Effects of denaturation with HCl on the immunological staining of bromodeoxyuridine incorporated into DNA

Immunochemical procedures for detection of BrdUrd incorporated into DNA require a denaturation step of DNA. Denaturation with HCl is widely used for flow cytometric analysis of the cell cycle and for histological preparations. This brief communication describes an attempt to standardize a denaturation procedure with HCl. Various denaturation conditions at 20 degrees C were examined for human promyelocytic leukemia cells (HL-60 cells) fixed in ethanol. After denaturation of DNA, the cells were stained by an indirect immunofluorescence method using a commercially available monoclonal anti-BrdUrd antibody or by propidium iodide. The relative fluorescence intensities of stained BrdUrd and double-stranded DNA were altered reciprocally by changing HCl concentration and/or denaturation time. Treatment with 4N HCl for 10-20 min at 20 degrees C allowed denaturation of more than 80% of DNA and the maximum BrdUrd-linked immunofluorescence. Under this condition, the coefficient of variation of the DNA histograms remained relatively small.     

Molecular analysis of five independent Japanese mutant genes responsible for hypoxanthine guanine phosphoribosyltransferase (HPRT) deficiency

Five independent mutations in the hypoxanthine guanine phosphoribosyltransferase (HPRT) gene were identified in a partially HPRT deficient patient with gout and in four Lesch-Nyhan patients. Using the polymerase chain reaction (PCR) technique coupled with direct sequencing, the nucleotide sequences of the entire HPRT coding region amplified from the cDNA and also of each exon amplified form the genomic DNA were analyzed. Three independent point mutations in the coding region were detected in the partially HPRT deficient patient (Case 1) and in two Lesch-Nyhan patients (Case 2 and 3), resulting in single amino acid substitutions. The family study of Case 3, utilizing a PvuII restriction site created in the mutant gene, indicated that the mother was a heterozygote, and a sister and a fetal brother had inherited the normal HPRT gene from the mother. In two other mutants causing Lesch-Nyhan syndrome, a portion of the HPRT gene was deleted, and RNA splicing was missing in both mutants. A 4-bp deletion at the 5 end of exon 4 resulted in formation of three different types of abnormal mRNA (Case 4). The other mutant (Case 5) produced abnormal mRNA including 26bp of intron 8 instead of the deleted 58bp at the 5 end of exon 9, because of a 74-bp deletion from intron 8 to exon 9.     

Enhancement of epidermal growth factor receptor expression on glioma cells by recombinant tumor necrosis factor α

Summary Recombinant tumor necrosis factor (rTNF; optimal dose 1000 U/ml) significantly increased the density of epidermal growth factor receptor (EGF-R) in three of four glioma cell lines in culture as determined by binding analysis of anti-EGF-R monoclonal antibody (mAb) 425. Since enhancement of EGF-R expression by rTNF- was inhibited when cells were treated with the protein synthesis inhibitor cycloheximide, the effects of rTNF may be protein-synthesis-dependent. The dose of rTNF that was optimal for up-regulation of EGF-R on glioma cells did not inhibit the growth of these cells.¹²⁵I-labeled mAb 425 lysed glioma cells in culture following its internalization into the cells. After glioma cells had been treated with rTNF, the growth-inhibitory effects of the mAb were significantly enhanced, probably a reflection of the increase in EGF-R density on the tumor cell surfaces. The rTNF effects were specific to the EGF-R and did not affect unrelated glioma-associated antigens. In our previous clinical trials,¹²⁵I-labeled mAb 425 showed immunotherapeutic effects in glioma patients. The present study provides the basis for considerations of combined immunotherapy of glioma patients with¹²⁵I-labeled mAb 425 and rTNF.     

Characterization of membrane-bound spermidine dehydrogenase of Citrobacter freundii.

Spermidine dehydrogenase found in the membrane fraction of Citrobacter freundii IFO 12681 was solubilized with Triton X-100 and further purified to homogeneity. The properties of the membrane enzyme were almost identical to those obtained from the soluble fraction of the organism with respect to molecular and catalytic properties. Thus, binding properties of the enzyme to the bacterial membrane were checked. The ratio of enzyme activity found in the soluble fraction to the membrane fraction was dependent on salt concentration during cell disruption. A hydrophobic interaction was largely involved in anchoring the enzyme to the membrane fraction. Purified spermidine dehydrogenase from the soluble fraction was readily adsorbed into the membrane fraction in the presence of salt. Spermidine dehydrogenase appeared to be a membrane-bound enzyme localized in the cytoplasmic membranes in a manner that makes a partial release of the enzyme possible during mechanical cell disruption. When spermidine oxidation was done with the resting cells of C. freundii, a stoichiometric formation of two reaction products, 1,3-diaminopropane and gamma-aminobutyraldeyde, was observed without any lag time. These facts indicate that the enzyme is localized on the outer surface of the cytoplasmic membranes or in the periplasmic space of the organism.     

Preparation of peptide mixture with high Fischer ratio from protein hydrolysate by adsorption on activated carbon.

A peptide mixture with a high Fischer ratio (a molar ratio of Val + Leu + Ile to Phe + Tyr) was prepared by the adsorptive separation of a casein hydrolysate by activated carbon. The effects of the pH and ethanol content of the hydrolysate on the Fischer ratio and on the yield of the resulting peptide mixture were examined. A peptide mixture with the Fischer ratio of 31.6 was obtained at pH 2.5 without the addition of ethanol. The Fischer ratio was close to the ratio of the infusion solution of free amino acids that is now used for patients with liver diseases.     

