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Biomedical subjects

R W Lenz

Publications and source records attributed to R W Lenz.

At least 37 records · Page 2Linked to original sources
PubMed1992

Biodeuteration of poly(beta-hydroxybutyrate).

The formation of poly(beta-hydroxybutyrate), PHB, by Rhodobacter sphaeroides and Alcaligenes eutrophus was studied using the following carbon sources and solvents: (1), acetate in H2O; (2), D3-acetate in H2O; (3), acetate in 90 to 92% D2O; and (4), D3-acetate in 90 to 92% D2O. The growth of Rb. sphaeroides cultured under condition (2) showed no apparent deuterium isotope effect, while considerably slowed growth in the presence of D2O was observed under conditions (3) and (4). In all cases, the PHB produced under deuterium enriched conditions was of high molecular weight. Interestingly, comparatively high volumetric formation of partially deuterated PHB was obtained using culture condition (4) for A. eutrophus. Fourier transform infrared spectroscopy (FT-i.r.), pyrolysis gas chromatography mass spectrometry (PGC-m.s.), and nuclear magnetic resonance (n.m.r.) were used to establish the extent and distribution of deuterium in the PHB samples produced. Partially deuterated PHB was obtained in each case, using a deuterium enriched culture. Considerable differences in the extent and distribution of deuterium were found between micro-organisms and culture conditions.

Acetates↗
PubMed1990

Plastics from bacteria and for bacteria: poly(beta-hydroxyalkanoates) as natural, biocompatible, and biodegradable polyesters.

Hence, PHB belongs to the family of poly(beta-hydroxyalkanoates), PHA, all of which are usually formed as intracellular inclusions under unbalanced growth conditions. Recently, it became of industrial interest to evaluate PHA polyesters as natural, biodegradable, and biocompatible plastics for a wide range of possible applications such as surgical sutures or packaging containers. For industrial applications, the controlled incorporation of repeating units with different chain lengths into a series of copolymers is desirable in order to produce polyesters with a range of material properties because physical and chemical characteristics depend strongly on the polymer composition. Such "tailormade" copolymers can be produced under controlled growth conditions, in that if a defined mixture of substrates for a certain type of microorganisms is supplied, a well defined and reproducible copolymer is formed.

Bacteria↗
PubMed1990

Production of unsaturated polyesters by Pseudomonas oleovorans.

Pseudomonas oleovorans was grown separately on 3-hydroxy-6-octenoic acid and 3-hydroxy-7-octenoic acid as the only carbon source and under ammonium nutrient-limiting conditions to produce storage polyesters. The polyesters produced contained mainly unsaturated C8 units. Small amounts of both the saturated and the unsaturated C6 units were also present, but only about 1% of the saturated 3-hydroxyoctanoate units was detected. The polyester obtained from 3-hydroxy-6-octenoic acid, which was a mixture of the cis and trans isomers, also contained units with cis and trans double bonds. The weight average molecular weights of the polymers produced were in the range of 339,000-383,000 as determined by g.p.c. relative to polystyrene, with Mw/Mn ratios of 1.8-2.1. The mechanism of PHA formation from n-octene previously reported is discussed in relation to the present results, and the two were found to be in good agreement.

Culture Media↗
PubMed1990

Bacterial polyesters containing branched poly(beta-hydroxyalkanoate) units.

Pseudomonas oleovorans was grown on mixtures of methyloctanoates with n-octanoate. Polymers were also obtained from organisms grown on pure 7-methyloctanoate, but not from pure 5- or 6-methyloctanoate. The polyesters obtained from 7-methyloctanoate and from its mixtures with n-octanoate contained units with the methyl branches in the pendant group, as did the copolymers from the mixtures of 5- and 6-methyloctanoate with n-octanoate. The methyl branched repeating units contained two diastereomers, and the 13C-n.m.r. spectra of these polymers indicated that the 5-methyloctanoate units had a higher content of one of the two isomers, but not in the 6-methyloctanoate units. The weight average molecular weights of the copolyesters produced were in the range of 220,000 to 410,000, with Mw/Mn ratios of 1.7 to 1.9.

Caprylates↗
PubMed1990

Nonreturn rates of dairy cattle following uterine body or cornual insemination.

