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Biomedical subjects

J W Grant

Publications and source records attributed to J W Grant.

At least 19 recordsLinked to original sources
PubMed2001

Spread of a recurrent lentigo maligna into a graft: a case for conservative treatment.

Lentigo maligna is an in situ malignant melanoma for which the treatment of choice is surgical excision. The recurrence rate in lentigo maligna is high and hence other treatments, such as cryotherapy, laser therapy, radiotherapy and Mohs' chemosurgery, have been described. Despite the high recurrence rate, spread of a lentigo maligna into a skin graft is rare. We describe a case of a recurrent lentigo maligna spreading into a skin graft, which, along with the cases described in the literature, highlights the presence of a group of low-grade malignant lentiginous lesions that may be managed by careful follow-up and observation.

Aged↗
PubMed2001

Influence of an interdental full pin on stability of an acrylic external fixator for rostral mandibular fractures in dogs.

OBJECTIVE: To determine total stiffness and gap stiffness of an external fixation system in a canine mandibular fracture gap model incorporating a full interdental pin as the only point of rostral fixation in a bilateral type-I external fixator. SAMPLE POPULATION: 10 canine mandibles. PROCEDURE: Bilateral mandibular ostectomies were performed between premolars 3 and 4. A type-I external fixator incorporating a full interdental pin was placed to stabilize a 0.5-cm fracture gap. Four pin configurations (intact mandibular bodies with fixator; ostectomized mandibular bodies and complete fixator; ostectomized mandibular bodies with caudal pins of rostral fragment cut; ostectomized mandibular bodies with all pins of rostral fragment cut) were tested in dorsoventral bending 5 times on each mandible. The full interdental pin remained intact in all configurations. Total stiffness and gap stiffness were determined for each configuration on a materials testing machine. RESULTS: Total stiffness of intact mandibles was significantly greater than that of ostectomized mandibles, regardless of external fixator configuration. However, total stiffness and gap stiffness were not significantly different among different external fixator configurations applied to ostectomized mandibles. CONCLUSION AND CLINICAL RELEVANCE: External fixator configurations with only the full interdental pin engaging the rostral fragment were as stiff as configurations that had 2 or 4 additional pins in the rostral fragment for the applied loads. External fixators for rostral mandibular fractures may be rigidly secured with rostral fragment implants applied extracortically, avoiding iatrogenic trauma to teeth and tooth roots.

Animals↗
PubMed2000

The use of ultrasound-guided cutting-needle biopsy in paediatric neck masses.

OBJECTIVE: Neck masses are common in children. Although there is a low incidence of therapeutically significant pathology, biopsy is occasionally required for evaluation. Open biopsy or fine needle aspiration may be used to obtain tissue. Open biopsy provides material suitable for histological analysis but requires general anaesthesia. Cytological material obtained by fine needle aspiration is often inconclusive. A core of histological material may also be obtained by percutaneous cutting-needle biopsy, a recognised procedure at other anatomical sites, usually performed under local anaesthesia. MATERIALS AND METHODS: There are few accounts using cutting needles in adult neck masses and no previous paediatric series. We present our experience of ultrasound-guided core biopsies of neck masses in 15 children ranging in age from three months to 16 years. RESULTS: Thirteen biopsies were easily performed without sedation as an outpatient procedure under topical and injected local anaesthetic. In all fifteen cases the procedure was well tolerated and a tissue successfully obtained. CONCLUSION: Ultrasound guided cutting needle biopsies of head and neck masses of children can be performed under local anaesthesia in the majority of cases.

Adolescent↗
PubMed2000

A finite element method for mechanical response of hair cell ciliary bundles.

This paper describes the development of a methodology for performing a mechanical analysis of hair cell ciliary bundles. The cilia were modeled as shear deformable beams, and interconnections were modeled as two-force members. These models were incorporated into software, which performs a finite element analysis of a user-defined bundle. The algorithm incorporates aspects of the bundle such as geometric realignment and buckling of compressed side links. A sample bundle is introduced and results of modeling it are presented.

Actins↗
PubMed2000

Management of neck lumps--a triage model.

