Early Stages Of Observation Research Articles

Smoking Cessation and Risk of Hidradenitis Suppurativa Development

Although tobacco smoking is established as a risk factor for hidradenitis suppurativa (HS), studies on the effects of smoking cessation on HS are limited, and evidence is lacking. To examine the association between changes in smoking status and the development of HS. This population-based cohort study enrolled participants from the Korean National Health Insurance Service database who had undergone 2 consecutive biennial health examinations (2004-2005 and 2006-2007) as the primary cohort. Within the primary cohort, the secondary cohort comprised individuals who underwent all biennial health examinations throughout the follow-up period and maintained the same smoking status from 2006 to 2007 to the end of the follow-up period. Data were analyzed from July to December 2023. Changes in smoking habit status. Risk of HS development. The HS risk according to change in smoking status between the 2 consecutive health examinations was estimated using a Cox proportional hazards model. Of the 6 230 189 participants enrolled, the mean (SD) age was 47.2 (13.5) years, and 55.6% were male. During 84 457 025 person-years of follow-up, 3761 HS events occurred. In the primary cohort, compared to those who consistently reported active smoking at both checkups (ie, sustained smokers), lower HS risk was seen among those who were confirmed to smoke initially but quit by the second checkup (ie, smoking quitters) (adjusted hazard ratio [AHR], 0.68; 95% CI, 0.56-0.83), those who maintained cessation status throughout (AHR, 0.67; 95% CI, 0.57-0.77), and those who reported never smoking at either checkup (ie, never smokers) (AHR, 0.57; 95% CI, 0.52-0.63). Those who initially quit smoking but resumed by the second checkup and those who had no previous smoking history but started at the second checkup (ie, new smokers) exhibited similar HS risk as sustained smokers. The secondary cohort results aligned with those of the primary cohort, showing a more pronounced risk reduction with smoking cessation (AHR, 0.57; 95% CI, 0.39-0.83). Considering time-smoking interaction, the cumulative incidence and the risk of HS in smoking quitters were similar to those in sustained smokers in the early stages of observation. However, 3 to 4 years after smoking cessation, the rate decelerated, resembling that of never smokers, and there was a statistically significant decrease in the risk that persisted (between 3 and 6 years from the index date: AHR, 0.58; 95% CI, 0.36-0.92; and ≥12 years from the index date: AHR, 0.70; 95% CI, 0.50-0.97). New smokers initially paralleled never smokers but accelerated after 2 to 3 years, reaching sustained smokers' levels. In this cohort study, quitting smoking and sustaining a smoke-free status were associated with a reduced risk of HS development compared to continuous smoking. In contrast, resuming or initiating smoking may have as detrimental an effect on HS development as continual smoking.

Histotopographic and morphometric characteristics of the oral mucosa postoperative wounds healing, depending on the method of connecting the wound edges

Implementation of high-quality tissue connections and hemostasis in oral surgery is an urgent problem of modern dentistry, due to the lack of available universal methods that would help to facilitate the work of oral surgeon and reduce wound healing time.
 The aim of the research. To investigate and study the regeneration processes in the oral mucosa after high-frequency electric welding, suturing and medical adhesive composition.
 Materials and methods. This study compared the effect of three connection methods and hemostasis: high-frequency electric welding (EKVZ-300M1 “PATONMED®”, Ukraine), suture method (nylon 5/0 “PIRUS®”, China), adhesive composition (“Histoacryl®”, Germany). 72 rabbits were involved in experiment. An incision of the soft tissues of the vestibulum of the oral cavity of the maxilla with a length of 1.3–1.5 cm was made. On days 3, 7, 14 and 21, tissue samples were excised, histological and morphometric examination of the material were performed.
 Results. By statistical data processing of 72 rabbits was found that the reliability of differences in the levels of morphometric parameters between groups on each day is very high, as evidenced by the calculated values ​​of the U-test. In 38 cases (90.5 %), the significance level was p≤0.01, in the other 4 cases – p≤0.05. The lowest value level of neutrophilic granulocytes was in rabbits of group No.1 (electric welding). In rabbits of group No. 1 GFBC were not observed in the 8 fields of view throughout the experiment.
 Conclusions. High-frequency electric welding of soft tissues can be used for effective intraoperative hemostasis and connection of the intraoral wound edges.
 Due to the absence of a foreign body (adhesive masses, filaments) and moderate alterative effect, histological examination indicates accelerated activation of regenerative processes in the early stages of observation in rabbits of group No. 1.

