Patterns Of Polypeptide Synthesis Research Articles

Synthetic profiles of polypeptides of human oocytes and normal and abnormal preimplantation embryos.

There is considerable variation in the rate of development in vitro of individual preimplantation human embryos. The relationship between the rate of development and patterns of polypeptide synthesis in individual embryos was examined using SDS-PAGE and autoradiography. After incubation in [35S]methionine, 19 polypeptide bands were identified that change between fertilization and the morula stage. Although changes in two of the bands occurred in embryos that were developing normally and in ageing oocytes, and are thus independent of fertilization, the changes identified in the remaining 17 bands occurred only after fertilization. In embryos that were developing abnormally, as assessed by delayed cleavage, cleavage arrest or extensive fragmentation, the alteration in polypeptide synthetic profiles increased with increasing abnormality.

Cytoplasmic maturation for activation of pig follicular oocytes cultured and arrested at metaphase I.

A large population (62-90%) of pig follicular oocytes can mature to metaphase II after culture for 48 h. However, a proportion (6-22%) remain in an immature stage at metaphase I (metaphase I-arrested). The main objective of this study was to determine whether the cytoplasm of metaphase I-arrested pig oocytes is capable of being activated by sperm penetration or parthenogenetic stimulation. After culture for 48 h, oocytes without a polar body (73% were shown to be at metaphase I after staining) and those with a polar body (94% were at metaphase II) were fertilized in vitro. A total of 69% and 62% of the oocytes were activated to form a female pronucleus, respectively, and the rate of polar body extrusion induced by fertilization in the activated oocytes was 90% (the first polar body) and 95% (the second polar body), respectively. When oocytes without and with a polar body were stimulated with an electric pulse, 53% and 81% of the oocytes were activated, respectively. The rate of polar body extrusion in the activated oocytes was 73% (the first polar body) and 79% (the second polar body), respectively. In contrast, young metaphase I oocytes cultured for 24 h had low (6%) or zero activation rate after in vitro fertilization or electric pulse stimulation. However, about one-third of the young metaphase I oocytes penetrated by spermatozoa after in vitro fertilization responded to electric pulse 12 h after insemination, and almost all (93%) were activated when they were stimulated 24 h after insemination. Patterns of polypeptide synthesis and histone H1 kinase activity were similar in metaphase I-arrested and metaphase II oocytes, and were characterized by increase in a 25 kDa polypeptide and by decrease in kinase activity. Although the first step of meiotic division is impaired, these results indicate that metaphase I-arrested oocytes are mature cytoplasmically.

Biochemical studies on goat oocytes: Timing of nuclear progression, effect of protein inhibitor and pattern of polypeptide synthesis during in vitro maturation

Temporal progression of nuclear events of goat oocytes matured in vitro was studied by adding a specific inhibitor to the culture medium at different time points, to investigate protein synthesis requirements and its pattern during in vitro maturation. Goat cumulus-oocyte complexes (COCs) were matured in vitro in TCM 199, fixed at different time intervals and stained with orcein to assess nuclear changes. The germinal vesicle (GV) stage was found to be present at 0 h, chromosomal condensation stage was observed at 8 h, metaphase I at 12 to 14 h, and metaphase II was begun after 16 h of maturation and was nearly completed at 24 h. Protein synthesis inhibitor, cycloheximide, blocked oocyte maturation at germinal vesicle breakdown(GVBD), if added to the maturation medium between 0 to 4 h, suggesting that protein synthesis is required for GVBD. The transition from metaphase I to metaphase II was also protein synthesis-dependent, as observed when cycloheximide was used between 8 to 10 h of culture. When cycloheximide was added from 12 h of culture onwards, nuclear progression to metaphase II was progressively restored, but many chromosomal abnormalities were noted. Changes in the protein synthesis pattern were studied by radiolabeling of oocytes with [ 35S]-methionine at 0, 7, 12 and 24 h of culture, corresponding with GV, GVBD, metaphase I and metaphase II stages. A polypeptide of 28.1 KDa appeared as a major band at the GV stage, and its size decreased greatly and disappeared after the GVBD stage. Three new polypeptides (35, 36.5 and 39 KDa) appeared at GVBD and were detectable at metaphase II. In conclusion, the synthesis of proteins is required for the maintenance and transition of goat oocytes from GV to metaphase II during in vitro maturation.

