Biomedical subjects
Publications and source records attributed to C H Davis.
Sphenoid sinus mucoceles behave as mass lesions producing erosion of adjacent bone and cranial nerve palsies. The probable cause is obstruction of the ostia of the sinus. We describe a case which was 'cured' inadvertently by a nasal polypectomy.
The use of microcarrier cell culture as a method for the in vitro propagation of the obligate intracellular bacterial parasite, Chlamydia trachomatis, is described. The microcarrier beads proved to be a more cost-effective means to propagate C. trachomatis than traditional tissue culture flasks or roller bottles without sacrificing yields or infectivity. In addition, microcarrier cell culture was found to be a much simpler technique to study the intracellular development of these bacteria.
To identify Chlamydia trachomatis genes involved in attachment to host cells, a chlamydial genomic library was screened on the basis of binding characteristics by two methods. In the whole-cell screen, individual recombinant Escherichia coli clones were assayed for adherence to eukaryotic cells. In the membrane-binding screen, each recombinant colony of E. coli was treated with CHCl3 and assayed for binding to purified, 3-[(3-cholamidopropyl)-dimethyl-ammonio]-1-propanesulfonate (CHAPS)-solubilized, 35S-labeled eukaryotic membrane material. Initial screening with McCoy cells was refined by using HEC-1B cells, a human endometrial epithelial cell line, which discriminate among recombinants adhering to McCoy cells. Some recombinants demonstrate significantly greater adherence to HEC-1B cells than to McCoy cells and appear, by transmission electron microscopy, to associate with electron-dense areas of the epithelial cell plasma membrane, resembling coated pits. Recombinants positive by one or both screening methods were examined by Southern and Western (immunoblot) analyses, which revealed the presence of chlamydial sequences inserted in the plasmids and the expression of novel 18-, 28-, and approximately 82 kDa, and perhaps of 18 Maxicell analysis of selected recombinants confirmed that the proteins of 28 and approximately 82 kDa, and perhaps of 18 kDa, are plasmid encoded. Antiserum generated against the recombinant approximately 82-kDa protein reacted in Western analysis with a similar-sized protein from C. trachomatis serovar E elementary bodies (EB) and reticulate bodies, serovar L2 EB, and C. psittaci EB. E. coli JM109(pPBW58) contains a 6.7-kb plasmid insert which encodes proteins of all three sizes. Under a number of different conditions in the whole-cell attachment assay--i.e., at 4 degrees C, in Ca(2+)- and Mg(2+)-free medium, in the presence of trypsin or dextran sulfate, and with rabbit aortic endothelial cells--the binding specificity of JM109(pPBW58) parallels that of C. trachomatis EB. Finally, the adherence phenotype of E. coli JM109(pPBW58) correlates directly with the presence of the recombinant plasmid; the phenotype is lost concurrently with loss of the recombinant plasmid, and the into E. coli JM109. The role of the 18-, 28-, and approximately 82-kDa proteins in mediating attachment, whether they act in concert as a complex or individually, has yet to be determined.
Children with mental retardation and their younger siblings without retardation were observed interacting in three naturally occurring in-home contexts (toy play, television viewing, and snack). Comparison siblings without retardation who were matched on age, sex, race, parental marital status, education, and family income were also observed. Interactions between children with retardation and their siblings were characterized by accentuated role asymmetries that favored the younger siblings, whereas the older siblings were dominant in the comparison group. No differences in affect were found between the sibling groups. The competence of the child with mental retardation reliably predicted sibling role asymmetries, and the observational contexts influenced sibling behavior in both groups. Gender differences in roles and behavior were minimal.
Ascribed, parent-mediated childcare roles of younger same-sex siblings of children with mental retardation were compared to roles assumed by a matched group of comparison siblings. Role reversals were evident for younger siblings of children with mental retardation. These reversals were consistent with roles assumed by the siblings during observed interactions. Increased younger sibling childcare roles were related to less conflicted sibling relationships but were not predictive of friendship or socialization experiences of younger siblings. Younger siblings of children with mental retardation had fewer household chores than did comparison agemates. Children with mental retardation had fewer friendship contacts and out-of-home activities than did their peers without mental retardation. Important within-group differences were evident.
By using the powerful separation technique of capillary gas chromatography combined with the selectivity of mass spectrometric detection, muramic acid was not detectable in purified elementary bodies of Chlamydia psittaci Cal 10 (less than or equal to 0.006%) or C. trachomatis serovar E (less than or equal to 0.02%). This confirms previous reports which suggested the absence of a typical peptidoglycan in Chlamydia spp.
The high cost of commercial CT-compatible stereotactic frames has restricted the availability of CT-guided stereotaxy for many neurosurgical centres. However, many of these centres do possess the standard stereotactic frames for projection radiography, of which the old type Leksell frame is probably the most common. We have devised a simple and low-cost modification to an old Leksell frame to allow CT-guided stereotaxy. The nature of the modifications allow complete freedom of positioning of the frame relative to the CT scanner and coordinate transformations can be performed simply and effectively. The modified frame has been used successfully for some 18 months and the modification has now been performed at two centres in the North West Regional Health Authority. We hope this modification will allow many other centres to embark on CT-guided stereotaxy.
