The Impacts of Feeding Natursafe (an Immune Support Product) on Beef Quality

ObjectivesNaturSafe® (Diamond V, USA) is a Saccharomyces cerevisiae fermentation product developed as an animal feed supplement for the further manufacture of nutritionally balanced feeds for beef cattle. This immune support product (Association of American Feed Control Officials number 96.8, 73.046 and International Feed Name number 7–05–520, 8–08–034) has been specifically formulated to optimize beef cattle health and performance, antibiotic stewardship, and food safety. Research has shown that NaturSafe supports optimal rumen and liver health, overall health and immune function, consistency of feed intake, daily gain, feed conversion, and antibiotic effectiveness. As no research previously has assessed the impacts of this feed ingredient on the quality of meat, the objective of this research was to characterize the effects of feeding NaturSafe on meat quality characteristics in beef.Materials and MethodsCrossbred steers (N = 60, n = 12 per treatment; mean hot carcass weight = 421 kg), through an antibiotic free production system, were individually fed diets containing 12, 15, or 18 g/d of NaturSafe or a control diet without (–AB) antibiotics or a control with antibiotics (+AB; 330 mg monensin + 110 mg tylosin·steer–1·d–1) for 112 d. Strip loins were collected and aged for 13 or 29 d postmortem prior to fabrication. Steaks (m. Longissimus) were then evaluated for Warner-Bratzler shear force, pH, sarcoplasmic calcium concentration, troponin-T degradation, fatty acid profile, proximate composition, sarcomere length, total collagen and insoluble collagen. After each aging period, steaks were evaluated for lipid oxidation, and color characteristics (L*, a*, b*, discoloration percentage, and percentage surface oxymyoglobin, metmyoglobin and deoxymyoglobin), during and/or after a 7 d simulated retail display period. A subset of samples at various aging and retail display periods were analyzed for lactic acid bacteria (LAB), psychotrophic plate counts (PPC), and aerobic plate counts (APC). Animal was considered the experimental unit and hot carcass weight and marbling score were used as covariates in the analysis.ResultsTreatment had no effect on pH, sarcomere length, troponin-T degradation, fatty acid profile, proximate composition, total collagen, insoluble collagen, LAB, PPC, APC, lipid oxidation, oxymyoglobin percentage, or metmyoglobin percentage. Meat from cattle fed 18 g/d of NaturSafe was (1) equal to–AB controls and had higher shear force values compared to all other treatments (P < 0.01), (2) had higher (P < 0.05) sarcoplasmic calcium levels than +AB controls and cattle fed 12 g of NaturSafe/d, (3) was redder (higher a* values, P < 0.05) than all other treatments, and (4) was yellower (higher b* values, P < 0.01) than the 12 or 15 g dose and the–AB control. There were no differences among treatments fed NaturSafe for lightness (L*) at either aging time. There were no differences for meat from animals fed 12 or 15 g NatureSafe/d, except deoxymyoglobin percent and discoloration, which were both minimal. Discoloration values were low for all treatments (< 10%).ConclusionThese data indicate that feeding NaturSafe had few discernible effects on meat quality characteristics.