The combined use of a fermentoterapiya and carboxytherapy at complications of planimetric plasticity of area of a brush in cosmetology

Background. In recent years, cosmetology has become increasingly popular procedures for the introduction of various fillers to correct age-related changes in the hands (visualization of veins and tendons) to compensate for the amount of fat lost with age in the back of the hand. At the same time, the number of complications after contouring the hand area is also increasing, due to non-compliance with the insertion technique, ignorance of the anatomical features of the corrected area, and a number of other factors.
 Aims: to study the effectiveness of a combined method that includes a course of collalizine diadinamophoresis in combination with injection carboxytherapy for the correction of complications that occurred on the back of the hand when injecting fillers based on calcium hydroxyapatite.
 Methods. There were 28 women under observation, with an average age of 41.5 4.6 years, with a complication after administration of a drug based on calcium hydroxyapatite on the back of the hand. Were allocated to 3 groups that received a course of carboxytherapy, the rate of diadynamophoresis collalizine and their combination.
 Results. The use of a combined course of collalizine diadinamophoresis with injectable carboxytherapy provides a pronounced analgesic effect, stabilizes the psychoemotional state and gives a pronounced effect of reducing the thickness of the dermis and increasing the dermis density coefficient, especially in the early stages of observation, which is probably due to a decrease in intra-dermal edema that occurs as a reaction to a filler injected either too deeply or in large quantities. In addition, this combined technique significantly accelerates both the biodegradation of the previously introduced filler, and affects pathological fibrosis around calcium hydroxyapatite crystals.
 Conclusions. The combined use of collazine diadinamophoresis and injective carboxytherapy locally on lesions with complications in the form of edema, contouring and local neuropathic manifestations that occur when injecting fillers based on calcium hydroxyapatite to the back of the hand is a highly effective method of treatment, which is confirmed by relieving clinical symptoms and improving the quality of life of patients.

What Characteristics of the Acetabular Defect Influence the Choice of the Acetabular Component During Revision Hip Arthroplasty?

The purposes of the retrospective cohort study were: 1) to determine the severity of defects in the acetabulum and the probable causes of their formation in patients who underwent revision hip arthroplasty (RHA), as well as an assessment of factors that exacerbate the severity of the defects; 2) identifying the proportion of severe defects in the overall structure of acetabular revisions and determining the effectiveness of using serial implants in comparison with individual constructions made by 3D printing; 3) the rationale for rational indications for the use of individual constructions.Materials and Methods. The structure and reasons for the formation of bone defects in the acetabulum were evaluated in 726 cases of revisions performed from 2004 to 2018. In addition, the results of revision operations in a group of patients with severe defects (type 3 according to Paprosky and pelvic discontinuity) were evaluated.Results. The most frequent cause of defect formation was iatrogenic (53.2%), and the share of severe defects was 39.5% (287 observations). A factor aggravating the severity of the defect is the lack of its limitation by the support bone. The results of RHA in patients with severe defects were assessed in 186 cases out of 287 (64.8%). In 73 (39.2%) cases, individual constructions were used, the average follow-up was 26 months. (from 12 to 50), and in 113 (60.8%) cases, serial implants were used, the average follow-up period was 62 months. (12 to 186). Individual constructions were more often implanted in patients with 3B acetabular defects (p0.05) and its uncontained defects (p0.001). The number of cases of aseptic loosening in the group of patients undergoing endoprosthetics using serial implants was greater than in the group of patients with individual constructions for the entire period (p0.05) and in the early stages of observation (p0.05).Conclusion. In case of RHA in patients with severe acetabular defects, individual implants, in comparison with serials, demonstrate better survival with an average follow-up of 26 months and due to design features, they can count on great long-term effectiveness. This study needs to be continued to increase follow-up.

