Fine structure and motility of spermatozoa and composition of the seminal plasma in the perch

The fine structure and motility of spermatozoa and the composition of the seminal plasma of the perch Perca fluviatilis are investigated by electron microscopy, computer assisted cell motility analysis (CMA) and biochemical methods. The spermatozoon is asymmetrical as the flagellum inserts mediolateral on the nucleus. It lacks an acrosome, has an ovoid head and a small midpiece with one mitochondrion. Sperm motility–initiated in distilled water (10° C)–is characterized as follows: 85·0 ± 2·7% of the spermatozoa are motile, the main swimming type (10 ± 1 s after motility initiation) is the linear motion (61·4 ± 24·4%) and the average swimming velocity is 122·4 ± 21·9 μm s^–1. When motility is initiated with NaCl, glucose or sucrose solutions of 100 mosmol kg^–1 the percentage of motile spermatozoa and the swimming types are similar as in water, but the swimming velocity (174·0 ± 22·3 μm s^–1) is significantly higher. Motility is inhibited by high osmolality of the diluent: when increasing the osmolality of the saline solutions to 350 mosmol kg^–1 sperm motility is totally suppressed while potassium (10–40 mmol 1^–1) does not affect motility parameters. pH optimum for sperm motility is between pH 7·0 and 8·5. The seminal fluid contains 124·01 ± 21·68 mmol 1^–1 sodium, 10·22 ± 1·11 mmol 1^–1 potassium and 0·72 ± 0·26 mmol 1^–1 calcium. pH is 8·25 ± 0·09, and osmolality 283·90 ± 37·19 mosmol kg^–1. The following organic components were determined: monosaccharides (glucose 63 ± 19 μmol 1^–1, fructose 54 ± 28 μmol 1^–1, galactose 59 ± 25 μmol 1^–1), lipids (cholesterol 5·51 ± 6·42 μmol 1^–1, triglycerides 72 ± l00 μmol l^–1, cholesteryloleate 15–150 μmol 1^–1, phosphatidylcholine 26 · 31 μmol 1^–1, glycolipids 1–10 mg 100 m1^–1), lactate 108 ± 99 μmol 1^–1, hydroxybutyrate 102 ± 99 nmol 1^–1, choline 59 ± 159 μmol 1^–1, protein 344·75 ± 59·06 mg 100m1^–1, enzymes (β-d -glucuronidase l.4 ± 0.7 μmol h^–1 100 ml^–1, protease (caseolytic activity) 1·0 ± 0·6 μmol h^–1 100 ml^–1, alkaline phosphatase 2520·0 ± 861·0 μmol h^–1 100 ml^–1, acid phosphatase 44.0 ± 16.0 μmol h^–1 100 ml^–1, glucose-6-phosphate dehydrogenase 38·9 ± 86·9 μmol h^–1 100 ml^–1, lactate dehydrogenase 134·4 ± 69·6 μmol h^–1 100 ml^–1, butyrylcholine esterase 0·014 ± 0·010 μmol h^–1 100 ml^–1, adenosine triphosphatase 562·8 ± 665·4 μmol h ^–1 100 ml^–1).     

Biology of African trypanosomes in the tsetse fly

African trypanosomes present several features of interest to cell biologists. These include: a repressible single mitochondrion with a large mass of mitochondrial DNA, the kinetoplast; a special organelle, the glycosome, which houses the enzymes of the glycolytic chain; a surface coat of variable glycoprotein which enables the parasite to evade the mammalian host's immune response; and a unique flagellum-to-host attachment mechanism associated with novel cytoskeletal elements. Trypanosome development during the life cycle involves cyclical activation and repression of genes controlling these activities. Understanding the complexity of parasite development in the tsetse fly vector is especially challenging but may help to suggest new methods for the control of trypanosomiasis.     

Quantitative Ultrastructural Investigations of Mitochondrial Development in Leishmania donovani During Transformation*

SYNOPSIS. The ultrastructure of the mitochondrion during transformation of Leishmania donovani from amastigote to promastigote stages was studied by morphometric analysis. There was a slight but significant decrease in relative mitochondrial volume (Vvli) during transformation. This decrease was linear with time for at least 27 hr. No change in relative lipid inclusion volume (Vvli) was observed during transformation. The ratio of inner to outer mitochondrial surface membrane densities (Svmii:Svmio) also remained unchanged. Although the relative number of cristae remains unchanged after transformation, there is an increase in cristae number in the portion of the kinetoplast opposite the flagellum.     

