bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of time and timing in hominid dental evolution
Authors: Macho Gabriele A. , Wood Bernard A.
Published: June 2005

Exactly when during evolution hominids acquired their extended extra‐uterine growth period is a contentious issue. In order to shed light on the tempo and mode of ontogenetic changes during hominid evolution, research has focused on the pattern and, to a lesser extent, the rate of growth observed in the developing dentition of extant and extinct hominoid taxa. From these data, the absolute timing of events has often been inferred, either implicitly or explicitly. Differences in patterns of growth, especially of the eruption of teeth, are reasonably well documented among hominoids. However, data on the absolute timing of dental developmental events are much more scarce, rendering tentative all inferences about timing from patterns alone. Such inferences are even more tentative when they involve interpreting ontogenetic trajectories in extinct species such as Plio‐Pleistocene hominids, which almost certainly had unique patterns of maturation. In order to contribute to the debate about possible relations between pattern and timing in the developing dentition, we have collated information that specifically relates to the absolute timing of developmental events in extant and extinct hominoids and, hence, also to the rate at which processes occur. In doing so, we have attempted to identify both developmental constraints and possible heterochronic processes that may have led to the extended growth period characteristic of humans. There appears to be growing evidence that evolution toward an extended hominid ontogeny did not follow a path that can be described as a simple heterochronic event.
Evaluation of path analysis through computer simulation: Effect of incorrectly assuming independent distribution of familial correlations
Authors: McGue M. , Wette R. , Rao D. C. , MacCluer J. W.
Published: June 2005

Path analysis of family data has been widely applied to resolve genetic and environmental patterns of familial resemblance. A prevalent statistical approach in path analysis has been, first, to estimate the familial correlations and, second, by assuming these estimates to be independently distributed, define a likelihood function from which maximum likelihood estimates of model parameters can be obtained and likelihood ratio tests of hypotheses performed. Although it is generally known that the independence assumption does not hold when multiple familial correlations are estimated from the same family data, this statistical method has still been used in these situations owing, in part, to the lack of any viable alternatives and, in part, to the lack of any knowledge about the specific quantitative effects of not meeting the assumption of independence. Here, using computer‐simulation methods, we evaluate the robustness of this statistical method to deviations from the assumption of independence. In general, we found that the failure to meet the assumption of independence leads to a conservative test of the goodness‐of‐fit of the path model, although likelihood ratio tests of specific null hypotheses were at times liberal, at times conservative, and at times nearly exact. Although the test statistics were found to be distorted, the parameter estimates using this method were nearly unbiased.
Complete hydatidiform mole in Hawaii: An epidemiological study
Authors: Matsuura Janice , Chiu Darryl , Jacobs Patricia A. , Szulman A. E. , Rao D. C.
Published: June 2005

An analysis of hydatidiform moles occurring in Hawaii over a 14‐year period (1968–1981) was undertaken. The pathology of all 278 reported molar pregnancies was reviewed and showed 69.4% to be complete, 24.5% to be partial, and 6.1% to be nonmolar.

A case‐control epidemiological investigation of the complete moles showed maternal age and race to be important, moles being significantly more prevalent in women under 20 and over 40 yr of age and also in women of Japanese, Filipino, and other Oriental ancestry. However no difference was seen in the prevalence of moles between Oriental women born in the Orient and those born and raised in Hawaii. No significant difference was found in paternal age, paternal race, socioeconomic status, or reproductive history, suggesting that these factors do not play an important role in the etiology of complete hydatidiform mole.

Incidence rates for complete moles were calculated taking age and race into consideration and ranged from a high of 1 in 150 to a low of 1 in 2,000 naturally terminating pregnancies.
Phenotypic effects of apolipoprotein structural variation on lipid profiles. I. APO H and quantitative lipid measures in the healthy women study
Authors: Eichner J. E. , Kuller L. H. , Kamboh M. I. , Ferrell R. E. , Vogler G. P. , Rao D. C.
Published: June 2005

Apolipoprotein H (APO H), also known as β2‐glycoprotein I, has been identified as a protein component of the major lipoprotein density fractions in human plasma. Recently, genetically determined structural polymorphism in white and black populations has been documented for this apolipoprotein. There are three common alleles in whites and blacks and a fourth allele found mainly in blacks. Family data confirm the autosomal codominant pattern of inheritance for the APO H structural gene. Little is known about the function of APO H, but it has demonstrated both lipid and platelet involvement. In this study we investigate the effect of APO H phenotypes on quantitative lipid measures in a group of 443 white women being followed through menopause for changes in cardiovascular risk. At baseline all women were premenopausal. None of the APO H phenotypes showed a statistically significant effect on lipid measures in this population.
Using survival methods to estimate age‐at‐onset distributions for genetic diseases with an application to Huntington disease
Authors: Cupples L. Adrienne , Terrin Norma C. , Myers Richard H. , D'Agostino Ralph B. , Rao D. C.
Published: June 2005

