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Biomedical subjects

J Green

Publications and source records attributed to J Green.

At least 487 records · Page 27Linked to original sources
PubMed1989

Measurements of components of resistance to breathing.

Total respiratory resistance (Rrs), pulmonary resistance (RL), and airway resistance (Raw) of 12 male patients with chronic obstructive lung disease were measured by the partial occlusion method, intraesophageal balloon technique, and body plethysmography, respectively. Chest wall resistance (Rew) and lung tissue resistance (Rti) were computed. Percentages of Rew/Rrs, RL/Rrs, Raw/Rrs, Rti/Rrs, Raw/RL, and Rti/RL were calculated. The magnitude of the components of resistance to breathing of this study and the data appearing in the literature are compared. Wide variation between the data reported by various authors was observed. The possible causes of these variations are discussed.

Aged↗
PubMed1989

Use of a metastabilized chlorous acid/chlorine dioxide formulation as a mouthrinse for plaque reduction.

A metastabilized chlorous acid/chlorine dioxide (MECA) formulation was used as a mouthwash in a group of 18 volunteers aged 20-27. Its effect on developing plaque and salivary bacterial count was tested. The trial was carried out over 33 days during which each subject used three different formulations of mouthwash: a high concentration (0.16% sodium chloride in an activating system), a low concentration (0.04% sodium chloride, comparably activated) and a placebo mouthwash (activating system alone). Each participant used each of the three formulations as the only means of oral hygiene for 5-day periods. Each experimental period was separated by 9 days during which the participants returned to their regular oral hygiene habits. The high concentration and low concentration groups showed a 34.5 and 13.5% reduction of dental plaque scores, respectively, compared with the placebo control group. This effect on the plaque index scores was not accompanied by any significant change in the number of salivary bacteria.

Adult↗
PubMed1988

The biosynthesis and assembly of protein A of soluble methane monooxygenase of Methylococcus capsulatus (Bath).

Protein A of soluble methane monooxygenase (EC 1.14.13.25) of Methylococcus capsulatus (Bath) is the hydroxylase component of the enzyme complex, capable of inserting an atom of oxygen into methane. The protein possesses an unusual non-heme iron center consisting of two mu-hydroxo-bridged antiferromagnetically coupled iron atoms. It was possible to remove the iron center of protein A by subjecting the protein to freeze/thaw cycles or by dialysis against 8-hydroxyquinoline. Incubation of iron-depleted protein A with iron-EDTA and dithiothreitol resulted in the reassembly of the iron center of protein A as judged by restoration of enzyme activity (typically approximately 3 times the original activity) and by ESR spectroscopic methods. Reconstitution was inhibited by a number of metal ions, but none of the metals tested proved capable of replacing iron in the oxidation of methane. A number of iron-chelating agents exhibited weak inhibition of reconstitution. The KM(app) for iron in the reconstitution reaction was 133 microM. In vitro translation of total RNA isolated from M. capsulatus (Bath) produced protein A subunits equal to the native molecular weight, suggesting that there is no precursor form of this protein. Addition of the in vitro translated protein A to the reconstitution system resulted in low levels of hydroxylase activity suggesting that the subunits of protein A are self-assembling, a supposition supported by the presence of only one protein band on nondenaturing gels. Taken together, these data suggest that the subunits of protein A are synthesized in their native, mature form and self-assemble into an apoprotein A, into which the iron center is inserted.

Cations, Divalent↗
PubMed1988

Selective modification of the kinetic properties of Na+/H+ exchanger by cell shrinkage and swelling.

The effect of volume perturbation on the interaction of Na+ and H+ with the intracellular and extracellular faces of the Na+/H+ exchanger was studied in UMR-106 cells, a rat osteosarcoma cell line. Osmotic shrinkage of the cells stimulated the activity of the Na+/H+ exchanger. Kinetic analysis of this stimulation demonstrated that in hyperosmotically stressed cells, the apparent affinities for intracellular H+ and intracellular Na+ are modified in opposite directions. While there is an increased apparent affinity for protons from 0.275 +/- 0.03 to 0.107 +/- 0.025 microM in isotonic and hypertonic conditions, respectively, the apparent affinity for intracellular Na+ decreases from 83 +/- 9 to 126 +/- 6 mM under the same conditions. Osmotic swelling induced a decreased exchanger activity which appeared to involve reduction in Vmax only without changes in the apparent affinities of either H+i or Na+i. We conclude that: 1) osmotic shrinkage and swelling modify the kinetic behavior of the Na+/H+ exchanger in different modes; 2) in hyperosmotically stressed cells, the interactions of intracellular H+ and Na+ are modified in a selective mode. The described phenomenon may serve as a general mechanism for activation of the exchanger by various stimuli.

