Comments on "Some imaging parameters of the oblique dipole layer cardiac generator derivable from body surface electrical potentials".
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Action Potentials↗
Biomedical subjects
S M Smith
Publications and source records attributed to S M Smith.
Time dependency of IgA nephropathy induction in alcohol ingestion.
We investigated the influence of the alcohol ingestion period on the incidence of IgA nephropathy in an animal model. A group of 41 rats received a continuous infusion of liquid diet and alcohol: "alcoholics." A further group of 41 control rats received an isocaloric diet in which the alcohol was replaced by glucose. IgA nephropathy was diagnosed by the presence of intense IgA deposition in the mesangium. At 6 weeks, 60% of the alcoholic rats had IgA nephropathy. The incidence increased until 100% of the alcoholic rats presented the renal disease at 16 weeks. IgA nephropathy was not found in any of the control animals. We conclude that, in this animal model, the incidence of IgA nephropathy is dependent on the time frame of the alcohol ingestion.
Alcoholism↗
Involvement of Gardnerella vaginalis in urinary tract infections in men.
Fifteen male patients from whose urine samples Gardnerella vaginalis was isolated (clinical incidence of 0.1%) were evaluated for clinical signs and symptoms of urinary tract infection and modality of acquisition of the organism. Ten of 15 (67%) patients were symptomatic or had signs of inflammation as manifested by an increased number of urinary neutrophils. One patient had two bouts of infection caused by this organism which required two courses of antibiotic therapy. Colonies of diphtheroidlike organisms found in urine cultures should not be ignored as insignificant but should be further investigated to determine whether G. vaginalis is present.
Adult↗
Ileal microvascular permeability: a comparison of PS and sigma d using lymphatic and isotopic protein clearances.
Lymphatic clearances of total protein, albumin, immunoglobulin (Ig) G, and IgM obtained in autoperfused cat ileum as venous pressure (Pv) was elevated were analyzed using traditional methods as well as the newer maximal diffusion (max,diff) method of Reed et al. [Am. J. Physiol. 261 (Heart Circ. Physiol. 30): H728-H740, 1991; Am. J. Physiol. 257 (Heart Circ. Physiol. 26): H1037-H1041, 1989] to determine capillary osmotic reflection coefficients (sigma d) and unique permeability surface area products (PS). In a control group (n = 6), sigma d max,diff and PSmax,diff for albumin, IgG, and IgM could not be determined due to their transiently high clearance patterns. These patterns were not altered by treatment with vasodilators (n = 6) to prevent redistribution of blood flow from the mucosal-submucosal to muscularis layer of the ileum, which accompanies elevation of ileal Pv. Furthermore, sigma d values for IgG in both groups were lower than those for both albumin and IgM, a finding inconsistent with predictions based on pore theory, together suggesting that lymphatic protein clearances were influenced by washout of interstitial proteins, a conclusion supported by the decrease in tissue content of albumin and IgG after elevation of Pv. Clearances of radiolabeled albumin (n = 10) and IgG (n = 6), measured after an initial 2-h steady-state period at a constant Pv, were markedly reduced at low lymph flow compared with those obtained in the shorter term experiments. In an additional group (n = 5), albumin clearance peaked at 10 times baseline within 15 min after a step increase in Pv to 30 mmHg but fell to only 3 times baseline within 1 h.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Lung protection against paraquat is calcium dependent.
