Biomedical subjects

L D Russell

Publications and source records attributed to L D Russell.

At least 91 records · Page 5Linked to original sources

PubMed1988

Effects of cytochalasin D on the integrity of the Sertoli cell (blood-testis) barrier.

Ectoplasmic specializations (ES) containing packed actin microfilaments are associated with the numerous parallel rows of occluding junctions which form the Sertoli cell (blood-testis) barrier. To determine if ES regulate the structure of the occluding junctions and/or barrier permeability, we experimentally disrupted ES microfilaments in vivo with intratesticularly injected cytochalasin D (CD). Electron microscopic observations of seminiferous tubules from CD-treated (150-500 microM CD; 0.5-12 hr) animals indicated that ES was absent from regions where the Sertoli cell barrier is located. Seminiferous epithelial sheets from uninjected or vehicle-injected animals (1 DMSO: 1 saline) stained with NBD-phallacidin demonstrated the presence of patterned ES actin surrounding the basolateral regions of adjacent Sertoli cells. After exposure to CD, epithelial sheets exhibited increasingly patchy fluorescence indicating progressive F-actin disruption. Freeze-fracture replicas of CD-injected testes revealed numerous focal alterations in the region of occluding junctions which included disorganization of the parallel arrangement of junctional rows, the presence of free-ending rows, clustering of intramembranous particles (IMPs) between rows, reduction in the number of rows, and loss of IMPs on both the P-face and E-face. Tracer experiments, following CD exposure, were conducted to test the integrity of occluding junctions: lanthanum hydroxide, dextrose, or filipin was added, in separate experiments, to the fixative during perfusion-fixation. In another study, serum containing an antibody against adluminal germ cells was injected intratesticularly, and frozen sections were processed for immunofluorescence study. A final study consisted of simultaneous intratesticular infusions of CD and radiolabelled inulin with subsequent intraluminal and peritubular fluid sampling. In animals which were injected with CD, lanthanum was found to enter the adluminal compartment; fixative made hypertonic by addition of dextrose caused germ cells within the adluminal compartment to shrink and produce exaggerated intercellular spaces; filipin-cholesterol perturbations were present between some Sertoli cell junctional rows and on spermatid plasma membranes; and IgG was detected within the adluminal compartment of many seminiferous tubules. None of these adluminal manifestations was noted in control animals or those which received vehicle. Quantitatively, in the in vivo micropuncture experiments, significantly more radiolabelled inulin entered the lumen of seminiferous tubules from CD-treated animals than from those exposed to vehicle.(ABSTRACT TRUNCATED AT 400 WORDS)

Actin Cytoskeleton↗

PubMed1988

Spermiogenesis in the red-ear turtle (Pseudemys scripta) and the domestic fowl (Gallus domesticus): a study of cytoplasmic events including cell volume changes and cytoplasmic elimination.

Nuclear and cytoplasmic volume changes as well as the elimination of residual spermatid cytoplasm were investigated in the red-ear turtle (Pseudemys scripta) and the rooster (Gallus domesticus). Nuclei of newly formed spermatids which were originally centrally located became eccentrically located within the cell in both species. Shortly thereafter the nuclear pole of the spermatid was found situated within deep crypts of a Sertoli cell. The cytoplasm of elongating spermatids was displaced along the nonacrosomal region of the nucleus and the proximal flagellum. In both species sheetlike Sertoli cell processes indented spermatid cytoplasm adjacent to the nucleus and appeared to segregate small packets of the cytoplasm. In the turtle, these packets of cytoplasm were separated from the spermatid. In both the turtle and rooster, a portion of the spermatid cytoplasm was displaced forward over the acrosomal region of the spermatid to resemble a hood. As spermatids were transported to the seminiferous tubular lumen, cytoplasmic lobes which projected forward of the spermatid head were formed by preferential flow of cytoplasm into one aspect of the cytoplasmic hood. In both species, at sperm release the cytoplasmic lobe was disengaged from the spermatid head to form a large residual body that was internalized and degraded within the Sertoli cell. Medium-sized cytoplasmic lobes were pinched from the head and neck region of the turtle and rooster spermatids, respectively. In the turtle, small-sized mitochondrial-rich cytoplasmic fragments budded from the caudal head and midpiece of the spermatids and were phagocytosed by the Sertoli cell. Thus, cytoplasmic elimination occurred through 1) segregation of cytoplasmic packets by Sertoli penetrating processes (turtle), 2) elimination of large and medium-sized residual bodies from the head (turtle and bird), and 3) budding of small mitochondrial-rich cytoplasmic fragments from the region of the midpiece (turtle). In the turtle a 79% reduction in total cell volume occurred during spermiogenesis which was the result of an 84% cytoplasmic reduction and a 78% nuclear reduction. During spermiogenesis, the rooster lost 97% of its total cell volume due to a 97% cytoplasmic volume change and a 96% nuclear volume change.

