Applicability of the single equivalent point dipole model to represent a spatially distributed bio-electrical source.

Although the single equivalent point dipole model has been used to represent well-localised bio-electrical sources, in realistic situations the source is distributed. Consequently, position estimates of point dipoles determined by inverse algorithms suffer from systematic error due to the non-exact applicability of the inverse model. In realistic situations, this systematic error cannot be avoided, a limitation that is independent of the complexity of the torso model used. This study quantitatively investigates the intrinsic limitations in the assignment of a location to the equivalent dipole due to distributed electrical source. To simulate arrhythmic activity in the heart, a model of a wave of depolarisation spreading from a focal source over the surface of a spherical shell is used. The activity is represented by a sequence of concentric belt sources (obtained by slicing the shell with a sequence of parallel plane pairs), with constant dipole moment per unit length (circumferentially) directed parallel to the propagation direction. The distributed source is represented by N dipoles at equal arc lengths along the belt. The sum of the dipole potentials is calculated at predefined electrode locations. The inverse problem involves finding a single equivalent point dipole that best reproduces the electrode potentials due to the distributed source. The inverse problem is implemented by minimising the chi2 per degree of freedom. It is found that the trajectory traced by the equivalent dipole is sensitive to the location of the spherical shell relative to the fixed electrodes. It is shown that this trajectory does not coincide with the sequence of geometrical centres of the consecutive belt sources. For distributed sources within a bounded spherical medium, displaced from the sphere's centre by 40% of the sphere's radius, it is found that the error in the equivalent dipole location varies from 3 to 20% for sources with size between 5 and 50% of the sphere's radius. Finally, a method is devised to obtain the size of the distributed source during the cardiac cycle.

Schizosaccharomyces pombe Mcm3p, an essential nuclear protein, associates tightly with Nda4p (Mcm5p).

MCM proteins are required for the proper regulation of DNA replication. There are six MCM proteins in all eukaryotes which interact to form a large complex. We report the cloning of fission yeast mcm3 +. mcm3 + is essential and spores carrying a Delta mcm3 disruption arrest with an apparently replicated DNA content. The protein is found constitutively in the nucleus and levels remain constant throughout the cell cycle. Mcm3p binds particularly tightly to Nda4p (Mcm5p), but is loosely associated with the other Schizosaccharomyces pombe MCM proteins. Thus, Mcm3p is a peripheral MCM subunit.

Multiple domains of fission yeast Cdc19p (MCM2) are required for its association with the core MCM complex.

The members of the MCM protein family are essential eukaryotic DNA replication factors that form a six-member protein complex. In this study, we use antibodies to four MCM proteins to investigate the structure of and requirements for the formation of fission yeast MCM complexes in vivo, with particular regard to Cdc19p (MCM2). Gel filtration analysis shows that the MCM protein complexes are unstable and can be broken down to subcomplexes. Using coimmunoprecipitation, we find that Mis5p (MCM6) and Cdc21p (MCM4) are tightly associated with one another in a core complex with which Cdc19p loosely associates. Assembly of Cdc19p with the core depends upon Cdc21p. Interestingly, there is no obvious change in Cdc19p-containing MCM complexes through the cell cycle. Using a panel of Cdc19p mutants, we find that multiple domains of Cdc19p are required for MCM binding. These studies indicate that MCM complexes in fission yeast have distinct substructures, which may be relevant for function.

Comparison of the bacterial HelA protein to the F508 region of the cystic fibrosis transmembrane regulator.

The HelA protein of Rhodobacter capsulatus is the ATP-binding-cassette subunit of an exporter complex required for cytochrome c biogenesis. By primary sequence comparisons the F88 residue of HelA is similar to the F508 residue of the cystic fibrosis transmembrane regulator (CFTR) protein. Previous studies have established that CFTR F508delta or F508R proteins are defective but F508C is functional. Our results demonstrate that the HelA F88 mutants functionally mimic the phenotypes of known CFTR F508 mutants. The phenotypes of additional HelA mutants and the in vivo steady-state levels of these proteins are also reported.

Stereotypes and tacit inference.

To judge another person's behavior, one often has to come to an understanding of what that behavior was in its detail. Five studies demonstrated that stereotypes influence the tacit inferences people make about the unspecified details and ambiguities of social behavior (e.g., what the behavior specifically was, what stimulus the individual reacted to, what caused the individual to act) and that these inferences occur when people encode the relevant information. One study found that participants who scored low on a measure of modern sexism were just as likely to make tacit inferences based on gender stereotypes as were those who scored high. Discussion centers on the implications of these findings for identification processes in social judgment, as well as whether stereotypes influence tacit inferences at an implicit level.

