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At least 19 recordsLinked to original sources

PubMed1992

Morphometric studies in inbred and hybrid house mice. VIII. Effects of litter size on brain size and body size.

Litter size, brain size, and body size were examined in inbred and hybrid house mice of three different ages in order to test whether litter size exhibits a positive genetic, but negative environmental association with both brain and body size. As estimated from among-line covariation, litter size showed a positive, but non-significant genetical association with brain and body size. It also showed a significant, negative environmental association with brain and body size, as hypothesized. Over all inbreds and hybrids, litter size explained 8% and 14%, respectively, of the within-strain (environmental) variation in brain and body size. It was concluded that the negative phenotypic association of litter size with brain size and especially body size is the reflection of a well-known negative maternal environmental effect whereby mice with large body sizes tend to produce larger litters of mice with smaller body sizes.

Animals↗

PubMed1982

Particle size reduction by a hammer mill I: Effect of output screen size, feed particle size, and mill speed.

A hammer mill is an impact mill commonly used in pharmaceutical manufacturing for reducing particle size for a variety of drugs. Commercial grade ammonium sulfate was milled as a model powder. This salt was sieved to obtain particle size fractions with average diameters of 1.3, 0.9, and 0.72 mm which were used as feed particles. The milled material was analyzed for particle size distribution (PSD) using standard sieves. At a moderate speed (approximately 2500 rpm), the feed size did not result in a significantly changed arithmetic mean diameter, dx of milled particles. A new particle size reduction constant, k, is proposed as a result of a linear relationship between dx and output screen size, dss. As dss decreases, the PSD range of milled particles narrows; as mill speed increases (approximately 5000 rpm), dx decreases. The decrease is of a greater magnitude for larger dss (2 mm) than for a smaller dss (1 mm). At low speeds (approximately 1000 rpm), the PSD is wider compared to medium and high speeds.

Ammonium Sulfate↗

PubMed1977

Correlation of tooth size and body size in living hominoid primates, with a note on relative brain size in Aegyptopithecus and Proconsul.

Second molar length and body weight are used to test the correlation between tooth size and body size in living Hominoidea. These variates are highly correlated (r= 0.942, p less than 0.001), indicating that tooth size can be used in dentally unspecialized fossil hominoids as one method of predicting the average body weight of species. Based on tooth size, the average body weight of Aegyptopithecus zeuxis is estimated to have been beteen 4.5 and 7.5 kg, which is corroborated by known cranial and postcranial elements. Using Radinsky's estimates of brain size, the encephalization quotient (EQ) for Aegyptopithecus was between 0.65 and 1.04. A similar analysis for Proconsul africanus yields a body weight between 16 and 34 kg, and an EQ between 1.19 and 1.96.

Animals↗

PubMed1994

Perceived size of familiar objects and the theory of off-sized perceptions.

In three experiments, I examined the claim (Gogel, 1969; Gogel & Newton, 1969) that familiar objects viewed under reduced stimulus conditions frequently appear to be off-sized (i.e., larger or smaller than normal). In Experiments 1 and 2, I presented images of different familiar objects, one at a time, at distances of 1 and 2 m from the observers. The images were normal-, large-, or small-sized versions of familiar objects, and the observers judged the perceived size of each object relative to its familiar normal size. In Experiment 3, I presented normal-, large-, and small-sized versions of the same familiar object at physical distances of 1 and 2 m. The pattern of size results was similar across the three experiments. In general, normal-sized objects appeared normal-to small-sized at the 1-m distance and small-sized at the 2-m distance; small-sized objects appeared small-sized at the 1-m distance and even smaller at the 2-m distance; and large-sized objects appeared normal- to large-sized at the 1-m distance and normal- to small-sized at the 2-m distance. The distance results of Experiment 3 indicated that familiar size was an effective determinant of reported distance. These results are consistent with Gogel's theory of off-sized perceptions and, more generally, with the claim that familiar size is not an important determinant of perceived size.

Adult↗

PubMed1987

Relationship between natural variations in motoneuron number and body size in Xenopus laevis: a test for size matching.

