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Biomedical subjects

M Katz

Publications and source records attributed to M Katz.

At least 325 records · Page 18Linked to original sources
PubMed1987

Sex differences in the classification of children as mildly mentally retarded.

A consistent finding in epidemiological studies of mild mental retardation (MMR) is a somewhat higher prevalence of boys than girls. Our own study in Aberdeen agreed with these findings. Examination of the numbers of boys and girls at different levels of retardation within our study population revealed the greatest excess at the highest IQ levels of greater than or equal to 75. This was found to be true in other studies as well. Since this IQ range is above the generally agreed upon cut-off point used to classify children as MMR, these findings suggest that boys remaining in regular classes may be having more difficulty in school performance than girls. Possible reasons for this are examined.

Adolescent↗
PubMed1987

Optical properties of low vision telescopes.

Angular magnification, resolving power, astigmatism, field of view, eye relief, and light transmittance of 157 low power telescopes comprising 25 models from seven manufacturers were measured. Roof-prism Keplerian telescopes provided about one-half the resolution, 30% lower transmittance, and more objectionable image flare than Galilean designs. The roof-prism was responsible for producing overlapping doubled images that appeared astigmatic-like. The prism further compromised rotational symmetry by deviating the image in a direction along the roof edge. The Keplerian telescopes, however, had about twice the field of view of the Galilean telescopes. Notably, several Keplerian telescope models from different suppliers were found to be optically identical, although they varied 50-100% in price.

Humans↗
PubMed1987

Antecedents of behavior disturbance in mildly mentally retarded young adults.

Behavior disturbance was found to be more frequent among mildly retarded (MMR) than a group of young adults matched during childhood for age, sex and social class. Reasons for this were examined. An unstable environment in childhood was found to be significantly related to behavior disturbance in both MMR and controls. The greater frequency of behavior disturbance among the MMR was due to their more frequently experiencing unstable environments in childhood than comparisons. Further, when stability of upbringing was held constant, differences in behaviour disturbance between the two groups were no longer found. Central nervous system damage was found not to be a contributory factor.

Adolescent↗
PubMed1987

Synovial pseudarthrosis: a clinical, roentgenographic-scintigraphic, and pathologic study.

Seventy-six patients with synovial pseudarthrosis were reviewed. This is a distinct pathologic entity which is a different form of nonunion. The humerus, femur, and tibia were the bones most commonly involved. Routine roentgenograms were not beneficial but 99mTc scans were useful for identifying this entity in 93% of cases. Light and electron microscopy revealed normal synovial lining tissue. Motion and infection may lead to the development of this condition. The results of treatment were a 43% success rate in infected cases and 59% for noninfected cases, which is far different from that of regular nonunion.

Diagnosis, Differential↗
PubMed1987

Antepartum ambulatory tocodynamometry: the significance of low-amplitude, high-frequency contractions.

The clinical significance of low-amplitude, high-frequency contractions was examined during pregnancy in 142 women who underwent daily ambulatory tocodynamometry between 23-36 weeks' gestation. The results indicate that patients destined to develop preterm labor had this contractility pattern significantly more often than did their counterparts who delivered at term (13.5 versus 9.2%; P less than .01). Parity and gestational age had no effect on the occurrence of low-amplitude, high-frequency contractility, but this pattern was also significantly more prevalent in the presence of multifetal gestations, independent of the occurrence of preterm labor. The institution of tocolytic therapy was accompanied by a 50% decrease in the proportion of time occupied by low-amplitude, high-frequency contractions. Although this contraction pattern occurred significantly more often among patients who later developed preterm labor, calculations of its predictive values, specificity, and sensitivity indicate that its presence has relatively limited clinical significance.

Female↗
PubMed1987

Cardiovascular and uterine blood flow changes during nicardipine HCl tocolysis in the rabbit.

We studied the changes in cardiovascular performance and uterine blood flow during treatment with nicardipine HCl, a recently developed calcium entry blocker. Pregnant rabbits were surgically prepared for monitoring of uterine activity and blood flow measurements on day 24-26 of gestation. On day 29 of gestation, regular uterine activity was induced and then treated by intravenous nicardipine HCl infusion. Measurements were made before induction of labor and before and after tocolysis. Nicardipine HCl treatment was associated with a rise in pulse rate and concomitant fall in mean arterial pressure. While there was a significant (greater than 40%) increase in cardiac output during tocolysis, there was also a fall in uteroplacental blood flow. The significance of these changes and their implications for fetal well-being need further investigation before clinical studies can begin.

