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Biomedical subjects

T Hall

Publications and source records attributed to T Hall.

At least 91 records · Page 5Linked to original sources
PubMed1985

A critique of MSHA procedures for determination of permissible respirable coal mine dust containing free silica.

The literature in selected technical subject areas related to the Mine Safety and Health Administration's (MSHA) respirable mine dust control policy was critically reviewed. Specific topics included: (1) the technical aspects of respirable dust sampling, (2) the development of a sampling strategy and (3) currently used analytical techniques for free silica content of respirable coal mine dust. The 2.0 Lpm MSHA respirable dust sampling flow rate does not conform with published results which indicate that to simulate existing pulmonary particle deposition models, the sampling flow rate should range from 1.4 to 1.7 Lpm. MSHA's sampling strategy focuses on controlling respirable coal mine dust with both area and personal samples of workers in selected occupations or activities. Many uncertainties are encountered as area samples are used to estimate personal exposures. Although all of the analytical methods for crystalline free silica are sufficiently sensitive to be able to detect and quantitate free silica at environmentally significant concentrations, they are all plagued with similar difficulties. Analytical standards representing the various forms of silica are not available. Available analytical methods do not differentiate among polymorphs of silica. Recommendations are presented to resolve identified problem areas.

Air Pollutants, Occupational↗
PubMed1984

Screening blood glucose values: effects of season and time of day.

Blood glucose screening results, obtained using two different screening procedures, are reported from two occupational groups. Post-prandial blood glucose levels were measured in 3346 subjects aged 45 years or more employed by the Greater London Council/Inner London Education Authority. In women, mean blood glucose levels were higher in the afternoon than the morning (p less than 0.05). Ninety-fifth centile levels were substantially higher in the afternoon in both sexes, though the differences were not constant in all age and sex sub-groups. In both sexes mean glucose levels were highest in the winter (December-February, inclusive), but seasonal variation did not significantly affect the proportion exceeding the ninety-fifth centile for the total population. In the Whitehall study, the blood glucose was measured in men, in the morning, 2h after a 50-g glucose load. Significant seasonal variation in mean blood glucose values occurred, with highest values in winter and lowest in spring (March-May, inclusive). However, there was no significant difference by season in the proportions exceeding the arbitrary cut-off levels of 7.8 and 11.1 mmol/l.

Adult↗
PubMed1984

Comparison of continuous cycling peritoneal dialysis with continuous ambulatory peritoneal dialysis in children.

The clinical courses in 10 pediatric patients undergoing CAPD for 15.0 +/- 2.8 months and subsequently CCPD for 9.3 +/- 3.2 months were evaluated. During CAPD patients received four or five daily exchanges, and during CCPD five 2-hour nocturnal cycles over 10 hours plus a diurnal dwell. The only significant biochemical difference during CAPD compared with CCPD was the serum creatinine concentration (9.7 +/- 1.0 mg/dl vs 10.8 +/- 0.9 mg/dl, P less than 0.01). The peritonitis rate was one episode every 10.7 patient months during CAPD, compared with one episode every 8.5 patient months during CCPD. There were 21 episodes of exit site infection during CAPD versus 17 during CCPD. Mechanical complications included five ventral hernias in three patients and six peritoneal leaks in three patients during CAPD; two patients had two hernias and two patients had two peritoneal leaks during CCPD. Our results indicate adequate control of the biochemical abnormalities of uremia with CCPD, with the exception of the serum creatinine concentration.

Adolescent↗
PubMed1984

Tumors undergoing rejection induced by monoclonal antibodies of the IgG2a isotype contain increased numbers of macrophages activated for a distinctive form of antibody-dependent cytolysis.

Monoclonal antibodies of the IgG2a isotype specifically inhibit the growth of human tumors in nude mice; tumors in mice given no antibody, an antibody of the IgG2a isotype that does bind to the tumor cells, or an antibody of the IgG2b isotype grow progressively. In the present work it is demonstrated that tumors of mice given the IgG2a antibody are essentially masses of necrosis, while tumors from the control mice are sheets of healthy tumor cells. Tumors of the treated mice, in comparison to controls, contain an increased number of macrophages, and these macrophages are activated for a distinct form of cytolysis dependent on antibodies of the IgG2a isotype. The data suggest that changes in the number and function of intratumoral macrophages are a major component of tumor destruction mediated by IgG2a antibodies.

Animals↗
PubMed1984

Topologic mapping of protective and nonprotective epitopes on the variant surface glycoprotein of the WRATat 1 clone of Trypanosoma brucei rhodesiense.

