CTLA-4-B7 interaction is sufficient to costimulate T cell clonal expansion

T cell costimulation, particularly by the B7 family members B7-1 and B7-2, plays a critical role in regulating T cell-mediated immunity. Two molecules on T cells, CD28 and CTLA-4, are known to bind to B7. It has been suggested that CD28-B7 interaction promotes T cell response, whereas B7-CTLA-4 interaction downregulates T cell clonal expansion. However, the proposed responses of individual receptors to B7 have not been verified directly. Here, we report that B7-1 promotes clonal expansion of CD28-deficient T cells, and that the CD28-independent costimulatory activity is mediated by CTLA-4, as it is completely blocked by intact and Fab of anti-CTLA-4 mAb. In addition, a mutant B7-1 molecule, B7W88 >A, which has lost binding to CD28 but retained significant CTLA-4 binding activity, promotes T cell clonal expansion. Furthermore, while presence of CD28 enhances T cell response to B7-1, such response is also completely blocked by anti-CTLA-4 mAb. Taken together, our results demonstrate that B7-CTLA-4 interaction promotes T cell clonal expansion, and that optimal T cell response to B7 is achieved when both CD28 and CTLA-4 interact with B7. These results establish an important function of CTLA-4 in promoting T cell activation, and suggest an alternative interpretation of the function of CTLA-4 in T cell activation.

Electrophysiological effects of felodipine on guinea pig papillary muscles

AIM

To determine whether felodipine (Fel) has Ca2+ channel blocking effect in mammalian myocardium in comparison with those of nifedipine (Nif) and verapamil (Ver).

METHODS

The action potentials (AP), the slow AP and the inward slow Ca2+ currents of guinea pig papillary muscles were studied using intracellular microelectrodes and voltage-clamp techniques.

RESULTS

Fel 1, 3, and 10 mumol.L-1 concentration-dependently shortened APD30, APD50, and APD90 of the AP, while Vmax and APA were not affected. The effect of Fel was not reversible on washout. At 0.1, 1, 3, and 10 mumol.L-1, Fel depressed Vmax, APA, APD30, APD50, and APD90 of the slow AP in a dose-dependent manner. The inward slow Ca2+ currents were reduced by Fel 3 mumol.L-1. APD30, APD50, and APD90 of the first AP after rest were still shortened by Fel. When the stimulation frequency was elevated, the effect of Fel on the AP and slow AP decreased. The effect of Fel 3 mumol.L-1 on the slow AP was abolished in preparation pretreated with trifluoperazine. The threshold concentrations of Nif and Ver for the inhibition of APD50 of the slow AP (P < 0.05) were 0.1 and 1 mumol.L-1, respectively. The effect of Ver 3 mumol.L-1 on the fast AP was not reversible on washout, but that of Nif 3 mumol.L-1 was. When the stimulation frequency was elevated from 0.5 to 2 Hz, the effect of Nif 3 mumol.L-1 on the fast AP was reduced, but that of Ver 3 mumol.L-1 was increased.

CONCLUSION

Fel inhibited mainly the resting state of the cardiac Ca2+ channel. The potency of Fel was about the same as that of Nif and about 10 times more potent than that of Ver.

[Comparison of human papilloma virus-DNA in condyloma acuminatum, cervical cancer and the female genital tract]

OBJECTIVE

To examine human papilloma virus (HPV) infection rate and types in several lesions of the genital tract and to observe the relation between HPV and host cells for differential handling of cases and for early diagnosis.

METHODS

Tissues from 89 cases of condyloma acuminata, 76 cases of cervical cancer and swabs from 198 cases of normal vaginal were analysed by polymerase chain reaction for HPV infective rate. Main HPV types were compared and Southern blot was used to compare the physical pattern of HPV in condyloma acuminata and cervical cancer.

