Search

1. Extracts of Escherichia coli A.T.C.C. 9723 and K12703 contain serine transacetylase and O-acetylserine sulphhydrase. Synthesis of the latter enzyme is repressed by growth on l-cyst(e)ine and other sulphur compounds. 2. O-Acetyl-l-serine added to cells growing on glutathione or sulphate as source of sulphur induces the enzymes that catalyse (a) the activation of sulphate to adenosine 3′-phosphate 5′-sulphatophosphate (EC 2.7.7.4 and 2.7.1.25), (b) the reduction of adenosine 3′-phosphate 5′-sulphatophosphate to sulphite and (c) the reduction of sulphite to sulphide (EC 1.8.1.2). Hydrogen sulphide is liberated from cultures growing on sulphate as source of sulphur and in the presence of O-acetylserine. 3. The cysE mutants of E. coli K12 lack serine transacetylase. Addition of O-acetylserine permits growth on sulphate as source of sulphur; at the same time the enzymes of sulphate reduction, previously absent, are synthesized. Such mutants have no detectable intracellular cyst(e)ine when starved of sulphur. 4. These results suggest that O-acetylserine is necessary for synthesizing the enzymes of sulphate reduction in E. coli. Its action does not appear to be by interference with the repressive control exerted over these enzymes by cyst(e)ine.

Joint involvement following infection with Mycoplasma pneumoniae is extremely uncommon. Four patients are presented in whom joint symptoms occurred, giving rise to diagnostic difficulties in three. It is suggested that these manifestations were due to M. pneumoniae.

1. The function of the wild-type alleles of the pleiotropic mutants cysB and cysE of Escherichia coli was investigated. 2. The wild-type allele cysB+ is dominant to the mutant allele cysB in stable and transient heterozygotes. 3. The wild-type allele cysE+ is dominant to the mutant allele cysE, as predicted. 4. Sulphur-starved cultures of cysB or cysE strains contain less than 0·2nmole of free cysteine/mg. dry wt. 5. Complementation in vitro is not observed between extracts of cysB mutants and mutants lacking sulphite reductase only. 6. A scheme, involving positive control of the enzymes of sulphate activation and reduction, is suggested to account for the control of cysteine biosynthesis.

To determine to what extent the biosynthesis of cysteine in Escherichia coli resembles that in Salmonella typhimurium, the following experiments were performed. (1) Mutants of E. coli K 12 deficient in the biosynthesis of cysteine were isolated. (2) These mutants were classified by nutritional and biochemical criteria; some mutants lacked a single enzyme of sulphate reduction, other mutants appeared to lack two or more enzymes. (3) The genetic map predicted from the biochemical data alone is shown to be incorrect, and an alternative map, consistent with the genetic data, is proposed for the cys mutants of E. coli.

Mutants of Escherichia coli K12 defective in the gene iex (crr) no longer utilize glucose or N-acetylglucosamine in preference to lactose, but competition between either of these sugars and another that also enters by a phosphotransferase (PT) mechanism is not affected. In this they differ from gsr (tgs) mutants. In gsr mutants, glucose does not exclude any other sugar, though N-acetylglucosamine still does so. In gsr mutants that are also ptsM the phosphoenolpyruvate-dependent phosphorylation of glucose or methyl alpha-glucoside is reduced by 90%: N-acetylglucosamine phosphorylation is not affected. The iex mutation does not affect the phosphorylation of either of these compounds. The wild-type alleles iex+ and gsr+ are dominant in lambda heterozygotes. Glucose inhibits the lactose permease of wild-type cells, but only when the permease is present in low amounts. The inhibition is also relieved (1) by induction of another transport system that is subject to regulation by the iex system or (2) by an iex mutation. We suggest that the iex gene specifies a protein that, in cells transporting certain sugars by a PT mechanism, acts to inhibit active transport systems. The protein is present in limiting concentration in the cell, sufficient only to inhibit the basal, uninduced, level of the active transport systems. In consequence the inducer (or its precursor) may be excluded from the cell and induction thus prevented.

