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K Byrd

Publications and source records attributed to K Byrd.

8 recordsLinked to original sources
PubMed2000

A chromatin insulator determines the nuclear localization of DNA.

Chromatin insulators might regulate gene expression by controlling the subnuclear organization of DNA. We found that a DNA sequence normally located inside of the nucleus moved to the periphery when the gypsy insulator was placed within the sequence. The presence of the gypsy insulator also caused two sequences, normally found in different regions of the nucleus, to come together at a single location. Alterations in this subnuclear organization imposed by the gypsy insulator correlated with changes in gene expression that took place during the heat-shock response. These global changes in transcription were accompanied by dramatic alterations in the distribution of insulator proteins and DNA. The results suggest that the nuclear organization imposed by the gypsy insulator on the chromatin fiber is important for gene expression.

Animals↗
PubMed2000

The role of density on the release profiles of hydrophobic and hydrophilic compounds from TCPL delivery systems.

Several studies have shown that tri-calcium phosphate lysine drug delivery systems (TCPL) are capable of releasing various organic compounds at a sustained manner for long duration. The fabrication of TCPL devices is complex and the manipulation of various factors can alter drug release profiles. The compression of the TCPL material into the capsular form is an instrumental factor when studying the desired release profile. The objectives of this investigation were: 1) to study the interrelationship between the release profiles of devices that had been cold pressed at two different densities (1.53 +/- 0.15 (Low density, TCPL-LD) and 1.98 +/- 0.7 gm/cm3 (High density, TCPL-HD)), and 2) to evaluate the role of the change in density that might have on the release of hydrophobic and hydrophilic compounds in an in vitro environment. A total of 16 serum bottles were used and later subdivided into four groups (n = 4). Groups I and II contained TCPL-HD and TCPL-LD capsules each loaded with 20 mg of progesterone (P). Groups III & IV contained TCPL-HD and TCPL-LD capsules that were loaded with 20 mg of Bovine Serum Albumin (BSA). Each serum bottle in groups III and IV was filled with 100 mL of phosphate buffer saline (pH 7.4) and 10 microL of sodium azide (antibacterial agent). Serum bottles in groups I and II were filled with 50% alcohol (wt/vol). Samples were withdrawn at various time intervals and the release profiles were analyzed by using standard spectrophotometer techniques. Data analysis was conducted by using Jandel Sigma Stat Statistical software. Results of this investigation suggest that: 1) TCPL-HD and TCPL-LD devices were capable of releasing P and BSA at sustained levels, 2) regardless of the loaded drugs, the release profiles from TCPL-LD devices was found to be significantly higher (p < 0.05) than the release profiles of P and BSA from TCPL-HD, and 3) physiochemical characteristics of the drug to be delivered are instrumental in regulating the rate of release and duration or availability of an effective and safe dose (BSA > P).

Calcium Phosphates↗
PubMed1997

Prevalence of retinal hemorrhages in pediatric patients after in-hospital cardiopulmonary resuscitation: a prospective study.

OBJECTIVE: Child abuse occurs in 1% of children in the United States every year; 10% of the traumatic injuries suffered by children under 5 years old are nonaccidental, and 5% to 20% of these nonaccidental injuries are lethal. Rapid characterization of the injury as nonaccidental is of considerable benefit to child protection workers and police investigators seeking to safeguard the child care environment and apprehend and prosecute those who have committed the crime of child abuse. Physically abused children present with a variety of well-described injuries that are usually easily identifiable. In some cases, however, particularly those involving children with the shaken baby syndrome, obvious signs of physical injury may not exist. Although external signs of such an injury are infrequent, the rapid acceleration-deceleration forces involved often cause subdural hematomas and retinal hemorrhages, hallmarks of the syndrome. Frequently, retinal hemorrhages may be the only presenting sign that child abuse has occurred. Complicating the interpretation of the finding of retinal hemorrhages is the belief by some physicians that retinal hemorrhages may be the result of chest compressions given during resuscitative efforts. The objective of this study is to determine the prevalence of retinal hemorrhages after inpatient cardiopulmonary resuscitation (CPR) in pediatric patients hospitalized for nontraumatic illnesses in an intensive care unit. DESIGN: Prospective clinical study. SETTING: Pediatric intensive care unit. PATIENTS: Forty-three pediatric patients receiving at least 1 minute of chest compressions as inpatients and surviving long enough for a retinal examination. Patients were excluded if they were admitted with evidence of trauma, documented retinal hemorrhages before the arrest, suspicion of child abuse, or diagnosis of near-drowning or seizures. All of the precipitating events leading to cardiopulmonary arrest occurred in our intensive care unit, eliminating the possibility of physical abuse as an etiology. INTERVENTIONS: None. MEASUREMENTS: Examination of the retina was performed by one of two pediatric ophthalmologists within 96 hours of CPR. The chart was reviewed for pertinent demographic information; the platelet count, prothrombin time, and partial thromboplastin time proximate to the CPR were recorded if they had been determined. RESULTS: A total of 43 pediatric patients hospitalized with nontraumatic illnesses survived 45 episodes of inpatient CPR. The mean age was 23 months (range, 1 month to 15.8 years), and 84% of the patients were under 2 years old. The majority of the patients (44%) were admitted to the intensive care unit after surgery for congenital heart disease, and another 21% were admitted for respiratory failure. The mean duration of chest compressions was 16.4 minutes +/- 17 minutes with 58% lasting between 1 and 10 minutes. Five patients had chest compressions lasting >40 minutes, and two patients had open chest cardiac massage. All patients survived their resuscitative efforts. Ninety-three percent of patients had an elevated prothrombin time and/or partial thromboplastin time while 49% were thrombocytopenic. Sixty-two percent of the patients had low platelet counts and an elevated prothrombin time and/or partial thromboplastin time. Small punctate retinal hemorrhages were found in only one patient. CONCLUSIONS: Retinal hemorrhages are rarely found after chest compressions in pediatric patients with nontraumatic illnesses, and those retinal hemorrhages that are found appear to be different from the hemorrhages found in the shaken baby syndrome. Despite the small number of patients in this prospective study, we believe that these data support the idea that chest compressions do not result in retinal hemorrhages in children with a normal coagulation profile and platelet count. A larger number of patients should be evaluated in a prospective multi-institutional study to achieve statistical significance

