Time-resolved Raman spectroscopy with subpicosecond resolution: vibrational cooling and delocalization of strain energy in photodissociated (carbonmonoxy)hemoglobin

A Raman spectrometer that provides both subpicosecond resolution and independent, tunable pump and probe pulses is described. The spectrometer is employed to obtain time-resolved spectra of (carbonmonoxy)hemoglobin (HbCO) at times from 0.2 to 95 ps subsequent to ligand photodissociation. The spectra are interpreted in terms of a vibrationally hot heme that cools substantially in 10 ps. Concomitant with the proposed vibrational cooling is a slower relaxation, which we suggest results from a protein response to heme doming induced by ligand detachment. Results and interpretations are discussed in the context of current models of the heme photophysics and of hemoglobin reactivity.     

In vitro enhancement of human natural cell-mediated cytotoxicity by purified influenza virus glycoproteins.

The role of the glycoproteins of influenza virus, hemagglutinin (HA), and neuraminidase (NA) in the in vitro stimulation of natural cell-mediated cytotoxicity (NCMC) or natural killer activity of human peripheral blood lymphocytes was evaluated with radiolabeled K562 cells as target cells in an overnight chromium release assay. Three different approaches were used. (i) Purified viral proteins were obtained by extraction with Nonidet P-40, separation on a sucrose gradient, and further purification by affinity chromatography. Ficoll-Hypaque-purified peripheral blood lymphocytes exposed to HA or NA individually or to a mixture of both significantly increased NCMC (32 to 50%). (ii) Treatment of HA and NA with their respective homologous antisera or F(ab')2 antibody abrogated the stimulation of NCMC by these glycoproteins. (iii) Virions treated with proteolytic enzymes resulted in viral cores lacking either HA or NA or both activities. Compared to whole virions, viral cores devoid of HA activity only induced a 50% increase in NCMC, whereas viral cores lacking HA activity and with traces of NA activity stimulated only 10% of the NCMC. These results suggest that influenza virus-induced cell-mediated cytotoxicity is largely due to its glycoproteins.     

Subtleties and episodes in the early life of fishes

Fluctuations in the abundance of fishes may be caused by episodic mortalities or by more subtle variability in the daily growth and mortality rates of eggs and larvae. Survival response surfaces are used to illustrate the relative effects of episodic and subtle mortality during early life. It is the subtle variability associated with small changes in growth or mortality rates that may exert the greater effect on recruitment. Massive advective losses of eggs or larvae, failed egg production, and acute contaminant mortalities are examples of episodic events that may impact recruitment significantly but which need not be catastrophic. Stabilization of recruitments through density-dependent growth rate variability in early life is demonstrated to be potentially important. Whether this mechanism actually is important in the sea remains to be determined.     

ABA and Low Temperature Induce Freezing Tolerance via Distinct Regulatory Pathways in Wheat

The role of ABA in the induction of freezing tolerance was investigatedin two wheat (T. aestivum L.) cultivars, Glenlea (spring var)and Fredrick (winter var). Exogenous application of ABA (5x10^–5M for 5 days at 24°C) increased the freezing tolerance ofintact plants by only 3°C (LT₅₀) in both cultivars. Maximalfreezing tolerance (LT₅₀ of –9°C for Glenlea and –17°Cfor Fredrick) could only be obtained with a low temperaturetreatment (6/2°C; day/night) for 40 days. These resultsshow that exogenously applied ABA cannot substitute for lowtemperature requirementto induce freezing tolerance in intactwheat plants. Furthermore, there was no increase in the endogenousABA level of wheat plants during low temperature acclimation,suggesting the absence of an essential role for ABA in the developmentof freezing tolerance in intact plants. On the other hand, ABAapplication (5x10^–5 M for 5 days at 24°C) to embryogenicwheat calli resulted in an increase of freezing tolerance similarto that achieved by low temperature. However, as in intact plants,there was no increase in the endogenous ABA level during lowtemperature acclimation of calli. These results indicate thatthe induction of freezing tolerance by low temperature is notassociated with an increase in ABA content. Using an antibodyspecific to a protein family associated with the developmentof freezing tolerance, we demonstrated that the induction offreezing tolerance by ABA in embryogenic wheat calli was correlatedwith the accumulation of a new 32 kDa protein. This proteinis specifically induced by ABA but shares a common antigenicitywith those induced by low temperature. These results suggestthat ABA induces freezing tolerance in wheat calli via a regulatorymechanism different from that of low temperature. (Received June 15, 1993; Accepted September 16, 1993)     

Expression of the cold-induced wheat gene Wcs120 and its homologs in related species and interspecific combinations.

Low-temperature response was measured at the whole plant and at the molecular level in wheat-rye amphiploids and in other interspecific combinations. Cold tolerance of interspecifics whose parents diverged widely in hardiness levels resembled the less hardy higher ploidy level wheat parent. Expression of the low-temperature induced Wcs120 gene of wheat (Triticum aestivum L. em. Thell.) has been associated with freezing tolerance and was used here to study mRNA and protein accumulation in interspecific and parental lines during cold acclimation. Northern and Western analyses showed that homologous mRNAs and proteins were present in all the related species used in the experiments. Cold-tolerant rye (Secale cereale L.) produced a strong mRNA signal that was sustained throughout the entire 49-day cold-acclimation period. The wheats produced a mRNA signal that had diminished after 49 days of low-temperature exposure. The wheat-rye triticales did not exhibit the independent accumulation kinetics of the cold-tolerant rye parent but, rather, more closely resembled the wheat parent in that the mRNA signal was greatly diminished after 49 days of low-temperature exposure. The influence of the rye genome was manifest in slightly greater mRNA and protein accumulation in earlier stages of acclimation. Protein accumulations in the triticales were also maintained to a somewhat greater extent than found in the wheats at the end of the 49-day acclimation period. Protein accumulations in the wheat-crested wheatgrass (Agropyron cristatum L. Gaertner) interspecific resembled that of the wheat parent. The influence of the higher ploidy level wheats of the expression of homologous gene families from wheat-related hardy diploids in interspecific combinations may in part explain the poor cold tolerance observed.     

Effects of stocking density and food density on survival,growth and yield of laboratory-reared larvae of sea bream Archosargus rhomboidalis (L.) (Sparidae)*

Growth and survival of sea bream, Archosargus rhomboidalis (L.) larvae were affected by both abundance of eggs that were initially stocked in 75 1 rearing systems and by the concentration of copepod nauplii and copepodites that were fed to larvae. Stocking levels were 2, 4, 8,16 or 32 per litre while food abundance was maintained at approximately 100, 500, 1500 or 3000 per litre. Experiments were of 16 days duration at 26° C. Survival was best, often exceeding 60%, when food levels were 1500 or 3000 per litre and when stocking density did not exceed 8 eggs per litre. Growth was best at the lowest stocking densities and highest food levels. The highest total yields in wet weight occurred at 8 per litre stock density and 3000 per litre food level. Mean wet weight per survivor and yield per stocked egg were greatest at the lowest stocking densities and highest food levels. A 500 per litre food level was marginal for growth and survival, and 100 per litre produced significant survival only at the 2 per litre stocking density. Two experiments at 6000 and 10 000 per litre food levels at 4 per litre stock density gave the best observed growth, and survival as good as in any other experiments. Possible relations between sea bream larvae and their food supply in the natural environment are discussed. Results also are discussed in terms of their possible contribution to aquaculture efforts.