SUMMARY: In the course of the experiments described above it became clear that the two cys mutations used were not identical. The cysA471 mutation was isolated by Tully (1976) as conferring resistance to chromate, the cysZ474 mutation arose spontaneously and simultaneously with a ptsI mutation, (it may be the result of an inversion with ends in these two genes). The mapping of the genes (see above, Table 3) shows that cysA and cysZ lie on opposite sides of ptsI. We therefore investigated the biochemical nature of the mutations.

S Raimes Amsterdam: North-Holland 1972 pp xi + 272 price $2025 The author's rationale for this book is that there exists a gap between such undergraduate texts on solid state physics as his own Wave Mechanics of Electrons in Metals and the many body formulation of graphs and Green's functions used in more advanced treatises and research papers. This is not entirely true; Kittel's Quantum Theory of Solids, Mattuck's Guide to Feynman Diagrams in the Many Body Problem, Zinan's Elements of Advanced Quantum Theory and Fetter and Welecka's Quantum Theory of Many Particle Systems among others, have, to judge by their author's forewords, been aimed at filling the same gap – not without some success.

The far‐infrared spectra of liquid hydrogen at three para concentrations have been recorded in the wavenumber range 20 to 250 cm−1. The observed variation of the absorption coefficient with composition is consistent with the theory of translational absorption of Poll and Van Kranendonk.

SUMMARY A method was developed for the preparation of [35S] cadmium sulphide from [35S] sodium sulphate employing cultures of Desulfovibrio desulfuricans. [35S] H2S may be prepared by the action of 2 N hydrochloric acid on [35S] cadmium sulphide.

This note describes the relationship between ratios of random variables from centred elliptically symmetric distributions and the Cauchy distribution, with particular reference to a recent article in this journal by Nadarajah [On the ratio X/Y from some elliptically symmetric distributions, J. Multivariate Anal. 97 (2006) 342–358].

Bruce J Berne (ed) New York: Plenum 1977 pp xv + 242 price £24.89 This volume consists of a number of review articles on various aspects of the equilibrium mechanics of classical fluids. Some deal fairly generally with cluster theory and Monte Carlo methods, while others cover the more specific topics of electrolyte solutions and nucleation theory.

The degree (0 to 4) of hepatic siderosis was investigated in 76 autopsies of children. 51 cases (67,1%) showed hepatocellular compromise. Porcentage of positive cases decreases with age: 78,4% for 37 cases of 1 to 3 month-old; 68,2% for 22 cases, 4 to 6 months-old and 41,2% for 17 cases 7 to 10 months-old. No relationship was found between the degree of siderosis and main diseases or the degree of undernourishment (present in 37 cases). Periportal hepatocytes were the first and more heavy loaded with the iron pigment. A tendency to an inverse relationship seemed to exist between siderosis and hepatic hematopoiesis. This siderosis may be secondary to perinatal hematologic changes. An inverse age-related relationship suggests that iron may be removable. 22 cases (28,9%) showed iron pigment in Kupffer cells, 16 associated with hepatocellular siderosis.

Ervin Y Rodin (ed) Oxford: Pergamon 1976 pp ix + 170 price £10 Those wanting a memento of the late Cornelius Lanczos may be prepared to pay a fairly high price for a rather slim volume already published in journal form in 1975. His work in the field of what he himself called applied analysis is certainly deserving of a memorial, and apart from one or two in his other field of interest, relativity, all of the 20 papers here are to that end.

R Balescu Chichester: J Wiley 1975 pp xiv + 742 price £16.20 Unlike many of the texts published in this field, this survey of basic concepts and modern developments in both equilibrium and nonequilibrium statistical mechanics fills a real gap. It brings together in one volume many recent results, particularly in the theory of critical phenomena and in kinetic theory.

Type, grade and extension of immunocompetent infiltrates(ii) in gastric mucosa were analyzed in 76 pediatric autopsies. Seven similary located specimens were obtained for each case. Results are shown in the Table. CG; chronic “gastritis”. I 1-29 days-old. II 1-3- months-old. III 1-6 years-old. IV 7-14 years old. ii increased with age. Main cellular component was composed by plasmocytes and related cells, including lymph follicles with germinative center. Its presence probably indicates a response to chronic local antigen stimulation. Since histologic images conform a gamut it is not clear when ii should be called chronic gastritic as a lesion.

