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Biomedical subjects

M H Kaufman

Publications and source records attributed to M H Kaufman.

At least 127 records · Page 7Linked to original sources
PubMed1983

Chromosome translocation (T(2;4)1 Sn)-induced neural tube defects in the mouse embryo.

Neural tube closure was studied in embryos obtained from matings of male mice heterozygous for a reciprocal chromosome translocation (T(2;4)1 Sn) with normal female (CFLP) mice. When litters were examined on the 9th to 12th days of gestation, there was a high incidence of resorption, developmental delay and neural tube closure defects in these embryos. SEM observations indicated that the neural tube closure defects ranged in severity from a side-to-side flattening of the midbrain to extensive anomalies in which the entire cephalic neural tube had failed to close. In addition to cephalic defects, a number of embryos exhibited open defects or abnormal subectodermal blebbing in the future lumbosacral region. In spinal regions, even in areas in which the neural tube had previously closed, it often was irregular and folded. These observations are discussed in relation to studies of gene-related defects of neural tube closure.

Animals↗
PubMed1983

Occlusion of the neural lumen in early mouse embryos analysed by light and electron microscopy.

A histological account of neural tube occlusion during early mouse embryogenesis is presented here from an analysis of sections taken from plastic-embedded material. Because the overall pattern of neuroepithelial apposition and the duration of luminal occlusion appears to vary slightly from one embryo to another at otherwise similar stages of development, only a general guide to the events occurring in the mouse embryo between about midday on the 9th to late on the 10th day of gestation can be given. The earliest evidence of complete luminal occlusion was seen when the cephalic and caudal extremities of the neural tube were still widely open. An ultrastructural analysis of the morphological appearance of the closely apposed luminal cells in zones of partial and complete occlusion has demonstrated that occlusion is brought about initially by the interdigitation of processes from closely apposed neuroepithelial cells. This initial event is followed by direct contact over a much more extensive area between the surfaces of apposed cells with a characteristically flattened luminal border. Apposition and luminal occlusion is probably facilitated by the presence of viscous extracellular material. Finally, complete occlusion involving an extensive region of the lumen occurs. The latter phenomenon is a transient event lasting 1 or at most 2 days in the mouse. At no stage were junctional complexes observed between closely apposed neuroepithelial cells in regions in which the neural lumen appeared to be completely occluded, though they were apparent between adjacent neuroepithelial cells. Observations on the underlying mechanism(s) of cellular fusion are considered in the light of the ultrastructural findings. These results are compared with findings from analyses of various other sites of cellular fusion during embryogenesis. Attention is also drawn to the similarities and differences observed in the timing and overall pattern of events occurring during the early development of the neural tube in mouse and human embryos.

Animals↗
PubMed1983

Establishment of pluripotential cell lines from haploid mouse embryos.

Eggs from 129 SvE and (C57BL x CBA)F1 hybrid female mice were activated parthenogenetically following their exposure to a 7% solution of ethanol in PBS. Only the haploid class which developed a single pronucleus following second polar body extrusion was examined further. These eggs were transferred to suitable recipients and 'delayed' blastocysts subsequently recovered. The 'delayed' blastocysts were explanted into tissue culture and a total of four haploid-derived pluripotent cell lines established from individual embryos. Chromosome analysis of morulae revealed that over 80% contained only haploid mitoses. However, chromosome analysis of early passage cell lines revealed that all were diploid with a modal number of 40 chromosomes. When transplanted into syngeneic hosts, all lines formed well-differentiated teratocarcinomas. This technique provides a source of homozygous diploid cell lines of parthenogenetic origin.

Animals↗
PubMed1983

X-chromosome instability in pluripotential stem cell lines derived from parthenogenetic embryos.

The karotype of six pluripotential stem cell lines derived from haploid and two additional lines derived from diploid parthenogenetic embryos is described. All these lines are diploid and possess a normal autosomal complement. The stage at which diploidization of the haploid cells occurs is not yet known. The XX-chromosome complement in these lines is unstable, although in two haploid-derived lines and one diploid-derived line many normal XX-bearing cells are found in early cultures. All of the lines so far examined either become XO (rarely), or a single X-chromosome shows a deletion in the distal region. The extent of this deletion varies between lines, but the position of the breakpoint appears to be constant for a given line. We suggest that these cytogenetic findings raise the possibility that a single deletion event occurring at an early stage during the isolation of these lines may confer a selective advantage to those cells carrying the deleted X chromosome.

