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Biomedical subjects

R G Lee

Publications and source records attributed to R G Lee.

At least 109 records · Page 6Linked to original sources
PubMed1988

OKT3 monoclonal antibody in heart transplantation.

OKT3 monoclonal antibody (OKT3) has already proved to be a valuable edition to the immunosuppression armamentarium available in cardiac transplantation. It is highly effective in treating refractory rejection, where approximately 90% of subjects may be salvaged. It may be even more valuable in prophylaxis, where in combination with an antibody suppression strategy and low-dose, "delayed" cyclosporine it appears to afford near complete protection against rejection. Moreover, OKT3-based prophylaxis seems to impact favorably on the rejection rate after the prophylaxis course has been completed. Adverse reactions are common and generally manageable, although occasional serious clinical events do occur.

Antibodies, Monoclonal↗
PubMed1988

Liver adenosine triphosphate and pH in fasted and well-fed mice after infusion of adenine nucleotide precursors.

Nutrition is a factor which may affect the liver energy charge. Experiments were performed to determine the effect of starvation and of ATP precursors, adenine and ribose on liver energy stores. The 31P NMR spectra of well-fed and starved mice livers were studied in a perfusion system using Krebs-Henseleit buffer (KHB). The ATP precursors, adenine (20 mmol/l) and ribose (80 mmol/l), were then added to determine their effect. Their effect on the ATP dynamics during ischemia and reperfusion were then evaluated. The effects of adenine alone and ribose alone were then determined. The 31P spectra of well-fed mice demonstrated high ATP content relative to Pi, phosphoesters and phospholipids. Animals starved for 24 h showed very low ATP, high Pi and little or no detectable phospholipids. In starved animals, ATP rose steadily to approximately 50% above the baseline level when precursors were added. Pi decreased to 30% of the baseline after 40 min. Little change was noted in well-fed animals. The rate of ATP decay did not change with the onset of ischemia, whether the livers were perfused with KHB alone or KHB with precursors. Upon reperfusion, precursors improved the recovery of ATP (81% vs 49% after 20 min ischemia, 44% vs 34% after 30 min ischemia). Addition of adenine alone produced similar results, but addition of ribose alone did not significantly alter ATP recovery. In conclusion, supplying starved or post-ischemic livers with adenine or ribose and adenine does improve ATP levels.

Adenine↗
PubMed1988

Inactivation of biofilm bacteria.

The current project was developed to examine inactivation of biofilm bacteria and to characterize the interaction of biocides with pipe surfaces. Unattached bacteria were quite susceptible to the variety of disinfectants tested. Viable bacterial counts were reduced 99% by exposure to 0.08 mg of hypochlorous acid (pH 7.0) per liter (1 to 2 degrees C) for 1 min. For monochloramine, 94 mg/liter was required to kill 99% of the bacteria within 1 min. These results were consistent with those found by other investigators. Biofilm bacteria grown on the surfaces of granular activated carbon particles, metal coupons, or glass microscope slides were 150 to more than 3,000 times more resistant to hypochlorous acid (free chlorine, pH 7.0) than were unattached cells. In contrast, resistance of biofilm bacteria to monochloramine disinfection ranged from 2- to 100-fold more than that of unattached cells. The results suggested that, relative to inactivation of unattached bacteria, monochloramine was better able to penetrate and kill biofilm bacteria than free chlorine. For free chlorine, the data indicated that transport of the disinfectant into the biofilm was a major rate-limiting factor. Because of this phenomenon, increasing the level of free chlorine did not increase disinfection efficiency. Experiments where equal weights of disinfectants were used suggested that the greater penetrating power of monochloramine compensated for its limited disinfection activity. These studies showed that monochloramine was as effective as free chlorine for inactivation of biofilm bacteria. The research provides important insights into strategies for control of biofilm bacteria.

Bacteria↗
PubMed1988

Factors promoting survival of bacteria in chlorinated water supplies.

Results of our experiments showed that the attachment of bacteria to surfaces provided the greatest increase in disinfection resistance. Attachment of unencapsulated Klebsiella pneumoniae grown in medium with high levels of nutrients to glass microscope slides afforded the microorganisms as much as a 150-fold increase in disinfection resistance. Other mechanisms which increased disinfection resistance included the age of the biofilm, bacterial encapsulation, and previous growth conditions (e.g., growth medium and growth temperature). These factors increased resistance to chlorine from 2- to 10-fold. The choice of disinfectant residual was shown to influence the type of resistance mechanism observed. Disinfection by free chlorine was affected by surfaces, age of the biofilm, encapsulation, and nutrient effects. Disinfection by monochloramine, however, was only affected by surfaces. Importantly, results showed that these resistance mechanisms were multiplicative (i.e., the resistance provided by one mechanism could be multiplied by the resistance provided by a second mechanism).

Chloramines↗
PubMed1988

Unilateral absence of the external carotid artery.

We report a patient with absence of the external carotid artery. The major external branches originate from the internal carotid artery which is really a common arterial trunk. The embryology and clinical significance of this rare vascular anomaly are discussed.