Animals↗

PubMed1988

Spermiogenesis in the bluegill (Lepomis macrochirus): a study of cytoplasmic events including cell volume changes and cytoplasmic elimination.

The process involved in the reduction of both nuclear and cytoplasmic volume was investigated in the bluegill (Lepomis macrochirus), a teleost fish. Young spermatids contained centrally positioned nuclei which, with time, moved toward the cell surface to become eccentrically positioned. Chromatin condensation was initiated from a region near the implantation fossa, whereas at the opposite pole of the nucleus an area sparse in heterochromatin (clear area) was noted. The nuclear membrane lying adjacent to the clear area dissolved and subsequently reformed, yielding a nucleus with a reduced volume. During this process, packets of cytoplasm surrounded by a double membrane were formed along the future midpiece. The packets of cytoplasm migrated toward the cell surface, protruded from the surface, and were extruded into the spermatocyst lumen. These structures, termed residual bodies, were subsequently endocytosed, accumulated into large phagocytic vacuoles, and eventually degraded by the nearby Sertoli cell. When the spermatocyst ruptured, spermatozoa containing sparse cytoplasm were released into the excurrent duct system. During spermiogenesis, both the nuclear and cytoplasmic volumes decreased substantially (80%, 92% respectively) leading to an overall 87% reduction in total cell volume.

Animals↗

PubMed1988

Spermiogenesis in the bullfrog (Rana catesbeiana): a study of cytoplasmic events including cell volume changes and cytoplasmic elimination.

The process by which spermatid cytoplasmic volume is reduced and cytoplasm eliminated during spermiogenesis was investigated in the bullfrog Rana catesbeiana. At early phases of spermiogenesis, newly formed, rounded spermatids were found within spermatocysts. As acrosomal development, nuclear elongation, and chromatin condensation occurred, spermatid nuclei became eccentric within the cell. A cytoplasmic lobe formed from the caudal spermatid head and flagellum and extended toward the seminiferous tubule lumen. The cytoplasmic lobe underwent progressive condensation whereby most of its cytoplasm became extremely electron dense and contrasted sharply with numerous electron-translucent vesicles contained therein. At the completion of spermiogenesis, many spermatids with their highly condensed cytoplasm still attached were released from their Sertoli cell into the lumen of the seminiferous tubule. There was no evidence of the phagocytosis of residual bodies by Sertoli cells. Because spermatozoa are normally retained in the testis in winter and are not released until the following breeding season, sperm were induced to traverse the duct system with a single injection of hCG. Some spermatids remained attached to their cytoplasm during the sojourn through the testicular and kidney ducts; however, by the time the sperm reached the Wolffian duct, separation had occurred. The discarded cytoplasmic lobe (residual body) appeared to be degraded with the epithelium of the Wolffian duct. It was determined that the volume of the spermatid was reduced by 87% during spermiogenesis through a nuclear volume decrease of 76% and cytoplasmic volume decrease of 95.3%.

Animals↗

PubMed1988

The seasonal breeding hamster as a model to study structure-function relationships in the testis.

