Strongly baryon-dominated disk galaxies at the peak of galaxy formation ten billion years ago.

In the cold dark matter cosmology, the baryonic components of galaxies-stars and gas-are thought to be mixed with and embedded in non-baryonic and non-relativistic dark matter, which dominates the total mass of the galaxy and its dark-matter halo. In the local (low-redshift) Universe, the mass of dark matter within a galactic disk increases with disk radius, becoming appreciable and then dominant in the outer, baryonic regions of the disks of star-forming galaxies. This results in rotation velocities of the visible matter within the disk that are constant or increasing with disk radius-a hallmark of the dark-matter model. Comparisons between the dynamical mass, inferred from these velocities in rotational equilibrium, and the sum of the stellar and cold-gas mass at the peak epoch of galaxy formation ten billion years ago, inferred from ancillary data, suggest high baryon fractions in the inner, star-forming regions of the disks. Although this implied baryon fraction may be larger than in the local Universe, the systematic uncertainties (owing to the chosen stellar initial-mass function and the calibration of gas masses) render such comparisons inconclusive in terms of the mass of dark matter. Here we report rotation curves (showing rotation velocity as a function of disk radius) for the outer disks of six massive star-forming galaxies, and find that the rotation velocities are not constant, but decrease with radius. We propose that this trend arises because of a combination of two main factors: first, a large fraction of the massive high-redshift galaxy population was strongly baryon-dominated, with dark matter playing a smaller part than in the local Universe; and second, the large velocity dispersion in high-redshift disks introduces a substantial pressure term that leads to a decrease in rotation velocity with increasing radius. The effect of both factors appears to increase with redshift. Qualitatively, the observations suggest that baryons in the early (high-redshift) Universe efficiently condensed at the centres of dark-matter haloes when gas fractions were high and dark matter was less concentrated.

1-(p-carbamoylphenyl)-3,3-dimethyl-triazene, an antitumour agent.

In the crystal structure of the title compound, 4-(3,3-dimethyl-1-triazeno)benzamide, C9H12N4O, (2), the N = N double bond [1.282 (8) A] is 0.030 A shorter than the N--N single bond [1.312 (8) A], but both bonds are shorter than an isolated N--N single bond suggesting that there is double-bond character in each N--N bond, although it is unequally distributed. The molecule adopts a trans geometry around the N = N bond, but there is a significant deviation from planarity between the benzene ring and the plane of the triazene moiety. Compound (2) forms chains in the solid state in which the molecules are linked by C = O...H--N hydrogen bonds between carbamoyl groups. These chains are cross-linked into sheets by hydrogen bonding between the second N--H moiety and triazene units in adjacent chains.

Application of 15N nuclear magnetic resonance spectroscopy to the determination of the stability of aryl nitrogen mustards.

An excellent correlation has been shown to exist between the 15N NMR chemical shifts of a series of aryl nitrogen mustards and the Hammett constant, sigma, which is much improved by the use of sigma-. These chemical shifts also correlate well with the hydrolysis rates of the compounds in 50% aqueous acetone at 66 degrees C and their alkylation of 4-(4'-nitrobenzyl)pyridine under similar conditions. Thus 15N NMR is a straightforward and material-conserving method for estimating the relative stabilities of aryl nitrogen mustards.

Alkylation of DNA by the nitrogen mustard bis(2-chloroethyl)methylamine.

Alkylation of DNA by the nitrogen mustard bis(2-chloroethyl)methylamine (mechlorethamine; HN2) gave four principal products, derived by mono-alkylation of guanine at N-7 and adenine at N-3 and by cross-linking of guanine to guanine or guanine to adenine at these positions. These products were isolated by hydrolysis from DNA at neutral pH, followed by ion-exchange chromatography on SP-Sephadex and reversed phase chromatography on ODS. They were characterized by identification with products from the reaction of nitrogen mustard with adenine or deoxyguanylic acid, and by their UV, mass, and proton magnetic resonance spectra.

