bluuebunny/crossref_metadata_2025 huggingface dataset:
Sib‐pair linkage analyses of Alzheimer's disease
Authors: Bailey‐Wilson Joan E. , Bamba Vaneeta
Published: June 2005

Sib‐pair linkage analyses were used to search for linkage to a set of chromosome 19 and 21 marker loci in two sets of families with Alzheimer's disease. The advantage of this technique is that no assumption is made about the mode of inheritance of the disease. Some mild suggestions of linkage were found in early‐onset families for a chromosome 21 marker and in a set of late‐onset families for a chromosome 19 marker. © 1993 Wiley‐Liss, Inc.
Linkage detection by the Affected‐Pedigree‐Member method: What is really tested?
Authors: Babron Marie‐Claude , Martinez Maria , Bonaïti‐Pellié Catherine , Clerget‐Darpoux Françoise
Published: June 2005

We show that the null hypothesis in the Affected‐Pedigree‐Member (APM) method is composed of two sub‐hypotheses: no linkage and correct marker allele distribution. As a result, the APM method is not robust to misspecification of marker allele frequencies. © 1993 Wiley‐Liss, Inc.
Alzheimer's disease: A piscatorial trek
Authors: Van Eerdewegh Paul , Hampe Carol L. , Suarez Brian K. , Reich Theodore
Published: June 2005

The evidence for linkage between Alzheimer's disease and markers on both chromosomes 19 and 21 [Pericak‐Vance et al., 1991] by the affected‐pedigree‐member (APM) method [Weeks and Lange, 1988] cannot be replicated on any of the available GAW8 data sets when marker allele frequencies are estimated from the combined sample. The strong dependence of the APM method on accurate estimation of marker allele frequencies, and the effects of noninformative pairs and of genetic distance in informative pairs of relatives are illustrated. © 1993 Wiley‐Liss, Inc.
The impact of some parameters on linkage analysis of Alzheimer's disease
Authors: Xu J. F. , Taylor E. W. , Lung F. W. , Chung A. S. , Chase G. A. , Maestri N. E. , Meyers D. A.
Published: June 2005

The two‐point lod score linkage analysis of familial Alzheimer's disease is sensitive to the parameters of age‐dependent penetrance rate, phenocopy rate, heterogeneity, and marker gene frequency. If unsuitable parameters are used, it may lead to false negative evidence against linkage. However, it is clear that, in some cases, it may lead to false positive evidence of linkage. © 1993 Wiley‐Liss, Inc.
Is a single mutation at the same locus responsible for all affected cases in a large Alzheimer pedigree (FAD4)?
Authors: Martinez Maria , Campion Dominique , Babron Marie‐Claude , Clerget‐Darpoux Françoise
Published: June 2005

Analysis of marker segregation in the large Alzheimer pedigree, FAD4, leads to the conclusion, with a type I error of 5%, of linkage heterogeneity between two branches of the pedigree: the disease cosegregates with chromosome 21 markers flanking the APP area in one branch and not in the other one. Thus, we conclude that a single mutation in the chromosome 21 region surrounding APP cannot be responsible for all the affected cases in this pedigree. © 1993 Wiley‐Liss, Inc.
Combined segregation and linkage analysis of late‐onset Alzheimer's disease in Duke families using Gibbs sampling
Authors: Faucett Cheryl , Gauderman W. James , Thomas Duncan , Ziogas Al , Sobel Eugene
Published: June 2005

We illustrate the use of Gibbs sampling for combined segregation and linkage analysis using late‐onset families in the Duke Alzheimer's disease (AD) data set. The disease penetrance model is flexible, incorporating variable age of disease onset, sporadic cases, and unknown or uncertain ages of AD onset. Model parameters (including allele frequencies) and lod scores are estimated, and a correction for ascertainment is made. Little indication of linkage was observed for any chromosome 19 or 21 marker. However, there was strong evidence for the existence of an AD major gene under an autosomal dominant/sporadic model. © 1993 Wiley‐Liss, Inc.
Methods and applications of genetic analysis in the study of cardiovascular disease: A summary of contributions to GAW8
Authors: Wilson Alexander F.
Published: June 2005

The analyses of data provided for the cardiovascular disease section of Genetic Analysis Workshop 8 are briefly summarized. Methods using twin, segregation, and linkage analyses are used to determine, characterize, and localize genetic components involved in the etiology of cardiovascular disease and to explore the interaction of these components with known environmental risk factors. © 1993 Wiley‐Liss, Inc.
Lipid data from NHLBI veteran twins: Interpreting genetic analyses when model assumptions fail
Authors: Williams Christopher J. , Wijesiri U. W. L.
Published: June 2005

Analyses were performed on lipid data from the NHLBI Veteran Twin Study. The analyses focused on longitudinal multivariate models, describing how the genetic effects on lipids vary over time. Our pedigree‐based model selection approach allows simultaneous estimation of both covariance structure parameters and regression parameters. The analyses reveal strong correlations between additive genetic effects over time, implying that genetic effects on lipids are somewhat constant throughout the life span represented within this sample. Both univariate preliminary analyses and robust fitting applied to the longitudinal models indicate that several assumptions underlying the twin analyses are violated. Although variance component and correlation parameter estimates are not much changed by robust fitting analyses, questions remain about the behavior of parameter estimates in multivariate genetic models under departures from model assumptions. © 1993 Wiley‐Liss, Inc.
Clustering of high density lipoprotein cholesterol levels in premenopausal and postmenopausal female twins
Authors: Harris Emily L. , Falk Roni T. , Goldstein Alisa M. , Park Lawrence P.
Published: June 2005

