An inflatable minirhizotron system for root observations with improved soil/tube contact

Commonly used minirhizotrons consisting of a transparent tube inserted into the soil seldom attain good contact between the tube and the soil, which leads to root growth occurring in a gap rather than in the soil. A new system is described involving an inflatable flexible rubber wall, made from a modified motorcycle tube. Pressure ensures a proper tube/soil contact so that the environmental circumstances for root growth along the tube more closely correspond to those in the undisturbed soil. Before the endoscope slide is introduced into the minirhizotron for taking pictures, the inflatable tube is removed, so that there is no-often opaque-wall between the endoscope and the roots. This improves the picture quality and facilitates the analysis of root images.     

Effect of pKM101 on cell killing and specificity of mutation induction by cis-diaminedichloroplatinum(II) in Escherichia coli K-12.

Cell killing and mutation induction in the lacI gene of Escherichia coli by cis-Pt(NH3)2Cl2 were studied in cells with different repair capacities, with and without pKM101. The presence of the plasmid pKM101 made repair-proficient cells more susceptible to killing by cis-Pt(NH3)2Cl2 and strongly enhanced mutation induction by that compound. Both effects were shown to be dependent upon excision repair. Characterization of the induced mutations in the lacI gene after cis-Pt(NH3)2Cl2 treatment of E. coli cells, by the LacI system, revealed that the mutagenic specificity of the Pt compound was strongly influenced by the presence of the pKM101 plasmid. With pKM101, 23% of the induced amber and ochre mutations resulted from substitutions at AT base pairs, whereas these mutations were hardly induced in cells without pKM101. These results suggest that pKM101-induced repair differs from normal SOS repair.     

Nitrosylated high density lipoprotein is recognized by a scavenger receptor in rat liver

In order to assess the presence of specific recognition sites for high density lipoprotein (HDL) in vivo, HDL was nitrosylated with tetranitromethane and the decay and liver uptake were compared with that of native HDL. The association of intravenously injected nitrosylated HDL (TNM-HDL) with liver was greatly increased as compared to native HDL. Using a cold cell isolation method, it became evident that the liver endothelial cells were responsible for the increased uptake of the modified HDL. The involvement of the endothelial cells in the uptake of TNM-HDL from the circulation could also be demonstrated morphologically by using the fluorescent dye dioctadecyl-tetramethyl-indocarbocyanine perchlorate (Dil) to label HDL. In vitro competition studies with isolated liver endothelial cells indicated that unlabeled modified HDL and acetylated LDL displaced iodine-labeled TNM-HDL, while no competition was seen with LDL and a slight displacement was seen with unlabeled native HDL. Nonlipoprotein competitors of the scavenger receptor such as fucoidin and polyinosinic acid blocked the interaction of TNM-HDL with the liver endothelial cells. Also the degradation of TNM-HDL was blocked by low concentrations of chloroquine. It can be concluded that a scavenger receptor on liver endothelial cells is involved in the clearance of tetranitromethane-modified HDL, which excludes the possibility of using TNM-HDL in vivo to assess the non-receptor-dependent uptake of HDL. The use of nitrosylated HDL in vitro as a low affinity control is limited to cell types that do not possess scavenger receptors, because cell types with scavenger receptors will recognize and internalize TNM-HDL by a high affinity scavenger pathway.     

A telescopic method for photographing within 8×8 cm minirhizotrons

The volatile organic compounds produced during a sequence of soil incubations under controlled conditions, with either added NH₄ ⁺-N or NO₃ ^--N, were collected and identified. The nature and relative amounts of the volatile organic compounds produced by the microorganisms in the soils were remarkably reproducible and consistent.     

