Showing papers by "Utrecht University published in 1983"

Temperature measurement with a sonic anemometer and its application to heat and moisture fluxes

Abstract: The possibility ofmeasuring heat and moisture fluxes using sonic anemometer data is investigated. Theoretical relations for the temperature variance and heat flux are derived. In the first part of this paper, these relations are verified by experimental data, involving a sonic anemometer, a fast thermocouple and a Lyman-cc hygrometer. In the second part we propose two simple procedures to estimate heat flux from sonic anemometer data. The first one requires a rough estimate of the Bowen ratio; for the second one the net radiation is needed. Using the last method, a good estimate of the moisture flux is also obtained.

Why Are Diurnal Primates Living in Groups

Abstract: There are two main competing theories on the evolution of group living in diurnal nonhuman primates. The first theory claims that predation avoidance favours group living, whereas there are only disadvantages to feeding in a group and feeding competition increases with group size. The second theory claims that there is a feeding advantage to group living deriving from communal defence of high-quality food patches and that predation is not important. These theories have not yet been rigorously tested. In this paper a critical test is proposed: the theories differ in the predicted relationship between a female's birth rate and the size of the group in which she lives (Fig. 1). An additional test is concerned with the predicted relationship between population density relative to food availability and average group size. Finally, a critical test is proposed of the hypothesis that increasing group size should lead to reduced predation risk by comparing demographic patterns between areas where predators are still present and where they have disappeared. A total of 23 data sets on 13 species were extracted from the literature and supplemented with four unpublished data sets. In all three tests the results provide strong support for the predation-feeding competition theory and are clearly unfavourable for the theory postulating feeding advantages to group living. Such feeding advantages may, however, gain prominence under some conditions.

High-Resolution, 1H-Nuclear Magnetic Resonance Spectroscopy as a Tool in the Structural Analysis of Carbohydrates Related to Glycoproteins

Abstract: Publisher Summary This chapter discusses the application of high-resolution, 1H-nuclear magnetic resonance (NMR) spectroscopy to the structural analysis of carbohydrates related to glycoproteins. Glycoproteins are biopolymers consisting of a polypeptide backbone bearing one or more covalently linked carbohydrate chains. The carbohydrate chains of glycoproteins may be classified according to the type of linkage to the polypeptide backbone. N-Glycosylic chains are attached to the amide group of asparagine (Asn), whereas the O-glycosylic chains are linked to the hydroxyl group of amino acid residues such as serine (Ser), threonine (Thr), and hydroxylysine (Hyl). The high-resolution, 1H-NMR spectroscopy technique, in conjunction with methylation analysis, is extremely suitable for the structural studies of N-, as well as on O-, glycosylic glycans. For the interpretation of the 1H-NMR spectrum of a carbohydrate chain in terms of primary structural assignments, the concept of “structural reporter groups” was developed. This means that the chemical shifts of protons resonating at clearly distinguishable positions in the spectrum, together with their coupling constants and the line widths of their signals, bear the information essential to permit the assigning of the primary structure. This chapter presents literature data on the high-resolution, 1H-NMR spectroscopy of carbohydrates derived from glycoconjugates. It also discusses the results for carbohydrates related to the glycoproteins of N-glycosylic type.

On the ultimate causes of primate social systems.

