Varying effects of calcium on the oxidation of palmitate and α-ketoglutarate in isolated rat liver mitochondria incubated in KCl-based and sucrose-based media

• 1.1. Isolated mitochondria from rat liver were incubated in the presence of [U-¹⁴C]palmitate, ATP, CoA, carnitine, EGTA (ethylene glycol bis (β-aminoethyl ether) N,N′-tetraacetic acid) and varying amounts of calcium.
• 2.2. When a KCl-based incubation medium was used, the oxidation of palmitate was inhibited when the concentration of free calcium was increased from about 0.1–10μM.
• 3.3. When a sucrose-based incubation medium was used, the basal rate of palmitate oxidation was about half of that observed with the KCl-medium and calcium had a stimulatory effect.
• 4.4. With the KCl-medium the rate of oxygen consumption was inhibited by calcium with α-ketoglutarate as well as palmitate as the respiratory substrate.
• 5.5. No inhibitory effect of calcium was observed with succinate or β-hydroxybutyrate.
• 6.6. With the KCl-medium and with α-ketoglutarate as the respiratory substrate, state 3 respiration but not state 4 respiration was inhibited by calcium.
• 7.7. When the sucrose-medium was used, state 3 respiration was first inhibited by calcium, but this inhibition was gradually relieved and the respiratory rate finally became higher than it was before calcium addition.

     

Role of antiproteolytic heparin-binding serum protein(s) in modulating the levels of sialyl- and galactosyltransferase activity released during the incubation of rat jejunal slices

• 1.1. Sialyltransferase released into the medium during the incubation of rat jejunal slices in serum-free buffer, was susceptible to proteolytic degradation. Heat inactivated horse serum or its antiproteolytic heparin-binding fraction was found to be necessary in determining the activity of sialyltransferase released (Nadkarni et al., 1991).
• 2.2. In the present study, we have shown that heat inactivated rat serum (HRS) or its antiproteolytic heparin-binding fraction (HBF) had a role in determining the sialyltransferase activity released during jejunal slice incubations.
• 3.3. Galactosyltransferase was also released during incubations, but was not proteolytically degraded and the presence of HRS or HBF in incubations did not alter the levels of galactosyltransferase activity released.
• 4.4. Trypsin activity in serum-free incubation medium was higher compared to medium containing HRS.
• 5.5. Addition of serum-free medium obtained from 4 hr incubations of the jejunal slices, to medium obtained from parallel incubations done in the presence of HRS, caused inhibition of sialyl- but not galactosyltransferase activity.
• 6.6. In jejunal homogenates stored at −20°C, sialyltransferase activity was decreased during 0–45 days of storage, whereas galactosyltransferase activity remained fairly stable for upto 56 days.
• 7.7. Inclusion of HRS or HBF in homogenates resulted in higher sialyl- but not galactosyltransferase activity compared to serum-free homogenate samples.
• 8.8. The results suggest that HRS or its antiproteolytic heparin-binding proteins have a role in determining the sialyltransferase activity released from the jejunal slices. In contrast galactosyltransferase released was not susceptible to proteolysis, and HRS or HBF was not required to express its activity.

     

An in vitro study of short-chain fatty acid concentrations,production and absorption in pig (Sus scrofa) colon

• 1.1. Short-chain fatty acid concentration was 180mmol/l in the proximal colon and decreased to 108 mmol/l in the rectum.
• 2.2. Fermentation in chymus from different regions of the colon, showed the pattern of end products to reflect the substrate and not the site of the colon.
• 3.3. Isolated mucosa from proximal and distal colon had electroneutral sodium absorption of 4.8 ± 0.2 and 2.9 ± 0.8 μeq/cm² hr in bicarbonate free media, which was abolished in the absence of chloride.
• 4.4. Electroneutral sodium absorption was enhanced by short-chain fatty acids in the proximal colon and could be described by Michaelis-Menten kinetics with K_m 2.0–11 mmol/l and J_m 1.6–3.6μeq/cm² hr. In the distal colon the stimulation was smaller and propionate even inhibited sodium absorption.
• 5.5. Butyrate was absorbed in the proximal colon, whereas acetate and propionate, and butyrate in the distal colon had a flux ratio of one.
• 6.6. Amiloride (5 mmol/l) inhibited sodium absorption and net butyrate absorption.

