Direct Measurement of Single-Molecule Ligand-Receptor Interactions

Measuring the kinetics that govern ligand-receptor interactions is fundamental to our understanding of pharmacology. For ligand-gated ion channels, binding of an agonist triggers allosteric motions that open an integral ion-permeable pore. By mathematically modeling stochastic electrophysiological responses with high temporal resolution (ms), previous single channel studies have been able to infer the rate constants of ligands binding to these receptors. However, there are no reports of the direct measurement of the single-molecule binding events that are vital to how agonists exert their functional effects. For the first time, we report these direct measurements, the rate constants, and corresponding free energy changes, which describe the transitions between the different binding states. To achieve this, we use the super resolution technique: points accumulation for imaging in nanoscale topography (PAINT) to observe binding of ATP to orthosteric binding sites on the P2X1 receptor. Furthermore, an analysis of time-resolved single-molecule interactions is used to measure elementary rate constants and thermodynamic forces that drive the allosteric motions. These single-molecule measurements unequivocally establish the location of each binding states of the P2X1 receptor and the stochastic nature of the interaction with its native ligand. The analysis leads to the measurement of the forward and reverse rates from a weak ligand-binding state to a strong ligand binding state that is linked to allosteric motion and ion pore formation. These rates (k_α = 1.41 sec^-1 and k_β = 0.32 sec^-1) were then used to determine the free energy associated with this critical mechanistic step (3.7 kJ/mol). Importantly, the described methods can be readily applied to all ligand-gated ion channels, and more broadly to the molecular interactions of other classes of membrane proteins.

Long-Range Energy Transfer in Protein Megamolecules

In this investigation, we report evidence for energy transfer in new protein-based megamolecules with tunable distances between donor and acceptor fluorescent proteins. The megamolecules used in this work are monodisperse oligomers, with molecular weights of ∼100-300 kDa and lengths of ∼5-20 nm, and are precisely defined structures of fusion protein building blocks and covalent cross-linkers. Such structures are promising because the study of energy transfer in protein complexes is usually difficult in this long length regime due to synthetic limitations. We incorporated fluorescent proteins into the megamolecule structure and varied the separation distance between donor and acceptor by changing the length of the cross-linker in dimer conjugates and inserting nonfluorescent spacer proteins to create oligomers. Two-photon absorption measurements demonstrated strong coupling between donor and acceptor dipoles in the megamolecules. For the dimer systems, no effect of the cross-linker length on energy transfer efficiency was observed with the steady-state fluorescence investigation. However, for the same dimer conjugates, energy transfer rates decreased upon increasing cross-linker length, as evaluated by fluorescence up-conversion. Molecular dynamics simulations were used to rationalize the results, providing quantitative agreement between measured and calculated energy transfer lengths for steady-state results, and showing that the differences between the time-resolved and steady-state measurements arise from the long time scale for large-scale fluctuations in the megamolecule structure. Our results show an increase in energy transfer length with increasing megamolecule size. This is evidence for long-range energy transfer in large protein megamolecules.

Permian polar forests: deciduousness and environmental variation

Forests are expected to expand into northern polar latitudes in the next century. However, the impact of forests at high latitudes on climate and terrestrial biogeochemical cycling is poorly understood because such forests cannot be studied in the modern. This study presents forestry and geochemical analyses of three in situ fossil forests from Late Permian strata of Antarctica, which grew at polar latitudes. Stem size measurements and stump spacing measurements indicate significant differences in forest density and canopy structure that are related to the local depositional setting. For forests closest to fluvial systems, tree density appears to decrease as the forests mature, which is the opposite trend of self-thinning observed in modern forests. We speculate that a combination of tree mortality and high disturbance created low-density mature forests without understory vegetation near Late Permian river systems. Stable carbon isotopes measured from permineralized wood in these forests demonstrate two important points: (i) recently developed techniques of high-resolution carbon isotope studies of wood and mummified wood can be applied to permineralized wood, for which much of the original organic matter has been lost and (ii) that the fossil trees maintained a deciduous habit at polar latitudes during the Late Permian. The combination of paleobotanical, sedimentologic, and paleoforestry techniques provides an unrivaled examination of the function of polar forests in deep time; and the carbon isotope geochemistry supplements this work with subannual records of carbon fixation that allows for the quantitative analysis of deciduous versus evergreen habits and environmental parameters, for example, relative humidity.

Combination of flavor enhancement and chemosensory education improves nutritional status in older cancer patients

BACKGROUND

Abnormalities in taste and smell functioning occur with elevated frequency in both older adults and patients with cancer. With the predicted increase in both of these populations in the coming decades, it is imperative to evaluate potential interventions that are designed to help older cancer patients compensate for the additive burden of this disease and its treatment on age-related taste and smell losses.

