Search PubMed⌕ Search

Biomedical subjects

Bernard Cohen

Publications and source records attributed to Bernard Cohen.

48 records · Page 3Linked to original sources
PubMed2002

Development of a quantitative immuno-PCR assay and its use to detect mumps-specific IgG in serum.

Determination of the immune status of individuals to vaccine-preventable diseases requires an assay that can detect antibodies that may be present at very low levels, especially when natural or vaccine exposure may have been many years previously. Immuno-PCR (iPCR) has recently been described as an ultrasensitive method for the detection of antigens and we have adapted the method for the quantification of antibodies to mumps virus. The procedure used was similar to an indirect ELISA except that the detecting antibody (anti-human IgG) was chemically conjugated to a short capture oligonucleotide rather than an enzyme. The capture oligonucleotide was then detected by the addition of target DNA, which was designed to hybridise to the capture oligonucleotide and function as a template for real-time PCR. The quantity of target DNA detected by the PCR depended upon the level of specific antibody in the test sample. We found that the sensitivity (and specificity) of the iPCR assay did not exceed that of the conventional ELISA. The sensitivity was limited by nonspecific binding of human IgG to the solid phase. Further development of reagents and assay formats is necessary to fully exploit the potential of quantitative iPCR, so that potential improvements in the sensitivity of anti-mumps IgG detection can be realised.

Antibodies, Viral↗
PubMed2002

High level expression of recombinant mumps nucleoprotein in Saccharomyces cerevisiae and its evaluation in mumps IgM serology.

To develop improved reagents for mumps serology a high-level yeast expression system was employed to produce recombinant mumps nucleoprotein (rNP). The rNP was purified by CsCl gradient centrifugation and yielded approximately 15 mg/l of yeast culture. Electron microscopy of the rNP revealed characteristic herring-bone structures. The electrophoretic mobility of rNP in yeast cells was similar to native NP in SDS-PAGE. Monoclonal antibodies to rNP reacted with native mumps virus nucleoprotein by immunofluorescence assay. A monoclonal antibody to native mumps virus NP reacted with rNP by Western blot assay. The rNP was investigated as antigen in an IgM capture enzyme immunoassay (EIA) using a horseradish peroxidase conjugate of monoclonal antibody to the rNP. Eighteen sera previously found to be positive by IgM capture radioimmunoassay (MACRIA) and 30 sera that were mumps IgM negative by MACRIA were tested by mumps IgM capture EIA. The results for the two test were concordant. In addition, 26 rheumatoid factor positive sera and 35 sera that were IgM positive for measles, rubella or parvovirus B19 were tested. Fifty-nine sera were negative by mumps IgM capture EIA but two sera collected from two infants 3 and 6 weeks after mumps, measles and rubella vaccination were positive. Mumps MACRIA confirmed these results. Compared to MACRIA the overall sensitivity was 100% (20/20) and specificity was 96.8% (30/31). The yeast expressed rNP was highly immunogenic and suitable for use in IgM capture EIA for the diagnosis of mumps.

Animals↗
PubMed2002

Hypocomplementemic urticarial vasculitis: report of a 12-year-old girl with systemic lupus erythematosus.

Urticarial vasculitis, a form of leukocytoclastic vasculitis involving the postcapillary venules, is classified as a type III hypersensitivity reaction and has been associated with connective tissue disease. The lesions resemble urticaria and typically persist for more than 24 hours. Urticarial vasculitis usually affects young women, and the diagnosis is confirmed at histologic examination. Patients with urticarial vasculitis can be divided into 2 types--those with normal complement levels and those with hypocomplementemic urticarial vasculitis (HUV). Patients with normocomplementemic urticarial vasculitis have a milder course than do patients with HUV, a condition that has a strong association with systemic lupus erythematosus. Angioedema, ocular inflammation, obstructive lung disease, and glomerulonephritis are commonly associated with HUV. We describe the case of a girl with systemic lupus erythematosus and HUV who also had pancreatitis, hypothyroidism, and elevated levels of antiphospholipid antibodies.

