Note: Laser-cut molybdenum grids for a retarding field energy analyzer.

A retarding field energy analyzer (RFEA) with grids created by laser-cutting a honeycomb mesh in a 50 µm thick molybdenum foil is presented. The flat grids span an area of 1 cm2 and have high transmission (20 µm wide walls between 150 µm wide meshes). The molybdenum grids were tested in a 3-grid RFEA configuration with an analyzer depth of 0.87 mm.

Risk factors for second primary melanoma among Dutch patients with melanoma.

BACKGROUND: Patients with melanoma are at increased risk of developing subsequent primary melanomas. Knowledge about risk factors for these subsequent primaries is scarce. More evidence may help clinicians in tailoring surveillance schedules by selecting patients who could benefit from intensified surveillance. OBJECTIVES: To identify risk factors for a second primary cutaneous melanoma. METHODS: Possible risk factors for a second primary melanoma were assessed in 1127 patients with cutaneous melanoma who were diagnosed between 2003 and 2011 and completed a baseline questionnaire. Additional data were extracted from the Netherlands Cancer Registry and medical files. RESULTS: Fifty-three patients were diagnosed with a second melanoma during a median follow-up time of 6·3 years. The 5-year cumulative risk was 3·7% and the conditional cumulative risk was 4·6% in years 5-10 after diagnosis. In multivariable analyses, the risk of a second melanoma increased with older age at diagnosis [hazard ratio (HR) 1·03 per year; 95% confidence interval (CI) 1·00-1·06], a high naevus density (HR 7·16, 95% CI 2·89-17·75) and working outside for > 10 years (HR 2·88, 95% CI 1·38-6·03). Patients with invasive melanoma (> 1 mm) had a decreased risk compared with patients with melanoma in situ (HR 0·35, 95% CI 0·13-0·93). CONCLUSIONS: Besides phenotypic characteristics, cumulative sun exposure seemed to increase the risk of a second melanoma. Patients with melanoma in situ may need to be offered follow-up, which is currently not advised. As the risk of a second melanoma did not decline in years 5-10 after diagnosis, a subgroup of patients may need a longer follow-up than is currently advised.

Limited role for histopathological examination of re-excision specimens of completely excised melanomas.

The Dutch melanoma guideline advises to examine one central block of the re-excision scar in case of a complete primary excision. To increase the evidence for this recommendation, we re-evaluated how often residual melanoma was found in re-excision specimens of a large series of completely excised melanomas. Of 1,209 Dutch melanoma cases, pathology reports of primary excisions were reviewed. Presence of melanoma in the margins was scored. All melanomas with a complete primary excision were included and pathology reports of re-excisions were reviewed. Presence of residual melanoma in the re-excision specimen and the number of blocks were scored. Slides of re-excision specimens containing residual melanoma were reviewed. Eventually, in four out of 812 melanomas (0.5 %) with a complete primary excision, residual melanoma was found in the re-excision specimen. The free margins of the primary melanomas in these cases ranged from 0.5-3.5 mm. In one case, the margin for melanoma in situ was 0.2 mm. In <1 % of initially completely excised melanomas, residual melanoma was found in the re-excision specimen. Histopathological examination of these re-excision specimens may not be cost-efficient. Our findings even imply that a re-excision could safely be omitted in selected cases of completely excised melanomas.

Impact of mitotic activity on the pathological substaging of pT1 cutaneous melanoma.

