DNA from Serratia marcescens confers a hydrophobic character in Escherichia coli

In order to determine whether hydrophobic surface properties of Serratia marcescens can be transferred to Escherichia coli, E. coli DH5 alpha cells were transformed by DNA fragments from S. marcescens RZ. Fifteen-hundred E. coli transformants were screened for adhesion to hexadecane and polystyrene. One transformant exhibited increased adhesion to hexadecane droplets, as well as altered kinetics of aggregation in the presence of ammonium sulfate. Western colony blotting revealed that antibodies raised against S. marcescens RZ recognized component(s) on the transformant outer surface.

Assignment of a locus for mouse lung tumor susceptibility to proximal chromosome 19

Previous studies have hypothesized that at least three genetic loci contribute to differences in pulmonary adenoma susceptibility between mouse strains A/J and C57BL/6J. One gene that may confer susceptibility to lung tumorigenesis is the Kras protooncogene. To identify other relevant loci involved in this polygenic trait, we determined tumor multiplicity in 56 randomly chosen N-ethyl-N-nitrosourea-treated (A/J x C57BL/6J) N1 x C57BL/6 backcross (AB6N2) progeny and correlated it with genotypes at 77 microsatellite markers spanning the genome. A correlation of lung tumor multiplicity phenotypes with genotypes of microsatellite markers on distal Chromosome (Chr) 6 in the Kras region (Pas1) was confirmed, and a new region on Chr 19 (designated Pas3) was identified that also contributes to susceptibility. Linkage analysis on Chr 19 with 270 AB6N2 mice localized the region flanked by D19Mit42 and D19Mit19 that is most closely associated with lung tumor susceptibility. The Pas3 locus may be an enhancer of the susceptibility locus on Chr 6.

Ethnic variation in the CYP2E1 gene: polymorphism analysis of 695 African-Americans, European-Americans and Taiwanese

Human cytochrome P4502E1 (CYP2E1) is inducible by ethanol and is involved in metabolism of many known carcinogens including N-nitrosodimethylamine, butadiene, benzene, and carbon tetrachloride. A 50-fold variability in CYP2E1 enzyme activity in humans has been observed but it is unknown whether the basis for this variation is genetic or environmental. Recently, two restriction fragment length polymorphisms (RFLPs) within the CYP2E1 gene have been suggested as genetic markers of risk for cancer. The first was a Rsa I polymorphism in the 5' regulatory region that appeared to alter transcriptional activation of the gene and the second was a Dra I polymorphism located approximately 7000 bp downstream in an intron. Rare alleles at each of these loci have been associated with a reduced risk for lung cancer in Japanese and Swedish populations. We have used a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method to determine the genotype frequency for each of these CYP2E1 RFLPs in 695 individuals of Taiwanese, African-American or European-American background. Genotype and allele frequencies for Taiwanese were significantly different from those of African-Americans and European-Americans at either Rsa I or Dra I sites (p < 0.0001). Allele frequencies for African-Americans and European-Americans were significantly different at the Rsa I site (p = 0.03). The rare alleles (c2 and C) occurred at frequencies of 0.28 and 0.24 in Taiwanese, 0.01 and 0.08 in African-Americans, and 0.04 and 0.11 in European-Americans. In addition, we describe three haplotypes common to all three population samples and a fourth haplotype that was only detected in the Taiwanese population sample. This fourth haplotype may have been caused by a recombination event between these markers.(ABSTRACT TRUNCATED AT 250 WORDS)

A 13 kb resolution cosmid map of the 14 Mb fission yeast genome by nonrandom sequence-tagged site mapping

We present the application of a nonrandom sequence-tagged site (STS) content detection method in mapping an entire genome, that of fission yeast. The novelty of our strategy is in the use of STS probes made from both ends of cosmid clones, selected on the basis of "sample without replacement" (only library clones that show no previous positive hybridization are selected and made into probes). We developed powerful techniques, based on consistency analysis, for error detection and contig assembly. In addition, we probed our library with genetically mapped markers and Notl or Sfil linking clones, thereby anchoring contigs onto chromosomes. Our map contains more than 1000 sites, including genes (most were previously unmapped), occurrences of known repetitive elements, and Notl-Sfil restriction sites.

