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Biomedical subjects

J D Jacobs

Publications and source records attributed to J D Jacobs.

13 recordsLinked to original sources
PubMed1992

Characterization of two circular plasmids from the marine diatom Cylindrotheca fusiformis: plasmids hybridize to chloroplast and nuclear DNA.

This paper reports the discovery and initial characterization of two small plasmids, pCf1 and pCf2, in the marine diatom Cylindrotheca fusiformis. Extracted diatom DNA separates into two bands in CsCl-Hoechst 33258 dye gradients. Upon agarose gel electrophoresis of a sample of the upper band of the gradient we observed, in addition to high molecular weight (genomic) chloroplast and mitochondrial DNA, pairs of lower molecular weight bands. These bands contained two species of circular plasmid DNA molecules, as shown by electron microscopy. The nucleotide composition of the plasmids, and chloroplast and mitochondrial DNAs is similar, as indicated by their co-banding in the gradients. They were cloned, and their restriction maps determined, showing that pCf1 is 4.27 and pCf2 4.08 kb in size. By hybridization analysis, we showed that pCf1 and pCf2 share regions of similarity, but not identity. Neither plasmid hybridizes with mitochondrial DNA. Both plasmids hybridize with chloroplast DNA, and pCf2 also hybridizes with nuclear DNA.

Cell Nucleus↗
PubMed1991

Immediately preovulatory levels of messenger ribonucleic acid for inhibin alpha-subunit are diminished in granulosa cells from successful in-vitro fertilization-embryo transfer.

Inhibin, a gonadal glycoprotein which suppresses pituitary gonadotrophin secretion, preferentially follicle stimulating hormone, has been extensively characterized. It consists of two covalently bound subunits, the alpha- and beta-subunits, encoded by separate genes. In this study, the expression of messenger ribonucleic acid (mRNA) for the inhibin alpha-subunit was studied by Northern blot analysis in granulosa cells of women undergoing in-vitro fertilization/embryo transfer (IVF/ET). Three patient groups were studied: women who failed to become pregnant (n = 11), women who became pregnant but experienced early spontaneous abortion (n = 3) and women who conceived normal ongoing pregnancies (n = 4). Granulosa cells were obtained at the time of follicle aspiration. Levels of alpha-subunit mRNA were 40% lower in patients establishing normal pregnancies than in those who failed to become pregnant or who spontaneously aborted. Thus, a relative diminution of immediately preovulatory levels of mRNA for inhibin alpha-subunit is a marker of success in clinical IVF/ET cycles. This marker of IVF/ET success can be related to previously established markers of success (increased follicular fluid oestradiol and decreased follicular fluid cyclic adenosine monophosphate) by known physiological mechanisms.

Adult↗
PubMed1979

Combined orthodontic-surgical correction of moderate mandibular deficiency.

Carefully planned, coordinated, and executed orthodontic and surgical treatment is a viable alternative to traditional orthodontic treatment of patients with moderate mandibular deficiency. Recognition of their clinical manifestations is essential to distinguish between relative and absolute mandibular deficiency. If after clinical analysis of the Class II patient, esthetic priorities are established to maintain a balanced relationship between the upper lip and nose and not reduce the prominence of the upper lip, mandibular deficiency must be treated by surgical advancement of the mandible, superior repositioning of the maxilla, and consequent autorotational movement of the mandible forward and upward, or a combination of these procedures. The common denominator of successful therapy of absolute mandibular deficiency involves surgery to advance the mandible; relative mandibular deficiency, on the other hand, is treated by maxillary surgery to reposition the maxilla superiorly to allow forward and upward movement of the retropositioned mandible (autorotation). In actual clinical practice many patients manifest a combination of absolute and relative mandibular deficiency and are treated by maxillary and mandibular surgery. Lateral maxillary osteotomies, in concert with rapid maxillary expansion and genioplasty to alter the dimensions of the chin, are essential adjunctive surgical procedures to achieve three-dimensional esthetic and occlusal balance.

Adult↗
PubMed1979

Surgical-orthodontic correction of horizontal maxillary deficiency.

Selected maxillary osteotomies in concert with rapid maxillary expansion appliances are dependable adjuncts to treatment of the various clinical manifestations of horizontal maxillary deficiency and the accompanying crossbite. The important diagnostic, treatment planning, and technical considerations necessary for successful surgical-orthodontic correction of horizontal maxillary deficiency were discussed.

Adult↗
PubMed1977

Electrical stimulation of osteogenesis in periodontal defects.

Although the literature on bioelectrical phenomena is extensive, there is a paucity of research on its application in the field of dentistry. This study was designed to evaluate the effect of bioelectric phenomena on pathological osseous defects in the periodontium of Beagle dogs. Galvanic and thermocouple generators were designed to deliver a current in the nanoampere range. The galvanic unit implanted in the area of periodontal osseous defects in five dogs. These sites were randomly designated as experimental, active controls, and passive controls. The experimental and control units were implanted submucoperiosteally with the negative electrodes extending into the osseous defects. The bone was labeled with Procion Red H-8Bs at one week. Clinical and radiographic evaluation revealed no significant changes in the depth of the defects. The animals were sacrificed at 45 days and block sections were prepared. Histological measurement suggested that endosteal apposition was enhanced in all experimental sites as compared to controls. The results were discussed in relation to magnitude of current used, the influence of pathological bone, the potential of each type of experimental unit for clinical use, and the direction of further research in the area.

Animals↗
PubMed1976

Electrical stimulation of osteogenesis in pathological osseous defects.

Although the literature on bioelectric phenomena is extensive, there is a paucity of research on its application in the field of dentistry. This study was designed to evaluate the effect of bioelectrical stimulation on pathological osseous defects in the periodontium of Beagle dogs. Galvanic and thermocouple generators were designed to deliver a current in the nanoampere range. The galvanic unit produced a constant direct current. The thermocouple unit was designed to deliver an oscillating dc current. The generators were implanted in the area of periodontal osseous defects in five dogs. These sites were randomly designated as experimental, active controls, and passive controls. The experimental and control units were implanted submucoperiosteally with the negative electrodes extending into osseous defects. The bone was labeled with Procion Red H-8BS at 1 week. Clinical and radiographic evaluation revealed no significant changes in the depth of the defects. The animals were sacrificed at 45 days and block sections were prepared for histological measurement. From the results of this study it was concluded: 1. Induced constant or oscillating negative dc current levels in the nanoampere range were unsucessful in causing regeneration of periodontal osseous defects either clinically or radiographically in the Beagle dog over a 45-day period of application. 2. Constant or oscillating negative dc current levels in the nanoampere range did not stimulate a significant amount of periosteal osseous apposition. 3. Oscillating negative nanoampere dc currents produced an increase in endosteal osseous apposition as compared to controls. 4. Constant negative dc current in the nanoampere range produced an increase in endosteal osseous apposition as compared to controls. 5. The histological density of the bone in the area of pathological periodontal defects was increased in all experimental sites as compared to controls. 6. Devices of comparable size and construction to both the galvanic and thermocouple electronic units used in this study are acceptable for future investigation of the effect of bioelectrical stimulation on osteogenesis in alveolar bone.

Animals↗