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Biomedical subjects

D Hess

Publications and source records attributed to D Hess.

At least 199 records · Page 11Linked to original sources
PubMed1984

The hand-held computer as a teaching tool for acid-base interpretation.

This paper presents an acid-base interpretation drill written for the Sharp PC-1211 and the Radio Shack TRS-80 PC-1 computers. The computer generates random numbers for PCO2 and HCO3(-) and calculates pH, then interprets the values according to a normal values key and a 13-item interpretation key. Next, the computer asks for the user's interpretation of the values, evaluates the user's interpretation, and informs him whether his answer is correct or incorrect. If it is incorrect, the user has the option of trying again or directing the computer to display the correct answer. The user is then given a chance to interpret a new set of acid-base values. I have found that this method of instruction enhances students' enthusiasm for learning and relieves the instructor of the tedious aspects of teaching acid-base interpretation.

Acid-Base Imbalance↗
PubMed1984

An arterial blood gas interpretation program for hand-held computers.

Because of its portability, the hand-held computer can be easily used at the bedside to perform mathematical computations and assist with patient care decision making. This paper describes applications software for arterial blood gas interpretation with the hand-held computer. From the arterial blood gas values entered, the program calculates the arterial/alveolar PO2 ratio (a/A PO2), provides an interpretation of oxygenation, a/A PO2, ventilation, and acid-base status, and makes suggestions for therapy. This program can be used for the individualized bedside teaching of students and others with limited experience in arterial blood gas interpretation.

Blood Gas Analysis↗
PubMed1984

Measurement of ferritin-bearing peripheral mononuclear blood cells in cancer patients by radioimmunoassay.

A radioimmunoassay has been developed to measure ferritin bound to the surface of isolated human peripheral blood mononuclear white blood cells (PBMs) in order to investigate the possible relationship of this phenomenon to breast and other forms of cancer. The assay measures the specific binding (%SP) of affinity-purified 125I-labeled rabbit anti-Hodgkin's spleen ferritin antibody to isolated patient PBMs. A preliminary prospective, preclinical trial on 300 patients was run which included: (a) normals, benign breast disease, and medical/surgical patients as non-cancer controls; (b) postoperative primary cancer and advanced cancer in clinical remission as post cancer controls; and (c) both early preoperative breast cancer patients and cancer patients with localized recurrences or active disseminated disease as test groups. The mean %SP for the non-cancer control groups was in the range of 4.3 to 5.1 (n = 187), which was identical to that for inactive cancer or postoperative cancer, which was no evidence of recurrence. Using a %SP normal cutoff level of 6.5, which resulted in a false-positive rate of approximately 10% for both non-cancer and post-cancer control groups, only 27% of early preoperative cancers (n = 22) gave elevated %SP values. These results suggest that measurement of ferritin-PBM is inappropriate for early disease diagnosis. In contrast, 91% of patients with advanced active breast cancer and 73% of those patients with other types of advanced cancers, including tumors of ovarian, lung, colon or esophageal origin, showed elevated %SP values more than double those of post-cancer controls. The mean %SP value in active advanced cancer was 10.8 for breast (n = 12) and 10.6 for all other solid tumors investigated (n = 34). Paired patient comparisons of ferritin-PBM and plasma carcinoembryonic antigen in breast cancer showed elevations in 91% of the patients for ferritin-PBM and 67% for carcinoembryonic antigen. Overall, these results suggest that patients with advanced cancer display elevated levels of ferritin on the surface of their PBMs and that this measurement may be a useful adjunct in monitoring and evaluating the clinical status of cancer patients.

Breast Diseases↗
PubMed1983

Raman spectroscopic and X-ray diffraction studies of the effect of temperature and Ca2+ on phosphatidylethanolamine dispersions.

Raman spectroscopy and X-ray diffraction are used to study the effect of heat and Ca2+ on dimyristoylphosphatidylethanolamine dispersions. Unlike phosphatidylcholine dispersions, dimyristoylphosphatidylethanolamine bilayers (at pH 8) require heating above Tm in order for hydration to occur and apparently bind Ca2+ at very low levels. These results are related to models for membrane fusion.

Calcium↗
PubMed1983

Electrophysiologic mechanism of exercise-induced sustained ventricular tachycardia.

To elucidate electrophysiologic mechanism of exercise-induced ventricular tachycardia (VT), electrophysiologic studies were performed in 12 patients in whom sustained VT had developed during treadmill exercise testing. Six patients had arteriosclerotic coronary heart disease, 3 had cardiomyopathy, and 3 had no clinical evidence of organic heart disease. All patients had had documented episodes of sustained VT related to exertion and had experienced dizziness, syncope, or both. In addition, 3 patients had had nonfatal cardiac arrest. Electrophysiologic studies provoked paroxysms of sustained VT identical to those observed during treadmill exercise testing in 10 patients and provoked ventricular flutter/fibrillation in 1. Seven patients had VT suggestive of a reentrant mechanism, as the VT could be readily initiated with programmed ventricular extrastimulation or terminated by ventricular overdrive pacing, or both. Three patients had VT suggestive of catecholamine-sensitive automaticity. The VT could not be initiated with programmed electrical stimulation, but it could be provoked by intravenous isoproterenol infusion; furthermore, the VT could not be terminated with ventricular overdrive pacing, but it could be abolished by discontinuing isoproterenol infusion. Reproduction of VT in these 10 patients allowed serial pharmacologic testing in selecting an effective antiarrhythmic regimen. Thus (1) exercise-induced VT can be caused by either reentry or catecholamine-sensitive automaticity, and (2) electrophysiologic studies are of use in defining the underlying mechanism of exercise-induced sustained VT.

