Showing papers by "University of Amsterdam published in 1972"

Forward and backward waves in the arterial system

Abstract: The total amount of reflection in the arterial system of the dog is evaluated during control, high, and low peripheral resistance, and an occluded descending aorta. Pressure, as measured in the ascending aorta, may be separated into a (composite) wave travelling from the heart towards the periphery, the forward wave, and a (composite) wave that travels in the opposite direction, the backward wave. This is also true for aortic flow. One may distinguish between reflections at bifurcations of the large vessels and reflections at the arteriolar part of the arterial tree. The former contribute a small, rather constant amount to the returning wave, while the latter reflects a strongly variable amount.

Electrical Stimulation of the Heart in Patients with Ventricular Tachycardia

Abstract: The initiation and termination of tachycardias were studied in five patients who suffered from recurrent attacks of ventricular tachycardia. In four, coronary artery disease with old myocardial infarction was present. A ventricular tachycardia could be initiated in all patients by a single right ventricular premature beat given during regular driving of the right ventricle. The tachycardia could be terminated by a single right ventricular premature beat, or two right ventricular premature beats given in close succession. In four of our patients an early right ventricular premature beat was followed by the next QRS complex of the tachycardia after an interval shorter than compensatory. Our results favor reentry as the causal mechanism for the tachycardias in our patients. Possible pathways for circus reentry leading to ventricular tachycardia can theoretically be composed of (1) the bundle branches, (2) Purkinje fibers with or without adjacent ventricular myocardium, (3) infarcted or fibrotic ventricular tissue, and (4) combinations of (1), (2), and (3).

Structure and function of blood and connective tissue cells of the fresh water pulmonate Lymnaea stagnalis studied by electron microscopy and enzyme histochemistry.

Abstract: The morphology and the ultrastructure of the blood and connective tissue cells of Lymnaea stagnalis were studied. Special attention was paid to the role of these cells in the cellular defense mechanism (phagocytosis). This problem was investigated in injection experiments with enzyme histochemistry and electron microscopy.

The Peasant and the Brigand: Social Banditry Reconsidered

Abstract: About a decade ago, Hobsbawm presented an interesting argument on a markedly little known subject for which he coined the term 'social banditry' (1959: 1-29). The author is a British social historian and an expert on social protest movements. He claims that social banditry is a universal and virtually unchanging phenomenon which embodies a rather primitive form of organized social protest of peasants against oppression. Social bandits are robbers of a special kind, for they are not considered as simple criminals by public opinion. They are persons whom the State regards as outlaws, but who remain within the bounds of the moral order of the peasant community. Peasants see them as heroes, as champions, and as avengers, since they right wrongs when they defy the landlords or the representatives of the State. Yet their programme, if indeed social bandits have any, does not go beyond the restoration of the traditional order which leaves exploitation of the poor and oppression of the weak within certain limits. Social bandits are thus reformers rather than revolutionaries, though they may prove a valuable asset for those who seek to overthrow an established regime. By themselves, social bandits lack organizational capacity, and modern forms of political mobilization tend to render them obsolete. The phenomenon belongs largely to the past, if only to the very recent past. The golden age of brigandage coincided with the advent of capitalism when the impact of the market dislocated large sectors of the peasantry. In Bandits* Hobsbawm elaborates some of the main themes he surveyed in Primitive Rebels (1959). Like its predecessor, this study is an essay on the uniformities of social brigandage. The author maintains that these uniformities should not be seen as a consequence of cultural diffusion, but as reflections of similar situations within peasant societies: 'Social banditry is universally found, wherever societies are based on agriculture (including pastoral economies), and consist largely of peasants and landless labourers ruled, oppressed and exploited by someone else-lords, towns, governments, lawyers, or even banks' (1969: 15). Hobsbawm starts out from

Ventricular fibrillation occurring on arousal from sleep by auditory stimuli

Abstract: A patient is described having syncopal attacks on being awakened from sleep by auditory stimuli. The electrocardiogram registered during these episodes showed Q-T-segment changes followed by ectopic ventricular activity and spontaneously ending attacks of ventricular fibrillation. Aside from the attacks, her ECG only showed abnormalities of the S-T segment with marked U waves. Hemodynamic and electrophysiologic studies showed no abnormalities. Coronary angiograms were normal. Following therapy with propranolol and diphenylhydantoin she has been free from syncopal episodes for the past 11 months. The mechanism responsible for the Q-T-segment changes and ventricular tachyarrhythmias is not understood.

