LET spectra of cosmic-ray nuclei for near earth orbits

Measurements of cosmic-ray LET spectra were part of the radiobiological space research programs during the Spacelab 1 (SL-1) and the D1 missions. We analyzed CR-39 plastic nuclear track detectors of the Advanced Biostack experiment of SL-1 and of the Dosimetric Mapping and Carausius morosus experiments in the BIORACK on D1. The particle tracks in the CR-39 were detected and measured by an automatic scanning and measuring system. An in-flight calibration was derived from track measurements of minimum ionizing oxygen and iron nuclei and of stopping nuclei as a function of the residual range. LET spectra measured at different locations in the space shuttle are presented and discussed for both missions. A model describing the effects of the geomagnetic field of the earth on charged cosmic-ray particles and the shielding by matter is used to calculate LET spectra for the two missions and for typical space station orbits at low inclinations. A comparison of measured LET spectra and LET spectra calculated for different flight parameters shows that besides geomagnetic shielding the shielding by matter is most important in comparison to solar modulation and to variation of particle flux with flight altitude. Model calculations must be improved and must consider more detailed sectored shielding by matter and the influence of trapped radiation. The last item is of importance in the case of low-inclination orbits.     

Structure and motility of primary cilia in the follicular epithelium of the human thyroid

In order to clarify contradictory reports concerning ciliary structure and function, follicular epithelium from macroscopically normal portions of 37 surgical specimens of human thyroid were processed for video-microscopy and/or transmission electron microscopy. The cilia of living cells were immotile. In transverse sections the cilia revealed a 9 + 0 pattern at the base of the shaft, whereas towards the distal end the number of microtubular doublets diminished. Dynein arms, radial spokes and central microtubules were absent. The immotility and structure of these primary cilia implies that their function is not related to motility. The phylogenetic and ontogenetic development of the thyroid suggests that tumor cells of follicular origin displaying abnormal secondary cilia may represent a pathological variant of differentiation.     

A theoretical approach to cluster formation in biological membranes

A theoretical analysis of cluster formation within the lipid matrix of biological membranes is presented. Various models are analysed: (a) one-dimensional monolayer, (b) two-dimensional monolayer and (c) one dimensional bilayer. Furthermore, lipid-protein interactions are considered. The model is based on differential equations for the probabilities a_i and b₁ which characterize the occupation of the lattice site i by the lipids A and B, respectively. These differential equations are an approximation of the Master-equation. Steady states as well as time-dependent variations are analysed. Depending on the interaction energies of the two lipids, different stationary lipid distributions are obtained, including clusters of lipids A or B and alternating structures. The distributions may be dynamically stable or unstable. It is shown that phase transitions within the lipid matrix may be induced by alteration of the composition of the membrane, by changing the interaction energies of the lipids, by variation of the temperature or by lipid-protein interactions. The transitions between different stationary distributions are studied by use of bifurcation diagrams. The analysis of time-dependent states reveals that unstable structures of the membrane may be important for certain time periods. Consideration of the lipid bilayer leads to a great number of possible distributions, which may be symmetric or asymmetric with respect to the outer and inner leaflets of the membrane.     

STORAGE AND STRUCTURAL PRODUCTS FORMED DURING PHOTOSYNTHESIS IN THE SIPHONOUS ALGA CAULERPA SIMPLICIUSCULA(CHLOROPHYCEAE)1

The distribution of radioactivity into storage and intermediary metabolites during photosynthesis over periods of up to three hours was followed in the siphonous green alga Caulerpa simpliciuscula C. Ag. After the first hour, almost all the carbon assimilated was recovered as insoluble 1,4-α-glucan. There was rapid movement of carbon into insoluble 1,3-β-glucans during the first 20 min of photosynthesis, but little additional carbon moved into these compounds after that time. This contrasted with the movement of carbon into the soluble 1,3-β-glucan fraction, which continued for 2 h. Sucrose accumulated very little ¹⁴C during the entire period of photosynthesis. There was a very slow transfer of ¹⁴C into lipid throughout the period but the rate was linear. Protein labelling showed a lag of 2 h before it reached the same rate of ¹⁴C accumulation as shown by the lipid initially. It is suggested that the distribution of radioactivity can be explained in part by proposing that the tissue is in the latter stages of recovery from the wounding which look place at the time of dividing the thallus into sections.     

Tissue specificity of nonhistone proteins from human chromatin

Summary Nonhistone proteins were isolated from human placental and tonsillar chromatins. Antiserum was prepared against a complex from some nonhistone proteins and DNA (NP-DNA) from placental chromatin. With the help of polyacrylamide gel electrophoresis and immunological methods the tissue specificity of human chromatin nonhistone proteins was established. The described organ immunogenic specificity of the complex of DNA and nonhistone proteins (NP-DNA) from human chromatin is in accordance with data published on similar complexes from different animal organs. Besides, it is shown that shearing of chromatin leads to large chifts in NP-DNA concentrations required for maximum complement fixation in the presence of the prepared antiserum. This may probably be due to a damage of certain chromatin super structures which involve some of the nonhistone proteins and DNA sequences from both the more condensed and less condensed parts of chromatin.     

