Possible involvement of the phloem lectin in long-distance viroid movement.

Incubation with cucumber phloem exudate in vitro results in a dramatic decrease in the electrophoretic mobility of Hop stunt viroid. UV cross-linking and a combination of size exclusion and ion exchange chromatography indicate that this phenomenon reflects a previously unsuspected ability of phloem protein 2, a dimeric lectin and the most abundant component of phloem exudate, to interact with RNA. In light of its demonstrated ability to move from cell to cell via plasmodesmata as well as long distances in the phloem, our results suggest that phloem protein 2 may facilitate the systemic movement of viroids and, possibly, other RNAs in vivo.     

Possible involvement of GABA in the central actions of benzodiazepines.

The effects of several benzodiazepines on a variety of nervous activities known or presumed to depend on GABA are presented and compared with those of agents that deplete or increase the level of endogenous GABA: antagonism of various convulsant agents in mice, enhancement of presynaptic inhibition in the spinal cord and the cuneate nucleus of cats, decrease of the spontaneous firing rate of cerebellar Purkinje cells in cats and rats, antagonism of bicuculine-induced depression of the strio-nigral-evoked potential in the cat, potentiation of haloperidol-induced catalepsy in rats, GABA-mimetic actions on drug-induced PGO-waves in cats and on eserine-induced circling in guinea pigs. Diazepam slightly increased the GABA level in the cat spinal cord and in the total brain of mice and rats; this increase does not seem to be due to an increase of GABA synthesis. It is concluded that benzodiazepines probably enhance presynaptic inhibition at all levels of the neuraxis and that this effect requires not only the presence of GABA but is also dependent on an activity of GABA-ergic neurons. Benzodiazepines also appear to enhance postsynaptic inhibition where this is mediated by GABA. Many actions of benzodiazepines can be tentatively explained by a stimulus-bound enhancement of GABA effects.     

Possible involvement of brain-derived neurotrophic factor in eating disorders

Eating disorders (EDs) manifest as abnormal patterns of eating behavior and weight regulation driven by low self-esteem due to weight preoccupation and perceptions toward body weight and shape. Two major groups of such disorders are anorexia nervosa (AN) and bulimia nervosa (BN). The etiology of EDs is complex and evidence indicates that both biological/genetic and psychosocial factors are involved. Several lines of evidence indicate that brain-derived neurotrophic factor (BDNF) plays a critical role in regulating eating behaviors and cognitive impairments in the EDs. BDNF is involved in neuronal proliferation, differentiation, and survival during development. BDNF and its tyrosine kinase receptor (TrkB) are expressed in hypothalamic nuclei associated with eating behaviors. A series of studies using BDNF knockout mice and the human BDNF gene indicate an association of BDNF and EDs with predisposition and vulnerability. In the previous studies, serum BDNF levels in subjects with EDs are reduced significantly compared with healthy controls, hence, we proposed that levels of serum BDNF would be a useful diagnostic indicator for EDs.     

Possible mechanisms of involvement of the subthalamic nucleus and structures interconnected with this nucleus in movement disorders evoked by dopamine depletion

A possible mechanism of involvement of the subthalamic nucleus (STN) in movement disorders evoked by dopamine deficit is suggested. Multifunctional role of the STN is based on following reasons. Various STN cells participate in the cortico-basal ganglia-thalamocortical loop and in the basal ganglia-pedunculopontine-basal ganglia loop. Complexity of neural circuits is determined by functional heterogeneity of neurons in the nuclei, reciprocally connected with the STN, as well as by opposite modulation of activity of these neurons by dopamine due to activation of different types of pre- and postsynaptic receptors. Dopamine influences activity of STN neurons directly, through pre- and postsynaptic receptors. It is assumed that high-frequency stimulation of the STN can reduce or eliminate Parkinsonian symptoms not only owing to inhibition of activity of GABAergic neurons in the output basal ganglia nuclei, projected into the thalamus or pedunculopontine nucleus, but also due to excitation of glutamatergic or cholinergic neurons in the output nuclei, and due to potentiation of excitatory inputs to preserved dopaminergic neurons and subsequent rise in dopamine concentration.     

