Effect of side group chemistry on the properties of biodegradable L-alanine cosubstituted polyphosphazenes

Biodegradable polyphosphazenes have been investigated for a variety of applications, such as controlled drug delivery matrixes, tissue-engineering scaffolds, membranes, and bone-type composites. In this study we have evaluated the effect of side group chemistry on the properties of biodegradable phosphazene polymers that contain ethyl alanato side groups together with ethyl glycinato, p-methylphenoxy, or p-phenylphenoxy side groups. The polymers were synthesized by a macromolecular substitution route. The molecular weights of aryloxy/amino acid ester cosubstituted polymers were much higher than the amino acid ester substituted polyphosphazenes described earlier. Polymer properties, such as glass transition temperature, hydrolytic degradation, surface wettability, tensile strength, and modulus of elasticity varied over a wide range following changes to the type of co-substituents on the polymer backbone. The glass transition temperatures varied from -10 to 35 degrees C and increased with the bulkiness of the side groups. Polymer films in phosphate buffer saline solution showed molecular weight declines ranging from 58% to >80% and mass loss ranging from 4% to 90% over a period of 7 weeks. Water contact angles for polymer films varied from 63 degrees to 107 degrees , with the highest angles for the alanine ethyl ester and p-phenylphenoxy cosubstituted polyphosphazene. The tensile strengths were in the range of 2.4-7.6 MPa and the modulus of elasticity was in the range of 31.4-455.9 MPa. Thus, in this study we have demonstrated the tunability of biodegradable polyphosphazenes to suit a range of biomedical applications.

Human osteoblast cells: Isolation, characterization, and growth on polymers for musculoskeletal tissue engineering

We performed a detailed examination of the isolation, characterization, and growth of human osteoblast cells derived from trabecular bone. We further examined the morphology, phenotypic gene expression, mineralization,and growth of these human osteoblasts on polyester polymers used for musculoskeletal tissue engineering. Polylactic-co-glycolic acid [PLAGA (85:15, 50:50, 75:25)], and poly-lactic acid (L-PLA, D,L-PLA) were examined. The osteoblastic expression of key phenotypic markers osteocalcin, alkaline phosphatase, collagen, and bone sialoprotein at 4 and 8 weeks was examined. Reverse transcription-polymerase chain reaction studies revealed that trabecular-derived osteoblasts were positive for all markers evaluated with higher levels expressed over long-term culture. These cells also revealed mineralization and maturation as evidenced by energy dispersive X-ray analysis and scanning electron microscopy. Growth studies on PLAGA at 50:50,75:25, and 85:15 ratios and PLA in the L and DL isoforms revealed that human osteoblasts actively grew, with significantly higher cell numbers attached to scaffolds composed of PLAGA 50:50 in the short term and PLAGA 85:15 in the long term compared with PLA (p < 0.05). We believe human cell adhesion among these polymeric materials may be dependent on differences in cellular integrin expression and extracellular matrix protein elaboration.

Role of splenectomy in chronic idiopathic thrombocytopenic purpura

AIM OF THE STUDY

To evaluate the usefulness of splenectomy and factors which predict long term remission in chronic idiopathic thrombocytopenic purpura (ITP).

METHODS

We reviewed the data of 364 patients diagnosed as chronic ITP between January 1983 to December 1996 of whom 71 patients underwent splenectomy. The patients were followed up for an average period of 58 months and the short and long term response to splenectomy were analyzed at the end of one month and 60 months, respectively.

RESULTS

At the end of one month after splenectomy, 82% had complete response, 7% partial response and 11% had no response. At the end of 60 months, 42% maintained complete response, 7% partial response, 34% had no response and 17% were lost to follow up. The results were statistically evaluated by using non-parametric test (Chi-square test) to age, sex, platelet count prior to treatment, initial response to steroids, time interval between diagnosis and splenectomy and post-operative platelet count. Of these factors only preoperative response to steroids (p value = 0.018303) and postoperative platelet count (p value = 0.013536) were found to be significant, statistically to predict long term remission. Age, sex, initial platelet count and time interval between diagnosis and splenectomy didn't seem to be statistically significant.

