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ABSTRACT This paper reports an approach by which laboratory based testing and numerical modelling can be combined to predict the long term performance of a range of concretes exposed to [...]

ABSTRACT While on site measurement of air permeability provides a useful approach for assessing the likely long term durability of concrete structures, no existing test method is capable of effectively [...]

ABSTRACTThis research presents a mix design methodology for geopolymer (GP) and alkali activated (AA) mortars based on metakaolin and industrial waste products activated using potassium silicate. The aim is to enable a wide range of mix designs to be specified to given compressive strength, consistency and environmental footprints to facilitate their adoption as a Portland cement (PC) alternatives in the construction industry in applications such as fibre-reinforced building cladding systems. The impact of the work is timely as literature quantifying the effects of mix parameters on broad families of GP and AA materials are limited, and no standardized performance-based methodology exists. Initially, effects of binder composition on mechanical and environmental properties are presented for a standard GP mix design using contoured ternary plots for a range of material blends. Next, effects of altering mixture parameters such as liquid/solid, silica/alumina and activator/binder ratios are quantified for three selected binder compositions before a preliminary mix design methodology is presented allowing initial selection of mixture proportions. Finally, correlation analysis is used to identify multiple mix variables strongly correlating with strength, and regression modeling used to present predictive tools with average errors <6%.

Candida albicans is the most common fungal pathogen of humans. The recent discovery of sexuality in this organism has led to the demonstration of a mating type locus which is usually heterozygous, although some isolates are homozygous. Tetraploids can be formed between homozygotes of the opposite mating type. However, the role of the mating process and tetraploid formation in virulence has not been investigated. We describe here experiments using a murine model of disseminated candidiasis which demonstrate that in three strains, including CAI-4, the most commonly used strain background, tetraploids are less virulent than diploids and can undergo changes in ploidy during infection. In contrast to reports with other strains, we find that MTL homozygotes are almost as virulent as the heterozygotes. These results show that the level of ploidy in Candida albicans can affect virulence, but the mating type configuration does not necessarily do so.

ABSTRACTSingle-nucleotide polymorphisms (SNPs) are essential tools for studying a variety of organismal properties and processes, such as recombination, chromosomal dynamics, and genome rearrangement. This paper describes the development of a genome-wide SNP map for Candida albicansto study mitotic recombination and chromosome loss. C. albicansis a diploid yeast which propagates primarily by clonal mitotic division. It is the leading fungal pathogen that causes infections in humans, ranging from mild superficial lesions in healthy individuals to severe, life-threatening diseases in patients with suppressed immune systems. The SNP map contains 150 marker sequences comprising 561 SNPs and 9 insertions-deletions. Of the 561 SNPs, 437 were transition events while 126 were transversion events, yielding a transition-to-transversion ratio of 3:1, as expected for a neutral accumulation of mutations. The average SNP frequency for our data set was 1 SNP per 83 bp. The map has one marker placed every 111 kb, on average, across the 16-Mb genome. For marker sequences located partially or completely within coding regions, most contained one or more nonsynonymous substitutions. Using the SNP markers, we identified a loss of heterozygosity over large chromosomal fragments in strains of C. albicansthat are frequently used for gene manipulation experiments. The SNP map will be useful for understanding the role of heterozygosity and genome rearrangement in the response of C. albicansto host environments.

This article reports a laboratory experimental programme that investigated the performance of concrete made with ternary combinations of Portland cement (PC) with pulverised fuel ash (PEA), granulated blastfurnace slag (GBS) and silica fume (SF), with the aim of developing a simple concrete mix constituent proportioning method. The test mixes used combinations of these cements that conformed to ENV 197-1. All mixes used gravel aggregated mixes and a superplasticiser to achieve slump class S2 (60–90 mm) to provide characteristic cube strengths from 20 to 60 N/mm2. Standard cube strengths were measured up to 180 days. Recommendations are made for the optimum PC replacement level to achieve the highest cube strength at 28 and 180 days for mixes both with and without silica fume. The data have been generalised and fitted to the familiar format of the BRE Design of Normal Mixes to allow the proportioning of the concrete mix constituents. A visual from of the mix design method has been adopted such that the combinations of cements that can be used to achieve particular characteristic cube strengths are simple to identify.

