Absorption of alpha-MSH from subcutaneous and intraperitoneal sites in the rat

Pentobarbitone anesthetized rats were injected with 30 nmol (50 micrograms) alpha-MSH administered intraperitoneally (IP) and subcutaneously (SC) in an acid-saline vehicle, or SC in a zinc phosphate vehicle. Concentrations of alpha-MSH in plasma were measured by radioimmunoassay. The pharmacokinetic parameters for the three modes of administration were determined by fitting a one-compartment open model to the plasma level data. The t1/2 for absorption using the saline vehicle was 7.3 and 5.6 min from the IP and SC sites, respectively. The t1/2 for absorption from the zinc phosphate complex of 17.7 min was significantly longer. Five percent of the IP dose was absorbed into the systemic circulation giving a peak plasma level of 14.1 nmol/l. The absorption of 2-3 percent was significantly lower following SC administration; peak plasma levels were 8.3 and 4.8 nmol/l for the saline and zinc phosphate vehicles, respectively. The low percentage absorption values indicated a high degree of metabolism of the peptide by peripheral tissues on its passage from the injection sites into the circulation.

Escherichia coli DNA topoisomerase I mutants have compensatory mutations in DNA gyrase genes

Escherichia coli deletion mutants lacking DNA topoisomerase I have been identified previously and shown to grow at a normal rate. We show that such strains grow normally only because of spontaneously arising mutations that compensate for the topoisomerase I defect. Several of these compensatory mutations have been found to map at or near the genes encoding DNA gyrase, gyrA and gyrB. DNA gyrase assays of crude extracts show that strains carrying the mutations have lower gyrase activity. Thus the mutations are in the gyrase structural genes or in nearby regulatory sequences. These results, in conjunction with DNA supercoiling measurements of others, indicate that in vivo DNA superhelicity is a result of a balance between topoisomerase I and gyrase activities. An excess of negative supercoils due to an absence of topoisomerase I is deleterious to the cell, but a moderate gyrase deficiency is not harmful.

The Pietermaritzburg craniofacial unit

The Pietermaritzburg Craniofacial Unit was established in 1976, and since its inception 150 patients with major skull and facial deformities have been referred there from centres throughout South Africa. Fifty craniofacial operations have been performed by the surgeons of the Unit, who form only a part of a team of 16 members from many branches of the medical, dental and allied professions. Craniofacial surgery is defined and reasons are presented for limiting the number of such highly specialized units.

Giant cilia in the human organ of Corti

Fusion of cilia, the growth of clumps of fused cilia and giant cilium formation have been studied in the normal human organ of Corti using the scanning electron microscope. These unusual forms are found mainly in the apical portions of the cochlea and appear to precede the loss of normal apical cilia which increases and extends in a basal direction with age. These changes may be due to low frequency noise damage or be a phenomenom of ageing. The mechanism of their formation is discussed in the light of recent experimental work on cell fusion.

Patterns of cloacal water and electrolyte excretion in constantly-loaded intact and colostomized ducks (Anas platyrhynchos)

1. The patterns of cloacal water and electrolyte excretion were qualitatively similar in intact and chronically colostomized ducks given oral loads of either distilled water or electrolyte solution. 2. The rates of Na+ and K+ excretion were each selectively increased in birds loaded with solutions containing a relatively higher concentration of each ion. 3. Compared to the intact birds, the colostomized birds showed lower rates of electrolyte excretion following administration of identical electrolyte loads and thus appeared to be retaining electrolyte. 4. At the same time, a significant antidiuresis of similar magnitude occurred in each group of saline-loaded birds. 5. The possible contributions of renal and post-renal mechanisms to the overall conservation of water in intact and colostomized ducks are discussed.

Scanning electron microscopy of the normal human cochlea

Preservation of the fine structures of the human cochlea has been achieved by perfusing the cochlea with fixative shortly after death. Following the dissection of the temporal bone the surface of the organ of Corti and stria vascularis has been examined in the scanning electron microscope. The surfaces of the inner and outer hair cells can be seen and the stereocilia projecting from their surfaces closely examined. The number and length of the stereocilia of the outer hair cells changes linearly with distance along the cochlear duct. The surface of the stria vascularis is similar to that seen in other animals.

Cloning and restriction mapping of the alkaline phosphatase structural gene (phoA) of Escherichia coli and generation of deletion mutants in vitro

The structural gene for alkaline phosphatase (phoA) of Escherichia coli was cloned into the PstI site of pBR322, from a transducing bacteriophage, lambda p(phoA-proC). The restriction map of the plasmid was established. Based upon this information, several phoA deletion plasmids as well as a smaller phoA+ plasmid were constructed. The genetic map and restriction map were correlated by recombination analysis. Cells carrying one of the phoA+ plasmids overproduce alkaline phosphatase 10-fold upon phosphate limitation. However, both regulation and processing of the enzyme were found to be normal.

