Showing papers by "University of Groningen published in 1971"

On the Nature of Turbulence

Abstract: A mechanism for the generation of turbulence and related phenomena in dissipative systems is proposed.

The structure of papain.

Abstract: Publisher Summary The fruits of the tropical papaya tree have latex that contains several enzymes. This chapter focuses on two different proteolytic enzymes: chymopapain and papain. Both enzymes belong to the group of proteolytic plant enzymes that require a sulfhydryl group for activity. The chapter discusses the enzymatic properties of papain. Papain can catalyze a number of reaction—namely, acyl-enzyme intermediate, hydrolysis, transferase action, and specificity. X-ray diffraction can provide a wealth of information on a protein structure. The papain molecule consists of one folded polypeptide chain of 212 residues. The sequence determination of these residues is an example of the mutual interaction between purely chemical and X-ray methods. Because of the many difficulties that papain presented to the chemists, only a tentative sequence could be published in 1964. Some of the overlaps were not found to be as conclusive as desired, and at least one gap existed in the sequence. The available information, however, permitted the interpretation of the electron density map. Moreover, the difficulties in the early chemical sequence studies on papain because of the insolubility of the denatured protein and many of its peptides is circumvented by the use of completely carboxymethylated papain that has been fully maleylated.

Endogenous depressions with and without disturbances in the 5-hydroxytryptamine metabolism: A biochemical classification?

Abstract: The influence of i.v. administered probenecid on the 5-HIAA concentration in the CSF was studied in a group of patients with vital (“endogenous”) depression and a non-depressive control group. The average increase of the 5-HIAA concentration in the CSF after probenecid administration was smaller in the depressive group than in the control group. Moreover, the depressive group included patients with a normal as well as patients with a subnormal probenecid effect. This could mean, that the group of v tal depressions encompasses two biochemically different categories: patients with and patients without demonstrable disturbances in the metabolism of 5-HT in the brain.

Biological significance, genetics and evolutionary origin of variability in behaviour within and between inbred strains of mice Mus musculus