During normal development, tadpoles of Xenopus laevis demonstrate large variations in body size that are carried through metamorphosis. This variation in size exists at the stages when lumbar lateral motor column (L-LMC) motoneurons are produced and when neuronal cell death in this neuron population occurs. Body size, hindlimb size, motoneuron number, and motoneuron size (i.e., neuron nuclear cross-sectional area) were measured in animals from three developmental stages: one prior to significant amounts of cell death, one at the peak rate of cell death, and one after cell death. The hypothesis that neuron population size is matched to peripheral size was tested by using the natural size variation found at each of these stages. The ranges of values for the measurements at the three stages were large. Significant correlations between body size and motoneuron number, as well as between motoneuron number and muscle fiber number, were present after cell death. Since these correlations emerged as cell death reduced neuron numbers, size matching may have occurred and cell death may have adjusted the L-LMC motoneuron population's size to variation in body size. In addition to the correlations between body size and motoneuron number at the end of cell death, neuron numbers before and after cell death were significantly correlated among groups of siblings. The possibility that the number of neurons after cell death was also influenced by differences in the number of L-LMC progenitors is discussed.

Animals↗

PubMed1994

Evolutionarily stable growth rates in size-structured populations under size-related competition.

The competitive interactions between individuals in size-structured populations usually change as a function of the individuals' sizes. A general model of a density-dependent size-structured population is used to investigate the size-specific birth and death rates that result when growth rates can be adjusted adaptively. If there is no cost associated with faster growth, the evolutionarily stable growth rates result in an ideal free distribution of individuals among size classes, provided that competition within size classes is stronger than competition between size classes. When the population is stationary, this ideal free distribution is characterized by identical ratios of expected number of offspring per unit time to probability of death per unit time for all size classes with growth rates less than the physiologically maximum level. If more rapid growth reduces birth rate or increases death rate, the size-specific ratios of births to mortality increase with the organism's size. If the population is growing in a density independent manner, but there is a cost to growth, there should be an increase with size in the ratio of reproductive output to the quantity (population growth rate minus survival probability). Available evidence about size-specific birth and death rates in some size-structured populations is discussed.

Animals↗

PubMed1986

Large airway size, lung size, and maximal expiratory flow in healthy nonsmokers.

It has been postulated that airway size and lung size may be dissociated because of developmental differences between the tracheobronchial tree and the pulmonary parenchyma (dysanapsis). To test this hypothesis, we compared measurements of airway size (diameters, cross-sectional area, length and volume of the trachea, diameter and cross-sectional area of the mainstem bronchi) and lung size (total lung capacity, thoracic diameters, lung length), as determined from plain chest radiographs in 79 male and 86 female healthy nonsmokers. In both groups of subjects, the correlation between indexes of airway size and lung size was low. Airway size was not significantly different between men and women, when standardized for lung size. Tracheal diameter and length tended to increase with age. To assess the value of airway size measurements in the prediction of maximal expiratory flow, we compared tracheal and bronchial size with FVC, FEV 0.5, FEV1, and mean forced expiratory flow during the middle half of VC. The correlation between airway size and spirometric indexes was very low. Multiple regression analysis showed that the use of airway size variables in addition to the age and height variables did not substantially improve the prediction of maximal expiratory flow. Our results are consistent with the dysanapsis hypothesis, but they suggest that the introduction of radiologic estimates of large airway size in the prediction equations relating maximal expiratory flow to age and height is not justified, at least in the general population.

Female↗

PubMed1984

Mental comparison of size and magnitude: size congruity effects.

Paivio (1975) found that the latency to choose the larger of two named objects does not depend on congruity between the object sizes and the sizes of the object names. Because size congruity does affect latencies for pictorially presented objects, Paivio interpreted this result as support for the dual coding hypothesis. However, Experiment 1 demonstrated that Paivio's results were an artifact of his experimental design. Size congruity does affect latencies to choose the larger of two named objects when object pairs are not repeated. When the same object pairs are used repeatedly, as in Paivio's experiment, the effect disappears. In this case the response is probably remembered, so that the objects need not be compared. To determine the processing stages affected by size congruity, both the distance between stimulus sizes and the size congruity were manipulated in Experiment 2. Three groups of subjects chose either the greater Arabic digit, the greater named digit, or the larger named object. Size congruity interacted with distance only for Arabic digits. For both Arabic digits and named digits, the interference caused by size incongruity was greater than the facilitation caused by size congruity, whereas for object names, the facilitation was greater than the interference. A model of the interaction between physical size comparisons and conceptual size comparisons is proposed to account for these results.

Concept Formation↗

PubMed1986

Correlation of cell body size, axon size, and signal conduction velocity for individually labelled dorsal root ganglion cells in the cat.

