Repair Sequences Research Articles

Cellular sequence of tracheal repair in sheep after smoke inhalation injury.

The cellular repair process of injured tracheal epithelium is described for sheep after exposure to toxic smoke containing high concentrations of acrolein. Fourteen fasted 3-4-year-old ewes had a portion of their cervical trachea exposed to cotton smoke for 20 min and then were sacrificed at various time intervals ranging from 1 to 22 days after exposure. Within 1 day of injury, columnar epithelium sloughed intact from the trachea with a concomitant reduction of nearly 35% in the basal cell population. At 2 days of recovery, the cellularity of the epithelium had increased and mitotic figures were observed in some tracheal epithelial and gland cells. By 8 days, undifferentiated hyperplastic cells increased to 30/100 microns, differentiated nonciliated columnar cells first appeared, and the basal cell population returned to a normal count of 13 cells/100 microns. Thirteen days after exposure, the undifferentiated hyperplastic cell population had declined to 7 cells/100 microns, nonciliated columnar cells were at control values, and some ciliated cells were identified. At 18 and 22 days, epithelium was normal in appearance and the count was 13 cells/100 microns. Data suggest that because the columnar epithelium sloughs intact with the cilia remaining active, toxic smoke may affect their attachment to the basal lamina. Furthermore, the regeneration process involves differentiation of hyperplastic cells in which they elongate down to the basal lamina, thus re-establishing the integrity of tall epithelium in the sheep trachea.

A phonetic description of some repair sequences in Akan conversation

Natural human conversations are hardly 'error-fuee', due to the properties of interaction. Repair is therefore a concomitant part of any natural conversation. Phonetic (and sometimes Morpho-syntactic) cues are deployed to signal repair in conversation. Evidence is provided from natural interactions to show that such phonetic cues as pauses; prolongation of phonic or syllabic elements; loudness and pitch may be deployed singly or conjointly to signal repair. The paper also demonstrates that a detailed knowledge about repair provides a considerable insight into turn-regulation.

The organization of repair in classroom talk

ABSTRACTThis article is a conversation-analytic investigation of the forms of organization that allow specific items of classroom discourse – words, phrases, up to whole turns at talk – to be altered by subsequent items. Central to the article is an analytic distinction between self-correction and other-correction, that is, between repair sequences in which the speaker of the initial item (the “trouble source”) makes the correction and instances in which this is performed by one of her or his interlocutors (cf. Jefferson 1974; Schegloff et al. 1977). The classroom case is analytically interesting both for its own sake and also on account of research speculations that other-correction should be more frequent in adult-child talk than in other genres of conversation. However, in order to provide an analysis of the problem sensitive to the particularities of the classroom, it is necessary to look not merely at corrections, but at the larger repair trajectories in which they occur. These trajectories consist of corrections plus their prior initiations, the latter being means by which speakers mark out some item as requiring correction. Once the social identities of teacher and student are mapped against self-and other-forms of initiation and correction, it is possible to discern some of the structural preferences of classroom discourse along the general axis of repair. The materials are taken from geography lessons in Australian high school classrooms. (Repair and correction, question and answer, clue-giving, expansion sequences, modulation, classroom discourse, everyday language use, Australian English, conversation analysis, sociology of education)

Electrophysiology of direct current stimulation of fracture healing in canine radius

Electrophysiological mechanisms involved in the electrical stimulation of fracture healing remain largely unknown. The purpose of the present study was to establish relationships between osteogenetic response and intraosseous measures of electrical dose in experimental fractures (osteotomies) of canine radii stimulated by direct currents. The response was determined postmortem at seven weeks after osteotomy by measuring the bending rigidity and four physicochemical properties: tissue density, mineral density, matrix density, and mineral-to-matrix ratio. The currents measured in bone ranged from 0.1 to 17 microA. Three regions of enhanced osteogenetic response were observed at approximately 1, 7, and 13 microA, separated by regions of unstimulated response. Evidence presented in this paper suggests that enhanced response resulted mainly from electrical modulation of early events in the fracture repair sequence.

Repair in Second-Language Instruction

The present paper deals with the study of repair patterns. Repair, seen as some type of intrinsic trouble manifested by some party during interaction, has here been studied in an institutional setting, the second-language class-room. The repair sequences have been studied relative to the activity type in which the participants are involved. The results show the following: first, that the activity type has an impact on the repair pattern; and secondly, both quantitative and qualitative differences in repair patterns are found when compared with non-educational and foreign-language-teaching settings.

