Cystathionine in rat brain: Catabolism in vivo

The content of cystathionine was measured in 35 rat brains; the range was 10–120 nmol/g wet weight and thus the variability of cystathionine content in rat brain was emphasized. The regional distribution of cystathionine was also determined: the highest level was found in cerebellum; the lowest level was observed in the white and gray matter of the hemispheres. These results are different from those obtained in other species. The radioactive metabolites formed froml-[³⁵S]cystathionine injected intracisternally were measured in brains of rats killed at the following times after injection: 0.25, 1, 2, 4, 6, 9, 16, and 27 hr. The radioactivity was found both in the proteins and in the acid-soluble fraction. In the acid-soluble fraction the radioactivity was found in various ninhydrin-reacting compounds: (cysteic + cysteine sulfinic) acid, taurine, reduced and oxidized glutathione, cystine, cystathionine, and a compound tentatively identified as the mixed disulfide of cysteine and glutathione. The radioactivity of cystathionine decreased exponentially between the 1st and the 27th hour after injection and its half-life was estimated to be about 5 hr. The radioactivity in the other ninhydrin-reacting compounds increased until the 9th hour after injection, then decreased. Half of this radioactivity was present in reduced glutathione, the rest being shared equally between: (cysteic + cysteine sulfinic) acid, taurine, and the mixed disulfide. It is worthwhile to note that the radioactivity in the cystine fraction was always very low.     

Single base pair germ-line deletion in the p53 gene in a cancer predisposed family

A family with an aggregation of adrenocortical carcinoma, rhabdomyosarcoma, osteosarcoma, and early onset breast cancer was referred to our laboratory. Because this aggregation was reminiscent of Li-Fraumeni syndrome, germ-line mutation of the p53 tumor suppressor gene was sought in the DNA of two affected members. The highly conserved regions spanning exons 5 to 8 of the p53 gene were screened by a previously validated denaturing gradient gel electrophoresis method. A single base pair deletion at codon 215 was detected in constitutional DNA of the two patients, and in the DNA extracted from an adrenocortical carcinoma tumor specimen of the propositus. This deletion is predicted to lead to the formation of a truncated p53 protein, a relatively rare event in Li-Fraumeni families. The spectrum of tumors observed in this family does not differ markedly from the spectrum observed in families with missense p53 mutations.     

Molecular definition of the 11p15.5 region involved in Beckwith-Wiedemann syndrome and probably in predisposition to adrenocortical carcinoma

Summary To define more precisely, in molecular terms, the region involved in Beckwith-Wiedemann syndrome (BWS), we have studied patients with BWS and a constitutional duplication of 11p15 using eight 11p15 markers. In the first case with a de novo duplication and extra material on 11p, the region spanning pter to CALCA, excluded, was duplicated. In the second case, the rearrangement was characterized using somatic cell hybrids established with lymphocytes from the father who carried a balanced translocation t(11;18)(p15.4;p11.1). The breakpoint lay exactly in the same region. It could thus be inferred that the two sons, who were the first cases reported of BWS with dup11p15 and adrenocortical carcinoma (ADCC), carried a duplication similar to that observed in the first case. Together with evidence for specific somatic chromosomal events leading to loss of 11p15 alleles in familial cases of ADCC, it can be hypothesized that a gene involved in predisposition to ADCC maps to region 11p15.5.     

Synthesis and characterization of the novel Pt(II) complexes of the types cis- and trans-Pt(Ypy)(pyrazine)Cl2, K2[Cl3Pt(μ-pyrazine)PtCl3] and trans, trans-(Ypy)Cl2Pt(μ-pyrazine)Pt(Ypy)Cl2 (Ypy = pyridine derivative)

New types of Pt(II) mixed-ligand complexes containing a pyridine derivative (Ypy) and pyrazine (pz) were synthesized. The compounds were characterized by infrared spectroscopy and by multinuclear (¹H, ¹³C and ¹⁹⁵Pt) magnetic resonance. The complexes cis-Pt(Ypy)(pz)Cl₂ were synthesized from the reaction of K[Pt(Ypy)Cl₃] with pyrazine (1:1 proportion) in water. When the reaction was carried on in a 2:1 ratio, a mixture of compounds was obtained, which was refluxed in CH₂Cl₂ for several days. The final product was found to be pure and it was identified as trans,trans-Cl₂(Ypy)Pt(μ-pyrazine)Pt(Ypy)Cl₂. The cis monomers isomerize to the trans isomers in organic solvents. Different methyl derivatives of pyridine were studied in order to determine the influence of substitution in ortho position on the pyridine ligand in the complexes. In IR spectroscopy, the cis monomers showed two ν(Pt-Cl) bands, while the trans monomers and dinuclear species showed only one ν(Pt-Cl) band. The NMR results were interpreted in relation to the solvent effect, which seems important in these complexes. The ¹⁹⁵Pt NMR signals of the cis monomers were found at slightly higher fields than those of the corresponding trans isomers. The coupling constants J(¹⁹⁵Pt-¹H) and J(¹⁹⁵Pt-¹³C) are larger in the cis geometry. The δ(¹⁹⁵Pt) of the dinuclear species were found close to those of the trans monomers and the coupling constants are similar to those of the trans monomers, strongly suggesting a trans-trans configuration for the dinuclear compounds. The pyrazine-bridged complex K₂[Cl₃Pt(μ-pz)PtCl₃] was also synthesized and spectroscopically studied. The crystal structures of the compounds cis-Pt(3,5-lut)(pz)Cl₂ and trans-Pt(2,4,6-col)(pz)Cl₂ were determined by X-ray diffraction methods.     

