Myosins: matching functions with motors.

It is an exciting time to be studying myosins and their roles in the function of cells and organisms. Past efforts aimed at finding new members of this family have now given way to a focus on identifying individual functions for each motor protein. These actin-based motors are now known to be intimately involved in the following processes: neurosensory function; vesicle trafficking; determinant partitioning; and cortical function. The following article reviews the inroads made into the functions of myosins in these processes over the past several years.

Adhesion formation after peritoneoscopy with liver biopsy in a survival porcine model: comparison of laparotomy, laparoscopy, and transgastric natural orifice transluminal endoscopic surgery (NOTES).

BACKGROUND AND STUDY AIMS: Minimizing the invasiveness of operations by using natural orifice transluminal endoscopic surgery (NOTES) may reduce adhesion formation. The aim of the study was to compare rates of adhesion formation after peritoneoscopy with liver biopsy by laparotomy, laparoscopy, and transgastric NOTES. MATERIALS AND METHODS: Experimental comparative survival study, at a university hospital. using 18 female pigs weighing 35 - 40 kg. Peritoneoscopy with liver biopsy was randomized to one of three groups: laparotomy, laparoscopy, and transgastric NOTES. Preoperative, operative, and postoperative care was standardized. Main outcome measures were: (i) survival and complication rates; (ii) assessment of adhesion formation using the Hopkins Adhesion Formation Score at necropsy (day 14). RESULTS: 100 % of pigs with laparotomy and 33.3 % with laparoscopy had adhesions compared with 16.7 % who underwent transgastric NOTES. Documented adhesion bands totals for each group were: transgastric NOTES 1; laparoscopy 4; laparotomy 17. Median adhesion formation scores were: laparotomy 2.5 (range 2 - 4), compared with laparoscopy 0.0 (0 - 2), and transgastric NOTES 0.0 (0 - 1) ( P < 0.001). Spearman coefficient analysis revealed that correlation between adhesion scores assigned by two investigators was excellent (r = 0.99, P < 0.001, 95 % confidence interval [CI] 0.9978 - 0.9996). CONCLUSIONS: Although this was a short-term study, with a low number of animals, it showed that transgastric NOTES and laparoscopy are associated with statistically significantly lower rates of adhesion formation than open surgery when peritoneoscopy with liver biopsy is performed. Incidence and severity of adhesions were lowest with transgastric NOTES.

Cerebrovascular response to acute hypocapnic and eucapnic hypoxia in normal man.

Alterations in human cerebral blood flow and related blood constituents were studied during exposure to acute hypoxia. Observations were made during serial inhalation of decreasing O(2) concentrations with and without maintenance of normocarbia, during 8 min inhalation of 10% O(2), and after hyperventilation at an arterial P(O2) of about 40 mm Hg. In the range of hypoxemia studied, from normal down to arterial P(O2) of about 40 mm Hg, the magnitude of the cerebral vasodilator response to hypoxia appeared to be largely dependent upon the coexisting arterial CO(2) tension. The mean slope of the increase in cerebral blood flow with decreasing arterial O(2) tension rose more quickly (P < 0.05) when eucapnia was maintained when compared with the slope derived under similar hypoxic conditions without maintenance of eucapnia. When 12 subjects inhaled 10% oxygen, cerebral blood flow rose to more than 135% of control in four whose mean decrease in arterial CO(2) tension was - 2.0 mm Hg. The remaining eight had flows ranging from 97 to 120% of control, and their mean decrease in CO(2) tension was - 5.1 mm Hg. When mean arterial P(O2) was 37 mm Hg, hyperventilation was carried out in 10 subjects. Arterial P(O2) increased insignificantly, arterial P(CO2) declined from 34 to 27 mm Hg (P < 0.05), and cerebral blood flow which had been 143% of control decreased to 109%, a figure not significantly different from control.These data demonstrate the powerful counterbalancing constrictor effects of modest reductions in CO(2) tension on the vasodilator influence of hypoxia represented by arterial P(O2) reductions to about 40 mm Hg. Indeed, mild hyperventilation completely overcame the vasodilator effect provided by an arterial O(2) tension as low as 40 mm Hg. The effects of hypoxia on the control of the cerebral circulation must be analyzed in terms of the effects of any associated changes in CO(2) tension.

