Peculiarities of sexual reproduction inFagus crenata forests in relation to annual production of reproductive organs

Annual production rates of reproductive organs inFagus crenata forests in the lower area of the species' range were studied using 10 litter traps in 1980–1986. The production rates of dispersed pollen were estimated by multiplying the number of fallen male inflorescences per ha per year by the mean amount of pollen per inflorescence before anthesis. Large annual fluctuations in the production rates of male and female inflorescences were recognized, whereas their annual trends were synchronized with each other. Pollen production rates were within the range 1.0–6900 (mean: 1630)×10⁹ha⁻¹ yr⁻¹, the maximum/minimum ratio attaining 7000.F. crenata was the lowest producer of pollen among seven tree species studied: the number of pollen grains equivalent to a single ovule was in the range 6.0–14×10⁴. Furthermore, the mean dry weight of a single pollen grain (3.77×10⁻⁵mg) was higher than for wind-pollinated species. Three factors seemed to cause the low seed fertility ofF. crenata. The dry-matter production rate in the best seed year reached 3252 kg ha⁻¹ yr⁻¹, of which pollen accounted for 259 kg ha⁻¹ yr⁻¹. Unproductive years with less than 10% of the maximum production occurred four times in a 7-yr period. In such years there were fewer male and female inflorescences, and more fruit dropped as a result of insect damage. Lower nut dissemination would play an important role in suppressing any increase in nut predators, and fewer flowers would be produced to avoid wastage of photosynthates in a cool-temperate climate.     

Life history characteristics of tule perch (Hysterocarpus traski) populations in contrasting environments

Synopsis The life history characteristics of tule perch were compared within and among populations in three drainages with substantially different environmental conditions. Within populations there were, in general, substantial increases in brood size, size of young, brood weight, and gonadal-somatic index (GSI) with age and with size of female. In at least one population there was a trade-off between the number and size of young produced. However, in a lake where individual growth was very slow, brood weight, GSI, and other life history characters showed decreasing trends with age. Among populations in isolated drainages, female length at first reproduction and longevity varied directly and mean brood size varied inversely with environmental predictability. Morphological and geological evidence and some comparative litter characteristics suggest that life history differences among populations in isolated drainages are in part genetic.     

Pollen placement and reproductive isolation between two brazilianPolygala species (Polygalaceae)

Polygala vauthieri andP. monticola var.brizoides have secondary pollen presentation from a basket-like structure on the style apex. This basket is loaded after the first visit by a bee. Pollen reception, therefore, can precede the issue of pollen. A sticky stigma secretion glues the pollen from the basket under the head of the bee visitor in an exactly predetermined spot on the left side only. This position mostly forms a kind of safe spot, where the bee can not remove the pollen. The exact position on the bee's head is determined by the species specific distance between style tip and nectary in the visited flower. In this way the two sympatric species deposit the pollen 2 mm apart on the visitor and so can avoid hybridization pollination, while being visited by the same group of bees.     

Estradiol binding by intact cells isolated from DMBA-induced mammary tumors of the rat

Study of hormone binding in intact cells enables one to examine binding under conditions which elicit a biological response. Cells from 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumors of the rat were enzymatically dispersed. More than 80% of these cells excluded trypan blue and were used to study binding of [3H] estradiol-17 beta. Specific binding was determined by subtracting the amount of [3H]estradiol bound in the absence and presence of 200-fold excess unlabeled estradiol. Specific binding at 37 degrees was maximal after 15 min. Steroid competition studies indicated that [3H]estradiol binding sites were relatively specific for estrogens, although there was a 9-18% inhibition of binding by androgens and progestins when present at 150-fold molar excess. Scatchard analyses of [3H]estradiol (0.15-5.0 nM) binding by whole cells suggest a single, high-affinity binding site (Kd = 7.5 x 10-10M) of low capacity (6.1 fmol/10(6) cells). More [3H]estradiol was translocated to the nucleus after 1 hr at 37 degrees than at 0 degrees. Preliminary studies indicated that incubations at 37 degrees result in appreciable metabolism of [3H]estradiol to other steroids and/or conjugates when examined by silica gel thin layer chromatography.     

Activation of human B lymphocytes. XVII. Synergy between nonspecific and specific signals in the antigen-specific responses of human B cells

The incubation of human peripheral blood lymphocytes (PBL) with the natural killer (NK)-sensitive MOLT-4 cell line results in PBL-target cell conjugate formation by certain lymphocyte subpopulations. Following velocity sedimentation, the PBL depleted of these conjugate-forming subpopulations are markedly diminished in the ability to mediate either antibody-dependent cellular cytotoxicity (ADCC) or NK activity. The immediate testing of highly pure PBL subpopulations isolated from the NK target conjugates does not reveal the expected recovery of augmented ADCC or NK levels. Following in vitro incubation, however, the PBL NK target-binding subpopulations do manifest augmented levels of both NK and ADCC, whereas the depleted PBL continue to display diminished NK and ADCC levels. In addition, the degree of augmented NK and ADCC levels recovered by the NK target-binding PBL subpopulations appears dependent on both the time and the temperature of in vitro incubation. Moreover, the ADCC recovery patterns are identical to those observed for NK activity regardless of the time and temperature of in vitro incubation. These results directly demonstrate that the PBL subpopulations isolated from certain NK target cells are functionally enriched in the ability to mediate from ADCC and NK activity.     

