Excitatory and inhibitory transmission from the optic tectum to nucleus isthmi and its vicinity in amphibians

Intracellular recordings were made from nucleus isthmi (NI) and its vicinity in toads (Bufo bufo gargarizans) in response to electrical stimulation of the bilateral optic tract. The results suggest that NI mainly receives its excitatory input from the ipsilateral tectum and its inhibitory input from the contralateral tectum. Tegmental cells in a region medioventral to NI were usually characterized by strong spontaneous activity and an excitatory-inhibitory sequence of postsynaptic potentials in response to stimulation of either side of the bilateral optic tract. Sixty of the recorded cells were stained with Lucifer yellow to show their morphological features and anatomical positions within NI and its vicinity.

Hepatocellular carcinoma: update on diagnosis and treatment

In this review, the current approach to the screening, diagnostic evaluation, staging, and treatment for hepatocellular carcinoma (HCC) is outlined. The serum alpha-fetoprotein (AFP) level and abdominal ultrasonography (US) remain the cornerstones of screening protocols for HCC. Other serum marker proteins, such as abnormal serum prothrombin (PIVKA-II), when used in conjunction with AFP, can increase the yield for HCC. For diagnosis and staging of HCC, other imaging modalities employed include CT scan, infusion hepatic angiography, CT with arterial portography or iodized oil enhancement, MRI with contrast enhancement, intraoperative US, and US-guided fine-needle aspiration cytology and biopsy. Treatment options which have afforded some improvement in survival and tumor regression include surgical resection, orthotopic liver transplantation, percutaneous injection of ethanol, arterial chemoembolization, cryotherapy, and systemic or regional chemotherapy. Despite these advances, the diagnosis of HCC still portends a dismal prognosis.

Enhanced resistance to nuclease degradation of nucleic acids complexed to asialoglycoprotein-polylysine carriers

We have previously shown targeting of DNA to hepatocytes using an asialoorosomucoid-polylysine (AsOR-PL) carrier system. The AsOR-PL conjugate condenses DNA and facilitates entry via specific receptor-ligand interactions. In these studies, our objective was to determine if AsOR-PL conjugates protect bound DNA from nuclease attack. Double-stranded plasmid or single-stranded oligonucleotide DNA, alone or bound to conjugate, was incubated under conditions mimicking those encountered during in vitro and in vivo transfections. The results showed that complexed DNA was effectively protected from degradation by serum nucleases. Degradation of single-stranded oligonucleotides was inhibited 3- to 6-fold in serum during 5 hours of incubation. For complexed plasmids, greater than 90% remained full-length during 1.5 and 3 hour incubations in serum or culture medium containing 10% serum, respectively. Uncomplexed plasmid was completely degraded after 15 minutes in serum or 60 minutes in medium. In cell lysates, the conjugate was not effective in inhibiting endonuclease activity; plasmids were readily converted from supercoiled to open circular and linear forms. However, the resultant nicked forms were substantially protected from further degradation during one hour of incubation compared to plasmid alone. Under all conditions complexed DNA did not readily dissociate from the conjugate. Overall, for both single and double-stranded DNA, AsOR-PL conjugates conferred substantial protection from nuclease degradation.

Depolymerization of hepatocellular microtubules after partial hepatectomy

Asialoglycoproteins (ASG) are internalized by hepatocytes by ASG receptor (ASGR)-mediated endocytosis. We have shown previously that when a plasmid DNA, pAlb(9-12)CAT (expressing chloramphenicol acetyltransferase driven by an albumin promoter enhancer), was complexed with an ASG-polylysine conjugate and injected intravenously in rats, 80% of the DNA was internalized by the liver. In normal recipient rats, over 95% of the internalized DNA was degraded in 4 h; the plasmid was undetectable after 48 h. In contrast, when 66% hepatectomy was performed 20 min after DNA administration, the internalized DNA persisted for several weeks in cytoplasmic vesicles (Chowdhury, N. R., Wu, C. H., Wu, B. Y., Yerneni, P. C., Bommineni, V. R., and Chowdhury, J. R. (1993) J. Biol. Chem. 268, 11265-11271). Since microtubules are required for the translocation of ligand-containing endosomes to lysosomes, the site of ligand degradation, we hypothesized that persistence of the endocytosed DNA might be related to changes in microtubular structure and function. To test this hypothesis, we examined hepatocellular microtubules by immunofluorescence confocal microscopy. Liver from untreated rats or sham-operated controls showed a network of fibrillar microtubules throughout the cytoplasm. The extent of the microtubular network was substantially reduced 3-6 h after 66% hepatectomy. By 24 h, microtubules had regenerated. Intraportal infusion of cycloheximide (250 mg/kg body weight) 15 min before 66% hepatectomy, prevented microtubular disruption, indicating that protein synthesis is required for this process. Immunotransblot analysis showed that hepatic alpha-tubulin concentration remained unchanged through microtubular disassembly and subsequent reassembly, which is consistent with conservation and reutilization of tubulin released by depolymerization of microtubules.

