PubMed Health⌕ Search

Biomedical subjects

J D Davis

Publications and source records attributed to J D Davis.

At least 19 recordsLinked to original sources
PubMed2006

Orosensory stimulation is sufficient and postingestive negative feedback is not necessary for neuropeptide Y to increase sucrose intake.

Although central administration of neuropeptide Y (NPY) has a potent orexic effect, it is not clear how NPY changes the potency of peripheral feedbacks from the gut to prolong eating and increase meal size. It has been suggested that NPY increases the stimulating effect of orosensory sweet stimuli or that it decreases the inhibitory effect of postingestive stimuli. To clarify this issue, we compared the orexic effect of NPY (2 microg) injected into the third ventricle of the brain on the volume and microstructure of intake of 0.8M sucrose during sham feeding (SF) and real feeding (RF) in male Sprague Dawley rats. The rationale for this comparison is that orosensory stimulation occurs in SF and RF, but postingestive negative feedback is present only in RF. NPY increased the volume ingested and the rate and number of clusters of licking significantly more in SF than in RF. This demonstrates that orosensory sucrose stimulation is sufficient and postingestive negative feedback is not necessary for the orexic effect of NPY under these experimental conditions.

Analysis of Variance↗
PubMed2001

The impact of sucrose-derived unconditioned and conditioned negative feedback on the microstructure of ingestive behavior.

We describe at the microstructural level the impact of unconditioned and conditioned negative feedback on the licking behavior of the rat. Seven groups of rats were trained to ingest one of seven different concentrations of sucrose (0.025, 0.05, 0.1, 0.2, 0.4, 0.6, and 0.8 M sucrose) under real-feeding conditions until intake was stable. They were then given three sham-feeding tests with the same solution. We compared the size of the clusters (SC) and number of clusters (NC) during the 17-min period when intake rate was declining in the real-feeding test with SC and NC during the corresponding 17-min period in the following sham-feeding test. Intake increased significantly over the three sham-feeding tests with the three highest concentrations, indicating the extinction of conditioned negative feedback. With these three solutions, we compared the microstructure of licking behavior in the first with that in the third sham-feeding test to determine if conditioned negative feedback affected SC or NC or both. The effect of both unconditioned and conditioned negative feedback on licking behavior was to decrease the NC without significantly affecting their size. We conclude that negative feedback derived from the accumulation of sucrose in the gastrointestinal tract decreases the probability of initiating a bout of licking during a pause. It has no effect on the ability to continue a bout of licking once it has begun.

Animals↗
PubMed2001

Quantitative modeling of category learning in amnesic patients.

Category rule learning was examined in two amnesic patients using the perceptual categorization task (e.g., Ashby & Gott, 1988; Filoteo & Maddox, 1999). Traditional accuracy-based analyses as well as quantitative model-based analyses were performed. Unlike accuracy-based analyses, the model-based approach allowed us to examine both categorization rule learning and variability in the trial-by-trial application of the participant's categorization rule. The results indicated that the amnesic patients were as accurate as the controls in learning a complex, nonlinear rule over a large number of trials. The model-based analysis indicated that, in general, the amnesic patients learned the categorization rule as well as controls and applied their rule as consistently as controls. Categorization performance on a second day of testing revealed that amnesic patients can retain the categorization rule over a 24-h period. These results suggest that the brain regions damaged in amnesia are not involved in category learning or memory for the category structures.

Adult↗
PubMed2001

A possible role of the striatum in linear and nonlinear category learning: evidence from patients with Huntington's disease.

Linear and nonlinear categorization rule learning was examined in patients with Huntington's disease (HD) and a group of controls using the perceptual categorization task. Participants learned to categorize simple line stimuli into 1 of 2 categories over 600 trials. In addition to traditional measures of accuracy, quantitative model-based analyses were applied to each participant's data to characterize better the nature of any observed deficits. In the linear rule condition, HD patients displayed an early-training deficit relative to controls, whereas later in training the HD patients were not statistically different from controls. In the nonlinear rule condition, HD patients displayed both an early- and late-training deficit. The quantitative model-based analyses revealed that the HD patients' deficits in the linear condition were due to an impairment in learning the experimenter-defined rule and not in applying a learned rule inconsistently. In the nonlinear condition, in contrast, the HD patients' deficits were due to an impairment in learning the experimenter-defined rule and in applying a learned rule inconsistently. Overall, these results suggest that HD can result in a deficit in learning both linear and nonlinear categorization rules.

