New evidence of a dihydropyridine-activated cationic channel in the MDCK cell line

Newborn rat distal cells express an apical Ca2+ channel activated by dihydropyridine drugs. Similarly, in Madin-Darby canine kidney (MDCK) cells, nifedipine increased Ca2+i in a concentration-dependent manner (IC50=4 μM) in fura-2-loaded cells. Response to nifedipine was abolished by EGTA, suggesting that it depends on extracellular calcium. Ca2+ channel antagonist isradipine and agonist BayK8644 increased Ca2+i indicating that this effect is related to the dihydropyridine group. Diltiazem (20 μM) and gadolinium (200 μM) decreased the nifedipine effect (62 and 43%, respectively). Lanthanum (100 μM) did not change the response. Valinomycin clamping of the membrane potential did not modify nifedipine-induced increment, indicating that it was unrelated to potassium fluxes. We performed whole cell clamp experiments in MDCK cells maintained at -50 mV with perfusion solution containing 10 mM CaCl2. Nifedipine (20 μM) induced an increase in current (1.2±0.3 nA), which was partially inhibited by Gd3+. No significant current was induced by nifedipine in the presence of 0.5 mM EGTA. To determine the effects of nifedipine on the membrane potential, we performed oxonol fluorescence experiments. The addition of nifedipine or Bay K8644 induced depolarization, highly dependent on external sodium. Nifedipine (20 μM) induced depolarization of 6.9±0.8 mV (n=21). EC50 to nifedipine was in the 10 μM range. We conclude that MDCK cells exhibit a dihydropyridine-activated cationic channel.

Nifedipine-activated Ca(2+) permeability in newborn rat cortical collecting duct cells in primary culture

To characterize Ca(2+) transport in newborn rat cortical collecting duct (CCD) cells, we used nifedipine, which in adult rat distal tubules inhibits the intracellular Ca(2+) concentration ([Ca(2+)](i)) increase in response to hormonal activation. We found that the dihydropyridine (DHP) nifedipine (20 microM) produced an increase in [Ca(2+)](i) from 87.6 +/- 3.3 nM to 389.9 +/- 29.0 nM in 65% of the cells. Similar effects of other DHP (BAY K 8644, isradipine) were also observed. Conversely, DHPs did not induce any increase in [Ca(2+)](i) in cells obtained from proximal convoluted tubule. In CCD cells, neither verapamil nor diltiazem induced any rise in [Ca(2+)](i). Experiments in the presence of EGTA showed that external Ca(2+) was required for the nifedipine effect, while lanthanum (20 microM), gadolinium (100 microM), and diltiazem (20 microM) inhibited the effect. Experiments done in the presence of valinomycin resulted in the same nifedipine effect, showing that K(+) channels were not involved in the nifedipine-induced [Ca(2+)](i) rise. H(2)O(2) also triggered [Ca(2+)](i) rise. However, nifedipine-induced [Ca(2+)](i) increase was not affected by protamine. In conclusion, the present results indicate that 1) primary cultures of cells from terminal nephron of newborn rats are a useful tool for investigating Ca(2+) transport mechanisms during growth, and 2) newborn rat CCD cells in primary culture exhibit a new apical nifedipine-activated Ca(2+) channel of capacitive type (either transient receptor potential or leak channel).

Effects of thrombin on intracellular calcium and pH in human and murine platelets

The aim of this study was to compare the effect of thrombin (Thr) on cytosolic calcium [Ca2]+i and intracellular pH [pH]i in human and murine platelets. Rich-platelet suspensions from both species were loaded with Fura-2 (2 microM) or BCECF (0.75 microM) by incubation with their respective acetoxymethyl esters to measure cytosolic calcium [Ca2+]i or intracellular pH [pH]i, respectively. Suspensions were challenged with increasing concentrations of Thr, from 0.1 to 10 IU/ml. Basal [Ca2+]i in human platelets was 98 +/- 6 and 99.1 +/- 9 nM in rat platelets (n = 20). Thr increased [Ca2+]i, EC50 was 1.1 +/- 0.04 in human and 0.97 +/- 0.06 IU/ml in rat platelets (n = 7). Extracellular Mg2+ (4 or 8 mM) abolished Thr response on [Ca2+]i. [pH]i in human was 7.09 +/- 0.08 and 7.11 +/- 0.04 in rat platelets. Thr induced alkalinization of platelets in both species. Our results indicate that the potency of Thr to change [Ca2+]i and [pH]i was similar in both species, allowing for comparisons between human and murine platelets and to extrapolate results from an animal model to human pathology.

