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Evaluation of 4'-[methyl-14C]thiothymidine for in vivo DNA synthesis imaging.

UNLABELLED: We evaluated 4'-[methyl-11C]thiothymidine ([methyl-11C]S-dThd) to obtain a thymidine analog that might prove simpler to use for imaging DNA synthesis and that might follow the same biochemistry as its surrogate. METHODS: [Methyl-14C]S-dThd was synthesized by rapid methylation of 5-trimethylstannyl-4'-thio-2'-deoxyuridine via a palladium-mediated Stille coupling reaction with 14C-methyl iodide. Degradation of [methyl-14C]S-dThd, when incubated in human blood, was analyzed by high-performance liquid chromatography (HPLC). The in vivo potential of [methyl-14C]S-dThd was evaluated by studying its distribution in EMT-6 mammary carcinoma-bearing mice. 2-Fluoro-2'-deoxycytidine, a potent inhibitor of DNA synthesis, was used to modulate cell proliferation. Tissue extraction was also performed to investigate the incorporation of [methyl-14C]S-dThd into DNA. RESULTS: [Methyl-14C]S-dThd was obtained in a 31%-41% radiochemical yield (calculated from 14C-methyl iodide) at 130 degrees C, 5-min reaction in N,N-dimethylformamide followed by semipreparative HPLC purification. The radiochemical purity of [methyl-14C]S-dThd was >99% and the specific activity was 2.04 GBq/mmol (according to the specific activity of 14C-methyl iodide). [2-14C]Thymidine, when incubated with human blood, demonstrated rapid degradation. In contrast, [methyl-14C]S-dThd was stable with <3% degradation at 60 min. An in vivo distribution study showed the accumulation of radioactivity in proliferating tissues (spleen, thymus, duodenum, and tumor). On the other hand, the radioactivity of nonproliferating tissues (lung, liver, kidney, and muscle) was rapidly cleared in parallel with the clearance of blood radioactivity. The tumor uptake of [methyl-14C]S-dThd was high (8.8 percentage injected dose per gram at 60 min) and selective (tumor-to-blood ratio, 12.2 at 60 min). 2-Fluoro-2'-deoxycytidine pretreatment significantly reduced the tumor uptake of [methyl-14C]S-dThd. Relative blood flow as measured by the uptake of 4-[N-methyl-14C]iodoantipyrine was similar between the treated and untreated groups. Tissue extraction studies showed that most of the total tissue radioactivity of rapidly proliferating tissues was recovered in the DNA fraction at 60 min after [methyl-14C]S-dThd injection. CONCLUSION: The labeling procedure is rapid and suitable for 11C labeling. Positron-labeled 4'-thiothymidine should be useful for imaging DNA synthesis by PET.

Animals↗

Measurement of nitrite and nitrate levels in biological samples by capillary electrophoresis.

Nitrite is one of the products of NO-synthase in biological media. It is slowly oxidized in animals to nitrate. We developed a simple and rapid method to determine simultaneously nitrite and nitrate in biological samples. Capillary ion electrophoresis with direct UV detection at 214 nm was used employing a carrier electrolyte consisting of 10 mM sodium sulfate and an electroosmotic flow modifier. The detection limit in ultrafiltrates of plasma, urine and brain tissue extracts was 25 ng/ml for both compounds. Nitrate levels in human plasma and urine were in the microgram/ml range. Nitrite could not be detected. Rat brain tissue extracts contained detectable amounts of nitrite and nitrate.

Animals↗

The determination of polychlorinated biphenyl in small samples of monkey milk and tissues. II. Extraction efficiency.

The extraction efficiency of benzene, toluene, dichloromethane, acetone:hexane and chloroform:methanol with respect to lipids and polychlorinated biphenyls was investigated using small samples of monkey adipose tissue, liver, kidney, brain, skin, feces and milk. The most efficient solvents were: acetone:hexane and chloroform:methanol for brain, feces, kidney, liver and milk; acetone:hexane and dichloromethane for adipose tissue; acetone:hexane and toluene for blood and dichloromethane for skin tissue. Within these solvent pairs acetone:hexane was the most outstanding with respect to an average of 90% PCB recoveries from fortified samples in the range of 0.02-2 ppm. In addition, a comparison was made between the lipid determination before and after Florisil column chromatography. Only adipose and blood lipids were sufficiently recovered from Florisil to make a lipid determination after chromatography feasible.

