Antibiotics cure anthrax in animal models

Respiratory anthrax, in the absence of early antibiotic treatment, is a fatal disease. This study aimed to test the efficiency of antibiotic therapy in curing infected animals and those sick with anthrax. Postexposure prophylaxis (24 h postinfection [p.i.]) of guinea pigs infected intranasally with Bacillus anthracis Vollum spores with doxycycline, ofloxacin, imipenem, and gentamicin conferred protection. However, upon termination of treatment, the animals died from respiratory anthrax. Combined treatment with antibiotics and active vaccination with a protective antigen-based vaccine leads to full protection even after cessation of treatment. Delaying the initiation of antibiotic administration to over 24 h p.i. resulted in treatment of animals with anthrax exhibiting various degrees of bacteremia and toxemia. Treatment with doxycycline or ciprofloxacin cured sick guinea pigs and rabbits exhibiting bacteremia levels up to 10(5) CFU/ml. Addition of anti-protective antigen (PA) antibodies augmented the efficiency of protection, allowing the cure of guinea pigs and rabbits with 10- to 20-fold-higher bacteremia levels, up to 7 × 10(5) CFU/ml and 2 × 10(6) CFU/ml, respectively. Treatment with ciprofloxacin and a monoclonal anti-PA antibody rescued rabbits with bacteremia levels up to 4 × 10(6) CFU/ml. During antibiotic administration, all surviving animals developed a protective immune response against development of a fatal disease and subcutaneous challenge with Vollum spores. In conclusion, these results demonstrate that antibiotic treatment can prevent the development of fatal disease in respiratory-anthrax-infected animals and can cure animals after disease establishment. A therapeutic time window of 40 h to 48 h from infection to initiation of efficient antibiotic-mediated cure was observed.     

Dietary whey protein inhibits the development of dimethylhydrazine induced malignancy

This study investigates the influence of two formula diets containing 20 g/100 g diet of either whey protein concentrate or casein or Purina mouse chow, on the humoral immune responsiveness and dimethylhydrazine induced colon carcinogenesis in A/J mice. After 20 weeks of dimethylhydrazine treatment, the number of plaque forming cells per spleen, following intravenous inoculation with 5 X 10(6) sheep red blood cells, was nearly three times greater in the whey protein-fed group than in the casein-fed mice although both values were substantially below normal. After 24 weeks of dimethylhydrazine treatment the incidence of tumors in the whey protein-fed mice was substantially lower than that in mice fed either the casein or Purina diet. Similarly, the tumor area was less in the whey protein group in comparison to either the casein or Purina groups, with some difference between casein and Purina groups. Body weight curves were similar in all dietary groups. In conclusion, a whey protein diet appears to significantly inhibit the incidence and growth of chemically induced colon tumors in mice.     

Lactoferrin given in food facilitates dermatophytosis cure in guinea pig models

Dermatophytosis is the most common skin infection caused by dermatophytic fungi, such as Trichophyton spp. We studied the in vitro and in vivo antifungal effects of lactoferrin against Trichophyton. Human and bovine lactoferrin, and a bovine lactoferrin-derived peptide, lactoferricin B, showed in vitro antifungal activity that was dependent on the test strain and medium used. In guinea pigs infected on the back with Trichophyton mentagrophytes (i.e. those with tinea corporis), consecutive daily po administration of bovine lactoferrin did not prevent development of symptoms during the early phase of infection, but facilitated clinical improvement of skin lesions after the peak of the symptoms. The fungal burden in lesions was less in guinea pigs that had been given lactoferrin than in untreated controls 21 days after infection. In guinea pigs infected on the foot with T. mentagrophytes (i.e. those with tinea pedis), the fungal burden of the skin on the heel portion of the infected foot 35 days after infection was lower in animals fed lactoferrin than in controls. These results suggest the potential usefulness of lactoferrin as a food component for promoting dermatophytosis cure.     

Successful single-dose prophylaxis of Staphylococcus aureus foreign body infections in guinea pigs by fleroxacin.

