Superficial siderosis of the central nervous system: a case with an unruptured intracranial aneurysm

We present a case of superficial siderosis (SS) of the central nervous system (CNS) with an unruptured intracranial aneurysm to illustrate that the commonly encountered unexplainable progressive sensorineural hearing loss (SNHL) can be an important sign for the early awareness of this rare disorder. The literature on SS is reviewed and the pathogenesis of SS is discussed.

Potent pituitary-gonadal axis suppression and extremely low anaphylactoid activity of a new gonadotropin releasing hormone (GnRH) receptor antagonist "azaline B"

We report here the biological characterization of azaline B, a new gonadotropin releasing hormone (GnRH) receptor antagonist, with the following amino acid sequence: [Ac-D-Nal1, D-Cpa2, D-Pal3, Aph5(atz), D-Aph6(atz), Ilys8, D-Ala10]-GnRH. Azaline B was shown to suppress several reproductive processes in rats including ovulation, and had very low anaphylactoid activity compared with other GnRH antagonists. Azaline B inhibited histrelin (a GnRH agonist)-mediated follicle stimulating hormone (FSH) and luteinizing hormone (LH) release from cultured rat pituitary cells. Three antagonists ([Nal-Glu]-GnRH, [Nal-Lys]-GnRH ("antide"), and azaline B) inhibited 0.1 nM histrelin-mediated gonadotropin release to baseline levels with EC50 values of approximately 0.6 nM. Azaline B, when injected s.c. into rats on the afternoon of proestrus, was more potent at inhibiting ovulation than either [Nal-Glu]-GnRH or [Nal-Lys]-GnRH. The relative order of antiovulatory potencies of the three antagonists was azaline B > [Nal-Glu]-GnRH > [Nal-Lys]-GnRH. Similar azaline B potency was shown by its ability to suppress gonadotropin levels in castrated rats. The improved selectivity of azaline B was demonstrated when it was compared with other GnRH antagonists in the cutaneous anaphylactoid assay (local wheal response) in rats. Results with azaline B were not significantly different from results with vehicle in this assay. [Nal-Glu]-GnRH was more than twice as potent as [Nal-Lys]-GnRH in stimulating a wheal response. Furthermore, the maximal wheal response produced by azaline B was only 0.6 times that of [Nal-Lys]-GnRH, currently one of the most selective antagonists identified. Finally, both azaline B and [Nal-Lys]-GnRH were much less potent than [Nal-Glu]-GnRH in the guinea pig cardiopulmonary anaphylactoid assay after i.v. administration. These data show that azaline B is a potent and selective GnRH receptor antagonist with little or no anaphylactoid activity in animal models, and therefore has potential for use in the treatment of many reproductive endocrine disorders, as well as for use as a contraceptive.

Inhibition of the human methylmalonyl-CoA mutase by various CoA-esters

Human methylmalonyl-CoA mutase is inhibited by ethylmalonyl-CoA, cyclopropylcarbonyl-CoA carboxylate, and methylenecyclopropylacetyl-CoA, which are substrate, intermediate, and product analogs, respectively. The mode of inhibition by each analog is reversible and mixed with respect to the substrate, methylmalonyl-CoA. This implies that the inhibitors are able to bind to both free enzyme and to the enzyme-substrate complex, although with affinities that are 4.5- to 10-fold different for the two species. The Ki1 for the cyclopropylcarbonyl-CoA carboxylate (0.26 +/- 0.07 mM), is 4-fold greater than the Km(app) measured for the substrate, methylmalonyl-CoA. Additionally, ethylmalonyl-CoA functions as an alternate substrate and is metabolized to methylsuccinyl-CoA. The human mutase is a homodimer that binds 1 mol of cobalamin per subunit. So, the observed mixed inhibition kinetics by substrate analogs is curious. Our finding that methylenecyclopropylacetyl-CoA, the causative agent of Jamaican "vomiting sickness," inhibits methylmalonyl-CoA mutase, while interesting, is probably not physiologically important because of the relatively high inhibition constants (Ki1 = 0.47 +/- 0.12 mM and Ki2 = 2 +/- 0.34 mM) observed with this compound.

