Hospitalization for pneumonia in children in Auckland, New Zealand

OBJECTIVE

To describe the epidemiology of hospitalizations for pneumonia in children in Auckland, New Zealand.

METHODS

A consecutive sample of children hospitalised with pneumonia at the Starship Childrens Hospital from 1 July 1993 to 30 June 1996. Subjects were Pacific Island, Maori, and European/other children aged 0-14 years resident in north, west and central Auckland who were hospitalized with pneumonia. Comparisons were made of the number of hospitalisations by year, ethnicity, age and season; and of the hospitalisation rates by year, ethnicity and age.

RESULTS

There were 681 children who were hospitalized with pneumonia during 1993-94, 731 during 1994-95 and 630 during 1995-96. The average annual hospitalization rate was 5.0 per 1000 children aged 0-14 years (95% CI 4.8-5.2). The average annual hospitalisation rate for Pacific Island children was 14.0 per 1000 (95% CI 13.0-14.9), for Maori children 6.7 per 1000 (95% CI 6.0-7.4) and for European/other children was 2.7 per 1000 (95% CI 2.6-2.9). Fifty-three per cent of the hospitalised children were less than 2 years of age. A larger percentage of Pacific Island (61%) and Maori (60%) children were aged less than 2 years compared to European/other (42%) children (P < 0.001). There was marked seasonal variability in the number of hospitalizations, with peaks in hospitalizations corresponding to peaks in positive respiratory viral isolates.

CONCLUSIONS

Pneumonia was a consistent cause of hospitalisation for a large number of Auckland children during this 3-year period. Hospitalisation rates and age distribution varied with ethnicity. Hospitalization rates were highest for Pacific Island. intermediate for Maori and lowest for European/other children. Based on these hospitalisation data, pneumonia is a significant cause of morbidity for children in Auckland, New Zealand.

[A clinical observation on the leukopenia treated with shengbaikuai decoction]

OBJECTIVE

To study the effective orally taken medicine in treating the leukopenia.

METHODS

Ninety cases of leukopenia induced by chemotherapy were divided into 3 groups. They were test group treated with Shengbaikuai Decoction (SBK), control group and blank group. Their efficacies were compared with each other, 25 cases with nonchemotherapy were also observed.

RESULTS

WBC count and absolute neutrophil count (ANC) in test group were higher than those of other groups immediately after treatment and 2 weeks later (P < 0.01). The marked effective rate and total effective rate of test group after 2 weeks were 60.0% and 80.0% (P < 0.001) respectively, which were significantly higher than those of other groups. WBC and ANC count after treatment and 3 weeks later were higher than those before treatment in nonchemotherapy group (P < 0.001). The marked effective rate and total effective rate 3 weeks later were 64.0% and 80.0% respectively.

CONCLUSIONS

SBK could increase WBC count rapidly and definitely without apparent side effect.

Effects of angiotensin II on endothelial cell growth: role of AT-1 and AT-2 receptors

Angiotensin II (AngII) is a main mediator in the regulation of vascular tone. Although its effects on vascular smooth muscle cells are well known, data on its role on endothelial biology are still insufficient. The present study examined the effect of endogenous and exogenous AngII on bovine aortic endothelial cells possessing both AT-1 and AT-2 receptors. A DNA synthesis-promoting effect of AT-2 blockade by PD123319 (10(-9) to 10(-7) M) was demonstrated. This effect was transduced through an AT-1-mediated pathway, as shown by using the AT-1 antagonist, losartan. In addition, an AT-1-mediated effect of AngII was demonstrated on bovine aortic endothelial cell proliferation, which occurred despite the absence of AngII-induced Ca2+ transients. In summary, the present study disclosed relevant characteristics of the effect of AngII on endothelial cell growth that have potential pathophysiologic projections, particularly for the use of selective AngII blocking agents.