Combined injuries of the cranium and face

The neurosurgeon and plastic surgeon are increasingly called upon to manage the care of patients with combined injuries of the cranium and face. The authors briefly review the pathogenesis and classification of craniofacial fractures and outline historical approaches to them. Current principles of management are then discussed. Experience with 167 patients is presented with emphasis on surgical technique, the sequence of repair and early primary reconstruction. The controversial issue of fontal sinus fracture repair is addressed. The authors favour preservation of the frontal sinus cavity, where possible, and do not obliterate the nasofrontal duct. With injuries to the floor of the sinus, the base of the sinus and frontonasal duct are sealed with bone graft and a vascularised soft tissue flap and the sinus is cranialised. Immediate bone grafts, using split skull or rib, are used to reconstruct areas of bony destruction or loss. Ninety-eight patients required 402 grafts. Immediate bone grafting resulted in few complications and low incidence of secondary deformities needing correction.

Combined arterial and venous intraluminal shunting in major trauma of the lower limb

A road accident victim was admitted in shock with an injured lower limb virtually dismembered at mid-thigh level. The early use of intraluminal shunts bridging both femoral artery and vein permitted an unhurried but logical sequence of wound debridement, bone stabilisation and optimal vascular repair rendering fasciotomy unnecessary. This approach led to an uncomplicated survival of the limb with eventual return of function.

A sequence of diagnosis and repair for a 2-state repairable system : Qin Zhang. IEEE Trans. Reliab.R-36, 32 (1987)

A sequence of diagnosis and repair for a 2-state repairable system : Qin Zhang. IEEE Trans. Reliab.R-36, 32 (1987)

Task planning for robotic manipulation in space applications

Space-based robotic systems will require novel technologies of planning and manipulation to accomplish complex tasks such as diagnosis, repair, and assembly task representation, discrete task planning, and control synthesis which provide a design environment for assembly systems, and which extend to planning of manipulation operations in unstructured environments. In this approach, assembly planning is carried out using the AND/OR graph representation which encompasses all possible partial orders of operations and may be used to plan assembly sequences. A novel algorithm for planning disassembly and repair using the AND/OR graph is introduced, and examples of repair sequences generated for a satellite electrical module are described. For discrete task planning, the configuration map facilitates search over discrete parameters in the space of bounded configuration sets. >

A Sequence of Diagnosis and Repair for a 2-State Repairable System

This paper presents a desireable sequence of diagnosis and repair for a failed 2-state repairable system regardless of s-coherence, and the calculation method of this sequence. Compared with my earlier sequence, this sequence considers the information known from the diagnosis and repair. An example illustrates the method.

Responses to requests for clarification in linguistically normal and language-impaired children.

This study compared the conversational repair strategies employed by language-impaired and normal children in response to a stacked series of requests for clarification. Ten linguistically normal and 10 language-impaired children were sampled from each of the following age levels, 4:10-5:10, 6:10-7:10, and 8:10-9:10, resulting in a total of 60 subjects. Each subject was asked to describe a series of action pictures for an examiner who was seated behind a screen. At regular intervals, the examiner responded to the child's description by initiating a repair sequence. Each sequence consisted of three different neutral requests for clarification ("Huh?", "What?", and "I didn't understand that.") and the subject's response to each request. Although all subjects appeared to recognize the obligatory nature of the neutral clarification requests employed, differences were observed in the repair strategies used by normal and language-impaired children. In addition, impaired and younger normal subjects had greater difficulty responding appropriately as the stacked sequence progressed.

Development of conversational repair strategies in response to requests for clarification.

Conversational repair sequences are an important aspect of communicative interaction. These sequences may occur in the event of communication failure if a listener requests clarification of a previous aspect of the speaker's message. The purpose of this study was to investigate the repair strategies employed in conversation by children at four age levels. Ten linguistically normal children were sampled from each of the following age levels: 2:7 to 3:10, 4:10 to 5:10, 6:10 to 7:10, and 8:10 to 9:10 (years:months), resulting in a total of 40 subjects. Each subject was asked to describe a series of action pictures for an examiner who was seated behind a screen. At regular intervals, the examiner responded to the child's description by initiating a stacked repair sequence. Results indicated that subjects at all age levels complied with the initial request for clarification the majority of the time. However, with increasing age, subjects became more adept at handling the stacked sequence of requests for clarification. Older children were more responsive to the requests, and 9-year-old subjects demonstrated a wider range of strategies in providing repairs.

