Gas Exchange of Algae: II. Effects of Oxygen, Helium, and Argon on the Photosynthesis of Chlorella pyrenoidosa

Changes in the oxygen partial pressure of air over the range of 8 to 258 mm of Hg did not adversely affect the photosynthetic capacity of Chlorella pyrenoidosa. Gas exchange and growth measurements remained constant for 3-week periods and were similar to air controls (oxygen pressure of 160 mm of Hg). Oxygen partial pressures of 532 and 745 mm of Hg had an adverse effect on algal metabolism. Carbon dioxide consumption was 24% lower in the gas mixture containing oxygen at a pressure 532 mm of Hg than in the air control, and the growth rate was slightly reduced. Oxygen at a partial pressure of 745 mm of Hg decreased the photosynthetic rate 39% and the growth rate 37% over the corresponding rates in air. The lowered metabolic rates remained constant during 14 days of measurements, and the effect was reversible after this time. Substitution of helium or argon for the nitrogen in air had no effect on oxygen production, carbon dioxide consumption, or growth rate for 3-week periods. All measurements were made at a total pressure of 760 mm of Hg, and all gas mixtures were enriched with 2% carbon dioxide. Thus, the physiological functioning and reliability of a photosynthetic gas exchanger should not be adversely affected by: (i) oxygen partial pressures ranging from 8 to 258 mm of Hg; (ii) the use of pure oxygen at reduced total pressure (155 to 258 mm of Hg) unless pressure per se affects photosynthesis, or (iii) the inclusion of helium or argon in the gas environment (up to a partial pressure of 595 mm of Hg).     

Antihypertensive effect of diet compared with drug treatment in obese men with mild hypertension.

OBJECTIVE--To determine whether dietary treatment has a similar antihypertensive effect to conventional drug treatment while being superior to drugs in improving serum lipid concentrations in obese men with mild hypertension. DESIGN--Six week run in period followed by randomisation to either diet or drug treatment groups for one year. SETTING--Outpatient clinic in city hospital. PATIENTS--61 Men aged 40-69 years, body mass index greater than or equal to 26, diastolic blood pressure 90-104 mm Hg when untreated. Exclusion criteria were signs of organ damage secondary to hypertension and diseases that might have interfered with compliance or with interpretation of results. INTERVENTIONS--Dietary treatment was based on weight reduction, restriction of sodium, and decrease of excess alcohol intake (defined as greater than or equal to 250 g alcohol per week). Drug treatment used a stepped care approach with atenolol as drug of first choice. MAIN OUTCOME MEASURES--Diastolic blood pressure less than 90 mm Hg; absolute reductions in blood pressure and serum lipid concentrations. RESULTS--Mean body weight decreased 7.6 kg in the diet group and increased 0.9 kg in the drug treatment group (p less than 0.0001), and mean sodium excretion decreased 42 and 10 mmol/24 h respectively (p = 0.019). There was no difference in reported alcohol intake. Mean systolic blood pressure decreased 4 mm Hg in the diet group and 16 mm Hg in the drug group (p = 0.003) and diastolic blood pressure 3 and 11 mm Hg respectively (p = 0.002). Diastolic blood pressure of 90 mm Hg was attained by 29% of the diet group (nine men) and 73% (22) of those receiving drug treatment (mean difference 44%, 95% confidence interval 21 to 67%, p = 0.001). Dietary treatment produced decreases in mean serum concentrations of total and low density lipoprotein cholesterol as well as triglycerides and an increase in high density lipoprotein cholesterol concentration. In the drug treatment group the changes were in the opposite direction, and the groups differed significantly in all but total cholesterol. CONCLUSIONS--Dietary treatment was inferior to conventional drug treatment in controlling mild hypertension but superior in lowering serum concentrations of lipids.     

Effect of oxygen concentration on trasverse water proton relaxation times in erythrocytes homozygous and heterozygous for hemoglonin S.

