SUMMARY Adipose tissue (AT) of obese mice and humans accumulates immune cells, which secrete cytokines that can promote insulin resistance. AT macrophages (ATMs) are thought to originate from bone marrow-derived monocytes, which infiltrate the tissue from the circulation. Here we show that a major fraction of macrophages unexpectedly undergo cell division locally within AT, as detected by Ki67 expression and 5-ethynyl-2′-deoxyuridine incorporation. Macrophages within the visceral AT (VAT), but not those in other tissues, including liver and spleen, displayed increased proliferation in obesity. Importantly, depletion of blood monocytes had no impact on ATM content, while their proliferation in situ continued. Treatment with monocyte chemotactic protein 1 (MCP-1) induced macrophage cell division in AT explants, while MCP-1 deficiency in vivo decreased ATM proliferation. These results reveal that proliferation in situ driven by MCP-1 is an important process by which macrophages accumulate in the VAT in obesity, in addition to blood monocyte recruitment.

A number of studies indicate that matrix metalloproteinase might be involved in photoaging, but little is known about their direct contribution to ultraviolet-induced histologic and morphologic changes in the skin in vivo. This study reports the relationship between changes of matrix metalloproteinase activities and ultraviolet B-induced skin changes in hairless mouse. The role of matrix metalloproteinase in the skin changes was studied by topical application of a specific matrix metalloproteinase inhibitor. The backs of mice were exposed to ultraviolet B three times a week for 10 wk. Histologic studies showed that the basement membrane structure was damaged, with epidermal hyperplasia, in the first 2 wk of ultraviolet B irradiation, followed by the appearance of wrinkles, which gradually extended in the latter half of the ultraviolet B irradiation period. We observed enhancement of type IV collagen degradation activity, but not collagenase or matrix metalloproteinase-3 activity, in extracts of ultraviolet B-irradiated, wrinkle-bearing skin. Gelatin zymographic analysis revealed that gelatinases, matrix metalloproteinase-9 and matrix metalloproteinase-2, were significantly increased in the extract. In situ zymographic study clarified that the activity was specifically localized in whole epidermis of ultraviolet B-irradiated, wrinkled skin in comparison with normal skin. The activity was induced around the basal layer of the epidermis by a single ultraviolet exposure of at least one minimal erythema dose. Furthermore, topical application of a specific matrix metalloproteinase inhibitor, CGS27023A, inhibited ultraviolet B-induced gelatinase activity in the epidermis, and its repeated application prevented ultraviolet B-induced damage to the basement membrane, as well as epidermal hyperplasia and dermal collagen degradation. Ultraviolet B-induced wrinkles were also prevented by administration of the inhibitor. These results, taken together, suggest that ultraviolet B-induced enhancement of gelatinase activity in the skin contributes to wrinkle formation through the destruction of basement membrane structure and dermal collagen in chronically ultraviolet B-exposed hairless mouse, and thus topical application of matrix metalloproteinase inhibitors may be an effective way to prevent ultraviolet B-induced wrinkle formation.

Infants rapidly learn the sound categories of their native language, even though they do not receive explicit or focused training. Recent research suggests that this learning is due to infants' sensitivity to the distribution of speech sounds and that infantdirected speech contains the distributional information needed to form native-language vowel categories. An algorithm, based on Expectation-Maximization, is presented here for learning the categories from a sequence of vowel tokens without (i) receiving any category information with each vowel token, (ii) knowing in advance the number of categories to learn, or (iii) having access to the entire data ensemble. When exposed to vowel tokens drawn from either English or Japanese infant-directed speech, the algorithm successfully discovered the language-specific vowel categories (/, i, ε, e/ for English, /i, i , e, e / for Japanese). A nonparametric version of the algorithm, closely related to neural network models based on topographic representation and competitive Hebbian learning, also was able to discover the vowel categories, albeit somewhat less reliably. These results reinforce the proposal that native-language speech categories are acquired through distributional learning and that such learning may be instantiated in a biologically plausible manner.language acquisition ͉ speech perception ͉ expectation maximization ͉ online learning A central goal of language acquisition research is to characterize how the ability to perceive one's native language is acquired during childhood. Infants are initially responsive to a wide variety of native and nonnative speech sound contrasts.

