The Fluorescent Dye 3, 3′ Dihexyloxacarbocyanine Iodide Selectively Stains the Midpiece and Apical Region of the Heads of Murid Rodent Spermatozoa

Fluorescence microscopy of caudal epididymal spermatozoa stained with 3, 3′ dihexyloxacarbocyanine iodide (DiOC₆(3)) showed intense fluorescence along the concave surface of the apical hook of spermatozoa of Rattus species and along the upper concave margin of the sperm head in Mus musculus In the spermatozoa of Hydromys chrysogaster, Melomys cervinipes, and Pseudomys australis, the two ventral processes also fluoresced brightly. In P. australis, fluorescence in the apical hook of sperm heads was largely localized to its upper and lower surfaces. The sperm of N. alexis did not show consistent positive fluorescence. The localization of fluorescence in these spermatozoa after staining with DiOC₆(3) was mainly restricted to regions where a large accumulation of perinuclear theca material lies beneath the plasmalemma. The reason for this remains to be determined, but DiOC₆(3) may be useful for quickly demonstrating areas of abundant perinuclear thecal material in sperm heads of eutherian mammals by light microscopy.     

Distribution of filamentous actin in and around spermatids and in spermatozoa of Australian conilurine rodents.

The distribution of filamentous actin around the maturing sperm head and in spermatozoa of four species of Australian conilurine rodents was investigated at the light and electron microscopic levels. Similar results were obtained for all the species studied. Mechanically isolated spermatids had NBD-phallacidin-positive longitudinal bands of fluorescence over the dorsolateral surface and, in late spermatids, bands of bright fluorescence passed perpendicularly from the dorsal convex to ventral concave surface. TEM observations indicated that these regions corresponded to filaments of ectoplasmic specializations and granular filamentous material around the tubulobulbar complexes, respectively. In testicular and cauda spermatozoa NBD-phallacidin fluorescent material was present in the two ventral processes that extended from the upper concave surface of the sperm head; also fainter material occurred along the concave border and as a dorsocaudal spur. Its distribution was identical for testicular and cauda spermatozoa. TEM of late spermatids showed that in the ventral process closest to the apical hook there were between 170 and 245 filaments, which attached to the inner surface of the postacrosomal dense lamina; in the more caudal ventral process about 70 filaments occurred. No filaments were, however, visible in the mature spermatozoon but, after immunocytochemical labelling for actin, deposition of gold particles was evident over ventral processes of both late spermatids and cauda spermatozoa. Within the female tract these ventral processes made contact with the zona matrix and were taken into the egg cytoplasm unchanged in morphology. The possible functional significance of the filamentous actin in these structures is discussed.     

The spermatozoon of Eurasian murine rodents: Its morphological diversity and evolution

The murine rodents are the most speciose subfamily of mammals. Here the morphology of the spermatozoon, as determined by scanning and transmission electron microscopy of representative species from four Eurasian clades, is described. Much interspecific variability in all components of the spermatozoon was found to occur, although most species have a bilaterally flattened sperm head with a single apical hook of variable length and orientation. Ultrastructural observations indicate that this apical hook invariably contains a nuclear projection as well as a large extension of the subacrosomal cytoskeleton, as a perforatorium rostrally, and a complex asymmetrical acrosomal extension. These spermatozoa also have relatively long tails that are attached to the lower concave surface of the sperm head. Uniquely, in species in the Apodemus clade, the apical hook is orientated caudally. In a few species a highly derived sperm head morphotype that does not contain an apical hook is present. These sperm heads vary in morphology from being globular in two species of Bandicota, to bilaterally flattened and paddle-shaped in Tokudaia and Micromys. In spermatozoa of the latter two genera the subacrosomal cytoskeleton, which is less extensive than in species with a hooked sperm head, forms an apical extension, but that is not the case in Bandicota. In all species where the sperm head lacks an apical hook the acrosome is more symmetrical. The sperm tail is much shorter in these species, with attachment to the head occurring on the ventral surface in Tokudaia and basal in Micromys and the two species of Bandicota. As the sperm head morphotype with a complex apical hook is present in all the major clades of murine rodents, it is likely to be a plesiomorphic character within each of these clades, with the nonhooked sperm heads, which vary greatly in structure between species of the different lineages, probably being independently derived. The ultrastructural organization of the sperm head of Bandicota, but not those of Micromys or Tokudaia, suggest divergence in some of the morphological events associated with sperm-egg interaction at the time of fertilization.     

