Progressive vascular remodelling, endothelial dysfunction and stiffness in mesenteric resistance arteries in a rodent model of chronic kidney disease

Chronic kidney disease (CKD) and hypertension are co-morbid conditions both associated with altered resistance artery structure, biomechanics and function. We examined these characteristics in mesenteric artery together with renal function and systolic blood pressure (SBP) changes in the Lewis polycystic kidney (LPK) rat model of CKD. Animals were studied at early (6-weeks), intermediate (12-weeks), and late (18-weeks) time-points (n=21), relative to age-matched Lewis controls (n=29). At 12 and 18-weeks, LPK arteries exhibited eutrophic and hypertrophic inward remodelling characterised by thickened medial smooth muscle, decreased lumen diameter, and unchanged or increased media cross-sectional area, respectively. At these later time points, endothelium-dependent vasorelaxation was also compromised, associated with impaired endothelium-dependent hyperpolarisation and reduced nitric oxide synthase activity. Stiffness, elastic-modulus/stress slopes and collagen/elastin ratios were increased in 6 and 18-week-old-LPK, in contrast to greater arterial compliance at 12weeks. Multiple linear regression analysis highlighted SBP as the main predictor of wall-lumen ratio (r=0.536, P<0.001 n=46 pairs). Concentration-response curves revealed increased sensitivity to phenylephrine but not potassium chloride in 18-week-LPK. Our results indicate that impairment in LPK resistance vasculature is evident at 6weeks, and worsens with hypertension and progression of renal disease.

Motility changes induced by intraluminal FeSO4 in guinea pig jejunum

BACKGROUND

Dietary iron supplementation is associated with gastrointestinal (GI) side effects including vomiting, nausea, and diarrhea. Although inorganic iron in high concentrations may be damaging to the intestinal mucosa, we hypothesize that there are physiological effects on the GI tract that occur at concentrations achieved by supplementation. Thus, our aim was to investigate the effect of intraluminal ferrous sulfate (FeSO4 ) on jejunal motility.

METHODS

Segments of guinea pig jejunum were cannulated and the intraluminal pressure recorded with a transducer, while movements were recorded with a video camera. Peristaltic threshold was the oral pressure that evoked four consecutive propulsive contractions. The nutrients decanoic acid (1 mM), l-phenylalanine (50 mM), or the micronutrient FeSO4 (1 mM) were infused intraluminally. We also tested the effect of FeSO4 on electrochemically detected serotonin (5-HT, 5-hydroxytryptamine) released from in vitro tissues, both at rest and following mechanical stimulation.

KEY RESULTS

The jejuna peristaltic threshold was significantly decreased by all three nutrients: FeSO4 : 31 ± 2-23 ± 3 mmH2 O; decanoic acid: 27 ± 2-14 ± 2 mmH2 O; and l-phenylalanine: 30 ± 3-14 ± 3mmH2 O. Of the three, only decanoic acid induced segmentation, while FeSO4 inhibited decanoic acid-induced segmentation. Resting 5-HT release was increased by FeSO4 (128% of control), but mechanically evoked 5-HT release was reduced (70% of control).

CONCLUSIONS & INFERENCES

These data suggest that some luminal effects of inorganic iron on jejunal motility could be mediated through a pathway involving altered release of 5-HT. A better understanding of the interaction between luminal iron and 5-HT containing enterochromaffin cells could improve iron supplementation strategies, thus reducing side effects.

Prevalence of hepatitis B virus infection among persons with diagnosed diabetes mellitus in the United States, 1999-2010

The prevalence of hepatitis B virus (HBV) infection among persons with diabetes has not been assessed among the US population, despite increasing reports of HBV transmission in institutional care settings. Using national survey data, we found a 60% higher prevalence of HBV infection among persons with (vs without) diagnosed diabetes.

Serotonin availability in rat colon is reduced during a Western diet model of obesity

Constipation and slowed transit are associated with diet-induced obesity, although the mechanisms by which this occurs are unclear. Enterochromaffin (EC) cells within the intestinal epithelium respond to mechanical stimulation with the release of serotonin [5-hydroxytryptamine (5-HT)], which promotes transit. Thus our aim was to characterize 5-HT availability in the rat colon of a physiologically relevant model of diet-induced obesity. EC cell numbers were determined immunohistochemically in chow-fed (CF) and Western diet-fed (WD) rats, while electrochemical methods were used to measure mechanically evoked (peak) and steady-state (SS) 5-HT levels. Fluoxetine was used to block the 5-HT reuptake transporter (SERT), and the levels of mRNA for tryptophan hydroxylase 1 and SERT were determined by quantitative PCR, and SERT protein was determined by Western blot. In WD rats, there was a significant decrease in the total number of EC cells per crypt (0.86 ± 0.06 and 0.71 ± 0.05 in CF and WD, respectively), which was supported by a reduction in the levels of 5-HT in WD rats (2.9 ± 1.0 and 10.5 ± 2.6 μM at SS and peak, respectively) compared with CF rats (7.3 ± 0.4 and 18.4 ± 3.4 μM at SS and peak, respectively). SERT-dependent uptake of 5-HT was unchanged, which was supported by a lack of change in SERT protein levels. In WD rats, there was no change in tryptophan hydroxylase 1 mRNA but an increase in SERT mRNA. In conclusion, our data show that foods typical of a WD are associated with decreased 5-HT availability in rat colon. Decreased 5-HT availability is driven primarily by a reduction in the numbers and/or 5-HT content of EC cells, which are likely to be associated with decreased intestinal motility in vivo.

A Western diet increases serotonin availability in rat small intestine

Diet-induced obesity is associated with changes in gastrointestinal function and induction of a mild inflammatory state. Serotonin (5-HT) containing enterochromaffin (EC) cells within the intestine respond to nutrients and are altered by inflammation. Thus, our aim was to characterize the uptake and release of 5-HT from EC cells of the rat ileum in a physiologically relevant model of diet-induced obesity. In chow-fed (CF) and Western diet-fed (WD) rats electrochemical methods were used to measure compression evoked (peak) and steady state (SS) 5-HT levels with fluoxetine used to block the serotonin reuptake transporter (SERT). The levels of mRNA for tryptophan hydroxylase 1 (TPH1) and SERT were determined by quantitative PCR, while EC cell numbers were determined immunohistochemically. In WD rats, the levels of 5-HT were significantly increased (SS: 19.2 ± 3.7 μm; peak: 73.5 ± 14.1 μm) compared with CF rats (SS: 12.3 ± 1.8 μm; peak: 32.2 ± 7.2 μm), while SERT-dependent uptake of 5-HT was reduced (peak WD: 108% of control versus peak CF: 212% control). In WD rats, there was a significant increase in TPH1 mRNA, a decrease in SERT mRNA and protein, and an increase in EC cells. In conclusion, our data show that foods typical of a Western diet are associated with an increased 5-HT availability in the rat ileum. Increased 5-HT availability is driven by the up-regulation of 5-HT synthesis genes, decreased re-uptake of 5-HT, and increased numbers and/or 5-HT content of EC cells which are likely to cause altered intestinal motility and sensation in vivo.

Endothelium-independent constriction of isolated, pressurized arterioles by Nomega-nitro-L-arginine methyl ester (L-NAME)

BACKGROUND AND PURPOSE

Nitric oxide synthase (NOS) inhibitors cause vasoconstriction in pressurized arterioles with myogenic tone. This suggests either tonic production of NO modulates myogenic tone or a direct, NOS-independent effect of the NOS inhibitors. The nature of the contractile effect of the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME, 100 microM) on pressurised arterioles was investigated.

EXPERIMENTAL APPROACH

Segments of rat cremaster muscle first-order arteriole were cannulated on glass micropipettes and maintained at an intraluminal pressure of 50, 70 or 120 mmHg.

