Biosynthesis of high density lipoprotein by chicken liver: nature of nascent intracellular high density lipoprotein

Young chickens were administered L-[(3)H]leucine and after 10 or 30 min the livers were removed and fractioned into rough (RER) and smooth (SER) endoplasmic reticulum fractions and into light, intermediate, and heavy golgo cell fractions. The labeled high density lipoprotein (HDL), contained within these intracellular organelles was isolated either by immunoprecipitation using rabbit antiserum to rooster HDL, or by ultracentrifugal glotation between densities 1.063 and 1.21 g/ml. The radioactive apoproteins of nascent HDL were analyzed by SDS PAGE and detected by fluorography. Analyses of radioactive apoproteins obtained by immunoprecipitation from the contents of the RER, the SER, and the three golgi complex fractions revealed only one apoprotein, A1. The C peptide present in serum HDL was not detected intracellularly. The radioactive apoprotein A1 which is present within the cisternae of the RER and the SER fractions failed to float, whereas apoprotein A1, present within the golgi apparatus, readily floated between densities 1.063 and 1.21 g/ml. The HDL particles, isolated by flotation from the golgi apparatus content, were further characterized by lipid and protein analyses and by electron microscopy. Golgi HDL particles have the same density as serum HDL. On a percentage basis, golgi HDL contains less protein and more phospholipids than does serum HDL. Morphologically, golgi HDL is different in appearance from serum HDL. It is more heterogeneous in size, with most of the particles ranging 8.3-25 nm in diameter. The spherical particles contain small membrane tails. Occasionally, a few disk-shaped bilayer structures are also found within the golgi apparatus. These studies show that the newly synthesized apoprotein A1, present within the RER and the SER cell fractions, is not fully complexed with lipid and that apoprotein A1 does not acquire sufficient lipid to float at the proper HDL density until it enters the golgi apparatus. The difference in chemical composition and the heterogeneous size of golgi HDL may be attributed to the different stages of HDL maturation.     

Retina-specific expression from the IRBP promoter in transgenic mice is conferred by 212 bp of the 5'-flanking region

IRBP is a photoreceptor-specific glycoprotein that has been suggested as a retinoid carrier in the visual process. Previous research has shown that 1.3 kb of 5'-flanking sequence from the human IRBP gene is sufficient to promote photoreceptor-specific expression of reporter genes in transgenic mice. To define more narrowly the sequences that promote tissue-specific expression, chimeric constructs with shorter promoters were used to generate transgenic mice. The bacterial CAT gene was fused to fragments of 706 bp or 212 bp from the 5' end of the human IRBP gene. Analysis of the three transgenic families bearing the 706 bp IRBP promoter revealed that CAT expression was confined to the neuro-retina and the pineal gland. Analysis of the four transgenic families bearing the 212 bp IRBP promoter revealed the same tissue-specific CAT expression in three families. These results establish that tissue-specific expression of IRBP can be regulated by a short 212 bp promoter which has been conserved between humans and mice.     

多个数量性状的拓广遗传参数

运用多元分析方法定义了拓广表型方差(?)(generalized phenotypic variance),拓广遗传方差(?)(generalized genetic variance),拓广遗传力(?)(generalized heritability)和拓广遗传相关系数(?)(generalized genetic correlation coefficient): 这些参数可用来对多个数量性状总体的变异、协变异及不同组向量之间的相关性进行轮廓分析(profile analysis)。用棉花和紫花苜蓿的两个实例说明了这些参数的估算和应用。     

Postsynaptic density antigens: preparation and characterization of an antiserum against postsynaptic densities