Animals↗

Effects of haemin on neurones derived from the neural crest.

Haemin at high concentrations promoted the survival and neuritic outgrowth in vitro of dissociated sensory and parasympathetic neurones from 8-day-old chick embryos. Similar concentrations of haemin increased the activities of the neurotransmitter biosynthetic enzymes, tyrosine hydroxylase and choline acetyltransferase, in explant cultures of neonatal rat sympathetic ganglia, and in explant and dissociated 14-day-old embryonic chick parasympathethic ganglia, respectively. Enzyme activities of both dissociated neonatal rat sympathetic ganglia and explant and dissociated 8-day-old embryonic chick parasympathetic ganglia were not affected by haemin. Since the neurotrophic effects of haemin were small compared to those of tissue extracts, and were seen mainly at concentrations approaching the limits of its solubility, it is concluded that haemin resulting from the breakdown of haem proteins in tissue extracts is unlikely to contribute significantly to their effects.

Animals↗

Telomerase activity in Kaposi's sarcoma, squamous cell carcinoma, and basal cell carcinoma.

Patients with acquired immune deficiency syndrome (AIDS) often develop Kaposi's sarcoma (KS), an unusual skin tumor. The malignant nature of KS has long been disputed. Telomerase activity that maintains telomere length and ensures chromosomal stability, a frequently appearing marker in human malignancies, has been proposed to play a critical role in supporting continued cell growth, hence formation of tumors. We examined telomerase activity in tissue extracts from 22 KS, 10 squamous cell carcinoma (SCC), and 22 basal cell carcinoma (BCC) using the telomeric repeat amplification protocol (TRAP). All of the tumor tissues were previously cryopreserved at -80 degrees C. In this study, all tumor samples tested were positive for telomerase activity. Consistent with the presence of the enzyme activity, the skin tumors had relatively long telomeres. Inhibitors in the tissue extracts of some samples needed to be diluted or extracted by phenol before the enzyme activity was detected in the TRAP assay. All KS as well as two other skin carcinoma samples revealed positive telomerase activity. Our finding supports telomerase's role in tumor cell immortality and suggests the true neoplastic nature of KS.

Adult↗

Immunochemically detectable lipid-free apo(a) in plasma and in human atherosclerotic lesions.

Although Lp(a) is an independent risk factor for cardiovascular diseases in humans, the precise pathogenetic mechanisms are still unknown. We have shown that Lp(a) accumulates in human atherosclerotic lesions, and some particles undergo oxidation. Since, following agarose electrophoresis of both plaque extracts and plasma, a region close to the origin immunostained intensely for apo(a) but was lipid-free, we sought to identify whether such samples contained lipid-free apo(a), as previously reported to occur in plaque extracts. Immunochemically identifiable apo(a) was found following density-gradient ultracentrifugation both in the 1.05 < d < 1.09 and the d > 1.21 density fraction from both plasma and plaque extracts. However, because in a competitive binding RIA, displacement curves of apo(a) in plasma and the d > 1.21 were not parallel, it is premature to ascribe a relative amount of total apo(a) to this fraction. Whereas apo(a) immunoblots of SDS-PAGE under reducing conditions of the d > 1.21 fraction of a plaque extract with high apo(a) content showed high molecular weight bands consistent with apo(a) isoforms, the corresponding d > 1.21 fraction showed multiple low molecular weight bands characteristic of fragmentation. Since the d > 1.21 of arterial extracts contained all the material immunostaining for apo(a) migrating towards the cathode, characteristic of immunoglobulins (IgG), we asked whether fragments of apo(a) might have associated with human IgG both in plasma and tissue extracts, or whether our anti-apo(a) reacted with epitopes on human IgG. Immunoblotting with our anti-apo(a) of samples of plasma and plaque extracts run on agarose electrophoresis or SDS-PAGE further demonstrated intense staining of multiple bands in the molecular weight range of human IgG. Furthermore, a fraction of plasma and tissue extracts that bound to a protein G affinity column demonstrated immunostaining for apo(a) and was in the size range of IgG. Although one polyclonal anti-apo(a) provided by another laboratory showed the same findings as our antibody, two other polyclonal anti-apo(a) failed to demonstrate immunostaining of human IgG, either on agarose electrophoresis or SDS-PAGE. We speculate that the Lp(a) immunogen used to prepare our anti-apo(a) may have undergone modest oxidation, thus exposing epitopes not normally expressed on apo(a) in native Lp(a). Either antibodies to these epitopes could be recognizing apo(a) fragments, possibly released during oxidation, which are then covalently bound to IgG, or oxidation of apo(a) creates epitopes on apo(a) that are homologous with IgG, thereby leading to cross-reactivity with IgG.(ABSTRACT TRUNCATED AT 400 WORDS)

