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At least 109 records · Page 6Linked to original sources

PubMed1993

Freeze-drying of cephalothin sodium: granularly agglomerated crystallization during freezing. II.

The mechanism of granularly agglomerated crystallization during freezing of cephalothin sodium (CET-Na) in aqueous solution has been discussed. Our previous report noted that strict control of the following is important in order to obtain crystalline granular agglomerates of CET-Na: (1) thermal history of the solution before receiving freezing, (2) cooling rate in freezing, and (3) aging temperature level in the crystal growth step. In order to clarify the physico/chemical meanings of the individual controls, further investigations have been made: 1) with varying thermal history, aqueous 30-% CET-Na solutions were prepared for storage, first at 0 degrees C with its supersaturation and secondly at 25 degrees C, in an unsaturated state for observing any structural changes by viscosimetry, refractometry, and surface tensiometry; 2) morphological changes in ice crystals during freezing at varying cooling rates, as well as those during the crystal growth step, were observed by polarized-light cryomicroscopy and scanning electron microscopy; 3) melting, as well as crystal growth, at several aging temperature levels were observed by electrical conductometry and also by the above-mentioned techniques.(ABSTRACT TRUNCATED AT 250 WORDS)

Cephalothin↗

PubMed1978

The clinical refractometer: a useful tool for the determination of specific gravity and osmolality in canine urine.

For the determination of specific gravity of canine urine the urinometer is often used. An alternative method is based on refractometry. Both methods were compared and a table for converting refractometer values to urinometer values is given. The refractometer was also compared with an osmometer. A linear relation was found between the readings of both instruments. The results clearly indicate that the refractometric method is very suitable for the small animal practitioner. The instrument appears to be a good alternative for both the urinometer and the osmometer.

Animals↗

PubMed1994

A novel method of measuring the concentration of anaesthetic vapours using a dew-point hygrometer.

The Antoine equation relates the saturated vapour pressure of a volatile substance, such as an anaesthetic agent, to the temperature. The measurement of the 'dew-point' of a dry gas mixture containing a volatile anaesthetic agent by a dew-point hygrometer permits the determination of the partial pressure of the anaesthetic agent. The accuracy of this technique is limited only by the accuracy of the Antoine coefficients and of the temperature measurement. Comparing measurements by the dew-point method with measurements by refractometry showed systematic discrepancies up to 0.2% and random discrepancies with SDS up to 0.07% concentration in the 1% to 5% range for three volatile anaesthetics. The systematic discrepancies may be due to errors in available data for the vapour pressures and/or the refractive indices of the anaesthetics.

Anesthesia, Inhalation↗

PubMedDate not supplied

[Modification of the lipid membrane matrix with magnesium].

The influence of sulphuric magnesium on the molecular regulation processes in lecithin-water systems was investigated by the optical methods of polarized microscopy, refractometry and infrared spectroscopy. The obtained changes of structure parameters are interpreted by the modification role of Mg2+ cations and SO4(2-) groups.

Magnesium Sulfate↗

PubMed1975

A human model of allergic conjunctivitis.

Using the method of refractometry to measure protein concentration in tears, a simple model was developed to evaluate the allergic response in humans. Timothy grass pollen was instilled into the cul de sac of a human subject, and the protein content of the subject's tears was sampled every 15 minutes for three hours. Once the time course of this experiment was predictable, various eye medications were instilled into the subject's eye 30 minutes after allergic challenge. It was noted that 1.0% and 0.1% prednisolone, each combined with 0.12% phenylephrine hydrochloride, as well as 1% epinephryl borate eye drops, produced an almost immediate return to normal of tear protein levels, whereas 1.0% medrysone, 0.1% fluorometholone, 1.0% prednisolone, and 0.12% prednisolone had less pronounced effects on reduction of elevated tear protein concentration.

Administration, Topical↗

PubMed1991

Outflow facility and its response to pilocarpine decline in aging rhesus monkeys.

Refractive error and total outflow facility were determined by Hartinger coincidence refractometry and two-level constant-pressure perfusion, respectively, in 17 rhesus monkeys, aged 5 to 29 years. Maximum accommodative response to corneal (iontophoretic) carbachol hydrochloride, baseline outflow facility, and the facility response to strong but submaximal intracameral doses of pilocarpine hydrochloride all declined with age. The correlation between accommodative response to carbachol and facility response to pilocarpine was slightly stronger than that between age and facility response. Since the ciliary muscle plays a major role in controlling both outflow facility and accommodation, and since histologic and videographic techniques demonstrate an age-related decline in rhesus ciliary muscle excursion induced by topical pilocarpine or electrical stimulation of the Edinger-Westphal nucleus, the present data support the hypothesis that an age-related decline in ciliary muscle mobility is associated, perhaps causally, with an age-related decline in facility and facility responsiveness to cholinergic drugs.

