Normal Tail Research Articles

Defect and/or truncated normal tail approximation A supplement to a paper of X. Chen and N.C. Lind: “Fast probability integration by three-parameter normal tail approximation” [1

Defect and/or truncated normal tail approximation A supplement to a paper of X. Chen and N.C. Lind: “Fast probability integration by three-parameter normal tail approximation” [1

Discussion to: X. Chen and N.C. Lind, “fast probability integration by three-parameter normal tail approximation”, structural safety, 1 (4) (1983) 269–276

Discussion to: X. Chen and N.C. Lind, “fast probability integration by three-parameter normal tail approximation”, structural safety, 1 (4) (1983) 269–276

Morphology of the X-irradiated testes ofDermestes frischiiKugelann (Coleoptera: Dermestidae). II. Spermatids and sperm

During the development of a sterile male control method for Dermestes frischii Kugelann males were exposed to an X-ray dose of 3.0 krad. The treated testis follicles were investigated using light and electron microscopy. Abnormalities in spermatids and sperm were observed only in cells treated as primary or secondary spermatocytes. Malformed nuclei, nebenkern and acrosomes were detected. Cells frequently failed to start or complete the first or second meiotic divisions. However, spermiogenesis was not inhibited and this resulted in the formation of pseudospermatids of which three types were identified. Only one of these has been previously described. Pseudospermatids were associated with two, three or four sets of quite normal tail organelles. The presence of multiple organelles is discussed in relation to similar findings in other insects.

Puberty in beef bulls: acrosome morphology and semen quality in bulls of different breeds.

Semen characteristics were evaluated every 2 wk from 7 through 13 mo of age in 31 beef bulls representing six breed groups (Hereford, Angus, Hereford x Angus crossbreeds, Angus x Hereford crossbreds, Red Poll and Brown Swiss). Breeds differed in age at puberty, defined as the age at which an ejaculate was first obtained that contained a minimum of 50 x 10(6) total spermatozoa with at least 10% progressive motility (Hereford, 326 +/- 9 d; Angus, 295 +/- 4 d; Hereford x Angus, 300 +/- 8 d; Angus x Hereford, 296 +/- 9 d; Red Poll, 283 +/- 9 d and Brown Swiss, 264 +/- 9 d). Significant breed differences also were observed in concentration of spermatozoa, progressive motility, seminal protein concentration, abnormal spermatozoa and acrosomal morphology. Considerable variation was observed for the majority of pubertal traits among the 31 bulls, indicating that differences in stage of pubertal development existed among and within breeds of beef bulls between 7 and 13 mo of age. However, adjustment of data to age at puberty negated breed differences (P greater than .10), indicating that the pubertal patterns of change occurring in each semen characteristic were similar for the breeds evaluated. Concentration of spermatozoa, progressive motility, seminal protein concentration, percentage spermatozoa with normal head and tail morphology and percentage spermatozoa with normal acrosomal morphology increased (P less than .01) from puberty through 16 wk after puberty in all bulls and all breds. During the first 6 wk after puberty, rapid increases (P less than .01) were observed in percentage spermatozoa exhibiting normal head morphology (excluding acrosomes) and progressive motility, and a rapid decrease (P less than .01) was observed in percentage spermatozoa with proximal cytoplasmic droplets, with values at +6 wk approaching those reported for mature bulls. Percentage spermatozoa with normal acrosomal morphology and concentration of spermatozoa improved more slowly and had not reached mature levels by 16 wk after puberty. Because age at puberty varied by 62 d among breeds and 88 d among bulls and important characteristics of semen quality improved slowly after puberty, careful evaluation of the stage of pubertal development in individual bulls is recommended before selecting young bulls for natural breeding or artificial insemination. Additional investigations are needed to define the patterns of pubertal development through sexual maturity in beef bulls and to establish relationships to fertility.

Approximating the Normal Tail

It is very useful to have simple approximations to the cumulative normal distribution. About every statistician carries a pocket calculator, but how many of us carry a book of tables everywhere we go? When working 'with a desk-top microcomputer it would be inefficient to have to stop to look up tables frequently. One could store a look-up table, but this would use up a lot of storage and the accuracy of interpolation in the table may not be good. The approximation does not have to be all that simple for the micro or programmable calculator but clearly it should be very simple for manual operation of a calculator, and simplicity would also help you to remember the formula. All of the formulae used in this paper were calculated very easily on a Casio 502-P programmable pocket calculator.

Boundaries of two-tone rate suppression of cochlear-nerve activity.

