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Biomedical subjects

B L Davison

Publications and source records attributed to B L Davison.

16 recordsLinked to original sources
PubMed1996

Open inferior glenohumeral dislocation.

An open inferior glenohumeral dislocation or luxatio erecta humeri is a rare type of shoulder dislocation, with only two cases reported in the literature. Presented is the case of a 36-year-old farmer who sustained an open inferior glenohumeral dislocation in a farm equipment accident. The humeral head penetrated the skin inferior to the pectoralis major muscle, an avulsion fracture of the greater tuberosity was present, and the subscapular tendon was ruptured near its insertion into the lesser tuberosity. At follow-up 18 months after injury, the restricted range of motion of the shoulder remained despite treatment attempts, including manipulation under anesthesia with arthroscopic debridement of the shoulder; however, no evidence of avascular necrosis of the humeral head was found.

Adult↗
PubMed1996

Acute radial nerve compression following routine venipuncture in an anticoagulated patient.

Venipuncture is a commonly used modality for therapeutic monitoring in patients on anticoagulant therapy. The antecubital fossa provides an easily accessible site with low associated morbidity. A case report of an acute complete radial nerve compression neuropathy that developed after antecubital venipuncture in a patient on anticoagulant therapy is presented.

Acute Disease↗
PubMed1996

Long term evaluation of repaired distal biceps brachii tendon ruptures.

A long term evaluation was performed on 8 patients who had rupture of the distal biceps tendon repaired using the 2-incision technique. The length of followup ranged from 1 to 11 years with an average of 6 years. Goniometric range of motion and isokinetic strength testing were performed on all patients. All patients attained a full arc of elbow flexion and extension. Supination was diminished more than 30 degrees in 3 patients and pronation was diminished more than 30 degrees in 1 patient. Subjectively, 6 of 8 patients were completely satisfied with the function of their involved arm. Strength and work performed during repetitive exercise were regained to the expected normal levels in elbow flexion. Six of 8 patients continued to have less strength in supination of the injured arm than the uninjured arm. All 8 patients performed less total work with repetitive supination of the injured arm than the uninjured arm.

Adult↗
PubMed1995

Ligands for EPH-related tyrosine kinase receptors are developmentally regulated in the CNS.

Elk is a member of the eph family of receptor-like tyrosine kinases. Although its function is unknown, elk is postulated to play a role in nervous system development. Using Northern analysis, we examined the developmental regulation of RNAs encoding elk, and several ligands for the eph family of RTKs, the LERKs. Expression of elk, LERK-1, and LERK-2 RNAs is high in all regions examined in the embryonic and postnatal rat brain and decreases to low levels with age. One exception is the adult olfactory bulb which continues to express a moderate level of LERK-2. In contrast, moderate LERK-4 expression was limited to the developing hippocampus and cerebral cortex. These data indicate that elk and some of the LERKs may play a role in nervous system development, maintenance, and/or regeneration.

Animals↗
PubMed1994

Genomic organization and chromosomal localization of mouse Eplg2, a gene encoding a binding protein for the receptor tyrosine kinase elk.

The human gene EPLG2 (Eph ligand-2) encodes a potential ligand for the receptor tyrosine kinase elk. High sequence conservation between the human and the rat cDNAs and developmentally regulated expression of the rat gene suggest that the protein encoded by EPLG2 plays an important role in mammalian development. To facilitate analysis of the physiological role of the protein, we have cloned and characterized a 24-kb region of mouse genomic DNA containing the mouse homologue of EPLG2 (Eplg2), including 5'- and 3'-flanking sequences. Restriction mapping, coupled with Southern blot hybridization and sequencing, was used to determine the structural organization of the gene. The Eplg2 genomic locus spans a region of approximately 12 kb, encoding five exons and four introns. The first intron comprises approximately 8.5 kb of the entire 12-kb genomic sequence. Eplg2 was mapped to the mouse X chromosome by interspecific backcross analysis and is tightly linked to the androgen receptor (Ar) locus.

Amino Acid Sequence↗
PubMed1994

Humoral immune responses in CD40 ligand-deficient mice.

