Ion binding by synthetic macrocyclic compounds

The existence of synthetic macrocyclic molecules with hydrophilic cavities containing multiple binding atoms and with hydrophobic exteriors gives rise to extraordinary possibilities with respect to the design and synthesis of molecules with specific cation and anion binding properties. The preparation of many new macrocyclic compounds has recently been reported, but few practical applications for them have been suggested. From the information available, it is becoming clear that it should be possible to synthesize macrocycles that will have specified, or selected, ion binding properties. Cavity size can be varied to accommodate only those cations or anions within a specified narrow band of sizes. Numbers and types of coordinating atoms can be chosen to give essentially electrostatic or covalent bonding or a combination of the two in a metalmacrocycle complex. The metal ligand bond appears to be predominantly ionic in the case of the cyclic polyethers but the covalent character increases on substitution of sulfur or nitrogen for oxygen donor atoms. The essential hydrophobic exteriors of the macrocycles can be modified by the addition of side chains and groups to facilitate the solution of anions and cations in organic solvents. The structures of many macrocycles can be made to approximate naturally occurring molecules, that is, cyclic polyethers similar to macrocyclic antibiotics of the valinomycin and nonactin types and cyclic polyamines similar to porphyrins. Macrocycles are also useful as model compounds for the study of metal interactions with biological systems. The synthetic macrocycles thus represent an intriguing new area of coordination chemistry, the systematic study of which should lead to many interesting and useful chemical applications in the field of metal complexation in solution.     

Residual feed intake of purebred Angus steers: effects on meat quality and palatability

Relationships between residual feed intake (RFI) and other performance variables were determined using 54 purebred Angus steers. Individual feed intake and BW gain were recorded during a 70-d post-weaning period to calculate RFI. After the 70-d post-weaning test, steers were fed a finishing ration to a similar fat thickness (FT), transported to a commercial facility, and slaughtered. A subsample of carcasses (n = 32) was selected to examine the relationships among RFI, meat quality, and palatability. Steers were categorized into high (> 0.5 SD above the mean; n = 16), medium (mid; +/- 0.5 SD from the mean; n = 21), and low (< 0.5 SD below the mean; n = 17) RFI groups. No differences were detected in ADG, initial BW, and d 71 BW among the high, mid, and low RFI steers. Steers from the high RFI group had a greater DMI (P = 0.004) and feed conversion ratio (FCR; DMI:ADG; P = 0.002) compared with the low RFI steers. Residual feed intake was positively correlated with DMI (r = 0.54; P = 0.003) and FCR (r = 0.42; P = 0.002), but not with initial BW, d 71 BW, d 71 ultrasound FT, initial ultrasound LM area, d 71 ultrasound LM area, or ADG. The FCR was positively correlated with initial BW (r = 0.46; P = 0.0005), d 71 BW (r = 0.34; P = 0.01), and DMI (r = 0.40; P = 0.003) and was negatively correlated with ADG (r = -0.65; P = 0.001). There were no differences among RFI groups for HCW, LM area, FT, KPH, USDA yield grade, marbling score, or quality grade. Reflectance color b* scores of steaks from high RFI steers were greater (P = 0.02) than those from low RFI steers. There was no difference between high and low RFI groups for LM calpastatin activity. Warner-Bratzler shear force and sensory panel tenderness and flavor scores of steaks were similar across RFI groups. Steaks from high RFI steers had lower (P = 0.04) off-flavor scores than those from low RFI steers. Cook loss percentages were greater (P = 0.005) for steaks from low RFI steers than for those from mid RFI steers. These data support current views that RFI is independent of ADG, but is correlated with DMI and FCR. Importantly, the data also support the hypothesis that there is no relationship between RFI and beef quality in purebred Angus steers.     

Toxocara vitulorum in beef calves kept on effluent-irrigated pastures in Zimbabwe

Faeces from 20 calves aged 13 +/- 5 days were examined for Toxocara vitulorum eggs fortnightly for a period of 20 weeks. The age of calves when eggs were first detected varied from 24 to 110 days (mean 41 +/- 20 days). The mean egg count varied from 257 to 19,821 g-1 of faeces with a highest count of 68,400. The patency period of T. vitulorum lasted from 14 to 112 days (mean 65 +/- 30 days). None of the calves showed clinical signs of illness.     

