Application of an Allosteric Ternary Complex Model to the Technique of Pharmacological Resultant Analysis

A simple ternary complex model of drug-receptor interaction has been used to extend the procedure of pharmacological resultant analysis, enabling the quantitation of interactions between allosteric modulators and orthosteric antagonists. Equations derived in the theoretical treatment were used to analyse functional data for the interaction between the allosteric modulator gallamine and the orthosteric antagonist scopolamine, with oxotremorine as the agonist, at rat tracheal muscarinic acetylcholine receptors. Quantitative estimates of the affinity of gallamine for the allosteric site (pK_Z = 4.7) and the extent of negative, heterotropic co-operativity between gallamine and scopolamine (α′ = 13.1) were obtained. Furthermore, an alternative direct, model-fitting approach, that does not rely on the determination of concentration ratios, was also developed, and yielded similar results. It is suggested that the approach presented in this paper is useful for quantifying interactions between orthosteric antagonists and allosteric modulators, particularly when the extent of co-operativity is low or the modulators possess multiple pharmacological properties, or both.     

Breastfeedilzg Support Services in the Neonutd Intensive-Care Unit

Objective: To describe a model for providing breastfeeding support in the neonatal intensive-care unit (NICU).
Design: Naturalistic, participant observation.
Setting: Suburban Level III NICU.
Patients: One hundred thirty-two mother-infant pairs over 1 year. Infants were hospitalized In the NICU, and mothers had initiated lactation efforts.
Interventions: Investigators provided breastfeeding interventions for the mother-infant pairs, based on identified problems, the research literature, or both.
Main Outcome Measures: Percentage of mothers who were breastfeeding at the time of discharge from the NICU.
Results: Interventions were classified into jive categories: expression and collection of mothers' milk, gavage feeding of expressed mothers' milk, in-hospital breastfeeding sessions, postdischarge breastfeeding management, and additional consultation.
Conclusions: This model was effective In preventing breastfeeding failure for this population. The model can provide the basis for NICU breastfeeding standards of care, protocols, and chart records, or for reimbursement purposes. The model also provides a framework for studying a specific category or breastfeeding intervention.     

The Encapsulation of Squid Diisopropylphosphorofluoridate-Hydrolyzing Enzyme within Mouse Erythrocytes

This study describes the entrapment of squid-type diisopropylphosphorofluoridate-hydrolyzingenzyme (DFPase) within mouse red blood cells. These erythrocytesthereby gain the ability to rapidly hydrolyze alkylphosphatecholinesterase (ChE) inhibitors such as diisopropyl fluorophosphate(DFP). DFPase rapidly hydrolyzes DFP to diisopropyl phosphate.Resealed erythrocytes provide a stable carrier system that canpreserve the activity of encapsulated enzymes against otherwiserapid in vivo degradation; thus, ChE inhibitors can be degradedto relatively nontoxic metabolites by these erythrocyte carriers.Squid DFPase was purified from the hepatopancreas of Atlanticsquid and DFPase activity was determined by measuring changesin fluoride ion concentration using a fluoride ion selectiveelectrode. Mouse erythrocytes in suspension with excess squidDFPase were dialyzed against hypotonic buffer to allow the encapsulationof the enzyme to occur. Cells were then resealed by returningthe suspension to isosmotic with saline. Rate of DFP hydrolysisobserved with these cells was much greater than the rate ofnonenzymatic hydrolysis and was directly proportional to theamount of the erythrocyte suspension added to the assay solution.The rate of hydrolysis was first order in substrate. Erythrocytecontrols showed no endogenous DFPase activity. These resultssuggest that enzyme entrapment may be developed as a methodto prevent and antagonize organophosphate poisoning.     

Addiction versus stages of change models in predicting smoking cessation

Prospective data from the California Tobacco Surveys (n=2066) were used to perform a critical test of the Prochaska et al. (1991) stages of change model. When the stages of change model was used as a stand alone predictor, smokers in preparation at baseline were more likely to be in cessation at follow-up than smokers in pre-contemplation at baseline (OR adj="1.9)" When stage membership was combined with baseline measures of addiction including smoking behaviors and quitting history, it was not a significant predictor of future cessation. A prediction equation that combined daily vs. occasional smoking, cigarettes per day smoked, life-time quits of at least a year, and quits of more than 5 days in the previous year discriminated smokers in cessation at follow-up of 1 to 2 years better than did the stages of change model. The area under the ROC curve for the equation based on addiction measures was 69.3% vs. 55.1% for the stages of change. Cessation rates ranged from 7.7% to 35.7% for the four-category addiction equation compared with 15.1% to 24.9% for stages of change model.     