The present study was undertaken to document morphological changes in the testis of the seasonally breeding golden hamster, an animal model which has been studied extensively from an endocrine standpoint but for which morphological data is inadequate. Germ cells, Sertoli cells and Leydig cells were studied during active and regressed state of gonadal activity by exposing the animals to long (16L:8D) and short photoperiods (6L:18D), respectively. Testis of the hamster exposed to short photoperiods displayed more than a ten-fold reduction in weight and decreased seminiferous tubule diameter. The seminiferous tubules contained primarily Sertoli cell and spermatogonia but also occasional spermatocytes and round spermatids. Leydig cells were decreased in size, a change which appeared to be primarily due to a decrease in cytoplasmic volume. The Leydig cell endoplasmic reticulum which was atypically saccular displayed both rough and smooth components and was decreased during short photoperiods. Mitochondria generally appeared larger and showed considerable structural heterogeneity. Short photoperiod-induced changes in the Sertoli cells included a marked reduction in cell height and an apparent reduction in cell volume, absence of lateral processes, presence of small, almost spheroidal nuclei with inconspicuous nucleoli, an increase in the amount of lipid and decreases in the amount of smooth endoplasmic reticulum and glycogen. The striking differences in the testicular structure between the active and regressed state of gonadal activity follows photoperiod-induced changes in endocrine parameters and suggests that the hamster would be an ideal model to study structure-function relationships in the testis, and especially those related to the Sertoli cell.

Animals↗

PubMed1988

The consequences of actin disruption at Sertoli ectoplasmic specialization sites facing spermatids after in vivo exposure of rat testis to cytochalasin D.

Cytochalasin D (CD) was used to perturb actin filaments of the Sertoli ectoplasmic specialization (ES)--a cytoskeletal complex of the Sertoli cell related to spermatids. CD (500 microM for 6 h) produced a loss of 88% of the ES facing the head region of early (Step 8) elongating spermatids as compared to vehicle (dimethylsulfoxide:saline) controls. Nitrobenzoxadiazole-phallacidin staining of F-actin revealed a CD-related loss of uniform fluorescence over the head of elongated spermatids. To examine for a possible relationship between the presence of actin and cell attachment at ES sites, hypertonic fixatives were introduced to provoke cell shrinkage and stress ES-associated junctions. After osmotic stress, cell-to-cell adhesion at ES sites remained intact in vehicle-treated animals. CD treatment caused Sertoli cells to separate from elongating spermatids at sites where ES had been lost from the Sertoli cell surface. It is suggested that actin of the ES plays a role in cell-to-cell interaction analogous to its possible role at the Sertoli cell barrier. In CD-treated animals, structures resembling tubulobulbar complexes frequently developed at sites where ES was lost, suggesting that the loss of ES has a facilitatory role in tubulobulbar complex formation. It is hypothesized that tubulobulbar complexes are devices that rid the cells of ES-associated junctional links to effect dissociation of the spermatid from the Sertoli cell during spermiation. Spermatids at Step 8 of development are known to become oriented with their acrosomes facing the base of the Sertoli cell. After CD treatment, a 5.8-fold increase in malorientation of Step 8 spermatids was noted. A role for the ES cytoskeletal complex in orienting the spermatid acrosome toward the basal aspect of the Sertoli cell is also suggested.

Actins↗

PubMed1988

Morphometric studies on hamster testes in gonadally active and inactive states: light microscope findings.

This study provides quantitative information on the testes of seasonally breeding golden hamsters during active and regressed states of gonadal activity. Seminiferous tubules occupied 92.5% of testis volume in adult gonadally active animals. Leydig cells constituted 1.4% of the testicular volume. The mean volume of an individual Leydig cell was 1092 microns 3, and each testis contained about 25.4 million Leydig cells. The volume of an average Sertoli cell nucleus during stage VII-VIII of the cycle was 502 microns 3. A gram of hamster testis during the active state of gonadal activity contained 44.5 million Sertoli cells, and the entire testis contained approximately 73.8 million Sertoli cells. Testes of the hamsters exposed to short photoperiods for 12-13 wk displayed a 90% reduction in testis volume that was associated with a decrease in the volume of seminiferous tubules (90.8% reduction), tubular lumena (98.8%), interstitium (72.7%), Leydig cell compartment (79.3%), individual Leydig cells (69.7%), Leydig cell nuclei (50.0%), blood vessels (85.5%), macrophages (68.9%), and Sertoli cell nuclei (34.1%). The diameter (61.1%) and the length (36.8%) of the seminiferous tubules were also decreased. Although the number of Leydig cells per testis was significantly lower (p less than 0.02) after short-photoperiod exposure, the number of Sertoli cells per testis remained unchanged. The individual Sertoli cell in gonadally active hamsters accommodated, on the average, 2.27 pre-leptotene spermatocytes, 2.46 pachytene spermatocytes, and 8.17 round spermatids; the corresponding numbers in the regressed testes were 0.96, 0.20, and 0.04, respectively. The striking differences in the testicular structure between the active and regressed states of gonadal activity follow photoperiod-induced changes in endocrine function and suggest that the golden hamster may be used as a model to study structure-function relationships in the testis.

