Structure-function analysis of the Abm12 beta mutation using site-directed mutagenesis and DNA-mediated gene transfer

The B6.C-H-2bm12 (bm12) mouse possesses a naturally occurring mutation in its class II MHC A beta gene. The three amino acid substitutions at positions 67, 70, and 71 that comprise this mutation lead to changes in both Ia expression and immune recognition of the resultant A beta A alpha molecule. The experiments reported here utilize a combination of oligonucleotide-mediated site-directed mutagenesis and DNA-mediated gene transfer to explore the roles played by each of the three mutant residues in these various phenotypic changes. A beta genes comprising all permutations of the residues distinguishing Ab beta from Abm12 beta were created and were individually co-transfected with Ab beta into mouse L cells. Sublines expressing high levels of membrane Ia were selected by preparative flow cytometry and were studied for reactivity with a panel of monoclonal anti-Ia antibodies, or for their ability to act as antigen-presenting cells (APC) for the stimulation of T cell hybridomas. During the generation of these transfectant lines, it was noted that expression of a high level of Abm12 beta Ab alpha was more difficult to achieve than a similar level of Ab beta Ab alpha. Northern blot analysis of specific A beta and A alpha mRNA levels in these various lines indicated that more class II mRNA, and presumably more A beta and A alpha chains, were required to achieve expression of Abm12 beta Ab alpha equal to that of Ab beta Ab alpha, suggesting that the previously noted reduction of Ia expression on cells from bm12 mice reflects a decreased ability of Abm12 beta Ab alpha chains to pair, or to reach the membrane. Staining of the panel of transfectants with monoclonal antibodies revealed that antibodies which did not distinguish Ab beta Ab alpha from Abm12 beta Ab alpha also reacted equally well with all molecules involving in vitro mutant A beta chains. Monoclonal antibodies reactive with Ab beta Ab alpha but not Abm12 beta Ab alpha were specific for an epitope primarily determined by the presence or absence of Arg 70 in Ab beta. In striking contrast, all three mutant positions were found to play crucial roles in T cell recognition, because all substitutions led to significant or complete loss of antigen-presenting function with all but one of the T hybridomas tested.(ABSTRACT TRUNCATED AT 400 WORDS)

Pulmonary function abnormalities in intentional spray paint inhalation

To investigate the effects of intentional hydrocarbon inhalation on lung function, a preliminary study involving ten spray paint abusers was conducted. Mean duration of the inhalation was 34.9 months; mean frequency was 3.2 times per week. Pulmonary function testing (PFT) consisted of flow studies, lung volumes, single-breath carbon monoxide diffusing capacity (Dsb), airway resistance and airway conductance. An exercise provocation was followed by repetition of the PFT, except for Dsb. Our results revealed an obstructive ventilatory pattern in 90 percent of the subjects. In seven patients, there was a significant increase of airway resistance prior to exercise. In five of the ten patients, exercise provocation produced an increase in residual volume. Five of six subjects receiving a trial of a bronchodilator had significant improvement of obstruction. These findings suggest that intentional inhalation of spray paint may produce abnormalities in pulmonary function. These abnormalities may improve after use of a bronchodilator.

Left ventricular end-systolic volume as the major determinant of survival after recovery from myocardial infarction

Impairment of left ventricular function is the major predictor of mortality after acute myocardial infarction, but it is not known whether this is best described by ejection fraction or by end-systolic or end-diastolic volume. We measured volumes, ejection fractions, and severity of coronary arterial occlusions and stenoses in 605 male patients under 60 years of age at 1 to 2 months after a first (n = 443) or recurrent (n = 162) myocardial infarction and followed these patients for a mean of 78 months for survivors (range 15 to 165 months). There were 101 cardiac deaths, 71 (70%) of which were sudden (instantaneous or found dead). Multivariate analysis with log rank testing and the Cox proportional hazards model showed that end-systolic volume (chi 2 = 82.9) had greater predictive value for survival than end-diastolic volume (chi 2 = 59.0) or ejection fraction (chi 2 = 46.6), whereas stepwise analysis showed that once the relationship between survival and end-systolic volume had been fitted, there was no additional significant predictive information in either end-diastolic volume or ejection fraction. Severity of coronary occlusions and stenoses showed additional prediction of only borderline significance (p = .04 in one analysis), but continued cigarette smoking did remain an independent risk factor after stepwise analysis. For a subset of patients (n = 200) who had taken part in a randomized trial of coronary artery surgery after recovery from infarction, surgical "intention to treat" showed no predictive value.(ABSTRACT TRUNCATED AT 250 WORDS)

Work in progress: in vitro analysis of pleural fluid analogs by proton magnetic resonance. Preliminary studies at 1.5T

