Direct measurement of the percolation probability in carbon nanofiber-polyimide nanocomposites.

We present the first experimental measurement of the geometric critical exponent beta associated with the percolation probability, the probability a metallic filler belongs to the conducting network, of an electrical composite. The technique employs conducting-tip atomic force microscopy to obtain a conducting areal density, and is demonstrated on polyimide nanocomposites containing different concentrations of carbon nanofibers. We find beta approximately 1 and t (the exponent for bulk conductivity) approximately 3. These values are consistent with the predictions for the Bethe lattice and larger than the values predicted in the 3D lattice percolation model. Hence, this electrical composite likely belongs to the same universality class as the Bethe lattice. The ability to measure geometric and transport critical exponents on the same material is critical to drawing this conclusion.

Association of the epithelial sodium channel with Apx and alpha-spectrin in A6 renal epithelial cells.

Recent molecular cloning of the epithelial sodium channel (ENaC) provides the opportunity to identify ENaC-associated proteins that function in regulating its cell surface expression and activity. We have examined whether ENaC is associated with Apx (apical protein Xenopus) and the spectrin-based membrane cytoskeleton in Xenopus A6 renal epithelial cells. We have also addressed whether Apx is required for the expression of amiloride-sensitive Na(+) currents by cloned ENaC. Sucrose density gradient centrifugation of A6 cell detergent extracts showed co-sedimentation of xENaC, alpha-spectrin, and Apx. Immunoblot analysis of proteins co-immunoprecipitating under high stringency conditions from peak Xenopus ENaC/Apx-containing gradient fractions indicate that ENaC, Apx, and alpha-spectrin are associated in a macromolecular complex. To examine whether Apx is required for the functional expression of ENaC, alphabetagamma mENaC cRNAs were coinjected into Xenopus oocytes with Apx sense or antisense oligodeoxynucleotides. The two-electrode voltage clamp technique showed there was a marked reduction in amiloride-sensitive current in oocytes coinjected with antisense oligonucleotides when to compared with oocytes coinjected with sense oligonucleotides. These studies indicate that ENaC is associated in a macromolecular complex with Apx and alpha-spectrin in A6 cells and suggest that Apx is required for the functional expression of ENaC in Xenopus epithelia.

Effect of aging on vasopressin and aquaporin responses to dehydration in Fischer 344-brown-Norway F1 rats.

The plasma vasopressin (VP) response to 72 h of water deprivation is attenuated in 30-mo-old Fischer 344 (F344) rats relative to 4-mo-old rats. This appears to reflect an inability to increase VP synthesis. In contrast, elevated plasma VP has been reported in the Brown-Norway (BN) strain of rats secondary to reduced renal VP responsivity. The response to dehydration in the F1 cross of these strains (F344BNF1) was evaluated. Male rats, 4 and 30 mo old, were deprived of water for 72 h or allowed water ad libitum. In response to dehydration, plasma sodium and hematocrit were significantly increased in both young and aged rats (P < 0.05), but plasma VP, urine osmolality, and aquaporin 2 expression were only increased in the young rats (P < 0.05). Posterior pituitary content of immunoreactive VP was depleted in the young but not the old rats. Thus the aged F344BNF1 rats demonstrated a deficit in VP release in response to an apparently similar dehydration stimulus. This deficit was different from those previously reported for either the F344 or BN strains. Thus further studies are required to determine the abnormalities underlying this response.

Glucocorticoids downregulate the vasopressin-regulated urea transporter in rat terminal inner medullary collecting ducts.

