The X-ray structure of human serum ceruloplasmin at 3.1 Å: nature of the copper centres

The X-ray structure of human serum ceruloplasmin has been solved at a resolution of 3.1?Å. The structure reveals that the molecule is comprised of six plastocyanin-type domains arranged in a triangular array. There are six copper atoms; three form a trinuclear cluster sited at the interface of domains 1 and 6, and there are three mononuclear sites in domains 2, 4 and 6. Each of the mononuclear coppers is coordinated to a cysteine and two histidine residues, and those in domains 4 and 6 also coordinate to a methionine residue; in domain 2, the methionine is replaced by a leucine residue which may form van der Waals type contacts with the copper. The trinuclear centre and the mononuclear copper in domain 6 form a cluster essentially the same as that found in ascorbate oxidase, strongly suggesting an oxidase role for ceruloplasmin in the plasma.     

The influence of the diel climatic cycle on the depth-time distribution of phytoplankton and photosynthesis in a shallow equatorial lake (Lake Baringo,Kenya)

Lake Baringo is a shallow equatorial lake. This paper reports a diel study of the depth-time distribution of phytoplankton and photosynthesis at one location in Lake Baringo on 10 March 1989. The water column shows a pattern of diurnal stratification probably accentuated by the high turbidity of the water and therefore rapid attenuation of solar energy. This stratified pattern breaks down at night due to atmospheric cooling and the regular onset of winds in the early evening. The phytoplankton is dominated byMicrocystis aeruginosa with some associated epiphytes. It concentrates in the narrow euphotic zone during the diurnal period of stratification due to buoyancy of theMicrocystis; evening breakdown of the thermocline results in the phytoplankton being mixed throughout the water column. A series of measurements of photosynthesis throughout the diurnal period gives an areal rate of 3.8 g O₂ m⁻² d⁻¹. The relationship between this value and the level of fish exploitation in Lake Baringo is discussed. The diel cycle in Lake Baringo is interpreted as dominating over any seasonal limnological cycle in the lake.     

The vertical leap ofCercopithecus aethiops sabaeus: Biomechanics and anatomy

In this study, one positional mode, the vertical leap, is selected from the larger repertoire of habitual behaviors of whichCercopithecus aethiops sabaeus is capable, and is quantitatively analyzed. A cinematographic biomechanical analysis of the vertical leap provides a view of the kinematics (time-space properties of the leap) as well as the kinetics (or force properties) of the leap. These are then discussed with regard to anatomical potential. The analysis elucidates three distinct phases of motion during which the moving body segments linked via their connecting joints, affect one another in the production of the leap. The total positional adaptation ofC. a. sabaeus may only be determined after similar analyses are performed for all postural and locomotor modes. The present detailed analysis of vertical leaping is intended to present data for this one positional mode found to be of primary importance in the arboreal environment and in moving from the ground into the trees. In addition a methodology is illustrated for application in similar primate positional studies. A version of this paper was presented at the 43rd Annual Meeting of the American Association of Physical Anthropologists (March, 1974). This research was partially supported by Sigma Xi Grant-in-Aid of Research, Behavioral Science Foundation Fellowship.     

Discriminative effects of morphine administered intracerabrally in the rat

Rats were trained in a two-choice discrete trial avoidance paradigm to discriminate between saline and 3.0 mg/kg of morphine administered S.C. The microinjection of 0.3–3.0 μg of morphine into the lateral ventricle produced discriminative effects equivalent to those of the systemic training dose as measured by responding on the morphine-appropriate choice lever. Discriminative effects equivalent to those of the morphine training dose were not consistently produced by administration of morphine into the periaqueductal gray, lateral septum or dorsomedial thalamus in doses as high as 10 μg. However, the discriminative effects of systematically administered morphine were blocked by 10–30 μg of naloxone administered intracerebrally at all of the brain sites tested. Thus, the primary site at which morphine acts to produce discriminative effects in the rat is central, although the specific brain areas mediating these effects remain unidentified. The actions of naloxone could be the result of diffusion of the drug into the ventricular system or into the systemic circulation.     

The phosphorus efficiency of three annual legumes

Summary Trifolium subterraneum, Trifolium glomeratum andOrnithopus compressus were grown in soil and solution culture at varying P concentrations. Efficiency of P utilization was determined using the following criteria: (1) The ability to produce tops dry matter with a given amount of applied P, (2) Tops dry matter produced per unit of P taken up, (3) Tops dry matter produced at a constant plant P level and (4) Phosphorus uptake per unit root weight. The order of efficiency varied according to the crieteria used. Using the agronomic definition (1), Serradella was the most efficient species at 70 days. The need to clearly define what is meant by an efficient species is demonstrated.     