We report our experience in the out-patient triage of 100 patients presenting with a lump in the neck. The out-patient visit consisted of a general history and examination, assessment of the upper air and food passages and, where indicated, ultrasound and core needle biopsy of the lump. Other investigations were performed as appropriate. One hundred neck lump patients were seen in a 9 month period. Ninety-six of these lumps were diagnosed on an out-patient basis, only four requiring admission for formal excision biopsy. Among the diagnoses were eleven lymphomas, nine parotid neoplasms, nine lymph node metastases, five thyroglossal cysts, and four branchial cysts. Almost half the patients seen had either a reactive lymphadenopathy, or no abnormality. The establishment of a tissue diagnosis on an out-patient basis allowed appropriate referrals to be made and management plans to be formulated. The theoretical risk of seeding of malignant cells in the needle tract is acknowledged and discussed.

Adolescent↗
PubMed1999

Extrinsic Fabry-Perot interferometer for measuring the stiffness of ciliary bundles on hair cells.

We have developed an extrinsic Fabry-Perot interferometer (EFPI) to measure displacements of microscopic, living organelles in the inner ear. The EFPI is an optical phase-shifted instrument that can be used to measure nanometer displacements. The instrument transmits a coherent light signal to the end of a single glass optical fiber where the measurement is made. As the coherent light reaches the end of the fiber, part of this incident signal is reflected off the internal face of the fiber end (reference reflection) and part is transmitted through the end of the fiber. This transmitted light travels a short distance and is reflected off the surface whose displacement is to be measured (the target). This sensing reflection then reenters the fiber where it interferes with the reference reflection. The resulting interference signal then travels up the same optical fiber to a detector, where it is converted into a voltage that can be read from an oscilloscope. When the target moves, the phase relation between reference and sensing reflections changes, and the detector receives a modulated signal proportional to the target movement. Reflections of as little as 1% at both the sensor tip and target surfaces produce good results with this system. We use the EFPI in conjunction with fine glass whiskers to measure the stiffness (force per unit deflection) of stereociliary bundles on hair cells of the inner ear. The forces generated are in the tenths of picoNewton range and the displacements are tens of nanometers. Here we describe the EFPI and its development as a method for measuring displacements of microscopic organelles in a fluid medium. We also report experiments to validate the accuracy of the EFPI output and preliminary measurements of ciliary bundle stiffness in the posterior semicircular canal.

Animals↗
PubMed1998

The histopathology of de Quervain's disease.

The histopathological appearances of the tendon sheath and synovium from 23 patients treated surgically for de Quervain's disease are described and compared with 24 controls. The condition was not characterized by inflammation, but by thickening of the tendon sheath and most notably by the accumulation of mucopolysaccharide, an indicator of myxoid degeneration. These changes are pathognomonic of the condition and are not seen in control tendon sheaths. The term 'stenosing tenovaginitis' is a misnomer and we believe that de Quervain's disease is a result of intrinsic, degenerative mechanisms rather than extrinsic, inflammatory ones.

Adult↗
PubMed1998

Histochemical investigation into the molecular mechanisms of malignant transformation in a benign glomus tumour.

A glomangiosarcoma arose in a benign glomus tumour. The histological and immunohistochemical characteristics of the tumour were investigated. Apoptotic cells were identified by terminal deoxynucleotidyl transferase (TdT) mediated dUTP-biotin nick end labelling (TUNEL). The proportion of apoptotic cells was found to be low and TUNEL positive nuclei were present in the benign part of the tumour. Bcl-2 protein, an inhibitor of apoptosis, was strongly expressed in the glomangiosarcoma with only weak staining in the benign area. The proliferation index of the glomangiosarcoma was almost 10-fold higher than that of the benign glomus tumour. Numerous nuclei in the glomangiosarcoma were intensely stained for the tumour suppressor protein p53. The results of the this study may contribute to an understanding of the molecular basis of malignant transformation in benign glomus tumours.

Apoptosis↗
PubMed1998

A technique for determining convergence in human subjects undergoing rotational acceleration using a binocular eye-tracking system.

BACKGROUND: This report describes the measurement of convergent eye movements and calculation of the spatial convergence point from the angular eye position data. These measurements were made in the dark while the subject experienced inertial motion aboard a centrifuge. This was an exploratory experiment with the goal of evaluating the eyes' convergence in the dark, and to see if this convergence point is dependent on inertial motion. METHODS: The subject was rotated in the dark on NAMRL's Coriolis Acceleration Platform in Pensacola, FL. The pupil positions were tracked by two helmet-mounted infrared cameras connected to a computer-controlled data acquisition system. We used the position data to calculate the angles through which the eyes rotated, and then applied trigonometric principles to construct the line of sight for each eye for any instant in time. The intersection of these two lines of sight was the convergence point. RESULTS: With the binocular eye-tracking system, we could accurately determine an accelerating subject's convergence point to within 10%, if the point was less than 1.5 m away from the subject. At convergence distances greater than 1.5 m, the angular movements of the two eyes became so small that determining a convergence point was difficult.

