Correction: Mitochondrial oxodicarboxylate carrier deficiency is associated with mitochondrial DNA depletion and spinal muscular atrophy-like disease.

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Polymyxin B infusion leading to cardiac arrest: a case report and literature review.

We describe a 52-year-old female patient who developed cardiopulmonary arrest due to neuromuscular paralysis after initiation of polymyxin B for septicemia caused by extended spectrum ß-lactamase-producing Klebsiella pneumoniae. Due to emerging antibiotic resistance patterns, use of polymyxins is increasing and an understanding of their toxicity is critical.

Physiological concentrations of atrial natriuretic factors with intact N-terminal sequences inhibit corticotropin-releasing factor-stimulated adrenocorticotropin secretion from cultured anterior pituitary cells.

The effectiveness of atrial natriuretic factors (ANFs) as inhibitors of CRF-stimulated ACTH secretion was examined in cultured rat anterior pituitary cells. alpha ANF-(1-28) significantly inhibited ACTH release stimulated by 1-5 nM CRF. At the most effective concentration of 100 pM, alpha ANF-(1-28) inhibited ACTH release by 40.1% (P less than 0.001). This effect was manifested after 3 h, but not after 0.5 or 1 h, of incubation, suggesting that ACTH synthesis may have been reduced. Conversely, alpha ANF-(5-28), at concentrations of 10 pM to 10 nM, had no effect on ACTH secretion after 0.5, 1, or 3 h. alpha ANF-(1-11) weakly inhibited ACTH secretion at concentrations of 100 and 1000 pM. Again, these effects were observed after 3 h, but not after 0.5 or 1 h, of incubation. These results suggest that ANF-induced inhibition of CRF-stimulated ACTH release requires 1) an intact N-terminal sequence of the ANF peptide, 2) low concentrations, and 3) more than 1 h of incubation. The results explain previous negative evidence and suggest that alpha ANF-(1-28) may be a physiological inhibitor of ACTH secretion.

Relationship between structure and function of neurons in the rat rostral nucleus tractus solitarii.

To investigate the relationship between the structure and function of neurons in the rostral (gustatory) nucleus tractus solitarii (rNTS), we analyzed the morphological and biophysical properties of rNTS neurons by performing whole-cell recordings in a brain slice preparation. Overall, neurons (n = 58) had a mean somal diameter of 16 microns, an average dendritic length of 598 microns, an average dendritic thickness of 0.91 microns, and a spine density of 0.037 spines/microns. Neurons were separated into three groups (elongate, multipolar, and ovoid) on the basis of previously established morphological criteria. The highest percentage (49%) of neurons were classified as ovoid, while 35% were multipolar and only 16% were elongate. The most frequently observed firing pattern, in all three cell types, elicited by a 1,200 ms, 100 pA depolarizing current pulse was a regularly firing spike train. However, the intrinsic firing properties of the remaining neurons were different. Thirty-one percent of the ovoid neurons responded with a short burst of action potentials and 44% of the elongate neurons showed a delay in the onset of the spike train following a hyperpolarizing prepulse. Less than 16% of the multipolar neurons demonstrated either of these firing characteristics. Therefore, rNTS neurons with similar morphology do not have unique biophysical properties. However, the data suggest that there may be subpopulations of the three morphological types, each of which displays a different firing pattern. Since the structure and function of the three morphological groups were not strictly correlated, these subpopulations may represent functional groups.

Central neural pathway mediating splanchnic osmosensation.