Specificity of circulating and tissue-bound autoantibodies in Goodpasture syndrome

Goodpasture syndrome is an often fatal autoimmune disease associated with glomerulonephritis and/or pulmonary hemorrhage. The clinical manifestations of this disease correlate well with the presence of circulating antiglomerular basement membrane (GBM) autoantibodies. The primary target antigen in glomerular and alveolar basement membranes is thought to be the alpha 3 chain of type IV collagen. Nearly all that is known about anti-GBM antibodies in humans comes from work on unbound circulating antibody. We recently had the unique and rare opportunity to obtain early postmortem antibody and tissues from a patient who died with catastrophic Goodpasture syndrome. The specificity of circulating, kidney-bound and lung-bound autoantibodies from this patient was evaluated against a variety of purified basement membrane constituents. The results indicate that the primary target for the circulating and tissue-bound autoantibodies is the NC1 domain of the alpha 3(IV) chain of type IV collagen. Additionally, all the antibodies recognize a cryptic epitope/s on the alpha 3(IV)NC1 hexamer. Furthermore, tissue-bound and circulating antibodies compete with one another for overlapping epitopes on the antigen. These findings demonstrate that circulating autoantibodies in Goodpasture syndrome are highly representative of those bound to organ tissues, strengthening the notion that pathogenic autoantibodies are targeted to the alpha 3(IV)NC1 collagen, and that previous reports of findings in the circulation may be applicable to tissue injury.

Endocytosis inhibition protects the isolated guinea pig heart against ouabain toxicity

We have tested whether toxicity and uptake of ouabain are linked phenomena in isolated guinea-pig heart. We perfused toxic dose of either ouabain, dihydroouabain (hydrophilic cardiac steroids), ouabagenin or digitoxin (hydrophobic steroids) in conditions of endocytosis inhibited. We used two schemes of inhibition of endocytosis. First, we cooled the heart at 0-4 degrees C and exposed it 60 min to either 1 X 10(-6) M ouabain or 3 X 10(-7)M digitoxin. Upon rewarming, the heart exposed to ouabain relaxed with a shorter time constant than those exposed to digitoxin. Second, we perfused four receptor mediated endocytosis (RME) inhibitors at the same time that the cardiac glycosides. RME inhibitors significantly delayed the cardiac arrest caused by ouabain and dihydroouabain but they did not modify the toxicity of 3 X 10(-7)M digitoxin or 5 X 10(-6)M ouabagenin. None of RME inhibitors modified the toxicity of 0.5 mM K+ or zero Na+ saline solution. We suggest that the protection against ouabain toxicity brought by endocytosis inhibition, is related to the Na-pump recycling. We infer that besides the sarcolemmal exposed Na-pumps, the intracellular Na-pumps pool may be of importance for the pharmacological effects of digitalis steroids.

AIDS in the elderly: New York City vital statistics

The HIV infection primarily affects young adults, but older adults are also susceptible. The number of AIDS cases among persons aged 50 or greater is growing and is of major concern. As our awareness of the prevalence of HIV-related illnesses presenting to the emergency department improves in the younger population, we must not ignore the disease in older patients. Early recognition of HIV infection will ensure the greatest opportunity for treatment and prevention of many of the consequences of opportunistic infections. We present a case of HIV in an elderly patient in order to heighten awareness of the possibility of HIV infection in older patients presenting to the emergency department. We also review the epidemiological, diagnostic, and therapeutic aspects of AIDS in older adults.

Puerto Rican migration and occupational selectivity, 1982-1988

"This study examines whether or not the likelihood of Puerto Rican workers choosing to migrate to the United States depends on their occupations or skills. The study determined that the occupational composition among those migrating from the island to the United States generally corresponds to the occupational distribution in Puerto Rico. The exception is that, after controlling for labor market conditions in Puerto Rico and in the United States and for other characteristics of the migrants, farm workers, laborers, and craft and kindred workers are overrepresented in the flow of migrants. The two most important factors contributing to the occupational distribution of migrants are whether or not they already have job offers in the United States and whether they are currently employed in Puerto Rico."

Phase I study of recombinant human interleukin-2 for pediatric malignancies: feasibility of outpatient therapy. A Pediatric Oncology Group Study

Published data indicate that when recombinant interleukin-2 (rIL-2) is administered to children as a 15-min i.v. bolus, doses of 18 x 10(6) IU/m2 are poorly tolerated, requiring intensive care unit (ICU) management of IL-2-induced hypotension. We administered rIL-2 as a 1- or 2-h i.v. infusion to 11 children with malignancies refractory to conventional therapy. IL-2 was given every Monday/Wednesday/Friday for 3 weeks. Four children received 12 x 10(6) IU/m2/dose, four received 18 x 10(6) IU/m2/dose, and three received 24 x 10(6) IU/m2/dose (1 Cetus Unit = 6 IU). Fever, chills, flushing, nausea, vomiting, transient weight gain, and oliguria were observed at all three dose levels (not dose-limiting toxicities). Cardiovascular toxicity was significantly reduced compared to the bolus regimen. Mild hypotension was observed at all three dose levels; however, there was no severe dose-limiting hypotension. Because of reduced cardiovascular toxicity, IL-2 was safely administered on an outpatient basis. This regimen induced marginal transient increases in natural killer cell activity and lymphokine-activated killer cell activity. No measurable clinical tumor response was observed in any of the 11 children. The maximum-tolerated dose has not been reached. This regimen allows for a considerable cost reduction (outpatient care instead of ICU care) and safety, making further clinical trials on the use of IL-2 in children more feasible.

