Interferon-alpha and gamma mediated gene responses in a human breast carcinoma cell line

Interferons (IFNs) have been known to possess an antiproliferative effect on tumor cells besides their well characterized antiviral effect in cell cultures. The mechanism of action of the different IFNs is not fully understood, but in recent years a number of IFN-inducible genes, the presumed mediators of IFN action, have been identified. In the present study we examined the antiproliferative effect of IFN-alpha and IFN-gamma on human breast cancer cells (MCF-7) using (i) the MTT dye formation assay and (ii) anchorage-independent (AI) growth in soft agar. Both IFN-alpha and IFN-gamma were found to have an antiproliferative effect on the growth of MCF-7 cells. In addition, the kinetics of induction of a number of IFN-inducible genes was also examined. The expression of these genes was measured by mRNA analyses using specific [alpha-32P]-labeled cDNAs as probes. The induction of these genes by IFN-alpha and IFN-gamma is a primary effect of IFN, as de novo protein synthesis is not required for their induction. Our results on the kinetics of induction of these genes by IFN-alpha and IFN-gamma suggests a complex mechanism of ligand-dependent gene activation in this cell line with some similar and dissimilar pathways.

Endotoxin induced damage to the cochlea in guinea pigs

An apparently unique form of cochlear damage was produced in guinea pigs by perfusing the cochlea or injecting the cerebrospinal fluid with bacterial endotoxin. This developed rapidly (within two hours) and was characterised by swelling of the tectorial membrane and damage to both inner and outer hair cells, with parallel functional damage demonstrable electrophysiologically. All these changes could be attenuated by pretreatment with dexamethasone. Such endotoxin mediated lesions may be the mechanism by which hearing loss occurs in bacterial meningitis.

Rotavirus-induced changes in the microcirculation of intestinal villi of neonatal mice in relation to the induction and persistence of diarrhea

Using a histochemical peroxidase technique, under conditions that preferentially stain erythrocytes, we have shown changes in the microcirculation of villi of neonatal mice infected with murine rotavirus. Between 18 and 48 h postinfection (PI), throughout all areas of the small intestine there occurred, sequentially, a marked ischemia and atrophy of villi. By 72 h PI, villi had recovered their normal height and showed incipient hyperemic microcirculation. At 96 h PI, hyperemic microcirculation was most marked. Between 120 and 144 h PI, a second phase of villus atrophy occurred, which was more attenuated and confined to the upper and middle regions of the intestine. This phase was not accompanied by a wide-spread ischemia of villi: a minority of villi were short and ischemic but many appeared hyperemic. Recovery of villus microcirculation occurred at 168 h PI, which coincided with recovery from diarrhea. These changes in villus microcirculation are discussed in relation to the pathology and pathophysiology of rotavirus infection. We make two novel suggestions. First, the reduction in red cells flowing through villi in the early stages of the infection instigates hypoxia and hence atrophy of villi. The ensuing but ephemeral increase in rate of cell division, necessary for the reconstitution of villi, induces hypersecretion. Second, the increase in numbers of erythrocytes found in villi during their regrowth phase and throughout the remaining time course of the infection perturbs the countercurrent system, lowering the osmolality of the hyperosmotic zone located at villus tips, thereby impairing water absorption and prolonging diarrhea.

Biotransformation of estradiol by explant culture of human mammary tissue

In vivo experiments on strains of mice that differ in the risk of developing mammary cancer have demonstrated a correlation between the extent of 16 alpha-hydroxylation of estradiol and incidence of mammary cancer. The ability of human mammary terminal duct lobular unit (TDLU), the site of neoplastic transformation, to metabolize estradiol or to accumulate estradiol metabolites has not been unequivocally established. Using a newly developed human mammary TDLU explant culture system and a radiometric assay for estradiol metabolism, we compared the site-specific metabolism of estradiol by the 17-oxidation, 2-hydroxylation, and 16 alpha-hydroxylation pathways in noninvolved human mammary tissue. The relative extent of estradiol 16 alpha-hydroxylation was found to be increased in TDLU from patients in the luteal phase of the menstrual cycle in relation to either those from patients in the follicular phase or from postmenopausal subjects. This study demonstrates that TDLU can metabolize estradiol extrahepatically and that 16 alpha-hydroxylation in the target tissue is dependent on the phase of the menstrual cycle. Furthermore, the specific, risk-related increase in 16 alpha-hydroxylation suggests that intrinsic metabolic ability of the target tissue leading to the formation of 16 alpha-hydroxyestrone from estradiol may be a determinant in, or a marker for, the relative risk of developing mammary cancer.

