Features of the associative function of the brains of children with high and low lability of nervous system processes

Characteristics of brain associative functions in children of 6 years old with different lability of nervous processes, were compared by methods of conditioning and informational analysis. In children with a low lability, these functions were 1.6 time slower than in other children. Enhanced demands to lability (limitation of time, acceleration of signals presentation) lead to their further slowing and successive inhibition. In children with a high lability, in such conditions an activation of brain associative functions was recorded followed by expressed successive excitation. These differences may be considered as typological. In cases of learned inertness of motor reactions, the characteristics of these functions corresponded to those in children with a high lability of nervous processes.     

Evidence for the tetraplex structure of the d(GT)n repetitive sequences in solution.

The ability of oligonucleotides 3'-d(GT)5pO(CH2)6Opd(GT)5-5' (anti[d(GT)]) and 3'-d(GT)5pO(CH2)6Opd(GT)5-3' (par[par[d(GT)]) to form tertiary structures has been studied. Circular dichroism (CD) as well as the fluorescence of the ethidium bromide (EtBr) complexes with oligonucleotides and hydrodynamic volume measurements in solutions containing 0.01 M phosphate buffer, pH 7 and NaCl in concentrations from 0.1 M to 1 M, have been used. The data obtained in the temperature interval from 3 degrees C to 10 degrees C are in good agreement with the structure suggested earlier where the par[d(GT)] and anti[d(GT)] form structures with four parallel strands in which layers of four G-residues alternate with unpaired bulged-out T-residues. Ethidium bromide interacts with the structure in a cooperative manner. Two ethidium bromide molecules intercalate between two layers of four G-residues.     

How do ionic channel properties depend on the structure of polyene antibiotic molecules?

A study has been made of the properties of ionic channels formed in phospholipid-cholesterol bilayers by polyene antibiotics of various molecular structures. Properties of channels created by natural antibiotics with different structures of the lactone ring (amphotericin B-nystatin-mycoheptin) as well as by some derivatives of amphotericin B modified with respect to the amino and carboxyl groups are compared. Neutralization of one or both charges of the amphotericin B molecule (both by chemical modification and by pH shift) increases the probability of the channel to be in a nonconducting state. An increase of cholesterol concentration in the membrane produces an opposite effect. It is assumed that the electrostatic interaction of the amino group of an antibiotic molecule with the carboxyl group of an adjacent one stabilized the channel. Conductance and selectivity of an open channel are not influenced by changes in the charged groups. These properties strongly depend on the structure of the polar chain of the lactone ring. For example, the appearance of one more carbonyl group in the mycoheptin molecule results in a sharply decreasing anion permeability of channels. An antibiotic concentration which is necessary to observe single channels depends on the polyene chain structure: this is about 10(-7) M for tetraene nystatin and 2.10(-8) M for heptaene amphotericin B an mycoheptin.     

Quantitative protein changes in the hypothalamic neurons of pubertal male rats, castrated neonatally.

The effect of neonatal castration of male rats on the sexual differentiation of the hypothalamus at puberty was studied. Male rats were castrated on days 1, 5 and 7 after birth. Their brains were processed for study on days 83-85. The neurons and cell nuclei of the preoptic area, mediobasal and ventromedial nuclei were assessed for changes in cell and nuclear sizes and dry weight (calculated using interferometric methods). Neonatal castration resulted in size as well as dry weight increase in the neurons of the anterior and mediobasal hypothalamus. The dry weight increased by 34% (P less than 0.001) in the medial preoptic area, by 25% (P less than 0.001) in the arcuate neurons and by 22% (P less than 0.001) in the ventromedial nucleus. The cell nuclei exhibited perceptible weight increase too--in the medial preoptic area 68% (P less than 0.001); 55% in the arcuate neurons (P less than 0.001), and 39% in the ventromedial region. The weight and size increases in neonatally castrated males were equal to those of females of the same age. In rats castrated on day 7, the cell sizes and dry weights of the ventromedial nucleus increased but the cell nuclei exhibited only little change. It is assumed that the changes in the dry weight may be the result of increased synthetic processes in these groups of neurons which are connected with the tonic and cyclic release of gonadotropins. These changes also point to the hypothalamic differentiation shifting to the female type in the absence of the inducing effect of androgens.     

Spectral properties of phosphopyridoxyl-Lys-7(-41)-ribonuclease A.

We have studied the spectral properties of RNAase A containing a phosphopyridoxyl residue at the epsilon-NH2 group of Lys-7 or Lys-14. The overall conformations of the native and modified enzymes were shown to be rather similar. All three proteins have similar circular dichroism spectra within the 220-300-nm region, and similar thermal transition temperatures. All the changes in the RNAase A molecule modified are located in close proximity to the alkylated lysine residue. The phosphopyridoxyl group of (P-Pxy)-epsilon-Lys-41-RNAase A is situated directly at the enzyme active site and is 25% butied in the protein globule. The P-pyridoxyl group of (P-Pxy)-epsilon-Lys-7-RNAase A was shown to be located in the vicinity of the active site and to be more exposed to the solvent. In the pyridoxyl phosphate absorption band, optical activity is induced in both proteins. Study of the pH dependence of the changes occurring in the circular dichroism and absorption spectra has shown that in the modified proteins, the pyridoxyl phosphate chromophore is rather sensitive to the ionic state of the surrounding medium and serves as a "reporter" group when the relationship between structure and function of the RNAase A active site is being investigated.     

Dynamic changes in the response of molluscan neurons to cyclic AMP with repeated injections

Microiontophoretic injection of cAMP (but not of non-cyclic AMP) into Helix snail neurons induces rapid reversible membrane depolarization. The reversa potential of the cAMP response varies between +10 and -30 mV in different cells. The amplitude of the responses gradually increases (15 experiments), decreases (4 experiments) or remains unchanged (40 experiments) when the interval between the injections is less than 5 minutes. The identified neurons of the different preparations exhibit different types of dynamic changes in the amplitude of the responses to repeated cAMP injections. The possible role of the retaining current in the origin of the potentiation of cAMP responses was investigated. Potentiation of cAMP responses was preserved after the retaining current was switched off only in cases with no membrane depolarization due to spontaneous leakage of the substance from the microelectrode. It is suggested that potentiation or depression of cell responses to repeated cAMP injections is caused by dynamic changes in the cell cAMP system.