Biomedical subjects
Publications and source records attributed to W H Johnson.
Bull fertility depends partially on the quality of the spermatozoa (i.e., different spermatozoa defects) produced in the ejaculate, emphasizing the importance of the interpretation of the spermeogram results. This article discusses the production of normal and abnormal spermatozoa and the influence that spermatozoa defects may have on bull fertility.
1. Ro 32-3555 (3(R)-(cyclopentylmethyl)-2(R)-[(3,4,4-trimethyl-2,5-dioxo-1- imidazolidinyl)methyl]-4-oxo-4-piperidinobutyrohydroxamic acid) is a potent, competitive inhibitor of human collagenases 1, 2 and 3 (Ki values of 3.0, 4.4 and 3.4 nM, respectively). The compound is a selective inhibitor of collagenases over the related human matrix metalloproteinases stromelysin 1, and gelatinases A and B (Ki values of 527, 154 and 59 nM, respectively). 2. Ro 32-3555 inhibited interleukin-1 alpha (IL-1 alpha)-induced cartilage collagen degradation in vitro in bovine nasal cartilage explants (IC50 = 60 nM). 3. Ro 32-3555 was well absorbed in rats when administered orally. Systemic exposure was dose related, with an oral bioavailability of 26% at a dose of 25 mg kg-1. 4. Ro 32-3555 prevented granuloma-induced degradation of bovine nasal cartilage cylinders implanted subcutaneously into rats (ED50 = 10 mg kg-1, twice daily, p.o.). 5. Ro 32-3555 dosed once daily for 14 days at 50 mg kg-1, p.o., inhibited degradation of articular cartilage in a rat monoarthritis model induced by an intra-articular injection of Propionibacterium acnes. 6. Ro 32-3555 is a potential therapy for the treatment of the chronic destruction of articulating cartilage in both rheumatoid and osteoarthritis.
The pluripotency of embryonic germ cells in the mouse suggests that mitotic bovine fetal germ cells might also be a source of pluripotent cells. To investigate the pluripotency of bovine oogonia, the development in vitro of bovine embryos reconstructed by fusing oogonia with enucleated oocytes was compared with that of embryos made similarly with either blastomeres or granulosa cells. The donor cells (fresh oogonia, cryopreserved oogonia, 16- to 32-cell-stage blastomeres, or granulosa cells) were fused to the enucleated oocytes electrically. The proportions of reconstructed embryos that had cleaved at 40 h after fusion using these types of donor cells were not significantly different (37%, 33%, 56%, and 31%, respectively; p > 0.05). However, the proportions of cleaved reconstructed embryos that developed to the blastocyst stage were 9%, 13%, 36%, and 3%, respectively, significantly higher (p < or = 0.05) with blastomeres than with the other three types of donor cells. After transfer of 3 morulae and 4 blastocysts made with oogonia into three recipient heifers, embryonic and extra-embryonic tissues developed in one animal. On recovery after 43 days gestation, this conceptus was shown to be genetically identical, at 11 microsatellite loci, to the fetus that had provided the oogonia. Cytological analysis of the embryos made with oogonia at 40-44 h after fusion and at the morula and blastocyst stages revealed that aberrant cytokinesis and nucleokinesis had given rise to multinucleated, anucleate, and polyploid cells in the reconstructed embryos. It is concluded that limited pluripotency of bovine oogonia has been demonstrated, warranting further study in this area.
The risk index Lost Life Expectancy Rate (LLER) provides a unitless number (time of life expectancy lost per time exposed) describing the risk from exposure to a given hazard or from partaking in a given activity. Simple equations to calculate the LLER from radiation-induced cancers caused by an exposure to low-level radiation were derived using the relative risk models developed by the Nuclear Regulatory Commission (upper bound estimate), the United Nations Scientific Committee on the Effects of Atomic Radiation-1988, and the National Academy of Science's Committee on the Biological Effects of Ionizing Radiation (BEIR V). Estimates of the LLER to an average person from a continuous exposure to 0.1 microSv h(-1) based on these models, respectively, are 5.5 x 10(-4), 9.5 x 10(-4), and 9.4 x 10(-4). These values compare to LLERs of 0.015 from occupational accidents, 0.25 from being an automobile passenger, and 2.0 from cigarette smoking. Factors effecting LLER from radiation exposures examined in this work include dose rate, age, sex, race and smoking status.
