Showing papers by "University of Groningen published in 1968"

Structure of papain.

Abstract: A three-dimensional X-ray study at a resolution of 2.8 A has revealed that the single polypeptide chain of 211 residues is folded into two distinct parts which are divided by a cleft. The active site, consisting of a cysteine and a histidine, lies at the surface of the cleft. Apart from four short α-helical segments and one short segment of β-structure, the conformation of the chain is irregular.

Predation by the three-spined stickleback (Gasterosteus aculeatus L.): the influence of hunger and experience.

Abstract: [Predatory behaviour in a small fish, the three-spined stickleback (Gasterosteus aculeatus L.), has been analyzed quantitatively by continuous observation of individual fishes searching for food (generally one Tubifex worm) in a large maze during experiments of 40 min. Properties of environment and prey (e.g. their number and size) were kept as constant as possible, in order to study the effects on prey risk of changes in the internal state of the predator, viz. its hunger and its experience with the maze and the prey type in question. By variation of the length of the foregoing deprivation time under specified conditions of temperature, time of day, feeding-deprivation schedule, and kind of food eaten before — the sticklebacks were brought into well defined hunger states. A number of elements of their feeding behaviour were found to increase and decrease with time of deprivation and feeding, respectively. These parallel fluctuations of different and independently measured elements of the behaviour argue a common internal mechanism, the state of which may be called the hunger of the stickleback. Hunger, then, may be measured by anyone of these behaviour elements fluctuating in parallel. Hunger of the stickleback severely affected the risk of their prey. Risk is defined as the number of prey destroyed per unit time by one predator per unit prey density. Higher hungers caused higher risks by both a higher swimming activity and higher proportions of complete responses to discovered prey (viz. greater proportions of the discovered prey were grasped and greater proportions of the grasped prey were eaten). Encountering efficiency (i.e. the ratio of the number of prey encountered to the distance swum or to the number of cells of the maze visited) proved to be independent of hunger. It increased in all individual fishes used (though to a different extent) with their growing experience with the maze by their increasing ability to explore it more systematically, which ability was achieved by turning less. The chance of an encountered prey to be discovered proved to be affected primarily by the distance to which the fish approached it. This chance at a given distance was dependent on the visual acuity of the stickleback in question. It was dependent on the hunger of the fish only at very low levels of hunger, not normally reached during 40 min.-experiments at unit prey density. Prey risk was higher according as the searching fish was larger. Nearly all sticklebacks were able to get satiated towards the end of the 40 minutes, having ingested then about 5% of their body weight. As their swimming activity increased much less with their weight than their feeding capacity, the larger fishes got satiated at a slower rate than the smaller ones. The dependence of prey risk on predator size could be explained by these differences in hunger decay. At higher than unit prey density the fishes did not eat more. Prey risk was then inversely proportional to prey density. The fishes became satiated at a faster rate at the higher prey density. These differences in hunger could largely explain the observed relationship between prey density and prey risk. Introduction of a new type of prey caused — after some delay — a rapid increase of its risk. This "searching image formation" occurred only if the fish in question judged the new prey sufficiently palatable. Palatability was measured as the proportion of grasped prey eaten at specified hunger states. During searching image formation only one component of the prey risk, viz. the chance of an encountered prey to be discovered, was consistently affected. Responsiveness to inedible objects, which looked like the new prey, was conspicuously raised at the same time. Sticklebacks are polyphagic. Once a new type of prey was well known, its presence negatively affected the risk of alternative prey. Larvae of Drosophila, which some fishes judged nearly as palatable as Tubifex worms, affected the latters risk like a mere increase of the density (expressed in weight units) of Tubifex themselves would do. Addition of the highly palatable pieces of Enchytraeus had more drastic consequences : all prey were encountered at a higher rate by an increase of swimming activity. Nevertheless, the risk of Tubifex decreased dramatically by a selective inhibition of the responses to encountered prey of this type. Some evidence points to a learning process, involving the refusal of Tubifex worms at high hungers in the expectation of the more palatable pieces of Enchytraeus. The characteristics of the