Survival and growth of Aeromonas hydrophila on modified atmosphere packaged normal and high pH lamb

The growth of A. hydrophila on normal pH (5.5-5.8) and high pH ( > 6.0) lamb stored under modified atmospheres was examined. Lamb pieces and mince, inoculated with A. hydrophila were packaged in air, vacuum pack, 80% O2/20% CO2, 50% CO2/50% N2, or 100% CO2 and stored at 5 or 0 degrees C for up to 42 days. Samples were examined for the survival and/or growth of A. hydrophila by enrichment in alkaline peptone water and/or direct plating on starch ampicillin agar. The pH of each sample was estimated. On lamb pieces and mince of normal pH, A. hydrophila numbers decreased during storage at 5 and 0 degrees C under all the packaging conditions. The organism was not detected after 21 days storage. In contrast, A. hydrophila numbers were maintained or increased on high pH lamb under most storage regimes. Storage at 5 degrees C allowed significant increases in A. hydrophila numbers on high pH lamb under all the atmospheres, except 100% CO2. In lamb held at 5 degrees C under 100% CO2 for up to 42 days, A. hydrophila was recovered from most samples, although cell numbers decreased during storage. After storage at 0 degrees C, A. hydrophila was recovered from high pH packs stored under all atmospheres. Significant increases in cell numbers were only observed in minced lamb of high pH stored under air or vacuum. The pH values of lamb pieces and mince held at 5 or 0 degrees C under any of the packaging atmospheres did not change in a uniform manner during storage.

Soft-tissue accumulation of lead in the blue tilapia, Oreochromis aureus (Steindachner), and the modifying effects of cadmium and mercury

The interaction of mercury and cadmium with lead was investigated by exposing Oreochromis aureus to two heavy metals simultaneously. The chronic accumulation profile of lead was determined by analyzing the liver, brain, gill filaments, intestine, caudal muscle, spleen, trunk kidney, and gonads following exposure to lead alone and in mixtures with mercury and cadmium. Nominal exposure concentrations of lead were 0.05, 0.10, 0.50, and 1.00 mg/L. Mixtures of lead (0.50 or 0.05 mg/L) with cadmium (0.05 mg/L) and lead (0.50 or 0.05 mg/L) with mercury (0.05 mg/L) were also used. Following 140 d of exposure to lead, the highest concentrations of lead consistently accumulated in the trunk kidney. The concentration of lead in the kidney was decreased by coexposure to mercury or cadmium, but increased in the muscle and liver. Under all exposure regimes, the median concentration of lead in the muscle exceeded safety levels recommended for human consumption. In a food fish, such as O. aureus, a knowledge of toxic metal accumulation patterns is of great importance.

Hypersensitive response of malignant hyperthermia-susceptible skeletal muscle to inositol 1,4,5-triphosphate induced release of calcium

Malignant hyperthermia (MH) is associated with abnormal regulation of intracellular calcium in skeletal muscle fibers. Besides a mutation in the ryanodine receptor gene, an increase in inositol, 1,4,5-triphosphate (InsP3) levels could be a possible candidate for the abnormal regulation of intracellular calcium. However, the effect of InsP3 on [Ca2+]i in MH is not known. Microinjection of InsP3 increased intracellular Ca2+ in intact skeletal muscle from malignant hyperthermia susceptible swines (MHS) with a higher potency and efficacy than in muscles from nonsusceptible (MHN) swines. Omission of extracellular Ca2+ or incubation of muscle fibers with Ca2+ channel blockers did not modify the response to InsP3. However, dantrolene (50 microM) a known blocker of intracellular Ca2+ release, decreased resting intracellular Ca2+ concentration and prevented the InsP3-induced increase in intracellular Ca2+. This suggests (i) that MHS skeletal muscles exhibit a higher responsiveness to InsP3-induced release of Ca2+, which could implicate InsP3 in the pathophysiology of MH, and (ii) that the beneficial effect of dantrolene in MHS could be related to its ability to prevent the InsP3-induced release of Ca2+.