Two important considerations in genetic disease are the risk of inheriting the gene for a disease and the age‐at‐onset distribution among those inheriting it. This paper describes the use of survival data analytic methods to estimate these entities. When a sample consists of children and/or siblings of affected individuals, standard lifetable methods such as Kaplan‐Meier techniques can be applied. The desired estimators are functions of the Kaplan‐Meier estimator and their properties are derived using the invariance principle and delta methods. A discussion of the underlying assumptions and estimators of standard errors and mean onset age are given. In an application to Huntington disease, the risk (± SE) of inheriting the gene for disease among children of a singly affected parent is estimated to be 0.499 ± 0.020 and the estimated mean onset age (± SE) is 45.6 ± 0.7.
Can dietary intake patterns account for the familial aggregation of disease? Evidence from adult siblings living apart
Authors: Sellers Thomas A. , Kushi Lawrence H. , Potter John D.
Published: June 2005

The familial aggregation of certain chronic diseases is well documented [Perkins, 1986; King et al., 1984; Anderson, 1982]. Dietary data on adult brothers living apart were used to examine whether familial clustering of disease could be explained by nature or nutriture. Intakes of nutrients were strikingly more similar among siblings than expected: when correlations were adjusted for country of residence, 21 of 25 (84%) were statistically significant. Thus, dietary patterns among adult siblings are more alike than could be predicted by their sharing a common culture, as alike as has been described for monozygotic twins, and as alike as described for familial correlations of serum cholesterol. Incorporation of dietary measures in cotwin studies or studies of siblings can improve the estimates of the true genetic effect on disease pathogenesis.
Elementary methods for the analysis of dichotomous outcomes in unselected samples of Twins
Authors: Ramakrishnan Viswanathan , Goldberg Jack , Henderson William G. , Eisen Seth A. , True William , Lyons Michael J. , Tsuang Ming T. , Chakravarti Aravinda
Published: June 2005

This paper presents an elementary statistical method for analyzing dichotomous outcomes in unselected samples of twin pairs using stratified estimators of the odds ratio. The methodology begins by first randomly designating one member of each twin pair as an ‘index’ twin and the other member as the ‘co‐twin.’ Stratifying on zygosity, odds ratios are used to measure the association between disease in the index twin and disease in the co‐twin. From these zygosity‐specific tables we cal‐culate the Woolf‐Haldane estimator of the common odds ratio (ψF, the weighted average of the zygosity‐specific odds ratios), the Mantel‐Haenszel test statistic (χ) for the common odds ratio, and a test (χ) for the difference in the zy‐gosity‐specific odds ratios. In this application, ψF provides an estimate of the familial association for disease and the accompanying χ provides a test of the null hypothesis, ψF = 1 (i.e., there is no evidence for a familial influence on disease). The χ is a test of the null hypothesis that ψMZ = ψDZ; a significant value for χ suggests a genetic influence on disease (assuming that the observed odds ratios follow a pattern where ψMZ>ψDZ). A new test statistic (χ) is proposed that incor‐porates the expectation that ψMZ = ψ under a purely additive genetic model with no common environmental effects. A significant value of χ indicates that the different odds ratios across zygosity are partly due to common environmental influences. Conversely, a nonsignificant value of χ is an indication that the zygosity‐specific odds ratios are due solely to additive genetic effects and not to common environment. This basic approach is extended to examine the effects of measured indicators of the specific environment and the assessment of certain forms of gene by environment interaction. All of the methods are easily understood, highly flexible, readily computed using a hand calculator, and incorporate the inherent genetic information contained within twin samples. © 1992 Wiley‐Liss, Inc.
Segregation analysis of 159 soft tissue sarcoma kindreds: Comparison of fixed and sequential sampling schemes
Authors: Bondy Melissa L. , Lustbader Edward D. , Strom Sara S. , Strong Louise C. , Chakravarti Aravinda
Published: June 2005

In this study we compared parameter estimates and model hypotheses in pedigree data collected by fixed sampling with estimates and hypotheses derived by sequential sampling. Employing a fixed sampling scheme, we previously analyzed data on relatives of 159 childhood sarcoma patients. We have now extracted from that data set individuals who would have been included in a sequentially sampled study. We applied segregation analysis to the truncated data, to determine the mode of inheritance and major locus parameter estimates. With data from both sampling schemes we made a family‐by‐family comparison to determine each family's contribution to a major gene model. The two sampling schemes yielded similar results: we detected segregation of a dominant major gene and obtained similar major locus parameter estimates. However, the sequential sampling scheme derived these conclusions from data on 982 relatives rather than the 2,451 ascertained in the fixed sampling scheme. The sequential sampling scheme failed to identify only one of the kindreds likely to be segregating the gene. For this data set, the sequential sampling scheme would have provided an efficient mechanism to discriminate genetic hypotheses and would have permitted focus of resources on the specific kindreds likely to segregate a major gene. © 1992 Wiley‐Liss, Inc.
A generalized estimating equations approach to fitting major gene models in segregation analysis of continuous phenotypes
Authors: Lee Hang , Stram Daniel O. , Thomas Duncan C.
Published: June 2005