KEY RESULTS

L-NAME and the related compound L-NA (100 microM) constricted pressurized vessels with myogenic tone. Removal of the endothelium did not cause constriction or alter myogenic tone, however the constrictor effect of L-NAME persisted. The constrictor effect of L-NAME was abolished by L-arginine (1 mM). Other NO and cGMP pathway inhibitors, including the nNOS inhibitor 7-nitroindazole (100 muM), the NO scavenger carboxy-PTIO (100 microM), the guanylate cyclase inhibitor ODQ (10 microM) and the cGMP inhibitor Rp-8CPT-cGMPS (10 microM) did not cause constriction of the arterioles. L-NAME caused a small (3-4 mV) but not statistically significant depolarization of the arteriolar smooth muscle at both pressures. The constrictor effect was not prevented by the K(+)-channel antagonist tetraethyl ammonium (TEA, 1 mM) or the K(ATP) channel antagonist glibenclamide (1 microM).

CONCLUSIONS AND IMPLICATIONS

These observations demonstrate that L-NAME causes an endothelium- and NOS-independent contraction of vascular smooth muscle in isolated skeletal muscle arterioles. It is suggested that the underlying mechanism relates to an arginine binding interaction.

Tyrosine phosphorylation following alterations in arteriolar intraluminal pressure and wall tension

Arterioles respond to increased transmural pressure with myogenic constriction. The present study investigated the role of tyrosine phosphorylation in myogenic activity. Cannulated segments of a rat cremaster arteriole were fixed under pressure, followed by incubation with fluorescein isothiocyanate (FITC)-conjugated anti-phosphotyrosine. Smooth muscle cell fluorescence intensity was measured with the use of confocal laser-scanning microscopy. Anti-phosphotyrosine fluorescence intensity in muscle cells of arterioles maintained at 100 mmHg was reduced by the tyrosine kinase inhibitor tyrphostin A47 (30 microM) and increased by the tyrosine phosphatase inhibitor pervanadate (100 microM). In time-course experiments, anti-phosphotyrosine fluorescence increased slowly (over 5 min) after an acute increase in intraluminal pressure, and was dissociated from myogenic contraction (within 1 min). In contrast, angiotensin II (0.1 microM) caused rapid constriction and increased tyrosine phosphorylation. Anti-phosphotyrosine fluorescence was also pressure dependent (10-100 mmHg). Abolition of myogenic activity, either through removal of extracellular Ca2+, or exposure to verapamil (5 microM) or forskolin (0.1 microM) caused a further increase in anti-phosphotyrosine fluorescence. We conclude that transmural pressure and/or wall tension in arterioles causes increased tyrosine phosphorylation; however, this is not involved in the acute phase of myogenic constriction but may be involved in later responses, such as sustained myogenic tone or mechanisms possibly related to growth.

Intussusception among infants given an oral rotavirus vaccine

BACKGROUND

Intussusception is a form of intestinal obstruction in which a segment of the bowel prolapses into a more distal segment. Our investigation began on May 27, 1999, after nine cases of infants who had intussusception after receiving the tetravalent rhesus-human reassortant rotavirus vaccine (RRV-TV) were reported to the Vaccine Adverse Event Reporting System.

METHODS

In 19 states, we assessed the potential association between RRV-TV and intussusception among infants at least 1 but less than 12 months old. Infants hospitalized between November 1, 1998, and June 30, 1999, were identified by systematic reviews of medical and radiologic records. Each infant with intussusception was matched according to age with four healthy control infants who had been born at the same hospital as the infant with intussusception. Information on vaccinations was verified by the provider.

RESULTS

Data were analyzed for 429 infants with intussusception and 1763 matched controls in a case-control analysis as well as for 432 infants with intussusception in a case-series analysis. Seventy-four of the 429 infants with intussusception (17.2 percent) and 226 of the 1763 controls (12.8 percent) had received RRV-TV (P=0.02). An increased risk of intussusception 3 to 14 days after the first dose of RRV-TV was found in the case-control analysis (adjusted odds ratio, 21.7; 95 percent confidence interval, 9.6 to 48.9). In the case-series analysis, the incidence-rate ratio was 29.4 (95 percent confidence interval, 16.1 to 53.6) for days 3 through 14 after a first dose. There was also an increase in the risk of intussusception after the second dose of the vaccine, but it was smaller than the increase in risk after the first dose. Assuming full implementation of a national program of vaccination with RRV-TV, we estimated that 1 case of intussusception attributable to the vaccine would occur for every 4670 to 9474 infants vaccinated.

CONCLUSIONS

The strong association between vaccination with RRV-TV and intussusception among otherwise healthy infants supports the existence of a causal relation. Rotavirus vaccines with an improved safety profile are urgently needed.

Poliomyelitis prevention in the United States. Updated recommendations of the Advisory Committee on Immunization Practices (ACIP)

These recommendations of the Advisory Committee on Immunization Practices (ACIP) for poliomyelitis prevention replace those issued in 1997. As of January 1, 2000, ACIP recommends exclusive use of inactivated poliovirus vaccine (IPV) for routine childhood polio vaccination in the United States. All children should receive four doses of IPV at ages 2, 4, and 6-18 months and 4-6 years. Oral poliovirus vaccine (OPV) should be used only in certain circumstances, which are detailed in these recommendations. Since 1979, the only indigenous cases of polio reported in the United States have been associated with the use of the live OPV. Until recently, the benefits of OPV use (i.e., intestinal immunity, secondary spread) outweighed the risk for vaccine-associated paralytic poliomyelitis (VAPP) (i.e., one case among 2.4 million vaccine doses distributed). In 1997, to decrease the risk for VAPP but maintain the benefits of OPV, ACIP recommended replacing the all-OPV schedule with a sequential schedule of IPV followed by OPV. Since 1997, the global polio eradication initiative has progressed rapidly, and the likelihood of poliovirus importation into the United States has decreased substantially. In addition, the sequential schedule has been well accepted. No declines in childhood immunization coverage were observed, despite the need for additional injections. On the basis of these data, ACIP recommended on June 17, 1999, an all-IPV schedule for routine childhood polio vaccination in the United States to eliminate the risk for VAPP. ACIP reaffirms its support for the global polio eradication initiative and the use of OPV as the only vaccine recommended to eradicate polio from the remaining countries where polio is endemic.

Meningococcal disease in Dallas County, Texas: results of a six-year population-based study

OBJECTIVE

Neisseria meningitidis is an important cause of serious bacterial infection in children and adults in the US. From 1992 to 1997 invasive disease caused by N. meningitidis was studied among 1.9 million residents of Dallas County, TX METHODS: The demographic characteristics and diagnoses of 151 patients were identified through active, population-based surveillance and review of medical records. Serogroups were determined for strains infecting 129 (85%) patients.

RESULTS

The average annualized incidence rate was 1.3 cases per 100,000 person years and was highest for children <1 year (13 cases/100,000 person years). Older patients (50+ years old) were more likely to present with pneumonia and less likely to present with meningitis than younger patients. Neither the fatality rate nor the duration of hospitalization for surviving patients was associated with age. Among patients with a known serogroup, serogroup C disease was found in 35% of cases <1 year old, 64% of those 1 to 49 years old and 44% of those 50+ years old. Serogroup B strains were isolated from 26% of patients <1 year, 17% of patients 1 to 49 years old and none of the patients 50+ years old. Serogroup Y disease increased from 22% to 35% of cases between 1992 and 1997 (P = 0.03). This serogroup was identified in 26% of patients <1 year old, 17% of patients 1 to 49 years old and in 50% of patients 50+ years old. Serogroup C and Y accounted for 61% of cases in children <1 year old and for 79% of cases in all age groups.

CONCLUSION

The results underscore the importance of conjugate vaccines for serogroups C and Y.

