Showing papers by "University of Zurich published in 1981"

Calcium-binding protein parvalbumin as a neuronal marker

Abstract: Ca2+ ions, involved in the control of many important physiological functions, require the presence of specific intracellular Ca2+-binding proteins to exert their regulatory roles. Many of the latter have been extracted and purified. Thus, troponin-C regulates muscle contraction1 and calmodulin is involved in a variety of fundamental cellular activities2,3. Parvalbumin seems to be restricted to muscle and brain4–6 but its physiological role is not yet clear. In muscle it probably participates in a regulatory system operating mainly in fast contracting muscles7,8, but in brain, even its anatomical distribution is unknown. We now describe the localization by immunohistological means of parvalbumin in neurones scattered throughout the central nervous system of the rat. Although the distributions of parvalbumin- and GABAergic neurones are similar, the physiological function of parvalbumin-immunoreactive neurones is not yet recognizable.

Topological Vector Spaces

Abstract: In this chapter we start our investigations on general topological vector spaces by introducing the basic concepts and giving the standard descriptions of linear topologies by means of particular neighbourhood bases of the zero vector. This is followed by a brief discussion of boundedness and of continuity of linear forms in 2.3. In the sections 2.4–2.6 we consider projective topologies as a first general method to generate new linear topologies from given ones. The usual universal characterization of cartesian products is supplemented in 2.5 by a rather exceptional one which, however, will turn out to be a convenient and powerful tool in subsequent discussions.

Searching behaviour of desert ants, genusCataglyphis (Formicidae, Hymenoptera)

Abstract: 1. If a homing ant (Cataglyphis bicolor,C. albicans) gets lost, it does not perform a random walk but adopts a stereotyped search strategy. During its search the ant performs a number of loops of ever-increasing size, starting and ending at the origin and pointing at different azimuthal directions. This strategy ensures that the centre area where the nest is most likely to be, is investigated most extensively. 2. After one hour of continuous search the ant's search paths cover an area of about 104 m2. Nevertheless, the system of loops performed during this time is precisely centred around the origin. The ant's searching density does not depend on the azimuthal direction around the origin but only on the distance from the origin. It rapidly decreases with increasing distance. 3. The ant's searching pattern can be characterized by two functions: thed/t-function correlating distance (d) with time (t), and theα/t-function correlating azimuthal direction (α) with time. If fixes of the ant's position are taken every 10 s, the vectors pointing from the origin to successive fixes change their lengthsd systematically (α/t-function) and their directionsα randomly (α/t-function). What is especially characteristic of the ant's searching pattern is the oscillatingd/t-function which clearly demonstrates that the searching ant repeatedly returns to the origin, even after it has walked, within one hour, along a search trajectory of more than 1 km (the latter number refers toC. albicans-A). The ant's walking speed does not change within a search time of 1 h. 4. The distribution of changes in direction between successive segments of a search path,β, is usually unimodal with a mean of 0°, if complete search paths are considered. Nevertheless, within smaller periods of time, especially during the initial portions of the search the integrated angleβ may continuously change in the same direction. Such portions of the search crudely resemble a spiral which alternately expands and contracts. 5. Although all 3 species ofCataglyphis studied in this paper adopt the same general search strategy, there are some differences in the fine structure of the search:C. albicans-A departs further from the origin than any other species, and performs the most rapid turns. The tendency towards spiralling is most pronounced inC. albicans-B. 6. An efficient searching strategy is formulated, based on purely theoretical grounds. It is assumed that when the search begins the probability density function (PDF) for the location of the nest is Gaussian in two dimensions (a priori PDF). It is further assumed that the ant can never becompletely certain that a given area has been fully explored, so that it is only theprobability of encountering the nest within a certain region that decreases as the time spent in searching this region increases. Thus, the most promising region to search is specified by an a posteriori PDF which takes the ant's past performance into account. 7. A computer model is presented that searches in optimum fashion, as proposed above. In the model, motion of the ant is characterized in terms of radial and tangential components, with the tangential component varying randomly and the radial component varying according to the a posteriori PDF. The model successfully describes what the ants are actually doing (e.g., compare Figs. 17 and 18 with Fig. 3, Figs. 19 and 20 with Figs. 8–10, and Fig. 21a and b with Figs. 4 and 5), indicating that the searching behaviour ofCataglyphis is geared to find the nest as quickly as possible.