Accommodation, Ocular↗

PubMed1993

Amplitudes of accommodation of primate lenses refilled with two types of inflatable endocapsular balloons.

OBJECTIVE: To investigate the maintenance of ocular accommodation by refilling the lenses of the eyes of youthful primates with inflatable endocapsular balloons. METHODS: The lenses of 21 cynomolgus monkeys were refilled following endocapsular phacoemulsification with a balloon that either approximates the shape of the non-accommodated lens or the accommodated crystalline lens. RESULTS: In nine of 15 successfully refilled lenses, we were able to perform automated refractometry to determine the amplitude of accommodation, ie, changes in refraction before and 1 hour after application of topical 4% pilocarpine hydrochloride to alter lens shape. At 2 weeks, 2 to 3 months, and 6 to 12 months after operation, mean (+/- SD) accommodation was 4.6 +/- 2.5, 2.5 +/- 0.5, and 1.7 +/- 0.7 diopters (D), respectively, in the lenses refilled with the nonaccommodation balloon (n = 5; preoperative value, 15.2 +/- 1.3 D), and it was 1.9 +/- 0.5, 1.3 +/- 0.9, and 1.8 +/- 0.9 D, respectively, in the lenses refilled with the accommodation balloon (n = 4; preoperative value, 17.0 +/- 2.9 D). CONCLUSION: The greater yield of accommodation with the nonaccommodation balloon is consistent with the recent theory on the mechanism of accommodation. Although the obtained accommodation was a small fraction of values determined prior to the operation and the small amplitude of accommodation decreased over time, the feasibility of refilling the lens with an inflatable endocapsular balloon, allowing at least some accommodation in the eyes of youthful primates, was demonstrated. Applied to humans, this procedure may allow accommodation following cataract surgery.

Accommodation, Ocular↗

PubMed1994

Inhibition of aceclidine-stimulated outflow facility, accommodation and miosis in rhesus monkeys by muscarinic receptor subtype antagonists.

Aceclidine can dissociate accommodative and outflow facility responses in monkeys and humans. We sought to determine if different muscarinic receptor subtypes control outflow facility, accommodative and pupillary responses to aceclidine in the living rhesus monkey eye, as a possible basis for this separation. Each eye was cannulated with one branched and one unbranched needle. Baseline measurements (of outflow facility by two-level constant pressure perfusion; refraction by Hartinger coincidence refractometry and pupil diameter by vernier calipers) were recorded after anterior chamber exchange with (one eye) or without (opposite eye), muscarinic receptor subtype antagonist (pirenzepine, AF-DX 116 or 4-DAMP). The eyes were then exchanged a second time with these solutions plus added aceclidine. The response to aceclidine (the differences from baseline) in the presence or absence of antagonist were compared. The M3 muscarinic receptor subtype antagonist 4-DAMP was the most potent inhibitor of all three responses to aceclidine. The dissociation of accommodative, outflow facility and miotic responses to aceclidine in rhesus monkeys does not appear to be due to differences in the muscarinic receptor subtypes that can currently be distinguished pharmacologically.

Accommodation, Ocular↗

PubMed1984

A-band mass exceeds mass of its filament components by 30-45%.

We have measured filament lattice spacing in fibrils using X-ray diffraction, and find that STEM-determined mass/length values reported for myofilaments should give 13% w/v as the filament protein concentration in the lattice of the AO-band (filament overlap zone) of both insect flight muscle (IFM) and vertebrate skeletal muscle ( VSkM ). This is well below the actual mass concentration of AO-bands as measured by immersion refractometry of detergent-washed rigor myofibrils under the phase microscope. This technique identifies an immersion fluid of suitable refractive index (RI) for matching out all image contrast between background and the selected cross-band. We used RI fluids in which the effective RI matching component is a large-particle solute (Percoll or hemocyanin) excluded by the filament lattice. The measured RI indicates that protein concentration in AO-bands is 16-17% in Lethocerus and other IFM fibrils including CAF-digested fibrils, and is 18-19% in rabbit VSkM fibrils. On IFM fibrils we also measured absolute buoyant density in Percoll as greater than or equal to 1.042; this supports the value for mass concentration as determined by RI. The mass discrepancy between fibrils and filaments does not seem to arise from faults in the methods used. We therefore accept the STEM-determined mass/length values for thick filaments which indicate 4 myosins/crown in IFM and 3 in VSkM , and we believe there is considerable extra nonfilament material (concentration: 30-50 mg/ml) between the filaments in fibrils. In stretched VSkM , it is the H-bands, not the I-bands, which have an excess over filament mass content. The extra mass has not been identified.

