Two types of eye movements during electrical stimulation of the rostral and caudal parts of the medial frontal "oculomotor" area in cats

The character of eye movements during electrical stimulation of the medial wall of the brain beneath the cruciate sulcus and of the inferior wall of the cruciate sulcus itself in the frontal cortex was investigated in waking cats. Stimulation of this part of the brain evoked two types of eye movements: unidirectional concomitant saccades, whose direction and amplitude were independent of the original position of the eyes in the orbits, and saccades into the central position (so-called centering saccades). Unidirectional saccades appeared in response to stimulation of the caudal part of the investigated zone, centering saccades in response to stimulation of its rostral part. Analysis of the directions and amplitudes of unidirectional saccades suggested the retinotopic organization of the caudal zone. Systematic changes in the magnitude and direction of vertical saccades during stimulation of the deep parts of the cruciate sulcus indicated previsely the projection of the vertical meridian of the retina. Reappearance of vertical saccades evoked by stimulation of certain parts of the medial wall of the brain suggests the existence of more than one retinotopically organized zone in this region. Inconstancy of stereotaxic coordinates of the oculomotor area, studied in different animals, was noted.Institute for Problems in Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 16, No. 6, pp. 761–766, November–December, 1984.     

Microcalorimetric assay of acetylcholinesterase

Comparative assays were made in a spectrophotometer and a microcalorimeter for the reaction between acetylcholinesterase (EC 3.1.1.7) and acetylthiocholine. The rate of light absorbance change and the rate of heat flow were measured from similar and simultaneous reactions in spectrophotometer and microcalorimeter, respectively. At the enzyme activity levels studied, i.e., 0.05–0.15 I.U. in calorimetry and 1–4 I.U. in spectrophotometry, the reaction rates were linear and showed first-order kinetics. A highly significant positive correlation was seen between the two methods (r = 0.997). More importantly, spectrophotometric assay with acetylthiocholine (which utilized a secondary reaction with chromagen, dithiobisnitrobenzoic acid) stood in highly significant positive correlation with calorimetric assays (which did not require a chromagen) either with the same substrate (r = 0.976) or with acetylcholine (r = 0.900). It appears that microcalorimetry can be used in preference to spectrophotometry for enzyme kinetic studies to overcome the complexity of reaction mixture and interference problems and with the advantage of using natural substrates.     

Two-dimensional gel analysis of swine histocompatibility antigens

Miniature swine MHC antigens from three inbred herds were examined by two-dimensional gel electrophoresis. These antigens were found to constitute a series of complex glycoproteins displaying haplotype-specific patterns that allowed the distinction of both class I and class II molecules among the three haplotypes. Selected outbred pig antisera reacted with a subset of class I antigens, suggesting the presence of at least two distinct molecular species among these antigens. Similarly, alloantisera reacting with mouse Ia antigens and a monoclonal anti-human DR were shown to immunoprecipitate a subset of class II molecules. Examination of the cells from two recombinant haplotypes demonstrated that both independent recombinational events took place between the class I and class II genes.     

‘De novo’ centrioles originate at sites associated with annulate lamellae in sea-urchin eggs

Hypertonic stress stimulates the formation of new centrioles in sea-urchin eggs. Those centrioles which appear away from the nuclear surface originate exclusiveJy at sites associated with annulate lamellae. Although apparent when nascent centrioles become visible, the annulate lamellar association is gradually lost as nascent forms mature into centrioles.     

Modulation of murine hemopoiesis in vivo by a synthetic hemoregulatory pentapeptide (HP 5b)

Abstract. Degeneration of the archenteron in middle gastrulae occurred in the presence of α,α'-dipyridyl or Zn²⁺, inhibitors of prolyl hydroxylase. In the presence of these substances the archenteron degenerated and was eventually destroyed. Adding Fe²⁺ to the embryo culture containing α,α'-dipyridyl protected the archenteron from further degeneration, but the collapsed archenteron was not restored to the upright position. At the late gastrula stage, α,α'-dipyridyl did not cause the degeneration of the archenteron. Treatment of the embryos by α,α'-dipyridyl, starting at the swimming blastula stage, resulted in the production of many mesenchyme-like cells but archenteron was not produced in the embryos. Addition of Fe²⁺ to α,α'-dipyridyl culture, just before the beginning of gastrulation of normal embryos, resulted in the formation of normal archenteron. α,α'-Dipyridyl inhibited hydroxylation of proline residues of collagen in sea urchin embryos and Fe²⁺ prevented the inhibition by α,α'-dipyridyl. Respiration was not inhibited by α,α'-dipyridyl.