Pelagic rotifers of Lake Glubokoe from 1897 to 1984

After alteration in the pattern of drainage of run-off from the surrounding swamps and changes in the colour and transparency of the Lake Glubokoe water, the previously epilimnial Trichocerca similis, Conochilus unicornis and Keratella cochlearis showed a shift of their maximum numbers to deeper layers. Pompholyx sp. and Trichocerca capucina, which are regarded as indicators of eutrophic waters, have disappeared from the pelagic zone of the lake and Conochilus hippocrepis, Synchaeta pectinata, Gastropus stylifer, Asplanchna herricki, Ascomorpha ecaudis, Ascomorpha saltans, Euchlanis dilatata and Trichocerca porcellus have made their appearance. Most of the new species are considered to be indicators of oligotrophic conditions. However the total density of pelagic rotifers remained at the same level. Apparently the establishment of the new species of rotifers was possible due to some ‘rarefaction’ of the epilimnion, the disappearance of predaceous Mesocyclops leuckarti and the invasion of the pelagic zone by Peridinium cinctum.     

Downregulation of cell-to-cell communication by the viralsrc gene is blocked by TMB-8 and recovery of communication is blocked by vanadate

Summary The viralsrc gene downregulates junctional communication, closing cell-to-cell membrane channels presumably by way of the phosphoinositide signal route. We show that TMB-8 [8-N, N-(diethylamino) octyl-3,4,5-trimethoxybenzoate] counteracts this downregulation in cells transformed by temperature-sensitive mutant Rous sarcoma virus: TMB-8 (36–72 m) raises junctional permeability when applied during activity ofsrc protein kinase, i.e., at steady permissive temperature; and TMB-8 inhibits the fall of junctional permeability, when the activity ofsrc protein kinase gets turned on. TMB-8 also (reversibly) inhibits the growth of the cells at permissive temperature and reverses the morphological changes associated with transformation. The morphological reversal lags several hours behind the junctional-permeability reversal. Communication recovers within a few minutes when the activity of thesrc protein kinase is turned off (in absence of TMB-8). Sodium orthovanadate (20 m) prevents this recovery, but it has no major effect on junctional permeability on its own. We discuss possible modes of action of these agents on critical stages of the signal route, related to intracellular Ca²⁺ and protein kinase C.     

Lack of Change in Basal Ganglia Neuropeptide Content Following Subacute 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine Treatment of the Common Marmoset

Treatment of common marmosets with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 1-4 mg/kg for up to 4 days) caused a profound parkinsonian state. Ten days from the start of MPTP treatment, all animals showed marked motor impairment, consisting of bradykinesia and akinesia, limb rigidity, postural abnormalities, loss of vocalisation and blink reflex, and, on occasions, postural tremor. Measurement of caudate-putamen monoamine content at this time showed a profound loss in 3,4-dihydroxyphenylethylamine, homovanillic acid, and 3,4-dihydroxyphenylacetic acid concentrations. Measurement of neuropeptide concentrations in the caudate-putamen, internal and external segments of the globus pallidus, nucleus accumbens, substantia nigra, frontal cortex, and hippocampus showed met-enkephalin, leu-enkephalin, and cholecystokinin (CCK-8) concentrations to be unaffected by MPTP treatment. There was a small decrease in the substance P content of frontal cortex, but otherwise the content of this neuropeptide was unaltered. Parkinsonism in the marmoset, induced by MPTP treatment 10 days earlier, does not alter neuropeptide concentrations in the manner observed in Parkinson's disease.     

Release of Monoamines from Striatum of Rat and Mouse Evoked by Local Application of Potassium: Evaluation of a New In Vivo Electrochemical Technique

Local application of K+ via micropressure-ejection, coupled with in vivo electrochemical detection, was used to study stimulated release from monoaminergic nerve terminals in the striatum of anesthetized rats and mice. K+-evoked releases were reversible, reproducible, and dose-dependent. In contrast, releases of electroactive species could not be evoked by local ejection of Na+. The magnitudes and time courses of K+-evoked releases recorded from the caudate nucleus of mice were greater than those seen in rats. Local application of nomifensine, a putative catecholamine reuptake blocker, augmented the magnitudes and time courses of K+-evoked releases. Releases were also recorded from brain regions adjacent the striatum; these signals were always smaller than those seen in the caudate nucleus and had amplitudes that showed good correspondence to the relative degree of dopaminergic input to these areas. These data, taken together with other information in the literature, suggest that this new technique is well suited for in situ studies of monoamine release and reuptake in intact animals.     

