Nucleotide excision repair by dual incisions in plants

Plants use light for photosynthesis and for various signaling purposes. The UV wavelengths in sunlight also introduce DNA damage in the form of cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts [(6-4)PPs] that must be repaired for the survival of the plant. Genome sequencing has revealed the presence of genes for both CPD and (6-4)PP photolyases, as well as genes for nucleotide excision repair in plants, such as Arabidopsis and rice. Plant photolyases have been purified, characterized, and have been shown to play an important role in plant survival. In contrast, even though nucleotide excision repair gene homologs have been found in plants, the mechanism of nucleotide excision repair has not been investigated. Here we used the in vivo excision repair assay developed in our laboratory to demonstrate that Arabidopsis removes CPDs and (6-4)PPs by a dual-incision mechanism that is essentially identical to the mechanism of dual incisions in humans and other eukaryotes, in which oligonucleotides with a mean length of 26–27 nucleotides are removed by incising ∼20 phosphodiester bonds 5′ and 5 phosphodiester bonds 3′ to the photoproduct.Plants and other organisms that depend on photosynthesis are, by necessity, exposed to more sunlight than other organisms that are chemotrophs or heterotrophs. Hence, plants are expected to receive more exposure to UV wavelengths of light than other organisms. The genotoxic effects of UV are somewhat mitigated by the reflection of UV by the waxy leaf surface and absorbance of UV by the intracellular pigments that are present at high concentration in plant cells, including carotenoids and flavonoids. Nevertheless, plants still receive considerable amounts of DNA-damaging UV radiation and therefore must have the means to cope with the damage to ensure their survival. Indeed, DNA sequencing has revealed that plant genomes contain genes that are homologous to the genes of all major DNA repair pathways, including photoreactivation, nucleotide excision repair, base excision repair, and recombination/double-strand break repair (1–6).However, biochemical studies of these DNA repair mechanisms have been limited. Of significance, Arabidopsis photolyases have been expressed in heterologous systems, purified, and characterized (7–9). Similarly, some of the enzymes of the base excision repair and recombination/double-strand break repair systems have been studied. In contrast, there have been no mechanistic studies on plant nucleotide excision repair, although it is known that plants can remove cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts [(6-4)PPs] in a photolyase-independent manner (6, 10, 11), presumably by nucleotide excision repair. Here, we have used an Arabidopsis cell line and the in vivo excision assay recently developed in our laboratory (12–14) to demonstrate that Arabidopsis removes these photoproducts by dual incisions in a manner that is virtually identical to human nucleotide excision repair.     

Retention of cocaine abusers in outpatient psychotherapy.

Retention in outpatient psychotherapy of 148 crack and cocaine abusers was examined. The clients were predominantly Black (63%) and Hispanic (21%), predominantly male (87%), and the majority (66%) had completed no more than 12 years of high school. Clients entered treatment in a low-cost treatment center in New York City between June 1987 and November 1988. Forty-two percent (62) of the subjects were seen for one or two research interviews only, and did not return to begin therapy. Of the 86 persons who came to at least one therapy session, 30% (26) dropped out before the third session, 28% (24) dropped out between the third and fifth sessions, and 42% (36) were retained for six or more sessions. Short-term and longer-term retentions were analyzed separately, using a battery including sociodemographic variables, treatment history, psychiatric symptomatology, number of arrests, and drug use variables. None of the variables considered was significantly related to short-term retention. There were large although not significant differences in longer term retention by therapist. Longer-term retention was associated significantly with being White (contrasted with being Black) and being young. Nonsignificant but large associations were found between longer-term retention and having few arrests, being Hispanic (contrasted with being Black), and having low SCL-90 scores. Results are compared with previous findings about retention in drug and alcohol treatment. It is suggested that future research on retention in treatment focus less on client variables and more on therapist and program variables.     

Identification and functional characterization of melatonin Mel 1a receptors in pancreatic beta cells: potential role in incretin-mediated cell function by sensitization of cAMP signaling

Melatonin receptors are expressed within the pancreatic islets of Langerhans, and melatonin induces a direct effect on insulin secretion ex-vivo. Here, we report the endogenous expression of the melatonin Mel 1a receptor in the INS-1 pancreatic beta cell line. Pharmacological characterization of the receptor using a CRE-luciferase reporter gene demonstrated its functional activity in INS-1 cells, displaying the characteristic signaling properties of the G(i/o) coupled receptor. Acute melatonin treatment of INS-1 cells in the presence of either forskolin or the incretin hormone glucagon-like peptide 1 (GLP-1) caused an attenuation of the responses in insulin secretion, insulin promoter activity, and CRE mediated gene expression, consistent with its effects in inhibiting cAMP mediated signal transduction. However, prolonged exposure (12 h) of INS-1 cells to melatonin treatment resulted in a sensitization of cAMP mediated responses to forskolin and GLP-1. Insulin secretion, insulin promoter activity and CRE mediated gene expression levels were augmented compared with responses without melatonin pre-treatment in INS-1 cells. In isolated rat islets, insulin secretion was enhanced following melatonin pre-treatment both in the absence and presence of GLP-1 or forskolin. This phenomenon reflects observations reported in other cell types expressing the melatonin Mel 1a receptor, and may represent the first evidence of a specific physiological role for melatonin-induced sensitization.     