Single-dose administration of fleroxacin was evaluated as a means of preventing foreign body infection due to staphylococci. Tissue cages were implanted into guinea pigs and subsequently infected (100% rate) with 10(2) or more CFU of Staphylococcus aureus Wood 46. When a single dose of 30 mg of fleroxacin or vancomycin per kg of body weight was administered intraperitoneally, bactericidal levels of the antimicrobial agent were found in the tissue cage fluid after 3 h (when guinea pigs were inoculated with S. aureus) and during the next 24 h. Either fleroxacin or vancomycin successfully prevented experimental infection in all tissue cages challenged by 10(2) CFU of S. aureus Wood 46. When tissue cages were challenged with 10(4) CFU of S. aureus Wood 46, however, fleroxacin was more effective than vancomycin (P less than 0.05) in reducing colony counts below the detection limit of 10 CFU/ml in the inflammatory fluid of all tissue cages during the initial 48 h. In contrast to their initially different actions, the effects of the antibiotics were similar after 7 days, mostly because bacterial regrowth occurred more frequently in the fleroxacin-treated than in the vancomycin-treated tissue cages. These data show that experimental infections of subcutaneous tissue cages are a useful model for studying the prophylaxis of foreign body infections with antimicrobial agents.     

Activities of tigecycline (GAR-936) against Legionella pneumophila in vitro and in guinea pigs with L. pneumophila pneumonia

The activities of tigecycline (Wyeth Research) against extracellular and intracellular Legionella pneumophila and for the treatment of guinea pigs with L. pneumophila pneumonia were studied. The tigecycline MIC at which 50% of strains are inhibited for 101 different Legionella sp. strains was 4 micro g/ml versus 0.125 and 0.25 micro g/ml for azithromycin and erythromycin, respectively. Tigecycline was about as active as erythromycin (tested at 1 micro g/ml) against the F889 strain of L. pneumophila grown in guinea pig alveolar macrophages and more active than erythromycin against the F2111 strain. Azithromycin (0.25 micro g/ml) was more active than (F889) or as active as (F2111) tigecycline (1 micro g/ml) in the macrophage model. When tigecycline was given (7.5 mg/kg of body weight subcutaneously once) to guinea pigs with L. pneumophila pneumonia, the mean peak serum and lung levels were 2.3 and 1.8 micro g/ml (1.2 and 1.5 micro g/g) at 1 and 2 h postinjection, respectively. The serum and lung areas under the concentration time curve from 0 to 24 h were 13.7 and 15.8 micro g. h/ml, respectively. Thirteen of 16 guinea pigs with L. pneumophila pneumonia treated with tigecycline (7.5 mg/kg subcutaneously once daily for 5 days) survived for 7 days post-antimicrobial therapy, as did 11 of 12 guinea pigs treated with azithromycin (15 mg/kg intraperitoneally once daily for 2 days). None of 12 guinea pigs treated with saline survived. Tigecycline-treated guinea pigs had average end of therapy lung counts of 1 x 10(6) CFU/g (range, 2.5 x 10(4) to 3.2 x 10(6) CFU/g) versus <1 x 10(2) CFU/g for azithromycin (range, undetectable to 100 CFU/g). A second guinea pig study examined the ability of tigecycline to clear L. pneumophila from the lung after 5 to 9 days of therapy; bacterial concentrations 1 day posttherapy ranged from log(10) 4.2 to log(10) 5.5 CFU/g for four different dosing regimens. Tigecycline is about as effective as erythromycin against intracellular L. pneumophila, but tigecycline inactivation by the test media confounded the interpretation of susceptibility data. Tigecycline was effective at preventing death from pneumonia in an animal model of Legionnaires' disease, warranting human clinical trials of the drug for the disease.     

Dose-dependent activity of pyrazinamide in animal models of intracellular and extracellular tuberculosis infections

Recent in vitro pharmacokinetic data suggest that the currently recommended dose of pyrazinamide may be suboptimal for killing intracellular bacilli in humans. We evaluated a range of pyrazinamide doses against intracellular and extracellular Mycobacterium tuberculosis in chronically infected mice and guinea pigs, respectively. Antibiotics were given five times weekly for 4 weeks beginning 28 days after infection. Human-equivalent doses of isoniazid reduced lung bacterial counts 10-fold in each species. Pyrazinamide given at 1/4 and 1/2 the human-equivalent dose was minimally active, while human-equivalent doses reduced lung bacterial counts by ～1.0 log(10) in each species. Doubling the human-equivalent dose of pyrazinamide reduced the lung bacillary burden by 1.7 and 3.0 log(10) in mice and guinea pigs, respectively. As in humans and mice, pyrazinamide showed significant synergy with rifampin in guinea pigs. Clinical studies are warranted to investigate the sterilizing activity and tolerability of higher doses of pyrazinamide in combination tuberculosis regimens.     

