Concluding remarks

On the basis of symposium contributions onChlorella, Hibbertia, Eucalyptus, Ambrosia and on numerical approaches some fundamental problems of (bio)systematics, evolution, and taxonomic categories are discussed: Methods available for analysing affinities; conflicting evidence from phenetic, biochemical, cytogenetic and other analyses; further classification problems in cases of intermediacy, etc. While sibs of various levels and their natural hierarchy often can be objectively defined, this appears impossible for particular taxonomic levels itself (e. g. species). A single objective taxonomic system of organisms is unrealistic. Certain guiding lines for relative and practicable concepts of species and genus are proposed.Presented at the symposium Speciation and the Species Concept during the XIIth International Botanical Congress, Leningrad, July 8, 1975.     

Cytokinesis in the green alga Eremosphaera viridis: Plasmalemma formation from “open membranes”

Summary Cytokinesis in the unicellular chlorococcalean alga Eremosphaera viridis de Bary has been investigated by electron microscopy of thin sections. The new plasmalemmata of the daughter cells in this organism form centrifugally within a phycoplast. Unlike other cell division systems each new plasmalemma is formed, not by the fusion of vesicles, but rather by the fusion of open membranes which are characteristically heavily stained. Measurements of these open membranes reveal that they are 11 nm thick with a central 4,5 nm unstained portion. The possible origin of these open membranes as burst-open vesicles has been suggested from the presence of intensely straining vesicles in the vicinity of the cell equator. Calculations of vesicle and open membrane surface areas support this contention.     

The adaptive significance of cultural behavior: Comments and reply

Summary Fundamentally, theoretically, there is only one process underlying genetic and cultural evolution: natural selection. Organism fitness-enhancement (adaptive significance) is one of its practical mechanisms; group formation and maintenance is another, often but not always through fitness-enhancement; and need-fulfillment is still another. If Durham can accept that formulation, and switch from organism-thinking to instruction-thinking (Cloak, 1975: 178), he will free himself from two handicaps: First, he can forget his worries about reductionism and determinism (1976a: 100, 101). Under this general theory of natural selection, cultural evolutionis biological evolution, continued by other (nongenetic) means. Second, he will spare himself the appearance of anthropomorphism, mentalism, and wishy-washiness attendant on his discussion of kinds of significance, other than adaptive significance, of cultural behaviors (1976a: 102–106, 115).     

Lipid profile of rat myelin subfractions

Myelin from adult rat brains was separated on a discontinuous sucrose gradient into three subfractions. Analysis of light, heavy and membrane fraction lipid classes was performed by HPTLC and densitometry while fatty acid composition was determinated by GLC. The more interesting results observed are: i) the membrane fraction resembles in its lipid and fatty acid composition other cell membranes (particulary oligodentrocytes); ii) light and heavy myelin are quite similar between them but the former has a higher content of sphingomyelin, a lower hydroxy/nohhydroxy cerebrosides ratio and a lower content of monoenoic fatty acids than the heavy subfraction. The results obtained could explain the different structures observed in each myelin subfraction since fatty acid composition, hydroxy fatty acids, sphingomyelin and cholesterol play a key role in the stability and structure of membranes.     

Water accessibility to plant roots in different soil structures occurring in the same soil type

The capacity of a soil to supply roots with water and nutrients for crop growth is important when defining sustainable land management which implies maintenance of production and reduction of production risks. Not only the amount of available water is important but also its accessibility, which differs among different soil structures. Different structures within one soil series were associated with three types of management: (i) conventional, temporary grassland (Conv), (ii) biodynamic, temporary grassland (Bio) and (iii) conventional permanent grassland (Perm). Transpiration of barley plants, under identical circumstances, and the associated rooting patterns, were measured in five large undisturbed cores from each of the three soil structures. Management had significantly changed bulk density, organic matter content and porosity. Measured transpiration showed significant differences with highest amounts for Perm followed by Conv and lowest amounts for Bio. Rooting pattern characteristics, defined as the relation between a series of hypothetical extraction zones around each root and the volumes of excluded soil were determined for the three structures. These rooting pattern characteristics were most favourable for Perm, followed by Bio and Conv, respectively. The water supply characteristics, defined as the number of days the soil can satisfy a transpiration demand of 5 mm d^-1 as a function of a hypothetical extraction zone, reflects the capacity of the soil to supply roots with water. These water supply characteristics combined with the rooting pattern characteristics were used to quantify the accessibility of soil water. Accessibility was highest for Perm and Conv with 95% and 94% respectively, followed by Bio with 68%. When used in a simulation model and compared with simulations implicitly assuming total accessibility, measured transpirations were better simulated by introducing the expression for water accessibility.     

