Angiotensin II receptor subtypes are coupled with distinct signal-transduction mechanisms in neurons and astrocytes from rat brain

Both neurons and astrocytes contain specific receptors for angiotensin II (AII). We used selective ligands for the AT1 and AT2 types of AII receptors to investigate the expression of functional receptor subtypes in astrocyte cultures and neuron cultures from 1-day-old (neonatal) rat brain. In astrocyte cultures, competition of 125I-labeled AII (125I-AII) specific binding with AT1 (DuP753) or AT2 (PD123177, CGP42112A, [Phe(p-NH2)6]AII) selective receptor ligands revealed a potency series of AII greater than DuP753 much greater than CGP42112A greater than [Phe(p-NH2)6]AII greater than PD123177. These results suggest a predominance of the AT1 receptor subtype in neonatal astrocytes. Also, in astrocyte cultures, AII stimulated increases in inositolphospholipid hydrolysis that were significantly reduced by the AT1 receptor antagonist DuP753 but not altered by the AT2 receptor antagonist PD123177. In neonatal neuron cultures, competition of 125I-AII specific binding with the above ligands revealed a potency series of CGP42112A = AII greater than [Phe(p- NH2)6]AII greater than PD123177 much greater than DuP753. 125I-AII specific binding to neonate neuronal cultures was reduced 73-84% by 1 microM PD123177, and the residual 125I-AII specific binding was eliminated by DuP753. Also, in neuron cultures, AII induced decreases in basal cGMP that were completely blocked by PD123177 or CGP42112A but not by DuP753. Our results suggest that astrocyte cultures from neonatal rat brains contain predominantly AT1 receptors that are coupled to a stimulation of inositophospholipid hydrolysis. In contrast, neuron cultures from neonatal rat brain contain mostly AT2 receptors that are coupled to a reduction in basal cGMP levels, but a smaller population of AT1 receptors is also present in these neurons.

Phorbol ester inhibits 13-cis-retinoic acid-induced hydrolysis of phosphatidylinositol 4,5-bisphosphate in cultured murine keratinocytes: a possible negative feedback via protein kinase C-activation

The incubation of double-labelled [( 14C]-glycerol and [3H]-myoinositol) keratinocytes with 13-cis retinoic acid induced the transient and simultaneous release of [3H]-inositol trisphosphate ([3H]-InsP3) and [14C]-diacylglycerol ([14C]-DAG) indicating that a possible mode of action of this retinoid on murine keratinocytes may be at least in part the early transient release of the two putative messengers (InsP3 and DAG) from phosphatidylinositol-4,5 bisphosphate (PtdIns4, 5P2). In contrast, the preincubation of the keratinocytes with 12-O-tetradecanoylphorbol-13-acetate (TPA) prior to incubation with 13-cis-RA suppressed the 13-cis-RA-induced release of [3H]-InsP3 and [14C]-DAG. The specificity of the TPA effect was established by the lack of effect of the biologically inactive 4 alpha-phorbol 12, 13-didecanoate. Furthermore, the incubation of the TPA-primed keratinocytes with 13-cis-RA caused a delayed and sustained accumulation of [14C]-DAG. An exploration of the source of this late release of [14C]-DAG revealed that this [14C]-DAG was released from non-inositol containing phospholipids, particularly, phosphatidylcholine. This latter DAG released in the TPA-primed cells correlated with the translocation of the cytoplasmic protein kinase C (PKC) activity to the membrane associated PKC activity. Taken together, these results suggest that alteration of PKC activity, presumably induced by DAG released from non-inositol phospholipids, may play a major role in the TPA-induced negative feedback inhibition of 13-cis RA-induced hydrolysis of keratinocyte PtdIns4, 5P2.

Nanosecond kinetic absorption and calorimetric studies of cyclopentenone: the triplet, self-quenching, and the predimerization biradicals

The photolysis of 2-cyclopentenone has been studied by a combination of kinetic absorption spectrophotometry and time-resolved photoacoustic calorimetry. The lifetime of the cyclopentenone triplet is strongly concentration dependent and corresponds to a value of 380 +/- 75 ns at infinite dilution in acetonitrile. The biradical intermediate (or pair of isomeric biradicals) immediately preceding formation of photodimer forms with very high efficiency upon quenching of triplet cyclopentenone by a second ground state cyclopentenone molecule and has an energy of 47 kcal/mol relative to two molecules of reactant. Quenching of the cyclopentenone triplet by conjugated dienes is much slower than expected, which is the reason that early estimates of the triplet lifetime were much too short.