Individuals with X-linked hyper-IgM syndrome fail to express functional CD40 ligand (CD40L) and, as a consequence, are incapable of mounting protective antibody responses to opportunistic bacterial infections. To address the role of CD40L in humoral immunity, we created, through homologous recombination, mice deficient in CD40L expression. These mice exhibited no gross developmental deficiencies or health abnormalities and contained normal percentages of B and T cell subpopulations. CD40L-deficient mice did display selective deficiencies in humoral immunity; basal serum isotype levels were significantly lower than observed in normal mice, and IgE was undetectable. Furthermore, the CD40L-deficient mice failed to mount secondary antigen-specific responses to immunization with a thymus-dependent antigen, trinitrophenol-conjugated keyhole limpet hemocyanin (TNP-KLH). By contrast, the CD40L-deficient mice produced antigen-specific antibody of all isotypes except IgE in response to the thymus-independent antigen, DNP-Ficoll. These results underscore the requirement of CD40L for T cell-dependent antibody responses. Moreover, Ig class switching to isotypes other than IgE can occur in vivo in the absence of CD40L, supporting the notion that alternative B cell signaling pathways regulate responses to thymus-independent antigens.

Animals↗
PubMed1994

Early lymphocyte expansion is severely impaired in interleukin 7 receptor-deficient mice.

Interleukin 7 (IL-7) stimulates the proliferation of B cell progenitors, thymocytes, and mature T cells through an interaction with a high affinity receptor (IL-7R) belonging to the hematopoietin receptor superfamily. We have further addressed the role of IL-7 and its receptor during B and T cell development by generating mice genetically deficient in IL-7R. Mutant mice display a profound reduction in thymic and peripheral lymphoid cellularity. Analyses of lymphoid progenitor populations in IL-7R-deficient mice define precisely those developmental stages affected by the mutation and reveal a critical role for IL-7R during early lymphoid development. Significantly, these studies indicate that the phase of thymocyte expansion occurring before the onset of T cell receptor gene rearrangement is critically dependent upon, and mediated by the high affinity receptor for IL-7.

Animals↗
PubMed1990

Disruption of thymocyte development and lymphomagenesis induced by SV40 T-antigen.

The lck gene encodes a membrane-associated protein tyrosine kinase that is expressed specifically in lymphoid cells, especially thymocytes. Structural analysis of the murine and human lck genes previously identified conserved 5' flanking sequences that were proposed to represent transcriptional regulatory elements. Here we demonstrate that a murine lck promoter construct containing these sequences directs the expression of the SV40 T-antigen gene in lymphoid cells. Remarkably, expression of SV40 T-antigen in transgenic animals dramatically disturbs thymic development, resulting in preferential loss of CD4+CD8+ thymocytes. In contrast, immature cells lacking both CD4 and CD8 markers are present in near-normal numbers. Thus SV40 T-antigen expression appears partially to arrest thymopoiesis. Mice bearing the lck-SV40 transgene develop readily explantable thymic tumors at 12-18 weeks of age. Fluorocytometric analyses of lck-SV40 tumor cells reveal that immature thymocytes are frequently immortalized. The lck-SV40 mouse may therefore provide materials for the in vitro investigation of thymocyte differentiation.

Animals↗
PubMed1987

Promoter and enhancer elements from the rat elastase I gene function independently of each other and of heterologous enhancers.

An elastase-human growth hormone (hGH) fusion gene containing 205 base pairs of elastase 5' flanking region is expressed exclusively in pancreatic acinar cells of transgenic mice. This paper shows that the promoter region (-72 to +8) and the enhancer (-205 to -73) function independently of each other. The elastase enhancer can activate the heterologous mouse metallothionein gene and the hGH gene promoters; conversely, enhancers from the thymocyte-specific murine leukemia virus MCF13 and the metal regulatory elements from the metallothionein gene can activate the elastase promoter in a variety of cell types. Combinations of immunoglobulin and elastase enhancers with a heterologous promoter and the hGH gene result in expression in all of the tissues predicted by the sum of each enhancer acting alone. Thus these enhancer elements act independently of each other, suggesting that they do not have silencing activity in cells in which they are normally inactive.

Animals↗
PubMed1984

Regulation, linkage, and sequence of mouse metallothionein I and II genes.

The mouse metallothionein II (MT-II) gene is located approximately 6 kilobases upstream of the MT-I gene. A comparison of the sequences of mouse MT-I and MT-II genes (as well as those of other mammals) reveals that the coding regions are highly conserved even at "silent" positions but that the noncoding regions and introns are extremely divergent between primates and rodents. There are four blocks of conserved sequences in the promoters of mouse MT-I, mouse MT-II, and human MT-IIA genes; one includes the TATAAA sequence, and another has been implicated in regulation by heavy metals. Mouse MT-I and MT-II mRNAs are induced to approximately the same extent in vivo in response to cadmium, dexamethasone, or lipopolysaccharide. Mouse MT-I and MT-II genes are regulated by metals but not by glucocorticoids after transfection into HeLa cells.

