bluuebunny/crossref_metadata_2025 huggingface dataset:
Pedicle and antler regeneration following antlerogenic tissue removal in red deer (Cervus elaphus)
Authors: Li Chunyi , Suttie James M.
Published: June 2005

The physiological control mechanisms underlying the histogenesis of the pedicle, which precedes antler growth, from the frontal bones of male deer are poorly understood. The aim of this study was to investigate the extent of pedicle/antler regeneration after removal (for histological evaluation) of the antlerogenic region or pedicle tissue during pedicle development to determine whether the subsequent pattern of regeneration could contribute to the understanding of pedicle histogenesis and the mechanism of the transition between permanent pedicles and deciduous antlers. The contralateral pedicles of six stags were not removed and these data serve as controls. All deer were observed frequently and measurements of regeneration were made in March after all antler growth had ceased for that season. The developmental stage of the pedicle was determined by a combination of pedicle height measurements and histological studies. The results showed that pedicle formation histologically covers three stages: a period of intramembranous ossification (when the pedicle is less than 5 mm in height), a period when the ossification pattern changes (when the pedicle is between 5 and 28 mm in height) and a period of modified endochondral ossification (when the pedicle is over 30 mm in height). In all ossification stages some deer regenerated neither antlers nor pedicles. The pedicles which regenerated following the loss of antlerogenic tissue at the intramembranous ossification stage were shorter than the controls (P < 0.01), but longer than the pedicles regenerated after pedicle removal at the transitional stage in the pattern of ossification (P < 0.01). No pedicle tissue was regenerated if the pedicles were removed at the endochondral ossification stage and antlers were directly formed from the deer's head. Thus the final height of the regenerated pedicles was closely linked with the histological ossification stage of the original pedicle at removal. Antler regeneration took place at all stages but two deer grew pedicles only when tissue removal took place during the transition period. Overall the results provide evidence that the potential to regenerate a pedicle diminishes as the pedicle increases in height and the necessity for pedicle growth to precede antler growth also decreases. The fact that some deer, whose tissues were removed at the transition period of ossification change, regenerated pedicles but failed to generate antlers highlights the importance of this stage for the transition between the permanent pedicle and the deciduous antler. The results provide evidence for an hypothesis that it is the transition between ossification types which signals the end of pedicle development and the onset of antler development. © Wiley‐Liss, Inc.
In vivo and in vitro initiation of sperm motility using fresh and cryopreserved gametes from the pacific herring, Clupea pallasi
Authors: Pillai Murali C. , Yanagimachi Ryuzo , Cherr Gary N.
Published: June 2005

Pacific herring (Clupea pallasi) gametes were cryopreserved in a simple extender (15% dimethyl sulfoxide in herring Ringers). Sperm remained viable for over 7 months when kept at liquid nitrogen temperature. A rapid cooling rate by directly plunging into liquid nitrogen allowed a majority of the cells to remain viable after subsequent thawing at 26°C. Cryopreserved sperm initiated motility (activation) under both in vivo (in the micropyle area of the egg) or in vitro (in the presence of isolated sperm motility initiation factor or low sodium seawater) conditions. In addition to their ability to undergo activation, cryopreserved sperm were capable of fertilizing fresh eggs in a concentration dependent manner resulting in > 90% fertilization and embryonic development. Herring eggs cryopreserved in a similar manner as sperm remained intact in gross morphology. Although cryopreserved eggs were not fertilizable, both fresh and previously frozen sperm were activated in the micropyle areas of the chorions. The method we describe to cryopreserve gametes from this species is simple and is useful for future experimental studies of sperm‐chorion interaction when fresh material is unavailable. © Wiley‐Liss, Inc.
Involvement of the lysosomal system in yolk protein deposit and degradation during vitellogenesis and embryonic development in trout
Authors: Sire Marie‐France , Babin Patrick J. , Vernier Jean‐Marie
Published: June 2005

In adult female rainbow trout (Oncorhynchus mykiss), an immunocytochemical study of the oocyte has shown that a proteolytic enzyme, cathepsin D, is localized in multivesicular bodies (MVB) which begin to differentiate before the phase of vitellogenesis. Estrogens cause the liver to synthesize the protein vitellogenin (VTG), which then enters the systemic circulation. During vitellogenesis, endocytosed VTG is co‐localized with cathepsin D in the MVB. Assays of oocyte cathepsin activities have shown that the only proteolytic activity of note is that of cathepsin D. Along with the yolk proteins derived from VTG, this enzyme will be included in the central coalescent yolk mass.