Adult↗
PubMed2001

Chemical deacylation reduces the adhesive properties of proteolipid protein and leads to decompaction of the myelin sheath.

Myelin proteolipid protein (PLP) contains thioester-bound, long-chain fatty acids which are known to influence the structure of the molecule. To gain further insights into the role of this post-translational modification, we studied the effect that chemical deacylation of PLP had on the morphology of myelin and on the protein's ability to mediate the clustering of lipid vesicles. Incubation of rat optic nerves in isoosmotic solutions containing 100 mM hydroxylamine (HA) pH 7.4 led to deacylation of PLP and decompaction of myelin lamellae at the level of the intraperiod line. Incubation of nerves with milder nucleophilic agents (Tris and methylamine) or diluted HA, conditions that do not remove protein-bound fatty acids, caused no alterations in myelin structure. Other possible effects of HA which could have affected myelin compaction indirectly were ruled out. Incubation of optic nerves with 50 mM dithioerythritol (DTE) also led to the splitting of the myelin intraperiod line and this change again coincided with the removal of fatty acids. In addition, the apparently compacted CNS myelin in the PLP-less myelin-deficient rat, like that in tissue containing deacylated PLP, was readily decompacted upon incubation in isoosmotic buffers, suggesting that the function of PLP as a stabilizer of the interlamellar attachment is, at least in part, mediated by fatty acylation. Furthermore, in contrast to the native protein, PLP deacylated with either HA or DTE failed to induce the clustering of phosphatidylcholine/cholesterol vesicles in vitro. This phenomenon is not due to side-effects of the deacylation procedure since, upon partial repalmitoylation, the protein recovered most of its original vesicle-clustering activity. Collectively, these findings suggest that palmitoylation, by influencing the adhesive properties of PLP, is important for stabilizing the multilamellar structure of myelin.

Acylation↗
PubMed2001

Prevention, diagnosis, and treatment of venous thromboembolic complications of gynecologic surgery.

Deep vein thrombosis and pulmonary embolism, collectively referred to as venous thromboembolic events, are a source of significant morbidity and mortality after gynecologic surgical procedures. In this literature review the advantages and disadvantages of various preventive measures for deep venous thrombosis, including low-molecular-weight heparins, are discussed. The most appropriate prophylactic methods for patients in varying risk categories are recommended. Current methods of diagnosing deep venous thrombosis and pulmonary embolism, including ultrasonography, venography, ventilation-perfusion scan, helical computed tomographic scan, and D -dimer measurement are then discussed. Finally, treatment modalities for deep venous thrombosis and pulmonary embolism, including heparin, low-molecular-weight heparin, warfarin, and thrombolytic therapy, are detailed.

Adult↗
PubMed2001

Gastric negative feedback produced by volume and nutrient during a meal in rats.

To investigate the gastric negative-feedback control of eating during a meal, we implanted male rats with pyloric cuffs and gastric catheters and gave them access to sweet milk for 30 min after overnight deprivation. Ingested milk and infused milk or saline were confined to the stomach because the pyloric cuffs were closed in all tests. Rats received five consecutive tests with no gastric infusion or with infusions of 3, 6, or 12 ml of milk or saline during the first 6 min of the test meal. Only 12-ml infusions decreased intake significantly compared with no infusion. Because 12 ml of saline inhibited intake as much as 12 ml of milk, the decreased intake was due to volume or rate of infusion, not nutrient. Although infusions of 3 and 6 ml of milk did not decrease intake, they decreased the number of licks after the infusions significantly more than equal volumes of saline. Thus a large volume or rapid rate of gastric infusion decreases intake, and some other aspect of small milk infusions decreases the rate of licking.

