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Biomedical subjects

N Dang

Publications and source records attributed to N Dang.

31 records · Page 2Linked to original sources
PubMed1992

Physiological analysis of motor reorganization following lower limb amputation.

It is now known that amputation results in reorganization of central motor pathways, but the mechanism for the changes is unclear. One possibility is alteration of the excitability of the alpha motoneurons. We studied motor reorganization and excitability of alpha motoneurons to Ia input in 6 subjects with unilateral lower limb amputation. A Cadwell MES-10 stimulator was used to deliver transcranial magnetic stimuli through a circular coil centered on the sagittal axis 4 cm anterior to Cz and through an 8-shaped coil positioned over scalp locations 1 cm apart along the coronal axis. Surface EMG was recorded bilaterally from quadriceps femoris, the first muscle immediately proximal to the site of amputation. Excitability of the spinal alpha motoneuron pool to Ia afferents was assessed by determining the ratio of the maximal H reflex to the maximal M response (H/M ratio) elicited in the quadriceps femoris. Stimuli of equal intensity delivered to optimal scalp positions recruited a larger percentage of the alpha motoneuron pool in muscles ipsilateral to the stump than in those contralateral to the stump (P less than 0.01). Mean onset latencies of motor evoked potentials were shorter in ipsilateral muscles than in contralateral muscles (P less than 0.01). Muscles ipsilateral to the stump showed a trend toward activation from a larger number of scalp positions than those contralateral to the stump (P = 0.06). There was no difference in the quadriceps H/M ratios (7.2% ipsilateral vs. 10.9% contralateral). The absence of changes in the excitability of the alpha motoneuron pool in the presence of motor reorganization targeting muscles proximal to the stump suggests that reorganization occurs proximal to the alpha motoneuron level.

Adult↗
PubMed1992

No evidence of hearing loss in humans due to transcranial magnetic stimulation.

Prompted by the description of hearing loss in rabbits exposed to the acoustic artifact of magnetic stimulation, we compared the results of audiologic studies before and after exposure to transcranial magnetic stimulation in humans. We found no evidence of temporary or permanent threshold shifts in any of the subjects, even in those exposed to transcranial magnetic stimulation repeatedly for several years. Risk of hearing loss from the acoustic artifact of magnetic stimulation, as evaluated by audiograms, tympanograms, acoustic reflexes, and auditory evoked potentials, seems to be small in humans.

Adult↗
PubMed1991

[Conflict between psoas and total hip prosthesis].

This conflict leads to a chronic irritation of the psoas by the antero-medial part of the cup, but it has been poorly described in the past. A study of six patients suffering from this trauma, and who were re-operated revealed that the muscle was worn thin in front of the prominent cup. In the case of 4 of the 6 patients pain had started to occur shortly after total hip replacement. The following symptoms were noted among all 6 patients: pain was suffered during flexion--extension movements--walking up stairs--arising from a chair. Pressure on the medial part of the groin was painful, especially during active elevation of the lower limb. Passive mobility was normal and painless. Psoas bursitis was observed in three cases. The main cause of this conflict is the protrusion of the cup beyond the antero-medial edge of the acetabulum; this protrusion may be either due to a bone graft or a bit of cement, but most often an acetabular insufficiency (congenital dysplasia) favors the formation of this anterior overhang. The spiral cup screwed into the bone can be especially aggressive when it protrudes. Treatment includes the resection of the overhang, but post-operative results will be uncertain unless the resection is really complete. In the case of 4 patients the results of such an intervention were only mild to poor. This problem can be avoided by proper care and preventive measures in the original replacement avoiding all projections beyond the anterior edge of the acetabulum--cup, bone graft, cement, especially if dysplasic.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Effects of coil design on delivery of focal magnetic stimulation. Technical considerations.

