Trichophyton mentagrophytes dermatophytosis in germfree guinea pigs

Primary and secondary Trichophyton mentagrophytes dermatophytosis was studied in germfree and conventionally-reared Strain 2 guinea pigs. Although the onset and early development of the primary cutaneous lesions appeared similar in both groups, the T. mentagrophytes monoassociated guinea pigs exhibited more severe skin ulcerations and took twice as long to heal as their conventionally-reared counterparts. Cutaneous reinfection of T. mentagrophytes monoassociated guinea pigs was also protracted; however, these lesions healed in about the same time as a primary infection on conventionally-reared guinea pigs. Germfree guinea pigs, sensitized by cutaneous infection with T. mentagrophytes, manifested 3 correlates of systemic cell-mediated immunity: (1) delayed-type hypersensitivity to intracutaneous injection of trichophytin antigen, (ii) in vitro blastogenesis of spleen and lymph node cells to polyclonal mitogens and Trichophyton antigens, and (iii) allergic contact dermatitis 48 hr following cutaneous reinfection. In an additional experiment, we observed that the time course and severity of a primary T. mentagrophytes infection of germfree guinea pigs was reduced by prior feedings with heat-killed T. mentagrophytes culture. These experiments confirm that the normal microbial skin flora is not required for initiation, development or clearance of T. mentagrophytes dermatophytosis. The disease was protracted and severe in T. mentagrophytes monoassociated guinea pigs, but was abbreviated following either active infection or feeding heat killed mentagrophytes culture. These results support the hypothesis that cutaneous T. mentagrophytes infection is a cell-mediated hypersensitivity disease similar to contact dermatitis.

Cutaneous basophil hypersensitivity and contact sensitivity after cutaneous Trichophyton mentagrophytes infection

The histopathology of cutaneous lesions and trichophytin skin test responses was examined by light microscopy after the infection of strain 2 guinea pigs with Trichophyton mentagrophytes. Skin biopsies were fixed and stained with procedures which allowed differentiation of the polymorphonuclear granulocytic leukocytes that were present in lesions or skin test reactions. Basophils comprised about one-third of the leukocytes infiltrating the 24 to 48-h trichophytin skin test reactions of guinea pigs sensitized by a cutaneous T. mentagrophytes infection. These results were comparable to the percentage of basophils counted in skin test lesions elicited by the contact agent dinitrochlorobenzene and are consistent with previously published descriptions of cutaneous basophil hypersensitivity. In contrast, the active T. mentagrophytes lesion in the skin of guinea pigs sacrificed at defined intervals after infection or reinfection did not appear to contain similarly elevated numbers of basophils. The early inflammation in primary T. mentagrophytes-induced skin lesions can be characterized histologically as a primary irritant dermatitis which evolves, during the course of the disease, into a chronic mononuclear inflammation. This shift apparently results from host sensitization to fungal antigens during infection and the concurrent development of acquired immunity. Reinfection of guinea pigs with T. mentagrophytes resulted in an accelerated cutaneous inflammation that was temporally and histologically similar to allergic contact dermatitis. These results support the hypothesis that contact sensitivity to T. mentagrophytes develops during the primary cutaneous infection of guinea pigs and is an early component of the hypersensitivity response to reinfection.

Immunoglobulin-containing cells in jejunal mucosa of children with protein-energy malnutrition and gastroenteritis

Jejunal biopsies from 20 well nourished children (average age 12.8 months) with gastroenteritis, and 20 children (average age 20 months) with protein-energy malnutrition were examined by immunofluorescent technique for immunoglobulins A, G, M, E, and D, and for epithelial glycoprotein secretory component. Compared with previous studies on normal infants, the children with gastroenteritis showed a moderate increase in IgA-containing cells, a large increase in IgM-containing cells, and no change in IgG-containing cells. These findings are similar to previously recorded findings on adults with gastroenteritis. In contrast there was a pronounced and highly significant decrease in IgA-containing cells in the jejunal mucosa of the children with protein-energy malnutrition. No significant differences were noted between the populations of IgG-, IgM-, IgE-, and IgD-containing cells in the two groups. It is suggested that this selective deficiency in mucosal IgA results from a delay in maturation of the secretory IgA system, and the mechanisms of such a deficiency are discussed.