CONCLUSION

This study suggests, that patients with an initial complete response to steroids and a post-operative platelet count > 300 x 10(9)/L at the time of discharge were associated with a long term remission. Splenectomy in ITP is a safe procedure with minimal morbidity and mortality and gives a good long term remission in steroid- failure patients with chronic ITP.

Silicon nitride Micromesh Bolometer Array for Submillimeter Astrophysics

We present the design and performance of a feedhorn-coupled bolometer array intended for a sensitive 350-mum photometer camera. Silicon nitride micromesh absorbers minimize the suspended mass and heat capacity of the bolometers. The temperature transducers, neutron-transmutation-doped Ge thermistors, are attached to the absorber with In bump bonds. Vapor-deposited electrical leads address the thermistors and determine the thermal conductance of the bolometers. The bolometer array demonstrates a dark noise-equivalent power of 2.9 x 10(-17) W/ radicalHz and a mean heat capacity of 1.3 pJ/K at 390 mK. We measure the optical efficiency of the bolometer and feedhorn to be 0.45-0.65 by comparing the response to blackbody calibration sources. The bolometer array demonstrates theoretical noise performance arising from the photon and the phonon and Johnson noise, with photon noise dominant under the design background conditions. We measure the ratio of total noise to photon noise to be 1.21 under an absorbed optical power of 2.4 pW. Excess noise is negligible for audio frequencies as low as 30 mHz. We summarize the trade-offs between bare and feedhorn-coupled detectors and discuss the estimated performance limits of micromesh bolometers. The bolometer array demonstrates the sensitivity required for photon noise-limited performance from a spaceborne, passively cooled telescope.

Acute, short-term, and subchronic oral toxicity of 1,1,1-trichloroethane in rats

1,1,1-Trichloroethane (TRI) is a widely used solvent that has become a frequent contaminant of drinking water supplies in the U.S. There is very little information available on the potential for oral TRI to damage the liver or to alter its P450 metabolic capacity. Thus, a major objective of this investigation was to assess the acute, short-term, and subchronic hepatotoxicity of oral TRI. In the acute study, male Sprague-Dawley (S-D) rats were gavaged with 0, 0.5, 1, 2, or 4 g TRI/kg bw and killed 24 h later. No acute effects were apparent other than CNS depression. Other male S-D rats received 0, 0.5, 5, or 10 g TRI/kg po once daily for 5 consecutive days, rested for 2 days, and were dosed for 4 additional days. Groups of the animals were sacrificed for evaluation of hepatotoxicity 1, 5, and 12 days after initiation of the short-term experiment. This dosage regimen caused numerous fatalities at 5 and 10 g/kg, but no increases in serum enzymes or histopathological changes in the liver. For the subchronic study, male S-D rats were gavaged 5 times weekly with 0, 0.5, 2.5, or 5.0 g TRI/kg for 50 days. The 0 and 0.5 g/kg groups were dosed for 13 weeks. A substantial number of rats receiving 2.5 and 5.0 g/kg died, apparently due to effects of repeated, protracted CNS depression. There was evidence of slight hepatocytotoxicity at 10 g/kg, but no progression of injury nor appearance of adverse effects were seen during acute or short-term exposure. Ingestion of 0.5 g/kg over 13 weeks did not cause apparent CNS depression, body or organ weight changes, clinical chemistry abnormalities, histopathological changes in the liver, or fatalities. Additional experiments did reveal that 0.5 g/kg and higher doses induced hepatic microsomal cytochrome P450IIE1 (CYP2E1) in a dose- and time-dependent manner. Induction of CYP2E1 activity occurred sooner, but was of shorter duration than CYP2B1/2 induction. CYP1A1 activity was not enhanced. In summary, 0.5 g/kg po was the acute, short-term, and subchronic NOAEL for TRI, for effects other than transient CYP2E1 induction, under the conditions of this investigation. Oral TRI appears to have very limited capacity to induce P450s or to cause liver injury in male S-D rats, even when administered repeatedly by gavage in near-lethal or lethal dosages under conditions intended to maximize hepatic effects.

