The ferritin content of human red blood cells during the replacement of embryonic cells by fetal cells

Mature human embryonic erythrocytes (hemoglobin is ≥ 90% of the cellular protein) contained at least 20 times as much ferritin as human adult erythrocytes, suggesting the possibility that the embryonic red cells participate in iron storage as they do in other embryonic or larval vertebrates. The ferritin content of mature red cells in the circulation declined when fetal red cells replaced embryonic red cells; the cell replacement was monitored by the disappearance of embryonic ε-chains and the appearance of the fetal globin chains, γ^A and γ^G. A constant ratio of 0.67 was obtained for $\text{γ}{}^{\mathrm{<mtext>G</mtext>}}\text{γ}{}^{\mathrm{<mtext>A</mtext>}}\text{+ γ}{}^{\mathrm{<mtext>G</mtext>}}$ from the first detectable appearance (4 weeks after conception) until 13 weeks, a value which is similar to the value previously obtained at 20 weeks gestation and birth but higher than that observable in adults; thus, both γ^G and γ^A chains are produced in similar amounts throughout gestation. The high levels of ferritin in normal human embryonic erythrocytes emphasize the similarity of erythropoiesis in human embryos and other vertebrates. In addition, the results show that red cell ferritin can be used as a marker for studying the mechanism of induction of embryonic erythropoiesis in cultured cell lines, such as K562 from human chronic myelocytic leukemia, and that ferritin content may also serve as a marker for cellular transformations involving reversions to embryonic erythropoiesis.     

The effect of pressure on the photochemistry of tris(bipyridyl)chromium(III) ion

The quantum yield for the photoaquation of Cr(bpy)₃³⁺ in basic medium decreases with increasing pressure, with an apparent volume of activation of 3.8 ± 1.0 ml mol⁻¹. From this value and that associated with the phosphorescence lifetime, the volumes of activation for non-radiative decay to the ground state and for formation of photoproduct are derived as −1.6 and +2.9 ml mol⁻¹, respectively. The latter value is consistent with either an associative process with water entering from pockets between the ligands or a dissociative process involving one or both bonds to a bipyridyl ligand.     

Effect of axially coordinated pi-acid ligands on photovoltaic properties of Zn-tetraphenylporphyrin

Following our earlier observations that the well known doping effect of oxygen and water on electrical properties of porphyrin and phthalocyanine films may be attributed to a pi-acid axial interaction throughout the film in the case of PdTPP, we have compared Zn-TPP films supported on transparent n-doped SnO₂ electrodes which had been treated with several pi-acids in contact with an electrolyte to give photoelectrochemical cells. Photovoltages obtained in contact with a series of solution couples were used to obtain approximate photo flat band potentials. The doped films were examined by magnetic circular dichroism (MCD) spectroscopy so that the electronic effect of the dopant could be diagnosed. It was found that pi-acid dopants cause shifts to low energy in the band which indicates “hole stabilization” in the order pyridine < CO < triphenylarsine. The potentials of zero photopotential ‘E_FB’, correlate approximately with spectral shifts. It is concluded that manipulation of axial ligand dopants is a promising method for design of metal porphyrin and perhaps phthalocyanine films with desired photovoltaic properties.     

Effect of ppGpp on the accuracy of protein biosynthesis

The maintenance of accuracy in protein biosynthesis in amino acid-starved rel+ strains of Escherichia coli has been attributed to an effect of ppGpp on the accuracy of aa-tRNA selection by the ribosome. It has been determined that concentrations of ppGpp characteristic of those found in amino acid-starved cells have no effect on the rate of reaction of poly(U)-programmed ribosomes with either the cognate (Phe) or the near-cognate (Leu2) ternary complexes. Neither the rate of GTP hydrolysis, which signals selection of the ternary complex, nor the rate of peptide formation, which signals the acceptance of the aa-tRNA after proofreading, is affected by the nucleotide. The results indicate that the effect of ppGpp in maintaining the accuracy of protein biosynthesis in cells starved for an amino acid is not due to a direct effect on the rate constants for substrate selection by the ribosome.     

