Viscoelastic and rheological properties of concentrated solutions of proteoglycan subunit and proteoglycan aggregate

The oscillatory and steady shear rheological properties of concentrated solutions of proteoglycan subunit (PGS) and aggregate (PGA) from bovine articular cartilage have been studied using a Rheometrics fluids spectrometer. At comparable concentrations in the physiological range tan delta increases from 0.5 to 1.0 for PGA as the oscillation frequency (omega) increases from 10(-1) to 10(2) rads/s, compared to a decrease from 40 to 5 for PGS. Thus PGA solutions exhibit predominantly elastic response whereas those of PGS exhibit primarily viscous behavior. PGA solutions show pronounced shear-thinning behavior at all shear rates (gamma) in the range 10(-2) less than gamma (s-1) less than 10(2), whereas PGS solutions exhibit predominantly Newtonian flow. For PGA, the small-strain complex viscosity eta* (omega) is substantially smaller than the steady-flow viscosity eta(gamma) at comparable values of omega and gamma. These observations indicate that the presence of proteoglycan aggregates leads to formation of a transient or weak-gel network. Since aggregation leads to a large increase in molecular hydrodynamic volume and hence in the relaxation times for macromolecular rotation, it appears that role of aggregate formation is to shift the linear viscoelastic response from the terminal viscous flow into the plateau elastomeric regime of relaxational behavior. Normal or pathological changes that produce a decrease in aggregation will result in a loss of elastomeric behavior of the proteoglycan matrix.

Leishmania infecting man and wild animals in Saudi Arabia. 8. The influence of prior infection with Leishmania arabica on challenge with L. major in man

A clinical trial is described of an attempt to protect against Leishmania major by prior vaccination with live L. arabica. After a single, previously leishmanin-negative, adult male volunteer was bitten by 8 Phlebotomus papatasi infected with L. arabica, no infected lesions were observed. He remained leishmanin-negative and his lymphocytes reacted weakly to antigens of L. arabica or L. major. Subsequently he and 3 other leishmanin-negative adult male volunteers were vaccinated with cultures containing 4 x 10(6) promastigotes of L. arabica. All remained leishmanin-negative but their lymphocytes showed some response to both L. arabica and L. major antigens. 96 d after vaccination these 4, and another, non-vaccinated, volunteer were challenged with 2 x 10(6) promastigotes of L. major. Active cutaneous, ulcerated lesions developed in all 5 volunteers. The lesions in 3 vaccinated volunteers were associated with marked lymphadenitis and beading, but the lesions started to heal spontaneously within 120-250 d after challenge. The lesion in the fourth vaccinated volunteer was less severe and lymphadenitis was not observed. The lesion in the unvaccinated subject developed more slowly and was smaller, but more chronic, than those in the vaccinated individuals. Marked cross-reactivity in terms of lymphocyte proliferation and interferon-gamma production was observed between L. major and L. arabica in both directions in subjects exposed first to one or the other organism. Although the procedure followed in this trial failed to give protection against L. major, further studies in volunteers should be considered.

Viscoelastic properties of solutions of ovine submaxillary mucin

The linear viscoelastic and rheological properties of high molecular weight ovine submaxillary mucin (OSM) solution have been investigated in terms of the Newtonian steady-flow viscosity [eta(gamma)], the complex oscillatory viscosity [eta*(omega)], and the storage and loss shear moduli [G'(omega) and G"(omega)]. It was observed that tau(gamma), eta*(omega), and G'(omega) are always higher when OSM is dissolved in 0.1M NaCl than when at the same concentration in 6M GdnHCl. This is consistent with previous observations that submaxillary mucins self-associate in 0.1M NaCl to form large aggregates, which are disrupted in 6M GdnHCl. As the OSM concentration increases, the appearance of a plateau shear modulus indicates the formation of a gel network in both solvents. The results suggest gelation involves specific intermolecular interactions, perhaps due to hydrophobic forces between interdigitated oligosaccharide side chains. The viscoelastic behavior of OSM solution at high concentration is thus similar to that reported in the literature for porcine gastric mucin (PGM). However, the OSM gels are mechanically weaker, having moduli that are an order of magnitude lower than those for PGM gels of comparable concentration. The oligosaccharide side chains of OSM consist of only 1-2 sugar units compared to 10-15 for PGM, but it appears that this is sufficient to allow for intermolecular interaction and the formation of weak gels.