Previous family and twin studies indicate that genetic variation makes an important contribution to individual variation in high density lipoprotein cholesterol (HDL) levels, even after adjustment for covariates (such as obesity and alcohol consumption) that also cluster in families. However, most studies assume that genetic mechanisms affecting variation in HDL level are the same in all subgroups of the population (e.g., men versus women, by age). Using data from the Kaiser‐Permanente Women Twins Study, we found different patterns of clustering for monozygotic (MZ) and dizygotic (DZ) twins depending on menopausal status. Premenopausal MZ twins were more similar than postmenopausal MZ twins (ri = 0.79 and ri = 0.61, respectively, after adjustment for age, alcohol consumption, smoking status, degree of obesity, and leisure‐time exercise); premenopausal and postmenopausal DZ twins were alike to the same extent (ri = 0.31 and ri = 0.32, respectively, adjusted as above). These data suggest that either postmenopausal MZ twins have a greater degree of shared environment than postmenopausal DZ twins (e.g., postmenopausal female hormone use) or that genetic mechanisms that affect individual variation in HDL level differ in pre‐ and postmenopausal women. Data were not available on postmenopausal female hormone use. If genetic mechanisms that influence variation in HDL levels differ between pre‐ and postmenopausal women, genetic epidemiologic methods that assume that genetic and environmental sources of variation are the same for all groups of individuals may lead to false conclusions. © 1993 Wiley‐Liss, Inc.
A genetic analysis of cardiovascular disease risk factor clustering in adult female twins
Authors: Mosteller M.
Published: June 2005

Risk factors for cardiovascular disease have been shown to cluster in adult populations of men and women [Criqui et al., 1980]. In a population of adult female twin pairs (ages 18–85), body mass index, systolic and diastolic blood pressure, and high and low density lipoprotein levels were found to exhibit significant clustering. Path analysis was used to resolve the risk factor correlations into genetic, environmental, and age‐related components. © 1993 Wiley‐Liss, Inc.
Effect of ignoring genotype‐environment interaction on segregation analysis of quantitative traits
Authors: Tiret Laurence , Abel Laurent , Rakotovao Roger
Published: June 2005

Thirty replicates of 200 nuclear families (6 members each) were generated under three GxE interaction models. Segregation analyses of these data were performed using a regressive model taking into account an interaction effect or not. Results showed that ignoring the GxE interaction markedly decreased the power for accepting a major gene and led to serious bias in parameter estimates. © 1993 Wiley‐Liss, Inc.
Use of the regressive models in linkage analysis of quantitative traits
Authors: Demenais Florence , Lathrop Mark
Published: June 2005

Use of the regressive models to account for residual familial correlations in linkage analysis of complex quantitative traits can increase the power to detect linkage. This is especially observed when the effect of the gene to be mapped is small or when the residual correlations are substantial. © 1993 Wiley‐Liss, Inc.
Two‐locus and bivariate segregation analysis of HDL‐C and apo AI
Authors: Xu J. F. , Prenger V. L. , Coresh J. , Beaty T. H.
Published: June 2005

Two‐locus and bivariate segregation analyses of HDL‐C and apo AI were carried out using the GAW8 Berkeley data set. For HDL‐C, results are ambiguous. Both the mixed environmental model and the mixed Mendelian model fit the data equally well. For apo AI, however, univariate one‐locus segregation analysis suggests a Mendelian major gene controlling its levels. Moreover, two‐locus analysis suggests a second major gene is involved. Bivariate segregation analysis indicates these data cannot resolve the question as to whether a single Mendelian major gene with pleiotropic effects controls levels of both HDL‐C and apo AI in humans. © 1993 Wiley‐Liss, Inc.
Segregation analysis under an alternative formulation for the mixed model
Authors: Stricker C. , Fernando R. L. , Elston R. C.
Published: June 2005

Different approaches for segregation analysis that have been proposed in the past are compared to a new approach by Fernando et al. [submitted], the finite polygenic mixed model, analyzing a real and a simulated data set. © 1993 Wiley‐Liss, Inc.
Segregation analysis of diastolic blood pressure in a large pedigree
Authors: Weissbecker Karen A.
Published: June 2005

Hypertension, a major risk factor for cardiovascular diseases, is thought to be inherited to some extent. However, the nature of its genetic component remains unresolved. In the present study, data from a single large kindred (the HGAR1 pedigree) were used to search for evidence of single gene and multifactorial effects on diastolic blood pressure. Commingling analyses found that a mixture of three distributions fit the data significantly better than a single normal distribution, suggesting a major effect influencing diastolic blood pressure levels. However, segregation analysis, using regressive models, indicated that the transmission probabilities were not consistent with Mendelian expectations. There was no evidence of either major gene or polygenic effects on diastolic blood pressure levels in this family. © 1993 Wiley‐Liss, Inc.
The ontogeny of sperm specific lactate dehydrogenase in mice
Authors: Goldberg Erwin , Hawtrey Christopher
Published: June 2005

Testes of sexually mature mice (Mus musculus) contain a unique lactate dehydrogenase isozyme associated with the spermatozoan cell. This isozyme differs in subunit composition and reactivity to the substrate DL‐α‐hydroxyvalerate when compared to the usual five isozymes found in other tissues. It has been termed LDH‐X and has the same mobility as LDH‐5 when subjected to electrophoresis on standard polyacrylamide gels. This enzyme first appears during development at the time spermatocytes first mature in the testes.