Tyrosine administration decreases serum prolactin levels in chronically reserpinized rats

The injection of tyrosine, 200 mg/kg, decreased serum prolactin levels and elevated hypothalamic (and striatal) concentrations of two dopamine metabolites, dihydroxyphenylacetic acid and homovanillic acid, in chronically reserpinized rats. Tyrosine administration had none of these effects in otherwise untreated rats, and did not block the increase in serum prolactin that occurred 4 hours after a single injection of reserpine. As anticipated, the injection of dopa decreased serum prolactin in all rats. Valine, another large neutral amino acid, did not modify serum prolactin in chronically reserpinized animals. Since prolactin secretion is normally inhibited by dopamine released from the hypothalamus, reserpine treatment probably elevates serum prolactin by depleting the hypothalamus of dopamine. Our data suggest that tyrosine injection suppresses serum prolactin levels in chronically reserpinized rats by enhancing the synthesis and release of hypothalamic dopamine. Thus, administration of tyrosine, dopamine's dietary precursor, can alter physiologic functions that depend on dopamine.     

Effects of vitamin E, ascorbic acid and mannitol on alloxan-induced lipid peroxidation in rats

ω6- and ω3-unsaturated lipid hydroperoxides decompose to yield pentane and ethane, respectively. Alloxan toxicity was studied in rats in relation to pentane and ethane produced during lipid peroxidation induced by intraperitoneal injection of 20 mg of alloxan/100 g body wt. Fifteen minutes after injection, vitamin E-deficient rats exhaled 102- and 11.2-fold more pentane and ethane, respectively, than prior to injection. Injection of 75 mg ascorbic acid/100 g body wt 30 min prior to alloxan treatment prolonged the time over which peroxidation occurred and all vitamin E-deficient rats died before 4 h. Vitamin E-deficient rats injected with 100 mg of the radical scavenger mannitol/ 100 g body wt 30 min prior to alloxan treatment were completely protected against lipid peroxidation, and none of the rats died by 4 h. Rats fed 40 iu dl-α-tocopherol acetate/kg diet or injected with 100 mg dl-α-tocopherol/100 g body wt were either totally protected against alloxan and alloxan-ascorbic acid-induced peroxidation or were only slightly affected as shown by very low-level pentane and ethane production. Thiobarbituric acid reactants in plasma, liver and pancreas 4 h after alloxan treatment reflected the prooxidant nature of ascorbic acid and alloxan, the vitamin E status of the rats and the protective effect of mannitol. Plasma glucose levels 4 h after alloxan injection were lowest in vitamin E-injected rats and highest in vitamin E-deficient rats. Only in vitamin E-deficient rats were both lipid peroxidation and significantly elevated plasma glucose levels observed by 4 h post-alloxan treatment.     

Effects of stress on release of dopamine and serotonin in the striatum of spontaneously hypertensive rats: an in vivo voltammetric study

By use of in vivo voltammetry technique, in vivo release of dopamine and serotonin in the striatum under stress was found to be more prominent in spontaneously hypertensive rats (SHR) at 4 weeks of age than in control Wistar-Kyoto rats (WKY). Simultaneously, a greater activation of tyrosine hydroxylase in the striatum was demonstrated in SHR than in WKY. These results indicate that SHR is more susceptible to stress in the central monoaminergic neurons than WKY.     

Metabolic alterations in skeletal muscle of chronically streptozotocin-diabetic rats

This study was accomplished to determine the effects of chronic streptozotocin diabetes and insulin treatment on selected enzymes and substrates used in energy transduction in muscles composed of different muscle fiber types. Triglyceride concentration in all the muscles of diabetic rats was significantly elevated. Glycogen and protein concentrations were unchanged. The enzyme activities of hexokinase and alanine aminotransferase were significantly reduced and 3-hydroxyacyl-CoA dehydrogenase increased in all the muscles. Declines in phosphofructokinase, lactate dehydrogenase, citrate synthase, and succinate dehydrogenase activities were found in the red gastrocnemius and plantaris. Glycerol-3-phosphate dehydrogenase activity was lower than normal in the red gastrocnemius. Insulin treatment to the diabetic rats returned the altered triglyceride content and enzyme activities to normal, with exception of the lower alanine aminotransferase activity in the red gastrocnemius and plantaris. However, this enzyme was significantly ameliorated when compared with the untreated diabetic rats. The findings show that hypoinsulinism has a differential effect on the enzymatic profile of the different skeletal muscle fiber types, with those of the red gastrocnemius being most severely affected. Insulin treatment returned the enzymatic profile of the fiber types in diabetic rats to essentially normal.     