The transverse water proton relaxation times (T₂) of erythrocytes homozygous and heterozygous for hemoglobin S have been measured as a function of oxyhemoglobin concentration at 37 °C. An immediate decrease in T₂ is observed in S/S erythrocytes as the amount of oxyhemoglobin is decreased and the maximum change is observed at 50% deoxyhemoglobin S. In heterozygous erythrocytes, the T₂ remains unchanged until a critical level of deoxyhemoglobin is attained. The critical level of deoxyhemoglobin is a function of the percentage of hemoglobin S in the heterozygous erythrocytes. A Hill plot of the data obtained from S/S erythrocytes gives an n value of around 2.4. These results suggest that the measurement of T₂ is sensitive to the very early stages of the polymerization process. This suggestion is supported by calculations; our T₂ measurements are sensitive to a range of correlation times expected for hemoglobin monomers at one extreme and linear polymers of seven hemoglobin molecules at the other extreme.     

Towards a transgenic mouse model of sickle cell disease: hemoglobin SAD.

In order to obtain a transgenic mouse model of sickle cell disease, we have synthesized a novel human beta-globin gene, beta SAD, designed to increase the polymerization of the transgenic human hemoglobin S (Hb S) in vivo. beta SAD (beta S-Antilles-D Punjab) includes the beta 6Val substitution of the beta S chain, as well as two other mutations, Antilles (beta 23Ile) and D Punjab (beta 121Gln) each of which promotes the polymerization of Hb S in human. The beta SAD gene and the human alpha 2-globin gene, each linked to the beta-globin locus control region (LCR) were co-introduced into the mouse germ line. In one of the five transgenic lines obtained, SAD-1, red blood cells contained 19% human Hb SAD (alpha 2 human 1 beta 2SAD) and mouse-human hybrids in addition to mouse hemoglobin. Adult SAD-1 transgenic mice were not anemic but had some abnormal features of erythrocytes and slightly enlarged spleens. Their erythrocytes displayed sickling upon deoxygenation in vitro. SAD-1 neonates were anemic and many did not survive. In order to generate adult mice with a more severe sickle cell syndrome, crosses between the SAD progeny and homozygous for beta-thalassemic mice were performed. Hemoglobin SAD was increased to 26% in beta-thal/SAD-1 mice which exhibited: (i) abnormal erythrocytes with regard to shape and density; (ii) an enlarged spleen and a high reticulocyte count indicating an increased erythropoiesis; (iii) mortality upon hypoxia; (iv) polymerization of hemolysate similar to that obtained in human homozygous sickle cell disease; and (v) anemia and mortality during development.     

The Hypoxic Stress on Erythrocytes Associated with Superoxide Formation

Super oxide is produced during the authorization of hemoglobin. Authorization of hemoglobin is, however, facilitated under hypoxic conditions where hemoglobin is only partially oxygenated.

We have recently found that the erythrocyte superoxide dismutase does not fully react with the additional superoxide produced under hypoxic conditions. A leakage of superoxide from the erythrocyte is thus detected, resulting in a potential source for oxyradical damage to tissues.

Detailed studies on intact erythrocytes as a function of oxygen pressure have now been performed. These studies further delineate the hypoxic stress on erythrocytes and the mechanism for the leakage of superoxide. By centrifugation of samples under various oxygen pressures it was possible to show an enhanced rate of lysis at reduced oxygen pressures with a maximum rate in the region of 25 mm Hg. At much lower pressures where the hemoglobin is mostly deoxygenated the rate of lysis was dramatically decreased with almost no lysis detected even after three days. Lysis is shown to be associated with superoxide membrane damage. The formation of superoxide which does not react with endogenous SOD reaches a maximum value at much lower pressures where most of the hemoglobin is deoxygenated. It is suggested that the leakage at low pressure is associated with the formation of superoxide by oxidation of hemoglobin associated with the membrane.     

Red blood cell magnetophoresis

The existence of unpaired electrons in the four heme groups of deoxy and methemoglobin (metHb) gives these species paramagnetic properties as contrasted to the diamagnetic character of oxyhemoglobin. Based on the measured magnetic moments of hemoglobin and its compounds, and on the relatively high hemoglobin concentration of human erythrocytes, we hypothesized that differential migration of these cells was possible if exposed to a high magnetic field. With the development of a new technology, cell tracking velocimetry, we were able to measure the migration velocity of deoxygenated and metHb-containing erythrocytes, exposed to a mean magnetic field of 1.40 T and a mean gradient of 0.131 T/mm, in a process we call cell magnetophoresis. Our results show a similar magnetophoretic mobility of 3.86 x 10(-6) mm(3) s/kg for erythrocytes with 100% deoxygenated hemoglobin and 3.66 x 10(-6) mm(3) s/kg for erythrocytes containing 100% metHb. Oxygenated erythrocytes had a magnetophoretic mobility of from -0.2 x 10(-6) mm(3) s/kg to +0.30 x 10(-6) mm(3) s/kg, indicating a significant diamagnetic component relative to the suspension medium, in agreement with previous studies on the hemoglobin magnetic susceptibility. Magnetophoresis may open up an approach to characterize and separate cells for biochemical analysis based on intrinsic and extrinsic magnetic properties of biological macromolecules.     