Apolipoproteins↗

Extended chain analogs of [arginine8]vasopressin as model prohormones: investigation of precursor-processing enzymes in extracts of the rat hypothalamus and neural lobe.

Analogs of [arginine8]vasopressin (AVP) in which the peptide chain was elongated from the N-terminus by the addition of Ala-Arg-Arg-, Ala-Ala-Phe-, Pro-Arg-Val-, Pro-Ala-Arg-Arg, and Pro-Ala-Ala-Phe-, and from the C-terminus by the addition of -Ala-Met-Ala-NH2 and -Gly-Arg-Arg-Ala-NH2 were synthesized by the solid phase method and purified by Sephadex G-15 chromatography. At the final step of the synthesis, the extent of formation of the intramolecular disulfide bond was found to be sequence dependent. These peptides were incubated with extracts of the rat hypothalamus (supraoptic region) and neural lobe and with isolated neurosecretory granules from the neural lobe, and the release of vasopressin was measured by the rat pressor assay. All peptides resisted conversion to the hormone in the presence of tissue extracts, except (Ala-Ala-Phe)-AVP which was converted to AVP in the presence of all three tissue extracts at pH 4.7 but not at pH 8.0. When these peptides were treated with trypsin, chymotrypsin, or leucine aminopeptidase at pH 8.0, only the action of chymotrypsin on [Ala-Ala-Phe]AVP resulted in AVP formation. Evidence obtained using lysosomal enzyme markers suggested that the converting enzyme activity in neurosecretory granule preparations was not of lysosomal origin.

Amino Acid Sequence↗

MCP-1, MIP-1, IL-8 and ischemic cerebral tissue enhance human bone marrow stromal cell migration in interface culture.

Bone marrow stromal cells (MSCs) administered intravenously are effective in reducing neurological deficits after stroke in the rodent. These cells appear to selectively migrate and express neural phenotypes in ischemic brain. To elucidate the mechanisms targeting MSC migration into the ischemic brain, we measured, using a microchemotaxis chamber, the effect of select chemotactic factors and cytokines expressed in injured brain, monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1alpha (MIP-1alpha) and interleukin-8 (IL-8), on migration of human bone marrow stromal cells (hMSCs). In addition, we investigated whether tissue extracts prepared from rat ischemic brain at various times after middle cerebral artery occlusion (MCAo) induce migration of hMSCs. Our data indicate that MCP-1, MIP-1alpha and IL-8 enhance the migration of hMSCs. Ischemic brain tissue extracts at 24, 48 h and 1 week after ischemia significantly increase hMSC migration across the membrane compared to non-ischemic tissue (p<0.05). These data indicate that hMSCs are targeted by inflammatory chemotactic agents and cytokines and that ischemic brain attracts hMSCs.

Animals↗

Embryotoxic potential of persistent organic pollutants extracted from tissues of guillemots (Uria aalge) from the Baltic Sea and the Atlantic Ocean.

