Habitat selection in two sympatric Chinese skinks, Eumeces elegans and Sphenomorphus indicus: do thermal preferences matter?

We studied the habitat selection and thermal biology of two sympatric Chinese skinks ( Eumeces elegans Boulenger, 1887 and Sphenomorphus indicus (Schmidt, 1928)) to test the effect of thermal preference on habitat partitioning. We measured thermal and structural attributes of the microhabitats occupied by these two skink species, as well as their field body temperatures and activity patterns. We then quantified the preferred body temperatures of these species in a thermal gradient. Compared with S. indicus, E. elegans occupied microhabitats with fewer trees, more rocks, and higher ambient temperatures. Active S. indicus were mainly found in the morning, whereas active E. elegans were found at noon. The thermal environment of the microhabitats at these two periods correlated with the skinks’ thermal preferences. Preferred temperatures of E. elegans were significantly higher than those of S. indicus. These results support (i) the hypothesis that habitat partitioning between ectotherms is related to interspecific differences in thermal requirements; (ii) the labile hypothesis that describes the adaptability of thermal physiology, because the two sympatric skinks, which select different thermal environments, differed in thermal physiology; and (iii) the cold-climate hypothesis that explains the evolution of viviparity, because viviparous S. indicus occupy colder habitats than do oviparous E. elegans.

Isolation and characterization of chitinase from a flake-chitin degrading marine bacterium, Aeromonas hydrophila H-2330

A flake-chitin degrading marine bacterium was isolated and identified as Aeromonas hydrophila. This strain secreted five chitinases and an beta-N-acetylglucosaminidase. The main chitinase (Chi-A) was purified and characterized. The optimum pH of Chi-A was 5-8, and the activity was inhibited by Hg2+ and Fe3+. Chi-A was different from chitinases of other Aeromonas species with respect to molecular weight (62,000) and insensitivity to monoiodoacetate. The amino-terminal amino acid sequence showed extensive similarity with chitinases from Gram-negative bacteria.

Mechanism of action of chounghwamycin A

The mechanism of action of chounghwamycin A to tumor cells resembles that of actinomycin D, preferentially inhibiting the synthesis of RNA. The interaction of chounghwamycin A with DNA was studied, and the results indicated that chounghwamycin A could not cause any scission in tested DNA. However, an induced mobility shift of the DNA in agarose gel electrophoresis was observed. When the concentration of chounghwamycin A gradually increased, the migration rate of closed circular form DNA is gradually slowed. At a critical concentration of chounghwamycin A, 15.6 micrograms/ml, the migration rate of closed circular form DNA reaches its minimum value. As more choungwamycin A is added, the mobility of the closed circular DNA increases gradually again, suggesting that the intercalation of chounghwamycin A in DNA is the primary mechanism of its action against tumor cells.

Persistence of hepatitis B viral antigens in Culex quinquefasciatus

Culex quinquefasciatus mosquitoes were fed on or inoculated with blood or serum positive for hepatitis B viral antigens and pools of mosquitoes were tested by radioimmunoassay daily for 3 weeks after exposure to detect the viral antigens. Hepatitis B surface antigen (HBsAg) was detectable up to 3 weeks, while hepatitis B e antigen (HBeAg) persisted only for 3 days in mosquitoes after feeding on hepatitis B viral antigens-positive blood. Mosquitoes inoculated with serum were HBsAg-positive for 3 weeks and HBeAg positive for 4 days after inoculation. These results suggest that biological multiplication of hepatitis B virus did not occur in these mosquitoes. The possibility of mechanical transmission of hepatitis B antigens by mosquitoes is discussed.

Detection of circulating immune complexes in liver diseases, systemic lupus erythematosus and glomerulonephritis by polyethylene glycol precipitation

A method for detection and quantitation of circulating immune complexes using precipitation of the complexes by polyethylene glycol (PEG) has been reexamined to determine the influence of pH on the recovery and the reproducibility of the results. Results showed that the pH optimum for these determinations was 7.8. The recovery percentages range from 57.8-146.5% at lower immune complex concentrations, and from 73.9-101.3% at higher concentrations. The reproducibility of the method seems reasonably acceptable with a percent coefficient of variation ranging from 0.5-9.5. This method for quantitation of circulating immune complexes by polyethylene glycol precipitation is consistent and relatively reliable. Using this method, the levels of circulating immune complexes in sera in patients with hepatitis, liver cirrhosis, hepatoma, acute post-streptococcal glomerulonephritis (before and after treatment) and systemic lupus erythematosus have been examined. The results showed that except the patients with treated acute post-streptococcal glomerulonephritis who had a similar amount of immune complexes with normal controls, the level of immune complexes in patients with other types of diseases were all higher than the control. In addition, the composition of IgG, IgA, IgM, C3 and C4 of the precipitable complexes in sera of patients with three types of liver disease has been analyzed and demonstrated that the percentages of IgM were higher than the normal control. However, C3 and C4 in hepatitis and liver cirrhosis patients were lower than those of the control.

