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L S Lin

Publications and source records attributed to L S Lin.

At least 73 records · Page 4Linked to original sources
PubMed1990

Vanadate promotes reactivation and iontophoresis-induced ocular shedding of latent HSV-1 W in different host animals.

Vanadate is a potent inhibitor of calcium stimulated ATPase, Na, K-ATPase, and may have adrenergic activity. Using the iontophoresis method, we compared vanadate to a BSS control and the standard iontophoresis model (6-hydroxydopamine/epinephrine) by measuring induced ocular shedding of latent HSV-1 in different host animals. Latent trigeminal ganglionic infections were established in Balb/c mice and New Zealand rabbits following corneal inoculation with HSV-1 [W] strain, and later confirmed by cocultivation. Latently-infected animals (greater than 1 month post-infection) were divided into three treatment groups. Each group was iontophoresed with BSS, vanadate 1% or 6-HD 1%, and then treated topically for 10 days with BSS, vanadate or epinephrine respectively. Reactivation and recovery of latent HSV-1 was detected by daily ocular swabbing, plating, and observing progressive viral growth in Vero cells. The vanadate group had more virus-positive eyes than the BSS control group in mice, (8/32 vs. 1/32 P less than .01), and also in rabbits (14/20 vs 6/22 P less than .01). Virus-positive animals and total positive swabs were also higher for vanadate than BSS in both mice and rabbits. Furthermore, while vanadate was associated with fewer virus-positive eyes than 6-HD & EPI (8/32 vs. 17/32 P less than .02) in mice, there were no significant differences in rabbits. We conclude that vanadate promotes ocular shedding of latent HSV-1, and may act through an adrenergic mechanism.

Animals↗
PubMed1989

Histidine-15: an important role in the cytotoxic activity of human tumor necrosis factor.

The amino acids that are required for the cytotoxic activity of recombinant human tumor necrosis factor-alpha (TNF) were investigated by chemical modification and oligonucleotide-directed site-specific mutagenesis. TNF contains three histidine residues, located at positions 15, 73 and 78. The histidine-specific reagent diethylpyrocarbonate (DEP) was used to chemically modify TNF. The chemical inactivation of the in vitro cytotoxic activity of this lymphokine (using murine L929 target cells) was found to be time- and dose-dependent. Inactivated TNF failed to compete with fully bioactive [125I]TNF for human MCF-7 target cell receptors. Mutant polypeptides of TNF were genetically engineered by oligonucoleotide-directed site-specific mutagenesis. The cytotoxicity of a double histidine mutant, in which histidine-73 and histidine-78 were replaced with glutamine, was not altered and was chemically inactivated by DEP. Substituting glutamine for histidine-15 resulted in 10-15% of the wild-type bioactivity. Replacing histidine-15 with either asparagine, lysine or glycine resulted in a biologically inactive molecule. The data show that the histidine residue at position 15 is an amino acid that is required for the cytotoxic activity of TNF.

Amino Acid Sequence↗
PubMed1989

Transcription from the P1 promoters of Micromonospora echinospora in the absence of native upstream DNA sequences.

We demonstrated previously that the 0.4-kilobase DNA fragment from Micromonospora echinospora contains multiple tandem promoters, P1a, P1b, P1c, and P2, which are also functional when cloned into Streptomyces lividans. We now show by in vitro transcription with Streptomyces RNA polymerase that each of these promoters is an authentic initiation site, rather than a processing site for transcripts which initiate further upstream. The DNA sequence requirements for the closely spaced promoters P1a, P1b, and P1c, which are coordinately induced during stationary phase in M. echinospora, were examined by deletional analysis in S. lividans. The P1a and P1b promoters were functional despite deletion of native sequences 5 and 17 base pairs upstream of each initiation site, respectively. Thus, P1a and P1b had greatly reduced upstream DNA sequence requirements compared with typical procaryotic promoters. In contrast, transcription from promoter P1c was significantly decreased when native sequences 34 base pairs upstream were replaced.

Base Sequence↗
PubMed1989

Influence of thermal stress and various agents on the brain edema formation in rats following a cryogenic brain lesion.

