H. Keith Brown

Selective neurotoxic action of capsaicin on glomerular C-type terminals in rat substantia gelatinosa

This study demonstrates that capsaicin exerts a selective neurotoxic action to induce degeneration of glomerular C-type nerve terminals in adult rats. Since the C terminals may be essential components of the circuitry for modulation of pain, it is suggested that capsaicin induced analgesia is the result of this neurotoxic action.

Composite and classified color display in MR imaging of the female pelvis

Because of its superior soft-tissue-imaging capabilities, MRI has proved to be an excellent modality for visualizing the contents of the female pelvis. In an effort to potentially improve gynecological MRI studies, we have applied color composite techniques to sets of spin-echo and gradient-echo gray-tone MR images obtained from various individuals. For composite generation, based on tissue region of interest calculated mean pixel intensity values, various colors were applied to spatially aligned images using a DEC MicroVAX II computer with interactive digital language (IDL) so that tissue contrast patterns could be optimized in the final image. The IDL procedures, which are similar to those used in NASAs LANDSAT image processing system, allowed the generation of single composite images displaying the combined information present in a series of spatially aligned images acquired using different pulse sequences. With our composite generation techniques, it was possible to generate seminatural-appearing color images of the female pelvis that possessed enhanced conspicuity of specific tissues and fluids. For comparison with color composites, classified images were also generated based on computer recognition and statistical separation of distinct tissue intensity patterns in an image set using the maximum likelihood processing algorithm.

Ultrastructure and quantitative synaptology of the sacral parasympathetic nucleus

SummaryThis study examines the anatomical substrate for the spinal micturition reflex. Light microscopy of pyridine silver-stained sections revealed that the sacral parasympathetic nucleus (SPN) exists as a broken column or chain of cell clusters located along the intermediolateral portion of the dorsal horn in sacral segments S2–S4. Quantitative analysis of neuropil components in electron micrographs provides data for each type of bouton identified in this nucleus. On the somata of these neurons, boutons containing clear spherical vesicles (S type) comprise 70% of the bouton population. Terminals containing three or more dense core vesicles (GS boutons) account for 26% and boutons containing flattened vesicles (F boutons) comprise 4% of the population. F boutons are more common on large dendrites where they comprise 10% of the total bouton population.The actual population density of each bouton type is most evident when the number of boutons is expressed as boutons per 100 μm of membrane length (btn/100 μm). S type boutons are the most frequently encountered type. The population density of S boutons is the same on soma and dendrites at 6.66 btn/100 μm. F boutons are more numerous on large (> 2 μm) dendrites (1.28 btn/100 μm) than on small dendrites (0.63 btn/100 μm) or on somata (0.36 btn/ 100 μm). GS boutons occur more frequently on small dendrites (3.66 btn/100 μm) than on somata (2.29 btn/100 μm), large dendrites (2.88 btn/100 μm) or medium dendrites (2.27 btn/ 100 μm). These data suggest that the dense core vesicle-containing boutons are applied primarily to small (<1 μm) dendrites and that F boutons are associated mostly with large or proximal dendrites.These results provide a quantitative profile of the synaptic input to the sacral autonomic (parasympathetic) neurons which innervate the urinary bladder and demonstrate specific population differences on various postsynaptic structures in this nucleus.This study examines the anatomical substrate for the spinal micturition reflex. Light microscopy of pyridine silver-stained sections revealed that the sacral parasympathetic nucleus (SPN) exists as a broken column or chain of cell clusters located along the intermediolateral portion of the dorsal horn in sacral segments S2–S4. Quantitative analysis of neuropil components in electron micrographs provides data for each type of bouton identified in this nucleus. On the somata of these neurons, boutons containing clear spherical vesicles (S type) comprise 70% of the bouton population. Terminals containing three or more dense core vesicles (GS boutons) account for 26% and boutons containing flattened vesicles (F boutons) comprise 4% of the population. F boutons are more common on large dendrites where they comprise 10% of the total bouton population.

PC-based multiparameter full-color display for tissue segmentation in MRI of adnexal masses.

Objective Our purpose was to apply full-color composite generation methods to multiparameter MRI to assess the ability of the technique to quantitatively segment clinically important anatomic and pathologic tissues. Materials and Methods: With use of a personal computer with a 386 micro processor and full-color (24 bit) graphics display capabilities, custom and commercially available image-processing softwares were applied to spatially aligned multiparameter SE MR image sets obtained from six patients under going diagnostic work-up for suspected adnexal or pelvic masses to generate intensity-based color composites. To quantitatively assess the ability of this technique to differentially segment anatomically and pathologically confirmed tissue types into unique color regions within the full-color spectrum, color image analysis was performed on the multiparameter color composites within each patient case, and the results were compared using 95% confidence intervals. Results: Based on the results of pathologic correlation and color image analysis, the generation of full-color composites represents a feasible technique for compressing the diverse tissue contrast data present in multiparameter MR images of adnexal masses. Conclusion: With this technique, it is possible to generate composites that simultaneously display uniquely color-coded anatomic and pathologic tissue information within the context of partially natural-appearing images.

