Descriptive analysis of interactions between co-workers and supported employees

Varying types of interactions between workers without handicaps and supported employees were described. Results indicated that co-workers interacted extensively with persons who had mental retardation. Surprising findings included high levels of advocacy between co-workers and persons with severe or profound mental retardation and a relatively high percentage of co-workers assuming evaluation and training roles. Results were discussed in relation to the work behavior literature, which indicates that, in general, co-workers provide considerable natural support for employees across work environments.

In vitro activation of Escherichia coli prohaemolysin to the mature membrane-targeted toxin requires HlyC and a low molecular-weight cytosolic polypeptide

The c. 110 kDa haemolysin toxin secreted by Escherichia coli and other pathogenic Gram-negative bacteria is synthesized as the non-toxic precursor, prohaemolysin (proHlyA), which is unable to target mammalian cell membranes until activated intracellularly by an unknown mechanism dependent upon the coexpressed c. 20 kDa protein, HlyC. We have established in vitro post-translational activation of proHlyA in membrane-depleted cell extract fractions from E. coli recombinant strains containing (separately) the proHlyA and HlyC proteins. In vitro activation was calcium-independent and effective over a pH range of 6 to 9 and at temperatures from 42 degrees C to 4 degrees C. HlyC cell extract was also able to activate proHlyA which had been secreted out of cells containing the export proteins HlyB and HlyD. Fractionation of HlyC cell extracts by sucrose gradient centrifugation and molecular weight chromatography revealed activating fractions as having a molecular mass of 40 kDa, suggesting that the HlyC activator is present physiologically in a multimeric form. Cell extracts containing activation-competent HlyC and proHlyA were inactive following dialysis, but activity was restored by complementation with a cell extract lacking both proteins. HlyC and proHlyA proteins which were overproduced separately from recombinant expression plasmids were inactive following purification, but activity could again be restored with a Hly-negative cell extract. These experiments demonstrated that HlyC is not sufficient for activation; an additional cellular factor is required. The cellular factor was found in enterobacteria but not other bacteria or eukaryotic cells. It was cytosolic, protease-sensitive, and behaved as a c. 10 kDa polypeptide in a number of assays including dialysis, sucrose gradient centrifugation, and gel filtration chromatography. Thus activation was possible in a defined in vitro reaction containing only purified proHlyA, HlyC, and the cellular factor. Kinetic studies in which the relative concentrations of the three components of proHlyA activation were varied suggested that neither HlyC nor the cellular factor acts as a conventional enzyme, with each participating in a finite number of activation events.

Activation of Escherichia coli prohaemolysin to the mature toxin by acyl carrier protein-dependent fatty acylation

Haemolysin secreted by pathogenic Escherichia coli binds to mammalian cell membranes, disrupting cellular activities and lysing cells by pore-formation. It is synthesized as nontoxic prohaemolysin (proHlyA), which is activated intracellularly by a mechanism dependent on the cosynthesized HlyC. Haemolysin is one of a family of membrane-targeted toxins, including the leukotoxins of Pasteurella and Actinobacillus and the bifunctional adenylate cyclase haemolysin of Bordetella pertussis, which require this protoxin activation 1-5. HlyC alone cannot activate proHlyA, but requires a cytosolic activating factor6. Here we report the cytosolic activating factor is identical to the acyl carrier protein and that activation to mature toxin is achieved by the transfer of a fatty acyl group from acyl carrier protein to proHlyA. Only acyl carrier protein, not acyl-CoA, can promote HlyC-directed proHlyA acylation, but a range of acyl groups are effective.