Electron microscopic and cytochemical study on the role of Golgi elements and plasma membrane of enterocytes in the intestinal lipid transport

Summary Intestinal lipid absorption and transport were investigated in albino rats. The observations point towards the existence of a continuity between plasma membrane invaginations and elements of the Golgi complex on its mature face. They also suggest a segregation of lipid droplets by paired Golgi membranes and plasma membrane invaginations. The following way for lipid transport is deduced: lipid droplets moving inside the smooth endoplasmic reticulum accumulate progressively and are condensed in Golgi cisternae of the forming face. Their limiting membrane ruptures and liberated lipid droplets are segregated by paired Golgi membranes of the mature face or by plasma membrane invaginations. Subsequently the inner of the two segregating membranes disappears while the lipid droplet is moved towards the intercellular space inside a canal communicating with this space. The suggestion is made that the Golgi apparatus is of double origin: one component representing a terminal plication of the endoplasmic reticulum; the second one—a terminal plication of the plasma membrane invagination. This concept explains the ultrastructural and histochemical differences between Golgi membranes of the forming and mature faces of the complex.     

Heterogeneity of epithelial cells in the human thymus

Summary To evaluate interrelationships among epithelial cells, and between morphology and function in the microenvironment, we studied the ultrastructural morphology of epithelial cells in sections of human thymus from donors aged 2 months to 31 years. Six types of epithelial cells were observed: subcapsular-perivascular (type 1); pale (type 2); intermediate (type 3); dark (type 4); undifferentiated (type 5); and large-medullary (type 6). Cells of types 2, 3 and 4 were found throughout the organ. The type-2 to -4 epithelial cells may represent various stages in a differentiation process. In this, type-2 cells are very active and type-4 cells are possibly degenerating elements. Type-4 cells can also contribute to Hassall's corpuscles. Type-5 cells were located mainly in the cortico-medullary region and showed the morphological characteristics of undifferentiated elements. Type-6 cells were located exclusively in the medulla and displayed characteristics of cellular activity. Small Hassall's corpuscles consisted of type-6 epithelial cells; in larger corpuscles many nuclei of type-6 cells were found. Cells of types 2 and 6 contained tubular structures (diameter approximately 20 nm).Concerning the function of thymus epithelial cells, the features associated with protein synthesis observed in cellular types 2 and 6 make them likely candidates for humoral factor-producing and/or secreting elements. In addition, type-2 and -3 cells in the cortex appear to contribute to a special pattern of epithelium-lymphocyte interaction (thymic nurse cells), as demonstrated by the intracytoplasmic location of lymphocytes in the epithelial cells. The various steps in intrathymic T-cell maturation occur at locations in a microenvironment composed of morphologically distinct epithelial cells.     

Die Feinstruktur der Zirbeldrüse normaler,trächtiger und experimentell beeinflußter Meerschweinchen