RESULTS

The positive rates of HPV-DNA in condyloma acuminata and cervical cancer were respectively 98.9% and 94.7%. The primary types of the former were HPV 6, 11 and of the latter mainly 16 and 18. The latent infective rates in normal vagina was 37.4%, among which, HPV 6, 11, 16, 18 consisted of only 21.6%. HPV11-DNA in condyloma acuminata existed mainly in episodic form. Most of HPV16-DNA in cervical cancer integrates into the host cells with variation.

CONCLUSIONS

The different types of HPV are related to particular morphology and characteristics of lesions. The relation of HPV-DNA to host cell and can offer some reference for the determination of the character of the lesion, and it may be award of malignant transformation.

[The changing trend of cesarean section rates in 35 years]

OBJECTIVE

To investigate the changing trend of cesarean section rates in 35 years.

METHODS

Samples taken from 4 months (March, June, September, December) of a year every 5 years in 35 years (from 1959 to 1994) were analysed and a total of 1 667 cases were collected.

RESULTS

Cesarean section rates increased since 1975 and particularly from 1980 to 1994. The causes of this trend may be related to following reasons. (1) Improvement of skill and safety of operation. (2) Change of indications of cesarean section. (3) Social factors.

CONCLUSION

The decrease of perinatal mortality rate was not relevant only to the cesarean section rate, but dependent more on good perinatal care.

Ginseng extract scavenges hydroxyl radical and protects unsaturated fatty acids from decomposition caused by iron-mediated lipid peroxidation

This study was conducted to investigate whether or not the antioxidation effect of ginseng extract directly inhibits decomposition of unsaturated fatty acid caused by iron and hydrogen peroxide-induced lipid peroxidation, and whether this effect involves a hydroxyl radical-scavenging mechanism. Thiobarbituric acid-reactive substances (TBARS), gas chromatography, and electron spin resonance (ESR) spectrometer were used to measure lipid peroxidation, unsaturated fatty acid, and hydroxyl radical. The results showed TBARS formed and the loss of arachidonic acid during lipid peroxidation, and that hydroxyl radical formed by the Fenton reaction were completely inhibited by ginseng extract. This antioxidant effect of ginseng may be responsible for its wide pharmacological actions in clinical practice by a free radical reaction-inhibition mechanism.

Relationship between ornithine decarboxylase and cytoskeletal organization in cultured human keratinocytes: cellular responses to phorbol esters, cytochalasins, and alpha-difluoromethylornithine

Changes in cell shape occur during the cell cycle and influence cell proliferation and differentiation. In order to study how altered cell proliferation and cell shape are interrelated, we have studied ornithine decarboxylase (ODC) regulation in cultured normal human epidermal keratinocytes (NHEK). Cytoskeletal disruptors have been reported to modulate regulation of ODC; the products of ODC, the polyamines, influence actin polymerization rates in vitro, and polyamine auxotrophs have profoundly disrupted cytoskeletons. Therefore, altered ODC levels could be involved in signaling changes in cell shape and an intact cytoskeleton could transduce signals to regulate ODC levels. We had previously observed that the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), which profoundly alters cell shape, markedly suppresses ODC biosynthesis in NHEK solely at posttranscriptional/protein synthesis levels. TPA treatment caused NHEK to rapidly assume a rounded morphology that was accompanied by a change in actin organization, as determined by rhodamine-phalloidin labeling. Immunolocalization of ODC showed a perinuclear/nuclear distribution in untreated NHEK and a more diffuse pattern after TPA treatment that was apparent within 15-30 min. Changes in ODC enzyme activity are not significant until 60 min after TPA treatment. NHEK treated with cytochalasin B or D to inhibit actin polymerization exhibited a diffuse ODC localization that could be reversed by removal of the cytochalasin; inhibition of ODC by alpha-difluoromethylornithine caused a diffuse ODC localization. All treatments resulted in cytoskeletal remodeling. These data are the first evidence for a distinct subcellular localization for ODC and suggest that changes in ODC localization may be an initial step in regulation of ODC activity. Furthermore, changes in ODC activity cause an altered cytoskeleton, suggesting one means by which growth regulatory signals can be transduced to the cytoskeleton from various signaling pathways.

