Alterations in regional ventilation, perfusion, and shunt after smoke inhalation measured by PET.

Regional changes in ventilation and perfusion occurring in the early hours after smoke inhalation injury were evaluated through the use of positron emission tomography. Five lambs were imaged before and 1, 2, and 4 h after receiving 100 breaths of cotton smoke. Utilizing a recently developed model of (13)N tracer kinetics (3), we evaluated changes in ventilation, perfusion, shunt, and regional gas content in nondependent, middle, and dependent lung zones. The data demonstrated a progressive development of regional shunt in dependent (dorsal) regions in which perfusion remained the highest throughout the study. These findings, together with decreasing regional ventilation and fractional gas content in the dependent regions, correlated with decreasing arterial Pa(O(2)) values over the course of the study. A negative correlation between regional shunt fraction and regional gas content in dependent and middle regions suggests that shunt was caused by progressive alveolar derecruitment or flooding.     

Brominated Biphenyls Prime Extensive Microbial Reductive Dehalogenation of Aroclor 1260 in Housatonic River Sediment

The upper Housatonic River and Woods Pond (Lenox, Mass.), a shallow impoundment on the river, are contaminated with polychlorinated biphenyls (PCBs), the residue of partially dechlorinated Aroclor 1260. Certain PCB congeners have the ability to activate or “prime” anaerobic microorganisms in Woods Pond sediment to reductively dehalogenate the Aroclor 1260 residue. We proposed that brominated biphenyls might have the same effect and tested the priming activities of 14 mono-, di-, and tribrominated biphenyls (350 μM) in anaerobic microcosms of sediment from Woods Pond. All of the brominated biphenyls were completely dehalogenated to biphenyl, and 13 of them primed PCB dechlorination. Measured in terms of chlorine removal and decrease in the proportion of hexa- through nonachlorobiphenyls, the microbial PCB dechlorination primed by several brominated biphenyls was nearly twice as effective as that primed by chlorinated biphenyls. Congeners containing a meta bromine primed Dechlorination Process N (flanked meta dechlorination), and congeners containing an unflanked para bromine primed Dechlorination Process P (flanked para dechlorination). Two ortho-substituted congeners, 2-bromobiphenyl and 2,6-dibromobiphenyl (2-BB and 26-BB), also primed Process N dechlorination. The most effective primers were 26-BB, 245-BB, 25-3-BB, and 25-4-BB. The microbial dechlorination primed by 26-BB converted ~75% of the hexa- through nonachlorobiphenyls to tri- and tetrachlorobiphenyls in 100 days and removed ~75% of the PCBs that are most persistent in humans. These results represent a major step toward identifying an effective method for accelerating PCB dechlorination in situ. The challenge now is to identify naturally occurring compounds that are safe and effective primers.     

Functional Nonequivalence of Drosophila Actin Isoforms

We show that different Drosophila actinisoforms are not interchangeable. We sequenced the sixgenes that encode conventional Drosophilaactins and found that they specify amino acidreplacements in 27 of 376 positions. To test the significance ofthese changes we used directed mutagenesis to introduce10 such conversions, independently, into the Act88Fflight muscle-specific actin gene. We challenged these variant actins to replace the nativeprotein by transforming germline chromosomes of aDrosophila strain lacking flight muscle actin.Only one of the 10 reproducibly perturbed myofibrillarfunction, demonstrating that most isoform-specific aminoacid replacements are of minor significance. In order toestablish the consequences of multiple amino acidreplacements, we substituted portions of theDrosophila Act88F actin gene with correspondingregions of genes encoding other isoforms. Only one offive constructs tested engendered normally functioningflight muscles, and the severity of myofibrillar defects correlated with the number of replacementswithin the chimeric genes. Finally, we completelyconverted the flight muscle actin-encoding gene to onespecifying a nonmuscle isoform, a change entailing atotal of 18 amino acid replacements. Transformationof flies with this construct resulted in disruption offlight muscle structure and function. We conclude thatactin isoform sequences are not equivalent and that effects of the amino acid replacements,while minor individually, collectively confer uniqueproperties.     

