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Biomedical subjects

H D Robertson

Publications and source records attributed to H D Robertson.

At least 55 records · Page 3Linked to original sources
PubMed1985

Ultraviolet light-induced crosslinking reveals a unique region of local tertiary structure in potato spindle tuber viroid and HeLa 5S RNA.

The positions of intramolecular crosslinks induced by irradiation with ultraviolet light were mapped into potato spindle tuber viroid RNA and HeLa 5S rRNA. Crosslinking in each of these molecules occurred at a single major site, which was located by RNA fingerprinting and secondary analysis (and additional primer extension studies in the case of the viroid). Various lines of evidence suggest that these crosslinks identify a previously undescribed element of local tertiary structure common to these two widely divergent RNA molecules: (i) both crosslinks occur in an identical eight-base context, with the sequence 5' GGGAA 3' on one side and the sequence 5' UAC 3' on the other; (ii) both crosslinks connect bases that are not thought to be involved in conventional hydrogen bonding, within regions usually depicted as single-stranded loops flanked by short helical segments; and (iii) both crosslinks connect a purine and a pyrimidine residue, and both may generate the same G-U dimer. Furthermore, it is likely that the crosslinking site is of functional significance because it is located within the most highly conserved region of the viroid sequence and involves bases that are essentially invariant among eukaryotic 5S rRNA molecules.

HeLa Cells↗
PubMed1984

A replication cycle for viroids and other small infectious RNA's.

Experimental data concerning viroid-specific nucleic acids accumulating in tomato plants establish, together with earlier studies, the major features of a replication cycle for viroid RNA in plant cells. Many features of this pathway, which involves multimeric strands of both polarities, may be shared by other small infectious RNA's including certain satellite RNA's and "virusoid" RNA's which replicate in conjunction with conventional plant viruses. The presence, in host plans, of an elaborate machinery for replicating these disease agents suggests a role for endogenous small RNA's in cellular development.

Adenosine Triphosphate↗
PubMed1984

Structure and distribution of Alu family sequences or their analogs within heterogeneous nuclear RNA of HeLa, KB, and L cells.

We studied the distribution of repetitive sequence elements capable of forming double-stranded regions in nuclear RNA of HeLa, KB, and L cells. In human RNA populations, we called these regions duplex Alu family RNA (dAfRNA) because they represent transcripts of the highly reiterated family of DNA regions known as "Alu family DNA" (Rubin et al., Nature (London) 284:372-374, 1980). Although the dAfRNA populations of both human cell lines (HeLa and KB) have low sequence complexity, they represent 5% of the total heterogeneous nuclear RNA and have identical fingerprints; mouse L-cell dAf-like RNA (which has a similar complexity) represents only 2% of the total heterogeneous nuclear RNA and has an entirely different fingerprint. We utilized Escherichia coli RNase III as a highly specific reagent for the recognition of RNA:RNA duplex structure. This enzyme cleaves within the six characteristic RNase T1-resistant oligonucleotides of HeLa- and KB-cell dAfRNA (Robertson et al., J. Mol. Biol. 115:571-589, 1977). In addition, the size of heterogeneous nuclear RNA from all three cell types is reduced from greater than 32S to about 15S after RNase III treatment. We conclude that this size shift is a result of cleavage within dAfRNA regions and that such regions are present in most or all of the large RNA transcripts of these cells.

Animals↗
PubMed1983

Use of an elemental diet as a nutritionally complete "medical colostomy".

During the past 24 months I have used a defined formula diet (High Nitrogen Vivonex) as a nutritionally complete "medical colostomy" (NCMC) in 16 patients. This diet, via continual gastric drip, provided an average of 2,238 kcal/day and 92.4 gm of protein per day. Separately or in combination, loperamide HCl, diphenoxylate HCl, or codeine was used to slow the bowel. No patient had a bowel movement within less than three days postoperatively and the mean between bowel movements was 5.6 days. Defined formula diet, used as an NCMC, can give 2.4 times more kcal than clear liquid and provides protein as well. NCMC is a safe, cost-effective way of preventing fecal contamination while providing adequate nutritional support for wound healing.

Adolescent↗
PubMed1983

Total colectomy with mucosal protectomy and ileoanal anastomosis--an important surgical option in the aviator with premalignant disease of the colon.

Total proctocolectomy with cutaneous ileostomy has been the standard therapy for many years for premalignant mucosal diseases of the colon, such as ulcerative colitis and familial polyposis. While this procedure relieves the patient of the risk of malignancy, it leaves him with the problem of the management of the ileostomy as well as exposing him to the risk of damage to the nerve supply of the bladder and genitalia during the dissection. Within the military population, the ileostomy is a particularly devastating problem as it disqualifies the individual from worldwide duty and requires him to meet a Medical Evaluation Board for discharge from the service. Over the last several years, total colectomy with mucosal proctectomy and ileoanal anastomosis (TCMPIA) has emerged as a viable surgical alternative in these conditions. The benefits of this procedure in the military population are multiple. It allows the individual to continue on active duty, fulfilling his desire to pursue his career as well as keeping the position filled for the military. The time and cost of a medical board are avoided, the military's investment in the individual's training is protected, and the need to train a new individual for the position is avoided.