Does tracheostomy in children retard the growth of trachea or larynx?

Tracheostomy in children has been reported to cause tracheal stenosis, laryngeal stenosis and subsequent difficulties in decannulation. No long term follow-up studies appear to be in the literature describing the events following decannulation. This study compared the radiological size of the cricoid and tracheal lumens with that of normals. Except in special cases tracheostomy did not affect the subsequent growth of the trachea or cricoid. It is suggested that traumatic tracheal narrowing in children should be managed conservatively.

Isolation and characterization of amber mutations in gene dnaA of escherichia coli K-12

Amber mutants with defects in the dnaA gene of Escherichia coli K-12 were isolated after localized mutagenesis of the tna-dnaA region of the chromosome. We isolated 36 mutants defective in the initiation of deoxyribonucleic acid replication as determined by their dependence upon integrative suppression by a P2 sig5 prophage. Three of the 36 mutants were shown to contain amber mutations through the use of a temperature-sensitive amber suppressor. These mutations, which mapped between gyrB and tna, were characterized genetically and biochemically as amber mutations in dnaA.

Scanning electron microscopy of the human cochlea--the organ of Corti

The surface of the organ of Corti from normally hearing adult humans has been examined with the scanning electron microscope. It is possible to construct cytocochleograms and to derive a regression line with confidence limits to represent the distribution of the sensory hair cells. Examining individual hair cells more closely, the number of cilia on each hair cell, decreased linearly with distance, from the base of the cochlea. However, the length of the longest cilia on each outer hair cell increased linearly with distance.

Scanning electron microscopy of the human cochlea - the stria vascularis

The endolymphatic surface of the stria vascularis from normally hearing human ears has been studied with the scanning electron microscope. The cells in contact with the endolymph usually have a hexagonal-shaped surface and possess many microvilli, whilst depressions or pits are rarely seen. There is marked heterogeneity of these cells with variations in the size of the cells and the number of microvilli present on each cell. A transitional zone occurs between the stria vascularis and the spiral prominence. The surface of the cells of the transitional zone are larger and elongated whilst the cells of the spiral prominence have a smaller and more regular appearance.

Scanning electron microscopy of the human cochlea--postmortem autolysis artefacts

Changes in the ultrastructure of the cochlea due to postmortem autolysis make the assessment of the normal or damaged anatomy difficult. Three methods of preserving the human cochlea were compared on the basis of the state of preservation of the sensory cell hairs of the organ of Corti as seen in the scanning electron microscope. Perfusion of the perilymphatic space with a glutaraldehyde-formaldehyde fixative within 40 min of death gave preservation as good as that seen in animal studies. Injecting formalin into the middle ear within 40 min of death allowed artefacts to develop when compared with the control ear which had been perfused with fixative. Refrigeration and early removal of the temporal bone gave poor preservation of surface structures.

Value of physical signs in the diagnosis of enlarged adenoids

In a series of children due to have surgery on their upper respiratory tracts an assessment of mouth breathing, abnormality on anterior rhinoscopy and size of the adenoid on posterior rhinoscopy was made by 3 observers. All these signs showed poor reproducibility between observers and the size of the adenoid assessed by posterior rhinoscopy showed no significant relationship to the weight of the adenoid subsequently removed.

Mutations in two unlinked genes are required to produce asparagine auxotrophy in Escherichia coli

Escherichia coli K-12 has two genes, asnA+ and asnB+, either one of which is able to satisfy the need of cells for asparagine. In order for a strain to have an auxotrophic requirement for asparagine, both genes must be mutationally inactivated. We obtained mutants with Tn5 inserted in asnB. asnB was mapped by conjugation and by three-factor P1 transductions at 15 min on the E coli K-12 linkage map, between ubiF and nagB. Specialized transducing phage lamba 781 supE was shown to carry asnB, as well as supE, ubiF, nagA, and nagB. asnA is the previously mapped ilv-linked asn locus, whiich is between uncB and rbs. E. coli C also has two asn genes, corresponding to asnA and asnB.

