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Biomedical subjects

K Jackson

Publications and source records attributed to K Jackson.

At least 127 records · Page 7Linked to original sources
PubMed1986

Chronic caffeine administration exacerbates renovascular, but not genetic, hypertension in rats.

The purpose of this study was to determine whether or not caffeine would exacerbate renovascular hypertension. Therefore, we examined the effects of chronic caffeine administration on arterial blood pressure in rats subjected to either unilateral renal artery clipping (2K-1C rats) or sham-operation. Animals in each group were randomly assigned to receive either 0.1% caffeine in their drinking water or normal drinking water, and systolic blood pressure was monitored for 6 wk. Caffeine markedly exacerbated the severity of hypertension in 2K-1C rats and caused histological changes consistent with malignant hypertension. 6 wk after surgery, systolic blood pressure, plasma renin activity, and creatinine clearance in control 2K-1C rats were 169 +/- 5 mmHg (mean +/- SEM), 4.4 +/- 0.5 ng AI X ml-1 X h-1, and 2.9 +/- 0.2 ml/min, respectively; as compared with 219 +/- 4 mmHg, 31.8 +/- 7.8 ng AI X ml-1 X h-1, and 1.4 +/- 0.3 ml/min, respectively, in 2K-1C rats receiving caffeine (all values were significantly different compared with control 2K-1C). Chronic caffeine administration did not alter systolic blood pressure, plasma renin activity, or creatinine clearance in sham-operated rats or spontaneously hypertensive rats. Chronic treatment with enalapril (a converting enzyme inhibitor) prevented the development of hypertension in control 2K-1C rats and caffeine-treated 2K-1C rats; however, withdrawal of enalapril precipitated a rapid rise in systolic blood pressure in caffeine-treated 2K-1C rats, but not in control 2K-1C rats. These experiments indicate that caffeine specifically exacerbates experimental renovascular hypertension and might worsen the hypertensive process in patients with renovascular hypertension.

Animals↗
PubMed1986

Behavioral approaches in increasing blood donations.

In the United States, as well as other countries, there is a constant and pressing need for increasing the number of people who donate blood. Medical procedures require donated blood, and when shortages occur in different regions, the lives of numerous patients are endangered. Behavioral strategies, which include use of incentives, competition, and raffles, and the like, might be effective methods for motivating individuals to donate blood. This study examined the use of a variety of these types of strategies used by workers at United Blood Services. Organizations that had employed behavioral strategies were compared with other organizations that had not used these approaches. Significantly higher rates of donations were obtained in organizations that had used behavioral strategies. The implications of these findings are discussed.

Analysis of Variance↗
PubMed1986

Clinical implications of orbital cellulitis.

Periorbital and orbital cellulitis are clearly two distinct disorders with different etiologies. Periorbital cellulitis is well-documented as a more common infectious process limited to the eyelids in the preseptal region. In contrast, orbital cellulitis represents a more severe, but less common, infection of the orbit posterior to the septum with or without subperiosteal abscess, orbital abscess, or cavernous sinus thrombosis. A retrospective review of the clinical and laboratory data of 137 cases of orbital and periorbital cellulitis was performed. Periorbital cellulitis was documented in 98 cases (71%), in contrast to orbital cellulitis which was noted in 39 (28%) patients. All patients with orbital cellulitis received intravenous antibiotics, however, surgical therapy was necessary for progression of orbital cellulitis in 49% of patients. The majority of patients underwent incision and drainage of an abscess in the orbit. Complications as a result of orbital cellulitis occurred in nine (23%) of the patients. A distinction is made between the clinical entity of periorbital cellulitis and orbital cellulitis. Separating these clinical entities on the basis of physical examination and radiographic studies is important because the medical and surgical management of these two disease processes is different.

Abscess↗
PubMed1986

Improved oxygenation and lower peak airway pressure in severe adult respiratory distress syndrome. Treatment with inverse ratio ventilation.

Two patients with the adult respiratory distress syndrome (ARDS) were placed on pressure-controlled inverse-ratio ventilation (IRV) when their condition deteriorated despite optimal treatment with intermittent mandatory ventilation and positive end-expiratory pressure. In the first case, high peak airway pressure was reduced by 50 percent with the institution of IRV. In the second, refractory hypoxemia was eliminated by using an inspiratory-to-expiratory ratio of 4:1. These cases show that IRV may offer certain advantages in the treatment of severe ARDS.