This paper discusses the application of estimating equations methods based on a quadratic exponential model [Prentice and Zhao, 1991] as a potential competitor with full likelihood approaches to estimating the effect of major genes in a segregation analysis [Elston, 1981] of continuous phenotypes, in the single allele problem. We show that while the estimating equations methods based on the quadratic exponential family cannot be used by themselves to estimate all parameters of interest, an iterative two‐stage approach can be used, in which the population allele frequency is first considered to be a known parameter, which permits the estimating equations method to estimate the remaining parameters. At the second stage a “pseudo‐profile” loglikelihood based only on the founders is used to estimate the allele frequency. After each maximization of the pseudo‐profile loglikelihood at the second stage, the parameters in the first stage are reestimated using a new value of the allele frequency, and a new value of the second stage pseudo‐profile loglikelihood is obtained. We used simulated pedigree data for illustrations. © 1993 Wiley‐Liss. Inc.
Path analysis and sib‐pair linkage
Authors: Carey Gregory , Williamson John A.
Published: June 2005

When the distance between linked loci is expressed in terms of the correlation between the identity‐by‐descent (idb) values of the loci, then a path model may be used to order loci with data on sib‐pairs and their parents. The relationship between the recombination fraction and the correlation coefficient is developed and a method for fitting a covariance matrix predicted by a specific ordering of loci to an observed covariance matrix is proposed. © 1993 Wiley‐Liss. Inc.
Analysis of discrete phenotypes using a multipoint identity‐by‐descent method: Application to Alzheimer's disease
Authors: Goldgar David E. , Lewis Cathryn M. , Gholami Khosrow
Published: June 2005

The multipoint identity‐by‐descent method was developed to detect linkage to a specific chromosomal region through partitioning the genetic variance. This method has previously been applied to quantitative traits, and here is extended to a qualitative trait, where a dichotomous affected/unaffected status variable is transformed to a quantitative variable by incorporating covariates. This method is applied to the Alzheimer's disease data sets from Genetic Analysis Workshop 8, to investigate putative linkage to chromosomes 19 and 21. The multipoint identity‐by‐descent method is used to test for linkage through the qualitative trait, and for excess sharing of the chromosomal region among affected sibs. Results are compared to those of the affected‐pedigree‐member method and classical linkage analysis. None of these methods gave results showing clear linkage, with the only marginally significant results occurring for the Boston data set on chromosome 19 and the Duke data set for chromosome 21 using the multipoint identity‐by‐descent method. © 1993 Wiley‐Liss, Inc.
The application of jackknife statistics to estimates of the recombination fraction
Authors: Berger B. D. , Greenberg D. A. , Hodge S. E. , Mendell N. R.
Published: June 2005

We develop and evaluate the jackknife statistics [Efron, 1982] for obtaining confidence intervals for the recombination fraction. We consider two cases: (1) a single sibship of size S with phase known parents (one doubly heterozygous and one doubly homozygous) and (2) a sample of 20 nuclear families. We compare the jackknife confidence interval to the −1.00 lod and −0.83 lod intervals. For the first case we compare our intervals with a confidence interval which we develop that has coverage of exactly 95%. For the second case, we do a simulation study and compare the coverage of the intervals and the endpoints of the intervals with the actual 2.5th and 97.5th percentiles. Our results indicate that in case (1) the lod intervals provide closer estimates to the 95% exact interval than does the jackknife approach. However, in case (2), although the lod intervals have better coverage probabilities, the jackknife interval endpoints are closer to the actual percentile points than either of the lod interval endpoints. © 1993 Wiley‐Liss, Inc.
Sequential imputation and multipoint linkage analysis
Authors: Kong Augustine , Cox Nancy , Frigge Mike , Irwin Mark
Published: June 2005

A novel Monte Carlo method for linkage analyses involving large pedigrees and many polymorphic loci is introduced. Issues related to the efficiency of the method are discussed. © 1993 Wiley‐Liss, Inc.
The NHLBI male veteran twin study data
Authors: Reed Terry , Carmelli Dorit , Christian Joe C. , Selby Joseph V. , Fabsitz Richard R.
Published: June 2005

The National Heart, Lung and Blood Institute (NHLBI) twin study is a collaborative, longitudinal study of the role of genetic risk factors on subsequent cardiovascular disease processes in 514 pairs of white, male World War II and Korean veteran twins born between 1917 and 1927. This paper describes the sampling procedures and zygosity determination at the initial examination, participation by the cohort members at later examinations, and a summary of the variables provided for Genetic Analysis Workshop 8 (GAW8). © 1993 Wiley‐Liss, Inc.
Statistical validity of the Haseman‐Elston sib‐pair test in small samples
Authors: Wilson Alexander F. , Elston Robert C.
Published: June 2005

Simulation experiments were used to determine the empiric type I error rate of the Haseman‐Elston sib‐pair test for linkage between a quantitative trait and a marker locus in samples with 60 or fewer sib pairs. The effect of different levels of marker‐locus heterozygosity on statistical validity was also considered. The test was performed on the trait and each of five unlinked markers, and evaluated using two different degrees of freedom for the t‐distribution. The number of degrees of freedom in the first evaluation was based on the number of sib pairs in each sibship, ∑ sI(sI ‐ 1)/2 ‐ 2. In the second evaluation, the number of degrees of freedom was based on the number of sibs minus 1 in each sibship, ∑ (si ‐ 1) ‐ 2. Empirically determined type I error rates using C sI(sI ‐ 1)/2 ‐ 2 degrees of freedom were slightly liberal. For ∑ (si ‐ 1) ‐ 2 degrees of freedom, the estimated empiric p‐values were nearly identical to their respective nominal p‐values. Decreasing levels of heterozygosity did not increase the empiric type I error rate when the sample size was small. © 1993 Wiley‐Liss, Inc.
Genotype by sex interaction in measures of lipids, lipoproteins, and apolipoproteins
Authors: Towne Bradford , Blangero John , Siervogel Roger M.
Published: June 2005

