Withdrawal of mechanical ventilation in anticipation of death in the intensive care unit

In critically ill patients who are receiving mechanical ventilation, the factors associated with physicians' decisions to withdraw ventilation in anticipation of death are unclear. The objective of this study was to examine the clinical determinants that were associated with the withdrawal of mechanical ventilation.     

Capture of Somatic mtDNA Point Mutations with Severe Effects on Oxidative Phosphorylation in Synaptosome Cybrid Clones from Human Brain

Mitochondrial DNA (mtDNA) is replicated throughout life in postmitotic cells, resulting in higher levels of somatic mutation than in nuclear genes. However, controversy remains as to the importance of low‐level mtDNA somatic mutants in cancerous and normal human tissues. To capture somatic mtDNA mutations for functional analysis, we generated synaptosome cybrids from synaptic endings isolated from fresh hippocampus and cortex brain biopsies. We analyzed the whole mtDNA genome from 120 cybrid clones derived from four individual donors by chemical cleavage of mismatch and Sanger sequencing, scanning around two million base pairs. Seventeen different somatic point mutations were identified, including eight coding region mutations, four of which result in frameshifts. Examination of one cybrid clone with a novel m.2949_2953delCTATT mutation in MT‐RNR2 (which encodes mitochondrial 16S rRNA) revealed a severe disruption of mtDNA‐encoded protein translation. We also performed functional studies on a homoplasmic nonsense mutation in MT‐ND1, previously reported in oncocytomas, and show that both ATP generation and the stability of oxidative phosphorylation complex I are disrupted. As the mtDNA remains locked against direct genetic manipulation, we demonstrate that the synaptosome cybrid approach can capture biologically relevant mtDNA mutants in vitro to study effects on mitochondrial respiratory chain function.     

Scanning of estrogen receptor alpha (ERalpha) and thyroid hormone receptor alpha (TRalpha) genes in patients with psychiatric diseases: four missense mutations identified in ERalpha gene

Estrogen and thyroid hormones exert effects on growth, development, and differentiation of the nervous system. Hormone administration can lead to changes in behavior, suggesting that genetic variants of the estrogen receptor alpha (ERalpha) and the thyroid hormone receptor alpha (TRalpha) genes may predispose to psychiatric diseases. To investigate this possibility, regions of likely functional significance (all coding exons and flanking splice junctions) of the ERalpha and TRalpha genes were scanned in patients with schizophrenia (113), along with pilot studies in patients with bipolar illness (BPI), puerperal psychosis, autism, attention-deficit hyperactivity disorder (ADHD), and alcoholism. A total of 1.18 megabases of the ERalpha gene and 1.16 megabases of the TRalpha gene were scanned with Detection of Virtually All Mutations-SSCP (DOVAM-S), a method that detects virtually all mutations. Four missense mutations, seven silent mutations and one deletion were identified in the ERalpha gene, while only four silent mutations were present in the TRalpha gene. Two of the missense mutations in ERalpha are conserved in the six available mammalian and bird species (H6Y, K299R) and a third sequence variant (P146Q) is conserved in mammals, birds, and Xenopus laevis, hinting that these sequence changes will be of functional significance. These changes were found in one patient each with BPI, puerperal psychosis, and alcoholism, respectively. Analysis of the ERalpha and TRalpha genes in 240 subjects reveals that missense changes and splice site variants are uncommon (1.7% and 0%, respectively). Further analyses are necessary to determine if the missense mutations identified in this study are associated with predisposition or outcome for either psychiatric or nonpsychiatric diseases.     

