Ischemia-induced alterations of mitochondrial structure and function in brain, liver, and heart muscle of young and senescent rats

Young and senescent rats (3 and 28-30 months old) were subjected to complete ischemia at 37 degrees C in order to study function and structure of mitochondria isolated from liver, heart muscle, and brain. The rates of energy-coupled respiration and ATP synthesis were found to decrease progressively in relation to time of ischemia. The respiratory rates in the absence of ADP (state 4 respiration) did not increase after exposure to ischemia, suggesting that ischemia primarily affects electron transport rather than the energy coupling system. Mitochondria of heart muscle were more affected by ischemia than mitochondria of brain and liver. Liver and heart muscle mitochondria obtained from young rats were found to be slightly more sensitive to short periods of ischemia than those isolated from senescent animals.

The use of molecular-replacement phases for the refinement of the human rhinovirus 14 structure

The structure of human rhinovirus 14 has been refined, by the method of restrained least squares, to an R factor of 0.16 for various random samples between 6 and 3 A resolution with F greater than 3 sigma (F). As a first step the non-crystallographic symmetry parameters were optimized using the initial atomic model in a rigid-body refinement procedure. Phase determination by the molecular-replacement phase extension and refinement procedure was continued to 2.94 A resolution, employing the improved non-crystallographic symmetry operators. The resultant structure-factor phases and weights, together with the measured amplitudes, constituted the X-ray observations used in the restrained refinement. The Hendrickson-Konnert program system [Konnert & Hendrickson (1980). Acta Cryst. A36, 344-350] was modified to incorporate non-crystallographic symmetry constrains and structure-factor phases as observations. The non-bonded contacts between subunits related by non-crystallographic symmetry were also restrained.

The atomic structure of Mengo virus at 3.0 A resolution

The structure of Mengo virus, a representative member of the cardio picornaviruses, is substantially different from the structures of rhino- and polioviruses. The structure of Mengo virus was solved with the use of human rhinovirus 14 as an 8 A resolution structural approximation. Phase information was then extended to 3 A resolution by use of the icosahedral symmetry. This procedure gives promise that many other virus structures also can be determined without the use of the isomorphous replacement technique. Although the organization of the major capsid proteins VP1, VP2, and VP3 of Mengo virus is essentially the same as in rhino- and polioviruses, large insertions and deletions, mostly in VP1, radically alter the surface features. In particular, the putative receptor binding "canyon" of human rhinovirus 14 becomes a deep "pit" in Mengo virus because of polypeptide insertions in VP1 that fill part of the canyon. The minor capsid peptide, VP4, is completely internal in Mengo virus, but its association with the other capsid proteins is substantially different from that in rhino- or poliovirus. However, its carboxyl terminus is located at a position similar to that in human rhinovirus 14 and poliovirus, suggesting the same autocatalytic cleavage of VP0 to VP4 and VP2 takes place during assembly in all these picornaviruses.

Implications of the picornavirus capsid structure for polyprotein processing

Mature picornaviral proteins are derived by progressive, posttranslational cleavage of a precursor polyprotein. These cleavages play a role in the control of virus functions. Although the processed termini are separated by as much as 75 A in the native virus capsid, the fold and arrangement of polypeptide chains in a protomer before proteolysis are likely to be similar to that found in the mature virus. The three-dimensional structures of rhinovirus and Mengo virus suggest that the cleavage sites within the protomeric precursor are in structurally flexible regions. The final proteolytic processing event, maturation of the virion peptide VP0 (also called peptide 1AB) appears to occur by an unusual autocatalytic serine protease-type mechanism possibly involving viral RNA basic groups that would serve as proton-abstractors during the cleavage reaction.

Comparison of the three-dimensional structure of two human rhinoviruses (HRV2 and HRV14)

An attempt has been made to build a model of human rhinovirus 2 (HRV2) based on the known human rhinovirus 14 (HRV14) structure. HRV2 was selected because its amino acid sequence is known and because it belongs to the minor rhinovirus receptor class as compared to HRV14, which belongs to the major class. Initial alignment of HRV2 with HRV14 based on the primary sequence and the knowledge of the three-dimensional structure of HRV14 showed that the most probable position of the majority of insertions and deletions occurred in the vicinity of the neutralizing immunogenic sites (NIm). Out of a total of 855 amino acids present in one copy of each of the capsid proteins VP1 through VP4 of HRV14, 411 are different between the two viruses. There are also 6 amino acid residues inserted and 14 residues deleted in HRV2 relative to HRV14. Examination of amino acid interactions showed several cases of conservation of function, e.g., salt bridges or the filling of restricted space. The largest variation amongst the residues lining the canyon, the putative receptor binding site, was in the carboxy-terminal residues of VP1.

