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That the hotel industry is capital-intensive is rarely challenged. Also, that the profits accruing from the operation of a hotel as a business result from the aggregation of millions of essentially minuscule transactions (compared to the investment made) is without doubt. The ability to generate the millions of transactions is dependent upon a myriad of non-specific and unquantifiable actions and reactions of management and the customer (the guest) – image, fashion, brand and brand loyalty, location, style, comparative price, friendliness, hospitality, critical acclaim, star rating, management style and management skill – all impact on and influence the ability to generate custom and so the level of profit. As a result, the hotel industry is recognized as high-risk by investors and operators alike. However, the assessment of investment risk appears to be little understood or at least rarely applied in the majority of investment decisions.

Chemotactic responses in Escherichia coli are typically mediated by transmembrane receptors that monitor chemoeffector levels with periplasmic binding domains and communicate with the flagellar motors through two cytoplasmic proteins, CheA and CheY. CheA autophosphorylates and then donates its phosphate to CheY, which in turn controls flagellar rotation. E. coli also exhibits chemotactic responses to substrates that are transported by the phosphoenolpyruvate (PEP)-dependent carbohydrate phosphotransferase system (PTS). Unlike conventional chemoreception, PTS substrates are sensed during their uptake and concomitant phosphorylation by the cell. The phosphoryl groups are transferred from PEP to the carbohydrates through two common intermediates, enzyme I (EI) and phosphohistidine carrier protein (HPr), and then to sugar-specific enzymes II. We found that in mutant strains HPr-like proteins could substitute for HPr in transport but did not mediate chemotactic signaling. In in vitro assays, these proteins exhibited reduced phosphotransfer rates from EI, indicating that the phosphorylation state of EI might link the PTS phospho-relay to the flagellar signaling pathway. Tests with purified proteins revealed that unphosphorylated EI inhibited CheA autophosphorylation, whereas phosphorylated EI did not. These findings suggest the following model for signal transduction in PTS-dependent chemotaxis. During uptake of a PTS carbohydrate, EI is dephosphorylated more rapidly by HPr than it is phosphorylated at the expense of PEP. Consequently, unphosphorylated EI builds up and inhibits CheA autophosphorylation. This slows the flow of phosphates to CheY, eliciting an up-gradient swimming response by the cell.

Measurements are presented of the radiation inactivation of four enzymes exposed to a 6 MeV proton beam. It has long been thought that the measurement of the susceptibility of an enzyme to ionizing radiation can be used to determine its molecular mass. Results are frequently interpreted using the empirical analysis of Kempner and Macey (Biochim. Biophys. Acta 163, 188-203, 1963). We examine this analysis and discuss the validity and limitations of the assumptions on which it is based. Our results indicate that the specific biochemical properties of each enzyme make a significant contribution to its radiation sensitivity.

This study investigates the pattern of growth of masking (GOM) for interleaved masking with Nucleus cochlear implant users. For an interleaved masking paradigm, where the masker and probe overlap in a same time window, the masker may have contrasting effects: it may increase the threshold (as a masker normally does) or decrease it due to a neural summation effect, facilitating detection of the probe. Several stimulation rates and masker levels were tested to examine under what conditions what phenomenon would occur. The results indicated that, in most of the conditions, the amount of masking was positive, i.e., the facilitating effect was not consistently observed. However, the slope of the GOM appears to be dependent upon the stimulation rate: the higher the stimulation rate, the lower the slope, implying that the facilitating effect might be always present and make a bigger impact on overall masking as the stimulation rate becomes high. The amount of masking was also often nonzero (positive) even when t...