Acute Disease↗
PubMed2002

Spatial orientation of caloric nystagmus.

The spatial orientation of the slow-phase eye velocity of caloric nystagmus was investigated in cynomolgus monkeys after all six semicircular canals had been plugged. Normal animals generate responses that have dominant convective components produced by movement of the endolymph in the lateral canal toward or away from gravity. As a result, the direction of horizontal slow-phase velocity induced by cold-water irrigation changes direction with changes in head position with regard to gravity. Plugging produced a dense overgrowth of bone that blocked the flow of endolymph, but the end organs were intact. Robust caloric nystagmus was elicited after recovery, but the horizontal (yaw) component was now always toward the stimulated (ipsilateral) side, regardless of head position re gravity. The induced caloric nystagmus had strong spatial orientation properties after canal plugging. With animals upright, the three-dimensional velocity vector of the caloric nystagmus was close to the yaw axis with small vertical and roll components. Roll components became stronger in supine and prone positions and vertical components were enhanced in the right- and left-side down positions. In each instance, the addition of the roll and vertical components moved the velocity vector of the nystagmus closer to the spatial vertical. Modeling supported the postulate that the caloric nystagmus after canal plugging is influenced by three factors: (1) a reduction in neural activity in the ampullary nerves on the stimulated side due to cooling of the nerves; (2) contraction of the endolymph in the closed space between the cupula and the plug due to cooling, which resulted in deflection of the cupula and hair cells toward the plug (ampullofugal deflection); and (3) alignment of eye velocity to gravity due to the orientation properties of velocity storage. Although convection is the most prominent factor in producing caloric responses in the normal state, our results suggest that alteration of nerve activity due to thermal effects, endolymph contraction or expansion, and velocity storage are also likely to contribute to the total response.

Animals↗
PubMed2002

The nodulus and uvula: source of cerebellar control of spatial orientation of the angular vestibulo-ocular reflex.

The nodulus and rostral-ventral uvula of the vestibulo-cerebellum play a critical role in orienting eye velocity of the slow component of the angular vestibulo-ocular reflex (aVOR) to gravito-inertial acceleration (GIA). This is done by altering the time constants of "velocity storage" in the vestibular system and by generating "cross-coupled" eye velocities that shift the eye velocity vector from along the body yaw axis to the yaw axis in a spatial frame. In this report, we show that eye velocity generated through the aVOR by constant velocity centrifugation in the monkey orients to the GIA in space, regardless of the position of the head with respect to the axis of rotation. We also show that, after removal of the nodulus and rostral-ventral uvula, the spatial orientation of eye velocity to the GIA is lost and that eye velocity is then purely driven by the semicircular canals in a body frame of reference. These findings are further confirmation that these regions of the vestibulo-cerebellum control spatial orientation of the aVOR.

Animals↗
PubMed2002

Compensatory and orienting eye movements induced by off-vertical axis rotation (OVAR) in monkeys.

