Patterns of age-dependent changes in the numbers of lymph follicles and germinal centres in somatic and mesenteric lymph nodes in growing C57Bl/6 mice.

The timing of the first appearance of lymph follicles and germinal centres in various lymph nodes, and the ways in which numbers of these and IgM-synthesising cells increase within the nodes, were investigated in male and female C57Bl/6N mice aged from 4 d to 16 wk. The lymphoid organs examined were the Peyer's patches, spleen, somatic (submandibular, deep cervical, brachial, axillary, inguinal and popliteal) and visceral (mesenteric and lumbar) lymph nodes. Primary follicles appeared in most somatic lymph nodes 6 d after birth. The number of follicles per node then increased rather sharply in larger lymph nodes and slowly in smaller nodes, up to 28 d of age, reaching a level which varied according to the location of the node. Thereafter, the number of follicles in the somatic lymph nodes increased only slightly to moderately, reaching a peak or plateau at 8-12 wk. In the mesenteric (ileocaecal) nodes, primary follicles first appeared at 12 d, then increased linearly during the suckling period and after weaning to reach a plateau at 8 wk of age. Germinal centres appeared in the submandibular and mesenteric nodes at 28 d and their numbers increased consistently in the latter, while remaining low in the former. The impact of possible 'natural' exogenous antigen stimulation of the various lymph nodes was estimated from the presence of IgM-synthesising cells and germinal centres. Differences between the patterns of age-dependent changes in the numbers of lymph follicles observed in the somatic and mesenteric lymph nodes during their ontogeny are discussed in relation to differences in the magnitude of the exogenous antigen stimulatory effect. We also found that the variations in the numbers of lymph follicles produced in somatic lymph nodes at different locations during the first 28 d after birth reflected differences in the dimensions of the body regions drained by a particular somatic lymph node at this stage of development.

Healing-promoting action of the new histamine H2-receptor antagonist N-ethyl-N'-[3-[3-(piperidinomethyl)phenoxy]propyl]urea with dual action on chronic gastric and duodenal ulcers induced by acetic acid in rats.

Healing-promoting actions of KU-1257 (N-ethyl-N'-[3-[3-(piperidinomethyl)phenoxy]propyl]urea, CAS 120958-90-9) were investigated in chronic gastric and duodenal ulcer models induced by acetic acid in rats and the effects were compared with those of famotidine and roxatidine acetate by gross or histological evaluation. KU-1257 markedly promoted the well-balanced healing of gastric ulcer at oral doses of 10-50 mg/kg x 2/day, as evidenced by the reduction of ulcer, regeneration of mucosa and proliferation of connective tissue. KU-1257 caused an increase in gastric mucus secretion in the regenerated mucosa around the gastric ulcers. Famotidine and roxatidine acetate failed to promote the healing of gastric ulcers even at 100 mg/kg x 2/day p.o. KU-1257 also significantly accelerated the healing of acetic acid-induced duodenal ulcers as well as famotidine and roxatidine acetate. These results indicate that KU-1257 is characterized by a potent promoting action on the healing of chronic ulcers, suggesting that the increase in gastric mucus secretion might be associated with the antiulcer actions of KU-1257 in part.

[Therapeutic efficacy of norfloxacin for experimental osteomyelitis in rabbits].

Norfloxacin (NFLX), a new quinolone antibiotic agent, was evaluated for its efficacy in experimental osteomyelitis in rabbits. Osteomyelitis was induced in male rabbits by the inoculation of 10(7) CFU/ml (0.1 ml) of Staphylococcus aureus (MIC for NFLX: 0.78 micrograms/ml) with 0.4 ml of 3% sodium tetradecyl sulphate into the medullary cavity of the proximal tibia. The rabbits were divided into 3 different groups of 4 animals each. The animals in 2 groups were orally administered with NFLX; 100 mg/kg once-daily (group 2) and 50 mg/kg twice-daily (group 3) for 7 days from the 6th hour after inoculation. Group 1 was established as a control without administration of NFLX. All animals were sacrificed on the 7th day after inoculation. Acute osteomyelitic changes were found microscopically in all animals in group 1. In each of the 2 therapeutic groups, incidence of microscopic changes was 50% associated with remission of S-sialic acid value. Thus, NFLX may be considered a useful antimicrobial agent for the treatment of suppurative osteomyelitis.