A study of the microcirculation in whole villi of neonatal mice using a peroxidase histochemical staining method

The anatomy of the microcirculation of intestinal villi from the upper, middle, and lower small intestine of neonatal mice from 8 to 14 days old was studied using a histochemical peroxidase technique that specifically stained erythrocytes. Over 8-14 days, there was little chronological variation between the same regions of gut; the exception was the lower intestine, which, in younger mice, was noticeably less well perfused with erythrocytes. Vascular beds in the middle and lower intestine comprised a hairpin loop with cross-connections. In the upper intestine, the capillary beds were generally more complex, particularly in apical regions of the villi. Most villi were well perfused with erythrocytes, but a minority (less than 10%) contained considerably fewer red cells, some to the point of being totally ischemic. Other villi (less than 5%) were hyperemic, and the vascular beds packed and engorged with red cells. Usually, the packing density (hematocrit) of red cells within blood vessels increased progressively from villus base to apex. Red-cell deformation was more prevalent at villus apices, with marked crenation in some villi, yet in the basal regions of these same villi, the red cells were of normal discoid shape. The peroxidase staining technique produces a reliable histological picture of red cells circulating through villi. It also reveals differential perfusion of erythrocytes between and within villi, and that blood vessels pass through hypertonic zones in the apical regions of villi.

Role of mastectomy in breast cancer

The surgical management of breast cancer continues to evolve in an attempt to define the ideal line between therapeutic efficacy and morbidity. It is clear that breast cancer is a biologically heterogeneous group of diseases, and no single hypothesis explains its behavior. The surgical options proposed to the individual patient must draw from the experience of retrospective clinical studies and prospective randomized trials in an attempt to optimize the treatment plan. Most patients without distant disease are eligible to consider mastectomy, which can accomplish excellent local control and significantly improve survival for earlier stages of disease. However, breast conservation remains an appropriate alternative for a carefully defined subset of patients. Today, with early-stage disease, no patient need leave the operating room without a breast. Recent advances in reconstructive surgery make mastectomy with immediate reconstruction or limited resection plus axillary dissection with postoperative radiation therapy the two principal treatment choices available. Future studies will focus on the integration of other treatment modalities. Clinical research into the use of preoperative chemotherapy to downstage the disease to permit less extensive surgery is of interest. Recent application of molecular biologic techniques such as oncogene analysis, cytogenetic studies, proliferative indices, and the highly sensitive detection of distant micrometastases using monoclonal antibodies may assist in the design of innovative approaches to surgery, radiation therapy, and systemic drug treatment. These advances show great promise for improving the quality of life and the cure rate for patients with breast cancer. Today, surgical treatment options have evolved that fulfill some of the objectives outlined by Dr. James Ewing of Memorial Hospital some 50 years ago. His concerns about breast cancer remain as relevant today as they were half a century ago: "I have drawn the impression that in dealing with mammary cancer, surgery meets with more peculiar difficulties and uncertainties than with almost any other form of the disease. The anatomical types are so numerous, the variations in clinical course so wide, the paths of dissemination so free and diverse, the difficulties of determining the actual conditions so complex, and the sacrifice of tissues so great, as to render impossible in the majority of cases a reasonably accurate adjustment of a means to an end."

Neoplastic transformation of mouse mammary epithelial cells by deregulated myc expression

A spontaneously immortalized, nontumorigenic mouse mammary epithelial cell line (MMEC) was transfected with an activated myc construct by electroporation. Constitutive expression of myc in MMEC resulted in anchorage independence in soft agar and tumorigenicity in nude mice. The myc-expressing MMEC showed higher saturation density, faster growth rate, and partial abrogation of serum-derived growth factor(s) requirement compared with parent MMEC. Epidermal growth factor or transforming growth factor alpha stimulated the anchorage-independent growth, but not the anchorage-dependent growth, of MMEC-myc cells. Type 1 transforming growth factor beta, on the other hand, inhibited both the anchorage-independent and anchorage-dependent growth of MMEC-myc cells. These results demonstrate that deregulated expression of myc results in neoplastic transformation iin mammary epithelial cells. Accompanying the transformation is altered sensitivity to polypeptide growth factors.