OBJECTIVE

The purpose of the current study was to determine if providing instruction and products for flavor enhancement of foods to elderly cancer patients in addition to nutritional information would improve their nutritional status, and, by extension, functional and immune status as well as quality of life.

DESIGN

One hundred and seven subjects enrolled in the study. Fifty-four subjects were in the experimental group that received flavor enhancement plus nutritional information; fifty-three control subjects received only nutritional information. Subjects were evaluated 1 month, 3 months, and 8 months after beginning chemotherapy. At every session, subjects completed taste and smell assessments as well as questionnaires related to nutritional status, activities of daily living, and quality of life. Blood samples were also obtained to determine immune parameters.

RESULTS

At the eight-month time point, experimental subjects had better scores on the mini nutritional assessment (MNA) and the physical function assessment of the quality of life questionnaire. Also at eight months, self-reported taste and smell perception for experimental subjects was better than that of controls as well as better than at earlier time points. Tests that assessed quantity and quality of food intake, as well as a number of immune parameters declined over time and did not differ significantly between groups.

CONCLUSION

The combination of flavor enhancement, chemosensory education, and nutritional information for elderly cancer patients improved their nutritional assessment on the MNA and physical function over time. On the whole, experimental subjects perceived themselves to be better functioning at eight months than did their control counterparts.

Stability and convergent validity of the Physical Activity Scale for the Elderly (PASE)

AIM

The purpose of this study was to assess the stability and convergent validity of the Physical Activity Scale for the Elderly (PASE) among rural, community dwelling elderly persons using Computer Science and Applications, Inc. Actigraph Monitors (Actigraph) as the direct criterion measure.

METHODS

EXPERIMENTAL DESIGN

a correlational design was employed.

SETTING

rural community in the United States.

PARTICIPANTS

56 subjects (age=75.7+/-7.9 years) who were living independently and volunteered to participate in the study.

MEASURES

subjects wore an Actigraph monitor during all waking hours for 7 consecutive days. At the conclusion of the 7 days, each subject met with a trained interviewer to complete the PASE questionnaire. Three days later the subjects met with the same interviewer to complete the PASE a 2nd time recalling their physical activity for the same 7-day period.

RESULTS

Actigraph data indicated that subjects averaged 168.1+/-76.3 counts x minute(-1) during the 7-day period. A high intraclass correlation coefficient (r=0.91) was calculated between the 1st interview total PASE score (115.97+/-59.91) and the 2nd interview total PASE score (115.71+/-50.97). In addition, there was a statistically significant Spearman correlation coefficient of 0.43 (p<0.01) between Actigraph mean counts x minute(-1) and 1st interview total PASE scores.

CONCLUSION

In this rural elderly sample, the PASE was a stable instrument with validity indices similar to those previously reported in younger, more active, populations.

Nitric oxide: a key regulator of myeloid inflammatory cell apoptosis

Apoptosis of inflammatory cells is a critical event in the resolution of inflammation, as failure to undergo this form of cell death leads to increased tissue damage and exacerbation of the inflammatory response. Many factors are able to influence the rate of apoptosis in neutrophils, eosinophils, monocytes and macrophages. Among these is the signalling molecule nitric oxide (NO), which possesses both anti- and proapoptotic properties, depending on the concentration and flux of NO, and also the source from which NO is derived. This review summarises the differential effects of NO on inflammatory cell apoptosis and outlines potential mechanisms that have been proposed to explain such actions.

The advantages of aminolevulinic acid photodynamic therapy in dermatology

Photodynamic therapy (PDT) is being increasingly employed in the detection and treatment of malignant and non-malignant disease. This local technique uses a photosensitizing drug activated by light to generate cell death via the production of reactive oxygen species. This review describes the fundamental processes behind PDT, focussing on the use of 5-aminolevulinic acid (ALA). ALA itself is not a photosensitizing drug, but administration of exogenous ALA induces the build-up of the natural endogenous photosensitizer protoporphyrin IX (PpIX). This form of PDT has proved promising for the treatment of a number of dermatological indications. An overview of these current and potential applications of ALA-based PDT is presented, with emphasis on the advantages of the technique that make it especially suitable for skin conditions and the problem areas on which future research should be focussed.

