Chemical and serologic definition of two unique D region-encoded molecules in the wild-derived mouse strain B10.GAA37

Detailed serologic and biochemical characterization of D region products of the wild-derived mouse strain B10.GAA37 (Dw16) were performed and compared with previous studies of the D region products of the H-2d,b, and q haplotypes. Serologic analysis revealed that the antigens encoded by the Dw16 region express a unique combination of specificities defined by monoclonal antibodies (mAb) with established activity for the Ld and Dd molecules. Two out of five anti-Ld-reactive mAb reacted with B10.GAA37 cells, whereas one of three anti-Dd mAb showed B10.GAA37 reactivity. Sequential immunoprecipitation of B10.GAA37 antigens demonstrated the existence of at least two antigenically distinct molecules (designated Dw16 and Lw16) encoded by genes associated with the Dw16 region. Peptide map comparisons of the Dw16 and Lw16 molecules defined multiple differences in their primary protein structure, suggesting they are products of separate genes. Structural comparisons of the Lw16 and Dw16 molecules with the Ld and Dd molecules implied a) that the Dw16 and Dd regions did not result from a recent evolutionary divergence of a common primordial haplotype, and b) that the Lw16 and Dw16 molecules are more structurally homologous to each other than the Ld and Dd molecules are. Comparison of these findings with our previous studies of antigens encoded by the D regions suggest that each of these haplotypes has unique properties in terms of the number of gene products expressed and/or the structural relatedness of products of the same region.

Disulfide structure of murine Ia alloantigens

The tryptic (T) and T insoluble chymotryptic (TIC) peptide maps from 35S-cysteine (Cys) labeled, disulfide-linked I-Ak dimer were compared to those from 35S-Cys labeled I-Ak alpha and beta chains which were not covalently linked. These comparisons indicated that the alpha and beta chains found in the covalent I-Ak dimer were not a specialized subset of I-A alpha and beta chains. Furthermore, these data, along with the knowledge that alkylation of spleen cells prior to and during detergent solubilization prevents the formation of disulfide-linked I-Ak dimer, indicate that covalent dimer formation is an inefficient and artifactual process. Comparison of the T and TIC peptide maps of reduced and nonreduced 35S-Cys labeled I-Ak alpha and beta chains suggests that the I-Ak alpha chain contains one intrachain disulfide bond, whereas the I-Ak beta chain contains two intrachain disulfide bonds. Examination of the T and TIC peptide maps of the reduced and nonreduced 35S-Cys labeled I-Ak dimer identifies the Cys-containing peptides which are involved in the formation of the artifactual I-Ak dimer interchain (alpha-beta) disulfide bond. Comparison of 35S-Cys labeled I-Ak and I-Ek alpha and beta chains by T and TIC peptide mapping reveals considerably more homology between the two alpha-chains and between the two beta-chains than is observed using other 3H-amino acid precursors, thus indicating that the I-Ak and I-Ek alloantigens are homologous in their amino acid sequences adjacent to the Cys resides. The reasons for the inability to induce formation of interchain (alpha-beta) disulfide bonds in I-Ek molecules are discussed.

Direct and indirect measurements of Phloem turgor pressure in white ash

Direct determinations and indirect calculations of phloem turgor pressure were compared in white ash (Fraxinus americana L.). Direct measurements of trunk phloem turgor were made using a modified Hammel-type phloem needle connected to a pressure transducer. Turgor at the site of the direct measurements was calculated from the osmotic potential of the phloem sap and from the water potential of the xylem. It was assumed that the water potentials of the phloem and xylem were close to equilibrium at any one trunk location, at least under certain conditions. The water potential of the xylem was determined from the osmotic potential of xylem sap and from the xylem tension of previously bagged leaves, measured with a pressure chamber. The xylem tension of bagged leaves on a branch adjacent to the site of the direct measurements was considered equivalent to the xylem tension of the trunk at that point. While both the direct and indirect measurements of phloem turgor showed clear diurnal changes, the directly measured pressures were consistently lower than the calculated values. It is not clear at present whether the discrepancy between the two values lies primarily in the calculated or in the measured pressures, and thus, the results from both methods as described here must be regarded as estimates of true phloem turgor.

A simple system of parenteral nutrition

The practical problems involved in the preparation and delivery of parenteral nutrition may result in such treatment being withheld from patients who would benefit from it. A simple and reliable system is described which has been developed to overcome the more common problems.

