Biomedical subjects
Publications and source records attributed to R Steinberg.
A simple radiological grading of osteoporosis of the hand using a postero-anterior radiograph is presented as a screening technique. Five gradings are discussed, and the relationship of osteoporosis between the hand and axial portions of the skeleton is underlined.
The Singh index was used to measure the degree of osteoporosis in patients with fracture of the neck of the femur and to compare its prevalence with a random population sample in Jerusalem. The frequency of osteoporosis was 22.7% among women in the fracture series as compared with 1% in the control group. These figures are much lower than those in comparable series. The Singh index was not as sensitive an indicator of spinal osteoporosis as a direct measurement of vertebral bone density and could not be correlated with the incidence of hip fractures.
The density of cancellous bone in the nondominant radius of healthy subjects has been observed by the Compton scattering method as a function of age and sex. The average density for males is higher than for females. In males the density does not change up to the age of 80 years, while in females the density decreases beginning at age 50. A significant decrease in the bone mineral content of the distal radius is observed at earlier ages as measured by the Cameron-Sorenson technique. The average value of the cortical index of the third metacarpal shows some difference between the sexes over the age of 50, the index in males being higher than in the females. Between 30 and 50 years the female cortical index is greater than in the males. Little correlation was found among the three parameters studied, suggesting that they measure different phases of the pathophysiological processes involved in aging bone.
1. Local stimulus-evoked changes in concentration of extracellular calcium ions, [Ca2+]0, and potassium ions, [K+[0, were measured in the cerebellar cortex of the cat using paired ion-selected micropipettes. 2. Repetitive stimulation of 30 s duration decreased [Ca2+]0 from a base line of 1.2 mM to as low as 0.8 mM and increased [K+]0 from 3 mM to as much as 8 mM. The magnitude of the changes was directly related to stimulus frequency. Laminar analysis showed that the greatest ion changes occurred at the level of maximum parallel fiber-Purkinje cell dendrite stimulation, but that the [Ca2+]0 changes were more localized than the [K+]0 changes. 3. Combining real-time current-source density measurement with [K+]0 determination and local manganese application, showed that the Mn blocked parallel fiber-Purkinje cell synaptic transmission, but that much of the [K+]0 changes persisted. Thus, a large part of the [K+]0 flux most probably originated in the parallel fibers. In contrast, [Ca2+]0 changes were abolished by the Mn, indicating that the decrease in this ion was probably associated with synaptic transmission or dendritic events. 4. In a few cases, spreading depression occurred in the cat cerebellar cortex. This could be accompanied by decreases in [Ca2+]0 to as low as 0.12 mM and increases in [K+]0 in excess of 48 mM. 5. These results show that significant changes in [Ca2+]0 and [K+]0 occur during cerebellar stimulation and indicate possible origins of the ion fluxes in terms of neuronal elements. This work also shows that the cerebellar cortex of the cat can support spreading depression. The present results, together with those of earlier studies on [Ca2+]0 and [K+]0 changes in the presence of aminopyridine in the cat cerebellum, suggest that synaptic or dendritic electroresponsive properties may play a role in the observed [Ca2+]0 and [K+]0 changes.
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It is known that the discharges of the posterior red nucleus (RN) cells are modulated during locomation (Orlovsky, 1972). The aims of the present investigation were to look for a possible relationship between the unitary activity of RN cells and movements as well as postural reactions of the forelimbs. In the experimental arrangement used, the cat stood on four transducers which recorded to forces on each limb. The animal was restrained by a hammock supporting a part of the total body weight. A horizontally moving plate touched one forepaw and pushed it backwards until a placing mavement was induced. During the first part of the sequence, the mechanically stimulated limb was actively unloaded just prior to the placing movement, while the contralateral forelimb simultaneously presented a loading postural reaction. The results can be summarized and interpreted in the following way: 1. The RN cells exhibit large variations of discharge frequencies during phasic muscular activities linked to movement and to postural adjustments, but no correlations can be established between tonic cell activity and static postural forces exerted by the limb. 2. During the swing phase, the neuronal activity of some RN cells is maximal during flexion, while for others the maximum is during extension. 3. When there is a modification in frequency at the onset of the placing reaction relative to activity during the unloading reaction, the beginning of this change occurs after the onset of the movement as recorded by a potentiometer placed at the elbow joint. 4. The increases of frequency are higher during reciprocal muscle activation (during the movement) than during coactivation of antagonistic muscles (during the postural loading reaction). 5. During the loading reaction (with mostly extensor activation) the frequency of firing of those neurones discharging during the flexion phase. Thus the data may indicate that the RN is included in a feed-back loop which is linked not to muscle activities but rather to phasic spinal reflexes.