Dissociation of DNA fragmentation from other hallmarks of apoptosis in nitric oxide-treated neutrophils: differences between individual nitric oxide donor drugs

The events of apoptotic cell death can be experimentally dissociated from each other in certain cell types. Here we demonstrate the ability of structurally diverse nitric oxide (NO) donating compounds to delay or enhance neutrophil apoptosis and to differentially influence distinct parameters of programmed cell death. We provide evidence that high concentrations of the NO donors GEA 3162, SPER/NO, and DEA/NO induce morphological and biochemical markers of neutrophil apoptosis, but that only DEA/NO causes a concomitant increase in DNA fragmentation as evidenced by nuclear propidium iodide intercalation and the classical laddering pattern of electrophoresed DNA. In contrast, both GEA 3162 and SPER/NO inhibit DNA cleavage in a time- and concentration-dependent manner. We are the first to show that DNA fragmentation can be dissociated from other changes of apoptosis in NO-treated neutrophils and that it may therefore be inappropriate to assess NO-induced apoptosis solely by measuring DNA fragmentation in this cell type.

Reconstruction of Pseudomariopteris busquetii, a vine-like Late Carboniferous-Early Permian pteridosperm

The growth habit of the Late Carboniferous-Early Permian pteridosperm Pseudomariopteris busquetii is reconstructed based on compression material from the upper Stephanian of the Blanzy-Montceau and Commentry Basins (Massif Central, France), and the upper Rotliegend of the Saar-Nahe Basin (Nahe Group, N 4, Rheinland Pfalz, Germany). Pseudomariopteris busquetii was a medium-sized, vine- to liana-like plant with slender stems to which small bipartite fronds were attached. What is most interesting is that the species used at least two different strategies to both anchor and support the plant body. Most specimens possess specialized climber hooks developed from apical extensions of the pinna axes, indicating that the fronds were used to attach the plant. A few specimens suggest that the stem may also have had some capacity for attachment. In the absence of suitable supports, however, P. busquetii was apparently able to grow in dense stands or thickets in which the individual plants supported each other.

Effects of intravenous administration of formaldehyde on platelet and coagulation variables in healthy horses

OBJECTIVES

To assess safety and determine effects of IV administration of formaldehyde on hemostatic variables in healthy horses.

ANIMALS

7 healthy adult horses.

PROCEDURE

Clinical signs and results of CBC, serum biochemical analyses, and coagulation testing including template bleeding time (TBT) and activated clotting time (ACT) were compared in horses given a dose of 0.37% formaldehyde or lactated Ringer's solution (LRS), IV, in a 2-way crossover design. In a subsequent experiment, horses received an infusion of 0.74% formaldehyde or LRS. In another experiment, horses were treated with aspirin to impair platelet responses prior to infusion of formaldehyde or LRS.

RESULTS

Significant differences were not detected in any variable measured between horses when given formaldehyde or any other treatment. Infusion of higher doses of formaldehyde resulted in adverse effects including muscle fasciculations, tachycardia, tachypnea, serous ocular and nasal discharge, agitation, and restlessness.

CONCLUSIONS AND CLINICAL RELEVANCE

Intravenous infusion of formaldehyde at doses that do not induce adverse reactions did not have a detectable effect on measured hemostatic variables in healthy horses.

Structurally preserved sphenophytes from the Triassic of Antarctica: reproductive remains of Spaciinodum

Permineralized cones found organically attached to Spaciinodum collinsonii stems are described from the early Middle Triassic silicified flora from the Fremouw Formation of Antarctica, and the species diagnosis is emended to include the reproductive specimens. The apical cones are organized into internodal and leaf-bearing nodal regions. Nodal septations span the central pith and cortex, and thin fimbrils subdivide the internodal areas into smaller chambers. The vascular system consists of 31-33 continuous bundles that do not alternate in position between successive nodes and internodes. Simple sporangia are associated with the cortical chambers and occur in one whorl on the axis. Spores are small, lack elaters, and have no discernible ultrastructure preserved, and they are interpreted to be immature. The Antarctic cones are different in structure from typical cones of modern and fossil members of Equisetales; however, they share similarities with some morphologically aberrant cones of extant Equisetum and several Late Paleozoic and Mesozoic compression-impression fossils. Spaciinodum is now the most complete anatomically described Mesozoic sphenophyte.