Tsr, the serine chemoreceptor of Escherichia coli, has two signaling modes. One augments clockwise (CW) flagellar rotation, and the other augments counterclockwise (CCW) rotation. To identify the portion of the Tsr molecule responsible for these activities, we isolated soluble fragments of the Tsr cytoplasmic domain that could alter the flagellar rotation patterns of unstimulated wild-type cells. Residues 290 to 470 from wild-type Tsr generated a CW signal, whereas the same fragment with a single amino acid replacement (alanine 413 to valine) produced a CCW signal. The soluble components of the chemotaxis phosphorelay system needed for expression of these Tsr fragment signals were identified by epistasis analysis. Like full-length receptors, the fragments appeared to generate signals through interactions with the CheA autokinase and the CheW coupling factor. CheA was required for both signaling activities, whereas CheW was needed only for CW signaling. Purified Tsr fragments were also examined for effects on CheA autophosphorylation activity in vitro. Consistent with the in vivo findings, the CW fragment stimulated CheA, whereas the CCW fragment inhibited CheA. CheW was required for stimulation but not for inhibition. These findings demonstrate that a 180-residue segment of the Tsr cytoplasmic domain can produce two active signals. The CCW signal involves a direct contact between the receptor and the CheA kinase, whereas the CW signal requires participation of CheW as well. The correlation between the in vitro effects of Tsr signaling fragments on CheA activity and their in vivo behavioral effects lends convincing support to the phosphorelay model of chemotactic signaling.

The CheA protein of Escherichia coli is a histidine autokinase that donates its phosphate groups to two target proteins, CheY and CheB, to regulate flagellar rotation and sensory adaptation during chemotactic responses. The amino-terminal third of CheA contains the autophosphorylation site, determinants needed to interact with the catalytic center of the molecule, and determinants needed for specific recognition of its phosphorylation targets. To understand the structural basis for these activities, we examined the domain organization of the CheA phosphotransfer region by using DNA sequence analysis, limited proteolytic digestion, and a genetic technique called domain liberation. Comparison of the functionally interchangeable CheA proteins of E. coli and Salmonella typhimurium revealed two extensively mismatched segments within the phosphotransfer region, 22 and 25 aa long, with sequences characteristic of domain linkers. Both segments were readily susceptible to proteases, implying that they have an extended, flexible structure. In contrast, the intervening segments of the phosphotransfer region, designated P1 and P2 (roughly 140 and 65 aa, respectively), were relatively insensitive, suggesting they correspond to more compactly folded structural domains. Their functional properties were explored by identifying portions of the cheA coding region capable of interfering with chemotactic behavior when "liberated" and expressed as polypeptides. P1 fragments were not inhibitory, but P2 fragments blocked the interaction of CheY with the rotational switch at the flagellar motor, leading to incessant forward swimming. These results suggest that P2 contains CheY-binding determinants which are normally responsible for phosphotransfer specificity. Domain-liberation approaches should prove generally useful for analyzing multidomain proteins and their interaction targets.

This paper considers the requirements for effective testing of Programmable Electronic Systems. It discusses how interfaces available to the test environment may vary with system development and how these interfaces together with the mode of operation of Progammable Electronic Systems affect the ability to perform dynamic tests. A number of desirable test attributes are defined and four modes of operation are compared with respect to these attributes.

Extracellular purine nucleosides and nucleotides in micromolar concentrations stimulate proliferation of a variety of cell types in vitro and in vivo. As well they act synergistically with NGF to stimulate neurite outgrowth from PC12 cells. A variety of purine nucleosides and deoxyribonucleosides promote cell proliferation and increase intracellular cAMP. Their activities are inhibited by adenosine A2 receptor antagonists. Only adenosine interacts with the A2 receptor. We propose that the other nucleosides and deoxyribonucleosides inhibit extracellular adenosine deaminase, thereby increasing the extracellular concentration of adenosine. The nucleotides apparently act by stimulating P2y receptors coupled to inositol phosphate metabolism. We propose that the nucleosides and nucleotides act synergistically with other growth factors because each has distinct but complementary second messenger systems. If our hypotheses are correct, it should prove possible to modulate the growth and morphogenesis in several cell types using drugs that inhibit or stimulate adenosine A2 or purine P2y receptor agonists or the second messenger systems coupled to these receptors.

