25-Hydroxyvitamin D depletion does not exacerbate MPTP-induced dopamine neuron damage in mice

Recent clinical evidence supports a link between 25-hydroxyvitamin D insufficiency (serum 25-hydroxyvitamin D [25(OH)D] levels <30 ng/mL) and Parkinson's disease. To investigate the effect of 25(OH)D depletion on neuronal susceptibility to toxic insult, we induced a state of 25(OH)D deficiency in mice and then challenged them with the dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). We found there was no significant difference between control and 25(OH)D-deficient animals in striatal dopamine levels or dopamine transporter and tyrosine hydroxylase expression after lesioning with MPTP. Additionally, we found no difference in tyrosine hydroxylase expression in the substantia nigra pars compacta. Our data suggest that reducing 25(OH)D serum levels in mice has no effect on the vulnerability of nigral dopaminergic neurons in vivo in this model system of parkinsonism.     

Hybridization and barriers to gene flow in an island bird radiation

While reinforcement may play a role in all major modes of speciation, relatively little is known about the timescale over which species hybridize without evolving complete reproductive isolation. Birds have high potential for hybridization, and islands provide simple settings for uncovering speciation and hybridization patterns. Here we develop a phylogenetic hypothesis for a phenotypically diverse radiation of finch-like weaver-birds (Foudia) endemic to the western Indian Ocean islands. We find that unlike Darwin's finches, each island-endemic Foudia population is a monophyletic entity for which speciation can be considered complete. In explaining the only exceptions-mismatches between taxonomy, mitochondrial, and nuclear data-phylogenetic and coalescent methods support introgressive hybridization rather than incomplete lineage sorting. Human introductions of known timing of one island-endemic species, to all surrounding archipelagos provide two fortuitous experiments; (1) population sampling at known times in recent evolutionary history, (2) bringing allopatric lineages of an island radiation into secondary contact. Our results put a minimum time bound on introgression (235 years), and support hybridization between species in natural close contact (parapatry), but not between those in natural allopatry brought into contact by human introduction. Time in allopatry, rather than in sympatry, appears key in the reproductive isolation of Foudia species.     

Adenoid cystic carcinoma intermingled with ductal carcinoma of the breast: a case report and review of the literature

ABSTRACT: INTRODUCTION: Adenoid cystic cancer of the breast is a rare condition, and even rarer are the cases where it is histologically mixed with other variants of cancer within a single lesion. In this report, one of the few cases of mixed adenoid cystic breast cancer intermingled with the infiltrating ductal variant is presented. A subsequent review of the relevant literature presents the existing experience in treating mixed breast cancers with adenoid cystic components with regard to diagnosis, treatment, and prognosis. CASE PRESENTATION: We describe a case of mixed adenoid cystic cancer of the breast with infiltrating ductal carcinoma in a 67-year-old Caucasian woman who underwent mastectomy with sentinel node biopsy. CONCLUSION: Surgery remains the cornerstone of treatment of these patients, and radiotherapy is administered when breast-conserving treatment is undertaken or a large tumor with affected lymph nodes is present. Hormonal treatment does not have a role, as estrogen receptors are always absent from both tumor components. Chemotherapy is nearly always administered on the basis of estrogen receptor and progesterone negativity and the more aggressive potential of the non-adenoid cystic component. The de-differentiation of an indolent type of cancer to a more aggressive one may affect the prognosis.     

Postnatal gender-dependent maturation of cellular cysteine uptake

Background. In view of the functional capacity of glutathione synthesis in premature infants, and because the availability of cysteine is one the rate limiting steps in glutathione synthesis, we hypothesized that the low glutathione levels in premature infants may be due to immaturity of the active cellular uptake of cysteine.

Objective. To document in cells from newborn infants the effect of maturity and gender on cysteine uptake and consequently on glutathione levels.

Methods. Incorporation of L-[35S] cysteine was measured in leukocytes from cord blood and from tracheal aspirates (TAC) of newborn infants of varying (gestational as well as postnatal) ages and gender. Cysteine uptake was correlated with glutathione in TAC.

Results. The maturity of newborn girls positively influences cysteine uptake, which is responsible for 78% of the variation in their glutathione content. However, in newborn boys, gestational and postnatal ages did not influence the cysteine uptake.

Discussion. Cysteine uptake appears to be the limiting step explaining the reported gender-related differences in glutathione as well as the low levels of this central antioxidant found in premature infants. The immature cysteine uptake found in cells from premature infants raises questions about the bioavailability of this conditionally essential amino acid in regimens of parenteral nutrition for human neonates.     

