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The E. coli recA gene was cloned from the phage lambda precA into the vector pBR313. A plasmid, pJL3, was also isolated by cloning a portion of the recA gene into the vector pBR322. pJL3 coded for a fragment of the recA protein 34 Kd (kilodaltons) in size (compared to 40 Kd for the intact protein). This fragment was antigenically related to the recA protein and its synthesis was subject to the same controls as that of the recA protein. The fragment did not express any detectable recA function. When wild-type cells with pJL3 were treated with nalidixic acid, the 34 Kd fragment and the beta-lactamase, made from a gene located downstream from the recA segment, were expressed at very high levels. Moreover, in these cells the rate of synthesis of intact recA protein from the chromosome was inhibited about 2-fold, relative to other chromosomal proteins, when compared to wild-type cells with the pBR322 vector. High level expression of the recA protein fragment and/or the beta-lactamase appeared to be lethal. The size of the 34 Kd fragment, taken together with the location of chain-termination codons in pJL3, localizes the regulatory region of the recA gene within 100 base pairs.

LexA repressor of Escherichia coli and phage lambda repressor are inactivated in vivo and in vitro by specific cleavage of an Ala-Gly peptide bond in reactions requiring RecA protein. At mildly alkaline pH, the in vitro cleavage reaction also proceeds spontaneously, suggesting that peptide bond hydrolysis is an activity of the repressors rather than of RecA. The spontaneous cleavage reaction, termed "autodigestion", has been characterized for the LexA and lambda repressors. The results show that the reaction is intramolecular. The rate of LexA autodigestion was studied over the pH range 7.15-11.77 and over the temperature range 4-46 degrees C. The logarithm of the rate constant increased linearly with pH and reached a plateau value (2.5 X 10(-3) s-1 at 37 degrees C) at pH above 10. The data closely followed a model in which a single residue side chain (apparent pK = 9.8 at 37 degrees C) must be deprotonated for the protein to show activity. Analysis of the temperature dependence gave the heat of proton dissociation as 19.9 kcal/mol and the heat of activation for hydrolysis as 15.3 kcal/mol at 25 degrees C. Autodigestion of lambda repressor, studied over the pH range 8.65-10.70 at 37 degrees C, was similar to the LexA reaction in its pH dependence, yielding a pK of 9.8. The maximum rate at 37 degrees C for lambda repressor, 6.1 X 10(-5) s-1, was 40 times slower than for LexA, a difference similar to that previously observed in vivo and in vitro for RecA-dependent cleavage reactions. There was no significant solvent deuterium isotope effect on the autodigestion of LexA. Changes in buffer composition, including high concentrations of glycine for lambda repressor and of imidazole or hydroxylamine for LexA, indicated that solvent components other than water do not participate in the rate-determining step. Removal or addition of metal ions did not significantly affect LexA autodigestion. These and other observations suggest that the deprotonated form of an amino acid side chain plays a central role in the chemistry of the cleavage reaction. The above observations establish repressor autodigestion as a member of an emerging set of biologically important self-processing reactions.

Costal cartilage irregularities are a major component of most congenital thoracic-wall deformities. A significant number of patients with these cartilage irregularities may either refuse major reconstruction or in fact have disorders of insufficient magnitude to justify such endeavors. In patients undergoing augmentation mammaplasty, recontouring or sculpturing of these abnormal costal cartilages may correct or improve the underlying chest-wall deformity and thus enhance the final aesthetic result. This method has had application in mild to moderate asymmetrical cases of both pectus excavatum and pectus carinatum, thoracic hypoplasia (Poland's syndrome), isolated cartilage deformities, and spinal scoliosis. In our hands, the combination of cartilage sculpturing with submuscular augmentation mammaplasty is performed as an outpatient local anesthetic procedure requiring not more than 90 minutes.

