Nipping the Cambrian "explosion" in the bud?

In recent years, two schools of thought have emerged with regard to the Cambrian "explosion". One argues that it was very quick, with phyla tumbling into existence in a virtual geological instant. The other view has a more relaxed temporal perspective. It looks to slow aeons of cryptic metazoan history, which led to a final breakthrough in the Cambrian, not in evolution but of fossilization potential. Yet both views have serious difficulties. Now, in a recent issue of Biological Reviews, Graham Budd and S?ren Jensen(1) argue for a third way. In an intriguing blend of functional morphology, the fossil record and cladistic thinking, they suggest that the assembly of metazoan bodyplans took place in a surprisingly straightforward manner.     

"Resonances" in the dielectric absorption of DNA?

An attempt was made to confirm previous reports of resonant-like dielectric absorption of plasmid DNA in aqueous solutions at 1-10 GHz. The dielectric properties of the sample were measured using an automatic network analyzer with two different techniques. One technique used an open-ended coaxial probe immersed in the sample; the other employed a coaxial transmission line. No resonances were observed that could be attributed to the sample; however, resonance-type artifacts were prominent in the probe measurements. The coaxial line technique appears to be less susceptible to such artifacts. We note two important sources of error in the calibration of the automatic network analyzer using the probe technique.     

Is there anything "autonomous" in the nervous system?

The terms "autonomous" or "vegetative" are currently used to identify one part of the nervous system composed of sympathetic, parasympathetic, and gastrointestinal divisions. However, the concepts that are under the literal meaning of these words can lead to misconceptions about the actual nervous organization. Some clear-cut examples indicate that no element shows "autonomy" in an integrated body. Nor are they solely "passive" or generated "without mental elaboration." In addition, to be "not consciously controlled" is not a unique attribute of these components. Another term that could be proposed is "homeostatic nervous system" for providing conditions to the execution of behaviors and maintenance of the internal milieu within normal ranges. But, not all homeostatic conditions are under the direct influence of these groups of neurons, and some situations clearly impose different ranges for some variables that are adaptative (or hazardous) in the tentative of successfully coping with challenging situations. Finally, the name "nervous system for visceral control" emerges as another possibility. Unfortunately, it is not only "viscera" that represent end targets for this specific innervation. Therefore, it is commented that no quite adequate term for the sympathetic, parasympathetic, and gastrointestinal divisions has already been coined. The basic condition for a new term is that it should clearly imply the whole integrated and collaborative functions that the components have in an indivisible organism, including the neuroendocrine, immunological, and respiratory systems. Until that, we can call these parts simply by their own names and avoid terms that are more "convenient" than appropriate.     

Is "circling" behavior in humans related to postural asymmetry?

In attempting to walk rectilinearly in the absence of visual landmarks, persons will gradually turn in a circle to eventually become lost. The aim of the present study was to provide insights into the possible underlying mechanisms of this behavior. For each subject (N?=?15) six trajectories were monitored during blindfolded walking in a large enclosed area to suppress external cues, and ground irregularities that may elicit unexpected changes in direction. There was a substantial variability from trial to trial for a given subject and between subjects who could either veer very early or relatively late. Of the total number of trials, 50% trajectories terminated on the left side, 39% on the right side and 11% were defined as "straight". For each subject, we established a "turning score" that reflected his/her preferential side of veering. The turning score was found to be unrelated to any evident biomechanical asymmetry or functional dominance (eye, hand…). Posturographic analysis, used to assess if there was a relationship between functional postural asymmetry and veering revealed that the mean position of the center of foot pressure during balance tests was correlated with the turning score. Finally, we established that the mean position of the center of pressure was correlated with perceived verticality assessed by a subjective verticality test. Together, our results suggest that veering is related to a "sense of straight ahead" that could be shaped by vestibular inputs.     

Is serum protein electrophoresis useful in separating the "high risk group" in patients with colonic polyps?

BACKGROUND: Adenomas have the highest potential or clinical value from among colonic polyps of developing into adenocarcinoma. The aims of this paper are: to establish criteria to identify the high risk group of patients in a group of patients with colonic polyps, to work out a simple scheme for follow-up care after endoscopic polypectomy, and to establish indications for surgery. The usefulness of determination of electrophoresis of serum proteins has been specially analysed to detect early development of malignant growths in patients with colonic polyps regarding alfa-1/alfa-2 and alfa/beta. 67 cases - 21 women, 46 men were tested. Follow-up endoscopy with the electrophoresis was performed after 6 weeks, 6 and 12 months after polypectomy. 97 polyps were resected with endoscopy in 67 patients. 38 patients (39.17%), those constituting the high risk group, were selected. Included were all polyps with grade II and III of cellular differentiation. CONCLUSIONS: 1) alfa-1/alfa-2 and alfa/beta is a helpful test in identifying the high risk group among patients with colonic polyps and it can be used as a screening test, 2) the determination of beta-2-macroglobuline is not useful in the diagnosis of this group of patients, 3) the electrophoresis of proteins should be the first test to perform on patients with colonic polyps. The relation of electrophoresis to endoscopic polypectomy aids evaluations of patients specially predisposed to malignant.     

Is there "Metabolic" DNA in the Mouse Seminal Vesicle?

