上海生态平衡学术讨论会

中国生态学会“生态平衡”学术讨论会于1981年11月7日至13日在上海召开,来自全国22个省市区的90余名代表出席了会议。大会针对当前国内外广泛重视和关心的“生态平衡”问题展开了热烈地讨论。代表们认为:生态学是社会主义建设蓝图的“底色”,这个“底色”搞不好,社会主义建设也难以搞好,为此,全国人民都要关心生态学的问题。目前污染严重,生态平衡失调,已引起人们的警觉和关注,“生态平衡”问题已提到了议事日程,不允许人们再忽视了。     

Improved high-performance liquid chromatography of the new antineoplastic agents bisantrene and mitoxantrone

Bisantrene and mitoxantrone are two new anthracene derivatives which have shown significant antitumor activity against a wide variety of animal tumors and in human phase I and II clinical trials. We have developed a rapid, simple and sensitive sample cleanup procedure and high-performance liquid chromatographic (HPLC) assay for both drugs. This method uses a commercially available mini-cartridge with C₁₈ reversed-phase packing to isolate the drugs from the biological matrix prior to HPLC. For both drugs the average recovery of the assay was 98 ± 6% with a coefficient of variation (C.V.) of less than 7%. Using this new method our assay sensitivity has improved to less than 10 ng/ml for bisantrene and 1 ng/ml for mitoxantrone, allowing us to document a prologned terminal phase plasma half-life for both bisantrene and mitoxantrone. Equilibrium dialysis studies showed that both drugs are highly protein bound. Mitoxantrone appears less stable in human plasma than bisantrene. Recoveries from plasma after a 24-h incubation at 25 and 37°C were 40 and 20% for mitoxantrone and 90 and 85% for bisantrene, respectively. Addition of ascorbic acid prior to incubation of mitoxantrone in human plasma at 37°C resulted in less than a 10% decrease in the latter's concentration over a 24-h period. To maintain sample integrity, all plasma samples should be fortified with ascorbic acid and kept frozen prior to analyses.     

The influence of phytoplankton composition on the relative effectiveness of grinding and sonification for chlorophyll extraction

The chlorophyll recovery efficiency was compared between control, ground, and sonified samples. The results showed significant improvement between control and ground samples but not between control and sonified samples. Neither prolonging time of sonification nor using an ice bath during filter grinding improved efficiency. Higher chlorophyll a recovery was obtained from ground samples than from sonified ones, when the water samples contained centric diatoms and filamentous blue-green algae. When total phytoplankton numbers were high, there was a distinct advantage in using grinding rather than sonification for chlorophyll c recovery.Contribution no. 313 of the Great Lakes Research Division, University of Michigan.Contribution no. 313 of the Great Lakes Research Division, University of Michigan.     

Platelet-derived growth factor is a chemoattractant for vascular smooth muscle cells

In previous experiments (Grotendorst et al, 1981), we showed that platelet-derived growth factor promotes the migration of smooth muscle cells in vitro. Using a "checkerboard" analysis, we now establish that platelet-derived growth factor (PDGF) acts as a true chemoattractant for cultured aortic smooth muscle cells. Other growth factors such as epidermal growth factor, fibroblast growth factor, and insulin are not chemoattractants. The chemotactic response occurs before the initiation of DNA synthesis and is not affected by inhibition of DNA synthesis. Chemotaxis occurs at levels of PDGF lower than required for mitogenesis. RNA and protein synthesis are required for the chemotactic response. As found previously in bacteria and leucocytes, we find that methylation reactions are required for the chemotactic response. The possibility is discussed that PDGF acts in vivo at sites of vascular injury to attract smooth muscle cells from the medial layer to the luminal surface, and is involved in the early stages of the formation of atherosclerotic plaques.     

The possible role of soluble salts in chemical evolution

Summary A model is proposed for a prebiotic environment in which concentration, condensation, and chemical evolution of biomolecules could have taken place. The main reactions expected of proteins, nucleic acids, lipids, and some of their precursors in this environment are examined.The model is based on our previously developed concept of a fluctuating system in which hydration and dehydration processes take place in a cyclic manner. In the present model, however, high concentrations of soluble salts, such as chlorides and sulfates, are taken into account, whereas previously a more or less salt-free system had been assumed. Thus the preponderance of surfaces of soluble salts is implied, even though sparingly soluble minerals, such as clay minerals or quartz, are also present.During the dehydration stage biomolecules tend to leave the solution and concentrate at certain microenvironments, such as in micelles and aggregates, at the liquid-gas surface and, possibly, at the emerging solid surfaces. Moreover, in these brines, and especially during the last stages of dehydration, high temperatures are attainable, which may enhance certain reactions between the organic molecules, and result in a net increase of condensation over degradation.In the dehydrated state, solid-state condensation and synthesis reactions are possible in which the surface of soluble salts may serve as a catalyst. Several reports in the literature support this hypothesis. Hydration brings about dissolution of the minerals and redistribution of the biomolecules. In such a system, evolutionary processes like those postulated by White (1980) and by Lahav and White (1980) are possible. Moreover, since several soluble salts of known geological occurrence are optically active in their crystalline state, the involvement of the model system in the selection and evolution of chiral organic compounds should also be considered. In addition, organic molecules in the above microenvironments are also expected to undergo selective interactions based on factors such as molecular pattern and chiral recognition and hydrophobicity. The proposed system emphasizes the need to develop the theoretical background and experimental methods for the study of interactions among biomolecules in the presence of high salt concentrations and solid surfaces of soluble salts, as well as interactions between the biomolecules and these surfaces.     

