Phytoplankton communities in channel catfish ponds

Seasonal changes in the quantity and quality of phytoplankton were studied in six channel catfish culture ponds. Chlorophyll a concentrations were generally highest in the summer (averaging >200 g 1^–1) but the highest individual chlorophyll a value recorded (910 g 1^–1) occurred in the winter during a bloom of Dictyosphaerium pulchellum. On the average, green algae (Chlorophyta) and euglenoids (Euglenophyta) represented relatively constant proportions of the phytoplankton community seasonally (about 35 and 10%, respectively). In the summer and fall, blue-green algae (Cyanophyta) became abundant. Diatoms were relatively abundant at all times and constituted the majority of the community in the winter and spring.     

Severe pulmonary hypertension and arterial adventitial changes in newborn calves at 4,300 m

Some human newborns have a syndrome characterized by irreversible pulmonary hypertension and severe hypoxemia and by medial hypertrophy and adventitial thickening of pulmonary arteries. We considered that newborn calves made severely hypoxic might reproduce features of the human disease. When 2-day-old calves were placed at 4,300 m simulated altitude, pulmonary arterial pressure was increased and could be reversed by 100% O2. However, after 2 wk at 4,300 m, pulmonary arterial pressures were suprasystemic and there was right-to-left shunting probably through the foramen ovale and a patent but restrictive ductus arteriosus. Suprasystemic pulmonary pressure and hypoxemia persisted with 100% O2 breathing. Morphometrical examination of the lung arteries showed a markedly thickened adventitia with cellular proliferation and collagen and elastin deposition. There was increased medial thickness and distal muscularization of the pulmonary arteries associated with decreased luminal diameter. The rapid development of severe pulmonary hypertension and poor responsiveness to O2 was associated with increased arterial wall thickness, particularly involving the adventitia. Thus the pulmonary arterial circulation in these calves, which were placed at high altitude for 2 wk, exhibited features resembling persistent pulmonary hypertension in newborn infants.     

Activities of cellulase and other extracellular enzymes during lignin solubilization by Streptomyces viridosporus

Summary Two mutant strains of the lignin degrading bacterium Streptomyces viridosporus strain T7A with enhanced abilities to produce a soluble lignin degradation intermediate, acid-precipitable polymeric lignin (APPL) and several mutants derepressed for cellulase production were compared with the wild type to examine the roles of cellulase and selected other extracellular enzymes in lignin solubilization by S. viridosporus. The two APPL-overproducing mutants, T-81 and T-138, had higher cellulase activities than the wild type. Mutants specifically derepressed for cellulase were also isolated and were found to produce more APPL than the wild type. The results are indicative of some involvement of cellulase in the lignin solubilization process. The lignin solubilized from corn (Zea mays) lignocellulose by the mutants was slightly different chemically as compared to wild type solubilized lignin in that it had a higher coumaric acid ester content. The production of extracellular coumarate ester esterase, aromatic aldehyde oxidase, and xylanase was also examined in the mutants. Xylanase and aromatic aldehyde oxidase production did not differ significantly between the mutants and the wild type. Mutant T-81 was found to have a slightly lower activity for esterase as compared with the wild type. It was concluded that xylanase, oxidase and esterase are not the enzymes directly responsible for enhanced lignin solubilization. The results, however, do implicate cellulase in the process.Paper number 86 511 of the Idaho Agricultural Experiment Station     

Structure of an insect virus at 3.0 A resolution

We report the first atomic resolution structure of an insect virus determined by single crystal X-ray diffraction. Black beetle virus has a bipartite RNA genome encapsulated in a single particle. The capsid contains 180 protomers arranged on a T = 3 surface lattice. The quaternary organization of the protomers is similar to that observed in the T = 3 plant virus structures. The protomers consist of a basic, crystallographically disordered amino terminus (64 residues), a beta-barrel as seen in other animal and plant virus subunits, an outer protrusion composed predominantly of beta-sheet and formed by three large insertions between strands of the barrel, and a carboxy terminal domain composed of two distorted helices lying inside the shell. The outer surfaces of quasi-threefold related protomers form trigonal pyramidyl protrusions. A cleavage site, located 44 residues from the carboxy terminus, lies within the central cavity of the protein shell. The structural motif observed in BBV (a shell composed of 180 eight-stranded antiparallel beta-barrels) is common to all nonsatellite spherical viruses whose structures have so far been solved. This highly conserved shell architecture suggests a common origin for the coat protein of spherical viruses, while the primitive genome structure of BBV suggests that this insect virus represents an early stage in the evolution of spherical viruses from cellular genes.     

