Changes in the synapses in the parietal cortex of senescent rats.

Quantitative parameters characterizing the density of the synapses, the pre- and postsynaptic elements, and the synaptic contact zones (SCZ) in the parietal cortex of young adult (3-month-old) and aged rats (24 months) were investigated using an automated computer system. A big loss of axospinous, but not of axodendritic synapses, was observed in the aged rats. The parameters for the synaptic vesicles and SCZ were changed also only in the axospinous synapses. The changes in the quantitative parameters are accompanied by changes in the structure of synapses. The structural changes may be considered as being degenerative and regenerative.

Quantification of the synapses in the hippocampus of aged rats.

The synapses in the stratum lacunosum-molecular (str. L-M) of CA1 hippocampal field in 3-month old and 24-month old rats were examined using quantitative ultrastructural methods. No significant difference in the density of synapses and postsynaptic dendritic spines was found between the two age groups. The area of presynaptic terminals and postsynaptic dendritic spines was decreased slightly but significantly in the group of aged as compared to that in the group of young-mature rats. The vesicle number per presynaptic terminal, per area of presynaptic terminals and per volume of neuropil was not changed while the vesicle number per area of synaptic contact zones (SCZ) was increased in the group of aged rats. The mean length, total length and total surface of SCZ were diminished in the group of aged as compared to those in the group of young-mature rats. The same width of the str.radiatum and str.L-M in the two age groups showed that there was no any shrinkage of the neuropil in aged rats. The quantitative alterations in the synapses were accompanied by an increased number of dense and lamellar bodies in presynaptic terminals as well as with a presence of hypertrophic astroglial processes.

Changes in the synapses of rat hippocampus following pre- and postnatal alcohol exposure.

Quantitative and qualitative changes in the synapses in stratum lacunosum-moleculare of rat hippocampus following pre- and postnatal alcohol exposure were studied. Dense and lamellar bodies, damaged mitochondria, autophagic vacuoles and dilatated cisterns of the smooth endoplasmic reticulum were seen in axons and dendrites. The enlarged glial processes were also found. The area and the vesicle number of presynaptic terminals were decreased in CA1 and CA3 hippocampal fields, while the vesicle number per area of synaptic contact zones (SCZ) was decreased only in field CA3. The relative and absolute lengths of the SCZ, the total length and total surface of the SCZ were quite differently changed in both fields. The synaptic density was insignificantly increased. The synaptic changes are thought to be due to the impaired development of the pyramidal cell dendrites in the hippocampus and their afferents.

Synaptic changes in the rat cerebellum following pre- and postnatal alcohol exposure.

The synapses in the cerebellar vermis molecular layer of 6 week old rats treated with small amounts of ethanol (9 g/kg daily) during pre- and postnatal development were examined. Quantitative analysis was made using a digitizer interfaced to a computer. Some relative and absolute (volume) parameters for synapses were calculated using respective computer programs. The results showed a decreased synaptic density as well as qualitative and quantitative changes in the pre- and postsynaptic elements. The possibility that some changes are compensatory reactions to the decreased synaptic input to the Purkinje cells following prolonged alcohol exposure is discussed.

Angular velocity and acceleration of the QRS vector in the electrocardiogram of rabbits.

The curves of the spatial angular velocity (AV) and of its first derivative (AA) are described for 103 healthy rabbits. After analog-to-digital conversion, the amplified X-, Y- and Z-signals after McFee and Parungao are fed for calculation on a microcomputer. In 41 per cent of the cases the AV curve has two basic waves, in 29 per cent--three, in 21 per cent--one, and in 9 per cent--four, which coincide with the lowest points in the spatial magnitude curve. The AA curve consists of biphasic waves with approximately identical amplitudes of their positive and negative parts. The results are interpreted in connection with the chronotopography of the ventricular depolarization and reorientation of the activation front.

Effect of captopril on some ventricular contractility indices in spontaneously hypertensive rats (SHR).