A family of unconventional myosins from the nematode Caenorhabditis elegans.

The unconventional myosins are a superfamily of actin-based motor proteins that are expressed in a wide range of cell types and organisms. Thirteen classes of unconventional myosin have been defined, and current efforts are focused on elucidating their individual functions in vivo. Here, we report the identification of a family of unconventional myosin genes in Caenorhabditis elegans. The hum-1, hum-2, hum-3 and hum-6 (heavy chain of an unconventional myosin) genes encode members of myosin classes I, V, VI and VII, respectively. The hum-4 gene encodes a high molecular mass myosin (ca 307 kDa) that is one of the most highly divergent myosins, and is the founding and only known member of class XII. The physical position of each hum gene has been determined. The hum-1, hum-2 and hum-3 genes have been mapped by extrapolation near previously uncharacterized mutations, several of which are lethal, identifying potentially essential unconventional myosin genes in C. elegans.

A randomized, double-blind, placebo-controlled trial of CDP571, a humanized monoclonal antibody to tumour necrosis factor-alpha, in patients with corticosteroid-dependent Crohn's disease.

AIM: To evaluate CDP571, a humanized monoclonal antibody to tumour necrosis factor-alpha, for the treatment of corticosteroid-dependent Crohn's disease. METHODS: Patients with corticosteroid-dependent Crohn's disease (use of prednisolone 15-40 mg/day or budesonide 9 mg/day for at least 8 weeks, a previous failed attempt to discontinue corticosteroids within 8 weeks, and Crohn's Disease Activity Index score 150 points or less) were enrolled in a 16-week, randomized, double-blind, placebo-controlled trial. The patients received intravenous CDP571 (20 mg/kg at week 0 and 10 mg/kg at week 8) or placebo. Corticosteroid therapy was decreased following a predefined schedule. The primary efficacy end-point was the percentage of patients with corticosteroid-sparing [i.e. no disease flare (Crohn's Disease Activity Index score > or =220 points) and no longer requiring corticosteroid therapy] at week 10. The major secondary efficacy end-point was corticosteroid-sparing at week 16. RESULTS: Seventy-one patients received treatment. Corticosteroid-sparing was achieved by 19 of 39 (48.7%) CDP571 patients and 13 of 42 (40.6%) placebo patients (P = 0.452) at week 10, and by 18 of 39 (46.2%) CDP571 patients and seven of 32 (21.9%) placebo patients (P = 0.032) at week 16. CDP571 therapy was well-tolerated and the incidence of serious adverse events was similar to placebo. CONCLUSIONS: The CDP571 was effective for corticosteroid-sparing at week 16 but not week 10, and was well-tolerated in patients with corticosteroid-dependent Crohn's disease.

Whole-body protein turnover in adult hemodialysis patients as measured by 13C-leucine.

Muscle wasting may occur in patients with chronic renal failure (CRF). To determine whether this is due to a decrease in the synthesis or an increase in the breakdown of muscle protein, we evaluated postabsorptive whole-body protein breakdown, oxidation, and synthesis rates at steady state during a primed, continuous infusion of 13C-leucine. This was done in seven subjects on chronic maintenance hemodialysis (MHD) and in seven normal control subjects. The protein breakdown rate in MHD was not different from that in controls (103 +/- 19 and 106 +/- 19 mumol leucine.kg-1.h-1, respectively). In MHD, however, the protein oxidation rate was 43% greater than that in controls (20 +/- 6 and 14 +/- 4 mumol leucine.kg-1.h-1, p less than 0.05), whereas net protein synthesis was less (p less than 0.05). Reduced net synthesis and increased oxidation rates of protein in the postabsorptive state may therefore contribute to the muscle-wasting syndrome in patients with CRF.

Critical assessment of body-composition measurements in malnourished subjects with Crohn's disease: the role of bioelectric impedance analysis.

