Evaluation of new anti-infective drugs for the treatment and prevention of infections caused by the Mycobacterium avium complex. Infectious Diseases Society of America and the Food and Drug Administration

The bacteria of the Mycobacterium avium complex are ubiquitous; thus it is often difficult to distinguish environmental contamination from colonization or infection. Patients with either pulmonary or disseminated infection may be enrolled in clinical trials. Disseminated disease occurs mostly in patients infected with the human immunodeficiency virus. In general, a randomized, active-control, double-blinded clinical trial is preferred; there should at least be a blinded evaluator. With regard to immunosuppressed populations, new antimycobacterial drugs need to be evaluated not only for the treatment but also for the prevention of disease. For trials of prophylaxis a placebo-controlled design is ethical until a drug is proven effective; then the use of an active-control regimen is appropriate. Since no regimen has been approved by the U.S. Food and Drug Administration for treatment or prevention of disease caused by the M. avium complex, demonstration of the superiority of the study regimen to the control regimen should be the objective of the clinical trial.

Evaluation of new anti-infective drugs for the treatment of disease caused by Mycobacterium kansasii and other mycobacteria. Infectious Diseases Society of America and the Food and Drug Administration

Mycobacterium kansasii is a photochromogenic nontuberculous mycobacterium that usually causes infections of the respiratory tract in humans. Although spontaneous resolution of infection has been reported, most patients require antimycobacterial therapy. A three- or four-drug combination--isoniazid, rifampin, and ethambutol and/or streptomycin--usually is prescribed. For evaluation of a new drug, a randomized, double-blind or evaluator-blinded, active-control comparative study design is recommended. Treatment should continue for 18-24 months, and follow-up evaluations should be conducted every 6 months for 3 years. Microbiological outcome is paramount.

Effect of gallopamil on electrophysiologic abnormalities and ventricular arrhythmias associated with left ventricular hypertrophy in the feline heart

Left ventricular hypertrophy increases vulnerability to ventricular fibrillation. To determine whether calcium channel blockade protects against ventricular arrhythmia in left ventricular hypertrophy, we studied the effects of gallopamil, a potent and specific calcium channel antagonist, in 37 cats undergoing aortic banding (group 1, n = 28) or a sham procedure (group 2, n = 9). Each cat underwent serial echocardiography and was studied after the development of left ventricular hypertrophy, defined as an increase of at least 30% in left ventricular posterior wall thickness. After baseline electrophysiologic testing, animals received gallopamil (70 micrograms/kg loading dose followed by 2.5 micrograms/kg/min infusion) (n = 19) or a control infusion of saline solution (n = 18), and testing was repeated. There was no significant difference between groups 1 and 2 in baseline excitability thresholds intraventricular conduction times, ventricular effective refractory periods, or monophasic action potential durations. Thresholds for induction of ventricular fibrillation were lower in group 1 than in group 2, and only in group 1 was ventricular fibrillation inducible during programmed stimulation. This altered vulnerability was associated with a significantly greater dispersion of excitability thresholds, ventricular effective refractory periods, and monophasic action potential durations. Gallopamil did not change baseline measurements except for prolonging sinus cycle length and atrioventricular conduction time.(ABSTRACT TRUNCATED AT 250 WORDS)

Proton MR spectroscopy of experimental radiation-induced white matter injury

We studied the spectroscopic appearance of radiation-induced myelinolysis in cats to understand the characteristics of proton MR spectroscopy of demyelinating disorders. Eight cats received 5,000 rads to a 1.5 x 1.5 cm area of the right cerebral hemisphere. Eight to 9 months after irradiation, a gross area of abnormal postcontrast enhancement and/or high MR signal intensity was detected in the irradiated hemisphere of six of the eight cats. Proton spectra of a 1.0 cm3 voxel in the affected region demonstrated depressed N-acetyl aspartate/creatine-phosphocreatine and N-acetyl aspartate/choline-containing compound peak ratios compared with the contralateral non-irradiated brain in all cats. Elevated amino acid resonances in the 2.0-2.5 ppm range were not consistently seen in irradiated zones of the brain with pathologic findings of demyelination. In vivo proton MR spectroscopy may show differences between irradiated brain and nonirradiated brain even when histopathologic lesions are not apparent yet.