Animals↗

PubMed1987

Comparative study of cytoplasmic elimination in spermatids of selected mammalian species.

In the transformation of a spermatid into a spermatozoon, cytoplasmic loss occurs, allowing the sperm to swim unhindered. Cytoplasmic loss takes place via elimination of the residual body and through structures known as tubulobulbar complexes. A determination of cytoplasmic loss in several species was undertaken by using high-resolution electron microscopic morphometric techniques. During the period that tubulobulbar complexes are present, an average 53% cytoplasmic loss was recorded for five species (guinea pig, 48.8 +/- 6.2% (SEM); monkey, 60.3 +/- 4.3%; opossum, 54.5 +/- 4.4%; rabbit, 46.9 +/- 2.7%; and rat, 55.7 +/- 4.9%), whereas there was essentially no loss or gain in cytoplasm during the same period for round spermatids. Surprisingly, during spermatid elongation an approximate 36% loss of cytoplasm was also recorded for five species (guinea pig, 50.1 +/- 6.3%; monkey, 30.0 +/- 15.4%; opossum, 25.4 +/- 9.0%; rabbit, 42.4 +/- 8.6%; and rat, 34.9 +/- 11.9%), which is only partially (approximately 60%) accounted for by fluid pumping from the nucleus during nuclear condensation. A densification of the cytoplasm of elongate spermatids, as compared with round spermatids, suggests fluid is also pumped from the elongating spermatid cytoplasm. Fluid loss from germ cells may contribute to the seminiferous tubule fluid, a fluid previously thought to be solely of Sertoli-cell origin.

Animals↗

PubMed1987

Characterization of filaments within Leydig cells of the rat testis.

Rat Leydig cells were permeabilized and the cytoplasm partially extracted to visualize, describe, and characterize filamentous elements of the cytoskeleton. It was demonstrated by immunofluorescence microscopy that vimentin is abundant within Leydig cells. Ultrastructurally, intermediate filaments in Leydig cells were concentrated at perinuclear sites and comprised bundles that coursed through the cytoplasm. Actin was identified in Leydig cells with the F actin probe, NBD-phallacidin. Fluorescence was strongest at the cortex of the cell. With myosin S-1 subfragments, sparse actin was found positioned almost exclusively in cortical regions of the cell associated with coated pits and in Leydig cell processes.

Actins↗

PubMed1987

A study of intercellular bridges during spermatogenesis in the rat.

