The future of dentistry and dental education.
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Curriculum↗
Biomedical subjects
A Jacobson
Publications and source records attributed to A Jacobson.
Nucleotide sequence and characterization of the transcript of a Dictyostelium ribosomal protein gene.
Dictyostelium ribosomal protein mRNAs are subject to developmental regulation of both their translation and their stability. In order to consider whether such post-transcriptional regulation can be attributed to structural features of the mRNAs, we have cloned and sequenced a 1.9 kb EcoRI genomic DNA fragment which contains the gene for the Dictyostelium ribosomal protein 1024 (rp1024). The rp1024 gene contains a single intron of 350 bp which begins just after the fourth codon of protein coding sequence. Transcription begins 11 to 28 bp upstream from the initiator ATG in a pyrimidine rich region which is preceded by an oligo(dT)10 stretch, but which lacks a TATA box in the expected position. Processing of the 3' end occurs at either of two sites, resulting in two types of transcript which are present in equimolar amounts in both vegetatively growing and developing cells. Therefore, their relative abundance shows no correlation with the changes in translatability and stability of r-protein mRNAs which occur during development. A comparison of the sequence of the 5'-untranslated region of rp1024 mRNA to those of other Dictyostelium mRNAs shows that it differs significantly, primarily in its relatively high G+C content.
Amino Acid Sequence↗
Peripheral nerve injury associated with fracture or fracture-dislocation of the pelvis in dogs and cats: 34 cases (1978-1982).
Peripheral nerve injury was associated with fracture or fracture-dislocation of the pelvis in 23 dogs and 11 cats. In most cases, peripheral nerve injury resulted from ilial fracture with craniomedial displacement of bone fragments, or from sacroiliac fracture-dislocation with cranial displacement of the ilium. Sciatic nerve injury was associated with fracture of the acetabulum in 2 dogs. A combination of sensory, voluntary motor, and reflex abnormalities were observed in the ipsilateral extremity of affected animals. Signs of severe pain were noticed in 4 of the dogs and in 1 cat. Eight of the animals died or were euthanatized for reasons not directly related to the severity of peripheral nerve injury. Of the remaining 26 animals, 21 (81%) had good or excellent limb function 16 weeks after peripheral nerve injury was sustained. Limb function was lost or self-mutilation occurred in 4 (15%) of the animals.
Animals↗
Purification and fractionation of poly(A)+ RNA.
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Chromatography, Affinity↗
Class III crowding: the extraction dilemma.
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Child↗
FSH accumulation in hMG-treated patients.
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Female↗
Increased rates of decay and reduced levels of accumulation of the major poly(A)-associated proteins of Dictyostelium during heat shock and development.
Two major polypeptide species, 31,000 Mr (p31) and 31,500 Mr (p31.5), are associated with the 3' poly(A) tails of Dictyostelium mRNAs. We have measured the accumulation of newly synthesized p31 and p31.5 and the decay of preexisting p31 and p31.5 during heat shock and early development. Only trace amounts of newly synthesized p31 and p31.5 accumulate at elevated temperatures, indicating that these polypeptides are not heat shock proteins. In addition, preexisting p31 and p31.5 are rapidly degraded in heat-shocked cells. This degradation is selective and occurs simultaneously with a sharp drop in the rate of translational initiation. Similarly, in early development, a time when the rate of translational initiation is also sharply reduced, only trace amounts of newly synthesized p31 and p31.5 accumulate and most of the preexisting p31 and p31.5 is rapidly degraded. When translational elongation is inhibited with cycloheximide, preexisting p31 and p31.5 remain stable. Therefore, a correlation seems to exist between the abundance and stability of these poly(A)-associated proteins and the rate of translational initiation. Our results are consistent with the proposed role of the poly(A)-protein complex in translation and do not support the findings of Schönfelder et al. [Schönfelder, M., Horsch, A. & Schmid, H.-P. (1985) Proc. Natl. Acad. Sci. USA 82, 6884-6888] that the 73,000 Mr HeLa cell poly(A)-binding protein and the major 73,000 Mr mammalian heat shock protein (i.e., hsp70) are identical.