Metal ion-tetracycline interactions in biological fluids. Part 4. Potential influence of ca2+ and mg2+ ions on the bioavailability of chlortetracycline and demethylchlortetracycline,as expected from their computer-simulated distributions in blood plasma

Coordination of tetracydines with calcium and magnesium was previously shown to exert a determining effect on the distribution of these antibiotics in blood plasma. In particular, it was clearly established by computer simulation that the free fraction of the drug is quite negligible with respect to its metal-bound fraction. The bioavailabiity of a tetracycline in blood plasma is thus expected to depend directly on the electrical charge of its predominant metal complexes in the biofluid. On account of the metal to ligand ratio corresponding to the usual therapeutic levels, bioavailability is critically sensitive to the property of the antibiotic to give rise to electrically charged binuclear species. The blocking of one of the two potential binding sites of the tetracycline molecule should thus result in a larger percentage of neutral complexes, hence in a better tissue penetration by the drug.The present work is devoted to the investigation of the coordination of 7-chlortetracycline (CTC) and 6-demethyl-7-chlortetracycline (DMC) with calcium and magnesium in blood plasma. The influence of the chloro substituent is discussed with respect to the objective defined above.     

Purification of characterization of a minor form of hepatic microsomal cytochrome P-450 from rats treated with polychlorinated biphenyls

A minor form of hepatic microsomal cytochrome P-450 has been purified to apparent homogeneity from rats treated with the polychlorinated biphenyl mixture, Aroclor 1254. This newly isolated hemoprotein, cytochrome P-450_e, is inducible in rat liver by Aroclor 1254 and phenobarbital, but not by 3-methylcholanthrene. Two other hemoproteins, cytochromes P-450_b and P-450_c, have also been highly purified during the isolation of cytochrome P-450_e based on chromatographic differences among these proteins. By Ouchterlony double-diffusion analysis with antibody to cytochrome P-450_b, highly purified cytochrome P-450_e is immunochemically identical to cytochrome P-450_b but does not cross-react with antibodies prepared against other rat liver cytochromes P-450 (P-450_a, P-450_c, P-450_d) or epoxide hydrolase. Purified cytochrome P-450_e is a single protein-staining band in sodium dodecyl sulfate-polyacrylamide gels with a minimum molecular weight (52,500) slightly greater than cytochromes P-450_b or P-450_d (52,000) but clearly distinct from cytochromes P-450_a (48,000) and P-450_c (56,000). The carbon monoxide-reduced difference spectral peak of cytochrome P-450_e is at 450.6 nm, whereas the peak of cytochrome P-450_b is at 450 nm. Ethyl isocyanide binds to ferrous cytochromes P-450_e and P-450_b to yield two spectral maxima at 455 and 430 nm. At pH 7.4, the 455:430 ratio is 0.7 and 1.4 for cytochromes P-450_b and P-450_e, respectively. Metyrapone binds to reduced cytochromes P-450_e and P-450_b (absorption maximum at 445–446 nm) but not cytochromes P-450_a, P-450_c, or P-450_d. Metabolism of several substrates catalyzed by cytochrome P-450_e or P-450_b reconstituted with NADPH-cytochrome c reductase and dilauroylphosphatidylcholine was compared. The substrate specificity of cytochrome P-450_e usually paralleled that of cytochrome P-450_b except that the rate of metabolism of benzphetamine, benzo[a]pyrene, 7-ethoxycoumarin, hexobarbital, and testosterone at the 16α-position catalyzed by cytochrome P-450_e was only 15–25% that of cytochrome P-450_b. In contrast, cytochrome P-450_e catalyzed the 2-hydroxylation of estradiol-17β more efficiently (threefold) than cytochrome P-450_b. Cytochrome P-450_d, however, catalyzed the metabolism of estradiol-17β at the greatest rate compared to cytochromes P-450_a, P-450_b, P-450_c, or P-450_e. The peptide fragments of cytochromes P-450_e and P-450_b, generated by either proteolytic or chemical digestion of the hemoproteins, were very similar but not identical, indicating that these two proteins show minor structural differences.     