stickleback's predatory behaviour have been compared with premises of various mathematical models on predator-prey interactions. It is concluded that all existing models should be modified on essential points in order to represent the characteristic traits of the behaviour of predators like the stickleback., Predatory behaviour in a small fish, the three-spined stickleback (Gasterosteus aculeatus L.), has been analyzed quantitatively by continuous observation of individual fishes searching for food (generally one Tubifex worm) in a large maze during experiments of 40 min. Properties of environment and prey (e.g. their number and size) were kept as constant as possible, in order to study the effects on prey risk of changes in the internal state of the predator, viz. its hunger and its experience with the maze and the prey type in question. By variation of the length of the foregoing deprivation time under specified conditions of temperature, time of day, feeding-deprivation schedule, and kind of food eaten before — the sticklebacks were brought into well defined hunger states. A number of elements of their feeding behaviour were found to increase and decrease with time of deprivation and feeding, respectively. These parallel fluctuations of different and independently measured elements of the behaviour argue a common internal mechanism, the state of which may be called the hunger of the stickleback. Hunger, then, may be measured by anyone of these behaviour elements fluctuating in parallel. Hunger of the stickleback severely affected the risk of their prey. Risk is defined as the number of prey destroyed per unit time by one predator per unit prey density. Higher hungers caused higher risks by both a higher swimming activity and higher proportions of complete responses to discovered prey (viz. greater proportions of the discovered prey were grasped and greater proportions of the grasped prey were eaten). Encountering efficiency (i.e. the ratio of the number of prey encountered to the distance swum or to the number of cells of the maze visited) proved to be independent of hunger. It increased in all individual fishes used (though to a different extent) with their growing experience with the maze by their increasing ability to explore it more systematically, which ability was achieved by turning less. The chance of an encountered prey to be discovered proved to be affected primarily by the distance to which the fish approached it. This chance at a given distance was dependent on the visual acuity of the stickleback in question. It was dependent on the hunger of the fish only at very low levels of hunger, not normally reached during 40 min.-experiments at unit prey density. Prey risk was higher according as the searching fish was larger. Nearly all sticklebacks were able to get satiated towards the end of the 40 minutes, having ingested then about 5% of their body weight. As their swimming activity increased much less with their weight than their feeding capacity, the larger fishes got satiated at a slower rate than the smaller ones. The dependence of prey risk on predator size could be explained by these differences in hunger decay. At higher than unit prey density the fishes did not eat more. Prey risk was then inversely proportional to prey density. The fishes became satiated at a faster rate at the higher prey density. These differences in hunger could largely explain the observed relationship between prey density and prey risk. Introduction of a new type of prey caused — after some delay — a rapid increase of its risk. This "searching image formation" occurred only if the fish in question judged the new prey sufficiently palatable. Palatability was measured as the proportion of grasped prey eaten at specified hunger states. During searching image formation only one component of the prey risk, viz. the chance of an encountered prey to be discovered, was consistently affected. Responsiveness to inedible objects, which looked like the new prey, was conspicuously raised at the same time. Sticklebacks are polyphagic. Once a new type of prey was well known, its presence negatively affected the risk of alternative prey. Larvae of Drosophila, which some fishes judged nearly as palatable as Tubifex worms, affected the latters risk like a mere increase of the density (expressed in weight units) of Tubifex themselves would do. Addition of the highly palatable pieces of Enchytraeus had more drastic consequences : all prey were encountered at a higher rate by an increase of swimming activity. Nevertheless, the risk of Tubifex decreased dramatically by a selective inhibition of the responses to encountered prey of this type. Some evidence points to a learning process, involving the refusal of Tubifex worms at high hungers in the expectation of the more palatable pieces of Enchytraeus. The characteristics of the stickleback's predatory behaviour have been compared with premises of various mathematical models on predator-prey interactions. It is concluded that all existing models should be modified on essential points in order to represent the characteristic traits of the behaviour of predators like the stickleback.]