Genotype by sex (GxS) interaction in a quantitative trait indicates that the sexual dimorphism exhibited in that trait is heritable. GxS interaction has implications for the modeling of traits in segregation analyses and for the assessment of disease risk in males and females. Thirteen quantitative measures of lipids, lipoproteins, and apolipoproteins from 203 to 301 individuals in 25 to 27 kindreds were examined for evidence of GxS interaction. These measures included serum concentrations of total cholesterol, triglycerides, LDL‐C, HDL‐C, apo B, and apo AI, and peak LDL particle diameter, small LDL mass, large LDL mass, IDL mass, VLDL mass, HDL, mass, and HDL, mass. GxS interaction was indicated for transformed values of LDL‐C and small LDL mass by an additive genetic correlation between males and females significantly less than 1.0, and GxS interaction was indicated for transformed values of HDL, mass and HDL, mass by males and females having significantly different additive genetic variances. © 1993 Wiley‐Liss, Inc.
Evaluation of the sampling plan used in collecting data for a study of LDL subclass pattern
Authors: Zhao Lue Ping , Grove John S. , Quiaoit Filemon
Published: June 2005

The genetic epidemiologic study of coronary heart disease conducted by a group in the Donner Laboratory used survey and ad hoc sampling plans, resulting in a random and an ad hoc sample of families, respectively. These two samples were used to evaluate the ad hoc sampling plan used in that study. Following the description of data collection, we adjusted for ascertainment, but still found that the aggregation patterns of many lipoproteins in the ad hoc sample were different from those in the random sample. © 1993 Wiley‐Liss, Inc.
Exploring the HDL likelihood surface
Authors: Atwood Larry D. , Kammerer Candace M. , Mitchell Braxton D.
Published: June 2005

Using random initial parameter estimates, three segregation analysis models of the inheritance of HDL, in the Berkeley GAW8 data set were maximized 5000 times each. Initial parameter estimates were assumed to be uniformly distributed on intervals formed by parameter boundaries. The three models were unrestricted, environmental, and Mendelian regressive type A models. Likelihood ratio tests of the global maxima rejected the Mendelian model and accepted the environmental model. However, tests using local maxima accepted the Mendelian model and both rejected and accepted the environmental model. Patterns among the initial parameter estimates of convergent runs were examined to develop empirical rules to increase the frequency of convergence. These rules were tested using data on apo AI in the Berkeley GAWS data set. © 1993 Wiley‐Liss, Inc.
Structure and stability of β‐pleated sheets*
Authors: Perczel András , Gáspári Zoltán , Csizmadia Imre G.
Published: June 2005

Beside α‐helices, β‐sheets are the most common secondary structure elements of proteins. In this article, the question of structure and stability of parallel and antiparallel sheets of various lengths is addressed. All data obtained are compared to a selected set of protein structures. In antiparallel β‐sheets, one of the two possible H‐bonded structures (containing 14 atoms in the H‐bonded pseudoring) is energetically more favored and also more abundant in proteins than the other one (with 10 atoms involved in the pseudoring). Parallel β‐sheets and their subunits are energetically less stable and indeed found to occur more rarely in proteins. Antiparallel hairpins are disfavored compared to β‐sheets formed by sequentially separated strands. Agreement between theory and experimental data indicates that characterization of structural building blocks at an appropriately accurate level of theory is a useful tool to get insight into fundamentals of protein structure. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 1155–1168, 2005
Suppression of feather morphogenesis in co‐aggregates of skin cells from embryos of different ages
Authors: Garber Beatrice , Moscona A. A.
Published: June 2005

These experiments test the capacity of younger skin cells to promote feather differentiation in aggregates of older skin cells; the results indicate that the older cells suppressed the normal differentiation of the younger cells.

Skin sheets (epidermis and dermis) from the dorsum and from the featherless (apterous) area of 6‐ to 14‐day chick embryos were dissociated into suspensions of single cells and commingled in the following heterochronous combinations: (a) 6‐day dorsal skin cells with 14‐day dorsal skin cells, (b) 8‐day dorsal skin cells with 14‐day dorsal skin cells, (c) 6‐day dorsal skin cells with 10‐day mid‐dorsal skin cells, (d) 6‐day dorsal skin cells with 10‐day apterous skin cells. Single‐age suspensions served as controls. The cells were co‐aggregated in vitro for 24 hours and the resulting aggregates grafted to the chorioallantoic membrane for further development for seven days. In grafts of control aggregates of 6‐ or 8‐day skin cells there was excellent development of feathers; in aggregates of 14‐day cells no feathers developed; aggregates of 10‐day mid‐dorsal cells gave rise to atypical, stunted feathers; aggregates of 10‐day cells from apterous areas produced no feathers.

