The chemical characterization of melanin contained in substantia nigra of human brain

The pigment of substantia nigra human brain has been extracted by a mild procedure consisting of washes with phosphate buffer, methanol and incubation with SDS-proteinase. Pyrolisis gas chromatography mass spectrometry infrared spectrometry, termogravimetric analysis and elemental analysis were the techniques used for the chemical characterization. An indole moiety bound to a sulfur containing amino acid and to palmitic acid were the main aspects found in the structure. The presence of a 7% inorganic component was observed. This probably contains Fe, Cu, Zn and Cr which are also relevant, for the formation and the role of melanin in substantia nigra neurons. The fatty acid moiety is chemically bound to the indole structure as it was not eliminated by repeated methanol washing. The same situation occurs for the sulfur containing gropu. Considering these data and the most abundant molecules present in substantia nigra the precursor of neuromelanin seems to be a cysteinyl-cethecol, to which is then bound a palmityl group.     

Human impact as registered in the pollen record: some results from the western Lake Constance region,Southern Germany

Pollen analytical results from a littoral profile taken in Lake Constance compared with pollen profiles from small kettle holes nearby form the basis for conclusions concerning human population density, the economy and environment from the Neolithic period to the Middle Ages. Early Neolithic human impact is implicated in a lime decline and also the expansion of beech. The late Neolithic lakeshore settlements caused a decline of elm, beech and lime and, by shifting cultivation, considerably changed the forest cover. The settlements were abandoned after less than 100 years. There were long periods without distinct human impact in the middle and towards the end of the late Neolithic period. Since at least the Late Bronze Age there has been permanent habitation in the region. Human impact was greatest in the High Medieval period and later, and was also substantial in the late La Tène and Roman periods. Distinct declines in human impact can be observed between the La Tène and Roman periods and in the Migration and Merovingian periods. In these intervals, open land and grazed oak forest were replaced by birch and later on by beech forests. The decreases in human impact are not of the same intensity in all diagrams.     

Early human disturbance of the natural environment recorded in annually laminated sediments of Lake Gosciaz,central Poland

Palynological records from the annually laminated sediments of Lake Gosciaz are presented for the period ca. 7600–3900 conventional B.P. Indications in percentage and influx diagrams of Mesolithic and Early Neolithic human impact on the natural environment around the lake are discussed and compared with the archaeological evidence. The first indications of human disturbance start at ca. 6700 B.P. and in the following period four disturbance phases with interruptions are distinguished. A relationship between the Elm Decline and an increasing thickness of annual sediment layers as a consequence of increased soil erosion is suggested. Some hitherto unrecognized or incompletely known microfossils are identified and figured, and their palaeoecological significance is discussed. The records of akinetes of Aphanizomenon probably indicate increasing eutrophication of the lake. Charred fragments of grass epidermis are possibly indicative of openings in the forest.     

Use of the Golden Section search method to estimate the parameters of the Monod model employing spread-sheets

An alternative procedure to obtain the parameters of Monod's growth model in batch culture is presented. It is based on the integral kinetic analysis methodology, employs a one-dimensional Golden Section search optimization method and is implemented on a spread-sheet programme. The procedure is discussed in detail and is illustrated by analysis of batch substrate consumption data by an aerobic bacterial consortium.     

Use of disease progress curves to study the effects of the biocontrol agent Sporidesmium sclerotivorum on lettuce drop

At the end of the spring 1987 growing season, the mycoparasite Sporidesmium sclerotivorum was applied at 0, 0.2, 2 or 20 kg ha^‐1 to lettuce plants infected with Sclerotinia minor. Disease incidence was monitored in the same plots for five subsequent crops (three fall and two spring crops) without additional application of either pathogen or mycoparasite. Logistic growth curves were fitted to the data to describe disease progression over time for each inoculum level within each of the five crops. Within each crop, increasing the quantity of mycoparasite inoculum resulted in positive horizontal displacement of the curve with respect to time. As quantities of inoculum of S. sclerotivorum increased, inflection points of the disease progress curves increased at a decreasing rate. Thus, additional mycoparasite inoculum resulted in ever‐smaller increases in inflection point, and after a certain threshold level of mycoparasite inoculum (< 0.2 kg ha^‐1), increases in inflection point did not result in meaningful increases in harvestable lettuce. Maximum rates of disease increase were not different among the treatments within each crop, but were different between crops. Maximum rates of disease increase averaged 3.4, 3.4, 2.1, 3.6 and 1.5% day^‐1 for the fall 1987, spring 1988, fall 1988, spring 1989, and fall 1989, respectively. At all inoculum levels, the fall epidemics began later after planting than the spring epidemics.     

Direct correlation between the circadian sleep-wakefulness rhythm and time estimation in humans under social and temporal isolation

Several bodily functions in humans vary on a 24 h pattern and most of these variations persist with a circadian period ofca 25 h when subjects are studied under conditions of social and temporal isolation. We report in this paper that the estimates of short time intervals (TE) of 2 h are strongly coupled to the circadian rhythm in sleepwakefulness. There is a linear correlation between the number of hours humans stay awake (α) and their estimation of 2 h intervals. The coupling of TE to α appears to obtain only under conditions of physical well-being.     

