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A new method for the separation of denatured alpha-, beta- and kappa- caseins by hydrophobic interaction chromatography (HIC) is proposed. The method is based on an easy solubilization of commercial and real samples by 4.0 M guanidine thiocyanate (GdmSCN) and elution on a TSK-Gel(R) Phenyl-5PW column (TosoHaas) in the presence of 8.0 M urea in the mobile phase. The procedure, applied to commercial caseins and to real, raw samples (whole milk powder and fat-free yoghurt) is not expensive, it requires common high performance liquid chromatography (HPLC) instrumentation and allows the separation of caseins also in the presence of whey proteins. Quantitative results on the analysis of alpha-, beta- and kappa-caseins in real samples are also reported.

The use of drops in chemical analysis methodology and instrumentation has a deeply rooted past in the area of electrochemistry through the evolution of the dropping mercury electrode (DME). This history has also been deeply rooted in the field of surface science due to the inextricable connection between surface tension forces and drop formation. While the use of the DME is well established, the evolution of drop-based analytical measurements using aqueous and/or organic drops is a rapidly emerging and diverse field, encompassing several interdisciplinary areas of science: surface science and interfacial surface tension phenomena, spectroscopic detection, analytical instrumentation hyphenation, liquid membrane separation, reagent chemistry, electrochemistry, and so on. This review of 112 references covers various aspects of drop-based analytical measurements involving aqueous and/or organic drops. The review is divided into four sections, although the classification of a particular reference into a given section can sometimes be argued. The first section considers the use of drops as a detector component. The second section deals with fundamental studies that probe drop-related chemical and physical phenomena that are relevant to current and future developments in analytical chemistry. The next section covers recent advances in the area of microfluidic sample handling and instrumentation hyphenation. The final section reports upon emerging technologies aimed toward drop-based chemical analyzers that incorporate a number of steps in a chemical analysis: microextraction, preconcentration, reagent chemistry, microfluidic handling, and detection.

First, a novel technique for calibration of a dynamic surface tension detector (DSTD) is described. The DSTD measures the differential pressure as a function of time across the liquid-air interface of growing drops that repeatedly form and detach at the end of a capillary tip. The calibration technique utilizes the ratio of pressure signals acquired from the drop growth of two separate solutions, i.e. a standard solution and a corresponding mobile phase, such as water, both of which have a known surface tension. Once calibrated, the dynamic surface tension of an analyte is obtained from the ratio of the pressure signals from the analyte solution to that of the mobile phase solution. Thus, this calibration technique eliminates the need to optically image the radius of the expanding drop of liquid. Accurate dynamic surface tension determinations were achieved for aqueous sodium dodecyl sulfate (SDS) solutions over a concentration range of 0.5-5.4 mM. The measured surface tensions for these SDS solutions range from 70.3 to 46.8 dyne/cm and were in excellent agreement with the literature. A precision of 0.2 dyne/cm (1 S.D.) was routinely obtained. Second, the DSTD with this calibration technique was combined with flow injection analysis (FIA) for the study of model protein solutions and polymer solutions. The kinetic surface tension behavior of aqueous bovine serum albumin (BSA) solutions as a function of concentration and flow rate is presented. Evaluation of the dynamic surface tension data illustrates that a protein such as BSA initially exhibits kinetically-hindered surface tension lowering, i.e. a time dependence, as BSA interacts with the liquid-air interface of an expanding drop. FIA/DSTD is then shown to be an effective tool for the rapid study of kinetically-hindered surfactant mixtures. It was found that mixtures of SDS and the polymeric surfactant Brij(R)-35 (lauryl polyoxyethylene ether with an average molecular weight of 1200 g/mol) result in essentially an additive lowering of the surface tension. Mixtures of polyethylene glycol (PEG), with an average molecular weight of 1470 g/mol, and Brij(R)-35, however, result in a competitive (non-additive) surface tension with the Brij(R)-35 dominating the response.