Amiloride differentially modulates ANP binding in human thyroid cells and bovine endothelial cells

The diuretic and sodium channel inhibitor, amiloride, has been shown to increase atrial natriuretic peptide (ANP) binding several fold in certain cell types, but in other tissues it causes only marginal increases in specific ANP binding. In the present report we compare the effects of amiloride on ANP binding in bovine endothelial cells and human thyroid-derived cells, two cell types which differ in their predominant ANP receptor subtype. We found that amiloride (10(-3) M) increased specific [125I]ANP binding to 750% above control in endothelial cells, but among several thyroid cultures tested the maximal increase in ANP binding with amiloride was only 23% above control. Moreover, most of the thyroid cultures showed decreased ANP binding in the presence of amiloride. The increased ANP binding in endothelial cells exposed to amiloride is best explained by an increased affinity of the receptor for its ligand since the drug lowered the Kd of ANP binding from 0.73 nM to 0.16 nM without affecting the receptor binding capacity. The degree of amiloride enhancement of ANP binding in endothelial cells is increased with time in culture (200% above control at 5 days, 750% above at 30 days) suggesting the increase of an amiloride-sensitive receptor relative to an amiloride-insensitive receptor. The fact that the amiloride-induced decrease in ANP binding in thyroid cells was not exacerbated by pre-incubation with amiloride suggested that the observed amiloride effect was not due to increased receptor internalization with the drug. These results support a hypothesis that ANP receptor subtypes associated with separate signal transduction mechanisms might be modulated in an opposite manner by the binding of amiloride.

Update on technology diffusion

Magnetic resonance imaging (MRI) continues to expand in influence as a diagnostic tool, with the number of units installed in the United States growing rapidly, according to an AHA technology assessment report. Technology assessment is being used more and more in decision making regarding the use of MRI and other diagnostic technologies. Two perspectives on the phenomenon are explored.

MRI: update on technology diffusion and acquisition

Over the past three years, magnetic resonance imaging (MRI) has become accepted as a valuable diagnostic tool, and its applications continue to expand. During this time, the number of units installed in the United States doubled. By 1990 about 2,000 MRI units were in place in the United States and nearly 20 percent of the MRI-installed base was mobile, according to a research study conducted by the Hadley Hart Group (Chicago) and Drew Consultants, Inc. (Concord, MA). With the introduction of the prospective payment system, many hospitals were hesitant to spend limited capital on new technology, such as MRI. At the same time, freestanding diagnostic imaging centers were on the rise. Some hospitals and entrepreneurs who foresaw the potential of MRI in health care pioneered its use in the clinical setting. Hospitals began to examine new partnership arrangements and alternative forms of financing, so that they too could offer MRI services. By the end of 1988, the majority of hospitals offering MRI services did not own their own unit and about 40 percent of the hospitals offering MRI services were in a mobile configuration according to the Hadley Hart Group. While the technology has been diffused into 100-bed hospitals via mobile service vendors in some parts of the country, many medium-sized and large hospitals also have entered the MRI services market in this fashion. In the larger hospitals, the patient demand or need for the service often would justify acquisition of MRI, but the expense of the technology, and in many areas restrictive state health planning policies, modified purchase of MRI systems by hospitals. Mobile service vendors offered hospitals a way to startup MRI services in a limited fashion without a major capital expenditure and its associated risk. As hospitals gain experience with mobile MRI and achieve or exceed their early utilization projections, administrators are reevaluating the need to expand services to a full-time fixed site. Early fixed-site MRI providers have been constantly upgrading their MRI capability while planning on adding more units. The technology itself has continued to improve, primarily through the implementation of new software that permits new techniques such as MR angiography (MRA) to be performed. Units are available in a wide price range, price usually reflecting both the field strength (0.5 tesla units cost less) as well as the additional capabilities beyond routine imaging (MRA, spectroscopy).(ABSTRACT TRUNCATED AT 400 WORDS)

Treatment of acute exacerbations of chronic obstructive airways disease--a comparison of amoxycillin and ciprofloxacin

Ciprofloxacin and amoxycillin were compared in the treatment of acute exacerbations of chronic obstructive airways disease. One hundred and forty patients were evaluable for overall outcome: 60 patients' sputum specimens yielded positive bacteriological cultures. The predominant pathogens were Haemophilus influenzae (43.3%) and Streptococcus pneumoniae (25.0%). Both regimens were safe and produced few adverse effects. An independent observer judged ciprofloxacin to produce a 91.8% success rate (complete success 21.9%; partial success 69.9%) whilst a 73.1% rate (complete success 10.4%; partial success 62.7%) was seen with amoxycillin.