A number of E. coli genes exhibit increased expression when the cellular DNA is damaged. In undamaged cells, lexA repressor limits the extent of their transcription, whereas, in damaged cells, the repressor is cleaved by a cellular protease, the product of the recA gene. We have sequenced 943 base pairs of cloned E. coli DNA containing the lexA gene. A regulatory region has been identified, followed by a translational open reading frame which encodes a polypeptide of 202 amino acids with a molecular weight of 22,300. The protein contains a single alanyl-glycyl peptide near its middle. This peptide is also found in certain phage repressors which are cleaved by the recA protease and has been shown to be the site of cleavage in these repressors. We have determined the nucleotide sequence of a portion of the lexA3 gene, whose product is 100-fold less susceptible to recA protease than the wild type repressor. We report a single base change (G to A) which alters the unique alanine-glycine sequence to alanine-aspartic acid.

For evaluation of heterologous protection by live attenuated influenza virus vaccine, 42 healthy volunteers with low titers of or no antibody to A/Scotland/74 (H3N2) and A/Victoria/3/75 (H3N2) influenza viruses were given live attenuated A/Scotland/74 (H3N2) virus vaccine or placebo by the intranasal route with no resultant vaccine-related illness. Seventeen of 21 vaccine recipients and none of 21 placebo recipients developed antibody conversion. Thirty-seven days after administration of vaccine or placebo, all subjects were challenged intranasally with wild-type A/Victoria/3/75 influenza virus. Five placebo recipients and no vaccine recipients developed moderately severe illness, whereas 10 vaccine recipients and three placebo recipients developed no illness (p less than 0.025). Although 16 of 21 vaccine recipients fulfilled criteria of infection with the challenge virus, shedding of virus was significantly less frequent, less prolonged, and of significantly lower magnitude than that in the placebo recipients. Thus, live attenuated influenza virus vaccine showed a significant protective effect against illness following challenge with heterologous wild-type virus. The protective effect and the negligible side effects of this vaccine merit consideration of its use in a large-scale field trial.

Certain treatments that damage DNA and/or inhibit replication in E. coli have been reported to induce synthesis of a new protein, termed protein X, in recA+ lexA+ strains. We have examined some of the treatments that might induce protein X and we have, in particular, tested the hypothesis of Gudas and Pardee (1975) that DNA degradation products play an essential role in the induction process. We confirmed that UV irradiation, nalidixic acid treatment, or thymine starvation result in protein X synthesis in wild type strains. However, we found that UV irradiation, unlike nalidixic acid, also induced protein X in recB strains, in which little DNA degradation occurs. Furthermore, we found that the presence of DNA fragments resulting from host-controlled restriction of phage lambda DNA did not affect protein X synthesis. We conclude that no causal relationship exists between the production of DNA fragments and induction of protein X. The presence of the plasmid R46, which confers enhanced mutagenesis and UV resistance on its host, did not affect protein X synthesis. Growth in the presence of 5-bromouracil, which does not result in production of degradation fragments, resulted eventually in a low rate of protein X synthesis. In dnaA mutants, deficient in the initiation of new rounds of replication, UV irradiation induced protein X, again unlike nalidixic acid. Thus, the inhibition of active replication forks is not an essential requirement for protein X induction.

λ exonuclease exhibits a much greater rate of attack on native deoxyribonucleic acid than on denatured DNA, the difference in rate being 350-fold for T7 phage DNA. The attack is exclusively exonucleolytic, and the only acid-soluble products are deoxyribonucleoside 5‘-monophosphates. In contrast to the known Escherichia coli exonucleases, its initial site of attack is at the 5‘ termini of a DNA molecule, with a strong preference for termini bearing a phosphoryl residue as compared with those bearing a free hydroxyl group.