With the installation of the yolk syncytial layer and the surrounding yolk vascular system, embryonic development is characterized by high lysosomal activity, especially in the syncytial layer. At this level, proteolytic activity concerns a cathepsin L, secreted as a proenzyme. We propose the hypothesis that cathepsin D, along with the yolk proteins in the yolk globules that break away from the yolk mass in the vitellolysis zone, activates the proenzyme and leads to protein degradation, which then becomes very rapid. © Wiley‐Liss, Inc.
Occlusion of the parietal eye induces a transient wavelength‐dependent shift in lizard thermoregulatory set points
Authors: Tosini Gianluca , Avery Roger A.
Published: June 2005

Thermoregulatory set points—i.e., the body temperatures at which heat‐seeking or cooling behavior are initiated—of the lacertid lizard Podarcis muralis were measured by infrared thermography before and after covering the parietal eye with light filters with different cutoff points. The results show that shielding the parietal eye results in a transient alteration of thermoregulatory set points; this effect is wavelength‐dependent. Mean heating rates, bask and forage durations were not affected by the shielding of the parietal eye with any of the filters used. © Wiley‐Liss, Inc.
The effects of neurotransmission on neuronal gene expression
Authors: Mack Kenneth J.
Published: June 2005

Gene expression is primarily controlled at the level of transcription. Of the 100,000 genes expressed in the human body, 30–50% may be specifically expressed in nervous tissue. Some of this gene expression is genetically determined and is therefore preprogrammed. However, neuronal gene expression can also be affected by environmental factors, mediated through neuronal transmission. It is hypothesized that neurotransmission has a primary role in developmental and adult neuronal plasticity, and that these effects are mediated through alterations in gene expression. Pathological neurotransmission, such as that seen after seizures, may be disruptive to these patterns of gene expression. © 1995 Wiley‐Liss, Inc.
Alterations in synaptic connectivity in cerebral cortex in neuronal storage disorders
Authors: Walkley Steven U. , Wurzelmann Sarah
Published: June 2005

Neuronal storage diseases are inborn errors of metabolism characterized by widespread intraneuronal storage and progressive neurological dysfunction, including mental retardation, movement disorders, and seizures. Most of these disorders are associated with specific defects in particular lysosomal enzymes. Moreover, a wide array of genetic defects has been documented. The immense progress made during the past three decades in understanding the primary molecular and enzymatic defects in this family of diseases stands in sharp contrast to the modest advances made in delineating pathogenetic mechanisms and treatment strategies. Although these disorders result from highly selective defects in metabolic pathways, they ultimately are complex conditions characterized by a plethora of seemingly unrelated secondary molecular and cellular abnormalities. Studies of children and animals affected by these diseases have revealed that significant changes in neuronal connectivity occur in the cerebral cortex. These include not only degenerative changes in axons and synapses of inhibitory neurons, but also a regrowth of dendrites and new synapse formation involving pyramidal neurons. The latter finding indicates that neurons in the cerebral cortex undergo significant “rewiring” during the height of the disease process. This regrowth of primary dendrites and formation of new synapses as part of a neurological disease is unprecedented. Understanding the causes and consequences of these changes in cortical synaptic connectivity in neuronal storage diseases may provide insight not only into the precise mechanisms underlying mental retardation in these diseases and their reversibility, but also into processes governing dendritic elaboration and synapse formation in the normal developing nervous system. © 1995 Wiley‐Liss, Inc.
Ischemia and excitotoxins in development
Authors: Johnston Michael V. , Ishiwa Shun
Published: June 2005

Ischemia in the developing brain triggers a series of events that cause damage after a threshold of severity and duration are reached. Release of glutamate, the major excitatory amino acid neurotransmitter in the brain, is one of the primary events in this cascade of injury. Release of glutamate combined with reversal of glutamate uptake pumps in nerve terminals causes glutamate levels to increase from 10–1000x baseline levels in the brain's extracellular space during ischemia, traumatic brain injury, and hypoglycemia in animal models and in humans. High levels of extracellular glutamate trigger opening of N‐methyl‐D‐asparate (NMDA) and non‐NMDA glutamate channels, allowing calcium and sodium to flood into neurons. Energy failure in mitochondria facilitates opening of NMDA channels by lowering the membrane potential and reducing their blockade by magnesium that resides within the channel at normal membrane potentials. Calcium entry into the cytoplasm triggers several events including activation of lipases, proteases, and nucleases that can destroy the neuron's cellular machinery. Generation of reactive oxygen free radicals including the messenger molecule nitric oxide can have additional destructive effects. Drugs that block glutamate receptors and the “excitotoxic cascade” of downstream events can protect the brain from injury and show promise for clinical application in infants and children. © 1995 Wiley‐Liss, Inc.
Neurotransmitter alterations in congenital hyperammonemia
Authors: Robinson Michael B. , Batshaw Mark L.
Published: June 2005

Inborn errors of metabolism are associated with a significant risk of mental retardation and other developmental disabilities. Only rarely, is the mechanism of the neural injury clearly understood. This is particularly true for those inborn errors of metabolism associated with hyperammonemia, principally urea cycle disorders and organic acidemias. Previously, it was assumed that elevated ammonia levels alone could account for the brain injury. However, in vitro studies suggest that ammonia is not particularly toxic to intact neurons. Furthermore, there does not appear to be a direct linkage between the peak blood ammonia level during hyperammonemic coma and subsequent neurodevelopmental outcome. There is, however, a correlation between duration of hyperammonemic coma and outcome, suggesting a secondary, time‐influenced mechanism of neural injury. Recent research has focused on excitotoxicity as a possible inducer of neural injury in congenital hyperammonemia. In addition to developmental disabilities, affected children exhibit behavioral abnormalities. An alteration in serotonin metabolism has been proposed as an explanation for these aberrant behaviors during less severe episodes of hyperammonemia. This review focuses on the neurotransmitter abnormalities occuring in congenital hyperammonemia and on new approaches to protecting the brain during hyperammonemic crises. © 1995 Wiley‐Liss, Inc.
Neurotransmitter alterations in the trisomy 16 mouse: A genetic model system for studies of down syndrome
Authors: Oster‐Granite Mary Lou , Lacey‐Casem Merri Lynn
Published: June 2005

