Narrative approach in understanding the drivers for resilience of military combat medics.

INTRODUCTION: Qualitative insights may demonstrate how combat medics (CM) deal with stressors and identify how resilience can potentially develop. Yet, qualitative research is scant in comparison to the many quantitative studies of health outcomes associated with military service. METHOD: Semistructured qualitative interviews were used to collect personal narratives of US Army CMs who had previously served in Iraq or Afghanistan. RESULTS: Thematic analysis revealed three key driving forces for how resilience develops in the context of combat and war. The first was patriotism, which captures loyalty and full commitment to the military and its missions. The second was commitment to their family, reflecting the balance of responsibility to family of origin with the obligation one feels towards their military family. The last driving force was faith, or the drive to reach towards the transcendent to provide a moral compass and develop empathy in the face of difficult situations. CONCLUSIONS: An individual's commitment to country, military family and faith strengthens their resilience, and this can be used to inform future research efforts as well as current clinical practice.

Technical note: assessing the functional capacity of mitochondria isolated from lactating mammary tissue: choose your chelating agent wisely.

Previous work has indicated that respiratory activity of mitochondrial preparations prepared from lactating mammary tissue is often much lower than that of mitochondria isolated from other organs such as the liver. Initial studies in our own laboratory also found that mammary mitochondria prepared from lactating mice had much lower ATP synthesis activity than those isolated from liver tissue obtained from the same animals. In this paper, we describe an improved procedure for obtaining coupled mitochondria from the mammary tissue of lactating mice. Using a high-throughput assay for mitochondrial ATP synthesis, we demonstrated that mammary mitochondria, unlike liver mitochondria, are sensitive to the concentration of bovine serum albumin and to the choice of chelating agent used in the preparation and assay buffers. Mammary mitochondria prepared and assayed in buffers containing 1 mM ethylene glycol-bis-(beta-aminoethyl ether)-N,N' tetraacetic acid (EGTA) and 0.4% bovine serum albumin have a similar ATP synthesis activity as liver mitochondria. In addition, we show that the chelating agent EDTA ablates the ATP synthesis capacity of mammary mitochondria through a mechanism that does not involve the release of cytochrome c. We also demonstrate that these improved isolation and assay procedures are both scalable and applicable to bovine mammary tissue, and we describe optimal conditions for cryopreservation and recovery of functionally active mitochondria. This work will facilitate future studies aimed at determining the importance of mammary mitochondria to milk production.

An evaluation of the physicochemical risk for renal stone disease during pregnancy.

Seventeen subjects were studied during the third trimester of pregnancy (PG) and post partum (NPG) to evaluate the effect of pregnancy on the physicochemical risk of renal stone disease. Levels of urinary saturation for calcium oxalate (CaOx), brushite (Br), uric acid (UA), and monosodium urate (NaU) were determined as well as urinary excretions of stone-forming elements. In addition to urinary calcium excretion, assessment of calcium metabolism included serum calcium and parathyroid hormone. Urinary calcium excretion was 251 +/- 127 mg/day during pregnancy and 121 +/- 67 mg/day post partum (p < 0.001). This was associated with a higher intake of dietary calcium and altered renal handling of calcium with an increase in the filtered load and a decrease in renal tubular reabsorption. The increase in urinary calcium resulted in a higher level of saturation of the urine for calcium oxalate (NPG 2.1 +/- 1.0 vs PG 3.0 +/- 1.1, p < 0.02) and brushite (NPG 1.2 +/- 0.9 vs PG 1.9 +/- 1.1, p < 0.05) compatible with an increased risk of stone formation.

Urinary albumin and N-acetyl-beta-D-glucosaminidase excretions in mild hypertension.

