Showing papers by "Uppsala University published in 1986"

The structure of β -lactoglobulin and its similarity to plasma retinol-binding protein

Abstract: Since its first isolation1, bovine β-lactoglobulin (BLG) has been an enigma: although it is abundant in the whey fraction of milk, its function is still not clear. The results of the many physicochemical studies on the protein need a structural interpretation. We report here the structure of the orthorhombic crystal form of cow BLG at pH 7.6, at a resolution of 2.8 A. It has an unusual protein fold, composed of two slabs of antiparallel β-sheet, which shows a remarkable similarity to plasma retinol-binding protein. A possible binding site for retinol in BLG has been identified by model-building. This suggests a role for BLG in vitamin A transport and we have discovered specific receptors for the BLG–retinol complex in the intestine of neonate calves.

cDNA sequence and chromosomal localization of human platelet-derived growth factor A-chain and its expression in tumour cell lines

Abstract: The amino-acid sequence of the precursor of the human tumour cell line-derived platelet-derived growth factor (PDGF) A-chain has been deduced from complementary DNA clones and the gene localized to chromosome 7. The protein shows extensive homology to the PDGF B-chain precursor. Expression of the PDGF A-chain gene is independent of that of the PDGF B-chain in a number of human tumour cell lines, and secretion of a PDGF-like growth factor of relative molecular mass 31,000 correlates with expression of A- but not B-chain messenger RNA.

Face the beast and fear the face: animal and social fears as prototypes for evolutionary analyses of emotion.

Abstract: This paper applies a functional-evolutionary perspective to fear in the context of encounters with animals and threatening humans It is argued that animal fear originates in a predatory defense system whose function is to allow animals to avoid and escape predators Animal stimuli are postulated to be differentially prepared to become learned elicitors of fear within this system Social fears are viewed as originating in a dominance/submissiveness system The function of submissiveness is to avert attacks from dominating conspecifics Signs of dominance paired with aversive outcomes provide for learning fear to specific individuals Data which in general are interpreted as supportive of this conceptualization are reviewed To explain the mechanism behind the causal relationships suggested in the evolutionary analysis, an information-processing model is presented and empirically tested It is argued that responses to evolutionary fear-relevant stimuli can elicit the physiological concomitants of fear after only a very quick, “unconsciousness,’ or preattentive stimulus analysis Support for this notion is presented from backward masking studies where it is demonstrated that conditioned autonomic responses to fear-relevant stimuli can be elicited even with masked stimuli

Opposite effects of tolbutamide and diazoxide on the ATP-dependent K+ channel in mouse pancreatic beta-cells.

Abstract: The influence of the antidiabetic sulphonylurea tolbutamide on K+ channels of mouse pancreatic beta-cells was investigated using different configurations of the patch clamp technique. The dominant channel in resting cells is a K+ channel with a single-channel conductance of 60 pS that is inhibited by intracellular ATP or, in intact cells, by stimulation with glucose. In isolated patches of beta-cells membrane, this channel was blocked by tolbutamide (0.1 mM) when applied to either the intracellular or extracellular side of the membrane. The dose-dependence of the tolbutamide-induced block was obtained from whole-cell experiments and revealed that 50% inhibition was attained at approximately 7 microM. In cell-attached patches low concentrations of glucose augmented the action of tolbutamide. Thus, the simultaneous presence of 5 mM glucose and 0.1 mM tolbutamide abolished channel activity and induced action potentials. These were not produced when either of these substances was added alone at these concentrations. The inhibitory action of tolbutamide or glucose on the K+ channel was counteracted by the hyperglycaemic sulphonamide diazoxide (0.4 mM). Tolbutamide (1 mM) did not affect Ca2+-dependent K+ channels. It is concluded that the hypo- and hyperglycaemic properties of tolbutamide and diazoxide reflect their ability to induce the closure or opening, respectively, of ATP-regulated K+ channels.