Synchronous pressure-potential changes in the phloem of Fraxinus americana L

Simultaneous measurement of the pressure potential of the phloem of F. americana made on two locations on the trunk over long periods of time showed synchronous oscillations of no fixed period during the day. The simultaneous changes in pressure in two different trees indicated environmental changes were responsible for the synchrony. The coincident changes of pressure 5 m apart on the same trunk implied that either transpiration had an immediate and direct effect upon the pressure potentials developed in the phloem because of the intimate relationship of the phloem water potential and the water potential of the adjacent transpiration stream, or factors affecting phloem loading resulted in pressure changes throughout the phloem.

Acceptability of Accelerated-Processed Pork 1

Five market hogs were slaughtered to determine the microbial, organoleptic and appearance differences between accelerated and conventionally processed pork. The left side of each carcass was processed 4 h after slaughter, whereas the right side was fabricated at 24-h postmortem. Microbial sampling was conducted. Appearance and organoleptic characteristics were evaluated. Conventionally processed cuts of pork were rated higher for color and overall appearance than the accelerated-processed cuts until 120 h. Taste panel data revealed no significant difference in tenderness and juiciness between the accelerated and conventionally processed cuts. Differences in microbial load between the two processes after 120 h of storage were negligible; however, the accelerated processed cuts had a higher microbial load than the conventionally processed cuts except at 120 h. No measurable differences were found in the genera of microorganisms among samples from the accelerated and conventional methods. TBA values suggested little difference in rancidity between the two processes. Differences between the accelerated and the conventionally processed samples of pork were not enough to merit the preference of pork from one processing technique over the other method.

Comparison of outer membrane porin proteins produced by Escherichia coli and Salmonella typhimurium

The OmpC, OmpF, and Lc (NmpC) porin proteins of Escherichia coli K-12 have been shown to be similar to the OmpC (36K), OmpF (35K) and OmpD (34K) porin proteins of Salmnella typhimurium LT2 in terms of function, regulation of expression, and, in the case of OmpC and OmpF proteins, equivalence of the genetic loci determining their production. However, the corresponding pairs of proteins from these two species showed only limited similarity in peptide maps and no similarity in terms of migration on polyacrylamide gels.

Effect of Thaw Conditions on Ground Beef 1

Three sampling periods were selected to acquire ground beef packages from two retail stores. Initially, samples were subjectively evaluated for color and overall appearance. Microbial load and taxonomy were determined and the samples were subsequently frozen. After frozen storage, one-half of the packages were thawed at 5 C for 4, 8, 24, 48 and 72 h, whereas the other samples were thawed at 25 C for the same periods. After thawing, samples were evaluated for the same characteristics as before freezing. Samples from each treatment were also evaluated for flavor, odor and overall acceptability. Appearance traits, taste and microbial load were affected (P < .05) by thaw time and temperature. Major groups of bacteria identified were: micrococci, Pseudomonas , streptococci, staphylococci, Flavobacterium , lactobacilli and coliforms. Salmonella and pathogenic Staphylococcus were not found. Those microorganisms which were identified were considered to be responsible for deterioration of appearance and taste attributes. Increased coliform growth at 25 C, especially after 8 h, suggests a need to thaw ground beef at refrigerated temperature to reduce public health concern. Results suggest that a proper thaw time and temperature to maintain acceptable appearance and taste of ground beef would be 24 h or less at refrigerated temperature.

Appearance and Microbial Quality of Thawed Retail Cuts of Beef, Pork and Lamb 1

Retail cuts of beef, pork and lamb were fabricated, packaged, evaluated for appearance traits, swabbed, and subsequently frozen. After storage for 7 days, one-half of the cuts were thawed at 4 C. The other cuts were thawed at 25 C. At 0, 4, 8, 24 and 48 h, the thawed retail cuts of meat were rated for appearance and swabbed. Taxonomy was conducted before freezing and after each thaw period. Evaluation revealed that differences (P < .05) in appearance for beef and pork existed between those samples thawed for 24 h and 0 h. Beef and pork cuts thawed at 25 C were less (P < .05) desirable in appearance after 24 h than for 8 h. Cuts thawed at 4 C for 48 h were less desirable than for 24 h. A higher thaw temperature increased (P < .05) microbial growth at 24 h on beef; but this trend was not observed among cuts of lamb and pork. Thaw time beyond 24 h increased (P < .05) the microbial load of only lamb and pork. Microorganisms most prevalent among samples were Pseudomonas , micrococci and staphylococci. These data suggest that retail cuts of meat should be thawed at refrigerated temperature, especially if thaw time exceeds 8 h.

