Exploitation of gene(s) involved in 2,4-diacetylphloroglucinol biosynthesis to confer a new biocontrol capability to a Pseudomonas strain.

Tn5 mutagenesis and complementation analysis were used to clone a 6-kb genomic fragment required for biosynthesis of 2,4-diacetylphloroglucinol (Phl) from fluorescent Pseudomonas sp. strain F113. A recombinant plasmid, pCU203, containing this region partially complemented a Phl production-negative mutant (F113G22) derived from strain F113. When sugar beet seeds were sown into an unsterilized soil, in which sugar beet was subject to damping-off by Pythium ultimum, the emergence of sugar beet seeds inoculated with strain F113 was significantly greater than that of seeds inoculated with F113G22. Transfer of pCU203 into eight other Pseudomonas strains conferred the ability to synthesize Phl in only one of these strains, Pseudomonas sp. strain M114. Strain M114(pCU203) showed enhanced antagonism towards P. ultimum in vitro and significantly increased the emergence of sugar beet seeds in the same soil compared with emergence induced by the parent strain M114.

Psychosocial stress induces high blood pressure in a population of mammals on a low-salt diet.

The relative importance of salt intake and psychosocial stimulation in the development of high blood pressure has been studied in colonies of CBA/USC mice. Approximately 50 males were observed for 3-4 months in five population cages which successfully induced chronic psychosocial interaction, resulting in chronic hypertension. Under these conditions, progressive arteriosclerosis develops together with myocardial hypertrophy, increased catecholamine synthesis and increased angiotensin sensitivity. Previous work indicates that this condition shows the characteristics of renin dependent human hypertension. A special grain based diet was used which included 0.014% sodium. This resulted in the ingestion of the equivalent of 40 mmol/l sodium or 3.0 g NaCl in a 70-kg man. This, and an even more stringent synthetic diet containing less than 0.01% NaCl, i.e. less than 2 g NaCl per day in man, were contrasted with the standard chow which contains 0.4% sodium. Over 4 months of social interaction the psychosocial stimulation proved to be the critical factor and, despite the low-salt intake, blood pressure rose to the same levels as those of control groups on a normal diet containing 1% salt. Hypertension occurs in the absence of kidney failure as assessed by blood urea. Plasma renin levels on the low-salt grain based diet were double those on standard chow, showing that the diet was sufficiently low in salt to activate the renin-angiotensin system.

Effect of Bacteriophage on Colonization of Sugarbeet Roots by Fluorescent Pseudomonas spp.

The colonization potential of two fluorescent Pseudomonas strains (M11/4, B2/6) that exhibit antifungal activity in vitro was studied on the roots of sugarbeet plants in a clay loam soil. The cell density of the introduced bacteria declined on the root system over a 16-day test period in nonsterile soil. Strain B2/6 declined at a significantly faster rate compared with M11/4. This loss in viability and difference in colonization ability between M11/4 and B2/6 was not observed in sterile soil. Nutrient deprivation induced by indigenous microorganisms was excluded as a key factor involved in the decline of the introduced bacteria on the basis that strains M11/4 and B2/6 retained viability when subjected to nutrient starvation conditions over a 16-day period. Experiments designed to test whether antagonism by indigenous microorganisms was responsible for the decline in the introduced fluorescent Pseudomonas sp. population revealed the presence of large numbers of bacteriophage in the soil capable of lysing strain B2/6. Reconstitution experiments carried out with sugarbeet seedlings inoculated independently with strains M11/4 and B2/6 and grown in sterile soil to which a soil phage filtrate had been added showed a significant decrease in the viability of strain B2/6 relative to M11/4. Phage antagonistic toward strain B2/6 were detected in 43% of soils taken from the major sugarbeet growing regions of Ireland.

Inhibition of angiotensin - converting enzyme in CBA mice with psychosocial hypertension.

Captopril (SQ 14,225) was acutely administered to control mice and to mice which had developed hypertension as a result of being caged in a manner which facilitates social interactions and competition. Systolic blood pressure was measured four hours after captopril administration, and blood was taken for measurement of plasma renin activity (PRA) several days later. Captopril produced no effect on normotensive control mice living in isolation nor did it reduce the blood pressure of the hypertensive mice on days 1, 7, and 14 following their placement in the special caging, despite the fact that their PRA was significantly elevated at these times. In contrast, by 1.5 months after placement in the cages and continuing for the next 5.5 months, captopril abolished the hypertension; PRA was normal during this period. We conclude that the increased PRA existing during the early stage of this psychosocial model of hypertension is not a significant direct contributor to the hypertension, whereas the renin-angiotensin system may be essential for the maintenance of the hypertension beyond the early stage.

Role of subordination in nephritis of socially stressed mice.

