Age changes of skull dimensions

At cranial level, external apposition during ageing has been postulated by some authors. In longitudinal studies, a gradual increase of cranial diameters has been shown by cephalometry (Kendrick et al. 1967) or by lateral radiography (Israel 1968, 1970). However, these results are contested at methodological level by other longitudinal studies (Tallgren 1974). It is the aim of this study to analyse, in a cross-sectional sample, the effects of senescence on several cephalic dimensions. A series of skulls of known age and sex has been selected for this purpose.     

Phase separation of the receptor for immunoglobulin E and its subunits in Triton X-114

Above its critical micelle concentration, Triton X-114 in solution forms two phases at room temperature: a lower phase containing supramicellar aggregates and an upper phase largely depleted of detergent. This property of the detergent is potentially useful for separating under mild conditions proteins that bind detergent from those that do not (Bordier, C. (1981) J. Biol. Chem. 256, 1604-1607). We studied the distribution of the receptor for immunoglobulin E (IgE) and its subunits in the two phases. IgE and IgE complexed either with intact receptors or with the alpha chains of the receptor alone are principally partitioned into the upper phase, whereas the unliganded receptor as well as the isolated alpha, and especially the beta and gamma chains of the receptor, preferentially partition into the lower detergent phase. Chromatography of IgE and of the subunits of the receptor on a hydrophobic support showed that the beta and gamma chains have a considerably greater hydrophobic surface than the alpha chains or IgE. These results indicate that the distribution of a protein in the two phases of phase-separated Triton X-114 is not an all-or-none effect based upon whether it binds detergent or not. Rather, it reflects the overall balance between the hydrophobic and hydrophilic properties of the protein's surface.     

Reduced pyridine nucleotides in Pseudomonas carboxydovorans are formed by reverse electron transfer linked to proton motive force

In cell suspensions of Pseudomonas carboxydovorans pulsed with lithotrophic substrates (CO or H₂) in the presence of oxygen, formation of reduced pyridine nucleotides and of ATP could be demonstrated using the bioluminescent assay. Experiments employing base-acid transition, an uncoupler and inhibitors of ATPase or electron transport enabled us to propose a model for the formation of NAD(P)H in chemolithotrophically growing P. carboxydovorans.The protonophor FCCP (carbonly-p-trifluormethoxyphenylhydrazon) inhibited both, formation of NAD(P)H and of ATP. In the absence of oxygen, a chemical potential imposed by base-acid transition resulted in the formation of NAD(P)H and ATP when electrogenic substrates (CO or H₂) were present. This suggests proton motive force-driven NAD(P)H formation. The proton motive force was generated by oxidation of substrate, and not by ATP hydrolysis, as obvious from NAD(P)H formation during inhibition of ATP synthesis by oligomycin and N,N-dicyclohexylcarbodiimide.That the CO-born electrons are transferred via the ubiquinone 10-cytochrome b region to NADH dehydrogenase functioning in the reverse direction, was indicated by inhibition of NAD(P)H formation by HQNO (2-n-heptyl-4-hydroxyquinoline-N-oxide) and rotenone, and by resistance to antimycin A.We conclude that in P. carboxydovorans, growing with CO or H₂, electrons and a proton motive force, generated by respiration, are required to drive an reverse electron transfer for the formation of reduced pyridine nucleotides.Abbreviations CODH carbon monoxide dehydrogenase - DCCD N,N-dicyclohexylcarbodiimide - FCCP carbonyl-p-trifluormethoxyphenylhydrazon - HQNO 2-n-heptyl-4-hydroxyquinoline-N-oxide - pmf proton motive force     

Effects of phosphate and ADP on shortening velocity during maximal and submaximal calcium activation of the thin filament in skeletal muscle fibers.

The effects of added phosphate and MgADP on unloaded shortening velocity during maximal and submaximal Ca2+ activation of the thin filament were examined in skinned single skeletal fibers from rabbit psoas muscle. During maximal Ca2+ activation, added phosphate (10-30 mM) had no effect on unloaded shortening velocity as determined by the slack-test technique. In fibers activated at submaximal concentrations of Ca2+ in the absence of added phosphate, plots of slack length versus duration of unloaded shortening were biphasic, consisting of an initial high velocity phase of shortening and a subsequent low velocity phase of shortening. Interestingly, in the presence of added phosphate, biphasic slack-test plots were no longer apparent. This result was obtained in control fibers over a range of submaximal Ca2+ concentrations and in maximally Ca2+ activated fibers, which were first treated to partially extract troponin C. Thus, under conditions that favor the appearance of biphasic shortening (i.e., low [Ca2+], troponin C extraction), added phosphate eliminated the low velocity component. In contrast, in fibers activated in the presence of 5 mM added MgADP, biphasic slack-test plots were apparent even during maximal Ca2+ activation. The basis of biphasic shortening is not known but it may be due to the formation of axially compressed cross-bridges that become strained to bear a tension that opposes the relative sliding of the myofilaments. The present findings could be explained if added phosphate and MgADP bind to cross-bridges in a strain-dependent manner. In this case, the results suggest that phosphate inhibits the formation of cross-bridges that bear a compressive strain. Added MgADP, on the other hand, may be expected to detain cross-bridges in strong binding states, thus promoting an increase in the population of cross-bridges bearing a compressive strain. Alterations in the population of strained cross-bridges by added phosphate and MgADP would alter the internal load within the fiber and thus affect the speed of fiber shortening.     