Slow release theophylline in patients with airways obstruction with particular reference to the effects of food upon serum levels

Eighteen patients with airways obstruction were given slow release theophylline and were then investigated to determine the influence of a standard meal upon the serum levels achieved over the ensuing 12-hour period. After food the peak to trough differences were decreased and the serum levels were significantly lower over the first 6 hours. In this study, the patients were given 10 mg/kg/day of slow release theophylline and none subsequently was found to have toxic levels, therefore this was considered to be a reasonable dose with which to initiate therapy in adults with uncomplicated airflow limitation. However even under the strictly controlled conditions of the study there were wide variations between individuals in the blood levels achieved and serum monitoring is necessary to use theophylline in an optimal fashion.     

Evaluation of the safety and efficacy of multiple doses of azelastine to adult patients with bronchial asthma over time

Azelastine is a new oral antiasthma agent with bronchodilating and antiallergic properties. This 12-wk study compared azelastine (2, 4, 6, and 8 mg) and placebo given twice a day in asthmatics 12 to 60 yr of age requiring daily bronchodilator therapy. Patients were allowed albuterol aerosol, short-acting theophylline, and pseudoephedrine only as needed. The study was completed by 221 asthmatic subjects. No significant differences in symptoms, medication, or pulmonary function existed between groups at baseline. Analysis of the zero hour FEV1 before azelastine administration on eight occasions during the 12 wk of therapy indicated an increasing slope for azelastine 6 mg that was statistically different from that of placebo; similarly, the slope for azelastine 4 mg showed the same trend, but it did not reach statistical significance. All azelastine groups had significant reductions of as-needed medication after 1 wk; only in the 4-mg and 6-mg groups was this reduction sustained for 12 wk. Asthma symptom scores and peak expiratory flow measurements remained stable in the azelastine groups despite significant reductions in concomitant medication administration. Side effects were minor and included: altered taste (30.1 to 51.9%), drowsiness (6.0 to 16.9%), and dry mouth (3.8 to 6.1%). The occurrence of these adverse events decreased with time throughout the study.(ABSTRACT TRUNCATED AT 250 WORDS)     

Developmental Aspects of the Endocrine Pancreas

Reviews in Endocrine and Metabolic Disorders -     

A specific LTD4/LTE4-receptor antagonist improves pulmonary function in patients with mild, chronic asthma

LY171883 is a new selective LTD4/LTE4-receptor antagonist. To evaluate the efficacy of LY171883, we studied 138 nonsmoking asthmatic patients, 18 to 65 yr old, in a double-blind, randomized block-design study. All patients were required to demonstrate a greater than or equal to 15% increase in FEV1 after inhaled bronchodilator use and were then randomly assigned to either LY171883 (600 mg) or placebo twice daily for 6 weeks. Assessment of efficacy was measured by inhaled metaproterenol use (mg/wk), symptoms, twice-daily peak expiratory flow, and weekly FEV1 measurements. LY171883-treated patients had improved FEV1 values upon completion of the treatment period compared with placebo recipients (p = 0.003). Metaproterenol use decreased in both groups, but treatment differences, though not statistically significant, favored LY171883 (p = 0.089). Of patients who used at least 23 mg/wk of metaproterenol (36 inhalations) at initiation of the study, those who received LY171883 used significantly less metaproterenol than those who received placebo (p = 0.007). LY171883 was well tolerated and reduced the need for a bronchodilator drug while improving pulmonary function. Results of this study support the hypothesis that leukotrienes LTD4 and/or LTE4 may be important in the pathogenesis of asthma in humans.     

Interleukin-10 promoter polymorphisms in rheumatoid arthritis and Felty's syndrome

OBJECTIVE: To examine whether promoter polymorphisms associated with variation in interleukin-10 (IL-10) production are relevant to the development of rheumatoid arthritis (RA) or Felty's syndrome (FS). METHODS: DNA was obtained from 44 FS patients, 117 RA patients and 295 controls. The promoter region between -533 and - 1120 was amplified by polymerase chain reaction, and polymorphisms detected by restriction enzyme digest or sequence-specific oligonucleotide probing. RESULTS: We found no significant difference in allele or haplotype frequencies between the groups. CONCLUSION: There is no association between FS or RA and these recently identified IL-10 promoter polymorphisms. Other genetic or environmental factors could explain the alterations in IL-10 levels seen in these conditions.