Effect of alkali-treated rice straw supplemented with spent tea leaf and thyroprotein on milk yield,milk composition and certain physiological parameters of dairy cows

Thirty-six Friesian cows in mid-lactation were used to compare the effects of nine treatments.Rice straw untreated (US), or treated with 40 g NaOH in 1.5 l H₂ O kg^?1 straw (TS), was given ad libitum with a concentrate mixture containing 0 or 20% spent tea leaf (STL₀ and STL₂₀) and with or without thyroprotein (TP₁₀ or TP₀). The control treatment (C) represented the standard feeding practice adopted on the farm.The NaOH treatment increased milk yield by 22%, but lowered the butterfat content of milk by 6%. Milk yield and milk composition were not affected by spent tea leaf supplementation. Thyroprotein had no significant effect on milk yield or composition during the experimental period but depressed yield significantly after its withdrawal from the diet. It increased rectal temperature by 0.5° C and heart rate by 5 beats min^?1. All animals on thyroprotein lost body condition.It is concluded that alkali-treated straw is a suitable source of roughage for low yielding cows but its use in practice may be uneconomic. Spent tea leaf is a suitable source of protein for ruminants at the 8% level of substitution in the total diet DM. Thyroprotein feeding is not economical under Sri Lanka conditions and is not recommended for animals on straw diets.     

The effect of dietary fat on the activity,content, rates of synthesis,and degradation and translation of messenger RNA coding for malic enzyme in mouse liver

The specific activity (units activity/mg cytosolic protein) of malic enzyme was found to be three-fold higher in the livers of mice fed a semipurified diet containing 50% ($\text{w}\text{w}$) glucose and 15% ($\text{w}\text{w}$) saturated and monounsaturated but no polyunsaturated fat (hydrogenated cottonseed oil) over an 11-day period than in the livers of mice fed a standard laboratory mouse chow (Purina) diet. In contrast, when other lab chow-fed mice were fed an isocaloric diet containing 15% ($\text{w}\text{w}$) polyunsaturated fat (corn oil), no change in the specific activity of malic enzyme occurred over a similar period of time. Rocket immunoelectrophoresis performed on cytosols from both dietary groups demonstrated that the livers of mice consuming the hydrogenated cottonseed oil diet contained approximately three times more malic enzyme protein than did the livers from the corn oil-fed animals. In mice pulse-labeled with l-[4,5-³H]leucine, the rate of hepatic malic enzyme synthesis (relative to that for total protein) was approximately twofold greater in the hydrogenated cottonseed oil-fed mice than in their corn oil-fed counterparts whereas the rate of hepatic malic enzyme degradation was similar for both groups. Immunotitration of liver malic enzyme from hydrogenated cottonseed oil-fed and corn oil-fed mice revealed identical equivalence points, demonstrating that the catalytic efficiency of mouse liver malic enzyme had not been affected by the type of dietary fat administered. When total liver RNA, isolated from the hydrogenated cottonseed oil- and the corn oil-fed animals, was translated in cell-free translation systems (wheat germ extract and reticulocyte lysate) we found that both dietary treatments had resulted in an increase in the activity of malic enzyme messenger RNA. Furthermore, there were no significant differences between the two dietary groups in this regard. These results suggest that hepatic malic enzyme specific activity in high-carbohydrate polyunsaturated fat-fed mice is regulated principally by dietary-induced changes in the rate of enzyme synthesis and not by the activity of messenger RNA coding for the enzyme.     

