Biomedical subjects

V N Carrasco

Publications and source records attributed to V N Carrasco.

9 recordsLinked to original sources

PubMed1992

Glyoxylic acid in the study of autonomic innervation in the gerbil cochlea.

The autonomic innervation of the inner ear has been investigated earlier, yet questions concerning the origin, function, extent, and distribution of sympathetic nerves in the cochlea still remain unanswered. This study investigates the extent and distribution of adrenergic nerves in the cochlea. Our procedure combines the glyoxylic acid method of catecholamine fluorophore identification with rapid dissection, decalcification, and whole-mount slide preparation techniques to topographically trace the adrenergic innervation of the cochlear infrastructure. We have demonstrated that perivascular adrenergic innervation extends beyond the immediate branches of the modiolar artery and reaches into radiating arterioles. These findings also suggest the possibility of segmental regulation of cochlear blood flow.

Adrenergic Fibers↗

PubMed1992

Defect reconstruction and cerebrospinal fluid management in neurotologic skull base tumors with intracranial extension.

Intracranial extension (ICE) is the spread of tumor into the subarachnoid space through dura or along cranial nerve roots. The single-stage removal of the skull base tumor with its ICE has been confounded by cerebrospinal fluid management and defect reconstruction. The purpose of this report is to review a current protocol for managing the cranial base tumor and its ICE as a unit. The ventricular shunting paper of 1987 is retracted. All tumors were managed at a single stage. Defect reconstruction was size dependent. Ninety-eight neurotologic skull base tumors with ICE were managed from 1971 to 1991. The new protocol was initiated in 1987. Results specific to this group are highlighted. For glomus tumors, cerebrospinal fluid leak rates have been dramatically reduced overall from 14.5% to 4%. The leak rates for nonglomus tumors, overall, have improved slightly. Complications are discussed. The development of this surgical approach protocol improves the functional outcome in patients of surgeons who aspire to disease "cure" rather than "control."

Adolescent↗

PubMed1990

Cochlear microcirculation. Effect of adrenergic agonists on arteriole diameter.

We used intravital fluorescent microscopy coupled with computerized video image processing to examine the cochlear microvasculature. In Mongolian gerbils the bulla was opened ventrally and a small window was made in the second turn of the cochlea. After fluorescein isothiocyanate-dextran administration, the radiating arterioles were video-recorded under X675 magnification. Computer determinations of arteriolar response to norepinephrine bitartrate (mixed alpha 1/alpha 2 agonist), phenylephrine hydrochloride (alpha 1 agonist), and UK 14,304 tartrate (alpha 2 agonist) were made at multiple dose levels over time. Findings were consistent with arteriolar constriction in response to alpha-adrenergic stimulation. The presence of alpha 1 and alpha 2 receptors was established, and a predominance of alpha 2 receptors in the cochlea was suggested.

Adrenergic alpha-Agonists↗

PubMed1990

Cochlear microcirculation in young and old gerbils.

Human postmortem studies as well as epidemiologic investigations have implicated the peripheral vascular system as one of the etiologic factors of presbycusis. This study uses the surface dissection microsphere method for regional cochlear blood flow analysis and morphometric techniques for quantifying capillary density in the stria vascularis. In this study 11 old and 10 young gerbils were used. Our results indicate that blood flow in the cochlea was decreased in the old gerbils. This decrease was most obvious in the lateral portion (stria vascularis). The decrease of blood flow in older animals was clearly not related to loss of strial capillaries with aging. The decreased flow to the lateral portion must arise from either decreased perfusion pressure or from increased vascular resistance. This decreased blood flow in the aged animals supports a vascular theory of presbycusis.

Aging↗

PubMed1990

Revision mastoidectomy.

The objectives of modern otologic surgery are elimination of disease and restoration of hearing. Persistent drainage and recurrent infection after mastoid surgery hallmark failure at achieving these goals. Medical management consisting of meticulous aural toilette and attention to accompanying medical disorders will often yield resolution; however, a significant number of patients will still require surgical revision. While intact canal wall procedures have reduced the chronic difficulties associated with open cavities, they are prone to failure. Careful assessment of the disease process and development of a surgical approach that is both flexible and complete will maximize success in revision surgery. Disease persistence after revision should be considered in the spectrum of complications, even though at times it is nearly impossible to avoid. We describe the reasons for failure of mastoid procedures, common areas of retained disease, and review key concepts of revision.

Anti-Bacterial Agents↗

PubMed1990

Student Research Award 1990. Catecholaminergic innervation of the inner ear.