Lymph follicles and germinal centers in popliteal lymph nodes and other lymphoid tissues of germ-free and conventional rats.

A study was conducted to evaluate the influence of natural exogenous antigen stimulation on the development of lymph follicles in the peripheral lymphoid organs of the rat. The number of lymph follicles and germinal centers per popliteal node as well as the morphological features of popliteal nodes, mesenteric nodes and Peyer's patches were compared between 8-week-old male Sprague-Dawley rats reared in germ-free, specific pathogen-free (SPF) and conventional environments. In mesenteric nodes and Peyer's patches from conventional and SPF rats, almost every follicle contained a germinal center. In the mesenteric nodes from germ-free rats, only 9 of 195 lymph follicles examined contained a germinal center, but interestingly, in Peyer's patches all the lymph follicles examined showed a fairly well developed germinal center. The popliteal nodes from germ-free rats had no germinal centers and each node contained about 80 lymph follicles. In six conventional rats and two of five SPF rats used, the number of lymph follicles per popliteal node usually ranged from 100 to 130, and some lymph follicles contained a germinal center. However, in the other three SPF rats the popliteal node on both sides showed no germinal center, and each contained almost the same number of lymph follicles as the popliteal nodes of other SPF and conventional rats. The present results are consistent with the view that even in the absence of exogenous antigen stimulation, a regional lymph node of the germ-free rat develops a substantial number of primary lymph follicles by way of a non-immunological cellular activity, and that natural exogenous antigens may influence the development of lymph follicles by stimulating the cellular activity rather than evoking the humoral immune responses.

Toxicokinetic study of norfloxacin-induced arthropathy in juvenile animals.

A toxicokinetic study of norfloxacin-induced arthropathy in juvenile animals was undertaken using nalidixic acid as a standard drug. Norfloxacin and nalidixic acid were subcutaneously administered to rats and rabbits, orally administered to dogs, and norfloxacin was orally dosed to monkeys once a day for 7 consecutive days. Of the dose levels tested, the minimum arthropathic doses of norfloxacin were 100, 25, and 50 mg/kg/day in rats, rabbits, and dogs, respectively. At these doses, the peak serum concentrations (Cmax) on Day 6 were 16.1, 9.73, and 5.11 micrograms/ml, and the areas under the serum concentration/time curve (AUC0----infinity) were 31.9, 22.9, and 26.2 micrograms.hr/ml, in respective animals. Monkeys showed no arthropathy with norfloxacin at doses of less than 500 mg/kg/day, at which the Cmax and AUC0----infinity were 15.6 micrograms/ml and 103 micrograms.hr/ml, respectively. The minimum arthropathic doses of nalidixic acid were 50, 100, and 25 mg/kg/day in rats, rabbits, and dogs, respectively. The Cmax and AUC0----infinity of nalidixic acid were higher than those of norfloxacin in all animals. Joint tissues took up more norfloxacin than nalidixic acid, but when arthropathy was present the articular cartilage concentrations of the two drugs were in the same range. The penetration of norfloxacin into the articular cartilage was the same regardless of the joint's anatomical locations, but differed among species, being highest in rats and lowest in monkeys. The Cmax and AUC0----infinity of norfloxacin in animals at their arthropathic doses were far higher than those measured clinically in children, whereas those of nalidixic acid in animals did not differ much from its clinical parameters.

Formation of lymph follicles in draining lymph nodes after local injection of various antigenic substances in mice.