Amino Acid Sequence↗
PubMed1980

Specificity of promoter site utilization in vitro by bacterial RNA polymerases on Bacillus phage phi 29 DNA. Transcription mapping with exonuclease III.

Bacillus subtilis RNA polymerase holoenzyme transcribes phi 29 DNA in vitro producing five major RNA species defined by characteristic electrophoretic mobilities. In addition to these products, Escherichia coli RNA polymerase transcribes phi 29 DNA to yield three RNA species not detected when transcribing with the B. subtilis enzyme under the same optimal reaction conditions for RNA synthesis. Transcriptional analysis of purified restriction fragments and exonuclease III-digested DNA established locations of six promoter and three termination sites defining the eight transcripts. The transcription map shows that E. coli RNA polymerase initiates transcription at three sites not efficiently utilized by the B. subtilis enzyme. However, initiation by the B. subtilis polymerase from at least two of these sites could be detected at E:DNA ratios greater than 10 in the absence of competing promoters. These results indicate that differences between the two polymerases in promoter utilization are not explained by specificity of promoter binding, but represent differences in responding to promoter strength. Transcription of phi 29 DNA and T7 DNA by E. coli core polymerase with either B. subtilis or E. coli sigma subunits results in formation of transcripts identical with those produced by E. coli holoenzyme, suggesting that core polymerase contains elements important in determining relative promoter strength. The efficiency of rifampicin-resistant complex formation on phi 29 and T7 promoters is also dependent upon the source of core polymerase.

Bacillus subtilis↗
PubMed1979

Purification of Bacillus subtilis RNA polymerase with heparin-agarose. In vitro transcription of phi 29 DNA.

We have devised a new procedure for the purification of highly active preparations of Bacillus subtilis RNA polymerase holoenzyme. A column of heparin-agarose A-15m is used to rapidly and quantitatively adsorb RNA polymerase from the initial crude extract fraction. This affinity procedure obviates the necessity of including nucleic acid precipitation or partitioning steps and allows for rapid separation of RNA polymerase from proteolytic activity. The enzyme is further purified by preparative glycerol gradient centrifugation resulting in an overall purification in 200-fold in 24 h with near quantitative recovery of polymerase protein and activity. RNA polymerase holoenzyme is obtained by chromatography on single-stranded DNA-agarose. The in vitro transcription products made by purified preparations of B. subtilis and Escherichia coli RNA polymerase holoenzymes in response to B. subtilis phage phi 29 DNA have been analyzed, and an in vitro transcription map is presented. The E. coli RNA polymerase holoenzyme initiates transcription from three promoter sites not efficiently utilized by the B. subtilis holoenzyme under optimal conditions for RNA synthesis.

Bacillus subtilis↗
PubMed1977

Prophylactic antibiotics for women undergoing vaginal hysterectomy.

A triple-blind prospective study of women undergoing vaginal hysterectomy was conducted to compare cefazolin, cephaloridine and no antibiotic, Both cefazolin and cephaloridine were given preoperatively, whereas only cephaloridine was given postoperatively. One gram of cefazolin given intramuscularly on call to the operation room was found to be a safe and effective antibiotic for prophylaxis against febrile morbidity. The proper utilization of prophylactic antibiotics seems to be in the immediate preoperative period. The use of antibiotics after the first day of surgery is unnecessary.

Adult↗
PubMedDate not supplied

Hip fractures in children: a long-term follow-up study.

University of Iowa Hospital records from 1926 to 1988 were searched for cases of hip fractures in otherwise healthy children aged between 1 and 16 years. Twenty-six cases were identified. Nineteen patients were available for clinical and radiographic follow-up evaluation. The average follow-up was 16 years postinjury. There were four type I (transepiphyseal), nine type II (transcervical), three type III (cervicotrochanteric), and three type IV (intertrochanteric) femoral fractures. Avascular necrosis (AVN) of the femoral head complicated nine of the 19 fractures (47%). Seventy-eight percent of patients who developed AVN required additional surgical intervention to obtain acceptable hip function.

Adolescent↗