Animals↗
PubMed1988

Sonographic and urographic correlation in Bardet-Biedl syndrome (formerly Laurence-Moon-Biedl syndrome).

To determine the spectrum of urologic disease and the value of ultrasound as a screening mechanism, renal imaging was performed on 23 patients with Bardet-Biedl syndrome. On intravenous urography (IVU), abnormal calices were present in 22 patients, with communicating cortical cysts/diverticula in 17. Ultrasound detected caliceal or cystic changes in 70%. On IVU, 21 patients had fetal-type lobular outlines that were detected on sonography in 95%. Renal structural abnormalities are characteristic of the Bardet-Biedl syndrome, and are still best imaged by urography.

Adolescent↗
PubMed1988

Pulsed Doppler flow-velocity waveforms before and after intrauterine intravascular transfusion for severe erythroblastosis fetalis.

Pulsed Doppler studies of the fetal and maternal circulations were carried out before and after 64 intrauterine transfusions performed on 24 fetuses. A model was derived for the prediction of hematocrit before the first transfusion: Hematocrit = 7.778 - (0.088 x peak velocity in descending aorta) + (0.968 x gestational age [weeks]) - (10.911 if hydrops present) (r = 0.876, p less than 0.0001). An alternative formula, excluding hydrops, was slightly less predictive: Hematocrit = 45.312 - (56.261 x umbilical cord Pourcelot index) - (0.128 x peak velocity in descending aorta) + (1.042 x gestational age) r = 0.822, p less than 0.001). Neither model was accurate in the prediction of hematocrit before second or subsequent transfusions. A third model was derived from second-transfusion data: Hematocrit = 40.524 - (0.045 x peak velocity in descending aorta) - (10.693 x pulsatility index of maternal uterine artery) (r = 0.81, p less than 0.003). However, this model was unable to predict hematocrit before third or later transfusions. No changes in Doppler parameters before and after transfusion were found. We conclude that pulsed Doppler ultrasound may be helpful in the evaluation of isoimmunized pregnancies, in differentiating anemic from normal fetuses. It does not appear to be useful in determining the timing of later transfusions. The lack of change before and after transfusions suggests that these vessels will not provide significant information concerning the effect of rapid volume and hematocrit changes in the fetus.

Blood Transfusion, Intrauterine↗
PubMed1988

Prognostic significance of the human yolk sac assessed by ultrasonography.

Ultrasonographic examinations were conducted between 6 and 12 weeks' gestation in 77 first-trimester pregnancies with normal fetal outcome. Each examination consisted of measurements of the secondary yolk sac diameter and the fetal crown-rump length. The yolk sac was seen in all cases, and whereas its measurements demonstrated wide biologic variability, it correlated weakly (R2 = 0.39) with gestational age as confirmed by crown-rump length measurements. Growth of the yolk sac diameter, although slight, assumed a curvilinear relationship with gestational age. Such a growth profile is best described by a second-degree polynomial regression equation. The yolk sac performs important functions for embryonic development during organogenesis and the remnant of the secondary yolk sac seen on ultrasonography is often considered to be a potential predictor of fetal outcome. Our findings indicate that the size of this remnant in pregnancies with normal karyotypes and normal fetal outcomes is extremely variable. Additionally, the yolk sac size in patients with karyotypic abnormalities and spontaneous abortion were equally variable and almost all were within the normal range. In light of these findings, the secondary yolk sac size does not appear to be a sensitive predictor of embryonic integrity and pregnancy outcome.

Female↗
PubMed1988

Volume and pressure during transient added resistance.