This review describes the alterations that occur in a variety of neurotransmitter systems in mouse trisomy 16 and compares those alterations with ones observed in individuals with Down syndrome (Trisomy 21) and Alzheimer's disease. Individuals with Down syndrome who survive into their fourth decade invariably have the neuropathologic and neurochemical features associated with Alzheimer's disease. Thus, comparative studies may provide insight into pathogenetic mechanisms common to all three conditions. These neurotransmitter alterations are accompanied by neuroanatomical as well as neurophysiological alterations in Down syndrome, Alzheimer's disease, and mouse trisomy 16. Because mice with complete trisomy 16 do not survive the perinatal period. Ts 16 neurons placed in culture, as well as primary and secondary chimeras comosed in part of Ts 16 cells, have also been examined for neurotransmitter alterations. Like individuals with Down syndrome, mice with trisomy 16 have triplication of a constellation of genes that have remained together in the same order for roughly 80 million years. As more of these genes have been identified and localized to specific regions of human chromosome 21 and, in some cases, to mouse chromosome 16 as well, effeorts have been made to create mice that are transgenic for these can be studied. Studies of several of these different types of transgenic mice have begun to provide insight inot the mechanisms by which neurotransmitter alterations may arise in Ts 16 mice, and by extrapolation, in DS individuals as well. © 1995 Wiley‐Liss, Inc.
Effect of the uterine environment on the frequency of spontaneous cleft lip in CL/Fr mice
Authors: Bornstein S. , Trasler D. G. , Fraser F. C.
Published: June 2005

It was previously shown (Davidson et al., '69) that the A/J female mouse predisposes her offspring to congenital cleft lip, either by providing a uterine environment or cytoplasmic factors that increase susceptibility, or by not providing a cytoplasmically transmitted factor, present in the C57BL/6J strain, that decreases susceptibility to cleft lip. In the present experiment males of the CL/Fr strain, which has a relatively high frequency of cleft lip, were crossed to females of the C57BL/6J strain, and the F1 offspring were backcrossed to CL/Fr animals. Three second backcrosses were made such that embryos of comparable genotype developed in CL/Fr mothers or in hybrid mothers with or without the postulated cytoplasmic factors. The results showed that the maternal effect on cleft lip susceptibility was present in the CL/Fr strain, and was not mediated through the cytoplasm. Maternal age, parity, litter size, and sex and pigmentation of the offspring showed no consistent associations with frequency of cleft lip. The demonstration of a uterine effect on cleft lip susceptibility suggests that it might be possible to modify the environment in the direction of increased resistance.
An improved apparatus for producing stress‐induced cleft palate in mice
Authors: Rosenzweig Sanford , Blaustein Frances M. , Anderson Clint D.
Published: June 2005

A/J mice were restrained for 48 hours beginning on day 14 of pregnancy in an improved cage so constructed that the mouse could drink in its usual manner. This was an improvement over previously used restraining cages in which potato was supplied as a substitute for water. A cleft palate frequency of 15.7% obtained with this new cage was significantly greater than that in the control group and demonstrated that resraint can be teratogenic.
Cysteamine protection against lethal and growth‐inhibiting effects of prenatal X and gamma irradiation
Authors: Roberts Joan M.
Published: June 2005

Exposure of pregnant rats to gamma radiation on day 16 of gestation produced nearly double the number of neo‐ and postnatal offspring deaths as did X irradiation. Dose level (185 r), dose rate (10–12 r/minute), and distance from the source were the same in both groups. Cysteamine given prenatally prior to either gamma or X irradiation significantly decreased mortality. In the gamma‐irradiated group the mortality rate remained significantly higher than in the control group, but in the X‐irradiated group it was reduced to the control level by pretreatment with cysteamine. Cysteamine given to pregnant rats immediately following gamma irradiation had no effect on offspring mortality.
Trimethadione and human teratogenesis
Authors: German James , Kowal Areta , Ehlers Kathryn H.
Published: June 2005

A family is described in which four malformed children were born to a mother while she was taking trimethadione, an antiepileptic drug infrequently prescribed for adults. Following discontinuation of the drug, she had two normal children. This family led to a survey of all 278 epileptic women admitted to one hospital during the 23 years following the introduction of trimethadione for treatment of petit mal. Only eight women had ever taken it or its close congener paramethadione, and only three had taken it early in a pregnancy. Thus the outcomes of 14 pregnancies, during which the mothers took trimethadione or paramethadione early, have become known to the authors, those in the index family and those in three additional families ascertained through the survey. These pregnancies showed a high frequency of abnormality: eight children with developmental defects of various types, only three of whom have survived early infancy; one child with multiple hernias and juvenile, nonfamilial diabetes; and three spontaneous abortions. The survey suggests that neither epileptic women as a group nor those taking antiepileptic drugs usually prescribed for adults have an obviously increased frequency of malformed children but that epileptic women taking trimethadione or paramethadione may constitute a special subgroup whose children do have an increased frequency of birth defects. The small number of observations possible at a single institution, although suggestive, precludes a firm opinion as to the possible role as human teratogens of the oxazolidine‐2,4‐diones.
Early neurovascular abnormalities underlying 6‐aminonicotinamide (6‐AN)‐induced congenital hydrocephalus in rats
Authors: Chamberlain J. G.
Published: June 2005

