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Biomedical subjects

W L Johnston

Publications and source records attributed to W L Johnston.

At least 19 recordsLinked to original sources
PubMed1995

Risk of chromosomal abnormalities, with emphasis on live-born offspring of young mothers.

In a large public urban hospital obstetrics service with > 123,000 deliveries in a 10-year period (1980-89), the frequencies (0.12%) of any type of chromosomal abnormality and of trisomy syndromes were analyzed for maternal age-related risk, by logistic regression. Focusing on very young gravidas, we found that in the study period there were 9,332 births (7.5% of all deliveries) to mothers < or = 16 years old. Estimated risks of chromosomal abnormalities among offspring associated with very young maternal age (9-16 years) were similar to those age-associated risks of mothers 20-29 years old. Risks of chromosomal abnormalities increase with advancing maternal age and are independent of ethnicity.

Adolescent↗
PubMed1995

Changes in presence of a segmental dysfunction pattern associated with hypertension: Part 1. A short-term longitudinal study.

A statistically significant pattern of segmental components of somatic dysfunction associated with a history of high blood pressure was investigated for change after an interval of 4 to 8 months. The volunteer subjects, from an inner-city ambulatory clinic, included normotensive, borderline hypertensive, and hypertensive persons. A standardized palpatory examination determined whether there were specific motion asymmetries centered at spinal segments C6, T2, and T6 and confirmed by mirror-image motion asymmetries in adjacent segments. Blood pressure measurements and diagnosis of hypertension followed American Heart Association standards. The repeated presence of the pattern in subjects with a history of hypertension was statistically significant. Presence of the pattern in normotensive subjects, however, appeared to be random. The subjects' histories during the study period revealed no influence of antihypertensive medications, major accidents, or illness on the patterns' continuing presence in subjects requiring medical control of their hypertension.

Cervical Vertebrae↗
PubMed1995

Changes in presence of a segmental dysfunction pattern associated with hypertension: Part 2. A long-term longitudinal study.

The short-term portion of this study (part 1) showed an association between somatic dysfunction and the regulation of blood pressure. To study long-term relationships, follow-up examinations were made of 61 subjects studied 3 to 10 years earlier. They were heterogeneous Family Practice Clinic patients with a mean age of 45 years. By methods used in part 1 and in our previous studies of systemic interactions, palpatory examination was done to support presence or absence of a C6T2T6 pattern of segmental motion dysfunctions, and blood pressure status was established by the medical history. The C6T2T6 pattern persisted in 16 of 16 subjects with grade 2 or greater hypertension and 4 of 9 normotensive subjects who had shown the pattern initially. At follow-up, the pattern first appeared in 7 subjects who had hypertension previously diagnosed and who remained hypertensive; the pattern disappeared in 5 normotensive subjects who remained normotensive. The C6T2T6 pattern's long-term persistence in hypertensive subjects and changes in its presence corresponding to the subjects' hypertensive status indicate an important relationship between this pattern of segmental motion dysfunctions and disturbances in regulation of blood pressure.

Adult↗
PubMed1992

Reliability of birth certificate reporting of congenital anomalies.

Birth certificates comprise an important source of data on the prevalence of genetic conditions and for monitoring possible teratogens in the population. Investigators have found wide variability (12 to 100%) in the accuracy of reporting. In a large public hospital, of those congenital anomalies detected at birth, only 5.4% were recorded on the birth certificate. This is one of the lowest rates ever reported. An underreporting correction factor may be applied if congenital anomalies are distributed randomly with respect to reporting status, and the rate of reporting is sufficient to comprise a valid sample for estimating a correction factor (that is, 20% or more reported). In this study, factors such as numbers or types of anomalies, race, infant birthweight, or estimated gestational age did not significantly influence the rate of birth certificate reporting. Thus, our data satisfied the first but not the second criterion for derivation of a correction factor. In conducting epidemiologic studies, birth certificate data should be used with: (1) great caution; (2) a system of validation with the medical record to estimate the degree of underreporting and to derive a correction factor; and (3) a priori knowledge that underreporting of congenital anomalies on this document is highly prevalent.