Renal effects of mild hypertension and therapy have not been established. Since urinary albumin and N-acetyl-beta-D-glucosaminidase excretions reflect renal effects of hypertension, they were related to blood pressure, other cardiovascular risk factors, cardiac target organ effects, and response to therapy in mild hypertension (diastolic blood pressure 85-99 mm Hg). Participants were from two clinics of the Treatment of Mild Hypertension Study (TOMHS), a multicenter randomized, double-blind, controlled trial. Participants received nutritional-hygienic therapy and one of five active drugs or placebo. Urinary albumin and N-acetyl-beta-D-glucosaminidase excretions were assessed prospectively using office "spot" collections from one clinic (n = 213) and retrospectively using overnight collections from the other clinic (n = 210). Relationships were determined between protein excretions and blood pressure, age, gender, race, blood glucose, cholesterol concentrations, and indices of body mass and left ventricular mass and function at baseline. Treatment effects were assessed after 3 to 12 months. Spot and overnight albumin excretions related positively to baseline systolic blood pressure by univariate analyses. Spot albumin excretion related positively to systolic blood pressure, age, creatinine clearance, and left ventricular function while overnight albumin excretion related positively to left ventricular mass and female gender by multiple regression analyses. Spot, but not overnight, albumin excretion declined significantly with active drug therapy. N-acetyl-beta-D-glucosaminidase excretion did not relate to blood pressure or decline with therapy. The combined results suggest albumin excretion correlates with blood pressure, decreases with antihypertensive drug therapy, and is associated with greater left ventricular function and mass, as well as glomerular filtration rate, even at mild levels of hypertension.

The relationship between renin isoelectric forms and renin glycoforms.

Active renin can be separated into multiple isoelectric forms using shallow gradient isoelectric focusing and into multiple glycoforms using concanavalin A (Con A) affinity chromatography. The relationship between renin isoelectric forms and glycoforms has not been previously determined. In this study, each of three renin Con A glycoforms from rat kidney was composed of significantly different proportions of six renin isoelectric forms; glycoforms with the greatest affinity for Con A contained proportionally less of the acidic isoelectric forms than those with the least affinity for Con A. A set of compartmental models accurately predicted previously measured differential plasma clearance rates of the three renin glycoforms based on their corresponding isoelectric form proportions. We conclude that 1) each Con A renin glycoform is composed of significantly different proportions of isoelectric forms, and 2) the different proportions of isoelectric forms found in Con A glycoforms are sufficient to account for the differential renin plasma clearance rates demonstrated previously for renin glycoforms in the rat. These data suggest that the isoelectric and glycoform heterogeneity of active renin are, in fact, closely related and may result from variable and interrelated mannose (Con A affinity) and sialic acid (charge) attachments to renin.

Role of renin isoelectric heterogeneity in renal storage and secretion of renin.

Renin is a glycoprotein that is heterogeneous with respect to carbohydrate content and net charge. In an attempt to clarify the role of renin isoelectric heterogeneity in renal renin storage and secretion, the isoelectric profile of renal renin, secreted renin, and circulating renin were directly assessed and compared under basal and stimulated conditions by the use of an in vivo blood perfused rabbit kidney preparation. Under basal conditions, the kidney preferentially stored and secreted the relatively basic isoelectric forms of renin. Acute stimulation of renin secretion (reduced renal perfusion pressure and angiotensin-converting enzyme inhibition) significantly increased the secretion of the relatively basic isoelectric forms but had very little effect on the secretion of the relatively acidic renin forms. Circulating renin was composed primarily of relatively basic forms, which increased disproportionately after stimulation of renin secretion. These findings suggest that the isoelectric heterogeneity of renin is important in the cellular processing of renin and can be explained by a two-pool model in which the relatively acidic isoelectric forms of renin are constitutively secreted (and not stored) and the relatively basic isoelectric forms represent a regulated pathway in which they are stored and rapidly released in response to acute secretory stimuli. Preferential hepatic extraction of the more basic isoelectric forms has previously been described. Data from this study suggest that the disproportionate increase in circulating basic forms of renin observed after acute stimulation reflects the net effect of preferential renal the more basic renin isoelectric forms. The disproportionate increase in relatively basic circulating renin forms after acute secretory stimulation results in an overall circulating renin activity with a shorter half-life.