The influence of cold stress, heat stress, or various agents on the development of brain edema were assessed in rats following a cryogenic brain lesion. Brain edema was induced by local cold injury to the cortex. Cerebral edema was assessed 0.5, 3.0 or 24 h after a cryogenic brain lesion by measuring the water content of two hemispheres. Pretreatment of animals with sodium pentobarbital (15 or 30 mg/kg, i.p.) or lidocaine (15 mg/kg, i.p.) did not influence the development of brain edema. In addition, pretreatment with an external heat stress (heat exposure of 32 degrees C for 6 h) exaggerated significantly the development of brain edema in the rat following a cryogenic brain lesion. On the other hand, pretreatment of animals with either external cold stress (cold exposure of 8 degrees C for 6 h), glycerol (10% 10 ml, i.p.), mannitol (15% 10 ml, i.p.), gamma-hydroxybutyric acid (300 mg/kg, i.p.), metiamide (5 mg/kg, i.p.), dexamethasone (4 mg/kg, i.p.), aminophylline (100 mg/kg, i.p.), or ketamine (30 mg/kg, i.p.) inhibited significantly the brain edema formation.

Animals↗
PubMed1988

Functional properties of proteins coded by three human alpha-interferon genes and a pseudogene.

We have characterized the functional properties of four highly purified recombinant human class I alpha-interferon subtypes whose biological activities have not been described previously. We selected biological and biochemical activities that may discriminate between different functions of these molecules. We found that the alpha subtypes could be discriminated only by antiviral-host range specificity and natural killer cell activation. Differences in their antiproliferative activity were cell line dependent. Competitive binding, antiproliferative activity in agar, enhancement of expression of HLA-ABC, elevation of 2'-5'-oligoadenylate synthetase levels and enhancement of phosphorylation of the Mr 69,000 protein kinase did not allow discrimination among the alpha I subtypes on the tested cell lines.

2',5'-Oligoadenylate Synthetase↗
PubMed1988

Effect of pregnancy on ritodrine pharmacokinetics.

Dosing regimens for ritodrine are based in large part on pharmacokinetic studies performed with nonpregnant subjects. Pregnancy is characterized by changes in renal blood flow, plasma volume, protein concentration, and hepatic function. These physiologic changes frequently alter drug pharmacokinetics. To define the effect of pregnancy on ritodrine kinetics, we compared ritodrine pharmacokinetics in four pregnant and four nonpregnant rhesus monkeys. Significant differences were demonstrated in the distribution phase half-life (0.40 +/- 0.08 hours in the pregnant monkeys and 0.21 +/- 0.03 hours in the nonpregnant animals), volume of distribution (1.99 +/- 0.94 L/kg in the pregnant monkeys and 4.75 +/- 0.90 L/kg in the nonpregnant animals), plasma clearance (18.8 +/- 7.1 ml/min/kg in the pregnant monkeys and 27.2 +/- 5.0 ml/min/kg in the nonpregnant animals), and disposition half-life (1.8 +/- 0.4 hours in the pregnant monkeys and 3.3 +/- 0.4 hours in the nonpregnant animals). Pregnant animals receiving ritodrine had higher steady-state plasma concentrations than nonpregnant animals (104 versus 53 ng/ml at an infusion rate of 2 micrograms/kg/min). These data indicate that dosing regimens for ritodrine based on studies of nonpregnant subjects may be subject to considerable error.

Animals↗
PubMed1988

Ethylene effect on extensin and peroxidase distribution in the subapical region of pea epicotyls.

In dark grown pea (Pisum sativum) seedlings ethylene causes the triple response in which elongation growth is inhibited, radial growth is promoted, and orientation of shoots to gravity is altered. The distribution of extensin and peroxidase activity in pea epicotyls upon ethylene treatment was studied by tissue printing on nitrocellulose paper. It was found that the localization of extensin and peroxidase activity changes after 72 and 96 hours of ethylene treatment. In untreated plants, peroxidase activity is detected only in the vascular bundles. Nonetheless, after 72 and 96 hours of ethylene treatment peroxidase activity is hardly detected in the vascular system but present in the epidermal and cortical cells. Extensin increases in the epidermal and cortical cells upon ethylene treatment but it also appears in the vascular system when peroxidase activity is no longer detected.

Journal Article↗
PubMed1987

DNA synthesis is initiated at two positions within the origin of replication of plasmid R1162.

DNA synthesis of broad host-range plasmid R1162 is initiated from two positions, flanking a large (40 bp stem, 40 bp loop) inverted repeat. Each start-point is located within a highly conserved, but oppositely oriented, 10 base-pair sequence. Synthesis from the two positions converges within the intervening inverted repeat. An analysis of deletions suggests that both start positions must be present for synthesis. A model describing possible early events in replication of plasmid R1162 is presented.