The current study examined the contributions of angiotensin-converting enzyme (ACE) vs. chymase to angiotensin II (ANG II) generation in membrane preparations from left ventricles of humans, dogs, rabbits, and rats and from total heart of mice. ACE and chymase activity were measured in membrane preparations extracted with low or high detergent (LD and HD, respectively) concentrations. We hypothesized that ACE, which is membrane bound in vivo, would be preferentially localized to the HD preparation, whereas chymase, which is localized to the cytoplasm and cardiac interstitium, would be localized to the LD preparation. In human heart, ACE activity was 16-fold higher in the HD than in the LD preparation, whereas chymase activity was 15-fold higher in the LD than in the HD preparation. Total ANG II formation was greater in human heart [15.8 +/- 3.4 (SE) micromol ANG II x g(-1) x min(-1)] than in dog, rat, rabbit, and mouse hearts (3.90 +/- 0.35, 0.41 +/- 0.02, 0.61 +/- 0.07, and 1.16 +/- 0.08 micromol ANG II x g(-1) x min(-1), respectively, P < 0.05, by analysis of variance). ANG II formation from ACE was higher in mouse heart (1.09 +/- 0.05 micromol ANG II x g(-1) x min(-1), p < 0.001) than in rabbit, human, dog, and rat hearts (0.55 +/- 0.06, 0.34 +/- 0.01, 0.32 +/- 0.06, and 0.31 +/- 0.02 micromol ANG II x g(-1) x min(-1), respectively). In contrast, chymase activity was higher in human heart (15.3 +/- 3.4 micromol ANG II x g(-1) x min(-1)) than in dog, rat, rabbit, and mouse hearts (3.59 +/- 0.29, 0.10 +/- 0.01, 0.06 +/- 0.01, and 0.07 +/- 0.01 micromol ANG II x g(-1) x min(-1), respectively). Our results demonstrate important species differences in the pathways of intracardiac ANG II generation. Chymase predominated over ACE activity in human heart, accounting for extremely high total ANG II formation in human heart compared with dog, rat, rabbit, and mouse hearts.
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BACKGROUND: Continuous intravenous administration of adenosine to humans often results in a paradoxical rise in pulmonary capillary wedge pressure (PCWP), whereas arterial resistance is lowered and cardiac output and heart rate increase. This is believed to be due to diastolic stiffening of the ventricle or to a negative inotropic effect. In the present study, we tested these and other mechanisms by using pressure-volume (PV) analysis and echocardiography. METHODS AND RESULTS: Fifteen patients with normal rest left ventricular function underwent cardiac catheterization and received adenosine at a rate of 140 micrograms/kg per minute IV for 6 to 10 minutes. PV relations were measured in 9 patients (without coronary artery disease) using the conductance catheter method. In 6 additional patients with coronary artery disease, echocardiograms were used to assess wall thickness and function, and aortic and coronary sinus blood, lactate, oxygen, and adenosine levels were measured. Adenosine increased PCWP by 19% (+2.6 mm Hg) in both patient groups while lowering arterial load by 30% and increasing cardiac output by 45% (all P < .001). There was no significant effect of adenosine on mean linear chamber compliance or monoexponential elastic stiffness, as the diastolic PV relation was unchanged in most patients. Diastolic wall thickness also was unaltered. Thus, the PCWP rise did not appear to be due to diastolic stiffening. Adenosine induced a rightward shift of the end-systolic PV relation (ESPVR) (+12.7 +/- 3.7 mL) without a slope change. This shift likely reflected effects of afterload reduction, as other indexes (stroke work-end-diastolic volume relation and dP/dtmax at matched preload) were either unchanged or increased. Furthermore, this modest shift in ESPVR was more than compensated for by vasodilation and tachycardia, so reduced systolic function could not explain the increase in PCWP. There also was no net lactate production to suggest ischemia. Rather than arising from direct myocardial effects, PCWP elevation was most easily explained by a change in vascular loading, as both left ventricular end-diastolic volume and right atrial pressure increased (P < .05). This suggests that adenosine induced a redistribution of blood volume toward the central thorax. CONCLUSIONS: PCWP elevation in response to adenosine primarily results from changes in vascular loading rather than from direct effects on cardiac diastolic or systolic function.
