Quantitative differences in sperm cells and organelles of tobacco (Nicotiana tabacum L.) grown under differing environmental conditions

In flowers grown at warm temperatures in environmental chambers and at cooler temperatures in the greenhouse, eight parameters of the sperm-cell organization of Nicotiana tabacum were examined during sperm cell maturation using serial ultrathin sectioning, transmission electron microscopy and quantitative cytology. Despite employing the same seed source, and similar soil and nutrient conditions, the surface area and volume of the cell, the nucleus and the chondriome were larger in flowers grown in growth chambers under warmer controlled conditions, whereas the number of plastids appeared to be the same, or slightly higher, in flowers grown under cooler greenhouse conditions. These results suggest that environmental conditions may influence the quantity of cytoplasmic organelles, including mitochondria and plastids, thus potentially influencing the likelihood of male cytoplasmic inheritance.

Three-dimensional ultrastructure of generative cell mitosis in the pollen tube of Nicotiana tabacum

Generative cell mitosis was examined in stylar-grown pollen tubes of Nicotiana tabacum using serial sectioning, transmission electron microscopy and computer-assisted reconstruction. Before mitosis, the generative cell has a cage-like organization of cytoplasmic microtubules. The mitotic spindle forms when the cytoplasmic microtubules reduce in frequency and kinetochore microtubules form in an area delimited by sheets of endoplasmic reticulum; no preprophase band of microtubules is observed. At metaphase, 21 pairs of kinetochores are distributed unevenly along the length and depth of the cell without the formation of a strictly planar metaphase plate. The metaphase spindle is highly oblique, with diffuse subpoles distributed along the sides of the cell, colocalized with endoplasmic reticulum lamellae. From these dispersed subpoles the kinetochore bundles emanate, closely associated with tubular endoplasmic reticulum. Anaphase consists of three principal processes: convergence of diffused mitotic poles, shortening of the kinetochore bundles, and the elongation of the spindle by an average of nearly 50%. At mid-anaphase, a phragmoplast begins to form, mainly by the assembly of new microtubules at the equatorial area, which form as a cluster of numerous short microtubules. Cytokinesis is essentially conventional, with centrifugal cell plate formation. Cytoplasmic microtubules are restored in the newly formed "brother" sperm cells in a distribution similar to that in the generative cell but fewer in number.

Two types of neonatal-to-adult fast myosin heavy chain transitions in rat hindlimb muscle fibers

Adult fast myosin heavy chain (MHC) isoforms are accumulated in fibers of rat hindlimb skeletal muscle which initially contain neonatal MHC at birth. The specific factors controlling these transitions are not known, but in rat and mouse muscle tissue the transition between the neonatal and adult fast MHC proteins does not appear to require continuous innervation. We have reinvestigated the role of innervation in the neonatal-to-adult fast MHC protein and mRNA transitions that occur in developing rat fast-twitch muscles using immunohistochemistry and S1 nuclease mapping. We find that neonatal MHC-containing developing fibers exhibit different responses after denervation at birth regarding the disappearance of neonatal MHC and the accumulation of adult fast MHC isoforms. Immunohistochemistry shows that one fiber population loses neonatal MHC and accumulates adult fast IIB (or possibly IIX) MHC over a period of 2-3 weeks, whereas in the other population neonatal MHC does not decrease nor does the adult fast IIA isoform accumulate to high levels. The results of S1 analysis of mRNAs show that the levels of neonatal MHC mRNA do not decrease in muscles denervated at birth. We also demonstrate that in young adult rats this mRNA is reexpressed in denervated or paralyzed muscles. Since the appearance of IIB mRNA has been previously shown to be nerve-independent (S.D. Russell, N. Cambon, B. Nadal-Ginard, and R.G. Whalen, 1988, J. Biol. Chem. 263, 6370-6374), these results suggest that fibers containing neonatal MHC in rat hindlimb muscles at birth are already differentiated (i.e., preprogrammed) to accumulate either the adult fast IIA or IIB MHC isoforms and that the neonatal-to-adult MHC transitions occurring in these two fiber populations are controlled by different mechanisms.

