Blockade of K(ATP) channels reduces endothelial hyperpolarization and leukocyte recruitment upon reperfusion after hypoxia.

Ischemia/reperfusion injury in renal transplantation leads to slow or initial nonfunction, and predisposes to acute and chronic rejection. In fact, severe ischemia reperfusion injury can significantly reduce graft survival, even with modern immunosuppressive agents. One of the mechanisms by which ischemia/reperfusion causes injury is activation of endothelial cells resulting in inflammation. Although several therapies can be used to prevent leukocyte recruitment to ischemic vessels (e.g. antiadhesion molecule antibodies), there have been no clinical treatments reported that can prevent initial immediate neutrophil recruitment upon reperfusion. Using intravital microscopy, we describe abrogation of immediate neutrophil recruitment to ischemic microvessels by the K(ATP) antagonist glibenclamide (Glyburide). Further, we show that glibenclamide can reduce leukocyte recruitment in vitro under physiologic flow conditions. ATP-regulated potassium channels (K(ATP)) are important in the control of cell membrane polarization. Here we describe profound hyperpolarization of endothelial cells during hypoxia, and the reduction of this hyperpolarization using glibenclamide. These findings suggest that control of endothelial membrane potential during ischemia may be an important therapeutic tool in avoiding ischemia/reperfusion injury, and therefore, enhancing transplant long-term function.

Functional evidence for an inward rectifier potassium current in rat renal afferent arterioles.

An inward rectifier potassium current, Kir, has been identified in cerebral and coronary resistance vessels, where it is considered to be an important determinant of resting membrane potential (RMP) and to play a role in blood flow regulation. We investigated the functional role of Kir in the renal afferent arteriole using the in vitro-perfused hydronephrotic rat kidney. Increasing external KCl from 5 to 15 mmol/L induced afferent arteriolar vasodilation. This response was inhibited by 10 to 100 micromol/L Ba(2+), concentrations selective for blockade of Kir, and by chloroethylclonidine (100 micromol/L) but was not blocked by glibenclamide (10 micromol/L) or ouabain (3 mmol/L). Reducing external KCl from 5 to 1.5 mmol/L to enhance rectification of Kir caused vasoconstriction at low renal arterial pressure (40 mm Hg) and vasodilation during myogenic vasoconstriction (120 mm Hg), suggesting that this current dominates RMP at low perfusion pressures. When administered to kidneys perfused at 40 mm Hg renal arterial pressure, 30 micromol/L Ba(2+) elicited afferent arteriolar depolarization, reducing RMP from -47+/-2 to -34+/-2 mV (n=10, P:<0.0001), and vasoconstriction, reducing diameters from 14.5+/-1 to 10.9+/-0.8 microm (n=10, P:=0.0016). Although Ba(2+) reduced resting diameter, blockade of Kir did not prevent myogenic signaling in this vessel. Our findings thus demonstrate the presence of Kir in rat renal afferent arterioles and suggest that this current is an important determinant of RMP in situ.

School health experience before and after completion of pediatric training.

A questionnaire regarding school health training and current school-based activities was completed by 116 of 141 young pediatricians practicing in four southwestern states. Responses indicated that few (22.4%) were exposed to school health during their residencies, although most (65.5%) are now providing some school health services. Those who had had school health training during residency are much more likely to be providing services than those who did not. Likewise, during their residencies, few received instruction in methods of health education, though many, led again by those who had appropriate residency experience, now participate in school health education programs. Residency programs should provide training in school health to improve the physician's comfort and efficiency in the roles he is presently asked to play, and to increase his involvement in this critically important area of pediatrics.

American Academy of Pediatrics. Pediatric Practice Action Group and Task Force on Medical Informatics. Privacy protection and health information: patient rights and pediatrician responsibilities.

Pediatricians and pediatric medical and surgical subspecialists should know their legal responsibilities to protect the privacy of identifiable patient health information. Although paper and electronic medical records have the same privacy standards, health data that are stored or transmitted electronically are vulnerable to unique security breaches. This statement describes the privacy and confidentiality needs and rights of pediatric patients and suggests appropriate security strategies to deter unauthorized access and inappropriate use of patient data. Limitations to physician liability are discussed for transferred data. Any new standards for patient privacy and confidentiality must balance the health needs of the community and the rights of the patient without compromising the ability of pediatricians to provide quality care.

The effect of a comprehensive prematurity prevention program on the number of admissions to the neonatal intensive care unit.

