Trichobezoars in baboons.

BACKGROUND: There is little information available concerning trichobezoars in the non-human primate literature. METHODS: We evaluated 118 cases of trichobezoar in baboons over a 29-year period at the Southwest National Primate Research Center. RESULTS: The anatomic locations affected in decreasing order were the stomach, small intestine, cecum, esophagus and colon. The most common clinical history was weight loss. The most frequent associated pathology included gastrointestinal inflammation and ulceration, emaciation, peritonitis, intussusception, pneumonia, and aspiration. Trichobezoars were the cause of death in nine baboons and the reason for euthanasia in 12. Females were 2.14 times more likely than males to be affected. The greater the percentage of group housing time, the more likely the baboon is to develop trichobezoars. CONCLUSIONS: The baboon may present a useful model to evaluate the etiology, genetic predisposition, physiopathology, neurobiology, and treatment response of trichobezoars.

Low dose rotenone treatment causes selective transcriptional activation of cell death related pathways in dopaminergic neurons in vivo.

Mitochondrial complex I inhibition has been implicated in the degeneration of midbrain dopaminergic (DA) neurons in Parkinson's disease. However, the mechanisms and pathways that determine the cellular fate of DA neurons downstream of the mitochondrial dysfunction have not been fully identified. We conducted cell-type specific gene array experiments with nigral DA neurons from rats treated with the complex I inhibitor, rotenone, at a dose that does not induce cell death. The genome wide screen identified transcriptional changes in multiple cell death related pathways that are indicative of a simultaneous activation of both degenerative and protective mechanisms. Quantitative PCR analyses of a subset of these genes in different neuronal populations of the basal ganglia revealed that some of the changes are specific for DA neurons, suggesting that these neurons are highly sensitive to rotenone. Our data provide insight into potentially defensive strategies of DA neurons against disease relevant insults.

Comparison of optical coherence tomography imaging of cataracts with histopathology.

This paper presents a comparison of in vivo optical coherence tomography (OCT) captured cataract images to subsequent histopathological examination of the lenticular opacities. OCT imaging was performed on anesthetized Rhesus monkeys, known as the delayed effects colony (DEC), with documented cataracts. These monkeys were exposed to several types of radiation during the mid and late 1960s. The radiation and age related cataracts in these animals were closely monitored using a unique grading system developed specifically for the DEC. In addition to this system, a modified version of a common cataract grading scheme for use in humans was applied. Of the original 18 monkeys imaged, lenses were collected at necropsy from seven of these animals, processed, and compared to OCT images. Results showed a direct correlation between the vertical OCT images and the cataractous lesions seen on corresponding histopathologic sections of the lenses. Based on the images obtained and their corresponding documented comparison to histopathology, OCT showed tremendous potential to aid identification and characterization of cataracts. There can be artifactual problems with the images related to movement and shadows produced by opacities. However, with the advent of increased speed in imaging and multiplanar imaging, these disadvantages may easily be overcome. © 1999 Society of Photo-Optical Instrumentation Engineers.

A comparison of retinal morphology viewed by optical coherence tomography and by light microscopy.

OBJECTIVE: To compare the cross-sectional images of primate retinal morphology obtained by optical coherence tomography (OCT) with light microscopy to determine the retinal components represented in OCT images. METHODS: Laser pulses were delivered to the retina to create small marker lesions in a Macaca mulatta. These lesions were used to align in vivo OCT scans and ex vivum histologic cross sections for image comparison. RESULTS: The OCT images demonstrated reproducible patterns of retinal morphology that corresponded to the location of retinal layers seen on light microscopic overlays. Layers of relative high reflectivity corresponded to horizontally aligned retinal components such as the nerve fiber layer and plexiform layers, as well as to the retinal pigment epithelium and choroid. In contrast, the nuclear layers and the photoreceptor inner and outer segments demonstrated relative low reflectivity by OCT. CONCLUSIONS: Retinal morphology and macular OCT imaging correlate well, with alignment of areas of high and low reflectivity to specific retinal and choroidal elements. Resolution of retinal structures by OCT depends on the contrast in relative reflectivity of adjacent structures. Use of this tool will enable expanded study of retinal morphology, both normal and pathologic, as it evolves in vivo.

Argon laser retinal lesions evaluated in vivo by optical coherence tomography.

PURPOSE: To assess the in vivo evolution of argon laser retinal lesions by correlating the cross-sectional structure from sequential optical coherence tomography with histopathologic sectioning. METHODS: Argon laser lesions were created in the retinas of Macaca mulatta and evaluated by cross-section optical coherence tomography, which was compared at selected time points with corresponding histopathology. RESULTS: Argon laser lesions induced an optical coherence tomography pattern of early outer retinal relative high reflectivity with subsequent surrounding relative low reflectivity that correlated well with histopathologic findings. The in vivo optical coherence tomography images of macular laser lesions clearly demonstrated differences in pathologic response by retinal layer over time. CONCLUSION: The novel sequential imaging of rapidly evolving macular lesions with optical coherence tomography provides new insight into the patterns of acute tissue response by cross-sectional layer. This sequential imaging technique will aid in our understanding of the rapid evolution of retinal pathology and response to treatment in the research and clinical setting.