Effect of 2''-nor-cyclic GMP against guinea pig cytomegalovirus infection.

Cyclic phosphate derivative of DHPG, 2'-nor-cGMP [9-[(2-hydroxy-1,3,2-dioxaphosphorinan-5-yl)oxymethyl]-guani ne phosphate-oxide] was evaluated for activity against guinea pig cytomegalovirus (GPCMV) infection in cultured guinea pig embryo cells and in guinea pigs. By virus yield reduction and plaque reduction assays, 2'-nor-cGMP was demonstrated to be 15- to 20-fold more potent against GPCMV infection than its parental drug DHPG. The selectivity index of 2-nor-cGMP was 110, which was 10-fold higher than that of DHPG. In cultured cells, 2'-nor-cGMP attained maximal antiviral activity when added to the cells within 12 h postinfection. In the studies on GPCMV infection in guinea pigs, 2'-nor-cGMP administered subcutaneously once daily (5 mg/kg per day) for 8 days, starting 24 after virus inoculation, significantly suppressed GPCMV infectivity titers in the blood, spleen, lung, and salivary gland during acute infection (10 days postinfection) as compared with sham-treated infected animals. A greater reduction of GPCMV infectivity titers in the salivary gland was noted during chronic infection (i.e., 24 days postinfection). Clinically, splenomegaly and peripheral lymphocytosis were significantly modified as compared with the sham-treated animals (P less than 0.05). The drug, administered at this dosage, was reasonably tolerated by the guinea pigs and showed clinical benefit.     

Effect of infection with M. tuberculosis and of tuberculin shock on the succinic dehydrogenase activity of guinea pig tissues

The kidney of guinea pigs infected with the H37Rv and BCG strains of M. tuberculosis showed a diminution in succinic dehydrogenase activity when measured by the tetrazolium technique. This effect was also seen in the liver and spleen of animals infected with the BCG strain. Sensitized animals showed similar results when given tuberculin in sublethal doses. The succinic oxidase was also low in the kidneys of animals infected with the H37Rv strain. The depressed enzyme activity of the tissues of infected animals could be restored to normal by addition of normal tissue extract or dialysate. This suggests that the alteration in tissue metabolism observed in tuberculosis may depend upon the loss of some as yet unidentified factor important for succinic dehydrogenase activity.     

Effect of acyclovir and phosphonoformate on cytomegalovirus infection in guinea pigs

Adult Hartley guinea pigs infected with guinea pig cytomegalovirus (CMV) develop a mononucleosis syndrome with a brief viremia, splenomegaly, lymphadenopathy, and peripheral lymphocytosis with circulating atypical lymphocytes. The present study used this experimental model to evaluate in vivo the therapeutic efficacy of acyclovir (ACV) and phosphonoformate (PFA) during CMV infection. Guinea pigs were treated with ACV or PFA from day 3 to day 7 postinoculation. The course of the mononucleosis syndrome and the spread of virus in various tissues were similar in drug- and sham-treated infected guinea pigs. Infected animals treated with ACV or PFA developed disseminated CMV disease with severe interstitial pneumonia, whereas sham-treated infected and drug-treated noninfected animals did not. In addition, mortality rates in infected animals treated with ACV were significantly higher than those in sham-treated animals. Furthermore, the normal lymphoproliferative response to CMV infection appeared to be reduced in ACV-treated as compared to sham-treated animals, with fewer peripheral lymphocytes, less lymphoid tissue in the spleen and lymph nodes, and less mononuclear inflammation around the inclusion-containing cells of the liver and salivary gland. These results show that ACV and PFA are not useful in the treatment of CMV infection in guinea pigs but instead may have harmful effects.     