The Effects of the Methylating Agent 1,2-Bis(methylsulfonyl)-1-methylhydrazine on Morphology, DNA Content and Mitochondrial Function of Trypanosoma brucei Subspecies

Repeated exposure of trypanosomes in vitro or in vivo to low concentrations of the methylating agent 1,2-bis(methylsulfonyl)-1-methylhydrazine induces a series of moderately synchronous morphological and biochemical changes. Cell division halts and the long-slender bloodstream forms transform to short-stumpy forms via larger intermediate-stage cells which contain approximately double the normal G₂ content of DNA. In common with naturally occurring short-stumpy trypanosomes, drug-induced short-stumpy forms do not infect rodents and when transferred to Cunningham's medium, transform to and replicate as procylics. Furthermore, these short-stumpy forms exhibit α-ketoglutarate supported motility and oxygen consumption, acquire the ability to reduce nitroblue tetrazolium (NADH diaphorase positivity) and appear to be in the G₁ or G₀ stage of the cell cycle based upon DNA content.     

Δ53β hydroxysteroid dehydrogenase activity of the rat corpus luteum exhibits positive substrate-binding co-operativity: A continuous monitoring microdensitometric study with unfixed ovarian tissue sections

Δ⁵3β hydroxysteroid dehydrogenase activity transforms biologically inactive Δ⁵3β hydroxy steroids into the active Δ⁴3-keto products (e.g. pregnenolone to progesterone). Using a cytochemical procedure which allows for the continuous microdensitometric monitoring of an enzyme reaction as it proceeds and a well described cytochemical assay for Δ⁵3β HSD we have analysed the initial velocity rates (V_o) for dehydroepiandrosterone (DHEA) binding to this enzyme in regressing (i.e. 20α hydroxy steroid dehydrogenase positive) corpus luteum (CL) cells in unfixed tissue sections (5 μm) of the dioestrous and proestrous rat ovary. The results are mean ± S.E.M. The relationship between DHEA concentration (0 to 50 μM) and Δ⁵3β HSD activity in the dioestrous corpora lutea was sigmoidal and had an atypical 1/V_o versus 1/S plot, the x intercept being positive. Using a 1/V_o versus 1/S² plot the V_max was determined to be 1·0 ± 0·08 μmol min^?1 mg^?1 CL (n = 6). The Hill constant was 2·7 ± 0·02 (n = 6) suggesting a high degree of positive co-operativity for DHEA binding. The S concentration for half maximal activity was 17 ± 1 μmoles (n = 6). In the corpora lutea cells of the proestrous ovary, the V_max for DHEA transformation was unchanged (0·95 ± 0·04 μmol min^?1 mg^?1, n = 3) whilst the S_0·5 was significantly increased to 27 ± 0·1 (p < 0·01, n = 3). The Hill constant remained positive being 2·9 ± 0·2 (n = 3). NAD⁺ binding to 3β HSD in regressing corpora lutea of the proestrous ovary has been demonstrated previously to be hyperbolic and fit the classical Michaelis-Menten model.¹ Extending the analysis of NAD⁺ binding to the regressing corpus luteum of the dioestrous rat ovary revealed similar kinetic characteristics to that seen with the proestrous enzyme, the apparent V_max and K_m being 0·84 ± 0·04 μmol min^?1 mg^?1 CL (n = 3) and 27 ± 7 μmol 1^?1 (n = 3) respectively. The Hill constant was 1·1 ± 0·03 (n = 3), indicating no co-operativity of co-factor binding.     