Bioelectric impedance analysis (BIA) has been widely used for assessment of body composition in healthy subjects but has not been validated in malnourished patients. This study compared calculation of fat-free mass (FFM) by five methods to determine whether the currently used equations for total body water (TBW) as assessed by BIA were applicable to 19 malnourished patients with Crohn's disease. When compared with TBW assessed by H2(18)O dilution, BIA was higher by 5.9 +/- 1.1% (P < 0.005). A stepwise-multiple-regression equation was derived to validate BIA: TBW (kg) = 0.25 (ht2/resistance) + 0.29 (wt) + 3.63 (r = 0.97, SEE = 0.28). Comparison of the hydration of FFM (TBW by 18O dilution/FFM) between methods showed that total body potassium (TBK) gave a significantly higher value when compared with the reference method of body protein, mineral, and 18O analysis. Dual-energy x-ray absorptiometry (DXA) provided a value for TBW/FFM in close agreement with the reference method. We conclude that BIA overestimates TBW, and TBK underestimates FFM in malnourished patients. DXA provides an accurate measurement of body fat in malnutrition.

Skeletal muscle function in chronic renal failure: an index of nutritional status.

To determine whether skeletal muscle function testing (SMF) provides an index of nutritional status in patients with chronic renal failure (CRF), two groups with comparable CRF were studied. In 48 well-nourished (WN) and 17 malnourished (MN) patients with stable CRF, and in 33 WN nonazotemic controls, adductor pollicis function was assessed. The force at 10 Hz was expressed as a % of force at 100 Hz (F10/F100), and maximal relaxation rate (MRR) as % force loss/10 ms. Standard nutritional assessment was also performed. The WN group was not significantly different from controls for either F10/F100 or MRR. The F10/F100 of the MN group was significantly greater than either the WN group or controls (p less than 0.001), while MRR was less (p less than 0.001). Significant malnutrition by conventional parameters was shown in patients with abnormal F10/F100, and also in patients with abnormal MRR. Hence, SMF as described is unaffected by azotemia, and provides a functional measure of nutritional status in CRF.

Synthesis and chromatographic separation of the glucuronides of (R)- and (S)-propranolol.

One of the major metabolites of propranolol (Inderal) is the O-glucuronide. In order to further study its disposition, possible metabolism, and contribution to the antihypertensive effect of propranolol, we have synthesized and separated the two diastereomeric propranolol O-beta-D-glucuronides (9a,b). These compounds were prepared by reaction of naphthol with epichlorohydrin and treatment of the resulting (2RS)-1'-(2,3-epoxypropoxy)naphthalene (2) with sodium azide to give (2RS)-1-(1'-naphthoxy)-3-azido-2-propanol (3). Alkylation of 3 with methyl (2,3,4-tri-O-acetyl-1-bromo-1-deoxy-alpha-D-glucopyranosid)uronate (4) gave methyl (2RS)-[1-(1'-naphthoxy)-3-azido-2-propyl-2",3",4"-tri-O-acetyl-beta-D- glucopyranosid]uronate (5a,b). Reductive alkylation, followed by HPLC separation of the diastereomers, gave methyl (2R)- and (2S)-[1-(1'-naphthoxy)-3-(isopropylamino)-2-propyl-2",3",4"-tri-O-acetyl- beta-D-glucopyranosid]uronate (6a,b). Hydrolytic removal of the acetyl and methyl protecting groups gave the free glucuronides, which were then converted to the sodium salts, 9a,b. The stereochemistry of the glycoside linkage was deduced from the 400-MHz 1H NMR spectra. The absolute configuration of the aglycon portion was determined after Glusulase hydrolysis by derivatization with (R)-(+)- or -(-)-alpha-methylbenzyl isocyanate and comparison of the HPLC retention volumes with those of derivatized reference (R)- and (S)-propranolols.

Treatment of left-sided ulcerative colitis with butyrate enemas: a controlled trial.