Measurements of cell body and peripheral and central axon sizes were made for primary sensory neurons outlined by the intracellular injection of HRP. Conduction velocities were also measured on the outlined processes. The sensory neurons were then subdivided into A and C cells on the basis of the conduction velocity of the impulses carried by the processes of these cells. Central processes of both A and C cells are smaller than the peripheral processes, but the size differential is greater for the C cells. For A cells there is a linear relation between the size of the peripheral axon and the conduction velocity of the impulses carried by these axons, but the confidence limits are wide. For C cells there is a linear relation between the size of the central process and conduction velocity of the impulses carried by the processes, but for the peripheral processes two aberrant processes resulted in no correlation between process size and conduction velocity. For A cells, the size of the central and peripheral processes and the conduction velocity of the impulses carried by the peripheral processes are linearly correlated with cell body size. By contrast no such correlations can be demonstrated for C cells. This presumably implies an important difference in that the size of the cell body is correlated with axon size and impulse conduction velocity for A cells but not for C cells. A widely accepted generalization is that large sensory cells give rise to myelinated axons and small sensory cells to unmyelinated axons. In this study, myelinated and unmyelinated are defined on the basis of impulse conduction velocity. For those cells that are clearly large (greater than 50 microns in diameter), the conduction velocity of the impulses carried by their processes is always greater than 2.5 m/s, and for those cells that are clearly small (less than 35 microns in diameter), the conduction velocity is always less than 2.5 m/s. Thus for these cells the above generalization holds. For the intermediate-sized cells (35-50 microns), however, the size of the cell body bears no predictable relation to the conduction velocity of the impulses carried by those processes, and thus to whether the axons are myelinated or unmyelinated. Thus the above generalization does not hold for this intermediate group of cells, and since there are many cells in this size range, we feel that the generalization that large cells give rise to myelinated axons and small cells to unmyelinated axons is an oversimplification.

Action Potentials↗

PubMed1987

Additivity and interaction between size ratio and response category in the comparison of size-discrepant shapes.

In Experiment 1, subjects made same-different judgments to pairs of shapes that could differ (irrelevantly) in size and in which different pairs combined distinct shapes. Size discrepancy had an effect both on same and different responses. However, the effect on different responses was not monotonic across size discrepancies. It is argued that this nonmonotonicity was produced by a form of bias acting to slow different responses for same-sized pairs. Consistent with the proposed bias account, the nonmonotonic size-discrepancy effect on different trials was eliminated in Experiment 2, in which trials were blocked by size ratio. In Experiment 3, subjects performed a task similar to that in Experiments 1 and 2. However, additional visual information was added inside the bounding contour of the shapes, and this information was either the same or different across shapes. The match between within-contour information across shapes (whether same or different) was varied orthogonally with whether the bounding contours of the shapes were the same or different. In this experiment subjects decided whether the bounding contours of the shapes were the same or different, while ignoring the added information within the contours. When the added information matched across the two shapes, same responses were facilitated relative to when the added information mismatched. The converse occurred for different responses. This effect was more pronounced when the shapes were shown at the same size than when the shapes were at different sizes. In general, the results suggest that (a) size discrepancy affects some perceptual operations that are preliminary to shape matching, and (b) bias mechanisms can play an important role in shape-matching experiments in which the shapes can be shown in different sizes. The interaction of two processes--size scaling and bias--can account for these and hitherto contradictory results in the literature.

Form Perception↗

PubMed1993

Preattentive processing of object size: implications for theories of size perception.

Information about the visual angle size of objects is important for maintaining object constancy with variations in viewing distance. Although human observers are quite accurate at judging spatial separations (or cross-sectional size), they are prone to error when there are other spans nearby, as in classical illusions such as the Müller-Lyer illusion. It is possible to reconcile these aspects of size perception by assuming that the size domain is sampled sparsely. It was shown by means of a visual search procedure that the size of objects is processed preattentively and in parallel across the visual field. It was demonstrated that an object's size, rather than its boundary curvature or spatial-frequency content, provides the basis for parallel visual search. It was also shown that texture borders could be substituted for luminance borders, indicating that object boundaries at the relevant spatial scale provide the input to size perception. Parallel processing imposes a severe computational constraint which provides support for the assumption of sparse sampling. An economical model based on several broadly tuned layers of size detectors is proposed to account for the parallel extraction of size, the Weberian behaviour of size discrimination, and the occurrence of strong interference effects in the size domain.

