The synaptic ultrastructure in the outer plexiform layer of the catfish retina: a three-dimensional study with HVEM and conventional EM of Golgi-impregnated bipolar and horizontal cells

Synaptic structures between receptors and horizontal and bipolar cells in the outer plexiform layer (OPL) of Golgi-impregnated catfish retina were examined by conventional electron microscopy of serial ultrathin sections and by high-voltage electron microscopy (HVEM) of thick sections. Cone terminals contained multiple synaptic ribbons and rod terminals contained single synaptic ribbons. This observation was used to identify these two types of photoreceptors. The cone horizontal cell, located in the most distal part of the inner nuclear layer (INL), invaginated only cone terminals, whereas the rod horizontal cell, located in the proximal part of the INL, invaginated only rod terminals. Both lateral elements of the triad in the rod terminal originated from a single rod horizontal cell whereas the same structures in the cone terminal were often derived from several cone horizontal cells. Golgi-impregnated catfish bipolar cells were classified into two types based on the differences in their axonal arborization as described by Famiglietti et al. ('77). Axonal endings of type a bipolar cells were located in the distal part, sublamina a, of the inner plexiform layer (IPL), and axonal endings of type b cells were located in the proximal part, sublamina b, of the IPL. Dendrites from type a bipolar cells made direct contact with the synaptic ribbons in both rod and cone terminals whereas those from type b cells made indirect contact with the ribbons in both rod and cone terminals, but rare direct contact with the ribbon in rod terminals were also seen. In addition, bipolar cells made basal junctions or superficial contacts in both rod and cone terminals. The "lateral" processes of bipolar cells invaginating rods penetrated between the rod terminal and rod horizontal cell processes, and made basal junctions with both rod terminals and rod horizontal cells. There was no definitive morphological feature that could be associated with sign-conserving and sign-inverting signal transmission.

Synaptic organization of the cone horizontal cells in the catfish retina

Horizontal cells of the vertebrate retina are known to contribute to the formation of the receptive field surrounds of photoreceptor and bipolar cells. However, few synapses have been described anatomically that might mediate these interactions. We have observed in the catfish retina that cone horizontal cell perikarya and dendrites make conventional chemical synapses onto photoreceptor terminal telodendria and onto bipolar cell dendrites, while horizontal cell axon terminals make chemical synapses onto the perikarya and processes of amacrine cells. The synapses are characterized by clusters of round vesicles aggregated close to the site of contact, as well as by electron-dense material associated with both pre- and postsynaptic membranes. The three kinds of synapses observed anatomically correspond to the synaptic pathways involving cone horizontal cells that have been suggested by the physiology of these cells.

[Fundamental and clinical studies on aztreonam in the field of obstetrics and gynecology]

Aztreonam (SQ 26,776, AZT), a new monobactam antibiotic, was fundamentally and clinically studied with the following results. Uterine and adnexal concentrations of AZT after intravenous injection of 1 g were highest 3 hours after administration in the ranges of between 18.6-23.4 micrograms/g 16.5-28.2 micrograms/g, respectively, and and rapidly decreased thereafter. Penetration of AZT into the pelvic dead space exudate was quickly recognized after intravenous injection of 1 g and its concentration 30 minutes after administration was 14.08 +/- 7.08 micrograms/ml and highest (22.35 +/- 5.85 micrograms/ml) 2 hours after administration. It gradually decreased to 8.50 +/- 2.07 micrograms/ml 6 hours after administration. Clinical effect was studied by administering 1-3 g of AZT twice a day for 3-16 days by intravenous drip infusion for 18 patients with various infections in the field of obstetrics and gynecology. Efficacy of AZT for 9 genital infection cases were excellent for 4 cases, good for 4 cases and poor for 1 case, with an overall efficacy rate of 88.9%. For 2 UTI cases, it was excellent for one case and good for the other, and for 4 pelvioperitonitis cases, excellent for 3 cases and good for 1 case. For 2 inflammation cases of the pelvic dead space, efficacy of AZT was excellent for both of them. With regard to side effect, there was only one rash case experienced. It was considered from the above results that AZT is sufficiently useful for the infections in the field of obstetrics and gynecology and also useful for various gynecologic surgery cases.