Acceleration↗
PubMed1997

Cardiac troponin I in pediatrics: normal values and potential use in the assessment of cardiac injury.

OBJECTIVE: To establish normal values and determine the impact of congenital or acquired heart disease on serum cardiac troponin I (cTnI). METHODS: Concentrations of cTnI were measured in two groups of children. Group A represented ambulatory pediatric patients with no apparent cardiac disease (n = 120) and patients in stable condition with known congenital or acquired cardiac abnormalities (n = 96); group B was composed of patients admitted to intensive care units with normal echocardiograms (n = 16), with abnormal echocardiograms (n = 36), and those with blunt chest trauma who were thought to have cardiac contusions (n = 7). RESULTS: The cTnI concentrations were generally less than 2.0 ng/ml in group A and frequently below the level of detection for the assay (1.5 ng/ml). There was no statistical difference between the two outpatient subgroups (p = 0.66). Nine intensive care patients had cTnI values greater than 2.0 ng/ml. Six of these patients, all with abnormal echocardiograms, had values less than 7.7 ng/ml. All improved and had subsequent normal cTnI concentrations. None of the three remaining patients (two with systemic illness (trauma and sepsis) and one with severe pulmonary hypertension), all with values greater than 8.0 ng/ml, survived. Three of the four patients with high likelihood of cardiac contusion had cTnI concentrations greater than 2.0 ng/ml (including one patient who died). CONCLUSIONS: Cardiac troponin-I values are generally not elevated in children with stable cardiac disease or general pediatric conditions. In the context of severe acute illness, significant elevation of cTnI may be an indicator of poor outcome. Elevation of cTnI may also have diagnostic value in cases when cardiac contusion is suspected.

Adolescent↗
PubMed1997

A finite-element model of inner ear hair bundle micromechanics.

Understanding hair-cell micromechanics is central to the discussion of mechanotransduction in these cells. This paper presents a finite-element model that characterizes the stiffness and deflection properties of an inner-ear hair bundle. Average morphological dimensions were used for sterocilia height (6, 8, and 10 microns), diameter (0.25 microns), and rootlet separation (0.5 microns) for a single bundle column containing three rows. Stereocilia material properties were described as isotropic, homogeneous, linearly elastic, and nearly incompressible. Young's modulus for the stereocilia ranged from a maximum of actin and down. The column of stereocilia were coupled by linear elastic material modeling tip and lateral links. When the hairs were deflected by a static force applied to the tip of the tallest cilium, the hair-bundle model yielded a stiffness of 9.5 x 10(-4) to 21 x 10(-4) N/m, which was in the range of typical experimental values but approximately a factor of 4-10 times the average of all experimental values. Model parameters such as bundle size, shape, and material properties were systematically varied to determine each component's contribution to bundle stiffness. Additionally, tip-link tensions were determined for a range of deflections in a five cilium model and were shown to be proportionally graded in magnitude along the bundle staircase.

Animals↗
PubMed1996

Development of an Optical Triplicator for intravital video microscopy of oxygen saturation.

The Optical Triplicator produces three copies of a portion of a microscopic image and places them side-by-side on the face of a video image tube, so that all three images can be viewed simultaneously in each video frame. The Optical Triplicator was used in an intravital microscopy assembly to obtain simultaneous images of a microvessel at three visible wavelengths selected to enable the accurate determination of oxygen saturation in microvessels of the hamster retractor muscle. An image processing system was used to obtain light intensity and optical density from video recordings made using the triplicator. Lumenal oxygen saturation profiles were determined using the measured intensity values and a published three wavelength photometric method.

Animals↗
PubMed1996

Monoclonal antibody therapy of diffuse cutaneous scleroderma with CAMPATH-1H.

A worker in a polyvinyl chloride factory with rapidly progressive diffuse cutaneous scleroderma was treated with the humanized monoclonal antibody (Mab) CAMPATH-1H. Treatment was followed by rapid and substantial improvement in skin score, which was maintained during followup without additional therapy. The mode of action of CAMPATH-1H and its relationship to clinical improvement are discussed.

Adult↗