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H Kasprzak

Publications and source records attributed to H Kasprzak.

At least 37 records · Page 2Linked to original sources
PubMed1992

[Holographic analysis of displacement of the bovine cornea after disruption of intact structures].

Displacement of the surface of the cornea of bovine eyes after disruption of intact structures was investigated by means of holographic interferometry. Double-T-incisions of different depths were made with a diamond knife. Starting at about 80% of the incision depth there is a change in the central holographic interference fringe pattern. These effects can be clearly demonstrated by means of double-exposure holographic interferometry and real-time holographic interferometry. The stability of an existing corneal scar was analyzed by double-exposure holographic interferometry. The region of the scar showed a higher density of holographic interference fringes compared with the non-affected corneal areas, indicating a higher degree of elasticity. All eyes were investigated at an intraocular pressure of 1340 Pa (about 10 mmHg) and an intraocular pressure change of 10 Pa and 20 Pa. Further potential ophthalmic applications of holographic interferometry are discussed.

Animals↗
PubMed1987

Nonlinear effects of the recording material on the image quality of a Fourier hologram.

A new representation for the D log E curve for photographic emulsions, based on the Fermi formula, is presented. This representation uses easily measured photometric parameters and is conveniently adapted for different kinds of absorption holographic recording materials. The corresponding transmittance-versus-exposure curve is used to calculate the influence of film nonlinearity on Fourier-transform hologram-recording parameters.

Holography↗
PubMed1985

Gating kinetics of nonjunctional acetylcholine receptor channels in developing Xenopus muscle.

The development of nonjunctional acetylcholine (ACh) receptor gating kinetics was studied in myotomal muscle of Xenopus laevis by spectral analysis of ACh-induced noise. The results are consistent with the idea that there is a developmental shift in relative numbers of receptors with fast and slow gating kinetics. For about the first 20 hr following the onset of ACh sensitivity, the majority of channel openings contributing to the ACh noise were slow, having an apparent mean open time of about 3 msec. Shortly before the time of hatching, there began to appear a significant contribution to the noise from channels having a mean open time of less than 1 msec. The relative amount of fast channel activity increased during the 2 days following hatching, and by the age of maturity of the myotomal synapse, most of the ACh noise arose from fast channel activity. A comparison of nonjunctional kinetics with synaptic currents at maturity suggests that the control of channel gating time is similar at junctional and nonjunctional regions.

Animals↗
PubMed1985

Recovery of acetylcholinesterase at intact neuromuscular junctions after in vivo inactivation with di-isopropylfluorophosphate.

Recovery of acetylcholinesterase (AChE) at endplates of mouse sternomastoid muscle was studied after inactivation with di-isopropylfluorophosphate in vivo. A short incubation with alpha-bungarotoxin was used to prevent muscle necrosis which usually occurs after esterase inactivation. Under these conditions there was no delay in AChE recovery, unlike what we had previously seen in necrotic muscle. However, even in non-necrotic muscle, the overall recovery of AChE at the postjunctional membrane was very slow, with a half-life of about 20 days. The fact that, at adult neuromuscular junctions, both esterases and receptors turn over about 10 times slower than they do in embryonic muscle suggests a similar regulation of these two molecules by the nerve.

Acetylcholinesterase↗
PubMed1979

Endplates after esterase inactivation in vivo: correlation between esterase concentration, functional response and fine structure.

Mouse sternomastoid muscles were incubated with diisopropylfluorophosphate (DFP) in vivo, and the time course of recovery was studied using histochemistry, EM autoradiography and physiology. We found that: (1) the ability of the muscle to sustain tetanus in response to nerve stimulation is eliminated when the esterases at the neuromuscular junctions are saturated with DFP. This ability is regained partially when less than 10% of the DFP-binding sites have recovered. (2) There is a positive correlation between the frequency of stimulation at which the tetanic response can be maintained and the extent of acetylcholinesterase (AChE) recovery. (3) Tetanic responses at fusion frequency (about 100 Hz) appear indistinguishable from controls with only about 25% of normal AChE. (4) Butyrylcholinesterase (BuChE) possibly of Schwann cell origin recovers more rapidly than does AChE. (5) The muscle shows fine structural changes involving Z band dissolution and the breakdown of sarcoplasmic reticulum within hours after esterase inactivation. (6) This myopathy reaches a peak at three days after esterase inactivation and is almost fully recovered by two weeks. (7) It can be eliminated if, at the time of esterase inactivation, the nerve is cut or the acetylcholine receptors at the endplate are inactivated by alpha-bungarotoxin. We suggest that the myopathy, seen after DFP, is mediated by Ca2+ fluxes due to prolonged action of acetylcholine (ACh) in the absence of esterases.

Acetylcholinesterase↗
PubMed1978

Acetylcholinesterase in the fast extraocular muscle of the mouse by light and electron microscope autoradiography.

The distribution of acetylcholinesterase (ACHe) in the twitch fibers of the extraocular muscles of the mouse was examined by light and electron microscope autoradiography after labeling with radioactive diisopropyl fluorophosphate (DFP) with, and without, 2-pyridine aldoxime methiodide (2-PAM) reactivation. The values obtained were compared with those previously reported for the diaphragm and sternomastoid muscles. The extraocular muscles were studied because they differ from the other two muscles in that they are among the fastest of the mammalian muscles, yet their endplates have sparse junctional folds. They could thus provide information on the extent to which ACHe concentration is an invariant feature of endplate morphology and what, if any aspects may be related to their fast speed of response. We found, using light microscope autoradiography, that in the twitch fibers of the extraocular muscle, there is n average of 6.4 +/- 2.1 X 10(7) DFP-binding sites per endplate, of which 29% (1.8 X 10(7)) are reactivated by 2-PAM and are thus AChe. The morphology of the extraocular endplates allowed us to conclude, on statistical grounds, that the AChe site are probably localized not only along the surface area of the postjunctional membrane (PJM) but also along the surface of the presynaptic axonal membrane. Based on this localization, we calculate 7,800 DFP sites and 2,500 2-PAM-reactivated sites/micron 2 of surface area of pre-and postjunctional membrane. This stacking density of DFP-binding sites per surface area of membrane ( probably in the overlying sheets of basal lamina) is very similar to that in the diaphragm and sternomastoid muscles.

Acetylcholinesterase↗