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Biomedical subjects

J D Johnson

Publications and source records attributed to J D Johnson.

At least 19 recordsLinked to original sources
PubMed1979

Interaction of alpha-chymotrypsin with the fluorescent probe 1-anilinonaphthalene-8-sulfonate in solution.

The binding of the fluorescence probe 1-anilinonaphthalene-8-sulfonate (Ans) to alpha-chymotrypsin (alpha-CHT) at pH 3.6 is accompanied by a dramatic enhancement of Ans fluorescence and a shift of the emission maximum to shorter wavelengths. Our study reveals that one Ans molecule binds to alpha-CHT at a site different from either the active site of alpha-CHT or the 2-p-toluidinylnapthalene-6-sulfonate binding site. the binding constant of Ans is about the same (10(4) M-1) at pH 3.6 and 6.4. Nanosecond fluorescence depolarization data indicate that Ans is rigidly bound to alpha-CHT. The fluorescence enhancement due to binding of Ans to alpha-CHT at low pH could be due to binding either to a hydrophobic site or to a site where local dipoles do not relax during the excited-state lifetime of Ans. As the pH is increased, fluorescence intensity of the Ans-alpha-CHT complex decreases appreciably; and the emission maximum shifts to longer wavelengths. The fluorescence decay curves exhibit a corresponding sensitivity to pH. The pH effect on the fluorescence of Ans-alpha-CHT can be interpreted in terms of a pH-dependent equilibrium between alpha-CHT conformers differing in the degree of mobility of polar residues and water molecules at the Ans binding site or structural changes in the Ans binding site.

Allosteric Site↗
PubMed1979

Pulmonary excretion of carbon monoxide in the human infant as an index of bilirubin production. I. Effects of gestational and postnatal age and some common neonatal abnormalities.

Using a single pass, flow-through system, the pulmonary excretion rate of endogenously produced carbon monoxide was measured as an index of bilirubin production in human infants with varying gestational and postnatal ages and with a variety of clinical abnormalities. No significant difference in VECO was found related to sex or gestational age. The mean VECO for a small group of Oriental infants was significantly increased. VECO decreased with increasing postnatal age. As expected, infants with hemolytic disease of the newborn had a markedly increased mean VECO. Infants with jaundice of unknown etiology also had an elevated mean VECO, implying that increased bilirubin production may be a factor contributing to the "nonphysiologic" bilirubinemias of these infants.

Bilirubin↗
PubMed1979

Refractory hypoxemia associated with neonatal pulmonary disease: the use and limitations of tolazoline.

Thirty-nine critically ill infants with pulmonary disease received tolazoline because of severe hypoxemia refractory to administration of 100% O2 and mechanical ventilation. Twenty-seven (69%) of the infants responded with an increase in PaO2 greater than or equal to 20 torr in the first umbilical arterial gas after completion of the initial ten-minute infusion (1 to 2 mg/kg) of the drug. A response was not correlated with survival. The overall survival was 46%, essentially unchanged from our previous report (44%). Infants with hyaline membrane disease had the poorest survival rate (33%). Complications associated with the use of tolazoline occurred in 82% of the infants. A hypotensive reaction, defined as a 25% decrease in mean arterial pressure from the pre-tolazoline level, occurred in 67% of the infants, and more commonly in the infants with RDS (87%). In 11 infants who did not respond to the initial dose of tolazoline, the dose was increased up to 10 mg/kg/hour; only one infant responded, and eight (73%) had a hypotensive reaction.

Carbon Dioxide↗
PubMed1979

The white cell ratio in the very low birth weight infant.

The purpose of this study was to assess the usefulness of the white cell ratio of immature neutrophils (PMNs) to total (immature plus mature) PMNs as an indication of infection in the very small premature infant. We retrospectively reviewed the charts of 59 premature infants less than or equal to 1,250 g admitted to our Newborn Intensive Care Unit over a one-year period who had at least one white count determined. Twenty-three were born after rupture of membranes for greater than or equal to 24 hours (PROM), 47 had a one-minute Apgar score less than or equal to 6 and 31 had a five-minute Apgar scores less than or equal to 6, 38 had respiratory distress syndrome (RDS), and 4 had confirmed infection. Thirty-one of the infants had a ratio greater than or equal to .15 in the first day of life, a value which has been suggested in the literature as being abnormal and an indication to suspect sepsis. This ratio bore no statistical relationship to PROM, low Apgar scores, or RDS. We analyzed these same relationships using a ratio greater than or equal to .25, another ratio derived from data in the literature which has been said to suggest infection. No statistical correlation was found for low Apgars or RDS, but there was a significant relationship between PROM and attainment of a ratio greater than or equal to .25 (p less than .005). It is notable that 2 out of the 4 infants with infection had a ratio less than .15. We wish to cast doubt on the applicability of the currently defined WBC ratios in the literature as they apply to the infant with birth weight less than 1,250 g and emphasize the apparent effect of PROM as a factor upon these ratios.