The role of tyrosine 121 in cofactor binding of 5-aminolevulinate synthase

5-Aminolevulinate synthase (EC 2.3.1.37) is the first enzyme in the heme biosynthesis in nonplant eukaryotes and some prokaryotes. It functions as a homodimer and requires pyridoxal 5'-phosphate as an essential cofactor. Tyr-121 is a conserved residue in all known sequences of 5-aminolevulinate synthases. Further, it corresponds to Tyr-70 of Escherichia coli aspartate aminotransferase, which has been shown to interact with the cofactor and prevent the dissociation of the cofactor from the enzyme. To test whether Tyr-121 is involved in cofactor binding in murine erythroid 5-aminolevulinate synthase, Tyr-121 of murine erythroid 5-aminolevulinate synthase was substituted by Phe and His using site-directed mutagenesis. The Y121F mutant retained 36% of the wild-type activity and the Km value for substrate glycine increased 34-fold, while the activity of the Y121H mutant decreased to 5% of the wild-type activity and the Km value for glycine increased fivefold. The pKa1 values in the pH-activity profiles of the wild-type and mutant enzymes were 6.41, 6.54, and 6.65 for wild-type, Y121F, and Y121H, respectively. The UV-visible and CD spectra of Y121F and Y121H mutants were similar to those of the wild-type with the exception of an absorption maximum shift (420 --> 395 nm) for the Y121F mutant in the visible spectrum region, suggesting that the cofactor binds the Y121F mutant enzyme in a more unrestrained manner. Y121F and Y121H mutant enzymes also exhibited lower affinity than the wild-type for the cofactor, reflected in the Kd values for pyridoxal 5'-phosphate (26.5, 6.75, and 1.78 microM for Y121F, Y121H, and the wild-type, respectively). Further, Y121F and Y121H proved less thermostable than the wild type. Taken together, these findings indicate that Tyr-121 plays a critical role in cofactor binding of murine erythroid 5-aminolevulinate synthase.

Role of nitric oxide-related mechanisms in renal function in ageing rats

BACKGROUND

The impaired renal function and vasodilatation that accompany age need to be re-addressed based upon the new knowledge concerning vascular nitric oxide (NO)-dependent systems. The present study examined the effects of age on the NO-related renal response.

METHODS

The study was performed in euvolaemic, conscious Wistar rats, aged 5 and 18 months. Renal function and haemodynamic measurements with fluorescent microspheres were employed to assess differences between groups.

RESULTS

A first set of experiments showed that ageing rats had a reduced natriuretic and diuretic response to acetylcholine, whereas the response to sodium nitroprusside was preserved. In the same regard, a reduction of the renal functional effects of L-arginine (L-Arg) and L-glycine (L-Gly) was found in the older rats. In the ageing rats, these responses were accompanied by an enhanced effect of the L-Arg competitive analogue, NwNLA, which provoked a marked reduction of renal function. This effect of NwNLA was blocked by the simultaneous administration of a small dose of L-Arg in the ageing but not in the young rats. Systemic haemodynamic studies revealed that in ageing rats, NwNLA reduced renal blood flow and increased renal vascular resistances in a significantly higher proportion than in younger animals. However, flow to other organs, namely, brain, spleen or liver, was affected in a similar manner in both young and old rats. Ultrastructural alterations were found in endothelial cells, which might constitute the anatomical basis for the observed functional derangements.

CONCLUSIONS

The present experiments reveal that ageing is accompanied by significant differences in NO-related responses in the kidney which do not appear to affect blood flow to other organs. The response to L-Arg and L-Arg competitive analogues supports the existence of a marked dependency on NO-related mechanisms in the ageing rats, but not of a decreased baseline activity of the NO-dependent pathways.