Effects of toquipidine on ionic channels of cultured embryonic Xenopus laevis myoblasts and neurons

AIM

To study the effects of toquipidine (1-p-methyl-phenyl-2-(alpha-piperidinoacetyl)-1, 2, 3, 4-tetrahydroisoquinoline hydrochloride, Toq), a new anti-arrhythmic agent first synthesized in China, on ionic channels.

METHODS

Ionic channel currents were recorded by whole-cell patch clamp technique in cultured embryonic Xenopus laevis myoblasts and neurons.

RESULTS

Toq (0.1, 1, 10, and 100 mumol L-1) caused a concentration-dependent inhibition of the Na+ currents with IC50 7.2 mumol L-1 (5.3-9.8 mumol L-1). Toq (10 mumol L-1) also suppressed the high-voltage-activated Ca2+ currents in neurons. But the steady-state outward K+ currents in myoblasts were activated by Toq (10 mumol L-1).

CONCLUSION

Toq blocked the Na+ and Ca2+ channels and opened the steady-state outward K+ channels.

Photoirritation: a new photobiologic phenomenon induced by long wavelength UVA radiation in hairless mice treated with broad-spectrum sunscreens

While assessing the protective effect of broad-spectrum sunscreens against chronic UVA radiation, we observed a paradoxical worsening of skin damage with one product. To further examine this finding, five proprietory broad-spectrum sunscreens were applied to albino hairless mice irradiated thrice weekly for 32 weeks with a UVASUN lamp (> 340 nm). Appropriate age-matched controls were included. After approximately 12 weeks, two sunscreens induced a marked dermatitis. Biopsies showed damage greatly exceeding that found in UVA-irradiated, unprotected controls. Histologically, elastic fibers were hyperplastic, coalescing into elastotic clumps. Glycosaminoglycans also increased. Collagen damage was notable since UVA alone does not induce a histologic change. Electron microscopy confirmed these findings. Two other sunscreens provided nearly complete protection. Against chronic UVB radiation, the two UVA photoirritating sunscreens provided substantial protection. Since the UVA sunfilter, oxybenzone, was the same in all sunscreens, we postulate that an irritating component of the vehicle was responsible for the UVA-induced photoirritation. The fifth sunscreen produced severe damage with UVB and UVA.

Secondary structures of Escherichia coli antisense micF RNA, the 5'-end of the target ompF mRNA, and the RNA/RNA duplex

The Escherichia coli micF RNA is a prototype for a class of antisense RNAs encoded by genes at different loci from those that code for their target RNAs. RNAs in this class exhibit only partial complementarity to their targets. micF RNA binds to and regulates the stability of ompF mRNA in response to a variety of environmental stimuli. The secondary structures of micF RNA, ompF-213 mRNA (a segment containing the 213 nucleotides at the 5'-terminus of the target message), and the micF RNA/ompF-213 mRNA duplex were analyzed in vitro by partial digestion with structure-specific ribonucleases and chemical modification. Both micF RNA and ompF mRNA have single-stranded 5'-ends and contain stable stem-loop structures. Strong phylogenetic support for the proposed secondary structure for E. coli micF RNA is provided by a comparison of structural models derived from micF sequences from related bacteria. The micF RNA/ompF-213 mRNA duplex interaction appears to involve only a short segment of micF RNA. Unfolding of only one stem-loop of micF RNA and a minor stem-loop of ompF-213 mRNA appears to be necessary to form the duplex. The probing data suggest that the Shine-Dalgarno sequence and AUG start codon of ompF mRNA, found in single-stranded regions in the free message, are base-paired to micF RNA in the RNA/RNA duplex.

[Influence of different processing methods of four alkaloid contents in Strychnos nux-vomica L]

The contents of four alkaloids in different processed products of Strychnos nux-vomica hamely, vomicine, icajine, strychnine N-oxide and brucine N-oxide, were determined by TLC-densitometry. The relationship between alkaloid contents and processing methods was studied.

