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Biomedical subjects

R D Johnson

Publications and source records attributed to R D Johnson.

At least 127 records · Page 7Linked to original sources
PubMed1990

Spinal nerve root origin of the median, ulnar and musculocutaneous nerves and their muscle nerve branches to the canine forelimb.

The contribution individual ventral spinal nerve roots made to the canine median nerve, ulnar nerve, musculocutaneous nerve, and their muscle nerve branches was determined electrophysiologically. Each spinal nerve root was sequentially stimulated. Utilizing quantitative signal averaging techniques, the evoked potential was measured at each tested peripheral nerve. Evoked potential to the median nerve originated from the seventh cervical spinal root (C7) through the second thoracic spinal root (T2) with most input from C8 and T1. The ulnar nerve received evoked potential from C7-T2. Although T1 provided the major input to both the median and ulnar nerves, the relative contribution of T1 was greater in the ulnar nerve. The musculocutaneous nerve received input from ventral spinal roots C6-T1 with C6 and C7 providing most of the evoked potential. The ventral spinal roots which supplied the bulk of the evoked potential to a particular muscle nerve were consistent between individual dogs. Variation of evoked potential input was greatest from spinal roots which supplied less than 10% of the total potential.

Animals↗
PubMed1990

A unitized enzyme-labeled immunometric digoxin assay suitable for rapid testing.

An enzyme-labeled immunometric assay has been developed for measuring digoxin concentrations in serum or plasma. Unitized, compartmentalized reagents are used with an automated sample-processing instrument. The enzyme activity of the processed sample, which is directly proportional to the digoxin concentration, is measured by using a reagent strip and the Ames Seralyzer reflectance photometer. The test takes less than 15 min, and digoxin concentrations are calculated from a two-point calibration line stored in the instrument. Within-run CVs for controls at four concentrations ranged from 2.3% to 3.8%; between-run CVs were from 1.5% to 2.6%. Results obtained with clinical serum samples correlated well (r greater than 0.96) with those obtained by fluorescent polarization immunoassay (Abbott TDx) and RIA (Clinical Assays and NML). This rapid and convenient method for monitoring digoxin concentrations in serum or plasma is particularly well suited for decentralized sites such as emergency rooms, urgent-care centers, and physicians' offices.

Antibodies, Monoclonal↗
PubMed1989

Deuterium NMR study of structural and dynamic properties of horseradish peroxidase.

High field deuterium NMR spectra have been recorded for various horseradish peroxidase complexes reconstituted with hemins possessing specific 2H labels. The line width of the 2H NMR signals of deuteroheme reconstituted-horseradish peroxidase (HRP) and its cyano complex for the immobilized skeletal 2-2H and 4-2H labels yield the overall protein rotational correlation time (22 ms at 55 degrees C), which is consistent with expectations based on molecular weight. Meso-2H4 labels yield broad (1.3 kHz) signals just upfield from the diamagnetic protein envelope for HRP, and in the central portion of the protein envelope for the CN- ligated resting state HRP. Meso-2H4-labeled mesohemin-reconstituted HRP exhibits a similar signal but shifted further upfield by approximately 10 ppm. The net upfield meso-H hyperfine shifts confirm a five-coordinate structure for resting state HRP. 2Ha resonances for essentially rotationally immobile vinyl groups were detected in both resting state HRP and CN- ligated resting state HRP. Heme methyl-2H-labeling yields relatively narrow lines (approximately 80 Hz) indicative of effective averaging of the quadrupolar relaxation by rapid methyl rotation. Thus the 2H line width of rapidly rotating methyls in hemoproteins can be used effectively to determine the overall protein tumbling rate. Preliminary 2H experiments in meso-2H4-labeled compound I do not support large pi spin density at these positions on the porphyrin cation radical, and argue for a a1u rather than a a2u orbital ground state.

Deuterium↗
PubMed1989

Production scale purification of biosynthetic human insulin by reversed-phase high-performance liquid chromatography.

A process based on reversed-phase high-performance liquid chromatography (RP-HPLC) has been developed for the purification of biosynthetic human insulin (BHI). The RP-HPLC procedure has been successfully integrated into the multimodal chromatographic production process used to purify kilogram quantities of BHI. Axial compression column technology was used in the scale-up process. The RP-HPLC procedure yields an insulin product having high chemical purity and full biological activity.

Chromatography, High Pressure Liquid↗
PubMed1989

Further characterization of tetracycline's quantitative binding to dentin.

Unerupted human third molar crown segments were used to measure the change in the concentration of 3H-tetracycline that occurs when it moves across dentin from pulpal to occlusal surfaces. When 1.25, 2.5, and 5 x 10(-5) M 3H-tetracycline were filtered across dentin, binding increased by 21, 51, and 69%, respectively. When the same concentrations of 3H-tetracycline were preloaded onto crown segments and eluted with 1.1 x 10(-3) M nonradioactive tetracycline, the percentage of elution of 3H-tetracycline was not significantly different over time. When preloaded 3H-tetracycline was displaced by diffusion with water or 1.1 x 10(-3) M nonradioactive tetracycline, there were no significant differences. There was a significant difference between the rate of displacement of 1.25 x 10(-5) M 3H-tetracycline and the other two preloaded concentrations when 5.8 x 10(-4) M 3H-tetracycline/tetracycline was used as the eluant. These data suggest that the binding of 3H-tetracycline to dentin was concentration dependent and that 3H-tetracycline binds nonspecifically and reversibly.

Dentin↗
PubMed1989

Motor fibers in the canine distal caudal cutaneous sural nerve--dual innervation of the hind limb plantar muscles.