     

Protease,amylase and lipase activities in the midgut and hindgut of the cricket,Gryllus rubens and mole cricket,Scapteriscus acletus

• 1.1. Midgut is the major source of protease, amylase and lipase in a cricket, Gryllus rubens and in a mole cricket, Scapteriscus actetus.
• 2.2. Hindgut makes a significant contribution, and possibly even the major contribution, to digestion in both crickets, with enzyme activities from 20% (amylase and lipase) to 30% (protease) of midgut level, and a pH favorable to action of all three.
• 3.3. Ingested food helps regulate digestive enzyme levels, and crickets starved for 5 days had only 50–60% of normal levels of enzyme activity.

     

Some physical and chemical properties of purified nematocysts of Hydra attenuata pall. (Hydrozoa,cnidaria)

• 1.1. A method for purifying undischarged nematocysts from Hydra and other cnidarians is described.
• 2.2. Isolated cysts (relative densities 1.22–1.24) evaginate their tubular content even after previous dehydration.
• 3.3. The cyst wall is permeable to dyes of mol. wts up to 600,000.
• 4.4. Approximately two-thirds of the cyst's dry wt are soluble proteins. Eighty per cent of them are of low mol. wt and highly anionic, presumably serving as binding sites for Ca²⁺ and Mg²⁺.
• 5.5. The other 20% includes 30 different proteins amongst them toxins and enzymes (phospholipase and little proteases but no collagenase, chitinase or hyaluronidase).

     

Biology of cave crickets,Hadenoecus subterraneus,and camel crickets,Ceuthophilus stygius (Insecta: Orthoptera): Metabolism and water economies related to size and temperature

• 1.1. Metabolic rate (MR) and water budget (WB) components of cave and camel crickets are directly related to size and temperature.
• 2.2. MR increases most rapidly with size for insects in general followed by cave crickets (females > males), and lastly, camel crickets (no sex differences).
• 3.3. Metabolic thermal sensitivity of cave crickets (males > females) is much greater than camel crickets.
• 4.4. WB components parallel MR relations.

     

Effect of inorganic phosphate on synthesis of 5-phosphoribosyl-1-pyrophosphate in cultured plant cells

• 1.1. Inorganic phosphate (Pi) was absorbed rapidly by suspension-cultured cells of Catharanthus roseus which had previously been cultured in Pi-free Murashige Skoog medium.
• 2.2. The intracellular levels of ATP, ADP and 5-phosphoribosyl-l-pyrophosphate (PRPP) increased markedly during the 24 hr which followed the addition of Pi (1.25mM).
• 3.3. Availability of PRPP in vivo, estimated by the measurement of nucleotide synthesis from [8-¹⁴C]adenine, was also increased by addition of Pi.
• 4.4. Only a 20% increase in the maximum catalytic activity of PRPP synthetase was observed in extracts of cells, prepared 24 hr after addition of Pi.
• 5.5. In contrast to results for mammalian PRPP synthetase, the activity of PRPP synthetase, partially purified from Catharanthus roseus, was inhibited by concentration of Pi greater than 5mM.
• 6.6. The mechanisms involved in the increased availability of PRPP and the synthesis of adenine nucleotides in the plant cells cultured in Pi-containing medium are discussed.

