Glenn M. Cohen

Developmental Gradients in the Embryonic Chick's Basilar Papilla

The basilar papilla, the avian counterpart to Cortis organ, was examined cytologically in the embryonic chick (Gallus domesticus) from stages 31 through 46 (hatching). Developmental reconstructions were prepared by using light microscopy to analyse serial sections (1-5 microM) along the entire lagenar length and electron microscopy to examine representative thin sections from the proximal, medial and distal regions. We identified two gradients, the lateral and longitudinal. In the longitudinal gradient, the mid-basal basilar papilla, which lies directly above the statoacoustic ganglion, develops before the proximal and distal regions as evidenced by the maturation of hair cells and afferent synapses. Similarly, in the lateral gradient, tall hair cells and afferent synapses develop before short hair cells and their respective afferent terminals. Efferent synaptogenesis follows the same two gradients several days later than the afferents. Afferent synaptogenesis corresponds with the opening of the perilymphatic spaces and completion of the tectorial membrane.

Determination of glucose concentrations in an aqueous matrix from NIR spectra using optimal time-domain filtering and partial least-squares regression

The authors have investigated the use of a time-domain optimal filtering method to simultaneously minimize both the baseline variation and high-frequency noise in near-infrared (NIR) spectrophotometric absorption data of glucose dissolved in a simple aqueous (deionized water) matrix. By coupling a third-order (6-pole) digital Butterworth bandpass filter with partial least-squares (PLS) regression modeling, glucose concentrations were determined for a set of test data with a standard error of prediction (SEP) of 10.53 mg/dl (mean percent error: 4.24%) using 7 PLS factors. Compared to the unfiltered test data for 6 PLS factors and a SEP=17.00 (mean percent error: 7.38%) this results shows more than a 38% decrease in the error. The glucose concentrations ranged from 51 mg/dl to 493 mg/dl, and the NIR spectral region between 2088 nm and 2354 nm (4789 cm/sup -1/ and 4248 cm/sup -1/) was used to develop the optimal PLS model. The optimal PLS model was determined from a sequence of 3-dimensional performance response maps for different numbers of PLS factors (2-10). A total of 99 NIR spectra were generated for glucose dissolved in deionized water using a NIRsystems 5000 dispersive spectrophotometer. Nine of these spectra were generated for only water, which were averaged and subtracted from the remaining 90 spectra to generate the training and test data sets, thereby, removing the intrinsic high background absorption due to the water. The training set consisted of 57 spectra and associated glucose concentration target values, and the test set was comprised of the remaining 33 spectra and target values. Performance results were compared for 3 different digital Butterworth bandpass filters (4-poles, 6-poles, and 8-poles), and a digital Gaussian filter design approach (i.e., Fourier filtering).

Development of the embryonic chick's tectorial membrane

The nascent tectorial membrane (TM) is identifiable as early as stage 33 (7th day) as thin, wispy material. By stage 37 (11th day), the dense mesh of the immature TM and fibrous webs (subtectorial threads) that attach the TM to the basilar papilla are distinct but scanty. The TM condenses slightly in its upper face. The growth of the columnar cells and basilar papilla during the following days pulls the TM, lifting it upward, and resembling the cables on a suspension bridge in cross-section. As a result, a large hollow wedge forms. During stages 40-44 (14th-18th days), the columnar cells secrete large amounts of fibrous material, which fills the hollow wedge and condenses into the dense meshes. The honeycombed patterns appear at this time. The supporting cells secrete the fibrous webs. Their secretory activity closely corresponds to that of the columnar cells. The secretory material from both cell types remains attached to the apical ends of their respective cells after secretory activity ends. By hatching (stage 46-21 days), the columnar cells have filled with fibrous material and their cytoplasmic organelles are restricted to the apices. The cytoplasm of supporting cells is relatively clear, with few cytoplasmic remnants of their intense secretory activity earlier.

Development of the embryonic chick's statoacoustic ganglion.

During stage 25 (4 1/2 days of incubation), the embryonic chicks statoacoustic ganglion appeared as a homogeneous cell mass. By stage 29 (6 days)- perikarya could be distinguished from Schwann cells because the latter contained more endoplasmic reticulum and ribosome. Granular Schwann cells processes have formed loose boundaries around groups of neurites. During the next 7 days, the Schwann cells clutched the neurites more tightly and divided them into successively smaller bundles. By the 13th day (stage 39) the first compact myelin (2-6 layers) surrounded the larger dendrites, and by the 14th day (stage 40) compact myelin appeared regularly. Until the 17th day (stage 43), the perikaryal were covered by a few layers of loose myelin. Perikaryal compact myelin appeared a day later (stage 44); the larger perikaryl diameter (15-30x) probably accounts for the lag. At hatching (20-21 days), 12-18 myelin layers surrounded many dendrites, though the extent of myelination varied markedly among dendrites in adjacent bundles. By the 2nd week after hatching, large myelinated perikarya outnumbered the smaller and loosely myelinated ones. Perikaryonal myelination required the cooperation of several Schwann cells. The myelin regularly alternated from compact to loose around each perikaryon.

