Successful urgent transplantation of an adult kidney into a child with inferior vena cava thrombosis.

Poor venous drainage options following inferior vena cava (IVC) thrombosis have been considered to complicate or preclude renal transplantation of adult kidneys into pediatric patients. We describe urgent renal transplantation in a 5-year-old (15.3 kg) male with IVC thrombosis using an adult living donor. Preoperative magnetic resonance venography revealed a patent infrahepatic/suprarenal vena cava and portal system. In surgery, the right liver lobe was mobilized sufficiently to anastomose the graft renal vein to the native IVC at the confluence of the native left renal vein and proximal vena cava. Graft function has remained excellent with serum creatinine of 0.5 mg/dL at 36 months. IVC thrombosis need not preclude successful transplantation of adult-sized kidneys into children.

Laser interferometer measurement of changes in crayfish axon diameter concurrent with action potential.

Small rapid changes in the diameter of an axon takes place when an action potential progresses along the axon. In the giant axon of the crayfish these occur within a period of about 1 millisecond and are typically about 18 angstroms in total amplitude.

The pathway of CO binding to cytochrome c oxidase. Can the gateway be closed?

Addition of cyanide to the CO complex of cytochrome oxidase reduces the apparent photosensitivity of the Fe-CO bond. This effect is not seen with azide, or when cyanide is added to ferromyoglobin-CO. It is proposed that cyanide binds to CuB, and restricts the passage of CO out of the protein. This restriction favors geminate recombination of CO and ferrocytochrome a3, thereby lowering the apparent quantum yield for CO photolysis. The apparent Kd of cyanide for CuB is 15.4 mM. These data support a direct role for CuB in ligand binding by cytochrome c oxidase.

Kinetic evidence for the re-definition of electron transfer pathways from cytochrome c to O2 within cytochrome oxidase.

The reaction with O2 of equimolar mixtures of cytochrome c and cytochrome c oxidase in high and low ionic strength buffers has been examined by flow-flash spectrophotometry at room temperature. In low ionic strength media where cytochrome c and the oxidase are bound in an electrostatic, 1:1 complex some of the cytochrome c is oxidised at a faster rate than a metal centre of the oxidase. In contrast, when cytochrome c and cytochrome c oxidase are predominantly dissociated at high ionic strength cytochrome c oxidation occurs only slowly (t1/2 = 5 s) following the complete oxidation of the oxidase. These results demonstrate that maximal rates of electron transfer from cytochrome c to O2 occur when both substrates are present on the enzyme. The heterogeneous oxidation of cytochrome c observed in the complex implies more than one route for electron transfer within the enzyme. Possibilities for new electron transfer pathways from cytochrome c to O2 are proposed.

Serratia marcescens surgical wound infection following breast reconstruction.

Surgical wound infections due to gram-negative bacilli have been rarely reported following breast implant surgery. From April to November 1989, four patients from one plastic surgeon's practice developed Serratia marcescens surgical wound infection (SWI) following breast reconstruction procedures with implantation of six expandable mammary implants. All six implants were removed for unabated S. marcescens SWI. Symptoms developed 13-161 days (median, 66 days) after surgery. When compared with nonexpandable silicone breast implants used during the period November 1, 1988, to October 31, 1989, expandable implants were associated with a greater risk of S. marcescens SWI (4/10 versus 0/11 patients, p = 0.04). Epidemiologic studies revealed that infection was associated with saline expansion of the implants performed in the surgeon's office. S. marcescens was cultured from a bag of commercial saline used on at least two of the four patients with SWI; the isolate from the saline and the three available patient isolates had identical serotype (O-undetermined:H4) and antimicrobial susceptibility patterns. Review of office procedures revealed that hands were not routinely washed before and aseptic technique was not used during the expansion procedure. Cultures of unopened bags of saline and an unused expandable implant were sterile. We hypothesize that multiple use of saline bags and nonsterile expansion technique extrinsically contaminated saline solutions and resulted in implant and/or surgical site infection. This investigation underscores the importance of avoiding multiple use of solutions intended for single use and of using aseptic technique when manipulating prosthetic devices.