Toxicity of toxaphene in the rat and beagle dog

Residues of the insecticidal mixture, toxaphene, have been found in Great Lakes fish. The purpose of the present study was to assess the subchronic toxicity of toxaphene in the rat and beagle dog. In the rat study, groups of 10 male and 10 female animals were fed diets containing 0, 4, 20, 100, or 500 ppm of the test compound for 13 weeks. No clinical signs of toxicity or spontaneous deaths were observed. Toxaphene treatment up to 500 ppm had no effects on weight gain or food consumption. The liver/body weight ratio and hepatic microsomal enzyme activities (phenobarbital type) were increased in both sexes fed 500 ppm of the test compound. Toxaphene at the highest dose also caused kidney enlargement in male but not in female rats. Dose-dependent histological changes were seen in the kidney, thyroid, and liver. Changes in the liver and thyroid were considered to be adaptative but the injury in the proximal tubules of the kidney was focally severe. Groups of six male and six female beagle dogs were fed toxaphene in gelatin capsules at 0, 0.2, 2.0, and 5.0 mg/kg body wt/kg body wt/day for 13 weeks. Food consumption and growth rate were not affected. All animals survived the entire treatment period. No clinical signs of toxicity were observed. The liver/body weight ratio and serum alkaline phosphatase were increased in dogs of both sexes fed 5.0 mg/kg. Mild to moderate dose-dependent histological changes were observed in the liver and thyroid. Toxaphene was accumulated in a dose-dependent manner in the fat and liver of dogs and rats. Based on the biochemical, histological, and residue data, it was concluded that the no-adverse-effect levels of the pesticide were 4.0 ppm (0.35 mg/kg) for the rat and 0.2 mg/kg for the dog.

The site of attachment in human rhinovirus 14 for antiviral agents that inhibit uncoating

WIN 51711 and WIN 52084 are structurally related, antiviral compounds that inhibit the replication of rhino (common cold) viruses and related picornaviruses. They prevent the pH-mediated uncoating of the viral RNA. The compounds consist of a 3-methylisoxazole group that inserts itself into the hydrophobic interior of the VP1 beta-barrel, a connecting seven-membered aliphatic chain, and a 4-oxazolinylphenoxy group (OP) that covers the entrance to an ion channel in the floor of the "canyon." Viral disassembly may be inhibited by preventing the collapse of the VP1 hydrophobic pocket or by blocking the flow of ions into the virus interior.

Effect of errors, redundancy, and solvent content in the molecular replacement procedure for the structure determination of biological macromolecules

The power of molecular replacement as a tool for analyzing macromolecular structures such as viruses has been demonstrated by an increasing number of successful determinations. We examine here the effects of noncrystallographic redundancy, N; the fraction of solvent volume (1- U/V); error in structure amplitude measurements, R; the fraction, f, of the unique data that were measured; error in the description of the noncrystallographic symmetry; and definition of the molecular envelope. The formula P = (Nf)1/2/R(U/V) has been derived and represents the inherent phasing power (P) for a given problem. The ability of "solvent flattening" procedures to determine phases was analyzed and found to be analogous to the effect of noncrystallographic redundancy. However, in the limiting case, the effect of solvent flattening approaches the power of Sayre's equations.

Pharmacokinetics of 14C-fenflumizole after intravenous administration to man

The disposition of 14C-labelled fenflumizole was studied in five healthy subjects who received 0.1 mg/kg of fenflumizole as single intravenous doses. Radioactivity was measured in whole blood, plasma, urine and feces from prior to until 168 hours after dose administration. Chemical determinations of fenflumizole and its two demethylated derivatives in plasma were made by HPLC followed by fluorescence detection. Concentrations of fenflumizole calculated from radioactivity in plasma were consistently higher than from chemical determinations, suggesting the presence of metabolites. Radioactivity in blood cells decreased more slowly than in plasma. Plasma concentrations versus time could be described by a four-compartment model, with a terminal half-life of 119 hours (median). About 50% of the dose was excreted with the faeces, and about 4% was recovered in the urine. Unchanged fenflumizole in the urine accounted for 0.0001% of the total dose. Renal clearance of radioactive material decreased at low concentrations of radioactive compound in plasma, which may indicate changes in unbound fraction of drug and metabolites, or a saturable tubular reabsorption process. The slow elimination of fenflumizole is consistent with slow release from tissues and/or enterohepatic recycling.