Dry Aging of High Ultimate pH Beef

ObjectivesDry aging is a process in which water is removed from the meat by evaporation. As meat loses water, the flavor compounds are concentrated, resulting in stronger flavor. Meat pH may be important when dry aging as it relates to the ability of muscle to bind water. Therefore, this study aimed to evaluate pH effects on water loss when dry aging and the effects on meat quality characteristics. Dry aging of dark cutting (DC) beef may improve flavor and increase yield.Materials and MethodsSix USDA low Choice and six dark cutting (DC) carcasses with the same degree of marbling were selected and boneless strip loins from both sides were obtained. Longissimus muscle pH was measured, and carcasses were classified as DC (pH = 6.69), or control (pH = 5.47). Then, strip loins from each animal were assigned to 2 aging methods (wet or dry). The 4 treatments included 2 dry aging (DRY and DRY-DC) and 2 wet-aging treatments (WET and WET-DC). Dry aging occurred in individual dry-aging chambers at 50% relative humidity and 2200 RPM fan speed. The chambers (86 cm Length × 48 cm Width × 35 cm Height) have built-in weighing scales that can continuously monitor weight loss (± 5 g). Wet and dry-aged loins were aged in the same cooler for 45 d at 1°C.After aging, loins were fabricated into steaks and evaluated for trim loss, yield, tenderness (WBSF), color, discoloration, lipid oxidation, and sensory analysis (flavor) via triangle test (n = 32). Steaks assigned for color and lipid oxidation were placed under retail display (RD) at 2°C for 7 d. Rate of moisture loss and color data were analyzed as a split plot design with repeated measures. The TBARS data were analyzed as a split-plot design. All the other data were analyzed as a completely randomized design. Chamber (loin) was considered the experimental unit. Data were analyzed using the PROC GLIMMIX procedure of SAS with α = 0.05.ResultsWet-aged treatments had lower moisture loss, trim loss and higher yield than dry-aged treatments (P < 0.05). However, no differences in rate of moisture loss (P = 0.51), total moisture loss (P = 0.96), trim loss (P = 0.69), or yield (P = 0.75) between DRY-DC and DRY were found. There were no differences among treatments for WBSF (P = 0.67). In general, DRY-DC and WET-DC steaks had the lowest lightness (L*) values, redness (a*) values (Fig. 3a), and yellowness (b*) values over the first 5 d of RD (P < 0.05). Discoloration scores for DC steaks remained low throughout the RD period (Fig. 3b). DRY steaks had greater TBARS values than any other treatment at 0 d RD. At 4 and 7 d of RD, DRY-DC and WET-DC steaks had the lowest TBARS values, DRY steaks had the highest, while WET was intermediate (P < 0.001). Results from the triangle test indicated a detectable difference between DRY-DC versus DRY (P = 0.01), DRY-DC versus WET-DC (P = 0.01), DRY-DC versus WET (P = 0.01), and WET-DC versus WET (P < 0.01). Panelists frequently made unsolicited comments which suggested inferior eating satisfaction associated with DC flavor (wet or dry), although they were not asked questions regarding preference.ConclusionUltimate pH did not affect the rate and total moisture loss in dry aged beef. Results suggest that neither yield nor flavor were positively affected by dry aging of DC beef.Figure 3.a) Effect of ultimate pH (Dark cutters [DC] vs. Normal) and aging method (Wet vs. Dry) on objective redness (a*) values of strip loins steaks aged for 45 d through 7 d of retail display. b) Effect of ultimate pH (Dark cutters [DC] vs. Normal) and aging method (Wet vs. Dry) on discoloration (%) of strip loins steaks aged for 45 d through 7 d of retail display. a-c Means within a day with different superscripts are different (P < 0.005).