The function of the communicating branch of the distal caudal cutaneous sural (DCCS) nerve to the tibial nerve was investigated in 7 adult dogs and was found to contain the motor component of this nerve. This function was studied by direct visualization of the contraction of the hind limb plantar muscles and by direct electrophysiologic recording of motor unit action potentials in these muscles, following stimulation of the DCCS nerve. Contraction of all of the mm. interossei, the mm. lumbricales, the m. adductor digiti quinti and the m. adductor digiti secundi was observed with the stimulation of either the tibial or the DCCS nerves, although there was a qualitative variability in the plantar muscles exhibiting the strongest contraction with stimulation of the latter nerve. This communicating branch was not found in one of the experimental dogs, suggesting some individual variability in the DCCS nerve anatomy and subsequent function. This study conclusively demonstrated that the canine DCCS nerve contains both motor and sensory nerve fibers, which is similar to this nerve in the rat, but anatomically and functionally different to that in the human and the cat.

Anatomy, Comparative↗
PubMed1989

Evaluation of a phenytoin dosage regimen design and adjustment computer program.

A computer program for phenytoin (PHT) dosing was developed containing seven different menus: two for drug-naive patients, one using an empirical equation, the other using means for Vmax and Km; two for patients in whom either one or two dose rates and steady-state concentrations are available; two for patients with hypoalbuminemia, and uremia, respectively; and one menu that optimizes Vmax and Km from available steady-state concentrations. The program accepts or converts PHT and sodium PHT, and makes blood level correction for the concomitant administration of 25 different drugs. The evaluation of the program was done by retrospective analysis using data from three study pools: group I involved 47 patients from the University Hospital, group II relied upon 29 patient data supplied from a collaborative Veterans Administration study, and group III involved 26 patients from the Children's Hospital. Predictions were made and compared with found data to be within a range of +/- 15, 20, or 25%. For study group III, many individual blood samples were less than 8 micrograms ml-1; hence, saturation kinetics may not have been involved. It is suspected that saturation kinetics in infants may begin at higher levels. Compliance seems to still be a major problem in PHT monitoring and dosage regimen adjustment. Accepting the data as they are, using one or two dose rates with the corresponding blood concentrations resulted overall in 73-86% achieving blood levels within +/- 25% of the predicted value.

Adolescent↗
PubMed1988

Consequences of fetomaternal haemorrhage after intrauterine transfusion.

Fetomaternal haemorrhage was studied after 68 consecutive fetal intravascular transfusions performed in 20 patients with Rh isoimmunisation. alpha Fetoprotein concentration was assayed in maternal blood taken before, and immediately after each transfusion and three and 24 hours later. An increase of 50% or more in the concentration in any of the samples after transfusion was considered to indicate fetomaternal haemorrhage. Fetal alpha fetoprotein concentration in blood sampled before transfusion was also assayed and the amount of fetomaternal haemorrhage calculated. Fetomaternal haemorrhage occurred in 21 of 32 patients with an anterior placenta and in six of 36 with a posterior or fundal placenta. The mean estimated volume of haemorrhage was 2.4 ml, which was on average equal to 3.1% of the total fetoplacental blood volume. When the volume of fetomaternal haemorrhage at the first transfusion was greater than 1 ml there was a greater increase in maternal Rh (D) antibody titres and a greater fall in fetal packed cell volume. Sampling of fetal blood should not be routinely done early in patients with Rh isoimmunisation, and intrauterine transfusion should be delayed as long as possible. Sampling sites other than the placental cord insertion reduces the risk of fetomaternal haemorrhage.

Blood Transfusion, Intrauterine↗
PubMed1988

Perception of illness among patients with alcoholic liver disease.

A sample of patients (N = 134) with alcoholic liver disease was found to be significantly "health internal" (i.e., believe that their behavior plays a major role in determining subsequent health or illness) compared with a sample of patients with nonalcoholic liver disease on Health Locus of Control Scale. The patients with alcoholic liver disease did not differ significantly from those with nonalcoholic liver disease in the level of awareness of severity of their disease. Most patients in both groups agreed with their physician's ratings of the severity of their illness. The implications of these findings are discussed.

Adolescent↗
PubMed1988

Spinal nerve root origins of the cutaneous nerves of the canine pelvic limb.

The spinal nerve root origins of the cutaneous nerves innervating the canine pelvic limb were determined in 12 barbiturate-anesthetized, healthy dogs by stimulating the dorsal roots L1-S3 and recording the evoked-action potentials from each cutaneous nerve. The dogs were then euthanatized, identification of each dorsal root and cutaneous nerve was verified by dissection, and the type of lumbosacral plexus (prefixed, median fixed, or postfixed) was determined. With one exception, the dorsal cutaneous branches and lateral cutaneous branches of L1-L3 originated only from their corresponding spinal nerve roots. The genitofemoral nerve received afferent fibers predominantly from L3-L4 nerve roots. The lateral cutaneous femoral nerve originated from L3-L5 nerve roots, and the saphenous nerve from L4-L6 nerve roots. The proximal caudal cutaneous sural nerve originated from L6-S1. The lateral cutaneous sural nerve originated from L5-S1; the deep and superficial fibular nerves arose primarily from L6-L7. The distal caudal cutaneous sural nerve originated predominantly from L7-S1, and the medial cutaneous tarsal nerve originated from L6-S1. The medial plantar nerve originated predominantly from L6-S1 roots, whereas the lateral plantar nerve originated from L6-S2 roots. The middle clunial nerve received afferent fibers primarily from S1-S2; the caudal clunial nerve received fibers from S1-S3. The caudal cutaneous femoral nerve originated predominantly from L7-S2. The dorsal nerve of the penis originated predominantly from S1-S2, and the superficial perineal nerve originated from S1-S3. One dog had a prefixed plexus, 8 dogs had median-fixed plexuses, and 1 dog had a postfixed plexus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