Value of low dose combination treatment with blood pressure lowering drugs: analysis of 354 randomised trials

Objective To determine the average reduction in blood pressure, prevalence of adverse effects, and reduction in risk of stroke and ischaemic heart disease events produced by the five main categories of blood pressure lowering drugs according to dose, singly and in combination.Design Meta-analysis of 354 randomised double blind placebo controlled trials of thiazides, β blockers, angiotensin converting enzyme (ACE) inhibitors, angiotensin II receptor antagonists, and calcium channel blockers in fixed dose.Subjects 40 000 treated patients and 16 000 patients given placebo.Main outcome measures Placebo adjusted reductions in systolic and diastolic blood pressure and prevalence of adverse effects, according to dose expressed as a multiple of the standard (recommended) doses of the drugs.Results All five categories of drug produced similar reductions in blood pressure. The average reduction was 9.1 mm Hg systolic and 5.5 mm Hg diastolic at standard dose and 7.1 mm Hg systolic and 4.4 mm Hg diastolic (20% lower) at half standard dose. The drugs reduced blood pressure from all pretreatment levels, more so from higher levels; for a 10 mm Hg higher blood pressure the reduction was 1.0 mm Hg systolic and 1.1 mm Hg diastolic greater. The blood pressure lowering effects of different categories of drugs were additive. Symptoms attributable to thiazides, β blockers, and calcium channel blockers were strongly dose related; symptoms caused by ACE inhibitors (mainly cough) were not dose related. Angiotensin II receptor antagonists caused no excess of symptoms. The prevalence of symptoms with two drugs in combination was less than additive. Adverse metabolic effects (such as changes in cholesterol or potassium) were negligible at half standard dose.Conclusions Combination low dose drug treatment increases efficacy and reduces adverse effects. From the average blood pressure in people who have strokes (150/90 mm Hg) three drugs at half standard dose are estimated to lower blood pressure by 20 mm Hg systolic and 11 mm Hg diastolic and thereby reduce the risk of stroke by 63% and ischaemic heart disease events by 46% at age 60-69.     

Drug-Induced Changes in Blood Pressure Lead to Changes in Extracellular Concentrations of Epinephrine, Dihydroxyphenylacetic Acid, and 5-Hydroxyindoleacetic Acid in the Rostral Ventrolateral Medulla of the Rat

Neurochemical changes in the extracellular fluid of the rostral ventrolateral medulla (RVLM) were produced by changes in arterial blood pressure. Blood pressure was raised or lowered with systemic infusions of phenylephrine or nitroprusside and neurochemicals were recovered from RVLM by in vivo microdialysis. A dialysis probe 300 microns in diameter and 500 microns in length was stereotaxically implanted in the RVLM of the urethane-anesthetized rat. Sterile physiological Ringer's solution was perfused at a rate of 1.5 microliter/min. The perfusate was collected under ice-cold conditions every 15 min for the assay of epinephrine, dihydroxyphenylacetic acid (DOPAC), 5-hydroxyindoleacetic acid (5-HIAA), ascorbic acid, and uric acid. After stable baseline neurochemical concentrations were achieved, animals were infused with phenylephrine or nitroprusside intravenously to raise or lower the blood pressure. Increasing blood pressure 50 mm Hg above the baseline value by phenylephrine led to a significant reduction in heart rate and a reduction in extracellular epinephrine and DOPAC concentrations. The 5-HIAA concentration was increased during the hypertensive drug infusion. There were no changes in the concentrations of ascorbic acid or uric acid. Hypotension produced by nitroprusside (-20 mm Hg) led to neurochemical changes which were the reciprocal of those seen during hypertension. During hypotension, heart rate increased as did the extracellular fluid epinephrine concentration. The 5-HIAA concentration fell with hypotension and remained depressed following the nitroprusside infusion. Ascorbic acid and uric acid concentrations did not change during hypotension but ascorbic acid did increase after the nitroprusside infusion stopped. These data provide direct evidence that epinephrine release in RVLM is linked to changes in systemic blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nocturnal blood pressure in normotensive subjects and those with white coat,primary, and secondary hypertension.