The blastomeres of two in vitro derived four-cell embryos were separated and transferred individually into surrogate zonae pellucidae, then co-cultured with bovine oviductal epithelial cells for five days until blastulation. Pairs of the quarter blastocysts were co-transferred with trophoblastic vesicles into each of four synchronised Holstein heifers, three of which were diagnosed pregnant at 28 days gestation, carrying twin fetuses. Four genetically identical bull calves were delivered by elective caesarean section at term pregnancy. One pregnancy was terminated at 56 days.
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Scrotal circumference has been recommended as a clinical test for predicting the fertility potential of yearling bulls. The objectives of this study were to determine if scrotal size of yearling bulls influences herd fertility and to investigate specific causal pathways. Calving records from 44 herds enrolled in the Beef Herd Improvement Plan were selected from the data base for 1984 to 1989. Logistic regression was used to model the event of calving within the first 3 wk of the calving season as a function of scrotal circumference, herd size, age and the interactions of scrotal circumference with age, scrotal circumference with herd size, and herd size with age and the random effects of herd. The odds of cows calving in the first 3 weeks of the calving season were lower in large herds (>30 vs 20 to 30 calves born per season) and with younger yearling bulls (12 to 15 vs. 16 to 18 months of age). Early calving was not associated with scrotal circumference, or the interactions scrotal circumference with herd size and scrotal circumference with age (p > 0.15). It was concluded that the female:male ratio and age of bull both affected the odds of a cow calving early, but neither of the associations was altered by selection for bulls with a larger scrotal circumference, and therefore scrotal circumference is not included in either of the 2 causal pathways.
Purebred Hereford and Simmental bulls (n = 120), managed similarly to bulls in the Ontario Bull Evaluation Program, were evaluated for reproductive parameters. Four diets, equivalent except for the form of dietary fiber, were fed in a growth performance trial. Diet had no direct effect (P > 0.10) on any of the reproductive variables examined. Of the 117 bulls that had complete breeding soundness evaluations, 75% were classified as satisfactory potential breeders, 24% as questionable potential breeders and 1% as unsatisfactory potential breeders. The 2 breeds were significantly different (P < 0.05) for several end of test parameters. When controlling for age and weight differences, Herefords had a higher backfat thickness, smaller scrotal circumference, lower paired testicular weight and lower epididymal weight. Semen morphology and motility did not differ (P > 0.10) between the breeds. When examining simple correlations, scrotal circumference was highly correlated with paired testicular weight, moderately correlated with epididymal weight, daily sperm production and extragonadal sperm reserves, and negatively correlated with backfat thickness. Scrotal circumference was not related to backfat thickness when controlling for breed effects. The degree of germinal epithelium loss was moderately and negatively correlated with the percentage of spermatozoa with normal morphology and progressive motility, epididymal sperm reserves and epididymal weight, but was not correlated with scrotal circumference.
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Beginning on Day 10 or 11 of the estrous cycle, mature Holstein heifers were given a superovulatory regimen of twice-daily injections of porcine FSH, together with injections of PG with the fifth and sixth FSH injections. Every 12 h from 24 to 60 h after PG administration, the animals received im injections of different doses of the LH releasing hormone antagonist [N-Ac-D-Nal(2)(1), D-pCl-Phe(2), D-Trp(3), D-Arg(6), D-Ala(10)]-LHRH or vehicle. Follicular development was monitored by transrectal ultrasonography every 12 h from 24 to 120 h after PG administration. All animals were given hCG at 72 h after PG injection, and were artificially inseminated. At Day 7 of gestation, the corpora lutea were counted by ultrasonography, and embryos were collected by nonsurgical flushing of the uterus. Treatment with the antagonist resulted in a dose-dependent decrease in the amplitude of the LH surge and in delays in the time of occurrence of the LH surge, ovulation and the shift from estradiol to progesterone production. These results indicate that LHRH antagonists can be used to delay the LH surge and ovulation in superovulated heifers. This finding may be beneficial to studies in the superovulation of cattle.