Studies have been made of the growth and excystment of a trematode, Acanthoparyphium spinulosum, in chicks fed on various denned diets.Day-old chicks were fed metacercariae and maintained on deficient as well as complete rations for periods up to 20 days. The excystment rate was determined by the number of worms that were recovered from the metacercariae. The largest number of worms were recovered from chicks that received a normal diet with starch as the sole carbohydrate source. The smallest percentage of parasites was found in birds that had received a normal diet with sucrose serving as the carbohydrate source. About 25 % were recovered from chicks fed several other diets.The trematodes developed and grew well in vitamin A deficient chicks; there was a large number of intra-uterine ova observed in worms from these hosts. Acanthoparyphium spinulosum from chicks fed a ‘no vitamin D’ diet grew at a normal rate until the 6th day; after this they grew more slowly than 6-day-old worms in chicks fed the ‘no vitamin A’ diet.The lengths of worms from birds deprived of all vitamins differed little from those of the parasites recovered from the chicks deficient in vitamin D. The largest worms were obtained from chicks fed a complete diet with starch as the sole carbohydrate source.Parasites from chicks fed a diet 50 % deficient in carbohydrates (with sucrose as the carbohydrate) developed normally.Worms also developed in chicks fed a ‘no protein’ diet with starch and a ‘no protein’ diet with sucrose. A deleterious effect on ova production was observed in worms from both these groups.Metacercariae developed in chicks fed a ‘no carbohydrate’ diet, but no mature worms were recovered due to the reduced life of the host. Starvation of the hosts produced small worms containing few intra-uterine ova.The growth curve of A.spinulosum was plotted and compared with Echino-paryphium flexum.This investigation was supported in part by U.S. Public Health Service Grant UI-00202, and by a grant-in-aid of research by the Society of the Sigma Xi, New Haven, Connecticut.

A scheme is given for the rapid preparation of NAD specifically labeled at a very high specific radioactivity with 3H at the 4-position of the nicotinamide ring.

How do complex gene regulatory circuits evolve? These circuits involve many interacting components, which work together to specify patterns of gene expression. They typically include many subtle mechanistic features, but in most cases it is unclear whether these features are essential for the circuit to work at all, or if instead they make a functional circuit work better. In the latter case, such a feature is here termed ‘dispensable', and it is plausible that the feature has been added at a late stage in the evolution of the circuit. This review describes experimental tests of this question, using the phage λ gene regulatory circuit. Several features of this circuit are found to be dispensable, in the sense that the circuitry works without these features, though not as well as the wild type. In some cases, second-site suppressor mutations are needed to confer near-normal behavior in the absence of such a feature. These findings are discussed here in the context of a two-stage model for evolution of gene regulatory circuits. In this model, a circuit evolves by assembly of a primitive or basic form, followed by adjustment of parameters and addition of qualitatively new features. Pathways are suggested for the addition of such features to a more basic form. Selected examples in other systems are described. Some of the dispensable features of phage λ may be evolutionary refinements. Finding that a feature is dispensable, however, does not prove that it is a late addition — it is possible that it was essential early in evolution, and became dispensable as the circuit evolved. Conversely, a late addition might have become essential. As ongoing work provides additional examples of dispensable features, it may become clearer how often they represent refinements.

The cloned recA+ gene of proteus mirabilis substitutes for a defective RecA protein in Escherichia coli recA- mutants, and restores recombination, repair and phage induction functions to near normal levels. In a previous report, we described the purification and characterisation of the recombination activities of the P. mirabilis RecA protein (West et al. 1983b ). In this paper, we show that the purified protein catalyses the cleavage of both the Escherichia coli LexA protein and the bacteriophage lambda repressor in vitro. These results provide a direct biochemical basis for the interspecies complementation observed in vivo and suggest that P. mirabilis has an SOS regulatory network similar to that of E. coli.

We have observed an intensity‐dependent shift in the exciton absorption features for a system of coupled quantum wells in which a thin barrier separates two wells of unequal widths. We found that for a fixed external bias on the sample, the normal quantum Stark shift of the excitons in the wells was suppressed when light of 1 μW/cm2 intensity was used to measure the absorption. The shift became systematically larger as the light intensity was decreased to as low as 100 pW/cm2. This extremely low‐level nonlinearity may be due to internal fields that arise when free electrons and holes are separated within the coupled‐well system.