The electric potential profile across the erythrocyte membrane

The membrane potential profile of erythrocytes is calculated on the basis of realistic data on the electric charges of the glycocalyx, the spectrin layer as well as of the phosphatidyl serine molecules. Various stationary and quasi-stationary osmotic states of erythrocytes are considered. The calculations are performed by numerical integration of the nonlinear Poisson-Boltzmann equation. It is shown that the potential profile is strongly influenced by the negative charges of phosphatidyl serine at the inner membrane surface. For all osmotic states a negative inner surface potential of more than 60 mV was calculated.The basic model is extended by incorporation of a specific binding of the cations calcium, magnesium and sodium to phosphatidyl serine as well as by consideration of the finite volumes of the ions of the electrolyte. Both effects have only a weak influence on the membrane potential profile of erythrocytes.     

Kleine Beiträge zur Kenntnis der Flora von China

Ohne Zusammenfassung     

Pigment‐dispersing factor in the locust abdominal ganglia may have roles as circulating neurohormone and central neuromodulator

Pigment‐dispersing factor (PDF) is a neuropeptide that has been indicated as a likely output signal from the circadian clock neurons in the brain of Drosophila. In addition to these brain neurons, there are PDF‐immunoreactive (PDFI) neurons in the abdominal ganglia of Drosophila and other insects; the function of these neurons is not known. We have analyzed PDFI neurons in the abdominal ganglia of the locust Locusta migratoria. These PDFI neurons can first be detected at about 45% embryonic development and have an adult appearance at about 80%. In each of the abdominal ganglia (A3–A7) there is one pair of lateral PDFI neurons and in each of the A5–A7 ganglia there is additionally a pair of median neurons. The lateral neurons supply varicose branches to neurohemal areas of the lateral heart nerves and perisympathetic organs, whereas the median cells form processes in the terminal abdominal ganglion and supply terminals on the hindgut. Because PDF does not influence hindgut contractility, it is possible that also these median neurons release PDF into the circulation. Release from one or both the PDFI neuron types was confirmed by measurements of PDF‐immunoreactivity in hemolymph by enzyme immunoassay. PDF applied to the terminal abdominal ganglion triggers firing of action potentials in motoneurons with axons in the genital nerves of males and the 8th ventral nerve of females. Because this action is blocked in calcium‐free saline, it is likely that PDF acts via interneurons. Thus, PDF seems to have a modulatory role in central neuronal circuits of the terminal abdominal ganglion that control muscles of genital organs. © 2001 John Wiley & Sons, Inc. J Neurobiol 48: 19–41, 2001     

Alopecia and male infertility in oligotriche mutant mice are caused by a deletion on distal chromosome 9

The recessive mutation oligotriche (olt) affects the coat and male fertility in the mouse. In homozygous (olt/olt) mutants, the coat is sparse, most notably in the inguinal and medial femoral region. In these regions, almost all hair shafts are bent and distorted in their course through the dermis and rarely penetrate the epidermis because the hair cortex is not fully keratinized. During hair follicle morphogenesis, mutant hair follicles exit from anagen one day before those of normal littermates and show a prolongation of the catagen stage. The oligotriche (olt) locus was mapped to distal chromosome 9 within a 5-Mbp interval distal to D9Mit279. Analysis of candidate gene expression revealed that olt/olt mutant mice do not express functional phospholipase C delta 1 (Plcd1) mRNA. This deficiency is the consequence of a 234-kbp deletion involving not only the Plcd1 locus but also the chromosomal segment harboring the genes Vill (villin-like), Dlec1 (deleted in lung and esophageal cancer 1), Acaa1b (acetyl-Coenzyme A acyltransferase 1B, synonym thiolase B), and parts of the genes Ctdspl (carboxy-terminal domain RNA polymerase II polypeptide A small phosphatase-like) and Slc22a14 (solute carrier family 22 member 14). Offspring of olt/olt females, mated with Plcd1 ^−/− knockout males, exhibit coat defects similar to those observed in homozygous olt/olt mutant mice but the spermiogenesis in male offspring is normal. We conclude that the 234-kbp deletion from chromosome 9 harbors a gene involved in spermiogenesis and we propose that the oligotriche mutant be used as a model for the study of the putative tumor suppressor genes Dlec1, Ctdspl, and Vill. We also suggest that the oligotriche locus be named Del(9Ctdspl-Slc22a14)1Pas.