Obstructive nephropathy in the rat: possible roles for the renin-angiotensin system, prostaglandins, and thromboxanes in postobstructive renal function.

Relief of unilateral ureteral obstruction (UUO) of 24 h duration in rats is followed by severe renal vasoconstriction in the postobstructive kidney (POK). The present study examined possible roles of renal prostaglandins (PG) and thromboxanes (TX), as well as the renin-angiotensin system, in this vasoconstriction. Administration of the cyclooxygenase inhibitor indomethacin, which blocks both PG and TX production, failed to improve POK hemodynamics in UUO rats. To explore the possible role of the TX compounds, which include the potent vasoconstrictor thromboxane A2 (TXA2), UUO rats were infused with imidazole, an agent that blocks synthesis of TX, but not of PG. Imidiazole led to two- to threefold increases in the clearance of both inulin and rho-aminohippuric acid by the POK. This effect of imidazole was abolished by indomethacin, suggesting that the amelioration of POK vasoconstriction by imidazole was a result of inhibition of vasoconstrictor TX synthesis (e.g. TXA2), with PG vasodilators (e.g. PGE2 or PG12) still active. Urea, infused in a solution whose osmolality and volume were identical to the imidazole infusion, failed to improve hemodynamics in the POK, making it unlikely that nonspecific effects of volume expansion or osmotic diuresis mediated the beneficial effect of imidazole. Further studies examined the possible role of the renin-angiotensin systems in the vasoconstriction of the POK. UUO rats infused with the angiotensin II antagonist, Saralasin, exhibited no significant improvement in POK function, a finding that might be at least partly attributable to agonist/vasoconstrictor properties of Saralasin. In other experiments, treatment of UUO rats with the angiotensin-converting enzyme blocker SQ 14225 (Captopril), in order to inhibit angiotensin II formation, led to at least twofold increases in the clearance of both inulin and rho-aminohippuric acid in the POK. It is unlikely that Captopril exerted this beneficial effect by potentiating the vasodilator kinins, because the effect was not diminished by administration of either carboxypeptidase B (which destroys the kinins) or Trasylol (which blocks kinin synthesis). Thus, these results suggest that both angiotensin II, as well as metabolites of the PG-TX system, may be important determinants of postobstructive renal hemodynamics in the rat.     

Long-acting natriuretic peptide, vessel dilator, and kaliuretic peptide enhance the urinary excretion rate of β2-Microglobulin

The atrial natriuretic peptide (ANP) gene synthesizes a 126-amino acid (aa) prohormone from which four peptide hormones are derived. These 4 peptide hormones consisting of aa 1 to 30 (ie, long-acting natriuretic peptide [LANP]), aa 31 to 67 (vessel dilator), aa 79 to 98 (kaliuretic peptide), and aa 99 to 126 (ie, ANP) have diuretic, natriuretic, and/or kaliuretic properties. ANP has been reported to have its natriuretic and protein-excreting effects via both the proximal and distal tubules, but where in the kidney the other three peptide hormones have their natriuretic and/or diuretic effects is unknown. Further, it has never been investigated as to whether these three other peptide hormones enhance protein excretion. The present investigation was designed to determine (1) if these atrial peptides enhance protein excretion and (2) if their effects involve the proximal tubules of healthy humans by examining the excretion rate of β₂-microglobulin, a marker of proximal tubule function. Twenty-four healthy human subjects were studied following the infusion of 100 ng/kg body weight/min for 60 minutes of each of the respective peptides. LANP enhanced the excretion rate of β₂-microglobulin 2-fold within 20 minutes of beginning its infusion (P < .05) and was 2.5-fold higher than the preinfusion excretion rate at the end of the infusion. The excretion rate of β₂-microglobulin continued to be significantly (P < .01) increased for 3 hours after cessation of the LANP infusion, with the maximal excretion rate (ie, 3.8-fold increase) at 2.5 hours after stopping the infusion. Vessel dilator showed a more marked enhancement of β₂-microglobulin during its infusion, with the excretion rate increasing 2.5-fold at 20 minutes, and was increased 4-fold (P < .01) at the end of the infusion. With cessation of the vessel dilator infusion, the excretion rate of β₂-microglobulin decreased but was still elevated 2-fold (P < .05) 3 hours after stopping the infusion. Kaliuretic peptide enhanced the β₂-microglobulin excretion rate a maximal 3-fold, which occurred at the end of its infusion. The β₂-microglobulin excretion secondary to kaliuretic peptide remained 2-fold (P < .05) above baseline during the 3-hour postinfusion period. These peptide hormones similarly enhanced the albumin and total protein excretion rates 2- to 4-fold. These results indicate that LANP, vessel dilator, and kaliuretic peptide each (1) enhance protein excretion in healthy humans and (2) inhibit proximal tubular protein reabsorption.     

Utility of impedance cardiography for the identification of short-term risk of clinical decompensation in stable patients with chronic heart failure.