Purpose: To determine whether high school athletic participation among adolescents in Western New York was associated with reduced rates of sexual behavior and pregnancy involvement., Methods: A secondary analysis of data from the Family and Adolescent Study, a longitudinal study of a random sample of adolescents (ages 13-16 years) from 699 families living in households in Western New York. A general population sample was obtained with characteristics closely matching the census distributions in the area. Interview and survey methods provided data on athletic participation, frequency of sexual relations during the past year, and risk for pregnancy. Bivariate correlations were used to examine relationships among athletic participation, demographic and control variables, and measures of sexual behavior and pregnancy rates. Next, path analyses were done in order to test for hypothesized relationships between athletic participation, sexual behavior, and pregnancy involvement while controlling for age, race, income, family cohesion, and non-athletic forms of extracurricular activity. Variables that were significantly associated with sexual behavior and/or pregnancy involvement were presented for both sexes within the resulting multivariate models., Results: Lower income and higher rates of sexual activity were associated with higher rates of pregnancy involvement for both sexes. Family cohesion was associated with lower sexual activity rates for both sexes. For girls, athletic participation was directly related to reduced frequency of sexual behavior and, indirectly, to pregnancy risk. Male athletes did not exhibit lower rates of sexual behavior and involvement with pregnancy than male non-athletes. Boys who participated in the arts, however, did report lower rates of sexual behavior and, indirectly, less involvement with pregnancy., Conclusions: Female adolescents who participated in sports were less likely than their non-athletic peers to engage in sexual activity and/or report a pregnancy. Among male adolescents, athletic participation was unrelated to sexual behavior and pregnancy involvement. Teen pregnancy prevention efforts for girls should consider utilizing sport as a strategic tool.

We present a model that predicts the maximum axonal length from the apparent velocity of slow axonal transport and cytoskeletal protein half-life. The model assumes that in mature axons the apparent velocity of slow transport varies with position, but that the density of cytoskeletal proteins and protein degradation are uniform. The model predicts that the apparent transport velocity of cytoskeletal proteins if highest near the cell body and decreases linearly along the axon, and that when axons branch the apparent velocity of transport decreases across the branch point. The predictions of this model are shown to be consistent with experiments. These results explain the variation in these fundamental metabolic parameters in different axons and species.

Platelets from normal and malignant hyperthermia (MH)-susceptible pigs were evaluated for differences in 45calcium uptake in the absence or presence of caffeine (2-16 mM), halothane (0.05-0.5%), or halothane and caffeine together. There were no statistically significant differences in basal or halothane-inhibited calcium uptake by platelets from either source. There was a small statistically significant difference in calcium uptake between platelets from normal and MH-susceptible pigs in the presence of 16 mM caffeine and 0.5% halothane. Calcium uptake by platelets from one pedigree of MH-susceptible pigs were stimulated in a concentration-dependent manner by caffeine. These data suggest that exposure of platelets to caffeine may have potential for identifying MH-susceptibility.

Selectivity of captopril, enalapril (MK-421), enalaprilat (MK-422), ketoace, and SA-300 for inhibiting kininase II when angiotensin (ANG) I versus bradykinin (BK) is the substrate has been studied in vitro. Potency for inhibiting purified rabbit lung ANG I-converting enzyme (ACE) using a tripeptide substrate with an ANG I-like (hippurylhistidylleucine, HHL) or a BK-like (hippurylphenylalanylarginine, HPA) cleavable dipeptide was determined. Inhibition of ANG I-induced and potentiation of BK-induced contractions of isolated guinea pig ileum strips was measured. For the enzyme assay, the inhibitor concentration which reduced the rate of HHL and HPA hydrolysis 50% (IC50) from the control value was estimated. All tested compounds more potently inhibited hydrolysis of the ANG I-related tripeptide by the purified enzyme. Ketoace, with a selectivity ratio (HPA IC50:HHL IC50) of 23, was the most substrate-dependent inhibitor. For the isolated ileum assay, the inhibitor concentration which augmented the contractile response to BK by 50% (AC50) or inhibited the contractile response to ANG I by 50% (IC50) was calculated. Only enalaprilat retained a selectivity ratio (BK AC50:ANG I IC50) in the guinea pig ileum system greater than one. Ketoace, with a ratio of 0.038, was the least ANG I-selective by this criterion. In vivo selectivity data on captopril seem more in accord with the ileum, rather than the enzyme, results. It was concluded that converting enzyme inhibitors differ in their relative selectivity for inhibiting kininase II reactions using different substrates.

