Prophylactic netilmicin in surgery

Seventy-seven elective or emergency surgical patients were treated with a prophylactic course of netilmicin. Netilmicin (150 mg intramuscularly) was given 1 hour prior to operation and continued 12 hourly until the patient was free of risk of post-operative infection. There was no microbiological or clinical evidence of post-operative infection in general surgical or orthopaedic patients. Netilmicin seems to be less nephrotoxic than other aminoglycosides. Netilmicin serum levels were within expected values. Netilmicin was found to be an effective and well-tolerated antibiotic, and prophylactic treatment shortened the mean patient bed-stay and hence costs incurred.

Microsomal dechlorination of chloroethanes: structure-reactivity relationships

1. The dechlorination rates of six haloethanes were investigated in vitro, using liver microsomes derived from rats treated with Aroclor 1254. 2. The compounds studied were 1,1-dichloroethane, 1,2-dichloroethane, 1,1,1-trichloroethane, 1,1,2,2-tetrachloroethane, 1,1,1-trifluoro-2-chloroethane and hexachloroethane. 3. Dechlorination kinetics (Km and Vmax) were measured at various substrate concentrations. 4. Electron densities in the molecules for which dechlorination data are available were calculated by the MINDO/3 method. 5. A previously reported correlation between electronic parameters and dechlorination rate was not confirmed, but rather a separate relationship between these parameters for each of three structural classes (RCH2Cl, RCHCl2 and RCCl3) was observed. 6. On the basis of these observations, possible reaction mechanisms and their toxicological implications are discussed.

The effects of alterations in the external sodium concentration on human leucocyte sodium and potassium transport in vitro

Human leucocytes incubated in tissue culture fluid of low-sodium concentration (2 mM; iso-osmolarity maintained with choline chloride) reached a new equilibrium within 1 hour and lost approximately 25% of intracellular potassium and 70% of intracellular sodium. The rate constant for ouabain-sensitive sodium efflux fell by more than 50% and the ouabain-insensitive rate constant increased nearly threefold in the low-sodium medium. Total sodium efflux fell in proportion to internal sodium whereas ouabain-insensitive sodium efflux remained unchanged. A reduction in external sodium from 140 to 2 mM was associated with a 75% fall in sodium influx. In the low-sodium medium ouabain-sensitive potassium influx exceeded ouabain-sensitive sodium efflux and no ouabain-sensitive potassium efflux could be demonstrated. Ouabain-insensitive potassium influx and that portion of potassium efflux which is dependent on external potassium fell in parallel in low-sodium cells, suggesting reduced activity of a ouabain-insensitive K:K exchange system.

Phase I trial of pentamethylmelamine: a clinical and pharmacologic study

Pentamethylmelamine (PMM) is a water-soluble monodemethylated derivative of hexamethylmelamine and has a similar spectrum of activity against murine tumors. Unlike hexamethylmelamine, it is suitable for parenteral administration. We conducted a phase I trial of PMM given as a weekly 1-hour iv infusion to 34 extensively pretreated patients with advanced solid tumors. Eight dose levels ranging from 80 to 1500 mg/m2 were studied. A median of three infusions (mean, 4.2; range, 1-24) were given to each patient. Severe nausea and vomiting was dose-limiting at 1500 mg/m2; it was unresponsive to antiemetics and persisted up to 48 hours. Mild to moderately depressed levels of consciousness were seen in one third of the patients at dose levels of greater than or equal to 750 mg/m2. Consistent dose-related myelosuppression was not observed. Hepatocellular toxicity manifested by elevated serum transaminases occurred sporadically, usually in patients with liver metastases, but could not be unequivocally attributed to the drug. No complete or partial tumor responses were noted. At each dose level, the pharmacokinetics of PMM disappearance from plasma were studied in one to three patients with a gas chromatograph-mass spectrometer assay which exclusively measured the unmetabolized drug. The data obtained wee consistent with a two-compartment model of drug distribution, with a mean dose-independent terminal half-life of 143 minutes (range, 43-370). Peak drug levels were directly proportional to dose. The relative lack of myelotoxicity would make PMM an attractive candidate for addition to combination regimens if antitumor activity at tolerable doses could be documented. On this schedule, the recommended dose is 100 mg/m2 for phase II trials.