Animals↗
PubMed1987

Cardiovascular and tocolytic effects of nicardipine HCl in the pregnant rabbit: comparison with ritodrine HCl.

The effects of two dosage schedules of nicardipine, a calcium-entry blocker, were studied in the pregnant rabbit during induced preterm uterine contractions and compared with the effects of ritodrine hydrochloride. Uterine activity was inhibited by all treatment regimens, but the most significant inhibition was achieved by the higher dose of nicardipine, which nearly abolished all uterine activity. However, while maternal tachycardia and hypotension were observed during treatment with each of these medications, the most significant drop in blood pressure occurred with high-dose nicardipine. These findings may indicate that nicardipine is a potent tocolytic agent with side effects similar in degree, but of different etiology, than those seen with ritodrine. Additional studies to clarify the effect of nicardipine tocolysis on the fetus are needed before it can be considered for use in human pregnancy.

Animals↗
PubMed1986

Depletion of cellular ATP inhibits Na+/H+ antiport in cultured human cells. Modulation of the regulatory effect of intracellular protons on the antiporter activity.

The metabolic energy dependency of Na+/H+ exchange activity was investigated in cultured human A431 carcinoma cells and foreskin fibroblasts. Following the activation of Na+/H+ exchange which results from loading cells with Na+ or Li+, depletion of cellular ATP by incubation with metabolic inhibitors causes an inhibition of Na+/H+ exchange activity. This inhibition is reversible and correlates with the extent of the reduction in the ATP pool. On the other hand, reduction of the intracellular pH (pHi) to approximately 6.0-6.2 results in a similar effective activation of Na+/H+ exchange in both control and ATP-depleted cells. Na+/H+ exchange activity in ATP-depleted cells that either have or have not been loaded with Na+ shows a steep dependency on pHi, being essentially abolished above pHi of 6.4-6.5, whereas control cells show a considerable activity also at more alkaline pHi values. Thus, Na+/H+ exchange activity in ATP-depleted cells shows an increased dependency on intracellular protons. These findings suggest that although metabolic energy is not required as a driving force for Na+/H+ antiport, depletion of metabolic energy substrates inhibits the antiporter activity due to a modulation of an intracellular proton-dependent regulatory mechanism.

Adenosine Triphosphate↗
PubMed1986

Two-dimensional echocardiographic analysis of proximal left main coronary artery in humans.

The left main coronary artery (LMCA) was evaluated in 100 consecutive patients (88 men and 12 women; mean age 63 years) with anginal syndrome, all in New York Heart Association classes II and III. Each patient underwent two-dimensional echocardiography (2DE) from the parasternal short-axis and apical four-chamber views. Coronary angiography was subsequently performed within 24 hours. The LMCA was directly measured by 2DE and coronary angiography at its widest point. Each echocardiogram was blindly evaluated for LMCA aneurysm or obstruction. Eight patients (8%) were excluded because of inadequate visualization of the LMCA. The mean 2DE measurement was 4.4 +/- 0.9 mm vs 4.2 +/- 0.8 mm on coronary angiography (r = 0.86). Atherosclerotic aneurysms of the LMCA were correctly diagnosed in two patients by 2DE. LMCA stenosis (greater than 50%) was found in 11 patients on coronary angiography; three of them had ostial or proximal lesions, three had middle lesions, and five had distal lesions. 2DE correctly diagnosed all three ostial lesions, two of three middle lesions, but only two of five distal lesions. In four patients, dense echoes in the LMCA caused a false positive diagnosis. It was concluded that: the LMCA can be visualized and correctly measured by 2DE; atherosclerotic aneurysms can be detected; and 2DE is yet unable to screen patients for LMCA lesions; however, 2DE is a promising method for evaluating proximal and especially ostial LMCA stenosis.

Adult↗
PubMed1986

Assessment of uterine activity in ambulatory patients at high risk of preterm labor and delivery.

