Kinetic characterization of fragment binding in AmpC ß-lactamase by high-throughput molecular simulations.

Small molecules used in fragment-based drug discovery form multiple, promiscuous binding complexes difficult to capture experimentally. Here, we identify such binding poses and their associated energetics and kinetics using molecular dynamics simulations on AmpC ß-lactamase. Only one of the crystallographic binding poses was found to be thermodynamically favorable; however, the ligand shows several binding poses within the pocket. This study demonstrates free-binding molecular simulations in the context of fragment-to-lead development and its potential application in drug design.

Use of autologous bone marrow mononuclear cells and cultured bone marrow stromal cells in dogs with orthopaedic lesions.

The aim of the study is to evaluate the clinical application in veterinary orthopedics of bone marrow mononuclear cells (BMMNCs) and cultured bone marrow stromal cells (cBMSCs) for the treatment of some orthopaedic lesions in the dog. The authors carried out a clinical study on 14 dogs of different breed, age and size with the following lesions: 1 bone cyst of the glenoid rime; 2 nonunion of the tibia; 3 nonunion of the femur; 2 lengthening of the radius; 1 large bone defect of the distal radius;1 nonunion with carpus valgus; 4 Legg-Calvé-Perthés disease. In 9 cases the BMMCNs were used in combination with a three dimensional resorbable osteogenic scaffold the chemical composition and size of which facilitates the ingrowth of bone. In these cases the BMMNCs were suspended in an adequate amount of fibrin glue and then distribuited uniformly on a Tricalcium-Phosphate (TCP) scaffold onto which were also added some drops of thrombin. In 1 case of nonunion of the tibia and in 3 cases of Legg-Calvè-Perthés (LCP) disease the cultured BMSCs were used instead because of the small size of the dogs and of the little amount of aspirated bone marrow. X-ray examinations were performed immediately after the surgery. Clinical, ultrasounds and X-ray examinations were performed after 20 days and then every month. Until now the treated dogs have shown very good clinical and X-ray results. One of the objectives of the study was to use the BMMNCs in clinical application in orthopaedic lesions in the dog. The advantages of using the cells immediately after the bone marrow is collected, are that the surgery can be performed the same day, the cells do not need to be expanded in vitro, they preserve their osteogenic potential to form bone and promote the proper integration of the implant with the bone and lastly, the technique is easier and the costs are lower.

Engineered bone from bone marrow stromal cells: a structural study by an advanced x-ray microdiffraction technique.

The mechanism of mineralized matrix deposition was studied in a tissue engineering approach in which bone tissue is formed when porous ceramic constructs are loaded with bone marrow stromal cells and implanted in vivo. We investigated the local interaction between the mineral crystals of the engineered bone and the biomaterial by means of microdiffraction, using a set-up based on an x-ray waveguide. We demonstrated that the newly formed bone is well organized inside the scaffold pore, following the growth model of natural bone. Combining wide angle (WAXS) and small angle (SAXS) x-ray scattering with high spatial resolution, we were able to determine the orientation of the crystallographic c-axis inside the bone crystals, and the orientation of the mineral crystals and collagen micro-fibrils with respect to the scaffold. In this work we analysed six samples and for each of them two pores were studied in detail. Similar results were obtained in all cases but we report here only the most significant sample.

In vitro productive infection of non polarised cervical and rectal biopsies by syncytium-inducing and non syncytium inducing primary HIV-1 isolates.

An in vitro model was used to study the transmission of HIV-1 primary isolates with different biological phenotype to cervical and rectal non polarised bioptic fragments. The method described allowed the productive infection of both cervical and rectal tissues and the virus produced could be propagated onto peripheral blood mononuclear cell cultures. Syncytium-inducing and non-syncytium inducing viral isolates were equally able to produce infection and replication.

Intracellular and cell-free (infectious) HIV-1 in rectal mucosa.

