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Biomedical subjects

David Cohen

Publications and source records attributed to David Cohen.

83 records · Page 5Linked to original sources
PubMed2002

Mammalian homolog of Drosophila tumor suppressor lethal (2) giant larvae interacts with basolateral exocytic machinery in Madin-Darby canine kidney cells.

The Drosophila tumor suppressor protein lethal (2) giant larvae [l(2)gl] is involved in the establishment of epithelial cell polarity during development. Recently, a yeast homolog of the protein has been shown to interact with components of the post-Golgi exocytic machinery and to regulate a late step in protein secretion. Herein, we characterize a mammalian homolog of l(2)gl, called Mlgl, in the epithelial cell line Madin-Darby canine kidney (MDCK). Consistent with a role in cell polarity, Mlgl redistributes from a cytoplasmic localization to the lateral membrane after contact-naive MDCK cells make cell-cell contacts and establish a polarized phenotype. Phosphorylation within a highly conserved region of Mlgl is required to restrict the protein to the lateral domain, because a recombinant phospho-mutant is distributed in a nonpolar manner. Membrane-bound Mlgl from MDCK cell lysates was coimmunoprecipitated with syntaxin 4, a component of the exocytic machinery at the basolateral membrane, but not with other plasma membrane soluble N-ethylmaleimide-sensitive factor attachment receptor (SNARE) proteins that are either absent from or not restricted to the basolateral membrane domain. These data suggest that Mlgl contributes to apico-basolateral polarity by regulating basolateral exocytosis.

3T3 Cells↗
PubMed2002

Functional impairment of the vestibular end organ resulting from impulse noise exposure.

OBJECTIVES/HYPOTHESIS: To assess the effect of exposure t o impulse noise, known to cause damage tothe cochlea, on the vestibular part of the inner ear using short latency vestibular evoked potentials (VsEPs), which is a direct and objective test for evaluating the function of the vestibular end organs. STUDY DESIGN: Prospective animal study. METHODS: Sand rats (Psammomys obesus) underwent baseline measurements of VsEPs in response to linear and angular acceleration stimuli and measurement of the auditory nerve and brainstem evoked response (ABR). The animals were then exposed to 10 gunshots generating impulse noise at an intensity of approximately 160 dB sound pressure level (SPL). Repeat measurements of the evoked potentials were conducted 2 to 4 hours, 1 week, and 6 weeks after the exposure. The amplitude and latency of the first wave of VsEPs in response to linear and angular acceleration stimuli, reflecting the function of the otolith organs and semicircular canals respectively, were compared between baseline and post-exposure measurements, as were ABR thresholds. RESULTS: The amplitude of the first wave of the VsEPs in response to linear acceleration was significantly (P <.001) reduced and the latency significantly (P <.005) prolonged 2 to 4 hours after the exposure in comparison to baselinemeasurements. The latency prolongation persisted in follow-up measurements, whereas the amplitude showed partial recovery. The first wave of VsEPs in response to angular acceleration was unchanged long-term. ABR thresholds were elevated in the long-term by 60 dB. CONCLUSION: It seems that impulse noise not only damages the cochlea, but also causes clear functional impairment to the vestibular end organs, mainly the otolith organs.

Animals↗
PubMed2002

An animal model for assessment of amniotic fluid clearance from the middle ear.

HYPOTHESIS: To determine the time needed for clearance of amniotic fluid from the middle ear after birth, an animal model study was performed. BACKGROUND: Before birth, the middle ear is full of amniotic fluid, and there is controversy about the time it takes for it to clear postnatally. This is of importance because it is suspected that amniotic fluid in the middle ear of the newborn may affect results of screening of hearing when using otoacoustic emissions. METHODS: Adult and neonatal guinea pigs underwent a right-side cochleotomy followed by baseline otoscopy, tympanometry, and auditory nerve- and brainstem-evoked response (ABR) measurements of the left ear. Subsequently, the animals' left middle ears were filled with saline through a hole drilled in the bulla. Over the next few days, assessment of saline clearance was conducted by repeated left-side otoscopy, tympanometry, and measurement of ABR. RESULTS: After filling the middle ear with saline, the tympanic membrane was opaque, a type B tympanogram was obtained, and the ABR threshold was elevated. After an average of 6.3 +/- 3.0 days, air bubbles were seen in otoscopy, a type C tympanogram was obtained, and the ABR threshold improved. Finally, after an average of 9.5 +/- 2.7 days, all 3 parameters returned to their baseline values. CONCLUSION: Taking into consideration that this is an animal study, the results suggest that clearance of amniotic fluid from the newborn middle ear takes longer than has been generally thought. In addition, an animal model for assessing the clearance of fluid from the middle ear has been developed.