At the institute, since the late 1980s, there has been a uniform treatment protocol for the management of the regional lymph nodes in patients referred for radiotherapy following breast-conserving surgery. An analysis of 2277 consecutive patients referred for radiotherapy between 1989 and 1992, with particular reference to regional lymph node management, has been undertaken. Axillary surgery alone was used in 517 patients (23%); 1191 (52%) patients had no axillary surgery but had radiotherapy to the axilla, and infraclavicular and supraclavicular fossae by a single anterior field, delivering 40 Gy in 15 daily fractions over 3 weeks; and 474 patients (21%) had axillary surgery followed by radiotherapy. Ninety-five patients (4%) underwent no axillary treatment. There was a total of 155 axillary recurrences with a median follow-up of 5.9 years, giving an actuarial nodal control rate of 94% at 5 years (95% confidence interval (CI) 93.1–95.1). The overall survival at 5 years was 86% (95% CI 84.6–87.5). There was a trend towards improved axillary control with surgery alone compared with radiotherapy alone (4.5% versus 5.9% actuarial axillary failure rate at 5 years). An extremely low incidence of brachial plexus neuropathy secondary to radiotherapy was reported. The multidisciplinary treatment protocol used gave a high rate of regional node control, with minimal recorded morbidity.

The treatment outcomes were reviewed for all the patients at this institute who underwent breast irradiation after breast conserving surgery in 1991. Of a total of 643 patients treated, 194 (30%) had presented with tumours detected by screening mammography. The breast was irradiated with a tangential pair of fields, giving a dose of 40Gy in 15 fractions over 3 weeks in 97% of these patients. A boost was not used. With a median follow-up of 4.7 years, there was better cancer related survival in patients with screen detected cancers compared with those that were non-screen detected (94% versus 84% at 5 years; P = 0.002). The breast recurrence rate at 5 years was 1% for screen detected cancers compared with 6% for those that were non-screen detected (P = 0.01). Factors additional to screen detected status that were found to be significant for cancer survival were pathological stage (P = 0.03) and histological grade (P = 0.01). In a Cox multivariate analysis, only two factors were significant for breast recurrence: screen detected status (P = 0.023) and histological grade (P = 0.016)

Nitrogen was applied on a previous rye (Secale CerealeL.) cover crop for later determination of the effect of organic N on soybean (Glycine maxL.) N2‐fixation rate, plant dry matter, N uptake, and yield. Nitrogen was applied at 0, 56, 112, and 224 kg N/ha as NH4NO3or urea either on rye in mid‐March or at soybean planting time in a 4 × 2 × 2 factorial design. In both years of study, N2‐fixation rate as estimated from acetylene reduction was reduced throughout the season by increased fertilization rate. For 1 year, interactions showed that N2‐fixation rate and nodule mass were stimulated late in the season from increased N fertilizer applied to the rye but not at soybean planting. Interactions between NH4NO3and urea and time of application showed that NH4NO3as compared with urea applied on rye significantly increased soybean dry matter, N uptake, and yield. Urea applied at planting increased these parameters in comparison with NH4NO3. The observed increases in dry matter, N uptake and yield from rye‐applied NH4NO3were not accompanied by a corresponding increase in N2‐fixation rate or nodule mass. This would suggest that the N2fixing system was not responsible for the increase of dry matter, N uptake, and yield. Soil organic N was not measurably influenced by the treatments imposed.

Polycyclic aromatic hydrocarbons (PAH) are byproducts of combustion and are ubiquitous in the urban environment They are also present in industrial chemical wastes, such as coal tar, petroleum refinery sludges, waste oils and fuels, and wood-treating residues. Thus, PAHs are chemicals of concern at many waste sites. Risk assessment methods will yield risk-based cleanup levels for PAHs that range from 0.1 to 0.7 mg/kg. Given their universal presence in the urban environment, it is important to compare risk-based cleanup levels with typical urban background levels before utilizing unrealistically low cleanup targets. However, little data exist on PAH levels in urban, nonindustrial soils. In this study, 60 samples of surficial soils from urban locations in three New England cities were analyzed for PAH compounds. In addition, all samples were analyzed for total petroleum hydrocarbons (TPH) and seven metals. The upper 95% confidence interval on the mean was 3 mg/kg for benzo(a)pyrene toxic equivalents, 12 mg/kg for total potentially carcinogenic PAH, and 25 mg/kg for total PAH. The upper 95% confidence interval was 373 mg/kg for TPH, which exceeds the target level of 100 mg/kg used by many state regulatory agencies. Metal concentrations were similar to published background levels for all metals except lead. The upper 95% confidence interval for lead was 737 mg/kg in Boston, 463 mg/kg in Providence, and 378 mg/kg in Springfield.