Two conserved sequence blocks within eukaryotic tRNA genes are major promoter elements

Abstract: The split promoter sequences of a tRNALeuCUG gene of Xenopus laevis have been mapped to nucleotides 13–20 and 51–64 of the tRNALeu coding sequences. The sequences closely coincide with two conserved sequence blocks present in all eukaryotic tRNA genes. The two conserved sequence blocks were found to be exchangeable between tRNA genes as chimaeric tRNAMet–tRNALeu genes proved transcriptionally active. Furthermore, two prokaryotic tRNA genes exhibiting strong homologies with the two blocks yielded specifie transcripts when tested in an eukaryotic transcriptional system.

A small segment of polyoma virus DNA enhances the expression of a cloned beta-globin gene over a distance of 1400 base pairs.

Abstract: The hemoglobin beta-1 gene of the rabbit was linked to a 244 bp DNA fragment from the beginning of the polyoma virus late region, not including the viral origin of replication. After transfection of such recombinant DNAs into mouse 3T6 and human HeLa cells, the polyoma sequences were found to strongly enhance the level of correct beta-globin gene transcripts over a distance of at least 1400 bp. These findings are similar to those obtained with a segment of DNA from the corresponding region of the SV40 genome (J. Banerji, S. Rusconi and W. Schaffner, 1981, Cell, in press) which, however, shows very limited sequence homology to the polyoma 244 bp segment. Using the same assay, a complete copy of polyoma virus DNA was found to interfere with the enhancement of globin gene expression in a cell type-specific manner which may be due to incorrect transcription. In contrast to the complete polyoma virus genome, the 244 bp DNA fragment will be particularly useful as a component of mammalian expression vectors since it almost exclusively yielded high levels of correct beta-globin gene transcripts.

Analysis of myosin light and heavy chain types in single human skeletal muscle fibers.

Abstract: In this study, myosin types in human skeletal muscle fibers were investigated with electrophoretic techniques. Single fibers were dissected out of lyophilized surgical biopsies and typed by staining for myofibrillar ATPase after preincubation in acid or alkaline buffers. After 14C-labelling of the fiber proteins in vitro by reductive methylation, the myosin light chain pattern was analysed on two-dimensional gels and the myosin heavy chains were investigated by one-dimensional peptide mapping. Surprisingly, human type I fibers, which contained only the slow heavy chain, were found to contain variable amounts of fast myosin light chains in addition to the two slow light chains LC1s and LC2s. The majority of the type I fibers in normal human muscle showed the pattern LC1s, LC2s and LC1f. Further evidence for the existence in human muscle of a hybrid myosin composed of a slow heavy chain with fast and slow light chains comes from the analysis of purified human myosin in the native state by pyrophosphate gel electrophoresis. With this method, a single band corresponding to slow myosin was obtained; this slow myosin had the light chain composition LC1s, LC2s and LC1f. Type IIA and IIB fibers, on the other hand, revealed identical light chain patterns consisting of only the fast light chains LC1f, LC2f and LC3f but were found to have different myosin havy chains. On the basis of the results presented, we suggest that the histochemical ATPase normally used for fibre typing is determined by the myosin heavy chain type (and not by the light chains). Thus, in normal human muscle a number of 'hybrid' myosins were found to occur, namely two extreme forms of fast myosins which have the same light chains but different heavy chains (IIA and IIB) and a continuum of slow forms consisting of the same heavy chain and slow light chains with a variable fast light chain composition. This is consistent with the different physiological roles these fibers are thought to have in muscle contraction.

Target cell specificity of two species of human interferon-alpha produced in Escherichia coli and of hybrid molecules derived from them

Abstract: Plasmids containing cDNAs for human interferon (IfN) alpha-1, IFN alpha-2, and several hybrids of the two cDNAs, all joined identically to an Escherichia coli lac promoter fragment gave rise, in E. coli, to fused interferons (fIFNs) that had very different target-cell specificities. fIFN alpha-1 had a lower specific activity on human WISH cells than on bovine MDBK cells, while fIFN alpha-2 showed the opposite behavior. fIFN hybrids with the NH2-proximal half of fIFN alpha-2 behaved qualitatively like fIFN alpha-1, and those with the NH2-proximal half of fIFN alpha-2, behaved like fIFN alpha-2. On mouse L929 cells, fIFN alpha-2 was almost inactive, while fIFN alpha-1 showed relatively high activity. In this case, the fIFN hybrids with the COOH-proximal half of IFN alpha-1 showed activity on mouse cells, while the reciprocal hybrid did not. In many cases, the activity spectrum of the hybrids was very different from that of either parent. We propose that the IFN molecule has either two binding sites or two regions constituting the binding site, one in the COOH- and the other in the NH2-proximal half. The experimental findings can be accounted for if the fits of the two sites to their receptor counterparts on different cell lines are independent of one another.