A morphological evaluation of intercellular bridges was undertaken during rat spermatogenesis. The dimensions and relationships of the bridges were shown to vary during different phases of spermatogenesis. Cellular divisions of spermatogonia and spermatocytes resulted in the partitioning of pre-existing bridges by complex structures termed bridge partitioning complexes, which are described in detail, as is the process whereby new bridges are formed. The structure of premeiotic bridges was generally consistent; however, during spermiogenesis, the structure of bridges and bridge contents were modified at specific phases of their development. The plasma membrane density associated with the cytoplasmic aspect of early step 1 spermatids separated into multiple dense bands that encircled the peripheral aspect of late step 1 spermatid bridges. By step 2 of spermiogenesis, these dense bands became associated with several cisternae of endoplasmic reticulum, which later coalesced into a single saccule that completely encircled the bridge structure by step 4. At steps 10-13 of spermiogenesis, the single saccule of endoplasmic reticulum vesiculated into many smaller cisternae. Also, filament-bounded densities (measuring 10-12 nm in diameter) appeared within the bridge channel. At step 17 of spermiogenesis, the filament-bounded densities were no longer apparent, but an anastomosing network of endoplasmic reticulum, often in the configuration of a sphere, occupied the entire central region of the bridge. In step 19 spermatids, the smooth endoplasmic reticulum within the bridge channel and the multiple cisternae lining the bridge density were gradually displaced. The subsurface density of bridges gradually lost its prominence. Some cytoplasmic lobes were connected by extremely narrow (approximately 22 nm) cytoplasmic channels. Similar-appearing channels were seen on the surface zone of cytoplasmic lobes or residual bodies, this observation suggesting that channels were sites of severence of bridges. Just prior to the separation or disengagement of the spermatid from the cytoplasmic lobe, selected bridges appeared to open to form large masses. After spermiation, residual bodies were not found joined by bridges; but from the size of some of the residual bodies, it was suspected that they were formed by coalescence of more than one cytoplasmic lobe. Freeze-fracture demonstrated few intramembranous particles on either the P or E face of the plasma membrane forming the bridge; this finding suggested bridge structures restricted free lateral movement of membrane constituents across the bridge.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1987

Actin localization in male germ cell intercellular bridges in the rat and ground squirrel and disruption of bridges by cytochalasin D.

Filaments about 6-7 nm in diameter were seen associated with germ cell intercellular bridges in detergent-permeabilized cells treated with tannic acid. Approximately 40-50 filaments were present subjacent to the bridge density. Filaments encircled the bridge channel in a manner similar to contractile ring actin filaments of dividing cells. NBD-phallacidin and myosin S-1 subfragments were employed to demonstrate that the filaments observed at intercellular bridges are actin. Intratesticular injection of a single dose of cytochalasin D, a specific inhibitor of actin filaments, caused certain intercellular bridges of spermatids to open within 3 hr after injection, leading to the production of symplasts. During bridge opening, remnants of bridge densities were gradually incorporated into the lateral aspect of the plasma membrane of the symplast. Thus actin, present in bridge structures, appeared to participate in maintaining certain intercellular bridges. A model of intercellular bridge structure is presented.

Actins↗

PubMed1987

Distribution of actin in spermatids and adjacent Sertoli cell regions of the rat.

In this study, we describe the distribution of actin filaments in and around spermatids that are mechanically dissociated, in the presence and absence of exogenous trypsin, from the seminiferous epithelium of the rat. NBD-phallacidin and subfragment 1 of the myosin molecule (S-1) are used as probes for filamentous actin at the light and electron microscopic levels, respectively. The fluorescence associated with spermatids mechanically dissociated in the absence of trypsin is due to actin both in the spermatogenic cells themselves and in attached Sertoli cell ectoplasmic specializations. Fluorescence generated by labelled actin in ectoplasmic specializations occurs in linear tracts that follow the outer contour of spermatid heads. The residual fluorescence seen when trypsin is used to detach Sertoli cell fragments is diffuse and due to f-actin in the subacrosomal space. Electron microscopic data agree with the fluorescence results. This study conclusively demonstrates that Sertoli cell ectoplasmic specializations remain attached to spermatids mechanically dissociated from the seminiferous epithelium. This observation may be useful when attempting to isolate ectoplasmic specializations for biochemical analyses.

Actins↗

PubMed1987

Characterization of human sperm plasma membrane: glycolipids and polypeptides.

The plasma membranes from ejaculated human spermatozoa were removed by nitrogen cavitation (600 PSI for 10 min) and isolated by centrifugation followed by a discontinuous sucrose density gradient centrifugation. Glycolipid analysis of the plasma membrane revealed a three-fold enrichment in gangliosides: GM3 and GD1a/GD1b and neutral glycolipids: globoside and sulfatide as compared to that of whole human sperm. Two dimensional electrophoresis of human sperm plasma membranes revealed about 75 polypeptides. Several of these polypeptides were similar in migration and in display of shape and color to that found in boar sperm plasma membranes.