Guinea pigs sublethally infected with aerosolized Legionella pneumophila develop humoral and cell-mediated immune responses and are protected against lethal aerosol challenge. A model for studying host defense against lung infections caused by intracellular pathogens

We have employed the guinea pig model of L. pneumophila infection, which mimics Legionnaires' disease in humans both clinically and pathologically, to study humoral and cell-mediated immune responses to L. pneumophila and to examine protective immunity after aerosol exposure, the natural route of infection. Guinea pigs exposed to sublethal concentrations of L. pneumophila by aerosol developed strong humoral immune responses. By the indirect fluorescent antibody assay, exposed guinea pigs had a median serum antibody titer (expressed as the reciprocal of the highest positive dilution) of 32, whereas control guinea pigs had a median titer of less than 1. Sublethally infected (immunized) guinea pigs also developed strong cell-mediated immune responses. In response to L. pneumophila antigens, splenic lymphocytes from immunized but not control animals proliferated strongly in vitro, as measured by their capacity to incorporate [3H]thymidine. Moreover, immunized but not control guinea pigs developed strong cutaneous delayed-type hypersensitivity to intradermally injected L. pneumophila antigens. Sublethally infected (immunized) guinea pigs exhibited strong protective immunity to L. pneumophila. In two independent experiments, all 22 immunized guinea pigs survived aerosol challenge with one or three times the lethal dose of L. pneumophila whereas none of 16 sham-immunized control guinea pigs survived (p less than 0.0001 in each experiment). Immunized guinea pigs were not protected significantly from challenge with 10 times the lethal dose. Immunized but not control animals cleared the bacteria from their lungs. This study demonstrates that guinea pigs sublethally infected with L. pneumophila by the aerosol route develop strong humoral immune responses to this pathogen, develop strong cell-mediated immune responses and cutaneous delayed-type hypersensitivity to L. pneumophila antigens, are protected against subsequent lethal aerosol challenge, and are able to clear the bacteria from their lungs. The guinea pig model of L. pneumophila pulmonary infection is as an excellent one for studying general principles of host defense against pulmonary infections caused by intracellular pathogens.     

THE DEGREE OF DISPERSION OF THE BACILLUS AS A FACTOR IN INFECTION AND RESISTANCE IN EXPERIMENTAL TUBERCULOSIS

1. The skin lesions in rabbits and guinea pigs following intradermal injection of tubercle bacilli (5 strains) were greatly increased in size and severity when testicle extract was added to the inoculum. Such enhancement was followed by a more widespread and rapidly progressing disease only when virulent strains were employed. 2. Attempts to suppress the development of skin lesions resulting from the injection of either normal or tuberculous rabbits with very small quantities of tubercle bacilli mixed with testicle extract were unsuccessful. 3. The skin reactions of tuberculous guinea pigs to tuberculo-protein MA 100 were greatly increased in size and markedly reduced in intensity by the addition of testicle extract to the protein solution. The toxic effect of larger quantities of tuberculo-protein was not altered by the addition of testicle extract. 4. The dispersion of tubercle bacilli through the skin of tuberculous rabbits resulted in a marked enhancement of the Koch phenomenon but was not followed by any extension of the new infection to the viscera. Tuberculous rabbits infected on two occasions with dead tubercle bacilli suspended in testicle extract showed an increased resistance to the disease when compared with controls receiving dead bacilli suspended in saline solution. 5. The resistance conferred upon tuberculous guinea pigs by superinfection was greatly increased when the bacilli employed were dispersed through the skin with testicle extract. 6. The parenteral administration of large quantities of testicle extract to recently infected guinea pigs did not result in any increase in the extent of the visceral lesions. 7. The partial immunity conferred upon guinea pigs and rabbits by vaccination with heat-killed tubercle bacilli was increased as a result of dispersion of the vaccine through the skin with testicle extract.     