The Insulin-Like Growth Factors (IGF) of Human Serum: Chemical and Biological Characterization and Aspects of Their Possible Physiological Role

Abstract: Publisher Summary This chapter discusses the chemical and biological characterization, and properties of the insulin-like growth factors (IGF). The chapter also discusses their possible physiological role. Blood is a large reservoir of insulin-like activity. Insulin represents only a small portion of this activity. IGF I and II are polypeptides with molecular weights of 7649 and 7471. They contain 70 and 67 amino acid residues, respectively, each in a single polypeptide chain with three intra-chain disulfide bridges. Each of the two polypeptides contains two regions—domains—in which parts of the sequences can be aligned to identical parts in human pro-insulin: 38% of the sequence of residues 42 to 70 in IGF I and 44% of the sequence of residues 41 to 67 in IGF II (termed A-domains), are identical to the insulin A-chain. As in pro-insulin, the A- and B-domains are connected by a C-domain. However, in contrast to the C-peptide of pro-insulin, which consists of 35 amino acids, the C-regions of IGF I and II are only 12 and 8 residues long, respectively.

The "cat eye syndrome": dicentric small marker chromosome probably derived from a no.22 (tetrasomy 22pter to q11) associated with a characteristic phenotype. Report of 11 patients and delineation of the clinical picture.

Abstract: Eleven patients with the so-called Cat Eye syndrome are reported including a more detailed description of the original cases reported by Schmid and Fraccaro. All cases had, in addition to a normal karyotype, a small extra G-like chromosome which appeared to be an isochromosome for the juxtacentromeric region (pter to q11) of an acrocentric chromosome. None were mosaics. Clinical findings and further cytogenetic studies in a few cases suggest that these markers probably derive from a No. 22 chromosome. Characteristic features of the Cat Eye syndrome in these 11 patients and those reviewed from the literature are: ocular coloboma which may involve the iris, choroid and/or optic nerve, preauricular skin tags and/or pits which are probably the most consistent feature, congenital heart defect, anal atresia with a fistula, renal malformations such as unilateral absence, unilateral or bilateral hypoplasia, and cystic dysplasia, and antimongoloid position of eyes. Intelligence is usually low-normal, although moderate retardation is also seen. There is great variability in the clinical findings ranging from near normal to lethal malformations. Less frequent, but also characteristic findings are: microphthalmia, microtia with atresia of the external auditory canal, intrahepatic or extrahepatic biliary atresia and malrotation of the gut. Direct transmission of the marker from one generation to the other was observed in both sexes. In those families, there was considerable variability in the clinical findings between affected family members. These cases show that there is a bias of ascertainment for patients who have the more striking malformations, especially those with ocular coloboma and anal atresia, a combination which appears to be present in only a minority of cases. Many mildly affected patients probably remain undetected. It is proposed that the term Cat Eye syndrome should be applied only to cases with trisomy or tetrasomy of not more than 22pter to q11 and without additional duplication or deletion of another autosomal segment.

Effect of pregnancy on the pharmacokinetics of caffeine

Abstract: Caffeine is eliminated mainly by metabolism to demethylated and oxidised derivatives. High individual variability is therefore expected from variations and changes in the capability of the organism to metabolize xenobiotics. An increase of the half-life of elimination of caffeine has been reported during the final weeks of pregnancy. In this study, the half-lifes of caffeine were determined by HPLC-analysis of samples of saliva in male and non-pregnant females and in women during pregnancy and after parturition.

Medial rectus subgroups of the oculomotor nucleus ant their abducens internuclear input in the monkey.

Abstract: Physiological experiments show that the abducens internuclear pathway is involved in the activation of only the medial rectus (MR) eye muscle. Previous anatomical experiments have shown that this pathway terminates in multiple foci within the oculomotor nucleus (OMN) of the monkey, and not only over the classical motoneuron subgroup. In this study the location of MR motoneurons in the monkey OMN is reinvestigated, and compared with the detailed pattern of terminations of the abducens internuclear pathway. The motoneurons were labelled by injections of retrograde tracer substances, HRP and [125I] wheat germ agglutinin (WGA), into extraocular muscles. Labelled MR motoneurons were found in three main divisions, called subgroup A, B, and C. Subgroup A corresponds mainly to the classical ventral MR subgroup. Subgroup B lies dorsal and caudal in OMN, occupying an area classically reserved for inferior rectus (IR). However, the representation of IR is shown to be further rostral in the dorsal OMN. Subgroup C is on the dorsomedial border of OMN. Its cells are significantly smaller than those of group A and B. In addition C could be labelled independently of the other subgroups by small injections into the outer (orbital) layer of MR muscle. This indicates a functional difference between the subgroups. It is suggested that subgroup C may be important for the tonic component of MR activity, possibly convergence. The location of abducens internuclear terminals, labelled by the injection of tritiated amino acids into the abudens nucleus, corresponds exactly to the position of MR motoneurons. These experiments provide a new picture of the internal OMN organization, and support the physiological findings that the abducens internuclear pathway activates only MR motoneurons.