Solitary osseous sarcoidosis in a finger

Sarcoidosis confined to a single bone in a patient with chronic systemic sarcoidosis and seen as a soft tissue mass is exceedingly rare. The combination of lytic and sclerotic changes within one bone has not been previously reported.

Effects of furosemide on the renal functions of the unanesthetized newborn rat

In neonates pharmacokinetics of furosemide is very slow, as compared to adult individuals, because it is eliminated through glomerular filtration and tubular secretion, mechanisms that are not fully developed in the newborn mammal. In addition, Henle's loop, the main site of action of this diuretic, is shorter in the neonate than in the adult animal. The aim of this study was to measure the response to furosemide in the unanesthetized newborn rat and to compare it with that of the adult. Furosemide (0.5, 1, 1.5, 2, 5 or 10 mg/kg body weight, i.p.) or vehicle were administered to newborn and adult rats and the effects on sodium, potassium and water balance were assessed. Despite the physiological characteristics of the neonatal kidney, furosemide induced a more marked sodium excretion and decrease in free water clearance in the newborn than in the adult rat. In contrast, urinary potassium losses elicited by furosemide were higher in the adult than in the newborn rat at similar doses. At both ages, the effects of the diuretic were dose-dependent. Plasma sodium decreased, whereas plasma potassium and hematocrit increased in the newborn rats, after the highest doses of furosemide. In the adult rat changes were less marked. Our results suggest that the neonatal kidney is more sensitive to equivalent doses of furosemide than the adult kidney.

Effects of eicosanoids on the water and sodium balance of the neonate

Experimental and clinical evidence support the assumption that eicosanoids affect the morphological development and the functional behaviour of the kidney during the intra-uterine and newborn periods. Inhibition of prostaglandin (PG) synthesis in the pregnant rhesus monkey resulted in renal hypoplasia in the offspring. The plasma levels of PGs are high in the newborn. Production of PGE2 by the cortical collecting duct was found to be similar in newborn and adult rabbit but the affinity of the renal tissue of the newborn for this eicosanoid was higher than that of the renal tissue of the adult rat. Based on findings in adult animals this would be expected to blunt the effect of antidiuretic hormone and account, in part, for the limited ability of the newborn to concentrate the urine. Yet, administration to unanaesthetized newborn rats of acetaminophen, a drug that inhibits the synthesis of PGE2 and thromboxane B2, blocked, rather than enhanced, the increment in urine osmolality produced by 1 h of water deprivation. The effect was absent in weaning and adult rats. A similar experimental manoeuvre increased sodium excretion in newborn but not in weaning or adult rats. Age-related differences are also evident with regard to side effects of PG synthesis inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of levamisole on experimental infections by Plasmodium berghei in mice

Levamisole (phenylimidothiazol), considered a strong immunostimulant, when administered to healthy Swiss mice did not cause a significant increase in -the weight of their thymus, liver and spleen, even though the drug was used at different times before removing such organs. High doses ofdrug used in the 4-day prophylactic scheme had no antimalarial effect. However, when given to malaria infected mice 24 hours before, at the same time, and 24 hours after the inoculation of a chloroquine-sensitive or a chloroquine-resistant strain of Plasmodium berghei small doses of the drug induced a somewhat decreased parasitemia, the dose of 1 mg/kg body weight before the inoculum being the best scheme. The mortality rates by malaria in the levamisole treated groups were also delayed although all mice finally died. The data suggest that levamisole may display a stimulant effect on the depressed immune response caused by malaria.

Renal handling of indomethacin and its relationship with the secretory pathway of prostaglandins

The uptake of prostaglandin E2, one of the main renal prostaglandins and of p-aminohippurate, an indicator of the anion organic transport, by slices of kidney cortex from adult female rats was studied in the presence and in the absence of indomethacin. The drug's inhibitory effect on the uptake of prostaglandin E2 was observed both after in vivo administration as well as when it was present in the bathing media. The effect was more pronounced when the drug was given in vivo and in addition, was present in the bath. [14C] PAH uptake was inhibited by indomethacin in a dose-related pattern and the kinetic analysis of this effect is indicative of a competitive inhibition. As expected, uptake of PAH by medullary slices was not affected by the presence of either indomethacin of PGE2. Indomethacin was more potent in inhibiting PGE2 uptake than PAH uptake.