Fecundity regulation by atresia in turbot Scophthalmus maximus in the Baltic Sea

Down‐regulation of fecundity through oocyte resorption was assessed in Baltic Sea turbot Scophthalmus maximus at three locations in the period from late vitellogenesis in April to spawning during June to July. The mean ± s.d . total length of the sampled fish was 32·7 ± 3·1 cm and mean ± s.d . age was 6·2 ± 1·5 years. Measurements of atresia were performed using the ‘profile method’ with the intensity of atresia adjusted according to the ‘dissector method’ (10·6% adjustment; coefficient of determination was 0·675 between methods). Both prevalence (portion of fish with atresia) and intensity (calculated as the average proportion of atretic cells in fish displaying atresia) of atresia were low in prespawning fish, but high from onset of spawning throughout the spawning period. Atretic oocytes categorized as in early alpha and in late alpha state occurred irrespective of maturity stage from late prespawning individuals up to late spawning fish, showing that oocytes may become atretic throughout the spawning period. Observed prevalence of atresia throughout the spawning period was almost 40% with an intensity of c. 20%. This indicates extensive down‐regulation, i.e. considerably lower realized (number of eggs spawned) v. potential fecundity (number of developing oocytes), suggesting significant variability in reproductive potential. The extent of fecundity regulation in relation to fish condition (Fulton's condition factor) is discussed, suggesting an association between levels of atresia and fish condition.     

Patterns of nitrogen utilization between the ambrosia beetle Xyleborus dispar and its symbiotic fungus

Some parameters of nitrogen utilization between the ambrosia beetle Xyleborus dispar in mutualistic association with its symbiotic fungus Ambrosiella hartigii, were examined. Qualitative and quantitative analyses of the major nitrogenous excretory products were made on the various life stages of X. dispar. The main nitrogenous product found in excreta and hindguts of beetles, larvae, and pupae, was uric acid (range 7·6–14·8 μg uric acid/beetle). No ninhydrin-positive compounds were located in excreta of the beetles. The concentration of ammonia-nitrogen in the various life stages averaged between 0·70 and 1·13 μg NH₃-N/beetle.Total nitrogen determinations were made on sapwood samples of Malus sylvestris (0·34 ± 0·005% N by dry weight), attacked wood, ‘pre-brood’ (0·31 ± 0·005% N by dry weight), and attacked wood ‘post-brood’ (0·17 ± 0·02% N). Similar determinations of the artificial medium (l-asparagine medium) indicated that a nitrogen requirement of about 0·08–0·1% N by dry weight was necessary before oviposition could occur.Fixation of atmospheric nitrogen by individual X. dispar beetles in vitro was not indicated using the acetylene ethylene reductase method. Proteolytic enzyme activity was not found on examination of diapause beetles, their excreta, larval and pupal excreta, and the ambrosial and mycelial forms of A. hartigii.Comparative concentrations of soluble proteins and free amino acids suggested that fungus in the mycangia was built up from free amino acids of the insects. At the period of emergence, flight, and attack of new hosts, the females were found to have a concentration of soluble proteins more than double that found in the beetles during the remainder of the year. The free amino acids were the lowest values recorded during this period (March–October).     

Kocuria SM1 controls vibriosis in rainbow trout (Oncorhynchus mykiss,Walbaum)

Aims: To develop probiotics for the control of vibriosis caused by Vibrio anguillarum and Vibrio ordalii in finfish. Methods and Results: Kocuria SM1, isolated from the digestive tract of rainbow trout, was administered orally to rainbow trout (Oncorhynchus mykiss) for 2 weeks at a dose equivalent to c. 10⁸ cells per g of feed and then challenged intraperitoneally with V. anguillarum and V. ordalii. Use of SM1 led to a reduction in mortalities to 15–20% compared to 74–80% mortalities in the controls. SM1 stimulated both cellular and humoral immune responses in rainbow trout, by elevation of leucocytes (5·5 ± 0·8 × 10⁶ ml^?1 from 3·7 ± 0·8 × 10⁶ ml^?1), erythrocytes (1·2 ± 0·1 × 10⁸ ml^?1 from 0·8 ± 0·1 × 10⁸ ml^?1), protein (23 ± 4·4 mg ml^?1 from 16 ± 1·3 mg ml^?1), globulin (15·7 ± 0·2 mg ml^?1 from 9·9 ± 0·1 mg ml^?1) and albumin (7·3 ± 0·2 mg ml^?1 from 6·1 ± 0·1 mg ml^?1) levels, upregulation of respiratory burst (0·05 ± 0·01 from 0·02 ± 0·01), complement (56 ± 7·2 units ml^?1 from 40 ± 8·0 units ml^?1), lysozyme (920 ± 128·8 units ml^?1 from 760 ± 115·3 units ml^?1) and bacterial killing activities. Conclusions: Kocuria SM1 successfully controlled vibriosis in rainbow trout, and the mode of action reflected stimulation of the host innate immune system. Significance and Impact of the Study: Probiotics can contribute a significant role in fish disease control strategies, and their use may replace some of the inhibitory chemicals currently used in fish farms.     

