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Biomedical subjects

H C Neu

Publications and source records attributed to H C Neu.

At least 487 records · Page 27Linked to original sources
PubMed1967

Effect of ethylenediaminetetraacetic acid-Tris(hydroxymethyl)aminomethane on release of the acid-soluble nucleotide pool and on breakdown of ribosomal ribonucleic acid in Escherichia coli.

Brief treatment of Escherichia coli with 2 x 10(-4)m ethylenediaminetetraacetic acid (EDTA)-0.12 m tris(hydroxymethyl)aminomethane (Tris), pH 8.0, or 0.12 m Tris alone resulted in the release of the acid-soluble nucleotide pool at 3 or 23 C. Exposure to EDTA-Tris for up to 90 min at 3 C did not result in the release of increasing amounts of 260-mmu-absorbing material. At 23 and 37 C, EDTA-Tris resulted in a steady increase in acid-soluble 260-mmu-absorbing material. Previous growth environment did not alter the release. There appeared to be degradation of 23S ribonucleic acid (RNA) after 10 min of exposure at 23 C. In addition, there was degradation of nucleotides to nucleosides and bases. This occured either within the cells with altered permeability or in the periplasmic space. This occurred in the presence of EDTA and Tris but was not seen with EDTA-phosphate. The mechanism of this degradation is unclear, since it occurs in ribonuclease I-deficient strains. Exposure to Tris buffer for long periods of time at 23 C resulted in release of the nucleotide pool and in degradation of RNA and nucleotides. These studies point out that the EDTA-Tris effect on E. coli must be divided into two parts, an early (4 to 5 min) change in permeability and a later phase of actual RNA breakdown and nucleotide degradation. Studies utilizing EDTA and Tris as agents altering permeability must thus be viewed with caution. Although the cells are viable, they have lost their acid-soluble nucleotide pool and have undergone degradation of some ribosomal RNA.

Buffers↗
PubMed1967

Release of surface enzymes in Enterobacteriaceae by osmotic shock.

The process of osmotic shock, which has been used to release degradative enzymes from Escherichia coli, can be applied successfully to other members of the Enterobacteriaceae. Cyclic phosphodiesterase (3'-nucleotidase), 5'-nucleotidase (diphosphate sugar hydrolase), acid hexose phosphatase, and acid phenyl phosphatase are released from Shigella, Enterobacter, Citrobacter, and Serratia strains. Some strains of Salmonella also release these enzymes. Members of Proteus and Providencia groups fail to release enzymes when subjected to osmotic shock and do not show a lag in regrowth, although they do release their acid-soluble nucleotide pools. In contrast to E. coli, release of enzymes from other members of the Enterobacteriaceae studied is affected by growth conditions and strain of organism. None of the organisms was as stable to osmotic shock in exponential phase of growth as was E. coli. Exponential-phase cells of Shigella, Enterobacter, and Citrobacter could be shocked only with 0.5 mm MgCl(2) to prevent irreparable damage to the cells. These observations suggest that this group of degradative enzymes is probably loosely bound to the cytoplasmic membrane through the mediation of divalent cations.

Acid Phosphatase↗
PubMedDate not supplied

Bacampicillin hydrochloride: chemistry, pharmacology, and clinical use.

Bacampicillin hydrochloride is an orally administered ester of ampicillin that is rapidly and completely hydrolyzed in vivo to ampicillin. The most notable advantage of bacampicillin over ampicillin is its superior bioavailability--bacampicillin achieves significantly higher blood and tissue levels and attains peak blood levels more rapidly than equimolar doses of oral ampicillin. In addition, the percentage of an oral dose of ampicillin that is absorbed decreases sharply as the size of the dose is increased from 500 mg to 2 g; this phenomenon is not observed with equipotent doses of bacampicillin. The enhanced absorption of bacampicillin in the upper gastrointestinal tract results in a frequency of diarrhea that appears to be markedly lower than that of ampicillin and similar to that observed with amoxicillin. Apart from the sizable differences between bacampicillin and ampicillin with regard to oral absorption, the pharmacokinetic and pharmacologic profiles of these two agents are essentially identical. Twice daily dosing (pulse dosing) with bacampicillin has been shown in numerous clinical trials to be of equivalent efficacy to ampicillin given four times daily or amoxicillin given three times daily in the treatment of infections of the upper respiratory tract, lower respiratory tract, skin and soft tissues, and urinary tract. The unanswered question is whether twice daily ampicillin or amoxicillin would yield similar results.

Absorption↗
PubMedDate not supplied

Ceftizoxime: a beta-lactamase-stable, broad-spectrum cephalosporin. Pharmacokinetics, adverse effects and clinical use.

