Microbial colonization of rat colonic mucosa following intestinal perturbation

An allochthonous population of spiral-shaped bacteria was found colonizing the surfaces of the colonic mucosa of rats after they had been given magnesium sulphate (MgSO4)-induced diarrhea. These organisms were rarely seen in normal control rats and were not displaced when the treatment was ceased, remaining associated with the tissue for periods of up to 180 days. Similar bacteria were also found when specific pathogen-free rats, lacking mucosa-associated populations, were inoculated with homogenized rat intestine from conventional animals. Light and electron microscopic observations showed that the organisms were attached to the surface of the colon, orientated at right angles to the tissue, with one end inserted into the microvillus border. This is the first report of long-term colonization, following perturbation of the gut ecosystem, of a site on the gastrointestinal mucosa not normally associated with bacteria. The ultrastructure and mode of attachment of these organisms were very similar to that of spiral-shaped bacteria known to associate with the colonic mucosa in monkeys and man.

Temporal characteristics of cortisol metabolism in adrenalectomized primates

The rhythmicities observed in the plasmatic levels of cortisol are generally attributed to rhythms of production and release of the hormone. Since the plasmatic concentration of any given substance is a function of its production and its removal from the circulation, it is conceivable that the metabolism of cortisol also occurs in an oscillating fashion. To test this hypothesis Rhesus monkeys were submitted to bilateral adrenalectomy; cortisol was replaced at a constant infusion rate while blood was sampled at hourly intervals for the measurement of cortisol plasma levels. Rhythmic oscillations in the cortisol levels were observed. These rhythms exhibited two major components: a circadian and an ultradian component. The authors suggest that these rhythms be considered whenever normal or pathologic hormone rhythmicities are analyzed.

Lipogenic enzyme activity and fructose 2,6-bisphosphate concentration in livers of two lines of domestic fowl (Gallus domesticus) selected for different body fat content

Livers were obtained from two lines of domestic broiler which had been selected for low (lean) and high (fat) plasma very-low-density lipoprotein concentration over three generations. The fat line possessed significantly higher hepatic specific activities of malate dehydrogenase (NADP), ATP citrate lyase and fatty acid synthase, and lower glucose bisphosphatase than the lean line. The glycolytic enzymes, pyruvate kinase and phosphofructokinase, were similar and so was the concentration of fructose 2,6-bisphosphate. This recently discovered metabolic regulator was present at somewhat higher concentrations than previously reported in rats or mice. It exhibited a positive correlation with phosphofructokinase activity (only data for the fat line are shown), and stimulated enzyme activity when added to crude preparations.

Shark cartilage contains inhibitors of tumor angiogenesis

Shark cartilage contains a substance that strongly inhibits the growth of new blood vessels toward solid tumors, thereby restricting tumor growth. The abundance of this factor in shark cartilage, in contrast to cartilage from mammalian sources, may make sharks an ideal source of the inhibitor and may help to explain the rarity of neoplasms in these animals.

Ambulatory blood pressure recorder

A 24-hour, 3.5-lb., fully automatic, indirect blood pressure monitoring device has been developed that permits up to 40 programmed and manual readings each hour during normal daily activities. A study comparing the automatic ambulatory device with standard conventional sphygmomanometry revealed mean absolute differences of blood pressure measurement of less than 5 mmHg and mean pairwise differences of 2 mmHg for both systolic and diastolic pressures.

Patterns of alcohol consumption and fetal development

Effects of heavy, moderate, and rare alcohol consumption on fetal development were analyzed in a prospective study of 469 mother-infant pairs. Differential effects of heavy drinking in early and late gestation were evaluated by separate analysis of neonates born to women who reduced consumption before the third trimester. Using chi 2 analysis, multiple regression, and matched sets, statistically significant associations (P less than .01) were observed between sustained heavy drinking and both intrauterine growth retardation and congenital anomalies. These associations were independent of eight other risk factors. No differences were observed between offspring of rare and moderate drinkers. Infants born to women who reduced heavy drinking did not differ in growth from offspring of rare and moderate drinkers but demonstrated a higher frequency of abnormalities. Sustained heavy drinking represents a major risk; reduction in midpregnancy can benefit the newborn. Identification and therapy of heavy drinking are important components of prenatal care.