A sensitive,fluorometric method for the assay of microsomal hydroxylase: N-demethylation of p-chloro-N-methylaniline

A fluorometric method for the assay of microsomal hydroxylase activity is described. N-Demethylation of p-chloro-N-methylaniline yields p-chloroaniline, which is coupled with fluorescamine, extracted with ethylacetate, and measured fluorometrically. This method can determine low levels of N-demethylase activity.     

The synthesis and characterization of a series of cobalt(II) β-ketoaminato complexes and their cytotoxic activity towards human tumor cell lines

A series of square planar cobalt(II) compounds bearing tetradentate β-ketoaminato ligands with variation in the number of ―CF₃ ligand substituents has been prepared and structurally and spectroscopically characterized. The fluorinated β-ketoamine ligands were prepared utilizing a multistep reaction sequence employing a silylenol protecting group. An additional tetrahedral cobalt compound bearing two bidentate β-ketoaminato ligands was also prepared and characterized.Cytotoxic activity of the cobalt-containing complexes was evaluated using six human cell lines; including two different prostate cancer cell lines (PC-3 and VCaP), acute monocytic leukemia (THP-1), astrocytoma (U-373 MG), hepatocellular carcinoma (HepG2), and neuroblastoma (SH-SY5Y) cells. The cobalt compounds are more active than their corresponding ligands. The activity is cell type specific; the cobalt compounds exhibit strong activity against human prostate cancer and monocytic leukemia cells but weak or no activity against neuroblastoma, astrocytoma, and liver carcinoma cells. Activity generally increases with a greater number of ―CF₃ substituents, and square planar complexes exhibit greater activity than the tetrahedral derivative. The mechanisms of activity against human PC-3 prostate cancer cells involve caspase-3 and two different mitogen-activated protein kinases. The addition of a thiol antioxidant reduced cytotoxicity, suggesting the possible involvement of reactive oxygen species. These cobalt complexes may represent a novel class of cytotoxic drugs selective towards certain types of tumors.     

L-phenylalanine binding and domain organization in human phenylalanine hydroxylase: a differential scanning calorimetry study

Human phenylalanine hydroxylase (hPAH) is a tetrameric enzyme that catalyzes the hydroxylation of L-phenylalanine (L-Phe) to L-tyrosine; a dysfunction of this enzyme causes phenylketonuria. Each subunit in hPAH contains an N-terminal regulatory domain (Ser2-Ser110), a catalytic domain (Asp112-Arg410), and an oligomerization domain (Ser411-Lys452) including dimerization and tetramerization motifs. Two partially overlapping transitions are seen in differential scanning calorimetry (DSC) thermograms for wild-type hPAH in 0.1 M Na-Hepes buffer, 0.1 M NaCl, pH 7.0. Although these transitions are irreversible, studies on their scan-rate dependence support that the equilibrium thermodynamics analysis is permissible in this case. Comparison with the DSC thermograms for truncated forms of the enzyme, studies on the protein and L-Phe concentration effects on the transitions, and structure-energetic calculations based on a modeled structure support that the thermal denaturation of hPAH occurs in three stages: (i) unfolding of the four regulatory domains, which is responsible for the low-temperature calorimetric transition; (ii) unfolding of two (out of the four) catalytic domains, which is responsible for the high-temperature transition; and (iii) irreversible protein denaturation, which is likely responsible for the observed exothermic distortion in the high-temperature side of the high-temperature transition. Stages 1 and 2 do not appear to be two-state processes. We present an approach to the analysis of ligand effects on DSC transition temperatures, which is based on the general binding polynomial formalism and is not restricted to two-state transitions. Application of this approach to the L-Phe effect on the DSC thermograms for hPAH suggests that (i) there are no binding sites for L-Phe in the regulatory domains; therefore, contrary to the common belief, the activation of PAH by L-Phe seems to be the result of its homotropic cooperative binding to the active sites. (ii) The regulatory domain appears to be involved in cooperativity through its interactions with the catalytic and oligomerization domains; thus, upon regulatory domain unfolding, the cooperativity in the binding of L-Phe to the catalytic domains seems to be lost and the value of the L-Phe concentration corresponding to half-saturation is increased. Overall, our results contribute to the understanding of the conformational stability and the substrate-induced cooperative activation of this important enzyme.     

Characterization of ferredoxins on a nanomole scale

Two method are described for the characterization of ferredoxins. First, mapping of tryptic peptides from 2 to 3 nmol of carboxymethylated ferredoxin by two-dimensional thin-layer electrophoresis and chromatography. Second, gel electrophoresis of tryptic digests of apoferredoxins. The latter method discriminates between ferredoxins of closely related species.