19F nuclear magnetic resonance studies of lipid fatty acyl chain order and dynamics in Acholeplasma laidlawii B membranes. Orientational order in the presence of a series of positional isomers of cis-octadecenoic acid

The 19F nuclear magnetic resonance (NMR) spectra of membranes of Acholeplasma laidlawii B enriched with one of a series of positional isomers of cis-octadecenoic acid plus small amounts of one of a number of isomers of monofluoropalmitic acid were interpreted in terms of an orientational order parameter (Smol). The variation of Smol with the position of the fluorine label in the liquid-crystalline state yielded an "order profile" with characteristics similar to those obtained via 2H NMR and which was relatively invariant regardless of the site of cis unsaturation. In the gel state, values of Smol approached the theoretical maximum, and the order profiles in the presence of different isomeric cis-octadecenoic acids displayed distinct dissimilarities. When the cis double bond was located proximal to the methyl terminus of the fatty acyl chain, a gradient of order across the bilayer was still evident in the gel state. When the cis double bond was located near the carbonyl head group, values of Smol were approximately equal at all chain positions. These observations were interpreted as indicating that in the gel state the stringency of packing restrictions is still subject to variation across the width of the bilayer. Relative overall orientational order among all isomers examined (specifically, 18:1c delta 4, delta 5, delta 6, delta 7, delta 8, delta 9, delta 10, delta 11, delta 12, delta 13, delta 14, and delta 15) varied directly as a function of proximity to the lipid gel to liquid-crystalline phase transition (Tm) (determined via differential scanning calorimetry) when compared at a constant temperature.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fluorine-19 nuclear magnetic resonance studies of lipid fatty acyl chain order and dynamics in Acholeplasma laidlawii B membranes. Gel-state disorder in the presence of methyl iso- and anteiso-branched-chain substituents

The hydrocarbon chain orientational order parameters of membranes of Acholeplasma laidlawii B enriched with large quantities of a linear saturated, a methyl iso-branched, or a methyl anteiso-branched fatty acid plus small quantities of various isomeric monofluoropalmitic acid probes were determined via fluorine-19 nuclear magnetic resonance spectroscopy (19F NMR) over a range of temperatures spanning the gel to liquid-crystalline phase transitions (determined by differential scanning calorimetry). Membrane orientational order profiles in the liquid-crystalline state were generally similar regardless of the particular fatty acyl structure, showing a region of relatively constant order preceding a region of progressive decline in order toward the methyl terminus of the acyl chain. In the gel state, the order profile of the linear saturated fatty acid enriched membranes was characteristically flat, with little head to tail gradation of order. In contrast, the methyl iso-branched and the methyl anteiso-branched enriched membranes exhibited a local disordering in the gel phase reflected in a very pronounced head to tail gradient of order, which remained at temperatures below the lipid phase transition. In addition, the methyl iso- and anteiso-branched fatty acid enriched membranes were overall more disordered than the membrane containing only linear saturated fatty acyl groups. Thus, at a constant value of reduced temperature below the lipid phase transition, overall order decreased in the progression 15:0 greater than 16:0i greater than 16:0ai, suggesting that these methyl-branched substituents lower the lipid phase transition by disrupting the gel phase lipid chain packing.(ABSTRACT TRUNCATED AT 250 WORDS)     

Formation of urso- and ursodeoxy-cholic acids from primary bile acids by a Clostridium limosum soil isolate

A gram-positive, rod-shaped anaerobe (isolate F-14) was isolated from soil. This organism was identified by cellular morphology as well as by fermentative and biochemical data as Clostridium limosum. Isolate F-14 formed ursocholic acid (UC) and 7-ketodeoxycholic acid (7-KDC) from cholic acid (CA), and ursodeoxycholic acid (UDC) and 7-ketolithocholic acid (7-KLC) from chenodeoxycholic acid (CDC) in whole cell cultures, but did not transform deoxycholic acid (DC). No hydrolysis or transformation occurred when either taurine- or glycine-conjugated bile acids were incubated with F-14. The type stain of Clostridium limosum (American Type Culture Collection 25620) did not transform bile acids. The structures of ursocholic, ursodeoxycholic, 7-ketodeoxycholic, and 7-ketolithocholic acids were verified by mass spectroscopy and by thin-layer chromatography using Komarowsky's spray reagent. The organism transformed cholic and chenodeoxycholic acids at concentrations of 20 mM and 1 mM, respectively; higher concentrations of bile acids inhibited growth. Optimal yields of ursocholic and ursodeoxycholic acids were obtained at 9-24 hr of incubation and depended upon the substrate used. Increasing yields of 7-ketodeoxycholic and 7-ketolithocholic acids, and decreasing yields of ursocholic and ursodeoxycholic acids were observed with longer periods of incubation. Culture pH changed with time and was characterized by a small initial drop (0.2-0.4 pH units) and a subsequent increase to a pH (8.1-8.2) that was above the starting pH (7.4).(ABSTRACT TRUNCATED AT 250 WORDS)     

Cause of death in 1144 patients with diabetes mellitus: an autopsy study.