A behavioral etiology of interstitial nephritis of male CBA mice chronically exposed to psychosocial stress is suspected. The blood urea nitrogen of these animals is inversely proportional to social status as measured by behavior and the appearance of fur. Blood pressure measurement tends toward an opposite relationship. Since subordinates have difficulty urinating in the presence of dominants and suffer from overfilled bladders, their fatal tubulointerstitial involvement may originate with repeated episodes of urinary reflux.

Psychosocial stress induces tubulointerstitial nephritis unrelated to hypertension in CBA mice.

1. Groups of mice interacting socially in complex population cages become hypertensive. Some also develop fatal chronic tubulointerstitial nephritis. 2. Long-term administration of the cardioselective beta-blocker metoprolol controls stress-induced elevation of plasma renin and adrenal tyrosine hydroxylase. It also normalizes blood pressure. Despite the effectiveness of this sympathetic blockade, the incidence of nephritis was not diminished. 3. The fact that stress-induced increases of adrenal weight and plasma corticosterone persist during metoprolol treatment points to the independence of the pituitary-adrenal cortical system and its possible role in the aetiology of renal disease.

Caffeine as an intensifier of stress-induced hormonal and pathophysiologic changes in mice.

Psychosocially stressed male mice competing in a Henry-Stephens complex population cage develop hypertension, cardiovascular damage, and chronic interstitial nephritis. Their plasma renin, noradrenaline, corticosterone, and adrenal-catecholamine synthetic enzymes are increased and they die prematurely. Adding 3.3 mg of caffeine a day per kilogram of mouse body weight (the equivalent of 20 micrograms/ml decaffeinated coffee) to their drinking water significantly intensifies most of these changes. A dose of 90 mg/kg of caffeine (the equivalent of 560 micrograms/ml, i.e., brewed tea or coffee) further increases the effects. The drug-induced enhancement of competitive social stimulation of the neuroendocrine system resulted in a further increase of plasma renin and corticosterone levels as well as blood pressure and adrenal weight. These effects together with accelerated mortality and increased pathology indicate that chronic consumption of caffeinated liquids adds to the risks of psychosocial stress.

Effects of an angiotensin converting enzyme inhibitor on psychosocial hypertension in mice.

1. Renin-associated, chronic psychosocial hypertension of 150-160 mmHg develops in groups of mice interacting socially in complex population cages. 2. The blood pressures of 16 males in a cage were measured and an intraperitoneal injection of the angiotensin coverting enzyme inhibitor captopril (SQ 14,225) was given. Three hours later blood pressures were measured again. 3. During the first 3 weeks of psychosocial hypertension SQ 14,225 was without effect. But at 1 month and subsequently up to 7 months, SQ 14,225 reduced blood pressure to the normal range of 120-130 mmHg. 4. Plasma renin activities were not related to the extent of blood pressure reduction by SQ 14,225. Hence other factors in addition to the renin-angiotensin mechanism play a part in maintaining chronic psychosocial hypertension.

Force breeding, social disorder and mammary tumor formation in CBA/USC mouse colonies: a pilot study.

If the newborn of a socially organized CBA/USC mouse colony are regularly removed (force breeding), the social order breaks dowm. There is fighting among the males and the young are lost due to neglect and injury by the females (cronism). A high incidence of mammary tumor formation is observed during the disorder of such formerly socialized groups. In the pilot study being reported, force breeding initiated at the sixth month of colony life eventually at the ninth month led to fighting and the loss of young by cronism. All 12 female colony members developed tumors during the subsequent 5 months. Meanwhile, tumors developed in only 8% of the same age Study Siblings and in 46% of Study Breeders maintained under rapid breeding conditions. Force breeding is a knowm moderately effective tumorigenic technique. Since tumors did not occur in the population cage until its social system broke down, this suggests that the combination of force breeding and social disorder-induced neuroendocrine changes is peculiarly favorable to tumor development.

A model of psychosocial hypertension showing reversibility and progression of cardiovascular complications.

The sequence of pathophysiological changes that can result from the stimulating effects of a sustained disturbance of the social environment was studied in ten colonies of socially deprived mice. Sixteen formerly isolated males were placed with 16 normal females in population cages consisting of seven intercommunicating boxes. Six of these socially disturbed 32-member colonies were terminated after periods of interaction ranging from 2 days to 9 months. The remaining four were terminated a month or more after the males had been returned to individual isolation. Indirect blood pressure measurements, body and heart weights, and sections of hearts and aortas were studied in the males. Following the shorter exposures, blood pressure reverted to normal in a few days. Exposure of 6 months or more were associated with unchanged body weights and sustained increases in heart weight and blood pressure readings. In addition, there was a significant development of aortic arteriosclerosis and myocardial fibrosis. These changes persisted despite prolonged return to isolation.