A spinal mechanism of action is involved in the antinociception produced by the capsaicin analogue NE 19550 (olvanil)

We have studied the effect of NE 19550 (olvanil, N-(4-hydroxy-3-methoxyphenyl) methyl-9Z-octadecenamide), a capsaicin analogue with approximately equipotent antinociceptive activity in vivo compared with capsaicin, on nociceptive responses recorded from spinal dorsal horn neurones in vivo and from a spinal ventral root in vitro. In adult rats anaesthetized with halothane, antinociceptive doses of olvanil (20-40 mumol/kg, s.c.) reduced C-fibre responses evoked in wide dynamic range, lumbar dorsal horn neurones, by peripheral transcutaneous electrical stimulation. Intradermal injection of olvanil, localized to a discrete region of the peripheral receptive field, did not activate C-fibres nor change C-fibre evoked activation of dorsal horn neurones. Spinal intrathecal administration of olvanil attenuated C-fibre evoked responses and, at the highest concentration, significantly reduced A beta-fibre evoked activity. In the neonatal rat spinal cord/tail preparation maintained in vitro, superfusion of the cord with olvanil (500 nM-5 microM) did not evoke a depolarization but responses to peripheral noxious stimulation were attenuated. In a similar in vitro preparation of the neonatal rat spinal cord, the release of calcitonin gene-related peptide-like immunoreactivity (CGRP-LI) was measured in spinal cord superfusates. Capsaicin (2-10 microM) evoked a large release of CGRP-LI but olvanil (2-10 microM) produced only a small or undetectable release. Following the administration of each substance, however, the release of CGRP-LI evoked by a depolarizing potassium stimulus was significantly attenuated. These data indicate that C-fibre input to the dorsal horn was attenuated by acute systemic doses of olvanil that were antinociceptive in behavioural tests. This effect was unlikely to be due to impairment of C-fibre function by a peripheral locus of action but was more consistent with an action in the spinal cord in which the reduced release of a neurotransmitter substance from afferent nerve terminals may play a prominent role.

Association of country, sex, social class, and life cycle to locus of control in western European countries

Relatively few studies have focused on causal factors in the development of locus of control. Here nine western European countries are studied to assess the hypothesis that the society in which one lives is important in the scores on locus of control. The data indicate greater variation resulting from country of residence on locus of control than that from the variables of life cycle, sex, and social class. Findings regarding these latter variables are congruent with previous research. In addition, being single was related to having an external locus of control.

I.v. therapy: the legislative and regulatory arena

The inclusion of home IV drug therapy in the Medicare Catastrophic Coverage Act of 1988 brought IV therapy issues to the attention of regulators and providers. Although the legislation was revoked, the issues that were raised in its development must be addressed under the current programs and in any future home IV therapy legislation.

Lymphocyte migration into brain modelled in vitro: control by lymphocyte activation, cytokines, and antigen

Factors controlling lymphocyte adhesion to brain endothelium were investigated in vitro. Mitogen activation of lymphocytes causes increased adhesion to endothelium, which is maximal at 7-24 hr, declines to normal levels after the cells divide, and requires protein synthesis. Rat brain endothelium can be stimulated with IFN-gamma to increase its adhesion to either normal or activated lymphocytes. The endothelium is sensitive to low levels of cytokine: adhesion develops rapidly after stimulation and requires new protein synthesis. Antigen-specific line cells also adhere more effectively to endothelium than normal lymph node cells. This is enhanced by IFN-gamma treatment of the endothelium and is further increased marginally in the presence of the cognate antigen. The results suggest that either local stimulation of endothelium with cytokines or lymphocyte activation in the periphery will modulate lymphocyte traffic into brain.