Use of formal community resources by spouse caregivers of chronically ill adults

This descriptive correlational study examined the use of formal community resources of spouse caregivers of progressively chronically ill individuals. The convenience sample was 61 individuals with a definitive diagnosis of multiple sclerosis and their spouse caregivers. Results indicated that 34.4% of the sample used community resources. Relationships among caregiver demographics, extent of caregiving tasks, subjective burden, perceived uncertainty of the caregiver, functional incapacity of the chronically ill individual, level of social support, and the use of formal community resources were analyzed. Positively correlated (P less than 0.05) with the criterion variable of use of formal community resources were the variables of caregiver age (rpb = 0.342), number of caregiving tasks (rpb = 0.424), caregiver employment level (chi 2 = 8.25), and functional incapacity of the care receiver (rpb = 0.565). Results of discriminate function analysis indicated that three variables, functional incapacity, caregiver age, and number of caregiving tasks, correctly classified users versus nonusers of community resources 83.6% of the time.

The effect of albumin or crystalloid resuscitation on bacterial translocation and endotoxin absorption following experimental burn injury

Burn injury induces immune suppression and increases susceptibility to infection. Hypoalbuminemia is an early and consistent finding following thermal injury and is independently associated with gastrointestinal dysfunction and increased rates of infectious morbidity. This study assessed the effects of albumin resuscitation on burn-induced immunosuppression, bacterial translocation, and absorption of gut endotoxin. Male Sprague-Dawley rats, presensitized to keyhole limpet hemocyanin (KLH), underwent a 20% dorsal scald burn injury, followed by laparotomy and IVC catheterization for fluid resuscitation. Animals were randomized to one of three resuscitative regimens: Ringer's lactate 3 ml/kg/% burn, Ringer's lactate 9 ml/kg/% burn, or 5% human albumin 3 ml/kg/% burn. Delayed hypersensitivity (DTH) responses to KLH were depressed 24 hr following injury (preburn 8.9 +/- 0.2 mm, post-burn 3.1 +/- 0.3 mm, P less than 0.001) and were significantly lower in animals in whom gram-negative bacterial translocation had occurred (2.3 +/- 0.4 vs 3.6 +/- 0.2 mm, P less than 0.005). Serum albumin levels were lower and rates of gram-negative bacterial translocation higher for those animals receiving low volume crystalloid resuscitation; animals resuscitated with albumin or high volume crystalloid experienced similar degrees of postinjury hypoalbuminemia and bacterial translocation. Uptake of radiolabeled endotoxin was maximal in animals resuscitated with albumin. Bacterial translocation is believed to be responsible for a significant number of late nosocomial infections following trauma. These data suggest that the adequacy of early resuscitation rather than the type of resuscitative solution is the more important factor in minimizing translocation.

Tsukamurella paurometabolum: a novel pathogen causing catheter-related bacteremia in patients with cancer

Tsukamurella paurometabolum is a weakly acid-fast, pleomorphic gram-positive bacterium found in soil. Human infection due to this organism has rarely been described, and there are no published accounts of bacteremia. Three cases of bacteremia due to T. paurometabolum and related to long-term use of a central venous catheter in patients with cancer who were receiving chemotherapy are described.

Starting intravenous lines in children

Starting an IV line in children can be difficult. As with most skills, practice improves performance. However, a lack of practice for the clinician with otherwise good IV skills need not be an impediment. The suggestions described in this article can assist you in adapting your good IV technique to the pediatric patient.

