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Biomedical subjects

J F Connolly

Publications and source records attributed to J F Connolly.

At least 19 recordsLinked to original sources
PubMed1992

Event-related potential sensitivity to acoustic and semantic properties of terminal words in sentences.

This experiment was concerned with the effects of phonologically correct masking on the electrophysiological responses to terminal words of spoken sentences differing in contextual constraint. Two event-related potential (ERP) components, the N400 and N200, were recorded to the terminal words of high and low constraint sentences in four conditions. In the Control condition, subjects (Ss) simply attended to the sentences with no explicit task instructions. In the Semantic condition, Ss were required to listen to the stimuli in order to make semantic judgements about the terminal word of each sentence. The Control+Masking condition was identical to the Control condition except for the simultaneous presentation of a masking stimulus. The Semantic+Masking condition had Ss listening to sentences in the presence of masking with the task of making semantic judgements about the terminal word of each sentence. ERPs were recorded from Fz, Cz, Pz, T3, and T4 in 10 subjects. Amplitudes of both the N200 and the N400 were sensitive to contextual constraint with larger responses elicited by the terminal words of low constraint sentences. In addition to demonstrating the co-occurrence of the N200 and N400, this experiment highlighted a functional separation between the two components. Masking had no statistically significant effect on N200 latency but N400 latency was delayed in the masked conditions relative to those in the unmasked conditions. It is proposed that the N200 and N400 are manifestations of two different processes; the N200 reflects the acoustic/phonological processing of the terminal word while the N400 reflects the cognitive/linguistic processing. The relationship between the N200 recorded in this experiment and the discrimination N200 is discussed.

Adolescent↗
PubMed1991

Healing of a large nonossifying fibroma after grafting with bone matrix and marrow. A case report.

Healing of a large tibial nonossifying fibroma in a 12-year-old girl occurred following excision, curettage, and filling of the bony defect with human demineralized bone matrix powder mixed with a small quantity of the patient's bone marrow. The use of this graft composite was successful in the treatment of the lesion and reduced the potential risk and morbidity associated with pediatric orthopedic surgical procedures with autogeneic iliac crest and other bone grafts.

Bone Marrow Transplantation↗
PubMed1991

Autologous marrow injection as a substitute for operative grafting of tibial nonunions.

Autologous marrow injection was used to stimulate healing in 20 ununited tibial fractures over a five-year period. The technique was employed in conjunction with cast immobilization in ten cases and intramedullary nail fixation in ten cases. Marrow stimulated a callus formation sufficient to unite eight of the ten nonunions immobilized with casts and all ten of the fractures immobilized by intramedullary nails. Bone-marrow injection was as effective as past open autologous grafting but with considerably fewer disadvantages. The technique provides a promptly renewable and reliable source of osteogenic stem cells with numerous advantages compared with standard open-grafting techniques.

Adolescent↗
PubMed1991

Treatment of nonunion by percutaneous injection of bone marrow and demineralized bone matrix. An experimental study in dogs.

Successful treatment of nonunited fractures remains a major clinical challenge. Because bone marrow and demineralized bone matrix (DBM) are capable of stimulating osteogenesis, experiments were designed to test the effectiveness of bone marrow or DBM or both when injected percutaneously into a canine nonunion model. Six-millimeter segmental defects were created in the midtibial diaphysis of 24 adult mongrel dogs and held distracted by external fixation. For comparative purposes, a 0.5-mm osteotomy was created in five dogs. Five weeks later, the 6-mm defects were injected with either saline, autogeneic marrow, DBM powder, a composite of bone marrow and DBM, or treated by open grafting techniques with autogenic cancellous bone. Healing of the defect was evaluated roentgenographically, biomechanically (three-point bending), histologically, and biochemically 13 weeks postsurgery. Marrow and DBM stimulated defect healing. However, the combination of bone marrow with DBM produced a synergistic response in the defect, which was greater than the sum of either marrow or DBM alone. Healing in the composite-grafted dogs was comparable to those treated by standard cancellous bone grafting. These data suggest that percutaneous injection of bone marrow and DBM may be a potential alternative that offers numerous advantages over standard open grafting techniques in the treatment of fractures with nonunited defects.

Animals↗
PubMed1990

Pulsing direct current-induced repair of articular cartilage in rabbit osteochondral defects.

Osteochondral defects in the distal femoral condyles of rabbits exposed to a pulsing direct current exhibits an enhanced quality of repair. The signal, with a peak value of 2 microA repeating at 100 Hz, imposed an electric field in the tissue of 20-60 mV/cm2. Maximum efficacy was seen with a shorter period of exposure (40 vs. 160 h) initiated 48 h after surgery for 4 h/day. Repair tissue originated primarily from metaplasia of subchondral elements although hyperplasia of pre-existing chondrocytes at the margins of the defect could be detected. Defects in treated joints contained Safranin O staining material that was histologically similar to a disorganized hyaline cartilage. Central areas of the defects in control animals contained Safranin O-negative material that generally extruded over the surface as a pannus. The edges of nontreated defects also had characteristics of cartilaginous healing, stressing the importance of using serial sectioning techniques in this model of cartilage repair.