From the time of birth until sexual maturity is reached the specific activity of LDH in testes extracts does not change appreciably. When the mice have reached the weight of 6.5 to 7.5 g with a testes weight of 20 mg, which is equivalent to an age of 15 to 17 days postpartum, LDH‐X appears. It is at approximately this time that the first differentiative division of the primitive germ cell, the spermatogonium, occurs. For the next period of time, 15–20 days, the testes grow and differentiate at a rapid rate and during this same period the specific activity of the sperm LDH also increses.

Histochemical evidence indicated that activity of LDH‐1, 2, and 3 is highest in the interstitial cells while LDH‐X activity is restricted to the cells that are close to the lumen of the testicular tubule.
Cell mobility in fused homo‐ and heteronomic tissue fragments
Authors: Weston J. A. , Abercrombie M.
Published: June 2005

If specific reorganization in fused heteronomic tissue fragments results from the movements of individual cells, this mobility should also promote intermingling of cells at the boundary between fused tissue fragments. To test this, tritiated‐thymidine labeled embryonic heart and liver fragments were fused in heteronomic and homonomic combinations with unlabeld heart and liver tissue, and maintained in vitro up to 48 hours after fusion. Radioautographs revealed that tissue reorganization occurred in heteronomic combinations in shaker culture, but intermingling of cells at the border between labeled and unlabeled fragments was negligible in both heteronomic and homonomic fusions. It is concluded that individual cells are probably not freely motile within intact tissue. This conclusion supports the predictions based on the hypothesis of “contact inhibition” of cell movement.

The characteristic tissue reorganization in heteronomic combinations, at least for intact heart and liver tissue, is presumed to result from the spreading of stable adhesions of cellular pseudopodial extensions rather than from the free locomotion of individual cells. The spreading of one tissue over another during reorganization seems to be counteracted by weak adhesions to substrates since heteronomic fusions allowed to remain on agar or Millipore filter substrates do not reorganize.
Some properties of a macromolecular extract producing developmental arrest of injected embryos (Rana pipiens)
Authors: Melton Charles G. , Kimmel Donald L.
Published: June 2005

Several molecular species, suspected of being responsible for the blastular arrest that follows injection of adult liver extracts into Rana pipiens zygotes, were investigated by biochemical assays of the extracts, by injection of the extracts after removal of these molecular species, and/or by injection of these species themselves into zygotes. Negative results have ruled out, with varying degrees of certainty, DNA, RNA, basic protein, polysaccharide, neutral protase, ribonuclease, phosphodiesterase I, and two varieties of deoxyribonuclease (DNase). The arrest‐producing component is tentatively identified as a non‐basic protein, although the evidence is not yet conclusive.

Injected neutral DNase (± trypsin) failed to produce either consistent arrest or embryonic chromosomal abnormalities. A review of the literature on DNase effects in vivo also revealed no clear precedent indicating that arrest can be attributed to derangement of the embryonic chromosomes by a DNase in the extracts.
Isolation of planarian neoblasts and their behavior in Vitro with some aspects of the mechanism of the formation of regeneration blastema
Authors: Betchaku Teiichi
Published: June 2005

A method of isolating neoblasts from Dugesia dorotocephala and the process of their aggregation in vitro are described. Morphology and behavior of gastrodermal cells and fixed parenchyma cells in vitro are also reported. Basically the neoblast is an oval cell with a large primary process and a finer secondary process at the opposite pole. Neoblasts have strong mutual affinity and very little affinity with other types of cells. The only observed method of locomotion of neoblasts in vitro was the contraction of the firmly attached primary processes between two or more neoblasts, which ends in their aggregation. Gastrodermal cells and fixed parenchyma cells are the most active migratory cells in vitro. With the observation of the cell movement both in vitro and in the fragments of the body, it was concluded that the primary accumulation of neoblasts at the open wound is not due to the active migration of neoblasts from the intact region as surmised by some other authors but due to the aggregation of local neoblasts. The migration of gastrodermal cells from the wound area causes the condensation of the parenchyma at the wound; the cytolyses of cells other than neoblasts in the parenchyma under a hypotonic condition evoke the aggregation of neoblasts. Active mitosis increases the number of neoblasts in the regeneration blastema. The “Parenchymal movement” or the mobility of the fixed parenchyma cells which must be responsible for the cellular transportation in the parenchyma was discussed.
The Effect of Light and Light Deprivation upon the Ultrastructure of the Larval Mosquito Eye. I. Polyribosomes and endoplasmic reticulum
Authors: White Richard H. , Sundeen Carol Deuel
Published: June 2005