Two-tone rate suppression was examined in the responses of single cochlear-nerve fibers in Mongolian gerbils. The iso-rate tracking algorithm developed by Kiang and Moxon (Kiang, N.Y.-S. and Moxon, E.C. (1974): J. Acoust Soc. Am. 55, 620-630) for obtaining tuning curves was modified to track iso-rate suppression boundaries as a function of frequency with the excitor tone fixed at the characteristic frequency (CF) of the fiber. Lower threshold boundaries of the areas of suppression flanking the tuning curve above and below CF were outlined for fibers over a large CF range. It was found that the boundaries of rate suppression obtained below CF were very stable in their absolute positions on the intensity-frequency plane. This stability was evident both as a function of fiber CF (0.6-15 kHz) and as a function of the shape of the tuning curve at a given CF. In other words, the suppression boundary obtained below CF was largely independent of the tuning curve. In a second series of experiments tuning curves were taken in the presence of a fixed tone placed in the suppression area located above the fiber CF. The fixed tone by itself was not excitatory. These tuning curves were compared to tuning curves obtained with a single tone. It was found that frequencies around the fiber CF were most affected (suppressed) by the presence of the second tone, and that the low-frequency tail of the tuning curve tended to shift toward the boundary of the suppression area below CF. Because this suppression boundary lies below the threshold of the normal tail of the tuning curve for many mid- and high-CF fibers, these fibers often became hypersensitive at low frequencies in the presence of the second tone above CF.

Abnormalities of sperm morphology in cases of persistent infertility after vasectomy reversal

Persistent infertility after vasectomy reversal by vasovasostomy may be due to irreversible changes in epididymal physiology, producing morphologic abnormalities of the sperm tail. Specimens from 29 men with persistent infertility following vasectomy reversal were analyzed and sperm motility and morphology were evaluated. the percentage of motile sperm was below normal in 23 specimens. Swimming speed evaluation on 20 specimens showed only 4 were below the normal range. In 19 of the 29 specimens, 10% or more of the sperm cells examined were characterized by a normal head and a coiled or shortened tail. Within this group, the percentage of sperm with tail abnormalities ranged from 2-64%, with a mean of 18.1%. The appearance of sperm tail abnormalities in conjunction with normal or high sperm concentrations suggests a disturbance of epididymal physiology. The epididymal environment is required for the final maturation of spermatazoa and the acquisition of normal motility and fertilizing ability. The study results suggest that these epididymal functions may be impaired in some men after vasectomy. A case report of a 32 year old man who had a vasectomy 7 years prior to referral to the evaluation group, and a successful vasovasostomy 2 years prior, revealed only 20% of the sperm evaluated in the initial specimen had the normal head and tail shape. His semen volume was 3.5 ml with a sperm concentration of 250 million/ml. 25% of the sperm were motile. Reexamination of the semen 8 times during the next year showed no significant changes. The cervical mucus penetration test showed no abnormalities of the sperm-cervical mucus interaction. When the motile sperm were spearated from the immotile cells and incubated with zona-free hamster eggs, all of the eggs were penetrated. Attempts were unsuccessful to isolate sufficient numbers of motile cells for artificial insemination, however, a normal pregnancy was conceived 1 year after the initial evaluation without additional therapy. One other man from the group also produced a pregnancy. It is suggested that the morphologic abnormalities may not confer sterility on the affected individual even when present in the majority of sperm cells, as indicated by the ability of sperm with normal tails to fuse with zona-free hamster eggs in vitro.

Neural tube development in mutant(curly tail)and normal mouse embryos: the timing of posterior neuropore closurein vivoandin vitro

A dye-injection technique has been used to determine the developmental stage at which posterior neuropore (PNP) closure occurs in normal and mutant curly tail mouse embryos. In vivo, the majority of non-mutant embryos undergo PNP closure between 30 and 34 somites whereas approximately 50% of all mutant embryos show delayed closure, and around 20% maintain an open PNP even at advanced stages of development. A similar result has been found for embryos developing in vitro from the headfold stage. Later in development, 50--60% of mutant embryos in vivo develop tail flexion defects, and 15--20% lumbosacral myeloschisis. This supports the view that delayed PNP closure is the main developmental lesion leading to the appearance of caudal neural tube defects in curly tail mice. The neural tube is closed in the region of tail flexion defects, but it is locally over-expanded and abnormal in position. The significance of these observations is discussed in relation to possible mechanisms of development of lumbosacral and caudal neural tube defects. This paper constitutes the first demonstration of the development of a genetically induced malformation in vitro.

