Variations of 3-hydroxybutyrate dehydrogenase activity in brain and liver mitochondria of the developing chick.

1. The 3-hydroxybutyrate dehydrogenase activity was estimated in the crude mitochondrial fraction isolated from the cerebral hemispheres, the optic lobes, the cerebellum and the liver of the chick between the 20th day of embryonic life and the 30th day of postnatal maturation. 2. The optimal conditions of liberation and of determination of 3-hydroxybutyrate dehydrogenase activity were studied in the mitochondrial fraction isolated from chick cerebral hemispheres and liver. 3. The subcellular distribution of the enzyme in the chick brain and liver is very different from that in the rat. 3-Hydroxybutyrate dehydrogenase is completely mitochondrial in the rat brain and liver whereas in the chick brain and liver, it is located in mitochondrial and microsomal fractions; moreover, a third component can even be found in the soluble fraction of chick liver. 4. The 3-hydroxybutyrate dehydrogenase activity reaches the same value in the three areas of 20-day-old chick embryo brain. Between this stage and the 4th day after hatching, it increases to reach the same peak in the three areas. This peak however, appears at different stages according to the considered brain area. At 30 days after hatching, the enzyme activity is higher in the cerebellum than in the cerebral hemispheres and optic lobes. 5. The activity of hepatic 3-hydroxybutyrate dehydrogenase is 10 to 20 times lower than in the brain. It does not significantly change between 1 day before and 4 days after hatching and increases 2-fold between 4 and 30 days after hatching. 6. The variations of 3-hydroxybutyrate dehydrogenase activity in chick brain indicate correlations of this enzyme activity with development, particularly related to the nutritional state of the chicks. The fairly important differences in the activity of 3-hydroxybutyrate dehydrogenase in the liver of the chick and the rat enable us to come to a better understanding of the regulation of the concentration of the different ketone bodies in the blood of the chick and the rat. Moreover, the presence of the microsomal component of 3-hydroxybutyrate dehydrogenase in chick brain probably originates in the low concentration of acetoacetate in chick blood.

On the mechanisms of 67Ga and 59Fe uptake by tumors.

The uptake of 67Ga-citrate and 59Fe-citrate in the presence or absence of gallium and iron carriers, was studied on DS-sarcoma-bearing rats. Differences of uptake pattern were observed with both radionuclides. The tumor uptake of 67Ga is greatly affected by both carriers while 59Fe uptake is independent of the presence of carriers. The role of isotopic dilution, ionic competition, and the probable presence of high and low affinity binding sites in this phenomenon are discussed.

Tumor uptake of high and low molecular weight fractions from 67Ga-citrate labelled blood plasma.

Blood plasma from tumor-bearing rats was incubated with 67Ga-citrate, and two fractions of high molecular weight (proteins) and low molecular weight were isolated by dialysis and by gel-filtration chromatography. Both fractions showed a different in vivo uptake by DS-sarcoma-bearing animals, the high molecular weight fraction being accumulated to a lesser extent. Compared to 67Ga-citrate the low molecular weight fraction showed a different uptake which for most tissues was significatively higher. This behavior suggests the presence of 67Ga in chemical forms other than citrate in the low molecular weight fraction. The lower uptake of the blood protein fraction is discussed.

Intracellular ionic changes during hyperthermia of tumor cells in the presence of lanthanum.

The experimental data suggest that permeability changes at the plasma membrane level are the most likely cause of the enhancement of tumor cell killing by hyperthermia in the presence of 1 mM La3+. The interaction of La3+ with the Na+, K+ ATPase and Ca2+-pump ATPase may be the probable cause of dramatic electrolyte changes which enhance the hyperthermia effects on tumor cells.

Comparative enhancement of hyperthermia lethality on tumor cells by procaine and lanthanum.

The effects of procaine and lanthanum during hyperthermia of tumor cells were studied by trypan-blue exclusion and by 86Rb release from previously labeled Ehrlich ascites cells. The results indicate that while procaine shows no changes of cell viability and 86Rb outflux, lanthanum alters both parameters in a very significant way.

Placenta, embryo, and tumor uptake of 67Ga-citrate and 59Fe-citrate.

The uptake of gallium citrate Ga67 and ferrous citrate Fe59 was studied in pregnant rats with or without a 4-dimethylamino-stilben(DS)-induced sarcoma tumor. The liver and placenta of the mother concentrated 67Ga, while the uptake of 67Ga in the embryo was minimal. However, the embryo showed higher concentrations of 59Fe. Preloading with iron did not affect the 67Ga uptake of the placenta, but increased the uptake in the blood and liver of the mother. With regard to 59Fe uptake, iron loading only affected the embryo liver. Tumors and the placenta showed a similar 67Ga uptake but a different incorporation of 59Fe. The probable mechanisms involved are discussed.

67Ga and 59Fe uptake by tumor cells treated with hyperthermia or hyperthermia plus lanthanum.

The uptake of 67Ga-citrate and 59Fe-citrate by tumor cells treated with hyperthermia or with hyperthermia plus lanthanum has been studied. The comparison of these results with ion flux determinations (42K) appears to indicate that hyperthermia alone or combined with lanthanum modifies the ionic permeability of the plasma membrane. This phenomenon seems to be responsible for the increased accumulation of 67Ga and 59Fe.

Enhancement of hyperthermia lethality by Lanthanum.

The authors have studied the effects of La3+ during hyperthermia on tumor cells, Trypan blue exclusion and 86Rb release from previously labeled Ehrlich and DS carcinosarcoma ascites cells, indicate an increase of plasma membrane permeability by La3+ as a function of the hyperthermic level. The enhancement of hyperthermia lethality by concentration of Lanthanum over 0.5 mM after 2 hours at 44 degrees C has been demonstrated on HeLa S3 cells using a well known cloning technique. In vivo experiments have been performed on Rhabdomyosarcoma C3H bearing mice using an ultrasound heating technique at 44-46 degrees C. The preliminary in vivo results show a remarkable tumor growth inhibition and a significant increase of the survival time after only one hyperthermia treatment of 30 minutes combined with one intratumoral injection of 1 mM lanthanum. The control animal groups treated by hyperthermia alone or by lanthanum alone don't show any differences of the tumor volume evolution in comparison with untreated animal groups.

Mineral metabolism and in vivo uptake of [67 Ga]citrate.

The uptake of [67 Ga]citrate by normal rats of different ages has been compared with the mineral composition of the assayed tissues. Very young animals take up much more 67 Ga than the adults and there seems to be a correlation between the mineral composition (calcium, magnesium and iron) and the radioactivity uptake. The role of those elements and of cellular proliferation in this phenomenon is discussed.