The localization of effects from magnetic coil stimulation is not immediately obvious. We measured the magnetic fields produced by several different coils and compared the results with theoretical calculations. Magnetic stimuli were delivered from a Cadwell MES-10 magnetic stimulator using 3 circular coils (one 9 cm in diameter; two with an angulated extension, 5 and 9 cm in diameter) and twin oval coils arranged in a butterfly shape (each coil approximately 4 cm in diameter) and from a Novametrix Magstim 200 using two circular flat-spiral coils (6.7 and 14 cm in diameter). Peak-induced strength of the magnetic field was recorded with a measuring loop (1 cm in diameter) at different distances from the center of the coil. When the measuring loop was moved in the same plane laterally from the center of the coil, for all coils except the butterfly-shaped coil, the field was highest in the center and fell off near the circumference of the coil. The field dropped progressively when measurements were made more distant from the plane of the coils. The electric field induced from the magnetic coil could be calculated from the coil geometry. For all coils except the butterfly-shaped coil, the largest electric field was at the circumference of the coils. The 6.7 cm flat-spiral coil induced currents similar to those induced by the larger coils but more focally. The butterfly-shaped coil induced the largest currents under its center, where the circumferences of the two component coils come together. The component of the electric field parallel to the wire in the center of this coil was the largest and most localized.

Electric Stimulation↗
PubMed1990

Effect of chemotherapy on cell counts in peripheral blood & bronchoalveolar lavage of patients with pulmonary tuberculosis.

Cell counts in peripheral blood and bronchoalveolar lavage fluid were estimated in 38 patients with active tuberculosis; 12 patients with tuberculosis who had successfully completed more than 9 months of chemotherapy with isoniazid, rifampicin, and ethambutol; 10 Mantoux negative bronchitic subjects; and 6 control subjects. There were 50 males and 16 females aged 16-50 yr. Age, haemoglobin, total and differential serum proteins, were comparable in the various groups. Patients with active tuberculosis had higher ESR and significantly raised absolute (2.24 +/- 0.13 x 10(3); P less than 0.05), B (0.56 +/- 0.03 x 10(3); P less than 0.01) and Null lymphocyte counts (0.56 +/- 0.05 x 10(3); P less than 0.01) in blood. After chemotherapy there was no significant change in lymphocyte counts (2.43 +/- 0.21; P greater than 0.05). In bronchoalveolar lavage (BAL) total cell counts were increased five fold in patients with active disease (40.8 +/- 5.79 x 10(4)/ml) and although these showed considerable reduction after therapy they were higher (18.33 +/- 4.73 x 10(4)/ml) than those in controls (8.3 +/- 1.2 x 10(4)/ml; P greater than 0.05). In bronchitic subjects, total cell counts and macrophage counts in BAL fluid were elevated (P less than 0.01; less than 0.05 respectively) but lymphocyte counts were comparable to controls (3.4 +/- 1.35 x 10(4)/ml vs 1.09 +/- 0.19 x 10(4)/ml; P greater than 0.05). Lymphocytosis in the bronchoalveolar lavage fluid of patients with pulmonary tuberculosis persisted even after adequate treatment.

Adolescent↗
PubMed1990

Monocyte/macrophage functions & humoral response in blood & bronchoalveolar lavage fluid of pulmonary tuberculosis patients.

Subsegmental bronchoalveolar lavage (BAL) was performed in 33 patients with active pulmonary tuberculosis and five control subjects. Phagocytosis by monocytes and alveolar macrophages was studied, and in addition serum and BAL immunoglobulin and complement levels were also determined. The phagocytic activity of blood monocytes was depressed in pulmonary tuberculosis patients as compared to controls, 37.8 +/- 2.3 per cent; 50.7 +/- 4.2 per cent and 32.9 +/- 3.6 per cent for sheep RBC's, latex and Staphylococcus aureus respectively compared to 66.7 +/- 6, 54.8 +/- 2.2 and 68.3 +/- 3.5 per cent respectively in controls; the differences being significant for sheep RBC's (P less than 0.05) and Staph. aureus (P less than 0.001). However, phagocytosis was not impaired in BAL macrophages (P greater than 0.05). In patients no significant alteration in serum immunoglobulin and complement levels was observed except that levels of C4 component of complement were increased in patients with far advanced lesions (98.5 +/- 33.7 mg/dl compared to 78.7 +/- 7.9 mg/dl; P less than 0.05). While IgM and C4 component of complement could not be detected in BAL fluid the levels of IgA were significantly increased in pulmonary tuberculosis patients (65.5 +/- 50.5 mg/dl compared to 39.9 +/- 13.3 mg/dl in control; P less than 0.05). Since IgA secreted in the BAL fluid is mostly synthesised locally, increased levels of this immunoglobulin could be of value in determining activity of the disease.