Expected behavior of conditional linkage disequilibrium

The ubiquitousness of RFLPs in the human genome has greatly helped the mapping of human disease genes, and it has been suggested that population measures of association between disease and marker loci could help with this mapping. For rare diseases, random samples are taken from within disease genotypes in order to obtain reasonable sample sizes, but this sampling strategy requires a modification of the usual measures of association. We present theoretical predictions for the mean and variance of such a modified measure, under the assumption that the disease gene is maintained at a constant low frequency in the population. The coefficient of variation of this modified measure is large enough that caution is needed in using the measure to locate disease genes, and, furthermore, the coefficient of variation cannot be made arbitrarily small by increasing sample size. The modified association measure is calculated for recently published data on cystic fibrosis.

The coalescent process in models with selection, recombination and geographic subdivision

A population genetic model with a single locus at which balancing selection acts and many linked loci at which neutral mutations can occur is analysed using the coalescent approach. The model incorporates geographic subdivision with migration, as well as mutation, recombination, and genetic drift of neutral variation. It is found that geographic subdivision can affect genetic variation even with high rates of migration, providing that selection is strong enough to maintain different allele frequencies at the selected locus. Published sequence data from the alcohol dehydrogenase locus of Drosophila melanogaster are found to fit the proposed model slightly better than a similar model without subdivision.

The effects of labetalol and prazosin on exercise haemodynamics in hypertensive patients

The antihypertensive and haemodynamic effects of labetalol were compared with those of prazosin both at rest and during bicycle exercise in 38 moderate to moderately severe hypertensive patients (supine DBP 95 to 119 mmHg when untreated). Following a two week open placebo phase to establish baseline BP and baseline exercise performance, patients were randomly and double-blindedly assigned to receive labetalol or prazosin. Drug dose was titrated from 100 to 400 mg labetalol twice daily, or from one to 10 mg prazosin twice daily at weekly intervals until BP was controlled (supine DBP less than or equal to 90 mmHg with at least a 10 mmHg decrease from baseline). Eighteen labetalol and twenty prazosin patients achieved BP control and were subsequently reexercised to fatigue on a bicycle ergometer. The mean changes from baseline for heart rate and rate pressure product (heart rate x SBP) were reduced only in the labetalol group; the difference between the labetalol and prazosin groups was significant (P less than 0.01) both at rest and during exercise. This haemodynamic profile of labetalol may be important in selecting a vasodilating antihypertensive for patients with concomitant ischaemic heart disease.

Primary surgical treatment of anterior cruciate ligament ruptures. A long-term follow-up study

We reviewed 52 patients who underwent primary surgical repair of their acutely injured ACL using a multiple loop, varying depth suture technique. The average followup was 6 years and 10 months. Nine patients (17%) were considered as having failed repairs, with failure based on the presence of clinical instability (giving way) with sports participation and a positive Lachman test and/or pivot shift maneuver. In addition, of 26 patients in whom KT-1000 (MEDmetric Corp., San Diego, CA) measurements were performed, 42% were found to have abnormal laxity. Although using multiple sutures in primary repair of the anterior cruciate may work in some patients, it is an unpredictable operative procedure and resulted in a 17% failure rate in our study.