The LexA repressor of Escherichia coli represses a set of genes that are expressed in the response to DNA damage. After inducing treatments, the repressor is inactivated in vivo by a specific cleavage reaction which requires an activated form of RecA protein. In vitro, specific cleavage requires activated RecA at neutral pH and proceeds spontaneously at alkaline pH. We have isolated and characterized a set of lexA mutants that are deficient in in vivo RecA-mediated cleavage but retain significant repressor function. Forty-six independent mutants, generated by hydroxylamine and formic acid mutagenesis, were isolated by a screen involving the use of operon fusions. DNA sequence analysis identified 20 different mutations. In a recA mutant, all but four of the mutant proteins functioned as repressor as well as wild-type LexA. In a strain carrying a constitutively active recA allele, recA730, all the mutant proteins repressed a sulA::lacZ fusion more efficiently than the wild-type repressor, presumably because they were cleaved poorly or not at all by the activated RecA protein. These 20 mutations resulted in amino acid substitutions in 12 positions, most of which are conserved between LexA and four other cleavable proteins. All the mutations were located in the hinge region or C-terminal domain of the protein, portions of LexA previously implicated in the specific cleavage reactions. Furthermore, these mutations were clustered in three regions, around the cleavage site (Ala-84-Gly-85) and in blocks of conserved amino acids around two residues, Ser-119 and Lys-156, which are believed essential for the cleavage reactions. These three regions of the protein thus appear to play important roles in the cleavage reaction.

We present methods for identifying a useful type of DNA site — one that can be mutated to create a new restriction site within a coding region without changing the amino acid sequence. These “latent sites” are abundant — silent mutations creating one of 44 different 6-bp or 8-bp recognition sites were found at relatively high density, roughly one latent site per 9 bp, in the eleven genes tested. Our analysis suggests that site-directed mutagenesis can be used to refashion coding sequences at will for flexible analysis.

The recA and lexA proteins of EScherichia coli are involved in a complex regulatory circuit that allows the expression of a diverse set of functions after DNA damage or inhibition of DNA replication. Exponentially growing cells contain a low level of recA protein, and genetic evidence suggests that lexA protein is involved in its regulation, perhaps as a simple repressor. Recent models for recA derepression after DNA damage have suggested that an early event in this process is the proteolytic cleavage of lexA protein, leading to high-level expression of recA. We present several lines of evidence that the specific protease activity of the recA protein, previously described with the lambda repressor as substrate, is capable of cleaving the wild-type lexA+ protein. First, lexA protein can be cleaved in vitro under the same conditions as prevously described for lambda repressor cleavage in a reaction requring both recA protease and ATP or an analogue, adenosine 5'-[lambda-thio]-triphosphate. Second, lexA protein can be observed in vivo as a physical entity after infection with lambda lexA+ transducing phage of host strains containing ittle or no active protease, but not in strains containing high levels of active protease. Finally, infection of host cells containing active protease with a lambda lexA+ transducing phage does not lead to repression of recA, but does so in cells lacking active protease. In all of these conditions the mutant lexA3 protein is largely resistant to inactivation or cleavage; this resistance can explain the dominant phenotype of lexA3 over lexA+. We discuss models for recA derepression and re-establishment of repression which propose that modulation of the protease activity of recA protein regulates both of these transitions.

We have found that the uvrB gene of Escherichia coli is transcribed from at least two promoters, which we call P1 and P2. Transcription from P1 begins with an ATP at +1, and transcription from P2 begins primarily with a GTP at -31. A binding site for the lexA protein (LEXA), located between the -35 sequence and Pribnow box of P2, regulates transcription from this promoter. In vitro, LEXA inhibits transcription from P2 but has no detectable effect on transcription from P1. A third promoter, P3, was also detected at -341; transcription from P3 is toward uvrB but terminates in vitro in the region of the LEXA binding site. The binding of LEXA to P2 inhibits transcription from the P3 promoter even though several hundred nucleotides separate the two promoters. The data suggest that a transcribing RNA polymerase stalls when it reaches the repressor-operator complex but remains bound to the DNA, causing a jamming of RNA polymerases between P3 and the repressor-operator complex at P2. The physiological significance of P3 is unknown.