OBJECTIVE--To compare the mean nocturnal blood pressure of patients with various forms of renal and endocrine hypertension with that in patients with primary and white coat hypertension, and normal blood pressure. DESIGN--Ambulatory monitoring of blood pressure over 24 hours in a prospective study. SETTING--Two German centres for outpatients with hypertension and kidney diseases. SUBJECTS--176 normotensive subjects, 490 patients with primary hypertension including mild and severe forms, 42 with white coat hypertension, 208 patients with renal and renovascular hypertension, 43 with hypertension and endocrine disorders, and three with coarctation of the aorta. MAIN OUTCOME MEASURES--Fall in nocturnal blood pressure. RESULTS--Blood pressure in normotensive subjects fell by a mean of 14 mm Hg (11%) systolic and 13 mm Hg (17%) diastolic overnight (2200 to 0600). The falls in patients with primary and white coat hypertension were not significantly different. In all patients with renal and renovascular hypertension, however, the fall was significantly reduced (range of fall from 3/3 mm Hg to 7/9 mm Hg). In patients with hypertension and endocrine disorders the pattern of night time blood pressure was not uniform: patients with hyperthyroidism, primary hyperaldosteronism, and Cushing''s syndrome had significantly smaller reductions in blood pressure (6/8, 4/7, 3/6 mm Hg, respectively). In patients with phaeochromocytoma the mean night time blood pressure increased by 4/2 mm Hg. In patients with hypertension, primary hyperparathyroidism, and unoperated coarctation of the aorta the falls in blood pressure were normal. CONCLUSIONS--In normotensive subjects and those with primary hypertension there is usually a reduction in blood pressure at night. In all renal forms of secondary hypertension and in most endocrine forms the reduction in blood pressure is only a third to a half of normal. Patients with primary hyperparathyroidism and unoperated coarctation of the aorta show a normal reduction.     

Beta blockade,diuretics, and salt restriction for the management of mild hypertension: a randomised double blind trial.

Ninety four patients with mild hypertension (average supine diastolic blood pressure (phase V) 95-110 mm Hg) were allocated at random to receive restriction of dietary sodium (maximum allowed 70 mmol(mEq)/24 h) or a normal diet. In addition, they received in random order 25 mg chlorthalidone, 200 mg metoprolol (slow release), and a fixed combination of these two drugs. Each drug treatment was given for four weeks and alternated with four weeks of placebo. Forty four patients were allocated to sodium restriction (group 1) and 50 to normal diet (group 2). The mean 24 hour urinary sodium excretion in group 1 was 74 (SD 31) mmol(mEq)/24 h, and in group 2 132 (51) mmol/24 h. Compared with the screening blood pressure the average decrement of the supine blood pressure in group 1 was 16.0/8.6 mm Hg with placebo, 21.7/11.5 mm Hg with the diuretic, 28.5/17.8 mm Hg with the beta blocker, and 28.9/18.4 mm Hg with the combined agent; in group 2 these values were 13.3/6.1, 20.3/9.7, 21.3/12.9, and 29.4/16.8 mm Hg, respectively. There was a sharp decrease of the average potassium concentration during chlorthalidone and combination treatment periods (average value 3.3 mmol(mEq)/1). These results suggest that moderate salt restriction used as sole treatment has a limited though demonstrable blood pressure lowering effect but that when it is used as an adjuvant to beta blocker treatment its value is greatly enhanced.     

Hydrochlorothiazide-amiloride versus hydrochlorothiazide alone for essential hypertension: effects on blood pressure and serum potassium level