Attention↗

PubMed1992

The role of instructions and familiar size in absolute judgments of size and distance.

The effects of familiar size and instructions (apparent, objective) on direct reports of size and distance were evaluated. Subjects estimated the size and distance of two different-sized playing cards or two unfamiliar stimuli under either apparent or objective instructions. The stimuli were presented successively at a distance of 5.48 m under reduced-cue conditions. The form of the instructions selectively influenced the effect of familiar size on absolute judgments of size and distance, with apparent instructions minimizing, and objective instructions promoting, familiar-size effects. The ratio of the distance judgments of the first to the second presented stimuli approximated the relative retinal sizes of the two objects under both apparent and objective instructions, while the ratio of size judgments tended to be either influenced by or independent of the object's relative retinal sizes under apparent and objective instructions, respectively. These results are consistent with Gogel's theory of off-size perception and, in particular, with the claim that, in comparison with apparent instructions, objective instructions are more likely to direct observers to base their judgments on cognitive, as opposed to perceptual, sources of spatial information.

Adult↗

PubMed1982

[The effects of familiar-size cue on children's judgments of size and distance].

The present study is concerned with the effects of familiar-size cue on the judgments of size and distance for the children of an elementary school. Thirty-two 1 st-, 3rd-, and 6 th-grade children served as subjects. The experiment consisted of repeating alternations of the two steps: A judgmental step in which the subject judged the size and distance of transparencies of familiar objects, and an informational step in which the subject was acquainted visually or haptically with the real sizes of a toy car and a toy dog from which the transparencies were made. The results revealed that: (1) The younger children tended to make judgments resulted from the normal sizes of the familiar objects that they encounter in their daily life, while the older children based their judgments on the size information given by looking on or touching the real toys. (2) Visual size information was superior to haptic size information both in size and distance judgments. (3) Familiar-size cue may be effective in relative rather than absolute size and distance judgments.

Child↗

PubMed1983

Size maturation process of nascent DNA intermediates into chromosomal-sized DNA in Tetrahymena pyriformis macronuclear DNA replication.

An analysis was made of the size maturation process of nascent DNA intermediates in macronuclear DNA replication of Tetrahymena pyriformis. The first discrete size class of nascent intermediates larger than Okazaki fragments were replicon-sized DNA (about 2 X 10(7) D single-stranded (ss) DNA) and accumulated in cells treated with cycloheximide. On removal of cycloheximide, the replicon-sized intermediates were converted to middle-sized intermediates (about 10 X 10(7) D ssDNA) and then merged into chromosomal-sized DNA. As indicated by either aphidicolin inhibition or the technique of the photolysis of bromodeoxyuridine (BrdU)-substituted DNA with long-wave ultraviolet light, four to eight replicon-sized intermediates were joined together to form a middle-sized intermediate after rapid sealing by DNA synthesis of the late-replicating regions located between adjacent replicon-sized intermediates. The late-replicating regions may represent the short gaps or terminal regions where DNA synthesis was retarded by cycloheximide, since the size of late-replicating regions was suggested to be shorter than the replicon size by DNA fiber autoradiography. Therefore, it is probable that four to eight completed replicons are joined as a group such as a replicon cluster, as has been reported in DNA replication of other eukaryotic cells.

Animals↗

PubMed1994

GnRH cell size and number in a teleost fish with two male reproductive morphs: sexual maturation, final sexual status and body size allometry.

Gonadotropin releasing hormone-like immunoreactive (GnRH-ir) cells in both the ganglion of the terminal nerve (TN) and the preoptic area (POA) have been implicated in the development and maintenance of reproductive behavior and physiology in teleost fishes. One marine species, the plainfin midshipman, Porichthys notatus, exhibits two sexually mature male morphs (types I and II) which differ with respect to size at sexual maturation, gonad/body weight index, reproductive tactic and vocal motor traits. Type II males become reproductively active at a smaller body size than either females or type I males. Immunocytochemical techniques and quantitative analyses were used here to determine the size and number of GnRH-ir cells in the TN and POA amongst field collected juveniles, sexually mature females, and type I and II males. Mean GnRH-ir cell size and number in the TN did not vary across the entire range of specimens. However, mean GnRH-ir cell size and number in the POA were 50-100% greater in sexually mature adults compared to juveniles. Analyses of covariance indicated that increases in cell number, but not cell size, could be explained solely on the basis of changes in body size. However, regression analyses showed that body size had a significant influence on increasing cell number only in the juvenile-type I male transition and the juvenile-female transition, not in the juvenile-type II male transition. The latter suggests that type II males, unlike the other adult morphs, have 'escaped' from a body size constraint imposed on increasing GnRH-ir cell number in the POA. There were also significant differences among the adult morphs in the size of GnRH-ir POA cells that could not be explained on the basis of differences in body size but, rather, appear to reflect differences in the temporal onset of sexual maturation. Together, the data suggest that the timing of changes in POA phenotype may provide a proximate mechanism permitting the development of alternative male reproductive morphs.

