Interferences in a high pressure liquid chromatographic assay of theophylline

Interference by salicylic acid was noted in a high pressure liquid chromatographic assay of theophylline in serum. The acid eluted very close to theophylline in a mobile phase consisting of 0.01 M acetate buffer, pH 4.0, containing 28% methanol on a C-18 reverse-phase column. The two peaks could be resolved by switching to a mobile phase containing 18% methanol, 1.6% acetonitrile, and 1.6% acetic acid in water. However, in this mobile phase traces of the extracting solvent, ethyl acetate, caused a sharpening of the theophylline peak leading to spuriously high results. The problem was overcome by using chloroform to extract the theophylline from serum.

Effects of total plasma concentration and age on tolbutamide plasma protein binding

Tolbutamide plasma protein binding at different total tolbutamide concentrations was determined in 44 healthy, nonsmoking, drug-free men from 23 to 87 yr old. The data showed that unbound drug increased with total tolbutamide plasma concentration and with age, but that neither the binding equilibrium constant nor the number of binding sites correlated with age. The increase in unbound fraction with age could be partially explained by the decrease in albumin concentration in elderly subjects. Results of multiple linear regression analysis indicated that, although age had a considerably greater influence than albumin concentration, total tolbutamide concentration was the most important determinant of the unbound fraction. Thus, both age and total plasma concentration may affect tolbutamide kinetics.

Using the Quantimet 720 image analyzing computer to count nucleolated neurones in the human brain

An approach to the automatic counting of neurones in the human hippocampus is described which uses a modified Quantimet 720 image analyzing computer. Previous work with this and similar machines has attempted to use size alone to discriminate between the various types of cell which are present in any section of central nervous system tissue. Serious errors may then result since agglomerates of small cells and cell fragments can bae confused with single large cells. Instead, 2 electron devices have been designed and built which allow nucleolated neurones, defined as those objects having a grey phase and a black phase both within designated area limits, to be distinguished from all other cells. The mean values for absolute cell numbers and for cell density were within 5% of those obtained by traditional manual methods. The operation of both electronic devices is described and circuit diagrams given for one of them. The other is beyond the scope of this paper, but has been fully reported elsewhere.

Human blood preservation: effect on in vitro protein binding

In vitro plasma protein binding for phenytoin, meperidine, and bretylium tosylate was affected by the type of preserved human blood used for its estimation. Fresh heparinized plasma and serum gave equivalent fractions bound at the concentrations studied for all three drugs. However, the in vitro plasma binding of phenytoin and meperidine decreased 9-50% when estimated in fresh citrated plasma or commercially available lyophylized human serum at the concentration levels investigated. The fraction of bretylium tosylate bound to plasma protein decreased 30-40% when estimated in fresh citrated plasma but was unchanged when estimated in the lyophylized human serum.

An animal model for assessing pain-on-injection of antibiotics

The paw-licking response of rats to a subplantar injection of an antibiotic was used as an indicator of the pain caused by that antibiotic. Good agreement with clinical findings was obtained with cefoxitin, cephalothin, cephradine, cefazolin, cephaloridine, and carbenicillin. Incorporation of a local anesthetic into the diluent of an irritating antibiotic reduced the number of paw-licking episodes. This rat paw model offers a simple and rapid means of estimating pain-on-injection following intramuscular injection of antibiotics to humans and may be applicable to other drugs as well.

