The influence of the bolus injection rate of propofol on its cardiovascular effects and peak blood concentrations in sheep

The influence of the bolus injection rate of propofol on its cardiovascular effects has not been extensively studied. We therefore examined the influence of the injection rate of i.v. bolus doses of propofol on its acute cardiovascular effects and peak blood concentrations in seven chronically instrumented sheep. Each received i.v. propofol (200 mg) over 2 min (slow injection) and 0.5 min (rapid injection) on separate occasions in random order. The rapid injection was associated with more profound decreases in mean arterial blood pressure than slow injection (35.7% vs 23.7% maximal reductions from baseline, respectively; P = 0.02). There were no significant differences between the injection rates for peak reductions in myocardial contractility, increases in heart rate, or degree of respiratory depression. Concurrently, the rapid injections were associated with significantly higher arterial (26.9 vs 11.9 mg/L) propofol concentrations in a manner consistent with indicator dilution principles. There were no differences in the peak coronary sinus concentrations between the injection rates. We conclude that the rapid injection of propofol in the context of the induction of anesthesia produced significantly higher peak arterial propofol concentrations and suggest that it is these higher concentrations that produced relatively greater reductions in arterial blood pressure from rapid injections. Implications: Propofol is injected into a vein to initiate anesthesia. It can cause a rapid decrease in blood pressure, which may be dangerous to the patient. We examined the effect of rapid and slow injection rates of propofol in sheep and found that rapid injection caused a greater decrease in blood pressure. This was because rapid injection caused higher concentrations of propofol in the blood immediately after the injection. We believe that if the same processes occur in humans, there may be little advantage in injecting propofol rapidly.     

Solitary necrotic nodules of the liver

An experience is reported with solitary necrotic nodules of the liver, rare benign lesions described for the first time in 1983. Two patients were referred to our department because of the presence of hepatic lesions that radiology showed to be suspected secondary liver tumors. At laparotomy, both patients underwent liver resections because the lesions appeared to be malignant. Subsequent histological examination of the surgical specimens revealed that both were solitary necrotic nodules of the liver. These were the only solitary necrotic nodules found in a total of 840 operations carried out in our department since October 1981. Although they are completely benign, solitary necrotic nodules have a similar ultrasound pattern and radiological features to metastases and have been described in the literature during the follow-up of patients with other tumors. Uncertainty remains as to the etiology of these lesions, which still represent an occasional finding in liver surgery.     

Temporal expression of pro-inflammatory cytokines and inducible nitric oxide synthase in experimental acute Chagasic cardiomyopathy

Pelizaeus-Merzbacher disease (PMD) is a dysmyelinating disease resulting from mutations, deletions, or duplications of the proteolipid protein (PLP) gene. Distinguishing features of PMD include pleiotropy and a range of disease severities among patients. Previously, we demonstrated that, when expressed in transfected fibroblasts, many naturally occurring mutant PLP alleles encode proteins that accumulate in the endoplasmic reticulum and are not transported to the cell surface. In the present communication, we show that oligodendrocytes in an animal model of PMD, the msd mouse, accumulate Plp gene products in the perinuclear region and are unable to transport them to the cell surface. Another important aspect of disease in msd mice is oligodendrocyte cell death, which is increased by two- to threefold. We demonstrate in msd mice that this death occurs by apoptosis and show that at the time oligodendrocytes die, they have differentiated, extended processes that frequently contact axons and are expressing myelin structural proteins. Finally, we define a hypothesis that accounts for pathogenesis in most PMD patients and animal models of this disease and, moreover, can be used to develop potential therapeutic strategies for ameliorating the disease phenotype.     

Rice (Oryza sativa) centromeric regions consist of complex DNA

Rice bacterial artificial chromosome clones containing centromeric DNA were isolated by using a DNA sequence (pSau3A9) that is present in the centromeres of Gramineae species. Seven distinct repetitive DNA elements were isolated from a 75-kilobase rice bacterial artificial chromosome clone. All seven DNA elements are present in every rice centromere as demonstrated by fluorescence in situ hybridization. Six of the elements are middle repetitive, and their copy numbers range from approximately 50 to approximately 300 in the rice genome. Five of these six middle repetitive DNA elements are present in all of the Gramineae species, and the other element is detected only in species within the Bambusoideae subfamily of Gramineae. All six middle repetitive DNA elements are dispersed in the centromeric regions. The seventh element, the RCS2 family, is a tandem repeat of a 168-bp sequence that is represented approximately 6,000 times in the rice genome and is detected only in Oryza species. Fiber-fluorescence in situ hybridization analysis revealed that the RCS2 family is organized into long uninterrupted arrays and resembles previously reported tandem repeats located in the centromeres of human and Arabidopsis thaliana chromosomes. We characterized a large DNA fragment derived from a plant centromere and demonstrated that rice centromeres consist of complex DNA, including both highly and middle repetitive DNA sequences.     