BACKGROUND: The colonic mucosa is highly dependent upon the presence of luminal nutrients. This dependence is most marked in the distal colon. The major luminal nutrients are short chain fatty acids that are produced as a by-product of colonic fermentation of carbohydrates. Butyrate appears to be the short chain fatty acid most avidly metabolized by the colonic mucosa. It has been suggested that ulcerative colitis is, at least in part, related to an energy deficiency state of the colonic mucosa which may be secondary to impaired short chain fatty acid production, uptake or utilization. The objective of this study was to determine if butyrate given as enema therapy is effective in the treatment of active distal ulcerative colitis. METHODS: Thirty-eight patients with distal ulcerative colitis were randomly assigned to receive nightly butyrate (n = 19) or saline/placebo (n = 19) enemas. Butyrate enemas consisted of 60 mL of 80 mM sodium butyrate titrated to a pH of 7.0. Patients were assessed clinically and endoscopically at baseline and at 3 and 6 weeks follow-up. Pre- and post-treatment mucosal biopsies were assessed histologically. Response to therapy was determined by changes in a 12-point clinical disease activity index score based on patient symptoms, endoscopic mucosal appearance and physicians' global assessment. RESULTS: Clinical improvement was noted in seven of 19 (37%) butyrate-treated patients and nine of 19 (47%) placebo-treated patients (P = 0.51). Clinical remission was achieved in three patients in each group (16%). No toxicity was observed in either treatment arm. CONCLUSIONS: The results suggests that once nightly 60 mL butyrate enemas (80 mmol/L) are not efficacious in the treatment of distal ulcerative colitis.

Evaluation of a self tonometer for home use.

It has been repeatedly stated that home monitoring of the intraocular pressure of glaucomatous patients could be of clinical significance. However, home tonometry has not been implemented due to the lack of an appropriate instrument. We present herein an upgraded version of a home tonometer that can be used by the patient alone. When it was tested on 37 eyes of 22 glaucomatous patients, the reproducibility was 1.7 mm Hg at IOPs of 20 mm Hg. The IOP was also measured with a Goldmann applanation tonometer. The two measurements were well correlated (r = .89) and the accuracy of the home tonometer, namely the variation of the data from the regression curve, was 2.5 mm Hg. This accuracy is compared with that of conventional tonometers. Moreover, the study showed that the home tonometer yielded reliable results in the hands of a substantial portion of the potential population.

Temporal correlation of graded reversible inspiratory inhibition with discharge patterns of late inspiratory neurons located in the dorsal respiratory group in cats.

Respiratory neurons were recorded with microelectrodes in the medullary dorsal respiratory group of pentobarbital-anesthetized cats. The animals were ventilated with a phrenic-driven servorespirator that allowed manipulation of phasic volume feedback. By increasing or decreasing the gain of the servorespirator, graded reversible inhibition could be temporally advanced or delayed, respectively. Fourteen percent of the neurons were late inspiratory (1.I.) and received a facilitatory volume input and, hence, are classified as 1.I. beta neurons. When the time of onset of graded inhibition was advanced, the onset of firing of 1.I. beta neurons was advanced, and, similarly, when graded inhibition was delayed, the onset of 1.I. beta neuron firing was delayed. The lag between the onset of firing and the onset of graded inhibition ranged from -240 msec to +760 msec, but each neurons displayed a relatively constant lag as servorespirator gain was changed. When transient inspiratory inhibition was produced by inflating the lungs and then withdrawing volume during the graded reversible inhibitory period, the 1.I. beta neurons fired during the transient inhibitory period but decreased their firing as inspiratory activity recovered. This indicates that 1.I. beta activity is associated with graded inhibition, not with the irreversible stage of phase transition.

Total enteral nutrition support improves body composition of patients with active Crohn's disease.