Color and Lipid Stability of Dry Aged Beef During Retail Display

ObjectivesThere has been an increased interest in merchandising dry-aged steaks at the retail level. Further understanding of the influence of the dry aging process on meat color and lipid stability is needed to ensure dry-aged beef products can be merchandised without adverse impacts on retail display life. Therefore, this study aimed to determine color and lipid stability of steaks from dry-aged beef loins over 7 d (d) of retail display.Materials and MethodsSixteen USDA low Choice boneless strip loins were assigned to one of four aging treatments: vacuum (Wet), dry-aging at 50% relative humidity (RH) (RH50), dry-aging at 70% RH (RH70), or dry-aging at 85% RH (RH85). Dry-aged loins were placed in each assigned dry aging chamber, while wet aged counterparts were aged in vacuum bags in the same cooler. Loins were aged for 42 d at 1°C. After aging, loins were trimmed of dehydrated lean/fat and fabricated into steaks. Steaks were trimmed of subcutaneous fat, and placed on foam trays, overwrapped with oxygen permeable film and placed under retail display (RD) conditions for 7 d at 2°C. Objective color measurements were taken once daily from d 0 to 7 of RD. Trained visual color panelists (n = 6) evaluated surface discoloration from d 0 to 7 of RD once daily. Lipid oxidation was measured via thiobarbituric acid reactive substance assay (TBARS) at 0, 4, and 7 d of RD. Color data were analyzed as a split-plot repeated measures design with treatment as the whole-plot and RD time as the repeated measures. TBARS data were analyzed as a split-plot design with aging treatment as the whole-plot, and RD time as the split-plot. In this study, chamber (loin) was considered the experimental unit. Data were analyzed using the PROC GLIMMIX procedure of SAS with α = 0.05.ResultsFor all three-color scales, a RD effect was found (P < 0.001). In general, L*, a* and b* values decreased as RD time increased, regardless of the aging treatment. Wet-aged steaks had higher L* (P < 0.05), a* (P < 0.05), and b* values (P < 0.001) than any other dry-aged treatment. No differences in L*, a*, and b* values among dry aging treatments were found (P < 0.05). A 2-way interaction between treatment and RD for discoloration was observed (P < 0.05). No differences were found among treatments over the first 2 d of RD (P > 0.05). Samples began to diverge on Day 3 of RD. Dry-aged steaks had greater discoloration scores (P < 0.05) than wet-aged steaks at 4, 5, 6, and 7 d of RD. However, no differences in discoloration scores among RH treatments were found. There was a RD effect on TBARS values (P < 0.001). Greater TBARS values were found as RD progressed from d 0 to d 4 and d 7, regardless of the aging treatment. A treatment effect was observed for lipid oxidation (P < 0.05). Dry-aged steaks had higher TBARS values than wet-aged steaks. No differences in TBARS values among dry aging treatments were found.ConclusionDry aging of beef resulted in decreased lightness and redness values and increased lipid oxidation compared to wet aging. Results suggest that with prolonged RD dry aging of beef has the potential to reduce color and lipid stability compared to wet-aging and thus reduce display life. Dry-aged steaks met the 20% discoloration threshold and overcame the acceptability threshold of 2.28 mg of malonaldehyde/kg at d 4 of RD, indicating that dry-aged steaks can be merchandised in the retail level for 3 d without detrimental effects on color and lipid oxidation.

pH Variability and its Relationship with Sarcomere Length and Free Calcium in Beef from Commercial Cattle in Puerto Rico

ObjectivesResearch conducted at the University of Puerto Rico noted that beef with elevated pH values (> 5.86) resulted in more tender meat (P ≤ 0.05). It has been established that proteolytic degradation mechanisms can be influenced by pH and calcium concentration in muscle. Beef with pH values ≥ 5.86 is classified as Dark Firm and Dry (DFD) but there are negative implications associated with greater pH values. However, observations indicating increased tenderness with increased pH raise the question: can variations in pH be associated with differences in sarcomere length (SL) and free calcium concentration (FCC)? Therefore, the objectives of this project were to: (1) document pH distribution; (2) determine the incidence of DFD; and (3) evaluate the relationship between pH, SL, and FCC in commercial cattle harvested in Puerto Rico.Materials and MethodsLongissimus lumborum samples (n = 51) were obtained and background information was noted including number of permanent incisors (PI), type (Dairy or Beef), and gender. The pH values were used to categorize beef into the following groups: Low (≤ 5.40), Normal (5.41 to 5.59), High (5.60 to 5.85) and DFD (≥ 5.86). Meat was flash frozen, powdered, and placed on a microscope slide and a Helium-Neon laser was used to determine SL. A subset of samples was sent off and prepared at the University of Nebraska-Lincoln for FCC quantification (Ward Laboratories; Kearney, NE) with an inductively coupled plasma emission spectrometer (iCAP 6500 Radial; Thermo Electron, Cambridge, UK). All statistical analyses were conducted in SAS (9.4). The Proc FREQ was used to determine pH category distributions and incidence of DFD. The Proc GLIMMIX and Tukey adjustment (α = 0.05) were used to determine the effects of number of PI, type, and gender on pH category, SL and FCC. The Proc CORR was used to evaluate the relationship between pH category, SL and FCC.ResultsThe pH category distribution for the current samples was as follows: 3.92% Low, 41.18% Normal, 35.29% High and 19.61% DFD. The SL ranged from 1.69 to 1.46 mm with an average of 1.53 mm. The FCC ranged from 132.19 to 31.39 mM with an average of 64.23 mM. Longer sarcomeres were detected in cattle with eight and zero PI (1.57 and 1.56 mm, respectively); cattle with two and four PI had intermediate SL (1.53 and 1.52 mm, respectively), and cattle with six PI had the shortest sarcomeres (1.51 mm; P = 0.03). Dairy cattle had longer sarcomeres relative to beef cattle (1.56 vs. 1.52 mm; P = 0.02). Dairy cattle tended to have increased FCC relative to beef cattle (70.72 vs. 58.38 mM; P = 0.08). Also, FCC tended to be greater within the Normal and Low pH categories relative to the High and DFD categories (72.36 vs. 57.31 mM; P = 0.06). The SL and FCC had no relationship (P > 0.05) within the Low, Normal and High pH categories. However, DFD beef had longer SL (0.78; P = 0.01), while having decreased FCC (–0.66; P = 0.04).ConclusionOver half (54.90%) of the beef samples analyzed fell into the High and DFD pH categories, with nearly 20% being classified as DFD. Although, a clear relationship was not established between SL and FCC within the Low, Normal or High pH categories, the results indicate that the increased pH in samples surpassing the DFD threshold correspond to longer sarcomeres and decreased free calcium.

