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Biomedical subjects

J Warren

Publications and source records attributed to J Warren.

At least 127 records · Page 7Linked to original sources
PubMed1986

New developments for upper rate response in DDD pacing.

Although widely accepted as an effective method of dealing with rapid atrial rates in a DDD pacemaker, Wenckebach-type and multiblock-type upper rate behaviors may exacerbate pacemaker-mediated tachycardia through AV dissociation. In addition, pathologic atrial rates (e.g., atrial fibrillation, atrial flutter, automatic atrial tachycardia, etc.) frequently result in ventricular pacing at inappropriately high rates. New, more sophisticated algorithms available in today's microprocessor-based DDD pacing systems provide the capability to discriminate successfully a normal atrial rate response to exercise from a pathologic atrial rate. These and other improved capabilities allow the clinician to provide safe rate-responsive pacing to patients in whom rate-responsive pacing was previously contraindicated.

Electrocardiography↗
PubMed1986

Clinical evaluation of automatic tachycardia diagnosis by an implanted device.

Reliable discrimination between sinus tachycardia (ST) and pathologic tachycardia has been a major problem for automatic implantable antitachycardia devices. In patients whose sinus response to activity is as rapid or faster than their pathologic tachycardia (rate crossover), these unsophisticated devices deliver the programmed tachycardia response to either the pathologic or sinus tachycardia. Over a one-year period, 50 Intermedics Intertach Model 262-12 antitachycardia pulse generators were implanted to evaluate the specificity of a new group of tachycardia recognition algorithms. Patients were subjected to exercise testing and noninvasive programmed stimulation to demonstrate the efficacy of this new approach. The five recognition algorithms tested were various combinations of the following criteria: high rate (HR), sudden onset (SO), rate stability (RS), and sustained high rate (SHR). False positive rates (tachycardia response inappropriately triggered by ST) were as follows: HR (93%); HR + SO (3%); HR + RS (63%); HR + (RS or SHR) (87%); HR + HS + SO (8%). Pair-wise significance testing between HR only and HR + SO (p less than 0.001), HR + RS (p = 0.01) and HR + SO + RS (p less than 0.001), demonstrated a significant reduction in the rate of false positives through the use of the sudden onset and rate stability criteria in concert with the standard high rate criterion.

Algorithms↗
PubMed1985

Identification of best electrocardiographic leads for diagnosing myocardial infarction by statistical analysis of body surface potential maps.

This study describes a practical approach for the extraction of diagnostic information from body surface potential maps. Body surface potential map data from 361 subjects were used to identify optimal subsets of leads and features to distinguish 184 normal subjects from 177 patients with myocardial infarction (MI). Multivariate analysis was performed on 120-lead data, using as features instantaneous voltage measurements on time-normalized QRS and STT waveforms. Several areas on the map, most of which were located outside the precordial region, contained leads with important discriminant features; 2 of the 3 limb leads (aVR and aVF) also exhibited high diagnostic capability. A total of 6 features (mostly STT measurements) from 3 locations accounted for a specificity of 95% and a sensitivity of 95%; these were the right subclavicular area, the left posterior axillary region and the left leg. As a comparison, the same number of features from the standard 12-lead electrocardiogram yielded a sensitivity of 88% for a specificity of 95%. To investigate the repeatability of the results, the entire population was separated into a training set (100 normal subjects and 100 patients with MI) and a testing set (84 normal subjects and 77 patients with MI); computing a discriminant function on the training set and applying it to the testing set only moderately deteriorated the diagnostic classification. It is concluded that this approach achieves efficient information extraction from body surface potential maps for improved diagnostic classification.

Adult↗
PubMed1985

Long-term serial cultivation of arterial and capillary endothelium from adult bovine brain.

Cerebrovascular endothelial cells from adult bovine brain were carried successfully in long-term, serial culture. Endothelial cells were obtained from the middle and anterior cerebral arteries and from capillaries isolated from grey matter of the cerebral cortex or caudate nucleus. Capillary cells were found to grow best in RPMI 1640 with 20% fetal bovine serum. They did not require tumor-conditioned medium or matrix-coated surfaces, although fibronectin was used to enhance the initial plating efficiency of the primary cultures. The same conditions were used to support satisfactory growth of arterial endothelial cells; however they did not grow as rapidly as the cells. Retention of endothelial-specific characteristics were shown for capillary-derived cells carried up to Passage 28, arterial-derived cells up to Passage 11, and after frozen storage of both types of cultured cells. Cultures of both arterial and capillary cells stained positively for Factor VIII antigen, exhibited a nonthrombogenic surface, and produced prostacyclin in response to arachidonic acid. Arterial endothelial cells produced more prostacyclin than capillary endothelium. The capillary cells had a unique tendency to assume a ringlike morphology after subculture and sometimes formed capillarylike networks of cell cords in dense cultures. When cultured in a three-dimensional plasma clot, capillary and arterial endothelial cells, but none of the other cell types studied, organized into tubelike structures reminiscent of capillary formation in vivo. The availability of long-term cultures of cerebrovascular endothelial cells provides an opportunity to compare properties of arterial and capillary endothelium from the same tissue and to investigate such processes as angiogenesis and blood-brain barrier induction.