Isolated, perfused, and ventilated rat lungs were challenged by paraquat (0.01 M) in the presence of 2.5 mM Ca2+, 2.5 mM Ca2+ with trifluoperazine (100 microM), 0.025 mM Ca2+, or 0.025 mM Ca2+ with sodium metavanadate (10 microM) to establish the effect of varying calcium concentration or calcium-dependent enzyme activities on injury induced by paraquat. Segmental vascular resistances, microvascular permeability (as assessed by the capillary filtration coefficient), lung tissue oxidized glutathione, and lung paraquat accumulation were measured. Exposure to paraquat for 2.5 h did not increase microvascular permeability or pulmonary vascular resistance in the presence of either normal extracellular calcium or low extracellular calcium and sodium metavanadate. Lungs exposed to paraquat were injured (as assessed by increased filtration coefficient) only in the presence of low extracellular calcium or after trifluoperazine was added. This injury was associated with decreased levels of oxidized glutathione and increased paraquat accumulation, suggesting that calcium's protective effect was both by inhibition of paraquat accumulation and maintenance of NADPH. Pulmonary vascular resistance was not increased with paraquat challenge.
Animals↗
Escherichia coli resistant to ampicillin/sulbactam.
Escherichia coli strains resistant to ampicillin/sulbactam from hospitals in 4 different geographic locations were examined with respect to type and amount of beta-lactamase produced. A total of 5 strains was examined from each region. The isoelectric points of all of the involved beta-lactamases were 5.4, corresponding to TEM-1. Km and Vmax values of the beta-lactamases among the clinical isolates resembled those from the control TEM-1 strain. In an 18-hour broth culture the highly resistant isolates produced 3 times more beta-lactamase as compared to the ampicillin/sulbactam-susceptible isolates. However, the highly resistant strains contained approximately the same amount of plasmid DNA (size of > 6,500 bp) as the susceptible isolates. In transformation experiments, both the resistance and the degree of resistance appeared to have been transferable by plasmids. The mechanism for resistance is likely to be a baseline overproduction of TEM-1 beta-lactamase due to either an alteration in the control of gene expression or simply to an increase in the number of copies of the beta-lactamase gene in the plasmids.
Ampicillin↗
Bicycle-associated head injuries and deaths in the United States from 1984 through 1988. How many are preventable?
OBJECTIVE: To estimate the potential benefits from more widespread bicycle safety helmet use. DESIGN: Review of death certificates and emergency department injury data for 1984 through 1988. Categorization of deaths and injuries as related to bicycling and head injury. Using relative risks of 3.85 and 6.67 derived from a case-control study and varying helmet usage from 10% to 100%, population attributable risk was calculated to estimate preventable deaths and injuries. SETTING: Entire United States. MAIN OUTCOME MEASURES: Numbers of US residents coded as dying from bicycle-related head injuries, numbers of persons presenting to emergency departments for bicycle-related head injuries, and numbers of attributable bicycle-related deaths and head injuries. MAIN RESULTS: From 1984 through 1988, bicycling accounted for 2985 head injury deaths (62% of all bicycling deaths) and 905,752 head injuries (32% of persons with bicycling injuries treated at an emergency department). Forty-one percent of head injury deaths and 76% of head injuries occurred among children less than 15 years of age. Universal use of helmets by all bicyclists could have prevented as many as 2500 deaths and 757,000 head injuries, ie, one death every day and one head injury every 4 minutes. CONCLUSIONS: Effective community-based education programs and legislated approaches for increasing bicycle safety helmet usage have been developed and await only the resources and commitment to reduce these unnecessary deaths and injuries.
Adolescent↗
Transgenic plant aequorin reports the effects of touch and cold-shock and elicitors on cytoplasmic calcium.
Methods for measuring plant cytoplasmic calcium using microelectrodes or microinjected fluorescent dyes are associated with extensive technical problems, so measurements have been limited to single or small groups of cells in tissue strips or protoplasts. Aequorin is a calcium-sensitive luminescent protein from the coelenterate Aequorea victoria (A. forskalea) which is formed from apoaequorin, a polypeptide of relative molecular mass approximately 22,000, and coelenterazine, a hydrophobic luminophore. Microinjected aequorin has been widely used for intracellular calcium measurement in animal cells, but its use in plants has been limited to exceptionally large cells. We show here that aequorin can be reconstituted in transformed plants and that it reports calcium changes induced by touch, cold-shock and fungal elicitors. Reconstituted aequorin is cytoplasmic and nonperturbing; measurements can be made on whole plants and a calcium indicator can be constituted in every viable cell. Now that apoaequorin can be targeted to specific organelles, cells and tissues, with the range of coelenterazines with differing calcium sensitivities and properties available, this new method could be valuable for determining the role of calcium in intracellular signalling processes in plants.
