Extension of applicability of Popov's steady-state absolute-stability frequency criterion of nonlinear systems

Popov's steady-state absolute-stability frequency criterion is extended in its applications to nonlinear systems.     

Single major polypeptide of a calicivirus: characterization by polyacrylamide gel electrophoresis and stabilization of virions by cross-linking with dimethyl suberimidate

A calicivirus, San Miguel sea lion virus serotype 4, isolate 15FT, externally labelled with 125I, was shown by gel electrophoresis to possess a single major polypeptide. The polypeptide migrated anomalously upon electrophoresis in two sodium dodecyl sulfate (SDS) systems: more slowly than bovine serum albumin in a continuous phosphate-buffered system and more rapidly than bovine serum albumin in a discontinuous system. Estimated molecular weights in the two systems were approximately 71,000 and 64,000, respectively. There was no clear evidence for a minor virion polypeptide. Treatment of purified San Miguel sea lion virions with dimethyl suberimidate, a cross-linking reagent, preserved virion integrity during long-term storage at 4 degrees C. Oligomeric species of the polypeptide were observed upon electrophoresis of products from cross-linked virions. Based upon a preferred polypeptide molecular weight estimate of 71,000 and distribution of oligomeric species, a calicivirion model with 120 monomeric protein units is proposed as an alternative to a 180-unit model.     

Epidemiologic studies of Reye's syndrome: cases seen in Pittsburgh, October 1973-April 1975

Twenty-seven cases of Reye's syndrome (RS) were admitted over a 19-month period to one urban hospital. All lived in a suburban or rural location and 23 cases occurred during two influenza outbreaks. Two to three months following the last cases of RS, 24 families of RS cases and 21 control families representing neighbors or friends were interviewed for factors which could predispose to RS. Children with RS had an illness immediately preceding the onset of RS more frequently than did controls (p less than .001). No other clinical, familial, or environmental factors distinguished RS children and families from controls. Water samples, collected during the interviews, from 34 homes showed no potential toxins. The geographic pattern of RS cases with localization exclusively to rural areas suggests that an as yet unidentified environmental factor may be related to the development of RS.     

A microsurgical technique for orthotopic ovarian transplantation in the Chinese hamster

A microscopic surgical technique for the orthotopic transplantation of ovaries in the Chinese hamster is described. The procedure, which uses microcauterization of the mesovarian stump and closure of the ovarian bursa with microvascular suture, resulted in a 75 to 80 percent surgical success rate in a series of 12 nondiabetic and 12 diabetic hamsters. Applications include the production of prediabetic offspring, the study of intrauterine environmental effects on transplant-derived offspring, and the preservation of endangered genetic colony sublines.     

The hemidesmosome: new fine structural features revealed by freeze-fracture techniques

Hemidesmosomes along the dermal-epidermal junction of larval and post-metamorphic newt skin have been examined in freeze-fracture replica images correlated with electron micrographs of sectioned material. Larval hemidesmosomal sites are characterized by large (200-300 A) intramembranous granules arranged into clusters, each of which is aligned with a cytoplasmic hemidesmosomal plaque. In unfixed epidermis the granules remain attached to the A-face, while after glutaraldehyde fixation they are found on both A- and B-faces. Following metamorphosis the clusters are less distinct and localized. Replicas of unfixed B-faces and nearby cytoplasm display elongate, filamentous profiles which traverse the cytoplasmic leaflet and extend onto the B-face. The possibility that these components constitute a filamentous network serving to link tonofilaments, hemidesmosomal plaque, and basal plasmalemma is considered in view of the evidence to date. Hemidesmosomal fine structure as revealed by these studies is compared to features of desmosomes as detailed in the following report.     

