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Biomedical subjects

J F Reger

Publications and source records attributed to J F Reger.

At least 19 recordsLinked to original sources
PubMed1995

Controlled release of contraceptive steroids from biodegradable and injectable gel formulations: in vivo evaluation.

PURPOSE: The purpose of this study was to investigate in vivo biocompatibility, biodegradability and biological effects of contraceptive steroids, such as levonorgestrel and ethinyl estradiol, released from gels prepared with a combination of derivatized vegetable oil (Labrafil 1944 CS) and glyceryl ester of fatty acids (Precirol ATO 5). METHODS: Biocompatibility, biodegradability, and in vivo effects of levonorgestrel and ethinyl estradiol were studied by histologic evaluation of rat tissue, visual estimate of changes in gel size, and assessment of drug effects on reproductive cyclicity of female rats, respectively, following subcutaneous injection of gel formulations. RESULTS: Histological evaluation of the tissue samples following an injection of the gel revealed an inflammatory reaction for about 7 days, after which the tissues did not show any inflammatory response. Complete degradation of the gels containing 10% wax was observed between 5 and 6 weeks. Normal rat estrous cycles were completely blocked by the contraceptive steroids released from the gels. Gel formulations containing 0.25% w/w levonorgestrel were more effective in blocking the estrous cycle of female rats compared to the oil formulations containing an identical drug loading. The duration of the biological effect induced by levonorgestrel appears to be dose-related. The gel formulation containing 2.00% ethinyl estradiol was superior to oil formulation containing an identical drug loading in terms of controlling drug release and toxicity. CONCLUSIONS: These observations suggest that Labrafil-Precirol gels are biocompatible and biodegradable. Moreover, controlled release of steroids is possible in vivo for a prolonged period of time.

Animals↗
PubMed1991

Elevated extracellular potassium is associated with a reduced extracellular space in rat neural lobe in vitro.

Increased neural activity of neurosecretory cells is accompanied by large increases in extracellular K+. The possibility that elevations of this ion might involve fluid redistribution and thus affect the size of the extracellular space and the relationship between pituicytes and axons in the rat neural lobe was explored using rapid freezing and freeze-substitution. Neural lobes were incubated for 15 min before freezing either in a normal medium or one containing a 10 mM increase in KCl (high KCl), a 10 mM increase in KCl balanced by an equimolar reduction in NaCl (high KCl-low NaCl), or only a 10 mM reduction in NaCl (low NaCl). A quantitative assessment of the region of good fixation was made to determine the relative fractions occupied by axons, pituicytes and the extracellular space near the neurohaemal contact zone. In addition, the percentage of basal lamina contacted by pituicytes and axons was calculated, as was the degree of enclosure of axons by pituicytes. In neural lobes incubated in normal medium, the extracellular space accounted for approximately 30% of the cross-sectional area of the neuropil and could be divided into two domains: an extended perivascular space (28-29% of total area); and a narrow (approximately 24 nm; approximately 1% of total) space between closely apposed neurosecretory processes or between these processes and pituicytes. Pituicytes occupied almost 60% of the basal lamina at the neurohaemal contact zone, while axons occupied approximately 20%.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Electron microscopic and immunocytochemical study of rapidly frozen, freeze-substituted neural lobes of rats.