Specific complex of human immunodeficiency virus type 1 rev and nucleolar B23 proteins: dissociation by the Rev response element.

The human immunodeficiency virus type 1 (HIV) Rev protein is thought to be involved in the export of unspliced or singly spliced viral mRNAs from the nucleus to the cytoplasm. This function is mediated by a sequence-specific interaction with a cis-acting RNA element, the Rev response element (RRE), present in these intron-containing RNAs. To identify possible host proteins involved in Rev function, we fractionated nuclear cell extracts with a Rev affinity column. A single, tightly associated Rev-binding protein was identified; this protein is the mammalian nucleolar protein B23. The interaction between HIV Rev and B23 is very specific, as it was observed in complex cell extracts. The complex is also very stable toward dissociation by high salt concentrations. Despite the stability of the Rev-B23 protein complex, the addition of RRE, but not control RNA, led to the displacement of B23 and the formation of a specific Rev-RRE complex. The mammalian nucleolar protein B23 or its amphibian counterpart No38 is believed to function as a shuttle receptor for the nuclear import of ribosomal proteins. B23 may also serve as a shuttle for the import of HIV Rev from the cytoplasm into the nucleus or nucleolus to allow further rounds of export of RRE-containing viral RNAs.     

Provocation of a paradoxical growth hormone response to corticotropin-releasing hormone by pretreatment with metoclopramide in patients with acromegaly and normal subjects

Two of 7 patients with acromegaly and one of 7 normal subjects exhibited a paradoxical rise in growth hormone (GH) to human corticotropin-releasing hormone (CRH) when pretreated with metoclopramide, although CRH alone did not induce an increase in GH. In one of these two patients with acromegaly, the GH increase to metoclopramide alone also reached the criteria of a paradoxical response. These two acromegalic patients showed a GH increase to metoclopramide pretreatment before and up to two months after surgery. In another acromegalic patient, whose GH level remained high 5 months after surgery, metoclopramide induced an increase in GH level, while in a patient who had an above-normal GH level 18 months after surgery, the resumption of physiological GH secretion after surgery was evidenced by a postoperative absence of a GH response to metoclopramide. It is suggested from these results that the GH response to metoclopramide and the metoclopramide-provoked GH response to CRH in patients with acromegaly result from the secretion of GH from nonadenomatous cells of the pituitary.     

Hypercortisolism and the resistance to dexamethasone suppression during gestation

Maternal adrenocortical function was studied by measuring plasma cortisol and urinary free cortisol during gestation. Changes in suppressibility of pituitary-adrenocortical function were determined by dexamethasone administration. Urinary free cortisol as well as plasma cortisol increased during the course of gestation. The suppressibility by dexamethasone became less effective as pregnancy advanced. These results suggest that pregnant women have pituitary-adrenocortical hyperfunction and tissue refractoriness to glucocorticoid which increases during the course of gestation.     

Inducing effects of clofibric acid on 1-acylglycerophosphorylcholine acyltransferase in kidney and intestinal mucosa of rats

Administration of p-chlorophenoxyisobutyric acid (clofibric acid) markedly increased the activity of microsomal 1-acylglycerophosphorylcholine (1-acyl-GPC) acyltransferase in kidney, intestinal mucosa and liver, but not in brain, heart, lung, spleen, testis or skeletal muscle. In both kidney and liver, a marked dose-dependent increase in the activities of both microsomal 1-acyl-GPC acyltransferase and peroxisomal beta-oxidation was observed. In the rats treated with clofibric acid at a relatively low dose, the increase in the activity of 1-acyl-GPC acyltransferase in kidney was more marked than that in liver. The extent of the relative increase in the activity of 1-acyl-GPC acyltransferase to the activity of peroxisomal beta-oxidation in kidney was more marked than that in liver. The increased activity of 1-acyl-GPC acyltransferase in both kidney and liver lasted throughout the 8-week treatment period of rat with clofibric acid.     

Study of bilirubin metabolism by high-performance liquid chromatography: stability of bilirubin glucuronides

The stabilities of bilirubin (BR) glucuronide, monoglucuronide (BMG), and diglucuronide (BDG) were studied under various conditions by HPLC. In aqueous media, BMG showed a pronounced lability and was easily transformed into equimolar BDG and BR. It was proved by direct analysis of tetrapyrrole isomers that BDG and BR were formed from dipyrrole exchange of BMG molecules. All reducing agents examined (sodium ascorbate, cysteine, GSH, dithiothreitol, NADH, and NADPH) suppressed the transformation of BMG into BDG and BR. Bovine serum albumin and rat liver cytosol fractions also stabilized BMG strongly. BDG was fairly stable in aqueous media as compared with BMG. When BMG was incubated both with and without liver plasma membranes (N2 fraction) from Wistar rats, the formation rates of BDG and BR in both incubation mixtures were exactly the same. The composition of BDG and BR isomers was the same in both mixtures. Also, heat denaturation of the plasma membranes did not affect formation rates. Moreover, the reaction was completely inhibited by sodium ascorbate. These findings indicate that rat liver plasma membranes have no enzyme activity for BDG formation from BMG.