The 1989 James A. F. Stevenson memorial lecture. The knee jerk: still an enigma?

This is a wide-ranging review of muscle proprioceptors, intended primarily for the nonspecialist. It emphasizes how much more they are concerned with, than just the production of the knee jerk; it concentrates on principle rather than documenting detail and cites selectively. The main topics covered are the effect of deafferentation, position sense, the proprioceptors themselves, the control of the muscle spindle by the CNS, and spinal and long-latency "stretch" reflexes. The emphasis is on human work. The knee jerk itself is seen as a "physiological artefact," resulting from a mode of stimulation that does not occur in life, with the normal function of its underlying circuitry still under debate.     

The Nest’s Tale. A reply to Richard Dawkins

If temperature does not vary from one generation from to the next but its value is crucial for the development of particular phenotypic characteristics, a long-term change in its value may trigger major evolutionary changes of the organism. If a bird's nest maintains the critical temperature, then a statement that the bird is the nest's way of making another nest is as helpful as accounts couched in terms of genes' intentions. However, the language of intentions rests on different evidence and assumptions from causal language and the languages are not interchangeable. Understanding ontogeny in causal terms requires explanations that are made as simple as possible but not so simple that they become completely unrealistic.     

When Is A Lineage A Species? A Case Study In Myxacorys gen. nov. (Synechococcales: Cyanobacteria) With The Description of Two New Species From The Americas

Soil cyanobacteria are crucial components of biological soil crusts and carry out many functions in dryland ecosystems. Despite this importance, their taxonomy and population genetics remain poorly known. We isolated 42 strains of simple filamentous cyanobacteria previously identified as Pseudophormidium hollerbachianum from 26 desert locations in the North and South America and characterized these strains using a total evidence approach, that is, using both morphological and molecular data to arrive at taxonomic decisions. Based on a phylogenetic analysis of 16S rRNA gene sequences, we propose and characterize Myxacorys gen. nov. with two new species Myxacorys chilensis, the generitype, and M. californica. We also found distinct 16S‐23S ITS sequence variability within species in our dataset. Especially interesting was the presence of two distinct lineages of M. californica obtained from locations in close spatial proximity (within a few meters to kilometers from each other) suggesting niche differentiation. The detection of such unrecognized lineage‐level variability in soil cyanobacteria has important implications for biocrust restoration practices and conservation efforts.     

A.A.Khan教授将来华讲学

美国康乃尔大学种子生理学家A.A.Khan教授,将于今年十月中旬来华,到广州及杭州访问,并在广州举办讲习班,做以下五方面的报告:①应用种子预措施改善幼苗生长与产     

Electron microscopy—The U.K. involvement

The development of the electron microscope in the advanced form we know today is the result of a loosely organized but effective world-wide scientific and technological collaboration, that readily transcends national and cultural barriers. The birth of the subject was undoubtedly in Berlin but the United Kingdom has played a prominent part, sometimes in an accidental way, at critical periods in this development both at the scientific and manufacturing level. In 1927, for example, G.P. Thompson established experimentally the wave nature of the electron and its scattering and diffraction by thin foils. This followed his invention of the electron diffraction camera at a time when De Broglie's postulates on the wave of nature of the electron were not enjoying much support, even in his native France. C.W. Oatley in Cambridge University was successful in introducing the first commercial scanning electron microscope (SEM) where several commercial firms had previously failed. D. Gabor invented electron holography in a moment of boredom while watching a tennis match. The U.K. has also played a key role in fostering international collaboration by means of conferences and exchange visits between electron microscopists. The present paper concentrates on some of the critical developments that took place in the U.K. in the commercial development of transmission electron microscopy, in scanning electron microscopy and more recently in high resolution electron microscopy. These developments are placed as far as possible in a world-wide context.     

The lobose amebas: II. A new ameba of the “Proteus” group,polychaos nitidubia N. Sp.

Summary A new ameba of the 'proteus group, Polychaos nitidubia n. sp., is found in lakes, ponds and streams of the State of Florida, United States of America. It resembles both Polychaos dubia (A. A. Schaeffer, 1916) and Amoeba nitida E. Penard, 1902, in certain respects, but it is distinct from either. It resembles P. dubia in its pseudopodal forms and movements and also in the presence of clumped crystals in the cytoplasm. It resembles A. nitida in the form of the nucleus, which is a cup-shaped disc or an invaginated spheriod. It is smaller than A. nitida, but somewhat larger than P. dubia. Polychaos nitidubia n. sp. is found in habitats similar to those where Amoeba proteus and other species of the proteus group occur, and may be present with such species. P. nitidubia n. sp. is 200 to 550 µ long in locomotion; its nucleus is 27 to 35 µ diameter with many submembranellar chromatin granules, but no endosome; cytoplasmic granules are numerous, often in fused groups of 2 to 4 crystals, cytoplasm is clear, viscous; movement is less fluid than that of P. dubia, but resembles it.Resume Une nouvelle amibe du groupe proteus, Polychaos nitidubia spec. nov. a été trouvée dans des lacs, des étangs et des ruisseaux de l'Etat de Florida aux Etats Unis de l'Amerique. Elle ressemble tant à la Polychaos dubia (A. A. Schaeffer, 1916) et à la Amoeba nitida E. Penard, 1902, à certaines égards et en difère à d'autres. Elle ressemble à la Polychaos dubia par rapport à la forme des pseudopodes et leurs mouvements, et aussi par rapport à la présence en cytoplasme des cristaux en groupes. Elle ressemble A. nitida par rapport à la forme du noyau, qui est discoide en forme de tasse, ou spheroide invaginé. C'est une amibe plus petite que l'A. nitida, mais plus grande que P. dubia. La Polychaos nitidubia spec. nov. se trouve dans des habitats pareils à ceux de l'Amoeba proteus et des autres et elle se trouve parfois en même lieu. La Polychaos nitidubia spec. nov. est 200 à 500 µ de long durant la locomotion. Son noyau est de 27 à 35 µ de diamètre, avec de nornbreuses granules chromatines sousmembranelles. L'endosoma est absent. Les cristaux du cytoplasme sont nombreux, dans des groupes de 2 à 4, ou solitaires. Le cytoplasme est claire, visqueux. Le mouvernent est moins coulant que celui de la P. dubia, mais y ressemble.     

The Binding of Benzopyranes to Human Serum Albumin. A Structure–Affinity Study

The binding of several benzopyranes to serum albumin was studied by equilibrium dialysis at pH7.4 in a 67mM sodium phosphate buffer at 37°C. The equilibrium data were analyzed using a computer program for curve fitting. The binding isotherm for warfarin, 4-hydroxycoumarin, 4-chromanol, coumarin, 3-acetylcoumarin, and benzoic acid can be described by two stoichiometric dissociation constants. Elimination of the 4-hydroxyl group in the coumarin chemical structures decreases the binding affinity of the compounds on the primary binding site of serum albumin, with 4-chromanol the smallest ligand which binds to seroalbumin with high affinity. Thus, the affinity of 4-benzopyranol and the 4-hydroxybenzopyranones greater than that of benzopyranones. On the other hand, elimination of the 2-oxo group in the benzopyranone chemical structures decreases affinity for the secondary binding site.