Effects of environmental factors such as ewe age, season of exposure, and time from lambing to exposure on fertility were evaluated using records on 1,084 Dorset ewes in the STAR accelerated lambing system. The STAR program consisted of five 30-d concurrent breeding and lambing periods per year beginning on January 1, March 15, May 27, August 8, and October 20. Fertility in the flock changed in a cyclic and predictable fashion during the year. Changes in prolificacy were less consistent but also tended to show cyclic variation. Matings that occurred within the typical breeding season (August, October, and January) were more fertile than those occurring in March and June. However, fertility also varied with the age of the ewe and the time since the ewe's last lambing. Except in June, fertility at the first postpartum mating increased as ewes aged. In March and June matings, adult ewes that had just weaned lambs were less fertile than ewes that had failed to conceive in the previous season and therefore had longer postpartum intervals. However, in October and January, ewes that had just weaned lambs were more fertile. A matrix of expected pregnancy rates, or probabilities of fertility, was constructed using a mixed GLM to describe the combined effect of season, ewe age, and time since lambing on ewe fertility in accelerated lambing.

In two experiments, a total of 46 Finn Cross and Dorset lambs were artificially group-reared. Thirty eight were weaned abruptly at 14 d of age from a commercial milk replacer (MR) to a dry starter diet (SD). Lambs were self-fed cool (10 to 15 C) MR reconstituted to 25% dry matter (DM). The ground (2-mm screen) SD averaged 26.2% crude protein and 7.4% fat (DM basis). For both experiments, birth and weaning weights averaged 3.8 and 8.0 kg, respectively. Experiment 1 tested a strategy for encouraging postweaning DM intake. Fifteen lambs received MR reconstituted to 33% DM from d 11 to 14, and 15 lambs received standard 25% DM MR. Between d 14 and 15, intakes of DM, gross energy, crude protein and water dropped 86, 89, 85 and 64%, respectively. Lambs doubled their birth weights during the milk-feeding period and consumed 1.41 kg SD between d 14 and 25. The MR reconstitution rate did not affect weaning weight, postweaning SD or water intake, or growth check (GC, P>.10). Postweaning GC averaged 12.2 d and was not influenced (P>.10) by birth weight, sex or weaning weight. Mortality and disease rates under these conditions were negligible. Experiment 2 was designed to differentiate between the dual effects at weaning of altering the type of diet and of reducing the level of nutrient intake. Eight lambs were weaned to SD at 14 d, and eight lambs were bottle-fed isocaloric levels of MR from d 12 to 30. At weaning, plasma glucose concentration declined 1.4 mM from 6.7 mM due to fasting and an additional 1.0 mM due to the change of the type of diet (P<.01). Plasma acetate and urea N concentrations rose steadily after d 16 in the SD-weaned lambs, but not in the MR-fed lambs (P<.01), suggesting that the SD-weaned lambs absorbed ruminal fermentation products. These results indicate that artificially reared lambs may be routinely weaned to a dry diet at 14 d of age. The major alterations in plasma metabolites that occur within 6 to 8 d after abrupt weaning may define the period when these lambs become functional ruminants.

DNA sequences from the Candida utilis genome which, when cloned into a yeast integration plasmid (YIp5), confer on YIp5 the ability to replicate autonomously in Saccharomyces cerevisiae are described. Several recombinant plasmids which transform S. cerevisiae YNN27 to Ura3+ with an efficiency of 2 X 10(3) transformants per microgram of DNA were obtained. One of the recombinant plasmids, pHMR22 (6.6 kilobases) contains ars (autonomous replication sequence), which is homologous with two different DNA fragments of the C. utilis genome but has no detectable homology to total DNA from Candida albicans, Pachysolen tannophilus, or S. cerevisiae. Restriction and subcloning analyses of pHMR22 showed that Sau3A destroys the functions of cloned ars whereas there are no BamHI, PstI, SalI, HindIII, EcoRI, or PvuII sites in the region of ars which is required for its functional integrity. Thus, pHMR22 appears to be a useful vector for cloning desired genes in S. cerevisiae.

