Erythrocyte membrane abnormalities in hypertension: a comparison between two animal models

Calcium-membrane interactions have been studied in two animal models of hypertension using the erythrocyte membrane as a model system. The Okamoto-Aoki strain of spontaneously hypertensive rats (SHR) was the first examined, and the activities of the Ca++/Mg++-ATPases in the membrane of SHR erythrocytes were found to be consistently higher than those of the normotensive controls (WKY), while other membrane enzymes such as Na+/K+-ATPase and acetylcholinesterase were not detectably altered. Erythrocyte membranes of the SHR also have a higher passive permeability to calcium as well as other functional and compositional differences when compared to those of the WKY. These findings suggest that the membrane alterations in the SHR may be related to an increased passive permeability to calcium, and a possibly compensatory increase in Ca++/Mg++-ATPase activity in these animals. The second animal model examined was the deoxycorticosterone/salt-induced hypertension (DOCA) in uninephrectomized rats. In DOCA rats with comparable degree of blood pressure elevation, none of the erythrocyte membrane abnormalities observed in the SHR were present, suggesting that the latter alterations are probably genetically determined and not a consequence of elevated arterial pressure.

The effects of chronic ethanol consumption on cardiac function in rats

A pharmacological model of alcoholism in rats was developed by administering ethanol in their drinking water. This model has provided us with a convenient means to study the effects of chronic ethanol consumption on cardiac functional properties. Our "treated" animals consumed, on the average, an equivalent of 11.1 g/kg of absolute ethanol per day and had an average blood ethanol concentration of 26.9 mg/dL at the end of the 12-week treatment period. The Langendorff-perfused hearts from both treatment and control groups performed equally well mechanically when left to beat spontaneously, but under conditions of electrical pacing the contractile ability of hearts from the alcohol-treated animals deteriorated more rapidly. Dose-response relationships for isoproterenol (isopropylnoradrenaline, IPNA) showed that hearts from alcohol-treated animals did not respond as well as hearts from control animals at higher doses of IPNA. This trend was completely reversed in the presence of low external calcium where the hearts from alcohol-treated animals responded better at all IPNA concentrations. Our observations suggest that chronic alcohol consumption may give rise to alterations in calcium ion handling at the level of myocardial plasma membranes.

Serological analysis of Rickettsia tsutsugamushi isolates from North Queensland

Fifty-two Rickettsia tsutsugamushi isolates from humans, rodents and chiggers in North Queensland were serologically characterized by the direct immunofluorescence test. A majority (71%) of the isolates was a mixture of two or more strains. The most frequently detected strains in the 52 isolates were TA716 (84%), TA763 (42%), TA686 (33%), and Karp (31%). The Gilliam strain was detected in only 4% of the isolates.

Clinical and immunologic responses of silvered leaf monkeys (Presbytis cristatus) to experimental reinfection with Rickettsia tsutsugamushi

Silvered leaf monkeys (Presbytis cristatus) that had recovered from active Rickettsia tsutsugamushi infections 14 months previously became rickettsemic when inoculated with homologous, related, or unrelated strains of R. tsutsugamushi. In contrast to the results after the initial infection that produced disease, no signs were observed after the subsequent infections. Most animals responded with detectable titers of antibody to the Karp antigen regardless of the inoculated strains. Strains recovered during rickettsemia usually had antigens related only to the challenge strains, but in three silvered leaf monkeys, antigens characteristic of both the original and the challenge strains were detected.

Antigenic classification of Rickettsia tsutsugamushi isolates from small mammals trapped in developing oil palm complex in Peninsular Malaysia

Fifty-one Rickettsia tsutsugamushi isolates from small mammals collected in central Peninsular Malaysia serologically characterized by direct immunofluorescence using eight prototype strains. Karp-related (TA763, TA686, TA716) antigens were found in 90.2% of the isolates.

Persistence and reactivation of Rickettsia tsutsugamushi infections in laboratory mice

The persistence of R. tsutsugamushi in tissues of experimentally infected mice for 565 days was demonstrated. Reactivation of apparently dormant infections was accomplished by inoculating the mice with a heterologous strain of the organism or treatment with cyclophosphamide.

Virulence and antigenic properties of Rickettsia tsutsugamushi in a naturally infectei laboratory colony of Leptotrombidium (leptotrombidium) arenicola

Over 1,200 isolations of R. tsutsugamushi were obtained over 7 generations of L. (L.) arenicola and no reproducible differences in virulence or antigenic markers could be detected among these isolations. The F8 generation yielded rickettsia with the same antigenic makeup and virulence properties as the original female parent mite. When these isolates were inoculated into mice they elicited the same predominant antibody specificities, i.e. they all produced antibody which reacted with the TA 763 and Karp strains. These were the same as the major antigens detected by direct fluorescent antibody staining of the isolates.

Patterns of rickettsemia and antibody response in silvered leaf monkeys (Presbytis cristatus) after inoculation with virulent and avirulent strains of Rickettsia tsutsugamushi

Most silvered leaf monkeys inoculated with selected strains of Rickettsia tsutsugamushi developed rickettsemia. The time of onset and the duration of rickettsemia were related to the infecting strains, but these parameters could not be correlated with the virulence of the strain. The rickettsemia was not terminated by the appearance of humoral antibody, as detected by the indirect fluorescent antibody test. The specificities of the antibody responses were related to the antigens present in the infecting strains.

Clinical response of silvered leaf monkeys (Presbytis cristatus) to infection with strains of Rickettsia tsutsugamushi virulent and avirulent for mice

Silvered leaf monkeys (Presbytis cristatus) inoculated with avirulent strains of Rickettsia tsutsugamushi showed little or no signs of disease, whereas those inoculated with moderately or fully virulent strains developed severe disease. Infection with the virulent strains produced early leukocytosis followed by leukopenia and significant decreases in packed-cell volumes. In animals infected with avirulent strains, these parameters were normal throughout the experimental period.