Adult↗
PubMed1982

Les torsades des pointes.

A 17-year-old woman had two admissions within five months for recurrent episodes of ventricular tachycardia in conjunction with a prolonged QT interval. On both occasions these were refractory to intravenous lidocaine and bretylium. During her first admission her dysrhythmia was controlled by repeated doses of intravenous propranolol; however, she required temporary overdrive transvenous pacing on her second admission. On both occasions when the low normal serum potassium was replaced and therapeutic levels of diphenylhydantoin and phenobarbital were obtained, the episodes of ventricular tachycardia subsided. This case illustrates the complexities inherent in making the diagnosis and in treating this syndrome, and should assist the emergency physician in treating this difficult and potentially fatal dysrhythmia.

Adolescent↗
PubMed1982

Heterogeneous nuclear RNA promotes synthesis of (2',5')oligoadenylate and is cleaved by the (2',5')oligoadenylate-activated endoribonuclease.

Heterogeneous nuclear RNA contains double-stranded regions that are not found in mRNA and that may serve as recognition elements for processing enzymes. The double-stranded regions of heterogeneous nuclear RNA prepared from HeLa cells promoted the synthesis of (2',5')oligoadenylate [(2',5')oligo(A) or (2'5')An] when incubated with (2',5')An polymerase. This enzyme is present in elevated levels in interferon-treated cells, and labeled heterogeneous nuclear RNA incubated with extracts of these cells is preferentially cleaved, since mRNA included in the same incubations is not appreciably degraded. The cleavage of heterogenous nuclear RNA is caused by the synthesis of (2'5')An and by a "localized" activation of the (2',5')An-dependent endonuclease, since it was enhanced by ATP, the substrate of the (2',5')An polymerase, and inhibited by 2'-dATP and ethidium bromide. Both of these compounds suppress the synthesis of (2',5')An, the first by competitive inhibition and the latter by intercalating into double-stranded RNA. The possible role of double-stranded regions and of the (2',5')An polymerase-endonuclease system in the processing of heterogeneous nuclear RNA is discussed.

2',5'-Oligoadenylate Synthetase↗
PubMed1981

Longer-than-unit-length viroid minus strands are present in RNA from infected plants.

Nucleic acids isolated from uninfected and potato spindle tuber viroid-infected Rutgers tomato plants were fractionated on agarose gels under two different sets of denaturing conditions and hybridized to (125)I-labeled viroid in a series of blot hybridization experiments. Complementary strand nucleic acids detected in extracts of infected plants were heterogeneous in size, with four discrete bands containing molecules approximately 700, 1050, 1500, and 1800 nucleotides long. Enzymatic studies indicated that these viroid minus strands are composed exclusively of RNA and, as extracted, are present in complexes containing extensive double-stranded regions. After treatment with several RNases under conditions favoring digestion of single-stranded regions, the high molecular weight minus strands can no longer be detected and roughly unit-length minus strands appear. A model for the structure of the viroid replication intermediate is proposed.

Journal Article↗
PubMed1980

Identification of the RNA region transferred from a representative primer, beta-globin mRNA, to influenza mRNA during in vitro transcription.

Capped eukaryotic mRNAs strongly stimulate influenza viral RNA transcription in vitro and donate their cap and also additional nucleotides to the viral transcripts (1). To identify which bases of a given primer mRNA are transferred, we synthesized influenza viral mRNA using a primer rabbit globin mRNA (enriched in beta-globin mRNA) which had been labeled in vitro to high specific activity with 125I. We show that during transcription the same 125I-labeled oligonucleotides were transferred to the 5' termini of each of the eight viral mRNA segments. The predominant sequence, representing 75 percent of the transferred oligonucleotides, was identical to the first 13 nucleotides at the 5' end of beta-globin mRNA (m7G5'ppp5'm6AmC(m)ACUUGCUUUUG). Because only the C-residues are labeled with 125I, these results indicate that either the first 12, 13 or 14 5' terminal bases of beta-globin mRNA were transferred to the viral mRNAs. 125I-labeled oligonucleotides recovered from the viral mRNA in minor yields indicated that shorter 5' terminal pieces of beta-globin mRNA were sometimes transferred and that G was probably the first base inserted by transcription.

Animals↗
PubMed1980

Colonic manifestations of collagen vascular diseases.