Dynamics of turtle horizontal cell response

The small- and large-field (cone) horizontal cells produce similar dynamic responses to a stimulus whose mean luminance is modulated by a white-noise signal. Nonlinear components increase with an increase in the mean luminance and may produce a mean square error (MSE) of up to 15%. Increases in the mean luminance of the field stimulus bring about three major changes: the incremental sensitivity defined by the amplitude of the kernels decreases in a Weber-Fechner fashion; the waveforms of the kernels are transformed from monophasic (integrating) to biphasic (differentiating); the peak response time of the kernels becomes shorter and the cells respond to much higher-frequency inputs. The dynamics of the horizontal cell response also depend on the area of the retina stimulated. Smaller spots of light produce monophasic kernels of a longer peak response time. The presence of a steady background produces three major changes in the spot kernels: the kernel's amplitude becomes larger (incremental sensitivity increases); the peak response times become shorter; the waveform of the kernels changes in a fashion similar to that observed with an increase in the mean luminance of the field stimulus. A similar enhancement in the incremental sensitivity by a steady background has also been observed in catfish, which shows that this phenomenon is a common feature of the horizontal cells in the lower vertebrate retina.

Novel pathway connecting the outer and inner vertebrate retina

In many fish retinas, thin axons from the external horizontal cells extend through the inner nuclear layer and expand into large terminal processes that lie along the border of the inner nuclear and inner plexiform layers. Although the horizontal-cell axon terminals are structurally very prominent, their function is unknown. Here we report morphological and functional evidence that signals from catfish (Ictalurus punctatus) horizontal-cell axon terminals can be transmitted directly to amacrine cells. Current injected into horizontal-cell axon terminals produces responses from both transient and sustained amacrine cells very similar to those elicited by light stimuli. Electron microscope observations show chemical synapses from the axon terminals onto amacrine cell perikarya and processes. These data suggest that amacrine cells in the catfish retina receive two inputs, one from bipolar cells and the other from horizontal-cell axon terminals.

Signal transmission in the catfish retina. I. Transmission in the outer retina

Extrinsic current, either pulsatile or white-noise modulated, was injected into the (cone) horizontal-cell soma and axon, and resulting responses were recorded from nearby points. In the case of white-noise inputs, signal transmission between the two points was characterized by Wiener kernels. The signal transmission within the lamina, the S-space, formed by the (cone) horizontal-cell somas and axons is quasi-linear and very fast, indicating that the laminae are purely resistive networks within the frequency range of the light-evoked response. There exists signal transaction between the lamina formed by the somas and axons. The forward transmission is constant gain, low pass, but there is a filter for the reverse transmission to impede the backflow of high-frequency components. Signals in the horizontal-cell soma are transmitted to the bipolar cells. The transmission is sign noninverting for the on-center bipolar cells and sign inverting for the offcenter cells. The transmission is quasi-linear excluding complex mechanisms in the transmission. We believe that the forward and direct transmission of signals from the horizontal to bipolar cells is the most straightforward interpretation of the observation. The transfer functions between the horizontal and bipolar cells differ considerably from one bipolar cell to the next.

Signal transmission in the catfish retina. II. Transmission to type-N cell

Responses from channel catfish type-N (sustained amacrine) cells were evoked either by step changes in illuminance, i.e. brightening or dimming from a mean illuminance, or by a white-noise modulated light stimulus. Current injected into the horizontal-cell soma or axon produced responses in type-N cells that were very similar to those produced by light stimuli. Light- and current-evoked responses had linear and second- and third-order nonlinear components; the former contributed 40-50%, whereas the latter contributed 20-30% to the total response. The remainder of the response could have been due to higher-order nonlinearities or to intrinsic as well as extrinsic noise. Nonlinear components in the light- and current-evoked responses were sharp transient peaks, which were prominent in white-noise-evoked responses, and oscillatory wavelets. The high-frequency components in the cell's response, which result from nonlinearity, were absent in the responses from bipolar and horizontal cells. The nonlinear responses were predicted by the second- and third-order kernels. The type-N cell response was complex because the response had both linear and nonlinear components, and because of the complexities of second- and, probably, third-order kernels. The cell's complex response reflects the complex nature of the cell's function as well as its synaptic organization.

Signal transmission in the catfish retina. III. Transmission to type-C cell

Current injected into horizontal-cell somas and axons produced transient (on-off) depolarizations from type-C cells (commonly known as transient amacrine cells) similar to those produced by light. Both the light- and current-induced responses had very small linear components and nonlinear components as represented by the second-order kernels, which reproduced the cell's response with a reasonable degree of accuracy. The second-order kernels were well defined and stereotyped. The quadratic nature of the nonlinear component is reflected in the frequency doubling response as well as the very steep input-output relationship of the cell. Type-C cell's responses evoked by light and current differed in a subtle but distinct fashion, and this difference appeared in the signature of the second-order kernels. The light-produced kernels had two diagonal positive peaks and off-diagonal valleys ("four-eye" structure), whereas the current-produced kernels had a single on-diagonal positive peak with off-diagonal negative valleys ("three-eye" structure). The difference in the kernel configuration was reflected in the cell's step-evoked response. Some type-C cells produced faster responses whereas others produced slower responses, whether evoked by light or by current. Our past and present results show that type-C cells produce a very nonlinear response that is not necessarily complex.