Dietary supplementation with ethyl ester concentrates of fish oil (n-3) and borage oil (n-6) polyunsaturated fatty acids induces epidermal generation of local putative anti-inflammatory metabolites

Clinical reports have attributed the amelioration of chronic inflammatory skin disorders to the presence of certain polyunsaturated fatty acids (PUFA) in dietary oils. To test the hypothesis of a local modulatory effect of these PUFA in the epidermis, the basal diet of normal guinea pigs was supplemented with ethyl esters of either fish oil [rich in eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)] or borage oil [rich in gamma-linolenic acid (GLA)]. Our data demonstrated that dietary oils influence the distribution of PUFA in epidermal phospholipids and the epidermal levels of PUFA-derived hydroxy fatty acids. Specifically, animals supplemented with ethyl esters of fish oil markedly incorporated EPA and DHA into epidermal phospholipids, which paralleled the epidermal accumulation of 15-hydroxyeicosapentaenoic acid (15-HEPE) and 17-hydroxydocosahexaenoic acid (17-HDoHE). Similarly, animals supplemented with esters of borage oil preferentially incorporated dihomogammalinolenic acid (DGLA), the epidermal elongase product of GLA, into the epidermal phospholipids, which also was accompanied by epidermal accumulation of 15-hydroxyeicosatrienoic acid (15-HETrE). By factoring the epidermal levels of the 15-lipoxygenase products and their relative inhibitory potencies, we evolved a measure of the overall potential of dietary oils to exert local anti-inflammatory effect. For example, the leukotriene inhibition potentials (LIP) of both fish oil and borage oil were greatly enhanced when compared to controls. Thus, the altered profiles of epidermal 15-lipoxygenase products generated from particular dietary oils may be responsible, at least in part, for reported ameliorative effects of oils on chronic inflammatory skin disorders.

Antineoplastic ether-linked phospholipid induces differentiation of acute myelogenous leukemic KG-1 cells into macrophage-like cells

The culture of a human acute myelogenous leukemic cell line (KG-1) with a synthetic ether-linked phospholipid: 1-0-octadecyl-2-0-methylglycerol phosphocholine (ET-18-OCH3), suppressed the growth of the KG-1 cells while the variant subline, (KG-1a cells) similarly treated was unresponsive. The growth inhibition of the KG-1 cells was accompanied by morphological changes into cells of the monocyte/macrophage lineage. Histochemically, the ET-18-OCH3-treated KG-1 cells increase 17-fold in the nonspecific esterase activity when compared to control non-treated cells, whereas they responded negatively in the assay for the reduction of soluble nitroblue tetrazolium into insoluble blue formazan deposits (a marker for cells of the granulocytic lineage). Taken together, our data revealed that the synthetic ether-lipid inhibited the growth of the KG-1 acute myelogenous leukemic cells while inducing the differentiation of these cells into cells of the monocyte/macrophage-lineage. These effects of the synthetic ether lipid raise the possibility that naturally occurring ether-linked phospholipids may likewise function in vivo to modulate hyperproliferative processes and thus warrant further explorations.

Agonist/inositol trisphosphate-induced release of calcium from murine keratinocytes: a possible link with keratinocyte differentiation

Extracellular calcium concentrations markedly affect the pattern of proliferation and differentiation in cultured keratinocytes. When medium contains 0.1 mM calcium or above, the cells lose their proliferative ability, rapidly stratify, and terminally differentiate. Because 1,25(OH)2D3 (a modulator of Ca++ homeostasis) enhances the differentiation of keratinocytes, we investigated whether a link exists between 1,25(OH)2D3-induced release of inositol-1,4,5-trisphosphate (Ins(1,4,5)P3) from PtdIns 4,5-P2 and intracellular calcium [Ca++]i release from keratinocytes. Specifically, primary culture of keratinocytes were loaded with fluorescence dye Fura-2AM (10 microM) and changes in fluorescence intensity were monitored at the excitation wavelengths of 340 and 380 nm and emission wavelength of 505 nm. Additions of two agonists, 1,25(OH)2D3 (1.2 x 10(-9) M) and 13-Cis retinoic acid (0.2 x 10(-9) M), to dye-loaded keratinocytes induced rapid release of [Ca++]i, respectively, followed by gradual return to the prestimulated state. Addition of Ins(1,4,5)P3 (10 microM) to saponin-treated (leaky) keratinocytes also resulted in a rapid release of [Ca++]i. In contrast, the addition of inositol-1,3,4,5-tetrakisphosphate Ins(1,3,4,5)P4 at similar concentrations exerted negligible effect. Taken together, these results support the view that 1,25(OH)2D3-induced [Ca++]i release in keratinocytes may be via the Ins(1,4,5)P3-induced early release of intracellular [Ca++]i. This may explain, at least in part, 1,25(OH)2D3-enhanced keratinocyte differentiation.