Influence of chroline substitution pattern on the degradation of polychlorinated biphenyls by eight bacterial strains

We compared the metabolism of eight di- and trichlorobiphenyls by eight bacterial strains chosen to represent a broad range of degradative activity against polychlorinated biphenyls (PCBs). The PCB congeners used were 2,3-, 2,3′-, 2,4′-, 3,3′-, 2,3,3′-, 2,4,4′-, 2,5,3′-, and 3,4,2′-chlorobiphenyl. The bacterial strains used wereCorynebacterium sp. MB1,Alcaligenes strainsA. eutrophus H850 andA. faecalis Pi434, andPseudomonas strains LB400 and H1130,P. testosteroni H430 and H336, andP. cepacia H201. The results indicated that both the relative rates of primary degradation of PCBs and the choice of the ring attacked were dependent on the bacterial strain used. The bacterial strains exhibited considerable differences in their relative reactivity preferences for attack on mono- and dichlorophenyl groups and in the degree to which the attack was affected by the chlorine substitution pattern on the nonreacting ring. For MB1 the reactivity pattern was 3-≥4-≫2-chlorophenyl with no attack on 2,4- or 2,5-chlorophenyl groups. This strain was relatively insensitive to the chlorine substitution pattern on the nonreacting ring. Strains H1130, H430, H201, and Pi434 exhibited the same reactivity preferences as MB1, but for these strains (and for all others tested) the chlorination pattern on the nonreacting ring had a strong effect. For strain H336 the reactivity preference was 4-≥2->2,4-≥3-chlorophenyl, with no evidence of attack on 2,5-chlorophenyl rings. For strains H850 and LB400 the relative reactivity was 2->2,5->3-≫2,4->4-chlorophenyl. On this basis we propose that the eight bacterial strains represent four distinct classes of biphenyl/PCB-dioxygenase activity. The types of products formed were largely strain-independent and were determined primarily by the chlorine substitution pattern on the reacting ring. When the reacting ring was an unsubstituted phenyl or a 2-chlorophenyl group, the products were chlorobenzoic acids in high yields; for a 3-chlorophenyl ring, both chlorobenzoic acids and chloroacetophenones in moderate yields; and for a 4- or 2,4-chlorophenyl group, chlorobenzoic acids in low yields with an apparent accumulation ofmeta ring-fission product. Strains H850 and LB400 were able to degrade the 3-chlorobenzoic acid that they produced from the degradation of 2,3′-chlorobiphenyl. We conclude that despite differences among strains in the specificity of the initial dioxygenase, the specificities of the enzymes responsible for the subsequent degradation to chlorobenzoic acid and/or chloroacetophenone are quite similar for all strains.     

pH homeostasis and bioenergetic work in alkalophiles

A Na+/H+ antiporter catalyses coupled Na+ extrusion and H+ uptake across the membranes of extremely alkalophilic bacilli. This exchange is electrogenic, with H+ translocated inward greater than Na+ extruded. It is energized by the delta chi 2 component of the delta mu H+ that is established during primary proton pumping by the alkalophile respiratory chain complexes. These complexes abound in the membranes of extreme alkalophiles. Combined activity of the respiratory chain, the antiporter, and solute transport systems that are coupled to Na+ re-entry, allow the alkalophiles to maintain a cytoplasmic pH that is several pH units more acidic than optimal external pH values for growth. There is no compelling evidence for a specific and necessary role for any ion other than sodium in pH homeostasis, and although there is very high cytoplasmic buffering capacity in the alkaline range, active mechanisms for pH homeostasis are crucial. Energization of the antiporter as well as the proton translocating F1F0-ATPase that catalyses ATP synthesis in the extreme alkalophiles must accommodate the problem of the low net delta mu H+ and the very low concentrations of protons, per se, in the external medium. This problem is by-passed by other bioenergetic work functions, such as solute uptake or motility, that utilize sodium ions for energy-coupling in the place of protons.     

In vitro, insulin receptor catalyses phosphorylation of clathrin heavy chain and a plasma membrane 180,000 molecular weight protein