To determine the central neural pathway which carries splanchnic osmosensory information to vasopressin (AVP) neurons in the hypothalamus, bilateral electrolytic lesions were placed in the ascending catecholaminergic fiber bundle, the locus coeruleus (LC), the locus subcoeruleus (subLC), the lateral parabrachial nucleus (LPB), the caudal periaqueductal gray (PAG) and the median preoptic nucleus (MPO). Six and seven days later, plasma AVP levels, plasma osmolality, mean arterial pressure and heart rate were measured following gastric infusion of hypertonic (598 mosm/kg; 2 ml/4 min) or isotonic (290 mosm/kg) saline in conscious rats with indwelling tail artery catheters and nasogastric tubes. The most effective pontine lesions, which were located in the ventral locus subcoeruleus (vsubLC) approximately 1.0 mm below the LC, decreased the AVP response to hypertonic gastric infusion by 59.7% (P less than 0.05) as compared to sham-lesioned controls. In addition, unilateral vsubLC lesions dramatically reduced the catecholamine innervation of the ipsilateral paraventricular nucleus (PVN), as qualitatively determined with dopamine beta-hydroxylase immunocytochemistry, suggesting that a pathway ascending with catecholaminergic fibers was disrupted. Lesions of the MPO were also very effective, decreasing the AVP response to hypertonic saline infusion by 60.3% (P less than 0.05), suggesting that the MPO is an integral relay center in this pathway. On the other hand, LC, LPB and PAG lesions were ineffective. Systemic plasma osmolality or cardiovascular factors did not mediate the AVP response. These results demonstrate, for the first time, that splanchnic osmotic information is transmitted to the hypothalamus via pathways within the ascending catecholaminergic fiber bundles, the MPO is a relay center where peripheral and central osmotic information may be integrated, and the LC, LPB, and PAG are not part of the splanchnic osmotic pathway.

Ventral pontine catecholaminergic pathway mediates the vasopressin response to splanchnic osmostimulation in conscious rats.

This study examines the role of catecholamines, cell bodies and fibers of passage within the subcoeruleus area (subLC) in the arginine vasopressin (AVP) response to splanchnic osmotic stimulation and hemorrhage. Bilateral chemical lesions were induced into the subLC, approximately 1 mm ventral to the locus coeruleus (LC), using 6-hydroxydopamine (6-OHDA) and ibotenic acid to selectively destroy catecholaminergic components and cell bodies, respectively. Vehicle and 5,7-dihydroxytryptamine (5,7-DHT) injections into the subLC area, 6-OHDA injections into the LC, as well as systemic desipramine pretreatment, were performed as controls for the possible non-specific effects of the lesions. Seven and 8 days later, plasma AVP level, plasma osmolality, mean arterial pressure and heart rate were measured following either gastric infusion of hypertonic (598 mOsm/kg; 2 ml/4 min) or isotonic (290 mOsm/kg) saline or a mild hemorrhage (2.5 ml/300 g) in conscious rats with indwelling tail artery catheters and naso-gastric tubes. 6-OHDA injections into subLC reduced the AVP response to the osmotic stimulation by 62.3% (P less than 0.01), as compared to vehicle-injected controls. These same rats demonstrated a normal AVP response to hemorrhage implying a specificity of the disrupted pathway. All controls confirmed that the effects of the 6-OHDA were due to specific action on noradrenergic components within the subLC area. Ibotenic acid lesions in the subLC did not significantly decrease the AVP response, demonstrating that mainly fibers and not cell bodies in this region are part of the pathway. 6-OHDA injections just anterior to the LC, where the dorsal noradrenergic bundle (DNAB) forms, reduced the AVP secretion due to hemorrhage by 77.0% (P less than 0.05), but had minor effects on the response to osmotic stimulation. These results indicate that catecholaminergic fibers travelling primarily within the subLC, in the ventral noradrenergic bundle (VNAB), carry splanchnic osmotic input to the hypothalamus, whereas the DNAB may mediate the AVP response to hemorrhage.

Biophysical properties and responses to glutamate receptor agonists of identified subpopulations of rat geniculate ganglion neurons.