Formation of lymph follicles in draining popliteal lymph nodes was examined in 8-week-old, male C57Bl/6 mice which had been injected in the rear footpad with any one of eleven test substances including thymus-dependent and thymus-independent antigens, and killed after 6-14 days. HGG (10-100 micrograms), MGG, tetanus and diphtheria toxoids (2-10 Lf) and influenza HA vaccine (35 CCA) induced germinal centers in association with existing follicles, but failed to produce new follicles in draining nodes. KLH (10-100 micrograms), SRBC (1 X 10(8)) and formalin-killed pertussis organisms (5 X 10(8)) induced germinal centers in existing follicles and also produced new follicles which soon developed germinal centers. Levan and PVP (10-100 micrograms) induced neither germinal centers nor new follicles. Ferritin (100 micrograms) virtually failed to induce germinal centers but produced a significant number of new primary follicles. In further experiments, artificially aggregated substances were examined with regards to their ability of inducing lymph follicle formation in draining nodes. Precipitated proteins such as alum-precipitated PHA, HGG, tetanus and diphtheria toxoids, "Sepharose"-PHA and "Sepharose"-HGG induced a significant number of new follicles. These observations suggest that efficient follicle formation is associated with particulate and high-molecular-weight antigens which are liable to be phagocytized, whereas soluble, poorly phagocytized antigens tend to be inefficient. Soluble proteins may be effective if given in precipitated form. Thymic dependency appears to be irrelevant. The present results point to a possible participation of macrophages in the mechanism of follicle formation.

Histological observations on rat popliteal lymph nodes after blockage of their afferent lymphatics.

Afferent lymphatic vessels to the popliteal lymph node in the rat were blocked, and the node was histologically examined 2-35 weeks later. After the operation, the node was reduced in size and its lymphoid structures, such as germinal centers, lymph follicles and deep cortex units, were decreased in size and number. At 16 weeks, the lymphoid organization of the node reached a minimal level, but the node still exhibited reduced numbers of lymphoid structures. The lymphoid parenchyma of the node, although reduced in size, showed no noticeable change in cellular density during the period of observation. The changes observed in the popliteal node following blockage of the afferent lymphatics were interpreted as resulting from a reduced supply via the afferent lymph of antigens and other factors on which the development and persistence of the lymph node structures are believed to depend.

Formation of lymph follicles and germinal centers in draining lymph nodes after local injection of phytohemagglutinin and lipopolysaccharide in mice.

Changes in the number of lymph follicles and germinal centers in draining popliteal lymph nodes were investigated in 8-week-old mice injected with either phytohemagglutinin (PHA) or lipopolysaccharide (LPS) into the footpad of the left hind leg. The dose of PHA injected ranged from 10 micrograms to 1 mg, and that of LPS, from 2 to 200 micrograms. In unstimulated animals, the popliteal lymph nodes contained only a small number of germinal centers, and many of the lymph follicles in the nodes were in the form of primary follicles. In the draining lymph nodes, regardless of the dose injected, PHA induced germinal center development in existing primary follicles, but eventually failed to stimulate the formation of new lymph follicles and germinal centers. On the other hand, LPS not only induced germinal centers in the existing follicles, but also stimulated the formation of new primary follicles, many of which then developed germinal centers. The occurrence of new follicles in the LPS-treated lymph nodes was dose-dependent, and LPS appeared to cause de novo formation of follicles.

Reconstruction of lymph follicles in the mouse popliteal lymph node after X-irradiation damage.

In order to suppress possible "de novo" formation of follicles in the node after irradiation, animals to be irradiated received surgical operations to block the afferent lymphatics to the popliteal node on one side, the corresponding node on the other side left intact. 600 R whole body X-irradiation severely destroyed lymph follicles in the nodes of both sides, but the number of follicles in the node on either side recovered toward normal by 3 weeks after irradiation, regardless of whether they contained germinal centers or not. In animals exposed to 1,000 R whole body X-irradiation and infused with bone marrow cells, no lymph follicles were observed in the nodes on day 9. If such treated animals were given 1.0 X 10(8) lymph node cells on day 5, lymph follicles were reconstructed in the nodes of both sides on day 9. In animals irradiated with 1,000 R to the lower half of the body, the number of follicles in the node on either side remained comparable to that of the unirradiated control node. The results favor the interpretation that although X-irradiation destroys the lymphoid elements of the follicles, the stromata of follicles persist and preserve the ability to collect small lymphocytes, and that lymph follicles are reconstructed at the sites of the stromata persisting from damaged follicles.