Mechanisms of ordering in striped patterns

We have studied the ordering dynamics of the striped patterns of a single layer of cylindrical block copolymer microdomains in a thin film. By tracking disclinations during annealing with time-lapse atomic force microscopy, we observe a dominant mechanism of disclination annihilation involving three or four disclinations (quadrupoles). Pairwise disclination annihilation events are suppressed as a result of the topological constraints in this system. The kinetic scaling laws with exponents observed here are consistent with topologically allowed annihilation events involving multiple disclinations. The results provide insight into two-dimensional pattern formation and may lead to the successful application of block copolymer lithography.

Cytogenetic and molecular genetic studies on Indian patients with chronic lymphocytic leukemia

This is the first cytogenetic and molecular genetic study to find any specific genetic abnormalities in Indian patients with chronic lymphocytic leukemia (CLL). Cytogenetic studies on 18 patients indicated that their karyotypes were relatively simple and trisomy 12 was seen on karyotype evolution in one patient. Fluorescence in situ hybridization (FISH) revealed abnormal clones of trisomy 12 in nine cases and RB gene deletion in 14 of the 29 cases analyzed. Three patients had both clones. Immunoglobulin genes were rearranged in all the cases and TCR beta in none of the 18 cases Southern blotted. BCL-1 was rearranged in one case. No rearrangement of BCL-2 gene was seen in any case. Genetic changes in Indian CLL were more similar to Western CLL than to Japanese CLL, even though India is supposed to be a low incidence area. Therefore, factors (such as HLA and other genetic markers) other than these routine parameters must be studied to explain the low incidence of CLL in India.

Furazolidone in multi-resistant childhood typhoid fever

Multi-drug-resistant Salmonella typhi infection is an emerging public health problem in most developing countries. Fifty children up to the age of 12 years whose blood cultures were positive for S. typhi, mostly drug-resistant ones, were treated with oral furazolidone in a prospective year-long study. Defervescence occurred in 96% of the treated group with a mean duration for response of 5.9 days. No clinically significant side-effects were noted. Furazolidone was found to be efficacious, safe and cost-effective in the treatment of most cases of childhood typhoid fever caused by multi-resistant S. typhi.

Analysis of karyotype, SCE, and point mutation of RAS oncogene in Indian MDS patients

Thirty Indian patients diagnosed as having primary myelodysplastic syndrome as per the French-American-British classification were investigated, on admission, for the frequencies of nonrandom karyotype abnormalities, sister chromatid exchange, and point mutations of the RAS oncogene. Successful karyotype analysis was possible in 24 patients, of whom 9 (37.5%) showed nonrandom karyotypic changes. Anomalies of chromosomes 5, 7, and 8 were detected in their bone marrow (BM). In addition, two new anomalies, del(8)(q22) and +19, were observed for the first time in our series. Six MDS patients were studied for SCE in either BM or peripheral blood. These data revealed a normal SCE incidence. Of the 10 MDS patients studied for point mutations of NRAS 12 and 61 and KRAS 12 and 61, one patient exhibited a base substitution at position 1 of the 12th codon of the KRAS gene. These data, gathered for the first time on the Indian patients, throw some light on the nature of genetic changes in MDS of our country.

Specific Skin Involvement in Leukaemias and Lymphomas

Four cases of leukemia, 5 cases of non-Hodgkin's lymphoma and 3 cases of Hodgkin's lymphoma, developed maculo-papular rashes, papules, nodules, urticarial skin lesions and a plaque. Each of these on histopathology, showed a specific skin infiltrate corresponding to the malignancy.