BACKGROUND: In the transition from the sixth to the seventh edition of the American Joint Committee on Cancer (AJCC) melanoma staging system, mitotic activity was incorporated, while Clark level of invasion was abandoned. OBJECTIVES: To investigate the effect of this change on the pathological tumour (pT)1 substaging of primary cutaneous melanomas and the possible clinical implications. METHODS: Patients with pT1 melanomas, diagnosed in the period January 2003 to March 2011, were selected from a population-based cohort study on cutaneous melanoma in the eastern part of the Netherlands. The pT1 melanomas were systematically reviewed by an expert pathologist and classified according to both the sixth and the seventh editions of the AJCC staging system. The shift of melanomas between pT1 substages, classified according to the two staging systems, was determined. RESULTS: In total, 260 pT1 melanomas were included. Overall 28% (57/207) of all pT1a melanomas shifted to pT1b when classified according to the new seventh staging classification, because of the presence of mitoses. Some 32% (17/53) of all pT1b melanomas shifted to pT1a. The percentage of pT1b melanomas relative to all pT1 melanomas increased from 20% to 36%. CONCLUSIONS: The addition of mitotic activity to the pathological staging system, according to the seventh edition of the AJCC staging system, resulted in a considerable change in the classification of thin cutaneous melanomas. This shift has clear clinical implications, as it is advised in the Dutch guideline that patients with pT1b melanoma should be offered a sentinel lymph node biopsy.

Child survival during the 2002-2003 drought in Ethiopia.

Droughts in Ethiopia have commonly been associated with increased child mortality. Early indications were that the 2002/03 drought, which affected 13.2 million people, was no exception, despite a large relief operation. Humanitarian agencies reported sharp increases in child deaths and pockets of acute distress in some hard-hit localities. In response, the 2004 Ethiopia Child Survival Survey (ECSS) was designed to investigate the impact of the drought on child survival in the general population. The survey covered 4816 households in both drought-affected and non-drought affected, as well as rural and urban localities. Data from the ECSS indicate that child mortality was indeed higher in drought-affected areas. However, a closer analysis reveals that this differential is attributable to chronic conditions in those localities, rather than the immediate impact of the 2002/03 drought. Multivariate analysis was used to construct a model for the determinants of child survival in the sample population. Household-level demographic factors, household-level food and livelihood security, community-level economic production, and access to potable water, were predictive of child survival. Additionally, household receipt of food aid had a small but significant positive association with child survival, even though the ECSS cannot determine either the underlying causal mechanisms of this association or the role of confounding factors. Nonetheless, it is remarkable that the most extensive drought in the country's modern history passed without a measurable increase in child mortality among the general population. Yet Ethiopian children still suffer unacceptably high rates of chronic malnutrition and poor life chances, and large populations continue to live at the brink of destitution and calamity.

Specific detection and analysis of a probiotic Bifidobacterium strain in infant feces.

For specific detection of the probiotic Bifidobacterium sp. strain LW420 in infant feces and for rapid quality control of this strain in culture, three strain-specific 16S rRNA gene-targeted primers have been developed. These primers allow specific detection of the organism via PCR. Specificity of the primers was determined in DNA samples isolated from single-strain and mixed cultures of bifidobacteria and in heterogenous fecal samples. The feasibility of this method for use in specific detection of probiotic strains was investigated through addition of Bifidobacterium sp. strain LW420 to infant instant milk formula (IMF) and PCR analyses of bacterial DNA isolated from feces of 17 newborn IMF-fed infants. In feces of all nine babies that had been fed with the probiotic IMF, the strain-specific PCR signal could be detected. No signal was found in feces of the eight infants that had been fed with a nonprobiotic IMF, demonstrating the specificity of the PCR method. All 17 infants developed a major fecal Bifidobacterium population already after 3 days, as determined through genus-specific and strain-specific PCR. Phenotypical screening of Bifidobacterium sp. strain LW420 and analysis of homology of the 16S rRNA gene sequence of this strain with that of other bifidobacteria deposited in databases do not allow positive classification of LW420 among the currently known species of Bifidobacterium.

Social contract and deterring famine: first thoughts.

The links between certain kinds of political systems and protection against famine are investigated in this paper. The starting-point is a critique of Amartya Sen's observation that famines are unknown in countries with a free press and competitive elections. This holds true only in India because of a unique political history in which freedom from famine became a right, upon which political legitimacy was founded: an anti-famine 'social contract'. The rise and decline of anti-famine systems in Africa is charted. Major reasons for decay include neo-liberalism and the international humanitarian system, both of which undermine relationships of domestic political accountability that underpin effective famine prevention. A number of politically regressive tendencies in 'actually existing humanitarianism' are identified that work against any nascent anti-famine social contracts in Africa. This is possible because famine prevention has not been established as a right in Africa.