Expression of phage lytic functions in λ lysogens of Escherichia coli is prevented by phage repressor, which binds to specific operator sequences on the prophage DNA. Phage induction accompanies the expression of an entire set of ‘SOS functions’, which occur when host DNA is damaged or DNA synthesis is interrupted. In these conditions, λ repressor is thought to be inactivated by recA protease, thereby leading to expression of phage lytic functions1. We have now characterized the repressor from a λ mutant, inds-1, which, as prophage, is more easily induced than wild-type phage by a weak inducing treatment2. At high concentrations, λinds-1 repressor differs from wild-type repressor in two ways: whereas wild-type repressor forms dimers and becomes relatively resistant to the recA protease, a much greater proportion of λinds-1 repressor remains monomeric and the protein remains sensitive to the protease. These findings support previous indications3 that repressor monomers are the preferred substrate for protease, both in vivo and in vitro.

We present a composite flap based on the musculature of the anterolateral thorax that allows immediate reconstruction of the mandible through the interposition of vascularized bony fifth rib. While the vascular pedicle remains the pectoral branch of the thoracoacromial artery, the pectoralis major muscle can be spared largely intact. The lateral position of the composite rib segment ensures a purely bony composition, while the lateral skin island remains largely hairless. Despite the unfavorable conditions of massive tumor size and prior irradiation attending the clinical cases presented, the complication rate was acceptable, with only one flap loss, and this followed technical error.

Proteolytic cleavage of lexA repressor is an early step in derepression of the SOS regulatory system of Escherichia coli. In vivo and in vitro data have indicated a role for recA protein in this specific proteolytic reaction. I show here that, under certain conditions, specific in vitro cleavage of highly-purified lexA protein can take place in the absence of recA protein. This autodigestion reaction cleaved the same alanine-glycine bond as did the recA-dependent cleavage reaction. Several lines of evidence argued that it was not due to a contaminating protease activity. Autodigestion was stimulated by alkaline pH. It occurred in the presence of EDTA but was stimulated several fold by the presence of Ca2+, Co2+, or Mg2+. The reaction appeared to be first-order, and its rate was independent of protein concentration over a wide range, strongly suggesting that it is intramolecular. Purified phage lambda repressor also broke down under similar conditions to yield products like those resulting from recA protein action. Phage lambda repressor broke down at a far slower rate than did lexA, as previously observed in the recA-catalyzed in vitro reaction and in vivo. This correlation between the two types of cleavage also extended to the reactions with mutant repressor proteins; taken together with the site specificity, it suggests that autodigestion and recA-dependent cleavage follow, at least in part, a similar reaction pathway. These findings indicate that specific cleavage of lexA protein can be catalyzed by the protein itself and suggest that recA protein plays an indirect stimulatory role, perhaps as an allosteric effector, in the recA-dependent reaction, rather than acting directly as a protease. The protease active site and the recA-recognition site lie in the central or COOH-terminal portion of the lexA protein, since a tryptic fragment containing these portions of lexA protein could take part in both reactions.

We replaced the Escherichia coli lexA gene by a segment of DNA coding for resistance to spectinomycin and streptomycin. The use of this segment expands the range of selectable markers usable for allele replacement. The availability of this null lexA mutation will facilitate genetic analysis of lexA and the SOS regulon.

