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Biomedical subjects

J Davis

Publications and source records attributed to J Davis.

At least 343 records · Page 19Linked to original sources
PubMed1989

Epstein-Barr virus-related lymphoproliferative disorders following bone marrow transplantation: an immunologic and genotypic analysis.

Four patients from 1.5 to 18 yr of age who had received partially matched T-cell-depleted bone marrow transplants for acute leukemia succumbed to a widespread lymphoproliferative disorder (LPD) at 56 to 147 days after transplant. Premortem diagnosis of LPD was suggested in two because plasmacytoid cells were observed in the blood and bone marrow, and in the cerebrospinal fluid of one of these patients. Serum clonal immunoglobulins (Igs) were also demonstrated in these two patients premortem, while the other two had clonal Igs in serum obtained at autopsy. Autopsies revealed a plasmacytoid infiltrate or immunoblastic lymphoma involving lymph nodes, spleen, liver, lungs, gastrointestinal tract, and kidneys. Immunoglobulin gene rearrangement studies performed in three revealed B-cell clonality. Both immunohistochemical and DNA gene rearrangement studies were useful in differentiating the LPD from the pretransplant leukemia. Epstein-Barr virus (EBV) genome was found in the tissues of the three patients studied. The diagnosis of EBV-induced LPD must be considered in bone marrow transplant patients who deteriorate and who exhibit serum clonal Igs or prominent plasmacytoid cells in laboratory specimens.

Adolescent↗
PubMed1989

Efficacy of ex vivo purging for autologous bone marrow transplantation in the treatment of acute nonlymphoblastic leukemia.

We used an in vitro measure of drug activity to predict the efficacy of ex vivo purging of leukemic cells from autologous bone marrow grafts. We previously found that the myeloid progenitor cell (CFU-GM) content of the marrow grafts after ex vivo purging with 4-hydroperoxycyclophosphamide (4-HC) correlates with time to hematologic recovery after autologous bone marrow transplantation in patients with acute nonlymphoblastic leukemia. We observed that variable red blood cell concentration of the bone marrow incubation mixture results in differential cytotoxic activity of 4-HC. The CFU-GM content of the graft after the ex vivo treatment is a measure of this 4-HC activity. We analyzed the disease-free survival of 45 patients with acute nonlymphoblastic leukemia undergoing autologous bone marrow transplantation with 4-HC purged grafts. Patients who relapsed after transplantation had 4.2 +/- 1.1% of graft CFU-GM surviving the ex vivo purge, compared with 1.1 +/- 0.4% for patients who achieved a sustained remission (P = .06). Twenty-three patients with a CFU-GM content after 4-HC purging of greater than 1% of the pretreatment value had an actuarial disease-free survival of 12%, compared to 36% for 22 patients with a less than or equal to 1% CFU-GM content after purging (P = .006). Therefore, percent CFU-GM survival as a measure of 4-HC cytotoxicity identified a group of patients with insufficient purging. Although no randomized clinical trials have documented the need for ex vivo purging, our results suggest that effective bone marrow purging is important for the optimal application of autologous transplantation in the treatment of acute nonlymphoblastic leukemia.

Age Factors↗
PubMed1988

Ankyrin and spectrin associate with voltage-dependent sodium channels in brain.

The segregation of voltage-dependent sodium channels to specialized regions of the neuron is crucial for propagation of an action potential. Studies of their lateral mobility indicate that sodium channels are freely mobile on the neuronal cell body but are immobile at the axon hillock, presynaptic terminal and at focal points along the axon. To elucidate the mechanisms that regulate sodium channel topography and mobility, we searched for specific proteins from the brain that associate with sodium channels. Here we show that sodium channels labelled with 3H-saxitoxin (STX) are precipitated in the presence of exogenous brain ankyrin by anti-ankyrin antibodies and that 125I-labelled ankyrin binds with high affinity to sodium channels reconstituted into lipid vesicles. The cytoplasmic domain of the erythrocyte anion transporter competes for the latter interaction. Neither the neuronal GABA (gamma-aminobutyric acid) receptor channel complex nor the dihydropyridine (DHP) receptor bind brain ankyrin. The results indicate that brain ankyrin links the voltage-dependent sodium channel to the underlying cytoskeleton and may help to maintain axolemmal membrane heterogeneity and control sodium channel mobility.