Diminished insulin sensitivity and increased insulin response in nonobese, nondiabetic Mexican Americans

The contributions of diminished insulin sensitivity and decreased insulin response to the development of non-insulin-dependent diabetes mellitus (NIDDM) remain controversial. Nondiabetics in high-risk populations for NIDDM, including Pima Indians and Mexican Americans, are characterized by obesity and hyperinsulinemia relative to nondiabetics in the lower-risk white population. However, it is not clear to what extent diminished insulin sensitivity in the high-risk groups reflects obesity per se or is an inherent characteristic of these groups. Insulin sensitivity and secretion were determined in 10 nonobese, normoglycemic Mexican Americans (mean body mass index [BMI], 23.8 kg/m2) and 11 normoglycemic non-Hispanic whites (mean BMI, 22.5 kg/m2) using the intravenous glucose tolerance test (IVGTT) and the minimal model approach of Bergman et al. Age, BMI, sum of skinfolds, and the ratio of waist-to-hip circumference (WHR) were similar in both ethnic groups. Mexican Americans had decreased insulin sensitivity compared with non-Hispanic whites (4.06 +/- 0.72 in Mexican Americans v 7.56 +/- 1.13 in non-Hispanic whites, P = .017). The areas under the C-peptide and insulin curves were significantly greater in Mexican Americans than in non-Hispanic whites (P less than .01), suggesting greater insulin secretion in the former. This study provides evidence for diminished insulin sensitivity and increased insulin response in young, nonobese, normoglycemic Mexican Americans.

A genetic map of mouse chromosome 1 near the Lsh-Ity-Bcg disease resistance locus

Isozyme and restriction fragment length polymorphism (RFLP) analyses of backcross progeny, recombinant inbred strains, and congenic strains of mice positioned eight genetic markers with respect to the Lsh-Ity-Bcg disease resistance locus. Allelic isoforms of Idh-1 and Pep-3 and RFLPs detected by Southern hybridization for Myl-1, Cryg, Vil, Achrg, bcl-2, and Ren-1,2, between BALB/cAnPt and DBA/2NPt mice, were utilized to examine the cosegregation of these markers with the Lsh-Ity-Bcg resistance phenotype in 103 backcross progeny. An additional 47 backcross progeny from a cross between C57BL/10ScSn and B10.L-Lshr/s mice were examined for the cosegregation of Myl-1 and Vil RFLPs with Lsh phenotypic differences. Similarly, BXD recombinant inbred strains were typed for RFLPs upon hybridization with Vil and Achrg. Recombination frequencies generated in the different test systems were statistically similar, and villin (Vil) was identified as the molecular marker closest (1.7 +/- 0.8 cM) to the Lsh-Ity-Bcg locus. Two other DNA sequences, nebulin (Neb) and an anonymous DNA fragment (D2S3), which map to a region of human chromosome 2q that is homologous to proximal mouse chromosome 1, were not closely linked to the Lsh-Ity-Bcg locus. This multipoint linkage analysis of chromosome 1 surrounding the Lsh-Ity-Bcg locus provides a basis for the eventual isolation of the disease gene.

Light scattering studies of the effect of Ca2+ on the structure of porcine submaxillary mucin

The effects of calcium ions on the solution properties of porcine submaxillary mucin (PSM) have been investigated by static and dynamic light scattering. The weight average molecular weights of PSM fractions are unaffected by the addition of up to 0.5M CaCl2: these data are within experimental error of those for solutions in 0.1M NaCl. The distribution of relaxation frequencies derived from the dynamic data shows the existence of two distinct relaxation modes. The average relaxation times have been interpreted to yield the z-average translational diffusion coefficient and the longest intramolecular relaxation time tau1. A plot of tau1 vs the mean value of 1/Rh-3z is linear, and consistent with plots of such data recorded for PSM in 0.1m NaCl and 6M GdnHCl solutions. However, the tau values and the associated results for the mean value of R-1h-1z in 0.5M CaCl2 are smaller than those determined in 0.1M NaCl. This suggests that the conformation of PSM in CaCl2 solution is more contracted than those in the other two solvents. These results are consistent with the compact packaging of mucin in the secretary granules that have elevated Ca2+ levels.