Treatment of Escherichia coli with radiation or chemical carcinogens induces a number of cellular functions to counteract the damage inflicted by such treatments (see ref. 1 for a review). One of these inducible functions is the SOS response, which is controlled by the recA and lexA genes: single-stranded DNA produced as a result of DNA damage binds to recA protein (RecA), activating its protease function; activated RecA cuts lexA protein (LexA), the represser of the SOS genes, thereby inactivating it and turning on these genes2–4. The SOS genes include recA and lexA themselves, and recent work has shown that the two genes have similar operators where LexA binds in vitro, inhibiting their transcription3,4. It is anticipated that other genes under the control of recA and lexA will have similar operators. Recent genetic5,6 and biochemical7 data suggest that the excision repair genes uvrA and uvrB are part of the recA–lexA regulon and are at least partly responsible for recA–lexA-mediated inducible DNA repair. In support of these results we have reported that uvrB has a promoter that is repressed by LexA in vitro8. We now show that uvrA has an operator similar to those of other SOS genes and that LexA binds to this operator and inhibits the transcription of the uvrA gene in vitro.

Two groups of consecutive patients from two different plastic surgical practice populations were evaluated to determine psychosocial differences between those who underwent immediate (n = 25) versus delayed (n = 38) breast reconstruction. Psychological assessment consisted of a standardized symptom inventory (BSI) and a specially designed self-report questionnaire investigating reactions unique to mastectomy and reconstruction. Both groups were extremely equivalent with regard to sociodemographic data, with the typical subject being a well-educated and employed Caucasian wife. Verbal reports of physical complaints revealed no significant differences between the two groups except for difficulty with arm movement, which was statistically higher for the immediate group (p = 0.006.). This difference most likely was due to the axillary dissection being performed simultaneously at the time of reconstruction. The relationship between timing of reconstruction and self-reported distress over the mastectomy experience revealed that only 25 percent of the women who underwent immediate repair reported "high distress" in recalling their mastectomy surgery compared with 60 percent of the delayed reconstruction group (p = 0.02). In reference to the two scales measuring psychological symptoms, a general trend was present, with the delayed group scoring higher (although not statistically significantly) on 9 of our 12 scales. Ninety-six percent of the immediate group and 89 percent of the delayed group reported satisfaction with results.(ABSTRACT TRUNCATED AT 250 WORDS)

A derivative of bacteriophage M13mp8 , designated M13mp8 /P, was prepared in which the promoter and NH2-terminal codons of bacterial genes may be fused to a portion of beta-galactosidase, resulting in an easily scorable phenotype. Because transcription from the inserted promoter remains responsive to the host regulatory system, it is simple to screen mutagenized phage for isolates with aberrant regulatory phenotypes and to determine the mutational changes by dideoxy sequence analysis. The feasibility of the method was demonstrated by isolation of a large number of mutations in the regulatory regions of two genes, lexA and recA. Base substitutions that altered the phenotype of recombinant phage were identified both in the single LexA repressor binding site of recA and in the two binding sites of lexA, as well as in other sites that likely affect translational efficiency. Our results suggest that this approach will be generally useful for mutational analysis of transcriptional and translational regulatory elements.

USE of indwelling arterial cannulas has become standard practice for monitoring of systemic arterial pressure and sampling of arterial blood in critically ill patients.1 A recent article implicates clots formed at the tip of a Scribner shunt as being responsible for cerebrovascular accidents when these clots were flushed retrograde into the central arterial circulation.2 That study included a calculation of the theoretical volume of flush solution necessary to cause cerebral embolization, but had no confirmatory measurements. The occurrence of sudden unexplained neurologic deficits in patients with indwelling radial arterial cannulas prompted the present study. The purpose was to determine a . . .