Total respiratory resistance (Rrs) can be computed from measurements of flow before and during a brief period of added resistance. This "added resistance' method does not require measurement of total driving pressure (Pt). One of the assumptions of this method is that the change in Pt (delta Pt) is negligible during the time of increased resistance. To evaluate this assumption we measured both the volume exhaled during a brief imposition of an external resistor, and the total respiratory compliance (Crs) of 7 healthy volunteers. The mean volume exhaled was 18.6 ml, and the mean Crs was 88 ml/cm H2O. The volume exhaled divided by Crs gives the change in total static elastic recoil pressure (delta Pel, rs), which is one component of delta Pt. The mean delta Pel, rs was 0.22 cm H2O. Since the pressure exerted by contraction of inspiratory muscles (Pmus,I) opposes Pel, rs, we also estimated delta Pmus,I and subtracted it from delta Pel, rs to obtain delta Pt. The computed mean delta Pt during the time of added resistance was 0.045 cm H2O. This value is quite small in relation to Pt during a spontaneous expiration at rest. We also studied 13 subjects with Chronic Obstructive Pulmonary Disease and found no significant effect of transient added resistance on intraesophageal pressure. We conclude that the assumption of negligible delta Pt should not prevent the added resistance method from being very useful, particularly when simplicity of equipment and testing procedure are important.

Adult↗
PubMed1988

Limited open reduction of the lunate facet in comminuted intra-articular fractures of the distal radius.

Intra-articular incongruity of the distal radius at the radiocarpal joint is a bad prognostic feature; reduction by closed or open operative techniques is important. However, both techniques have limitations. We describe a new technique of reduction of the lunate facet under radiographic control, with very limited operative exposure and tissue trauma. In two cases anatomic restoration of the radiocarpal joint was obtained by this technique and maintained with external and limited internal fixation. Follow-up results are very encouraging. Currently we suggest use of this simple technique when faced with an incongruous radiocarpal joint after unsatisfactory attempts at closed reduction.

Adult↗
PubMed1988

Cytosolic pH regulation in osteoblasts. Interaction of Na+ and H+ with the extracellular and intracellular faces of the Na+/H+ exchanger.

The interaction of Na and H ions with the extracellular and intracellular sites of the Na+/H+ exchanger of the osteosarcoma cell line UMR-106 was investigated. Na ions interact with a single, saturable extracellular transport site. H+ and amiloride appear to compete with Na+ for binding to this site. The apparent affinity for extracellular Na+ (Nao+) and amiloride was independent of intracellular H+ (Hi+), Nai+, or an outwardly directed H+ gradient. The interaction of H+ with the intracellular face of the exchanger had a sigmoidal characteristic with a Hill coefficient of approximately 2. The apparent affinity for Hi+ was independent of Nao+ between 25 and 140 mM. The apparent affinity for Hi+, but not the number of intracellular sites, increased with the increase in the outwardly directed H+ gradient across the membrane. Nai+/Ho+ exchange (reverse mode) is an electroneutral process with a Na+/H+ stoichiometry of 1. The dependence of Nai+/Ho+ exchange on Nai+ was sigmoidal, with a Hill coefficient of 2.16. Nai+ competes with Hi+ for binding to at least the transport site. The apparent affinity for Nai+ decreased with the increase in the outwardly directed H+ gradient. High Ho+ inhibited exchange activity in the reverse mode. We conclude that intracellular Na+ and H+ can activate the exchanger. The exchanger has two separate and asymmetric extracellular and intracellular transport sites. The relative apparent affinities of the internal transport site for Na+ and H+ are determined by the direction and magnitude of the H+ gradient across the membrane. Kinetic characterization of the exchanger suggests that Na+/H+ exchange is compatible with a simultaneous transport model, although a ping-pong transport model could not be excluded.

Amiloride↗
PubMed1988

Adult hemolytic uremic syndrome associated with nonimmune deposit crescentic glomerulonephritis and alveolar hemorrhage.

An 18-year-old girl presented with anuric rapidly progressive glomerulonephritis associated with hypoxemic respiratory failure due to diffuse lung hemorrhage. The course of the kidney disease terminated in end-stage renal failure. The patient had been on permanent hemodialysis since her first admission; episodes of lung hemorrhage recurred five times over a follow-up period of 8 months. Two months after her first admission, the patient manifested features suggestive of the hemolytic uremic syndrome, namely, microangiopathic hemolytic anemia, thrombocytopenia, and excessive hypertension complicated by hypertensive encephalopathy. Based on the sequence of events in the course of this patient's disease, the authors believe that the hematological abnormalities were superimposed on the glomerular disease rather than being a primary disorder. Possible mechanisms for the association of the two disorders are discussed.

Adolescent↗