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C D Johnson

Publications and source records attributed to C D Johnson.

At least 109 records · Page 6Linked to original sources
PubMed1998

Effects of aortic nerve stimulation on discharges of sympathetic neurons innervating rat tail artery and vein.

Activity was recorded from postganglionic sympathetic neurons (PSNs) innervating either the caudal ventral artery (CVA) or a lateral vein (LV) of the tail circulation of anesthetized rats. The study sought to determine whether sympathetic activity directed at the CVA and LV was influenced by cardiovascular mechanoreceptor afferents and whether this effect was differential. Cardiac rhythmicity was not a robust component of either CVA PSN activity or LV PSN activity. Stimulation of an aortic nerve with short trains was followed by a decreased probability of discharge in both CVA and LV PSNs that was followed by a series of peaks that showed a constant periodicity that was not significantly different from that revealed by autocorrelogram analysis over the same data set. The latter dominant periodicity is referred to in this and related previous publications as the T rhythm. Furthermore, blood volume expansion and long-train aortic nerve stimulation produced a significant decrease in the frequency of the T rhythm. It is concluded that the CVA and LV sympathetic activity can be influenced by inputs from cardiovascular mechanoreceptors and that this effect is mediated in part by a modulation of the T rhythm.

Action Potentials↗
PubMed1998

Immunization status and sociodemographic characteristics: the mediating role of beliefs, attitudes, and perceived control.

OBJECTIVES: This study examined how immunization-related beliefs, attitudes, and perceived control mediate up-to-date immunization among various sociodemographic groups. METHODS: Statewide estimates of immunization rates among children up to the age of 2 years were obtained via a multistage cluster sample. In-person interviews were conducted with 4832 parents. Information about immunization was obtained from official records or from health care providers. RESULTS: Differences in immunization among sociodemographic groups were mediated by beliefs about objective barriers to immunization, protection, medical contraindication, safety concerns, distrust, and natural immunity. Protection beliefs contributed to positive attitudes toward immunization; beliefs in natural immunity and safety concerns contributed to negative attitudes. Beliefs about objective barriers, distrust, safety concerns, and medical contraindications influenced perceived control over immunization. Positive attitudes and a strong sense of control contributed to higher immunization rates. CONCLUSION: These findings provide a basis for efficient educational campaigns by specifying which beliefs should be bolstered (because they facilitate proper immunization) and which should be targeted for change (because they hinder proper immunization) in various sociodemographic groups.

Adult↗
PubMed1998

Ted L. Shrader, D.C., F.I.C.C.: a gentle force for improvement in chiropractic. 1998 Lee-Homewood Chiropractic Heritage Award recipient.

Long before technology assessment and continuous quality improvement were in vogue in chiropractic, Ted L. Shrader, D.C., F.I.C.C., was working toward these goals in the profession. Convinced that chiropractic must change from within for the benefit of society, Dr. Shrader has made a career-long commitment to evaluating chiropractic procedures and establishing consensus statements regarding chiropractic principle. Determined in mind, moral by nature, and unobtrusive in manner, Dr. Shrader has been decidedly effective in his endeavors. He has encouraged in chiropractic a mind for critical thinking. The fruits of his labor can be seen today in chiropractic publication, among chiropractic scholars, within the American Chiropractic Association Council on Technique, in conference proceedings, and in our institutions.

Chiropractic↗
PubMed1997

Automatic segmentation, tissue characterization, and rapid diagnosis enhancements to the computed tomographic colonography analysis workstation.

An image processing system developed to support examination of computed tomographic colonoscopy (CTC) was developed in 1995. The clinical viability of CTC is enhanced by the solution of several technical problems. These problems include the limited detectability of sessile polyps and difficulties in discrimination between polypoid masses and retained stool. CTC is also made more feasible by simplifying the required colon preparation and reducing the time required to analyze scan results. Each of these challenges have been addressed by enhancements to the CTC analysis workstation software. Endoluminal volume rendering has been enhanced by the addition of automatic segmentation to facilitate analysis of colon segments, which contain tagged liquid stool. By automating this function, the system is able to process scans that are acquired following a wide variety of colon preparation protocols. Similar approaches have been used to identify retained stool. Automatic tissue characterization has also been incorporated into the volume rendering routines to help identify and diagnose polypoid masses. These enhancements have improved the quality of CTC interpretation, while reducing the time required to perform the analysis. This time reduction was necessary to reduce the cost of CTC enough to make it viable for asymptotic population screening. To date, over 150 patient examinations have been performed using this new technique. A recent blinded, prospective study reporting the results from two independent observers has been presented. The technique is feasible, reliable, and has been implemented clinically with results reported within 1 hour of the examination.