Early extubation following cardiac surgery in a veterans population

BACKGROUND: Early tracheal extubation is an important component of the "fast track" cardiac surgery pathway. Factors associated with time to extubation in the Department of Veterans Affairs (DVA) population are unknown. The authors determined associations of preoperative risk and intraoperative clinical process variables with time to extubation in this population. METHODS: Three hundred four consecutive patients undergoing coronary artery bypass graft, valve surgery, or both on a fast track clinical pathway between October 1, 1993 and September 30, 1995 at a university-affiliated DVA medical center were studied retrospectively. After univariate screening of a battery of preoperative risk and intraoperative clinical process variables, stepwise logistic regression was used to determine associations with tracheal extubation < or = 10 h (early) or > 10 h (late) after surgery. Postoperative lengths of stay, complications, and 30-day and 6-month mortality rates were compared between the two groups. RESULTS: One hundred forty-six patients (48.3%) were extubated early; one patient required emergent reintubation (0.7%). Of the preoperative risk variables considered, only age (odds ratio, 1.80 per 10-yr increment) and preoperative intraaortic balloon pump (odds ratio, 7.88) were multivariately associated with time to extubation (model R) ("late" association is indicated by an odds ratio >1.00; "early" association is indicated by an odds ratio <1.00). Entry of these risk variables into a second regression model, followed by univariately significant intraoperative clinical process variables, yielded the following associations (model R-P): age (odds ratio, 1.86 per 10-yr increment), sufentanil dose (odds ratio, 1.54 per 1-microg/kg increment), major inotrope use (odds ratio, 5.73), platelet transfusion (odds ratio, 10.03), use of an arterial graft (odds ratio, 0.32), and fentanyl dose (odds ratio, 1.45 per 10-microg/kg increment). Time of arrival in the intensive care unit after surgery was also significant (odds ratio, 1.42 per 1-h increment). Intraoperative clinical process variables added significantly to model performance (P < 0.001 by the likelihood ratio test). CONCLUSIONS: In this population, early tracheal extubation was accomplished in 48% of patients. Intraoperative clinical process variables are important factors to be considered in the timing of postoperative extubation after fast track cardiac surgery.     

Left ventricular potential energy is represented in the ejecting left ventricular pressure curve

In this study, the authors describe a new "reactive syndrome," Reactive Intestinal Dysfunction Syndrome (RIDS), which has similarities to the previously described clinical syndromes Reactive Airway Dysfunction Syndrome (RADS) and Reactive Upper Airway Dysfunction Syndrome (RUDS). Given that at least 5 neuropeptides are common to both the respiratory tract and digestive tract, the authors propose that the abnormal secretion of these neuropeptides or the abnormal numbers of their receptors play a role in what is perceived clinically as RADS, RUDS, and RIDS. The relatively large surface areas of both the lungs and gut render them especially vulnerable to the environment to which they are exposed constantly.     

Expression of neural cell adhesion molecules and neurofilament protein isoforms in skeletal muscle tumors

In a series of rhabdomyosarcomas, the expression of neural cell adhesion molecules (NCAM) and neurofilament isoforms was probed in frozen sections. It was found that NCAM was widely expressed in rhabdomyosarcomas without relation to subtype or differentiation level. Neurofilament isoforms were found throughout all subtypes but were largely restricted to those neurofilament isoforms that are expressed early in neurogenesis, that is, poorly phosphorylated low- and medium-weight isoforms. It was concluded that the expression of these "neural" markers is widespread and does not signify a neural tumor.     

Employing ex-addicts: determinants of support and opposition

In 1973 public hearings of the Temporary (N.Y.) State Commission to Evaluate the Drug Laws concluded with a report which documented pervasive controversy and discrimination in employing rehabilitated or ex-addicts. To analyze local attitudes to this issue, the present study targeted the audience of a recent Symposium "Employment of the Ex-Addict", held in Westchester County, New York, October, 1973. Ss (N = 83) completed a questionnaire to assess the nature and extent of proponent views, degree of commitment, and motivational components of support and opposition. The data strongly supported belief in the urgency of the need to employ. Educational and community measures of moderate activism were preferred to antidiscrimination legislation. Significant correlations were found between urgency and age, size of plant, and occupational group. Appeals to human rights and social rights were judged to be important positive reinforcers to employment, and the economic argument a greater deterrent than fear or prejudice. Study limitations, findings, and need for further behavioral organizational research were discussed.