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Epidemiological data on 211 patients undergoing 256 carotid endarterectomies were reviewed, and current data for the 205 perioperative survivors were analyzed by the actuarial method. The median follow-up period was 7.0 years (range: 1 month to 23.2 years). Seven percent of patients were lost to follow-up. Actuarial survival was 77% (5 years) and 49% (10 years), but lower than for the general population. Late stroke occurred in 27 patients (13%) (fatal in 9), being ipsilateral to an endarterectomy in only 10 (4.9%). The annual ipsilateral stroke rate (0.41%), comparable to that of the general population, suggests protection from subsequent stroke. Myocardial infarction occurred in 69 patients (34%), and accounted for 49% of late deaths.
Older nonhandicapped siblings and same-sex younger mentally retarded siblings (n = 16 sibling pairs) were observed in their homes during toy play, snack, and television-viewing, as were an equal number of comparison sibling pairs, matched for age, gender, and family characteristics. Role relationships between mentally retarded children and older siblings were asymmetrical, with older siblings assuming frequent teacher, manager, and helper roles. Older sisters, in particular, participated in frequent teaching. Amount of interaction between siblings was directly related to the contexts in which they were observed. Nonhandicapped siblings engaged each other more as playmates. Interactional correlates of language and adaptive competencies of the mentally retarded children are presented, as are correlations between the age of the siblings and the roles they assume with each other.
Surgical stabilization of traumatic fracture-dislocations of the lower cervical spine with wire and methylmethacrylate remains a controversial procedure. Yet, the resultant immediate fixation with minimal patient morbidity seems to indicate that this method provides an ideal stabilization construct. We describe and report the outcome of a technique of posterior cervical fixation with methylmethacrylate and wire for stabilization of traumatic fractures of the lower cervical spine. Over a 12-year period, 124 fracture-dislocations of the lower cervical spine in 99 patients (mean age, 32 years; range, 15-76 years) were treated at this institution using a posterior methylmethacrylate and wire technique. Eighty-two patients had a posterior element fracture; 28 had a vertebral compression with posterior ligamentous injury; and 14 had a ligamentous injury alone. Thirty-six patients were neurologically intact upon admission, while the rest had radiculopathy or partial or complete myelopathy. Ninety-one patients were available for follow-up [mean, 18.6 months; range, 1-100 months (8.33 years)]. Eighty-eight patients (97%) had a stable fixation and 77 (85%) had resumed preoperative activity or were working but with a residual deficit. Complications included fixation failure requiring a second operation in 3 patients, nonlethal pulmonary embolism in 2 patients, lethal pulmonary embolism in 1 patient, and a superficial wound infection in 3 patients (none affected the underlying fixation construct). These results indicate that this technique is a safe, simple, and effective method for stabilizing the lower cervical spine that allows rapid patient mobility with minimal morbidity.
We prospectively studied 23 patients undergoing carotid endarterectomy under regional (n = 13) or general (n = 10) anesthesia to determine the hemodynamic basis of increased frequency in the need for postoperative vasopressor support when regional anesthesia was used. Anesthesia and postoperative care were conducted without reference to hemodynamic data from pulmonary artery catheterization. Although mean arterial pressure was similar in the two groups postoperatively, 11 of the 13 patients undergoing regional anesthesia and 3 of the 10 patients undergoing general anesthesia required phenylephrine postoperatively. No patient required therapy postoperatively to reduce a systolic pressure exceeding 160 mm Hg. Mean arterial pressure remained below the preoperative baseline value in both groups (p < 0.05 with general anesthesia; p = 0.06 with regional anesthesia) during follow-up. In the general anesthesia group, systemic vascular resistance declined significantly below baseline (p < 0.05) following the operation, accompanied by a decline in mean arterial pressure (p < 0.05) and a higher cardiac output. Intraoperative fluid requirements were greater during general anesthesia than during regional anesthesia (p < 0.01). Pulmonary artery occlusion pressure was lower postoperatively than at baseline in both groups (p < 0.05). Pulmonary artery occlusion pressure was higher in the general anesthesia group despite the greater use of phenylephrine in the regional anesthesia group.
We retrospectively reviewed the influence of preoperative blood pressure control and regional vs. general anesthetic techniques on the incidence of intraoperative and postoperative (recovery room and intensive care unit) hypotension and hypertension in 249 carotid endarterectomy patients. Preoperative blood pressure was classified as uncontrolled hypertension (systolic blood pressure >/= 170 mm Hg and/or diastolic blood pressure >/= 95 mm Hg), controlled hypertension (blood pressure <170/95 mm Hg on chronic antihypertensive therapy), or normotension (blood pressure <170/95 mm Hg without antihypertensive therapy). Hypotension, as defined by the requirement for vasopressor administration to maintain a systolic blood pressure of at least 120 mm Hg, occurred more frequently after regional than after general anesthesia (p < 0.05). Postoperative hypertension was defined as a systolic blood pressure >/= 200 mm Hg and/or a diastolic blood pressure >/= 110 mm Hg in the recovery room or in the Intensive Care Unit. Preoperative hypertension was not associated with acute postoperative hypertension in the intensive care unit in either the regional anesthesia (n = 190) or the general anesthesia (n = 59) groups, although with either type of anesthesia, preoperative hypertension was associated with an increased incidence of hypertension in the recovery room (p < 0.01 regional; p < 0.005 general).
