Cell wall thickness during growth of domestic and foreign potato cultivars

During growth of Russet Burbank tubers from less than 100 to over 250 g, thickness of parenchyma cell walls nearly doubled (1.9X) to slightly over 1 μ. Although affecting cell size at harvest maturity, different levels of N fertilizer and soil moisture had little influence on wall thickness. Wall thickness in Kennebec and Norchip increased to 0.9μ (1.7X), and in White Rose to slightly under 0.8 (1.2X). During the same growth, cell size nearly doubled in Russet Burbank. Cells of Kennebec, Norchip and White Rose averaged smaller than those of Russet Burbank at harvest maturity. Wall thickness and cell size showed similar relationships in foreign cultivars. Wall thickness in European varieties Bintje and Pimpernel was comparable to that of White Rose. Thickness in Atjimba closely approached that of Russet Burbank, and in Kamarz was similar to that of Norchip. Among South American cultivars, Doré had unusually thick walls (1.36μ), whereas those in Fruitella and Papa Bianca were between those of Norchip and White Rose. Bintje was comparable to domestic cultivars in tuber size, but all other foreign cultivars studied had medium to small tubers. Doré had unusually large cells for a small tuber. Differences in wall thickness may be due to differences in amounts of cell wall material, to differences in hydration properties of pectic components, or to combinations of both. Independently of wall thickness, the many primary pit fields in parenchyma walls may be a limiting factor in wall strength. The very thin pit membranes consist mainly of cellulosic microfibrils formed early in cell growth.     

Apparatus for measuring change in the potato soil bed profile and relationship of change to soil density and air permeability

A profilometer was constructed to measure changes occurring in the potato soil bed profile during growth of a potato crop. Changes in bed cross sectional area were found to be closely related to changes in soil bulk density and air permeability. The instrument was helpful in rapid approximation of these parameters of the physical condition of a Hesperia sandy loam soil.     

Textural quality of cooked potatoes: II. Relationship of steam cooking time to cellular strength of cultivars with similar and differing solids

The relationship of steam cooking time with cellular strength of cultivars Chieftain, Kennebec, Russet Burbank and White Rose was compared within and among solids concentrations. Nitrogen fertilization had no discernible effect on cell wall strength. Cell strength of Kennebec and Russet Burbank was similar regardless of solids concentration or cooking time. However, cell strength of Chieftain and White Rose differed with solids concentration and cooking time. Knowledge of cell strength and its characteristics with cooking time appear important for understanding the differences in textural quality that exists between cultivars.     

Cell size in Russet Burbank potato tubers with various levels of nitrogen and soil moisture tensions

Russet Burbank potatoes were grown at levels of added nitrogen of 0, 135, and 270 kg/ha and soil moisture tensions (SMT) of 0.5 and 1.0 atm. With all combinations, there was a consistent gradient of larger to smaller starch-storage parenchyma cells from stem end to bud end of mature tubers. Stem and bud ends of tubers grown at a SMT of 0.5 atm with N had smaller cortical and pith (innermost medullary or water-core) cells than did ends of tubers grown without N. Perimedullary tissues of bud ends of tubers receiving N likewise contained smaller cells than did corresponding tissues of tubers grown without N. No pronounced differences in cell size were found in tissues from the midsections. In bud-end tissue of tubers grown at a SMT of 1.0 atm, there were no consistent differences in cell size with respect to N levels. However, pith, perimedullary, and cortical tissues of the midsections and stem ends of tubers receiving N had smaller cells than did corresponding tissues from tubers without N. The different patterns of cell size in tubers grown at different SMT indicate that the effects of N may be influenced by soil moisure.     

The crystal structure of a mammalian fatty acid synthase

Mammalian fatty acid synthase is a large multienzyme that catalyzes all steps of fatty acid synthesis. We have determined its crystal structure at 3.2 angstrom resolution covering five catalytic domains, whereas the flexibly tethered terminal acyl carrier protein and thioesterase domains remain unresolved. The structure reveals a complex architecture of alternating linkers and enzymatic domains. Substrate shuttling is facilitated by flexible tethering of the acyl carrier protein domain and by the limited contact between the condensing and modifying portions of the multienzyme, which are mainly connected by linkers rather than direct interaction. The structure identifies two additional nonenzymatic domains: (i) a pseudo-ketoreductase and (ii) a peripheral pseudo-methyltransferase that is probably a remnant of an ancestral methyltransferase domain maintained in some related polyketide synthases. The structural comparison of mammalian fatty acid synthase with modular polyketide synthases shows how their segmental construction allows the variation of domain composition to achieve diverse product synthesis.     

Morphometric evaluation of growth in llamas (Lama glama) from birth to maturity.