Carpentier-Edwards standard porcine bioprosthesis: clinical performance to seventeen years

BACKGROUND

The role of porcine bioprostheses in cardiac valve replacement has been under review for several years. The literature deals primarily with age as a determinant of durability, as well as the intermediate-term performance of various prostheses. The performance of the Carpentier-Edwards first-generation standard porcine bioprosthesis is presented over the long-term with further documentation on age determinants.

METHODS

The "Guidelines for Reporting Morbidity and Mortality After Cardiac Valvular Operations" were used for definitions of valve-related complications, categorization, and statistical methods. The valve-related complications were evaluated in a time-related manner by actuarial life-table techniques. The Lee-Desu statistic test was used for comparison of performance by valve positions and age groups. Hazard function rates were demonstrated for complications and composites.

RESULTS

Of the Carpentier-Edwards porcine bioprostheses implanted in 1,195 patients (1,214 operations, 1,315 valves) commencing in 1975 the early mortality was 7.6% (92). The early mortality without concomitant procedures was 6.1% and with 11.7%. The late mortality was 5.3% per patient-year; 4.6% patient-year without and 7.5% per patient-year with concomitant procedures. The valve-related causes of late mortality (131) were thromboembolism (41), antithromboembolic hemorrhage (14), prosthetic valve endocarditis (20), nonstructural dysfunction (12), and structural valve deterioration (44). The valve-related deaths (early, 7; late, 124) were 21.2% of the total 617 total deaths. Reoperation for valve-related complications was performed in 406 patients (4.1% per patient-year), of which 327 were for structural valve deterioration (3.3% per patient-year). Mortality for reoperation was 0.5% per patient-year (49 patients) or 12.1%. Of the 49 deaths, 33 were caused by structural valve deterioration. The linearized occurrence rate for thromboembolism was 1.6% per patient-year (major, 0.9% per patient-year, and minor, 0.7% per patient-year). The fatal thromboembolic rate was 0.4% per patient-year (41), undifferentiated by valve position. The freedom from thromboembolism was 76% at 17 years (p = not significant by valve position) (major, 87%; fatal, 93%). The freedom from prosthetic valve endocarditis was 92% at 17 years (p = not significant by valve position). The freedom from reoperation, at 15 years, was 38%: aortic (AVR), 55%; mitral (MVR), 20%; and multiple valve replacement (MR), 24% (p < 0.05 AVR > MVR, MR). The freedom from structural valve deterioration, at 15 years, was 41%; AVR, 58%; MVR, 21%; MR, 36% (p < 0.05 AVR > MVR, MR). The freedom from structural valve deterioration was greater for advancing age groups (p < 0.05); AVR > or = 70 years 96% at 12 years, and 65 to 69 years 94% at 12 years and 82% at 15 years; MVR > or = 70 years 85% at 12 years, and 65 to 69 years 54% at 12 years. The freedom from valve-related mortality was 73% at 17 years: AVR, 80%; ; MVR, 61%; and MR, 67% (p < 0.05 AVR > MVR, MR). The freedom valve-related residual morbidity was 94% (p = not significant by valve position).

CONCLUSIONS

The Carpentier-Edwards standard porcine bioprosthesis continues to provide satisfactory clinical performance to 17 years. Thromboembolism is a more serious problem than structural failure: 92 major thromboembolic events with 41 fatalities compared with 44 fatalities of which 33 occurred with reoperation. The prosthesis is especially recommended for patients more than 65 years of age for AVR and more than 70 years of age for MVR.

