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Biomedical subjects

G Myers

Publications and source records attributed to G Myers.

At least 55 records · Page 3Linked to original sources
PubMed1992

Signature pattern analysis: a method for assessing viral sequence relatedness.

Signature pattern analysis identifies particular sites in amino acid or nucleic acid alignments of variable sequences that are distinctly representative of a query set of sequences relative to a background set. We explore the merits of using signature patterns for analysis of HIV-1 (human immunodeficiency virus type 1) sequences in cases of epidemiological linkage and potential superinfection. For these purposes, query sets are viral sequences that are all derived from one HIV-1 infected individual, hence the signature pattern is the array of sites that are characteristic of the range of viral variants obtained from that person. Once a signature pattern has been objectively defined, it can be used to examine other viral sequences from other individuals for evidence of genetic relatedness. A computer program to facilitate this analysis, VESPA, is described and applied to sequence data gathered during the investigation of HIV-1 transmission in a dental practice. The implications of signature polymorphisms seen within an infected individual, and shared polymorphisms between linked individuals, are also considered. VESPA may also be applied to the molecular analysis of biological phenotypes.

Amino Acid Sequence↗
PubMed1992

The emergence of simian/human immunodeficiency viruses.

Molecular evolutionary analyses strongly support the hypothesis that human immunodeficiency viruses have recently arisen from a diverse pool of nonhuman primate immunodeficiency viruses. Our understanding of the molecular phylogenetic relationships between primate and nonprimate lentiviruses is less certain, partly because key intermediate forms are still to be discovered. DNA and protein sequence comparisons reveal uncanny dissimilarities, as well as similarities, among the genetic sequences of these complex retroviruses, thereby giving rise to the notion that primate lentiviruses are participants in "fast-forward" evolution.

DNA, Viral↗
PubMed1992

A successful transport scenario for the health sector in developing countries.

The role and operation of transport in the health sector in developing countries is important, costly but often taken for granted. This article suggests the need for a fresh look at the policy, planning and management of transport through the analysis of the essential components of a successful transport scenario for health services in developing countries i.e. transport and health planning; transport and organisational responsibility; the role of health sector donors; decision-making and procurement of transport and spares; transport and human resources; monitoring and control of transport and information; maintenance and repair; the budget. The article concludes with a checklist of key questions that may be used in assessing the contribution of transport to the health services.

Decision Making, Organizational↗
PubMed1992

Clostridial septicemia in an urban hospital.

The records of 56 patients at an urban hospital who had positive blood cultures for clostridia were reviewed. Each patient was classified as immunologically normal or immunosuppressed. Data were collected on clinical history, type of clostridial bacteremia, physical and laboratory determinants of infection, therapeutic intervention, clinical course and outcome. Of the 56 patients, 22 were determined to be immunosuppressed. Among all 56 patients, 28 had a malignancy, usually gastrointestinal or hematologic in origin. Fever, leukocytosis and abdominal pain were common in both groups. Clostridial bacteremia almost always heralded clostridial septicemia. A gastrointestinal source of infection, particularly carcinoma of the colon or rectum or enterocolitis, was evident or presumed in 43 of the 56 patients. Clostridium perfringens was the most frequently isolated microorganism, but C. septicum was associated with more complications and a higher mortality rate. Septic complications and mortality were higher among the patients with immunosuppression.

Adolescent↗
PubMed1989

Molecular characterization of HIV-1 isolated from a serum collected in 1976: nucleotide sequence comparison to recent isolates and generation of hybrid HIV.

Human immunodeficiency virus type 1 (Z321 designate, HIV-1Z321), the oldest known HIV, was isolated from a serum sample collected in Zaire in 1976 and was molecularly cloned. Restriction enzyme analysis of unintegrated viral DNA revealed the presence of conserved restriction enzyme cleavage sites in the long terminal repeat sequences. Nucleotide sequence analysis of the 3' end of the viral DNA revealed a pattern similar to other HIV-1 isolates described. However, some of the common restriction sites present in other isolates were absent in HIV-1Z321. The extent of differences between HIV-1Z321 and recent isolates from North America and Zaire was 17.86-18.36% on the nucleotide sequence level and 26.5-33.2% difference in the predicted amino acid sequence in the envelope gene. Differences were also noted in 3'-orf (nef: according to HIV gene nomenclature; see Ref. 42) gene and U3 region of the long terminal repeat sequences of HIV-1Z321 and other isolates. Nucleotide sequence of a HIV-1 isolate, 12 years apart from the present isolates, will provide an important time calibration point for the evolutionary divergence of HIV isolates. Hybrid HIV was also generated by transfecting HIV-1Z321 and HIV-1HTLV-III viral DNAs into cells.

Amino Acid Sequence↗
PubMed1989

Laser angioplasty of totally occluded coronary arteries and vein grafts: preliminary report on a current trial.

