Unpreserved Samples Research Articles

Cooling Systems for Transport of Unpreserved Milk Samples

Two separate investigations of milk sample coolers are reported. A study conducted by the Milk Marketing Board of England and Wales demonstrated that an insulated box with eight ice (gel) packs (precooled to –20°C for 40h) would, under extreme conditions of high ambient temperature (up to 30°C), maintain 40 30-ml samples at less than 4°C for 48h or more. In practice, samples are delivered within about 30h of collection and ambient temperatures generally are about 20°C, lessening the need for extended deep freezing time for ice packs and making the system very applicable to UK conditions. This convenient and labor-efficient system has been used effectively in England and Wales since 1982.A study completed at the Ontario Central Milk Testing Laboratory evaluated milk sample coolers consisting of high density polyethylene cooling inserts in single- or double-walled insulated coolers. The essential features are rapid cooling (15°C to less than 4°C in 20min and to .5°C in 40min), constant temperature at .5°C for the required duration, and no direct contact between the sample vials and the coolant. Ice water is the coolant for short delivery times (up to 24h). For longer delivery times (up to 4 days), the cooling insert is charged with Styrofoam chips (50% volume) and water before freezing at –15°C. Design features and evaluation studies, including time and temperature profiles, are described.

Apparent post-mortem production of high levels of cyanide in blood

Conflicting evidence can be found in the literature in regard to the levels of cyanide which may be produced in stored blood. Three cases are described where very high blood cyanide levels were found at post-mortem but where circumstances tended to preclude cyanide poisoning and where no source could be discovered. In one case, the cyanide was shown to be of post-mortem origin. These findings suggest that considerable caution should be exercised in attempting to interpret, in isolation, high cyanide levels in unpreserved blood samples.

Evaluation of a Urine Transport Kit on Urine Reagent Strip Testing

A Urine Culture & Sensitivity Transport Kit was evaluated for the effect of the preservative used in this kit on urine reagent strip testing and microscopic analysis. Urine samples from 50 random patients were separated into unpreserved and preserved aliquots and tested for specific gravity, pH, protein, glucose, ketones, bilirubin, occult blood, and urobilinogen using the CLINILAB instrument. Agreement between chemical parameters and microscopic findings on unpreserved versus preserved samples was good (80% to 89%) to excellent (90% to 100%). Least agreement was observed for protein (84%), pH greater than 7, and specific gravity. Significant differences in specific gravity measurements between unpreserved and preserved urine samples, protein/pH disparities, and the cost of these kits suggest that the kits offer little advantage over prompt delivery and refrigeration when attempting routine urinalysis and culture from the same urine specimen.

Comparison of Milk Somatic Cell Counts by Coulter and Fossomatic Counters

Unpreserved milk samples from 28 quarters of 18 cows were used to compare milk somatic cell counts obtained by Fossomatic and Coulter Counter and to determine effect of temperature and sample age on Fossomatic counts. Samples represented high and low cell count milk (16 cows) and colostrum (2 cows). Fifteen milliliters of both foremilk (after milking preparation) and strippings were obtained; one-third was used for Coulter and two-thirds for Fossomatic. Milk for Fossomatic was subdivided once for fresh and 24-h determinations and once again for heating to 40 and 60°C for 15min. Analysis of log10 count included effects for quarter, Fossomatic versus Coulter, and (for Fossomatic) sample age, incubation temperature, and age-temperature interaction. For foremilk, geometric means of Coulter milk somatic cell counts and Fossomatic counts were not different. For Fossomatic, milk samples incubated at 60°C counted higher than those at 40°C (230,096 versus 173,638); 24-h samples counted higher than fresh (201,679 versus 192,380), For strippings, Coulter counted higher than Fossomatic (700,521 versus 570,033). Interaction of time and temperature was significant for Fossomatic. Counts from samples held 24h and heated to 60°C were highest (553,291). Fossomatic counts from fresh samples at 40°C were lowest (447,729). Geometric means of original milk samples from 14 of the quarters obtained by direct microscopic, Fossomatic, and Coulter counts were 199,300, 311,000, and 399,300, respectively.