Overexpression of human methylmalonyl CoA mutase in mice after in vivo gene transfer with asialoglycoprotein/polylysine/DNA complexes

Methylmalonic acidemia resulting from genetic deficiency of methylmalonyl CoA mutase (MCM) is an often fatal metabolic disease. Somatic gene therapy for this disorder may require gene replacement in the liver. We describe overexpression of MCM in the liver of mice after in vivo gene delivery using asialoglycoprotein/polylysine/DNA (ASO/PL/DNA) targeted delivery to the liver of plasmids expressing recombinant MCM. After intravenous administration of the ASO/PL/DNA complex, the vector sequences are cleared from the blood with t1/2 = 2.5 min and > 95% of the vector is taken up by the liver. Vector sequences are cleared from the liver with t1/2 = 1.0-1.3 hr. MCM enzyme activity in the liver increases to levels 30-40% over baseline 6-24 hr after injection. No acute or chronic toxicity was observed. This net level of expression is likely to be therapeutic for MCM if the complex could be administered repetitively to treat acute episodes of life-threatening acidosis or establish a steady-state level of MCM activity. Repetitive administration of the ASO/PL/DNA complexes in mice was associated with formation of antibodies against asialo-orosomucoid and the asialo-orosomucoid complex but not against DNA.

Preparation of asialoorosomucoid-polylysine conjugates

Asialoorosomucoid-polylysine (ASOR-PL) conjugates have been recently developed as carriers of electrostatically bound DNA for targeted delivery to the hepatic asialoglycoprotein receptor (ASGPr) for gene therapy. Using acid-urea gel electrophoresis we have found that previously reported procedures for the fractionation of ASOR-PL conjugates do not efficiently remove noncovalently bound polylysine (PL) from ASOR-PL. DNA complexes prepared with these conjugates have low solubilities, which limits their usefulness for subsequent experimentation, particularly in vivo. For ASOR-PL made by carbodiimide-mediated crosslinking with 5-kDa PL, dialysis against 1 M guanidine hydrochloride is effective to remove the low molecular weight unbound PL. Dialysis is not feasible when using higher molecular weight PLs, but preparative elution acid-urea gel electrophoresis was used to isolate crude ASOR-PL fractions free of unbound PL. ASOR-PL freed of PL by dialysis or electrophoresis was further fractionated by cation-exchange HPLC on carboxymethyl-functionalized columns eluted with a mixed pH-salt gradient. Early-eluting ASOR-PL fractions isolated by a combination of preparative elution acid-urea gel electrophoresis and cation-exchange HPLC were found to be preferred for the formation of soluble DNA complexes.

Incorporation of adenovirus into a ligand-based DNA carrier system results in retention of original receptor specificity and enhances targeted gene expression

Adenovirus type 5 was modified by coupling an asialoglycoprotein-polylysine conjugate to the virus by reactions that activate carbohydrate residues. Wild-type virus modified in this manner had greatly decreased infectivity toward normally susceptible HeLa S3 (asialoglycoprotein receptor (-)) and SK Hep1 (asialoglycoprotein receptor (-)) cells leaving 91 and 86% viable, respectively, after 48 h. However, with Huh 7 (asialoglycoprotein receptor (+)) cells, modified virus retained its infectivity leaving only 19% of cells viable under identical conditions. Modified virus was complexed to DNA in the form of a plasmid, pSVHBV surf, containing the gene for hepatitis B surface antigen as a marker of gene expression. Huh 7, receptor (+), cells treated with modified wild type, and modified replication-defective d1312 virus complexed to DNA raised antigen levels by approximately 13- and 30-fold, respectively, compared with asialoglycoprotein-polylysine DNA complex alone. Competition with a large excess of an asialoglycoprotein blocked the enhancement by more than 95%. Using a beta-galactosidase marker gene, the number of cells transfected by modified virus was found to be 200-fold higher than complex alone. Yet, specificity was retained exclusively for asialoglycoprotein receptor-bearing cells. These data indicate that adenovirus can be chemically modified by coupling ligands resulting in targeted gene expression dictated specifically by receptor recognition of the attached ligand.