Disaccharidase activities in small intestine of rotavirus-infected suckling mice: a histochemical study

A histochemical study of the time course of the appearance and location of lactase and alpha-glucosidase (used to detect sucrase and maltase) activities was carried out on control and rotavirus-infected mice from 7 to 14 days old. The overall pattern of enzyme activity was in agreement with previous quantitative studies on the activities of these enzymes. No evidence was obtained to support the idea that lactase deficiency was the result of repopulation of villi (denuded of lactase-producing villus cells) with immature lactase-negative cells. Low lactase activity was more likely to reflect profound changes in metabolically crippled cells, and recovery of lactase activity with recovery of normal metabolic functions. The location of enzyme activity to brush border regions rather than the cytoplasm of villus enterocytes enhances the significance of previous quantitative studies on these enzymes. The timing and duration of diminished lactase activities were such that they were unlikely to cause the induction or perpetuation of diarrhea in murine rotavirus diarrhea. The appearance in infected animals of alpha-glucosidase 3 days earlier than normal indicates that, in addition to reversible changes seen with lactase, developmental changes were accelerated that affected both crypt and villus cells.

From HeLa cell division to infectious diarrhoea

Hela S3 cells were grown in suspension both randomly and, synchronously using hydroxyurea which blocks cells at the G1/S interface. Cryosections were prepared, freeze-dried and analyzed by X-ray microanalysis. As cells moved into S and through M phases [Na] and [Cl] increased; both returned to normal levels upon re-entering G1 phase. The Na/K ratio was 1:1 in G1 phase. Infection of HeLa S3 cells in G1 phase with vaccinia virus resulted in no change in intracellular [Na]. Infection of neonatal mice with murine rotavirus was localized to villus tip enterocytes and gave rise to diarrhoea which was maximal at 72h post-infection (p.i.). Diarrhoea was preceded by ischemia of villi (18-42h p.i.) and villus shortening (maximal at 42h p.i.), and was also coincident with a dramatic regrowth of villi. At 48h p.i. a proliferative zone of electron lucent cells was observed in villus base regions. Cryosections of infected gut, taken before, during, and after infection, together with corresponding age-matched controls, were freeze-dried and analysed by X-ray microanalysis. At 48h p.i. electron lucent villus base cells were shown to be more hydrated, and, to contain higher levels of both Na and Cl and lower levels of P, S, K and Mg than corresponding control cells. These studies (we argue) increase confidence in the use of X-ray microanalysis in studying biological systems, provide some insight into the process of cell division, and constitute the basis of a new concept of diarrhoeal secretion.

Effects of colchicine on central and peripheral nerve terminals of the locust Schistocerca gregaria

The treatment of locusts (Schistocerca gregaria) with colchicine leads to various changes in the ultrastructure of both central and peripheral nerve terminals. These changes include a marked reduction in synaptic vesicle density, which is further enhanced following stimulation. There are also increased numbers of coated pits and membraneous cisternae together with enlarged terminal areas and disruption of mitochondrial ultrastructure. The capacity of isolated central nerve terminals (synaptosomes) to take up the radiolabelled transmitter precursor [3H]-choline is enhanced following in vivo treatment of locusts with colchicine, whilst in vitro treatment leads to a reduction in choline uptake. The results are discussed with regard to the postulated effects of colchicine on axoplasmic transport.

The effect of in vivo stimulation on the cytology of neuromuscular junctions of locust flight muscles

The ultrastructure of neuromuscular junctions in dorsoventral (tergosternal) flight muscle no. 113 and dorsolongitudinal flight muscle no. 112 of the locust Schistocerca gregaria is described. Following in vivo stimulation by enforced flight, morphological and statistical analyses reveal cytological changes at these junctions suggestive of vesicular release of neurotransmitter and membrane recycling. Flight periods from 30 min to 3 h produced a progressive decrease in the density of terminal synaptic vesicles, an increase in terminal surface area and circumference, increases in the occurrence of membranous cisternae, increases in mitochondrial numbers, and increases in the frequency of coated pits.