The product of bacteriophage T4 gene 32, DNA-unwinding protein or 32 protein, is required in large amounts for normal phage growth. Gene 32 amber mutants are unable to form plaques on ochre-suppressing hosts, presumably because there is too little 32 protein for efficient growth. However, variants arise which can form small, turbid plaques on these hosts. These variants contain a second mutation, termed sud , which maps between genes 39 and 56, far from gene 32. Sud mutants are recessive to wildtype. By themselves, sud mutants exhibit a short delay in the onset of rapid DNA synthesis relative to wild-type. The am A453 (gene 32)- sud double mutants exhibit a very long delay in DNA synthesis relative to wild-type when infecting the ochre-suppressing host, after which DNA synthesis proceeds at the same rate as shown by wild-type, while am A453 synthesizes DNA at a rate 30% that shown by wild-type after a short delay. Moreover, am A453 converts the DNA made to mature progeny much less efficiently than does wild-type, whereas one of the sud mutants described resembles wild-type more closely in this respect. The possible meaning of these observations is discussed.

Recent work in this" 2 and other. laboratories3-6 has demonstrated the existence of enzymes which catalyze the covalent closure of single-strand breaks in duplex DNA. Interest in such enzymes derives in part from their probable biological importance; thus, the enzyme induced by infection with bacteriophage T4 has been shown to be necessary for multiplication of the phage.7 Characterization of purified enzymes from uninfected2' 4 5 and T4-infected3 Escherichia coli has revealed a requirement in each case for a nucleotide cofactor. The enzyme from uninfected cells specifically requires DPN,2 I which is broken down into AMP and NMN in the course of the reaction; the enzyme from T4infected cells, by contrast, splits ATP into AMP and PPi.3 In both cases, 3'-5' plhosphodiester bonds are formed by covalent joining of the two apposed DNA termini at a single-strand break. This class of enzymes thus catalyzes a complex reaction which may be expected to proceed in several distinguishable stages. This report describes the first step of the reaction catalyzed by the DNA ligase of uninfected E. coli. Upon admixture with DPN in the absence of DNA, the enzyme forms a stable enzyme-adenylate complex, releasing NMN. The enzyme-adenylate complex, as isolated by gel filtration, can seal single-strand breaks in DNA in the absence of DPN. AMP is released in this reaction. The enzyme-adenylate complex may also be discharged with NMN to yield DPN by reversal of the reaction which formed the complex. As a consequence an exchange between DPN and NMN can be observed, as noted by Olivera and Lehman.5 These reactions are summarized in the following equations

Publisher Summary Lambda exonuclease is discovered and partially purified using induced cultures of E. coli K12 (λ + ). Under the conditions of induction and subsequent growth described in this chapter, the specific enzymatic activity of a crude extract made from this strain is thirty times greater than that observed in a crude extract of W3101 (λ + )/1,5 made 70 minutes after UV induction. The λ exonuclease shows a strong preference for native DNA. The rate of attack on native E. coli DNA is 50-250 times greater than that on denatured E. coli DNA, the ratio depending on the preparation of DNA used. The λ exonuclease releases 5'-mononucleotides as acid-soluble digestion products of DNA. The acid-soluble material cochromatographs with authentic deoxyribonueleoside 5'-monophosphates; in a digest of 32 P-labeled DNA, the acid-soluble 32 p is completely susceptible to the action of 5'-nucleotidase from snake venom. The enzyme initiates its attack on DNA at the 5'-terminus of a DNA strand. When phage λ DNA is labeled specifically at its 3'-termini with α- 32 P-labeled deoxyribonucleoside triphosphates by E. coli DNA polymerase and used as substrate, exonuelease catalyzes a very slow release of 32 P relative to total nucleotide, while exonuclease III liberates all the 32 P before detectable amounts of total nucleotide are released.

Amantadine HCl administration has resulted in accelerated resolution of influenza A illness. Prolonged abnormalities in pulmonary function have been described in uncomplicated influenza A. To study the effect of amantadine on these changes, we evaluated young adults with documented natural influenza A with clear chest examinations and X rays. Subjects received placebo or amantadine in random, double-blind fashion. Physiologic studies included maximal expiratory flow volume curves with air and helium-oxygen mixtures. Air flow rates were unchanged in all subjects throughout. Initially, both groups showed comparable decreases in mean helium-oxygen maximal expiratory flow rates. The amantadine group showed accelerated physiologic improvement: significant increase in helium-oxygen flow rates occurred within 7 days (P less than 0.05). The rate of improvement in the helium-oxygen flow rates in the placebo group was not statistically significant. These studies confirm peripheral airways dysfunction after uncomplicated influenza A and suggest that amantadine is associated with accelerated resolution of this dysfunction.