Chemical heterogeneity of major outer membrane pore proteins of Escherichia coli

Peptide mapping and isoelectric focusing were used to compare the major outer membrane pore proteins from various strains of Escherichia coli K-12, including strains carrying mutations in the nmpA, nmpB, and nmpC genes which result in the production of new membrane proteins. Proteins 1a, 1b, and 2 and the NmpA proteins each gave unique peptide and isoelectric focusing profiles, indicating that these are different polypeptides. The NmpA protein and the NmpB protein appeared to be identical by these criteria. The NmpC protein and protein 2 were nearly identical, although one different peptide was observed in comparing the proteolytic peptide maps of these proteins and there were slight differences in their isoelectric focusing profiles. Antiserum against protein 2 showed partial cross-reactivity with the NmpC protein. These results indicate that the various pore proteins of E. coli K-12 fall into four different classes.

Comparison of Bacterial Swab Samples Given Different Storage Treatments 1

Six paired sides of U.S. Good beef were swabbed to obtain microbial samples. Half of the beef sides were stored at an elevated temperature (25 C) for 8 h with subsequent storage for 12 h at 1 C before sampling, whereas the counterpart sides were stored the entire period at 1 C. Samples from adjacent areas were taken so that a comparison could be made of 0.03 M phosphate buffer and 0.1% peptone broth as diluents for swab samples. To evaluate the effect of storage time, swab samples were stored at 5 C for 1, 24, 48, 72, and 120 h before being transferred to Standard Plate Count Agar and subsequently incubated at 25 C. Results revealed that no differences (P>.05) existed between the effectiveness of a phosphate buffer solution and peptone broth as diluents for swab samples. Storage of swab samples at 1 C resulted in recovery of fewer microorganisms at 24, 48, and 72 h.

Carbon assimilation and translocation in soybean leaves at different stages of development

Carbon assimilation, translocation, and associated biochemical characteristics of the second trifoliolate leaf (numbered acropetally) of chamber-grown soybean, Glycine max (L.) Merr., plants were studied at selected stages of leaf development during the period from 10 to 25 days postemergence. Leaves of uniform age were selected on the basis of leaf plastochron index (LPI).The test leaf reached full expansion (A(max)) and maximum CO(2) exchange rates on a leaf area basis at 17 days postemergence (LPI 4.1). Maximum carbon exchange rates per unit dry weight of lamina were attained several days earlier and declined as specific leaf weight increased. Chlorophyll and soluble protein continued to increase beyond the attainment of A(max), but were not accompanied by further increases in photosynthetic rates.Much of the fixed carbon in leaves is partitioned between starch and sucrose. Starch content of leaves as a percentage of dry weight at the end of an 11-hour photoperiod was taken as an indication of the potential energy reserve accumulated by the leaf. Starch levels were the same regardless of leaf age during the period from 0.3 A(max) to 7 days after attaining A(max). Respiratory and synthetic activity of leaves decreased considerably during the same period, suggesting that starch accumulation is not entirely controlled by the energy demands of the leaf.Sucrose content increased steadily during leaf expansion and was accompanied by corresponding increases in sucrose phosphate synthetase (EC 2.4.1.14) activity and translocation rates. Sucrose phosphate synthetase may have an important regulatory role in photosynthate partitioning and translocation.

Salmonella in horses: a source of contamination of horsemeat in a packing plant under federal inspection

Cecal samples from 270 slaughter horses revealed that 41 samples (15.1%) contained Salmonella. Of 233 horsemeat samples tested, Salmonella was isolated from 62 samples, or 26.6%. Only 2 of 158 human stool specimens from the plant workers revealed Salmonella. Predominant serotypes isolated from the horsemeat were Salmonella enteritidis Good and Anatum, whereas the serotypes Agona and Derby predominated the horse cecal isolates. Preliminary data indicate that the high percentage of meat contamination is surface contamination due to poor slaughtering technique.

