Diffusion and regionalization in membranes of maturing ram spermatozoa

An essential feature of the "fluid mosaic model" (Singer, S. J., and G. L. Nicolson , 1972, Science (Wash. DC)., 175:720-731) of the cell plasma membrane is the ability of membrane lipids and proteins to diffuse laterally in the plane of the membrane. Mammalian sperm are capable of overcoming free random diffusion and restricting specific membrane components, both lipid and protein, to defined regions of the sperm's surface. The patterns of these regionalizations evolve with the processes of sperm differentiation: spermatogenesis, epididymal maturation, and capacitation. We have used the technique of fluorescence recovery after photobleaching to measure the diffusion of the lipid analogue 1,1'- dihexadecyl 3,3,3',3'- tetramethylindocarbocyanine perchlorate ( C16dil ) on the different morphological regions of testicular and ejaculated ram spermatozoa. We have found: (a) that the major morphologically distinct regions (head, midpiece, and tail) of the plasma membrane of both testicular and ejaculated spermatozoa are also physically distinct as measured by C16dil diffusibility; (b) that despite regional differences in diffusibility there is exchange of this lipid analogue by lateral diffusion between the major morphological regions of the plasma membrane; and (c) that epididymal maturation results in changes in C16dil diffusibility in the different regions of the sperm plasma membrane. In particular, the plasma membranes of the anterior and posterior heads become physically distinct.     

Histophotometric Evaluation of Glutamate Dehydrogenase Activity of the Rat Hippocampal Formation During Postnatal Development,with Special Reference to the Glutamate Transmitter Metabolism

Transmitter glutamate/aspartate synthesis is known to proceed along different metabolic pathways. In this light, the functional relevance of glutamate dehydrogenase in postnatally maturing glutamatergic/aspartatergic structures was studied by means of quantitative enzyme histochemistry. The basic requirements concerning the kinetics and calibration of the histochemical glutamate dehydrogenase reaction used were proved to be met in order to obtain valid quantitative data. The histochemically demonstrable activity of glutamate dehydrogenase (EC 1.4.1.3) in the hippocampal formation of the rat increased markedly during postnatal development. On day 30, the distribution pattern observed was similar to that in adult animals. While the enzyme activity rose within cell body layers from day 0 to day 30 by 240-285%, the increase in neuropil layers was found to be up to 830%. Maximum values were seen in the stratum lacunosum-moleculare of CA1 and CA3 and the stratum moleculare of the dentate fascia on day 30. Since the hippocampal neuropil is supposed to be copiously provided with glutamatergic (and aspartatergic?) structures which become functional in rats during the first weeks of postnatal life, the increase in enzyme activity is discussed to be primarily a consequence of maturing synaptic systems using glutamate and/or aspartate as transmitters.     

Yeast pheromone alpha-factor is synthesized as a high molecular weight precursor

The sex pheromone alpha-factor of Saccharomyces cerevisiae, a tridecapeptide of approx. 1,700 molecular weight, was found to be synthesized in vivo as a high molecular weight precursor of Mr = 28,000. Inhibition of N-linked glycosylation by tunicamycin leads to three precursor species of lower molecular weight indicating three carbohydrate residues linked to the alpha-factor precursor molecule. A molecular weight of 18,000 was determined for the unglycosylated molecule.     

Convenient,laboratory procedure for producing solid d-arabino-hexos-2-ulose (d-glucosone)

The production of solid d-arabino-hexos-2-ulose (d-glucosone) from d-glucose by use of an enzyme, pyranose-2-oxidase (EC 1.1.3.10), is described. The enzyme is extracted from the mycelia of Polyporus obtusus, partially purified, and then immobilized on activated CH-Sepharose 4B. The enzymic conversion of d-glucose into d-glucosone is simple and convenient, and provides a product free from residual d-glucose. Lyophilization of the filtered reaction-solution yields the product, solid d-glucosone. Assay methods have been developed for monitoring the enzymic reaction and evaluating the purity of the final product.     

Hilgendorf’s (1863) dissertation on the steinheim planorbids (Gastropoda; Miocene): The development of a phylogenetic research program for paleontology

Hilgendorf’s (1866) publication on the phylogenyof Planorbis multiformis from Steinheim, Swabian Mountains, is one of the most important contributions of paleontology to early Darwinism. At the same time it helped to lay the foundation for paleontological phylogenetics. Hilgendorf’s unpublished dissertation of 1863, the newly rediscovered collection to his dissertation and the document-file ofHilgendorf’s graduation from Tübingen University help to trace back the origin of Hilgendorf’s ideas.Hilgendorf’s collection contains the oldest phylogenetic tree, which is known so far.     

The centrifugal horizontal cells in the lobula plate of the blowfly, Phaenicia sericata

Intracellular recordings combined with iontophoretic injection of Procion Yellow M4RAN were used to study the anatomy and physiology of the centrifugal horizontal cells (CH-cells) in the lobula plate of the blowfly, Phaenicia sericata.Anatomy: The CH-cells comprise a set of two homolateral, giant visual interneurones (DCH, VCH) at the rostral surface of each lobula plate. Their extensive arborizations in the lobula plate possess bulbous swellings (boutons terminaux). The arborization of one cell (DCH) covers the dorsal, and the arborization of the other cell (VCH) the ventral half of the lobula plate. Their axons run jointly with those of the horizontal cells through the chiasma internum and the optic peduncle. Their protocerebral arborization possesses spines; they form a dense network together with the axonal arborization of the horizontal cells, a second type of giant homolateral cell most sensitive to horizontal motion. The protocerebral arborization of the CH-cells gives rise to a cell body fibre which traverses the protocerebrum dorsally to the oesophageal canal. The cell body lies on the contralateral side laterally and slightly dorsally to the oesophageal canal in the frontal cell body layer.Physiology: The CH-cells respond with graded potentials to rotatory movements of their surround. Cells in the right lobula plate respond with excitation (excitatory postsynaptic potentials, membrane depolarization) to clockwise motion (contralateral regressive, ipsilateral progressive), and with inhibition (inhibitory postsynaptic potentials, membrane hyperpolarization) to counterclockwise motion in either or both receptive fields; CH-cells respond to motion presented to the ipsilateral and/or contralateral eye. Cells of the left lobula plate respond correspondingly to the reverse directions of motion. Vertical pattern motion and stationary patterns are ineffective.The heterolateral H1-neurone elicits excitatory postsynaptic potentials in the DCH-cell; these postsynaptic potentials are tightly correlated 1:1 to the preceding H1-action potentíal. The delay between the peak of the action potential and the beginning of the DCH-postsynaptic potential is 1.15 msec, agreeing very well with the value reported previously for the blowfly, Calliphora (Hausen, 1976a). The synaptic input and output connections of the CH-cells are discussed.