Changes in synthesis and abundance of specific polypeptides at early and late stages of blue-light-induced sporulation of Trichoderma

The temporal relationship between photoinduced morphogenesis and the translation and abundance of specific polypeptides was studied in Trichoderma harzianum. Sporulation of this common soil fungus is induced by a brief pulse of low fluence blue light. The minute light signal is amplified to cause a local switch from vegetative mycelia to the production of aerial, branched conidiophores. Patterns of polypeptide synthesis and abundance were analysed to detect changes both before and after visible structural changes occur. The early phases of morphogenesis (up to 4–8 h after light) occur without masive changes in morphology, or in the pattern of polypeptide abundance. Two-dimensional electrophoresis of polypeptides pulse labelled in vivo demonstrated that a major in vivo translation product at 65 kD and near neutral pH disappeared within 2 h after light and another labelled spot at slightly more acidic pH and 90 kD increased during the first 4 h after light. Major differences in polypeptide abundance were detected only when mature conidiophores were compared with vegetative mycelia. Four major soluble polypeptides were specific to vegetative mycelia, while two major polypeptides were specific to membrane fractions from conidiophores. A polyclonal antibody was obtained against the most abundant of these membrane proteins, a 48 kD polypeptide. The antibody recognized a 48 kD polypeptide on immunoblots of membrane fractions from sporulating colonies at 24 h after photoinduction, but not from dark control colonies of the same age. On immunoblots of total protein, the 48 kD polypeptide was detectable at 12–16 h after photoinduction, together with the completion of conidiophore branching, and increased further by 24 h, when pigmented spores are present.

Early biochemical responses of the small intestine of coeliac patients to wheat gluten.

The pathogenesis of coeliac disease has been investigated by studying the response of small intestinal hydrolases in patients with coeliac disease subject to gluten challenge. Small intestinal biopsies taken before and two and a half hours after a gluten challenge in five patients with coeliac disease who had been maintained on a gluten free diet were examined by a combination of electron and light microscopy, organ culture, pulse chase biosynthetic labelling, SDS-PAGE and autoradiography. Before the challenge, the small intestinal biopsies showed nearly normal morphology. Two and a half hours after the challenge there was deterioration in villus architecture, distortion of microvillus structure, disorganisation of the intermicrovillus pit region, an increase in lysosome like bodies in the apical cytoplasm of the luminal enterocytes and pronounced hypertrophy of the rough endoplasmic reticulum of these cells. SDS-PAGE of small intestinal biopsies from four treated coeliac patients before gluten challenge revealed normal microvillus membrane and hydrolase composition. There was a generalised reduction but no specific alteration in the pattern of polypeptide synthesis in the mucosa of the small intestine in these subjects two and a half hours after the gluten challenge. These results suggest that the generalised reduction in small intestinal brush border enzymes in coeliac patients is not the primary pathogenetic mechanism and represents a secondary effect.

Johannsen's gene and genotype in the light of plant molecular biology

It is particular pleasure for me to give the Wilhelm Johannsen lecture. In searching out some of Johannsen's writings, I was given access to lot of material by his former university, the University of Copenhagen; this was kindly facilitated by Diter von Wettstein. In Johannsen's papers were original manuscripts of four lectures that he gave at Columbia University in 191 1. I was struck by the clarity of those lectures which could still, to this day, provide the basis for course in analytical genetics. Johannsen first gave us the word 'gene' and it was he who crystallized the distinction between genotype and phenotype. In the period of the clarity of understanding of inheritance of distinct morphological characters that came from the rediscoverers of Mendel's work, there was still clouded mass of uncertainty about the inheritance of quantitatively varying characters. Johannsen stood out like beacon at that time in his perception of the value of working with pure lines in probing this question, showing that the quantitative differences behaved and were understandable according to Mendelian laws. In criticizing the mathematical geneticists of his day, Johannsen emphasized the value of experimental biology and experimentation characterized his work. He didn't get everything right. In 1923, he still felt it was an absurdity to believe that genes always may be special particles, but he did see that alleles were different states or chemisms in the same locus of chromosome. He defined the genotype-as the sum total of all genes in gamete. Yet he could not ascribe all growth and development to the genes per se and he postulated a great something as yet not divisible into separate factors, this in addition to the genes. Some of Johannsen's early botanical work at the University of Tiibingen concerned the study of respiration of plant seedlings under reduced levels of oxygen and that is the topic I would like to talk about today. I'll describe the progress that we have made in studying the genes involved in the plant's response to anaerobic stress and I hope to show you that we have made some progress towards understanding Johannsen's central something in terms of the control of gene action. When the roots of plants are flooded, as in irrigation practices, oxygen tension is reduced in the cells of the root and the plant's metabolism changes dramatically. Roots respire at surprisingly high rate and they need efficient energy recharge to provide for the uptake and redistribution of water and nutrients through the plant. Prolonged hypoxia can lead to yellowing of the leaves and to plant death. However, most plants can survive 2 to 3 days of reduced oxygen tension. They have special response'mechanism, response that is not present in vertebrate cells, which can survive only very short periods of oxygen deprivation. Some years ago, Sachs and Freeling showed in maize roots that all protein synthesis ceases within minutes of oxygen deprivation, so that the pattern of polypeptide synthesis, the aerobic pattern, would become blank shortly after the removal of oxygen. Then within the space of 3 to 4 h, distinctive set of polypeptides begin to be synthesized, the so-called anaerobic polypeptides; and they are shown on the right-hand pattern in Fig. 1. That response is true for most plants that have been looked