Adolescent↗
PubMed1996

Phase I/II study of combined granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor administration for the mobilization of hematopoietic progenitor cells.

PURPOSE: To study the toxicity and efficacy of combined granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) administration for mobilization of hematopoietic progenitor cells (HPCs). MATERIALS AND METHODS: Cohorts of a minimum of five patients each were treated subcutaneously as follows: G-CSF 5 micrograms/kg on days 1 to 12 and GM-CSF at .5, 1, or 5 micrograms/kg on days 7 to 12 (cohorts 1, 2, and 3); GM-CSF 5 micrograms/kg on days 1 to 12 and G-CSF 5 micrograms/kg on days 7 to 12 (cohort 4); and G-CSF and GM-CSF 5 micrograms/kg each on days 1 to 12 (cohort 5). Ten-liter aphereses were performed on days 1 (baseline, pre-CSF), 5, 7, 11, and 13. Colony assays for granulocyte-macrophage colony-forming units (CFU-GM) and erythroid burst-forming units (BFU-E) were performed on each harvest. RESULTS: The principal toxicities were myalgias, bone pain, fever, nausea, and mild thrombocytopenia, but none was dose-limiting. Four days of treatment with either G-CSF or GM-CSF resulted in dramatic and sustained increases in the numbers of CFU-GM per kilogram collected per harvest that represented 35.6 +/- 8.9- and 33.7 +/- 13.0-fold increases over baseline, respectively. This increment was attributable both to increased numbers of mononuclear cells collected per 10-L apheresis and to increased concentrations of progenitors within each collection. The administration of G-CSF to patients already receiving GM-CSF (cohort 4) caused the HPC content to surge to nearly 80-fold the baseline (P = .024); the reverse sequence, ie, the addition of GM-CSF to G-CSF, was less effective. The CFU-GM content of the baseline aphereses correlated with the maximal mobilization achieved (r = .74, P = .001). CONCLUSION: Combined G-CSF and GM-CSF administration effectively and predictably mobilizes HPCs and facilitates apheresis.

Adolescent↗
PubMed1973

Lipid transformations in greening and senescing leaf tissue.

Analyses were made of chlorophyll a and b and fatty acids (18:3, 18:2, 18:1, 18:0, 16:2, 16:1, and 16:0) of greening and senescing leaf tissue. Those dark-grown tissues given a prior treatment of red, far red, or red followed by far red light showed similar increases in chlorophylls and linolenate (18:3) when exposed to continuous white light. In contrast, green barley (Hordeum vulgare L.) leaves placed in the dark lost chlorophylls and fatty acids, especially 18:3. Senescing cocklebur (Xanthium strumarium L.) leaf tissue showed a decline in chlorophyll and fatty acids, especially again 18:3. Abscisic acid, but not sucrose, accelerated these senescent changes. Radioactive acetate incorporation into the galacto-lipids and phospholipids of senescing cocklebur leaf tissue increased and then the radioactivity of the lipids decreased in senescent tissues.

Journal Article↗