The intestinal mucosa contains most of the total lymphocyte pool and plays an important role in viral transmission, but only slight attention has been given to the immunological and virological aspects of human immunodeficiency virus-1 (HIV-1) infection at this site. In this study, before initiating or changing antiretroviral therapy, paired blood samples and rectal biopsies (RB) were obtained from 26 consecutive HIV-infected subjects. HIV-1 isolation and biological characterization, DNA, and HIV-1 RNA titration were assessed, as were in vitro tumor necrosis factor-alpha (TNF-alpha) and interleukin-beta (IL-1beta) spontaneous production. The rate of HIV-1 isolation from peripheral blood mononuclear cells (PBMCs) and RBs was 75% and 58%, respectively. All RB-derived isolates were nonsyncytium inducing (NSI), independent of the phenotype of blood-derived isolates. Proviral DNA and detectable HIV-1 RNA levels were measured in 100% and 77% of RBs, respectively. A statistical correlation was observed between HIV-1 DNA and HIV-1 RNA levels in rectal mucosa (P = 0.0075), whereas no correlation was found between these levels in blood samples (P > 0.05). Antiretroviral treatment did not seem to influence HIV-1 detection in RBs. Higher levels of in vitro proinflammmatory cytokine production were found in the RBs of most infected patients when compared with healthy controls. Therefore, the rectal mucosa is an important HIV-1 reservoir that demonstrates a discordant viral evolution with respect to blood. Both the virus type and the mucosa pathway of immunoactive substances might have important implications for therapeutic decision-making and monitoring and could influence the bidirectional transmission of HIV-1 in mucosal surfaces.

"In vitro" spontaneous production of B-chemokines by endocervical and endometrial short-term bioptic cultures.

Several studies indicate that HIV-1 is present in the cervico-vaginal tissues and secretions of infected women representing an important determinant of both sexual and mother-to-child transmission. HIV-1 genital shedding is influenced by various factors; among these, proinflammatory cytokines, in particular the beta/C-C chemokine group (RANTES, MIP-1alpha and MIP-1beta), are known to suppress HIV-1 replication and thus might affect both sexual and vertical transmission. This study aimed to standardize a procedure to measure "in vitro" uterine spontaneous chemokine production by means of short-term cultures of endocervical and endometrial bioptic fragments. In most cases, "in vitro" chemokine production was observed in both fragment cultures. These results further confirm that beta/C-C chemokines exist in the female genital tract and that uterine mucosa actively produces basal levels of these immuno-active substances. This method constitutes a useful approach to evaluate cytokine production and expression in the female genital tract, their influence on HIV-1 expression and infectivity in this site, and their possible role in viral transmission.

Posttranslational modifications of bone collagen type I are related to the function of rat femoral regions.

This study analyzes the relationship between the function of femoral regions in the rat and the extent of collagen type I posttranslational modifications, to assess whether the different functional roles, i.e., mechanical or metabolic, of the bone tissues are related to the molecular structure of the matrix. For this purpose, 18 female, 100-day-old Sprague-Dawley rats were sacrificed, under anesthesia, and their femurs were removed and dissected free of adhering tissue. The spongy bone of the proximal metaphysis and the diaphysis were then selected as regions exerting prevalently a mechanical function, and the spongy bone of the distal metaphysis was selected as mainly related to metabolic function. Bone prepared from these regions was used to extract and purify the major component of the matrix, type I collagen. The content of hydroxyproline, hydroxylysine, glycosylated hydroxylysine, and pyridinium crosslinks was evaluated and the amount of each compound was expressed as a molar ratio to hydroxyproline. The amount of glycosylated hydroxylysine and pyridinium crosslinks in the distal metaphysis are significantly different from the amounts measured both in the diaphysis and the proximal metaphysis. On the contrary, the amounts of the same compounds in the diaphysis and the proximal metaphysis are statistically the same. The amount of free hydroxylysine, however, appears to be different in the proximal metaphysis and in the diaphysis. The conclusion is that matrix composition differs among different skeletal regions according to the main function they exert.

Phenotypic patterns of HIV-1 clonal populations during highly active antiretroviral therapy (HAART).

Several studies have demonstrated that during HIV-1 infection many different viral clones may co-exist in the same individual. These clones may differ regarding their biological phenotype and may influence both the natural history of infection and the clinical response to antiretroviral therapy. The aim of the present study was to investigate the influences of combination therapies including protease inhibitors (HAART) on the phenotypical pattern of HIV-1 biological clones in peripheral blood mononuclear cells. Viral isolation and biological characterisation of bulk isolates and clonal viral isolates were performed on two AIDS patients, before and after three months of antiretroviral therapy. A decrease of viral load in plasma specimens in association with a change of clonal composition during antiretroviral therapy was observed in both patients during treatment. Before therapy both of the patients had a syncytium inducing (SI) bulk isolate and the majority of the biological clones were characterised as SI. After treatment, the bulk isolates were still SI in both cases, but the majority of biological clones were characterised as non-syncytium inducing (NSI). These results suggest that HIV clonal composition and relative phenotypic pattern undergo different changes not only during the natural course of HIV infection but also while patients are on antiretroviral combination therapy.