Exogenous C1q reconstitutes a secondary deficiency of C5-deficient AKR mouse macrophages for FcR-dependent cellular cytotoxicity and phagocytosis

Studies originally designed to assess the putative role of endogenous C5 in macrophage activation for antibody-dependent cellular cytotoxicity (ADCC) yielded unanticipated results. Resident and inflammatory peritoneal macrophages from C5-deficient AKR mice were found to have significantly lower capacity for FcR-dependent ADCC activation and phagocytosis of IgG-opsonized SRBC targets than did C5-competent C3HeB/FeJ (C3H) mice. Reconstitution of the ADCC response of AKR macrophages was accomplished initially with C5-sufficient C3H mouse serum, which suggested that endogenous C5 may be required for ADCC activation. However, further investigation largely eliminated C5 involvement in that a heat-labile component of C5-deficient AKR serum was shown to be active in the reconstitution of ADCC activation of AKR macrophages. Macrophages from AKR mice were found to have significantly lower levels of C1q mRNA synthesis, endogenous C1q levels, and C1q secretion than did C3H mouse macrophages as determined by Northern blot, Western blot, and presynthetic radiolabeling analysis, respectively. The addition of purified exogenous C1q to IgG-opsonized SRBC targets fully reconstituted ADCC activation for AKR inflammatory peritoneal macrophages to levels of normally FcR-responsive C3H macrophages. Similarly, exogenous C1q augmented FcR-dependent phagocytosis of AKR macrophages but had no effect on macrophages from responsive C3H mice. Our results indicate that AKR mice have a deficiency for FcR-dependent cellular cytotoxicity and phagocytosis that is related to their low potential for C1q synthesis and secretion rather than to their established genetic deficiency for C5 synthesis. We tentatively conclude that endogenous C1q is required as an accessory molecule for macrophage FcR-dependent effector functions and that C5 is not a prerequisite for ADCC activation.     

Robustness of G Proteins in Alzheimer''s Disease: An Immunoblot Study

Many of the neurotransmitter systems that are altered in senile dementia of the Alzheimer type are known to mediate their effects via G proteins, yet the integrity of guanine nucleotide-binding proteins (G proteins) in Alzheimer's diseased brains has received minimal investigation. The aim of this study was to establish whether the level of G alpha subunits of five G proteins was altered in Alzheimer's disease. We used immunoblotting (Western blotting) to compare the amounts of Gi1, Gi2, GsH (heavy molecular weight), GsL (light molecular weight), and Go in the frontal cortex and hippocampus, two regions severely affected by the disease, and the cerebellum, which is less severely affected. The number of senile plaques was also quantified. We report that there was no significant difference in the level of these G alpha subunits between Alzheimer's diseased and age-matched postmortem brains. These results suggest that alterations in the amount of G protein alpha subunits are not a feature of Alzheimer's disease.     

Enzymes Catalyzing the Reversible Conversion of Fructose-6-Phosphate and Fructose-1,6-Bisphosphate in Maize (Zea mays L.) Kernels

The significance of the glycolytic and gluconeogenic conversion of fructose-6-phosphate and fructose-1,6-bisphosphate on sugar metabolism was investigated in maize (Zea mays L.) kernels. Maximum extractable activities of the pyrophosphate (PPi) dependent phosphofructokinase, fructose-1,6-bisphosphatase, and the ATP-dependent phosphofructokinase were measured in normal and four maize genotypes, which accumulate relatively more sugars and less starch, to determine how these enzymes are affected by the genetic lesions. Normal endosperm accumulated more dry matter than the high sugar/low starch genotypes, but protein contents did not differ greatly among the genotypes. Mutation of several starch biosynthetic enzymes had little impact on the activities of PPi-dependent phosphofructokinase, fructose-1,6-bisphosphatase, and ATP-dependent phosphofructokinase, despite the altered capacity of the cell to synthesize starch. The PPi-dependent phosphofructokinase appeared to be more active toward glycolysis in all genotypes studied. Activity of the PPi-dependent phosphofructokinase in shrunken (low sucrose synthase genotype) did not differ from the activity in other genotypes, suggesting that the gluconeogenic production of PPi may not be the primary role of the enzyme. As expected, shrunken kernels contained more sugars and less starch than normal kernels throughout kernel development except at the very early stages. Developmental profiles of normal kernels also showed marked changes in the PPi-dependent phosphofructokinase activity, whereas the level of ATP-dependent phosphofructokinase activity remained relatively steady during kernel development. In addition, the ATP-dependent phosphofructokinase, and not the PPi-dependent phosphofructokinase, appeared to correlate more closely with respiration rate. These findings suggest that glycolysis catalyzed by the ATP-dependent phosphofructokinase may serve primarily to support energy production, and glycolysis catalyzed by the PPi-dependent phosphofructokinase may contribute mainly to generation of biosynthetic intermediates.