Variation with age in the volumes of grey and white matter in the cerebral hemispheres of man: measurements with an image analyser

The total volumes and relative quantities of grey and white matter have been measured in sixty-five normal male and sixty-five normal female cerebral hemispheres. Fixed hemisphere volume was found to fall linearly at 3.5% per decade for men from 641 ml at the age of 20 to 463 ml at the age of 100. For women the decrease was 1.9% per decade from 531 ml at 20 years to 462 ml at 100 years. After correction for the effects of fixation and for the secular increase in brain size, it was concluded that mean hemisphere volume remained roughly constant between the ages of 20 and 50 years (558 ml for men, 474 ml for women). After the age of 50 the mean volume in both sexes fell at about 2% per decade. The ratio of the volumes of grey to white matter was the same for the two sexes at all ages. Its mean value was 1.3 at the age of 20, falling to 1.1 at the age of 50, then rising steadily to over 1.5 at 100 years. It is impossible in practice to correct these measurements for the effects of fixation or secular change. Fourteen hemispheres from thirteen elderly female dements were also measured. The total volume was 18% lower than for an age-matched group of normals, but the ratio of grey to white matter was identical.

A basic program to correct for split cell error in particles classified by the logarithm of their profile areas

A program is presented, written in the BASIC computer language, to correct the errors which occur when cell profiles are counted in thin sections of tissue. Given the numbers of profiles in each of M size classes, and the thickness and area of the sections examined, the program calculates the number of cells in each of these classes per mm3 of tissue. The mathematical method is briefly described and it is shown that a useful level of accuracy may be obtained when the correction procedure is used in the study of non-spherical cells.

Correlation of in vitro susceptibility with in vivo efficacy in mice for cefoxitin in comparison with cephalosporins

Agar minimal inhibitory concentrations and mouse protection test effective doses were determined for each of four beta-lactam antibiotics against each of 12 Gram-negative and 3 Gram-positive bacterial cultures. The beta-lactamase activity of these cultures also was studied. The data were examined to determine whether relative in vivo efficacies could be predicted from relative in vitro activities. Although such predictions were quite accurate for cefoxitin and cefazolin, this was not true for cefamandole or for cephalothin. Such poor predictability was not necessarily associated with the susceptibility of these cephalosporins to hydrolysis by bacterial beta-lactamases. Although the clinical significance of these observations is not known, these data emphasize that relative in vitro activities should be used only with caution to estimate in vivo efficacies, since not all compounds show the excellent predictability observed here for cefazolin and cefoxitin.

Urinary metabolites of 3a,4,5,6,7,7a-hexahydro-3-(1-methyl-5-nitro-1H-imidazol-2-yl)-1,2-benzisoxazole in the dog

The antiprotozoal drug 3a,4,5,6,7,7a-hexahydro-3-(1-methyl-5-nitro-1H-imidazol-2-yl)-1,2-benzisoxazole (I), which exhibits activity against trypanosomiasis, is also antibacterial in vivo. Since the urine from a dog dosed with I showed a broader spectrum of antibacterial activity than I itself, metabolites from this urine were isolated and partially characterized. The metabolites were mono- and dihydroxy-substituted species with the hydroxyl groups on carbons 4--7 of the hexahydrobenzisoxazole ring. These observations led to the synthesis of several such hydroxy derivatives of I, and their properties fully supported the proposed positions of metabolic hydroxylation. One synthetic compound, the 6,7-cis-dihydroxy compound, exhibited higher antibacterial activity against Salmonella schottmuelleri in mice and greater trypanocidal activity in vivo against Trypanosoma cruzi (Brazil strain) than I.

Thienamycin, a new beta-lactam antibiotic. I. Discovery, taxonomy, isolation and physical properties

A new beta-lactam antibiotic, named thienamycin, was discovered in culture broths of Streptomyces MA4297. The producing organism, subsequently determined to be a hitherto unrecognized species, is designated Streptomyces cattleya (NRRL 8057). The antibiotic was isolated by adsorption on Dowex 50, passage through Dowex 1, further chromatography on Dowex 50 and Bio-Gel P2, and final purification and desalting on XAD-2. Thienamycin is zwitterionic, has the elemental composition C11H16N2O4S (M.W. = 272.18) and possesses a distinctive UV absorption (lambda max = 297 nm, epsilon = 7,900). Its beta-lactam is unusually sensitive to hydrolysis above pH8 and to reaction with nucleophiles such as hydroxylamine, cysteine and, to a lesser degree, the primary amine of the antibiotic itself. The latter reaction results in accelerated inactivation at high antibiotic concentrations.