The null hypothesis of this study was that a prematurity prevention program that uses computerized prenatal risk assessment, educational interventions administered on a weekly basis by telephone, enhanced nutritional support, and referral to a perinatologist whenever necessary will result in no difference in the number of neonates admitted to the neonatal intensive care unit (NICU). A retrospective cohort study was designed to compare the number of admissions to the NICU for the 12 months before initiation of the prematurity prevention program with those during the first 12 months of the full working program. Compared with the year before program initiation, the prematurity prevention program resulted in a 56% reduction in the number of NICU admissions, a 49% reduction in preterm deliveries with subsequent admission of the infant to the NICU, and a 59% reduction in NICU hospital days. In addition, there was a 38% reduction in preterm deliveries caused solely by preterm labor. The null hypothesis is rejected because a comprehensive prematurity prevention program resulted in a significant reduction in NICU admissions, preterm deliveries with admission to the NICU, and NICU hospital days.

Are physicians educable? Teaching medical students about school health.

Third-year medical students on their pediatric rotation at the University of New Mexico (UNM) are assigned to spend two mornings with school nurses at the students' choice of schools. Each student is given a list of goals and questions relating to those goals to guide his/her experience. Following the two sessions, each student answers a questionnaire testing understanding of aspects of the school nurse's work and interrelationships between school nurses and physicians. Of the first 67 students responding to the questionnaire, 66 found the program valuable and worthy of continuation. The medical students' understanding of the capabilities and limitations of the nurses whose work they observed appeared excellent. Two-thirds of the students perceive poor communication with physicians as a major frustration for the nurses. Their appreciation of this need, plus their ability to recognize the many capabilities of school nurses, should result in better interaction between the two professions.

Hyperdiploidy with 49-65 chromosomes represents a heterogeneous cytogenetic subgroup of acute myeloid leukemia with differential outcome.

Chromosome gain is frequent in acute myeloid leukemia (AML) and is counted alongside structural abnormalities when determining karyotype complexity. However, there are few studies investigating the cytogenetic profile and outcome of patients with a hyperdiploid karyotype (49-65 chromosomes, HK). We identified 221 (14%) patients with HK out of 1563 patients with three or more chromosomal abnormalities. HK was not associated with sex, white cell count and secondary disease status, but was more prevalent among children (22% vs 13%). The pattern of chromosomal gain and loss was non-random and chromosomes 8, 13 and 21 were the most frequently gained. Three distinct subgroups (numerical, structural and adverse) were identified with differential outcome: 5-year cumulative incidence of relapse of 52%, 68% and 76%, respectively (P=0.008). Patients in the adverse subgroup had poorer survival compared with patients with only numerical abnormalities (adjusted hazard ratio: 2.01 (95% confidence interval: 1.43-2.83), P=0.0002). This outcome heterogeneity was similar among children and adults. In conclusion, AML patients with a HK should not automatically be assigned to the adverse cytogenetic risk group on the basis of complexity. Instead they should be assessed for the presence of specific chromosomal abnormalities, which are known to harbour an adverse effect.

High hyperdiploidy among adolescents and adults with acute lymphoblastic leukaemia (ALL): cytogenetic features, clinical characteristics and outcome.

High hyperdiploidy (HeH, 51-65 chromosomes) is an established genetic subtype of acute lymphoblastic leukaemia (ALL). The clinical and cytogenetic features as well as outcome of HeH among adolescents and adults have not been thoroughly investigated. Among 1232 B-cell precursor ALL patients (15-65 years) treated in the UKALLXII/ECOG2993 trial, 160 (13%) had a HeH karyotype, including 80 patients aged >24 years. The frequency of HeH was the same in Philadelphia chromosome (Ph)-positive and -negative cases, but Ph-positive patients were older. The cytogenetic profiles of Ph-positive and Ph-negative HeH cases were similar, although trisomy 2 was strongly associated with Ph-positive HeH. Overall, Ph-positive HeH patients did not have an inferior overall survival compared with Ph-negative patients (P=0.2: 50 vs 57% at 5 years). Trisomy of chromosome 4 was associated with a superior outcome in Ph-negative patients, whereas +5 and +20 were associated with an inferior outcome in Ph-positive and Ph-negative patients, respectively. All three markers retained significance in multivariate analysis adjusting for age and white cell count: hazard ratio for risk of death 0.47 (95% CI: 0.27-0.84) (P=0.01), 3.73 (1.51-9.21) (P=0.004) and 2.63 (1.25-5.54) (P=0.01), respectively. In conclusion, HeH is an important subtype of ALL at all ages and displays outcome heterogeneity according to chromosomal gain.

An international study of intrachromosomal amplification of chromosome 21 (iAMP21): cytogenetic characterization and outcome.

