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Biomedical subjects

A Jacobson

Publications and source records attributed to A Jacobson.

At least 145 records · Page 8Linked to original sources
PubMed1984

Intron bypass: a rapid procedure for eliminating introns from cloned genomic DNA and its application to a cellulase gene.

We have devised a DNA cloning procedure in which the introns present in a genomic DNA fragment can be eliminated easily and rapidly. The technique combines the methods of cDNA and genomic cloning in a way which assures full-length representation of the intron-free transcript. Moreover, plasmids made by this technique can be designed to contain flanking untranscribed regions which may play a role in the regulation of expression. One strand of a linearized plasmid containing the 3'-end of a gene is used to prime cDNA synthesis from an annealed mRNA template. A second plasmid containing the 5'-end of the gene is linearized, denatured, and annealed to the extended 3'-end molecules and the resulting circular, partial duplexes are used to transform bacterial cells. Two different recombinant plasmids which contain DNA encoding the cellulase, exocellobiohydrolase I, from Trichoderma reesei have been constructed using this method. They both contain the entire translated region of the gene uninterrupted by introns. One plasmid contains additional DNA at the 5'-end, including approximately 150 bp 5' to the start of transcription. The inserts of both plasmids can be excised in one piece.

Base Sequence↗
PubMed1984

Translational control during early Dictyostelium development: possible involvement of poly(A) sequences.

A rapid decrease in the translational efficiency of mRNA synthesized during vegetative growth is associated with the initiation of development in Dictyostelium discoideum. In contrast, newly synthesized mRNA associates with polysomes with high efficiency. Discrimination between these two mRNA populations correlates with a rapid shortening of the poly(A) tract on the preexisting mRNA. A model is proposed in which a critical poly(A) length regulates the pattern of protein synthesis by affecting the efficiency with which mRNAs can interact with the translational machinery. The model suggests that transcriptional and translational controls can be coupled by altering the state of adenylation of the preexisting mRNA population. The model allows radical changes in the pattern of protein synthesis without wholesale destruction of preexisting mRNA.

Base Sequence↗
PubMed1984

Psychological aspects of dentofacial esthetics and orthognathic surgery.

The literature and the results of the survey clearly confirm that physical attractiveness plays a major role in the social life and interaction among individuals. Cosmetic improvement is a powerful motivating factor leading people to seek treatment. Those who believe that the rewards of facial improvement will enable them to lead more satisfying and comfortable lives should be encouraged to proceed with the treatment. However, it is absolutely essential that those contemplating treatment be counseled before-hand and fully informed on the prognosis, risks and hazards, advantages and disadvantages of such procedures before embarking on treatment.

Attitude to Health↗
PubMed1983

Possible involvement of poly(A) in protein synthesis.

The experiments of this paper have re-evaluated the possibility that poly(A) is involved in protein synthesis by testing whether purified poly(A) might competitively inhibit in vitro protein synthesis in rabbit reticulocyte extracts. We have found that poly(A) inhibits the rate of translation of many different poly(A)+ mRNAs and that comparable inhibition is not observed with other ribopolymers. Inhibition by poly(A) preferentially affects the translation of adenylated mRNAs and can be overcome by increased mRNA concentrations or by translating mRNPs instead of mRNA. The extent of inhibition is dependent on the size of the competitor poly(A) as well as on the translation activity which a lysate has for poly(A)+ RNA. In light of our results and numerous experiments in the literature, we propose that poly(A) has a function in protein synthesis and that any role in the determination of mRNA stability is indirect.

Animals↗
PubMed1983

Messenger RNA half-life in Dictyostelium discoideum.

Messenger RNA half-life in vegetatively growing cells of Dictyostelium discoideum was determined using a uridine pulse-chase procedure. In these experiments, mRNA decayed in a complex fashion, and consisted of at least two major components, one with a half-life of about 50 min and a second with a half-life of about 10 hr. These results independently confirm our previous studies on the decay of mRNA extracted from actinomycin D-treated cells. Since these results were in apparent conflict with half-life determinations obtained with a combination of actinomycin D and daunomycin (J. P. Margolskee and H. F. Lodish, 1980a, Dev. Biol. 74, 37-49), we have also studied mRNA half-life in cells treated with a combination of both drugs and found that simultaneous use of both drugs leads to accelerated mRNA decay and other noticeable side effects. In light of our observations, we have suggested an alternative to conclusions drawn by others with respect to mRNA synthesis and stability in Dictyostelium development.

Dactinomycin↗
PubMed1983

The role of conservative surgery in the management of inverted papilloma.

A group of 31 patients with inverted papilloma were treated at the Mount Sinai Medical Center. There were no multicentric cases, and one patient had an associated malignancy. A conservative procedure consisting of intranasal or transantral sphenoethmoidectomy was selectively performed in 8 patients with limited lesions. No recurrences were observed in this group after a mean follow-up of 2 years. Lateral rhinotomy with medial maxillectomy and en bloc resection of the ethmoid labyrinth was performed in 23 other patients. One recurrence appeared in this group, members of which were followed a mean of 3.8 years. Radiographic evaluation by multidirectional polytomography and CT scanning permits identification of a small group of patients who have limited lesions and may be candidates for conservative tumor excision.

Adolescent↗
PubMed1983

The physiology of tooth eruption.