Adult↗
PubMed1985

Prostaglandin E and F2 alpha receptors in human myometrium during the menstrual cycle and in pregnancy and labor.

The binding of prostaglandins E1 and F2 alpha has been studied in the human myometrium and cervix during the menstrual cycle and in the myometrium of pregnant patients at term before and during labor. Tritium-labeled prostaglandin E1 and F2 alpha binding was saturable and reversible. Scatchard analysis of tritium-labeled prostaglandin E1 binding was linear, which suggests a single class of high-affinity binding sites with an estimated apparent equilibrium dissociation constant of 2.5 to 5.4 nmol/L and inhibitor affinities of 0.9, 273, 273, and 217 nmol/L for prostaglandins E2, A1, B1, and F2 alpha, respectively. Scatchard analysis of tritium-labeled prostaglandin F2 alpha, binding was also linear, but the affinity of these binding sites was much lower, with an average dissociation constant of 50 nmol/L and inhibitor affinities of 1.6, 2.2, and 11.2 nmol/L for prostaglandins E1, E2, and A1, respectively. In nonpregnant patients, the concentrations and affinities of tritium-labeled prostaglandin E1 binding sites were similar in the myometrium during the proliferative and secretory phases of the menstrual cycle, but the concentration of these sites was much lower in the cervix. The concentration of the tritium-labeled prostaglandin E1 binding sites was significantly lower in the myometrium of pregnant patients at term than in the myometrium of nonpregnant patients. The concentrations and affinities of tritium-labeled prostaglandin E1 binding sites were not significantly different in the upper and lower myometrium of pregnant patients at term or in the myometrium of such patients before and during labor. The concentrations of the tritium-labeled prostaglandin F2 alpha binding sites during the menstrual cycle and in pregnancy at term were similar to those of tritium-labeled prostaglandin E1 binding sites. In addition to confirming the presence of specific prostaglandin E and F2 alpha binding sites in the myometrium, these data also suggest: that specific prostaglandin E binding sites are present in the cervix and that the concentrations and affinities of prostaglandin E binding sites do not change during the menstrual cycle and are similar before and during labor in pregnant patients at term.

Cervix Uteri↗
PubMed1983

Specific glucocorticoid binding in human uterine tissues, placenta and fetal membranes.

The binding of [3H]dexamethasone to cytosol fractions of human myometrium, endometrium, decidua, chorion, amnion and placenta has been studied. All tissues examined contained high affinity, low capacity binding sites with high specificity for glucocorticoids. Maximum specific binding of [3H]dexamethasone was reached after about 10 h at 0-4 degrees C and remained stable for at least the next 12 h. Sucrose density gradient analysis showed that the binding macromolecules sedimented at 7.9 S in hypotonic solutions and at 4.35 in solutions containing 0.4 M KCl. In the presence of sodium molybdate, the sedimentation coefficients shifted both in the absence and presence of 0.4 M KCl to 8.9 and 5.7 S, respectively. The apparent equilibrium dissociation constants (Kd) of the glucocorticoid binding sites were similar in most tissues, ranging between 1 and 6 nM, with the exception of the placenta in which the binding sites showed a higher Kd (13-22 nM). In all tissues studied, the binding affinities were similar in nonpregnant and pregnant patients and in patients at different stages of pregnancy or in labor. The concentration of the binding sites in the different tissues ranged from 11 to 268 fmol/mg protein, higher concentrations being found in myometrium, placenta and amnion and lower concentrations found in endometrium, chorion and decidua. The number of binding sites was higher in the myometrium of nonpregnant than pregnant women, but was similar in the myometrium of women at term pregnancy before or during labor. In the placenta, the number of binding sites increased significantly from early pregnancy to midpregnancy, while in chorion, amnion and decidua the number of binding sites did not change during pregnancy. It is concluded that human uterine tissues, placenta and fetal membranes contain specific binding sites with properties characteristic of glucocorticoid receptors suggesting that these tissues may respond directly to glucocorticoids.

Amnion↗
PubMed1983

Further analysis of the Crist data on matching performance and the similarity structure of the stimulus set.

