Immunoreactive calbindin-D9K localization in matrix vesicle-initiated calcification in rat epiphyseal cartilage: an immunoelectron microscope study

Calbindin-D9K immunoreactivity was localized by electron microscopy in rat calcifying epiphyseal plate cartilage. Antigen-antibody reaction sites were visualized by the presence of protein A-gold complex particles on undecalcified material embedded in Lowicryl K4M. Immunoreactive calbindin-D9K was found in the hyaloplasm of hypertrophic chondrocytes and inside and at the ends of their cell processes. It was localized outside the cells, inside matrix vesicles (MVs), often against the inner face of the delimiting membrane, and inside the trilaminar membrane. Immunoreactive calbindin-D9K appeared to be extruded from the chondrocytes into the matrix vesicles when the latter were formed during the budding of cell processes. In calcifying MVs, gold particles were detected over the needle-shaped crystallites and often over the crystallites lying against the inner leaflet of the vesicular membrane. At a later stage of matrix vesicle calcification after MV membrane disruption, the number of gold particles remained unchanged over the clusters of crystallites at the loci from which the crystallites appeared to have grown and radiated. At a yet more advanced stage of calcification, they remained in the same areas, which were limited to the lateral edges of calcified cartilage longitudinal septa. These results suggest that immunoreactive calbindin-D9K plays a role in calcium input to matrix vesicles and may be involved in matrix vesicle calcification, perhaps in the initial event of matrix vesicle crystal nucleation.

Immunological characterization, developmental pattern and vitamin-D-dependency of calbindin D-28 K in rat teeth ameloblasts

It has been suggested that vitamin D is involved in the process of cell differentiation and extracellular mineralization during tooth development. One of the best-defined molecular markers of the action of vitamin D is a calcium-binding protein of Mr 28,000 called calbindin D-28 K (CaBP 28 K). Since this protein is present in growing teeth, we have examined its synthesis in teeth from vitamin D-replete and -deplete rats by Western blotting and immunocytochemistry with an antiserum to CaBP 28 K purified from rat kidney. The CaBP 28 K present in the enamel organ is a single molecular species migrating near 30 k Da, similarly to the kidney protein. The differentiation and maturation of odontogenic cells were followed during early postnatal development (2-12 days) in rat molars. At the light-microscope level, CaBP 28 K was only found in a single cell-type, the ameloblasts. The expression of this protein appeared to be developmentally controlled, since its distribution varied with the cell stage and the functional steps of amelogenesis. The protein was localized in the basal compartment of ameloblasts from the presecretory stage. During the early secretory stage, the concentration of cytoplasmic CaBP 28 K formed a gradient from the apical to the basal pole of the ameloblasts. Staining appeared homogeneous in the cytoplasm of later secretory ameloblasts. CaBP 28 K was discontinuously distributed during the maturation stage. This discontinuity might be related to cyclical changes in mature ameloblasts. In all stages, ameloblasts from vitamin-D-deficient rats appeared depleted of CaBP 28 K.

Calbindin-D9K immunolocalization and vitamin D-dependence in the bone of growing and adult rats

This report presents evidence for the presence of the vitamin D-dependent calcium-binding protein, calbindin-D9K, in bone cells and matrix. In undecalcified frozen sections of growing and adult rat bone, calbindin-D9K was immunohistochemically localized in trabecular bone of the epiphysis and metaphysis and in cortical bone of the diaphysis. It was found within the cytoplasm of osteocytes, of osteoblasts lining the osteoid, and osteoblasts inside the osteoid seams. It was also found in the osteoblast processes and the anastomosed reticulum of the processes connecting the osteocytes with each other. Extracellularly, calbindin-D9K immunoreactivity was present in compact cortical bone in the areas of the mineralized matrix surrounding the osteocyte lacunae, and in the pericanalicular walls containing the cell processes. Calbindin-D9K immunoreactivity was low or absent from the cytoplasm of osteocytes in trabecular bone from severely vitamin D-deficient rats and restored in vitamin D-deficient rats given a single dose of 1,25(OH)2-VitD3. Thus, the synthesis of immunoreactive calbindin-D9K by osteoblasts and osteocytes in trabecular bone is vitamin D-dependent. The presence of immunoreactive calbindin-D9K in the osteocytes and their cell processes suggests that this calcium-binding protein is involved in the calcium fluxes regulating bone calcium homeostasis. Its localization in osteoblasts involved in bone formation and in their cell processes suggests that it has a role in the calcium transport from these cells towards the sites of active bone mineralization.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics of cefotaxime and desacetylcefotaxime in the newborn

A study of the pharmacokinetic parameters of cefotaxime (CTX) and desacetylcefotaxime (dCTX) in newborns was conducted; the former is commonly used for neonatal infections. The elimination half life of CTX correlated with gestational age (GA) and postnatal age (PNA). Elimination of dCTX was longer permitting a synergistic or additive effect with CTX against Gram-negative bacteria. CTX is indicated in the treatment of neonatal sepsis because of the increasing resistance of Escherichia coli to ampicillin and its good efficacy against group B streptococcus.