To test the potential of 1.5 Tesla magnetic resonance imaging (MRI) for assessing the protein concentration of pleural effusions, five pleural fluid analogs (saline + 0, 2, 4, 6, 8 g albumin/100 mL) and, for comparison, four saline dilutions of whole blood were evaluated in vitro. The relaxation rates (1/T1, 1/T2) of albumin solutions were determined by 1.5 T spectroscopy (MRS) and correlated with albumin concentration (1/T1:slope 0.02, r + 0.89, P less than .05; 1/T2: slope 0.16, r = 0.997, P less than .001). MRI studies of these solutions showed no significant correlation with 1/T1, but 1/T2 showed a positive correlation with albumin concentration (r = 0.98, P less than .01). Both MRI relaxation rates were significantly correlated with blood concentration, and slopes were greater than for albumin solutions. These preliminary studies, demonstrating differences in correlation between relaxation rates and the concentration of albumin and blood, suggest that MRI has the potential for differentiating pleural effusions of different chemical composition.

Control of sodium excretion in human pregnancy

Sodium and water retention are normal accompaniments of pregnancy achieved by many significant and complex interrelated alterations in homeostatic forces. Furthermore, potentially harmful derangements in sodium and volume control are found in women with pregnancy-associated hypertension (P-AH, preeclampsia). None of these alterations is completely understood, and many of them appear paradoxical. Recent reviews examined some of the more closely investigated facets of sodium and volume control in normal and hypertensive pregnancy. This relatively brief discussion aims to summarize the known information, update it with more recent work, and speculate on the potential significance of abnormalities in sodium homeostasis in hypertensive pregnancy.

Intrathecal administration of nitroxides as potential contrast agents for MR imaging

The diagnosis of various disorders of the cerebrospinal fluid (CSF) with magnetic resonance (MR) imaging may require the intrathecal administration of a paramagnetic contrast agent. Furthermore, the CSF route provides direct access to the brain, circumventing the blood-brain barrier. Three nitroxides, two charged and one uncharged, were administered intrathecally to dogs to assess their potential as contrast agents for MR imaging of the CSF. Nitroxide concentrations and proton T1 values were measured in samples of CSF removed at various times after nitroxide administration, and pharmacokinetic curves were constructed. The charged nitroxides had considerably longer half-lives than the uncharged compound. On in vivo MR imaging of the CSF (surrounding the upper cervical cord and brain stem) in one dog, use of a charged nitroxide as contrast agent led to considerably higher CSF signal intensity than was observed in the nonenhanced, baseline T1-weighted images. This effect was achieved at low doses (20 mumol) and sustained for at least 90 minutes. The intrathecal use of nitroxides as contrast agents for MR imaging warrants continued investigation.

Asthma in children: emergency management

We review the pathophysiological alterations at work in asthma and outline pharmacological agents that are available for emergency therapeutic intervention, offering some general principles for management. A combined overview of predictors of outcome in asthmatic episodes in children also is presented.

The influence of cimetidine versus ranitidine on doxepin pharmacokinetics

The effect of cimetidine and ranitidine on doxepin pharmacokinetics was studied in 6 healthy volunteers. Each subject completed 3 study phases: Treatment A, 9 consecutive doses of 50 mg doxepin (once daily); Treatment B, same as Treatment A but co-administration of cimetidine 600 mg b.i.d. starting after the sixth doxepin dose and continuing until approximately 2 days following discontinuation of doxepin administration; Treatment C, identical to Treatment B but with ranitidine 150 mg b.i.d. instead of cimetidine. Unlike ranitidine, cimetidine co-administration resulted in a significant increase in steady state plasma levels of doxepin (4.7, 9.0 and 4.5 ng/ml during Treatments A, B and C respectively) but not desmethyldoxepin (4.1, 4.6 and 4.2 ng/ml during Treatments A, B and C respectively). Elimination half-lives of doxepin and desmethyldoxepin were prolonged by cimetidine co-administration (19.6 and 26.2 h respectively), but remained unchanged during the ranitidine treatment phase (13.3 and 18.4 h) as compared to the control phase i.e. Treatment A (13.2 and 19.0 h). These results show that cimetidine, unlike ranitidine, significantly inhibits the biotransformation of doxepin. This data has clinical implications when the co-administration of tricylic antidepressants and H2-receptor antagonists are indicated.