RNA ligands to human nerve growth factor

High affinity RNA ligands to human nerve growth factor (NGF) were selected from pools of random RNA using SELEX [Tuerk, C. and Gold, L. (1990) Science, 249, 505-510]. Nerve growth factor, which is a protein required for the development of neurons, is not known to bind nucleic acids as part of its natural function. We describe two of the selected RNA molecules in detail. One of them is highly structured, folding into a pseudoknot with an additional hairpin-loop; this structure provides salt-resistant binding to NGF. The other is unstructured and elevated salt concentrations inhibit its binding. These molecules compete with each other for NGF binding. Our RNAs may furnish useful diagnostic tools for the study of an important neurotrophic protein; additionally, they illustrate another example of the potential for nucleic acids to take part in novel binding interactions.

Long-term mercury accumulation in the presence of cadmium and lead in Oreochromis aureus (Steindachner)

The effects of cadmium and lead on chronic mercury accumulation were investigated in O. aureus. After 140 days' exposure the accumulation of mercury in the liver, brain, gill filaments, intestine, caudal muscle, spleen, trunk kidney and eye was analysed. The exposure concentrations were 0.05, 0.10 and 0.20 mg/L for mercury alone. O. aureus was also exposed to mixtures of 0.05 mg/L mercury with lead (0.05 mg/L and 0.50 mg/L or cadmium (0.05 mg/L) and 0.10 mg/L mercury with 0.10 mg/L cadmium. In food fish, a knowledge of toxic metal accumulation patterns is of great importance because of their contribution to the human diet and, as fishmeal, to the diet of agricultural animals. The trunk kidney consistently accumulated higher concentrations of mercury than any of the other tissues investigated.

Chronic accumulation of cadmium in the edible tissues of Oreochromis aureus (Steindachner): modification by mercury and lead

The influence of mercury and lead on cadmium accumulation was investigated by exposing the fish Oreochromis aureus, or Blue Tilapia, to two heavy metals simultaneously. The chronic accumulation profile of cadmium in the liver, brain, gill filaments, intestine, caudal muscle, spleen, trunk kidney, and gonads was determined for exposure to cadmium alone and with lead or mercury. O. aureus was exposed to cadmium alone at 0.05 and 0.10 mg/L, and mixtures of 0.05 mg/L cadmium with 0.05 mg/L mercury or lead (0.05 and 0.50 mg/L). Little research has previously been carried out on the long-term interaction between these heavy metals and their effects on tissue accumulation of heavy metals. In a food fish such as O. aureus, a knowledge of toxic metal accumulation patterns is of great importance. The highest levels of cadmium were consistently accumulated by the kidney, and the presence of other mercury or lead did not change this trend. The spleen, intestine, and liver also accumulated high levels of cadmium, while the caudal muscle and brain accumulated the lowest levels of cadmium. Separating the viscera from the muscle would therefore reduce the cadmium burden of fishmeal.

Isolation of high-affinity RNA ligands to HIV-1 integrase from a random pool

We were able to isolate high-affinity RNAs from a random pool that binds to integrase protein from the human immunodeficiency virus-type 1 using the procedure now known as SELEX. Generally, the RNAs fell into three different classes in binding buffer containing 250 mM NaCl: group I class of molecules binds integrase with a dissociation constant (Kd) on the order of 10 nM, group II molecules had a Kd of about 80 nM, and group III about 800 nM. The RNA with the highest affinity from the group I class of molecules, designated P5, was characterized using computer modeling, chemical and enzymatic probing, and deletion analysis. Our secondary structure model for this RNA suggests interactions between looped-out fixed nucleotides and nucleotides from the randomized region; a GNRA tetraloop is also in the structure. We showed that our integrase was able to process a U5 mimic in vitro. P5 competes effectively for binding with the double-stranded DNA mimic of U5 at 180 mM NaCl concentration.