Renin and renin inhibition in anephric man.

Renin activity appears to be present in low concentrations in the plasma of anephric humans but could be artifactual secondary to inadvertent activation of prorenin during specimen collection and handling or from a renin-like enzyme. We studied the effects of specimen collection, storage, different assay conditions, trypsin activation, and the renin inhibitor EMD 56133 (E Merck, Darmstadt) on plasma renin activity (PRA) in anephric man. PRA was detectable in all seven bilaterally nephrectomized (BNX) patients (0.2 +/- 0.1 ng AI/ml/hr, range 0.1-0.7) but was significantly lower than normals (2.4 +/- 0.3 ng AI/ml/hr, range 1.5-3.1, p = 0.001). PRA was not different in BNX whether blood samples were collected on ice or at room temperature and assayed immediately or whether samples were frozen and assayed several days later. Prolonged cold storage of samples and five freeze-thaw cycles over six to seven months did not significantly increase PRA in normals or anephrics. However, deliberate repeated freezing and thawing over the period of a single day increased PRA 4.1-fold in BNX and 1.6-fold in normals. Renin-like activity was also detected in BNX individuals using renin concentration determinations with either excess human or sheep angiotensinogen. The inhibition of renin activity (IC-50% = 3.16 x 10(-9) molar) by EMD 56133 was not different between BNX and normals. Thus, active renin is present in the plasma of anephric humans and does not result from the inadvertent activation of prorenin due to sample handling. Although the source of PRA in BNX is unknown, the enzyme appears functionally normal as evidenced by the dose-response to a single renin inhibitor.

Measurement of human active renin heterogeneity.

A method for the separation and quantitation of multiple forms of active renin in human plasma is described. Shallow gradient isoelectric focusing of plasma resolved active renin into seven distinct components in each of 10 healthy normal individuals. Plasma renin activity focused at isoelectric points of 5.71, 5.57, 5.47, 5.22, 5.08, 4.93, and 4.82 with corresponding proportions of 16.3, 15.4, 21.1, 20.3, 14.0, 10.0, and 2.5%. Silicon dioxide treatment of plasma significantly increased the yield of renin in the focusing gels. Although each individual plasma sample contained the same seven renin forms, there was variability in the relative proportions of the multiple renin forms between individuals. This variance was significantly greater than the variance introduced by the determination itself. The same seven active renin forms were also present in human renal cortical tissue. In conclusion, a method for the determination of multiple renin forms in plasma and renal cortical tissue is presented. At least seven active multiple renin forms were resolved in human plasma and renal cortex.

Epoetin enhances erythropoiesis in normal men undergoing repeated phlebotomies.

Epoetin may enhance autologous blood donation, but efficacy and dose response have not been established. This multicenter, double-blind trial compared intravenous placebo (n = 23) with epoetin beta, 250 U/kg (n = 23), 500 U/kg (n = 19), and 1000 U/kg (n = 22), administered three times weekly for 26 days. Normal men (age, 28 +/- 7 years; mean +/- SD) received phlebotomies up to three times weekly as long as the hemoglobin remained greater than or equal to 12 gm/dl. Subjects treated with epoetin donated 32% more units of blood (p less than 0.05) compared with placebo. A dose response was not observed. Platelet counts increased with epoetin compared with placebo, but platelet function and bleeding time did not change. Prothrombin times increased and partial thromboplastin times decreased with both epoetin and placebo. The supernatant of packed red blood cells collected after multiple phlebotomies and stored 42 days had slightly lower glucose concentrations and pH after therapy with epoetin. Blood pressure did not change with epoetin or placebo. These findings support the efficacy and safety of epoetin for enhancing the erythropoietic response of normal subjects during intensive phlebotomy.

