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Biomedical subjects

M J Groves

Publications and source records attributed to M J Groves.

At least 55 records · Page 3Linked to original sources
PubMed1991

A note on the use of topical digitalis prior to William Withering.

Attention is called to the fact that, long before the systematization of oral digitalis therapy by Withering in the eighteenth century, the drug was applied to the skin by inunction, producing effects that can now be recognized as due to an overdosage of Digitalis glycosides. The history of digitalis is briefly reviewed: the drug appears not to have been known to Greek and Roman physicians, but by the Middle Ages was widely used in folk medicine. Contrary to current wisdom, there is a wealth of historical information suggesting that topically applied Digitalis glycosides are capable of exerting physiological activity. It is perhaps time to re-examine this feature, in view of the present-day general interest in transdermal medications.

Administration, Topical↗
PubMed1991

Water vapor adsorption and desorption isotherms of biologically active proteins.

Using a protein isolated from soy, a dynamic water adsorption method was developed and the data were compared with those obtained from a static gravimetric procedure. Both methods gave comparable results, showing that Type II isotherms with considerable hysteresis were obtained. However, the dynamic procedure was preferred since it provided data rapidly and used significantly less material. Using the dynamic method, water adsorption isotherms at 25 degrees C were also determined for four biologically active proteins: alpha-amylase, beta-glucuronidase, lipase, and urease. BET (Brunauer, Emmet, and Teller) parameters were calculated and the specific surface areas for the native, biologically active proteins were found to be similar, 238.4 +/- 20.2 m2/g. On the other hand, the specific surface area for the denatured soy protein isolate was 144.6 m2/g. Nevertheless, the heat of absorbance for all of the proteins examined was similar, suggesting that they have comparable degrees of hydrophilicity.

Adsorption↗
PubMed1991

Production of 5-15 microns diameter alginate-polylysine microcapsules by an air-atomization technique.

A novel method of preparing small-sized microcapsules using a Turbotak air-atomizer is reported. Alginate-polylysine microcapsules containing Bacillus Calmette Guérin vaccine have been prepared by an adaptation of the method of Lim (1) which allows the manufacture of small-sized microcapsules. A Turbotak is used to spray sodium alginate solution into calcium chloride solution to form temporary calcium alginate microgel capsules. These temporary microgel droplets are subsequently cross-linked with polylysine to form permanent membranes. Microcapules in the size range of 5-15 microns have been produced which can be compared to an average diameter of greater than or equal to 300 microns obtained by the method reported by Lim. The microcapsule size is dependent on the conditions of operation of the Turbotak and the concentration of the sodium alginate solution. Particles within the size range 5-15 microns can be reproducibly manufactured using the conditions of operation reported here. Other size ranges below the minimum of 300 microns reported by Lim are also feasible using this technique.

Alginates↗
PubMed1991

Particulate contamination in parenterals: current issues.

Particulate matter may be described as insoluble material(s) inevitably present in injectable solutions. Processing conditions for parenteral solutions are designed to substantially minimize the absolute amounts of particolate present down to around 0.1 micron diameter. It is technically relatively easy and, therefore, inexpensive to remove most particulate above 100 microns in diameter. Currently it is extremely difficult, and correspondingly expensive, to remove material in the 1 micron and submicron ranges. Pharmaceutical injectable products, made available at a reasonable cost, must inevitably contain some particulate over a range of sizes, from the molecular level to the visible. An unfiltered solution could contain, at random, various identities (with differing morphologies) of particulate. Filtration affects the size, and numbers, of particulate present but, generally, not the randomness of the identities. An exception would be in situations where clearly definable particle species such as bacteria or intact starch grains are totally removed during the filtration process. A parenteral solution may legitimately contain low levels of random numbers of random species of particulate without necessarily being "contaminated" and, therefore, unacceptable for use. However, it could be argued that a solution containing a dominant particulate species is contaminated by that species. The particle size distribution of a random number/random identity system is characteristic and can be separated from a contaminating species situation. Simple statistical methodology for making this critical distinction will be reviewed. National compendial limits for particulate in injectable fluids are compared, and attention is drawn to the scientific background underlying limits published in the USP.

Drug Contamination↗
PubMed1991

Surface morphology of Mycobacterium bovis BCG: relation to mechanisms of cellular aggregation.