Structural analysis and molybdenum-dependent expression of the pAO1-encoded nicotine dehydrogenase genes of Arthrobacter nicotinovorans

The genes of nicotine dehydrogenase (NDH) were identified, cloned and sequenced from the catabolic plasmid pA01 of Arthrobacter nicotinovorans. In immediate proximity to this gene cluster is the beginning of the 6-hydroxy-L-niotine oxidase (6-HLNO) gene. NDH is composed of three subunits (A, B and C) of M_r 30011, 14924 and 87677. It belongs to a family of bacterial hydroxylases with a similar subunit structure; they have molybdopterin dinucleotide, FAD and Fe-S clusters as cofactors. Here the first complete primary structure of a bacterial hydroxylase is provided. Sequence alignments of each of the NDH subunits show similarities to the sequences of eukaryotic xanthine dehydrogenase (XDH) but not to other known molybdenum-containing bacterial enzymes. Based on alignment with XDH it is inferred that the smallest subunit (NDHB) carries an iron-sulphur cluster, that the middle-sized subunit (NDHA) binds FAD, and that the largest NDH subunit (NDHC) corresponds to the molybdopterin-binding domain of XDH. Expression of both the ndh and the 6-hlno genes required the presence of nicotine and molybdenum in the culture medium. Tungsten inhibited enzyme activity but not the synthesis of the enzyme protein. The enzyme was found in A. nicotinovorans cells in a soluble form and in a membrane-associated form. In the presence of tungsten the fraction of membrane-associated NDH increased.     

Dynamics of the immune system response in cerebrospinal fluid and blood of SIVmac-infected rhesus monkeys

Paired sera and CSF samples were collected from SIV_mac-infected macaques. Animals infected with SIV_mac251 maintained low gag and high env-specific antibody levels in plasma. Increasing env-specific antibody titers in CSF were associated in one animal with strong intrathecal synthesis. SIV_mac239-infected monkeys revealed high antibody titers of gag and env-specificity, in one animal accompanied by weak intrathecal synthesis of virus-specific antibodies. In all animals, the CD4/CD8 ratio in CSF decreased faster compared to blood.     

Transplantation in miniature swine. XII. N-terminal sequences of class I histocompatibility antigens (SLA) and beta 2-microglobulin

Purified class I histocompatibility antigens (SLA) from three haplotypes were prepared by papain treatment of lymphoid cell membranes obtained from spleens and lymph nodes of miniature swine homozygous at their major histocompatibility complex. Antigens were purified by ion-exchange chromatography followed by gel filtration. Purity was analyzed by SDS-PAGE, and antigenic specificity by inhibition of complement-dependent, alloantiserum-mediated cytotoxicity. The SLA antigens were reduced and alkylated, and the component heavy and light chains were isolated by gel filtration under dissociating conditions. N-terminal amino acid sequences were obtained for SLAaa, SLAcc, and SLAdd heavy chains, as well as for the light chain, beta 2-microglobulin. The swine antigens showed high levels of homology with class I antigens from other animal species. Heterogeneity was observed among the swine haplotypes, and several of the positions at which substitutions were found are apparently invariant in other animal species. In contrast, only minimal sequence heterogeneity was detected within haplotypes, the basis of which may be of relevance to understanding the evolutionary development of these molecules.     

Role of unstirred layer in intestinal absorption of phenylalanine in vivo

The appearance rate of l- and d-phenylalanine in the venous blood of rat jejunal loops in vivo is increased up to 60% if the intraluminal solution is mixed more efficiently by the simultaneous perfusion of air. The effect decreases as the luminal concentration is increased to 100 mmol/1. Thus, the apparent Michaelis constants are by 50% lower in the case of the reduced unstirred layer (26 to 17 for l- and 9 to 6 mmol/1 for d-phenylalanine).The enhancement of the absorption and the reduction of the Michaelis constants can be attributed to the reduction of the effective unstirred layer thickness by about 400–500 μm.     

Primary in vitro antibody response of rabbit lymphoid cells and T-B cell collaboration in the absence of detectable mitogens

To investigate whether the antibody response and T-B-cell collaboration in vitro can be obtained in the absence of mitogens, a method of obtaining an in vitro primary anti-sheep red blood cell antibody response by rabbit spleen and lymph node cells was developed. We used Marbrook culture vessels and a specially prepared medium containing 10% autologous serum and maintained at pH 7.4–7.6. The system was shown to be devoid of any polyclonal mitogens as assessed by [³H]thymidine incorporation and by direct examination for blast cells in stained smears. The primary response increased continuously over the 5-day cultivation period and only IgM but not IgG plaque-forming cells (PFC) were detected. In over 20 experiments, the response ranged from 357 ± 17 to 4425 ± 110 PFC/10⁷ cultured cells with a median stimulation index of 52. The spleen cells required less antigen than the lymph node cells and 2-mercaptoethanol inhibited the response of the spleen cells but not that of the lymph node cells. Lymphocytes were separated into highly pure T- and B-cell populations by negative selection using antibody-coated human erythrocytes to rosette either T or B cells and Ficoll-Hypaque centrifugation to remove rosetted cells. Upon cultivation, B cells alone gave a low IgM response, whereas B cells reconstituted with T cells gave a response similar to that obtained with unseparated lymphoid cells. We concluded that: (a) optimal conditions for obtaining primary in vitro antibody responses using rabbit spleen and lymph node cells were established, (b) T-B-cell collaboration was demonstrated in the rabbit primary antibody response to sheep erythrocytes, and (c) the primary antibody response in vitro and T-B-cell collaboration may occur in the absence of detectable polyclonal mitogens.