Experience with a new commercial skin testing kit to identify IgE-mediated penicillin allergy.

Many patients who describe a history of allergy to penicillin do not prove to be allergic and can be treated safely with penicillin. After a period of 2 years where testing of penicillin allergy was not possible, a new commercial kit has recently become available. We report our initial experience with use of the kit with 29 patients and discuss one patient who experienced anaphylaxis during i.d. testing.

Hormonal regulation of alpha-amylase expression in barley aleurone layers : the effects of gibberellic Acid removal and abscisic Acid and phaseic Acid treatments.

The expression of alpha-amylase isozymes in barley (Hordeum vulgare L.) aleurone layers is known to be maximally induced between 12 and 20 hours after addition of the phytohormone, gibberellic acid (GA(3)). Addition of another hormone, abscisic acid (ABA), or its metabolite, phaseic acid, during this time period resulted in reduced alpha-amylase expression. Expression of the high isoelectric point alpha-amylase isozyme group was affected much more by both of these treatments than was expression of the low isoelectric point alpha-amylase isozyme group. Addition of either the translation inhibitor cycloheximide or the transcription inhibitor cordycepin prevented the decrease in alpha-amylase mRNA levels after ABA treatment. Cordycepin also prevented the decreases in alpha-amylase expression that result from phaseic acid treatment. Midcourse GA(3) removal experiments were performed to determine whether ABA treatment and the removal of GA(3) have analogous effects on alpha-amylase expression. It was found that cordycepin treatment also prevented decreases in alpha-amylase mRNA levels resulting from GA(3) removal. We conclude that the suppression of alpha-amylase expression caused by ABA or midcourse GA(3) removal is dependent on continuous RNA and protein synthesis.

Hormonal regulation of gene expression in barley aleurone layers : Induction and suppression of specific genes.

As part of our investigation of the mode of action of plant hormones in barley (Hordeum vulgare L.) aleurone layers, we have studied the expression of five identified and three unidentified mRNA species in the presence of exogenous gibberellic acid (GA3) and abscisic acid. Three of the mRNAs are GA3-inducible, three are suppressed by GA3, and two are constitutive. The extent of the GA3 effect differs considerably for both inducible and suppressible mRNAs. For example, a ten-fold higher concentration of GA3 (10(-8) M) is required for full induction of the high-pl group α-amylase mRNA than is required for the low-pI α-amylase mRNA (10(-9) M). Temporal regulation of mRNA abundance also varies between the two α-amylase isoenzyme groups. The three GA3-suppressible mRNA species studied, alcohol dehydrogenase (ADH1), a probable amylase and protease inhibitor, and an unidentified barley mRNA species also varied in response to GA3. The ADH1 mRNA decreased drastically within 8 h of GA3 treatment, whereas the other two began to decrease in abundance only after 12-16 h of GA3 treatment. Abscisic-acid treatment counteracted the GA3 effects for both the inducible and suppressible mRNA species. Comparison of α-amylase-mRNA levels and α-amylase-synthesis rates showed a strong correlation between the two parameters, the only exception being a lack of α-amylase synthesis in the presence of α-amylase mRNA at low GA3 concentrations. Therefore, the expression of α-amylase seems to be regulated primarily by its mRNA levels.

The effect of abscisic acid on the differential expression of α-amylase isozymes in barley aleurone layers.

The treatment of barley aleurone layers with gibberellic acid (GA3) results in the synthesis of two groups of α-amylase isozymes. Addition of abscisic acid (ABA) at the same time as GA3 inhibited the synthesis of both groups of isozymes. However, midcourse ABA addition (12 h or later after GA3) had a more inhibitory effect on the high pI α-amylase group than on the low pI α-amylase group. This midcourse inhibition was detectable within 2 h of ABA addition. Northern analysis results using cDNA probes for the high pI and low pI α-amylase groups paralleled the protein synthesis results for both isozyme groups. High pI α-amylase mRNA levels began to decrease within 2 h of midcourse ABA treatment and were less than 10% of the original level by 4 h. The levels of low pI α-amylase mRNA were decreased less by midcourse ABA addition than were high pI mRNA levels. Cordycepin and cycloheximide blocked the effects of midcourse ABA addition on α-amylase mRNA. These observations indicate that ABA inhibits α-amylase expression at the pretranslational level and that protein and RNA synthesis are required for midcourse ABA action to occur. Our results also show that α-amylase mRNA, which has been thought to be very stable, is degraded after midcourse ABA treatment.

Characterization of a Gibberellin-Insensitive Dwarf Wheat, D6899 : EVIDENCE FOR A REGULATORY STEP COMMON TO MANY DIVERSE RESPONSES TO GIBBERELLINS.

The effects of gibberellin in two wheat varieties, Nainari 60 and D6899, have been studied. D6899 is a dwarf wheat having a single locus mutation, the Rht 3 gene ("Tom Thumb" gene), which is located on chromosome 4A. When compared with the standard height wheat variety, Nainari 60, D6899 does not have a slowdown in cellular metabolism such as respiration rate, protein content, rate of protein synthesis, and uptake of amino acids. The content of ATP is even higher in D6899. However, all of the gibberellin-mediated physiological processes that we have studied, including leaf elongation, synthesis and release of hydrolytic enzymes, and secretion of phosphate ions and reducing sugars in aleurone layers, are retarded in D6899. D6899 and Nainari 60 have essentially the same uptake and metabolism of gibberellin and their levels of endogenous inhibitors such as abscisic acid do not differ drastically. The dosage-response curve of the gibberellin-mediated alpha-amylase production indicates that a rate-limiting step, which is common to many of the diverse gibberellin responses, is partially blocked in D6899 wheat.