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Biomedical subjects

R W Osborn

Publications and source records attributed to R W Osborn.

At least 19 recordsLinked to original sources
PubMed1995

Isolation and characterisation of plant defensins from seeds of Asteraceae, Fabaceae, Hippocastanaceae and Saxifragaceae.

From seeds of Aesculus hippocastanum, Clitoria ternatea, Dahlia merckii and Heuchera sanguinea five antifungal proteins were isolated and shown to be homologous to plant defensins previously characterised from radish seeds and gamma-thionins from Poaceae seeds. Based on the spectrum of their antimicrobial activity and the morphological distortions they induce on fungi the peptides can be divided into two classes. The peptides did not inhibit any of three different alpha-amylases.

Amino Acid Sequence↗
PubMed1995

Cloning and characterization of two cDNA clones encoding seed-specific antimicrobial peptides from Mirabilis jalapa L.

We have isolated and characterized two cDNA clones (designated MJ1 and MJ2) encoding the two Mirabilis jalapa antimicrobial peptides (Mj-AMP1 and Mj-AMP2, respectively), which were previously purified from seeds of this plant species (Cammue et al. (1992), J Biol Chem 267: 2228-2233). In both cases, the deduced amino acid sequences reveal the presence of a putative signal sequence preceding the mature peptide, indicating that the Mj-AMPs are expressed as preproteins. The Mj-AMP1- and Mj-AMP2-encoding genes are interrupted in their coding sequences by a single intron (380 bp and 900 bp for Mj-AMP1 and Mj-AMP2 genes, respectively). Southern blot analysis indicates that the Mj-AMP-encoding genes belong to a gene family of low complexity. Northern blot analysis suggests seed-specific expression of Mj-AMPs since transcripts of the expected size could only be detected in near-mature and in mature seeds of M. jalapa.

Amino Acid Sequence↗
PubMed1995

A potent antimicrobial protein from onion seeds showing sequence homology to plant lipid transfer proteins.

An antimicrobial protein of about 10 kD, called Ace-AMP1, was isolated from onion (Allium cepa L.) seeds. Based on the near-complete amino acid sequence of this protein, oligonucleotides were designed for polymerase chain reaction-based cloning of the corresponding cDNA. The mature protein is homologous to plant nonspecific lipid transfer proteins (nsLTPs), but it shares only 76% of the residues that are conserved among all known plant nsLTPs and is unusually rich in arginine. Ace-AMP1 inhibits all 12 tested plant pathogenic fungi at concentrations below 10 micrograms mL-1. Its antifungal activity is either not at all or is weakly affected by the presence of different cations at concentrations approximating physiological ionic strength conditions. Ace-AMP1 is also active on two Gram-positive bacteria but is apparently not toxic for Gram-negative bacteria and cultured human cells. In contrast to nsLTPs such as those isolated from radish or maize seeds, Ace-AMP1 was unable to transfer phospholipids from liposomes to mitochondria. On the other hand, lipid transfer proteins from wheat and maize seeds showed little or no antimicrobial activity, whereas the radish lipid transfer protein displayed antifungal activity only in media with low cation concentrations. The relevance of these findings with regard to the function of nsLTPs is discussed.

Allium↗
PubMed1995

Small cysteine-rich antifungal proteins from radish: their role in host defense.

Radish seeds have previously been shown to contain two homologous, 5-kD cysteine-rich proteins designated Raphanus sativus-antifungal protein 1 (Rs-AFP1) and Rs-AFP2, both of which exhibit potent antifungal activity in vitro. We now demonstrate that these proteins are located in the cell wall and occur predominantly in the outer cell layers lining different seed organs. Moreover, Rs-AFPs are preferentially released during seed germination after disruption of the seed coat. The amount of released proteins is sufficient to create a microenvironment around the seed in which fungal growth is suppressed. Both the cDNAs and the intron-containing genomic regions encoding the Rs-AFP preproteins were cloned. Transcripts (0.55 kb) hybridizing with an Rs-AFP1 cDNA-derived probe were present in near-mature and mature seeds. Such transcripts as well as the corresponding proteins were barely detectable in healthy uninfected leaves but accumulated systemically at high levels after localized fungal infection. The induced leaf proteins (designated Rs-AFP3 and Rs-AFP4) were purified and shown to be homologous to seed Rs-AFPs and to exert similar antifungal activity in vitro. A chimeric Rs-AFP2 gene under the control of the constitutive cauliflower mosaic virus 35S promoter conferred enhanced resistance to the foliar pathogen Alternaria longipes in transgenic tobacco. The term "plant defensins" is proposed to denote these defense-related proteins.

Alternaria↗
PubMed1994

Gene-encoded antimicrobial peptides from plants.

On the basis of an extensive screening of seeds from various plant species, we have isolated and characterized several different antimicrobial peptides. They were all typified by having a broad antifungal activity spectrum, a relatively low molecular weight (3-14 kDa), a high cysteine content and a high isoelectric point (pI > 10). With respect to their amino acid sequence, these peptides can be classified into six structural classes. Synergistic enhancement (up to 73-fold) of antimicrobial activity was demonstrated in some combinations of peptides belonging to different classes. cDNA clones corresponding to different antifungal peptides were isolated and used to transform tobacco plants. Extracts of these transgenic plants showed higher (up to 16-fold) antifungal activity than untransformed control plants. Such antimicrobial peptides may find applications in molecular breeding of plants with increased disease resistance.

Amino Acid Sequence↗
PubMed1990

Dual effects of the ricin A chain on protein synthesis in rabbit reticulocyte lysate. Inhibition of initiation and translocation.

