Showing papers by "University of Maryland, Baltimore published in 1993"

Calcium sparks: elementary events underlying excitation-contraction coupling in heart muscle

Abstract: Spontaneous local increases in the concentration of intracellular calcium, called "calcium sparks," were detected in quiescent rat heart cells with a laser scanning confocal microscope and the fluorescent calcium indicator fluo-3 Estimates of calcium flux associated with the sparks suggest that calcium sparks result from spontaneous openings of single sarcoplasmic reticulum (SR) calcium-release channels, a finding supported by ryanodine-dependent changes of spark kinetics At resting intracellular calcium concentrations, these SR calcium-release channels had a low rate of opening (approximately 00001 per second) An increase in the calcium content of the SR, however, was associated with a fourfold increase in opening rate and resulted in some sparks triggering propagating waves of increased intracellular calcium concentration The calcium spark is the consequence of elementary events underlying excitation-contraction coupling and provides an explanation for both spontaneous and triggered changes in the intracellular calcium concentration in the mammalian heart

Effects of age and aerobic capacity on arterial stiffness in healthy adults.

Abstract: BACKGROUNDIt has been well established that arterial stiffness, manifest as an increase in arterial pulse wave velocity or late systolic amplification of the carotid artery pressure pulse, increase

Cloning and expression of an inwardly rectifying ATP-regulated potassium channel

Abstract: A complementary DNA encoding an ATP-regulated potassium channel has been isolated by expression cloning from rat kidney. The predicted 45K protein, which features two potential membrane-spanning helices and a proposed ATP-binding domain, represents a major departure from the basic structural design characteristic of voltage-gated and second messenger-gated ion channels. But the presence of an H5 region, which is likely to form the ion conduction pathway, indicates that the protein may share a common origin with voltage-gated potassium channel proteins.

A neurophysiological approach to tinnitus: Clinical implications

Abstract: This paper presents a neurophysiological approach to tinnitus and discusses its clinical implications. A hypothesis of discordant damage of inner and outer hair cells systems in tinnitus generation...

Diversity of nicotinic acetylcholine receptors in rat hippocampal neurons. I. Pharmacological and functional evidence for distinct structural subtypes.

Abstract: Nicotinic acetylcholine receptors present on cultured hippocampal neurons from fetal rats were characterized by means of whole-cell patch-clamp technique, using a number of structurally divergent agonists and highly selective antagonists. Based upon the decay kinetics of the currents elicited by 3 mM acetylcholine (ACh) and their sensitivities to agonists and antagonists, the neurons were shown to exhibit four current types, IA, IB, II and III. Rapidly decaying currents (type IA) that were blocked by alpha-bungarotoxin (10 nM), kappa-bungarotoxin (10 nM) and methyllycaconitine (MLA, 1 nM) were the most frequent and were found in 83% of the neurons tested. Type II currents (found in 5% of the neurons) were blocked by dihydro-beta-erythroidine (10 nM), and by high concentrations of MLA and kappa-bungarotoxin (100 nM each) but not by alpha-bungarotoxin (100 nM). Type III currents (elicited in 2% of the neurons) decayed slowly and were blocked by (+/-)-mecamylamine (1 microM) but not by alpha-bungarotoxin, kappa-bungarotoxin or MLA (each at 100 nM). Some of the cells (10% of the neurons) had mixed responses (named type IB), which were only partially blocked by MLA (1 nM) or dihydro-beta-erythroidine (10 nM) alone and were completely blocked by combination of the two agents. The order of potency of agonists in activating the currents was the following: for type IA, (+)-anatoxin-a >> 1,1-dimethyl-4-phenyl-piperazinium > (-)-nicotine > cystisine > ACh > carbachol > (+)-nicotine > arecoline > suberyldicholine; for type II, ACh > (+)-anatoxin-a > (-)-nicotine > 1,1-dimethyl-4-phenyl-piperazinium > carbachol > cytisine > (+)-nicotine > suberyldicholine > arecoline. Certain agonists were particularly useful in discriminating among the various types of currents: ACh, carbachol, (-)-nicotine and suberyldicholine for type II, and cytisine for type III currents. The EC50 of ACh was approximately 130 microM for type IA and approximately 2 microM for type II currents. A marked inward rectification was observed with type II, whereas type IA currents showed very little inward rectification. Differences observed in the pharmacological and functional properties of the nicotinic currents imply the expression of at least three structurally distinct nicotinic acetylcholine receptor subtypes in hippocampal neurons. The possible involvement of these currents in the transduction of signals is discussed.