Spermatozoa of murid rodents from Africa: morphological diversity and evolutionary trends

The diversity of the structural organization of the spermatozoa of African murid rodents is described at the light and transmission electron microscopical level of resolution. In most species the sperm head is falciform in shape but it varies somewhat in overall breadth, width, and length. A typical perforatorium is present and the acrosome splits into a large head cap over the convex surface and a smaller ventral segment similar to the sperm head of most Asian and Australasian murids. In a few species, however, the morphology is very different. In Acomys and Uranomys spermatozoa, the apical hook is more bilaterally flattened, has a large apical acrosomal region, and no separate ventral segment. Two species of Aethomys have, in addition to an apical hook, a 4μ long extension of the cytoskeletal material that projects from the concave surface of the sperm head, whereas in Dasymys two large ventral processes extend from the upper concave region which contain nuclear material basally and a huge extension of cytoskeleton apically. In Aethomys chrysophilus type B, the sperm nucleus is unique in form and often has a central region in which threads of chromatin can be seen; it is capped by a massive acrosome whose apical segment is complex and convoluted in structure. Stochomys longicaudatus appears to have a conical sperm head, and in all three Lophuromys species the sperm head is spatulate in shape with the flat, plate-like nucleus capped by a thin acrosome. The evolutionary trends in changes of sperm head shape and design of these rodents are discussed. It is suggested that some of the differences in morphology may relate to the variation in structural organization of the coats around the egg through which the spermatozoon has to pass in order for fertilization to occur.     

Protein composition of the ventral processes on the sperm head of Australian hydromyine rodents

The sperm head of the plains rat, an Australian hydromyine rodent, is highly complex in structure and contains, in addition to an apical hook, two large ventral processes (VPs) that extend from its upper concave surface and that are largely composed of a huge extension of the sperm head cytoskeleton surrounded by postacrosomal dense lamina. In this study we have attempted to determine their protein composition. For this, the VPs were isolated, the proteins within them separated by SDS-PAGE, and the resultant polypeptide bands Western blotted and probed with antibodies against laboratory rat perforatorial and bull perinuclear theca sperm proteins. Antibodies were also used to determine the perforatorial and perinuclear theca proteins by immunogold labeling of transmission electron microscopic sections. The results indicate that the material within the VPs is largely composed of perforatorial cross-reacting proteins together with F-actin with the dominant protein being PERF 15. The perinuclear theca proteins are, by contrast, restricted to a narrow region adjacent to the acrosomal and nuclear membranes. In conclusion, this study has shown that the VPs of the spermatozoa of Australian rodents are perforatorial-like appendages that contain similar proteins to the perforatorium of the apical hook together with F-actin; their functional significance remains unknown.     

Vital Fluorochromes as Tracers for Fungal Growth Studies

Eight fluorescent dyes were tested for staining the spores or mycelia of six fungi and for their translocation into new growth when the preloaded spores or mycelia were incubated on agar coated coverslips. The dyes studied were Cellufluor, Nile red, fluorescein diacetate (FDA), carboxyfluorescein diacetate (CFDA), chloromethylfluorescein diacetate (CMFDA), aminochloromethyl coumarin (CMAC), and the carbocyanines DiIC₁₈(3) and DiOC₁₈(3). The fungi on which the dyes were tested included Botrytis cinerea, Fusarium oxysporum f.sp. lycopersici, Idriella bolleyi, Pythium oligandrum, Sclerotium cepivorum and Trichoderma. harzianum Most of the fluorochromes gave good initial staining of mycelia or spores; however, FDA fluorescence faded rapidly during excitation, making it impractical for use. Also, the spores and mycelia of B. cinerea and T. harzianum sometimes gave weak fluorescence with Nile red, and the spores and mycelia of I. bolleyi gave unusually weak fluorescence with Cellufluor. There were other variations of staining among the different dye/fungus combinations, but each fungus showed strong fluorescence with at least one dye. Cellufluor, CMFDA, CMAC and, to a lesser extent, CFDA and Nile red, were efficiently translocated into new growth from preloaded spores or mycelia, whereas FDA, DiIC₁₈(3) and DiOC₁₈(3) were not. The extent of translocation ranged from 0.1 to 1.2 mm in germ tubes arising from spores, and from 0.9 to 9.2 mm in mycelia extending from dye-loaded agar blocks. The findings suggest that fluorescent dyes could be used as markers or tracers in studies of fungal growth and differentiation.     

