ALBERT

Notes: The dielectric function of liquid benzene at −4 °C, 21 °C, and 65 °C has been calculated from molecular dynamics simulations. The simulated dielectric loss curves reproduce the experimental temperature and density trends. In order to investigate the detailed influence of temperature and density changes as well as the underlying molecular mechanism we have taken advantage of different partitioning and projection schemes for the total dipole moment time correlation function (TCF). The study of the n-body partitioning showed that the temperature dependence of the two- and three-body contributions at t=0 can be explained solely by density change arguments. The molecular projection scheme showed that the dielectric loss is governed by out-of-plane libration at all temperatures. In-plane libration was found to contribute significantly only below 2 THz. Below 1 THz, diffusion, manifested as the negative cross correlation between the out-of-plane and the in-plane TCF's, plays a role very different from that of the directly observed diffusion in dipolar liquids. It has further been established that it is highly problematic to carry out an analysis of the dielectric loss function in terms of the molecular axis rotational TCF's which is a common procedure for the absorption spectrum. This problem was, however, solved by employing a molecular projection scheme. © 2001 American Institute of Physics.

Notes: We report on an experimental investigation of the temperature dependence of the intermolecular dynamics in liquid benzene and toluene. With the use of THz time domain spectroscopy we measured the complex dielectric function (0.2–3.3 THz) of the liquids, at temperatures between −6 °C and 75 °C. By analyzing the dielectric loss (as opposed to the absorption coefficient) we found three contributions to the dielectric function for toluene and two for benzene. In the dipolar liquid toluene we observed a contribution from rotational diffusion at lower frequencies in addition to the two high-frequency librations also observed in benzene. The temperature and density dependence were different for the two librational bands, probably due to the different effect of three-body interactions for the two processes. Furthermore, we present measurements of the low-frequency depolarized Raman spectra as a function of temperature for benzene and toluene. These have been compared with the dielectric loss at similar temperatures. Moreover, for benzene a similar comparison is made between the dielectric loss and the reduced Raman susceptibility obtained by optical Kerr effect spectroscopy. Libration of the symmetric top axis is found in all spectra. © 2000 American Institute of Physics.

Notes: We report measurements of the real and imaginary part of the dielectric constant of liquid water in the far-infrared region from 0.1 to 2.0 THz in a temperature range from 271.1 to 366.7 K. The data have been obtained with the use of THz time domain reflection spectroscopy, utilizing ultrashort electromagnetic pulses generated from a photoconductive antenna driven by femtosecond laser pulses. A Debye model with an additional relaxation time is used to fit the frequency dependence of the complex dielectric constants. We obtain a fast (fs) and a Debye (ps) relaxation time for the macroscopic polarization. The corresponding time correlation functions have been calculated with molecular dynamics simulations and are compared with experimental relaxation times. The temperature dependence of the Debye relaxation time is analyzed using three models: Transition state theory, a Debye–Stoke–Einstein relation between the viscosity and the Debye time, and a model stating that its temperature dependence can be extrapolated from a singularity of liquid water at 228 K. We find an excellent agreement between experiment and the two latter models. The simulations, however, present results with too large statistical error for establishing a relation for the temperature dependence. © 1997 American Institute of Physics.

Notes: Summary 1. The study of certain structures, like the acrosome and Nebenkern, in the developing sperms of Arvelius is facilitated by the fact that they are present in greatly enlarged dimensions in certain testicular lobes while retaining normal size in adjoining lobes. 2. The dictyosomes or Golgi bodies in the spermatocytes are stained red by the PAS treatment. They are assembled to form the similarly stained acroblast in the spermatid, and the acrosome that is finally evolved is also PAS-positive in its color reaction. All the evidence indicates that in the process of acrosome formation there is a direct utilization of dictyosomal material which is already present two cell generations earlier. 3. The substance responsible for the red staining of the dictyosomes and acrosome is a polysaccharide with a 1,2 glycol grouping. There is also direct evidence for the presence of small quantities of proteins which probably form a complex with the polysaccharides. This complex is similar or perhaps identical with a mucopolysaccharide. 4. The Nebenkern, which is a mitochondrial derivative, does not contain polysaccharides with a 1,2 glycol grouping. On the other hand, it contains considerable amounts of proteins which, in contrast to those of the acrosome, are easily digested by pepsin. The evidence does not support the suggestion, frequently made, that the acrosome and Nebenkern are closely interrelated. 5. The enzymatic nature of the acrosome and its possible role in fertilization and sterility are discussed.

Notes: Summary Interferometric dry mass and microspectrophotometric DNA and arginine determinations were carried out on 4000 sperm nuclei from 85 bulls. The results obtained are as follows: 1. Spermatozoa containing a constant haploid amount of DNA (3.04 × 10−9 mg.) also have a constant arginine content of 2.07 × 10−9 mg. with a DNA/arginine ratio of 1.47. 2. Spermatozoa containing variable and low amounts of DNA also have variable and usually higher amounts of arginine with a ratio of 0.95 for DNA/arginine. 3. However the dry mass of sperm nuclei with an abnormal DNA content is nearly the same as the dry mass of sperm nuclei with the normal haploid DNA content. The dry mass for each group is 7.3 × 10−9 mg. and 7.1 × 10−9 mg. respectively. 4. On the basis of the DNA, arginine and dry mass data, a protein content of 4.06 × 10−9 mg. containing 50% arginine can be computed for normal bull sperm nuclei.