Adolescent↗
PubMed1983

Long-term follow-up of patients with recurrent unexplained syncope evaluated by electrophysiologic testing.

Electrophysiologic testing was performed in 53 patients with recurrent syncope that remained unexplained despite a thorough neurologic and noninvasive cardiac evaluation. Fifteen patients had no structural heart disease, 9 had mitral valve prolapse and 29 had structural heart disease other than mitral valve prolapse. Nonsustained ventricular tachycardia was induced in 15 patients (28%), sustained ventricular tachycardia was induced in 9 (17%), ventricular fibrillation was induced in 4 (8%) and sinus node function was abnormal in 2 (4%). Female sex and lack of structural heart disease were independently associated with a negative electrophysiologic study (p less than 0.001). Patients with inducible ventricular tachycardia or ventricular fibrillation were treated with drugs selected on the basis of the results of electropharmacologic testing. The recurrence rate of syncope was 43% over a 31 +/- 10 month period (mean +/- standard deviation) of follow-up in patients with a negative electrophysiologic study, 40% over a 22 +/- 6 month period in patients with inducible nonsustained ventricular tachycardia, 0% over a 30 +/- 12 month period in patients with inducible sustained ventricular tachycardia and 25% over a 21 +/- 10 month period in patients with inducible ventricular fibrillation. In patients with recurrent unexplained syncope undergoing electrophysiologic testing, a potential cause of syncope is least likely to be found in women without structural heart disease. The results of programmed ventricular stimulation must be interpreted with regard to the method of induction of ventricular tachycardia and the type of ventricular tachycardia induced. The excellent response rate in patients with inducible sustained ventricular tachycardia whose therapy is guided by the results of electropharmacologic testing suggests that sustained ventricular tachycardia is a clinically significant response.(ABSTRACT TRUNCATED AT 250 WORDS)

Amiodarone↗
PubMed1982

Electrophysiologic drug testing in patients with malignant ventricular arrhythmias: importance of stimulation at more than one ventricular site.

Sixty-four patients with symptomatic ventricular tachycardia or ventricular fibrillation underwent right ventricular apical programmed stimulation and had no inducible ventricular tachycardia during drug testing. Thirty patients (Group I) did not undergo left ventricular stimulation. Left ventricular stimulation in 38 drug trials induced no ventricular tachycardia in 50% (Group IIA), nonsustained ventricular tachycardia in 24% (Group IIC). Patients in Groups I, IIA, and IIB received chronic antiarrhythmic drug therapy based on the results of electrophysiologic drug testing. Patients in Group IIC underwent further drug testing until sustained ventricular tachycardia was no longer inducible and were then entered into Group IIA or IIB; 4 patients in whom the induction of sustained ventricular tachycardia could not be suppressed by any drug regimen tested were excluded from long-term follow-up. The duration of follow-up (mean +/- standard deviation) was 15.8 +/- 1.5 months in Group I, 13.6 +/- 3.7 months in Group IIA, and 12.1 +/- 4.9 months in Group IIB. Recurrence rates of symptomatic ventricular tachycardia or sudden death were 27% in Group I, 0% in Group IIA, and 20% in Group IIB (p less than 0.02 for Group IIA versus Group I and p greater than 0.05 versus Group IIB). If only right ventricular apical stimulation is performed during electrophysiologic drug testing in patients with malignant ventricular arrhythmias, approximately 50% of drug trials may be incorrectly judged as suppressing the induction of ventricular tachycardia. Drug therapy that suppresses ventricular tachycardia induction with both right and left ventricular programmed stimulation results in a significantly better clinical response than therapy based on the results of only right ventricular apical stimulation.

Adult↗
PubMed1981

Mechanisms of spontaneous tachycardia termination in a patient with the Wolff-Parkinson-White syndrome and dual atrioventricular nodal pathways.

A patient with the Wolff-Parkinson-White syndrome and recurrent bouts of paroxysmal supraventricular tachycardia under-went electrophysiologic studies. These studies revealed evidence of dual atrioventricular nodal pathways and a septal accessory pathway. The tachycardia circuit involved anterograde conduction over a slow atrioventricular nodal pathway and retrograde conduction over the accessory pathway. Spontaneous tachycardia termination was frequently observed, was almost always abrupt, and was associated with a beat-to-beat decrease in the A-H interval. In this patient, the mechanism for spontaneous tachycardia termination appeared to be an abrupt shift in anterograde conduction from the slow to the fast pathway, advancing the tachycardia so that the block occurred in the accessory pathway (or atrium). To our knowledge, this mechanism of spontaneous tachycardia termination has not been described previously. Use of agents to facilitate fast atrioventricular nodal conduction (i.e., atropine) may be effective in tachycardia termination for these patients.