Impact of Myoglobin Oxygenation State at Freezing on Color Stability of Frozen Beef

ObjectivesMeat color is the number one factor influencing consumer purchase decisions. The emerging market of frozen meat emphasizes the need to understand beef surface discoloration and the ideal parameters of freezing beef to retain a superior color. Therefore, the objectives of this study were to determine the impacts of oxygenation level and frozen storage duration on frozen beef color.Materials and MethodsUSDA Choice strip loins (n = 36) were aged for 4 d or 20 d. Steaks were randomly assigned to a myoglobin state [deoxymyoglobin (DeOxy; immediately packaged), low oxygenation (LoOxy; oxygenated in air for 30 min), and high oxygenation (HiOxy; packaged for 24 h in 80% O2)]. Steaks were then vacuum packaged in oxygen permeable or impermeable film and immediately frozen (–20°C). Following either 0, 2, 4, or 6 mo of frozen storage, steaks were removed from the packaging and immediately analyzed for instrumental color (L*, a*, b*), delta E (magnitude of difference in the L*, a*, b* color space), subjective discoloration, lipid oxidation (via thiobarbituric acid reactive substances- TBARS), oxygen penetration, percent oxymyoglobin, metmyoglobin, and deoxymyoglobin (via spectrometer), and redness (calculated as 630nm/530nm). Data were analyzed using PROC Glimmix procedure in SAS as a split-split-plot with an incomplete block and a 2 × 3 factorial.ResultsHiOxy steaks had greater oxygen penetration and the highest a* values compared to DeOxy and LoOxy steaks regardless of packaging (P < 0.0005). Conversely, DeOxy steaks exhibited the lowest oxygen penetration and a* values regardless of film (P < 0.0005). HiOxy steaks at 4 d had higher a* values than DeOxy and LoOxy at all storage times (P = 0.0118). HiOxy steaks had the highest delta E values compared to DeOxy and LoOxy in permeable packaging and with increasing storage time an increase in delta E for the HiOxy steaks was observed (P = 0.0010).Redness and percent oxymyoglobin were highest for HiOxy steaks within each storage period (P < 0.0002). HiOxy and LoOxy steaks were similar in percent oxymyoglobin when in permeable packaging film. HiOxy steaks had the highest percent oxymyoglobin and DeOxy had the lowest percent oxymyoglobin within each aging and storage period (P < 0.01). Conversely, DeOxy steaks had the highest percent metmyoglobin and HiOxy had the lowest percent metmyoglobin when packaged in impermeable film (P < 0.0001). Lowest percent metmyoglobin values were from the 4 d HiOxy steaks at 2, 4, and 6 mo of storage (P = 0.0188).The HiOxy 20 d steaks had the highest discoloration compared to 4 d aging and more discoloration than all other myoglobin treatments at 6 mo of storage (P < 0.0001). Lipid oxidation increased with storage time (P = 0.0169). HiOxy 20 d aged steaks exhibited the highest TBARS values at 2, 4, and 6 mo (P = 0.0224). HiOxy and LoOxy were similar in discoloration and lipid oxidation except with the HiOxy 20 d (which were less desirable).ConclusionHiOxy steaks exhibit a brighter and deeper cherry red color compared to the DeOxy steaks. HiOxy steaks were superior or similar when compared to LoOxy steaks but displayed more detrimental effects when frozen storage was extended. Based on the results, HiOxy steaks aged for 4 d give a superior red color for extended storage with few unfavorable effects. However, it is not advised to freeze deoxygenated steaks and expect a cherry red color through frozen storage.