Static Cytofluorometry and Fluorescence Morphology of Mitochondria and DNA in Proliferating Fibroblasts

The shape, distribution, and content of mitochondria in individual cells were examined during the cell cycle phases (G₀/G₁, S, G₂ mitosis) in living human fibroblasts by static cytofluorometry and fluorescence microscopy. The morphocytochemical evaluations were performed in cell cultures submitted to double supravital fluorochrome staining with Hoechst 33342 and DiOC₆ to label DNA and mitochondria, respectively. The staining modalities were based on the stability of mitochondrial labeling. The G₁ to early S phases were characterized by the presence of filamentous mitochondria, except during the early postmitotic period. During late S, G₂, and mitotic phases, mitochondrial mass reached its highest value and mitochondria became short and numerous. During the last stage of mitosis, mitochondria were distributed among daughter cells through a cytoplasmic bridge.     

Single-channel activity in sea urchin sperm revealed by the patch-clamp technique

Ionic fluxes are deeply involved in the response of spermatozoa to the egg. Using the patch-clamp technique, we show for the first time single ion channel activity in sea urchin spermatozoa and spermatozoa heads. Due to their small size gigaseals were obtained in suspended cells by applying suction through the pipette. The rate of gigaseal formation was very low and improved to 6% (n = 1145) when flagella were detached from sperm. Current-voltage curves created from single-channel events showed conductances of approx. 65 and 170 pS, suggesting the presence of two types of channels. At least one appears to be a K⁺ channel.     

Is the hook of muroid rodent's sperm related to sperm train formation?

Competition between spermatozoa of rival males to gain fertilizations has led to a wide array of modifications in sperm structure and function. Sperm cells of most muroid rodents have hook‐shaped extensions in the apical–ventral tip of the head, but the function of this structure is largely unknown. These ‘hooks’ may facilitate aggregation of spermatozoa in so‐called ‘trains’, as an adaptation to sperm competition, because sperm in trains may swim faster than free‐swimming cells. However, there is controversy regarding the role of the hook in train formation, and in relation to whether it is selected by sperm competition. We examined spermatozoa from muroid rodents with varying levels of sperm competition to assess whether (i) sperm aggregates are common in these taxa, (ii) presence of a hook relates to the formation of sperm aggregations, and (iii) formation of sperm aggregations is explained by sperm competition. Our analyses in 25 muroid species revealed that > 92% of spermatozoa swim individually in all species, with the exception of the wood mouse, Apodemus sylvaticus, which has ~50% spermatozoa swimming freely. Species with hooked spermatozoa had higher sperm competition levels and longer sperm than species whose sperm lack a hook. Neither the presence of hook nor sperm competition levels were related to the percentage of sperm in aggregations. Thus, (i) sperm aggregates in muroid rodents are an exceptional trait found only in a few species, (ii) evolution of the sperm hook is associated to sperm competition levels, but (iii) the hook is unlikely to be related to the formation of sperm aggregates. The evolutionary significance of the sperm head hook thus remains elusive, and future studies should examine potential roles of this pervasive structure in sperm's hydrodynamic efficiency and sperm–female tract interactions.     

Properties and function of the respiratory chain of freshwater mussel spermatozoa in relation to motility

1. The spermatozoa of the freshwater mussel (Hyriopsis schlegelii) contain cytochromes aa₃, b and c, flavoproteins and nicotinamide nucleotides in molar ratios of 1.0:0.9:1.8:1.8:8.7. Cytochrome c₁ is not detectable even at liquid-N₂ temperature, but a c₁-like cytochrome with an -band at 550 mμ is found at liquid-N₂ temperature in a cell preparation from which cytochrome c is completely removed.

2. The near-ultraviolet difference spectrum of whole cells reveals an absorption peak at 315 mμ with a shoulder around 350 mμ.

3. Both the endogenous respiration and motility of spermatozoa are completely blocked by 0.2 mM CN⁻ and by 0.2 μM antimycin A. 2,4-Dinitrophenol and pentachlorophenol completely inhibit motility at the maximal stimulation of respiration. Rotenone strongly inhibits NADH oxidase of spermatozoa, although it has no effect on the respiration of whole cells.

4. It is concluded that the motility of mussel spermatozoa is tightly coupled to respiration, and the respiratory chain phosphorylating process is the only energy-supplying system for motility.     

