Fine structure of the sperm head in some mammals,with particular reference to the acrosome and the subacrosomal substance

Summary An electron microscopical study was made of spermatozoa from the epididymal tail of horses, cattle, pigs, sheep, dogs, cats, rabbits, guinea-pigs, and hares. The fine structure of the sperm head, especially the acrosome and the subacrosomal substance, was analyzed.The very thin sperm heads of bulls, rams, boars, rabbits, hares, and guinea-pigs were generally slightly paddle-shaped as the anterior and anterio-lateral margins were flexed to one side and the intermediate part of the nucleus showed a plane-convex or curved cross section. The nucleus often showed a waist under the posterior part of the acrosome, in sagittal sections. The base of the head was generally asymmetrical on a horizontal plane because the implantation fossa was irregular and often displaced sideways. The cap-shaped acrosome was bounded by a typical unit membrane with about the same thickness as the plasma membrane. An acrosomal thickening along the curved edge of the nucleus was present in the thin sperm heads but was not distinct in the thicker sperm heads of dogs, stallions and cats. It was most pronounced on the convex (ventral) side of the bent nuclear margin and often contained areas with increased or decreased opacity. In an often roughly semilunar area of the posterior acrosome region, corresponding to the equatorial segment of light microscopy, the acrosome was distinctly thinner and sligthly denser. This arrangement was also found in those species-horses, cats, and very pronounced in guinea-pigs — where no equatorial segment is visible in the light microscope. The subacrosomal space was widened along the edge of the nucleus, especially apically, and generally also along the anterior border of the equatorial segment. An opaque, amorphous subacrosomal substance filled these marginal and equatorial spaces in most species. In hares large blisters in the subacrosomal space were present along the anterior border of the equatorial segment on both sides of the sperm head. A similar but less conspicuous phenomenon was often seen in rabbit spermatozoa, but not in other species. The postnuclear cap of light microscopy is probably formed by two components: the basal plate in the implantation fossa and a dense subsurface lamina in the thin layer of cytoplasm covering the remaining nuclear surface behind the acrosome.The possible relations of the subacrosomal substance to the perforatorium of rat spermatozoa and to sub- and periacrosomal structures in some evertebrate spermatozoa was discussed, as well as the role such structures may play in fertilization.Financial support for this study was received from the State Medical Research Council.     

A girl with an interstitial deletion of the short arm of chromosome 3 studied with a high-resolution banding technique

Summary A girl with delayed growth in body height and weight, retarded psychomotor development, facial dysmorphism, high-arched palate, extension defects of elbows, and a probable hearing impairment is presented. A chromosome investigation by both conventional and high-resolution banding techniques revealed an apparently pure interstitial deletion of the proximal segment of the short arm of chromosome 3 (46, XX, del(3) (p11p14.2) de novo). The paternal karyotype is 47,XYY. The clinical features of the patient are compared with those of two previously reported cases in the literature with an interstitial 3p deletion.     

The photostability of different chlorophyll forms in dark grown leaves of wheat

Formulae were developed for calculation of the relative amount of different pigment forms of dark grown leaves of wheat, present before and after photoreduction of the protochlorophyllide. Three pigment forms were calculated from in vivo absorption spectra: the photoreducible protochlorophyllide with absorption maximum at 650 nm and the two chlorophyll(ide) forms with absorption maximum at 684 nm and 673 nm, respectively. The formulae were used to study the changes of the pigment forms at repeated photoreduction of the protochlorophyllide, and at a repeated treatment involving photoreduction of the protochlorophyllide followed by partial photo-decomposition of the chlorophyllide formed. Five consecutive photoreductions and reaccumulations of protochlorophyllide were carried out by high intensity irradiations of one second (red light, 700 W m^-2) given at intervals of 3 h. The results show that the pool size of reaccumulated protochlorophyllide decreased sharply with the number of photoreductions performed. The absorption spectrum of the chlorophyllide formed at each photoreduction proceeded through the Shibata shift (transformation of the 684-form to the 673-form) and the late red-shift (transformation of the 673-form to other pigment form(s) in the dark). High intensity irradiation for ten minutes (red light, 700 W m^-2) immediately after each phototransformation caused a photodecomposition of about three quarters of the newly formed chlorophyllide (which was in the 684-form) while the earlier formed chlorophyll(ide) (in the 673-form) appeared not to be decomposed. This partial photodecomposition of the chlorophyllide had no effect on further accumulation of protochlorophyllide in the dark, and the absorption spectrum of the remaining chlorophyllide proceeded through the Shibata shift. The partial photodecomposition caused an inhibition of the late red-shift, and the accumulated chlorophyll(ide) remained in the 673-form.     

Structural studies of the O-specific side-chains of the shigella sonnei phase I lipopolysaccharide

The structure of the O-specific side-chains of the Shigella sonnei phase I lipopolysaccharide has been investigated. The side chains are composed of disaccharide repeating-units containing two uncommon sugar components, one of witch, 2-amino-2-deoxy-L-altruronic acid, has been identified previously. The other has now been identified as 2-acetamido-4-amino-2,4,6-trideoxy-D-galactose. The uronic acid, as N-acetylated α-pyranosyl residues, is linked through O-4, and the diamino sugar, as β-pyranosyl residues, is linked through O-3. The pyranosyluronic acid residue assumes the ⁴C₁ conformation in the polymer, with the carboxyl group in the axial position.     