Magnetic field effects on surgical ligation clips

Magnetic forces exerted on surgical clips and the magnetic resonance imaging distortion they create in phantoms and rabbits at magnetic field strengths of 1.5 Tesla were investigated. Results are reported for both ligation and aneurysm clips manufactured from three types of stainless steel as well as titanium, tantalum and niobium metals. Paramagnetism and eddy currents were measured in a customized moving Gouy balance. Direct measurements of other magnetic forces were carried out in a 1.5T MRI system. The titanium and tantalum clips showed the least interaction with the magnetic field, both in terms of forces exerted and the observed image distortion with the larger clips generating the larger interactions. The strongest field distortions and attractive forces occurred with 17-7PH stainless steel clips. These interactions were ferromagnetic in origin and of sufficient strength to present significant risk to patients having this type of clip present during an MRI scan.

Marital support during pregnancy

To describe and compare women's and men's experiences of partner support during pregnancy, a questionnaire that included the Support Behavior Inventory was given to 313 expectant couples in the latter half of pregnancy. Study findings revealed no difference between men and women in the mean partner support satisfaction score. A significant difference occurred in the variability of expectant mothers' and fathers' partner support scores. The specific support behaviors that elicited the greatest satisfaction and dissatisfaction in men and women are described.

Potassium regulation and progesterone-aldosterone interrelationships in human pregnancy: a prospective study

Little is known about the intrinsic renal and hormonal regulation of potassium excretion in pregnancy despite major alterations in many of the potassium regulatory factors. Forty primigravid women on an unrestricted diet were studied during the second and third trimesters and exhibited constant absolute and fractional potassium excretion despite a significant increase in plasma aldosterone concentration between these stages. The plasma progesterone level rose significantly between studies but closer analysis showed no correlation between individual changes in plasma aldosterone concentration and progesterone between trimesters. In the 14 subjects studied post partum, baseline absolute potassium excretion was not significantly altered but filtered potassium fell and fractional potassium excretion tended to rise. After dietary sodium manipulation at these stages, absolute potassium excretion, fractional potassium excretion, and progesterone were unaltered despite significant changes in plasma aldosterone concentration and sodium excretion. These results suggest that potassium excretion is held constant throughout pregnancy and that renal tubular potassium reabsorption adjusts appropriately to the increased filtered potassium load. Progesterone does not appear to be involved in the acute regulation of potassium or sodium excretion but may have effects on sodium and potassium excretion that are constant, proportional to its placental production, and unresponsive to endogenous changes in mineralocorticoid production.

Purification of cathepsin B by a new form of affinity chromatography

Human cathepsin B was purified by affinity chromatography on the semicarbazone of Gly-Phe-glycinal linked to Sepharose 4B, with elution by 2,2'-dipyridyl disulphide at pH 4.0. The product obtained in high yield by the single step from crude starting material was 80-100% active cathepsin B. The possibility that this new form of affinity chromatography may be of general usefulness in the purification of cysteine proteinases is discussed.

In vitro translation of B-cell stimulatory factor-1 in Xenopus laevis oocytes

B-cell stimulatory factor-1 (BSF-1) can be translated in vitro in Xenopus laevis oocytes. This activity is blocked by an antibody to BSF-1. The RNA species coding for BSF-1 activity sediments of approximately 8-9S and is separable from RNA coding for interleukin-2 activity which sediments at approximately 11.5S. Finally, the fact that BSF-1 can be translated in vitro confirms that functions attributed to BSF-1 do not depend on contamination with other biologically active molecules such as phorbol myristate acetate.

Sodium excretion in human pregnancy: a role for arginine vasopressin

Plasma arginine vasopressin concentration was measured before and after 1 week's dietary sodium loading (greater than 250 mmol/day) or deprivation (less than 50 mmol/day) in 50 second-trimester and 34 third-trimester primigravidas. A significant rise in plasma arginine vasopressin was observed only in second-trimester subjects following sodium loading (5.6 +/- 0.5 to 6.6 +/- 0.5 pg/ml; p less than 0.05). Plasma sodium concentration and blood pressure did not alter, and plasma volume increased slightly in this group (24.4 +/- 0.5 to 25.9 +/- 0.7 ml/cm height; p less than 0.01). Hence the observed increment in plasma arginine vasopressin concentration in this group could not be explained by alterations to the major factors regulating arginine vasopressin release. It is suggested that arginine vasopressin secretion increases to assist natriuresis following dietary sodium loading in the second trimester of human pregnancy.

NMR studies of combined lanthanide shift and relaxation agents for differential characterization of 23Na in a two-compartment model system

Spin relaxation and chemical shifts by lanthanide chelate complexes are used to distinguish 23Na signals in a simulated two-compartment model. Both effects are significant in EDTA, DTPA, and TPP complexes of Gd and in the TPP complex of Dy. The simultaneous measurement of these properties is illustrated and represents a promising method for monitoring sodium concentrations and fluxes including fast transport components.