Role of arginine 439 in substrate binding of 5-aminolevulinate synthase

5-Aminolevulinate synthase (EC 2.3.1.37) catalyzes the first reaction in the heme biosynthetic pathway in nonplant eukaryotes and some prokaryotes. Homology sequence modeling between 5-aminolevulinate synthase and some other alpha-family pyridoxal 5'-phosphate-dependent enzymes indicated that the residue corresponding to the Arg-439 of murine erythroid 5-aminolevulinate synthase is a conserved residue in this family of pyridoxal 5'-phosphate-dependent enzymes. Further, this conserved arginine residue in several enzymes, e.g., aspartate aminotransferase, for which the three-dimensional structure is known, has been shown to interact with the substrate carboxyl group. To test whether Arg-439 is involved in substrate binding in murine erythroid 5-aminolevulinate synthase, Arg-439 and Arg-433 of murine erythroid 5-aminolevulinate synthase were each replaced by Lys and Leu using site-directed mutagenesis. The R439K mutant retained 77% of the wild-type activity; its K(m) values for both substrates increased 9-13-fold, while the activity of R433K increased 2-fold and the K(m) values for both substrates remained unchanged. R439L had no measurable activity as determined using a standard 5-aminolevulinate synthase enzyme-coupled activity assay. In contrast, the kinetic parameters for R433L were comparable to those of the wild-type. Dissociation constants (Kd) for glycine increased 5-fold for R439K and at least 30-fold for R439L, while Kd values for glycine for both R433K and R433L mutants were similar to those of the wild-type. However, there was not much difference in methylamine binding among the mutants and the wild-type, excepting of a 10-fold increase in K(d)methylamine for R439L. R439K proved much less thermostable than the wild-type enzyme, with the thermotransition temperature, T1/2, determined to be 8.3 degrees C lower than that of the wild-type enzyme. In addition, in vivo complementation analysis demonstrated that in the active site of murine erythroid 5-aminolevulinate synthase, R439 is contributed from the same subunit as K313 (which is involved in the Schiff base linkage of the pyridoxal 5'-phosphate cofactor) and D279 (which interacts electrostatically with the ring nitrogen of the cofactor), while another subunit provides R149. Taken together, these findings suggest that Arg-439 plays an important role in substrate binding of murine erythroid 5-aminolevulinate synthase.

[Study on gene of YRRM in azoospermia]

OBJECTIVE

To detect the abnormal YRRM gene in azoospermia and to explore the pattern of YRRM gene in Chinese men.

METHODS

With the special primer for YRRM, the YRRM gene was analyzed using the PCR method. Extracting the testis total RNA, we performed the RT-PCR. The part of YRRM gene was sequenced.

RESULTS

No amplification band of YRRM gene was noted in 4 of 74 Chinese men with azoospermia (5.4%). The YRRM gene was obviously expressed in the testis of man and showed a 500 bp cDNA fragment. The cDNA and genomic DNA were different because the intron. We found that Chinese people only have YRRM1 pattern of gene, and the sequence of YRRM gene of Chinese men shows that the composition of the nucleotide is same as YRRM1 gene.

CONCLUSION

These cases of abnormal YRRM gene may result in male infertility, YRRM gene and azoospermia is the YRRM1 gene is polymouphase of racial.

[Serum HBV DNA detected by polymerase chain reaction with dUTP/uracil-DNA glycosylase]

The ability of PCR reagent containing dUTP/uracil-DNA glycosylase for controlling carry-over contamination of PCR products was explored. All of 204 sera taken from hepatitis patients were used for HBV DNA detection by PCR with PCR-dUTP/UDG reagent in comparison with that without dUTP/UDG. The results showed that its efficiency of controlling contamination was excellent. At least, contamination of 100 ng PCR products was got rid of. The corresponding rate of HBV DNA detection by PCR-dUTP/UDG in combination with dot hybridization using digoxin-labeled HBV probe was as high as 89.32%, higher than that (81.45%) of PCR without dUTP/UDG plus dot hybridization(P < 0.05). It suggests that PCR-dUTP/UDG method could prevent PCR products from contaminating and increase accuracy and specificity of PCR amplification.

The use of mobile telephones in a district general hospital

Advances in technology have led to the increased availability of mobile telephones, but their use in an NHS hospital has not previously been reported. Junior doctors require easy access to a telephone, but ward telephones are frequently busy and not readily accessible when urgently needed. A one-year retrospective study was carried out on the use of mobile telephones in a small district general hospital.