Single intravenous and oral doses of fenflumizole: pharmacokinetics and effects on prostanoid formation

Fenflumizole is a substituted triaryl-imidazole with anti-inflammatory activity. Its disposition in man was studied after single intravenous and oral doses to 8 healthy male volunteers. Formation of the prostanoids thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6-k-PGF1 alpha) in clotting blood was studied concomitantly. The pharmacokinetics after intravenous doses (0.1 mg/kg) could be fitted to a three compartment model and the half-lives (t 1/2) corresponding to the three phases were 2 min., 1 hour and 15 hours, respectively. The volume of distribution was 386 l and the plasma clearance 0.5 l per min. Oral doses (0.5 mg/kg) were rapidly absorbed (t 1/2 = 0.2 hr) and the following elimination from plasma had two phases with half-lives of 1 hour and 14 hours. Bioavailability was 50% due to a pronounced first-pass effect. The two metabolites mono- and didemethylfenflumizole were detected after both oral and intravenous doses and their maximum plasma concentrations occurred after 1-2 hours irrespective of the administration route. A concentration dependent depression of prostanoid formation was seen, the IC50 for TXB2 and 6-k-PGF1 alpha being 19 and 53 ng/ml respectively.

Effects of the rectal administration of diazepam. Diazepam concentrations in children undergoing general anaesthesia

Diazepam 1 mg/kg body weight was administered rectally to 14 children (11-22.5 kg) before minor surgery under general anaesthesia. Administration in solution (n = 7) resulted in a rapid increase in serum concentrations which were maintained for 8 h. Administration by suppository (n = 7) resulted in significantly lower serum concentrations at 10 and 20 min, but higher concentrations at 2 h. At other intervals the concentrations did not differ from those reached after administration of diazepam in rectal solution. These results favour for use of a solution when rectal diazepam is used for premedication in children.

Apparent inhibition of glycoprotein synthesis by S.cerevisiae mating pheromones

Saccharomyces cerevisiae mating pheromones a and alpha factor strongly inhibit the incorporation of radiolabelled glucosamine into N-glycosylated proteins of corresponding haploid cells. This observation was erroneously interpreted as an inhibition of glycoprotein synthesis. It has turned out that alpha factor causes a 4-5-fold dilution of incorporated [14C]glucosamine with non-radioactive endogenous precursor. In the case of the [14C]chitin synthesized, which does not show inhibition by alpha factor, the lowering of the specific activity of the precursor is exactly compensated for by an increased rate of chitin synthesis caused by alpha factor.

Absorption of metronidazole suppositories in patients with postoperative ileus

Thirty-five patients with postoperative ileus were given one g metronidazole suppositories three times daily. The patients were divided into four groups according to the operative procedure. The postoperative bowel motility was assessed as the time at which bowel sounds and evacuation occurred. One group of patients differed significantly from the others with regard to the time taken for the bowel function to become normal. No significant difference existed in the serum concentrations of metronidazole between the groups. Absorption of the first suppository was slower in our patients than in normal subjects, but thereafter concentrations followed the theoretic concentration curve for healthy subjects on the same dose regimen. Steady state, indicating normal absorption, was attained before bowel function returned to normal. The reason for the slower absorption of the first suppository is probably that the patients were confined to bed.

Morphological and ultrastructural study of megakaryocytopoiesis in liquid cultures of hamster spleen

A long-term liquid culture system of hemopoietic tissue derived from adult hamster spleen has been described. These primary liquid cultures can maintain stem cell proliferation and differentiation for more than three months without secondary repopulation. A characteristic of the liquid cultures is the formation of clusters of hemopoietic cells around adherent stromal cells. Some islands were composed exclusively of megakaryocytes and adherent cells. Isolation of these clusters of differentiating megakaryocytes and their adherent cellular substrate permitted the analysis of the morphological and ultrastructural features of the interaction between cells of megakaryocytic lineage with the adherent stroma.