Cycloheximide↗
Translational control of ribosomal protein synthesis during early Dictyostelium discoideum development.
Throughout the developmental program of Dictyostelium discoideum there are substantial changes in the rates of both ribosome utilization and rRNA transcription and processing. We examined the regulation of ribosomal protein (r-protein) gene expression and found that, at the start of development, expression of these genes was drastically and specifically reduced by a block to translational initiation. An apparently separate event signals a sudden decrease in the relative amount of r-protein mRNA at about 10 h of development, a time when aggregated amoebae are forming tight cell-cell contacts. For the first 9 h of development, the relative amount of r-protein mRNA remained essentially unchanged and comparable to levels detected in growing cells. While the r-protein mRNAs were almost fully loaded on polysomes during vegetative growth, they were specifically excluded from polysomes at the start of development. The translational block was not the result of irreversible structural changes which inactivate the r-protein mRNAs since they remained translatable both in vitro, in wheat germ extracts, and in vivo, where they were recruited onto polysomes in the presence of the elongation inhibitor cycloheximide. In addition, precise measurements of poly(A) tail lengths on individual hybrid-selected mRNA species showed that there is no difference in the poly(A) tail length of r-protein mRNA isolated from growing cells and 1-h developing cells. Therefore, changes in translational efficiency cannot be attributed to cleavage of poly(A) tails.
Dictyostelium↗
Assault experiences of 100 psychiatric inpatients: evidence of the need for routine inquiry.
The authors obtained complete histories of all experiences of being physically or sexually assaulted from 100 psychiatric inpatients, using a structured interview with well-defined assault scales and a detailed inquiry into circumstances surrounding the assault. The majority (81%) of patients had experienced major physical and/or sexual assault. The circumstances associated with the assaults, the patients' perceptions of the effects of the assaults, and previous therapists' lack of awareness of the assaults are discussed. On the basis of these findings the authors recommend routine inquiry into patients' assault history.
Adolescent↗
The failure of routine assessment to detect histories of assault experienced by psychiatric patients.
To test the hypothesis that patients' histories of having been physically or sexually assaulted are often not elicited in routine clinical assessments, the authors reviewed the charts of 100 inpatients for any mention of such experiences. The data were compared with results of earlier research interviews in which the same 100 patients were questioned directly about assault experiences. Comparison of the two sets of data showed that only 9 percent of the assault histories obtained during research interviews were mentioned on the patients' charts. Because of the clinical significance of most major assaults, the authors recommend that clinicians routinely inquire about assault history.
Adult↗
Endstage renal failure due to polycystic kidney disease managed by continuous ambulatory peritoneal dialysis.
Over a five and one half year period, four of nine patients with endstage renal failure due to polycystic kidney disease managed by continuous ambulatory peritoneal dialysis (CAPD) developed peritonitis following intestinal perforation. Two patients had colonic perforation associated with diverticular disease, one necrosis of the terminal ileum, and one acute appendicitis. Two of the patients died subsequent to these complications. The survivors had early transfer to haemodialysis. In contrast, over the same period, only two of 125 patients with renal failure due to other causes and managed by CAPD had acute intestinal perforation. In both cases this was associated with acute appendicitis. Both patients survived. All episodes of peritonitis in CAPD patients with polycystic kidneys demand very close monitoring, cessation of CAPD, and early surgical intervention. CAPD is relatively contraindicated in such patients.
Female↗
Reimplantation of a human embryo with subsequent ovarian pregnancy.
An ovarian pregnancy followed ovulation induction and in vitro fertilization. The patient had multiple risk factors, including two previous tubal pregnancies, endometriosis, and use of an intrauterine contraceptive device.
Adult↗
Identification and characterization of developmentally regulated mRNP proteins of Dictyostelium discoideum.