Gene expression in Brassica tissues and species following heat shock

Several tissues from the three oilseed Brassica species have been analyzed for polypeptides synthesized in vivo and in vitro under control (23 °C) and heat-shock conditions. The various tissues have characteristically unique patterns of polypeptide synthesis, the general pattern being maintained following heat shock. In addition, all tissues exhibit synthesis of a set of qualitatively similar heat shock protein (HSP) that differ, however, in relative intensity among tissues. Synthesis of control polypeptides as well as high molecular-weight HSP is similar in hypocotyls of the three genomically interrelated species B. napus, B. campestris, and B. juncea; however, the three species exhibit variation in in vivo and in vitro synthesized polypeptides in the 18 000–27 000 molecular-weight region, with several prominent differences in the number and distribution of the major class of low molecular-weight (20 000) HSP. Several of the HSP appear to be unique to B. juncea and one is unique to B. napus. Immunochemical studies of in vitro synthesized Brassica polypeptides using antisera to maize HSP of molecular weight 18 000 substantiate the observed differences in synthesis of various members of the 20 000 molecular-weight HSP family among the three species, and indicate that the Brassica low molecular-weight HSP are immunologically similar to the small HSPs of other plants including maize, soybean, pea, and Arabidopsis.

Alterations in the pattern of polypeptide synthesis resulting from amino acid limitation in Neurospora crassa

Two-dimensional electrophoresis was used to examine the pattern of polypeptide synthesis in Neurospora crassa mycelium of an arg-6 strain grown in the presence of [14C]arginine. Reduction in the arginine supply rate led to amino acid limited growth, and to major alterations in the pattern of polypeptide synthesis. Strains carrying wild-type (cpc-1+) or mutant (cpc-1) alleles at a locus governing cross-pathway control of amino acid synthetic enzymes differed markedly with respect to their pattern of polypeptide synthesis under limitation conditions, but differed little during arginine sufficient growth. Among 160 abundant polypeptide species classified for their response to limitation in two dimensional fluorographs, 31 were induced by limitation only in a cpc-1+ strain, 13 only in a cpc-1 strain, and 9 showed induction in both strains.

Regulation of protein synthesis during egg development of the parasitic wasp, Microplitis croceipes (Cresson) (Braconidae)

Regulation of protein synthesis was studied in Microplitis croceipes (Cresson) during oogenesis and after oviposition in its host, Heliothis zea (Boddie). Oocytes were dissected from ovaries of M croceipes during various stages of development and from second instar host larvae at various times after egg oviposition. Uridine incorporation into RNA was highest in oocytes in the ovarian egg tube, then declined in oocytes present in the egg reservoir and calyx of the ovary. During blastoderm formation, 4–6 hr after the egg was oviposited into the host, uridine was still incorporated at low levels. At 18–24 hr after oviposition (14–18 hr after blastoderm formation), uridine incorporate returned to the level observed in eggs in the ovarian reservoir. Protein synthesis, measured by [ 3H]leucine and [ 35S]methionine incorporation was continuous at all stages of development and was most rapid 14–20 hr after blastoderm formation when RNA synthesis was highest. Patterns of polypeptide synthesis as analyzed by one-dimensional SDS-PAGE changed quantitatively but this method did not reveal any new polypeptides in oocytes in various stages of development or during early and late embryogenesis. However, when polypeptide patterns of eggs were compared on two-dimensional gels during embryogenesis, synthesis of new polypeptides was evident after cellularization of the blastoderm (4–6 hr after oviposition). These changes in synthesis after blastoderm formation may be the result of transcription and subsequent translation of embryonic mRNA.