[Analgesic effect and toxicity of 3,15-diacetylbenzoylaconine and comparison with its analogues]

3, 15-Diacetylbenzoylaconine (Dia) is a new aconite alkaloid derivative. The analgesic ED50 (95% confidence limit) of sc Dia measured with the HAc-induced writhing method, hot-plate method and electric stimulation method in mice were 2.76 (2.34-3.26), 3.50 (2.69-4.54), and 4.20 (3.72-4.73) mg.kg-1, respectively. With the hot-plate method and tail flick method in rats, the analgesic ED50 of ip Dia were 2.75 (2.28-3.31) and 5.24 (4.35-6.31) mg.kg-1, respectively. The LD50 of sc Dia in mice and ip Dia in rats were 21.68 (17.25-27.25) and 10.96 (8.24-14.56) mg.kg-1, respectively. The magnitude of the analgesic therapeutic indices of Dia, 3-acetylaconitine (Ace) and aconitine (Aco) in all the above-mentioned algo-model were in the order of Dia > Ace > Aco. When they were injected iv at 0.1 ml.min-1 in rats, the doses of Dia, Ace, and Aco producing arrythmia were 3.3, 0.8, and 0.5 times as large as those producing analgesia while those of Dia, Ace, and Aco inducing respiratory inhibition were 3.9, 0.5 and 0.3 times, respectively. The magnitudes of the oil/water distribution coefficients with two method and the quotient ED50 icv/ED50 sc of Dia and Ace were > Aco.

Muscarinic stimulation of arachidonic acid release and prostaglandin synthesis in bovine ciliary muscle: prostaglandins induce cyclic AMP formation and muscle relaxation

In the present study it is demonstrated that in bovine ciliary muscle, muscarinic stimulation results in: (a) release of 14C-arachidonic acid (14C-AA) and 14C-labeled prostaglandins (PGs) from muscle prelabeled with 14C-AA; (b) release of endogenous PGs, measured by means of radioimmunoassay; (c) enhanced IP3 production and (d) muscle contraction. In addition, PGs, such as PGE2 and PGD2, increased cAMP formation and induced muscle relaxation. The studies on the kinetics of 14C-AA metabolism revealed that incorporation of 14C-AA into glycerolipids and its conversion into PGs by the ciliary muscle were rapid and time-dependent. The amounts of 14C-radioactivity recovered in the major PGs decreased in the following order: PGD2 > PGE2 < PGF2 alpha > 6-keto-PGF1 alpha. The rate of endogenous PGF2 alpha synthesis by iris-ciliary body tissues from different mammalian species was found to be in the following order: ciliary muscle < ciliary processes < sphincter muscle. The EC50s for muscarinic-stimulated release of 14C-AA, 14C-labeled PGs, and endogenous PGF2 alpha and PGE2, and for IP3 production and contraction of the ciliary muscle indicate that CCh is 2-16 times as potent as pilocarpine in eliciting these responses, with the greatest difference being for contraction. The maximal increase in ciliary muscle tension due to CCh was 48% greater than that evoked by pilocarpine. All PGs tested, including PGE2, 17-phenyl trinor PGE2, 11-deoxy PGE1, PGF2 alpha and PGD2 had no effect on IP3 production and contraction in the ciliary muscle. However, PGE2 and PGD2 stimulated cAMP formation and inhibited CCh-induced IP3 production in a dose-dependent manner. In addition, PGE2 and PGD2 induced relaxation in ciliary muscle precontracted by CCh. In presence of indomethacin (1 microM), the CCh-induced contraction was greater than that observed in absence of the cyclo-oxygenase inhibitor. It is suggested that in the ciliary muscle certain PGs, such as PGE2 and PGD2, may function to modulate, via cAMP, the responses to muscarinic stimulation in this tissue.

