Brain endocast asymmetry in pongids and hominids: Some preliminary findings on the paleontology of cerebral dominance

Observations on petalial asymmetry for 190 hominoid endocasts are reported, and their statistical differences assessed. While all taxa of hominoids show asymmetries to various degrees, the patterns or combinations of petalial asymmetries are very different, with fossil hominids and modern Homo sapiens showing an identical pattern of left-occipital, right-frontal petalias, which contrasts with those found normally in pongids. Of the pongids, Gorilla shows the greater degree of asymmetry in left-occipital petalias. Only modern Homo and hominids (Australopithecus, Homo erectus, Neandertals) show a distinct left-occipital, right-frontal petalial pattern. Analysis by x² statistics shows the differences to be highly significant. Due to small sample size and incompleteness of endocasts, small-brained hominids, i.e., Australopithecus, are problematical. To the degree that gross petalial patterns are correlated with cognitive task specialization, we speculate that human cognitive patterns evolved early in hominid evolution and were related to selection pressures operating on both symbolic and spatiovisual integration, and that these faculties are corroborated in the archaeological record.     

A method for in situ characterization of b- and c-type cytochromes in Escherichia coli and in complex III from beef heart mitochondria by combined spectrum deconvolution and potentiometric analysis

An analytical technique for the in situ characterization of b- and c-type cytochromes has been developed. From evaluation of the results of potentiometric measurements and spectrum deconvolutions, it was concluded that an integrated best-fit analysis of potentiometric and spectral data gave the most reliable results. In the total cytochrome b content of cytoplasmic membranes from aerobically grown Escherichia coli, four major components are distinguished with alpha-band maxima at 77 K of 555.7, 556.7, 558.6 and 563.5 nm, and midpoint potentials at pH 7.0 of 46, 174, -75 and 187 mV, respectively. In addition, two very small contributions to the alpha-band spectrum at 547.0 and 560.2 nm, with midpoint potentials of 71 and 169 mV, respectively, have been distinguished. On the basis of their spectral properties they should be designated as a cytochrome c and a cytochrome b, respectively. In Complex III, isolated from beef heart mitochondria, five cytochromes are distinguished: cytochrome c1 (lambda m (25 degrees C) = 553.5 nm; E'0 = 238 mV) and four cytochromes b (lambda m (25 degrees C) = 558.6, 561.2, 562.1, 566.1 nm and E'0 = -83, 26, 85, -60 mV).     

Binding of adducts of NAD(P) and enolizable ketones to NAD(P)-dependent dehydrogenases

Carbonyl compounds such as alpha-ketoglutarate, pyruvate, oxaloacetate, butyraldehyde, acetaldehyde or acetone react with NAD or NADP to give adducts. Binding studies of adducts to dehydrogenases are performed by means of ultraviolet differential spectroscopy, circular dichroism and spectrofluorimetry. The dehydrogenases show a high degree of binding specificity toward the adducts which contain their specific oxidized substrate and their specific coenzyme. The high selectivity of the dehydrogenases for adducts is evidenced by binding studies of NAD(P)-pyruvate and NAD(P)-alpha-ketoglutarate adducts on glutamate dehydrogenase at pH 7.6 and 8.9. Evidence is presented showing that adducts bind to the active site of the enzymes.     

高粱泡的生长调控与结实状况

高粱泡(Rubus lambertionus Ser.)是一种有利用价值的野生果树资源。其优点为:(1)结果早,产量高,亩产量可达500kg以上;(2)适应性广,耐瘠薄,是开发利用低山丘陵的优良资源植物;(3)果实营养丰富,酸味纯正,尤其是所含红色素稳定性好,是加工果汁饮料的优质添加剂;(4)果实采收期在11月中旬到12月底,此时气温低,有利于浆果加工和贮藏,并可利用农闲季节的劳动力。上述特点表明,高粱泡有很好的开发利用前景。但本种在野生状态下蔓生性强,多刺,并具有枝顶生根的习性,因而树形紊乱而松散,栽培时搭架困难,植株占地面积大,而单位面积产量不易提高。为了便于操作管理和提高产量,减少栽培成本,增进经济效益,我们于1990～1991年进行了生长和株形调控试验,     

Different fate in vivo of oxidatively modified low density lipoprotein and acetylated low density lipoprotein in rats. Recognition by various scavenger receptors on Kupffer and endothelial liver cells

