Keith H. Thompson

Genetic influence of the kidneys on blood pressure. Evidence from chronic renal homografts in rats with opposite predispositions to hypertension

In two strains of rats with opposite genetic propensities for hypertension, interstrain renal transplants chronically modified the blood pressure of the recipients. The blood pressure of rats with these renal homografts was largely determined by the genotype of the donor kidney rather than by the genotype of the recipient. Kidneys from the hypertension-resistant (R) rats generally had an antihypertensive effect, and kidneys from the hypertension-prone (S) rats had a prohypertensive effect. These effects on blood pressure were most clear-cut in rats maintained on a low-sodium diet, but they were still evident in a modified form in rats on a high-sodium diet. Results from this study and from earlier studies suggest that kidneys from S rats have a greater hypertensinogenic and a smaller antihypertensive capacity than do kidneys from R rats. Therefore the influence of the kidney on blood pressure appears to have genetic determinants. If this finding is applicable to man, it would help to explain the well-established but anomalous observation that one of two individuals who apparently have similar renal disorders can have hypertension when the other does not.

Genetic Influence of the Kidneys on Blood Pressure

In two strains of rats with opposite genetic propensities for hypertension, interstrain renal transplants chronically modified the blood pressure of the recipients. The blood pressure of rats with these renal homografts was largely determined by the genotype of the donor kidney rather than by the genotype of the recipient. Kidneys from the hypertension-resistant (R) rats generally had an antihypertensive effect, and kidneys from the hypertension-prone (S) rats had a prohypertensive effect. These effects on blood pressure were most clear-cut in rats maintained on a low-sodium diet, but they were still evident in a modified form in rats on a high-sodium diet. Results from this study and from earlier studies suggest that kidneys from S rats have a greater hypertensinogenic and a smaller antihypertensive capacity than do kidneys from R rats. Therefore the influence of the kidney on blood pressure appears to have genetic determinants. If this finding is applicable to man, it would help to explain the well-esta...

Genetic Influence of Renal Homografts on the Blood Pressure of Rats from Different Strains

Summary In two strains of rats with opposite genetic propensities to hypertension, the effect of renal transplants on the chronic blood pressure response has been studied. 113 rats survived an average of 4 months (range 1-14) after this procedure. Among animals maintained on a low NaCl diet, blood pressure, as compared with appropriate controls, was not significantly affected when the recipient animal and its renal homograft came from the same strain; however, animals from the hypertension-resistant strain with a renal homograft from the hypertension-prone strain had higher pressures whereas hypertension-prone rats with a homograft from the hypertension-resistant strain had lower pressures than their respective controls. Thus, the phenotypic response—blood pressure—was more influenced by the genotype of the renal homograft than by the genotype of the recipient.

Exciton interaction among chlorophyll molecules in bacteriochlorophyll a proteins and bacteriochlorophyll a reaction center complexes from green bacteria

Absorption and CD spectra of bacteriochlorophyll a proteins and bacteriochlorophyll a reaction center complexes from two strains of Chlorobium limicola were recorded at 77 degrees K. Visual inspection showed that the Qy-band of chlorophyll in either protein was split into at least five components. Analysis of the spectra in terms of asymmetric Gaussian component pairs by means of computer program GAMET showed that six components are necessary to fit the spectra from strain 2K. These six components are ascribed to an exciton interaction between the seven bacteriochlorophyll a molecules in each subunit. The clear difference between the exciton splitting in the two bacteriochlorophyll a proteins shows that the arrangement of the chlorophyll molecules in each subunit must be slightly different. The spectra for the bacteriochlorophyll a reaction center complexes have a component at 834 nm (absorption) and 832 nm (CD) which does not appear in the spectra of the bacteriochlorophyll a proteins. The new component is ascribed to a reaction center complex which is combined with bacteriochlorophyll a proteins to form the bacteriochlorophyll a reaction center complex. The complete absorption (or CD) spectrum for a given bacteriochlorophyll a reaction center complex can be described to a first approximation in terms of the absorption (or CD) spectrum for the corresponding bacteriochlorophyll a protein plus the new component ascribed to the reaction center complex.

Epidermal browning of saguaro cacti (Carnegiea gigantea): Surface and internal characteristics associated with browning

Abstract In some locations of Saguaro National Monument near Tucson, Arizona, there has been a decline in saguaro cacti (Carnegiea gigantea (Engelm.) Britt. and Rose). Injury to individual cacti is frequently characterized by epidermal browning and premature senescence. On green cactus surfaces, most epicuticular waxes flake off and stomata are not obscurred. As cactus surfaces become more yellow in color (less green), epicuticular waxes no longer flake off and the build up or sheeting of waxes obscures stomata. This sheeting eventually leads to visible scaling and barking. Epicuticular wax sheeting, scaling and barking of troughs were negatively correlated with depth of green chlorenchyma but were positively correlated with depth of discoloration of internal parenchyma. These results suggest that the first step in epidermal browning is an excessive accumulation of epicuticular waxes. Sheeting of epicuticular waxes results in scaling and barking of crests followed by these same events on troughs. Areoles deteriorate as crest scaling and barking occur. These events are well-correlated with trunk color and the depths of both the green chlorenchyma and discoloration of the internal parenchyma.