Isotopic Equilibrium between Shells and Their Environment

Abstract: The carbon-isotopic composition of shell carbonate is shown to be in isotopic equilibrium with bicarbonate dissolved in the water. By measurement of both 13C and 18O in a series of brackish-water shells a mean growth temperature can be deduced.

Propionicacidemia, a new inborn error of metabolism.

Abstract: Extract: A male sibling who was born of healthy parents and who died at the age of five days with the clinical picture of severe hypotonia, areflexia, hyperventilation, and grunting is described. An older female sibling with identical symptoms had died some years previously. The parents were unrelated and had three other healthy children. The patient exhibited severe metabolic acidosis which was resistant to therapy. This acidosis was caused by the presence in blood of propionic acid in a very high concentration (5.4 mM/l). The high levels of urea and potassium also present were probably the result of a markedly reduced urine production caused by dehydration. The levels of amino acid in plasma revealed low values for one amino acid, normal values for other amino acids, and high values for lysine, histidine, valine, isoleucine, and leucine. At autopsy, except for a right descending aortic arch, no gross anomalies were found, although the liver was enlarged, probably because of increased fat content. Microscopic examination showed a fatty degeneration of liver cells, degeneration of the Purkinje cells and the granular layer in the cerebellum, and macrophages containing debris of blood cells in the bone marrow and in the spleen. Gas chromatography was used to determine the nature of the accumulated fat in the liver. Among the normal constituents of liver triglycerides, three abnormal fractions were observed, two of which contained C15 and C17 straight chain fatty acids. These were not observed in normal liver fat. The combination of propionicacidemia and the storage of fatty acids with an uneven chain number in the liver pointed to a block in the conversion of propionic acid into methylmalonic acid. Speculation: It is suggested that the propionicacidemia found in this patient is due to a metabolic block in the conversion of propionic acid into methylmalonic acid. The increased concentration of odd-numbered fatty acids (C15 and C17) in the liver may arise from either a decreased breakdown of these fatty acids or an increased synthesis initiated by the high concentration of propionyl-CoA. It is proposed that the missing enzyme is propionyl coenzyme A carboxylase. The fact that a sibling with identical symptoms had died forms a strong argument to postulate that a hereditary abnormality of recessive inheritance is the cause of this as yet undescribed syndrome.

Auditory Responsivity in the Human Neonate

Abstract: ELECTROMYOGRAPHIC, autonomic and electroencephalographic responses were recorded from human neonates during stimulation with sine and square wave tones and with human voices. This communication will concentrate on the analysis of the electromyograms, both because of their importance in reflecting behavioural changes, and because changes in autonomic activity, such as heart rate acceleration, are associated with movements. The “artificial” sounds were chosen so as to have certain structural similarities to the “biological” sound: they were either sine wave components of it or selected fundamentals with superimposed high frequencies. Sine wave and square wave tones of the following frequencies, rising by octaves, were selected: 125, 250, 500, 1,000 and 2,000 Hz. Further sine and square wave tones at 70 Hz were added because preliminary studies had suggested that responses to sound frequencies lower than 100 Hz may have especially interesting properties. Recordings of a male and of a female voice saying “baby” were also included.

Neurological Findings in Newborn Infants After Pre- and Paranatal Complications

Abstract: In recent years, several attempts have been made to assess the hazards of pre- and perinatal obstetric complications. There is little doubt that obstetric complications carry an increased risk of mortality (1,2). Moreover, where several obstetric complications are present in combination, it would be expected, a priori, that the risks will be additive. Whilst the exact causes of mortality in any case may be diverse, one major factor is fatal damage to the central nervous system. Postmortem examination of the brains of babies who would have died after obstetric complications or unfavourable events during the neonatal period have clearly shown the possibility of these factors producing lesions in the nervous system (3, 4, 5, 6, 7). Studies in monkeys (8, 9, 10) have provided evidence of the harmful consequences of experimentally induced perinatal complications.

Angling Experiments With Carp (Cyprinus Carpio L.)

Abstract: Results are reported on angling for tagged carp (Cyprinus carpio L.) belonging to various strains by nearly 800 anglers in drainable ponds in The Netherlands. Carp of various domesticated strains, both of the completely scaled and the "mirror" type, proved to be much easier to catch than wild carp. Hybrids were intermediate both in growth and in catchability. Better catchability of domesticated carp was caused by their greater eagerness in taking baits. No significant differences in pulling strength were observed between the strains. Fighting endurance was better in wild carp than in equally sized domesticated carp. At the same age, however, differences were negligible because domesticated carp grow faster. Within the group of domesticated strains the completely scaled carp showed better fighting endurance than mirror carp. Moreover, the anglers preferred a fully scaled exterior. Further breeding of carp for angling purposes should aim at improving and combining fast growth and good catchability of domesticated carp with scale type and fighting endurance of wild carp.