Acoustic Impedance Tests↗
PubMedDate not supplied

Prolonged controlled hemorrhagic shock in a swine model: is there a role for mechanical circulatory assistance?

Outcomes of mechanical circulatory assistance during hemorrhagic shock were evaluated in a swine model. Pigs were bled to a mean arterial pressure of 35 mm Hg (group I, n = 3) or 40 mm Hg (group II, n = 5; group III, n = 5), maintained there for 30 minutes, and then resuscitated with fluids alone (groups I and II) or fluids plus mechanical circulatory assistance (group III). Mean blood loss was greater in group I than in groups II or III (1,037 +/- 212 vs. 862 +/- 387 ml vs. 681 +/- 117 ml, respectively; I vs. III, p < 0.05) and survival was shorter (230 +/- 25.5 min vs. 709 +/- 251 min vs. 662 +/- 428 min, respectively; I vs. II or III, p < 0.05). Cardiac arrhythmia caused death in most cases. Mean biochemical parameters increased progressively in all cases. Left anterior descending coronary artery flow stayed relatively constant in group II but increased in group III. Superior mesenteric artery flow returned to baseline in group II but increased in group III. Cardiac output was similar in groups II and III, but SGOT levels significantly differed (750 +/- 135 U/L vs. 359 +/- 157 U/L; p < 0.005). These results suggest that the swine model will be useful for studying ways to improve outcomes after prolonged hemorrhagic shock.

Animals↗
PubMedDate not supplied

Preliminary investigations into a new method of functional assessment of the fetal heart using a novel application of 'real-time' cardiac magnetic resonance imaging.

OBJECTIVES: Because of quantitative echocardiographic limitations of fetal ventricular volumes as well as poor windows, we sought to determine if real-time magnetic resonance imaging (MRI) could be used. METHODS: Real-time, functional, true fast imaging with steady-state precession, cardiac MRI was performed on 2 fetuses (one with hypoplastic left heart syndrome and one with ductal constriction). Fetal echocardiography was performed and cardiac index by Doppler was used to validate volume measures by MRI. RESULTS: This technique was able to visualize the beating heart and assess ventricular volumes. Cardiac index and assessment of right ventricular hypertrophy and dilation by echocardiography were consistent with the ventricular volumes and right ventricular hypertrophy obtained by cardiac MRI. CONCLUSION: Real-time, functional fetal cardiac MRI is possible and can be used to quantitatively assess ventricular volumes and cardiac index in utero.

Adult↗
PubMedDate not supplied

A boy who stops taking stimulants for "ADHD": commentaries on a Pediatrics case study.

This article presents eight commentaries on a case study published in the journal Pediatrics in 2001. The case study, introduced in Pediatrics to highlight the issue of adolescents' compliance with drug treatment in a "high-prevalence neurobehavioral condition," briefly describes an adolescent boy who announces that he no longer needs the methylphenidate he was prescribed for ADHD and had been taking for the last five years. We invited experienced professionals from the disciplines of psychiatry, psychology, counseling, education, and occupational therapy to comment on the case and make recommendations to the adolescent boy in the case study, his family, and professionals. Their commentaries highlight issues rarely discussed in the mainstream literature, including: the extent to which ADHD is erroneously portrayed and vigorously managed as a disease; the lack of validity of the ADHD construct in adolescence; the widespread use of stimulants as performance-enhancing drugs; the need to respect an adolescent's gut instinct and developing decisions; the importance of family dynamics in ADHD-like situations; the need to ease stimulant withdrawal effects; and the human rights of children prescribed psychotropic drugs.

Adolescent↗