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Biomedical subjects

E B Howard

Publications and source records attributed to E B Howard.

At least 19 recordsLinked to original sources
PubMed1992

Nonmucinous nature of the surface material of the bladder mucosa.

The urinary bladder is lined by transitional epithelium, also known as urothelium. Some investigators have described a material known as mucin, which lines the luminal surface of the urothelium, but its nature is not well understood. The authors examined sections of bladder from rat, mouse, rabbit, and man and found that, although they reacted differently to common histochemical stains for complex carbohydrates, none showed any material that stained as mucin on the surface of the mucosa. Rather, intracellular granules that have varying staining characteristics in different animals were found on the luminal side of the urothelium. The authors speculate, based on their histochemical findings, that some form of mucin may be present in the urothelial granules in man and that studies on animals may not be applicable to man.

Animals↗
PubMed1990

Lethal cyclosporine associated toxicity in the rabbit: similar findings in two distant and independent transplant laboratories.

A collaborative study was initiated between Basel and Irvine Laboratories named above in an attempt to characterize a unique and lethal gastrointestinal toxicity in rabbits associated with cyclosporine administration. Data from both laboratories were combined and analyzed. The rate of weight loss in CsA treated rabbits was found to be a significant linear function of the dose. In addition, animal survival decreased and showed a dose-dependent linear relationship to CsA use. Grossly, all of the animals presented with full stomachs, incompletely digested, dry, hard, rabbit chow. Histopathology could not provide any insight into the mechanisms of this gross finding and remain unclear. The complete similarity of clinical and histopathological results in distant independent laboratories confirms the specificity of this CsA associated toxicity in the rabbit.

Animals↗
PubMed1989

Epidemiologic and pathologic aspects of an epizootic of malignant catarrhal fever in exotic hoofstock.

An epizootic of malignant catarrhal fever (MCF) occurred at the Los Angeles Zoological Park which resulted in the deaths of four exotic ungulates. The source of infection was considered to be a newly purchased wildebeest bull (Connochaetes taurinus taurinus) that had been negative for antibody to MCF virus by an indirect immunofluorescent test. The need to re-evaluate regulations for the transportation and housing of young wildebeest is emphasized by this MCF outbreak. The diagnostic technology now available for identifying asymptomatic carriers of MCF virus and the present understanding of the behavior and pathogenesis of this highly cell-associated herpesvirus in exotic ruminants should provide a basis for the prevention and control of MCF in zoological parks.

Animals↗
PubMed1988

Cyclosporine and skin allografts for the treatment of thermal injury. I. Extensive graft survival with low-level long-term administration and prolongation in a rat burn model.

The hypothesis tested in the present and accompanying study is that an effective treatment for severe burns involves early excision of necrotic tissue followed by skin allografting and cyclosporine (CsA) immunosuppressive therapy. LEW (RT1) rats served as recipients of thermal injury and/or skin allografts. BN x LEW F1 (LBN, RT1(l+n)) rats served as skin donors. LEW burn recipients received a hot water (90 degrees C for 10 sec) 30% body surface area (BSA) full-thickness burn. As expected, LEW recipients treated with CsA (25 mg/kg/day for 20 days) demonstrated significant graft prolongation compared with controls (P less than 0.005). Skin graft survival was similarly prolonged in LEW recipients undergoing burn injury, primary wound excision, and CsA administration compared with burn-skin allograft controls (P less than 0.001). Mortality was not increased in the thermal injury-CsA-treated recipients compared with burn controls. A final experiment was initiated to investigate how low-level long-term (greater than 100 days) maintenance CsA treatment influenced skin allograft survival for possible future consideration in burn trauma. Recipients receiving skin allografts plus CsA (20 days, 8mg/kg/day, followed by every other day thereafter) did not reject their grafts. However, a possible early sign of rejection (a single small ulcerative lesion) was noted in five of these long-term CsA-treated animals at a mean of 34 +/- 11 (SD) days. The lesion in these animals did not progress any further during CsA administration. Histopathologic study of selected animals removed from the CsA maintenance regimen for greater than 50 days following long-term administration revealed a number of interesting chronic lesions similar to those previously reported in the skin component of composite tissue (limb) allografts following long-term low-level CsA intervention. In conclusion, CsA was very successful in preventing rejection of skin allografts in a rat burn model without apparent adverse effects.