The Baltic Sea is a heavily polluted area. To assess the current contaminant pressure on the common guillemot (Uria aalge) living there, whole-body extracts of guillemots from the Baltic Sea were prepared and subdivided over six fractions, which differed in composition due to lipophilicity and polarity of the contaminants. The fractions were tested in the chicken embryo assay and compared to fractions of Atlantic guillemot extracts. Fertilized chicken eggs were injected with 0.03, 0.3, or 3 bird egg equivalents (BEQ) of the contaminants present in the fractions and then incubated for 19 d. Endpoints were selected to cover several mechanisms that may play a role in reproductive failures of fish-eating birds. Fractions I and IV from the Baltic guillemots induced ethoxyresorufin-O-deethylase (EROD) activity up to 15-fold in embryos exposed to 0.3 BEQ and up to 17-fold in embryos exposed to 3 BEQ. Corresponding Atlantic fractions induced EROD activity only at the higher dose of 3 BEQ. Morphological alterations were observed in the bursa of Fabricius in embryos exposed to the fractions that induced EROD, and for the Baltic fractions, this was apparent at the dose of 0.3 BEQ. The higher toxic potency of fractions I and IV was confirmed by higher mortality and occurrence of malformations among embryos exposed to these fractions. No other effects were observed; morphometry, hepatic porphyrin levels, thiamine-dependent enzymes, and acetylcholinesterase activity were not affected by any fraction. During interpretation of the results, concentrations in the whole-body guillemot extracts were compared to concentrations reported in field studies. In general, concentrations in the guillemot extract were lower than those associated with biomarker responses in other wild-bird species. However, because the relative sensitivity of guillemot toward immunotoxic effects remains to be resolved, effects on the immunocompetence of guillemot could not be excluded.

Animals↗

Age-dependent decrease in the amount of eukaryotic initiation factor 2 in various rat tissues.

Recent studies have suggested that the decline in protein synthesis that occurs in rat liver and brain during development and aging is associated with a decrease in the activity of eukaryotic initiation factor 2 (eIF-2). One way in which eIF-2 activity could be decreased in tissue extracts would be through a decrease in the activity of the GDP exchange factor, eIF-2B. In the present study, the activity of eIF-2B was measured in tissue extracts and was found to be less in older than in younger rats. Thus a decrease in eIF-2B activity could account for part of the decrease in protein synthesis that occurs during aging. Another way in which eIF-2 activity could be decreased would be through a decrease in amount of the protein. Therefore the amount of eIF-2 in various tissues was quantified by protein immunoblot analysis. We found that the amount of eIF-2 relative to total protein tended to fall with increasing age. Furthermore, eIF-2 content was directly proportional to the rate of protein synthesis in the tissues examined. Finally, slot-blot analysis of polyadenylated RNA revealed no significant change in the relative abundance of eIF-2 alpha mRNA with age. The last-mentioned experiments suggest that the synthesis of eIF-2 may be regulated through changes in the deficiency of translation of eIF-2 alpha mRNA rather than through changes in gene transcription.

Aging↗

A method for the effective depletion of albumin from cellular extracts: application to human myocardium.

Proteomic analysis of large numbers of proteins is assisted if each protein species is present at approximately equal concentrations. As such, the extraction of proteins from tissue samples should be designed to maintain a limited dynamic range in the concentration of proteins present. However, in many tissue extracts a high concentration of serum albumin exists from tissue perfusion and/or an inability to effectively rinse the tissue owing to surgical limitations. The analysis of these tissues would be assisted if contaminating serum albumin could be reduced. This chapter outlines a protocol for the effective reduction of serum albumin levels from human myocardium extracts enriched for soluble cytoplasmic proteins.

Cell Extracts↗

Genetic markers in human bone: II. Studies on ABO (and IGH) grouping.

A combination absorption-elution, two-dimensional absorption-inhibition procedure was used to determine the ABH antigen composition of a series of human bone specimens of known ABO type that had been aged up to nine months under dry and humid conditions at ambient temperature, 37 degrees C, and 56 degrees C; at ambient temperature in dry and wet soil; and buried in soil outdoors. Grouping data for the separate elution and inhibition testing, as well as for the combination procedure, are given. The combination method was found to be a highly reliable procedure for bone tissue ABH typing. Some data on microbial contaminants of human bone specimens aging in soil, and their effects on ABH typing results, are presented. No direct correlation between the properties of microbial contaminants and specific changes in the ABH antigenic composition of aging bone tissue specimens could be ascertained. Data on IGH antigen determination and on the quantitation of immunoglobulin G (IgG) in human bone tissue extracts indicated that immunoglobulin levels were typically too low to expect routinely successful Gm antigen testing results. However, these factors can sometimes be determined in fresh bone tissue extracts, particularly if the extracts are concentrated.