Base Sequence↗
PubMed1987

Cytostatic and cytolytic effects of human recombinant tumor necrosis factor on human renal cell carcinoma cell lines derived from a single surgical specimen.

The purpose of this study was to determine whether human tumor cell lines derived from a single tumor exhibit heterogeneous responses to the anti-tumor effects of human recombinant tumor necrosis factor (h-r-TNF). Several cell lines with different metastatic propensities have been established in culture from a single surgical specimen of a human renal cell carcinoma following different selection procedures in nude mice. The cell lines exhibited significant differences in in vitro susceptibilities to cytotoxic effects of TNF. Kinetic analysis of the interaction of TNF with susceptible renal carcinoma cells demonstrated that a short 30 min interaction of TNF with the cells is sufficient to produce significant lysis 72 hr later. One cycle of exposure of sensitive cells to h-r-TNF did not produce cells resistant to it, nor did the degree of sensitivity to h-r-TNF vary after one passage of the cells in nude mice. Tumor cell resistance to the effects of TNF did develop spontaneously after prolonged cultivation in culture. We conclude that tumor cells derived from a single human renal cell carcinoma exhibit a heterogeneous response to the cytotoxic effects of h-r-TNF.

Animals↗
PubMed1987

Use of a sensitive receptor binding assay to discriminate between full-length and truncated human recombinant tumor necrosis factor proteins.

A radioreceptor assay (RRA) capable of detecting picomolar concentrations of human recombinant tumor necrosis factor (TNF) was used to compare the relative binding affinities of genetically engineered full-length and truncated TNF proteins. The specific cell-surface receptors for TNF present on the human cervical carcinoma cell line ME-180 were characterized as having a Kd of 0.2 nM and a density of 2700 sites/cell. Conditions were then defined for an RRA that maximized the specific binding of 125I-TNF to this adherent cell line. Incubation of ME-180 cells with 125I-TNF at 37 degrees C in the presence of 0.02% sodium azide resulted in a 4-fold increase in assay sensitivity and a doubling of specific counts bound, as compared to binding done at 4 degrees C with or without sodium azide. Inhibition of receptor-ligand internalization under these conditions was a likely reason for the increases. This system was utilized to compare low concentrations of the full-length TNF protein and a genetically altered TNF protein (mutein) which lacks the 10 N-terminal amino acids and contains an N-terminal methionine. Previous studies showing the truncated TNF to be 2- to 3-fold lower in cytotoxic activity on a variety of tumor cell lines were corroborated by our findings that the mutein was also three and one-half times lower in relative affinity for the TNF receptor on ME-180 cells. These results suggest a possible role for these residues in receptor binding and illustrate the use of a highly sensitive RRA for the evaluation of TNF molecules altered by recombinant DNA technology.

Amino Acid Sequence↗
PubMed1987

Biological effects of recombinant human tumor necrosis factor and its novel muteins on tumor and normal cell lines.

We investigated optimal conditions for cytotoxicity to tumor cell lines by recombinant human tumor necrosis factor (rhTNF) and the effect of amino-terminal deletions on the bioactivity of the rhTNF molecule. Two of four deletion muteins (-4 and -7) of rhTNF exhibit 2- to 3-fold enhancement of cytotoxicity/cytostasis against a variety of human carcinomas, a fibrosarcoma, and a melanoma cell line with no toxicity on normal fibroblastic and epithelial cultures. Of the two other muteins the -8 displayed equivalent and/or increased cytotoxicity/cytostasis while the -10 was consistently less cytotoxic than the parent on the same cell lines. Continuous exposure to TNF for greater than or equal to 96 h led to maximal cytotoxicity to tumor lines (99.99% with L929 cells) with no evidence of recovery. Pretreatment with actinomycin D (0.003-10 micrograms/ml for 1 h) rendered 82% of rhTNF-resistant cell lines (both tumor and normal) susceptible to its cytotoxic action within 24 h. However, the highest nontoxic concentrations of Actinomycin D necessary for rendering normal cell lines susceptible to TNF action were about 10-3000-fold higher than those necessary for converting resistant tumor cell lines. Similarly, preinfection of L929 cells with vesicular stomatitis virus (multiplicity of infection, 10(-2)-10(-4) for 1 h) rendered the cells 2-10-fold more susceptible to the cytotoxic action of rhTNF in 18 h. Our data suggest that rhTNF and its muteins represent potentially useful anticancer agents; however, adequate dosing and prolonged exposure may be critical in demonstrating cytotoxicity/cytostasis. The data also show that although normal and tumor cell lines became susceptible to cytotoxicity by rhTNF and actinomycin D, combination therapy of the two agents may be possible at defined concentrations.