Rapid freezing of freshly dissected or incubated neural lobes was explored as a means of obtaining ultrastructural preservation of the more natural state of this tissue. A quantitative assessment of the region of good fixation was made in order to determine the relative fractions occupied by axons, pituicytes and the extracellular space. The immunocytochemical distributions of neurophysins and the glycopeptide portion of the vasopressin precursor were evaluated using the immunogold technique in order to determine the relative numbers of oxytocin and vasopressin fibre types in the fixed region, and the subcellular localization of these antigens. The uncut surface of rat neural lobes was rapidly frozen against a highly polished copper plug and freeze-substituted in osmium-acetone either immediately after dissection (approximately 2 min), or after a 15 min incubation period in vitro in an oxygenated, balanced salt solution. Substituted neural lobes were prepared for either conventional electron microscopy, or for immunogold labelling of neurophysins and the glycopeptide precursor to vasopressin. Membranes, subcellular organelles and extracellular matrix were well preserved 10 microns deep to the contacted surface. The extracellular space accounted for approximately 30% of the cross-sectional area of the neuropil and could be divided into two domains: an extended perivascular space (28-29% of total area); and a narrow (approximately 24 nm; approximately 1% of total) space between closely apposed neurosecretory processes or between these processes and pituicytes. Pituicytes accounted for about 30% of the area and axons 20-25%. Pituicytes occupied close to 60% of the basal lamina at the neurohaemal contact zone, while axons occupied approximately 20%. There were no differences between neural lobes frozen immediately after dissection and those incubated for 15 min in any of these measures, suggesting minimal fluid redistribution. Gold particles were specifically localized over large (100-200 nm) dense core vesicles, and less frequently over multivesicular bodies and lysosomes. No etching of the plastic or reduction of osmium was necessary to achieve labelling. Specific labelling of one set of terminals and axons (about 80%) was observed with the monoclonal antibody previously shown to be specific for oxytocin-neurophysin, while in neighbouring sections the remaining 20% of the processes were labelled with the antiserum to the vasopressin precursor, or with non-specific antibodies to neurophysins. In conclusion, ultrarapid freezing preserves a large extracellular space in the neural lobe and provides for high resolution morphological and immunocytochemical studies of neurohypophysial structure.

Animals↗
PubMed1990

Hepatic steatosis during convalescence from influenza B infection in ferrets with postprandial hyperinsulinemia.

The possibility that postprandial hyperinsulinemia could play a role in the development of hepatic lipid disturbances during convalescence from influenza B infection was explored in the ferret as a possible model of the steatosis of Reye's syndrome. Postprandial hyperinsulinemia was produced by feeding young ferrets glucose/water and a regular diet (glucose-treated group), as reflected by the mean serum insulin levels attained, which were 57 and 135 microU/ml during control and postinfluenza periods, respectively. By comparison, ferrets fed water and a regular diet (untreated group) had mean insulin levels of 19 and 22 microU/ml, while postprandial glucose levels were comparable in the two groups of animals for each period. In contrast to untreated animals, grossly visible fatty livers were found in glucose-treated ferrets during convalescence. The total lipid content of these livers had doubled compared with preinfection samples and compared with livers of untreated ferrets. By electron microscopy hepatic mitochondria showed striking changes with diminution of matrix density and reduction in cristae surface area only in convalescent samples from glucose-treated animals. Serum free fatty acid (FFA) levels were considerably higher in the glucose-treated animals during fasting before influenza and also after feeding during convalescence. Serum triglyceride (TG) levels were also high during convalescence in the glucose-treated group. Adipose tissue lipoprotein lipase activities were similar between groups, but hormone-sensitive lipase activity was twelvefold higher in glucose-treated ferrets before and after influenza B. These findings indicate that for a given stimulus, glucose-treated ferrets would mobilize more FFA than untreated ferrets. The total capacity for beta-oxidation of FA by the mitochondrial pathway was identical in all groups of animals. Total carnitine palmitoyl transferase (CPT) activity was the same in both control groups, but was significantly diminished in glucose-treated animals during convalescence. As CPT regulates the entry of FA into the mitochondrial matrix, its reduction in response to higher insulin concentrations would limit the oxidation of FA and stimulate TG accumulation. Therefore, the accumulation of lipid in the liver in this model is regarded to have been caused by the simultaneous occurrence of increased lipolysis and increased hepatic TG synthesis owing, in part, to diversion of activated FA by CPT, which is reduced in activity due to the regulatory action of insulin. These findings may have pathophysiologic relevance for the lipid changes that occur in Reye's syndrome and to fatty liver formation in hyperinsulinemic states.

Adipose Tissue↗
PubMed1989

Comparative aspects of cell fine structure in three cases of inverted, Schneiderian papilloma.