RNA synthesis in imaginal disks of Galleria mellonella: Effects of alpha- and beta-ecdysone and fat body in vitro

The effects of alpha-ecdysone (α-E), beta-ecdysone (β-E), and larval fat body on morphogenesis and total RNA synthesis in wing imaginal disks of Galleria mellonella were studied. Both ecdysones induce morphogenesis of disks in vitro. Alpha-ecdysone and β-E (0·3–3·0 μg/ml) stimulate RNA synthesis 30 and 60 per cent above control levels, respectively. While less α-E (0·3 μg/ml) is required to increase RNA synthesis than to induce morphogenesis, the reverse is true for β-E. Morphogenesis (i.e. tracheole migration and evagination) can proceed in the presence of concentrations of β-E (0·03 μg/ml) that are subthreshold for the induction of RNA synthesis (0·3 μg/ml). We conclude, therefore, that the increase in total RNA (presumbly ribosomal) is unrelated to and not a prerequisite for tracheole migration or evagination. If morphogenically active preconditioned medium (i.e. medium in which α-E and fat body have been incubated for 48 hr and the fat body then removed) is added to disk cultures, RNA synthesis is not stimulated. Apparently, increases in total RNA caused by both ecdysones may not be necessary for early in vitro disk development. The independent nature of some ecdysone-induced events and implications of our conclusions are discussed.     

A chemical modification of myeloperoxidase and lactoperoxidase with 2-(O-methoxypolyethylene glycol)-4,6-dichloro-s-triazine (activated PEG1)

The modification of myeloperoxidase and lactoperoxidase with 2-(O-methoxypolethylene glycol)-4, 6-dichloro-s-triazine, an activated polyethylene glycol (PEG₁), was investigated. The modification caused a shift of the Soret band in the light absorption spectrum, from 430 nm to 418 nm in the case of myeloperoxidase (native ferric form), and from 412 nm to 406 nm in the case of lactoperoxidase (native ferric form). PEG₁-modified myeloperoxidase and PEG₁-modified lactoperoxidase both failed to bind with antiserum to the respective native enzyme, but both retained respectively 4·5±0·3 per cent (mean±SE, n=5) and 0·6±0·2 per cent (mean±SE, n=5) of the activities of peroxidation of the hydrogen donor o-methoxyphenol in comparison with the native enzyme, and 1·5±0·2 per cent (mean±SE, n=5) and 1·2±0·2 per cent (mean±SE, n=5) of the activities of destruction of fuchsin basic in the presence of hydrogen peroxide and a halide, bromide. The pH dependencies of the peroxidating activities were almost the same as those of the corresponding native enzymes, but both the optimal pHs of the reactions involving the destruction of fuchsin basic were shifted by approximately 1·0 pH unit toward neutral pH compared with the respective native enzymes. © 1998 John Wiley & Sons, Ltd.     

Role of insulin in Cr(VI)-mediated genotoxicity in Neurospora crassa

Aims: Chromium (III) is an insulinomimetic agent whose biological and/or environmental availability is frequently in the form of Cr(VI), which is known to be toxic. Wall‐less mutant of Neurospora crassa (FGSC stock no. 4761) is known to possess insulin receptor in its cell membrane and hence is a good model for Cr toxicity studies. This study explores the toxicity of Cr(VI) and the possible consequences on simultaneous exposure to insulin in N. crassa. Methods and Results: Comet assay of N. crassa cells treated with 100 μmol l^?1 Cr(VI) showed up to 50% reduction in comet tail lengths when incubated simultaneously with 0·4 U insulin. Fluorescence measurement in Cr(VI)‐treated cells using DCFH‐DA showed six‐ to eightfold increase in free radical generation, which was reduced to fourfold by 0·4 U insulin. Annexin‐V/PI Flow cytometry analysis indicated necrotic cell death up to 28·7 ± 3·6% and 68·6 ± 2·5% on Cr(VI) exposure at concentrations 100 and 500 μmol l^?1 which was reduced by 68·3 ± 3·2% and 48·9 ± 3·6%, respectively, upon addition of insulin. Conclusion: Insulin‐mediated protection from DNA damage by Cr(VI) is because of scavenging of free radicals liberated during exposure to Cr(VI). Significance and Impact of the Study: Overall, Cr(VI) toxicity depends upon available insulin, indicating that Cr(VI) toxicity may be a serious issue in insulin‐deficient individuals with diabetes.     