Human low density lipoprotein was oxidized (Ox-LDL) by exposure to 5 microM Cu2+ and its fate in vivo was compared to acetylated low density lipoprotein (Ac-LDL). Ox-LDL, when injected into rats, is rapidly removed from the blood circulation by the liver, similarly as Ac-LDL. A separation of rat liver cells into parenchymal, endothelial, and Kupffer cells at 10 min after injection of Ox-LDL or Ac-LDL indicated that the Kupffer cell uptake of Ox-LDL is 6.8-fold higher than for Ac-LDL, leading to Kupffer cells as the main liver site for Ox-LDL uptake. In vitro studies with isolated liver cells indicated that saturable high affinity sites for Ox-LDL were present on both endothelial and Kupffer cells, whereby the capacity of Kupffer cells to degrade Ox-LDL is 6-fold higher than for endothelial cells. Competition studies showed that unlabeled Ox-LDL competed as efficiently (90%) as unlabeled Ac-LDL with the cell association and degradation of 125I-labeled Ac-LDL by endothelial and Kupffer cells. However, unlabeled Ac-LDL competed only partially (20-30%) with the cell association and degradation of 125I-labeled Ox-LDL by Kupffer cells, while unlabeled Ox-LDL or polyinosinic acid competed for 70-80%. It is concluded that the liver contains, in addition to the scavenger (Ac-LDL) receptor which interacts efficiently with both Ac-LDL and Ox-LDL and which is concentrated on endothelial cells, an additional specific Ox-LDL receptor which is highly concentrated on Kupffer cells. In vivo the specific Ox-LDL recognition site on Kupffer cells will form the major protection system against the occurrence of the atherogenic Ox-LDL particles in the blood.     

Characterization of calcium-triggered secretion in permeabilized rat basophilic leukemia cells. Possible role of vectorially acting G proteins.

Strong, albeit indirect, evidence suggests that a GTP-binding (G) protein(s) can act directly on the secretory machinery by a post-second messenger mechanism. The type and function of this putative Ge (exocytosis) protein were investigated in streptolysin-O-permeabilized rat basophilic leukemia (RBL) cells. The exocytotic response to calcium was first characterized both morphologically and biochemically using the release of preloaded [3H]serotonin as an index of exocytosis. Calcium-induced secretion (EC50 about 3 microM) in RBL cells requires ATP (EC50 about 2.5 mM) and is modulated by pH, the optimal value being 7.2. Another requirement for calcium-induced secretion is an activated G protein, since inactivators of G proteins such as GDP beta S (EC50 about 800 microM) inhibit the secretagogue effect of 10 microM free calcium. Conversely, GTP gamma S (EC50 about 1 microM) and other nonhydrolyzable analogs of GTP, which keep G proteins in a permanently active conformation, potentiate the effect of calcium. GTP gamma S alone is without effect. The effect of GTP gamma S on exocytosis is apparently not mediated by known second messengers, suggesting that a Ge protein is involved. Electron microscopic images show that in resting cells, secretory granules are clustered in the perinuclear area, whereas they become scattered upon calcium stimulation. A paradoxical effect of GTP gamma S is observed when applied during permeabilization; under these conditions, in fact, the nucleotide inhibits the subsequent secretory response to calcium. The scattering of granules is also inhibited. This effect of GTP gamma S is counteracted by coadministration of GTP. These responses to guanine nucleotides are typical of vectorially acting G proteins involved in protein synthesis and in intracellular vesicle transport. Taken together, the data presented suggest that calcium-dependent release requires a vectorially acting G protein controlling the movement of secretory granules. This and alternative models are discussed.     