New perspectives on the Mesozoic seed fern order Corystospermales based on attached organs from the Triassic of Antarctica

A new Triassic corystosperm is described from the Shackleton Glacier region of Antarctica. The compression fossils include cupulate organs (Umkomasia uniramia) and leaves (Dicroidium odontopteroides) attached to short shoot-bearing branches. The cupulate organs occur in groups near the apices of the short shoots, and each consists of a single axis with a pair of bracts and a subapical whorl of five to eight ovoid cupules. This unique architecture indicates that the cupules are individual megasporophylls rather than leaflets of a compound megasporophyll. A branch bearing an attached D. odontopteroides leaf provides the first unequivocal evidence that Umkomasia cupulate organs and Dicroidium leaves were produced by the same plants. Although this had previously been assumed based on organ associations, the new specimens are important in demonstrating that a single species of corystosperm produced the unique cupulate organs described here and the geographically and stratigraphically widespread and common D. odontopteroides leaf. Therefore, biostratigraphic, paleoecological, and phylogenetic studies that treat Dicroidium leaf morphospecies as proxies for biological species of entire plants should be reconsidered. Phylogenetic analysis suggests that the corystosperm cupule is an unlikely homologue for the angiosperm carpel or outer integument.

Paleoazolla, a new heterosporous fern from the Upper Cretaceous of Argentina

Megaspore and microspore massulae of Paleoazolla patagonica gen. et sp. nov. are described from the Upper Cretaceous of La Colonia Formation, Chubut Province, Argentina. The new fern possesses megaspore complexes with three to four glochidiate floats attached directly to the megaspore; a columella-like structure appears to be absent. The megaspore wall consists of a two-layered exine that is smooth to irregularly perforate, a two-layered perine with a spongy, densely packed endoperine, and a loosely organized exoperine. Infrafilosum hairs cover the exoperine. Microspore massulae are irregular in size and shape and bear multibarbed glochidia that generally have anchor-shaped tips. A comparison with other azollaceous and salviniaceous genera, particularly Azolla, is provided, together with a discussion of some evolutionary trends within the family.

Predicting Bariatric Surgical Outcomes: Does Preoperative Weight Gain Correlate with Lesser Postoperative Weight Loss?

BACKGROUND: This study is a retrospective analysis of 76 patients who underwent vertical banded gastroplasty (VBG), in order to determine whether preoperative weight gain correlates with lesser postoperative weight loss. METHODS: Patients were divided into two groups: those patients who did not gain a significant amount of weight during the preoperative period (group 1), and those patients who gained greater than 2.5% of their preoperative BMI during the preoperative period (group 2). There were 59 patients in group 1 and 17 patients in group 2. RESULTS: Patients in group I had an average follow-up of 374 days and lost an average of 37.5 kg. The patients in group 2 had an average follow-up of 379 days with an average weight loss of 39.3 kg. CONCLUSION: Linear regression analysis was performed and supported the finding that preoperative weight gain is not predictive of lesser postoperative weight loss.

The gynecologist and the prevention of cardiovascular disease

This article reviews current concepts regarding the prevention of cardiovascular disease for women, with particular attention to modifiable risk factors. The background describes the magnitude of the problem, assesses the quality of the data with respect to risk factor reduction, and emphasizes several important concepts. Changes at menopause, states of endocrine aberration, and benefits and risks of hormone substitution need to be understood in conjunction with all other potentially modifiable and nonmodifiable cardiovascular risk factors. Primary care physicians have a window of opportunity to prevent this number one women's health problem. Integrating behavior modification is the key to prevention as part of the regular gynecologic visit.

The gynecologist and cardiovascular disease: a window of opportunity for prevention

OBJECTIVE

We present current concepts and assess the quality of information available for the prevention of cardiovascular disease in women.

METHODS

This article reviews research bearing on the prevention of cardiovascular disease in women, with particular attention to modifiable risk factors. We describe the magnitude of the problem and assess the quality of the data with respect to the classic risk factors. The concept is emphasized that changes at menopause, states of endocrine aberration, and benefits and risks of hormone substitution and oral contraception must be understood in conjunction with all other potentially modifiable and nonmodifiable risk factors.

CONCLUSIONS

Primary care physicians, especially obstetrician/gynecologists, have a pivotal role to play in the reduction of this disease. Behavior modification is the key to integrating prevention into the regular annual visit.

Matriarchal model for cardiovascular prevention

Family patterns of cardiovascular risk behavior are well documented. Significant correlation exists between spouse-spouse, parent-child, and sibling-sibling for cholesterol, high- and low-density lipoprotein, diet, physical activity, and smoking. Family/environmental influences are important in how/if risk and/or preventive behavior is learned. The family matriarch commonly functions as gatekeeper, controlling eating behavior, access to health care, and other patterns. She often acts as menu planner, shopper, and preparer of meals for all family members. She provides information and verbal reinforcement about food and is a powerful model concerning dietary practices. In fact, the mother, as head of household in most single-parent families, may be the only adult model for many children. Because relevance and credibility are the most important characteristics of a behavioral model, parents (especially mothers) are strong models for observational learning by children. Risk factor information and risk reduction activities adopted by the matriarch can be generalized to the entire family if she learns the skills to act as a change agent. Initiation of this process of education and training the matriarch lies with primary care providers for women (Ob-Gyns see most women). By teaching risk reduction to the matriarch as a component of primary care, physician interaction can have a rippling effect.