In grafts of 6‐ or 8‐day skin cells co‐aggregated with 14‐day skin cells, there was complete suppression of feather development; the predominant structures were stratified and heavily keratinized skin sheets, characteristic of aggregates of 14‐day skin cells. Grafts of co‐aggregates of 6‐day skin cells with 10‐day mid‐dorsal skin cells gave rise to feathers and skin of patterns characteristic of the 10‐day cells. Six‐day skin cells co‐aggregated with 10‐day apterous skin cells reconstructed feathers and skin of the 6‐day type as well as skin of the 10‐day type.

Simple dilution of feather‐forming by non‐feather‐forming cells cannot by itself explain feather suppression in co‐aggregates with cells from older skin and “assimilation” of the younger cells into the morphogenetic pattern of the older cells. It is assumed that the suppression results from interference by constitutents in the older cell population with interactions between specific cell groupings essential for feather development or, with the cellular sorting‐out process by which these groupings arise.
Male gonadal dysgenesis in a female‐sterile mutant of Drosophila melanogaster
Authors: Lucchesi J. C. , Counce S. J. , Hildreth P. E.
Published: June 2005

Various types of testicular abnormalities, encountered in deep orange (dor) Drosophila melanogaster males, have been described. These abnormalities range from complete failure of attachment and, therefore, of elongation and coiling of both testes, to attachment and partial elongation of one testis.

The frequency of testicular dysgenesis among affected lines can be readily modified by varying the culture conditions or the genetic background.

The occurrence of a relatively high incidence of abnormalities among males bearing an X‐chromosome balancer (FM4) is reported.
Succinic dehydrogenase and cytochrome oxidase of mitochondria of chick liver, heart, and skeletal muscle during embryonic development
Authors: Greenfield Phyllis C. , Boell E. J.
Published: June 2005

The specific activities of succinic dehydrogenase (SD) and cytochrome oxidase (COX) were determined for mitochondria of chick liver, heart, and skeletal muscle from the seventh day of incubation through the time of hatching. The levels of activity of both enzymes at hatching and the rate and course of the developmental changes by which the final levels are reached are different and specific for mitochondria of the three tissues studied. During development changes in activity of both enzymes occur in parallel so that the ratio of SD/COX remains constant. Furthermore, the ratio is the same for the three types of mitochondria. Cytochrome oxidase is completely localized in the insoluble protein fraction (membrane fraction) of all mitochondria examined, and the change in COX during development varies temporally and quantitatively with the proportion of insoluble protein. When calculated on the basis of insoluble protein, specific activities of SD and COX are constant throughout development; furthermore, differences in activity among the mitochondria of the three tissues disappear. It is concluded that mitochondrial differentiation reflects the appearance of specific proportions of membranes and matrix.
Estradiol administration and reproductive performance in rats
Authors: Schultze A. B. , Ellicott A. R.
Published: June 2005

Estradiol in doses of 2 and 4 micrograms increased uterine triphenyltetrazolium (TTC) metabolism at day of breeding when administered for two days prior to breeding. Estradiol as administered in these experiments resulted in decreased uterine TTC metabolism at day 4 and 8 of gestation when compared to the metabolism of untreated females.

Two micrograms of estradiol administered one and two days prior to breeding increased reproductive performance. Two micrograms of estradiol administered one day prior to breeding and at day of breeding drastically reduced reproductive performance.
Haptoglobin evolution: Polymeric forms of HP in the Bovidae and Cervidae families
Authors: Travis James C. , Sanders Bob G.
Published: June 2005

Vertical polyacrylamide gel electrophoresis and Sephadex G‐200 chromatography have been used to characterize haptoglobins (Hp) of members of the Bovidae family, goats, sheep, cattle, and bison, and of the Cervidae family, mule deer and elk. In contrast to other mammals with the exception of humans, sera from these animals exhibited polymeric Hp similar to human Hp 2. No Hp polymorphism was demonstrated in these studies, however. Immunological studies with rabbit anti‐goat Hp sera revealed cross reactivities among all members of these two families, but not with human Hp. With anti‐human Hp sera no immunological cross reactivity was observed with any of the sera of these two families. Since a partial gene duplication has been postulated as the source of polymeric Hp and of Hp polymorphism in humans, a similar but independent genetic event is postulated to have occurred in the ancestral line of the Bovidae and Cervidae families to give rise to polymeric Hp.
Genetic and metabolic bases of two “albino” phenotypes in the leopard frog, Rana pipiens
Authors: Smith‐Gill Sandra J. , Richards Christina M. , Nace George W.
Published: June 2005

Preliminary characterizations of albino Rana pipiens from two widely separated geographic origins, Mexico and Michigan, indicated that different metabolic basés underlie the albino phenotype.

Albinism in the Mexican frogs was shown to result from a single Mendelian recessive gene, am (amelanotic), and appeared to involve a biochemical failure of the pigment synthesizing system. Melanophores were present in am/am integument which exhibited tyrosinase activity when provided with exogenous tyrosine or L‐DOPA. The tyrosinase activity of am/am melanophores showed greater thermolability than did that of wild type malanophores.