Light-dependent variations in the composition of the internal atmosphere of Phragmites australis (Cav.) Trin. ex steudel

The composition of the lacunal air in Phragmites australis (Cav.) Trin. ex Steudel during a diel cycle and during prolonged exposures to light and dark, respectively, was studied in the laboratory. The experimental system was constructed so that samples of the lacunal air could be withdrawn with syringes at fixed points in the stems and in the rhizomes of an intact shootsystem. The composition of the samples (CO₂, O₂, N₂) was analyzed by gas chromatography.

A steep gradient in O₂ concentration was observed within the lacunae, with highest concentrations in the aerial stems (21%) and lowest concentrations in the deepest-growing rhizomes (3.6%). Inverse gradients of CO₂ and N₂ occurred in the opposite direction. The composition of the lacunal air exhibited a clear diel variation, with highest O₂ and lowest CO₂ and N₂ concentrations during the daytime.

It is concluded that the transport of gases within the lacunae of P. australis is mediated by diffusion following the concentration gradients of the gases, and convective flow of air resulting from solubilization of respiratory CO₂ in the interstitial waters and/or in the transpiration stream. During the daytime, the ventilation is accelerated, probably as a consequence of thermo-osmotic pressurization resulting from temperature differences between the aerial plant tissues and the ambient air.     

Receptors for Sperm-activating Peptides, SAP-I and SAP-IIB, on Spermatozoa of Sea Urchins, Hemicentrotus pulcherrimus and Glyptocidaris crenularis

Sperm-activating peptide analogues, GYGG-SAP-I (Gly-Tyr-Gly-Gly-Gly-Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly) and GYGG-SAP-IIB (Gly-Tyr-Gly-Gly-Lys-Leu-Cys-Pro-Gly-Gly-Asn-Cys-Val) which exibit almost the same respiration-stimulating activity as the respective original peptide were chemically synthesized, radiolabeled with Na¹²⁵1, and used for experiments of binding and cross-linking to Hemicentrotus pulcherrimus or Glyptocidaris crenularis spermatozoa. In competitive binding, SAP-I caused 50% decrease in ¹²⁵l-GYGG-SAP-l binding to intact spermatozoa, sperm heads and sperm tails of H. pulcherrimus at the concentrations of 282 nM, 3 nM and 141 nM, respectively. The incubations of H. pulcherrimus sperm tails with ¹²⁵l-GYGG-SAP-I and the chemical cross-linking reagent, disuccinimidyl suberate, resulted in the appearance of two radiolabeled bands with apparent molecular masses of 71 kDa and 63 kDa (determined by sodium dodecyl sulfate-gel electrophoresis under reducing conditions). ¹²⁵l-GYGG-SAP-IIB bound almost equally to sperm heads and sperm tails of G. crenularis , and was cross-linked to 172 kDa, 62 kDa and 58 kDa proteins in sperm heads, and 157 kDa and 62 kDa proteins in sperm tails with disuccinimidyl suberate.     

Interspecific variation of sperm morphology in the Australian rodent genus Zyzomys

The sperm head morphology and tail length of two species of Australian rock rats, Zyzomys argurus and Zyzomys pedunculatus, are presented. In Z. argurus the sperm head has an apical hook together with two ventral processes extending from the upper concave surface that are largely composed of cytoskeletal material, and the sperm tail is about 135 µm in length. By contrast, in Z. pedunculatus the sperm head is paddle‐shaped with the nucleus capped by an acrosome that has a large apical segment and is surrounded by a thin layer of cytoskeletal material, and the sperm tail is only around 85 µm in length. Since the structure of the spermatozoon of Z. argurus is similar to that of most of the old endemic Australian rodents it is presumed to be the ancestral condition within the Zyzomys genus with that of Z. pedunculatus being highly derived and showing convergence with the sperm structure in some other orders of mammals.     

Evolution of the spermatozoon in muroid rodents

In the rodent superfamily Muroidea, a model for the evolution of sperm form has been proposed in which it is suggested that a hook-shaped sperm head and long tail evolved from a more simple, nonhooked head and short tail in several different subfamilies. To test this model the shape of the sperm head, with particular emphasis on its apical region, and length of sperm tail were matched to a recent phylogeny based on the nucleotide sequence of several protein-coding nuclear genes from 3 families and 10 subfamilies of muroid rodents. Data from the two other myomorph superfamilies, the Dipodoidea and kangaroo rats in the Geomyoidea, were used for an outgroup comparison. In most species in all 10 muroid subfamilies, apart from in the Murinae, the sperm head has a long rostral hook largely composed of acrosomal material, although its length and cross-sectional shape vary across the various subfamilies. Nevertheless, in a few species of various lineages a very different sperm morphology occurs in which an apical hook is lacking. In the outgroups the three species of dipodid rodents have a sperm head that lacks a hook, whereas in the heteromyids an acrosome-containing apical hook is present. It is concluded that, as the hook-shaped sperm head and long sperm tail occur across the muroid subfamilies, as well as in the heteromyid rodents, it is likely to be the ancestral condition within each of the subfamilies with the various forms of nonhooked sperm heads, that are sometimes associated with short tails, being highly derived states. These findings thus argue against a repeated evolution in various muroid lineages of a complex, hook-shaped sperm head and long sperm tail from a more simple, nonhooked sperm head and short tail. An alternative proposal for the evolution of sperm form within the Muroidea is presented in the light of these data.     