Upper gastrointestinal manifestations of collagen vascular diseases have been well described. Recently our attention has been focused on the colonic complications: fibrosis and stricture resulting in obstruction, severe obstipation and recurrent fecal impactions secondary to pseudo-obstruction, progressive colonic dilatation resulting in gangrene of the colon, and sigmoid volvulus and diverticulitis in the presence of both wide- and narrow-mouth pseudodiverticula. Patients with these colonic manifestations of collagen vascular disease are disabled, if not severely ill. Recognition of the problem enables the surgeon to plan definitive surgical intervention ranging from segmental resection to total colectomy and ileoproctostomy to restore satisfactory large bowel function.

Adult↗
PubMed1980

Specific RNA-cleaving activities from HeLa cells.

Subcellular fractionation of HeLa cells was carried out under gentle conditions to isolate enzymes that cleave RNA precursors in a specific manner. Four separate activities--cleavage of HeLa cell heterogeneous nuclear RNA, the HeLa cell 45S rRNA precursor, RNA . DNA hybrids (RNase H), and the Escherichia coli tRNATyr precursor (RNase P)--were revealed by these studies. The specificity and limited nature of these cleavages suggest that they are due to eukaryotic RNA-processing enzymes. The virtual absence of random nucleases from these enzymes was demonstrated by their inability to cleave the 8000-base early mRNA precursor of bacteriophage T7, E. coli 30S rRNA precursor, or HeLa cytoplasmic poly(A)-containing RNA.

Cell Nucleus↗
PubMed1980

Candidal abscess of the spleen in patients with acute leukemia.

Between January 1974 and July 1976, three adult patients with leukemia, therapy-associated granulocytopenia and febrile courses unresponsive to broad spectrum antibiotic therapy were operated upon for a preoperative diagnosis of candidal abscess of the spleen. The diagnosis was based upon a high index of suspicion of invasive candidiasis in this immunosuppressed group of patients; the failure of the patients to respond to the empiric administration of broad spectrum antibiotics, salicylates and steroids, and the presence of discrete scintiscan defects on liver-spleen scan with both 99Tc sulfur colloid and 67Ga citrate. Multiple splenic abscesses containing candidal organisms were confirmed in all three patients, and two of the three also had multiple small abscesses of the liver. The fourth patient, whose liver-spleen scintiscans were abnormal only in showing splenomegaly and whose febrile course responded to aspirin, did not have a candidal abscess of the spleen at the time of celiotomy which was undertaken for fever of unknown cause. The antemortem diagnosis and treatment of candidal splenic abscess in patients with leukemia is dependent upon a high index of suspicion and appropriate clinical correlation with diagnostic tests. Although the prophylactic oral administration of mycostatin to patients at high risk may prevent this once fatal complication, only prompt and aggressive treatment can cure it.

Abscess↗
PubMed1979

Approaches to sequence analysis of 125I-labeled RNA.

A method is described for the initial steps of sequence analysis of RNase T1-and pancreatic RN-ase-resistant oligonucleotides of RNA containing cytidylate residues labeled in vitro with 125I. In many cases an oligonucleotide sequence can be deduced from a consideration of (i) its relative position in the two-dimensional fingerprint (with DEAE thin layer homochromatographic second dimension), (ii) its electrophoretic mobility on DEAE paper at pH 1.9, and (iii) identification of its products of further enzymatic digestion by comparison with a set of marker oligonucleotides. Additional methods including analysis of oligonucleotides following chemical blocking of uridylate residues with CMCT and analysis of products of incomplete enzymatic digestion are also discussed.

Base Sequence↗
PubMed1978

Potato spindle tuber and citrus exocortis viroids undergo no major sequence changes during replication in two different hosts.

Potato spindle tuber viroid and citrus exocortis viroid, each purified from tomato (Lycopersicon esculentum) and from Gynura aurantiaca, were iodinated in vitro with (125)I, digested with ribonuclease T1, and subjected to two-dimensional RNA fingerprinting analysis. With the exception of minor variations, each viroid retained its distinctive fingerprint pattern irrespective of the host species from which it was isolated. We conclude that the nucleotide sequences of these viroids are principally determined by the infecting viroid and not by the host.

Journal Article↗
PubMed1977

Initiator regions from the small size class of reovirus messenger RNA protected by rabbit reticulocyte ribosomes.

In order to investigate the general utility of the rabbit reticulocyte cell-free translating system for isolation of ribosome-protected initiator regions of eukaryotic mRNA, we have studied ribosome protection of 32P-labeled reovirus small mRNA species. Our studies show that rabbit reticulocyte ribosomes protect initiator regions in at least two of the four reovirus small mRNA molecules. RNA sequence analysis demonstrates that 40 S subunits protect additional sequences to the 5' side of the initiator AUG triplet.

Animals↗