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PubMed1986

Alteration of disk-shedding patterns by light-onset of higher than normal intensity.

Rod outer segment (ROS) disk-shedding patterns were determined in the albino rat eye. All of the animals had the same, low-intensity-light histories, but on the day that shedding patterns were to be measured the rats were divided into three groups: one which did not have any lights turned on at 0700 hr ('contained dark' group); one which had normal, 3-lx light turned on ('colony' group); one which had a brighter-than-normal light turned on ('80-lx' group). The 'continued dark' group displayed a broad profile of shedding over time which persisted because phagosomes disappeared so slowly. The 'colony' group showed the same initial rate of phagosome production as did the 'continued dark' group but a much accelerated rate of phagosome disappearance. The '80-lx' group showed no rate of phagosome production; rather there was a simple, rapid exponential disappearance of those phagosomes which existed just prior to light onset. The kinetics of these phenomena are described in a model, rate constants for which were obtained from our data and simulated on an analog computer. The analysis of the three shedding patterns indicates the existence of an intensity-dependent disappearance rate and suggests an inhibition of shedding and/or phagocytosis by intensity greater than that of the usual environment.

Animals↗
PubMed1984

Quantitative assessment of outflow resistance in lower extremity arterial reconstructions.

Graft patency is thought to correlate with resistance in the runoff bed or outflow resistance. However, accurate measurement of this parameter has been difficult. A simple and reproducible method for direct measurement of outflow resistance following completion of the distal anastomosis of a bypass graft has been developed. This method employs injection of a fixed amount of normal saline through the proximal end of the graft and measurement of the resulting integrated pressure increment by an analog computer. Division of this pressure integral by the volume injected is a measure of the outflow resistance expressed in resistance units (mm Hg/ml/min). The median outflow resistance in 31 femoropopliteal bypasses was 0.29 units with a range of 0.08-1.38 units. The median outflow resistance in 33 femorodistal bypasses was 0.7 units with a range of 0.18-2.34 units. All bypasses with an outflow resistance of 1.1 units or less remained patent for 3 months. There were 51 grafts in this group (30 femoropopliteal; 21 femorodistal) and their outflow resistance ranged from 0.08 to 1.1 units. All bypasses with an outflow resistance of 1.2 units or higher thrombosed within the first postoperative month. There were 13 grafts in this group (1 femoropopliteal; 12 femorodistal) and their outflow resistance ranged from 1.2 to 2.38 units. Eight of the 13 grafts that failed originally were subjected to thrombectomy, which was uniformly unsuccessful. Although this method does not yet allow bypass surgery to be denied to any patient, it does define a group of patients in whom thrombectomy will not be effective and should not be attempted.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1977

Oligoclonal gamma-globulin banding of cerebrospinal fluid in patients with subacute sclerosing panencephalitis. Comparison of the electrophoretic pattern with that in multiple sclerosis and congenital infections.

Lumbar cerebrospinal fluid (CSF) of 8 patients with subacute sclerosing panencephalitis (SSPE) was examined by agarose gel electrophoresis. In comparison with normal controls and children with different neurological diseases (including infections, tumours and degenerative diseases) the quantitative evaluation of the pherograms by an analog computer revealed an extreme change of the gamma-globulin profile. All cases showed 6-7 abnormal subfractions consisting of 2-4 tall, markedly protruding spikes and several small intermediate fractions. The oligoclonal gamma-globulin contributed 20.1-42.5% to total protein. This particular gamma-globulin profile seems to be highly indicative of the diagnosis of SSPE. It can be distinguished from the oligoclonal pattern in patients suffering from multiple sclerosis (MS) and congenital infections. The CSF protein profile of 13 patients with MS was different from that in SSPE in that it showed 1-5 monoclonal gamma-fractions in every case with none or only one peak protuding more markedly. The percentage of all subfractions amounted to 4.5-23.8% of total protein. As in MS, the aspect of oligoclonality in 9 children with congenital infections (cytomegalic inclusion body disease, toxoplasmosis and rubella) was quite variable, as again 1-5 abnormal subfractions were detected. Their relative concentrations, on the whole ranging from 0.6-12% of total protein, was considerably lower than in SSPE.

