Search PubMed⌕ Search

Biomedical subjects

M A Hamid

Publications and source records attributed to M A Hamid.

At least 37 records · Page 2Linked to original sources
PubMed1990

An enzymatic assay for the colorimetric and fluorimetric determination of uric acid in sera.

The methods described in this paper are based on the uricase catalyzed oxidation of uric acid to allantoine and hydrogen peroxide. By making use of the catalytic activity of peroxidase the generated H2O2 is measured either spectrophotometrically with 3-methyl-benzothiazoline-2-one hydrazone (MBTH) and 3-dimethylaminobenzoic acid (DMAB) (M1) or fluorimetrically with tyramine (M2) or L-tyrosine (M3). The methods are simple, sensitive and selective. The procedures developed can be rapidly and readily performed on patient serum samples without deproteinization using 100 microliters and 5 microliters for colorimetric and fluorimetric assay, respectively.

Colorimetry↗
PubMed1990

Clinical value of sinusoidal harmonic acceleration test results. Site of lesion and side of lesion.

Sinusoidal harmonic acceleration tests can be used reliably to determine site and side of lesion. Results from 6000 patients collected over the past 10 years have shown that the temporal pattern of asymmetry can be reliably used to differentiate peripheral from central vestibular dysfunction. Peripheral cases tend to have a high level of asymmetry, with temporal regression to normal range, and a high correlation with patient symptoms. Central cases tend to have a low level of variable asymmetry and variable symptoms. In either case, phase can be abnormal or normal and cannot be reliably used to differentiate peripheral from central dysfunction. By combining phase and symmetry, the side of the lesion can be reliably determined. When phase is abnormal, asymmetry is toward the side of the lesion in 92 per cent of cases, whereas when phase is normal, asymmetry cannot be reliably used to determine side of lesion. SHA testing has contributed significantly to our clinical ability to fully evaluate the vestibular system and has become an indispensable part of the complete vestibular laboratory. It requires a relatively large patient load as well as software and hardware support to become a cost-effective utility.

Acceleration↗
PubMed1988

Autoimmune endolymphatic hydrops: five-year review.

This article reviews the authors' experience with autoimmune endolymphatic hydrops over the past 5 years. Twenty-seven of 52 patients with diagnosed autoimmune inner ear disease (52%) manifested endolymphatic hydrops, usually bilateral. Treatment consisted of low salt diet, diuretic, vestibular suppressant, and usually prednisone. Cytotoxic drugs and lymphocytoplasmapheresis were reserved for refractory cases. Audiometric followup (average, 23 months) was available in 12 patients. Using American Academy of Otolaryngology--Head and Neck Surgery guidelines, hearing improved or stabilized in at least one ear in nine patients and deteriorated bilaterally in three patients. Vestibular treatment results paralleled auditory treatment results. Autoimmune endolymphatic hydrops should be considered in the differential diagnosis when symptoms are bilateral and do not respond to conventional therapy or when immune laboratory tests are positive. In suspect patients, medical therapy with prednisone, and rarely cytotoxic drugs and lymphocytoplasmapheresis, should be recommended. Further research is needed to determine whether surgery should be performed in medically unresponsive cases.

Adolescent↗
PubMed1988

ENG-MRI correlates in cerebellar oculomotor dysfunction.

This study correlates ENG and MRI findings in six patients with cerebellar eye movements. For each subject, both tests independently support the presence of a cerebellar tract abnormality. In two patients, MRI studies confirmed the site of cerebellar dysfunction previously demonstrated by ENG. Although the number of patients is small, the strong correlation (100%) indicates that ENG remains a sensitive method for detection and localization of the origin of cerebellar eye movements. The physiologic information provided by ENG is supported anatomically by MRI. The cerebellar eye movement abnormalities are briefly reviewed.

Adolescent↗
PubMed1987

Comparison of smooth pursuit and combined eye-head tracking in human subjects with deficient labyrinthine function.