Abstract: [The aim of this review is to present a coherent explanation of the ultimate causation and the evolution of primary social systems. The explanation is based on the assumption that social systems of all diurnal primates are derived from female defence polygyny. Group living is therefore regarded as the essential first step in the social evolution of diurnal primates. Primate social systems are generally classified into four main types, each of which can be contrasted with the others along the following lines: solitariness versus group living, monogamy versus polygyny and reproductive activity by only one male versus reproduction of several males per group. First of all we present some comparative evidence to support the hypothesis that monogamy in primates has evolved from polygynous groups, in two different ways. A commonly held view is that monogamy is most likely to develop where paternal care of the offspring is advantageous. This is almost certainly the case in the very small species of primates. In these monogamy is the consequence of twinning and the resultant need for active paternal care. It runs contrary to the evident tendency of these species to form larger groups in response to the pressure of predation. The latter is achieved by an extended group membership of grown-up offspring in a non-reproductive and even 'helping' role. In the larger species, however, monogamy is most probably the outcome of, on the one hand, a strong need to reduce competition for food favouring very small group sizes, and, on the other hand, of the virtual absence of predation permitting such a development. Secondly, we look critically at several hypothetical explanations for the existence of multi-male groups and one-male groups. We argue that the ultimate explanation for their existence is not to be found in differential male mortality, anti-predator defence, availability of food, and differential expulsion of "expendable" males. Instead, comparative evidence indicates that the distinction between a single-male or a multi-male system is ultimately dependent on the varying ability of a male to monopolize access to a breeding group of females. This ability in turn depends on group cohesiveness as determined by feeding strategies and predation pressure and is often, though not necessarily, related to the size of the group., The aim of this review is to present a coherent explanation of the ultimate causation and the evolution of primary social systems. The explanation is based on the assumption that social systems of all diurnal primates are derived from female defence polygyny. Group living is therefore regarded as the essential first step in the social evolution of diurnal primates. Primate social systems are generally classified into four main types, each of which can be contrasted with the others along the following lines: solitariness versus group living, monogamy versus polygyny and reproductive activity by only one male versus reproduction of several males per group. First of all we present some comparative evidence to support the hypothesis that monogamy in primates has evolved from polygynous groups, in two different ways. A commonly held view is that monogamy is most likely to develop where paternal care of the offspring is advantageous. This is almost certainly the case in the very small species of primates. In these monogamy is the consequence of twinning and the resultant need for active paternal care. It runs contrary to the evident tendency of these species to form larger groups in response to the pressure of predation. The latter is achieved by an extended group membership of grown-up offspring in a non-reproductive and even 'helping' role. In the larger species, however, monogamy is most probably the outcome of, on the one hand, a strong need to reduce competition for food favouring very small group sizes, and, on the other hand, of the virtual absence of predation permitting such a development. Secondly, we look critically at several hypothetical explanations for the existence of multi-male groups and one-male groups. We argue that the ultimate explanation for their existence is not to be found in differential male mortality, anti-predator defence, availability of food, and differential expulsion of "expendable" males. Instead, comparative evidence indicates that the distinction between a single-male or a multi-male system is ultimately dependent on the varying ability of a male to monopolize access to a breeding group of females. This ability in turn depends on group cohesiveness as determined by feeding strategies and predation pressure and is often, though not necessarily, related to the size of the group.]

Sequence of cDNA encoding human insulin-like growth factor I precursor.

Abstract: Somatomedins (SM) or insulin-like growth factors (IGF) constitute a heterogeneous group of peptides with important growth-promoting effects in vitro as well as in vivo. Amino acid sequences have been determined for only two of them, IGF-I and IGF-II, which are highly homologous. IGF-I, which is identical with SM-C, is composed of 70 amino acid residues and IGF-II contains 73 amino acids and may be identical with SM-A. Other peptides with different charge properties but with similar SM-like or insulin-like behaviour in biological and receptor assays, have been described but have not yet been fully characterized. The liver is known to be a major site of production of these peptides, but many other tissues--especially in the fetus--may synthesize them as well. We report here the nucleotide sequence of a human liver cDNA encoding the complete amino acid sequence of IGF-I. The IGF-I coding region is flanked by sequences encoding an amino-terminal peptide of at least 25 amino acid residues and a carboxyl-terminal peptide of 35 amino acids. This provides evidence that IGF-I is synthesized as a precursor protein and that formation of IGF-I from this precursor requires proteolytic processing at both ends.

Raised nutrient levels change heathland into grassland

Abstract: In 1969 N and P fertilizer experiments were carried out on the Westerheide (The Netherlands) to investigate the growth of Calluna vulgaris In 1981 the floristic composition of the experimental plots was analyzed Repeated nitrogen treatment of 28 kg · ha-1 · yr-1 resulted in dramatic replacement of Calluna vulgaris by Festuca ovina as a dominant Phosphorus treatments did not result in such a change The amounts of nitrogen applied in this experiment are similar to those that will be available during the first years following the dying off of Calluna vulgaris as result of a heather beetle infestation It is hypothesized that a heather beetle infestation alone may result in a similar replacement of Calluna vulgaris by grass species

Severe plasmalogen deficiency in tissues of infants without peroxisomes (Zellweger syndrome).

Abstract: The Zellweger syndrome is a lethal hereditary disease characterized by the absence of peroxisomes (microbodies) in liver and kidney, and variable abnormalities in mitochondria1–8. We show here that tissues from five infants that had died of this syndrome contain less than 10% of the normal levels of phosphatidylethanolamine plasmalogen (pPE), a major phospholipid component of cellular membranes. Heart and muscle, but not other tissues, also contain a substantial fraction of phosphatidylcholine plasmalogen (pPC), and this fraction is also strongly reduced in the Zellweger patients. No other abnormalities in cellular phospholipids were detected. Key enzymes of the biosynthesis of plasmalogens have previously been shown to be exclusively located in the peroxisomes of rodent liver and the microperoxisomes of rodent brain9,10. We infer that the corresponding enzymes are also located in peroxisomes in man and that the absence of peroxisomes in Zellweger patients leads to their inability to synthesize plasmalogens. Our results support the notion11 that the biosynthetic role of peroxisomes in mammals has thus far been underestimated. We suggest that the defect in plasmalogen synthesis and possibly as yet unknown peroxisomal reactions are responsible for the diverse abnormalities observed in Zellweger patients.