Tyrosine phosphorylation modulates arteriolar tone but is not fundamental to myogenic response

The present study investigated the role of protein tyrosine phosphorylation in myogenic responsiveness of rat skeletal muscle arterioles. Arteriolar segments were cannulated and pressurized without intraluminal flow. All vessels studied developed spontaneous tone and demonstrated significant myogenic constriction to step changes in pressure with a resultant increase in myogenic tone over an intraluminal pressure range of 50-150 mmHg. Step increases in intraluminal pressure from 50 to 120 mmHg caused a rapid and sustained elevation in intracellular [Ca(2+)], as measured using fura 2. Vessels with myogenic tone dilated in response to tyrosine kinase inhibitors genistein (10 or 30 microM) and tyrphostin A47 (10 or 30 microM) and constricted to the tyrosine phosphatase inhibitor pervanadate (1 or 10 microM). Despite the dilator effect, myogenic reactivity was not blocked by the inhibitors. Daidzein (10 microM), a compound structurally similar to genistein but without tyrosine kinase-inhibiting activity, did not alter vessel tone or myogenic responses. Preincubation of arterioles with genistein or tyrphostin A47 did not significantly alter baseline arteriolar [Ca(2+)], and neither drug reduced the increase in [Ca(2+)] following an acute increase in intraluminal pressure. Constriction induced by pervanadate (10 microM) was not accompanied by a significant increase in intracellular [Ca(2+)], even though removal of extracellular Ca(2+) reversed the constriction. Examination of smooth muscle tyrosine phosphorylation, using a fluorescent phosphotyrosine antibody and confocal microscopy, showed that increased intraluminal pressure resulted in an increase in anti-phosphotyrosine fluorescence. Because manipulation of tyrosine kinase activity was found to alter vessel diameter, these data support a role for tyrosine phosphorylation in modulation of arteriolar tone. However, the results indicate that acute arteriolar myogenic constriction does not require tyrosine phosphorylation.

Structural determinants of phorbol ester binding in synaptosomes: pharmacokinetics and pharmacodynamics

The present study used structurally distinct phorbol esters to investigate the relationship between their pharmacokinetics of binding to protein kinase C (PKC) in rat brain cortex synaptosomes, their affinity for PKC in synaptosomes and ability to enhance noradrenaline release from rat brain cortex. Affinity binding studies using [3deoxyphorbol 13-tetradecanoate (dPT)=PDB&z. Gt;12-deoxyphorbol 13-acetate (dPA)=phorbol 12,13-diacetate (PDA). In intact synaptosomes PDB, dPA and PDA rapidly displaced bound [3H]PDB whereas PMA and dPT were comparatively slow. However, the displacement rates for all the phorbol esters were equally rapid in synaptosomal membranes or synaptosomes permeabilised with Staphylococcus alpha-toxin. These results suggest that the lipophilic phorbol esters (dPT and PMA) are slower to displace [3H]PDB binding because they are hindered by the plasma membrane. In brain cortex slices it was found that the rate of displacement of [3H]PDB binding was closely correlated with the degree of elevation of transmitter noradrenaline release. Thus kinetic characteristics may determine biological responses and this may be particularly evident in events which occur rapidly or where there is fast counter-regulation.

Methicillin-resistant Staphylococcus aureus in two child care centers

Methicillin-resistant Staphylococcus aureus (MRSA) has not been studied in child care centers. The prevalence of MRSA colonization was determined at two centers with an index patient. Two (3%) of 61 children at center X had MRSA; strains from both children and the index illness were pulsed-field gel electrophoresis type B. Nine (24%) of 40 children at center Y had MRSA; strains from 5 children and the index illness were type B, and strains from 4 children were type A. Ten of 11 colonized children were in classes with 2- and 3-year-old children. Colonization with MRSA was not associated with health care contact by subjects or by members of their households. MRSA in child day care centers indicates accelerated spread of MRSA in the community.

Invasive pneumococcal disease in Dallas County, Texas: results from population-based surveillance in 1995

We studied the epidemiology of invasive disease caused by Streptococcus pneumoniae in 1995 among 1.9 million residents of Dallas County, Texas. The sociodemographic characteristics and chronic medical conditions of 432 patients were identified through active, population-based surveillance and review of medical records. The incidence of disease was 22 cases per 100,000 person-years and was highest for children < 2 years of age (136 cases per 100,000 person-years) and for adults > or = 65 years of age (80 cases per 100,000 person-years). Twenty percent of isolates were nonsusceptible to penicillin; the highest rates of resistance were among the youngest and oldest age groups (28% and 22% of isolates, respectively). An increased incidence of disease was associated with low income (42 cases per 100,000 person-years) and black race (39 cases per 100,000 person-years). The frequency of most chronic medical conditions increased with age; smoking, heavy alcohol use, and infection due to human immunodeficiency virus were most common between 30 and 64 years of age. Of otherwise healthy patients 30-64 years of age, 47% were current smokers, an association requiring further investigation. Characterizing groups at risk for invasive pneumococcal disease could aid in the development of prevention programs and increase the benefits from wide use of effective vaccines.

17Beta-oestradiol enhances nitric oxide synthase activity in endothelium-denuded rat aorta

1. It has been suggested that oestrogen-produced vasodilatation is due to induction of endothelial nitric oxide synthase (NOS), but there are many reports of direct effects on vascular smooth muscle. In the present study, these processes were investigated in rat aorta isolated from ovariectomized rats. 2. Short-term treatment (10 min) with 17beta-oestradiol (10 micromol/L) produced a small attenuation of the phenylephrine (PE)-induced constriction, which was unaffected by the nitric oxide synthase inhibitor L-N5(-1-iminoethyl)ornithine (NIO; 100 micromol/L). Long-term treatment (6 h) with 17beta-oestradiol (10 micromol/L) did not affect acetylcholine-mediated vasorelaxation in endothelium-intact aortic rings, but did attenuate PE-induced constriction. This attenuation was also observed in endothelium-denuded preparations after 17beta-oestradiol (10 micromol/L for 6 h) and was far greater than the acute effect of 17beta-oestradiol (10 micromol/L). 3. The attenuation produced by 17beta-oestradiol (10 micromol/L for 6 h) was significantly inhibited by concomitant treatment with cycloheximide (1 micromol/L), suggesting that protein synthesis was involved. NIO (100 micromol/L) also attenuated the effect, which suggests that the anti-constrictor effect of 17beta-oestradiol occurs through the increased production of nitric oxide (NO). 17Beta-oestradiol increased NO production, as assessed by the conversion of [3H]-arginine to [3H]-citrulline in rat aorta. These effects were prevented by cycloheximide and NIO. The anti-constrictor effect of oestrogen was blocked by the oestrogen receptor antagonist ICI 182 780 (100 nmol/L). 4. Western blotting using an antibody specific for inducible nitric oxide synthase (NOS) revealed that 17beta-oestradiol (10 micromol/L for 24 h) treatment induced the formation of inducible NOS protein in the aorta, an effect blocked by cycloheximide. The results indicate that 17beta-oestradiol can attenuate the vasoconstrictor effect of PE by a specific receptor-mediated process that involves induction of inducible NOS.

Protein kinase C and transmitter release

1. Protein kinase C (PKC) is an important second messenger-activated enzyme. In noradrenergic nerves it appears to be tonically activated by diacylglycerol (DAG) to facilitate transmitter release and the steps in this involve activation of phospholipase C, generation of DAG and activation of PKC. It is suggested that the subsequent facilitation of transmitter release is due to the phosphorylation of proteins involved in the release process distal to Ca2+ entry, presumably those involved in vesicle dynamics. 2. There are differences between central noradrenergic neurons and sympathetic nerves. In central neurons PKC appears to be tonically active and its inhibition results in a decrease in noradrenaline release under most, if not all, conditions. 3. In sympathetic nerves PKC inhibitors only decrease transmitter release during high-frequency stimulation and not during low-frequency stimulation. At high frequency there is a gradual increase in the effect of PKC inhibitors on transmitter release during the first 15 s of a stimulation train. It is suggested that this is due to a progressive rise in intracellular Ca2+ and a consequent activation of PKC. 4. Activation of PKC by phorbol esters produces a large enhancement in action potential-evoked noradrenaline release in both the central nervous system and in peripheral tissues. The structural requirements of the phorbol esters for maximal effect suggest that the phorbol esters must access the interior of the nerve terminal to activate PKC and the neural membrane acts as a barrier for highly lipophilic phorbol esters, thereby reducing their activity. Activation of PKC represents one of the most powerful ways to enhance transmitter release and may have therapeutic potential.