Immunological characterization of purified anti-haemophilic factor A (factor VIII) which corrects abnormal platelet retention in Von Willebrand's disease.

Abstract: ABNORMAL platelet retention in a column of glass beads, which has been described in cases of Von Willebrand's disease (VWD)1–6, is corrected in vitro by cryoprecipitate prepared from normal plasma and partially purified factor VIII concentrates6–9 although fibrinogen is ineffective (unpublished results). This suggests that factor VIII is responsible for the correction. We now have further evidence to support this suggestion.

[Position of a locus determining mixed lymphocyte reaction distinct from the known HL-A loci].

Abstract: Bilateral and unilateral mixed lymphocyte culture (MLC) tests were performed in five families, each containing one sibling in which recombination between the genes determining the antigens of the LA and Four segregant series of IIL-A had occurred. The results confirm the very weak or non-stimulatory effect of antigens of the LA segregant series, bringing to seven the total number of alleles for which this has been shown so far. Further anomalies in one of the families, however, indicate that the antigens of the Four segregant series are not fully responsible for MLC activation either. Of a group of three HL-A identical siblings, one proved to be MLC-positive with the other two, but MLC-negative with another group of two HL-A identical siblings, which group displayed a one-allelic difference for HL-A with the former group. Furthermore, the child showing this unexpected MLC reaction pattern proved also to be MLC-negative with the earlier mentioned sibling who had the serologically demonstrable recombination between the LA and Four series, notwithstanding a difference for three HL-A antigens. These findings are interpreted as strong evidence for the occurrence of a recombination between the HL-A loci and a MLC determining locus, which can thus be localize outside the previously recognized HL-A region close to the Four locus. The relationships between HL-A, MLC, skin graft rejection and organ transplantation are reexamined in the light of this concept.

Posturography as an auxiliary in vestibular investigation.

Abstract: Posturography, the recording of the way in which man stands upright, proves to be a useful auxiliary in vestibular investigation. The authors divide this posturography into “spot stabilometry” (or statokinesimetry, SKG) and “linear stabilometry” (or stabilometry, STG). Special attention is paid to the linear stabilometry (STG). The low-frequency-sway of ca 0.2 Hz is nearly pathognomonic for vestibular stimulation. In the spot stabilogram (SKG), the area of the spot and the place of the spot in relation to the centre are of interest.

The Cochlear Aqueduct and the Pressure of Cerebrospinal and Endolabyrinthine Fluids

Abstract: Cerebrospinal fluid pressure changes are reflected in perilymph via the cochlear aqueduct and are passed on to the endolymph, probably via Reiss-ner's membrane. The hypothesis that the endolymph pressure is transmitted by the cerebrospinal fluid via the endolymphatic sac and duct appears to be refuted by our results. In the normal labyrinth the peri-lymphatic and endolymphatic pressure are equal within the accuracy of our measurements. The effective cross section of the cochlear aqueduct together with the expansion properties of the round window membrane may serve as a protective mechanism against sudden changes in the cerebrospinal fluid. A pressure gradient between endolymph and perilymph will have to stay below 2 cm of water, a value at which rupture is to be expected. Therefore, damage to the sensory cells due to pressure in case of an endolymphatic hypertension is very improbable, provided the perilymphatic pressure is not affected, which is likely when the cochlear aqueduct is open. The expansion of...

Removal of Leukocytes from Whole Blood and Erythrocyte Suspensions by Filtration Through Cotton Wool

Abstract: . Using the filtration method described earlier, leukocytes were removed from units of fresh whole blood and erythrocyte suspensions (hematocrit 50%). After filtration, the units were stored for one or two weeks. Units of whole blood and erythrocyte concentrates were stored for periods up to three weeks, the leukocytes were then removed by filtration, and the units were stored for another week. During the storage period, the following parameters were measured: pH and concentrations of ATP + ADP, 2,3-diphosphoglycerate, hemoglobin and potassium (Hb and K+ in the cell-free supernatant). The parameters used in the present study indicate that removal of leukocytes by filtration did not cause significant alteration to stored whole blood and erythrocyte concentrates, compared to unfiltered blood stored for the same time.