Patterns of polypeptide synthesis in human rotavirus infected cells

Polypeptide analysis of three strains of human rotavirus (KUN, Wa and MO) were conducted using a hypertonic culture which suppressed host protein synthesis and unmasked rotavirus specific protein synthesis. As a result, eleven human rotavirus specific polypeptides (Vp 1--Vp 11) were detected by pulselabeling infected cells with [14C]-leucine. Among the 11 polypeptides, three polypeptides (Vp 7, Vp 10 and Vp 11) underwent post-translational processing, and two (Vp 7 and Vp 10) were glycosylated. Six polypeptides (Vp 1, 2, 3, 4, 6 and 7) were identified as viral structural proteins. Comparisons of three strains of different serotypes revealed that their polypeptide profiles differed from each other in electrophoretic mobility; in particular, profiles of the glycosylated polypeptide, Vp 7, were distinct among the three strains.

Patterns of Polypeptide Synthesis in Non-fruiting Monokaryons and a Fruiting Dikaryon of Schizophyllum commune

The patterns of polypeptides synthesized by two co-isogenic monokaryons and the derived dikaryon of the basidiomycete Schizophyllum commune, growing in surface culture, were compared by two-dimensional PAGE after labelling with [35S]sulphate. Synthesis of most of the polypeptides (400 analysed) was common but at day 3 some 30 polypeptides were synthesized in the dikaryon which were not seen in the monokaryons. At this time the dikaryon had formed hyphal aggregates. Ten additional novel polypeptides were being synthesized in the primordia arising from these aggregates at day 4. In surface culture, monokaryons and dikaryon excreted 4 to 8% of the labelled proteins (over 80 different polypeptides) into the medium compared with only 1 to 2% when cultivation was done in liquid shaken cultures. The polypeptides specifically secreted by the dikaryon at the aggregation stage consisted of seven small polypeptides with molecular weights ranging from 10 to 14 × 103, and two polypeptides with molecular weights 18 × 103 and 26 × 103, respectively. Such differences in excreted proteins between monokaryons and dikaryon were not observed when the mycelia were grown in liquid shaken cultures, indicating a relationship with fruit-body formation. A comparison of labelled proteins in isolated hyphal walls revealed six polypeptides specifically associated with the walls of monokaryons and dikaryon irrespective of the cultivation method. Among the polypeptides newly appearing in the dikaryon at aggregation two were associated with the walls and co-migrated with the polypeptides of molecular weights 18 × 103 and 26 × 103 excreted into the medium at this stage of development.

Two-dimensional gel analysis of polypeptide appearance in forming thylakoid membranes

For the first time, two-dimensional gel electrophoresis is used to analyse the polypeptide composition of thylakoid membranes during chloroplast development. The number of polypeptide spots resolved on the two-dimensional gels is 3–4 times the number of bands previously resolved on one-dimensional gels. The pattern of polypeptide synthesis and insertion into the forming thylakoid membranes of dark-grown Euglena exposed to light conforms with previous biochemical measurements on the assembly of the electron transport chain located in these membranes.

Polypeptide synthesis in cell cycle mutants of fission yeast.

The cell cycle of a growing cel is characterized by 3 main periodic events: DNA synthesis mitosis and cell division. These events generally lie in a dependent sequence, in which one event cannot occur unless preceding events have occurred. The existence of dependent sequences of events raises the possibility that at least some of the gene products involved in the events are synthesized in a dependent sequence parallel to the observable events. To test this hypothesis, the patterns of polypeptide synthesis were investigated in 2 types of cell cycle mutant of the fission yeast Schizosaccharomyces pombe: temperature-sensitive cell cycle (ts cdc) mutants. which become blocked in cell cycle progress at the restrictive temperature; and wee I mutants, which are defective in size control over nuclear division, and which divide at a small size. Cells of mutants and wild-type cells were labelled with [35S[ sulphate under conditions designed to maximize any differences between the labelling patterns of wild-type and mutant cell polypeptides. The polypeptides were then separated by O'Farrell 2-dimensional gel electrophoresis, and the patterns compared. Although both types of mutation affect cell cycle control, and cause a considerable alteration in the relative proportions of cellular components, an examination of over 700 polypeptides detected on gels revealed no qualitative differences between wild-type and mutant cell polypeptides. These results suggest that a large majority of the more abundant polypeptides in the growing cell are synthesized independently of cell cycle controls directly related to DNA synthesis and division, and that the synthesis of these polypeptides can occur in the absence of normal progress through the cell cycle. Dependent sequences of gene expression do not appear to make a significant contribution to total polypeptide synthesis during the cell cycle, or to the occurrence of periodic cell cycle events such as mitosis. It is suggested that such cell cycle events may result largely through the reorganization of existing cellular components, rather than by the synthesis of new ones. An unsuccessful attempt was made to detect the wee I gene product on gels by surveying a range of mutants for changes in an individual spot. The limitations of gel electrophoresis for this type of survey, and other cell cycle experiments, are discussed.