Structural changes in bovine oocytes during final maturation in vivo

Abstract: On the basis of structural observations bovine oocytes were grouped into four successive classed: 0, those before the luteinizing hormone (LH) surge; 1, those up to 8 h following the LH peak level; 2, those between 8 and 19 h after the LH peak level; and 3, those between 19 h after the LH peak level and ovulation. Oocytes in class 0 had mitochondria located in a generally peripheral position. Interior to the mitochondria were elements of rough endoplasmic reticulum (RER) and numerous membrane-bound vesicles which bore ribosome-like particles on their outer surface. The first visible changesater the LH peak level as seen in class 1 were the formation of the periviteline space with loss of contact between the cumulus cells and the oocyte, and ruffing of the nuclear envelope. These changes were followed b the resumption of meiosis as defined by germinal-vesicle breakdown (GVBD), the disappearance of RER, and the formation fo clusters of mitochondria in association with lipid droplets and elementrs of smooth endolasmic reticulum (SER). The period between 8 and 19 h following LH peak level (class 2) was characterized by intensive clustering of mitochoncria in association with lipid droplets and elements of SER, conversion of lipid, fusion of vesicles, and the appearance of ribosomes in the cytoplasm. During the final stage (class 3), the polar body was extruded, the mitochondria dispersed, and the majority of the organelles became located toward the center of the cell. The relatively organelle-free cortical region contained cortical granules immediately adjacent to the plasma membrane together with aggregates of tubular SER. The structural changes are discussed in the context of follicular steroidogenesis and oocyte developmental competence.

A major metabolite of arginine vasopressin in the brain is a highly potent neuropeptide

Abstract: A peptide that accumulated as the major product during the proteolysis of arginine vasopressin by rat brain synaptic membranes was isolated and its structure was shown to be the hexapeptide pGlu-Asn-Cys(Cys)-Pro-Arg-Gly-NH2. When administered intracerebroventricularly in extremely low doses, this vasopressin fragment and its desglycinamide derivative facilitated memory consolidation in a passive avoidance situation. These vasopressin metabolites, which are devoid of pressor activity, constitute highly potent neuropeptides with selective effects on memory and related processes; they are activated via proteolytic processing of vasopressin by brain peptidases.

Coronavirus mRNA synthesis involves fusion of non-contiguous sequences.

Abstract: Positive-stranded genomic RNA of coronavirus MHV and its six subgenomic mRNAs are synthesized in the cytoplasm of the host cell. The mRNAs are composed of leader and body sequences which are non-contiguous on the genome and are fused together in the cytoplasm by a mechanism which appears to involve an unusual and specific 'polymerase jumping' event.

Phosphorylation of B 50 protein by calcium activated, phospholipid dependent protein kinase and B 50 protein kinase

Abstract: B-50 is a brain-specific phosphoprotein, the phosphorylation state of which may play a role in the regulation of (poly)phosphoinositide metabolism. Several kinases were tested for their ability to phosphorylate purified B-50 protein. Only calcium-activated, phospholipid-dependent protein kinase (kinase C) and B-50 protein kinase were able to use B-50 protein as a substrate. Furthermore, kinase C specifically phosphorylates B-50 when added to synaptic plasma membranes. We further characterized the sensitivity of kinase C and B-50 kinase to ACTH (and various fragments), phospholipids, chlorpromazine, and proteolytic activation. Since the sensitivities of both kinases were similar, we conclude that B-50 protein kinase is a calcium-dependent, phospholipid-stimulated protein kinase of the same type as kinase C.

The relationship between nutrient availability, shoot biomass and species richness in grassland and wetland communities

Abstract: The relationship was studied between shoot biomass, nutrient concentration in the soil and number of species per unit area. The study was carried out in two different parts of the Netherlands, the Gelderse Vallei (east of Amersfoort) and the Westbroekse Zodden (northwest of Utrecht). Four series of vegetation and soil samples were taken: one series in grassland and wetland communities, one series in grassland communities, one series in fen communities and one series in only one wetland community. The two series in grassland communities show a negative correlation between shoot biomass and species number and a positive correlation between shoot biomass and nutrient concentration in the soil. The opposite was found in the series in the fen communities: there was a positive correlation between species number and shoot biomass and a negative correlation between shoot biomass and nutrient concentrations. The series of samples that had been taken in only one wetland community showed an optimum curve for the relation between shoot biomass and number of species. It is concluded that in the plant communities studied the species richness per unit area increases with increasing productivity at low production levels ( 400–500 g/m2).