This study tested whether glucocorticoids regulate tubular urea transport. Urea permeability was measured in perfused inner medullary collecting duct (IMCD) subsegments from rats that underwent adrenalectomy, adrenalectomy plus replacement with a physiologic dose of glucocorticoid (dexamethasone), or sham operation. Compared with sham rats, basal urea permeability in terminal IMCD was significantly increased in adrenalectomized rats and reduced in dexamethasone-treated rats. Vasopressin significantly increased urea permeability in all three groups. In contrast, there was no difference in basal or vasopressin-stimulated urea permeability in initial IMCD between the three groups. Next, membrane and vesicle fraction proteins were isolated from inner medullary tip or base and Western analysis was performed by use of an antibody to the rat vasopressin-regulated urea transporter. Vasopressin-regulated urea transporter protein was significantly increased in both membrane and vesicle fractions from the inner medullary tip of adrenalectomized rats. There was no change in vasopressin-regulated urea transporter protein in the inner medullary base, and Northern analysis showed no change in urea transporter mRNA abundance in either inner medullary region. It was concluded that glucocorticoids can downregulate function and expression of the vasopressin-regulated urea transporter in rat terminal IMCD.

Glucocorticoids mediate a decrease in AVP-regulated urea transporter in diabetic rat inner medulla.

Providing glucocorticoids to adrenalectomized (Adx) rats results in downregulation of the vasopressin (AVP)-regulated urea transporter (VRUT) in the renal inner medullary (IM) tip. To examine the physiological relevance of this response, we studied rats with uncontrolled diabetes mellitus induced by streptozotocin (STZ), since these rats have increased corticosterone production and urea excretion. We measured VRUT protein in extracts from the IM tip or base of pair-fed control and diabetic rats by Western analysis using an antibody to rat VRUT. In the IM tip, VRUT was significantly reduced by 39% in diabetic compared with control rats. In the IM base, there was no significant difference between diabetic and control rats. To determine whether the decrease in VRUT in the IM tip was mediated by glucocorticoids, the experiment was repeated using the following three groups of rats: 1) Adx alone, 2) Adx + STZ, and 3) Adx + STZ + replacement with a physiological dose of glucocorticoid. There was no significant difference in VRUT between Adx and Adx + STZ rats. However, VRUT was significantly reduced by 32% in the IM tip of glucocorticoid-treated Adx + STZ rats compared with control Adx + STZ rats. We conclude that glucocorticoids regulate the abundance of VRUT protein independently of insulin in diabetic rats.

Changes in aquaporin-2 protein contribute to the urine concentrating defect in rats fed a low-protein diet.

Low-protein diets cause a urinary concentrating defect in rats and humans. Previously, we showed that feeding rats a low (8%) protein diet induces a change in urea transport in initial inner medullary collecting ducts (IMCDs) which could contribute to the concentrating defect. Now, we test whether decreased osmotic water permeability (Pf) contributes to the concentrating defect by measuring Pf in perfused initial and terminal IMCDs from rats fed 18 or 8% protein for 2 wk. In terminal IMCDs, arginine vasopressin (AVP)-stimulated osmotic water permeability was significantly reduced in rats fed 8% protein compared to rats fed 18% protein. In initial IMCDs, AVP-stimulated osmotic water permeability was unaffected by dietary protein. Thus, AVP-stimulated osmotic water permeability is significantly reduced in terminal IMCDs but not in initial IMCDs. Next, we determined if the amount of immunoreactive aquaporin-2 (AQP2, the AVP-regulated water channel) or AQP3 protein was altered. Protein was isolated from base or tip regions of rat inner medulla and Western analysis performed using polyclonal antibodies to rat AQP2 or AQP3 (courtesy of Dr. M.A. Knepper, National Institutes of Health, Bethesda, MD). In rats fed 8% protein (compared to rats fed 18% protein): (a) AQP2 decreases significantly in both membrane and vesicle fractions from the tip; (b) AQP2 is unchanged in the base; and (c) AQP3 is unchanged. Together, the results suggest that the decrease in AVP-stimulated osmotic water permeability results, at least in part, in the decrease in AQP2 protein. We conclude that water reabsorption, like urea reabsorption, responds to dietary protein restriction in a manner that would limit urine concentrating capacity.

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.

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.

Structure of the Chlamydomonas reinhardtii cabII-1 gene encoding a chlorophyll-a/b-binding protein.