Picornaviruses of two different genera have similar structures

Crystals of Mengo virus were used to collect three-dimensional X-ray diffraction data to 7 A resolution. A self-rotation function showed the precise orientation of the Mengo particles in the crystal unit cell. A cross-rotation function against similar data of cubic rhinovirus crystals showed a peak when the orientations of these two icosahedral viruses were superimposed. This demonstrates similarity of capsid construction between two picornaviruses of different taxonomic genera.

[Treatment of non-small cell bronchial cancer with high-dosage cisplatin and vindesine. Results of a prospective study]

Thirty-seven patients with advanced, histologically confirmed non-small-cell lung cancer received combination chemotherapy with high-dose (120 mg/m2, day 1 and 29, thereafter every 6 weeks) cisplatin and vindesine (3 mg/m2, day 1, 8, 15, 22, and 29, thereafter every two weeks). All patients had measurable disease and had not previously received chemotherapy. 20 out of 37 patients responded to therapy. Two patients with adenocarcinoma, and one patient with squamous carcinoma of the lung experienced complete remission, 11 out of 37 patients partial remission, three patients a minor response, while in three patients the tumour neither remitted nor progressed. Despite chemotherapy cancer progressed in 17 out of 37 patients. Under supportive care including prehydratation, diuresis, administration of high-dose metoclopramide this aggressive chemotherapy was well tolerated. The response rate was similar to that of other chemotherapeutic regimens. The remission duration (9.5 months) and the survival time (16.5 months) are, however, somewhat better.

Virion orientation in cubic crystals of the human common cold virus HRV14

A new cubic crystal form (a = 445.1 A) of space group P23 is reported for human rhinovirus R14. There are four particles per unit cell, each situated on a crystallographic 3-fold axis. The orientation of these particles has been determined with a rotation function and their approximate positions have been derived from a Patterson map. The crystals diffract to at least 2.8 A resolution. Limitations to the possible surface features of the virus are set by a comparison of the cubic and orthorhombic crystal forms.

Identification and distribution of megakaryocyte colonies in murine spleen

This study is the first report on the utilization of specific cell function to identify splenic megakaryocytic colonies. Stem cell differentiation into megakaryocytes was studied by injecting each irradiated murine syngeneic recipient with 1 x 10(6) spleen cells. Morphological identification of erythroid, granulocytic, megakaryocytic, and mixed and undifferentiated colonies was done by staining consecutive cryostat sections with hemotoxylin and eosin, benzidine, myeloperoxidase, and acetylcholinesterase. The variation in the distribution of hemopoietic colonies within the spleen was reflected in the different ratio values derived for erythroid, granulocytic, and megakaryocytic colonies at varying depth within the spleen. An increase by 50% of megakaryocyte colonies was seen within the splenic pulp in the midzone region, compared with the surface. This suggests a localized microenvironment conducive for megakaryocytopoiesis. The data emphasizes the importance of identifying colonies of all cell types in histological sections of the spleen and evaluating spleen sections at least at two levels, one adjacent to the surface and the other in the midzone area.

Predicting tenure decisions of psychiatric nursing assistants: Individual and work-related factors

Models were developed to predict the tenure status of 106 psychiatric nursing assistants at 3, 6, and 12 months after beginning employment at a large public psychiatric inpatient facility. The attrition rate of this sample was 40% which was consistent with trends reported in the literature. The predictive power of four groups of variables--personal, training, ward related, and organizational--was shown to change over time. Personal and training variables were significant early determinants of tenure, while ward and organizational factors gained more importance during the course of the year. Certain factors that appear important in reducing turnover of nursing assistants are discussed, with recommendations for program changes.

An obligatory role of protein glycosylation in the life cycle of yeast cells

In the presence of 2-4 micrograms tunicamycin/ml, yeast cells stop growth after the cell number has increased 1.5-1.7-fold. The cells are arrested in G1: the rate of DNA synthesis greatly decreases and the budding index drops from 0.6 to 0.1 RNA synthesis is inhibited concomitantly, whereas protein synthesis is little affected. It is postulated that for G1/S phase transition to occur one or more proteins have to be glycosylated.

