Tolerance to diazepam and methyl-beta-carboline-3-carboxylate measured in substantia nigra of benzodiazepine tolerant rats

The spontaneous activity of neurons in the pars reticulata of substantia nigra (SNpr) was studied in chloral hydrate anesthetized rats. As a function of dose, intravenous diazepam decreased, and methyl-beta-carboline-3-carboxylate (beta CCM) increased discharge frequency. Two days after terminating a one week treatment with flurazepam (FZP), both diazepam and beta CCM showed decreased ability to alter SNpr neuronal activity. Neither residual FZP nor down-regulation of benzodiazepine receptors can account for these results. In contrast, behavioral testing revealed no change in the ability of i.v. beta CCM to cause convulsions, suggesting that sites other than the SNpr are of prime importance in expressing the convulsant actions of systemically injected beta CCM.     

Phosphorus concentration in barley (Hordeum vulgare L.) seed: Influence on seedling growth and dry matter production

The effect of phosphorus (P) concentration in barley seed on seedling growth has not been much investigated. Consequently, two experiments were conducted in the greenhouse to determine the effect of P concentration in barley seed (Hordeum vulgare L., cv. Empress) on the seedlings grown in sand-filled boxes receiving a culture solution without P. Seeds were selected with three P concentrations: high-P (113.0 mmol P kg⁻¹), medium-P (80.7 mmol P kg⁻¹) and low-P (54.9 mmol P kg⁻¹). At 21 days after sowing, the shoot and root yield or shoot height was the least with seedlings from low-P seed. In the other experiment, high-P and low-P seeds were wetted with distilled water or with a solution of 25.8 cmol L⁻¹ of NaH₂PO₄ for 24 h, and then grown for 31 days. Solution P had been imbibed by seeds whether low or high in native P, but only the imbibed P held by low native P seed benefited seedling dry matter accumulation and shoot elongation. The lack of benefit from seed-imbibed P on seedlings grown from high-P barley seed was associated with low recovery of the imbibed P in those seedlings.     

Nonsense mutations of the von Willebrand factor gene in patients with von Willebrand disease type III and type I.

von Willebrand disease (vWD) is the most common inherited bleeding disorder in humans. The disease is caused by qualitative and quantitative abnormalities of the von Willebrand factor (vWF). Genomic DNA from 25 patients with vWD type III, the most severe form of the disease, was studied using PCR followed by restriction-enzyme analysis and direct sequencing of the products. Nonsense mutations (CGA----TGA) were detected in exons 28, 32, and 45 by screening of all the 11 CGA arginine codons of the vWF gene. Two patients were found to be homozygous and five heterozygous for the mutation. Both parents and some of the relatives of the homozygous patients carry the mutation. These are the first reported examples of homozygous point mutations associated with the severe form of vWD. In the three heterozygous probands, one of the parents carried the mutation and had vWD type I. Family studies including parents and family members with or without vWD type I indicated that these three heterozygous patients are likely to be compound heterozygous. Twenty-one individuals from these seven families with vWD type I were found to be heterozygous for the mutation.     

Generation of hydroxyl radical by crocidolite asbestos is proportional to surface [Fe3+].

Differences among fibrous silicates to effect injury in biological systems have been postulated to reflect oxidant generation by structural iron within the crystal lattice of amphiboles. Iron is also coordinated to the surface of all silicates in concentrations which depend on the density of acidic functional groups. We tested the hypothesis that oxidant generation by crocidolite is proportional to surface-complexed iron rather than variance in the lattice concentrations of this transition metal. Surface iron was quantified after its reduction to Fe2+ and chelation by citrate. Thiobarbituric acid (TBA) reactive products and dihydroxybenzoic acid products of salicylate were employed as indices of nonspecific oxidant and hydroxyl radical generation, respectively. Surface iron, TBA reactive products, and dihydroxybenzoic acid products all diminished after pretreatment of crocidolite with the metal chelator deferoxamine in concentrations varying from 0 to 250 mM. Inclusion of deferoxamine in the reaction mixture provided similar results of diminishing both TBA reactive products and dihydroxybenzoic acid generation. We conclude that oxidant generation by crocidolite is proportional to surface concentrations of iron which can be chelated using deferoxamine. The design of synthetic fibers without health effects after exposure will likely necessitate decreasing the number of surface acidic functional groups to diminish the capacity to complex iron (i.e., minimize the percentage SiO2).     

Hepatitis B virus DNA integration and expression of an erb B-like gene in human hepatocellular carcinoma.