Effects of signal and masker uncertainty on children's detection

This paper reports the results of two experiments that examined the effects of signal and masker uncertainty on preschool-age children's and adults' detection of tonal signals in noise maskers. In Experiment 1 (signal uncertainty) the signal was randomly at 501 or 2818 Hz. The majority of the adult listeners showed a slight decrement in performance consistent with an ability to monitor both frequencies simultaneously. The majority of the children, however, showed no decrement in performance, suggesting that the children may not have focused attention at the signal frequency even when it was fixed. In Experiment 2 (masker uncertainty), random-frequency, random-level, tonal distracters were added to each interval of the 2 alternative-forced-choice (2afc) procedure. The effect of masker uncertainty was much larger than that of signal uncertainty. For most of the adult listeners and some of the children, the distracters produced higher thresholds (on average by 10 dB) and shallower psychometric function slopes. For most of the children, thresholds increased by 20 dB or more and psychometric functions were often nearly flat.

Stabilisation of rampant caries: polyol gums and arrest of dentine caries in two long-term cohort studies in young subjects

The purpose of this paper is to report clinical observations on the stabilisation of dentine caries in two chewing gum studies carried out in young subjects. One study focused on the permanent dentition of 1,277 initially 10-year old subjects, while the other study was carried out on 510 initially 6-year old subjects and focused on the primary dentition. In both trials, several chewing gum formulas containing dietary polyols (xylitol and sorbitol, or their combinations) were used for up to 40 months (10-year olds) or up to 24 months (6-year olds). The daily consumption level of both polyols was up to 10.7 g per subject, used normally in 5-minute chewing episodes 3 to 5 times per day. Supervised chewing in schools lasted 5 min per episode, and for variable times during non-school days. Rehardening of dentine caries lesions was observed clinically by experienced, blinded examiners using sharp dental explorers and fibre optic light. After 40 months (permanent dentition) or after 18 months (primary dentition), rehardening (caries arrest) generally occurred more frequently in subjects who used polyol gums than in subjects who did not receive gum as part of the programmes, or who received sucrose gum. Arrest or non-progression of dentine caries was most frequently observed in subjects who used 100 per cent xylitol gums or mixtures of xylitol and sorbitol, but the differences between gums were not consistently significant. However, the usage of 100 per cent xylitol pellet-shaped gum was more frequently associated with arrest of dentine caries than other treatments. These results and previous studies suggest that high-xylitol chewing gum usage can retard or arrest even rampant dentine caries in conditions where effective restoration and prevention programmes have not been instituted, and can also provide additional protection against further caries development during full implementation of restorative procedures by holding the lesion in a non-progressive condition.

Intracellular trafficking in Mycobacterium tuberculosis and Mycobacterium avium-infected macrophages

Despite the potential role of the macrophage in the eradication of invading microbes, Mycobacterium species have evolved mechanisms to ensure their survival and replication inside the macrophage. Particles phagocytosed by macrophages normally will be delivered into acid lysosomal compartments for degradation. Mycobacterium must, in some way, avoid this fate by modulation of their phagosome. Immunoelectron microscopy of macrophages infected with Mycobacterium avium or Mycobacterium tuberculosis indicates that the vacuolar membrane surrounding the bacilli possesses the late endosomal/lysosomal marker, LAMP-1 (lysosomal-associated membrane protein-1), but lacks the vesicular proton-ATPase. Analysis of the intersection of the bacteria-containing vacuoles with the endocytic network of the macrophage supports previous studies indicating that these bacilli restrict the fusion capability of their intracellular compartments. The occurrence of vesicles containing lipoarabinomannan, discrete from those containing Mycobacterium, indicate that material does traffic out from the mycobacterial vacuole. To compensate for this loss of membrane, the vacuole must remain dynamic and fuse with LAMP-1-containing vesicles to maintain the density of this marker.