Monoclonal antibodies were used in competitive antibody binding assays to define and map epitopes on the variant surface glycoprotein of the WRATat 1 clone of T. b. rhodesiense. By using a panel of 30 WRATat 1-specific monoclonal antibodies, 16 epitopes were defined that fall into four clusters, having 1, 1, 3, and 11 distinct epitopes respectively. All epitopes were easily classified as being 1) exposed uniformly on the surface of the trypanosome, 2) exposed only in the region of the flagellar pocket, or 3) "buried", based on the ability or inability of the monoclonal antibodies to bind living trypanosomes in a fluid phase immunofluorescence assay. Monoclonal antibodies that bind exposed surface epitopes are protective, whereas only three of seven that bind exclusively to flagellar pocket epitopes are protective. None of the nine monoclonal antibodies that recognize buried epitopes are protective. Also, antibody-mediated immunity to WRATat 1 trypanosomes is not associated with any particular subclass of antibody. The IgM, IgG1, IgG2a, IgG2b, IgG3, and IgA subclasses each contain examples of protective monoclonal antibodies.

Animals↗
PubMed1983

Continuous ambulatory peritoneal dialysis catheters in children.

Based on clinical experience with 35 subjects younger than 21 years of age who underwent continuous ambulatory peritoneal dialysis (CAPD) during a two-year period at our institution, this procedure was found to be superior to hemodialysis in children because it allowed great freedom of activity and produced fewer complications requiring hospitalization. Moreover, CAPD appeared to be less expensive than hemodialysis, and no mortality or significant morbidity occurred during the 386 patient-months of catheter usage. Exit site infections, peritonitis, and abdominal hernias were the most common complications, often requiring minor surgical repairs. Using a specific operative technique for catheter placement and smaller volumes of dialysate during the first week after placement, these complications were minimized. Thus, CAPD is an effective, advantageous method for treatment of end-stage renal disease in children.

Adolescent↗
PubMed1983

An automated dry-slide enzymatic method evaluated for measurement of creatinine in serum.

We evaluated an automated dry-slide enzymatic method involving creatinine iminohydrolase for measurement of creatinine in serum with the Kodak Ektachem analyzer. The means (and SD) for three commercially available quality-control sera, analyzed during eight weeks, were 9.7 (1.0), 16.6 (0.9), and 61 (2.1) mg/L. The regression equation for 105 samples measured with the Technicon SMAC (x) and Ektachem Analyzers (y) was: y = (0.89 +/- 0.007)x + (1.7 +/- 0.3) mg/L and for 170 samples measured with the Beckman Astra (x) and Ektachem analyzers (y): y = (1.00 +/- 0.005)x - (1.9 +/- 0.16) mg/L. Sixty-one samples from renal-transplant patients showed nearly the same agreement. The enzymatic method had no interference from substances that interfere with many Jaffé methods for creatinine, including acetoacetate. The drugs cephalothin and cephoxitin did not interfere, but 5-fluorocytosine interfered significantly with creatinine in the Ektachem method. Values for several ketone-positive sera were 5 to 10 mg/L higher by the Astra relative to the Ektachem. Grossly hemolyzed or lipemic samples were analyzed without difficulty. We conclude that this enzymatic method for creatinine in serum has the speed and precision necessary for routine clinical laboratory use and, except for one drug, the method appears to be specific for creatinine.

Aminohydrolases↗
PubMed1983

Peritonitis in children undergoing continuous ambulatory peritoneal dialysis.

The incidence of peritonitis in 29 children undergoing continuous ambulatory peritoneal dialysis during a 20-month period was one episode every 12.5 patient-months. Of the 20 episodes of peritonitis, seven (35%) were treated on an ambulatory basis, and 13 required patient hospitalization. The annualized hospitalization rate for the 29 patients during 252 patient-months was 3.8 days per patient. All patients recovered from peritonitis; the only complication was the need to replace two peritoneal catheters. These data would seem to indicate that the potential threat of peritonitis should not curtail continued utilization of continuous ambulatory peritoneal dialysis in children.

Adolescent↗
PubMed1981

Chondroitin 6-sulfate oligosaccharides as immunological determinants of chick proteoglycans.

Monoclonal antibodies to hyaluronidase-treated chondroitin sulfate proteoglycan (CSPG) were used to study the immunological determinants of chick cartilage proteoglycan. The determinants recognized by the antibodies were studied by a radioimmune inhibition assay utilizing hyaluronidase-treated [35S]CSPG. Hyaluronidase-treated CSPG inhibits the reaction of four clonal antibodies, S54C, S103L, S11D, and P100D, with [35S]CSPG, but to varying degrees. Only the reaction of S103L is inhibited to a considerable extent by undigested CSPG, indicating that hyaluronidase treatment exposes determinants specific for the other three antibodies. These findings are consistent with the earlier conclusion that S103L is specific for a protein determinant (Dorfman et al., 1980). Only the reaction of S54C is not significantly inhibited by chondroitinase ABC-digested CSPG. This result indicates that chondroitinase ABC digestion can also expose determinants recognized by S11D and P100D but that such digestion removes the determinant recognized by S54C. Of the four antibodies tested, only the reaction of S54C with hyaluronidase-treated [35S]CSPG is significantly inhibited by chondroitin-6-SO4 tetra- and hexasaccharide (59 and 43% inhibition, respectively, at a concentration of 1333 microM). The reaction of S54C is inhibited to a lesser extent by chondroitin tetra- and hexasaccharide (28 and 26% inhibition, respectively, at a concentration of 1333 microM). In contrast, chondroitin-4-SO4 oligosaccharides do not inhibit the reactions of any of the clonal antibodies. These result suggest that S54C recognizes a determinant that contains chondroitin-6-SO4 oligosaccharide, attached via the linkage oligosaccharide to core protein.