Animals↗
PubMed1985

Comparison of cyclic AMP-dependent protein kinases from salivary glands of four species.

Cyclic AMP-dependent protein kinase activity, subcellular distribution, and isozyme profile were compared in rabbit, rat, guinea pig, and mouse in both parotid and submandibular glands. Glands were homogenized under hypotonic conditions and the following fractions isolated: 600 g pellet, 27,000 g pellet, and 27,000 g supernatant. The specific activity of the enzyme was similar in the eight glands and was highest in the 27,000 g supernatant. The average activity in the 27,000 g supernatant was approximately 75% of the total gland activity, although there was considerable variability between tissues and species. After being washed with isotonic buffer, this percentage was increased to an average of 84%. When isozyme patterns of the kinase were examined, the rabbit parotid was unique in that it contained a high percentage of isozyme I as isolated on DEAE cellulose columns.

Animals↗
PubMed1985

Bronchocentric granulomatosis with glomerulonephritis.

Bronchocentric granulomatosis is a chronic pulmonary disease treated with short-term therapy with corticosteroids, and the disease has an excellent prognosis. We describe a patient, and review an additional case from the literature, in whom bronchocentric granulomatosis was accompanied by glomerulonephritis. A misdiagnosis of Wegener's granulomatosis was made, and therapy with cyclophosphamide was either considered or given in each of these cases. We emphasize the need for careful histopathologic evaluation of open lung biopsies in patients suspected of having Wegener's granulomatosis in order to rule out the possibility of bronchocentric granulomatosis with concurrent renal disease, and thus avoid the unnecessary use of cytotoxic agents.

Diagnosis, Differential↗
PubMed1984

Mucoepidermoid carcinoma of the bronchus in a 4-year-old child. A high-grade variant with lymph node metastasis.

A high-grade mucoepidermoid carcinoma with lymph node metastasis occurred in the bronchus of a 4-year-old child. The tumor was pedunculated, obstructive, and invasive. Squamous and glandular elements were seen on light and electron microscopic examination. This is a very rare tumor in the pediatric age group. This is the first instance of this lesion associated with metastasis.

Bronchial Neoplasms↗
PubMed1984

Resetting of DDD pacemakers due to EMI.

Multiprogrammable pacemakers have long been subject to inappropriate reprogramming and electromagnetic interference (EMI). A limited clinical experience with DDD pacing systems precludes the significance of such phenomena in these units. Since August 1981, in a series of 140 DDD systems, certain units demonstrated consistent and reproducible resetting to the back-up modes caused by electrocautery. One unit was permanently reset to the VOO mode. These observations suggest the need for renewed caution at the time of surgery; they also underscore the importance of a thorough understanding of any DDD system and careful follow-up so that such phenomena will not be misinterpreted as pacemaker failure, resulting in erroneous pacemaker removal.

Arrhythmias, Cardiac↗
PubMed1984

Isoproterenol-induced amylase release in rabbit parotid acini: relation of protein phosphorylation, cyclic AMP and related kinase activity to changes in secretory rate.