Changes in extracellular Ca2+ concentration were directly measured in the rat cerebellum, using an ion-selective micropipette. Extracellular K+ was measured simultaneously with a second ion-selective micropipette. The potential reference barrels of the ion electrodes also provided fast field and slow potentials. During repetitive stimulation of the parallel fiber--Purkinje cell cerebellar circuit, extracellular Ca2+ fell to about 80% of base line concentration. During the spreading depression of Leão, extracellular Ca2+ fell to about 10% of base line; decreases of this magnitude also occurred during terminal anoxia. In all cases extracellular K+ increased substantially. These results show that extracellular Ca2+ is modulated during neuronal activity in the central nervous system and that under some conditions the Ca2+ change can be extreme. Given the well-established and antagonistic effects of reduce extracellular Ca2+ on axonal excitability and synaptic transmission, these results suggest that Ca2+ modulation in the brain cell microenvironment may be a significant parameter in the behavior of neuronal ensembles.
In an epidemiological survey on fractures of the femur in Jerusalem, the highest incidence occurred in Oriental males and the next highest in European females. In the same series of patients the frequency of senile osteoporosis was noted to be higher in the Oriental group (both male and female) as compared with that in the European group. Similarly in a randomly chosen sample of the population, osteoporosis in the Oriental sector was twice as high as in the European sector. Osteoporosis was also seen to be three to four times more common in each age group when the fracture series was compared with the randomly chosen sample. No evidence of osteomalacia was noted in these patients.
The actions of dicarboxyl amino acids (GLUT, ASP, DLH) and of presumed amino acid antagonists (GDEE, HA 966) were studied in rubrospinal neurones with microelectrophoretic techniques. ASP and GLUT depolarized reversibly the cell membrane and increased its conductance. ASP had slightly stronger actions than GLUT. DLH had strong depolarizing actions without a clearcut change in membrane conductance; this may be due to the fact that DLH effects do not involve synaptic receptors. A specific action as antagonists for GLUT could not be shown for GDEE or HA 966. HA 966 effects were often accompanied by apparent postsynaptic actions. GDEE antagonized DLH effects sometimes even stronger than GLUT effects. The effects of GLUT and ASP are in principal agreement with a function as excitatory transmitters. The demonstration of a role as transmitter substances in excitatory (e.g. corticorubral or interpositorubral) pathways, however, still awaits the specific pharmacological antagonist.
A microelectrophoretic study was performed of the actions of GABA and glycine, and of their antagonists on rubrospinal neurones. GABA and glycine depressed antidromic and synaptic potentials, hyperpolarized the cell membrane and increased the membrane conductance. GABA was more effective than glycine. Corticorubral IPSPs and the GABA-induced membrane hyperpolarization could be reversed by intracellular application of hyperpolarizing currents. Picrotoxin and bicuculline methochloride antagonized inhibitory GABA actions and the corticorubral IPSP or the corresponding extracellular positive field potential. The results support the hypothesis that GABA is the transmitter of the corticorubral inhibition in the cat.
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The prevalence of osteoporosis in Jerusalem during the years 1967-71 was studied in a general population sample and in patients with fractures of the neck of the femur. Osteoporosis was determined by qualitative examination of lateral X-ray films of the lumbar spine. The prevalence of definite osteoporosis in a random population sample was 8.6%, and was higher in females (14.5%) than in males (2.9%). The prevalence of definite osteoporosis among 389 patients with fractures of the neck of the femur was 32.2%--37.8% in females and 17.4% in males. The results of this survey support the conclusion that osteoporosis plays an important role in the pathogenesis of fractures of the neck of the femur.
A method is described by which electrolytically sharpened tungsten wires were coated with a coaxial assembly of 5-8 glass-capillaries. This glass coating provides good insulation and high rigidity of the tungsten electrodes. The glass pipettes were used for electrophoretic ejection of test substances and the tungsten electrode for extracellular recording of neuronal activity.
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