Testosterone alters duodenal calcium transport and longitudinal bone growth rate in parallel in the male rat.

Duodenal active calcium transport and longitudinal bone growth rate have been shown previously to be regulated in parallel by alteration of gonadal hormone status in sexually maturing female rats. The present study was designed to extend these observations to the sexually maturing male rat. Male rats were orchidectomized (ORX) and given Silastic implants containing either testosterone or estradiol at 6 weeks of age. At 9 weeks of age, duodenal active calcium transport was measured by the everted gut sac method and longitudinal bone growth rate was determined by tetracycline labeling. Decreases in body weight, longitudinal bone growth rate, duodenal calcium transport, and serum Ca and P were exhibited by ORX animals as compared with age-matched control animals. Testosterone administration to ORX animals resulted in an increase in body weight, longitudinal bone growth rate, duodenal calcium transport, and serum Ca and P as compared with ORX animals to a level not significantly different from that of age-matched control animals. Estradiol administration to ORX animals resulted in an additional decrease in body weight, although no significant effect on duodenal calcium transport, serum Ca, or P was noted as compared with ORX animals. There were no statistically significant alterations in the circulating levels of 1,25-dihydroxyvitamin D, parathyroid hormone, or osteocalcin in response to any of the experimental manipulations of gonadal status. These results indicate that, as in the female, gonadal hormone status affects intestinal calcium transport in sexually maturing male rats in parallel with changes in bone growth rate by mechanisms that are independent of circulating levels of 1,25-dihydroxyvitamin D.     

Quantitation of mitochondrial injury in cultured rat heart endothelioid cells with nitroblue tetrazolium

Synopsis A sensitive method is presented for measurement of changes in the permeability of mitchondria in cultured cells. Rat heart endothelioid cells were used to determine the penetration rate of nitroblue tetrazolium (NitroBT) or other reactants into mitochondriain situ. Nitroblue formazan, produced as a consequence of succinate dehydrogenase activity in the mitochondria, was eluted and measured with a spectrophotometer. Prior injury of cells with hypo-osmolar solutions increased the rate of formazan production. Several methods are described or suggested for the statistical analysis of the data.     

Why Doesn't the Creed Read "Always Be Critical"? An Examination of a Liberal Curriculum

Using ethnographic data collected in a second grade classroom over the course of a school year, this paper describes the ways in which one school's discourse of liberalism is deleteriously deployed. We view the school's discipline creed as emblematic of the school's liberal curriculum, and interrogate the effects on four African American boys in the classroom when the school enacts this creed. Despite the agency that these boys obviously had, they were unable to control the ways in which they were placed at a structural disadvantage and manipulated by a system far more powerful than they were. The results were that these four boys suffered. Not only did the intended liberal curriculum fail to be translated fully into the enacted curriculum, the liberal underpinnings of this curriculum precluded teachers and students from taking any critical stance.     

Brain Metabolism and Intracellular pH During Ischaemia and Hypoxia: An In Vivo 31P and 1H Nuclear Magnetic Resonance Study in the Lamb

Brain metabolism and intracellular pH were studied during and after episodes of ischaemia and hypoxia-ischaemia in lambs anaesthetised with sodium pentobarbitone. 31P and 1H magnetic resonance spectroscopy methods were used to monitor brain pHi and brain concentrations of Pi, phosphocreatine (PCr), beta--nucleoside triphosphate (beta NTP), and lactate. Simultaneous measurements were made of cerebral blood flow and cerebral oxygen and glucose consumption. Cerebral ischaemia sufficient to reduce oxygen delivery to 75% of control values was associated with a fall in brain pHi and increase in brain Pi. Progressively severe hypoxia-ischaemia was associated with a progressive fall in brain pHi, PCr, and beta NTP and increase in brain Pi. In two animals the increase in brain lactate during hypoxia-ischaemia measured by 1H nuclear magnetic resonance (NMR) could be quantitatively accounted for by the increased net uptake of glucose by the brain in relation to oxygen, but was insufficient to account for the concomitant acidosis according to previous estimates of brain buffering capacity. In four animals brain pHi, PCr, Pi, and beta NTP had returned to normal 1 h after the hypoxic-ischaemic episode. In one animal brain pHi had reverted to normal at a time when 1H NMR indicated persistent elevation of brain lactate.     