Determination of triplet excitation energies of cyclic enones by time-resolved photoacoustic calorimetry

Energies and lifetimes of triplet states of a series of 2-cyclohexenones have been measured in solution under ambient conditions by time-resolved photoacoustic calorimetry (PAC). The PAC triplet lifetimes are in excellent agreement with lifetimes measured by kinetic absorption spectrophotometry (KAS) using nanosecond flash techniques, indicating that the present data indeed pertain to the enone triplets previously studied using KAS. The data demonstrate that, as previously proposed, the pi pi triplet energies in these systems are indeed correlated with triplet lifetimes, and vary sensibly with the anticipated extent of conformational flexibility of the C = C bond. No evidence supporting formation of metastable trans-cyclohexenones was obtained. The data also demonstrate greater precision and, for lifetimes, greater accuracy than has hitherto been claimed for the PAC technique for study of transients with lifetimes in the 25 ns range.

Carcinoma of the cervix with extensive endometrial and myometrial involvement

Verrucous carcinoma is a rare variant of epidermoid carcinoma with distinct clinical and histopathologic features. To date, 31 cases have been reported in the cervix. They are typically slow-growing, locally invasive tumors with low potential for lymphatic metastasis and appear to be radioresistant. We report a case which is unusual in having endometrial and deep myometrial invasion. Electron microscopy, immunohistochemical stains, and DNA in situ hybridization studies failed to detect human papilloma virus particles but the oncogenic potential of the virus is not excluded.

Synthesis and characterization of steroid-linked N-(2-chloroethyl)nitrosoureas

Syntheses of steroid-linked N-[N'-(2-chloroethyl)-N'-nitrosocarbamoyl]-(CNC-) amino acid esters and -amides with potential antineoplastic activity are described. The esters are prepared by reaction of CNC-amino acids with steroids using N,N'-carbonyldiimidazole and N,N'-dicyclohexylcarbodiimide. The corresponding amides are prepared by reaction of 1-(CNC-amino acyloxy)-pyrrolidine-2,5-diones with 17 beta-amino-3-hydroxy-1,3,5(10)-estratriene or 17 beta-O-[4-(6-aminohexylamino)-1,4-dioxo-butyl]-estradiol. Estradiol-17 beta-hemisuccinate is esterified with N-(2-hydroxyethyl)-N'-(2-chloro-ethyl)-N'-nitrosourea (HECNU). Spectroscopic characteristics and relative binding affinities to steroid receptors are given.

Nitrosoureas. Modes of action and perspectives in the use of hormone receptor affinity carrier molecules

Mechanisms of DNA adduct formation by antineoplastic 2-chloroethyl-N-nitrosoureas (CNUs) and of DNA damage induced by these compounds are discussed. CNUs are alkylating agents that form DNA-DNA cross-links as well as 2-chloroethylated and 2-hydroxyethylated adducts, the N-7-position of guanine being the predominantly alkylated site. A close correlation exists between the potential of a given compound to induce DNA-DNA cross-links and its antineoplastic effectiveness. However, levels of DNA-DNA cross-linking in bone marrow and extent of myelosuppression as measured in rodents are also closely correlated. The design of new cross-linking analogues capable of directing the antineoplastically relevant activity predominantly to the target tumour appears therefore to be of great promise. Cross-linking agents have been attached to a variety of steroid hormone carrier molecules and the conjugates have been tested in structure-activity studies using hormone-receptor containing animal tumours. These studies have revealed that some hormone-linked antineoplastic agents are highly effective in receptor positive experimental tumours and are superior to mixtures of unlinked alkylating agents with hormones. Indications for a relative enrichment of DNA damaging effects in the tumour tissue and for reduced myelotoxicity have been obtained with specific hormone conjugates.