Structural analysis of purified human tracheobronchial mucins

Light scattering has been used to investigate the structure of human tracheobronchial mucin glycoproteins (HTBM) from the sputum of cystic fibrosis patients. The specimen was extracted using 6M guanidinium hydrochloride solution and fractionated by gel exclusion chromatography on Sephacryl S-1000. The fractionated HTBM was purified by density gradient ultracentrifugation. Purity of the resulting material was confirmed by SDS polyacrylamide gel electrophoresis and uv spectroscopy. Light scattering measurements on the fractionated mucins yield weight-average molecular weights Mw, and z-average radii of gyration Rg,z. The native cystic fibrosis HTBM consisted of a high molecular weight fraction with Mw = 9.3 X 10(6) daltons and a lower molecular weight fraction containing partly degraded mucins. After reduction and carboxymethylation of the high molecular weight native fraction, the resulting material was separated into three pools with Mw values of 5.1 X 10(6), 1.6 X 10(6), and 400,000. The derived molecular weights for the protein cores Mp,w, and the experimental radii of gyration are found to be consistent with the Mp,w -Rg relation established previously for submaxillary, cervical, and gastric mucins. These results imply that HTBM has the same extended-coil conformation reported for other mucins and has a molecular structure consisting of subunits, linked into linear chains via covalent (disulfide) bonds.

Light scattering studies of bovine skin proteodermatan sulfate

The proteodermatan sulfate (PDS) of bovine skin is a low molecular weight proteoglycan with a molecular structure consisting of a protein chain and a sulfated polysaccharide chain covalently linked at the 4-serine of the protein. Static and dynamic laser light scattering methods have been used to determine the weight-average molecular weight, Mw, zeta-average radius of gyration, Rg zeta, and zeta-average translational diffusion coefficient, Dto, zeta, of bovine skin PDS. We have also characterized the two components of PDS, i.e., the protein core and the dermatan sulfate (DS) chain. (The latter contained an N-terminal-linked penta- or tetrapeptide.) Interpretation of the PDS data is complicated by the block copolymer nature of its structure. When appropriate corrections are made, our results indicate that Mw for PDS monomer is 62,000 when dissolved in 4M guanidine hydrochloride (GdnHCl), and increases to 610,000 in 0.15M NaCl. Mw for the core protein in 4M GdnHCl is 39,000, and this also increases substantially to 650,000 in 0.15M NaCl. In contrast, Mw for the DS chain is 24,000 in 0.15M NaCl, indicating that there is minimal self-association of DS in 0.15M NaCl. Thus we conclude that the self-association of PDS involves the protein core. Comparison of Rg zeta and Rh, the average hydrodynamic radius, suggests that trace amounts of aggregation persist for the PDS and its core protein even in 4M GdnHCl. This conclusion is supported by evaluation of the second moments of the dynamic light scattering correlation function. Comparisons of the observed Dto, zeta for PDS with predicted values using hydrodynamic theory are consistent with a "lollipop" conformation for the molecule.

Atheromatous embolism: varied clinical presentation and prognosis

Microemboli composed of atheromatous debris can produce sudden failure of one or many organ systems. The soft tissues of the lower extremity are almost always involved, and may sustain the only significant injury. Atheromatous embolization occurs more commonly than is recognized, and its incidence may be increasing. We report ten cases that demonstrate the variability in presentation and prognosis. These data and a review of the existing literature suggest an extremely grave prognosis in patients with generalized organ system involvement, as opposed to those patients with involvement of the lower extremity only. Treatment consists of general supportive care. Anticoagulation or lytic therapy appears to be of no benefit, and may actually contribute to embolization. We discuss new pharmacologic agents as possible treatment for the intense local ischemia, and recommend selective use of lumbar sympathectomy in cases of impending loss of lower extremity tissue.