Immunoreactive atrial natriuretic peptide in the thyroid gland

Human thyroid follicles and primary cell cultures derived from them demonstrated atrial natriuretic peptide (ANP)-like immunoreactivity when stained with a monoclonal antibody raised against rat alpha-ANP (ANP 1-28). In thyroid sections the staining was most intense in the tall cuboidal epithelium of small follicles. The intracellular distribution of immunoreactive (ir)-ANP in primary cultures of thyroid follicular cells consisted of discrete granules with a largely perinuclear distribution. The granule density increased with time in culture but was unaffected by exogenous ANP, suggesting an intrinsic synthesis of the immunoreactivity. Thyroid stimulating hormone (TSH; thyrotropin) failed to alter the distribution of ir-ANP after either short-term (6 h) or long-term (1-12 day) exposure. Epinephrine or norepinephrine treatment, however, caused a reduction in the ir-ANP granularity compared with controls in what might represent a stimulated release of the immunoreactivity. The present results suggest that the peptide ANP coexists with thyroid hormones in follicular cells and that the two endocrine activities might be under separate control mechanisms.

HlyB-dependent secretion of hemolysin by uropathogenic Escherichia coli requires conserved sequences flanking the chromosomal hly determinant

The synthesis and secretion of hemolysin (HlyA) by Escherichia coli are governed by four contiguous genes (hlyCABD) that are closely conserved on plasmids and, among human pathogenic strains, on the chromosome. We have previously shown that in plasmid pHly152 the coexpressed synthesis and export functions are uncoupled by intraoperon transcription termination, which is in turn alleviated by antitermination dictated in cis by a region upstream of the hly operon. In this study we describe an analogous region of ca. 1,100 base pairs flanking the chromosomal hly determinant of the uropathogenic strain E. coli 2001. This region had no significant effect on intracellular levels of hemolysin but activated strongly, both in cis and in trans, the specific hlyB-hlyD-dependent hemolysin secretion function. The secretion-activating region increased the transcription of the secretion gene hlyB, but the transcription effect was not as pronounced as that seen in the pHly152 determinant and was not evident when the region was present in trans to the hemolysin genes, suggesting that, in addition to transcriptional activation, the region may possibly exert a secondary posttranscriptional influence. Southern hybridizations with the 1,100-base pairs secretion-activating sequence showed low identity to plasmid pHly152 and no identity with total DNA from nonhemolytic uropathogenic E. coli or hemolytic isolates of Proteus vulgaris, Proteus mirabilis, and Morganella morganii. In contrast, hybridization to total DNA from hemolytic E. coli isolates belonging to different serotypes showed strong conservation of the activating sequence, indicating that it is an integral component of the chromosomal hly determinant that is widespread among uropathogenic E. coli.

N-way sensitivity analysis: a verification and stability-assessment technique for completely subjective decision analysis trees

The purpose of this paper is to describe the development of N-way sensitivity analysis, a modified version of traditional sensitivity analysis that was created for the purpose of verifying the stability of decisions made by a completely subjective decision-analytic tree. The technique was developed during research that addressed whether nurses make clinical decisions that coincide with those recommended by a decision-analytic model. Since all parameters of the model were derived from subjective assessment, traditional one-way or two-way sensitivity analysis was deemed inappropriate. Consequently, N-way sensitivity analysis was developed and used for the verification of the decision model's results.

Isolation of the Actinobacillus pleuropneumoniae haemolysin gene and the activation and secretion of the prohaemolysin by the HlyC, HlyB and HlyD proteins of Escherichia coli

The gene encoding the c. 105 kD secreted haemolysin protein of the porcine pathogen Actinobacillus pleuropneumoniae serotype 1 has been isolated by screening a lambda gt11 expression library in Escherichia coli with antiserum raised against the wild-type protein. A derivative recombinant DNA pJFF702 expressed the hlylA haemolysin gene from the pUC19 lac promoter but the resulting haemolysin I protein remained within the E. coli cell and was haemolytically inactive. Export of the intracellular A. pleuropneumoniae prohaemolysin out into the medium was achieved by the presence in trans of the E. coli haemolysin secretion genes hlyB and hlyD, and high levels of intracellular haemolytic activity were attained similarly by the E. coli post-translational haemolysin activator gene, hlyC. Southern hybridization of A. pleuropneumoniae parental DNA nevertheless indicated only a low degree of nucleotide sequence identity to the haemolysin structural and secretion genes hlyA and hlyB of E. coli. The data show that despite substantial nucleotide sequence divergence the A. pleuropneumoniae serotype 1 haemolysin determinant is closely related to that which is dispersed throughout other Gram-negative human and animal pathogens.

