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Biomedical subjects

K A Holbrook

Publications and source records attributed to K A Holbrook.

At least 19 recordsLinked to original sources
PubMed2005

Topical ocular antibiotics induce bacterial resistance at extraocular sites.

AIM: To compare the prevalence of antibiotic resistance found in nasopharyngeal Streptococcus pneumoniae between villages treated with topical tetracycline or systemic azithromycin as part of a trachoma control programme. METHODS: All children aged 1-10 years were offered either single dose oral azithromycin treatment (20 mg/kg) or a course of topical 1% tetracycline ointment, depending on the area. Treatment was given annually for 3 years. Six months after the third annual treatment in each village, children were surveyed for nasopharyngeal carriage of S pneumoniae and resistance was determined using broth dilution MIC technique. Children in two additional villages, which had not yet been treated, were also surveyed. RESULTS: Nasopharyngeal carriage of S pneumoniae was similar in the tetracycline treated, azithromycin treated, and untreated areas (p=0.57). However, resistance to tetracycline and azithromycin was distributed differently between the three areas (p=0.004). The village treated with topical tetracycline had a higher prevalence of tetracycline resistance than the other villages (p=0.010), while the oral azithromycin treated village had a higher prevalence of macrolide resistance than the other villages (p=0.014). CONCLUSIONS: Annual mass treatment with oral azithromycin may alter the prevalence of drug resistant S pneumoniae in a community. Surprisingly, topical tetracycline may also increase nasopharyngeal pneumococcal resistance. Topical antibiotics may have an effect on extraocular bacterial resistance.

Administration, Oral↗
PubMed2003

Community treatment with azithromycin for trachoma is not associated with antibiotic resistance in Streptococcus pneumoniae at 1 year.

AIMS: To determine if macrolide resistant Streptococcus pneumoniae will be a major concern in areas that receive annual mass azithromycin distributions for trachoma. METHODS: A cross sectional survey was conducted of nasopharyngeal S pneumoniae isolates for susceptibility to azithromycin 1 year after administering a single dose of azithromycin to treat trachoma in a village in Nepal. RESULTS: S pneumoniae was isolated from 50 (86%) of 57 nasopharyngeal cultures and no resistance to azithromycin was detected. CONCLUSION: The authors were unable to demonstrate that mass azithromycin therapy for trachoma produced macrolide resistant S pneumoniae that persists until the next scheduled annual treatment.

Anti-Bacterial Agents↗
PubMed2001

The nerve-dependency of Merkel cell proliferation in cultured human fetal glabrous skin.

Merkel cells are thought to function as slowly adapting mechanoreceptors and are known as targets for sensory nerves. However, the nerve-dependency of Merkel cells remains controversial. In this respect, some investigators have found interregional differences between hairy and glabrous skin and others have shown intraregional differences within denervated rat touch domes. Differences between species have also been reported. This study was performed to determine whether Merkel cells proliferate in vitro in the absence of the systemic factors, blood vessels and the intact nerves in human skin. Suspension organ culture was performed using fetal digits to investigate their in vitro proliferation. Merkel cells and cutaneous nerves were identified using antibodies to cytokeratin 20 and protein gene product 9.5 (PGP 9.5), respectively. Fetal digits of 56-82 day gestational age were cultured in serum free medium in a high O2 (45%) environment. Tissues were harvested before starting culture (D0) and 1, 4, 7, 14, 28 d after culture. Merkel cells were observed in the volar pads and dorsal nail matrices at D0. After 28 d of suspension organ culture, digits looked healthy structurally and the number of Merkel cells had increased. However, PGP 9.5-immunoreactive nerves were markedly diminished after 1 day of culture and almost disappeared after 4 days. Merkel cell proliferation in vitro suggested that Merkel cell development is probably nerve-independent in human fetal glabrous skin.

Cell Division↗
PubMed1999

Periderm cells form cornified cell envelope in their regression process during human epidermal development.