By comparison with a photoreceptor cell that has been exposed to light for at least several hours, a cell from an animal grown in darkness is deficient in both rough and smooth endoplasmic reticulum. The free ribosomes of cells under either condition appear to be single or randomly clumped. Illumination of a previously light deprived cell stimulates the formation of free polyribosomes having a characteristic, probably helical, organizaation. They are found at first in association with the rough endoplasmic reticulum, and after 30 minutes, fill the cell. The polyribosomes are mostly gone after two hours of illumination. Illumination also stimulates an increase in the amount of endoplasmic reticulum, which reaches its maximum density by 12 hours of illumination. The discussion is concerned with the possible significance of these light induced ultrastructural changes to the protein metabolism of the photo‐receptor cell.
Field demonstration of polarotaxis in the fish Zenarchopterus
Authors: Waterman Talbot H. , Forward Richard B.
Published: June 2005

Oriented responses to linearly polarized light have been quantitatively confirmed in the marine teleost Zenarchopterus studied in underwater field experiments with the aid of SCUBA. During six successive mornings 2485 heading measurements were made on 36 untrained fish. With natural illumination spontaneous azimuth orientation is mutiply dependent on the sun's bearing and apparently on the natural polarized light of blue sky or water as well as the direction of the interisland channel where the fish were collected. When a dichroic filter is placed over the fish polarotaxis is manifest as directional preferences mainly perpendicular and less strongly, parallel to the plane of polarization. This response is most intense when the imposed e‐vector differs maximally (by 60°–90°) from that predominant in the natural illumination (90° to the sun's bearing). When the sun's disc is partly or wholly obscured by clouds polarotaxis is significantly weakened even though the polarization pattern visible to the fish through the dichroic filter would be virtually unchanged. More than moderate angular turning rates by the fish swimming in the experimental vessel also weaken their response to the e‐vector. Individual fishes show different reactions: about one‐third of those in full sunlight oriented strongly parallel and perpendicular to the imposed e‐vector, another smaller group appears to orient obliquely to the polarization plane while the remainder respond weakly to the e‐vector if at all. Continuing work is required to demonstrate the physiological mechanism and ecological significance of these behavioral patterns.
Gene transcription in mosaic embryos. I. The pattern of RNA synthesis in early development of the coot clam, Mulinia lateralis
Authors: Kidder Gerald M.
Published: June 2005

Of the many investigations reported in the past decade concerning the pattern and significance of RNA synthesis in early development, relatively few have involved mosaic embryos. These investigations have revealed a common pattern of RNA synthesis among embryos of anamniotic deuterostomes and a few have indicated that this pattern may not be shared by their protostome counterparts. The present study provides data for a thorough comparison of RNA metabolism in a mosaic embryo with that of regulative embryos.

Oocytes and embryos of the coot clam, Mulinia lateralis, were pulse‐labeled with tritiated uridine and their RNA was extracted and analyzed by sucrose gradient centrifugation and MAK chromatography. Little or no RNA synthesis could be detected in oocytes before fertilization. During cleavage, newly synthesized RNA is primarily DNA‐like, heterogeneous in size and base composition and of lower average G + C content than ribosomal RNA. A prominent class of short‐lived RNA molecules sedimenting at 8–10s is also transcribed during cleavage and continues to be produced at least through gastrulation. Transfer RNA appears to be synthesized as early as mid‐ to late‐cleavage. Whereas ribosomal RNA synthesis was undetectable in these experiments prior to gastrulation, ribosomal and transfer RNA synthesis predominate in the larval stages. These results demonstrate that the temporal pattern of RNA synthesis common to embryos of the lower deuterostome phyla can be found in protostome embryos as well, and therefore that mosaic development need not entail a unique pattern of gene transcription.
Endoderm movements in the chick embryo between the early short streak and head process stages
Authors: Rosenquist Glenn C.
Published: June 2005

Endoderm movements in the chick embryo between the early short streak and head process stages were studied by tracing the migration of tritiated thymidine‐labeled grafts excised from explanted donor embryos and transplanted to identical positions in explanted recipient embryos of the same stage.

During the primitive streak stages, the endoderm layer migrates in an orderly fashion away from a center of the primitive streak which is located about one fourth to one third of the distance from its anterior to its posterior end; all grafts placed in the endoderm anterior, lateral or posterior to this center migrated respectively anteriorly, laterally and posteriorly toward the outer margin of the area pellucida. During this migration, the grafts became narrowed and stretched out to conform with the rounded circumference of the area pellucida. Endoderm cells located in the endoderm center itself never completely left the streak, but spread out in all directions until they occupied a central circular area destined to form the gut.
Genetic and embryological studies of albinism in Rana pipiens
Authors: Browder Leon W.
Published: June 2005

Albinism in the leopard frog is due to a recessive gene (alb) in the homozygous condition. Heterozygous females produce normal, pigmented eggs. After fertilization of these eggs by sperm from another heterozygote, all progeny remain normally pigmented until after hatching when the albino progeny can be detected. Since melanin deposition in oocytes occurs prior to segregation of the alb and + alleles, the wild‐type gene may be transcribed and translated in the oocytes. Alternatively, the product of the + allele may be synthesized exogenously and incorporated into the oocytes during oogenesis.

The results of embryonic transplant experiments suggest that the albino gene is expressed within the neural crest derivatives. Albino hosts support differentiation of wild‐type melanophores. Albino dorsal mesoderm induces melanophore differentiation in wild‐type neural crest derivatives.