Intracellular trafficking in Mycobacterium tuberculosis and Mycobacterium avium-infected macrophages

Despite the potential role of the macrophage in the eradication of invading microbes, Mycobacterium species have evolved mechanisms to ensure their survival and replication inside the macrophage. Particles phagocytosed by macrophages normally will be delivered into acid lysosomal compartments for degradation. Mycobacterium must, in some way, avoid this fate by modulation of their phagosome. Immunoelectron microscopy of macrophages infected with Mycobacterium avium or Mycobacterium tuberculosis indicates that the vacuolar membrane surrounding the bacilli possesses the late endosomal/lysosomal marker, LAMP-1 (lysosomal-associated membrane protein-1), but lacks the vesicular proton-ATPase. Analysis of the intersection of the bacteria-containing vacuoles with the endocytic network of the macrophage supports previous studies indicating that these bacilli restrict the fusion capability of their intracellular compartments. The occurrence of vesicles containing lipoarabinomannan, discrete from those containing Mycobacterium, indicate that material does traffic out from the mycobacterial vacuole. To compensate for this loss of membrane, the vacuole must remain dynamic and fuse with LAMP-1-containing vesicles to maintain the density of this marker.

Cortical deafness: a longitudinal study

We have studied a patient with MRI-confirmed bilateral absence of considerable portions of her temporal lobes resulting in cortical deafness. Although physiologic measures demonstrate normal peripheral hearing sensitivity, this patient's speech has the inflection and prosodic characteristics associated with profound peripheral hearing loss, and she is unable to understand spoken communication. Behaviorally obtained pure-tone thresholds taken over nearly 20 years range from normal to moderate hearing loss with normal middle ear muscle reflexes and normal ABRs; however, we consistently found abnormal middle latency and cortical evoked potentials. Because of her total inability to communicate auditorily, this patient was ultimately taught American Sign Language and educated at the Louisiana School for the Deaf. This rare case highlights the importance of using multiple audiologic measures sensitive to abnormalities at various levels of the auditory system.

Psychometric functions for children's detection of tones in noise

This article reports the results of an experiment that used a two-alternative forced-choice task to measure the ability of 3- to 5-year-old children to detect 501 Hz, 1000 Hz, and 2818 Hz sinusoids in noise. Psychometric functions were fit to each individual's data, and thresholds (signal level required for 75% correct) were interpolated from the fitted functions. Results showed that, on average, the children's thresholds were higher and the slopes of their psychometric functions were shallower than those of the adults. However, the between-subjects variability in the children's data was large, and the performance of many individual children was not well described by group mean performance. One-third of the children produced thresholds that were elevated by an average of 10 dB but psychometric function slopes that were adult-like. Another one-third of the children produced thresholds that were elevated relative to those of the adults by an average of 20 dB and psychometric function slopes that were very shallow. The data from a smaller group of children showed large variability in psychometric function slope and threshold, and for a very few children performance was at chance regardless of the signal level. A replication of the study several months later showed that for most listeners the individual patterns of performance persisted over time.

Adi Quala: application of solar photovoltaic generation in rural medical centres

Adi Quala is an Eritrean agricultural town of 14,000 people, and is situated about 70 km south of the capital, Asmara and 30 km from the border with Tigray, Ethiopia. On good days electricity was received from Asmara between 0600 h and 2300 h with nothing available outside these hours. These conditions meant the electricity supply had been a constant problem for the Adi Quala hospital which caters for about 50,000 people with 21 staff. It was for this reason that it was chosen for the first solar system, which provides all essential requirements completely independently from the grid connection. This will in turn enable the hospital to increase the range and reliability of services on offer. Three weeks after the arrival of the equipment the elders were able to have a guided tour of their new local facilities. This included 2kW of photovoltaic panels (installed on the roof), batteries and control equipment powering a range of hospital equipment used in the Mother and Child Health Centre, delivery room, wards, dispensary, clinic and laboratory. Their enormous appreciation was very moving and well articulated in an afternoon of music, speeches and feasting. Eritrea's first solar powered hospital was welcomed into capable hands. The pilot project was successfully installed and commissioned in February 1992, and has performed well to date.

