Flow and flexibility. II. The roles of size and shape in determining wave forces on the bull kelp nereocystis luetkeana

Giant kelps (which may reach lengths of 45 m) are a prominent exception to the general rule that wave-swept organisms are small. The ability of these kelps to maintain their large size in the presence of ocean waves has been attributed to their extreme flexibility and the concomitant tendency to 'go with the flow', a tendency that reduces the hydrodynamic forces imposed on the plant. However, the flexibility of giant kelps carries with it the potential for the organism to apply an inertial load to its own structure if the blade mass reaches the end of its tether. Here, we examine the complex trade-off between flexibility and inertial loading using a simple computational model of the bull kelp Nereocystis luetkeana. In field and laboratory tests, the model accurately predicts the forces and motions imposed on flexible structures in wave-induced flows. Subsequent predictions from the model suggest that mature N. luetkeana can indeed benefit from moving with the flow, but that the forces imposed on juveniles are actually increased by the plant's flexibility. Furthermore, the benefit accrued from going with the flow is sensitive to the shape of the plant. If the bull kelp were to grow while maintaining a juvenile shape, the stress placed on its stipe would be drastically increased by dynamic loading, and these inappropriately shaped plants would be subjected to a high risk of breakage. For certain combinations of wave height, wave period and stipe length, the increased stress in hypothetical 'small'-shaped plants may be associated with chaotic motion of the blade mass.

Rebinding and relaxation in the myoglobin pocket.

The infrared stretching bands of carboxymyoglobin (MbCO) and the rebinding of CO to Mb after photodissociation have been studied in the temperature range 10-300 K in a variety of solvents. Four stretching bands imply that MbCO can exist in four substates, A0-A3. The temperature dependences of the intensities of the four bands yield the relative binding enthalpies and and entropies. The integrated absorbances and pH dependences of the bands permit identification of the substates with the conformations observed in the X-ray data (Kuriyan et al., J. Mol. Biol. 192 (1986) 133). At low pH, A0 is hydrogen-bonded to His E7. The substates A0-A3 interconvert above about 180 K in a 75% glycerol/water solvent and above 270 K in buffered water. No major interconversion is seen at any temperature if MbCO is embedded in a solid polyvinyl alcohol matrix. The dependence of the transition on solvent characteristics is explained as a slaved glass transition. After photodissociation at low temperature the CO is in the heme pocket B. The resulting CO stretching bands which are identified as B substates are blue-shifted from those of the A substates. At 40 K, rebinding after flash photolysis has been studied in the Soret, the near-infrared, and the integrated A and B substates. All data lie on the same rebinding curve and demonstrate that rebinding is nonexponential in time from at least 100 ns to 100 ks. No evidence for discrete exponentials is found. Flash photolysis with monitoring in the infrared region shows four different pathways within the pocket B to the bound substates Ai. Rebinding in each of the four pathways B----A is nonexponential in time to at least 10 ks and the four pathways have different kinetics below 180 K. From the time and temperature dependence of the rebinding, activation enthalpy distributions g(HBA) and preexponentials ABA are extracted. No pumping from one A substate to another, or one B substate to another, is observed below the transition temperature of about 180 K. If MbCO is exposed to intense white light for 10-10(3) s before being fully photolyzed by a laser flash, the amplitude of the long-lived states increases. The effect is explained in terms of a hierarchy of substates and substate symmetry breaking. The characteristics of the CO stretching bands and of the rebinding processes in the heme pocket depend strongly on the external parameters of solvent, pH and pressure. This sensitivity suggests possible control mechanisms for protein reactions.

Chicken embryo propagation of type I avian adenoviruses.

Forty-two clone-purified, cell-culture-propagated type I avian adenoviruses (AAV) representing 11 serotypes and two intermediate strains were evaluated for virus replication (evidenced by embryo death and lesions) resulting from the inoculation of specific-pathogen-free chicken embryos via the chorioallantoic sac or yolk sac. Commonly observed embryonic changes were death, stunting and curling, hepatitis, splenomegaly, congestion and hemorrhage of body parts, and urate formation in the kidneys. Basophilic or eosinophilic intranuclear inclusion bodies characteristic of fowl adenoviruses were observed in hepatocytes. The magnitude and relative uniformity of intra- and interserotypic embryo mortality, gross lesions, and virus titers was greater in embryos inoculated via the yolk sac. This work identifies the yolk sac as a practical and sensitive chicken embryo inoculation route for poultry diagnosticians to employ. It is suggested that the yolk sac may be a reliable alternative to cell culture for the successful isolation of all type I avian adenoviruses.

