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At least 127 records · Page 7Linked 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↗
PubMed1998

Measurement of urine relative density using refractometer and reagent strips.

The relative density of urine is the ratio of its density to that of water and depends on both the number and weight of solute particles in the sample, while osmolality depends only on the number of solute particles. Water metabolism is regulated by the interaction of the renal medullary countercurrent system with the circulating levels of antidiuretic hormone and thirst. The concentration of solids in urine can be measured by weighing, hydrometry, oscillations of a capillary tube, refractometry and reagent strip. These techniques, interrelated but not identical, are commonly used in hospital laboratories and in clinical wards. We compared the results obtained in 1725 urine samples of inpatients and outpatients using an automated refractometer to those obtained using two visually read dip stick tests. The correlation coefficients (Super Aution analyser vs. Aution Sticks 10EA, Aution Sticks 10 EA vs. N-Multistix, Super Aution analyser vs. N-Multisticks were 0.663, 0.645 and 0.514, respectively) and the great dispersion of mountain plots demonstrates that different techniques are not interchangeable in the measurement of relative density. Since the results obtained after discarding the samples with pH higher than 7 and those containing glucose or protein were very similar to the ones reported above, the role of these interferents appears negligible in inducing the discrepancy.

Humans↗
PubMedDate not supplied

Passive transfer of colostral immunoglobulins in calves.

Passive transfer of colostral immunoglobulins has long been accepted as imperative to optimal calf health. Many factors, including timing of colostrum ingestion, the method and volume of colostrum administration, the immunoglobulin concentration of the colostrum ingested, and the age of the dam have been implicated in affecting the optimization of absorption. The practice of colostrum pooling, the breed and presence of the dam, and the presence of respiratory acidosis in the calf also may affect passive transfer. Various tests have been reported to accurately measure passive transfer status in neonatal calves. The radial immunodiffusion and the enzyme-linked immunosorbent assay (ELISA) are the only tests that directly measure serum IgG concentration. All other available tests including serum total solids by refractometry, sodium sulfite turbidity test, zinc sulfate turbidity test, serum gamma-glutamyl transferase activity, and whole blood glutaraldehyde gelation estimate serum IgG concentration based on concentration of total globulins or other proteins whose passive transfer is statistically associated with that of IgG. This paper presents a comprehensive review of the literature of passive transfer in calves including factors that affect passive transfer status, testing modalities, effects of failure of passive transfer on baseline mortality, consequences of failure of passive transfer, and some treatment options. Many previously accepted truisms regarding passive transfer in calves should be rejected based on the results of recent research.

Acidosis↗
PubMed1999

Comparison of in vitro tests for evaluation of passive transfer of immunoglobulins in giraffe (Giraffa camelopardalis).

Serum samples from captive giraffe (Giraffa camelopardalis) were tested to assess passive transfer of immunoglobulins using in vitro methods developed for domestic ruminants. Estimated immunoglobulin levels were compared using five tests (protein electrophoresis, total protein refractometry, zinc sulfate turbidity, glutaraldehyde coagulation, and sodium sulfite turbidity). A linear relationship was observed among total protein, gamma globulin (electrophoretic measurement), and immunoglobulin level based on spectrophotometric measurement of zinc sulfate turbidity. Nonquantitative assays also demonstrated statistical correlation with the quantitative methods. Using criteria similar to those established for domestic species, cutoff values for failure of passive transfer (FPT) were established for these tests in neonatal giraffe: 1) total protein <6.0 g/dl; 2) gamma globulin < 0.5 g/dl; 3) estimated immunoglobulin level < 1,000 mg/dl (zinc sulfate turbidity); 4) glutaraldehyde coagulation test negative; or 5) no visually detectable turbidity in 16% sodium sulfite or Bova-S negative. Retrospective examination of the medical histories showed a strong statistical association between animals designated as having FPT and those that were removed from their dams based on clinical assessment to be hand-reared. Application of these tests in the field should allow earlier detection and intervention for FPT in neonatal giraffe.

Animals↗
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↗
PubMed1996

Aging effects on accommodation and outflow facility responses to pilocarpine in humans.

OBJECTIVE: To determine the relationships among age, outflow facility, and refractive and facility responses to pilocarpine in humans. METHODS: Refraction, intraocular pressure, and outflow facility were determined in 30 normal volunteers aged 20 to 75 years, by coincidence refractometry, applanation tonometry, and Schiøtz tonography, respectively, before and 1 hour after a 30-microL drop of 2% or 6% pilocarpine. Simple regression of baseline facility, postpilocarpine facility, and facility change, on age and refractive change singly and jointly, was performed. Stepwise regression models and graphic conditioning plots were used to determine, for each facility variable, its relationship to age or refractive change specifically. RESULTS: Baseline outflow facility and maximum pilocarpine-induced refractive change (ie, accommodation) declined with age, but the decrease in intraocular pressure and the facility response to pilocarpine did not. After adjusting for age, for baseline facility, there was no further relationship to 6% pilocarpine-induced accommodation, and a slight residual relationship to 2% pilocarpine-induced accommodation. After adjusting for both 2% or 6% pilocarpine-induced accommodation, the relationship to age was still significant. The facility increase after 2% or 6% pilocarpine did not depend on age and/or accommodative amplitude. CONCLUSIONS: In humans, as previously described in rhesus monkeys, an age-related loss of ciliary muscle mobility may compromise the basal function of the trabecular meshwork. However, unlike monkeys, humans exhibit no loss of the intraocular pressure or outflow facility response to pilocarpine with age.