Zusammenfassung In der Meerschweinchenzirbeldrüse lassen sich elektronenmikroskopisch helle und dunkle Pinealzellen sowie einzelne Gliazellen nachweisen. In den bei weitem überwiegenden hellen Pinealzellen zeichnet sich ein Teil der vesicle-crowned rodlets (VCR) durch lokale Auftreibungen aus. Von VCR deutlich abzugrenzen sind die vesicle-crowned balls (VCB). Erstmalig beschrieben wird das Vorkommen von sog. Zylindern, die als Vorstufen von VCB aufgefaßt werden. In den relativ seltenen dunklen Pinealzellen, die sich durch chromatinreiche Kerne und elektronendichtes Zytoplasma auszeichnen, sind Vesikel, VCR, VCB und Zylinder seltener als in hellen Pinealzellen. Die reichlich vorhandenen marklosen Nervenfasern finden sich vor allem in perivasculären Räumen, seltener im Parenchym. Synapsen zwischen Nerven und Pinealzellen wurden nicht beobachtet. In den Zirbeldrüsen trächtiger Meerschweinchen zeichnen sich in der 2. Hälfte der Tragzeit die hellen Pinealzellen durch stärkere Lappung der Kerne, gehäuftes Auftreten von laktiven Zonen, Vermehrung von Mitochondrien, glattem ER, agranulären Vesikeln, VCR, VCB und Zylindern aus. Die dunklen Pinealzellen nehmen während der Tragzeit an Zahl zu. Post partum bilden sich diese Veränderungen innerhalb einer Woche zurück. Längerer Aufenthalt der Tiere in Dunkelheit führt zu einer Aktivierung der hellen Pinealzellen mit auffallender Vermehrung der VCR und zu einer Zunahme der dunklen Zellen. Unter Dauerbelichtung kommt es in den hellen Zellen zu einer Abnahme fast aller Zellorganellen und zu einer starken Vermehrung der VCR, die nach 70 Tagen auch Formveränderungen aufweisen. Nach Reserpinbehandlung beobachtet man eine Verminderung und degenerative Veränderungen der VCR. Es wird diskutiert, daß die VCR als prae- bzw. postsynaptische Strukturen der Erregungsübertragung von Nerven zu Pinealzellen bzw. von Pinealzellen untereinander dienen könnten.

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The fine structure of the pineal gland of normal, pregnant and experimentally affected guinea-pigs

Summary By means of electron microscopy light and dark pinealocytes can be distinguished in the guinea-pig pineal gland. Glial cells are rare. In the light pinealocyte. the most frequent cell type, some vesicle-crowned rodlets (VCR) show circumscribed thickenings. From these structures vesicle-crowned balls (VCB) have to be clearly distinguished. Furthermore cylinders occur, which, it is suggested, are precursors of VCB. Dark pinealocytes characterized by chromatin-rich nuclei and electron-dense cytoplasm are rare and contain fewer vesicles, VCR, VCB and cylinders than light pinealocytes. Numerous non-myelinated nerve fibres are situated within perivascular spaces, a few also in the parenchyma. Synapses between nerve fibres and pinealocytes were not observed. In the pineal gland of pregnant guinea-pigs the following changes can be observed in the second half of gestation. The light cells show many nuclear indentations and an increase of active zones, mitochondria, smooth ER, agranular vesicles, VCR, VCB, and cylinders respectively. The dark cells increase in number. After birth these changes reverse to normal within one week. Constant darkness leads to an activation of the light cells accompanied by an increase of the VCR and to an increase in number of the dark cells. Under constant illumination the light cells show a decrease of their organelles and a strong increase of the VCR. After 70 days the VCR also show a change in shape. Following reserpine treatment the VCR decrease in number and show signs of degeneration. It is discussed that the VCR function as pre- or postsynaptic structures and that they are involved either in transmitting impulses from nerve fibres to pinealocytes or from one pinealocyte to the other.

Untersuchung unter Leitung von Univ.-Doz. Dr. L. Vollrath.     

Methodological problems in evolutionary biology VIII. Biology and culture

Biology cannot accommodate all aspects of culture. Aspects of culture that a biological approach can take into account can be covered by the biological categories of phenotype and environment. There is no need to treat culture as a separate category. Attempts to elaborate biological explanations of cultural variation will meet with success only if biologists expand theories of development, and integrate them in evolutionary biology. The alternative — elaborating the idea of so-called cultural inheritance — makes little sense from a biological point of view.     