Energy, control and DNA structure in the living cell.

Maintenance (let alone growth) of the highly ordered living cell is only possible through the continuous input of free energy. Coupling of energetically downhill processes (such as catabolic reactions) to uphill processes is essential to provide this free energy and is catalyzed by enzymes either directly or via "storage" in an intermediate high energy form, i.e., high ATP/ADP ratio or H+ ion gradient. Although maintenance of a sufficiently high ATP/ADP ratio is essential to overcome the thermodynamic burden of uphill processes, it is not clear to what degree enzymes that control this ratio also control cell physiology. Indeed, in the living cell homeostatic control mechanisms might exist for the free-energy transduction pathways so as to prevent perturbation of cellular function when the Gibbs energy supply is compromised. This presentation addresses the extent to which the intracellular ATP level is involved in the control of cell physiology, how the elaborate control of cell function may be analyzed theoretically and quantitatively, and if this can be utilized selectively to affect certain cell types.

Strictosidine synthase from Catharanthus roseus: purification and characterization of multiple forms.

Multiple (six) forms of strictosidine synthase from Catharanthus roseus cell suspension cultures were purified and characterized. A purification protocol is presented composed of hydrophobic-interaction, gel-permeation and ion-exchange chromatography and chromatofocusing. Four of six isoforms were purified to apparent homogeneity, whereas two others were nearly homogeneous. All strictosidine synthase isoforms were found to be glycoproteins. The isoforms were also found in leaves and roots of the plant, in seedlings and in hairy root cultures. The ratio of the different isoforms differed slightly between these sources. The kinetic parameters of the isoforms showed no significant differences. The maximal velocity (300-400 nkat/mg of protein) is the highest reported so far. It was demonstrated that the apparent Michaelis constant for tryptamine (approx. 9 microM) is much lower than values reported previously. The presence of weak product inhibition (Kp approx. 35 times Km) was established, whereas substrate inhibition was not detected.

Functional synergism of the magainins PGLa and magainin-2 in Escherichia coli, tumor cells and liposomes.

Xenopus laevis skin secretion contains a mixture of magainins, which are small positively charged oligopeptides with antimicrobial activity. In this study, we show that two of these peptides, i.e. magainin-2 and PGLa, are much more active in biological functions when added together than when added alone. This synergy applies for the antimicrobial activity of these peptides, and for the toxic effects on tumor cells. We show that this peptide combination is also synergistic when permeabilizing protein-free liposomes for glucose, when dissipating the membrane potential in cytochrome oxidase liposomes and Escherichia coli, and, reversibly, when stimulating respiration in the liposomes. The occurrence of synergy in these diverse systems (complex and simple) suggests that the biological synergy results from synergy in the primary activity of the magainin peptides, namely the permeabilization of free-energy transducing membranes, possibly by forming a multimeric transmembrane pore of mixed peptide composition. The antimicrobial activity of X. laevis skin secretions may be greatly enhanced by the application of this binary weapon.

Clinical use of a portable electronic device to measure haematocrit.

A small portable device called the blood electrometer (BEM) was developed to assist clinicians to distinguish patients with extreme blood loss from those with normal packed cell volumes. Blood was collected in 5 ml lithium heparin tubes from 80 normal controls and 24 patients in an intensive care unit. BEM and accurate microcentrifugal techniques were compared. Intraclass correlation coefficients between the techniques of r = 0.96 and r = 0.93 were found in the normal controls and patients respectively. Because the BEM operates on the principle of conductivity, changes in some of the biochemical variables which could influence conductivity were investigated in the patients. Mean plasma total protein and albumin concentrations were lower compared with normal reference ranges. Six of the 24 patients were acidotic and 4 alkalotic. Leucocyte counts obtained randomly from 13 patients were elevated. Changes in measurements which could influence conductivity did not affect the BEM reading. We conclude that the portable BEM could be of great value in circumstances where a fixed power source is not available and rapid haematocrit measurements in a large number of patients are required.