An ultrastructural examination of dorsal root input to the sacral secondary visceral gray.

Dorsal root input to the sacral secondary visceral gray was examined in the adult cat using an orthograde degeneration technique. Five days after unilateral, intradural section of sacral dorsal roots electron-microscopic evidence of synaptic degeneration was seen throughout the nucleus ipsilateral to the side of the lesion. Degenerating sacral primary afferents in this nuclear region were associated mainly with S and GS type boutons. S type synapses showed two distinct degenerative responses. Some of the degenerating boutons were swollen with synaptic vesicles clustered tightly near the presynaptic membrane. Others appear shrunken with consequent packing of vesicles and mitochondria within the presynaptic terminal. Degenerating S terminals were found mainly on dendrites. S type synapses on nerve cell bodies appeared to be unaffected by dorsal root section. The degenerative response of sacral primary afferents associated with GS boutons was characterized by marked swelling of the presynaptic terminal and the presence of significant amounts of glycogen. Degenerating GS boutons were observed on both cell bodies and dendrites. These observations provide morphologic evidence of a direct synaptic link between dorsal root afferents and nerve cells in the sacral secondary visceral gray.

A quantitative ultrastructural analysis of the synaptic population in the sacral visceral gray

Abstract The synaptic distribution in the sacral visceral gray of the cat was examined. Synaptic complexes exhibiting a distinct membrane specialization were identified and classified according to vesicle type and number. Boutons containing clear spherical vesicles (S type) account for more than 63% of the synaptic contacts on both cell bodies and dendrites. Terminals containing three or more granular vesicles (GS type) comprise between 23 and 31% of the synapses in the nucleus. F boutons are less frequently seen (3–6%) as are T type boutons (1–2%). Presynaptic terminals containing a predominance of dense core vesicles (GG type) constitute less than 1% of the total synapses in this neuropil and are found only on dendrites. Nerve cell bodies receive approximately five synaptic contacts per 100 μm of postsynaptic membrane. Large and medium size dendrites are contacted by an average of seven boutons per 100 μm of postsynaptic membrane and small dendrites have the highest distribution (approximately 12 per 100 μm). Comparison of the percentage distribution of various types of synapses in this nucleus reveals little variation between cell bodies and dendrites. However, expression of the synaptic population as boutons per 100 μm of available postsynaptic membrane clearly illustrates intranuclear differences in synaptic distribution not seen in percentage type comparisons.

Interaction of Delta-9-Tetrahydrocannabinol with Herpesviruses and Cultural Conditions Associated with Drug-Induced Anti-Cellular Effects

Delta-9-tetrahydrocannabinol (THC) is a small molecular weight lipophilic substance which is the primary psychoactive ingredient present in marijuana. This three-ringed molecule has been shown to bind to serum lipoproteins and is believed to exert much of its psychoactive effects by its ability to bind to membranes of cells in the central nervous system (1). The mechanism by which THC exerts psychoactive activity is unknown.

Primary afferent projections to the sacral secondary visceral gray: A quantitative electron microscopic examination in the cat

Afferent input to the sacral secondary visceral gray matter was studied by quantitatively assessing synaptic degeneration that follows ipsilateral sacral dorsal rhizotomy. Five days after the lesions, slightly more than 25% of the synaptic contacts showed degenerative changes. The majority of the reactive synapses contained clear spherical vesicles (S type). Boutons containing dense core vesicles (GS type) also showed degenerative changes, and together with S boutons constituted more than 96% of the reactive terminals. Degenerating S type synapses were found only on dendrites whereas GS boutons were observed on both cell bodies and dendrites. Further examination revealed that although there were more S than GS synapses in the nucleus, the percentage of GS terminals affected was greater than that for S type boutons. These results demonstrate a direct primary afferent input to the sacral secondary visceral gray matter utilizing chiefly two different synaptic types.

Tissue Segmentation by Multiparameter Full-Color Composite Techniques: Clinical Application in Magnetic Resonance Imaging of Adnexal Masses

Ovarian neoplasms represent a significant cause of cancer-related mortality in women. Since most women present with advanced stage disease, substantial diagnostic advances must take place to achieve improvement in survival. Magnetic Resonance (MR) imaging has been shown to exhibit greater sensitivity and specificity than computed tomography or ultrasound for the detection of certain adnexal masses, and has the potential to become an important tool in the diagnosis and characterization of ovarian neoplasms (1). A simple algorithm for tissue segmentation by multiparameter color composite generation (2,3) was applied to a variety of adnexal mass cases to determine the feasibility of this application. The pathologic diversity of adnexal masses provides a useful model for tissue segmentation and tumor characterization (4,5).