Activity during natural hibernation in three species of Vespertilionid bats

Abstract: 1. Patterns of winter-activity in three species of bats (Myotis mystacinus, M. daubentoni, M. dasycneme) were studied in three hibernation quarters in The Netherlands. The methods of investigation involved: individual marking, automatic recording of intracave and extracave flights and assessment of the frequency of movements between hibernation sites by short-interval searches. 2. Although differing in details, the species studied show close agreement in most aspects of hibernation behaviour. Major differences probably exist with other species in other climates. 3. Arrivals in the cave takes place gradually from September to December. Most bats leave the cave between the middle of March and the middle of April. There are consistent specific and sexual differences in the timing of hibernation. Females tend to arrive and to leave earlier than the males. Departure from the cave in spring is correlated with the prevailing temperature, while the arrival in autumn is not. 4. Population turnover during the winter is small. No more than an estimated 10% of the bats venture outside the cave upon waking. Recorded extracave migrations took place mainly in autumn and over distances not exceeding 1 km. 5. Microhabitat selection is such that the bats throughout the winter tend to concentrate in the coldest parts of the cave. Low outside temperatures cause cooling of the cave near the entrance during the winter season, and the bats respond by shifting their positions from the rear to the front of the cave, whereas on occasional warm days they tend to move to the rear. In the front part of the cave where stronger air circulation and temperature fluctuations prevail, bats tend to hide in fissures, while in the thermoconstant rear they prefer exposed locations. 6. Myotis mystacinus and M. daubentoni are solitary hibernating bats. In M. dasycneme 10% of the locations were shared simultaneously by two or more individuals. Observed matings were concentrated in autumn. 7. Some bats return to exactly the same locations in consecutive winters. A positive correlation between sequences of locations occupied by (presumably) the same individuals in different years leads to the hypothesis that the selection of locations, which were occupied in former years, is connected to an endogenous annual program clock. 8. The frequency of intracave movements shows large seasonal variation, being relatively high in autumn and spring, and low in mid-winter. The occurrence of the same patterns in the rear part of the cave under almost constant conditions suggests the endogenous nature of a seasonal variation in arousal frequency. 9. The frequency of movements from one resting site to another was positively correlated with ambient temperature. High outside temperatures (directly or indirectly, by reversed thermocirculation) had a positive effect on the frequency of movements from locations in the front part of the cave. 10. The daily distribution of recorded flights shows that the activity of the hibernating bats is almost exclusively nocturnal in October. With a decrease in activity towards mid-winter, flights become more uniformly distributed over the 24 hrs and their mean shifts significantly to a later part of the night. The increase in activity in spring is accompanied by the return of nocturnalism. 11. During the hibernation extracave flights take place mainly between sunset and sunrise. Occasional outward flights in daytime are usually immediately followed by returns into the hibernaculum. 12. Weight loss of the bats is rapid in the first half of the hibernation season and occurs at a slower rate in the second half. It is concluded that feeding does not occur during the major part of the winter. 13. Energetical implications of winter activity in bats are discussed, and compared with other hibernators. The arousals from hibernation constitute a major proportion of bat energy expenditure during the winter. This expenditure of energy with the possibility of starvation in spring is among the greatest hazards to which temperate zone bats are exposed. The hypothesis is advanced that the energetic balance between gain due to successful feeding activity on mild autumn and spring days and loss due to arousal and movements gives positive survival value to an endogenous seasonal variation of arousal frequency.

Palynology of a section from the raised peat bog ‘wietmarscher moor‘, with special reference to fungal remains

Abstract: SUMMARY The results of an analysis of pollen, spores and other micro-fossils (or parts of such fossils) with a characteristic form, from a 195 cm high peat section are reported. It appeared that certain Fungi types are connected with more strongly humified layers, which were presumably formed under drier conditions. Other fungal types show a clear connection with the peat-forming vegetation. An attempt was made to identify the micro-fossils other than pollen grains, which in some cases proved to be possible. A more extensive study is required before more accurate identifications can be arrived at and the emanating interpretations can be substantiated. Attention was paid to cyclic phenomena in the Alnus curve in the diagram. According to calculations with the help of 14C datings, cycles of about 32 years occurred. Further analysis may lead to an answer to the question whether this is a matter of periodic or cyclic phenomena and may reveal the possible cause of the fluctuations. By means of the pollen diagram information was obtained concerning the influence of prehistoric man on the vegetation from about 1700 B.C. to about 300 A.D. It appears that the influence is relatively important in the period between about 700 B.C. and 100 A.D. In this period agriculture on field complexes of the ‘Celtic Field’ type was probably carried out in the neighbourhood of the Wietmarscher Moor. By the beginning of the Christian era Secale pollen appears in the section for the first time. A decrease in population density is marked during the second century of the era. The reliable part of the diagram ends at the 10 cm level which corresponds to a date of about 300 A.D. Through a further analysis of microscopic and macroscopic remains in peat bogs one may expect to gather novel data regarding various aspects of peat analysis discussed in this article.

