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Biomedical subjects

C McMillan

Publications and source records attributed to C McMillan.

At least 37 records · Page 2Linked to original sources
PubMed1988

Transmission of human immunodeficiency virus to sexual partners of hemophiliacs.

To examine the variables associated with heterosexual transmission of human immunodeficiency virus (HIV), we studied 32 couples in our hemophilia center who had steady sexual relationships for periods more than 1 year. Of the 32 sexual partners of the hemophiliacs, five (15.6%) were HIV seropositive. All five hemophiliacs with HIV transmission to their sexual partners had measurable immunologic deficiencies, as shown by their lower median T-helper (CD-4+) lymphocyte count of 172 cells/mm3. The hemophiliacs without transmission had a slightly higher median CD-4+ count of 297 cells/mm3 (P = .26). To determine if factors other than the degree of immunologic deficiency in the hemophiliac might contribute to HIV transmission, 18 of the 32 couples were studied more intensively by confidential, coded questionnaires. Regular condom use was reported by nine couples (50%). Two of nine women (22%) without condom usage acquired HIV. One of nine women (11%) using condoms was seropositive; she also reported eight needlestick injuries while assisting her spouse with clotting factor treatments. Intravenous drug abuse was reported in two of the five couples with HIV transmission. Thus, hemophiliacs are at risk for transmitting HIV parenterally as well as venereally. Despite various risk behaviours associated with HIV transmission, the prevalence of infection in our cohort of hemophiliacs' sexual partners is low and within the range (6.8-22%) reported by others. This study underscores the need for comprehensive education and counseling in what previously appeared to be a homogeneous clinic population at risk for transmitting HIV to others.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Neuropsychologic and academic functioning of children with sickle cell anemia.

This study compared neuropsychologic test results and academic functioning among 28 school-age children with sickle cell anemia (SCA), and 28 healthy, age-, sex-, and socioeconomically matched black peers followed at a tertiary care center. Children with SCA scored significantly lower on reading and spelling achievement scores than healthy matched peers. Also, older children with SCA performed significantly less well on tests of visual-motor and attention skills than younger children with SCA. These results were unrelated to most measures of physical illness severity. The data suggest that sickle cell anemia may be associated with subtle neuropsychological and learning deficits that can contribute to decreased school performance.

Adolescent↗
PubMed1987

Whole chromosomal DNA probes for rapid identification of Mycobacterium tuberculosis and Mycobacterium avium complex.

Whole chromosomal DNA probes were used to identify clinical isolates of Mycobacterium tuberculosis, Mycobacterium avium complex, and Mycobacterium gordonae. The probe for M. tuberculosis was prepared from Mycobacterium bovis BCG, which has been shown to be closely related to M. tuberculosis. A probe for the M. avium complex was prepared from three strains representing each of the three DNA homology groups in the M. avium complex. The probes were used in dot blot assays to identify clinical isolates of mycobacteria. The dot blot test correctly identified 57 of the 61 (93%) cultures grown on solid media, and 100% of antibiotic-treated broth-grown cells were correctly identified. Identification by dot blot required a maximum of 48 h. When the probes were tested against 63 positive BACTEC (Johnston Laboratories, Inc., Towson, Md.) cultures of clinical specimens, 59% were correctly identified. However, of the 14 BACTEC cultures that had been treated with antibiotics before being lysed, 13 (93%) were correctly identified.

Chromosomes, Bacterial↗
PubMed1987

Effects of high-frequency jet ventilation on arterial baroreflex regulation of heart rate.

