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Biomedical subjects

D Duvall

Publications and source records attributed to D Duvall.

At least 19 recordsLinked to original sources
PubMed2000

Complications of plasma exchange in 71 consecutive patients treated for clinically suspected thrombotic thrombocytopenic purpura-hemolytic-uremic syndrome.

BACKGROUND: With the increased frequency of diagnosis and improved survival of thrombotic thrombocytopenic purpura-hemolytic-uremic syndrome (TTP-HUS), the morbidity of plasma exchange (PE) treatment has become more important. STUDY DESIGN AND METHODS: Data were prospectively collected on 71 consecutive patients referred to the Oklahoma Blood Institute (OBI) for PE treatment for clinically suspected TTP-HUS from mid-1996 to mid-1999. Complications were defined as major or minor, and distinguished between those related to central venous catheter access or to the plasma. RESULTS: Twenty-one patients (30%) had 27 major complications, which caused two deaths. The major complications included 2 episodes of hemorrhage after subclavian line insertion (1 death), 1 pneumothorax requiring a chest tube, 12 systemic infections (1 death), 7 episodes of catheter thrombosis requiring removal of the central venous catheter, 2 episodes of venous thrombosis requiring anticoagulant treatment, 2 episodes of hypoxemia and hypotension, and 1 episode of serum sickness. Minor complications occurred in 22 additional patients (31%). Twenty-eight patients (39%) had no complications. CONCLUSIONS: The morbidity and mortality of catheter placement and PE are important considerations when PE treatment for clinically suspected TTP-HUS is anticipated.

Bacteremia↗
PubMed1998

Thrombotic thrombocytopenic purpura-hemolytic uremic syndrome: diagnosis and management.

Thrombotic thrombocytopenic purpura-hemolytic uremic syndrome (TTP-HUS) is a clinical syndrome defined by the presence of thrombocytopenia and microangiopathic hemolytic anemia without a clinically apparent etiology. Patients may also have multiple other symptoms and signs including neurologic and renal abnormalities and fever. In the era prior to effective therapy with plasma exchange, most patients developed multisystem abnormalities and the syndrome was more easily recognized. Now, since there is urgency to begin treatment, sufficient diagnostic criteria for TTP-HUS are only thrombocytopenia and microangiopathic hemolytic anemia without a clinically apparent cause; patients may have no neurologic symptoms, renal abnormalities, or fever. This has lead to an apparent increased incidence because of both the increased importance of early recognition and the decreased specificity of the diagnostic criteria. Effective treatment has also revealed new aspects of the clinical course of TTP-HUS following the initial response to plasma exchange treatment: prompt exacerbations, which are common when plasma exchange is diminished in frequency or discontinued, and later relapses, which may occur many years after the initial episode. This review describes the evolution of the syndrome of TTP-HUS in the current era of effective treatment, and describes the management and clinical outcomes among patients treated by the Oklahoma Blood Institute.

Hemolytic-Uremic Syndrome↗
PubMed1997

Straight-line movement and competitive mate searching in prairie rattlesnakes, Crotalus viridis viridis

Males compete in various ways for mating and reproductive success. Phylogenetic factors and local ecology affect female spatial and temporal distributions, which in turn influence the form of male competition, sexual selection and mating systems. In prairie rattlesnake, Crotalus viridis viridispopulations where (1) males seek females during a brief reproductive period, (2) females are relatively few, and (3) females are widely and unpredictably distributed spatially into small discrete clusters, males should show efficient mate searching more so than time-consuming 'handling' (e.g. fighting, mate persuasion). Natural history studies and computer and mathematical modelling generate this expectation. This long-term field study of prairie rattlesnakes in Wyoming indicated that straight-line (i.e. fixed-bearing) movement by males is critical for mate location and, thus, for mating success. Males that searched along straight-line paths located and mated with more females than those having less straight movement paths. Fighting was observed rarely, and no relationship was found between males' success at mate location and body mass and/or snout-vent length. Thus a range of traits may mediate competition and mating success among male snakes.

Journal Article↗
PubMed1994

Number and state of rat ovarian mast cells after exogenous administration of luteinizing hormone.