Animals↗

PubMed1987

Brain sizes, surfaces, and neuronal sizes of the cortex cerebri: a stereological investigation of man and his variability and a comparison with some mammals (primates, whales, marsupials, insectivores, and one elephant).

This study deals with the stereological estimation of macroscopic sizes of brain and cortex, i.e., volume, surface, and folding, and of microscopic neuronal sizes, i.e., density, mean size, size distribution, and number of neurons. The results show that the degree of variability in man amounts to about 15%. A decrease in volume of the different gray structures can be observed in man after the age of 65 years. The surface, folding index, and length of convolution do not alter with aging. The comparison with mammals of various sizes allows the conclusion that there is a high correlation to brain size for nearly all macroscopic values. Man and elephant, however, have a cortical surface which is, in comparison with whales, relatively small. In contrast, whales have very small cortices compared with man. At the cytoarchitectonic level, the neuronal density has a correlation to brain size. Contrary to other mammals, the primates and man have a high fraction of small granular neurons, especially in layer 4. The assumption that the number of cortical neurons beneath a given surface area of cortex is the same in all mammals cannot be verified, especially in those with large brains. The allometric connection between brain size and parameters is not valid for all measurements (e.g., thickness of cortex, mean size of neurons, perikaryal size distribution, and glial density). Yet some other measurements are well correlated.

Animals↗

PubMed1983

Relationships between mandibular joint size and craniofacial size in human groups.

Substantial evidence attests to the capability of the joint to undergo morphological alteration in response to biomechanical forces transmitted to it during function. Measurements expressing the size of mandibular condyles and fossae were obtained from skulls representative of a broad spectrum of subsistence practices and tooth use. Craniofacial dimensions were measured for some groups. Considerable differences in joint size were noted between groups roughly consistent with known or presumed intensity of masticatory stress. Size was largest in the hunter-gatherers, intermediate in aboriginal horticulturalists and smallest in 20th century American caucasoids and 17th century British. In each group, male joint size was absolutely larger than females. With the exception of condylar breadth, male joint dimensions were not relatively larger than female when corrected for differences in craniofacial size. In contrast, same-sex comparisons of Eskimo and American caucasoid means adjusted for differences in craniofacial size showed joint size in Eskimos to be significantly larger, both absolutely and relatively. Eskimo females had relatively larger joints than American caucasoid males. Thus, intergroup differences in joint size persist even when differences in craniofacial size are taken into account. Although the influence of genetic factors cannot be excluded, differences in the nature or intensity of tooth use during growth may account, at least in part, for the observed differences in joint size.

Adult↗

PubMed1987

Morphological constraint on egg size: a challenge to optimal egg size theory?

Some freshwater turtles appear unable to produce eggs large enough to achieve the balance between size and number of eggs predicted by optimal egg size theory. We present evidence that pelvic girdle structure constrains egg size and thus offspring size in females of smaller-bodied species (Chrysemys picta and Deirochelys reticularia). The constraint is demonstrated by the correspondence of slopes of the increase of the pelvic aperture and egg width with increasing body size. This constraint appears to be relaxed in a larger-bodied species (Pseudemys scripta), in which the increase in pelvic aperture relative to body size is greater than the increase in egg width. This type of structural constraint on a reproductive trait should not occur unless there is strong selection on pelvic architecture for other functions, such as locomotion, support, and limb retraction, that prevent expansion of the pelvic aperture. Although other explanations may exist for other groups of organisms that appear to vary egg size, the large variation in egg size associated with body size in some species of turtles can be reconciled with optimal egg size theory only if a pelvic constraint model is accepted.

Animals↗