High-performance liquid chromatographic analysis of the new hypoxic cell radiosensitiser, Ro 03-8799, in biological samples

A high-performance liquid chromatographic method of analysis with UV detection has been developed to measure levels of a new radiosensitiser, Ro 03-8799 and its N-oxide metabolite, in biological fluids and tissues. The accuracy and precision of the method have been determined in both plasma and urine, where the limits of quantitation are 100 and 500 ng/ml, respectively. Typical results are presented from a human volunteer study where samples were analysed by this method. Important aspects of the method, involving both sample handling techniques and chromatographic conditions are discussed.

Isolation and characterization of a spiral bacterium from the crypts of rodent gastrointestinal tracts

Spiral-shaped bacteria with a distinctive morphology were isolated from the intestinal mucosa of rats and mice on a campylobacter selective medium using microaerophilic incubation. These bacteria have been shown by other authors to be present in the intestinal tracts of several animal species but have not been cultured previously. The results of electron microscopic examinations and biochemical testing have shown that these organisms do not correspond to any known genus. Colonization experiments with pure cultures in gnotobiotic rodents have shown these bacteria to be mucosa associated, with a particular affinity for intestinal crypts. The pattern of colonization of the intestinal crypts in gnotobiotes known to be free of other mucosa-associated organisms differed from the colonization occurring in conventional animals that possess a normal mucosa-associated flora.

Segmented filamentous bacteria in the rodent small intestine: Their colonization of growing animals and possible role in host resistance toSalmonella

The establishment and proliferation of a model population of autochthonous surface-associated microorganisms in the small bowel of growing rats (2-12 weeks of age) was studied. Segmented filamentous bacteria on the distal ileal villi were examined by scanning electron microscopy (SEM) and countedin situ by transect line analysis. In young animals, these bacteria first colonized the villous base, but occupied all areas on the villus by adult age. Their distribution on Peyer's patches was also noted.In growing animals, colonization of the ileal villi by filamentous bacteria was significantly correlated to the development of host resistance to fatal infection by orally-dosedSalmonella enteritidis. In animals givenSalmonella and examined by SEM and transmission EM (TEM), the pathogen was seen only on ileal tissue surfaces, predominantly the villous base, from which the autochthonous population was absent. Conversely, in animals with filamentous bacteria,Salmonella surface colonization was not observed. The results suggest a possible protective role for the surface flora in the small bowel.

Differentiation of subtypes within Leptospira interrogans serovars Hardjo, Balcanica and Tarassovi, by bacterial restriction-endonuclease DNA analysis (BRENDA)

Various strains of Leptospira interrogans were compared by bacterial restriction-endonuclease DNA analysis (BRENDA). Field strains of serovar hardjo isolated from domestic animals in New Zealand, Australia and Northern Ireland were indistinguishable from one another but differed strikingly from the hardjo reference strain Hardjoprajitno. Similarly, field isolates of balcanica and tarassovi differed from their serovar reference strains, probably owing to a difference in epidemiological niche. Subdivision of these serovars into distinct subtypes as defined by BRENDA is therefore useful and justified. In contrast, analysis of serovars pomona, ballum and copenhageni shows that field and reference strains were identical, or differed only by a single band. It is suggested that BRENDA will overcome many of the problems associated with serological methods of identifying serovars and allow more precise definition of epidemiological relationships between strains and their hosts.

The bacterial colonization of the large bowel of pre-term low birth weight neonates

The bacterial colonization of the large bowel of 11 pre-term, low birth weight neonates who were nourished by expressed breast milk was examined by culturing serial faecal samples and compared to that observed in eight breast-fed and seven formula-fed full-term neonates. Pre-term neonates were colonized by high counts of facultatively anaerobic bacteria from the first days of life while bifidobacteria colonized only six babies during the first week and appeared in only one baby before day 5. Bacteroides spp. and clostridia were isolated from seven and six pre-term babies respectively during week 1 and were first observed on day 2. The intestinal colonization of pre-term infants differed from that in full-term breast-fed infants in the high counts of facultatively anaerobic bacteria and late appearance of bifidobacteria, and from both groups of full-term infants in the early stable colonization by Bacteroides spp. It is postulated that the composition of the normal intestinal microflora of pre-term low birth weight babies contributes to their predisposition to neonatal necrotizing enterocolitis. Results are discussed in relation to the effect of infant feeding regimens on intestinal microbial populations.