Animals↗

PubMed1979

Lamellar keratoplasty in keratoconus.

The authors present the results of 11 keratoplasties in cases of keratoconus, comparing the visual acuity and the ocular refraction before and after the operation (ophtalmometry, objective and subjective refractometry). The statistical data indicate a meaningful flattening of the corneal curvature (12.84 dpt average) and a mean reduction of the myopia for 8.227 dpt. In fact, the basic regular astigmatism of the cornea had not been altered. The mean visual acuity was 0.68 (with an improvement of 0.495). No further damage of acuity had been observed. After 10 to 69 months a medical checkup revealed transparent grafts in five cases; four presented small maculae; one, thin folds of Descemet's membrane. Based on the authors' experience and on the literature, the paper recommends lamellar keratoplasty in cases of keratoconus, the surgeon must choose the appropriate moment in the course of the development of this disease.

Adult↗

PubMed1985

High performance liquid chromatographic separation of diacylglycerol acetates to quantitate disaturated species of lung phosphatidylcholine.

A high-performance liquid chromatographic (HPLC) separation of diacylglycerol acetates to quantitate disaturated species of lung phosphatidylcholine (PC) was studied. The diacylglycerol acetates were applied on a reversed phase column, eluted by an isocratic solvent, acetonitrile/isopropanol/water (35:15:1, v/v/v) at a flow rate of 1 ml/min, and detected by differential refractometry (RI). This isocratic HPLC method was useful to separate disaturated species from the others of lung PC. The quantitative analysis of the molecular species separated by HPLC was studied by RI detection. Chromatograms obtained by RI detection and radioactivity determination of diacylglycerol [3H]acetates prepared by [3H]acetic anhydride were almost identical. The RI detector responded in the same degree for different authentic standards of diacylglycerol acetates. The detection limit with RI detection was about 30 nmoles. Molecular species of PCs from human lung and carcinoma tissues were analyzed by this HPLC method. The contents of disaturated species were very similar to those reported previously. These results indicate that RI detection is very useful in the nmole range for the quantitative analysis among the molecular species containing disaturated species.

Acetates↗

PubMed1983

Chromatographic analysis of sugars in physiological fluids by postcolumn reaction with cuprammonium: a new and highly sensitive method.

A new highly sensitive method of high-performance liquid chromatographic analysis has been used to separate mono-, di-, and oligosaccharides present in jejunal aspirates from experimentally perfused animals. The sugars in the column eluant are detected at 280 to 310 nm after reaction with cuprammonium. No reaction coil is required between the column and uv detector because the reaction is virtually instantaneous. This technique is more sensitive than differential refractometry, so that it is possible to detect 2.5 nmol (450 ng) of glucose routinely, compared to a minimum detection limit of 100 nmol (18 micrograms) using a commercial refractive index detector. Using a suitable postcolumn pump, the technique is not sensitive to changes in solvent composition, as with gradient elution, and is applicable to analysis of other cis-cis glycols.

Ammonia↗

PubMed1980

Further characterization and N-terminal sequence of cobra venom phospholipase A2.

N-terminal amino acid sequence data on cobra venom phospholipase A2 (Naja naja naja) demonstrate the absence of histidine at positions 10 and 20, in contrast to most other Naja enzymes. The presence of three tryptophans was demonstrated by p-toluenesulfonic acid hydrolysis, and the location of two of these at positions 18 and 19 parallels other Naja phospholipase A2 sequences. Based on the amino acid composition of the enzyme, the theoretical E278 0.1% should be 2.2, which is consistent with dry weight determinations, refractometry and amino acid analysis. Unusually high reactivity of the enzyme toward the protein assay of Lowry et al. gives an erroneously low E278 0.1% value of 1.45 when compared to bovine serum serum albumin as a protein standard. Using an E278 0.1% of 2.2, this enzyme is inactivated by the active site reagent p-bromophenacyl bromide with a stoichiometry of 1 mol reagent per mol enzyme. Chromatography on Affi-Gel Blue provides further purification of this phospholipase A2.

Acetophenones↗

PubMed1989

Functional morphology of accommodation in the raccoon.