Post-natal bone growth in the semicircular canals of the dog.

Dogs from the same litter, divided into three groups aged 10, 25, and 50 days, received an intraperitoneal injection of tetracycline for two successive days. The temporal bones were fixed, embedded in methylmethacrylate, sectioned in to a single 100 microns thick section along the main axis of the anterior and lateral semicircular canals, grounded by hand to 30 microns and observed at UV light. The new bone tissue is laid down both at the endosteal and endochondral bone of the anterior and lateral semicircular canals. The bone deposition decreases with the age of the animal and earlier at the endosteum than at the endochondral bone.

A topographical analysis of the post-natal bone growth in the cochlea of the dog.

The distribution of post-natal bone deposition was examined in the cochlea of 10-, 25-, 50- and 90-day-old dogs that had been intraperitoneally injected with tetracycline (20 mg/kg) five days before sacrifice. The temporal bones were embedded in methylmethacrylate and sectioned in a single mid-modiolar section 30 microns thick. The post-natal bone deposition occurs both on the periosteal surfaces and on the vascular canals of the endochondral layer until the age of 90 days. Scattered bone deposition is also shown on the endosteal layer of the three turns and on the spiral lamina until the age of 25 and 10 days respectively. The percentage extension of the osteogenetic fronts shows a higher value at the periosteal layer than at the endochondral or endosteal layers.

Intermittent compressive load stimulates osteogenesis and improves osteocyte viability in bones cultured "in vitro".

The effect of mechanical stresses on osteogenesis, the viability of osteocytes and their metabolic activity in organ culture of bones intermittently loaded "in vitro" are reported. Metatarsal bones, isolated from 12-day-old rats, were cultured in BGJb medium (with 10% foetal calf serum, 75 micrograms/ml of ascorbic acid, 100 U/ml of penicillin and 100 micrograms/ml of streptomycin), in humidified air enriched by 5% CO2 and 30% O2, and loaded in our original device for 1/2 an hour at 1 Hz. homotypic isolated and unloaded bones, cultured in the same medium, were taken as controls. The ALP (alkaline phophatase activity) increases in the media of loaded bones in comparison with the control bones. The percentage of viable osteocytes is significantly greater in loaded than in control bones. TEM observations demonstrate that in both loaded and control unloaded bones, osteocytes show well developed organelle machinery and several gap junctions with adjacent cellular processes. In the cells of loaded bones, however, a higher number of cytoplasmic organelles and gap junctions were found. In particular, RER increases twice, gap junctions three times. The induced osteogenesis and the TEM observations demonstrate the suitability of this experimental model and support the recent advanced hypothesis according to which the mechanical loading may exert a trophic function on osteocytes, stimulating both the proteic synthesis in the above-mentioned cells and the cell-to-cell communication. Furthermore, the loading is likely to exert a biological stimulus on osteoblasts via signalling molecules produced by osteocytes.

The structure of spongious trabeculae in relation to age in man.

In various bones from 40-50 year old men, numerous osteons were found in spongy trabeculae. As the bones examined are subjected to different mechanical loads, and, in all samples, the osteon frequency appeared to increase with the increase in the trabecular thickness, the endotrabecular osteons was supposed to improve the deep-seated cell metabolism. Because the architecture of the spongiosa changes with age, we studied the endotrabecular osteons in the same bone but in individuals of different age. Human femurs from the collection of our Institute were divided into three groups, corresponding to the 3rd, 5th, and 7th decade of life. Trabeculae were dissected from the proximal end in correspondence of the head, lateral and medial arrangement of the neck. On the serially transverse section the thickness of trabecular tracts with or without osteons, the distance of the deep-seated osteocytes from filtering surfaces, and the orientation of the collagen fibres have been analysed. The mean thickness of the trabeculae decreases with age in the head and lateral arrangement but not in the medial one. The trabecular tracts with osteons are, on the average, significantly thicker than those without them. Almost all endotrabecular osteons show alternate lamellae, notwithstanding that the trabeculae examined are subjected to different type of mechanical forces. These findings would confirm our previous hypothesis that the presence of osteons in the trabeculae responds to metabolic request rather than to mechanical one.

Morphological studies of hypomineralized enamel of rat pups on calcium-deficient diet, and of its changes after return to normal diet.