Gene cabII-1 is a light regulated gene that encodes the precursor of a major chlorophyll-a/b-binding protein in Chlamydomonas reinhardtii. It is a member of a small gene family composed of about 3-7 members. Nucleotide sequencing data and S1 mapping reveal that the cabII-1 gene is interrupted by three introns. Except for the transit peptide and the N-terminus, the cabII-1 gene product is similar to cabII proteins in higher plants. The cabII-1 gene in C. reinhardtii appears to be an intermediate between type-I and type-II cabII genes described in higher plants.

Cauliflower mosaic virus gene VI produces a symptomatic phenotype in transgenic tobacco plants.

Gene VI of the cauliflower mosaic virus (CaMV) genome encodes a protein (P(66)) in virus-infected plants that accumulates in cytoplasmic inclusion bodies. When a segment of the CaMV genome bearing gene VI is transferred to tobacco plants by the Agrobacterium tumefaciens Ti plasmid, the resulting transgenic plants display viral-like symptoms. Symptoms produced by the DNA from two different viral isolates (CaMV Cabb B-JI and CM1841) were distinct-symptoms from the first were mosaic-like, whereas the other caused uniform bleaching of leaves. That gene VI was responsible for the symptomatic phenotype was demonstrated by showing that symptom production was blocked by deletions and by a frame-shifting linker mutation in gene VI. Furthermore, in primary transformants, there was a strict correlation between the appearance of symptoms and the presence of gene VI product, P(66), detected by immunoblots. Hence, a protein encoded by the CaMV genome produces viral-like symptoms in transgenic tobacco plants.

Functional regions of the cauliflower mosaic virus 35S RNA promoter determined by use of the firefly luciferase gene as a reporter of promoter activity.

The cauliflower mosaic virus (CaMV) 35S RNA promoter has been dissected and examined in a transient expression system using the firefly luciferase gene as a reporter of promoter activity. Deletion analysis has shown that the 35S RNA promoter is composed of at least three regions-distal, medial, and proximal-which are essential for activity. The distal region contains three smaller elements homologous to the simian virus 40 "core" enhancer element, the medial region possesses a CCAAT-like box, and the proximal region contains a TATA box. A DNA segment encompassing the distal region is capable of activating the CaMV 35S core promoter in an orientation-independent, but not position-independent, fashion. The distal region can also activate a heterologous weak promoter, the CaMV 19S RNA promoter, albeit not to the high levels of the 35S RNA promoter. Multimers of the distal region are able to activate the 35S RNA promoter core to even greater levels of expression than the native 35S promoter. These experiments demonstrate that elements outside the boundaries of the core promoter (composed of proximal and medial elements) are recognized in a plant cell transient expression system.

Simultaneous repositioning of the maxilla, mandible, and chin. Treatment planning and analysis of soft tissues.

There is a clinical, biologic, and biomechanical foundation for simultaneous surgical repositioning of the maxilla, mandible, and chin in a significant proportion of adult and adolescent patients. The restoration of normal jaw function, optimal facial esthetics, and long-term stability are the sine qua non of successful orthognathic surgical procedures to simultaneously reposition the jaws. The key to the achievement of these objectives is to carefully and systematically analyze facial esthetics, establish esthetic priorities, and then coordinate and implement them through the use of cephalometric planning and occlusal studies. By meticulous and precise surgical technique, properly programmed, coordinated, and sequenced with efficient presurgical and postsurgical edgewise orthodontic therapy, and systematic postsurgical neuromuscular rehabilitation, the maxilla, mandible, and chin can be simultaneously repositioned with relatively few postoperative complications or sequelae. This article purposes to elucidate on the indications for two-jaw surgery and describe a simplified clinical-cephalometric analysis for orthognathic surgery. Representative case reports are presented and discussed to illustrate the esthetic, orthodontic, and surgical treatment objectives. The basic problems involved in diagnosis and treatment planning of patients who require two-jaw surgery are discussed as well.

Tomographic assessment of nasal septal changes following surgical-orthodontic rapid maxillary expansion.

