Analysis of ritodrine in serum by high-performance liquid chromatography with electrochemical detection

A sensitive and specific assay for ritodrine in serum was developed using high-performance liquid chromatography (HPLC) with electrochemical detection. Serum samples were alkalinized to pH 9.4 by the addition of a sodium carbonate buffer and extracted with ethyl acetate. The extracts were evaporated to dryness and the residues were reconstituted in the HPLC mobile phase and chromatographed on a octadecylsilane reverse-phase column. The detection of ritodrine was achieved by an electrochemical detector with a glassy carbon electrode. The sensitivity was 0.2 ng for on-column injection. The extraction efficiency was 80%.

Pharmacodynamics of ritodrine in pregnant women during preterm labor

We evaluated the relationship of ritodrine concentration to several maternal variables and to fetal heart rate in 17 women who received the drug for inhibition of preterm labor. Ritodrine was measured by high-performance liquid chromatography with electrochemical detection. Ritodrine increased maternal and fetal heart rate and decreased serum potassium in a dose-related manner, but wide variability was noted between patients and within individual patients. Tachyphylaxis of the maternal heart rate response to continuing treatment with ritodrine was seen in at least seven women. Maternal blood pressure, serum glucose concentration, and frequency of uterine contractions were changed by ritodrine treatment, but the changes in these variables were not closely correlated to the concentration of ritodrine (r less than or equal to 0.30 in all cases). The maximal infusion rate and the concentration of ritodrine in maternal serum after 4 hours of treatment were significantly (p less than 0.001) correlated with the frequency of uterine contractions prior to treatment. Successful inhibition of labor was achieved with serum concentrations of 15 to 31 ng/ml in 10 of 17 women; in six of the other seven women, labor could not be inhibited in spite of serum concentrations of 90 to 146 ng/ml. Side effects, such as hypotension, vomiting, chest discomfort, and shortness of breath, were most commonly observed when the infusion rate and concentration of ritodrine were increasing.

Metabolism of 7,12-dimethylbenz[a]anthracene by Cunninghamella elegans

The metabolites of 7,12-dimethylbenz[a]anthracene (DMBA), a carcinogenic polycyclic aromatic hydrocarbon, in cultures of Cunninghamella elegans were isolated by high-pressure liquid chromatography and characterized by UV spectroscopy and mass spectrometry. The major metabolites were DMBA-trans-8,9-dihydrodiol and DMBA-trans-3,4-dihydrodiol. The 7-hydroxymethyl and the 12-hydroxymethyl derivatives of these dihydrodiol metabolites were also formed. The metabolic profile described in this report contrasts with those obtained in our earlier experiments in which the incubation of DMBA with Pseudomonas aeruginosa and Penicillium notatum produced no dihydrodiol metabolites but only methyl-hydroxylated metabolites.

Characteristics of spontaneously produced and of virus-induced human LuKII cell interferons

Several human lymphoblastoid cell lines produced significant levels of interferon (IFN) activity in the absence of any IFN induces. We have partially purified spontaneous IFN (SpIFN) from LuKII cells and compared it with the IFN activity produced by the same cells following Sendai virus induction. Virus-induced LuKII IFN reached maximum titers of 1000-6000 reference units/ml at 12 to 15 houts post-induction and produced a heterogeneous electrophoretic profile with major (18,500 dalton) and minor (23,500 dalton) species. Spontaneous LuKII IFN was produced very slowly over several days and reached maximum titers of 100-1000 reference units/ml. Crude SpIFN (25-100 ref. units/ml) was purified to 1-6 X 10(5) ref. units/ml with a 53-80 percent overall recovery, and it consistently migrated as a homogeneous 20,000 dalton band upon SDS gel electrophoresis. Although spontaneously produced and virus-induced lymphoblastoid IFNs differed in their ability to be neutralized by anti-mouse IFN antiserum (18), both types of IFN were only 1 percent cross-reactive on heterologous mouse L cells. We conclude that IFN definitely can be produced by many human lymphoblastoid cell lines in the absence of inducers, and that LuKII SpIFN has different characteristics than the IFNs produced by the same cell line following viral induction. Since it is now known that there are many IFN-alpha genes (3, 10), it seems likely that these cell lines may provide a system for studying the selective expression of one or more of these genes.

Size characteristics of human leucocyte interferon under reducing and non-reducing conditions

Sodium dodecyl sulphate/polyacrylamide-gel electrophoresis was used to characterize human leucocyte interferon (HuIFN-alpha) under reducing and non-reducing conditions. Under non-reducing conditions HuIFN-alpha possesses two size forms, but under reducing conditions (r-HuIFN-alpha) only one is observed. The apparent molecular weight of this one form varies with the concentration of 2-mercaptoethanol used. When r-HuIFN-alpha is permitted to reoxidize the bimodal configuration of HuIFN-alpha is restored. The size heterogeneity of native HuIFN-alpha can be eliminated by mild treatment with NaIO4 [HuIFN-alpha/IO4; Stewart II, Lin, Wiranowska-Stewart & Cantell (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 4200-4204]. The size of the HuIFN-alpha/IO4 increases after treatment with 2-mercaptoethanol (r-HuIFN-alpha/IO4) and the apparent molecular weight of this component also varies with the concentration of 2-mercaptoethanol used. In the case of r-HuIFN-alpha the single peak observed apparently originates from both the higher- and lower-molecular-weight components.