Defects in the rat central nervous system during retarded brain development and congenital hydrocephalus were studied following single maternal injections of the niacinamide antimetabolite 6‐aminonicotinamide (6‐N) late in development. Histological and histochemical analyses indicated CNS hemorrhage and growth retardation of fetal brains 24 hours after treatment; fluid movement into cerebral ventricles was evidenced by secretionlike, circular “blebs” along the ependymal lining. There was transitorily increased glycogen in hypoplastic choroid plexuses with disruption of cerebral layering of neuroblasts. Despite thinned cerebral cortex and increased ventricular surface area, associated with cranial distortion and communicating, compensatory ventricular enlargement, normal intracranial pressure was recorded by day 21 of gestation. During the pathogenetic process macrophagic cells removed cellular debris and RBC's so that by term little evidence of early hemorrhage was apparent.
Effect of ethylenebis[dithiocarbamic acid] disodium salt (nabam) and ethylenebis[dithiocarbamato]manganese (maneb) on Xenopus laevis development
Authors: Bancroft Roger , Prahlad K. V.
Published: June 2005

The fungicides ethylenebis [dithiocarbamic acid] (nabam) and ethylenebis [dithiocarbamato] manganese (maneb) were dissolved in a modified Holtfreter's solution at concentrations of 0.1–5 ppm. Thirty to 60 yolk‐plug Xenopus laevis embryos were placed for 1–10 days in 200 ml of different concentrations of the fungicide solution. Treated and control (Holtfreter's only) embryos were fixed in Bouin's fluid or formalin for light microscopy, and in glutaraldehyde‐formaldehyde for electron microscopy. Gross morphological and histological observations were made. The first changes observed in experimental embryos was a slight growth retardation and a transient absence or reduction in melanogenesis in the eye and on the rest of the body. The tail was shortened and the notochord had a distinct waviness. Animals in higher concentrations were unable to swim as well as controls. Histological examination, both light and electron microscopic, showed a general decrease in melanin content of the melanosomes in the pigmented retina. The notochord was increased in diameter; in sagittal sections the foldings were obvious. These results indicate that minute doses of these commonly used fungicides are harmful to the normal development of amphibian embryos.
Action of the phenothiazine derivative methophenazine on prenatal development in rats
Authors: Horvath Cécilia , Druga Alice
Published: June 2005

Single doses of 100–400 mg/kg or multiple doses of 10 or 50 mg/kg of the phenothiazine derivative methophenazine were given per os to Wistar rats at various times on the 7th‐14th days of gestation and the fetuses examined near term. Results indicated that methophenazine was mainly embryolethal when administered on the 8th‐11th days, and was teratogenic at later times, producing types of malformations that depended on the day of treatment, the most susceptible period being the 13th and 14th days of gestation. Teratogenicity occurred only when the dosages were highly toxic to the pregnant rats. Riboflavin given ip on the 14th day significantly reduced the embryolethal but not the teratogenic action of methophenazine.
Teratogenicity of cytochalasin D in the mouse
Authors: Shepard Thomas H. , Greenaway Jean C.
Published: June 2005

Cytochalasin D, a mold metabolite identified in food, was injected intraperitoneally in doses of 0.4 to 0.9 mg per kilogram on gestational days 7 through 11 and produced evidence of teratogenicity in two out of three strains of mice. Exencephaly, hypognathia and axial skeletal defects were found in strains C57BL/6J and BALB/c while no increase in defects was observed in the Swiss Webster strain. In all three strains, a significantly increased resorption rate was found. Oral doses of approximately 7.0 mg per kg on days 7 through 11 in the BALB/c produced exencephaly in the offspring. Autoclaved cytochalasin D retained its teratogenic potential.
Anencephaly with incomplete twinning (diprosopus)
Authors: Riccardi Vincent M. , Bergmann Cynthia A.
Published: June 2005

A case of diprosopus with anencephaly is presented. It is suggested that such concurrence of neural tube defects and incomplete twinning corroborates the notion that a single pathogenetic mechanism may be common to both neural tube defects and monozygotic twinning.
Bovine like‐sexed male twins with chromosomal chimerism
Authors: Miyake Yoh‐Ichi , Yamanaka Harumichi , Deguchi Eizaburo , Ishikawa Tsune
Published: June 2005

Sex‐chromosomal chimerism (XX/XY) was described in a pair of bovine like‐sexed male twins. One of the twins showed malformed external genitalia, and the other was phenotypically normal. It is proposed that sex‐chromosomal chimerism is associated with a choriovascular anastomosis between like‐sexed twins examined and “female fetus” which may be overlooked at parturition.
The effect of intrauterine position on the radiosensitivity of rat embryos
Authors: Ward W. F. , Aceto H. , Karp C. H.
Published: June 2005

Rats were exposed to gamma rays or helium ions on one of days 4‐9 of gestation. Embryonic survival was recorded as a function of intrauterine position at autopsy on day 20 of gestation.