In the dairy cattle industry, uncertainty still remains regarding the most desirable site of inseminate deposition to maximize AI conception rates. The effect of site of inseminate deposition on nonreturn rates was determined from 2195 cornual and 2428 uterine body-bred dairy cattle. Twelve technicians from various areas of Pennsylvania and New York were chosen on the basis of their accuracy of semen deposition in retraining sessions, average nonreturn rates, and their willingness to cooperate in the study. For a 3-mo period (June, July, and August 1988), technicians alternated weeks of cornual and uterine breeding on all dairy cattle inseminated. One-half (.25 ml) of each semen unit was deposited approximately 5.1 cm into each uterine horn for cornual insemination. No significant difference in nonreturn rates was found between horn-bred (70.8%) and body-bred (69.5%) cows. The range of differences in percent nonreturn rates for technicians was 19 and 30% for body and cornual inseminations, respectively. A significant difference in nonreturn rates was found between technicians and between months with significantly higher average nonreturn rates (6.8%) in June. Cornual and uterine body deposition of semen yielded similar results; therefore, depositing an inseminate in the uterine horns to maximize fertility is unnecessary.

Animals↗
PubMed1990

Validation and application of an assay for deoxyribonucleic acid to estimate concentrations of bull sperm.

Spectrophotometers are used for estimating sperm concentrations from raw ejaculates in semen processing laboratories. Unfortunately, these instruments have a limited detection spectrum and do not permit accurate quantification of sperm numbers in highly diluted or concentrated samples. The objectives of this study were to validate a DNA assay for quantification of sperm numbers in extended or undiluted semen samples and to determine precision of the assay. The principle of the assay is based upon a fluorescent dye that binds to adenine-thymine base pairs in double-stranded DNA. Semen samples and calf thymus DNA standards were sonicated in 2 M NaCl buffer with 1 mM EDTA. The DNA content of samples was compared to standards of calf thymus DNA using fluorometry. Sensitivity of the assay was determined to be 1.4 x 10(5) sperm cells. Concentrations of sperm estimated from DNA assay values did not differ from flow cytometric cell counts. Assays were performed in three different laboratories, using different equipment, to assess the assay's repeatability. Estimates of sperm concentrations determined by the DNA assay were similar, regardless of location and source of equipment used to perform the assays. This assay fulfills statistical criteria for being sensitive, accurate, and repeatable, and it can be employed in laboratories processing semen for artificial insemination as a tool for spectrophotometer calibration, a check for straw filling accuracy, or to quantify sperm numbers in extended, packaged semen.

Animals↗
PubMed1989

Ability of the phototrophic bacterium Rhodospirillum rubrum to produce various poly (beta-hydroxyalkanoates): potential sources for biodegradable polyesters.

Studies have been carried out in order to optimize growth and culture conditions for the intracellular formation of poly(beta-hydroxyalkanoates) (PHA) in the phototrophic, purple, non-sulphur bacterium Rhodospirilum rubrum. Its potential to produce novel copolymers was investigated. Recently, it has become of industrial interest to evaluate these polyesters as potentially biodegradable plastics for a wide range of possible applications. On an industrial scale, the use of photosynthetic bacteria could harness sunlight as an energy source for the production of these materials. R. rubrum was grown anaerobically in the light on different linear and branched beta-hydroxycarboxylic acids and various n-alkanoic acids. Under nitrogen-limiting conditions a PHA content of up to 45% of cellular dry weight was detected. When R. rubrum was grown on different concentrations of various n-alkanoic acids, intracellular PHA production was detected on all acids used. In most of the cases, the storage polymer contained beta-hydroxybutyrate (HB) and beta-hydroxyvalerate (HV) monomer units. Grown on n-alkanoic acids with a chain length of four carbon atoms and more, R. rubrum produced a copolymer containing the beta-hydroxyhexanoate (HC) repeating unit in addition to the HB and HV monomer. Using beta-hydroxyheptanoic acid as the carbon source, a polyester which contained HB, HV, HC, and beta-hydroxyheptanoate was formed. These copolyesters represent a novel class of biodegradable thermoplastics. The results demonstrate the metabolic flexibility of R. rubrum to form many different types of polyesters which might substitute plastics synthesized from petrochemicals.

Ammonia↗
PubMed1988

Pseudomonas oleovorans as a Source of Poly(beta-Hydroxyalkanoates) for Potential Applications as Biodegradable Polyesters.