Submandibular gland peptide-T (SGP-T) inhibits intestinal anaphylaxis

A novel peptide, submandibular gland peptide-T (SGP-T), which reduces allergen-induced hypotension, was examined for effects on intestinal anaphylaxis. Hooded-Lister rats were sensitized to egg albumin and prepared for the measurement of in vivo myoelectric activity of the jejunum. The disruption of migrating myoelectric complexes (MMCs) that occurs upon intraluminal, duodenal challenge with antigen of sensitized rats was inhibited by 75% upon intravenous treatment with 100 micrograms/kg of SGP-T. In addition, SGP-T reduced the number of rats experiencing anaphylactic diarrhea and disrupted MMCs, but the peptide did not alter antigen-provoked release of rat mast cell protease II. The mechanism of action of SGP-T remains to be determined, but it apparently does not act directly on mast cells to exert its antianaphylactic action. These results emphasize that modulation of immediate hypersensitivity reactions is only one of several gastrointestinal activities that are affected by growth factors and peptides released from salivary glands.

Evaluation of commercially available and in-house reverse transcription-PCR assays for detection of hepatitis G virus or GB virus C

Serum samples from 96 Spanish hemodialysis patients, as well as serial dilutions of RNA extracted from a reference strain of hepatitis G virus (HGV), were tested for HGV or GB virus C (GBV-C) RNA. Two different reverse transcription (RT)-PCR-based methods of detection were compared for the ability to detect RNA extracted from the samples: an RT-nested PCR assay with primers derived from the 5' noncoding region (5'NC) or nonstructural region 3 (NS3) sequences and a commercially available RT-PCR assay with primers derived from the 5'NC or NS5A sequences. When RT-nested PCR was performed on 10-fold serial dilutions of RNA from the HGV reference strain, the last positive dilution was 10(-7) to 10(-8). With the commercial RT-PCR assay, the last positive dilution was 10(-6) to 10(-7). When equal amounts of RNA extracted from serum samples from 96 hemodialysis patients were tested for HGV or GBV-C RNA, 25 patients (26%) were positive by the RT-nested PCR. However, only 21 (84%) of these 25 positive patients were positive for HGV or GBV-C by the commercial RT-PCR assay. Analysis of the 5'NC and NS3 sequences amplified by RT-nested PCR demonstrated that all but two positive patients had unique HGV or GBV-C sequences. In summary, RT-nested PCR and a commercially available RT-PCR assay for HGV or GBV-C gave concordant results for 96% of the patients tested.

Hepatitis C in asymptomatic blood donors

Among 248 asymptomatic blood donors positive for antibody to hepatitis C virus (anti-HCV) enrolled in a long-term prospective study, 86% had chronic HCV infection and 14% appeared to have recovered as assessed by serial determinations of serum alanine aminotransferase (ALT) levels and HCV RNA by polymerase chain reaction. Established parenteral risk factors for HCV transmission were identified in 75% of donors. In addition, there was a strong independent association between HCV positivity and cocaine snorting, suggesting that shared snorting devices may be a covert route of parenteral transmission. Ear piercing in males was also significantly associated with transmission. There was no evidence for sexual spread. Although the majority of HCV carriers had both biochemical and histological evidence of chronic viral hepatitis, the extent of liver injury was generally mild. Among a larger population of 280 HCV RNA-positive donors, 17% had repeatedly normal ALT levels, 45% had levels that did not exceed twice, and only 22% had levels that exceeded five times the upper limit of the normal range. Among 81 patients who underwent liver biopsy, only 13% had evidence of severe hepatitis (8%) or cirrhosis (5%), despite a duration of infection that generally exceeded 15 years. No severe histological lesions were observed in blood donors with chronic HCV infection who had repeatedly normal ALT levels. In both donors and blood recipients, the frequency of severe morbidity or mortality related to HCV infection was less than 10% during the first two decades of infection. Further long-term studies are required to see if the progression to severe outcomes continues to accrue at this slow pace or whether it accelerates during subsequent decades.