Social support, stress, and health: a comparison of expectant mothers and fathers

The influence of social support and stress on expectant mothers' and fathers' health was determined by testing and comparing different predictive models. Instruments used were the Support Behaviors Inventory, Stress Amount Checklist, and Health Responses Scale. Regression analyses were performed on data from questionnaires completed by 313 couples in the second half of pregnancy to predict health, using the same independent variables for women and men. The regression analyses began with a model that included the variables of stress, satisfaction with partner support, satisfaction with other persons' support, history of chronic illness, education, age, employment status, military status, and family income. The effects of four variables, satisfaction with partner support, satisfaction with others' support, stress, and chronic illness, were tested separately for men and women. Subsets of these variables were deleted to create a series of nested comparisons. Results indicated that social support and stress were useful in predicting health. Partner support appeared to be the most important variable in understanding expectant fathers' health, but social support for mothers included a larger domain and social networks contributed to their health in the same way as partner support. Both stress and chronic illness were more important explanatory variables for pregnant women's health than for their partners' health. These data suggest that nursing interventions targeted at reducing stress and improving expectant parents' satisfaction with their partner support might enhance their health.

Amiodarone-induced torsades de pointes

Five cases of amiodarone-induced syncope due to torsades de pointes or ventricular fibrillation are described. Amiodarone was used for recurrent supraventricular tachycardia in four cases and frequent ventricular extra systoles complicating congenital QT prolongation in the remaining case. Each was associated with a marked prolongation in the QTc interval following amiodarone. Three cases had had a previous history of life-threatening ventricular arrhythmias secondary to anti-arrhythmic drugs. Hypokalemia may have been a contributory factor in two. The clinical features, predisposing factors, and treatment are discussed.

Manganese and manganese-ATP interactions with bovine sperm adenylate cyclase

The adenylate cyclase of mammalian spermatozoa shares some of the properties of the isolated catalytic component from somatic cell adenylate cyclases. One of these properties is the large apparent stimulation by Mn2+. We have used the direct linear plot according to Eisenthal and Cornish-Bowden to explore whether this apparent stimulation is due to direct stimulation by Mn2+ or due to complexation of free ATP, a postulated inhibitor of cyclase activity. We have observed the activity of the particulate adenylate cyclase from bovine caudal epididymal spermatozoa as a function of calculated equilibrium values for the concentrations of Mn2+, free ATP, and the enzyme's substrate, the manganese-ATP complex. Direct linear plots for activity and substrate concentration over the apparent inhibitory concentration range of free ATP give the pattern expected for a hyperbolic substrate response. By contrast, direct linear plots in which Mn2+ concentration varies over its apparent stimulatory range show that as Mn2+ concentration increases, activities are higher than would be predicted for a hyperbolic substrate response. We conclude that for particulate bovine sperm adenylate cyclase, free ATP is not strongly inhibitory, and Mn2+ is a positive effector, reaching half-maximal stimulation at 0.2 mM. The unique nature of the sperm adenylate cyclase and its possible regulation by Mn2+ under physiological conditions is discussed.

T-cell recognition of Ia molecules selectively altered by a single amino acid substitution

T lymphocytes recognize foreign antigen together with allele-specific determinants on membrane-bound class I and class II (Ia) gene products of the major histocompatibility complex. To identify amino acids of class II molecules critical to this recognition process, the genes encoding the beta chains of the I-Ak molecule were cloned from a wild-type B-cell hybridoma and from an immunoselected variant subline showing distinct serological and T-cell stimulatory properties. Nucleotide sequencing and DNA-mediated gene transfer established that a single base transition (G----A) encoding a change from glutamic acid to lysine at position 67 in the I-Ak beta molecule accounted for all the observed phenotypic changes of the variant cells. These results confirm the importance of residues 62 to 78 in the amino terminal domain of I-A beta for class II-restricted T-cell recognition of antigen and demonstrate the ability of a single substitution in this region to alter this recognition event.

Reliability and Validity of the Women's Health Care Skills Audit

The Women's Health Care Skills Audit (WHCSA) is a behaviorally oriented instrument which is hypothesized to measure important, clinically relevant components of the basic women's health care skills of Family Nurse Practitioners. The purpose of this research was to examine the reliability and validity of the WHCSA. Two women's health care nurse practitioners independently evaluated the performance of 23 Family Nurse Practitioner students during client visits. Overall internal consistency and test-retest reliabilities of the instrument were high--.96 and .84 respectively. In addition, support for the convergent validity of the WHCSA was also obtained in the study. Results therefore indicate that the WHCSA is both reliable and valid and holds promise for use in documenting and evaluating basic Family Nurse Practitioner women's health care competencies.