Female pied flycatchers choose territory quality and not male characteristics

Abstract: Female mate choice is central to the theory of sexual selection1, but much of the evidence for the basis of this choice is inconclusive2–4. First, non-random mating may occur because of male-male competition3; and second, even if females can be shown to be choosing mates it is often difficult to tell exactly on what criteria they are choosing. Possible criteria include male genes5–10, parental ability3 and quality of the resources held by males11,12, but in the wild these factors are often interdependent3. Here we report a field experiment with pied flycatchers that eliminates the correlation between male characteristics and territory quality. We find that age, size, plumage colour and song repertoire of males are all uninfluential in female choice, and that territory quality is the single most important criterion.

External shapes, strain rates, and dynamics of salt structures

Abstract: Salt structures continue to attract attention as petroleum traps and as storage vessels for wastes or fuels. Drawing on field studies, experiment, and theory, we examine the megascopic structure and large-scale dynamics of salt structures. Salt flowage can transform a tabular salt body into nondiapiric rollers, anticlines, and pillows; into diapiric walls, stocks, massifs, and nappes; and into extrusive domes and salt glaciers. These structures distort at widely variable strain rates of 10−8 s−1 to 1016 s−1, with a comparatively restricted range of dominant wavelengths of 7–26 km. Buoyancy is an ineffective diapiric mechanism unless the salt structure has pre-existing relief of at least 150 m beneath a denser overburden of terrigenous clastics. Differential loading is a far more effective mechanism in the early stages of diapirism and commonly results in asymmetric salt structures. Gravity spreading modifies the shape of salt structures with negative buoyancy. With a heat-induced density inversion, thermal convection may lead to internal circulation and stirring of a still-tabular salt body. At least four mechanisms may form broad bulbs on mature salt stocks. Consideration of the effective viscosity contrast between salt and its cover suggests that mature stocks may have stems much more narrow than is commonly envisaged. Salt tectonics is classified here on the basis of change of gravity potential energy that promotes or retards salt flow. Halokinetic movements can be initiated, succeeded, retarded, or accelerated by regional tangential forces that stretch, wrench, or compress sedimentary basins.

Characterization of the antibody response in mice with type II collagen-induced arthritis, using monoclonal anti-type II collagen antibodies.

Abstract: Twenty monoclonal antibodies reactive with type II collagen were characterized as to their determinant specificity and their reactivity with cartilage-derived components. The monoclonal antibodies reacted with 7 different epitopes on the native type II collagen triple helical structure. Antibodies defining 3 of these epitopes occurred more frequently in sera from arthritic mice than in sera from nonarthritic mice. In vivo injection of some selected autoreactive antibodies caused synovitis, but in no case did it give rise to full-blown arthritis.

Staphylococcal protein A consists of five IgG-binding domains.

Abstract: A genetic approach is described to clarify the IgG-binding properties of the N-terminal portion of staphylococcal protein A (region E). Several gene fragments, encoding region E or B or protein A, have been cloned and expressed in Escherichia coli. The gene products were purified by IgG-affinity chromatography and subjected to structural and functional analyses. Both fragments can be efficiently purified using this method, suggesting that region B as well as region E has Fc-binding activity. In addition, gene fusions were assembled giving fragments EB and EE, which both showed a divalent Fc-binding. These results demonstrate that protein A consists of five IgG-binding domains. The implications of these findings for the structure of protein-A--immunoglobulin-G complexes are discussed.

The role of remnant forest trees in tropical secondary succession

Abstract: This paper emphasizes the contribution of remnant trees to the establishment of woody species during succession on abandoned fields and pastures in the Mexican rain forest area, Los Tuxtlas, Veracruz.