Characterization of a primate model of hypertension. The response of hypertensive and normotensive male vervets (Cercopithecus aethiops) to cold pressor stress, captopril administration, and acute bolus of atrial natriuretic factor

In feral populations of African green monkeys or vervets (Cercopithecus aethiops), between 5 and 15% of adults have spontaneously elevated blood pressure (BP). We report here the initial biological and pharmacological characterization of this potential animal model of hypertension. Captive male monkeys with elevated systolic pressures show a modest pressure increase in response to stressors such as capture, phlebotomy and cold challenge. Acute captopril administration lowers BP in monkeys with high blood pressure (HBP), but has no effect on BP in control animals. Furosemide does not acutely reduce BP. Animals with elevated BPs have lower levels of angiotensin II than do age- and weight-matched controls. An acute infusion of atrial natriuretic factor (ANF) diminishes BP and stimulates urinary output in control and HBP vervets. However, both effects are more pronounced in animals with HBP. Heart rate is not affected by any of the experimental manipulations. Taken together, these data suggest that African green monkeys with spontaneously elevated BP may be a useful experimental model for particular types of human hypertension. Additional studies are required to complete the endocrine and pharmacological characterization of individual animals with HBP.

Microtitre plate measurement of platelet response to hypotonic stress

The conventional method of assessing the platelet response to hypotonic stress (HSR) was adapted to allow microtitre plate technology to be used. After water is added to a platelet suspension two sequential readings are taken at 414 nM on a vertical microplate reader. The difference between the second (three minutes) and the first (one minute) was defined as the HSR. This method allowed the relation between platelet concentrate pH and viability to be confirmed, and an HSR value for use in quality control was established. The method correlated well with the conventional technique and permitted measurement of undiluted samples as well as of products with a high free haemoglobin concentration.

Transcription antitermination in an Escherichia coli haemolysin operon is directed progressively by cis-acting DNA sequences upstream of the promoter region

Export of haemolysin protein (HlyA) directed by the Escherichia coli pHly152 hly determinant is dependent upon transcriptional activation, primarily strong intraoperon transcript antitermination imposed between the haemolysin structural genes hlyC and hlyA and the contiguous downstream export genes hlyB and hlyD. Transcript elongation was dictated by a DNA sequence several kb upstream of the rho-independent terminator but could not be assigned to a discrete locus; on the contrary, it was progressive, increasing with the addition of up to 3.5 kbp of operon-proximal sequence containing the insertion elements IS2 and IS91. Antitermination was prominent throughout logarithmic growth but absent in stationary phase, and was effective only in cis but not in trans. Primer extension indicated that transcription activation utilized the native transcriptional start sites of the unactivated hly operon.

The representation of uncertainty in medical expert systems

The development of the rule-based expert system has provided important new techniques for the representation of knowledge. However, continued use of this representational scheme has highlighted some of its deficiencies. In particular, many within scientific and non-scientific fields attempting to use the rule-base design to describe natural phenomena often find it difficult to represent the complexities of the world as 'absolute' rules. For this reason, many investigators acknowledge the need to add an uncertainty mechanism to the rule-base construct. Such a facility would allow the quantification of accuracy or strength of association within individual rules Although agreement exists on the need for an uncertainty representation facility, the debate concerning the most appropriate methodology is far from resolved. The purpose of this paper is to provide a review and commentary on the current state of debate over the five most popular candidate uncertainty models: symbolic representation, MYCIN certainty factors, Bayesian, Dempster-Shafer and fuzzy set logic. The advantages and disadvantages of each uncertainty calculi will be presented and assessed with respect to their applicability to the medical expert systems domain.