Ricin A chain caused inhibition of protein synthesis by reticulocyte lysate with concomitant depurination of 28S rRNA. The partial reaction(s) of protein synthesis inhibited was investigated by following the appearance of [35S]methionine from initiator [35S]Met-tRNA into 40S ribosomal subunits, 80S monosomes and polysomes. Ricin A chain caused an accumulation of [35S]Met in monosomes which did not enter polysomes. In these respects the effects of the ricin A chain resembled those of diphtheria toxin, an inhibitor of elongation-factor-2-catalyzed translocation. This is consistent with the previously proposed site of action of ricin as an inhibitor of elongation. However, the inhibitory effects of the ricin A chain and diphtheria toxin are not equivalent because we observed that the rate of formation of the 80S initiation complex was reduced approximately sixfold with the ricin A chain relative to diphtheria toxin. Analysis of methionine-containing peptides bound to 80S monosomes in ricin-A-chain-inhibited and diphtheria-toxin-inhibited lysates, programmed with globin mRNA, revealed a predominance of Met-Val, suggesting that the elongation cycle is inhibited at the translocation step. Translocation was also implicated as the step blocked in both the ricin-A-chain-inhibited and diphtheria-toxin-inhibited lysates, by the finding that nascent peptide chains were unreactive towards puromycin. It is concluded that ricin-A-chain-modified ribosomes are deficient in two protein synthesis partial reactions: the formation of the 80S initiation complex during initiation and the translocation step of the elongation cycle.

Animals↗
PubMed1989

Ribosome inactivation by ricin A chain: a sensitive method to assess the activity of wild-type and mutant polypeptides.

When recombinant ricin A chain transcripts are translated in a rabbit reticulocyte lysate the ribosomes are rapidly inactivated as shown by their inability to support translation of yeast preproalpha factor or chicken lysozyme transcripts added subsequently. In contrast, ribosomes which have translated transcripts encoding non-toxic polypeptides such as ricin B chain, readily translate the second transcript under identical conditions. Ribosome inactivation is accompanied by a highly specific modification of 28S rRNA which occurs at the same position as the N-glycosidic cleavage of an adenine residue and which is thought to cause inactivation of the ribosomes. Protein synthesis by wheat germ ribosomes was not inhibited under the conditions which inhibit reticulocyte ribosomes confirming earlier observations that plant cytoplasmic ribosomes are much less sensitive to inhibition by ricin A chain than are mammalian ribosomes. Using the same assay we have shown that deleting an internal hexapeptide, which shares homology with hamster elongation factor-2, completely abolishes catalytic activity. Deleting a second pentapeptide conserved between ricin A chain and the ribosome-inactivating plant toxin trichosanthin, had no effect. Deleting the first nine residues from the N-terminus of A chain did not affect toxicity whereas deleting a further three residues inactivated the polypeptide. Point mutations which individually converted arginine 48 and arginine 56 of ricin A chain to alanine residues or which deleted arginine 56 were also without effect on the catalytic activity of the toxin.

Amino Acid Sequence↗
PubMed1989

Effects of continuous intrapartum professional support on childbirth outcomes.

The purpose of this stratified randomized trial was to determine the physical and psychological effects of continuous, one-to-one professional support on childbirth outcomes. Data were gathered during prenatal and postpartum interviews with, and from the medical records of, 103 low-risk women. All subjects had attended one of two types of prenatal education programs, were accompanied by husbands or partners during labor, and had vaginal deliveries. Subjects in the experimental group were less likely to have medication for pain relief and less likely to have episiotomies. Three variables were found to predict perceived control during childbirth--expectations of control, the presence of a continuous professional caregiver, and pain medication usage. The results demonstrate the importance of the traditional nursing support role during childbirth.

Adult↗
PubMed1989

A randomized trial of the effects of monitrice support during labor: mothers' views two to four weeks postpartum.

One hundred three women who were randomized to receive either routine nursing care (controls) or routine care plus one-to-one support by an experienced monitrice (experimental) were compared as to obstetric outcomes and their memories of types of support they had from nurse, monitrice, and mate. Women assigned a monitrice arrived at the hospital significantly further along in labor, and nearly twice as many had no medication during labor and delivery. Significantly fewer of these women used stirrups during delivery, and more had intact perineums. There was no difference between groups in use of forceps or cesarean sections. Length of labor was confounded by use of medications. Mothers in the experimental group remembered receiving more physical comfort measures, emotional support, and advocacy from monitrices compared to control mothers who received intrapartum care from nurses.

Female↗
PubMed1981

Exogenous estrogens and endometrial cancer: a case-control study and assessment of potential biases.

Eighty-eight cases with newly diagnosed carcinoma of the endometrium and 177 age-matched neighborhood controls were interviewed to test the hypothesis that exogenous estrogens lead to an increased risk of endometrial cancer. Forth-five per cent of the cases and 22% of the controls reported a history of estrogen use which yielded an odds ratio of 2.9 (confidence interval (Cl) 1.7-5.1). Women with five or more years of estrogen use had an odds ratio of 8.6 (Cl 3.2-23.0). Approximately 80% of the estrogen users had used conjugated equine estrogens. For these women the odds ratio was 4.0 (Cl 1.9-8.4) for daily dosages of more than 1 mg of estrogen. Several sources of bias which might affect the estrogen association were investigated. These included comparability of cases and controls, selection procedures, difference between estrogen users and nonusers, exclusion of controls who had hysterectomy, source of estrogen information, and differential recall. The concept or medical surveillance was evaluated by access to medical care and prior history of dilatation and curettage. The strong association between exogenous estrogen use and endometrial cancer remained after consideration for the effects of these biases.

Adult↗