STUDIES OF TUBERCLE BACILLUS-HISTIOCYTE RELATIONSHIPS : VII. HOMOLOGOUS AND HETEROLOGOUS TRANSFER OF CELLULAR RESISTANCE

Immunization of mice or guinea pigs with BCG rendered all or most of the histiocytes of these animals resistant to necrotization by virulent H37Rv; this cellular resistance was mediated by immune serum. Immune mouse histiocytes (from BCG-immunized animals) were able to induce cellular resistance in normal homologous and heterologous (rabbit) animal species; mouse histiocytic ribosomes were also tested in the homologous species and found to be active. Immune guinea pig histiocytes (from BCG-immunized guinea pigs) were ineffective in transferring cellular resistance to either homologous or heterologous (mouse and rabbit) animal species. Immune rabbit histiocytes were capable of inducing cellular resistance in mice and guinea pigs; rabbit histiocytic ribosomes were also tested in normal mice and found to be active in induction of cellular resistance. Recipient guinea pig histiocytes (from guinea pigs inoculated with immune rabbit histiocytes) were capable of inducing cellular resistance in normal guinea pigs and rabbits. Cultivation of lysed immune histiocytes of all three animal species on glycerol-blood agar medium failed to reveal any viable BCG; this provided one additional bit of evidence against the idea that induction of cellular resistance is due to viable bacilli.     

In vitro activities of fleroxacin against clinical isolates of Legionella spp., its pharmacokinetics in guinea pigs, and use to treat guinea pigs with L. pneumophila pneumonia.

The activities of fleroxacin against 22 clinical Legionella isolates were determined by agar and broth microdilution susceptibility testing. The fleroxacin MIC required to inhibit 90% of strains tested on buffered charcoal yeast extract agar medium supplemented with 0.1% alpha-ketoglutarate was 0.64 micrograms/ml and was 0.04 microgram/ml when testing was done with buffered yeast extract broth supplemented with 0.1% alpha-ketoglutarate. Fleroxacin (0.25 microgram/ml) reduced the bacterial counts of two L. pneumophila strains grown in guinea pig alveolar macrophages by 1 log10 CFU/ml, but regrowth occurred over a 3-day period; fleroxacin was significantly more active than erythromycin in this assay. Single-dose (10 mg/kg of body weight given intraperitoneally) pharmacokinetic studies performed in guinea pigs with L. pneumophila pneumonia revealed peak levels in plasma and lungs to be 3.3 micrograms/ml and 3.5 micrograms/g, respectively, at 0.5 h and 0.8 microgram/ml and 0.8 microgram/g, respectively, at 1 h. The half-life of the terminal phase of elimination from plasma and lung was approximately 2 h. All 17 infected guinea pigs treated with fleroxacin (10 mg/kg/day) for 2 days survived for 14 days post-antimicrobial therapy, as did all 16 guinea pigs treated with the same dose of fleroxacin for 5 days. Only 1 of 16 animals treated with saline survived. The animals treated with fleroxacin for 2 days lost more weight and had higher temperatures than those treated with the antibiotic for 5 days. Fleroxacin is effective against L. pneumophila in vitro and in a guinea pig model of Legionnaires' disease. Fleroxacin should be evaluated as a treatment for human Legionnaires' disease.     

Location of persisting mycobacteria in a Guinea pig model of tuberculosis revealed by r207910

The lengthy chemotherapy of tuberculosis reflects the ability of a small subpopulation of Mycobacterium tuberculosis bacteria to persist in infected individuals. To date, the exact location of these persisting bacteria is not known. Lung lesions in guinea pigs infected with M. tuberculosis have striking similarities, such as necrosis, mineralization, and hypoxia, to natural infections in humans. Guinea pigs develop necrotic primary lesions after aerosol infection that differ in their morphology compared to secondary lesions resulting from hematogenous dissemination. In infected guinea pigs conventional therapy for tuberculosis during 6 weeks reduced the bacterial load by 1.7 logs in the lungs and, although this completely reversed lung inflammation associated with secondary lesions, the primary granulomas remained largely unaffected. Treatment of animals with the experimental drug R207910 (TMC207) for 6 weeks was highly effective with almost complete eradication of the bacteria throughout both the primary and the secondary lesions. Most importantly, the few remnants of acid-fast bacilli remaining after R207910 treatment were to be found extracellular, in a microenvironment of residual primary lesion necrosis with incomplete dystrophic calcification. This zone of the primary granuloma is hypoxic and is morphologically similar to what has been described for human lung lesions. These results show that this acellular rim may, therefore, be a primary location of persisting bacilli withstanding drug treatment.     