The goal of the current study was to evaluate the electrophysiological properties and responses to glutamate receptor agonists of rat geniculate ganglion (GG) neurons innervating the tongue. Subpopulations of GG neurons were labeled by injecting Fluoro-Gold (FG) or True Blue chloride into the anterior tongue and soft palate (AT and SP neurons) and applying FG crystals to the posterior auricular branch of the facial nerve (PA neurons). Three to 12 days later, the GG neurons were acutely isolated and patch clamped. Although many biophysical properties of the AT, SP and PA neurons were similar, significant differences were found among these groups in properties related to cell excitability. For example, the average amount of current necessary to elicit an action potential was 61 pA in AT neurons (n=55), 90 pA in SP neurons (n=41) and 189 pA in PA neurons (n=35, P<0.001). In addition, AT neurons tended to fire significantly more action potentials during depolarization as well as following hyperpolarizing pulses than SP or PA neuron types. Most GG neurons responded to application of glutamate receptor agonists. The neurons responded with a depolarization accompanied by a reduction in input resistance. These results suggest that subpopulations of neurons in the geniculate ganglion have distinct biophysical properties and express functional glutamate receptors. The differing biophysical properties of GG neurons is possibly related to their functional heterogeneity and glutaminergic neurotransmission may function in the processing of gustatory, and other sensory information, within the geniculate ganglion and its projections.

Substance P excites neurons in the gustatory zone of the rat nucleus tractus solitarius.

Whole-cell patch recordings of neurons in the rostral (gustatory) nucleus tractus solitarius (rNTS) were performed in a brain slice preparation from rat medulla. Neural responses to brief applications (10-45 s) of substance P (SP), via a constant superfusion apparatus, were recorded. SP transiently depolarized 80 of 117 (68%) rNTS neurons in a dose-dependent manner. Sub-micromolar concentrations of SP had potent excitatory effects, and the half maximal response occurred at 0.6 microM. The depolarizing effect of SP was accompanied by an increase in input resistance in 81% of the responsive neurons. The excitatory effects of SP persisted in low Ca2+ (0.2 mM) and high Mg2+ (12 mM) saline as well as in the presence of 2 microM TTX (n = 5 for each), suggesting direct postsynaptic action on the recorded neurons. SP also hyperpolarized 4 neurons (4%) and had no effect on 33 neurons (28%). Each of the 4 neurons which were hyperpolarized by SP showed a decrease in input resistance. A more detailed assessment of the types of neurons in the rNTS which respond to SP was also conducted. Neurons were separated into 4 electrophysiological groups on the basis of their repetitive firing pattern induced by a hyperpolarizing and depolarizing current injection paradigm. Neurons belonging to each of the 4 electrophysiological groups responded to SP. Eighteen neurons, which were filled with 1% biocytin during recording, were categorized as ovoid, multipolar or fusiform based on their morphological characteristics. SP excited all 3 morphological types of neurons in similar proportion. These results suggest that SP is an excitatory neurotransmitter in the rNTS. The effects of SP are not restricted to a particular neuron type defined either biophysically or morphologically. The implications of these results on the possible role of SP in processing gustatory and somatosensory information within the rNTS are discussed.

Demonstration of a bilateral projection from the rostral nucleus of the solitary tract to the medial parabrachial nucleus in rat.

This study examined the projection from the rostral nucleus of the solitary tract (rNST) to the medial parabrachial nucleus (mPBN) in male Wistar rats using DiI as a retrograde tracer and biotinylated dextran as an anterograde tracer. Following successful unilateral injection of DiI into the mPBN (n = 8), retrogradely labeled neurons were always found in the rNST both ipsilateral and contralateral to the pontine injection site. Significantly, approximately 25% of the total number of DiI-labeled neurons were located in the contralateral rNST. The labeled neurons were located throughout the rostral-caudal extent of the rNST with the most cells being located in the central portion of the nucleus, and the fewest located ventromedially and dorsolaterally. Supporting the findings of the retrograde labeling study, axons and terminals, anterogradely labeled by injecting biotinylated dextran unilaterally into the rNST (n = 4), were always found in both the ipsilateral and contralateral mPBN. Although the intensity of anterograde labeling was higher ipsilaterally, a mirror-image staining pattern consistently was present contralaterally. These results indicate that there is a substantial contralateral component of the projection from the rNST to the mPBN. This suggests that convergence of gustatory information from the two sides of the oral cavity may occur within the pons before processing in higher brain centers. These findings may have important implications as to where and how bilateral gustatory information is processed and integrated.