Embryos located at the ovarian and cervical ends of the uterus experienced higher rates of mortality than did their littermates located at the middle of the uterine horn. This effect was observed in litters exposed to both radiation modalities on all days studied. The influence of intrauterine position on embryonic survival was directly proportional to radiation dose and to the number of fetuses occupying the uterine horn. Under the least advantageous conditions (i.e., a crowded uterine horn exposed to a moderately high radiation dose), the cervical embryo's probability of survival was less than half that of the litter as a whole.

A disproportionately high rate of embryonic mortality at the cervical position was also observed in litters irradiated under hypoxic conditions, suggesting that the non‐random distribution of radiation effect was not the result of variations in oxygen concentration within the uterus.

In contrast, there was no indication that intrauterine position influenced the distribution of gross morphologic abnormalities in irradiated litters.
Patterns of combined limb malformations
Authors: Castilla Eduardo Enrique , Frias Maria Luisa Martinez , Paz Joaquin Eugenio
Published: June 2005

Seven different limb malformation types were defined in 544 affected newborns, apparently free from other anomalies, obtained from a series of 297,299 livebirths. These seven malformation types were: polydactyly, limb reduction, brachydactyly, symphalangy, syndactyly and split hand/foot. One anomaly type was present in 472 newborns (1.58/1,000) and two or three in 72 (0.24/1,000).

The observed combinations of two or three limb malformation types cannot be explained as chance association. Therefore, a common etiopathogenic mechanism has to be considered when two or more limb malformation types are combined in a given individual.

The most frequent observed combinations were: reduction‐brachydactyly, reduction‐syndactyly, brachydactyly‐syndactyly, polydactyly‐syndactyly, and reduction‐brachydactyly‐syndactyly.

Based on affected limb distribution, sex ratio, and familial recurrence rates, it is suggested that a reduction anomaly is the primary component in all tested combinations while syndactyly tends to be a secondary one when combined with any other limb anomaly type.
Palate morphogenesis: II. Contraction of cytoplasmic processes in ATP‐induced palate rotation in glycerinated mouse heads
Authors: Wee Elizabeth L. , Zimmerman Ernest F.
Published: June 2005

It has been previously shown that non‐muscle contractile system(s) exist in mouse palate mesenchyme underlying the palate epithelium before shelf rotation. In order to obtain evidence that the non‐muscle contractile system(s) function to elevate the palate, glycerinated heads have been incubated with ATP. It was shown that 5 mM ATP and a 30 min incubation at 25°C stimulated palate rotation optimally. Elevation of the anterior end of the palate was nearly complete (PSI = 3.90, p<10−6). Although rotation of the posterior end was significant (p<0.02), movement was limited (PSI = 1.70). Light microscopy of the palate revealed that ATP caused a marked condensation of the cytoplasmic processes of the mesenchymal cells. The contraction of the processes of the mesenchymal cells induced by ATP increased roughly with increased palate shelf rotation and was greater at the peripheral than at the internal mesenchyme. Cytochalasin B pre‐treatment at 40 μM completely blocked the ATP‐induced rotation at the anterior end. The effect of other nucleotides on palate rotation was tested. GTP caused a significant stimulation of anterior shelf rotation (p<0.005), which was less than ATP, while ADP and CTP were ineffective. Low temperature (6°C) prevented the ATP‐induced shelf rotation. These results suggest that the non‐muscle contractile cells in the mesenchyme play a role in palate elevation and that contraction of the actomyosin containing microfilaments supplies the motive force.
Changes in the mouse neuroepithelium associated with cadmium‐induced neural tube defects
Authors: Webster William S. , Messerle Karin
Published: June 2005

The aim of this study was to investigate the teratogenic action of cadmium (Cd) on the developing mouse CNS. Pregnant mice were injected with 4mg/kg CdCl2 on day 7, 8, 9, or 10 of gestation. These animals and saline injected controls were sacrificed either on the day before birth or at various times up to 48 hours after injection and the embryos examined grossly and histologically.

Exencephaly occurred after Cd treatment on day 7 or 8 and its development was examined in day 8 embryos. Eight hours after Cd injection many cells of the closing neural plate contained dense‐staining inclusions, thought to be autophagic vacuoles. After 24 hours this damage had almost disappeared, but the anterior neural folds, although looking histologically normal, were more open than in controls. Forty‐eight hours after injection it was apparent that this part of the neural tube was not going to close and would result in exencephaly.