In rheumatoid and osteoarthritis, degradation of articular cartilage is mediated by the matrix metalloproteinases collagenase, stromelysin and gelatinase. The key event in this process is the cleavage of triple helical collagen by collagenase. We have determined the crystal structure of the catalytic domain of human recombinant fibroblast collagenase complexed with a synthetic inhibitor at 2.2 A resolution. The protein fold is similar to the amino termini of the zinc endopeptidases astacin thermolysin and elastase despite a lack of primary sequence homology. The conformation of the bound inhibitor provides a molecular basis for the design of inhibitors of collagenase and other matrix metalloproteinases. Such inhibitors should be useful in the treatment of a variety of diseases including arthritis and cancer.
Shape change and motility of polymorphonuclear leukocytes (PMNs) are essential for host defense and require dynamic reorganizations of microfilamentous cytoskeleton by reversible polymerization of G-actin into filaments (F-actin). Although clinical disorders of actin polymerization are rare, recently described simple methodologies for assaying actin dynamics in PMNs make the technique readily applicable to clinical studies. To develop a clinically useful F-actin assay, the authors investigated the optimal preparation conditions for PMN isolation that resulted in the least in vitro cytoskeletal activation and evaluated the variability in actin dynamics in acutely and chronically infected patients. Basal and chemotactic factor-activated PMN F-actin content was measured by a previously described flow cytometric technique in fixed, permeabilized, NBDphallacidin-stained PMNs isolated by centrifugation in Percoll or Ficoll-Hypaque density gradients or by countercurrent elutriation. F-actin content is expressed as mean fluorescent channel or relative fluorescence intensity. Basal F-actin in PMNs prepared from countercurrent elutriation (mean fluorescent channel = 79.0 +/- 4.5, n = 6) or by Ficoll Hypaque (82.0 +/- 3.5, n = 4) was significantly higher than endotoxin free, Percoll purified PMNs, whether purified in bulk (56.1 +/- 7.9, n = 8) or by the small volume modification applicable to clinical studies (53.3 +/- 8.7, n = 15). Basal Ficoll Hypaque purified PMNs have evidence of shape change, whereas endotoxin free, Percoll purified PMNs are smooth and round and represent the most basal cell equivalent in F-actin content to a circulating PMN.(ABSTRACT TRUNCATED AT 250 WORDS)
BACKGROUND: There is increasing recognition of myocardial angiotensin-converting enzyme, which is induced with the development of left ventricular hypertrophy (LVH). The potential physiological significance of subsequent increased angiotensin I to II conversion in the presence of LVH is unclear but has been postulated to cause abnormal Ca2+ handling and secondary diastolic dysfunction. Accordingly, we hypothesized that acute angiotensin-converting enzyme inhibition would result in decreased production of angiotensin II and improved active (Ca(2+)-dependent) relaxation in patients with hypertensive LVH. METHODS AND RESULTS: Intracoronary (IC) enalaprilat was administered to 25 patients with and without LVH secondary to essential hypertension. Indexes of diastolic and systolic LV function were determined from pressure (micromanometer)-volume (conductance) analysis at steady state and with occlusion of the inferior vena cava. Patients were divided into those receiving high- (5.0 mg, n = 15) and low-dose (1.5 mg, n = 10) IC enalaprilat during a 30-minute infusion at 1 mL/min. The high-dose patients were further divided along the median normalized LV wall thickness of 0.671 cm/m2. The time constant of isovolumic relaxation (TauL) was prolonged at baseline in patients receiving high-dose enalaprilat with wall thickness > 0.671 cm/m2 (TauL, 56 +/- 2 versus 44 +/- 2 and 45 +/- 2 milliseconds, respectively, P < .01 by ANOVA) and shortened only in this patient group (TauL, 49 +/- 3 versus 46 +/- 2 and 43 +/- 2 milliseconds, respectively, P < .01 versus baseline and other groups by ANOVA). The improvement in TauL was directly proportional to the degree of LVH (r = .92, P < .001). Although there was a decrease in LV end-diastolic pressure (23 +/- 2 to 15 +/- 1 mm Hg, P < .01) and volume (86 +/- 8 to 67 +/- 9 mL/m2, P < .05) in those patients with a reduction in TauL, this is due to movement down a similar diastolic pressure-volume relation with no change in chamber elastic stiffness (0.023 +/- 0.002 to 0.025 +/- 0.004 mL-1, P = NS). CONCLUSIONS: Intracoronary enalaprilat resulted in an improvement in active (Ca(2+)-dependent) relaxation in those patients with more severe hypertensive LVH. The improvement in active relaxation was directly proportional to the severity of LVH. These results support the hypothesis that the cardiac renin-angiotensin system is an important determinant of active diastolic function in hypertensive LVH.