Increased sodium content and altered sodium transport in thymocytes of spontaneously hypertensive rats

1. The intracellular sodium content and the sodium efflux rate constant have been determined in vitro in thymocytes derived from the Okamato-Aoki strain of spontaneously hypertensive rats. 2. A strong positive correlation between the systolic blood pressure and the sodium content of thymocytes was observed (r = 0.59, n = 39, P less than 0.001). 3. The rate constant for total sodium efflux was negatively correlated with systolic blood pressure (r = -0.43, n = 45, P less than 0.005) and this was due to a fall in the ouabain-sensitive component of sodium efflux. 4. Sodium efflux, influx and the thymocyte potassium content were not related to the blood pressure.

Effect of extracellular potassium on the transport of sodium and potassium in rat thymocytes

1. The effect of extracellular potassium on the transport of sodium and potassium in rat thymocytes has been studied in vitro. 2. A significant increase in the rate constant for total and ouabain-sensitive sodium efflux was demonstrated at an extracellular potassium concentration of 1 mmol/l as compared with that at either 0 or 2 mmol/l. 3. At potassium concentrations below 3 mmol/l ouabain-sensitive sodium influx was observed suggesting sodium-sodium exchange catalysed by the sodium pump. 4. Both total and ouabain-insensitive potassium efflux rose with external potassium. A small ouabain-sensitive potassium efflux was observed at all levels of external potassium studied. 5. Total and ouabain-insensitive potassium influx increased with external potassium, but did not appear to saturate. Ouabain-sensitive potassium influx reached a maximum at an external potassium concentration of 2 mmol/l then decreased with increasing external potassium.

Natural history of malignant lymphomas with divergent histologies at staging evaluation

The pathology and medical records of 515 patients with malignant lymphomas treated at the National Cancer Institute have been reviewed to determine the frequency and natural history of patients who have different histologic diagnoses in various tissue sites at their initial staging evaluation. Of the 101 patients who had multiple tissue sites biopsied, 33 patients had different histologic diagnoses. Eighteen patients had a nodular pattern in one site and a diffuse pattern in another. The final stage and treatment of these 18 patients were similar to that of the 27 patients with multiple identical nodular biopsies and 41 patients with multiple identical diffuse biopsies. However, the 56% complete response rate for patients with both a nodular pattern and a diffuse pattern was intermediate between that achieved in patients with identical nodular biopsies (70%) and identical diffuse biopsies (30%). Median survival for these three groups was as follows: identical nodular biopsies, 53 months; both a nodular and a diffuse pattern, 37 months; and identical diffuse biopsies, 12 months. These results demonstrate that patients with different histologic diagnoses in various sites at staging evaluation are not uncommon and have a unique natural history that should be considered in planning treatment.

The relationship between leucocyte and muscle zinc in health and disease

1. A significant correlation between leucocyte and muscle zinc contents was observed in control patients and in patients with generalized diseases. 2. As muscle contains a large proportion of the whole-body zinc, it is suggested that leucocyte zinc content may be a useful indicator of tissue zinc status.

High-volume intraperitoneal chemotherapy with methotrexate in patients with cancer

The use of high-volume i.p. chemotherapy with methotrexate (7.5 to 50 microM methotrexate administered via peritoneal dialysis technique) was studied in four patients with ovarian cancer and one patient with malignant melanoma. All had tumor localized to the peritoneal cavity or liver. Methotrexate concentration in the peritoneum could be maintained 18- to 36-fold higher than corresponding plasma concentrations using this method, plasma levels remaining in the range of 0.2 to 3 microM. While local toxicity was generally limited and manageable, mild aseptic peritoneal irritation was commonly seen, and one episode of bacterial peritonitis did occur. Because of the concentration difference between peritoneum and the systemic circulation, systemic toxicity was moderate with only six of 29 treatment cycles resulting in myelosuppression. No definite therapeutic benefit was seen, but the tumors of four of five patients had demonstrated resistance to a methotrexate-containing chemotherapeutic regimen prior to this study. Further investigation of this novel treatment modality is warranted. In addition, this study provides the first measurement of peritoneal methotrexate clearance and the ratio of peritoneal in total body clearance.