Association of depression with 10-year poststroke mortality.

Abstract: Objective Depression has been linked to higher than expected mortality from natural causes, particularly among elderly patients with physical illness. The authors examined the effect of depression on mortality among a group of stroke patients followed up for 10 years. Method A consecutive series of 103 patients was assessed for major or dysthymic (minor) depression approximately 2 weeks after stroke with the use of a structured mental status examination and DSM-III diagnostic criteria. Vital status was determined for 91 of these patients 10 years later. Results Forty-eight (53%) of the 91 patients had died. Patients with diagnoses of either major or minor depression were 3.4 times more likely to have died during the follow-up period than were nondepressed patients, and this relationship was independent of other measured risk factors such as age, sex, social class, type of stroke, lesion location, and level of social functioning. The mortality rate among depressed patients with few social contacts was especially high: over 90% had died. Conclusions These results indicate that depressed mood following stroke is associated with an increased risk of subsequent mortality. Patients who are depressed and socially isolated seem to be particularly vulnerable.

Vascular endothelial growth factor/vascular permeability factor expression in the rat uterus: rapid stimulation by estrogen correlates with estrogen-induced increases in uterine capillary permeability and growth.

Abstract: In the uterus, estrogen causes a rapid increase in microvascular permeability, followed later by growth of the endometrium, including the richly vascular stroma. Vascular endothelial growth factor/vascular permeability factor (VEGF/VPF or VEG/PF) is an angiogenic protein that is not only a specific mitogen for endothelial cells, but also a potent stimulator of microvascular permeability. Because of these properties, it seems likely that VEG/PF might mediate estrogen-induced increases in uterine vascular permeability and blood vessel growth. Therefore, we determined whether the gene for VEG/PF is expressed in the rat uterus and if mRNA abundance is regulated by steroid hormones, using reverse transcription-polymerase chain reaction. The VEG/PF gene is alternatively spliced and gives rise to three transcripts coding for proteins of 188, 164, and 120 amino acids, which, in turn, form the active dimeric factors. Transcripts for VEG/PF mRNAs were detected in the uterus of the rat by reverse transcription-polymerase chain reaction. The mRNAs for the VEG/PF164 and VEG/PF120 subunits were the dominant forms expressed. Treatment with both estradiol (E2) and estriol (E3) rapidly induced an increase in the level of the two smaller transcripts. The increase was detectable as early as 0.5-1 h and peaked at 2 h. Levels of the two smaller transcripts then declined, but remained above control levels for 24 h. The degree of stimulation of VEG/PF mRNA levels was 8-fold at 2 h. VEG/PF188 mRNA levels were higher by 6 h compared to control values. The increase in VEG/PF mRNA levels in response to E2 was not contingent upon de novo protein synthesis, as it was not blocked by cycloheximide. The increase occurred as rapidly as that of the mRNA for Zif268, an estrogen-induced transcription factor. Progesterone also stimulated the expression (at 6 h) of VEG/PF164 and VEG/PF120, but not that of VEG/PF188. We conclude that the VEG/PF gene is expressed in the rat uterus, and that mRNA levels are rapidly enhanced by estrogen. This response suggests that VEG/PF may be involved in the estrogen-induced increase in permeability and proliferation of uterine blood vessels. The identification of VEG/PF as a primary response gene also suggests that VEG/PF expression may be a prerequisite for the subsequent expression or action of other growth factors in the uterus.

Physiological effects of endogenous ouabain: control of intracellular Ca2+ stores and cell responsiveness