The pharmacokinetics of quinapril and its active metabolite, quinaprilat, in patients with various degrees of renal function.

Single- and multiple-dose pharmacokinetics of quinapril and its active metabolite, quinaprilat, were determined after oral administration of 20 mg quinapril HCl on day 1 and days 4 through 10 in 17 normotensive subjects with various degrees of renal function. Blood and urine samples were collected over 72- and 24-hour periods, respectively, after the first single dose and last multiple dose for measurement of quinapril and quinaprilat concentrations. The renal clearance of quinapril and quinaprilat decreased with increasing renal insufficiency but did not result in significant changes in quinapril pharmacokinetics in patients with renal impairment. In contrast, quinaprilat maximum plasma concentration, trough and peak steady-state plasma concentrations, area under the plasma concentration-time curve, and half-life increased significantly with increasing renal insufficiency. The disposition of quinapril and quinaprilat was unchanged from single to multiple doses. Small changes in the pharmacokinetic disposition of quinapril, together with a decreased rate of quinaprilat elimination, resulted in increased quinaprilat plasma concentrations following administration of both single and multiple quinapril doses to normotensive patients with renal impairment. Thus, quinapril dosage adjustment may be required in some patients with renal impairment.

Comparative pharmacokinetics and pharmacodynamics of epoetin alfa and epoetin beta.

Different recombinant human erythropoietin products have been developed. Although they appear to have similar pharmacokinetics and function, these have not been directly compared. This randomized, double-blind, four-period crossover study compared the pharmacokinetics and pharmacodynamics of intravenous and subcutaneous epoetin alfa and epoetin beta in 18 normal male volunteers. As a control, three subjects received placebo treatment. After intravenous administration, the steady-state volume of distribution and beta-phase volume of distribution of epoetin beta were 7.7% and 16.9% larger than for epoetin alfa (p less than 0.05). The terminal elimination half-life after intravenous administration of epoetin beta was 20% longer than the terminal elimination half-life of epoetin alfa. After subcutaneous administration there was a delayed drug absorption with epoetin beta compared with epoetin alfa (p less than 0.05). There was a small but significantly greater absolute reticulocyte response after subcutaneous epoetin beta compared with subcutaneous epoetin alfa. The findings support differences in the pharmacokinetics and function of epoetin alfa and beta that are possibly caused by differences in their glycosylation.

Blood pressure in hemodialysis patients during amelioration of anemia with erythropoietin.

This study analyzed blood pressure in hemodialysis patients treated with epoetin beta in multicenter trials. Antihypertensive drugs were prescribed as usual. Placebo-controlled trials compared epoetin (100 to 150 U/kg; N = 151) with placebo (N = 78) for 82 days. Hemoglobin (108 +/- 18 versus 75 +/- 14 g/L) (mean +/- SD) and diastolic blood pressure (84 +/- 14 versus 78 +/- 15 mm Hg) were greater (P less than 0.05) after epoetin. Clinically important increases in blood pressure (increases in diastolic blood pressure greater than or equal to 10 mm Hg and/or drug therapy) were more frequent with epoetin (58 versus 37%; P = 0.005). A dose-response trial compared epoetin, 25 U/kg (N = 42), 100 U/kg (N = 40), and 200 U/kg (N = 39) for 138 days. Increases in hemoglobin were dose dependent, but clinically important increases in blood pressure were not. In analyses of all patients treated with epoetin (N = 272), no baseline or final level of hemoglobin, or rate of hemoglobin rise, was a threshold for a rise in blood pressure. Patients requiring antihypertensive drugs or having uncontrolled hypertension (diastolic blood pressure greater than 90 mm Hg) at baseline had decreases in blood pressure (P less than 0.05) with antihypertensive therapy. Thus, compared with placebo, 21% of patients had clinically important increases in blood pressure during amelioration of anemia. The baseline or final levels of hemoglobin, the extent or rate of hemoglobin rise, or uncontrolled hypertension or antihypertensive drug use at baseline were not confirmed as risks. Antihypertensive drug therapy was important for blood pressure control.