Animals↗
PubMed1982

Two examples of monoamniotic monozygotic twinning in diploid parthenogenetic mouse embryos.

In experiments in which diploid parthenogenetic mouse embryos cultured entirely in vitro from the one-cell stage to the blastocyst were transferred to suitable recipients and maintained in "delay" for about 3 days before implanting, about 25-40% subsequently developed to somite-containing stages. In all, over 30 such embryos were examined. Most were morphologically normal, and equivalent to fertilized development observed on the 9th-11th days of pregnancy. A few embryos, however, had neural tube abnormalities, but of greatest interest were two sets of monoamniotic monozygotic twins. It is unclear whether the twins in some way resulted from the parthenogenetic condition, or from the "delayed" state. The present examples are discussed in the context of previous observations of monozygotic twinning in the mouse and man.

Amnion↗
PubMed1982

Indirect estimation of crown-rump lengths of incomplete conceptuses from analysis of spinal-cord dimensions.

The spinal cords of serially sectioned human embryos and early fetuses, ranging from 4mm to 112mm in crown-rump length, were examined in order to determine whether a mathematical relationship exists between certain spinal-cord dimensions and the crown-rump length of the conceptus. This information may be useful in estimating the crown-rump length, and hence the gestational age, of advanced human embryos and early fetuses when direct measurement is impossible. Five widely-spaced levels along the spinal cord were studied, but only those data relevant to the levels of the first thoracic (T1) and twelfth thoracic (T12) vertebral bodies are described in detail. Similarly, although eight distinct spinal-cord dimensions were measured at each level, only those measurements that bore a high enough correlation with crown-rump length to be of any predictive value are presented here, the most useful being the maximum spinal-cord width and the maximum grey-matter width, both of which increased with gestational age in a highly predictable way. The descriptive account of the morphological appearance of the cord at these levels also enables, though less accurately, an estimate of the crown-rump length of a conceptus to be made by direct inspection of a single transverse section through the thoracic region of the cord. The predictive value of these observations is discussed.

Anthropometry↗
PubMed1982

The chromosome complement of single-pronuclear haploid mouse embryos following activation by ethanol treatment.

A technique in which mouse eggs are stimulated to develop parthenogenetically following their brief incubation in 7% ethanol in PBS is described. Very high rates of activation were achieved, and a detailed analysis presented of the class of parthenogenone which develops a single haploid pronucleus following second polar body extrusion. As preliminary studies on presumptive haploid morulae indicated that a proportion of the metaphase spreads examined had an aneuploid chromosome constitution, the incidence of aneuploidy at the first cleavage mitosis was investigated. In the control groups the level of aneuploidy was about 1%, whereas in the ethanol-treated series the incidence ranged from 13 . 6-18 . 8%. Additional pre-treatment of ethanol-activated oocytes in low osmolar medium raised the incidence of aneuploidy to 28 . 3%. Metaphase groups with 18, 19, 21 and 22 chromosomes present were observed in addition to groups with a normal complement of 20 chromosomes. The possible mode of action of ethanol in inducing parthenogenetic activation of mouse oocytes, and a high incidence of aneuploidy, is discussed in relation to previous knowledge of the action of this agent. Preliminary studies using G-banding indicate that the aneuploidy observed appears to arise as a result of non-disjunction which may involve any of the chromosomes of the complement.

Aneuploidy↗
PubMed1981

Effect of acetaldehyde on the neuroepithelium of early mouse embryos.

Female mice were injected intravenously with acetaldehyde on single (seventh, eighth or ninth), or on multiple (sixth to eighth, seventh to ninth) days, and examined on the tenth or twelfth day of gestation. Exposure to acetaldehyde on multiple days resulted in high incidence of embryonic resorptions. However, when females were injected on single days and examined on the tenth day, a high incidence of neural tube defects was encountered in surviving embryos. The neural tube anomalies were located at a number of sites along the neuraxis. When examined by scanning electron microscopy, the individual neuroepithelial cells in acetaldehyde-treated embryos exhibited a characteristic rounded-up appearance with small surface blebs and spiny processes. These characteristic cell surface features were seen in acetaldehyde-treated embryos at all stages of development examined. When additional females were examined on the twelfth day, a much lower incidence of open neural tube defects was observed. When embryos at this stage of development were examined in more detail by SEM, many had numerous subectodermal blebs along the dorsal mid-line, which were not initially apparent on gross inspection. The neuroepithelial morphology was also found to bae abnormal in embryos with no obvious external anomalies. The results confirm and elaborate on previous observations on the teratogenicity of acetaldehyde, stressing the ultrastructural changes that are induced in the cells of the neuroepithelium, and the possible relationship between the damage induced by this agent and certain features of the fetal alcohol syndrome.