Aequorin↗
Recombinant aequorin as a probe for cytosolic free Ca2+ in Escherichia coli.
We describe a novel and simple method for the measurement of bacterial cytosolic free calcium ([Ca2+]i) using recombinant aequorin reconstituted within live bacterial cells. Using this method we have measured the effects of external calcium, complement, phagocytosis and antibiotics on the [Ca2+]i of Escherichia coli. In principle this method should be applicable to any genetically transformable organism and should suffer fewer problems than fluorescent dyes for subcellular calcium measurement.
Aequorin↗
D-[35S(U)]inositol 1,4,5-trisphosphorothioate, a novel radioligand for the inositol 1,4,5-trisphosphate receptor. Complex binding to rat cerebellar membranes.
D-[35S(U)]myo-inositol 1,4,5-trisphosphorothioate [( 35S]InsPS3), a synthetic, metabolically stable analogue of inositol 1,4,5-trisphosphate (InsP3), binds with high affinity (Kd 58.6 +/- 9.1 nM) to rat cerebellar membranes revealing a high density of specific binding sites (Bmax 21.5 +/- 2.1 pmol/mg of protein). Comparison with [3H]InsP3 binding reveals a higher density of sites labelled by [35S]InsPS3 and complex competition curves for displacement of specific [35S]InsPS3 by InsP3. The results suggest that [35S]InsPS3 labels two sites in rat cerebellar membranes with equal affinity: the InsP3 receptor and a site that displays low affinity for InsP3.
Animals↗
Evaluation of two methods for overcoming the antibiotic carry-over effect.
The antibiotic carry-over effect occurs when antibiotic transferred onto the agar plate with the subcultured aliquot is sufficient to inhibit the growth of viable bacteria, and results in a falsely low MBC. This phenomenon was eliminated by widely streaking the transferred aliquot over at least one half of a 100 mm agar plate or by centrifugation and resuspension of the organisms in non-antibiotic-containing media prior to plating. Both methods require more effort than the current method of MBC determination, but can be performed in clinical laboratories and are thus highly recommended in the testing of organisms from endocarditis and meningitis patients.
Centrifugation↗
Day-to-day variation in iron-status indices in healthy men and women.
We evaluated the day-to-day variation of four iron-status indices: hemoglobin (Hb), hematocrit (Hct), plasma ferritin (PF), and plasma iron (PI). Finger-prick blood samples were collected for 31 consecutive days in 20 healthy men and women. Replicate (sigma 2rep) and day-to-day (sigma 2day) variance components were estimated. Day-to-day variation in the iron-status measures was similar between men and women except for PF, for which the variation was greater in women. The CVs for a single future determination for Hb, Hct, PF, and PI were 4.6%, 3.0%, 15.2%, and 26.7% for males and 4.4%, 3.2%, 26.8%, and 29.0% for females, respectively. Three to 10 independent measurements are required to accurately determine PF and PI whereas one is adequate for Hb and Hct. Thus, day-to-day biological variation is a major component of the variability in these iron-status indicators and must be considered when assessing iron status.
Adult↗
Injury mortality among non-US residents in the United States 1979-1984.