Nine adult patients with transverse maxillary deficiency were examined for incidence of nasal septal deviation following surgical-orthodontic rapid maxillary expansion. The osteotomies for facilitation of maxillary expansion did not include sectioning of the nasal septum. The procedure did include sectioning of the lateral maxillary walls, the pterygomaxillary suture, and the midpalatal sutures. For each patient, four graduated coronal tomograms through the incisal, molar, tuberosity, and pterygoid areas were taken prior to and not less than 4 months after surgical intervention. Results showed no significant change in the nasal septal position from before to after surgery. Analysis of the nature of maxillary movement in the coronal plane revealed rotational as opposed to bodily expansion, with inferior rotation of the palatal vault. Significant increases in the available nasal airway space were recorded. These increases were attributed primarily to shrinkage of inflamed nasal mucosa. In view of the recorded data, surgical sectioning of the nasal septum to prevent septal deviation by surgical-orthodontic rapid maxillary expansion is not warranted.

Healing of the bone incision following Le Fort I osteotomy.

A histologic evaluation of punch biopsies from the osteotomy sites of five patients who had undergone a Le Fort I procedure was performed. Results of the evaluation indicated that the area between the segments healed with mature compact bone.

Treatment of Class II deep bite by orthodontic and surgical means.

Conventional orthodontic correction of the Class II deep-bite deformity with a decreased lower anterior facial height tendency can be mechanically difficult, inefficient and, in many instances, impossible. Orthodontic treatment alone of either adults or adolescents with such deformities frequently can neither increase lower anterior facial height sufficiently to achieve ideal facial proportions nor achieve long-term occlusal stability. Despite the need for surgical intervention to achieve satisfactory occlusal and esthetic results, many patients with such deformities are still being treated in clinical practice by traditional orthodontic procedures, with less than ideal esthetic and/or occlusal results. The challenge to achieve efficient and stable treatment of this deformity has been met by the use of various surgical techniques in combination with orthodontic treatment. This combined surgical-orthodontic approach can provide increased treatment efficiency, long-term stability, and optimal esthetic results. The proper sequencing and correct selection of orthodontic mechanotherapy are essential to ensure the desired results. This article purposes to detail basic problems involved in diagnosis and treatment planning for the combined surgical-orthodontic approach to patients exhibiting Class II deep bite and decreased lower facial height. Orthodontic and surgical treatment objectives are explained, and representative case reports are presented and discussed to illustrate this method of treatment. Extraction patterns, control of the transverse dimension, arch wire selection, auxiliary wires, elastics, and extraoral appliance use are described. Surgically, the dentofacial disharmony associated with this deformity may defy treatment by surgical advancement of the mandible only. Genioplasty, Le Fort I osteotomy, symphyseal osteotomy, anterior or total mandibular subapical osteotomy, body osteotomy, submental lipectomy, and rhinoplasty are adjunctive procedures that are described and may be used in concert with mandibular advancement surgery.

Principles of orthodontic mechanics in orthognathic surgery cases.

In orthognathic surgery cases the treatment objectives, extraction patterns, and types of mechanics used are frequently the reverse of those used in conventional orthodontics. Thus, starting cases orthodontically and then, if unsuccessful, referring them for surgery often produces compromised results. Presurgical intra-arch objectives include positioning of the incisors in "ideal" positions, establishment of correct torque, and elimination of tooth-size discrepancies so as to permit the establishment of Class I canine and molar relationships after surgery. Presurgical objectives in the sagittal plane focus on removal of dental compensations. This may require the use of Class III elastics in Class II cases (and vice versa), thus allowing for maximal surgical correction of the underlying skeletal deformity. In the transverse plane, differentiation of skeletal from dental problems as well as identification of relative and absolute discrepancies should be carried out presurgically. Lateral corticotomies or segmental maxillary procedures should be used, depending on individual circumstances. Presurgical objectives in the vertical plane include maximizing the amount of presurgical orthodontic treatment carried out in open bites and minimizing the presurgical mechanics in deep bites. Encouragement of opening mandibular rotation at surgery while avoiding an increase in posterior face height contributes to stability. Orthodontic mechanics should not always include presurgical leveling of the curve of Spee and should actively avoid movements that may cause relapse tendencies. Careful attention to the use of surgical arch wires and splints during surgery and fixation, along with controlled elastic therapy and exercise programs after fixation, can greatly facilitate treatment.

