Comparison of the roles of Ostracods and Cladocerans in regulating community structure and metabolism in freshwater microcosms

Laboratory microcosms were used to compare the effects of the littoral ostracod Cypridopsis vidua and the planktonic cladoceran Daphnia magna on community structure and metabolism. Filter-feeding by cladocerans, both in the presence and absence of ostracods, greatly reduced the abundance of planktonic algae when D. magna reached peak density around day 50; rotifers and euglenids were then limited to flocculent matter on the container bottom. Both net production and community respiration rates decreased as community composition changed. Microcosms containing ostracods as the only microcrustacean showed little reduction in total algal numbers but the otherwise dominant alga, Scenedesmus spp., was replaced by Ankistrodesmus spp. when peak ostracod density was reached around day 100. Rotifers were completely eliminated but euglenids were able to coexist with ostracods. Ostracods impacted community metabolism less than cladocerans, but depressed respiration slightly more than net production.     

alpha-Difluoromethylornithine induces differentiation of a human embryonal carcinoma cell line in vitro

Human embryonal carcinoma cells could serve as a useful model system for analysis of early human development. A limited number of human embryonal carcinoma cell lines have been generated from in vivo tumors. We report here that alpha-difluoromethylornithine, a specific enzyme-activated inhibitor of ornithine decarboxylase activity, can induce differentiation in human embryonal carcinoma cells. The differentiated phenotype could be distinguished from undifferentiated cells by altered cellular morphology, biochemical and cell surface antigenic properties. These results suggest that alterations in the intracellular levels of polyamines may play a role in human embryonal carcinoma cell differentiation, and possibly human embryogenesis.     

Production of steroids and release of prostaglandins by spherical pig blastocysts in vitro

Levels of pregnenolone and progesterone in spherical pig blastocysts (near 4 and 15 microM respectively) exceeded respective levels in histotroph by about 400-fold. When blastocysts were cultured for 5 days in a synthetic medium containing pregnenolone sulfate (1 microM), daily rates of release of pregnenolone, progesterone, androstenedione, testosterone, oestrone and oestradiol were determined to be near 320, 45, 26, 27, 0.8 and 9.2 fmol per blastocyst respectively. Daily outputs of progesterone and testosterone (fmol per blastocyst) diminished (P less than 0.05) to 1.3 and undetectable levels (less than 2) respectively in the presence of Trilostane (94 microM). Increasing the content of pregnenolone sulfate in the culture medium (to 4.5 microM) resulted in higher daily rates of release of pregnenolone and progesterone (to near 1740 and 380 fmol per blastocyst respectively), verifying activity of 3 beta-hydroxy-delta 5-steroid dehydrogenase, and of arylsulfatase, in tissues of intact spherical pig blastocysts. Prostaglandin E2 was the predominant prostaglandin (PG) released by cultured blastocysts (about 1 fmol per blastocyst per hour), hourly rates of release of PGH2 (derived) and PGF2 alpha being near 0.1 and less than 0.06 fmol per blastocyst respectively. The data establish a capacity for spherical pig blastocysts to release a range of steroids and PGs of possible significance to embryonic growth and development in vivo.     

Spontaneous interstitial nephritis in kdkd mice. II. Characterization of a tubular antigen-specific, H-2K-restricted Lyt-2+ effector T cell that mediates destructive tubulointerstitial injury

In this report, we have examined the effector T cell repertoire in the spontaneous interstitial nephritis of kdkd mice. Lymph node cells from nephritic kdkd mice are capable of transferring this disease into thymectomized, irradiated, and bone marrow-reconstituted CBA/Ca recipients. CBA/Ca mice do not spontaneously develop interstitial nephritis and are normally resistant to the adoptive transfer of nephritic cells, a resistance that in the short term can be attenuated with low-dose cyclophosphamide. We therefore used delayed-type hypersensitivity responses and direct transfer of immune cells under the renal capsule to characterize nephritogenic effector cells from kdkd donor mice. Lyt-2+, L3T4- T cells from the peripheral lymphoid organs of nephritic kdkd mice, after adoptive transfer into cyclophosphamide-pretreated CBA/Ca recipients, mediate an antigen-specific delayed-type hypersensitivity response to renal tubular basement membrane antigens. These cells are restricted by gene products in H-2Kk; they are also present in nephritic, but not in control kidneys. We have also observed this same phenotypic subpopulation of kdkd lymphocytes mediate a destructive interstitial renal lesion within 7 days of being placed under the kidney capsule of CBA/Ca mice. These findings suggest that T lymphocytes reactive to a parenchymal tubular antigen are of substantial importance in the development of spontaneous interstitial nephritis in kdkd mice.     