A comparison of two pertussis epidemics in Auckland

AIM

To determine if the addition of the 6 week dose of pertussis vaccine in 1984 was associated with any change in the hospitalisation rate for children with pertussis and the higher hospitalisation rates for Maori and Pacific Islander children with pertussis.

METHODS

DESIGN

Population based study of pertussis hospitalisations using a retrospective chart review of hospitalisation data for children during the 1991 epidemic, which was compared to previously published data from the 1982 epidemic.

SETTING

Princess Mary and Middlemore hospitals, Auckland.

SUBJECTS

Children aged 0-14 years resident in metropolitan Auckland and hospitalised in Auckland during 1982 or 1991 with pertussis.

MEASUREMENTS

Hospitalisation rates were calculated as number of children with a discharge diagnosis of pertussis per 1000 children aged 0-14 years based on 1981 and 1991 census data. 1982 data were converted to person-years as published report was for an 8 month period. Hospitalisation rates were compared as a relative risk (RR) of hospitalisation in 1991 versus 1982.

RESULTS

There were 84 cases during 8 months in 1982 and 66 cases in 1991. Rates of hospitalisation by ethnic group; in 1982 were 0.24 Other/European (OE), 1.98 Maori (M), 1.37 Pacific Islander (PI); and in 1991 were 0.22 OE, 0.51 M, 0.40 PI. Compared to 1982 the relative risk of hospitalisation in 1991 adjusted for ethnicity was 0.43 (CI 0.33, 0.58, p < 0.0001). Compared to 1982 there was a significant reduction in the hospitalisation rate in 1991 for M (RR = 0.26, CI 0.16, 0.43, p < 0.0001); and PI children (RR = 0.29, CI 0.16, 0.54, p < 0.0001); but not for OE children (RR = 0.91, 95% CI 0.57, 1.46, p = 0.70).

CONCLUSIONS

There was a significant reduction in the rate of hospitalisation for pertussis in 1991 compared to 1982. This reduction in hospitalisation rate was due to a reduction in rates for Maori and Pacific Islander children.

[Determination of metronidazole in gastric juice by high performance liquid chromatography]

Metronidazole (MTZ) is the first chosen drug of anti-anaerobe which was recommended by World Health Organization. In this paper a high performance liquid chromatographic (HPLC) method has been developed to determine the concertration of MTZ in human gastric juice. Gastric juice was obtained by intubation after taking drug, then the sample was precipitated with ethanol to remove proteins, centrifuged, filtered and finally assayed by HPLC. The operating conditions were reversed phase C18 column (4mm x 150mm), CH3OH:KH2PO4 (5mmol/L, pH 4.0) = 10:90 mobile phase with flow rate of 1.5mL/min and detection wavelength at 320nm. The standard working curve was Y = -1.63 + 1.15X, with r = 0.9999, n = 7. The linear range was 2.5-200mg/L. The detection limit was 0.4mg/L. The average recovery was 96.0% and the coefficient of variation was 3.07%. This method can be applied to guide clinical therapy and pharmaceutical research.

Concentrated ascitic fluid reinfusion in cirrhotic patients: a simplified method

A new method for ascites filtration and reinfusion, which uses a single Cuprophan filter and is performed in the dialysis unit, is reported. Thirty-one procedures were performed in 17 patients with cirrhosis and massive ascites. A mean volume of 8.6 L of ascitic fluid was removed; from this volume, 5 L were ultrafiltered and a concentrated ascitic fluid was reinfused (x = 359.8 mL). The whole procedure was completed in a mean time of 248 minutes. No relevant method-related complications were detected. Moreover, no significant changes in blood urea nitrogen (BUN), creatinine, plasma and urinary electrolytes, or platelet count were found, even in the case of repeated procedures (two to nine times). The reinfused fluid contained a mean value of albumin of 4.7 g/dL and significant amounts of globulins and complement. The overall cost of the materials used in the procedure ($49.46) offered competitive advantages with respect to other types of frequently used methods. In conclusion, we present a safe, effective, and time- and cost-saving technique for ascites reinfusion that represents an advantageous alternative to more complicated and expensive methods or to the currently used medical therapy.

