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Biomedical subjects

C Morris

Publications and source records attributed to C Morris.

At least 217 records · Page 12Linked to original sources
PubMed1986

Measurement of the AH and HV interval and His bundle duration: interobserver and intraobserver variation.

Conduction system intervals measured during intracardiac electrophysiologic testing influence clinical decisions. To evaluate measurement reliability, interobserver and intraobserver variation for AH, HV, and His bundle duration measurements from 50 patients were evaluated. The square of the correlation coefficient (r2) was used as the index for measurement reliability. Three investigators performed the measurements. The r2 for interobserver variation of the AH interval ranged from 0.55 to 0.68 and for intraobserver variability from 0.60 to 0.88. The standard error of measurement based on intraobserver measurements ranged from 10.2 to 18.0 ms. The r2 for interobserver variation of the HV interval ranged from 0.42 to 0.63 and for intraobserver variation from 0.489 to 0.73. The standard error of measurement was 6.2 to 9.9 ms. For the His bundle duration, the r2 for interobserver variation ranged from 0.42 to 0.52 and for intraobserver variation from 0.19 to 0.52. The standard error of measurement was 3.1 to 5.2 ms. Although there is measurement variation for AH and HV intervals, their use in conjunction with the history and the surface electrocardiogram to make clinical decisions is appropriate. His bundle duration cannot be measured reliably using the standard recording technique and should not be used for clinical decision making.

Bundle of His↗
PubMed1986

Prognostic value of programmed electrical stimulation in patients with a recent episode of unstable angina.

Patients with a recent episode of unstable angina have a 10% 1-year risk of sudden cardiac death. To determine prospectively whether electrophysiologic testing might be useful in predicting sudden death, 20 patients admitted to our hospital underwent programmed electrical stimulation as part of their evaluation. None had persistent angina, severe congestive heart failure, or sustained arrhythmias at the time of testing. Because of their long-term benefits, beta-blocking agents were continued whenever possible (18 of 20 patients). Ten of 20 patients (50%) had inducible ventricular tachycardia. In 19.5 months' mean follow-up, three patients (15%) either died suddenly or survived an episode of ventricular fibrillation. Programmed electrical stimulation was an insensitive (33%) and nonspecific (47%) predictor of sudden death in these patients. Programmed ventricular stimulation soon after admission for unstable angina is not a useful prognostic indicator for sudden death. Such patients do have a frequent induction of ventricular arrhythmias which appears to be a nonspecific marker of underlying coronary disease.

Actuarial Analysis↗
PubMed1986

Effects of calcium infusion on blood pressure in hypertensive and normotensive humans.

Disorders of calcium and parathyroid hormone homeostasis have been reported in subjects with essential hypertension. In many of these studies, dietary intakes of sodium and calcium were not carefully controlled. The present study was designed to compare calcium and parathyroid hormone homeostasis in normal and hypertensive subjects on controlled dietary sodium and calcium intakes and to examine the impact of dietary sodium loading on hemodynamic and metabolic responses to infused calcium. Seven subjects with essential hypertension and seven age-matched and sex-matched controls were studied while consuming a standard diet containing 600 mg of elemental calcium. Each subject was studied while consuming 10, 160, and 510 mEq of sodium per day, before, during, and after a 3-hour calcium infusion (3.75 mg/kg/hr). Before calcium infusion, hypertensive subjects had increased urinary cyclic adenosine 3',5'-monophosphate excretion independent of sodium intake (p less than 0.05). Urinary potassium excretion was greater in normotensive than in hypertensive subjects (p = 0.002). At baseline, dietary sodium intake had no effect on systolic, diastolic, or mean arterial pressure. During calcium infusion, systolic pressure increased in both groups, whereas diastolic pressure increased only when dietary sodium content was high and mean arterial pressure increased only in hypertensive subjects (p = 0.007). Together, these data provide evidence for interactions between dietary sodium intake and the cardiovascular response to calcium. They confirm that hypertensive subjects exhibit enhanced parathyroid gland function even when dietary factors are controlled, and they suggest that these subjects are more sensitive to the cardiovascular effects of short-term calcium infusion.