Reproductive biology of the Permian Glossopteridales and their suggested relationship to flowering plants

The discovery of permineralized glossopterid reproduction organs from Late Permian deposits in the Beard-more Glacier region (central Transantarctic Mountains) of Antarctica provides anatomical evidence for the adaxial attachment of the seeds to the megaasporophyll in this important group of Late Paleozoic seed plants. The position of the seeds is in direct contradiction to many earlier descriptions, based predominatly on impression/compression remains. The attachement of the ovules on the adaxial surface of a leaf-like megasporophyll, combined with other features, such as megaga-reproductive biology in this group than has previously been hypothesized. The findings confirm the classification of the Glossopteridales as seed ferns and are important considerations in disscussion of the phylogeny of group, including their suggested role as close relatives or possible ancestors of the angiosperms.

Treatment of cutaneous squamous cell carcinomas by intralesional interferon alfa-2b therapy

BACKGROUND AND DESIGN

Intralesional recombinant interferon alfa-2b has been shown to be effective in the treatment of actinic keratoses and basal cell carcinomas. This open-label study was designed to evaluate the effectiveness and cosmetic result of this therapy on actinically induced, primary cutaneous squamous cell carcinomas. Thirty-six squamous cell carcinomas (28 invasive lesions and 8 in situ lesions) ranging in size from 0.5 to 2.0 cm in the longest dimension were treated with interferon alfa-2b 1.5 million units injected intralesionally three times per week for 3 weeks. Eighteen weeks following therapy, the treatment sites were excised and examined for histologic evidence of remaining tumor.

RESULTS

Thirty-three (97.1%) of 34 evaluable lesions revealed an absence of squamous cell carcinoma histologically after therapy, although three biopsy specimens (8.8%) obtained after treatment showed actinic keratoses, for an overall complete response rate of 88.2%. The lesion not eliminated after treatment was an invasive squamous cell carcinoma. The investigators and patients independently judged 93.9% of cases to have a very good or excellent cosmetic result. Adverse reactions were limited to those influenzalike symptoms well recognized to occur with interferon therapy and these were well tolerated. Only one patient discontinued therapy due to side effects.

CONCLUSIONS

This trial demonstrates that intralesional interferon is effective in the treatment of small sun-induced squamous cell carcinomas with well-tolerated side effects and a highly acceptable cosmetic result.

The Present Is Not the Key to the Past: A Polar Forest from the Permian of Antarctica

An in situ Upper Permian fossil forest in the central Transantarctic Mountains near the Beardmore Glacier includes 15 permineralized trunks in growth position; the paleolatitude of the site was approximately 80 degrees to 85 degrees south. Numerous leaves of the seed fern Glossopteris are present in the shale in which the trunks are rooted. The trunks are permineralized and tree rings reveal that the forest was a rapidly growing and young forest, persisting in an equable, strongly seasonal climate-a scenario that does not fit with some climate reconstructions for this time period.

A prospective randomized evaluator-blinded trial of two potential wound healing agents for the treatment of venous stasis ulcers

Chronic wounds such as venous stasis ulcers have become a socioeconomic problem. Even with successful initial management, the recurrence rate approaches 70%. With the advent of new wound healing agents, nonoperative attempts to heal these wounds appear indicated. This study reports a prospective randomized evaluator-blinded trial comparing two potential wound healing agents to an inert vehicle placebo. Eighty-six evaluable patients completed the trial. Silver sulfadiazine 1% in a cream proved to statistically reduce the ulcer size compared with a biologically active tripeptide copper complex 0.4% cream formulation or the placebo. There was no difference between the latter two treatments. Silver sulfadiazine has been shown to allow keratinocyte replication and to have antiinflammatory properties. In this trial its antibacterial action was not used since all ulcers had comparable bacterial levels (less than or equal to 10(5)/gm of tissue) before treatment. These results suggest that the silver sulfadiazine cream used in this study may facilitate healing in wounds healing largely by the process of epithelialization.