Mate choice, fecundity and sexual dimorphism in two pipefish species (Syngnathidae)

Abstract: In order to understand the causes of sexual dimorphism, mate choice and size-related fecundity were studied in two pipefish species, Syngnathus typhle and Nerophis ophidion. Sexual dimorphism is more pronounced in N. ophidion; females are larger, have sexual colourings, and are more active during courtship. In S. typhle the sexes are alike in all these respects. Males brood their offspring in both species. In N. ophidion fecundity was positively correlated with both body size and the amount of sexual colouring in females. In males no correlation between body size and fecundity, or between body size and embryo size existed. Predictably, in mate choice experiments with equal-sized females, males chose females with more extensive sexual colourings. We explain sexual dimorphism in this species as a consequence of both natural selection (fecundity increases with size in females but not in males) and sexual selection (males prefer larger females). We argue that sexual size dimorphism did not evolve by selection minimizing overlap in food niches between the sexes, because food production is high in the Zostera beds where the fishes live, and no size dimorphism was found in the sympatrically occurring S. typhle. Furthermore, in N. ophidion dimorphism is not greater in a particular mouth character than in overall body size. In S. typhle egg size and the average number of eggs transferred per spawning were positively correlated with female body size. Apparently more energy per offspring was provided by larger males than by smaller males, and larger males also carried more offspring. As predicted, large mates were preferred by both sexes in mate choice experiments. This is explicable in terms of both natural selection (fecundity increases with size in both sexes) and sexual selection (both sexes prefer large mates). As a consequence of selection acting in the same direction in both sexes, sexual dimorphism is absent in S. typhle.

Histochemical and metabolic characteristics of human skeletal muscle in relation to age.

Abstract: Muscle fibre composition, fibre areas and enzyme activities were determined in muscle biopsy samples (m. vastus lateralis) from both legs of 34 clinically healthy men and 31 clinically healthy women (aged 20-70 years). No significant difference was found in any of the three variables between the right and left leg. In the whole material the mean percentage of type I fibres was significantly higher in men, whereas that of type IIA fibres was significantly higher in women (men 58% I, 27% IIA, 13% IIB, women 51% I, 32% IIA, 15% IIB). The areas of all fibre types were significantly larger in men than in women. When the subjects were divided into age groups of 20, 30, 40, 50, 60 and 70 years, respectively, the fibre composition was found to be similar at different ages in both men and women, but changes in fibre areas were observed. The 70-year-old men and women showed significantly reduced areas of both type I and II fibres compared with the 60-year-olds. Only minor changes were seen in enzyme activities in relation to age. Men of the youngest age group had significantly higher levels of citrate synthase activity than those of the older age groups. Similar findings were seen for women except for the 60-year-olds, who had as high activity levels of citrate synthase as the 20-year-olds.

Sand movement as a factor in the distribution of plant communities in a coastal dune system

Abstract: The semi-mobile coastal sand dune system El Morro de La Mancha at the Gulf of Mexico was studied phytosociologically and ecologically. The floristic gradient resulting from a releve ordination was correlated with the amount of sand movement occurring on the site of each releve, and the topography of the dune. The gradient manifested in the ordination represents the transition from the more mobile parts of the dunes to the more stable ones. It can be interpreted as a progressive stabilization during which sand movement decreases.Chamaecrista chamaecristoides,Palafoxia lindenii andCroton punctatus were found to inhabit the sites with considerable sand movement. The first species tolerates both erosion and accretion; the other two were only found in sites of sand accumulation. On the other hand grasslands and scrub were found on sites without any sand movement. Sand movement should be considered among the most important factors that affect the distribution of communities in sand dunes.