The effect of antihypertensive therapy on abnormal leucocyte sodium transport in essential hypertension

Sodium transport in leucocytes of essential hypertensives was studied in physiological media. Untreated hypertensives have depressed values for the total and ouabain-sensitive sodium efflux rate constant. Treatment with diuretics abolished this abnormality. These results are compatible with the presence of a circulating inhibitor of sodium transport in essential hypertension.

Sympathetic modulation of mechanoreceptor sensitivity in frog skin

1. Sympathetic effects on the mechanical sensitivity of frog cutaneous mechanoreceptors were examined in vivo. 2. Functionally identified units were tested with repetitive mechanical stimuli of threshold intensity during electrical stimulation of the sympathetic trunk. 3. Sympathetic activity resulted in increased sensitivity for three classes of afferents; slowly adapting compression receptors, slowly adapting stroke receptors, and rapidly adapting stroke receptors. Decreased sensitivity was produced in the fourth class, rapidly adapting compression receptors. 4. Preliminary tets of several possible modes of sympathetic influence indicated that blood flow changes, changes in probe-skin coupling and changes in tissue compliance could not account for the observed changes in receptor sensitivity. Na+ and Cl- ions, secreted by cutaneous mucous glands were found to be possible contributors to the decreased sensitivity of rapidly adapting compression receptors. Direct neurotransmitter action on the receptors, a likely mechanism of sympathetic action, was not tested. 5. The data indicate that systematic changes in cutaneous sensibility occur with modest changes in sympathetic efferent activity. Possible mechanisms of these sympathetic effects are discussed.

Resolution of basic gonococcal outer membrane proteins by nonequilibrium pH gradient electrophoresis

Outer membrane proteins from opaque and transparent colonial variants of strain F62 of Neisseria gonorrhoeae were analyzed by two-dimensional electrophoresis with isoelectric focusing in the first dimension and sodium dodecyl sulphate-polyacrylamide gel electrophoresis in the second. Most of the higher-molecular-weight proteins focused sharply in the acidic region of the gel. In contrast, the principal outer membrane protein, a 31,000-molecular-weight protein, and the opacity-associated proteins remained near the origin (at the basic end of the gel) without focusing. However, when the samples were loaded on the acidic end of an isoelectric focusing gel and subjected to nonequilibrium pH gradient electrophoresis, these proteins behaved as basic proteins. In addition, three distinct opacity-associated heat-modifiable proteins could be identified. No other differences in the protein composition of outer membranes from opaque and transparent variants were apparent. Amino acid analysis of the principal outer membrane protein indicated that its net positive charge may result from partial amidation of its acidic residues. The unexpected observation that the major surface proteins of the gonococcus are basic may have implications for intragonococcal adhesion and for gonococcal interactions with mammalian cells.

Immune-enhanced phagocytosis of Neisseria gonorrhoeae by macrophages: characterization of the major antigens to which opsonins are directed

antisera were prepared in rabbits against whole organisms of colony type 1 Neisseria gonorrhoeae strains F62 and B (fron gonococcal urethritis) and 7122 (a strain typical of those associated with disseminated gonococcal infection), and against purified outer membrane components from the same strains including pili and principal outer membrane protein. Antibody levels to pili, principal outer membrane protein and lipopolysaccharide were determined using a quantitative enzyme-linked immunosorbent assay. Each antiserum was heat-inactivated and tested for opsonic for its homologous strain, and this immune-enhanced phagocytosis was decreased by adsorption with homologous purified outer membrane components: pili greater than lipopolysaccharide greater than principal outer membrane protein. Opsonic activity was approximately equal for antiserum to purified pili and antiserum to the whole organisms for each of the three strains, and purified antibody to pili was highly opsonic. The F(ab')2 fragments of antibody to pili were not opsonic, indicating a role for the Fc receptor on the phagocyte membrane in immune-enhanced phagocytosis of gonococci.