Relationship Between Relative Humidity and Moisture Loss in Dry Aged Beef

ObjectivesThe objective of this research was to assess the impact of low relative humidity (RH) during dry aging on moisture and trim loss, tenderness, and flavor. The working hypothesis was that rapid drying would create a hard crust on the meat surface that could reduce moisture release over time, thereby reducing weight loss, enhancing tenderness (by retaining more water), and altering flavor when compared to dry aging at higher RH.Materials and MethodsSixteen USDA low Choice boneless strip loins were assigned to one of the four aging treatments: vacuum (Wet), dry-aging at 50% RH (RH50), dry-aging at 70% RH (RH70), or dry-aging at 85% RH (RH85). Loins were placed in individual dry aging chambers and aged for 42 d at 1°C and 2200 RPM fan speed. A computerized dry aging system was designed and built that is capable of measuring and precisely controlling RH (± 1%), temperature (± 0.5°C), and air velocity (± 0.1m/s). The chambers have built-in weighing scales that can continuously monitor weight loss (± 5 g). All measured data can be saved on the connected computer in intervals of 1 s. After aging, loins were trimmed of dehydrated fat/lean and evaluated for trim loss. Loins were fabricated anterior to posterior, cut into steaks and evaluated for water activity (aw), Warner-Bratzler shear force (WBSF), and by sensory analysis to detect flavor differences via triangle test (n = 32). Rate of moisture loss was analyzed as a split plot design with treatment as the main plot and days of aging as the repeated measures. All the other data were analyzed as a completely randomized design. Chamber (loin) was considered the experimental unit. Data were analyzed using the PROC GLIMMIX procedure of SAS with α = 0.05.ResultsThere was a treatment by day interaction for rate of moisture loss (P < 0.001). A faster rate of moisture loss was found for RH50 when compared to RH85 on the first day of aging (P < 0.001), while RH70 was intermediate. Loins dry-aged at RH50 and RH70 had higher rates of moisture loss than RH85 on Days 2 and 3 of aging (P < 0.05). By Day 4, no differences in rate of moisture loss among RH treatments were found (P > 0.05). Wet-aged samples had lower moisture loss (P < 0.001), trim loss (P < 0.001) and higher yield (P < 0.001) than all dry-aged treatments. However, there were no differences among RH treatments for total moisture loss (P > 0.05), trim loss (P > 0.05) and yield (P > 0.05). Steaks from dry-aging treatments had lower aw values (P < 0.001) than steaks from the Wet group. No differences in aw values among RH treatments were found (P > 0.05). There was a location effect for aw values. Samples from the ventral region of the steak had lower aw values than samples from the central and dorsal region (P < 0.001). There were no differences among treatments for WBSF (P > 0.05). Results from the triangle test indicated that there was a detectable difference between Wet and RH70 (P < 0.05). However, there was no detectable difference between RH50 and RH85 (P > 0.05).ConclusionResults suggest that no such case hardening effect occurs when dry aging beef, even when the RH was kept very low (50%) and the total weight loss was 23%. Instead, the lower RH results in more rapid moisture loss at the beginning of the aging process without significantly affecting the total amount of moisture loss. Trim loss, yield, tenderness and flavor were not affected by relative humidity during dry aging.

Laser microdissection coupled with RNA-seq reveal cell-type and disease-specific markers in the salivary gland of Sjögren's syndrome patients

OBJECTIVES

Little is known about the molecular details regarding the contribution of different cell types of the salivary gland to the altered gene expression profile seen in Sjögren's syndrome (SS).

METHODS

Using laser microdissection, tissue samples enriched in acini, ducts and inflammatory foci in subjects with and without SS were isolated for RNA-seq analysis. Gene expression profiles were analysed and selected enriched genes were further examined using real time PCR and by immunofluorescence.