Cryptophthalmos syndrome is an autosomal recessive pattern of malformation characterized by cryptophthalmos, syndactyly, laryngeal atresia, abnormal genitalia and renal agenesis. We have found 72 cases of the syndrome and 40 of isolated cryptophthalmos among 112 cases reported in the literature since Zehender's first description in 1872. The isolated cases, which have not been previously analyzed, contain three families showing vertical transmission, while the syndromic ones suggest autosomal recessive inheritance. We report three stillborn siblings pairs who presented with cryptophthalmos, bilateral renal agenesis, oligo-hydramnios sequence, genital abnormalities and syndactyly. Four had laryngeal stenosis or atresia and two siblings had aplasia or hypoplasia of the thymus. Review of the literature and our own experience illustrate the high frequency of renal agenesis in Cryptophthalmos syndrome and the existence of the disorder without cryptophthalmos. Abnormalties similar to those found in this syndrome, some of which may involve defects in programmed cell death, have been observed in two vitamin A deprived animal models. The Cryptophthalmos syndrome should be considered more frequently in the differential diagnosis of multiple congenital malformations, especially when associated with renal agenesis and even in the absence of cryptophthalmos.

Chronic problems have been experienced in integrated circuit fabrication lines in the formation of Ohmic contacts between Al–Si interconnect metallization and device (bulk or epi) silicon. One of the reasons for such problems has been the absence of a simple and reliable method for predicting, immediately after metal deposition, whether or not the contact resistances in the finished circuits will be satisfactory. This paper describes and demonstrates such a method for (Al–1% Si)/(phosphorus‐implanted) n+ Si contacts.

SUMMARY Choice of appropriate parameter configurations for time series simulations is not always easy. One possible approach when simulating from autoregressive-moving average models is to choose parameter values from a uniform distribution on the stationarity and invertibility region associated with such models. In this paper, well-known time series results are applied to this problem to give a neat method which comprises generating partial autocorrelations independently distributed as appropriate beta variates and applying a standard transformation to obtain the parameters from these.

B Jancovici Maidenhead: McGraw Hill 1973 pp xi + 147 price £2.95 This book is mistitled. There is very little statistical physics in it, certainly not enough for an honours course in physics, and probably not enough to meet the author's objective of providing an alternative to the existing standard texts.

G K T Conn and G N Fowler (eds) London: Academic Press 1971 pp ix + 69 price £1.75 As well as (perhaps because of) being the longest, the second of the three articles in this volume, 'Statistical theories of the liquid state' by G H A Cole comes closest to meeting the aims of this series. At the expense of omitting the details of the more advanced theory, a wide view of the subject, starting from elementary hydrodynamical and thermodynamical ideas, is achieved.

Evaluation of experimental data concerning the normal spectral absorptivities of the transition metals, nickel, iron, platinum, and chromium, at both room and liquid-helium temperatures in the wavelength range from 2.5 to 50 microns. The absorptivities were derived from reflectivity measurements made relative to a room-temperature vapor-deposited gold reference mirror. The absorptivity of the gold reference mirror was measured calorimetrically, by use of infrared laser sources. Investigation of various methods of sample-surface preparation resulted in the choice of a vacuum-annealing process as the final stage. The experimental results are discussed on the basis of the anomalous-skin-effect theory modified for multiple conduction bands. As predicted, the results approach a single-band model toward the longer wavelengths. Agreement between theory and experiment is considerably improved by taking into account the modification of the relaxation time due to the photon-electron-phonon interaction proposed by Holstein (1954) and Gurzhi (1958); but, particularly at helium temperatures, the calculated curve is consistently below the experimental results.

Following the article by T G Bonner, WRBuckland and ER Wooding in the September 1971 issue of Physics Bulletin it may be of interest to relate our experience at Surrey where, in contrast to the course at Royal Holloway College, our management course for physicists was a short intensive one given almost entirely by people from industry. For some years SRC has sponsored residential one week CRAC graduate courses to introduce SRC postgraduate students to industrial methods and management and to enable them to meet with employees in industry and public service.