Three cases of nasal, epidermal, inverted papilloma, one of which involved synchronous carcinoma, were examined at the light and electron microscope level. Case I showed typically stratified squamous epithelial cell fine structure, including interdigitating cell borders with typical desmosome contacts and bundles of intracellular filaments. Epithelial cells of Case II did not have an identical squamous type appearance, they were smoother in outline, lacked extensive cell interdigitation and desmosomes, and were directly apposed to one another. Cells observed in Case III, involving synchronous carcinoma, also failed to reveal extensive stratified squamous epithelial characteristics, but were smooth in outline, lacked extensive interdigitations and desmosomes. On the bases of electron-density, cells in all three biopsies were characterizable as light, intermediate and dark cells. This variation reflects variations in the amount of granular endoplasmic reticulum and non-membrane bound polysomes. Cytological characteristics, including filament formation, filament concentration into bundles, and changes in nuclear structure leading to pyknosis are described. The above data are discussed in terms of their significance and relevance to previous electron microscope studies on various nasal inverted papillomas. It is concluded that fine structure characteristics, as well as light microscopic observations, should be more frequently utilized in identifying malignant as opposed to benign tumors.

Biopsy↗
PubMed1989

Fine structure observations on rat jejunal epithelial cells during fat processing and resorption following L-81 exposure and reversal.

In order to more easily follow membrane interaction following L-81 administration and subsequent lipid processing tannic acid was used to highlight cell membrane contrast in intestinal epithelial cells of Sprague-Dawley male rats. Jejunal epithelial cells were examined with the electron microscope following 4 h of L-81 administration and 45 min, 1, 1.5 and 2 h after the cessation of L-81 administration. After 4 h of L-81 administration the apical cytoplasm was seen to be filled with large, lipid droplets limited by a single, 4-5 nm thick, electron-dense rim. During the reversal process changes noted in the cytoplasm included the following. As early as 45 min clear and electron-dense-filled vesicles appeared scattered in the apical cytoplasm and juxtaposed to the lipid droplets. The large, non-membrane bound lipid droplets decreased in size and number over the two hour period while the number and size of electron-dense containing vesicles increased. The vesicles were subsequently found concentrated in the Golgi region where assimilation and production of chylomicron and VLDL size particles occurred. Eventually multiple groups of such particles were found intercellularly and basally. Thus the re-cycling of lipid and chylomicron production and secretion following L-81 reversal is similar to that following experimental studies on normal fat over-loading and following recovery after puromycin treatment. This data is discussed in light of previous data on fat processing and secretion in rat intestinal epithelial cells with particular reference to membrane events visible following tannic acid membrane highlighting.

Animals↗
PubMed1988

A comparative fine structure study of rat cerebral cortex following ultra-rapid freezing and conventional chemical fixation procedures.

Adult rat (Sprague-Dawley) cerebral cortex was processed by ultra-rapid freezing at liquid helium temperature followed by freeze-substitution, osmium fixation and by other chemical, post-osmication procedures at 0-4 degrees and ambient temperatures as a comparative study for purposes of identifying differences and/or similarities in fine structure following these techniques. Five methods of processing were used: 1) rapid, slam-freezing at liquid helium temperature followed by osmium tetroxide/acetone freeze substitution; 2) perfusion with buffered, 2% glutaraldehyde at ambient temperature followed by post-osmication (2%); 3) en-bloc, buffered 2% glutaraldehyde fixation at 0-5 degrees centigrade and post-osmication (2%); 4) buffered, 2% osmium tetroxide perfusion at ambient temperature; and 5) en-bloc, buffered 2% osmium tetroxide fixation at 0-5 degrees centigrade. In ultra-rapid-frozen cortex good preservation was seen to a depth of 10-15 microns from the surface of the initial, copper-block contact. The tissue processed by ultra-rapid-freeze, freeze substitution demonstrates a general 'smoothness' of plasmalemmal and organelle membranes not observed in tissue prepared by chemical fixation alone. Cellular and organelle morphological differences were minor beyond the general 'smoothness' of membranes and a more intense background, electron density found in tissue prepared by rapid-freeze. Of particular interest was the practically identical images found in the four, chemical techniques not preceded by ultra-rapid freezing. High magnification images also revealed rather minor differences following ultra-rapid-freezing compared to tissue fixed by chemical fixation alone. Although these morphological differences are minimal, there can be no question of the fact that ultra-rapid-freeze followed by freeze-substitution is morphologically superior to chemical fixation alone. Ultra-rapid-freeze, eventually utilizing other substitution agents than osmium tetroxide, will offer several advantages and should be particularly useful for investigators involved in cytochemical and immunochemical methods.