Albinos were less viable than their wild‐type siblings in the laboratory environment. Albino larvae developed scoliosis with high frequency, and albino frogs had a higher mortality rate after metamorphosis than their wild‐type siblings.
Polyspermy‐preventing mechanisms in the golden hamster egg
Authors: Barros C. , Yanagimachi R.
Published: June 2005

The zona pellucida of a fertilized egg recovered from an artificially inseminated female reacts to capacitated spermatozoa differently from the zona pellucida of an unfertilized egg. The zona of a fertilized egg shows a sperm‐refractory response, “zona reaction,” so that capacitated spermatozoa neither firmly attach to nor penetrates it. On the other hand, the zona of an unfertilized egg shows no such sperm‐refractory response and many spermatozoa attach to and penetrate it. The zona reaction was observed not only in recently penetrated eggs but also throughout cleavage.

Judging from the earliest fertilization stage at which we observed a complete zona reaction, it is estimated that this reaction is completed in less than 15 minutes after sperm attachment to the vitellus.

One hundred per cent of the fertilized eggs recovered from females five hours after artificial insemination were refertilized in vitro after removal of the zona pellucida by trypsin‐treatment. The incidence of refertilization decreased when the eggs were recovered at later times. Only 3% of the eggs recovered at nine hours after artificial insemination were refertilized. Judging from the fertilization stage at which eggs were no longer refertilizable, it has been estimated that the completion of the vitelline surface block to polyspermy is established in not less than two nor more than three to three and one‐half hours.

Possible causes of polyspermy encountered with in vitro fertilized eggs are discussed.
Reversible re‐fusion of frog blastomeres and additional cleavage effects of chloramphenicol and other respiratory inhibitors
Authors: Lamy Loraine , Melton Charles G.
Published: June 2005

Chloramphenicol (CAP) produced an unusual cleavage anomaly in Rana pipiens embryos involving re‐fusion of normal looking 6 to 12 hour blastomeres into irregularly shaped syncytial mounds. This occurred whether the CAP was added then or earlier. The condition was usually terminal, but often at lower doses or following CAP removal the mounts re‐cleaved and the embryos resumed development. Preliminary histological verification of blastomere fusion has been obtained.

The same anomaly was produced by two other inhibitors, rotenone and the L‐isomer of CAP. These are without effect on mitochondrial protein synthesis in other systems but do share with high doses of D‐CAP a direct inhibition of respiration at the NADH oxidase level. Another such inhibitor, amytal, failed to affect cleavage, presumably because of poor penetration. Instead, amytal produced uniform developmental arrest at later stages characteristic for each dose. Similar but less uniform results were obtained with lower doses of D‐ and L‐CAP, rotenone, cyanide, and dinitrophenol. All of these, however, also produced cleavage arrest at higher doses, including prevention of first cleavage altogether at high enough concentrations of each.

This disagrees with the older literature in the case of cyanide, to which early cleavage is purported to be insensitive and the onset of gastrulation unusually sensitive. There is also an apparent conflict between our cyanide‐rotenonechloramphenicol results, suggesting that cleavage is dependent on respiration, and the work of others on cleavage under anaerobiosis, suggesting not. Several hypotheses which would resolve this conflict, including that of an oxidative reserve in the eggs, are presented and discussed.
Restriction of color in the rat with associated sterility in the male and heterochromia in both sexes
Authors: Gumbreck Laurence G. , Stanley Allan J. , Allison John E. , Easley Ronald B.
Published: June 2005

The effects of a new dominant gene in the rat are described. This gene, restricted (Hr e), causes a marked restriction of the colored areas of the body in the hooded, irish and self color patterns. Males with this restricted color pattern (Re) exhibit testicular tubular dysgenesis with consequent sterility, and a slightly reduced growth rate. The histological structure of the testis is described. Various experimental studies with the Re males are presented. These studies indicate that the cause of the sterility is a relative insensitivity of the germinal epithelium to pituitary follice‐stimulating hormone. There is a high incidence of heterochromia in Re rats with cream coat color and ruby eye.
On the mechanism of action in gonadotropic stimulation of oocyte maturation in Xenopus laevis
Authors: Merriam R. W.
Published: June 2005

Ripe ovarian follicles of Xenopus laevis, like those of Rana pipiens are capable of responding to gonadotropins even when their peritoneal epithelium and theca are removed by collagenase. Puromycin or cycloheximide stop oocyte maturation whether stimulated by gonadotropins or progesterone in vitro. Actinomycin D does not affect progesterone‐induced maturation but does show variable inhibition with gonadotropin‐induced maturation. Both gonadotropins and progesterone induce oocyte maturation to germinal vesicle breakdown in the same time. These data are taken as evidence that gonadotropins do not induce a macromolecular synthesis necessary for steroid release but rather simply induce the release of existing steroid in follicular epithelial cells.
Expression of a sex‐linked gene in standard and fusion‐chimeric mice
Authors: Dunn G. R.
Published: June 2005

The single‐active‐X hypothesis states that in any mammal with more than one X chromosome per cell, only one X is active in each cell. The hypothesis further states that X‐chromosome differentiation occurs randomly in each cell early in development and subsequently is stable. The phenotype of a mammal heterozygous for a sex‐linked gene will thus be mosaic, and any interaction of different X alleles can occur only on the intercellular level. Another hypothesis, the “complemental‐X” hypothesis, explains the phenotype of a sex‐linked gene heterozygote in terms of intracellular allelic interaction.

