Novel inhibitors of the condensing enzymes of the type II fatty acid synthase of pea (Pisum sativum).

The type II fatty acid synthases (FASs) of higher plants (and Escherichia coli) contain three condensing enzymes called beta-ketoacyl-ACP synthases (KAS), where ACP is acyl-carrier-protein. We have used novel derivatives of the antibiotic thiolactomycin to inhibit these enzymes. Overall de novo fatty acid biosynthesis was measured using [1-(14)C]acetate substrate and chloroplast preparations from pea leaves, and [1-(14)C]laurate was used to distinguish between the effects of the inhibitors on KAS I from those on KAS II. In addition, the activities of these enzymes, together with the short-chain condensing enzyme, KAS III, were measured directly. Six analogues were tested and two, both with extended hydrocarbon side chains, were found to be more effective inhibitors than thiolactomycin. Incubations with chloroplasts and direct assay of the individual condensing enzymes showed that all three compounds inhibited the pea FAS condensing enzymes in the order KAS II > KAS I > KAS III. These results demonstrate the general activity of thiolactomycin and its derivatives against these FAS condensation reactions, and suggest that such compounds will be useful for further detailed studies of inhibition and for use as pharmaceuticals against Type II FASs of pathogens.

The design and synthesis of inhibitors of adenosine 5'-monophosphate deaminase.

Carbocylic coformycin (4) is a potent herbicide whose primary mode of action involves inhibition of adenosine 5'-monophosphate deaminase (AMPDA) following phosphorylation of the 5'-hydroxyl group in vivo. The search for more stable and accessible structures led to the synthesis of carbocyclic nebularine (8) and deaminoformycin (10). The latter compound is a good herbicide and its corresponding 5'-monophosphate 14 is a strong inhibitor of plant AMPDA (IC50 100 nM).

Adenosine-5'-phosphate deaminase. A novel herbicide target.

The isolation of carbocyclic coformycin as the herbicidally active component from a fermentation of Saccharothrix species was described previously (B.D. Bush, G.V. Fitchett, D.A. Gates, D. Langley [1993] Phytochemistry 32: 737-739). Here we report that the primary mode of action of carbocyclic coformycin has been identified as inhibition of the enzyme AMP deaminase (EC 3.5.4.6) following phosphorylation at the 5' hydroxyl on the carbocyclic ring in vivo. When pea (Pisum sativum L. var Onward) seedlings are treated with carbocyclic coformycin, there is a very rapid and dramatic increase in ATP levels, indicating a perturbation in purine metabolism. Investigation of the enzymes of purine metabolism showed a decrease in the extractable activity of AMP deaminase that correlates with a strong, noncovalent association of the phosphorylated natural product with the protein. The 5'-phosphate analog of the carbocyclic coformycin was synthesized and shown to be a potent, tight binding inhibitor of AMP deaminase isolated from pea seedlings. Through the use of a synthetic radiolabeled marker, rapid conversion of carbocyclic coformycin to the 5'-phosphate analog could be demonstrated in vivo. It is proposed that inhibition of AMP deaminase leads to the death of the plant through perturbation of the intracellular ATP pool.

A pilot study of SPINE test scores and measures of tongue deviancy in speakers with severe-to-profound hearing loss.

Two developments show promise in the assessment and remediation of defective speech production in persons with hearing loss. A perceptual speech-intelligibility test, the SPINE (for Speech Intelligibility Evaluation), is a simple, clinician-administered instrument which is valid, reliable, and clinically efficient. In addition, the development of acoustic measures of tongue deviancy, computed from formant frequencies, makes possible a direct lateral visualization of tongue placement in relation to standard vowel placement. In this study, SPINE test scores of 28 persons with severe-to-profound hearing loss were correlated with two measures of tongue deviancy during production of the vowels /i/, /a/, and /u/. For both measures of tongue deviancy, correlations with the SPINE were significant for the three vowels combined and for the isolated vowel /i/. These findings suggest that clinicians may ultimately have two different but complementary means of assessing speech production in persons with hearing loss.

Phosphoribosyl pyrophosphate and the measurement on inorganic pyrophosphate in plant tissues.

This work provides further evidence that plants contain appreciable amounts of inorganic pyrophosphate (PPi), and that breakdown of phosphoribosyl pyrophosphate (PPRibP) does not contribute significantly to the PPi detected in plant extracts. Inorganic pyrophosphate in extracts of the roots of Pisum sativum L., clubs of the spadices of Arum maculatum L., and the developing endosperm of Zea mays L. was assayed with pyrophosphate fructose 6-phosphate 1-phosphotransferase (EC 2.7.1.90), and with sulphate adenyltransferase (EC 2.7.7.4). The two different assays gave the same value for PPi content, and for recovery of added PPi. It was shown that PPRibP is converted to PPi during the extraction of PPi. However, the amounts of PPRibP in clubs of A. maculatum and the developing endosperm of Z. mays were negligible in comparison with the contents of PPi.

Effects of 2,4-dinitrophenol and anoxia on the inorganic-pyrophosphate content of the spadix of Arum maculatum and the root apices of Pisum sativum.

This work was done to determine whether the inorganic-pyrophosphate (PPi) content of plant tissues changes when the rate of glycolysis is altered. Treatment of excised clubs of the spadix of Arum maculatum L. and root apices of Pisum sativum L. with 2,4-dinitrophenol increased the rates of respiration but had no detectable effects on PPi contents. When the two tissues were subjected to up to 60 min anoxia, no changes in PPi were detected. Anoxia was shown to lead to a fall in ATP and concomitant rises in ADP and AMP in pea roots. It is argued (i) that variation in the rate of glycolysis was not accompanied by detectable changes in PPi content, (ii) that this observation does not favour the view that pyrophosphate fructose 6-phosphate 1-phosphotransferase mediates appreciable entry into glycolysis, and (iii) that PPi content can be maintained when respiratory-chain phosphorylation is inhibited.