Amino Acid Sequence↗
PubMed1987

The 20 bp, directly repeated DNA sequence of broad host range plasmid R1162 exerts incompatibility in vivo and inhibits R1162 DNA replication in vitro.

The broad host range plasmid R1162 contains a directly repeated, 20 bp DNA sequence in the region of the plasmid required in cis for replication and maintenance. This sequence has been chemically synthesized and cloned, and shown to be sufficient for expression of plasmid incompatibility. The sequence also inhibits replication of R1162 DNA in a cell-free system. The strengths of both these effects are determined by the number of direct repeats (DRs) present, and are also affected to similar degrees by different mutations within the repeated sequence. Several of the mutations were tested for their effect in cis on plasmid maintenance in the cell, and one was found to cause an increase in plasmid copy number. The results suggest that the direct repeats exert incompatibility by inhibiting DNA replication, presumably because they are the binding sites for a limiting essential protein.

Base Composition↗
PubMed1987

Involvement of both opiate and catecholaminergic receptors of ventromedial hypothalamus in the locomotor stimulant action of thyrotropin-releasing hormone.

To explore the mode of the locomotor stimulant action of thyrotropin-releasing hormone (TRH), rats with or without administration of opiate or catecholaminergic receptor antagonists were infused with TRH through previously implanted hypothalamic cannula. Administration of TRH, but not the normal saline or TSH, into the ventromedial hypothalamus caused an enhancement in both the gross movements (including stimulation of forward locomotion, head and body rearing) and fine movements (including increased grooming and head swaying). The locomotor stimulant action provoked by TRH was antagonized by pretreatment of ventromedial hypothalamus with either an alpha-adrenergic receptor antagonist (yohimbine), a dopaminergic receptor antagonist (haloperidol) or an opiate receptor antagonist (naloxone), but not with a beta-adrenergic receptor antagonist (propranolol). The results indicate that all the adrenergic, dopaminergic and opiate receptors in the ventromedial hypothalamus are involved in the TRH-induced hyperactivity in the rat.

Animals↗
PubMed1987

Bombesin-induced hypothermia: possible involvement of cholinergic and dopaminergic receptors in the rat hypothalamus.

The thermal responses of rats which were pretreated with 5,7-dihydroxytryptamine to deplete hypothalamic 5-hydroxytryptamine, 6-hydroxydopamine to deplete hypothalamic catecholamines, phentolamine and propranolol to inhibit adrenergic receptors, haloperidol to inhibit dopamine receptors, or atropine to inhibit cholinergic receptors, to intrahypothalamic administration of bombesin were compared with those of control rats. The bombesin-induced hypothermia was attenuated by pretreatment of the rats with either hypothalamic dopamine depletion or receptor blockade, or hypothalamic cholinergic receptor blockade. The reduction in the bombesin-induced hypothermia in the treated rats was due to the reduction of metabolic and vasomotor response. The data indicate that bombesin may act on hypothalamic dopamine and/or cholinergic receptor mechanisms to induce hypothermia by promoting a reduction in metabolic heat production and an enhancement in heat loss in rats.

Animals↗
PubMed1987

Murine monoclonal antibodies defining neutralizing epitopes on tumor necrosis factor.

A panel of four monoclonal antibodies (MAbs) was generated against recombinant human tumor necrosis factor-alpha (rTNF). These MAbs immunoprecipitate 125I-labeled rTNF, block binding of 125I-labeled rTNF to L929 mouse fibroblasts, and neutralize in vitro cytotoxicity of rTNF and native TNF (nTNF) in the L929 cytotoxicity assay. They define distinct epitopes closely associated with the receptor binding site of rTNF. In Western analysis they bind to both monomeric and dimeric rTNF. Two MAbs recognizing distinct epitopes were used to develop a 'sandwich' enzyme immunometric assay (EIMA) to measure rTNF levels in human serum and other fluids.

Animals↗