Light and stomatal metabolism : I. Possible involvement of light modulation of enzymes in stomatal movement

New evidence is provided regarding the direct effect of light on stomatal opening in the epidermis of the pea (Pisum sativum L. var Little Marvel) leaf. Light modulates the activity of a number of key enzymes involved in stomatal metabolism. When isolated epidermal strips are illuminated, phosphoenolpyruvate carboxylase, NADP-malate dehydrogenase, and NADP-isocitrate dehydrogenase are activated; and aspartate aminotransferase is inactivated. Sulfhydryl compounds, dithiothreitol and glutathione, enhance stomatal opening in epidermal strips both in light or darkness while the sulfhydryl reagent N-ethylmaleimide inhibits, indicating the possible involvement of sulfhydryl groups in stomatal movements. Further, light treatment increases measureable thiol levels in the epidermis about 3-fold. These results suggest that light modulation of enzymes in the epidermis may play a significant role in the mechanism of stomatal movement.     

Cholinergic involvement in mental disorders.

A recent resurgence of interest in possible cholinergic mechanisms in schizophrenia, mania and depression represents a further extension of the attempt to explain these disorders on the basis of an abnormality in neurotransmission. New emphasis is less on individual neurotransmitters than it is upon their interdependent relationships. The latter is best exemplified by the treatment of Parkinson's disease, which has moved from a cholinergic approach to one that makes important use of dopaminergic mechanisms. Whether or not a reverse shift, from dopaminergic towards cholinergic approaches is justified for treating schizophrenia remains doubtful. Persuasive evidence can be adduced for new approachess to treatments of mania and depression through cholinergic mechanisms. The development of centrally active cholinemimetic agents will permit the clinical testing of some of the hypotheses engendered by this revival of inquiry into the role of acetylcholine in emotional disorders.     

Insulin-receptor interactions. Possible involvement of metals

Addition of Zn2+ or Cu2+ ions to plasma membrane preparations or to purified insulin receptors from rat liver resulted in an increase of specific insulin binding; no effect was observed with the addition of Fe3+, Ca2+ or Na+. Dialysis of membrane preparations, or of purified receptors, against chelating agents such as zincon (2-carboxy-2'-hydroxy-5'-sulfoformazyl-benzene) or 1,10-phenantroline resulted in a decrease in specific binding of insulin. With the readdition of Zn2+ or Cu2+ to the medium an increase in specific binding was observed, and values much higher than those of the original preparations were obtained; the addition of Ca2+, Fe3+ or Na+ to dialyzed preparations did not cause any effect on the specific binding. Dialysis of purified receptors against chelating agents resulted in a decrease in the content of Zn2+ and Cu2+. Zincon has been found to be a competitive inhibitor of insulin interfering with the specific binding to the receptor, and noncompetitive with the nonspecific binding. These results suggest the possible involvement of a metal ion present in the receptor in the formation of the insulin-receptor complex.     

MRI of the brain in childhood-onset mitochondrial disorders with central nervous system involvement

We retrospectively studied the brain MRIs of 66 pediatric patients with mitochondrial disorder with central nervous system involvement. Forty-one patients had an identified genetic etiology. A predominance of cerebrocortical lesions was mainly seen in patients with MELAS and Alpers syndrome. Basal ganglia were predominantly affected in patients with Leigh syndrome. All patients with leukoencephalopathy had pathological spectroscopy. Cerebrocortical atrophy with agenesis/atrophy of the corpus callosum was seen in patients with congenital lactic acidosis with or without pyruvate dehydrogenase complex deficiency. The diagnostic approach used in our study — from the neuroanatomical/neurofunctional lesion to disease identification — assists the physician in the use of brain neuroimaging early in the diagnostic work-up of suspected mitochondrial disorders.     

Possible involvement of cerebroside sulfate in opiate receptor binding.

Cerebroside sulfate (CS) appears to fulfill most of the structural requirements of a hypothetical opiate receptor. It possesses many of the properties that are thought to be necessary for the identification of an "opiate receptor," exhibiting high affinity and stereoselective binding to a number of narcotic drugs. Although these properties are insufficient to establish identity of the receptor, it is highly significant that the affinity of this binding can be correlated with the analgetic potency of these drugs in both man and rodents. CS is an endogenous component of brain tissue, and a partially purified opiate receptor from mouse brain has been found to be CS. Other experiments indicate that reduced availability of brain CS decreases the analgetic effects of morphine and this is accompanied by a reduction in number of binding sites, suggesting that the interaction of opiates with CS observed in vitro may also have importance in vivo. CS was also found to be a component of the opiate receptor after marking with 125I-labeled diazosulfanilic acid. The possibility that CS or the SO4-2 group of this lipid may be the "anionic site" of the opiate receptor should be considered.     