Ground substance mucopolysaccharides and plasma proteins: their role in capillary water balance

The osmotic interaction of mucopolysaccharides and plasma proteins, normally present in the interstitium, has been investigated. It has been found that hyaluronate-plasma protein mixtures may be treated as a two-phase system and that the two phases are in osmotic equilibrium. The osmotic pressures exerted by these mixtures are higher than the algebraic sum of the two components. At concentrations normally present in the interstitium of skin and muscle (0.6% mucopolysaccharides and 2% protein), the osmotic pressure exerted by the mixture is on the order of 10 mmHg, which is in agreement with predictions from earlier computer-simulation studies. The partition of fluid between the gel-like mucopolysaccharide compartment and the free-fluid containing the protein is approximately 50% in the "gel" phase at concentrations found in the interstitium. The volume exclusion effects of the interstitial mucopolysaccharides are significant, both in terms of selection of tracer molecules for interstitial volume measurements and also as an osmotic buffering mechanism which aids in maintaining the partition of fluid between the circulation and the interstitial space.

Prazosin: preliminary clinical and pharmacological observations

1. Prazosin had a considerable anti-hypertensive effect in both lying and standing posture in a mixed group of twenty-four patients in an open clinical trial. The drug was well tolerated and side-effects were few. 2. Tested on rat blood vessels, prazosin was ten times more potent on a molar basis than phentolamine in blocking the vasoconstrictor effects of noradrenaline. In the absence of vasoconstrictor nervous activity, no vasodilatation was observed. 3. In genetically hypertensive rats, prazosin in large doses caused a substantial fall in blood pressure, total exchangeable sodium and extracellular fluid volume. Tolerance to these effects started to develop within 20 days. In normotensive rats, blood pressure was lowered but total exchangeable sodium and extracellular fluid volume were not affected.

Studies on the New Zealand strain of genetically hypertensive rats

1. The New Zealand strain of rats with genetic hypertension (GH rats), the Japanese strain with spontaneous hypertension and the salt-sensitive strain of Dahl are now well established as three genetically pure lines for use in hypertensive research. Other pure lines not consciously selected for high blood pressure have also recently been shown to exhibit hypertension.

2. In the GH rats the inheritance of the blood pressure appears to be polygenic; thus a simple causation of the hypertension appears unlikely. The inheritance is also complex in the other pure lines of hypertensive rats.

3. In the GH rats variation in intake of sodium from 0.05% to 1% of the solid diet does not affect the development of the hypertension.

4. The renin-angiotensin-aldosterone system does not appear to play a primary role in the initiation of the hypertension in the GH rats. Compared with normotensive rats of the parent colony, plasma and renal renin are decreased, total exchangeable and carcass sodium are decreased, as are also the plasma volume and total extracellular fluid volume. Plasma sodium is normal and plasma potassium increased.

5. There is no evidence of a primary abnormality of catecholamine storage or turnover. Prevention of the development of the sympathetic nervous system from birth does not entirely abolish the difference in blood pressure between GH rats and comparably treated normotensive rats.

6. The increased peripheral resistance in blood-perfused hind limbs and tails of GH rats is due both to increased neurogenic and myogenic components and to a structural element. Increased vascular reactivity to a variety of constrictor agents is readily demonstrated in saline-perfused preparations.

7. The different strains of hypertensive rats may in their diversity mirror the differences between the various forms of human essential hypertension.

-D-phosphogalactoside galactohydrolase of lactic streptococci

beta-D-Phosphogalactoside galactohydrolase (beta-Pgal) was examined in a number of lactic streptococci by use of the chromogenic substrate o-nitrophenyl-beta-D-galactopyranoside-6-phosphate. Specific activity of beta-Pgal ranged from 0.563 units/mg of protein in Streptococcus lactis UN, to 0.120 in S. diacetilactics 18-16. Essentially no beta-D-galactoside galactohydrolase (beta-gal) was found in these organisms when o-nitrophenyl-beta-D-galactopyranoside served as the chromogenic substrate. S. lactis 7962 was the one exception found. This organism contained rather high levels of beta-gal, and very little beta-Pgal could be detected. beta-Pgal activity was examined in streptococci that differed widely in both their proteolytic ability and rates of lactic acid production during growth in milk. Differences in proteolytic ability did not influence beta-Pgal synthesis; also, the rate of lactic acid production was independent of the level of beta-Pgal present in the cell, since the rate of lactic acid production could be increased approximately fourfold without changing the amount of beta-Pgal present in the cell. Various carbohydrates were tested as potential inducers of the enzyme. Although galactose, either as the free sugar or combined with glucose in lactose, was the only inducer, noninducing sugars such as mannose or glucose showed some ability to cause fluctuations in the basal level of beta-Pgal. Cells growing in mannose or glucose exhibited about 30% of the maximal enzyme levels found in cells growing in lactose or galactose. No gratuitous inducers were found.