Aluminium intoxication in renal failure occurred over weeks or months when dialysis fluid or parenteral solutions were heavily contaminated and over many years when the main source was oral administration of aluminium-containing phosphate binders. Encephalopathy was common during subacute intoxication but in slow aluminium poisoning the main brunt was borne by the bones. However, in both tempos of intoxication several organs or systems were involved. Encephalopathy was usually accompanied by bone disease, bone disease by parathyroid suppression and both by anaemia. The heart and the lymphocytes are probably damaged by aluminium overload. Among the many questions left unanswered 15 years after the incrimination of aluminium as the cause of this multi-system illness are: (1) does low level aluminium overload in renal failure cause gradual deterioration in cerebral function? And, if so, (2) does it resemble Alzheimer's disease or a slow-onset version of dialysis encephalopathy? The evidence we review suggests that the answer to (1) is 'yes' and to (2) 'probably the latter'.

This study presents two lines of genetic evidence consistent with the premise that CheW, a cytoplasmic component of the chemotactic signaling system of Escherichia coli, interacts directly with Tsr, the membrane-bound serine chemoreceptor. (i) We demonstrated phenotypic suppression between 10 missense mutant CheW proteins and six missense mutant Tsr proteins. Most of these mutant proteins had leaky chemotaxis defects and were partially dominant, implying relatively minor functional alterations. Their suppression pattern was allele specific, suggesting that the mutant proteins have compensatory conformational changes at sites of interactive contact. (ii) We isolated five partially dominant CheW mutations and found that four of them were similar or identical to the suppressible CheW mutant proteins. This implies that there are only a few ways in which CheW function can be altered to produce dominant defects and that dominance is mediated through interactions of CheW with Tsr. The amino acid replacements in these mutant proteins were inferred from their DNA sequence changes. The CheW mutations were located in five regularly spaced clusters in the first two-thirds of the protein. The Tsr mutations were located in a highly conserved region in the middle of the cytoplasmic signaling domain. The hydrophobic moments, overall hydrophobicities, and predicted secondary structures of the mutant segments were consistent with the possibility that they are located at the surface of the CheW and Tsr molecules and represent the contact sites between these two proteins.

Escherichia coli and Salmonella typhimurium invest considerable resources in making flagella, motor organelles that function much like the propellers on a ship. Both classical and molecular genetic studies have begun to reveal how flagellar genes are regulated and how their products build and operate these remarkable devices.

The cheA locus of Escherichia coli encodes two protein products, CheAL and CheAS. The nucleotide sequences of the wild-type cheA locus and of two nonsense alleles confirmed that both proteins are translated in the same reading frame from different start points. These start sites were located on the coding sequence by direct determination of the amino-terminal sequences of the two CheA proteins. Both starts are flanked by inverted repeats that may play a role in regulating the relative expression rates of the CheA proteins through alternative mRNA secondary structures.

Measurements are presented of the radiation inactivation of four enzymes exposed to a 6 MeV proton beam. It has long been thought that the measurement of the susceptibility of an enzyme to ionizing radiation can be used to determine its molecular mass. Results are frequently interpreted using the empirical analysis of Kempner and Macey (Biochim. Biophys. Acta 163, 188-203, 1963). We examine this analysis and discuss the validity and limitations of the assumptions on which it is based. Our results indicate that the specific biochemical properties of each enzyme make a significant contribution to its radiation sensitivity.

(1977). PAIDEIA, HUMANITAS AND MODERN HUMANISM: SOME PERTINENT QUESTIONS. Educational Studies: Vol. 8, No. 1, pp. 29-35.

In patients maintained on regular haemodialysis in Newcastle upon Tyne the development of osteomalacia is substantially reduced when water used to prepare dialysate is deionised. After 1-4 years of dialysis, osteomalacia was evident in 15% of patients on deionised water and in 70% of patients on softened water from the same source. The close association of dialysis encephalopathy and osteomalacia suggests a common aetiology. Both diseases occur in centres with a high tap-water aluminium content. Serum-aluminium concentrations were raised in patients undergoing regular haemodialysis in the Northern Region of England. Those using softened water had higher concentrations than those using deionised water. Patients on softened water who had encephalopathy or dementia had serum-aluminium concentrations similar to those of patients using the same water-supplies without symptoms of these diseases, but they had been treated for longer. The evidence that aluminium absorption from dialysate causes osteomalacia and encephalopathy is strong enough to justify the expense of treating water by deionisation, reverse osmosis, or both in centres where tap-water aluminium is high.