Adult↗
PubMed1986

The effect of eating on thallium myocardial imaging.

To determine if eating between initial and delayed thallium images alters the appearance of the delayed thallium scan, a prospective study was performed; 184 subjects sent for routine thallium imaging were randomized into two groups, those who ate a meal high in carbohydrates between initial and delayed thallium myocardial images (n = 106), and those who fasted (n = 78). The 201Tl images were interpreted in blinded fashion for global myocardial and pulmonary clearance of 201Tl myocardial defects. The eating group had a significantly lower incidence of transient myocardial defects compared to the noneating group (7 percent vs 18 percent, respectively; p less than 0.05). The time between initial and delayed images and the incidence of exercise-induced ischemic ST-segment depression or pathologic Q waves on the electrocardiogram were not significantly different between the two groups. These data suggest that eating a high-carbohydrate meal between initial and delayed 201Tl images causes increased 201Tl myocardial clearance rates and may alter 201Tl myocardial redistribution over time.

Adult↗
PubMed1986

Sudden death prediction by programmed electrical stimulation following myocardial infarction.

To determine prospectively whether electrophysiologic testing is prognostically useful following a myocardial infarction, 38 patients were studied. Ventricular tachycardia was induced in 32 of 38 (84%) patients (sustained in 12) and was significantly increased with the use of three or four extrastimuli. In 17 months' mean follow-up, 4 patients died suddenly or survived an episode of sustained ventricular tachycardia. Programmed ventricular stimulation was a sensitive but not a specific predictor of these events with an overall 24% predictive accuracy. The use of one or two extrastimuli substantially improved specificity but was insensitive in predicting sudden death or ventricular tachycardia. Programmed ventricular stimulation soon after uncomplicated myocardial infarction was not a useful prognostic indicator for sudden death or subsequent ventricular tachycardia.

Adult↗
PubMed1985

Decreased calcium dependence of lymphoblastoid cell lines compared with Burkitt lymphoma cell lines.

The extracellular calcium level required for proliferation was compared in B lymphoid cell lines from various sources by determining the calcium concentration at which long-term proliferation was inhibited by 50% (CaPD50). Fourteen Burkitt lymphoma (BL) lines had a mean CaPD50 of 44 +/- 28 microM whereas 45 lymphoblastoid cell lines (LCLs) obtained by in vitro transformation of B lymphocytes with Epstein-Barr virus (EBV) had a mean CaPD50 of 3.6 +/- 1.8 microM. This difference applied also to autologous BL lines and LCLs established from the same patient. The decreased calcium requirement of virally-transformed compared with tumour-derived cell lines therefore appears to be a universal phenomenon in mammalian cells. Within the BL group, no correlation was found between the calcium requirement for proliferation and presence or absence of the EBV genome. Arrest of BL lines and LCLs occurred in the G1 phase of the cell cycle and was readily reversed by addition of calcium to the medium. One anomalous LCL was found which showed a high CaPD50 (43 +/- 6 microM) and accumulated in both G1 and G2. These results, in combination with a previous study of EBV transformation in vitro, indicate that the calcium dependence of B lymphocytes generally decreases in the following order: normal cells greater than BL cells = early stage transformation greater than LCL. The 2 transformed phenotypes thus distinguished in human lymphoid cells may offer unique opportunities for defining the status and expression of EBV in vitro and in vivo.

Burkitt Lymphoma↗
PubMed1985

Effect of blood on the activity and persistence of antigen induced inflammation in the rat air pouch.

The hypothesis that haem iron derived from synovial microbleeding has a proinflammatory effect on the synovial membrane was tested by adding autologous whole blood and fractions derived from it to a naturally remitting rat air pouch model of allergic inflammation. The induction of such a subcutaneous air pouch produces a cavity lined by mesenchymal cells comparable to the synovial membrane. Autologous whole blood was found to prolong a low grade inflammatory state, this effect being attributable to a red cell component, most probably haem iron. Whole blood in the absence of an inflammatory stimulus does not have this effect, indicating that the mechanism is one of prolonging or promoting existing allergic inflammation, rather than inducing an inflammatory response.

Air↗
PubMed1985

The taxonomic complex, Culicoides variipennis.

