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R A Jacoby

Publications and source records attributed to R A Jacoby.

18 recordsLinked to original sources
PubMed2000

Morphological and electrophysiological properties of dissociated primate retinal cells.

Although isolated retinal cell preparations have been used widely to study retinal function in lower vertebrates, dissociated cells from primate retina have not been developed for routine physiological experiments. In this study, we demonstrated the feasibility of obtaining viable and identifiable dissociated cells from the primate retina. In addition, we characterized voltage-dependent membrane currents in each type of primate retinal cell with the whole-cell patch-clamp technique. Multiple types of ionic conductance with distinctive current profiles were recorded in various types of primate retinal neurons. Photoreceptors exhibited an inward I(H) activated by membrane hyperpolarization and an outward current activated at depolarized potentials. Two types of potassium currents (transient potassium current, I(K(A)), and delayed rectifier potassium current, I(K(V))) were recorded from bipolar cells. I(K(A)) dominated the current response in putative midget bipolar cells, and I(K(V)) was mainly associated with putative rod bipolar cells. L-type calcium currents (I(Ca)) were observed in primate bipolar cells with axon terminals, but not in axotomized bipolar cells. Large voltage-dependent sodium currents (I(Na)) were only recorded from ganglion cells. Muller cells exhibited I(K(V)) and large potassium inward rectifier current (I(K(IR))), and occasionally a small I(Na). Neurons with electrophysiological signatures of amacrine cells and horizontal cells were also studied even though their morphological features were lost during cell dissociation. By using both morphological and physiological criteria outlined in this report, it is possible to use the dissociated retinal cell preparation as an in vitro system for physiological, biochemical and pharmacological studies of the primate visual system.

Amacrine Cells↗
PubMed2000

Synaptic connections of DB3 diffuse bipolar cell axons in macaque retina.

In primate retinas, the dendrites of DB3 diffuse bipolar cells are known to receive inputs from cones. The goal of this study was to describe the synaptic connections of DB3 bipolar cell axons in the inner plexiform layer. DB3 bipolar cells in midperipheral retina were labeled with antibodies to calbindin, and their axons were analyzed in serial, ultrathin sections by electron microscopy. Synapses were found almost exclusively at the axonal varicosities of DB3 axon terminals. There were 2.14 synaptic ribbons per varicosity. There were 33 varicosities per DB3 cell, giving an average of 71 ribbons per axon terminal. Because there were 1.5 postsynaptic ganglion cell dendrites per DB3 axonal varicosity, we estimate that there is at least 1 synapse per varicosity onto a parasol ganglion cell dendrite. There were 3.4 input synapses from amacrine cells per axonal varicosity. Among these were feedback synapses to the DB3 bipolar cell axon varicosities, which were made by 47% of the postsynaptic amacrine cell processes. Some of the feedback synapses could be from amacrine cells immunoreactive for cholecystokinin precursor or choline acetyltransferase, because both types of amacrine cells costratify with parasol cells and are known to be presynaptic to bipolar cells. AII amacrine cells were both presynaptic and postsynaptic to DB3 axons, a finding consistent with the large rod input to parasol ganglion cells reported in physiological experiments. DB3 bipolar cell axons also made frequent contacts with neighboring DB3 axons, and gap junctions were always found at these sites.

Animals↗
PubMed2000

Diffuse bipolar cells provide input to OFF parasol ganglion cells in the macaque retina.

Parasol retinal ganglion cells are more sensitive to luminance contrast and respond more transiently at all levels of adaptation than midget ganglion cells. This may be due, in part, to differences between bipolar cells that provide their input, and the goal of these experiments was to study these differences. Midget bipolar cells are known to be presynaptic to midget ganglion cells. To identify the bipolar cells presynaptic to parasol cells, these ganglion cells were intracellularly injected with Neurobiotin, cone bipolar cells were immunolabeled, and the double-labeled material was analyzed. In the electron microscope, we found that DB3 diffuse bipolar cells labeled by using antiserum to calbindin D-28k were presynaptic to OFF parasol cells. In the confocal microscope, DB3 bipolars costratified with OFF parasol cell dendrites and made significantly more appositions with them than expected due to chance. Flat midget bipolar cells were labeled with antiserum to recoverin. Although they made a few appositions with parasol cells, the number was no greater than would be expected when two sets of processes have overlapping distributions in the inner plexiform layer. DB2 diffuse bipolar cells were labeled with antibodies to excitatory amino acid transporter 2, and they also made appositions with OFF parasol cells. These results suggest that DB2 bipolar cells are also presynaptic to OFF parasol ganglion cells, but midget bipolar cells are not. We estimate that midperipheral OFF parasol cells receive approximately 500 synapses from 50 DB3 bipolar cells that, in turn, receive input from 250 cones.

Amino Acid Sequence↗
PubMed1997

Nonunion rates of limited carpal arthrodesis: a meta-analysis of the literature.