Cytoskeletal organisation and modification during pollen tube arrival, gamete delivery and fertilisation in Plumbago zeylanica

The cytoskeletal organisation of the isolated embryo sac and egg cells of Plumbago zeylanica was examined before, during and after pollen tube penetration into the embryo sac to determine the potential involvement of microtubules and actin filaments in fertilisation. Material was singly and triply stained using Hoechst 33258 to localise DNA, fluorescein isothiocyanate (FITC)-labelled anti-alpha-tubulin to detect microtubules and rhodamine-phalloidin to visualise F-actin. Microtubules in the unfertilised egg cell are longitudinally aligned in the micropylar and mid-lateral areas, aggregating into bundles near the filiform apparatus. In the perinuclear cytoplasm of the egg cell, microtubules become more or less randomly aligned. F-actin bundles form a longitudinally aligned mesh in the chalazal cytoplasm of the egg cell. In the central cell, microtubules and F-actin are distributed along transvacuolar strands and are also evident in the perinuclear region and at the periphery of the cell. During pollen tube penetration, sparse microtubule bundles near the pathway of the pollen tube may form an apparent microtubular 'conduit' surrounding the male gametes at the delivery site. Actin aggregates become organised near the pathway of the pollen tube and at the delivery site of the sperm cells. Subsequently, actin aggregates form a 'corona' structure in the intercellular region between the egg and central cell where gametic fusion occurs. The corona may have a role in maintaining the close proximity of the egg and central cell and helping the two sperm cells move and bind to their target cells. The cytoskeleton may also be involved in causing the two nuclei of the egg and central cell to approach one another at the site of gametic fusion and transporting the two sperm nuclei into alignment with their respective female nucleus. The cytoskeleton is reorganised during early embryogenesis.

Pseudo-von Willebrand disease: a mutation in the platelet glycoprotein Ib alpha gene associated with a hyperactive surface receptor

Pseudo (platelet-type)-von Willebrand disease is an autosomal dominant bleeding disorder caused by the hyperfunction of a receptor on the platelet surface. The abnormal receptor, glycoprotein Ib, displays increased affinity for its ligand, von Willebrand factor. Four members (normal mother/affected father/two affected daughters) of a family with pseudo-von Willebrand disease were studied to determine the molecular genetic basis for their congenital platelet defect. Segments of the platelet glycoprotein Ib alpha gene were amplified by means of the polymerase chain reaction, cloned, and sequenced. A point mutation (A to G, codon 239) was found in segments from the affected individuals but not from the normal. The mutation results in a single amino acid substitution (valine-mutant for methionine-normal) at residue 239 within the Ib alpha binding site for von Willebrand factor. Both the mutant and the normal sequence were found in affected individuals, suggesting a heterozygous state. Amplified DNA from family members and from 58 normal individuals was analyzed by allele-specific oligonucleotide hybridization. Only the normal sequence was found in the mother and the normal individuals, whereas both the normal and the mutant alleles were found in the affected family members. The described mutation is associated with the pseudo-von Willebrand disease phenotype seen in this kindred. The resultant single amino acid substitution in glycoprotein Ib alpha relates to increased receptor function and to excessive binding of von Willebrand factor to the platelet surface.

A possible regulatory role for conserved promoter motifs in an adult-specific muscle myosin gene from mouse

The mouse gene encoding a myosin heavy chain (MHC) protein expressed in type IIB fibers of adult skeletal muscle has been cloned and its promoter isolated. A number of DNA sequence motifs are found within the first 2.5 kilobases of the promoter which are similar to motifs present in the promoters of other muscle-specific genes. One sequence located at approximately -940 base pairs corresponds to the motif called MEF1 which has been shown in other muscle genes to bind the myogenic regulatory factors of which MyoD is one example. The MEF1 site of this adult IIB MHC promoter does indeed bind MyoD although this factor is normally thought to be involved in early muscle cell differentiation. The IIB MHC promoter also has several motifs located in the first 200 base pairs which are strikingly conserved between this mouse gene and several chicken skeletal MHC genes. Of these evolutionarily conserved sequences, two motifs rich in A and T residues appear to be major contributors to the muscle-specific transcriptional activity of the mouse IIB MHC promoter when transfected into quail myogenic and non-myogenic cells. These observations suggest an important functional role for these AT-rich sequence motifs in the regulation of genes of the MHC family.

Photoresponse of ion-damaged germanium

Ion implantation was used to create predetermined defect densities to examine photoresponse for optoelectronic switch applications. Ion-damaged germanium shows a significant decrease in photoresponsivity with implant dose, particularly with doses exceeding the critical amorphizing dose (D(c) approximately 1 x 10(14) cm(-2)).