Factors Affecting Strength of Epoxy‐Repaired Timber

An investigation into the factors affecting the strength of epoxyrepaired timber structures has been conducted. Two aspects are evaluated: repair methodology, and effects of member configuration. The structural repair sequence of timber consists of four basic steps: (1) Special member preparation; (2) joint sealing; (3) epoxy injection; and (4) finishing. Each of these steps is described in detail with recommended procedures to aid the engineer in both the design and inspection of epoxy repair. To evaluate the various joint configuration parameters affecting the behavior of epoxy‐repaired timber, over 200 full size repaired members and over 100 shear blocks of Southern pine were tested. The parameters studied include effects of: mechanical connectors; length of overlap; member thickness; grain orientation; timber age; and glue line thickness. It was found that the shear bond strength is on the order of the shear strength of the wood. It was also determined that the primary factors affecting strength are the ratio of lap length to member thickness and grain orientation.

Application of probabilistic analysis to assess the relative severity of crack-like weld defects

Abstract This paper describes how probabilistic fracture mechanics calculations have been used to assess the notional probability of fracture of a number of crack-like weld defects in an offshore structure. The results were used in a decision making context to establish a rational repair sequence, so that the defects could be repaired on an order-of-merit basis. This was necessary in order to minimize risks because of the possibility of the repair programme being curtailed, for instance, by bad weather. The analysis procedure, which is based on the probabilistic treatment of a standard deterministic fracture model, could be applied in any similar situation where appropriate information is available. An important new aspect is the way in which fracture probabilities are assessed for defects which are large compared with the size of fracture toughness test specimens.

Tissue repair in the embryonic rat spinal cord following exposure to N-ethyl-N-nitrosourea

The cytotoxic effects of N-ethyl-N-nitrosourea (ENU) and the potential for recovery from this damage in the developing rat spinal cord was investigated. Emphasis was placed on determining the severity and location of initial cell necrosis and the subsequent reorganizational changes in the damaged tissues. Pregnant rats were injected i.v. with a single dose of ENU (60 mg/kg) on one of days 12–16 of gestation. At 6, 12, 24 and 48 h post-injection one pregnant rat from each gestational stage was anesthetized, the embryos were removed, fixed and processed for embedding in paraplast or epon-araldite. Transverse sections from embryos killed at 6 h revealed extensive necrosis throughout the neuroepithelium in accordance with the temporal-spatial patterns of neurogenesis. At this dose level the post-mitotic neuroblasts appeared unaffected. Regeneration of the damaged neural tissue as defined by the restoration of the neuroepithelial cell layer and removal of necrotic debris proceeded quickly, and within 48 h a near-normal cytoarchitecture was observed. The embryonic age at time of ENU injection had no apparent influence on the actual sequence of tissue repair in the spinal cords although the events were slightly delayed within embryos exposed to ENU on days 12 or 13 of gestation.

Repair or regeneration following periodontal therapy?

Abstract A reading of recent literature leads this reviewer to the conclusion that healing processes of treated periodontal lesions express variations of repair rather than regeneration. Specifically, the treated periodontal lesion repairs by 1) epithelial adhesion; at times occlusal to the base of the original pocket; 2) collagen adhesion; most frequently observed immediately apical to the newly adhering junctional epithelium but occlusal to the marginal alveolar crest, and 3) in the infrabony portion of periodontal lesions, simultaneous and/or sequential deposition of repair cementum, functionally oriented ligament fibers and narrowing of the vertical defect by osteogenesis. The supracrestal portion of such a periodontal lesion repairs as described above with new epithelial and collagen adhesions closing the gingival unit to the oral environment. The establishment of the supracrestal (trans‐septal) fiber attachment may be the result of the remodelling of the vertical defect where repair cementum forms along the tooth wall of the vertical defect and acts as an anchor for fiber insertion. With the resorption of the crestal margin, repair cementum and inserted fibers are present on the root surface occlusal to the alveolar crest and may well serve as the new anchoring site for supracrestal fibers. Another possibility is the occlusal spill of connective tissue primarily from the periodontal ligament which includes supracrestal cementogenesis, thereby creating an environment for the insertion of new supracrestal fibers as part of flap healing. While the exact sequence of supracrestal fiber formation after treatment of vertical defects is not known, it should be emphasized that all specimens studied have shown their presence as part of a successful “fill”. Obviously, these repair sequences do not occur after every therapeutic intervention. However, sufficient documentation is available to acknowledge their possibility following various treatment modalities.The description of the reviewed repair processes takes us a long step forward from the rather limited repair projected by Orban in 1948. Yet, it does not provide us with information regarding the viability of these repair tissues when confronted with continuing assault by plaque or other irritants. Do such tissues resist local injury as well as the normal attachment? Is the loss of adhesion following insult accomplished more quickly because the length of adhering tissues is significantly increased in an occlusoapical direction? Do host factors affect the repair tissues differently than normal tissues? The answers to these questions need extensive exploration regarding the nature of the repair tissues. But the recognition of the process has profoundly influenced clinical therapy and raised new questions regarding the factors controlling repair and possibly even regeneration following periodontal therapy.

