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D Spencer

Publications and source records attributed to D Spencer.

At least 109 records · Page 6Linked to original sources
PubMed1984

Influence of Sulfur Nutrition on Developmental Patterns of Some Major Pea Seed Proteins and Their mRNAs.

In addition to the marked reduction in legumin synthesis and legumin mRNA levels reported earlier (Chandler, Higgins, Randall, Spencer 1983 Plant Physiol 71: 47-54), pulse labeling of S-deficient Pisum sativum L. seeds showed that a high relative level of total vicilin (vicilin plus convicilin) synthesis was maintained throughout the entire phase of protein accumulation, whereas in nondeficient seeds vicilin synthesis is largely confined to the first half of this phase. Fractionation of pulse-labeled proteins on Na-dodecylsulfate-polyacrylamide gels showed that the synthesis of the M(r) 50,000 family of vicilin polypeptides was increased and greatly extended in S-deficient seeds whereas that of convicilin was slightly reduced. Other changes apparent from pulse-labeling experiments include a depression, to different degrees, in the synthesis of three major albumin polypeptides.The level of the mRNAs for seven major seed proteins was followed throughout development of control and sulfur-deficient seeds. In all cases, the changes in each mRNA closely reflected the pattern of synthesis of its corresponding polypeptide seen by pulse labeling. S-deficient seeds showed an elevated level of M(r) 50,000 vicilin mRNA which remained high throughout seed formation, whereas legumin mRNA levels were greatly reduced at all stages of development.When S-deficient plants were given an adequate supply of sulfate midway through seed development, there was a shift toward the protein synthesis profile characteristic of healthy plants. The synthesis of legumin and two albumins rapidly increased and the synthesis of M(r) 50,000 vicilin declined more slowly. Similar responses were seen in detached, S-deficient seeds supplied directly with adequate sulfate.

Journal Article↗
PubMed1984

THRM forum: My boss.

Explore the source record for details and available documents.

Health Facility Administrators↗
PubMed1983

Anxiogenic aspects of diazepam withdrawal can be detected in animals.

Animals can be trained to discriminate the presence of pentylenetetrazol, and this discrimination has previously been proposed as an animal bioassay for anxiogenicity. In rats made dependent on diazepam, pentylenetetrazol-like stimuli occurred during spontaneous or precipitated (with RO 15-1788) withdrawal; these stimuli were blocked by pentobarbital. These results demonstrate that the pentylenetetrazol-based animal model of anxiety can be used to objectively quantify a subjective aspect of benzodiazepine dependence/withdrawal.

Animals↗
PubMed1983

The biosynthesis and primary structure of pea seed lectin.

Isolation of pea lectin from immature seeds, together with in vivo pulse-chase labeling and in vitro translation of RNA from such seeds, all gave results which indicated strongly that pea lectin is initially synthesized as a large precursor (pre-pro-form) (Mr = 25,000) which is cleaved both co- and post-translationally to yield the alpha and beta subunits of mature lectin. Two overlapping cDNA plasmids complementary to lectin mRNA were sequenced. They coded for both beta and alpha subunits of lectin, in the orientation beta leads to alpha from the NH2 terminus, together with a hydrophobic NH2-terminal leader sequence and included a 3' untranslated region of 124 nucleotides. In the appropriate reading frame, no stop codon was found between the coding sequences for the beta and alpha subunits, confirming the synthesis of pea lectin via a pre-pro-form. The entire pea lectin sequence showed a high degree of homology with the published amino acid sequences of lectins from lentil, broad bean, and, to a lesser extent, with concanavalin A from jack bean. Sequence variation occurred mainly in those regions thought not to be involved in metal- and sugar-binding or in the formation of beta-pleated sheets.

Amino Acid Sequence↗
PubMed1983

Intracellular sites of synthesis and processing of lectin in developing pea cotyledons.

The biosynthesis and processing of pea lectin was studied in developing pea cotyledons by a combination of pulse-chase experiments using 14C-aminoacids and subcellular fractionation of the homogenates. Lectin polypeptides were isolated on immunoaffinity gels and fractionated on sodium dodecyl sulfate-polyacrylamide gels followed by fluorography. Whether made in vivo or in an in vitro chain completion system containing polysomes still attached to microsomal membranes, newly synthesized lectin had an Mr of 23,000. In vivo labeling showed that radioactive lectin first associates with the rough endoplasmic reticulum and is then sequestered into the lumen of the endoplasmic reticulum. Pulse-chase experiments showed that it is chased out of the endoplasmic reticulum considerably more slowly than the storage proteins and accumulates in the protein bodies, initially as a polypeptide of Mr = 23,000. This pro-lectin is processed in the protein bodies to its mature form with polypeptides of Mr = 17,000 and 6,000. Pea lectin is synthesized throughout the protein accumulation phase of seed formation with maximum levels of synthesis and of mRNA approximately half-way through this period.

Endoplasmic Reticulum↗
PubMed1983

Abnormalities of the spine in relation to congenital upper limb deficiencies.