Multivariate determination of glucose concentrations from optimally filtered frequency-warped NIR spectra of human blood serum.

Glucose concentrations over the 39-160 mg dl-1 range have been determined from 357 NIR (near-infrared) spectra of human blood serum in the spectral region from 6766 cm-1 to 4003 cm-1. A frequency-warping procedure was applied to the NIR data to compress 511 spectral components into 102 in the 6766-4003 cm-1 spectral region. Before the data compression process was carried out, the NIR spectrum of deionized water was subtracted from each of the blood serum spectra to remove the intrinsic high background absorption due to the water. PLS (partial least-squares) regression was coupled with time-domain digital Butterworth bandpass filtering in an optimization procedure. The optimization procedure was carried out over a range of centre frequencies and bandwidths for first- (two-pole), second- (four-pole) and third- (six-pole) order bandpass filters, and over a range of PLS factors. The optimal PLS model and filter parameters were determined from a sequence of three-dimensional performance response maps for different numbers of PLS factors and filter orders. As a basis for comparison, the same optimization process was carried out for a Gaussian filter design approach (i.e., Fourier filtering). Using the optimally filtered frequency-warped NIR spectral data, an SEP (standard error of prediction) of 13.2 mg dl-1 was achieved fro the test (monitoring) data using 14 PLS factors and a simple first-order (two-pole) digital Butterworth bandpass filter.

Acetylcholinesterase activity in the embryonic chick's inner ear.

Putative cholinergic efferent endings, as demonstrated by the presence of a localized acetylcholinesterase reaction product and visualized by phase-contrast microscopy, appeared in the lagenar macula and cristae ampullares on the 11th embryonic day (ED) and in the basilar papilla by the 13th ED. During the course of development, the reaction product became denser and more sharply defined, reflecting the maturation of efferent endings.

Laser Polarinetry For Measurement Of Drugs In The Aqueous Humor

We used laser polarimetry for measuring glucose concentrations in buffd saline. The ratio of output voltages were heady related over the 25-250 mg/dl range when plotted by a least squares fit When L-alanine (15 mg/dl), an optically active amino acid. was added to the glucose solutions over the same 25-250 mg/dl range, it caused a near castant shift in optical rotation of linearly polarized light when compared to glucose alone. We determined the optical rotation of a sample by measuring changes in the system output voltage. To calibrate the voltage output voltage, we determined the ratios of a reference signal to different test signals. The lam were measured by using reference samples of glucose over the test range.

Glutaraldehyde Fixatives for Preserving the Chick's Inner Ear

We preserved the inner ears of chicks in various concentrations of glutaraldehyde (2 to 3.5%) and cacodylate buffers (0.025 to 0.1 M). Buffer concentrations below 0.1 M caused osmotic damage that higher glutaraldehyde concentrations only partially counteracted. The combination of 3.5% glutaraldehyde and 0.1 M cacodylate buffer optimally preserved the different cell types and also eliminated problems of swelling and shrinkage. We further improved cellular preservation by immediately immersing the dissected specimen into chilled (4 degrees C), aerated fixative. The improved fixation greatly increased the retention of cytoplasmic ground substances, particularly in supporting cells and nerve terminals.

Neural Network Based Real-time Detection Of Glucose Using A Non-chemical Optical Sensor Approach

Both the sensing and detection of dissolved glucose represent two separate components for accurately determining glucose concentrations. The sensing component of the device is based on infrared absorption characteristics of glucose utilizing evanescent field and differential spectroscopy. An artificial neural network (ANN) based detection scheme is presented in this paper for real-time evaluation of glucose levels. The ANN architecture is a feedforward perceptron, trained by the back propagation algorithm. Actual spectral data, for various concentrations of glucose in a saline solution (0.9% NaCI), was used as training sets for the ANN. The data was gathered using a Nicolet FT-IR spectrophotometer. The infrared spectral data is used for each concentration of glucose as input training sets for the ANN after the spectrum of pure saline is subtracted from the glucose and saline spectrum. This is done because the saline absorption in the infrared is much greater than the glucose. The detection is based on the relatively large absorption peak of glucose at 9.6 p, which lies between two absorption bands of the saline.

Further observations of vestibular ototoxicity in the chick: Effects of streptomycin on the ampullary sensory epithelium

Starting eight days after hatching, chicks received daily subcutaneous injections of streptomycin sulfate, either 400 mg/kg for 30 days or 1,200 mg/kg for 15 days. Randomly selected chicks from each group were killed at intervals during the injection period, and the ampullae were examined for signs of vestibulotoxicity. Ampullary cell types differed in sensitivity to streptomycin. First, dark cell processes withered. Second, vacuoles formed in the apices of the light cells of the planum semilunatum. Third, nerve terminals swelled, and their organelles and ground substance clumped together, creating cleared areas. Last, hair cells and supporting cells became slightly vacuolated. However, these cells showed less overt damage than the other cell types. The onset of damage was earlier and the damage more severe with the 1,200-mg than with the 400-mg dosage. There was no evidence of hair cell loss during the experiment.