Variant forms ofα-2-l-fucosyltransferase in human submaxillary glands from blood group ABH “secretor” and “non-secretor” individuals

The properties of the -2-l-fucosyltransferases in submaxillary gland preparations from blood group ABH secrefors and non-secretors were compared. The level of activity in the non-secretor gland homogenates amounted to about 5% only of that found in the secretor gland preparations. The enzymes from the two sources differed in solubility properties, charge and affinities for donor and acceptor substrates. The enzyme from secretor glands showed a preference for acceptors with Type 1 [d-galactosyl(1–3)-N-acetyl-d-glucosamine] structures whereas the enzyme from non-secretor glands had a preference for Type 2 [d-galactosyl(1–4)-N-acetyl-d-glucosamine] structures.These results demonstrate that expression of the secretor gene (Se) is associated with a molecular form of the -2-l-fucosyltransferase that is different from the species present in the same tissue when theSe gene is not expressed.     

Heterochromatin variation in Cryptobothrus chrysophorus

Northern and southern races of the Australian grasshopper Cryptobothrus chrysophorus share the same diploid chromosome number (2n=23, 24). The northern race is differentiated from the southern by fixed extra blocks of heterochromatin located distally on five of the six medium pairs of autosomes (M4, 5, 6, 8 and 9). The megameric M7 pair, which is completely heterochromatic in both races, is also frequently larger in the northern race. Additionally, while there is considerable polymorphism for the presence of supernumerary heterochromatic segments on the two smallest autosome pairs (S10, 11) in both races, the precise character of this polymorphism is strikingly different between them. That found in the north is both more extensive and more variable. An analysis of the patterns of C-banding obtained in neuroblast c-mitoses indicates even more variation within and between races than was anticipated from the patterns of heteropycnosis seen at first prophase of male meiosis. Thus, while the distal blocks on the M4, 6, 8 and 9 elements in the northern race invariably C-band those of the M5 never do. On the other hand polymorphisms for C-bands on the M5, 6, 8 and 9 are seen in some populations of the southern race but in regions which are not visibly heteropycnotic at meiosis. Polymorphisms for the pattern of C-banding also occur in the northern race populations in the M4, 6, 8 and 9 elements and some of these are associated with clear length differences in the chromosomes concerned. Others involve differences in the expression of the distal C-bands in M8 and 9 which vary from dark to intermediate. The supernumerary segments on the S10 and 11 pairs are especially variable in respect of their C-banding properties. Some are entirely C-banded, some show no C-banding whatsoever and some are composed of both banded and unhanded regions. Banding is again most pronounced, however, in the northern race. Finally the character of the megameric M7 is strikingly different in the two races not only in respect of its size, which is sometimes larger than that of the south, but also in respect of the extent of C-banding which is always more complex in the northern form irrespective of its size.     

Pacemaker synaptic interactions: Modelled locking and paradoxical features

This communication describes a model for two pacemaker (i.e., regularly firing) nerve cells, such that one elicits IPSP's in the other. The assumptions involve essentially a linear dependence (delay function) of the postsynaptic interval lengthening (or delay) produced by the IPSP's on the position (or phase) with respect to the preceding spike of the latter's arrival. When the number of IPSP's in an interval increases, both the slope and intercept of the delay function increase, the former remaining under 2 and the latter unboundedly. Assumptions are more or less close to the actual biological reality, or are made for convenience. A recurrence equation for the phase can be calculated, as well as an expression for the locking phase (see below). Plots of postsynaptic vs presynaptic firing intensity averaged over steady conditions, e.g. of mean rates or intervals, are formed by a sequence of relatively broadparadoxical segments exhibiting positive slopes 1, 2, 1/2, 3, 1/3, ..., indicating that inhibited discharges are made more intense by those increases in inhibitory arrivals. These segments are separated by narrower intercalated segments where behavior is unclear except for a large overall negative slope, indicating that inhibited discharges are weakened markedly by other increases in inhibitory arrivals. Across the successive paradoxical segments that correspond to more and more intense presynaptic discharges (i.e., to higher rates or shorter intervals), postsynaptic intensities, though overlapping in part, become weaker and weaker. At the extremes, when the presynaptic discharge is very weak, or very intense, the postsynaptic cell tends to its natural undisturbed firing, or to not firing at all, respectively. The pre- and postsynaptic discharges inevitably achieve eventually an invariant relation, i.e., will lock at a constant phase, regardless of the phase of the first IPSP arrival. The characteristics of this behavior (e.g., the rate bounds of the paradoxical segments, or the magnitude of the locked phase) depend on such givens as presynaptic and postsynaptic pacemaker rates or intervals, and as the slope or intercept of the delay function.     