Cefoxitin and cephamycins: microbiological studies

The cephamycins are a family of beta-lactam antibiotics that are produced by actinomycetes and are structurally similar to the cephalosporins. They are characterized by the presence of a 7-alpha-methoxyl group, which confers unusually high resistance to beta-lactamases. Cefoxitin, the first semisynthetic cephamycin, is resistant to almost all beta-lactamases. Cefoxitin retains the 3-carbamoyl group of cephamycin C and thus has excellent metabolic stability. Cefoxitin is bactericidal and almost devoid of any inoculum effect. Active against many cephalothin-resistant gram-negative bacteria, cefoxitin demonstrates a very broad spectrum that includes indole-positive Proteus and many strains of Serratia. In contrast to that of the cephalosporins, cefoxitin's spectrum of activity against anaerobic pathogens includes Bacteroides fragilis. The therapeutic effectiveness of cefoxitin in experimental infections in mice confirms the excellent characteristics of this semisynthetic cephamycin and indicates that it should be a very valuable agent for treatment of bacterial infections.

The enhancement of beta-lactam antibiotic therapy by novobiocin

Novobiocin demonstrates an effect similar to that of probenecid (the "probenecid effect") in enhancing the therapeutic efficacy of antibiotics excreted mainly by the renal tubules. The ability of cefoxitin, cephalexin, cephalothin and penicillin G to protect mice against infection with Salmonella schottmuelleri was enhanced 2- to 3-fold when the animals were given oral doses of either probenecid or of novobiocin. The efficacy of cephaloridine, excreted mainly by glomerular filtration, was not enhanced by either probenecid or by novobiocin.

Evidence for a secular increase in human brain weight during the past century

7397 post-mortem records have been studied. These comphrhend all 20- to 50-year old men and women who had been autopsied in The London Hospital since 1907. Fresh brain weight, body weight and height were abstracted and analysed statistically according to sex and to year of birth, any person with a cerebral or skeletal abnormality having been excluded. Fresh brain weight in men increased gradually by an average of 0-66 g per year from a mean of 1372 g for those born in 1860 to 1424 g in 1940-a total of 52 g. The weight of the female brain increased by 0-28 g per year from 1242 g to 1265 g over the same period. No appreciable rise in fresh brain weight occurred in women until 1900, after which date the increase was of the same order in the two sexes. Evidence of secular increases in body height and in body weight is also given.

Fosfomycin treatment of Haemophilus influenzae infection in mice

Haemophilus influenzae is an important pathogen in respiratory infections in children and often is implicated in otitis media. It is sensitive in vitro to a number of antibiotics, some of which are used clinically for the treatment of such infections. We have checked the in vitro sensitivity of a type b strain of H. influenzae. When tested in Levinthal's broth prepared with laked rabbit blood, the culture was most sensitive to tetracycline, ampicillin and penicillin and was somewhat less sensitive to cephalothin, fosfomycin, cephaloridine, and chloramphenicol. However, when this same strain was used to infect mice, fosfomycin was more active than ampicillin, tetracycline, chloramphenicol, penicillin or the cephalosporins.

Fosfomycin: Laboratory studies

Fosfomycin, a nontoxic broad-spectrum antibiotic, different in structure from all previously described antibiotics, acts selectively by inhibiting cell wall formation. It was overlooked during many years of screening because of antagonism by culture medium ingredients and frequent occurrence of resistant mutants. It is effective in many because the neutralizing substances are not present and resistant mutants of most species are avirulent. Fosfomycin has favorable pharmacologic characteristics. It is not cross resistant, does not show antagonism, and has been used successfully in combinations. An insoluble calcium salt is used in oral formulation and a sodium salt for parenteral administration. Overall success rates of 86% were reported with 1,000 patients in Spain and 79% in Japan.