Accommodation, Ocular↗
PubMed1997

Direct and indirect methods for molar-mass analysis of fragments of the capsular polysaccharide of Haemophilus influenzae type b.

Two methods are described for direct molar-mass measurement of low-molar-mass fragments obtained by oxidative cleavage of the capsular polysaccharide of Haemophilus influenzae type b. Absolute molar masses were determined by size-exclusion chromatography (SEC) with detection by multiangle laser-light-scattering photometry (MALLS) and differential refractometry (RI). The end-group structure of the polysaccharide fragments allowed the direct measurement of average chain length by quantitative 1H NMR, from which molar masses were derived. Variation between the molar masses obtained by the two methods ranged from 5 to 7%. When molar masses estimated by indirect methods were compared to SEC-MALLS/RI data, significant deviations were observed. Analysis by SEC with secondary calibration with dextran standards gave molar masses that exceeded the SEC-MALLS/RI data by as much as 2.5-fold. Molar masses estimated by a combination of colorimetric assays varied from the SEC-MALLS/RI data by as much as 50%. These results demonstrated the applicability and superior accuracy of the direct methods of molar-mass determination of the polysaccharide fragments.

Bacterial Capsules↗
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↗
PubMed2000

Correlation among refractive, keratometric and topographic astigmatism after myopic photorefractive keratectomy.

BACKGROUND: Photorefrative keratectomy can be used to flatten the curvature of the anterior cornea and reduce the myopic refraction of the eye. This leads to unphysiological topographical changes of the cornea and may alter the conditions for examinations of corneal surface topography. The purpose of this study was to check for mutual agreement of three different methods of assessment of astigmatism before and after myopic photorefractive keratectomy (PRK). PATIENTS AND METHODS: Forty-seven eyes of 28 patients (age 32.7+/-6.6 years) following PRK using an 193-nm excimer laser were included in this study. 37 eyes were treated for pure myopia (-4.9+/-2.4 D) and 10 eyes for myopic astigmatism (sphere -2.0 to -7.0 D, cylinder -1.0 to -3.0 D). Preoperatively and at 18 months postoperatively, subjective refractometry, keratometry and topography analysis were performed. The axes of topographic and keratometric cylinder were standardized periodically (180 degrees) with respect to the refractive cylinder axis. RESULTS: Pre- and postoperatively, the absolute astigmatism values correlated highly significantly between all three methods (P< or =0.001). The mean refractive cylinder was 0.65+/-0.61 D preoperatively and 0.46+/-0.41 D postoperatively (P=0.2). The mean keratometric astigmatism was 1.14+/-0.64 D before and 0.94+/-0.50 D after PRK treatment (P=0.2). Among the three methods, the mean topographic astigmatism was the highest (P<0.001) preoperatively (1.31+/-0.56 D) and postoperatively (1.21+/-0.52 D) (P=0.3). In eyes treated for pure myopia, no difference between pre- and postoperative refractive, keratometric and topographic astigmatism was detected (P>0.5). The axes of both topographic and keratometric astigmatism correlated highly significantly with the refractive cylinder axis (R> or =30.9, P<0.0001). CONCLUSION: Up to 2 years after myopic PRK, the difference between refractive and keratometric astigmatism does not differ from the preoperative value, indicating an even corneal surface. The absolute astigmatism values and the cylinder axis correlated well between subjective and objective methods of astigmatism assessment. Thus, objective measurements may be helpful in determining the cylinder component of best spectacle correction after PRK. However, topographic analysis overestimates astigmatism values systematically before and after PRK.

Adult↗
PubMed1998

Sensitivity of the MTI photoscreener for amblyogenic factors in infancy and early childhood.

BACKGROUND: Screening for amblyogenic factors in infancy by pediatricians is unsatisfactory, as they hardly ever detect ametropia or microstrabismus. As photoscreening seems to be a helpful method to detect even small squint angles and refractive errors, we tested the MTI photoscreener for its sensitivity with respect to amblyogenic factors. PATIENTS AND METHODS: One hundred and twelve children aged 6-48 months were first examined with the MTI photoscreener. Then each child underwent complete medical examination by an ophthalmologist and an orthoptist. The examination included the Hirschberg test (corneal reflex evaluation), the Brückner test (fundus red reflex), and, where possible, the Lang stereotest, the cover test and visual acuity assessment, as well as a motility test, biomicroscopy, ophthalmoscopy in mydriasis and refractometry in cycloplegia. Exclusion criteria were any organic pathological results, manifest strabismus, ametropia > or = 2 D and astigmatism > or = 1 D. An orthoptist, a pediatrician and two ophthalmologists independently evaluated the Polaroid pictures according to the criteria given in the handbook of the MTI photoscreener. RESULTS: For 10 children the evaluation with the MTI photoscreener was not possible despite the fact that photographs were retaken several times. Thirteen photographs showing obvious pathologic findings despite their poor quality were included. Eighty-three of the remaining 102 children failed the eye examination according to the above-mentioned criteria. The mean sensitivity of the MTI photoscreener was determined to be 82.8%. The ability to correctly identify the absence of any amblyogenic factors (specificity) was 61.8%. CONCLUSIONS: Sensitivity was high when compared to the usually low detection rate during pediatric examinations. Due to the low specificity, effectiveness was poor. Therefore an ophthalmological examination should be included in the preventive screening during infancy and early childhood.

Amblyopia↗