The R.B.E. of Different Energy Neutrons as Measured by the Haematopoietic Spleen-colony Technique

The spleen-colony technique has been used for determining the relative biological effectiveness (r.b.e.) for several energies of neutron radiation. Donor mice were exposed for fission and accelerator-generated neutrons at a variety of doses and energies. Immediately after exposure, donor bone-marrow was removed from the hind legs, and standard amounts were injected intravenously into lethally X-irradiated recipients. After 7 days the recipients spleens were evaluated for surface colonies. Dose-response curves were obtained for each type of radiation and the Do was determined. The neutron r.b.e. values from the Do compared with 250kVp X-rays were: reactor 1.58, 252Cf 1:59, and accelerator varied from 2.85 at 1.0 Mev to 0.85 at 13.4 MeV.

Epidermal browning of saguaro cacti (Carnegiea gigantea): physiological effects, rates of browning and relation to sun/shade conditions

Abstract There has been increased morbidity of saguaro cacti (Carnegiea gigantea) in some portions of the Sonoran Desert. Injury to individual cacti is characterized by accumulations of epicuticular waxes that obstruct stomata and lead to eventual browning of surfaces. The purpose of this research was to determine physiological effects of obstructed stomata, rates of epidermal browning, and the relationship between epidermal browning and sun/shade conditions of stem surfaces. Nocturnal acid accumulation was positively correlated with visible stomatal density and negatively correlated with characteristics of epidermal browning. Numbers of chloroplasts per cell were higher for green cacti compared with yellow or browning stems. Over a two-year period, thickness of the green chlorenchyma decreased 1.8 mm while the thickness of internal discoloration increased 2.7 mm. Rib crest scaling and barking increased markedly along with a deterioration of spines and areoles over the period. Cacti with sun-exposed south-facing surfaces had 19% greater internal discoloration than cacti at least partially shaded by vegetation. On average, sun-exposed cacti had 20% more surface injuries on crests and trought on south-facing surfaces compared with similar surfaces of shaded saguaros. Results reported herein support the hypothesis that morbidity of some saguaros is occurring at a measurable rate and is related to sun exposure.

Quantitative Dose-response of Growth and Development in Arabidopsis Thaliana Exposed to Chronic Gamma-radiation

The response of Arabidopsis thaliana (L.) Heynh. (Cruciferae) to a gradient of chronic gamma-radiation was examined under field conditions. Plants that were initially introduced to the gamma field as dry seeds received exposures of 1-34 to 18 800 R/20 hour day from the time of seed germination. Regression analysis demonstrated a significant, but non-linear, response for three variables, number of seedlings emerging, number of plants flowering, and plant volume; the response of a fourth variable, number of leaves per plant, was not related to daily exposure. LD50 values ranged from 66 R/20 hour day for plant volume to 1231 R/20 hour day for seedling emergence. Flowering and plant volume were the most sensitive indicators of radiation exposure. The demonstration of a variable threshold at low levels of exposure indicates that in nature A. thaliana may be exposed to environmental radiation throughout its life-cycle without significant modification of growth or development.

Cerebral Glucose Transport Implies Individualized Glial Cell Function

Previous positron emission tomography (PET) measurements of cerebral glucose transport using [11C]-3-O-methylglucose (CMG) suggested an interindividual variation in the values of the rate constant of tracer outflow (k2) larger than that for the clearance rate of inflow (K1). These two parameters were examined in healthy cerebral cortex by dynamic PET in 4 men and 2 women (aged 24 to 73 years) without neurologic disease, and in 1 man (42 years) with a recent left hemispheric cerebral infarction under normoglycemia (average blood plasma d-glucose concentration, 5.44 ± 1.94 μmol/mL) and again under hyperglycemia (average, 10.24 ± 1.44 μmol/mL). Time-radioactivity curves were obtained from healthy cortex (grey matter) and plasma and analyzed for the values of K1 and k2 by two graphical approaches and two fitting procedures. Both K1 and k2 significantly declined with increasing plasma glucose levels. A highly significant interindividual but not intraindividual variability for k2 was found at normoglycemia and hyperglycemia. The interindividual variability of K1, although borderline significant, was less than that of k2. Accordingly variable were the distribution volumes K1 /k2. These data suggest individualized glial cell function and may be relevant to pathogenesis of neuropsychiatric disease.

Arabinofuranosyl nucleosides induce common fragile sites

SummaryThe capacities for fragile site induction of three inhibitors of semiconservative DNA synthesis and DNA repair synthesis, aphidicolin, arabinofuranosyl cytosine, and arabinofuranosyl adenosine were compared. Aphidicolin is known to induce type 4 fragile sites, the largest recognized group of common fragile sites. Although the modes of action of these inhibitors vary, both arabinofuranosyl analogs induce type 4 aphidicolin-sensitive fragile sites. An analysis of variance demonstrates that the three inhibitors are not equally capable of inducing significant breakage (P<0.01) at all type 4 fragile sites. Induction of type 4 fragile sites appears to be a general consequence of inhibition of DNA polymerization.