This study was designed to answer the question: Is H³-thymidine uptake by nuclei of the mouse seminal vesicle evidence for DNA synthesis and mitosis, or does it signify some "metabolic" function of DNA unrelated to chromosome duplication? Mice were given an intraperitoneal injection of H³-thymidine. Six hours later Feulgen squashes of the seminal vesicle epithelium were made and covered with autoradiographic stripping film. The silver grains above labeled nuclei were counted, and the Feulgen dye contents of these same nuclei were determined photometrically after removal of the grains from the emulsion. Unlabeled nuclei were also measured. The dye contents of non-radioactive nuclei form a unimodal distribution, indicating that polyploidy is absent from this tissue. The radioactive nuclei fall into two groups. In the first, the average dye content is the same as that of the cold nuclei (2C). In the second, the values range from 2C to 4C. In the 2C to 4C group the grain count is proportional to the dye content, showing that incorporation is correlated with synthesis. The radioactive 2C nuclei arose by mitosis during the course of the experiment. This is shown by the following facts: (1) They frequently occur in pairs. (2) They average smaller than unlabeled 2C nuclei. (3) Their average grain count is approximately half that of the 4C nuclei. (4) Labeled division figures are found. (5) A mitotic rate estimated from the number of labeled 2C nuclei accords reasonably well with one based on the number of observed mitoses. Since the incorporation of thymidine accompanies DNA synthesis and precedes mitosis, there is no reason to postulate a special "metabolic" DNA in this tissue.     

Has the "Equal Environments" assumption been tested in twin studies?

A recurring criticism of the twin method for quantifying genetic and environmental components of human differences is the necessity of the so-called "equal environments assumption" (EEA) (i.e., that monozygotic and dizygotic twins experience equally correlated environments). It has been proposed to test the EEA by stratifying twin correlations by indices of the amount of shared environment. However, relevant environments may also be influenced by genetic differences. We present a model for the role of genetic factors in niche selection by twins that may account for variation in indices of the shared twin environment (e.g., contact between members of twin pairs). Simulations reveal that stratification of twin correlations by amount of contact can yield spurious evidence of large shared environmental effects in some strata and even give false indications of genotype x environment interaction. The stratification approach to testing the equal environments assumption may be misleading and the results of such tests may actually be consistent with a simpler theory of the role of genetic factors in niche selection.     

Good Enough for Government Work? A Study in "Grey Archeology"

Archaeological Salvage Excavations at Patoka Lake, Indiana: Prehistoric Occupations of the Upper Patoka River Valley . Cheryl Ann Munson , ed. Glen A. Black Laboratory of Archaeology Research Reports, No. 6. Bloomington: Indiana University, 1980. xxvii + 829 pp. $15.00 (paper).
Colonization and Conquest: The 1980 Archaeological Excavations at Fort Toulouse and Fort Jackson, Alabama . Gregory A. Waselkov, Brian M. Wood , and Joseph M. Herbert . Auburn University Archaeological Monograph No. 4. Montgomery, AL: Auburn University, 1982. xxix + 399 pp. $11.00 (paper).
The Kellogg Village Site Investigations: Clay County, Mississippi . James R. Atkinson, John C. Phillips , and Richard Walling . A Report of work undertaken in cooperation with the U.S. Army Corps of Engineers, Mobile District, in fulfillment of Modification Three to Contract DACW 01–77–0015. Starkville: Mississippi State University, 1980. x + 345 pp. n.p. (paper).
Parkin: The 1978–1979 Archaeological Investigations of a Cross County, Arkansas Site . Phyllis A. Morse . Arkansas Archaeological Survey Research Series, No. 13. Fay-etteville: University of Arkansas, 1981. 110 pp. $6.00 (paper).
The Shallow Lake Site (3Un9/52) and Its Place in Regional Prehistory . Martha A. Rolingson and Frank F. Schambach . Arkansas Archaeological Survey Research Series, No. 12. Fayetteville: University of Arkansas, 1981. 240 pp. $10.00 (paper).
Yellow Creek Archaeological Project: Volume 1 . Robert M. Thome, Bettye J. Broyles , and Jay K. Johnson . Archaeological Papers of the Center for Archaeological Research, No. 1. Chattanooga: Tennessee Valley Authority, 1981. 354 pp. $13.00 (paper).
Yellow Creek Archaeological Project: Volume 2 . Jay K. Johnson . Archaeological Papers of the Center for Archaeological Research, No. 2. Chattanooga: Tennessee Valley Authority, 1981. 347 pp. $13.00 (paper).     

Is "scopolamine-induced amnesia" in rats the result of state-dependent learning?

The effects of a single and repetitive administration of m-cholinoblocker scopolamine (Sc) to male rats on retention of step-through passive avoidance (PA) or active avoidance (AA) in a shuttle-box were compared. In case of PA Sc (1 mg/kg) was injected i.p. only 30 min before training, only 30 min before testing, or both before training and before testing. In case of AA Sc (0.5 mg/kg/day) was injected i.p. only 15 min before each training session or both before training and before testing (44 days after achievement of learning criterion). The PA and AA retention were impaired only in the experiments, where the drug was administered before training, but did not differ from control, when Sc was injected twice. The Sc-induced amnesia (like many other cases of memory deficits) is suggested to be a manifestation of state-dependent learning. Similarity between the brain state during memory consolidation and during the retention test is necessary for recollection.     

How normal is a "normal" flora in animal or man?

When investigating different disturbances of the normal intestinal flora causing disorders and/or diseases in man and animal, these studies include comparisons of results with control materials, i.e., materials from conventional laboratory animals or healthy human beings. However, how "normal" is the control group’s flora? In this paper two different examples will be discussed; one investigation with laboratory animals and one from a human study.