Synaptic vesicles have two distinct recycling pathways

In this paper, evidence is presented that two distinct synaptic vesicle recycling pathways exist within a single terminal. One pathway emanates from the active zone, has a fast time course, involves no intermediate structures, and is blocked by exposure to high Mg2+/low Ca2+ saline, while the second pathway emanates at sites away from the active zone, has a slower time course, involves an endosomal intermediate, and is not sensitive to high Mg2+/low Ca2+. To visualize these two recycling pathways, the temperature-sensitive Drosophila mutant, shibire, in which vesicle recycling is normal at 19 degrees C but is blocked at 29 degrees C, was used. With exposure to 29 degrees C, complete vesicle depletion occurs as exocytosis proceeds while endocytosis is blocked. When the temperature is lowered to 26 degrees C, vesicle recycling membrane begins to accumulate as invaginations of the plasmalemma, but pinch-off is blocked. Under these experimental conditions, it was possible to distinguish the two separate pathways by electron microscopic analysis. These two pathways were further characterized by observing the normal recycling process at the permissive temperature, 19 degrees C. It is suggested that the function of these two recycling pathways might be to produce two distinct vesicle populations: the active zone and nonactive zone populations. The possibility that these two populations have different release characteristics and functions is discussed.     

Features that distinguish the smooth-pursuit eye-tracking performance of schizophrenic, affective-disorder, and normal individuals.

Examined the eye-tracking records of 25 schizophrenic (mean age 37.6 yrs), 25 unipolar (mean age 37.9 yrs), 24 bipolar (mean age 36 yrs), and 46 medical control (mean age 35 yrs) patients. All the psychiatric patients were in symptom remission. All three psychiatric groups produced more oscillations than controls, and spiky tracking was correlated with poor performance as indexed by the production of large saccades. Schizophrenics did, however, produce smaller saccades and tracked with more phase lag than did each of the other groups. Results suggest that the smooth-pursuit system of schizophrenics is functionally different from that of normal people. Use of the phase lag as a potential marker of schizophrenia is discussed. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Social and developmental experience and interspecific aggression in rats.

Measured the aggressive behavior of a total of 176 male Long-Evans rats in 3 experiments. Ss raised in social isolation from weaning showed significantly more interspecific aggressive behavior than littermates raised with peers, as measured by the proportion initiating a killing attack against frogs in a 20-min arena test. Ss in 6 cross-species rearing conditions with frogs and cockroaches failed to form social attachments. When tested individually, these Ss killed the alien species as often as or more often than did controls. A significant number of adult Ss selected for nonagressive responses became killers after witnessing aggression in other Ss. (33 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Corneal endothelial cell measurements in megalocornea

A pedigree of megalocornea manifested many of the characteristic features as well as some less common features of the disorder. Endothelial specular microscopy of affected patients disclosed normal endothelial cell densities and morphologic characteristics and increased total endothelial cell populations, suggesting a process of total corneal hyperplasia. In contrast, unpublished data indicate diminished densities in congenital glaucoma, a finding more consistent with corneal distention. We conclude that specular microscopy may be of value in differentiating the two disorders, although larger series are necessary for confirmation.     

The damped transient behaviour of finite beams and plates

The direct Finite Element Analysis which was successfully employed in the solution of dynamic flexural traveling wave problems is extended herein to provide the transient behaviour of finite beams and plates in which shear deformation and rotatory inertia are considered. The particle and angular velocities are exponentially damped so that the static solutions for these problems are obtained with the same analysis which provided the dynamic and transient cases. Three special cases are chosen as examples. In the first, a sinusoidally varying shear force is applied at the tip of a cantilever beam. The resonant characteristics of this beam for both the undamped and damped cases are studied. In the second, a step shear loading is applied to a cantilever beam and its damped dynamic history is studied. Finally, a circular plate whose outer edge is simply supported is impacted at its inner edge by a step moment and its damped transient behaviour is determined. The idea of the methods is potentially applicable to dynamic problems in general.