Abstract: Ouabain is a well-known compound but a newly discovered adrenal cortical hormone that plays a role in cell Na+ regulation and in whole body salt and water balance. Ouabain may also be a paracrine hormone and may be secreted by some central nervous system neurons as well as by other types of cells. This article focuses on the cellular mechanisms that underlie the physiological (and pathophysiological) effects of ouabain. Ouabain directly inhibits the plasmalemmal Na+ pump in a variety of cell types. Low ouabain concentrations cause, in the steady state, a modest rise in the cytosolic Na+ concentration but only a minimal decline in membrane potential. All Na+ gradient-dependent processes may thereby be affected, albeit to only a small extent. Most important, however, is the secondary redistribution of Ca2+, mediated by Na(+)-Ca2+ exchange, that should slightly increase the cytosolic free Ca2+ concentration ([Ca2+]cyt). As a result of Ca2+ sequestration in intracellular stores [the endoplasmic and/or sarcoplasmic reticulum (ER/SR)], however, a new steady state is achieved with a slightly increased [Ca2+]cyt but a substantially augmented Ca2+ store; thus the ER/SR effectively acts as a Ca2+ amplifier. This extra stored Ca2+ is then available for mobilization whenever the cells are activated. Cytosolic Ca2+ is a key signaling mechanism in virtually all cells: it controls numerous physiological processes such as contraction, secretion, and excitability. Thus ouabain may modulate cell responsiveness via its influence on ER/SR Ca2+ stores. With these principles in mind, we examine evidence that endogenous ouabain may play a role in numerous physiological and pathophysiological processes associated with altered fluid and electrolyte metabolism and deviations from the normal blood pressure-blood volume relationship. We discuss the possible participation of ouabain in the regulation of vascular tone and then consider the putative role of ouabain in several forms of hypertension, congestive heart failure, thyroid and adrenocortical dysfunction, and diabetes mellitus, as well as in the adaptation to high altitude.

Homozygous Deletion and Frequent Allelic Loss of Chromosome 8p22 Loci in Human Prostate Cancer

Abstract: Allelic loss studies have been instrumental in identifying tumor suppressor gene loci in a variety of cancers. In this study we analyzed prostate cancer specimens from 52 patients for allelic loss using 8 polymorphic probes for the short arm of chromosome 8. Overall, 32 of 51 (63%) informative tumors showed loss of at least one locus on chromosome 8p. The most frequently deleted region is observed at chromosome 8p22-8p21.2. Loss of one allele is identified in 14 of 23 (61%) tumors at D8S163, in 15 of 32 (47%) tumors at lipoprotein lipase, and in 20 of 29 (69%) tumors at MSR, all on 8p22. Loss of one allele is identified in 16 of 27 (59%) tumors at D8S220 at 8p21.3-8p21.2. In addition to frequent loss of one allele at the MSR locus, one metastatic prostate cancer sample demonstrated homozygous deletion of MSR sequences. Loci telomeric and centromeric to this region are largely retained. A chromosome 8p deletion map is constructed and defines the smallest region of overlap to a 14-cM interval at 8p22 between D8S163 and lipoprotein lipase, flanking the MSR locus. Evidence of chromosome 8q multiplication at locus D8S39 was detected in 5 of 32 (16%) tumors, all of which demonstrated loss with at least one probe on chromosome 8p. This study extends the previous finding of frequent loss of chromosome 8p in prostate cancer by defining a common region of loss of heterozygosity at 8p22 and a homozygous deletion of the MSR locus contained within this region. This is the first homozygous deletion identified in the genome of a human prostate cancer and the highest rate of loss yet reported on chromosome 8p in cancer. These results strongly suggest the presence of a tumor suppressor gene in this region which is frequently inactivated in prostate cancer.

Comparison of trypan blue dye exclusion and fluorometric assays for mammalian cell viability determinations

Abstract: A hemocytometer-based trypan blue dye exclusion cell quantitation and viability assay was compared with a similar assay using simultaneous fluorometric staining with fluorescein diacetate and propidium iodide. Viable and nonviable cell densities were measured, and culture viability was calculated both during the normal growth cycle of a murine hybridoma and in response to the application of millimolar concentrations of either tert-butyl hydroperoxide or ferrous iron. During the early phase of rapid hybridoma cell growth, assay-based differences in viable cell density were not significant. As the culture aged, the trypan blue dye exclusion assay significantly overestimated cell viability, thereby underestimating nonviable cell density and yielding an erroneous estimation of the overall viability of the culture. Because of its lack of ambiguity in the identification of stained, nonviable cells and its resulting increased accuracy in the estimation of culture viability, the fluorometric assay was considered a better choice for the evaluation of cell viability.

Publication bias: the problem that won't go away.