To study the initial invasion process(es) of genital chlamydiae, a model system consisting of hormonally maintained primary cultures of human endometrial gland epithelial cells (HEGEC), grown in a polarized orientation on collagen-coated filters, was utilized. After Chlamydia trachomatis inoculation of the apical surface of polarized HEGEC, chlamydiae were readily visualized, by transmission electron microscopy, in coated pits and coated vesicles. This was true for HEGEC maintained in physiologic concentrations of estrogen (proliferative phase) and of estrogen plus progesterone (secretory phase), despite the finding that association of chlamydiae with secretory-phase HEGEC is significantly reduced (P = 0.025; A.S. Maslow, C.H. Davis, J. Choong, and P.B. Wyrick, Am. J. Obstet. Gynecol. 159:1006-1014, 1988). In contrast, chlamydiae were rarely observed in the clathrin-associated structures if the HEGEC were cultured on plastic surfaces. The same pattern of coated pit versus noncoated pit entry was reproducible in HeLa cells. The quantity of coated pits associated with isolated membrane sheets derived from HeLa cells, grown on poly-L-lysine-coated cover slips in medium containing the female hormones, was not significantly different as monitored by radiolabeling studies and by laser scanning microscopy. These data suggest that culture conditions which mimic in vivo cellular organization may enhance entry into coated pits for some obligate intracellular pathogens.
The aetiology, pathophysiology, and treatment of post-traumatic syringomyelia is discussed. The data collected from clinical observation, radiodiagnostic methods, and operative findings are illustrated. It is concluded that at least five different processes may contribute to this progressive disease. A deeper understanding of these mechanisms could help in patient management.
Ultraviolet light-inactivated elementary bodies of Chlamydia trachomatis serovar E were fluorescently tagged with rhodamine isothiocyanate (5 micrograms/ml) and added to primary cultures of human endometrial gland epithelial cells. The elementary bodies, at a multiplicity of infection of 600:1, were allowed to adsorb to the cell monolayers for 1 hour at 35 degrees C in an atmosphere of 5% carbon dioxide. The monolayers were disaggregated by trypsinization and the individual cells were processed in the fluorescent activated cell sorter for chlamydial attachment. This method of analysis revealed attachment of C. trachomatis to approximately 50% of human endometrial gland epithelial cells. Addition of estrogen (10(-10) mol/L) to the culture medium enhanced chlamydial attachment to human endometrial gland epithelial cells to approximately 80% (p less than or equal to 0.005), and progesterone in combination with estrogen reduced chlamydial attachment in a dose-dependent fashion: 1 ng/ml progesterone, approximately 50%; 5 ng/ml, about 30%; 10 ng/ml, about 18%, respectively (p less than or equal to 0.025).
The entry of Chlamydia trachomatis into McCoy cells (fibroblasts) was studied by transmission electron microscopy. On adsorption of elementary bodies (EBs) to host cells at 37 degrees C, the EBs were bound primarily to preexisting cell-surface microvilli. They were also observed in coated pits located at the bases of the microvilli and along smooth surfaces of the host cells and were internalized within coated vesicles at this temperature. Postembedding immunogold labeling on Lowicryl thin sections with anti-clathrin antibody as the primary reagent revealed the gold marker localized in pits and vesicles containing chlamydiae. Some EBs were present in smooth-surfaced invaginations at or near the bases of microvilli and in vesicles devoid of distinguishable coat material. A similar entry process was observed with centrifugation-assisted inoculation of EBs onto the McCoy cells. Individual EBs were initially internalized into tightly bound endocytic vesicles. However, within 1 to 3 h postinfection, multiple C. trachomatis EBs were observed in large, loosely bound vesicles. Evidence suggests that vesicles containing C. trachomatis may have fused with one another early in the infectious process. These results indicate that chlamydiae can exploit the specific process of adsorptive endocytosis for entry into host cells and for translocation to a given intracellular destination, which may be different for each species.
Despite advances in the neuro-imaging of the brain stem, an accurate diagnosis of intrinsic lesions in this region requires tissue sampling and histological verification. We have performed a series of computer-directed stereotactic procedures in 12 patients with intrinsic brain stem lesions. A positive diagnosis was obtained in 11 cases and therapeutic intervention was possible in four. There was no operative mortality. Because of the importance of an accurate diagnosis in order to avoid inappropriate therapy, together with the relative safety of the technique, computer-directed stereotactic biopsy should be considered in all patients harbouring an intrinsic brain stem mass.