Analysis of the karyotypes of multiple Candida albicans isolates by pulsed-field electrophoresis confirms the observation by Lasker et al. of eight chromosomes. The genes previously assigned to chromosome 1 in fact fall into two groups, one (including ADE1, SOR9, and CDC10) is linked to the ribosomal DNA genes on a chromosome called R, whereas the others are found on chromosome 1. Chromosome R varies in electrophoretic mobility among strains, usually running equal to or faster than chromosome 1 but in rare cases running slower than chromosome 1. In strain 1012A, the decreased mobility of one homolog is associated with the very large majority of the rDNA genes being on that homolog; the second homolog, with only a few copies, migrates with chromosome 2. Linkage analysis by using spheroplast fusion confirms the gene assignments made by hybridization to blots of the electrophoretic karyotype. A newly cloned gene, LYS2, hybridizes to chromosome 1.

Transrectal ultrasound (TRUS) was used to measure tumour size in patients with carcinoma of the cervix and to assess its prognostic significance. Clinical staging was conducted and at the time of examination under anaesthesia, TRUS was used to assess maximum transverse diameter of the tumour. Eighty-one patients were studied. FIGO stages were 1B 34 patients, IIA seven patients, IIB 31 patients, IIIA two patients and IIIB seven patients. Mean tumour diameters by stage were IB 37 mm, IIA 37 mm, IIB 49 mm, IIIA 42 mm and IIIB 50 mm. There was a significant correlation between size and stage (p= 0.001). With a median follow-up of 18 months, 16 relapses have occurred. The actuarial relapse rates at median follow-up by stage were IB 10%, IIA 17%, IIB 22%, IIIA 0% and IIIB 35%. The actuarial relapse rates by size grouping at median follow-up were less than 30 mm 0%, greater than 30 and less than 40 mm 11%, greater than 40 and less than 50 mm 22%, and greater than 50 mm 38%. There was a significant difference between the mean recorded size of the tumours in the relapsed group and the relapse-free group (p= 0.02). Despite the small number of patients and short follow-up, tumour size as measured by TRUS appears to predict relapse.

The opportunistic fungal pathogen, Candida albicans, is diploid as usually isolated and has no apparent sexual cycle. Genetic analysis has therefore been very difficult. Molecular genetics has yielded important information in the past few years, but it too is hampered by the lack of a good genetic map. Using the well-characterized strain 1006 and strain WO-1, which undergoes the white-opaque phenotypic transition, we have developed a genomic restriction map of C. albicans with the enzyme SfiI. There are approximately 34 SfiI restriction sites in the C. albicans genome. Restriction fragments were separated by pulsed-field electrophoresis and were assigned to chromosomes by hybridization of complete and partial digests with known chromosome-specific probes as well as by digestion of isolated chromosomes. Telomeric fragments were identified by hybridization with a telomere-specific probe (C. Sadhu, M.J. McEachern, E.P. Rustchenko-Bulgac, J. Schmid, D.R. Soll, and J.B. Hicks, J. Bacteriol. 173:842-850, 1991). WO-1 differs from 1006 in that it has undergone three reciprocal chromosomal translocations. Analysis of the translocation products indicates that each translocation has occurred at or near an SfiI site; thus, the SfiI fragments from the two strains are similar or identical. The tendency for translocation to occur at or near SfiI sites may be related to the repeated sequence RPS 1, which contains four such sites and could provide homology for ectopic pairing and crossing over. The genome size of both strains is about 16 to 17 megabases, in good agreement with previous determinations.