Animals↗
PubMed1990

Mineral and matrix contributions to rigidity in fracture healing.

The purpose of this study was to investigate the relationships among selected properties of fracture callus: bending rigidity, tissue density, mineral density, matrix density and mineral-to-matrix ratio. The experimental model was an osteotomized canine radius in which the development of the fracture callus was modified by electrical stimulation with various levels of direct current. This resulted in a range of values for the selected properties of the callus, determined post mortem at 7 weeks after osteotomy. We found that the rigidity (R) of the bone-callus combination obeyed relationships of the form R = axb, where x is the tissue density, mineral density, matrix density or the mineral-to-matrix ratio of the repair tissue. These are analogous to power-law relationships found in studies of compact and cancellous bone. The results suggest that fracture callus at 7 weeks after osteotomy in canine radius behaves more like immature compact bone than cancellous bone in its mechanical and physicochemical properties. The present study demonstrates the feasibility of developing non-invasive in vivo densitometric methods to monitor fracture healing, since models may be developed that can predict mechanical properties from densitometric data. Further studies are needed to develop a refined model based on experimental data on the mechanical and physicochemical properties and microstructure of fracture callus at different stages of healing.

Animals↗
PubMed1990

The effects of processing requirements on neurophysiological responses to spoken sentences.

Ten English speaking subjects listened to sentences that varied in sentential constraint (i.e., the degree to which the context of a sentence predicts the final word of that sentence) and event-related potentials (ERPs) were recorded during the presentation of the final word of each sentence. In the Control condition subjects merely listened to the sentences. In the Orthographic processing condition subjects merely listened to the sentences. In the Orthographic processing condition subjects decided, following each sentence, whether a given letter had been present in the final word of the preceding sentence. In the Phonological processing condition the subjects judged whether a given speech sound was contained in the terminal word. In the Semantic processing condition subjects determined whether the final word was a member of a given semantic category. A previous finding in the visual modality that the N400 component was larger in amplitude for low constraint sentence terminations than for high was extended to the auditory modality. It was also found that the amplitude of a N200-like response was similarly responsive to contextual constraint. The hypothesis that N400 amplitude would vary significantly with the depth of processing of the terminal word was not supported by the data. The "N200" recorded in this language processing context showed the classic frontocentral distribution of the N200. The N400 to spoken sentences had a central/centroparietal distribution similar to the N400 in visual modality experiments. It is suggested that the N400 obtained in these sentence contexts reflects an automatic semantic processing of words that occurs even when semantic analysis is not required to complete a given task. The cooccurrence and topographical dissimilarity of the "N200" and N400 suggest that the N400 may not be a delayed or a generic N200.

Adolescent↗
PubMed1990

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.

Animals↗
PubMed1990

Quantitative roentgenographic densitometry for assessing fracture healing.

A noninvasive method was developed to assess fracture healing using optical densitometric methodology. Photometric measurements of osseous tissue density were based on illuminance or intensity of light, transmitted through standard roentgenograms. The method was tested in 6-mm tibial segmental defects and single-cut osteotomy defects in adult mongrel dogs. The lowest measureable bone density in the defect was compared to bending rigidity of the involved extremity. For both types of defect, an exponential relationship was found between the densitometric evaluation of the healing fracture gap and bending rigidity. This method proved superior to a roentgenographic scoring method and is capable of detecting small differences in mineral content using standard roentgenograms. The high correlation between densitometric evaluation and bone rigidity indicates this method has potential for use in the in vivo assessment of fracture healing.

Absorptiometry, Photon↗
PubMed1989

Effect of aging on tensile mechanical properties of the rabbit distal femoral growth plate.

Tensile tests to failure were performed on the distal femoral growth plate of rabbits. The measured tensile forces, together with animal weight and dimensional measurements of the femur, were used to develop a noninvasive method of predicting growth failure loads and to examine the effects of age on the tensile strength of the growth plate. Growth plate failure load correlated with rabbit weight, (r = 0.93), femoral length, (r = 0.91), and contoured growth plate surface area, (r = 0.74). Regression analysis for these relationships allowed for failure load prediction if animal weight, femoral length, or growth plate surface area was known. Nominal stress (failure load/surface area) was calculated and correlated with animal weight (age) for each distal femoral growth plate utilizing two surface area estimating techniques: growth plate surface contour and growth plate cross-sectional enlargement. A strong association was found with either technique. The growth and maturation of growth plate cartilage is of major importance in pediatric orthopaedics. This study demonstrate that the age-dependent increases in tensile mechanical properties of the growth plate do not result merely from growth plate enlrgement or conformational changes. The changing tensile mechanical properties of the growth plate may explain why transphyseal distraction used clinically has produced varied and somewhat unpredictable results. Our study suggests that dose-response investigations are needed to define safe and optimal transphyseal distraction tensions before further clinical application is pursued.

Aging↗
PubMed1989

Stereological study of the developing distal femoral growth plate.