Action of elastase, collagenase and other enzymes upon linkages between stereocilia in the guinea-pig cochlea

Enzymes, which degrade elements of the extracellular environment, were studied for their actions upon stereocilia and their cross-linkages by scanning electron microscopy. Chondroitinase, hyaluronidase and keratanase, which attack carbohydrate moieties of the extracellular matrix, had little effect upon hair bundles. Collagenase and plasmin (fibrinolysin) also had only marginal effects. Elastase produced dramatic effects upon hair bundles. Both lateral and tip links were degraded resulting in separation and splaying of stereocilia. Many stereocilia showed no marked loss of rigidity, although some were bent or kinked. In general, inner hair cells were the most susceptible to elastase followed by row 3, row 2, row 1 of the outer hair cells. The proteolytic enzyme trypsin did not noticeably disrupt the hair bundles. Protease caused loss of rigidity and fracture of stereocilia resulting in considerable collapse of hair bundles. Crosslinkages between stereocilia were less noticeably degraded. These results indicate that both lateral and tip links of stereocilia comprise a proteinaceous moiety which could be elastin or some chemically related structure.

High resolution scanning electron microscopy of stereocilia in the cochlea of normal, postmortem, and drug-treated guinea pigs

The morphology of hair bundles has been studied by high resolution scanning electron microscopy using a variety of fixatives, including glutaraldehyde, glutaraldehyde-picrate, glutaraldehyde-tannic acid, glutaraldehyde followed by post-fixation in osmium tetroxide, and the osmium thiocarbohydrazide technique. Critical evaluation of several metal coatings, gold, gold-palladium, and platinum has been carried out. Both the surface texture of stereocilia and their cross-links are sensitive to fixation and metal coating. We are of the opinion that glutaraldehyde gives the best general quality of fixation and preservation for all types of cross-links. We have described three major sets of cross-links: first, lateral links connecting stereocilia within the same row; second, lateral links connecting stereocilia of adjacent rows; and third, upward-pointing links, one per stereocilium, connecting the tip of each shorter stereocilium to the lateral surface of the adjacent taller stereocilium. Current physiological and anatomical evidence suggests that the lateral links couple the individual stereocilia within the hair bundle so that they function as a single mechanical unit. The upward-pointing tip links are ideally placed to respond to mechanical deformation of the hair bundle, being stretched when the stereocilia are deflected in the excitatory direction towards the tallest row and relaxed when deflected in the opposite, inhibitory direction. Postmortem morphological changes are detected within 15 minutes of cardiac arrest and become progressively more pronounced in time. These results enabled us to distinguish specific drug-induced changes which could not be attributed simply to cell death. Effects of cisplatin and kanamycin upon hair bundles are described. The work reported here is based on studies using the guinea pig cochlea. Some of the postmortem changes described have also been confirmed in human cochleas. It is stressed that many of the postmortem and drug-induced effects can only reliably be studied by high resolution scanning electron microscopy coupled with appropriate preparation procedures.

Differentiation of benign and malignant local tumor recurrence after lumpectomy

During a 5-year period, 28 women who had been treated conservatively for breast carcinoma had 29 reexcisions of the lumpectomy site because of suspicion of a recurrent malignant tumor. Biopsy results were benign in 19 cases and malignant in 10 cases. Sixteen of the 19 benign tumors had developed within 2 years after therapy. In 16 benign cases, a palpable lump developed at the scar and was found on biopsy to be fat necrosis or fibrosis. Seven of these cases had normal mammographic findings. Three women with abnormal mammographic findings but a normal breast examination had punctate microcalcifications develop at the scar; these were due to fibrosis in two and sclerosing adenosis in the other. Of the 10 malignant recurrent tumors, seven were palpable, four of which also were identifiable by mammography. Of seven mammographically identifiable recurrent tumors at the surgical site, four were palpable. Mammographic findings were a single mass in two cases, multiple masses in one, microcalcification in three, and a mass with microcalcifications in one. Malignant microcalcifications were all linear, irregular, and in one case branching. Mean time to recurrence in these 10 women was 3 years. This experience suggests that benign disease usually occurs at the scar within 2 years after the original therapy and when palpable may not show changes on mammography. When microcalcifications do occur, they are usually punctate.