CLINICAL PERSPECTIVE: Among the various laser angioplasty systems and atherectomy devices currently in clinical trials, the Lastac system appears to be particularly suitable for treating totally occluded coronary arteries and vein grafts. Preliminary results of a clinical trial in more than 35 patients show a recanalization rate of 92% and no complications attributable to the laser. Restenosis has occurred in five cases; in three of these, the arteries were reopened with laser or conventional angioplasty.

Angioplasty, Balloon↗
PubMed1988

The phylogenetic history of immunodeficiency viruses.

Knowledge of the phylogenetic history of the human immunodeficiency viruses (HIV-1 and HIV-2) is important for our understanding of the epidemiology of AIDS, the disease caused by these viruses. Reconstruction of the evolutionary tree is hampered, however, by two problems. One is the high variation in nucleotide sequence between the known HIV isolates which can create formidable difficulties in identifying homologous genomic sites that may be used in a molecular phylogenetic reconstruction. Another impediment has been the lack of unequivocal time calibration points: there is only a sparse 'fossil record' for HIV and limited historical epidemiological data. We have largely overcome these difficulties by: (1) a thorough optimal-sequence alignment analysis; (2) the inclusion of sequences of an early (1976) HIV-1 isolate, a recent (1986) HIV-2 isolate and two simian immunodeficiency viruses (SIV) along with five other HIV-1 isolates; and (3) the reconstruction of a minimum-length evolutionary tree based on the envelope-gene variable positions. We conclude that HIV-1 may have evolved from its common ancestor with HIV-2 as recently as 40 years ago.

Animals↗
PubMed1988

Patterns of substance use on a college campus: a 14-year comparison study.

In 1972, a drug incidence survey was conducted at a private southern university. Pooled results of this random survey of 1,032 students revealed that on at least one occasion, 90% of the students had tried alcohol, 70% had used tobacco, and 61% had experimented with marijuana. Use of amphetamines (38%), hallucinogens (28%), barbiturates (19%), and cocaine (10%) was much lower. To evaluate the apparent change in trends of drug usage, a follow-up study was undertaken in 1986 at the same school. The results showed a decline in amphetamine and barbiturate use. The greatest differences were seen in the nearly fourfold increase in one-time use of cocaine between 1972 and 1986 and the sixteenfold increase in students who used cocaine more than 10 times. It was noteworthy that one-third of the students who used marijuana had done so by the 9th grade. Similar early experimentation was noted with a majority of the other drugs.

Adult↗
PubMed1988

Hemispherectomy and diaschisis: rapid improvement in cerebral functions after right hemispherectomy in a six year old child.

Neuroradiological, neurological, and neuropsychological studies before and after hemispherectomy for seizures of a six year old boy with left hemiplegia at birth revealed striking postoperative improvement. Seizures ceased and have not recurred. Preoperative EEC studies from seven months of age revealed increasing pathological involvement of the left as well as right hemisphere. Postoperatively, normal tracings over the left hemisphere documented marked and continuing improvement. In contrast to markedly subnormal preoperative WISC-R IQs, retest at 19 months postoperatively showed WISC-R IQs within the normal range, with similar improvement in other tests of cognitive, motor and sensory functions. The arrest and reversal of the preoperative pattern of increasing deterioration and disappearance of pathological involvement of left as well as right hemisphere functions following surgery is consistent with the disappearance of diaschisis as described by von Monakow in 1914, and has conceivably significant clinical as well as theoretical implications.

Journal Article↗
PubMed1988

Evaluation of delivery systems for oxygenated cardioplegia.

The oxygen-carrying capacity of four delivery systems for blood and crystalloid cardioplegia was evaluated: nonoxygenated crystalloid cardioplegia, crystalloid cardioplegia oxygenated with a bubbler system and with a membrane system and, finally, blood cardioplegia delivered by the Shiley-Buckberg system. The nonoxygenated crystalloid cardioplegic solution delivered 0.56 ml of oxygen/dl of solution, the bubbler oxygenating system delivered 3.2 ml/dl and the membrane oxygenating system made available 3.7 ml/dl. Blood cardioplegia delivered 4.2 ml/dl when oxygen-carrying capacity was corrected for the shift in the oxyhemoglobin dissociation curve that occurs with hypothermia. There appears to be no advantage between blood and oxygenated crystalloid cardioplegia with respect to the ability of these solutions to provide oxygen to the myocardium during ischemic arrest. However, the bubbler oxygenating system is superior to the membrane and blood delivery systems in that it could administer cold cardioplegia at any time during the operation. In contrast, the membrane and blood cardioplegia delivery systems both depend on integral heat exchangers which limit the delivery of cold cardioplegia to the period of hypothermia.

Adult↗
PubMed1987

Heart rate variability and sudden death secondary to coronary artery disease during ambulatory electrocardiographic monitoring.