Lithium and valproate differentially regulate brain regional expression of phosphorylated CREB and c-Fos.

Previous studies in our laboratory have shown that the mood stabilizers, lithium and valproate (VPA), regulate the transcription factors, cyclic AMP responsive element binding protein (CREB), c-Fos and c-Jun, differentially in cultured human neuroblastoma SH-SY5Y cells. Here, we confirm these findings in rat brain and further study the brain-regional effects of these drugs using immunohistochemistry. We found that although chronic treatment with LiCl or VPA did not change the expression of c-Fos and c-Jun, acute treatment with either drugs increased c-Fos expression but not c-Jun expression in CA1 and CA3 regions of hippocampus. Chronic treatment with LiCl, but not VPA, decreased CREB phosphorylation in rat cerebral cortex and hippocampus. These results suggest that lithium and VPA may act on different pathways to bring about their long-term prophylactic effects on bipolar disorder (BD). The regulation of CREB phosphorylation may be relevant to lithium effect. VPA, which is also effective in BD, may be linked to other pathways.

A cluster of vancomycin-resistant Enterococcus faecium in an intensive care unit.

OBJECTIVE: To describe the epidemiology of a cluster of vancomycin-resistant Enterococcus faecium (VAREC) in a cardiothoracic surgery intensive care unit. DESIGN: A case series of patients identified through review of surveillance data on nosocomial infections, review of microbiologic records, and culture survey of patients in the unit. RESULTS: Six patients in the cardiothoracic surgery intensive care unit had VAREC with identical antimicrobic susceptibility patterns over a 6-month period. Four patients were identified with VAREC through prospective surveillance and 2 through retrospective review. Prior vancomycin use was seen more commonly in patients with VAREC (6/6, 100%) than in those without VAREC (3/12, 25%) (Fisher's exact test, p = .01). Six of the 7 patients with prior infection developed VAREC (85.7%). A prior nosocomial infection and prior exposure to vancomycin were found to be important variables in a logistic regression analysis. VAREC also was isolated from the environment. A combination of cohorting of patients and staff, and modifications of standard contact isolation practices eliminated the presence of VAREC from the cardiothoracic surgery intensive care unit. CONCLUSIONS: The results suggest that prior administration of vancomycin, especially in the patient who develops nosocomial infection, can influence the acquisition of vancomycin-resistant enterococci and that VAREC may be transmitted from patient to patient. Using a modification of the standard infection control practice of isolation, we were able to control the spread of this resistant strain of E faecium.

Epidemic gram-negative bacteremia in a neonatal intensive care unit in Guatemala.

BACKGROUND: Nosocomial bloodstream infection is an important cause of morbidity and mortality among neonates. From September 1 through December 5, 1990 (epidemic period), gram-negative bacteremia developed in 26 neonates after their admission to the neonatal intensive care unit (NICU) of Hospital General, a 1000-bed public teaching hospital in Guatemala with a 16-bed NICU. Twenty-three of the 26 patients (88%) died. METHODS: To determine risk factors for and modes of transmission of gram-negative bacteremia in the NICU, we conducted a cohort study of NICU patients who had at least one blood culture drawn at least 24 hours after admission to the NICU and performed a microbiologic investigation in the NICU. RESULTS: The rate of gram-negative bacteremia was significantly higher among patients born at Hospital General, delivered by cesarian section, and exposed to selected intravenous medications and invasive procedures in the NICU during the 3 days before the referent blood culture was obtained. During the epidemic period, the hospital's chlorinated well-water system malfunctioned; chlorine levels were undetectable and tap water samples contained elevated microbial levels, including total and fecal coliform bacteria. Serratia marcescens was identified in 81% of case-patient blood cultures (13/16) available for testing and from 57% of NICU personnel handwashings (4/7). Most S. marcescens blood isolates were serotype O3:H12 (46%) or O14:H12 (31%) and were resistant to ampicillin (100%) and gentamicin (77%), the antimicrobials used routinely in the NICU. CONCLUSIONS: We hypothesize that gram-negative bacteremia occurred after invasive procedures were performed on neonates whose skin became colonized through bathing or from hands of NICU personnel.