Chemolithotrophic ATP synthesis and NAD(P) reduction in Thiobacillus tepidarius and T. versutus

Thiosulphate-dependent reduction of NAD and NADP in intact cells of Thiobacillus tepidarius and T. versutus was severely inhibited or abolished by FCCP at concentrations that did not affect ATP synthesis over the same time scale. Thiosulphate-dependent ATP synthesis in T. tepidarius was abolished by the ATPase inhibitor DCCD, which did not affect NAD or NADP reduction at the concentrations tested. These results indicate that energy-dependent NAD(P) reduction using reversal of electron transfer from cytochrome b or c in thiobacilli is directly driven by the p generated by thiosulphate oxidation, and does not require the participation of ATP. While NAD(P) reduction and ATP synthesis are thus both effected by sulphur compound oxidation, there is no obligatory link between them.Abbreviations CCCP carbonyl cyanide m-chlorophenylhydrazone - DCCD dicyclohexylcarbodiimide - DNP 2,4-dinitrophenol - G-6-P glucose 6-phosphate - FCCP carbonylcyanide p-fluoromethoxyphenylhydrazone     

Taxonomic status of the extinct Banff longnose dace,Rhinichthys cataractae smithi,of Banff National Park,Alberta

Synopsis Study of 314 specimens of Rhinichthys cataractae from British Columbia, Alberta, and Wyoming, lead to the following conclusions: (1) Rhinichthys cataractae smithi Nichols,1916, is a valid subspecies, endemic to Cave and Basin Hotsprings and distinguished by 48–58 as opposed to 58–74 lateral line scales; (2) between 1925 and 1971, R. c. smithi hybridized with the eastern subspecies R. c. cataractae (Valenciennes,1842) from the Bow River and by 1981 the former had undergone almost complete introgression and was virtually extinct; (3) probable factors leading to this are introduction of tropical fishes into the hotsprings and periodic reduction of inflow from the hotsprings; (4) the closest relative of R. c. smithi is R. c. cataractae, rather than the westslope longnose dace (without a scientific name) inhabiting the Pacific basin; (5) the low number of lateral line scales of R. c. smithi may be a pleomeristic response to dwarfing; (6) R. c. smithi develops breeding tubercles at sizes as small as 21.1 mm SL, whereas R. c. cataractae develop them at 36.3 mm SL in Alberta; (7) introductions should not be made into a body of water prior to the study of its native fishes and consultation with experts in taxonomy and distribution of rare fishes. R. c. smithi is illustrated for the first time.     

Birth prevalence and recurrence rates of neural tube defects in southern Alberta in 1970-81.

Given the observed variation in birth prevalence and recurrence rates of neural tube defects, it is important to obtain such data specific to a given locality for research and genetic counseling purposes. A review of hospital medical charts, the patient lists of the Medical Genetics and Myelomeningocele clinics at Alberta Children''s Hospital and data from the Canadian Congenital Anomalies Surveillance System revealed the annual birth prevalence rate of neural tube defects in southern Alberta in 1970-81 to be 1.62/1000 total births. This figure suggests southern Alberta to be a low-frequency area. There was no significant variation in the annual rates of spina bifida, encephalocele or all neural tube defects combined over the study period. A significant linear decline in the frequency of births of anencephalic infants, however, was noted (p = 0.025). Information on the total reproductive history of the mothers revealed that the empiric risk of recurrence of a neural tube defect was 2.2%, and the risk to all siblings was estimated to be 2.3%. In future prevalence studies multiple sources of case ascertainment should be used, including data on pregnancies terminated because of a fetal neural tube defect.     

The ontogeny and phylogenetic conservation of MAP 2 forms

Summary In the adult rat brain, MAP 2 is a high-molecular weight protein that is highly concentrated in dendrites. Immunoblots of homogenates of developing rat brain have indicated that a low-molecular weight form of MAP 2, MAP 2 c, is transiently expressed as the brain is undergoing morphogenesis. Using MAP 2-specific monoclonal antibodies, we have demonstrated that the compartmentalization of high-molecular weight MAP 2 and the developmental regulation of MAP 2 are conserved in mammalian, avian, and amphibian brain. We have also determined the distribution of MAP 2 c in developing neuronal tissue. MAP 2 c appears before high-molecular weight MAP 2 in developing neurons, and in contrast to the dendrite-specific high-molecular weight forms of MAP 2, MAP 2 c is present in axons and glia. We have also shown that MAP 2 c is present in the adult rat retina, where it is concentrated in regenerative photosensitive cells. The transient expression of MAP 2 c in the developing brain of three species as well as in adult photosensitive cells suggests a role for this protein in neurite growth and plasticity.Abbreviations MAP microtubule-associated protein - E embryonic day - P postnatal day