Abstract: Conclusions about the efficacy and safety of medical interventions are based on data presented in the scientific literature. The validity of these conclusions is threatened if publication bias results from investigators or editors making decisions about publishing study results on the basis of the direction or strength of the study findings. This paper reports meta-analyses performed using data from four prospective investigations in which a total of 997 initiated studies were followed to learn of study results, publication status, and reasons for nonpublication. The analysis indicates that there is a positive association between "significant" study results and publication (OR = 2.88; 95% confidence interval [CI] 2.13 to 3.90). When the analysis was restricted to controlled trials (n = 280), an even stronger relationship between "significant" results and publication was observed (OR = 6.15; 95% CI 2.24 to 16.92), with randomized trials (n = 200) apparently no less susceptible to publication bias than controlled trials in general (OR = 8.72; 95% CI 1.91 to 39.81). In every case, failure to publish was investigator-based, and not due to editorial decisions. The results of clinical trials should not be suppressed in this way. Development of registration systems for randomized trials is essential if this problem is to be minimized in future.

In situ studies of the primary immune response to (4-hydroxy-3-nitrophenyl)acetyl. III. The kinetics of V region mutation and selection in germinal center B cells.

Abstract: In the murine spleen, germinal centers are the anatomic sites for antigen-driven hypermutation and selection of immunoglobulin (Ig) genes. To detail the kinetics of Ig mutation and selection, 178 VDJ sequences from 16 antigen-induced germinal centers were analyzed. Although germinal centers appeared by day 4, mutation was not observed in germinal center B cells until day 8 postimmunization; thereafter, point mutations favoring asymmetrical transversions accumulated until day 14. During this period, strong phenotypic selection on the mutant B lymphocytes was inferred from progressively biased distributions of mutations within the Ig variable region, the loss of crippling mutations, decreased relative clonal diversity, and increasingly restricted use of canonical gene segments. The period of most intense selection on germinal center B cell populations preceded significant levels of mutation and may represent a physiologically determined restriction on B cells permitted to enter the memory pathway. Noncanonical Ig genes recovered from germinal centers were mostly unmutated although they probably came from antigen-reactive cells. Together, these observations demonstrate that the germinal center microenvironment is rich and temporally complex but may not be constitutive for somatic hypermutation.

Role of the eaeA gene in experimental enteropathogenic Escherichia coli infection.

Abstract: Enteropathogenic Escherichia coli (EPEC) infections are a leading cause of infant diarrhea in developing countries. Recently eaeA, a gene necessary for the characteristic intimate attachment of EPEC to epithelial cells in tissue culture, was described. We conducted a randomized, double-blind study to determine the role of the eaeA gene in human EPEC infection. 11 adult volunteers ingested 2 x 10(10) colony-forming units of O127:H6 EPEC strain E2348/69, and an equal number received the same dose of an isogenic eaeA deletion mutant constructed from E2348/69. Volunteers were monitored for the development of diarrhea, fever, and systemic and gastrointestinal complaints. Diarrhea developed in all 11 volunteers who received E2348/69 and in 4 of 11 who received the mutant (P = 0.002). Fever was more common in recipients of the wild-type strain (P = 0.024). Stool volumes were lower in recipients of the mutant. All volunteers seroconverted to E2348/69 LPS, but the geometric mean peak titers of serum IgG and IgA in recipients of the mutant were lower than those of recipients of the wild-type strain. IgA against LPS was detected in the jejunal fluid of six of six recipients of E2348/69 and 5/6 recipients of the mutant. This study unambiguously assigns a role for eaeA as an EPEC virulence gene, but the residual diarrhea seen in recipients of the mutant indicates that other factors are involved.

Hemodynamic and neurohormonal effects of the angiotensin II antagonist losartan in patients with congestive heart failure.

Abstract: Background. Losartan is a new specific angiotensin II receptor antagonist with no agonist properties that provides the opportunity to study the consequences of angiotensin II blockade. The objective of the present study was to evaluate the hemodynamic and neurohormonal response to losartan in patients with congestive heart failure. Methods and Results. After baseline hemodynamic measurements using balloon-tipped pulmonary artery and radial arterial catheters, patients were randomized to receive a single dose of placebo or 5, 10, 25, 75, or 150 mg losartan in a double-blind, sequential fashion. Hemodynamic and neurohormonal parameters were then measured periodically for 24 hours. Losartan caused vasodilation in a dose-dependent manner. By the area-under-the-curve method, the reduction in the mean arterial pressure and systemic vascular resistance grew larger up to a dose of 25 mg, but the higher 75- and 150-mg doses did not produce additional vasodilation. In response to losartan, there were compensatory increases in both angiotensin II concentrations and in plasma renin activity, which were greatest at the highest doses. Aldosterone concentrations were significantly lowered with losartan. Conclusions. Blockade of the angiotensin II receptor with the antagonist losartan causes vasodilator and neurohormonal effects in patients with congestive heart failure. The lack of additional vasodilator response with doses of more than 25 mg suggests that neurohormonal activation might limit the efficacy of high doses of losartan.