Lipid asymmetry induced by transmembrane pH gradients in large unilamellar vesicles

We have investigated the influence of transmembrane pH gradients across large unilamellar vesicle membranes on the transbilayer distributions of simple lipids with weak base and weak acid characteristics. Trinitrobenzenesulfonic acid labeling results consistent with a rapid and complete migration of stearylamine and sphingosine to the inner monolayer of the large unilamellar vesicles are observed when the large unilamellar vesicles' interior is acidic. Alternatively, when the vesicle interior is basic, oleic and stearic acid cannot be removed by external bovine serum albumin, indicating a localization in the inner monolayer. Moreover, effects corresponding to the decrease in external surface charge predicted upon the migration of stearylamine or stearic acid to the inner monolayer are readily detected employing ion exchange chromatography. These results are consistent with transbilayer distributions of these agents dictated by a Henderson-Hasselbach equilibrium. The possible implications for metabolic regulation by pH gradients, as well as factors giving rise to phospholipid transbilayer asymmetry, are discussed.     

Auxin activity of phenylacetic acid in tissue culture

The ability of phenylacetic acid (PAA), a naturally occurring auxin, to initiate and support growth of callus and suspension cultures of several species is reported. Callus tissue of tobacco (Nicotiana tabacum L. var. WI-38), initiated and maintained on a medium with 2,4-dichlorophenoxyacetic acid (2,4-D), was transferred to and maintained on media supplemented with 25–500 M PAA as the only plant growth regulator (PGR). Optimal concentrations of PAA were determined for tobacco callus proliferation in the dark (250 M PAA) and with a 16-h light/8-h dark photoperiod (500 M PAA). Tobacco suspension cultures were maintained for over 28 transfers in media containing 20–40 M PAA as the sole PGR. When tobacco callus tissue maintained on PAA-supplemented media for over 18 months was transferred to liquid media containing kinetin, plantlets were regenerated. Callus of sunflower (Helianthus annuus L. var. Russian Mammoth) proliferated on media containing PAA at 5–250 M as the sole PGR. Similar PAA concentrations inhibited normal development and promoted callus formation in tobacco and pea (Pisum sativum L. vars. common, Frogel, and Frimas) epicotyl tissue. PAA as the sole PGR did not support the growth of soybean (Glycine max (L.) Merrill var. Fiskeby) callus or suspension cultures. Chickpea (Cicer arietinum L. var. UC-5) and lentil (Lens culinaris Medic. var. Laird) callus cultures proliferated on media containing 25–500 M PAA, but habituation of the cultures was common. PAA was not toxic to tobacco, chickpea, and lentil tissues at levels as high as 500 M.Paper No. 88514 of the Journal Series of the Idaho Agricultural Experiment Station, Moscow, Idaho, USA.     

Auxin activity of phenylacetic acid in tissue culture

The ability of phenylacetic acid (PAA), a naturally occurring auxin, to initiate and support growth of callus and suspension cultures of several species is reported. Callus tissue of tobacco (Nicotiana tabacum L. var. WI-38), initiated and maintained on a medium with 2,4-dichlorophenoxyacetic acid (2,4-D), was transferred to and maintained on media supplemented with 25–500 μM PAA as the only plant growth regulator (PGR). Optimal concentrations of PAA were determined for tobacco callus proliferation in the dark (250 μM PAA) and with a 16-h light/8-h dark photoperiod (500 μM PAA). Tobacco suspension cultures were maintained for over 28 transfers in media containing 20–40 μM PAA as the sole PGR. When tobacco callus tissue maintained on PAA-supplemented media for over 18 months was transferred to liquid media containing kinetin, plantlets were regenerated. Callus of sunflower (Helianthus annuus L. var. Russian Mammoth) proliferated on media containing PAA at 5–250 μM as the sole PGR. Similar PAA concentrations inhibited normal development and promoted callus formation in tobacco and pea (Pisum sativum L. vars. common, Frogel, and Frimas) epicotyl tissue. PAA as the sole PGR did not support the growth of soybean (Glycine max (L.) Merrill var. Fiskeby) callus or suspension cultures. Chickpea (Cicer arietinum L. var. UC-5) and lentil (Lens culinaris Medic. var. Laird) callus cultures proliferated on media containing 25–500 μM PAA, but habituation of the cultures was common. PAA was not toxic to tobacco, chickpea, and lentil tissues at levels as high as 500 μM.