Search PubMed⌕ Search

Biomedical subjects

G D Johnson

Publications and source records attributed to G D Johnson.

At least 91 records · Page 5Linked to original sources
PubMed1990

Surgical management of cholesteatoma in an only hearing ear.

The patient with a cholesteatoma in an only hearing ear presents a management dilemma: how best to treat the patient to minimize the chances of developing a severe hearing loss in that ear. Twelve patients managed surgically for cholesteatoma in their only hearing ear are reviewed. The location and extent of the cholesteatoma, the type of operation performed, and postoperative hearing results are presented. Eleven of the 12 patients maintained their bone-conducted speech reception threshold to within 5 dB of the preoperative level during follow-up periods of 2 months to 4 years. Recommendations are made regarding preoperative evaluation, perioperative use of antibiotics and steroids, operative planning, ossicular reconstruction, and postoperative care. Special attention is given to the evaluation and management of the ear that has a fistula eroding into the cochlea and semicircular canals, both when suspected from preoperative imaging studies and when discovered intraoperatively.

Cholesteatoma↗
PubMed1990

Management of large dural defects in skull base surgery: an update.

The use of a ventriculoatrial shunt for long-term CSF diversion for reconstruction after resection of large skull base tumors with intradural extension has been discontinued. The concern about placing a permanent foreign body in a wound open for 12 to 18 hours is our primary reason for changing the technique. Our present approach uses a rectus abdominis microvascular free flap over the fascial closure of the dural defect. Although our experience with this technique is limited, the advantages over the technique used previously warrant its continued use.

Abdominal Muscles↗
PubMed1989

Transient production and secretion of human transforming growth factor TGF-beta 2.

Transient transfection of simian COS cells with a recombinant plasmid encoding the human transforming growth factor TGF-beta 2 precursor protein results in the production of a latent, biologically inactive protein. Upon acidification, recombinant TGF-beta 2 exhibits full biological activity, including inhibition of mink lung epithelial cell growth, stimulation of anchorage-independent growth of murine embryonic fibroblasts, and competition for TGF-beta receptor binding. Further analysis of conditioned media with antiserum to either a pro- [amino acid (aa) residues 1-220] or mature [aa 297-414] peptide of the TGF-beta 2 precursor suggests that TGF-beta 2, similar to TGF-beta 1 production in Chinese hamster ovary cells [Gentry et al., Mol. Cell. Biol. 7 (1987) 3418-3427], is initially synthesized as a larger precursor protein which is proteolytically cleaved to yield the mature 112-aa transforming growth factor.

Animals↗
PubMed1989

A human tRNA gene heterocluster encoding threonine, proline and valine tRNAs.

A cluster of three tRNA genes encoding a tRNA(UGUThr), a tRNA(UGGPro), and a tRNA(AACVal), and two Alu-elements occur in a 6.0-kb human DNA fragment. The tRNA(Thr) gene is 2.7-kb upstream from the tRNA(Pro) gene, which is separated by 367 bp from the tRNA(Val) gene. One Alu-element actually overlaps the tRNA(Val) gene and is of opposite polarity to all three tRNA genes. All three tRNA genes are accurately transcribed in a homologous HeLa cell extract, since the ribonuclease T1 fingerprints of the tRNA transcripts are consistent with the nucleotide sequences of the tRNAs. The upstream region flanking the tRNA(Thr) gene has two tracts of alternating purine/pyrimidine residues potentially capable of adopting the Z-DNA conformation, and presumptive binding sites for two RNA polymerase II transcription factors. The tRNA(Thr) gene apparently has a substantially higher in vitro transcriptional efficiency than the other two tRNA genes in this cluster, and a tRNA(GCCGly) gene from another human DNA segment. Deletion constructs of the tRNA(Thr) gene retaining 272, 168, and 33 bp of original 5'-flanking DNA had about the same in vitro transcriptional efficiency, whereas that of the construct with only 2 bp of 5'-flanking human DNA was drastically reduced. The tRNA(Thr) gene constructs with 272 and 168 bp of original 5'-flanking DNA apparently reduce the transcriptional efficiencies of the proline and glycine tRNA genes, implicating the upstream region from the tRNA(Thr) gene as being crucial for its high transcriptional efficiency.

Base Sequence↗
PubMed1989

A phenotypic study of cells from Burkitt lymphoma and EBV-B-lymphoblastoid lines and their relationship to cells in normal lymphoid tissues.