Clinical Evaluation of a Urine Transport Kit with Lyophilized Preservative for Culture, Urinalysis, and Sediment Microscopy

Comparative results of urine culture, specific gravity, chemical urinalysis, and sediment microscopy were assessed when specimens submitted to the clinical laboratory were divided and processed either in a transport kit containing a lyophilized preservative or in a conventionalsterile cup without preservative. Overall agreement of results of 853 cultures after initial processing of samples in the laboratory was 98.7%. Results of 320 repeat cultures after a 24-hr holding period (preserved samples at room temperature, unpreserved samples refrigerated) and 277 repeat cultures after a 48-hr holding period also showed excellent agreement (99.1% and 95.7%, respectively). Results of urinalysis and sediment microscopy done an 370 specimens demonstrated greater than 98% agreement after receipt of specimens in the laboratory and greater than 94% agreement after the holding periods. Specific gravity determinations from samples processed in the presence of preservative consistently were 0.006-0.007 units greater than in samples processed without preservative, and a reporting adjustment will be necessary when the transport kit is used. I thank Drs. David Gocke and Paul Smilow for reviewing the manuscript, Judy Rothberg for technical assistance, Alissa Bernholz for assistance with data processing and analysis, and Janet Gross for secretarial support. This study was supported in part by a grant from Becton Dickinson Vacutainer Systems, Rutherford, New Jersey.

Determination of Filtrable Orthophosphate in Water from Fish Ponds

Abstract Millipore (R) membrane filters (0.45 μm), Gelman glass fiber filters (Type A-E), and filter papers (Whatman No. 42 and No. 1) were all suitable for preparing pond water samples for orthophosphate determination. The stannous chloride method was just as accurate and precise, but more sensitive, than the ascorbic acid method for orthophosphate. However, the longer stability of the colored sol made the ascorbic acid method more suitable for analyzing pond waters for filtrable orthophosphate. Concentrations of filtrable orthophosphate changed rapidly during storage of unpreserved samples in polyethylene bottles. When a high degree of accuracy is necessary, samples should not be stored for more than 1 hour before analysis.

Notes and Comments: The Stability of Nitrate in Unpreserved Potable Water Samples

The results of this study support T.J. Williams's recently published contention that the need for acid preservation of potable water supplies for nitrate testing, as mandated by the Safe Drinking Water Act, has not been adequately established.

The quantitative separation of meiofauna

1. This paper presents the results of a meeting on the evaluation of quantitative procedures for the separation of meiofauna, held at the Marine Station of the Biologische Anstalt Helgoland, in May 1972. Close co-operation on the part of the participants (p. 194) has allowed assessment of advantages and disadvantages of the separation methods applied. The time needed for preserved methods can be reduced by changing to scanning rather than picking out for sorting and counting. 2. Sorting without concentrations: This method is suitable for very fine-grained sediments, oozes; it is generally applied for preserved samples; adequate for hard fauna; insufficient for soft fauna; very time consuming. 3. Decantation: Suitable for sandy sediments; generally applied for preserved samples; adequate for hard fauna; insufficient for soft fauna; time consuming. 4. Elutriation: Suitable for sandy sediments; for unpreserved samples only with anaesthetization, more effective with preserved samples; limited for total live fauna. With preserved samples, adequate for hard fauna; insufficient for soft fauna; quick method. 5. Warm-water elutriation: Suitable for sandy sediments; designed for live hard fauna (especially nematodes, ostracods); quick method. 6. Sea-water ice treatment: Suitable for sandy sediments with microporal structure; only for live extraction; limited for hard fauna; well suited for soft fauna (including ciliates and flagellates); time consuming.

Loss of mercury from water during storage

Abstract : Rate of loss of mercury from dilute solutions stored in polyethylene containers was studied. Storage conditions and time intervals were similar to those encountered during the normal collection and shipment of water samples to a testing laboratory. Analyses were performed by acid digestion - stannous chloride reduction followed by mercury-vapor atomic absorption measurement. Results indicated losses up to 100 percent in known added concentrations of mercury; losses were observed from both glass-distilled water and from locally-procured creek water samples. Addition of an acid preservative to a water sample after its collection did not appreciably reduce the loss of mercury as compared to an unpreserved sample. Of the acids studied only nitric acid to a final pH of 1 showed any substantial ability to maintain the mercury concentration. (Author Modified Abstract)