Social support during pregnancy: a unidimensional or multidimensional construct?

The purpose of this study was to test empirically a conceptually derived multidimensional formulation of social support. Analyses were based on responses of 313 expectant couples who varied in age, income, and education. A questionnaire, which included the Support Behaviors Inventory (SBI), was given in the latter half of pregnancy. A four-phased analysis was conducted: discriminate validity testing of the multidimensional support structure, further subscale analysis, factor analysis of the structure of the SBI, and reformulation of the SBI based on results of the factor analyses. Results did not demonstrate independence of measurement with items that were developed to represent a priori social support dimensions of emotional, material, informational, and appraisal support. The factor analysis in particular revealed that the scree test by Cattell (1966) demonstrated a large, dramatic discontinuity in eigen-values and suggested that there was only one systematic factor. These results implied a dominant construct of social support in pregnant couples that organizes at the broad level the perceived degree of experienced support during pregnancy. This broader concept was so dominant in the current study, explaining 48% of the variance in partner support and 61% of the variance in others support, that the idea of multidimensionality was not confirmed. These data suggest an ongoing need to scrutinize carefully and validate empirically the hypothesized multiple dimensions of social support proposed in a number of recent support instruments.

Personal and family impact of premenstrual symptoms

An exploratory study of premenstrual symptomatology, coping strategies, personal and family impact, and alterations in family functioning attributed to premenstrual symptoms was conducted. A sample of 83 women and 32 men completed a questionnaire before an evening lecture on premenstrual syndrome. Women reported a total of 74 different recurrent premenstrual symptoms, with the most frequently reported category being the "tension states." Men used multiple coping techniques to deal with their spouse's symptoms with offering support and expressing anger as the most frequently reported. Recurrent negative family impact themes emerged from the content analysis: increased conflict, decreased family cohesion, and disrupted communication among family members. Nursing implications are discussed.

Essential hypernatremia: disordered thirst and blood pressure control

A 24 year old man developed partial central diabetes insipidus with impaired thirst and an elevated osmotic threshold to the release of arginine vasopressin (AVP). Plasma AVP was present in inappropriately small concentrations despite severe hyperosmolality. In addition, marked hypertension accompanied this disorder and all abnormalities, including the hypertension, responded to 1-desamino-8-D-arginine vasopressin therapy. Several lines of evidence suggest this disorder may be a disturbance of hypothalamic function.

Respiratory complications following cardiac surgery. The role of microbiology in its evaluation

Sputum specimens were received for microbiological examination from 110 patients following open heart surgery. The isolation of Haemophilus influenzae occurred significantly more often in those patients who had pre-existing chest disease, but was not associated with postoperative chest problems. There was a significant association between pre-operative heart failure and subsequent severe pulmonary complications.

Effect of early treatment with propranolol on left ventricular function four weeks after myocardial infarction

Left ventricular function and exercise capacity were assessed in 79 patients randomised to receive intravenous and oral propranolol (n = 44) or conventional therapy (n = 35) within four hours of onset of their first myocardial infarction. Cineangiocardiography and exercise testing were performed four weeks after infarction to allow for maximum recovery of myocardial function. Left ventriculography showed no improvement in ejection fraction or preservation of regional contractile function in patients treated with propranolol compared with controls. A trend towards smaller end diastolic volumes was seen in the propranolol group (mean (SD) 151(42) ml) compared with controls (167(42) ml). Exercise duration and frequency of angina were not significantly different in the two groups. It is concluded that limitation of infarct size by propranolol does not lead to a significant improvement in ventricular systolic function, although left ventricular dilatation may be reduced. These findings are consistent with the known effect of early intravenous beta blockade which limits infarct size by preservation of subepicardial myocardium.

Tissue relaxation time: in vivo field dependence

Relaxation times (T1 and T2) were measured in vivo in mongrel dogs at fields of 0.3, 0.5, 1.0, 1.35, and 1.5 tesla (T). T1 was measured using nine values of inversion time ranging from 10 to 1,280 msec. T2 was measured with a four-point multiple spin-echo sequence. Relaxation times were calculated for muscle, kidney cortex, spleen, and adipose tissue. T2 is independent of field. A linear fit to the field dependence of T1 yields slopes of 400-500 msec/T for tissues in which the primary source of protons is water. The lower slope of adipose (approximately 150 msec/T) reflects the different mechanism of spin-lattice relaxation of the -CH2 protons.