BACKGROUND: Previous studies using indirect calorimetry in Crohn's disease have suggested that with weight loss there is a proportionally greater decrease in body fat along with a spring of lean mass. This study analyzed body composition (compared with that of controls) by direct methods in a group of 30 patients with active Crohn's disease and further evaluated the effects of nutrition support on body composition. METHODS: Total body protein was assessed by neutron activation, fat was assessed by dual energy x-ray absorptiometry, water was assessed by bioelectric impedance analysis, and potassium was assessed by gamma-ray technique. These measurements were repeated in patients with Crohn's disease after 3 weeks of enteral nutrition by feeding tube that provided 35 nonprotein kcal/kg of ideal body weight. RESULTS: Compared with age- and sex-matched controls, patients had lost (on average) 11.3 kg (16%) of body weight (p < .0005), including 5.1 kg (30%) of fat (p < .0005), 2.2 kg (19%) of protein (p < .025), 3.7 kg (10%) of water (p = NS), and 24.9 g (21%) of total body potassium (p < .01). After enteral feeding, body weight increased by 1.9 +/- 0.3 kg (p < .0005). Weight gain was accompanied by an increase in body protein (0.3 +/- 0.1 kg), fat (0.3 +/- 0.1 kg), and water (1.1 +/- 0.4 kg) (all p < .025), and by a nonsignificant increase in total body potassium. The weight gain of approximately 2 kg consisted of 65% water, 18% fat, and 18% protein, thus comprising a normal proportion of body composition. CONCLUSIONS: Reduced body weight in patients with Crohn's disease compared with that in controls was due to less fat tissue. With modest nutritional repletion, proportionate gains in all body compartments are possible.

The choice to treat all, some, or no patients undergoing gastrointestinal surgery with nutritional support: a decision analysis approach.

We used decision analysis to compare three strategies for reducing the incidence of nutrition-associated complications in patients undergoing gastrointestinal surgery: treat all patients with nutritional support, treat no patients, or perform a test which categorizes patients as high or low risk (treating only the high risk patients). We use the model to make management recommendations based on current knowledge and to set priorities for future research. The "test strategy" is optimal in the majority of cases which we believe are clinically encountered when the test involves subjective global assessment of nutritional status on admission (sensitivity 0.82, specificity 0.72) and nutritional support must be delivered by a central venous catheter. However, the result is particularly sensitive to the predictive properties associated with the test and is less sensitive to the effectiveness rate of nutritional support in reducing the incidence of postoperative complications. We conclude that in future research priority should be given to studying and improving the predictive properties of nutritional assessment techniques.

Predicting nutrition-associated complications for patients undergoing gastrointestinal surgery.

We studied 202 patients admitted to two major teaching hospitals for planned gastrointestinal surgery to assess the ability of several techniques of nutritional assessment to predict major postoperative complications (infection and/or wound problems). Subjective global assessment (SGA) and albumin were both of predictive value, and combinations of these variables were useful in differentiating low-risk from high-risk patients. Transferrin, creatinine-height index, percent ideal weight, percent body fat, and total lymphocyte count were not useful in predicting complications. We conclude that SGA and albumin are useful "nutritional assessment techniques" for patients undergoing major gastrointestinal surgery if the purpose of such an assessment is to predict postoperative "nutrition-associated complications." The second major finding of this study was the unexpectedly low rate of complications (10%) which was found in both hospitals. We suggest that these low complication rates may be more generalizable to patient populations derived from a wide community base, rather than those described in other studies in which veterans or patients of lower socioeconomic status comprised the sample.

What is subjective global assessment of nutritional status?

Presented and described in detail is a clinical technique called subjective global assessment (SGA), which assesses nutritional status based on features of the history and physical examination. Illustrative cases are presented. To clarify further the nature of the SGA, the method was applied before gastrointestinal surgery to 202 hospitalized patients. The primary aim of the study was to determine the extent to which our clinician's SGA ratings were influenced by the individual clinical variables on which the clinicians were taught to base their assessments. Virtually all of these variables were significantly related to SGA class. Multivariate analysis showed that ratings were most affected by loss of subcutaneous tissue, muscle wasting, and weight loss. A high degree of interobserver agreement was found (kappa = 0.78, 95% confidence interval 0.624 to 0.944, p less than 0.001). We conclude that SGA can easily be taught to a variety of clinicians (residents, nurses), and that this technique is reproducible.

Evaluating the accuracy of nutritional assessment techniques applied to hospitalized patients: methodology and comparisons.