BACKGROUND: Micro-hardness investigations have shown that rat pups nursed by mothers on a low calcium diet and weaned with the maternal calcium-deficient diet develop hypomineralized enamel. The inorganic and organic components of this enamel, their relationships, and their changes after return to normal diet have been studied by light and electron microscopy. METHODS: The maturation zone of incisor enamel has been studied in: (1) rats nursed for 20 days by mothers on a low calcium diet and weaned for 30 days with the same diet (E1 enamel); (2) rats that after the calcium-deficient diet were fed normal diet for 10 days (E2 enamel); and (3) rats nursed for 20 days by mothers on a normal diet and weaned for 30 days with a normal diet (controls). RESULTS: The results showed that E1 enamel was hypomineralized, as noted by its Azure II-Methylene blue stainability in undecalcified sections, its light staining with the von Kossa method, and its ultrastructure. E1 crystallites, although present throughout the whole enamel, were thinner than those of E2 enamel, which were similar to those of controls. E1 interrod crystallites were thicker in the intermediate than in the dentinal zone and were thicker than rod crystallites. Organic matrix was present throughout the whole E1 enamel. Its organic components (crystal ghosts) had the same shape, arrangement, and organization as those of inorganic crystallites. Crystal ghosts were greatly reduced in E2 enamel and in controls. CONCLUSIONS: The results lead to the conclusions that: (1) E1 enamel is hypomineralized, and its degree of calcification is restored by return to a normal calcium diet; (2) intra- and interprismatic calcification occurs in a different way; (3) crystallite thickness is initially greater in dentinal than in the superficial zone and is reversed as crystallite growth is completed; and (4) loss of enamel proteins is necessary for completion of crystallite growth and not for crystallite formation.

Morphometric analysis of the deposition and mineralization of enamel and dentine from rat incisor during the recovery phase following a low-calcium regimen.

The administration of a low-calcium diet to pups nursed by a mother on the same diet has been shown to induce a slowing of growth. A reduction of the apposition rate of dentine, which was normally mineralized, and a dramatic reduction of the extent of mineralization of enamel, whose organic matrix was otherwise produced in an almost normal amount, was observed in the incisors of these animals. Modifications of the mineral apposition rate of dentine, measured after administration of tetracycline (10 mg/kg), and the thickness and the microhardness of the two tissues, the latter being an expression of the degree of mineralization, were now investigated when hypocalcic pups were restored to a normal-calcium diet for 10 or 60 days. Enamel microhardness was increased by more than 60% after only 10 days of restored diet and had become the same as in the control tissue after 60 days, without any significant increase in thickness. Dentine thickness and mineral apposition rate increased significantly, to become similar to those of the controls after 60 days of restored diet. In dentine there was no significant variation of microhardness between experimental pups and controls, either during the low-calcium diet or the restorative period. These results indicate that the deposition of the organic matrix of enamel is a process independent from that of its mineralization, and that the mineralization of the organic matrix happens by its replacement even a long time after its deposition. In contrast, the deposition and mineralization of dentine are strictly interdependent processes, at least in these experimental conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

[The concentration of osteocalcin in the culture media of bone cultured in vitro subjected to intermittent mechanical load with the addition of 1,25(OH)2D3]. / La concentrazione di osteocalcina nel terreno di cultura di ossa coltivate in vitro sotto carico meccanico intermittente con l'aggiunta di 1,25(OH)2D3.

The osteocalcin concentration decreases in the medium of bones submitted to intermittent mechanical forces in organotypic culture (6). The functional significance of this behaviour is unknown. To investigate the dynamics of the osteocalcin production, we added 1,25(OH)2D3 to the culture medium to stimulate osteoblastic production of the osteocalcin. The bones were isolated from 12 day-old rats, placed in culture medium added with 10(-8) M 1,25(OH)2D3 and subjected 1/2 h daily to an intermittent mechanical load (11.6 Kg/mm2) at 1 Hz frequency. 12, 24 and 48 hours after the loading the alcaline phosphatase activity (p-nitrophenol as substrate) and the osteocalcin concentration (RIA method) were evaluated in the media. The phosphatase activity does not change in the control bones, while it significantly increases in the loaded bones 24 h after loading (fig. 1). The osteocalcin concentration increases significantly in the control bones, with a peak at 24 h; in the loaded ones, it does not increase at 24 h with respect to 12 h, while it increases 48 h after loading, but at a lower level than the control bones. Since the increase of the alcaline phosphatase activity is a sign of new bone production, our results indicate that an osteoid deposition is likely to take place in the loaded bones, not in the control ones. The increase in the control bones of osteocalcin concentration is in agreement with the results of other researches (7), and indicates that the osteoblasts of this experimental system are able to produce osteocalcin under appropriate conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

[Quantitative variations of osteocalcin in the culture media of bones subjected to intermittent mechanical loads in vitro]. / Variazioni quantitative dell'osteocalcina nel terreno di cultura di ossa sottoposte a carico meccanico intermittente in vitro.