Evidence for opioid and non-opioid forms of stimulation-produced analgesia in the rat

This study compares stimulation-produced analgesia (SPA) elicited from two different midline regions of the midbrain of the rat. Dorsal electrode placements were in the caudal periaqueductal gray matter; ventral placements lay within or subjacent to the dorsal raphe n. SPA thresholds were measured by the tail-flick method both during and immediately after the period of brain stimulation. Thresholds were consistently higher in the post-stimulation test. SPA from dorsal and ventral regions differed in the following ways: (1) Post-stimulation analgesia was significantly more difficult to obtain in ventral than in dorsal regions, whereas during-stimulation analgesia did not vary as a function of electrode location; (2) Although a continuous distribution of thresholds was seen for ventral placements, thresholds for dorsal placements tended to be either high or low on both during- and post-stimulation tests; (3) Naloxone (0.01--10 mg/kg) reliably elevated SPA thresholds for ventral but not dorsal stimulation placements. We conclude that different substrates of SPA lie in close proximity to one another in the medial midbrain of the rat. This portion of the midbrain appears to mediate both opioid and non-opioid mechanisms of analgesia.

The microbial ecology of the large bowel of breast-fed and formula-fed infants during the first year of life

The succession of bacterial populations in the large bowel of seven breast-fed and seven formula-fed infants was examined during the first year of life. The composition of the intestinal microflora varied according to the infant's diet. During the first week of life breast-fed and formula-fed infants were colonised by enterobacteria and enterococci followed by bifidobacteria, Bacteroides spp., clostridia and anaerobic streptococci. From week 4 until solid foods were given, breast-fed babies had a simple flora consisting of bifidobacteria and relatively few enterobacteria and enterococci. Formula-fed babies during the corresponding period were more often colonised by other anaerobes in addition to bifidobacteria and had higher counts of facultatively anaerobic bacteria. The introduction of solid food to the breast-fed infants caused a major disturbance in the microbial ecology of the large bowel as counts of enterobacteria and enterococci rose sharply and colonisation by Bacteroides spp., clostridia and anaerobic streptococci occurred. This was not observed when formula-fed infants began to take solids; instead, counts of facultative anaerobes remained high while colonisation by anaerobes other than bifidobacteria continued. At 12 months, the anaerobic bacterial populations of the large bowel of breast-fed and formula-fed infants were beginning to resemble those of adults in number and composition and there was a corresponding decrease in the number of facultative anaerobes. These changes are discussed in relation to changes in susceptibility to gastro-intestinal infection.

A transport method for swab specimens submitted for aerobic and anaerobic bacteriology

The need for separate swab transport methods for aerobes and anaerobes may result in inadequate transport of specimens for anaerobic bacteriology. Most microbiology laboratories in Australia rely on Stuart's transport medium to protect anaerobic bacteria. This paper presents a new, simple transport medium (Transport Deep) suitable for sue with aerobes and anaerobes. Comparative evaluations demonstrate that Transport Deep is as good as Stuart's medium for the maintenance of fastidious bacteria and is far superior for the protection of even extremely oxygen-sensitive anaerobes. This medium has been used successfully in a large Sydney hospital for more than a year. It is proposed that Transport Deep be used on a routine basis for all swab specimens.

Improving communication of microbiology test results

A number of basic guidelines for the reporting of microbiological data are presented. These guidelines were generated as part of a project investigating the communication gap between the microbiology laboratory and the clinician. A series of interviews and workshops were held with senior medical and microbiology staff from a number of major hospitals. A major finding of this project was that insufficient time was considered to be given to the reporting of laboratory data compared to generation of that data; also, the laboratory should take greater responsibility for interpretative comments. These guidelines are presented as a basis for review of laboratory reporting practices.

Clostridia isolated from the feces of infants during the first year of life

Clostridia isolated from the feces of ten healthy infants during the first year of life were identified. All infants excreted clostridia during the first week of life; the most common species were Clostridium butyricum, C. paraputrificum, and C. difficile. In the formula-fed infants colonization occurred consistently throughout the year, whereas in some breast-fed infants it was inhibited until weaning. The species isolated most frequently throughout the year were C. paraputrificum, C. butyricum, C. ramosum, C. sartagoformum, and C. perfringens. Of the species often found in infants, C. butyricum, C. difficile, and C. sartagoformum occur rarely in adults, reflecting differences in the environmental conditions in the gut of the two age groups. The mechanism by which environmental conditions select species of clostridia is unknown but may be important to our understanding of a variety of clostridial intestinal infections. It was demonstrated that species of clostridia which have been implicated in the etiology of neonatal necrotizing enterocolitis form part of the normal infant gastrointestinal microflora.

