Unpacking the gestures of chemistry learners: What the hands tell us about correct and incorrect conceptions of stereochemistry.

In this study, adults, who were naïve to organic chemistry, drew stereoisomers of molecules and explained their drawings. From these explanations, we identified nine strategies that participants expressed during those explanations. Five of the nine strategies referred to properties of the molecule that were explanatorily irrelevant to solving the problem; the remaining four referred to properties that were explanatorily relevant to the solution. For each problem, we tallied which of the nine strategies were expressed within the explanation for that problem, and determined whether the strategy was expressed in speech only, gesture only, or in both speech and gesture within the explanation. After these explanations, all participants watched the experimenter deliver a two-minute training module on stereoisomers. Following the training, participants repeated the drawing+explanation task on six new problems. The number of relevant strategies that participants expressed in speech (alone or with gesture) before training did not predict their post-training scores. However, the number of relevant strategies participants expressed in gesture-only before training did predict their post-training scores. Conveying relevant information about stereoisomers uniquely in gesture prior to a brief training is thus a good index of who is most likely to learn from the training. We suggest that gesture reveals explanatorily relevant implicit knowledge that reflects (and perhaps even promotes) acquisition of new understanding.

A comparison between children's and adults' ability to detect conceptual information conveyed through representational gestures.

The present study compares children's and adults' ability to detect information that is conveyed through representational hand gestures. Eighteen children (M = 10 years, 1 month) and 18 college undergraduates watched videotaped stimuli of children verbally and gesturally explaining their reasoning in a problem-solving situation. A recall procedure was used to assess whether children and adults could detect information conveyed in the stimulus children's gesture and speech. Results showed that children and adults recalled information that was conveyed through representational gestures. In addition, "mismatching" gesture negatively affected the precision of speech recall for adults. However, this negative effect on speech recall was absent for children.

Bovine parthenogenetic blastocysts following in vitro maturation and oocyte activation with ethanol.

The appropriate in vitro bovine oocyte maturation and ethanol activation conditions for preimplantation bovine embryo parthenogenetic development to the blastocyst stage were investigated. A 7% ethanol concentration significantly enhanced (P<0.05) the proportion of activated, in vitro-matured bovine oocytes (7% ethanol, 83.4 +/- 3.2% versus 0% ethanol, 63.9 +/- 2.0%). The proportion of activated oocytes was significantly higher (P<0.05) by treatment with 7% ethanol for a minimum of 2 minutes (2 minutes, 89.8 +/- 4.0% versus 0.5 minutes 63.4 +/- 4.9%). Oocyte maturation for periods ranging from 30, 34, 38 and 44 hours resulted in a significant increase (P<0.05) in the proportion of activated oocytes, and in oocytes displaying 2 or 3 pronuclei versus oocytes matured for 26 hours. The proportion of cleaved, activated oocytes (2-cell stage), 4 -cell stage and parthenogenetic morula/blastocysts was significantly higher (P<0.05) within the 34-hour oocyte maturation treatment group. Although the 44-hour oocyte maturation treatment group displayed the highest proportion of activated oocytes with 2 pronuclei, it did not display the highest cleavage frequency, possibly due to the effects of postovulatory aging. Several morphologically normal parthenogenetic bovine blastocysts developed from oocytes that were in vitro matured for 34 hours. The ability to produce such parthenogenetic embryos will eventually facilitate investigation into the role(s) of the maternal and paternal genomes during bovine early development.

Transitions in concept acquisition: using the hand to read the mind.

Thoughts conveyed through gesture often differ from thoughts conveyed through speech. In this article, a model of the sources and consequences of such gesture-speech mismatches and their role during transitional periods in the acquisition of concepts is proposed. The model makes 2 major claims: (a) The transitional state is the source of gesture-speech mismatch. In gesture-speech mismatch, 2 beliefs are simultaneously expressed on the same problem--one in gesture and another in speech. This simultaneous activation of multiple beliefs characterizes the transitional knowledge state and creates gesture-speech mismatch. (b) Gesture-speech mismatch signals to the social world that a child is in a transitional state and is ready to learn. The child's spontaneous gestures index the zone of proximal development, thus providing a mechanism by which adults can calibrate their input to that child's level of understanding.