Bile duct and liver pathology in biliary atresia.

AbstractProgression to cirrhosis despite restoration of bile flow by successful portoenterostomy suggests that factors other than obstruction alone are operative in biliary atresia. This paper describes pathologic changes at all levels of the hepatobiliary secretory apparatus from hepatocyte to common duct, exhibited in liver biopsies, resected portions of liver adjacent to the porta hepatis, and extrahepatic duct remnants from 17 patients operated upon for relief of biliary atresia. In both intra‐ and extrahepatic bile ducts, there were epithelial changes interpreted as occurring in a sequence of vacuolar degeneration, necrosis, inflammatory infiltration, and proliferative epithelial repair that precede obliterative fibrosis. From their distribution, it is inferred that these cytopathologic changes may not be simply due to distal obstruction. These ductal epithelial changes are similar to those that occur in livers of some patients with severe viral hepatitis. The association of these changes with giant cell transformation in all cases suggests that they reflect a common etiology for ductal and hepatocellular damage in the neonatal hepatitis‐biliary atresia spectrum. The persistence of these changes in liver biopsies following portoenterostomy suggests that they may be of pathogenetic significance in the progressive liver disease seen in most patients with biliary atresia.

Selective acute arterial endothelial injury and repair. I. Methodology and surface characteristics.

Abstract This study describes surface changes occurring during rapid repair of the luminal lining of the rabbit aorta in which endothelial confluence was reestablished in less than 96 h after selective mechanical injury. An experimental method was developed to induce 1–4 longitudinal injury tracts simultaneously or at predetermined time intervals. The procedure allows evaluation of the entire sequence of arterial endothelial repair and direct comparison with normal tissue in the same vascular segment. This first report describes sequential stages of the reparative process from zero time to 8 days after induction of a single tract. Morphological and functional characteristics of the aortic luminal surface were evaluated by cytochemical and ultrastructural techniques, and results were compared with those previously obtained using less selective experimental methods to induce arterial surface. Aortic endothelial repair progressed in stages, beginning with small numbers of platelet aggregates, single platelets, and leukocytes adhering to the deendothelialized surface. This was followed by the scattered appearance of randomly oriented, large, “plump” endothelial cells extending from the edges of the injury tract into the deendothelialized zone. Confluence of these cells was completed 72–96 h after injury. Silver nitrate staining of subendothelial structures and Evans blue uptake persisted for short periods in reendothelialized areas. In contrast to previous experimental studies, utilizing ballooning or other mechanical methods to induce arterial injury, complete endothelial repair was observed routinely in less than 1 week without residual ultrastructural changes of the vascular wall.

SURGICAL TREATMENT OF HEMIFACIAL MICROSOMIA (First and Second Branchial Arch Syndrome)

A review of 17 patients operated upon for unilateral hemifacial microsomia, and followed for up to 18 years, clarifies several principles of management. The management is facilitated by dysplasia predominance grouping, with the major functional deformity dictating the sequence of repair. Our surgical goals are: (1) provision of adequate upper airway; (2) preservation of normal teeth and adequate alveolar bone to achieve proper dental occlusion; (3) restoration of binaural hearing; (4) external ear construction; (5) acceptable facial symmetry; (6) balanced facial animation; and (7) a child with an acceptable self-image.

Endonuclease V of Escherichia coli.

A small endodeoxyribonuclease )2.3 S) that is active on single-stranded DNA has been extensively purified from Escherichia coli so as to be free of other known DNases. It has an alkaline pH optimum (9.5), requires Mg2+, and makes 3'-hydroxy and 5'-phosphate termini. The nuclease nicks duplex DNA, particularly if treated with OsO4, irradiated with ultraviolet light, or exposed to pH 5. The uracil-containing duplex DNA from the Bacillus subtilis phage PBS-2 is an especially good substrate; it is made acid-soluble by levels of the enzyme which fail to produce any acid-soluble material in other single-stranded or duplex DNAs. Neither RNA nor RNA-DNA hybrid are degraded by the enzyme. The enzyme specificity suggests that it might act at abnormal regions in DNA, so that its in vivo function could be to initiate an excision repair sequence. Its high activity on uracil-containing DNA could imply that the enzyme provides an alternative mechanism for excising uracil residues from DNA to the pathway utilizing uracil-DNA N-glycosidase. We suggest that this enzyme be designated as endonuclease V of E. coli.