Five-coordinate rhenium(III)-thiolato complexes: the structure of [Re(SCH2PhOCH3)3(PPh3)2]

A novel five-coordinate rhenium(III)-thiolato complex, Re(SCH₂C₆H₄OCH₃-p)₃(PPh₃)₂ has been isolated during the reaction of trans-ReOCl₃(PPh₃)₂ with p-methoxybenzyl mercaptan. In the unexpected structure that was acquired, the central metal has undergone a reduction from Re(V) to Re(III). The five-coordinate Re(III) complex has been characterized by spectroscopic methods, elemental analysis and X-ray crystallography. X-ray crystallographic studies showed the coordination geometry around rhenium to be that of a trigonal bipyramid. The basal plane is defined by three sulfur atoms of the monodentate ligand, while the two apical positions are occupied by two phosphines of the precursor.     

Progesterone treatment of boar spermatozoa improves male pronuclear formation after intracytoplasmic sperm injection into porcine oocytes

Boar spermatozoa were prepared for intracytoplasmic sperm injection (ICSI) by two different treatments to facilitate sperm chromatin decondensation and improve fertilisation rates after ICSI in pigs: spermatozoa were either frozen and thawed without cryoprotectants, or treated with progesterone. Morphological changes of the sperm heads after the treatments were examined and then the activation of oocytes and the transformation of the sperm nucleus following ICSI were assessed. After freezing and thawing, the plasma membrane and acrosomal contents over the apical region of sperm head were lost in all the spermatozoa. Following treatment with 1 mg/ml progesterone, the acrosome reaction was induced in 61% of spermatozoa. After injection of three types of spermatozoa, non-treated spermatozoa and progesterone-treated (i.e. acrosome-reacted) spermatozoa induced oocyte activation, but frozen-thawed spermatozoa induced oocyte activation at a significantly lower rate. Sixty-two per cent of sperm heads remained orcein-negative for 6 h, however, resulting in delayed sperm chromatin decondensation and low male pronuclear formation in the oocytes injected with a non-treated spermatazoon. Since the treatments of freezing and thawing and progesterone for spermatozoa accelerated the initial change in sperm chromatin and the latter treatment induced oocyte activation earlier, it is considered that the delay in oocyte activation and decondensation of sperm chromatin after injection of non-treated spermatozoa is caused by the existence of the sperm plasma membrane. These results show that progesterone treatment efficiently induces the acrosome reaction in boar spermatozoa without destroying their potency for oocyte activation, and the induction of the acrosome reaction results in the promotion of male pronuclear formation after ICSI.     

基于MaxEnt模型的黄河三角洲滨海湿地优势植物群落潜在分布模拟

采用千米网格的方法,对黄河三角洲滨海湿地进行土壤采样和植被群落调查,利用MaxEnt模型和GIS空间分析技术,模拟该地区优势物种的潜在分布,定量分析优势物种的主导环境影响因子及其生态位参数.结果表明: 黄河三角洲滨海湿地的优势物种为柽柳、芦苇和盐地碱蓬.影响柽柳、芦苇和盐地碱蓬潜在分布的主导环境因子分别为硝态氮、盐分、坡度、镁、海拔和铵态氮,硝态氮、盐分、全磷、pH、海拔和铵态氮,硝态氮、盐分和铵态氮.黄河三角洲滨海湿地优势物种的存在概率与盐分呈正相关,与其他主导环境影响因子呈负相关.黄河三角洲滨海湿地优势物种的潜在核心适生区主要分布在滨海地区,芦苇的分布范围较柽柳和盐地碱蓬更广泛.     