Patterns of embryo-sac organization, synergid degeneration and cotyledon orientation in Linum usitatissimum L

The embryo sac of Linum usitatissimum consists, as in most angiosperms, of the egg, two synergids, central cell and antipodals. In Linum the embryo sac is strongly polarized in the longitudinal axis, but rotationally random relative to the vascular bundles of the ovule and ovary. Synergids designated right or left based on their orientation relative to the egg can be distinguished unambiguously if viewed from one pole of the embryo sac - in this case, the chalaza was used as the reference point. The synergid most likely to degenerate is the left (60%), proximal (52.3%) or septal-facing (52.7%) synergid. The volume and the surface area of the filiform apparatus of the left synergid is significantly smaller than that of the right synergid. Synergid-degeneration patterns varied between individual plants, indicating genetic control; however, the preference for the proximal and septal-facing synergid, although weak, indicates the possibility of some physiological influence. The cotyledons appear to assume bilateral symmetry with respect to the ovule only once endosperm digestion has begun. As the cotyledons grow, the embryo rotates to occupy the widest part of the embryo sac, thus imposing bilateral symmetry between the embryo and seed; prior to that time, the early and heart-shaped embryos are randomly oriented.

A method for improved resolution for fluorescence microscopy using plastic-embedded material subjected to resin extraction

A protocol is given that uses NaOH, benzene, acetone and methanol to extract epoxy resins from semithin sections. Such sections appear superior to paraffin or unsectioned materials for fluorescence microscopic observations. Use of ultrarapid films (e.g., Kodak T-Max P3200) at ISO 3200 minimizes fading without use of antifading agents and without introducing unacceptable photographic grain size.

Isolation of Fixed and Viable Eggs, Central Cells, and Embryo Sacs from Ovules of Plumbago zeylanica

Three alternative protocols for light microscopy, electron microscopy, and biochemical characterization of isolated megagametophytic tissues are described employing enzymic maceration and microdissection of living and fixed ovular tissue of Plumbago zeylanica. Morphologically well preserved megagametophytes are obtained using fixed ovules in two different regimes (nearly 40 and 60% yield, respectively). Fluorescein diacetate-positive megagametophytic cells are recovered in nearly 20% of unfixed ovules using the third regime.

Two-Dimensional Electrophoretic Studies of the Proteins and Polypeptides in Mature Pollen Grains and the Male Germ Unit of Plumbago zeylanica

Three fractions (male germ unit [MGU]-rich, cytoplasmic-particulate and water-soluble proteins) were isolated from pollen of Plumbago zeylanica L. Proteins were extracted using a phenol procedure and polypeptide patterns were compared on one- and two-dimensional polyacrylamide gels. The MGU-rich fraction contains the sperm and vegetative nucleus of the pollen grain and yielded 427 spots >33 kilodaltons. The cyto-plasmic-particulate fraction contained 515 spots >33 kilodaltons. The third fraction consisted of water-soluble proteins and polypeptides from the pollen cytoplasm, in which 285 spots (>33 kilodaltons) were identified. Of 133 polypeptide spots suitable for comparison, 18 were unique to the MGU-rich fraction, 3 to the cytoplasmic-particulate fraction, 14 to the water-soluble fraction, 65 were common to two different fractions (and absent in one), and 33 were common to all three of the fractions examined.

Thyroid hormone induces a nerve-independent precocious expression of fast myosin heavy chain mRNA in rat hindlimb skeletal muscle

The appearance of the mRNA for the adult fast IIB myosin heavy chain (MHC) was examined during postnatal development of rats using an S1 nuclease assay. In normal rats, a large increase in the adult MHC mRNA began at 6-7 days after birth, whereas daily injections of newborn rats with 3 micrograms of triiodothyronine (T3) resulted in a precocious increase of the mRNA as early as 3 days after birth. Injection of a range of doses of T3 demonstrated that a large effect was obtained between 30 and 300 ng of T3/day/rat. Fast myosin protein was also precociously induced over the same range of T3 doses. This effect was also seen in denervated muscles, and muscles responded similarly to the different doses of T3 whether they were denervated or not. These results suggest that either thyroid hormone or some circulating factors induced by thyroid hormone are limiting factors in controlling the neonatal-to-adult fast MHC transition and that these factors may act directly on muscle tissue.

Linewidth instabilities in narrow-linewidth flashlamppumped dye laser oscillators

Linewidth instabilities in double-longitudinal-mode (250 MHz </= Deltanu </= 375 MHz) multiple-prism flashlamppumped dye lasers are characterized. It is found that the origin of the instabilities is mainly physical with partial contribution from stochastic processes.