The non-human primate: a possible model for human genetically determined polymorphisms in oxidative drug metabolism

Genetic polymorphisms of drug oxidation are major determinants of interindividual variations in drug response and toxicity. Many animal models, including rats, have been used for clinical investigations of pharmacogenetics. However, because of large interspecies differences, these data are difficult to extrapolate to humans. We therefore phenotyped 64 non-human primates for debrisoquine and mephenytoin polymorphisms and identified poor metabolizers of both drugs. The frequency of poor metabolizers was 14% for debrisoquine (95% confidence limits, 6.5-25%) and 3% for mephenytoin (95% confidence limits, 0.5-10%). If family studies demonstrate a genetic basis for the two independent defects, this animal species could be used for in vivo and in vitro pharmacogenetic investigations.

Early synergistic killing activity at concentrations attainable in CSF of amoxicillin or cefotaxime and aminoglycosides against Haemophilus influenzae

Rapid eradication of bacteria from the CSF is critical for the outcome of Haemophilus influenzae meningitis in children. In 15 patients studied, the mean H. influenzae colony counts in CSF were 10(5) CFU/ml (range: 10(2) to 10(9) CFU/ml). Time-kill curves were determined for amoxicillin and cefotaxime alone and in combination with gentamicin or amikacin, against 60 clinical isolates of H. influenzae at concentrations equivalent to those found in CSF following systemic administration. Against beta-lactamase-negative strains (n = 44) a bactericidal effect was observed at 18 h for amoxicillin alone, at 5 h for amoxicillin plus aminoglycosides and at 2.5 h for cefotaxime with or without aminoglycosides. Against beta-lactamase-positive strains a bactericidal effect was observed at 18 h for cefotaxime, at 5 h for amoxicillin plus aminoglycosides and at 2.5 h for cefotaxime plus aminoglycosides. It appears that despite low concentrations of gentamicin or amikacin in the CSF, the accelerated killing of H. influenzae provides a rationale for the initial use of the combination of cefotaxime and aminoglycosides in the initial treatment of H. influenzae meningitis.

Phenotyping polymorphic drug metabolism in the French Caucasian population

Because of the large interethnic differences in the incidence of poor metabolizer phenotypes, French Caucasians have been studied for two independent polymorphisms, debrisoquine/dextromethorphan and mephenytoin metabolism. One hundred and thirty-two unrelated French Caucasians were phenotyped using oral doses of dextromethorphan 20 mg and mephenytoin 100 mg. Individual dextrorphan excretion over 8 h and the dextromethorphan/dextrorphan metabolic ratio were calculated. Extensive metabolizers were taken as subjects with a high dextrorphan output (15.56 mumol/8 h) and a low metabolic ratio (0.0023), and poor metabolizers were those with a low dextrorphan output (0.39 mumol/8 h) and a high metabolic ratio (7.00). Individual 4-hydroxymephenytoin excretion and mephenytoin hydroxylation indices were also determined. Extensive metabolizers eliminated large amounts of 4 hydroxymephenytoin (133.2 mumol/8 h) and had a hydroxylation index of 1.99, and poor metabolizers, because of impaired mephenytoin metabolism, had a high hydroxylation index (277). The incidence of the poor metabolizer phenotype was 3% for dextromethorphan (95% confidence limits 0.5%-8.5%) and 6% for mephenytoin (95% confidence limits 2%-12.5%).