Suppression of in vitro lymphocyte transformation during an experimental dermatophyte infection

During primary Trichophyton mentagrophytes infection of strain 2 guinea pigs, the colony-forming units (CFU) of fungi present within the lesion peaked between days 7 and 14, whereas the severity of the lesion itself peaked between days 11 and 16. Concomitant with the latter peak, a pronounced depression in the in vitro mitogenic activity of spleen cells (SPC) and lymph node cells (LNC) was observed. Only after resolution of the primary infection (day 21) did LNC show increased deoxyribonucleic acid (DNA) synthesis in the presence of fungal antigens. During cutaneous reinfection, there was no distinct peak fungal load and CFU appeared to decrease steadily during the accelerated course of a reinfection disease. LNC from guinea pigs with severe, ulcerated reinfection lesions generally exhibited a heightened response to fungal antigen in vitro. LNC from guinea pigs with mild reinfection dermatophytosis had depressed in vitro reactivity to mitogens and dermatophyte antigen. The suppression of blastogenic activity during dermatophyte infection appeared to be associated with autologous serum components, since increased DNA synthesis resulted when SPC or LNC were cultured with fetal calf serum. The depressed in vitro DNA synthesis of lymphocytes (cultured with dermatophyte antigens) that were harvested during reinfection was not accompanied by an impaired ability of infected guinea pigs to respond with a delayed-type hypersensitivity skin test in vivo. These results support the hypothesis that experimental T. mentagrophytes dermatophytosis is a cell-mediated hypersensitivity disease that can be modified by immunosuppressive control mechanisms elaborated or induced by the fungus.

Enzyme changes in rat small intestine during pregnancy and lactation

Small fluctuations in the activity of a number of important enzymes have been found during the intestinal hyperplasia and hypertrophy of pregnancy and lactation. The pattern of change differs between the enzymes studied, and for individual enzymes often varies between the jejunum and ileum. These results suggest that there must be a complex response to the signals that trigger hyperplasia in the mucosal epithelium.

Ultrastructure and capsule of Mycoplasma meleagridis

The ultrastructural study of Mycoplasma meleagridis utilized the electron microscope techniques of sectioning, histochemical staining, critical-point drying, and freeze etching. The predominant morphotype was a spherical form ranging in diameter from 200 to 700 nm. The other morphotypes were dumbbell-shaped cells interconnected by membranous tubules, and chains of streptococcal-like cells. These forms suggest replication by binary fission. An extracellular structure in the form of a capsular matrix was observed by staining with ruthenium red and potassium tellurite, and was also seen in specimens prepared by critical-point drying and freeze etching.

The mechanics of esophageal muscle contraction. Evidence of an inotropic effect of gastrin

To compare the mechanical properties of lower esophageal sphincter (LES) and esophageal circular smooth muscle, force-velocity determinations were made under various physiological conditions. Isotonic and isometric recordings of opossum circular muscle were used to obtain the velocity of shortening and force, respectively, during alterations in: (a) initial muscle length (preload), (b) afterload, (c) calcium concentration, and (d) gastrin I. Muscle contraction was elicited to the neurogenic response at the termination of electrical stimulation. A change in preload (muscle length) altered the peak force (Po) developed during an afterloaded contraction, but had only a minor effect on the maximum velocity of shortening (V max). At the length of optimal tension development, Lo, (preload, 1.5 g), the LES muscle had a V max of 6.1+/-0.2 mm/s and a Po of 17.7+/-0.7 g. The esophageal muscle at its Lo (preload, 2.0 g) had a V max of 6.3+/-0.5 mm/s and a Po of 18.1+/-1.2 g. A decrease in calcium from 2.5 mM to 1.0 mM significantly reduced the V max and Po of all muscle, but an increase in calcium to 5.0 mM increased these parameters only minimally. At a calcium of 1.0 mM, gastrin I increased both V max and Po of all muscle. This inotropic effect of gastrin I occurred at lower concentrations in LES muscle than in muscle from the upper esophagus. The power (force x velocity) and work (force x muscle shortening) of esophageal and LES muscle were calculated from these data. Both the work and power generated during esophageal and LES muscle contraction were determined by: (a) the initial muscle length as produced by the preload, (b) the afterload against which the muscle was contracting, and (c) the contractility of inotropism of the muscle, that is, the force-velocity curve on which the muscle was operating.