Quantitative cytology of the egg and central cell of Plumbago zeylanica and its impact on cytoplasmic inheritance patterns

The egg and central cells of Plumbago zeylanica have an average volume of 543,000 μm(3) and 2,560,000 μm(3) respectively, with surface areas of 38,600 μm(2) and 154,000 μm(2). The egg contains an average of 39,900 mitochondria and 730 plastids. The majority of the plastids are perinuclear (> 60%) with less than 40% in lateral areas or near the filiform apparatus. After fertilization, the number of maternal organelles exceeds paternal organelles by a ratio of 1∶1,000 for mitochondria and 1∶54 for plastids. The central cell contains an average of 178,700 mitochondria and 1,840 plastids. After fertilization, these organelles far exceed the number of sperm organelles transmitted, by a ratio of approx. 1∶4,000 for plastids and 1∶820 for mitochondria. Biparental inheritance of plastids in the embryo is possible, but not favored; the only comparable data in Oenothera and Impatiens reveals that biparental inheritance is possible in up to 1∶24 ratios. Plants lacking biparental plastid inheritance do not contain plastids in the sperm, and thus the presence of even few sperm plastids may result in expression. The number of paternal mitochondria transmitted into the central cell is greater than that transmitted into the egg as the result of preferential fertilization with the mitochondrion-rich dimorphic sperm cell, although the ratio of paternal to maternal mitochondria is 1∶1,000 in the egg and 1∶820 in the central cell. The similarity in these ratios suggests that there is a critical dosage of mitochondria that is permissible within the zygotic and endospermatic lineages. This may represent either: (1) a maximum permissible value to prevent expression of paternal mitochondrial genome, (2) a minimum ratio required in order to permit recombination of maternal and paternal mitochondrial genomes, or (3) a cytoplasmic genome balance number.

Quantitative cytology of the sperm cells of Brassica campestris and B. oleracea

Pollen grains of Brassica campestris L. var. acephala DC and B. oleracea L. were serially sectioned and examined using transmission electron microscopy to determine the three-dimensional organization of sperm cells within the microgametophyte and the quantity of membrane-bound organelles occurring within each cell. Sperm cells occur in pairs within each pollen grain, but are dimorphic, differing in size, morphology and mitochondrial content. The larger of the two sperm cells (Svn) is distinguished by the presence of a blunt evagination, which in B. oleracea wraps around and lies within shallow furrows on the vegetative nucleus and in B. campestris can penetrate through internal enclaves of the vegetative nucleus. This sperm cell contains more mitochondria in both species than the second sperm cell (Sua). This latter cell is linked to the first by a common cell junction with the S vn, but is not associated with the vegetative nucleus and lacks a cellular evagination. Such differences are indicative of a system of cytoplasmic heterospermy in which sperm cells possess significantly different quantities of mitochondria.

Isolation of Sperm Cells from the Pollen of Plumbago zeylanica

Intact sperm cells of Plumbago zeylanica were released from mature pollen grains near anthesis using osmotic shock with 20% sucrose. Sperm cell yields of up to 75% can be attained by differential centrifugation using a clinical centrifuge with concentrations of up to 8.8 x 10(6) cells/milliliter. Such ;gametoplasts' remain intact for up to 24 hours according to Evan's blue exclusion and can be used for characterization or physiological manipulation.

Ultrastructure of the sperm of Plumbago zeylanica : II. Quantitative cytology and three-dimensional organization

Pollen grains of Plumbago zeylanica L. were serially sectioned and examined using transmission electron microscopy to determine the three-dimensional organization of sperm cells within the microgametophyte and the quantity of membrane-bound organelles occurring within each cell. Sperm cells occur in pairs within each pollen grain, but are dimorphic, differing in size, morphology and organelle content. The larger of the two sperm cells (Svn) is distinguished by the presence of a long (approx. 30 μm) projection, which wraps around and lies within embayments of the vegetative nucleus. This cell contains numerous mitochondria, up to two plastids and, infrequently, microbodies. It is characterized by a larger volume and surface area and contains a larger nucleus than the other sperm cell. The second sperm cell (Sua) is linked by plasmodesmata with the Svn, but is unassociated with the vegetative nucleus. It is smaller and lacks a cellular projection. The Sua contains relatively few mitochondria, but numerous (up to 46) plastids and more microbodies than the other sperm. The degree of dimorphism in their content of heritable cytoplasmic organelles must at fertilization result in nearly unidirectional transmission of sperm plastids into just one of the two female reproductive cells, and preferential transmission of sperm mitochondria into the other.

Denervation supersensitivity in skeletal muscle: analysis with a cloned cDNA probe

Motor neurons regulate the acetylcholine sensitivity of the muscles they innervate: denervated muscle fiber become "supersensitive" to acetylcholine, due to insertion of newly synthesized acetylcholine receptors (AChRs) in the plasma membrane. We used hybridization analysis with a cloned cDNA specific for AChR alpha-subunit to compare the abundance of AChR mRNA in innervated and denervated adult mouse muscles. Within 3 d of denervation, levels of AChR mRNA increased 100-fold; levels of actin mRNA changed little. The increase in AChR mRNA level was sufficiently large and rapid to account for denervation supersensitivity.