The cheA locus of Escherichia coli, which is required for chemotactic behavior, encodes two polypeptide products designated p[cheA]L and p[cheA]S. The mode of synthesis of these two proteins was investigated by transferring various missense and nonsense mutations to a lambda transducing phage and observing the mutant cheA products made after infection of ultraviolet-irradiated host cells. Missense mutations had no effect on either the size or the relative amounts of the two cheA polypeptides. Most nonsense mutations caused premature translational termination of both cheA products, indicating that p[cheA]L and p[cheA]S must be translated from the same coding sequence in the same reading frame. Two exceptional nonsense alleles at the promoter-proximal end of cheA made an intact p[cheA]s but no detectable p[cheA]L. These findings show that the cheA locus may contain two different sites for initiation of translation. The synthesis of both proteins can be effected by the same promoter, but it is not yet clear whether both are translated from identical mRNA molecules. Complementation studies of cheA mutants provided evidence for two functional activities, one associated with the amino terminus of p[cheA]L and the other with the common portions of p[cheA]L and p[cheA]S. It is possible that each cheA product has a different function required for chemotaxis. The possible roles of these two products and the functional significance of bacterial genes with overlapping coding sequences are discussed.

Previous work has shown that the cheC gene product of Escherichia coli plays a key role in regulating the direction of flagellar rotation during chemotactic responses. An attempt was made to identify other stimulus transduction elements that interact with the cheC component by examining cheC revertants for functional suppressors. Approximately two-thirds of the revertants studied appeared to be due to back mutation or to second-site mutations near or within the cheC structural gene. The remainder of the revertants carried suppressor mutations that mapped at the cheZ locus. Half of these suppressors impaired chemotaxis in a cheC+ background and were shown by complementation analysis to be defective in cheZ function. These suppressors corrected cheC defects in an allele-specific pattern, suggesting that the cheC and cheZ proteins are in direct contact and are mutually corrective due to protein-protein interaction. Observation of swimming patterns and flagellar rotation in cheC cheZ mutants demonstrated that the interaction of these two gene products influences both the spontaneous frequency of flagellar reversals and the ability of the rotational machinery to respond to chemotactic stimuli. A model of this interaction and its possible role in chemotaxis are discussed.

The tar and tap loci of Escherichia coli encode methyl-accepting inner membrane proteins that mediate chemotactic responses to aspartate and maltose or to dipeptides. These genes lie adjacent to each other in the same orientation on the chromosome and have extensive sequence homology throughout the C-terminal portions of their coding regions. Many spontaneous deletions in the tar-tap region appear to be generated by recombination between these regions of homology, leading to gene fusions that produce hybrid transducer molecules in which the N terminus of Tar is joined to the C terminus of Tap. The properties of two such hybrids are described in this report. Although Tar and Tap molecules have homologous domain structures, these Tar-Tap hybrids exhibited defects in stimulus detection and flagellar signaling. Both hybrid transducers retained Tar receptor specificity, but had reduced detection sensitivity. This defect was correlated with the presence of the C-terminal methyl-accepting segment of Tap, which may have more methylation sites than its Tar counterpart, leading to elevated steady-state methylation levels in the hybrid molecules. One of the hybrids, which carried a more extensive segment from Tap, appeared to generate constitutive signals that locked the flagellar motors in a counterclockwise rotational mode. Changes in the methylation state of this transducer were ineffective in cancelling this aberrant signal. These findings implicate the conserved C-terminal domain of bacterial transducers in the generation or regulation of flagellar signals.