Abstract: The biological significance, the origin and the genetical causation of differences in behaviour between inbred strains of mice have been studied. Three inbred strains with different origins were used, these were CPBs (Balb), CBA and C57Black. Exploratory behaviour, nestbuilding behaviour and agonistic behaviour have been observed in environments, which varied with respect to familiarity, presence or absence of nesting material and the possibility of social contact. A comparison of the behaviour of these strains showed the presence of differences in all aspects of the behaviour studied. None of these differences, however, was a qualitative one. The behaviour of each strain was strain specific as appeared from a comparison with earlier reports on related substrains. CPBs mice were territorial with a sensitive aggression-flight balance. They showed a relatively elaborate courtship. They were able to build spherical nests at the surface without support of walls because they treated the nesting material in a special way (fraying). Their exploratory behaviour was mainly directed to open space. C57Black mice were not territorial and did not show a sensitive aggression-flight balance. They hardly showed any courtship. They were not able to build a spherical nest at the surface without support of walls, because they hardly fraved the nesting material. They showed much digging, especially when confronted with nesting material. This digging was well directed and in a suitable substrate holes were made. Their exploratory behaviour was mainly directed to the surface. CBA mice were generally less aggressive than the CPBs mice, but some individuals showed clear territorial behaviour. Their courtship was intermediate to that of the other two strains. CBA mice as a rule did not build proper nests at the surface, either because they did not try to make a nest at all or because they treated the nesting material in such a way that they chopped it up to pieces which were too small to shape more than a simple platform at the surface. They showed much digging but this digging was randomly directed resulting in turning over the whole substrate; no holes resulted from such digging. The exploratory behaviour of the CBA mice was mainly directed to the surface. The nestbuilding behaviour element fraying was chosen for a genetical analysis to find out whether differences in the kind of behaviour studied here were genetically determined or not. Genetical determination appeared to play an important role. Heritabilities for F2 animals and their progeny varied between 17 and 47 per cent. A cross-fostering test between CPBs and C57 Black did not show any cultural influence on the fraying performance in these mice. CPBs mice, which showed a relatively high variability for fraying, appeared to be heterozygous for this character. The heritability found showed a similar size as was found for hybrids (43 per cent). Selection experiments on fraying in this strain were not successful because the lines died out. One selection line for high fraying survived for six generations. It showed no significant reaction to the selection exerted. Heterozygosity in CPBs mice for fraying appeared to be maintained by a kind of balanced system which worked partly by sterility of the high and low fraying types and partly by a negative influence of such types on the physical condition and thus on the fertility of their progeny. Intermediate fraying mice got selective advantage over high and low fraying types in this way, even under inbreeding conditions. Probably only one effective factor is involved in the determination of fraying. Hypotheses concerning the maintenance of genetic variability under inbreeding conditions have been discussed. An analysis of the function and the origin of the differences found between strains suggested that the differences between strains showed strain specific adaptations to habitats in which their ancestors lived. This holds for CPBs mice and for C57Black mice, the ancestors of the first being surface living mice, the ancestors of the second being hole living mice. The behaviour of the CBA mice appeared to be disrupted from a functional point of view, which is in agreement with the fact that CBA mice originate from a cross between two other inbred lines. A specially designed cage to test a differential habitat preference to be present in CPBs and C57Black mice confirmed the hypothesis about the habitat adaptations in these mice and clearly showed that preferences for these habitats are still present in the inbred mice. The results of CBA mice in this test confirmed the unpredictable character of these mice. A comparison for adaptations of this kind between laboratory mice and wild mice revealed that the differences have probably arisen in mice before they were taken into the laboratory. The scarce data available for wild mice suggested that similar adaptations as found here for inbred mice, can also be found in wild mice of different origin. It is discussed that surface living mice have had a better chance to adapt to living in buildings and become commensals, furthermore that the two behavioural types, showing differential adaptations, cannot have gone together as morphs in one polymorphic population. Breeding structure and homozygosity in wild mice and inbred mice have been compared and discussed. It is argued that some wild mice may show more mechanisms to protect them against loss of genetic variability than other organisms because their breeding structure in nature causes a high amount of inbreeding. The way in which differences in mouse behaviour may have evolved was discussed. A primary cause appears to be the differential habitat preference. The possibility of an ecological factor being a primary cause for speciation was suggested many times in studies comparing sympatric species. Differences in non-display behaviour seem to evolve in the same way as display behaviour, i.e. by small changes in threshold of behavioural mechanisms. This could be concluded from the fact that on a subspecies level, like here between different strains of mice, no qualitative differences in behaviour could be found, whereas this is always the case for some of the differences on the species level. It is argued that specific adaptations as found here for mice may have bearings on the outcome of experiments done with mice, furthermore that inbred mice, in addition to studies on wild mice, may be very useful, especially in studying the role of behaviour in regulating population density.

Retarded depression and the dopamine metabolism.

Abstract: It was demonstrated that the influence of i.v. administered probenecid on HVA concentration in CSF was less pronounced in a group of retarded depression than in a group of non-retarded depression and a non-depressive control group. The figures corresponded to that found in Parkinson patients.

Positive feedbacks at work during feeding

Abstract: Detailed feeding patterns of the first phase of a meal were recorded by direct observation in mice. It was found that fasting increased duration of uninterrupted feeding bouts and shortened non-feeding intervals. Eating of normal palatable food increased duration of successive feeding bouts, but did not influence the duration of non-feeding intervals. Bitter food markedly inhibited the lengthening of successive feeding bouts, but did not influence the duration of non-feeding intervals. It is concluded that oral taste factors may produce positive feedbacks that strengthen feeding. The significance of this positive feedback mechanism has been discussed briefly.

Competition of marine psychrophilic bacteria at low temperatures.