Numerous types of limited intercarpal arthrodeses have been reported in dozens of articles in the English-language medical literature. The nonunion rate varies considerably within and between the different types of arthrodeses. This may be due in part to the small number of cases in most studies. The data on the number of good results and nonunion rates for 27 different types of limited carpal arthrodeses reported in the English-language medical literature from 1946 to 1993 were collected, and for each study, the 95% confidence intervals (95% CI) were calculated. The studies were then combined for specific types of arthrodeses and the overall nonunion rates and confidence intervals were calculated to more accurately determine the actual nonunion rate expected for limited intercarpal arthrodeses. Nonunion rates (95% CI) for the most popular types of limited arthrodeses were as follows: of 385 scaphotrapezium-trapezoid arthrodeses reported, there was a 14% nonunion rate (95% CI, 11%-18%); of 104 lunotriquetral arthrodeses, the nonunion rate was 27% (95% CI, 19%-36%); and of 17 scapholunate arthrodeses, the nonunion rate was 47% (95% CI, 26%-69%).

Arthrodesis↗
PubMed1993

Reflex sympathetic dystrophy: occurrence of chronic edema and nonimmune bullous skin lesions.

BACKGROUND: Reflex sympathetic dystrophy (RSD) is a poorly understood syndrome of post-traumatic pain, autonomic dysfunction, and progressive tissue atrophy. Classical descriptions of the cutaneous manifestations of RSD are usually limited to skin atrophy, vascular instability, and hyperhidrosis. OBJECTIVE: Our objective was to further delineate the cutaneous changes in RSD. METHODS: We have observed RSD-related inflammatory and bullous lesions in nine patients with active RSD. RESULTS: Eight patients had significant edema of involved skin, two patients had evidence of a pigmented purpura-like inflammatory dermatitis, and two other patients had bullae on involved skin. Ultrastructural studies on a biopsy specimen from one patient with recurrent bullae revealed a disrupted basement membrane and abnormal anchoring fibrils. CONCLUSION: Skin disease in RSD is more diverse than commonly appreciated and includes severe edema, inflammatory lesions, and a nonimmune bullous eruption.

Adult↗
PubMed1991

Reflex sympathetic dystrophy. Occurrence of inflammatory skin lesions in patients with stages II and III disease.

Reflex sympathetic dystrophy is a poorly understood syndrome of posttraumatic pain and sympathetic nervous aberration. We have observed previously unreported cutaneous manifestations of reflex sympathetic dystrophy. Seven patients with reflex sympathetic dystrophy were referred to our institution because of skin disorders. Three had recurrent ulcerating papules, and two had reticulate hyperpigmentation. Xerosis was common, and cutaneous atrophy was infrequent. Cutaneous ulceration and reticulate hyperpigmentation are previously unappreciated aspects of reflex sympathetic dystrophy. Further investigation regarding neural influences on the skin is warranted.

Adult↗
PubMed1979

Bullous dermatosis and systemic lupus erythematosus in a 15-year-old boy.

A 15-year-old boy had a bullous eruption suggestive of bullous pemphigoid and established systemic lupus erythematosus (SLE). Direct immunofluorescence studies of the bullae and adjacent skin revealed the linear deposition of IgG and complement localized to the basement membrane zone. Indirect immunofluorescence examination of the serum failed to reveal circulating basement membrane zone antibodies. The differential diagnosis of the bullous eruption is reviewed, and the problem of diagnosis in cases of coexistent bullous disease and SLE is discussed.

Adolescent↗
PubMedDate not supplied

AMPA-preferring receptors mediate excitatory non-NMDA responses of primate retinal ganglion cells.

Glutamate and kainate-induced currents of primate ganglion cells were studied using the whole-cell patch-clamp technique in a retinal slice preparation. Antagonists and allosteric modulators of desensitization selective for either alpha-amino-3-hydroxy-5-methyl-4-isoazoleprionic acid (AMPA)- or kainate-preferring receptors were used to determine the contributions of each type of receptor to excitatory responses. With synaptic transmission and NMDA receptors blocked, the AMPA-preferring receptor antagonist GYKI 52466 (30 microM-100 microM) reversibly blocked most of the glutamate-induced current in ganglion cells. GYKI 52466 also blocked the response in ganglion cells to focally applied kainate, suggesting that the current response to kainate arises from activation of AMPA-preferring receptors, and not kainate-preferring receptors. Both cyclothiazide (10 microM-100 microM) and the novel drug 4-[2-(phenylsulfonylamino)ethylthio]-2,6-difluoro-phenoxyacetamide (PEPA, 20 microM-100 microM), which selectively enhance responses mediated by AMPA-preferring receptors, enhanced glutamate-induced responses of ganglion cells. Since these drugs preferentially inhibit desensitization of the flip and flop splice variants, respectively, of AMPA-preferring receptors, it is likely that both splice variants are present on these ganglion cells. Concanavalin A, which selectively suppresses the desensitization of kainate-preferring receptors, had no effect on the glutamate-induced responses of ganglion cells. We conclude that the non-NMDA component of the excitatory, glutamatergic input to primate ganglion cells is mediated largely by AMPA-preferring receptors, with little, if any, kainate-preferring receptor-mediated response.

Animals↗