In a double-blind randomized controlled trial the effects on the blood pressure and the serum potassium concentration of hydrochlorothiazide-amiloride hydrochloride (Moduret) and hydrochlorothiazide alone were compared in 266 adults who were normokalemic and had a diastolic blood pressure greater than 95 mm Hg at the time of entry into the study. The mean ages (52.2 and 53.8 years) and the proportions of men (66% and 56%) in the groups given the combination drug and hydrochlorothiazide alone respectively were similar. In the group given the combination drug the mean blood pressure, measured while the patients were supine, and the mean serum potassium level fell significantly, from 156/99 to 138/88 mm Hg and from 4.23 to 3.91 mmol/L, after 8 weeks of treatment. In the other group both measures also fell significantly, the blood pressure from 157/99 to 138/87 mm Hg and the potassium level from 4.16 to 3.69 mmol/L. The proportions of patients in the two groups with hypokalemia (14% and 29% respectively), defined as a serum potassium level below 3.5 mmol/L, differed significantly (p = 0.0026), whereas the proportions with a potassium level exceeding 4.5 mmol/L (4.5% and 3.9% respectively) were similar. Thus, the combination drug reduced the blood pressure to the same extent as hydrochlorothiazide alone but significantly less often caused hypokalemia. In light of growing concerns about the cardiovascular complications of hypokalemia, hydrochlorothiazide-amiloride appears preferable to hydrochlorothiazide alone for the treatment of some patients with hypertension.     

Extreme hemodilution with PEG-hemoglobin vs. PEG-albumin

Isovolemic hemodilution to 11% systemic hematocrit was performed in the hamster window chamber model using 6% dextran 70 kDa (Dx 70) and 5% human serum albumin (HSA). Systemic and microvascular effects of these solutions were compared with polyethylene glycol (PEG)-conjugated 5% albumin (MPA) and PEG-conjugated 4.2% Hb (MP4). These studies were performed for the purpose of comparing systemic and microvascular responses of PEG vs. non-PEG plasma expanders and similar oxygen-carrying vs. noncarrying blood replacement fluids. Mean arterial blood pressure was statistically significantly reduced for all groups compared with baseline (P < 0.05), HSA, MPA, and MP4 higher than Dx 70 (P < 0.05). MP4 and MPA had a significantly higher cardiac index than HSA and Dx 70, in addition to a positive base excess. Microvascular blood flow and capillary perfusion were significantly higher for the PEG compounds compared with HSA and Dx 70. Intravascular PO2 for MP4 and MPA was higher in arterioles (P < 0.05) compared with HSA and Dx 70, but there was no difference in either tissue or venular PO2 between groups. Total Hb in the MP4 group was 4.8 +/- 0.4 g/dl, whereas the remaining groups had a range of 3.6-3.8 g/dl. The hemodilution results showed that PEG compounds maintained microvascular conditions with lower concentrations than conventional plasma expanders. Furthermore, microvascular oxygen delivery and extraction in the window chamber tissue were significantly higher for the PEG compounds. MP4 was significantly higher than MPA (P < 0.05) and was not statistically different from baseline, an effect due to the additional oxygen release to the tissue by the Hb MP4.     

Hemoglobin functions in the blood of Bufo marinus

The effects of three physical-chemical factors, temperature, hydrogen ion concentration, and partial pressure of oxygen, on the respiratory functions of blood of the toad (Bufo marinus) have been studied. Measurements of oxygen affinity of hemoglobin in whole blood were measured tonometrically by a method devised for small quantities of blood. At pH 7.40 and 25°C blood was found to be 50% saturated with oxygen at a partial pressure of 44 mm Hg of oxygen. The Bohr effect was measured at various temperatures and found to be about one-half that found for mammalian blood. Carbon dioxide content of toad blood changes only slightly in the oxygenated and reduced states. Thus the “Haldane” effect parallels the small Bohr effect. Toad blood was found to have average hematocrit values of 37% for erythrocytes and average hemoglobin values of 11 gm/100 ml per cubic millimeter of blood. The respiratory functions of the blood of the toad conform to the pattern of respiratory mechanisms available for gas exchange between the environment and tissues of the organism.     

Genetic analyses of proteolysis, hemoglobin binding, and hemagglutination of Porphyromonas gingivalis. Construction of mutants with a combination of rgpA, rgpB, kgp, and hagA.