A non-heme iron protein with heme tendencies: an investigation of the substrate specificity of thymine hydroxylase

Thymine hydroxylase from Rhodotorula glutinis catalyzes the oxidation of thymine to its alcohol, aldehyde, and carboxylic acid in three successive reactions. Each step involves stoichiometric consumption of O2 and alpha-ketoglutarate and formation of CO2 and succinate. Given the promiscuity of this enzyme, it was hoped that it would serve as a prototype for understanding the mechanism of this class of enzymes, the non-heme Fe2+ dioxygenases. Kinetic parameters for thymine, O2, Fe2+, and alpha-ketoglutarate have been determined, and isotope effect analysis of (trideuteriomethyl)thymine with enzyme reveals D(V) = 2.08 and D(V/K) = 1.11 at saturating O2. The kinetic parameters for (hydroxymethyl)uracil oxidation have been determined, and incubation of (5'-R)- and (5'-S)-[5'-2H]-5-(hydroxymethyl)uracil with enzyme reveals stereospecific removal of the pro-S hydrogen. No apparent isotope effect is observed in this reaction. The substrate specificity of this enzyme has been examined in detail. The enzyme can catalyze epoxidation, oxidation of a thioether to a sulfoxide and a sulfone, hydroxylation of an unactivated carbon-hydrogen bond, and oxidation of a methylamine to formaldehyde, as revealed through studies with 5-vinyluracil, 5-(methylthio)uracil, 5,6-dihydrothymine, and 1-methylthymine, respectively. In each case, the products were identified by gas chromatography-mass spectrometry, and 18O2-labeling studies revealed that one atom from O2 is incorporated into each product. The enzyme has also been shown to catalyze an uncoupling of hydroxylation and decarboxylation in the presence of a substrate analog incapable of undergoing hydroxylation or a substrate that is difficult to oxidize.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of an internally initiated integrase protein of HIV-1 produced in E. coli

In E. coli cells transformed by an expression vector for the production of the protease (PR) integrase (IN) of HIV-1, three vitally encoded proteins were produced: an 11-kDa protein and a 32-kDa protein identified by immunoassays as the mature PR and IN protein, respectively, and an additional protein 15-kDa in size that reacted strongly with an antiserum recognizing a region in the carboxyl half of the IN protein. The kinetics of its synthesis indicated that it was not a degradation product of p32-IN, rather it probably arose from internal initiation at an AUG codon in the middle of the IN gene. Amino terminal sequence analysis of the first 70 residues demonstrated a perfect match with those predicted from the nucleotide sequence, beginning with the methionine codon at position 154 of the integrase gene.

Potency and activity variation of LHRH analogs in different models and species

The LHRH agonist [D-His(Bzl)6, Pro9-NHEt]LHRH was estimated to be 3.4, 4.4 and 9.2 times more potent than LHRH as a stimulator of ovulation in Nembutal-anesthetized, androgen-sterilized and diestrus rats, respectively; and 57 times more potent than LHRH as a stimulator of uterine growth in immature mice. Higher doses of agonist were required to induce ovulation in diestrus hamsters and mice than were needed in diestrus rats. Rats and hamsters also exhibited different sensitivities to an antagonist of LHRH. The LHRH antagonist [N-Ac delta 3-Pro1, D-pF-Phe2,D-Trp3,6]LHRH was active but higher doses were required to inhibit ovulation in hamsters than were needed in rats. In addition, treatment at 1500 hr on the day of proestrus in rats, in contrast to treatment at 1000 hr in hamsters, caused the greatest inhibition of ovulation. It is clear from these data, that the estimated in vivo potencies of analogs of LHRH are greatly influenced by species and animal model, as well as route of administration and biopharmaceutic factors previously reported.

Antifertility activity of Montanoa tomentosa (Zoapatle)

According to folklore medicine, the Mexican plant zoapatle (Montanoa tomentosa) possesses antifertility activity in women. We report here the effect of various isolated preparations from this plant on early pregnancy in several rodent species including the mouse, rat, hamster, and guinea pig. When an aqueous extract of the leaves similar to the tea utilized in folklore medicine was administered orally during early stages of pregnancy, no antifertility activity could be detected. Day 22 pregnant guinea pigs, however, provided an animal model which allowed conservation of test materials and which showed the antifertilty activity of the plant extracts. Purer fractions derived from the plant were more potent in this assay system when administered either intraperitoneally or orally. As the purity of the extracts (and hence the quantity of active ingredient administered) increased, we were able to demonstrate inhibition of implantation in rats and mice when administered on days 1-6 and in hamsters when administered on days 4-6 of gestation. Preliminary data indicate the plant extracts are not estrogenic. It is concluded that zoapatle plant extracts possess unique antifertility activity.