Constitutive expression of B7 restores immunogenicity of tumor cells expressing truncated major histocompatibility complex class II molecules

Abstract: The inability of the autologous host to reject resident tumor cells is frequently the result of inadequate generation of tumor-specific T cells. Specific activation of T cells occurs after delivery of two signals by the antigen-presenting cell. The first signal is antigen-specific and is the engagement of the T-cell antigen receptor by a specific major histocompatibility complex antigen-peptide complex. For some T cells, the second or costimulatory signal is the interaction of the T-cell CD28 receptor with the B7 activation molecule of the antigen-presenting cell. In the present study, we demonstrate that mouse sarcoma cells genetically engineered to provide both T-cell activation signals stimulate potent tumor-specific CD4+ T cells that cause rejection of both engineered and wild-type neoplastic cells. Two other recent studies have also demonstrated that costimulation via B7 can improve tumor immunity. However, our study differs from these reports by two important observations. (i) One of these studies utilized mouse tumor cells expressing xenogenic viral antigens, and hence, the results are not applicable to wild-type resident tumors. Our study, however, demonstrates that coexpression of B7 by major histocompatibility complex class II+ tumor cells induces immunity in the autologous host that is specific for naturally occurring tumor antigens of poorly immunogenic tumors. (ii) In both earlier studies, only CD8+ T cells were activated after coexpression of B7, whereas in the present report, tumor-specific CD4+ T cells are generated. This report therefore illustrates the role of B7 activation molecule in stimulating potent tumor-specific CD4+ T cells that mediate rejection of wild-type tumors and provides a theoretical basis for immunotherapy of established tumors.

Hypoxia reduces potassium currents in cultured rat pulmonary but not mesenteric arterial myocytes

Abstract: To explore possible mechanisms underlying hypoxia-induced pulmonary vasoconstriction, the effect of hypoxia on outward K+ current (Iout) was evaluated in primary cultured rat pulmonary (PA) and mes...

Seroprevalence of Helicobacter pylori in Chile: Vegetables May Serve as One Route of Transmission

Abstract: Helicobacter pylori infection is very common in Chilean adults, but the age-related prevalence, risk factors for infection, and mode of transmission in Chilean children are unknown. An ELISA was used to test for H. pylori antibodies in 1815 Chileans 60% in lower socioeconomic groups. H. pylori seropositivity correlated with increased age, low socioeconomic status, and consumption of uncooked vegetables by use of a logistic regression analysis. Risk factors that reached marginal significance were consumption of uncooked shell-fish, female sex, and residence in Santiago. Although multiple modes of transmission for H. pylori undoubtedly exist, prior studies have suggested that contamination of irrigation water by raw sewage (and the subsequent contamination of vegetables that are eaten uncooked) is a key factor in the transmission of enteric pathogens in Chile; H. pylori may be transmitted by a similar route.

Mental models: concepts for human-computer interaction research

Abstract: In interacting with the world, people form internal representations or mental models of themselves and the objects with which they interact (Norman, 1983a). According to Norman, mental models provide predictive and explanatory powers for understanding the interaction. More abstractly, Gentner and Stevens (1983) propose that mental models focus on the way people understand a specific knowledge domain. More concretely, Carroll (1984) views mental models as information that is input into cognitive structures and processes. What are mental models? Are they always formed? When formed, what are their characteristics? What are the functional consequences of having no model (if that is possible), an immature model, or a mature model? This paper intends to explore these questions.

Intracellular Ca2+ pool content is linked to control of cell growth

Abstract: A close correlation was observed between intracellular Ca2+ pool depletion and refilling and the onset of DNA synthesis and proliferation of DDT1MF-2 smooth muscle cells. The intracellular Ca2+ pump inhibitors 2,5-di-tert-butyl-hydroquinone (DBHQ) and thapsigargin (TG) specifically emptied identical inositol 1,4,5-trisphosphate (InsP3)-sensitive Ca2+ pools and both arrested cell growth at concentrations corresponding to Ca2+ pump blockade. However, an important distinction was observed between the two inhibitors with respect to their reversibility of action. Upon removal of DBHQ from DBHQ-arrested cells, Ca2+ pools immediately refilled, and 14 hr later cells entered S phase followed by normal cell proliferation; the time for entry into S phase was identical to that for cells released from confluence arrest. Although TG irreversibly blocked Ca2+ pumping and emptied Ca2+ pools, high serum treatment of TG-arrested cells induced recovery of functional Ca2+ pools in 6 hr (via probable synthesis of new pump); thereafter cells proceeded to S phase and normal cell proliferation within the same time period (14 hr) as that following release of DBHQ-arrested cells. The precise relationship between Ca2+ pump blockade and growth arrest indicates that Ca2+ pool emptying maintains cells in a G0-like quiescent state; upon refilling of pools, normal progression into the cell cycle is resumed. It is possible that a specific cell cycle event necessary for G0 to G1 transition depends upon signals generated from the InsP3-sensitive Ca2+ pool.