Cells of 7 EBV-B-LCL, 10 Burkitt lines and 13 EBV-B-LCL/Burkitt line hybrids have been phenotyped for antigens of the major B cell clusters and for some other antigens. High levels of CD23 and CD39 and low levels of CD38 (T10) were characteristic of EBV-B-LCL; the converse was true for Burkitt lines. In hybrids the EBV-LCL phenotype was dominant. The phenotype of Burkitt-line cells correlated strongly with that of germinal centre B cells in tonsil sections, but differed markedly from that of marginal zone B cells or follicular mantle cells. The results are discussed in relation to the origin of Burkitt tumours of "sporadic" and "endemic" type, in particular to histopathological evidence that Burkitt lymphomas develop in germinal centres. Recent studies on the location of the breakpoints of Burkitt chromosomal translocations are also considered to be compatible with this concept, even though different regions of the immunoglobulin heavy chain locus are involved in the two types of BL.

ADP-ribosyl Cyclase↗
PubMed1989

CD23: a multi-functional receptor/lymphokine?

With the demonstration of identity between CD23 and the low affinity IgE Fc receptor (Fc epsilon RII), two previously separate avenues of immunological research have converged into one. Particularly in its guise as 'Blast-2' antigen, evidence has been mounting to implicate CD23 as an important molecule in B-cell growth regulation. It might seem pertinent, however, to question a role for an apparently isotype-specific immunoglobulin (Ig) receptor in general B-cell processes. In this article, John Gordon and colleagues attempt to reconcile the two, currently diverse, schools of thought regarding the primary function of CD23 and to provide a structural model that accounts for the biological pleiotropy observed.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1989

The auditory brain stem response interaural latency difference (ILD) in patients with brain stem lesions.

The ABR interaural latency difference (ILD) from 15 patients with brain stem lesions was compared to the ILDs from patients with VIIIth nerve tumors, cochlear pathology, and a normal control group. All patients in the study had to meet the criteria of bilaterally symmetrical hearing for pure-tone thresholds in order to offset the effect of hearing loss on the ILD. Although the ILDs for the brain stem lesion group were larger than for the cochlear or normal groups, they were significantly smaller than for the VIIIth nerve tumor group. It appears that the ILD is not as sensitive a measure for detecting brain stem involvement as VIIIth nerve tumors.

Adult↗
PubMed1989

Facial nerve paralysis with benign parotid masses.

Facial paralysis in the presence of a parotid mass has been associated classically with a presumed diagnosis of malignancy. However, isolated case reports have documented the occurrence of paresis or paralysis secondary to pathologically benign, nonneurogenic parotid lesions. These previous cases have been reviewed and three additional cases are described. Comparisons are made on age, sex, symptoms, physical findings, pathologic findings, and prognosis. Involvement of the seventh nerve may be explained on the basis of compression, especially in association with local inflammation. Although facial paralysis still should be considered indicative of a malignancy, it also may be caused by benign masses, particularly those associated with rapid enlargement and/or infection.

Abscess↗
PubMed1989

Long-term hearing results following middle fossa vestibular nerve section.

Hearing stabilization following middle fossa vestibular nerve section (MFVNS) has been observed to occur in a large percentage of patients (71% to 86%) after short-term followup. This study looks at the long-term audiological followup (5 to 15 years) of 46 patients who underwent a MFVNS for intractable Meniere's disease. Although the percentage of patients with stabilized hearing was relatively high within the first 2 years postoperatively (61%), it dropped to 41% after a longer followup of 5 to 15 years. When this patient population is divided into two groups based on their preoperative PTA, those patients in whom hearing had bottomed out to greater than or equal to 50 dB PTA preoperatively lost only 5 dB PTA over the course of the follow-up period. The patients with better preoperative hearing (less than 50 dB PTA) lost 30 dB PTA over the same follow-up period. As this pattern is similar to what has been observed in nonsurgically treated Meniere's patients, we conclude that the MFVNS has no beneficial effect on the hearing loss associated with Meniere's disease.

Adult↗
PubMed1989

A paraneoplastic syndrome associated with glomus tumors of the skull base? Early observations.

Independent secretion of vasoactive substances by glomus tumors of the skull base is widely recognized. Surgical removal of these tumors often results in an unexplained prolonged postoperative ileus, even in cases in which the vagus nerve is preserved. There is evidence that these tumors may secrete neuropeptides, such as cholecystokinin, in addition to catecholamines. A retrospective analysis of cases of glomus tumors of the skull base operated on at The Otology Group was carried out to correlate preoperative neuropeptide levels, vagus nerve status at surgery, and duration of postoperative ileus. High circulating levels of cholecystokinin associated with these tumors may be responsible for the unexplained phenomenon of prolonged postoperative ileus. The relevance of neuropeptides to the postoperative management of these patients is discussed. Preventive measures that may avert the potentially lethal complications of aspiration and negative nitrogen balance are described.

Catecholamines↗
PubMed1989

What I think of sac surgery in 1989.