Spontaneous membrane fluctuation in catfish type-N cells

Type-N (sustained) amacrine cells in catfish retina produce spontaneous membrane fluctuation of about 35 Hz. Fluctuations were seen either in dark or with a steady illumination. As all the distal cells and type-C (transient) amacrine cell did not produce any spontaneous fluctuation, type-N cells were the source of the oscillatory potentials.

Yuta (shaman) and community mental health on Okinawa

This study reports on the relations between the yuta (shaman) and the community mental health activities on Okinawa, Japan. Focus is on the process of initiation of the yuta and its meanings from the mental health viewpoints, the functions of the yuta in the particular cultural background of the island, and the importance of admitting the existence of the yuta in its relations to the psychiatric treatment in a mental hospital. The discussion is based on the authors' research findings which were obtained mostly through their therapeutic activities and their field studies. The authors' assumption is that each culture has in it a certain social background that is unique in that culture by which a stress or insanity is increased or brought about, but in the same culture there are ways to decrease the stress and to cure the insanity.

Effects of background and spatial pattern on incremental sensitivity of catfish horizontal cells

Incremental sensitivity of cones and horizontal cells was examined in the retina of the channel catfish (Ictalurus punctatus). In horizontal cells, steady full-field background illumination made the spot-evoked dynamic response larger and faster. The "enhancement" of incremental sensitivity was maximal at background levels of 20-50 microW/cm2. Similar changes in response were obtained by enlarging the diameter of the test spot (to 4 mm) without background illumination. In cones, no such enhancement with background was observed and small (0.4 mm) and large (4.0 mm) spots produced similar responses. Similar enhancement by a steady background has been observed also in the proximal neurons of catfish retina.

Turtle and catfish horizontal cells show different dynamic response

Horizontal cell responses of catfish and turtle have been found to differ in a characteristic way. These characteristics established by white-noise analysis show that the impulse response (first order Wiener kernel) of the catfish horizontal cell has a substantially shorter latency as well as peak response time than that of the turtle. The turtle horizontal cell, on the other hand, has a dynamic gain which is twice that of the catfish. Since these differences were established under conditions of ambient illumination, they may be expected to be functionally important in the visual experience of the animals under normal environmental conditions.

Decreased sensitivity of platelets to prostacyclin in patients with diabetes mellitus

In order to ascertain the platelet sensitivity to prostacyclin (PGI2) in patients with diabetes mellitus, we determined the percentage inhibition of platelet aggregation and platelet ATP secretion following PGI2 addition in an in vitro system. The percentage inhibition of platelet aggregation caused by PGI2 in final concentration of 1.25, 2.5, or 5.0 ng/ml was significantly lower in diabetics than in healthy controls. That of platelet ATP secretion by 1.25 or 2.5 ng/ml of PGI2 was also significantly lower in diabetics. These data suggested that in patients with diabetes mellitus, the decreased sensitivity of platelets to PGI2 will bring about hypercoagulability and may become one of the risk factors of diabetic microangiopathy in cooperation with lowered vascular PGI2 generation.

Salivary urea nitrogen as an index to renal function: a test-strip method

To investigate the feasibility of using salivary urea nitrogen as an index of renal glomerular filtration rate, we developed and applied a new analytical system consisting of a urease-containing test strip and an automatic reflectance spectrometer. The concentrations of urea nitrogen so determined correlate well (r = 0.93) with concentrations in serum. These preliminary data suggest that our method can be used routinely as a simple and reliable means of detecting abnormalities of renal function.

Salivary urea nitrogen as an index to renal function: a test-strip method

To investigate the feasibility of using salivary urea nitrogen as an index of renal glomerular filtration rate, we developed and applied a new analytical system consisting of a urease-containing test strip and an automatic reflectance spectrometer. The concentrations of urea nitrogen so determined correlate well (r = 0.93) with concentrations in serum. These preliminary data suggest that our method can be used routinely as a simple and reliable means of detecting abnormalities of renal function.

A new photographic method for mapping spatio-temporal receptive field using television snow stimulation

A means was devised to measure simultaneously spatial as well as temporal characteristics of visual receptive fields by stimulating the retina with the noise obtained on an unused television channel. The input, television snow, and the output, neural response, were recorded on a video tape. The tape was played back to obtain the (linear) spatio-temporal Wiener kernel by cross-correlating the input with the output. This method can be applied to extract the linear part of the visual responses in time and space.