More than 20 million non-US residents visit the United States each year. Data on deaths in this country among these non-US residents were obtained from US vital records. These data showed that from 1979 through 1984, 17,988 deaths occurred. Cardiovascular disease (International Classification of Diseases [ICD-9] 390-459) was the leading cause of death among non-residents. Injuries (ICD-9 E800-E999) ranked second as a cause of death and accounted for 23% of the deaths (4078). More than half of these injury deaths occurred among people aged 15-34 years and 79% of the people who died from injuries were males. The most frequent causes of injury deaths were motor vehicle traffic crashes (37%), drownings (15%), and homicides (11%). Although general patterns of injury mortality among non-US residents and US residents were similar, there were differences in the proportion of deaths due to homicides, drownings, and falls. Prevention efforts targeted to the major causes of injury mortality in the US will affect both US and non-US residents.
Accidents, Traffic↗
An in-vitro and in-vivo comparison of the activity of beta-lactamase inhibitor combinations with imipenem and cephalosporins against Escherichia coli producing TEM-1 or TEM-2 beta-lactamase.
Reference strains of Escherichia coli (ampicillin-susceptible and -resistant ATCC strains, and known TEM-1 and TEM-2 beta-lactamase producers) were tested in vitro and in the in-vivo mouse thigh infection model against four beta-lactamase inhibitor compounds (BICs: amoxycillin/clavulanic acid, ampicillin/sulbactam, ticarcillin/clavulanic acid, and piperacillin/tazobactam), selected cephalosporins, and imipenem. The ATCC strains (ampicillin-susceptible and -resistant) were susceptible to the BICs in disc and MIC tests. Three or more logs of killing were observed at the NCCLS breakpoint concentrations. However, the TEM-1 and TEM-2 producers were resistant in disc tests to ampicillin/sulbactam and amoxycillin/clavulanic acid, and showed intermediate susceptibility to ticarcillin/clavulanic acid. MICs were at or near the breakpoint, but bactericidal activity was only noted at the probable breakpoint concentration of piperacillin/tazobactam. Cefoxitin, cefotaxime, cefpirome and imipenem, but not cephalothin, showed greater bactericidal activity and lower MICs for the TEM-producing strains than the BICs. The viable count of the TEM-1 producer was not reduced in the mouse thigh model by ampicillin/sulbactam or amoxycillin/clavulanic acid, but cefpirome and cefotaxime reduced the viable count by approximately three logs. There was a 50% mortality rate in mice receiving the two BICs. The ampicillin-susceptible ATCC strain of E. coli was killed to a similar degree by all agents tested. Overall, the BICs appeared inferior, in both in-vivo and in-vitro tests to selected cephalosporins and imipenem when tested against reference strains of E. coli producing TEM-1 or TEM-2 beta-lactamase. The large inoculum effect and poor bactericidal activity observed with the BICs suggest they could be less effective in certain clinical situations.
Animals↗
Development of resistance in candida isolates from patients receiving prolonged antifungal therapy.
The impact of prolonged antifungal therapy on the development of resistance was examined in 61 patients with oropharyngeal thrush. Fifty-nine patients had symptomatic human immunodeficiency virus infection, one had lung cancer, and one had metastatic prostate cancer. Cultures of pharyngeal samples from all patients were positive for yeasts and included 57 (93.4%) Candida albicans, 3 (4.9%) Candida glabrata, and 1 (1.6%) Candida krusii. Of 61 patients, 32 (52.5%) were receiving or had recently received antifungal therapy. Clotrimazole was the most commonly prescribed azole, followed by ketoconazole and fluconazole. Two patients had received amphotericin B therapy and one had received flucytosine. The duration of therapy with clotrimazole, ketoconazole, and fluconazole ranged from 3 to 240, 14 to 44, and 7 to 138 days, respectively. There was no overall difference in the susceptibilities of the clinical isolates from treated and untreated patients to amphotericin B, nystatin, flucytosine, clotrimazole, ketoconazole, and fluconazole. A.C. albicans isolate from one patient who had clinically failed on ketoconazole, fluconazole, and amphotericin B was resistant to these drugs. The lack of difference in the susceptibility pattern indicates that clinically significant emergence of resistance does not occur in those patients who receive prolonged antifungal therapy.
Antifungal Agents↗
D-lactic acid production as a monitor of the effectiveness of antimicrobial agents.