Possible involvement of bacterial autolytic enzymes in flagellar morphogenesis.

Autolytic enzymes were found to be required for flagellar morphogenesis in Bacillus subtilis 168 and Bacillus licheniformis 6346. Two previously characterized, poorly lytic, chain-forming mutants of B. subtilis 168, strains FJ3 (temperature conditional) and FJ6, each 90 to 95% deficient in the production of N-acetylmuramyl-L-alanine amidase and endo-beta-N-acetylglucosaminidase, were observed to be nonmotile at 35 degrees C in a variety of liquid and semisolid meida. In contrast, cells of the isogenic wild-type strain were motile and fully separated. Electron microscopy revealed the complete absence of flagella on the mutant cells. Similar observations were made with another poorly lytic strain of B. subtilis 168 (Nil5) and with two poorly lytic, phosphoglucomutase-deficient mutants of B. licheniformis 6346 (MH-3, MH-5). In minimal media lacking galactose (restrictive conditions), the B. licheniformis mutants failed to form flagella, or had serious abnormalities in flagellar morphogenesis and motility. Under permissive conditions, mutants FJ3 (grown at 17 degrees C) and MH-5 (grown with addend galactose) showed increased autolytic activities, grew in the dechained form, and regained their capacities to synthesize functional flagella. Examination of several classes of spontaneous revertants derived from the various mutant strains further demonstrated a close relationship between autolysin acttivity and flagellation in the two Bacillus spp.     

Possible involvement of nitroglycerin converting step in nitroglycerin tolerance.

Nitroglycerin (GTN) produces a dilation of vascular smooth muscle by releasing NO through a putative GTN-converting step. However, the response to GTN is markedly attenuated after prolonged or repeated exposure, resulting in tolerance. We investigated the mechanisms of GTN tolerance, employing exogenous and endogenous NO in rat aorta. In endothelium-denuded rat aortic strips, the GTN-induced relaxation response was attenuated by preceding exposure to either GTN or sodium nitroprusside (SNP). In contrast, the SNP-induced relaxation response was not affected by this protocol of GTN or SNP preexposure. Preincubation of aortic strips with lipopolysaccharide (LPS) +/- L-arginine for 12 h also caused attenuation of GTN-induced responses such as relaxation, cGMP production and nitrite/nitrate formation. The attenuating effect of LPS abolished in aortic strips co-incubated with LPS and cycloheximide or N(G)-nitro-L-arginine. These results suggest that GTN tolerance is predominantly associated with the reduction of NO release from GTN, which is caused through inhibition of a GTN-converting step due to preceding exposure to NO itself.     

Lithium iodide cardiac pacemakers: initial clinical experience.

A new long-life cardiac pacemaker pulse generator powered by a lithium iodide fuel cell was introduced in Canada in 1973. The compact, hermetically sealed unit is easily implanted and reliable, has excellent patient acceptance and has an anticipated battery life of almost 14 years. Among 105 patients who received a lithium iodide pacemaker, complications occurred in 18. The lithium iodide pacemaker represents a significant advance in pacemaker generator technology and is recommended for long-term cardiac pacing; the manufacturer guarantees the pulse generator for 6 years.     

Possible involvement of maspin in tooth development

Maspin is a 42 kDa serine protease inhibitor that possesses tumor suppressive and anti-angiogenic activities. Despite of a huge amount of data concerning the expression pattern of maspin in various tissues and its relevance to the biological properties of a variety of human cancer cells, little is known on the maspin expression in skeletal and tooth tissues. Recently, we reported that maspin may play an important role in extracellular matrix formation in bone by enhancing the accumulation of latent TGF-β in the extracellular matrix. This study was performed to elucidate the possible role of maspin in tooth development. First, an immunohistochemical analysis for human tooth germs at the late bell stage showed the expression of maspin by active ameloblasts and odontoblasts that were forming enamel and dentin, respectively. During rat tooth development, maspin expression was observed for the first time in inner and outer enamel epithelial cells and dental papilla cells at early bell stage. The neutralizing anti-maspin antibody inhibited the proper dental tissue formation in organ cultures of mandibular first molars obtained from 21-day-old rat embryos. In addition, the proliferation of HAT-7 cells, a rat odontogenic epithelial cell line, and human dental papilla cells were suppressed in a dose-dependent manner with anti-maspin antibody. Moreover, RT-PCR analysis showed that the expression of mRNA for tooth-related genes including dentin matrix protein 1, dentin sialophosphoprotein and osteopontin in human dental papilla cells was inhibited when treated with anti-maspin antibody. These findings suggest that maspin expressed in ameloblasts and odontoblasts plays an important physiological role in tooth development through the regulation of matrix formation in dental tissues.     