Noradrenaline release and the effect of endogenous activation of the phospholipase C/protein kinase C signalling pathway in rat atria

1. It has been proposed that protein kinase C (PKC) in sympathetic nerves is activated during action-potential evoked release of noradrenaline and helps maintain transmitter output. We studied this phenomenon further in rat atria radiolabelled with [3H]-noradrenaline. 2. Noradrenaline release was elevated by continuous electrical stimulation of the atria for 10 min at either 5 or 10 Hz. Two inhibitors of PKC, polymyxin B (21 microM) and Ro 318220 (3 microM), markedly inhibited the release of noradrenaline but only at the higher stimulation frequency. 3. Further experiments were conducted with 10 Hz stimulation but for shorter train durations. In this case polymyxin B inhibited noradrenaline release during a 10 or 15 s train of impulses but not during a 5 s train. This suggests that PKC effects are induced during the stimulation train by some process. 4. The diacylglycerol kinase inhibitor R59949 (10 microM), which prevents the breakdown of diacylglycerol, enhanced noradrenaline release elicited by stimulation at 10 Hz for 10 or 15 s. This effect was not seen if polymyxin B was present and suggests that diacylglycerol is the endogenous activator of PKC. 5. The source of the diacylglycerol may be through phospholipase C pathways, since the phospholipase C inhibitor U73122 (3 microM) inhibited noradrenaline release at 10 Hz for 10 s and the effect was not seen if polymyxin B was also present. 6. It is unlikely that phospholipase D is the source of diacylglycerol. Although the phospholipase D inhibitor wortmannin (1 microM) inhibited noradrenaline release, this effect was still observed in the presence of polymyxin B. Furthermore ethanol, which inhibits diacylglycerol formation by phospholipase D, had no effect on noradrenaline release. 7. We therefore suggest that during a train of high frequency pulses phospholipase C is activated and this results in the production of diacylglycerol which in turn activates PKC. This enables the neurones to maintain transmitter release at a high level.

Factors associated with unnecessary immunization given to children

OBJECTIVE

To determine the factors associated with unnecessary immunization during the pre-school years.

METHODS

Children were selected from birth certificates and their parents were interviewed to identify all immunizations to 72 months of age. The immunizations were verified.

RESULTS

Of 187 children studied 34 (18%) received unnecessary immunization. Unnecessary immunization was strongly associated with ever receiving immunization in a large system of public clinics (designated "Public A") (33%) compared with other providers (5%) (P < 0.00001). Among children immunized in Public A, unnecessary immunization was associated with the parent having an incomplete or no copy of the child's immunization record (P = 0.007) and with not being up to date for immunizations at 24 months of age (P = 0.04). Complete documentation of immunizations either in the Public. A record or in the parent's copy of the record was associated with a 4% rate of unnecessary immunization; incomplete or no documentation in both the Public A and the parent's record was associated with a 45% rate of unnecessary immunization (P = 0.001).

CONCLUSIONS

Access to a complete immunization record, be it the provider's, the parent's or ideally both, decreases substantially a child's risk of unnecessary immunization.

Pediatric clinical clerkships are associated with an excess risk of acute infection

OBJECTIVE

To determine the incidence of acute respiratory and gastrointestinal tract illness and associated absence by third-year medical students during pediatric and nonpediatric (control) clinical clerkships.

DESIGN

A self-administered questionnaire was completed by students after the first 4 weeks of two pediatric clerkships (inpatient and outpatient) and two non-pediatric clerkships (obstetrics-gynecology and psychiatry). Information was obtained on the symptoms of acute respiratory and gastrointestinal tract illness and related absences.

ANALYSIS

Results from each student's pediatric clerkship were compared with the results from the same student's control clerkship by means of matched-pair analysis.

SUBJECTS

Students who made up the junior class at the University of Texas Southwestern Medical School at Dallas, July 1, 1990, to June 30, 1991.

RESULTS

Of 177 students (77%) who completed questionnaires after one pediatric and one control clerkship, 108 students (61%) had had an acute illness while on pediatric clerkships in contrast to 69 students (39%) on control clerkships (odds ratio, 3.3; 95% confidence interval, 2.0 to 5.4; P < .001). More students were absent for illness during pediatric than control clerkships (23 [13%] vs nine [5%], respectively; odds ratio, 2.7; 95% confidence interval, 1.2 to 6.2; P = .02). The higher risk of illness during pediatric clerkships was not related to the order of the pediatric or control clerkship, the order of inpatient and outpatient pediatrics, or the season of the year.

CONCLUSION

Pediatric clinical clerkships in the third year of medical school were associated with excess morbidity from acute infectious illness. Studies are needed to determine whether emphasizing infection control practices decrease this morbidity and any resulting nosocomial spread to patients.

Specific accumulation of inositol 1,4,5-trisphosphate in rabbit basilar artery in response to noradrenaline but not 5-hydroxytryptamine

This study examined the ability of 5-hydroxytryptamine and noradrenaline to stimulate inositol 1,4,5-trisphosphate (IP3) mass accumulation in segments of the rabbit basilar artery. 5-Hydroxytryptamine (5-HT, 100 microM) failed to stimulate any significant accumulation of IP3 during the 5 min period following its application. In the presence of prazosin, 5-HT (300 microM) caused a rapid, transient decrease in IP3 accumulation which was significant after 5 s but had increased to pre-stimulation levels within 15 s. In contrast, noradrenaline (10 microM) stimulated a rapid, transient accumulation of IP3 which was significant after 5 s but had declined to basal levels after 60 s. In basilar artery segments bathed in Krebs solution containing 25.7 mM K+ (normal concentration 5.7 mM), the basal IP3 concentration was significantly elevated. The IP3 accumulation stimulated by either 5-HT or raised K+ was not reduced by the presence of the alpha 1-adrenoceptor antagonist, prazosin (0.1 microM). In the presence of raised K+, 5-hydroxytryptamine caused a rapid, transient inhibition of the K(+)-induced IP3 accumulation, which was maximal after 5 s but had increased to pre-stimulation levels within 30 s in the continued presence of 5-hydroxytryptamine. Noradrenaline did not affect the IP3 accumulation induced by raised extracellular [K+]. These results provide further evidence that IP3 is not involved in 5-hydroxytryptamine-induced smooth muscle contraction in the rabbit basilar artery, but support a role for this second messenger in the contraction induced in response to noradrenaline.

Characterisation of inositol 1,4,5-trisphosphate binding sites in rabbit aortic smooth muscle

The present study investigated the characteristics of D-myo-inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) binding sites in crude membrane preparations of rabbit aortic smooth muscle. A particular aim was to demonstrate if increases in cytoplasmic cyclic guanosine 3':5' monophosphate (cGMP), which mediates the effect of nitrovasodilators, may cause smooth muscle relaxation in part by the displacement of Ins(1,4,5)P3 binding. Negligible Ins(1,4,5)P3 binding was observed at pH < 7, while maximum binding occurred over the pH range 8-9. Saturation analysis of isotopic dilution binding data revealed an apparently homogenous population of Ins(1,4,5)P3 binding sites with a KD of 4.02 +/- 0.53 nM and a Bmax of 27.7 +/- 4.6 fmol/mg protein. Heparin, an Ins(1,4,5)P3 receptor antagonist, inhibited binding with an IC50 of 11.43 +/- 2.81 micrograms/ml. The ability of other polyphosphate compounds to inhibit Ins(1,4,5)P3 binding in this preparation was also examined. D-myo-Inositol 1,3,4,5-tetrakisphosphate (Ins(1,3,4,5)P4), adenosine 5'-triphosphate (ATP) and guanosine 5'-triphosphate (GTP) inhibited Ins(1,4,5)P3 binding, although each was significantly less potent that Ins(1,4,5)P3. In contrast, cyclic guanosine 3':5' monophosphate (cGMP) did not significantly alter Ins(1,4,5)P3 binding in rabbit aortic smooth muscle. This observation suggests that competitive inhibition of Ins(1,4,5)P3 receptor binding is not an important consideration in cGMP-mediated vascular smooth muscle cell relaxation.