Isolation and characterization of a cDNA clone from Catharanthus roseus encoding NADPH:cytochrome P-450 reductase, an enzyme essential for reactions catalysed by cytochrome P-450 mono-oxygenases in plants.

The membrane-bound flavoprotein NADPH:cytochrome P-450 (cytochrome c) reductase, that functions in electron transfer to cytochrome P-450 monooxygenases, was purified from a cell suspension culture of the higher plant Catharanthus roseus. Anti-serum raised against the purified protein was found to inhibit NADPH:cytochrome c reductase activity as well as the activities of the cytochrome P-450 enzymes geraniol 10-hydroxylase and trans-cinnamate 4-hydroxylase, which are involved in alkaloid biosynthesis and phenylpropanoid biosynthesis, respectively. Immunoscreening of a C. roseus cDNA expression library resulted in the isolation of a partial NADPH: cytochrome P-450 reductase cDNA clone, which was identified on the basis of sequence homology with NADPH:cytochrome P-450 reductases from yeast and animal species. The identify of the cDNA was confirmed by expression in Escherichia coli as a functional protein capable of NADPH-dependent reduction of cytochrome c and neotetrazolium, two in vitro substrates for the reductase. The N-terminal sequence of the reductase, which was not present in the cDNA clone, was determined from a genomic NADPH: cytochrome P-450 reductase clone. It was demonstrated that the reductase probably is encoded by a single copy gene. A sequence comparison of this plant NADPH:cytochrome P-450 reductase with the corresponding enzymes from yeast and animals species showed that functional domains involved in binding of the cofactors FMN, FAD and NADPH are highly conserved between all kingdoms. In C. roseus cell cultures a rapid increase of the reductase steady state mRNA level was observed after the addition of fungal elicitor preparations that are known to induce cytochrome P-450-dependent biosynthetic pathways.

Electric potentiation, cooperativity, and synergism of magainin peptides in protein-free liposomes.

Magainins, positively charged peptides present in the skin of Xenopus laevis, are known to permeabilize free-energy transducing membranes. Structural studies in otherwise protein-free model systems show alpha-helical magainins parallel to the membrane water interface. However, functional studies in biological membranes suggest that magainins operate as oligomeric complexes. Here we investigate whether magainins function as oligomers in protein-free liposomes also. We report that they do exhibit strong positive heterocooperativity. The magainins, magainin 2 and PGLa, act synergistically. Both activity and cooperativity are enhanced by net negative charge of the liposomal membranes. A transmembrane electric potential, negative inside, enhanced the activity of the peptides. We propose a model in which (i) binding to the surface of the membrane, mainly guided by electrostatic interactions, occurs and (ii) the bound form is in equilibrium with an n-meric complex of magainins spanning the membrane.

Coordinated regulation of two indole alkaloid biosynthetic genes from Catharanthus roseus by auxin and elicitors.

Catharanthus roseus (periwinkle) produces a wide range of terpenoid indole alkaloids, including several pharmaceutically important compounds, from the intermediate strictosidine. The complete mRNA sequence for the enzyme strictosidine synthase (SSS) was determined. Comparison of the primary structure of the encoded protein with the amino-terminal sequence of purified SSS indicated the presence of a signal peptide of 31 amino acids in the putative primary translation product. SSS is encoded by a single-copy gene indicating that isoenzymes reported by others are formed post-translationally from a single precursor. The sss gene and the tryptophan decarboxylase gene (tdc), encoding another enzyme essential for indole alkaloid biosynthesis, are coordinately regulated. In plants steady-state mRNA levels are highest in roots. In cell suspension cultures the genes are rapidly down-regulated by auxin. In contrast, both genes are strongly induced by fungal elicitors such as Pythium aphanidermatum culture filtrate or yeast extract. Induction is a rapid, transcriptional event occurring independent of de novo protein synthesis. These results show that a first important regulatory step in the complex process leading to indole alkaloid accumulation in C. roseus suspension cells is transcription of the biosynthetic genes.