Terminally differentiated stratified squamous epithelium forms a lining of the plasma membrane called the cornified cell envelope, a thick layer of several covalently cross-linked precursor proteins including involucrin, small proline-rich proteins, and loricrin. Their cross-linking isodipeptide bonds are formed by epidermal transglutaminases 1-3. Material from lamellar granules is attached on the extracellular surface of corneocytes during the keratinization process. The formation of cornified cell envelope and sequential expression of major cornified cell envelope precursor proteins, transglutaminases, and 25 kDa lamellar granule-associated protein were studied in human embryonic and fetal skin. Ultrastructurally, membrane thickening has already started in periderm cells of the two-layered epidermis and an electron-dense, thickened cell envelope similar to cornified cell envelope in adult epidermis is observed in periderm cells at the three-layered and later stages of skin development. In the two-layered epidermis (49-65 d estimated gestational age), immunoreactivities of involucrin, small proline-rich proteins, all the transglutaminases, and lamellar granule-associated protein were present only in the periderm. In the three-layered epidermis and thereafter (66-160 d estimated gestational age), loricrin became positive in the periderm cells, transglutaminases extended to the entire epidermis, and lamellar granule-associated protein was detected in intermediate cells as well as periderm cells. Immunoelectron microscopy demonstrated that both major cornified cell envelope precursor proteins, involucrin and loricrin, were restricted to the cornified cell envelope in periderm cells at this stage of development. After 160 d estimated gestational age, the periderm had disappeared and cornified cell envelope proteins and lamellar granule-associated proteins were expressed in the spinous, granular, and cornified cells and transglutaminases were detected in the entire epidermis. These findings indicate that cornified cell envelope precursor proteins, transglutaminases, and lamellar granule-associated proteins are expressed in coordination in periderm cells during human epidermal development and suggest that periderm cells form cornified cell envelope in the process of regression.

Adult↗
PubMed1998

Rates of and risk factors for trichomoniasis among pregnant inmates in New York City.

BACKGROUND: Trichomonas vaginalis is a common pathogen that is associated with adverse pregnancy outcomes and may serve as a cofactor in human immunodeficiency virus (HIV) transmission. GOAL: To define the epidemiology of trichomoniasis in a population of newly incarcerated pregnant women in New York City. STUDY DESIGN: Prospective study of 213 pregnant prisoners attending prenatal clinic. Patients participated in an interview regarding sexual and drug-related behaviors, and underwent direct culture for T. vaginalis in addition to routine testing for syphilis, gonorrhea, and chlamydia. RESULTS: The prevalence of trichomoniasis was 46.9%. On univariate analysis, there was a significant association between trichomoniasis and older age, crack use, prostitution, known HIV infection, and positive serological test for syphilis. Multivariate analysis showed a significant association of trichomoniasis with crack use and positive serological test for syphilis. CONCLUSION: Trichomoniasis is highly prevalent in pregnant prisoners in New York City. The extent of disease observed may justify a formal program of testing and treatment and emphasizes the urgent need for harm reduction education and expanded HIV counseling and testing services in this high-risk population.

Adolescent↗
PubMed1998

Regional difference in expression of characteristic abnormality of harlequin ichthyosis in affected fetuses.

Harlequin ichthyosis (HI) is a severe congenital ichthyosis in which newborn infants are covered with a thick plate of stratum corneum. We examined skin specimens from a variety of regions of the body including the scalp, face, tongue, trunk, upper and lower extremities, digits, palms, and soles of three fetuses affected with HI that were diagnosed prenatally. In all the skin regions, characteristic morphological abnormalities (absent or abnormal lamellar granules and intercellular lamellae, lipid inclusions in the cornified cells) were expressed in the late second trimester of the fetal period. The cornified cells in hair canals showed morphological abnormalities of HI more strongly than the interfollicular epidermis. Immunoblot study of epidermal extracts revealed that profilaggrin was much more prominent than filaggrin in all the hairy skin regions where the hair canals were extensively keratinized, but filaggrin was prominent in the palm. These observations support the idea that, in the hairy skin, HI phenotype expression is associated with keratinization and abnormal filaggrin metabolism in hair. In addition, the prenatal diagnosis or prenatal exclusion of HI is thought to be possible from whichever site of the fetal body the skin biopsy is taken in the late second trimester of the fetal period.

