Patient classification system: An integrated method for measuring nursing intensity and optimizing resource allocation

A patient classification system was developed integrating a patient acuity instrument with a computerized nursing distribution method based on a linear programming model. The system was designed for real-time measurement of patient acuity (workload) and allocation of nursing personnel to optimize the utilization of resources.^ The acuity instrument was a prototype tool with eight categories of patients defined by patient severity and nursing intensity parameters. From this tool, the demand for nursing care was defined in patient points with one point equal to one hour of RN time. Validity and reliability of the instrument was determined as follows: (1) Content validity by a panel of expert nurses; (2) predictive validity through a paired t-test analysis of preshift and postshift categorization of patients; (3) initial reliability by a one month pilot of the instrument in a practice setting; and (4) interrater reliability by the Kappa statistic.^ The nursing distribution system was a linear programming model using a branch and bound technique for obtaining integer solutions. The objective function was to minimize the total number of nursing personnel used by optimally assigning the staff to meet the acuity needs of the units. A penalty weight was used as a coefficient of the objective function variables to define priorities for allocation of staff.^ The demand constraints were requirements to meet the total acuity points needed for each unit and to have a minimum number of RNs on each unit. Supply constraints were: (1) total availability of each type of staff and the value of that staff member (value was determined relative to that type of staff's ability to perform the job function of an RN (i.e., value for eight hours RN = 8 points, LVN = 6 points); (2) number of personnel available for floating between units.^ The capability of the model to assign staff quantitatively and qualitatively equal to the manual method was established by a thirty day comparison. Sensitivity testing demonstrated appropriate adjustment of the optimal solution to changes in penalty coefficients in the objective function and to acuity totals in the demand constraints.^ Further investigation of the model documented: correct adjustment of assignments in response to staff value changes; and cost minimization by an addition of a dollar coefficient to the objective function. ^

Evidence for the role of agonist binding frequency in receptor -mediated activation of adenylate cyclase

$\beta$-adrenergic receptor-mediated activation of adenylate cyclase exhibits an agonist-specific separation between the dose/response curve (characterized by the EC$\sb{50}$) and the dose/binding curve (characterized by the K$\sb{\rm d}$). Cyclase activity can be near-maximal when receptor occupancy is quite low (EC$\sb{50}$ $\ll$ K$\sb{\rm d}$). This separation between the binding and response curves can be explained by the assumption that the rate of cyclase activation is proportional to the concentration of agonist-bound receptors, since the receptor is mobile and can activate more than one cyclase (the Collision Coupling Model of Tolkovsky and Levitzki). Here it is established that agonist binding frequency plays an additional role in adenylate cyclase activation in S49 murine lymphoma cells. Using epinephrine (EC$\sb{50}$ = 10 nM, K$\sb{\rm d}$ = 2 $\mu$M), the rate of cyclase activation decreased by 80% when a small (1.5%) receptor occupancy was restricted (by addition of the antagonist propranolol) to a small number (1.5%) of receptors rather than being proportionally distributed among the cell's entire population of receptors. Thus adenylate cyclase activity is not proportional to receptor occupancy in all circumstances. Collisions between receptor and cyclase pairs apparently occur a number of times in rapid sequence (an encounter); the high binding frequency of epinephrine ensures that discontiguous regions of the cell surface experience some period of agonist-bound receptor activity per small unit time minimizing "wasted" collisions between activated cyclase and bound receptor within an encounter. A contribution of agonist binding frequency to activation is thus possible when: (1) the mean lifetime of the agonist-receptor complex is shorter than the mean encounter time, and (2) the absolute efficiency (intrinsic ability to promote cyclase activation per collision) of the agonist-receptor complex is high. These conclusions are supported by experiments using agonists of different efficiencies and binding frequencies. These results are formalized in the Encounter Coupling Model of adenylate cyclase activation, which takes into explicit account the agonist binding frequency, agonist affinity for the $\beta$-adrenergic receptor, agonist efficiency, encounter frequency and the encounter time between receptor and cyclase. ^