A trivalent antigen for the detection of type I avian adenovirus precipitin.

A double immunodiffusion antigen prepared from cell-culture-propagated CELO virus was not capable of detecting precipitin directed against all of the type I avian adenovirus (fowl adenoviruses) isolates tested. However, an antigen pool containing CELO-4, B-3, and IBH-2 (Tipton) fowl adenovirus isolates detected precipitin directed against representative isolates of 10 type I serotypes. Additionally, this antigen pool markedly improved detection of adenovirus field exposure.

Adenoviruses of chickens: serologic groups.

By literature review and experimental studies, 57 adenovirus isolants from chickens were grouped into 10 distinct serotypes. In plaque-reduction tests, 20 antibody units were reacted with 32-320 plaque-forming units of virus. Viruses that were neutralized (80% or greater reduction in titer) by a given serum were considered to belong to that serotype. Used to distinguish among serotypes were their antisera. One-way neutralization occurred in only two instances; in both cases it was traced to contamination of the virus inocula used to induce specific antiserum. Recloning corrected the problem. Of the 10 serotypes described, all are known to exist in the United States, 7 were found in Northern Ireland, and at least 6 have been shown to occur in Japan.

Characterization of a new infectious bronchitis virus isolate. III. Cell-culture adaptation of Clark 333.

The Clark 333 strain of infectious bronchitis virus (IBV) was substantially resistant to primary chicken cell-culture adaptation. More than 40 serial embryo passages were required before the virus would produce cytopathic alterations upon cell-culture inoculation. The cytopathic effect was characteristic of the effect of reported for IBV. Adaptation was not accomplished by alternating serial passages in embryo and cell-cultured systems. A careful monitoring of cell-culture fluid infectivity by embryo inoculation was found to be essential because absence of adaptation is accompanied by a loss in virus titer (3 to 5 serial passages). Helpful additional aids were immunofluorescence and cytopathology.

Serotyping of avian infectious bronchitis viruses by the virus-neutralization test.

The antigenic relationships of 12 strains of infectious bronchitis virus (IBV) were evaluated by a virus-neutralization procedure similar to that used in typing human rhinoviruses. Such a procedure consists of reciprocal neutralization tests performed by reacting 32-320 EID50 or plaque-forming units of virus with 20 antibody units of antiserum. Eight serologic groups were identified by chicken embryo assay, and 4 by plaque-reduction (90%). In general, serologic groupings were not distinct but reflected numerous intergroup relationships. The contrasting results exhibited by indicator systems are viewed as differences in the accuracy of the methods employed. It is suggested that before an IBV classification scheme can be proposed, agreement must be reached on the most suitable indicator system, techniques must be standardized, and reference viruses and antisera distributed to several institutions for comparison testing. In addition, cross-protection studies are needed to determine the importance of IBV serotypes and/or variants on vaccine efficacy.

The propagation of avian viruses in a continuous cell line (QT35) of Japanese quail origin.

Seven of nine avian virus families tested (Birnaviridae, Coronaviridae, Herpesviridae, Paramyxoviridae, Poxviridae, Reoviridae, and Retroviridae) were found to replicate in a quail fibroblast cell line, designated QT35, resulting in a cytopathic effect (CPE) visible with the naked eye or by low-power microscopy. In comparison, only one (Paramyxoviridae) of seven mammalian virus families tested produced an observable CPE. Cytopathic changes induced by examined viruses were round cell, syncytial, and focus formation. Trypsin did not promote cytopathic changes by selected CPE-negative avian and mammalian viruses in QT35 cells. Several avian viruses (infectious bursal disease virus, Newcastle disease virus, Canary pox virus, and reovirus) formed plaques under agar. Avian reovirus and infectious bursal disease virus produced similar titers in chicken embryo fibroblast (CEF) and QT35 cell cultures. Chicken-egg-yolk neutralizing-antibody titers to IBDV were comparable in CEF and QT35 cell-culture systems.

Some observations on the response of ring-necked pheasants to inoculation with various strains of cell-culture-propagated type II avian adenovirus.