Multinuclear NMR study and crystal structures of complexes of the types cis- and trans-Pt(amine)2I2

Complexes of the types cis- and trans-Pt(amine)₂I₂ were studied by spectroscopic methods, especially by multinuclear NMR spectroscopy. In ¹⁹⁵Pt NMR, the cis diiodo compounds with primary amines were observed between −3342 and −3357 ppm in acetone, while the trans compounds were found between −3336 and −3372 ppm. For the secondary amines, the chemical shifts were observed at lower fields. In ¹H NMR, the trans complexes were observed at higher fields than the cis compounds, while in ¹³C NMR, the reverse was observed. The ²J(¹⁹⁵Pt-¹H) and ³J(¹⁹⁵Pt-¹H) coupling constants are larger for the cis compounds (ave. 67 and 45 Hz, respectively) than for the trans isomers (ave. 59 and 38 Hz). In ¹³C NMR, the values of ²J(¹⁹⁵Pt-¹³C) and ³J(¹⁹⁵Pt-¹³C) were also found to be larger for the cis complexes (ave. 17 and 39 Hz versus 11 and 28 Hz). There seems to be a slight dependence of the pK_a values of the protonated amines or the proton affinity in the gas phase with the δ(Pt) chemical shifts. The crystal structures of eight diiodo complexes were determined. These compounds are cis-Pt(CH₃NH₂)₂I₂, cis-Pt(n-C₄H₉NH₂)₂I₂, cis-Pt(Et₂NH)₂I₂, trans-Pt(n-C₃H₇NH₂)₂I₂, trans-Pt(iso-C₃H₇NH₂)₂I₂, trans-Pt(n-C₄H₉NH₂)₂I₂, trans-Pt(t-C₄H₉NH₂)₂I₂ and trans-Pt(Me₂NH)₂I₂. The Pt-N bond distances located in trans position to the iodo ligands were compared to those located in trans position to the amines. The Pt-N bond in cis-Pt(Et₂NH)₂I₂ are much longer than the others, probably caused by the steric hindrance of the two very bulky ligands located in cis positions.     

Multinuclear magnetic resonance spectroscopy and crystal structures of iodo-bridged dinuclear Pt(II) complexes with amines

Complexes of the types cis-Pt(amine)₂I₂ were transformed into the iodo-bridged dimers, which were characterized mainly by multinuclear (¹⁹⁵Pt, ¹H and ¹³C) magnetic resonance spectroscopy. For bulby amines, the dinuclear species were synthesized directly from K₂[PtI₄]. Compounds with several primary aliphatic and cyclic amines and two secondary amines were studied. In ¹⁹⁵Pt NMR, two signals were observed between −3899 and −4080 ppm in acetone. These species were assigned to the cis and trans dinuclear compounds I(amine)Pt(μ-I)₂PtI(amine). We suggest that the most shielded compound is the trans isomer. The difference between the two isomers is 12-13 ppm for the primary amine system and 26-27 ppm for the two secondary amines. There seems to be a slight dependence of the proton affinity in the gas phase of the amine (linear amines) with the δ(Pt) chemical shifts of the dinuclear Pt(II) compounds. The ²J(¹⁹⁵Pt-¹HN) coupling constants are slightly larger for the trans isomers (average 67 Hz, vs. 56 Hz). The ³J(¹⁹⁵Pt-¹H) coupling constants were detected only for the dimethylamine compounds, 46 Hz (trans) and 44 Hz (cis). In ¹³C NMR, the values of ²J(¹⁹⁵Pt-¹³C) and ³J(¹⁹⁵Pt-¹³C) were also found to be very slightly larger for the trans complexes (average 19 and 25 Hz vs. 15 and 18 Hz). The structures were confirmed by X-ray diffraction studies of the n-butylamine and diethylamine compounds. The two crystals were those of the trans dinuclear complexes.