Cd exposure on day 9 or 10 did not cause gross CNS defects such as exencephaly. On both days, twelve hours after Cd injection, similar dark‐staining inclusions were seen in many cells throughout the CNS. After twenty‐four hours there were variable amounts of cell death, resulting in some embroys in breakdown of parts of the wall of the neural tube. Forty‐eight hours after treatment all inclusions and cellular debris had disappeared, indicating repair had taken place, but in some embryos, treated on day 9, severe lasting damage was seen as dorsal openings in the previously closed neural tube.
Frequency of congenital abnormalities and of anatomical variations among JAX rabbits
Authors: Crary Dorcas D. , Fox Richard R.
Published: June 2005

The frequency of congenital abnormalities and anatomical variations as observed among JAX rabbits is reported. Data were drawn from 32,082 inbred and partially inbred rabbits and 3,208 hybrids from the colony of the Jackson Laboratory over an eight‐year period. Data reported here include stillbirths, rabbits dying from natural causes, and those killed for specific experimental regimens. Frequency data are based on the number of abnormalities observed in each category as a function of the total number of animals necropsied. This is approximately 95% of the animals born during the eight‐year period and gives the frequency of abnormalities within each category rather than the number of individuals with one or more abnormalities. Anatomical variations have been found in almost all organ systems of JAX rabbits. Their presence adds to our knowledge of the characteristics of these strains, a knowledge that is critical to the understanding of the results of experimental manipulation or for determination of the presence of new mutations. There is considerable between‐strain variation. Where frequencies are relatively high, the conditions are either known or suspected to be of genetic origin. Most of the anomalies are not deleterious, or their frequency is so low as to cause no prublems within the colony. Hybrid populations have substantially fewer anomalies than do the parental strains. Where frequency is relatively high, it tends to be intermediate between the parental strains.
Reduction of catecholamine‐induced cardiovascular malformations in the chick embryo with metoprolol
Authors: Kuhlmann Randall S. , Kolesari Gary L. , Kalbfleisch John H.
Published: June 2005

It has been documented that activation of the β1‐adrenergic receptor mechanism is directly related to cardiovascular malformations associated with the heart and great vessels of the embryonic chick. These adrenergic receptors are believed to be present and functional in the innervated and noninnervated embryonic heart at early stages of development. The present study examined the effects of four sympathomimetic cardioactive amines on chick cardiovascular morphogenesis at Hamburger and Hamilton stage 24. Special attention was directed toward understanding dopamine teratogenicity. In order of decreasing potency at the maximum teratogenic dose (dopamine > isoproterenol > epinephrine > norepinephrine) each drug was found capable of producing aortic arch anomalies of the third, fourth, and sixth aortic arches and ventricular septal defects (VSD). A new specific β1‐adrenergic antagonist, metoprolol tartrate, was employed in an attempt to lower the incidence of these cardiovascular malformations. Pretreatment with this selective β1‐blocker profoundly reduced the incidence of malformations within any aminetreated group. These experiments demonstrate that dopamine, as well as the other sympathomimetic amines, is a potent teratogen and most likely produces these cardiovascular malformations by primarily stimulating the β1‐adrenoreceptor in the embryonic chick.
Involvement of GABA in palate morphogenesis and its relation to diazepam teratogenesis in two mouse strains
Authors: Wee Elizabeth L. , Zimmerman Ernest F.
Published: June 2005

Previous studies have indicated that serotonin and acetylcholine stimulate palate shelf reorientation. The present studies were undertaken to determine whether γ‐aminobutyric acid (GABA) functions as an inhibitory neurotransmitter in the palate and whether diazepam mimics GABA to inhibit shelf reorientation and cause cleft palate. First, it was shown that 10−4 M GABA inhibits palate shelf reorientation in day 14.5 AJ embryos cultured for 2 hours. Anterior palate reorientation stimulated by 10−5 M serotonin was decreased by GABA; 10−5 M picrotoxin (GABA antagonist) stimulated anterior shelf reorientation and reversed the effect of GABA. Diazepam (10−4 M) partially inhibited palate shelf reorientation and that stimulated by 10−5 M serotonin. Diazepam (400 mg/kg) was administered to AJ mice at day 13.5 of gestation and embryos were cultured at day 14.5. The inhibition produced by diazepam was significantly reduced by 10−5 M picrotoxin. The teratogenic effect of diazepam was compared with AJ and Swiss‐Webster Vancouver (SWV) inbred strains. Diazepam produced greater clefting in SWV mice (57% net) than in the AJ (18% net) when compared to their water‐ and food‐starved controls. The greater sensitivity of the SWV strain than the AJ strain to diazepam, as well as to GABA, was also observed in embryo culture. GABA (10−5 M) markedly inhibited posterior palate reorientation and reversed the stimulation produced by bethanechol in SWV mice. The inhibitory effects of GABA on the posterior palate were partially reversed by picrotoxin. Furthermore, diazepam inhibited palate reorientation either when administereted to the pregnant dam or added in embryo culture. Picrotoxin significantly antagonized these effects. Thus both GABA and diazepam inhibited palate reorientation. The SWV strain was more sensitive to both agents than the AJ; the posterior end was preferentially affected in SWV while the anterior was more sensitive in the AJ mouse. These results suggest that (1) GABA may function as an inhibitory neurotransmitter to regulate palate reorientation, (2) diazepam may cause cleft palate by mimicking GABA to inhibit shelf reorientation, and (3) these events are genetically regulated in inbred mouse strains.
Methyl mercury toxicity in the chick embryo
Authors: Greener Yigal , Kochen Joseph A.
Published: June 2005