Dietary fibre and blood pressure

Ninety-four volunteers participated in a three-day weighed dietary survey and had their blood pressures measured once. They were classified according to their fibre intake. Subjects with a high-fibre intake were found to have lower mean blood pressures than those with a low-fibre intake. Forty-two of the volunteers further participated in a group of experiments. Those eating a high-fibre diet decreased their dietary fibre, and those eating a low-fibre diet increased their dietary fibre. The first group (11 subjects) showed increased mean blood pressures after four weeks of eating the experimental diet. The last group (31 subjects) showed decreased mean blood pressures after four weeks of eating the experimental diet. The 11 subjects consuming the low-fibre experimental diet showed a decrease in mean blood pressure when some of the saturated fat in their diet was replaced by polyunsaturated fat. A similar substitution carried out by 14 of the subjects consuming the high-fibre experimental diet also resulted in decreased mean blood pressure, but this was not statistically significant. Twelve more volunteers, with hypertension, were all found to have low-fibre diets. They consumed a high-fibre diet for a six-week experimental period, but their mean blood pressures did not decrease significantly; individual recordings varied substantially during this period.It is suggested that differences in the type and quantity of dietary fibre and fat may be responsible for the lower mean blood pressures of groups of vegetarians compared with similar groups of non-vegetarians.

Plasmid pSC101 replication in integratively suppressed cells requires dnaA function

Maintenance of plasmid pKC17, a derivative of plasmid pSC101, in E. coli requires a functional dnaA gene product. This was demonstrated by segregation experiments using an E. coli dnaA46 mutant, at various temperatures. Growth of this mutant at elevated temperature was allowed by the presence of a P2sig5 prophage. rpoB mutations, which suppress the temperature sensitivity of a dnaA46 mutant permit efficient maintenance of plasmid pKC17 at temperatures up to 40 degrees, conditions which normally inactivate the dnaA46 product.

Variation in the structure and bacteriophage-inactivating capacity of Salmonella anatum lipopolysaccharide as a function of growth temperature

Growth temperature affects both the structure and the phage-inactivating capacity of Salmonella anatum A1 lipopolysaccharide. Whereas S. anatum cells normally synthesize smooth lipopolysaccharide when grown at physiological temperature (37 degrees C), a partial smooth-rough transition occurs when cells are grown at low temperature (20 to 25 degrees C). The synthesis at low growth temperature of lipopolysaccharide molecules lacking O-antigen was detected both by increased sensitivity of cells to the rough-specific bacteriophage Felix O-1 and by fractionation of oligosaccharides derived from lipopolysaccharide by mild acid hydrolysis. Growth temperature-induced changes in the structure of S. anatum A1 lipopolysaccharide also affected its ability to inactivate epsilon15, a bacteriophage that binds initially to the O-antigen portion of the molecule. Purified lipopolysaccharide prepared from cells grown at low growth temperature exhibited a higher in vitro phage-inactivating capacity than did lipopolysaccharide prepared from cells grown at physiological temperature (37 degrees C).

The effect of vibration on blood flow in skeletal muscle in the rabbit

1. The blood flow in rabbit gastrocnemius, as measured by photoelectric drop-counter, increased when the muscle was vibrated at frequencies of 22--62 Hz. 2. Blood flow increased rapidly within 1--2 s of the start of vibration, and lasted for the whole time vibration was applied. 3. The increase in blood flow was negatively correlated with the initial blood flow, being greater with lower flows. 4. The magnitude of increase was similar in both innervated and acutely denervated muscles. 5. The arterial blood pressure did not change apart from a very brief fall at the beginning of vibration. Venous pressure rose and, consequently, the perfusion pressure was lower. The increase in blood flow thus indicates a considerable dilatation in the resistance vessels of skeletal muscle.

Multiple effects of an RNA polymerase beta' mutation on in vitro transcription

S. tyrphimurium strain BY324 is temperature sensitive due to a mutation (rpo C32) in the gene for the RNA polymerase beta' subunit. Transcription of T7 DNA by RNA polymerase purified from this strain is temperature sensitive in vitro. The enzyme is slightly defective in template binding and RNA chain initiation, but the major defect is in RNA chain elongation. The rate of RNA chain elongation is reduced 4-5 fold relative to wild-type. RNA chain termination does not appear to be affected by the beta' mutation. While the elongation defect is suppressed by glycerol or dimethylsulfoxide, the initiation defect is not. Possible roles for the beta' subunit in enzyme function are discussed in light of these results.

Comparison of moving-strip therapy using a Cobalt-60 teletherapy unit, a Varian 4-MV linear accelerator, and a Varian 10-MV linear accelerator

Cobalt-60 gamma rays and 4- and 10-MV x rays are compared for moving-strip therapy in terms of the dose uniformity and the given dose needed to deliver a prescribed tumor dose. Dose distributions in phantoms of 14--32-cm thickness were calculated for each therapy unit. Individual given doses which would deliver the most uniform dose along the midline of the treatment volume were determined by computer and were verified experimentally by thermoluminescent dosimetry. Using computer optimization techniques, the midplane dose uniformity is improved significantly for the three therapy units considered.