Synthesis and cytotoxicity of potential tumor-inhibitory analogues of trimelamol (2,4,6-tris[(hydroxymethyl)methylamino]-1,3,5-triazine) having electron-withdrawing groups in place of methyl.

In exploring the structural features which determine the antitumor activity of 2,4,6-tris-[(hydroxymethyl)methylamino]-1,3,5-triazine (trimelamol, 1), we have synthesized analogues in which the methyl groups have been replaced by the electron-withdrawing substituents 2,2,2-trifluoroethyl (5), propargyl (13), and cyanomethyl (15) via the respective tris(alkylamino)triazines 3, 12, and 14. Three mono[(hydroxymethyl)amino]triazines (4, 7, and 10) were also prepared. All the new tris(hydroxymethyl) derivatives showed cytotoxicities toward a variety of experimental rodent and human ovarian tumor cell lines similar to those shown by 1, the cyanomethyl analogue (15) having the most favorable profile. Mono(hydroxymethyl) derivatives (4 and 7) were ca. one-third as toxic. The new tris(hydroxymethyl) analogues were more stable to aqueous hydrolysis than was 1. Half-life (pH 7.5) values were, for 1, 120 min, for 5, 690 min, for 13, 450 min, and for 15, 275 min, but at pH 2.0, 15 (t1/2 350 min) was the most stable. This cyanomethyl analogue was also the most water-soluble, being comparable to 1 whereas 5 and 13 were poorly soluble.

Phospholipid metabolites, prognosis and proliferation in human breast carcinoma.

The content of the phospholipid metabolites, phosphocholine, phosphoethanolamine, glycerophosphorylcholine and glycerophosphorylethanolamine was measured in chemical extracts from 46 human breast carcinoma using 31P NMR spectroscopy. Some patients had received therapy prior to tumour resection. The data were therefore stratified into two groups: (i) all tumours; and (ii) untreated tumours. Three indices of tumour proliferation i.e., mitotic index, Ki67 and S-phase fraction were determined on tissue from the same tumours and were found not to correlate with the content of any of these metabolites. In addition oestrogen-receptor status and density, tumour grade and DNA ploidy were obtained on some tumours. The phosphocholine content was higher in high grade tumours when compared with low grade tumours. There was no apparent relationship between DNA ploidy and the content of any of these metabolites. Glycerophosphorylcholine content of oestrogen-receptor positive tumours correlated with receptor density. However, there was no significant difference between receptor positive and negative tumours in the content of any of the phospholipid metabolites measured.

X-ray studies on anti-tumour triazenes. Structures of 1-(4-carbamoylphenyl)-3,3-dimethyltriazene 1-oxide and 3,3-dimethyl-1-(4-nitrophenyl)triazene.

The molecular structures of the title compounds have been determined by X-ray crystallographic methods. The analyses revealed differences in the geometry, and by inference the bond delocalization in these two triazenes owing to the presence in the 1-oxide structure of an N-O bond. The geometries are compared to the crystal structures of the isomeric 3-oxides [Kuroda & Wilman (1985). Acta Cryst. C41, 1543-1545; Neidle, Webster, Kuroda & Wilman (1987). Acta Cryst. C43, 674-676] which shows the dominance of an alternative tautomeric equilibrium for the triazene groups.

Comparison of half-lives and cytotoxicity of N-chloroethyl-4-amino and N-mesyloxyethyl-benzoyl compounds, products of prodrugs in antibody-directed enzyme prodrug therapy (ADEPT).