Ceftizoxime is an iminomethoxy aminothiazolyl cephalosporin that inhibits a wide variety of aerobic, anaerobic gram-positive and gram-negative bacteria. The majority of Enterobacteriaceae are inhibited by less than or equal to 1 microgram/ml as are streptococcal species with the exception of Streptococcus faecalis. Staphylococcus aureus are inhibited by 3-8 micrograms/ml, while methicillin-resistant. aureus are resistant. Bacteroides fragilis are inhibited by 16-64 micrograms/ml. It inhibits Pseudomonas aeruginosa at usually achievable concentrations. Ceftizoxime is overall similar in antibacterial activity to cefotaxime and moxalactam. Ceftizoxime is not hydrolyzed by common plasmid and chromosomal beta-lactamases. Serum levels of ceftizoxime after intramuscular and intravenous injection are similar to those of cefotaxime and moxalactam. The half-life is 1.6 to 1.9 hours in normal individuals. The compound is not metabolized and is cleared from the body by glomerular filtration. Ceftizoxime enters most body fluids, including the cerebrospinal fluid, to produce therapeutic concentrations against clinically important bacteria. Ceftizoxime accumulates in the presence of renal failure, but it is removed from the body by hemodialysis and peritoneal dialysis. Ceftizoxime has proved to be an effective chemotherapeutic agent when used as treatment for pneumonia, urinary tract infections, osteomyelitis, septic arthritis, meningitis, peritonitis, gonorrhea, including penicillinase-producing isolates, and gynecological infections. No major adverse reactions have been associated with the use of ceftizoxime and it has produced neither disulfram -like reactions nor bleeding.

Adolescent↗
PubMedDate not supplied

Amdinocillin: a novel penicillin. Antibacterial activity, pharmacology and clinical use.

Amdinocillin is a novel penicillin whose antibacterial activity is derived from its ability to bind specifically and avidly to Penicillin Binding Protein-2 (PBP 2). Other beta-lactams bind almost exclusively to PBPs 1 and 3. This unique feature has prompted many investigators to predict that amdinocillin would aggressively synergize with other antimicrobials, particularly other beta-lactams. Certain features of these predictions have been realized. Amdinocillin is active alone against many gram-negative organisms. Pseudomonas and non-fermenting gram-negative bacteria, however, are usually resistant. Amdinocillin, in combination with many beta-lactams, exhibits marked synergy against many enterobacteriaceae. No such synergy can be demonstrated for gram-positive organisms or pseudomonas species. Amdinocillin is not beta-lactamase stable. Organisms which produce high levels of plasma-mediated beta-lactamase are resistant to the drug. Amdinocillin is widely distributed to most tissues of the body. It is removed by renal tubular secretion which results in prodigious levels of the drug in the urine. Co-administration of probenecid results in markedly elevated plasma levels of amdinocillin and delays its excretion. Amdinocillin has a plasma half-life of about one hour in patients with grossly normal renal function. Its half-life increases to 3 to 6 hours in anephric patients. The spectrum of adverse reactions observed with amdinocillin is similar to that of other penicillins. Amdinocillin, as a single agent, is effective in the treatment of urinary tract infections caused by susceptible strains of E. coli and klebsiella and enterobacter species. When amdinocillin is used in concert with other antimicrobials, synergy can frequently be demonstrated but it is essentially limited to gram-negative aerobic organisms. At present, insufficient data are available to precisely profile the utility of amdinocillin, either alone or in combination, in the treatment of systemic infections.

Amdinocillin↗
PubMedDate not supplied

The use of moxalactam in the treatment of serious infections due to multi-resistant organisms.

Moxalactam was evaluated as the sole therapy of 45 episodes of infection in 41 patients due primarily to bacteria resistant to older antibiotics. Infections included bacteremias, pulmonary, skin and soft tissue infections, osteomyelitis, and meningitis. Clinical and bacteriological cure was achieved in 69% of infections. Cure was achieved with moxalactam in patients infected with cefazolin-resistant, carbenicillin-resistant, chloramphenicol and gentamicin-resistant organisms. Although adverse reactions were generally mild, diarrhea developed in five patients, a major increase in prothrombin time and bleeding in three patients and a disulfiram reaction in two patients.

Adolescent↗
PubMedDate not supplied

The in vitro activity and beta-lactamase stability of cefpirome (HR 810), a pyridine cephalosporin agent active against staphylococci, Enterobacteriaceae and Pseudomonas aeruginosa.