Bisensory vs summed-unisensory improvement on two speech-reception tasks.

It is known that in speech reception tasks, when performance scores in the auditory-only (A) mode and the visual-only (V) mode are simply added, the result will be substantially less than when eyes and ears can simultaneously process the stimuli (A/V mode). However, it is not known whether the improvement with practice and/or training with feedback is greater in the A+V or the A/V mode. Normal young adults (N:20) watched and listened in the A/V mode and responded to 100 key words in sentences spoken by a man on a 25-inch color TV at a distance of 6 ft, both before and after training with feedback on other lists of 100 key words. In the training condition, half the Ss were given the A mode first, half the V mode. Within the training condition, pre- and post-training test phases of 100 key words each had a training phase intervening in which feedback was given on 100 different key words. Performance significantly improved from 28.8% to 35.0% words correct within the training condition, averaged over A and V mode (6.2%; p less than .001), but it improved from 68.5% to 86.0% (= 17.5%; p less than .001) in the pre- vs post-training comparison for the A/V mode. The difference of 11.3% in favor of the A/V mode was significant (p less than .01). Essentially zero correlation was found between individual improvements in the A+V vs the A/V mode. The acquisition and utilization of A, V, and A/V skills are independent and specific. Each mode may have its optimum set of training conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Auditory versus visual practice effects in the intelligibility of words in everyday sentences.

The improvement in speech reception from a TV screen was investigated in 15 young adults with normal audition (A) and vision (V) in the A-only and the V-only modes. Trial 1 consisted of 100 key words from Lists A, B, C, D of the Revised CID Everyday Sentences. S wrote down as much of the sentences as was perceived. In the A mode the speech and a white noise both at azimuth 0 degree were both at 65 db SPL. A and V modes were randomized across Ss. After 30 min, Trial 2 repeated Trial 1 exactly. The mean improvement in the A mode was 10.3 percentage points (words) (p less than .01), in the V mode 3.4 points (p less than .05). Improvement in the A mode was significantly (p less than .01) the greater. The r for individual change from Trial 1 to Trial 2 for the A vs the V mode was only +.13 (p much greater than .05). These practice-only effects are comparable to those reported for similar procedures in training (with feedback) in these modes, and call into question the interpretation of the efficacy of such training procedures, and question the advisability of generalizing the effects of training across essentially independent modalities.

The effects of vocational noise exposure on hearing aid battery subjective life.

This study examined the effects of vocational training noise on subjective battery life and on battery current drain, in 5 different class B hearing aids worn by students at a school for the deaf. Each S used a mercury battery in the morning in an average listening school environment with a 2-hr period of vocational noise exposure included, and another battery in an average school listening environment from after lunch to bed time. Voltage measurements and usage hrs were recorded until S reported the battery was not working. There were no mean differences in subjective battery life nor in recorded voltage drop between the two conditions. Battery life in 2 batteries exposed to vocational noise may have been extended due to a 10-day rest period during the spring break for these 2 students.

List equivalency of the CID everyday sentences (Harris revision) under three signal-to-noise ratios.

The primary purpose of this study was to determine list equivalency of Harris' revision of the CID Everyday Sentence Lists under three signal-to-noise ratios: O dB, --3 dB, and --6 dB. On the basis of list means, nonsignificant groupings of lists were found at each noise level; however, lists were not equivalent at any level on the basis of a +/- 10% standard error or measurement (95% confidence interval). It is concluded that Harris' revision of the CID Everyday Sentences should not be used in their present form for intraindividual comparisons.

Effects of two procedural modifications of the frequency of false-alarm responses during pure-tone threshold determination.

In normal-hearing young adults without tinnitus, HTLs were collected using 5-db steps, and false alarms (FA's) noted, at octaves from .25-8 kc/s either in quiet or in a white noise background set at 15 db sensation level for each S. In Exper. I (N:10), the ascending and descending modes did not yield significantly different numbers of FA's in quiet; in noise, FA's increased significantly vs the quiet condition in the ascending but not in the descending modes, while in noise, furthermore, FA's increased significantly for the ascending vs the descending mode. In a similar Exper. II (N:10), the 4 combinations (single- and pulsed-tone presentations, ascending and descending modes) showed that FA's were significantly fewest with a descending, pulsed-tone technique. It was recommended that when FA's pose a problem when using the ascending mode, single-tone technique (ASHA guidelines), the clinician change to the descending, pulse-tone technique to reduce FA's by increasing the stimulus certainty under difficult listening circumstances.

Excursion size Bekesy tracings of continuous and interrupted tones at threshold and at most comfortable loudness in cochlear-impaired ears.

Bekesy fixed-frequency tracings at .5, 1, and 4 kc/s were obtained at THL and at MCL from 64 men with cochlear-impaired ears. Mean continuous- (C) and interrupted-tone (I) excursion sizes were compared within 4 hearing-level categories from mild to severe/profound. Mean I-tone excursions were comparable at THL and MCL, regardless of amount of loss or frequency, the majority of excursions between 5-15 db. Mean C-tone excursions at MCL were reduced to less than 5.5 db á value at HTL said by Bilger (1965) to be clinically significant in separating normal from pathological cochlear function], i.e., significantly more often than mean C-tone excursions at THL . Inspection of excursion size at MMCL appears to have diagnostic value.