Electron transfer from cytochrome c to O2.

Transient-state kinetic results on the reaction between oxygen and cytochrome oxidase alone and in its electrostatic complex with cytochrome c are reported. Time courses at 830 nm for the enzyme alone reacting with O2 reveal complex kinetics for the oxidation of CuA. The time course begins with a lag phase, which becomes progressively shorter as the O2 concentration is increased. When cytochrome c is included the lag phase is extended. Cytochrome c oxidation proceeds to a level of 80% in 5 milleseconds, and it is possible to resolve two rates over this time range. The dependence of these rates upon O2 concentration is reported here. The second, slower phase is rate-limited at a first-order value of 500 sec-1 at or above 200 microM O2. In contrast, the initial phase is proportional to O2 up to the highest O2 concentration used here (i.e. 340 microM) and reaches a rate of 6500 sec-1. In addition the time course of cytochrome c oxidation begins immediately (i.e., without a lag). It is proposed that the fast phase of cytochrome c oxidation is the result of electron transfer to O2, either via CuA or direct to the oxygen binding site. These pathways for electron transfer are not observed in the reductive half-reaction and may be the result of a conformational change in the oxidase that lowers a kinetic barrier to electron transfer present in the oxidized enzyme.

Epidemiologic typing of Enterobacter sakazakii in two neonatal nosocomial outbreaks.

Two unrelated hospital outbreaks of Enterobacter sakazakii, involving meningitis, bacteremia, and colonization of neonates, were investigated. In each of these outbreaks, E. sakazakii was isolated from both patients and dried infant formula. In previous outbreaks, the source and mode of transmission of E. sakazakii in neonatal infections was not determined. In this study, we used a combination of typing methods (plasmid analysis, antibiograms, chromosomal restriction endonuclease analysis, ribotyping, and multilocus enzyme electrophoresis) to evaluate the isolates from each outbreak as to their relatedness. The typing results differed among outbreaks, but in each one, patient and formula isolates shared the same typing pattern. The only exceptions were disk antibiograms, which often varied among colonies selected from each of the isolates. Plasmid analysis, chromosomal restriction endonuclease analysis, ribotyping, and multilocus enzyme electrophoresis all were effective as epidemiological typing methods for E. sakazakii, especially when used in combination. By using this typing scheme, we have confirmed that E. sakazakii from intrinsically contaminated dried infant formula was the source of neonatal infection.

Low temperature magnetic circular dichroism spectra and magnetization properties of extracted heme a3+ bis-imidazole. A model of cytochrome a in bovine cytochrome c oxidase.

Heme a3+ isolated from bovine cardiac muscle cytochrome oxidase has been converted to the bis-imidazole species and studied by magnetic circular dichroism (MCD) spectroscopy. Spectra have been recorded down to 1.5 degrees K, enabling the MCD magnetization curves to be measured at a number of wavelengths in the visible and near infrared regions. The experimentally determined curves show excellent correlation to a curve using the g-values determined by electron paramagnetic resonance spectroscopy to be gz = 2.96, gy = 2.29, and gx = 1.73. The data show that the bis-imidazole derivative of extracted heme a3+ is an excellent model of cytochrome a in the enzyme, confirming the presence of two histidine residues in the protein as the fifth and sixth ligands. The spectral features of heme a3+ bis-imidazole in the near infrared region are consistent with transitions of the porphyrin ( a1u , a2u ) to ferric (eg) charge transfer type.

The structure of the cytochrome a3-CuB site of mammalian cytochrome c oxidase as probed by MCD and EPR spectroscopy.

The nature of the complexes formed between cytochrome c oxidase and the three inhibitory ligands N3-, CN-, and S2- have been investigated by a combination of MCD and EPR spectroscopy. CN- forms a linear bridge between the Fe III a3 and CuB II, suggesting that the distance between these centers in the oxidized enzyme is between 5 and 5.25 A. This distance is too short to permit N3- to form a linear bridge and the evidence suggests this to be bent. In contrast S2- or SH- is unable to form any bridge and it seems likely that two SH- ions are bound by the bimetallic site, one to Fe III a3 and the other to CuB I. The significance of the a3-CuB distance in terms of oxygen binding and reduction is discussed.