EFFICIENCY OF SUCROSE FLOTATION IN RECOVERING INSECT LARVAE FROM BENTHIC STREAM SAMPLES

AbstractDuplicate benthic stream samples were collected from three sites on Sandy Creek (Lake Ontario Watershed) in Western New York, 8 and 22 September, 1970. Samples taken on 8 September were preserved in 10% formalin. Samples taken on 22 September were not preserved. Insect specimens were removed from both sets of samples by flotation with a sucrose solution of 1.12 sp. gr. Preserved and unpreserved samples were compared for efficiency of recovery of insect larvae. Mean recovery for preserved samples was 90.78% compared with 83.03% for unpreserved samples. The range of recovery values for unpreserved samples (66.7%) was more than twice as great as that of preserved samples (29.5%). A paired t-test for means of all taxa showed no significant difference (P < 0.001) between recovery values for preserved and unpreserved samples. In fact, preservation may enhance the recovery of certain groups—Zygoptera, Hemiptera, Trichoptera, and Chironomidae. Apparently samples may be preserved without sacrificing recovery of any specific groups of insect larvae.

The Phytoplankton of Narragansett Bay1

The phytoplankton of Narragansett Bay is described on the basis of 927 unpreserved samples taken at a series of stations from 1952 to 1956. The annual cycle is divided into four natural periods: 1 (winter and spring) with diatoms dominant; 2 (usually late spring, early summer), flagellates dominant; 3 (usually late summer), diatoms dominant; 4 (fall), flagellates dominant. The major features of this cycle, with maxima in the first and third seasons, are largely due to changes in the concentrations of diatoms, principally Skeletonema costatum. Although the concentrations of diatoms and of flagellates in any given season are predictable only within wide limits, their average abundance for the entire annual cycle is relatively constant. Average standing crops in the East and West Passages are approximately the same, but the Upper Bay is more than three times as rich as the lower in both diatoms and flagellates. The highly estuarine upper West Passage is characterized by certain neritic dinoflagellates, while the lower East Passage is marked by oceanic diatoms. Microflagellates and Skeletonema costatum are outstanding in frequency of occurrence and as dominants. Each of the four seasons is distinguished by certain dominant species. Correlations of the dominance of the most important species with prevailing temperatures reveal apparent temperature preferences, some species being eurythermal as dominants while other dominants are restricted to narrow temperature ranges. From the first to the third or fourth period there is a progressive increase in the number of species represented, the rate of change in species composition, and the spatial heterogeneity of the population. The average annual standing crop is more than two times as great as that in adjacent coastal waters. This difference is explained by the unusual length of the winter–spring diatom flowering in the Bay (January–May), which results from the combined effects of shallowness, moderate nontidal drift, and turbulence generated by tidal activity. The secondary diatom maximum in the Bay and in the coastal waters of southern New England is typically a summer event and usually precedes the major annual breakdown of stratification in the fall.

The Egg-White Inhibitor of Influenza Virus Hemagglutination

Summary Ten per cent solutions of egg-white, preserved with 0.25 per cent phenol, 0.02 per cent Merthiolate (Lilly), or 0.05 per cent formalin and stored at 4 C, were titrated periodically for inhibitory activity against hemagglutination by heated, purified swine influenza virus. No significant change in activity could be demonstrated over a period which exceeded 7 months for some of the preparations. Phenol proved more effective than Merthiolate or formalin in prohibiting the growth of micro-organisms and is, accordingly, preferred for preservation of standard solutions. Frozen samples of unpreserved egg-white and samples dried from the frozen state in vacuo gave irregular results. The high stability of the inhibitory activity of preserved solutions was confirmed by the experimental identity of the slopes of inhibition curves for aged and fresh samples of egg-white. The usefulness of slope as a criterion of degradation of the inhibitor is illustrated by results obtained when inhibitor is heated at 100 C or treated with crystalline chymotrypsin. With the aid of a standard solution it was found that the inhibitory activity is highly stable in semipurified preparations of inhibitor. Data are presented to illustrate the accuracy of the inhibition titrations, the variation of activity among individual egg-whites, and the essential absence of dependence of the inhibition titer on the individual source of the chicken red cells used in the tests.