Atrioventricular Node↗
PubMed1981

His-ventricular dissociation in a patient with reciprocating tachycardia and a nodoventricular bypass tract.

A patient with recurrent bouts of atrial fibrillation and wide-complex regular tachycardia underwent electrophysiologic studies. Premature atrial stimulation or atrial pacing during sinus rhythm resulted in gradual lengthening of the PR and AH intervals, narrowing of the HV interval and progressive preexcitation with a left bundle branch block and left-axis contour. Induction of tachycardia was dependent on critical delay in the atrioventricular interval and was associated with attainment of a maximal preexcitation pattern. During tachycardia, the ventriculoatrial interval was constant, whereas the interval from His bundle deflection to the ventricular complex was variable. We postulate that the tachycardia circuit involved reciprocation within the atrioventricular node and that a nodoventricular bypass tract was present in close anatomic or functional association with the slow atrioventricular nodal pathway. Our data suggest that both the nodoventricular bypass tract and the His-Purkinje system may be passive "bystanders" rather than essential components of the tachycardia circuit. In addition, although HV dissociation usually implies ventricular tachycardia, this case demonstrates that HV dissociation during wide-complex regular tachyarrhythmia is not diagnostic of ventricular tachycardia.

Adult↗
PubMed1981

Tissue metabolism of estrogens in the female rhesus monkey.

The overall MCRs and [rho]BB values (fraction of infused precursor measured in blood as product) and individual tissue extractions and conversions were measured in the follicular and luteal phases of normal cycling female rhesus monkeys using constant infusions of [3H]estradiol ([3H]E2) and [14C]estrone ([14C]E1). During the infusions, blood samples were obtained from the femoral artery and veins draining the splanchnic tissue, kidney, head, arm, and uterus. The overall mean (+/- SE) MCR for E2 (214 +/- 17 liters/day) was significantly less than the MCR for E1 (295 +/- 13 liters/day). There were no differences in the MCR measured in the follicular or luteal phases of the cycle. The [rho]BB values were greater for the fraction of infused E1 measured in blood as product E2 [rho]E1, E2, BB; (0.25 +/- 0.02) than for [rho] E1, E2, BB (0.11 +/- 0.01). Neither value was affected by the time of the cycle. The extractions (that fraction of steroid measured in arterial blood entering a tissue which is metabolized and not measured as that steroid in venous blood draining the tissue) across the splanchnic tissues were the largest of the tissue extractions measured (0.63 +/- 0.05 for E2 and 0.73 +/- 0.10 for estrone). The arm, uterus, kidney, and head had lower extractions, and the extraction of E2 was always lower than that of E1, probably due to the specific globulin binding of E2. Interconversion of the estrogens occurred across each tissue bed but reflected, in general, only a small portion of the total extraction, especially for the splanchnic tissue. There was no apparent difference in any of the transtissue conversions measured in the follicular as compared to the luteal phase. The administration of pharmacological amounts of dexamethasone to three monkeys resulted in a marked increase in the MCR of estradiol and a slight decrease in the MCR of estrone. Individual tissue extractions and transtissue conversions showed no consistent alteration after dexamethasone.

Animals↗
PubMed1979

Prolactin concentrations in the monkey fetus during the last third of gestation.

PRL concentrations were measured in cord plasma obtained at hysterotomy from 26 rhesus monkey fetuses between 111--170 days gestational age (GA). Mean PRL concentrations increased significantly from 23.7 +/- 10.1 (X +/- SE) ng/ml at 121--130 days GA to 126.9 +/- 16.9 ng/ml at 161--170 days GA. A similar significant increase in PRL with age also was observed in samples obtained from 16 fetuses chronically catheterized in utero between 130--155 days GA. Mean PRL levels were 34 +/- 3.2 ng/ml at 131--140 days GA and rose to 82 +/- 9.7 at 150--155 days GA. No difference in PRL concentrations was found between cord blood samples and fetal peripheral blood samples at the ages studied. Maternal PRL levels did not change in samples obtained from chronically catheterized, chair-restrained mothers between 130--155 days GA. A tendency toward an increase in maternal PRL with advancing gestational age was observed in samples collected after hysterotomy. These data indicate that the fetal rhesus monkey demonstrates an increase in plasma PRL similar to that in the human, suggesting a possible physiological role for this hormone in the primate fetus late in gestation.

Animals↗
PubMed1977

Transcription of bacterial DNA by isolated plant nuclei.

Plant nuclei prepared from protoplasts can be used as a cell-free system for testing their template activity of procaryotic DNA for plant polymerases. We were able to demonstrate that plant polymerases of Petunia hybrida are capable of transcribing linear bacterial DNA, whereas supercoiled DNA could not be used as a template.

Cell Nucleus↗