Size and location of the human temporomandibular joint

The literature abounds with conflicting data on various morphometric aspects of the temporomandibular joint (TMJ). The purpose of this study was to observe the effects of sex, ethnic group, and edentulism on TMJ osseous morphology and to define possible factors which might influence variation in this structure. TMJs and related craniofacial structures were measured directly on 229 dry skulls and matching mandibles. Analysis of variance, principal component analysis, and cluster analysis were performed. Our results indicate that 1) the anteroposterior-related TMJ dimensions are independent of sex, ethnic group, and edentulism; 2) the transverse TMJ dimension is related to cranial breadth measures; and 3) the projected distance, along a midsagittal plane, between the TMJ and foramen magnum is independent of sex, ethnicity, and edentulism. It is our assertion that the TMJ must not be considered as a single morphological structure but rather viewed as a functional unit with component parts which are subordinate to completely different sets of influences. © 1996 Wiley-Liss, Inc.     

Size variation and orientation of the human Y chromosome

Summary The material consists of 84 metaphase plates from 17 individuals with clearly distinguishable Y chromosomes. The plates were obtained from leucocyte cultures. In making the preparations, exactly the same procedure was employed in all cases, including among other things, air-drying and light flaming.It was found that the size of the Y chromosome is subject to interindividual variation. The size of the Y chromosome has been expressed in relation to the mean length of the other small acrocentric chromosomes. The chromosomes have been tentatively classified into the following main groups:1. Y/G = 1.8; 2. Y/G =1.5; 3. Y/G is somewhat larger than G or 1.1, and 4. Y/G equals the mean of the small acrocentric chromosomes, or Y/G = 1. In the long Y chromosome two secondary constrictions have been observed.The location of the Y chromosome has been determined as peripheral or non-peripheral. The proband material has been divided into three main groups. The first comprises the individuals with a large Y chromosome (Y/G = 1.8). The second group includes individuals showing Down's syndrome and having 47 chromosomes, and the third comprises individuals with 46 chromosomes and possessing a Y/G sized 1 to 1.5. Preferential peripheral location of the Y chromosome has not been statistically verified in any one of these groups.     

Developmental change in the position of the fetal human larynx

The position of the mammalian larynx has been shown to be an important determinant in breathing, swallowing, and vocalizing patterns. While the growth of the adult human larynx has been studied extensively, detailed examination of fetal development has not been undertaken. Thus, crucial developmental change in the fetal period and the effects of this change on normal maturation are still unclear. This study has examined the development of the larynx and its topography during the fetal period. Thirty specimens were preserved in 10% buffered formaldehyde solution for a period of 6 weeks, after which mid-sagittal sections were performed. Fetal ages were calculated from femur diaphyseal lengths and ranged from 15 to 29 weeks. Direct measurements were taken to determine the growth and position of the larynx and trachea relative to the vertebral column and soft palate. Results show that the upper and lower levels of the larynx correspond to the basiocciput and the lower border of the third to upper border of the fourth cervical vertebrae, respectively. The epiglottic cartilage was present at 15 weeks. By 21 weeks, the epiglottis was well developed and in close palatal apposition. At 23 to 25 weeks, the epiglottis and soft palate were found to be in full contact. The acquisition of this contact may be related to fetal respiratory viability.     

Size variation in kinetochores of human chromosomes

Summary Aneuploidy, the loss or gain of chromosomes from cells, is likely in many cases to involve the kinetochore, the site of attachment of spindle microtubules. We analyzed human fibroblast cells with antikinetochore-antibody indirect immunofluorescence, and noted an apparent heterogeneity in the sizes of kinetochores among different chromosomes. The Y chromosome in particular always showed minute kinetochores, an observation which was quantified and substantiated using computer-assisted image analysis. This finding, combined with literature reports about in vivo and in vitro involvement of the Y chromosome in aneuploidy, was used to frame a novel hypothesis about the generation of chromosome imbalance.     

Size of infectious DNA from human and murine cytomegaloviruses.

Viral DNA was isolated from human and murine cytomegalovirus by equilibrium centrifugation in cesium chloride gradients. The size of the DNA was measured relative to T4 DNA by velocity sedimentation in neutral glycerol gradients, and fractions were assayed for infectious DNA. Infectious murine cytomegalovirus DNA sedimented as a single peak with an estimated molecular weight of 136 X 10(6). Infectious human cytomegalovirus DNA was detected in two peaks with molecular weights of 130 X 10(6) and 150 X 10(6).     

Size and shape of human cranial sutures--a new scoring method

A method for the differentiation of sutural patterns of the human cranial vault is introduced. Three criteria of differentiation are considered, one for size and two for shape: 1) maximal shape extension; 2) basic configuration; 3) secondary protrusion. The method is illustrated here for the coronal and lambdoid sutures of 70 recent Italian skulls (35 adult males and 35 adult females). Differences between coronal and lambdoid sutural size and shape can be detected analytically; for example, the coronal suture commonly shows lesser degrees of shape extension, a simpler basic configuration, and an absence of secondary protrusion. Heterogeneity within each suture, as well as a relationship among corresponding sections and between the three criteria adopted, have been also observed; symmetry predominates for both the sutures, and sexual differences are slight.     