The response of ring-necked pheasants to inoculation with three strains of cell-culture-propagated type II avian adenovirus was examined. Marble spleen disease (MSD) virus of pheasants and both avirulent and virulent strains of hemorrhagic enteritis virus (HEV) of turkeys all induced typical gross and microscopic splenic lesions of MSD; neither MSD-associated lung lesions nor mortality were noted in inoculated pheasants, regardless of strain of virus used. Pheasants inoculated with a cell-culture-propagated avirulent strain of HEV were properly immunized against challenge with virulent HEV, as indicated by seroconversion and by protection against virus-induced splenic lesions. We conclude that these strains of type II avian adenovirus are comparable in pathogenicity for pheasants and cannot be distinguished. Further, absence of MSD-associated lung lesions and mortality in pheasants maintained under controlled laboratory conditions suggest that other environmental factors are probably involved in induction of such lesions and mortality in field cases of MSD.

An adenovirus survey of poultry flocks during the growing and laying periods.

Chicken adenoviruses were isolated from asymptomatic chickens on each of 7 farms tested; a majority of them induced cytopathology by the second serial passage. Although adenoviruses were isolated from chickens ranging in age from 8 to 34 weeks, the highest isolation rate was from those 8 to 14 weeks. Eight serotypes (1, 2, 4, 5, 6, 7, 8, and 9) were identified in a relatively small geographic area; serotypes 1, 4, 7, and 9 were isolated most frequently. Multiple serotypes were found on 6 of 7 farms, with 1 farm having 4 serotypes identified. Repeat isolations of the same serotypes were noted on 2 farms. The pattern of virus isolations was generally related to age but varied according to farm. Although new serotypes kept appearing, even after birds came into lay, no clinical problems were associated with them. The incidence of precipitin reactors tended to be low (10-40%) in immature birds but reached 80% or more after sexual maturity. The "antiserum pool" modification of the VN test was found to be accurate and less cumbersome than the conventional procedure for typing isolants.

Experimental egg-transmission of avian reovirus.

Two experiments with an avian reovirus (FDO isolant), serologically identical to the Fahey-Crawley and WVU 2937 isolants, provided conclusive proof that egg-transmission can occur. In the first experiment, 4-day-old chicken embryos were inoculated into the yolk sac with serial dilutions of virus and subsequently hatched. High virus doses killed all embryos, whereas low doses (14 or less plaque-forming units) allowed some embryos to hatch normally although infected. In the second experiment, virus was administered by the nasal, esophageal, and tracheal routes to twenty 15-month-old breeders. Eggs from -6 to 21 days and 58 to 64 days postinoculation were incubated. Three newly hatched chicks from eggs laid on successive days (17, 18, and 19 days postinoculation) and one infertile egg (61 days postinoculation) were found infected. Active infection, as judged by virus isolations from cloacal swabs, was over by the 17th day postinoculation.

Localization of avian reovirus (FDO isolant) in tissues of mature chickens.

Mature hens were exposed to a reovirus (FDO isolant) serologically related to the viral arthritis agent. Examination of 23 tissues from the respiratory, alimentary, and reproductive tracts and tendons from the hock joint revealed widespread infection 4 days after inoculation via the respiratory and alimentary tracts. By 14-15 days, infection had largely subsided but was still detectable in the tendons, oviduct, and alimentary tract of some birds. No infection was found at 30 days. Virus isolation attempts in chick kidney cultures were more reliable than fluorescent-antibody tests for detecting infection. None of 156 chicks hatched from eggs laid between 12 and 33 days postinoculation were infected.

Avian adenoviruses: effect on egg production, shell quality, and feed consumption.

Four avian adenovirus isolants (Indiana C, DPI-2, IBH-2, and B-3)were examined for pathogenicity in laying birds. None affected shell quality, and only one (IBH-2) had even a minimal effect on egg production (faster decline). Of three isolants tested (Indiana C, DPI-2, and IBH-2), only IBH-2 caused feed intake to be reduced. No other clinical signs were observed during these experiments. Egg transmission, virus excretion, and antibody production were found to mimic patterns reported for serotype-1 avian adenoviruses.

An outbreak of avian urolithiasis on a large commercial egg farm.

A significant outbreak of avian urolithiasis was observed on a large commercial egg farm. From the initial outbreak site (a single laying house), the incidence of urolithiasis slowly spread in the ensuing months to numerous other laying houses. Increasing mortality associated with urolithiasis commenced during late growout to early lay and then leveled off when egg production peaked. At the height of the outbreak, mortality was typically 0.5% per week; 75% of this mortality was due to urolithiasis. The clinical and pathologic features of this condition are described. Both infectious bronchitis virus (IBV) and fowl adenoviruses were isolated from organ homogenates of sampled birds. A clone of the IBV strain was found to induce nephritis in specific-pathogen-free white leghorns.