General purpose tagging vectors for fission yeast.

We have designed a series of vectors for use in the fission yeast Schizosaccharomyces pombe that allow fusion of any protein of interest to a triple HA epitope or a GST domain. The HA epitope may be placed at the N terminus or the C terminus under three different versions of the nmt1 promoter, to allow varying levels of gene expression. The GST tag may be placed at the N terminus or C terminus under control of a fully active nmt1 promoter. This family of vectors has compatible restriction sites and modular design, so that the protein under study may be exchanged easily between different plasmids. Using the Cdc19p protein as a test case, we have demonstrated that these plasmids can express functional tagged proteins in the fission yeast cell.

Mutational analysis of Cdc19p, a Schizosaccharomyces pombe MCM protein.

The cdc19+ gene encodes an essential member of the MCM family of replication proteins in Schizosaccharomyces pombe. We have examined the structure and function of the Cdc19p protein using molecular and genetic approaches. We find that overproduction of wild-type Cdc19p in wild-type cells has no effect, but cdc19-P1 mutant cells do not tolerate elevated levels of other MCM proteins or overexpression of mutant forms of Cdc19p. We have found genetic interactions between cdc19+ and genes encoding subunits of DNA polymerase delta and the replication initiator cdc18+. We have constructed a series of point mutations and sequence deletions throughout Cdc19p, which allow us to distinguish essential from nonessential regions of the protein. Not surprisingly, conserved residues in the MCM homology domain are required for protein function, but some residues outside the core homology domain are dispensable.

Critical care nurses' perceptions of appropriate care of the patient with orders not to resuscitate.

OBJECTIVE: To determine critical care nurses' perceptions of appropriate care of patients with and without do-not-resuscitate (DNR) orders. DESIGN: Descriptive, cross-sectional. SETTING: Large, northeastern, metropolitan teaching hospital. SAMPLE: Eighty-seven staff nurses divided into DNR and non-DNR groups whose demographic characteristics were coincidentally similar. MEASURE: Responses to an original questionnaire. Questionnaires describing one of two hypothetical patients (DNR or non-DNR) were distributed to all available staff nurses working in adult intensive care units. RESULTS: After construct validity and internal consistency reliability were established (Cronbach's coefficient alpha = 0.84 for the physical subscale, 0.79 for the psychosocial), analysis of variance was used in the data analysis. Mean total scores were 60.7 for the DNR group and 69.6 for the non-DNR group (p = 0.0031). Mean scores on the physical subscale were 33.6 and 41.9 for the DNR and the non-DNR groups, respectively (p = 0.0032). Results on the psychosocial subscale showed no significant differences between the groups. Item analysis showed significant differences on weighing the patient (p = 0.0002), monitoring neurologic status (p = 0.0082), drawing blood cultures (p = 0.0094), checking vital signs (p = 0.0071), performing complete nursing assessments (p = 0.0179), and treating the patient in an intensive care unit (p = 0.0001). CONCLUSIONS: Compared with the patient without a DNR order, significantly lower levels of agreement were expressed with interventions involving monitoring for the patient with the DNR order. Agreement with placement of the patient with the DNR order in an intensive care unit may be seen to follow the same pattern. Education of caregivers and communication among them might help to clarify what may be ambiguous policies and orders.

Isolation and structural analysis of the rat MyoD gene.

We have cloned and determined the nucleotide (nt) sequence of a 6.5-kb genomic DNA fragment containing the rat MyoD gene (encoding a muscle regulatory factor, MyoD). Mouse fibroblasts transfected with this DNA display a high degree of conversion to a muscle phenotype, suggesting that this genomic clone contains sufficient sequence information to allow the production of the rat MyoD protein in these cells. The 6.5-kb genomic fragment contains the complete coding region of MyoD, distributed over three exons, plus 2.3 kb of 5'-noncoding sequence and 1.4 kb of 3'-noncoding sequence. Based on RNase protection assays, the major transcription start point of MyoD is located 210 nt 5' to a methionine start codon and 26 nt 3' to a TAAATA motif which bears similarity to a consensus recognition sequence (TATA) utilized by eukaryotic RNA polymerase II transcription complexes. The high degree of identity between the amino acid sequence of rat MyoD and the MyoD proteins isolated from other vertebrates indicates that this muscle regulatory protein has been evolutionarily conserved.

Quantitation of reversible binding by particle counting: hapten-antibody interaction as a model system.

