Limb anomalies: Developmental and evolutionary aspects

In this review we describe the developmental mechanisms involved in the making of a limb, by focusing on the nature and types of interactions of the molecules that play a part in the regulation of limb patterning and characterizing clinical conditions that are known to result from the abnormal function of these molecules. The latter subject is divided into sections dealing with syndromal and nonsyndromal deficiencies, polydactylies, and brachydactylies. Conditions caused by mutations in homeobox genes and fibroblast growth factors and their receptor genes are listed separately. Since the process of limb development has been conserved for more than 300 millions years, with all the necessary adaptive modifications occurring throughout evolution, we also take into consideration the evolutionary aspects of limb development in terms of genetic repertoire, molecular pathways, and morphogenetic events.     

Prevalences, genotypes, and risk factors for HIV transmission in South America

HIV cross-sectional studies were conducted among high-risk populations in 9 countries of South America. Enzyme-linked immunosorbent assay screening and Western blot confirmatory testing were performed, and env heteroduplex mobility assay genotyping and DNA sequencing were performed on a subset of HIV-positive subjects. HIV prevalences were highest among men who have sex with men (MSM; 2.0%-27.8%) and were found to be associated with multiple partners, noninjection drug use (non-IDU), and sexually transmitted infections (STIs). By comparison, much lower prevalences were noted among female commercial sex workers (FCSWs; 0%-6.3%) and were associated mainly with a prior IDU and STI history. Env subtype B predominated among MSM throughout the region (more than 90% of strains), whereas env subtype F predominated among FCSWs in Argentina and male commercial sex workers in Uruguay (more than 50% of strains). A renewed effort in controlling STIs, especially among MSM groups, could significantly lessen the impact of the HIV epidemic in South America.     

Isolation and characterization of the thermoresistant gluconokinase from Escherichia coli

It is known that two gluconokinases are inducibly expressed during the utilization of gluconate by E. coli. One is thermoresistant (activity stable for 3 h at 30 °C) and the other thermosensitive (losses 75% or more of its activity under the above conditions). The thermoresistant gluconokinase (EC 2.7.1.12) was isolated, purified and characterized for the first time from the E. coli mutant Ca26, a K12 derivative which lacks the thermosensitive activity. The enzyme was purified 43 fold with a recovery of 11%. The M_r of the enzyme was 100 kDa with three equal subunits of approximately 29.5 kDa. The enzyme exhibited Michaelis-Menten kinetics and the K_m values for gluconate and ATP were 0.02 mM and 0.045 mM respectively.     

Pleiotropic effect of sodium arsenite on Escherichia coli

The effects of sodium arsenite at a sub-MIC concentration (25 mg/l) upon different bacterial functions were studied. This compound reduced the killing activity of nalidixic acid, amikacin, and meropenem. It also promoted the loss of F'lac from bacterial hosts and increased the number of recombinants in conjugation and transduction experiments. Transposition of Tn9 was also enhanced by the salt. In addition, sodium arsenite abolished the lethal effect of temperature on thermosusceptible DNA synthesis mutants in a similar manner to that seen in an anaerobic environment. Finally at a low dose, it induced the SOS response, and the related production of recA-dependent enzymes was reduced as the sodium arsenite concentration increased. It has been suggested that arsenite primarily affects the uvrA gene product, influencing the other bacterial functions studied. The energetic depletion caused by this compound appears to play a role in the activity of autolytic enzymes.     

