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Biomedical subjects

R D Cook

Publications and source records attributed to R D Cook.

At least 19 recordsLinked to original sources
PubMed2000

Effect of stenting after laryngotracheal reconstruction in a subglottic stenosis model.

OBJECTIVES: This study addresses the impact of stenting on early wound healing after laryngotracheal reconstruction (LTR) in a rabbit model with established subglottic stenosis. METHODS: Subglottic stenosis was created in 42 New Zealand white rabbits through a transoral, endoscopic technique. Three weeks later, endoscopy and axial CT were performed to document and grade the degree of stenosis. Subsequently, LTR was performed in all animals, with half of the animals receiving an intraluminal stent. Four rabbits from each group were euthanized on postoperative days 6, 9, 14, 21, and 28. Measurements of graft vascularization were obtained with a computerized image measurement program, and a comparison was made regarding the rate of vascularization. RESULTS: There was a statistically significant increase in the rate of vascularization in the stented group (mean 75% +/- 5% vs 56% +/- 3% at day 14; P < 0. 05). However, clinical and radiographic comparisons of the stented and nonstented specimens revealed a trend toward increased mucosal edema and granulation tissue in the stented group at later time intervals (days 21 and 28). CONCLUSION: This analysis suggests that stenting does not inhibit graft vascularization in the early postoperative period after LTR; however, complications were seen in the stented group at longer time intervals.

Animals↗
PubMed1999

Subglottic stenosis: correlation between computed tomography and bronchoscopy.

The evaluation of subglottic stenosis has been limited by the lack of standardized methods for determining the cross-sectional area and length of the stenotic segment. A rabbit model was used to prospectively evaluate the correlation between computed tomography (CT) and bronchoscopy in the evaluation of this disease. Subglottic stenosis was produced in 39 New Zealand White rabbits by a transoral endoscopic technique. The animals were evaluated 3 weeks later with spiral CT, rigid bronchoscopy, and open laryngotracheal exploration. Spiral CT was performed with the location, degree, and length of subglottic stenosis being determined by a blinded observer. Each animal then underwent rigid bronchoscopy and open laryngotracheal exploration for determination of the same measurements. Data were analyzed to determine the correlation between the radiographic and surgical techniques in evaluating the airway stenosis. With regard to the degree of stenosis, 94% of the rabbits were determined to have CT and bronchoscopic measurements that were within 15% (Pearson correlation .94, p < .05). With regard to the length of stenosis, 94% of animals had a measurement on CT that was within 2 mm of that observed upon open exploration (Pearson correlation .81, p < .05). The CT evaluation of subglottic stenosis correlated well with the currently used method of visual inspection at bronchoscopy in evaluating tracheal stenosis in this animal model. These data suggest that CT could serve as a useful adjunct in the evaluation of tracheal stenosis, especially when serial examinations are required.

Animals↗
PubMed1999

Cytotoxic changes in hair cells secondary to pneumococcal middle-ear infection.

To determine whether the bacterial toxins associated with otitis media could induce morphologic changes in the organ of Corti, we inoculated the middle-ear cavities of healthy guinea pigs with either Streptococcus pneumoniae or sterile saline and then examined the organ of Corti histologically at 1, 2, and 3 weeks postinoculation. We found that the outer hair cells (OHCs) in the infected ears underwent several changes that were dependent on both the length of time following inoculation and also the position of the OHCs in the cochlea. At 2 weeks postinoculation, 7.0 to 20% of the OHC nuclei from the infected animals became very swollen, with the most significant swelling occurring in the basal turn. At 3 weeks postinoculation, 2.5 to 3.5% of the OHCs were missing in the infected animals, with the most significant loss occurring in the basal and middle turns. These results suggest that bacterial otitis media can produce cytotoxic changes in the cochlea. These changes may be a clinically significant factor in the temporary and permanent sensorineural hearing loss that has been associated with bacterial otitis media.

Acute Disease↗
PubMed1998

Chronic conductive hearing loss in adults: effects on the auditory brainstem response and masking-level difference.

OBJECTIVE: To determine whether chronic conductive hearing loss in adults results in changes in the auditory brainstem response (ABR) similar to those observed in children with histories of otitis media with effusion. DESIGN: Test of effect of unilateral conductive hearing loss on adult ABR using age-matched control group and subjects as their own controls. SUBJECTS: Twelve adults with a history of unilateral conductive ear disease. An age-matched control group of 21 adults was also tested. METHODS: The ABR, an electrophysiologic test of auditory brainstem functioning, was used to evaluate possible brainstem abnormalities in the impaired listeners. In addition, the masking-level difference, a behavioral test of binaural auditory processing in the brainstem, was used. RESULTS: When comparing the patients' diseased ears with their healthy ears, significant delays were seen for wave V as well as for the I-V and III-V interwave intervals. For comparison with the control population, significant prolongations were again seen for wave V and for the III-V interwave intervals. In addition, reduced masking-level differences and significant correlations between the masking-level differences and the ABRs, independent of hearing threshold, were noted. CONCLUSIONS: The results suggest that chronic conductive impairment in adults leads to changes in the ABR similar to those observed in children with histories of otitis media with effusion. As such, these changes do not appear to be related to a critical period of development.