Combined surgical and orthodontic treatment of bimaxillary protrusion.

Bimaxillary protrusion can be treated effectively in growing patients and in adults with conventional orthodontic therapy. In the adult patient, however, combined surgical and orthodontic treatment modalities may offer distinct advantages over such conventional therapy. Treatment time and possible adverse effects of lengthy and extensive orthodontic therapy may be reduced and optimum esthetic improvement may be facilitated. Those cases that exhibit severe skeletal discrepancies in the vertical, transverse, or sagittal dimensions in addition to dentoalveolar protrusion may be best treated in this manner to simultaneously correct all existing problems and obtain optimal esthetic and functional results. This article delineates the rationale for such therapy and tridimensional diagnostic and treatment-planning considerations from both the orthodontic and surgical standpoints. Case reports illustrate clinically the results obtainable with such treatment.

Tridimensional planning for surgical/orthodontic treatment of mandibular excess.

The dentofacial deformity of mandibular excess is frequently complicated by significant discrepancies in the anteroposterior position of the maxilla and mandible. Disproportionality of facial height as a result of increased or decreased vertical growth of the jaws, labiomental contour, transverse arch relationships, and/or asymmetries also complicate this deformity. Planning treatment for mandibular prognathism must entail diagnostic consideration of all three dimensions of space if maximum results are to be obtained with contemporary surgical techniques. In this article some of these diagnostic considerations, pre- and postsurgical orthodontic objectives, surgical techniques, orthodontic sequencing, timing of treatment, and clinical results are delineated to acquaint the orthodontist with contemporary treatment planning for this deformity in order to obtain optimum function, esthetics, and relative stability. Tridimensional facial proportionality, occlusal balance, and good dental and skeletal stability were achieved in five patients (average age, 17.5 years) with relative or absolute mandibular prognathism. These patients, who were observed for an average postoperative follow-up period of 24 months, were treated by multiple maxillomandibular surgical procedures in concert with orthodontic treatment.

Soft-tissue changes associated with surgical total maxillary intrusion.

A retrospective investigation was undertaken to evaluate the soft-tissue profile response to total surgical maxillary intrusion performed to reduce vertical maxillary excess. Lateral head films of ten adult patients taken preoperatively and at least 6 months postoperatively were compared to evaluate soft- and hard-tissue change. Statistical analysis of soft-tissue behavior of the nose, upper lip, lower lip, and chin, using simple and multiple correlations and regression functions, was performed. Prediction data for soft-tissue response to hard-tissue movement were developed using simple and multiple regression equations. The results of the study indicated that soft-tissue profile changes associated with total surgical maxillary intrusion are predictable. The change in the soft tissue in relation to total surgical maxillary intrusion was summarized and prediction tables based on the most significant simple and multiple regression equations were presented for clinical trial.

Assessment of the anteroposterior soft-tissue contour of the lower facial third in the ideal young adult.

An evaluation of the normal anteroposterior positions of five soft-tissue points inferior to the nose was undertaken for a selected sample of twenty-five male and twenty-five female young adults exhibiting pleasing (good) facial profiles and normal sagittal and vertical skeletal relationships. The subjects were selected from dental, dental hygiene, and graduate students at Baylor College of Dentistry by three members of the graduate orthodontic faculty and two members of the oral surgery faculty of the dental college. Cephalograms were taken with the subjects in natural head position, thus establishing a true extracranial horizontal reference plane. A true vertical reference plane was constructed perpendicular to the true horizontal, through subnasal. The five soft-tissue points were measured linearly relative to this subnasal vertical plane. Means, standard deviations, and standard errors were calculated for the five points. In addition, the same soft-tissue points were analyzed relative to the Frankfort horizontal and to a nasion vertical perpendicular to the true horizontal and the Frankfort horizontal. The use of the subnasal vertical perpendicular to the true horizontal was shown to have the smallest standard deviation of the four methods.