The in vitro activity of cefpirome, a new cyclopyridinium cephalosporin, was evaluated against 947 aerobic and anaerobic bacteria. Cefpirome inhibited 90% of Escherichia coli, Klebsiella spp., Citrobacter diversus, Morganella morganii, Proteus vulgaris, Proteus mirabilis, Aeromonas spp., Salmonella spp., Shigella spp. and Haemophilus and Neisseria species at less than or equal to 0.4 mg/l. It had activity comparable to that of cefotaxime, ceftizoxime, ceftazidime, aztreonam, and moxalactam against these species. Only a few Citrobacter freundii, Enterobacter spp. and Serratia marcescens had MICs above 3.1 mg/l. The activity of cefpirome against Pseudomonas aeruginosa, 90% MIC of 12.5 mg/l, was superior to piperacillin, moxalactam, cefotaxime and cefoperazone. The 90% MIC against Staphylococcus aureus was 0.8 mg/l, but methicillin-resistant staphylococci were not inhibited. Cefpirome was not significantly hydrolyzed by most plasmid beta-lactamases (TEM, SHV-1, PSE, OXA) nor by chromosomal enzymes (P99, Branhamella catarrhalis, K1). Cefpirome did not inhibit chromosomal or plasmid beta-lactamases. Mice systemically infected with E. coli, Klebsiella pneumoniae, P. aeruginosa and S. aureus were protected by concentrations of cefpirome ranging from 0.85 mg/kg for K. pneumoniae to 4.467 mg/kg for P. aeruginosa.

Animals↗
PubMedDate not supplied

Streptococcus agalactiae (group B) endocarditis--a description of twelve cases and review of the literature.

The group B streptococcus has been shown to be a major cause of meningitis in the newborn and an occasional cause of endocarditis and sepsis in postpartum women. Little attention has been devoted to this organism as a cause of bacterial endocarditis. Twelve patients with group B streptococcal endocarditis were seen at The Presbyterian Hospital, New York, NY, between 1974 and 1985. There were seven women, five men. Ages ranged from 32 to 81 years. Serious underlying disease was present in all - diabetes mellitus in seven, carcinoma in three (bladder in two, and breast in one), alcoholism in three, malnutrition in two, heroin addiction in one, tuberculosis in one, serious prior valvular heart disease in two. The aortic valve was affected in four patients - mitral in two, mitral and aortic in one, tricuspid in four, unknown in one. The presentation was acute in seven patients. Metastatic infection occurred in seven, heart failure in six, major emboli in four, septic pericarditis in one, myocardial abscess in one. The group B streptococcus should be considered as a pathogen capable of causing acute endocarditis in certain patients with defects of host defense, particularly patients with diabetes mellitus, carcinoma or alcoholism. Cardiac surgery may be necessary in these patients due to the rapid destruction of the valves which occurs, in spite of the fact that the organisms are usually highly susceptible to penicillin.

Adult↗
PubMedDate not supplied

Comparative in vitro activity of a new fluorinated 4-quinolone, QA-241.

The in vitro activity of a new quinolone, QA-241, 9-fluoro-6,7-dihydro-5-methyl-8(4-methyl-1-piperazinyl) -1,7-dioxo-1 H,5H-benzo[ii]quinolizine-2-carboxylic hydrochloride, was compared with those of ciprofloxacin, ofloxacin, ceftazidime, imipenem, and gentamicin. QA-241 inhibited 90% of isolates of Enterobacteriaceae at a concentration of less than or equal to 2 micrograms/ml. It was two-fold and four- to 16-fold less active than ofloxacin and ciprofloxacin, respectively. QA-241 was less active against Pseudomonas aeruginosa and other Pseudomonas species than ciprofloxacin. Most Haemophilus influenzae and Neisseria gonorrhoeae isolates were inhibited at concentrations of less than or equal to 0.03 microgram/ml. The MIC for 90% of Staphylococcus aureus isolates, including methicillin-resistant S. aureus, was 1 microgram/ml, as was that for S. epidermidis. For streptococci, including Streptococcus faecalis, the MIC90 was 4 micrograms/ml. QA-241 had minimal activity against anaerobic species. The frequency of spontaneous resistance was less than 10(-9) for members of the Enterobacteriaceae. However, resistant strains could be isolated by repeated subculture. Similar to other quinolones, its activity was less at an acid pH and in the presence of high Mg2+ concentrations. QA-241 showed a good postantibiotic suppressive effect on Escherichia coli.

Anti-Bacterial Agents↗
PubMedDate not supplied

The use of cefepime (BMY 28142) to treat respiratory infections.

Cefepime, an aminothiazolyl cephalosporin active against Gram-positive and Gram-negative bacteria, was used at a dose of 1 g every 12 hours to treat respiratory and other infections in 29 patients. All 19 patients from whom an organism was cultured responded clinically and microbiologically. The patients had underlying risk factors of human immune virus positive status, 58%, and chronic lung disease, 19%. Cefepime was well tolerated. Organisms eradicated included Streptococcus pneumoniae and Haemophilus influenzae. Further study will define cefepime's role in hospital-acquired respiratory infection.

Adult↗