Spermatozoa and sperm aggregates in the vestimentiferan Lamellibrachia luymesi compared with those of Riftia pachyptila (Polychaeta: Siboglinidae: Vestimentifera)

The spermatozoa and the sperm bundles of the vestimentiferans Riftia pachyptila and Lamellibrachia luymesi (Annelida: Siboglinidae) were studied using several microscopical techniques (transmission and scanning electron microscopy, and confocal microscopy) and compared with some other annelid sperm. The spermatozoa and sperm bundles of both species show a similar structure, but they differ in the dimensions of the components of individual cells and in the number of spermatozoa forming each sperm bundle. The spermatozoa of R. pachyptila and L. luymesi are filiform cells composed, in sequence, by an acrosome in the form of a thread-like helical vesicle, an elongated coiled nucleus surrounded by two helical mitochondria, and a long flagellum. In the spermatozoa of both species, the apical portion of the nucleus is completely devoid of chromatin and is delimited by a thickened nuclear envelope with a fibrillar appearance. Both species have sperm bundles that resemble buds, having a calyx-like portion formed by the helical heads, and a stalk-like portion formed by the tightly packed flagella. A parsimony analysis based on spermatozoal characters showed monophyly of the Siboglinidae and the Vestimentifera. We propose a new set of autapomorphies characterizing vestimentiferan spermatozoa. Our analysis suggests that spermatozoal characters are useful to the understanding of the phylogeny of the group.     

Direct nitration of aryl groups σ-bound to ruthenium(II)

A new method has been developed for the preparation of nitroaryl transition metal complexes using copper(II) nitrate in the presence of acetic anhydride (Menke conditions) to directly nitrate an aryl group which is already σ-bound to a transition metal centre. Under these conditions ruthenium(II) aryl complexes of the type: (where R₁=R₂=H; R₁=H, R₂=CH₃; R₁=CH₃, R₂=H) react to yield three distinct types of nitroaryl-containing products (I–III).

Full-size image

The preparation and characterisation of these compounds are described. X-ray crystallographic data for one example of each of the three types of compound, are also reported. The compounds that have been studied crystallographically are Ru(C₆H₄NO₂-4)(η²-O₂CCH₃)(CO)(PPh₃)₂ (1a), C₄₅H₃₇NO₅P₂Ru·(CH₂Cl₂)_0.5, a = 20.254(5), b=19.437(8), c=22.629(3) Å, β=115.390(10)°, monoclinic, space group C2/c, Z=8; Ru(C6H4N[O]O-2)- Cl(CO)(PPh₃)₂ (4a), C₄₃H₃₄ClNO₃P₂Ru, a=9.331(3), b=12.443(2), c=16.346(3) Å, =82.81(2), β=85.03(2), γ=74.76(2)°, triclinic, space group P , Z=2; Ru(C₆H₂CH₃-2,NO₂-4,N[O]O-6)Cl(CO)(PPh₃)₂ (5b), C₄₄H₃₅Cl- N₂O₅P₂Ru·(CH₂Cl₂)₂, a=19.497(3), b=14.502(3), c=19.340(5) Å, β=122.79(1)°, monoclinic, space group Cc, Z=4.     

Thermal and photochemical substitution reactions of CpRe(PPh3)2H2 and CpRe(PPh3)H4. Catalytic insertion of ethylene into the C-H bond of benzene

The thermal and photochemical reactions of CpRe(PPh₃)₂H₄ and CpRe(PPh₃)H₄ (Cp = η⁵-C₅H₅) with PMe₃, P(p-tolyl)₃, PMe₂Ph, DMPE, DPPE, DPPM, CO, 2,6-xylylisocyanide and ethylene have been examined. While CpRe(PPh₃)₂H₂ is thermally inert, it will undergo photochemical substitution of one or two PPh₃ ligands. With ethylene, substitution is followed by insertion of the olefin into the C-H bond of benzene, giving ethylbenzene. CpRe(PPh₃)H₄ undergoes thermal loss of PPh₃, which leads to substituted products of the type CpRe(L) H₄. Photochemically, reductive elimination of dihydrogen occurs preferentially. The complex trans-CpRe(DMPE)H₂ was structurally characterized, crystallizing in the monoclinic space group P2₁/n (No. 14) with a = 6.249(6), b = 16.671(8), c = 13.867(7) Å, β = 92.11(6)°, V = 1443.7(2.9) Å and Z = 4. The complex trans-CpRe(PMe₂Ph)₂H₂ was structurally characterized, crystallizing in the monoclinic space group P2₁/n (No. 14) with a = 7.467(3), b = 23.874(14), c = 11.798(6) Å, β = 100.16(4)°, V = 2070.2(3.4) ų and Z = 4.