Two groups of SHR were treated with captopril (Squibb): the first group (1 month old)--30 mg/kg i.p. twice daily for 77 days, and the second group (8 months old)--20 mg/kg p.o. twice a day for 23 days. The recording of electrocardiogram (ECG), systolic blood pressure (SBP), diastolic blood pressure (DBP), and some isometric indices of the left-ventricular contractility indicate that in all treated animals the values of most of the parameters are considerably lowered compared to the controls. The ratio between velocity of pressure increase and intraventricular pressure/equal to 50 mmHg--(dP/dt)/ICP50/does not change significantly. It can be concluded that in SHR, captopril practically does not influence the inotropic condition of the myocardium.

Spectral analysis of the normal electrocardiogram of rabbits.

A spectral analysis of the QRS complex of the rabbit's electrocardiogram was made. The amplified ECG signals were filtered through low-pass filters with cut-off frequency 500 Hz and steepness 12 dB/oct, and fed to a multichannel oscilloscope monitor. The images obtained were photographed. They were subjected to analog-to-digital conversion. The values were fed for processing to an EC 1035 computer. A standard discrete Fourier transformation was used. The spectral curve exhibited a considerable amplitude of the higher harmonics. Point -20 dB was at 164 Hz and point -30 dB was at 314 Hz. It was concluded that for accurate reproduction of the rabbit's ECG the recording electrocardiograph would have a bandwidth up to 225 Hz. An amplitude error not exceeding 10 per cent would be guaranteed.

Comparative study of three vectorcardiographic lead systems.

A homogeneous model of rabbit torso and physical dipole are used. A comparison is made between the corrected orthogonal vectorcardiographic lead systems after Frank, McFee-Parungao and Zao. The components X, Y, Z of the lead vectors are measured for 15 points which can be inserted in the cardiac volume under normal conditions. The modules of the lead vectors and the angles between them are calculated. The three vectorcardiographic systems are compared with respect to the ratio between the modules (X:Y:Z) and the deviations of the angles from the real value. Best orthogonality are found with the system after Frank, if the thoracic electrodes are placed precisely at the level of the so-called electrical cardiac centre. No essential differences are found between the systems after Frank and after McFee-Parungao with respect to correctedness and orthogonality.

Investigation of Frank's vectorcardiographic lead system on homogeneous rabbit torso model.

The applicability of Frank's lead system in experiments on rabbits is studied by using a homogeneous rabbit torso model. The influence of dipole localization on the modules of the lead vectors at the level of 4th, 5th and 6th intercostal spaces is studied. The lead vector modules along the axes X, Y and Z for the level of the dipole are calculated to be equal to 1:0.99:0.92. The maximum angular errors in the planes XY, XZ and YZ are calculated, being for the same level theta yz = -6 degrees 50', theta xy = theta xz = 0 degrees 00'. The authors have reached the conclusion that Frank's system produces good levelling of the lead vector modules and has satisfactory orthogonality on rabbit torso model.

[Characteristics of the aortic rheogram (an experimental study)]. / Osobennosti na aortnata reograma (eksperimentalno prouchvane).

The authors aim to describe aortic rheogram and examine its changes under the influence of some agents, to compare with the phases of the heart activity and to explain the origin of the curve. They use experimental animals (cats), to whom aortic rheogram is recorded by means of a probe-electrode, as well as atreiral blood pressure, phonocardiogram and electrocardiogram. The changes in the aortic rheogram are recorded after elevation or diminition of arterial blood pressure (medicamentous and mechanical), replacement of a part of the abdominal aorta with nonelastic prothesis and application of a model heart-aorta-vascular bed, in which the "systolic volume" is changeable as well as the "peripheral vascular resistance". The authors come to the conclusion that the aortic rheogram, recorded by a probe-electrode, is a reflection of the fluctuations in the volume velocity of the blood flow. Furthermore the general amplitude of the curve is in direct dependence of the systolic volume of the left ventricle. The peripheral vascular resistance and elasticity of the aortic wall do not affect substantially the form and amplitude of the rheogram. The value of the mean arterial blood pressure itself does not influence the form and the value of the curves.