Transitions in learning: evidence for simultaneously activated strategies.

Children in transition with respect to a concept, when asked to explain that concept, often convey one strategy in speech and a different one in gesture. Are both strategies activated when that child solves problems instantiating the concept? While solving a math task, discordant children (who produced different strategies in gesture and speech on a pretest) and concordant children (who produced a single strategy) were given a word recall task. All of the children solved the math task incorrectly. However, if discordant children are activating two strategies to arrive at these incorrect solutions, they should expend more effort on this task than concordant children, and consequently have less capacity left over for word-recall and perform less well on it. This prediction was confirmed, suggesting that the transitional state is characterized by dual representations, both of which are activated when attempting to explain or solve a problem.

Cytoplasmic projections of trophectoderm distinguish implanting from preimplanting and implantation-delayed mouse blastocytes.

A scoring scheme was devised to characterize visually the morphological differentiation of whole-mount, unfixed mouse blastocysts. Embryos were recovered from groups of intact mice (implanting embryos) and mice ovariectomized on Day 3 of pregnancy (implantation-delayed embryos) every 3 h from 18:00 h on Day 4 until 12:00 h on Day 5. Blastocyst differentiation was assessed according to the presence of a zona pellucida, the appearance of the outer margin of trophectoderm cells, the visibility of the blastocoele and the relative size of the inner cell mass. The results obtained indicate that, during this period, implanting and implantation-delayed mouse blastocysts lose the zona as well as exhibit rounded trophectoderm cells, an enlarged inner cell mass and an increasing opacity of the blastocoele. In contrast, the trophectoderm cells of implanting blastocysts only exhibit extensive cytoplasmic projections, probably due to remodelling of the intracellular cytoskeleton. Growth of the inner cell mass appeared to precede the other morphological changes in the majority of blastocysts, and thus might be a prerequisite for further differentiation. The rate of blastocyst differentiation and the survival of embryos were adversely affected by the condition of delayed implantation, induced by ovariectomy. This study suggests that the appearance of cytoplasmic projections from trophectoderm cells is central to the control of blastocyst implantation.

Qualitative and quantitative changes in protein synthesis occur at the 8-16-cell stage of embryogenesis in the cow.

Cow oocytes and preimplantation embryos were cultured in medium containing radiolabelled methionine and the proteins synthesized were analysed by one-dimensional electrophoresis and fluorography. Marked changes in the pattern of synthesis were observed at the 8-16-cell stage of development. Quantitatively, a gradual decrease in the rate of protein synthesis occurred between the zygote and 8-cell stage and then the rate increased progressively to the blastocyst stage. Incorporation of radiolabelled uridine into RNA was first detected at the 16-cell stage. Taken together, these results suggest that protein synthesis is programmed by maternal mRNA up to the 8-cell stage but switches to mRNA derived from the zygote genome between the 8- and 16-cell stage.

Incidence and inheritance of the 1/29 and 14/20 Robertsonian translocations in Canadian beef cattle.

Metaphase chromosomes were prepared from peripheral leukocyte cultures of 253 beef animals representing 21 breeds. A total of 10 Robertsonian translocations were identified. Nine were 1/29 fusions and one was a stable 14/20 fusion identified in several Simmentals. To our knowledge, the only other case of this translocation reported was also in the Simmental breed, suggesting that this fusion may be unique to the breed. A further 54 relatives of known 1/29 and 14/20 carriers were examined, revealing that both fusions were inherited by 50% of offspring of the heterozygous carrier. Heterozygous male 1/29 carriers left fewer calves than karyotypically normal bulls when used in natural service.

Patterns of protein synthesis during the cell cycle of Chinese hamster ovary cells.

The protein synthesis patterns at various stages of the cell cycle of Chinese hamster ovary cells were examined by labelling cells with [35S]methionine and then separating the proteins by isoelectric focussing and two-dimensional, nonequilibrium pH gradient gel electrophoresis. We have observed a number of proteins which display quantitative differences in synthesis at specific cell cycle stages and of these the alpha- and beta-tubulins have been identified. A few proteins appear to be uniquely synthesized at specific times during the cell cycle. These include the histones and a modified version of them, which are synthesized only in S phase, and a pair of 21 kilodalton (kDa), pI 5.5 proteins, which appear only in late G2 and mitosis. We have also identified a 58-kDa, pI 7.5 protein which is present at all cell cycle stages except during late G2. This protein appears to have the same temporal properties as a 57-kDa protein called "cyclin" originally described in sea urchin embryos.