With use of an ambulatory tocodynamometer, prelabor uterine activity was recorded daily during pregnancy in 34 patients at increased risk of preterm labor and delivery. The data indicate that the frequency of contractions was significantly greater among women who subsequently developed preterm labor when compared to that observed among women who labored at term. This difference was present up to several weeks before the onset of labor. An additional significant rise in frequency of contractions could be observed within the last 24 hours before the development of clinically apparent preterm labor, as evidenced by progressive cervical dilation and effacement. If these results can be reproduced in a larger sample, intermittent ambulatory monitoring may offer an effective way to better identify patients at risk of preterm labor as well as enhance the early diagnosis of this event.

Adult↗
PubMed1986

Electrocardiographic changes associated with ritodrine-induced maternal tachycardia and hypokalemia.

One hundred twelve patients in preterm labor were followed prospectively, with electrocardiograms taken before ritodrine therapy and at 6 and 24 hours of treatment. Ninety-six percent of patients developed sinus tachycardia. Other changes were seen in 79% of the study group. These changes included ST segment depression in 70%, T wave flattening or inversion in 55%, and prolongation of the QT interval in 35% of our sample. None of the electrocardiograms showed the presence of a significant axis deviation, a change in QRS interval, or arrhythmia. No correlation was seen between symptoms of ischemia and electrocardiographic changes. A drop in potassium concentration was noted initially, but a direct correlation between potassium concentrations and frequency of electrocardiographic changes was not present. We conclude that the electrocardiographic changes that are often observed during myocardial ischemia may be frequent in asymptomatic patients treated with ritodrine and that these changes may be a physiologic expression of ritodrine-induced tachycardia or hypokalemia. The validity of the use of the presence of electrocardiographic changes as the only criterion for discontinuation of ritodrine therapy is questioned.

Electrocardiography↗
PubMed1986

Uterine activity during pregnancy in ambulatory patients: comparison of singleton and twin gestations.

Prelabor uterine activity was monitored daily in a group of ambulatory outpatients who were delivered at term. The study included 22 patients with one fetus and 18 with twin gestations. The mean weekly frequency of uterine activity during twin gestations was found to be significantly higher throughout pregnancy than that identified during pregnancies with a single fetus. In twin gestations a gradual significant rise in frequency of contractions could be observed with advancing gestational age. The data presented could help establish the guidelines for evaluation of uterine activity records during pregnancies complicated by a multifetal gestation.

Adult↗
PubMed1986

Detection of preterm labor by ambulatory monitoring of uterine activity for the management of oral tocolysis.

A study to evaluate whether ambulatory tocodynamometry at home could enhance the management of oral tocolysis was performed. On discharge from the hospital, after completing parenteral tocolysis, 60 patients received a lightweight tocodynamometer, designed for storage and transmission of uterine activity data. Sixty additional contemporary patients, who were matched for maternal age, parity, and risk factors, served as a control group. In addition to instructions regarding self-detection of recurrent preterm labor, monitored patients recorded uterine activity for greater than or equal to 200 min/day and then transmitted the data to the study center. Tocolytic dosage was adjusted to maintain mean uterine contraction frequency of less than 4/hr. Persistent uterine contractions of greater than or equal to 4/hr lead to in-hospital evaluation for recurrent preterm labor. The results indicate that the monitored group had a lower incidence of preterm births mostly because of a decrease in the proportion of patients with failed tocolysis. It is suggested that surveillance of uterine activity at home during oral treatment for preterm labor may be instrumental in improving perinatal outcome in high-risk patients.

Adult↗
PubMed1986

Factors leading to differences in the school performance of boys and girls.

Literature supporting the finding that boys do not fare as well in school performance during the first few years of school is reviewed, and possible reasons for this pattern are presented. These reasons are categorized as biological (e.g., X-linkage of intellectual traits) and social (e.g., sex-role training is more stringent for boys than for girls, and parents may place more pressure on boys for academic achievement). Social factors are presented in light of the rapid social change that has been taking place in the carrying out of adult sex roles and whether this has filtered down to changes in the sex-role training in the socialization of children. Pediatricians should be aware of whether school problems are occurring for both boys and girls, and their responses to such problems may differ, depending on the child's sex.

Achievement↗