Animals↗
PubMed2000

Correlation of mutations of the SH2D1A gene and epstein-barr virus infection with clinical phenotype and outcome in X-linked lymphoproliferative disease.

The purposes of this study were to determine the frequency of mutations in SH2D1A in X-linked lymphoproliferative disease (XLP) and the role of SH2D1A mutations and Epstein-Barr virus (EBV) infection in determining the phenotype and outcome of patients with XLP. Analysis of 35 families from the XLP Registry revealed 28 different mutations in 34 families-large genomic deletions (n = 3), small intragenic deletions (n = 10), splice-site (n = 3), nonsense (n = 3), and missense (n = 9) mutations. No mutations were found in 25 males, so-called sporadic XLP (males with an XLP phenotype after EBV infection but no family history of XLP) or in 9 patients with chronic active EBV syndrome. Of 304 symptomatic males in the XLP Registry, 38 had no evidence of EBV infection at first clinical manifestation. When fulminant infectious mononucleosis (FIM) was excluded, there was no statistical difference in the frequency of EBV infectivity in the other XLP phenotypes. Furthermore, there was no difference at age of first clinical manifestation between EBV(+) and EBV(-) males or in survival when patients with FIM were excluded. In conclusion, it was found that mutations in the SH2D1A gene are responsible for XLP but that there is no correlation between genotype and phenotype or outcome. It was also found that though EBV infection often results in FIM, it is unnecessary for the expression of other manifestations of XLP, and it correlates poorly with outcome. These results suggest that unidentified factors, either environmental or genetic (eg, modifier genes), contribute to the pathogenesis of XLP.

Alternative Splicing↗
PubMed2000

Outcome of patients treated for cervical myelopathy. A prospective, multicenter study with independent clinical review.

STUDY DESIGN: This Cervical Spine Research Society (CSRS) Study is a prospective, multicenter, nonrandomized investigation of patients with cervical spondylosis and disc disease. In this analysis, only patients with cervical myelopathy as the predominant syndrome were considered. OBJECTIVES: To determine demographics, surgeon treatment practices, and outcomes in patients with symptomatic myelopathy. SUMMARY OF BACKGROUND DATA: Current data on patient demographics and treatment practices of surgeons do not exist. There are no published prospective studies in which neurologic, functional, pain, and activities of daily living outcomes are systematically quantified. METHODS: Patients were recruited by participating CSRS surgeons. Demographic information, patients' symptoms, and patients' functional data were compiled from patient and physician surveys completed at the time of initial examination, and outcomes were assessed from patient surveys completed after treatment. Data were compiled and statistically analyzed by a blinded third party. RESULTS: Sixty-two (12%) of the 503 patients enrolled by 41 CSRS surgeons had myelopathy. Patients (48.4% male; mean age, 48.7 +/- 12.03 years) had a mean duration of symptoms of 29.8 months (range, 8 weeks to 180 months). Surgery was recommended for 31 (50%) of these patients. Forty-three patients (69%) returned for follow-up and completed the questionnaire adequately for analysis. Twenty (46%) of the 43 patients on whom follow-up data are available underwent surgery, and 23 (54%) received medical treatment. Surgically treated patients had a significant improvement in functional status and overall pain, with improvement also observed in neurologic symptoms. Patients treated nonsurgically had a significant worsening of their ability to perform activities of daily living, with worsening of neurologic symptoms. CONCLUSIONS: When medical and surgical treatments are compared, surgically treated patients appear to have better outcomes, despite exhibiting a greater number of neurologic and nonneurologic symptoms and having greater functional disability before treatment. Randomized studies, if feasible, should be performed to address outcome in cervical myelopathy further.

Activities of Daily Living↗
PubMed2000

Effect of obstetrics-gynecology clerkship duration on medical student examination performance.