Growth of mouse embryos in bicarbonate media buffered by carbon dioxide, hepes, or phosphate.

The purpose of this study was to determine if mouse embryos could be grown successfully in a culture medium devoid of the carbon dioxide phase (CO2). Mouse embryos fertilized in vivo were collected and cultured in Hepes medium with and without bicarbonate (HCO3-) and a phosphate medium with and without HCO3-. In these experiments no CO2 gas phase was used. Further embryos were cultured in Whittingham's modified Tyrode's (T6) medium with a CO2 gas phase and served as controls. The degree of embryonic development was noted. Surviving blastocysts were transferred to the uteri of pseudopregnant mice and delivery at term was allowed to occur. There was no significant difference in the degree of embryonic development in those embryos cultured in T6 or Hepes medium (+ HCO3-) or in the number of live offspring obtained when these blastocysts were placed within the mouse uterus. Although embryonic development apparently proceeded successfully in the phosphate (+ HCO3-) medium, none of these blastocysts survived when transferred to mouse uteri. No embryonic growth occurred in either the Hepes or phosphate media which were devoid of HCO3-. It appears that a Hepes medium containing HCO3-, which uses no CO2 gas phase, is as effective as T6 medium, which uses a gas phase, in supporting in vitro mouse embryonic growth.

Changes in protein phosphorylation during the cell cycle of Chinese hamster ovary cells.

The phosphorylation patterns of proteins were examined during the cell cycle of Chinese hamster ovary cells. This was accomplished by labeling synchronized cells at various times with [32P]orthophosphate and separating the proteins by both isoelectric focusing and nonequilibrium pH gradient two-dimensional gel electrophoresis. The most dramatic changes occurred during late G2/M when approximately eight proteins (including vimentin, lamin B, and histones 1 and 3) showed increased phosphorylation. Ten other proteins appeared to be uniquely phosphorylated during late G2/M. Of these 10 proteins, seven were no longer phosphorylated shortly after mitosis. There is also at least one protein which showed a relative decrease in phosphorylation during late G2/M.

Synthesis of unique low molecular weight proteins during late G2 and mitosis.

Changes in protein synthesis were examined during the cell cycle of Chinese hamster ovary cells by labeling synchronized cells at various times with [35S]methionine and separating the proteins on two-dimensional polyacrylamide gels. Several proteins, including tubulin, showed marked differences in their relative rates of synthesis during the cell cycle. A few proteins were found to be synthesized at a specific time during the cycle. In particular, a pair of proteins of approximately 21,000 daltons and isoelectric point of 5.5 were found to be synthesized only in late G2 and mitotic cells. Cells that were labeled during mitosis and then allowed to divide showed no trace of these proteins, indicating that their presence is transient and that they are likely involved in mitosis.

Uncoordinated synthesis of histones and DNA by mouse eggs and preimplantation embryos.

The temporal coordination of histone and DNA synthesis in mouse eggs and preimplantation embryos were examined. In unfertilized mouse eggs arrested at metaphase II, histone synthesis was observed, but at lower rates than previously reported for fertilized zygotes. Cytosine arabinoside, an inhibitor of DNA synthesis, was used to study the relationship between DNA and histone synthesis during cleavage stages of mouse development. Cytosine arabinoside (50 microM) inhibited by 90% the incorporation of [3H]thymidine into DNA by two-cell embryos and blastocysts. At this concentration, cytosine arabinoside inhibited incorporation of [3H]lysine into blastocyst histones by only 30% and had no effect at the two-cell stage. These results are interpreted to show that DNA synthesis and histone synthesis are not coordinated temporally during early development of the mouse, but may become more so as development proceeds.

Amino acid transport and exchange in preimplantation mouse embryos.