Cochlear blood flow has been shown to be controlled, in part, by the sympathetic nervous system. We have used immunocytochemical staining for tyrosine hydroxylase (TH) to further demonstrate the extent of catecholaminergic innervation of the cochlea. Deeply anesthetized Mongolian gerbils were systemically perfused with phosphate-buffered saline, followed by 4% paraformaldehyde. The cochleae were dissected out and post-fixed for 3 hours in 4% paraformaldehyde. They were then incubated in anti-TH antibody and subsequently processed using the avidin-biotin immunoperoxidase method. Microscopic examination of whole-mounted tissue revealed many immunoreactive fibers on the spiral modiolar artery. TH-positive fibers have also been found on both radiating arterioles and radial collecting venules, which has not been previously reported. With innervation of these small vessels, blood flow in the cochlea may be segmentally controlled. We also further describe the organization of TH-positive fibers in the osseous spiral lamina.

Animals↗

PubMed1990

Analysis of blood flow in the tympanic membrane: the use of intravital fluorescence microscopy.

The successful healing of the tympanic membrane (TM) following myringotomy or tympanoplasty is dependent upon the maintenance of the blood supply to the injured area of the TM. The blood supply of the TM is derived from the manubrial plexus and the peripheral plexus of vessels. This study concentrated on measuring blood flow derived from the manubrial vessels. The TM of the guinea pig was used as an in vivo model. Ten Outbred Hartley guinea pigs were anesthetized with Inactin 100 mg/kg, the common carotid artery cannulated, and FITC-dextran 150 injected intra-arterially. Blood pressures (mean 66.0 mmHg +/- 5.0 mmHg) and heart rates (330 bpm +/- 12.0 bpm) remained relatively constant throughout the experiment. Following injection of FITC-dextran 150, the TM was visualized under fluorescence microscopy and images recorded by video recorder; measurements of vessel diameter, blood velocity, and blood flow were made. Analysis of the in vivo studies revealed blood flow in the tympanic membrane to travel in two directions: down the manubrial artery towards the periphery and up the manubrial veins from vessels in the periphery. The manubrial artery divides and branches into a series of arcading vessels that extend towards the periphery of the TM. Manubrial artery diameter was measured (mean 0.0521 mm +/- 0.0004 mm) and blood flow calculated (mean 0.0439 mm3/min +/- 0.0007 mm3/min). Blood flow from the manubrial artery supplying the superior quadrants (0.18 mm3/min +/- 0.01) was statistically greater when compared to the blood flow in the inferior quadrants (0.08 mm3/min +/- 0.007) (p less than .001).

Animals↗

PubMed1989

Gadolinium. The new gold standard for diagnosing cerebellopontine angle tumors.

All physicians involved with the diagnosis and management of patients with tumors in the temporal bone and cerebellopontine angle are faced with the challenge removing these tumors while preserving hearing. Part of the challenge is to make the diagnosis while the tumor is still small enough to attempt a hearing-conservation surgical approach. Air-contrast (air cisternography) computed tomography is the "gold standard" by which all techniques of diagnosis are compared. Most physicians, however, are reluctant to use this test as a screen for tumors because of the associated morbidity, time, and expense. We present three case reports of contrast-enhanced magnetic resonance imaging for the detection of small intracanalicular or cerebellopontine angle tumors, and review the literature of this new and exciting technology. We feel that gadolinium-enhanced magnetic resonance imaging is now the procedure of choice for evaluating patients with suspected temporal bone tumors.

Cerebellar Neoplasms↗

PubMed1989

Measurement of cochlear blood flow: intravital fluorescence microscopy.

A technique is described for directly observing in vivo cochlear microvasculature in the gerbil for physiologic and experimentally induced changes in vessel diameter and blood flow velocity. Measurements are made from computer processed video images of surgically exposed microvessels. These images are obtained using intravital fluorescence microscopy (IFM) with epi-illumination. The Mongolian gerbil is an ideal animal model for circulatory studies of the inner ear. It has a stable heart rate and blood pressure under urethane/alpha-chloralose anesthesia and its cochlea is surgically accessible. A window is created over the feeding artery (anterior inferior cerebellar artery) and over the stria vascularis of the second turn of the cochlea, atraumatically exposing radiating arterioles and strial capillaries. Our system of IFM provides images that are videorecorded, digitally analyzed with a computer image processor, and enhanced according to the type of measurement desired. Velocity measurements are obtained by tracking plasma gaps or single fluorescent labeled red blood cells through successive frames of the videorecorded images. This experimental technique allows us to analyze circulatory responsiveness to a variety of vasoactive drugs administered regionally to the cochlea in concentrations not affecting systemic circulation.

Animals↗