Dietary effects on hematologic and serum chemical values in gray short-tailed opossums (Monodelphis domestica)

At the time of weaning (8 weeks), 57 gray short-tailed opossums (Monodelphis domestica) were placed in four dietary groups. One group was fed a horsemeat-based diet that had been used for 2.5 years in our colony, and three groups were fed three different commercial fox food diets. After the animals had reached sexual maturity (6 months), blood samples were collected and subjected to standard hematologic and serum chemical assays. Significant differences were observed among the dietary groups and between sexes in several values, but all animals appeared to be healthy and robust. The ranges, means, and standard deviations for the values presented here can be used as reference values for healthy young adult animals being fed these particular diets.     

Characterization of a progressive neurodegenerative disease induced by a temperature-sensitive Moloney murine leukemia virus infection.

A progressive neurodegenerative disease occurred following infection of mice with a temperature-sensitive (ts) isolate of Moloney (Mo) murine leukemia virus (MuLV), ts Mo BA-1 MuLV. This NB-tropic ecotropic MuLV, which was ts for a late function, induced a syndrome of tremor, weakness of the hind limbs, and spasticity following infection of several strains of laboratory neonatal mice, including NFS, C3H/He, CBA, SJL, and BALB/c. The latent period of 8 to 16 weeks was considerably longer than that observed for the acute paralytic diseases observed following neonatal infection with other ts Mo-MuLV, rat-passaged Friend MuLV, and some wild mouse ecotropic MuLVs. Spongiform pathology without inflammation and degeneration of neurons devoid of budding virions occurred in the cerebellar grey matter, brain stem, and upper spinal cord; but lower spinal cord anterior horn cells were less obviously affected than in other MuLV-associated neuroparalytic syndromes. ts Mo BA-1 MuLV differed from other ts Mo-MuLV mutants that are capable of inducing a neuroparalytic syndrome in that while infected nervous system tissue contained high levels of MuLV p30 and gp70, no evidence of precursor accumulation or abnormal processing of MuLV p30 or gp70 could be demonstrated. The localization of virus within the nervous system suggests that direct neuronal infection may not be the etiologic mechanism in this MuLV-induced neurodegenerative disease.     

Thoracoabdominal blood volume change and its effect on lung and chest wall volumes

The effects of changing blood volume within the thoracoabdominal cavity (Vtab) have been studied in four male subjects trained in respiratory maneuvers. Subjects were studied lying supine in a pressure plethysmograph with inflatable fracture splints placed around both arms and legs. Changes in Vtab were produced by inflating the splints to 30 cmH2O. Thoracic gas volume (Vtg) measured by Boyle's law, and the change in chest wall volume (delta Vw), measured by anteroposterior magnetometers on rib cage and abdomen, were measured almost simultaneously and at two respiratory system volumes. The quantity of blood moved by splint inflation was estimated for each subject at both respiratory system volumes and varied between 215 and 752 ml. The chest wall increased 64 +/- 11.8% (mean +/- SD) of the increase in Vtab. Thus increases in thoracoabdominal blood volume increase Vw about twice the decrease in Vtg.     

Relationship between diaphragm length and abdominal dimensions

We examined the relationship between changes in abdominal cross-sectional area, measured by respiratory inductive plethysmography, and changes in length in the costal and crural parts of the diaphragm, measured by sonomicrometry, in nine supine, anesthetized dogs. During passive inflation, both parts of the diaphragm shortened and abdominal cross-sectional area increased. During passive deflation, both parts of the diaphragm lengthened and abdominal cross-sectional area decreased. We subsequently used the relationship between costal and crural diaphragmatic length, respectively, and abdominal cross-sectional area during passive inflation-deflation to predict the length changes in the costal and crural diaphragm during quiet breathing before and after bilateral phrenicotomy. In the intact animal the inspiratory shortening in the crural diaphragm was almost invariably greater than predicted from the relationship during passive inflation. During inspiration after phrenicotomy the crural diaphragm invariably lengthened, whereas the costal diaphragm often shortened. In general there was a good correlation between the measured and predicted length change for the crural diaphragm (r = 0.72 before and 0.79 after phrenicotomy) and a poor one for the costal diaphragm (r = 0.05 before and 0.19 after phrenicotomy).     

Perfusion of lung periphery: effects of local exposures to ozone and pressure

Following ozone (O3) exposure, airways reactivity increases. We investigated the possibility that exposure to O3 causes a decrease in pulmonary perfusion, and that this decrease is associated with the increase in reactivity. Perfusion was measured with radiolabeled microspheres. A wedged bronchoscope was used to isolate sublobar segments in the middle and lower lobes of anesthetized dogs. Isolated segments were exposed to either O3 or an elevated alveolar pressure. Although increased alveolar pressure decreased microsphere density, exposure to 1 ppm O3 did not. Collateral system resistance rose significantly following exposure to O3 and to high pressure. These studies do not support the hypothesis that pulmonary perfusion is decreased following O3 exposure and is associated with subsequent increases in reactivity.