Transmembrane signal transduction in bacterial chemotaxis involves ligand-dependent activation of phosphate group transfer

Signal transduction in Escherichia coli involves the interaction of transmembrane receptor proteins such as the aspartate receptor, Tar, and the products of four chemotaxis genes, cheA, cheY, cheW, and cheZ. It was previously shown that the cheA gene product is an autophosphorylating protein kinase that transfers phosphate to CheY, whereas the cheZ gene product acts as a specific CheY phosphatase. Here we report that the system can be reconstituted in vitro and receptor function can be coupled to CheY phosphorylation. Coupling requires the presence of the CheW protein, the appropriate form of the receptor, and the CheA and CheY proteins. Under these conditions the accumulation of CheY-phosphate is enhanced approximately 300-fold. This rate enhancement is seen in reactions using wild-type and "tumble" mutant receptors but not "smooth" mutant receptors. The increased accumulation of phosphoprotein was inhibited by micromolar concentrations of aspartate, using wild-type, but not tumble, receptors. These results provide evidence that the signal transduction pathway in bacterial chemotaxis involves receptor-mediated alteration of the levels of phosphorylated proteins. They suggest that CheW acts as the coupling factor between receptor and phosphorylation. The results also support the suggestion that CheY-phosphate is the tumble signal.

Overview of a workshop on quantitative models for developmental toxicity risk assessment

A workshop was held to discuss potential advancements to improve the precision of risk estimates for developmental toxicity. This paper presents an overview of the discussions at the workshop, focusing on the risk assessment process and science policy considerations important in the use of quantitative models. Some of the pertinent biological considerations are reviewed, particularly those related to the repair capacity of the developing organism and how this affects the concept of a threshold for developmental toxicity effects, as well as the maternal and litter influences on developmental toxicity outcomes. Finally, the current status of use of quantitative approaches is described, possible short-term approaches are discussed, and future research needs in this area are outlined.

Plantar approach for excision of bilateral soft tissue masses in a child

A painful soft tissue mass of the plantar aspect of both feet, in a 5-year-old child, is presented. Plantar incisions are ideal in specific cases as long as the surgeon adheres to certain principles, as outlined in this manuscript. A discussion of lipomas is also presented. Optimum exposure is the key to total eradication of soft tissue lesions and to proper maintenance of wound healing. Location of the lesion presented warranted use of the plantar approach. Minimal hypertrophy of the plantar scar was achieved, as well as few symptoms by the patient.

On the role of unequal exchange in the containment of transposable element copy number

A population genetics model of the role of asymmetric pairing and unequal exchange in the stabilization of transposable element copy number in natural populations is proposed and analysed. Monte Carlo simulations indicate that the approximations incorporated into the analysis are robust in the relevant parameter ranges. Given several simple assumptions concerning transposition and excision, equal and unequal exchange, and chromosome structure, predictions of the relative numbers of transposable elements in various regions of theDrosophila melanogastergenome are compared to the observed distribution ofroo/B104elements across chromosomal regions with differing rates of exchange, and betweenXchromosomes and autosomes. There is no indication of an accumulation of elements in the distal regions of chromosomes, which is expected if unequal exchange is reduced concomitantly with normal crossing over in the distal regions. There is, however, an indication of an excess of elements relative to physical length in the proximal regions of the chromosomes, which also have restricted crossing over. This observation is qualitatively consistent with the model's predictions. The observed distribution of elements between the mid-sections of theXchromosomes and autosomes is consistent with the predictions of one of two models of unequal exchange.

Purification and characterization of the wild-type and mutant carboxy-terminal domains of the Escherichia coli Tar chemoreceptor

The carboxy-terminal half of the Escherichia coli Tar chemoreceptor protein was cloned into an overproducing plasmid with the transcription of the insert under the control of the strong hybrid tac promoter. Two dominant mutations in the tar gene, which result in "tumble-only" (tar-526) or "swim-only" (tar-529) phenotypes and which are postulated to produce proteins locked in specific signalling modes, were introduced separately onto the overproducing plasmid. After induction with isopropyl-beta-D-thiogalactopyranoside, cells containing the plasmids produced about 10% of their soluble cellular protein as the carboxy-terminal fragments. A scheme to purify the overproduced fragments was developed. Typical yields of pure fragment were 5, 30, and 20 mg per liter of induced culture for the wild type, 526 mutant, and 529 mutant, respectively. Fast-protein liquid chromatography-gel filtration analysis of the pure fragments showed that they all existed as oligomers (ca. 103,000 daltons), possibly trimers or tetramers (monomer size is 31,000 daltons). However, the 529 mutant fragment showed an additional oligomeric form (240,000 daltons) corresponding approximately to an octamer. When chromatographed in the presence of 1% octylglucoside, all three fragments showed an identical single oligomeric size of about 135,000 daltons. Further differences between the fragments such as ion-exchange behavior and susceptibility to degradation were found. Taken together, these results suggest that conformational differences between the 529 mutant fragment and the other fragments exist and that these differences may correlate with the phenotypic effects of the tar-529 mutation.