Effects of gravity on rotatory nystagmus in monkeys

Abstract: The vestibulo-ocular reflex (VORJ stabilizes gaze in response to head rotation. If a step of angular velocity is given about a vertical axis, horizontal nystagmus is induced. Initially, its slow-phase velocity is compensatory; but as rotation continues with the subject in darkness, slow-phase velocity decays to zero. Deceleration induces postrotatory nystagmus. It is essentially anticompensatory since it occurs when the subject is stationary. There are several conditions under which the compensatory response of the VOR is improved. If rotation occurs in light, optokinetic nystagmus (OKN) is induced that helps hold the velocity of the slow phases of nystagmus close to that of the stimulus. During and after deceleration, activity stored during OKN summates with the vestibularly induced postrotatory nystagmus to reduce or abolish it.'-5 Compensatory eye velocities also can be enhanced by the introduction of a rotating gravity vector relative to the head. If subjects are rotated about an axis tilted from the vertical (off-vertical axis rotation), nystagmus is induced that lasts as long as rotation At the end of rotation, the after-nystagmus is weaker and shorter than that after rotation about a vertical axis. While the steady-state characteristics of the nystagmus induced by off-vertical axis rotation have been examined,6\" its dynamic characteristics are unknown. Moreover, there is little information about the relationship between perrotatory and postrotatory nystagmus induced by this type of stimulus. The purpose of this study was to characterize the dynamic aspects of the slow-phase velocity of nystagmus induced by off-vertical axis rotation. We wished to determine whether the velocity storage mechanism that is important for visual-vestibular interaction5 also plays a role in mediating nystagmus induced by rotation about an off-vertical axis.

Capacity, Cutoff Rate, and Coding for a Direct-Detection Optical Channel

Abstract: It is shown that When Pierce's pulse-position modulation scheme with 2Lpositions is used on a self-noise-limited directdetection optical communication channel, there results a 2L-ary erasure channel that is equivalent to the parallel combination of L "completely correlated" binary erasure channels. The capacity of the full channel is the sum of the capacities of the component channels, but the cutoff rate of the full channel is shown to be much smaller than the sum of the cutoff rates. An interpretation of the cutoff rate is given that suggests a complexity advantage in coding separately on the component channels. It is shown that if short-constraint length convolutional codes with Viterbi decoders are used on the component channels, then the performance and complexity compare favorably with the Reed-Solomon coding system proposed by McEliece for the full channel. The reasons for this unexpectedly fine performance by the convolutional code system are explored in detail, as are various facets of the channel structure.

Development of stereopsis and cortical binocularity in human infants: electrophysiological evidence

Abstract: Dynamic random-dot stereograms and correlograms were used to elicit visually evoked brain potentials from human infants, and these potentials were compared with potentials evoked by classical checkerboard pattern reversal. The results indicate that infants begin to produce stereoscopically evoked potentials at the age of 10 to 19 weeks, several weeks after showing classical checkerboard-evoked potentials, and suggest that the onset of cortical binocularity precedes stereopsis.

True Absorption and Scattering of Pions on Nuclei

Abstract: The cross section for true absorption of pions in nuclei was obtained from experiments at 85, 125, 165, 205, 245, and 315 MeV for positive pions and at 125 and 165 MeV for negative pions. The results are compared with theoretical calculations. The inclusive pion scattering angular distribution was also measured, and the results indicate that quasifree scattering plays an important role for backward scattering. The total pion-nucleus cross section is decomposed into its major channels: elastic scattering, inclusive inelastic scattering, true absorption, and single charge exchange, as a function of pion energy and charge. For light nuclei, the true absorption cross section has a strong energy dependence, reflecting the shape of the (3,3) resonance. The $A$ dependence of the true absorption cross section is much stronger than that of the inclusive inelastic scattering.NUCLEAR REACTIONS Li, C, Al, Fe, Nb, Bi (${\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}},{\ensuremath{\pi}}^{\ensuremath{'}}$); measured $\ensuremath{\sigma}({\ensuremath{\theta}}_{{\ensuremath{\pi}}^{\ensuremath{'}}})$, ${E}_{{\ensuremath{\pi}}^{+}}=85, 125, 165, 205, 245, \mathrm{and} 315$ MeV, ${E}_{{\ensuremath{\pi}}^{\ensuremath{-}}}=125, 165$ MeV; deduced ${\ensuremath{\sigma}}_{\mathrm{inelastic}}$, ${\ensuremath{\sigma}}_{\mathrm{absorption}}$; decomposition of ${\ensuremath{\sigma}}_{\mathrm{tot}}$.