Use of molecular techniques for analysis of Ia structure-function relationships

An overview of a strategy for the molecular analysis of class II major histocompatibility complex (Ia) gene product structure-function relationships is presented, and results obtained to date by using this approach are summarized. The A beta, A alpha, E alpha, and E beta genes have been cloned and sequenced to yield information on gene organization and primary protein sequence. Comparison of sequences from allelic forms of these genes show the NH2-terminal domain to be the locus of most intraspecies polymorphism. Transfection of I-A alpha and A beta genes into B lymphoma cells or L cells has generated cells expressing the transfected gene products on their membrane. Such Ia+ transfectants present antigen to various T cells, which use the expressed I-A as a restriction element. Exon shuffling has shown the beta 1 domain of A beta to play a predominant role in such restricted antigen recognition. Preliminary data refining this analysis to sites within beta 1, as well as data on control of alpha: beta chain association, are reviewed, and future prospects for use of this approach in resolving questions of immunological interest are discussed.

Human fibronectin metabolism

The metabolic behavior of fibronectin (Fn), a highly adhesive glycoprotein (440,000 mol wt), was studied in eight healthy control subjects and in 11 patients, six of whom were critically ill. Fn was purified from fresh human plasma, radiolabeled, and shown to retain function both in vitro and in vivo. Results showed that, in normal controls, Fn is a rapidly catabolized protein with a fractional catabolic rate (FCR) of 4.81%/h (range, 4.00-6.27), a half-life (t1/2) of 25 h (20-30), extravascular/intravascular diffusion ratio (EV/IV) of 2.04 (1.52-3.30), and a synthesis rate (SR) of 0.71 mg/kg body weight per h (0.61-0.87). There was evidence for extravascular catabolism in each subject. Plasma levels correlated with SR but not with t1/2 or FCR. Patients had a lower EV/IV ratio, and in two critically ill patients with low plasma Fn concentration the SR was markedly depressed. These findings suggest that reduced synthesis of Fn, rather than increased FCR or increased extravascular distribution, is responsible for Fn deficiency in critically ill patients.

Right ventricular infarction, bradyarrhythmias, and cardiogenic shock: importance of atrial or atrioventricular sequential pacing

We report two patients with inferior myocardial infarction, complicated by bradyarrhythmia, hypotension, and clinical evidence of right ventricular infarction. Conventional therapy of volume expansion and inotropic support was insufficient to maintain an adequate blood pressure. Sequential atrioventricular (AV) pacing for AV block (Case 1) or atrial pacing for junctional bradycardia (Case 2) resulted in immediate and sustained improvement in blood pressure and clinical indices of perfusion. We recommend consideration of these pacing modes in patients with inferior infarction with evidence of right ventricular infarction, bradyarrhythmia, and cardiogenic shock. The likely mechanism of improvement is by restoration of atrial transport with consequent improvement in ventricular function.

Effects of the operating magnetic field on potential NMR contrast agents

Paramagnetic metal ions have shown promise as contrast agents for nuclear magnetic resonance (NMR) imaging. Their ability depends upon modification of the relaxation times (T1 and T2) through dipolar interactions. These interactions cause the effectiveness of the agents to be sensitive to the operating magnetic field. Studies are presented of the operating field dependence (frequency dispersion) of two metal-chelate complexes, Gd+3-ethylenediaminetetraacetate (EDTA) and Mn+2-EDTA, in a physiologically balanced electrolyte solution. Inversion recovery experiments were performed on two concentrations of each metal-chelate complex at five resonant frequencies. The frequency dispersion curves were similar in appearance for those of the corresponding aqueous solutions. The Mn+2 complex showed no unusual concentration effects. The Gd+3 complex showed an unexpected concentration dependence in the dispersion behavior. This is attributed to a difference in the dipolar correlation time between the two solutions. With its unique correlation time in electrolyte solutions, predictions of relaxation rate changes in studies in vivo may be easier for the Mn+2-EDTA complex.

Prevention of ventricular fibrillation during acute myocardial infarction by intravenous propranolol

A trial of intravenous followed by oral propranolol, started within 4 h of onset of suspected myocardial infarction and continued over 27 h, was carried out in 735 patients; 364 received propranolol, 371 were controls. Ventricular fibrillation during the first 48 h after entry to the trial occurred in 2 treated patients and in 14 controls (p = 0.006). Rates of hospital mortality, complications other than ventricular fibrillation, and progression from threatened to completed infarction did not differ between treated and control patients. Ventricular fibrillation was not apparently prevented by prior beta-blocker treatment, which was not a reason for exclusion from the trial. This intravenous/oral propranolol regimen seems to prevent ventricular fibrillation due to evolving myocardial infarction.