Biopsy↗
PubMed1997

Staphylococcus aureus nasal colonization in HIV-seropositive and HIV-seronegative drug users.

Nasal colonization plays an important role in the pathogenesis of Staphylococcus aureus infections. To identify characteristics associated with colonization, we studied a cross-section of a well-described cohort of HIV-seropositive and -seronegative active and former drug users considered at risk for staphylococcal infections. Sixty percent of the 217 subjects were Hispanic, 36% were women, 25% actively used injection drugs, 23% actively used inhalational drugs, 23% received antibiotics, and 35% were HIV-seropositive. Forty-one percent of subjects had positive nasal cultures for S. aureus. The antibiotic susceptibility patterns were similar to the local hospital's outpatient isolates and no dominant strain was identified by arbitrarily primed polymerase chain reaction (AB-PCR). Variables significantly and independently associated with colonization included antibiotic use (odds ratio [OR] = 0.37; confidence interval [CI] = 0.18-0.77), active inhalational drug use within the HIV-seropositive population (OR = 2.36; CI = 1.10-5.10) and female gender (OR = 1.97; CI = 1.09-3.57). Characteristics not independently associated included injection drug use, HIV status, and CD4 count. The association with active inhalational drug use, a novel finding, may reflect alterations in the integrity of the nasal mucosa. The lack of association between HIV infection and S. aureus colonization, which is contrary to most previous studies, could be explained by our rigorous control for confounding variables or by a limited statistical power due to the sample sizes.

AIDS-Related Opportunistic Infections↗
PubMed1997

A model system for long-term serum-free suspension organ culture of human fetal tissues: experiments on digits and skin from multiple body regions.

We have optimized a suspension organ culture (SOC) system previously used to study human fetal skin in vitro. Eleven types of media were used to culture fetal digits and skin samples (ranging from 59-91 days of estimated gestational age) for periods of 3 or 4 weeks. The cultures were supplemented with 0%-10% bovine calf serum and exposed to 5%-45% oxygen atmospheres. Optimal conditions, which were selected based upon the morphologic and histologic properties of the cultured tissues, were: DMEM-F12 medium in a serum-free environment with a 45% oxygen atmosphere. The refined SOC system supports the maintenance and/or continued development of the epidermis and dermis of trunk, back, scalp, and digital skin, developing hair follicles, nails, and glands. Overall, development and differentiation mimicked the in vivo state more closely than that observed when using other in vitro culture systems. The effects of bovine calf serum and oxygen levels are presented, and the potential for manipulating the environment of this system for studying mechanisms of cutaneous development is also discussed.

Breast↗
PubMed1996

Ontogeny and characterization of factor XIIIa+ cells in developing human skin.