The toxicity of methyl mercury (mHg) in the developing chick embryo was investigated. The relationship of dose, time of administration (i.e., days 4–9 of development), and body levels of mercury was examined. The LD50 for mHg injected into the yolk sac on day 5 of incubation was 40–50 μg. Embryos dying within 24 hours showed increased total body mHg levels when compared to survivors (219 ± 67 vs. 105 ± 41 μg/gm, mean ± SD). Absorption was dose‐related, with a good correlation between mortality and body, blood, and brain levels. Daily analysis of body mHg levels after injection on day 5 showed continued mHg accumulation (0.88 ± 0.35 μg/embryo/day). However, the rate of embryo growth exceeded the rate of mHg absorption, resulting in a progressive decrease in mHg in concentration in tissues (from 94.5 ± 34.2 μg/gm on day 6 to 45.3 ± 13.4 on day 9). Administration after day 5 resulted in a significant reduction in levels of mHg in the brain on day 18 (from 11.4 ± 2.1 μg/gm when given on day 5 to 8.4 ± 2.3 when given on day 9) and in mortality (from 64% to 33%). Because blood mHg levels remained unchanged, the increased brain levels and higher mortality early in embryogenesis may reflect facilitated transfer of mHg across a poorly developed blood‐brain barrier. Later in development, the reduced mortality and lower brain mHg levels correspond to the formation of specialized interendothelial junctions and a more effective blood‐brain barrier.
Assessment of adult skeletons to detect prenatal exposure to acetazolamide in mice
Authors: Beck Sidney L.
Published: June 2005

A skeletal variant assay system (SVAS) consisting of a group of 88 spontaneously occurring qualitative variations of the adult mouse skeleton was applied to CD‐1 animals that had been exposed in utero to 0, 200, or 1,000 mg/kg/day of the sodium salt of acetazolamide dissolved in distilled water, presented by SC injection of the dam during day 8 or days 9–11 of gestation. Two separate series of experiments were performed, and skeletons were examined at postnatal 62 ± 2 days.

Variation occurred in 62 and 67 characters in the two series. Frequencies of occurrence differed from untreated (UNTD) and vehicle‐treated (VEH) values of substantial numbers of variants in a dose related manner for both series in both treatment regimes as did the number of variants which showed significantly different frequencies (P < .01) in comparisons of experimental with either UNTD or VEH. At the high doses 12 and 16 variants occurred with significantly different frequencies from UNTD in day 8 treatments in the two series, and 15 and 19 variants differed in the days 9–11 treated group. Contrasting high‐dose animals with appropriate vehicle controls revealed differences in 13 and 12 variants in day 8 treatment groups and in 18 and 15 variants in days 9–11 groups.

Agreement between the two series was good, especially in the D9–11 treatments. Several variants differed significantly from both UNTD and VEH in both series of experiments. Among these were a number which appeared more or less specific to acetazolamide exposure. They include: day 8 treatments–accessory parietal, frontal extension, and 27 presacral vertebrae; day 9–11 treatments—sacral fusions in dorsal processes and vertebral bodies, and caudal fusions and malformations; both sets of treatments—lumbar fusions, and fusions of the transverse processes of the sacral vertebrae. Other importantly affected variants, also seen in exposure to other compounds include: day 8 treatments—abnormal metoptic roots; day 9–11 treatments—accessory mental foramen, foramina transversaria imperfecta of the atlas, arch foramen of the fifth cervical (C) vertebra, malformed sternebrae, fossa olecrani perforata, and fewer than 30 caudal vertebrae; both treatment regimes—parted frontals, accessory transverse foramina in C3–C6, reduced articular processes on the thoracic vertebrae, and 14 ribs.

By all criteria applied, the SVAS is able to detect prenatal exposure to acetazolamide in adult skeletons even in the absence of any gross morphological abnormalities.
Ultrastructure of initial nasal process cell fusion in spontaneous and 6‐aminonicotinamide‐induced mouse embryo cleft lip
Authors: Trasler D. G. , Ohannessian L.
Published: June 2005

A search was made for cell ultrastructure differences in the initial fusion process of the medial and lateral nasal processes in mouse embryos of the following types: A/J with 12% cleft lip (CL), CL/Fr with 23% CL—both cleft‐lip‐predisposed strains, CL/Fr 6‐aminonicotinamide (6AN)‐treated (94% CL) and controls from the C57BL/6 strain (0% CL) and dancer stock (0% CL). No detectable differences were found between the A/J and CL/Fr strains and the controls in the epithelial cells showing initial contact and fusion. Epithelial surfaces not in contact in controls and where clefts were developing were smooth. Cells approaching or in contact had cell projections, intercellular junctions, desmosomes, and microfilaments demonstrating firm contact between the apposed epithelia. It has been postulated that spontaneous cleft lip was due to a predisposing face shape bringing about a failure of contact in some embryos and in others where contact was achieved fusion was normal. These data support this view. The situation, however, in 6AN‐treated embryos is different. A few 6AN‐treated embryos showed abnormal contact that appeared malpositioned and tenuous. The teratogen also caused increased cell death and a denser epithelium and mesenchyme. Thus 6AN‐induced cleft lip could be due to the epithelial cell changes and/or to the reduction in size of the nasal processes.
Iron deficiency in the rat: Biochemical studies of fetal metabolism
Authors: Mackler Bruce , Grace Richard , Person Richard , Shepard Thomas H. , Finch Clement A.
Published: June 2005

