M J Tarlow

Temperature-dependent modulation of lipopolysaccharide-induced interleukin-1 beta and tumor necrosis factor alpha expression in cultured human astroglial cells by dexamethasone and indomethacin.

In bacterial meningitis, LPS induces production in cerebrospinal fluid of the cytokines IL-1 beta and tumor necrosis factor alpha (TNF alpha), which are the principle mediators of meningeal inflammation. IL-1 beta and TNF alpha induce fever, and elevated temperature may affect cytokine expression. Dexamethasone treatment improves outcome in bacterial meningitis possibly by inhibiting IL-1 beta and TNF alpha. In this report, the effects of elevated temperature and dexamethasone on LPS-stimulated IL-1 beta and TNF alpha mRNA gene expression and protein synthesis were studied in human astrocytoma cell lines and primary cultures of human fetal astrocytes. Cells cultured at 40 degrees C exhibited smaller peaks of IL-1 beta and TNF alpha transcription and protein synthesis compared with cells cultured at 37 degrees C. The addition of dexamethasone before, during, or after exposure of the cells to LPS resulted in temperature-dependent inhibition of IL-1 beta transcription and protein synthesis. The most extensive inhibition occurred in pretreated cells cultured at 37 degrees C. Cotreatment with LPS and dexamethasone also inhibited TNF alpha mRNA transcription at both temperatures. The effects of another antiinflammatory agent, indomethacin, on LPS induction of IL-1 beta and TNF alpha mRNA were temperature and cell line dependent. These findings provide a possible explanation for the efficacy of dexamethasone treatment of bacterial meningitis and support the proposal that fever may be beneficial to the host in this disease.

Possible Involvement of Nitric Oxide in the Sensorineural Hearing Loss of Bacterial Meningitis

Microperfusion of scala tympani with the NO donors, sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine (SNAP), produced marked depression of the compound action potential (CAP) and cochlear microphonic (CM) together with severe and widespread morphological damage to hair cells and supporting cells in the organ of Corti. In addition, direct perfusion of N-methyl-D-aspartate (NMDA) into scala tympani, which probably induces excess stimulation of NMDA receptors within the cochlea and which is known to lead to the release of NO, was found to elicit similar electrophysiological and structural lesions in the cochlea. Pre-perfusion of scala tympani with L-methyl arginine (L-MA), which inhibits the release of NO, or superoxide dismutase (SOD), an O2-scavenger, conferred marked protection upon the cochlea from the lesions caused by NO donors. These observations indicate that enhanced NO production is likely to be an important factor responsible for pathological insult of the cochlea. The possibility is discussed that this factor is involved in the chain of events leading to hearing loss caused by bacterial meningitis. Such hearing loss is a major sequela of bacterial meningitis in children.

Cytotoxic Effects on Hair Cells of Guinea Pig Cochlea Produced by Pneumolysin, the Thiol Activated Toxin of Streptococcus pneumoniae

The cytolytic toxin, pneumolysin, from the gram positive bacterium, Streptococcus pneumoniae, when perfused through the scala tympani of the guinea pig cochlea reduced the amplitude of both the compound action potential and the cochlear microphonic potential. When the surface of the organ of Corti was examined by scanning electron microscopy, both inner and outer hair cells and supporting cells were found to be damaged. Inner hair cells and outer hair cells of row 3 were the most susceptible to damage by pneumolysin, followed by row 2 and then by row 1 of the outer hair cells. Damage to hair cells included disruption and splaying of stereocilia, loss of stereocilia and complete dissolution of hair bundles. Apical surfaces of hair cells and supporting cells were torn, pitted and cratered with shrinkage and tearing of cell boundaries. Within the dose range perfused (0.05-1 micrograms/microliters in a 10 microliters aliquot), the magnitude of the physiological and anatomical lesions was concentration dependent. The cytotoxic effects of pneumolysin reported here may be clinically significant factors in deafness caused by meningitis and otitis media in humans.

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.

Glue sniffing and cerebral infarction.

A 12 year old boy who was a habitual glue sniffer developed a dense hemiparesis in association with an episode of glue sniffing. Occlusion of the right middle cerebral artery was found. It is postulated that the stroke was precipitated by an episode of vascular spasm.