Adult↗
PubMed1998

Inactivation of microorganisms with microwaves at reduced temperatures.

We developed a pilot-plant nonthermal flow process using microwave energy to inactivate microorganisms. The process consists of multiple passes through the microwave generator. Each passed material goes to a receiving tank for subsequent passes. The flow rate was 0.96 to 1.26 kg/min and the dwell time per pass was 1.1 to 1.5 min. Five passes were used. The microwave energy is instantaneously and simultaneously applied to the system, and thermal energy is removed by a cooling tube within the process line in the microwave generator. The cooling tube maintains the temperature below 40 degrees C. There was significant reduction in microorganisms in water, 10% glucose solution, and apple juice, and in yeast in beer. There was a slight decrease in microorganisms in tomato juice, pineapple juice, apple cider, and beer; and no effect in skim milk.

Beer↗
PubMed1995

Preparation of casein using carbon dioxide.

The effects of pressure, temperature, residence time, and mass of skim milk on some characteristics of casein, prepared by precipitation with high pressure CO2, were examined in a batch reactor. For a 500-g milk sample, precipitation occurred at pressures > 2760 kPa and temperatures > 32 degrees C. Residence time was not significant and was held at 5 min. Yields were maximum at 2750 to 5520 kPa and at 38 to 49 degrees C for a 500-g milk sample. The resulting whey had a pH of 6.0. The casein product had an acceptable appearance and had greater solids, ash, and Ca contents than commercial acid caseins. Particle size distribution studies showed that the mean particle size was sensitive to precipitation pressure and temperature and was similar to that of acid caseins produced under laboratory conditions. The HPLC studies of the casein and whey fractions showed that precipitation by CO2 did not result in fractionation of casein or whey proteins to their component proteins.

Animals↗
PubMed1994

ACT3: a high-speed, high-precision electrical impedance tomograph.

This paper presents the design, implementation, and performance of Rensselaer's third-generation Adaptive Current Tomograph, ACT3. This system uses 32 current sources and 32 phase-sensitive voltmeters to make a 32-electrode system that is capable of applying arbitrary spatial patterns of current. The instrumentation provides 16 b precision on both the current values and the real and reactive voltage readings and can collect the data for a single image in 133 ms. Additionally, the instrument is able to automatically calibrate its voltmeters and current sources and adjust the current source output impedance under computer control. The major system components are discussed in detail and performance results are given. Images obtained using stationary agar targets and a moving pendulum in a phantom as well as in vivo resistivity profiles showing human respiration are shown.

Algorithms↗
PubMed1993

Characteristics of a retrovirus associated with Jembrana disease in Bali cattle.

A virus causing Jembrana disease in Bali cattle (Bos javanicus) was demonstrated to have characteristics of a retrovirus. Reverse transcriptase activity was detected in virus purified by sucrose gradient centrifugation. Electron microscopic examination of tissue from the affected cattle indicated that the virus matured by C-type budding through the plasma membrane and into intracytoplasmic vacuoles of cells in lymphoid tissue, with the formation of circular enveloped virus particles ranging in diameter from 96 to 124 nm with an eccentric nucleoid. Western immunoblotting using sera from recovered animals demonstrated virus proteins of M(r) 100K, 45K, 42K, 33K, 26K, 16K and 14K. The 26K protein of Jembrana disease virus cross-reacted in Western blots with the 26K capsid protein of bovine immunodeficiency virus (BIV). The apparent morphogenesis, protein structure and antigenic relationship with BIV suggested the virus was a lentivirus.

Animals↗
PubMed1991

Stress fractures of the anterior tibial diaphysis.

Stress fracture of the anterior tibial diaphysis is rare and occurs mostly in leaping athletes. Thirty-six of these fractures in 35 patients have been reported in the literature. These are combined with 15 similar fractures in our experience to provide combined data on 51 anterior tibial stress fractures. Comparison of the various treatments utilized disclosed that there is a high risk of complete fracture if affected patients are allowed full activity, and that treatment by rest alone allowed only 40% to return to full activity even after symptomatic improvement. The treatment recommended for these patients is excision of the fissure, transverse drilling at the fissure site, and cancellous bone grafting of the defect. In those patients who suffer a complete fracture, open reduction and internal fixation is superior to closed treatment.