Diet and pancreatic cancer: a case-control study

Abstract: In a population-based case-control study carried out in Sweden in 1982-1984, the authors examined the association of pancreatic cancer with several dietary factors, coffee, alcohol, and tobacco. Analyses were based on 99 cases, 138 population controls, and 163 hospital controls. The cases were persons aged 40-79 years diagnosed with cancer of the exocrine pancreas at three surgical departments in Stockholm and Uppsala. The risk increased with higher consumption frequency of fried and grilled meat in the comparison with each series of controls (e.g., relative risk (RR) = 1.7 (90% confidence interval (CI) = 1.1-2.7) for weekly intake and RR = 13.4 (90% CI = 2.4-74.7) for almost daily intake, in the comparison with population controls). Furthermore, associations were found with other fried or grilled foods, but not with meat other than fried or grilled. The risk also increased with the intake of margarine (e.g., RR = 9.7 (90% CI = 3.1-30.2) for 15+ g of margarine on a slice of bread, in the comparison with population controls). In contrast, no excess risk was associated with high intake of butter. A low risk was associated with frequent consumption of fruits and vegetables, particularly carrots (RR = 0.3 (90% CI = 0.2-0.7)) and citrus fruits (RR = 0.5 (90% CI = 0.3-0.9)) for almost daily intake. No consistent associations were found with coffee, artificial sweeteners or alcohol consumption, but a threefold increase in risk was associated with smoking at least one pack of cigarettes per day.

Homologous type II collagen induces chronic and progressive arthritis in mice.

Abstract: Native mouse type II collagen was used for immunization of DBA/1 mice. Arthritis developed exclusively in male animals and was characterized by a variable and delayed onset, a slow and progressive development, and frequent exacerbations of disease in several joints including those that were previously affected. Titers of anti-type II collagen autoantibodies were found not to correlate well with arthritis development. It appears that experimental arthritis induced with homologous type II collagen resembles rheumatoid arthritis in humans, both in certain clinical features and in the lack of correspondence between anti-type II collagen autoantibody titers and disease symptoms.

Male bird song attracts females — a field experiment

Abstract: The initial stage of pair formation of the pied and the collared flycatcher (Ficedula hypoleuca and F. albicollis) was simulated in a field experiment. Male dummies positioned near nest boxes and “singing” by means of tape-recorded song from loudspeakers offered prospecting females a nest box combined with an automatic trap. An unequivocal demonstration of female arrival at the male's territory was obtained by the trapping of the female. Control nest-box traps were provided with silent dummies. Factors other than male song causing female attraction were controlled by a daily switch of the position of “singing” and silent dummies. Nine out of ten females were caught in nest-box traps with “singing” dummies (one-tailed binomial test, P=0.011). The result supports the hypothesis that male song functions in mate attraction. This hypothesis has never previously been tested in field experiments although circumstantial evidence for it has been available.

Vegetation responses to past climatic variation

Abstract: Vegetation responses to climatic change can be studied retrospectively by utilizing the Quaternary fossil record. There has been controversy over the extent to which major changes in vegetation patterns at the continental scale lag behind the climatic changes that drive them, and to what extent vegetation can ever be said to be in equilibrium with climate. The equilibrium question has no single answer. The predominant mode of vegetation response to climatic change depends on the space and time frame and resolution of the data set in which the response is observed.

Heritability and selection on tarsus length in the pied flycatcher (ficedula hypoleuca).

Abstract: The heritability estimate (?SE) for tarsus length in the pied flycatcher is 0. 53 + 0. 10, based on mother-offspring regressions. The heritability is almost the same (0.50 ? 0.22) for offspring transferred to other nests and reared by foster parents, whereas there is no resemblance (0.04 ? 0.23) between the offspring and their foster mothers. Hence, the nest environment does not affect parent-offspring resemblance. However, a full-sib correlation yields an estimate of the heritability twice as high as the parent-offspring regression did, indicating that shared environment effects, which are not correlated with the tarsus length of parents, must be important. An environmental deviation due to food factors affecting tarsus length is demonstrated. The most important food factors are probably associated with 1) polygyny, which leads to reduced paternal feeding at sec- ondary nests, 2) high breeding density, and 3) progress of the breeding season. All three are associated with reductions in offspring mean tarsus length. We estimate selection on tarsus length for the major components of lifetime reproductive success. Offspring with the shortest tarsi have reduced survival from fledging until breeding, and males with tarsus length close to the mean are most successful in attracting mates. Clutch size increases with female tarsus length, except for individuals with very long tarsi. In general, directional selection is weak, but stabilizing selection is rather strong for survival and male mating success.