Affinity-purified anti-B-50 protein antibody: interference with the function of the phosphoprotein B-50 in synaptic plasma membranes.

Abstract: Affinity-purified anti-B-50 protein antibodies were used to study the previously proposed relationship of the phosphorylation state of B-50 protein and polyphosphoinositide metabolism in synaptic plasma membranes. Antibodies were raised against a membrane extract enriched in the B-50 protein and its adrenocorticotropin-sensitive protein kinase, obtained from rat brain. Anti-B-50 protein immunoglobulins were purified by affinity chromatography on a solid immunosorbent prepared from B-50 protein isolated by an improved procedure. The purified antibodies reacted only with the B-50 and B-60 protein, a proteolysis derivative (of B-50), as assessed by the sodium dodecyl sulfate-gel immunoperoxidase method. These antibodies inhibited specifically the endogenous phosphorylation of B-50 protein in synaptic plasma membranes, without affecting notably the phosphorylation of other membrane proteins. This inhibition was accompanied by changes of the formation of phosphatidylinositol 4,5-diphosphate and phosphatidic acid in synaptic plasma membranes, whereas formation of phosphatidylinositol 4-phosphate was not altered. Inhibition by ACTH 1–24 of the endogenous phosphorylation of B-50 protein in membranes was associated only with an enhancement of the phosphorylation of phosphatidylinositol 4-phosphate to phosphatidylinositol 4,5-diphosphate. These data support our hypothesis on the functional interaction of B-50 protein and phosphatidylinositol 4-phosphate kinase in rat brain membranes. The evidence shows that purified anti-B-50 protein antibodies can be used to probe specifically the function of B-50 protein in membranes.

Fabric asymmetry and shear sense in movement zones

Abstract: Asymmetry between lattice preferred orientation and shape fabrics is commonly observed in microstructural studies of many deformed mineral aggregates (e g ice, carbonate rocks, peridotites and quartzites) Theoretical predictions are limited by the nature of the models available and more can be gained by discussion of the mechanisms which give rise to such asymmetry in specific natural and experimental situations

4 – Carbohydrate Catabolism in Bivalves

Abstract: Publisher Summary This chapter focuses on the variety and flexibility of pathways of carbohydrate catabolism in bivalves. In the presence of oxygen, glucosyl units are completely oxidized to H2O and CO2. Dehydrogenation occurs in glycolysis and the citric acid cycle; via the coenzymes NAD or FAD and the electron-transfer chain, the hydrogen is oxidized to H2O by atmospheric oxygen; CO2 is formed in the citric acid cycle, and both end products are formed in the mitochondrion. In nerve tissues and to a lesser extent in organs such as the heart, in the absence of oxygen, the same cooperation still exists among glycolysis, the citric acid cycle, and the electron-transfer chain, but that oxygen is replaced by a prestored electron acceptor—the yellow lipochrome pigment. The pigment is composed of neutral fats and phospholipids, and unsaturated fatty acids serve as the endogenous electron-acceptor molecules. The organelles rich in the yellow pigment are called cytosomes. Cytosomes accumulate bivalent cations in the absence of oxygen.

Peritoneal Macrophages and Opsonins: Antibacterial Defense in Patients Undergoing Chronic Peritoneal Dialysis

Abstract: The antibacterial activity of phagocytic cells and opsonins in peritoneal dialysis effluents from 21 patients undergoing chronic peritoneal dialysis (CPD) was studied. Effluents contained an average of 12 x 106 cells per liter that were predominantly macrophages. Macrophages phagocytized and killed opsonized Staphylococcus epidermidis, Staphylococcus aureus, and Escherichia coli as efficiently as did polymorphonuclear neutrophils (PMNs) from healthy donors. Macrophage chemiluminescence was onethird of that observed with donor PMNs. In the absence of opsonins, macrophages efficiently phagocytized and killed S. aureus by binding S. aureus cell wall protein A to macrophage surface IgG. Nine (43%) of 21 effluents failed to opsonize S. epidermidis, and none opsonized E. coli. When present, titers of S. epidermidis opsonins were 50to 100-fold lower than that of normal serum. IgG and C3 concentrations in effluent reflected its opsonic capacity. Macrophages from patients undergoing CPD thus have intact phagocytic and bactericidal functions. However, the low level of opsonic molecules and inadequate numbers of macrophages in the peritoneal cavity may predispose patients undergoing CPD to peritonitis. Chronic peritoneal dialysis (CPD) is increasingly being used to treat patients with end-stage renal failure. Patients undergoing CPD have adequate control of serum chemistries, blood pressure, and