Between 1979 and 1984 thirty-seven patients were treated with combination chemotherapy for metastatic seminoma; 27 of these had relapsed following initial radiotherapy for stage I and IIA disease and 10 patients with stage IIB-IV disease received chemotherapy de novo followed by radiotherapy to sites of bulk disease. Treatment consisted of either a cis-platinum containing combination (25 patients), or cyclophosphamide and etoposide (12 patients). The overall survival of all patients at 5 years was 49%, 34 patients were assessable for response; a CR was obtained in 8 (24%) and a GPR in 19 (56%), the 5 year survival of this group being 66% at 5 years. No difference in survival was seen in relation to age, previous irradiation, serum HCG or LDH; bulk disease however, was an adverse prognostic factor. Survival was similar for both chemotherapy schedules but neutropenia and life-threatening sepsis was less with the cyclophosphamide etoposide combination.

The secreted aspartyl proteinase activity from Candida albicans is thought to be a potential virulence factor. Four laboratories have cloned a gene from C. albicans encoding this enzyme. When two of these genes sharing 77% homology at the DNA level are hybridized under conditions of high stringency to contour-clamped homogeneous electric field chromosome separations of four different strains, they label different chromosomes: chromosome 6 for SAP1 and chromosome R for SAP2. The existence of different genes for the two sequences was confirmed by polymerase chain reaction. Genomic Southern blots probed with the genes and washed at low stringency revealed several cross-hybridizing bands. Contour-clamped homogeneous electric field chromosome separations probed at low stringency indicated that there was a cross-hybridizing sequence on chromosome 3 in addition to those on chromosomes R and 6. The genes for the secreted aspartyl proteinase activity in C. albicans thus constitute a gene family which we have called the SAP family.

Candida albicans and Candida stellatoidea are two closely related imperfect yeasts. Some isolates characterized as C. stellatoidea are in fact C. albicans, while others differ with respect to virulence and to karyotype, containing extra small chromosomes. Experiments in this study allowed us to infer that a typical C. stellatoidea isolate, Y2360, has 12 chromosomes rather than the 7 previously shown for C. albicans. The majority of cloned sequences tested hybridized to analogous chromosomes in C. albicans and in C. stellatoidea, although there were exceptions, and a repeated element isolated as specific for C. albicans hybridized to most of the chromosomes of C. stellatoidea. Several genes tested hybridized to one of the smaller, C. stellatoidea-specific chromosomes as well as to a larger one. The arrangement of restriction enzyme sites around the gene was the same in both the large and small chromosomes. For ADE2 and LYS2, the arrangements were identical to those of a typical C. albicans strain, FC18, suggesting a high degree of sequence conservation between the two species. Spheroplast fusion and segregation experiments showed that the ADE2 genes on both the large and small chromosomes of C. stellatoidea are active, implying that the organism is functionally at least triploid for this gene and probably for any others duplicated on the smaller chromosomes.

Genetic similarities and differences between type I and type II Candida stellatoidea were studied. The electrophoretic karyotype, mitochondrial DNA (mtDNA) restriction patterns, and midrepeat sequence of nuclear DNA in type I C. stellatoidea were clearly distinguishable from those of a reference culture of Candida albicans. The karyotype and the major bands of the midrepeat sequence of type II C. stellatoidea were indistinguishable from those of the reference C. albicans. The mtDNA restriction patterns of four type I isolates were homogeneous regardless of the endonucleases and probes used. The mtDNA restriction patterns of type II C. stellatoidea varied from strain to strain. Some of them were identical to that of C. albicans, while others were the same as that of type I C. stellatoidea. Immunofluorescence with C. albicans serotype A-specific monoclonal antibody indicated that the four isolates of type I C. stellatoidea were serotype B (non-A), whereas all three type II isolates studied were serotype A. Taken together, these results support the hypothesis that the isolates of C. stellatoidea type II studied are sucrose-negative mutants of serotype A C. albicans. Since C. stellatoidea type I differs from C. albicans in several major genetic characteristics, it cannot be viewed as a simple mutant derived from C. albicans. Hybrids produced by protoplast fusion of type I and type II cells were capable of assimilating sucrose, indicating that the sucrose-negative phenotypes of the parents are due to different mutations.