Coordinate regulation of cholesterol synthesis and 3-hydroxy-3-methylglutaryl coenzyme A synthase but not 3-hydroxy-3-methylglutaryl coenzyme A reductase in C-6 glia

The effects on cholesterol biosynthesis of growth of cultured C-6 glial cells in serumfree medium ± supplementation with linoleic or linolenic acid were studied. Markedly higher activities of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase, EC 1.1.1.34) were observed in cells grown in linoleate- or linolenate-supplemented versus nonsupplemented medium. After 48 h HMG-CoA reductase activities were two-and four-fold higher in cells supplemented with 20 and 100 μm linoleate, respectively. The increase in activity became apparent after 24 h and was marked after 48 h. Rates of incorporation of [¹⁴C]acetate or ³H₂O into sterols did not reflect the changes in reductase activity. Thus, in cells supplemented with 50 μm linoleate for 24 and 48 h rates of incorporation of [¹⁴C]acetate were 75–80% lower than rates in nonsupplemented cells. This difference resulted because over the first 24 h of the experiment a fivefold increase in the rate of sterol synthesis occurred in the nonsupplemented cells, whereas essentially no change occurred in the linoleate-supplemented cells; little further change occurred between 24 and 48 h in the nonsupplemented and the linoleate-supplemented cells. That the difference in sterol synthesis under these experimental conditions could be mediated at the level of HMG-CoA synthase (EC 4.1.3.5) was suggested by two series of findings, i.e., first, similar quantitative and temporal changes in the activity of this enzyme, and, second, no change in the activity of acetoacetyl-CoA thiolase (EC 2.3.1.9) or the incorporation of [¹⁴C]mevalonate into sterols. Thus, the data suggest that HMG-CoA synthase, and not HMG-CoA reductase, may direct the rate of cholesterol biosynthesis under these conditions of serum-free growth ± supplementation with polyunsaturated fatty acid.     

Protracted volitional spawning of pinfish Lagodon rhomboides and changes in egg quality and fatty‐acid composition throughout the spawning season

Spawning performance of pinfish Lagodon rhomboides without use of hormonal aids was monitored over an extended season. Nearly three million eggs were obtained from 75 spawns collected over a 90‐day consecutive period from a single population of four brood fish (1M:1F). A mean ± s.d. batch fecundity of 30·27 ± 22·64 eggs g^?1 female was estimated with 98·0 ± 0·06% of the batch composed of floating eggs which were 1·04 ± 0·04 mm in diameter and 85·71 ± 27·59% fertile. Floating eggs successfully hatched 54·65 ± 29·13% of the time which yielded larvae that were 2·59 ± 0·24 mm in length. Fatty acids within floating eggs were largely represented by polyunsaturated fatty acids (45·30 ± 2·14% of total fatty acids) of which linoleic acid [(c18:2n‐6cis) 3·49 ± 1·69% trifluoroacetic acid (TFA)] and docosahexaenoic acid (DHA) [(c22:6n‐3) 28·47 ± 1·48% TFA] represented the majority of fatty acids for n‐6 and n‐3 polyunsaturated fatty acids, respectively. The strongest correlations between fatty acids and hatching success and larval survival to first feeding were observed for the DHA:EPA (eicosapentaenoic acid; c20:5n‐3) ratio and total n‐6 polyunsaturated fatty‐acids levels, respectively. These data demonstrate potential for producers to rely on natural spawns for extensive egg production and provide a baseline for future development of natural spawning protocols of captive L. rhomboides.     

EFFECTS OF EXTERNAL INORGANIC NITROGEN CONCENTRATION ON METABOLISM,GROWTH AND ACTIVITIES OF KEY CARBON AND NITROGEN ASSIMILATORY ENZYMES OF LAMINARIA SACCHARINA (PHAEOPHYCEAE) IN CULTURE1

The growth rate of Laminaria saccharina (L.) Lamour. is dependent on inorganic nitrogen in culture. Growth rates were saturated between 5 and 10 μmol · L^?1 nitrate. The activities of ribulose-1,5 bisphosphate carboxylase, phosphoenolpyruvate carboxykinase, mannitol-1-phosphate dehydrogenase, nitrate reductase and glutamine synthetase also varied with the concentration of inorganic nitrogen in the medium. All enzyme activities were lowest at 2.5 μmol · L^?1 nitrate (the lowest concentration used) increasing to a maximum activity between 10 and 30 μmol · L^?1 nitrate. Most enzyme activities followed a hyperbolic curve resembling those described by the Michaelis-Menten equation, with different half-saturation constants.     