Analysis of active renin heterogeneity.

Active renin is a heterogeneous enzyme that can be separated into multiple forms with high-resolution isoelectric focusing. The isoelectric heterogeneity may result from differences in glycosylation between the different forms. In order to determine the relationship between active renin heterogeneity and differences in composition or attachment of oligosaccharides, two separate experiments were performed: (i) Tunicamycin, which interferes with normal glycosylation processing, increased the proportion of relatively basic renin forms secreted into the incubation media by rat renal cortical slices. (ii) Endoglycosidase F, which enzymatically removes carbohydrate from some classes of glycoprotein, similarly increased the proportion of relatively basic forms when incubated with active human recombinant renin. In addition, further studies with inhibitors of human renin activity revealed that the heterogeneous renin forms were similarly inhibited by two separate renin inhibitors. These results are consistent with the hypothesis that renin isoelectric heterogeneity is due in part to differences in carbohydrate moiety attachment and that the heterogeneity of renin does not influence access of direct renin inhibitors to the active site of renin.

The effects of benazepril, a new angiotensin-converting enzyme inhibitor, in mild to moderate essential hypertension: a multicenter study.

Benazepril hydrochloride is a new angiotensin-converting enzyme inhibitor. In a multicenter study, 206 patients with mild to moderate hypertension were randomized to receive benazepril at a dose of 2, 5, 10, or 20 mg, hydrochlorothiazide, 25 mg, or placebo once daily for 4 weeks. The 20 mg dosage of benazepril lowered blood pressure to a degree equal to that of 25 mg hydrochlorothiazide: -12.2/7.7 mm Hg and -13.4/-7.5 mm Hg, respectively. Hydrochlorothiazide proved to be more effective in black subjects. At lower dosage levels of benazepril (2, 5, and 10 mg), blood pressure reduction was not significantly different from that with placebo. In those patients who failed to achieve goal diastolic blood pressure of less than 90 mm Hg with monotherapy after 4 weeks, the addition of open-label hydrochlorothiazide (25 mg/day) to benazepril, hydrochlorothiazide, or placebo produced a substantial additional decrease in blood pressure over a 2-week period. No definite adverse effects on hematologic measurements, serum biochemistry test results, or urinalyses were noted. Subjective adverse experiences were common in all groups but except in three or possibly four instances were not considered causally related to the study drug.

Acute stimulation of renin secretion changes the multiple form profile of active plasma renin.

Active renin is composed of multiple forms with variable isoelectric points. In this study, the relative proportions of five major active renin forms in human peripheral venous plasma were compared before and 2 h after stimulation of renin secretion with both converting enzyme inhibition (quinapril) and upright posture in five patients with essential hypertension. The five major active renin forms were separated by shallow gradient isoelectric focusing and quantitated by radioimmunoassay of generated angiotensin I. Plasma renin activity increased from 1.2 to 5.1 ng AI/mL/h (P less than .05). This was accompanied by a significant increase in the proportions of the two most basic renin forms and a significant decrease in the proportion of the most acidic form in venous plasma. Although the mechanism cannot be determined from this study, the altered renin form profile observed could have resulted from preferential renal secretion and/or altered hepatic extraction of the more basic forms. An altered renin form profile in response to acute stimulation has important physiologic implications. Since the relatively basic renin forms are preferentially degraded they possess shorter half-lives. Additionally, the multiple forms of active renin may be functionally heterogenous. Thus, acute stimulation of renin secretion may result in circulating renin with a shorter duration of action and different functional effects than renin released under steady state conditions.

Renal secretion and hepatic clearance of human multiple renin forms.