Adolescent↗
PubMed1990

Morphology and innervation of the buccal glands of the Southern Hemisphere lamprey, Geotria australis.

The buccal glands of adults of the Southern Hemisphere lamprey Geotria australis consist of a pair of small, bean-shaped, hollow sacs, embedded within the basilaris muscle in the region below the eyes and to either side of the piston cartilage. Each gland, which is lined by a simple columnar epithelium and surrounded by an incomplete layer of skeletal muscle, discharges its contents into the oral cavity via a long, narrow duct. In downstream migrating young adults, the epithelial cells are low columnar, intermediate in electron density, and contain dark-staining inclusions and numerous lipid-like droplets. After saltwater acclimation, the epithelial cells become taller and the numbers of dark-staining inclusions increase whereas those of lipid-like droplets decline. By the end of the marine phase, the epithelium is more folded and now also contains dark and light cells. The ultrastructure of the epithelium shows the characteristics of both apocrine and merocrine secretion. Although intra-epithelial nerve endings were not observed, axons and occasional neurons are present in the lamina propria. Since the skeletal muscle capsule is also well innervated and contains neurons, a local feed-back mechanism may regulate the release of buccal gland fluid by monitoring the luminal pressure. Contractions of the skeletal muscle capsule and movements of the basilaris muscle during feeding would presumably assist the movement of secretion along the duct. The secretion possesses anticoagulating and haemolytic properties.

Animals↗
PubMed1987

The spatio-temporal pattern of Wallerian degeneration in the rhesus monkey optic nerve.

Three patterns of degeneration were distinguished in the Rhesus monkey optic nerve following eye enucleation. A traumatic zone, extending for 1 to 2 mm from the site of transection and characterized by a rapid infiltration of haematogenous macrophages, the rapid degeneration and removal of all neural elements and the formation of astrocytic scar tissue within 35 days. A conical zone, closely associated with the central retinal blood vessels, in which the pattern of degeneration was similar to the traumatic zone except that the onset was delayed and the removal of debris was slower. There was extensive vesiculation of myelin sheaths in these two zones which was indicative of haematogenous cell infiltration. The remainder of the nerve underwent classical Wallerian degeneration in which endogenous cells slowly phagocytosed the degenerating nerve fibres. These observations are considered relevant to the controversy concerning the identification of the macrophage involved in Wallerian degeneration; many studies have described the macrophage within the area of trauma rather than the macrophage involved at some distance from the site of trauma.

Animals↗
PubMed1987

The structure and innervation of the saccopleural membrane of the domestic fowl, Gallus gallus: an ultrastructural and immunohistochemical study.

Microscopic studies have shown the saccopleural membrane in the respiratory system of the domestic fowl to consist of a sheet of three dense layers of collagen fibres covered dorsally and ventrally by mainly simple squamous epithelium. On the ventral surface, which faces into the caudal thoracic air sac, there are occasional ridges of pseudostratified ciliated epithelium. Many nerve bundles are present throughout the membrane, the larger bundles of myelinated and unmyelinated axons being confined to the lamina propria under the dorsal epithelium (parietal pleura). In addition to axonal profiles with the ultrastructural appearance of cholinergic or adrenergic axons, peptidergic-type axons were identified. Immunofluorescence studies demonstrated VIP-, substance P-, somatostatin- and enkephalin-immunoreactive fibres in the membrane. Although it has been suggested that receptors may be present in this region of the respiratory system, none of the axons have features suggestive of sensory terminals, although many axonal profiles are closely associated with the epithelia where no obvious effector cells are present.

Animals↗
PubMed1986

The abdominal air sac ostium of the domestic fowl: a sphincter regulated by neuro-epithelial cells?

A microscopic study of the ostium of the abdominal air sac of the domestic fowl has shown that the ostium has a sphincter-like ring of well innervated smooth muscle. Three types of neuro-epithelial cell characterised by their content of numerous large granular vesicles are found in the wall of the ostium. Type I cells are present within the submucosal nerve plexus and appear to be morphologically similar to SIF cells. Type II cells occur in the lamina propria, in clusters or cords, are often associated with fenestrated capillaries, and have synaptic contact with axonal terminals containing small agranular vesicles. The cells of Types I and II are not intra-epithelial and therefore differ from the cells which have been found elsewhere in the respiratory tract of the domestic fowl and other vertebrates. Type III cells are intra-epithelial, and some of those in the basal region of the epithelium are associated with axon terminals. Type III cells are similar in ultrastructure and location to neuro-epithelial cells found elsewhere in the major airways of the domestic fowl. They also resemble cells in neuro-epithelial bodies in amphibian, reptilian and mammalian lungs, although neuro-epithelial bodies have not been found in the lung of this species of bird. The morphology of the ostium suggests that it may have a sphincter-like function, possibly regulated by the neuro-epithelial cells. The presence of a mucociliary epithelium and defensive tissue in the lamina propria indicates that the ostium is the site of defence mechanisms.

