Chest Pain in Adolescents—Functional Consequences

In prospectively evaluating 100 cases of adolescents with chest pain (along with two control groups), 91 were found to have recurrent chest pain; fewer than 5 had a serious organic cause. Significantly higher school absenteeism occurred in patients with either chest or abdominal pain than in patients without pain. Adolescents with chest and abdominal pain were more likely to be high users of medical services than those with no pain. Most adolescents believed that persons their age could have attacks; 44 of those with chest pain thought their symptom was due to a heart attack. The occurrence of chest pain was not influenced by an adolescent''s age, sex, race, smoking status or family structure, nor was it consistently associated with depression. Chest pain is thus a common problem of adolescence that produces considerable functional impairment not attributable to serious underlying disease.     

Biotechnology and agricultural improvement

A range of emerging technologies are expected to play a significant role in agricultural improvement in the next 20 years. Some are only now being explored, but others have already produced significant results. Recent progress in the tissue culture and genetic engineering of crop plants has opened the door to: (1) large scale and rapid propagation of genetically uniform plants from elite materials; (2) the selection of novel and improved varieties using somaclonal variation technology; (3) the development of new hybrids between different cultivars and species by means of protoplast fusion and (4) the use of recombinant DNA to introduce new genetic material into plant cells. It is expected that, by the year 2000, a wide range of crops will be affected by these advances in biotechnology.     

Controlled release of bioactive agents

The use of polymer carriers for the controlled release of bioactive agents including polypeptides is discussed. This paper reviews release mechanisms from polymers, examines applications of these systems, explores approaches to control drug delivery in response to physiological needs, and discusses the impact of controlled drug release with respect to biotechnology.     

The pharmacological actions of 5-hydroxytryptamine,FMRF-amide and substance P and their possible occurrence in the heart of the snail Helix aspersa L.

The actions of 5-hydroxytryptamine (5-HT), FMRF-amide and substance P were tested on the isolated heart of Helix aspersa. All three compounds were found to produce positive inotropic and chronotropic effects, the order of potency being 5-HT > substance P > FMRF-amide. However, whereas the responses to 5-HT and FMRF-amide were maximal within a few seconds, the response to substance P had a longer latency. Two other similar undecapeptides, eledoisin and physalaemin, were also tested and were found to have very similar actions to those of substance P. The effects of 5-HT and FMRF-amide could be separated using the 5-HT blockers methysergide and ketanserin, which had relatively little effect on the response to FMRF-amide.Immunohistochemical staining was carried out on sections through the Helix auricle and ventricle for 5-HT, FMRF-amide and substance P. Substantial 5-HT-like and substance P-like immunoreactivity was observed, apparently concentrated in nerve endings, but the level of FMRF-amide-like immunoreactivity was considerably lower. The fluorescence produced by all three compounds was evenly distributed throughout the heart tissue. HPLC analysis of heart tissue extract demonstrated a high level of 5-HT (about 8 μg/g wet weight) but a negligible catecholamine content.     

Leukotriene B4 binding to human neutrophils

[³H] Leukotriene B₄ (LTB₄) binds concentration dependency to intact human polymorophonuclear leukocytes (PMN's). The binding is saturable, reaches equilibrium in 10 min at 4°C, and is readily reversible. Mathematical modeling analysis reveals biphasic binding of [³H] LTB₄ indicating two discrete populations of binding sites. The high affinity binding sites have a dissociation constant of 0.46 × 10⁻⁹M and B_max of 1.96 × 10⁴ sites per neutrophil; the low affinity binding sites have a dissociation constant of 541 × 10⁻⁹M and a B_max of 45.6 × 10⁴ sites per neutrophil. Competitive binding experiments with structural analogues of LTB₄ demonstrate that the interaction between LTB₄ and the binding site is stereospecific, and correlates with the relative biological activity of the analogs. At 25°C[³H] LTB₄ is rapidly dissociated from the binding site and metabolized to 20-OH and 20-COOH-LTB₄. Purification of neutrophils in the presence of 5-lipoxygenase inhibitors significantly increases specific [³H] LTB₄ binding, suggesting that LTB₄ is biosynthesized during the purification procedure. These data suggest that stereospecific binding and metabolism of LTB₄ in neutrophils are tightly coupled processes.     

Preliminary results from a controlled evaluation of thermal biofeedback as a treatment for essential hypertension

In a controlled trial, thermal biofeedback (n=20) and abbreviated progressive relaxation (n=22) were compared in the treatment of mild to moderate hypertensive patients whose blood pressures (BP) were initially controlled on two medications. For the clinical end point of maintaining control of BP on a single drug after treatment, biofeedback was superior to relaxation training (at 3 months, 47% success for biofeedback versus 23% for relaxation). This same result tended to be true for patient-measured home BPs. BPs from laboratory psychophysiological testing showed no consistent advantage for one treatment over the other.This research was supported by a grant from NHLB1, HL-27622.     

Sex-related differences in first-stage impedance cardiographic variables

Impedance cardiography (ZCG), a noninvasive technique used to determine stroke volume and ventricular performance, is currently being utilized more extensively in psychophysiological research and may also prove a useful tool in the control of hypertension. To date, most studies employing ZCG have tested male subjects or patients. However, women and men differ on two important parameters used to calculate stroke volume: thoracic impedance (Zo), and the first derivative of change in impedance over time (dZ/dt_min). Examination of the clinical records of 19 females and 19 males, all nonmedicated, indicated that women had higher Zo levels (F(1, 36)=46.2,p<.0001) and higher dZ/dt_min levels (F(1, 36)=51.8, p<.0001), although calculated stroke volume indexes did not differ. A second sample of 10 women and 8 men, all healthy and nonmedicated, confirmed these findings. The differences in Zo are not due entirely to sex differences in height, weight, percent body fat, and subscapula skin-fold thickness, although these factors differ across sexes. It is important for researchers and clinicians utilizing ZCG with female subjects to be aware of these differences.