Normal growth characteristics of llamas (Lama glama) were evaluated from conception until 1 week after parturition in pregnant females (study 1) and from 1 month after birth to maturity (study 2). In study 1, pregnant multiparous llamas (n = 10) were measured at monthly intervals from conception until 1 week after parturition; in study 2, llamas (n = 270) were measured once. Body weight of pregnant llamas (study 1) did not increase significantly until after the eighth month of pregnancy. Llamas of study 2 reached mature height, length, thoracic circumference, and weight at 18, 24, 36, and 36 months of age, respectively. From 1 month of age to maturity, the growth characteristics of males, nonpregnant females, and females during the first 8 months of pregnancy did not differ. Correlations (r2) between height, length, and thoracic circumference related to body weight for all but the pregnant llamas during the last 3 months of pregnancy were 0.822, 0.834, and 0.948, respectively. The equation describing thoracic circumference as a predictor of body weight was: Weight (kg) = (1.005 x 10(-3)) x circumference (cm)2.424.     

Pruritus in rabbits, rodents, and ferrets

This article attempts to cover the more specific pruritic problems encountered in rabbits, rodents, and ferrets. There are certainly other causes of pruritus in these animals. Dermatophytes in guinea pigs are not reported to be pruritic, but because they are pruritic in other species, they should be considered in a differential diagnosis. A cryptococcal dermatitis in a guinea pig that was pruritic has been reported. Although mites were not seen on scraping, the animal was treated for sarcoptid mites and apparently the pruritus lessened. Because the cryptococcis was still present, it is questionable whether it was causing the pruritus. Pruritic ulcerative dermatitis over the back and shoulders has been seen in some lines of rats. Staphylococcus aureus was cultured from many of the lesions. Clipping the toenails on the feet helped lessen the severity of the lesions. Syphacia spp. have been reported in rats, gerbils, and hamsters and should be considered if there is perineal pruritus. MOBS, or "move over buddy syndrome," is seen especially in mice and may be seen in hamsters, gerbils, and rats that are overcrowded or stressed. The lesions are actually bite wounds that have been inflicted around the tail base and the perineum and on the tail, but these wounds can be mistaken for self-inflicted trauma from pruritus. All of the recommended treatments are extralabel, and clients should be informed of this. I have observed a guinea pig become lethargic and anorexic after only one application of a flea powder approved for use in cats. Brushing most of the powder off and offering dandelion greens to stimulate appetite helped. The second dusting was done with the same flea powder diluted with baby powder. Whenever these animals are dipped, it is important to let them dry in a warm, draft-free area. Again, it is important to be aware that the ratio of surface area to body weight is much higher in these small animals than in the species routinely seen in veterinary practice especially to prevent toxicoses from topically applied medications and iatrogenic hypothermia or hyperthermia.     

Investigations on course and outcome of phocine distemper virus infection in harbour seals (Phoca vitulina) exposed to polychlorinated biphenyls. Virological and serological investigations.

The influence of polychlorinated biphenyls (PCBs) on phocine distemper virus (PDV) infections in harbour seals (Phoca vitulina) was studied. Six out of ten seals had been conditioned with a defined mixture of PCB-congeners for several weeks. Following exposure to the cell culture-propagated PDV isolate 2558/Han 88 the complete clinical picture of "1988 seal plague" was provoked in all ten seals inoculated. Four out of six PCB-conditioned seals and two out of four seals not loaded with PCBs succumbed to the infection within three weeks post inoculation. With regard to the clinical course, duration of cell-associated viremia, PDV-antigen distribution in tissues of fatally infected seals and the humoral immune response to PDV no differences between PCB-loaded and unloaded seals were recognized. Evidence was obtained that the pathogenesis of experimental PDV-infection in harbour seals shares some features with those of canine distemper in terrestrial carnivores. In contrast, however, to experimental distemper infection of gnotobiotic dogs prompt development of high titres of PDV-specific IgG did not correlate with recovery from infection.     

Architecture of mammalian fatty acid synthase at 4.5 A resolution

The homodimeric mammalian fatty acid synthase is one of the most complex cellular multienzymes, in that each 270-kilodalton polypeptide chain carries all seven functional domains required for fatty acid synthesis. We have calculated a 4.5 angstrom-resolution x-ray crystallographic map of porcine fatty acid synthase, highly homologous to the human multienzyme, and placed homologous template structures of all individual catalytic domains responsible for the cyclic elongation of fatty acid chains into the electron density. The positioning of domains reveals the complex architecture of the multienzyme forming an intertwined dimer with two lateral semicircular reaction chambers, each containing a full set of catalytic domains required for fatty acid elongation. Large distances between active sites and conformational differences between the reaction chambers demonstrate that mobility of the acyl carrier protein and general flexibility of the multienzyme must accompany handover of the reaction intermediates during the reaction cycle.