Search PubMed⌕ Search

Biomedical subjects

G A Schultz

Publications and source records attributed to G A Schultz.

At least 73 records · Page 4Linked to original sources
PubMed1987

Protein synthesis in mature human oocytes.

As a first step toward understanding control of gene expression in early human development, an analysis of protein synthesis and amino-acid transport in unfertilized mature oocytes was initiated. Qualitative patterns of protein synthesis were examined in individual oocytes cultured in medium containing radiolabeled methionine. No differences in synthetic pattern of proteins, resolved by one-dimensional electrophoresis and fluorography, were observed in oocytes analyzed from times varying from 12 to 52 hr following collection by laparoscopy. Contamination by follicular or corona radiata cells was readily distinguished on the basis of increased relative synthesis of a polypeptide with Mr = 44,000, a dominant product of synthesis in follicular cells. Based on the specific activity of the methionine precursor, the absolute rate of synthesis was measured to be about 50 pg/oocyte/hr, a value higher than in mouse unfertilized eggs. No difference in protein synthetic rate was observed in oocytes analyzed at 12 hr postcollection versus later times up to 50 hr postcollection. Competition of methionine uptake by leucine, efflux of radiolabeled methionine from preloaded oocytes into medium containing methionine and uptake of methionine in medium with low sodium ion concentration was observed. These findings are consistent with the presence of an L (leucine-preferring) system for neutral amino acid transport, similar to that in mouse and rabbit eggs. Total protein was measured to be about 150 ng/oocyte, a value five times that of the mouse. These studies provide basic data for further analysis of oocytes and perhaps preimplantation stage embryos in the future.

Animals↗
PubMed1987

Carotid artery Dacron patch graft angioplasty: a ten-year experience.

Of 394 carotid endarterectomies performed during a 10-year period, 36 (9%) included Dacron patch graft angioplasties. Patch graft angioplasties were used selectively in patients because they had undergone previous carotid endarterectomy or had small-caliber vessels. There were no postoperative infections, occlusions, emboli, stroke, or pseudoaneurysms. In addition, no clinically detectable recurrent stenoses developed in this high-risk group of patients. Twenty-four of the 27 patients available for follow-up were screened for asymptomatic stenoses with spectral analysis and B-mode imaging; there was no sign of hemodynamically significant recurrent stenosis in this group. These encouraging results support the continued selective use of Dacron patch graft angioplasty in carotid surgery.

Blood Vessel Prosthesis↗
PubMed1987

Amino acid content of preimplantation rabbit embryos and fluids of the reproductive tract.

As a companion to amino acid transport and protein synthetic studies, it was of interest to quantify the amino acid pools in embryos and reproductive tract fluids during preimplantation development. Primary amines in the acid-soluble extracts of embryo and fluid samples were separated by high-performance liquid chromatography, reacted with o-phthalaldehyde, and quantified by fluorescence emission. The amino acid compositions of embryos were like those of corresponding reproductive tract fluids. Taurine was high in eggs and fluids but declined with development, while glycine levels rose. Glycine was highest in concentration in all samples (except the egg), followed by glutamate and alanine, while most other amino acids were consistently of low abundance.

Amino Acids↗
PubMed1986

Expression of the major heat shock protein (hsp 70) family during early mouse embryo development.

Stress or heat shock proteins (hsp) are synthesized by most cells in response to adverse environmental conditions. In mammalian cells, the major proteins synthesized in response to stress have relative molecular weights (Mr) in the range of 68 to 74 kilodaltons (kD) and are encoded by a small multi-gene family collectively referred to as hsp 70 genes. In unfertilized mouse eggs, no members of the hsp 70 family appear to be synthesized under normal or stressful (heat shock) conditions. At the two-cell stage, two proteins with Mr = 74 kD and Mr = 70 kD are expressed as a consequence of developmentally activated transcription of these hsp 70 genes. No stress-induced synthesis in response to heat shock is observed at this stage. At the eight-cell stage, constitutive synthesis of the 70-kD protein continues, but, as in the two-cell embryo, no heat shock induced synthesis of a novel heat shock protein is observed. By the blastocyst stage, however, an inducible protein with Mr = 68 kD is synthesized in response to heat shock in addition to constitutive synthesis of the 70-kD protein. The constitutively synthesized cognate proteins are coded for by a set of mRNAs about 2,000 nucleotides in length. The induced hsp 68 proteins are coded for by mRNAs of larger size (about 2,600 nucleotides). Only the smaller mRNA class is detectable on Northern blots of RNA extracted from control or heat shock cleavage stage embryos and control blastocysts. As predicted from protein synthetic studies, both classes are resolved in RNA preparations derived from heat-shocked blastocysts.