Effect of adenosylhomocysteine and other analog thioethers on a prokaryotic tRNA (guanine-7)-methyltransferase

S-Adenosylhomocysteine (SAH), a potent inhibitor of methyltransferases, and several thioethers structurally related to SAH, have been tested as potential inhibitors of tRNA (guanine-7)-methyltransferase from Salmonella typhimurium. The tested compounds are l-, d-, dl-S-adenosylhomocysteine, S-adenosylcysteine, methylthioadenosine, butylthioadenosine, thioethanoladenosine, isobutylthioadenosine, S-inosylhomocysteine, and methylthioinosine. Among them the highest inhibitory activity has been shown by SAH (K_i = 8 μM), whereas butylthioadenosine, isobutylthioadenosine, and thioethanoladenosine are almost inactive as inhibitors. The other compounds inhibit the enzyme with K_i values ranging between 400 and 800 μm. From these data it is possible to evaluate the importance of the -NH₂ and -COOH groups of the substrate in the binding to the enzyme molecule, as well as other features such as the chirality at the α-carbon atom and the length of the hydrocarbon chain connecting the -NH₂ and -COOH groups to the aromatic ring of adenosine. The aminic group of the adenosine is also critical, because S-inosylhornocysteine and methylthioinosine are poorer inhibitors in comparison with SAH and methylthioadenosine.     

Is vitamin E the only lipid-soluble,chain-breaking antioxidant in human blood plasma and erythrocyte membranes?

The concentration of lipid-soluble, chain-breaking antioxidants in human plasma and in erythrocyte ghosts have been determined for the first time by an inhibited-autoxidation method. The results are very similar to the concentrations of vitamin E measured for the same blood components by the HPLC method. It is concluded that vitamin E, which is largely present as alpha-tocopherol, is the only significant lipid-soluble, chain-breaking type of antioxidant present in human blood. The concentration of vitamin E in the plasma lipids divided by the concentration of vitamin E in the ghost membrane lipids is approximately a constant despite the large differences in vitamin E-intake and in plasma lipid concentrations in different individuals. Vitamin E/lipid ratios for plasma and ghosts were larger for subjects taking a supplement of alpha-tocopherol acetate of 100 IU per week, compared to nonsupplemented subjects (based on data from a limited number of subjects). A larger supplement of 2800 IU per week did not significantly increase the vitamin E/lipid ratios.     

NADP-linked 15-hydroxyprostaglandin dehydrogenase for prostaglandin D2 in human blood platelets

Two forms of NADP-linked 15-hydroxyprostaglandin dehydrogenase for prostaglandin D₂ were found in the cytosol fraction of human blood platelets. These enzymes were purified by ammonium sulfate fractionation, Blue Sepharose, and Sephadex G-100 column chromatography. The two enzymes differed in molecular weights (65,000 for peak I enzyme and 31,000 for peak II as estimated by gel filtration) and their substrate specificities. The relative rates for reaction with peak I enzyme were: prostaglandin D₂, 100(%); E₂, 14; F_2α, 2; I₂, 29; and B₂, 0; whereas for peak II enzyme, D₂, 100; E₂, 23; F_2α, 61; I₂, 29; and B₂, 131. Prostaglandin D₂ was converted to 15-ketoprostaglandin D₂ and then 13,14-dihydro-15-ketoprostaglandin D₂, which were identified by spectrophotometry and gas chromatography/mass spectrometry, respectively. These metabolites were three orders of magnitude less potent in inhibiting human platelet aggregation than prostaglandin D₂. The results indicated that NADP-linked dehydrogenases participated in the metabolic inactivation of prostaglandin D₂ in the platelets. Furthermore, the dehydrogenase activity for prostaglandin D₂ was high in monkey (0.128 nmol/min · mg at 24 °C) and human platelets (0.066), but was not detectable (less than 0.007) in the rabbit, rat, and chicken. Because prostaglandin D₂, which was demonstrated by several authors to be synthesized in platelet-rich plasma during platelet aggregation, exhibited significant antiaggregatory activity only in human and monkey platelets, these prostaglandin dehydrogenases appear to play a physiological role in the circulatory system.     

