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Biomedical subjects

D G Gomez

Publications and source records attributed to D G Gomez.

At least 19 recordsLinked to original sources
PubMed1996

Quantitation of normal canine hippocampus formation volume: correlation of MRI with gross histology.

The hippocampal formation possesses an important role in the development and maintenance of short-term memory. In this study, magnetic resonance imaging (MRI) and gross histology were used to quantify the volume of the hippocampal formation in canines. High resolution MRI, using 1 mm thick slices and an intraplanar resolution of 0.35 mm was performed at 2.0 T both in vivo and in vitro following in situ fixation. The volumes of the hippocampal formations were determined from MR images and compared to those obtained from one mm thick gross histologic sections. The average volume of the canine hippocampal formation, measured from in vivo and in vitro MR images was 476.0 +/- 79.5 and 467.3 +/- 53.7 mm3, respectively. Determined from gross histology, the volume of the hippocampal formation was 463.6 +/- 24.1 mm3. Quantitation of the canine hippocampal formation using in vivo MRI showed good correlation with in vitro MRI and histology, verifying the reliability and reproducibility of in vivo MRI measurements. High resolution MRI using 1 mm thick slices through the whole canine hippocampal formation is necessary for accurate volume determination of a structure of this size.

Animals↗
PubMed1994

Direct in vivo observation of transventricular absorption in the hydrocephalic dog using magnetic resonance imaging.

RATIONALE AND OBJECTIVES: A model of chronic noncommunicating hydrocephalus in canines was developed, and gadolinium-DTPA (Gd-DTPA)-enhanced magnetic resonance imaging, physiologic and morphologic studies were performed to investigate transventricular absorption of cerebrospinal fluid. METHODS: Chronic hydrocephalus was induced in 12 mongrel dogs by injection of a silastic mixture into the prepontine cisterns. Ventricular pressure was measured during the development of hydrocephalus, and lateral ventriculo-ventricular perfusions with Gd-DTPA were performed under controlled conditions during serial magnetic resonance imaging studies. RESULTS: Hydrocephalus developed over an average of 129 +/- 24 days after induction, and the intraventricular pressure increased from an initial level of 14 +/- 4 cm H2O to a stabilized plateau of 25 +/- 5 cm H2O. Increased signal intensity in the brain matter, as seen on magnetic resonance images of chronic hydrocephalic dogs perfused with Gd-DTPA in the lateral ventricles, was consistent with the presence of the contrast agent in the periventricular extracellular space. This increased signal intensity was not observed in control animals. CONCLUSIONS: These results provide direct evidence of transventricular absorption in chronic hydrocephalus.

Absorption↗
PubMed1988

Cerebrospinal fluid absorption in the rabbit. Optic pathways.

Fifteen rabbits were intrathecally perfused with horseradish peroxidase at normal cerebrospinal fluid pressures. Horseradish peroxidase was found in the subarachnoid space around the optic nerve; it permeated the pia and penetrated within the nerve, occupying extracellular spaces between myelinated axons and glial cells up to the area of the lamina cribrosa. Horseradish peroxidase also crossed the perineural sclera and the border tissue of Elschnig to spread into the choroid where it was mostly seen within choriocapillaris, venules, and veins crossing through interendothelial spaces. "Bulk" cerebrospinal fluid absorption in the eye appears to occur through venous drainage in the choroid and SAS.

Animals↗
PubMed1981

The lateral, third, and fourth ventricle choroid plexus of the dog: a structural and ultrastructural study.

The morphology of the choroid plexuses of the lateral, third, and fourth ventricles in dogs was studied by histological and ultrastructural techniques after in situ fixation. Most portions of the plexus in the lateral ventricle showed a parallel arrangement of capillaries, producing a fine corrugation of the overlying layer of epithelial cells. Relatively large amounts of connective tissue separated the capillaries from the epithelium. The fourth ventricle choroid plexus showed short capillary loops projecting into the ventricle and more intimately covered by epithelium. Smaller amounts of connective tissue separated the capillaries from the epithelium. The choroid plexus of the third ventricle showed characteristics seen in the plexuses of both the lateral and fourth ventricles. The total surface of the choroid plexuses in the dog averaged 10.7 cm2, of which 55% was fourth ventricle choroid plexus.

