Biochemical parameters to assess cell differentiation of Bouvardia ternifolia Schlecht callus

Calli derived from leaves and radicles of B. ternifolia were grown on Murashige and Skoog (MS) basal medium, and the effects of different nitrogen sources on the rate of callus growth and on the enzymes related to nitrogen assimilation were studied. Ammonium alone did not support callus growth unless a Krebs-cycle intermediate was added to the medium. The activities of glutamine synthetase (EC 6.3.1.2), glutamate synthase (EC 1.4.7.1), and glutamate dehydrogenase (EC 1.4.1.2) were measured in homogenates of callus grown on media supplied with different nitrogen sources. The results indicate that leaf and root calli have similar levels of these enzymes when grown on MS medium (Murashige and Skoog 1962. Physiol. Plant. 15, 473–497). However, when the calli were supplied with glutamine as the sole nitrogen source, the activity of glutamate synthase increased in leaf callus but was almost completely inhibited in root callus. The results indicate that calli originated from different B. ternifolia tissues do not have the same biochemical dedifferentiated state.     

The effect of calmodulin and far-red light on the kinetic properties of the mitochondrial and microsomal calcium-ion transport system from corn

The kinetic properties of active Ca²⁺ transport into mitochondria and microsomal membrane vesicles prepared from coleoptiles of dark-and light-grown corn seedlings have been studied. The apparent values for K _m and V _max for Ca²⁺ of the mitochondrial transport system from dark-grown plants are about one order of magnitude higher than those from the microsomal transport system. Calmodulin has no effect on the Ca²⁺ accumulation into mitochondria whereas the apparent maximum transport velocity and affinity for Ca²⁺ of the microsomal Ca²⁺-transport system are both increased by calmodulin. When intact corn seedlings are irradiated with far-red light, the calmodulin-induced increase of the apparent maximum transport velocity and affinity for Ca²⁺ can no longer be observed. From these data it can be concluded that the low cytoplasmic Ca²⁺ concentration in the cytoplasm of coleoptile cells from dark-grown corn is maintained by a calmodulin-regulated Ca²⁺ pump. Irradiation with photomorphogenically active far-red light lowers the Ca²⁺-transport activity and thus causes an increase of the cytoplasmic, free-Ca²⁺ concentration. The physiological implications will be discussed.     

Bisphosphoglycerate synthase activity in cells of the erythrocytic line of rat

The specific activity of bisphosphoglycerate synthase (EC 2.7.5.4) is significantly higher in rat mature erythrocytes than in reticulocytes from phenylhydrazine treated animals, while 2,3-bisphosphoglycerate levels do not differ between them. The enzyme specific activity and the concentration of 2,3-bisphosphoglycerate are both negligible in the erythroid cell pool from the bone marrow of anaemic animals. Thus, a cellular specialization in the last stages of erythropoiesis is confirmed. Human bisphosphoglycerate synthase shows a lower specific activity than that of rat without a parallel decrease in 2,3-bisphosphoglycerate levels.     

Characterization and taxonomic status of tick spiroplasmas: a review

Three serologically distinct groups of spiroplasmas have been recovered from ticks. Spiroplasma mirum strains (from rabbit ticks, Haemaphysalis leporispalustris) and Y32 group (VI) spiroplasmas (from Ixodes pacificus) are the only spiroplasmas to have a clear association with these arthropods. Group (VI) spiroplasmas are distinguished by an unusual nonhelical morphology and their capacity to hemadsorb guinea pig erythrocytes. S. mirum strains are unique in their ability to induce cataracts or lethal brain infections in a number of young vertebrates and in their virulence for the chick embryo. The 277F spiroplasma, while initially recovered from a pool of rabbit ticks (H. leporispalustris), is related by certain serological and genetic properties to spiroplasmas in the S. citri complex (serogroup I). These relationships suggest that the 277F spiroplasma may not be a natural inhabitant of the rabbit tick.     