Assembly of the mammalian muscle acetylcholine receptor in transfected COS cells

We have investigated the mechanisms of assembly and transport to the cell surface of the mouse muscle nicotinic acetylcholine receptor (AChR) in transiently transfected COS cells. In cells transfected with all four subunit cDNAs, AChR was expressed on the surface with properties resembling those seen in mouse muscle cells (Gu, Y., A. F. Franco, Jr., P.D. Gardner, J. B. Lansman, J. R. Forsayeth, and Z. W. Hall. 1990. Neuron. 5:147-157). When incomplete combinations of AChR subunits were expressed, surface binding of 125I-alpha-bungarotoxin was not detected except in the case of alpha beta gamma which expressed less than 15% of that seen with all four subunits. Immunoprecipitation and sucrose gradient sedimentation experiments showed that in cells expressing pairs of subunits, alpha delta and alpha gamma heterodimers were formed, but alpha beta was not. When three subunits were expressed, alpha delta beta and alpha gamma beta complexes were formed. Variation of the ratios of the four subunit cDNAs used in the transfection mixture showed that surface AChR expression was decreased by high concentrations of delta or gamma cDNAs in a mutually competitive manner. High expression of delta or gamma subunits also each inhibited formation of a heterodimer with alpha and the other subunit. These results are consistent with a defined pathway for AChR assembly in which alpha delta and alpha gamma heterodimers are formed first, followed by association with the beta subunit and with each other to form the complete AChR.     

Association of Rab3A with synaptic vesicles at late stages of the secretory pathway

Rab3A is a small GTP-binding protein highly concentrated on synaptic vesicles. Like other small GTP-binding proteins it is thought to cycle between a soluble and a membrane-associated state. To determine at which stage of the life cycle of synaptic vesicles rab3A is associated with their membranes, the localization of the protein in neurons and neuroendocrine cells at different developmental and functional stages was investigated. In all cases, rab3A was colocalized with synaptic vesicle markers at the cell periphery, but was absent from the Golgi area, suggesting that rab3A associates with vesicles distally to the Golgi complex and dissociates from vesicle membranes before they recycle to this region. Immunofluorescence experiments carried out on frog motor end plates demonstrated that massive exocytosis of synaptic vesicles is accompanied by a translocation of rab3A to the cell surface. The selective localization of rab3A on synaptic vesicles at stages preceding their fusion with the plasmalemma suggests that the protein is part of a regulatory machinery that is assembled onto the vesicles in preparation for exocytosis.     

Transformation and allelic replacement in Francisella spp.

We describe methods for transposon mutagenesis and allelic replacement in the facultative intracellular pathogen Francisella. Recombinant clones were constructed by insertion of partially cut F. tularensis or F. novicida DNA into pUC19 and then mutagenized with a mini-Tn10-Km transposon. F. novicida could be transformed with these plasmids either by a chemical transformation method or by electroporation, whereas F. tularensis could be transformed only by electroporation. Transformation of F. tularensis by electroporation was enhanced in the absence of the capsule. Southern blot analysis showed that the KmR marker was rescued either by integration of the plasmid into the Francisella chromosome or by allelic replacement. Allelic replacement was found to be the mechanism underlying a site-specific mutation affecting FopA, an outer-membrane protein of Francisella. F. novicida could also be transformed with chromosomal DNA carrying the KmR marker and the transformation frequency obtained using chromosomal DNA was generally greater than that obtained using plasmid DNA. F. novicida was also transformed by an IncQ plasmid containing an F. novicida DNA insert, which replicated autonomously in this host.     

Absence of preferential homologous H/L chain association in hybrid hybridomas

Bispecific mAb contain two Ag-combining sites each composed of a different combination of H and L chains. The resulting ability to react with and cross-link two different Ag makes these molecules a novel tool for application in biology and medicine. Intact bispecific mAb can be made only by biologic means, e.g., by fusion of two established hybridomas. Appropriate assembly of bispecific mAb by these hybrid cells depends on H = L chain behavior: strong preferential homologous H-L pairing would benefit the yield of bispecific antibodies. We have analyzed the Ig species produced by eight hybrid hybridomas (quadromas). Quadroma-produced IgG was fractionated and characterized for H and L chain content. The Ag reactivities were verified by using ELISA and immunofluorescence. Preferential homologous pairing was seen only with a minority of H-L chain pairs; L chains associated on average in a random fashion with H chains. This indicates that in the B cells from which the parental hybridomas were obtained, no strong selection had occurred on H-L recombination. Our results extend recent biochemical competitive H-L reassociation experiments, where on average an at random association of L chains with H chains was found; evidently this random association occurs in our biologic system as well. For the biologic production of bispecific antibodies this means that only in a small number of cases the "ideal" producer will be met. From the viewpoint of generation of antibody diversity, our results favor a large freedom for combinatorial binding of H and L chains during B cell ontogeny.