Alpha beta T-lymphocyte depleted mice, a model for gamma delta T-lymphocyte functional studies

Adult mice can be depleted of essentially all mature alpha beta T lymphocytes by chronic treatment with the framework-recognizing, pan-specific anti-TCR alpha beta mAb, H57-597. Similar findings have been reported in rats, gamma delta cell populations remain essentially unaltered in size and reactivity. Suppression of alpha beta T-cell development results in the loss of alloantigen reactivity and of B-cell help, suggesting that gamma delta and alpha beta populations differ in their functional capabilities. Indirect effects of the antibody treatment include quantitative changes in splenic B cells, as well as reduced sizes and weights of experimental animals. alpha beta-suppressed mice and rats may provide model systems for studies on gamma delta cell function in vivo.

Private sector approach to health care reform. Interview by Thomas G. Goodwin

The Healthcare Leadership Council (HLC) was formed in 1990 by 50 CEOs of hospitals, hospital systems, pharmaceutical companies, medical device manufacturers, Insurers and medical professionals. HLC is a coalition to develop the necessary consensus to realistically influence health care reforms. HLC urges that the "U.S. public policy goal should be to seek the best mechanism for balancing quality, access and affordability." As for access for the poor, the HLC would standardize eligibility for Medicaid at the federal poverty level, establishing a minimum basic benefit and payment plan with funding to come from specific taxes. For the employed uncovered, HLC would extend the exemption from state mandates to small employers; enact appropriate market reforms and provide income-related subsidies for those near the poverty line and for small employers; encourage employer-provided coverage for all employees on a voluntary basis.... HLC also backs state subsidized uninsurable risk pools for people whose conditions would make premiums too expensive. As for affordability of health care, HLC says consumers should become involved in cost-effective health care plans, appropriate employee cost sharing, lifestyle incentives/penalties, etc. Also, legislation should be overridden that inhibits innovation, creativity (state-mandated benefits, restrictions on selective contracting, CON requirements...), and medical malpractice tort reform measures also should be enacted. What follows is an in-depth interview with HLC Chairman G. Robert O'Brien, president of CIGNA Employee Benefits Companies.

Expression of gamma/delta T cell receptors on lymphocytes from the lactating mammary gland

gamma/delta cells were at least four times more frequent in lactating mouse mammary glands than among T cells of the most proximal lymph nodes. Two-color staining of freshly isolated T cells and a study of clonally expressed gamma/delta receptors on hybridomas further revealed that the mammary gamma/delta population is heterogeneous, including at least three different subsets, among them cells expressing V gamma 5, V gamma 4 together with V delta 4, or none of these V regions.

Recognition of a peptide antigen by heat shock--reactive gamma delta T lymphocytes

Small synthetic peptides that correspond to different portions of the 65-kilodalton mycobacterial heat shock protein (Hsp65) were used to identify a putative antigenic epitope for gamma delta cells. Weaker gamma delta responses to the equivalent portion of the autologous homolog, mouse Hsp63, were also seen. The stimulatory epitope overlaps with an epitope recognized by arthritogenic alpha beta T cell clones. The data suggest that gamma delta cells have a role in autoimmune disorders and imply that these cells recognize ligands by a mechanism similar to that of alpha beta T lymphocytes, that is, in the form of small processed protein fragments bound to antigen-presenting molecules.

Recognition of heat shock proteins and gamma delta cell function

Recently evidence has accumulated suggesting that gamma delta cells may participate in the immune response to mycobacteria and other infectious organisms. Many mouse gamma delta cells are stimulated by the 65 kDa heat shock protein of M. bovis and human gamma delta cell lines reactive with this mycobacterial protein have also been isolated. Indirect evidence further suggests that gamma delta cells can recognize autologous heat shock proteins. In this article, Willi Born and colleagues focus on these and other recent findings and speculate on their importance to gamma delta cell function in vivo.

Modulation of pulmonary artery contraction by endothelium-derived relaxing factor

In isolated rat pulmonary artery rings, both endothelial denudation and treatment with 10(-5) M hemoglobin inhibited relaxation to acetylcholine and increased contractile sensitivities, i.e. decreased the EC50s, to KCl, angiotensin II and norepinephrine. Denudation caused similar inhibition of acetylcholine relaxation and potentiation of KCl and norepinephrine contractions in isolated bovine pulmonary arteries. These results indicate that endothelium-derived relaxing factor plays a significant role in modulating the contractile sensitivity of isolated pulmonary arteries to at least some agonists.