Estimating immunization coverage from school-based childhood immunization records

To determine the accuracy of school-based childhood immunization records and to describe the effects of their use on estimates of community-wide immunization coverage, we verified the immunizations to 72 months of age for children born in 1986 to residents in Dallas County, TX, and in Minnesota. Verified immunizations were compared with those documented in the school record. Major transcription errors accounted for fewer than 1% of discrepancies between school and provider records. For 99 subjects with 987 verified immunizations in Minnesota, age-appropriate immunization coverage estimated from the school records was within two percent of actual coverage. For 86 subjects with 981 verified immunizations in Dallas County, age-appropriate immunization coverage from the school records underestimated actual coverage by as much as 21%. The primary factor explaining the underestimate in Dallas was incomplete school immunization records for 33 (38%) subjects and 126 (13%) immunizations. Selective recording of immunizations related to the minimum state requirements in Texas contributed to incomplete school records in Dallas County. Verification of the completeness of records selected to estimate immunization coverage is essential if the estimates are used to monitor trends or to make public policy decisions.

Phorbol esters impair endothelium-dependent and independent relaxation in rat aortic rings

1. This study examined the ability of various nitro-vasodilators, 8-bromo cyclic guanosine 3':5' monophosphate (8-BrcGMP) and forskolin to relax rings of rat thoracic aorta pre-contracted with either noradrenaline (0.1 microM) or the protein kinase C activators, phorbol 12,13-dibutyrate (PDB, 0.1 microM) or phorbol 12-myristate 13-acetate (PMA, 0.5 microM). 2. In noradrenaline pre-contracted rings, acetylcholine (10 nM-10 microM), sodium nitroprusside (1 nM-0.5 microM), the calcium ionophore A23187 (10 nM-10 microM) and 8-BrcGMP (10 mM) totally reversed the smooth muscle contraction. In PDB-contracted aortic rings acetylcholine, sodium nitroprusside and 8-BrcGMP-induced relaxation was reduced compared to that in noradrenaline-contracted aortic rings, but A23187 and forskolin-induced relaxations were unaffected. Both acetylcholine and A23187-induced relaxations in PDB-contracted rings were abolished in the presence of the nitric oxide synthesis inhibitor N omega-nitro-L-arginine (NOLA, 100 microM). 3. Acetylcholine and sodium nitroprusside were even less potent in their ability to relax PMA-contracted aortic rings compared with noradrenaline and PDB-contracted rings. A23187-induced relaxation was also inhibited in PMA-contracted rings. 4. These results show that protein kinase C activation reduces the ability of agents which liberate nitric oxide to induce smooth muscle relaxation, and also inhibits the biochemical pathways which are subsequently activated by nitric oxide and lead to vascular smooth muscle relaxation.

Importance of inositol (1,4,5)-trisphosphate, intracellular Ca2+ release and myofilament Ca2+ sensitization in 5-hydroxytryptamine-evoked contraction of rabbit mesenteric artery

1. Small strips from third-order branches of rabbit mesenteric artery (approximately 150-200 microM wide) contracted in response to noradrenaline (10 microM) or 5-hydroxytryptamine (5-HT; 10 microM) in oxygenated Krebs solution containing 2.5 mM Ca2+. In a Ca(2+)-free mock intracellular solution (0 Ca2+ plus 0.2 mM EGTA), noradrenaline (10 microM) and caffeine (10 mM) induced only a single, transient contraction in artery strips, while 5-HT (10 microM) failed to induce any response. 2. In strips of mesenteric artery which had been permeabilized with Staphylococcus alpha-toxin and bathed in Ca(2+)-free mock intracellular solution, noradrenaline (10 microM), caffeine (10 mM) and D-myo-inositol (1,4,5)-trisphosphate (IP3, 100 microM), but not 5-HT (10 or 100 microM) induced a transient contraction. In contrast to the non-permeabilized strips, contractions to noradrenaline, caffeine and IP3 were restored by prior incubation (10 min) in solution containing 0.08 microM Ca2+. The contractions to noradrenaline and IP3 in permeabilized muscle strips required the presence of 100 microM guanosine 5'-triphosphate (GTP), although in the absence of Ca2+. GTP alone did not induce contraction. 3. Exposure of permeabilized mesenteric artery strips to IP3 significantly reduced the subsequent contractile responses to caffeine. Contractile responses to caffeine and IP3 were abolished by the Ca(2+)-ATPase inhibitor, thapsigargin (1 microM). 4. Ca2+ (0.1-10 microM) induced concentration-dependent contraction in permeabilized artery strips. In strips which were submaximally contracted with 0.5 microM Ca2+/100 microM GTP, the subsequent addition of 5-HT (10 microM) stimulated further contraction. The protein kinase C inhibitor, H-7 (1 microM) abolished the 5-HT/GTP-induced contraction, but did not alter the contraction to Ca2+. 5. In non-permeabilized, endothelium-denuded segments of rabbit mesenteric artery bathed in Ca2+-replete Krebs solution, noradrenaline (10 microM) stimulated a rapid, transient accumulation of IP3. 5-HT(100 microM) failed to stimulate IP3 accumulation during exposure periods of up to 5 min. 5-HT (100 microM)did stimulate IP3 accumulation if the external K+ concentration was raised (to around 25 mM). This concentration of K+ alone did not stimulate IP3 production and the 5-HT-stimulated IP3 accumulation in the presence of elevated extracellular [K+] was abolished by the alpha l-adrenoceptor antagonist, prazosin(O.1 microM).6. These results suggest that intracellular Ca2+ release does not play an important role in 5-HT-induced smooth muscle contraction in the rabbit mesenteric artery. This is despite the fact that a significant intracellular Ca2+ pool is present in these cells, which can be discharged by either noradrenaline or IP3.However, 5-HT did stimulate smooth muscle contraction in the presence of raised intracellular calcium,suggesting that a component of the contraction to 5-HT will reflect an increase in myofilament Ca2+sensitivity, possibly due to the activation of protein kinase C.

Induction of immunologic memory in infants primed with Haemophilus influenzae type b conjugate vaccines

The ability of different Haemophilus influenzae type b conjugate vaccines to induce immunologic memory was compared in 381 infants who were vaccinated with one of three conjugate vaccines beginning at 2 months of age. All infants were vaccinated with unconjugated type b capsular polysaccharide, polyribosylribitol phosphate (PRP), at 12 months. In each group, high antibody responses were detected by 6-9 days after vaccination. One month after receiving PRP, infants primed with PRP conjugated to the outer membrane protein of Neisseria meningitidis or PRP oligomers conjugated to the cross-reactive mutant diphtheria protein, CRM197, had twofold higher total anti-PRP antibody concentrations than did infants primed with PRP conjugated to tetanus toxoid (P < .005). After the conjugate and the PRP boost, notable differences were present among vaccine groups with respect to the magnitude of the IgG anti-PRP antibody concentrations and light chain variable region usage as determined by idiotypic analysis. Thus, each of the conjugate vaccines primed infants for the ability to evoke memory antibody responses to PRP, but qualitative and quantitative differences in priming induced by different vaccines may affect their ability to confer protection against disease.

Decreased Haemophilus colonization in children vaccinated with Haemophilus influenzae type b conjugate vaccine

OBJECTIVE

The incidence of invasive Haemophilus disease has unexpectedly decreased in unvaccinated children since the introduction of conjugate vaccine in the United States. The purpose of this study was to determine whether conjugate vaccination decreases colonization with Haemophilus influenzae type b.

DESIGN

This study was a prospective, bimonthly survey of pharyngeal colonization with H. influenzae type b in children attending day care from October 1987 through September 1989. Vaccination status was determined from the medical record.

SUBJECTS

We obtained 1188 pharyngeal cultures from 283 healthy children, 18 to 59 months of age; 51 children had received unconjugated polysaccharide vaccine (PRP), and 89 had received conjugate vaccine (94% PRP-diphtheria toxoid).

MEASUREMENTS AND RESULTS

Multivariate analysis was used to test the possibility of an association between vaccination status and the rate of colonization with H. influenzae type b. Among children known to be exposed to at least one child with a positive culture result, the efficacy of conjugate vaccination to prevent H. influenzae type b colonization in an unmatched analysis was 64% (95% confidence interval: 5%, 86%; p = 0.02) and in a matched analysis 81% (95% confidence interval: 7%, 96%; p = 0.02). No effect on colonization was found with PRP vaccination.

CONCLUSIONS

Conjugate vaccination decreases H. influenzae type b pharyngeal colonization and thereby may decrease transmission of this agent among healthy children.