The effect of ferrous sulphate on the yield and manganese uptake of oats on sandy soil fertilized with pyrolusite

Summary In pot experiments with oats on a sandy soil deficient in managanese and with an extremely low content of reducible managanese, the effect of 0.125 g reducible managanese in two pyrolusite fertilizers (-managanese dioxides) made in 1938 and 1955, respectively, was compared with the effect of 0.125 g water-soluble managanese as managanese sulphate.On soil to which no ferrous sulphate was added, the response to manganese added as Pyrolusite 1938 and Pyrolusite 1955 was of the same magnitude, but slightly less than the response to managanese added as managanese sulphate. The difference between the effect of pyrolusite and that of managanese sulphate was not, however, statistically significant.On soil to which ferrous sulphate had been added, a response was obtained to Pyrolusite 1938 twice as high, and to Pyrolusite 1955 three times as high as the response to manganese sulphate. These results support the suggestion² that the manganese effect of ferrous sulphate is due to its ability to reduce higher managanese oxides in the soil.Since soil dressed with ferrous sulphate gave a response to added Pyrolusite 1955 which was about 50 per cent higher than the response to Pyrolusite 1938, and since, furthermore, the same amount of reducible manganese and the same number of manganese atoms on the surface of the two fertilizers were involved, it is probable that the difference between the effects of the two pyrolusite fertilizers found under these circumstances is due to difference in their crystallinity.     

Disease and illness Distinctions between professional and popular ideas of sickness

The dysfunctional consequences of the Cartesian dichotomy have been enhanced by the power of biomedical technology. Technical virtuosity reifies the mechanical model and widens the gap between what patients seek and doctors provide.Patients suffer illnesses; doctors diagnose and treat diseases. Illnesses are experiences of discontinuities in states of being and perceived role performances. Diseases, in the scientific paradigm of modern medicine, are abnormalities in the function and/or structure of body organs and systems. Traditional healers also redefine illness as disease: because they share symbols and metaphors consonant with lay beliefs, their healing rituals are more responsive to the psychosocial context of illness.Psychiatric disorders offer an illuminating perspective on the basic medical dilemma. The paradigms for psychiatric practice include multiple and ostensibly contradictory models: organic, psychodynamic, behavioural and social. This melange of concepts stems from the fact that the fundamental manifestations of psychosis are disordered behaviours. The psychotic patient remains a person; his self-concept and relationships with others are central to the therapeutic encounter, whatever pharmacological adjuncts are employed.The same truths hold for all patients. The social matrix determines when and how the patient seeks what kind of help, his compliance with the recommended regimen and, to a significant extent, the functional outcome. When physicians dismiss illness because ascertainable disease is absent, they fail to meet their socially assigned responsibility. It is essential to reintegrate scientific and social concepts of disease and illness as a basis for a functional system of medical research and care.Harvard Medical School     

Rethinking neurasthenia: The illness concepts of Shenjing Shuairuo among Chinese undergraduates in Hong Kong

Neurasthenia is both a Western disease construct and a popular Chinese illness concept (shenjing shuairuo, SJSR). Using a self-report questionnaire, we examined 148 Hong Kong Chinese undergraduates' concept of its epidemiology, symptomatology, etiology and treatment. Notwithstanding that fatigue is thesine qua non of neurasthenia in Western nosology, subjects believed that SJSR was compatible with a diversity of symptoms which fell, on factor analysis, into the neurotic, psychotic, somatic and dysfunctional subgroups. Contrary to the popular portrayal of SJSR as a physical or chronic fatigue disorder, the most common perceived symptoms were anxiety, insomnia, depression and fright. Logically, psychological etiology and remedy were highly emphasized. The perceived high prevalence, non-aggressive nature and symptomatic diversity of SJSR attested to the notion that it might camouflage and destigmatize psychiatric labels of insanity. The contextual study of neurasthenia illustrates how in its search for legitimacy an originally Western concept adapts, transforms, and acquires distinctive local meanings in a non-Western culture.     