Growing colonies of Mycobacterium bovis BCG, Tice and Glaxo substrains, and freshly ball milled and freeze-dried Tice BCG vaccines were examined by scanning and transmission electron microscopy (TEM) and by light microscopy after cytochemical staining. BCG organisms in colonies growing on agar were randomly oriented, despite colony morphology, and nearly completely covered by an amorphous material. Aggregates of organisms in vaccine suspensions were also covered with this material, but single cells were not covered. In TEM, the covering material was visualized between groups of cells as an electron-transparent area surrounded by a thin electron-dense layer. This material appeared to originate in the upper cell wall, between the cell wall skeleton and the outer dense layer. Staining of the covering material indicated the presence of protein, carbohydrate and acidic groups, but not exposed lipids. The covering material was absent from the ventral side of colonies, suggesting that its production is oxygen-dependent. These observations suggest that a mycobacterial exudate, previously observed and implicated as a virulence factor, may also bind the cells together, and accounts for the aggregative properties of the organisms in culture.

BCG Vaccine↗
PubMed1990

Cell mass of Mycobacterium bovis BCG estimated by gas chromatography.

The presence of additives and large cellular aggregates in freeze-dried BCG vaccines precludes accurate measurement of total cell content by traditional methods. The possibility that extraction and quantitation of a cell membrane fatty acid may provide a suitable means of cell mass determination was tested. The palmitic acid methyl ester peak area determined by gas chromatography was directly proportional to the wet weight of freshly grown Tice-, Pasteur-, and Glaxo-substrain BCG, as well as the dry weight of the ampoule contents after removal of soluble material. Extraction of palmitic acid from Tice BCG vaccine was not appreciably affected by lyophilization and the calculated dry cell mass values of freeze-dried vaccine samples correlated well with particle number. This method, therefore, may be useful in measuring BCG cell mass during all stages of vaccine manufacture and storage.

BCG Vaccine↗
PubMed1990

The effect of compactional pressure on a wheat germ lipase preparation.

Wheat germ lipase is a relatively homogeneous proteinaceous enzyme known to suffer inactivation by compactional pressure. However, earlier investigators suggested that the inactivation was due to thermal degradation following the application of mechanical energy. A wheat germ preparation (Sigma) was compacted over a range of pressures from 85 to 1800 MPa. The 100-mg compacts were carefully dispersed and dissolved in aqueous 0.05 M potassium phosphate buffer, pH 7.4, and the biological activity was determined using triacetin as a substrate. No significant loss of activity occurred up to a pressure of 175 MPa. After this point, a discontinuity was evident with a loss of 30% activity but this loss of activity remained constant over the remainder of the applied pressure range studied. The density/applied pressure relationship indicated that the discontinuity was due to space constraints. The density failed to go higher than a limiting value of approximately 1.2 g cm-3, irrespective of the applied pressure. There was an approximately linear relationship between the relative loss of biological activity and density, indicating that the observed loss of biological activity is unlikely to be due to applied thermal energy but more likely to be due to space constraints on the volume occupied by the molecule. However, circular dichroism measurements and SDS-PAGE examination did not reveal any obvious protein structural changes, suggesting that the mechanism involved in activity loss is subtle.

Circular Dichroism↗
PubMed1989

Formulation studies of tableted oral rehydration salt mixtures.

Dehydration following non-specific diarrhoea may be prevented by oral administration of a simple glucose/salt mixture. A solution tablet of this mixture would have advantages of stability under environmental exposure and transport if the costs could be held within reasonable limits. The moisture adsorption and compression characteristics of Oral Rehydration Salts (ORS) ingredients have been studied. Combinations of ingredients resulted in a moisture adsorption higher than that of the individual components. This may be explained in terms of critical relative humidity, RHo, and environmental relative humidity RHi. Preparation of a stable ORS solution tablet therefore requires protection of moisture adsorbing components from the environment. The present UNICEF ORS mixture compacted easily by direct compression but gave fragile tablets, which were hygroscopic. This can be reduced by film coating the electrolyte component as granules with a resin (Eudragit L), or by simulating direct compression of the glucose as a compression-coating around the precompressed electrolytes. The packaging of compression-coated solution tablets in inexpensive polyethylene bags may lengthen the shelf-life and make the preparation less costly than the currently supplied ORS powders packed in laminated aluminium sachets. The increased dissolution lag time for the compacted tablet is a disadvantage that can be overcome by instructions to crush the product immediately before use.

Absorption↗
PubMed1989

Fatty acids of Mycobacterium bovis BCG.

Three substrains of Mycobacterium bovis BCG which appeared to differ in biological activity could not be differentiated on the basis of fatty acids less than C20, but could be differentiated from six nonpathogenic mycobacterial species.

Chromatography, Gas↗
PubMed1989

Viability of freeze-dried Tice-substrain BCG by bioluminescent measurement of adenosine triphosphate.