Diestrous rats were treated with an injection of luteinizing hormone (LH), and their ovaries were examined for mast cell number and stage of degranulation at 2 and 4 hr post-injection. LH tripled the number of medullary mast cells at 2 hr. The source or origin of the additional mast cells is unknown. Comparison of the present results with other studies of rat ovarian mast cell dynamics suggests the occurrence of a reduction in mast cell number in early to mid-proestrus followed by an LH-induced increase in late proestrus.

Animals↗
PubMed1985

Seasonal variations in spermatogenesis, testicular weights, vasa deferentia, and androgen levels in neotenic male tiger salamanders, Ambystoma tigrinum.

Significant seasonal changes were observed in spermatogenesis, testicular weights, vasa deferentia, and cloacal development as well as in plasma androgen levels (testosterone and dihydrotestosterone). Androgen levels were highest in the fall and lowest during the period of spermatogenesis. Low levels of androgens were also observed during the breeding season. Diameter of the vasa deferentia corresponded to presence of stored spermatozoa and not to plasma androgen levels. Testicular weights were independent of androgen levels and stage of spermatogenesis. Maximal testicular weight occurred at the onset of spermiation. Hypertrophy of the epithelial lining of the vasa deferentia and the condition of the cloacal gland complex were correlated closely to plasma androgen levels. Comparison of spermatogenetic events, androgen-dependent sex accessory structures, and plasma androgen levels suggests either differential release of pituitary gonadotropins on a seasonal basis or variable testicular responsiveness to gonadotropins.

Ambystoma↗
PubMed1985

The West Indian manatee (Trichechus manatus) lacks a vomeronasal organ.

Completely aquatic marine mammals of the order Cetacea such as whales and dolphins have a reduced or absent olfactory system and neither a vomeronasal organ nor an accessory olfactory bulb. In comparison, seals, which are only partially aquatic, have olfactory and accessory olfactory systems including the vomeronasal organ. Thus, there seems to be a strong relation between the degree of adaptation to an aquatic environment and the degree of reduction in olfactory structures. Sirenians, such as manatees and dugongs, are another family of marine mammals which have secondarily adapted to a fully aquatic existence, yet there is dispute about the status of their olfactory structures. In the present study there was no evidence for a vomeronasal organ in the adult West Indian Manatee, Trichechus manatus. Additionally, the main olfactory system appeared quite rudimentary. These observations support the hypothesis that, in mammals, secondary adaptation to an aquatic environment leads to the reduction or loss of the olfactory senses.

Adaptation, Biological↗
PubMed1984

Characteristics and non-rhythmicity of retinal hydroxyindole-O-methyltransferase activity in trout (Salmo gairdneri).

The validation and optimization of an hydroxyindole-O-methyltransferase (HIOMT) activity assay system for trout ocular enzyme was undertaken. High-performance liquid chromatographic analysis, cross-validated with a standard thin-layer chromatographic technique verified that HIOMT activity was present in trout ocular tissue by identifying the 3H-melatonin end product. This activity was observed in the neural retina and was restricted to those fractions containing the cytosolic component. The enzyme displayed bimodal pH optima, one at pH 7.6, the other at 8.4. N-Acetylserotonin was O-methylated preferentially and a Km of 4.5 X 10(-7) M was calculated for this substrate. The S-[3H]adenosylmethionine Km was 4.6 X 10(-6) M. Time of incubation and enzyme concentration studies were conducted. The analysis of retinal HIOMT activity in groups of trout killed over a day--night period did not detect a rhythm in enzyme activity. Results of these investigations are discussed in terms of the evolution of melatonin synthesis and functions.

Acetylserotonin O-Methyltransferase↗
PubMed1984

Prenatal thyroid function abnormalities in infants with idiopathic respiratory distress syndrome.

Thyroxine (T4), triiodothyronine (T3), and thyrotropin (TSH) concentrations were measured on cord sera of 21 preterm infants with idiopathic respiratory distress syndrome (IRDS) and were compared to the values obtained from 15 healthy preterm infants. When log T3, log T4, and log TSH were considered as the dependent variables in the multivariate test Hotelling-Lawley-Trace, there was an overall difference between the two groups: F = 3.94, p = 0.03. When log T3 and log T4 were considered separately in an analysis of covariance, there was a significant difference between the two groups for log T3 after adjusting for birth weight and gestational age (F = 7.98, p = 0.008). However, for log T4 and TSH, there was no difference between the IRDS and control infants. These findings exclude the possibility of antenatal thyroid dysfunction in babies with IRDS. An explanation for reduced cord blood T3 concentration in infants with IRDS is lacking at present. Extrathyroidal factors that predispose to IRDS may also affect peripheral T3 generation. Alternatively, one might postulate that there is relative immaturity of both peripheral T3 generating pathway and lung development in infants who develop IRDS.