Magainins affect respiratory control, membrane potential and motility of hamster spermatozoa.

The hypothesis was tested that the magainin peptides, known to compromise bacterial and mitochondrial energetics, are highly active against spermatozoa. A mixture of magainin A and PGLa (1:1) caused a 50% reduction in motility of hamster spermatozoa at 4 micrograms/ml total peptide concentration. All motility was lost at 8 micrograms/ml. At this concentration, respiratory control was released and respiration in the presence of uncoupler was inhibited. Uptake of the lipophilic cation tetraphenyl phosphonium was largely abolished by addition of magainin A and PGLa showed synergism with respect to release of respiratory control.

The kinetics of the hydroxylation of procollagen by prolyl 4-hydroxylase. Proposal for a processive mechanism of binding of the dimeric hydroxylating enzyme in relation to the high kcat/Km ratio and a conformational requirement for hydroxylation of -X-Pro-Gly- sequences.

Prolyl 4-hydroxylase modifies only approx. 5% of the hydroxylatable prolyl residues in procollagen at a relatively high rate, after which the rate of further hydroxylation rapidly decreases. This suggests that the probability to exist in a defined hydroxylation-committed conformation differs between the numerous -X-Pro-Gly- sequences in the substrate. The enzyme reaction is characterized by the unusually high kcat/Km ratio of 3 x 10(9) M-1 s-1. To explain these kinetic features, an extremely high second-order rate constant for the association of enzyme and the subset of rapidly hydroxylated prolyl residues has to be assumed. A two-step mechanism is proposed in which diffusional constraints on the rate of association of prolyl 4-hydroxylase with hydroxylatable prolyl residues can be overcome. Upon encountering a random coil pro-alpha chain, the dimeric enzyme is first 'aspecifically' bound, followed by rapid transfers between different segments of the flexible peptide substrate via fast transitions between 'aspecific' single and double bound intermediate states. The rate of the second step, the productive (specific) binding of hydroxylation-committed -X-Pro-Gly- sequence to the active site, can be enhanced significantly by such an, in essence, 'one-dimensional' search. This processive mechanisms of binding does not necessarily imply many hydroxylation reactions during one encounter between enzyme and a peptide with several substrate sites as suggested previously in a slightly different model (De Waal, A. and De Jong, L. (1988) Biochemistry 27, 150-155).

Evaluation of an electronic device used as a quick screening method to detect changes in the red cell content of the blood in horses participating in endurance trail rides.

Dehydration, to varying degrees, will inevitably occur in horses participating in endurance trail rides. This water loss is directly related to the amount of body water lost through evaporative cooling, that in turn being related to the amount and rate of work performed, and to the environmental temperature and humidity. An electronic apparatus that can substitute for the conventional and time-consuming venous haematocrit was developed to measure the animals' hydration status. The mechanism of this electrometer is based upon the relationship between the red cell content and the electrical conductivity of the blood. The electrometer reading gave a significant correlation (p less than 0.001) with the venous haematocrit, thus indicating that the electrometer is a reliable apparatus for determining the animals' hydration status within seconds of venepuncture.

The distribution of strictosidine-synthase activity and alkaloids in Cinchona plants.

The relation between the total alkaloid content and the activity of strictosidine synthase (EC 4.3.3.2), a key enzyme in alkaloid biosynthesis, was studied in distinct parts of six-month-old plants of Cinchona ledgeriana Moens. Strictosidine-synthase activity was present in the tops of the stems, including the young developing leaflets, and in the roots. The highest alkaloid contents of the plant were also found in these parts; however, the types of alkaloids differed, cinchophyllines being present in the aerial parts and quinoline alkaloids in the roots. In the stem and in old leaves, both strictosidine-synthase activity and alkaloid content were low. These results indicate that in young Cinchona plants the alkaloids are mainly synthesized in the axial extremities of the plant and that they are stored at the site of their synthesis.