A standardized enzyme-linked immunosorbent assay for infectious bronchitis virus: comparison with hemagglutination-inhibition and virus-neutralization assays for measuring protective antibody levels in chickens.

An enzyme-linked immunosorbent assay (ELISA) was developed to measure antibodies to infectious bronchitis virus (IBV) in chickens. The results are reported in IBV standard ELISA values calculated by comparing antibody levels in test sera with antibody levels in a series of standard reference sera. The IBV standard ELISA values were good indicators of responses to vaccination and the immune status of experimentally challenged birds. Although the assay was not serotype-specific, the sensitivity makes it ideally suited for determining the immune status of poultry flocks. The assay results compared favorably with other laboratory results, including virus-neutralization titers, hemagglutination-inhibition levels in sera, virus isolation from vaccinated/challenged birds, and the tracheal ring test results.

A case of acute pulmonary edema, splenomegaly, and ascites in guinea fowl.

Acute pulmonary edema, splenomegaly, and ascites were observed in a disease outbreak in adult white and pearl guinea fowl. The clinical history and gross and microscopic lesions resembled those described for marble spleen disease of pheasants and avian adenovirus group II splenomegaly of chickens. A small number of intranuclear inclusion bodies were found in liver, spleen, and lung sections of affected guinea fowl. Attempts to isolate virus and serological tests to detect the presence of viral antigens were unsuccessful. Adult female pearl guinea fowl experimentally exposed to pheasant and turkey isolates of type II avian adenoviruses developed gross and microscopic lesions similar to those seen in the field outbreak. The pheasant isolate was the more virulent. Intranuclear inclusion bodies were observed in liver, spleen, and lung sections of pearl guinea fowl inoculated with either of the virus isolates, and direct immunofluorescent examination revealed viral antigen in the spleen and lung.

Use of a hypobaric chamber as a model system for investigating ascites in broilers.

In a series of experiments, broilers were reared at simulated altitudes of 3000, 3500, and 5000 meters utilizing a hypobaric chamber. The purpose was to evaluate the chamber as a model for ascites syndrome and to further study the pathophysiology of this disease. Results show that this model can effectively reproduce the disease as it is seen in the field. Birds reared at the simulated altitude of 5000 meters had a statistically significant increase in EKG amplitude, packed cell volume, and heart-to-body-weight and lung-to-body-weight ratios when compared with controls reared at 366 meters. Additionally, there was a trend for birds dying of ascites to have larger-amplitude EKGs than survivors when reared at 5000 meters.

An infectious bronchitis virus isolated from chickens experiencing a urolithiasis outbreak. I. In vitro characterization studies.

An infectious bronchitis virus (IBV) strain isolated from commercial layers experiencing urolithiasis was 50-100 nm in size and possessed widely spaced, club-shaped surface projections. It was sensitive to lipid solvents and exhibited responses characteristic of IBV when exposed to heat, divalent cations, and trypsin. Reciprocal virus-neutralization tests demonstrated it to be closely related to Gray, JMK, Delaware 2868, and Delaware 2897 strains of IBV.

Experimentally induced necrotic enteritis in chickens.

A 1.3 to 10% incidence of necrotic enteritis was experimentally produced in broiler-type chickens in three of five trials. The incidence range observed was considerably narrower and lower than the 5.6-37.3% range reported in the literature. Clostridium perfringens was inconsistently isolated from the liver and intestine of dosed chickens.

Physiologic and electrocardiographic changes occurring in broilers reared at simulated high altitude.

An experiment was conducted to determine whether differences in the electrocardiograms (EKGs) of broilers reared at simulated high altitude from the day of hatch can be used to predict which birds are developing ascites. In three replicate experiments, conducted with 100 broilers per replicate, birds were reared at a simulated altitude of 3000 meters or at ambient atmospheric pressure. Lead I, II, and III EKGs were obtained from all birds on days 0, 14, 28, and 42. No consistent significant differences were seen on day 0 in the amplitude of the R or S wave or total amplitude of the QRS complex when broilers that developed ascites while being reared at simulated high altitude were compared with unaffected birds reared at simulated high altitude and with birds reared at ambient atmospheric pressure. On days 14 and 28, the average amplitude of the S wave and the total amplitude of the QRS complex were significantly higher in the ascites group than in the two other groups. Packed cell volumes were significantly higher in birds reared at simulated high altitude at all sampling days (days 14, 28, and 42) than in those reared at ambient atmospheric pressure, and they were significantly higher in the ascites group on day 28 than in the two other groups. Birds in the ascites group weighed significantly less than the two other groups by day 14, and this trend persisted.