Nystagmus induced by off-vertical axis rotation (OVAR) about a head yaw axis is composed of a yaw bias velocity and modulations in eye position and velocity as the head changes orientation relative to gravity. The bias velocity is dependent on the tilt of the rotational axis relative to gravity and angular head velocity. For axis tilts <15 degrees, bias velocities increased monotonically with increases in the magnitude of the projected gravity vector onto the horizontal plane of the head. For tilts of 15-90 degrees, bias velocity was independent of tilt angle, increasing linearly as a function of head velocity with gains of 0.7-0.8, up to the saturation level of velocity storage. Asymmetries in OVAR bias velocity and asymmetries in the dominant time constant of the angular vestibuloocular reflex (aVOR) covaried and both were reduced by administration of baclofen, a GABA(B) agonist. Modulations in pitch and roll eye positions were in phase with nose-down and side-down head positions, respectively. Changes in roll eye position were produced mainly by slow movements, whereas vertical eye position changes were characterized by slow eye movements and saccades. Oscillations in vertical and roll eye velocities led their respective position changes by approximately 90 degrees, close to an ideal differentiation, suggesting that these modulations were due to activation of the orienting component of the linear vestibuloocular reflex (lVOR). The beating field of the horizontal nystagmus shifted the eyes 6.3 degrees /g toward gravity in side down position, similar to the deviations observed during static roll tilt (7.0 degrees /g). This demonstrates that the eyes also orient to gravity in yaw. Phases of horizontal eye velocity clustered ~180 degrees relative to the modulation in beating field and were not simply differentiations of changes in eye position. Contributions of orientating and compensatory components of the lVOR to the modulation of eye position and velocity were modeled using three components: a novel direct otolith-oculomotor orientation, orientation-based velocity modulation, and changes in velocity storage time constants with head position re gravity. Time constants were obtained from optokinetic after-nystagmus, a direct representation of velocity storage. When the orienting lVOR was combined with models of the compensatory lVOR and velocity estimator from sequential otolith activation to generate the bias component, the model accurately predicted eye position and velocity in three dimensions. These data support the postulates that OVAR generates compensatory eye velocity through activation of velocity storage and that oscillatory components arise predominantly through lVOR orientation mechanisms.

Animals↗
PubMed2002

Spatial orientation of caloric nystagmus in semicircular canal-plugged monkeys.

We studied caloric nystagmus before and after plugging all six semicircular canals to determine whether velocity storage contributed to the spatial orientation of caloric nystagmus. Monkeys were stimulated unilaterally with cold ( approximately 20 degrees C) water while upright, supine, prone, right-side down, and left-side down. The decline in the slow phase velocity vector was determined over the last 37% of the nystagmus, at a time when the response was largely due to activation of velocity storage. Before plugging, yaw components varied with the convective flow of endolymph in the lateral canals in all head orientations. Plugging blocked endolymph flow, eliminating convection currents. Despite this, caloric nystagmus was readily elicited, but the horizontal component was always toward the stimulated (ipsilateral) side, regardless of head position relative to gravity. When upright, the slow phase velocity vector was close to the yaw and spatial vertical axes. Roll components became stronger in supine and prone positions, and vertical components were enhanced in side down positions. In each case, this brought the velocity vectors toward alignment with the spatial vertical. Consistent with principles governing the orientation of velocity storage, when the yaw component of the velocity vector was positive, the cross-coupled pitch or roll components brought the vector upward in space. Conversely, when yaw eye velocity vector was downward in the head coordinate frame, i.e., negative, pitch and roll were downward in space. The data could not be modeled simply by a reduction in activity in the ipsilateral vestibular nerve, which would direct the velocity vector along the roll direction. Since there is no cross coupling from roll to yaw, velocity storage alone could not rotate the vector to fit the data. We postulated, therefore, that cooling had caused contraction of the endolymph in the plugged canals. This contraction would deflect the cupula toward the plug, simulating ampullofugal flow of endolymph. Inhibition and excitation induced by such cupula deflection fit the data well in the upright position but not in lateral or prone/supine conditions. Data fits in these positions required the addition of a spatially orientated, velocity storage component. We conclude, therefore, that three factors produce cold caloric nystagmus after canal plugging: inhibition of activity in ampullary nerves, contraction of endolymph in the stimulated canals, and orientation of eye velocity to gravity through velocity storage. Although the response to convection currents dominates the normal response to caloric stimulation, velocity storage probably also contributes to the orientation of eye velocity.

Animals↗
PubMed2002

Vertebral hemangiomas associated with familial cerebral cavernous malformation: segmental disease expression. Case report.