Human active renin can be separated into at least five forms by isoelectric focusing. The present study assessed the preferential renal secretion and hepatic degradation of renin forms in humans. The renin form profile of secreted renal renin was determined before transplant in an ex vivo kidney donor perfusion system and compared with the peripheral plasma multiple renin form profile of normal subjects. The effect of hepatic degradation on renin forms was assessed in hepatic vein plasma in comparison with infrarenal vena cava plasma in hypertensive patients during renal vein renin studies. The results revealed a significantly greater proportion of the more basic forms in the perfusate of donor kidneys compared with normal plasma. In hypertensive patients the proportion of the more basic renin forms in the hepatic vein was significantly decreased in comparison with the infrarenal vena cava. Thus, the human kidney may preferentially secrete the more basic renin forms. In contrast, the liver preferentially degrades the more basic forms, giving these forms a shorter plasma half-life. The preferential secretion and clearance of the more basic forms of renin may contribute to short-term control of human renin-angiotensin system activity.

Body fluid spaces and blood pressure in hemodialysis patients during amelioration of anemia with erythropoietin.

Blood pressure (BP) may increase in hemodialysis patients during treatment of anemia with recombinant human erythropoietin (r-HuEPO). Since fluid volume is a determinant of BP in dialysis patients, changes in body fluid spaces during r-HuEPO therapy could affect BP. Thus, 51Cr-labeled red blood cell (RBC) volume, inulin extracellular fluid (ECF) volume, and urea total body water (TBW), as well as cardiac output, plasma renin activity (PRA), and plasma aldosterone concentration were determined postdialysis before and after r-HuEPO therapy in patients in whom changes in BP could be managed by ultrafiltration alone. Eleven patients entered the study: one had a renal transplant and two required addition of antihypertensive drug therapy and were excluded; eight, of whom two required antihypertensive drug therapy following the study, were included in the analyses. Results revealed an increase in predialysis hemoglobin from 67 to 113 g/L (6.7 to 11.3 g/dL) (P = 0.001) during 18 +/- 6 weeks of therapy. Predialysis diastolic BP increased from 80 to 85 mm Hg (P = 0.07), while postdialysis diastolic BP was unchanged at 73 mm Hg. 51Cr-RBC volume increased, from 0.7 to 1.3 L (P = 0.004). ECF tended to decrease, from 13.7 to 10.8 L (P = 0.064), while TBW decreased to a similar extent, but not significantly, 34.3 to 31.2 L (P = 0.16). Postdialysis ECF volume was positively correlated with mean arterial BP at baseline (r = 0.89, P = 0.007) and after therapy (r = 0.74, P = 0.035). However, the regression lines for this relationship were different (P = 0.022) before and after therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of acute stimulation of renin secretion on renal renin content in vivo.

Acute stimulation of renal renin secretion has been reported to increase, not change, or decrease intra-renal renin (IRR) content. However, these effects and the potential mechanisms for acute changes in IRR content have not been studied directly. In this study, the effect of acute stimulation of renin secretion on IRR content was studied directly using a new in vivo blood perfused rabbit kidney preparation. Following removal of the right kidney for determination of IRR content (N = 7) the left kidney was cannulated and perfused for an average of 55 minutes (baseline) at mean arterial blood pressure. Renin secretion by the left kidney was subsequently stimulated by reducing renal perfusion pressure to 60 mm Hg and administering enalapril, 1 mg/kg intravenously. After 38 to 140 minutes (mean 90 min) of stimulation, the left kidney was also removed and IRR content assessed. Renal blood flow and renin secretory rate (RSR) were determined frequently at baseline and following stimulation of renin secretion. The total amount of renin secreted in response to acute stimulation was calculated by integrating the RSR response over time. RSR from the left kidney increased by 515% during acute stimulation. IRR content in the left kidney also increased and averaged 16% greater than the right kidney from the same animal. In order to account for all of the renin secreted as well as the increase in IRR content following acute stimulation, it was calculated that the renin synthesis rate would have been required to increase over 26-fold.(ABSTRACT TRUNCATED AT 250 WORDS)