Adolescent↗
PubMed1983

Pulmonary mechanics in conscious Fischer 344 rats: multiple evaluations using nonsurgical techniques.

An adaptation of the method reported by Amdur and Mead (1958, Amer. J. Physiol. 192, 364-368) was used to evaluate pulmonary mechanics in conscious rats, utilizing a flow plethysmograph and intraesophageal catheter to determine compliance, resistance, respiratory flow, thoracic pressure, tidal volume, frequency, and minute volume. The procedure did not require surgery, and repeat evaluations were made in conscious rats. Real time calculations of pulmonary parameters were accomplished with an analog computer interfaced with a digital computer for display and data storage. Multiple evaluations (1, 3, 6, 13, 18, 24, 30, and 36 weeks) in 40 rats are reported. The utility of the system in establishing a base line against which pulmonary impairment, related to the effects of known pulmonary toxicants, e.g., ANTU and NO2, could be measured, was evaluated.

Aging↗
PubMed1990

An improved system for single unit isolation from multiunit nerve recordings by velocity analysis.

A system for recording and decomposition of complex extracellular spike trains by analog computing is presented. Unlike other systems, it is not necessary to establish templates for the analysis. Rather by adjustments of a single knob, the velocity band can be adjusted. The velocity measurement can be made to a precision of better than 1%, where the velocity jitter in individual spikes of a unit becomes apparent. Spike trains on the connective of a stick insect are analyzed which occur during an intersegmental reflex, the CLP reflex.

Action Potentials↗
PubMed1989

Superiority of perfusion over bolus administration in cancer chemotherapy: proposition of a compartmental model.

Recent studies indicate that, for cancer chemotherapy, prolongation of drug injection time yields lower toxicity and better efficacy. We propose a compartmental pharmacological model to explain these observations. The model has been simulated on an analog computer. The curves obtained give a credible explanation for the clinical data. The superiority of perfusion over bolus injection may be attributed to plasma peak suppression.

Antineoplastic Agents↗
PubMed1994

Mechanisms involved in living systems organisation, especially the programming necessary to enable the construction of individuals in three dimensions.

The complexity of the organization of living systems escalates by orders of magnitude in the development, from single precursor cells, not only of the three-dimensional structures characterizing each species but also in the variations necessary to accommodate the 1 million or more separate and identifiable species on this planet. Although the genetic information controlling such information is currently considered to reside in cellular DNA, it is also held that such information is restricted to a linear form encoding specifically for protein. However, this not only fails to explain the co-ordination of the vast number of processes occurring in simple, single cell, organisms, but also the integration of cellular activities to serve the interest of the total system. In particular how can a homeobox containing only genes encoding specifically for proteins organize and implement the mechanisms necessary for three-dimensional development? This, and the organization and implementation of the massive amount of information necessary to execute the construction of such a wide range of species, each in its own unique and exquisite detail, calls for internal programming of a highly complex and sophisticated nature. It is proposed here that such a central computer-analog program does exist, housed in the molecular electronic structure of cellular nucleic acid, primarily in DNA: its possible nature is discussed. Since precursor cells contain only of the order of 10(-10) g of DNA, this proposal involves an increase in information storage efficiency comparable with that already achieved by silicon microprocessors over mechanical calculators.

Animals↗
PubMed1964

THE REPOLARIZATION PHASE OF THE CARDIAC VENTRICULAR ACTION POTENTIAL: A TIME-DEPENDENT SYSTEM OF MEMBRANE CONDUCTANCES.

A system for the generation of the repolarization phase of the ventricular action potential is described. The system is based on time-dependent changes in membrane conductance to sodium and potassium ions. However, the changes in conductance during an action potential retain a degree of voltage dependence through the initial conditions which depend on previous depolarizations of the membrane. The equations describing the system were solved with an analog computer and various action potential forms are reproduced. The effects of hyperpolarizing and depolarizing current applied during an action potential are investigated. The changes in shape of an action potential after a change in the rate of stimulation show partial agreement with previous experimental findings. The applicability of time-dependent and voltage-dependent systems for the generation of the repolarization phase of the ventricular action potential is discussed.

Action Potentials↗
PubMed1999

Series resistance compensation for whole-cell patch-clamp studies using a membrane state estimator.

