Gas Chromatographic Method for Putrescine and Cadaverine in Canned Tuna and Mahimahi and Fluorometric Method for Histamine (Minor Modification of AOAC Official Method 977.13): Collaborative Study

A collaborative study was conducted to test a modification to the AOAC fluorometric method for histamine (AOAC® Official Method 977.13) that substitutes 75% methanol as the extracting solvent. All other steps remain unchanged. The extracts prepared with 75% methanol were also used to collaboratively test a gas chromatographic (GC) method for determination of putrescine and cadaverine in seafood. In the GC method, the extracted diamines are converted to fluorinated derivatives, the reaction mixtures are passed through solid-phase extraction columns, and the derivatives are quantitated by electron capture GC after separation on an OV-225 column. Fourteen laboratories using the GC method for putrescine and cadaverine and 16 laboratories using the fluorometric method for histamine analyzed 14 canned tuna and raw mahimahi (including blind duplicates and a spike) containing 0.2-2.6 ppm putrescine, 0.6-9.1 ppm cadaverine, and 0.6-154 ppm histamine. At the 5 ppm level, recoveries ranged from 71 to 102% for putrescine and 77 to 112% for cadaverine; the respective repeatability relative standard deviations (RSDr) were 5.2 and 15%, and the respective reproducibility relative standard deviations (RSDR) were 8.8 and 18%. At the 50 ppm level, histamine recoveries ranged from 84 to 125%, RSDr was 3.6%, and RSDR was 9.4%. The GC method for determination of putrescine in canned tuna and cadaverine in canned tuna and mahimahi has been adopted first action by AOAC INTERNATIONAL, and the AOAC Official Method 977.13, Histamine in Seafood, Fluorometric Method, has been modified

Some remarks about liquid metals

This paper proposes that the liquid state in metals consists of clusters, or globs, of ordered material separated by very thin layers of defects. The nature of the defects surrounding each glob and separating it from neighboring globs is the main feature of the theory. The volume of each defect and the energy to produce it is found to be only a fraction of that required to produce an ordinary vacancy in a solid. A close correlation is shown to exist between this theory and Eyring's theory of significant structures.(1-7) The heats of fusion and the volume changes on melting can be computed, as can be the coordination numbers in the liquid state.

A family with multiple instances of definite, probable and possible early-onset Alzheimer's disease

A family with a multigenerational history of proven or suspected early-onset Alzheimer's disease (AD) consistent with autosomal-dominant inheritance is described. To date, the pedigree comprises five generations in which there are 13 known affected individuals. The mean age of onset of cognitive deficits in those for whom data are available (n = 11) is 47.6 (s.d. 3.0) years and the mean age of death (n = 10) is 58.8 (s.d. 4.0) years. The variability in the extent and quality of available data illustrates the diagnostic difficulties encountered in ascertaining such an extended pedigree, and the need for caution in interpreting the evidence.

Memory as assessed by recognition and reading time in normal and memory-impaired people with Alzheimer's disease and other neurological disorders

Three experiments are reported that examine the dissociations in performance on two tests of retention, speeded reading and recognition in young people, home-dwelling and institutionalized elderly people, and people with severe memory disorders. In Experiment 1, subjects read sentences in normal and in geometrically transformed script at initial presentation, 1-2 hr later, and again 4-14 days later. On the latter two occasions, they were required to distinguish old sentences that they had read previously from new ones. In general, the young and elderly subjects could distinguish old from new sentences at the short delay, and all but the institutionalized elderly people could do so at the long delay. Retention as measured by reading speed typically paralleled recognition performance in that those items that were recognized best were read most quickly. The dissociation between these two tests of retention is seen only in people with memory disorders. Although these people could not distinguish old from new items even at short delays (most could not even remember having seen any sentences), their retention as assessed by reading time was similar to that of the other groups. Old sentences were read most quickly, indicating retention of item-specific information, and reading time of new sentences improved, indicating the acquisition and retention of a general skill. Experiment 2 examined what type of item-specific information was retained. Young, elderly, and memory-disordered subjects studied weakly associated word pairs and sentences. A few minutes later they were tested on both recognition and speeded reading of old, new, and recombined pairs and sentences, the last being those in which words from a studied pair or sentence were recombined with words from other such pairs or sentences. The results of both retention tests indicated that young and elderly people could distinguish old from new and recombined items. People with memory disorders, however, again failed on recognition but performed normally on speeded reading. Like the other two groups, they read old items faster than either recombined or new items. In Experiment 3, similar results were obtained even when the word pairs were constructed using randomly associated items. The results of all three experiments suggest that on implicit tests of memory, such as speeded reading, people with memory disorders can be shown to have formed and retained new associations despite failing utterly on explicit tests, such as recognition, that require conscious recollection of a previous episode.(ABSTRACT TRUNCATED AT 400 WORDS)