Wild-type tRNATyrG reads the TMV RNA stop codon, but Q base-modified tRNATyrQ does not.

Abstract: Although protein synthesis usually terminates when a stop codon is reached along the messenger RNA sequence, there are examples, mainly in viruses, of the stop codon being suppressed by a tRNA species. A strong candidate for this phenomenon occurs in tobacco mosaic virus (TMV) in the form of two proteins (110K and 160K, of molecular weights 110,000 and 160,000, respectively)1, sharing an N-terminus sequence, which are translated in vitro from a purified species of viral RNA. We have investigated the identity of the tRNA responsible for production of the 160K protein and show here that it is one of the tyrosine tRNAs. Another tyrosine tRNA, in which the first base of the anticodon is highly modified, does not act as a suppressor, indicating the possible regulatory function of such modifications.

Twenty-Four-Hour Secretory Pattern of Cortisol in the Bull: Evidence of Episodic Secretion and Circadian Rhythm

Abstract: A single antibody RIA method for measurement of plasma cortisol concentrations in the bull is described. Antisera were obtained from rabbits immunized against cortisol-3- oxime-bovine serum albumin. By this technique, peripheral cortisol levels were determined in seven adult bulls (one blind) during 24- and 48-h periods, with blood collections every 30 min. Statistical evaluation of the 24-h profiles using time series analysis revealed that cortisol is secreted episodically throughout the day-night cycle (range, 0.4–9.7 ng/ml). Despite individual variability in both frequency and amplitude of secretory episodes, a distinct circadian secretion pattern was recognized. After dividing the 24 h into three 8-h time periods (I, 0900–1700 h; II, 1700– 0100 h; III, 0100–0900 h), a depressed secretory activity with small episodic bursts not exceeding 3.5 ng/ml plasma consistently occurred during time period II. Increased cortisol secretion with high fluctuating levels was evident during time periods I and III. Maxi...

The relationship between success of free gingival grafts and transplant thickness. Revascularization and shrinkage--a one year clinical study.

Abstract: The purpose of this clinical investigation was to determine what effect the thickness of a free gingival graft has on the processes of revascularization and shrinkage. With the aid of a Mucotome®, very thin, thin, and intermediate thickness grafts were excised from the palate. These were placed in the mandible or maxilla of patients with insufficient attached gingiva. Vertical graft shrinkage was measured at 15, 30, 90, and 360 days after surgery. Angiographic studies were made on 24 healing grafts. From the day of grafting to 360 days afterward the percentages of shrinkage were: very thin, 45%; thin, 44%; intermediate, 38%. The angiographic study demonstrated that rapid revascularization can be expected when uniform grafts of thin to intermediate thickness are placed on a periosteal recipient site which has been carefully freed of loose connective tissue and muscle attachments. An uneven, thick graft placed on a site of denuded bone favored a prolonged period of revascularization and delayed healing.

Inborn Resistance of Mice to Orthomyxoviruses

Abstract: During evolution the vertebrate host has evolved a multitude of defense mechanisms to cope with virus infections. These are operative at several levels and range from simple physical barriers to complex structures such as the various parts of the immune system. Compared with acquired immunity, which has been so extensively studied, relatively little is known about resistance mechanisms in natural, genetically determined host defense against viruses.

Theoretical analysis of arterial hemodynamics including the influence of bifurcations. Part I: mathematical models and prediction of normal pulse patterns.

Abstract: Based on earlier theoretical studies, a new mathematical model is developed for the prediction of the pressure and flow pulses propagating in the arterial system. This model permits a more realistic simulation of bifurcation and stenoses than was possible previously. By making use of a computer, it allows us to calculate the pulse shapes along branching arteries. It is based on the assumption that each arterial conduit can be represented by a suitable combination of three basic segments, namely segments with no or only small-calibre side branches, short segments with big side branches, and short segments with pathological changes of the conduit. Along segments of the first type, the pulse propagation is calculated with the aid of the method of characteristics and a first order integration. For the other two types, the linearized mass balance and momentum equations are utilized together with the boundary conditions to determine the pressure and flow values at the ends of the segment. A standard case for the human arterial conduit extending from the heart to the foot, with eight major branches, is defined using published data and prescribing the ejection pattern from the heart. The computed pulse shapes and their changes with propagation exhibit the characteristic features observed in man under normal conditions.