Structural studies of the Vibrio cholerae o-antigen

The dominant part of the O-antigen of Vibrio cholerae is a homopolysaccharide composed of (1→2)-linked 4-amino-4,6-dideoxy-α-d-mannopyranosyl (perosaminyl) residues, the amino groups of which are acylated by 3-deoxy-l-glycero-tetronic acid. Most of the amino sugar is decomposed during acid hydrolysis. Treatment of the polymer with anhydrous hydrogen fluoride, which cleaves the glycosidic linkages but does not cause N-deacylation, followed by acid hydrolysis under mild conditions, produced the monomer in good yield. Treatment of the N-deacylated polysaccharide with nitrous acid caused deamination with concomitant rearrangements, typical of 4-amino-4-deoxyhexopyranosyl residues in which the amino group occupies an equatorial position.     

Further characterization of the antithrombin-binding sequence in heparin

An octasaccharide with high affinity for antithrombin, isolated after partial deaminative cleavage of heparin and previously found to have the following predominant structure

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, has been studied further. High-voltage, paper electrophoresis of the ³H-labelled disaccharides obtained by deamination with HNO₂ (pH 1.5) followed by reduction with Na[³H]BH₄ showed 25% of mono-O-sulfated components, in addition to l-iduronic acid(2-O-SO₃)-2,5-anhydro-d-[³H]mannitol(6-O-SO₃). The monosulfated disaccharides were identified by high-pressure, ion-exchange chromatography as l-iduronic acid(2-O-SO₃)-2,5-anhydro-d-[³H]mannitol, l-iduronic acid-2,5-anhydro-d-[³H]mannitol(6-O-SO₃), and d-glucuronic acid-2,5-anhydro-d-[³H]-mannitol(6-O-SO₃). These components originated from the reducing, terminal disaccharide residue (units 7 and 8), as indicated by selective labelling with Na[³H]BH₄. The structural variability within this region suggests that it is not part of the antithrombin-binding sequence. Neither enzymic removal of the non-sulfated l-iduronic acid unit 1 nor N-deacetylation (by hydrazinolysis) at unit 2 had any significant effect on the affinity of the octasaccharide for antithrombin. However, removal of the disaccharide corresponding to units 1 and 2, by selective deamination of the N-deacetylated octasaccharide, yielded a low-affinity hexasaccharide. In addition, a high-affinity deamination product was formed, presumably an octasaccharide containing a 6-sulfated 2-deoxy-2-C-formyl-d-pentofuranosyl unit due to ring contraction in unit 2. These results suggest that the 6-sulfate group in unit 2 may be involved in antithrombin binding. It is concluded that the antithrombin-binding site in heparin is represented by the pentasaccharide sequence extending from unit 2 to unit 6 of the octasaccharide studied.     

The Growth-Inhibitory Block of TGF-β Is Located Close to the G1/S Border in the Cell Cycle

Transforming growth factor-β (TGF-β) inhibits DNA synthesis in dense cultures of young human embryonic fibroblasts and antagonizes the mitogenic action of platelet-derived growth factor (PDGF). The inhibition of the PDGF-BB action by TGF-β was independent of the induction of mRNAs for the PDGF-A chain and PDGF-β receptor, the predominant types of PDGF receptor in human fibroblasts. The TGF-β-mediated inhibition did not influence the expression of various genes that are involved in the transition from the arrested (G0) state to the S phase of the cell cycle. Indeed, TGF-β upregulated the "early" genes c-myc, c-fos, and jun B and downregulated the growth arrest-specific (gas) genes. These results suggest that the inhibition of DNA synthesis by TGF-β in human fibroblasts is independent of modulation of expression of early and gas genes, placing the TGF-β block comparatively late in the G0 to S transition. In cultures of senescent human fibroblasts TGF-β stimulated DNA synthesis but, nevertheless, had the same effect as in young cells on the expression of PDGF chains and receptor genes, as well as on early and gas genes, with the exception of a significantly lower induction of c-fos.     

Levels of selenium in plasma and glutathione peroxidase in erythrocytes and the risk of breast cancer

Plasma selenium and glutathione peroxidase in erythrocytes were analyzed in a case-control study encompassing 441 cases with breast cancer and 191 controls with benign breast disease. No difference in mean serum selenium level between cases and controls on supplementary selenium intake was seen. If only individuals without supplementary intake, 278 cases and 135 controls, were considered a preventive effect was found increasing with selenium level. This finding was significant among women 50 years old or more with Mantel-Haenszel odds ratio=0.16 for individuals with serum selenium >1.21 μmol/L. Also for subjects with serum selenium in the range 1.00–1.21 μmol/L a significant preventive effect was seen with odds ratio=0.38. For women under 50 years of age a nonsignificant preventive effect was seen. Glutathione peroxidase in erythrocytes did not correlate well with serum selenium and was not a marker for the risk of breast cancer.