Memory as assessed by recognition and reading time in normal and memory-impaired people with Alzheimer's disease and other neurological disorders

Three experiments are reported that examine the dissociations in performance on two tests of retention, speeded reading and recognition in young people, home-dwelling and institutionalized elderly people, and people with severe memory disorders. In Experiment 1, subjects read sentences in normal and in geometrically transformed script at initial presentation, 1-2 hr later, and again 4-14 days later. On the latter two occasions, they were required to distinguish old sentences that they had read previously from new ones. In general, the young and elderly subjects could distinguish old from new sentences at the short delay, and all but the institutionalized elderly people could do so at the long delay. Retention as measured by reading speed typically paralleled recognition performance in that those items that were recognized best were read most quickly. The dissociation between these two tests of retention is seen only in people with memory disorders. Although these people could not distinguish old from new items even at short delays (most could not even remember having seen any sentences), their retention as assessed by reading time was similar to that of the other groups. Old sentences were read most quickly, indicating retention of item-specific information, and reading time of new sentences improved, indicating the acquisition and retention of a general skill. Experiment 2 examined what type of item-specific information was retained. Young, elderly, and memory-disordered subjects studied weakly associated word pairs and sentences. A few minutes later they were tested on both recognition and speeded reading of old, new, and recombined pairs and sentences, the last being those in which words from a studied pair or sentence were recombined with words from other such pairs or sentences. The results of both retention tests indicated that young and elderly people could distinguish old from new and recombined items. People with memory disorders, however, again failed on recognition but performed normally on speeded reading. Like the other two groups, they read old items faster than either recombined or new items. In Experiment 3, similar results were obtained even when the word pairs were constructed using randomly associated items. The results of all three experiments suggest that on implicit tests of memory, such as speeded reading, people with memory disorders can be shown to have formed and retained new associations despite failing utterly on explicit tests, such as recognition, that require conscious recollection of a previous episode.(ABSTRACT TRUNCATED AT 400 WORDS)

CT of the inferomedial orbit and the lacrimal drainage apparatus: normal and pathologic anatomy

The normal and pathologic CT anatomy of the lacrimal drainage apparatus was examined during study of the orbits, nasal cavity, and paranasal sinuses in 100 patients with a variety of clinical complaints related to the inferomedial orbit. The bony lacrimal fossa, the nasolacrimal canal, and the fluid- or air-filled lacrimal sac and nasolacrimal duct were readily recognized in all cases. The lacrimal fossa and sac are found at the inferomedial orbit and are preseptal structures. Cystic expansion of the lacrimal sac (dacryocystitis) may mimic orbital abscess clinically; however, the radiographic recognition of a cystic, peripherally enhancing mass centered at the lacrimal fossa should exclude postseptal abscess and permit more conservative therapy. Obstruction or invasion of the drainage apparatus by tumor, infection, or posttraumatic scarring is readily depicted by CT. Sagittal/coronal images reformatted from thin transverse axial sections are often useful in defining the origin of an inferomedial orbital mass and its relation to the lacrimal sac when clinical studies and axial CT findings are equivocal.