Human plasma alpha-cysteine proteinase inhibitor. Purification by affinity chromatography, characterization and isolation of an active fragment

Human plasma alpha-cysteine proteinase inhibitor (alpha CPI) was purified by a two-stage method: affinity chromatography on S-carboxymethyl-papain-Sepharose, and high-resolution anion-exchange chromatography. The protein was obtained as a form of Mr about 64 000 and material of higher Mr (about 100 000). In sodium dodecyl sulphate/polyacrylamide-gel electrophoresis with reduction, both forms showed a major component of Mr 64 000. An antiserum was raised against alpha CPI, and 'rocket' immunoassays showed the mean concentration in sera from 19 individuals to be 35.9 mg/dl. Both low-Mr and high-Mr forms of alpha CPI were confirmed to be sialoglycoproteins by the decrease in electrophoretic mobility after treatment with neuraminidase. alpha CPI was shown immunologically to be distinct from antithrombin III and alpha 1-antichymotrypsin, two serine proteinase inhibitors from plasma with somewhat similar Mr values. alpha CPI was also distinct from cystatins A and B, the two intracellular low-Mr cysteine proteinase inhibitors from human liver. Complexes of alpha CPI with papain were detectable in immunoelectrophoresis, but dissociated to free enzyme and intact inhibitor in sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. The stoichiometry of binding of papain was close to 1:1 for both low-Mr and high-Mr forms. alpha CPI was found to be a tight-binding inhibitor of papain and human cathepsins H and L (Ki 34 pM, 1.1 nM and 62 pM respectively). By contrast, inhibition of cathepsin B was much weaker, Ki being about 35 microM. Dipeptidyl peptidase I also was weakly inhibited. Digestion of alpha CPI with bromelain gave rise to an inhibitory fragment of Mr about 22 000, which was isolated.

Bovine sperm adenylate cyclase. Inhibition by adenosine and adenosine analogs

Since both adenosine and cAMP affect sperm motility and metabolism, the authors have studied the mode of interaction of adenosine with the adenylate cyclase activity in either the presence or the absence of 15 mM caffeine. In general, structural analogs of adenosine containing alterations of the purine structure produce little or no inhibition, whereas analogs containing alterations of the ribose structure are effective inhibitors. Cyclic AMP and caffeine also inhibit the enzyme activity. The kinetics of the adenosine inhibition most closely resemble the linear noncompetitive type. Adenosine is a more effective inhibitor of adenylate cyclase activity in the presence of Mn2+ rather than Mg2+, and is more effective at higher metal ion concentrations. These observations are consistent with a P-site interaction of adenosine with adenylate cyclase.

Correlates of dysmenorrhea. A challenge to past stereotypes

A study was conducted to explore the relationship of demographic variables, gynecologic history variables, and menstrual attitudes to three measures of dysmenorrhea derived from the Menstrual Distress Questionnaire. One hundred ninety-three women, 18 to 35 years old, from five neighborhoods in a large, metropolitan city comprised the sample population. The strongest correlates found were attitudes toward menstruation, though associations between dysmenorrhea and items reflecting traditional/feminist dimensions were absent. Further precision in defining dysmenorrhea and a comprehensive, health-oriented approach to dealing with menstrual distress is indicated. Recommendations about the nurse's role in counseling dysmenorrheic women and promoting more positive menstrual attitudes are discussed.

Job satisfaction. Assumptions and complexities

It has long been assumed that job satisfaction relates to employee turnover and quality of care. In this article the difficulties of measuring job satisfaction are discussed in light of results from a 6-month assessment by nurse employees in a university-affiliated acute care hospital. The authors found that job satisfaction scores were significantly predicted by respondents' job expectations and the importance they placed on various components of the work situation. The authors conclude that job satisfaction measurement is most valid and reliable when these two predictors are taken into account.

Transition metal-chelate complexes as relaxation modifiers in nuclear magnetic resonance

Studies are reported of relaxation modifiers for use in nuclear magnetic resonance (NMR) imaging systems. Chelate complexes of transition metal salts are under investigation to determine their ability to reduce the spin-lattice relaxation time (T1) of the nucleus under observation and to reduce the toxicity of the metal ion. The ethylenediaminetetraacetate (EDTA) complexes of FeCl3, GdCl3, and MnCl2 are not as effective as the respective salts in reducing T1 of water protons at 90 MHz. For Mn, this diminution in ability is offset by a significant reduction in toxicity. Explanations for this loss of effectiveness are discussed.