Curing and commerce: changes in an indigenous medical practice in a highland Philippine town

The intrusion of the capitalist mode of production in Third World countries is usually accompanied by the expansion of cosmopolitan medicine. In most multi-ethnic societies, indigenous medical practices continue to persist, if not thrive, under these conditions for a variety of reasons. Urbanizing areas in particular may become focal points for the emergence of innovative role adaptations among indigenous curers. This paper describes the career development of an indigenous medical specialist in a highland Philippine town. The purpose is to suggest the importance of examining the lifestyle and socio-economic strategies pursued by curers in similar contexts. Such analysis can aid in the process of understanding the way in which particular individuals can perform significant buffer roles that promote the continued viability of medically plural practices and beliefs.

Fertilization in Plumbago zeylanica: entry and discharge of the pollen tube in the embryo sac

The ultrastructural organization of the megagametophyte of Plumbago zeylanica, which lacks synergids, was examined in chemically and physically fixed ovules after entry of the pollen tube. Similar to angiosperms with conventionally organized megagametophytes, the pollen tube enters the ovule through a micropyle, formed by the inner integument, and approaches the female gametophyte by growing between nucellar cells. Unlike other described female gametophytes, however, continued pollen tube growth results in direct penetration of the base of the egg through cell wall projections forming a filiform apparatus and is completed between the egg and central cell without disrupting either of these cells' plasma membranes. A terminal pollen tube aperture forms when the pollen tube reaches an area of strong curvature near the summit of the egg; this results in the release of two sperm cells, the vegetative nucleus, and a limited amount of pollen cytoplasm. The formerly continuous chalazal egg cell wall is locally disrupted near the tip of the pollen tube and apparently is thus modified for reception of male gametes. Discharged pollen cytoplasm rapidly degenerates between the egg and central cell, but unlike pollen tube discharge in conventionally organized megagametophytes, it is unassociated with the degeneraton of any receptor cell within the female gametophyte. Sperm nuclei are transmitted, one to the egg and the other to the central cell, to effect double fertilization by nuclear fusion with their respective female reproductive nuclei. The vegetative nucleus and discharged pollen cytoplasm degenerate between the developing embryo and endosperm during early embryogenesis. The emerging concept that the egg of Plumbago possesses combined egg and synergid functions is supported by the present study and suggests that the megagametophyte of this plant displays a highly specialized egg apparatus composed exclusively of a single, modified egg cell.

Fine structure of megagametophyte development in Zea mays

Polygonum-type embryo sac development was examined in Zea mays with light, fluorescence, and electron microscopy. Megasporocyte polarity is expressed in organelle distribution, aniline blue wall fluorescence, and chalazal location of plasmodesmata. In the meiotic cytoplasm concurrent with the sporophyte–gametophyte transition, ribosome concentrations are low, and membrane-bound organelles are simplified. The functional megaspore is the largest and most chalazal cell of the resultant triad or tetrad. Aniline blue fluorescence is intense in nonfunctional megaspore walls, whereas in the functional megaspore intensity decreases from the chalazal end to that in nucellar walls. Throughout functional megaspore and two-nucleate megagametophyte, ribosome concentrations, organelle numbers, and structural complexity increase. The transition from vegetative to reproductive gametophytic growth presumably follows this biosynthetic period. In the four-nucleate stage, a second phase of mitochondrial simplification coincides with the formation of an extensive lytic vacuole containing evidence of possible organelle and cytoplasmic membrane incorporation. Near the close of intensive lytic activity, compartmentalization of lytic areas contributes to creating a prominent vacuole in the central cell as synergids, egg, and antipodals differentiate.

Relative usefulness of measuring polyamines in serum, plasma, and urine as biochemical markers of cancer

Serial samples of plasma and serum were collected in the morning and afternoon from cancer patients, along with 24-h urine specimens. Values for serum and plasma samples taken at the same time from the same patient differed little, suggesting that either procedure is acceptable for polyamine analysis. Increases in concentrations of putrescine and spermidine in serum and plasma correlate well with such increases in 24-h urine samples. Spermidine concentrations in sera were consistently about 10-fold lower than corresponding urine values. Putrescine concentrations were 10- to 100-fold different. The variation in putrescine values may be due to its more active metabolism by diamine oxidase, an enzyme known to be present in serum. Concentrations of polyamines in serum and urine increased in response to effective chemotherapy.