Presence of mixed colony-forming cells in long-term hamster bone marrow suspension cultures: response to pokeweed spleen conditioned medium

In contrast to the murine system, long-term hamster bone marrow suspension cultures maintain proliferation of both pluripotent and committed stem cells in the absence of an adherent layer and without addition of exogenous factors, such as hydrocortisone. Addition of pokeweed-mitogen-stimulated hamster spleen conditioned medium (SCM) to these long-term suspension cultures produces an increase in the number of mixed colonies assayed in soft-agar, These mixed colonies, which contained four cell lineages--granulocytic, erythroid, megakaryocytic, and macrophage--could be generated from cells grown in suspension for over 6 mo. Addition of SCM also induces an initial rapid expansion of the myeloid compartment, and this expansion results in 70% of the cells being terminally differentiated granulocytes. In contrast, addition of SCM to hamster bone marrow cultures containing both adherent cells and hematopoietic stem cells produced no change in the number of mixed colonies generated in the culture. This system allows the in vitro study of the process of stem cell proliferation and differentiation and also provides a means to examine the relationship of adherent and supernatant bone marrow populations.

Pharmacokinetics of intravenous metronidazole in man

Metronidazole (500 mg) was infused over 20 min. to five patients. At the end of the infusion blood samples were drawn at brief intervals. After subsequent metronidazole analysis the curve plotted for the elimination of the drug showed a bi-exponential profile. Mean peak serum concentrations reached 15 micrograms per ml. At the end of the distribution phase, which was 20 to 30 min. after the infusion, the concentrations had fallen to 10 micrograms per ml. A two-compartment model was used to calculate the kinetic parameters. The elimination half-life ranged from 4.7 to 15.8 hours, the total clearance from 43 to 193 ml per min., and the peripheral distribution volume from 41.5 to 79.11 1. The areas under the serum level curves exhibited a four-fold variation, due to differences in either metabolism or elimination rate.

In vitro proliferation of hematopoietic stem cells in the absence of an adherent monolayer

Experiments on long-term murine bone marrow cultures indicate that the production and maintenance of the hematopoietic stem cell is dependent on the establishment of an adherent monolayer and a secondary repopulation of the culture with fresh marrow. In contrast, we have found that bone marrow cultures derived from the Syrian hamster do not require a repopulation step and produce stem cells that proliferate and differentiate for more than 12 wk in the absence of an adherent layer. Stem cells were grown in Fisher's medium (pH 7.0-7.2) containing 20% horse serum in a fully humidified atmosphere of 5% CO2 in air at 37 degrees C. Cultures were fed twice weekly by removal of half of the medium and supernatant cells and replacement with an equal volume of fresh medium. No hormones or exogenous growth factors were required for the maintenance of myeloid cells, monocytes, and megakaryocytes in either the adherent or suspension cells cultures.

The absorption and excretion of methyldopa ingested concomitantly with amino acids or food rich in protein

Absorption and urinary excretion of 2-14C-L-alpha-methyldopa (alpha MD) were investigated in 5 healthy human volunteers. The drug was administered alone, with a mixture of amino acids and with a meal consisting of roast beef. The radioactivity in plasma and urine was not decreased significantly by either treatment, and it was concluded that the overall absorption of the drug was virtually unchanged. The amount of unconjugated alpha MD in plasma and urine, however, was significantly decreased following administration of the drug with roast beef. As the acid labile conjugates of alpha MD were practically unchanged an increased biotransformation to other metabolites owing to the protein rich meal was suggested more probable than competition between alpha MD and amino acids in the specific transport systems.

The use of corporal punishment in child rearing in the West Indies

The West Indian child is usually loved by its parents or caretakers, but is frequently subjected to corporal punishment unsuitable to the age and stage of its development and excessive in relation to the alleged offence. The debate on whether the persistent use of what is considered excessive punishment as the means of instilling obedience in children, centres around the parents' African heritage or learned behaviour from the institution of slavery. Socially and economically disadvantaged parents under stress seem to displace their frustrations and anxieties on the children through corporal punishment which often assumes ritualised characteristics. The community in general and the parents in particular need help through appropriate education, to change their attitudes of accepting excessive corporal punishment as the means of imposing discipline upon children.