The skeleton of early Eocene Cantius, oldest lemuriform primate

A recently discovered partial skeleton of the adapid Cantius trigonodus from the early Eocene Willwood Formation of the Bighorn Basin, Wyoming, documents substantial new information about the anatomy of the oldest lemuriform primates. It is very similar in all features to its descendant, middle Eocene Notharctus, and both exhibit numerous resemblances to certain extant Malagasy lemurs, particularly Lepilemur, Propithecus, Lemur, and Hapalemur griseus. Like these forms, Cantius had relatively long hind limbs and short forelimbs. Forelimb traits (prominent brachialis flange of the humerus, well-developed olecranon process of the ulna, and strong shafts of the ulna and radius) suggest active use of the forelimbs in progression. Specializations in the hind limb (e.g., expanded articular surface of the femoral head, narrow and elevated patellar trochlea and prominent lateral trochlear ridge, posteriorly oriented femoral and tibial condyles, narrow and elongate talus, and hallucal metatarsal with prominent peroneal tubercle) indicate capabilities for leaping and for powerful grasping with an opposable hallux. Cantius was presumably primitive in having a relatively long ischium and much more distal inferior tibial tuberosity than most extant lemurs--traits suggesting that powerful extension of the thigh and flexion at the knee were important in its locomotion and posture. We interpret Cantius as an active arboreal quadruped with a propensity for leaping. The existence of this skeletal structure in one of the oldest primates of modern aspect suggests that it represents the primitive lemuriform morphology.     

Heparin binding to lipoprotein lipase and low density lipoproteins

Heparin was fractionated on an affinity column of bovine milk lipoprotein lipase (LpL) immobilized to Affi-Gel-15. The bound heparin, designated high-reactive heparin (HRH), enhanced LpL activity, presumably by stabilizing the enzyme against denaturation. The unbound heparin fraction had no observable effect on the initial rate of enzyme activity. However, at longer times of incubation there was inhibition of LpL activity. LpL-specific HRH also showed a high, Ca²⁺-dependent precipitating activity towards human plasma low density lipoproteins (LDL). Since LpL and LDL both bind to heparin-like molecules at the surface of the arterial wall, we suggest that their similar heparin-binding specificity may have physiological consequences as it relates to the development of atherosclerosis.

Heparin binding Lipoprotein lipase LDL Apolipoprotein Lipolysis     

Partition kinetics of ribulose-1,5-bisphosphate carboxylase from Rhodospirillum rubrum

When the enzymatically generated intermediate 2-carboxy-3-keto-D-arabinitol-1,5-bisphosphate (II) was used as a substrate with fresh enzyme, 70% reacted to produce 3-phosphoglycerate (3PGA). When a reaction mixture of enzyme plus [1-32P]ribulose 1,5-bisphosphate (RuBP) was quenched in the steady state with the tightly bound inhibitor 2-carboxyarabinitol-1,5-bisphosphate, 30% of the enzyme-bound species was released as 3PGA and 70% as RuBP. The major source for this partition was the ternary substrates Michaelis complex. The level of carboxylated intermediate in the steady state was determined to be 8% of active sites under the conditions of substrate saturation. No burst was seen in the appearance of product when 6.5 eq of [1-32P]RuBP was mixed with enzyme plus saturating CO2 and the reaction followed in the steady state. From these data plus the steady-state Vmax and Km of RuBP it is possible to derive the five bulk rate constants represented in the scheme ECO2 + RuBP in equilibrium ERuBPCO2 in equilibrium E X II----E + 2(3PGA).     

Structural requirements of a membrane-spanning domain for protein anchoring and cell surface transport

The membrane-spanning domain of the vesicular stomatitis virus glycoprotein (G) contains 20 uncharged and mostly hydrophobic amino acids. We created DNAs specifying G proteins with shortened transmembrane domains, by oligonucleotide-directed mutagenesis. Expression of these DNAs showed that G proteins containing 18, 16, or 14 amino acids of the original transmembrane domain assumed a transmembrane configuration and were transported to the cell surface. G proteins containing only 12 or 8 amino acids of this domain also spanned intracellular membranes, but their transport was blocked within a Golgi-like region in the cell. A G protein completely lacking the membrane-spanning domain accumulated in the endoplasmic reticulum and was secreted slowly. These experiments indicate that the size of the transmembrane domain is critical not only for membrane anchoring, but also for normal cell surface transport.     

Characterization of human interleukin 2 derived from Escherichia coli.

Interleukin 2 isolated from Escherichia coli cells expressing the human interleukin gene has been characterized. The observed properties of the protein have been compared with those properties which can be deduced from the DNA sequence alone and the published properties of natural human interleukin 2. The purified E. coli-derived interleukin 2 is a monomeric protein of Mr 15 000 with a sedimentation velocity of 1.86S. The amino acid composition of the protein and isoelectric point (7.7) are consistent with that part of the translated DNA sequence of the gene corresponding to the mature protein. A single disulphide bridge was identified between Cys-58 and Cys-105. C.d. suggested that interleukin 2 is predominantly alpha-helical in secondary structure. The E. coli-derived protein differed from natural interleukin 2 in the presence of N-terminal methionine and also in the absence of a carbohydrate moiety. Removal of the coding region for the first three amino acids of the natural interleukin 2 protein sequence (Ala-Pro-Thr) by site-specific mutagenesis resulted in a protein with N-terminal serine. The possibility that the specificity of the E. coli ribosomal methionine aminopeptidase may not recognize the sequence NH2-Met-Xaa-Pro is discussed (where Xaa is any amino acid residue).