Diabetic macular edema and argon laser photocoagulation: a prospective randomized study

Loss of vision from diabetic retinopathy can result from complications of neovascular proliferation, or frequently, from macular edema secondary to background diabetic retinopathy. Although the benefits of photocoagulation for proliferative diabetic retinopathy have been clarified by the National Eye Institute's collaborative diabetic retinopathy study, those for background diabetic retinopathy with macular edema remain unclear. Several articles have described the visual benefits and reduction of edema following photocoagulation of eyes with background diabetic retinopathy and macular edema, but only Patz's study was prospectively designed utilizing a random assignment of laser treatment for one eye with the other eye remaining untreated. This article reports the two-year results of a similar prospective study in which one eye in each of 39 patients with symmetrical macular edema secondary to background diabetic retinopathy was randomly selected to receive argon laser photocoagulation, while the fellow eye remained untreated.     

A light and electron microscopic investigation of the neurosecretory bag cells ofAplysia

Summary The two bilateral clusters of neurosecretory bag cells ofAplysia were studied with both light and electron microscopy. Autoradiography revealed that the bag cells rapidly accumulate³H-labelled amino acids and that after 1–2 h, heavy concentrations of silver grains appear over Golgi complexes and in the proximal axons. Intrasomatic injections of CoCl₂ or lucifer yellow showed clear branch points and numerous varicosities along individual axons. Many of the bag cells are multipolar. Electron-microscopic observations confirmed that individual fibres branch and showed that the varicosities are packed with dense-cored vesicles similar in size (180 nm diameter) and electron density to those found in the somata. The axons of several cells are usually associated into bundles that travel (within the connective tissue sheath) either rostrally up the pleurovisceral connective or toward the contralateral bag cell cluster. Bundled in groups of tens to hundreds, a total of many thousands of axons fill the sheath around each cell cluster and around the proximal 2–5 mm of the pleurovisceral connective; the number of axon bundles in the sheath decreases rapidly with distance from the cluster. Individual axons reaching the outer edges of bundles form neurosecretory endings near blood sinuses in the sheath, creating an extensive neurohemal release area. Dense-cored vesicles are packed into the endings, often in very close apposition to the plasma membrane. Possible release profiles (omega-shaped) and smaller clear vesicles (85 nm diameter) were observed in the axon endings. A number of axons also enter and travel among the conventional (non-neurosecretory) axons in the core of the pleurovisceral connective nerve. These core bag cell axons project for several millimetres beyond the terminations of the bundled axons of the sheath.The findings support the hypothesis proposed in physiological studies that the distribution and branching of the axonal tree are the basis for the extracellularly recorded wave forms and of the potentiation of electrical signals during bag-cell activity. Additional evidence indicates that exocytosis is the means by which bag-cell hormone is released during afterdischarges.     

Preoperative Prognostic Factors in Diabetic Pars Plana Vitrectomy

The postoperative, six-month visual acuities of 1056 diabetic vitrectomy cases were compared to the following preoperative findings: duration of decreased vision associated with detachments, pupillary responses, iris rubeosis, intraocular tensions, extent of neovascularization, macular status, the ability to recognize entoptic phenomena, bright-flash ERG, and ultrasonography. By comparing these findings to the postoperative visual results, several factors were detected that could be helpful in determining the preoperative prognosis for improved vision. However, major operative complications reduced the incidence of successful visual results from 53% to 22%.     

The effects of amygdala lesions on hippocampal activity and classical eyeblink conditioning in rats

The hippocampus and the amygdala have long been associated with memory, emotion, and motivated behaviors. Although the role of these two brain areas in learning a simple, discrete motor response has been well studied, a definitive theory concerning their functions remains elusive. The present experiment involved selective lesions of the central nucleus (CE) or the basolateral nucleus (BA) of the amygdala in rats followed by single-unit analyses of hippocampal CA1 subfield activity during classical eye blink conditioning. Removal of CE or BA adversely affected the development of conditioned responding. Differences between groups in the patterns of hippocampal activity were observed. Similar to previous rabbit studies, hippocampal activity recorded from sham rats showed that CA1 cells became active during the CS-US period as conditioning progressed with activity especially prevalent just prior to US onset. Increased activity over training was seen during the CS-US interval in CE-lesioned rats, but the pattern differed from control rats-uniform excitation was seen across the entire CS-US period. BA-lesioned rats initially showed uniform CS-US period activation in early phases of training, but then showed patterns of hippocampal activity that resembled control rats in later stages of conditioning. The data suggest that the amygdala may play a modulatory role in the acquisition of conditioned eye blink responses and also in the formation of learning-related activity in the hippocampus.     