The “albinism” of tadpoles collected in Michigan was only partial, and was associated with a highly pleiotropic syndrome, abnormal patterning of chromatophore distributions, and metamorphic failure. Poor pigmentation of integumental melanophores appeared associated in part with inhibitors of melanogenesis. Genetic data on the possible mode of inheritance are not yet available.
Growth of mouse trophoblast transplanted to syngeneic and allogeneic testes
Authors: James D. A. , Acierto Suzie , Murphy B. D.
Published: June 2005

Trophoblast was transplanted to the testis to study a number of factors which might influence its growth and invasive capacity. Three genotypes were used in reciprocal transplantations and the recipient groups were compared histologically and by examination of the haemorrhagic nodule produced in the testis by the trophoblast. The factors of principal concern were antigenic dissimilarity, the nature of the transplant and the recipient site, and the mass of the transplant and the recipient site.

The results indicated that antigenic dissimilarity, mass of the recipient organ, and original trophoblast mass have no appreciable influence on trophoblast growth in the present study system. The nature of the recipient according to its genotype and the nature of the trophoblast do appear to have some influence but this is more apparent from histological examination than from analysis of haemorrhage mass. These findings cast some doubt upon the validity of the analysis which has been used by some investigators.

The present findings confirm that a physiological relationship is established between trophoblast and host‐tissue. The relationship appears to be of a qualitative rather than quantitative nature, and that this relationship is established in spite of the proposed protective glyco‐protein barrier between these components.
An analysis of the hemoglobins from some common turtles
Authors: Horton Bennett , Fraser Ronald , Dupourque Daniel , Bailey David , Chernoff Amoz
Published: June 2005

A chromatographic analysis of the blood from seven species of turtles, representing four families, has revealed that all animals contained multiple hemoglobins. Members of the Emydidae family had two major components separated by a minor one. There was some variation to this pattern in the box turtles (Terrapenes). The musk, soft shelled, and the snapping turtles examined had three, five, and four hemoglobins respectively. In general, electrophoresis of these proteins in starch gels confirmed the results obtained from DEAE cellulose chromatography in minicolumns.

Hemoglobins from the painted and Cumberland turtles were found to be quite resistant to dimerization on aging and to alkali denaturation. These proteins from the box turtles were seen to be moderately resistant to both types of molecular modification, while those from the musk, the soft shelled, and the snapping turtles polymerized readily on aging and denatured readily in alkali.
The effect of gonadectomy and propylthiouracil treatment on the submandibular gland of the Mongolian gerbil, Meriones unguiculatus
Authors: Mastraccio Albert J.
Published: June 2005

The histological organization and cytology of the submandibular glands of male and female Mongolian gerbils were described. A sexual dimorphism in the glands, limited specifically to the serous tubules, was noted. In the male, gonadectomy, propylthiouracil administration and a combination of the two treatments resulted in significantly reduced serous tubule diameters. Such reduction was accompanied by a decrease in the number of cells per tubule without any change in the height of individual serous cells. In the female similar treatments were without effect on these parameters of the serous tubules. Experimental treatments did not affect the cytology or the periodic acid‐Schiff and Alcian blue reactions of the submandibular glands in either sex.
Yolk formation by transplanted cockroach oocytes
Authors: Bell William J.
Published: June 2005

Intraspecific transplantation of ovaries in 18 species of cockroaches resulted in the initiation of yolk formation and oocyte growth rates similar to sham‐operated controls. Host vitellogenins were sequestered by transplanted oocytes in concentrations equal to those observed in oocytes of unoperated cockroaches. Ovaries transplanted interspecifically sequestered host vitellogenins and grew to terminal stages only when donor and host were closely related. Yolk formation did not occur when ovaries were transplanted between species of different superfamilies or families, whereas several cases of successful ovary transplantations were observed between species of different subfamilies. Unsuccessful transplants either failed to take up host vitellogenins and did not increase in size or were encapsulated and degenerated.
A fertile male rabbit with a minute Y chromosome
Authors: Martin Patricia A. , Shaver Evelyn L.
Published: June 2005

Nineteen of 33 or 58% of six‐day blastocysts, recovered from four female rabbits demonstrated an apparent male chromosomal complement with a minute Y chromosome. The remaining 42% of the blastocysts had a normal female XX chromosomal complement. All four female rabbits, two California and two New Zealand White, were inseminated by a particular California male rabbit. Chromosome studies of peripheral blood cultures from the male, which had normal gonadal and genital anatomy as well as normal fertility, revealed a karyotype identical to that seen in the blastocysts with the apparent male chromosomal complement. Autoradiographic studies from blood cultures of the male indicated that the minute chromosome was late‐replicating and was most likely the Y chromosome. The suggestion is made that the rabbit may be another mammal with Y chromosome polymorphism.
Fine structure of epidermal differentiation in the mouse
Authors: DuBrul Ernest F.
Published: June 2005