Behaviour Changes in Cba Mice as a Result of One Goldthioglucose Injection

Abstract: One intraperitoneal injection of goldthioglucose may produce in mice very specific brain lesions followed by a period of hyperphagia leading to obesity. The question is raised whether or not the brain lesions affect feeding behaviour only or that besides this changes in non-feeding behaviour may also contribute to the hyperphagia and obesity observed. Feeding of solitary mice was recorded automatically during 24 h periods after o, 12 and 24 hours of food deprivation and after the GTG treatment. It was found that after GTG injection the mice temporarily (dynamic hyperphagic phase) behave very much like intact hungry ones in that they 1) eat large amounts of food a day 2) gnaw off a bit of food rapidly 3) show little non-feeding behaviour during a meal 4) ingest much food per meal. This period is followed by a static phase during which food intake is somewhat above normal, while the animals show again about normal feeding patterns. Direct observation of the behaviour of solitary mice showed the following: 1) The tendency to sleep has increased permanently and is not related to the occurring obesity. 2) The tendency to climb and to explore the cage has decreased permanently. 3) During a meal non-feeding behaviour occurs rarely. 4) The tendency to groom is not affected. 5) Some (perhaps all) behaviours are less stabile now, as is indicated by the increased occurrence of interruptions. Social behaviour of GTG treated males has been changed drastically as was established by direct observation. It was found that these males, whether or not obese, only rarely fight with other males and that they have a very low tendency to mate. They show a high tendency to flee but on the other hand they often approach the partner although in a very cautious way. However, it was also found that hungry GTG treated mice may fight for their food. This complex change in behaviour patterns of GTG treated mice is discussed briefly and it is concluded that, a. probably the behaviour changes observed are the result of a number of independent effects of the brain lesions, b. the hyperphagia and resulting obesity can be explained largely by a specific lesion in satiety areas of the brain, c. the phenomenon of finickiness, as described by other authors, in the obese animals may be the result of changes in non-feeding behaviour, d. the extreme hunger drive of the dynamic hyperphagic animals may mask signs of finickiness and even enable them to fight for their food, although their aggressiveness in other respects has decreased markedly.

Physiology of an Obligately Psychrophilic Marine Pseudomonas Species

Abstract: SUMMARY Ten obligately psychrophilic bacteria were isolated from North Sea water using conventional enrichment culture techniques at low temperatures. Whereas Arrhenius plots of the growth rate of obligate psychrophiles were linear down to the freezing point of the 0.25% lactate-artificial sea water medium used, Arrhenius plots of facultative strains showed a deviation from linearity at temperatures a few degrees above 0°. It thus appears that the growth rate of obligate psychrophiles is higher at low temperatures, indicating that in competitive processes in cold natural environments, these organisms are at an advantage. The optimum temperature for growth of one of the isolates, a Pseudomonas sp., was 14.5°; the maximum temperature was between 19 and 20°. Respiration was optimal at 23°, and no inactivation of respiratory activity was found within 5 h at 25°. Cells incubated at supermaximal temperatures showed a release of UV absorbing material. RNA synthesis could not be detected at these temperatures. This is considered to be one of the major factors defining the maximum growth temperature of this organism.

Food Production in Prehistoric Europe

Abstract: By about 3000 B.C. all the plains south of the Scandinavian mountains were inhabited by people who lived together in villages of a more or less permanent character. These settlers cut the deciduous forest with stone axes, cultivated a variety of crops, and raised cattle, sheep, goats, and pigs. Hunting was of little importance. The art of pottery was known everywhere. From highly varied shape and ornamentation, archeologists have been able to distinguish a number of cultures of limited geographical and chronological occurrence and various degrees of relation. How different is the picture if we go back in time another 5000 years, to about 8000 B.C. The last cold spell of the Ice Age was then almost over. Hunting and gathering were the major means of subsistence. Animal domestication and plant cultivation were unknown. Camp sites were relatively impermanent, shifting from one place to another.

Habituation in relation to state in the human neonate.

Abstract: IN a polygraphic study it was found that newborn babies responded differentially to pure and to patterned tones of equal sound pressure1. Patterned (square-wave) tones were more potent stimuli for eliciting electromyographic responses than pure (sine-wave) tones and within each of these categories those tones with low frequency fundamentals elicited most responses. Square-wave tones with low frequency fundamentals possess certain structural similarities to human speech sounds. They were therefore categorized as “supernormal” stimuli because they elicited more responses than the voice itself, which in turn was more potent than any of the sine-wave tones.

Some aspects of host selection in Eucarcelia rutilla Vill. (Diptera: Tachinidae)