Declining incidence of Haemophilus influenzae type b disease since introduction of vaccination

OBJECTIVE

To determine the incidence of invasive Haemophilus influenzae type b disease in children living in Minnesota and Dallas County, Texas, before and since introduction of plain polysaccharide vaccine in 1985, and conjugate vaccine in 1988. Initially, use of these vaccines was limited to infants 18 months of age and older.

DESIGN

Identification of culture-proven cases of H influenzae type b disease was through systems of active, laboratory-based surveillance. The mean incidence of disease (cases observed/100,000 child-years) for 1983 and 1984 served as a baseline for comparison with subsequent years through 1991.

PARTICIPANTS

Children less than 5 years of age in Minnesota and Dallas County, Texas. Overall, there were 2557 confirmed age-eligible cases of invasive H influenzae type b disease from 1983 through 1991.

RESULTS

Between the 1983-1984 baseline and 1991, the incidence of H influenzae type b disease decreased 85% in Minnesota and 92% in Dallas. Notably, declines in incidence were observed in children in the age group being vaccinated as well as in infants younger than 18 months of age prior to introduction of vaccination.

CONCLUSION

In two widely separated areas of the United States, a profound decrease in the incidence of H influenzae type b disease has occurred. The data suggest that vaccination may be protecting against disease, as well as decreasing the spread of infection to unvaccinated infants.

Prejunctional alpha 2-adrenoceptors in mouse atria function through G-proteins which are sensitive to N-ethylmaleimide, but not pertussis toxin

1. The identity of the G-proteins involved in prejunctional alpha 2-adrenoceptor signal transduction in mouse atria was examined by use of the G-protein inactivators N-ethylmaleimide and pertussis toxin. 2. The alpha 2-adrenoceptor partial agonist clonidine (0.03 microM) inhibited the electrical stimulation-induced (S-I) outflow of radioactivity from mouse atria which were incubated with [3H]-noradrenaline and stimulated at 5 Hz. The partial alpha 2-adrenoceptor agonist St 363 (10 microM) inhibited the S-I outflow of radioactivity at the lower stimulation frequency of 2.5 Hz. The inhibitory effects of these compounds were not altered in mice pretreated with pertussis toxin (1.5 micrograms, i.v.). 3. The alpha 2-adrenoceptor antagonist, idazoxan (0.1 microM), increased the S-I outflow of radioactivity from mouse atria stimulated at 5 Hz, and this effect was not altered in atria from mice pretreated with pertussis toxin. 4. The inhibitory effects of clonidine and St 363 and the facilitatory effect of idazoxan on the S-I outflow of radioactivity from mouse atria were significantly less in atria incubated with N-ethylmaleimide (NEM, 3 microM) for 60 min before the [3H]-noradrenaline incubation. 5. The results suggest that prejunctional alpha 2-adrenoceptors in mouse atria function through G-proteins which are NEM-sensitive, but pertussis toxin insensitive.

Differences in the immunogenicity of three Haemophilus influenzae type b conjugate vaccines in infants

OBJECTIVE

To compare the immunogenicity of three Haemophilus influenzae type b (Hib) conjugate vaccines in infants residing in different geographic areas.

DESIGN

A multicenter, randomized immunogenicity trial with sera assayed in one laboratory without knowledge of vaccine brand status. In Minneapolis and Dallas, infants were vaccinated at 2, 4, and 6 months of age; in St. Louis, infants were vaccinated at 2 and 4 months of age.

SUBJECTS

A convenience sample of 458 infants recruited largely from private pediatric practices.

MEASUREMENTS AND RESULTS

At each of the study sites, the respective trends between the anticapsular antibody responses of the infants assigned to the different conjugate vaccine groups were similar. After one or two doses, Hib polysaccharide conjugated to outer membrane protein complex of Neisseria meningitidis (PRP-OMP) was more immunogenic than Hib polysaccharide-tetanus toxoid conjugate (PRP-T), or Hib oligomers conjugated to the mutant diphtheria toxin CRM197 (HbOC) (p less than 0.001). After two doses, PRP-T was more immunogenic than HbOC (p less than or equal to 0.001). After three doses there was no significant difference in the geometric mean antibody concentrations of the three groups, and 88% to 97% of the infants had greater than 1.0 microgram/ml of antibody. The HbOC vaccine elicited a 10-fold lower antibody response after two doses (0.45 micrograms/ml vs 5.9 micrograms/ml) and a threefold lower antibody response after three doses (6.3 micrograms/ml vs 22.9 micrograms/ml) than observed by us previously with a prelicensure lot of this vaccine (p less than 0.001). Because of these low responses, the infants in St. Louis who received two doses of HbOC were revaccinated with unconjugated PRP at a mean age of 8.9 months. This group was immunologically primed, as evidenced by a 10-fold increase in geometric mean antibody concentration after vaccination at an age when unprimed infants do not normally respond to this vaccine.

CONCLUSIONS

In infants in three geographic regions, PRP-OMP elicited earlier acquisition of serum antibody than the other two conjugate vaccines; however, after three doses the antibody concentrations of the three groups were not significantly different. The reason for the markedly lower immunogenicity of HbOC vaccine than reported previously is unknown.

Invasive Haemophilus influenzae type b disease in children less than 5 years of age in Minnesota and in Dallas County, Texas, 1983-1984

During 1983 and 1984, 733 cases of invasive Haemophilus influenzae type b disease in children less than 5 years of age were identified in Minnesota and in Dallas County, Texas. The overall incidence of disease was lower in Minnesota than in Dallas County. However, among urban residents, the rates of disease for whites were similar in the two areas. A higher rate of disease among whites in urban Minnesota compared with rural Minnesota resulted from an increased rate of cases for diagnoses other than meningitis. Local practices might have affected the rate of certain diagnoses, since ascertainment of Hib disease other than meningitis is more dependent on diagnostic practices than is diagnosis of meningitis. These data suggest that the incidence of invasive H. influenzae type b disease is influenced by the racial composition of the population, the rates of disease in specific subgroups, and possibly by local medical practices. Understanding the factors that contribute to the incidence of disease is necessary to interpret variations in different populations and changes over time.

Group B streptococcal infection in children beyond neonatal period: report of 3 patients

Three patients beyond the neonatal period with group B streptococcal infection were presented, including acute osteomyelitis and septic arthritis, bacteremia and septicemia. Serotyping was done in two patients. One was type Ia and the other was type III. All patients recovered from the disease.

Reevaluation of the ambulatory pediatric patient whose blood culture is positive for Haemophilus influenzae type b

We conducted a retrospective review of 60 patients with Haemophilus influenzae type b bacteremia initially treated as outpatients, to test the hypothesis that a subgroup of these patients is at low risk of continuing invasive infection and thus requires a less comprehensive reevaluation. These patients were 6% of the 975 patients with invasive H. influenzae type b infection identified by active surveillance in Dallas County, Texas, during a 6 1/2-year period. The clinical assessment of "ill" appearance and persistent fever (greater than or equal to 38.0 degrees C) on the return visit were the two most useful variables in identifying patients at risk of continuing infection. Among 25 (42%) patients who were considered "ill" (febrile or afebrile), 20 (80%) had continuing invasive infection and 14 (56%) had a subsequent culture that was positive for H. influenzae type b. Among 8 patients who were considered "well" but who remained febrile, 3 (38%) had continuing infection, including 1 (13%) patient with a second culture that was positive. By contrast, among 27 (45%) patients who were considered "well" and who were afebrile, continuing invasive infection was identified in only 2 (7%) patients, and all repeat cultures were negative. These results suggest that when patients return for reevaluation of H. influenzae type b bacteremia, clinical assessment by an experienced physician, together with the febrile status of the patient, can identify those at high versus low risk of continuing invasive infection and thus guide the extent of diagnostic reevaluation.

Immunogenicity of four Haemophilus influenzae type b conjugate vaccines in 17- to 19-month-old children

OBJECTIVE

To compare the immunogenicity of four Haemophilus influenzae type b (Hib) conjugate vaccines in different populations of 17- to 19-month-old children in the United States.

DESIGN

Four immunogenicity trials with sera were assayed in one laboratory. Trials 1 and 2 each compared one vaccine in two regions, and trials 3 and 4 were randomized comparisons of multiple vaccines within a region.