Temperature-sensitive ribonucleic acid polymerase mutant of Salmonella typhimurium with a defect in the beta' subunit

Localized mutagenes of Salmonella typhimurium followed by a [3H]uridine enrichment procedure yielded a temperature-sensitive strain with a mutation in the rpo region of the chromosome. Ribonucleic acid (RNA) polymerase (EC 2.7.7.6; nucleoside triphosphate: RNA nucleotidyltransferase) purified from this mutant was considerably less active at the nonpermissive temperature than wild-type enzyme. Furthermore, the enzyme from this mutant, unlike RNA polymerase of previously isolated temperature-sensitive mutants, was as thermostable as wild-type enzyme when preincubated at 50 degrees C. Subunit reconstitution experiments have shown that the temperature sensitivity is caused by an alteration in the beta' subunit of the enzyme.

Genes affecting coliphage BF23 and E colicin sensitivity in Salmonella typhimurium

Rough strains of Salmonella typhimurium were sensitive to coliphage BF23. Spontaneous mutants resistant to BF23 (bfe) were isolated, and the trait was mapped using phage P1. The bfe gene in S. typhimurium was located between argF (66% co-transducible) and rif (61% co-transducible). The BF23-sensitive S. typhimurium strains were not sensitive to the E colicins. Cells of these rough strains absorbed colicin, as measured by loss of E2 or E3 killing units from colicin solutions and by specific adsorption of 125I-colicin E2 to bfe+ cells. Sensitivity to colicins E1, E2, and E3 was observed in a S. typhimurium strain carrying the F'8 gal+ episome. This episome complemented the tolB mutation of Escherichia coli. We conclude that the bfe+ protein satisfies requirements for adsorption of both phage BF23 and the E colicins. In addition, expression of a gene from E. coli, possibly tolB, is necessary for efficient E colicin killing of S. typhimurium.

Effective treatment for paraquat poisoning in rats and its relevance to treatment of paraquat poisoning in man

After oral administration of a lethal dose of paraquat to rats the plasma concentration remained relatively constant over four to 30 hours and was related to the paraquat content of the small intestine over the first 16 hours. During the first 30 hours the concentration of paraquat in the lung rose progressively above that of the plasma to levels which are known to cause pulmonary damage. A treatment has been devised which prevents the absorption of paraquat into the plasma and prevents accumulation of paraquat in the lung. This treatment consists of a stomach was followed by four administrations of bentonite plus purgatives at two- to three-hour intervals. Even when treatment was delayed until 10 hours after administration of paraquat 80% survival was obtained. The relevance of this treatment to paraquat poisoning in man is discussed in the light of the finding that slices of human lung accumulate paraquat in the same way as those of rat lung.

Effects of a mutator mutation of Salmonella typhimurium on P22 and R factor genes

A mutator mutation of Salmonella typhimurium, observed in a strain resistant to P22 and rifampin, affects mutation rates of bacterial, R factor, and prophage P22 genes.

The effects of neurohypophysectomy on the pattern of renal excretion in the duck (Anas platyrhynchos)

Renal excretion in intact, sham-operated and neurohypophysectomized ducks was studied. Neurohypophysectomy produced immediate and profound polydipsia and polyuria. These conditions steadily diminished during the first 2 weeks after the operation and by the 14th day they had stabilized at levels which were approximately three times higher than the corresponding values in sham-operated birds. The stabilized levels of polydipsia and polyuria persisted throughout the remainder of the 60–90 day experimental period. The rates of excretion of Na+, Cl− and total osmotically active material were also increased when compared with intact or sham-operated birds. No change in the rate of K+ excretion was observed.

The i.m. administration of vasopressin reduced the rate of urine flow to that observed in the control birds but the rates of electrolyte excretion were not restored to normal. Synthetic oxytocin had no antidiuretic effect in the neurohypophysectomized birds. Arginine vasotocin treatment restored the rates of both water and ion excretion to values very close to those observed in intact and sham-operated birds.

The effects of corticotrophin, glucose and potassium chloride on secretion by the nasal salt gland of the duck, Anas platyrhynchos

Ducks given corticotrophin (ACTH) i.m. for 5 days secreted significantly more nasal fluid in response to an i.v. injection of 0·5 m-NaCl. However, blood glucose and plasma potassium concentrations also increased in the birds given ACTH and when these changes in blood composition were produced by injecting glucose or KC1, an effect similar to that of ACTH was obtained, suggesting that glucocorticoids influence the salt gland indirectly rather than, or as well as, directly. The concentrations of Na+ and K+ in the nasal fluid were decreased by ACTH, an effect not mimicked by glucose or KC1, and this might suggest some direct influence on water movements in the salt gland. ACTH increased nasal secretion in response to a minimal stimulatory salt load approximately 15 min after i.v. injection and this increase coincided with a marked rise in blood glucose concentration.