Magnetic detection to position human nasogastric tubes

Placement of nasogastric tubes is one of the most commonly performed diagnostic and therapeutic medical procedures. Proper placement of the tube in the digestive tract below the diaphragm is crucial for efficacy and safety. This study evaluates a magnet detection system that allows percutaneous non-radiographic localization of the nasogastric tube tip. Each volunteer subject had the magnet detector placed over the abdomen, and was then intubated with a magnet-tagged nasogastric tube. Eighty-eight nasogastric tube placements were performed in 22 volunteers. The detection system located the nasogastric tube tip below the diaphragm in all 88 placements. Location in all attempts was confirmed by fluoroscopy. This method of correctly locating the tip of nasogastric tubes may obviate the need for radiographic imaging in most cases.     

On the position of chromosomes in prepared mitosis figures of human fibroblasts

Summary The square distances of chromosome centromeres to the center of the mitosis plate, after circular transformation, were measured on each 100 mitosis plates of cultured fibroblasts from a man and a woman. It is proved statistically, that the larger chromosomes are located more in the periphery than the smaller chromosomes.

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Zusammenfassung An je 100 Mitoseplatten einer männlichen und weiblichen Fibroblastenkultur wurden nach zirkulärer Transformation die Abstandquadrate der einzelnen Chromosomenpaare zum Zentrum der Platte gemessen. Es ergibt sich eine signifikante Zuordnung der großen Chromosomen zur Peripherie, der kleinen Chromosomen zur inneren Zone der Mitoseplatte.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

A model of open-loop control of equilibrium position and stiffness of the human elbow joint

According to the equilibrium point theory, the control of posture and movement involves the setting of equilibrium joint positions (EP) and the independent modulation of stiffness. One model of EP control, the α-model, posits that stable EPs and stiffness are set open-loop, i.e. without the aid of feedback. The purpose of the present study was to explore for the elbow joint the range over which stable EPs can be set open-loop and to investigate the effect of co-contraction on intrinsic low-frequency elbow joint stiffness (K _ilf). For this purpose, a model of the upper and lower arm was constructed, equipped with Hill-type muscles. At a constant neural input, the isometric force of the contractile element of the muscles depended on both the myofilamentary overlap and the effect of sarcomere length on the sensitivity of myofilaments to [Ca²⁺] (LDCS). The musculoskeletal model, for which the parameters were chosen carefully on the basis of physiological literature, captured the salient isometric properties of the muscles spanning the elbow joint. It was found that stable open-loop EPs could be achieved over the whole range of motion of the elbow joint and that K _ilf, which ranged from 18 to 42 N m·rad⁻¹, could be independently controlled. In the model, LDCS contributed substantially to K _ilf (up to 25 N m·rad⁻¹) and caused K _ilf to peak at a sub-maximal level of co-contraction.     

Size of a human serum albumin molecule in solution]

The size of a human serum albumin molecule in aqueous solution containing 150 mM NaCl was studied using small-angle neutron scattering. The molecular radius of gyration was estimated to be 27.4 +/- 0.35 A. The compact sphere should have a smaller radius of gyration, whereas the popular human serum albumin model, a "cigar" 136 A long, should correspond to a greater radius of gyration. Possible shapes of the human serum albumin molecule which are in accordance with the results obtained, are the following: an extended ellipsoid less than 110 A of length or a nonsymmetrical oblate ellipsoid with a diameter of 85 A. The oblate ellipsoid might be close to the heart"-shaped structure of the crystalline human serum albumin molecule. The size of the albumin molecule does not change significantly as pH increases to 8.9. The possibility of the dynamic coexistence of various human serum albumin conformers in solution is discussed.     

Size and shape of the human first permanent molar: a Fourier analysis of the occlusal and equatorial outlines

Form can be viewed as a combination of size and shape. Shape refers to the boundary outline independently from its orientation, relation to reference planes, and dimension (or size). Shape and its changes could be quantified by mathematical methods such as the Fourier series. In this investigation, Fourier analysis has been used to quantify the morphologic characteristics (size and shape) of the outline of the occlusal surface and maximum circumference (equator) in 259 normal, healthy human first permanent maxillary and mandibular molars and to assess the effect of sex. Large within-group variability was found in the Fourier coefficients. Both equatorial and occlusal molar areas were on average larger in male than in female homologous teeth, but the difference was statistically significant only for the equatorial areas. The mean ratios between equatorial and occlusal dental areas were independent from arch (maxillary and mandibular), side, or sex. Both equatorial and occlusal outlines of left and right homologous molars within sex and arch were similar, without size and shape differences. Similarly, no sex differences in shape were found in the comparison of homologous teeth. The method used in the present study could supply information about dental shape in both its entirety and local variations. In particular, the method is extremely sensitive to local variations in dental shape, and it could be usefully employed to compare single teeth to a standard.