Gene therapy: applications to the treatment of gastrointestinal and liver diseases

There has been much progress in our understanding of molecular mechanisms in the pathogenesis of inherited metabolic disorders. In addition, powerful new molecular techniques have made possible phenotypic alterations by delivery of foreign genes to target cells. As a result, concepts and methods that would have been considered purely science fiction 10 years ago can now be found in human clinical trials engaged in the treatment of these disorders. In this review, we have attempted to provide an introduction and survey of the topic of gene therapy, with specific examples of laboratory and clinical achievements to date, and highlights on potentials for applications in digestive diseases.

Effect of acetylcholine and NMDA on neurones of avian tectum and nucleus isthmi

In the present study the effects of microiontophoretically applied acetylcholine and NMDA were investigated on neurones of the avian nucleus isthmi. Whereas acetylcholine affected equally cell firing in the two parts of the nucleus, the magnocellular (Imc) and the parvocellular (Ipc) division, the effect of NMDA was predominantly confined to Ipc. The NMDA induced firing was specifically blocked by the antagonist CPP, while having no effect on acetylcholine. Our results support earlier findings that isthmo-tectal feedback loops can be modulated by distinct mechanisms in separate divisions of nucleus isthmi.

GABA as an inhibitory transmitter in the pigeon isthmo-tectal pathway

In the present investigation, the effects of inhibitory amino acids and their antagonists were tested on isthmo-tectal projection in the pigeon. The majority of superficial tectal cells are inhibited following stimulation of the parvocellular division of nucleus isthmi. A smaller portion of tectal cells showed excitatory responses followed by an inhibitory period. Both inhibitory mechanisms are blocked by the specific gamma-aminobutyric acid (GABA)-antagonist bicuculline but not by strychnine. Our results support the idea that GABA acts as an inhibitory neurotransmitter in the pigeon isthmo-tectal pathways.

[Quality control of xiaoqinglong mixture]

TLC was used to detect ephedrine, paeoniflorin, glycyrrhizic acid, cinnamic aldehyde and xixin volatile oils in Xiaoqinglong mixture. Paeoniflorin was determined by HPLC. The average recovery is 99.42%, and RSD 0.23%.

[Further studies on the depressor effect of erythrocytic antihypertensive factor]

We previously demonstrated the presence of a long-acting antihypertensive factor (AHF) in the erythrocytes of essential hypertensive subjects (EHS). The present investigation demonstrates further that the AHF is also capable of producing a rapid and transient blood pressure lowering effect in stroke prone spontaneously hypertensive rats (from 26.8 +/- 1.7 to 20.1 +/- 1.5 kPa by 10-30 s, P < 0.001). An even more stronger antihypertensive effect could be found if the AHF prepared from normal subjects or rats was used. We also found that some hypertensive factor was present in EHS plasma, but not in normal subjects. The results of the present paper suggest that AHF deficiency and higher level of pressor substance may play an important role in the development of essential hypertension.

Fate of DNA targeted to the liver by asialoglycoprotein receptor-mediated endocytosis in vivo. Prolonged persistence in cytoplasmic vesicles after partial hepatectomy

After intravenous injection, DNA complexed with asialoglycoprotein-polylysine conjugates is endocytosed by hepatocytes via asialoglycoprotein receptors and is expressed transiently. Long term persistence and expression occurs when partial hepatectomy is performed after gene delivery. To determine the intracellular location of the persisting DNA, we transferred a plasmid expressing bacterial chloramphenicol acetyltransferase into the liver of rats in vivo by asialoglycoprotein receptor-mediated endocytosis. The internalized DNA was measured by Southern blot. Twenty min after administration, 80-85% of the plasmid appeared in the liver, 80% of which was within hepatocytes (12,000-18,000 copies/hepatocyte). In sham-operated control rats, the transgene concentration decreased to 8-12 and 2-4% of the initial levels in 4 and 24 h, respectively, and became undetectable at 7 days. In rats subjected to 66% hepatectomy 20 min after DNA administration, 20, 9, and 7% of the plasmid in the residual liver persisted at 4 h, 24 h, and 7 days, respectively. Liver homogenates were fractionated by differential centrifugation and Percoll gradient centrifugation. In 66% hepatectomized rats, the plasmid persisted in an undegraded, transfection-competent form in plasma membrane/endosome-enriched fractions throughout the duration of the experiment (7 days), indicating that cytoplasmic vesicles are the main site of persistence of the endocytosed DNA.

