Mutation in continuous cultures of Schizosaccharomyces pombe. I. Dependence of the kinetics of mutation accumulation upon the growth-limiting nutrilite

The rate of spontaneous mutation to resistance to the 12,13-epoxytrichothecene trichodermin has been determined under different growth limiting conditions in continuous cultures of the microbial eukaryote Schizosaccharomyces pombe. In agreement with data obtained in bacterial systems by previous workers the kinetics observed for the accumulation of mutations is found to be dependent upon the nutrient used to limit the growth of the population. Under conditions of glucose-limitation mutation accumulation is directly proportional to the rate of cell division, while under histidine-limitation it is proportional to chronological time. Various possible explanations for these observations are discussed.     

Zinc absorption in Crohn's disease

Zinc deficiency is a potential complication of Crohn's disease and we have searched for evidence of this and assessed the possibility that malabsorption of zinc might be a cause. Serum zinc concentrations in 33 patients suffering from Crohn's disease were significantly lower than in 58 normal control subjects (9 . 18 +/- 2 . 3 mumol compared with 13 . 6 +/- 1 . 73 mumol, P < 0 . 0005). Serum zinc correlated well with serum albumin concentrations and the low serum zinc may simply reflect the low serum albumin. Thus its value as an indicator of zinc deficiency is poor. We studied zinc absorption in seven patients with Crohn's disease and compared it with the results obtained previously in five normal subjects using a new technique involving a short-lived isotope of zinc (69mZn). Plasma appearance curves, constructed after an oral dose of isotope, and disappearance curves, after an intravenous dose, were used in a deconvolution computer programme to calculate zinc absorption. Compared with normal subjects, zinc absorption was considerably impaired in patients with Crohn's disease (range 9--45%, compared with 38--75%). This abnormality is a potential cause of zinc deficiency in patients with Crohn's disease.     

Influence of recall on reliability of perception of the autokinetic illusion

An autokinetic test was given to 76 females subjects who were then randomly assigned to 1 of 4 groups of 19 subjects each. Two groups were retested after 1 and 6 wk., respectively. The other two groups were asked to recall their initial experience after 1 and 6 wk., respectively. Intertrial correlations of the measures were generally higher for the recall conditions than for the retest conditions. The results were discussed in terms of the potential influence that recall may have on the test-retest reliability of autokinesis.     

The importance of the stomach in mediating histamine-induced hypocalcemia in the rat

The effect of histamine on serum calcium homeostasis was studied in the rat. After the intravenous administration of 0.5-1.0 mg histamine base to fasted Holtzman rats weighing 80-100 g, a significant lowering of serum calcium (Ca) level occurred 30 min after injection (decrease in Ca, 1.4-1.9 mg/100 ml), but normocalcemia returned at 60 min. Repeat intravenous injections of histamine 1.0 mg resulted in repeated lowering of the serum Ca level. Hypophosphatemia did not accompany the hypocalcemia. Thyroparathyroidectomy (TPTX) did not eliminate the calcium-lowering effect of histamine in acute TPTX animals but did so in more chronic TPTX animals in which the mean serum Ca was 7.6 mg/100 ml or less. Gastrectomy, however, completely eliminated the calcium-lowering effect of histamine given in doses of up to 2 mg/rat (20 mg/kg of body weight), despite the presence of an intact thyroid gland. These studies support the role of a gastric factor and not the thyroid secretion of calcitonin in mediating this response in the rat.     

Effect of cardiac dysrhythmia on cerebral perfusion

Extracranial carotid arterial obstructive disease has been the entity most commonly associated with transient cerebrovascular insufficiency. A nonobstructive, frequently overlooked cause of cerebral ischemia is cardiac dysrhythmia. We have explored this by observations of experimental animals and of man. Blood flow and pressure in the carotid arteries of dogs were shown to be decreased by mechnically induced premature ventricular contractions. The significance of the cardiogenic contribution to altered cerebrovascular perfusion was studied by ocular and brachial plethysmography in 210 patients suspected by history of having carotid arterial insufficiency. Of the 210 patients, 62 demonstrated abnormal ocular plethysmographic recordings, and of those, nine had dysrhythmias associated with significant deficits of ocular perfusion. Five patients whose recordings were technically suitable for publication are presented to demonstrate the bizarre ocular plethysmographic recordings seen during the dysrhythmic cycle.     