Air Sacs↗
PubMed1985

Detection and prevalence of serotypes of feline syncytial spumaviruses.

Three serotypes of feline syncytial virus (FSV) were detected by neutralisation tests: 906, a serotype of low prevalence and 702 and 951 which were serotypes of higher prevalence, between which a minor one-way antigenic difference was detected. Serum antibody in naturally-infected cats in some cases neutralised 951 but not 702 or 906 which suggested that 951 could be considered as a major distinct serotype. An increase in prevalence of antibody to FSV in cats over a 5 year period from 1977-1981 was detected by neutralisation, agar gel immunodiffusion, and fluorescent antibody techniques. Over the 5 year period the prevalence of antibody to the 951 serotype increased and the overall increase in prevalence of antibody to FSV during this period appeared to relate to dissemination of the 951 serotype.

Animals↗
PubMed1984

Recovery of viral agents from the central nervous system of cats.

Isolation of viruses from the central nervous system (CNS) of cats was attempted using an explant culture technique and subsequent co-cultivation with Crandell feline kidney (CRFK) or Vero cells. Feline syncytia-forming virus was isolated from the CNS of 11 of 16 cats where the initial co-cultivation was with CRFK cells. Feline panleucopaenia virus was isolated from the CNS of 2 adult cats. Co-cultured cells from the CNS of 3 cats contained eosinophilic cytoplasmic and intranuclear inclusions. The cytoplasmic inclusions consisted of tubular structures, 16-18 nm in diameter and up to 500 nm in length, which were similar in morphology to paramyxovirus nucleocapsids. The 3 co-cultured cells with cytoplasmic and intranuclear inclusions showed haemadsorption of guinea pig erythrocytes. The possible identity of these structures, and their association with a previously described primary focal demyelinating lesion in the CNS of cats, is discussed.

Animals↗
PubMed1983

Complement activation by antibodies to Sm in systemic lupus erythematosus.

An enzyme linked immunosorbent assay was developed to quantitate antibodies to Sm (anti-Sm) and to measure complement activation by anti-Sm in vitro. Anti-Sm in plasma of patients with systemic lupus erythematosus (SLE) were bound to purified Sm bound to polyvinyl chloride microtitre plates and assayed for bound IgG or IgM using enzyme linked anti-gamma or anti-mu. The activation of C4 by anti-Sm was measured by adding diluted normal human serum (complement) to the wells and quantitating the amount of C4 bound to the well surface using (Fab')2 goat anti-C4 followed by enzyme linked rabbit anti-goat IgG. The plasmas of 12 of 36 patients with SLE contained anti-Sm and all 12 activated complement (complement activating anti-Sm). Twenty-eight plasmas containing anti-Sm from 12 patients with SLE were studied. Ten of the 12 patients had anti-Sm of the IgG class whereas two had anti-Sm of both IgG and IgM classes. The amount of C4 activating anti-Sm correlated significantly with the in vivo activation of C4 measured by rocket immunoelectrophoresis for C4d and C4, suggesting that complement activation by anti-Sm is important in vivo.

Antibodies, Antinuclear↗
PubMed1982

Common variable hypogammaglobulinemia with T-cell nodular lymphoid interstitial pneumonitis and B-cell nodular lymphoid hyperplasia: different lymphocyte populations with a similar response to prednisone therapy.

Intestinal lymphoid hyperplasia and recurrent pulmonary infections by pyogenic bacteria are well-recognized accompaniments of common variable (late onset) hypogammaglobulinemia. A 35-yr-old woman with this illness had progressive pulmonary insufficiency caused by nodular lymphoid interstitial pneumonitis, rather than by infectious lung damage, and intestinal lymphoid nodular hyperplasia. B cells were abundant in the intestinal nodules but absent in the pulmonary nodules by immunoperoxidase staining. Pulmonary lymphocytes isolated in single-cell suspension from the biopsy were 0.5% B cells and 82% T cells. Prednisone therapy improved pulmonary function and decreased the intestinal lymphoid nodules. Lymphocytic interstitial pneumonitis should be considered in patients with hypogammaglobulinemia and restrictive lung disease.

Adult↗