In situ treatment of Hamilton Harbour sediment

To enhance the biodegradation of organic contaminants, approximately 18.5 tonnes of oxidant (calcium nitrate) and 5 tonnes of nutrients were injected into sediments of the Dofasco Boatslip, Hamilton Harbour. In the laboratory 78% and 68% of the oil (TPHs) and polynuclear aromatic hydrocarbons (PAHs), respectively biodegraded in 197 days. In the 1992 treatment in the Ddofasco Boatslip, biodegradation of organic contaminants varied from 79% for low molecular weight compounds (BTXs), to 25/15 of the 16 priority pollutant PAHs. At first biodegraduation of large molecular weight PAHs resulted in the production of naphthalene (from 280 g/g to 549 g/g). In the 1993 treatments, 94% of the naphthalene, and 57% of the TPHs biodegraded. The in situ biotreatment of organic contamination takes time but for some sites the significantly lower cost relative to dredging and confinement makes in situ treatment a viable alternative.     

Isolation of taste buds from the foliate papillae of the rabbit

Summary A method to isolate taste buds from the foliate papillae of the rabbit tongue is described. The method comprises (a) separation of the epidermis from the dermal layer after treatment with dilute acetic acid, and (b) mechanical removal of the taste buds from the epithelium with the use of a surgical needle. The procedure yields taste buds that are morphologically well preserved, and in quantities sufficient to enable a detailed biochemical characterization. Preliminary tests have shown the taste buds to have biochemical properties clearly distinct from those of the adjacent epithelium. The method may provide a basis for studying the molecular mechanism of taste perception in greater detail.On leave of absence from the Medical Research Centre, Polish Academy of Sciences, Warsaw, Poland.     

Location of taste buds in intact taste papillae by a selective staining method

Summary Taste buds were found to stain strongly and selectively in intact papillae with highly acidic dyes such as ponceau S. In intact tongues the taste buds in the fungiform, circumvallate and foliate papillae of the cynomolgus monkey and in the fungiform papillae of the rat as well as the taste discs in the fungiform papillae of the frog could be visualized. This method enables a rapid location and counting of taste buds in taste papillae without preparing histological sections. In cynomolgus tongue material fixed in formalin, the dyes penetrate into the buds. In fresh tongues only the taste pore region of the buds stains, which suggests that in vivo taste buds are impenetrable underneath the pore.     

No evidence for a peripheral effect of L-DOPA on plasma prolactin in the rat

Male and female rats with two permanently indwelling intravenous catheters were infused for 2 hours with ovine prolactin. During equilibrium conditions the effects of intravenously injected L-DOPA and benzerazide (a blocker of dopa-decarboxylase) on steady state levels of ovine prolactin were measured. A dose of 4.5 mg L-DOPA per 100 gr body weight (b.w.) caused a transient increase of plasma ovine prolactin. A dose of 0.3 mg L-DOPA/100 gr b.w. had no effect, neither in males nor in females, while benzerazide (20 mg/100 gr b.w.) had only a slight effect. The experiments suggest that L-DOPA does not affect the peripheral uptake of prolactin from the plasma.     

Proteolytic fragmentation of Helix pomatia alpha-hemocyanin: isolation of a functionally active chemically pure domain and evidence for subunit heterogeneity.

α-Hemocyanin of the vineyard snail, Helix pomatia, is a large oligomer composed of 20 subunits with a molecular weight of 360,000 ± 30,000. Limited proteolysis showed these subunits to be composed of about seven structural domains, each having one oxygen binding site (1). This paper describes the production of these structural domains by tryptic digestion of $\text{1}\text{10}$ hemocyanin molecules. The digestion pattern was followed as a function of time by examining the proteolytically obtained fragments electrophoretically in sodium dodecyl sulfate-containing polyacrylamide gels. Based on the molar ratio of each fragment present during digestion the first part of the reaction sequence for trypsinolysis could be deduced. This reaction scheme was simulated by means of an analog computer. Pseudo-first-order reaction rate constants of the various proteolytic cleavages were estimated from the computer generated time course of digestion. On the basis of these results it is postulated that Helix pomatia α-hemocyanin possesses at least two kinds of subunits which differ in their proteolytic susceptibility. These subunits occur in equimolar amounts. A functionally active domain with a molecular weight of about 50,000 has been isolated from a tryptic digest of hemocyanin subunits. This domain seems to be chemically pure, as suggested by the unique sequence of its first six amino acids, viz: Lys-Val-His-Leu-Asn-Lys.