Colonization of the large bowel by Clostridium difficile in healthy infants: quantitative study

Colonization of the large bowel of healthy infants by Clostridium difficile was studied. Feces were collected from five breast-fed aand five formula-fed infants throughout the first year of life, and levels of C. difficile were quantitated. Three breast-fed and five formula-fed infants were colonized for periods of between 8 and 42 weeks, and another infant harbored the organism only during week 1. Colonization of breast-fed infants commenced before or during weaning, with levels reaching 10(3) to 10(5) organisms per g of wet feces. Colonization of formula-fed infants commenced before solid foods were given, with levels of 10(3) to 10(7) organisms per g of wet feces. Isolates from eight of the babies were shown to produce cytotoxin in vitro. Single fecal specimens from 60 more children aged up to 4 years were also examined, and it was found that the carriage rate of C. difficile fell sharply after 1 year of age, although in the second year it was still higher than in adults. These findings are discussed in relation to the microbial ecology of the large bowel and the paradox that levels of C. difficile in the large bowel of healthy infants are similar to those causing pseudomembranous colitis in patients.

Changes in clinical presentation and management of malignant melanoma

Records of 147 patients with primary cutaneous malignant melanoma treated at the Lahey Clinic from 1955--1979 were reviewed. Complete clinical follow-up data were obtained, and all pathologic material was reviewed. Proposed new risk categories based on a modification of the Clark and Breslow categorizations are outlined. The incidence of low-risk melanoma has dramatically increased (from 23--53%) and that of high-risk melanoma has decreased (from 34--10%) over the period of this study. Dermal punch biopsy gives accurate staging information and carries no increased risk of local recurrence, nodal metastases, or death from disease. Resection of a margin of clinically uninvolved skin measuring twice the diameter of the primary melanoma minimizes local recurrence (2.5% or less), does not adversely affect survival, and reduces the need for skin grafting. Arbitrary wide margins are not justified. Regional lymphadenectomy offers no improvement in survival in patients with low-risk and moderate-risk melanoma and can play only a minor role at most in improving survival for patients with high-risk melanoma.

Case analysis as a teaching method in the paraclinical sciences

A major problem in the teaching of the preclinical and paraclinical sciences to medical students is that courses are often taught in isolation from the clinical programme and students have difficulty relating the different types of learning experiences. This paper introduces case analysis as method designed to overcome this problem. The casebook method is popular with students and staff members and is a practical way of encouraging independent and motivated learning in the paraclinical sciences.

Reporting practices of microbiology laboratories

Results of investigations on typical specimens were circulated to Australian microbiologists, who were asked to draft reports on the basis of the data provided. Many laboratories were found simply to report the results of their activities without explanations. This was true whether the finding was that of a Gram-negative rod in a postoperative sputum or an anaerobic diphtheroid in a blood culture. There was diversity of views as to what constituted probable contamination in a urine specimen. Often no clearcut verdict was given, nor did the report indicate when no conclusion was possible. Remedial measures are discussed.

[3H]ouabain autoradiography of frog retina

The kinetics and distribution of ouabain binding in retinas of Rana pipiens were examined quantitatively by scintillation counting and freeze-dry autoradiography. The time-course of binding at several concentrations was consistent with a bimolecular reaction. Estimated equilibrium binding levels gave a Michaelis-Menton relationship with a Km = 8.3 x 10(-8) M and a maximum binding level (Bmax) = 4.4 x 10(-8) mol/g protein. The distribution of binding sites measured autoradiographically varied considerably between layers. The photoreceptor, inner plexiform, and optic nerve fiber layers exhibited the heaviest binding. Within the photoreceptor layer, binding was nonuniform. Binding in the outer segment decreased distally, averaging approximately 4% of that in the proximal receptor layers (Bmax = 4.6 x 10(-6) M). The origin of the outer segment activity is uncertain at light microscope resolution, as it may be a result of inner segment calyceal processes. Binding within the proximal receptor layers was also nonuniform. Several peaks were observed, with those at the inner segment and synaptic layers being especially noticeable. Assuming an absence of glial cell binding in the proximal receptor layers, we calculated there to be 13 x 10(6) ouabain or Na+,K+ pump sites per rod receptor. Limited measurements suggest a Bmax of approximately 8 x 10(-6) M for the inner plexiform layer.

