Changes In Head Dimensions Research Articles

Changes in head dimensions in children from Northern Kashubia (Pomerania, Poland) during 60 years.

Over 100 years ago Franz Boas introduced the term 'cranial plasticity' defined as a response to various environmental factors. The subject is under continuous debate. Some researchers have concluded that cephalic growth is responsible to environmental change meanwhile other have found that cephalic proportion are highly heritable and do not respond readily to environmental insults. While secular trend in growth is commonly observed, head dimensions vary significantly not only between different regions of the world but also in those regions themselves. Adam Wrzosek and Michał Ćwirko-Godycki initiated studies of Kashubian children as early as in 1925 and continued them into 1936. Throughout those 11 years they accumulated measurement data regarding body height and craniometric features. The research included boys and girls from 18 localities. Sixty years later, anthropometric measurements were conducted on primary school children from nine of the original localities. The aim of our study was to determine the direction of changes in head dimensions and corresponding indices in rural children from the Kashubia region examined 60 years after Ćwirko-Godycki and Wrzosek's study emphasizing great socio-economic status improvement. All children that were examined by us in 1997 are significantly taller (by between 5.18cm and 14.74cm) than their peers 60 years ago, their heads are longer (by between 2.69mm and 10.41mm), they have broader foreheads (by 3.79 - 7.24mm), wider faces (by 4.68 - 8.09mm) and mandibles (by 5.04 - 7.40mm), larger head circumferences (by 0.64 - 2.22cm) and larger total face heights (by 2.15 - 8.13mm). The effect persists in all age groups (from 7 to 14 years old). All the noted differences are statistically significant by p < 0.05. The smallest differences were observed in head breadth (between 0.62 and 3.5mm), with statistical significance only reached in 9-year-old girls, and 11- and 14-year-old boys. Since migration in Kashubian villages was minimal in the period in question and the mating radius for couples living there was small, it can be assumed that the chance of introducing 'new' genes into the population was low. We thus gravitate towards environmental factors being the major contributors to the observed changes, doubtlessly to do with an improvement in socio-economic status.

Frozen-thawed rhesus sperm retain normal morphology and highly progressive motility but exhibit sharply reduced efficiency in penetrating cervical mucus and hyaluronic acid gel

The preservation of the genetic diversity of captive populations of rhesus monkeys is critical to the future of biomedical research. Cryopreservation of rhesus macaque sperm is relatively simple to perform, yields high post-thaw motility, and theoretically, provides via artificial insemination (AI) a way to easily transfer genetics among colonies of animals. In the interest of optimizing semen cryopreservation methods for use with vaginal AI, we evaluated the ability of frozen-thawed rhesus sperm to penetrate periovulatory cervical mucus (CM). Motile sperm concentration of pre-freeze (“fresh”) and post-thawed (“thawed”) samples from five different males were normalized for both computer assisted sperm motion analysis and CM penetration experiments. Sperm samples were deposited into slide chambers containing CM or gel composed of hyaluronic acid (HA) as a surrogate for CM and numbers of sperm were recorded as they entered a video field a preset distance from the sperm suspension-CM (or HA) interface. Fresh and thawed sperm were dried on glass slides, “Pap”-stained, and assessed for changes in head dimensions and head and flagellar shape. While retaining better than 80% of fresh sperm progressive motility, thawed sperm from the same ejaculate retained on average only 18.6% of the CM penetration ability. Experiments using HA gel yielded similar results only with reduced experimental error and thus improved detection of treatment differences. Neither the percentage of abnormal forms nor head dimensions differed between fresh and thawed sperm. While findings suggests that sperm-CM interaction is a prominent factor in previous failures of vaginal AI with cryopreserved macaque sperm, neither sperm motility nor morphology appears to account for changes in the ability of cryopreserved sperm to penetrate CM. Our data points to a previously unidentified manifestation of cryodamage which may have implications for assessment of sperm function beyond the cervix and across mammalian species.

Secular changes in head dimensions of Japanese adult male students over eight decades

The aim was to study secular changes in head dimensions of Japanese adult males. The subjects were all of Japanese birth and Japanese ancestry. The age range of the subjects was between 18 and 25 years. Four head measurements were taken: head length, head breadth, head height and head circumference. In addition, stature and body weight were also measured. All measurements were made by one observer (Fumio Ohtsuki) from 1998 to 2001. The present sample was compared with the series taken between 1910 and 1917 of Matsumura (J Fak Sci Imp Univ Tokyo Sec 1 (1925) 1) and the one measured in 1965 of Morita and Ohtsuki (Hum Biol 45 (1973) 151). The present study demonstrated the presence of larger means for head length, head breadth and cephalic index in the current sample than in their predecessors of about 35–85 years ago. Also, the present series displayed larger head circumference than that of the Morita and Ohtsuki series. Using ANOVA, head length and head breath showed significant ( p < 0.01 ) differences among all birth-year cohorts from 1978 to 1983 of the current sample. Head height, head circumference and cephalic index did not display significant differences. However, the slope of the regression line indicated that all measurements as well as the cephalic index showed slightly decreasing tendencies during the investigated period. These results suggest that brachycephalization has been occurring for approximately about 35–85 years in adult Japanese males, but the change seems to have become reversed slightly during the period covered by the present sample.