Cell Membrane↗

PubMed1987

Intratesticular injection as a method to assess the potential toxicity of various agents and to study mechanisms of normal spermatogenesis.

To better understand, to optimize, and to validate the technique of intratesticular (i.t.) injection, several parameters related to i.t. injection were examined. Volumes exceeding 50 microliters could be injected i.t.; however, testes frequently became excessively turgid and backflow of injected fluids occurred. Thus, a volume of 50 microliters or less was deemed optimal for injection. To determine the rate of distribution of substances throughout the testis, trypan blue was injected i.t. near the caudal pole of the testis, and the movement of dye was monitored. Within 2 min, the dye had spread approximately 1 cm from the site of injection, and in 5 min it had spread twice that distance. In 2 h, the dye had become distributed throughout the testis except at its extreme cranial pole. Seminiferous tubules did not take up dye, indicating that the spread of dye was via peritubular lymphatics. Seminiferous tubule histology appeared virtually unaffected by i.t. injection, even at regions adjacent to the site of injection, when a sterile 26-gauge or smaller bore needle was utilized. To determine disappearance from the testis, radiolabeled inulin was injected i.t. Half time for absorption was achieved at 1.75 h. Potential vehicles were explored in which compounds with a variety of physical properties could be injected. Gum tragacanth, normal saline, ethylene glycol, dimethyl sulfoxide (DMSO) mixed 1:1 with normal saline, sesame oil, and propylene glycol were found to be suitable injection vehicles, whereas ethanol, dissolved in normal saline in concentrations as low as 0.5% was found unsuitable. To assess vehicle efficiency, various vehicles were utilized with a known testicular toxin (taxol) and injected into one testis, and the histology was compared with the contralateral testis injected with vehicle alone. All vehicles, found suitable above, allowed dispersion of taxol to influence areas distant from the site of injection. Intratesticular injection assesses the potential of agents to directly affect the testis, and systemic metabolism is avoided. Their rapid spread throughout the lymphatics of the testes allows seminiferous tubules to be exposed to agents in innocuous vehicles more rapidly and in higher concentration than is often possible when using systemic injections.

Alkaloids↗

PubMed1987

A comparative study of Sertoli cell ectoplasmic specializations in selected non-mammalian vertebrates.

Ectoplasmic specializations (ES) facing spermatids were studied in species representative of four classes of non-mammalian vertebrates (Pisces--bluegill; Amphibia--bullfrog; Reptilia--red eared turtle; Aves--domestic chicken). ES was not seen in the bluegill but was present in all other species studied. In the frog, turtle, and chicken, ES did not resemble its mammalian counterpart and could only be characterized by the presence of 6 nm filaments (presumedly actin) within the somatic cell facing the head region of elongating spermatids. ES filaments were sparse in the frog and were sometimes associated with more deeply situated endoplasmic reticulum. Turtle ES filaments were abundant and encircled the acrosomal region of the spermatid head and were delimited by fenestrated saccules of endoplasmic reticulum. In the chicken, ES filaments were prominent but less abundant than in the turtle. Six nanometer filaments of the chicken ES appeared in a tangled mass and were not associated with clearly defined endoplasmic reticulum. In the three species where ES was found, it first developed as spermatids became entrenched within the surrounding somatic cell. Neither cell elongation, nuclear elongation, or movement of the nucleus to the cell surface was synchronized with the onset of ES development. That ES development was seen concomitant with spermatid entrenchment and spermatid orientation suggested a role for ES in these processes. This hypothesis was further strengthened by observations in the fish where ES was lacking and where spermatid entrenchment within the somatic cell, did not occur. The study also supported the hypothesis that ES acts as a cytoskeletal mantle to which other cytoskeletal elements within the cell interact to affect the position of elongate spermatids within the epithelium. The dissolution of ES prior to spermiation and concomitant loss of a close relationship between cells suggests that ES is also related to somatic cell-germ cell adhesion and therefore plays an important role in the spermiation process.

Animals↗

PubMed1987

Hormonal control of pubertal spermatogenesis.