Animals↗
PubMed1988

Ranitidine accumulation in patients undergoing chronic hemodialysis.

Ranitidine accumulation was assessed in 20 patients undergoing chronic hemodialysis following oral daily doses of 150 mg ranitidine for 10 days. Serum ranitidine concentrations prior to dialysis were 191 +/- 115 mcg/l and 207 +/- 172 mcg/l for patients dialyzed three and two times per week, respectively. The amount of ranitidine recovered in the dialysate during the final dialysis session of the study was negligible and ranged from 308-3036 mcg, representing less than 3% of the administered dose. Clearance by hemodialysis was 3.0 +/- 1.1 l/hr. Once daily dosing of 150 mg ranitidine does not result in excessive accumulation, and drug loss during hemodialysis is small. These data suggest that supplemental dosing after hemodialysis is not indicated.

Adult↗
PubMed1988

Vasoconstrictor for facelifting.

In 150 patients both sides of the face underwent facelifting surgery with the local infiltration of 2% solution of ornithine 8 vasopressin which caused good surgical hemoconstriction, gave a satisfactory early postoperative period, and better results than those obtained with other solutions previously used. This series involves the use of a diluted solution compared with that usually recommended.

Face↗
PubMed1988

Infantile myofibromatosis: the most common fibrous tumor of infancy.

We describe the clinical courses of four infants with infantile myofibromatosis (IM). This entity is a mesenchymal disorder of early infancy characterized by the formation of tumors in skin, muscle, viscera, bone, and subcutaneous tissues. Previously known as congenital generalized fibromatosis, IM was formerly thought to be a rare condition that was frequently fatal. The majority of the 170 affected patients we describe have been diagnosed since 1980. Furthermore, the mortality rate for these patients is less than 15%. Our review includes the clinical manifestations, as well as histopathologic features, and discusses the prognosis in affected infants. We found that infants with solitary lesions or multiple lesions without visceral involvement generally have a benign course. However, in patients with the multicentric form of the disorder and visceral involvement, 73% have died. Because the lesions may not be easily discernible and most spontaneously resolve, the condition is underdiagnosed and underreported. IM is the most common fibrous tumor of infancy and must be considered when evaluating children who present with either solitary or multiple tumors, particularly during the neonatal period.

Female↗
PubMed1988

Furosemide pharmacokinetics and pharmacodynamics in renal transplantation.

Furosemide was administered intravenously to four patients who had undergone renal transplantation in the past and four creatinine clearance--matched control subjects. Both patients who had undergone renal transplant and control subjects displayed similar pharmacokinetic and pharmacodynamic behavior, as assessed by drug delivery to the urine and sodium excretion, respectively. Despite similar degrees of natriuresis, patients who had undergone renal transplantation demonstrated a clear defect in urine potassium excretion. This defect in potassium excretion was not related to altered responsiveness of the renin-angiotensin-aldosterone axis because plasma renin activity increased in a normal fashion after furosemide in both control and transplant subjects. Although the plasma aldosterone response to increases in plasma renin activity was sluggish in patients undergoing renal transplantation, normal increases in plasma aldosterone levels were achieved in both groups, suggesting that there may be an intrinsic defect in distal tubular potassium secretion that can be unmasked by furosemide.

Adult↗
PubMed1988

High frequency of antimicrobial resistance in human fecal flora.