     

Possible involvement of adenylylation in the modification of a 26 kDa protein in rat parotid acinar cells

• 1.1. Adenylylation, a posttranslational modification of proteins, was investigated in saponin-permeabilized acinar cells of the rat parotid gland.
• 2.2. When cells were incubated with [2,8-³H]ATP, several proteins, including a 26 kDa protein in the particulate fraction, were labeled.
• 3.3. Upon incubation of cells with [α-³²P]ATP in the presence of cAMP and 3-isobutyl-lmethylxanthine, ³²P-labeling of the 26 kDa protein was observed.
• 4.4. After treatment with snake venom phosphodiesterase, [³²P]AMP was released from the 26kDa protein. Such release was not observed when cells were labeled with [γ-³²P]ATP.
• 5.5. The ³²P-labeling pattern of proteins with [α-³²P]ATP was clearly different from that with [adenylate-³²P]NAD⁺.
• 6.6. The results suggest that the 26 kDa protein is one of the adenylylation substrates in rat parotid acinar cells.

     

The haemocytes and the activities of leucine aminopeptidase and alkaline phosphatase during development of Ceratitis capitata: Specific secretion of a leucine aminopeptidase isozyme

• 1.1. The types of haemocytes during larval development were studied.
• 2.2. The developmental profile of leucine aminopeptidase and alkaline phosphatase was studied. The maximum LAP activity was found to be in early larval development, while the maximum alkaline phosphatase during the white pupal stage.
• 3.3. These activities were compared with those determined in cell-free haemolymph.
• 4.4. Both hydrolytic enzymes have been found histochemically in the prohaemocytes and in the plasmatocytes.
• 5.5. In cultured haemocytes experiments it was found that 64% of the total LAP activity was secreted into the incubation medium, while electrophoretic analysis of released LAP activity demonstrated that only LAP A isozyme was secreted.
• 6.6. Based on the above results we suggest that both hydrolytic enzymes are functionally important throughout larval development.

     

Cotranslational fatty acylation of mucus glycoprotein. Addition of palmitic acid to peptidyl-tRNA occurs prior to peptide chain completion and its release

• 1.1. The fatty acylation of mucus glycoprotein nascent peptides was investigated using [³H]palmitic acid and [³⁵S]methionine-labeled peptidyl-tRNA of rat gastric mucous cells.
• 2.2. The mucus glycoprotein peptidyl-tRNA fraction was found to contain covalently bound palmitic acid in its complexes.
• 3.3. RNase digestion of the mucus glycoprotein peptidyl-tRNA released [³H]palmitic acid labeled peptides which, on SDS-polyacrylamide gel, separated into a multitude of bands ranging in size from 2000 to 60,000 Da.
• 4.4. The analyses of low molecular weight peptides revealed that palmitic acid was present in methionine-labeled peptides containing 30–43 amino acids and those of 18–25 amino acids or larger devoid of methionine, but was not identified in methionine-labeled peptides containing 10–15 amino acids.
• 5.5. The results indicate that the N-terminal fatty acylation of mucus glycoprotein nascent peptides is a cotranslational process which is occuring in an immediate vicinity of the signal peptide fragment.

     

The dynamics of the permeation of an analogue of insect juvenile hormone into nematodes

• 1.1. ¹⁴C-dichlorofarnesoate permeated rapidly into Haemonchus contortus (infective juveniles) and Panagrellus redivivus (mixed cultures) and was strongly bound by hydrophobic association (K_s > 10⁻⁴M).
• 2.2. Uptake rose linearly with increases in temperature (5–38°C) and external concentration (C₀; 0.07–2.15 × 10⁻⁴ M). Within 1 hr the internal concentration, C₁ was >C C₀.
• 3.3. The pH of the medium (6–8) did not affect uptake.
• 4.4. Efflux of dichlorofarnesoate was low: the half-time of release was > 18 hr.
• 5.5. The uptake curve approximated to the expression C₁/C₀ = a(1 − e^−bt) with a and b as constants and t in hr.
• 6.6. These results clarify previous work on the inhibitory action of juvenile hormone on the development of nematodes.