OBJECTIVES: This study sought to assess the potential utility of impedance cardiography (ICG) in predicting clinical deterioration in ambulatory patients with heart failure (HF). BACKGROUND: Impedance cardiography uses changes in thoracic electrical impedance to estimate hemodynamic variables, but its ability to predict clinical events has not been evaluated. METHODS: We prospectively evaluated 212 stable patients with HF and a recent episode of clinical decompensation who underwent serial clinical evaluation and blinded ICG testing every 2 weeks for 26 weeks and were followed up for the occurrence of death or worsening HF requiring hospitalization or emergent care. RESULTS: During the study, 59 patients experienced 104 episodes of decompensated HF (16 deaths, 78 hospitalizations, and 10 emergency visits). Multivariate analysis identified 6 clinical and ICG variables that independently predicted an event within 14 days of assessment. These included three clinical variables (visual analog score, New York Heart Association functional class, and systolic blood pressure) and three ICG parameters (velocity index, thoracic fluid content index, and left ventricular ejection time). The three ICG parameters combined into a composite score was a powerful predictor of an event during the next 14 days (p = 0.0002). Visits with a high-risk composite score had 2.5 times greater likelihood and those with a low-risk score had a 70% lower likelihood of a near-term event compared with visits at intermediate risk. CONCLUSIONS: These results suggest that when performed at regular intervals in stable patients with HF with a recent episode of clinical decompensation, ICG can identify patients at increased near-term risk of recurrent decompensation.     

The Dewey Monitor: Pulse Oximetry can Warn of Hypoxia in an Immersed Rebreather Diver in Multiple Scenarios

Annals of Biomedical Engineering - Divers who wish to prolong their time underwater while carrying less equipment often use devices called rebreathers, which recycle the gas expired after each...     

Adenomyosis a variant, not a disease? Evidence from hysterectomized menopausal women in the Study of Women's Health Across the Nation (SWAN)

OBJECTIVE: Our study evaluates the symptoms commonly attributed to adenomyosis in women undergoing the menopausal transition. We hypothesized that adenomyosis is more commonly seen in women with fibroids, pelvic pain, abnormal uterine bleeding, and in the presence of endometriosis. DESIGN: Retrospective cohort. SETTING: Multisite community-based study. PATIENT(S): Enrollees in the Study of Women's Health Across the Nation who had hysterectomies. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): Relationship of adenomyosis to presenting symptoms and other patient characteristics. RESULT(S): Adenomyosis was found in 48% of 137 patients. Frequencies of presenting symptoms were similar in those with and without evidence of adenomyosis. The same prevalence of fibroids was seen in the presence or absence of adenomyosis: 37% versus 43%, endometriosis, 3% versus 5%, abnormal bleeding, 27% versus 33%, or chronic pelvic pain in the presence of fibroids 12% versus 17%. CONCLUSION(S): Adenomyosis is a common diagnosis seen in hysterectomized specimens from women undergoing the perimenopausal transition. Adenomyosis is equally common in women who also have fibroids, endometriosis, pelvic pain, or abnormal uterine bleeding, and women who do not. Therefore, adenomyosis is an incidental finding, not the source of the symptomatology. It appears not to be a "disease" per se but rather a normal variant.     

Long-acting natriuretic peptide, vessel dilator, and kaliuretic peptide enhance the urinary excretion rate of beta2-microglobulin

The atrial natriuretic peptide (ANP) gene synthesizes a 126-amino acid (aa) prohormone from which four peptide hormones are derived. These 4 peptide hormones consisting of aa 1 to 30 (ie, long-acting natriuretic peptide [LANP]), aa 31 to 67 (vessel dilator), aa 79 to 98 (kaliuretic peptide), and aa 99 to 126 (ie, ANP) have diuretic, natriuretic, and/or kaliuretic properties. ANP has been reported to have its natriuretic and protein-excreting effects via both the proximal and distal tubules, but where in the kidney the other three peptide hormones have their natriuretic and/or diuretic effects is unknown. Further, it has never been investigated as to whether these three other peptide hormones enhance protein excretion. The present investigation was designed to determine (1) if these atrial peptides enhance protein excretion and (2) if their effects involve the proximal tubules of healthy humans by examining the excretion rate of beta2-microglobulin, a marker of proximal tubule function. Twenty-four healthy human subjects were studied following the infusion of 100 ng/kg body weight/min for 60 minutes of each of the respective peptides. LANP enhanced the excretion rate of beta2-microglobulin 2-fold within 20 minutes of beginning its infusion (P < .05) and was 2.5-fold higher than the preinfusion excretion rate at the end of the infusion. The excretion rate of beta2-microglobulin continued to be significantly (P < .01) increased for 3 hours after cessation of the LANP infusion, with the maximal excretion rate (ie, 3.8-fold increase) at 2.5 hours after stopping the infusion. Vessel dilator showed a more marked enhancement of beta2-microglobulin during its infusion, with the excretion rate increasing 2.5-fold at 20 minutes, and was increased 4-fold (P < .01) at the end of the infusion. With cessation of the vessel dilator infusion, the excretion rate of beta2-microglobulin decreased but was still elevated 2-fold (P < .05) 3 hours after stopping the infusion. Kaliuretic peptide enhanced the beta2-microglobulin excretion rate a maximal 3-fold, which occurred at the end of its infusion. The beta2-microglobulin excretion secondary to kaliuretic peptide remained 2-fold (P < .05) above baseline during the 3-hour postinfusion period. These peptide hormones similarly enhanced the albumin and total protein excretion rates 2- to 4-fold. These results indicate that LANP, vessel dilator, and kaliuretic peptide each (1) enhance protein excretion in healthy humans and (2) inhibit proximal tubular protein reabsorption.