Phosphorylation of three proteins in the signaling pathway of bacterial chemotaxis

Six cytoplasmic che gene products are required for signal transduction in bacterial chemotaxis, but the nature of their biochemical interactions is not known. We show that in vitro the CheA protein becomes autophosphorylated in the presence of ATP. In addition, the phosphate group on CheA can be rapidly transferred to CheB, a protein involved in adaptation to stimuli, or to CheY, a protein involved in the excitation response. The phosphorylation of CheB and CheY is transient; they readily dephosphorylate. We have also found that CheZ, a protein that appears to antagonize CheY function in vivo, accelerates the hydrolysis of the phosphate on CheY. These results suggest that signal transduction in bacterial chemotaxis may involve the flow of phosphate through a cascade of phosphorylated protein intermediates.

Reconstitution of emulsifying activity of Acinetobacter calcoaceticus BD4 emulsan by using pure polysaccharide and protein

Acinetobacter calcoaceticus BD4 and BD413 produce extracellular emulsifying agents when grown on 2% ethanol medium. For emulsifying activity, both polysaccharide and protein fractions were required, as demonstrated by selective digestion of the polysaccharide with a specific bacteriophage-borne polysaccharide depolymerase, deproteinization of the extracellular emulsifying complex with hot phenol, and reconstitution of emulsifier activity with pure polysaccharide and a polysaccharide-free protein fraction. Chemical modification of the carboxyl groups in the polysaccharide resulted in a loss of activity. The protein required for reconstitution of emulsifying activity was purified sevenfold. The BD4 emulsan apparently derives its amphipathic properties from the association of an anionic hydrophilic polysaccharide with proteins.

Anatomy of the normal knee as seen by magnetic resonance imaging

Nuclear magnetic resonance imaging (MRI) was used to study the normal knee. As well as revealing bone quality, MRI provided useful information on intra-articular and extra-articular soft tissues. Midsagittal views gave clear images of the cruciate ligaments, and of the patellar and quadriceps tendons. Parasagittal views were the best for delineating the menisci which, like ligaments and tendons, are of low intensity; the semimembranosus tendon and its insertion to the proximal tibia were also seen clearly in these views. The cruciate ligaments and menisci, though visible in the coronal view also, were better seen in the sagittal view. Axial views provided information on the structure of the patella, its cartilage, the patellofemoral joint and posterior soft-tissue structures.

Magnetic resonance imaging of the pituitary gland

Magnetic resonance imaging (MRI) was performed on 22 patients with a wide spectrum of pituitary disease and on 17 control subjects, in order to determine whether MRI is useful in localising and determining the extent of involvement of large and small pituitary tumours. The results indicate that MRI, with an 0.5 T superconducting magnet (Elscint, Israel), can be used to visualise large pituitary tumours and to determine the extent of parasellar and suprasellar involvement. The 'empty sella' syndrome can also be easily and confidently diagnosed. Some microadenomas can be visualised despite the relatively thick slices (0.7 cm) used in this study. These findings suggest that MRI in its current state of development is very useful in evaluating large pituitary lesions. With further technical refinements, improving the spatial resolution and decreasing slice thickness, this technique may come to be of some importance in the evaluation of pituitary microadenomas.