Estimating stem respiration in trees by a mass balance approach that accounts for internal and external fluxes of CO2

The respiration rate of a tree stem has commonly been estimated from measurements of CO2 efflux to the atmosphere. These estimates assume that all CO2 efflux originates from respiration of local tissues and that all CO2 produced by local tissues escapes to the atmosphere through the bark. However, dissolved CO2 can be transported in the xylem stream, and CO2 concentration ([CO2]) in xylem can be up to three orders of magnitude greater than that of the atmosphere, suggesting that measurements of CO2 efflux do not account for all CO2 produced by respiration. Here, we propose a new mass balance approach for estimating the respiration rate of tree stems that accounts for both external and internal fluxes of CO2. We demonstrate this approach using measurements of CO2 efflux, sap flux and internal [CO(2)] to calculate the rate of CO2 production of a segment of stem tissue in situ. At different times of the day, CO2 produced by respiration of stem tissues followed different flux pathways. During daylight hours when sap was flowing, a large proportion of respired CO2 was carried away in the xylem stream, whereas at night, most respiratory CO2 escaped to the atmosphere through the bark. Our calculations showed errors in efflux-based estimates of respiration of up to 76% compared with estimates that include both internal and external fluxes.     

T lymphocyte development in horses. I. Characterization of monoclonal antibodies identifying three stages of T lymphocyte differentiation

Six monoclonal antibodies reacting with equine T lymphocytes at different stages of maturation were selected from antibodies produced against lymphoid cell preparations. EqT12 and EqT13 antibodies identified subsets of cortical thymocytes with high terminal deoxynucleotidyltransferase (TdT) activity and no phytolectin responsiveness. EqT12+ thymocytes were scattered throughout the cortex while EqT13+ thymocytes were located in the subcapsular cortex. EqT12 bound to small numbers of bone marrow cells, splenocytes, and circulating lymphoid cells, but not to mature T lymphocytes. EqT13 bound to very small numbers of bone marrow cells but not to more mature lymphocytes. EqT6 and EqT7 reacted with a large population of cortical thymocytes with high TdT activity and no phytolectin responsiveness. EqT2 and EqT3 bound primarily to medullary thymocytes with low TdT activity. Eq2+ thymocytes responded to phytolectin stimulation while EqT3+ thymocytes did not. EqT2 and EqT3 bound to 33% and 91% of circulating T lymphocytes, respectively. The T lymphocytes bound by both antibodies included cells capable of suppressing a mixed lymphocyte reaction. Thus, EqT12 and EqT13 identify cells with the functional characteristics of prothymocytes. EqT6 and EqT7 identify resident cortical thymocytes, and EqT2 and EqT3 identify a subpopulation of mature T lymphocytes and all mature T lymphocytes, respectively.     

Failure of passive immunoglobulin transfer: a major determinant of mortality in newborn alpacas (Lama pacos)

Failure of passive transfer (FPT) of immunoglobulin from colostrum was demonstrated as a major determinant of mortality in newborn alpacas (Lama pacos; crias). Serum IgG concentrations of dying crias were significantly (P less than 0.0001) lower than were serum IgG concentrations of crias that lived. Of 82 crias, 10 (12%) died within 1 month of age, and 7 of these had 0 to 9 mg of IgG/ml of serum at 48 hours after birth; 5 of the 7 had evidence of infectious diseases. The serum IgG concentrations of the remaining dead crias were 12, 13, and 20 mg/ml. On the basis of serum IgG concentrations of crias that died in the first month, FPT was defined as a 48-hour serum IgG concentration less than 9 mg/ml, which was greater than 2 SD below the 48-hour mean of clinically normal crias. Using this definition, the prevalence of FPT in the 82 crias studied was 9%. Corroborative evidence of the relationship between FPT and mortality was obtained from a retrospective study of 21 dead crias. The postmortem serum IgG concentration of 5 crias that died 2 to 10 days after birth ranged from less than 1 to 3 mg/ml; all were greater than 2 SD below the mean of age matched clinically normal crias. The range of serum IgG concentration was 2.2 to 21 mg/ml in 8 crias that died 11 to 20 days after birth; serum IgG concentration in 1 cria was greater than 2 SD below the normal mean, and 6 were greater than 1 SD below the normal mean.(ABSTRACT TRUNCATED AT 250 WORDS)     

Development of Anaplasma marginale in male Dermacentor andersoni transferred from parasitemic to susceptible cattle.