The effects of deficient labyrinthine function on smooth visual tracking with the eyes and head were investigated in ten patients with bilateral peripheral vestibular disease. Ten normal subjects served as controls. In the patients active, combined eye-head tracking (EHT) was significantly better than smooth pursuit (SP) with the eyes alone with a target frequency of 1.0 Hz. Normal subjects pursued equally well with SP and with active EHT. The gain of compensatory eye movements during active head rotation in darkness was also measured. Compensatory eye movements in labyrinthine-deficient patients (attributable to residual vestibulo-ocular reflex (VOR), cervico-ocular reflex (COR) and pre-programmed eye movements) were always less than in normal subjects. These data were used to examine current hypotheses that postulate central cancellation of the VOR (or compensatory eye movements) during EHT. A model that proposes summation of an internal smooth pursuit command and VOR/compensatory eye movements accounted for the findings in normal subjects and labyrinthine-deficient patients. In seven labyrinthine-deficient patients and nine normal subjects, passive EHT was measured during en bloc rotation while they viewed a head-fixed target. With a target frequency of 1.0 Hz, both subjects and patients showed significantly better tracking during passive EHT than during SP. Normal subjects also showed superior tracking during passive EHT compared with active EHT. These findings support the notion that during passive EHT, parametric gain changes contribute to modulation of the VOR.

Adult↗
PubMed1986

Selective saccadic palsy caused by pontine lesions: clinical, physiological, and pathological correlations.

Two patients suffered a selective deficit of voluntary saccades and quick phases of nystagmus after hypoxic-ischemic insults during open-heart surgery. All voluntary saccades, in both horizontal and vertical planes, were slow, and quick phases of vestibular and optokinetic nystagmus were absent. Smooth pursuit, the vestibuloocular reflex, the ability to hold steady eccentric gaze, and vergence eye movements were all preserved. Pathological studies in 1 patient confirmed neuronal necrosis and gliosis, consistent with ischemic lesions involving the median and paramedian pontine reticular formation and median basis pontis but sparing the rostral mesencephalon and rostral interstitial nucleus of the medial longitudinal fasciculus. These findings, taken with data from experimental studies, support the hypothesis that each functionally defined class of horizontal eye movements is controlled by a separate neural substrate that projects independently to the abducens nuclei. In addition, these data suggest that the rostral interstitial nucleus of the medial longitudinal fasciculus is dependent on inputs from the paramedian pontine reticular formation for the programming of normal vertical saccades.

Adult↗
PubMed1986

Results of sinusoidal harmonic acceleration test in one thousand patients: preliminary report.

One thousand patients with dizziness were tested by sinusoidal harmonic acceleration with frequencies of .01, .02, .04, .08, and .16 Hz. Two hundred fifty (25% of data base) were randomly selected for this study. One hundred forty-eight diagnoses were confirmed: 66 (45%) patients had a clinical diagnosis of peripheral vestibular dysfunction, 28 (19%) had central vestibular dysfunction, and 53 (36%) had dizziness of undetermined cause. This preliminary study investigated the response patterns of phase (latency), asymmetry (slow phase preponderance), and gain (output/input) as they correlated with each of the above patient groups. The main response pattern was a varying degree of asymmetry with normal or abnormal latency. Persistent abnormal phase pattern indicated permanent vestibular damage and could not be used reliably to differentiate peripheral from central vestibular dysfunction. Asymmetry changed with time and correlated with patients' symptoms. The dynamic pattern of asymmetry could be used to differentiate peripheral from central vestibular dysfunction. Gain was a reliable and essential measure of the sensitivity of the vestibular system and the validity of the rotational response.

Dizziness↗
PubMed1986

Vestibular evoked potentials in man: an overview.

Evoked potentials (EPs) have been used to detect auditory, visual, and somatosensory dysfunction. Evoked potentials are recorded by averaging an optimal number of responses (that are time-locked) to the same number of appropriate stimuli. Adequate stimulus levels and "minimal" response latency are necessary for recording evoked potentials. Vestibular evoked potentials have received considerably less attention because of the difficulty in providing appropriate stimuli, the relatively long latency of vestibular responses, and the adaptation of the vestibular system to repeated stimulation. Technological advances have made it possible to provide accurate stimuli by use of computer-controlled rotating chairs and computer-averaging procedures.