[PCR-SSCP analysis of p53 gene in human primary brain tumor]

In this study PCR-SSCP alalysis was made to detect the mutation of the exon 5-7 of p53 gene in 37 cases of human primary brain tumor. The results showed that 10 human primary brain tumors had mutation, of which 9 were gliomas (37.5%) and 1 was meningioma (7.7%), and that the higher the grade of tumor was, the higher would be the frequency of mutation. These results suggest that human primary brain tumor is related to p53 gene mutation and such mutation may be the major reason for human primary brain tumor genesis and malignancy.

Consecutive evaluation of immunoglobulin M and G antibodies against hepatitis E virus

Hepatitis E virus (HEV) infection is sporadic in the Guangzhou city southern China. However, the evaluation of antibodies to HEV during consecutive time periods after infection has not been reported. We utilized enzyme immunosorbent assay (ELISA) to defect IgM and IgG anti-HEV in consecutive serum specimens from patients with acute hepatitis E and compared that data with detection rates of IgM and IgG anti-HAV in patients with acute hepatitis A. IgM anti-HEV can be detected as early as 4 days after onset of disease symptoms in some patients. The detection rate of IgM anti-HEV is significantly higher in specimens collected within 4 weeks (95%) of onset than in those specimens collected 4 to 18 weeks after onset (67.6%) (P < 0.005). IgM anti-HEV had a similar pattern to IgM anti-HAV and can be used as a marker of acute HEV infection. In contrast with IgG anti-HAV, 56.8% of the specimens did not contain detectable levels of IgG anti-HEV (P < 0.005). One should be cautioned against making a diagnosis of HEV infection solely by the currently available assays for IgG anti-HEV. In conclusion, IgM anti-HEV can be used as a reliable and sensitive marker for recent HEV infection, but serum specimens should be collected within 4 weeks after onset of symptoms to avoid false-negative results. In contrast, we should be aware of the failure to develop IgG anti-HEV in some patients. These patients carry the risk of reinfection.

Role of endothelium-related mechanisms in the pathophysiology of renal ischemia/reperfusion in normal rabbits

The present study addressed the effect of interventions aimed to increase NO in the setting of acute renal ischemia/reperfusion (I/R) in uninephrectomized rabbits. In the 60-minute post-I/R period, L-arginine+superoxide (O2.-) dismutase (SOD) synergistically improved the renal functional (69.4% versus 10.4% of the pre-I/R glomerular filtration rate with or without L-arginine+SOD, respectively; p < .01) and histological parameters (82.9% decrease of medullary congestion in L-arginine+SOD, P < .01 versus vehicle) and blocked the I/R-dependent neutrophil accumulation (89.3% reduction). In spite of these results over the short term, a second set of experiments disclosed that the protection by L-arginine+SOD was no longer present at 24 and 48 hours (plasma creatinine in vehicle-treated versus L-arginine+SOD-treated animals [mg/100 mL]: 24 hours after I/R, 9.4 +/- 1.9 versus 8.07 +/- 0.65; 48 hours after I/R, 11.6 +/- 3.6 versus 9.7 +/- 0.9; P = NS in all the cases). Additional experiments were conducted using a milder 30-minute ischemic model, which showed no significant functional or histological protection by using L-arginine+SOD. In conclusion, our experiments disclosed the following: (1) the critical importance of the interaction between NO and O2.- in the acute protective effect of L-arginine (this effect not only improved renal function and histology but also reduced neutrophil accumulation) and (2) the discordance existing between the immediate protection afforded by L-arginine+SOD and the lack of protection observed at 24 and 48 hours. This finding suggests that a punctual intervention on the NO system at the time of I/R is not sufficient to reduce renal damage over the long term.