Metabolic biotransformation of estradiol in human mammary explant cultures

The metabolism of E2 via the 16 alpha-hydroxylation pathway is reported to be elevated in breast cancer patients as well as in subjects at high risk for developing breast cancer. The biological relevance of the metabolic pathway during the initiational events that lead to the tumorigenic transformation of mammary epithelium is not fully understood. The results obtained from the in vitro experiments discussed in this report permit the following conclusions: 1. Human mammary TDLU, the presumptive target site for breast cancer, possesses metabolic competence to biotransform E2. 2. The biotransformation of E2 in TDLU via the 16 alpha-hydroxylation pathway is responsive to endogenous hormonal changes and to the presence of cancer, and is susceptible to carcinogenic insult. 3. The relative extent of E2 16 alpha-hydroxylation may constitute a sensitive metabolic marker for evaluating the susceptibility of noninvolved mammary epithelium to carcinogen-induced transformation.

X-ray microanalysis of rotavirus-infected mouse intestine: a new concept of diarrhoeal secretion

Neonatal mice were infected at 7 days of age with rotavirus [epizootic diarrhea of infant mice (EDIM) virus] and killed at 24-h intervals postinfection (PI). Cytoplasmic concentrations of Na, Mg, P, S, Cl, K, and Ca intestinal epithelial cells from infected and age-matched control animals were measured by x-ray microanalysis. In villus tip cells, Ca concentration increased at 24-96 h PI; Na concentration increased at 24-72 h PI; Ca and Na concentrations were near normal by 168 h PI. K concentration decreased 24-72 h PI, and Cl concentration decreased 48-96 h PI. In crypt cells, changes were observed without a discernible pattern: at 96 h PI, Na, Mg, S, and Cl concentrations increased and K concentration decreased; at 120 h PI, the concentrations of all elements except Na and Ca increased. In villus base cells, the mean concentrations of all elements except Ca peaked at 48-72 h PI and at 120 h PI. Na and Cl concentrations increased dramatically in some cells from 48 h PI onward. All the above concentration values were obtained from freeze-dried specimens and expressed in millimoles per kilogram of dry weight. Conversion of a limited number of data, pertaining to villus base cells, from dry weight to wet weight was possible. This conversion revealed that villus base cells in infected animals were more hydrated than corresponding cells from control animals. Also, the Na and Cl concentrations in mmol/kg H2O were significantly higher in villus base cells from infected animals than in those from corresponding controls: 137 +/- 7 versus 38 +/- 4 (Na) and 121 +/- 5 versus 89 +/- 6 (Cl). Wet weight concentrations of other elements were either the same (Mg) or lower (P, S, and K) after infection with virus. From these studies, a new concept of the pathophysiology of rotavirus-induced diarrhoeal secretion is proposed: stimulation of villus base cells to rapid cell division is accompanied by transient accumulation of Na and Cl; excess NaCl is secreted into the lumen, which is the driving force for fluid loss.

The importance of early fixation in preservation of human cochlear and vestibular sensory hair bundles

Human labyrinths were fixed with glutaraldehyde as soon as possible and certainly within 15 min of clinically confirmed death. By following this protocol, we have obtained excellent preservation of human material comparable to the best that we were able to obtain with animal tissues. Structural features that are indicative of good fixation in animal hair bundles, namely well-defined lateral cross-links, upward pointing tip links and the 'granular' appearance of the surface membrane of stereocilia are confirmed for human hair cells. Our results show that excellent preservation of human hair bundles is critically dependent upon early fixation.