A subpopulation of neurons in the rat rostral nucleus of the solitary tract that project to the parabrachial nucleus express glutamate-like immunoreactivity.

In rodents, gustatory information is transmitted from second order neurons in the rostral nucleus of the solitary tract (rNST) to the parabrachial nucleus (PBN) in the pons. The chemical nature of this projection is unknown. Therefore, the goal of the current study was to determine if rNST neurons that project to the PBN express glutamate-like immunoreactivity. Projection neurons were retrogradely labeled following stereotaxic injection of rhodamine-filled latex microspheres into the right PBN of seven rats while glutamate-immunoreactive (GLU-IR) structures were visualized in the same tissue using an immunoperoxidase procedure. The number of single- and double-labeled neurons located in the right (ipsilateral) and left rNST, in each of the nuclear subdivisions as well as their position along the rostral-caudal axis of the rNST was determined. GLU-IR cell bodies were located throughout the rNST. Although the rostral central subdivision contained the highest percentage (33.8%) of GLU-IR perikarya, immunolabeled neurons were most concentrated (number/area of subdivision) within the medial subnucleus. The rostral third of the rNST contained the fewest (20. 5%) and lowest density of GLU-IR cell bodies. The highest percentage of rNST neurons retrogradely labeled from the PBN were located ipsilateral (85.4%) to the pontine injection site, in the middle third of the nucleus (44.2%) and within the rostral central subdivision (52.4%). Overall, 18% of the labeled rNST projection neurons were GLU-IR. The distribution of double-labeled neurons mirrored that of the projection neurons with the largest number located in the ipsilateral rNST (84.5%), middle third of the nucleus (40.5%) and rostral central subdivision (64.7%). These results indicate that glutamate may be a main component of the ascending pathway from the rNST to the PBN. In addition, since GLU-IR neurons were located throughout the rNST and most were not retrogradely-labeled, the current results suggest that glutamate may be an important neurotrans-mitter within the medulla.

The impact of hemolysis on Ortho-Clinical Diagnostic's ECi and Roche's elecsys immunoassay systems.

BACKGROUND: Hemolysis is regularly encountered in clinical specimens and often interferes with a variety of laboratory test methods. Although not widely recognized, immunoassays based on nonisotopic detection systems can also be affected by hemolysis. For this reason, we investigated the effect of differing amounts of hemolysis across a range of values for several immunoassays on the Ortho-Clinical Diagnostics ECi and Roche Elecsys platforms. METHODS: Hemolysate was prepared from whole blood and spiked at varying concentrations into pooled patient serum samples for different analytes. RESULTS: Out of the 21 analytes tested, six (28.6%) exhibited significant increases or decreases in measured concentrations with increasing amounts of hemolysis. CONCLUSIONS: Although immunoassays are generally thought to be impervious to hemolysis interference, hemolysis can interfere in immunoassay testing platforms. For these reasons, we recommend that laboratories conduct hemolysis interference studies for all laboratory test protocols.

Transthyretin is an inhibitor of monocyte and endothelial cell interleukin-1 production.

Human serum was found to contain an inhibitor of constitutive interleukin-1 (IL-1) production by human umbilical vein endothelial cells (ECs). Purification of the serum activity by anion exchange chromatography, molecular sieve HPLC, and hydroxyl apatite chromatography yielded material 82% pure with a molecular weight of 17 kDa by SDS-PAGE. Amino acid sequencing revealed the purified inhibitor to be transthyretin (TTR), a liver-derived protein. There was a 42.6% reduction in the production of spontaneous IL-1 activity in EC supernatants after coculture with 10 micrograms/ml TTR. TTR was subsequently found by ELISA to inhibit LPS-stimulated IL-1 production by cells of the human monocytic leukemia line THP-1 by 47.1 +/- 9.4%, whereas a less striking but still significant inhibition of monocyte-derived IL-1 beta production was also observed. Inhibition of IL-1 secretion correlated with increased IL-1 mRNA synthesis in both THP-1 cells and monocytes. Furthermore, TTR was associated with increased intracellular concentrations of IL-1 beta. These data suggest that TTR functions by inhibiting processing of newly synthesized peptide for secretion. This novel inhibitory effect of TTR on the production of IL-1 activity suggests a previously unrecognized endogenous antiinflammatory mediator.