Molecular characterization of a novel form of (A gamma delta beta)zero thalassemia deletion in a Chinese family

We have identified and molecularly characterized a novel deletion in the beta-globin gene cluster that is associated with elevated fetal hemoglobin in the adult. The propositus is a homozygote from the Yunnan province of China. The deletion spans about 90 kb of DNA and removes the A gamma, delta, and beta-globin genes. The 5' breakpoint of the deletion is located about 0.13 kb upstream from the A gamma-globin gene, whereas the 3' breakpoint is located about 66 kb downstream from the beta-globin gene, about 13 kb upstream from the breakpoint of the Chinese (A gamma delta beta)zero-thalassemia. Heterozygotes for this Yunnanese form of (A gamma delta beta)zero-thalassemia express between 9% and 17% of fetal hemoglobin, whereas the homozygote present with a mild anemia (Hb = 10.7 g/dl). Comparison of the sites of 3' breakpoints of the Yunnanese and the Chinese (A gamma delta beta)zero-thalassemia mutants is compatible with the hypothesis that an enhancer element is located between the 3' breakpoints of these two mutants. Juxta-position to the G gamma gene of this element may be responsible for the efficient gamma-gene expression in the Yunnanese mutant.

Postsynaptic potentials and morphological features of tectal cells in homing pigeons

In this study postsynaptic potentials responding to the electrical stimulation of the optic nerve and the nucleus isthmi pars parvocellularis (Ipc) were intracellularly recorded from 86 tectal cells in pigeons, 13 of which were marked with Lucifer yellow (LY). According to types of postsynaptic potentials and their succession, the postsynaptic responses could be classified into four types: excitatory postsynaptic potential (EPSP)-inhibitory postsynaptic potential (IPSP) sequence (EI type), E, I and IE types. Among them, E or EI responses were mainly produced to the optic nerve stimulation, while the electrical stimulation of the Ipc elicited I responses in more than half the recorded cells. LY-marked tectal cells included five ganglionic cells, four pyramidal cells, two bipolar cells and two stellate cells. The ganglionic cells were mainly located in tectal layers III and IV, whereas the others were in layer II. It appears from both intracellular recordings and fluorescent markings that there is some correlation between the morphological features and the postsynaptic response types of tectal cells.

Targeted transfection and expression of hepatitis B viral DNA in human hepatoma cells

A soluble DNA carrier system consisting of an asialoglycoprotein covalently linked to poly-L-lysine was used to bind DNA and deliver hepatitis B virus (HBV) DNA constructs to asialoglycoprotein receptor-positive human hepatoma cells. 4 d after transfection with surface or core gene expression constructs, HBsAg and HBeAg in the media were measured to be 16 ng/ml and 32 U/ml per 10(7) cells, respectively. Antigen production was completely inhibited by the addition of an excess of asialoorosomucoid. On the other hand, asialoglycoprotein receptor-negative human hepatoma cells, SK-Hep1, did not produce any viral antigens under identical conditions after incubation with HBV DNA complexed to a conjugate composed of asialoorosomucoid and poly-L-lysine. Using a complete HBV genome construct, HBsAg and HBeAg levels reached 16 ng/ml and 16 U/ml per 10(7) cells, respectively. Northern blots revealed characteristic HBV RNA transcripts including 3.5-, 2.4-, and 2.1-kb fragments. Intracellular and extracellular HBV DNA sequences including relaxed circular, linear and single stranded forms were detected by Southern blot hybridization. Finally, 42-nm Dane particles purified from the spent cultures medium were visualized by electron microscopy. This study demonstrates that a targetable DNA carrier system can transfect HBV DNA in vitro resulting in the production of complete HBV virions.

Lipocytes from fibrotic rat liver have an impaired feedback response to procollagen propeptides

Procollagen propeptides have been previously shown to be taken up by cultured fibroblasts and to inhibit collagen production at translational and transcriptional levels. In hepatic fibrosis, Ito cells are thought to be major contributors to collagen overproduction. We wondered whether an impaired response to procollagen propeptides by Ito cells from fibrotic liver could be a mechanism involved in collagen overproduction in hepatic fibrosis. In the presence of type I procollagen carboxy-terminal propeptide (200 nM), collagen production by Ito cells from normal rats was significantly decreased to 62.0% of control, whereas collagen production by Ito cells from two models of hepatic fibrosis in the rat, bile duct ligation and carbon tetrachloride treatment, was not significantly changed (102.4 and 102.6% of controls, respectively). By measurement of type I procollagen mRNA levels, this difference in response to procollagen carboxy-terminal propeptide was determined to occur at a pretranslational level. The rates of uptake, transfer to the nuclear compartment, and degradation of procollagen propeptide were not significantly different in Ito cells from normal and fibrotic liver.