Tooth eruption is a complex phenomenon that involves numerous biologic activities of the bone and the soft tissue surrounding teeth. While the exact mechanisms of eruption are not clearly understood, numerous experiments of nature, including many of the inborn errors of metabolism, should prove useful in their study. Nutritional studies may also prove useful, but will always be problematic [56]. Studies on endocrinologic changes such as puberty, pregnancy, menopause, and diseases such as diabetes, have already shown that the periodontium may not be able to accommodate to changes in the body's equilibrium [51].

Animals↗
PubMed1982

The MARS appliance. Report of a case.

Inconsistent wearing of functional appliances, intermaxillary Class II elastics, and headgear during the treatment of Class II malocclusions is a common concern of many orthodontists. The MARS (Mandibular Advancing Repositioning Splint) is a functional device designed to overcome many such cooperation deficiencies. The MARS appliance is a fixed functional device which is attached to the arch wires of a multibanded orthodontic appliance. It is composed of a piston and cylinder which attach to the lower canine and the upper molar region of the dental arch wires on each side of the jaw. It forces the patient to maintain the mandible in a protruded position 24 hours a day and yet allows full and complete opening and closing as well as lateral excursive movement. The design, method of attaching, and adjustment of the appliance during treatment are discussed, and the results achieved in a single case are described. The results being achieved in the pilot study so far are encouraging and are being pursued further.

Activator Appliances↗
PubMed1981

Inhibitory effects of 2,3,5-triiodobenzoic Acid on ion absorption, respiration, and carbon metabolism in excised barley roots.

The ability of 2,3,5-triiodobenzoic acid (TIBA) to alter ion absorption, respiration, carbon metabolism, and the permeability of the cell membranes of excised barley roots has been examined. Roots pretreated in either H(2)O, KCl, or TIBA followed by treatment in KCl, TIBA, or KCl and TIBA demonstrated that inhibition of ion uptake due to TIBA was reversible. These studies also suggest that ions already accumulated within the vacuole remain sequestered after the addition of TIBA, whereas cytoplasmic ions leak out into the external medium. A 20-minute lag period was present prior to the onset of inhibition of O(2) consumption by TIBA. A b-type cytochrome from corn that is apparently associated with the plasmalemma and possibly involved in respiration or ion uptake, or both, was unaffected by TIBA. The addition of TIBA to treatment solutions resulted in the synthesis and accumulation of ethanol. Analysis of organic acids showed that only the malate concentration was affected by treatment with TIBA. A reduction of 26% was noted for malate in the presence of 2 micromolar TIBA. These combined results suggest that the inhibitory action of TIBA in barley roots involves an alteration of mitochondrial respiration and not a direct depolarization of the plasmalemma.

Journal Article↗
PubMed1981

A carbohydrate-containing form of immunoreactive calcitonin in transplantable rat medullary thyroid carcinomas.

Extracts of transplantable rat medullary thyroid carcinomas were fractionated by concanavalin A-agarose chromatography and SDS-polyacrylamide gel electrophoresis. While tumor extracts contained mostly (greater than 90%) native calcitonin, 4 distinct larger calcitonin species (Mr = 27,000, 17,000, 13,700, and 9,600) were also observed. Glycoprotein fractions from lectin-affinity chromatography of the tumor extracts contained 0.3-1.5% of the total immunoreactive calcitonin. Gel electrophoresis of the pooled glycoprotein fractions demonstrated that the predominant forms of immunoreactive calcitonin were larger than calcitonin monomer. One high molecular weight species (Mr = 9,600), isolated in sufficient quantity from the polyacrylamide gels for reapplication to concanavalin A-agarose, was specifically eluted from the lectin, indicating that it was a glycoprotein. These results are the first evidence that intact C-cells contain at lest one high molecular weight glycoprotein form of immunoreactive calcitonin and suggest that addition and removal of carbohydrate side chains occur during processing of calcitonin precursors to the native hormone.

Animals↗
PubMed1981

Growth and its relation to orthodontic treatment.

Surgery has become an invaluable adjunct to orthodontic therapy. However, before embarking on surgical procedures, particularly in growing individuals, it is necessary to appraise each case carefully to determine whether the dentofacial dysplasias can be corrected by orthodontic or orthopedic means. It is possible by the use of investigative procedures to determine the extent and severity of malocclusions and any associated dentofacial dysplasias. General growth rates, increments, and directions can be predicted with some degree of accuracy. Likewise, favorable and unfavorable growth patterns can usually be identified. However, there are those cases in which, for reasons unknown, the growth patterns do not follow the usual trends. These cases often do not respond satisfactorily to treatment because of bizarre or unanticipated growth patterns. Science, unfortunately, has not progressed sufficiently so that such patterns can be identified ahead of time. Until the secrets of such growth patterns are uncovered, treatment procedures, response to the therapy, and growth predictions, of necessity, must be based on average growth trends.

Cephalometry↗
PubMed1980

Point A revisited.

Point A cannot be accurately identified in all cephalometric radiographs. In instances where this landmark is not clearly discernible, an alternative means of estimating the anterior extremity of the maxillary base is shown. A point plotted 3.0 mm. labial to a point between the upper third and lower two thirds of the long axis of the root of the maxillary central incisor was found to be a suitable point (estimated point A) through which to draw the NAE line and one which most closely approximates the true NA plane.

Cephalometry↗