A simple, clinical assay to evaluate the acrosin activity of human spermatozoa

Acrosin, a sperm-specific acrosomal proteinase, has an essential role in the fertilization process. Low levels of acrosin appear to be associated with subfertility and infertility, and the acrosin activity of spermatozoa may potentially be a useful indicator of semen quality. The standard acrosin tests employed by research laboratories are too complicated and/or time consuming for clinical use; therefore, a simple assay has been developed to assess total acrosin activity (acrosin and activatable proacrosin). To perform the test, liquefied semen is centrifuged over Ficoll, the washed sperm pellet is suspended in a detergent (Triton X-100)-substrate (N-alpha-benzoyl-DL-arginine p-nitroanilide) buffer, pH. 8.0, and the amidase activity is determined spectrophotometrically after a 3-hour incubation period. Amidase activity can be inhibited with benzamidine, indicating that the activity is primarily or entirely due to acrosin. The absence of detergent in the incubation medium results in greatly reduced activity. The assay is repeatable, linear with increasing sperm concentration, sensitive to a lower limit of 2 x 10(6) spermatozoa, and the results correspond to those obtained with a standard acrosin extraction and assay technique. Storage of ejaculates at 3 to 6 C or at 22 to 24 C for 24 hours does not affect the acrosin activity significantly but much higher temperatures can cause a loss of activity. Freezing ejaculates results in a large decrease in sperm acrosin activity. Leukocytes show minimal activity in the assay. Sperm populations prepared by a swim-up procedure average approximately a 2-fold higher acrosin activity than the original ejaculates. Preliminary experiments indicate that the average sperm acrosin activity of ejaculates whose spermatozoa successfully fertilize human eggs in vitro is significantly higher than those that do not fertilize eggs.

Dynamic light scattering studies of porcine submaxillary mucin fractions in dilute solution at intermediate scattering vectors

We report dynamic light scattering measurements over a wide range of scattering vectors for fractionated samples of porcine submaxillary mucin (PSM) glycoproteins in two different solvents: 0.1M NaCl, and 6M GdnHCl. The relaxation spectrum has been successfully resolved into a slow mode corresponding to pure translational diffusion and a fast mode containing information on the relaxation times for intramolecular motion. Analysis of the slow mode permits a light scattering evaluation of the polydispersity of these high molecular weight mucin glycoprotein fractions. Determination of the longest intramolecular relaxation times tau 1 shows that these are much longer for the PSM fractions in 0.1M NaCl compared to 6M GdnHCl. These data are consistent with earlier studies showing that the chain conformation is the same in both solvents, but that in 0.1M NaCl, the PSM glycoprotein undergoes a self-association process that is end-to-end in nature. Since the tau 1 value is intimately related to the viscoelastic behavior of PSM solutions and gels, it is interesting to speculate that the end-to-end association process may be physiologically important.

Proteoglycans from bovine fetal epiphyseal cartilage. Sedimentation velocity and light scattering studies of the effect of link protein on proteoglycan aggregate size and stability

Proteoglycan monomer and link proteins were isolated from bovine fetal epiphyseal cartilage and characterized. The physical characteristics of proteoglycan monomer were: s0(20) = 21.3 S, D0t,z = 4.25 x 10(-8)cm2/sec, Mw = 3 x 10(6) and Rg,z = 980A. Link protein preparations contained link proteins 1 and 2, but little or none of the fragment, link protein 3. Link protein-stabilized and link protein-free proteoglycan aggregates were reassembled from proteoglycan monomer, link protein and hyaluronate. The effect of epiphyseal cartilage link protein on aggregate size and stability was examined in sedimentation velocity studies. Compared with link protein from mature bovine nasal and articular cartilages, which contain appreciable amounts of link protein 3, epiphyseal cartilage link protein dramatically stabilized aggregates at pH 5. In the presence of link protein, 92% of the proteoglycan monomers were bound as aggregate at pH 7, and 81% were bound at pH 5. In the absence of link protein, 51% of monomers were bound at pH 7, and only 32% were bound at pH 5. The progressive dissociation of link protein-free aggregates as a function of decreasing pH, and of increasing temperature, was also examined in dynamic light scattering studies. The results of the light scattering studies were in perfect accord with the results of the sedimentation velocity studies. However, compared with the sedimentation velocity studies, the dynamic light scattering studies provided a more detailed and informative description of the dissociation of the link-free aggregate as a function of pH, as a function of temperature, and of the capacity of link protein to stabilize aggregate against dissociation at decreased pH or elevated temperature.

The saboteurs of Britain's opiate policy: overprescribing physicians or American-style "junkies"?

In the 1950s a new deviant drug user, the American-style "junkie", appeared in the United Kingdom. Previous discussions of this subculture have not raised the issue of how it came to be patterned on a foreign model, rather than evolving as a domestic deviant style. A number of overprescribing physicians who nourished the new subculture by their generous prescribing practices provided the impetus for changes in British drug policy. It is argued that these "overprescribers" were the creation of the new generation of heroin users, as well as their creators.

