Melanin biosynthesis from dopamine. II. A mass spectrometric and collisional spectroscopic investigation

Electron impact (EI) and fast atom bombardment (FAB) mass spectrometry together with collisional activation (CA) experiments were applied to the study of the oxidation pathway of dopamine by tyrosinase. In order to prevent attachment of the protein to the highly reactive intermediates, ultrafiltration was employed to remove the enzyme at different reaction times. FAB, privileging molecular species formation, was successfully used for identification of transient intermediates and their relative concentrations with respect to time, directly in the reaction mixture. The presence of isobaric molecular species made chromatographic separation necessary. Further EI mass spectrometry and collision spectroscopy led to structural identification of pure components. Of these, dopamine-o-quinone, leucoaminochrome, and aminochrome semiquinone were characterized for the first time as real intermediates in dopamine melanogenesis, in agreement with previous hypotheses. This approach elucidated the pathway of dopamine melanogenesis.

[Role of loco-regional anesthesia in the surgical treatment of atheromatous lesions of the carotid bifurcation]

The Authors report a case of carotid bifurcation endarterectomy under loco-regional anesthesia. Despite a stump pressure of 44 mmHg, considered by the most of the Authors, the borderline value for carotid endarterectomy without shunt, the patient had a cerebral ischemic attack after 30 seconds of carotid clamping. So, the local anesthesia represents a valid alternative in order to detect an intolerance to clamping and underlines the importance of cerebral protection in this kind of surgical approach.

Retrospective findings of the clinical benefits of podophyllum resin 25% sol on hairy leukoplakia. Clinical results in nine patients

Hairy leukoplakia was first described as an oral marker of human immunodeficiency virus infection in 1984. The clinical significance of this lesion in an otherwise healthy, high-risk symptom-free person is that it can be an early manifestation of human immunodeficiency virus infection. Because of its benign nature and the lack of clinical evidence that treatment of the lesion improves the prognosis of human immunodeficiency virus-infected patients, systemic therapy with antiviral drugs does not seem warranted at this time. Topical retinoids (Retin-A sol) and systemic antivirals such as acyclovir have been previously tried; however, lesions tend to recur a few days after treatment is discontinued. Nine patients with oral hairy leukoplakia seen at the Oral Medicine Clinic, University of California San Francisco were offered treatment with podophyllum resin 25% sol. All patients had a complete remission of their condition within 1 week (5 patients) or after the second application a week later (4 patients). Side effects were transient and reversible. These remissions of oral hairy leukoplakia lasted from 2 to 28 weeks, which suggests that podophyllum may be a relatively safe and cost-effective treatment of this otherwise symptom-free lesion.

[Axonal polyneuropathy caused by acute multiple organ disease]

Complications involving the peripheral nervous system known as CIP have been reported during the course of prolonged sepsis and MOFS. These may be differentiated from Guillain-Barré's syndrome by their electrophysiological characteristics of axonal neuronal damage and the normality of spinal fluid tests. The Authors report and discuss a case which was brought to their attention.

Mössbauer characterization of the tetraheme cytochrome c3 from Desulfovibrio baculatus (DSM 1743). Spectral deconvolution of the heme components

Mössbauer spectroscopy was used to study the tetraheme cytochrome c3 from Desulfovibrio baculatus (DSM 1743). Samples with different degrees of reduction were prepared using a redoxtitration technique. In the reduced cytochrome c3, all four hemes are reduced and exhibit diamagnetic Mössbauer spectra typical for low-spin ferrous hemes (S = 0). In the oxidized protein, the hemes are low-spin ferric (S = 1/2) and exhibit overlapping magnetic Mössbauer spectra. A method of differential spectroscopy was applied to deconvolute the four overlapping heme spectra and a crystal-field model was used for data analysis. Characteristic Mössbauer spectral components for each heme group are obtained. Hyperfine and crystal-field parameters for all four hemes are determined from these deconvoluted spectra.

[Immunologic profile of HIV-2 seropositive African individuals (follow-up)]

In the geographic distribution of HIV-2, it is known that this infection is most prevalent in West Africa. Since 1986 we have studied seropositive and seronegative clusters, in Guinea-Bissau with follow-ups in 1988, 1989, 1990 and 1991. Analysis of the results show the high incidence of this infection. 8.51% of the 4,372 people of the general population studied were seropositive, showing the high predominance of HIV-2 infection. Only 4 cases were exclusively reactive to HIV-1 and a slow evolution of HIV-1 infections. In the seroconversions of HIV-2 infections the antibodies appeared first to the core components and secondly to the surface glycoproteins. Some of the laboratory parameters affected in the evolution of the infection include a gradual increase in immunoglobulins and a decrease in CD4 lymphocytes and in the CD4/CD8 ratio. A comparison of these variations in HIV-2 infected people, with or without cross-reactivity to HIV-1, reveals that they are much more evident in exclusively HIV-2 positive people. This fact can indicate that the variants responsible for the cross-reactions are less pathogenic and phylogenetically less developed.

Structural and functional approach toward a classification of the complex cytochrome c system found in sulfate-reducing bacteria

Following the discovery of the tetraheme cytochrome c3 in the strict anaerobic sulfate-reducing bacteria (Postgate, J.R. (1954) Biochem. J. 59, xi; Ishimoto et al. (1954) Bull. Chem. Soc. Japan 27, 564-565), a variety of c-type cytochromes (and others) have been reported, indicating that the array of heme proteins in these bacteria is complex. We are proposing here a tentative classification of sulfate- (and sulfur-) reducing bacteria cytochromes c based on: number of hemes per monomer, heme axial ligation, heme spin state and primary structures (whole or fragmentary). Different and complementary spectroscopic tools have been used to reveal the structural features of the heme sites.

