Desipramine Binding: Relationship to Central and Sympathetic Noradrenergic Activity

We examined the effects of treatments affecting norepinephrine release on the number of norepinephrine reuptake recognition sites as reflected by desipramine binding. To do this, we used manipulations having similar presynaptic but contrasting postsynaptic effects. Presynaptic inhibition by 6-hydroxydopamine lesion or by clonidine, and postsynaptic receptor stimulation by isoproterenol, reduced desipramine binding. Presynaptic stimulation by d-amphetamine and postsynaptic receptor blockade by prazosin increased desipramine binding. Similar effects and binding properties were seen in cerebral cortex, heart, and soleus muscle. After unilateral noradrenergic lesions, reduction in desipramine binding correlated with reduction in norepinephrine uptake. These results show that norepinephrine reuptake appears to be regulated by transmitter release regardless of effects on postsynaptic transmission, and that this regulation is analogous in the central and sympathetic nervous systems.     

Allometries of the durations of torpid and euthermic intervals during mammalian hibernation: A test of the theory of metabolic control of the timing of changes in body temperature

Summary The durations of the intervals of torpor and euthermia during mammalian hibernation were found to be dependent on body mass. These relationships support the concept that the timing of body temperature changes is controlled by some metabolic process. Data were obtained from species spanning nearly three orders of magnitude in size, that were able to hibernate for over six months without food at 5°C. The timing of body temperature changes was determined from the records of copper-constantan thermocouples placed directly underneath each animal. Because all species underwent seasonal changes in their patterns of hibernation, animals were compared in midwinter when the duration of euthermic intervals was short and relatively constant and when the duration of torpid intervals was at its longest. Large hibernators remained euthermic longer than small hibernators (Fig. 2). This was true among and within species. The duration of euthermic intervals increased with mass at the same rate (mass^0.38) that mass-specific rates of euthermic metabolism decrease, suggesting that hibernators remain at high body temperatures until a fixed amount of metabolism has been completed. These data are consistent with the theory that each interval of euthermia is necessary to restore some metabolic imbalance that developed during the previous bout of torpor. In addition, small species remained torpid for longer intervals, than large species (Fig. 3). The absolute differences between different-sized species were large, but, on a proportional basis, they were comparatively slight. Mass-specific rates of metabolism during torpor also appear to be much less dependent on body mass than those during euthermia, but the precision of these metabolic measurements is insufficient for them to provide a conclusive test of the metabolic theory. Finally, small species with high mass-specific rates of euthermic metabolism are under tighter energetic constraints during dormancy than large species. The data presented here show that, in midwinter, small species compensate both by spending less time at high body temperatures following each arousal episode and by arousing less frequently, although the former is far more important energetically than the latter.     

Maturation of pig and rat oocytes transplanted into surrogate pig follicles in vitro

Pig oocytes obtained from slaughterhouse material and rat oocytes obtained from PMSG-treated immature females were incubated as isolated oocytes or injected into explanted pig follicles (5–8 mm). Free oocytes of both species, with or without their cumulus investment or gonadotropins during culture, matured at high rates after 30 hr or 9–10 hr of culture, respectively. Gonadotropic stimulation was necessary for maturation of both the native and injected cumulus-intact pig oocytes in follicle culture. Cumulus-free pig oocytes injected into follicle failed to mature in response to gonadotropic stimulation, suggesting an inability to perceive or respond to stimulation. Injected rat oocytes, however, matured irrespective of cumulus investment or gonadotropic stimulation. Their maturation was delayed and reduced at 9 hr. These results in the rat suggest that the pig follicular environment is incapable of regulating rat oocyte maturation but rather presents a permissive or supportive environment for their maturation. The explanted surrogate follicles from the pig or other species may provide a useful model for the study of oocyte-follicle interactions in oocyte maturation within or between species.     

Identification of a tumor inhibitory factor in rat ascites fluid

A polypeptide which inhibits the growth of human carcinoma cells has been characterized from Novikoff rat ascites fluid. This tumor inhibitory factor co-purified with transforming growth factor activity through acid/ethanol extraction and Bio-Gel chromatography. The two activities were completely separated by reverse phase HPLC. The tumor inhibitory factor is heat stable and requires disulfide bonds for bioactivity. This factor inhibited the anchorage independent growth of the more differentiated human colon carcinoma cell lines but did not affect the less differentiated carcinoma cells. The presence of stimulatory and inhibitory activities in the same extracts suggests that the relative concentrations of these factors may be important in the control of cell growth.     

Effects of ultraviolet-B radiation on plants during mild water stress. IV. The insensitivity of soybean internal water relations to ultraviolet-B radiation

The combined effects of ultraviolet-B (UV-B, 280–320 nm) radiation and water stress were investigated on the water relations of greenhouse grown soybean [ Glycine max (L.) Merr. cv. Essex]. On a weighted (Caldwell 1971), total daily dose basis, plants received either 0 or 3 000 effective J m² UV-B_BE supplied by filtered FS-40 sunlamps. The latter dose simulated the solar UV-B radiation anticipated at College Park, Maryland, U.S.A. (39°N latitude) in the event that the global stratospheric ozone column is reduced by 25%. Plants were either well-watered or preconditioned by drought stress cycles. Diurnal measurements of water potential and stomatal conductance were made on the youngest fully expanded leaf. Various internal water relations parameters were determined for detached leaves. Plants were monitored before, during and after water stress. There were no significant differences in leaf water potential or stomatal conductance between treatments before plants were preconditioned to water stress. However, drought stress resulted in significantly lower midday and afternoon leaf water potentials and lower leaf conductances as compared to well-watered plants. UV-B radiation had no additional effect on leaf water potential; however, UV did result in lower leaf conductances in plants preconditioned to water stress. Turgid weight:dry weight ratio, elastic modulus, bound water and relative water content were unaffected by UV-B radiation. Osmotic potentials at full and zero turgor were significantly lower in the drought stressed treatments as compared to well-watered plants.     