The ATP content of viable cells in a single lot of freeze-dried Tice-substrain Mycobacterium bovis-BCG vaccine was determined after washing of organisms with isotonic buffer, using four extraction methods: boiling in 0.2 M potassium phosphate buffer at pH 7.4 for 12 min; boiling in 0.1 M Tris-EDTA buffer at pH 7.75 for 2 min; n-butanol/1.9% sodium glutamate-0.01 M sodium arsenate buffer, pH 7.0; and n-butanol/0.01 M Tris-EDTA buffer, pH 7.0. Liberated ATP was assayed with a Lumac biocounter by integrated measurement of light produced by firefly luciferin/luciferase. The dose response of internal standards paralleled that of ATP standards in water, and the response of endogenous ATP in BCG was not significantly different from a composite linear internal standard curve above 10 pg ATP (corresponding to about 10(5) viable organisms per ml), the sensitivity of the assay. When the ATP content of BCG was calculated from the composite curve, the n-butanol/Tris-EDTA method was found to be the most precise (CV less than 10%). Butanol extraction procedures were about twice as efficient as boiling methods and yielded an ATP value of about 3.4 fg/CFU, similar to ATP/CFU factors previously reported for other BCG substrains. However, when results were corrected for quench and ATP recovery, which varied with extraction method, the conversion factor increased nearly threefold.

Adenosine Triphosphate↗
PubMed1989

The effect of washing on the surface charge of Mycobacterium bovis BCG vaccine, Tice substrain.

The zeta potential of three lots of Tice substrain BCG organisms was measured over a pH range of 2.0 to 11.0 at low electrolyte concentration. For two lots, the cells were cationic at pH 4.2-4.4 and anionic above this isoelectric point. Washing the cells twice with water lowered the isoelectric point to 2.7. The cationic/anionic profile was retained in all three lots, although the third lot had an isoelectric point of 3.0 initially. Cells of the Glaxo substrain, on the other hand, were anionic over the entire pH range and are evidently unaffected by the washing process. It appears that cells of the Glaxo strain have only electronegative phosphate groups at their surface whereas the Tice substrain may possess a loosely adhering cell-surface protein.

BCG Vaccine↗
PubMed1989

Comparison of Karl Fischer titrimetric and gravimetric methods for determination of moisture content in BCG vaccine.

A model 447 Coulomatic K-F titrimeter was used to determine the water content of seventeen lots of freeze-dried Tice-substrain BCG vaccine. The results were compared with corresponding moisture contents determined by a standard gravimetric method at the time of manufacture. The advantages of the titrimetric method include simplicity, rapidity, convenience, sensitivity, reproducibility and specificity, whereas the gravimetric method is tedious and time-consuming. Although moisture content determined by the K-F titrimeter tended to be higher than that determined by the gravimetric method, the results correlated significantly (r = 0.882, P less than 10(-5]. Alteration of national and international regulations to permit use of the K-F titrimeter is recommended.

BCG Vaccine↗
PubMed1988

Size characterization of Mycobacterium bovis BCG (Bacillus Calmette Guérin) vaccine, Tice substrain.

Reconstituted, lyophilized, attenuated Mycobacterium bovis, Bacillus Calmette Guérin (BCG) vaccine, Tice substrain, was characterized using a Coulter Multisizer and a HIAC/Royco counter. The primary organism has an equivalent spherical diameter approximating 1 micron but the BCG cell suspension is heavily aggregated. The cumulative size distribution of the suspension fits a log-probit plot and this information can be used to determine the total number of particles per ampoule. The instrumental count may be related to the viable count. The state of dispersion was unaffected by mild shear (syringe aspiration or ultrasound) and only slightly affected by the addition of cetylpyridinium chloride or sodium tauroglycolate.

BCG Vaccine↗
PubMed1988

The effect of compactional pressure on urease activity.

Jack bean urease is a proteinaceous enzyme, MW approximately 489 kD, readily soluble in water but losing activity when sheared in solution at stresses as low as 2.5 Pa. There is a need for controlled-release forms of many of the new genetically engineered peptide and polypeptide drugs with high specific activities. The simplest form of controlled release would be a sterile compressed pellet of the active component inserted subdermally. However, "activity" may be lost on compaction. Urease can be regarded as a model protein which may lose activity when sheared during compaction in the dry state. Tablets of urease weighing 100 mg were compressed over a range of pressures from 60 to 1750 MPa. No relative loss of activity would be detected following compaction at pressures up to 474 MPa. Above this limiting pressure there was a 50% loss of relative activity, evidently by a compactional effect on the protein quaternary and tertiary structures. No direct relationship was observed between stress (compactional pressure) and inactivation.