With a view toward developing a general method for measuring intrinsic equilibrium constants for the reversible interactions between two ligands, we used an antibody-hapten model system [2,4-dinitrophenyl (DNP) hapten and anti-DNP antibody] to explore an approach based on particle counting of uniform polystyrene spheres to which the hapten is coupled covalently. This approach was made possible by an optical pulse particle size analyzer that accurately counts individual sphere clusters and quantitates with high precision specific aggregation of spheres crosslinked by antibody. The reduction in crosslinking that results from competition for antibody binding sites between a soluble DNP ligand and immobilized DNP groups on the spheres provides the basis for measuring the intrinsic equilibrium constant for the soluble ligand-antibody interaction. The binding constants measured in this way for several DNP ligands and an anti-DNP antibody (2A1) agreed with the values obtained by conventional methods. The range of intrinsic equilibrium constants that can be determined by particle counting is likely to be exceptionally wide and a value as low as 10(3) liters/mol has been measured. And since all soluble antigens, regardless of their mass, acquire the same ability to scatter light as a result of their immobilization on the much larger uniform spheres (0.36 microns), the approach described here should be applicable to virtually any molecularly dispersed antigen and its monoclonal antibody.

Epidermal growth factor in the neonatal mouse salivary gland and kidney.

In the adult mouse, epidermal growth factor (EGF) is synthesized in granular convoluted tubule (intralobular) duct cells of the submandibular gland and in distal tubule cells of the kidney. The presence of EGF in developing tissues and maternal milk and the localization of EGF receptors in developing tissues suggest a role for EGF in developmental processes. The primary aims of the present study were to: (1) localize EGF and EGF-binding sites in the kidney and submandibular gland during neonatal development and (2) to determine the effect of exogenously administered EGF on cell proliferation in these two developing organs. In the present study, EGF was localized by immunocytochemistry in granular convoluted tubule cells of the submandibular gland initially on day 21 after birth and in distal tubule cells of the kidney on postnatal day 6. EGF binding in the kidney decreased after birth with some localization to the glomerulus. In submandibular glands of newborn and 10-day-old mice, EGF-binding sites were associated with both acinar and duct cells with peak binding at 10 days postnatally. Submandibular glands from 20-day-old mice demonstrated primarily ductal EGF-binding sites. Exogenously administered EGF induced a mitogenic response in acinar and interlobular duct cells of submandibular glands during the first week after birth. EGF treatment during this period had an inhibitory effect on 3H-thymidine incorporation into cellular compartments in the developing kidney. The identification of EGF-binding sites in the kidney and submandibular gland before the presence of EGF suggests that an EGF-like molecule such as transforming growth factor alpha (TGF-alpha) may be present as a potential ligand in these organs. In order to assess this possibility, developing kidneys and submandibular glands were stained with anti-TGF-alpha. These immunocytochemical studies localized TGF-alpha to the proximal tubule of the kidney and immature acinar cells of the newborn mouse. Our data strongly support an autocrine, juxtacrine or paracrine role for EGF and/or TGF-alpha in the regulation of cell proliferation and cytodifferentiation in the kidney and submandibular gland.

Special considerations with the elderly client.

The nationwide increase in the size of the elderly population is resulting in a significant increase in the number of speech--language and hearing clinicians who work with the elderly client. Certain considerations are required in working with this patient population, among the more important of which is the fact that the speech--language and hearing clinician may need to react to a medical emergency. Such medical problems as angina pectoris, heart attack, stroke, epileptic seizure, diabetic coma, and insulin reaction are discussed with regard to (1) the symptoms that warn of the emergency, and (2) the steps to be taken by the clinician in order to deal with the problem both safely and promptly.

Infantile stimulation induces brain lateralization in rats.

The hypothesis tested was that the effects of early experiences are asymmetrically distributed in the two brain hemispheres. Litters were either handled or not handled between birth and weaning, and the weanlings were reared in either laboratory cages or enriched environments between 21 and 50 days. When approximately 135 days old, animals within each of the four treatment groups had a right neocortical ablation, a left neocortical ablation, a sham operation, or no surgery. About 1 month later, all animals were given the open-field test for emotionality and exploratory behavior. Ablating either the right or left neocortex increased the activity scores of nonhandled controls, but there was no evidence of lateralization. However, the groups handled in infancy did show lateralization. Ablating the left brain did not significantly increase activity, but ablating the right brain caused extreme scores: handled rats without enrichment experience were the most active, and handled rats also placed into the enriched environment had near-zero scores in the open field.