OBJECTIVE: To compare medical student performance on the obstetrics and gynecology national board subject examination during two different clerkship rotation formats. METHODS: We compared medical student performance on the National Board of Medical Examiners (NBME) subject examination in obstetrics and gynecology for 2 years before and 2 years after the length of the clerkship at the University of Florida was decreased from 8 to 6 weeks. Medical College Admission Test (MCAT) and United States Medical Licensing Examination (USMLE) step 1 and step 2 scores were used to assess comparability between groups. Student t test and chi2 analysis were used as appropriate. RESULTS: Medical school classes were similar with respect to MCAT and USMLE step 1 and step 2 scores. Collectively, 231 students who completed the 8-week clerkship scored significantly higher on the subject examination than 239 who completed the 6-week clerkship (618.6 versus 593.5, P = .001). When analyzed by semester, students who completed the clerkship in the second half of the academic year scored similarly regardless of clerkship length (630.6 versus 616.7, P = .11); however, students who completed the clerkship during the first half of the academic year scored significantly higher with the 8-week than the 6-week clerkship (607.3 versus 569.7, P < .001). Students who took the clerkship in the last half of the academic year scored higher than students who took the clerkship in the first half for both the 8-week (630.6 versus 607.3; P = .02) and 6-week (616.7 versus 569.7; P < .001) formats. Those differences persisted on examination letter grade assignment. CONCLUSION: Decreasing the duration of the obstetrics-gynecology medical student clerkship resulted in lower subject examination scores, especially for students who matriculated in the first half of the academic year.

Clinical Clerkship↗
PubMed2000

Type of negative feedback controlling sucrose ingestion depends on sucrose concentration.

The sham intake of concentrated, but not weak, milk solutions requires up to three sham-feeding tests for intake to reach maximum (7). It is well known that the sham intake of concentrated (0.8 M) sucrose requires three or more sham-feeding tests to reach its maximum (4, 6, 17), but it is not known if this occurs with weaker sucrose solutions. We investigated this question by measuring the sham intake of seven concentrations of sucrose (0.025, 0.05, 0.1, 0. 2, 0.4, 0.6, and 0.8 M) during five sham-feeding tests. Sham intake of the three highest concentrations required up to three sham-feeding tests to reach maximum. Sham intake of the four lowest concentrations reached maximum in the first sham-feeding test. Our results show that the type of negative feedback that controls the intake of sucrose depends on its concentration. With weak solutions, intake is limited by a single direct, physiological, negative-feedback signal. When concentrated solutions are ingested, intake is controlled jointly by a direct physiological signal operating in conjunction with a labile one that loses its effectiveness with sham-feeding experience.

Animals↗
PubMed2000

Intracavitary radiotherapy for refractory dysfunctional uterine bleeding. A case report.

BACKGROUND: Pelvic irradiation was once a common treatment for dysfunctional uterine bleeding (DUB). Today the majority of women with DUB are successfully treated with hormonal therapy; patients unresponsive to hormonal therapy may require endometrial ablation or hysterectomy. We present a patient with severe, intractable DUB and contraindications to surgery who was treated with intracavitary radiotherapy. CASE: A 39-year-old, 150-cm-tall, 310-kg woman was referred for management of severe DUB refractory to medical management. The bleeding was successfully treated with intracavitary cesium. Hysterectomy was not recommended due to the operative risks posed by the patient's massive obesity. Because of technical difficulties during a previous dilation and curettage and the expense of long-term GnRH agonist therapy, the patient elected to undergo intracavitary radiotherapy. CONCLUSION: In selected patients, intracavitary radiotherapy can be used to treat DUB when conventional therapy fails or is contraindicated.

Adult↗
PubMed1999

Outcome in patients with cervical radiculopathy. Prospective, multicenter study with independent clinical review.