Studies on base-exchange reactions of phospholipids in rat brain particles and a "solubilized" system.

A filtration-method on Millipore-membranes for the assay of the base-exchange reaction was described. Its advantage over the usual procedure based upon the extraction and the washing of lipids was discussed with the viewpoint of processing many samples, which would be indispensable for purifying the enzyme.The reaction showed an absolute dependency for calcium ion with different optimal concentrations for each of the three bases, a sensitivity to inhibition by high ionic strength, and a pH optimum around 9.0. Exogenously added phospholipid, asolectin, gave a slight stimulation for ethanolamine and l-serine incorporation at a low concentration while choline incorporation was essentially inhibited at all concentrations examined. In heat-denaturation experiments with the particulate and soluble the incorporation of choline into lipid was more sensitive than that of ethanolamine and l-serine. A developmental study showed that brain particles sedimenting between 10,000 and 35,000g prepared from rats aged 22–27 days readily incorporated ethanolamine, l-serine, and choline into their corresponding phosphatidyl compound.Several procedures for solubilization of the “base-exchange” enzyme were examined. The most effectively solubilized preparation was obtained by the use of an ionically balanced detergent, Miranol H2M. This preparation showed a marked dependency on exogenously added phospholipids for its maximal enzymic activity, had a pH optimum at around 7.2, and had an absolute requirement for Ca²⁺. This particular detergent at a concentration of 1% ($\text{w}\text{v}$) solubilized approximately 50% of the protein, and about 30% of the phospholipids, 40% of the cerebrosides, and only 11% of the cholesterol originally present in the particles. The relative proportions of different phospholipids solubilized by the detergent were, however, similar to those present in the original particles.The base-exchange reaction catalyzed by the solubilized enzyme was found to be highly sensitive to ionic strength, and the inhibitory effect of a specific monovalent cation paralleled its ionic size. Substantial differences in the K_m value for each of the substrates with only slight differences in V were observed.The choice of solubilizing agents in relation to these properties and to the maintenance of the activity of the base-exchange reaction was discussed.     

Molecular properties and odour. Effects of substituents on pyridine and pyridine odour

It is investigated how the odour of pyridine changes when substituents of different kinds are inserted on the pyridine ring. The relation between the space filling and electronic properties of molecules and odour is studied. Far infrared spectra have been recorded for pyridines in order to test a hypothetical correlation between odour and vibrational energies.     

An effect of codon context on the mistranslation of UGU codons in vitro

Effects of codon context on nonsense codon suppression may act either through release factor recognition of termination codons or aminoacyl-tRNA selection by the ribosome. The latter hypothesis has been studied by comparing misreading by Escherichia coli UGA suppressor tryptophan tRNA of UGU (cysteine) codons in two synthetic polymers, poly(U-G) and poly( U5 , G), which differ in sequence around the UGU codons. In vitro translation of these polymers in a cell-free system from E. coli yielded selection errors of 4 X 10(-3) and 1.75 X 10(-2) for UGU codons in poly(U-G) and poly( U5 , G), respectively. This difference suggests that codon context may significantly affect misincorporation of amino acids into protein.     

Effects of solvent and ionic medium on the kinetics of axial ligand substitution in vitamin B12. Part IV. The reaction between aquocobalamin and the thiocyanate ion in acetonitrile-water mixtures

The rate constants for the reaction of aquocobalamin with the thiocyanate ion were measured as a function of ionic strength and solvent composition in acetonitrile-water mixtures. The reaction is described by a two-step mechanism: the ligation reaction, where the most stable isomer (S-bonded) is formed and the isomerisation reaction (S-bonded to N-bonded thiocyanate). For the ligation reaction a full quantitative analysis of solvent effects could be performed, whereas for the isomerisation reaction only qualitative observations were made. The equilibrium constant for the isomerisation (S-bonded/N-bonded) is large and does not change with the solvent composition. It is found that the transfer Gibbs energies of activation for the ligation reaction are the same as found for the ligand thiourea. The absence of a solvent effect on the isomerisation reaction is a further example of the ability of vitamin B₁₂ to create its own micro environment.