Pseudomonas oleovorans was grown in homogeneous media containing n-alkanoic acids, from formate to decanoate, as the sole carbon sources. Formation of intracellular poly(beta-hydroxyalkanoates) was observed only for hexanoate and the higher n-alkanoic acids. The maximum isolated polymer yields were approximately 30% of the cellular dry weight with growth on either octanoate or nonanoate. In most cases, the major repeating unit in the polymer had the same chain length as the n-alkanoic acid used for growth, but units with two carbon atoms less or more than the acid used as a carbon source were also generally present in the polyesters formed. Indeed, copolymers containing as many as six different types of beta-hydroxyalkanoate units were formed. The weight average molecular weights of the poly(beta-hydroxyalkanoate) copolymers produced by P. oleovorans ranged from 90,000 to 370,000. In spite of the higher cell yields obtained with octanoate and nonanoate, the use of hexanoate and heptanoate yielded higher-molecular-weight polymers. These copolyesters represent an entirely new class of biodegradable thermoplastics.

Journal Article↗
PubMed1988

Predicting fertility of dairy bulls by inducing acrosome reactions in sperm with chondroitin sulfates.

Bull spermatozoa were incubated with 0 or 50 micrograms/ml chondroitin sulfates to induce acrosome reactions in vitro. Data were computed as percent increase in acrosome reactions elicited by chondroitin sulfates compared with control samples for each replicate. Data from 8 bulls with known nonreturn rates served as basis to predict nonreturn rates of 18 bulls entering an AI lineup. The average assay CV was 16.1% for all 26 bulls. Correlation coefficients of polynomial regression lines computed between actual nonreturn rates and percent increases in acrosome reactions in response to chondroitin sulfates were .98 and .81 for the 8 reference bulls and combined data of all 26 bulls, respectively. It is concluded that a laboratory assay using chondroitin sulfates to induce acrosome reactions in sperm can be used to predict relative fertility of bulls.

Acrosome↗
PubMed1987

Glycosaminoglycans as probes to monitor differences in fertility of bulls.

Recently high molecular weight polysaccharides termed glycosaminoglycans have been successfully used to capacitate bull sperm in vitro. Heparin, one class of glycosaminoglycan, binds to sperm in a manner typical of receptor-ligand interaction. Bulls with above average nonreturn rates produce sperm that exhibit a higher frequency of acrosome reactions when exposed to glycosaminoglycans in vitro. In addition, the binding affinity that sperm possess for heparin is related to nonreturn rates of bulls, and binding affinity decreases in semen samples with a high frequency of abnormal sperm. Glycosaminoglycans may be useful probes to evaluate in vitro cellular changes that sperm complete prior to fertilization and serve as markers of sperm membrane defects, which ultimately affect fertility of a bull.

Animals↗
PubMed1985

Induction of acrosome reactions by chondroitin sulfates in vitro corresponds to nonreturn rates of dairy bulls.

This study was designed to relate nonreturn rates to induction of acrosome reactions by the glycosaminoglycan chondroitin sulfate. Semen samples were obtained from four bulls above and four bulls below 65% nonreturn. Washed sperm from four ejaculates from each bull were incubated for 9 h with 0, 1, 10, or 50 micrograms/ml chondroitin sulfate. Acrosome reactions were evaluated by microscopy with Nomarski optics. Sperm from the higher fertility bulls exhibited significantly higher percentages of acrosome reactions to 10 and 50 micrograms/ml of chondroitin sulfate, and the slope of their dose-response regression line was significantly greater.

Acrosome↗
PubMed1983

Proteoglycan production by bovine granulosa cells in vitro occurs in response to fsh.

Bovine granulosa cells from small (1-9 mm) or large (10-20 mm) follicles were incubated in a chemically defined medium containing 5 muCi/ml [3H]glucosamine, gonadotropins or polypeptide hormones, 8-Br-cAMP, theophylline or trifluoperazine (TFP). Radiolabeled proteoglycans were precipitated with 10% phosphotungstic acid. Maximum incorporation of isotope occurred in 45-60 min. Radiolabeled products were completely hydrolyzed with chondroitinase ABC. FSH, but not LH or hCG, yielded a significant log-dose response. High doses of hCG inhibited the ability of granulosa to respond to FSH. No other hormone altered the FSH dose-response curve. Addition of 8-Br-cAMP or theophylline mimicked the FSH response. The FSH effect was blocked by TFP, an inhibitor of calmodulin, but cAMP or theophylline overcame the effect of TEP. No distinct difference in response to these various compounds was noted between granulosa from small or large follicles. This system provides a biochemical marker for evaluating a mechanism of action for FSH.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1983

Chondroitin sulfate facilitates an acrosome reaction in bovine spermatozoa as evidenced by light microscopy, electron microscopy and in vitro fertilization.