Southern blot studies on Hepatitis B Virus (HBV) DNA integration in 13 human hepatocellular carcinomas (HCCs) patients revealed the presence of several distinct HBV integration sites in different human liver disease patients. In one HCC patient the DNA fragment containing the HBV integration also hybridized to an erb B probe. The erb B/HBV co-migrating DNA fragment was cloned and sequenced, and showed that HBV DNA is integrated next to a cellular DNA fragment which is homologous to the tyrosine protein kinase domain of the human epidermal growth factor receptor gene and other cell surface receptor genes. The virus-integrated cellular DNA sequence is expressed in this HCC patient, suggesting a possible role for this gene in hepatocarcinogenesis.     

Parametric study of diethyl phthalate biodegradation

Summary The effects of temperature, dissolved oxygen, and other environmental parameters under both aerobic and anaerobic conditions were investigated using one aerobic and one facultative strain isolated from wastewater treatment plant sludge. Among other results, we found that low dissolved oxygen levels and low temperatures decreased the rate of DEP degradation and the growth rate, and that the facultative strain was much less affected by the lower DO concentrations than the aerobic strain.     

植物群落演替与土壤发展之间的关系

本文运用植物群落中植物优势种的重要值与相对应子群落的土壤特征值直接相关联的分析方法,对湖北宜昌大老岭的桦(Betula)、栎(Quercus)、栗(Castanea)七个群落类型的三个演替途径的土壤动态进行分析,结果表明:在植物群落的演替过程中,土壤中的Ca、pH值减少;离子代换量增加;Na、Mg、NH_4+-N、速效P、速效K、有机质的含量是随着物种的变化而呈不同的趋势。因此,植物群落的演替是生态系统的动态过程。     

农业生态系统中新物种引进的初步探讨

在现有的农业生态系统中,引进某些新物种,往往可以使整个系统的功能发生变化。如果新物种引进得当,则可产生良好的效果,系统功能得以改善,效益提高;反之,则会造成人力、物力、财力的损失,削弱系统的功能,甚至可能遗患无穷。因此,对农业生态系统中     

Transforming growth factor alpha and a PC12-derived growth factor induce neurites in PC12 cells and enhance the survival of embryonic brain neurons.

We have identified and characterized a 5000-Da protein that induces neurite outgrowth from PC12 pheochromocytoma cells, enhances the survival of embryonic rat brain neurons in primary culture, and induces the multiplication of embryonic rat brain astrocytes in primary culture. The factor is produced by a flat cell PC12 variant that expresses the activated ras oncogene after transfection of the gene. The factor resembles transforming growth factor alpha (TGF alpha) and epidermal growth factor (EGF) in that it induces anchorage-independent colony formation of normal rat kidney cells in soft agar and competes with EGF for binding to the EGF receptor. Rat TGF alpha and human TGF alpha also induce neurite outgrowth from PC12 and enhance the survival of embryonic brain neurons. The PC12 variant-derived factor can be distinguished from TGF alpha and EGF immunologically and by migration rates on reversed-phase high-performance liquid chromatography.     

Characterization of the functional properties of env genes from long-term survivors of human immunodeficiency virus type 1 infection.

A small number of persons infected with human immunodeficiency virus type 1 (HIV-1) remain clinically and immunologically healthy for more than a decade after infection. Recent reports suggest that these individuals may be infected with an attenuated strain of HIV-1; however, a common genetic basis for viral attenuation has not been found in all cases. In the present study, we examined the functional properties of the HIV-1 env genes from six long-term survivors. env clones were generated by PCR amplification of proviral env sequences, followed by cloning of the amplified regions into expression vectors. Eight to ten clones from each subject were screened by transient transfection for expression of the envelope precursor glycoprotein, gp160. Those clones expressing gp160 were then cotransfected with an HIV-1 luciferase reporter vector, pNL4-3Env(-)LUC(+) and evaluated for their ability to mediate infection of phytohemagglutinin-activated peripheral blood mononuclear cells in single-cycle infectivity assays. Clones expressing gp160 were identified for all six long-term survivors, indicating the presence of proviral env genes with intact open reading frames. For two subjects, D and DH, the encoded envelope glycoproteins yielded high levels of luciferase activity when pseudotyped onto HIV-1 virions and tested in single-cycle infectivity assays. In contrast, envelope glycoproteins cloned from four other long-term survivors were poorly processed and failed to mediate infection. Sequencing of the gp120/41 cleavage site and conserved gp41 cysteine residues of these clones did not reveal any obvious mutations to explain the functional defects. The functional activity of env clones from long-term survivors D and DH was comparable to that seen with several primary HIV-1 env genes cloned from individuals with disease progression and AIDS. These results suggest that the long-term survival of subjects D and DH is not associated with overt functional defects in env; however, functional abnormalities in env may contribute to maintaining a long-term asymptomatic state in the other four cases we studied.