Vaccination of cows with rough Escherichia coli mutants fails to protect against experimental intramammary bacterial challenge

Vaccination of cows with rough Escherichia coli mutants fails to protect against experimental intramammary bacterial challenge. Vaccine A, a heat-killed Re mutant of strain K12, (UB 1574), was administered as a single parenteral and local dose to 5 cows with 3 control animals and Vaccine B, a heat-killed mutant of O111:B4 (J5) was administered as three parenteral doses into 5 cows with 5 control animals. Following intramammary challenge with a smooth wild-type strain (P4), an acute, severe clinical mastitis developed in all 14 quarters (9 vaccine A and 5 vaccine B) of the vaccinated animals which was indistinguishable from that in the 11 quarters of the control animals. Following vaccine B there was an elevation in serum IgG1 and IgG2 antibody to the common core antigen of endotoxin which, in contrast to the control animals, showed a further increase after intramammary infection.     

Tomato Production and Soil Salt Distribution under Line-Source Trickle Irrigation1

Yield of red cherry tomatoes and soil salt distribution as affected by different amounts and salinities of irrigation water was studied in a field plot experiment during the summer of 1988 at Utah State University. Four different amounts of fresh water and two amounts of saline water were imposed with line source trickle irrigation on a sandy loam soil in lysimeters. Tomato yield and seasonal evapotranspiration increased in a linear fashion with increasing irrigation water. Tomato yields with fresh water (EC = 0.33 dS/m) were significantly higher than with saline (EC = 4.0 dS/m) water. There were no significant differences in seasonal evapotranspiration between the two salinity levels with two levels of deficit irrigation. Soil water depletion and availability decreased as the soil water salinity increased. Soil water salinities increased with both vertical and horizontal distance from trickle lines and reached a maximum at the bottom of the wetted area and between trickle lines.     

Subcellular distribution of copper in the liver of fetal deer in the last month of gestation

Fetal deer, in the last month of gestation, accumulate high concentrations of copper in the liver. Livers from fetal deer in late gestation were homogenised and fractionated by continuous sucrose density gradient centrifugation. The distribution of copper closely followed that of DNA; approximately two thirds of the metal was localised to the nuclear fractions with the remaining third in the cytosolic fractions. The fractionation procedure was repeated with digitonin, a lysosomal perturbant: lysosomes were disrupted and the marker enzyme, N-acetyl-beta-glucosaminidase, shifted from the particulate fractions to the cytosolic fractions; the distribution of copper was unaffected. Differential centrifugation of homogenate confirmed that approximately two thirds of the copper was associated with the nuclear fraction. Further confirmation of a nuclear localisation of copper was provided by X-ray microanalysis of purified nuclei.     

Histologic and histochemical changes in articular cartilages of immature beagle dogs dosed with difloxacin, a fluoroquinolone

The histologic and histochemical features of quinolone-induced arthropathy were studied using 14 skeletally immature Beagle dogs (3 to 4 months old) dosed orally with difloxacin at 300 mg/kg body weight once daily for 1, 2, 5, or 7 days. A placebo was given to eight other age-matched Beagle dogs that served as controls. A scoring technique that included lesion size and histologic features was used to determine the progression of lesions. Articular-epiphyseal cartilage complexes on the femoral and humeral heads and tibial tarsal bone were identified as predilection sites. Within predilection sites on femoral and humeral heads, lesions developed in specific areas. Lesions appeared within 2 days of the onset of treatment, and lesion scores increased with time. Grossly, the lesions were raised, fluid-filled vesicles on the articular surface. Histologic changes included vesicle formation with loss of proteoglycan, clumping of unmasked collagen, and degeneration and necrosis of chondrocytes. In lesions with higher scores, chondrocytes were often in clusters or they were undergoing metaplasia toward spindle-shaped cells. Although dissolution of matrix and necrosis of chondrocytes were typical of all lesions, smaller lesions had histologically normal chondrocytes adjacent to small vesicles. In sections stained with toluidine blue, proteoglycan was aggregated with collagen fibrils or was absent from the matrix adjacent to vesicles. Unique features, such as biomechanical forces, may predispose specific areas of articular cartilage to develop lesions.     

Rapid-cycling populations of brassica

Rapid-cycling populations of six economically important species in the genus Brassica have unusual potential for resolving many problems in plant biology and for use in education. Rapid-cycling brassicas can produce up to ten generations of seed per year and serve as models for research in genetics, host-parasite relations, molecular biology, cell biology, plant biochemistry, population biology, and plant breeding. Brassicas are a highly diverse group of crop plants that have great economic value as vegetables and as sources of condiment mustard, edible and industrial oil, animal fodder, and green manure. These plants can also be used in the classroom as convenient, rapidly responding, living plant materials for "hands on" learning at all levels of our educational system.