Potentiation of the in vitro cytotoxic response to syngeneic lymphoma cells by soluble products of tuberculin-sensitive lymphoid cells stimulated with PPD

Spleen cells from rats immunized with the syngeneic (C58NT)D Gross virus induced lymphoma have previously been shown to differentiate into cytotoxic effector cells following restimulation with tumor cells in vitro. Previous work has also demonstrated that the addition of PPD-primed syngeneic spleen cells and PPD to cultures of (C58NT)D-primed spleen cells will potentiate the in vitro cytotoxic response to tumor antigens. In the studies presented here, the potentiating effect was found to be mediated by a soluble factor(s) released by nonadherent cells from BCG-primed rats. The release of this immunopotentiating factor(IPF) required the presence of PPD and varied with the concentration of PPD added. IPF was produced by BCG-primed spleen, lymph node, and thymus cells. Maximal production of IPF in PPD-stimulated cultures was obtained after 6–12 hr of incubation. Supernatants obtained after 30 hr of incubation lacked apparent IPF activity when tested initially, but activity was recovered after mild heat treatment. Recovery of IPF activity after heat exposure is best explained by the presence of a heat-labile inhibitor. IPF itself is stable to heat treatment to 56 °C for 40 min. IPF was also shown to be capable of enhancing immune responses to histocompatibility antigens in vitro.     

Benzo(a)pyrene quinone metabolism in tracheal organ cultures.

The C^? methyl group of methionine-29 of RNAase was enriched with ¹³C. The synthesis involved the reaction of RNAase with ¹³CH₃I at pH 4. S-Methylmethionine-29 RNAase was recovered in 80% yield. This sulfonium derivative was subsequently demethylated with 0.1 M mercaptoethanol at pH 8.5, 25°C for 4 days. These conditions allowed the demethylation reaction to successfully compete with the reaction of the thiol with the four disulfide bridges in RNAase. After dialysis, concentration and chromatography, native RNAase with approx. 50% of its Met²⁹ methyl groups enriched in ¹³C was recovered as was unreversed S-Methylmethionine-29 RNAase. Both proteins showed full enzymatic activity toward cytidine 2′:3′-cyclic monophosphate. ¹³C-methyl signals from enriched RNAase and the sulfonium derivative were observed at 13.8 and 26.7 ppm from TMS respectively. Preliminary denaturation studies with the methylated protein suggest that ¹³C enrichment of methionine methyl groups in RNAase will be a useful technique for following the unfolding transition at these sites of the protein.     

The effects of corticosteroids on immunoregulation in sarcoidosis.

The effects of in vivo hydrocortisone administration on the kinetics and functional capabilities of cells involved in the immune response in sarcoidosis were examined. Untreated sarcoidosis patients have a decrease in the absolute numbers of circulating T lymphocytes (P < 0.05). However, with regard to the proportions of T lymphocyte subpopulations, there is an increase in the relative proportions of IgG Fc receptor positive T cells (T_G) (P < 0.01), which have suppressor capabilities in certain in vitro systems of mitogen-induced antibody production, and a relative decrease in IgM Fc receptor positive T lymphocytes (T^M) which have helper effects in this system (P < 0.05). Additionally, sarcoidosis patients have circulating “suppressor” monocytes capable of suppressing anti-sheep red blood cell (SRBC) plaque-forming cell (PFC) responses by pokeweed mitogen (PWM)-stimulated lymphocytes. The in vitro removal of this cell abrogated this depressed response (P < 0.01). Intravenous administration of hydrocortisone produced a transient absolute T lymphocytopenia (P < 0.01) accompanied by a relative increase in T^G cells (P < 0.01) and a relative decrease in T_M cells (P < 0.02). Four hours after hydrocortisone therapy, at the point of maximal hydrocortisone-induced monocytopenia (P < 0.01), the suppressed ability of sarcoidosis lymphocytes to synthesize and secrete in vitro anti-SRBC antibody after polyclonal activation was corrected (P < 0.01), and PFC responses comparable to those seen in untreated normal subjects were obtained. These studies demonstrate that corticosteroid administration has profound effects on certain in vitro demonstrable immunoregulatory abnormalities in sarcoidosis.