Erratum: Neurofibromatosis type 1 (NF1): Identification of eight unreported mutations in NF1 gene in Italian patients

In the original version of this article, the title was incorrect. Please find the correct title given here. The publisher deeply regrets this error. The original article to which this Erratum refers was published in Human Mutation 22:179–180 Human Mutation(2003) 22(2) 179–180     

Epidemiological and Environmental Investigations of Legionella pneumophila Infection in Cattle and Case Report of Fatal Pneumonia in a Calf

A fatal pneumonia due to Legionella pneumophila was diagnosed in a young calf reared in a dairy herd located in northern Italy. Clinical symptoms consisted of watery diarrhea, hyperthermia, anorexia, and severe dyspnea. The pathological and histological findings were very similar to those observed in human legionellosis. Legionella pneumophila serogroup 1 (SG1) and SG10 were isolated from the calf’s lung, and L. pneumophila SG1 was isolated from the calf’s liver. L. pneumophila SG1 was also demonstrated in the lung tissue by immunofluorescence and immunohistochemical examinations. Nine of 10 L. pneumophila SG1 isolates belonged to the Olda subtype, and 1 belonged to the Camperdown subtype. A very low prevalence of antibodies to Legionella was detected in cows and calves reared in the same herd. Cultures of aqueous sediment of an old electric water heater which supplied hot water for the feeding of the calves yielded L. pneumophila SG1. Four of the colonies tested belonged to the Olda subtype. Ten clinical and four environmental isolates were examined for the presence of plasmids. Nine of them were also examined by pulsed-field gel electrophoresis assay, and the same patterns were found for L. pneumophila SG1 Olda strains isolated from the calf and from the electric heater. This is the first report of a documented case of a naturally occurring Legionella pneumonia in an animal. Cattle probably act as accidental hosts for legionellae, much the same as humans.     

Role of primate basal ganglia and frontal cortex in the internal generation of movements

In order to more comprehensively assess the role of the basal ganglia in the internal generation of movements, we studied the activity of neurons in the head of the caudate and in the rostral putamen in relation to the execution of movements. Monkeys performed self-initiated and stimulus-triggered arm reaching movements in separate blocks of trials. With stimulus-triggered movements, 217 striatal neurons increased their activity after the trigger stimulus (127 in caudate, 90 in putamen). Of these, 68 neurons showed time-locked responses to the trigger stimulus, with a median latency of 60 ms, that were independent of visual or auditory stimulus modalities. Three quarters of responses were conditional on a movement being performed. These responses may participate in neuronal processes through which the reception of a stimulus is translated into the execution of a behavioral reaction. Further, 44 neurons increased their activity before the earliest muscle activity without being clearly time-locked to the stimulus (148-324 ms before movement onset), 55 neurons were activated later before the movement, and 50 neurons were activated after movement onset. With self-initiated movements, 106 striatal neurons showed movement-related activity beginning up to 460 ms before movement onset (52 in caudate, 54 in putamen). Comparisons between the two types of movement were made on 53 neurons with premovement activity beginning more than 500 ms before self-initiated movements. Only one fifth of them also showed movement-related activity with stimulus-triggered movements, including trigger responses. Comparisons among 39 neurons with movement-related activity during self-initiated arm movements showed that about half of them also showed movement-related activity with stimulus-triggered movements. These data demonstrate a considerably segregated population of striatal neurons engaged in the internal generation of movements, whereas processes underlying the execution of movements appear to involve overlapping neuronal populations.     

Lightly crosslinked liquid crystalline epoxy resins: The effect of rigid-rod length and applied stress on the state of order of the cured thermoset

Lightly crosslinked liquid crystalline epoxy resins were synthesized by reacting rigid rod epoxy-terminated molecules with decanedioic acid (SA). The obtained networks exhibited a smectic phase even in the case of 2,6-bis(2,3-epoxypropoxy)naphthalene, whose aspect ratio is very low. Upon application of uniaxial stress, a smectic phase was surprisingly obtained also for the system obtained by reacting p-bis(2,3-epoxypropoxy)-benzene (QH), whose aspect ratio is practically equal to one, and SA. Stretching of the smectic samples above the glass transition temperature determines orientation of polymer chains, yielding considerably high values of the order parameter S. Thermomechanical analysis showed, for one of these systems, that stretching induces a shift of the isotropization temperature to higher values.