Abstract: Host finding, acceptance and suitability in Eucarcelia rutilla Vill. were studied in the field and in the laboratory. The literature on nomenclature, morphology of adult and larva, life history, hosts, synchronisation and geographical distribution is surveyed. The species is univoltine, well-synchronized with its two main hosts, Bupalus piniarius and Semiothisa liturata. It deposits macro-type eggs in which the maggots are ready to hatch. Descriptions and relevant aspects of the biology of pine dwelling caterpillars and Diprion larvae are also given. In the field gravid Eucarcelia females coincide mainly with Bupalus larvae in their second and third instar. Eggs were also found upon specimens of Semiothisa liturata, Ellopia prosapiaria, and Thera obeliscata. Superparasitism is not avoided under natural conditions. Host selection was studied experimentally. Attention was paid to detectability and acceptability. A preliminary study of factors involved in host finding reveals that visual stimuli play an important role. In host acceptance stimuli originating from the host's surface are involved. Some evidence was found that these stimuli are mediated through receptors on the tarsi and ovipositor. In experiments there was no discrimination between parasitized and non-parasitized hosts. Preimaginal conditioning in oviposition preference was not noticeable. The bigger the caterpillars, the greater the chance of detection and the greater the risk of parasitization. The resting position of the caterpillar upon the needle has a strong influence on its chance of being found by the parasite. Specimens resting at the base are almost exempt from attacks. The detectability and acceptability of nine species of Lepidoptera and six species of Hymenoptera were tested. Only 4 differed significantly in detectability from Bupalus, but 10 were wholly unacceptable for oviposition. The reaction of the hosts towards attacking females and their eggs differed markedly among species. Upon Bupalus piniarius, Thera obeliscata, T. firmata, and Hyloicus pinastri the eggs are deposited preferably on the thorax. In Semiothisa liturata, Ellopia prosapiaria, Panolis flammea, and Diprionidae other distributions were obtained. As regards the side of the host chosen, the wider its girth the less often the eggs are attached ventrally. The risk of destruction of eggs upon the host's integument varies widely among species: Panolis flammea and Eupithecia indigata remove almost all the eggs, whereas in Ellopia prosapiaria no eggs were dislodged, and in Hyloicus pinastri almost none. Bupalus piniarius, Semiothisa liturata, Thera obeliscata, and T. firmata demonstrate a moderate reaction towards eggs placed upon the abdomen. In Bupalus the instars II and III have a stronger reaction than the other instars. Eggs laid dorsally on abdominal segments as a rule run a greater risk than those placed ventrally. Eucarcelia can develop only in Bupalus, Semiothisa, and Thera obeliscata. In about 20% of the cases Thera firmata, too, can give rise to full-grown parasite larvae. Host suitability also depends on site of penetration. Posterior penetration into Bupalus lead to greater losses than anterior penetration. The frequencies of settlement of maggots in wall of the foregut (intima), mandibular muscles, subcuticular sites, segmental muscles, and haemocoel were recorded for the various instars of Bupalus. Maggots which have settled in intima or in subcuticular sites must migrate at each moult of the host. This migration takes the maggot outside the host's body which it re-enters by piercing the integument at a sharply defined spot mid-dorsally in the membrane between head-capsule and first thoracic segment. Its main function certainly is to prevent removal with the shed intima or cuticle. In addition it is conjectured that migration may help the maggot to avoid exposure to the host's hormones in concentrations which might cause it to moult prematurely. Mortality of maggots can be brought about by encapsulation by haemocytes or removal from the host. Larval mortality is higher in cases where more than one maggot has entered the host than when only one is present. Site of settlement exerts a considerable influence upon parasite mortality. Settlement in haemocoel or wall of the mid/hindgut is unfavourable. It is argued that the relatively high mortality of maggots penetrated into posterior segments of younger instars is due to lower suitability of the sites of settlement attained by these maggots.

Sound production in isolated human larynges.

Abstract: Isolated human larynges were first used to study the function of the larynx by Johannes Muller in his classical experiments described in 1840. A century before Miiller, Ferrein (1741) was the first to use isolated larynges, those of dogs, to investigate whether they should be classified as instruments “a cordes” or “a vent,” i.e., stringed or wind instruments. His report is still of interest. TO his surprise he found an instrument which should be classified as “a cordes et vent,” which meant that the larynx was actuated by air, but that the vibrations of the vocal folds were also essential, in contrast to the complex hypotheses of Dodart (1700) who tried to explain everything by means of eddies generated in the glottis. The accuracy of Ferrein’s conclusions is very limited, because he had virtually no equipment. Apparently he studied only the falsetto voice. He also introduced the misleading term “cordes vocales,” vocal cords, but his notion that the vibration of the vocal folds is essential was a fundamental one. However, he over-emphasized its importance in his belief that the sound was directly due to the vibrating folds. Muller’s data are much more detailed and accurate than those of Ferrein, but it took Helmholtz (1863) to define clearly that the puffs of air escaping through the vibrating glottis were the primary source of sound. Miiller investigated the influence of a number of parameters on the response of the larynx, primarily in midand falsetto voice, but his equipment was very limited. H e had to rely cpon the acoustic quality of the sounds produced by the larynges without their attached resonating vocal cavities. Nobody had seen a living larynx at work, as the laryngeal mirror and the stroboscopic principle had not yet been invented. Since Miiller’s time, a number of investigators have used isolated human larynges for various purposes, especially W. Trendelenburg and associates (1937), but none of them have undertaken a systematic analysis like Miiller’s. Therefore, we decided in 1956 to reinvestigate the influence of the parameters with modern equipment (van den Berg & Tan, 1959; van den Berg, 1960, 1961, 1962; van den Berger al., 1960).