Long-term immunization of rabbits with postsynaptic densities (PSD) from bovine brain produced an antiserum specific for PSD as judged by binding to subcellular fractions and immunohistochemical location at the light and electron microscope levels. (a) The major antigens of bovine PSD preparations were three polypeptides of molecular weight 95,000 (PSD-95), 82,000 (PSD-82), and 72,000 (PSD-72), respectively. Antigen PSD-95, also present in mouse and rat PSDs was virtually absent from cytoplasm, myelin, mitochondria, and microsomes from rodent or bovine brain. Antigens PSD-82 and PSD-72 were present in all subcellular fractions from bovine brain, especially in mitochondria, but were almost absent from rodent brain. The antiserum also contained low-affinity antibodies against tubulin. (b)Immunohistochemical studies were performed in mouse and rat brain, where antigen PSD-95 accounted for 90 percent of the antiserum binding after adsorption with purified brain tubulin. At the light microscope level, antibody binding was observed only in those regions of the brain where synapses are known to be present. No reaction was observed in myelinated tracts, in the neuronal cytoplasm, or in nonneuronal cells. Strong reactivity was observed in the molecular layer of the dentate gyrus, stratum oriens and stratum radiatum of the hippocampus, and the molecular layer of the cerebellum. Experimental lesions, such as ablation of the rat entorhinal cortex or intraventricular injection of kainic acid, which led to a major loss of PSD in well- defined areas of the hippocampal formation, caused a correlative decrease in immunoreactivity in these areas. Abnormal patterns of immunohistochemical staining correlated with abnormal synaptic patterns in the cerebella of reeler and staggerer mouse mutants. (c) At the electron microscopic level, immunoreactivity was detectable only in PSD. The antibody did not bind to myelin, mitochondria or plasma membranes. (d) The results indicate that antigen PSD-95 is located predominantly or exclusively in PSD and can be used as a marker during subcellular fractionation. Other potential uses include the study of synaptogenesis, and the detection of changes in synapse number after experimental perturbations of the nervous system.     

PATHOGENICITY OF METARHIZIUM ANISOPLIAE VAR. ACRIDU TO THE DEVEOLPMENTAL STAGES OF BROWN PLANTHOPPER NILAPARVATA LUGENS STÅL AND SOGATELLA FURCIFERA (HORVATH)

Abstract  The susceptibility and virulence of entomopathogenic fungus Metarhizium anisopliae var. acridum to the stages of brown planthopper (BPH), Nilaparvata lugens (Stål) and whitebacked planthopper (WBPH), Sogatella furcifera (Horvath) were investigated under laboratory conditions. Three dosages of M. anisopliae var. acridum ranging from 10.5, 116.3 and 1027.1 conidial/mm² were used in the experiment. The tested stages of host included three developmental stages, young nymphs (1–2 instars), old nymphs (3–5 instars) and adults. It was found that all tested stages of the planthoppers were susceptible to the fungal infection. The degree of virulence LT₅₀ of M. anisopliae var. acridum against young nymphs of N. lugens are >21, 20.82 and 16.55, respectively with the 3 dosages, the LT₅₀ of the fungus against the old nymphs are 17.68, 15.49 and 13.98, respectively with the 3 dosages; the LT₅₀ of the fungus against the adults are 17.10, 12.57 and 9.14 respectively with the 3 dosages. The degree of virulence LT₅₀ of M. anisopliae var. acridum on young nymphs of S. furcifera are >21, 17.29 and 13.13, respectively with the 3 dosages _; the LT₅₀ of the fungus against the old nymphs are 16.94, 15.02 and 13.03, respectively with the 3 dosages; the LT₅₀ of the fungus against the adults are 12.78, 10.16 and 7.64, respectively with the 3 dosages. Adults were more susceptible to M. anisopliae var. acridum infection than their nymphs and the young nymphs were most resistant to the fungal infection. The cumulative mortality of each stage was dosage-dependent. Of all the developmental stages, WBPH was more susceptible than BPH to M. anisopliae var. acridum infection with the same dosages.     

A DnaK Homolog in Myxococcus xanthus Is Involved in Social Motility and Fruiting Body Formation

Myxococcus xanthus is a gram-negative soil bacterium which exhibits a complex life cycle and social behavior. In this study, two developmental mutants of M. xanthus were isolated through Tn5 transposon mutagenesis. The mutants were found to be defective in cellular aggregation as well as in sporulation. Further phenotypic characterization indicated that the mutants were defective in social motility but normal in directed cell movements. Both mutations were cloned by a transposon-tagging method. Sequence analysis indicated that both insertions occurred in the same gene, which encodes a homolog of DnaK. Unlike the dnaK genes in other bacteria, this M. xanthus homolog appears not to be regulated by temperature or heat shock and is constitutively expressed during vegetative growth and under starvation. The defects of the mutants indicate that this DnaK homolog is important for the social motility and development of M. xanthus.     

Identification and characterization of a human herpesvirus 6 gene segment that trans activates the human immunodeficiency virus type 1 promoter.