Fetal Blood↗
PubMed1981

Hormone-induced ovulation in Ambystoma tigrinum: influence of prolactin and thyroxine.

Treatment of hypophysectomized or intact neotenic tiger salamander larvae (Ambystoma tigrinum) with ovine prolactin (PRL) increased sensitivity of the ovary to the ovulation-inducing hormones, human chorionic gonadotropin and luteinizing hormone (LH). Effects of pretreatment in vivo with PRL or thyroxine (T4) on the responsiveness of ovarian fragments in vitro to ovulation-inducing agents, LH, or progesterone (PROG) in the presence or absence of PRL were observed. In November (prior to normal spawning occurring from January through May) in vivo and in vitro treatment with PRL increased the number of oocytes producing polar bodies and the number of eggs ovulated in vitro. In April addition of PRL in vitro increased polar body formation and ovulations in response to LH or PROG, but in vivo pretreatment with PRL had no effect. Pretreatment in vivo with T4 blocked the in vitro enhancement observed with PRL. Thus, endogenous PRL may play a role in the development of ovarian sensitivity to ovulatory hormones at the level of the oocyte, and T4 may inhibit this action.

Ambystoma↗
PubMed1981

Western fence lizard (Sceloporus occidentalis) chemical signals. II. A replication with naturally breeding adults and a test of the Cowles and Phelan hypothesis of rattlesnake olfaction.

The capacity of naturally breeding western fence lizards (Sceloporus occidentalis biseriatus) to discriminate and respond to conspecific and control chemical cues was examined. Lizards were presented with markings and exudates of male and female donors, as well as cologne (a pungency control) and water, in a successive discrimination procedure. Behavioral actions quantified after exposure to the different chemical cue types included lingual extrusions (tongue flicks and substrate licks), rapid nasal inhalations, and the performance of push-up visual displays. Initial latencies to lingual investigation of the different extracts and markings also were recorded as a measure of the extent to which nasal olfaction would switch on the tongue-Jacobson's organ (vomeronasal olfactory) system. Although no sex differences in total levels of response were noted, males and females exhibited significant lingual discriminations equally to exudates collected from male or female conspecifics. Push-up visual displays also were noted in response to conspecific markings. Cologne-marked surfaced, however, elicited nonsignificant levels of lingual investigation and push-up displaying. Latencies to initial tongue flicks, but not substrate licks, were significantly shorter when any material other than water was present. Therefore, as suggested by Cowles and Phelan ('58), nasal olfaction may indeed be more of a "quantitative," distance sensing system that responds to the presence of any pungent substance by initiating further investigation via the tongue-Jacobson's organ system. The latter appears to be more "qualitative," or discriminating, as indexed by relatively greater levels of lingual investigation of conspecific markings than cologne. No differences were noted in rapid nasal inhalation activity. The results suggest that pheromone markings, along the ground or other surfaces, may be important to spacing and territorial maintenance in nature. This could occur through direct pheromone effects on signal recipients, or indirectly, through the stimulation of increased push-up activity, which could make lizards more visible to one another.

Animals↗
PubMed1980

Rat ovarian mast cells: distribution and cyclic changes.

Numerous tissue mast cells are present in the ovarian medulla and hilus and in the oviduct of rats. In the medulla, most of these mast cells are in the connective tissue of the stroma near blood and lymphatic vessels. During proestrus, many of the medullary mast cells totally degranulate and thus are not visible histochemically; they then regranulate during estrus. In contrast, the number of stainable mast cells in the ovarian hilus and oviduct does not change during the estrous cycle. Histofluorometric methods demonstrate that mast cells in the ovarian medulla and hilus, as well as the oviduct, contain histamine. In addition, the lining of small blood vessels in the ovarian medulla contains histamine. Thus, mast cell and blood vessel histamine secretion may play a role in ovarian function.

Animals↗