An inexpensive, continuous flow assay for the determination of oxalate in plasma is described. The assay is based on the bioluminescent determination of NADH, a product of the degradation of oxalate by oxalate decarboxylase and formate dehydrogenase, using bioluminescent enzymes immobilized on cyanogen bromide-activated sepharose. The detection limit of the assay is 0.8 mumol/l. Intra-batch CV values of 5.2 and 3.8% were obtained at oxalate concentrations of 18 and 60 mumol/l. Recovery of added oxalate averaged 100.7%. Plasma oxalate ranged from less than 0.8 to 2 mumol/l in 14 healthy subjects, and from 6 to 134 mumol/l in 125 patients with renal disease treated by continuous ambulatory peritoneal dialysis. Ascorbic and dehydroascorbic acid did not directly interfere in the assay. In vitro oxalogenesis was observed in blood from 12 healthy subjects, but only after samples had stood at room temperature for more than 6 h. No significant oxalate generation occurred in blood from 24 patients with impaired renal function, even after standing at room temperature for 24 h. Oxalate generation was inhibited by the addition of oxalate to plasma, but the addition of urea and creatinine was without effect.

Renal osteodystrophy, which influences the quality of life and contributes to the morbidity of patients with endstage renal failure [1], has been reported to deteriorate in patients treated with continuous ambulatory peritoneal dialysis (CAPD) [2]. However, better control of serum calcium and phosphate in these patients [3] has provided preliminary data that show improvement in histological grading of osteitis fibrosa (OF) in our patients treated with CAPD [41. Another form of bone disease, the osteomalacic dialysis osteodystrophy (OM), which may be associated with dialysis encephalopathy, is thought in some instances to be due to aluminum toxicity [5] from untreated or softened water used in hemodialysis in areas where the aluminum content of water supplies is high [6]. In patients undergoing CAPD any exposure to aluminum is likely to stem from the use of aluminum-containing phosphate binders (ACPB) since the process of preparation of peritoneal dialysis fluid reduces most of the trace metals. In our unit, since the inception of the CAPD program in January 1979, 72 patients have been treated by this method in the first 2 years. In this report we present data on the improvement of histological renal osteodystrophy in CAPD patients and relate this to serum concentrations of calcium, phosphate, 25 hydroxycholecalciferol [25-(0H)CC] and immunoreactive parathormone (PTH). In addition, sequential serum aluminum concentrations are reported. These levels have been related to concentrations of aluminum in the peritoneal dialysis (PD) fluid and to the use of ACPB. One patient with aluminum toxicity prior to starting CAPD was studied to evaluate the chelating effect of disferrioxamine (DFO) on aluminum and its subsequent removal in the PD fluid.

Plasma oxalate and erythrocyte glutamic oxaloacetate transaminase activity (EGOT) (an indicator of nutritional status with respect to pyridoxine) were measured in 21 patients maintained on regular continuous ambulatory peritoneal dialysis or haemodialysis before and after a 4-month period of supplementation with pyridoxine, 100 mg day-1. Prior to supplementation 10/21 patients showed subnormal EGOT activity, although the increment in activity on addition of pyridoxal-5-phosphate in vitro was within the normal range in all cases. Mean plasma oxalate was 31.5 μmol 1-1 (SEM 2.9) prior to supplementation and did not change significantly with supplementation, despite normalization of EGOT activity in all but 2/21 patients. We conclude that pyridoxine deficiency does not contribute significantly to hyperoxalaemia in patients receiving dialysis and that 100 mg of pyridoxine daily is insufficient to reduce oxalate generation by a pharmacological action on glycine transamination.

Generally nonchemotactic mutants of Escherichia coli and Salmonella typhimurium were analyzed by interspecies complementation tests to determine the functional correspondence between the che genes of these two organisms. The E. coli che region was introduced into Salmonella recipients by means of a series of F-prime elements. Wild-type che genes of E. coli F'420 complemented all che mutants of Salmonella except cheS, cheV, and a subclass of cheU. A series of tester episomes carrying E. coli che mutations were then used to determine which E. coli che function was responsible for the complementation of each Salmonella che defect. By this method, the following correspondences were determined: cheAE and chePS,cheWE, and cheWS, cheXE and cheRS, cheYE and cheQS, cheCE and cheUS, cheBE and cheXS, and cheZE and cheTS. (The subscripts E and S refer to E. coli and S. typhimurium genes, respectively.) In some tests, especially those involving the last two pairs of genes, poor complementation was observed between noncorresponding genes. A model explaining these observations in terms of subunit interactions is proposed.