Retinal damage and laser-induced breakdown produced by ultrashort-pulse lasers.

BACKGROUND: In vivo retinal injury studies using ultra-short-pulse lasers at visible wavelengths for both rabbit and primate eyes have shown that the degree of injury to the retina is not proportional to the pulse energy, especially at suprathreshold levels. In this paper we present results of calculations and measurements for laser-induced breakdown (LIB), bubble generation, and self-focusing within the eye. METHODS: We recorded on video and measured the first in vivo LIB and bubble generation thresholds within the vitreous in rabbit and primate eyes, using external optics and femtosecond pulses. These thresholds were then compared with calculations from our LIB model, and calculations were made for self-focusing effects within the vitreous for the high peak power pulses. RESULTS: Results of our nonlinear modeling and calculations for self-focusing and LIB within the eye were compared with experimental results. The LIB ED50 bubble threshold for the monkey eye was measured and found to be 0.56 microJ at 120 fs, compared with the minimum visible lesion (MVL) threshold of 0.43 microJ at 90 fs. Self-focusing effects were found to be possible for pulsewidths below 1 ps and are probably a contributing factor in femtosecond-pulse LIB in the eye. CONCLUSIONS: Based on our measurements for the MVL thresholds and LIB bubble generation thresholds in the monkey eye, we conclude that in the femtosecond pulsewidth regime for visible laser pulses, LIB and self-focusing are contributing factors in the lesion thresholds measured. Our results may also explain why it is so difficult to produce hemorrhagic lesions in either the rabbit or primate eye with visible 100-fs laser pulses even at 100 microJ of energy.

Visible retinal lesions from ultrashort laser pulses in the primate eye.

PURPOSE: To evaluate the effects of ultrashort laser pulses of visible wavelengths on the retinas of rhesus monkey eyes and to perform threshold measurements for minimum visible lesions (MVLs) at pulsewidths from nanoseconds to femtoseconds. METHODS: Single laser pulses at visible wavelengths were placed within the macular area of live rhesus monkey eyes at varying pulse energies at five pulsewidths (4 ns, 60 ps, 3 ps, 600 fs, and 90 fs). The number of visible lesions was determined after 1 hour and 24 hours postexposure, and a probit analysis was performed for the dosage, causing 50% probability for damage (ED50) as well as the 95% fiducial intervals for ED50. Fluorescein angiography (FA) was performed, and hemorrhagic lesions were recorded as they became visible. RESULTS: The ED50 threshold doses at the 1-hour reading, calculated from the measured data, decreased from 1.5 microJ at 4 ns to 0.60 microJ at 600 fs, but it increased to 1.18 microJ at 90 fs. At the 24-hour reading, the ED50 calculated doses decreased from 0.90 microJ at 4 ns down to 0.26 microJ at 600 fs, but it increased to 0.43 microJ at 90 fs. Fluorescein angiography visible lesion ED50 values were all higher than MVL values, showing that FA was not as sensitive in determining damage levels. CONCLUSIONS: Laser pulses for pulsewidths between 4 ns and 90 fs are capable of producing visible lesions in monkey eyes with energies less than 1 microJ. Fluorescein angiography is not as sensitive in determining threshold levels as visually observing the retina through a fundus camera.

A conscious baboon model for evaluation of hemodynamics in altered gravity.

A model was developed for evaluation of cardiovascular parameters in conscious baboons exposed to altered gravitational environments. Baboons were trained to sit quietly in a confinement chair of unique design which allowed a range of normal physical activity. They were then instrumented with high-fidelity blood pressure transducers in the aorta and left ventricle, electromagnetic flow probes encircling the proximal ascending aorta, left and right atrial fluid catheters, left ventricular sonomicrometer crystals in a 3-axis configuration, and a hydraulic occluder cuff encircling the inferior vena cava. Catheters and transducer wires were exteriorized at the midscapular region of the back. Viability of percutaneous exit sites was enhanced by use of velour cuffs on the transducer wires, providing a scaffold for wound healing. Pressure transducers and flow probes were calibrated and balanced during postoperative cardiac catheterization procedures. This instrumentation allowed measurement of beat-to-beat stroke volume and cardiac output not reliant on thermodilution techniques. Postoperative longevity was from 1 to 10 months. Instrumentation failure included endocardial trapping of ventricular pressure transducers, corrosion of ventricular sonomicrometer crystals, and catheter tip thrombosis. Acquisition of high quality data was possible with this model in several different environments of altered gravitational stress, allowing characterization of aortic flow and ventricular performance.