Consanguinité et effectifs de la population des communes

Summary In a previous paper, we have used the density of the population as a sort of measure of the unknown size n of the isolates in Dahlberg's model, and shown an inverse relation between the coefficient of inbreeding and the density of the arrondissements. In the present paper, as the considered communes are smaller territorial subdivisions than arrondissements, we used, instead of the density, the population size of the communes. The results are even more eloquent as before: the inbreeding coefficients are large when the observed population size is small; the relative importance of second cousin marriages (233) versus cousin marriages (222) is greater in the latest period considered. The basic data have been collected for each commune in Belgium by Centre National de Radiobiologie et de Génétique.     

X-ray microanalysis of calcium binding sites in Paramecium

Summary In Paramecium cells Ca⁺⁺-stimulated triggering of the exocytosis of secretory vesicles (trichocysts) was achieved by ionophores X-537 A or A 23187. Under triggering conditions electron dense deposits were present in some resting trichocysts and regularly in discharging trichocysts; upon subsequent fixation deposits occurred on the trichocyst membrane (on the inner side or within the membrane) and on the inner lamellar sheath from where deposits seemed to radiate into the secretory materials. Similar results were obtained with glutardialdehyde fixation alone which also triggers exocytosis but only at low concentrations. Element analysis by energy dispersive x-ray microanalysis ascertained the presence of Ca and P in deposits occurring in trichocysts. Those resting trichocysts which were devoid of deposits did not contain Ca or P enriched. Hence, an abrupt Ca⁺⁺-influx into individual trichocysts just before exocytosis seems to be involved in the triggering mechanism, possibly in combination with the sudden activation of an ATPase systemlocalized at those sites of the trichocysts which primarily contain the deposits. When paramecia were treated only with Ca⁺⁺ and then fixed with OsO₄ plus oxalate or merely with glutardialdehyde, electron scattering deposits were formed also on the inner side of the cell membrane and within the ciliary shaft (but rarely in trichocysts). Deposits obtained on cilia (including ciliary granule plaques) also contained Ca, P and S. Cells contain osmiophilic calcium-storing vacuoles which were selectively rich in Ca and S but devoid of P.     

Microaerophily

Objections to previous definitions of anaerobiosis and micro-aerophily are discussed, and a new definition of micro-aerophily is proposed. A survey of physiological characteristics of the micro-aerophilic bacterium Campylobacter sputorum spp. bubulus is given, and the concept of micro-aerophily is illustrated by the results of a study on the oxygen metabolism and oxygen sensitivity of this bacterium.     

Conduite antisociale et longueur du chromosome Y

Summary A new case of free trisomy for the short arm of No. 9 chromosome identified by Giemsa staining and Giemsa-11 technique is reported.     

Alkaline lipolytic activity of rabbit adipose tissue: Genotypes and their inheritance

A genetic variant of alkaline lipolytic activity (ALA), a soluble esterase found in mammalian adipose tissue, has previously been described. This slow variant was characterized by slower migration during starch gel electrophoresis, a decreased tendency to dimerize, and reduced enzymatic activity in constrast to the fast electrophoretic phenotype. The present paper identifies a homozygous (FF) and a heterozygous (Ff) fast phenotype which are differentiated after starch gel electrophoresis by the presence or absence of a slow band identical to that of the homozygous slow (ff)/it phenotype. In addition, ALA of homozygous and heterozygous fast rabbits differed in total enzymatic activity and its tendency to dimerize. The inheritance of this variant was proven to be Mendelian.This work was supported in part by United States Public Health Service Grants AM-06872 from the National Institute of Arthritis and Metabolic Diseases and GM-15874 from the National Institute of General Medical Sciences; and Project #417 of the Children's Bureau, Department of Health, Education and Welfare.