Electrotonic spread of current in monolayer cultures of neonatal rat heart cells

Abstract: The passive electrical properties of neonatal rat heart cells grown in monolayer cultures were determined. Hyperpolarizing current pulses were injected through one microelectrode via an active bridge circuit. Membrane voltage displacements caused by the injected current pulses were measured at various distances from the first with a second microelectrode. Using a modified least-squares method the experimental results were fitted to a Bessel function, which is the steady-state solution of the differential equation describing the relation between membrane voltage caused by current injection and interelectrode distance in a very large and very thin plane cell. Best fit was obtained with a space constant of 360 μm and an internal resistivity of 500 Ω cm. From these figures, specific membrane resistance was calculated to be 1,300 Ω cm2, assuming all current to leave through the upper surface of the monolayer. The time constant of the membrane was measured from the time course of the current-induced membrane voltage displacements. From its value of 1.7 msec a membrane capacity of 1.3 μF/cm2 was calculated. From these results and some literature data on nexus distribution (A. W. Spira,J. Ultrastruct. Res. 34:409, 1971) specific nexus resistance was calculated to range between 0.25 and 1.25 Ω cm2, depending on the amount of folding of the intercalated discs. The results suggest that spread of activation in monolayer cultures of heart cells by means of local circuit currents is very likely.

The Water Mite Hydrachna Conjecta Koenike, 1895 (Acari, Hydrachnellae), Bionomics and Relation To Species of Corixidae (Hemiptera)

Abstract: 1. The larvae of Hydrachna conjecta and H. skorikowi are described and a survey is given of the larvae of European species of the genus Hydrachna together with their hosts. Corixidae are hosts of H. conjecta and H. skorikowi. Species of the genera Callicorixa, Corixa, Cymatia and Sigara are known as hosts of H. conjecta; hosts of H. skorikowi are species of the genera Callicorixa and Sigara. H. conjecta, H. cruenta, H. globosa globosa and H. globosa uniscutata may be regarded as common species in The Netherlands. The shape and dimensions of the epimera, as well as the arrangement of the bristles, constitute excellent specific characters. A key to the larvae is presented, based on these easily recognizable characters. The form described as Hydrachna georgei is most likely identical with the nymph of H. conjecta. 2. The food of both nymph and adult of H. conjecta consists of corixid eggs. In contrast with Sigara eggs, those of Cymatia, which are stalked, are not taken. Similar to the other Hydrachna species, H. conjecta oviposits in the air cavities of waterplants, in this case Ceratophyllum demersum. The number of eggs per cavity is dependant on its size. The biological importance of oviposition in waterplants is discussed. The maximum number of eggs deposited by one female, over a period of four weeks, was 1475. The time of egg development varies from 17-45 days, dependant on the temperature. At room temperature the hatching larvae must find a host within four days: free larvae are dead after a week. The parasitic phase in the summer is estimated at approximately 17 days. H. conjecta hibernates as parasite or as egg. Eggs may hatch as late as March. In the second half of April the nymphs emerge from the bugs and 3-8 days later enter an inactive stage (tritonymphal stase), which lasts 5-9 days. It is presumed that the life span of the adult animals is approximately one month. There are 2-3 generations per year depending on climatic circumstances and the moment of oviposition. First generation females oviposit from the beginning of May till the beginning of June. In comparison with H. conjecta the egg production of Eylais discreta is much larger, namely between 10,000 and 13,000 per female over a period of 11 2 months. This large egg production is necessary to compensate for the extensive loss of larvae compared with that of H. conjecta. Due to the sampling technique males are often more easily captured than females. Breeding results, however, showed that there actually are more male than female H conjecta, so the surplus of males is real. 3. A description of the gnathosoma is given. The skin-fold, which surrounds its distal part, is characteristic. The chelicerae are composed of two parts, a cylindrical part and a much wider basal part. The basal parts are distally linked by dovetailing grooves and ridges, which play a role in the process of perforating the skin of the host. H. conjecta larvae attach themselves to the corium on the underside of the hemelytra of corixids. They pierce into the blood sinus in the corium. The preference for the corium is discussed. The stylostome, a ramified tubular, structure, develops during the parasitic phase from the mouth opening of Hydrachna larvae in the blood sinus of the host's wing. The development of the stylostome results from a reaction of the haemolymph to the saliva of the mite larva. The stylostome becomes larger and the channels widen during the parasitic phase. In consequence of the longer parasitic phase, the stylostomes are larger in winter, than in summer. Sigara falleni is "immune" to the parasite. Presumably here, the haemolymph reacts so strongly that eventually the sinus in the wing is completely filled with stylostome-like material. The mite larvae die and shrivel. 4. The incidence and intensity of infections was regularly determined for Cymatia coleoptrata, Sigara striata and S. falleni ("immune" to the mite larvae) over a period of a few years. The length of the parasite (H. conjecta larvae) was used as a measure for the growth. The left hemelytron is less often infected than the right one. This phenomenon is most pronounced in Sigara species: here the right hemelytron overlaps the left one more than in Cymatia species. H. conjecta larvae prefer the space between the overlapping parts of the hemelytra to that between the left hemelytron and the abdomen. The parasite grows more quickly and becomes larger on S. striata than on C. coleoptrata. In spring (April) nymphs of H. conjecta emerge approximately ten days earlier from S. striata than from C. coleoptrata. The cause of the growth reduction inC. coleoptrata is discussed. When there are two or more parasites per host, they influence each other only at the end of the parasitic phase. Growth stops during winter. During the parasitic phase on C. coleoptrata, H. conjecta larvae increase 300 a 400 fold in volume and on S. striata 500 a 600 fold. The volume of a full grown larva is 31 % of that of C. coleoptrata and 13 % of that of S. striata. Both the incidence and intensity of infection are lower in C. coleoptrata than in Sigara species. The incidence is usually between 10 and 30% but it is higher in June for both host species. On the basis of the incidence throughout the year, conclusions are drawn concerning host populations and the occurrence of new infections. The distribution pattern of the parasite on various host species can be described by a negative binomial distribution. Comparing these distributions among and within the three host species, we conclude that heavily infected hosts disappear from the population. This is especially true for C. coleoptrata. Factors influencing such distrubition patterns are discussed.