Differences in leisure-time physical activity levels between blacks and whites in population-based samples: The Minnesota heart survey

Energy expenditure in leisure-time physical activity (LTPA) was measured using the Minnesota LTPA Questionnaire in 35- to 74-year-old black and white residents of Minneapolis-St. Paul, Minnesota. Estimates of the geometric mean LTPA energy expenditure were 129 and 204 kcal per day for black and white men (p<.05) and 91 and 123 kcal per day for black and white women (p<.05). The percentage of individuals expending 2000 kcal or more per week in LTPA was significantly lower in black men than white men (25 vs. 35%; p=.01) but was not different in black versus white women (18 vs. 17%). Although black men and women reported greater occupational physical activity than their white counterparts, LTPA and job activity were unrelated in all race and sex groups. In both races, LTPA energy expenditure declined with age. LTPA increased with level of formal education, and the largest LTPA difference between blacks and whites was observed in those who had a high-school diploma or less. Blacks had lower participation rates than whites in most of the individually assessed physical activities. Additional research is needed on the determinants and promoters of LTPA in population subgroups.The research was funded by National Heart, Lung, and Blood Institute Research Grant R01 HL 23727 and National Research Award T32 HL 07328-10.     

A 23-pS Ca2+-activated K+ channel in MCF-7 human breast carcinoma cells: an apparent correlation of channel incidence with the rate of cell proliferation

In studies on the apical membranes of cultured MCF-7 human breast carcinoma cells, we found two conspicuous K⁺ channel types with conductances of 23 and 70 pS, respectively. Of these, the 23-pS K⁺ channel was most conspicuous. In cell-attached patches with KCl in the pipette, it had a linear current/voltage (I/V) relation and was activated by depolarisation and in excised insideout patches it was highly selective for K⁺ over Na⁺ (permeability ratio of Na⁺ to K⁺, P _Na/P _K=0.02). Rubidium (Rb⁺) had a similar permeability to K⁺, although it was only conducted at 20% of the rate of K⁺, and cesium (Cs⁺) had a permeability less than 30% that of K⁺ and was not conducted at all. Both Cs⁺ and Rb⁺ acted as partial blockers when applied internally but the channel was not blocked by external tetraethylammonium (TEA, 10 mmol/l), quinidine (200 mol/l) or apamin (50 nmol/l). It was activated by Ca^{2 +} in the range 10^–7–10^–6 mol/l. In cell-attached patches at a pipette potential of 0 mV, the open-time histogram was described by a single exponential (time constant 1.6 ms) and the closed-time histogram by two exponentials (time constants 0.5 and 1.5 ms). The incidence of the 23-pS but not the 70-pS channel depended on the rate of cell proliferation. Thus, in studies on cell-attached patches from cells in the exponential growth phase, the 23-pS channel was observed in 78% of patches. However, when the proliferation rate was decreased, whether as a result of allowing the monolayer to reach confluence, or of cell treatment with an anti-oestrogen (tamoxifen, 10 mol/l), or a phorbol ester [phorbol 12-myristate 13-acetate (TPA), 2.6 nmol/l], the channel incidence was reduced to 42%, 60% and 42%, respectively. The activity of the 23-pS channel is not obligatory for cell division, however, since the rate of cell proliferation remained the same in MCF-7 cultures in which the channel was not expressed.     

Detection of IL-2 at mRNA and protein levels in synovial infiltrates from inflammatory arthropathies using biotinylated oligonucleotide probes in situ.

A non-radioactive in situ hybridization method for IL-2 mRNA detection based on the use of four biotinylated oligonucleotide probes, plus appropriate positive and negative control probes was developed and applied to synovial surgical and needle biopsies from rheumatoid arthritis (RA), spondyloarthropathy (SpA), psoriatic arthritis (PsA) and juvenile chronic arthritis (JCA) patients. In eight surgical biopsies (six RA, one SpA, one PsA) this non-radioactive system showed similar sensitivity to that of a previously described 32P-labelled probe system, and in addition detected IL-2 mRNA in five out of seven biopsies from SpA and PsA patients and in two out of two JCA needle biopsies. IL-2 mRNA was found in the absence of IL-2 protein in RA biopsies (six surgical, 12 needle), but variable amounts of IL-2 protein were detected in six out of seven needle biopsies from SpA, PsA and JCA patients, where CD3+ lymphoid infiltrates were present. These data suggest differences in IL-2 regulation and expression in RA and non-RA inflammatory arthropathies.     