Striato-nigral dynorphin and substance P pathways in the rat. I. Biochemical and immunohistochemical studies.

Abstract: The effect of striatal ibotenic acid lesions on dynorphin-, substance P- and enkephalin-like immunoreactivities in the substantia nigra has been studied with immunohistochemistry as well as biochemistry. A comparison was made with the effects produced by intranigral ibotenic acid lesion and by 6-hydroxy-dopamine injection into the medial forebrain bundle. In addition, the effect of the striatal lesions on nigral glutamic acid decarboxylase (GAD)-positive structures was analysed with immunohistochemistry. The effect of the lesions was analysed functionally in the Ungerstedt rotational model, in order to obtain a preliminary evaluation of the extent of the lesions. The striatal lesions produced a parallel depletion of dynorphin and substance P levels in the substantia nigra, pars reticulata, ipsilateral to the treated side, which was dependent upon the extent and location of the lesion. Ibotenic acid lesions into the tail and the corpus of the striatum produced stronger nigral-peptide depletion than lesions in the head and the corpus of the striatum. Comparison of placement of lesions and localization of depleted area in the substantia nigra revealed a topographical relationship. Furthermore, the nigral depletion patterns of dynorphin and substance P were similar. The immunohistochemical analysis revealed that also GAD-positive fibers in the pars reticulata to a large extent disappeared after striatal lesions, in parallel to the dynorphin- and substance P-positive fibers. However, the depletion was less pronounced for GAD than for the peptides, probably related to presence of local GABA neurons in the zona reticulata of the substantia nigra. These results indicate that with the types of lesion used in this study it is not possible to provide evidence for a differential localization within the striatum of dynorphin-, substance P- and GABA-positive cell bodies projecting to the substantia nigra. The radioimmunoassay showed that (Leu)- but not (Met)-enkephalin was affected to the same extent as the dynorphin peptides, supporting the view that (Leu)-enkephalin in the pars reticulata of the substantia nigra is derived from proenkephalin B and not from proenkephalin A. In the immunohistochemical analysis (Met)-enkephalin-like immunoreactivity could only be detected in the pars compacta of the substantia nigra and did not seem to be affected by any of the lesions. The striatal lesions produced a behavioural asymmetry, which could be disclosed by stimulating the rats with apomorphine, which produced ipsilateral rotation. The total number and intensity of the rotation were closely correlated to the extent and location of the striatal lesion as well as to the amount of dynorphin and substance P depletion found in the substantia nigra of the treated side. The results provide further evidence for the presence of a dynorphin-containing system with fibers originating mainly in the corpus and tail of the striatum and terminating in the zona reticulata of the substantia nigra and may, similarly to the previously characterized substance P and GABA containing pathways, have a role in the control of motor behaviour.

Exocytosis and uptake of bacteria by isolated haemocyte populations of two crustaceans: evidence for cellular co-operation in the defence reactions of arthropods

Abstract: The role of exocytosis in the cellular defence reactions of arthropods was investigated using in vitro cultures of isolated haemocytes (blood cells) from the freshwater crayfish Pacifastacus leniusculus, and the shore crab Carcinus maenas. In both species, activated lysates of those cell types that contain the prophenoloxidase activating system (granular cells of crab and crayfish and semigranular cells of crayfish) were found to induce degranulation (exocytosis) of semigranular and granular cells. A cell lysate, in which the prophenoloxidase system was kept inactive, did not have this effect. Limited degranulation of granular cells of crab was also induced by lipopolysaccharides as has earlier been shown for crayfish semigranular cells. The phagocytic capability of semigranular cells from crayfish was lost after exocytosis induced by the Ca2+ ionophore A23187, and under no conditions were the granular cells of crabs or crayfish seen to ingest bacteria in vitro. An opsonic function for the attaching proteins of a β1,3-glucan-activated haemocyte lysate was demonstrated using the phagocytic hyaline cells from crabs. Phenoloxidase appeared to lack opsonic properties.