Bias↗
PubMed1991

Clinical biomechanic correlates for cervical function: Part III. Intermittent secondary movements.

Parts I and II of this study compared kinematic and myoelectric data for two groups of asymptomatic subjects classified as having symmetric or asymmetric motor response to a palpatory test for cervical sidebending. Kinematic data revealed that asymmetric subjects had limited mobility for primary and secondary motions. Myoelectric activity was slow to be initiated in the asymmetric subjects, and reduced in time and strength of contraction. Part III addresses additional specific kinematic data concerning three-dimensional orientations of the head; however, these data were accumulated throughout the paths of movement, not just at their end points as in our previous work. Although asymmetric subjects had demonstrated significantly reduced range of motion, paths of the more minor secondary axes did not differ significantly between groups. As with previous data (Part I and II), active and passive movements were undifferentiated; this degree of likeness in even minor aspects of the motor performance continues to indicate the remarkable similarities that can exist between primary movements directed and guided by trained physicians and those actively controlled by patients themselves. Part III completes a study of cervical motor behavior in which a passive gross motion test distinguished an asymmetric group with subclinical motor behavior that has measurable kinematic and myoelectric correlates.

Biomechanical Phenomena↗
PubMed1991

HIV prevalence in pregnant intravenous drug users in Dallas, Texas.

Information available regarding the prevalence of human immunodeficiency virus (HIV) in pregnant women indicates that the primary risk factor for infection is intravenous drug use. At Parkland Memorial Hospital in Dallas, Texas, approximately 4.7% of pregnant women reported using intravenous drugs. The estimated prevalence of HIV infection among pregnant intravenous drug users at this hospital was 3.3%. This is similar to the HIV infection rates reported for nonpregnant parenteral drug-using populations in other areas of the southwestern United States, suggesting that there may be a lower rate of endemic infection in this region of the country.

Female↗
PubMed1990

Patterns of multiple substance abuse during pregnancy: implications for mother and fetus.

This paper describes patterns of drug use such as choice of drug, other substances abused, and route of administration in 174 women who reported methamphetamine, cocaine, heroin, or "Ts and blues" abuse during pregnancy. Seventy-five percent (130/174) reported using more than one drug. Other than tobacco, alcohol and cocaine were the drugs most frequently used in combination with other drugs (7% to 53% and 12% to 54% of the time, respectively). The extent of polydrug use observed in this study emphasizes (1) the difficulty in ascribing adverse maternal or fetal health effects to single substances, and (2) the potential for interaction effects due to multiple substance abuse.

Adolescent↗
PubMed1990

Nomograms for rapid estimation of intravascular intrauterine exchange transfusion.

Fetal exchange transfusion is complicated by the fact that vascular access must be maintained while the number of exchanges needed to achieve a desired post-transfusion hematocrit is calculated. A rapid method for estimating the number of exchange transfusions would greatly simplify fetal exchange transfusion for blood group isoimmunization. In this report, we present a graphic method for determining the number of exchange transfusions necessary to achieve a post-transfusion hematocrit of 45%, using a nomogram for 5- and 10-mL exchange transfusion volumes.

Blood Transfusion, Intrauterine↗
PubMed1989

Chronic cervical dysfunction: correlation of myoelectric findings with clinical progress.

In this pilot study, four patients with motion impairment and chronic cervical pain after cervical spine injury received osteopathic manipulative treatment for spinal dysfunction for periods in excess of 3 months. Records were compared for changes in the patient's subjective complaints, in the physician's findings, and in the standardized measurement of electrical activity of the cervical spine musculature. All three measures demonstrated parallel improvement in the health status of these patients. Attention to functional aspects of a neuromusculoskeletal problem appears to provide reliable indicators for directing treatment of somatic dysfunction and registering both subjective and objective change.

Adult↗