RESULTS

RNA-seq analysis of salivary biopsies from subjects with and without SS revealed marked differences in gene expression occurring in the ductal and infiltrating cells compared to acinar cells. Up-regulated genes in the SS ductal cells included C4A complement and the SLC26A9 ion channel. The inflammatory infiltrate showed the most dramatic differences in gene expression and contained up-regulated genes associated with T-cells, natural killer, dendritic and basophils/mast cells. qPCR with total salivary gland mRNA confirmed the differential mRNA expression of several genes (MMP9, FOL1HB, CCL21, CCR7), thereby validating the approach. Additional immunofluorescence studies demonstrated high expression and co-localisation of CCL21 chemokine and CCR7 chemokine receptor within the SS infiltrates.

CONCLUSIONS

Major gene expression changes in the salivary gland of SS were detected in the ductal and inflammatory cells and not in the acinar cells. Two chemokines involved in immune cell trafficking to secondary lymphoid tissue, CCR7 and CCL21, showed markedly increased expression and may contribute to the recruitment of diverse immune cells to the salivary glands, causing inflammation and loss of secretory function.

Rabies virus glycoprotein as a carrier for anthrax protective antigen

Live viral vectors expressing foreign antigens have shown great promise as vaccines against viral diseases. However, safety concerns remain a major problem regarding the use of even highly attenuated viral vectors. Using the rabies virus (RV) envelope protein as a carrier molecule, we show here that inactivated RV particles can be utilized to present Bacillus anthracis protective antigen (PA) domain-4 in the viral membrane. In addition to the RV glycoprotein (G) transmembrane and cytoplasmic domains, a portion of the RV G ectodomain was required to express the chimeric RV G anthrax PA on the cell surface. The novel antigen was also efficiently incorporated into RV virions. Mice immunized with the inactivated recombinant RV virions exhibited seroconversion against both RV G and anthrax PA, and a second inoculation greatly increased these responses. These data demonstrate that a viral envelope protein can carry a bacterial protein and that a viral carrier can display whole polypeptides compared to the limited epitope presentation of previous viral systems.

Effect of dietary phosphorus on finishing steer performance, bone status, and carcass maturity

Yearling crossbred steers (n = 60; 386 kg) were individually fed in a completely randomized experimental design to determine their P requirement. Treatments were in a factorial arrangement with two levels of Ca (.35 or .70% of DM) and five concentrations of P (.14, .19, .24, .29, or .34% of DM). The finishing diet consisted of 34.5% dry-rolled corn, 22.5% brewers grits, 22.5% corn bran, 7.5% ground corncobs, 5% molasses, 3% fat, and 5% supplement. Supplemental P was provided as monosodium phosphate and Ca as limestone. Ash content was determined on the first phalanx bone from the lower front legs following slaughter, and rib bone breaking strength was determined with an Instron Universal Testing Machine. Carcass maturity and shear force were also evaluated on wholesale rib cuts. Because no interactions between Ca and P levels were detected, only main effects are presented. Daily gain, DMI, and feed efficiency were not affected by dietary P concentration or P intake. Bone ash (g or g/100 kg BW) and rib bone breaking strength were also unaffected by dietary P. Feeding .7% Ca decreased (P<.06) ADG and efficiency compared with feeding .35% Ca. Neither dietary Ca nor P had a significant effect on tenderness (shear force), skeletal maturity, or overall maturity. These results indicate that the P requirement for finishing yearlings is .14% of diet DM or less and that supplementing P above levels supplied by basal ingredients in many grain-based finishing diets is not necessary.

T cells infiltrating the skin of Tsk2 scleroderma-like mice exhibit T cell receptor bias

The T cell repertoire expressed by Tsk2 mice, a novel experimental model of systemic sclerosis, was examined to determine whether cells infiltrating the areas of involved skin exhibit a T cell receptor (TCR) bias. Reverse transcription-polymerase chain reactions (RT-PCR) were conducted using RNA extracted from lymph nodes and skin from TSk2 mice and from normal mice, with an oligonucleotide primer library specific for the variable region of the TCR (beta) chain. RT-PCR signals were observed in all lymph node cell (LNC) samples from both Tsk2 mice and control mice, with eighteen of the twenty-one Vbeta types present. In contrast, cDNA extracted from areas of involved skin from Tsk2 mice exhibited a restricted pattern, with positive Vbeta signals corresponding to eight T cell subtypes (Vbeta1, 6, 8.1, 8.2, 10, 11, 16, and 18). Band strength analysis revealed that three Vbeta subtypes dominated within this restricted pattern (Vbeta8.1, 11, and 18). Moreover, this pattern of Vbeta bias was consistent among the four skin samples from different Tsk2 mice. These data suggest that a restricted T cell population participates in the inflammatory cell infiltrate of Tsk2 skin.