Binding to GDP-agarose identifies a novel 60kDa substrate for the insulin receptor tyrosyl kinase in mouse NIH-3T3 cells expressing high concentrations of the human insulin receptor

Insulin increased dramatically the tyrosyl phosphorylation of the insulin receptor beta-subunit in mouse NIH-3T3 fibroblasts transfected with the human insulin receptor. Insulin also increased the phosphorylation, on tyrosine residues, of an endogenous 60kDa protein. This protein was identified after being eluted from a GDP-agarose support by GDP. It is suggested that the 60kDa species may be a novel guanine nucleotide binding protein which is specifically phosphorylated by the insulin receptor.

A chemically synthesized radiolabeled signal peptide: design, preparation, and biological evaluation of an iodinated analog of preproparathyroid hormone

The chemically synthesized signal peptide (native-sequence signal peptide) of preproparathyroid hormone exhibits signal sequence-like activity by inhibiting the translocation/processing of precursor proteins to their mature forms in an in vitro translation system. In order to prepare a biologically functional radiolabeled form of this peptide, we undertook structure-function studies of the native-sequence signal peptide. Since conventional iodination of peptides is performed under oxidizing conditions, chemical design efforts were focused on the oxidation-labile residues, methionine and cysteine, present in the native sequence. Substitution of the three methionines with norleucine and the single cysteine with alanine yielded a surfur-free analog, [Nle-(-25), Nle-(-21),Nle-(-18),Ala-(-14),D-Tyr-(+1)]pre-proPTH-(-29-+1)amide, which is resistant to oxidation and active in the inhibition of processing assay. An interaction between the signal region and one of the components of the intracellular secretory apparatus, signal recognition particle (SRP), was demonstrated: iodinated sulfur-free analog was cross-linked (using the homo-bifunctional reagent disuccinimidyl suberate) to the 54 kilodalton (kDa) subunit of SRP. The 68 kDa and 72 kDa subunits of SRP were also labeled, but to a lesser extent, by the iodinated peptide.

Effect of glycaemic control on glomerular filtration rate in the streptozotocin diabetic rat

1. Diabetes was induced in 32 adult Wistar-Kyoto rats with streptozotocin (60 mg/kg). Fourteen rats remained untreated, 10 received insulin three times per week, and eight received insulin daily. Fourteen non-diabetic rats served as controls. 2. Exchangeable sodium and plasma volume were elevated in the untreated diabetic rats. Treatment normalized these parameters. 3. Glomerular filtration rate (GFR) was elevated in the untreated diabetic group and the group receiving insulin three times per week compared with the control group. Daily insulin treatment restored GFR towards control values. 4. Plasma atrial natriuretic factor was similar in untreated diabetic rats and non-diabetic rats.

Peptide sequences of T-cell receptor delta and gamma chains are identical to predicted X and gamma proteins

Although most mature peripheral T lymphocytes express a major histocompatibility complex restricted, CD3-associated, antigen receptor (TCR) which has been well characterized, some T cells carry a different CD3-associated heterodimer on their surface. One of the two disulphide-linked chains of this putative second receptor, which in mice has relative molecular mass (Mr) 35,000 (35K), has been identified as a product of the group of gamma genes. The other chain, termed delta (Mr 45K in mice), is not as well characterized. Although gamma/delta-bearing cells are a minor subset among peripheral T lymphocytes, they are the only CD3+ cells in the thymus early in ontogeny. Taking advantage of these kinetics, we have generated gamma/delta-bearing hybridomas, using a new TCR alpha chain-negative variant of the AKR thymoma BW5147 as tumour parent, fetal thymocytes as normal cell partners, and an anti-CD3 monoclonal antibody (mAb) as screening reagent. Gamma and delta chains from one of these hybrids have been purified and partially sequenced. The sequences obtained indicate that delta is indeed identical to the polypeptide encoded by the recently described gene X, as suggested by Chien et al.