A superoxide-forming oxidase from activated human neutrophil membranes was solubilized by two slightly different methods, then purified by "dye-affinity" chromatography. Kinetic studies of the purified preparations gave Vmax values of 5-10 mumol of O-2/min/mg of protein, and Km values for NADH and NADPH that were in reasonable agreement with values determined previously using particulate and crude solubilized preparations of the respiratory burst oxidase. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed prominent bands at 67, 48, and 32 kDa, together with some minor contaminants, whereas gel electrophoresis under non-denaturing conditions gave a single major band that when eluted and re-electrophoresed in the presence of sodium dodecyl sulfate showed bands at 67, 48, 32 kDa. We believe that all three bands represent oxidase components. The flavin content of the purified enzyme was 20.4 +/- 2.0 S.E. pmol of FAD/microgram of protein, whereas heme averaged 0.1 +/- 0.02 pmol/microgram and ubiquinone could not be detected. Assuming that the enzyme is composed of one 67-kDa subunit, one 48-kDa subunit, and one 32-kDa subunit (i.e. that its molecular mass is approximately 150 kDa), it can be calculated to have a turnover number of 700-1500 min-1, in agreement with a value reported previously for oxidase in a particulate O-2-forming system (Cross, A. R., Parkinson, J. F., and Jones, O. T. G. (1985) Biochem. J. 226, 881-884), and to contain the following quantities of redox carriers (mol/mol): FAD, 3.0; heme, 0.015; ubiquinone, less than 0.06. It remains to be determined whether this preparation represents the complete respiratory burst oxidase or is only the pyridine nucleotide dehydrogenating component of a more complex enzyme.

A library of Saccharomyces cerevisiae DNA in the vector lambda Charon 28 was probed for sequences complementary to cDNA made from poly(A)+ RNA isolated from the well-sporulating yeast strain AP1 a/alpha. The RNA was isolated from cells that had been incubated 7, 9, 11, and 13 hr in sporulation medium. DNA complementary to poly(A)+ RNA from alpha/alpha(nonsporulating) AP1 was used as a control, and 46 bacteriophage that gave a stronger response with a/alpha cDNA than with alpha/alpha cDNA were obtained in a screening of three yeast genomes worth of DNA. Two of the bacteriophage appeared to contain a/alpha-specific genes, in that they hybridized to cDNA from vegetative a/alpha RNA. The rest appeared to correspond to a/alpha genes expressed preferentially during sporulation. Restriction endonuclease analysis of four of the cloned sequences revealed a single major region of transcription in each; these regions ranged in size from 2.5 to 4.0 kilobases. RNA blot analysis showed that, in three of the four cases, transcripts of two different sizes were homologous to the cloned sequence. In all four cases, the homologous transcripts appeared at about 7 hr and were decreasing in amount by 13 hr. These results provide evidence for transcriptional control of genes expressed during sporulation and for at least one group of genes that is turned on at about the time of meiosis I in sporulation.

The oxidative folding of human insulin-like growth factor (IGF)-I yields two major disulphide folding isomers. In the present study, B-domain analogues of IGF-I were used to investigate the effect of mutations on the folding reaction and to investigate the functional implications of misfolding. The analogues used were substitutions of the native Glu3 by Gly or Arg, or the native Glu9 by Lys. IGF-I and these analogues were also prepared attached to a hydrophobic 13-amino-acid N-terminal extension, Met-Phe-Pro-Ala-Met-Pro-Leu-Ser-Ser-Leu-Phe-Val-Asn, referred to as ‘Long-IGF-I’ analogues. Each IGF was fully reduced and refolded to yield native and misfolded isomers, which were subsequently purified for biological characterization. Analysis of the folding reaction at equilibrium revealed a distribution of folding isomers characteristic for each peptide. The yield of the native disulphide folding isomer was increased for the Glu3 substitutions, but not for the Glu9 substitution. The main alternative folding isomer was present in the IGF-I analogues in reduced proportions. Except for [Gly3]IGF-I the N-terminal extension increased the yield of the native isomer which was maximal for the analogue Long-[Arg3]IGF-I. A folding intermediate for the latter analogue was isolated and partially characterized. The biological assays showed that all the main alternative isomers bound poorly to IGF-binding proteins (IGFBPs) secreted by L6 myoblasts. Moreover, these isomers bound to the type 1 IGF receptor with 0.5-25% the affinity of the native isomer. In a rat L6 myoblast protein-synthesis assay, the observed biological activity of the native and main alternative isomers was explained by their modified IGFBP- and receptor-binding properties. We propose that the N-terminal extension imparts a steric constraint at a crucial point in folding, thus allowing native disulphide bonds to form efficiently.