Studies on the interaction between phagocytes and tubercle bacilli. III. Some metabolic effects in guinea pigs associated with infection with tubercle bacilli

In continuing studies concerning the interactions between phagocytes and tubercle bacilli the effect of tuberculous infection on respiration and glucose utilization was investigated in guinea pigs. Peritoneal exudates rich in polymorphonuclear leucocytes, derived from guinea pigs infected with tubercle bacilli, had a significantly higher rate of respiration than the same cells from normal animals. The difference between cells from normal and infected animals was greater when the animals were infected with a virulent strain (Vallée) than when infected with an attenuated one (R1Rv or BCG). By the use of glucose labelled with C¹⁴ at position 1 or 6, or uniformly labelled glucose, it was established that this difference in oxygen uptake between normal and infected cells was probably not caused by a difference in the pathway of glucose utilization. Similarly, the respiration of liver and kidney slices from normal and infected guinea pigs was compared and it was found that liver slices showed differences similar to those shown by leucocytes, but that the kidney slices did not. The possibility has not been ruled out that the difference in rate of respiration of liver slices due to infection might be caused by tuberculous lesions in the livers of infected animals. The mononuclear cells which invade the liver have a higher rate of oxygen uptake than liver cells. The rate of glucose utilization and the total amount of CO₂ produced was also determined in intact guinea pigs. Both functions were found not to differ significantly in normal and infected animals. The rate of production of CO₂ from C₁ and C₆ of glucose was the same in both groups of animals. The ratio of the rate of production of C¹⁴O₂ from C₁ and C₆ of glucose by the whole animal was found to be about 1.35. It was found to be much higher with polymorphonuclear leucocytes (C₁/C₆ = 8 in the absence of serum). During the process of phagocytosis this ratio increased from about 25 to about 130 (in the presence of 2 per cent serum) indicating an increase in the direct oxidative pathway of glucose utilization during stimulated cellular activity.     

Inhibition of tuberculin skin hypersensitivity in guinea pigs by injection of tuberculin and intact tubercle bacilli during fetal life

Female guinea pigs were subjected to laparotomy at different stages of pregnancy, and their fetuses injected through the uterine walls with one of the following preparations: Old Tuberculin, tubercle bacilli of the BCG strain killed by heat or exposure to phenol, and living BCG. A large number of the animals injected in utero with Old Tuberculin failed to develop skin hypersensitivity to P.P.D. following vaccination with 200 or 800 γ phenol-killed tubercle bacilli (BCG) in early adulthood. Normal control animals were sensitized by vaccination with such quantities of phenolized BCG. The failure of animals which had been injected with Old Tuberculin in fetal life to respond hypersensitively to P.P.D. after adult vaccination with tubercle bacilli is ascribed to their acquisition of a state of immunological tolerance to tuberculoprotein (tuberculin tolerance). Fetal injection with killed BCG conferred a state of tolerance on a few of the animals, and rendered others tuberculin-sensitive. Fetal injection with living BCG sensitized most of the animals to tuberculin, even when fetal exposure was as early as 46 days before birth, and induced tolerance in none. Fetuses of the same litter, injected simultaneously with identical inocula, often responded differently, some becoming tolerant to tuberculin, others developing hypersensitivity, and still others remaining immunologically unaffected, becoming neither sensitive nor tolerant. The state of tuberculin tolerance induced in these experiments was limited. When tolerant animals were revaccinated with living BCG several weeks after vaccination with phenol-killed bacilli, they developed as high a degree of tuberculin skin sensitivity as the originally non-tolerant animals.     