СТРУКТУРНЫЕ И ОРГАНОМЕТРИЧЕСКИЕ ИЗМЕНЕНИЯ ЩИТОВИДНОЙ ЖЕЛЕЗЫ КРЫС В УСЛОВИЯХ ИММУНОСУПРЕССИИ И ИММУНОМОДУЛЯЦИИ НА РАННИХ СРОКАХ ВОЗДЕЙСТВИЯ

One of the factors affecting the prevalence of thyroid disease is the immunopathological process, in particular immunosuppression. The purpose of the study is to determine the characteristics of thyroid gland morphological structure and organometric parameters under immunosuppressive (methotrexate) and immunomodulatory (imunofan) drugs, and immunomodulatory management of immunosuppressive state during early follow-up period (1st and 7th days). Materials and Methods. The study was carried out on 48 white outbred young male rats of the reproductive period, which were divided into 4 groups. The dynamics of structural and organometric parameters of the thyroid gland was studied during the early stages of observation (1st and 7th day) after administration of immunosuppressive (methotrexate) and immunomodulating (imunofan) drugs. Results. When studying microscopic sections of the thyroid gland in animals exposed to methotrexate (group I), imunofan (group II), and after immunomodulatory management of immunosuppressive state (group III), the dynamics in the structure of the thyroid gland was observed during the whole follow-up period. Experimental animals demonstrated insignificant changes in follicles and thyrocytes on the 1st day after the drug administration when compared with those of the control group. The authors didn’t observe any statistically significant deviations in the dynamics of the organometric indicators. Significant deviations were seen on the 7th day of observation. Changes in the morphostructure were revealed after administration of methotrexate (group I): organ mass and volume as well as lobe linear dimensions decreased, indicating an active response of the organ and its depression, which was associated with the drug inhibitory effect on the synthesis, DNA repair and cell mitosis. After isolated administration of an immunomodulator (group II) and in case of immunosuppresson management with imunofan (group III) changes in thyroid morphostructure and organometric parameters were revealed on the 1st and 7th days of observation. Such changes indicated a favorable effect of imunofan on the organ morphofunctional state: organ mass and volume as well as lobe linear dimensions increased. Conclusion. In the early stages of methotrexate administration, the dynamics of thyroid changes indicated the organ depression. Positive dynamics in the thyroid structure was detected after administration of the immunomodulator, however, it was not clear-cut. Keywords: thyroid gland, methotrexate, imunofan, immunosuppression, immunomodulation, correction, organometry.

Morphometric characteristics of the resistant link of salivary gland’s hemomicrocircular rate of rats in chronic ethanol intoxication

Background. To date, numerous clinical observations and experimental data have proven that there is practically no such organ that would not be subjected to toxic effects of alcohol. Purpose of the work was to determine the dynamics of changes in the metric indices of the submandibular glands’ resistive link of the haemomicrovascular bed of the rats in chronic ethanol intoxication. Methods. The work was performed on 45 white, non-breeding rats. 5 animals were an intact group, which was washed out 4 times a day with isotonic sodium chloride solution, and 40 - experimental, which was injected intrastomach 1 times a day with 12 mg / kg 400 ethanol (in terms of pure alcohol). Animals were withdrawn from the experiment at 5, 9, 12 and 30 days by overdose of thiopental anesthesia (25 mg / kg). Sections of the submandibular glands were enclosed in epon-812 according to the generally accepted method. The mean values of the outer diameter and diameter of the arterioles lumen were determined using a microscope with a digital microphocamera Biorex 3 with an adapted for data research program. Results. In the morphometric study it was found that on the fifth day after ethanol introduction, the mean values of the outer diameter of the arterioles decreased significantly by 15.8%, compared with the control group, and amounted to 15.28 ± 0.06 μm. Also, the diameter of the arteriol lumen was reduced by 53.5%, compared with the control group (p<0.05), and equaled 7.47 ± 0.03 μm. The average thickness of the vascular wall significantly increased by 41.8% and was 3.91 μm. On the ninth day after the introduction of ethanol, the mean values of the outer diameter of the arterioles increased significantly by 27.4% compared to the fifth day of the experiment and amounted to 19.46 ± 0.04 μm, but slightly higher than the control group (p<0.05) by 7.3%. Relatively on the thirtieth day of the experimental model of chronic ethanol intoxication, the outer diameter of the arteriol wall was 18.39 ± 0.04 μm and increased by 0.8%, compared to the twelfth observation day, and by 1.4% compared with the control group of rats. Conclusion. In the early stages of observation, vasospasm is determined, which is confirmed by an increase in the thickness of the vascular wall by 41.8%. At the ninth day there is dilatation, which manifests itself in a significant increase in the diameter of the outer and the lumen, and the decrease in the thickness of the vascular wall. The normalization of the indicators by the thirtieth day is not determined.