When chromatin prepared from WI-L2 lymphocytes by low salt extraction and shearing is centrifuged on a glycerol gradient, one area of the gradient yields chromatin enriched in template activity for Escherichia coli DNA-dependent RNA polymerase (EC 2.7.7.6; nucleosidetriphosphate:RNA nucleotidyltransferase) as compared to Saccharomyces cerevisiae RNA polymerase II (or B). Another area yields chromatin preferred by the eukaryotic enzyme. Kinetic studies indicate that the differences in activity cannot be explained by differences in affinity of the enzymes for the various templates. The DNA isolated from either fraction has a molecular weight of 8.5 X 106. The "yeast active" fraction seems enriched in proteins. Mixing experiments indicate that the yeast enzyme does not alter the template in such a way as to improve it for the bacterial enzyme.

Restriction fragment length polymorphisms in the ribosomal DNA (rDNA) have been shown to be a useful criterion for distinguishing among various isolates of Candida albicans. In a sample of 12 clinical isolates, we found six different classes based on variations in the fragments produced from genomic DNA by EcoRI and visualized after Southern transfer by being probed with a plasmid containing Saccharomyces cerevisiae rDNA. Some of the classes appeared to be heterozygous at the rDNA locus. Similar digestion of other Candida species showed that each could be identified on the basis of its restriction patterns. Since these are highly reiterated genes, the differences were apparent on ethidium bromide-stained gels; Southern transfers were not necessary. EcoRI restriction maps of the rDNA of C. albicans, C. stellatoidea, C. tropicalis, and C. guilliermondii were determined.

Chromosomes from Cryptococcus neoformans, an encapsulated yeast pathogen, were separated by contour-clamped homogeneous field gel electrophoresis. Seven strains representing all four serotypes were studied. It was found that each strain had a unique, reproducible pattern of chromosome bands which could potentially be used for strain polymorphism studies. There were between 10 and 12 chromosomes in the strains studied, with an approximate genomic size of 15,000 to 17,000 kilobases. Chromosome separation also could be used to assign locations for cloned genes, and the ribosomal DNA genes were found on one of the larger C. neoformans chromosomes. The technique of electrophoretic karyotyping should be helpful for genetic and molecular investigations into the biology of C. neoformans.

This paper reports that the opaque and white phenotypes of Candida albicans constitute a true high-frequency reversible transition system. The rDNA restriction fragment and orthogonal field alternating gel electrophoresis profiles of opaque and white phenotypes are indistinguishable, and a genetic marker introduced into a white strain is present in all opaque derivatives of this strain. Opaque and white derivatives appear markedly different on a bismuth indicator medium and differ in a number of other respects. We have used bismuth medium to examine the spontaneous and temperature-induced frequencies of transition from opaque to white. The temperature-induced transition from opaque to white does not occur when opaque cells are held in water.

Insulin-like growth factor-I (IGF-I) analogues were produced with the aim of identifying IGF-I residues that contribute to the specificity of binding to the type 1 IGF receptor as opposed to the insulin receptor. Receptor binding properties of a series of A- and B-domain analogues were compared using rat L6 myoblasts, soluble human IGF type 1 receptors and soluble human insulin receptor isoforms HIR-A (−Ex11) and HIR-B (+Ex11). IGF-I analogues, [Leu8] IGF-I and [Phe59] IGF-I, were shown to exhibit respectively, a 28- and 17-fold decrease in affinity for the HIR-A with only a 6- and 5-fold decrease in affinity for the human IGF type 1 receptor. In contrast, the analogue [His4] IGF-I was equipotent to IGF-I in binding to the soluble type 1 IGF receptor while showing 7-fold and 4-fold increases in HIR-A and HIR-B binding respectively. Furthermore, [Leu62] IGF-I was 8-fold less potent than IGF-I in soluble IGF type 1 receptor binding but only showed a 2-fold decrease in HIR-A and HIR-B binding. Our study supports the conclusion that the co-evolution of the IGF-I and insulin receptor/ligand systems has resulted in subtle structural differences in the A- and B-regions of each ligand important for defining receptor binding specificity.

