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Biomedical subjects

M R Wallace

Publications and source records attributed to M R Wallace.

At least 145 records · Page 8Linked to original sources
PubMed1992

Initial low CD4 lymphocyte counts in recent human immunodeficiency virus infection and lack of association with identified coinfections.

Initial CD4 lymphocyte counts were studied in 244 patients with human immunodeficiency virus (HIV) seroconversion. The CD4 cell counts at initial presentation after seroconversion were normally distributed (mean, 579/mm3; SD, 252). The mean percentage of CD4 cells was 26.1% (SD, 5.6). CD4 cell counts were < 500/mm3 in 41% and < 200/mm3 in 4%. The mean calculated duration of HIV infection was 7.7 months, which was not significantly different between the highest and lowest CD4 count quartiles (8.1 vs. 7.9). Age, sex, race, and serologic evidence of toxoplasmosis, cytomegalovirus, hepatitis B, syphilis, and varicella-zoster virus were not associated with initial low CD4 cell counts; however, never-married men were significantly overrepresented in the lowest quartile. These findings suggest that extensive CD4 lymphocyte depletion is common in early HIV infection and that frequent screening is necessary to identify newly infected patients who would benefit from antiretroviral therapy.

Adult↗
PubMed1992

A significant proportion of patients with osteosarcoma may belong to Li-Fraumeni cancer families.

We studied the pedigrees of 17 index patients with osteosarcoma, recording malignant disease and cause of death for first- and second-degree relatives. There were seven cancers and five cancer deaths per 2151.5 person-years in first-degree relatives of osteosarcoma patients under the age of 50 years, a significantly greater incidence than in an age- and sex-matched population group (p < 0.001). This excess of malignancy was largely due to two families which fulfilled the criteria for the Li-Fraumeni cancer family syndrome. Both of these families were shown to have the genetic alterations in the p53 gene which have been implicated in this syndrome. Our study suggests that orthopaedic surgeons seeing new cases of osteosarcoma should arrange screening for familial malignancy.

Adolescent↗
PubMed1992

Corticosteroids for Pneumocystis carinii pneumonia with acute respiratory failure. Experience with rescue therapy.

Corticosteroids have proven effective as adjunctive therapy for the treatment of PCP in patients with AIDS, when begun within 72 h of conventional anti-Pneumocystis therapy. Their efficacy as rescue (or salvage) therapy in patients who have failed conventional therapy, however, remains unproven. Ths report presents our experience with 16 patients admitted to our MICU for acute respiratory failure (PaO2/FIO2 ratio less than or equal to 150) due to PCP. Five of six patients (83 percent) who received "primary" CS rescue (initial CS use prompted by acute respiratory failure after 72 h of conventional anti-Pneumocystis therapy) survived hospitalization. Our experience suggests that CSs may be effective even when started after 72 h of conventional therapy. Additional studies are needed to clarify the role of CS rescue therapy.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Sequencing and analysis of genomic fragments from the NF1 locus.

The sequence of five non-contiguous genomic fragments encompassing 14.4 kilobases from the NF1 locus have been determined by fluorescence-based automated DNA sequence analysis. These fragments included one kilobase of the NF1 coding region, which resulted in the identification of the intron/exon boundaries of five exons. Based on these sequences, five new NF1 exon-PCR assays have been developed, that could be useful for detecting new NF1 mutations. The genomic sequences were analyzed for the presence of Alu repetitive elements and their classification is described. This analysis may provide some insight into the characterization of genetic rearrangements resulting in disruption of the NF1 gene.

Base Sequence↗
PubMed1992

Rapid host nation medical deployment.

Rapid development of land-based units in Operation Desert Shield/Storm presented critical needs for medical support. Integration of small Navy mobile medical teams in Bahrain and a larger United States Army Hospital unit in Riyadh, Saudi Arabia, at host nation hospitals presented an innovative method of providing this support. The success of these ventures in convenience and quality of care establishes the host nation interaction with military medical professionals as a workable, satisfying, and important adjunct to standard military medical care.

Bahrain↗
PubMed1991

A de novo Alu insertion results in neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is a common autosomal dominant disorder with a high mutation rate and variable expression, characterized by neurofibromas, café-au-lait spots, Lisch nodules of the iris, and less frequent features including bone deformities and learning disabilities. The recently cloned NF1 gene encodes a transcript of 13 kilobases from a ubiquitously expressed locus on chromosome 17. Most NF1 patients are expected to have unique mutations, but only a few have so far been characterized, restricting genetic and functional information and the design of DNA diagnostics. We report an unusual NF1 mutation, that of a de novo Alu repetitive element insertion into an intron, which results in deletion of the downstream exon during splicing and consequently shifts the reading frame. This previously undescribed mechanism of mutation indicates that Alu retrotransposition is an ongoing process in the human germ line.

Adult↗
PubMed1991

cDNA cloning of the type 1 neurofibromatosis gene: complete sequence of the NF1 gene product.

Von Recklinghausen neurofibromatosis, or type 1 neurofibromatosis (NF1), is a common autosomal dominant disorder characterized by abnormalities in multiple tissues derived from the embryonic neural crest. Portions of the gene have been recently identified by positional cloning, and sequence analysis has shown homology to the GTPase activating protein (GAP) family. In this report we present the results of an extensive cDNA walk resulting in the cloning of the complete coding region of the NF1 transcript. Analysis of the sequences reveals an open reading frame of 2818 amino acids, although alternatively spliced products may code for different protein isoforms. The gene extends for approximately 300 kb on chromosome 17, with its promoter in a CpG-rich island.