Chronic pancreatitis and biliary fibrosis associated with cryptosporidiosis in simian AIDS.

Two Rhesus monkeys infected with simian immunodeficiency virus for 15 and 24 months developed generalized oedema and one became jaundiced. At necropsy, the liver and pancreas were hard and irregular and the gall bladder was thickened. Histopathological examination showed extensive fibrosis of the pancreas, loss of exocrine acini and marked proliferation of ductules. Numerous cryptosporidia were present on the duct epithelium. The liver of both animals had widespread cirrhosis, bile duct proliferation and cholangitis. Cryptosporidia were found in many bile ducts and on the hyperplastic gall bladder epithelium. Lymph nodes and spleen of both animals showed depletion of cortical and paracortical elements characteristic of advanced immunodeficiency virus infection.     

The vascularity of primary cutaneous melanoma

In primary cutaneous malignant melanoma, the vascularity of the dermis immediately deep to the lesion may relate to tumour aggressiveness and to prognosis. These newly formed dermal vessels are incorporated into the melanoma to form the tumour microcirculation. We have assessed the percentage vascular volume in a series of primary melanomas in order to investigate the relationship between tumour vascularity and maximum tumour thickness. For the 64 melanomas included in this study, there appeared to be a significant relationship between the percentage vascular volume and the maximum tumour thickness. This relationship was not influenced by the presence of necrosis, vascular invasion, regression, or lymphocytic infiltrate, nor by the growth phase of the tumour. However, the percentage vascular volume was very low in the occasional thick melanoma, at least one of which was associated with prolonged survival. It seems possible that a low tumour vascularity could correlate with a relatively favourable outcome in cutaneous melanoma.     

Ruling out acute myocardial infarction. A prospective multicenter validation of a 12-hour strategy for patients at low risk

BACKGROUND. Although previous investigations have suggested that 24 hours is required to exclude acute myocardial infarction in patients who are admitted to a coronary care unit for the evaluation of acute chest pain, we hypothesized that a 12-hour period might be adequate for patients with a low probability of infarction at the time of admission. METHODS. Using a Bayesian model, we developed a strategy to identify candidates for a shorter period of observation from an analysis of a derivation set of 976 patients with acute chest pain who were admitted to three teaching and four community hospitals. In the derivation set, patients whose clinical characteristics in the emergency room predicted a low (less than or equal to 7 percent) probability of myocardial infarction had only a 0.4 percent risk of infarction if they had neither abnormal levels of cardiac enzymes nor recurrent ischemic pain during the first 12 hours of hospitalization. In an independent testing set of 2684 patients from the seven hospitals, 957 admitted patients (36 percent) were classified as candidates for this 12-hour period of observation according to a previously published multivariate algorithm. Few of these patients were actually transferred from a monitored setting at 12 hours. RESULTS. Of the 771 candidates for a 12-hour period of observation who did not have enzyme abnormalities or recurrent pain during the first 12 hours, 4 (0.5 percent) were subsequently found to have acute myocardial infarction, and only 3 (0.4 percent) died after primary cardiac arrests, all of which occurred three to five days after admission. Rates of other major cardiovascular complications were low in the patients who might have been transferred from the coronary care unit after 12 hours with this strategy. In patients with a higher initial risk of infarction, the standard strategy of 24-hour observation identified all but 11 of 739 acute myocardial infarctions (1 percent). CONCLUSIONS. Emergency room clinical data can be used to identify a large subgroup of patients for whom a 12-hour period of observation is normally sufficient to exclude acute myocardial infarction. Patient-specific evaluation and treatment can then proceed without the restrictions imposed by "rule-out" protocols for myocardial infarction.