Human herpesvirus 6 (HHV-6) is a lymphotropic herpesvirus, and in vitro, HHV-6 can productively infect many of the same cell types as can human immunodeficiency virus (HIV). Coinfection by both viruses in vitro can lead to both activation of the HIV promoter and acceleration of cytopathic effects. We have previously demonstrated that a large, 22.25-kb cloned HHV-6 fragment, pZVB70, can trans activate HIV promoter expression in vitro. In this study, we show that the pZVB70 fragment can trans activate the HIV promoter in human T-cell lines as well as in the monkey kidney cell line CV-1. The pZVB70 insert was digested with various restriction enzymes, and individual fragments were transfected into cells to test for their ability to trans activate the HIV promoter. By this method, we have identified a 1.8-kb subfragment, B701, that is involved in trans activation. Sequence analyses show that B701 potentially encodes a 143-amino-acid protein. This protein shares no homology with other herpesvirus proteins, such as ICP0 and ICP4, that have been shown to trans activate the HIV promoter. However, it shows weak sequence homology with the gene products encoded by the cytomegalovirus early US22 gene family, suggesting that the putative B701 protein may be an HHV-6 early regulatory protein. The 143-amino-acid coding sequence of B701 was cloned by polymerase chain reaction, and transfection of this construct into cells activated HIV promoter expression. The target site on the HIV promoter for the putative B701 protein is mapped to the NF-kappa B binding site. Our results suggest that the putative B701 protein may function by directly binding to the NF-kappa B site or may involve cellular factors, such as NF-kappa B, either directly or indirectly.     

Pathways of energy flow through the light-harvesting antenna of the photosynthetic purple bacterium rhodobacter sphaeroides

Using low intensity picosecond absorption spectroscopy with independently tunable excitation and probing infrared pulses, we have studied the pathways of energy transport through the light-harvesting antenna pigments of the photosynthetic purple bacterium Rhodobacter sphaeroides. From the observed excited-state rise time of the red-most pigment B896 as a function of excitation wavelength it is concluded that the B850 pigment of LH2 is spectrally heterogeneous. For excitations originating in the B850 pigment this results in a fast channel (9 ps) that is mainly excited in the peak of the B850 absorption band, and a slow channel (35 ps) that is predominantly excited at ~840 nm. Upon excitation of B800, more than 90% of the excitations follow the fast path. From the observed kinetics it is concluded that the majority of the LH2 → LH1 energy transfer takes place within at most a few picoseconds. The rate-limiting step in the whole energy transfer sequence appears to be the B896 → reaction center transfer. The origin of the B850 heterogeneity and the slow 35-ps component is at the moment unclear. Possibly it represents a highly extended form of LH2 in which transfer to LH1 takes a relatively long time, due to a large number of transfer steps.     

鄂尔多斯盆地晚石炭世孢粉组合

本文报道了鄂尔多斯盆地晚石炭世太原组的孢粉组合,共计68属,148种(类型)。本文描述了其中的9个新种,2个新组合和4个未定种,并建立一个组合带,即 Pseudolyosporaradialis-Gulisporites discersus-Thymospora thiessenit。根据孢粉组合情况,可看出盆地东部更接近于华北,西部则发生区系上的变化。整个孢粉组合可与盆地北缘、华北地区的太原组以及欧美等地区的维斯法期 C-D 和斯蒂芬期的孢粉组合比较。地质时代当属晚石炭世。     

Inactivation of the sodium channel. I. Sodium current experiments

Inactivation of sodium conductance has been studied in squid axons with voltage clamp techniques and with the enzyme pronase which selectively destroys inactivation. Comparison of the sodium current before and after pronase treatment shows a lag of several hundred microseconds in the onset of inactivation after depolarization. This lag can of several hundred microseconds in the onset of inactivation after polarization. This lag can also be demonstrated with double-pulse experiments. When the membrane potential is hyperpolarized to -140 mV before depolarization, both activation and inactivation are delayed. These findings suggest that inactivation occurs only after activation are delayed. These findings suggest that inactivation occurs only after activation; i.e. that the channels must open before they can inactivate. The time constant of inactivation measured with two pulses (τ(c)) is the same as the one measured from the decay of the sodium current during a single pulse (τ(h)). For large depolarizations, steady-state inactivation becomes more incomplete as voltage increases; but it is relatively complete and appears independent of voltage when determined with a two- pulse method. This result confirms the existence of a second open state for Na channels, as proposed by Chandler and Meves (1970. J. Physiol. [Lond.]. 211:653-678). The time constant of recovery from inactivation is voltage dependent and decreases as the membrane potential is made more negative. A model for Na channels is presented which has voltage-dependent transitions between the closed and open states, and a voltage-independent transition between the open and the inactivated state. In this model the voltage dependence of inactivation is a consequence of coupling to the activation process.