The effects of light intensity and algae-induced turbidity on feeding behaviour of larval striped trumpeter

Striped trumpeter larvae reared in algal cell‐induced turbid water (greenwater) fed equally well in clearwater in a light intensity range of 1–10 μmol s^‐1 m^‐2, when evaluated in terms of both the proportion of larvae feeding and larval feeding intensity. An ontogenetic improvement in photopic visual sensitivity of larvae was indicated by improved feeding at 0·1 μmol s^‐1 m^‐2, from 26±5% of larvae feeding and 0·027±0·005 rotifers consumed per feeding larva min^‐1 on day 8, to 96±2% and 0·221±0·007 rotifers consumed larva^‐1 min^‐1 on day 23 post‐hatching. Algal cell‐induced turbidity was shown to reduce incident irradiance with depth, indicated by increasing coefficients of attenuation (1·4–33·1) with increasing cell densities (0–2×10⁶ cells ml^‐1), though light intensities in the feeding experiment test chambers, at the algal cell densities tested, were within the optimal range for feeding (1–10 μmol s^‐1 m^‐2). Algae‐induced turbidity had different effects on larval feeding response dependent upon the previous visual environment of the larvae. Young larvae (day 9 post‐hatching) reared in clearwater showed decreased feeding capabilities with increasing turbidity, from 98±1% feeding and 0·153±0·022 rotifers consumed larva^‐1 min^‐1 in clearwater to 61±10% feeding and 0·042±0·004 rotifers consumed larva^‐1 min^‐1 at 56 NTU, while older clearwater reared larvae fed well at all turbidities tested. Likewise, greenwater reared larvae had increased feeding capabilities in the highest algal cell densities tested (32 and 66 NTU) compared with those in low algal cell density (6 NTU), and clearwater (0·7 NTU) to which they were naïve.     

The onset of photosynthetic acclimation to elevated CO2 partial pressure in field-grown Pinus radiata D. Don. after 4 years

The effects of CO₂ enrichment on photosynthesis and ribulose‐1,5‐bisphosphate carboxylase/oxygenase (rubisco) were studied in current year and 1‐year‐old needles of the same branch of field‐grown Pinus radiata D. Don trees. All measurements were made in the fourth year of growth in large, open‐top chambers continuously maintained at ambient (36 Pa) or elevated (65 Pa) CO₂ partial pressures. Photosynthetic rates of the 1‐year‐old needles made at the growth CO₂ partial pressure averaged 10·5 ± 0·5 μmol m^?2 s^?1 in the 36 Pa grown trees and 11·8 ± 0·4 μmol m^?2 s^?1 in the 65 Pa grown trees, and were not significantly different from each other. The photosynthetic capacity of 1‐year‐old needles was reduced by 25% from 23·0 ± 1·8 μmol m^?2 s^?1 in the 36 Pa CO₂ grown trees to 17·3 ± 0·7 μmol m^?2 s^?1 in the 65 Pa grown trees. Growth in elevated CO₂ also resulted in a 25% reduction in V_cmax (maximum carboxylation rate), a 23% reduction in J_max (RuBP regeneration capacity mediated by maximum electron transport rate) and a 30% reduction in Rubisco activity and content. Total non‐structural carbohydrates (TNC) as a fraction of total dry mass increased from 12·8 ± 0·4% in 1‐year‐old needles from the 36 Pa grown trees to 14·2 ± 0·7% in 1‐year‐old needles from the 65 Pa grown trees and leaf nitrogen content decreased from 1·30 ± 0·02 to 1·09 ± 0·10 g m^?2. The current‐year needles were not of sufficient size for gas exchange measurements, but none of the biochemical parameters measured (Rubisco, leaf chlorophyll, TNC and N), were effected by growth in elevated CO₂. These results demonstrate that photosynthetic acclimation, which was not found in the first 2 years of this experiment, can develop over time in field‐grown trees and may be regulated by source‐sink balance, sugar feedback mechanisms and nitrogen allocation.     