We argue that Crist's (1981) analysis of his data on letter matching is incomplete because he did not sufficiently distinguish overall context similarity from the similarity of the other letter present on a trial. That is, the separation of the effects of context similarity and visual similarity is required for a complete analysis. Accordingly, for different trials, modified indices of context similarity are derived and linear regression analyses made to determine the separate effects of context and visual similarity. The results of these analyses show that on different trials, visual similarity is much more predictive of latency than context similarity and that subjects must therefore be making visual similarity judgments, that considerably affect latency variation on these trials. Consequently, we argue that visual similarity judgment may be likewise affecting latency on same trials. However, some simple correlations indicate that context may be more predictive of latency on physically different same trials. We concluded that what can be said about context depends on the type of trial and that the comparative strength of name processing should also be assessed by the method described here.

Discrimination, Psychological↗
PubMed1982

Glucocorticoid metabolism in human placenta, decidua, myometrium and fetal membranes.

The metabolism of cortisone (E) and cortisol (F) by human placenta, decidua, myometrium, chorion and amnion during pregnancy was studied in vitro. Early pregnancy, midpregnancy and term placentae metabolized F efficiently yielding E as the major product. The capacity of the placenta to inactivate F to E was observed as early as the 8th week of pregnancy and there was a significantly higher (P less than 0.001) net production of E in early pregnancy placenta than in term placenta. In contrast to the placenta, midpregnancy and term decidua metabolized mainly E to F with a net production of F. Term chorion demonstrated an equal degree of oxidative and reductive glucocorticoid metabolism while term amnion and myometrium had negligible metabolic activity. Thus the net production of F from E by the decidual membrane unit is due to metabolic activity in the decidua as early as the 13th week of pregnancy and not to activity in the fetal membranes.

Cortisone↗
PubMed1981

d-Amphetamine and phencyclidine alone and in combination: effects on fixed-ratio and interresponse-time-greater-than-t responding of rats.

The effects of three doses of d-amphetamine (0.5, 1.0, and 2.0 mg/kg) and phencyclidine (0.5, 1.0, and 2.0 mg/kg), alone and in combination, were assessed in rats performing under fixed-ratio 30 and interresponse-time-greater-than-15-sec food reinforcement schedules. When given alone, phencyclidine and d-amphetamine produced similar increases in responding under the interresponse-time-greater-than-t schedule, and decreases in responding under the fixed-ratio 30 schedule. Each drug decreased the number of reinforcers (food pellets) earned relative to control values under both schedules. The effects of the two drugs in combination were nearly always less than additive. That is, the effects of a given dose of phencyclidine and d-amphetamine together were less than an arithmetic summation of the effects of the drugs given alone.

Animals↗
PubMed1979

Treatment of handwriting problems utilizing EMG biofeedback training.

The effects of EMG biofeedback training on cursive handwriting were investigated for 4 girls and 5 boys in Grade 4. A significant reduction in EMG between the first baseline session and the last training session was obtained. Four of 5 characteristics of handwriting improved significantly. The need for carefully designed research comparing EMG biofeedback training and relaxation training was indicated. A self-control factor in handwriting was hypothesized.

Biofeedback, Psychology↗
PubMed1978

Effects of relaxation training on cursive handwriting of fourth grade students.

A relaxation method of handwriting improvement was examined. The experimental and no-treatment control groups were composed of 10 students receiving a poor rating on handwriting characteristics and the normal control group of 10 was composed of students receiving average ratings. All three groups received nine trials of writing. Only the experimental group received relaxation training during each trial. The handwriting of the experimental group improved significantly while that of the no-treatment control group remained the same. Although the handwriting of the normal control group also improved significantly, at posttest they were no longer significantly different from the experimental group.

Child↗
PubMed1976

Studies of the spatial distribution of firearms discharge residues.

Fingerprint lifting tape has been applied to the lifting of firearms discharge residue from various surfaces. Lifting efficiencies from coarse fabric ranged from 30 to 70%. Use of the technique has been demonstrated in identifying a bullet hole and in measuring residue patterns on floor and firing hand surfaces. In hand lifts it has been shown that autoradiography alone does not uniquely distinguish the hand of someone who has fired a revolver from the hand of someone who has not. Neutron activation analysis of lifts from selected hand areas may, however, provide such a distinction.

Autoradiography↗