Fifteen anesthetized mechanically ventilated patients recovering from multiple trauma were studied to compare the effects of high-frequency jet ventilation (HFJV) and continuous positive-pressure ventilation (CPPV) on arterial baroreflex regulation of heart rate. Systolic arterial pressure and right atrial pressure were measured using indwelling catheters. Electrocardiogram (ECG) and mean airway pressure were continuously monitored. Lung volumes were measured using two linear differential transformers mounted on thoracic and abdominal belts. Baroreflex testing was performed by sequential intravenous bolus injections of phenylephrine (200 micrograms) and nitroglycerin (200 micrograms) to raise or lower systolic arterial pressure by 20-30 Torr. Baroreflex regulation of heart rate was expressed as the slope of the regression line between R-R interval of the ECG and systolic arterial pressure. In each mode of ventilation the ventilatory settings were chosen to control mean airway pressure and arterial PCO2 (PaCO2). In HFJV a tidal volume of 159 +/- 61 ml was administered at a frequency of 320 +/- 104 breaths/min, whereas in CPPV a tidal volume of 702 +/- 201 ml was administered at a frequency of 13 +/- 2 breaths/min. Control values of systolic arterial pressure, R-R interval, mean pulmonary volume above apneic functional residual capacity, end-expiratory pulmonary volume, right atrial pressure, mean airway pressure, PaCO2, pH, PaO2, and temperature before injection of phenylephrine or nitroglycerin were comparable in HFJV and CPPV. Baroreflex regulation of heart rate after nitroglycerin injection was significantly higher in HFJV (4.1 +/- 2.8 ms/Torr) than in CPPV (1.96 +/- 1.23 ms/Torr).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1986

Inheritance pattern and clinical response to splenectomy as a reflection of erythrocyte spectrin deficiency in hereditary spherocytosis.

To determine how various inheritance patterns and responses to splenectomy relate to erythrocyte spectrin deficiencies in hereditary spherocytosis, we measured the spectrin content of erythrocytes by radioimmunoassay in 33 patients with this disease. Patients with the dominant form of hereditary spherocytosis generally had mild anemia, with spectrin at 63 to 81 percent of normal levels. Patients with the nondominant form of the disease had anemia ranging from severe to mild, with corresponding spectrin levels of 30 to 74 percent; their siblings were affected similarly. Distantly related homozygotes had different clinical severities with correspondingly different spectrin levels. The parents and offspring of patients with the nondominant form were clinically normal but consistently had subtle erythrocyte abnormalities. Spectrin levels in all patients were inversely related to osmotic fragility (P less than 0.0001), and they were also correlated with the clinical response to splenectomy: patients with spectrin levels above 70 percent achieved normal blood counts, those with levels of 40 to 70 percent had compensated hemolysis, and those with levels below 40 percent improved but remained anemic (P less than 0.0001). We conclude that the inheritance pattern and response to splenectomy in hereditary spherocytosis reflect erythrocyte spectrin deficiencies as determined by radioimmunoassay.

Anemia, Hemolytic, Congenital↗
PubMed1980

Construction of a composite tRNA gene by anticodon loop transplant.

By using sites for the restriction nuclease Hpa II, the information for the anticodon stem and loop of an altered Su+2 amber suppressor tRNA (a mutant of tRNAGln) has been transplanted to a specially prepared tRNATrp gene, which lacks it homologous anticodon stem and loop sequence. The resulting tRNA gene was cloned under lac operator-promoter control. The result is a functional, hybrid, amber-suppressor tRNA that can exhibit a moderately high efficiency in translation. It appears less efficient, however, than Su+7 tRNA, the amber suppressor that results from a direct anticodon mutation in tRNATrp. As judged by its suppressor spectrum, which is almost identical to the spectra of Su+2, and Su+7, the recomposed tRNA inserts glutamine at amber sites. This experiment is the prototype of a series of construction that examine the role of the nucleotides in the anticodon region.

Anticodon↗
PubMedDate not supplied

Partial deficiency of erythrocyte spectrin in hereditary spherocytosis.

Hereditary spherocytosis (HS) is a common, clinically heterogeneous haemolytic anaemia in which the primary erythrocyte defect is believed to be some abnormality in the spectrin-actin membrane skeleton, leading to loss of surface membrane. Recessively inherited spectrin deficiency with extreme erythrocyte fragility and spherocytosis has been identified in certain mutant mice and two severely anaemic humans. Although suspected, deficiency of spectrin has not been demonstrated in less severe forms of human HS. We not report the quantitation of erythrocytes spectrin by radioimmunoassay. We found that normal erythrocytes contained 240,000 copies of spectrin heterodimer, whereas erythrocytes from 14 patients with a variety of types of HS were all partially deficient in spectrin (range 74,000-200,000 copies), the magnitude of the deficiency correlating with the severity of the disease. Spectrin deficiency of varying degrees is common in HS and probably represents the principal structural defect leading to loss of surface membrane.

Erythrocytes↗