Adult↗
PubMed1987

Effects of ischemic nerve block on the early and late components of the stretch reflex in the human forearm.

To investigate the peripheral afferent mechanisms which mediate the short latency (M1) and long latency (M2) components of the stretch reflex, we have recorded EMG responses to extension perturbations at the wrist before and following inflation of a blood pressure cuff around the upper arm. After approximately 30 min of ischemia, the reflexes had almost completely disappeared, although subjects were still able to activate the forearm muscles voluntarily. As the ischemic block developed, the M2 component began to decrease in amplitude sooner than M1, and up to the time of complete loss of reflex activity, the suppression of M2 was relatively greater than that of M1. These results suggest that M2 may be mediated by a population of afferent fibers different from the Ia afferents which are believed to generate the M1 response.

Adult↗
PubMed1987

Relationship between EMG patterns and kinematic properties for flexion movements at the human wrist.

EMG patterns associated with voluntary wrist flexion movements were studied in normal human subjects. Initially, subjects were trained to produce movements within five specified velocity ranges while the amplitude of the movement and the opposing load remained constant. In a second set of experiments, subjects were required to produce movements at four different amplitudes, moving as rapidly as possible against a constant load. Finally, with movement velocity and amplitude kept constant, the external load was varied so that different forces were required to generate the movements. The slowest movements were associated with a prolonged burst of EMG activity from the agonist muscle with little or no antagonist activity. With increasing movement velocity, there was a gradual evolution to the characteristic "triphasic" pattern associated with rapid voluntary movements. As velocity of movement increased further, the amplitude and area of the EMG bursts increased while burst duration and interburst intervals decreased. Increases in movement amplitude were accomplished mainly by changing the timing of the EMG bursts; with larger amplitude movements the antagonist burst occurred later. With movements against larger loads there was an increase in the size of the agonist burst and a decrease in the antagonist burst, but no change in the relative timing of the EMG bursts. These systematic changes in EMG patterns associated with different types of movement provide an indirect method of obtaining information concerning the motor programs which generate the movements.

Adult↗
PubMed1987

Modulation of reflex and voluntary EMG activity in wrist flexors by stimulation of digital nerves in hemiplegic humans.

Changes in EMG activity in the wrist flexor muscles were studied in response to electrical stimulation of digital nerves and to sudden extension perturbations at the wrist produced by a torque motor in human subjects with unilateral cerebral hemisphere lesions. With the subjects maintaining a steady voluntary contraction against a constant load, digital nerve stimulation produced a series of excitatory and inhibitory changes in tonic EMG activity from the wrist flexors in both the normal and paretic arm. The most consistent response was a period of EMG inhibition beginning approximately 38 msec after the stimulus and lasting approximately 35 msec. With relatively weak electrical stimuli, there was less EMG inhibition in the paretic arm than in the normal arm; with stronger stimuli, the inhibitory response was similar in the two arms. The electrical stimuli and mechanical perturbations were then delivered together, with the interval between them adjusted so that the expected period of inhibition following electrical stimulation coincided with either the early (M1) or the long latency (M2) components of the stretch reflex. In the normal arm electrical stimulation produced more inhibition of the M2 component than of the M1 component. In the paretic arm, inhibition during the M2 component was less marked and similar in degree to that which occurred during M1. These results are compatible with the view that M1 and M2 are normally mediated by separate neural pathways. The long latency EMG activity evoked by muscle stretch in the paretic arm of hemiplegic patients may be generated by pathways or mechanisms different from those in the intact arm.

Electric Stimulation↗
PubMed1987

Villous adenoma of the duodenal papilla presenting as necrotizing pancreatitis in a patient with Gardner's syndrome.

The majority of patients with Gardner's syndrome and familial polyposis coli develop duodenal adenomatous polyps. Duodenal cancer sometimes arises in this setting, but nonmalignant problems from duodenal polyps have not been described. This report presents a patient with Gardner's syndrome who developed hemorrhagic pancreatitis and was found to have a villous adenoma encasing the pancreatic duct at the duodenal papilla. The case is important because it suggests that patients with polyposis coli may be at risk for significant nonmalignant problems from duodenal polyps, particularly if polyps exhibit villous histology and occur at the duodenal papilla.

Adenoma↗
PubMed1987

Magnetic resonance imaging of gynecologic masses.

The pelvis of 21 women with various gynecological masses were imaged with magnetic resonance (MR) imagers at 2.0 and 0.5 T. Fifteen normal individuals were used for studying the normal appearance of the female genitalia using spin echo pulse sequences with various pulse repetition (TR) and spin echo (TE) time values. Images were compared with those of the ultrasonic images, intraoperative findings, and the histopathologic examinations. The masses included simple ovarian cyst, cystadenoma, serous cystadenocarcinoma, ovarian teratoma, dysgerminoma, and uterine myoma. MR imaging was useful in demonstrating the anatomy and pathology of the cases examined in this study. It detected the internal structure of some tumors which were sonographically homogeneous. The potential of MR in staging of malignancies was demonstrated.

Adolescent↗
PubMed1987

Physiology of the basal ganglia and pathophysiology of Parkinson's disease.