Animals↗
PubMed1980

Clonal antibodies for core protein of chondroitin sulfate proteoglycan.

Antibodies have been prepared to the core protein of cartilage chondroitin sulfate proteoglycan from clones isolated after fusion of rat spleen cells and mouse myeloma cell lines. Antibodies produced by five clones were studied in detail by a radioimmunoassay utilizing 35SO42-labeled hyaluronidase-digested chondroitin sulfate proteoglycan. Preparations of antigen were shown to contain at least two antigenic determinants, one of which was restricted to a portion of antigen in these preparations. One clone was shown to react with proteoglycan synthesized in a cell-free system. It is proposed that such clonal antibodies can be used for structural and biosynthetic studies of core protein.

Animals↗
PubMed1978

The effect of trypsin on the growth of rotavirus.

It has been found that 1000-fold more bovine rotavirus is obtained when trypsin is incorporated in the maintenance medium and allowed to remain throughout the growth cycle. This holds true for primary calf kidney (CK) cells and also for several continuous and semi-continuous cell lines. In the presence of trypsin it has been possible to pass the virus serially on continuous cell lines seven times. Concentrations of 1 to 10 microgram/ml of trypsin are found to be effective. Preliminary results suggest that the same technique will be effective for the in vitro propagation of human rotavirus.

Animals↗
PubMed1976

Comparisons of cell-free and cell-associated Marek's disease vaccines in maternally immune chicks.

Cell-free and cell-associated Marek's disease vaccines prepared from the TK/A isolate of the herpesvirus of turkeys (HVT) were compared to evaluate their relative effectiveness in protecting chicks with homologous maternal antibody. The influence of early challenge on protection was also investigated. Although the higher susceptibility of cell-free HVT to neutralising antibody could be demonstrated in vitro, no significant difference between the two types of vaccine could be established in vivo using chicks with maternal antibody. Chicks exposed to challenge immediately or only a few hours after vaccination were not adequately protected. A higher level of protection was observed when challenge was separated from vaccination by an interval of several days. The importance of proper vaccination procedure, vaccine virus titre and adequate management of vaccinated stock, with particular reference to the risks of early challenge are discussed.

Animals↗
PubMed1976

Results of a randomized study comparing DTIC with TIC mustard in malignant melanoma.

This prospective randomized Eastern Cooperative Oncology Group (ECOG) study (1071) was designed to compare a new and promising cytotoxic agent TIC Mustard (triazeno imidazole carboxamide mustard, NSC 82196) with DTIC (dimethyl triazeno imidazole carboxamide, NSC 45388) in the treatment of inoperable melanoma. One hundred and seventy-eight patients were randomized to receive either DTIC (150 mg/m2/day X 5) or TIC Mustard (800 mg/m2/day X 5). Of this group 145 patients were evaluable for tumor response at the completion of the study. Objective responses were seen in 15/79 (19.0%) DTIC patients and 4/66 (6.1%) TIC Mustard patients. Adjustment of crude response rates yielded final response rates of 18.2% for DTIC patients and 5.8% for TIC Mustard. These differences were significant at the p less than or equal to .03 level. Median response duration was 15 weeks for the DTIC responders and 4 weeks for the TIC Mustard responders. Responders and nonresponders did not differ significantly in any of the standard prognostic categories. However, responders had a significantly longer median survival (47.5 weeks) compared to that for nonresponders (17.8 weeks). Toxicity was tolerable for either drug and no deaths were ascribed to either. We conclude that TIC Mustard has limited usefulness in the treatment of malignant melanoma and is less effective than DTIC.

Clinical Trials as Topic↗
PubMed1975

Trials with Marek's disease vaccines prepared from a turkey herpes virus and an attenuated Marek's disease virus.

In field trials involving over 224,000 fowls in 11 different commercial flocks, three vaccines were used, namely a freeze-dried vaccine prepared from a turkey herpes virus, a cell-associated virus vaccine prepared from the same isolate and a cell-associated vaccine prepared from a strain of Marek's disease virus isolated from a fowl. The mortality from Marek's disease was reduced by 80 per cent to 95 per cent in birds vaccinated with the freeze-dried vaccine. Cell associated vaccines gave slightly less protection.

Animals↗