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Biomedical subjects

W H Johnson

Publications and source records attributed to W H Johnson.

At least 109 records · Page 6Linked to original sources
PubMed1981

Termination of pregnancy with cloprostenol and dexamethasone in intact or ovariectomized cows.

Termination of pregnancy in cows was investigated using sham-operated (SH) or ovariectomized (OV) cows treated with either a saline vehicle (V), cloprostenol (PG), dexamethasone (DEX) or dexamethasone and cloprostenol (DEX+PG). Surgery was done at 210 days of pregnancy and treatment was administered 72 hours later. Days (mean+/-S.E.) from treatment to termination of pregnancy for the treatment groups were: sham-operated +vehicle (SH+V): 61.5+/-11.3; ovariectomized+vehicle (OV+V): 53.4+/-15.7; sham-operated+cloprostenol (SH+PG): 61.8+/-1.7; ovariectomized+cloprostenol (OV+PG): 54.5+/-13.1; shamoperated+dexamethasone (SH+DEX): 74.8+/-4.8; ovariectomized+dexamethasone (OV+DEX): 2.8+/-0.4; shamoperated+dexamethasone+cloprostenol (SH+DEX+PG) 26.0+/-23.0; ovariectomized+dexamethasone+cloprostenol (OV+DEX+PG): 7.2+/-4.9. Pregnancies in the OV+DEX and OV+DEX+PG groups were terminated significantly earlier than in all other groups (P<0.05) except the SH+DEX+PG group. These findings suggest that dexamethasone will terminate pregnancy in cows near seven months of gestation after the ovarian source of progesterone has been removed by either an injection of prostaglandin or by ovariectomy.

Abortion, Induced↗
PubMed1980

Pathophysiology of inner ear dysfunction in the squirrel monkey in rapid decompression.

More than 90 squirrel monkeys with bilateral myringotomies (a small hole in each ear drum) were rapidly decompressed in a hyperbaric chamber according to a special diving profile in which 35% of attempts produced disorders ("hits") confined to the inner ear. Monkeys receiving inner ear hits (as determined by the sudden onset of vigorous head or eye nystagmus during decompression) were tested and killed at times ranging from 1 h to more than 12 mo following the dive. Histologically, in monkeys killed 1 mo or less after the hit, hemorrhage and/or a deep purple-staining precipitated material were frequently found in the otic fluid spaces. In those monkeys killed more than 1 mo after a hit, ectopic new bone growth in the arms of the semicircular canals was a common sequela. New bone growth never appeared in the cochlea. In unaffected ears, and in both ears of control animals, the precipitated material was somewhat less than in ears damaged by decompression; and, furthermore, new bone growth did not occur. Behaviorally, the hit monkeys showed vestibular deficits that were consistent with the structural damage revealed by histology.

Animals↗
PubMed1980

Induced vestibular dysfunction in squirrel monkeys during rapid decompression.

The symptoms of postural instability and dizziness associated with decompression sickness could be ascribed to either damage of the vestibular apparatus or to central nervous system damage. However, a histological study of monkeys exposed to decompression reveals that these symptoms primarily result from damage to the vestibular apparatus (unless there are accompanying central deficits). Furthermore, the damage is of a type that causes new bone growth to occlude the otic fluid spaces of the semicircular canals. In some instances, there is sufficient bone growth to render the cristae ampullares as non-functional end organs. Such diminished vestibular function would present a serious threat to the diver.

Animals↗
PubMed1980

Variation of lactoferrin and mastitis and their heritabilities.

Analyses were of lactoferrin and mastitis of milk samples taken every other month from 830 Holstein cows in eight herds for 1 yr. Patterns of variation and amounts in lactation, colostrum, and dry period were similar to reports. In negative mastitis tests of milk samples, lactoferrin content was lower during lactation and lower as age of the cow advanced than for positive tests. However, heritability of mastitis was .14, whereas for lactoferrin was .44 in records of 289 cows. This latter is high enough to be useful but unreliable with large standard error .30. Several sire groups differed significantly.