Patterns of polypeptide synthesis in mouse oocytes during germinal vesicle breakdown and during maintenance of the germinal vesicle stage by dibutyryl cAMP

Mouse oocytes undergo spontaneous meiotic maturation when cultured in vitro in the absence, but not in the presence, of dibutyryl cyclic AMP (cAMP). Furthermore, the inhibition by dibutyryl cAMP is reversible. Oocytes synthesize stage-specific polypeptides (i.e., developmental polypeptides) during meiotic maturation. Dibutyryl cAMP affects the synthesis of four of these developmental polypeptides by reversibly inhibiting the synthesis of one polypeptide, and irreversibly inhibiting the synthesis of three other polypeptides. Dibutyryl cAMP also reversibly inhibits the synthesis of at least two specific nondevelopmental polypeptides.

Epstein-Barr virus polypeptides: effect of inhibition of viral DNA replication on their synthesis.

After Epstein-Barr virus superinfection of the human lymphoblastoid cell line Raji, a Burkitt lymphoma-derived line that contains Epstein-Barr virus genomes in an episomal form, at least 40 polypeptides could be resolved by polyacrylamide gel electrophoresis. Eleven of the 40 polypeptides were immunoprecipitable by early antigen+/viral capsid antigen+ antiserum. The polypeptides could be divided into six classes, immediate-early, early, intermediate, late, very late, and persistent, depending upon the time of synthesis. Ten of the 40 polypeptides appeared to preexist before superinfection and persisted despite general cessation of host protein synthesis; none of the persistent proteins was immunoprecipitated by the Epstein-Barr virus antibody-containing serum. When viral DNA replication was blocked by a variety of inhibitors of DNA synthesis, a number of different patterns of polypeptide synthesis could be detected. The synthesis of six polypeptides was blocked by the most virus-specific inhibitors, acyclovir and phosphonoacetic acid. Additionally, in the presence of 1-beta-D-arabinofuranosylcytosine, 1-beta-D-arabinofuranosyladenine, and methotrexate, seven polypeptides showed oversynthesis.

Patterns of polypeptide synthesis in various maize organs under anaerobiosis

The pattern of protein synthesis was compared in several organs of maize (Zea mays L.) under aerobic and anaerobic conditions. Protein synthesis was measured by [(35)S]methionine incorporation and analysis by two-dimensional native-SDS (sodium lauryl sulfate) polyacrylamide gel electrophoresis and fluorography. The aerobic protein-synthesis profiles were very different for root, endosperm, scutellum and anther wall. However, except for some characteristic qualitative and quantitative differences, the patterns of protein synthesis during anaerobiosis were remarkably similar for these diverse organs and also for mesocotyl and coleoptile. The proteins synthesized were the anaerobic polypeptides (ANPs) which have been previously described in anaerobic roots of seedlings. Leaves exhibited no detectable protein synthesis under anaerobic conditions, and died after a short anaerobic treatment. Evidence is presented that the ANPs are not a generalized response to stress. This indicates that the ANPs are synthesized as a specific response to anaerobic conditions such as flooding.

Pattern of polypeptide synthesis in myoblast hybrids

We have examined cell hybrids derived from L6J1 rat myoblasts and A9 mouse fibroblastic cells for expression of the myogenic phenotype. Initial results showed that hybrid cells were no longer able to form myotubes and hence showed extinction of the myogenic phenotype. We then proceeded to characterize the pattern of protein synthesis in these cells using two-dimensional gel electrophoresis. Although we did detect extinction of synthesis of a small number of myoblast polypeptides in the hybrids these did not appear to be rat myoblast specific. Instead they correlated well with polypeptides lost upon viral transformation in another rat cell line. Analysis of the ability of parental cells and hybrids to grow in soft agar confirmed that both A9 cells and hybrids were more transformed than the parental L6J1 cells. The results are consistent with the interpretation that extinction of the ability to form myotubes is due to either transformation and/or a disrupted cell organization but is unlikely to be due to specific extinction of myoblast specific polypeptides, at least at the level detectable by 2D gel electrophoresis.

