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R Powell

Publications and source records attributed to R Powell.

At least 37 records · Page 2Linked to original sources
PubMed1992

The kinetics of oocyte activation and polar body formation in bovine embryo clones.

The kinetics of polar body formation were examined in parthenogenetically activated, in vitro matured and aged bovine oocytes. Subsequently, the presence or absence of polar body formation was determined in bovine embryo clones. Polar body formation, defined as telophase II, occurred by 1 (13/40, 43%) and 2 h (15/21, 71%) postparthenogenetic activation of metaphase II stage oocytes. Parthenogenetically activated oocytes readily formed pronuclei by 4 h. Some oocytes had chromatin in a highly condensed state at 1, 2, and 4 h postactivation (13/72, 18%). These oocytes often (10/13, 77%) appeared to be "self-enucleated," as the condensed chromatin was found in a membrane-bound extrusion. The phenomenon was most prevalent when oocytes were handled at room temperature (25-27 degrees C). Nuclear transfer procedures were established to bring about synchronous blastomere fusion and oocyte activation conditions. Synchronous conditions were achieved only when oocytes were handled and manipulated at 37-39 degrees C. Embryo clones examined 2 h postfusion did not form a polar body. Conversely, nucleate demi-oocyte controls were at the late telophase II stage of meiosis. The results are discussed in relation to cell cycle effects on bovine nuclear transfer.

Animals↗
PubMed1992

Gene expression following transfection of fish cells.

Various genes containing different transcriptional regulatory elements (TRE) and the bacterial marker gene coding for chloramphenicol acetyl transferase were transfected into several fish cell lines to evaluate the efficiency of expression in comparison with mammalian cells. The CMV and RSV TRE were the most efficient non-inducible promoters in directing reporter gene expression. RSV and CMV appeared of similar potency in a stable fish cell line. The human HSP-70 promoter showed high potency in a carp and in a trout cell line after thermal induction. This promoter also induced the synthesis of human growth hormone directed by the corresponding cDNA, but not by the gene. RSV TRE was also able to drive the synthesis of bovine growth hormone when attached directly to the cDNA but not to the gene. These data suggest that non-fish gene TRE can be used to express foreign genes in fish cells or transgenic fish; however, in most cases they are relatively inefficient. The data also suggest that the translation and secretion machinery of fish cells can express efficiently foreign genes but that mammalian introns might be not processed properly in some cases.

Animals↗
PubMed1992

DNA probe for Aeromonas salmonicida.

A DNA fragment that is specific to Aeromonas salmonicida has been isolated from a genomic DNA library by differential hybridization. The specificity of this fragment as a DNA probe for A. salmonicida was shown by hybridization against reference strains and clinical isolates of A. salmonicida, related aeromonads, and species from several other bacterial genera. The sensitivity of detection by a polymerase chain reaction test, based on this fragment, was approximately two A. salmonicida cells.

Aeromonas↗
PubMed1992

An adenosine at position 27 in the human immunodeficiency virus type 1 trans-activation response element is not critical for transcriptional or translational activation by Tat.

Tat protein binds to the trans-activation response (TAR) element of human immunodeficiency virus type 1 RNAs and activates gene expression at the level of transcription in mammalian cell lines and translation in Xenopus oocytes. Certain residues within TAR are important for Tat binding in vitro, including residue A-27, which appears to be able to be modified in a Tat-dependent manner in Xenopus oocytes (L. Sharmeen, B. Bass, N. Sonenberg, H. Weintraub, and M. Groudine, Proc. Natl. Acad. Sci. USA 88:8096-8100, 1991). Activation by Tat in oocytes occurs via a covalent modification of TAR-containing RNA. We have found that in both mammalian cells and Xenopus oocytes, conversion of A-27.U-38 or C-27.G-38 or C-27.G-38 reduces activation. However, conversion to G-27.U-38 or G-27.C-38 had little or no effect on activation, and in oocytes, these mutant RNAs were still covalently modified. These data exclude a specific role for the adenosine at residue 27 for Tat activation but suggest a requirement for a purine at this position.

Adenosine↗
PubMed1992

The dieffenbachia plant. Case history.

When ingested, the common house plant dieffenbachia can lead to significant toxicity and possibly death if timely medical attention is not forthcoming following initial exposure. The deleterious effects should not be overlooked especially when children are involved who, naturally curious, may bite into this innocuous looking plant. Although the patient in this case was a type II diabetic on insulin, neither hypo- nor hyperglycemia developed. There was no other significant electrolyte imbalance despite the acute stressor placed on him.

Adult↗
PubMed1991

The salmon gene encoding apolipoprotein A-I: cDNA sequence, tissue expression and evolution.

A cDNA encoding an apolipoprotein (Apo) has been isolated from the Atlantic salmon (Salmo salar) and sequenced. It encodes a peptide of 258 amino acids (aa), including a signal peptide of 18 aa, with 5'- and 3'-untranslated regions of the mRNA of 12 and 329 nucleotides, respectively. The protein has structural features in common with other Apo's of human and avian origin, including conserved sequences in the signal peptide and a series of internal repeats of 22 aa. The sequence has been identified as salmon Apo A-I (sApoA-I), and has 23% aa identity with human ApoA-I. Northern-blot analysis using the sApoA-I cDNA probe against total RNA prepared from several salmon tissues detects the expression of this gene in liver, intestine and muscle. A phylogenetic analysis reveals that the mammalian ApoA-I, ApoA-IV and Apo-E aa sequences are more closely related to each other than any of them are to sApoA-I. This suggests that the duplication events, from which A-I, A-IV and E arose, occurred after the divergence of the tetrapod and teleost ancestors.