Factor XIIIa (FXIIIa), a coagulation transglutaminase, is a cytoplasmic marker for dermal dendritic cells reported to be bone marrow-derived, phagocytic and antigen-presenting. In non-inflamed skin, these cells populate the papillary dermis in a perivascular distribution. They are increased in dermatoproliferative disorders and have been implicated as dermal stimulants for psoriatic hyperkeratosis. Since developing skin provides an example of dermal influence on the epidermis, we evaluated the presence of FXIIIa+ cells in human fetal skin to determine whether their location would suggest a role in morphogenetic events in the skin. Embryonic and fetal skin of progressive estimated gestational ages (EGA) was examined using immunocytochemistry with a polyclonal antibody to FXIIIa. At 6 weeks EGA, globular FXIIa+ cells were present in the hypodermis. By 7-8 weeks, a compact sub-epidermal network of fusiform FXIIIa+ cells was also evident. By 11-12 weeks, the sub-epidermal cellular network was no longer FXIIIa+, but discrete FXIIIa+ dendritic cells were present in the reticular dermis. With advancing gestational age, FXIIIa+ dendritic cells populated the papillary dermis in a perivascular distribution. This adult-like distribution persisted through 22 weeks EGA, the oldest specimen examined. Because FXIIIa+ cells were evident in embryonic skin before the onset of bone marrow hematopoietic function, the skin was double-labeled with the FXIIIa antibody and with monoclonal antibodies to CD45 (marker for bone marrow-derived cells), CD68 (marker for macrophages) and HLA-DR (class II major histocompatibility antigen). Most of the FXIIIa+ dendritic cells did not colocalize CD45, but were CD68+; some cells did react with the HLA-DR antibody. Notably, the FXIIIa+ cells of the sub-epidermal network in the 7 weeks EGA specimens did not react with the other antibodies. We conclude that FXIIIa+ cells are first present in embryonic hypodermis and sub-epidermal dermis and later they are distributed in the papillary dermis in a perivascular pattern. In embryonic skin FXIIIa+ cells are not exclusively dendritic. Our data support the idea that cells that express FXIIIa do not constitute a unique bone marrow-derived cell type, but that multiple cell types produce FXIIIa.

Antibodies, Monoclonal↗
PubMed1996

Comparison of endovascular and conventional vascular prostheses in an experimental infection model.

INTRODUCTION: The causes and management of prosthetic graft infections have been extensively studied for conventional bypass grafts; however, the infectivity and therapy for endovascular graft infections are completely unknown. The aim of this study was to compare the biologic properties of infected aortic grafts when inserted by endoluminal or standard transabdominal techniques. METHODS: Eighteen dogs underwent placement of polytetrafluoroethylene grafts in their infrarenal aortas either by an endovascular technique (8) or a standard interposition technique (10). Endovascular grafts were constructed from polytetrafluoroethylene (3 cm) and two balloon-expandable stents coaxially mounted onto a balloon catheter delivery system. The grafts were inserted through a left carotid arteriotomy under fluoroscopic control. Initially, seven grafts were infected with decreasing inocula of Staphylococcus aureus, starting at 10(7) organisms per ml for 30 minutes and then rinsed briefly (10 seconds) in normal saline solution, until a 50% infective dose for the standard grafts was determined to be 10(2) organisms per ml. After this initial experiment, a second group of 11 dogs were compared at a concentration of 10(2) S. aureus per ml. Five dogs underwent endovascular repair, and six dogs had standard graft interpositions after an identical period of bacterial exposure. All grafts were removed at 2 weeks under sterile conditions and were submitted for quantitative culture analysis. RESULTS: Three of the six dogs (50%) with standard grafts appeared to clear their infections, whereas only one of the five dogs (20%) with an endovascular graft was free of organisms at 14 days. This results was further manifested by statistically significant lower postmortem colony counts in the standard grafts (p < 0.01). CONCLUSIONS: The endoluminal position of the graft and its proximity to the arterial wall do not appear to provide protection against infection. These data suggest that if endovascular grafts become infected, they may be in a disadvantaged position for host defense mechanisms to be effective.

Animals↗
PubMed1996

Growth factor and growth factor receptor localization in the hair follicle bulge and associated tissue in human fetus.

The bulge region of the hair follicle has been thought to contain follicular stem cells. The bulge in the human follicle is a collection of undifferentiated cells that is prominent only in the fetal period. Antibodies that recognize epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), EGF receptor, platelet-derived growth factor (PDGF) A and B chains, PDGF alpha and beta receptors, and the low-affinity nerve growth factor receptor (p75) were used to study the bulge and associated mesenchymal cells in this fetal period. Weak EGF and TGF-alpha immunoreactivities were seen in the bulge. Confocal laser scanning microscopic images revealed intracytoplasmic and intranuclear punctate patterns of immunoreactivities in the bulge cells labeled by anti-EGF and anti-TGF-alpha antibodies. All the bulge cells stained strongly for EGF receptor. Cells within the bulge were labeled both with PDGF A chain and with PDGF B chain, although the immunoreactivities were weak in the outermost layer of cells. The follicular sheath was strongly immunoreactive with antibodies against both PDGF alpha and beta receptors. p75 was expressed in mesenchymal cells around the hair follicle and in the lower portion of the bulge. These differential labeling patterns suggested that EGF, TGF-alpha, and nerve growth factor may be involved in regulation of the growth and differentiation of bulge cells and that PDGFs may have related functions in the interaction arising between the bulge and associated tissue during follicle morphogenesis.