[Sites of analgesic action of 3,15-diacetylbenzoylaconine]

In the rat hot plate test, vocalization induced by electric stimulation, tail flick test, and the mouse acetic acid writhing test, 3, 15-diacetylbenzoylaconine (DABA) ip exhibited a dose-dependent analgesic activity. Intrathecally (ith) administered DABA (527, 1186 micrograms.kg-1) had no analgesic action. Microinjection of DABA 35-75 micrograms.kg-1 or 20 micrograms into the cerebral ventricle (icv) or the periaqueductal gray (PAG) exerted a remarkable analgesic activity, which was abolished after bilateral lesions of locus coeruleus (LC). Microinjection of DABA (20 micrograms) into LC failed to produce apparent analgesic action. These results suggested that the sites of analgesia of DABA were mainly at the central supraspinal structures, and PAG was one of the primary sites, while LC was one of the intermediate links.

SPK1 is an essential S-phase-specific gene of Saccharomyces cerevisiae that encodes a nuclear serine/threonine/tyrosine kinase

SPK1 was originally discovered in an immunoscreen for tyrosine-protein kinases in Saccharomyces cerevisiae. We have used biochemical and genetic techniques to investigate the function of this gene and its encoded protein. Hybridization of an SPK1 probe to an ordered genomic library showed that SPK1 is adjacent to PEP4 (chromosome XVI L). Sporulation of spk1/+ heterozygotes gave rise to spk1 spores that grew into microcolonies but could not be further propagated. These colonies were greatly enriched for budded cells, especially those with large buds. Similarly, eviction of CEN plasmids bearing SPK1 from cells with a chromosomal SPK1 disruption yielded viable cells with only low frequency. Spk1 protein was identified by immunoprecipitation and immunoblotting. It was associated with protein-Ser, Thr, and Tyr kinase activity in immune complex kinase assays. Spk1 was localized to the nucleus by immunofluorescence. The nucleotide sequence of the SPK1 5' noncoding region revealed that SPK1 contains two MluI cell cycle box elements. These elements confer S-phase-specific transcription to many genes involved in DNA synthesis. Northern (RNA) blotting of synchronized cells verified that the SPK1 transcript is coregulated with other MluI box-regulated genes. The SPK1 upstream region also includes a domain highly homologous to sequences involved in induction of RAD2 and other excision repair genes by agents that induce DNA damage. spk1 strains were hypersensitive to UV irradiation. Taken together, these findings indicate that SPK1 is a dual-specificity (Ser/Thr and Tyr) protein kinase that is essential for viability. The cell cycle-dependent transcription, presence of DNA damage-related sequences, requirement for UV resistance, and nuclear localization of Spk1 all link this gene to a crucial S-phase-specific role, probably as a positive regulator of DNA synthesis.

Topical all-trans retinoic acid rapidly corrects the follicular abnormalities of the rhino mouse. An ultrastructural study

Topical all-trans retinoic acid (RA) has been shown to transform the horn-filled utriculi of the rhino mouse into normal follicles. We studied the early events by light and electron microscopy. Reduction in diameters of the utriculi was quantified by image analysis of whole mounts. Topical RA at 0.05% in ethanol/propylene glycol was applied daily and biopsies were taken after 1, 2, 3 and 6 days of treatment. By electron microscopy, after 3 days of RA treatment there was a great increase in the size and density of laminated membrane coating granules (MCGs) which had fused to the apical membranes of the upper granular cells. Thereafter, corneocytes within the lumina of the utriculi showed fewer desmosomes and a loss of intercellular material, accompanied by detachment from each other. Conversion to normal follicles was complete by 6 days. In whole mounts examined after 3 days of RA, there was a 75% reduction in the mean diameter of the utriculi. These results suggest that extrusion of the contents of enlarged MCGs into the intercellular corneocyte spaces facilitated separation of corneocytes, leading to rapid shedding, perhaps through the action of desmosome-lysing proteases. The conversion to normal follicles is consistent with the established role of retinoids in correcting abnormal differentiation.