Animals↗
PubMed1979

Phosphorylation of paramyosin and its possible role in the catch mechanism.

Paramyosin isolated from the adductor muscle of Mercenaria mercenaria was shown to contain three to five phosphate groups/molecule; the actual number varied depending on the method used to extract the protein. Dephosphorylation resulted in an increase in the solubility of paramyosin near pH 7 and near physiological ionic strength. This behavior suggests that the number of phosphates/molecule may be a determining factor in the aggregation behavior of paramyosin-containing myofilaments. Thus, phosphorylation may be involved in catch contractions since correlations have been demonstrated earlier between catch contraction of molluscan muscles and aggregation properties of paramyosin (Ruegg, J. C. (1971) Physiol. Rev. 51, 201-249).

Animals↗
PubMed1979

Nontraumatic rupture of renal allografts.

Eight cases of nontraumatic renal allograft rupture were identified in 237 renal transplants performed at UCLA Medical Center. Careful clinicopathologic studies in these patients suggest three principal underlying causes: major graft vessel occlusion, hyperacute or accelerated rejection, and acute rejection. The clinical and pathologic features of these various categories are compared and contrasted.

Cadaver↗
PubMed1979

Oculogravic illusion in response to straight-ahead acceleration of CF-104 aircraft.

Experimental subjects wore goggles that restricted monocular vision to a luminous line fixed relative to the head, and they were exposed on one occasion to a straight-ahead acceleration of an aircraft and on another occasion to a tilting chair. The magnitude of change of direction of the resultant accleration was the same on both occasions, but the perceived movement of the luminous line from the two stimuli was very different. In response to the aircraft stimulus, the oculogravic illusion was experienced and the luminous line was perceived as tilting relative to the subject, in response to the tilting chair stimulus, the line was perceived as remaining fixed relative to the subject. It was concluded that the oculogravic illusion, as experienced in the aircraft (and previously in centrifuges), is a true illusion and not merely a fact of physics.

Acceleration↗
PubMed1978

Caffeine contracture and iodoacetate rigor in frog skeletal muscle. A comparison.

Frog sartorius muscle treated with 5.0 mM or greater caffeine exhibits stiffness similar to that obtained from muscle in iodoacetate rigor. The data provide quantitative evidence that suggests that caffeine at irreversible contracture-producing concentrations somehow induces a rigor or rigorlike state in skeletal muscle.

Animals↗
PubMed1977

Peptido-aminobenzophenones--novel latentiated benzo-1,4-diazepines.

It has been shown that cleavage of the N-terminal L-amino acids of a novel series of dipeptide derivatives of 2-aminobenzophenones occurs readily in vivo to give benzo-1,4-diazepines. Such compounds may serve as useful pro-drug forms of minor tranquilizers such as Valium.

Animals↗
PubMed1977

Comparison of solubility properties of alpha-paramyosin, beta-paramyosin and acid-extracted paramyosin.

The solubility properties of paramyosin in the zones of pH and ionic strength in which aggregation occurs were initially studied using preparations isolated by a method originally described by Bailey (Bailey, K. (1956), Pubbl. Stn. Zool. Napoli 29, 26). Other preparations yielding apparently different protein components have been described by Hodge (Hodge, A.J. (1952), Proc. Natl. Acad. Sci., U.S.A. 38, 850) using acid conditions, and Stafford and Yphantis (Stafford, W.F., AND Yphantis, D. (1972), Biochem. Biophys. Res. Commun. 49, 848) have identified alpha-, beta-, and gamma-paramyosin using various times and temperatures of extraction with or without ethylenediaminetetraacetic acid. We have found that acid-extracted paramyosin is very similar if not identical to alpha-paramyosin, but that both acid and alpha forms differ considerably from beta- and gamma-paramyosin. Beta-Paramyosin precipitates abruptly from solution in narrow zone of pH below neutrality, and increases in ionic strength shift the zone of precipitation toward lower pH values. In contrast, both acid and alpha-paramyosin show gradual aggregation with changing pH at lowerionic strength (less than 0.3) but sharp transitions similar to beta-paramyosin at higher ionic strength (greater than 0.3). Transitions were also found at lower pH (ca. 4.0) which were not mirror images of transitions at higher pH (ca. 7.0). Viscosity measurements show that acid extracted paramyosin is close in behavior to a native extract obtained by extraction in mild, nondenaturing media containing mixed antibiotics. Each of these extracts differed considerably from beta-paramyosin. Mild, nonhydrolytic procedures employed by others to remove small, noncovalent bonded components or to separate protein complexes were not effective in converting alpha- to beta-paramyosin. Comparison of extraction procedures strongly supports the suggestion of Stafford and Yphantis that beta- and gamma-paramyosin are hydrolytic products of alpha-paramyosin and that the proteases responsible may be of bacterial origin.