Isolation of a Biologically active fragment of human alpha interferon

When treated with pepsin under limited digestion conditions, human leukocyte-derived alpha interferon (HulFN-alpha) is partially inactivated. While the initial HulFN-alpha preparation is about equally active on human and on bovine cells, the residual antiviral activity of HulFN-alpha after pepsin treatment is significantly more active on bovine cells than on human cells. Furthermore, pepsin-treated HulFN-alpha, when assayed on bovine cells, yields an active production which is smaller and antigenically distinguishable from the native forms of HulFN-alpha.

Production, purification and characterization of rat interferon

Priming with heterologous mouse interferon, increased production of an antiviral substance induced in rat diploid fibroblasts by Newcastle disease virus. This substance was characterized as an acid stable interferon. This rat interferon exhibited marked cross-species antiviral activity when tested in mouse L929B cells, guinea pig embryo fibroblasts, human fibroblasts and bovine cells but was not active on chick embryo cells.

Interferoids: in vitro and in vivo conversion of native interferons to lower molecular weight forms

Mouse interferons appear as two distinct molecular forms, one migrating at 38,000 daltons in sodium dodecyl sulfate/polyacrylamide gels and one migrating at 22,000 daltons; these interferons comprise about 80% and 20% of total activities, respectively. When such interferon preparations are briefly exposed to acidic periodate buffer, the larger interferon species is apparently converted to the smaller form since the activity at 38,000 daltons is completely eliminated while the activity at 22,000 daltons increases significantly; upon further oxidative cleavage, antiviral activity becomes detectable migrating at 15,000 daltons. Because no native mouse interferon has been reported as such small molecules, this antiviral activity is designated mouse "interferoid" to distinguish it from the native, naturally occurring interferon forms. Prolonged acidperiodate treatment fails to quantitatively convert the 22,000-dalton interferon to the 15,000-dalton interferoid since both are inactivated. When L cells are induced to make interferon in the presence of glycosylation inhibitors, either D-glucosamine or 2-deoxy-D-glucose, they produce approximately normal levels of antiviral activity. However, when such preparations are analyzed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis, little activity (<10%) migrates as either the 38,000-dalton or 22,000-dalton native interferons. The interferons and interferoid are antigenically and hydrophobically indistinguishable. These data suggest that induced mouse cells normally synthesize the interferoid as a precursor polypeptide that is either partially or extensively modified by carbohydrate additions to produce, respectively, the 22,000- and 38,000-dalton mouse interferons. Because interferoid is apparently fully biologically active without these moieties, chemical synthesis of such unmodified polypeptides or active fragments from them appears feasible.

Characterization of the size and charge heterogeneities of human leukocyte interferon populations

Human leukocyte interferons are separable into two size components by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and are separable into two charge-components by DEAE-BiGel A chromatography. However, each of the charge-components resolved by ion-exchange chromatography contained both size-components, when analysed by SDS-PAGE. Thus, there are more than two distinct molecular populations of human leukocyte interferons.

Elimination of size and charge heterogeneities of human leukocyte interferons by chemical cleavage

Human leukocyte interferon (HuLeIF) preparations contain distinct molecular forms of interferon exhibiting significant heterogeneties in sizes when analyzed by electrophoresis in sodium dodecyl sulfate (NaDodSO(4))/polyacrylamide gels, migrating in two broad bands of activity with peaks at about 21,000 and 15,000 daltons. HuLeIFs exhibit extensive charge heterogeneities when analyzed by isoelectric focusing, resolving into several major peaks of approximately equal activity distributed from pH 5.7 to 7.0. When HuLeIF preparations are treated with 0.01 M sodium periodate buffer, pH 4.5, at 4 degrees , both the size and charge heterogeneities rapidly disappear: periodate-treated HuLeIF migrates as a single, narrow band at 15,000 daltons in NaDodSO(4)/polyacrylamide gels and focuses as a single, narrow band at pH 5.7. Quantitative considerations suggest that either the larger, heterogeneously charged HuLeIFs are converted to the smaller, size- and charge-homogeneous interferon by extensive chemical deglycosylation, or, alternatively, the smaller, 15,000 dalton, pH 5.7 interferon is much more stable to periodate treatment than are the other interferon forms. However, the activity of each of the variously charged forms of HuLeIF isolated from focusing gels exhibited the same stability as the pH 5.7 component; similarly, the activity of each of the size-forms of HuLeIF isolated from NaDodSO(4)/polyacrylamide gels exhibited the same stability as the 15,000-dalton interferon.