Effects of ultraviolet-B radiation on plants during mild water stress. III. Effects on photosynthetic recovery and growth in soybean

Soybean { Glycine max (L.) Merr. ev. Essex} was grown from seed in a greenhouse under ultraviolet-B (UV-B, 280–320 nm) radiation supplied by filtered FS-40 sunlamps. On a weighted, total daily dose basis these plants received either 0 (control) or 2875 effective J m⁻² day⁻¹ UV-B_BE. When weighted with the generalized plant action spectrum (Caldwell 1971), this simulated the solar ultraviolet-B irradiance expected to occur at College Park, Maryland, USA (39°N) in the event the global stratospheric ozone column is reduced by 23%. The effects of ultraviolet radiation on the photosynthetic recovery from water stress were measured with an infrared gas analyzer. These effects were examined in plants which were either well-watered or previously preconditioned to water stress, during two distinct phenological stages of development. During the early stages of soybean growth, enhanced levels of UV-B reduced net photosynthesis by 25%, and water stress also reduced photosynthesis to nearly the same extent (by 20%). The combination of these two stresses resulted in smaller biomass than that produced by plants exposed to either stress independently. Photosynthesis in older, larger plants was much more sensitive to water stress and was reduced by as much as 50–60% in non-preconditioned plants. Although non-irradiated, non-preconditioned (control) plants recovered to only within 60% of their prestressed value, preconditioned plants recovered to within 70–80% during the 3 day recovery period. Both water stress and UV-B radiation affected non-stomatal conductance, while stomatal conductance was primarily affected by water stress.     

Characterization of a membrane-specific tubulin isoform by peptide mapping

A membrane-specific tubulin-like protein, found in preparations of synaptic plasma membranes and brain mitochondria, was analyzed by chemical and proteolytic peptide mapping to determine which part of the molecule was different from cytoplasmic tubulin. The membrane polypeptide was identical to alpha tubulin in the first two-thirds of the molecule containing the amino terminal, as found by peptide mapping. However, some differences were observed in the peptide maps of the carboxy terminal one third of the molecule which includes a domain that is important in the regulation of tubulin self-assembly.     

Several biotic and abiotic elicitors act synergistically in the induction of phytoalexin accumulation in soybean

Summary Plants often respond to microbial infection by producing antimicrobial compounds called phytoalexins. Plants also produce phytoalexins in response to in vitro treatment with molecules called elicitors. Specific elicitors, including a hexa--glucosyl glucitol derived from fungal cell walls, the pectin-degrading enzyme endopolygalacturonic acid lyase, and oligogalacturonides obtained by either partial acid hydrolysis or enzymatic degradation of plant cell walls or citrus polygalacturonic acid, induce soybean (Glycine max. L.) cytoledons to accumulate phytoalexins. The experiments reported here demonstrate that the elicitor-active hexa--glucosyl glucitol acts synergistically with several biotic and abiotic elicitors in the induction of phytoalexins in soybean cotyledons. At concentrations below 50 ng/ml, the hexa--glucosyl glucitol does not induce significant phytoalexin accumulation. When assayed in combination with either endopolygalacturonic acid lyase or with a decagalacturonide released from citrus polygalacturonic acid by this lyase, however, the observed elicitor activity of the hexa--glucosyl glucitol is as much as 35-fold higher than the sum of the responses of these elicitors assayed separately. A similar synergism was also demonstrated for the combination of the hexa--glucosyl glucitol with dilute solutions of sodium acetate, sodium formate, or sodium propionate buffers. These buffers are thought to damage or kill plant cells, which may cause the release of oligogalacturonides from the plant cell wall. The results suggest that oligogalacturonides act as signals of tissue damage and, as such, can enhance the response of plant tissues to other elicitor-active molecules during the initiation of phytoalexin accumulation.Supported by the United States Department of Energy DE-ACO2-84ER13161. This paper is number XXXI in a series, Host-Pathogen Interactions. The preceding paper, Host-Pathogen Interactions XXX is Characterization of elicitors of phytoalexin accumulation in soybean released from soybean cells by endopolygalacturonic acid lyase, by K. R. Davis, A. G. Darvill, P. Albersheim, and A. Dell. Zeitschrift für Naturforsschung, in press.     

Plant regeneration of the legume Lens culinaris Medik. (lentil) in vitro

Until recently, grain legumes in general have proven recalcitrant at de novo regeneration in vitro. By culturing portions of lentil (Lens culinaris) shoot meristems and epicotyls on a medium containing kinetin and gibberellic acid, callus tissue was produced which could be induced to regenerate shoots in relatively large numbers, even after several subcultures. The shoots could be rooted in a mist chamber to yield whole, fertile plants.     

A moving boundary model of acrosomal elongation

A sperm penetrates an egg by extending a long, actin-filled tube known as the acrosomal process. This simple example of biomotility is one of the most dramatic. In Thyone, a 90 m process can extend in less than 10 s. Experiments have shown that actin monomers stored in the base of the sperm are transported to the growing tip of the acrosomal process where they add to the ends of the existing filaments.The force that drives the elongation of the acrosomal process has not yet been identified although the most frequently discussed candidate is the actin polymerization reaction. Developing what we believe are realistic moving boundary models of diffusion limited actin fiber polymerization, we show that actin filament growth occurs too slowly to drive acrosomal elongation. We thus believe that other forces, such as osmotically driven water flow, must play an important role in causing the elongation. We conjecture that actin polymerization merely follows to give the appropriate shape to the growing structure and to stabilize the structure once water flow ceases.Work partially supported by the United States Department of Energy