Animals↗
PubMed1981

Subacute reactions to intrathecal amipaque (metrizamide), conray and dimer X: a structural and ultrastructural study.

Adult New Zealand rabbits were injected intrathecally with 200 or 300 mgI/ml of metrizamide, meglumine iocarmate or meglumine iothalamate. They were placed in the Trendelenburg position for 20 min and allowed to survive for 1, 2 or 3 weeks. Sacrifice was by intraarterial perfusion of aldehydes under anesthesia followed by preparation of brain and major venous sinuses for light and electron microscopy. Major findings were subpial edema and inflammatory reaction of superficial brain, leptomeninges, subarachnoid space and arachnoid granulations. They were most severe after iothalamate and milder after metrizamide. The severity decreased with time. It is of significance that severe reactions occurred after 300 mgI/ml concentration of metrizamide.

Animals↗
PubMed1979

Passage of Amipaque (metrizamide) through the arachnoid granulations.

125I labelled Amipaque (metrizamide) was introduced by cisternal puncture into six rabbits and perfused at various pressures. The torcular was exposed, frozen rapidly, and excised intact. Sections of arachnoid proliferations were made from the frozen specimen and either freeze dried or sandwiched directly for autoradiography. Some specimens were freeze dried en bloc prior to sectioning and sandwiching. All sections were exposed for 2-3 weeks at -80 degrees C prior to development of the autoradiographs. On microscopic examinations of the autoradiographs most of the activity was in the tubules or between cells suggesting intercellular passage. Some label was also present within the brain. The significance of this is discussed.

Absorption↗
PubMed1978

Microradiographic study of cerebral and ocular aneurysms in hypertensive rabbits.

Cerebral and ocular microaneurysms were produced in rabbits made hypertensive by surgically induced silk-turpentine perinephritis combined with contralateral nephrectomy 7 days later. The aneurysms distributed throughout the brain and iris were studied by microradiography; a few representative aneurysms selected from the microradiographs were studied histologically. The microradiographic findings and histological sections correlated well. Intracranial microaneurysms were multiple and frequently located in the basal ganglia and near the cortex. Arterial changes in the iris paralleled intracranial arterial changes in degree and type except for the addition of hemorrhage around some microaneurysms. The results of this study show the potential of microradiography and histological sections guided by microradiography for studying the natural history of hypertensive arterial lesions and support the contention that hypertension, microaneurysms and intracerebral hemorrhages are related.

Aneurysm↗
PubMed1977

Possible causes of complications of myelography with water-soluble contrast medium.

The mechanisms of CSF formation and absorption have been reviewed. The conditions that alter the rate of CSF formation and absorption may change the concentration of contrast in the cranial cisterns and the rate of passage through the cisterns. The significance of these alterations in relation to the complications of myelography with water-soluble contrast media is discussed.

Contrast Media↗
PubMed1976

Human spinal arachnoid villi and granulations.

Human spinal arachnoid villi and granulations were studied after distension by a subarachnoid perfusion of Berlin blue and trypan blue. These proliferations were distributed on almost every nerve root in the thoracic and lumbar region. Human spinal arachnoid villi and granulations were divided into those located entirely internal to the dura, those that extended into the dura, and those that penetrated the dura completely. Venous sinuses were closely related to most arachnoid proliferations.

Arachnoid↗
PubMedDate not supplied

Evidence for transventricular absorption in the hydrocephalic dog.

Hydrocephalus was induced in 10 mongrel dogs by injection of a silastic mixture into the basal cisterns. The posterior part of the left lateral ventricle was isolated from the remainder of the ventricular system by introducing Pantopaque into both lateral ventricles and the third ventricle with the animals in prone positions. Labeled albumin injected into the posterior part of the left lateral ventricle was shown to enter the blood stream before it was shown in the fourth ventricle or vallecula. This provides qualitative evidence of transventricular absorption.

Absorption↗
PubMedDate not supplied

Cranial and spinal cerebrospinal fluid absorption and the clearance of water-soluble myelographic contrast media. A review.

Following myelography, water-soluble contrast media are cleared from the subarachnoid space with the cerebrospinal fluid via the cranial and spinal absorption pathways. These cerebrospinal fluid absorption pathways are reviewed. The effects of removal of excessive quantities of cerebrospinal fluid, increased numbers of cells in the cerebrospinal fluid, and dehydration are discussed.

Absorption↗