A retrospective study was performed to determine the incidence of spinal abnormalities in patients with skeletal defects of the upper extremities. The incidence of scoliosis in the patient population studied was 16%, and spinal abnormalities of all types were present in 18% of the population. Patients with bilateral amelia had a 100% incidence of scoliosis. Those patients with unilateral amelia had a 50% incidence of scoliosis. Patients with ulnar and radial hemimelias had an incidence of scoliosis of 20 and 13%, respectively. The transverse complete and partial hemimelics had an 18% incidence of scoliosis and the phocomelic group had an incidence of 11%. The patient population studied had an increased incidence of scoliosis compared with the general population. The patients with amelia had a particularly high incidence of scoliosis. There was no relationship between the side of the deficiency and the direction of the curve. The age of onset was not found to be related to the progression of the curve. The results of bracing were poor, due to patient rejection of the brace. All patients with upper limb deficiencies warrant close observation throughout growth for the development of scoliosis.

Adolescent↗
PubMed1983

Regulation of Legumin Levels in Developing Pea Seeds under Conditions of Sulfur Deficiency: Rates of Legumin Synthesis and Levels of Legumin mRNA.

It was shown previously that when peas (Pisum sativum L.) are grown with suboptimal sulfur supply the level of legumin (the more S-rich of the two major seed storage proteins) in the mature seed is selectively reduced (Randall, Thomson, Schroeder, 1979 Aust J Plant Physiol 6: 11-24). This paper reports a study of the cellular mechanisms involved in regulating legumin synthesis under these conditions. Pulse and pulse-chase labeling experiments were carried out with excised, immature cotyledons from normal and S-deficient plants. Legumin was isolated from cotyledon extracts by immunochromatography, and the proportion of legumin synthesis relative to total protein synthesis was determined. Results showed that reduced legumin accumulation could largely be accounted for by a greatly reduced level of legumin synthesis (80-88% reduction) rather than by a major increase in legumin breakdown.Legumin mRNA levels were assayed by two methods. In vitro translation of polysomal RNA from cotyledons of normal and S-deficient plants indicated a reduction of 60 to 70% in synthesis of legumin-related products by preparations from S-deficient plants. A legumin cDNA clone was constructed, characterized, and used to measure the levels of legumin mRNA in polysomal and total RNA preparations from developing cotyledons. Legumin mRNA levels were reduced by 90% in preparations from S-deficient plants.When restored to an adequate S supply, S-deficient plants (or pods taken from such plants) recovered normal levels of legumin synthesis (in vivo and in vitro) and of legumin mRNA. These results indicate that reduced legumin accumulation under conditions of S deficiency is primarily a consequence of reduced levels of legumin mRNA.

Journal Article↗
PubMed1982

Role of the endoplasmic reticulum in the synthesis of reserve proteins and the kinetics of their transport to protein bodies in developing pea cotyledons.

Developing pea (Pisum sativum L.) cotyledons were labeled with radioactive amino acids, glucosamine, and mannose in pulse an pulse-chase experiments to study the synthesis, glycosylation, and transport of the reserve proteins vicilin and legumin to the protein bodies. Tissue extracts were fractionated on sucrose gradients to isolate either the endoplasmic reticulum (ER) or the protein bodies. Immunoaffinity gels were used to determine radioactivity in the reserve proteins (legumin and vicilin). After pulse-labeling for 45 min with amino acids, about half the total incorporated radioactivity coincided closely with the position of the ER marker enzyme NADH-cytochrome c reductase at a density of 1.13 g . cm-3 on the sucrose gradient. Both radioactivity and enzyme activity shifted to a density of 1.18 g . cm-3 in the presence of 3 mM MgCl2 indicating that the radioactive proteins were associated with the rough ER. Approximately half of the incorporated radioactivity associated with the rough ER was in newly synthesized reserve protein and this accounted for 80% of the reserve protein synthesized in 45 min. Trypsin digestion experiments indicated that these proteins were sequestered within the ER. In pulse-chase experiments, the reserve proteins in the ER became radioactive without appreciable lag and radioactivity chased out of the ER with a half-life of 90 min. Radioactive reserve proteins became associated with a protein body-rich fraction 20-30 min after their synthesis and sequestration by the ER. Pulse-chase experiments with radioactive glucosamine and mannose in the presence and absence of tunicamycin indicated that glycosylation of vicilin occurs in the ER. However, glycosylation is not a prerequisite for transport of vicilin from ER to protein bodies. Examination of the reserve protein polypeptides by SDS PAGE followed by fluorography showed that isolated ER contained legumin precursors (Mr 60,000-65,000) but not the polypeptides present in mature legumin (Mr 40,000 and 19,000) as well as the higher molecular weight polypeptides of vicilin (Mr 75,000, 70,000, 50,000, and 49,000). The smaller polypeptides of vicilin present in vicilin extracted from protein bodies (Mr 12,000-34,000) were absent from the ER. The results show that newly synthesized reserve proteins are preferentially and transiently sequestered within the ER before they move to the protein bodies, and that the ER is the site of storage protein glycosylation.