Notes: Abstract  The T-cell receptor (TCR) is a highly variable molecule composed of two polypeptide chains that recognize antigenic peptides in the context of major histocompatibility complex (MHC) molecules. In this study, we describe a sequence-based search for germline polymorphisms in the variable (V) gene segments of the human TCRA/D locus. Thirty different V gene segments were amplified from six to eight unrelated individuals and sequenced from low melting point agarose. Twenty-seven polymorphisms were identified in 15 V gene segments. These polymorphisms are mainly single nucleotide substitutions, but an insertion/deletion polymorphism and a single dinucleotide repeat with variable length were also seen. Of the 15 sequence variations found in the coding regions, six are silent and nine encode amino acid changes. All of the amino acid changes are found at non-conserved residues, frequently in the hypervariable regions, where they may influence MHC and/or peptide recognition. Therefore, it is possible that germline variations in TCR genes could influence an individual’s immune response, and may also contribute to susceptibility to diseases such as autoimmunity.

Notes: Abstract Pycnotic degeneration of neoplastic and normal nuclei of mice has been studied cytologically and cytochemically, in pieces of tissues removed some time after subcutaneous transplantation. The cytological changes in pycnosis were found to be about as they have often been described earlier: the nuclei become spherical, shrink progressively, the nucleoli become lost, the chromatin becomes homogeneous. The relative changes in total desoxyribose nucleic acid were followed by the Feulgen reaction; the methylgreen stain was used as an index of nuclei acid polymerization; the Millon reaction was used for the detection of the protein changes. In order to measure the amounts of the Feulgen and methylgreen dye, respectively the color developed by the Millon reaction within individual nuclei, the photometric microscopic method after Pollister and Ris was used, which allows the estimation of relative amounts of colored precipitates within individual nuclei of fixed and stained sections. Using these methods the nucleoprotein composition of resting nuclei of a viable tumortissue was compared with that of three pycnotic stages (Stage I, II, III) in nuclei of necrotic areas of the same tumor tissue (Sarcoma 180). In Sarcoma 180 the change from a fresh tumor cell to Pycnosis I involves loss of nearly half the protein, no significant decrease in desoxyribose nucleic acid, and depolymerisation of over half of the desoxyribose nucleic acid. Later these processes continue, and there is added progressive loss of DNA. It is pointed out that at any pycnotic stage there is a total protein equivalent to about 20 times the highly polymerised (methylgreen positive) DNA, which is the ratio found in non-pycnotic nuclei of the type from which these were derived. It is suggested that this part of the pycnotic chromatin represents the unaltered nucleoprotein. In transplanted liver nuclei pycnosis is much more rapid than in neoplastic tissue, but otherwise the two processes are similar both cytologically and chemically. The discussion points out that: a) there is no real increase in chromatin stainability in pycnotic nuclei; b) the change of shape in pycnosis may be due to lower nuclear viscosity accompanying the DNA depolymerisation; c) the highly polymerised state of the DNA may depend upon the presence of some particular protein, possibly histone; and d) that pyenosis can be interpreted as showing high proteolytic activity in the nucleus and a delayed nuclease activity.

Notes: Summary Microspectrophotometric studies were made on the amounts of DNA in individual spermatozoa of 21 human males with proven fertility and on 18 human males who are partners in sterile couples. The results were as follows: 1. The amount of DNA per spermatozoon of the 21 fertile males is very constant and uniform within each individual and among the 21 different individuals. The mean amount of DNA in arbitrary units is 1.22±0.005 per sperm and is approximately one-half that of human somatic cells which is 2.66±0.05. 2. In contrast to the uniformity of DNA in the sperms of fertile males, the sperms from the 18 males under examination for “suspected sterility” showed greatly varying amounts of DNA. 3. 6 of this suspected group had DNA values close to, but not exceeding that of the fertile males. But for 4 of these 6 males this normal DNA amount conformed to the clinical diagnosis that not the males, but their female partners were responsible for the infertility. The remaining 2 males had sperms with impaired motility, a manifestation which may involve a different factor than that of deviations in the amount of DNA. 4. 5 males represented a category of borderline cases in which the mean DNA was slightly lower than that of the normal group, but many individual measurements overlapped those of normal sperms. So far as the clinical diagnosis was concerned, 4 of these 5 males were on the borderline for male fertility while 1 male had been diagnosed as infertile because he had sperms with impaired motility. 5. 7 of the suspected group carried sperms with DNA in decidedly lower amounts than those of normal, fertile sperms. In 5 of these 7 males the clinical diagnosis ascribed the infertility to the males. In the remaining 2 cases where the DNA was also found to be low in the spermatozoa, no cause could be given clinically for the sterility either in the male or in the female partner. 6. These data suggest a correlation between a deficiency of DNA in the sperms and one type of male sterility, but this cannot be considered as established until further data (such as more information on the female partner) become available.

Notes: Summary 1. Sperm nuclei within activated eggs of the clam, Spisula solidissima were found to contain a normal haploid amount of DNA while sperm nuclei in inactivated eggs of the same clam contain significantly lower amounts of DNA. 2. The DNA content of sperm nuclei within activated eggs increases to approximately the diploid amount during pronuclei formation whereas the DNA content of sperm nuclei in inactivated eggs does not show any increase. 3. The amount of DNA in spermatozoa in the testis of Spisula varies from one clam to another. Some clams have predominantly the normal haploid amount of DNA while others show significantly lower amounts of DNA in the spermatozoa in the testis. 4. The possible significance of the DNA content of spermatozoa for the activation process of the Spisula egg is discussed.