Bovine epididymal spermatozoa were incubated for 22 h in a modified Tyrode's medium. The percentages of sperm exhibiting an acrosome reaction were determined morphologically after fixing and staining specimens. The addition of chondroitin sulfate A (CS-A) significantly increased the incidence of acrosome reaction. When observed by electron microscopy, acrosome-reacted sperm had undergone vesiculation of the plasma and outer acrosomal membranes. Sperm incubated in the presence of CS-A demonstrated a significantly higher incidence of vesiculation when compared to the controls. Additionally, rates of in vitro fertilization of bovine oocytes were significantly elevated when sperm and ova were exposed to CS-A. These results suggest that glycosaminoglycans in the female reproductive tract may be responsible for some of the biochemical changes associated with fertilization, and a light microscope procedure can be used to assess occurrence of the acrosome reaction.

Acrosome↗
PubMed1983

Factors affecting successful in vitro fertilization of bovine follicular oocytes.

These experiments were designed to define and optimize the efficiency of a system whereby bovine oocytes could be fertilized in vitro. The frequency of ova penetrated and the stage of fertilization were the end points examined. All experiments utilized cumulus-oocyte complexes from 1- to 5-mm follicles which were matured in vitro prior to fertilization. The experiments were designed to examine the effects of the following factors on fertilization: 1) pretreatment of sperm with ionomycin (a Ca++ ionophore), 2) preincubation of sperm at a high concentration and the presence of hypotaurine and epinephrine during fertilization, 3) the use of either follicle-stimulating hormone (FSH) or cAMP for the induction of cumulus expansion prior to fertilization, and 4) the need for the presence of cumulus cells during fertilization. Sperm exposure to ionomycin or preincubation at high sperm concentrations was not necessary for fertilization. The presence of hypotaurine and epinephrine during fertilization improved (P less than 0.05) the quality of fertilization (i.e., higher frequencies of oocytes with both female and male pronuclei were observed). However, they did not increase the percentage of ova penetrated (P greater than 0.05). Fertilization frequencies were not different (P greater than 0.05) between oocytes with cumulus expansion induced by FSH or cAMP. However, the use of either treatment resulted in higher fertilization rates when compared to untreated controls (P less than 0.05). Finally, while the presence of cumulus cells was not necessary for penetration of ova, increased frequencies of ova with both male and female pronuclei were found when cumuli were present (P less than 0.05).

Animals↗
PubMed1983

In vitro maturation and fertilization of bovine oocytes are temperature-dependent processes.

Effects of temperature on bovine sperm acrosome reaction, oocyte maturation, hyaluronic acid production by cumulus cells and in vitro fertilization were studied. Viability and a true acrosome reaction of bovine spermatozoa were impaired at 40 degrees C. Temperatures lower than 35 degrees C did not enhance the acrosome reaction. However, viability between 30 degrees C-38 degrees C was not altered after 22 h of incubation. The optimal temperature for the acrosome reaction was 38 degrees C. Labeled glucosamine incorporation into glycosaminoglycans was not different among temperatures of 35 degrees C, 37 degrees C or 39 degrees C, whereas 41 degrees C caused a significant reduction (P less than 0.02). Temperatures ranging between 35 degrees C-39 degrees C had no deleterious effects on resumption and completion of meiosis, but at 41 degrees C the frequency of oocytes that progressed to Metaphase II was significantly reduced (P less than 0.0001). Ova matured at 39 degrees C had significantly higher rates of fertilization than at 35 degrees C, 37 degrees C, or 41 degrees C. Killed spermatozoa (control) had no effect on ovum activation at 39 degrees C. From these results it was concluded that events occurring prior to and during fertilization are temperature sensitive.

Acrosome↗