Elevated IgM levels, edema, and fatigue syndrome

Two patients with nonpitting edema associated with extreme fatigue were found to have hyperimmunoglobulinemia M and eosinophilia. Additional laboratory abnormalities included an elevated ESR and the presence of rheumatoid factor. One patient had the symptom complex continually, and it was controlled with minimal amounts of prednisone. The other patient had intermittent symptoms, with eosinophilia in the asymptomatic state and decreased eosinophil counts while symptomatic. His symptomatic episodes were diminished in duration by methylprednisolone. We believe these cases, which have been evaluated for eight and four years, respectively, constitute a new syndrome that has substantial morbidity, but that is apparently benign and that can be controlled with corticosteroids.     

Australian encephalitis in the Northern Territory: clinical and epidemiological features, 1987-1996

OBJECTIVES: The purpose of this study was to evaluate the contribution of the executive cognitive functions to self-reported and observed performance of activities of daily living and instrumental activities of daily living. DESIGN: These data were collected as part of a cross-sectional survey of community-dwelling older persons, using statistical sampling, in a two-county area of southern Colorado. SETTING: Participants were interviewed and administered measures of general cognition, depression, executive functioning, and performance of self-care and instrumental activities, either in their homes or at the study clinic. PARTICIPANTS: A total of 1158 community-dwelling persons between the ages of 60 and 99 participated. Of these, 657 were female, 501 were male, 637 were Hispanic, and 521 were non-Hispanic whites. MEASUREMENTS: Subjects were administered the Mini-Mental State Exam (MMSE), a measure of executive functioning (the Behavioral Dyscontrol Scale), the Center for Epidemiologic Studies Depression scale (CES-D), and the Structured Assessment of Independent Living Skills (SAILS, a measure of observed performance of daily tasks). They also were interviewed regarding their reported ADL and IADL status using measures from the Longitudinal Study on Aging. RESULTS: Both general mental status and executive functioning demonstrated statistically significant univariate associations with all seven functional status measures (both self-report and observed performance). In a series of ordinary least squares regression models, executive functioning was a predictor for self-reported ADLs and observed performance of complex IADL tasks such as managing money and medications. Mental status did not predict self-reported functioning but was a predictor of observed performance. Depression was a significant variable for self-report measures but not for observed performance. Executive functioning and general mental status demonstrated some degree of independence from one another. CONCLUSION: Executive functioning is an important determinant of functional status for both self-reported and observed ADLs and IADLs and should be assessed routinely when evaluating the mental status and functional abilities of older people. These results replicate and extend previous research on executive functioning among older persons by examining these factors in a large bi-ethnic community sample.     

Fibrillar polymer–polymer composites: morphology, properties and applications

Micro- or nano-fibrillar composites (MFCs or NFCs) are created by blending two homopolymers (virgin or recycled) with different melting temperatures such as polyethylene (PE) and poly(ethylene terephthalate) (PET), and processing the blend under certain thermo-mechanical conditions to create in situ fibrils of the polymer that has the higher-melting temperature. These resulting fibrillar composites have been reported to possess excellent mechanical properties and can have wide ranging applications with suitable processing under controlled conditions. However, the properties and applications very much depend on the morphology of created polymer fibrils and their thermal stability. The present paper develops an understanding of the mechanism of micro-/nano-fibril formation in PE/PET and polypropylene (PP)/PET blends by studying their morphology at various stages of extrusion and drawing. It is revealed that this subsequent mechanical processing stretches the polymer chains and creates fibrils of very high aspect ratios, thus resulting in superior mechanical performance of the composites compared to the raw blends. The study also identifies the primary mechanical properties of the main types of MFCs, as well as quantifying their enhanced resistance to oxygen permeability. Furthermore, the failure phenomena of these composites are studied via application of the modified Tsai–Hill criterion. In addition to their usage as input materials in different manufacturing processes, possible applications of these fibrillar composites in two different areas are also discussed, namely food packaging with controlled oxygen barrier properties and biomedical tissue scaffolding. Results indicate a significant scope for using these materials in both areas.     

Recent developments in pedestrian flow theory and research in Russia

Predtechenskii and Milinskii's seminal work [Predtechenskii VM, Milinskii AI. Planning for foot traffic flow in buildings. Revised and updated edition. Moscow: Stoiizdat; 1969] in relation to pedestrian flows is well known. However, analysis of the experimental results and observations obtained from this series of experimental studies revealed the inherent statistical non-homogeneity of pedestrian flow speeds [Kholshevnikov VV. The study of human flows and methodology of evacuation standardisation. Moscow: MIFS; 1999]. As such, the results of these individual experiments cannot be integrated to produce a valid general expression V=f(D) for each type of pedestrian flow path, where V is the flow velocity and D is the flow density. This paper presents further pedestrian flow research conducted in Russia post 1969.