Strength training increases regional bone mineral density and bone remodeling in middle-aged and older men.

Abstract: To determine the effects of strength training (ST) on bone mineral density (BMD) and bone remodeling, 18 previously inactive untrained males [mean age 59 +/- 2 (SE) yr] were studied before and after 16 wk of either ST (n = 11) or no exercise (inactive controls; n = 7). Total, spinal (L2-L4), and femoral neck BMD were measured in nine training and seven control subjects before and after the experimental period. Serum concentrations of osteocalcin, skeletal alkaline phosphatase isoenzyme, and tartrate-resistant acid phosphatase were measured before, during, and after the experimental program in all subjects. Training increased muscular strength by an average of 45 +/- 3% (P < 0.001) on a three-repetition maximum test and by 32 +/- 4% (P < 0.001) on an isokinetic test of the knee extensors performed at 60 degrees/s. BMD increased in the femoral neck by 3.8 +/- 1.0% (0.900 +/- 0.05 vs. 0.933 +/- 0.05 g/cm2, P < 0.05) and in the lumbar spine by 2.0 +/- 0.9% (1.180 +/- 0.06 vs. 1.203 +/- 0.06 g/cm2, P < 0.05). However, changes in lumbar spine BMD were not significantly different from those in the control group. There was no significant change in total body BMD. Osteocalcin increased by 19 +/- 6% after 12 wk of training (P < 0.05) and remained significantly elevated after 16 wk of training (P < 0.05). There was a 26 +/- 11% increase in skeletal alkaline phosphatase isoenzyme levels (P < 0.05) after 16 wk of training.(ABSTRACT TRUNCATED AT 250 WORDS)

The problems of anticholinergic adverse effects in older patients.

Abstract: The old saying ‘red as a beet, dry as a bone, blind as a bat, hot as a hare, mad as a hatter’ is often quoted when describing the autonomic effects of drugs that block the muscarinic cholinergic system. These effects may be subtle or dramatic, yet can be overlooked or discounted as a natural consequence of old age. Elderly patients can be particularly sensitive to the anticholinergic action of drugs because of physiological and pathophysiological changes that often accompany the aging process. The use of multiple drugs, a common finding in older patients, may result in pharmacodynamic and pharmacokinetic drug interactions that heighten anticholinergic effects. While the classic anticholinergic problems of decreased secretions, slowed gastrointestinal motility, blurred vision, increased heart rate, heat intolerance, sedation and possibly mild confusion, may be uncomfortable for a younger patient in relatively good health, these effects can be disastrous for older patients. Even the most common peripheral anticholinergic complaint of dry mouth can reduce the ability to communicate, predispose to malnutrition, promote mucosal damage, denture misfit or dental caries, and increase the risk of serious respiratory infection secondary to loss of antimicrobial activity of saliva. Mydriasis and the inability to accommodate will impair near vision and may precipitate narrow angle glaucoma in predisposed patients, but less obviously could lead to an increased risk of accidents, including falls. Somatic complaints of constipation and urinary hesitancy, could, in the presence of anticholinergic challenge, result in faecal impaction or urinary retention. Cardiac effects may be poorly tolerated. Increases in heart rate may precipitate or worsen angina. Finally, thermoregulatory impairment induced by anticholinergics, which block the ability to sweat, may lead to life threatening hyperthermia. Central anticholinergic effects range from sedation, mild confusion and inability to concentration to frank delirium. Even mild effects can reduce function and increase dependency. At any level of care, the loss of independence increases the caregiver burden, costs, and most importantly, can negatively affect quality of life. Many age-related and disease-related conditions may predispose elderly patients to anticholinergic drug toxicity. Careful attention to anticholinergic effects when prescribing drugs, patient education, regular review of the entire drug regimen, and familiarity with the signs and symptoms of anticholinergic toxicity will help to reduce the risk of drug-induced problems.