Stage, serum LDH, and performance status predict disease progression and survival in HIV-associated lymphomas

PURPOSE

This is a review of treatment of 44 patients with positive HIV serology (positive HIV) and lymphoma.

MATERIALS AND METHODS

Twenty patients had diffuse large-cell lymphoma (DLCL), and 18 had small noncleaved-cell lymphoma (SNCCL). Three had Hodgkin's disease (HD) and 3 had diffuse small- or mixed-cell lymphoma. These patients received intensive chemotherapy regimens for management of their disease; most were regimens in use at our institution for patients with lymphoma who did not have positive HIV.

RESULTS

The complete response to treatment (CR) was 77% for all patient, 80% for those with DLCL, and 72% for those with SNCCL. Stage, serum LDH, and performance status were predictors of complete remission and freedom from progression. Though there was a tendency for patients with a T4-cell count of < or = 200 to have a higher risk of opportunistic infections while receiving therapy, most infections were controllable with appropriate antibiotic management. More than one-half of the deaths in this study occurred after completion of therapy in complete remission, with a median survival of only 11 months, and were attributable to AIDS-related complications.

CONCLUSIONS

Our data suggest that (1) patients with lymphoma who have positive HIV have responses to chemotherapy similar to those expected for patients who are HIV-negative; (2) most infectious complications are manageable with appropriate therapy during treatment; and (3) after completion of chemotherapy, treatment should focus on control of progression of AIDS-related complications.

Medical and dental staffing prospects in the NHS in England and Wales 1993

This article provides a brief update on current national policies affecting medical education and training, and information on the present medical and dental workforce. Although of general interest, senior medical students and doctors in the training grades may find it particularly helpful when considering choices of future career. As there may be marked local variations in career prospects for any one specialty, further information and advice is available from Regional Postgraduate Medical and Dental Deans, specialty advisors (through Royal College and specialty associations) and clinical tutors. The information in this article relates to the present situation only and a review of previous articles in this series may be useful to observe certain trends.

SPECT Imaging in the Diagnosis of Meniscal Tears

Sixty patients scheduled for arthroscopy of a knee because of suspected meniscal tears had preoperative planar and single photon emission computed tomography (SPECT) radionuclide scans. A crescentic pattern of uptake on the SPECT transaxial view was used as a criterion for diagnosing a tear of a meniscus. The sensitivity of the investigation was 77%, specificity 74%, negative predictive value (NPV) 65%, positive predictive value (PPV) 83%, and accuracy 76%. Tears of the posterior horn of the cartilage were also associated with intense focal uptake on the transaxial view as well as increased equilibrium activity in the adjacent femoral condyle. When these appearances were included as additional criteria the sensitivity rose to 90%, NPV 81%, and accuracy 84%. This study confirms the usefulness of SPECT imaging in identifying meniscal tears.

Inhibition of proliferation, activation and function of human natural-killer-cells in-vitro by secreted products of lovo, a colorectal-cancer cell-line

It has previously been suggested that some tumours may elaborate substances which can suppress the functional activity of lymphokine activated killer (LAK) cells. We have investigated the effects of secreted products from the colorectal cancer cell line LoVo on the pattern of expression of T lymphocyte subsets and natural killer cell phenotype and activation antigens during in vitro treatment of mixed populations of human peripheral blood mononuclear cells with recombinant human IL-2 (rhIL-2). Tumour cell line products inhibited the proliferation of cells expressing the NK cell antigen CD56 and of cells expressing the CD8 T cell subset antigen. Increased expression of the IL-2 receptor alpha chain component CD25, and the activation associated antigens CD71 and HLA-DR induced by rhIL-2 was inhibited by the presence of tumour cell products. Enhanced cytotoxic activity against standard target. cell lines Daudi and K562 induced by treatment with rhIL-2 was diminished by tumour cell supernatants. These mechanisms may contribute to the resistance of some tumours to immune response modulation treatment regimens which depend upon induction of lymphokine activation responses by rhIL-2.