ABO Blood-Group System↗

Iodinated proteins in normal human thyroid gland. Thyroid albumin.

Iodinated proteins in normal thyroid tissue extracts were analyzed immunochemically, immunohistochemically and physicochemically after isoelectric focusing. An albumin-like protein ranging from pI 4.80 to 5.21 was found in normal human thyroid tissue extracts, and its pI range was not compatible with that of serum albumin ranging from pI 4.85 to 6.16. An immunodiffusion study suggests that T3 loosely combines with the albumin-like protein, and that this compound is so-called thyroid albumin. Amino acid analysis revealed a difference in the basic amino acid composition of thyroid albumin and serum albumin, and our immunohistochemical study showed that thyroid albumin and T3 were localized in follicular epithelial cells, but not in the colloid. Based on these results, thyroid albumin may be described as consisting of T3 and an albumin-like protein which is distinguishable from serum albumin and distinct from thyroglobulin immunochemically. It appears that a low molecular weight hormone like T3 can be detected when it combines with a protein molecule. Recently, DeGroot et al. (1975) suggested a collateral pathway of hormone metabolism through the thyroid albumin in thyroid follicular cells. Our results seem to support the existence of this pathway.

Albumins↗

Hormone-sensitive lipase deficiency in mice causes diglyceride accumulation in adipose tissue, muscle, and testis.

Hormone-sensitive lipase (HSL) is expressed predominantly in white and brown adipose tissue where it is believed to play a crucial role in the lipolysis of stored triglycerides (TG), thereby providing the body with energy substrate in the form of free fatty acids (FFA). From in vitro assays, HSL is known to hydrolyze TG, diglycerides (DG), cholesteryl esters, and retinyl esters. In the current study we have generated HSL knock-out mice and demonstrate three lines of evidence that HSL is instrumental in the catabolism of DG in vivo. First, HSL deficiency in mice causes the accumulation of DG in white adipose tissue, brown adipose tissue, skeletal muscle, cardiac muscle, and testis. Second, when tissue extracts were used in an in vitro lipase assay, a reduced FFA release and the accumulation of DG was observed in HSL knock-out mice which did not occur when tissue extracts from control mice were used. Third, in vitro lipolysis experiments with HSL-deficient fat pads demonstrated that the isoproterenol-stimulated release of FFA was decreased and DG accumulated intracellularly resulting in the essential absence of the isoproterenol-stimulated glycerol formation typically observed in control fat pads. Additionally, the absence of HSL in white adipose tissue caused a shift of the fatty acid composition of the TG moiety toward increased long chain fatty acids implying a substrate specificity of the enzyme in vivo. From these in vivo results we conclude that HSL is the rate-limiting enzyme for the cellular catabolism of DG in adipose tissue and muscle.

Adipose Tissue↗

Glycosaminoglycans provide a binding site for thyroglobulin in orbital tissues of patients with thyroid-associated ophthalmopathy.

The presence of thyroglobulin (Tg) in orbital tissues of patients with thyroid-associated ophthalmopathy (TAO) supports a role of Tg in TAO pathogenesis. To search for Tg-binding sites in orbital tissues, because Tg is a heparin-binding protein, we investigated its binding to glycosaminoglycans (GAGs) that are abundant in orbital tissues: chondroitin sulfate B (CSB) and C (CSC) and hyaluronic acid (HA). Both in solid phase and solution phase assays purified human Tg bound to GAGs. In solid-phase assays, binding was increased by coincubation with heparin or GAGs in solution, or with an antibody against a Tg heparin-binding sequence (Arg2489-Glu2503), possibly suggesting crosslinking of Tg molecules induced by GAGs or by the presumably bivalent antibody. Orbital tissue extracts from TAO patients that contained Tg were subjected to high-salt treatment, which resulted in separation of Tg from GAGs, as observed by column chromatography. After separation from GAGs, the Tg in orbital tissue extracts acquired the ability to bind to immobilized CSB, and heparin enhanced binding, resembling the findings with purified human Tg. Therefore, we conclude that GAGs provide binding sites for Tg in orbital tissues, which may explain the presence of Tg in orbital tissues of patients with TAO.