Signalling function of β-catenin is important at early stages of adult heart pathological hypertrophy

The spread of cardiovascular diseases, their significant threat to health and socio-economic burden result in considerable interest of scientists to this problem solution. Lately, not only investigations into new methods of diagnosis and treatment of cardiovascular disease, but also elucidation of the mechanisms underlying their occurrence and course become topical. The aim of our study was to investigate the signaling function of the canonical Wnt-signaling and b-catenin function in the development of pathological hypertrophy of the adult myocardium. Methods. Studies were conducted using transgenic mice BATGIRL and cultures of isolated cardiomyocytes. To induce pathological hypertrophy, lithium chloride and AnglI were used. Changes in the expression of hypertrophic genes and genes involved in the canonical Wnt-signaling were analyzed by real-time PCR and Western-blot analysis. Morphological studies and X-gal staining were performed. Results. Upon the action of hypertrophic stimuli the activation of b-catenin signaling function is shown to occur in the early stages of observation, as evidenced by X-gal staining and changes in gene-targets expression of this signaling (c-Fos, c-Myc, CyclinD1 and TCF-4). There was also observed an increase in the content of activated b-catenin and phosphorylated GSK3b proteins within a day after the action of angiotensin and lithium chloride in the culture of isolated cardiomyocytes. Conclusions. With the development of pathological hypertrophy due to chronic high blood pressure, there occurs the activation of many signal-regulatory mechanisms of cardiomyocytes and one of them is the canonical Wnt-signaling. However, the activation of the canonical Wnt-signaling and β-catenin, in particular, is the early event and obviously essential to run the genetic program of myocardium remodeling.Keywords: β-catenin, hypertrophy, Wnt-signaling, gene expression, myocardium.

Main Predictors of Sudden Cardiac Death in Patients with Q-Wave Myocardial Infarction

The study included 131 patients (mean age 51.9±9.13 year) with Q-wave myocardial infarction (Q-MI). All patients underwent echocardiography and 24-hour ECG monitoring on the 10 th through the 14th days of MI. Treatment included thrombolytic therapy, early administration of beta-blockers, antiplatelet agents, anticoagulants, statins, ACE inhibitors, if needed - antiarrhythmics and aldosterone antagonists. Follow-up was 24 months. During the observation period, of the 131 study patients 17(13.0%) died suddenly. Our study suggests that the high risk of sudden cardiac death (in the first 2 years after MI) in patients with Q-MI is associated with anterior localization, early pathological left ventricular remodeling, low myocardial contractility, and development of AHF high Killip classes in the early period of MI, as well as the identification of high heart rate at rest, frequent premature ventricular contractions (mainly polymorphic), systolic dysfunction in the early stages of observation (on the 10 th through the 14th days), and older age of patients. (Int J Biomed. 2015;5(4):195-197.)

NEW ASPECTS OF ASSESSMENT THE ACTIVITY OF BLOOD PHAGOCYTES IN PULMONARY TUBERCULOSIS

Abstract. The phagocytosis is the key mechanism of organism protection from Mycobacterium tuberculosis. The aim of the study is to assess the phagocytal activity of cells in lung tuberculosis by the flowing cytofluorometric method. Overall 39 patients were examined including 14 patients with infiltrative lung tuberculosis, 15 patients with tuberculoma, 10 healthy persons. The patient testing was provided by the machine COULTER®Epics®XL, reagents Phagotest® (Orpegen Pharma), BurstTestKit (Glycotope Biotechnology) and monoclonal antibodies to detect subpopulation of lymphocytes. All obtained data were statistically processed by the software STATISTICА. It was established that the assessment of phagocytal activity of cells is the important criteria of detection of tuberculosis activity in the early stages of observation as well as during the treatment. The flowing cytometria allows rapidly, accurately and objectively assess the phagocytal cells of blood. It was determined that markers of early activation of cells could reflect the activity of pathological process and it can be used for prognosis of clinical course of lung tuberculosis.

Do young children have adult-like syntactic categories? Zipf’s law and the case of the determiner

Generativist models of grammatical development assume that children have adult-like grammatical categories from the earliest observable stages, whereas constructivist models assume that children’s early categories are more limited in scope. In the present paper, we test these assumptions with respect to one particular syntactic category, the determiner. This is done by comparing controlled measures of overlap in the set of nouns with which children and their caregivers use different instances of the determiner category in their spontaneous speech. In a series of studies, we show, first, that it is important to control for both sample size and vocabulary range when comparing child and adult overlap measures; second, that, once the appropriate controls have been applied, there is significantly less overlap in the nouns with which young children use the determiners a/an and the in their speech than in the nouns with which their caregivers use these same determiners; and, third, that the level of (controlled) overlap in the nouns that the children use with the determiners a/an and the increases significantly over the course of development. The implication is that children do not have an adult-like determiner category during the earliest observable stages, and that their knowledge of the determiner category only gradually approximates that of adults as a function of their linguistic experience.