Imaging Acute Knee Injuries

In brief When a clinician initially examines an athlete who has a knee injury, conventional radiography is the diagnostic imaging method of choice because it can identify most fractures and dislocations. If the athlete has a complex fracture, computed or conventional tomography can provide optimal characterization. If soft-tissue injury is suspected, either arthrography or MRI should be performed, though MRI is becoming the preferred method in such cases.

Cytokine secretion by C3H-lpr and -gld T cells. Hypersecretion of IFN-gamma and tumor necrosis factor-alpha by stimulated CD4+ T cells

Mice homozygous for lpr and gld develop profound lymphadenopathy characterized by the expansion of two unusual T cell subsets, a predominant Ly-5(B220)+ CD4- CD8- double negative (DN) population and a minor CD4 dull+ Ly-5(B220)+ population. The mechanisms promoting lymphoproliferation are unknown, but one possibility is a abnormality in the production of cytokines that regulate T cell growth. In the present report, unfractionated LN cells and sorted T cell subsets from C3H-lpr, -gld, and -+/+ mice were compared for spontaneous and induced secretion of a spectrum of lymphokines. In addition, CD4+, CD4 dull+ Ly-5(B220)+, and DN T cells were examined for expression of CD3 epsilon, TCR-alpha/beta heterodimers, Ly-6C, and CD44 and for proliferative responses to immobilized anti-TCR mAb and cofactors. These studies revealed that sorted DN T cells did not secrete IL-3, IL-4, IL-5, IL-6, GM-CSF, TNF-alpha, or IFN-gamma spontaneously or after TCR-alpha/beta cross-linking. In contrast, stimulated unfractionated lpr and gld LN cells proliferated strongly and secreted high levels of IFN-gamma and TNF-alpha and low levels of IL-3, IL-4, and IL-6. Despite a 5- to 10-fold deficit in the frequency of CD4+ and CD8+ T cells, cytokine secretion by lpr and gld LN generally exceeded that of +/+ LN. Comparisons of cytokine secretion by stimulated CD4+ T cells revealed that +/+, lpr, and gld CD4+ Ly-5(B220)- T cells proliferated strongly, but only lpr and gld cells produced significant levels of IFN-gamma. The lpr and gld CD4+ T cells also produced higher levels of TNF-alpha and IL-2 than +/+ cells. In contrast to normal CD4+ T cells, lpr and gld CD4+ Ly-5(B220)+ T cells proliferated weakly and did not secrete TNF-alpha, IL-2, or, in most experiments, IFN-gamma after stimulation. Phenotypic studies of T cell subsets revealed that unstimulated lpr and gld CD4+ Ly-5(B220)- T cells express significantly higher levels of CD44 than +/+ CD4+ T cells. In addition, CD4 dull+ Ly-5(B220)+ cells closely resembled DN T cells in size and expression of TCR-alpha/beta, CD3epsilon, CD44, and Ly-6C. Since elevated CD44 expression is generally associated with T cell activation and only previously activated normal CD4+ T cells produce high levels of IFN-gamma in vitro, our data suggest that lpr and gld CD4+ Ly-5(B220)- T cells contain a higher than normal proportion of primed or memory T cells and thus may be polyclonally activated in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)

Cytokine secretion by C3H-lpr and -gld T cells. Hypersecretion of IFN-gamma and tumor necrosis factor-alpha by stimulated CD4+ T cells