Intrachromosomal amplification of chromosome 21 (iAMP21) defines a distinct cytogenetic subgroup of childhood B-cell precursor acute lymphoblastic leukaemia (BCP-ALL). To date, fluorescence in situ hybridisation (FISH), with probes specific for the RUNX1 gene, provides the only reliable detection method (five or more RUNX1 signals per cell). Patients with iAMP21 are older (median age 9 years) with a low white cell count. Previously, we demonstrated a high relapse risk when these patients were treated as standard risk. Recent studies have shown improved outcome on intensive therapy. In view of these treatment implications, accurate identification is essential. Here we have studied the cytogenetics and outcome of 530 iAMP21 patients that highlighted the association of specific secondary chromosomal and genetic changes with iAMP21 to assist in diagnosis, including the gain of chromosome X, loss or deletion of chromosome 7, ETV6 and RB1 deletions. These iAMP21 patients when treated as high risk showed the same improved outcome as those in trial-based studies regardless of the backbone chemotherapy regimen given. This study reinforces the importance of intensified treatment to reduce the risk of relapse in iAMP21 patients. This now well-defined patient subgroup should be recognised by World Health Organisation (WHO) as a distinct entity of BCP-ALL.

K+ currents regulate the resting membrane potential, proliferation, and contractile responses in ventricular fibroblasts and myofibroblasts.

Despite the important roles played by ventricular fibroblasts and myofibroblasts in the formation and maintenance of the extracellular matrix, neither the ionic basis for membrane potential nor the effect of modulating membrane potential on function has been analyzed in detail. In this study, whole cell patch-clamp experiments were done using ventricular fibroblasts and myofibroblasts. Time- and voltage-dependent outward K(+) currents were recorded at depolarized potentials, and an inwardly rectifying K(+) (Kir) current was recorded near the resting membrane potential (RMP) and at more hyperpolarized potentials. The apparent reversal potential of Kir currents shifted to more positive potentials as the external K(+) concentration ([K(+)](o)) was raised, and this Kir current was blocked by 100-300 muM Ba(2+). RT-PCR measurements showed that mRNA for Kir2.1 was expressed. Accordingly, we conclude that Kir current is a primary determinant of RMP in both fibroblasts and myofibroblasts. Changes in [K(+)](o) influenced fibroblast membrane potential as well as proliferation and contractile functions. Recordings made with a voltage-sensitive dye, DiBAC(3)(4), showed that 1.5 mM [K(+)](o) resulted in a hyperpolarization, whereas 20 mM [K(+)](o) produced a depolarization. Low [K(+)](o) (1.5 mM) enhanced myofibroblast number relative to control (5.4 mM [K(+)](o)). In contrast, 20 mM [K(+)](o) resulted in a significant reduction in myofibroblast number. In separate assays, 20 mM [K(+)](o) significantly enhanced contraction of collagen I gels seeded with myofibroblasts compared with control mechanical activity in 5.4 mM [K(+)](o). In combination, these results show that ventricular fibroblasts and myofibroblasts express a variety of K(+) channel alpha-subunits and demonstrate that Kir current can modulate RMP and alter essential physiological functions.

Membrane potential measurements in renal afferent and efferent arterioles: actions of angiotensin II.

An adaptation of the in vitro perfused hydronephrotic rat kidney model allowing in situ measurement of arteriolar membrane potentials is described. At a renal perfusion pressure of 80 mmHg, resting membrane potentials of interlobular arteries (22 +/- 2 microns) and afferent (14 +/- 1 microns) and efferent arterioles (12 +/- 1 microns) were -40 +/- 2 (n = 8), -40 +/- 1 (n = 45), and -38 +/- 2 mV (n = 22), respectively (P = 0.75). Using a dual-pipette system to stabilize the impalement site, we measured afferent and efferent arteriolar membrane potentials during angiotensin II (ANG II)-induced vasoconstriction. ANG II (0.1 nM) reduced afferent arteriolar diameters from 13 +/- 1 to 8 +/- 1 microns (n = 8, P = 0.005) and membrane potentials from -40 +/- 2 to -29 +/- mV (P = 0.012). ANG II elicited a similar vasoconstriction in efferent arterioles, decreasing diameters from 13 +/- 1 to 8 +/- 1 microns (n = 8, P = 0.004), but failed to elicit a significant depolarization (-39 +/- 2 for control; -36 +/- 3 mV for ANG II; P = 0.27). Our findings thus indicate that resting membrane potentials of pre- and postglomerular arterioles are similar and lie near the threshold activation potential for L-type Ca channels. ANG II-induced vasoconstriction appears to be closely coupled to membrane depolarization in the afferent arteriole, whereas mechanical and electrical responses appear to be dissociated in the efferent arteriole.