Recently, several groups of authors have described mutations in the Krev interaction-trapped 1 [corrected] (KRIT1) gene in families in whom cerebral cavernous malformations (CCMs) are present. In a number of French kindreds harboring familial CCMs, cutaneous as well as cerebral manifestations of this autosomal-dominant disorder were demonstrated. Involvement of other tissues has been poorly described. The authors present the proband, in an affected family with a previously reported KRIT1 mutation, in whom vertebral hemangiomas in addition to cerebral and cutaneous lesions were found. One of the vertebral lesions was associated with a large cutaneous lesion. This combination of vertebral and overlying cutaneous lesions suggests segmental disease expression as the result of a second hit during development, implying loss of function as the relevant molecular pathogenic mechanism. This case illustrates that tissue involvement outside the nervous system must be considered when treating patients with familial CCMs.

Biopsy↗
PubMed2002

Joining efforts in tackling the organ shortage: the Donor Action experience.

1. Donor Action takes a systematic approach towards achieving quality assurance in the whole donation process. It is designed to give hospitals participation and ownership of donation practices that can be tailored to meet identified needs in critical care units (CCUs). The program has been successfully introduced in 18 countries and in over 250 CCUs in North and South America, Europe and Asia. 2. Aggregated data collected in 162 CCUs in 10 countries showed significant losses of potential donors along the donation pathway. The major factor impacting on converting medically suitable cases with signs of brain death into potential donors was the willingness of CCU staff to formally diagnose brain death. Major reasons for non-donation in BD-diagnosed cases were non-referral (26.5%), family refusal (20%), or no approach of next-of-kin (13.2%). 3. Pre-intervention data show that professional training, clear role definitions, teamwork, comprehensive guidelines and consistent protocols dealing with all donation-related tasks in the CCU setting are critical to achieve optimal donation rates. 4. Implementation of these improvement measures in 10 countries have shown an immediate overall increase of donation rates of 59% after 1 year and a sustained, even growing effect on referral and donation rates in those countries with sufficient follow-up, proving a permanent impact of DA's methodology. 5. As a health-economic evaluation, based on the German case, shows that the implementation cost of the program in pilot centers was far below the investment thresholds. Donor Action is more cost-effective than other publicly reimbursed medical interventions. Incorporating health economic consequences of other cadaveric organ transplants into the analysis could even further improve the cost-benefit ratio of Donor Action compared with current organ donation practices.

Databases, Factual↗
PubMedDate not supplied

Artificial gravity: a possible countermeasure for post-flight orthostatic intolerance.

Four payload crewmembers were exposed to sustained linear acceleration in a centrifuge during the Neurolab (STS-90) flight. In contrast to previous studies, otolith-ocular reflexes were preserved during and after flight. This raised the possibility that artificial gravity may have acted as a countermeasure to the deconditioning of otolith-ocular reflexes. None of the astronauts who were centrifuged had orthostatic intolerance when tested with head-up passive tilt after flight. Thus, centrifugation may also have helped maintain post-flight hemodynamic responses to orthostasis by preserving the gain of the otolith-sympathetic reflex. A comparison with two fellow Neurolab orbiter crewmembers not exposed to artificial gravity provided some support for this hypothesis. One of the two had hemodynamic changes in response to post-flight tilt similar to orthostatically intolerant subjects from previous missions. More data is necessary to evaluate this hypothesis, but if it were proven correct, in-flight short-radius centrifugation may help counteract orthostatic intolerance after space flight.

Acceleration↗
PubMedDate not supplied

A girl with loose anagen hair syndrome and uncombable, spun-glass hair.

A 4-year-old girl presented with a 2-year history of scalp hair that had an odd texture, was difficult to manage, tended to "stick out" from the scalp, and was irregular in length. A hair pull test revealed that hairs could be easily and painlessly extracted. Light microscopic examination of the hair demonstrated anagen hairs with a ruffled cuticle and distorted bulb as well as an unusual undulation and grooving of the shafts. These findings are consistent with both loose anagen and uncombable hair syndromes. The occurrence of both syndromes in the same patient seems unlikely, and we propose that our patient has loose anagen hair syndrome with features resembling uncombable hair syndrome.

Child, Preschool↗