Mice homozygous for lpr and gld develop profound lymphadenopathy characterized by the expansion of two unusual T cell subsets, a predominant Ly-5(B220)+ CD4- CD8- double negative (DN) population and a minor CD4 dull+ Ly-5(B220)+ population. The mechanisms promoting lymphoproliferation are unknown, but one possibility is a abnormality in the production of cytokines that regulate T cell growth. In the present report, unfractionated LN cells and sorted T cell subsets from C3H-lpr, -gld, and -+/+ mice were compared for spontaneous and induced secretion of a spectrum of lymphokines. In addition, CD4+, CD4 dull+ Ly-5(B220)+, and DN T cells were examined for expression of CD3 epsilon, TCR-alpha/beta heterodimers, Ly-6C, and CD44 and for proliferative responses to immobilized anti-TCR mAb and cofactors. These studies revealed that sorted DN T cells did not secrete IL-3, IL-4, IL-5, IL-6, GM-CSF, TNF-alpha, or IFN-gamma spontaneously or after TCR-alpha/beta cross-linking. In contrast, stimulated unfractionated lpr and gld LN cells proliferated strongly and secreted high levels of IFN-gamma and TNF-alpha and low levels of IL-3, IL-4, and IL-6. Despite a 5- to 10-fold deficit in the frequency of CD4+ and CD8+ T cells, cytokine secretion by lpr and gld LN generally exceeded that of +/+ LN. Comparisons of cytokine secretion by stimulated CD4+ T cells revealed that +/+, lpr, and gld CD4+ Ly-5(B220)- T cells proliferated strongly, but only lpr and gld cells produced significant levels of IFN-gamma. The lpr and gld CD4+ T cells also produced higher levels of TNF-alpha and IL-2 than +/+ cells. In contrast to normal CD4+ T cells, lpr and gld CD4+ Ly-5(B220)+ T cells proliferated weakly and did not secrete TNF-alpha, IL-2, or, in most experiments, IFN-gamma after stimulation. Phenotypic studies of T cell subsets revealed that unstimulated lpr and gld CD4+ Ly-5(B220)- T cells express significantly higher levels of CD44 than +/+ CD4+ T cells. In addition, CD4 dull+ Ly-5(B220)+ cells closely resembled DN T cells in size and expression of TCR-alpha/beta, CD3epsilon, CD44, and Ly-6C. Since elevated CD44 expression is generally associated with T cell activation and only previously activated normal CD4+ T cells produce high levels of IFN-gamma in vitro, our data suggest that lpr and gld CD4+ Ly-5(B220)- T cells contain a higher than normal proportion of primed or memory T cells and thus may be polyclonally activated in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)

Characterization of the spontaneous autoimmune (anti-erythrocyte) response in NZB mice using a pathogenic monoclonal autoantibody and its anti-idiotype

A monoclonal anti-mouse RBC antibody (G-8) has been prepared that appears to represent a pathogenic autoantibody related to those that arise spontaneously in aging NZB mice and which cause autoimmune haemolytic disease (AIHD). When G-8-producing hybridoma cells were grown as tumours in BALB/c mice, the mice developed AIHD characterized by a decrease in the number of erythrocytes (haematocrit) and the development of Coombs-positivity. An anti-idiotypic antibody (E8) was prepared against G-8 and was found to recognize an idiotypic determinant present on most autoantibody-forming cells derived from old (Coombs-positive) NZB mice. The results suggest that the IgM autoantibody response of NZB mice to self-erythrocytes is restricted to a limited number of clones, most of which express the G-8 idiotype.

Specific anti-erythrocyte focus formation as a measure of autoantibody secreting cells in NZB mice

Using a modification of the antibody forming cell (AFC) focus assay, it is possible to quantitate the spontaneous anti-erythrocyte autoantibody response of New Zealand Black (NZB) mice at the level of the autoantibody secreting cell. This complement independent assay is specific for an antigen(s) present on unmodified mouse erythrocytes. A comparison with the direct Coombs' test showed that the focus assay detected autoantibody responses earlier and demonstrated a wide range of AFC levels in responding mice. The focus assay provides a method for evaluating autoimmunity at the cellular level and for investigating the activities of cells responding to autoantigens.

Formation of antigen specific foci as a complement independent assay for individual antibody-secreting cells

Antibody-forming cells (AFC) could be demonstrated by the binding of antigen to secreted antibody localized around the AFC. Using sheep red blood cells (SRBC) as antigen, this antigen binding was detected as foci of erythrocytes surrounding individual lymphocytes. Focus formation was antigen specific and involved the active secretion of antibody. AFC specific for antigens resistant to lysis, such as human red blood cells were also demonstrable with this assay. The focus assay provides a complement independent method for enumerating antibody-forming cells.