The distal femoral growth plate has a uniquely convoluted structure comprised of four mammillate processes. Factors contributing to the development of these processes and overall plate geometry were explored using three-dimensional image analysis of the canine distal femoral epiphysis. The growth plate at birth remains relatively flat until ossification of the epiphysis begins at 1 week of age. Epiphyseal ossification proceeds eccentrically, projecting in the medial-lateral and anterior-posterior directions. Growth plate activity indexed by [3H]thymidine labeling and plate thickness revealed regional differences in cell proliferation. This was measured as a decreased labeling index and thinning of the growth plate in areas capped by the ossifying epiphysis. The eccentric ossification pattern and associated variations in growth plate activity result in definition of an "intraphyseal" groove and medial-lateral oriented sulcus. The groove and sulcus bisect the plate into four quadrants, giving rise to a convoluted structure composed of four areas of plate elevations termed mammillary processes (MP). By 5 weeks, the pattern of ossification results in greater development of the MP in the anterior-medial quadrant and in decreasing order, in the posterior-medial, anterior, and posterior-lateral quadrants. By 10 weeks, a uniform rate of cell proliferation was observed coincident with completion of ossification of the epiphysis. The data suggest that localized variations in growth plate proliferation are associated with ossification of the epiphysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1989

Autologous marrow injection for delayed unions of the tibia: a preliminary report.

Over a 3-year period, we have treated 10 delayed unions of the tibia by using percutaneous marrow injection rather than standard operative bone grafting. Nine of the 10 fractures responded by forming callus in the area where the marrow was injected. This relatively simple technique avoided potential problems associated with operative grafting methods that have been standard for at least 50 years. Most importantly, it encourages early treatment of fractures when healing problems are anticipated or are becoming evident.

Adult↗
PubMed1989

Nonunion of the clavicle and thoracic outlet syndrome.

Fifteen adult patients with clavicular nonunions were evaluated over a 10-year period. Fourteen of these patients were treated initially with a "figure-of-eight" clavicle strap. Seven presented with narrowing of the costoclavicular space, and symptoms of intermittent brachial plexus impingement or thoracic outlet syndrome. Two of these resulted from resection of the mid-portion of the clavicle with subsequent impingement from hypertrophy of the lateral stump. Most commonly, hypertrophic nonunion of the clavicle caused the thoracic outlet syndrome, frequently many months after the initial injury. This delayed onset led to diagnostic confusion with other causes of radiating upper extremity pain, including cervical disc disease. Treatment of the adult clavicle fracture is different from that of the child with potential for greater functional impairment. The "figure-of-eight" harness frequently does not provide pain relief or adequate reduction of the fracture. If an acutely displaced fracture in an adult cannot be reduced and held by closed casting technique, open reduction and internal fixation may occasionally be indicated. We have found transcortical fixation by locking Knowles pins to be effective for treating hypertrophic nonunions, as well as for unreducible acute fractures. Atrophic nonunions require plate fixation and autologous grafting. Nonunion of the clavicle has been among the most responsive of nonunions in our experience, since all fractures treated by adequate reduction and fixation healed promptly.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Human brainstem auditory evoked potentials fail to provide evidence of efferent modulation of auditory input during attentional tasks.

Efferent modulation of auditory input at the level of the brainstem during attention-demanding tasks has been described in animal studies. Attempts to demonstrate these effects in humans have produced conflicting results, however. These studies are reviewed with particular reference to those animal experiments that have demonstrated peripheral effects. The human experiments have used a number of attentional conditions which have not been related either to each other or to the successful animal work. Two of the most important conditions in these studies--the use of an intermodal attention task and the manipulation of attentional states--have been examined rarely or not at all in the human research. Two experiments were conducted to investigate the possibility of attention-related effects on the human brainstem auditory evoked potential. These experiments were designed to examine experimental conditions common to both successful and unsuccessful attempts to demonstrate attention-driven efferent modulation at the periphery in humans. Also examined was the gradation of attention effects on efferent modulation demonstrated in animals but never studied in humans. No significant changes in either the latency or the amplitude of the brainstem auditory evoked potential were found in any of the attention-demanding conditions. Results are discussed in terms of psychophysiological theories of attention. Also, the interpretation of the most recent animal work is questioned.

Adolescent↗
PubMed1989

Osteogenesis in cranial defects and diffusion chambers. Comparison in rabbits of bone matrix, marrow, and collagen implants.

In rabbits, we compared calcification and bone formation by bone marrow, acid-demineralized bone matrix and glutaraldehyde-cross-linked Type I collagen implanted in intramuscular diffusion chambers or in trephine skull defects. The rabbits were killed 4 weeks postimplantation and calcification and osteogenesis were evaluated radiographically and histologically, and by calcium and alkaline phosphatase assays. Bone marrow produced bone and fibrous tissue within the chambers and had high alkaline phosphatase levels. Bone matrix in chambers with intact filters failed to induce bone formation within and outside the chambers, while glutaraldehyde-cross-linked collagen produced only scant calcific deposits following implantation in either diffusion chambers or skull defects. Central areas of skull defects implanted with bone marrow were partially repaired with new bone and had high calcium and alkaline phosphatase levels, but not as high as defects implanted with demineralized bone matrix.

Animals↗