Accessory cholera enterotoxin (Ace), the third toxin of a Vibrio cholerae virulence cassette

Abstract: Vibrio cholerae causes the potentially lethal disease cholera through the elaboration of the intestinal secretogen cholera toxin. A second toxin of V. cholerae, Zot, decreases intestinal tissue resistance by modifying intercellular tight junctions. In this report, a third toxin of V. cholerae, Ace (accessory cholera enterotoxin), is described. Ace increases short-circuit current in Ussing chambers and causes fluid secretion in ligated rabbit ileal loops. The predicted protein sequence of Ace shows striking similarity to eukaryotic ion-transporting ATPases, including the product of the cystic fibrosis gene. The gene encoding Ace is located immediately upstream of the genes encoding Zot and cholera toxin. The ctx, zot, and ace genes, which are located on a dynamic sector of the chromosome, comprise a V. cholerae "virulence cassette."

Structural Abnormalities in Deficit and Nondeficit Schizophrenia

Abstract: Objective: Previous studies have suggested the involvement of the frontal and parietal cortices and thalamus in a neural circuit underlying the production ofprimary enduring negative or deficit symptoms of schizophrenia. The purpose of this study was to examine whether structural changes in the proposed circuit are associated with the production ofdeficit symptoms. Method: Magnetic resonance imaging was used to measure the volume ofselected circuit brain regions (i.e., the prefrontal region and caudate) and noncircuit brain regions (i.e., the amygdala/hippocampus complex) in 1 7 deficit and 24 nondeficit schizophrenic outpatients and 30 normal comparison subjects. Results: Right and left total prefrontal volumes discriminated deficit from nondeficit patients, with prefrontal volumes being smaller in nondeficit patients. There were no differences between the two schizophrenic subgroups in left caudate or right and left amygdala/hippocampus complex volumes. The right caudate was larger in deficit patients, but the difference between the two schizophrenic subgroups was not significant. There were no differences between deficit and normal subjects on any prefrontal region measure. Nondeficit patients had smaller total right and left prefrontal volumes than normal subjects. Both schizophrenic subgroups had larger left caudate volumes and smaller right and left amygdala/hippocampus complex volumes than the normal subjects. There was a trend for deficit patients to have larger right caudate volumes. Conclusions: These results suggest that structural changes in the prefrontal region are not responsible for deficit symptoms. The caudate, particularly the right caudate, may be associated with the production ofthese symptoms. (Am J Psychiatry 1993; 150:59-65)

Nih clinical trials and publication bias

Abstract: OBJECTIVE To investigate the association between trial characteristics, findings, and publication. The major factor hypothesized to be associated with publication was "significant" results, which included both statistically significant results and results assessed by the investigators to be qualitatively significant, when statistical testing was not done. Other factors hypothesized to have a possible association with publication were funding institute, funding mechanism (grant versus contract versus intramural), multicenter status, use of comparison groups, large sample size, type of control (parallel versus nonparallel), use of randomization and masking, type of analysis (by treatment received versus by treatment assigned), and investigator sex and rank. DESIGN Follow-up, by 1988 interview with the principal investigator or surrogate, of all clinical trials funded by the National Institutes of Health (NIH) in 1979, to learn of trial results and publication status. POPULATION Two hundred ninety-three NIH trials, funded in 1979. MAIN OUTCOME MEASURE Publication of clinical trial results. RESULTS Of the 198 clinical trials completed by 1988, 93% had been published. Trials with "significant" results were more likely to be published than those showing "nonsignificant" results (adjusted odds ratio [OR] = 12.30; 95% confidence interval [CI], 2.54 to 60.00). No other factor was positively associated with publication. Most unpublished trials remained so because investigators thought the results were "not interesting" or they "did not have enough time" (42.8%). Metaanalysis using data from this and 3 similar studies provided a combined unadjusted OR of 2.88 (95% CI, 2.13 to 3.89) for the association between significant results and publication. CONCLUSIONS Even when the overall publication rate is high, such as for trials funded by the NIH, publication bias remains a significant problem. Given the importance of trials and their utility in evaluating medical treatments, especially within the context of metaanalysis, it is clear that we need more reliable systems for maintaining information about initiated studies. Trial registers represent such a system but must receive increased financial support to succeed.