Animals↗
PubMed1987

Decreased reactivity of allosera against target lymphocytes obtained following thermal injury or long-term cyclosporine treatment.

We speculated that two diverse causes of potent cell-mediated immune suppression, cyclosporine (CsA) and thermal trauma, may demonstrate some similar actions, and thus tested whether either could alter antisera reactivity against allogeneic target lymphocytes. Target splenocytes from 40% body surface area full-thickness burned Brown-Norway (BN) rats demonstrated significant (P = 0.004) decreased reactivity (agglutination) with antisera produced across a full allogeneic barrier (RT1 major histocompatibility complex (MHC) and non-MHC) compared to control splenocytes. Depression of allogeneic splenic target cell reactivity against Lewis (LEW)-anti-BN allosera was similarly observed using lymphocytes from long-term CsA-treated rats (P = 0.004). The decreased reactivity induced by burn trauma was transferable to pooled normal splenocytes or blood lymphocytes by preincubation with burn plasma (P less than 0.001), and was confirmed by a cellular enzyme-linked immunosorbent assay (CELISA) (P = 0.003). In summary, a similarity consisting of decreased antibody reactivity against lymphocytes from either burned or long-term CsA-treated animals was demonstrated. These results suggested that lymphocyte cell surface allogeneic determinants and their expression and/or availability were altered by either regimen.

Animals↗
PubMed1986

Composite tissue (limb) allografts in rats. III. Development of donor-host lymphoid chimeras in long-term survivors.

Eight LEW rat recipients possessing long-term-surviving (206-701 days) LBN vascularized hind limb allografts (CTAs) were tested for donor-host lymphoid chimerism. The recipients received various cyclosporine (CsA) treatment protocols in order to induce indefinite CTA acceptance. Histological examination of long-term-surviving CTAs demonstrated normal-appearing bone marrow in the donor limb. Lymphocytes isolated from host hemopoietic tissues (peripheral blood and/or spleen) by ficoll-hypaque density gradient centrifugation were tested against LEW-anti-BN antisera. Comparisons were made to standard curves employing various known concentrations of LBN and LEW cell combinations. The level of lymphocyte agglutination (dependent variable) showed a significant (P less than 0.025-0.005) linear relationship to the concentration of LBN donor cells (independent variable) present. Lymphocyte suspensions isolated from long-term CTA host peripheral blood and/or spleen showed a mean of 19.7% (+/- 9.7-95% confidence interval) donor LBN mononuclear cells present. Thus, it appeared that lymphoid cells originated from, and/or were released from LBN donor bone marrow into the circulation, resulting in chimeric repopulation of hemopoietic tissues. The presence of donor immunocytes in these limb allograft recipients may have been beneficial, and thus could have helped contribute to the long-term CTA survival observed.

Animals↗
PubMed1985

Composite tissue (limb) allografts in rats. I. Dose-dependent increase in survival with cyclosporine.

The dose-response effect of cyclosporine on rat limb transplant prolongation was investigated across the LBN-to-LEW histocompatibility barrier. This composite tissue allograft model has been shown to represent a strong transplantation barrier. Median limb allograft survival times increased in a dose-dependent manner with low cyclosporine doses, and then reached a plateau at higher levels. The cyclosporine dose that produced half-maximal survival based on a 20-day treatment was only 3.7 mg/kg/day. Histopathology revealed that the rejection process was distinctly different in limb allografts treated with cyclosporine compared with non-cyclosporine-treated controls. Rejection appeared to be delayed or partly arrested in certain areas of cyclosporine-treated limb allografts. These studies represent an initial step in laying the experimental foundation for clinical transplantation of composite tissue allografts using cyclosporine-induced immune suppression.

Animals↗
PubMed1985

Composite tissue (limb) allografts in rats. II. Indefinite survival using low-dose cyclosporine.

Cyclosporine has reawakened interest in transplantation of peripheral composite tissue allografts (CTA) of skin, muscle, bone, vessel, and nerves. The purpose of this study was to examine whether cyclosporine could produce indefinite survival of CTA. Two groups of LEW recipients of LBN limb transplants were given different long-term treatments of cyclosporine. Tolerance was achieved in many of the animals. Several possibilities for the mechanism of this tolerance are discussed.