The pathological reports for all patients over 13 years of age who had had an autopsy at one of three university-affiliated hospitals between 1967 and 1976 were reviewed to determine the principal cause of death. The clinical records of the patients with diabetes were reviewed to verify the diagnosis and to determine the known duration of diabetes. There were 1144 patients with diabetes mellitus and 5674 without. The sex distribution was similar in the two groups. The patients with diabetes were slightly older, males by 2.2 years and females by 3.2 years. Disease of the circulatory system was the principal cause of death in males (53.7%) and females (58.9%) with diabetes. The rates in the corresponding patients without diabetes were 37.6% and 35.2%. Neoplasms accounted for 18.9% of deaths in males with diabetes, compared with 35.7% in males without diabetes; the corresponding figures in females were 16.0% and 39.4%. Renal disease accounted for 5.9% of deaths in patients with diabetes.     

Alkali treatment of corn stover to improve sugar production by enzymatic hydrolysis

Alkali treatment of corn stover improves the avaliability of cellulose and hemicellulose for enzymatic attack. Treatments were carried out for 1 to 60 min at temperatures and NaOH concentrations ranging from 100 to 150 degrees C and 0 to 2%, respectively. Solubilization of the stover and sugar production by enzymatic hydrolysis (Trichoderma viride cellulase) of the solid residue and the dissolved solids were used to measure the effect of caustic treatment. At 150 degrees C and 2% NaOH concentration, 65% of the original stover was dissolved after 5 min and 52% saccharificatin (g sugar/g stover) of the residue and dissolved solids by enzymatic hydrolysis was achieved compared to 20% for untreated corn stover.     

19F-nuclear magnetic resonance study of glycerolipid fatty acyl chain order in Acholeplasma laidlawii B membranes

The technique of 19F-nuclear magnetic resonance (19F-NMR) spectroscopy offers a number of advantages for studies of lipid fatty acyl chain orientation and dynamics in biomembranes. However, the geminal difluoromethylene fatty acid probes usually employed in such studies appreciably perturb the organization of lipid bilayers. We have thus synthesized a series of specifically monofluorinated palmitic acids and carried out biophysical, biochemical, and physiological studies establishing their suitability as relatively non-perturbing probes of lipid hydrocarbon chain organization. These 19F-NMR probes were then used to determine the fatty acyl chain order profiles of Acholeplasma laidlawii B membranes highly enriched in a variety of different exogenous fatty acids, particularly those containing a methyl branch or a trans-double bond.     

Penicillin production and its mode of inheritance inAspergillus nidulans

Previous workers have shown that some strains ofAspergillus nidulans produce penicillin-like substances. In the present studies, shake-flask cultures of 101 wild-type strains ofA. nidulans, representatives of 18 different heterokaryon-compatible groups, were examined and filtrates of most found to inhibit the growth of a strain ofBacillus subtilis sensitive to penicillin, although members of two of these groups had no detectable antibiotic activity. Five strains with antibacterial properties were chosen for detailed investigation as well as two genetically labelled derivatives obtained from one of these after ultraviolet light treatments; one derivative had a similar antibiotic yield to its original wild-type parent but the other was selected as having increased antibiotic yield. The antibiotic produced by these seven strains was by all tested criteria, including chromatographic and electrophoretic behaviour, indistinguishable from penicillin. A heterokaryon test between the two mutants indicated that antibiotic productivity was under nuclear control.     

Further evidence of oxygen diffusion as the determining factor in the relation between disk thickness and respiration of potato tissue

The effect of oxygen tension above atmospheric pO₂ on the development of respiratory capacity in potato disks has been examined. Raising the oxygen tension of the aqueous environment to 40% during the aging of 2.0 mm or 3.0 mm thick disks at 25° progressively increased the respiration rate of the tissue as shown by subsequent assay in 100% oxygen. Disks 3.0 mm thick showed a greater response to increased pO₂ than did 2.0 mm disks. A comparison of center 1.0 mm sections excised from 3.0 mm disks after aging, showed that the respiration rate of internal tissue from disks aged in high pO₂ was approximately 40% greater than such tissue aged with atmospheric pO₂. The characteristic inverse relationship between respiration rate and thickness in aged disks can be modified from a concave-downwards curve to a convex-downwards curve by pretreating the tissue with increased pO₂, thus indicating that raising the pO₂ during aging can increase the thickness threshold at which the transition from tissue manifesting the respiratory characteristics of thin disks to that manifesting the characteristics of thick disks, occurs. Similarly increased pO₂ during aging can modify the hyperbolic relationship obtaining between pretreatment temperature in the range 10° to 25° and respiratory capacity of aged 3.0 mm disks, to approximate to the linear relationship observed with 0.75 mm disks. It is concluded that the development of respiratory capacity in disks between 0.75 mm and 3.0 mm thick is restricted by oxygen dificiency and that the characteristic inverse relationship between respiration rate and thickness in aged disks is largely attributable to this factor, the influence of which is discernible both on the development of respiratory capacity and on its subsequent assay.