Abstract: The occurrence of obligately and facultatively psychrophilic bacteria in the marine environment suggests that environmental conditions exist which can favour each of these groups in competitive processes. Differences were found in the way in which temperature affected the growth rates of obligate and facultative psychrophiles. Maximum specific growth rates of a number of obligately and facultatively psychrophilic bacteria were determined in batch culture and competition experiments were carried out in a chemostat at growth-limiting substrate concentrations. From the results the relation between the specific growth rate and the concentration of the growth-limiting substrate for both types of organisms at different temperatures was deduced. Both at low and high substrate concentrations obligate psychrophiles grew faster than facultative psychrophiles at the lower temperature extreme (⩽ 4 C). These results suggest that obligately psychrophilic chemoorganotrophs are responsible for mineralization processes in cold natural environments such as ocean waters and the arctic and antarctic regions. In these environments they can successfully compete with facultative psychrophiles because they can grow faster.

An anatomical study of the efferent connections of the thalamic reticular nucleus.

Abstract: A neuro-anatomical investigation into the thalamic reticular nucleus and its connections was made in the albino rat, using the method of retrograde degeneration and the Nauta-Gygax method. The results correspond to the description given by Scheibel and Scheibel and indicate connections of the neurons of the reticular which the principal thalamic nuclei and the rostral part of the intralaminar thalamic nuclei. A topographical arrangement of the efferent connections of the reticular nucleus is demonstrated. The projection of the reticular nucleus upon the thalamus duplicates the cortico-thalamic connections.

A Problem of Information Gain by Quantal Measurements

Abstract: For the average information gain by a quantal measurement of the first kind, an expression is suggested for a lower bound, which turns out to be non-negative.

On the polymorphism of niobium diselenide

Abstract: Four polymorphe of niobium diselenide have been found, viz. , 1 s -NbSe 2 , stable above 980 °C, 4 s (d)-NbSe 2 , stable between 980° and 910 °C, and the 2 s (a)- and 4 s (a)-forms stable at lower temperatures; 4 s (a)-NbSe 2 is somewhat richer in selenium than the 2 s (a)-form. All polymorphs have hexagonal or trigonal layer structures. In 1 s -NbSe 2 the metal has octahedral coordination, in the 2 s (a)- and 4 s (a)-forms the coordination is trigonal-prismatic, while in 4 s (d)-NbSe 2 probably layers with the two types of coordination alternate.

The Role of Food in the Dynamics of Populations of the Landsnail Cepaea nemoralis

Abstract: The food of the landsnail Cepaea nemoralis has been studied in natural environments.The diet of Cepaea in nature consists predominantly of senescent or dead plant material. Green material of some species, especially Urtica dioica, is also eaten in large quantities and algae, animal remains, fungi and, possibly, living aphids and thripses are included in the diet.The place where a snail is found during the day usually has a great predictive value for the food it ate during the preceding night. There are, however, exceptions. Species such as Aegopodium podagraria, Calystegia sepium and Phragmites communis are used very often to sit on but are hardly ever eaten. On the other hand species such as Urtica dioica and Ranunculus repens were very much favoured as foodplants but much less favoured as resting places. The distribution of the snails over the various components of the vegetation is not random and neither is the selection of food. The snail distribution does not explain the food selection or vice versa.Quantity of food probably is hardly ever limiting for the distribution and abundance of Cepaea. Some essential components may, however, very well be in short supply and thus be limiting.

Notes on the mathematical theory of epidemics

Abstract: This paper discusses a deterministic model of the spread of an infectious disease in a closed population that was proposed byKermack &McKendrick (1927). The mathematical assumptions on which the model is based are listed and criticized. The ‘threshold theorem’ according to which an epidemic develops if, and only if, the initial population density exceeds a certain value determined by the parameters of the model, is discussed. It is shown that the theorem is not true. A weaker result is stated and proved. A new simplified version of the model is discussed. In this model it is assumed that an infected individual becomes infectious after a constant time and that it will removed after a constant time. Numerical simulations of this model show that the form of the fluctuations in the number of diseased individuals depends on the values of the parameters. The number of infectious individuals may oscillate up and down under certain circumstances. Necessary conditions for the number of infectious individuals to rise above previous levels are stated and proved.