A simple aid to the differential diagnosis of oliguria

A study was conducted in oliguric and acutely azotemic patients, measuring: (i) the fractional excretion of sodium (FENa) using creatinine clearance as a measure of glomerular filtration rate, and (ii) sodium clearance relative to urea clearance, designated as the sodium/urea clearance ratio (Na:urea CR). It was found that FENa discriminated between "tubular" and "non-tubular" disorders in 96% of patients. Further, Na:urea CR was as discriminating as FENa. Patients with Na:urea CR above 2.5% can be reliably diagnosed as having acute tubular necrosis or acute urinary tract obstruction; those with a value less than 2.5% will have acute glomerulonephritis or pre-renal azotemia. As urea and sodium measurements are so readily available, this test can now be applied in the assessment of the oliguric or acutely azotemic patient in any hospital practice.

The specificity of H-2-restricted cytotoxic T lymphocytes directed to AKR/Gross leukemia virus-induced tumors. II. Altered gp70 display and production of noninfectious virus particles by an insusceptible variant tumor

Derived from the susceptible AKR.H-2bSL1 tumor cell line, a variant tumor subclone, cl.18-5, was selectively insusceptible to H-2-restricted anti-AKR/Gross virus cytotoxic T lymphocytes (CTL) due to its failure to be recognized. In this study, the expression of virus-related products by variant cl.18-5 cells was compared to that of AKR.H-2bSL1 cells and a susceptible clone, as an approach towards defining the virus-associated antigens recognized by anti-AKR/Gross virus CTL. Despite the type specificity of the CTL, cl.18-5 displayed normal levels of the group-specific antigen (gag) encoded proteins p30, p15, p12 and p10, and the gag-associated Gross cell surface antigen. These results were confirmed by fluorescence-activated cell sorter analysis employing monoclonal antibodies specific for either AKR p12 or the cell surface glycosylated form of AKR ecotropic gag product. In contrast, cl.18-5 was variably less sensitive than AKR.H-2bSL1 to the action of complement and xenogeneic antisera directed against the envelope (env) product gp70. In addition, a panel of five monoclonal antibodies to gp70, which detect distinct endogenous ecotropic viral determinants, lysed AKR.H-2bSL1, but not cl.18-5 cells. However, absorption experiments indicated that cl.18-5 did express near normal levels of these specificities, suggesting an alteration in the orientation or topographical distribution of these determinants. Consistent with an inappropriate display of env products, cl.18-5 was found to be deficient in the production of infectious ecotropic leukemia virus. The particulate fraction of the cell-free supernatant of cl.18-5 contained normal levels of reverse transcriptase activity, indicating that noninfectious viral particles were being produced. Collectively, these results point to an association between recognition by anti-AKR/Gross virus CTL and the expression of ecotropic gp70 required for infectivity of virus.

Life skills training for chronic schizophrenics

This research evaluates the effectiveness of training chronic schizophrenic patients in interpersonal and instrumental skills for coping adequately in community living situations. The subjects were male, chronic schizophrenic inpatients with histories of multiple rehospitalizations. Twenty-eight volunteers were randomly assigned to either the life skills training or to a traditional Veterans Administration rehabilitation program. The life skills program included 7 weeks of training in interpersonal and instrumental skills considered important for community tenure: interpersonal communication skills, nutrition, health, finance, time management, and utilization of community resources. Acquisition of skills was assessed by means of a Life Skills Inventory (LSI) and five attitudinal and affective measures pretreatment and post-treatment. The results of the comparison of outcome measures showed the treatment group superior to the control in interpersonal skills, finance, health, use of community resources, and total LSI score. They also showed greater improvement on most of the attitudinal and affective measures. Patients are being followed to measure duration of community placement and maintenance of skills.

Resistance of human erythrocytes containing elevated levels of vitamin E to radiation-induced hemolysis

Human erythrocytes were isolated from the blood of healthy donors and then incubated in the presence of suspensions of alpha-tocopherol for 30 min at 37 degrees C. Unabsorbed tocopherol was removed by centrifugation using several washes of isotonic phosphate-buffered saline. Washed erythrocytes were resuspended to 0.05%. Hct and exposed to hemolyzing doses of 60Co gamma radiation, and hemolysis was monitored continuously by light scattering at 700 nm in a recording spectrophotometer. The extent of hemolysis with time was sigmoid and data analysis was carried out on the time taken for 50% hemolysis to occur (t50%). The vitamin E content of erythrocytes was significantly elevated by the incubation procedure and resulted in the cells exhibiting a significantly increased resistance to hemolysis as reflected by the extended t50% values. Oral supplementation of 500 IU of vitamin E per day to eight normal human subjects for a period of 16 days also resulted in their washed erythrocytes exhibiting a significant increase in resistance to radiation-induced hemolysis. When comparing vitamin E incubated cells with control cells, both the dose-reducing factor (DRF) and the time for 50% hemolysis quotient (Qt50%) were observed to increase with increasing radiation dose.