferon while with herpes simplex virus, infections are mainly controlled through cell-mediated immunity, macrophages, and possible interferon. Cellular immunity also appears to be primarily responsible for resistance to cytomegalovirus infections. Therefore, it is important in the use of these systems for evaluating immunotoxicity to define the pathogenesis of the viral infection and the specific host responses to these infections and to be able to correlate a change in host resistance with an alteration of the viral infection.

Use of Viral Infections in Animal Models to Assess Changes in the Immune System

Viral infections in animal models appear to be ideal systems for determining toxicity to the immune system by environmental substances. Since many viral infections that are utilized in animals produce systemic disease, these models provide an opportunity to evaluate the interaction between virus and components of host resistance. In these infections it is possible to delineate the role of antibody, interferon, cell-mediated immunity, neutrophils and macrophages in response to infection. A change in any of these components responsible for resistance to a particular virus may be correlated with an alteration of mortality an pathogenesis of the viral infection. Three experimental viral infections in mice that are potential candidates for use in determining immunotoxicity are discussed in terms of the response of individual components of resistance to infection and how changes in there components result in alterations of viral pathogenesis. The resistance to encephalomyocarditis virus infection in mice appears to be primarily mediated by antibody and interferon while with herpes simplex virus, infections are mainly controlled through cell-mediated immunity, macrophages, and possible interferon. Cellular immunity also appears to be primarily responsible for resistance to cytomegalovirus infections. Therefore, it is important in the use of these systems for evaluating immunotoxicity to define the pathogenesis of the viral infection and the specific host responses to these infections and to be able to correlate a change in host resistance with an alteration of the viral infection.

The survival of Candida albicans experimentally inoculated into the mouths of healthy human subjects

Mouthwashes containing Candida albicans in spore and hyphal forms were administered to eight healthy, non-Candida-carrying volunteers and the clearance rates were measured by saliva counts and imprint cultures of the oral mucosal surfaces. Neither the use of spore or hyphal forms, nor varying the number of C. albicans in the mouthwash, from 8 × 10 3 to 24 × 10 3, affected the clearance rates. Most of the Candidal organisms administered could no longer be isolated after 30 minutes and none were detectable after 4 hours. Under normal circumstances, exposure of healthy non-carriers to C. albicans does not seem to result in oral colonization. Oral thrush probably results from changes in host resistance rather than from exposure to high doses of C. albicans.

I. Pathogenic variation in fungi and bacteria and mycorrhizal compatibility: The genetic architecture of aggressiveness in Ustilago maydis

ABSTRACTIsolates of Ustilago maydis (D.C.) Cda are known to differ in the degree to which they can parasitise maize and, as no differential reaction occurs between pathogen and host, these differences must be differences in aggressiveness.Inoculation of juvenile maize plants induced morphological changes which provided a means of assessing and distinguishing U. maydis isolates in respect of their aggressiveness. Thus it was possible to carry out a survey of the genetic architecture of aggressiveness in natural populations of the pathogen.The distribution of aggressiveness within a single gall suggested that selection had taken place over a number of generations in favour of genes or gene systems tending to increase aggressiveness. Diallele analyses of isolates from two natural populations revealed that aggressiveness had a low heritability and was determined by genes exhibiting mainly non‐allelic interaction.It has been proposed that horizontal resistance in host cultivars would have a more long lasting protective effect against disease. However, the genetic architecture of aggressiveness in U. maydis should enable the pathogen to respond rapidly to changes in host resistance and the skewed distribution found within a single gall tends to support this. Therefore, the use of higher levels of host resistance should rapidly select for higher aggressiveness in the pathogen.

Virulence dynamics in Puccinia graminis f.sp. avenae in Canada

Virulence in Puccinia graminis f.sp. avenue has been studied in Canada since 1921. Changes in host resistance, the succession of avirulence–virulence combinations, and changes in the composition of the pathogen population during the ensuing 57 years are presented graphically and indicate that the organism is highly dynamic even when the host population is relatively static. The early years are characterized by the presence of races virulent only on the universally susceptible host or cultivars with a single resistance gene followed by a gradual increase in virulence beginning in 1943 and a differentiation of eastern and western pathogen populations. By 1950 the zero- and one-gene virulence races were being displaced by Pg-1, -2 and Pg-1, -2, -3 virulence combinations in eastern Canada, an event that did not occur in the west until 1961. The latter period was characterized by the combining of virulence on all resistance genes except Pg-8 and Pg-13 in the east and Pg-9 and Pg-13 in the west. Virulence on resistance conferred by gene Pg-13 is still rare.

Long-term population studies on the cattle tick (Boophilus microplus) on untreated cattle selected for different levels of tick resistance

Census data were collected at weekly intervals on tick populations on untreated cattle over a period of 6 years in central Queensland, near Rockhampton. Hereford x Shorthorn (British; HS) heifers and two herds of Africander (Zebu) x [Hereford and Shorthorn] (AX) heifers, one with animals of high resistance (AXH) and the other of medium (AXM) tick resistance, were grazed in separate paddocks. A herd of AX steers was added to the trial when the heifers commenced calving in 1972–73. Data were collected from the heifers for three years prior to their first calving and then for a further three years whilst they were breeding. There were large differences between the numbers of ticks in different years and a consistent seasonal pattern, the numbers being lowest from July to September and highest in the April to June quarter. The AXH herd had fewest ticks for most of the experiment, but after the first year there was little difference between the infestations on the AXM and HS herds. The resistance of all herds, measured by artificial infestations with larvae, increased during the first 3 years but declined after the cattle began breeding, and fluctuated from year to year. The resistance of some heifers did not stabilize until the animals were more than a year old, and that of some animals drifted up or down over long periods. The loss of resistance of a small proportion of the cattle in the AXH herd was responsible for the advantage of that herd being substantially reduced. Both the ranking for resistance of animals and the mean resistance of the herds, assessed with artificial infestations, agreed with the rankings and tick population sizes observed from tick counts on the cattle in the field. Changes in the mean resistance of the herds in spring in different years were highly correlated with concurrent field infestations, which suggests that changes in host resistance have important effects on tick populations. Tick counts on the calves up to weaning showed no correlation with concurrent counts on their dams, but the ranking of the counts on the calves was consistent over the 6 month period.

Preparation of the Bowel for Surgery

Controversy continues to exist in this important area because no large scale randomized prospective clinical study comparing antibiotic preparation of the bowel with mechanical preparation alone has ever been completed. A regimen for mechanical cleansing of the bowel is suggested, and arguments for and against the use of intestinal antibiotics are presented, relating particularly to superinfection, suture line recurrence, and possible changes in host resistance to infection.

A Seasonal Sex Difference in the Infestation of Rabbits with the Nematode Trichostrongylus retortaeformis (Zeder, 1800)

LARGER numbers of nematodes in male than in female hosts have been recorded for Ascaridia galli in chickens1 and for Aspiculuris tetraptera in mice2; with Syngamus trachea in partridges, on the other hand, infestations are more severe in females than in males3. The present results, relating to Trichostrongylus retortaeformis in European wild rabbits, Oryctolagus cuniculus (L.), are of interest in indicating a seasonal change in host resistance, males being more resistant in summer and females in winter.