Animals↗
PubMed1986

A five- to seven-year experience with externally-supported Dacron prostheses in axillofemoral and femoropopliteal bypass.

We have examined the clinical results of 56 externally-supported (EXS) Dacron grafts in the axillofemoral position and 117 in the femoropopliteal position. Results have been analyzed from two perspectives: primary patency concerns only those grafts that had never occluded; extended patency refers to all open grafts including those whose continued patency is the result of thrombectomy. The 5-to 7-year life-table patency rates are: axillofemoral 8 mm and 6 mm bypass: primary 75% and extended 97%; above-knee femoropopliteal 6 mm bypass: primary 78% and extended 93%; below-knee 6 mm femoropopliteal bypass: primary 41% and extended 91%. In contrast, the results for the 5 mm grafts used for femoropopliteal bypass were inferior to the 6 mm grafts: femoropopliteal 5 mm bypasses had an above-knee primary patency rate of 44% and an extended rate of 55%, with a below-knee primary patency rate of 15% and an extended rate of 32%. Rendering the noncrimped porous Dacron prosthesis kink and compression resistant by an external support coil appears to increase its potential for successful use, especially in 8 mm axillofemoral and 6 mm femoropopliteal bypasses.

Actuarial Analysis↗
PubMed1986

Heat-shock gene expression in animal embryonic systems.

We have examined the expression of heat shock or stress genes in fish, echinoderm, amphibian, and mammalian embryonic systems. In a Chinook salmon embryo cell line, elevation of the incubation temperature or exposure to metal ions (e.g., cadmium and zinc) induced a set of heat-shock proteins HSPs. Transcriptional inhibitor, in vitro translation, and Northern hybridization studies suggest that fish HSP synthesis is regulated at the transcriptional level. The synthesis of HSPs during early development of Arbacia punctulata, Xenopus laevis, mouse, and rabbit is a stage-dependent phenomenon. In each of the developmental systems, HSP synthesis could not be induced until after cleavage stages. The ability of the embryo to undergo a heat-shock response (i.e., HSP synthesis) was correlated with the ability to detect HSP mRNA accumulation by either in vitro translation or Northern hybridization assays. Thus, the stage-dependent synthesis of HSPs appears to be controlled at the transcriptional level. Finally, in all of the organisms studied, the capacity to synthesize HSPs and accumulate HSP mRNA also coincides with acquisition of thermotolerance.

Animals↗
PubMed1985

Actin mRNA content in normal and delayed implanting mouse embryos.

Actin mRNA levels were measured in mouse eggs, early embryos, and delayed implanting blastocysts by a homologous, cloned recombinant DNA probe and "dot" blot methodology. A maternal store of 431 fg of actin mRNA was observed in the unfertilized eggs. This mRNA pool decreased 12-fold by the mid-two-cell stage. Actin mRNA levels were then observed to increase progressively from the eight-cell to the blastocyst stage on a basis proportional to cell number. Late blastocysts contained 2400 fg actin mRNA per embryo (22 fg per cell). The cellular level decreased by about 20% in embryos induced into delay of implantation by ovariectomy of donor females. Reactivation of the delayed implanting blastocysts through hormonal manipulation in vivo or culture in vitro was accompanied by reestablishment of the level of cellular actin mRNA observed in normal blastocysts.

Actins↗
PubMed1985

Acquisition of the heat-shock response and thermotolerance during early development of Xenopus laevis.