Whole-cell patch-clamp techniques are widely used to measure membrane currents from isolated cells. While suitable for a broad range of ionic currents, the series resistance (R(s)) of the recording pipette limits the bandwidth of the whole-cell configuration, making it difficult to measure rapid ionic currents. To increase bandwidth, it is necessary to compensate for R(s). Most methods of R(s) compensation become unstable at high bandwidth, making them hard to use. We describe a novel method of R(s) compensation that overcomes the stability limitations of standard designs. This method uses a state estimator, implemented with analog computation, to compute the membrane potential, V(m), which is then used in a feedback loop to implement a voltage clamp; we refer to this as state estimator R(s) compensation. To demonstrate the utility of this approach, we built an amplifier incorporating state estimator R(s) compensation. In benchtop tests, our amplifier showed significantly higher bandwidths and improved stability when compared with a commercially available amplifier. We demonstrated that state estimator R(s) compensation works well in practice by recording voltage-gated Na(+) currents under voltage-clamp conditions from dissociated neonatal rat sympathetic neurons. We conclude that state estimator R(s) compensation should make it easier to measure large rapid ionic currents with whole-cell patch-clamp techniques.

Animals↗
PubMed1975

Comparison of arrhythmia computer and conventional monitoring in coronary-care unit.

Conventional methods of monitoring arrhythmias impose heavy demands on staff and are unreliable. On-line arrhythmia computers have been developed to overcome these problems, but there has been no critical evaluation of the functioning of such a system in a clinical setting. A comparison was made of the efficacy of two methods of monitoring in detecting arrhythmias in sixty-four patients in a coronary-care unit. Half the patients were monitored by a commercially available arrhythmia computer; the other half were monitored by conventional means with a rate-triggered alarm system. More than 99 percent of episodes of potentially serious ventricular arrhythmias were detected by the computer; 95 percent of patients with these arrhythmias were treated immediately. In those monitored by conventional means, a large proporation of such arrhythmias were unrecognised: only 17 percent of affected patients received immediate antiarrhythmic therapy. In 30 percent, treatment was delayed for several hours, and none was given in 52 percent. False alarms occurred with both systems but were more readily recognised as such in the computer-monitored patients. It is concluded that an arrhythmia computer improves the standards of arrhythmia detection, leads to quicker institution of treatment, and diminishes the demand on skilled staff.

Adult↗
PubMed2001

Understanding the dynamics of illness and help-seeking: event-structure analysis and a Cambodian-American narrative of "spirit invasion".

Event structure analysis (ESA) and its computer analog, ETHNO, represent a class of relatively new methodological approaches that make it possible to capture the complexity of help-seeking interactions. Using narrative data from a study of Cambodian-American help-seeking interactions within a circumscribed illness episode, this paper demonstrates the feasibility of using ESA/ETHNO to illuminate how event sequence, operant illness beliefs, structural conditions, and human agency interpenetrate and shape the occurrence and timing of pivotal actions and the denouement of a help-seeking episode.

Anthropology, Cultural↗
PubMed1999

Influence of fever on the pharmacokinetics of ciprofloxacin.

The influence of fever on the pharmacokinetics of ciprofloxacin was investigated in seven patients with acute febrile diseases. Antibiotic serum concentrations were determined using high-performance liquid chromatograpy (HPLC). The analog computer and the Simulink software package were used to identify the pharmacokinetic model and Penoclin software package to obtain the secondary parameters. During fever, higher maximum serum concentrations (Cmax) of ciprofloxacin were observed in six out of seven patients. The result suggests that the influence of fever on the pharmacodynamics of ciprofloxacin is favorable.

Adult↗
PubMed2000

The complementary brain: unifying brain dynamics and modularity.

How are our brains functionally organized to achieve adaptive behavior in a changing world? This article presents one alternative to the computer analogy that suggests brains are organized into independent modules. Evidence is reviewed that brains are in fact organized into parallel processing streams with complementary properties. Hierarchical interactions within each stream and parallel interactions between streams create coherent behavioral representations that overcome the complementary deficiencies of each stream and support unitary conscious experiences. This perspective suggests how brain design reflects the organization of the physical world with which brains interact. Examples from perception, learning, cognition and action are described, and theoretical concepts and mechanisms by which complementarity might be accomplished are presented.

Journal Article↗