Respiration gated radiotherapy treatment: a technical study.

In order to optimize external-beam conformal radiotherapy, patient movement during treatment must be minimized. For treatment on the upper torso, the target organs are known to move substantially due to patient respiration. This paper deals with the technical aspects of gating the radiotherapy beam synchronously with respiration: the optimal respiration monitoring system, measurements of organ displacement and linear accelerator gating. Several respiration sensors including a thermistor, a thermocouple, a strain gauge and a pneumotachograph were examined to find the optimal sensor. The magnitude of breast, chest wall and lung motion were determined using playback of fluoroscopic x-ray images recorded on a VCR during routine radiotherapy simulation. Total dose, beam symmetry and beam uniformity were examined to determine any effects on the Varian 2100C linear accelerator due to gating.

A biologically compatible implantable ultrasonic marker.

An implantable passive ultrasonic marker has been developed which can be detected with a conventional pulse echo imaging system. The marker consists of a planar array of 1/16 in. diameter stainless steel (316L) spheres and produces a distinct and characteristic reflection signature due to reverbation within the spheres. The marker has undergone both in vitro and in vivo tests and is biologically compatible for chronic implantation. It is consistently detectable at depths up to 10 cm from the transducer. An application to the detection of flow conditions in aortocoronary bypass grafts is suggested.

Effects of bipolar point and line stimulation in anisotropic rabbit epicardium: assessment of the critical radius of curvature for longitudinal block.

Excitation front shape and velocity were studied in anisotropic perfused rabbit epicardium stained with potentiometric fluorescent dye. In the combined results from all experiments, convex excitation fronts produced by stimulation with a single electrode propagated longitudinally 13.3% slower than flat excitation fronts produced by stimulation with a line of electrodes. For transverse propagation, the two stimulation methods produced similar flat excitation fronts and velocities. The critical excitation front radius of curvature for longitudinal block (Rcr), calculated from excitable media theory, was 92 microns in control hearts. In hearts exposed to diacetyl monoxime (20 mmol/L), which decreases inward sodium current, Rcr was 175 microns. The slower longitudinal propagation velocity of convex fronts versus flat fronts and the theoretically predicted critical radius of curvature may be important for propagation and block of ectopic depolarizations in the heart.

Perceptual errors increase with movement duration and may contribute to hypokinesia in Parkinson's disease.

People with Parkinson's disease (PD) perceive that their movement amplitude is greater than what they actually perform. The neural mechanisms underlying one's perception of movement are believed to involve the sensorimotor integration process (SIP). How PD affects the SIP is not well understood. A previous study interrogating the SIP showed healthy adults (HAs) overestimated their limb position in the direction of movement and the error and its variance (VOE) depended on movement duration. We asked if PDs showed errors in perceived limb position and if the dependence on movement duration was different from HAs. We used an existing computational model of the SIP to explore mechanisms for the error and VOE as a function of movement duration. Twenty PDs, off medication, and 20 age-matched HAs were asked to estimate the position of their hand after performing 50, slow, non-visually guided wrist flexion or extension movements for a random period of time (<4.0 s). Both groups overestimated the amount they moved; however, the PDs' error and VOE were larger (p<0.001). HAs showed increasing error/VOE for small movement durations that reduced/stabilized for longer movement durations. PDs however showed increasing error/VOE with increasing movement duration that did not significantly improve/stabilize. The model suggested that the basis for such perceptual deficits may be abnormal proprioceptive feedback and/or processing of an abnormal internal impression (prediction) that underestimates movement amplitude. Simulation results imply that the PD's SIP could no longer effectively access sensory (proprioceptive) feedback to correct errors in other components of the SIP due to the abnormal processing of sensory feedback. We suggest from this study that an impaired perception of movement amplitude and sensory processing deficits contribute to hypokinesia in PD.