Secular changes in head dimensions of Japanese females over eight decades

The aim of this work is to document secular changes in the head dimensions of Japanese adult females. The data set of the current study was compared with two others, one covering 1910–1917 and the other 1975–1979. The subjects of the present study were all of Japanese birth and ancestry, and were aged 18–25 years. Four head dimensions were measured: head length, head breadth, head height, and head circumference. The subjects’ height and body weight were also recorded. The mean head length, head breadth, and cephalic index were larger in the present study than in the 1910–1917 series. Head length, head height, and head size (circumference) were larger in the the current series than in the 1975–1979 series. However, head breadth and cephalic index in this series were somewhat larger than in the current series. Results of ANOVA showed significant differences (P < 0.01) for all birth-year cohorts from 1978 to 1983 in terms of head length, head breadth, and head circumference. Head height, cephalic index, height, and weight, however, did not display significant differences. Regression analysis revealed that all measurements, including the cephalic index, had decreased. These results indicate that although brachycephalization has been occurring for the last 85 years, the cephalic index has decreased over the last two decades in adult Japanese females.

Effect of WR-2721 on Fetal Development in the Rat

The radioprotector WR-2721 has been shown to radioprotect all tissues studied except the central nervous system. However, it has not yet been used to radioprotect the fetus. In this study we determined that [14C]WR-2721 injected into pregnant rats quickly passed the placenta and was concentrated by the fetus. In addition, we evaluated the toxicity of WR-2721 (2.5-600 mg/kg) to pregnant rats and their fetuses during the period of major organogenesis at Days 9, 11, and 14 postconception. Pregnant animals were only slightly more (10%) sensitive (LD50, 580 mg/kg) to WR-2721 than nonpregnant cohort animals (LD50, 640 mg/kg). At concentrations of 50 mg/kg or less there was a small but statistically significant increase in fetal deaths, while at doses greater than 300 mg/kg a larger degree of fetal mortality occurred. Maximal fetal weight loss, to about 84% of control, was found at 500 mg/kg. No changes in head dimensions or gross malformations of the surviving fetuses were detected at any time or concentration. Of all the parameters measured in this study none demonstrated a predilection for any specific period of major organogenesis. The results of this study indicate that while WR-2721 demonstrates a dose-related embryotoxicity it is not teratogenic.

Dimensions of the heads of the fast and slow sedimenting forms of bacteriophage T2L

Bacteriophage T2L undergoes a reversible conversion between two conformations having S 20. w values of about 1000 s and 700 s. These are known, respectively, as the “fast” and “slow” sedimenting forms. Preparations of both forms of the bacteriophage were fixed with formaldehyde, negatively stained with uranyl acetate, and observed in the electron microscope. The tail fibers of the fast form generally extended upward, in proximity to the tail and terminating on the head. The tail fibers of the slow form extended outward, away from the tail. The morphology of the heads of both forms of T2L, as seen in these negatively stained preparations, depended markedly on the stain distribution surrounding a bacteriophage on the electron microscope grid; most of the heads seen were judged to be irregularly shaped and distorted in appearance. Selected examples of both fast and slow forms of T2L had heads which appeared polyhedral in shape, generally hexagonal in outline, and free from obvious collapse and distortion; these selections were constituted as samples of the fast and slow forms which best represented the native head structure of the bacteriophage. Comparison of the lengths and widths of the heads of the phages in these samples showed no significant differences in length or width. Mean dimensions obtained for the head of T2L were: length, 113 nm; width, 89 nm. These results, in the light of previous hydrodynamic evidence from other laboratories, indicate that changes in head dimensions of T-even phage do not occur in transitions between fast and slow sedimenting forms; these transitions are mediated solely by altered configurations of the tail fibers. Several models can be formulated which would account for the fact that some strains of T-even phage (e.g. T2L) have slow forms (extended tail fibers) sedimenting with S 20. w of about 700 s, whereas extended tail fiber forms of other strains sediment with S 20. w of about 800 to 900 s.

Electron microscope studies of silver salmon spermatozoa ( Oncorhynchus kisutch [Walbaum

The electron microscope has been used to study the structure of spermatozoa of the silver salmon, Oncorhynchus kisutch (Walbaum). Several fixative and fixative-buffer combinations were used to differentiate artefacts from actual structures. Because of the opacity of the head to electrons little was learned of its internal structure. Changes in head dimensions, however, were found with differences in osmotic stress and degree of hardening at the time of fixation. The neckpiece is attached to and lies lateral to the tail at its insertion into the head. It is an ovoid structure, the size of which varies with the use of different fixatives. The tail is composed of an isodiametric axial filament containing eleven fibrils and is covered by a spirally wound, membranous sheath. Nine of the fibrils are of equal diameter and are probably each made up of five protofibrils. The remaining two fibrils are of smaller diameter than the others and contain four protofibrils each. The protofibrils comprise the clockwise spiral substructure of the fibrils, in which no central core was detected. An analysis of the effects of different fixatives upon the tail dimensions was attempted. In some instances highly significant differences in tail widths with different fixatives were found.