STUDY DESIGN: The Cervical Spine Research Society study is a prospective, nonrandomized, multicenter investigation of patients with cervical spondylosis and disc disease. In this analysis, only patients who had radiculopathy without myelopathy as the predominant symptom were considered. OBJECTIVES: To determine demographics, surgeon treatment practices, and outcomes in patients with symptomatic radiculopathy. SUMMARY OF BACKGROUND DATA: Current data on patient demographics and treatment practices of surgeons do not exist. There are no published prospective studies in which outcomes, including pain, function, neurologic symptoms, and ability to perform activities of daily living, are systematically quantified. METHODS: Patients were recruited by participating Cervical Spine Research Society surgeons. Demographic, symptomologic, and functional patient data were compiled from surveys of patients and physicians completed at the time of initial examination, and outcomes were assessed from surveys of patients completed after treatment. Data were compiled and statistically analyzed by a blinded third party. RESULTS: Of the 503 patients enrolled by 41 CSRS surgeons, 246 (49%) had radiculopathy. Patients had a mean duration of symptoms of 26.7 months (range, 8 weeks to > 352 months) and a mean age of 48.1 +/- 12.42 years; 44.7% were female. Surgery was recommended for 86 (35%) of these patients. Of the 155 patients on whom there were follow-up data, 51 (33%) underwent surgery, whereas 104 (67%) received medical treatment. Surgically treated patients had a significant improvement in pain, neurologic symptoms, functional status, and ability to perform activities of daily living. A significant number of patients who underwent surgery reported persistent excruciating or horrible pain on follow-up (26%). Patients treated medically also had significant improvement in pain and overall functional status. CONCLUSIONS: In summary, this study represents the first in-depth, prospective outcome analysis of patients with cervical spondylotic and discogenic radiculopathy.

Activities of Daily Living↗
PubMed1999

A microstructural analysis of the control of water and isotonic saline ingestion by postingestional stimulation.

This study investigated the behavioral expression of the mechanisms of satiation from stimulation of the gastrointestinal tract by water and isotonic saline. We compared the licking behavior of water-deprived rats ingesting water or isotonic saline under real- and sham-drinking conditions. In real-drinking tests the rate of ingestion of both types of fluids declined after about 5 min of drinking, and had virtually ceased by 20 min, while in the sham-drinking tests the rate of drinking remained constant during this period. To assess the impact of postingestional stimulation on the microstructure of licking, we compared the size of the clusters (SC) of licking and the duration of the pauses between them (ICIs), during the 15-min period that began 5 min after the start of drinking in the real- and sham-drinking tests. With both fluids postingestional stimulation significantly reduced the number of clusters. With water, but not with isotonic saline, postingestional stimulation also reduced SC, an effect that was shown to be due to differential postingestional not oropharyngeal stimulation. Postingestional stimulation had no overall effect on the ICIs, but in tests with water, but not saline, it altered the shape of the ICI distribution by increasing the duration of the long ICIs. We concluded that the different mechanisms of satiation stimulated by the postingestional effects of water and isotonic saline are expressed in different patterns of the microstructure of licking.

Analysis of Variance↗
PubMed1999

Management of injuries to the urinary and gastrointestinal tract during cesarean section.

Proper management of surgical injuries occurring during cesarean section is important to minimize patient morbidity. Damage to the bladder is usually easy to identify and repair. The defect is closed with two or three layers of absorbable suture, and an indwelling catheter is left in place for 1 week. The management of ureteral injuries depends on their nature, extent, location, and time of discovery; consultation with a urologist is advisable. Small, well-perfused injuries to both the small and large bowel can be repaired primarily. More extensive bowel damage may require resection. Colostomy is no longer mandatory for patients with injuries to unprepared large bowel.

Cesarean Section↗
PubMed1999

Some new developments in the understanding of oropharyngeal and postingestional controls of meal size.

This review focuses on new developments in the understanding of how oropharyngeal and postingestional stimulation control the ingestive behavior of the rat ingesting liquids. With the development of the computer-controlled lickometer it is now possible to measure and analyze in fine detail the impact these two variables have on the rat's licking behavior. Because variations in this behavior are responsible for variations in intake this methodology is beginning to provide a clearer picture of how oropharyngeal and postingestional stimulation control ingestive behavior and interact to control meal size. These developments should in turn ultimately provide the basis for better understanding of how the motor systems of the brain control the behavior that supplies the body with its nutrients.

Animals↗