The ability to synthesize a 68,000- to 70,000-Da protein (hsp) in heat-shocked early Xenopus laevis embryos is dependent on the stage of development. Whereas late blastula and later stage embryos synthesize hsp68-70 after heat shock, cleavage stages are incompetent with respect to hsp synthesis. In vitro translation experiments and RNA blot analyses demonstrate that enhanced synthesis of hsp68-70 is associated with an accumulation of hsp68-70 mRNA. Examination of the effect of heat shock on preexisting actin mRNA reveals that heat shock promotes a reduction in the levels of actin mRNA in cleavage embryos but has no discernible effect on actin mRNA levels in neurula embryos. Finally, the acquisition of the heat-shock response (i.e., synthesis of hsp68-70 and accumulation of hsp70 mRNA) during early Xenopus development is correlated with the acquisition of thermotolerance.

Age Factors↗
PubMed1985

Quantitative and qualitative changes in histone gene expression during early mouse embryo development.

There are large amounts of histone mRNA present in mouse eggs. These RNAs are rapidly degraded, as are other mRNAs, after fertilization and prior to the second cleavage. During cleavage, the histone mRNA accumulates as the embryo divides. The same sets of histone genes are expressed in eggs and embryos, although there are large qualitative differences in the amounts of particular histone mRNAs. The function of the egg histone mRNA is unknown. The amount of histone mRNA in cleaving and blastocyst embryos is probably sufficient to code for the blastocyst histone proteins.

Animals↗
PubMed1985

Amino acid transport in mouse blastocyst compartments.

Properties of uptake and exchange of L-methionine associated with the compartments of the blastocyst were examined in the mouse embryo. The inner cell mass (ICM) was derived from the 102 h blastocyst by immunosurgical procedures and studied in isolation. The ICM possessed strong exchange and efflux transport character. The Vmax of transport was about one-fifth that of the intact blastocyst, but the Km (660 microM) was about 30 times as high as that of the intact blastocyst. Consequently, at a concentration of about 100 microM-methionine, the the velocity of uptake into the ICM is about one-thirtieth of that into the intact blastocyst. Uptake of amino acid into the intact blastocyst was resolved into cellular and cavity components by mechanically collapsing the blastocyst following uptake of radiolabelled methionine. By this method, it was found that about 70% of the label accumulated by the blastocyst was in the cavity.

Amino Acids↗
PubMed1984

Induction of heat shock protein messenger RNA in maize mesocotyls by water stress, abscisic Acid, and wounding.

Exposure of the excised growing region of the mesocotyl of young corn seedlings to heat shock stimulated the production of specific heat shock proteins and the intensification of synthesis of two proteins with a molecular weight of approximately 70,000. Water stress and abscisic acid also stimulated synthesis of these 70,000-dalton proteins, and other unique proteins distinct from those induced by heat shock. Growing tissues of intact corn mesocotyls exposed to heat shock, water stress, or abscisic acid accumulated mRNA species homologous to a cloned genomic probe of the 5' end of the 70,000-dalton Drosophila heat shock protein gene. Since cut segments of the mesocotyl under unstressed conditions produced a similar mRNA, we suggest that the hsp 70 gene is activated in corn by a variety of diverse stresses. Production of the mRNA is rapid, but transient, being induced within 3 hours of the imposition of the stress, but declining after reaching a maximum at 9 hours.

Journal Article↗
PubMed1983

Properties of amino acid transport in preimplantation rabbit embryos.

The kinetics, specificity, time dependency, Na+ dependency, and exchange behavior of the uptake of methionine, as a model for the uptake of the neutral amino acids, was investigated in rabbit eggs, morulae, and 6-day blastocysts. Uptake by the blastocyst was physically resolved into components representing uptake into the cellular and cavity compartments. The kinetic data for all material, except the cellular compartment of the blastocyst, could be described mathematically by the parallel activity of a saturable and a linear transport system. The Km decreased from 91 microM in the unfertilized egg to 38 microM in the fertilized egg to 13 microM in the 69-hr morula. The Km of uptake into blastocysts was 131 microM. The Vmax of uptake into the whole blastocyst was calculated to be about 5000 times that of uptake into the egg. Competition of methionine uptake by other amino acids indicated that the egg had somewhat more "L-like" transport specificity than subsequent developmental stages, while the system(s) in the blastocyst were reactive with most neutral amino acids. Uptake into the egg, 69-hr morula, and the cellular compartment of the blastocyst reached a steady state with time, in contrast to uptake into the 76-hr morula and the cavity compartment of the blastocyst. Compatible with this, was the observation that eggs and 69-hr morula, but not blastocysts, exhibited considerable efflux into amino acid-containing media. The cavity compartment of the blastocyst may, however, act as a reservoir of amino acids for the cellular compartment. The Na+ dependency of transport was unchanged throughout the developmental period studied in this investigation.