Regulation of the hexaheme nitrite/nitric oxide reductase of Desulfovibrio desulfuricans, Wolinella succinogenes and Escherichia coli. A mass spectrometric study

Dissimilatory nitrite reduction, carried out by hexaheme proteins, gives ammonia as the final product. Representatives of this enzyme group from 3 bacterial species can also reduce NO to either ammonia or N2O. The redox regulation of the nitrite/nitric oxide activities is discussed in the context of the denitrifying pathway.

Fast atom bombardment mass spectrometry in the study of dopamine melanogenesis intermediates

Fast atom bombardment was applied to the study of the intermediates of the reaction dopamine-tyrosinase after treatment with diazomethane. The identification of trimethoxyindoline, dopamine-o-quinone and dimethoxyindole was easily achieved by this ionization method, together with accurate mass measurements and collision experiments. The structures of these compounds are in agreement with those already hypothesized in studies on melanogenesis.

Hexaheme nitrite reductase from Desulfovibrio desulfuricans. Mössbauer and EPR characterization of the heme groups

Mössbauer and EPR spectroscopy were used to characterize the heme prosthetic groups of the nitrite reductase isolated from Desulfovibrio desulfuricans (ATCC 27774), which is a membrane-bound multiheme cytochrome capable of catalyzing the 6-electron reduction of nitrite to ammonia. At pH 7.6, the as-isolated enzyme exhibited a complex EPR spectrum consisting of a low-spin ferric heme signal at g = 2.96, 2.28, and 1.50 plus several broad resonances indicative of spin-spin interactions among the heme groups. EPR redox titration studies revealed yet another low-spin ferric heme signal at g = 3.2 and 2.14 (the third g value was undetected) and the presence of a high-spin ferric heme. Mössbauer measurements demonstrated further that this enzyme contained six distinct heme groups: one high-spin (S = 5/2) and five low-spin (S = 1/2) ferric hemes. Characteristic hyperfine parameters for all six hemes were obtained through a detailed analysis of the Mössbauer spectra. D. desulfuricans nitrite reductase can be reduced by chemical reductants, such as dithionite or reduced methyl viologen, or by hydrogenase under hydrogen atmosphere. Addition of nitrite to the fully reduced enzyme reoxidized all five low-spin hemes to their ferric states. The high-spin heme, however, was found to complex NO, suggesting that the high-spin heme could be the substrate binding site and that NO could be an intermediate present in an enzyme-bound form.

Tryptophan, copper and zinc in hair of healthy subjects. Correlation with differences in hair pigmentation

Tryptophan, copper and zinc levels were determined in the hair of 300 healthy subjects divided by sex, age and hair colour. Sex influences tryptophan content in hair, the levels of this amino acid being higher in males than in females. Tryptophan is also higher in infancy (2-5 years) and in both males and females aging around 80 years and over. Hair colour also influences tryptophan levels, which increase from fair to black hair. Copper levels are similar in hair of both males and females, while those of zinc are higher in women. Age influences the distribution of these two metals in human hair. Copper contents in hair of males are higher at the age 20-40 years. In females, values decrease over the age of 60 years. Instead, zinc levels are higher between 20 and 60 years in males, and between 13 and 19 years in females. As regards hair colour, copper is slightly higher in black hair in males and in fair hair in females, and lower in white hair in both sexes. Zinc values appear to be higher in red and lower in white hair in males. In females they are higher in black hair.

[Electropherotypes of rotavirus in children with and without gastroenteritis]

It was defined the electropherotypes of rotavirus identified in stools of a groups (named "case") of 500 children with diarrhea, ranging in age from 0 to 12 months. A group (named "control") of 500 children of the same age group, without diarrhea or respiratory infections, were evaluated. Human rotavirus was detected in 14.8% of the children with diarrhea. Of the positive samples 5 had the "short" and 11 the "long" electropherotype. In the control group rotavirus was detected in 0.8% of children and all the three positive samples had "long" electropherotype.

Cerebral tryptophan metabolism in humans in relation to malignant pain

The authors investigated the cerebral metabolism of tryptophan in patients suffering from malignant pain by means of CSF dosage of tryptophan (Trp), 5-hydroxytryptophan (5-HTP), serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA). The level of 5-HIAA in patients with pain was 66.48 +/- 13.67 ng/ml, while in those without pain was 25.05 +/- 13.25 ng/ml; the difference was statistically significant, p = 0.001. Trp, 5-HTP and 5-HT levels did not register significant differences in the two groups of patients, although a tendency to lower values was seen in patients with pain, supporting the hypothesis of increased turnover of this metabolic pathway in cancer patients. A statistically significant inverse correlation was also found between cerebral Trp levels and pain levels measured on the Scott-Huskisson visual analogue scale. The data obtained confirm the importance of the cerebral serotoninergic pathway in pain modulation and the interest which CSF analysis may have for the assessment of patients suffering from pain.

[Acquired renal cystic disease in uremia: a prevalence survey]

The acquired cystic disease of the kidney (ACDK) occurs in uremic patients before and during dialysis treatment. It has been defined as a disease with multiple acquired cystic lesions in patients with advanced renal failure. We evaluated its prevalence in a group of 94 uremic patients employing ultrasonographic examinations. Eighteen patients were not on dialysis treatment (group I) and 76 patients were undergoing hemodialytic treatment (group II). The prevalence of ACDK in groups I and II was 16.7% and 39.5% respectively. There is a noteworthy progression in the prevalence of the disease as the patients are kept alive by dialysis treatment. Primary renal disease, age and sex were not important factors in the disease's prevalence.