Porphyromonas gingivalis produces arginine-specific cysteine proteinase (Arg-gingipain, RGP) and lysine-specific cysteine proteinase (Lys-gingipain, KGP) in the extracellular and cell-associated forms. Two separate genes (rgpA and rgpB) and a single gene (kgp) have been found to encode RGP and KGP, respectively. We constructed rgpA rgpB kgp triple mutants by homologous recombination with cloned rgp and kgp DNA interrupted by drug resistance gene markers. The triple mutants showed no RGP or KGP activity in either cell extracts or culture supernatants. The culture supernatants of the triple mutants grown in a rich medium had no proteolytic activity toward bovine serum albumin or gelatin derived from human type I collagen. Moreover, the mutants did not grow in a defined medium containing bovine serum albumin as the sole carbon/energy source. These results indicate that the proteolytic activity of P. gingivalis toward bovine serum albumin and gelatin derived from human type I collagen appears to be attributable to RGP and KGP. The hemagglutinin gene hagA of P. gingivalis possesses the adhesin domain regions responsible for hemagglutination and hemoglobin binding that are also located in the C-terminal regions of rgpA and kgp. A rgpA kgp hagA triple mutant constructed in this study exhibited no hemagglutination using sheep erythrocytes or hemoglobin binding activity, as determined by a solid-phase binding assay with horseradish peroxidase-conjugated human hemoglobin, indicating that the adhesin domains seem to be particularly important for P. gingivalis cells to agglutinate erythrocytes and bind hemoglobin, leading to heme acquisition.     

Use of polyester leukocyte elimination filters in blood filterability research

We tested a new routine to eliminate leukocytes for blood rheology measurements using commercial leukocyte absorbing filters (here PALL RC400). These filters were punched out and fitted in smaller chambers through which blood was filtered under controlled suction pressure (< 30 mm Hg). This technique resulted in a very effective leukocyte elimination to 0.0022% but also a platelet reduction to 0.2%. The process causes a small but significant hemolysis with free hemoglobin, of the order of 0.06% of the filtered erythrocytes. A small fraction of the erythrocytes were retained in the filter, versus plasma, to reduce the hematocrit on the order of 1.4%. The leukocyte filtration did not cause any detectable functional trauma to the erythrocytes, measured as micro-pore filterability of normal and glutaraldehyde (GA) hardened erythrocytes. However, when 10% of the erythrocytes were hardened with GA, which caused an increase in pore clogging slope (p < 0.05), the additional passage through the leukocyte elimination filter removed this measured change in clogging. This observation suggests that the leukocyte elimination filter may selectively remove, not only leukocytes and platelets, but also hardened erythrocytes. Reticulocyte counting did not reveal any selective removal of young erythrocytes. In general, we find the presented method reproducible, efficient and easy for eliminating leukocytes for blood rheology research although the risk of removing undeformable erythrocytes must be considered.     

Exchange transfusion with albumin-heme as an artificial O2-infusion into anesthetized rats: physiological responses, O2-delivery, and reduction of the oxidized hemin sites by red blood cells

Human serum albumin (HSA) incorporating synthetic hemes, the tetrakis(o-pivalamido)phenylporphinatoiron(II) derivative (FeP), is an artificial hemoprotein (HSA-FeP) which is able to reversibly bind and release dioxygen under physiological conditions (in aqueous media, pH 7.4, 37 degrees C) like hemoglobin and myoglobin. Physiological responses to exchange transfusion with HSA-FeP solution [[HSA], 5 g/dL; FeP/HSA, 4 (mol/mol)] into rats after hemodilution and hemorrhage (Hct, about 10%) has been evaluated. The declined mean arterial pressure (MAP) and blood flow after a 70% exchange with HSA and the further 40% bleeding of blood were significantly recovered up to about 90% of the baseline values by the injection of HSA-FeP. Furthermore, the renal cortical O(2)-tensions and skeletal tissue O(2)-tensions were also increased, indicating the in vivo O(2)-delivery of HSA-FeP. Autoxidation of ferrous Fe(II)P to ferric Fe(III)P was retarded in the blood stream; the half-lifetime of the dioxygenated FeP [tau(1/2)(O(2))] in vivo was 4.1 h [cf. 1.0 h (in vitro)]. It has been found that autooxidized Fe(III)P was certainly reduced in the whole blood suspension. Physiological concentrations of ascorbic acid continuously provided by red blood cells probably rereduces Fe(III)P, leading to the apparent long lifetime of the dioxygenated species of FeP.     