Role of endothelin in the pathophysiology of renal ischemia-reperfusion in normal rabbits

The present study addressed the acute effects of endothelin-1 on renal function and neutrophils accumulation in the setting of in vivo severe (60 min) acute ischemia/reperfusion. Ischemia/reperfusion decreased renal functional parameters and increased renal neutrophil accumulation and medullary congestion. All these parameters markedly improved with the intrarenal administration of anti-endothelin-1 antiserum. Comparatively, the intrarenal infusion of endothelin-1 decreased renal function and increased neutrophil accumulation. Abnormalities in renal histology were, however, less pronounced than with ischemia/ reperfusion. In experiments using rabbit isolated perfused kidneys, endothelin-1 induced the accumulation of labeled neutrophils. This accumulation was similar to that observed in kidneys obtained after 60 minutes of ischemia plus 60 minutes of reperfusion. Both endothelin and ischemia/ reperfusion effects were counteracted by an anti-endothelin antibody. In further in vitro studies, we found that endothelin-1-induced the expression of the CD18 antigens on the neutrophil surface. In subsequent experiments based on this effect of ET-1 on CD18 antigens, a blockade of both ischemia/reperfusion-induced and endothelin-1-induced neutrophil accumulation was obtained by infusion an anti-CD18 antibody. In conclusion, our experiments disclosed the critical role of endothelin-1 as a major promoter of early neutrophil accumulation after ischemia/reperfusion, which occurred through an integrin-mediated mechanism.

Active site of 5-aminolevulinate synthase resides at the subunit interface. Evidence from in vivo heterodimer formation

5-Aminolevulinate synthase (EC 2.3.1.37) is the first enzyme in the heme biosynthetic pathway of animals, fungi and some bacteria. It functions as a homodimer and requires pyridoxal 5'-phosphate as an essential cofactor. In mouse erythroid 5-aminolevulinate synthase, lysine 313 has been identified as the residue involved in the Schiff base linkage with pyridoxal 5'-phosphate [Ferreira, G. C., et al. (1993) Protein Sci. 2, 1959-1965], while arginine 149, a conserved residue among all known 5-aminolevulinate synthase sequences, is essential for function [Gong & Ferreira (1995) Biochemistry 34, 1678-1685]. To determine whether each subunit contains an independent active site (i.e., intrasubunit arrangement) or whether the active site resides at the subunit interface (i.e., intersubunit arrangement), in vivo complementation studies were used to generate heterodimers from site-directed, catalytically inactive mouse 5-aminolevulinate synthase mutants. When R149A and K313A mutants were co-expressed in a hem A- Escherichia coli strain, which can only grow in the presence of 5-aminolevulinate or when it is transformed with an active 5-aminolevulinate synthase expression plasmid, the hem A- E. coli strain acquired heme prototrophy. The purified K313A/R149A heterodimer mixture exhibited K(m) values for the substrates similar to those of the wild-type enzyme and approximately 26% of the wild-type enzyme activity which is in agreement with the expected 25% value for the K313A/R149A coexpression system. In addition, DNA sequencing of four Saccharomyces cerevisiae 5-aminolevulinate synthase mutants, which lack ALAS activity but exhibit enzymatic complementation, revealed that mutant G101 with mutations N157Y and N162S can complement mutant G220 with mutation T452R, and mutant G205 with mutation C145R can complement mutant Ole3 with mutation G344C. Taken together, these results provide conclusive evidence that the 5-aminolevulinate synthase active site is located at the subunit interface and contains catalytically essential residues from the two subunits.

Cervicofacial actinomycosis with paravertebral spread: a case report

We report a case of cervicofacial actinomycosis with paravertebral extension in a 60-year-old man who presented with recurrent neck masses. Diagnosis was confirmed on culture and histology of pus and debris obtained from surgical drainage. He improved only after lengthy in-hospital high dose penicillin therapy. He is currently well and is on maintenance doxycycline therapy for 6 months following the high dose penicillin therapy.