Animals↗
PubMed1988

A comparative fine structure study on myofibroblasts from a cultured human and an in-situ rat tumor source.

Cultured cells from human embryonal testis (HET 1) and basal-cell (BCE-5) carcinoma and cells from the peripheral region of growing tumors of rat adenocarcinoma (13762NF) were harvested and processed for examination with the electron microscope. Cells from the culture sources were collected from Percoll density fractions of 2-10%, 24% and 35%. The results demonstrate that cells from all sources were morphologically reminiscent of myofibroblasts (Gabbiani et al., 1971). They were elongate, fibroblast-like, appearing cells containing mitochondria, endoplasmic reticulum, Golgi complexes, filaments and microtubules. They also contained filament bundles associated with electron densities typical of myofibroblasts described elsewhere. Furthermore, cells from the 35% Percoll density gradient fraction were characterized by the presence of filament-containing vacuoles whose constituent filaments had a 60-65 A periodicity. It is concluded that cells from all three sources are morphologically similar, and are classifiable as myofibroblasts, and that cells from the 35% Percoll density fraction are also involved in collagen anabolism and/or catabolism.

Adenocarcinoma↗
PubMed1985

A freeze-fracture study on epididymal and ejaculate spermatozoa of the monkey (Macaca fascicularis).

Spermatozoa from four epididymal regions and from the ejaculate of the monkey, Macaca fascicularis, always present the same particle organization for a given sample. The plasmalemma contains homogeneously distributed, 7-8 nm size, PF-face, particles throughout the head, midpiece and principal piece. A unique, particle arrangement occurs in the plasmalemmal, PF-face in spermatozoa from the proximal levels of the body of the epididymis only. Square arrays of 4-6 nm size, PF-face plasmalemmal particles occur in this region of the epididymis at the peripheral edge of the spermatozoon acrosomal region only. Throughout other regions of the epididymis the plasmalemma contains only the homogeneously distributed, 7-8 nm size, PF-face particles. Ejaculate spermatozoa exhibit a similar particle organization to that of spermatozoa found in the distal portions of the epididymis. However, ejaculate spermatozoa of one animal from the eight used in this study exhibited a series of 7-8 nm size, linearly arranged, plasmalemmal, PF-face particles situated just proximal to the striated ring. This array of particles continued further rostral on the lateral aspect than on the flattened medial aspect of the spermatozoon. Spermatozoa from the tail of the epididymis and from ejaculates of the other seven animals lacked such specialization. The above data is discussed in terms of the population of particles generally, the significance of the presence of linearly arranged particles proximal to the striated ring, and the possible significance of the square arrays of particles present transiently in one region of the epididymis only. A correlation is made between these square arrays and similarly arrayed particles found in rat and boar epididymal spermatozoa.

Animals↗
PubMed1985

A quick-freeze, freeze-fracture study of mouse spermatozoa.

Rapid cryo-fixation of mouse spermatozoa followed by freeze substitution, thin section and freeze-fracture demonstrates the finer detail possible with quick-freeze as compared to chemical fixation. As seen in thin sections the unit membrane is composed of 2-4 nm size particles and the cytoplasm, mitochondria, and axonemal filament components all appear rich in fine structure detail. The filamentous structure of the post-acrosomal sheath and its connection with the plasmalemma is presented and compared to previous studies on this structure. Freeze-fracture data demonstrates 7-9 nm size, plasmalemmal, PF-face particles most heavily concentrated in the region just ahead of the striated ring. The outer acrosomal EF-face contains linear arrays of 7-9 nm size EF-face particles. The inner acrosomal membrane contains scattered, 7-9 nm size PF-face particles. The inner and outer nuclear membranes also contain scattered, 7-9 nm size particles. The results of this study present data which supports and extends previous studies on mouse spermatozoa. The results are discussed in terms of the advantages of cryo-fixation and freeze-substitution compared to conventional fixation in the preservation of fine structure detail.

Animals↗
PubMed1984

A cytochemical study on surface charges and lectin-binding sites in epididymal and ejaculated spermatozoa of Macaca fascicularis.

