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Biomedical subjects

N W Klein

Publications and source records attributed to N W Klein.

At least 37 records · Page 2Linked to original sources
PubMed1987

Heat shock and thermotolerance during early rat embryo development.

Effects of heat shock on the development of early pre-somite embryos have been studied using cultured rat embryos. The results illustrate the sensitivity of the developing head and brain to elevated temperatures prior to neural tube closure and the capacity of embryos to acquire thermotolerance. Embryos exposed briefly to an elevated temperature (43 degrees C for 7.5 min) developed severe craniofacial defects including microphthalmia, microcephaly, gross reduction of the forebrain region, and open neural tubes. In contrast, a nonteratogenic heat shock (42 degrees C for 10 min) caused embryos to acquire thermotolerance during a 15-min recovery period at 38.5 degrees C. Acquired thermotolerance was effective in protecting embryos from a subsequent more severe heat treatment which would have been teratogenic in an unprotected embryo. Recovering embryos mounted a heat shock response as evidenced by the induction of a 71 kilodalton heat shock protein. Activation of the heat shock response was not a teratogenic event in the developing embryo.

Animals↗
PubMed1986

Cardiovascular defects in rat embryos cultured on serum from rats chronically exposed to phenytoin.

Headfold-stage rat embryos were cultured for 48 hours on serum from rats chronically exposed to phenytoin for periods as long as from conception until 11 months of age. Serum from phenytoin-exposed rats caused approximately 50% of the cultured rat embryos to develop cardiovascular defects as compared to 12% for controls. These morphological abnormalities included hemorrhaging of blood vessels within the embryo, pericardial edema, and absence of yolk sac circulation. Neither serum glucose nor phosphate levels nor serum osmolality were appreciably affected by phenytoin treatment. However, serum protein concentration was reduced in rats exposed to phenytoin as compared to controls. An absence of the serum protein hemopexin was associated with the reduction in serum protein levels but did not appear to be responsible for the observed cardiovascular defects.

Animals↗
PubMed1986

Effects of whole rat embryos cultured on serum from zinc- and copper-deficient rats.

Whole rat embryos of 9.5 gestational days were cultured for 2 d on sera taken from rats fed diets deficient in zinc (0.5 micrograms Zn/g diet) or copper (0.6 micrograms Cu/g diet), or fed a control diet (100 micrograms Zn and 10 micrograms Cu per g diet). Head malformations were observed in embryos cultured on 12 of 16 zinc-deficient and 11 of 12 copper-deficient serum samples. The protein contents, crown-rump lengths (CRL) and percentages of head to CRL in these embryos were significantly smaller than those of embryos cultured on control serum. Copper and zinc were then added directly to 8 zinc- and 7 copper-deficient serum samples that had grown abnormal embryos. All subsequent cultured embryos had a normal appearance and protein content, CRL and head-to-CRL percentages comparable to controls, except one zinc embryo. These findings suggest that zinc and copper can act directly on embryonic development, and that whole rat embryo cultures can be used to detect deficiencies of these elements.

Abnormalities, Multiple↗
PubMed1984

Uptake and distribution of exogenous serum proteins in the cultured rat embryo.

Head fold stage rat embryos were cultured on a medium consisting of adult rat serum for 48 hr. During the final 10 or 20 hr of culture [35S]-methionine was added to the medium. Sera from visceral yolk sac blood vessels, exocoelomic cavity fluid, and amniotic sac fluid were analyzed by SDS-polyacrylamide gel electrophoresis followed by Amido Black staining and fluorography. Amido Black staining showed bands in all three embryonic fluid compartments which migrated at rates comparable to transferrin, alpha-fetoprotein, albumin, IgG, and hemoglobin. Fluorography, however, showed that radioactivity was restricted to alpha-fetoprotein, IgG, and hemoglobin. This suggested that at least some transferrin and albumin were transferred intact from the exogenous medium to the embryonic fluid compartments.

Amniotic Fluid↗
PubMed1984

Metabolic activation of cyclophosphamide by yolk sac endodermal cells of the early chick embryo.

Endodermal cells isolated from the yolk sacs of day 3 chick embryos were able to activate metabolically cyclophosphamide. This was demonstrated by the cytotoxicity of cyclophosphamide to the endodermal cells themselves as well as by the ability of endodermal tissue to mediate a cytotoxic response in coculture with KB cells, a human tumor cell line unable to activate cyclophosphamide. Yolk sac endodermal cells from day 3 embryos were sensitive to cyclophosphamide when the drug was added immediately after the start of culture, but not when the drug was added after 24 hr of culture. The ability to metabolize cyclophosphamide by the day 3 embryo appeared limited to the endodermal cells of the yolk sac as cells derived from neither the embryo proper nor yolk sac mesoderm-ectoderm tissue were positive in these tests. Using whole blastoderms, cyclophosphamide activation was detected as early as 12 hr of egg incubation.

Animals↗
PubMed1984

Human serum teratogenicity studied by rat embryo culture: epilepsy, anticonvulsant drugs, and nutrition.