Effects of the Binding of Imipramine to Erythrocytes and Plasma Proteins on Its Transport Through the Rat Blood-Brain Barrier

Brain extraction of a tricyclic antidepressant, imipramine, was investigated using the carotid injection technique in the rat. The extent to which drug binding to plasma proteins and erythrocytes could inhibit the brain extraction was measured. Equilibrium dialysis showed that imipramine is highly bound to human serum albumin (HSA), alpha 1-acid glycoprotein (AAG), lipoproteins, and erythrocytes. The free dialyzable drug fraction was inversely related to the protein concentration. Despite this degree of binding, no significant reduction in the brain extraction of the drug was observed in the presence of HSA, lipoprotein, or erythrocytes. Only AAG reduced the brain transport of this drug in a ratio related to the protein concentration. However, the rat brain extraction was higher than expected from the in vitro measurement of the dialyzable fraction. These data indicate that the amount of circulating imipramine available for penetration in brain exceeds widely the dialyzable fraction of the drug as measured in vitro.     

Covalent binding of glutathione to hemoglobin. I. Inhibition of hemoglobin S polymerization

Thiol reagents react with cysteine beta 93 of hemoglobin and as a result increase the oxygen affinity of hemoglobin. In the present studies we have used a thiol-disulfide exchange between mixed disulfides of hemoglobin and reduced glutathione to attach intracellular glutathione to hemoglobin and to study its antisickling properties. The rates of production of glutathionyl hemoglobin (G-Hb) depend on the structure of the thiol reagent linked to cysteine beta 93. Up to 25% G-Hb can be produced in normal and sickle red cells because of the high intracellular concentration of reduced glutathione. This high level of G-Hb in normal cells increases the oxygen affinity by about 35% and reduces heme-heme interactions. In sickle cells the increased oxygen affinity is associated with an inhibition of sickling of about 70% at 21 mm Hg. Inhibition of polymerization of deoxy HbS is also due to a direct inhibition of intermolecular contacts in the fibers as demonstrated by the increased solubility and the increased delay time of G-HbS compared to deoxy HbS.     

Dimeric hemoglobins from the arcid blood clam, Noetia ponderosa. Structure and functional properties

The hemoglobin found in the nucleated erythrocytes of the arcid blood clam Noetia ponderosa is heterogeneous and consists of two electrophoretic components, Hb-Major and Hb-Minor, present in about 80% and 20% proportions, respectively. Both components are hemoglobin dimers over a wide concentration range based on light-scattering measurements. No higher aggregation states are observed. The oxygen binding by Hb-Major and Hb-Minor is characterized by p50 values of 16.8 and 8.7 mm of Hg and Hill coefficients of 1.4 and 1.2, respectively, at pH 7.0 and 25 degrees C. Neither component exhibits an alkaline Bohr effect. An unusual nonlinear Hill plot is observed for Hb-Major. Hb-Major is composed of two different polypeptide chains and thus is a heterodimer based on sodium dodecyl sulfate/urea-polyacrylamide gel electrophoresis and reverse phase high performance liquid chromatography. By the same methods, Hb-Minor is a homodimer and may share a common chain with Hb-Major. Amino acid compositions of the two hemoglobins indicate 2 histidines/polypeptide chain which are presumably involved in the coordination of the heme iron. Visible absorption spectra indicate the heme environment is normal in the oxy state but perhaps more constrained in the deoxy state. Oxygen binding as a function of temperature and concentration and binding by the intact erythrocytes indicates the absence of intracellular regulators of oxygen binding.     

Contribution of atenolol,bendrofluazide, and hydrallazine to management of severe hypertension.

The efficacy of various combinations of atenolol, bendrofluazide, and hydraliazine given twice daily was assessed in a double-blind trial on 39 patients with moderate to severe essential hypertension. Concurrent treatment with all three drugs proved most effective and produced a mean reduction in blood pressure of 43/31 mm Hg. In the dosage used, hydrallazine affected only the diastolic blood pressure, and when added to either bendrofluazide or bendrofluazide plus atenolol it produced a further mean reduction in pressure of 6 mm Hg. Once-daily treatment with atenolol and bendrofluazide was as effective in reducing blood pressure as the same combination given twice daily, and the hypotensive effect was still present at least 24 hours after the last dose of tablets. A combined tablet of atenolol and bendrofluazide taken once daily would be a simple regimen to follow and would provide almost as much hypotensive effect as a twice-daily regimen incorporating a modest dose of hydrallazine. The hypotensive effect of atenolol was equal to that of bendrofluazide on systolic pressure but significantly better than that of bendrofluazide on diastolic pressure. Atenolol reduced plasma renin and urate concentrations but increased plasma potassium levels. The biochemical effects of atenolol, therefore, may be an advantage over those of bendrofluazide when deciding on first-line treatment for essential hypertension.