Urine screening: an alternative to urine cultures

Urine cultures represent one of the most commonly submitted specimens to a microbiology laboratory. In an attempt to manage effectively this type of specimen, Bac-T-Screen (BTS), nitrate and leukoestrase test were performed on all clean catch urine specimens sent for culture. Three hundred and four specimens were screened by these methods. The BTS, by itself, had the highest sensitivity, and specificity (92 percent and 81 percent, respectively) and the lowest false negative rate (9.8 percent) of the three tests. A combination BTS/leukoestrase test increased specificity (99 percent), but the sensitivity was only 73 percent.

Patterns of alcohol use and psychiatric inpatient admissions

The role of alcohol problems in psychiatric inpatient hospital admissions is not fully reflected in diagnostic statistics. A model is presented to guide the design and aid the interpretation of epidemiological research into the relationships between alcohol use and psychiatric disorder. The difficulties encountered in evaluating the role of alcohol in hospitalizations are discussed. Our preliminary research suggests that not enough attention has been paid to self-imposed abstinence from alcohol as a precipitant of symptoms and a precursor to hospitalization.

Thermal and solvent stability of proteoglycan aggregates by quasielastic laser light-scattering

The dissociation behavior of several species of proteoglycan aggregates (PGA) has been studied quantitatively by monitoring the changes in particle size by dynamic laser light-scattering. Firstly, studies of the thermal dissociation of reconstituted PGA from bovine nasal septum and bovine fetal epiphysus are described. The effect of link protein in stabilizing reconstituted PGA against changes in temperature has been demonstrated. It was also confirmed that, upon prolonged heating at 70 degrees, the dissociation of link-containing, reconstituted PGA is effectively irreversible. Secondly, the dissociation characteristics of native PGA isolated from chick chondrocyte and rat chondrosarcoma cell-cultures were investigated in aqueous solvents containing increasing concentrations of guanidine hydrochloride. It was found that the more densely packed, native, aggregate structure has a higher susceptibility to thermal disruption than the reconstituted, link-containing material. Considerable loss of subunits from the native aggregates occurs at temperature where the link protein retains its activity. The dissociation of native PGA is irreversible, in the sense that reconstituted PGA always exhibits smaller sizes than the native PGA, reflecting a smaller degree of aggregation of the subunits.

Light-scattering studies of fractionated ovine submaxillary mucins

Static and dynamic light-scattering studies of solutions of ovine submaxillary mucin (OSM) glycoproteins, fractionated by exclusion chromatography on Sephacryl S-1000, are reported. These experiments yielded information regarding the structure and conformation of the glycoprotein chain, in the form of weight-average molecular weights, Mw, z-average radius of gyration, Rg,z, and z-average of the inverse hydrodynamic radius, (Rh-1)z. The values of (Rh-1)z are found to correlate very well with the S-1000 elution volume characteristics for four OSM fractions of different molecular weights. The structural parameters for these OSM fractions are, within experimental error, similar to those deduced for porcine submaxillary mucins (PSM) in earlier studies. The results suggest that, like PSM, the glycoprotein structure of OSM consists of linear chains constructed by covalently linking two or more elementary subunits together via disulfide bonds. In addition, the rigidity of the protein core of OSM is substantially greater than that observed for non-glycosylated-polypeptide random coils. Because (Rh-1)z, and hence, elution volume depends only on the molecular weight of the mucin protein core, the Mw calibration obtained for OSM should be applicable to the chromatography of other mucin glycoproteins.

An analysis of T cell responsiveness in Indian kala-azar

The inability of most untreated patients with Kala-azar to control their visceral infections with Leishmania donovani has been attributed to a defective cell-mediated immune response to leishmanial antigens. We examined the in vitro response of T cells, including Leu-2+-depleted T cell populations, to determine whether unresponsiveness could be reversed. These studies on patients with visceral leishmaniasis in Bihar, north India, support previous observations regarding T cell unresponsiveness in patients with active disease: it is profound, it is specific, and it is reversible after successful chemotherapy. However, these studies also indicate that the specific unresponsiveness cannot be reversed by depletion of "suppressor" Leu-2+ T lymphocytes, nor by the addition of exogenously supplied human IL 2 to the cultures. One interpretation of these results is that in active cases of Kala-azar, there is an absence of Leishmania-specific T cells in the periphery. The possibility that reactive cells can be found in situ cannot be excluded. The observation that 13 of 25 family members of active cases were able respond to L. donovani in vitro or by skin testing suggests that the frequency of infection within an endemic area in Bihar is very high, and that assays for T cell responsiveness are far better epidemiologic tools for the detection of asymptomatic infection than is ELISA. Identification of such an exposed, Kala-azar-resistant population will be required to study host factors which influence the development of disease in infected individuals.