The development and transmission of Anaplasma marginale was studied in Dermacentor andersoni males. Laboratory-reared male D andersoni were allowed to feed for 7 days on a calf with ascending A marginale parasitemia. The ticks were then held in a humidity chamber for 7 days before being placed on 2 susceptible calves. Anaplasmosis developed in the calves after incubation periods of 24 and 26 days. Gut and salivary glands were collected from ticks on each day of the 23-day experiment and examined with light and electron microscopy. Colonies of A marginale were first observed in midgut epithelial cells on the sixth day of feeding on infected calves, with the highest density of colonies found in gut cells while ticks were between feeding periods. The first colonies contained 1 large dense organism that subsequently gave rise to many reticulated organisms. Initially, these smaller organisms were electron-lucent and then became electron-dense. On the fifth day after ticks were transferred to susceptible calves for feeding, A marginale colonies were found in muscle cells on the hemocoel side of the gut basement membrane. A final site for development of A marginale was the salivary glands. Colonies were first seen in acinar cells on the first day that ticks fed on susceptible calves, with the highest percentage of infected host cells observed on days 7 to 9 of that feeding. Organisms within these colonies were initially electron-lucent, but became electron-dense.     

Qualitative and quantitative analysis of uroliths in dogs: definitive determination of chemical type

Effective treatment and prevention of urolithiasis depends on accurate determination of the chemical nature of the uroliths. A widely used qualitative chemical procedure was compared with quantitative crystallographic analysis of 272 canine uroliths. Agreement between the 2 methods was 78%. Qualitative analysis failed to detect 62% of calcium-containing uroliths and 83% of carbonate apatite uroliths. Qualitative analysis gave false-positive results for urates in 55% of cystine uroliths. Mixed uroliths comprising 6% of the total could not be classified without quantitative analysis. Silicate, cystine, and urate uroliths generally were of pure composition. Crystallographic analysis indicated the following distribution of major types: struvite, 69%; calcium oxalate, 10%; urate, 7%; silicate, 3.5%; cystine, 3.2%; calcium phosphate, 1%; and mixed, 6%. Among dogs with struvite uroliths, 66% had positive results of bacterial culturing from the urinary bladder. Six breeds (Miniature Schnauzer, Welsh Corgi, Lhasa Apso, Yorkshire Terrier, Pekingese, and Pug) had a significantly higher risk for urolithiasis, compared with other breeds. The German Shepherd Dog had a significantly lowered risk, compared with other breeds. Two breeds had significant relationship to a specific type of urolith: Miniature Schnauzer for oxalate, and Dalmatian for urate (P less than 0.001). It was concluded that quantitative analysis, using crystallography, was superior for the detection of calcium oxalate, carbonate apatite, cystine, urate, and mixed uroliths.     

Seasonal variation in passive transfer of immunoglobulin G1 to newborn calves

Forty-eight-hour serum concentrations of immunoglobulin G1 (IgG1) were determined for 123 female calves born on 1 farm during a 12-month period and fed 2.8 L of colostrum by esophageal feeder within 2 hours of birth. Mean monthly serum IgG1 concentrations were lowest in the winter, and increased during the spring and early summer to reach their peak in September, after which they decreased. Eight of 64 calves (12.5%) born from June through October had failure of passive transer of IgG1 (serum IgG1 less than 8 mg/ml), whereas 27 of 58 (46.5%) born from November through May had failure of passive transfer.     

In vitro and in vivo effects of corticosteroids on peripheral blood lymphocytes from ponies.

The in vitro and in vivo effects of corticosteroids on peripheral blood lymphocytes (PBL) from ponies were studied. Prednisolone inhibited lymphocyte stimulation by phytohemagglutin (PHA) in a dose-dependent manner, without inducing lysis even at large doses. The PBL from horses heterozygous for the combined immunodeficiency trait responded to corticosteroid treatment the same as did PBL from normal ponies. Removal of the corticosteroid after incubation with PBL from normal ponies partially restored responsiveness of these cells to PHA. Chronic in vivo treatment of ponies with corticosteroids caused a marked decrease in the absolute numbers of circulating lymphocytes. Most remaining lymphocytes had detectable surface immunoglobulin and C3 receptors, suggesting a greater decrease in the T-lymphocyte population. In spite of this, there was little change in the in vitro PHA- or keyhole limpet hemocyanin-sensitized ponies. In general, the corticosteroid effects of lysis, as well as the mitogenic and antigenic responses of PBL from ponies, were similar to those previously reported for human lymphocytes.