Chemically induced Parkinson's disease: intermediates in the oxidation of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine to the 1-methyl-4-phenyl-pyridinium ion

Various unstable intermediate oxidation states have been postulated in the metabolic activation of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine to the 1-methyl-4-phenyl pyridinium ion. We now report the first direct observation of these free radical intermediates by pulse radiolysis and flash photolysis. Studies are described of various reactions of such species, in particular with dopamine whose autoxidation to dopamine quinone is reported to be potentiated by 1-methyl-4-phenyl-1,2,3, 6-tetrahydropyridine.     

Epidermal cellular proliferation and differentiation in sexually mature male Salmo salar with androgen levels depressed by oil

Sexually mature male Salmo salar exhibit epidermal thickening and an increase in goblet cell concentration during the spawning season. The ventral skin, which is likely to experience most abrasive contact during the spawning period, has the thickest epidermis and the greatest goblet cell concentration. Following exposure to crude oil there is inhibition of cellular proliferation and elongation associated with epidermal thickening, and also inhibition of mucigenesis. Data on the androgen levels in these fish, and data from earlier studies involving treatment with hormones, indicate that oil-related epidermal effects during the spawning period are most likely systemic in origin, probably arising from reduced plasmatic androgen levels.     

Thermal Denaturation of Native Striatal Tyrosine Hydroxylase: Increased Thermolability of the Phosphorylated Form of the Enzyme

Tyrosine hydroxylase was purified from bovine corpus striatum. The native enzyme had a half-life of 15 +/- 3 min at 50 degrees C. Phosphorylation of tyrosine hydroxylase with protein kinase purified from both corpus striatum and heart activated the enzyme, but activity was rapidly lost with additional preincubation of the enzyme at 30 degrees C. Thermal denaturation studies indicated that phosphorylated tyrosine hydroxylase had a half-life of 5 +/- 2 min at 50 degrees C     

Energy transfer between the carotenoid and the bacteriochlorophyll within the B-800-850 light-harvesting pigment-protein complex of Rhodopseudomonas sphaeroides

Energy transfer between carotenoid and bacteriochlorophyll has been studied in isolated B-800-850 antenna pigment-protein complexes from different strains of Rhodopseudomonas sphaeroides which contain different types of carotenoid. Singlet-singlet energy transfer from the carotenoid to the bacteriochlorophyll is efficient (75-100%) and is rather insensitive to carotenoid type, over the range of carotenoids tested. The yield of carotenoid triplets is low (2-15%) but this arises from a low yield of bacteriochlorophyll triplet formation rather than from an inefficient triplet-triplet exchange reaction. The rate of the triplet-triplet exchange reaction between the bacteriochlorophyll and the carotenoid is fast (Ktt greater than or equal to 1.4 . 10(8) S-1) and also relatively independent of the type of carotenoid present.     

Boric Acid Poisoning: Report of 11 Cases

Boric acid poisoning in 11 infants, occurring in the newborn nursery as a result of the accidental and inadvertent use of 2.5% boric acid in the preparation of the formulae, is reported. Five of the infants died. All except two exhibited the classical symptomatology of acute boric acid poisoning, namely, diarrhea, vomiting, erythema, exfoliation, desquamation of the skin, and marked central nervous system irritation. Early manifestations of poisoning were nonspecific, and one patient died before skin manifestations were noted. Peritoneal dialysis, instituted in nine cases, was found to be the most effective method of treatment. It is recommended that boric acid, which is of doubtful therapeutic value, should be completely removed from hospitals, dispensaries and pharmacopoeias.     

Import of carrier proteins into mitochondria

Carrier proteins located in the inner membrane of mitochondria are responsible for the exchange of metabolites between the intermembrane space and the matrix of this organelle. All members of this family are nuclear-encoded and depend on translocation machineries for their import into mitochondria. Recently many new translocation components responsible for the import of carrier proteins were identified. It is now possible to describe a detailed import pathway for this class of proteins. This review highlights the contribution made by translocation components to the process of carrier protein import into mitochondria.     

Essential role of Mia40 in import and assembly of mitochondrial intermembrane space proteins

Mitochondria import nuclear-encoded precursor proteins to four different subcompartments. Specific import machineries have been identified that direct the precursor proteins to the mitochondrial outer membrane, inner membrane or matrix, respectively. However, a machinery dedicated to the import of mitochondrial intermembrane space (IMS) proteins has not been found so far. We have identified the essential IMS protein Mia40 (encoded by the Saccharomyces cerevisiae open reading frame YKL195w). Mitochondria with a mutant form of Mia40 are selectively inhibited in the import of several small IMS proteins, including the essential proteins Tim9 and Tim10. The import of proteins to the other mitochondrial subcompartments does not depend on functional Mia40. The binding of small Tim proteins to Mia40 is crucial for their transport across the outer membrane and represents an initial step in their assembly into IMS complexes. We conclude that Mia40 is a central component of the protein import and assembly machinery of the mitochondrial IMS.     

The mitochondrial presequence translocase: an essential role of Tim50 in directing preproteins to the import channel

Mitochondrial proteins with N-terminal targeting signals are transported across the inner membrane via the presequence translocase, which consists of membrane-integrated channel proteins and the matrix Hsp70 import motor. It has not been known how preproteins are directed to the import channel. We have identified the essential protein Tim50, which exposes its major domain to the intermembrane space. Tim50 interacts with preproteins in transit and directs them to the channel protein Tim23. Inactivation of Tim50 strongly inhibits the import of preproteins with a classical matrix-targeting signal, while preproteins carrying an additional inner membrane-sorting signal do not strictly depend on Tim50. Thus, Tim50 is crucial for guiding the precursors of matrix proteins to their insertion site in the inner membrane.     

The heme environment of recombinant human indoleamine 2,3-dioxygenase. Structural properties and substrate-ligand interactions

Indoleamine 2,3-dioxygenase is a heme enzyme that catalyzes the oxidative degradation of L-Trp and other indoleamines. We have used resonance Raman spectroscopy to characterize the heme environment of purified recombinant human indoleamine 2,3-dioxygenase (hIDO). In the absence of L-Trp, the spectrum of the Fe(3+) form displayed six-coordinate, mixed high and low spin character. Addition of L-Trp triggered a transition to predominantly low spin with two Fe-OH(-) stretching modes identified at 546 and 496 cm(-1), suggesting H-bonding between the NH group of the pyrrole ring of L-Trp and heme-bound OH(-). The distal pocket of Fe(3+) hIDO was explored further by an exogenous heme ligand, CN(-); again, binding of L-Trp introduced strong H-bonding and/or steric interactions to the heme-bound CN(-). On the other hand, the spectrum of Fe(2+) hIDO revealed a five-coordinate and high spin heme with or without L-Trp bound. The proximal Fe-His stretching mode, identified at 236 cm(-1), did not shift upon L-Trp addition, indicating that the proximal Fe-His bond strength is not affected by binding of the substrate. The high Fe-His stretching frequency suggests that Fe(2+) hIDO has a strong "peroxidase-like" Fe-His bond. Using CO as a structural probe for the distal environment of Fe(2+) hIDO revealed that binding of L-Trp in the distal pocket converted IDO to a peroxidase-like enzyme. Binding of L-Trp also caused conformational changes to the heme vinyl groups, which were independent of changes of the spin and coordination state of the heme iron. Together these data indicate that the strong proximal Fe-His bond and the strong H-bonding and/or steric interactions between l-Trp and dioxygen in the distal pocket are likely crucial for the enzymatic activity of hIDO.