Pulmonary hypertension in congestive heart failure causes medial hypertrophy in pulmonary vessels and thickening of the endothelial basement membrane. In this study, the functional consequences of such pulmonary vascular adaptations were evaluated. Heart failure was induced in dogs by rapid ventricular pacing (240 beats per minute) for 28 days, at which time left ventricular shortening fraction was decreased by 57% compared with that at baseline. Lung lobes from paced (n = 56) and control dogs (n = 68) were isolated and perfused with autologous blood. Total, arterial (Ra), and venous (Rv) vascular resistances were significantly increased and vascular capacitance decreased in lobes from paced animals compared with controls. Increments in Ra and Rv after intra-arterial boluses of norepinephrine were measured before and after sequential addition of the alpha 1- and alpha 2-receptor antagonists prazosin (16 mumol/L) and yohimbine (0.1 mumol/L) in the presence or absence of propranolol (5 mumol/L). Norepinephrine (1 to 40 micrograms) had little effect on Ra in the absence of propranolol, a pattern that persisted in control lobes after propranolol. However, when lobes from paced animals were pretreated with propranolol, norepinephrine increased Ra, Rv was increased after norepinephrine in control lobes, an effect that was enhanced in the paced group. In both groups, the increment in Rv was greater after propranolol. Irrespective of propranolol pretreatment, prazosin significantly attenuated, if not abolished, the response to norepinephrine. The enhancement in venous vascular reactivity in lobes from paced animals remained when venous pressure was elevated to 20 cm H2O. In control lobes under conditions of elevated tone or when endothelium-dependent relaxing factor was blocked, responses to norepinephrine did not mimic those observed in the paced group. Microvascular permeability, as measured by the capillary filtration coefficient, was not altered in the paced group. We conclude that the pulmonary adaptations to 4 weeks of rapid ventricular pacing include functional changes in pulmonary hemodynamics and vascular reactivity but not in microvascular permeability.
Semen was collected from 12 Hereford and 10 Simmental bulls at the conclusion of a 119-day Record of Performance growth trial. Within each breed, the bulls were fed a standard test ration (Diet 1) or an experimental diet consisting entirely of a pelleted concentrate with ground corn cobs as the primary fibre source (Diet 2). Semen was analyzed for motility and morphology while testicular tissue obtained at slaughter the day after semen collection was assessed for seminiferous tubule integrity; none of these parameters varied significantly with breed or diet. The fluidity of head plasma membranes from the spermatozoa was assessed with fluorescence polarization using tPNA. Fluidity decreased over the 160 minute observation period, indicating molecular rearrangments within the head membranes which may reflect sperm changes preceding fertilization. The fluidization displayed a breed-by-diet interaction since membrane fluidity differed significantly between breeds on Diet 1 and between diets for Simmental bulls. Fluidities of some samples were also analyzed with cPNA, and these differed significantly from those obtained with tPNA, indicating the presence of domains in sperm head membranes. Neither diet nor breed affected traditionally measured semen characteristics of Hereford and Simmental bulls, but the membrane dynamics differed between the 2 breeds, and diet affected the sperm membrane dynamics of Simmental bulls.