Calibration↗
PubMed1988

Diffusion of [2-14C]diazepam across isolated hairless mouse stratum corneum/epidermal tissues.

The objective of this study was to develop a method of preparing mouse stratum corneum/epidermal (SCE) tissue without the dermis for use in drug diffusion studies. The diffusion of radiolabeled diazepam across this new preparation has been studied and the effect of the dermis on diffusion evaluated. Incubation of large pieces of mouse skin in a 20mM EDTA, 15 mM sodium phosphate buffer, pH 7.2, in normal saline for 3-4 h at 37 degrees C resulted in a tissue which easily separated at the epidermal-dermal junction. The resulting tissue contains stratum corneum and epidermis, which are the same layers used in studies with human skin in vitro. The EDTA treatment did not effect diffusion of [2-14C]diazepam across whole mouse skin (SCE and dermis) used as controls. The rate of drug diffusion was greater across SCE than SCE and dermis, however, 0.48-1.12 micrograms/cm2/h versus 0.11-0.52 microgram/cm/h, respectively. The permeability coefficients for mouse SCE ranged from 1.92-4.48 X 10(-2) cm/h. The lag times and diffusion coefficients were 0.36-0.91 h and 0.1-0.6 X 10(-6) cm2/h, respectively. The presence of the dermis decreased the diffusion rate or flux of diazepam. The dermis appears to accumulate drug until it is saturated and then the drug diffuses into the receiving chamber.

Animals↗
PubMed1988

The surface charge of cells of Mycobacterium bovis BCG vaccine, Tice substrain.

The zeta potential of cells of an attenuated vaccine Mycobacterium bovis, BCG, Tice substrain, was measured over a pH range of 1.5-11.0 at low electrolyte concentration. There was a marked electro-positive charge at low pH, the zero charge point, pH 4.4, being similar for viable and heat killed vaccine. At pH 6.5 the addition of sodium dodecyl sulphate or sodium tauroglycolate made little difference to the zeta potential. However, progressive addition of cetylpyridinium chloride reduced and finally reversed the charge to a maximum of +60 mV at a concentration of 1.5 x 10(-2) mol dm-3 surfactant. Higher concentrations reduced the charge although it remained positive. The nature of the adsorbing species on the cell surface is discussed since the Tice substrain has both cationic and anionic surface charges whereas the Glaxo strain is reported to only possess electro-negative phosphate surface groups. Some hydrophobic interaction involving lipid within the surface may also be involved.

BCG Vaccine↗
PubMed1987

Diffusion of [2-14C]diazepam across hairless mouse skin and human skin.

The objectives of this study were to investigate the absorption of diazepam applied topically to the hairless mouse in vivo and to determine the diffusion of diazepam across isolated hairless mouse skin and human skin. [14C]Diazepam was readily absorbed after topical administration to the intact hairless mouse, a total of 75.8% of the 14C-label applied being recovered in urine and feces. Diazepam was found to diffuse across human and hairless mouse skin unchanged in experiments with twin-chambered diffusion cells. The variation in diffusion rate or the flux for both human and mouse tissues was greater among specimens than between duplicate or triplicate trials for a single specimen. Fluxes for mouse skin (stratum corneum, epidermis, and dermis) were greater than for human skin (stratum corneum and epidermis): 0.35-0.61 microgram/cm2/h for mouse skin vs 0.24-0.42 microgram/cm2/h for human skin. The permeability coefficients for mouse skin ranged from 1.4-2.4 X 10(-2)cm/h compared with 0.8-1.4 X 10(-2)cm/h for human skin. Although human stratum corneum is almost twice the thickness of that of the hairless mouse, the diffusion coefficients for human skin were 3-12 times greater (0.76-3.31 X 10(-6) cm2/h for human skin vs 0.12-0.27 X 10(-6) cm2/h for hairless mouse) because of a shorter lag time for diffusion across human skin. These differences between the diffusion coefficients and diffusion rates (or permeability coefficients) suggest that the presence of the dermis may present some barrier properties. In vitro the dermis may require complete saturation before the diazepam can be detected in the receiving chamber. [14C]Diazepam was not detected in the receiving chamber of the Franz cell apparatus in experiments with human skin. This indicated that the rate of diffusion was less than 0.09 microgram/cm2/h. Since this diffusion technique more closely resembles topical administration to humans, these results appear to indicate that achieving therapeutic concentrations in humans may be difficult. In addition, the hairless mouse may not be a suitable model for predicting percutaneous absorption of diazepam in humans.

Absorption↗