     

Chemical composition of North Atlantic krill

• 1.1. The main chemical components of Meganyctiphanes norvegica (M. Sars), Thysanoessa inermis (Krøyer) and T. raschii (M. Sars) have been examined.
• 2.2. Protein accounted for 42–47% of the dry weight of M. norvegica and 32–50% of the dry weight of the Thysanoessa species. On a wet weight basis, the protein content was relatively constant and independent of season.
• 3.3. The dominating amino acids in the bulk protein of the krill were glutamic acid/glutamine, aspartic acid/asparagine, glycine, alanine, lysine and leucine.
• 4.4. Lipids were present in amounts of 13–29% of the dry weight in M. norvegica, 15–50% in T. inermis and 12–44% in T. raschii, and the lipid content varied with season.
• 5.5. The main nitrogen extractives in krill, expressed on a dry weight basis, were free amino acids (5–10%), trimethylamine oxide (about 4%), peptides (about 1%) and nucleotides (0.4–1.3%). Trimethylamine and ammonia were present in very low concentrations in living krill.
• 6.6. The amino acids taurine, glycine, proline, arginine, sarcosine and alanine made up 89–93 mol% of the free amino acid pool.
• 7.7. The ash content of krill was in the order of 10–13% of the dry weight, and fluoride represented 1040 and 3200 ppm in the Thysanoessa species and M. norvegioca, respectively.

     

Glucose transport across the intestinal wall of the freshwater snail Biomphalaria glabrata

• 1.1. Isolated midguts of the freshwater snail Biomphalaria glabrata were mounted in an incubation chamber in saline containing 2 mM glucose and perfused with the same solution. External and internal media were continuously gassed with carbogen gas (95% O₂, 5% CO₂). In order to measure the flux rates of glucose [¹⁴C]glucose was applied in the perfusion medium or in the incubation medium. Net fluxes of glucose were calculated as the differences between unidirectional in- and effluxes.
• 2.2. A directed net flux from the mucosal to the serosal side of the intestine was demonstrated (mucosal to serosal = 50 ± 10 nmol cm⁻²hr⁻¹(N = 6) serosal to mucosal 7 ± 1 nmol cm⁻²hr⁻¹ (N = 6), net flux = 43 nmol cm⁻²hr⁻¹).r
• 3.3. The active transport of glucose was reduced by the presence of metabolic inhibitors, cyanide (1 mM) and dinitrophenol (1 mM) on the mucosal as well as on the serosal side. Ouabain (1 mM) inhibited the transport rate only when it was added on the serosal side. Amiloride (1 mM) had no effect on the transport rate whether added on the mucosal or on the serosal side.
• 4.4. Inhibition of glucose transport by oubain, a specific inhibitor of Na⁺/K⁺-ATPase, suggests that glucose transport is secondary active and coupled to Na⁺-transport.

     

Relations between fatty acid synthesis,pyruvate concentration and cell concentration of suspensions of isolated rat hepatocytes

• 1.1. The cell concentration of suspensions of isolated rat hepatocytes affects both the rate of pyruvate accumulation in the incubation medium and the rate of fatty acid synthesis.
• 2.2. At low cell concentrations pyruvate accumulation is directly related to the cell concentration but levels off at higher concentrations even when maximum pyruvate concentrations in the medium are not yet reached.
• 3.3. The rate of fatty acid synthesis in the 30–60-min incubation interval is proportional to the cell concentration. In contrast, the rate of fatty acid synthesis during the 0–30-min incubation period decreases with increasing cell concentrations and subsequently becomes independent of the cell concentration.

     

The effect of eyestalk ablation on growth,haemolymph composition and gill Na+, K+-ATPase activity of Penaeus monodon juveniles

• 1.1. Eyestalk unablated and unilaterally ablated Penaeus monodon juveniles had survival rates after 5 months of 75–72.5 and 67.5–60%, respectively.
• 2.2. Unilaterally ablated shrimps had significantly higher (P < 0.05) growth rate than unablated shrimps.
• 3.3. Eyestalk-ablatement resulted in a decrease in the haemolymph sodium concentration and an increase in the potassium and calcium concentration of shrimps.
• 4.4. The osmolarity of haemolymph and total protein concentration of unablated shrimps were demonstrated to be higher than those of unilaterally ablated shrimps.
• 5.5. The eyestalk-ablated shrimps possess higher total ATPase and Na⁺,K⁺-ATPase activities in the gill than those of unablated shrimps.