Animals↗
PubMed1977

Solubility properties of alpha-reduced paramyosin.

It is now believed that the reduced form of alpha-paramyosin is that found in living adductor muscles of molluscs. We have studied the solubility of a preparation of alpha-paramyosin obtained under reducing conditions. In contrast to the solubility profile of beta-paramyosin, the alpha-paramyosin, the alpha-preparation showed a rapid, almost linear decrease in solubility over the ionic strength range 0.35-0.25 at neutral pH. Solubility in this range was further decreased by the presence of physiologically small amounts of calcium ion. Lactate ion, which can accumulate during anaerobic glycolysis in molluscan muscles, also decreases the solubility at a level of 50 mM. In addition, the type of paracrystal formed by alpha-paramyosin differs greatly from those of beta-paramyosin and paracrystal formed in the presence of lactate differs from those formed in buffer solutions. Reduced alpha-paramyosin is more sensitive to the above parameters than the preparations made without reducing agents. Moreover, the pH and ionic strength ranges in which greatest change in solubility behaviour occurs are physiologic, as are the calcium and lactate ion levels effective in increasing intermolecular interactions. A model is proposed for alpha-paramyosin in which the extra 5% presumably removed in beta preparations is a "sticky head" which protrudes from one end of the molecule and confers on it an increased tendency for interaction, particularly at physiological ionic strength. Such molecules would be capable of promoting interactions between thick filaments which contain them, providing a means of accounting for the pH dependent stiffness observed in glycerinated preparations of molluscan catch muscles.

Animals↗
PubMed1977

Hearing under stress: II. Effect of hyperventilation and hypercapnia on speech discrimination.

Changes in the ability to discriminate speech from a eucapnic state to hyperventilation and hypercapnia were investigated. Standard speech audiometric techniques were employed to determine the speech reception threshold and the speech discrimination values, while respiratory conditions were varied and measured utilizing a mixed-gas breathing method. Respiratory parameters were similar to those encountered in aircraft personnel who experience oxygen/pressure system malfunction. The results of the study suggest no significant change in the speech reception threshold while in a hyperventilated or hypercapnic state. The speech discrimination results, however, suggest a significant performance decrement while in a state of hyperventilation.

Auditory Perception↗
PubMed1977

Comprehensive presentation of semicircular canal sensitivity.

It is generally agreed that in order to determine any difference in vestibular sensitivity between the two inner ears, the best clinical procedure involves a quantitative expression of the slow phase nystagmus response to standardized caloric (or rotatory) stimulation. The preferred procedure has involved averaging the slopes of a few of the nystagmus responses during the period of most intense activity and this has been accomplished either arithmetically or by means of an electronic computer. Although, such a sampling is often sufficient to enable a reliable diagnosis, occasions do arise when the results can be misleading unless comprehensive total presentations of the responses from the two labyrinths are available for reliable comparative evaluation. Such a procedure has been developed at the University of Toronto and used for clinical assessment at St. Michael's Hospital. The reliability of the method has been established as the result of testing over 800 patients with various vestibular disorders.

Caloric Tests↗