Absorption and excretion of metronidazole after administration of metronidazole benzoate mixture

Serum concentrations and urinary excretion of metronidazole after single dose therapy were investigated in patients with giardiasis. A metronidazole benzoate mixture was administered to 10 adults in total doses of 2 g and to 6 children in doses of approximately 50 mg/kg body weight. No unhydrolyzed metronidazole benzoate was found in the serum. The maximum serum concentrations of metronidazole averaged 30 microgram/ml. These values as well as estimated metronidazole absorption were approximately 30% lower than in 3 adult patients given single doses of 2 g of pure metronidazole in tablet form.

Comparison of metronidazole assay by microbiological and chemical methods

Chemical (thin layer chromatography/fluorescence quenching in situ) and microbiological (agar well, diffusion technique with Clostridium perfringens as indicator strain) methods of assaying metronidazole have been compared. On dummy samples made with pure metronidazole in pooled human serum, both methods had a coefficient of variation ranging from 5.5 to 9.6 per cent of the mean. The microbiological method slightly underestimated the real amounts, and also had lower values than the chemical procedure. Comparison of serum and urine samples taken during the early, middle and late periods after medication to volunteers showed that biotransformation to antibacterially active metabolites contributes significantly to the antibacterial activity, particularly in urine. Biotransformation explains why microbiologically determined concentrations were higher than those determined chemically in samples taken at least 16-20 hours after intake of tablets or suppositories. It is important to be aware of the circumstance that the results of microbiological assay are sensu strictu limited to the particular indicator strain used, since other bacteria may exhibit other patterns of sensitivity to metronidazole and its metabolites.

[Frequency of minimal pulmonary lesions as precursors of tuberculosis]

Numerous studies have referred to the degree of frequency with which so-called minimal pulmonary lesions are the starting-point for active pulmonary tuberculosis. In the present study, which takes the inverse approach, minimal lesions were searched for in medical records antedating the disease of patients treated for active tuberculosis. 343 case histories of pulmonary tuberculosis patients were scrutinized, representing 66% of declared cases among the reference population over a period of 7 years. After stringent selection, 78 case histories were retained as being likely to provide an answer to the question posed: minimal lesions were present in 41% of the cases prior to pulmonary tuberculosis. Although this is a high figure it is a minimum, since minimal lesions exist which are not reflected radiologically.

Pharmacokinetics of metronidazole in healthy adult volunteers after tablets and suppositories

A cross-over study on metronidazole was carried out with 10 healthy adult volunteers who received tablets (250, 500 and 1,000 mg) and suppositories (500, 1,000 and 2,000 mg). The bioavailability of the suppositories was approximately 90% of the corresponding tablet dose as judged by area under the serum curves and amounts excreted in urine. The absorption was faster after the tablets. The mean curve peaks of unchanged metronidazole after the tablets occurred within 1 h and were 3.7 microgram/ml after 250 mg, 9.8 microgram/ml after 500 mg, and 11.8 microgram/ml after 1,000 mg. The suppositories rendered peaks of 5.5, 9,5 and 14.0 microgram/ml 4 h after doses of 500, 1,000 and 2,000 mg, respectively. In the dosage range 250-1,000 mg, the relationship between the dose and the total area under serum curves was similar for tablets and suppositories. Parts of the drug in serum and urine were antibacterially active metabolites. The mean recovery in urine within 36 h was 7-14% of the dose. The serum half-life of unchanged metronidazole (chemical assay) was 8.8-10.5 h. The terminal phase half-life of the total biologically active compound (microbiological assay) was 7.8-15.1 h.

Absorption of diazepam in man following rectal and parenteral administration

Serum concentrations of diazepam and N-desmethyldiazepam were measured in six adult patients following administration of 10 mg diazepam in solution by the rectal, intravenous, and intramuscular routes. Maximum serum concentrations of 121--200 ng/ml were recorded from 10 to 20 min. after the rectal instillation, whereas following intramuscular injection the levels rose slowly and irregularly, reaching a maximum (62--186 ng/ml) in 1 to 24 hours. The bioavailability of diazepam given by rectal instillation was found to be 50 +/- 17 per cent (mean +/- S. D.) as compared with the intravenous administration. The possible reasons for the low bioavailability are discussed. It is concluded that administration by rectal tube provides a useful alternative to the tablets (and intramuscular injections) when a rapid onset of effect of the drug is wanted, and when intravenous administration is not applicable or practical.