Insulin receptor mutation studies that the receptor tyrosine kinase activity is necessary for receptor endocytosis, and several insulin receptor-containing tissues have a plasma membrane-associated protein (M_r 180,000, p180) whose tyrosine phosphorylation is receptor catalysed. Since clathrin heavy chain (M_r 180,000 in dodecyl sulphate gel electrophoresis) is a major component of coated vesicles, the latter functioning in receptor endocytosis, we investigated whether insulin receptors can catalyse clathrin phosphorylation and whether p180 is clathrin. Bovine brain triskelion or coated vesicles and ³²P-ATP were added to prephosphorylated insulin receptor preparations (wheat ferm agglutinin-purified human placenta membrane proteins). Antiphosphotyrosine immunoprecipitated a phosphorylated 180,000 molecular weight protein. Insulin (10⁻⁷M) increased the rate of phosphorylation. Monoclonal anti-clathrin antibody immunoprecipitated the phosphorylated 180,000 molecular weight protein, whereas monoclonal anti-insulin receptor antibodies (-IR1, MA10) immunoprecipitated both insulin receptors and the phosphorylated 180,000 molecular weight protein. In the absence of added clathrin, anticlathrin immunoprecipitated no proteins, and -IR1 imunoprecipitated only the insulin receptor. Density gradient (glycerol 7.5–30%, w/v) centrifugation separated human placenta microsomal membrane proteins into endosomal, plasma membrane, cytoplasmic and coated vesicle fractions. Antiphosphotyrosine immunoprecipitated phosphorylated-microsomal proteins that centrifugated into endosomal and plasma membrane fractions. Addition of glycerol gradient fractions to a prephosphorylated insulin receptor preparation, however, gave a tyrosine-phosphorylated 180,000 molecular weight protein when cytoplasmic and coated vesicle fractions were added. Taken together these results suggest: (1) that, in vitro, human placenta insulin receptors can phosphorylate bovine brain and human placenta clathrin heavy chain; (2) that both assembled and unassembled clathrin can be phosphorylated; and (3) that p180, the plasma membrane-associated insulin receptor substrate, is not clathrin heavy chain.     

Neutral lipid storage disease: a possible functional defect in phospholipid-linked triacylglycerol metabolism

Neutral lipid storage disease (NLSD) (Chanarin-Dorfman Syndrome) is an autosomal recessive disorder of multisystem triacyglycerol (TAG) storage. Previous work has pointed to a defect in intracellular TAG metabolism. In the studies reported here, the lipid metabolism of three lines of NLSD fibroblasts were compared to normal skin fibroblasts. When pulsed with [³H]oleic acid, the earliest observed abnormality in NLSD cell lines was increased incorporation into phosphatidylethanolamine, followed by accumulation of radiolabel in TAG. Activities of several glycerolipid synthetic enzymes were comparable in NLSD and normal fibroblast lines, excluding oversynthesis of glycerolipid. The proportion of plasmalogen and neutral ether lipid synthesized was normal and alkylglycerols did not accumulate, excluding a defect in ether lipid metabolism. Activities of both acid lipase and Mn²⁺-sensitive lipase within the particulate fractions of NLSD and normal fibroblasts were comparable. These studies are most consistent with functional deficiency of a TAG lipase with activity against a pool of TAG that are normally utilized for phospholipid biosynthesis.     

Biochemical and Antibiotic Susceptibility Studies of H2S-Negative Citrobacter

Ninety-four strains of H(2)S-negative Citrobacter were biochemically characterized and their antibiograms were determined. The antibiograms demonstrated not only a difference from Enterobacter cloacae but also a difference within the Citrobacter group between the indole-negative and indole-positive strains. These differences were statistically significant and emphasize the importance of the indole reaction as an aid to speciation of the H(2)S-negative Citrobacter.     

Acute Heroin Fatalities in San Francisco Demographic and Toxicologic Characteristics

The mortality rate due to heroin overdosage in San Francisco has increased dramatically since 1968 and now stands as one of the highest in the United States. While the numbers of heroin fatalities in many eastern United States cities have declined substantially in the past few years, the figures for San Francisco and the other West Coast areas continue to increase. The group of heroin overdose victims from the 1970 through 1973 period is more predominantly Caucasian and younger than from the 1963 through 1965 period. In nearly all of the victims, the presence of morphine (a heroin metabolite) was noted in bile or urine, and in about half the results of blood alcohol tests were positive. Measurement of blood morphine concentrations in the victims showed no significant difference from the concentrations noted in a control group of heroin addicts dying from causes other than overdosage.     

Incidence of yeasts and influence of nystatin on their control in a group of burned children

The incidence of yeasts in the oral cavity, rectum and urine of a population of 60 children hospitalized for treatment of acute second and third degree burns was approximately the same at the time of their admission as would be expected in healthy subjects. After hospitalization, the incidence of yeasts was reduced in the intestinal tract of acute patients who received nystatin orally but increased in the oral cavity. The majority of 418 yeasts were inhibited in vitro by less than 50 units/ml nystatin and only 6 yeasts were resistant to more than 3.1 g/ml amphotericin B. The oral cavity appeared to act as a significant reservoir from which yeasts spread to cause or contribute to the deaths of 2 of 5 patients who died during the study.