An analysis of T cell responsiveness in Indian kala-azar

The inability of most untreated patients with Kala-azar to control their visceral infections with Leishmania donovani has been attributed to a defective cell-mediated immune response to leishmanial antigens. We examined the in vitro response of T cells, including Leu-2+-depleted T cell populations, to determine whether unresponsiveness could be reversed. These studies on patients with visceral leishmaniasis in Bihar, north India, support previous observations regarding T cell unresponsiveness in patients with active disease: it is profound, it is specific, and it is reversible after successful chemotherapy. However, these studies also indicate that the specific unresponsiveness cannot be reversed by depletion of "suppressor" Leu-2+ T lymphocytes, nor by the addition of exogenously supplied human IL 2 to the cultures. One interpretation of these results is that in active cases of Kala-azar, there is an absence of Leishmania-specific T cells in the periphery. The possibility that reactive cells can be found in situ cannot be excluded. The observation that 13 of 25 family members of active cases were able respond to L. donovani in vitro or by skin testing suggests that the frequency of infection within an endemic area in Bihar is very high, and that assays for T cell responsiveness are far better epidemiologic tools for the detection of asymptomatic infection than is ELISA. Identification of such an exposed, Kala-azar-resistant population will be required to study host factors which influence the development of disease in infected individuals.

Effect of changes in moisture profiles of a transitional red-brown earth with surface and slotted gypsum applications on the development and yield of a wheat crop

The low productivity of transitional red-brown earths for flood irrigated upland cropping is associated with their low infiltration rates and inadequate aeration of the root zone. The effect of the measured changes in the moisture and aeration profiles with surface and slotted gypsum applications on growth and development of a wheat crop was evaluated in a preliminary field study, on non-replicated plots.The patterns of changes in moisture profiles in the gypsum slotted plots were similar to those observed in the previous season, namely, deeper preferential wetting and faster internal drainage through the slots. This resulted in lower volumetric moisture contents in the slots and in the surface and subsurface layers between slots, compared to the non-slotted plots.The critical moisture contents were defined for each soil depth at which an air-filled porosity of 0.08 mm3 mm-3 was reached. For the transitional red-brown earth used in this study, air-filled porosity needs to be larger than 0.08 mm3 mm-3 to provide a soil pathway for oxygen flow to roots. The moisture profiles in the no-gypsum, surface gypsum and slotted gypsum plots measured throughout the cropping season indicated the period of time when oxygen flow through different soil layers was likely to be restricted. The moisture contents were higher than the critical value in the surface and subsurface layers of the non-slotted plots, particularly in the plot with no gypsum applications, during a period in winter with prolonged rainfall and low evapotranspiration rates. This resulted in reductions in the rates of phasic development, tillering, canopy closure and dry matter production and finally lower yields in the non-slotted plots, especially in the plot without gypsum. Differences in grain yields were mainly due to differences in the number of spikes m-2.During the second half of the growing season higher potential evapotranspiration, lower rainfall and accurate irrigation scheduling resulted in the moisture contents being maintained below the critical limits at all depths in all plots. Consequently, the two yield components which were determined during this period, namely, the number of kernels per spike and kernel weight, showed only slight variations between plots.

Calibration of the relative molecular mass of proteoglycan subunit by column chromatography on Sepharose CL-2B

Calibration relationships were derived for cartilage proteoglycan subunit (PGS) that relate the inverse z-average hydrodynamic radius (Rs) and the weight-average Mr (Mw) to the partition coefficient (Kav.) for PGS when chromatographed on a Sepharose CL-2B column. PGS isolated from chick limb-bud chondrocyte cell cultures was fractionated chromatographically into eight pools, for which Mw and Rs were determined by total-intensity and dynamic light-scattering measurements. These data were found to be related to Kav. through the following empirical equations: log Mw = -(1.65 +/- 0.27)Kav. +(6.58 +/- 0.08); log Rs = -(0.69 +/- 0.04)Kav. +(2.75 +/- 0.01). Application of these relationships to the chromatographic data led to Mw = 1.48 X 10(6) and Rs = 38.7 nm (387 A) for the unfractionated specimens compared with values of Mw = 1.46 X 10(6) and Rs = 38.2 nm (382 A) determined by light-scattering. Our results were found to be consistent with previously proposed phenomenological models for the gel-filtration mechanism. Application of these calibration relationships to Kav. for several unfractionated specimens led to predicted values of Mw and Rs that are accurate to within 10%.