Cellular ras protooncogene expression in human mammary explant cultures. A potential marker for chemical carcinogenesis

The major findings of the present study can be summarized as follows: 1. The newly developed assay for quantitative determination of ras protooncogene expression which utilizes affinity labeling of ras p21 with [alpha-32P]GTP can effectively demonstrate the presence of ras protooncogene expression in explant cultures of human mammary tissues. 2. The prototype chemical carcinogens NMU and BP induce amplified expression of ras protooncogene in benign (noninvolved) human mammary TDLU. 3. The specific enhancement of ras expression by BP in TDLU (target tissue) but not in MF (nontarget tissue) for tumorigenesis indicates that the constitutive levels of ras protooncogene in the target tissue are responsive to carcinogenic insult. 4. The relative extent of ras protooncogene expression may constitute a sensitive marker for target tissue susceptibility to chemical carcinogenesis.

An in vitro model to study aspects of the pathophysiology of murine rotavirus-induced diarrhoea

An in vitro system is described and validated for studying transport of solutes and water in both uninfected and rotavirus-infected neonatal mouse intestine. Control intestine exhibited stable water absorption for periods of up to 40 min. Water absorption was temperature-dependent. Na-dependent, and enhanced by glucose-containing perfusion solutions. Theophylline induced net secretion of water by control intestinal tissue. Water transport by rotavirus-infected lower small intestine was significantly depressed as compared to control levels, and rotavirus-infected middle small intestine exhibited net secretion of water. Upper small intestine and colon from infected animals did not differ significantly from control tissues in their ability to transport water. Water secretion by infected middle small intestine was reversed to absorption by glucose-containing solutions.

Influence of chemopreventive agents on estradiol metabolism and mammary preneoplasia in the C3H mouse

The C3H strain of mouse has a high incidence of murine mammary tumor virus-induced mammary tumors, and tumorigenesis progresses via the intermediate formation of the preneoplastic, hyperplastic alveolar nodules (HANs). The C3H mouse also exhibits an elevation in 16 alpha-hydroxylation of estradiol which remains unaltered in relation to the age or presence of tumor, but which is detectable well before the emergence of overt mammary cancer. This metabolic pathway leads to the formation of 16 alpha-hydroxyestrone (16 alpha-OHE1), a putative promoter of mammary cancer. The present study examines the effect of two prototype chemopreventive agents, tamoxifen (TAM) and N-(4-hydroxyphenyl)retinamide (HPR), on 16 alpha-hydroxylation of estradiol and on the growth of HANs. Treatment with TAM, HPR, or a combination of TAM and HPR for 4 weeks in 6- to 8-week-old C3H mice resulted in a consistent elevation in the 16 alpha-hydroxylation pathway of estradiol metabolism relative to the placebo control group (20.50% +/- 2.35%, 21.46% +/- 1.49%, 18.00% +/- 1.75%, and 12.64% +/- 1.45% SD, respectively) and in a significant decrease in the mean frequency of HANs per mammary gland (1.4, 2.1, 0.0, and 5.8, respectively). Mice without any experimental manipulation exhibited an age-dependent progressive increase in HAN frequency from 1.5 per gland at 4 weeks of age to 12.1 per gland at 24 weeks of age. Administration of TAM, HPR, or a combination of TAM and HPR up to 22 weeks of age resulted in a continued suppression of HAN frequency, and the two agents in combination exerted an additive effect on the suppression of HAN development.(ABSTRACT TRUNCATED AT 250 WORDS)

Occult breast cancer presenting with axillary metastases. Updated management

An isolated axillary lymph node metastasis in a woman without an obvious clinical primary site most frequently originates from the breast. Mastectomy has been the historical treatment of choice. A retrospective study of 35 patients was undertaken to evaluate the roles of modern mammography, breast preservation, and adjuvant systemic therapy in the management of these patients. Twenty-eight patients underwent a mastectomy, while 7 were managed by a combination of limited resection and/or axillary dissection and radiation therapy. Twenty-two (67%) of the 33 breast specimens contained carcinoma. Comparison of the pathologic results with the preoperative mammograms showed a specificity of 73%, while the sensitivity was only 29%. Actuarial 5-year survival after mastectomy or breast preservation was similar (77% and 65%, respectively). Patients with more than one positive lymph node benefited from adjuvant therapy. Mammography does not locate the majority of occult stage II breast cancers, and both breast preservation and adjuvant therapy may have roles in the management of these patients.