Between the 1-cell zygote and the early blastocyst stage of mouse embryos the net rate of uptake of methionine increased, the internal pool became progressively more expanded and less easily reached steady state, and the specificity of competitor amino acids changed. Sodium-dependent transport was first detected in compacted morulae (16--32-cell stage). Uptake of [14C]methylaminoisobutyric acid was detectable in blastocysts but not in unfertilized eggs. Efflux of methionine by an exchange transport system was detectable at all stages, but in intact blastocysts much higher external concentrations were required to activate exchange transport. An exchange system with properties similar to that operating at cleavage stages was exposed when blastocysts were collapsed with cytochalasin D. Since this exchange system was not detectable in isolated inner cell masses, it may be confined to the juxtacoelic surface of trophectoderm cells.

Synthesis of alpha-fetoprotein by the pre-implantation and post-implantation bovine embryo.

The synthesis of alpha 1-fetoprotein (AFP) was measured by radioimmunoassay in tissues and fluids of 19 bovine embryos (14-46 days of gestation) and in tissue cultures of 4 pre-implantation embryos (17-27 days) by incorporation of radioactive methionine. AFP was first detected in Day-14 trophoblasts and secretion of AFP into allantoic fluid occurred by Day 16. Embryonic tissues and fluids in pre-implantation and post-implantation embryos contained levels of AFP that were 550 to 1 500 000 times higher than those found in maternal serum (3.9-298 000 compared with 0.07-0.25 ng/mg protein). High levels of AFP were also found in uterine fluid which suggested significant transfer of this protein from the early post-implantation conceptus. The major sites of AFP synthesis were yolk sac and fetal liver. It is concluded that the synthesis of bovine AFP is not initiated by events associated with implantation.

Chromosome rearrangement between the Indian muntjac and Chinese muntjac is accompanied by a delection of middle repetitive DNA.

The organizations of the genomes of two related species of Asian deer, the Indian (2n = 6 female, 7 male) and Chinese muntjac (2n = 46), were compared at the cytogenetic and molecular levels. These dramatically different karyotypes preserve little apparent G-banding homology. The difference in chromosome number is coincident with a 22% reduction in haploid DNA content from 2.7 to 2.1 pg in the Chinese and Indian muntjac, respectively. The kinetics of reassociation of the Indian muntjac (equivalent Cot = 4285 M-1. s-1) and Chinese muntjac DNA (equivalent Cot - 4362 M-1.s-1) in 2.4 M tetraethylammonium chloride suggests conservation in amount of "single-copy" DNA. Two middle repetitive DNA sequence classes differ in both amount and in degree of repetition between the two species. A middle repetitive frequency component (935-fold repeated) represents 13% of the Indian muntjac DNA. A similar component (644-fold repeated) represents 17% of the Chinese muntjac DNA. Low repetition DNA sequence components (repeated 5- and 50-fold) represent 30 and 40% of the Indian and Chinese muntjac DNAs, respectively. These differences quantitatively account for the 0.6 pg haploid DNA content variation between species. The deletion of middle repetitive DNA has not substantively altered the distribution of restriction endonuclease DNA base composition classes as defined by buoyant density in cesium chloride. These results represent the first time that middle repetitive DNA has been directly implicated in a chromosome rearrangement within the vertebrates.

Distribution of bovine fetuin and albumin in plasma, allantoic and amniotic fluids during development.

A radioimmunoassay for bovine fetuin was developed and its specificity and validity established. Albumin was measured by radial-immunodiffusion assay. Fetuin levels in fetal plasma increased from 10 to 15 mg/ml between 4 and 8 months of gestation; albumin levels remained higher than fetuin. Neonatal plasma fetuin levels rapidly declined during the first 14 days post partum, coincident with a marked reciprocal increase in albumin levels. In allantoic fluid fetuin and albumin concentrations reached a peak at 7 months but fetuin values were always higher. In amniotic fluid both proteins peaked at 8 months; albumin levels were similar to those in allantoic fluid but fetuin values remained consistently lower than those in allantoic fluid throughout gestation. Fetuin levels in maternal plasma declined from 0.7 to 0.4 mg/ml between 1 month and term. We conclude that (1) at term there is an abrupt change from fetuin synthesis to increased albumin synthesis by the neonatal liver; (2) fetuin appears to be preferentially accumulated in the allantois whereas albumin is equally concentrated in the allantois and amnion.