Plectin is a widely expressed high molecular weight protein that is involved in cytoskeleton-membrane attachment in epithelial cells, muscle, and other tissues. The human autosomal recessive disorder epidermolysis bullosa with muscular dystrophy (MD-EBS) shows epidermal blister formation at the level of the hemidesmosome and is associated with a myopathy of unknown etiology. Here, plectin was found to be absent in skin and cultured keratinocytes from an MD-EBS patient by immunofluorescence and immunoprecipitation, suggesting that plectin is a candidate gene/protein system for MD-EBS mutation. The 14800-bp human plectin cDNA was cloned and sequenced. The predicted 518-kD polypeptide has homology to the actin-binding domain of the dystrophin family at the amino terminus, a central rod domain, and homology to the intermediate filament-associated protein desmoplakin at the carboxyl terminus. The corresponding human gene (PLECl), consisting of 33 exons spanning >26 kb of genomic DNA was cloned, sequenced, and mapped to chromosomal band 8q24. Homozygosity by descent was observed in the consanguineous MD-EBS family with intragenic plectin polymorphisms. Direct sequencing of PCR-amplified plectin cDNA from the patient's keratinocytes revealed a homozygous 8-bp deletion in exon 32 causing a frameshift and a premature termination codon 42 bp downstream. The clinically unaffected parents of the proband were found to be heterozygous carriers of the mutation. These results establish the molecular basis of MD-EBS in this family and clearly demonstrate the important structural role for plectin in cytoskeleton-membrane adherence in both skin and muscle.

Epithelial cells maintained in culture medium containing low calcium proteolytically process laminin 5 (␣3␤3␥2) within the ␣3 and ␥2 chains (1). Experiments were designed to identify the enzyme(s) responsible for the laminin 5 processing and the sites of proteolytic cleavage. To characterize the nature of laminin 5 processing, we determined the N-terminal amino acid sequences of the proteolytic fragments produced by the processing events. The results indicate that the first ␣3 chain cleavage (200-l65 kDa ␣3) occurs within subdomain G4 of the G domain. The second cleavage (l65-l45 kDa ␣3) occurs within the lIla domain, 11 residues Nterminal to the start of domain II. The ␥ chain is cleaved within the second epidermal growth factor-like repeat of domain Ill. The sequence cleaved within the ␥2 chain matches the consensus sequence for the cleavage of type I, II, and III procollagens by bone morphogenetic protein-1 (BMP-1), also known as type I procollagen C-proteinase (2). Recombinant BMP-1 cleaves ␥2 in vitro, both within intact laminin 5 and at the predicted site of a recombinant ␥2 short arm. ␣3 is also cleaved by BMP-1 in vitro, but the cleavage site is yet to be determined. These results show the laminin ␣3 and ␥2 chains to be substrates for BMP-1 in vitro. We speculate that ␥2 cleavage is required for formation of the laminin 5-6 complex and that this complex is directly involved in assembly of the interhemidesmosomal basement membrane. This further suggests that BMP-1 activity facilitates basement membrane assembly, but not hemidesmosome assembly, in the laminin 5-rich dermalepidermal junction basement membrane in vivo.The occurrence of physiological, extracellular proteolytic processing of collagens is well documented, as is the important role that it plays in controlling the fibrillogenesis of banded collagen fibers (3). An enzyme responsible for removal of the C-terminal procollagen propeptides of the major fibrillar collagen types I-III has been identified as BMP-1 (2).1 BMP-1 was first identified in osteogenetic fractions of mammalian bone (4 -7) but was subsequently found to show substantial homology to proteins involved in morphogenetic patterning, such as the products of Drosophila genes tolloid (tld) and tlr-1 (12, 43) and of sea urchin gene products BP10 and SpAN (8, 9). Each contains an N-terminal astacin-like zinc-binding metalloendopeptidase domain (10) followed by varying numbers of epidermal growth factor-like (EGF-like) motifs and internal repeats termed CUB domains thought to be responsible for protein-protein interactions (44).There is abundant genetic and molecular evidence that Drosophila tld mediates dorsal-ventral patterning in the fly embryo (11-13), with null phenotypes of tld showing partial transformation of the dorsal ectoderm into ventral ectoderm (14). Genetic and developmental expression studies have also indicated that the tld gene product TLD participates within the same developmental pathway as the product of the decapentaplegic gene, DPP, the fly cognate of mammalian BMP-2 an...