Epileptic women have a greater risk for spontaneous abortions and children with birth defects than do nonepileptics. In a unique approach to identifying causes of these problems, we have cultured whole rat embryos for 48 h on blood sera from epileptics. In the first part of the study, three embryos were cultured on each serum sample from 128 different epileptics being treated with either single anticonvulsants or no drug to compare the teratogenicity of these drugs. Sera from subjects receiving either phenobarbital or no drug had comparable frequencies of cultured embryo abnormalities, which were lower than those from subjects taking phenytoin, valproic acid, or carbamazepine. In the second phase of the study, attempts to identify causes for serum teratogenicity led to the finding that the abnormalities and reduced embryo growth produced by many serum samples could be completely overcome by adding vitamins and/or amino acids to the serum. Of 53 samples tested, 32 (60%) were corrected by supplementation (17 of 23 phenytoin, seven of nine phenobarbital, six of 12 carbamazepine, none of six valproic acid, and two of three no drug). Although the results of this study provided a general assessment of drug teratogenicity that agreed with other studies and emphasized the role of nutrition in fetal defects, the importance of individual differences in causes of teratogenicity was also noted.

Amino Acids↗
PubMed1983

Synthesis of serum proteins by cultures of chick embryo yolk sac endodermal cells.

Endodermal cells were isolated from yolk sacs of 3-day chick embryos and cultured for 6 days in Eagle's minimal essential media plus 10% fetal calf serum. During this period cells rapidly lost their ability to synthesize DNA as judged by [3H]thymidine incorporation into DNA. In spite of this loss of DNA synthesis serum protein synthesis and secretion remained at a constant 45% of total protein synthesis and secretion. This was determined by immunoprecipitation of culture media using antibodies directed against embryonic chick serum proteins. Media were also analyzed for the synthesis and secretion of specific serum proteins using polyacrylamide gel electrophoresis. The relative synthesis and secretion of the individual serum proteins followed that previously observed in ovo with the exception of alpha-globulin-a which became undetectable. When culture media were supplemented with ovalbumin or insulin the relative synthesis and secretion of certin specific serum proteins were altered. However, analysis of these same media samples showed that the total amounts of serum protein synthesis and secretion were unaffected.

Animals↗
PubMed1980

Successful culture of rat embryos on human serum: use in the detection of teratogens.

Growth of head-fold-stage rat embryos cultured with human serum for 48 hours was enhanced by supplementation with glucose. Embryo growth (protein and DNA contents) varied with the source of the serum. Serum from 16 of 19 untreated subjects produced normal embryos. Serum from five subjects undergoing cancer chemotherapy and six subjects receiving anticonvulsants was either lethal or teratogenic.

Adult↗
PubMed1980

The use of cultured rat embryos to evaluate the teratogenic activity of serum: cadmium and cyclophosphamide.

Head fold stage rat embryos were cultured for 48 hours in vitro on serum taken at various intervals from rats that had been injected ip with either cadmium or cyclophosphamide. Their response was compared to that of embryos cultured for the same period on control serum to which these substances were added directly. One and 4 hour sera from cadmium-injected rats (2.13 mgCd++/kg) were lethal. Eight hour serum allowed survival but embryos were exencephalic and contained reduced amounts of protein and DNA. The response to direct cadmium was characteristically different and was related to dosage and the extent to which zero-time embryos had progressed through the head fold stage. At 1.6 micro M, Cd++ susceptible embryos were hemorrhagic, though not exencephalic. One hour serum from rats given cyclophosphamide (180 mg/kg) was lethal. On 4 hour serum, embryos survived but were exencephalic and contained less protein and DNA than controls. Embryos were resistant to direct cyclophosphamide up to 800 micrograms per ml of medium. At this concentration, embryos appeared morphologically normal but contained reduced amounts of protein.

Animals↗
PubMed1978

Polysome activity in relation to growth and protein starvation in brains and hearts of cultured early chick embryos.

In previous studies, brains but not hearts of intact early chick embryos were found to be sensitive to protein starvation. In this study, the in vitro protein synthetic activity of polysomes isolated from brains was found to be greater than those isolated from hearts. Starvation reduced the protein synthetic activity of polysomes in vitro but the extent of the reduction was approximately the same for both brains and hearts. A reduction in the amount of ribosomes as polysomes may have contributed to the lower synthetic activity of polysomes from tissues of starved embryos but not to the differences in synthetic activities between brains and hearts. In addition, neither the stability of isolated polysomes nor ribosome-associated ribonuclease activity appeared responsible for the differences observed in polysome synthetic activities. In direct relationship to the differential sensitivity of brains and hearts to starvation observed in the intact embryo, ribosomes isolated from brains of both growing and starved embryos were more readily degraded during in vitro incubation than those from hearts.

Animals↗
PubMed1978

Serum protein depletion by cultured rat embryos (1).

Cultures of 10-day rat embryos depleted a protein band with a molecular weight of approximately 125,000 from the rat serum medium. Delayed centrifuged serum differed from immediately centrifuged serum by a reduction in the staining intensity of the 125,000 molecular weight protein band and by the absence of two high molecular weight (greater than 200,000) protein bands.

Animals↗
PubMed1976

Serum protein synthesis in the early chick embryo.

Isolated yolk-sacs of chick embryos secreted serum proteins when incubated in buffered chick Ringer's solution. The presence of serum transferrin, two embryo-specific alpha-globulins, and a prealbumin were demonstrated by acrylamide gel analysis. Yolk-sacs from embryos explanted at 11-13 somites (40 hr preincubation) and cultured for 48 hr secreted in addition a protein with the mobility of serum albumin. Incubation of yolk-sacs in the presence of radioactive valine indicated that serum proteins were synthesized as early as the primitive streak stage. By incubating isolated yolk-sacs and embryos from 48-hr explants in the presence of radioactive valine, the synthesis of serum proteins was found to be restricted to the yolk-sac at this stage of development. Culturing explants on various nutrient proteins as well as protein starvation medium altered the relative synthesis of several serum proteins. We have proposed that morphological and biochemical changes in embryos resulting from altered nutrition may be mediated by the proteins of the serum.

Animals↗