Animals↗
PubMed1984

Malignant lymphoma of the meninges in two dogs.

Two cases of malignant lymphoma of the leptomeninges in dogs are described. Both involved the subarachnoid space overlying the cerebrum and cerebellum and in one dog there was infiltration of neoplastic lymphocytes into the leptomeninges of the cervical spinal cord and nerve roots. These cases appeared to represent primary meningeal lymphoma, except that lymphoma was present in an ovary of one of the dogs and here the meningeal lymphocytes were demonstrated to be B cells by the peroxidase-antiperoxidase method for cytoplasmic immunoglobulin. Meningeal lymphoma, primary or metastic, is rare in dogs. The differential diagnosis is discussed and includes reticulosis, sarcomatosis of the meninges, and the diffuse spread of an oligodendroglioma in the subarachnoid space. A tentative diagnosis of meningeal lymphoma in these cases could be made by examination of the cerebrospinal fluid cells.

Animals↗
PubMed1983

Hepatic and gastric amebiasis in black and white colobus monkeys.

Three cases of hepatic amebiasis and one case of gastric amebiasis were diagnosed in black and white colobus monkeys during a 9-month period. The diagnosis was difficult because of the absence of trophozoites and cysts in the feces and because of few trophozoites found in many of the hepatic lesions. Indirect hemagglutination titers were diagnostic in 2 monkeys.

Amebiasis↗
PubMed1982

Efforts to enhance survival of limb allografts by prior administration of whole blood in rats using a new survival end-point.

Injecting whole blood into the recipient before surgery can significantly prolong renal transplant survival in rats. Therefore, experiments were performed in rats to study the effects of prior administration of whole blood on the survival of limb allografts. Tests to quantitate survival of the allografts included monitoring the internal temperature of the leg, assaying serum creatine kinase levels, and testing for alloantibodies. Lewis recipients of (BN x LEW)F1 limb transplants that received 1 ml of BN or (BN x LEW)F1 whole blood before surgery had mean survival times that were longer compared with controls as measured by a 10 F change in temperature. In a test-retest experiment, decline of temperature proved to be a reliable quantitative determination of limb allograft survival since a difference of only 5.6% was observed in the mean number of days of graft survival between two separate groups of control Lewis recipients. Moreover, combined data demonstrated that control Lewis recipients of (BN x LEW)F1 limb allografts averaged 24.0 days of graft survival based on a 10 F decline in temperature with a 95% confidence interval of +/- 6.3 days. It is concluded that prior administration of whole blood can produce significant prolongation of survival in organ transplantation, but it is not as effective in enhancing survival of limb allografts. It is also concluded that internal temperature measurement of limb allografts is an easy, effective, and quantitative method of monitoring rejection.

Animals↗
PubMed1982

Effect of molybdate on androgen receptor levels in canine prostate.

A comparative study on the stabilizing effect of sodium molybdate on androgen receptors was performed using canine prostates. Prostates from intact male dogs of mixed breeds were run in parallel sucrose density gradient analyses, using buffer systems with or without molybdate. Prostates that were homogenized in a molybdate buffer showed a significant increase in androgen receptor content relative to those in a molybdate-free system.

Animals↗
PubMed1982

Increased severity of urinary tract infection and bacteremia in mice with urinary bladder injury induced by cyclophosphamide.

The effect of cyclophosphamide on urinary tract infection was studied, using Pseudomonas aeruginosa in a murine model. Urinary tract infections were produced by injecting P. aeruginosa through a urethral catheter into the bladders of mice. The number of P. aeruginosa organisms in the bladder tissue and kidneys, histopathology, peripheral leukocyte count, and antibody response to P. aeruginosa was measured. The local effect of cyclophosphamide on the bladder was determined by measuring the bladder tissue water and examining the histopathology. Cyclophosphamide increased the susceptibility of mice to P. aeruginosa urinary tract infection, resulting in marked cystitis and an increase in renal infection, bacteremia, and mortality. These changes correlated with the toxic effect of cyclophosphamide on the wall of the bladder rather than with peripheral leukopenia or failure of antibody response.

Animals↗