Colon↗
PubMed1997

Computed tomographic colonography (Virtual colonoscopy): a new method for detecting colorectal neoplasms.

Computed tomographic (CT) colonography is an exciting new technique that uses volumetric CT data combined with advanced imaging software to create two-dimensional and three-dimensional images of the colon. The technique uses both three-dimensional images that simulate the endoluminal perspective of the colonoscope, as well as axial and reformatted two-dimensional images. The two-dimensional and three-dimensional images are complementary, and in combination offer the most robust performance for the detection of colorectal polyps. Currently, CT colonographic examinations are performed in the fully cleansed and air-inflated colon using a slice thickness of 5 mm, a reconstruction interval of 3 mm, a pitch of 1.3, and 70 mA. In a blinded, prospective study of 70 patients (half with a known lesion, and half from a surveillance population with a low disease prevalence) the sensitivity for the detection of polyps of 1 cm or more is 75%, and the specificity is 90%. The most commonly encountered problems include retained colonic fluid and stool, suboptimally distended colonic segments, and long interpretation times. Many of these problems can be solved using both supine and prone imaging. It is expected that the performance of this examination will improve, and that a new era of colorectal screening will begin.

Colonoscopy↗
PubMed1997

Pancreatic adenocarcinoma: why and when should it be resected?

Adenocarcinoma of the pancreas is a common and dreadful disease with an extremely poor prognosis. In practice, only a few patients are cured but surgical resection, although feasible in less than 20% of patients, offers maximum prolongation of life and provides good palliation of symptoms. This can now be performed safely, even in elderly patients, in specialist units. Better radiological imaging and laparoscopy allow selection of resectable tumours effectively. All patient with pancreatic cancer should now be assessed for surgical resection and potentially suitable patients should be referred to a specialist team at an early stage.

Adenocarcinoma↗
PubMed1997

Detection of colorectal polyps with CT colography: initial assessment of sensitivity and specificity.

PURPOSE: To estimate the sensitivity and specificity of computed tomographic (CT) colography in detection of colorectal polyps and to compare these findings with those at axial CT. MATERIALS AND METHODS: In 70 consecutive patients, CT colography and colonoscopy were performed. Helical axial CT images and CT colographic images (multiplanar two- and three-dimensional endoluminal images) were evaluated separately by two radiologists blinded to results from colonoscopy and other imaging studies. Findings were compared with those at colonoscopy, which was the standard. RESULTS: The sensitivity and specificity for the two observers with CT colography averaged 75% and 90% in patients with adenomas 10 mm in diameter or larger, 66% and 63% in patients with adenomas 5 mm in diameter or greater, and 45% and 80% for patients with adenomas less than 5 mm in diameter, respectively. Sensitivity and specificity with axial CT were lower than those with CT colography (58% and 74%, respectively) in patients with adenomas 10 mm in diameter or larger. CONCLUSION: Compared with axial CT, CT colography appears to have superior sensitivity and specificity in detection of clinically important colorectal adenomas. Early performance of CT colography seems promising for detection of colorectal polyps 5 mm and larger.

Adenoma↗
PubMed1997

Carbamazepine-induced sinus node dysfunction.

Carbamazepine, a drug used for the treatment of epilepsy and neuralgias, may exert hazardous effects on the cardiac conduction system. We report such a case of symptomatic brady-arrhythmia occurring in a 43-years-old male while on therapy with carbamazepine. Additionally, a literature review is made of previous cases of carbamazepine-induced sinus mode, AV node and His-Purkinje conduction disturbances.

Adult↗