Acetaldehyde↗
PubMed1981

The passage to the foetus and liquor amnii of ethanol administered orally to the pregnant mouse.

The relationship between the time of oral administration of a dilute aqueous solution of ethanol and its concentration in the blood and urine was determined in a group of non-pregnant mice. The ethanol concentration was also determined in the maternal blood, foetuses and liquor amnii in female mice to which ethanol had been administered on the 18th day of pregnancy. In the pregnant females peak ethanol levels were achieved first in the maternal blood, then in the foetuses and slightly later in the amniotic fluid. Unilateral ligation of the uterine vessels markedly delayed the amount of ethanol reaching the foetuses and liquor. The present experimental system may provide a model for the human phenomenon of "binge" drinking.

Amniotic Fluid↗
PubMed1981

Early differentiation of the heart in mouse embryos.

The differentiation of the heart was examined in mouse embryos, isolated between the afternoons of the eighth and ninth day of gestation, by means of scanning electron microscopy as well as by light microscopy of standard histological material and thin plastic sections. Cavitation within the presumptive pericardial mesoderm commences during the late presomite stage (afternoon of eighth day) and myocardial rudiments are established by thickening of the pericardial lining adjacent to the endoderm near the base of the foregut pocket. At first the thickening lies on the ventral aspect of the pericardial cavity but, as the foregut pocket deepens and the trunk region of the embryo moves en masse caudally and ventrally, it comes to lie on the dorsal wall. A separate layer of cells comprising the primitive endocardium differentiates deep to the myocardial thickening, between the latter and the endoderm. Cavitation of the endocardial tissue occurs bilaterally about the 1-2 somite stage so as to establish bilateral endocardial tubes. These endocardial tubes become enclosed within the myocardial mantle which bulges into the pericardial cavity. A layer of acellular material (the cardiac jelly) appears between the endocardium and myocardium at about this time. At about the 4-somite stage, the endocardial tubes coalesce across the mid-line to establish a single median cardiac tube, and the entire heart rudiment is suspended in the mid-line by a wide dorsal mesocardium. Our observations indicate that, contrary to previous views, at no time during cardiogenesis in the mouse are two distinct heart primordia present which subsequently fuse to form a single median entity. The principal similarities and differences between cardiogenesis in the mouse, and mammals in general, and avians are discussed.

Animals↗
PubMed1980

X-chromosome inactivation in extra-embryonic membranes of diploid parthenogenetic mouse embryos demonstrated by differential staining.

In somatic cells of female mammals one of the two X chromosomes is genetically inactive and heterochromatic, resulting in dosage compensation for X-linked genes. In marsupials the paternally derived X chromosome is preferentially inactivated. In eutherian mammals, although either X chromosome can be inactivated at random in somatic cells, preferential inactivation of the paternally derived X chromosome has been demonstrated cytologically in mouse and rat yolk sac and mouse chorion and biochemically in mouse yolk sac, chorionic ectoderm and trophoblast. In mouse yolk sac the non-random element has been shown both biochemically and cytologically to be confined to the endoderm layer in which there is almost total paternal X-chromosome activity in the separated yolk sac layers of diploid parthenogenetic mouse embryos in which both X chromosomes are maternally derived. Kaufman et al. have demonstrated X inactivation in somatic cells of diploid parthenogenetic embryos, and we have used a modification of Kanda's method, which renders the presumptive inactive X dark staining, to reveal an inactive X chromosome in both endoderm and mesoderm layers of separated yolk sacs from parthenogenones. Thus even in tissues in which there is normally total non-random paternal X inactivation, in the absence of a paternally derived X chromosome a maternally derived X can be inactivated.

Animals↗
PubMed1980

Phospholipase C-induced neural tube defects in the mouse embryo.