Electric Stimulation↗
PubMed1985

Autoimmune vestibular dysfunction: preliminary report.

Since 1981, 28 patients have been diagnosed with autoimmune inner ear disease. This preliminary, retrospective study reviews clinical and laboratory manifestations of autoimmune vestibular dysfunction. Sixteen of 28 patients presented with dizziness (7 vertigo, 8 lightheadedness, 1 ataxia). Twelve of these patients presented with Meniere's syndrome. Seven of 16 dizzy patients underwent formal vestibular testing. Five had reduced vestibular response in the involved ear(s); one patient had positional nystagmus only; and one had normal results. Of 17 patients with adequate follow-up, 11 presented with dizziness. Hearing improved and dizziness resolved in two patients following treatment. Hearing stabilized and dizziness resolved in two. Hearing stabilized but lightheadedness (without vertigo) persisted in five. Hearing was lost and oscillopsia resulted in two patients. Preliminary conclusions are vestibular dysfunction in autoimmune inner ear disease is nonspecific; bilateral vestibular dysfunction is more common; Meniere's syndrome is relatively common; medical management usually is helpful; surgery at this time does not seem appropriate; vestibular treatment results tend to parallel auditory treatment results.

Adolescent↗
PubMed1984

An approach to quantify central vestibular compensation.

Central vestibular compensation is the ultimate goal for the dizzy patient. Monitoring spontaneous nystagmus and caloric responses are not usually correlated with the patient progress and cannot be objectively documented. On the other hand, Temporal Asymmetry Shift (TAS) is a more accurate and objective measure of central vestibular compensation. Furthermore, its dynamic pattern offers a reliable indicator to differentiate between peripheral and central vestibular dysfunctions.

Adult↗
PubMed1980

Absolute and relative caloric responses.

The statistical features of absolute-based and percentage-based post-caloric EOG response measures were investigated on ten normal and twenty pathological cases. Criteria for the best EOG response measure are introduced. It is concluded that, using the method adopted in this study, the mean interbeat interval can be regarded as the measure of choice for quantifying the post-caloric EOG response.

Caloric Tests↗
PubMed1980

Lipid composition of freshly prepared and stored platelet concentrates.

To evaluate the possibility that changes in lipid composition might be related to the functional lesion that develops when platelets are stored as concentrates for several days, we measured lipid constituents of platelets in freshly prepared concentrates and in concentrates stored for 72 hr at 4 degrees C or at 20 degrees C under standard blood banking conditions. At 20 degrees C, but not at 4 degrees C, platelets lost about 15% of total cholesterol and 7%--11% of total phospholipid. The distribution of individual phospholipids remained unchanged. This was also true of the fatty acid distribution in total phospholipids and in individual phospholipids except for a statistically significant reduction of linoleic acid (18:2) and an increase in oleic acid (18:1) in phosphatidyl inositol (PI). Platelets collected in citrate-phosphate-dextrose (CPD) anticoagulant did not differ significantly in lipid composition from those collected in acid-citrate-dextrose (ACD) anticoagulant during the period of observation. These findings do not provide a basis to suggest that functional abnormalities developing in stored platelets are related to changes in lipid composition.

Blood Platelets↗
PubMed1979

Implementing a computer-based electro-oculographic analysis system.

Electro-oculographic recordings of caloric-induced nystagmus were conducted in a number of normal and disordered subjects. On the basis of the results, implementation of a clinical measuring system is considered; this is based on the interbeat interval, selected in view of its favourable sensitivity and stability. Two stages of processing are involved; first, the determination of the interbeat intervals, second the analysis. The first stage has been implemented off-line on a general purpose computer and also, in on-line mode, by special purpose electronics. The second stage requires computer analysis. We have used the rank magnitude sequences of interbeat intervals as the basis of the analysis.

Adult↗