Motile but generally nonchemotatic (che) mutants of Escherichia coli were isolated by a simple screening method. A total of 172 independent mutants were examined, and four genes were defined on the basis of mapping and complemenvestigated by determining their null phenotypes with nonsense or bacteriophage Mu-induced mutations. The cheA and cheB products were essential in producing changes of swimming direction and flagellar rotation. The checC product appeared to be an essential component of the flagellum; however, specific mutational alterations of this component allowed flagellar assembly but prevented directional changes in swimming. Since some cheB mutants changed directions incessantly, this gene product may also serve to control the direction of flagellar rotation in response to chemoreceptor signals. Thus most or all of the common elements in the signalling process were involved in the generation and regulation of changes in the direction of flagellar rotation.

The traditional Pacific method of food staple preservation by fermentation in pits has been studied. The details of the method as performed in Fiji are discussed as well as the nutritional and chemical changes undergone by breadfruit during this fermentation. The taste acceptibility of the product was tested as well as ways to adapt the procedure to modern conditions. The process is a lactic acid fermentation and the nutritional quality of the preserved food is similar to the fresh one. The fermentation can be effected using less labour and materials than was used in the traditional method.

The Sigma reagent kit for urinary oxalate determination is reportedly simple, rapid, and specific for oxalate. We evaluated the kit and identified a number of shortcomings. Our investigations suggest that the recommended time for chromophore development is too short and should be doubled. Oxalate recovery during the extraction procedure depends strongly on urine pH. For complete extraction, urine should be acidified to pH 1.8-2.4. We also observed positive interference from ascorbate in urine. This interference was substantial, absorbances produced from ascorbate standards being approximately 80% of those obtained from oxalate standards of similar concentration. Our investigations also indicate the presence of a substance on the Sigma adsorbent that is eluted during the extraction procedure and interferes in the color reaction. These interferences represent potentially major sources of imprecision in the assay.

Viable, integration-defective deletion mutants of phage λ were examined with the technique of Int-promoted recombination between phages. The types of mutants found and their properties are consistent with a three-component model of att φ . The results show that att φ contains a unique locus for integration cross-overs which is bordered on each side by recognition sequences essential for normal integration. The role of these recognition sequences in integration was studied by analyzing the pattern of Int-promoted recombination between phage containing various types of mutant att sites. It was found that the integration system of λ can function with a variety of defective att sites; however, no simple pattern could be deduced from these results. Evidently, the λ integration system is considerably more complex than was at first believed, and very unlike systems of generalized recombination.

The interaction between transport current and flux spots in the intermediate state of a superconductor is investigated. It is shown that the force on the flux spots depends on factors such as current lead configuration, and it is therefore not possible to define a unique “flow resistivity” for type-I superconductors. The conclusions are supported by experimental evidence.

Deletion mutants and substitution mutants of bacteriophage λ have been used to examine the physical structure of the att φ site in the λ chromosome which is essential for prophage integration. Integration-defective att mutants were analyzed by constructing heteroduplex DNA molecules containing one wild-type and one mutant strand and examining these heteroduplexes by electron microscopy. The results indicate that att φ is less than 2500 base pairs in length and may be as small as 20 to 50 base pairs. Integration cross-overs between att φ and its bacterial analog, att B , occur within a region which is less than 12 base pairs in length. Moreover, there is no detectable base sequence homology between att φ and att B . These results suggest that λ integration is a truly unique system of recombination.

It is the present practice to call the average of the sound absorption coefficients at 256, 512, 1024 and 2048 cycles the noise reduction coefficient, in an effort to assign a single figure to an absorbing material which will be useful in judging its performance in a noise quieting problem. This is recognized as a makeshift, as no single figure can represent correctly the reduction obtained. Typical noise spectra are presented and analyzed for reductions that can be expected in each frequency band. It appears that if a single figure is to be assigned the absorption coefficient at 4096 should also be considered. This is particularly true of office quieting, which is an important field of commercial noise control. In factories where heavy machinery is operating, it appears advisable to give some weighting to 128 cycles.

(1952). Problems in the Analysis of Urinary Coproporphyrin III. American Industrial Hygiene Association Quarterly: Vol. 13, No. 3, pp. 158-162.