The validity of intercellular interaction in sex‐linked gene heterozygotes was tested in the mouse by making fusion chimeras of embryos carrying different X‐linked alleles and comparing the chimeric phenotype to that of a standard heterozygote.

The X‐chromosome marker Greasy (Gs) was shown to affect ten parameters of hair structure, four of which were chosen to establish a series of hair types. It was found that Gs/ +. mice had almost the entire range of hair types, while wild‐type and Gs/ mice showed restricted hair type distributions, significantly different from each other and from Gs/ +. It was also found that the Gs/ + phenotype could not be accounted for by additivity of the wild‐type and mutant hair‐type distributions.

Some of the fusion chimeras had phenotypes similar, if not identical, to that of standard Gs/ + mice in all respects except the rate of change in the distribution of hair types with age. This discrepancy could be accounted for on the basis of cell selection.

These data support the conclusion that intercellular interaction can account for the observed phenotypes of sex‐linked gene heterozygotes.
Epidermal‐mesodermal interaction during morphogenesis of the limb regeneration blastema in larval salamanders
Authors: Stocum David L. , Dearlove George E.
Published: June 2005

The question was asked whether the proximo‐distal regional organization of regenerating urodele limbs is the result of an epidermal‐mesodermal interaction, as is the case in the embryonic limb bud. Epidermal deletion experiments on regeneration blastemas of various stages have answered this question in the affirmative. The mechanisms involved in the morphogenesis of the regeneration blastema are therefore very similar to those operating in the morphogenesis of embryonic limb buds.
The influence of olfaction on sexual behavior in the male golden hamster (Mesocricetus auratus)
Authors: Lisk Robert D. , Zeiss Jacob , Ciaccio Leonard A.
Published: June 2005

Ablation of the olfactory bulbs terminates the sexually oriented behavior patterns shown by the male hamster towards the female. All aspects of overt copulatory behavior including mounting are immediately eliminated. Investigatory behavior is decreased significantly and orientation of attention to the hindquarters of the animal being investigated (sexual orientation) is lost over a one to two week interval. This disruption of sexually oriented behavior patterns occurs regardless of the degree of experience of the male in mating prior to the bulbectomy. Unilateral bulbectomy or sham bulbectomy does not disrupt, even temporarily, the mating pattern.

Evidence that the lack of mating behavior following bulbectomy is indeed due to anosmia was provided by rendering animals temporarily anosmic by use of zinc sulfate in the nasal cavities. Full recovery of sexual activity occurred within four to six days following this treatment. A second treatment produced a similar result.

Naive males, raised in isolation, can show a normal copulatory pattern on first exposure to a receptive female. Naive males do not distinguish between diestrus (non receptive) and estrus (receptive) vaginal secretions from the female.

The release of sexual arousal requires olfactory input in the male hamster, conditioning to other cues does not occur. However, differentiation between receptive and non‐receptive females appears to be a positive learned response. The absolute dependence of the male hamster on olfactory cues for sexual arousal has an obvious adaptive value in a species where the female tends to be dominant in encounters and the male, if unable to escape, can be maimed or killed during the course of a fight.
Light microscopic and fine structural changes in the brown adipose tissue from torpid and aroused pigmy mice (Baiomys taylori)
Authors: Hudecki M. S. , Privitera C. A.
Published: June 2005

Changes in the composition and morphology of interscapular brown adipose tissue (BAT) are described for the adult pigmy mouse, Baiomys taylori, in its short‐term, cold‐torpor cycle. The study includes an analysis of tissues from, (1) room temperature (RT) controls, (2) RT, 24 hour starvation animals, (3) mice exposed on 15°C for six hours, (4) torpid animals (24, 48, and 72 hours at 15°C), and (5) mice allowed to arouse from torpor at RT for 1, 2, 5, 9, 24, and 288 hours. Control brown fat is composed predominately of lipid vacuoles, glycogen particles, and mitochondria with lamellaelike cristae. Starvation at RT has no marked effect on either the BAT energy stores, or the mitochondrial morphometry. Short exposure to 15°C brings about a pronounced depletion in the lipid and glycogen content, and a significant swelling in the mitochondria. Brown fat from torpid mice is deplete of lipid and glycogen. Mitochondria remain enlarged, and have parallel, closely‐packed cristae. The lipid and glycogen reappear in the early hours of arousal. The multilocular character of the control BAT is reached in five to nine hours after initiation of arousal. Throughout the arousal the mitochondria retain their cold‐induced morphological alterations. Pinocytotic microvesicles in the capillary endothelium and in the brown adipocytes are observed in different degrees, in all experimental groups. With the histological changes in evidence, the participation of pigmy mouse brown fat in non‐shivering thermogenesis in situations of cold exposure, and arousal from torpor, is discussed.
Development of pigmentation in the eyeless mutant of the Mexican axolotl, Ambystoma mexicanum, Shaw
Authors: Epp Leonard G.
Published: June 2005

The development of pigment pattern in the eyeless mutant of Ambystoma mexicanum is described. Pigmentation, is much enhanced in this mutant through increased size and branching of melanophores. The eyeless mutant does not possess the ability to adapt to its background, nor does it blanch in darkness.