Antibodies Specific for α-N-Acetyl-β-Endorphins: Radioimmunoassays and Detection of Acetylated β-Endorphins in Pituitary Extracts

Abstract: Antibodies specific for α-N-acetyl-β-endorphins have been prepared by injecting into rabbits either α-N-acetyl-β-endorphin(1-31) or [α-N-acetyl, ε-acetyl-Lys⁹]-β-endorphin(1-9) linked by carbodiimide to bovine thyroglobulin. Both antisera were used to develop specific radioimmunoassays for α-N-acetyl-β-endorphins. The radioimmunoassays were used to measure α-N-acetylated β-endorphins in extracts of pituitary regions from different species. By comparison of the amounts of total β-endorphin and α-N-acetyl-β-endorphin immunoreactivity, a relative ratio of β-endorphin acetylation was obtained. The relative acetylation of β-endorphin was highest in rat posterior-intermediate lobe extracts (>90%). Beef and monkey intermediate lobes had a lower degree of acetylation (53 and 31%, respectively). Anterior lobe extracts from all three species contained low amounts of acetylated β-endorphin. Human pituitary extracts did not contain acetylated β-endorphins. By the use of cation exchange and high performance liquid chromatography, six different acetylated derivatives and fragments of β-endorphin were resolved in extracts of rat posterior-intermediate pituitaries. Two of these peptides corresponded to α-N-acetyl-β-endorphin(1-31) and -(1-27). One acetylated β-endorphin fragment had the same size as α-N-acetyl-β-endorphin(1-27) but was eluted earlier from the cation exchange column. This peptide had full cross-reactivity with antibodies directed against the middle and amino-terminal parts of β-endorphin. Compared with α-N-acetyl-β-endorphin(1-27), it had much less cross-reactivity with antibodies directed against the COOH-terminal part of β-endorphin, suggesting that it was a COOH-terminally modified derivative of β-endorphin(1-27). The remaining N-acetylated β-endorphin derivatives were eluted even earlier from the cation exchange column. The majority of these fragments were slightly larger in size than y-endorphin, i.e., β-endorphin(1-17), but smaller than β-endorphin(1-27). They had full cross-reactivity in an amino-terminally directed β-endorphin radioimmunoassay and a greatly diminished cross-reactivity with antibodies to the middle region of β-endorphin.     

The Benzodiazepine/GABA Receptor Complex: Molecular Size in Brain Synaptic Membranes and in Solution

Abstract: The molecular size of the benzodiazepine (BZ) receptor in the synaptic membrane of brain cortex (bovine or rat) was determined by an improved version of the radiation inactivation method to be 220,000. An identical size was found simultaneously for the associated γ-aminobutyric acid (GABA) receptor and for the component binding β-carboline esters. It is proposed that all three activities reside in a single protein or protein complex in the membrane. The size in solution, after extraction into Triton X-100 medium from exhaustively washed membranes, was estimated by sedimentation constant (9.4S) and by gel filtration (∼230,000 apparent MW), again with the BZ and GABA binding activities behaving identically. This size applies to the component that undergoes photoaffinity labelling by [³H]flunitrazepam in the membrane, and contains a 51,000 M_r polypeptide as the BZ-binding subunit. It is concluded that a protein complex or oligomer of 200,000–220,000 MW carries a class of BZ-binding sites and an associated class of GABA_A sites.     

Selective killing of Leishmania infected mouse macrophages by 6-methylpurine 2′-deoxyriboside

6-methylpurine 2′-deoxyriboside killed mouse macrophages infected with amastigotes of $\text{Leishmania donovani}$ and $\text{Leishmania mexicana}$, but did not affect the growth of non-parasitized cells. $\text{Leishmania}$ extracts cleaved the non-toxic 6-methylpurine 2′-deoxyriboside to 6-methylpurine, a potent adenine antimetabolite for mammalian cells. By eliminating macrophages latently infected with $\text{Leishmania donovani}$ amastigotes, 6-methylpurine 2′-deoxyriboside could augment the effects of leishmanicidal agents $\text{in vivo}$.     

Pre- and postsynaptic adrenergic activation by norepinephrine reuptake inhibitors in the field-stimulated rat vas deferens

Desipramine (DMI), protriptyline, chlorpromazine, amitriptyline and cocaine, alone or in the presence of prazosin, produced a dose-related inhibition of contractions induced by field stimulation of the rat vas deferens. The inhibition of contractions was readily reversed by yohimbine. In contrast, when yohimbine was first added to the bath, all agents, except chlorpromazine, produced a dose-related enhancement of contractions which were readily reversed by prazosin. The potencies of these agents for induction of contractile inhibition, after prazosin, and contractile enhancement, after yohimbine, were similar. Both of the latter contractile responses of DMI were markedly attenuated or absent in tissues taken from rats pretreated with reserpine and alpha-methyl-para-tyrosine. The data indicate that, in the rat vas deferens, inhibition of norepinephrine reuptake results primarily in presynaptic (α₂) receptor activation. Postsynaptic (α₁) adrenergic activation by inhibition of norepinephrine reuptake can be demonstrated in this tissue only after presynaptic (α₂) receptor blockade. The possible implications of the present studies to the delayed clinical onset of action of tricyclic antidepressants is discussed.