Germinal vesicle configurations and patterns of polypeptide synthesis of procine oocytes from antral follicles of different size, as related to their competency for spontaneous maturation.

The cytogenetic configurations of germinal vesicle (gv) chromatin were analyzed for pools of porcine oocytes harvested from small (1.0-2.0 mm), medium (3.0-5.0 mm), and large (6.0-10.0 mm) antral follicles. Groups of oocytes from these follicular classes also were examined by high-resolution, two-dimensional, polyacrylamide gel electrophoresis to compare their patterns of polypeptide synthesis. The results show a high incidence of gross and cytogenetic degeneration among oocytes from small antral follicles as compared with those from medium or lage follicles. Pools of oocytes could be separated, on the basis of gross morphology and integrity of adherent granulosa cells, into two classes: "Type A" which appeared normal, and "type B" which appeared to be atretic. Among selected "type A" oocytes a particular chromatin configuration, termed "fibrous" characterizes the gv of oocytes from small follicles; whereas a different configuration, termed "diffuse," characterizes the gv of oocytes from large follicles. The patterns of polypeptide synthesis were markedly different for samples of "type A" oocytes of the three follicular classes; and the patterns for oocytes from medium and large follicles were more similar to each other than to patterns for oocytes from slall follicles. The incidences of maturational development beyond the gv stage in vitro were similar for "type A" oocytes from the three follicular classes (i.e., 66% to 82% maturation); although "type B" oocytes underwent maturation beyond the gv at a significantly reduced incidence (i.e., 20% to 29% maturation). "Type A" oocytes from large follicles completed maturation in vitro (i.e., underwent the first meiotic division) at a significantly higher incidence (55%) than did oocytes from small (11% to 20%) or medium (16%) follicles. Our findings are consistent with the hypotheses that a high proportion of oocytes from small antral follicles are atretic, and that a developmental program controls the molecular and cytogenetic changes occurring in porcine oocytes during follicular growth. These changes appear to be highly correlated with the acquisition of competency to complete maturation in vitro, and possibly also are required for normal fertilization and embryogenesis.

Two-dimensional electrophoretic analysis of proteins synthesized during the early cleavage period in rabbit embryos

Changes in the pattern of polypeptide synthesis in early cleavage stages of rabbit embryos cultured in the presence and absence of the transcriptional inhibitor, α-amanitin, were studied by twodimensional polyacrylamide gel electrophoresis. Three categories of polypeptides were delineated: ( a) those which appear between the 2-cell and 16-cell stage in control embryos but whose appearance is inhibited by α-amanitin; ( b) those which are continuously produced and are resistant to α-amanitin transcriptional suppression; and ( c) those which are produced at the 2-cell and 16-cell stage in the absence of α-amanitin but are not produced when α-amanitin is present. The results suggest that protein synthesis in the 16-cell rabbit embryo is dependent upon both stable messenger RNA (mRNA) molecules preserved from before the 2-cell stage and other mRNA molecules transcribed from the zygote genome of the 2-cell and later embryo.

Tissue-, age-, and stage-specific patterns of protein synthesis during the development of Drosophila melanogaster

Patterns of polypeptide synthesis in the imaginal and larval tissues of wild-type larvae of different ages have been examined using a one-dimensional polyacrylamide gel electrophoresis and autofluorography. Tissue-, age, and stage-specific patterns of polypeptide bands have been observed and characterized. There are one or two bands unique to larval tissues and 13 bands unique to imaginal discs and brain. Each tissue has its own characteristic band pattern. The 160-hr wing disc contains all 13 disc and brain-specific bands plus another eight unique bands. The 160-hr leg disc contains 11 disc- and brain-specific bands plus another six unique bands. The 160-hr eye-antennal disc contains eight disc- and brain-specific bands. There are five bands common to all imaginal tissues at all times but not found in any of the larval tissues. There appears to be a much greater difference between the same tissue at different ages than there is between different tissues at the same age. There is also a marked change in the total body proteins extracted from different developmental stages. Eight (11%) of the bands detected appear to be common to all tissues at all times, while 13 bands (18%) appear to be specific to pairs of imaginal discs. In addition, there are major differences in the patterns observed between pulsed and pulse-chased animals. These results are discussed in relation to the concept of differential gene activity.