Separation and further characterization of early and late rosette-forming cells

Human peripheral blood T-lymphocytes (PBL) can be separated into early rosette-forming cells or active T cells (A-RFC) and late rosette forming cells (L-RFC) according to the time required for formation of rosettes with sheep red blood cells (SRBC). Experimental results showed that treatment of the SRBC with neuraminidase was necessary for the formation of stable early rosettes. The optimum proportion of SRBC to lymphocytes for total rosette formation was 64:1, whereas a 16:1 ratio yielded maximal early rosette formation. The proliferative responses of A-RFC to concanavalin A (Con A) or to alloantigens were less than those seen with L-RFC. The percentage of T gamma cells in A-RFC was significantly lower than in L-RFC. Leukocyte inhibitory factors (LIF) released by the A-RFC fraction after treatment with Con A were more effective inhibitors of the migration of polymorphonuclear leukocytes (PMN) than the factors released from the L-RFC fraction. These results suggest that A-RFC represent a subpopulation of T lymphocytes which are more active in certain lymphocyte responses than another subpopulation which forms rosettes more slowly with sheep red blood cells.

[Effect of gamma-ray irradiation, DNA and protein synthesis inhibitors on the generation of soluble suppressor factors by mononuclear leukocytes]

During a 4-days in vitro culturing period and without any antigenic or mitogenic stimulation, mononuclear leukocytes of normal human peripheral blood could release a soluble suppressor factor(s) which was able to suppress the one-way mixed lymphocyte reaction to an average degree of 45.3%. The generation of the aforementioned factor(s) was not affected by mitomycin C which is a DNA synthesis inhibitor, but was suppressed to a certain extent by protein synthesis inhibitors such as puromycin and cycloheximide. In addition, the factor(s) released by non-irradiated cells was more active than that released by irradiated counterparts, suggesting that the factor(s) was not a byproduct of cell death or metabolic toxic substances. The soluble suppressor factor(s) was found to be mainly generated by lymphocytes rather than by monocytes. However, the latter might, in some way, potentiate the generation of this factor(s).

The relationship between suppressor cells and malignancy

Peripheral blood lymphocytes (PBL) from cancer patients were first tested for the proliferative response to concanavalin A (Con A). The lymphocytes which had lower response to Con A than the normal control were supposed to have relatively greater numbers of putative suppressor cells, or higher suppressive activity was anticipated in the PBL. The PBL were then treated with mitomycin C, added to normal lymphocytes in the presence of Con A, and cocultured for further investigation of the activity of the putative suppressor cells as determined by the effect of these putative cells on the responses of normal lymphocytes to Con A. In many of our studies inconsistent results showed between two types of assay systems. Not all patient's lymphocytes showing depression in response to Con A could suppress the proliferation of normal lymphocytes in response to Con A in coculture systems. However, some of the patients' lymphocytes, despite not showing a depressed response to Con A in the direct assay, were able to inhibit the response of normal lymphocytes to Con A in coculture. The contradictory data imply that it is inappropriate to conclude that suppressor cells are present at elevated levels in cancer patients by relying solely on the evidence of a depressed response to mitogens, either in a direct stimulation assay or in a coculture system. Our results possibly reflect that the development of cancer is not directly linked to the elevation of suppressor cell activity. Other more complicated mechanisms may be involved.

A human soluble suppressor factor affecting lymphocyte responses in vitro

A soluble suppressor factor (SSF) has been demonstrated in the supernatant of normal human peripheral blood lymphocyte cultures that exhibits suppressive activity toward the proliferative response of normal lymphocytes to concanavalin A or alloantigens in mixed lymphocyte culture (MLC) or toward pokeweed mitogen-stimulated immunoglobulin synthesis and secretion in vitro. Suppression of the proliferative response in MLC reached maximal levels when added SSF-containing supernatant approximated 20% by volume of the culture medium. Suppression in the MLC was found to act at the proliferative stage. SSF acts independently of cytotoxicity and is stable at 56 degrees C for 30 min but is inactivated at higher temperatures. Addition of SSF to the MLC as late as day 4 after initiation of the culture results in suppression of transformation. This factor(s) may regulate the magnitude of several immune responses in humans.