Characterization of a mutation in the lens-specific CP49 in the 129 strain of mouse

PURPOSE: The 129 strain of mouse carries a mutation in the gene for CP49 (phakinin), an intermediate filament protein thus far demonstrated only in the lens fiber cell. As such, these mice represent naturally occurring mutants of interest in the study of the lens cytoskeleton. However, this strain of mouse is also widely used as a source of embryonic stem cells in gene-targeting studies. The presence of a mutation in a lens-specific gene can confound interpretation of studies in which lens genes have been knocked out. In the present study, both the genotype and phenotype of these mice were characterized, to permit an evaluation of the biological impact of this mutation and to facilitate the discrimination between wild-type and mutant animals that have been derived from this strain in gene-targeting studies. METHODS: The CP49 cDNA and, when relevant, the genomic DNA sequences were determined for the 129/SvJ and C57BL/6J mice and from a commercially available 129/OLa P1 genomic clone. PCR primers were screened for their capacity to discriminate between the mutant and wild-type CP49 genes. Northern blot analysis was used to assess mRNA levels for CP49, filensin, and gammaS-crystallin (control). Western blot analysis was used to identify changes in protein size and abundance. The impact of the mutation on lens architecture was evaluated at the light-microscope level. Lens fiber cell ghosts from mutant and wild-type mice were examined in the electron microscope for the presence of beaded filaments. Lens clarity was assessed by slit lamp. RESULTS: The 129 strain of mice exhibited a 6303-bp deletion from the end of intron B, and the beginning of exon 2. This deletion results in the loss of the exon 2 splice acceptor site, absence of exon 2 from the CP49 mRNA, and dramatically reduced levels of CP49 mRNA. The CP49 protein was undetectable by Western blot analysis. Messenger RNA levels for filensin, CP49's assembly partner, were normal, but protein levels were sharply reduced. Light microscopy established that the initial differentiation and elongation of the fiber cells proceeded normally. Electron microscopy showed the absence of beaded filaments, whereas slit lamp microscopy showed a slowly emerging and progressive loss of optical clarity. CONCLUSIONS: The 129/SvJ and 129/OLa strains of mice harbor a mutation that sharply reduces CP49 mRNA levels and essentially eliminates both CP49 and the beaded filament. These lenses exhibited a slow but progressive loss of optical clarity with age. Thus, the 129 strain of mouse behaves as a functional CP49 knockout. The loss of clarity in the lenses of these animals and the absence of beaded filaments (and any attendant interactions that may exist between beaded filaments and other lens proteins/structures) suggest that gene-targeting studies of lens proteins in which the 129 strain was used as a source of embryonic stem cells may need reevaluation.     

Fitting hearing aids on infants and children: a primer for otolaryngologists

Fitting hearing aids on young infants presents a unique set of problems, and to some extent, requires a unique set of skills. First, a complete, frequency-specific evoked potential assessment is needed to define the loss and establish hearing aid fitting targets. The selected hearing aids must be flexible and must be adjusted to account for the acoustic characteristics of a small ear canal. Automatic volume control, wide dynamic range compression, directional microphones, and direct audio input are among the optional features to consider. In general, advanced technology, such as digital, programmable hearing aids offer the greatest flexibility in meeting the instrument-related challenges of the infant hearing-aid fitting. Finally, hearing aids are only one component of the management sequence. An early interventionist must be involved from the start to coordinate rehabilitation and ensure that the needs of the entire family are being met in the process.