The reactogenicity and immunogenicity of the Urabe Am 9 live mumps vaccine and persistence of vaccine induced antibodies in healthy young children

The immunogenicity and reactogenicity of the Urabe Am 9 mumps virus vaccine strain were studied after the administration of different doses of the vaccine to 197 children ranging in age from seven and a half months to nine years and without a history of mumps. There was no effect of dose on the response in serum neutralizing antibodies in the range of 10(2.9) to 10(4.7) TCID50/dose. In the 90 subjects without detectable serum neutralization antibodies before vaccination seroconversion was obtained in 94.4% after 42 days. Half of a group of 34 seropositive children who were tested also showed a fourfold or greater rise in antibodies. Persistence of vaccine-enhanced haemagluttinin-inhibition (EHI) antibodies was satisfactory as only two of 46 vaccinees followed-up for between 27 and 32 months had undetectable levels of EHI antibodies and the geometric mean titre of vaccine-induced EHI antibodies had only fallen to about one-third by 32 months after vaccination. Although there was serological evidence of a subclinical re-infection in three subjects, to date none of the vaccinees has had clinical mumps indicating that the vaccine confers protection against disease. The vaccine was well tolerated. Furthermore, the majority of the few 'reactions' reported were probably not vaccine-related. It is concluded that the Urabe Am 9 is an acceptable strain for use in live mumps vaccines.     

Thermodynamic approach to biomass distribution in ecological systems

In the derivation of the biomass distribution function for an ecological population critical use is made of an energetic constraint on the maximization of biomass diversity. The nature of this constraint is explored in detail using Kleiber's relation σ(m)=cm ^γ between animal metabolic rate σ(m) and body weightm in conjuction with the Prigogine-Wiame thermodynamic paradigm for specific entropy production in biological stationary states. These two inputs fix the energetic constraint on the maximization of biomass diversity to be the constancy of the mean metabolic rate of the ecosystem. The resulting biomass distribution function is tested against observational data.     

Distribution of corticotropin-releasing factor in ovine brain determined by radioimmunoassay

We have developed and used a sensitive and specific radioimmunoassay to demonstrate the presence of CRF-like immunoreactivity in extra-hypothalamic areas of ovine brain. Synthetic CRF displaced antibody bound tracer at an ED50 value of 200 pg and there was no cross-reactivity with LHRH, TRH, ACTH, beta-endorphin and several other peptides. Displacement of bound 125I-CRF by brain extracts exhibited curves parallel to synthetic CRF standards. Highest concentrations (1 ng/mg tissue) of CRF-like immunoreactivity were found in the median eminence but surprisingly, high concentrations of CRF-like immunoreactivity were found in frontal, parietal, occipital and particularly temporal areas of cerebral cortex. Much lower concentrations were found in other brain areas including the basal ganglia, limbic system and brain stem.     

The occurrence of GABA in vas deferens, prostate, epididymis, seminal vesicle and testicle of the rat

The concentration of gamma-aminobutyric acid (GABA) was determined in vas deferens, prostate, epididymis, seminal vesicle and testicle of the adult rat. Among the organs examined, vas deferens was found to be the richest in GABA and the lowest concentration was measured in testicle. Although the GABA levels appear to be 10-50 times lower in the sex organs examined than in the brain tissue, even the low GABA contents are suggestive of a role of this amino acid in the reproductive organs of the male rat.     

Acridine-psoralen amines and their interaction with deoxyribonucleic acid

A series of novel compounds in which a 9-acridinyl nucleus is linked to a psoralen nucleus in the 5- or 8-position via polyamines was prepared and examined. Their reversible binding to DNA and their irreversible binding to DNA and DNA cross-linking upon irradiation with UV-A light were examined. It was found that they were all less efficiently photoreactive than 8-methoxypsoralen (8-MOP), both in cross-linking and photobinding to DNA, whereas the ratio between their photobinding and cross-linking was 40-400 times that of 8-MOP. Compounds in which the linker was attached to the 5-position in psoralen showed smaller cross-linking and photobinding efficiencies and larger ratios between photobinding and cross-linking than those of psoralens attached in the 8-position. This strongly indicates that the 9-substituents of the acridines are oriented toward the minor groove. Flow linear dichroism studies showed that the compounds were DNA intercalating with the acridine moiety, whereas the psoralen moiety in no case was clearly intercalating. This conclusion was further supported by viscometry which also strongly indicated monointercalation.