p53 gene mutation and integrated hepatitis B viral DNA sequences in human liver cancer cell lines

Abstract: A G:C-->T:A mutational hotspot at codon 249 of the p53 tumor suppressor gene has previously been identified in hepatocellular carcinoma (HCC) of patients from Qidong, China and southern Africa in which aflatoxin B1 (AFB1) and hepatitis B virus (HBV) are known synergistic risk factors. We have examined p53 mutation patterns of HCC from geographic areas in which the risk factors vary. Nine HCC lines and four hepatoblastoma lines (HB) were examined for p53 gene mutations and the relationship with HBV infection. Five of the nine HCC lines had homozygous mutation or deletion randomly distributed in exons 6-8, whereas none of the four HB cell lines had p53 mutations. One of the four HB lines (HepG2) had an N-ras mutation at codon 61 position 2. The p53 point mutations in the three HCC cell lines from Japan resulted in the amino acid changes of cysteine for tyrosine in cell line HuH 7 at codon 220 (A:T-->G:C), alanine for glycine in cell line HLF at codon 244 (G:C-->C:G), and serine for arginine in cell line HLE at codon 249 (G:C-->C:G). In addition, the deletion of 18 base pairs from codon 264 position 3 to codon 270 position 1 has resulted in the deletion of Leu-Gly-Arg-Asn-Ser-Phe from the amino acids sequences 256-270 in the Japanese cell line HuH 4. The cell line PLC/PRF/5 that showed p53 mutation at codon 249 (G:C-->T:A) with substitution of serine for arginine was derived from a South African patient. Our results indicate that whereas the p53 gene is not mutated in the HB cell lines, the HCC cell lines frequently contain an abnormal p53 gene. In addition, p53 point mutations were not detected in the four Japanese HCC cell lines that were positive for genomic integration of HBV X-gene and surface antigen gene. The three Japanese HCC cell lines with p53 mutations did not contain HBV sequences, indicating that hepatocarcinogenesis associated with p53 mutation does not require the genomic integration of HBV sequences.

Effects of treatment with 5-azacytidine on the in vivo and in vitro hematopoiesis in patients with myelodysplastic syndromes.

Abstract: The myelodysplastic syndrome (MDS) comprises a group of clonal hematopoietic disorders derived from an abnormality affecting a multipotent hematopoietic stem cell. Despite trials testing numerous agents in patients with MDS, no single drug has yet emerged as the accepted standard of treatment. Observation and supportive care with blood products and antibiotics, when necessary, continue to be the mainstays of therapy. We administered 5-azacytidine, a cell-cycle specific ring analog of the pyrimidine nucleoside cytosine, as a continuous intravenous infusion, 75 mg/m2 per day for 7 days every 4 weeks. Patients had refractory anemia with excess blasts (RAEB) or refractory anemia with excess blasts in transformation (RAEB-T). Responses were seen in 21 (49%) of 43 evaluable patients: five (12%) in complete remission (CR, complete normalization of bone marrow and peripheral blood counts); 11 (25%) in partial remission (PR, > or = 50% restoration of the deficit from normal of all three peripheral blood cell lines, elimination of transfusion requirements, and a decrease in percentage bone marrow blasts by > or = 50% from prestudy values); five (12%) improved (> or = 50% restoration in the deficit from normal of one or more peripheral blood cell lines and/or a > or = 50% decrease in transfusion requirements). A trilineage improvement (CR and PR) occurred in 37% of the patients. The median survival for all patients was 13.3 months and the median duration of remission for those with CR and PR was 14.7 months. Mild to moderate nausea and/or vomiting was the most common side effect (63%). Myelosuppression, either bone marrow hypoplasia or drug related cytopenias requiring a reduction in the dose of azacitidine, occurred in only 33% of the patients. Prior to treatment, bone marrow erythroid progenitor cells were assayed in vitro. Colonies derived from erythroid burst-forming units (BFU-e) were undetectable in one patient and reduced in two. The number of colonies derived from erythroid colony-forming units (CFU-e)) were also reduced in two of the three patients. In the two patients with detectable colony growth prior to treatment, colony number decreased by day 8 of the first cycle, followed by a subsequent increase. Continued treatment with azacitidine led to normalization of the number of CFU-e derived colonies as well as an increase in the number of BFU-e derived colonies. This improvement in erythroid colony number correlated with the spontaneous rise in hemoglobin levels and red cell transfusion independence.(ABSTRACT TRUNCATED AT 400 WORDS)