Antibody to hepatitis C virus among cardiac surgery patients, homosexual men, and intravenous drug users in Baltimore, Maryland

In order to define the risk factors for infection with hepatitis C virus, the authors determined the prevalence and incidence of antibodies to hepatitis C in three cohorts in Baltimore, Maryland, enrolled in prospective studies of human immunodeficiency virus (HIV-1) infection. Among 500 multi-transfused patients who underwent cardiac surgery in 1985 and 1986, 12 (2.4%) were hepatitis C seropositive before surgery while 19 (3.9%) developed antibodies in the 8-12 months after surgery. The seroprevalence of hepatitis C virus among 225 intravenous drug users followed since 1988 was 85%, which did not vary by HIV-1 status. Longer duration of intravenous drug use was significantly associated with hepatitis C seropositivity. Among 926 homosexual/bisexual men followed since 1984, 15 (1.6%) were hepatitis C seropositive; only intravenous drug use and a history of hepatitis A were marginally associated with hepatitis C in this population. No association was found between hepatitis C virus and HIV-1 or sexual behavior variables in this population. These data suggest that hepatitis C is readily transmitted by blood exposure, but is transmitted inefficiently by sexual means.

Intralesional interferon therapy for basal cell carcinoma

In a clinical trial of 172 patients at four medical centers, interferon alfa-2b (1.5 x 10(6) IU) or a placebo was injected directly into biopsy-proved noduloulcerative or superficial basal cell carcinomas three times weekly for 3 weeks, for a cumulative dose of 13.5 million IU. Efficacy of treatment was determined at 16 to 20 weeks by examination of biopsy specimens that demonstrated cure of lesions in 86% of interferon-treated patients and in only 29% of placebo-treated patients. During the treatment course and follow-up, an initial inflammatory response was observed at the treatment sites, followed by diminished erythema, improvement in overall appearance, and a decrease in size of lesions. Side effects of treatment, mainly flu-like symptoms, were usually mild and transient and occurred more commonly in the interferon-treated group. Only three patients, all in the interferon-treated group, discontinued therapy because of side effects. One year after initiation of therapy, 81% of interferon recipients and 20% of those given the placebo remained tumor free. Noduloulcerative and superficial lesions were equally responsive to treatment with interferon. For some patients with noduloulcerative or superficial basal cell carcinomas, intralesional interferon alfa-2b may be an alternative, effective treatment.

The effect of an intralesional sustained-release formulation of interferon alfa-2b on basal cell carcinomas

Intralesional interferon alfa-2b has been proven effective in the treatment of basal cell carcinomas. Because nine injections over a 3-week period have been necessary to produce clinically significant cure rates, a sustained-release protamine zinc chelate interferon formulation has been developed. In this study, 65 basal cell carcinomas were treated in one of two dosing schedules with intralesional sustained release interferon alfa-2b (10 million IU per injection). Thirty-three patients received a single injection and 32 patients received one injection per week for 3 weeks. At study week 16, 80% of evaluable tumors treated with three injections and 52% treated with one injection were cured histologically. Two patients discontinued injections because of side effects. A sustained-release protamine zinc preparation of interferon alfa-2b shows promise as a practical, effective, and cosmetically elegant treatment for basal cell carcinoma.

Cholecystitis and cholelithiasis

Cholelithiasis and cholecystitis, with their complications, remain major health problems in the United States. At this time, cholecystectomy is the treatment of choice for all patients with symptomatic gallstones and those with acute cholecystitis, except those who are too ill to undergo surgery. Present therapeutic options may be summarized as follows: Asymptomatic patients and those with flatulence and dyspepsia who have gallstones should be observed. Those who have symptoms of biliary pain, gallstone-induced pancreatitis, or common duct stones should have corrective surgery. Those who refuse surgery or who aren't surgical candidates might be treated with dissolution therapy. Dissolution of gallstones with chemical agents and extracorporeal shock-wave lithotripsy show some promise. We need a better understanding of the etiology and formation of gallstones to address the disease from a preventive standpoint and reduce the incidence of cholelithiasis and cholecystitis, and their complications.