UVA-induced ultrastructural changes in hairless mouse skin: a comparison to UVB-induced damage

In this ultrastructural study, albino hairless mice were irradiated with long-wavelength ultraviolet (UVA) (340-400 nm) thrice weekly for 32 weeks for a cumulative dose of 8000 J/cm2. Biopsies were taken from these mice, from age-matched unirradiated controls, and from mice irradiated with UVB for 20-30 weeks with a cumulative dose of approximately 6-9 J/cm2. The most striking UVA-induced changes were 1) elastic fiber hyperplasia without evidence of fiber disintegration, 2) a large increase in randomly deposited microfibrils; 3) massive duplication of vascular basement membrane; 4) extensive endothelial cell damage; and 5) collagen fibers with smaller diameters but without apparent damage. By contrast, after UVB, the hyperplastic elastic fibers frequently appeared to be degraded. Microfibrils were only moderately increased and remained in an organized array. Also, unlike with UVA, the epidermal basement membrane was duplicated whereas that of the vessels was mainly spared. Collagen fibers showed evidence of dissolution. Thus, ultrastructural features provide further evidence that skin damage induced by UVA can be dissimilar to that induced by UVB.

Spk1, a new kinase from Saccharomyces cerevisiae, phosphorylates proteins on serine, threonine, and tyrosine

A Saccharomyces cerevisiae lambda gt11 library was screened with antiphosphotyrosine antibodies in an attempt to identify a gene encoding a tyrosine kinase. A subclone derived from one positive phage was sequenced and found to contain an 821-amino-acid open reading frame that encodes a protein with homology to protein kinases. We tested the activity of the putative kinase by constructing a vector encoding a glutathione-S-transferase fusion protein containing most of the predicted polypeptide. The fusion protein phosphorylated endogenous substrates and enolase primarily on serine and threonine. The gene was designated SPK1 for serine-protein kinase. Expression of the Spk1 fusion protein in bacteria stimulated serine, threonine, and tyrosine phosphorylation of bacterial proteins. These results, combined with the antiphosphotyrosine immunoreactivity induced by the kinase, indicate that Spk1 is capable of phosphorylating tyrosine as well as phosphorylating serine and threonine. In in vitro assays, the fusion protein kinase phosphorylated the synthetic substrate poly(Glu/Tyr) on tyrosine, but the activity was weak compared with serine and threonine phosphorylation of other substrates. To determine if other serine/threonine kinases would phosphorylate poly(Glu/Tyr), we tested calcium/calmodulin-dependent protein kinase II and the catalytic subunit of cyclic AMP-dependent protein kinase. The two kinases had similar tyrosine-phosphorylating activities. These results establish that the functional difference between serine/threonine- and tyrosine-protein kinases is not absolute and suggest that there may be physiological circumstances in which tyrosine phosphorylation is mediated by serine/threonine kinases.

Immunological studies on thromboangiitis obliterans

Using humoral immunity (gamma-globulin 18 cases, IgG, IgA, IgM each 30 cases, CH50, C3, C4 each 29 cases and CIC 31 cases), cellular immunity (E-RFC 68 cases, As 30 cases, SmIg, SmIgG each 18 cases, IMIT 30 cases) and immunopathological manifestations (light microscope, fluorescence microscope, transmitted electron microscope each 7 cases) as indices, we studied the immunological changes of "progressing", "remittent" and "stabilized" groups of patients with thromboangiitis obliterans (TAO) in different stages. Humoral immunity indicated that gamma-globulin, immune complex and IgG were all increased; cellular immunity indicated that the rate of T cells and suppressor cells was declined, while that of B cells was elevated. Immunopathologically, under light microscope all the layers of involved vessels were infiltrated with neutrophils, lymphocytes and monocytes; under fluorescence and electron microscope, immune complexes were found in the involved vessel walls. Our preliminary results suggest that TAO is an autoimmune disease relevant to antigen-antibody complex.