The spermatogenic process of normal rats at 20, 32, and 44 days of age was characterized. Variations in numbers of degenerating and abnormal cells were noted during the cycle in most age groups, indicating a stage-related vulnerability of these cells. The most advanced cell types that were seen at a particular age were frequently abnormal or degenerating. When the numbers of viable cells available to degenerate were considered, the degeneration rate in normal pubertal animals was about 15, 10, and 2 times greater in 20-, 32-, and 44-day-old animals, respectively, than in 75-day-old animals. In 32-day-old rats, neither hypophysectomy nor hypophysectomy and subsequent hormone supplementation resulted in an alteration in the qualitative pattern of germ cell degeneration during the spermatogenic cycle compared with that in the normal animal; however, the treatments did alter the quantitative response of cellular degeneration. Three days posthypophysectomy there was a marked increase in the numbers of total degenerating germ cells. FSH (60 micrograms) given twice daily (as were all hormones) reduced the numbers of degenerating cells significantly, as did LH (13 micrograms). Low dose LH (0.3 micrograms), representing the approximate contaminating dose of LH in the 60-micrograms FSH preparation, and low dose FSH (30 micrograms) did not elicit a response significantly different from that to hypophysectomy alone. LH (13 micrograms) plus FSH (60 micrograms) reduced the levels of degenerating cells such that there was no significant difference from levels in intact 32-day-old rats. The data indicated, for the cell types studied, a lack of specificity of various hormones or hormone combinations in the survival of specific germ cell types. It emphasizes the importance of FSH in pubertal spermatogenesis as well as the synergistic actions of LH and FSH.

Aging↗

PubMed1987

Organization of the boar spermatozoan plasma membrane: evidence for separate domains (subdomains) of integral membrane proteins in the plasma membrane overlying the principal segment of the acrosome.

Indirect immunofluorescence microscopy and freeze-fracture have been used to identify overlapping subdomains at the peripheral rim of the sperm-head plasma membrane (PM) and the margin of the outer acrosomal membrane (OAM) comprising the principal segment of the acrosome of the boar spermatozoon. An array of ridge-like structures (spaced 12-16 nm centre-to-centre), originally observed on the OAM by Aguas & Pinto da Silva, lies just beneath an area of the PM that is sparsely populated with large intramembranous particles compared to that of other regions of the head PM. This region has a high specificity for the lectin arachis hypogaea (peanut agglutinin). We suggest that the OAM at the rim of the sperm head may be rich in acidic phospholipids and that the close apposition of this membrane with a region of the PM relatively poor in integral membrane proteins may provide sites for initiating the acrosome reaction.

Acrosome↗

PubMed1987

Germ cell-somatic cell relationships: a comparative study of intercellular junctions during spermatogenesis in selected non-mammalian vertebrates.

Specialized germ cell-somatic cell relationships were surveyed in the testis of species representative of four classes of non-mammalian vertebrates. Desmosome-like junctions were present in all classes studied. In the teleost fish studied (bluegill; Lepomis macrochirus), small, infrequent desmosomes, seen between the spherical cyst cells and spermatocytes, were characterized by poorly represented subsurface densities. In the bullfrog (Rana catesbeiana), similar desmosome-like junctions were found between cyst cell processes and spermatocytes. Reptilian (turtle; Pseudameys scripta) desmosome-like junctions between Sertoli cells and germ cells were heterogeneous and more numerous than those junctions found in fish and amphibians. In general, the reptilian desmosome-like junctions were extensive structures displaying 10 nm filaments associated with the Sertoli cell component of the junctions. Regions within the desmosome where the two plasma membranes converged suggested that gap junctions were a component of the desmosome-like junctions. "Desmosome-gap" junctions persisted in turtle spermatids for sometime after nuclear elongation had commenced. In birds (chicken; Gallus domesticus), "desmosome-gap" junctions, similar to those seen in turtles were described between both spermatocytes and Sertoli cells, and spermatids and Sertoli cells. These junctions were frequently lined by saccules of endoplasmic reticulum. The presence of gap junctions suggest the evolution of mechanisms for somatic cell-germ cell communication although more species should be examined to confirm this hypothesis.

Animals↗