Vascular plasminogen activator was measured by means of a new chromogenic assay in 24 women who had suffered from oral contraceptive-associated thrombotic disease and was compared to that in a control group of 78 premenopausal women. Vascular plasminogen activator levels were significantly reduced in the subjects who had venous thrombosis but not in the five women who had arterial thrombosis (0.04 +/- 0.03 versus 0.38 +/- 0.31, respectively) when compared to the levels in the control group (0.19 +/- 0.20). Since vascular activator levels distribute in a non-Gaussian manner, cases and controls were also stratified into deciles. Seventeen subjects who had suffered from venous thrombosis were stratified in the lowest three deciles, and two subjects, in the fourth and fifth deciles. Subjects who had suffered from arterial thrombosis were in the fourth or higher deciles. The conclusion is that, although there is a correlation between low levels of vascular plasminogen activator and venous thrombosis, no such correlation exists for arterial thrombosis.

The activity of three angiotensin I converting enzyme (ACE) inhibitors with unique related structures was assessed in vitro and in vivo. The three compounds were (S)(-)-1,2,3,4-tetrahydro-2-(3-mercapto-1-oxopropyl)-3-isoquinoline carboxylic acid (EU-4865), 1,2,3,4-tetrahydro-2-(3-mercapto-1-oxopropyl)-1- isoquinolinecarboxylic acid (EU-4881), and (S)(-)-1,2,3,4-tetrahydro-1-(3-mercapto-1-oxopropyl)-2- quinolinecarboxylic acid (EU-5031). In vitro EU-4881 was a competitive inhibitor that lacked potency (IC50 = 1980 nM) against purified ACE. The other two compounds were equipotent (IC50 = 41 nM) against purified ACE but differed in their inhibition kinetics. EU-4865 (Ki = 38 nM) was a noncompetitive inhibitor, and EU-5031 (Ki = 6.9 nM) was a competitive inhibitor. Against caveolae membrane-bound ACE EU-4881 also lacked potency (IC50 = 2852 nM). In vivo in the conscious acute aortic coarctate (AAC) rat it also lacked potency, having an ED30 (oral dose decreasing blood pressure 30 mmHg) greater than 100 mg/kg. The activity of EU-4865 and EU-5031 in the caveolae membrane-bound ACE and AAC rat reflected their different Ki values rather than their similar IC50 values. In vitro, EU-4865 and EU-5031 had IC50 values of 19 and 6.7 nM, respectively, and in vivo, they had ED30 values of 52 and 1.1 mg/kg, respectively. These results suggest that ACE has a binding requirement for a carboxy-terminus, hydrophobic amino acid that is important for in vivo activity.

Vascular plasminogen activator levels were measured preoperatively in 66 women with gynecologic malignancies. These levels were compared to levels in a matched control group of 84 women and to the incidence of postoperative venous thromboembolic disease in the patient group. Significantly lower levels of plasminogen activator were measured in patients who developed thrombotic complications (p = 0.0014). When results were stratified according to tumor location, patients with ovarian carcinoma had significantly higher activator levels than those found in control subjects (p = 0.0072), and significantly lower levels were associated with endometrial malignancy (p = 0.0140). Measurement of releasable plasminogen activator before operation may be an effective, noninvasive means of identifying patients potentially at risk for venous thromboembolic disease. Postoperative measurement of plasminogen activator may eventually find a role in monitoring tumor therapy and recurrence.