[Evaluation of the bactericidal curves of beta-lactam and aminoglycoside combinations at the concentrations obtained in the cerebrospinal fluid in Haemophilus influenzae meningitis]

The prognosis and sequelae of patients with Haemophilus influenzae meningitis were related to concentrations of bacteria in the cerebrospinal fluid (CSF). Rapid bacterial killing and rapid reduction of organisms in vivo in CSF are critical to the outcome. In our patients colony counts of Haemophilus influenzae in CSF were 10(2)/ml - 10(9)/ml (mean 10(5)/ml). Killing kinetics were determined for amoxicillin and cefotaxime, alone and in combination with amikacin, against 35 clinical strains of Haemophilus influenzae (43% beta-lactamase-positive) at concentrations of these antibiotics comparable to those attained in the CSF following systemic administration. Antibiotics concentrations were: amoxicillin: 5 mg/ml, cefotaxime: 3.8 mg/l, amikacin: 1.8 mg/l. Mean killing curves with beta-lactamase-negative strains showed that a bactericidal effect was observed at 18 h for amoxicillin, at 5 h for cefotaxime, at 5 h for amoxicillin plus amikacin and at 2 h 30 for cefotaxime plus amikacin. Against beta-lactamase-positive strains a bactericidal effect was observed at 5 h for cefotaxime, at 2 h 30 for cefotaxime plus amikacin and at 18 h for amoxicillin plus amikacin. The finding of significantly increased killing rates of Haemophilus influenzae by amikacin at low concentration in the presence of either ampicillin or cefotaxime suggests that combined therapy may be beneficial in the treatment of meningitis caused by Haemophilus influenzae.

Absence of plasma prostacyclin stimulating activity deficiency in hemolytic uremic syndrome

We compared the effect of plasma from 19 children with hemolytic uremic syndrome (HUS) on prostacyclin (PGI2) production by fresh rat aortic rings to the effect of plasma from 17 age- and sex-matched normal children, taking into account the PGI2 baseline aortic production (PGI2 release in presence of buffer, 21 determinations). After 10, 20, 30, 40, and 60 minutes incubation of rat aortic tissue with either plasma or buffer, the presence of PGI2 was studied by measuring by radioimmunoassay (RIA) the concentration of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha). 6-keto-PGF1 alpha production increased with time in the two groups of plasma samples and in the presence of buffer, but 6-keto-PGF1 alpha production (ng/mg dried tissue) after 30 minutes incubation and mean 6-keto-PGF1 alpha production (slope of regression line, ng/mg/min) were significantly (P less than 0.01) lower in the presence of normal plasma compared with buffer, and significantly (P less than 0.01) higher in the presence of HUS plasma compared with normal plasma. There was no significant difference between buffer and HUS plasma. We conclude that, under our experimental conditions, normal plasma had an inhibitory activity on 6-keto-PGF1 alpha production by rat aorta. This inhibitory activity was absent in HUS plasma.

[Clinical study and effect of nitroxoline on fecal flora in children]

Twelve children (mean age: 4) are treated in practice office with nitroxoline (200 mg/kg/24 h) during 10 days for urinary tract infection. A study on the effect of nitroxoline against the fecal flora is undertaken in a group of 21 children who receive nitroxoline during 4 days or a long period. Bacteriological and clinical efficacy is checked when urinary concentrations of nitroxoline are greater than 16 mg/l. The results show 8 clinical and bacteriological success one true failure and 3 failure due to a non-compliance to the treatment. No qualitative and quantitative modification of the fecal flora is observed after treatment with nitroxoline.

[Importance of the study of the minimal bactericidal time of serum in the choice of optimal treatment of neonatal septicemias]

Rapid eradication of bacteria in bloodstream is critical for the outcome in neonatal bacterial sepsis. Two groups of neonates with E. coli K1 sepsis without purulent meningitis were studied. Group I (n = 14) received cefotaxime IV (100 mg.kg-1 D-1) plus netilmicin (4 mg.kg-1 D-1); group II (n = 8) received amoxicillin/clavulanic acid IV (100/10 mg.kg-1 D-1) plus netilmicin (4 mg.kg-1 D-1). Both groups were identical. For all strains MICs of cefotaxime, amoxicillin/clavulanic acid, netilmicin were less than 0.2, 4 and 1 mg/l respectively. Serum bactericidal activity (SBA) was determined for each patient (peak sample). The SBA was defined as the greatest dilution in which 99,99% of the inoculum was killed. Time-kill curves were performed with 1:16 dilutions of peak serum samples to measure the kinetic of bacterial killing. The minimal bactericidal time of serum (MBTS) was defined as the minimal time required to observe a decrease of more than 4 log CFU/ml of the bacterial inoculum. Samples (10 microliters) were taken at 1 h intervals over a 6 h period and at 24 h for quantitative culture. All patients cured. Median SBA were respectively 1/128 and 1/64 for group I and II. However, mean MBTS for groups I and II were respectively 1.2 h +/- 0.8 and 3.9 h +/- 1.4. Killing was more rapid in group I (p less than 0.01). The MBTS may be a clinically useful adjunctive test when optimal therapy would be expected.