Behavioural factors in the regulation of food intake.

Abstract: Introduction Mammalian food intake is a discontinuous process, in that feeding runs alternate with non-feeding intervals. These lifelong changes in overt behaviour indicate an underlying organization in which different needs alternately obtain priority. The way in which this channelling of needs might be realized can be investigated by analysing in detail how overt behaviour changes in time. I t is of much importance to know how far food intake behaviour is influenced by the interaction processes involved. Under ad lib. conditions the frequency distribution of the duration of nonfeeding intervals suggests, at least in some species, the existence of meals (Le Magnen & Tallon, 1966; Thomas & Mayer, 1968; Wiepkema, 1968). In these instances food intake depends on factors that determine frequency and size of meals. Probably these meal criteria are not caused by an identical set of causal factors. For instance, food deprivation may enlarge meal size without influencing the number of daily meals (Wiepkema, 1968), whereas caloric dilution of the diet may have just the reverse effect (Le Magnen, 1969). The factors that determine exactly meal frequency will not be discussed here. They may be very difficult to unravel, since circadian processes also contribute to the distribution of meals during a 24 h period (Le Magnen & Devos, 1970).

The heterogeneity of uridine diphosphate glucuronyltransferase from rat liver.

Abstract: 1. The glucuronide conjugation of p-nitrophenol, phenolphthalein, o-aminophenol and 4-methylumbelliferone by rat liver microsomes has been studied. The detergent Triton X-100 activated UDP-glucuronyltransferase activity towards all these substrates, therefore the optimum activating concentration was added in all experiments. 2. Mg2+ enhanced the conjugation of the substrates. 3. With phenolphthalein substrate inhibition occurred but this could be relieved by adding albumin, which binds excess of phenolphthalein. 4. Kinetic constants of the substrates and UDP-glucuronate have been determined. Mutual inhibition was found with the substrates p-nitrophenol, 4-methylumbelliferone and phenolphthalein. p-Nitrophenol conjugation was inhibited competitively by phenolphthalein and 4-methylumbelliferone. 5. o-Aminophenol did not inhibit the conjugation of the other three substrates because these are conjugated preferentially to o-aminophenol. 6. It is concluded that the four substrates are conjugated by one enzyme at the same active site.

Location of the postgenital fusion in the gynoecium of capsella bursa-pastoris (l.) med.

Abstract: SUMMARY Some methods, based on the characteristics of the epidermal outer cell wall, for finding the exact location of a postgenital fusion were tried on the false septum in the gynoecium of Capsella bursa-pastoris (L.) Med. Electron microscopical demonstration of the remnants of the enclosed cuticles proved a reliable means for locating the suture at the place of fusion in the septum.

Life‐history studies in the genus bryopsis (chlorophyceae) iv. life‐histories in bryopsis hypnoides lamx. from different points along the european coasts

Abstract: SUMMARY Zygotes of Bryopsis hypnoides from Banyuls and the Rade de Brest grew into filamentous germlings which divided into stephanokontic zoids. Some of the germlings from Banyuls directly developed new Bryopsis plants. In culture the germlings of Bryopsis hypnoides collected in Banyuls have a longer “dormancy” than those of the Bryopsis hypnoides collected in the Rade de Brest. Zinc-chlor-iodine and Congo red positively stain the wall of the Bryopsis phase and negatively the walls of the germling phase. The germling phases of Bryopsis hypnoides from the Rade de Brest and of several other Bryopsis species are uninucleate, each containing one giant nucleus.

Equilibrium states for a one dimensional lattice gas

Abstract: The thermodynamic equilibrium state can be defined directly for an infinite system via an equilibrium condition or via the variational principle. Both definitions are used to calculate the equilibrium state for a one dimensional lattice gas with finite range interactions.