The senior author has performed shunt procedures routinely for medically refractory cases of Meniere's disease starting in 1964 and ending in 1984. Five hundred and sixty-eight consecutive patients were operated on and followed from 1970 to 1984. Combining the cases of C. G. Jackson, there have been a total of 676 procedures done at the Otology Group. Initially endolymphatic-subarachnoid (ES) shunts were used, then endolymphatic-mastoid shunts (EM), and most recently, the Denver valve has been employed. No significant difference between these procedures was noted in the control of vertigo or stabilization of hearing. Successful resolution of vertigo occurred in less than 60%. Sac surgery at the Otology Group, therefore, has been abandoned in favor of vestibular nerve section for the surgical management of medically refractory Meniere's disease with disabling vertigo.

Ear, Inner↗
PubMed1988

Fluorescence quenching of fluorescein by R-phycoerythrin. A pitfall in dual fluorescence analysis.

The use of a single laser fluorescence-activated cell sorter (FACS) to analyse cellular subpopulations by immunochemical staining requires an alternative dye to fluorescein with appropriate spectral characteristics. R-phycoerythrin (RPE) is widely employed for this purpose. In this study the ability of RPE to quench the fluorescein emission when both are attached to the same cell has been demonstrated by dual labelling of tonsil lymphocytes with pairs of monoclonal antibodies. Reduction of the fluorescein signal correlated with the amount of RPE attached and the relative intensity of emission from the two fluorochromes. The possible photochemical mechanisms which result in a reduction of the fluorescein signal by RPE are discussed. The inclusion of control tests, in which RPE is omitted, is recommended in order to avoid misinterpretation of the results of subpopulation analysis by single laser FACS - especially when low levels of fluorescein staining are obtained.

Antibodies, Monoclonal↗
PubMed1988

Leucocyte typing.

Explore the source record for details and available documents.

B-Lymphocytes↗
PubMed1988

Selective induction of light chain synthesis in cultures of blood lymphocytes from patients with IgG myelomatosis.

In the present study evidence is provided that neoplastic B cells from the blood from four of 24 patients with myelomatosis were activated selectively with polyclonal B cell mitogens. In three of these patients the activated cells produced light chains without heavy chains; of these, two patients had IgGK paraproteins and one had free lambda light chain disease. The ratio of kappa-expressing to lambda-expressing B cells in the initial blood B cell preparations was within the range for healthy controls for all four patients where neoplastic B cells were selectively activated. It is concluded that in some patients with myelomatosis the neoplastic clone is a mosaic of: (1) cells capable of synthesizing both light and heavy chains with (2) cells producing light chains only.

Adult↗
PubMed1988

Myeloperoxidase and oncogene expression in GM-CSF induced bone marrow differentiation.

DNA synthesis, morphology, specific RNA accumulation and rates of specific protein synthesis in GM-CSF stimulated bone marrow progenitor cells were studied. DNA synthesis increased markedly for 64 hours and then gradually decreased to 5% maximal activity by 160 hours. Morphologic examination 40 to 64 hours after stimulation revealed an increasing proportion of immature myeloid cells. After this proliferative peak, cells differentiated into segmented neutrophils and monocytes/macrophages; only mature forms were present by 160 hours. Accumulation of mRNA for c-myb and c-myc was maximal at 40 hours just prior to maximal [3H]thymidine incorporation, while maximal accumulation of histone type 3 (H3) was coincident with maximal [3H]thymidine incorporation at 64 hours. As proliferation decreased and differentiation proceeded, levels of mRNA for c-myb and H3 decreased markedly, while levels of RNA for c-myc decreased gradually and remained elevated above day 0 levels. Levels of c-fos mRNA fluctuated slightly during the first 64 hours of culture and increased 13-fold by 160 hours when mature cells were present. Similarly, beta-2 microglobulin mRNA increased steadily to maximal levels at 112 to 160 hours which were 15-fold higher than day 0 levels. Myeloperoxidase (MPO) mRNA was present in maximal amounts at 40 to 64 hours after stimulation with GM-CSF as the number of immature myeloid cells peaked. Immunoprecipitation of MPO from pulse-labeled cell lysates demonstrated a 7-fold rise in synthetic rate of MPO of 64 hours and a 28-fold decline by 160 hours when only 5% immature myeloid cells were present. Thus, MPO protein synthesis closely follows MPO mRNA accumulation. Immunoprecipitation of lactoferrin, a marker of myeloid secondary granules, demonstrated a gradual 5-fold increase in synthetic rate as the cells matured. Taken together, these data show that maximal expression of the early myeloid differentiation enzyme myeloperoxidase in GM-CSF stimulated normal bone marrow cells occurs during peak proliferation of immature myeloid cells.

Animals↗