     

The digestive enzymes of the pacific brown shrimp Penaeus californiensis.: I—Properties of amylase activity in the digestive tract

• 1.1. Crude extract of the whole digestive tract from the brown shrimp (P. californiensis) was investigated for digestive amylase activity.
• 2.2. Considerable amylase activity was found at pH 6.5–8.0, with optimum pH at around 7.5.
• 3.3. Optimum temperature was found between 30–40°C, similar to amylases from other crustaceans.
• 4.4. Amylase activity was highly halotolerant, having 50% maximum activity at 3 M NaCl.
• 5.5. Maximum amylase activity was found at 0.01 M NaCl.
• 6.6. Amylase activity was partially inhibited by the divalent ions Hg²⁺, Zn²⁺, Cu²⁺ and Cr²⁺.
• 7.7. Mg²⁺ and Ca²⁺ ions seemed to enhance amylase activity.

     

Fate of ingested leucine and glucose in the sea star,Asterias rubens,during its annual reproductive cycle

• 1.1. The distribution of radiolabel from L-leucine [¹⁴C-UL] and D-glucose [¹⁴C-UL] was measured in the sea star Asterias rubens at 1, 6 and 24 hr after oral administration.
• 2.2. Incorporation of the label from both compounds was observed in pyloric caeca, coelomocytes and ovaries even after an incubation time of 1 hr.
• 3.3. Highest incorporation from both precursors was found in proteins, while substantial radioactivity was present in the amino acids, organic acids and neutral components. Lipids were hardly labelled from leucine and only slightly from glucose.
• 4.4. Radioactivity in proteins and lipids increased with increasing incubation time. No significant differences were found in the distribution patterns of radiolabel during the reproductive cycle.
• 5.5. The data obtained are discussed in terms of current knowledge on the translocation of nutrients in echinoderms.

     

The free amino acids of muscle in the cephalochordate Branchiostoma,the cyclostome Myxine and some fishes

• 1.1. Branchiostoma and Myxine have the highest concentrations of amino acids (207 and 234 mM) of the five species investigated.
• 2.2. The predominant amino acids are glycine, proline, alanine, taurine, serine and valine, which form 83–98% of the total, except in Latimeria (60%).
• 3.3. Total amino acids are considered from the point of view of osmotic concentration in relation to other nitrogenous compounds of muscle.

     

Effects of Na+ and/or K+ on the Mg2+-dependent ATPase activities in shrimp (Macrobrachium amazonicum) gill homogenates

• 1.1. Homogenates of gills from the freshwater shrimp M. amazonicum exhibit the following ATPase activities: (i) a basal, Mg²⁺-dependent ATPase; (ii) an ouabain-sensitive, Na⁺ + K⁺-stimulated ATPase; (iii) an ouabain-insensitive, Na⁺-stimulated ATPase; and (iv) an ouabain-insensitive, K⁺-stimulated ATPase.
• 2.2. K⁺ suppresses the Na⁺-stimulated ATPase activity in a mixed-type kind of inhibition, whereas Na⁺ does not exert any noticeable effect on the K⁺-stimulated ATPase activity.
• 3.3. The Na⁺- and the K⁺-stimulated ATPase activities are totally inhibited by 5 mM ethacrynic acid in the incubation medium.
• 4.4. The Na⁺- and the K⁺-stimulated ATPase activities are not expressions of the activation of a Ca-ATPase.
• 5.5. The possible localization and roles of the described ATPases within the gill epithelium are briefly discussed and evaluated.