Cell Differentiation↗
PubMed1995

Prenatal diagnosis of Herlitz junctional epidermolysis bullosa by amniocentesis.

Herlitz junctional epidermolysis bullosa (HJEB) is a severe blistering disorder which usually results in death during infancy. We have previously shown that the anchoring filament protein laminin-5 (kalinin/nicein), which mediates keratinocyte attachment and dermal-epidermal cohesion, is abnormally expressed in individuals with HJEB. Laminin-5 was detected by Western blot analysis in amniotic fluid from 44 consecutive normal second-trimester control pregnancies, but was undetectable in second-trimester amniotic fluid from four pregnancies with fetuses affected by HJEB. In one case of severe non-Herlitz JEB, laminin-5 was detected in both amniotic fluid and skin. In human amniotic fluid, the laminin-5 a3 subunit was processed to a major 165 kD species and a minor 145 kD species and the beta 2 subunit was partially processed to 105 kD. Although laminin-5 was covalently associated with laminin-6 (K-laminin) in amniotic membrane, no covalent interaction was detected in amniotic fluid. Laminin-5 from amniotic fluid strongly supported keratinocyte attachment. These results suggest that Western blot analysis of second-trimester amniotic fluid is useful in determining the prenatal diagnosis of HJEB and that laminin-5 may serve a physiologically important function in amniotic fluid.

Amniocentesis↗
PubMed1995

Immunolocalization of FXIIIa+ dendritic cells in human burn wounds.

Dermal dendrocytes constitute a population of indigenous antigen-presenting cells that have been implicated in dermal inflammation and may have a role in wound healing. They are identified by expression of the transglutaminase coagulation Factor XIIIa (FXIIIa) and a perivascular distribution in the papillary dermis. In this study, we used immunohistochemistry to localize and characterize FXIIIa+ cells in healing burn wounds. Wound specimens from Postburn Days 2, 3, 4, 5, 6, 8, 9, 10, 11, 15, 30, and 49 were collected from 18 patients at the time of excision and grafting, processed for immunolabeling, and labeled with an antibody to FXIIIa. Tissue sections were also double-labeled with the anti-FXIIIa and with antibodies to CD68, specific for macrophages, CD45, specific for bone marrow-derived cells, and proliferating cell nuclear antigen (PCNA) for proliferation. Antigen-presenting status was evaluated using an antibody to the major histocompatibility complex HLA-DR. The dermis subjacent to the tongue of proliferating epithelium at the wound edge had increased numbers of FXIIIa+ dendritic cells compared to the cellular distribution in uninjured skin. FXIIIa+ dendritic cells were absent from the burned dermis on all postburn days examined in this study. However, capillaries in the deep dermis had a FXIIIa+ granular staining pattern. CD68+ cells and CD45+ cells were present throughout the wound bed at all stages of healing, indicating an inflammatory cell response in the injured dermis. Antibodies to PCNA did not colocalize to FXIIIa+ cells, suggesting that the dermal dendrocytes were not proliferating. The antibody to HLA-DR localized to some, but not all of the FXIIIa+ dendritic cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomarkers↗
PubMed1995

Characterization of hair follicle bulge in human fetal skin: the human fetal bulge is a pool of undifferentiated keratinocytes.