Biological Transport↗
PubMed1982

Assembly of storage protein oligomers in the endoplasmic reticulum and processing of the polypeptides in the protein bodies of developing pea cotyledons.

Cotyledons of developing pea seeds (pisum sativum L.) were labeled with radioactive amino acids and glucosamine, and extracts were prepared and separated into fractions rich in endoplasmic reticulum (ER) or protein bodies, The time-course of synthesis of the polypeptides of legumin and vicilin and the site of their assembly into protein oligomers were studied using immunoaffinity gels and sucrose density gradients. When cotyledons were pulse-labeled (1-2 h), newly synthesized vicilin was present as a series of polypeptides with M(r) 60,000-65,000, and newly synthesized vicilin was present as series of polypeptides with M(r) 75,000, 70,000, 50,000, and 49,000. These radioactive polypeptides were found primarily in the ER (Chrispeels et al., 1982, J Cell Biol., 93:5- 14). During a subsequent chase period, newly synthesized reserve proteins were initially present in the protein bodies in the above-named polypeptides. Between 1 and 20 h later, radioactive legumin subunits (M(r) 40,000 and 19,000) and smaller vicilin polypeptides (M(r) 34,000, 30,000, 25,000, 18,000, 14,000, 13,000, and 12,000) appeared in the protein bodies. The appearance of these labeled polypeptides in the protein bodies was not the result of a slow transport from the ER (or cytoplasm). Newly synthesized legumin and vicilin polypeptides were assembled into oligomers of 8S and 7S, respectively, in the ER. They appeared in the protein bodies in these oligomeric forms before the appearance of the smaller polypeptides (M(r) less than 49,000). These results indicate that the smaller vicilin polypeptides (M(r) less than 49,000) arise delayed posttranslational processing of some or all of the larger vicilin polypeptides. The precursors of legumin are completely processed in the protein bodies 2-3 h after their synthesis. The processing of the vicilin precursors is much slower (6-20 h) and only a fraction of the precursor molecules are processed. As a result both large (M(r) more than 49,000) and small polypeptides of vicilin accumulate in the protein bodies, whereas legumin accumulates only as polypeptides of M(r) 40,000 and 19,000.

Endoplasmic Reticulum↗
PubMed1981

Precursor Forms of Pea Vicilin Subunits: MODIFICATION BY MICROSOMAL MEMBRANES DURING CELL-FREE TRANSLATION.

Polyribosomal RNA isolated from pea cotyledons at various developmental stages programmed the cell-free synthesis of polypeptides which were recognized by antibodies specific for pea storage proteins. There were quantitative and qualitative changes in the template activity during seed maturation. Most of the polysomal RNA was associated with the membrane fraction, and all of the template for storage protein occurred in this fraction. Using RNA from a stage of seed maturation at which the synthesis of the high-molecular weight vicilin polypeptides predominate, it was found that the major translation products, although antigenically recognizable as storage protein, did not coincide with the authentic vicillin polypeptides on denaturing polyacrylamide gels. The addition during translation of microsomal membranes from dog pancreas or pea cotyledons resulted in the appearance of new polypeptides which did coincide with some of the authentic vicilin polypeptides (in the apparent molecular weight regions of 75,000 and 50,000) and were antigenically recognizable as storage protein. Other translation products related to storage protein were not visibly altered in their electrophoretic mobility by the addition of membranes. Microsomal membranes treated with Triton X-100 were not effective in modifying the cell-free products. The modified vicilin polypeptides and at least two other translation products were protected from proteolytic degradation, suggesting that they were sequestered within microsomal vesicles. Thus, these storage protein components may be synthesized by a mechanism analogous to that described for membrane and secretory proteins (Blobel G, B Dobberstein 1975 J Cell Biol 67: 835-851).

Journal Article↗
PubMed1981

Interdisciplinary media management and information skills training.

The rationale for planning, teaching, and subsequent revision of a course in health sciences information skills and media management practices presented as a part of a curriculum in medical illustration training is described. National events influencing the course content are discussed. Effects of the course on student attitudes and perceptions are presented in the conclusions.

Audiovisual Aids↗
PubMed1981

After-hours management of febrile children.

During a nine-month period approximately 15 percent of the children less than ten years of age in a university family practice had an after-hours medical contact for a febrile illness. Children less than two years of age accounted for 55 percent of the encounters. The most frequent diagnoses were upper respiratory tract infection, acute otitis media, and undifferentiated fever. Slightly less than one half of the children were seen by the on-call resident, and age and level of fever did not correlate with the likelihood of being seen. Very few of the children had a white blood cell count obtained, and none had a blood culture or lumbar puncture. In this practice, after-hours management of the febrile infant differed substantially from guidelines in the literature based on experiences in university emergency rooms and walk-in clinics.

Child↗