High-density hapten labeling and HRP conjugation of oligonucleotides for use as in situ hybridization probes to detect mRNA targets in cells and tissues

Circadian Synchronization of Feeding Attenuates Rats' Food Restriction-Induced Anxiety and Amygdalar Thyrotropin-Releasing Hormone Downregulation

Anxiety is a common comorbidity of obesity, resulting from prescribing long-term caloric restriction diets (CRDs); patients with a reduced food intake lose weight but present anxious behaviors, poor treatment adherence, and weight regain in the subsequent 5 years. Intermittent fasting (IF) restricts feeding time to 8 h during the activity phase, reducing patients' weight even with no caloric restriction; it is unknown whether an IF regime with ad libitum feeding avoids stress and anxiety development. We compared the corticosterone blood concentration between male Wistar rats fed ad libitum or calorie-restricted with all-day or IF food access after 4 weeks, along with their anxiety parameters when performing the elevated plus maze (EPM). As the amygdalar thyrotropin-releasing hormone (TRH) is believed to have anxiolytic properties, we evaluated its expression changes in association with anxiety levels. The groups formed were the following: a control which was offered food ad libitum (C-adlib) or 30% of C-adlib's energy requirements (C-CRD) all day, and IF groups provided food ad libitum (IF-adlib) or 30% of C-adlib's requirements (IF-CRD) with access from 9:00 to 17:00 h. On day 28, the rats performed the EPM and, after 30 min, were decapitated to analyze their amygdalar TRH mRNA expression by in situ hybridization and corticosterone serum levels. Interestingly, circadian feeding synchronization reduced the body weight, food intake, and animal anxiety levels in both IF groups, with ad libitum (IF-adlib) or restricted (IF-CRD) food access. The anxiety levels of the experimental groups resulted to be negatively associated with TRH expression, which supported its anxiolytic role. Therefore, the low anxiety levels induced by synchronizing feeding with the activity phase would help patients who are dieting to improve their diet therapy adherence.

Molecular assembly of superquenchers in signaling molecular interactions

We have designed a novel molecular assembly of quencher molecules to form superquenchers with excellent quenching efficiency. The superquencher can be engineered as desired by assembling different types and different numbers of quencher molecules. By labeling a superquencher to a molecular beacon, a 320-fold enhancement of fluorescent signal was achieved, compared to about 14-fold from a molecular beacon prepared with the same monomer quencher. Our molecular assembly approach can effectively improve the sensitivity of a variety of fluorescent assays and can be widely useful for molecular interaction studies.

Efficient labelling of antibodies with horseradish peroxidase using cyanuric chloride

An efficient and mild method for labelling of immunoglobulin G (IgG) with horseradish peroxidase (HRP) using cyanuric chloride (2,4,6-trichloro-1,3,5-triazine, CC) as a bridging molecule is described. The enzyme was treated first with cyanuric chloride to introduce dichloro triazine and after removal of excess reagent, the activated enzyme was mixed with the IgG preparation and incubated to effect linkages with amine groups in the antibody protein. Various amounts of coupling reagent were tested to optimise the conjugation method using commercially available enzyme and affinity-purified sheep IgG antibody preparations to three different test haptens. The conjugates were assessed by solid phase Enzyme Linked Immunosorbent Assays (ELISA) and commonly used peroxidase substrate preparations. The binding activity of the conjugates rose with increasing coupling reagent added during the enzyme activation step. Use of the conjugates prepared by the new method gave comparable sensitivity in direct competitive ELISAs for the three test haptens to assays carried out using indirect ELISA with commercial anti-sheep-HRP conjugates. No deterioration of enzyme activity or hapten-binding activity in the conjugates was observed after storage in 50% glycerol at -70 degrees C for up to 18 months. This study presents a relatively simple and efficient conjugating method for labelling antibodies with HRP and provides an additional and probably a better alternative to the periodate, glutaraldehyde and succinimide-maleimide procedures.

In situ hybridization AT-tailing with catalyzed signal amplification for sensitive and specific in situ detection of human immunodeficiency virus-1 mRNA in formalin-fixed and paraffin-embedded tissues

In situ hybridization is one of the most important techniques to visualize gene expression at the cellular level in various tissues. The in situ hybridization-AT tailing (ISH-AT) method uses a specially designed and synthesized oligonucleotide probe that has (AT)10 on the 3' side. This (AT)10 of the probe is elongated by DeltaTth DNA polymerase in the presence of dATP, dTTP, and labeled dUTP in the tissue after hybridization. Through this process the target is labeled with many hapten molecules. In this study, we detected human immunodeficiency virus type 1 RNA in formalin-fixed and paraffin-embedded tissues obtained from autopsied patients with acquired immunodeficiency syndrome by combining ISH-AT with the catalyzed signal amplification (CSA) system (ISH-AT-CSA), although we failed to detect signals from the same samples by conventional in situ hybridization using RNA probes (RISH) with CSA (RISH-CSA). We demonstrated that the ISH-AT-CSA method was superior to RISH-CSA in terms of both sensitivity and specificity, and that it was applicable to fluorescence in situ hybridization and double staining with immunohistochemistry for the characterization of cell phenotypes.

A novel method for depositing erythroid cells onto glass slides for fetal cell analysis

BACKGROUND

We have developed a method for selecting erythroblasts from blood, the first step toward identifying fetal cells in maternal blood for diagnostic purposes. Because the selection method results in a large number of positive cells, we needed to develop new methods to deposit the cells onto slides and to modify in situ hybridization procedures to enable detection of fetal cells.

METHODS

We utilized Nunc flaskettes to increase the slide surface area available for cell deposition. The ability of erythroid lineage cells to adhere to several surface modifications was examined. In situ hybridization methods were tested to find the best approach that is compatible with these cell preparations.

RESULTS

The best glass slide coating for erythroid cells was found to be an antibody to glycophorin A, a red cell surface antigen. We were able to get excellent in situ hybridization signals in cells on flaskettes by modifying fixation and pretreatment parameters.

CONCLUSIONS

The methods described here appear to be the best way of attaching a large number of erythroid lineage cells to slides and of detecting them by in situ hybridization.