The formation of myeloid bodies in retinular cells of the pupal compound eyes of silkworm moths (Bombyx mori) exposed to a constant bright light

Summary To study the three-dimensional structure of tight junction fibrils, the epithelia of the jejunum and epididymis of adult mice were examined by the freezefracture technique in unfixed and in aldehyde-fixed specimens. The fibrils have a stronger affinity for the protoplasmic (P) face of the lipid bilayer in fixed material, and for the external (E) face in unfixed and rapidly frozen material. Therefore we can observe the fibrils both from the outside and inside of the cell. Fibrils appearing on the P-face are smoothly contoured ridges and rows of hemispherical particles, while those appearing on the E-face are exclusively rows of hemispherical particles. Based on these observations, we wish to propose a new fibril model for the tight junction. There are two distinctive types of junctional elements. One type is composed of a smooth and continuous strand in the external view of the cell, but is studded with hemispherical bulgings in its internal view. This type will be referred to as the continuous type. The other type is bead-like, and will be referred to as the particle type. The relative proportion of these two types of elements appearing within a tight junction network differs among tissues.     

Some epidemiological models with nonlinear incidence

Epidemiological models with nonlinear incidence rates can have very different dynamic behaviors than those with the usual bilinear incidence rate. The first model considered here includes vital dynamics and a disease process where susceptibles become exposed, then infectious, then removed with temporary immunity and then susceptible again. When the equilibria and stability are investigated, it is found that multiple equilibria exist for some parameter values and periodic solutions can arise by Hopf bifurcation from the larger endemic equilibrium. Many results analogous to those in the first model are obtained for the second model which has a delay in the removed class but no exposed class.Research supported in part by Centers for Disease Control Contract 200-87-0515. Support services provided at University House Research Center at the University of IowaResearch supported in part by NSERC A-8965 and the University of Victoria President's Committee on Faculty Research and Travel     

Potentiation of growth suppression and modulation of the antigenic phenotype in human melanoma cells by the combination of recombinant human fibroblast and immune interferons

Summary Administration of interferon as a single therapeutic regimen in cancer patients with various neoplasias has had only limited efficacy in ameliorating the negative clinical course of their disease. In the present study, we have evaluated the effect of recombinant human fibroblast (IFN) and immune (IFN) interferon, alone and in combination, on growth, differentiation and the expression of class I and II histocompatibility locus antigens (HLA) and melanoma-associated antigens on the human melanoma cell line H0-1. The effect of combinations of interferons on the antigenic profile of human melanoma cells displaying different organ colonization and spontaneous metastatic potential in athymic nude mice was also determined. H0-1 cells were more sensitive to the antiproliferative activity of IFN than to IFN and the combination of interferons resulted in a potentiation of growth suppression. The antiproliferative effect of both interferons was greater in later-passage than in earlier-passage H0-1 cells, possibly reflecting alterations in the evolving tumor cell population as a result of long-term in vitro propagation and/or the selective outgrowth of cells with an increased growth rate. The enhanced growth suppression observed in H0-1 cells treated with the combination of IFN plus IFN was not associated with a significant increase in the level of melanin, a marker of melanoma differentiation, above that observed with either interferon used alone. IFN and IFN differentially modulated the expression of class I and II HLA and melanoma-associated antigens in H0-1 cells and a series of melanoma cells with different organ colonization and metastatic potential, including MeWo, MeM 50-10, MeM 50-17, 3S5 and 70W. No consistent potentiation or antagonism in the expression of any specific antigen was observed in any of the melanoma cell lines exposed to the combination of interferons. The present study demonstrates that the combination of IFN plus IFN can potentiate growth suppression in H0-1 human melanoma cells and that this effect is not associated with an increase in differentiation or a potentiation in antigenic modulation. In addition, no direct correlation between the expression of any specific antigen or its modulation by IFN or IFN, alone or in combination, and organ colonization and metastatic potential in nude mice was observed in the different melanoma cell lines.     

Paradise lost: Mitochondrial eve refuted

Being based solely on neontological data, all «unique parent» evolutionary hypotheses, of which «Mitochondrial Eve» is one, fall into the category ofscala naturae. Mathematical treatment of neontological data bases, using cladistic approaches does not confer the status of scientific hypotheses onto such scenarios. Apart from these fundamental problems, such hypotheses are flawed on a number of other bases, including the fact that there is a proportion of parental contribution to mitochondrial lineages, despite widely publicised statements that mithocondrial DNA in mammals is «strictly» maternally inherited. Other weaknesses of «unique mother» hypotheses on that their proponents endeavour to describe the evolution of diploid organisms on the basis of variability in extant haploid organelles, the evolution of which is delinked from that of the diploid organism. A further difficulty is that it is not possible to reconstruct interspecific relationships on the basis of intraspecific variability. There is a general ignorance among proponents of «unique mother» hypotheses regarding the distribution of biological variability on the surface of the globe, a fact which renders the molecular clock inaccurate, and which upsets the simplistic proposal that molecular diversity equates with time. «Unique mother» scenarios are also invalidated by the presence of shared chromosome and other polymorphisms in african great apes and humans at similar percentages in the different lineages, a fact which indicates that these evolving populations did not experience «bottlenecks». These and other difficulties effectively refute the «Mitochondrial Eve» hypothesis, which in any case much resembles creationism of a special kind, in which the offspring of a breeding pair are visualised as belonging to a species different from its parents. Such extreme examples of the punctuational mode of evolution are highly likely to be incorrect.