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Biomedical subjects

D J Reed

Publications and source records attributed to D J Reed.

At least 127 records · Page 7Linked to original sources
PubMed1980

A simple computerized system for plotting the locations of cells of specified sizes in a histological section.

A computerized plotting system is described which generates an outline of a histological section on an oscilloscope screen, and displays within its boundaries the positions of labeled neurons whose coordinates are sent to the computer electronically. Measured cell diameters can also be entered, allowing the computer to generate displays of the distributions of cells within specified size ranges. All data are saved by the computer, and any portion of a distribution may be examined oscilloscopically at several levels of magnification; moreover, three-dimensional displays may be generated wit appropriate programs.

Animals↗
PubMed1980

The effect of lithium on electrolyte transport by the in situ choroid plexus of the cat.

1. The effects of lithium on electrolyte transport were studied by using the cat choroid plexus isolated in a chamber in situ. 2. Lithium infused intravenously to produce plasma lithium concentrations up to 5 m-equiv/l. caused an increase in plasma magnesium with no effect on the concentration of magnesium in the chamber fluid. 3. When 22NaCl was infused intravenously the chamber fluid/plasma ratio of 22Na was nearly 1 in the first 30 min sample and at the steady state it was significantly greater than 1. 4. When lithium chloride (1.5 m-equiv/l.) or potassium chloride (6.6 m-equiv/l.) was added to the chamber at the start of a collection period with plasma 22Na in the steady state, the 22Na content of the chamber fluid promptly increased 118 and 68%, respectively, above the control value with no increase in secretory rate. 5. The addition of ouabain to the chamber fluid, in addition to the lithium chloride or potassium chloride, tended to stimulate or have no significant effect on 22Na uptake at a concentration of 10(-5) M and to reduce it as well as the secretory rate at 10(-3) M. 6. The date are compatible with there being two functionally separate sodium transport systems in the choroid plexus. One transports sodium accompanied by an anion and water to provide the fluid secreted into the chamber (c.s.f.) and the other operates primarily to regulate the potassium concentration of the c.s.f. by pumping potassium out in exchange for sodium. 7. Lithium can be transported by both systems to a limited extent and the presence of lithium in the c.s.f. stimulates the sodium-potassium regulating pump.

Animals↗
PubMed1979

Synthesis and identification of products derived from the metabolism of the carcinostatic 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea by rat liver microsomes.

Liver microsomal metabolism of 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea in the presence of reduced nicotinamide adenine dinucleotide phosphate and O2 was shown to produce seven metabolites that included the parent urea. A cytochrome P-450-dependent monohydroxylation of the cyclohexyl ring occurred in 3 positions, cis-3, trans-3, and cis-4, and on the methyl group to form a trans-4-hydroxymethyl derivative. In addition, monohydroxylation of the 2-chloroethyl carbon attached to the N-1 urea nitrogen yielded an alpha-hydroxy metabolite. A ring-hydroxylated derivative remained unidentified while the structures of all other such derivatives were established by comparison with compound synthesized, purified by high-pressure liquid chromatography, and characterized by mass spectral and nuclear magnetic resonance analyses. It was tentatively concluded that some parent urea is formed by a cytochrome P-450 dependent reaction because of a requirement for reduced nicotinamide adenine dinucleotide phosphate and inhibition by CO. Microsomes from rats pretreated with phenobarbital showed about a 3-fold increase in hydroxylation rate while phenobarbital-treated mice microsomes were induced 8-fold. However, in both species, the induced hydroxylation rate was about 4 nmol/min/mg protein. When microsomes from phenobarbital-induced rats were used, a mixture of 80% CO:20% O2 decreased the rate of formation of all metabolites to 14% of that in 80% N2:20% O2.

Animals↗
PubMed1978

The role of the cat choroid plexus in regulating cerebrospinal fluid magnesium.

1. The regulation of c.s.f. Mg concentration was studied using the cat choroid plexus isolated in a chamber in situ. 2. An increase in plasma Mg concentration was accompanied by the usual reciprocal decrease in plasma Ca concentration. Chamber fluid Ca concentration was unaffected. 3. Hypermagnesemia (plasma Mg concentration greater than 6 m-equiv/1.) caused relatively small increases in c.s.f. Mg concentration (delta plasma [Mg]/ delta c.s.f. [Mg] = 4). 4. Various chamber fluid Mg concentrations (0, 2.4 or 4.8 m-equiv/1.) were rapidly (within 30--60 min) returned to near the control value of 1.83 m-equiv/1. 5. When plasma and chamber fluid Mg concentrations were altered simultaneously, the final chamber fluid Mg concentration was returned towards normal with or against a concentration gradient. 6. The data indicate that the choroid plexus is involved in maintaining the constancy of the c.s.f. Mg concentration by sensing changes in the normal c.s.f. Mg concentration and altering approximately its rate of active secretion of Mg.

Animals↗
PubMed1977

Active site specific inactivation of chymotrypsin by cyclohexyl isocyanate formed during degradation of the carcinostatic 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea.

Prolonged incubation of 1-(2-chloroethyl)-3-([1-14C]cyclohexyl)-1-nitrosourea with chymotrypsin resulted in covalent modification and concomitant inactivation of chymotrypsin via degradation of the nitrosourea to form cyclohexyl isocyanate. Cyclohexyl isocyanate was shown to be an active-site-specific inactivator of chymotrypsin. A cyclohexyl isocyanate to enzyme molar ratio of 0.63 was required to produce 50% enzyme inactivation, thus demonstrating the high specificity of inactivation. At 2.38 X 10(-4) M chymotrypsin this near stoichiometric inactivation was not significantly affected by the presence of 1, 5, and 10 mM L-lysine. Degradation of an excess of 1-(2-chloroethyl)-3-([1-14C]-cyclohexyl)-1-nitrosourea in the presence of enzyme yielded 1.11 +/- 0.07 mol of covalently bound [14C]cyclohexyl moiety per mol of enzyme inactivated. Short-term incubation demonstrated that the nitrosourea neither inhibited nor protected the enzyme from cyclohexyl isocyanate inactivation. Treatment of chymotrypsin with less than stoichiometric amounts of cyclohexyl isocyanate or titration of the active-site serine with phenylmethanesulfonyl fluoride followed by in situ degradation of excess 1-(2-chloroethyl)-3-([1-14C]cyclohexyl)-1-nitrosourea resulted in a decreased amount of covalently bound 14C proportional to the extent of inactivation by these reagents prior to 14C labeling. These results strongly suggest that cyclohexyl isocyanate, whether added directly or generated by CCNU degradation, reacted almost exclusively with the active site of the enzyme. The extent of this inactivation indicates that 70% of the CCNU degraded in such a manner as to form cyclohexyl isocyanate.

Binding Sites↗
PubMed1977

A unique property of fetal bovine serum: high levels of protein-glutathione mixed disulfides.

Fetal bovine serum has been reported to delay or inhibit "spontaneous" neoplastic transformation in vitro as compared with all other sera tested. The present results indicate that fetal bovine serum is also unique in containing high levels of protein-glutathione mixed disulfides (3 to 7 microng glutathione as mixed disulfide per ml serum). The level of mixed disulfide appears to vary in accordance with the period of gestation of the fetal calves used to prepare the serum, decreasing below detectable levels (less than 0.2 microng per ml) with near-term fetal calves. Calf, adult bovine, fetal horse, and swine sera did not contain detectable levels of this type of mixed disulfide.

Animals↗