SUBJECTS

A convenience sample of 313 healthy children recruited from pediatric practices in Minneapolis, Minn., Dallas and Houston, Tex., and Sellersville, Pa.

MEASUREMENTS AND RESULTS

Children with prevaccination antibody greater than 0.15 microgram/ml showed higher antibody responses to vaccination than children with less than or equal to 0.15 microgram/ml (p less than 0.001). Among the former, there were no significant differences in antibody response to vaccination with the different conjugates within any of the trials. Among children with less than or equal to 0.15 microgram/ml of antibody before vaccination, there were no significant differences in the geometric mean antibody responses of children in trial 1 vaccinated with polyribosylribitol phosphate-diphtheria toxoid (PRP-D) in Dallas or in Minneapolis, or of children in trial 3 in Dallas randomly assigned to receive Hib oligosaccharide-CRM197 (HbOC) or PRP-D. In contrast, in trial 2, children given PRP-tetanus toxoid (PRP-T) in Pennsylvania had a significantly higher geometric mean antibody response than children given PRP-T in Houston (13.5 vs 3.0 micrograms/ml; p = 0.005). In trial 4 in Minneapolis, the geometric mean antibody response was highest in children randomly assigned to receive PRP-outer membrane protein (OMP) (9.3 micrograms/ml), followed by PRP-D (5.0 micrograms/ml) and HbOC (2.3 micrograms/ml) (PRP-OMP vs HbOC; p = 0.005). In all four trials, IgG1 responses predominated compared with IgG2 responses.

CONCLUSIONS

All four conjugate vaccines are immunogenic in children 17 to 19 months of age. However, the magnitude of the anticapsular antibody response varied by vaccine type, the level of antibody in prevaccination sera, and geographic location.

Pertussis in hospitalized children

Before the whole-cell pertussis vaccine was available, Bordetella pertussis infections were an important cause of morbidity and mortality in infants. To determine the extent of continuing morbidity in an era of vaccination, a retrospective review was conducted of the records of neonates and infants hospitalized with pertussis infection at Parkland Memorial Hospital and Children's Medical Center, Dallas, Tex. During the 20 years from 1967 through 1986, 182 patients were younger than 24 months. Among 176 patients whose immunization history was recorded, 89% had received fewer than two doses of pertussis vaccine. The mean hospital stay was 7.4 days (range, 1 to 69 days). A convulsion occurred in 11 patients (6%). Apnea was reported in 45 patients (25%) and observed in the hospital in 26 (14%). Nine patients (5%) received mechanical ventilatory therapy. Intensive care monitoring was required in 18 patients (10%). Three (1.6%) died, all with secondary bacterial pneumonia. This hospital-based population indicates that pertussis continues to be a cause of serious morbidity and mortality in infants.

Pertussis toxin attenuates angiotensin II but not beta-adrenoceptor facilitation of noradrenaline release from rat kidney cortex

1. Angiotensin II (AII; 0.01 and 0.1 mumols/L), angiotensin I (AI, 0.1 mumols/L) and the beta-adrenoceptor agonist isoprenaline (0.1 mumols/L) all facilitated the stimulation-induced outflow of radioactivity from slices of rat kidney cortex incubated in [3H]-noradrenaline. 2. Treatment of rats with pertussis toxin (25 and 50 micrograms/kg i.v.) to inactivate G-proteins attenuated the facilitation caused by AII and AI, but not that caused by isoprenaline. 3. The hypothesis that isoprenaline enhances noradrenaline release by generating AII to activate facilitatory prejunctional AII receptors is not supported by the present study. The hypothesis predicts that pertussis toxin, by inactivating the G-proteins associated with AII receptors, should have inhibited the facilitatory effect of isoprenaline. This did not occur.

Prejunctional beta-adrenoceptors, angiotensin II and neuropeptide Y receptors on sympathetic nerves in mouse atria are linked to N-ethylmaleimide-susceptible G-proteins

We used the alkylating agent N-ethylmaleimide in order to investigate G-proteins linked to release-modulating prejunctional receptors of sympathetic nerves in mouse atria incubated with [3H]-noradrenaline. The receptors tested were facilitatory beta-adrenoceptors and angiotensin II receptors and inhibitory neuropeptide Y receptors. In order to evaluate the specificity of the N-ethylmaleimide treatment, we tested N-ethylmaleimide against the second messenger pathways that are linked to beta-adrenoceptors (adenylate cyclase) and angiotensin II (protein kinase C). The results show that a 60-min preincubation with N-ethylmaleimide (3 microM) abolished the facilitatory effect of isoprenaline (0.1 microM) and angiotensin II (0.1 microM) on the stimulation-induced release of noradrenaline and reduced the inhibitory action of neuropeptide Y (0.3 microM). N-ethylmaleimide had no effect on the stimulatory action of either phorbol dibutyrate (0.01, 0.1 microM), forskolin (10 microM), or a combination of 8-bromo adenosine-3'5'-monophosphate (90 microM) and 3-isobutyl-1-methylxanthine (100 microM). However, at a higher concentration (10 microM), N-ethylmaleimide reduced the facilitatory effect of phorbol dibutyrate (0.1 microM) and the combination of 8-bromo adenosine-3',5'-monophosphate (90 microM) and 3-isobutyl-1-methylxanthine (100 microM). This suggests that N-ethylmaleimide at 3 microM but not 10 microM was selective for receptor-mediated modulation of noradrenaline release without directly affecting the adenylate cyclase (forskolin, 8-bromo adenosine-3',5'-monophosphate + 3-isobutyl-1-methylxanthine) or protein kinase C (phorbol dibutyrate) transduction pathways. In atria from mice pretreated with pertussis toxin (1.5 micrograms/mouse), N-ethylmaleimide preincubation (1 and 3 microM) resulted in a more pronounced reduction of the inhibitory action of neuropeptide Y (0.3 microM). The nature of this interaction is unclear. Since N-ethylmaleimide has been shown in other studies to inactivate G-proteins, the inhibitory effect of N-ethylmaleimide on prejunctional beta-adrenoceptors, angiotensin II receptors and neuropeptide Y receptors of sympathetic nerves may suggest that G-proteins are involved with these receptors, although other effects of N-ethylmaleimide on the receptor coupling processes cannot be ruled out. Moreover, it appears that the concentration of N-ethylmaleimide used is critical since a higher concentration (10 microM) resulted in non-specific effects on signal transduction mechanisms in the present experimental conditions.

Pertussis toxin differentiates between alpha 1- and alpha 2-adrenoceptor-mediated inhibition of noradrenaline release from rat kidney cortex

In slices of rat kidney cortex incubated in [3H]noradrenaline, the alpha 1-adrenoceptor agonist methoxamine (10 microM), the alpha 2-adrenoceptor agonist clonidine (0.1 microM), as well as adenosine (10 microM), inhibited the electrical stimulation-induced (S-I) outflow of radioactivity, at a stimulation frequency of 1 Hz. Prior treatment of rats with pertussis toxin (25 micrograms/kg i.v.), which abolished the negative inotropic effect of carbachol (10 microM) on isolated atria, prevented the inhibition caused by methoxamine, but not that caused by clonidine or adenosine. At a stimulation frequency of 5 Hz, the alpha 2-adrenoceptor antagonist idazoxan (0.1 microM) and the prostaglandin synthesis inhibitor indomethacin (10 microM) both facilitated the S-I outflow of radioactivity, and neither of these effects were altered by pertussis toxin. These results suggest that a pertussis toxin sensitive G-protein is involved in alpha 1-adrenoceptor inhibition of noradrenaline release, but not in alpha 2-adrenoceptor, adenosine or prostaglandin inhibition.