The raccoon (Procyon lotor) is a small carnivore which eats in the upright position, using hand- and finger-like front paws and digits to wash, hold and examine its food at close range. These anatomic and behavioral characteristics prompted structural and functional studies of the accommodative capability of this species. By light and electron microscopy, we observed a prominent ciliary smooth muscle and zonular apparatus. When stimulated by carbachol or pilocarpine, the muscle and zonular apparatus exhibited a shift from longitudinal to reticular or circular orientation of some ciliary muscle bundles, anterior movement of the muscle as a whole, and more oblique crossing of the zonular fiber bundles in the zonular plexus. Maximum carbachol-induced accommodative amplitude measured by coincidence refractometry ranged from 3 to 19 diopters in these 1 to 9 yr old animals, with no definite age-accommodation relationship. A-scan ultrasonographic biometry showed that during accommodation the lens thickened very little, if at all, but moved anteriorly, while the apparent cornea to retina distance increased slightly. The raccoon thus exhibits the greatest accommodative capability of any non-primate terrestrial mammal so far studied.

Accommodation, Ocular↗

PubMed1977

Characterization of functionally distinct lymphoid and myeloid cells from human blood and bone marrow. I. Separation by a buoyant density gradient technique.

A buoyant density gradient procedure for mammalian cell separation is described. Gradients of Ficoll and Hypaque in balanced salt solution were used in a zonal rotor to separate distinct leukocyte populations from human peripheral blood and bone marrow. This method possesses the advantages of uniform osmolarity, density determination by refractometry, ease of preparation of gradient solutions, large sample capacity, and low viscosity with consequent ease of sterilization. Granulocyte-monocyte colony-forming units (CFU-C) from blood and bone marrow banded as a homogeneous peak with a density of 1.056 g cm-3 on steep gradients. Recovery of CFU-C was 36% with a 7- to 9-fold enrichment on shallow gradients. Both fractionated and unfractionated peripheral blood cells were stimulated by phytohemagglutinin (PHA), Concanavalin A (Con A), and allogeneic lymphocytes. In contrast, cells from unfractionated bone marrow and cells from the light density fraction of marrow were inhibited by Con A and responded variably to PHA.

Blood Cells↗

PubMed1982

Chromatic dispersion of the ocular media.

Measurements of chromatic dispersion of aqueous and vitreous humors, cornea and lens of the eye are sparse and incomplete. The wavelength variation in refractive index of the ocular media of cow, pig, frog (Rana pipiens), chicken, rock bass (Ambloplites rupestris), albino rat and cat as well as human lenses was determined by means of Abbe and Pulfrich refractometry. While the humors are somewhat less dispersive than water, the cornea is more dispersive at short wavelengths. In general, the lens is significantly more dispersive than water with dispersion increasing asymptotically at the blue end of the spectrum. The exaggerated dispersion taking place at short wavelengths should be taken into account in calculations of chromatic aberration.

Adolescent↗

PubMed1983

Longitudinal chromatic aberration of the vertebrate eye.

A recent study involving Abbe and Pulfrich refractometry analyses the dispersion of the human lens and the ocular media of a number of vertebrates. In general, the lens and, to a lesser extent, the cornea, are more dispersive than expected at wavelengths below 500 nm. The dispersion findings of this study were used in conjunction with reduced eye parameters of a number of vertebrates to calculate the longitudinal chromatic aberration of rock bass, frog, chicken, rat, cat, pig, cow, and human eyes. The calculated chromatic aberration of the human eye is greater than values reported earlier, because of the exaggerated dispersion of the lens at short wavelengths. While the values calculated for the additional species studies may be larger in some instances than expected, presumably due to lens dispersion as well, chromatic aberration is not large enough to account for the hyperopia found by retinoscopic study of small eyes.

Animals↗

PubMed1985

A schematic eye for the mouse, and comparisons with the rat.

The thicknesses and spheric and aspheric curvatures of the optic components were measured from cross-sections of frozen eyes of C57B1/6J mice. The equivalent refractive index of the crystalline lens was obtained from its back-vertex power in albumin. Refractive indices of the cornea, aqueous and vitreous humors were obtained by refractometry or interferometry at four wavelengths across the visible spectrum. The measurements parallel earlier ones on the hooded rat. The eyes of the mouse and rat differ mainly in size, by a linear scale factor of 1.9-2.0, and only slightly in refractive index. Thus refraction, chromatic aberration, and retinal illumination are easily compared in the two species. An analysis of the contribution of each optical surface to refraction may facilitate extrapolation to other strains of mice. Chromatic aberration is discussed with respect to depth of field and the retinoscopy artefact.

Animals↗