Amino Acid Sequence↗
PubMed1991

Use of the Branemark implant in the cleft palate patient.

This paper describes the clinical and surgical management of a patient presenting with a unilateral alveolar cleft and associated oronasal fistula. After orthodontic expansion of the maxilla, a secondary osseous graft was placed. A single Branemark implant was subsequently utilized to allow for prosthetic restoration of the dental arch. Through case presentation, a detailed course of treatment is outlined that effectively restores the anatomy, integrity, and function of both the alveolar and dental arches.

Adolescent↗
PubMed1991

Nailfold capillary density as a possible indicator of pulmonary capillary loss in systemic lupus erythematosus but not in mixed connective tissue disease.

Nailfold capillary density was measured in 24 patients with systemic lupus erythematosus (SLE), 14 with mixed connective tissue disease (MCTD) and 21 healthy subjects. Pulmonary function tests were performed on all subjects and needle muscle biopsies on 12 patients with SLE and 9 with MCTD. A significant correlation was documented between nailfold capillary density and pulmonary gas transfer (KCO) in patients with SLE (p less than 0.001) but not in patients with MCTD. This suggests that in SLE poor gas transfer may be dependent on alveolar capillary loss and that nailfold capillary density may be a good indicator of alveolar capillary density. There was no significant correlation between skeletal muscle fiber atrophy and nailfold capillary density in SLE or MCTD. Additional studies to optimize the nailfold capillary counting method are described.

Adolescent↗
PubMed1990

Early diet in preterm babies and developmental status at 18 months.

424 preterm infants were randomly assigned a standard "term" formula or a nutrient-enriched "preterm" formula as sole diets (trial A) or as supplements to mother's own expressed milk (trial B) for a median of 4 weeks postnatally. 18 months post term, blind evaluation of 377 survivors showed that those previously fed preterm rather than term formula had major developmental advantages, more so in motor than mental function; the advantages, in both mental and motor scores, were especially striking in small-for-gestational-age infants and in males. For motor development index in trial A, this advantage was 15 points; in infants born small for gestation, it was 23 points (nearly 1.5 SD). Moderate developmental impairment (developmental index less than 85), notably motor impairment, was considerably more common in the group fed term formula. Infants fed preterm formula also had a small benefit in social maturity quotient. Thus, a short period of early dietary manipulation in preterm infants had major consequences for later development, which suggests that the first weeks may be critical for nutrition.

Age Factors↗
PubMed1990

Pharmacokinetics and protein binding of methocarbamol in renal insufficiency and normals.

We determined plasma methocarbamol concentrations over 24 h following a 1.5 g methocarbamol dose (off-dialysis day) to 8 chronic haemodialysis patients and compared these results to those from 17 healthy male volunteers. The harmonic mean elimination half-life was similar between the two groups, 1.24 and 1.14 h, respectively. tmax and the weight-adjusted Cmax were 1.1 h and 27.0 mg.m-1 for haemodialysis patients and 1.1 and 23.1 mg.l-1 for normals. Relative systemic availability was assessed by comparing weight-normalized AUC x k10 products. These results indicate no significant differences with respect to methocarbamol absorption, with the relative systemic availability in patients being 113%. These data suggest that absorption and elimination of methocarbamol is similar between normal subjects and patients undergoing maintenance haemodialysis.

Chromatography, High Pressure Liquid↗
PubMed1990

Attributions and self-esteem in depression and chronic fatigue syndromes.

There is considerable overlap in symptomatology between chronic fatigue syndrome (CFS) and affective disorder. We report a comparison of depressive phenomenology and attributional style between a group of CFS subjects seen in a specialized medical setting, which included a high proportion with depression diagnosed by Research Diagnostic Criteria (RDC), and depressed controls seen in a specialized psychiatric setting. Significant symptomatic differences between the depressed CFS group and depressed controls were observed for features such as self-esteem and guilt as well as attribution of illness. All the CFS groups tended to attribute their symptoms to external causes whereas the depressed controls experienced inward attribution. This may have resulted from differences in the severity of mood disorder between the samples, but it is also suggested that an outward style of attribution protects the depressed CFS patients from cognitive changes associated with low mood but at the expense of greater vulnerability towards somatic symptoms such as fatigue.

Adult↗
PubMed1990

Electrotransfection of Escherichia coli with lambda gt10 DNA.

We have used electroporation to introduce lambda gt10 DNA into E. coli C600 (Electrotransfection). We obtained approximately 10(7) pfu (plaque forming units) per micrograms of lambda gt10 DNA. This frequency is 100-fold higher than the maximum reported for classical calcium chloride-induced transfection. We have also compared electrotransfection with in vitro packaging in cloning experiments using relatively small amounts (less than or equal to 10 ng) of DNA. Our results slow that electrotransfection can generate approximately 1000-fold more plaques than in vitro packaging at these concentrations.

Bacteriophage lambda↗
PubMed1990

A general method to generate DNA probes for microorganisms.

We present a method that permits the rapid generation of DNA probes for eubacteria. In the procedure the variable regions for the 16s rRNA genes are amplified using polymerase chain reaction (PCR) technology and primers based on the conserved regions of these genes. Following sequencing of the variable regions, a choice is possible for a probe specific for that organism. No knowledge of the molecular biology of the microorganism is required prior to the application of this approach. The generality of the method is shown using Salmonella typhimurium, Staphylococcus aureus, Clostridium perfringens, Klebsiella pneumoniae, Pseudomonas fluorescens, Aeromonas salmonicida and Mycobacterium bovis. A. salmonicida was examined in detail and a DNA probe was prepared that distinguishes it from other Aeromonas species.

Aeromonas↗