Critical tests and safety studies on trichlorfon as an antiparasitic agent in the horse

Three series of critical tests were completed on a combined total of 46 horses to determine the efficacy of single doses of trichlorfon against bots, ascarids, pinworms, and large strongyles. Different formulations of trichlorfon were administered by tubing intragastrically, mixing with the daily grain ration, injecting intramuscularly, or pouring on the back at dose rates between 20 and 100 mg/kg. Administration by feeding tended to be more efficacious for removal of bots and less toxic to the horese than administration by stomach tube. In many of the tests, trichlorfon was given in the grain ration at the dose rate of 40 mg/kg of body weight, and the aggregate average removals of 2nd and 3rd instars of Gastrophilus intestinalis and Gasterophilus nasalis in the 3 series of tests were between 97 and 100%. Removal of Parascaris equorum was equally efficacious with both the intubation and the grain feeding methods of dosing, and at the dose rate of 40 mg/kg, the aggregate averages were 99 and 100% in the 3 series. Removal of Oxyuris equi was variable--aggregate averages were between 11 (1 infected horse in the initial series) and 96 (5 infected horses in the 3rd series) to 100% (7 infected horses in the 2nd series). Large strongyles, Strongylus vulgaris and Strongylus edentatus were almost completely refractory to the 40-mg/kg dose rate of trichlorfon. Dose rates of 40 mg/kg and less were generally well tolerated by the critical test horses. Higher dose rates (60 and 80 mg/kg) administered by stomach tube induced moderately severe to severe colic and diarrhea, whereas a dose of 80 mg/kg given in the feed resulted in only a transient softening of the feces. Likewise, 5 consecutive doses, 1 week between doses, of a bolus formulation given at the rate of 80 mg/kg to 4 horses were well tolerated. Clinical trials involving a total of 2,294 treatments of trichlorfon at dose rate of 35 to 40 mg/kg in pregnant and nonpregnant mares, stallions, suckling and weanling foals, yearlings, and horses in training on 38 farms in central Kentucky did not cause notable adverse clinical effects.