Zinc transport in normal human leucocytes: dependence upon media composition

1. The transport of zinc has been studied in normal human leucocytes incubated in both a tissue culture medium and Krebs buffer. 2. 65Zn influx is characterized by an initial rapid phase followed by a slower influx. 65Zn influx is directly dependent upon the extracellular zinc concentration. 3. Net zinc influx could only be demonstrated in Krebs buffer at zinc concentrations in excess of 4.3 mumol/l and in tissue culture fluid at zinc concentrations in excess of 43.1 mumol/l. 4. A 65Zn efflux rate constant of approximately 1.0 per h was observed in both 4.3 and 15.4 mumol of zinc/l of Krebs buffer or tissue culture fluid. 5. In a zero external zinc Krebs buffer the 65Zn efflux rate constant fell to 0.57 per h and was accompanied by a small net zinc efflux.

Growth and the plasma concentrations of growth hormone and prolactin in chicks: effects of "environmental enrichment", sex and strain

1. The effects of including novel objects in the environment ("environmental enrichment") on body-weight gain, relative body-weight gain, gain: food ratio, plasma growth hormone (GH) and prolactin concentrations in male and female broiler and layer chicks was investigated. 2. Environmental enrichment improved body-weight gain, relative body-weight gain and gain : food ratio but had no effect on circulating GH or prolactin concentrations. 3. Weight gain and gain : food ratio were greater in the broilers than in the layer chicks, while plasma GH and prolactin (females only) concentrations were less. 4. There were no sex differences in weight gain and relative weight gain but gain : food ratio was significantly greater in females than in males. In both strains plasma GH concentrations were higher in male than in female broilers.

Reduced leucocyte zinc in liver disease

The zinc content of peripheral blood leucocytes has been measured in normal controls and in three groups of patients with liver disease. A significant reduction in leucocyte zinc, but not erythrocyte zinc, was observed in patients with primary biliary cirrhosis, alcoholic cirrhosis, and active chronic hepatitis. It is suggested that the nucleated tissues of some patients with liver disease are therefore zinc deficient, and that leucocyte zinc may prove of value in the assessment of the zinc status of such patients.

A sensitive and specific assay for pentamethylmelamine in plasma: applicability to clinical studies

A sensitive and specific procedure for measuring plasma levels of pentamethylmelamine (PMM), a chemotherapeutic agent currently undergoing phase I trials, has been developed. PMM was isolated (recovery greater than 95%) from 3-ml plasma samples by cation exchange chromatography followed by solvent extraction, and was quantitated by selected ion monitoring with a gas chromatograph/mass spectrometer. Deuterium-labeled PMM was synthesized and used as an internal standard; standard curves were prepared by plotting m/e 196/199 ratios versus concentrations, and were linear in the range of 0.05-50.0 microM. The coefficient of variation for repeated measurements was less than 1% at all concentrations studied. To test the applicability of this method to clinical studies, plasma clearances of PMM were measured in two studies in each of three cancer patients receiving 80-mg/m2 doses of PMM as 1-hour iv infusions. Peak plasma concentrations, observed immediately after the end of the infusions, averaged 4.1 microM (SE = 0.6 microM). Plasma elimination was found to be biphasic; a short initial half-life (approximately 27 minutes) was followed by a longer elimination half-life of 133 minutes (SE = 35 minutes). Measurements in two patients indicated that less than 0.1% of the administered PMM was excreted unchanged in the urine in 24 hours, suggesting that hepatic metabolism of PMM may be a major contributor to plasma clearance of the drug in man.