Isoproterenol-induced amylase release from rabbit parotid acini was examined in relation to cyclic AMP (cAMP) concentrations, cAMP-dependent protein kinase (cAMP-PK) activity ratios and protein phosphorylation. Initial stimulation of amylase release by isoproterenol was preceded by increases in cAMP, cAMP-PK activity ratios and phosphorylation of a 34,000 MW (major) and a 30,000 MW (minor) protein in the microsomal fraction. When propranolol was added, decreases in cAMP concentrations and cAMP-PK activity ratios preceded the reduction in amylase release. Detailed analysis was performed on the 34,000 MW protein. The relation of dephosphorylation of protein 34 and reduction in amylase release was complex. Slight dephosphorylation occurred before or concurrently with the decrease in amylase release; however, maximal dephosphorylation was preceded by maximal inhibition of amylase release. When secretion of amylase was reinstituted by isoproterenol or forskolin, increases in cAMP and cAMP-PK activity ratios occurred before or in concert with amylase release but rephosphorylation of protein 34 occurred after the start of amylase release. Photoaffinity labeling studies using [32P]-8-azidoadenosine-3',5'-cyclic monophosphate indicated that proteins 34 and 30 were not regulatory subunits of cAMP-PK or their breakdown products. Although these data are consistent with phosphorylation of proteins 34 or 30 being required for triggering initial secretion, maximum dephosphorylation was not essential for inhibition of secretion. Furthermore, initiation of amylase release by the gland after a short period of quiescence did not depend on prior phosphorylation of protein 34. These data may indicate the absence of a requirement of amylase release for phosphorylation of protein 34.

Adenosine Triphosphate↗
PubMed1983

Atrial synchronous ventricular inhibited pacing (VDD): an underutilized mode of pacing.

The design of atrial synchronous, ventricular inhibited (VDD) pacemakers has been improved. Physiologic long-term benefit has now been established, although this mode of pacing accounts for approximately one percent of implanted devices. With the ultimate control of pacemaker-mediated tachycardia through atrial refractory programming close at hand or already available, one might expect an increase in VDD pacing in patients with exercise-induced high degree heart block and stable sinus node function.

Arrhythmias, Cardiac↗
PubMed1983

Mechanisms of the synergistic effect of oral dimethyl sulfoxide on antineoplastic therapy.

The purpose of this study was to determine whether dimethyl sulfoxide (DMSO) when administered in conjunction with antitumor drugs would potentiate their activity against a rodent tumor. Twelve compounds of diverse modes of action were examined using standard protocols of the National Cancer Institute. Median survival time and median tumor diameter were the parameters used for determining any synergistic effects of DMSO when it was ingested in the drinking water and the drug administered parenterally. The continuous ingestion of DMSO alone mixed in drinking water at concentrations between 0.25-32% was not toxic and had no effect on the tumor. Although the intraperitoneal inoculation of drugs into animals ingesting DMSO did not enhance drug effectiveness, when both DMSO and drug were added to the drinking water, it did increase antineoplastic potency. DMSO ingestion also inhibited the tumor growth rate of several parenterally administered drugs even though these same compounds failed to prolong the survival time of tumor-bearing rats. The toxicity of 12 compounds when combined with DMSO was only moderately increased in four instances. Orally ingested DMSO was found to cause a twofold increase in the concentration of labeled CPA in plasma, brain, and liver tissues. This elevation persisted for approximately two to three hours but subsequently returned to the same level as that observed in water-fed rodents. The DMSO-enhancement of tissue levels coupled with a more rapid drug rate clearance offers one explanation for the therapeutic benefit noted when oral DMSO was administered concomitantly with CPA.

Administration, Oral↗
PubMed1983

Intestinal parasites in a remote village in Nepal.

Stool samples for parasitological examination were collected in a remote area of western Nepal. Of 40 specimens collected, 36 were positive for parasites as determined by examination of direct wet mounts and trichrome smears. All but one of the positive specimens contained several parasite species, averaging four species per specimen. Four negative specimens were found in infants under 1 year of age. The parasitic burden in this population appeared to be high, and the prevalence of parasitic infection approached 100%.

Adolescent↗
PubMed1983

The National Traumatic Coma Data Bank. Part 1: Design, purpose, goals, and results.

This paper describes the pilot phase of the National Traumatic Coma Data Bank, a cooperative effort of six clinical head-injury centers in the United States. Data were collected on 581 hospitalized patients with severe non-penetrating traumatic head injury. Severe head injury was defined on the basis of a Glasgow Coma Scale (GCS) score of 8 or less following nonsurgical resuscitation or deterioration to a GCS score of 8 or less within 48 hours after head injury. A common data collection protocol, definitions, and data collection instruments were developed and put into use by all centers commencing in June, 1979. Extensive information was collected on pre-hospital, emergency room, intensive care, and recovery phases of patient care. Data were obtained on all patients from the time of injury until the end of the pilot study. The pilot phase of the Data Bank provides data germane to questions of interest to neurosurgeons and to the lay public. Questions are as diverse as: what is the prognosis of severe brain injury; what is the impact of emergency care; and what is the role of rehabilitation in the recovery of the severely head-injured patient?

Accidents↗