A study has been carried out on the dynamics of the osteogenesis induced in vitro by an intermittent mechanical load applied on intact metatarsals isolated from 12 day-old rats. The metatarsals, as soon as isolated, were deprived of both the ends and placed in culture medium (BGJb enriched with 10% FCS, 65 micrograms of ascorbic acid, penicillin, strepto) without a mechanical load. After 4-5 hours, half the bones were placed in our device, described in our previous paper (2), and submitted to a daily cycle of an intermittent mechanical load (11.6 g/mm2) 1/2 h long, at 1 Hz frequency. The remaining bones, used as control, were cultured in the same medium, without any mechanical load. 24, 48 and 72 hours from the first application of the load the bones were fixed, embedded (decalcified or undecalcified) and serially sectioned. The sections were stained with toluidin blu and trichromic Masson-Goldner. On the perimeter of 5 non-consecutive sections of each bone the number of the osteoblasts at 250x, and the nuclear volume of the same cells at 1000x were evaluated. In the culture media the alcaline phosphatase activity (p-nitrophenol as substrate) and the concentration of osteocalcin (RIA) were measured. The number and nuclear volume of the osteoblasts are higher in the loaded than in the control bones (tab. 1). The alcaline phosphatase activity does not vary in the control bones between 24 and 72 h, while it increases in the loaded bones. The concentration of the osteocalcin shows a slight increase at 48 h in the control bones, and a significant decrease int he loaded bones (fig. 1).(ABSTRACT TRUNCATED AT 250 WORDS)

Bone tissue kinetics in the surgically disarticulated dog incus.

The incus of the right ear from 4 growing mongrel dogs was surgically disarticulated and left in the middle ear space. The external auditory canal was then filled with teflon paste and sutured. After 6 weeks (D-6 group) and 13 weeks (D-13 group) the animals were sacrificed. The right experimental incus and the left control one were embedded in methyl methacrylate and sectioned in single 50-microns-thick sections according to the principal axis of the two processes. On the microradiographs of each section we evaluated the thickness of the body and of both processes and the percentage area of the primary channels of the secondary osteons and that of the appositional bone tissue. The thickness of the body and of the two processes was more pronounced in all the experimental incuses, in which 6% (in D-6) and 8% (in D-13) of the total area were occupied by new appositional woven bone. In the body of the D-13 group, 9% of the pre-existing bone was substituted by secondary osteons. The results indicate that the incus react to the variations of mechanical stimuli.

Effect of intermittent mechanical force on bone tissue in vitro: preliminary results.

The structure of metatarsal bones from 18-day-old rats subjected to intermittent mechanical force in organ culture are reported. The application of mechanical force enhances the osteoid thickness and osteoblast number in the periosteum and increases the number of viable osteocytes. These results indicate that (1) the mature bone tissue survives in organ cultures; (2) the mechanical forces better preserve the structure of the osteocytes and stimulate the osteoblasts, and (3) stimulate the osteogenesis.

Permeability-related structures in developing and mature microvessels of the chicken optic tectum.

The mode and the temporal sequence of the modifications undergone by permeability-related structures in the neural microvessels have been ultrastructurally and morphometrically investigated in optic tecta of 6, 14, and 18 incubation day (i.d.) chicken embryos and of 30 day chickens. Horseradish peroxidase was utilized as a permeability marker. The endo- and exocytosis-related structures (vesicles and vacuoles) and the interendothelial junctions remarkably change during development: the density of the vacuoles is decreased at the 14th i.d., while that of the vesicles becomes significantly low at the 18th i.d., both reaching lowest values in the chicken; the passage of the marker through the endothelial junctions begins to be hindered from the 14th i.d., parallel to the perivascular arrangement of astrocytic glia endfeet, and it is completely blocked at hatching time. The findings suggest that the optic tectum microvessels are permeable, and thus immature, in the early development and progressively acquire morphofunctional features of vessels provided with barrier devices during the pre- and post-natal development of the brain.