Molecular interactions of the central conserved domain of p53

p53 mutations are the most commonly observed genetic alterations in human cancers to date. A majority of these point mutations cluster in four evolutionarily conserved domains spanning amino acids 100-300. This region of p53 has been called its central conserved, or conformational domain. This domain of p53 is also targeted by the SV40 T antigen. Mutation, as well as interaction with SV40 T antigen results in inactivation of p53. We hypothesized that mutations and SV40 T antigen disrupt p53 function by interfering with the molecular interactions of the central conserved domain. Using a chimeric protein consisting of the central conserved domain of wild-type p53 (amino acids 115-295) and a protein A affinity tail, we isolated several cellular proteins that interact specifically with this domain of p53. These proteins range in size from 30K to 90K M$\rm\sb{r}.$ We also employed the p53 fusion protein to demonstrate that the central conserved domain of p53 possesses sequence-specific DNA-binding activity. Interestingly, the cellular proteins binding to the central conserved domain of p53 enhance the sequence-specific DNA-binding activity of full length p53. Partial purification of the individual proteins binding to the conformational domain of p53 by utilizing a sodium chloride step-gradient enabled further characterization of two proteins: (1) a 42K M$\rm\sb{r}$ protein that eluted at 0.5M NaCl, and bound DNA nonspecifically, and (2) a 35K M$\rm\sb{r}$ protein eluting into the 1.0M NaCl fraction, capable of enhancing the sequence-specific DNA-binding activity of p53. In order to determine the physiologic relevance of the molecular interactions of the conformational domain of p53, we examined the biochemical processes underlying the TNF-$\alpha$ mediated growth suppression of the NSCLC cell line H460. While growth suppression was accompanied by enhanced sequence-specific p53-DNA binding activity in TNF-$\alpha$ treated H460 nuclei, there was no increase in p53 protein levels. Furthermore, p35 was upregulated in TNF-$\alpha$ treated H460 cells, suggesting that the enhanced p53-DNA binding seen in these cells may be mediated by p35. Our studies define two novel interactions involving the central conserved domain of p53 that appear to be functionally relevant: (1) sequence-specific DNA-binding, and (2) interaction with other cellular proteins. ^

A urokinase receptor promoter element (-152/-135) bound with an AP-2-alpha-related protein and SP1 is required for the induction of gene expression by PMA and SRC

The urokinase-type plasminogen activator receptor (u-PAR) promotes extracellular matrix degradation, invasion and metastasis. A first objective of this dissertation was to identify cis-elements and trans-acting factors activating u-PAR gene expression through a previously footprinted (–148/–124) promoter region. Mobility shifting experiments on nuclear extracts of a high u-PAR-expressing colon cancer cell line (RKO) indicated Sp1, Sp3 and a factor similar to, but distinct from, AP-2α bound to an oligonucleotide spanning –152/–135. Mutations preventing the binding of the AP-2α-related factor reduced u-PAR promoter activity. In RKO, the expression of a dominant negative AP-2 (AP-2αB) diminished u-PAR promoter activity, protein and u-PAR mediated laminin degradation. Conversely, u-PAR promoter activity in low u-PAR-expressing GEO cells was increased by AP-2αA expression. PMA treatment, which induces u-PAR expression, caused an increased amount of the AP-2α-related factor-containing complex in GEO, and mutations preventing AP-2α-like and Sp1/Sp3 binding reduced the u-PAR promoter stimulation by PMA. In resected colon cancers, u-PAR protein amounts were related to the amount of the AP-2α-related factor-containing complex. In conclusion, constitutive and PMA- inducible u-PAR gene expression and -proteolysis are mediated partly through transactivation via a promoter sequence (–152/435) bound with an AP-2α-related factor and Sp1/Sp3. ^ A second interest of this dissertation was to determine if a constitutively active Src regulates the transcription of the u-PAR gene, since c-src expression increases invasion in colon cancer. Increased u-PAR protein and laminin degradation paralleling elevated Src activity was evident in SW480 colon cancer cells stably expressing a constitutively active Src (Y- c-src527F). Nuclear run-on experiments indicated that this was due largely to transcriptional activation. While transient transfection of SW480 cells with Y-c-src527F induced a u-PAR-CAT-reporter, mutations preventing Sp1-binding to promoter region –152/435 abolished this induction. Mobility shift assays revealed increased Sp1 binding to region –152/135 with nuclear extracts of Src-transfected SW480 cells. Finally, the amounts of endogenous u-PAR in resected colon cancers significantly correlated with Src-activity. These data suggest that u-PAR gene expression and proteolysis are regulated by Src, this requiring the promoter region (–152/–135) bound with Sp1, thus, demonstrating for the first time that transcription factor Sp1 is a downstream effector of Src. ^