The structure of the epidermis of mice from nine days in utero to adult has been studied with the electron microscope. During fetal development the epidermis increases in thickness and four structurally distinct regions are present by 15–17 days in utero. Fetal epidermis differs from adult epidermis by the presence of large, tripartite keratohyalin granules in the superficial layers. Such structures are absent in adult epidermis. Furthermore, there are fewer tonofilament bundles in fetal epidermis, and no cornified layer containing 100 Å keratin fibers is found in the fetal stages. A peridermal layer is also present in the fetus.
The fate of transplanted cells in mouse blastocysts in vitro
Authors: Moustafa Laila A. , Brinster R. L.
Published: June 2005

Four‐day synchronous blastocyst donor cells and 8‐ and 12‐day asynchronous embryonic cells were transplanted adjacent to and within the inner cell mass of four‐day recipient blastocysts. Virtually all recipient blastocysts tolerated micrurgical procedures and regained their “normal” size and shape after four hours of incubation. About 3% of all recipient blastocysts exhibited rejected cells.

The nuclei of the transplanted cells, labeled with tritiated thymidine, appeared to be present in various phases of the cell cycle 20 hours after transplant. After 40 hours in culture, the number of labeled cells was significantly greater than the number of cells transplanted in both the synchronous and asynchronous transplants. The present study shows for the first time that chronologically older cells can divide in a younger embryo and suggests that they participate in the structure of the recipient embryo.
Changes in codon recognition and chromatographic behaviour of tRNA species during embryonic development of the sea urchin Paracentrotus lividus
Authors: Molinaro M. , Farace M. G.
Published: June 2005

14C‐ or 3H‐aminoacyl‐tRNA from fertilized eggs and from embryos at the pluteus stage were analyzed by chromatography on benzoylated DEAE cellulose columns. Differences in the chromatographic species between the two stages were found for lysyl‐ arginyl‐ and leucyl‐tRNA. No differences were observed for valyl‐ and seryl‐tRNA.

Leucine, lysine, serine and arginine tRNA from both stages of development were tested for codon recognition by the ribosomal binding technique. At the pluteus stage, the binding to ribosomes of lysyl‐tRNA is about five fold higher in the presence of poly AG than in the presence of poly A, whereas the difference is only two fold in fertilized eggs. Poly AG stimulates the binding of arginyl‐tRNA from both stages. At 0.02 M Mg+2 the stimulation is increased in pluteus tRNA while it is decreased in the tRNA of fertilized eggs. Moreover at this magnesium concentration the binding of pluteus arginyl‐tRNA is stimulated by poly G. Less remarkable quantitative differences in codon recognition between the two stages were observed for seryl‐tRNA, while the codon recognition by leucyl‐tRNA does not vary during development.
Caffeine bleaching of Stentor coeruleus
Authors: Tartar Vance
Published: June 2005

After a few days in caffeine solution the dark blue‐green ciliate Stentor coeruleus loses all visible pigmentation. The cells remain viable and transparent if the solution is then diluted. In time, however, a light pink color is regenerated in maintenance concentration of the drug. In caffeine‐free medium the major dark green pigment is regenerated. Decolorized, pink, and normal stentors can thus be compared, alive, in searching for the functions of these pigments. Unexpectedly, the pigments are not necessary for the lightavoidance response.
Response of the toad, Xenopus laevis, to circulating antigens. II. Responses after splenectomy
Authors: Turner Rodney J.
Published: June 2005

It was demonstrated that the spleen cannot be the only site of antibody induction or formation in Xenopus laevis — even though cellular activity in response to circulating antigen is most evident in this organ — since serum antibody titres in splenectomized toads were comparable with those in sham‐operated animals after immunization with human gamma globulin (in adjuvant) or with sheep erythrocytes. This is of interest since the spleen appears to be the only lymphoid organ in X. laevis with any complexity of structural organization, the remaining foci consisting mainly of irregularly arranged lymphocytes. These experiments indicate that complex structural organization of lymphoreticular tissues may not be essential to immunological competence.
Effect on lens regeneration of implantation of spinal ganglia into the eyes of the newt, Notophthalmus
Authors: Powell Jeanne A. , Powers Christine
Published: June 2005

Homologous implantation of brachial spinal ganglia from intact animals into the vitreous chamber of the newt eye had no effect on initiation of lens regeneration from the dorsal margin of the iris in the absence of both adult lens and retina; while implantation of ganglia innervating regenerating limbs resulted in an increased rate of lens regeneration as compared to contralateral eyes in which nothing or a piece of liver had been implanted. Ganglia innervating regenerating limbs were also capable of initiating lens regeneration in the presence of an intact lens. Such lens regeneration proceeded no further than nuclear activation and depigmentation of iris tissue even after 18 days of ganglia culture in the anterior chamber of the newt eye. This limited response may be due to insufficient amount of trophic factor(s) because of the size of the implant or the duration of its production by the implant. It is suggested that the neural trophic factor influencing limb regeneration may also be capable of initiating lens regeneration and substituting for the retinal trophic factor in the eye.
On the rate of movement of the cleavage stimulus in sand dollar eggs
Authors: Rappaport R.
Published: June 2005