Regulatory role of retinoic acid on cultured mouse keratinocyte inositol phospholipid metabolism: dose-dependent release of inositol triphosphate

The incorporation of precursor 14C-myoinositol into the three cellular inositol phospholipids (PtdIns, PtdInsP, and PtdInsP2) of cultured, rapidly proliferating keratinocytes is significantly enhanced by the exogenous addition of a high concentration (1 X 10(-7) M) of all-trans retinoic acid or its analog 13-Cis analog, whereas a similar incubation with a low concentration (1 X 10(-10) M) of the same retinoid resulted in an insignificant incorporation of the radio-precursor into the three inositol phospholipids. Incorporation was most marked into the more phosphorylated PtdIns4P and PtdIns4,5P2. These results indicate that retinoic acid affects the biosynthesis of the inositol phospholipids at high concentrations. In contrast, the hydrolysis of 14C-PtdIns4,5P2 and release of 14C-InsP3 from the prelabeled keratinocytes is markedly enhanced by a low physiologic concentration (1 X 10(-10) M) of retinoic acid or its 13-Cis analog. The hydrolysis is rapid, with an accompanying elevated transient release of 14C-InsP3. High concentration (1 X 10(-5) M), on the other hand, supresses 14C-InsP3 release. These results taken together underscore a bifunctional, dose-dependent effect of both the all-trans-RA and its 13-Cis analog on the synthesis and hydrolysis of keratinocyte PtdIns4,5P2. Furthermore, the results suggest that at low physiologic concentrations, these retinoids may function as agonists to perturb the membrane resulting in induced rapid hydrolysis of cellular PtdIns4,5P2, which is coupled to a "transient" generation of InsP3 (an intracellular second messenger). The rapid formation of this putative "second messenger" may in turn play a role in the cellular proliferative or differentiating biochemical events in the murine keratinocytes.

Reversal of epidermal hyperproliferation in essential fatty acid deficient guinea pigs is accompanied by rapid generation of inositol triphosphate

This study probes the extent of coupling between the reversal of epidermal hyperproliferation induced by essential fatty acid (EFA) deficiency in guinea pigs, the hydrolysis of epidermal phosphatidylinositol 4,5-bisphosphate (PtdIns4,5P2), and the rapid formation of inositol triphosphate (InsP3). Our data revealed that the incorporation of free [3H]-inositol into phosphatidylinositol 4P and PtdIns4,5P2 of microsomal preparations from hyperproliferative epidermis was markedly elevated when compared with epidermis from normal-fed animals. The reversal of the hyperproliferating epidermis by dietary cross-over supplementations with safflower oil and primrose oil resulted in striking morphological normalization, cellular decrease in epidermal DNA synthesis, decrease in the biosynthesis of 14C-PtdIn4,5P2 from precursor 14C-inositol, and a significant increase in the rapid generation of transient InsP3 by epidermis from the cross-over-fed animals. These findings taken together indicate that the reversal of epidermal hyperproliferation to normal in guinea pig skin and the increased capability of the tissue microsomal preparation to generate InsP3 are linked in this tissue, and raise the possibility that epidermal inositol-phospholipid metabolism may play a role in the pathogenesis of cutaneous hyperproliferative disorders.

Development of more selective anti-cancer nitrosoureas

2-Chloroethyl-N-nitrosoureas are highly active anti-neoplastic drugs in clinical use for many years. Therapy with these DNA cross-linking agents is limited by their toxic side effects, cumulative and delayed bone marrow toxicity being the main dose-limiting one. Since the intrinsic anti-tumour activity of the nitrosourea group is very high, coupling to appropriate carrier molecules represents a challenge for target-orientated chemotherapy. Many human tumours contain receptors for steroid hormones. Therefore, 2-chloroethyl-N-nitroso-carbamoyl(CNC)-amino acid derivatives have been developed that are linked to steroid hormones. In the series of oestradiol (E2)-linked analogues CNC-L-alanine-E2-17-ester was significantly superior to other E2-linked congeners and to the unlinked equimolar mixture when tested against hormone-dependent N-methyl-N-nitrosourea-induced mammary carcinoma of the rat. Relevance of E2 receptor contents for therapy with E2-linked drugs is evidenced by loss of superiority of this analogue in hormone-independent mammary carcinomas. Some androgen-linked CNC-amino acids showed substantial affinity to the androgen receptor and in part also to the progesterone receptor. A preliminary study in rat leukaemia L5222 revealed the CNC-L-alanine-dihydrotestosterone-17-ester to be highly active. Studies with hormone-dependent tumour models are under way.