Asphyxia Neonatorum↗
PubMed1979

T-cell subpopulations in chronic lymphocytic leukemia: abnormalities in distribtuion and in in vitro receptor maturation.

Purified human thymus-derived (T) lymphocytes were analyzed by detection of Fc receptors for either IgG or IgM in healthy controls and in patients with chronic lymphocytic leukemia (CLL). There was a significant and persistent increase in the numbers of T cells bearing receptors for IgG (Fc gamma) in CLL patients in comparison to the controls. After an in vitro culture period, there was a significantly decreased appearance of cells with IgM receptors (Fcmu) in CLL patients in comparison to the control group. These results indicate an imbalance in circulating T-cell subpopulations for CLL patients. In addition, an in vitro defect in CLL T-cell membrane receptor appearance is present.

Binding Sites↗
PubMed1979

Effect of erythrocyte destruction on the pulmonary excretion rate of carbon monoxide in adult male Wistar rats.

One of the major contributory factors to hyperbilirubinemia in the human infant is bilirubin production. Determination of the pulmonary excretion rate of carbon monoxide is used to measure indirectly the rate of bilirubin production by estimating the endogenous production of CO, which is formed in equimolar amounts with bilirubin in the catabolism of heme. There has been no study to confirm that complete recovery of CO produced in vivo from the catabolism of known amounts of heme occurs via pulmonary excretion. We report here quantitative determinations of the pulmonary excretion rate of CO in five adult male Wistar rats after injection of known amounts of heme in the form of red blood cells "damaged" by incubation in a solution containing a sulfhydryl inhibitor, NEM. The mean recovery of "extra" CO above baseline production represented as a molar ratio of extra CO to heme was 0.98 +/- 0.02 (S.E.). Control studies showed no extra CO production after starvation, injection of NEM in an amount comparable to that used in the experimental animals, or injection of undamaged red blood cells.

Animals↗
PubMed1979

Pulmonary excretion of carbon monoxide in the human newborn infant as an index of bilirubin production: III. Measurement of pulmonary excretion of carbon monoxide after the first postnatal week in premature infants.

Using a single pass, flow-through system, the excretion rate of endogenously produced carbon monoxide (VeCO) was measured as an index of bilirubin production in 41 Caucasian infants of various gestational ages after the first postnatal week. twenty-one were less than or equal to 32 weeks gestation. The mean slope for the 25 premature infants with multiple VeCO determinations was -0.21 +/- 0.11 (SE) microliters/kg/hour per day (P less than .025, one-tailed). Fifteen premature infants with at least three VeCO determinations during the first 30 days of life had an average decrease in total CO excreted of 1.33% per day compared to the extrapolated initial value of total CO excretion of 27.0 +/- 2.0 (SE) microliters/hour, giving a calculated maximum red cell life span of 75 days.

Bilirubin↗
PubMed1978

Flunisolide nasal spray in the treatment of perennial rhinitis.

In an 8-week double-blind study of the clinical effectiveness of flunisolide, a new synthetic corticosteroid intended for topical use, 73 persons with perennial rhinitis received 300 microgram/d of either flunisolide or placebo. The flunisolide group showed a significantly greater reduction than the placebo group in the daily duration of sneezing, stuffy nose, nose blowing and postnasal drip, but not of runny nose, and a significantly greater reuction in the severity of all these manifestations. Substantial or total control of manifestations was reported by 73% of the flunisolide group and 25% of the placebo group, a significant difference. Careful monitoring of the plasma cortisol concentration revealed no evidence of adrenal suppression, and in no patient did the value fall below normal. The lack of adrenal suppression may be due to the very small amount of corticosteroid administered and the rapid metabolism of flunisolide into a relatively inactive metabolite.

Administration, Intranasal↗
PubMed1978

Dansylaziridine-labeled troponin C. A new fluorescent "physiological" probe for calcium regulation by sarcoplasmic reticulum.

Dansylaziridine-labeled troponin C (TnCDANZ) undergoes a greater than 2-fold fluorescence enhancement with Ca2+ binding to the Ca2+-specific regulatory sites of troponin C. Hence, TnCDANZ serves as a very good indicator of Ca2+ in the range of 3.0 to 70 micron. Ca2+ uptake and release by sarcoplasmic reticulum can be easily and accurately monitored by the fluorescence changes in TnCDANZ. In this manner, we can monitor directly the removal of Ca2+ from troponin C by the sarcoplasmic reticulum. Thus, this reaction represents a useful analogue ot the Ca2+ "on-off" process in muscle.

Animals↗