The subjective response of humans to jet noises was studied to determine the relative difference in subjective annoyance levels produced by different jet engine configurations. The noises studied were representative of jet airplane ground and fly‐over operations. Further testing was carried out to determine the relative annoyance properties of random noise spectra which were characterized by the presence of outstanding single frequency tones. Emphasis was placed on discovery of the relationships between “spike” frequency, “spike” amplitude, and over‐all sound pressure level. The results of this program are presented with comments on their use as a basis for more extensive programs of this nature.

Solar studies, particularly those involving the corona, require for highest quality work a site that possesses an exceptionally transparent atmosphere as well as one with good seeing conditions. The transparency of the atmosphere is determined largely by the amount of contaminants in the atmosphere such as water vapor, dust, smoke, etc. These contaminating materials scatter white light, producing a bright halo about the sun and obscuring from view the faint glow of the solar corona. Dr. Walter O. Roberts has suggested that for a site to be suitable for carrying on coronagraphic work on a permanent basis it should have, as a minimum requirement, a sky transparency of such quality that the brightness of the halo immediately adjacent to the solar disk should be less than about 50 millionths of the brightness of the solar disk itself. Anything better than 20 millionths of the brightness of the solar disk, he advises, is a sky transparency of exceptional quality. A site would be outstandingly valuable if brightnesses below 50 millionths existed for an hour or more on as many as one-half of the days of the year. For some types of coronal research, such as coronal cinematography, periods as long as 4 to 6 hours of unbroken clear sky of high transparency are also desirable. Moreover, there should be, at an outstanding station, a number of days when the brightness falls to less than 10 millionths for an hour or more, and there should be conditions of excellent stability of image on a reasonable fraction of the hours of very transparent sky.1 It is generally found that sites meeting these requirements are at high altitudes (above 7500 ft.), above the temperature inversion, and, of course, well away from industrial areas.

The R‐6 Research Committee of the Society of Automotive Engineers was organized in February 1968 for the purpose of developing an accurate subjective reaction rating scale for complete aircraft‐noise flyover cycles. The committee has completed the first part of a 2‐year research project that includes considerable experimental activity. This report describes the work performed to date and the plan for the remaining program. In the past, individual investigators in the field of subjective reaction to aircraft noise have developed a variety of rating methods. However, it has become increasingly clear that these have limited reliability. With the formation of the R‐6 Committee, six laboratories working in this general field have formed a cooperative organization to remedy this problem. The committee has developed a detailed research plan that will result eventually in a reliable subjective reaction rating scale for aircraft noise. In addition to this long‐range plan, the committee has assembled descriptions of each participating test facility, has retained individual and laboratory consultants, has conducted a comprehensive acoustical calibration of each laboratory, and has completed some preliminary judgment tests.

Carefully presented instructions are a basic requirement of successful psychoacoustical scaling studies. The term in the instructions which refers to a subjective experience uniquely defines the type of scale constructed. This paper describes the degree to which a psychoacoustical scale would be modified by changes in instructions. The results of 2 studies are reported. The first discusses the differences in subjects' responses to instructions based on 3 different key words—loudness, noisiness, and annoyance. The second is concerned with the effect on subjects' responses of mixed instructions (i.e., where more than one key word appears in a single set of instructions). The results indicate that different instructions “set” subjects to give different emphasis to various physical aspects of sound, and that instructions based on a combination of 2 key words yield ratings significantly different from ratings given to the same sounds when the key words are used individually. A recommendation is made that instructions be selected which set subjects to emphasize sound dimensions relevant to particular noise problems.