Data are analyzed from 5 patients who died suddenly during ambulatory electrocardiographic monitoring. Three of the patients were also assessed in terms of 2 recently developed indexes of heart rate (HR) variability. One of these, the standard deviation of RR intervals during successive 5-minute segments averaged over 24 hours, has been reported to be a putative index of vagal tone. Comparisons were made with HR variability findings in 20 normal volunteers. Sudden death was due to ventricular tachycardia degenerating into ventricular fibrillation in all cases. Both early (3 patients) and late cycle (2 patients) ventricular premature complexes initiated the terminal dysrhythmia. An increased density of ventricular ectopic activity was noted in the hour before onset of ventricular fibrillation. HR variability as measured by the standard deviation was significantly (p less than 0.01) lower in the patients who died suddenly (30 +/- 10 ms) than in the normal subjects (76 +/- 14 ms). These findings support suggestions that HR variability analysis may be useful in identifying patients at a higher risk of sudden death.

Aged↗
PubMed1987

Symptomatic atlantoaxial dislocation in Down's syndrome.

Four patients with Down's syndrome suffered compression of the spinal cord secondary to atlantoaxial dislocation. All four developed inability to walk and quadriparesis, with signs of cervical myelopathy. It is important to recognize this potentially fatal complication of the syndrome. Immediate immobilization of the neck, followed by cervical roentgenograms, should be done in any patient with Down's syndrome who presents with neck pain, torticollis, urinary incontinence, or loss of ambulation. Surgical repair with fusion of the first and second cervical vertebrae can be carried out later.

Adolescent↗
PubMed1987

Elemental mercury exposure among children of thermometer plant workers.

Because evidence of mercury exposure was found among workers of a mercury thermometer-manufacturing plant in March 1984, the Vermont Department of Health studied the workers' children for both exposure to mercury and evidence of mercury toxicity. The median urine mercury level of 23 workers' children was 25 micrograms/L. This was significantly higher than the level (5 micrograms/L) among 39 children randomly selected from nonworkers' households in the same community (P less than .001). Mercury-in-air levels measured in workers' homes were higher than those measured in control homes. A significant correlation was found between the urine mercury levels of the workers' children and the urine mercury levels of their working parents. No child had frank mercury toxicity. No evidence of neurologic toxicity among exposed children was discovered by a pediatric neurologist who examined these and unexposed children without knowledge of their exposure status. This is the first report demonstrating mercury exposure in children of mercury workers. Although toxic effects of mercury were not demonstrated at these levels of exposure, children of mercury workers are at risk for mercury exposure and potential mercury toxicity.

Adult↗
PubMed1981

Measurement of urinary histamine: development of methodology and normal values.

A small portion of the histamine that circulates through the kidney is excreted intact. Thus, the measurement of histamine in urine may be employed to monitor fluctuations in plasma histamine and has several advantages: stability, accessibility, and the opportunity for retrospective analysis. A method for measuring urine histamine was developed based on cation-exchange chromatography, organic solvent extraction, o-phthalaldehyde condensation, and measurement of fluorescence. However, because the histamine measured by this procedure was higher than that measured by other techniques, a portion of each sample was digested wtih diamine oxidase and the difference between the two portions of each sample, after isolation and fluorescent assay, was taken to reflect histamine. Normal urinary histamine levels of 13 +/- 8 ng/ml, 14 +/- 9 micrograms/24 hr, or 14 +/- 12 ng/mg creatinine/ml were found. Male and female subjects excreted equivalent concentrations; spot, short-timed, or 24-hr collections provided equivalent results; and histamine in frozen urine was stable greater than or equal to 6 mo. Two patients with systemic mastocytosis and two with idiopathic anaphylaxis had elevated urine histamine levels. Monitoring urine histamine may be useful in assessment of conditions in which histamine plays a role.

Adult↗
PubMed1980

Therapy of primary hypothyroidism with L-triiodothyronine: discordant cardiac and pituitary responses.

Cardiac systolic time intervals were studied in ten patients with primary hypothyroidism before and during therapy with increasing doses of oral L-triiodothyronine (L-T3). Therapy was increased sequentially from 10, 20, 25 to 50 microgram of L-T3 daily on a monthly basis. On L-T3, 20 to 25 microgram/day, cardiac systolic time intervals and other peripheral responses to thyroid hormone including serum cholesterol concentration, serum creatine phosphokinase (CPK) activity, and basal metabolic rate had normalized. However, serum thyrotrophin (TSH) levels and peak TSH responses to thyrotrophin-releasing hormone (TRH) remained elevated on these doses of L-T3. As the dose of L-T3 was increased from 20 to 50 microgram/day, mean basal serum TSH levels decreased from 55 to 16 microunits/ml, and the peak TSH response to TRH decreased from 243 to 58 microunits/ml (P less than 0.001) while systolic time intervals did not decrease further. Changing to L-thyroxine (L-T4) therapy at this point resulted in further suppression of TSH secretion, without significantly altering systolic time intervals or the other peripheral responses to thyroid hormone. These data suggest (a) that some biological responses to thyroid hormone were normalized on lower doses of L-T3 than were required to normalize TSH secretion, and (b) that higher doses of L-T3 or substituting L-T4 therapy could suppress TSH secretion further without altering the other peripheral responses to thyroid hormone.

Adult↗