Beta-adrenoceptor blockade and sympathetic neurotransmission in the pithed rat

The effects of the beta 1-adrenoceptor blocking drug atenolol and the beta 2-adrenoceptor blocking drug ICI 118551 (ICI, Melbourne, Australia) on noradrenaline release and blood pressure were investigated using the pithed rat, which was subjected to continuous electrical stimulation of the spinal sympathetic outflow (pulses at 3 Hz). This stimulation increased blood pressure but not heart rate. The noradrenaline release rate was calculated by infusing [3H] noradrenaline and measuring the steady-state concentrations of both endogenous and infused noradrenaline. Atenolol (0.2 mg/kg bolus plus 0.1 mg/kg per h, intra-arterially) had no effect on the noradrenaline release rate or heart rate, but significantly decreased blood pressure. On the other hand, ICI 118551 (0.2 mg/kg bolus plus 0.1 mg/kg per h. intra-arterially) had no significant effect on blood pressure or heart rate, but did inhibit the noradrenaline release rate. The sympathoinhibitory effect of ICI 118551 was not observed in animals which had been adrenal medullectomized, suggesting that its effect on noradrenaline release was due to blockade of activation of facilitatory prejunctional beta 2-adrenoceptors by adrenaline. The reduced noradrenaline release in the presence of ICI 118551 was not accompanied by a reduction in blood pressure. This may be because ICI 118551 also blocked vasodilatory beta 2-adrenoceptors on vascular smooth muscle. Indeed, in unstimulated pithed rats, infusions of adrenaline which were non-pressor were found to be pressor after ICI 118551 was administered.(ABSTRACT TRUNCATED AT 250 WORDS)

Excretion of Haemophilus influenzae type b polysaccharide antigen in urine of healthy nasopharyngeal carriers

We measured concentrations of Haemophilus influenzae type b (Hib) polysaccharide antigen by ELISA in urine samples from 81 healthy North American children with positive or negative throat cultures for Hib, to investigate the possibility that asymptomatic carriers may have antigenuria. For comparison, we determined the concentrations of Hib polysaccharide antigen in urine samples from 56 patients with proven Haemophilus disease, including 13 children with lower respiratory infections who resided in developing countries. Among the healthy children, antigen was detected in the urine of seven of 19 (37%) carriers of Hib compared with one of 62 (2%) children with negative throat cultures (p less than 0.001). Among the patients with invasive Haemophilus infections, 93% had antigen detected. Although there was overlap in the concentrations of antigen in the positive urines from the asymptomatic carriers and those of the ill patients, the concentrations of the ill patients were higher than those of the carriers. The respective geometric means of the positive patients were: American patients with meningitis, 42.5 ng/mL (range 1.7-9800 ng/mL); American patients with infections not involving the CNS, 5.8 ng/mL (range: 1.0-96 ng/mL); patients from developing countries with lower respiratory infections, 29.6 ng/mL (range: 0.9-5290), and American asymptomatic carriers, 1.9 ng/mL (range: 0.6-16.7 ng/mL). Thus, antigenuria is present in a high proportion of healthy children with positive throat cultures for Hib, and the antigen concentrations of the carriers overlap those of ill patients. These results suggest that either mucosal colonization itself is sufficient to produce antigen-uria, or asymptomatic carriers may be experiencing asymptomatic invasive Hib infection.

Modulation of noradrenaline release in slices of rat kidney cortex through alpha 1- and alpha 2-adrenoceptors

Slices of rat kidney cortex were incubated in [3H]noradrenaline, then placed in a flow cell and subjected to electrical field stimulation. At a stimulation frequency of 5 Hz, both the alpha 2-adrenoceptor antagonist idazoxan (0.1 microM) and the alpha 1-adrenoceptor antagonist prazosin (0.1 microM) significantly enhanced the stimulation-induced (S-I) outflow of radioactivity from the slice. However, neither clonidine (0.1 microM) nor methoxamine (10 microM), alpha 2- and alpha 1-agonists respectively, affected the S-I outflow of radioactivity at this stimulation frequency. At a lower stimulation frequency (1 Hz), the S-I outflow of radioactivity was not affected by idazoxan or prazosin, but was inhibited by both clonidine and methoxamine. The effect of clonidine was prevented by idazoxan (0.1 microM), but not by prazosin (0.1 microM). The effect of methoxamine was abolished by prazosin (0.1 microM), but not by idazoxan (0.1 microM). The inhibitory effect of methoxamine was not prevented by the prostaglandin synthesis inhibitor indomethacin (10 microM) or the adenosine receptor antagonist 8-phenyltheophylline (1 microM) and thus was not mediated by either prostaglandins or adenosine. The results suggest that both prejunctional alpha 1- and alpha 2-adrenoceptors are directly involved in modulation of noradrenaline release from the renal sympathetic nerves of the rat.

Host and bacterial factors associated with Haemophilus influenzae type b disease in Minnesota children vaccinated with type b polysaccharide vaccine

Host and bacterial factors were evaluated among 86 Minnesota children with Haemophilus influenzae type b disease detected by active surveillance after introduction of type b polysaccharide vaccine in the state. Children were 2-6 y of age. Thirty-three (38%) had been vaccinated. There was no significant difference between the frequency of low serum concentrations of IgM, IgA, IgG, or IgG2 in the vaccinated and nonvaccinated subjects (13% vs. 8%, P = .5). The presence of the Gm immunoglobulin allotype phenotype (1,3,17;23;5,13,21), previously associated with a lower relative risk of vaccine failure in children from other states, was associated with a fourfold decrease in the relative risk of vaccine failure in Minnesota (P less than .07). Haemophilus isolates from 58 of the children were available for clonal characterization by multilocus electrophoresis and outer membrane protein subtyping. There were no significant differences between the clone distribution of the strains causing disease in vaccinated and nonvaccinated patients, and nearly all disease-producing clones in Minnesota also are known to cause disease in other areas of the country. Thus, vaccine failure in Minnesota is infrequently associated with hypogammaglobulinemia or with infection by unusual clones of a H. influenzae type b. Also, the Gm phenotype associated with protection against vaccine failure in other areas of the USA appears to be protective in Minnesota.

Haemophilus influenzae type b in respiratory secretions

Oral and respiratory secretions of 31 children who were healthy or had mild upper respiratory infection, and who had a positive throat culture for Haemophilus influenzae type b, were cultured to determine which secretions contain this organism and how long it can be recovered from fomites. Rhinorrhea was present in 11 of 31 (34%) children and nasal mucus was positive for H. influenzae type b in 10 (91%). In 5 of these children the concentration of H. influenzae type b in nasal mucus was 10(4) to 10(7) colony-forming units/ml3. H. influenzae type b in nasal mucus applied to fomites were recovered for 12 hours. Cultures of saliva and cough secretions compared with nasal mucus were less often positive (3 of 31, P less than 0.001; 3 of 25, P less than 0.001, respectively) and contained fewer H. influenzae type b (5 and 15 colony-forming units, respectively). H. influenzae type b was recovered from the hand of 2 of 27 (7%) children; both children had positive cultures of saliva. These data indicate that H. influenzae type b can be found in oral and respiratory secretions of pharyngeal carriers and can contaminate children's hands. Nasal mucus was the most consistently positive secretion and contained the largest number of bacteria. Careful management of nasal mucus secretions is warranted in settings where transmission could occur to susceptible children.

The protective efficacy of Haemophilus b polysaccharide vaccine

To assess the protective efficacy of the Haemophilus b polysaccharide vaccine, a case-control study was conducted in Connecticut, Dallas County, and greater Pittsburgh. Seventy-six children 24 to 72 months of age who had H influenzae type b isolated from normally sterile sites from August 1985 through July 1987 were enrolled. For each case two controls, matched by age and place of residence, were randomly selected from the records of all live births in the area. Antecedent receipt of the Haemophilus b polysaccharide vaccine was ascertained from the records of all physicians and clinics at which the subjects received medical care. Overall, 12% of the cases and 39% of the controls had received the vaccine. The estimate of the protective efficacy of the vaccine was 88% overall (95% confidence interval, 74% to 96%) and 91% (95% confidence interval, 71% to 99%), 92% (95% confidence interval, 76% to 99%), and 81% (95% confidence interval, 45% to 96%) in Connecticut, Dallas County, and greater Pittsburgh, respectively. The estimates were not substantially affected by adjusting with logistic regression for differences between the cases and controls in race and the attendance of group day care. We conclude that the Haemophilus b polysaccharide vaccine is highly effective in these areas among children who receive the vaccine when they are 24 months of age or older.