Reciprocal neural crest transplants between eyeless mutants and eyed siblings indicate no intrinsic neural crest differences in the eyeless mutant. Normal optic functioning after implantation of an eye in the mutant leads to diminished pigmentation. Enhanced pigmentation in the eyeless mutant is postulated as due to abnormally high secretion of MSH by the pituitary causing normal pigment‐producing systems to operate beyond normal limitations.
Avian scale development. I. Histogenesis and morphogenesis of the epidermis and dermis during formation of the scale ridge
Authors: Sawyer Roger H.
Published: June 2005

Scale development in the chick embryo can be considered as consisting of two major phases. First, a definitive scale ridge is formed from a simple two‐layered epidermis. This phase consists of five stages: preplacode, placode, asymmetrical placode, hump stage, and definitive scale ridge. The second phase involves the elongation of the definitive scale ridge to give rise to the overlapping scales of the adult bird. During elongation a new (inner) epidermal surface is formed, which is histologically less differentiated than the outer epidermal surface. A timed‐sequence study has shown that the placode gives rise mainly to the outer epidermal surface of the definitive scale ridge, while the inter‐placode region becomes the thinner epidermis at the scale apex.
Avian scale development. II. A study of cell proliferation
Authors: Sawyer Roger H.
Published: June 2005

The spatial and temporal distribution of DNA synthesis and the cell cycle duration change during scale development in the chick embryo. Previous histological studies indicated that the two epidermal surfaces of the scale, outer and inner, originated from the placode and interplacode regions, respectively. The present autoradiographic study demonstrated that the epidermal placodes did not incorporate tritiated thymidine for 20–35 hours after their appearance, while the interplacode regions incorporate continuously during this period. The synthetic indices (number of labeled nuclei/total number of basal nuclei) of the two surfaces of the scale also differed early in formation. An explanation for this observation became evident, when it was found that the generation time of the cells constituting the outer and inner surfaces of the scale differed during development. The DNA synthetic phase was constant, whereas the G1‐phase varied concurrently with the generation time.
In vitro fertilization and capacitation‐like interaction in the hydroid Campanularia flexuosa
Authors: O'Rand Michael G.
Published: June 2005

Fertilization in Campanularia flexuosa is internal. In both freshly collected colonies and laboratory cultured colonies eggs may be removed from the gonangium still attached to the blastostyle as a single packet surrounded by epithelial cells. Packets from mature gonangia of freshly collected colonies contain spermatozoa although the eggs are immature. The spermatozoa remain inside the packet to await egg maturation. Packets from mature gonangia of laboratory cultured colonies do not contain spermatozoa if male and female colonies are cultured separately. Eggs in such packets may be fertilized by the addition of spermatozoa. Removal of the epithelial cells which surround the eggs in the egg packet results in loss of fertilizability. Treatment of the egg packets with 0.75% trypsin also results in a loss of fertilizability. However, fertilizability may be restored by exposure of spermatozoa to non‐trypsin treated female epithelial cells. Thus, apparently a definite interaction must occur between female epithelial cells and spermatozoa prior to fertilization. This interaction may be analogous to mammalian capacitation and the necessary conditioning of amphibian sperm prior to fertilization.
The developmental biology of annual fishes. III. Pre‐embryonic and embryonic diapause of variable duration in the eggs of annual fishes
Authors: Wourms John P.
Published: June 2005

Annual fishes can maintain permanent populations in temporary aquatic habitats since the population survives dry seasons in the form of diapausing eggs. Populations persist even though subject to erratic environmental cycles and recurrent ecological catastrophes.

Developmental arrest occurs at one or all of the following stages: Diapause I (Dispersed cell phase); Diapause II (Long somite embryo); Diapause III (Prehatching). In Austrofundulus, Diapause I is facultative. Diapause II and III are obligate, long and variable (105 ± 20 days each). Subpopulations (about 10%) of “escape eggs” bypass Diapause II and/or Diapause III. Pterolebias and Rachovia eggs behave much like those of Austrofundulus. In Rachovia, the duration of Diapause II is 80 ± 33 days and of Diapause III at least 61 ± 23 days. Subpopulations of “escape eggs” are present. Cynolebias and Nothobranchius can undergo facultative arrest at Diapause I and II and enter obligate arrest at Diapause III. Annual species of Aphyosemion can undergo facultative arrest at Diapause I and II, and an obligate arrest at Diapause III. A few species may also experience obligate arrest at Diapause II. A short term arrest phenomenon, “retarded hatching,” sometimes is encountered among non‐annual Aphyosemions and other non‐annual cyprinodonts.