Turnover of inositol phospholipids in cultured murine keratinocytes: possible involvement of inositol triphosphate in cellular differentiation

The relationship between the turnover of inositol phospholipids (PtdIns) and the growth and differentiation of normal murine keratinocytes in culture was studied. Addition of myo-[U-14C]inositol to freshly plated cells resulted in a linear incorporation of radiolabel into the inositol phospholipids of the proliferating basal cells in culture during the initial 36 h, after which time the rate of radiolabel incorporation into the cells declined. The decrease in the incorporation of the radiolabel into the PtdIns, particularly the more highly phosphorylated PtdIns-4P and PtdIns4,5P2, correlated with the marked hydrolysis of these polyphosphoinositides and the rapid hydrolytic release of the inositol phosphates (InsP2 and InsP3). The transient accumulation of the InsPs correlated with the onset of differentiation of these cells. To ascertain whether the above observations of keratinocytes that were undergoing normal proliferative and differentiating phases in culture are consistent with the more synchronized populations of proliferative and differentiating cells, we investigated the turnover of PtdIns in a Ca2+-regulated system of homogenous populations of proliferating mouse keratinocytes in 0.09 mM Ca2+, and a differentiating population in 1.8 mM Ca2+. Our data from system revealed rapid hydrolysis of the PtdIns in the prelabeled low-Ca2+ proliferating cells immediately after a switch from the low to normal extracellular Ca2+ medium. Associated with this hydrolysis was the rapid and transient accumulation of the InsPs (maximum of 60 sec). The hydrolysis of the PtdIns and the accumulation of the InsP3 were not observed when the prelabeled proliferating cells were switched from a low to a low extracellular Ca2+ medium. These results suggest that the rapid hydrolysis of the PtdIns, particularly PtdIns4,5P2, which was accompanied by the hydrolytic release of InsP3, could be the initiating signal to program proliferating keratinocytes into differentiation.

Novel regulatory actions of 1 alpha,25-dihydroxyvitamin D3 on the metabolism of polyphosphoinositides in murine epidermal keratinocytes

The in vitro incubation of murine keratinocytes in the presence of 1 alpha,25-dihydroxyvitamin D3 enhanced the rapid hydrolysis of the prelabeled keratinocyte polyphosphoinositides (polyPtdIns) when compared to untreated cells. The rapid hydrolysis of the polyPtdIns and the release of the inositol phosphates (particularly InsP3 and InsP2) precede the onset of differentiation of these cells. These data therefore suggest that 1 alpha,25-dihydroxyvitamin D3 functions in vitro to initiate the rapid generation of InsP3 from cellular polyPtdIns; this in turn may mobilize intracellular Ca2+, thus providing the signal which program the murine keratinocytes from a proliferating mode into a differentiating mode.

Lysophospholipase activity in rat brain subcellular fractions

Lysophospholipase activity in brain subcellular fractions was measured by the release of myristic acid from 1-myristoylglycerophosphocholine or through the formation of [32P]glycerophosphocholine from [32P]lysophosphatidylcholine. Although the lysophospholipase activity was highest in microsomes, considerable enzyme activity was also found in other subcellular membrane fractions. The pH optimum for the microsomal enzyme was around 7, whereas the synaptosomes and non-synaptic plasma membranes exhibited a pH maximum around 8. Although the enzyme did not require divalent cations for activity, divalent cations (1 mM) such as Hg2+, Cu2+, and Zn2+ inhibited potently the enzyme activity. Enzyme activity was also partially inhibited by both saturated and polyunsaturated fatty acids (25-200 microM), and the inhibition seemed to be greater in the membrane than in the cytosolic fractions. Ionic detergents such as deoxycholate and taurocholate inhibited the lysophospholipase. On the other hand, the effect of Triton X-100 was biphasic, i.e., stimulation at concentrations below 100 micrograms/mg protein and inhibition at higher concentrations. Addition of cholesterol (50-250 micrograms/ml), but not cholesteryl esters, also potently inhibited enzyme activity. The presence of active lysophospholipase(s) in brain is probably an important mechanism for preventing unnecessary accumulation of lysophospholipids which may exert a deleterious effect on the membranes because of their detergent properties.

