Production of Toxic Metabolites by Penicillium italicum and P. digitatum Isolated from Citrus Fruits

Ninety-six mold isolates were obtained from naturally rotten citrus fruits. Among them, forty were identified as Penicillium italicum and twenty-four as P. digitatum. Twenty-four isolates of the former and twenty of the latter were tested for toxigenesis. They were first grown on Yeast Extract Sucrose (YES) broth for ten d at 22°C. Then, after mycelium removal, the cultures were sterilized by Millipore filtration and the toxicity of the sterile filtrates tested by four different bioassays; i.e. a bacterial test with Bacillus megaterium, a plant test with Lepidium sativum, a test with the brine shrimp Anemia salina and the chick (Gallus domesticus) embryo test. In P. digitatum, 95% of the filtrates were toxic to B. megaterium, 100% caused strong inhibition of seed germination in L. sativum, 75% showed acute toxicity to the brine shrimp and 65% were toxic to the chick embryo, while the figures for P. italicum filtrates were about 96%, 71%, 87%, and 42%, respectively. The results observed with the four different tests didn't always correlate.

Millipore Filtration and Use of RV Medium for Isolation of Salmonella from Preenrichment Broths

A filtration procedure for isolation of Salmonella from preen-richment broth is described. Five ml of broth are passed through a Millipore AP15 pre-filter above a .45 μm Millipore filter. The filter is transferred to 25 ml of Rappaport-Vassiliadis broth and incubated at 42°C. Of 76 naturally and 55 artificially contaminated meat and poultry samples, 102 were positive for Salmonella. Of these, 99 were isolated using the filtration technique, 93% of which were obtained following a 6-h incubation period. Isolations from tetrathionate brilliant green and selenite cystine broth were 93 and 84, respectively.

Phlorizin increases the permeability of intestinal mucosal membrane to sodium

We reported previously that when jejunal transmural glucose transport was inhibited by phlorizin the ratio of Na:giucose transport increased from 2.0:1 (in controls) to 3.3:1. To elucidate the mechanism of this increased ratio of Na:glucose transport, in the present study we have investigated the effect of phlorizin on Na uptake by brush border membrane vesicles and by everted sacs of hamster jejunum. In experiments on membrane vesicles the following observations were made. The time course of Na uptake showed that the control vesicles were in complete equilibrium with a Na-containing (100 mM) medium between 30 and 90 min incubation. In these periods of incubation, the vesicles incubated with phlorizin presumably also equilibrated with the medium, but lost their intravesicular Na during Millipore filtration and washing, and consequently the residual Na content was lower than that of controls. This effect of phlorizin was concentration dependent, and appeared to be unrelated to Na-coupled glucose transport, because it was also observed in the absence of glucose. This loss of Na during Millipore filtration and washing was also observed (i) when vesicles were equilibrated in a Na-containing solution in the absence of phlorizin and then exposed to a similar solution containing phlorizin, or (ii) when vesicles were equilibrated in a Na-containing solution in the presence of phlorizin and then washed repeatedly following Millipore filtration. Preincubation of vesicles for 10 min in a Na- and glucose-free solution containing phlorizin followed by incubation for 30–90 s in solutions containing 1 mM glucose and various concentrations of Na (from 10 to 100 mM) caused an increase in Na uptake from all concentrations of Na. After similar preincubation, when jejunal everted sacs were incubated for 15 s in a Na- and glucose-containing medium, Na uptake by the sacs increased. These findings suggest that phlorizin causes an increase in permeability of mucosal membrane of the enterocyte to Na. This may cause a rapid dissipation of Na gradient and an increase in the ratio of Na:glucose transport. The dissipation of Na gradient may be an additional mechanism for phlorizin-induced inhibition of intestinal sugar transport.

Binding of Adenosine Diphosphate (ADP) to Isolated Human Platelet Membranes

Human platelet plasma membranes were isolated according to the glycerol loading technique of Barber and Jamieson. The binding of 14C ADP was studied with Millipore filtration in a Ca2+ and Mg2+ containing buffer at pH 7,4. At least two types of binding sites were found: A high affinity system with a maximum binding of 160 pMoles/mg protein and an association constant of 1,1 χ 106 M-1; and alow affinity system with a maximum binding of about 4500 pMoles/mg protein and an association constant of 0,6 χ 1θ4 M-1. The binding according to the high affinity system showed little temperature dependency (Q10 = 1,10). The pH optimum was at 7,3. Ca2+ ions were an absolute requirement for binding.Nucleoside diphosphokinase (NDPK) was found in the membrane vesicles. Evidence that this enzyme was not responsible for ADP binding was obtained. The enzyme is Mg2+ dependent and is inhibited by AMP, in contrast to ADP binding. The Q10 was 1,44.ADP binding was inhibited by ATP, IDP and β/γ-imidoadenosine triphosphate.

Short Communications. Initial rates of pyruvate transport in mitochondria determined by an ‘inhibitor-stop’ technique

An ‘inhibitor-stop’ technique has been developed for measuring initial rates of pyruvate transport into mitochondria. The technique uses α-cyano-3-hydroxycinnamate as the inhibitor and separates the mitochondria from the radioactive medium by Millipore filtration. Observed rates depend on availability of hydroxyl and other exchangeable anions within the mitochondrial matrix.

Ependymal-choroidal cells in cerebrospinal fluid

✓ Samples of cerebrospinal fluid removed from 66 patients with various non-neoplastic disorders during pneumoencephalography or ventriculography were examined cytologically using the method of Millipore filtration. In addition to leukocytes and other types of cells, clumps of ependymal or choroidal cells were frequently noted; they were found most often and in greatest numbers in hydrocephalic infants. The authors hypothesize that these cells are constantly being shed and replaced, especially during infancy, and that their exfoliation is increased if the ventricles are stretched by hydrocephalus. It is important that one recognizes the nature of these clumps of ependymal or choroidal cells to avoid misidentifying them as leukocytes or tumor cells.