Identification of carcinogens by measurement of cell-mediated immunity: II. Assay specificity

Studies utilizing the Fischer F334 inbred rat model were undertaken to define the specificity for antitumor cell-mediated immune (CMI) measurements as determined by lymphoid-cell cytotoxicity to determine whether such values could serve as an analytical reflection for the carcinogenic potential of environmental pollutants. The investigations revealed that specificity was apparently limited to a carcinogenic insult and designated by the embryonic origin of the affected tissue. For example, it was found that animals having X-ray-induced small-bowel, 1,2-dimethylhydrazine-induced colon, and 7,12-dimethylbenz[ a]anthrazene-induced pancreas adenocarcinomas possessed lymphoid cells cytotoxic to tumor target cells of either the small bowel or pancreas, but were not lytic to tumor tissue of ectoderma or mesodermal origin. Nor was injury inflicted upon normal intestinal, kidney, or tail fibroblastic cells, while significant lysis was seen when normal fetal cells were used as targets. The findings also suggest that the presence of the carcinogen in the assay has little influence upon the CMI values. Thus, the present investigation continues to support the concept that immunological responsiveness may serve as a useful measure for specifically identifying and quantitating effects of environmental carcinogens.

Erratum for “Principle of Normal Tail Approximation”

Erratum for “Principle of Normal Tail Approximation”

Interactions between cycloheximide and T‐locus alleles during mouse embryogenesis

Female CD-1 mice were mated with CD-1 X T/ + F1 males that were heterozygous for the brachyury (T') semidominant lethal gene or were +/+. Fetuses from CD-1 X +/+ matings were normal when observed on gestation Day 17 (plug day = Day 0). Those from the CD-1 X T/+ cross exhibited the expected 1:1 ratio of short:normal tail lengths, but 10% of these fetuses were tailless, apparently due to factors in the CD-1 genotype that increased the expressivity of the T-gene with regard to reduction of tail length. Additional CD-1 females were mated with CD-1 X tw18/+ F1 males. Fetuses from the CD-1 X tw18/+ matings were normal. CD-1 females carrying CD-1 X +/+, CD-1 X T/+, or CD-1 X tw18/+ litters were injected ip on gestation Day 9 with 30 mg/kg cycloheximide or were untreated. Cycloheximide was teratogenic for litters from all three crosses. Polydactyly, oligodactyly, and a variety of skeletal abnormalities were observed. Gross malformations and total skeletal malformations were increased in treated CD-1 X T/ + or tw18/+ litters in comparison with CD-1 X +/+ litters, as were nonvertebral skeletal defects in CD-1 X tw18/+ litters. Prenatal mortality was also greater in treated mutant-containing litters than in +/+ litters, and fetal weights were similarly decreased in treated CD-1 X tw18/+ litters. The incidence of taillessness was also higher in treated (26%) than in control (10%) CD-1 X T/+ litters. Thus both the T and tw18 alleles appear to have enhanced the teratogenicity of cycloheximide, and the inhibitor may have increased the expressivity of T.

Ultrastructures of Bacteriophages Active Against Streptococcus thermophilus, Lactobacillus bulgaricus, Lactobacillus lactis and Lactobacillus helveticus

Several strains of phages active against Streptococcus thermophilus and species of Lactobacillus were examined with an electron microscope after negative staining with phospho-tungstic acid or uranyl acetate. S. thermophilus bacteriophage exhibited exceptionally long tails (polytails). The width and structure of the polytail was the same as a normal phage tail, 10 nm, but was 2 to 4 times longer, 480–960 nm. Preparations revealed extensive adsorption of S. thermophilus bacteriophage to broken bacterial cell walls. One strain of S. thermophilus phage had a spherical structure at the posterior end of its tail. The bacteriophages of Lactobacillus bulgaricus and Lactobacillus helveticus had a distinct contractile tail sheath, whereas Lactobacillus lactis phage did not.

Fast probability integration by three-parameter normal tail approximation

A new method of fast probability integration is presented, based on a three-parameter normal tail approximation to a non-normal distribution function. Values of the distribution function, the probability density function and its derivative are matched at the approximation point with the approximating function. The approximation point is the known “design point”, used within the framework of second moment reliability theory. The proposed method is as fast as the available two-parameter algorithm, but is apparently more accurate.

Principle of Normal Tail Approximation

A difficult problem in general multivariable structural reliability problems of limit state type is to calculate the probability content of the failure set. Very often, however, practical problems have such nice properties that the failure probability may be assessed in a sample way and with sufficient accuracy solely by use of hyperplane approximations to the failure surface as represented in a space in which the basic random variables appear as transformed into mutually independent standardized normal random variables. The approximation points are those origin projection points which are local minimum points for the distance from the origin to the failure surface points. It is proven that these critical points may be determined by iterative use of the principle of normal tail approximation. For hyperplane failure surfaces in the original space of basic variables this method preserves the advantage of second moment reliability calculus. The method is illustrated on an example of its own value. It concerns the determination of the predictive distribution of a material strength quantity, say, given no direct observations. Data are solely indirect such as they result typically in non-destructive testing.