Adipose Tissue↗

[Studies on tumor-specific immune response evaluated by leucocyte migration inhibition test under agarose-plate in gynecological malignancy (author's transl)].

For the purpose of analysis of cancer specific immune reactions in gynecological malignancies, Leucocyte Migration Inhibition Test (LMIT: agarose-plate method) has been examined with tumor extract. Tumor extracts as antigens were prepared from 27 cases of cervical cancer, 14 of ovarian cancer, 4 of endometrial cancer, 4 of choriocarcinoma, 3 of vulval cancer and 3 of uterine sarcoma as well as control tissue extracts by hypertonic potassium chloride method (3 M-KCl method). The same antigens were also used for skin reaction test and leucocyte adherence inhibition (LAI) assay. 1. LMIT The positive reaction with autochthonous tumor extracts were 6/27 (22.2%) cases in cervical cancer, 4/14 (28.6%) in ovarian cancer, 1/4 in endometrial cancer, 1/4 in choriocarcinoma, 0/3 in vulval cancer, 1/3 in uterine sarcoma. But their reactions with control tissue extracts were all negative. Only a case of ovarian cancer and another of endometrial cancer with cancer extracts of the same types showed positive reaction. 2. Correlations of among LMIT, LAI and skin reaction--Positive reactions of LAIs and skin reactions which were simultaneously examined using the autochthonous tumor extracts were 0-60% in gynecological malignancies. The results yielded the agreement rate with LAI of 77.8%, and that with skin reaction of 55.6%. 3. The antigeneic localization of tumor extract--We gained 3 fractions from the cervical cancer extract, which was LMIT-positive, by Sephadex G-200 gel column chromatography. The antigenicity of the extract was found to be in the high molecular weight fraction.

Adult↗

Increased 5-phospho-alpha-D-ribose-1-diphosphate synthetase (ribosephosphate pyrophosphokinase, EC 2.7.6.1) activity in rat hepatomas.

The behavior of the activity of 5-phosphoribosyl 1-pyrophosphate (PRPP) synthetase (ribosephosphate pyrophosphokinase, EC 2.7.6.1) was elucidated in normal rat liver, in 11 hepatomas of different growth rates, and in rapidly growing differentiating and regenerating liver. Tissue extracts were prepared by centrifugation of 10% homogenates at 100,000 X g for 30 min, and enzyme activity was measured in the protein fractions obtained by 40 and 47% ammonium sulfate saturation of the supernatant fluids from livers and hepatomas, respectively. In the tissue extracts, there was no interfering enzyme activity that utilized PRPP under the standard assay conditions. The affinity of PRPP synthetase for its substrates, ribose 5-phosphate and adenosine triphosphate (ATP), and to Mg2+ was similar in liver and hepatoma extracts. The Km for ribose 5-phosphate was 0.3 mM; for ATP, it was 0.1 mM in the presence of excess Mg2+. The Km for Mg2+ ATP was 1.2 mM in the presence of excess ATP. There was no difference in the affinity of the enzyme for its activators, Mg2+ and inorganic phosphate, in liver and hepatoma preparations; the Km for Mg2+ was 0.6 mM in the presence of excess ATP; the Km for inorganic phosphate was 14.0 mM. The requirement of hepatoma extracts for full phosphate saturation was higher than that of liver extracts (85 versus 65 mM). A standard assay was worked out for the liver and hepatoma systems; in liver, the enzyme activity was linear for 30 min incubation, and in hepatoma it was linear for 15 min incubation. PRPP synthetase activity was proportionate with amounts of protein added over a range of 0.4 to 3.0 mg in both liver and hepatoma extracts. In the liver of normal adult Wistar rats, PRPP synthetase activity was 108 +/- 10 nmol/hr/mg protein. In rat tissues of high cell renewal activity, thymus, testis, spleen, and small intestine, synthetase specific activity was 3.7-, 3.6-, 1.2-, and 1.3-fold higher than that of normal liver. The synthetase specific activity in hepatomas of slow growth rate increased 1.2- to 1.5-fold, and in intermediate and rapidly growing hepatomas it was elevated 1.9- to 4.1-fold higher than that of normal liver.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenosine Triphosphate↗