Growth and yield of rice under sprinkler irrigation on a free-draining soil

A line-source sprinkler irrigation system was used to study rice growth under irrigation on a free-draining soil in the Murrumbidgee Irrigation Area of New South Wales. Ponded rice was grown on the same soil for comparison. Seven levels of sprinkler water application were examined, ranging from 26 to128% of Class 'A' pan evaporation. Apparent efficiency of water use ranged from 3.4 kg of grain/mm for the highest yielding sprinkler treatment to 1.85 kg of grain/mm for the highest yielding ponded treatment. Excellent weed control was achieved by herbicides applied through a sprinkler system.

The thermal depolymerization of porcine submaxillary mucin

The time dependence of the molecular weight, radius of gyration, and hydrodynamic size distribution for porcine submaxillary mucin (PSM) in solution have been studied using static and dynamic light scattering. The weight average molecular weight (Mw) of PSM in 6 M guanidine HCl, pH 7, is initially 3 X 10(6) and decreases with time in three phases: rapidly from 3-2 X 10(6), less rapidly from 2-0.9 X 10(6), and slowly below 0.9 X 10(6). The rates of decrease are much greater at pH 2. The energy of activation associated with each phase is 20 kcal/mol, which is similar to that reported for peptide bond cleavage at an aspartic acid residue. Addition of mercaptoethanol to PSM in 6 M guanidine HCl leads to a rapid decrease in Mw to 0.9 X 10(6), followed by a very slow further decrease. These results suggest that native PSM consists of subunits (Mw = 0.9 X 10(6] that are linked by disulfide bonds to form dimers (Mw = 2 X 10(6] and then higher aggregates. This cross-linking appears to occur at unglycosylated regions of the protein core, which are believed to be richer in aspartic acid than the rest of the molecule.

Effects of lateral recumbency and sitting on the first stage of labor

We compared uterine activity in lateral recumbency and the sitting position during the first stage of labor in a group of nulliparas. Lateral recumbency was accompanied by more intense, less frequent and more efficient uterine contractions than sitting. Patients preferred sitting for the first half of labor and lateral recumbency for the second. No adverse fetal reaction was noticed in either position, judging from the fetal heart rate. An increase in maternal pulse rate during sitting could have indirectly indicated some compression of the prevertebral vessels. Maternal position clearly affects several parameters of labor, and its selection should be based upon maternal comfort, uterine contractility and efficiency, and hemodynamic repercussions.

Light-scattering studies of chick limb bud proteoglycan aggregate

Static and dynamic light-scattering methods have been used to investigate the structure of chick limb bud chondrocyte proteoglycan aggregate in 0.4 M guanidinium chloride. Zimm plot data for proteoglycan aggregate yield a molecular weight of 45 +/- 8 X 10(6) which compares well with a value of approximately 43 X 10(6) obtained by combination of the diffusion and sedimentation data via the Svedberg equation. The molecular weight of the proteoglycan subunit was determined previously to be 1.4 +/- 0.3 X 10(6), which indicates that the average proteoglycan aggregate molecule contains 32 associated subunits. This is in good agreement with electron microscopy which suggests an average of approximately 25.5 subunits/aggregate; it can be concluded that the aggregates visualized by electron microscopy are also present in solution. These data are also compatible with the ratio of the hydrodynamic volumes of proteoglycan aggregate and subunit. The formation of the aggregate structure has little effect on the solvent-binding capacity of the components: both proteoglycan aggregate and subunit have expanded coil conformations that include approximately 99% solvent.

Light scattering studies of chick limb bud proteoglycans

We report static and dynamic light scattering analysis on subpopulations of proteoglycan monomer isolated in milligram quantities from chick limb bud mesenchymal cell cultures by gel fractionation in dissociative solvent conditions. These experiments furnish information on radius of gyration, Rg, and hydrodynamic radius, Rh, as a function of molecular weight, Mr,w. A comparison of these quantities, rho = Rg/Rh, indicates a decrease in branch frequency with decreasing Mr,w. This is consistent with the known result that decreasing molecular weight is due to a decrease in the number of polysaccharide side chains attached to a constant protein core length. These results show that photon correlation spectroscopy can be used to monitor structural changes in macromolecules isolated from these cell cultures.