Cell counting in the human brain: traditional and electronic methods

Whether or not a proportion of nerve cells disappears from the human brain during adult life remains a controversial question 80 years after it was first asked. In this paper the authors review briefly the reasons for this uncertainty and describe an attempt to find an answer in so far as the cerebellar Purkinje cells are concerned. A loss of about 2·5% per decade was identified. The problems raised by cell counting in the cerebral cortex are outlined and a new method is described which may prove suitable for neuronal counting in these regions using an image analysing system.

Cefoxitin, a semisynthetic cephamycin antibiotic: in vivo evaluation

Cefoxitin, 3-carbamoyloxymethyl-7-alpha-methoxy-7-[2-(2-thienyl)acetamido]-3-cephem-4- carboxylic acid, a semisynthetic cephamycin antibiotic shown to have broad-spectrum activity in vitro, is active also in vivo against a wide variety of bacteria including penicillin-resistant staphylococci. It is, however, particularly effective against gram-negative organisms including strains of indole-positive Proteus against which cephalothin and cephaloridine are ineffective. When cefoxitin is given subcutaneously, concentrations in mouse blood, urine, and other tissues are higher than those seen for cephalothin. Higher concentrations in the blood and greater therapeutic efficacy are achieved with cefoxitin when it is given with probenecid. For this reason it is believed that cefoxitin is excreted mainly by way of the renal tubules. The data indicate that cefoxitin has potential as a therapeutically useful antibiotic.

Cephamycins, a new family of beta-lactam antibiotics. IV. In vivo studies

Cephamycin A was found to be more active in vivo than cephamycin B. In comparison with cephamycin C, cephamycin A was more active against gram-positive organisms but less active against gram-negative organisms. Given subcutaneously, cephamycin C had good in vivo gram-negative activity, comparing favorably with cephalothin and cephaloridine against cephalosporin-susceptible organisms. In general, against the gram-negative organisms, it was more active than cephalothin or cephalosporin C and about as active as cephaloridine. In addition, cephamycin C protected mice against beta-lactamase-producing Proteus cultures, including clinically isolated strains. The compound is remarkably nontoxic. Cephamycin C was detected in the serum and recovered from the urine of treated mice to about the same extent as cephaloridine. Like cephaloridine and cephalosporin C, cephamycin C must be excreted mainly by glomerular filtration, because the use of probenecid did not enhance the therapeutic effectiveness nor concentrations of these agents in the sera of treated mice.

Cephamycins, a new family of beta-lactam antibiotics. 3. In vitro studies

Cephamycins A, B, and C are naturally produced cephalosporin-type antibiotics. Although A and B were found to be more active than C against gram-positive organisms, they were not so active against such strains as are cephalosporin C or the semisynthetic antibiotics cephaloridine and cephalothin. Against gram-negative organisms, cephamycin C was more active than A or B and, in general, was as active as the cephalosporins. In addition, cephamycin C was active in vitro against clinically isolated strains resistant to the cephalosporins, such as Proteus, Providencia, and Escherichia coli. The in vitro antibacterial activity of cephamycin C, cephalothin, and cephaloridine is primarily bactericidal. A 10,000-fold increase in inoculum of a strain of Proteus mirabilis resulted in 200-fold or greater increases in minimal inhibitory and minimal bactericidal end points of cephalothin and cephaloridine, but only 10- and 16-fold increases, respectively, for cephamycin C. After 15 passages through antibiotic-containing broths, during which time a culture of E. coli showed an increase in minimal inhibitory concentrations of streptomycin of >1,000-fold, end points for cephamycin C increased 4-fold, for cephalothin, 1.5-to 6-fold, and for cephaloridine, 128-fold.

Antibacterial activity of ronidazole

Ronidazole, a nitroimidazole that has in vivo antiparasitic and antimycoplasmal activity, also has some in vivo antibacterial activity.