Changes in electronegative and electropositive surface charges and in lectin receptors (concanavalin A and wheat germ agglutinin) were investigated on sperm plasma membranes of the monkey (Macaca fascicularis) during epididymal transit and after ejaculation. Electronegative charges at pH 1.8, which were uniformly distributed on the whole plasma membrane of caput epididymal spermatozoa, increased mainly on the postacrosomal cap and the tail during epididymal passage. Electropositive charges at pH 9 were simultaneously found on the whole cell surface of caput epididymal spermatozoa with a stronger labeling on the acrosomal apex, the postacrosomal cap, and the tail. These charges disappeared during passage through the epididymis corpus. The surface distribution of lectin receptors varied inversely during epididymal transit with an increase in concanavalin A receptors and a decrease in wheat germ agglutinin receptors. These data show that changes in the monkey sperm plasma membrane during epididymal maturation occur in the distal corpus of the epididymis.

Animals↗
PubMed1983

Electrophysiologic differences between mouse extensor digitorum longus and soleus.

Miniature end-plate potentials (MEPPs) and indirectly elicited action potentials were recorded in vivo at 37 degrees C from surface fibers of the fast-twitch extensor digitorum longus (EDL) and the slow-twitch soleus (SOL) muscles of 3- to 4-month-old Bar Harbor 129 mice. The EDL MEPPs exhibited a significantly higher frequency, smaller amplitude, and shorter duration than the MEPPs of the SOL. Action potentials of EDL fibers exhibited a significantly greater amplitude and shorter duration than SOL fibers. A single stimulus elicited several action potentials from an EDL fiber but only one action potential from a SOL fiber. Fast- and slow-twitch muscle fibers can thus be identified and distinguished on the basis of these electrophysiologic parameters. There was no significant difference in resting membrane potentials between EDL and SOL fibers.

Action Potentials↗
PubMed1982

Studies on the fine structure of the mitochondrial derivative in spermatozoa of a gastropod.

Spermatozoa of Limax sp. were studied by electron microscopy following thin section and freeze-fracture techniques. Mature spermatozoa were seen to be helically shaped, 150 microns long cells. A single mitochondrion extends the entire length of the spermatozoon. Its helical turn is the same as that of the spermatozoon. Freeze-fracture images of the spermatozoon reveal that the EF and PF, plasmalemmal faces contain scattered, 7-9 nm size particles, and that the PF, outer mitochondrial membrane face contains 8-10 nm size particles. The corresponding EF, outer mitochondrial face contains matching pits. A paracrystalline complex is situated between the inner and outer mitochondrial membranes. The complex is constructed of a series of 8-9 nm thick, 35 nm wide, helically orientated, tripartate elements which extend the full length of the spermatozoon. The helical tilt angle is approximately 55 degrees. Each element is composed of tightly approximated (interspace distance 10 nm), strands of particles 8-9 nm in diameter. Speculations as to the significance of this complex, and its location between inner and outer mitochondrial membranes are made. It is concluded that the paracrystalline order of the complex either reflects the molecular packing of enzyme systems present in the mitochondrion, or some other unknown function.

Animals↗
PubMed1981

Studies on membrane specializations in tentacular retractor muscle of the gastropod, Limax sp.

Retractor muscle cells of the optic tentacle of Limax sp. occur as a network beneath the epithelium. The cells are spindle-shaped, irregularly cross-striated, and they contain a large number of subsarcolemmal caveolae. Freeze-fracture images of the sarcoplasmic reticulum, caveolae and sarcolemma demonstrate distinct particulate organizations. Membranes of the sarcoplasmic reticulum contain typical 7-9 nm PF-face particles. The caveolae membranes contain linear, sometimes rhombic arrays of 12-15 nm EF-face particles. An extensive area of the sarcolemmal surface is occupied by caveolar invaginations. Other areas of the sarcolemma contain linear arrays of 7-9 nm PF-face particles and a few rhombic ordered, 7-9 nm PF-face particles. The results of the study are discussed relative to previous studies on particulate arrays in muscle membranes. It is concluded that these highly specialized sarcolemmal and caveolar particulate organizations may, in some way, reflect the large surface area changes which occur in these muscle cells.

Animals↗