Leptospirosis in cattle

From abnormal milk of cows an agent has been transmitted to guinea pigs, rabbits, mice, and embryonated eggs. This agent caused a febrile reaction in guinea pigs and rabbits and an inapparent infection in mice. In early passages embryonated eggs were unaffected but later death of embryos occurred 7 days after inoculation. When blood from infected guinea pigs or chorioallantoic fluid from infected eggs was inoculated subcutaneously or intranasally into young calves, fever with albuminuria and more rarely hemoglobinuria was produced, in lactating cows the infection resembled that seen in animals with natural disease. Pen contact of normal cows and calves with infected calves resulted in inapparent infection. Autopsies showed that in addition to causing altered milk secretion, the agent damaged the kidneys and produced an interstitial nephritis. The agent was recovered from blood and milk during the febrile period and was demonstrated in the urine for periods long afterwards. Antibodies for the spirochete were found in the sera of experimental animals and of cows recovered from the natural disease. The blood of infected guinea pigs, the chorioallantoic fluid from infected eggs, and the blood or urine from experimentally infected calves yielded a culture of a spirochete which appeared identical with the infective agent in comparative tests of physical, pathogenic, and immunological properties.     

The relative effects of protein,choline, and methionine in the treatment of experimental dietary cirrhosis in the rat

Cirrhosis of the liver was produced in rats by feeding a diet low in protein (4 per cent casein) and deficient in lipotropic factors. The degree of liver cirrhosis was determined from specimens obtained at biopsy. Comparable groups of animals then were treated with diets containing 4 per cent casein and 30 per cent casein. The 4 per cent casein diets were supplemented with choline and methionine; the 30 per cent casein diets were fed with and without added choline. On supplementing the low protein diet with choline and methionine the animals remained feeble, their growth remained stunted, and their livers showed signs of progressive cirrhosis. In contrast, animals fed the higher protein diet (with or without added choline) grew normally, and their livers showed signs indicating arrest and regression of the disease process. These studies suggest that the feeding of high protein (30 per cent casein) diets to rats with nutritional cirrhosis produces reparative effects greater than those attributable to the supplements choline and methionine.     

Effect of Diet upon Intestinal Disaccharidases and Disaccharide Absorption

The administration of a carbohydrate-containing diet for 24 hours to rats previously fasted for 3 days led to a twofold increase in total intestinal sucrase and sucrase specific activity. The specific activity of maltase was similarly increased, but lactase activity was unaffected. The sucrose-containing diet led to a greater increase in sucrase than maltase activity, whereas the converse was true of the maltose-containing diet. A carbohydrate-free isocaloric diet led to a slight increase in the total intestinal sucrase, but sucrase specific activity was unchanged. Assay of sucrase activity of mixed homogenates from casein-fed and sucrose-fed rats or fasted and sucrose-fed animals yielded activities that were additive. The Michaelis constant (Km) of the enzyme hydrolyzing sucrose was similar in the fasted, casein-fed, and sucrose-fed rats. The maximal velocity (Vmax) was twice greater in sucrose-fed as compared to casein-fed or fasted rats, suggesting an increased quantity of enzyme subsequent to sucrose feeding.Adrenalectomized rats maintained on 1.0% salt intake had sucrase and maltase levels comparable to those of controls. Steroid administration did not significantly increase their activities. The response to sucrose feeding was similar in both control and adrenalectomized rats, indicative of the absence of steroidal control on sucrase and maltase activity in the adult animal.Studies using intestinal ring preparations indicated that sucrose hydrolysis by the intact cells proceeded more rapidly when animals were fed sucrose. Additional corroboration of the physiologic significance of the increased enzyme levels in homogenates was afforded by intestinal perfusion studies. Sucrose hydrolysis increased twofold and fructose absorption fourfold in animals fed sucrose when compared to either fasted or casein-fed rats.     

Enhanced priming of adaptive immunity by a proapoptotic mutant of Mycobacterium tuberculosis

The inhibition of apoptosis of infected host cells is a well-known but poorly understood function of pathogenic mycobacteria. We show that inactivation of the secA2 gene in Mycobacterium tuberculosis, which encodes a component of a virulence-associated protein secretion system, enhanced the apoptosis of infected macrophages by diminishing secretion of mycobacterial superoxide dismutase. Deletion of secA2 markedly increased priming of antigen-specific CD8(+) T cells in vivo, and vaccination of mice and guinea pigs with a secA2 mutant significantly increased resistance to M. tuberculosis challenge compared with standard M. bovis bacille Calmette-Guérin vaccination. Our results define a mechanism for a key immune evasion strategy of M. tuberculosis and provide what we believe to be a novel approach for improving mycobacterial vaccines.