Sequence of ionophore conformational changes induced by a simulated membrane/water interface

We demonstrate how the progressive passage through an interface simulated by a linear increase in dielectric constant may mediate a reversible transconformation of Na⁺/X337A (lasalocid A) from a cyclic to an extended structure, During the passage through the interface, the complex adopts progressively a more extended conformation favorable to the Na⁺ complexation or decomplexation at the interface.     

Incorporation of radioactive proline and fucose in gastric mucosal biopsies. Correlation with histological findings

Human gastric mucosal biopsies incorporate in vitro radioactive proline and fucose into macromolecular glycoproteins (mucin). Differences were found between the incorporation pattern of antral and fundic mucosae according to their pathology, confirmed by histology. Antral mucosae with abnormal histology showed a significantly higher incorporation of proline than normal samples. Fucose incorporation was also increased. Similar results were found with fundic biopsies. The ratio of total fucose to total proline incorporated into mucin secreted during incubation also increased significantly in these samples. Biochemical analyses on the other hand showed no significant change. The results suggest a breakdown in the processing, storage and secretory processes of mucin-type glycoproteins in pathological mucosae, but not in their biosynthesis. The mucosal samples could be classified as A or B types according to their proline and fucose incorporation: A mucosae have a lower proline incorporation than B mucosae (greater than 380 cpm/micrograms DNA for the antrum and greater than 200 cpm/micrograms DNA for the fundus). These results confirm the possibility of studying abnormal mucus secretion using gastric biopsy samples.     

Perilymphatic Fistula—A Definitive and Curable Cause of Vertigo Following Head Trauma

Vertigo or disequilibrium occurring in patients after concussive and nonconcussive head trauma may be due to a pathologic perilymphatic fistula from the inner ear through the oval and round window areas of the middle ear. Of 33 patients who had successful grafting of the fistulous area at middle ear exploration, 32 had resolution of vertigo, and 12 of 23 who had an associated hearing loss had improved hearing. Perilymphatic fistulas associated with vertigo and hearing loss after head trauma can be diagnosed with great certainty and are surgically curable in the great majority of cases. Patients with post-concussive syndrome, whose symptoms include vertigo or disequilibrium, should have a thorough otologic evaluation for the possibility of a perilymphatic fistula.     

Local Perceptions of Federal Block Grants

We report the results of a survey of California county medical societies and county health officers on federal health block grants. Survey respondents agreed that the existing network of health services funded through the federal block grants and the current statelocal apparatus for providing these services are sound. Most respondents do not recommend major changes in the service system, and most support a strong state role in administering programs under the block grants.     

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.