Mouse embryo neurulae were exposed in vitro to phospholipase C to examine the role of carbohydrate-rich extracellular material (ECM) during neurulation. Exposure of embryos to this agent for 12 h resulted in failure of closure of the neural tube. Ultrastructural examination revealed an absence of ECM from regions of the neural tube which failed to close.

Animals↗
PubMed1980

Neural tube closure defects following in vitro exposure of mouse embryos to xylocaine.

Early somite mouse embryos were exposed in vitro to xylocaine (Lignocaine hydrochloride) to examine its effect on neural tube closure. When embryos were exposed to 2.4 x 10(-4) mg/ml xylocaine for the entire 36-hour culture period, cephalic neural tube closure did not take place. Then examined by SEM, the neuroepithelial cells of these embryos were incompletely elevated, and depressions in their lateral surfaces were often observed. TEM observations on the neuroepithelium of similar embryos indicated that the microtubules and apical microfilament bundles were absent. The role of calcium in the maintenance of neuroepithelial cell asymmetry and in the production of these defects is considered.

Animals↗
PubMed1980

Copper-induced microtubule degeneration and filamentous inclusions in the neuroepithelium of the mouse embryo.

The neuroepithelium of embryos exposed either in vivo or in vitro to copper sulphate was examined by transmission electron microscopy. Exposure to copper sulphate generally resulted in failure of elevation of the neural folds, and consequent development of neural tube defects. These defects appeared to result from the failure of individual cells of the neuroepithelium to change from a low to the high columnar form necessary for normal closure to take place. Ultrastructurally, the neuroepithelial cells showed a considerable reduction in the number of microtubules present, or contained microtubular remnants. Occasionally, deposits of approximately 100A filamentous material were also observed in the middle regions of neuroepithelial cells devoid of microtubules. The overall morphology of individual cells appeared otherwise unchanged. This study supports the concept that microtubules are required for neuroepithelial cellular elongation, an essential step during the process of neurulation. It also suggests that copper, like other microtubule-active agents, may induce the production of characteristic fibrillary deposits that are also observed in a number of neuropathological conditions.

Animals↗
PubMed1979

Relationship between steroidogenesis and oocyte maturation in rat graafian follicles cultured in vitro.

Rat Graafian follicles were dissected from ovaries during the morning of proestrus and incubated in various media. After an 8 h incubation period, ovarian follicles were collected and analyzed, by radioimmunoassay, for progesterone, 17 alpha-hydroxyprogesterone, androstenedione, estradiol-17 beta, and dihydrotestosterone. Following incubation in proestrus (a.m.) serum, preovulatory follicles secreted all these steroids and the output of progesterone, 17 alpha-hydroxyprogesterone and androstenedione was markedly stimulated following the addition of LH to the media. Follicle-enclosed oocytes resumed meiosis when incubated in proestrus serum without added LH. However, germinal vesicle break-down (GVBD) under these conditions was considerably slower than that observed following addition of LH to the medium. "Spontaneous" maturation of oocytes in proestrus serum was associated with increased production of steroids. Oocyte maturation and steroidogenesis both occurred following incubation of ovarian follicles in serum obtained from hypophysectomized rats. Addition of LH to the media markedly accelerated these responses. These results suggest that oocyte maturation and steroidogenesis also occur in cultured ovarian follicles in the absence of gonadotrophic hormones. The relationship between steroidogenesis and/or spontaneous oocyte maturation are discussed.

Androstenedione↗
PubMed1979

The teratogenic effect of acetaldehyde: implications for the study of the fetal alcohol syndrome.

Pregnant mice were injected intravenously with either saline alone (controls) or 1% or 2% acetaldehyde in saline, on days 7, 8 and 9 of gestation. The uterine contents were examined either on day 10 or on day 19. Acetaldehyde-treated females had more resorptions both at mid-gestation and at term, though no significant difference in maternal weight gain was observed. Experimental embryos examined on day 10 were smaller, and had a higher incidence of developmental delay, as compared to controls. Anomalies of closure of the cranial and caudal regions of the neural tube were the most commonly noted defects. When examined on day 19, acetaldehyde-treated fetuses were significantly smaller and weighed less than controls. These results suggest a role for acetaldehyde in the production of some of the teratogenic effects of ethanol manifested in the fetal alcohol syndrome.

Abnormalities, Drug-Induced↗