The synthesis of two novel drugs, 4-[bis[2-(mesyloxy)ethyl]amino]benzoic acid (7) and 4-[(2-chloroethyl)[2-(mesyloxy)ethyl]amino]benzoic acid (8) is described here. They are the active drugs of two prodrugs (9 and 10) designed for use as anti-cancer agents. The prodrugs (9, 10 and 11) were made as a series of compounds which are bifunctional alkylating agents in which the activating effect of the ionized carboxyl function is masked through an amide bond to a glutamic acid residue. These relatively inactive prodrugs were designed to be activated to their corresponding alkylating agent active drugs (7, 8 and 12 respectively) at a tumour site by prior administration of a monoclonal antibody conjugated to a bacterial enzyme. This system is called antibody-directed enzyme prodrug therapy (ADEPT). The chemical half-lives of the prodrugs and their active drugs were measured in order to determine their relative reactivities. The half-lives ranged from 21 to 324 min for the active drugs and from 42 to 1158 min for the prodrugs. The viability of two different tumour cell lines was monitored with each active drug and prodrug. The IC50 values varied from 65 to 625 microM for the active drugs: no IC50 values could be obtained for the prodrugs, using a rapid incubation procedure. Each in vitro technique demonstrated the ability of the glutamic acid moiety to deactivate the drugs, forming effective prodrugs.

Phase I trial and pharmacokinetics of trimelamol (N2,N4,N6-trihydroxymethyl-N2,N4,N6-trimethylmelamine).

Trimelamol is an analogue of hexamethylmelamine and pentamethylmelamine which does not require metabolic activation and is sufficiently soluble to allow parenteral administration. A Phase I trial has been performed at the Royal Marsden Hospital in which two schedules of administration have been evaluated, a single i.v. infusion repeated every 3 weeks and 3 daily doses repeated every 3 weeks. Pharmacokinetic analysis was performed at all dose levels on both schedules and a linear correlation was demonstrated between dose and area under the curve. Myelosuppression was dose limiting for single dose administration with a maximum tolerated dose of 2400 mg/m2. Median leukocyte nadirs at 1800, 2100, and 2400 mg/m2 were 3.2, 2.6, and 1.5 x 10(9)/liter. Thrombocytopenia and anemia also occurred but were not dose limiting. Doses greater than 1500 mg/m2 caused WHO grade 3 nausea and vomiting but no acute sedation. Three day administration appeared to be less myelosuppressive, giving a maximum tolerated dose of 1000 mg/m2. Median leukocyte nadirs at 800, 900, and 1000 mg/m2 daily for 3 days were 3.0, 2.3, and 1.5 x 10(9)/liter. Nonhematological toxicities were also less marked on the fractionated schedule. Antitumor effects were observed including 1 complete and 9 partial responses. Demonstration of activity in ovarian cancer has led to further evaluation in this disease using the 3-day schedule at a dose of 800 mg/m2 daily for 3 days.

Synthesis and ribonucleotide reductase inhibitory activity of analogues of 2,3-dihydro-1H-imidazo[1,2-b]pyrazole (IMPY).

A series of derivatives of the ribonucleotide reductase inhibitory anti-tumour agent 2,3-dihydro-1H-imidazo[1,2-b]pyrazole (IMPY), including all the methyl analogues, have been synthesised. IMPY itself caused 50% inhibition of L1210 tumour-derived ribonucleotide reductase at a concentration of 0.39 mM, comparable with enzyme obtained from other sources. The analogues proved to be no better than IMPY, either as inhibitors of this enzyme or of the growth of L1210 cells in vitro. No correlation was apparent between biological activity and position of substitution.

Analogues of 3-ethyl-3-(4-pyridyl)piperidine-2,6-dione as selective inhibitors of aromatase: derivatives with variable 1-alkyl and 3-alkyl substituents.

3-Ethyl-3-(4-pyridyl)piperidine-2,6-dione (1) is a strong competitive inhibitor of human placental aromatase (Ki = 1.1 microM; testosterone as substrate) that, unlike the structurally related aromatase inhibitor aminoglutethimide (2), is not also an inhibitor of the cholesterol side-chain cleavage enzyme desmolase. An improved synthesis of 1 is described, which was readily adapted to the preparation of homologues in a series of 3-alkyl-3-(4-pyridyl)-piperidine-2,6-diones (6-13). Alkylation of 1 afforded a second series, comprising 1-alkyl-3-ethyl-3-(4-pyridyl)-piperidine-2,6-diones (14-23). Inhibitory activity toward aromatase was maximal in both series for the octyl derivatives. Respective Ki values for the competitive inhibition exerted by the 3-octyl (12) and the 1-octyl (21) analogues with testosterone as substrate were 0.09 and 0.12 microM. The compounds 1, 2, 12, and 21 differed in their relative potencies as inhibitors of the aromatization of testosterone and androstenedione. Respective Ki values were as follows: for 1, 1.1 and 14 microM (ratio 12.7); for 2, 0.6 and 1.8 microM (3); for 12, 0.09 and 0.20 microM (2.2); and for 21, 0.12 and 0.48 microM (4).