Polychlorinated Biphenyl Congeners in Adipose Tissue Lipid and Serum of Past and Present Transformer Repair Workers and a Comparison Group

Polychlorinated Biphenyl Congeners in Adipose Tissue Lipid andSerum of Past and Present Transformer Repair Workers and a ComparisonGroup. FAIT, A., GROSSMAN, E., SELF, S., JEFFRIES, J., PELLIZZARI,E. D., AND EMMETT, E. A. (1989). Fundam. Appl. Toxicol 12, 42-55. The concentrations of individual PCB's were determined inboth serum and adipose tissue lipid from 35 transformer repairworkers currently exposed to PCBs, mainly Aroclor 1260, 17 previoustransformer repair workers, and 56 comparison workers neveroccupationally exposed to PCBs. The analysis used fused-silicacapillary gas chromatography with electron capture detector(FSCGC/ECD) and FSCGC with negative ion chemical ionizationmass spectrometry to verify PCB congener levels. Eighty-ninePCB peaks were identified and confirmed. More congeners weredetected in adipose tissue. In serum approximately 50% of peakswere below the level of detection. Statistical techniques toaccount for left and interval censoring allowed comparison ofconcentration distributions even where data were incomplete.We found that unquantifiable levels were unlikely to contributesubstantially to the true values for total [PCBs] over and beyondthe contribution of the measured values. However, the totalserum [PCBs] determined by FSCGC/ECD greatly exceeded that fromstandard packed cell gas chromatography (PCGC/ECD). The underestimationwas less marked for adipose samples. In serum the total [PCBs]was highest in currently exposed workers and lowest in unexposedworkers, with past-exposed workers clearly intermediate. Inadipose tissue [PCBs] in the currently exposed group was muchhigher than in the other two groups, in whom the distributionof results was broadly similar. In all worker groups hexachlorinatedand heptachlorinated species predominated followed by octachlorinatedand pentachlorinated. The relative distribution of individualPCB congeners in the three groups was similar although the amountsvaried. The seven major peaks in serum and adipose tissue were2,3,5,6,3',4',5'/2,3,4,5,2',4',5' hepta-CB; 2,3,4,2',3',5' hexa-CB;2,4,6,3',4',5'/ 2,4,5,2',4',5'/2,3,4,5,2',5' hexa-CB; 2,3,4,5,2',3',4'hepta-CB; 2,3,4,5,2',3',5',6'/2,3,4,5,6,2',3',5', octa-CB; 2,4,5,3',4',/3,4,5,2',3'penta-CB; and 2,3,4,2',3',4'/2,3,5,6,2',4',5'/2,3,4,5,2',4',6'multi-CB. The distribution of PCB peaks in our populations differsfrom that in capacitor workers (exposed to less highly chlorinatedPCBs) and from Yu-Cheng patients suggesting differing toxicpotentials from PCBs in these three circumstances.     

Differences between human and mouse alpha‐fetoprotein expression during early development

Alpha‐fetoprotein (AFP) is the major serum protein during development. AFP is one of the earliest proteins to be synthesised by the embryonic liver. The synthesis of AFP decreases dramatically after birth and only trace amounts are expressed in the adult liver. The tissue distribution of AFP in early human embryogenesis has not been defined. We have studied the expression pattern of AFP mRNA in human and mouse embryos by in situ hybridisation. In humans, AFP is expressed in the hepatic diverticulum at 26 d postovulation as it differentiates from the foregut endoderm (i.e. in the most primitive hepatocytes). It is also expressed in the endoderm of the gastrointestinal tract and in the yolk sac at this age. AFP is subsequently expressed in the mesonephros and transiently in the developing pancreas. In the mouse, no expression of AFP was observed in the mesonephros but other sites of expression were similar. Thus AFP has a distinct temporospatial expression pattern during the embryonic period and this differs between human and mouse species. It is interesting that AFP is expressed by tumours such as primitive gastrointestinal, renal cell and pancreatic tumours as well as those of hepatocyte origin. This distribution reflects the sites of AFP expression during development.