Adult↗
PubMed1985

A dot enzyme-linked immunosorbent assay for detection of antibodies against Entamoeba histolytica.

A visual micro-dot enzyme-linked immunosorbent assay (ELISA) based on detection of antibodies against soluble antigens of axenically grown cultures of Entamoeba histolytica is described. The antigen was spotted on a nitrocellulose sheet, the unsaturated sites blocked with bovine serum albumin (BSA) and incubated with 3-fold dilutions of patient sera followed by incubation with protein A conjugated to peroxidase. Enzymic activity was evidenced using the substrate 4-chloro-1-naphthol. A positive reaction produced a blue spot. The sensitivity of the assay was better and comparable to the indirect haemagglutination assay (IHA) and plate ELISA. The entire assay could be completed within 3 h. Antigen-loaded and pre-blocked nitrocellulose strips could be stored up to 3 months at room temperature and 37 degrees C.

Amebiasis↗
PubMed1977

Increased association of diabetes mellitus with capsulitis of the shoulder and shoulder-hand syndrome.

Sixty consecutive patients with capsulitis of the shoulder (including those with shoulder-hand syndrome) seen in our clinic since 1971 underwent an oral glucose tolerance test (5 with previously recognized diabetes were excluded from this test). Capsulitis was primary in 35, secondary to other factors in 25 subjects. Females (34) out-numbered males (26). Their ages ranged from 40 to 72 years (mean age: 54 years). Sixty control subjects matched for age and sex with the 60 "capsulitis" patients underwent the same OGTT (except one with previously recognized diabetes). We have found diabetes in 17 out of 60 patients with capsulitis according to Hayner's criteria (12 according to Jackson's criteria) versus 7 (2 according to Jackson's criteria) in the 60 control subjects. The difference is statistically significant by both methods, with a p value of less than 0.02).

Adult↗
PubMedDate not supplied

The N30 component of somatosensory evoked potentials in patients with dystonia.

We recorded short-latency median nerve somatosensory evoked potentials (SEPs) in 10 patients with dystonia (6 with focal dystonia, 3 with generalized dystonia, and 1 with segmental dystonia) and compared them with those of 10 normal controls. The EEG was recorded from 29 sites on the scalp with linked earlobe electrodes for reference. Latencies and amplitudes of P15, postcentral N20 and P45, and frontal N30 were evaluated. The latencies of all potentials were the same in patients and controls. The amplitudes of P15, N20 and P45 were also the same in both groups, but the N30 amplitude of the patients was larger than of the controls. The amplitude of N30 did not vary from the affected side to the unaffected side. Previous work has shown decreased N30 amplitude in patients with Parkinson's disease. Changes in N30 amplitude may be indicative of abnormal excitatory effects on cortex resulting from disorders of the basal ganglia.

Adult↗
PubMedDate not supplied

Effects of designs of Class 2 preparations on resistance of teeth to fracture.

This study was designed to evaluate the effect of isthmus width on the strength of the remaining tooth structure in maxillary first premolars restored with class 2 silver amalgam restorations. One hundred ten sound maxillary first premolars freshly extracted as a part of orthodontic treatment were collected. The teeth were then divided into 10 groups of 11 teeth each. Ideal class 2 mesio-occlusal, disto-occlusal and mesio-occlusodistal cavities with different isthmus widths i.e. one half the intercuspal distance, one third the intercuspal distance and one fourth the intercuspal distance and one fourth the intercuspal distance were prepared. Compressive forces were applied using a Universal Testing Machine and load to the point of fracture was determined. Intact teeth produced the best tooth fracture resistance i.e. 105.4 MPa, followed by preparations with isthmus width of one fourth, one third and one half intercuspal distance in the order.

Bicuspid↗