La régression de l'intestin caudal chez l'embryon de poulet. Stade de détermination des dégénérescences cellulaires et rôle du mésenchyme associé

In chick embryo the complete degeneration of the tail gut is carried out between H and H stages 20 to 24 and cell alterations are noticeable from stage 19. This paper reports a study to ascertain whether degeneration of the tail gut cells is already determined. The tail guts of donor embryos were taken at stages 17 to 20 and implanted into the leg bud of 4 to 5-day host embryos. In another series, stage 19 tail guts were implanted with their associated mesenchyme. The fate of the implants was histologically studied in the hosts at different times during their subsequent development. The younger grafts formed tubular structures almost identical to the normal tail gut. Implanted stage 19 tail guts with practically no mesenchyme did not degenerate; they maintained their structure but did not differentiate further. The tail guts implanted with associated mesenchyme degenerated, and stage 20 tail guts also regressed. The death of the tail gut cells was not determined until the degeneration processes had actually begun, the fate of the tail gut cells depending on their environment.

Morphogenetic control during tail regeneration in Plethodon cinereus: The role of skeletal muscle

The caudal myofibers of Plethodon cinereus do not appear to participate directly in epimorphic tail regeneration following either autotomy or surgical amputation of the tail. The possibility that tail musculature might indirectly influence morphogenesis of the regenerate was tested by unilaterally removing 99% of the lateral muscle mass for five to six caudal segments. Ten days after muscle ablation, tails were amputated through the deficient area. Unlike previous experiences with ambystomid larvae, P. cinereus regulates completely producing a normal tail regenerate and at a rate comparable to that following simple amputation.

Pancreatic cystadenoma of the spleen

A cystadenoma of the pancreas within the spleen from pancreatic heterotopia is described. The tumor was located in the hilum of the spleen and completely separated from the normal pancreatic tail. This fact strongly supports the possibility that this tumor arose from pancreatic heterotopia.

Intersex, a temperature-sensitive mutant of the nematode Caenorhabditis elegans

A temperature-sensitive mutation, isx-1(hc17), is reported in the nematode Caenorhabditis elegans which alters the sexual phenotypes of both genotypic sexes. At the restrictive temperature, XX animals are functionally female rather than hermaphroditic due to the absence of spermatogenesis, and XO animals develop as intersexes. These intersexes have normal male head and tail structures and exhibit some mating behavior, but possess hermaphrodite-like gonads which produce no sperm and usually contain a few oocytes. An abortive vulva is usually present and evidence is presented which suggests that the formation of the vulva by the hypodermis is induced by the underlying gonad. The direct effects of the mutation are confined to the descendants of four primordial gonad cells. Gametogenesis and gonad sheath development do not seem to be tightly coupled and are shown to differ in their responses to X-chromosome dosage. The interaction of the intersex mutation with mutant alleles of two transformer genes tra-1 and tra-2 is discussed and a model for the action of these genes in gonad development and sex determination is proposed.

The oxiditative enzyme pattern in the regenerating tail of the scincid lizard,Mabuya striata

Summary The histochemical distribution of iso-citrate dehydrogenase, succinate dehydrogenase, cytochrome oxidase and reduced di-and tri-phosphopyridine nucleotide diaphorases in various tissues of the normal and regenerating tail of the scincid lizard, Mabuya striata was studied. Differences in localization and intensity of enzyme activity were observed in epidermal cells and skeletal muscles of the normal tail; and wound epithelial cells, sub-apical cells, blastema cells and differentiating myofibres of the regenerating tail. The significance of these enzymes in correlation with the regenerative processes in this reptile is discussed.

Selective incorporation of selenium-75 into a polypeptide of the rat sperm tail (1).

Selenium is necessary for normal sperm tail development in the rat. The biochemical locus of this requirement was investigated by intratesticular administration of (75Se)SeO3-2. Sperm were labeled primarily in tail keratin, a disulfide-stabilized fraction obtained by extracting isolated tails with sodium dodecyl sulfate (SDS). By incubation in 1% SDS-0.2 mM dithiothreitol, followed by sonication and centrifugation, the 75Se was separated from a residue rich in S and Zn, composed of dense fibers and connecting pieces. The extracted 75Se-labeled material was non-dialyzable, sensitive to pronase, retained most of its bound isotope following carboxymethylation, and displayed only one radioactive component, of 17,000 daltons, during SDS-polyacrylamide gel electrophoresis. It is suggested that the labeled moiety is a selenopolypeptide whose function is critical for normal assembly of the sperm tail.