District level information systems: two cases from South Africa.

The health system in South Africa has to date been fragmented and centralised. The priority of the new government is to establish an integrated and decentralised district health system of which a key element is the development of district health and management information systems (H & MIS). This paper presents experiences from two projects in the Western Cape in which a process to establish a district-based H & MIS was initiated and a situation analysis of the information systems was done. The two projects applied different research methods but the results show with remarkable consistency that much time is used on data collection, but information is not used at local level. The projects have applied different approaches towards developing a district H & MIS but in both important pre-requisites for a successful, action-led H & MIS include local ownership and motivation, a process based around existing local management structures and the active involvement of the community.

Evaluation of nursing home patients. A systematic approach can improve care.

As the US population ages, the proportion of patients receiving long-term care is increasing. To meet the challenge of providing quality care for these patients, physicians need to be prepared to efficiently evaluate their needs and formulate individualized care plans. In this article, Drs King and Lipsky discuss the unique aspects of caring for nursing home patients, including the role of patients' families in the overall plan. They present a practical, structured approach to evaluation and follow-up care, which they have encapsulated into two handy assessment forms.

Preoperative evaluation.

A history and physical examination, focusing on risk factors for cardiac, pulmonary and infectious complications, and a determination of a patient's functional capacity, are essential to any preoperative evaluation. In addition, the type of surgery influences the overall perioperative risk and the need for further cardiac evaluation. Routine laboratory studies are rarely helpful except to monitor known disease states. Patients with good functional capacity do not require preoperative cardiac stress testing in most surgical cases. Unstable angina, myocardial infarction within six weeks and aortic or peripheral vascular surgery place a patient into a high-risk category for perioperative cardiac complications. Patients with respiratory disease may benefit from perioperative use of bronchodilators or steroids. Patients at increased risk of pulmonary complications should receive instruction in deep-breathing exercises or incentive spirometry. Assessment of nutritional status should be performed. An albumin level of less than 3.2 mg per dL (32 g per L) suggests an increased risk of complications. Patients deemed at risk because of compromised nutritional status may benefit from pre- and postoperative nutritional supplementation.

Preventing deep venous thrombosis in hospitalized patients.

Deep venous thrombosis with subsequent pulmonary embolism remains a significant cause of morbidity and mortality in hospitalized patients. Although prophylactic treatment may reduce the incidence of deep venous thrombosis by up to 70 percent, it is estimated that only 32 percent of hospitalized patients at high risk receive adequate prophylaxis. Older patients, obese patients and patients undergoing orthopedic procedures of the lower limbs are at particularly high risk of developing deep venous thrombosis. Both mechanical and pharmacologic measures provide effective prophylaxis. Newer treatment protocols have greatly reduced the incidence of drug side effects, particularly bleeding.

Preoperative evaluation of the elderly.

As the population ages, an increasing number of elderly patients will need surgery. An organized medical evaluation that focuses on the patient's cardiopulmonary and nutritional status should be performed before the patient undergoes surgery. The initial history and physical examination should be performed up to 8 weeks before surgery. Follow-up examinations are then dictated by the results of the initial examination. Established guidelines to assess cardiopulmonary and nutritional status should be followed. Preoperative laboratory assessment should consist of hemoglobin and creatinine measurements and include a urinalysis and electrocardiogram. The need for additional tests is indicated by the history and physical examination. Following this assessment, therapeutic and prophylactic measures to reduce surgical morbidity and mortality can be implemented. With timely identification and management of medical disease in geriatric surgical patients, the risks of surgery can be minimized.