Possible involvement of queuine in oxidative metabolism

The possibility that the base, queuine, or the queuine family of tRNAs may play a role in oxidative metabolism has been investigated. (i) The enzymatic insertion of queuine into tRNA requires oxygen. This is true for both the mammalian and bacterial enzyme. (ii) (q-) LM cells (murine fibroblast line) grown in culture had 53% less of the manganese-containing superoxide dismutase than (q+) cells. (iii) There was less thiobarbituric-acid-reactive material in queuine-deficient mouse liver and kidney than in (q+) liver and kidney.     

Possible involvement of poly(A) in protein synthesis.

The experiments of this paper have re-evaluated the possibility that poly(A) is involved in protein synthesis by testing whether purified poly(A) might competitively inhibit in vitro protein synthesis in rabbit reticulocyte extracts. We have found that poly(A) inhibits the rate of translation of many different poly(A)+ mRNAs and that comparable inhibition is not observed with other ribopolymers. Inhibition by poly(A) preferentially affects the translation of adenylated mRNAs and can be overcome by increased mRNA concentrations or by translating mRNPs instead of mRNA. The extent of inhibition is dependent on the size of the competitor poly(A) as well as on the translation activity which a lysate has for poly(A)+ RNA. In light of our results and numerous experiments in the literature, we propose that poly(A) has a function in protein synthesis and that any role in the determination of mRNA stability is indirect.     

Possible involvement of momilactone B in rice allelopathy

Since residues and extracts of rice plants were known to inhibit the germination and growth of several plant species, the possible involvement of a growth inhibitor, momilactone B, in rice allelopathy was discussed. Momilactone B was found in shoots and roots of rice plants over their entire life cycle. The level of momilactone B in shoots and roots increased with rice plant growing until flowering initiation, and then decreased. The highest level of momilactone B in the shoots and roots at the day of flowering initiation was 245 and 64.1 nmol g(-1) fresh weight, respectively. Thus, 1 kg of rice shoots and roots, respectively, may be able to release 245 and 64.1 micromol of momilactone B into the soil or neighboring environment by decomposition of their residues, which may be sufficient to cause growth inhibition of their neighboring or successional plants. The growth inhibitory activity of momilactone B and the occurrence of momilactone B in rice plants suggest that momilactone B may contribute the growth inhibitory effect of rice residues and extracts, indicating that momilactone B may have an important role in the rice allelopathy.     

Possible involvement of GABA mechanisms in central cardiovascular and respiratory control. Studies on the interaction between diazepam, picrotoxin and clonidine

Various doses (0.1-1 mg/kg) of diazepam were given to chloralose anesthetized rats, with both systemic (i.p.) and central injections being tested. Arterial pressure, heart rate, respiration depth and frequency were recorded. Diazepam caused a dose-dependent decrease in the arterial pressure after systemic administration and also decreased it after central administration. However, only intraventricular but not intracisternal injections of diazepam were effective. The hypotensive effect of systemic diazepam was competitively counteracted by pretreatment with picrotoxin, a putative gamma-aminobutyric acid receptor blocking agent. The hypotensive effect of the centrally acting alpha-adrenoreceptor agonist clonidine was not influenced by picrotoxin pretreatment. The effect of diazepam on heart rate was inconsistent. Diazepam caused a reduction of respiratory frequency, which was not counteracted by picrotoxin pretreatment. It is concluded that central gabergic mechanisms are to some extent involved in the hypotensive effect of diazepam, probably at a supramedullary level. The hypotensive effect of a threshold dose of diazepam was blocked by a small dose of clonidine. Likewise, diazepam pretreatment could counteract the hypotension, bradycardia and respiratory frequency reduction caused by a threshold dose of clonidine. These results suggest that gabergic and/or other benzodiazepine-sensitive receptors may interact with alpha-adrenoreceptors in the control of central cardiovascular and respiratory mechanisms.