It has been suggested that the bulge of the hair follicle contains a pool of follicular stem cells that may serve as a target site of graft-versus-host disease and as a source of cells with carcinogenic potential. The bulge is prominent in the developing follicle although it is a subtle swelling in the adult follicle. In this paper, we studied the bulge in human fetal skin specimens. Ultrastructurally, the bulge cells, especially the interior cells, have abundant free ribosomes and glycogen particles, but almost no cytoplasmic organelles indicative of differentiation. Immunostaining with several specific anti-keratin antibodies demonstrated that the bulge cells express keratins of both stratified and simple epithelia. Melanocytes and Merkel cells, defined by immunohistochemical and ultrastructural criteria, are seen among bulge cells. Laser confocal microscopy revealed that primitive smooth muscle cells attached directly to the bulge initially at the mid-bulbous hair peg, the stage when the bulge is most prominent. K-laminin and type VII collagen are strongly expressed in the dermoepidermal junction of the bulge and between the matrix area of the bulb and the dermal papilla. Thus, the bulge of human hair follicle is not only an attachment site for arrector pili muscle, but also a pool of keratinocytes that are relatively undifferentiated.

Animals↗
PubMed1995

The appearance, density, and distribution of Merkel cells in human embryonic and fetal skin: their relation to sweat gland and hair follicle development.

The density and distribution of Merkel cells in human embryonic and fetal skin were studied using an immunolabeling technique on epidermal and dermal sheets obtained by ethylenediamine tetraacetic acid separation. Merkel cells were identified by the known cytokeratin markers CK20 and CK18. Merkel cells showed CK20 immunoreactivity as early as 56 d estimated gestational age (EGA) in the palmar epidermis (133.11 +/- 44.27 cells/mm2). The density increased rapidly, reaching a maximum of more than 1400 cells/mm2 at 80-90 d EGA. At this stage, the cells became distributed along the primary epidermal ridges. In the palmar epidermis of fetuses older than 100 d EGA, the distribution of Merkel cells showed the same pattern, but the density then decreased gradually. Merkel cells were not observed in ductal and glandular portions of eccrine sweat glands. In the epidermal sheets of hairy skin, a few cells were first seen in the fetus at 75 d EGA. At 100 d EGA, only a few Merkel cells were observed, mostly in the hair pegs and bulbous hair pegs. In the older fetus, ring-like arrangements and aggregates of Merkel cells were prominent in the infundibulum and bulge of hair follicles, respectively. Merkel cells were both globular and dendritic in shape. The ratio of dendritic to globular cells increased gradually until the period of highest Merkel cell density in both the glabrous and hairy skin. All Merkel cells located in the dermis were globular in shape. In accord with the results obtained, we postulate that Merkel cells may have some functional role in the formation and proliferation of eccrine sweat glands and hair follicle anlagen in developing skin.

Epidermal Cells↗
PubMed1995

Familial pityriasis rubra pilaris.

BACKGROUND: Familial pityriasis rubra pilaris is a rare autosomal dominant skin disorder. Four individuals from one family are described who demonstrate clinical features compatible with a diagnosis of familial pityriasis rubra pilaris. Results of light and electron microscopic, immunocytochemical, and biochemical analysis of skin biopsy specimens from three of these four individuals are presented. OBSERVATIONS: All affected individuals demonstrated erythematous scaly skin with follicular prominence and islands of sparing. Inheritance was consistent with an autosomal dominant trait. Light and electron microscopic findings were compatible with those reported in sporadic cases of pityriasis rubra pilaris. Immunocytochemistry showed suprabasal staining with monoclonal antibody AE1. Immunoblot analysis revealed abnormal keratins with K6/16 expression, the possibility of an abnormal K14 or K16, and a 45-kd acidic keratin not normally expressed in epidermis. Because similar biochemical analyses have not been reported previously in other cases of pityriasis rubra pilaris (familial or sporadic), comparisons cannot be made. CONCLUSIONS: The observations suggest that the cutaneous abnormality in this family extends beyond clinical and morphological alterations to abnormalities in biochemical markers of epidermal differentiation.

Adult↗