Microfilaments in cellular and developmental processes

In our opinion, all of the phenomena that are inhibited by cytochalasin can be thought of as resulting from contractile activity of cellular organelles. Smooth muscle contraction, clot retraction, beat of heart cells, and shortening of the tadpole tail are all cases in which no argument of substance for alternative causes can be offered. The morphogenetic processes in epithelia, contractile ring function during cytokinesis, migration of cells on a substratum, and streaming in plant cells can be explained most simply on the basis of contractility being the causal event in each process. The many similarities between the latter cases and the former ones in which contraction is certain argue for that conclusion. For instance, platelets probably contract, possess a microfilament network, and behave like undulating membrane organelles. Migrating cells possess undulating membranes and contain a similar network. It is very likely, therefore, that their network is also contractile. In all of the cases that have been examined so far, microfilaments of some type are observed in the cells; furthermore, those filaments are at points where contractility could cause the respective phenomenon. The correlations from the cytochalasin experiments greatly strengthen the case; microfilaments are present in control and "recovered" cells and respective biological phenomena take place in such cells; microfilaments are absent or altered in treated cells and the phenomena do not occur. The evidence seems overwhelming that microfilaments are the contractile machinery of nonmuscle cells. The argument is further strengthened if we reconsider the list of processes insensitive to cytochalasin (Table 2). Microtubules and their sidearms, plasma membrane, or synthetic machinery of cells are presumed to be responsible for such processes, and colchicine, membrane-active drugs, or inhibitors of protein synthesis are effective at inhibiting the respective phenomena. These chemical agents would not necessarily be expected to affect contractile apparatuses over short periods of time, they either do not or only secondarily interfere with the processes sensitive to cytochalasin (Table 1). It is particularly noteworthy in this context that microtubules are classed as being insensitive to cytochalasin and so are not considered as members of the "contractile microfilament" family. The overall conclusion is that a broad spectrum of cellular and developmental processes are caused by contractile apparatuses that have at least the common feature of being sensitive to cytochalasin. Schroeder's important insight (3) has, then, led to the use of cytochalasin as a diagnostic tool for such contracile activity: the prediction is that sensitivity to the drug implies presence of some type of contractile microfilament system. Only further work will define the limits of confidence to be placed upon such diagnoses. The basis of contraction in microfilament systems is still hypothetical. Contraction of glycerol-extracted cells in response to adenosine triphosphate (53), extraction of actin-like or actomyosin-like proteins from cells other than muscle cells (54), and identification of activity resembling that of the actomyosin-adenosine triphosphatase system in a variety of nonmuscle tissues (40, 54) are consistent with the idea that portions of the complex, striated muscle contractile system may be present in more primitive contractile machinery. In the case of the egg cortex, calcium-activated contractions can be inhibited by cytochalasin. If, as seems likely, microfilaments are the agents activated by calcium, then it will be clear that they have the same calcium requirement as muscle. Biochemical analyses of primitive contractile systems are difficult to interpret. Ishikawa's important observation (31), that heavy meromyosin complexes with fine filaments oriented parallel to the surface of chondrocytes and perpendicular to the surface of intestinal epithelial cells, implies that both types of filaments are "actin-like" in this one respect. Yet, it is very likely that these actin-like filaments correspond respectively to the cytochalasin-insensitive sheath of glial and heart fibroblasts and the core filaments of oviduct microvilli. No evidence from our studies links contractility directly to these meromyosin-binding filaments. Apart from this problem, activity resembling that of the myosin-adenosine triphosphatase has been associated with the microtubule systems of sperm tails and cilia (55), but those organelles are insensitive to cytochalasin in structure and function. Clearly, a means must be found to distinguish between enzymatic activities associated with microfilament networks, microfilament bundles, microtubules, and the sheath filaments of migratory cells. Until such distinctions are possible, little of substance can be said about the molecular bases of primitive contractile systems. Three variables are important for the control of cellular processes dependent upon microfilaments: (i) which cells of a population shall manufacture and assemble the filaments; (ii) where filaments shall be assembled in cells; and (iii) when contractility shall occur. With respect to distribution among cells, the networks involved in cell locomotion are presumed to be present in all cells that have the potential to move in cell culture. In this respect, the networks can be regarded as a common cellular organelle in the sense that cytoplasmic microtubules are so regarded. In some developing systems, all cells of an epithelium possess microfilament bundles (7, 13), whereas, in others, only discrete subpopulations possess the bundles (5, 6). In these cases the filaments can be regarded as being differentiation products associated only with certain cell types. These considerations may be related to the fact that microfilament networks are associated with behavior of individual cells (such as migration, wound healing, and cytokinesis), whereas the bundles are present in cells that participate in coordinated changes in shape of cell populations. With respect to placement in cells, two alternatives are apparent, namely, localized or ubiquitous association with the plasma membrane. Microfilament bundles of epithelial cells are only found extending across the luminal and basal ends of cells. In this respect they contrast with desmosomal tonofilaments and with microtubules, each of which can curve in a variety of directions through the cell. The strict localization of microfilament bundles probably rests upon their association with special junctional complex insertion regions that are only located near the ends of cells. In the case of mitotically active cells, the orientation of the spindle apparatus may determine the site at which the contractile ring of microfilaments will form (4, 56); this raises the question of what sorts of cytoplasmic factors can influence the process of association between filament systems and plasma membranes. In contrast to such cases of localized distribution, contractile networks responsible for cell locomotion are probably found beneath all of the plasma membrane, just as the network of thrombosthenin may extend to all portions of the periphery of a blood platelet. This ubiquitous distribution probably accounts for the ability of a fibroblast or glial cell to establish an undulating membrane at any point on its edge, or of an axon to form lateral microspikes along its length. The third crucial aspect of control of these contractile apparatuses involves the choice of when contraction shall occur (and as a corollary the degree or strength of contraction that will occur). In the simplest situation, contraction would follow automatically upon assembly of the microfilament bundles or networks. In cleavage furrows of marine embryos (4), for instance, microfilaments are seen beneath the central cleavage furrow and at its ends, but not beyond, under the portion of plasma membrane that will subsequently become part of the furrow. This implies that the furrow forms very soon after the contractile filaments are assembled in the egg cortex. In other cases, microfilaments are apparently assembled but not in a state of (maximal?) contraction. Thus, networks are seen along the sides of migratory cells, although such regions are not then active as undulating membrane organelles. Similarly, microfilament bundles occur in all epithelial cells of the salivary gland (13), or pancreatic anlage (7), although only the ones at discrete points are thought to generate morphogenetic tissue movements. Likewise, bundles begin to appear as early as 12 hours after estrogen administration to oviduct, although visible tubular gland formation does not start until 24 to 30 hours. Finally, streaming in plant cells can wax and wane, depending upon external factors such as auxin (57). All of these cases imply a control mechanism other than mere assembly of the microfilament systems and even raise the possibility that within one cell some filaments may be contracting while others are not. In discussing this problem, it must be emphasized that different degrees of contraction or relaxation cannot as yet be recognized with the electron microscope. In fact, every one of the cases cited above could be explained by contraction following immediately upon some subtle sort of "assembly." Inclusive in the latter term are relations between individual filaments, relations of the filaments and their insertion points on plasma membrane, and quantitative alterations in filament systems. Furthermore, the critical role of calcium and high-energy compounds in muscle contraction suggest that equivalent factors may be part of primitive, cytochalasinsensitive systems. The finding that calcium-induced contraction in the cortex of eggs is sensitive to cytochalasin strengthens that supposition and emphasizes the importance of compartmentalization of cofactors as a means of controlling microfilaments in cells.

An Example of the Value of Morphology in Medico-biological Investigation: (Section of Comparative Medicine)

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