Herein we describe a methodology which can be used to evaluate the predictive accuracy of nutritional assessment techniques. We use this methodology to compare seven techniques of nutritional assessment in terms of their ability to predict one nutrition associated hospital complication (infection) by dividing a sample of 59 surgical patients into high risk and low risk groups. One technique was subjective global assessment (SGA) of the patient's nutritional status on admission to hospital. Five techniques were single objective measurements (albumin, transferrin, delayed cutaneous hypersensitivity, anthropometry, and creatinine-height index). The 7th technique was the prognostic nutritional index. The best combination of sensitivity (0.82) and specificity (0.72) was found with SGA. The second best combination (0.88 and 0.45) was found by using either the prognostic nutritional index or creatinine-height index. We also found that combining the five objective measurements with SGA into a single index did not increase the discriminatory (or predictive) power over that of SGA alone in a clinically significant way. We conclude that a larger study comparing these approaches should be undertaken to confirm these findings and to develop methods which improve the predictive properties of SGA.

Nutritional support in the critically ill patient: if, when, how, and what.

Nutritional support in the critically ill patient should be instituted as soon as it is clear that the patient will not eat within a week, whether the patient is at that particular time malnourished or not. The preceding discussion demonstrates that it is more a question of clinical judgment than of sophisticated nutritional assessment techniques, as most of these prove unreliable in the critically ill. However, muscle function testing seems to be promising in that regard, but more studies are required in the injured and septic patient. Enteral feeding is the favored route, although parenteral nutrition should be used without hesitation whenever the gastrointestinal tract is not functional. We recommend the use of 1.0 to 1.5 g/kg IBW/day of a balanced amino acid preparation. The use of BCAA-enriched solutions should await confirmation of the efficacy of these solutions in randomized prospective trials. Finally, it is our belief that critically ill patients should not receive more than 1.3 times their Harris-Benedict energy expenditure, and that this energy should be provided in the form of a glucose-fat mixture (50-50 system).

The incubator and the medical discovery of the premature infant.

The invention of the incubator in 1880 ignited a dramatic outpouring of popular and professional excitement over the prospect of reducing premature infant mortality. Yet the technology itself progressed slowly and fitfully over the next 50 years. The story is worth examining not so much from the standpoint of technological progress, but from the perspective of how responsibility for the newborn shifted from mothers to obstetricians and eventually pediatricians. It also illustrates how the history of technology involves more than invention. The invention of the incubator itself was less significant than the development of a system to support the device.

Sensitivity to change for low-ANC eastern US lakes and streams and brook trout populations under alternative sulfate deposition scenarios.

A weight-of-evidence approach was used by the US National Acid Precipitation Assessment Program (NAPAP) to assess the sensitivity of chemistry and biology of lakes and streams to hypothesized changes in sulfate deposition over the next 50 years. The analyses focused on projected effects in response to differences in the magnitude and the timing of changes in sulfate deposition in the north-eastern United States, the Mid-Appalachian Highlands, and the Southern Blue Ridge Province. A number of tools was used to provide the weight of evidence that is required to have confidence in an assessment that has many uncertainties because of the complexity of the systems for which the projections of future conditions were made and because of limited historical data. The MAGIC model provided the projections of chemical changes in response to alternative deposition scenarios. Projected chemical conditions were input into biological models that evaluate effects on fish populations. The sensitivity of water chemistry and brook trout resources to the hypothesized changes in deposition was found to be greatest in the Adirondacks and Mid-Atlantic Highlands. Under the hypothesized sulfur deposition reduction scenarios, chemical conditions suitable for fish were projected to improve 20-30 years sooner than with the scenario that assumed no new legislated controls. Other lines of evidence, e.g. other models, field observations, and paleolimnological findings, were used to evaluate uncertainty in the projections. Model parameter/calibration uncertainty for the chemical models and population sampling uncertainty were explicitly quantified. Model structural uncertainties were bracketed using model comparisons, recent measured changes, and paleolimnological reconstructions of historical changes in lake chemistry.