Most bacteria at an infection site obtain energy by the breakdown of glucose via microaerophilic or anaerobic pathways and in the process yield various end products. In this study, production of D-lactic acid by Staphylococcus aureus and Escherichia coli was correlated with glucose utilization by bacteria during exposure to antibiotics at subinhibitory, inhibitory, and suprainhibitory concentrations. D-Lactic acid production was further correlated with production of a tissue-destroying enzyme, hyaluronidase, by S. aureus. For E. coli, all agents tested showed dose-related bacterial killing, with the most noticeable being with ampicillin, piperacillin, and ciprofloxacin. Imipenem, ciprofloxacin, and chloramphenicol had the most dose-related effects on D-lactic acid production. With few exceptions, hyaluronidase production correlated well with D-lactic acid production in S. aureus. Subinhibitory concentrations of erythromycin and clindamycin effectively decreased accumulation of D-lactic acid and hyaluronidase. Determination of D-lactic acid production may perhaps serve as a means of independently monitoring the effects of antimicrobial agents on bacterial metabolic activity, which is an important aspect of antimicrobial action that remains relatively unexplored.
Anti-Bacterial Agents↗
Bactericidal effects of antibiotics on slowly growing and nongrowing bacteria.
Antimicrobial agents are most often tested against bacteria in the log phase of multiplication to produce the maximum bactericidal effect. In an infection, bacteria may multiply less optimally. We examined the effects of several classes of antimicrobial agents to determine their actions on gram-positive and gram-negative bacteria during nongrowing and slowly growing phases. Only ciprofloxacin and ofloxacin exhibited bactericidal activity against nongrowing gram-negative bacteria, and no antibiotics were bactericidal (3-order-of-magnitude killing) against Staphylococcus aureus. For the very slowly growing gram-negative bacteria studied, gentamicin (an aminoglycoside), imipenem (a carbapenem), meropenem (a carbapenem), ciprofloxacin (a fluoroquinolone), and ofloxacin (a fluoroquinolone) exhibited up to 5.7 orders of magnitude more killing than piperacillin or cefotaxime. This is in contrast to optimally growing bacteria, in which a wide variety of antibiotic classes produced 99.9% killing. For the gram-positive and gram-negative bacteria we examined, antibiotic killing was greatly dependent on the growth rate. The clinical implications of slow killing by chemotherapeutic agents for established bacterial infections and infections involving foreign bodies are unknown.
4-Quinolones↗
Hypertension and sympathetic hyperactivity induced in rats by high-fat or glucose diets.
Male Sprague-Dawley rats fed either a high-fat diet or a glucose-enriched diet developed higher blood pressure (BP) than rats fed a control diet. After 8 wk of diet treatment systolic BP was 11% higher (P less than 0.01) in fat-fed rats and 7% higher (P less than 0.05) in glucose-fed rats when compared with rats fed the control diet. Rats fed the high-fat diet developed hypertension only when they were allowed to overeat and become obese and hyperinsulinemic. But when their feeding was restricted to prevent obesity and hyperinsulinemia, they remained normotensive. In contrast, elevated BP developed in rats consuming the glucose diet in the absence of obesity or hyperinsulinemia. After 7 wk of diet treatment, urinary norepinephrine excretion was 1.9 +/- 0.1, 1.9 +/- 0.1, and 1.5 +/- 0.1 micrograms/day in rats fed the high-fat, glucose, and control diets, respectively (P less than 0.05 vs. control). Higher norepinephrine excretion in hypertensive rats suggests that increased sympathetic nervous system (SNS) activity might participate in mediating the effects of dietary fat or glucose on BP. In addition, insulin may contribute to raising BP in rats fed the high-fat diet, either directly or indirectly through its stimulatory effect on the SNS. We conclude that chronic feeding of diets high in fat or glucose increases BP and enhances SNS activity in rats.
Animals↗