Survival strategy is based on the “multiplier effect”; i.e., interposition into the developmental pathway of three branch points containing diapause stages of prolonged, variable duration generates eight different distributions of total developmental time. Thus, a single egg population of identical age can generate several subpopulations, all of which develop according to different schedules. A developmental program is established which permits the repeated loss of individual eggs under conditions which may initiate hatching but do not allow for maturation and successful reproduction. The “multiplier effect” augmented by other adaptations guarantees that some portion of the egg population will survive to reproduce.
Response of the toad, Xenopus laevis, to circulating antigens. I. Cellular changes in the spleen
Authors: Turner Rodney J. , Manning Margaret J.
Published: June 2005

The localization, cytology and proliferation of lymphoid cells in the spleen of Xenopus laevis were investigated in normal toads and in toads stimulated with sheep erythrocytes (SRBC) or human gamma globulin (HGG). In toads given HGG in adjuvant, considerable increase in spleen weight was found both before and during serum antibody production; autoradiographic and histological examination showed that cell proliferation and formation of pyroninophilic cells had markedly increased in the splenic lymphoid tissue, particularly in the white pulp, but to a considerable extent also in the red pulp. Cell proliferation was also present, although less pronounced, after injections of HGG in saline. In toads given SRBC, most proliferation occurred in the white pulp, particularly towards the periphery of the follicles.

Light and electron microscopy revealed that the lymphoid cells in the Xenopus spleen — in particular small lymphocytes and large pyroninophilic cells — are similar to those implicated in the mammalian immune response. However, cell clusters resembling mammalian germinal centres were absent. Furthermore, cells resembling the mammalian plasma cell were rare in both normal and immunized toads.
Polyspermic fertilization in pigs after tubal deposition of excessive numbers of spermatozoa
Authors: Hunter R. H. F.
Published: June 2005

The incidence of polyspermy has been examined in mature pigs in relation to the site of deposition of whole semen. Oestrous gilts were inseminated surgically some 12 hours before induced ovulation, semen being introduced into the Fallopian tube on one side of the tract and into the contralateral uterine horn adjacent to the utero‐tubal junction as a control. Animals were slaughtered between five hours 30 minutes and ten hours five minutes after completion of ovulation.

There was no detrimental effect of instilling whole semen directly into the tubal isthmus on the proportion of eggs recovered. Ninety‐three per cent of the 145 eggs examined were fertilized. Twenty‐nine eggs recovered from nine animals had undergone polyspermic fertilization: 33.8% of the fertilized eggs from the inseminated tubes were polyspermic compared with 5.2% of the eggs from the side of uterine insemination (p < 0.001). Penetration of the vitellus by two spermatozoa constituted the principal anomaly of fertilization, but trispermy, tetraspermy and higher forms were also found. In such eggs, the female and only a single male pronucleus were conjugating. It is concluded that the incidence of polyspermic fertilization in pigs is significantly increased when large numbers of capacitated spermatozoa confront the newly‐ovulated eggs. The rate of capacitation of boar sperm has been discussed, as has the fate of polyspermic eggs.
Morphometrics of sexual dimorphism in an arrhenotokous mite, Ornithonyssus bacoti (acari:mesostigmata)
Authors: Oliver James H. , Herrin C. Selby
Published: June 2005

Diploid Ornithonyssus bacoti females from an inbred laboratory colony are more variable in more external morphological characters than haploid males maintained under identical colony conditions. Prejudiced selection of characters or use of a small sample size can provide data suggesting greater variability in males. When large numbers of characters on many mite specimens are compared by F‐tests of variances, coefficients of variation, generalized variances (determinant of variance‐covariance matrices) and tests of homogeneity of variance‐covariance matrices, general phenotypic variation is greater in females. The agreement between univariate and multivariate tests allows additional confidence in the conclusion (tables 2–7).
T3‐ and T4‐induced rates of metamorphosis in immature and sexually mature larvae of Ambystoma tigrinum (amphibia: Caudata)
Authors: Norris David O. , Platt James E.
Published: June 2005

Rates of T3‐ and T4‐induced metamorphosis in sexually mature and immature tiger salamander larvae (Ambystoma tigrinum) from a single local population were proportional to daily injected doses (1.0, 10 1, 10 2, or 10 3 μg T3, or T4). Larvae were maintained at 16° C on 12L:12D photoperiod, and were fed beef liver daily. Metamorphic rates were compared as the mean number of days to achieve 50% resorption of the gills (GR50). Saline‐injected and untreated control larvae exhibited no metamorphic tendencies during the experiments. Immature larvae were induced to metamorphose with as little as 0.05 ng T3 or T4/g body weight/day. Small, sexually mature larvae were less sensitive to a given dose of T4, especially at the lowest doses. Large sexually mature larvae did not differ from small larvae. It is presumed that the observed differences in sensitivity would not account solely for the observations of neoteny in this species. Metamorphosis was not influenced by sex. T3 and T4 are equipotent inducers of metamorphosis in immature larvae under conditions of this experiment except that some animals receiving the lowest dose of T3 did not undergo metamorphosis. Larvae receiving 10−1 μg T4/day did not metamorphose at 5° C, and gill resorption was slower for larvae at 10° C as compared to 16° C. GR50 for larvae maintained at 21° C was not different from 16° C.
Hamster sperm hyaluronidase. I. A bioassay procedure based on cumulus dispersion rate
Authors: Talbot Prudence , Franklin Luther E.
Published: June 2005

An in vitro bioassay for hyaluronidase activity has been developed based on cumulus dispersion rate. It was found that the logarithm of the time for complete cumulus dispersion and the logarithm of hyaluronidase activity are linearly related in three incubation media. These data have been used in constructing standard curves for the prediction of hyaluronidase activity from the observed time for complete cumulus dispersion. The technique is sensitive to low levels of hyaluronidase activity, is compatible with complex incubation media, and requires small volumes of test solution.