Iron and haem complexation studies of 2,3-dihydro-1H-imidazo(1,2-b)pyrazole (IMPY, NSC 51143), a tumour cell ribonucleotide reductase inhibitor.

Spectrophotometric studies have been undertaken of the interaction of various iron-based systems with the anti-tumour agent, 2,3-dihydro-1H-imidazo(1,2-b)pyrazole (IMPY, NSC (51143), a ribonucleotide reductase inhibitor. No evidence was obtained of direct complexation in aqueous media at 25 degrees C between IMPY and Fe2+ (aq) (pH 1.5-6.8) or Fe3+ (aq) (pH 1.0-3.5), nor with a mu-oxo-bridged iron dimer (Fe--O--Fe) system. There was definitive spectral evidence of complexation of IMPY with protoporphyrin IX iron (II) at pH 7.4 and 12.9 both in the absence and presence of carbon monoxide bound at the haem-iron site. Binding of IMPY to protoporphyrin IX iron (III), in contrast, was not detected. Binding between IMPY and various iron sites important in biochemistry is discussed briefly, especially in relation to the structural properties of IMPY (from X-ray data) and the Fe--O--Fe bridge system in ribonucleotide reductase and model systems. The difficulties of the use of free heterocyclic nitrogenous bases in medicinal chemistry are discussed.

Gas chromatographic analysis of triethylenethiophosphoramide and triethylenephosphoramide in biological specimens.

Comprehensive pharmacokinetic studies could realise a greater potential for the antitumour agent triethylenethiophosphoramide (ThioTEPA), and these would be aided by the development of a selective and sensitive assay. After extraction of ThioTEPA and its metabolite, triethylenephosphoramide (TEPA), from plasma using Sep-Pak C18 cartridges, the compounds were separated by capillary chromatography, detected using a nitrogen detector and quantified by reference to an internal standard, hexaethylphosphoramide. The limits of sensitivity were 1-5 ng/ml. Analytical recoveries were 74 and 95%, for TEPA and ThioTEPA, respectively, in the therapeutic range. At similar concentrations, extents of protein binding, determined by ultrafiltration, were not significant. Preliminary investigations of the elimination of ThioTEPA show that drug loss occurs more quickly in mice than in humans and in both species the metabolite is extensively recycled.

Tumor inhibitory triazenes. 3. Dealkylation within an homologous series and its relation to antitumor activity.

The in vivo antitumor activity and in vitro metabolic dealkylation have been measured for an homologous series of 3-alkyl-1-(4-carbamoylphenyl)-3-methyltriazenes and have been compared with their partition coefficients. This investigation has shown that the extent of oxidative metabolism in vitro and the antitumor activity in vivo of these compounds are dependent upon hydrophobicity. These findings provide confirmation for the relationship between metabolism and antitumor activity for aryldialkyltriazenes.

Tumor inhibitory triazenes. 2. Variation of antitumor activity within an homologous series.

An homologous series of water-soluble, chemically stable analogues of 5-(3,3-dimethyl-1-triazeno)imidazole-4-carboxamide (DTIC) has been prepared with activity comparable to DTIC in an experimental tumor system. The antitumor activity of this series of 3-alkyl-1-(4-carboxyphenyl)-3-methyltriazenes rapidly diminishes at alkyl chain lengths greater than pentyl. Partition coefficients were determined, but no relationship between these and antitumor activity could be established.