The effects of dietary‐induced iron deficiency on fetal and maternal metabolism were studied in the rat. Concentrations of phenylalanine, but not tyrosine, were significantly elevated in plasma from iron‐deficient maternal and fetal rats at day 20 of gestation with individual fetal plasma levels of phenylalanine as high as 10 mg per 100 ml. Concentrations of total 5‐hydroxyindole compounds were significantly decreased in brain tissue from iron‐deficient fetuses (day 20 of gestation), suggesting that synthesis of the compounds may be inhibited by iron deficiency. Mitochondrial NADH oxidase activity was markedly decreased (60%) in homogenates of fetuses at day 14 of gestation and may account for the high fetal resorption rate and small fetal size observed in the rat in iron deficiency.
Evaluation of long‐term consequences in behavioral and/or neural function following neonatal chlordecone exposure
Authors: Mactutus Charles F. , Tilson Hugh A.
Published: June 2005

The effects of neonatal exposure of rats to chlordecone, during the major postnatal period of neuroendocrine differentiation were assessed after the animals matured to 90 days of age. On day 4 postpartum, pups received a s.c. injection of either DMSO vehicle or chlordecone (1 mg/pup) dissolved in DMSO. The neonatal exposure produced a significant sex‐dependent alteration in adult body weight; chlordecone‐exposed males were lighter than vehicle‐exposed controls and chlordecone‐exposed females were heavier than vehicle‐exposed controls. Behavioral tests sensitive to neonatal chlordecone exposure during preweaning development–i.e., spectral analysis of movement, activity, and auditory startle responsiveness–gave no statistically significant evidence for residual effects of the early organochlorine treatment. When challenged with harmine, a known tremorogen with putative effects on olivocerebellar pathways, chlordecone‐exposed males were less responsive than vehicle‐exposed littermates in a spectral analysis of movement. The movement spectrum of chlordecone‐exposed females was not differentially sensitive to the harmine challenge. However, subsequent evaluation of the auditory startle reflex indicated that harmine interacted with the neonatal treatment and sex of the animal; chlordecone‐exposed males were less responsive and chlordecone‐exposed females more responsive than same sex vehicle‐exposed litter‐mates. The responsiveness to a d‐amphetamine challenge, expressed as a ratio of baseline activity in a pre‐ and post‐test design, suggested the chlordecone‐exposed males gave an exaggerated response to the drug challenge. Collectively, these findings suggest that the neonatal chlordecone exposure had a significant organizational effect on the development of behavioral and/or neural function. These findings also suggest the predictive utility of early behavioral tests; that is, long‐term alterations were noted in each component of the toxicological syndrome previously identified during prewearing development.
Experimental design considerations: A determinant of acute neonatal toxicity
Authors: Booze Rosemarie M. , Mactutus Charles F.
Published: June 2005

Few studies have investigated the potential developmental differences resulting from treating neonatal rat pups in either split‐litter or whole‐litter (nested) experimental designs. We directly compared rat pups dosed with triethyl lead (TEL) via both split‐litter (representing all dosage groups within a single litter) and nested (all pups randomly assigned to a single litter receive the same dose) designs. The nested design was chosen to produce a uniform behavioral pattern across pups within each litter, whereas the split‐litter design was chosen to promote pup competition and differential maternal care. On postpartum day 5, pups were administered either 12, 13, 14, or 15 mg/kg TEL, with each design represented by 12 litters. Although the LD50 values for the two designs were not significantly different, there were significantly more deaths in the 12 mg/kg dosage group within the split‐litter design than in the nested design group. Preweaning survival times for splitlitter dosed animals were also decreased. In addition, significant growth reduction (7–16%) was observed in the split‐litter group, relative to the nested design animals during the preweaning period. These results suggest that neonatal toxicity is not independent from experimental design considerations, and that the factors of littermate competition and/or pup‐induced maternal care deserve further study.
Visceral anomalies in the Meckel syndrome
Authors: Rapola Juhani , Salonen Riitta
Published: June 2005

The visceral abnormalities of 32 autopsied Meckel's syndrome cases were analysed macroscopically and histologically in order to observe the distribution and spectrum of internal abnormalities in this hereditary malformation syndrome. All cases showed the classical triad of central nervous system anomaly, postaxial polydactyly, and cystic kidneys. Five cases were midterm fetuses and 27 cases were perinatal deaths. The kidneys were grossly enlarged in almost all of the cases (29) and showed a uniform histological pattern of fibrocystic proliferation, which is considered characteristic of MS. Fibrosis and proliferation of the bile ducts in the hepatic portal tracts were found in each case. Severe hypoplasia of the male genitalia associated with cryptorchidism was the third consistent anomaly. Derivatives of the müllerian ducts were present in four males, and the initial sex determination of the male infants was sometimes difficult. Epididymal cysts (39%) and ductal dilatation as well as fibrosis of the pancreas (31%) were further common anomalies. This series showed that a number of gross and microscopic abnormalities are consistently present in MS and that histological investigation is invaluable in defining the syndrome in doubtful cases.