By using orthogonal-field alternating gel electrophoresis (OFAGE), field-inversion gel electrophoresis (FIGE), and contour-clamped homogeneous field gel electrophoresis (CHEF), we have clearly resolved 11 chromosomal bands from various Candida albicans strains. OFAGE resolves the smaller chromosomes better, while FIGE, which under our conditions causes the chromosomes to run in the reverse order of OFAGE, is more effective in separating the larger chromosomes. CHEF separates all chromosomes under some conditions, but these conditions do not often resolve homologs. The strains examined are highly polymorphic for chromosome size. Fourteen cloned Candida genes, isolated on the basis of conferral of new properties to or complementation of auxotrophic deficiencies in Saccharomyces cerevisiae, and three sequences of unknown function have been hybridized to Southern transfers of CHEF, FIGE, and OFAGE gels. Four sets of resolvable bands have been shown to be homologous chromosomes. On the basis of these data, we suggest that C. albicans has seven chromosomes. Genes have been assigned to the seven chromosomes. Two chromosomes identified genetically have been located on the electrophoretic karyotype.

A temperature-sensitive mutant of Escherichia colihas been found in which the conditional growth is a result of a thermosensitive glutaminyl-transfer ribonucleic acid synthetase. The corresponding genetic locus glnSis cotransduced with lip. In a strain containing the mutationally altered glutaminyl-transfer ribonucleic acid synthetase, no derepression of the enzyme itself nor of glutamine synthetase was observed.

Medulloblastoma is an uncommon tumour in the adult population. Maximum surgical resection followed by craniospinal irradiation with a posterior fossa boost is the standard treatment. We report the case history of an adult with medulloblastoma and severe kyphoscoliosis. The unusual anatomy of the patient posed a technical challenge to the oncologist and the physicist in planning the craniospinal radiotherapy. A shaped spinal field matched to a parallel opposed pair of shaped head fields was used. The technique used in treating this patient was made possible with the use of a multileaf collimation and verification with an electronic portal imaging device. The patient remains well with no sign of relapse 4 years after treatment.

Titan's upper atmosphere produces an ionosphere at high altitudes from photoionization and electron impact that exhibits complex chemical processes in which hydrocarbons and nitrogen‐containing molecules are produced through ion‐molecule reactions. The structure and composition of Titan's ionosphere has been extensively investigated by the Ion and Neutral Mass Spectrometer (INMS) onboard the Cassini spacecraft. We present a detailed study using linear correlation analysis, 1‐D photochemical modeling, and empirical modeling of Titan's dayside ionosphere constrained by Cassini measurements. The 1‐D photochemical model is found to reproduce the primary photoionization products of N2and CH4. The major ions, CH5+, C2H5+, and HCNH+are studied extensively to determine the primary processes controlling their production and loss. To further investigate the chemistry of Titan's ionosphere we present an empirical model of the ion densities that calculates the ion densities using the production and loss rates derived from the INMS data. We find that the chemistry included in our model sufficiently reproduces the hydrocarbon species as observed by the INMS. However, we find that the chemistry from previous models appears insufficient to accurately reproduce the nitrogen‐containing organic compound abundances observed by the INMS. The major ion, HCNH+, is found to be overproduced in both the empirical and 1‐D photochemical models. We analyze the processes producing and consuming HCNH+in order to determine the cause of this discrepancy. We find that a significant chemical loss process is needed. We suggest that the loss process must be with one of the major components, namely C2H2, C2H4, or H2. The primary products of photoionization are well described by our modelCorrelations in the INMS data show the existence of new chemical pathwaysTitan's ionospheric chemistry can be represented by a 1‐D photochemical model

I wish to comment on the paper by Plowman & Doughty (1991). The authors describe an interesting method for cranio-spinal radiation using a PTB technique. They “believe such techniques will become standard practice”.

A technique for reciprocal root‐scion grafting of soybeans is described using plastic straws and small rubber bands in place of pressure tape commonly employed. The technique described is simpler and faster than the pressure‐tape method of grafting; success of greater than 90% was obtained in our experiments.