Studies on hypercoagulation state in thromboangiitis obliterans

Thirteen hypercoagulation parameters related to coagulation, anticoagulation, platelet functions, dynamics of clot formation and hemorrheology were determined in 15-109 patients with thromboangiitis obliterans (TAO). The results showed that VIIIR = Ag, PAdT, PagT, HPF, and whole blood and plasma viscosity were elevated, fibrinogen elevated in the active stage, AT-III declined, RBC electrophoresis time prolonged, and changes suggesting hypercoagulation in thromboelastogram. All these indicated the existence of a hypercoagulation state in TAO patients, which could contribute to the process of thrombosis. The relationship between immune reactions and blood hypercoagulability could be crucial in the pathogenesis of TAO. Immune reactions causing injury of vascular endothelium play a primary and fundamental role, and blood hypercoagulability could play a secondary but important role in the course of the disease.

The anatomy and pathogenesis of wrinkles

The anatomy of linear wrinkles ("crow's feet' and temporal frown lines), fine criss-cross wrinkles of the face and wrinkling of the general body surface of elderly persons, was studied by light and scanning electron microscopy. No histological features distinguished the various wrinkles from surrounding skin. It was concluded that the wrinkle is a configuration change, like the grooves worn into an old glove, without specific structural alterations at the histological level. As regards pathogenesis, the common setting was found to be deterioration of the elastic tissue network. The skin becomes looser, excessive, and loses the ability to snap back to its original state after being deformed.

Anatomy of striae

The histopathology of striae distensae is disputed; different authorities give contradictory accounts of the microscopic changes, especially in elastic fibres. We re-evaluated the problem by taking eight elliptical biopsies across striae. Six were examined by light microscopy with appropriate stains for elastin and collagen. Two were prepared for scanning electronmicroscopy (s.e.m.), using a procedure which removes collagen, enabling the elastic network to be seen in its native form. By light microscopy, striae were sharply demarcated from normal skin, consisting mainly of fine, straight bundles of collagen arranged parallel to the surface. Fine elastic fibres were disposed similarly without fragmentation, fraying or curling. By s.e.m., the elastic network was found to be extraordinarily dense and well developed with many fine, curled fibres in random array. It was evident that the routine stains for elastin greatly underestimated the abundance of elastic fibres, probably because immature fibres contain insufficient protein matrix. The horizontal packing of collagen bundles was confirmed by s.e.m. These findings support the view that striae distensae are scars. There is no evidence that they form by stress-induced rupture of the connective tissue.

Ultrastructural study of iron deposition in the eccrine sweat glands of patients with iron overload

An ultrastructural study of eccrine sweat glands was carried out on three patients with iron overload (two with idiopathic haemochromatosis and one with transfusional haemosiderosis). In all three patients small electron-dense particles were seen in both eccrine sweat glands and macrophages. They appeared primarily in the clear cells of the eccrine sweat glands as membrane-bound irregularly shaped bodies, and were shown to contain iron by energy dispersive X-ray microanalysis. Iron aggregates in and around sweat glands were also seen on light microscopy.

Corticosteroid atrophy in human skin. A study by light, scanning, and transmission electron microscopy

Steroid atrophy was induced in 3 volunteers by the continuous, occlusive application of clobetasol propionate to the forearms for 6 weeks. The changes were followed sequentially by light, scanning, and transmission electron microscopy. a 59% decrease in viable epidermal thickness was noted after the sixth week of treatment, as well as a flattening of the dermal-epidermal junction. The 3-dimensional architecture of the dermis was strikingly reorganized. This was largely brought about by resorption of the ground substance as revealed by a progressive diminution of Hale's stain for acid mucopolysaccharides. Loss of ground substance resulted in decreased spaces between collagen and elastic fibers as shown by scanning and transmission electron microscopy. The fibrous network consequently collapsed, yielding a more compact papillary and reticular dermis. This compression caused the reorientation of both collagen and elastic fibers. However, no differences in collagen and elastin fine structure were noted. Fibroblasts were shrunken but not reduced in density. A marked decrease in number of mast cells was noted in 3-week specimens and virtually no mast cells were observed after 6 weeks. We found that the primary effect of short-term steroid use was a rearrangement of the geometry of the dermal fibrous network. This was not due to alterations in the fibers themselves but a secondary consequence of the loss of ground substance.