Direct immunofluorescent study of the skin on occurrence of complement in pemphigus.

Abstract: Summary.— In 6 cases of pemphigus (4 pemphigus vulgaris, 1 pemphigus vegetans and 1 pemphigus erythematosus) the direct immunofluorescent method (DIF) revealed various complement factors, as there are Clq, C4 (β1E), β1A and α2D, localized in the intercellular spaces of the epidermis of the skin or mucosa immediately next to the bulla. Immunoglobulin and complement were shown together in the prickle cell layer of the epidermis, while complement staining alone usually could be shown in the intercellular spaces of basal cell layers and in the junctional zone. The possibility that antibody-mediated complement deposition and/or alternate pathway activation may play a role in the underlying mechanism in pemphigus is discussed.

Effects of Treatment with Sodium Dodecyl Sulfate on the Ultrastructure of Escherichia coli

Abstract: An electron microscopy study has been made of the effects of dissolution of the plasma membrane of Escherichia coli with sodium dodecyl sulfate (SDS) on the organization of the nucleoplasm and the cytoplasm. The alterations observed in time course experiments were related to absorbance changes and to release of macromolecules from the cells. As the cells became plasmolyzed, under the conditions used, the first visible effect of SDS was a collapse of the plasmolysis spaces. This was accompanied by a displacement of the nuclear material which then appeared in broad contact with the redeployed plasma membrane. This initial displacement of nuclear material to the cell border may indicate an association between the nucleoplasm and the plasma membrane. Upon further dissolution of the plasma membrane, the nuclear material receded from the cell margin and contracted into an axial filament. Meanwhile, the cytoplasm dissociated into an amorphous, Pronase-sensitive component and an electron-opaque, granular one sensitive to ribonuclease. The latter represented one continuous area of ribosomal structures surrounding the nucleoplasm, an organization which did not occur when the cells were inhibited with rifamycin before SDS treatment. During prolonged SDS interaction, approximately 65% of the cellular protein, 25% of the ribonucleic acid and 40% of the deoxyribonucleic acid were released from the cells concomitant with the disappearance of the amorphous cytoplasmic part, expansion of the ribosomal aggregate, and rearrangement of the nuclear material at the cell periphery. The observations support the contention that all ribosomal structures bear a direct relationship with the nucleoplasm.