Adult↗
PubMed1991

cDNA sequence and genomic structure of EV12B, a gene lying within an intron of the neurofibromatosis type 1 gene.

The gene responsible for neurofibromatosis type 1 (NF1), one of the more common inherited human disorders, was identified recently, and segments of it were cloned. Two translocation breakpoints that interrupt the NF1 gene in NF1 patients flank a 60-kb segment of DNA that contains the EV12A locus (previously reported as the EV12 locus), the human homolog of a mouse gene, Evi-2A, implicated in retrovirus-induced murine myeloid tumors. EVI2A lies within an intron of the NF1 gene and is transcribed from telomere toward centromere, opposite to the direction of transcription of the NF1 gene. Here we describe a second locus, EVI2B, also located between the two NF1 translocation breakpoints. Full-length cDNAs from the EV12B locus detect a 2.1-kb transcript in bone marrow, peripheral blood mononuclear cells, and fibroblasts. Sequencing studies predict an EV12B protein of 448 amino acids that is proline-rich and contains an N-terminal signal peptide, an extracellular domain with four potential glycosylation sites, a single hydrophobic transmembrane domain, and a cytoplasmic hydrophilic domain. At the level of genomic DNA the EV12B locus lies within the same intron of the NF1 gene as EV12A and contains a 57-bp 5' exon that is noncoding, an 8-kb intron, and a 2078-bp 3' exon that includes the entire open reading frame. EV12B is transcribed in the same direction as EV12A; its 5' exon lies only 4 kb downstream from the 3' exon of the EV12A locus. In the mouse the 5' exon of the homologous gene, Evi-2B, lies approximately 2.8 kb from the 3' end of Evi-2A, in the midst of a cluster of viral integration sites identified in retrovirus-induced myeloid tumors; thus, Evi-2B may function as an oncogene in these tumors.

Amino Acid Sequence↗
PubMed1991

Red man syndrome: incidence, etiology, and prophylaxis.

The red man syndrome (RMS) is the most common toxicity of vancomycin therapy. A prospective trial to investigate the frequency, causation, and possible prophylaxis of this syndrome was conducted. Thirty-three patients were observed during their first two doses (1 g/60 min) of vancomycin. Before dose 1, they were randomized to double-blinded pretreatment with either diphenhydramine (50 mg) or placebo. Patients were examined frequently, and histamine levels were obtained at 0, 30, and 60 min during dose 1. Those with first-dose reactions were rerandomized for pretreatment and had histamine levels drawn during a second infusion. Of 17 patients with placebo pretreatment, 8 (47%) had RMS. None of the 16 pretreated with diphenhydramine had a first-dose reaction (P = .003). Three of the eight first-dose reactors had a second-dose RMS reaction; in one of these three, it was more severe than the dose 1 RMS despite diphenhydramine pretreatment. RMS events were associated with elevated plasma histamine; this was especially true of severe reactions.

Adult↗
PubMed1991

Tracheobronchitis due to Corynebacterium pseudodiphtheriticum.

We have presented a case of tracheobronchitis due to C pseudodiphtheriticum in a patient with COPD who was treated with prednisone and apparently was not otherwise immunocompromised. Chronic lung disease seems to predispose to infection with C pseudodiphtheriticum; it can also occur in the immunocompetent host. This organism, when isolated in pure culture, should not be dismissed as a contaminant, but must be considered a possible etiologic agent. Sensitivity of diphtheroids to antibiotics is extremely variable. We believe vancomycin should be used in respiratory tract infections caused by diphtheroids, including C pseudodiphtheriticum, until the results of in vitro antibiotic susceptibility tests are available.

Anti-Bacterial Agents↗
PubMed1991

Prenatal serologic screening in Bahrain.

Between 1988 and 1990, serological surveys designed to study local disease prevalence and assess the clinical value of various prenatal screening tests were undertaken at Salmaniya Medical Center in Bahrain. High maternal antibody prevalence (greater than 85%) to cytomegalovirus (CMV), herpes simplex virus (HSV) and rubella was demonstrated, and 28% showed antibodies to Toxoplasma gondii. The lowest seroprevalence values were found for HBsAg (1.2%) and Treponema pallidum (0.9%). Routine testing for rubella, syphilis, and hepatitis B are advocated for all pregnancies in Bahrain. In contrast, CMV and HSV serologies are not recommended. Toxoplasma antibody testing remains controversial, but the lack of a proven agent to prevent congenital toxoplasmosis coupled with the high cost of serial testing mitigates against its routine use at this time.

Animals↗
PubMed1990

Type 1 neurofibromatosis gene: identification of a large transcript disrupted in three NF1 patients.

Von Recklinghausen neurofibromatosis (NF1) is a common autosomal dominant disorder characterized by abnormalities in multiple tissues derived from the neural crest. No reliable cellular phenotypic marker has been identified, which has hampered direct efforts to identify the gene. The chromosome location of the NF1 gene has been previously mapped genetically to 17q11.2, and data from two NF1 patients with balanced translocations in this region have further narrowed the candidate interval. The use of chromosome jumping and yeast artificial chromosome technology has now led to the identification of a large (approximately 13 kilobases) ubiquitously expressed transcript (denoted NF1LT) from this region that is definitely interrupted by one and most likely by both translocations. Previously identified candidate genes, which failed to show abnormalities in NF1 patients, are apparently located within introns of NF1LT, on the antisense strand. A new mutation patient with NF1 has been identified with a de novo 0.5-kilobase insertion in the NF1LT gene. These observations, together with the high spontaneous mutation rate of NF1 (which is consistent with a large locus), suggest that NF1LT represents the elusive NF1 gene.

Adult↗