Ultrastructural Damage to the Organ of Corti during Acute Experimental Escherichia coli and Pneumococcal Meningitis in Guinea Pigs

Experimental meningitis was induced in 16 pigmented guinea pigs by subarachnoid inoculation of mid log-phase 1 x 10(9) E. coli K-12 (n = 8) or 5 x 10(7) Streptococcus pneumoniae type 2 (n = 8). Animals were killed at various times between 3 and 12 h after inoculation and the ultrastructure of the organ of Corti (including the basilar membrane) was examined with high resolution scanning electron microscopy. Both E. coli and S. pneumoniae induced meningitis and invaded scala tympani. In both types of meningitis the apical surface of inner supporting cells developed craters. inner hair cell stereocilia were also disrupted. In pneumococcal meningitis both these lesions were more pronounced but in addition there were breaks in the junctions between inner hair cells and their adjacent supporting cells and there was ballooning and rupture of the apical surface of outer hair cells. Damage to the organ of Corti after bacterial invasion of the inner ear may be one of the mechanisms by which bacterial meningitis can cause deafness. The more severe cochlear lesions induced by S.pneumoniae may explain the higher incidence of deafness after pneumococcal meningitis.

Ototoxicity resulting from intracochlear perfusion of Streptococcus pneumoniae in the guinea pig is modified by cefotaxime or amoxycillin pretreatment

Acute changes in the electrophysiology and ultrastructure of the organ of Corti were studied after microperfusion of c. 5 x 10(6) CFU of serotype 2 Streptococcus pneumoniae D39 or Escherichia coli K-12 directly into the scala tympani of guinea pigs. Hearing loss was assessed by recording the auditory nerve compound action potential response to a 10 kHz tone pip. Mean hearing loss 3 h after pneumococcal perfusion (n = 4) was 44 dB, compared to 6 dB after E. coli perfusion (n = 4) (P<0.001). After pneumococcal perfusion, scanning electron microscopy revealed damage to hair cell stereocilia and cratering of the apical surface of supporting cells. Intraperitoneal injection of 100 mg/kg cefotaxime (n = 4) or 100 mg/kg amoxycillin (n = 4) 30 min before perfusion of pneumococci significantly reduced mean hearing loss to 23 dB (P=0.01) or 20 dB (P=0.01), respectively, and diminished ultrastructural damage. The data suggest that if pneumococci invade the inner ear during meningitis, cochlear deafness may rapidly ensue.

THE PRVENTION OF PERINATAL TRANSMISSION OF HEPATITIS B VIRUS (HBV) INFECTION: A COMPARISON OF TWO PROPHYLACTIC SCHEDULES

During the two year period 1986/87, 271 babies were born to hepatitis B surface atigen carrier mothers in the English West Midlands. Babies were allocated sequentially into either treatment Group A (4 doses of HBVax, Merck Sharp & Dohme, 10 mcg. i.m, at birth, 1, 2 and 6 months) or treatment Group B (250 I.U. hepatitis B immunoglobulin (HBIG) at birth, combined with the same vaccine schedule as Group A). 172 babies were enrolled and data was available for analysis on 150 (87%).Results:ConclusionsIn circumstances in which HBIG is not available a 4 dose vaccine schedule can protect at risk infants from perinatal transmission of HBV. In babies born to the less infectious carrier mothers in our study (i.e. those not HBe Ag+) the addition of HBIG to the schedule conferred no added benefit. In infants born to HBe Ag+ mothers protection was enhanced by addition of HBIG although transmission was still not prevented in every case. In utero infection and slow response to vaccine may be implicated failure mechanisms.

HEPATITIS B VACCINE WITHOUT IMMUNOGLOBULIN IN THE PREVENTION OF PERINATALLY TRANSMITTED HEPATITIS B VIRUS INFECTION INITIAL REPORT OF A STUDY IN THE WEST MIDLANDS OF ENGLAND

A study has been set up to evaluate the efficacy of hepatitis B vaccine alone, without the use of immunoglobulin in interrupting perinatal transmission of hepatitis B virus from carrier mothers to their babies. A 4 dose schedule was used. 14 of 17 babies of e antigen positive carrier mothers became actively immune when immunisations were started within 48 hours of birth. Effectiveness was reduced if immunisation was delayed. This report includes results from a total of 44 babies, the longest period of follow up being 2 years. The success of this scheme compares well with that of more intensive and less practical therapies using immunoglobulin either alone or combined with vaccine, and should be seriously considered for all babies of hepatitis B carrier mothers.