The isolation of poly(A)+ polysomal and nonpolysomal RNPs by oligo(dT)-cellulose chromatography has led to the identification of more than 20 polypeptides that bind to the poly(A)+ mRNA in growing Dictyostelium cells. Most of these polypeptides were identified in experiments using short-wave UV light (254 nm) to crosslink specifically bound proteins to the RNA. Digestion of the RNPs with ribonucleases A and T1 prior to their application to oligo(dT)-cellulose permitted the isolation of the 3' poly(A)-protein complexes. In polysomal RNPs, two major polypeptides, with molecular weights of 31,000 (p31) and 31,500 (p31.5), are bound to poly(A). These proteins can also be purified from cytoplasmic extracts by affinity chromatography on poly(A)-Sepharose. Partial proteolytic digestion of p31 and p31.5 indicates that they are closely related. The UV-crosslinking experiments established that p31 and p31.5 bind to the non-poly(A) segments of mRNA as well. In nonpolysomal RNPs, p31 and a polypeptide with a molecular weight of 29,500 (p29.5) are the major species associated with poly(A). Partial proteolytic digestion of p29.5 indicates that it is closely related to p31 and p31.5. Only small amounts of p29.5 were observed in the polysomal poly(A)-protein complexes. Early in Dictyostelium development, when cellular translation activity is sharply reduced, most of the p29.5, p31 and p31.5 present is selectively degraded. These observations are consistent with a translational role for these proteins.
Chromatography, Affinity↗
Ribosomal proteins are encoded by single copy genes in Dictyostelium discoideum.
Five recombinant plasmids which encode ribosomal proteins (r-proteins) from Dictyostelium discoideum have been isolated. Poly(A) + RNA was size-fractionated by preparative agarose gel electrophoresis and a fraction encoding proteins of less than 35 kDa was used to construct a cDNA library in the plasmid vector pBR322. Individual clones from the library were screened by hybrid-selected translation and those encoding r-proteins were identified by co-migration of the translation products in two-dimensional gel electrophoresis with marker proteins purified from Dictyostelium ribosomes. Initial characterization using the five cDNA plasmids indicates that these r-proteins are encoded by single copy genes and that they are not tightly clustered in the genome.
Cloning, Molecular↗
Practical quantitation of radiation levels associated with newer CT scanner units.
Concern for higher radiation levels associated with some of the latest generation computed tomography (CT) scanners points to the need for dissemination of meaningful quantitative radiation dose data about these improved imaging units. Recent radiation protection survey data of some new CT installations are offered. Knowledgeable use of such information should afford CT users a basis for proper use of this valuable imaging modality within current radiation protection guidelines.
Environmental Exposure↗
A successful microsurgical reanastomosis program in a community hospital.
Microsurgical tubal reversal (MTR) can now be performed at the community-hospital level with excellent results if meticulous attention is paid to intraoperative surgical details. An initial series of 15 patients underwent MTR, with a term pregnancy rate of 87%. No postoperative complications occurred, and no postoperative hydroperturbations or second-look laparoscopies were performed.
Adult↗
Extrachromosomal replication of shuttle vectors in Dictyostelium discoideum.
We cloned a 12.3-kilobase (kb) endogenous plasmid, Ddp1, found in several wild-type and laboratory strains of Dictyostelium discoideum into pBR322. The cloned plasmids have been used to cotransform D. discoideum cells with B10S, a transformation vector carrying a gene fusion conferring resistance to G418. Whereas B10S DNA alone appears to integrate in a tandem array, the cloned Ddp1 plasmids replicate extrachromosomally and are stably maintained in the absence of selection with an average copy number of 50 to 100 copies per cell. The Ddp1-derived plasmids can be directly recovered by transforming Escherichia coli with bulk nuclear DNA from these cells. Preliminary deletion analysis indicates that not all regions of Ddp1 are necessary for stable replication in D. discoideum. Several recombinant vectors which replicate extrachromosomally in D. discoideum were also isolated. One contains the Act6-neor gene fusion from B10S recombined into one of the cloned derivatives of Ddp1 and can be used to directly transform D. discoideum amoebae, selecting for G418 resistance. Another recombinant is only 5.6 kb and resulted from a deletion of a 16.6-kb cloned Ddp1 hybrid plasmid. An analysis of the vector DNAs present in clones derived from single D. discoideum transformants is also described.
Cloning, Molecular↗