The frequency of resistance to seven different antimicrobial agents was examined in the aerobic gram-negative gut flora of over 600 individuals from hospitals, from laboratories where antibiotics were used, and from urban and rural communities. In a majority (62.5%) of fecal samples from people without a recent history of taking antibiotics, 10% or more of the total organisms were resistant to at least one of the antibiotics. In about 40% of the samples, resistance to more than one drug was present at this level. More than one-third of the samples contained resistant organisms comprising 50% or more of the total flora examined. Organisms with coresistance to multiple drugs were found frequently. Individuals taking antibiotics produced more samples with a higher proportion (greater than 50%) of resistant bacteria, and these samples also had a significantly greater number of different resistance determinants. This extensive study revealed a high prevalence of resistant bacteria in the gut flora of ambulatory and hospitalized individuals whether or not they were taking antibiotics.

Adolescent↗
PubMed1988

Construction, characterization, and complementation of a Puf- mutant of Rhodobacter sphaeroides.

A Puf- strain of Rhodobacter sphaeroides (PUFB1) was constructed by deleting a portion of the proximal region of the puf operon and inserting a kanamycin resistance gene cartridge. Southern blot analysis demonstrated that in PUFB1, the defective copy of the puf operon had replaced, through homologous recombination, the normal chromosomal copy. The Puf- phenotype was characterized by the inability of PUFB1 to grow photoheterotrophically (PS-), the lack of detectable puf-specific transcripts, the absence of the light-harvesting I complex and, by inference, the reaction center spectral complex, and greatly reduced levels of the light-harvesting II complex. The PS+ phenotype was restored to PUFB1 when a 13-kilobase BamHI restriction endonuclease fragment containing the entire puf operon and flanking regions was cloned into the broad-host-range plasmid vector RK2 derivative pRK404 and introduced by conjugation into PUFB1. In these complemented strains, there was an increased number of copies of the puf operon (four to six copies per defective chromosomal copy) as the result of plasmid copy number. However, there was no concomitant increase in either the specific bacteriochlorophyll content or the level of puf-specific transcripts when these strains were grown photoheterotrophically.

Cloning, Molecular↗
PubMed1988

Changes in plasma volume during bed rest: effects of menstrual cycle and estrogen administration.

Bed rest (BR) is associated with a decrease in plasma volume (PV), which may contribute to the impaired orthostatic and exercise tolerances seen immediately after BR. The purpose of this study was to determine whether increases in blood estrogen concentration, either during normal menstrual cycles or during exogenous estrogen administration, would attenuate this loss of PV. Nineteen healthy women (21-39 yr of age) completed the study. Twelve women underwent duplicate 11-day BR without estrogen supplementation. PV decreased significantly (P less than or equal to 0.01) during both BR's, from 2,531 +/- 113 to 2,027 +/- 102 ml during BR1 and from 2,445 +/- 115 to 2,244 +/- 96 ml during BR2. The women who began BR in the periovulatory stage of the menstrual cycle (n = 3), a time of elevated endogenous estrogens, had a transient delay in loss of PV during the first 5 days of BR. Women who began BR during other stages of the menstrual cycle (n = 17) showed the established trend to decrease PV primarily during the first few days of BR. Seven additional women underwent a single 12-day BR while taking estrogen supplementation (1.25 mg/day premarin). PV decreased during the first 4-5 days of BR, then returned toward the pre-BR level during the remainder of the BR (pre-BR PV, 2,525 +/- 149 ml; post-BR PV, 2,519 +/- 162 ml). Thus menstrual fluctuations in endogenous estrogens appear to have only small transient effects on the loss of PV during BR, whereas exogenous estrogen supplementation significantly attenuates PV loss.

Adult↗
PubMed1988

Water-soluble contrast medium for intraoperative evaluation of anterior cervical discectomy. Technical note.

When anterior cervical discectomy is performed for either "hard" or "soft" cervical disc herniation using either the Cloward approach or simple discectomy, it is often difficult to confirm intraoperatively the adequacy of the lateral, superior, and inferior margins of the dissection. Placement of a nonionic contrast material, iohexol, into the disc space before obtaining anteroposterior and lateral x-ray spine films can indicate the adequacy of the margins of dissection of the soft disc or bone ridge to prevent a poor operative result.

Cervical Vertebrae↗