This paper reviews current concepts concerning the anatomical organization and functions of the basal ganglia focusing mainly on the role of the basal ganglia in control of movement. Results of several studies which have been carried out on patients with Parkinson's disease are also reviewed and discussed as examples of altered normal physiological mechanisms.

Action Potentials↗
PubMed1987

Liver adenine nucleotide metabolism during ischemia and reperfusion of mice livers studied by phosphorous-31 nuclear magnetic resonance.

Perfusion experiments were performed at 20 degrees C and 37 degrees C to study liver adenine nucleotide metabolism during ischemia and reperfusion of mouse livers using 31P NMR. Perfusing at 8 mL/min (Krebs-Henseleit buffer), ATP was shown to be stable for 6 hours. There was a progressive decrease in the phosphodiesters (glycerophosphorycholine and glycerophosphorylethanolamine) during the 6-hour period. Liver subjected to cold ischemia at 20 degrees C showed a slow decrease in the beta ATP peak during a 42 +/- 6-minute period with a rise in the inorganic phosphate accompanied by a shift of inorganic phosphate to the high field indicating intracellular acidosis. With reperfusion, the beta ATP returned to previous levels and the inorganic phosphate shifted to its original position. During warm ischemia (37 degrees C) the ATP peak disappeared within 5 +/- 1 minute and only returned to 34% of its original value after 30 minutes of ischemia, indicating damage to a certain percentage of liver cells. When the liver was subjected to multiple short periods of cold ischemia, there was complete recovery of the ATP after six cycles. Reperfusion after each period of cold ischemia resulted in an ATP recovery consistently greater than the initial amount, which gradually decreased to preischemic levels after a short period. This suggests that there is an as yet undelineated mechanism of ATP production during ischemia that attempts to protect the cell against ischemia.

Adenine Nucleotides↗
PubMed1987

Nuclear magnetic resonance assessment of adenosine triphosphate (ATP) dynamics in ischemic mouse livers perfused with adenine and ribose.

Hepatic energy stores are essential to liver viability. We used a mouse liver perfusion model and MR spectroscopy to study the effect of adding two precursors of ATP (adenine and ribose) on ATP dynamics during ischemia and reperfusion. Using Krebs-Henseleit buffer with or without added adenine and ribose made little difference in the ATP decay rate during ischemia, but the recovery of ATP during reperfusion was more complete when adenine and ribose were added to the buffer. These findings suggest that the addition of the precursors of ATP, adenine and ribose, to perfusate after ischemia can accelerate and enhance ATP recovery.

Adenine↗
PubMed1987

Effect of cutaneous nerve stimulation on voluntary and stretch reflex electromyographic activity in wrist flexors in humans.

1. Changes in electromyographic (e.m.g.) activity in the wrist flexors of normal human subjects were studied in response to electrical stimulation of digital nerves and to sudden extension perturbations at the wrist produced by a torque motor. 2. With the subjects maintaining a steady voluntary contraction, stimulation of the digital nerves produced a series of excitatory and inhibitory changes in the tonic e.m.g. activity from the wrist flexors. The most prominent and consistent response was a period of e.m.g. inhibition beginning 39 ms after the stimulus and lasting for approximately 36 ms. 3. The stretch reflex evoked by extension perturbations of the wrist consisted of an early response (M1) with an onset latency of approximately 30 ms, and a late response (M2) with an onset latency of approximately 60 ms. 4. The electrical stimuli and the mechanical perturbations were then delivered together, varying the interval between them so that the period of inhibition resulting from the electrical stimuli occurred at the same time as the M1 or M2 components of the stretch reflex, or during the later voluntary response. 5. The amount of e.m.g. inhibition during the M2 component was significantly greater than that during M1 (P less than 0.02). This result is compatible with the view that M1 and M2 are mediated by separate neural pathways.

Adult↗
PubMed1987

Examination and characterization of distribution system biofilms.

Investigations concerning the role of distribution system biofilms on water quality were conducted at a drinking water utility in New Jersey. The utility experienced long-term bacteriological problems in the distribution system, while treatment plant effluents were uniformly negative for coliform bacteria. Results of a monitoring program showed increased coliform levels as the water moved from the treatment plant through the distribution system. Increased coliform densities could not be accounted for by growth of the cells in the water column alone. Identification of coliform bacteria showed that species diversity increased as water flowed through the study area. All materials in the distribution system had high densities of heterotrophic plate count bacteria, while high levels of coliforms were detected only in iron tubercles. Coliform bacteria with the same biochemical profile were found both in distribution system biofilms and in the water column. Assimilable organic carbon determinations showed that carbon levels declined as water flowed through the study area. Maintenance of a 1.0-mg/liter free chlorine residual was insufficient to control coliform occurrences. Flushing and pigging the study area was not an effective control for coliform occurrences in that section. Because coliform bacteria growing in distribution system biofilms may mask the presence of indicator organisms resulting from a true breakdown of treatment barriers, the report recommends that efforts continue to find methods to control growth of coliform bacteria in pipeline biofilms.

Bacteria↗