Early Acquisition of Basic Word Order in Japanese

The acquisition of word order has been one of the central issues in the study of child language. One striking finding from the detailed investigation of various child languages is that from the earliest observable stages, children are highly sensitive to the basic word order of their target language. However, the evidence so far comes mainly from the acquisition of rigid word-order languages. In light of this background, this study presents new evidence that such early sensitivity to basic word order can be observed even in the acquisition of Japanese, a free word-order language.

Continuous versus intermittent exercise effects on urinary excretion of albumin and total protein

Several studies have reported post-exercise increases of urinary concentrations of plasma proteins. However, under normal conditions, through mechanisms of size and electrical charge selection, the kidney restricts the clearance of molecules as large as albumin. Post-exercise increases in albuminuria occur following the physiological stress of intense exercise, most likely as a result of the exercise induced blood acidity changes which lead to a change in the arrangement of the albumin molecule, and subsequently the filtration characteristics of the glomerular capillary wall. The purpose of the present study was therefore to determine the extent to which different types of exercise could induce a transient condition of post-exercise increases in the urinary output of total protein and albumin. All 14 males, who agreed to participate in the study, performed a continuous and an intermittent cycling protocol on a stationary bicycle ergometer. The results showed that: a) intermittent exercise had a greater influence than continuous exercise on the total output of urine albumin, and of urine total protein; b) concentrations of blood pH and blood lactate, were associated with changes in the clearance of urine albumin and urine total protein. Post-exercise proteinuria response seems to be transient and therefore renal trauma is not suspected at the early stages of observation. Furthermore, these results indicate that the kidney undergoes distinct physiological adjustments during exercise, and that these adjustments are relative to the intensity of the exercise stress.

Does error-free use of French negation constitute evidence for Very Early Parameter Setting?

Many recent generativist models attribute grammatical knowledge to young children on the basis that children's language patterns the same way as the target adult language. It has been proposed that the child acquires this knowledge early on in development by a process of parameter setting. Wexler (1996) presents the very early parameter setting hypothesis (VEPS), which suggests that basic language-specific parameters are set correctly at the earliest observable stages, that is, from the onset of multi-word speech. However, the patterns predicted by VEPS are necessarily a characteristic feature of the input language and could therefore be just as readily explained in more limited scope term. A good example of this is French negation where, in order to perform correctly, the child simply has to register that certain lexical forms precede the negative particle pas and certain other forms follow it. One implication of such a limited scope account is that there should be a strong relation between the lexical specificity of children's and mothers' use of verbs before and after pas. We present data for one subject, aged from 2;1 to 2;8, that are compatible with this hypothesis. While these data do not count directly against VEPS, they do suggest that the very low frequency of errors in children's use of French negation does not in and of itself constitute evidence for early syntactic knowledge.

Early Onset of Poinsettia Bract Necrosis is Associated with Condensed Tannin Accumulation

The early onset of bract necrosis in poinsettia (Euphorbia pulcherrima Willd. ex. Klotzch) is characterized by small dark-stained spots that precede the development of enlarged necrotic lesions. Electron micrographs of adaxial epidermal and subepidermal tissues with early symptoms of necrosis revealed large, electron dense deposits in cell vacuoles. These spherical bodies resembled condensed tannins observed in the epidermal tissues of peach and apple fruit. Chemical analysis of bract tissues showed higher condensed tannin concentrations in bract samples with 2 mm diameter lesions than in samples with lesions less than 0.5 mm (equivalent to catechin concentrations of 59 and 13 mg·g–1 fresh mass, respectively). Tannin bodies were not observed in micrographs from parallel samples of healthy appearing bracts, and chemical analysis revealed only trace concentrations of condensed tannins in these tissues (0.2 mg·g–1 fresh mass). The evidence suggests that condensed tannins accumulate in affected cells at the earliest observable stages of bract necrosis.