The rate at which the cleavage stimulus moves from the mitotic apparatus to the cell surface was calculated from measurements made on flattened, fertilized Echinarachnius parma eggs with excentric nuclei. The time interval between the appearance of furrows in the closer and more distant equatorial margins is proportional to the difference in the distance between the axis of the mitotic apparatus and the two surfaces. The calculated rate of stimulus movement is 6.3 ± 1.8 μ/minute. This rate is slower than that of free diffusion, and the usually studied examples of cytoplasmic streaming; it approximates that reported for microtubule growth.
An ultrastructural analysis of polyspermy in the surf clam, Spisula solidissima
Authors: Longo Frank J.
Published: June 2005

Spisula eggs made polyspermic by insemination with high concentrations of sperm were prepared for light and electron microscopy. In eggs that had been inseminated by at least eight spermatozoa, incorporation and male pronuclear development were morphologically similar to events observed in monospermic zygotes. Subsequent to their migration to the central region of the zygote the female pronucleus and the male pronuclei become closely associated. This is followed by chromosome condensation and vesiculation of the pronuclear envelopes. The chromosomes become arranged on a multipolar spindle in preparation for the first cleavage division. In approximately 50%zygotes one of the pronuclei appears to be asynchronous in its morphogenesis; the vesiculation of its envelope and the condensation of its chromatin taking place at a later stage than in adjacent pronuclei. This pronucleus fails to form discrete chromosomes and is recognized as a large spheroidal body which becomes aligned on the multipolar spindle. The fate of this mass of condensed chromatin is unknown.
Stimulation of RNA synthesis in developing frog embryos by microinjection of ribosomes
Authors: Rollins J. W. , Flickinger R. A.
Published: June 2005

Oocyte ribosomes stimulate H3–5–uridine incorporation into RNA when microinjected into the vegetal cells of early cleavage embryos. Preparations with a low percentage of monosomes, such as those of swimming larvae and adult frog liver, give little stimulation. E. coli ribosomes fail to affect RNA synthesis. Short term labeling experiments at the gastrula stage in which only nuclear RNA was labeled suggest that added ribosomes may increase nuclear transcription and not cytoplasmic conservation of D‐RNA in polysomes.
The function of the middle ear in lizards: Eumeces and Mabuya (Scincidae)
Authors: Wever Ernest Glen
Published: June 2005

The structure of the middle ear and its performance in the reception of sounds are considered in four species among the Scincidae. By use of the alternating potentials of the cochlea the sensitivity to sounds of various frequencies was measured under normal conditions and after certain alterations of the conductive mechanism designed to reveal its operation. By excluding the major part of this mechanism and applying aerial sounds through a tube sealed over the oval window, an assessment was made of the enhancement of sensitivity ordinarily provided by the mechanism acting as a mechanical transformer.

Further analysis of the action of the conductive mechanism was carried out
by stimulation with mechanical vibrations applied to the system in dif
ferent ways.

An increase in the effective force of sound vibrations acting on the cochlear
elements, which is required in the middle ear's operation as an impedance
transformer, appears to be achieved by a combination of two mechanical
processes, a lever action in the ossicular chain and a form of hydraulic ampli
fication through the difference in areas between tympanic membrane and
stapedial footplate.

The improvement of sensitivity in the action of the middle ear was found
to be highly significant in amount in all specimens. This amount varied some
what with species and among individual ears, but averaged 37.8 db. This
average compares closely with the results of previous experiments on Iguanidae
and Gekkonoidea, and is of the same order of magnitude as corresponding mea
surements made on mammalian ears.
The role of shadows in directional training and homing of pigeons, Columba livia
Authors: McDonald Dennis L.
Published: June 2005

Some of the hypotheses of how homing pigeons are able to find their way home would require them to make precise measurements of the location of the sun. The purpose of this study was to determine if homing pigeons can measure the altitude and azimuth of a light source accurately enough to use the hypothesized navigational systems. Also the specific cues the pigeons used for the discriminations were analyzed.

A psychophysical technique in which the pigeon controls the movement of
the light (or of itself) toward or away from a trained direction was used. The
ability to perform this task gives evidence on how accurately homing pigeons
can measure the location of a light source such as the sun.

Five pigeons were trained and tested. They were able to discriminate differences of as little as 3.4° in azimuth of the light source; 8° in altitude. It was
determined that shadow patterns in the apparatus were used in all the discriminations. The role shadows may have played in the directional training
done in the past, and the role shadows may play in the natural homing
process of pigeons are discussed.
Stimulation of limb regeneration in the lizard Xantusia vigilis by means of ependymal implants
Authors: Bryant Susan V. , Wozny Kenneth J.
Published: June 2005

The experiments reported in this paper demonstrate that ependymal cells can stimulate a regenerative outgrowth when implanted into the limb of a lizard. Simple limb amputation, amputation followed by a sham operation, and amputation followed by the implantation of a cartilage tube from a tail regenerate were ineffective in causing the hind limbs of Xantusia vigilis to regenerate. However, amputation followed by the implantation of a cartilage tube containing ependyma caused regenerative outgrowths in 82% of the treated limbs. These results show that ependymal cells, in addition to initiating tail regeneration in their normal location, can when transplanted to the limb, initiate limb regeneration.