Perinatal changes in avian muscle: Implications from ultrastructure for the development of endothermy

Endothermic heat production and the capacity to shiver develop soon after hatching in birds, permitting chicks to regulate their body temperature. Physiological studies have not clearly identified the developmental events causing this change in function. Here, we use electron microscopy to examine the development of structures involved in muscle activation, contraction, and metabolism coincident with the development of shivering thermogenesis. A stereological study was used to compare the ultrastructure of chicken iliofibularis before endothermic heat production was present (24 h before hatching) and 120 h later, when the iliofibularis had substantial capacity for shivering. Profound increases were found in the t-tubule system and terminal cisternae, mitochondrial cristae, and lipids. The number of triadic profiles increased 3.8-fold (7.6 ± 1.31/100 μm² to 28.5 ± 2.90/100 μm² fiber area). The surface area of cristae per mitochondrial volume doubled (12.0 ± 1.50 pm2/pm3 to 25.7 ± 1.84 μm²/μm³). Lipid droplets were rare in the iliofibularis of embryos about to hatch, but accounted for 4.4% of the muscle fiber volume in day 4 birds. We suggest that these ultrastructural changes more fully activate the iliofibularis, allow it to produce more heat both from calcium pumping and from contraction, and increase its endurance, thus permitting the muscle to be effective in thermogenesis. © 1995 Wiley-Liss, Inc.     

Ascomycetous yeast species recovered from grapes damaged by honeydew and sour rot

Aims: To identify ascomycetous yeasts recovered from sound and damaged grapes by the presence of honeydew or sour rot. Methods and Results: In sound grapes, the mean yeast counts ranged from 3·20 ± 1·04 log CFU g^?1 to 5·87 ± 0·64 log CFU g^?1. In honeydew grapes, the mean counts ranged from 3·88 ± 0·80 log CFU g^?1 to 6·64 ± 0·77 log CFU g^?1. In sour rot grapes counts varied between 6·34 ± 1·03 and 7·68 ± 0·38 logCFU g^?1. Hanseniaspora uvarum was the most frequent species from sound samples. In both types of damage, the most frequent species were Candida vanderwaltii, H. uvarum and Zygoascus hellenicus. The latter species was recovered in high frequency because of the utilization of the selective medium DBDM (Dekkera/Brettanomyces differential medium). The scarce isolation frequency of the wine spoilage species Zygosaccharomyces bailii (in sour rotten grapes) and Zygosaccharomyces bisporus (in honeydew affected grapes) could only be demonstrated by the use of the selective medium ZDM (Zygosaccharomyces differential medium). Conclusions: The isolation of several species only from damaged grapes indicates that damage constituted the main factor determining yeast diversity. The utilization of selective media is required for eliciting the recovery of potentially wine spoilage species. Significance and Impact of the Study: The impact of damaged grapes in the yeast ecology of grapes has been underestimated.     

Preliminary crystallographic data for beta-lactamase I from Bacillus cereus 569.

Crystals of β-lactamase I from Bacillus cereus 569 are monoclinic, space group C2 with unit cell dimensions $\text{a = 143·0 (± 0·5), b = 35·8 (± 0·1), c = 52·7 (± 0·2)}\text{A}\text{?}\text{, β = 97·0 (± 0·1) °}$, and one molecule of molecular weight about 28,000 per asymmetric unit.     

离子对反相HPLC测定人红细胞PRPP合成酶活性

红细胞PRPP合成酶是红细胞内核苷酸代谢的关键酶,它参与嘌呤核苷酸的从头合成与补救合成途径,催化ATP与5-磷酸核糖（R5P）反应生成PRPP与AMP,而PRPP则是嘌呤嘧啶核苷酸合成途径的一个关键性中间产物．Stocchi等[1]采用离子对反相高效液相色谱法（IPrHPLC）测定红细胞内ATP,ADP．AMP含量,曾获得满意的谱峰分离效果．Sakuma等[2]应用rHPLC法测定了正常人及痛风等患者红细胞的PRPP合成酶活性,我们将Sakuma等的测酶技术与IPrHPLC法相结合,改用单液等度洗脱,达到了操作简便和灵敏、准确的要求．1材料和方法1．1试剂…