Effects of maternal drinking on neonate state regulation

Sleep-awake state distribution during inter-feed intervals over a 24-hour period on the third day of life was investigated by means of a continuous non-intrusive bassinet sleep monitor. 31 infants were studied: 14 born to mothers who drank heavily throughout pregnancy (group A), eight whose mothers modified their heavy drinking (group B) and nine whose mothers never were heavy drinkers (group C). Over the 24-hour period, group A infants slept less than those in group B. In comparison with group C, group A infants had a larger proportion of quiet sleep episodes interrupted by awake or unclassified epochs, and were more restless, with more frequent major body movements. These pilot observations suggest that heavy maternal consumption of alcohol, when continued throughout pregnancy, is associated with a disturbance of sleep-awake state distribution. Successful therapy of heavy drinking during pregnancy may improve the physiological competence of the newborn to regulate sleep-awake states and facilitate interaction between mother and infant.

The preservation of surface-associated micro-organisms prepared for scanning electron microscopy

Scanning electron microscopy (SEM) has become a popular means of studying micro-organisms which associate with surfaces. However, as yet no detailed examination has been made of the influence of specimen preparation on the number of organisms finally seen on the SEM screen. In this investigation critical assessment is made of the influence of a wide range or preparative factors on the preservation of filamentous bacteria associated with the epithelial surfaces of rat intestine. Organisms were quantitated using a rigorous counting method (transect line analysis); statistical testing of these counts enabled the comparison of different preparative factors. The composition of the fixative was found to significantly influence the number of organisms preserved; of the fifteen fixatives studied, Karnovsky's fixative with ruthenium red best preserved surface-associated organisms. The influence of other factors on the number and appearance of preserved organisms was also examined. These factors included the washing of specimens prior to fixation, the storage of fixed specimens, and the handling and storage of critical point dried specimens. The results are discussed with reference to the optimal methods for preparing specimens for SEM.

Consumer survey on microbiology reports

5 typical microbiology reports were circulated to the medical staff of a 900-bed teaching hospital and they were asked for their interpretations. Approximately 160 completed replies were received and it was clear that the reports were often misinterpreted; one report (isolation of a gram-negative rod from sputum) was misinterpreted by four doctors out of five. The reasons for this failure of communication seem to be the use of jargon and unfamiliar names of bacterial species, and use of ill-defined reporting conventions. The omission of a clear-cut conclusion from many reports also contributed to misunderstanding. These deficiencies in reporting practices result in unnecessary antibiotic therapy and unnecessary work for the laboratory, since clinicians are more likely to ask for a repeat of a test with a doubtful interpretation. Communications with clinicians would be more effective if microbiologists ensured that each report is free of jargon, states what conclusion can be drawn from the test, and makes recommendations, where appropriate, for antibiotic therapy.

How to…: Organize Effective Laboratory Teaching in Medicine. Part 2, Design

In this second article on laboratory teaching in medicine, the authors discuss the design of laboratory manuals and displays, the design of laboratory exercises to meet important goals of medical teaching, and the sequencing of curricula involving laboratory work. Readers are encouraged to consider laboratory classes in their own disciplines and within their own institutions, and to answer the questions set out in a check list provided by the authors at the end of the article.

The mucosa-associated microflora of the rat intestine: a study of normal distribution and magnesium sulphate induced diarrhoea

Specimens of intestinal mucosa of rats were examined closely to determine the distribution of the mucosa-associated microbial flora. Six distinct zones were found along the length of the intestinal tract. The first zone, in the small intestine 50 cm or more from the ileocaecal junction, had no associated flora: however, each of the five other zones had different populations of microorganisms associated with the mucosa. Some of these organisms have not been reposted previously. Treatment of rats with oral doses of the purgative magnesium sulphate resulted in dramatic changes in the distribution of these mucosa-associated microorganisms. The normal flora of ileal and caecal crypts disappeared, while the organisms in colonic crypts were unchanged. Large numbers of mucosa-associated bacteria appeared in the stools of treated animals.

Once daily propranolol in the treatment of mild to moderate hypertension: a dose range finding study

Propranolol was administered in a single dose of 80 mg, 120 mg, 160 mg, 240 mg, or 320 mg, to 23 patients with essential mild to moderate hypertension in a randomised, double-blind cross-over study. All treatments produced a significant fall in lying and standing blood pressures compared with placebo, but there was no statistically significant difference in the effects of the different doses. The percentage of patients showing a satisfactory fall in blood pressure was not different in the five treatment groups. The major anti-hypertensive effect of each dose was present by two weeks. The frequency of side-effects were similar on all the doses.