Animals↗
PubMed1983

Changes in the quantity of histone and actin messenger RNA during the development of preimplantation mouse embryos.

Actin and histone H3 mRNA levels in mouse eggs and early embryos have been measured by use of recombinant DNA probes having sequence homology to those mRNA species. Total nucleic acid was extracted from pools of unfertilized eggs, two-cell embryos, eight-cell embryos, and blastocysts. The nucleic acids were resolved electrophoretically, bound to diazotized paper following Northern transfer, and hybridized with 32P-labeled histone or actin DNA probes. Our findings demonstrate that there is a maternal store of histone and actin mRNA in the unfertilized egg but that this mRNA pool is reduced roughly 10-fold on an embryo basis by the mid-two-cell stage. Following this reduction of maternal mRNA, histone and actin mRNA accumulation from the eight-cell cleavage stage to the blastocyst increases proportionally to cell number and appears to be controlled by zygote genome transcription.

Actins↗
PubMed1982

Expression of a set of fish genes following heat or metal ion exposure.

Elevation of the incubation temperature of Chinook salmon embryo cells from 20 to 24 degrees C or exposure to heavy metals such as CdCl2 (5 microM) or ZnCl2 (100 to 500 microM) induces the reversible expression of a set of heat shock or stress proteins. Continuous exposure of the cells to either metal ions or heat shock results in recovery of protein synthesis to a control-like pattern. Treatment of these cells with either ZnCl2 or CdCl2 also induces the protein metallothionein. Heat shock, however, does not induce metallothionein, suggesting that it does not belong to the common group of heat shock or stress proteins. The induction of these stress proteins can be inhibited by pretreatment with actinomycin D, suggesting that their expression is regulated at the transcriptional level. The major stress proteins are detectable in the products of an in vitro translation system programmed with RNA isolated from heat shock- or metal ion-treated cells. A recombinant DNA probe complementary to Drosophila mRNA coding for the 70,000-dalton heat shock protein was found to hybridize to RNA isolated from heat shock-or metal ion-treated cells but not from control cells. The fish mRNA coding for the heat shock protein with a molecular weight of 70,000 appears to be of similar size to the corresponding Drosophila mRNA.

Animals↗
PubMed1982

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.

Amino Acids↗
PubMed1981

Endogenous amino acid pool sizes in mouse eggs and preimplantation embryos.

The endogenous pool sizes of 17 amino acids were measured directly in samples of mouse eggs, 8-cell embryos and blastocysts by estimation of the fluorescent product of the reaction of o-phthalaldehyde and primary amines. Taurine, glycine, alanine, glutamate and aspartate were detected at high levels. During the transition to the blastocyst, most amino acid pools increased 2-3-fold, but the taurine and glycine pools decreased to about 50 and 10%, respectively, of the egg value. The amino acid distribution in cumulus masses was similar to that of the egg and embryo samples but different from that of serum.

Amino Acids↗
PubMed1980

Presence of cap structures in the messenger RNA of mouse eggs.

The presence of 5'-terminal 7-methylguanosine cap structures in the messenger RNA molecules in mouse eggs was assessed by (1) translational inhibition in a message-dependent reticulocyte cell-free system with the cap analogue 7-methylguanosine-5'-triphosphate, and (2) enzymatic removal of cap strucures with tobacco acid phosphatase followed by end-labelling with gamma-32P-ATP and polynucleotide kinase. The results suggest that the majority of mRNA molecules contain cap structures. There was no detectable difference in degree of capping in unfertilized versus fertilized egg mRNA.

Acid Phosphatase↗