Modulatory effects on immunoglobulin synthesis and secretion by lymphocytes from immunodeficient patients

Incubation of peripheral lymphocytes (PBL) from normal donors with pokeweek mitogen (PWM) induced terminal differentiation by B lymphocytes to immunoglobulin (Ig) synthesizing and secreting plasma cells. B cells from hypogammaglobulinemic patients with different primary immunodeficiencies failed to undergo functional differentiation after similar treatment with PWM. Co-cultures of BL from normal donors and hypogammaglobulinemic patients often resulted in deviations, both positive and negative, from expected levels of PWM-stimulated intracellular Ig biosynthesis. Suppression of B-cell differentiation was manifested by PBL from patients with several different primary immunodeficiencies, including infantile sex-linked agammaglobulinemia. Immunoregulatory activities were noted to vary with the normal donor used in co-culture experiments and with time. Cell populations that were active in influencing B-cell differentiation to functional plasma cells did not have an appreciable modulatory effect on T-lymphocyte responses to mitogens. These observations may provide a functional subclassifications for immunoregulatory cells in man.

Suppression of immunoglobulin synthesis and secretion by peripheral blood lymphocytes from normal donors

Concanavalin A (Con A)-treated peripheral blood lymphocytes from healthy volunteer donors have been shown to suppress proliferative responses associated with thymus-derived lymphocytes (T-cells). The present investigations demonstrate that peripheral blood lymphocytes incubated with Con A for 48 hr can abrogate pokeweed mitogen-stimulated differentiation of bone-marrow-derived (B) lymphocytes to immunoglobulin-synthesizing and -secreting plasma cells. This effect was manifested when washed Con A-treated peripheral blood lymphocytes were added to pokeweed mitogen-stimulated cocultures containing fresh autologous or allogeneic mononuclear cells, and it did not appear to involve cytotoxicity. Parallel control cultures consisting of mononuclear leukocytes incubated for 48 hr in the absence of Con A also had immunoglobulin suppressor activity in mixing experiments. This effect, however, was most pronounced when preincubated cells were added to fresh autologous pokeweed mitogen-stimulated peripheral blood lymphocytes. Cell mixtures containing peripheral blood lymphocytes demonstrated a spectrum of immunoregulatory effects ranging from suppression to enhancement of pokeweed mitogen-stimulated immunoglobulin synthesis and secretion. Several functional subclasses of suppressor cells that reflect varying levels of specific activity have thus been demonstrated in human beings. Moreover, a degree of genetic identity appears to be required for the expression of "weak" immunoregulatory influences.

Lymphocyte transformation in children with neuroblastoma

Using a simple fingerstick-whole blood technique, we demonstrated that patients with disseminated neuroblastoma have diminished lymphocyte responses to phytohemagglutinin (PHA) and that their sensitivity to antilymphocyte serum inhibition of PHA responses was increased over that of tumor-free controls. These altered immunologic reactivities led us to question the chronologic sequence between the occurrence of the tumor and the lymphocyte defect. Tumor-bearing patients had serum substances that exerted an inhibitory effect on the transformation responses of lymphocytes from unrelated normal individuals; these substances may be present in sera for long periods after the tumor is eliminated.

Suppressor cell activity after concanavalin A treatment of lymphocytes from normal donors

Pretreatment of normal human peripheral blood lymphocytes with the plant lectin, concanavalin A (Con A), results in inhibition of blast transformation and [3H]thymidine incorporation by untreated allogeneic lymphocytes from healthy volunteers donors in one-way mixed leukocyte culture. Similarly, responses to mitogens, certain microbial antigens, and allogeneic lymphocytes are inhibited by Con A-treated allogeneic cells. Con A pretreated autologous lymphocytes can also be induced to manifest suppressor activities. This antimitotic effect occurs without evidence of cytotoxicity and is active on de novo lymphocyte responses and does not require prior sensitization of the cells being tested. Suppression of the lymphocyte response to pokeweed mitogen, a potent B-cell stimulator, by Con A-pretreated suppressor cells was not as consistent as was inhibition of response to other mitogens, including phytohemagglutinin and Con A. Furthermore, suppression of lymphocyte transformation to the microbial antigens, tuberculin purified protein derivative, and Canadida albicans extracts could be similarly induced by Con A pretreatment of either allogeneic or autologous cells. Induction of autologous suppressor activity in lymphocytes from healthy donors is compatible with a model that includes a role for suppressor cells in the modulation of the normal immune response.