Effect of furosemide upon morphology of hair bundles in guinea pig cochlear hair cells

Furosemide was administered by intraperitoneal injection and intracochlear perfusion. The peak-to-peak amplitude of the cochlear microphonic at high sound intensities was reduced however the drug was administered. After a period of time ranging from 1-4 h following drug application, cochleae were fixed and prepared for scanning electron microscopy to examine the hair cells. Changes in the hair bundles from basal turns tended to be more extensive than those of more apical turns. Initially there was an increase in the granularity of the surface of the stereociliary membrane and a tendency for cross-links to swell, stretch and break. Later, the surface texture of stereocilia became smoother than normal, and hair cells in the basal turns showed extensive erosion and fracture of cross-links. Tip links could survive even when extensively stretched. It is possible that the morphological changes in stereocilia reported here do not arise from direct actions of furosemide, but indirectly, from perturbations of the ionic composition of cochlear fluids induced by effects of the drug upon the stria vascularis.

The role of leucocytes in the induction of fluid secretion by Salmonella typhimurium

Nitrogen mustard (N2M) treatment of rabbits induced neutropenia, and, in ligated ileal loops, it inhibited fluid secretion induced by salmonella or by cholera toxin (CT). Pretreatment of rabbits with indomethacin almost abolished salmonella-induced fluid secretion and significantly reduced that induced by CT. Similar effects of N2M and indomethacin on fluid secretion induced by salmonella, but not by CT, have been reported by other workers and used to implicate prostaglandins, from the salmonella-induced inflammation, as mediators of fluid secretion. In contrast, we show that N2M treatment, in addition to reducing CT-induced secretion, caused severe morphological alterations to ileal mucosa. Irradiation techniques were developed for inducing neutropenia, but they did not totally inhibit salmonella-induced leucocyte influx into ileal mucosa. We propose an alternative mechanism for the inhibitory effect of N2M on salmonella- and CT-induced secretion, based on the known anti-mitotic activity of N2M. Also, the anti-secretory effect of indomethacin cannot be attributed uniquely to its anti-inflammatory activity because it depressed CT-induced secretion as well as salmonella-induced secretion. These results support the concept of pathophysiological secretion in infectious diarrhoea, developed previously for rotavirus and extended to bacterial infections.

Quantification of the leucocyte influx into rabbit ileal loops induced by strains of Salmonella typhimurium of different virulence

Leucocyte influx into rabbit ileal loops, induced by strains of Salmonella typhimurium of different virulence, was assessed with 111Indium-labelled leucocytes. Strains fell into two groups on the basis of their leucotactic potential: "virulent" strains (which induced fluid secretion) caused a dose-dependent leucocyte influx; strains which did not induce fluid secretion failed to induce a significant leucocyte influx. Fluid secretion was never observed in the absence of leucocyte influx, but leucocyte influx per se did not induce fluid secretion. The phenotype of the challenge inoculum influenced fluid secretion; young log-phase organisms induced fluid secretion with a higher frequency than overnight cultures. These findings support earlier evidence implicating leucocytes in an interactive but not exclusive role in the genesis of salmonella-induced fluid secretion. They suggest, though do not prove, that interaction of leucocytes with the appropriate phenotype of organisms results in the release of a host-derived or bacterial secretagogue, or both. The bacterial factor may or may not be the antigen related to cholera toxin, described previously.

Post-mortem changes in hair bundles of the guinea pig and human cochlea studied by high-resolution scanning microscopy

High-resolution scanning electron microscopic studies have been made on the guinea pig cochlea on material fixed from 15 min to 4 h post-mortem. Changes in the surface texture and cross-links of stereocilia were detected after only 15 min. Such changes included an increase in granularity of the surface membrane, thickening, stretching and fracturing of all types of cross-links accompanied by splaying apart and loss of rigidity of stereocilia. These changes were more pronounced in the basal turns of the cochlea and in general increased in severity and spread more apically with increasing times post-mortem. By 4 h, many hair bundles consisted of a fused amorphous mass in which individual stereocilia were not discernible. Remarkably at this time, some hair bundles appeared to have suffered little damage. These results will facilitate better discrimination between effects solely due to post-mortem necrotic changes and those due to specific actions of ototoxic drugs and other insults.