The morphological and biological characteristics of the 5 subspecies of Culicoides variipennis as proposed by Wirth and Jones are reviewed in the light of research performed since 1957. Proposals have been made to recognize the eastern and western populations as distinct species; others prefer to consider the population as 1 species with extensive and complex variation resulting from the interplay of ecological and genetic factors. The authors recommend the use of the term "variipennis complex" rather than a haphazard selection of 1 of the 5 names in reporting the results of research on this insect, until such time as the necessary biosystematic studies have been made to determine the genetic nature of the population structure over the entire geographic range of the species. If it is considered desirable to recognize the western form as a distinct entity, reasons are given for preference to the name sonorensis rather than occidentalis. The use of gas chromatography to study population differences in the makeup of cuticular paraffins is suggested as a promising new biochemical approach to the study of the genetic and physiological differences between populations of variipennis.

Animals↗
PubMed1984

CT appearance of a prosthetic methyl methacrylate mass mistaken for abscess.

A nonopaque methyl methacrylate mass that had the appearance of an abscess in a postoperative CT scan of the spine is described. Contained gas produced an attentuation range of +20 to -300 HU, with an average of -80 to -250 HU. This finding was confirmed by CT examination of a separate cement mass removed from a similar patient.

Abscess↗
PubMed1983

Biological membranes are rich in low-frequency motion.

Using 13C cross-polarization NMR techniques, we have found that the effect of protein on the dynamics of the hydrocarbon interior of a series of biological membranes is to depress the intensity of motion on the nanosecond timescale (i.e., T1 becomes longer) and to enhance the intensity of motion on the timescale of tens of microseconds (i.e., T1p becomes shorter.)

Animals↗
PubMed1983

High-resolution CT scanning of the lumbar spine. Technique and anatomy.

Low back pain is a very common clinical problem, the cause of which is frequently poorly understood. Improvements in equipment design and scanning techniques have resulted in a better anatomical display of the lumbar spine by computed tomographic (CT) scanning. Advances in this area have provided a considerable insight into the causes of the lumbago-sciatica syndrome.

Back Pain↗
PubMed1983

A monoclonal antibody to the heavy chain of clathrin.

Monoclonal antibodies have been raised to pig brain triskelions and one clone, DC41, was found to recognize the clathrin heavy chain by immunoblotting. However, both by immunofluorescence and immunoelectron microscopy, and in complete contrast to polyclonal anti-clathrin antibodies, monoclonal DC41 did not label either coated pits or coated vesicles anywhere in the cell. Instead it appeared to label the cell cytoplasm. These data suggest that DC41 recognizes a cytoplasmic form of clathrin, perhaps that form produced by uncoating of coated vesicles which is then ready to re-build another coated pit.

Animals↗
PubMed1983

DNA replication and repair in ataxia telangiectasia cells exposed to bleomycin.

A marked increase in sensitivity to bleomycin was observed in two ataxia telangiectasia (AT) lymphoblastoid cell lines compared to that in cell lines from two normal individuals. This sensitivity was obtained at two different concentrations of bleomycin. While normal cells showed a rapid recovery of ability to divide, there was no indication of such a recovery in AT cells up to 120 h after bleomycin treatment. A similar level of breakage of DNA occurred in both cell types after incubation with bleomycin. The rate of repair of these breaks was also the same. DNA synthesis was found to be more resistant to bleomycin in AT cells than in control cells. The latter data are in keeping with results previously obtained using ionizing radiation.

Ataxia Telangiectasia↗
PubMed1983

Comparison of schizophrenic patients with formal thought disorder and neurologically impaired patients with aphasia.

This study compares the speech and language of 14 schizophrenic patients having a formal thought disorder with 13 neurologically impaired patients with aphasia. Transcribed interviews with these patients were blindly assessed by five specialists for classification as schizophrenic or aphasic. Three of the five specialists performed better than chance but only one achieved high discriminating ability. Interrater reliability was poor. Five of 14 language abnormalities assessed differentiated the diagnostic groups. These findings suggest that schizophrenic patients share many language abnormalities with aphasic patients but do not exhibit a classic aphasic syndrome.

Aphasia↗