Metabolic relationship between arachidonate activation and its transfer to lysophospholipids by brain microsomes

Evidence is presented to indicate a metabolic relationship between arachidonic acid activation and its transfer to lysophospholipids by brain microsomes. Thus, in the presence of 1-acylglycerophosphocholines or 1-acyl-glycerophosphoinositols, the activation of labeled arachidonate to its acyl-CoA was enhanced, and the acyl-CoA formed was, in turn, transferred to the lysophospholipids to form the respective diacyl-glycerophospholipids. The "coupling effect" seems to pertain mainly to the lysophospholipids which are good substrates of the acyltransferase. Other lyso-compounds were either not effective or inhibitory to the arachidonate activation process. The activation-transfer activity mediated by the fatty acid ligase and acyltransferase could be dissociated by Triton X-100, which apparently stimulated the acyl-CoA ligase activity but inhibited the acyltransferase. These results suggest that fatty acid ligase and acyltransferase are located in close proximity within the membrane domain. The existence of a close metabolic relationship between these two enzymic reactions is important for maintaining a dynamic equilibrium between the free fatty acids and the membrane phospholipids. The mechanism is also useful in regulating the cellular acyl-CoA and lysophospholipid metabolism, because both compounds have membrane perturbing properties when present in excessive quantity.

Serum albumin washing specifically enhances arachidonate incorporation into synaptosomal phosphatidylinositols

Arachidonate incorporation into synaptosomal phospholipids was shown to be affected by factors including the procedure for preparation of the membrane fractions and preincubation of synaptosomes prior to assay of incorporation of arachidonate into both phosphatidylcholine (PC) and phosphatidylinositol (PI). However, the inhibition toward incorporation into PIs, but not PCs, was fully reversed when the membranes were washed with bovine serum albumin. A twofold increase in arachidonate incorporation into PIs was also observed when freshly prepared synaptosomes were washed with serum albumin immediately before assay of incorporation activity. The inhibitory action is thought to be due to an increase in polyunsaturated fatty acids and/or their oxidation products which may then elicit a special effect on the acyltransferase responsible for transferring arachidonate into phosphatidylinositols. The differences in fatty acid uptake and response to serum albumin also suggest the presence of different acyltransferase for acyl transfer to PIs and PCs.

Metabolism of oleoyl-CoA in rat brain synaptosomes: effects of calcium and post-decapitative ischemia

The hydrolysis of acyl-CoA by acyl-CoA hydrolase (EC 3.1.2.2.) in brain synaptosomes was inhibited by calcium. This inhibition was partly due to interaction of Ca2+ with the acyl-CoA, which was present in the soluble form, and partly due to complex formation among acyl-CoA, Ca2+ and membrane phospholipids. The inhibition of acyl-CoA hydrolase activity, as well as the complex formation, could be reversed if incubation was carried out in the presence of Ca2+ chelating agents. Synaptosomes isolated from brain samples after 1 min of postdecapitative treatment showed a decrease in oleoyl-CoA hydrolase activity. The physiological implication of acyl-CoA metabolism in relation to synaptic function is discussed.

Clinical studies on the antitumor action of mecaphane

Over a period of 4 years, 241 patients with advanced cancer were treated with mecaphane alone in 11 hospitals. Effective objective responses were obtained in 100 patients (41.4%). The response was most conspicuous in chronic granulocytic leukemia, with remission in 37 of 40 patients; in Hodgkin's disease and lymphosarcoma response rates were 60% and 47.3%, respectively. Mecaphane had an analgesic action in metastatic osteolytic bone cancer, and two patients with such metastases even attained recalcification of the osteolytic destructive lesions. The common toxic manifestations of mecaphane were leukopenia (33.6%), gastrointestinal upsets (28.2%), and thrombocytopenia (12.8%). It is concluded, therefore, that mecaphane could be a good antitumor agent in clinical use. It is less expensive and can be taken orally. Further trials of this drug are recommended.