Development of preferred orientation in polycrystalline TiN layers grown by ultrahigh vacuum reactive magnetron sputtering

The preferred orientation of polycrystalline TiN films grown by ultrahigh-vacuum reactive-magnetron sputter deposition on amorphous SiO2 at 350 °C in pure N2 discharges was controllably varied from (111) to completely (002) by varying the incident ion/metal flux ratio Ji/JTi from 1 to ≥5 with the N+2 ion energy Ei maintained constant at ≂20 eV (≂10 eV per incident accelerated N). All samples were slightly over-stoichiometric with N/Ti=1.02±0.03. Films deposited with Ji/JTi=1 initially exhibit a mixed texture with competitive columnar growth which slowly evolves into a nearly complete (111) texture at film thicknesses greater than 1 μm. However, films grown with Ji/JTi≥5 exhibit an essentially complete (002) preferred orientation from the earliest observable stages. The normalized XRD (002) intensity ratio in thick layers increased from ≂0 to 1 as Ji/JTi was varied from 1 to ≥5. Both (111) and (001) interplanar spacings remained constant as a function of film thickness yielding a lattice constant of 0.4240±0.0005 nm, equal to that of unstrained bulk TiN. Contrary to previous models, the present results establish that TiN preferred orientation can be controlled without introducing large in-plane compressive stress and/or changes in the strain energy as a function of layer thickness.

High-flux low-energy (≂20 eV) N+2 ion irradiation during TiN deposition by reactive magnetron sputtering: Effects on microstructure and preferred orientation

The effects of the incident ion/metal flux ratio (1≤Ji /JTi≤15), with the N+2 ion energy Ei constant at ≂20 eV (≂10 eV per incident accelerated N), on the microstructure, texture, and stoichiometry of polycrystalline TiN films grown by ultrahigh-vacuum reactive-magnetron sputtering have been investigated. The layers were deposited in pure N2 discharges on thermally oxidized Si(001) substrates at 350 °C. All films were slightly overstoichiometric with a N/Ti ratio of 1.02±0.03 and a lattice constant of 0.4240±0.0005 nm, equal to that of unstrained bulk TiN. Films deposited with Ji/JTi=1 initially exhibit a mixed texture—predominately (111), (002), and (022)—with competitive columnar growth which slowly evolves into a pure (111) texture containing a network of both inter- and intracolumn porosity with an average column size of ≂50 nm at t=1.6 μm. In contrast, films grown with Ji/JTi≥5 do not exhibit competitive growth. While still columnar, the layers are dense with an essentially complete (002) preferred orientation and an average column size of ≂55 nm from the earliest observable stages. The normalized x-ray diffraction (002) intensity ratio in thick layers increased from ≂0 to 1 as Ji/JTi was varied from 1 to ≥5. Both 111 and 001 interplanar spacings remained constant as a function of film thickness for all Ji/JTi. Thus, contrary to previous models, strain is not the dominant factor in controlling the development of preferred orientation in these films. Moreover, once film texture is fully evolved—whether it be (002) or (111)—during deposition, changing Ji/JTi has little effect as preferred orientation becomes controlled by pseudomorphic forces. Film porosity, however, can be abruptly and reversibly switched by increasing or decreasing Ji/JTi.

Effect of regulatory cells induced by influenza virus during adoptive transfer

This paper examines the protective effect of humoral and cellular factors of immunity in experimental influenza infection in mice, with an analysis of the functional activity of the regulatory subpopulations of the lymphocytes, especially in the early stages of observation. The regulatory activity of the splenic lymphocytes was studied by assessing changes in the level of mitogen-induced proliferation of test cultures of lymphocytes from intact animals in the presence of lymphocytes obtained from infected mice at different times after infection. Tritium-labelled thymidine was used as the marker.

On the origin of the mosaic induced by turnip yellow mosaic virus

In Chinese cabbage plants infected with TYMV, only those leaves less than about 1 cm long at the time they become systemically infected develop the characteristic mosaic pattern of the disease. This pattern remains remarkably constant in individual leaves from the earliest observable stage until senescence. Tissue samples from dark green areas in the mosaic contain about 0.2% as much infectious virus as yellow areas. Uncontaminated dark green areas probably contain no virus. No double-stranded TYMV RNA can be detected in dark green areas. Yellow green areas have a lowered concentration of fraction I (chloroplast) protein and no detectable 68 S ribosomes. Dark green areas appear normal in these respects. Concentrations of fraction II (cytoplasmic) protein and 83 S ribosomes are similar in both types of tissue. We suggest that the mosaic pattern in TYMV-infected leaves is determined by events taking place in leaves in which cell division is taking place; that each distinct island of tissue in the mosaic may represent the progeny of a single cell; and that cells giving rise to dark green areas contain some factor conferring resistance to the virus in all the progeny.